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The Daye district represents one of the largest concentrations of skarn deposits in eastern China. There are two major types of skarn deposits (Fe skarn vs. Cu skarn) within this district, both genetically related to late Mesozoic high-K calc-alkaline granitoids. In this study, we present in situ compositional and Sr-Nd isotopic investigations of apatite from granitoids associated with Fe skarn and Cu skarn deposits to put constraints on the magma source, evolution, and volatile composition, which provide significant new insights into the genesis of the two contrasting mineralization styles in the Daye district. Apatite from granitoids related to Cu skarns and Lingxiang Fe skarn has [epsilon].sub.Nd(t) values of - 8 to - 4, similar to that of the contemporaneous mafic rocks in the Daye district, which were dominantly derived from an enriched lithospheric mantle source. Apatite in granitoids associated with the Chengchao Fe skarn has lower [epsilon].sub.Nd(t) values of - 15 to - 9, suggesting larger degrees of contaminations from ancient lower crust materials. Fractionation models based on apatite Sr/Y and Eu/Eu* ratios, suggest that magmas related with the Cu skarns have experienced amphibole-dominated fractionation under high pressure and hydrous conditions, whereas those associated with Fe skarns have undergone plagioclase-dominated fractionation at relatively low pressure and dry conditions. Based on results of apatite compositional analysis and apatite-melt partitioning data, the estimated magma Cl contents for the Fe skarn range from 3260 to 13,940 ppm, significantly higher than those for the Cu skarn (Cl = 430-5990 ppm). Apatite from Fe skarn-related intrusions has (.sup.87Sr/.sup.86Sr).sub.t ranging from 0.7073 to 0.7082, whereas the variety from Cu skarn-related intrusions displays lower (.sup.87Sr/.sup.86Sr).sub.t of 0.7054-0.7061. These Sr isotope data, combined with whole-rock S isotopes of this study and previous investigations suggest that the Fe skarn-related intrusions have assimilated larger amount of evaporite-bearing carbonate during magma ascent and emplacement. The assimilation process may have not only promoted magmatic water exsolution but also provided sufficient amount of Cl.sup.- and [Formula omitted], which facilitated effective complexation and transportation of Fe.sup.2+ and subsequent oxidization of ferrous Fe to precipitate magnetite, respectively. We suggest that evaporite assimilation into the granitoid magmas has played a crucial role in the large-scaled Fe skarn mineralization in the Daye district. This study highlights that apatite is a sensitive petrogenetic-metallogenic indicator for granitoids and thus can be useful in mineral exploration., Author(s): Run-Jie Zhou [sup.1], Guang Wen [sup.1], Jian-Wei Li [sup.1], Shao-Yong Jiang [sup.1] [sup.2], Hao Hu [sup.1], Xiao-Dong Deng [sup.1], Xin-Fu Zhao [sup.1], Dai-Rong Yan [sup.3], Ke-Tao Wei [sup.4] [sup.5], [...]

Although an extensive continental arc magmatism was recorded in the northern North China Craton (NCC) during the Carboniferous, a general geodynamic model has not been constructed, and associated crust–mantle processes are not fully understood. Here, we carried out systematic geochronological and geochemical investigations on the alkali‐feldspar granite pluton in the Zhaojinggou area, northern NCC. U–Pb dating of high‐U–Th zircons failed to obtain concordant ages due to severe metamictization, while apatite U–Pb dating yielded a perfect age of 327.6 ± 4.1 Ma, indicating the emplacement of granites in the Early Carboniferous. The granites have high SiO2 (74.99–76.88 wt%) and K2O (5.73–6.43 wt%) contents and exhibit enriched LREEs, K, Rb, Th, U, and Pb, and depleted Nb, Ta, P, and Ti contents, which are typical of highly fractionated, I‐type high‐K granites formed under a continental arc setting. Moreover, the high‐K granites show highly enriched Nd isotopic compositions (with whole‐rock and apatite εNd(t) of −33.6 to −16.3) that are distinctly lower than other Carboniferous continental arc rocks in the northern NCC (εNd(t) from −18.5 to −9.9). These geochemical characteristics indicate that the high‐K granites possibly originated by partial melting of the Archean TTG gneisses and mafic rocks in the lower crust. Involvement of mantle‐derived fluids is crucial to induce the low‐temperature melting, and sufficient fractional crystallization was reached during subsequent magmatic evolution. Previous studies suggest that the Carboniferous continental arc rocks in the northern NCC have mantle‐derived or crust–mantle mixed sources. Our study, however, indicates that there also exist coeval crust‐derived magmatic rocks in this area. In combination with previous work and this study, we support the hypothesis that the widespread Carboniferous continental arc magmatism in the northern NCC is related to the southward subduction of the Palaeo‐Asian Ocean (PAO), and the different magma sources and extensive crust–mantle interactions are responsible for the formation of diverse types of magmatic rocks with contrasting isotopic compositions. We also draw attention to the fact that phosphate minerals such as apatite may be a preferable chronometer relative to high‐U–Th zircon in a highly fractionated igneous system. [ABSTRACT FROM AUTHOR]

The Early Cretaceous peralkaline Baerzhe pluton hosts a potentially large REE-Nb-Zr-Be deposit in inner Mongolia, northeastern China. The mechanism responsible for the extreme enrichment of rare metals and rare earth elements in the pluton is still ambiguous. This study presents new evidence for silicate melt immiscibility as the key mechanism at Baerzhe using amphibole-group minerals from spherulite granite, which contains spherulites with abundant REE- and HFSE-bearing minerals. The spherulite from the transsolvus granite is composed of two distinct zones, i.e., a dark-colored core consisting of arfvedsonite aggregates and a light-colored rim consisting mostly of quartz and feldspar, rare amphibole, and abundant HFSE- and REE-bearing minerals. Four types of amphibole (Amp I, Amp-IIa, Amp-IIb and Amp-III) from the transsolvus granite and one type (Amp-IV) from the subsolvus granite are recognized, and all of them are magmatic fluoro-arfvedsonite. The earliest phase consists of euhedral inclusions of Amp-I within quartz or feldspar. They show an enrichment in HREEs relative to LREEs and a depletion in medium REEs, consistent with the REE pattern controlled by the mineral lattice. This implies that Amp-I likely formed in an initial homogeneous mel relatively depleted in REEs; thus, the mineral structure played a dominant role in REE partitioning. Compared with other types of amphiboles, Amp-IIa and Amp-IIb from the spherulite phase display the highest REE contents, with flat LREEs and MREEs and a slight upward HREE pattern. Combined with the significant accumulation of REE- and HFSE-bearing minerals in the rim zone, differences in REE patterns among different amphibole types imply that the spherulite crystallized in a volatile-rich silicate melt and was probably the product of silicate melt immiscibility. Interstitial Amp-III with lower REE contents from the matrix phase crystallized in the separate volatile-poor silicate melt. The Amp-IV from the subsolvus granite has the lowest CaO content, with strong depletion in LREEs relative to HREEs, suggesting a more evolved melt composition. It is concluded that silicate melt immiscibility may serve as an important key mechanism that occurred in the early stage of magmatic evolution, resulting in the enrichment of REEs and HFSEs, which played a critical role in the formation of large to giant ore deposits such as the Baerzhe deposit. [Display omitted] • Both transsolvus spherulite granite and subsolvus granite in the Baerzhe deposit. • Amphibole textures and compositions indicate the silicate melt immiscibility. • REE and HFSE minerals associated in the rims of spherulite granite. • Large-scale silicate melt immiscibility occurred in the early magma stage. [ABSTRACT FROM AUTHOR]

The Mufushan area, which has abundant rare-metal pegmatites within and around the Mufushan Granite Complex, has become a major target for Ta-Nb-(Li-Be) exploration in South China. The age and origin of the pegmatites and associated rare-metal mineralization are still under debate. Here, we report the in situ U-Pb ages and geochemical characteristics of granites and pegmatites in the Guanyuan and Duanfengshan districts, which are located in the central and northern parts of the Mufushan Complex. Combined zircon, apatite and monazite U-(Th)-Pb dating revealed that biotite, two-mica, and muscovite granites from the Guanyuan and Duanfengshan districts were emplaced at 143–139 Ma, which overlaps with the U-Pb ages of columbite-group minerals (CGM) from different internal zones of the Duanfengshan pegmatites (142–140 Ma). Whole-rock major and trace element compositions and Sr-Nd-Hf isotope data reveal that the granites and pegmatites experienced continuous evolution from biotite, two-mica, and muscovite granites to pegmatite and that the magma originated from the partial melting of mica schists that are abundant in the Mufushan area. Temporal, chemical and mineralogical evidence indicates a genetic link between muscovite granite and Ta-Nb pegmatites. The textures and chemical compositions of CGM from different pegmatites exhibit features typical of magmatic CGM, indicating that fractional crystallization was the driving force that promoted Ta-Nb enrichment. The increasing alumina saturation index [ASI: molar Al/(Ca–1.67P + Na + K)] of pegmatitic melt due to albite crystallization may have been the main factor controlling CGM deposition, explaining why major Ta-Nb mineralization is bound to albite pegmatites. The Duanfengshan and other rare-metal pegmatites in the Mufushan area are derivatives of the most evolved granitic facies (i.e., muscovite granite) of the Mufushan Complex. The Duanfengshan and Renli pegmatite fields indicate that the Early Cretaceous (∼140 Ma) may have been an important, underappreciated epoch for the formation of pegmatite-related rare-metal resources in the Mufushan area and beyond in South China. [Display omitted] • The rare metal pegmatites have genetic relationship with the muscovite granite in the Mufushan area. • In-situ U-Pb dating of columbite-group minerals indicate the rare metal mineralization occurred at 142–140 Ma. • Prolonged fractional crystallization is the driving force to promote rare metal mineralization in granite-pegmatite system. • Early Cretaceous is an important epoch for the formation of pegmatite rare-metal resources in South China. [ABSTRACT FROM AUTHOR]

The large Hebaoshan gold deposit (41.5 t Au, average grade: 3.5 g/t) is located in a hitherto poorly documented gold province in the northeastern part of the South China Block. It is hosted by Precambrian metasedimentary rocks that experienced Triassic greenschist- to amphibolite-facies metamorphism. Three hydrothermal stages can be distinguished: quartz + sericite + pyrite + pyrrhotite (stage I), quartz + magnetite + sulfide (stage II), and quartz + carbonate + pyrite + hematite (stage III). Auriferous pyrite samples yielded a Rb-Sr isochron age of 234 ± 3 Ma (2σ, MSWD = 0.24), and ore-related hydrothermal sericite yielded a 40Ar-39Ar plateau age of 226.4 ± 2.0 Ma (2σ, MSWD = 1.01), which are distinctly younger than ca. 430 Ma granitic rocks in the mining district and older than 170–130 Ma granites in the region, ruling out any genetic link between granite emplacement and gold mineralization. The mineralizing fluid system can be described as carbonic-aqueous with low to moderate salinity (2.2–10.1 wt% NaCl equiv.) and medium temperature of 290 to 350 °C (stage I) and 230 to 280 °C (stage II). The δ18O quartz ranges from 13.3 to 15.4 ‰, and the δD values for fluid inclusions in quartz range from − 97 to − 60 ‰. The calcite has C-isotopes ranging from − 6.1 to − 3.8 ‰ and O-isotopes from 2.8 to 13.6 ‰. H-O-C isotope data are consistent with a metamorphic fluid derived from devolatilization of Neoproterozoic basement rocks during regional metamorphism in the Late Triassic Indosinian period. The δ34S values of sulfides for stages I, II, and III are 0.1 to 7.8 ‰, − 10.6 to 5.1 ‰, and − 18.9 to − 14.1 ‰, respectively, indicating an increase in oxygen fugacity during fluid ascent which resulted in more negative sulfur isotope values of sulfides and precipitation of gold. Pyrite separates have 206Pb/204Pb ratios of 17.340 to 17.687, 207Pb/204Pb ratios of 15.539 to 15.604, and 208Pb/204Pb ratios of 37.749 to 38.094. The S-Pb isotope data suggest derivation of S and Pb from the Precambrian metasedimentary country rocks. Auriferous pyrite yielded elevated 3He/4He ratios (0.78–1.46 Ra), which suggest a mantle component as can be expected from fluids derived from a subduction setting. It is concluded that Hebaoshan is an orogenic gold deposit that formed during Triassic flat-slab subduction of the paleo-Pacific plate beneath the South China Block and thus constitutes the first Triassic deposit of this type recognized in the coastal area of Southeast China. [ABSTRACT FROM AUTHOR]

