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Abstract: The Jinshajiang suture zone, located in the eastern part of the Tethyan tectonic domain, is noticeable for a large-scale distribution of Late Jurassic to Triassic granitoids. These granitoids were genetically related to the evolution of the Paleo-Tethys Ocean. Beiwu, Linong and Lunong granitoids occur in the middle zone of the Jinshajiang Suture Zone, and possess similar geochemical features, indicating that they share a common magma source. SIMS zircon U–Pb dating reveals that the Beiwu, Linong and Lunong granitic intrusions were emplaced at 233.9±1.4Ma (2σ), 233.1±1.4Ma (2σ) and 231.0±1.6Ma (2σ), respectively. All of these granitoids are enriched in abundances of Si (SiO2t =65.2–73.5wt.%), and large-ion lithophile elements (LILEs), but depleted in high field strength elements contents (HFSEs, e.g., Nb, Ta, and Ti). In addition, they have low P2O5 contents (0.06–0.11wt.%), A/CNK values ([molecular Al2O3/(CaO+Na2O+K2O)], mostly <1.1) and 10,000Ga/Al ratios (1.7–2.2), consistent with the characteristics of I-type granites. In terms of isotopic compositions, these granitoids have high initial 87Sr/86Sr ratios (0.7078–0.7148), Pb isotopic compositions [(206Pb/204Pb)t =18.213–18.598, (207Pb/204Pb)t =15.637–15.730 and (208Pb/204Pb)t =38.323–38.791], zircon δ18O values (7.3‰–9.3‰) and negative εNd(t) values (−5.1 to −6.7), suggesting they were predominantly derived from the continental crust. Their Nb/Ta ratios (average value=8.6) are consistent with those of the lower continental crust (LCC). However, variable εHf(t) values (−8.6 to +2.8) and the occurrences of mafic microgranular enclaves (MMEs) suggest that mantle-derived melts and lower crustal magmas were involved in the generation of these granitoids. Moreover, the high Pb isotopic ratios and elevated zircon δ18O values of these rocks indicate a significant contribution of the upper crustal composition. We propose a model in which the Beiwu, Linong and Lunong granitoids were generated under a late collisional or post-collisional setting. It is possible that this collision was completed before Late Triassic. Decompression induced mantle-derived magmas to be underplated and provided the heat for the anatexis of the crust. Hybrid melts including mantle-derived and the lower crustal magmas were then generated. The hybrid melts thereafter ascended to a shallow depth and resulted in some degree of sedimentary rock assimilation. Such three-component mixing magma source and subsequent fractional crystallization could be responsible for the formation of the Beiwu, Linong and Lunong granitoids. [Copyright &y& Elsevier]

Abstract: The Longwood Igneous Complex (LIC) is located in Southland, New Zealand on the eastern side of the Carboniferous to Cretaceous, I-type, Median Batholith. Intrusives of the Complex range in age from Permian to Jurassic and show trace element characteristics typical of subduction-related magmas. Gabbro, gabbroic diorite and basaltic dyke rocks show trace and minor element patterns and isotopic compositions indicating that they represent magmas generated in an intra-oceanic subduction system. Radiometric ages decrease across the LIC from 254Ma in the east to 142Ma in the west and mineral chemistry and mineral phase relationships indicate emplacement at depths between 15 and 25km. Thus the petrology and geochemistry of the LIC provides the basis for evaluating the composition of lower–middle crust assembled above a long lived intra-oceanic subduction system and we estimate this to be andesitic and similar to bulk continental crust. Rocks of the LIC range in composition from troctolite and gabbro through diorite to trondhjemite and granite. All of the ultramafic rocks and most of the gabbros have petrographic and geochemical features consistent with a cumulate origin and mineral chemistry shows similarities with arc cumulate sequences from elsewhere. Few of the plutonic rocks making up the LIC have direct analogues among modern intra-oceanic volcanic rocks. The latter are the end products and the former the leftovers from magmatic processes that included fractional crystallisation, crustal assimilation and magma mixing and mingling. Longwood intrusions do not represent magma chambers. They formed as crystal cumulates and mushes left over from the processes that generated magmas erupted at the contemporary volcanic arc. A correlation between decreasing age of emplacement and Sr and Nd isotopic compositions and inheritance in zircons dated by ion probe are indications of crustal recycling. The generation of felsic rocks in the Longwood intra-oceanic arc involved crustal anatexis and, over the 100million year history of the arc, the crust evolved towards a composition similar to bulk continental crust and average andesite. Dioritic rocks of the LIC contain abundant mafic enclaves, which are argued to represent fragments of mafic magma, derived by fractional crystallisation from basalt, which was intruded into a hot but solid or near solid diorite. Heating and remobilisation of the dioritic host disrupted and disaggregated the intruding mafic magma to form enclaves and zones of intrusion breccia that show every variation from liquid–liquid to liquid–solid mingling and mixing. They were then further modified chemically and mineralogically by diffusion of H2O, Na, P, Ba, REE, and, to a lesser extent, Rb. Mafic dykes occur throughout the Complex and a number of these are composite with compositions ranging from dolerite through andesite to dacite. The components of composite dykes do not define unequivocal linear mixing trends and hybridisation processes that took place within them have only localised significance; mingling and hybridisation in the composite dykes do not appear to have controlled geochemical variation among the major intrusive units of the Complex. [Copyright &y& Elsevier]

