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The Huashandong W deposit (7.7 Mt @ 0.26% WO3) is a newly discovered Neoproterozoic scheelite-dominated deposit in the world-class Jiangnan tungsten belt, South China. It occurs largely in metasedimentary rocks near the western margin of the Neoproterozoic Jiuling batholith and mainly consists of W-bearing exogreisen, hydrothermal breccias, and quartz veins. Two episodes of Neoproterozoic granite magmatism are identified with zircon U-Pb ages of ca. 830–823 and 807–804 Ma, respectively. According to cross-cutting relationships and mineral assemblages, two periods of hydrothermal alteration and W mineralization, corresponding to the two episodes of granite magmatism, are recognized in the Huashandong deposit. The early period is dominated by greisenization and associated scheelite mineralization whereas the late period is characterized by sericitization, hydrothermal brecciation, quartz veining, and associated scheelite and minor wolframite mineralization. Molybdenite Re-Os dating indicates that the early- and late-period W mineralization took place at ca. 828 and 800 Ma, respectively. Zircon trace element characteristics suggest that the Jiuling granite crystallized from reduced granitic magmas and has the potential for W mineralization. The petrologic and geochemical features of the Jiuling granite, coupled with the zircon U-Pb ages and Hf isotopic signatures and molybdenite Re-Os ages, imply that the Huashandong W deposit is genetically related to two phases of evolved granodiorites in the Jiuling batholith. The magmatic-hydrothermal nature of both metallogenic events is confirmed by H-O isotopes on hydrothermal quartz. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogenic belt in the world and its formation involved a complicated process of arc–continent collision. Large‐scale Mesozoic volcanic activity in the Great Xing'an Range (GXAR) in northeastern China, which constitutes part of the eastern CAOB, has received much recent research attention. However, the petrogenesis and formation mechanism of the late Mesozoic igneous rocks remain enigmatic. This paper investigates the geochronology, petrogenesis, and formation mechanism of late Mesozoic magmatic rocks in the Kelihe area of the GXAR based on zircon U–Pb dating, petrology, and geochemistry. Late Mesozoic magmatism in the Kelihe area occurred during the Late Jurassic (165–155 Ma) and Early Cretaceous (130–120 Ma). These igneous rocks generated by this magmatism are characterized by high SiO2 (69.97–75.49 wt%) and low MgO (0.11–0.68 wt%), Cr (10–30 ppm), Co (0.2–2.6 ppm), and Ni (0.5–1.6 ppm) contents. Trace elements show enrichment in Rb, Th, U, Zr, and K, and depletion in Ba, P, Nb, and Ti. These features indicate that the rocks were derived from partial melting of the crust. Furthermore, the rhyolites have high Na2O (5.02–5.44 wt%) and K2O (3.94–4.88 wt%) contents, similar to those of melts formed by the partial melting of basaltic crust. Combining the present results with the findings of previous studies, it is inferred that the Mesozoic igneous rocks formed in a post‐collisional extensional setting related to lithospheric thinning and asthenospheric upwelling after the closure of the Mongol–Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

The Permian Tarim large igneous province (TLIP) is located in the Tarim basin, NW China. Although the flood basalt of the TLIP has been intensively studied, other igneous components within TLIP have not yet been sufficiently investigated. The Wajilitag igneous complex is outcropped with a rather limited exposure by regional tectonic uplift. However, various igneous rocks, both mafic–ultramafic and syenitic, can be observed as either intrusions or extrusions in this area. It is an ideal location for studying the magmatic evolution of different components within the TLIP. We systematically examine the geological, geochronological, and geochemical characteristics of the Wajilitag complex, to further constrain the petrogenesis of each component and their interrelationships, as well as the implications to the petrogenetic model of TLIP. The igneous rocks in Wajilitag complex can be classified into two series based on their geochemical features: Series A and Series B. Series A are more alkalic, more trace element enriched and more isotopically depleted than Series B. Series A includes nephelinite, aegirine–nepheline syenite (ANS), and syenite porphyry (SP), whereas the Series B consists of clinopyroxenite, gabbro, diorite, hornblende-bearing syenite (HS), and quartz syenite (QSN). Dolerites can either belong to Series A or Series B depend on its geochemistry. Kimberlitic rocks are independent of the Wajilitag complex geologically, geochemically, and geochronogically. The temporal sequences of Wajilitag complex would be clinopyroxenite→gabbro→ diorite/syenite→nephelinite. The dolerite can be emplaced later than the syenite but can extend to an earlier period. In contrast to the Tarim basalts, the Wajilitag complex belongs to the second stage of magmatism in the TLIP. The mantle source for the Tarim basalts, the Series B and Series A gradually changed from SCLM-dominated to plume-dominated component. [ABSTRACT FROM AUTHOR]