A comprehensive study of zircon U–Pb ages, major and trace elements, whole‐rock Sr–Nd–Pb isotopes and zircon Hf isotopes of the gneissic granite and quartz monzonite in the Tongbai Complex is conducted in an attempt to unravel their petrogenesis and shed new light on the tectonic evolution and crust thickening process of the Tongbai orogen. Zircon U–Pb dating indicates that the emplacement of gneissic granite was early at 144.2 ± 1.3 Ma, whereas the quartz monzonite formed later at 130.2 ± 1.7 Ma. Both the gneissic granite and quartz monzonite samples share many chemical similarities, such as high Al2O3, K2O, Sr contents and low MgO contents, together with high Sr/Y, high La/Yb ratios, suggesting an C‐adakitic affinity and possibly derived from partial melting of the thickened lower crust. The later quartz monzonites may have involvement of much more proportion of mantle‐derived materials (such as the metamorphosed mafic rocks, ecologite) in the lower crust during partial melting for its petrogenesis, due to its higher MgO, Cr, Ni, and V contents than the gneissic granites. The formation of the gneissic granite and quartz monzonite records the evolution history for the lower crust thickening beneath the Tongbai orogen at the Cretaceous. Nearly all granitoids in the Tongbai orogen currently found have an emplacement age of >130 Ma and have higher Sr/Y ratios and lower MgO, Cr, Ni, and V contents with respect to the granitoids in the Dabie orogen which occurs in two stages of granitic magmatism of >130 Ma and <130 Ma. The Tongbai orogen lacks the granitoids formed by significant crust–mantle mixing that occurred in the Dabei area at <130 Ma. These results indicate that the lower crust was continuing thickening but probably not delaminated beneath the Tongbai orogeny during the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The North Wuyi area is an important metallogenic belt in South China and hosts many Pb–Zn–Ag deposits within the Jurassic–Cretaceous volcanic basins. These deposits are mostly genetically associated with Late Jurassic magmatism. The Cretaceous granitic rocks in the Lizikeng basin, at the eastern part of the North Wuyi area, were investigated for their mineralogical and geochemical characteristics in this study. Three types of granitic rocks, quartz monzonite, granite porphyry, and monzogranite, occur, and zircon U–Pb dating reveals that they all formed during the short period of 133–129 Ma, corresponding to the early Cretaceous volcanic-intrusive activities in South China. The whole-rock geochemistry indicates that all three granitic rocks have I-type affinity. The quartz monzonite and granite porphyry have consistently low whole-rock εNd(t) values of − 10.4 to − 9.6 and zircon εHf(t) values of − 14.2 to − 8.2, and they were likely derived from Proterozoic crustal sources without any significant contribution of mantle-derived material. The monzogranite, which shows also negative but slightly higher εNd(t) and εHf(t) values of − 7.6 to − 7.1 and − 9.3 to − 7.0, respectively, might also be derived from a major Proterozoic crustal source but with some input of mantle magma. The geochemical data show that the monzogranite belongs to tungsten-bearing granite with highly evolved characteristics, and with high Nb and W contents similar to the typical rare-metal and W-bearing granites in South China. A large number of typical hydrothermal rare-metal minerals are identified in the monzogranite, such as W-bearing rutile, niobian rutile, and columbite-group minerals as well as ferberite. The discovery of the early Cretaceous granitic rocks with tungsten mineralization potential indicates that the North Wuyi area is prospective for rare-metal mineralization, which opens a new window for rare-metal prospecting in the volcanic basins, as this type of ore deposit was previously thought to occur in granites from mountain range areas in South China, such as the Nanling Range. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calc-alkaline magma can exsolve high REE fluid. • High F content can facilitate the transportation of REE from magma into fluid. • The assimilation of evaporates enhances REE transportation. Hydrothermal fluids associated with carbonatites and peralkaline silicate rocks typically exhibit high REE content, but this is generally not the case for calc-alkaline rocks. However, the Tieshan skarn Fe-Cu deposit in the Edong district of Hubei Province in China demonstrates economic REE mineralization potential linked to calc-alkaline rocks. To investigate the presence of REE enrichment in the fluid, we present textural and compositional data of rock-forming mineral amphibole from the quartz diorite in the Tieshan deposit. Three distinct types of amphibole are identified in the Tieshan quartz diorite, namely Early amphibole , Main-stage amphibol e, and Late amphibole , following the crystallization sequence. Early amphibole (813–864 °C, 115–152 MPa) crystallized when the magma was emplaced at a depth of approximately 4.8 km. Main-stage amphibol e (741–806 °C, 58–103 MPa) crystallized at a depth of roughly 3 km. Between the early and main-stage amphibole crystallization, the magma experienced fractional crystallization of pyroxene, amphibole, and plagioclase, resulting in a REE enrichment in the residual melt. Late amphibole crystallized subsequent to the transition from lithostatic to hydrostatic stress states (656–729 °C, 27–52 MPa). Significantly, the transport of REE from the magma system initiated towards the end of Main-stage amphibol e crystallization. A comparison with the Tonglvshan granitic rocks in the same district indicates an elevated F content and extended fractional crystallization history in the Tieshan magma, contributing to REE enrichment in its melt. Furthermore, the high F content lowered the solidus temperature of the Tieshan magma, thereby facilitating the more efficient removal of REE into the fluid. The assimilation of evaporate into the magma possibly led to heightened sulfur and chlorine levels in the fluid, enabling the transport of a significant amount of REE. [ABSTRACT FROM AUTHOR]

The Jiangnan Orogen, located at the southeastern margin of the Yangtze Block, South China, records the complete history of assembly and evolution between the Yangtze and Cathaysia blocks. Neoproterozoic sedimentary sequences are widespread in the Jiangnan Orogen, with a regional angular unconformity separating the Sibao and Danzhou groups. U-Pb geochronology and Lu-Hf isotope analyses were carried out on detrital zircons across this unconformity and also the associated granites in the western Jiangnan Orogen in this study. Our new results, combined with previous data, indicate that the Sibao and Danzhou groups were deposited at 860–832 and 803–764 Ma, respectively. Thus, this unconformity was constrained to be 832–803 Ma. Detrital zircons from the Sibao and Danzhou groups have generally similar age populations, with three major peaks at 2000–1550, 1000–880, and 850–830 (760) Ma and one minor at 2600–2400 Ma. The most important generation of juvenile crust appears to have occurred at 2600–2400 Ma. Both recycling of ancient crustal materials and addition of juvenile mantle components took place in the time intervals of 2000–1550 and 1000–880 Ma. Detrital zircons in the age population of 850–830 (760) Ma were probably derived from proximal magmatic rocks in the western Jiangnan Orogen, reflecting fast erosion of newly formed igneous rocks. The Sibao and equivalents were deformed and intruded by granites posterior to the deposition of the Sibao and equivalent sequences after 832 Ma but before deposition of the Danzhou and equivalent units before 803 Ma. The pre-Danzhou deformation marked a collision along the southeast margin of the Yangtze Craton. The regional angular unconformity sealed the Jiangnan Orogeny, and thus the collision between the Yangtze and Cathaysia blocks was during 832–803 Ma. The Danzhou and equivalent units unconformably overlying the Sibao Group record the onset of rifting along the southeastern Yangtze margin beginning around 803 Ma. [ABSTRACT FROM AUTHOR]

[Display omitted] • Huangjiagou Paleoproterozoic pegmatites underwent ca. 1.75 Ga high-temperature metamorphism and ca. 130 Ma metasomatism. • The Cretaceous fluids provide additional REEs and redistribute REE and U to form economic minerals. • Primary allanite from pegmatite shows three zones with different U-Pb ages but a reliable Sm-Nd age at 1.8 Ga. • Hydrothermal overprinting caused Sm-Nd systems from incomplete equilibration to equilibration. Sm-Nd and U-Pb isotope systems are widely used to dating various magmatism and tracing geological processes, but their behaviors during post-magmatic metamorphic and/or hydrothermal disturbances remain unclear. Here, we investigated the trace elements, U-Pb and Sm-Nd isotope systems of accessory minerals (allanite, titanite, and apatite) from the Huangjiagou Paleoproterozoic rare-earth pegmatite, to determine the timing of magmatism and also the overprinted metamorphic and hydrothermal events, with a particular emphasis on the isotopic behavior of these accessory minerals under metamorphic event and fluid-rock reaction. Two-period accessory minerals are identified: Group I allanite, crystallized in the magmatic period but was modified by high-temperature metamorphism and hydrothermal metasomatism; and Group II allanite, titanite and apatite, which newly precipitated in the late hydrothermal event. In-situ U-Pb dating of the Group I allanite (type Ia) yielded a magmatic age of ca. 1.82 Ga, whereas the type Ib allanite record the high-temperature anhydrous thermal metamorphism at ca. 1.75 Ga. Group II allanite and titanite yielded U-Pb ages of ca. 131 Ma, indicating a Mesozoic hydrothermal metasomatism overprinting, due to the emplacement of neighboring granites. Group I allanite exhibits different zones and inconsistent U-Pb ages, but they exhibit an identical Sm-Nd isochron age (∼1.83 Ga) broadly consistent with the pegmatite age, indicating immobility nature of the Sm-Nd system. Group II titanite and allanite exhibit a Sm-Nd isochron age of ∼130 Ma with initial ε Nd (t) values of −27.5 to −29.8, consistent with the whole-rock ε Nd (t = 130 Ma) values of granitic rocks, implying a total redistribution of the REEs. While, Group II apatite and coexisting allanite did not produce geologic meaningful Sm-Nd ages with a wider initial ε Nd (t) range of −15.8 to –23.7, indicating the fluid has incompletely equilibrated Sm-Nd isotopic system due to various fluid-rock reaction. Our study provides a typical example to illustrate the robustness of the Sm-Nd isotopic system of magmatic allanite under the disturbance of later metamorphism and metasomatism, and shows the different degree equilibration of Sm-Nd isotopes in hydrothermal systems under various fluid-rock reactions. [ABSTRACT FROM AUTHOR]

The Pengshan Sn and Pb-Zn polymetallic deposits are located in the south margin of the Jiujiang-Ruichang (Jiurui) district of the Middle-Lower Yangtze River Metallogenic Belt in South China. Four large deposits include Huangjinwa, Zengjialong, Jianfengpo, and Zhangshiba, the former three are Sn-dominant deposits which occur as stratiform orebodies in the contact zones of the Pengshan granites and within the country rock strata, whereas Zhangshiba consists of stratiform Pb-Zn orebodies within the Precambrian metasedimentary strata. In this study, we present results on zircon U-Pb ages, major and trace elements, and mineral chemistry as well as Sr-Nd-Hf isotope data of the granites, Pb and S isotopes of both the Sn-dominant and Pb-Zn dominant deposits, and U-Pb dating of cassiterite from the Pengshan district. SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the Pengshan granites were emplaced in the Early Cretaceous (129-128 Ma), which is in good agreement with the U-Pb dating (130-128 Ma) of cassiterite from the Jianfengpo Sn deposit. The Pengshan granites consist mainly of weakly peraluminous highly fractionated I-type affinity granitic rocks. Detailed elemental and isotopic data suggest that the granites formed by partial melting of Mesoproterozoic metamorphic basement materials with minor input of mantle-derived melts. The mineral chemistry of biotite demonstrates that the Pengshan granitic magma had a low oxygen fugacity, thereby precluding the tin dominantly partitioning into the rock-forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages. Sulfur isotopes show a relatively heavy sulfur isotopic composition from 5.8 to 17.6 ‰, and no difference for sulfur isotopes between the Sn deposits (5.8-13.4 ‰, Huangjinwa, Zengjialong, Jianfengpo) and the Pb-Zn deposit (mostly 7.1-13.0 ‰, except for one 17.6 ‰, Zhangshiba). The sulfur isotope data of pyrite from the host sedimentary rocks show relatively higher δS values of 22.7-28.7 ‰. Lead isotopes indicate that the granites have higher Pb/Pb, Pb/Pb, and Pb/Pb ratios than the host Precambrian metasedimentary rocks, and the sulfide minerals from the orebodies fall in between them. Again, there is no difference for Pb isotopes between the Sn deposits (Huangjinwa, Zengjialong, Jianfengpo) and the Zhangshiba Pb-Zn deposit. The coincidence in S and Pb isotope compositions for Sn and Pb-Zn deposits suggests that similar sources for these mineralization, possibly derived from a mixed source of the granitic magmas and the Precambrian metasedimentary rocks. These data therefore favor of a magmatic-hydrothermal origin for both the Sn and Pb-Zn polymetallic mineralization in the Pengshan district. [ABSTRACT FROM AUTHOR]