Abstract: The Xutai and Lujiagou plutons, exposed in the Songshan–Jishan area in the southern margin of the North China Craton (NCC), are studied to constrain the tectonic regime of the NCC between 2.5 and 2.4Ga. The Xutai pluton (dated at 2509±33Ma) mainly consists of tonalite and monzogranite with a calc-alkaline affinity (Rittmann Index (δ)<3.3). Low 10,000Ga/Al (1.15 to 1.38) and zircon saturation temperature (T Zr =612 to 779°C) and a negative correlation between P2O5 and SiO2 classify them as I-type granite. Enriched LREE, low Y and Yb with high Sr/Y ratios are attributed to garnet in the residue, indicating a deep source for the pluton. Zircon grains have positive ε Hf(t) values (+4.6 to +9.4) with T DM C ages ranging from 2708 to 2435Ma (average of 2502Ma), close to the crystallization age of the pluton, indicative of a juvenile crust source. Negative Nb, Ta and Ti anomalies of the pluton and its intrusive contact relationship with older subduction-related amphibolites are supportive of an arc setting. The Lujiagou pluton (dated at 2399±24Ma) mainly consists of syenogranite with a calc-alkaline affinity (δ<3.3). High SiO2 (73.25 to 75.21wt.%) and K2O (5.38 to 8.03wt.%) and low P2O5 (0.01 to 0.04wt.%) indicate that the primitive magmas of the rocks have experienced fractionation. The rocks have 10,000Ga/Al (0.71 to 2.55) and T Zr (614 to 796°C) lower than those for A-type granite and negative correlation between P2O5 and SiO2, consistent with highly fractionated I-type character. Zircon ε Hf(t) values (−0.2 to +4.4) with T DM C from 2909 to 2652Ma are indicative of mantle-derived components, contaminated by older crust. However, the rocks have high SiO2, K2O and low Mg#, precluding their derivation from a juvenile source. Considering the LREE enriched nature, low Y, negative Eu anomalies and zircon Hf and whole rock Nd isotopic components identical to TTGs, we propose that the Lujiagou pluton inherited from preexisting Songshan TTGs, consistent with formation in an extensional setting. We thus propose that the Xutai and Lujiagou plutons record a tectonic transition from compressive to extensional setting in the southern margin of the NCC during 2.5 to 2.4Ga. [Copyright &y& Elsevier]

Abstract: The Sakarya Zone is intruded by several Late Paleozoic granitoids, of which the Sarıcakaya intrusive rocks in the central Sakarya (Eskişehir) region, is the least-studied. The Sarıcakaya intrusive rocks consist mainly of quartz diorite-granodiorite, granodiorite and granite. They are, geochemically, divided into two groups: diorites and granites. The former is medium-K and calc-alkaline (mainly I-type), whereas the latter is high-K to shoshonite and calcic (I-type). Typical minerals for both rock types are plagioclase, K-feldspar, quartz, biotite, hornblende and Fe–Ti oxides. Chondrite-normalized REE patterns for the Sarıcakaya intrusive rocks are moderately fractionated and have small negative Eu anomalies. They are enriched in LILE and LREE relative to HFSE showing characteristics of arc-related granitoids. Geochemical characteristics of the Sarıcakaya intrusive rocks indicate a hybrid origin through partial melting of lower crustal source rocks. [ABSTRACT FROM AUTHOR]

Magnetite–apatite deposits in the Alborz volcano–plutonic belt, southeast Zanjan, in Iran, have blade, lenzoid, and vein forms, which extend in an E-W direction. There are many magnetite–apatite veins and veinlets in this region, and some of them are economically important, such as Zaker, Morvarid, Sorkheh–Dizaj, and Aliabad. The sizes of the vein orebodies vary between 2 and 16 m in width, 10–100 m in length, and 5–40 m in depth. Microscopic examination of thin sections and polishes indicate that they are composed of magnetite and apatite, with minor amounts of goethite, hematite, actinolite, quartz, muscovite–illite, talc, dolomite, and calcite. The geochemistry and mineralogy of the granitic host rock reveals that it is calc-alkaline and I-type. Field observations, mineral paragenesis, the composition of the orebodies, and the composition of the fluid inclusions in the apatite minerals with low salinity (less than 20 wt.% NaCl equivalent) indicate that these magnetite veins were hydrothermally generated at about 200–430°C and are not related to silica–iron oxide immiscibility, as are the major Precambrian magnetite deposits in central Iran. [ABSTRACT FROM AUTHOR]

A wide variety of rock types were produced by the latest Cretaceous magmatism in the Central Anatolian Crystalline Complex. These rocks can be divided into three distinct units: (i) caic-alkaline, (ii) subalkaline/transitional, and (iii) alkaline. The calc-alkaline rocks are mainly metaluminous (I-type) ranging from monzodiorite to granite. The subalkaline/transitional rocks are also metaluminous (I-type) ranging from monzonite to granite. The alkaline rocks are mainly peralkaline (A-type), ranging from feldspathoid-bearing monzosyenite to granite. Whole-rock oxygen isotope data from the complex have a considerable range of δ18O values between 6.S%o and 14.8%o. Initial 87Sr/86Sr versus 143Nd/144Nd ratios, and both ratios versus δ18O values diagrams show that the intrusive rocks are derived from a subduction-modified mantle and also have experienced fractional crystallisation coupled with crustal assimilation. Delamination of a thermal boundary layer, and/or slab breakoff is the likely mechanisms for the initiation of the diverse magmatism in the complex. [ABSTRACT FROM AUTHOR]