Zircon is a common accessory mineral in granites. Zircon Hf isotope analysis has been widely applied in the studies of crustal evolution and granite genesis. However, previous studies have demonstrated that zircon can be altered by reacting with fluids. At present, it is poorly known how hydrothermal fluids exsolved from evolved magmas may affect the Hf isotope system of zircon. To address this issue, we carried out a case study by evaluating the U-Pb and Lu-Hf isotope systems as well as trace element analyses on zircons from granites of the Yashan pluton, South China, which is well-known for the Nb-Ta ore deposit related to magmatic-hydrothermal activities. Previous geochronological studies indicate that the crystallization and mineralization ages are contemporaneous, at ca. 150–160 Ma. The hydrothermal fluids that are responsible for hydrothermal alteration and mineralization were exsolved from late evolved magmas. Based on micro-textures and trace element compositions, zircon in these rocks can be categorized into three types: magmatic, early hydrothermally altered, and lately hydrothermally altered. Magmatic zircons in these rocks are characterized by typical oscillatory zones in CL images, crystalline zircon bands in Raman spectrum, high major element concentrations (32.5 wt% SiO 2 and 61.6 wt% ZrO 2), and steeply increasing chondrite-normalized REE patterns from La to Lu with positive Ce anomalies. Early altered zircons display inward-penetrating dendritic dark zones and cracks in BSE images. Furthermore, these zircons have flat LREE patterns, redshift and wide Raman characteristic peaks, suggestive of fluid influence. Lately hydrothermally altered zircons are distinguished by four types of secondary textures: featureless domains, porous domains with abundant inclusions, irregular patchy reaction zones and domains containing both pores and patchy reaction zones. They have disturbed U-Pb dates, disappeared Raman characteristic peaks, relatively lower major element concentrations and higher trace element concentrations relative to the magmatic zircons. The lately altered zircons were formed by coupled dissolution-reprecipitation and diffusion-reactions. Magmatic zircons have largely varied ε Hf (t) values (at 150 Ma) of −10.5 to −1.2 (mean = −7.4) and the first and third quartiles (Q1 and Q3) of −8.4 and − 6.7. Such a variation could be related to incremental assembly of distinct magma batches with different isotopic compositions from the heterogeneous magma sources. Similarly, lately hydrothermally altered zircons have largely varied ε Hf (t) values of −9.4 to −3.7 and − 12.2 to 1.3 for different samples. We speculate that the large Hf isotope variations of this zircon type were inherited from heterogeneous magmas. It indicates that even if melts in the late periods of magma evolution are rich in fluorine and thus can efficiently transport high field strength elements like Hf, the resultant zircons do not have homogeneous Hf isotope compositions as previously suggested. Therefore, the circulation scales and durations as well as the contents of complexing agents may all determine whether Hf isotopes can be homogenized in the later stages of magma evolution. • Zircon from the Jurassic Yashan pluton, South China, was investigated. • Magmatic and hydrothermally altered zircons can be distinguished. • Both types of zircons display largely varied Hf isotope compositions. • Hydrothermal solutions may not necessarily homogenize Hf isotope system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Textural and chemical features of beryl can trace magmatic-hydrothermal evolution. • Cs in beryl is an ideal trace element to monitor the magmatic evolution. • Fluid exsolution can promote the remobilization of Ta and Rb. In the large Shihuiyao Rb-Nb-Ta-Be deposit, a beryl-bearing granite was identified with three texturally different zones that show an increasing degree of fractionation, including the albite granite (bottom zone), albite granite with pegmatite pockets (intermediate zone), and intercalation of granite and pegmatite layers (top zone). Beryl occurs both in the intermediate and top zones. Microtextural (SEM), Raman spectra, and trace-element (LA-ICP-MS) data on beryl from these zones shed new light on the behavior of trace elements during magmatic-hydrothermal evolution. In the intermediate zone, magmatic beryl (Brl-1) has a homogeneous texture, while beryl in the top zone (Brl-2) can be divided into magmatic (Brl-2a) and metasomatic subtypes (Brl-2b). The magmatic Brl-2a shows oscillatory zonation, whereas the metasomatic Brl-2b is darker in BSE images and highly porous. Fractional crystallization led to an increase in Na, Sc, Fe, Rb, and Cs contents from Brl-1 to Brl-2a. Comparing these data with those of beryl in other pegmatites worldwide reveals that Cs in beryl is an ideal trace element to monitor the magmatic evolution of the pegmatite host. Distinct textural and chemical features of Brl-2a and Brl-2b reflect metasomatic alteration by a dissolution-reprecipitation process for Brl-2b. In combination with published experimental and fluid inclusion data, we propose that metasomatic fluids exsolved from the magma during late-magmatic stages could transport large amounts of rare metals, such as Ta and Rb. The higher content of Ta in Brl-2b compared to Brl-2a suggests that metasomatic fluids exsolved from the magma play a favorable role in Ta mineralization. In contrast, decreasing Rb contents in Brl-2b is attributed to the high mobility of Rb in the fluid. Such Rb-rich fluids are expected to generate Rb orebodies of economic value surrounding the ore-bearing granite, implying that more investigation into hydrothermal Rb mineralization in the Shihuiyao district is warranted. [ABSTRACT FROM AUTHOR]