The Lingshan granite batholith (Jiangxi province, southeast China) is a rather unique example of Nb-Ta-rich rare-metal granite, and three different types of tourmalines have been identified in the marginal granite zone, including (i) quartz-tourmaline nodules (Tur-N type) in the fine-grained biotite granite, (ii) tourmaline segregations and/or tourmaline-filled cavities (Tur-P type) and (iii) tourmaline veins (Tur-PV type) in pegmatite dykes. The extensive fractional crystallization process from the fine-grained biotite granite to pegmatite has been revealed by the geochemical and boron isotope compositions from the Tur-N to the Tur-P and/or Tur-PV type tourmalines, such as increasing Fe contents, decreasing Nb/Ta and Zr/Hf ratios, as well as restricted boron isotopes (δ11B, −12.0 to −9.0‰). Particularly, the Nb and Ta contents increase from the Tur-N to the core of the Tur-P type tourmaline, and then decrease towards the rim of the Tur-P type tourmaline. It is, therefore, possible that the decreasing variations of Nb and Ta from the core to the rim within the Tur-P type tourmaline more likely record the compositional and environmental evolution from the late boron-rich magma to the exsolved hydrothermal fluids. The late-stage Tur-PV type tourmaline as the hydrothermal product contains the lowest F contents. Thus, we suggest that the Nb Ta mineralization in the Lingshan granite batholith dominantly occurs in the highly-evolved granitic melt rather than during the post-magmatic aqueous fluid. Furthermore, the Nb and Ta contents of Lingshan tourmaline overlap with previous reported tourmaline data from W Sn rare-metal deposits instead of Au deposit. This signature is comparable to the fact that small volumes of W Sn mineralization occur in the Songshugang Ta-Nb-(W Sn) deposit. Hence, the Nb and Ta contents in tourmaline can be used as potential parameter to explore the Nb-Ta-(W Sn) mineralization not only in the Lingshan granite and pegmatite but also in similar granite batholith elsewhere in the world. [Display omitted] • Three types of tourmalines are identified in the Lingshan granite batholith. • Tourmaline formed either by magmatic or hydrothermal processes. • Nb/Ta and Zr/Hf in tourmaline demonstrate a fractional crystallization trend. • Volatile increase of tourmaline is consistent with the Nb Ta enrichment processes. • Tourmaline Nb Ta contents can indicate the Nb-Ta-(W Sn) mineralization. [ABSTRACT FROM AUTHOR]

The Miao'ershan uranium ore district is one of the most important granite-hosted uranium producers in South China. There are several Triassic granite plutons in the Miao'ershan batholith, but uranium ore deposits mainly occur within the Douzhashan granitic body. Precise zircon U–Pb dating indicated that these Triassic granite plutons were emplaced during 204 to 215 Ma. The Douzhashan U-bearing granite lies in the central part of the Miao'ershan batholith, and has higher U contents (8.0 to 26.1 ppm, average 17.0 ppm) than the nearby Xiangcaoping granite (5.0 to 9.3 ppm, average 7.0 ppm) and the Yangqiaoling granite (6.4 to 18.3 ppm, average 11.5 ppm) in the south part of the batholith. The Douzhashan granite is composed of medium-grained two-mica granite, whereas the Xiangcaoping and Yangqiaoling granites are composed of porphyritic biotite granite. Both the Xiangcaoping and Douzhashan granites have high A/CNK ratios (> 1.10), high ( 87 Sr/ 86 Sr) i ratios (> 0.720) and low ε Nd (t) values (− 11.3 to − 10.4), suggesting that they belong to strongly peraluminous S-type granites. The Douzhashan granite has low CaO/Na 2 O ratios, high Rb/Sr and Rb/Ba ratios, indicating a partial melting origin of clay-rich pelitic rocks. In contrast, the Xiangcaoping granite formed from clay-poor psammite-derived melt. The Yangqiaoling granite shows different geochemical characteristics with the Douzhashan and Xiangcaoping granites, indicating a different magma source. The Yangqiaoling granite has higher ε Nd (t) of − 9.4 to − 8.3 and variable A/CNK values from 0.98 to 1.19, suggesting a mixture source of meta-sedimentary rocks and meta-igneous rocks. Crystallization fractionation is not the main mechanism for U enrichment in the Douzhashan granite. We suggest that U-rich pelitic rock sources may be the key factor to generate peraluminous U-bearing granites in South China. Searching for those granites which are reduced, strongly peraluminous and were derived from U-rich pelitic rocks, is the most effective way for exploring granite-hosted U deposits. [ABSTRACT FROM AUTHOR]

Four types of tourmaline in the Qitianling granitic batholith, South China, were identified in this study: euhedral disseminated tourmaline (DT type) in the early stage of granite consolidation; typical interstitial nodular tourmaline (NT type) formed late in the crystallization history; radial tourmaline veinlet (RT type) and vein tourmaline (VT type) of hydrothermal origin. We performed major and trace element analysis by in situ electron microprobe and laser ablation inductively coupled plasma mass spectrometry on these four tourmaline types. Compositionally, these tourmalines fall into the alkali group and schorl-dravite solid solution series. There is clear correlation between trace and major elements in VT-type tourmalines, likely related to co-variations of these elements in the hydrothermal fluid from which the tourmaline precipitated. Tourmaline from granites displays low REE abundances and negative LREE trends, positive Eu anomalies, and HREE below or close to their detection limits. The DT-type tourmalines show a positive Eu anomaly, which is probably due to a preferential incorporation of Eu over Eu. REE depletion in NT-type tourmalines may reflect co-crystallization of REE-rich minerals. The positive Eu anomaly in NT-type tourmalines is due to late-stage release of Eu caused by tourmaline replacement of early feldspar. Vein tourmalines (RT and VT type) display similar slopes from La to Nd, without an Eu anomaly. The chondrite-normalized REE patterns in tourmalines from veins display a concave upward-shaped, MREE-depleted pattern, with minimum values at Ho increasing steadily to Lu, and may reflect the REE characteristics of the precipitated medium. HREE enrichment in hydrothermal fluid can be attributed to the formation of REE-fluoride complexes during the internal fluid evolution. [ABSTRACT FROM AUTHOR]

The Luoboling granodiorite porphyry and Zhongliao porphyritic biotite-granodiorite occur within the Zijinshan ore field in Fujian Province, southeast China. LA–ICP–MS zircon U–Pb dating yields ages of 103.1 ± 1.1 Ma (2σ, MSWD = 3.1) and 95.9 ± 0.6 Ma (2σ, MSWD = 1.2) for the Luoboling and Zhongliao intrusions, respectively. All rocks show high SiO2, K2O, and light rare earth element levels, variable CaO and Fe2O3T, but low heavy rare earth element and high field strength element (Nb, Ta, Ti) concentrations. They also exhibit uniform initial87Sr/86Sr ratios (0.7064–0.7068) and εNd(t) values (−4.0 to −2.6), falling within the compositional field of Cretaceous basalts and mafic dikes in the Cathaysia Block. Together with their relatively high Hf isotopic ratios (εHf(t) = −5.8 to +0.7), these data suggest that the Luoboling and Zhongliao intrusions were derived from a subduction-enriched mantle source. We infer fractional crystallization processes involving early fractionation of clinopyroxene and olivine, and subsequent fractionation of garnet forming the Luoboling granodiorite porphyry, eventually followed by amphibole- and biotite-dominated crystallization, with minor accessory mineral contribution, producing the (younger) Zhongliao porphyritic biotite-granodiorite. Asthenospheric mantle sources may have also contributed to generating the melts as indicated by initial Pb isotopic compositions and Hf isotopic compositions. The generation of these intrusions was associated with the Pacific subduction in an extensional setting during the Cretaceous. [ABSTRACT FROM AUTHOR]

As a world-class tin–tungsten province, South China is well known for its extensive Mesozoic granitic magmatism. The Dulong district, located in the western Cathaysia Block of the South China tin–tungsten province, is characterized by widespread Mesozoic granitoids and accompanying Sn-polymetallic ore deposit (~ 30 Mt of Sn). It is one of the most important polymetallic tin ore districts in China. In this study, three mineralization-related granite types were identified in the Dulong district, including the Dulong coarse-grained granite (DCG), the Dulong fine-grained granite (DFG), and the Dulong porphyritic granite (DPG). Detailed studies are presented on zircon U–Pb ages, major and trace elements, mineral chemical and Nd–Hf isotopic compositions of the tin-bearing granites from the Dulong district. LA-ICP-MS U–Pb dating of zircon grains from these three granite bodies yields ages of 90.1 ± 0.7 Ma, 89.7 ± 0.8 Ma and 86.0 ± 0.5 Ma, respectively. Geochemically, the granites are strongly peraluminous, with high contents of alkalis, enrichment in P, Li, Rb, Cs, Ta, Sn, W and U, depletion in Ti, Mg, Co, Ni, Sr, Ba, Zr, Hf, Th and rare earth elements. Fractional crystallization of plagioclase and K-feldspar was the principal process of magmatic differentiation that controlled Rb, Sr, Ba and Eu concentrations, whereas rare earth elements were fractionated by accessory minerals, such as apatite and monazite. The geochemical data suggest that the rocks are highly fractionated S-type granites. The granites show bulk rock ε Nd (t) values in the range of − 12.2 to − 10.8 and zircon ε Hf (t) values from − 15.5 to − 2.5, with Meso-Paleoproterozoic T DM C ages for both Nd and Hf isotopes. Geochemical and isotopic data suggest that these highly fractionated S-type granites DCG, DFG and DPG were originated from the same episode of partial melting of the protolith, which have analogous components of metamorphosed pelitic rocks from the Meso-Paleoproterozoic continental crust. Extreme fractional crystallization resulted in enrichment of tin in the evolved granitic magma, and the reduced magmas (fO 2 below NNO) would efficiently remove Sn into a hydrothermal fluid, and lead to deposition of Sn-rich mineral phases. The association of Dulong and Gejiu magmatism in the western Cathaysia Block may be likely to mark the onset of back-arc extension or intra-arc rift in the region during Late Cretaceous. The upwelling of asthenospheric mantle may have triggered partial melting of metasedimentary rocks in the overlying crust to generate the S-type granitic magmas. [ABSTRACT FROM AUTHOR]