We report geochronological, geochemical and isotopic data for the Mesozoic Shangshuiquan granite from the northern margin of the North China craton. The granite is highly fractionated, with SiO2 > 74%. Occurrence of annitic biotite, high contents of alkalis (K2O + Na2O), Rb, Y, Nb and heavy rare earth elements, high FeOt/MgO, low contents of CaO, Al2O3, Ba, and Sr, and large negative Eu anomalies, makes it indistinguishable from typical A-type granites. A mantle-derived origin for the rocks of the granite is not favored because their high initial 87Sr/86Sr (≥0.706) and low εNd ( t) (<−15) are completely different from either those of the lithospheric or asthenospheric mantle. In fact, their Sr–Nd isotopes fall within the range of Sr–Nd isotopic compositions of the Archean granulite terrains and are comparable to those of Mesozoic crustal-derived I-type granitoids in the region. Therefore, the Shangshuiquan granite is considered to be dominantly derived from partial melting of the ancient lower crust. Its parental magmas prove to be similar to I-type magmas and to have undergone extensive fractionation during its ascent. This is supported by the fact that some of the nearby Hannuoba feldspar-rich granulite xenoliths can be indeed regarded as the early cumulates in terms of their mineralogy, chemistry, Sr–Nd isotopes and zircon U–Pb ages and Hf isotopes. It is furthermore argued that some of highly fractionated granites worldwide, especially those with A-type characteristics and lacking close relationship with unfractionated rocks, may in fact be fractionated I-type granites. This suggestion can explain their close temporal and spatial associations as well as similar Sr–Nd isotopes with I-type granites. Our study also sheds new light on the petrogenesis of deep crustal xenoliths. [ABSTRACT FROM AUTHOR]

The Deng-Deng intrusive complex belongs to the Central African Fold Belt (CAFB) in eastern Cameroon and includes granodiorite and diorite. Both rocks are classified as metaluminous to slightly peraluminous, high-K calc-alkaline, and I-type granitoids (A/CNK <1.1). Primitive mantle-normalized trace-element patterns display large-ion lithophile elements (LILE) enrichment, such as Rb, Cs, Ba and K, and depletion in high-field-strength elements (HFSEs), such as Nb, Ti, Ta and P. The studied rocks are enriched in LREEs relative to HREEs and exhibit weak negative Eu anomalies (Eu/Eu* = 0.61–0.92 and 0.59–0.67 for the granodiorite and diorite, respectively), suggesting active continental margin arc affinity. The emplacement temperatures of these granitoids are estimated between 775 and 806 °C. Combined with their diagnostic ratios (e.g., Th/Ta, Rb/Sr, Nb/La, and La/Sm), we propose that the Deng-Deng granitoids were sourced by mixing between mafic magma derived from the lithospheric mantle and felsic magma derived from partial melting of a lower crust in a convergent margin setting. • Pan-African granitoids investigated at Deng-Deng area in eastern Cameroon. • Deng-Deng granitoids comprise deformed granodiorites and undeformed quartz monzonites. • The studied granitoids display I-type and metaluminous signatures. • Deng-Deng granitoids derived from partial melting of mantle and lower crust sources. • Emplacement at 775–806 °C in convergent margin setting. [ABSTRACT FROM AUTHOR]

Abstract: Two granitoid complexes in the eastern Kyrgyz Tien Shan, situated north and south of the Southern Tien Shan Suture, were studied. The suture formed as a result of the closure of the Turkestan Ocean and collision of the Tarim microcontinent in the south with the Middle Tien Shan in the north. The timing of collision is still disputed. The deformed calc-alkaline Terektinsky complex, situated immediately north of the suture, represents one of the largest shear-zone related intrusions in the Tien Shan (130×5–15 km in size). Small stocks of evolved A-type granites of the Inylchek complex, hosting economic tin mineralization, were emplaced immediately south of the suture opposite the Terektinsky complex. Two samples from the Terektinsky complex and 3 samples from three A-type stocks were collected for U–Pb zircon SHRIMP-II geochronology. The ages at 2σ level obtained for the Terektinsky complex north of the suture (294+5 Ma and 291+5 Ma) and ages of the small granite bodies south of the suture (299+4 Ma, 295+4 Ma, 289+6 Ma; Tashkoro, Inylchek and Maida''adir intrusions, respectively) are nearly identical, within error limits. They show that the Southern Tien Shan Suture in the eastern Kyrgyz Tien Shan had already formed by ~295 Ma, and had evolved into a transcrustal mega-shear zone controlling emplacement of granitoids. Geochemical distinction between the two magmatic systems is based on 10 original bulk and trace analyses of rocks from this study and on a large dataset extracted from previously published research and unpublished reports. Geochemically, the rocks of the Terektinsky complex comprise calc-alkaline (high potassium I-type) series while the granites of the Inylchek complex are typical A-type granites with an elevated alumina saturation index and higher boron contents compared to a “standard” A-type rapakivi granite. Contrasting metallogenic features of the two granitoid complexes south and north of the Southern Tien Shan Suture are defined by their sources: a fertile fore-arc complex, and/or passive margin sediments of Tarim to the south, and barren metamorphic Precambrian basement of the Middle Tien Shan to the north. [Copyright &y& Elsevier]