Granite-hosted uranium ore deposits are the most important commercial U-producers in South China. These U-bearing granites generally contain high-U-concentration zircons. Zircons in the U-bearing Douzhashan Granite show black rims in cathodoluminescence images, which have very high U concentrations of up to > 25,000 ppm. The high-U black rim domains of zircons show similar REE patterns to those of low-U mantle domains with oscillatory zoning, but have higher REE concentrations and weaker positive Ce anomalies. The high-U black rim domains of zircons may have formed from late-stage evolved U-rich and H 2 O-rich magma. We carried out a SHRIMP U-Pb dating for these zircons and the results show that the high-U (12,007–26,706 ppm) rim domains of the zircons always yield older 206 Pb/ 238 U ages (268 ± 9 Ma, n = 5, MSWD = 2.7) than the low-U (558–3667 ppm) mantle domains (228 ± 11 Ma, n = 4, MSWD = 3.1), and both of these ages are older than the emplacement age (211 ± 3 Ma) of the U-barren Xiangchaoping Granite, which was intruded by the Douzhashan Granite. Hence, these results demonstrate a matrix effect associated with SHRIMP U-Pb analyses of high-U zircons. The reverse discordance for SHRIMP results of high-U zircons was produced by analytical artifact. However, our LA-ICP-MS analyses show that the black rim domains (12,840–26,018 ppm U) of the zircons have the same U-Pb ages as the low-U mantle domains (1215–4075 ppm U). Both domains yield a weighted mean 206 Pb/ 238 U age of 203 ± 4 Ma (n = 13, MSWD = 1.4), which is consistent with the 40 Ar- 39 Ar age (207 ± 4 Ma) of muscovite from this granite. It thus indicates that LA-ICP-MS U-Pb analyses for high-U zircons (up to 26,000 ppm U) show an insignificant matrix effect and likely yield more reliable U-Pb ages for the high-U zircons than SHRIMP analyses. In order to get reliable U-Pb ages using the LA-ICP-MS method for the high-U zircons, a pulse-analog cross calibration for the ICP-MS collector should be performed. Our precise U-Pb dating and geochemical studies indicate that the U-bearing Douzhashan Granite was emplaced during the late Indosinian stage and formed in a post-collisional setting of the Indosinian Orogeny. It is distinct from most U-bearing Granites in South China, which were largely emplaced during the early Indosinian stage and formed in a syn-collisional setting. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Lingshan complex a ring-like multiphase batholith all formed at ca. 133 Ma. • They formed from discrete source process rather than fractional crystallization of a single magma. • The marginal units formed after rejuvenation and extraction from the crystal mush reservoirs. • The Nb-Ta enrichment is related to the extensive fractional crystallization of granitic magma. The Lingshan granite complex, located in the northeast part of the Qin-Hang Belt, Jiangxi Province, southeast China, has produced the largest Ta-Nb deposits in China, i.e., the Huangshan Nb-Ta and Songshugang Ta-Nb-(W-Sn) deposits. This complex is spatially a ring-like multiphase batholith, and comprises a series of granitic rocks from the central to marginal units. Mafic microgranular enclaves (MMEs) occur only in the central unit. Geochronologic results show that the magmatic activities at Lingshan district took place at Early Cretaceous, with similar emplacement ages (133–134 Ma) between the central and marginal units. The Lingshan granites are metaluminous to weakly peraluminous (most A/CNK < 1.1), and display typical A-type affinity. However, the whole-rock REE contents and Zr/Hf and (La/Yb) N ratios exhibit an abnormal increase from the central to marginal units. The Li, Rb and Cs elements of biotite as well as the Zr/Hf ratios of zircon do not exhibit a continuous enrichment trend from the central towards marginal granites. All these features suggest that the generation of Lingshan granites is more complex than the fractional crystallization from a single parental magma. Alternatively, a crystal mush model could be applied to better interpret the geochemical and isotopic contrasts between different granite phases. The marginal granites were likely formed by later crystallization events after the rejuvenation and extraction from the crystal mush reservoirs, while the central granites were formed from the residual crystal-rich mush with a relatively low terminal porosity. Moreover, the Nb and Ta contents of biotite exhibit a gradual enrichment with increasing fluorine contents in the marginal granites. The enrichment of lithium and fluorine in the granitic melt can significantly promote the proportion of non-bridging oxygens (NBOs) for coordinating Nb and Ta in the melt, further enhancing the solubility of columbite and tantalite, and eventually causing the Nb and Ta elements either incorporate into the mineral lattice of micas in the early marginal granites or form columbite-group minerals in the pegmatite/altered granite. In summary, we propose that the Ta-Nb enrichment event in the Lingshan district is spatially and genetically related to the extensive fractionation evolution from central to marginal units. [ABSTRACT FROM AUTHOR]

The Miao’ershan–Yuechengling batholith (MYB) is one of the largest granitic batholiths in South China. At least five individual phases have been identified for the Paleozoic granites in the MYB. SHRIMP and LA–ICP–MS zircon U–Pb dating results imply that these granites were emplaced at 435±4Ma, 427±3Ma, 417±6Ma, 404±6Ma and 382±2Ma, respectively. The ages gradually decreased from the southeast to the northwest, implying that the MYB was incrementally emplaced from the southeast to the northwest lasting from early Silurian to late Devonian. Most granites are metaluminous to weakly peraluminous, and contain low P2O5 contents (<0.15%). These granites show enrichment of Rb, Th, U and depletion of Ba, Sr, Eu, Ti. They show relatively high (87Sr/86Sr)i ratios (>0.715), low ε Nd(t) values (−8.9 to −6.7), and low zircon ε Hf(t) values (−9.5 to −4.0). These geochemical and isotopic characteristics indicate that these granites may have formed from partial melting of Paleoproterozoic basement rocks. Slight geochemical differences between different phases can be interpreted as resulting from partial melting of heterogeneous sources or different proportion mixing of meta-igneous and meta-sedimentary rocks. Zircon Hf isotope model ages vary from 1.77 to 1.93Ga, with an average value of 1.84±0.07Ga. These data indicate that crust growth in this region took place mainly during the Paleoproterozoic (ca. 1.84Ga), and the basement in the MYB should belong to the Cathaysia Block. The formation of the Paleozoic granites in the MYB was suggested to be related to the late orogenic magmatism of the Wuyi–Yunkai orogeny. Thus, the late orogenic magmatism in the northwestern part of the Wuyi–Yunkai orogeny must have lasted until ca. 381Ma and took place also to the east of the Anhua–Luocheng Fault. [ABSTRACT FROM AUTHOR]

In the Longwangzhuang area along the southern margin of the North China Craton (NCC), a layer of Cretaceous K-feldspar granites surrounds Paleoproterozoic granites. The Paleoproterozoic granites are enriched in sodic ferrogedrite and show low Al2O3 (12.3-13.0 wt%) and aluminum saturation index (ASI) (0.93-1.09) with high Zr (609-966 ppm), Y (47.2-96.7 ppm) and Nb (58.7-97.7 ppm) concentrations, resembling A-type granites. The Cretaceous K-feldspar granites have relatively high Sr (145-419 ppm), Ba (1252-1660 ppm), Sr/Y (19-127), La/Yb (36-56) ratios, but low Y (4.01-8.88 ppm) and Yb (0.46-0.99 ppm), geochemically resembling adakite-like rocks. However, these Cretaceous adakite-like K-feldspar granites have rather low MgO (0.08-0.26 wt%), Al2O3 (13.6-14.5 wt%), Mg# (11-23), Cr (2.30-4.61 ppm) and high initial 86Sr/87Sr (0.7098-0.7118), as well as abundant K-feldspar minerals, and are different from typical adakite. Zircon LA-ICP-MS geochronology shows that the two types of granites investigated in this study formed at 1616 ± 20 Ma and 140 ± 1 Ma, respectively. However, zircons from both the Paleoproterozoic and Cretaceous granites yield similar two-stage Hf model ages at ca. 2.5-2.6 Ga, suggesting the reworking of Late Archean juvenile crust. The Paleoproterozoic A-type granites show enriched Nd-Hf isotopic features but high whole-rock oxygen isotopes. These rocks may have formed from partial melting of restitic crustal material during lithospheric thinning, along with extension and experienced crystal fractionation of plagioclase, apatite and magnetite. The Cretaceous adakite-like K-feldspar granites were formed by local anatexis of TTG rocks from the Taihua Group, with amphibole as the major residual phase. The local anatexis and accompanying migmatisation suggest crustal compression and possible transpression. Therefore, the lithospheric thinning in the NCC should have taken place after 140 Ma on the southern margin of the NCC. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The Linglong granite is one of the most important Mesozoic plutons in the Shandong Peninsula, eastern China, and its petrogenesis has long been controversial, particularly with regard to the nature of source region and geodynamic setting. Our new precise zircon U–Pb dating results reveal that the Linglong granite was emplaced in the Late Jurassic (157–160Ma). In addition, abundant inherited zircons are identified in the granite with four groups of age peaked at ~208, ~750, ~1800 and ~2450Ma. Geochemical studies indicate that the Linglong granite is weakly peraluminous I–type granite, and is characterized by high SiO2, Sr and La, but low MgO, Y and Yb contents, strongly fractionated REE pattern and high Sr/Y and La/Yb ratios. It also exhibits high initial 87Sr/86Sr ratios (0.7097 to 0.7125), low εNd(t) (−17.7 to −20.3) and variable zircon εHf(t) (−22.2 to −8.7) values. Calculation of the zircon saturation temperature (TZr) reveals that the magma temperatures are 760±20°C, and the lowest TZr value of 740°C may be close to initial magma temperature of this inheritance-rich rock. Interpretation of the elemental and isotopic data suggests that the Linglong granite has some affinities with the adakite, and was most likely derived from partial melting of thickened lower crust without any significant contribution of mantle components. The presence of a large number of inherited zircons and variable Sr–Nd–Hf isotopic compositions reveal that the Linglong granite probably has multiple sources consisting of the lower crust of both South China Block and North China Block, as well as the collision-related alkaline rocks and UHP metamorphic rocks. The continental arc-rifting related to the Izanagi plate subduction was the most likely geodynamic force for formation of the Jurassic Linglong adakatic granite in the Shandong Peninsula. [Copyright &y& Elsevier]

Abstract: A detailed study utilizing zircon U–Pb dating, major and trace element geochemistry, and Sr–Nd–Hf isotope geochemistry has been carried out for the Caijiang granite in Jiangxi Province and the Gaoxi granite in Fujian Province, South China. The new data indicate that the Caijiang and Gaoxi granites are Triassic (228–230Ma) and have the petrographic and geochemical characteristics of A-type granites. In both granites, biotite occurs along the boundary of euhedral plagioclase and quartz, which implies that the primary magma could have been anhydrous. The two granites show high contents of total alkalis (Na2O+K2O=7.81–12.15%), high field strength elements (e.g. Zr=240–458ppm, Y=16.8–38.0ppm, Nb=13.5–33.8ppm and Zr+Nb+Ce+Y=382–604ppm) and rare earth elements (total REE=211–373ppm) as well as high Ga/Al ratios (10000×Ga/Al=2.41–3.53). The lowest magmatic temperatures estimated from zircon saturation thermometer were 800–840°C for the Caijiang granite and 820–850°C for the Gaoxi granite, respectively. The Caijiang granite has relatively high (87Sr/86Sr)i ratios of 0.71288 to 0.72009, low ε Nd(t) values of −9.9 to −9.3, and low zircon ε Hf(t) values (peak value of −7.5). Whole-rock Nd isotopic model ages and zircon Hf isotopic model ages mostly vary from 1.65Ga to 1.80Ga. The Gaoxi granite has also high (87Sr/86Sr)i ratios of 0.71252 to 0.71356, low ε Nd(t) value of −13.8 and low zircon ε Hf(t) values (peak value of −12.0). Whole-rock Nd isotopic model ages and zircon Hf isotopic model ages mostly vary from 1.95Ga to 2.10Ga. According to these data, we suggest that the two granites might have been derived from partial melting of Precambrian crustal rocks that had been granulitized during an earlier thermal event. Our study of the Caijiang and Gaoxi granites, together with previous studies on two Triassic alkaline syenites (Tieshan and Yangfang) in Fujian Province and one A-type granite (Wengshan) in Zhejiang Province in South China, indicate a wide transtensional tectonic environment in the Cathaysia Block that lasted at least from 254Ma to 225Ma. Combined with extant data for the Indosinian granites and tectonic evolution in South China, we suggest that the formation of A-type granites was related to the local NE-trending extensional faults probably caused by collision between the South China Block and the Indochina Block or the North China Block. [Copyright &y& Elsevier]