Abstract: Neoproterozoic magmatism in the Yangtze Block of South China produced voluminous S- and I-type granites, and sparse A-type granites. The Daxiangling A-type granitic pluton is spatially associated with the Shimian I-type pluton at the western margin of the Yangtze Block. Both plutons have similar SHRIMP zircon U–Pb ages of ∼800 Ma and are slightly younger than the tonalite–trondhjemite–granodiorite (TTG) gneisses in the area. The Shimian pluton is composed of granite and monzogranite with high SiO2 (69.3–76.6 wt.%), Na2O (2.79–3.80 wt.%) and K2O (3.94–5.87 wt.%), and low Fe2O3 (0.96–3.06 wt.%) and MgO (0.12–0.50 wt.%). The Daxiangling pluton consists of alkali–feldspar granites with higher SiO2 (76.3–79.3 wt.%) and lower Al2O3 (10.6–11.9 wt.%) and CaO (0.21–0.55 wt.%) than the Shimian granites. Both plutons are slightly peraluminous (A/CNK=1.00–1.12) and belong to the high-K, calc-alkaline series. The Daxiangling alkali-feldspar granites have much higher Zr, Hf, Ga and HREE, and lower Sr than the Shimian granites. On the chondrite-normalized REE diagram, both plutons are enriched in LREE, but the rocks of the Daxiangling pluton show relatively flat patterns because of their higher HREE contents. Their primitive-mantle normalized spidergrams display negative Eu, Nb, Ta, Sr, P and Ti anomalies. Both plutons have nearly identical whole-rock Nd and zircon Hf isotopic compositions (ε Nd(t)=+1 and ε Hf(t)=+5 to +9), similar to the TTG gneisses. We suggest that the I-type granites of the Shimian pluton were produced by dehydration melting of the TTG rocks as a result of underplating of mantle-derived mafic magmas. The rocks above the I-type magma source may have been converted to charnockites by heating and dehydration. With increasing temperatures, the charnockites underwent partial melting at temperatures >900 °C to produce A-type magmas. Both the A- and I-type granites formed at an extensional active continental margin, perhaps in a back-arc environment. A-type granites with mantle-like isotopic signatures may be reworked or recycled from juvenile crustal rocks. The association of A- and I-type granites suggests that aluminous A-type granite is most probably derived from a charnockite source heated by large-scale magmatic underplating, rather than a tonalite source. [Copyright &y& Elsevier]

The Rutog granitic pluton lies in the Gangdese magmatic arc in the westernmost part of the Lhasa Terrane, NW Tibet, and has SHRIMP zircon U-Pb ages of c. 80 Ma. The pluton consists of granodiorite and monzogranite with SiO[sub2] ranging from 62 to 72 wt % and Al2 03 from 15 to 17 wt%. The rocks contain 2.33-4.93 wt% K[sub2]O and 3.42-5.52 wt% Na[sub2]O and have Na[sub2]O/K[sub2]O ratios of 0.74-2.00. Their chondrite-normalized rare earth element (REE) patterns are enriched in LREE ((La/Yb)n = 15 to 26) and do not show significant Eu anomalies (SEu = 0.68-1.15). On a primitive mantle-normalized trace element diagram, the rocks are rich in large ion lithophile elements (LILE) and poor in high field strength elements (HFSE), HREE and Y. Their Sr/Y ratios range from 15 to 78 with an average of 30. The rocks have constant initial [sup87]Sr/[sup86]Sr ratios (0.7045 to 0.7049) and slightly positive ϵ[subNd](t) values (+0.1 to +2.3), similar to I-type granites generated in an arc setting. The geochemistry of the Rutog pluton is best explained by partial melting of a thickened continental crust, triggered by underplating of basaltic magmas in a mantle wedge. The formation of the Rutog pluton suggests fiat subduction of the Neo-Tethyan oceanic lithosphere from the south. Crustal thickening may have occurred in the Late Cretaceous prior to the India-Asia collision. [ABSTRACT FROM AUTHOR]

Abstract: In the Kyrgyz Tien Shan (also known as Tian Shan in literature) the Caledonian (Cambro-Silurian) intrusions comprise an extensive magmatic arc stretching from east to west for more than 1000km. The characteristic feature of the arc is its relatively homogeneous composition of rock types over the whole structure. The Kichy-Naryn and Djetim intrusions presented in this study are slightly elongated in an east–west direction and occupy an area of ca. 100km2. The main rock types are diorite, granodiorite and granite. Geological and geochemical features of the Kichy-Naryn and Djetim intrusions demonstrate characteristics of I-type granite series. Rocks of the two intrusions define a continuous high-K calc-alkaline series. Diorite and granite of the Kichy-Naryn intrusion yielded early Silurian crystallisation ages of 436±2Ma (U–Pb, zircon). Diorite from pebbles in the conglomerate sampled close to the contact of the Kichy-Naryn intrusion yielded a significantly older early Ordovician crystallisation age of 466±10Ma. The obtained ages of 466 and 436Ma match ages of two major regional magmatic pulses at ca. 435–440 and 460–470Ma which took place during continuous subduction from the Cambrian to the Silurian. The amount of granites in the Northern Tien Shan, their prolonged history of formation and pronounced I-type geochemical characteristics suggest their formation in an Andean-type active margin environment. [Copyright &y& Elsevier]