Abstract: The widespread occurrence of Mesozoic granites in the Gan-Hang Belt in Southeast China is associated with similarly widespread, economically important mineralization, but the precise timing, origin, and plate tectonic significance of these granites are not well understood. We have studied two of these (Early Cretaceous) granite bodies, the Yangmeiwan granite and the Daqiaowu granitic porphyry, from the northeastern part of the Gan-Hang Belt in western Zhejiang Province by zircon U-Pb geochronology, major and trace element analyses, and Nd–Hf isotopic analyses. LA-ICP-MS and SHRIMP U–Pb dating of zircon grains from these two granites yield ages of 133–136Ma, representing a Early Cretaceous magmatic event. These granitic rocks are metaluminous to weakly peraluminous and have a pronounced A-type geochemical signature with high Na2O+K2O, Fe2O3*/MgO and Ga/Al ratios. They show low CaO, MgO and TiO2 contents, enrichment in some LILEs (such as Rb and Th) and HFSEs (such as Zr, Y), depletion in Sr, Ba, P, Eu and Ti. They also show A2 subtype affinity and were probably formed at a high temperature (~810°C for Yangmeiwan granite and ~850°C for Daqiaowu granitic porphyry). These A-type granitic rocks show bulk rock εNd(t) values in the range of −6.5 to −3.6 and zircon εHf(t) values from −7.8 to −0.9, with Mesoproterozoic TDM c ages for both Nd and Hf isotopes. Geochemical and isotopic data suggest that these A-type granitic rocks were generated largely by partial melting of granulitized Mesoproterozoic metamorphic basement rocks (including parametamorphic and orthometamorphic rocks), with a possible input of mantle-derived materials and followed by subsequent fractional crystallization. Our new data together with previous published data suggest that the Cretaceous A-type granitic rocks with ages between 137Ma and 122Ma occurred along the Gan-Hang Belt, indicating an important Mesozoic extensional event in Southeast China. This event represents either a back-arc extension or an intra-arc rift due to the roll-back of the paleo-Pacific plate, and it started as early as ~137Ma in Xiangshan and Xinlu basins. It is earlier than ~130Ma as previously suggested in the studied region and later than that along the south part of the Shi-Hang Zone. With ongoing extension during slab roll-back of paleo-Pacific plate, the crust and lithospheric mantle became progressively thinned. The upwelling of asthenosphere would have triggered crustal rocks to partially melt, generating granitic magmas. Our new geochemical data also suggest that mantle-crust interaction in the formation of the A-type granitic magma along the Gan-Hang Belt gradually intensified from early to late stages between ca. 137 and ca. 122Ma. [Copyright &y& Elsevier]

Abstract: The Huashan complex granitic batholith, occurred in the core of the Xiaoqinling orogen and gold mineralization belt along the south margin of the North China Craton, consists of amphibole monzogranite and biotite monzogranite in the Wengyu and Fangshanyu valleys, respectively. Zircon LA-ICP-MS U–Pb dating yields ages of 205±2Ma and 132±1Ma for the Wengyu and Fangshanyu granites, respectively, which represent the two major episodes of Mesozoic magmatism in the region. These rocks are characterized by metaluminous, high silica and total alkalinity, and have high FeOtotal/(FeOtotal +MgO) ratios, high large-ion lithophile elements (LILEs, especially Sr and Ba) and light rare earth elements (LREEs), and low heavy rare earth elements (HREEs) and Y concentrations and insignificant negative Eu anomalies. The Wengyu granites have higher Ba and Sr contents, which can be classified as high Ba–Sr granites, whereas the Fangshanyu granites show much lower Ba and Sr contents and display an adakitic affinity. Elemental and isotopic compositions suggest that the main sources of both the Wengyu and Fangshanyu granites are likely the ancient basement materials of Taihua Group. However, the high Ba and Sr contents of the Wengyu granites require addition of small amounts of enriched lithospheric mantle metasomatised by fluid/melt derived from pelagic sediments-bearing subducted slab in the sources. The Wengyu granites were most likely generated earlier by partial melting of the lowest part of the crust due to the subducted slab break-off under the post-collision extensional stage of the continental collision orogeny. The Fangshanyu granites might be mainly derived later from the partial melting of thickened lower crustal materials, representing by the Taihua Group basement rocks, corresponding to the tectono-magmatism of the post-orogeny to rift extensional environment during the tectonic transition from the Paleo-Tethys subduction-collision system to the Paleo-Pacific regime. [Copyright &y& Elsevier]

Abstract: The Shi-Hang zone is an important NE trending Mesozoic magmatic belt composed of granites with relative high εNd(t) values and young TDM model ages in South China. However, the petrogenesis and the tectonic environment for the Shi-Hang zone magmatic rocks remain controversial. We report here mineral chemistry, geochemical and Sr–Nd–Hf isotopic data for the Cailing and Furong granites and mafic microgranular enclaves (MMEs) from the Qitianling granite batholith in southern Hunan province, South China. The Qitianling granite batholith is a multi-staged composite pluton with three phases (Cailing, Furong, and Huangtangling) according to their ages and petrography. The Cailing (163–160Ma) and Furong (157–153Ma) phases are mainly composed of porphyritic amphibole–biotite monzogranite, and they share similar geochemical and isotopic characteristics. Both of them show similar SiO2 contents from 66.50 to 70.28%, and metaluminous A/CNK values of 0.80 to 0.98. The granites are characterized by high contents of large ion lithosphile elements (LILE) such as Rb, Th, U, Pb; high field strength elements (HFSE) such as Nb, Ta, Zr, Hf; and Zr+Nb+Ce+Y contents >350ppm, and high 10,000∗Ga/Al ratios >2.6. Chondrite-normalized REE patterns show relative enrichment of light rare earth elements (LREEs) and significant negative Eu anomalies. Mineralogical and geochemical features suggest that the Cailing and Furong granites are A-type, which can be further classified as A2 subtype. They have relatively lower (87Sr/86Sr)i ratios (0.7091–0.7132), higher εNd(t) values (−5.5 to −7.6) and younger Nd isotopic model ages (1.48–1.56Ga) than those common S-type granites in South China. Zircon εHf(t) values vary from −8.1 to −3.7. The MMEs in the Cailing phase show similar trace element and Sr–Nd isotopic characteristics with the host granites. But zircons from the MMEs show different εHf(t) values (−6.4–+2.6) with those from the host granites (−8.1 to −3.7). This indicates that the MMEs and host granites were crystallized from different sources of magmas, providing direct evidence for mafic–felsic magma mixing processes. The isotope data indicate that the Cailing and Furong granites from the Qitianling batholith were derived from a hybrid magma consisting of about 80% felsic magma derived from old crust and about 20% mantle-derived mafic magma. The strong magma mixing at about 160–155Ma caused by intra-arc rifting or back arc extension related to subduction of the Paleo-Pacific plate, is favored to explain the petrogenesis of the Cailing and Furong granites, as well as the Shi-Hang zone. [Copyright &y& Elsevier]

Abstract: The behavior of boron and its isotopes in fluid-dominant processes and hydrothermal alteration of granites is examined using fresh and altered granite samples from the Qitianling granite and associated hydrothermal tin deposits in South China. Boron concentrations are highest in the fresh granite (37ppm) and depleted as a result of two stages of fluid mobility and fluid–rock interaction within the granite. Constraints provided both by δ 11 B and δ 18 O data suggest that the first stage was related to exsolution of aqueous fluids from the granite magma at a temperature of >450°C. This was followed by further boron depletion in the granite by hydrothermal circulation of meteoric water at lower temperatures (~350°C) and low water/rock ratios. The sensitivity of coupled boron and oxygen isotope systematics to these processes suggests that they can provide valuable constraints on of fluid mobility in granite and associated mineralization. [Copyright &y& Elsevier]

Abstract: The Taoshan uranium ore district is one of the most important granite-hosted uranium producers in South China. The Taoshan granitic complex can be petrographically classified into several units of Caijiang, Huangpi, Daguzhai, and Luobuli, but the uranium deposits only occur within the Daguzhai granite unit. LA-ICP-MS zircon U–Pb dating indicates that both the Daguzhai granite and the Huangpi granite were emplaced at 154±2Ma. U contents (average 19.5ppm) of the Daguzhai granite are higher than those of the Huangpi granite (average 7.3ppm). The Daguzhai granite is composed of medium-grained two-mica granite, and the Huangpi granite is composed of medium- to coarse-grained biotite granite. These two granites show obvious differences in major element, trace element and isotopic geochemical characteristics. Compared to the Huangpi granite, the Daguzhai granite has higher A/CNK ratios, higher P2O5 contents and lower CaO contents, and is more enriched in Rb, Ba, U, and more depleted in Sr, Eu and Ti. The εNd(t) values of the Daguzhai granite vary from −12.2 to −11.0 with two-stage model ages of 1.84 to 1.93Ga. The εNd(t) values of the Huangpi granite are slightly higher (−9.7 to −8.6) and the Nd model ages are younger (1.64 to 1.73Ga). Comparative studies imply that the Daguzhai granite belongs to typical S-type and might be derived from the partial melting of parametamorphic rocks from metamorphic basement of the Zhoutan Group. In contrast, the Huangpi granite belongs to fractioned I-type, which might be derived from the partial melting of a mixture of ortho- and para-metamorphic rocks of the Zhoutan Group. These different magma sources might explain the different U contents of the two granites. In general, the source factor is an important controlling factor for the genesis of U-bearing granites in South China. U-bearing granites in South China show some common mineralogical and geochemical characteristics, which can be used to guide further exploration of granite-hosted U deposits. [Copyright &y& Elsevier]

The Late Mesozoic geology of Southeast China is characterized by extensive Jurassic to Cretaceous magmatism consisting predominantly of granites and rhyolites and subordinate mafic rocks, forming a belt of volcanic-intrusive complexes. The Xiangshan volcanic-intrusive complex is located in the NW region of the belt and mainly contains the following lithologies: rhyodacite and rhyodacitic porphyry, porphyritic lava, granite porphyry with mafic microgranular enclaves, quartz monzonitic porphyry, and lamprophyre dyke. Major and trace-element compositions, zircon U-Pb dating, and Sr-Nd-Hf isotopic compositions have been investigated for these rocks. The precise SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the emplacement of various magmatic units at Xiangshan took place within a short time period of less than 2 Myrs. The stratigraphically oldest rhyodacite yielded a zircon U-Pb age of 135 ± 1 Ma and the overlying rhyodacitic porphyry has an age of 135 ± 1 Ma. Three porphyritic lava samples yielded zircon U-Pb ages of 136 ± 1 Ma, 132 ± 1 Ma, and 135 ± 1 Ma, respectively. Two subvolcanic rocks (granite porphyry) yielded zircon U-Pb ages of 137 ± 1 Ma and 137 ± 1 Ma. A quartz monzonitic porphyry dyke, which represented the final stage of magmatism at Xiangshan, also yielded a zircon U-Pb age of 136 ± 1 Ma. All these newly obtained precise U-Pb ages demonstrate that the entire magmatic activity at Xiangshan was rapid and possibly took place at the peak of extensional tectonics in SE China. The geochemical data indicate that all these samples from the volcanic-intrusive complex have an A-type affinity. Sr-Nd-Hf isotopic data suggest that the Xiangshan volcanic-intrusive complex derived mainly from remelting of Paleo-Mesoproterozoic crust without significant additions of mantle-derived magma. However, the quartz monzonitic porphyry, which has zircon Hf model ages older than the whole-rock Nd model ages, and which has ε(T) value higher than the other rocks, may indicate involvement of a subordinate younger mantle-derived magma in its origin. Geochemical data indicate that the various rocks show variable REE patterns and negative anomalies of Ba, Nb, Sr, P, Eu and Ti in the trace element spidergrams, suggesting that these rocks may have undergone advanced fractional crystallization with separation of plagioclase, K-feldspar and accessory minerals such as allanite. We suggest that this Cretaceous volcanic-intrusive complex formed in an extensional environment, and the formation of the Xiangshan mafic microgranular enclaves can be explained by the injection of mafic magma from a deeper seated mantle magma chamber into a hypabyssal felsic magma chamber at the crustal emplacement levels. [ABSTRACT FROM AUTHOR]