Abstract: The Upper Triassic Siah-Kuh granitoid stock is part of a series of Triassic-Cretaceous intrusions in the Phanerozoic Sanandaj-Sirjan zone in the Zagros orogenic belt, south-central Iran. The Siah-Kuh stock intrudes Lower Paleozoic amphibolites of the Abshur metamorphic complex and Upper Devonian-Lower Carboniferous greenschists of the Sargaz metamorphic complex. The Siah-Kuh granitoid stock consists mainly of coarse to medium grained leucogranodiorite, leucomonzogranite and alkali granite with subordinate syenite. It also contains a number of mafic enclaves of different sizes and is intruded by alkali granite and granophyre dikes along with monzonitic and a few dioritic dikes. The Siah-Kuh granitoid rocks are characterized by enrichment in large ion lithophile elements (LILE) such as Rb, Ba, K, Ce and depletion in high field strength elements (HFSE) such as Y, Nb and Zr. The chondrite normalized REE patterns are characterized by moderate LREE enrichment [(La/Yb)N =1.31–4.82] and unfractionated HREE [(Gd/Yb)N =0.50 to 1.33]. Granodiorites with the least fractionated HREE and a general absence of Eu anomalies suggest the involvement of plagioclase and absence of garnet during the melting processes. Alkali granites with the highest (La/Yb)N values and pronounced negative Eu anomalies are more differentiated products. Nd isotope analyses of the Siah-Kuh granitoids yield an “errorchron” age of 199±30Ma (MSWD=1.30), consistent with the field relationships and give Nd model ages (T DM) from 0.81 to 1.64Ga and εNd(T) values from +1.81 to +2.45 at 200Ma. These geochemical data suggest that the Siah-Kuh granitoid stock has characterisitics of metaluminous to slightly peraluminous, calc-alkaline, I-type granite formed in a volcanic arc setting. The onset of subduction of the Neotethys oceanic crust beneath the Central Iranian microcontinent in Triassic time could have accounted for the continental arc volcanism. Dehydration of subducted oceanic crust and partial melting of mantle wedge caused partial melting of subcontinental lithosphere, which resulted in the formation of metasomatised and enriched mafic arc magmas, at variable water fugacity and led to the formation of the Siah-kuh granitoid rocks. [Copyright &y& Elsevier]

Abstract: The Middle Jurassic Boroujerd Granitoid Complex of the Sanandaj-Sirjan Zone (with a U–Pb zircon age of 169–172Ma) was emplaced in an active continental margin setting. This complex consists of three main units: an elongate NW–SE extending granodioritic unit (SiO2 =58–71wt%), which is widespread throughout the area, a quartz-dioritic unit (SiO2 =52–63wt%), exposed as small stocks within the granodioritic body, and a monzogranitic unit (SiO2 =70–75wt%), widely scattered as separate small outcrops through the southern part of the area. A series of NW trending aplites and pegmatites are present in the granodioritic unit and its aureole. Geochemically this complex is metaluminous to slightly peraluminous, typical of I-type granites. It belongs to high-K calc-alkaline series and displays the geochemical characteristics typical of volcanic arc granites related to an active continental margin (e.g. significant Nb, Ti, P and Sr depletion). Isotopic data (Sri =0.7062–0.7074 and εNdt =−3.02 to −3.62) are consistent with a crustal protolith. In addition, fractional crystallization may have played an important role in the formation of the whole spectrum of the granitoid types that occur in the Boroujerd area. [Copyright &y& Elsevier]

Abstract: The Shah-Kuh granitic pluton of eastern Central Iran was emplaced ∼165Ma ago, in an active continental margin setting. It is made of two main units: a granodioritic unit (SiO2=63–71wt%) to the north–west and a syenogranitic unit (SiO2=73–77wt%) to the south–east. The former unit displays seriate medium-grained textures and contains locally abundant mafic enclaves. The latter unit is medium- to coarse-grained and porphyritic, with 0.5–3cm long K-feldspar megacrysts. Fine-grained granitic bodies are present in both units. The rocks are metaluminous to slightly peraluminous (I-type) and peraluminous (S-type) and belong to the ilmenite-series granites. Fractional crystallization appears to have been a very effective differentiation process in both units, and the fractionated mineral assemblages are determined by mass balance calculations. Isotopic data (Sri=0.7065 and εNdt=−2.5) are consistent with a young upper crustal protolith. Tin mineralization in sheeted quartz-tourmaline (-cassiterite) veins is spatially associated with the granodioritic unit. The veins formed by hydraulic fracturing when the granodioritic to monzogranitic magma became water-saturated and exsolved a fluid phase during crystallization. The reduced nature of this magma is responsible for the incompatible behaviour of Sn, likely to favour Sn concentration in the residual melt and then in the exsolved fluid. Another fluid phase was exsolved by the syenogranitic magma and was responsible for local greisenized granites, characterized by high Y and HREE-contents and non-fractionated REE distribution patterns. Field and mineralogical data show that the (B, Sn) vein-forming fluid was different from the (F, Li) greisen-forming fluid. [Copyright &y& Elsevier]