The Shihuiyao deposit is a recently discovered giant Rb deposit in association with other rare metals (Nb-Ta-Be-Li) in Inner Mongolia of northeastern China. Six ore-bearing plutons were emplaced at the Late Jurassic (ca. 145 Ma) in the Shihuiyao mining area and composed of siderophyllite monzogranite, muscovite granite, muscovite–albite granite, zinnwaldite–albite granite, and zinnwaldite–amazonite granite. Micas in these granites include siderophyllite, muscovite and zinnwaldite, and they show an increase of Rb 2 O and F contents and decrease of K 2 O/Rb 2 O ratios, reflecting the magmatic fractionation evolution trend. Field relationships, whole-rock data, and mineralogical features do not show a continuous progression of these granites in the Shihuiyao deposit, which can be interpreted as that they experienced different fractional processes in the magma source. Hence, combined with field evidence and Nd isotopic composition, a model was established for the petrogenesis of these granites. The oceanic slab tear led to rapid asthenosphere upwelling, which causes the partial melting of a Neoproterozoic juvenile crust, i.e., a mixed lithology composed of a major mantle-derived component with less amount of ancient crust component. Initial magmas ascended and accumulated to form a magma chamber in the upper crust. Magmas in the chamber underwent a series of fractional processes and were then discharged by a series of intrusive magmatic activities, thus forming the ore-bearing granites in the Shihuiyao mining area. In the late stages of magmatic fractionation, co-existing aqueous hydrothermal fluids most likely controlled the trace element distribution in these ore-bearing granites. In the Shihuiyao deposit, not only the fractional crystallization of magma, but also the hydrothermal fluids, exsolved from the magma and extracting elements from the wall rocks or primary granite phases, played an important role in Rb mineralization. Also, the content of F in the melt may affect the enrichment of Rb. The presence of a deep magma chamber suggests that the Shihuiyao and its surrounding areas have good prospecting potentials for rare metals mineralization. • Rb-rich granites in the Shihuiyao deposit all emplaced at ca. 145 Ma. • Mica compositions indicate a good magmatic evolution trend for the granites. • Fractional processes occur at the source, not at the final level of emplacement. • Fractional crystallization and fluid-rock interaction control Rb mineralization. [ABSTRACT FROM AUTHOR]

Abstract: Multi-stage formation of tourmaline occurs in the Hnilec granite-related hydrothermal tin mineralisation system from the Western Carpathians, Slovakia. The tourmalines belong to the schorl–dravite series and have two major stages of formation: the majority crystallized during the first stage (defined as M-stage), forming zoned tourmaline crystals with the cores being generally more Fe, Al, and Mn rich than the rims. During the second stage (defined as L-stage), tourmaline formed as small veins or irregular patches along fractures and cracks in the M-stage tourmaline grains. In the contact metapelites near the granite body, the L-stage tourmalines are more Mg-rich and Fe, Al, Mn depleted than the M-stage tourmalines. In the granites, the L-stage tourmalines have generally similar compositions to those of the M-stage tourmaline rims. The boron isotopic compositions of the M-stage tourmalines vary from −10.3‰ to −15.4‰; with no clear variation between the cores and the rims, however, some of the tourmaline grains from the contact metapelites show a slightly higher δ 11B in the cores than in the rims. The L-stage tourmalines have lower δ 11B value of −16.0‰ to −17.1‰. We suggest that these trends reflect a changing fluid source from a dominant magmatic–hydrothermal fluid derived from the granites to a late-stage metamorphic fluid derived from the regional metamorphism (chlorite and biotite zone) in the metapelites. The significantly higher Fe3+ in the L-stage than the M-stage tourmalines reflect changing redox conditions towards a more oxidising environment. This redox condition change may have important implications for the hydrothermal tin mineralisation in the area. [Copyright &y& Elsevier]

Abstract: SHRIMP zircon U–Pb dating, mineral chemical, element geochemical and Sr–Nd–Pb–Hf isotopic data have been determined for the Yulong monzogranite-porphyry in the eastern Tibet, China. The Yulong porphyry was emplaced into Triassic strata at about 39 Ma. The rocks are weakly peraluminous and show shoshonitic affinity, i.e., alkalis-rich, high K2O contents with high K2O/Na2O ratios, enrichment in LREE and LILE. They also show some affinities with the adakite, e.g., high SiO2 and Al2O3, and low MgO contents, depleted in Y and Yb, and enrichment in Sr with high Sr/Y and La/Yb ratios, and no Eu anomalies. The Yulong porphyry has radiogenic 87Sr/ 86Sr (0.7063–0.7070) and unradiogenic 143Nd/ 144Nd (ε Nd =−2.0 to −3.0) ratios. The Pb isotopic compositions of feldspar phenocrysts separated from the Yulong porphyry show a narrow range of 206Pb/ 204Pb ratios (18.71–18.82) and unusually radiogenic 207Pb/ 204Pb (15.65–15.67) and 208Pb/ 204Pb (38.87–39.00) ratios. In situ Hf isotopic composition of zircons that have been SHRIMP U–Pb dated is characterized by clearly positive initial ε Hf values, ranging from +3.1 to +5.9, most between +4 and +5. Phenocryst clinopyroxene geothermometry of the Yulong porphyry indicates that the primary magmas had anomalously high temperature (>1200 °C). The source depth for the Yulong porphyry is at least 100 km inferred by the metasomatic volatile phase (phlogopite–carbonate) relations. Detailed geochemical and Sr–Nd–Pb–Hf isotopic compositions not only rule out fractional crystallization or assimilation-fractional crystallization processes, but also deny the possibility of partial melting of subducted oceanic crust or basaltic lower crust. Instead, low degree (1–5%) partial melting of a metasomatized lithosphere (phlogopite–garnet clinopyroxenite) is compatible with the data. This example gives a case study that granite can be derived directly by partial melting of an enriched lithospheric mantle, which is important to understand the source and origin of diverse granites. [Copyright &y& Elsevier]

[Display omitted] • Two episodic Nb-Ta mineralization occurred in the Zhaojinggou rare metal deposit. • The first and major ore-forming episode occurred at ~130 Ma, the second but subordinate ore-forming episode occurred at ~114 Ma. • The ore-bearing granitic rocks for two discrete episodes showing A-type affinity, were originated from similar magma reservoir by high-temperature partial melting. The Zhaojinggou rare-metal deposit is located in the Wulashan-Daqingshan region, central north margin of the North China Craton. Nb-Ta mineralizations are mainly hosted in the biotite alkali-feldspar granite (BAG) and albite granite (AG), with subordinate mineralization in the alkali-feldspar aplite dyke (AFA), the amazonite granitic pegmatite dyke (AGP), and the greisen (black + white colored greisen). In this paper, we present a systematic work of geochronology (CGM U-Pb combined with cassiterite U-Pb, monazite U-Th-Pb, and muscovite 40Ar-39Ar dating), whole-rock geochemistry, and Sr-Nd isotopes to understanding the timing of mineralization, petrogenesis, geodynamic setting, and ore-forming processes. Our geochronological data reveal two episodic Nb-Ta mineralization events in the Zhaojinggou deposit during the Early Cretaceous. The first and major ore-forming episode occurred at ~130 Ma, forming a sequence of ore-bearing rocks of the BAG-AG-greisen-AFA. The second but subordinate ore-forming episode occurred at ~114 Ma, forming the ore-bearing AGP. The whole-rock geochemistry indicates the granitic rocks (the BAG-AG-AFA and AGP) from the two episodes are highly evolved with analogous trace element and REE patterns, and have A-type affinity. The whole-rock ε Nd (t) values of these granitic rocks are relative similar, ranging from −9.6 to −7.6, with corresponding T 2DM ages of 1490–1713 Ma. These features suggest that these A-type granites from the two discrete episodes are derived from the same magma reservoir by high-temperature partial melting of the Middle Proterozoic basement in an infracrustal extensional environment. These A-type granites experienced extremely fractional crystallization during emplacement. The whole-rock REE tetrad effects, element ratios (Nb/Ta, Zr/Hf and K/Rb), and Nb-Ta fractionation modeling indicate that both magmatic and hydrothermal processes are involved to form the two episodic Nb-Ta mineralizations. High degree of factional crystallization and magmatic-hydrothermal processes after high-temperature anataxis are crucial to form the Zhaojinggou rare-metal deposit. Moreover, these highly-evolved A-type granites (the BAG-AG-AFA and AGP) formed during the Early Cretaceous (at ~ 130 Ma and ~ 114 Ma respectively) are the important targets for rare-metals prospecting in the central north margin of the NCC. [ABSTRACT FROM AUTHOR]

• Apatite U-Pb ages show the Zhuxi granites formed at ca. 153 Ma. • Geochemistry of apatite in the Zhuxi granites records the magma evolution process. • Tungsten is enriched in apatite from the most evolved granite porphyry. • Non-CHARAC Y/Ho and Zr/Hf ratios of apatite reflect a magma-fluid interaction. • Fluorine plays a vital role in the formation of the Zhuxi W-Cu skarn deposit. Apatite is a ubiquitous mineral in granites and crystallizes from the beginning of magma evolution to the latest magma-fluids transitional stage, and thus, is able to record petrogenetic-metallogenic information. In order to figure out the role of granites in the formation of the Zhuxi deposit, textures and compositions of apatites in the Zhuxi granites were investigated. Granites related to the Zhuxi W-Cu deposit include biotite granite, muscovite granite, and granite porphyry. Apatites in these granites are named Group A, Group B (core – Group B1; rim – Group B2), and Group C, respectively. Along this sequence, geochemical characteristics of apatites show gradual enrichment of total rare earth elements (ΣREE), high-field strength elements (HFSE; Th, U, Nb, Ta, Zr, and Hf), as well as ore-forming element W, and depletion of Sr. Meanwhile, Ga content in these apatites consecutively increased, indicating the reduction of oxygen fugacity in the Zhuxi magmatic system. Non-chondritic Y/Ho (mostly > 34) and Zr/Hf (broadly < 5) ratios in Group C apatite reflect the high volume of fluids interacted with the magma of the most evolved granite porphyry. Constant high F contents (3.4–4.4 wt%) in all apatite samples show abundant F in the Zhuxi magmas, which played an important role in the formation of the Zhuxi deposit in terms of facilitating W enrichment in magma and exsolution of W into hydrothermal fluids. The Zhuxi granites formed at ca. 153 Ma when South China Block was in an extensional tectonic setting, and the granite porphyry is the most potential intrusion to cause the mineralization of the Zhuxi deposit. [ABSTRACT FROM AUTHOR]

The Tongbai orogen is located in the northern Hubei and southern Henan provinces, together with the Qinling, Hong'an and Dabie orogens they constitute one of the most important orogenic belt separated the North China Block and Yangtze Block. Among these orogens, the Tongbai receives less attention and its magmatic and tectonic evolution is still unclear. In this paper, we present a detailed study on geochronology, geochemistry and Sr-Nd-Pb-Hf isotopes of the five plutons (Daxianduo, Jinziling, Sanguanduo, Sanhedian and Zhoulou) that composes the Qijianfeng Granite Complex in Suizao area, in order to better understanding the Late Mesozoic magmatic and tectonic evolution of the Tongbai orogen. The LA-ICP-MS U Pb dating of zircon suggests an Early Cretaceous emplacement age (135–139 Ma) for the Qijianfeng Granite Complex. All the five plutons of the Qijianfeng Granite Complex are weakly peraluminous and belong to high-K calc-alkaline series and post-collisional I type granites. The chemical and isotopic compositions of the Qijianfeng Granite Complex show SiO 2 contents of 69.84–74.36 wt%, Al 2 O 3 of 13.85–15.62 wt%, MgO of 0.16–0.52 wt%, N 2 O/K 2 O of 0.99–1.73; 506–1205 ppm Sr, 3.4–12.9 ppm Y, 0.49–1.25 ppm Yb; Eu/Eu* values of 0.7–1.0, LREE/HREE values of 3.1–9.5; 87Sr/86Sr values of 0.7057–0.7080 and ε Nd(t) values of −16.59 to −6.18, which share similarities with the C-type (high-K) adakite. The low MgO, Ni and Cr contents further suggest that the Qijianfeng Granite Complex belongs to adakite derived from partial melting of thickened lower continental crust. Combined with the geochemical characteristics of other contemporaneous intrusions in the whole orogen, our study shows that the extensive Early Cretaceous adakitic magmatic activity is triggered by lower crustal thickened, mountain-basin coupling and crust-mantle interaction in the Tongbai orogeny. • The Qijianfeng complex was formed at 135–139 Ma. • The Qijianfeng complex is a typical adakitic I-type granite. • The granites formed mainly by partial melting of a thickened lower continental crust. • Crust-mantle magma mixing contributes to the granite petrogenesis. • The mountain-basin coupling plays a role in the granite petrogenesis. [ABSTRACT FROM AUTHOR]