Northeastern (NE) China is the easternmost part of the Central Asian Orogenic Belt (CAOB), which is celebrated for its accretionary tectonics and the world''s most important juvenile crust production in the Phanerozoic era. Abundant granitoids occur in the Great Xing''an, Lesser Xing''an and Zhangguangcai Ranges in NE China. This paper presents partial results of a series of studies on the granitoids from this region, aiming to understand their role in the building of new continental crust in eastern Asia. Three composite granite plutons (Xinhuatun, Lamashan and Yiershi) were chosen for geochemical and isotopic study in order to determine their emplacement ages and petrogenesis. Petrographically, they range from granodiorite (minor), monzogranite, syenogranite to alkali-feldspar granite. Quartz and perthitic feldspar are principal phases, accompanied by minor amounts of plagioclase, biotite (<5%) and other accessory minerals. In addition, many contain abundant miarolitic cavities which suggest that they were emplaced at shallow levels with extensive fractional crystallization. Geochemically, the granites are silica-rich, peraluminous and have high contents of alkalis. They invariably show enrichment in light rare earth elements (LREE) and significant negative Eu anomalies. All the granitic rocks demonstrate the characteristic negative anomalies in Ba, Nb, Sr, P, Eu, and Ti, and a positive anomaly in Pb in the spidergram.The emplacement of the Xinhuatun pluton took place at 184±4 Ma as revealed by zircon SHRIMP U–Pb data. This is also supported by the slightly younger Rb–Sr whole-rock (WR) isochron age of 173±3 Ma. A whole-rock (WR) Rb–Sr isochron age of 154±3 Ma was obtained for the Lamashan pluton, which is interpreted as close to the time of emplacement. The Yiershi pluton was intruded at about 140 Ma as evidenced by a zircon U–Pb age of 137±2 Ma and WR Rb–Sr isochron age of 143±5 Ma. Biotite-WR Rb–Sr isochrons and 40Ar/39Ar ages of feldspars allow us to estimate the cooling rate of each pluton.Geochemical data suggest that the rocks are highly fractionated I-type granites. Fractionation of biotite and feldspars was the principal process of magmatic differentiation and responsible for major element variation. Rb, Sr and Ba concentrations were controlled by feldspar separation, whereas REE elements were fractionated by accessory minerals, such as apatite, allanite and monazite. [Copyright &y& Elsevier]

Many of the granites in southeastern Australia possess compositional, petrographic, zircon age inheritance and other features that cannot be accounted for satisfactorily by the classical models of petrogenesis. The restite model was developed to account for these features and recognises that unmelted but magmatically equilibrated source material (restite) may be entrained in a partial melt, together comprising magma. Variation in the degree of separation of those two components, leading to differences in the ratio of melt to restite, is responsible for the variation in composition within many suites of granites. A popular alternative view, that variation within suites resulted from magma mixing or mingling, conflicts with simple observations of the rock compositions and cannot be sustained. Several strong arguments can be made against another alternative view that fractional crystallisation was the dominant process in producing variation within those suites. New and conclusive evidence against that process is provided by the fact that zircon age inheritance is present in most of these granites where that has been examined. That has shown that the S-type and most of the I-type granites formed at low magmatic temperatures and confirmed that the compositional variation within those suites must have resulted from restite fractionation. The Ordovician sedimentary rocks exposed in the Lachlan Fold Belt are not sufficiently feldspathic to have produced the voluminous S-type granites and volcanic rocks of the Bullenbalong Supersuite. The view that those granites and volcanic rocks were derived from more feldspathic metasedimentary rocks is supported by much evidence and confirmed by the fact that the pelitic enclaves in those granites are relatively high in Ca. The presence of a once-thick metasedimentary basement in those areas in which these S-type granites occur is inferred. The I-type granites of the Lachlan belt are not compositionally analogous to the more calcic... [ABSTRACT FROM AUTHOR]

[Display omitted] • The Early Paleozoic I-type granites were generated through partial melting, magma mixing and fractional crystallization. • Mantle-derived magmas provided the heat and material for the formation of the granites. • The granites formed during an intracontinental orogeny. • The granites were related to the assembly of northern East Gondwana. The tectonic setting of the Early Paleozoic granites in the South China Block (SCB) remains enigmatic, and it is uncertain as to whether they are related to intracontinental orogenic processes or oceanic subduction. Previous studies mostly focused on Early Paleozoic S–type granitoids in the SCB, and relatively little attention has been paid to Early Paleozoic I–type granitoids. Here we present whole–rock major and trace elemental data and LA–ICP–MS zircon U–Pb age and Lu–Hf isotopic data for hornblende monzogranites, monzogranites, and mylonitic granites of I–type granites affinities that comprise the Daning and Guiling plutons in the southwest part of the Wuyi–Yunkai orogen in the SCB. These rocks contain zircon with U–Pb ages of 422–418 Ma, taken as the age of emplacement. They are rich in LREEs and moderately depleted in Eu (δEu = 0.49–0.64), with negative Ba, Sr, Nb, and Ti anomalies, and positive in Rb, Th, U, and Pb anomalies. Our studies of these granites and their abundant enclaves indicate that they formed via complicated petrogenetic processes, including the partial melting of a mixed source of meta–sedimentary rocks and meta–basalts in the lower crust, magma mingling and mixing of crust–mantle materials, and fractional crystallization. Mantle–derived magma played an important role in the formation of these Early Paleozoic granites. Although an ancient and enriched mantle source might have made a significant contribution to these Early Paleozoic granites, the input of juvenile mantle–derived magma might have been insignificant. Taking into account all the other geological evidence from the Wuyi–Yunkai region, we suggest that the tectono–magmatic events of the Early Paleozoic took place during intraplate orogenesis rather than oceanic subduction and collision, and that these events were triggered by a far–field tectonic response to the assembly of northern East Gondwana. [ABSTRACT FROM AUTHOR]