Most tin deposits in the world are genetically related to tin granite and form during complex magmatic-hydrothermal processes. Zircon is a common accessory mineral in granite and related ore systems and can host a number of ore metals, such as Sn, W, Nb, Ta, U and Th, in its crystal lattice. However, whether metal enrichment/depletion can trace ore-forming processes is still unclear. Here, we report that the metal concentrations in various types of zircons from the Mopanshan tin granites in the southern Great Xing'an Range (Northern China) can be used as good indicators of fluid metasomatism and Sn mineralization. Two lithological zones are developed in the Mopanshan pluton, including porphyritic syenogranite (PG) in the center and fine-grained syenogranite (FG) at the margin. Zircons in the PG (PGZ-1, PGZ-2, and PGZ-3) are all magmatic in origin, while zircons in the FG can be categorized into magmatic zircons (FGZ-1 and FGZ-2) and metasomatic zircons (FGZ-3). The PGZ-1 and FGZ-1 grains are transparent prismatic crystals with bright oscillatory zonation, whereas the PGZ-2 grains are murky crystals with dark oscillatory zonation. PGZ-3 and FGZ-2 grains occur as overgrowths of previously formed zircon (PGZ-1, PGZ-2, and FGZ-1) or as brown individual crystals, showing dark and homogeneous cathodoluminescence (CL) textures. The metasomatic FGZ-3 grains are translucent-opaque porous crystals with vermicular CL zonation and commonly replace FGZ-2. The trace element compositions of magmatic zircons are completely melt controlled, providing a record of magmatic evolution as a constant decrease in Zr/Hf ratios and a gradual increase in Th, U, Nb, and Ta contents. Moreover, the structure of magmatic zircons transforms from a crystalline state to an amorphous state as a consequence of radioactive decay of U and Th. A coupled dissolution-reprecipitation process is proposed for the formation of metasomatic FGZ-3. The reactive fluid is the magmatic fluid that exsolved from the melt in the late magmatic stage. The magmatic fluid replaced biotite and rare earth phosphates (mainly monazite and apatite) enclosed within biotite, resulting in significant amounts of Nb, Ta, Sn, P, Al, Ca, Fe, and REEs, which subsequently reacted with the FGZ-2 zircons to leach Th, U, Y, and HREEs. Eventually, REEs, Y, Th, and U in the fluid combined with P to form monazite and xenotime, while the other elements partially precipitated with the crystallization of the FGZ-3 zircons. Although the alteration of biotite only released approximately 190 ppm of Sn into the fluid, this is still a significant Sn source for the Sn deposits surrounding the Mopanshan pluton, taking the granite size (∼50 km2) and the volume proportion of biotite (∼5%) into account. Furthermore, based on previous studies on tourmaline from the Mopanshan granite and regional geochemistry, it may be inferred that the addition of wall rock components may also play an important role in Sn mineralization. [Display omitted] • Magmatic and metasomatic zircons have been identified in the Mopanshan granite. • Formation of metasomatic zircon is due to a dissolution-reprecipitation process. • Zircon records the enrichment of Sn during magmatic-hydrothermal process. • The release of Sn by biotite alteration is a significant Sn source for Sn deposits. [ABSTRACT FROM AUTHOR]

Abstract Abundant tourmaline occurs in Late Triassic biotite-muscovite granites of Mashhad (NE Iran), with several distinct morphologies including tourmaline nodules in granite, pegmatitic tourmalines, aplitic tourmalines, and vein-related tourmalines (quartz-tourmaline vein, tourmaline-rich vein and radial tourmalines). Pegmatitic and aplitic tourmalines are compositionally Fe-rich schorl and the nodule, radial and vein tourmalines are Mg-rich schorl. The tourmalines have generally low abundances for most trace elements except for Sr, Ga, Li, Be, Sn, Pb and some transition elements. Tourmalines have low REE abundances and are enriched in LREE and depleted in HREE (mostly below detection limits) with positive Eu anomalies. The concentration of several trace elements (e.g., Pb, Be, Sn, Ga, Sr, Pb, and REE) correlates well with the major element composition of the tourmalines (e.g. Mg# (Mg/Mg + Fe), vacancy/)X-site vacancy + Na(and Na/)Na + Ca(). Trace element data of coexisting minerals with tourmaline indicate that the oligoclase and albite show the most preference in Sr, Pb and Eu and LREEs, biotite readily incorporates Rb, Ba, Zn, Li, Cs and Nb; K-feldspar has high contents of Rb, Ba, Sr and Pb; and garnet incorporates HREEs and Y during magma differentiation. The B-O-H isotopic compositions for all tourmalines are consistent with an S-type granite source, that was derived from partial melting of the continental crust. The pegmatitic and aplitic tourmalines with Fe-rich schorl composition indicate magmatic conditions and the radial, vein, and nodule tourmalines with Mg-rich schorl composition formed during the transition from magmatic to hydrothermal conditions due to the internal evolution of the granitic magma. Highlights • Various types of schorl-dravite tourmaline occur in Mashhad granite, NW Iran. • Mg-rich schorls have more Sr, La, Ce, Pr, Eu, Eu/Eu*, Nd and ∑REE than Fe-rich schorls. • Coexisting minerals with tourmaline show different trace element preferences. • The B-O-H isotopic compositions tourmalines are consistent with an S-type granite source. • Tourmaline formation records the evolution from magmatic transition to hydrothermal conditions. [ABSTRACT FROM AUTHOR]

The Late Cretaceous to Paleogene granitoids occur widespread in the Sibumasu block within Myanmar (SE Asia), which show a close association with tin-tungsten mineralization. However, the precise timing, petrogenesis and tectonic significance of these granitoids are poorly constrained so far. In this study, we present a detailed study on geochronology, elemental and Sr-Nd-Hf isotopic geochemistry for the Hermyingyi and Taungphila granites in southern Myanmar, with the aim of determining their petrogenesis and tectonic implications. LA-ICP-MS U–Pb dating of zircon grains from the two granites yield ages of 69–70 Ma, indicating a Late Cretaceous magmatic event. These granitic rocks are weakly peraluminous and belong to the high-K calc-alkaline series. They are both characterized by high SiO 2 , K 2 O + Na 2 O, FeO T /(FeO T + MgO) and Ga/Al ratios and low Al 2 O 3 , CaO, MgO, P 2 O 5 and TiO 2 contents, enriched in Rb, Th, U and Y, but depleted in Ba, Sr, P, and Eu, suggesting an A-type granite affinity. Moreover, they display prominent tetrad REE patterns and non-CHARAC trace element behavior, which are common in late magmatic differentiates with strong hydrothermal interaction or deuteric alteration. The granites belong to A 2 -type and probably formed at a high temperature and anhydrous condition. They have zircon ε Hf ( t ) values from − 12.4 to − 10.0 and whole-rock ε Nd ( t ) values from − 11.3 to − 10.6, with Paleoproterozoic T DM2 ages (1741–1922 Ma) for both Hf and Nd isotopes. Geochemical and isotopic data suggest that these A-type granites were derived from partial melting of the Paleoproterozoic continental crust dominated by metaigneous rocks with tonalitic to granodioritic compositions, without significant input of mantle-derived magma and followed by subsequent fractional crystallization. By integrating all available data for the regional tectonic evolution in SE Asia and adjacent regions, we attribute the formation of the Late Cretaceous A-type granites to a back-arc extension in the hinterland behind the subduction zone, which is induced by the rollback of the flat Neo-Tethyan subducting slab around ca. 70 Ma. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Jinkeng deposit formed in two stages (∼147 Ma and ∼141 Ma, respectively). • Different metallogenic potential for the two granitic rocks. • The regional compression occurred in the range of 147–144 Ma. The Jinkeng Sn-Cu polymetallic deposit in South China consists of two different types of orebodies: 1) NE-striking skarn- and vein-type Cu-Pb-Zn-Sn orebodies in volcanic rocks suffering subsequent ductile shear deformation, and 2) NW-striking quartz-cassiterite-sulfide veins filled in the faults at the porphyritic granodiorite outward from the fine-grained granite which does not exhibit deformation. The relationships among Sn-Cu polymetallic mineralization, regional magmatism, and deformation metamorphism are still controversial. To address it, the geochronological, whole-rock and mineral geochemical research along with the detailed field investigation were conducted in this study. Our zircon U-Pb dating results show that the volcanic rocks formed at 158–162 Ma, earlier than the porphyritic granodiorite which yields the emplacement age of 146–147 Ma. In-situ LA-ICP-MS U-Pb dating of cassiterite from the deformed skarn ores indicates the early-stage mineralization occurred at 146 ∼ 148 Ma, which is similar to the emplacement age of the porphyritic granodiorite, but earlier than the formation of quartz-cassiterite-sulfide veins and the fine-grained granite (141∼144 Ma). Further, the whole-rock and biotite geochemistry, and zircon Hf isotope compositions suggest that the porphyritic granodiorite exhibits a lower degree of magma differentiation, higher oxygen fugacity, higher Cl and lower F contents than the fine-grained granite. The porphyritic granodiorite might provide the most Cu-Pb-Zn budget accompanied by minor Sn for early-stage mineralization. Overall, our study suggests that the Jinkeng Sn-Cu polymetallic deposit formed in two scenarios where the early dominated Cu-Pb-Zn and minor Sn mineralization related to the emplacement of the porphyritic granodiorite is superimposed by the late vein-type Sn-dominated mineralization related to the emplacement of the fine-grained granite. The two isolated mineralizing events (∼147 Ma and ∼141 Ma, respectively) in Jinkeng were probably responded to the regional magmatic activities triggered by the tectonic transformation where two extensional tectonic events were separated by a short contractional event (147–144 Ma). [ABSTRACT FROM AUTHOR]

[Display omitted] • We identified W-rich zircons from the granite in the Hukeng deposit. • These W-rich zircons record the activity of W-rich ore-forming fluids. • W/Gd ratios of zircons can be used as an indicator to estimate mineralization potential. South China is endowed with copious hydrothermal tungsten ore deposits, which are generally suggested to be associated with highly fractionated granites. However, the mechanism of tungsten enrichment and mineralization during magmatic-hydrothermal processes is not clear. Here, we clearly identified W-rich zircons (up to several thousand ppm) from the granite in the Hukeng tungsten deposit in South China. W-rich zircons are generally dark in cathodoluminescence images with irregular cracks, cavities and blurry oscillatory zones. They also show high contents of U, Nb, REEs, and high W/Gd ratios, which are not possible to be produced only by magma differentiation. Raman spectra of zircons indicate that these W-rich zircons have experienced different degrees of metamictization. Thus, these W-rich zircons should be crystallized from the late magma and subsequently altered by W-rich magmatic-hydrothermal fluids. W-rich zircons record the activity of W-rich ore-forming fluids which were exsolved from the granitic magma. We suggested that the W/Gd ratios of > 0.2 of zircons can be used as an indicator to estimate the W mineralization potential of a granite. This study provides a new pathway for using zircon to record tungsten mineralization processes and to guide tungsten ore prospecting. [ABSTRACT FROM AUTHOR]

Triassic magmatism in Thailand provides the critical geological record for understanding the evolution of the Paleo-Tethys Ocean. This paper presents zircon U-Pb dating, zircon trace element compositions, elemental geochemistry and Sr-Nd-Hf isotopes for the newly identified Late Triassic granite intrusions in the Upper Peninsula of Thailand where voluminous Late Cretaceous-Paleogene granite intrusions occur. Zircon U-Pb dating results indicate that the two-mica granites were emplaced at ca. 217–216 Ma. The unaltered two-mica granite samples are high silicic (SiO 2 = 74.03–75.06 wt%) and display strongly peraluminous characteristics, with A/CNK ratios of 1.21–1.33 and CIPW normative corundum contents of 2.86–3.88 wt%. They have fractionated REE patterns ((La/Yb) N = 5.64–7.34) and notable negative Eu anomalies (Eu/Eu* = 0.35–0.49), with enrichment of Rb, Th, U, Ta and Pb and depletion of Ba, Nb, Sr and Ti. The two-mica granites can be assigned as the highly fractionated S-type granites. They have negative whole-rock ε Nd (t) (−13.2 to −12.3) and zircon ε Hf (t) (−11.5 to −7.4) values with corresponding two-stage Nd and Hf model ages ranging from 1.99 to 2.06 Ga and from 1.72 to 1.98 Ga, respectively, indicating a Paleoproterozoic crustal source. The combined geochemical and isotopic data reveal that these rocks were derived by fluid-absent muscovite melting of metapelite at the middle-upper crustal depths and modified by fractional crystallization. In combination of the results in this study with regional geological data, it can be concluded that the two-mica granites were more likely formed during the post-collisional stage of the Sibumasu-Indochina collision, induced by slab break-off of the Paleo-Tethys Ocean. Based on the integrated consideration of a set of factors, including temporal and spatial proximity, source lithology and source enrichment, redox state, and fractional crystallization coupled with melt-fluid interaction, it is suggested that the ca. 216 Ma two-mica granites exhibit high Sn mineralization potential and could be helpful for exploring the primary Sn deposit of Late Triassic age nearby. [Display omitted] • Late Triassic (216 Ma) granites occur in the Upper Peninsula of Thailand. • The two-mica granites formed in a post-collisional setting. • Magmas were derived from fluid-absent muscovite melting of metapelite. • The two-mica granites exhibit high Sn mineralization potential. [ABSTRACT FROM AUTHOR]

Most primary tin deposits are intimately associated with highly-fractionated granites (HFGs), but the factors controlling the formation of tin mineralization; including source enrichment, partial melting, fractional crystallization, and fluid processes, are still subject to debate. The potassium-rich Yanbei volcanic-intrusive complex is part of the world-class Nanling W Sn metallogenic belt in South China and contains both barren and Sn-rich igneous rocks. We report here Ba isotope compositions of these rocks in an effort to elucidate the relationship between HFGs and related Sn mineralization. Overall, the results show δ138/134Ba values ranging widely from −0.83 to +0.21‰. The δ138/134Ba of the barren volcanic rocks (−0.11 to +0.21‰) are correlated with SiO 2 , Sr, and Ba contents, and Eu/Eu* values in a manner indicating that fractional crystallization is the main control over their Ba isotope variation. The most fractionated volcanic rocks have the highest δ138/134Ba due to crystallization of alkali-feldspar rich in light Ba isotopes. In contrast, the highly-fractionated tin granites have low Ba contents and δ138/134Ba values of −0.83 to −0.23‰. These low values cannot be explained by either addition of mantle-sourced melts and magmatic fluids, or fractional crystallization and fluid circulation at the shallow emplacement level. Rather, these geochemical features are likely inherited from an isotopically lighter crustal source with enhanced tin contents related to the recycling of intensely chemically weathered sediments. When combined with bulk-rock chemical data, the Ba isotope data suggest that assimilation of this tin-enriched source played a key role in forming the tin granites and related tin deposits. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Tourmaline often occurs in boron-rich granites and its genesis is still in dispute either formed from residual boron-rich silicate melt or from magmatic hydrothermal fluids with or without external fluid involvement. Here, we present a systematic investigation of in-situ major, trace elemental and boron isotopic variations of tourmaline from the Sanfang granite in Guangxi Province of South China, which demonstrate both the magmatic and hydrothermal origin for the formation of the tourmalines. The tourmaline occurs mainly in quartz-tourmaline nodules and tourmaline pegmatitic segregations within the Sanfang granite. Four types of tourmaline are identified: (1) isolated and disseminated tourmaline (Tur-D type) distributed in granite; (2) euhedral and subhedral tourmaline in quartz-tourmaline nodules (Tur-N type); (3) the earlier stage tourmaline (Tur-PE type) in pegmatitic segregations and (4) the later stage tourmaline (Tur-PL type) which replaced the Tur-PE type tourmaline in pegmatitic segregations. All the tourmalines belong to the alkali group representing dravite-schorl solid solution series with the former three types being schorl and the Tur-PL type being dravite. Petrography, chemical discrimination diagrams and Al occupations in the Y-site suggest that the Tur-D, Tur-N and Tur-PE type tourmalines are of magmatic origin and the Tur-PL type tourmalines are of hydrothermal fluid origin. Elemental and boron isotopic composition variations of tourmalines reflect the compositional and environmental evolution from late boron-rich magma to exsolved hydrothermal fluids. Chemical variations from the Tur-D to the Tur-N tourmalines are controlled by magma differentiation. The increase of Mg/(Mg + Fe) and Ca/(Ca + Na) ratios from the Tur-N to the Tur-PE tourmalines suggests the contamination of surrounding strata (e.g. the Sibao Group). Hydrothermal tourmalines have higher Mg/(Mg + Fe) and lower Na/(Na + Ca) ratios than the magmatic tourmalines. There is clear correlation at least in some trace elements (e.g. Sr, Pb) with major elements for all tourmalines, indicating the potential crystal chemical effects on their incorporation. Other trace element incorporation in tourmaline is largely controlled by melt and fluid composition. Hydrothermal tourmalines have high and stable V, Co and Ni contents, indicating relatively constant partition coefficient between hydrothermal tourmalines and the fluid. Hydrothermal tourmalines exhibit lower total REE contents but more pronounced positive Eu anomalies than the magmatic tourmalines. The δ11B values of all tourmalines from the Sanfang granite vary from −14.4‰ to −9.3‰, which indicate the boron in the Sanfang granite was mainly derived from partial melting of the metasedimentary source rocks. Boron isotopic variations of tourmaline are controlled by fractionation between melt-fluid and Rayleigh fractionation. [ABSTRACT FROM AUTHOR]

The giant Yanbei tin ore deposit is the largest porphyry-type tin deposit in South China. The orebodies are hosted by the granite porphyry in the central part of the Yanbei volcanic basin in southern Jiangxi Province. The Yanbei volcanic-intrusive complex mainly consists of dacitic-rhyolitic volcanic rocks, granite, granite porphyry and diabase dikes. In previous papers, the granite porphyry was considered as subvolcanic rocks, which came from the same single magma chamber with the volcanic rocks. In this study, zircon U-Pb ages and Hf isotope data, as well as whole-rock geochemical and Sr-Nd isotopic compositions of different magmatic units in the Yanbei complex are reported. Geochronologic results show that various magmatic units have different formation ages. The dacite yielded a zircon U-Pb age of 143 ± 1 Ma, and the granite porphyry has the emplacement age of 138 ± 1 Ma. Diabase dikes which represented the final stage of magmatism, yielded a zircon U-Pb age of 128 ± 1 Ma. Distinctive whole rock Sr-Nd and zircon Hf isotopic compositions suggest that these magmatic units were derived from different magma sources. The volcanic rocks were mainly derived from the partial melting of Paleoproterozoic metasedimentary rocks without additions of mantle-derived magma. The granite porphyry has an A-type geochemical affinity, and was derived from remelting of Paleo-Mesoproterozoic crustal source with involvement of a subordinate mantle-derived magma. The granite porphyry is also a typical stanniferous granite with high F (4070–6090 ppm) and Sn (7–39 ppm) contents. It underwent strongly crystal fractionation of plagioclase, K-feldspar, and accessory minerals (like apatite, Fe-Ti oxides), which may contribute to the tin mineralization. The diabase was derived by partial melting of enriched lithospheric mantle which had been metasomatised by slab-derived fluids. The change of magmatic sources reflected an increasing extensional tectonic environment, perhaps induced by slab rollback of subducted paleo-Pacific plate. [ABSTRACT FROM AUTHOR]

Details on processes of the early-middle Paleozoic Wuyi–Yunkai orogeny in South China remain poorly defined. Most Silurian–Devonian granites in South China are S-type or I-type granites, which are suggested to be petrogenetically related to the Wuyi–Yunkai orogeny. This paper firstly reported a systematic study on two Devonian A-type granites in the central Jiangxi Province. LA-ICP-MS zircon U–Pb dating results imply that the Huitong and Epo granites were emplaced at about 415 Ma. Both of the two granites have the petrographic and geochemical characteristics of A-type granites. Interstitial biotites occur along the boundary of euhedral plagioclase and quartz and they formed later than plagioclase and quartz. It implies that the primary magma could have been anhydrous. Biotites from the two granites are Fe-rich and have high Fe 2 + /(Fe 2 + + Mg 2 + ) ratios (0.60–0.74). The magmatic temperatures estimated from zircon saturation thermometer are 802–920 °C for the two granites, higher than common I-type and S-type granites. The two granites show high contents of total alkalis (Na 2 O + K 2 O = 6.96–9.39 wt.%), high field strength elements (e.g. Zr = 181–437 ppm, Y = 22.1–39.7 ppm, Nb = 18.6–30.3 ppm and Zr + Nb + Ce + Y = 324–555 ppm), rare earth elements (total REE = 155–312 ppm) as well as high Ga/Al ratios (10,000 × Ga/Al = 2.50–3.44). These geochemical characteristics are similar to those of A-type granites. The Huitong and Epo granites have relatively low ε Nd (t) values of − 10.4 to − 7.7, and low zircon ε Hf (t) values (peak value of − 8.0). Whole-rock two stage Nd isotopic model ages and zircon Hf isotopic model ages mostly vary from 1.78 Ga to 2.00 Ga. According to these data, we suggest that the two granites might have derived from partial melting of pre-Cambrian sedimentary rocks which had been granulitized during an earlier thermal event. The two granites contain abundant contemporaneous mafic microgranular enclaves (MMEs). The MMEs display igneous textures and contain acicular apatites, suggesting quenching of mafic magmas that have co-mingled with the host granites. The MMEs might have derived from the enriched lithospheric mantle source. This study on the Devonian Huitong and Epo A-type granites, together with previous studies on Paleozoic granites in South China, indicated that the Wuyi–Yunkai orogeny in South China had changed from syn-collisional crustal thickening to post-collisional extension at least from 415 Ma. [ABSTRACT FROM AUTHOR]

Highlights: [•] First reported Neoproterzoic (∼740Ma) igneous rock in Chinese Central Tianshan. [•] The granite is an A1-type granite developed in a rift-like environment. [•] Central Tianshan recorded Neoproterozoic rift-related igneous events related to the breakup of Rodinia. [ABSTRACT FROM AUTHOR]

• Cassiterite U-Pb dating yielded the mineralization timing of ca. 100 Ma for the Shanhu W-Sn deposit. • The Yantianling granite near the Shanhu deposit was emplaced at ca. 100 Ma. • The Yantianling granite belongs to S-type and has strong W-Sn mineralization potential. • The Shanhu W-Sn mineralization formed under the regional lithospheric extension environment. Abundant Jurassic-Cretaceous W-Sn ore deposits are distributed in the Nanling Range in South China. However, the exact mineralization ages, relationships between mineralization and granitic rocks, and tectonic settings of these deposits remain controversial. As a giant quartz vein-type W-Sn deposit hosted in Devonian sedimentary strata, the Shanhu orebodies are featured by located about 4 km far away from the Yantianling muscovite granite. Zircon U-Pb dating of the Yantianling granite yielded ages of 101.0 ± 1.5 Ma and 100.4 ± 1.1 Ma, consistent with cassiterite U-Pb ages of quartz vein ores (100.2 ± 1.0 Ma and 100.5 ± 1.1 Ma), indicating a close genetic relationship between the granitic magmatism and quartz vein-type W-Sn mineralization. The Yantianling muscovite granite is characterized by highly silicious (72.01–74.62 wt%), high alkali (Na 2 O + K 2 O = 5.32–7.89 wt%) and strongly peraluminous (A/CNK = 1.11–1.81). The granite is enriched in Rb, Ta, Nd and U, and depleted in Sr, Ti and P. It displays right-declining chondrite-normalized REE patterns with strongly negative Eu anomalies, and has low Nb/Ta and Zr/Hf ratios, indicating that the granite experienced strong magmatic differentiation. The Yantianling granite has low whole-rock ε Nd (t) values (−9.5 to −9.3), zircon ε Hf (t) values (−12.7 to −7.8) and Paleoproterozoic model ages. The granite belongs to S-type and was derived from partial melting of meta -sedimentary crust. The low Ce4+/Ce3+ ratios (averaging 47) of zircon from the Yantianling granite indicated low oxygen fugacity, similar to other W-bearing granites in South China. This study indicated that Cretaceous granitic magmatism in the Nanling Range also has strong W-Sn mineralization potential. Combined with previous studies on coeval magmatic rocks and tectonic activities, we propose that the Yantianling S-type granite and associated W-Sn mineralization in the Nanling Range were formed during the regional lithospheric extensional environment. [ABSTRACT FROM AUTHOR]