• Paleoproterozoic magmatism and sedimentation were first discovered in Susong area. • ∼2.0 Ga I-type granite was formed by reworking of ancient crust during orogenic event. • Metasedimentary strata and mafic dikes representing post-orogenic extensional environment. • Paleoproterozoic rocks represent the tectonic transition from collisional to extensional. Paleoproterozoic and Archean rocks in the poorly exposed Yangtze Craton provide a unique proxy for understanding early cratonic evolution. In this study, we report the newly discovered Paleoproterozoic granitoids, mafic dikes, and metasedimentary rocks in the Susong area near the northern margin of the Yangtze Craton. The zircon U–Pb analysis results of the Luohanjian granite (hereinafter referred to as LHJ-granite) and mafic dikes yielded 207Pb/206Pb ages of 2020–2002 Ma and 1837 ± 21 Ma, respectively. Metasedimentary strata that were intruded by the mafic dikes yielded detrital zircon 207Pb/206Pb ages of 2.55–2.32 Ga and 2.15–1.93 Ga, suggesting a depositional age of ∼ 1.90–1.85 Ga for the metasedimentary rock. The whole-rock ε Nd (t) and zircon ε Hf (t) values of the LHJ-granite were negative and ranged from − 10.4 to − 9.4 and − 11.4 to − 9.0, with corresponding T DM2 model ages of 3.3–3.2 Ga and ∼ 3.1 Ga, respectively. This implies that the granitic magma originated from the reworking of ancient pre-existing crustal components. The granitoids were weakly peraluminous (A/CNK = 1.00–1.18) with high SiO 2 concentrations of 71.98–76.00 wt%, LREE enrichment, high (La/Yb) N values of 26.55–100.49, and moderately negative Eu anomalies, characterized by the enrichment of Rb, Ba, Th, U, and Nd, and the relative depletion of Nb, Ta, Sr, P, and Ti. These granite samples exhibited a negative correlation between SiO 2 and P 2 O 5 and low Rb/Ba (0.15–0.33) and Rb/Sr (0.30–1.55) ratios. All these features indicate that the LHJ-granite is most likely belongs to I-type granite, which may have formed via the reworking of the TTG gneiss during subduction–collisional events. In combination with the mafic dikes and metasedimentary strata, our study proposes a mid–late Paleoproterozoic geological transition from a compressional to an extensional setting, indicating a tectonic shift from a collision orogeny (2.0 Ga) to a post-collision extensional environment (1.84 Ga) in the Susong region. [ABSTRACT FROM AUTHOR]

[Display omitted] • The granitic stock in the Xingluokeng W deposit was intruded at ca. 152 Ma. • Petrographic variations within the stock are ascribed to co-magmatic evolution via fractionation. • The granites show I-type affinity, mainly derived from Paleoproterozoic meta -igneous rocks. • Fractionation crystal and fluid-rock interaction have contributed to the W mineralization of the Xingluokeng deposit. The Xingluokeng deposit is the largest tungsten deposit discovered in the Wuyi metallogenic belt, with 30.43 Mt WO 3 reserves averaging at 0.23%. The main orebody mainly occurs in an altered granitic stock, comprising veinlet-disseminated and vein-type scheelite and wolframite mineralization. A comprehensive study of field investigations with whole-rock and in-situ geochemical and isotopic compositions was conducted on different intrusive phases of the Xingluokeng ore-bearing granitic stock, aiming to constrain the petrogenesis and its genetic link to W mineralization. The Xingluokeng stock is mainly composed of the porphyritic biotite granite (G1) as the upper part of the stock, intruded by the medium- to fine-grained biotite granite (G2) in the deep. Petrographic observations suggest that the stock experienced intense fractional crystallization as well as assimilation of country rocks close to stock margins. Zircon U − Pb geochronology and trace element analyses indicate that G1 and G2 were emplaced coevally at ~152 Ma at a relatively lower oxygen fugacity condition (Ce4+/Ce3+ = 44 ± 18 for G1, and 104 ± 41 for G2). Ti-in-zircon thermometer and AlT-in-biotite geobarometer reveal average crystallization temperature and depth at 762 ℃−740 ℃ and 7.3–7.0 km, respectively. Geochemically, obvious negative correlation between SiO 2 and P 2 O 5 and low A/CNK values (mostly < 1.1) indicate that they belong to the weakly peraluminous I-type granite, rather than S-type granite as proposed previously. Whole-rock geochemical compositions from G1 to G2 display systematic variations, with a general decrease in major oxides (such as Al 2 O 3 , TiO 2 , FeOT, MgO, CaO) and Zr/Hf ratio, but a gradual increase in DI value, Rb/Sr ratio and δEu with increasing SiO 2 , suggesting fractional crystallization is the major factor that controls the compositional variations between G1 and G2. They have consistent initial 87Sr/86Sr ratios of 0.71170 to 0.71477 and ε Nd (t) values of −12.5 to −10.8, as well as zircon ε Hf (t) values of −17.4 to −9.2 with Paleoproterozoic Nd − Hf model ages (1783–2081 Ma), suggesting a mixed crustal source of about 88% Paleoproterozoic meta -basaltic rocks and about 22% Paleoproterozoic gneissic granites, with minor assimilation of country rocks. These results favor that the Xingluokeng granites were formed by co-magmatic evolution via K-feldspar-dominated fractionation. High degrees of fractional crystallization have immensely enriched W in reduced magma, then intensive fluid-rock interaction liberated Ca from the G1 to form the scheelite and some Fe might come from the country rocks (biotite hornfels) to precipitate the wolframite. [ABSTRACT FROM AUTHOR]

• Three late Mesozoic (166–102 Ma) I-type granites identified in eastern Guangdong. • They were generated by mixing of crust- and mantle-derived magmas. • Variable Sr–Nd–Hf–O isotope data show a progressive crust–mantle interaction. • Changing subduction direction of the oceanic plate induced large-scale extension. Zircon U–Pb dating and in-situ Hf–O isotopic compositions, combined with whole-rock geochemical and Sr–Nd isotope data, are systematically presented to constrain the timing and petrogenesis of the late Mesozoic granitoids in eastern Guangdong Province, SE China. Zircon U–Pb chronology shows that two intrusions were emplaced from the Middle Jurassic to Early Cretaceous (166–144 Ma). All the granitoids are classified as calc-alkaline I-type granites with highly diverse elemental and isotopic compositions. The systematic variations in zircon Hf–O isotopes show that the granites can be categorized into three groups. The Donggang granitic porphyries (166 Ma) have the highest zircon δ18O values of 6.3–8.2‰ (average of 7.7‰) but the lowest ε Hf (t) values of −8.0 to −1.4, with the oldest Hf model ages of 1.30–1.70 Ga. The Liuzhoushan monzogranites (144 Ma) have intermediate zircon δ18O values of 6.0–6.9‰ (average of 6.4‰) and ε Hf (t) values of −5.0 to 0.3, with Hf model ages of 1.17–1.51 Ga. The late Early Cretaceous granitoids have the lowest δ18O values of 4.9–6.6‰ (average of 5.5‰) but the highest ε Hf (t) values of −3.2 to 3.3, with the youngest Hf model ages of 0.95–1.36 Ga. Zircon saturation temperatures of the Donggang, Liuzhoushan, and Xinwei (Sanrao) intrusions are calculated to be 642 °C, 722 °C, and 748 °C, respectively. Together with the variations in Sr–Nd isotopes, it appears that these granitoids were derived from the mixing of different proportions of mantle-derived components with Paleoproterozoic basement crust-derived magmas. The underplating of mantle-derived magmas into the continental crust, which supplied both heat and material contribution, was likely responsible for the generation of the most late Mesozoic I-type granites in eastern Guangdong. From Middle Jurassic to late Early Cretaceous, the increasing ε Hf (t) and ε Nd (t) values as well as the decreasing δ18O values and T DM 2 ages indicate a progressive role of the crust–mantle interaction, corresponding to a gradually enhanced extensional tectonic environment. The northeast (NE)-ward younging trend and the enhanced crust–mantle interaction along coastal SE China were probably induced by the changing direction of the subducted plate from oblique to parallel to the continental margin. [ABSTRACT FROM AUTHOR]

• Granite gneisses from the Xinghuadukou Complex yielded zircon U-Pb ages of 1.84–1.87 Ga. • These granites have I-type, likely formed by partial melting of a thickened crust and subsequently experienced extensive fractional crystallization. • The Xing'an Block in the CAOB was a micro-continental block with Paleoproterozoic basement and originally part of the Columbia supercontinent. The Precambrian evolution of the Central Asian Orogenic Belt (CAOB) in NE China remains enigmatic. The Xinghuadukou Complex, located in the Xing'an Block of NE China, contains important records of the Precambrian geological evolution of the eastern CAOB. In this study, we present petrographic observations, zircon U–Pb ages, and major and trace element data of Precambrian granitic gneisses from the Xinghuadukou Complex. The granitic gneisses are characterized by high SiO 2 (69.62–80.66 wt%) and K 2 O (2.15–3.80 wt%), enrichments in Rb, Th, Ba, and Pb, depletions in Nb, Ta, Sr, Ti, and P, and negative Eu anomalies. These geochemical signatures suggest that the granitic gneisses were derived from high-K, calc-alkaline, I-type granites, which were formed in a volcanic arc setting from magmas involving partial melting of thickened crust and extensive fractional crystallization. A total of 133 zircons in six granitic gneiss samples yielded weighted mean 207Pb/206Pb ages of 1865 ± 10, 1847 ± 13, 1858 ± 12, 1852 ± 9, 1872 ± 9, and 1859 ± 13 Ma, respectively. All the zircons combined define a weighted-mean 207Pb/206Pb age of 1861 ± 4 Ma, indicating a Paleoproterozoic basement in the Xing'an Block. In combination with data from previous studies, we suggest that the Xing'an Block was a microcontinent, likely part of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]