Volcanism provides a reliable record of local and global tectonic events and substantially influences both modern and ancient environments, climates, and the evolution of life. The Ordovician–Silurian (O–S) transition is a special period because intensive volcanism occurred globally, including in the Yangtze region of South China. Volcanic events during this period are a symptom of plate tectonic behaviour and are thought to be responsible for the remarkable changes in climate in the early Palaeozoic, though the relationships between these events remain unclear and controversial. Coeval igneous rocks and volcanic sediments (VS) are primarily used to resolve this issue. However, limited studies have been performed on VS from the O–S transition in South China. Recently, a typical VS-bearing section was found in the Lower Yangtze region, which contains ∼100 thin, interbedded volcanic ash layers across the O–S transition. Detailed petrographic and geochemical analyses of the volcanic ashes were conducted to determine their isotopic ages, magma sources, evolutionary processes, and tectonic settings. Our preliminary results suggest that volcanic eruptions in South China lasted for more than 22 Ma across the O–S boundary, from ∼449.3 ± 3.6 to 427.6 ± 4.1 Ma, where 445.14 Ma is the lowermost graptolite biozone for Metabolograptus extraordinarius , as well as the initiation of the Late Ordovician mass extinction (LOME) event in the Yangtze region. The evolutionary history of the parental magma was constructed from a depleted mantle source in the early stage and from a crustal source in the late stage, with several transitional features in the middle. The mantle source and arc-related geochemical indicators for the volcanic ashes support the disputed "subduction-collision orogeny" model. We propose that the strong volcanism in South China, accompanied by volcanism in numerous other regions worldwide, was an important trigger for the LOME and was likely responsible for oceanic 87Sr/ 86Sr fractionation and other climatic changes during the O–S transition. • Ash layers reveal that volcanism in the Yangtze region lasted for ∼22 Ma across the O–S. • Volcanic evolution was characterised by two stages from mantle to crustal sources. • Mantle-sourced and arc volcanism supports subduction-collision in South China. • Global subduction-related volcanism may have decreased oceanic 87Sr/86Sr and triggered the LOME. [ABSTRACT FROM AUTHOR]

The Junggar orogenic collage in Central Asia is characterized by the accretion of multiple Paleozoic intra-oceanic arc terranes developed within the Junggar Ocean, yet magmatic records relating to the construction of these ancient oceanic arcs are largely disrupted. Here, we report new petrological and geochemical data of mafic-ultramafic rocks documented from the Early Cambrian Saleinuohai ophiolitic mélange in southern West Junggar. The mafic rocks include dolerites and basalts, which show geochemical features (e.g., lower TiO 2 and Zr relative to MORB, depleted LREE, and high ε Nd(t)) resembling those of forearc basalts from the Izu-Bonin-Mariana arc. Thus, they may represent the upper section of newly-accreted oceanic crust formed during subduction initiation, upon which a nascent arc is soon built. In contrast, the ultramafic rocks include dunite, wehrlite, and clinopyroxenite, which display cumulate textures with a crystallization order of olivine-clinopyroxene-plagioclase. Similar cumulate sequences are commonly observed in island-arc environments, presumably crystallized under a relatively hydrous and high-pressure condition. The calculated equilibrium melts for these cumulates further resemble those adakitic rocks previously reported from the Saleinuohai ophiolitic mélange. Thus, they may represent the basal section of mature island arc crust that formed during intracrustal fractionation. Our data, together with previous results, provide a complete magmatic record of the development of an Early Cambrian intra-oceanic arc within the Junggar Ocean. • Forearc basalts from West Junggar ophiolitic mélanges indicate subduction initiation. • Ultramafic cumulates from the same mélanges represent the basal part of a mature arc. • A complete magmatic record of an Early Cambrian intra-oceanic arc was described. [ABSTRACT FROM AUTHOR]

Understanding the enrichment of heavy rare earth elements (HREE) and high HREE/LREE (light REE) ratios in the granites is critical to understand the ore-genesis of exclusive ion-adsorption HREE deposits in South China. In this study, we conducted geochronological, whole-rock and apatite geochemical, and isotopic studies on the Xinfeng pluton, of which only parts show high HREE/LREE ratios and are ore-related. Both the ore-related granite and ore-unrelated granite from the Xinfeng pluton are characterized by high SiO 2 contents, the same Late Jurassic age (ca. 155 Ma), and enriched Nd isotopic compositions. However, the ore-related granite has lower TiO 2 , CaO, P 2 O 5 , Fe 2 O 3, Ba, Sr, Eu, and LREE contents, lower La/Yb, Zr/Hf and Th/U ratios, higher Rb, Cs, Nb, Ta, Pb, and HREE contents, and higher Rb/Sr ratios than the ore-unrelated granite. These features indicate that the ore-unrelated and ore-related granite are cogenetic and their geochemical differences can be explained by magmatic differentiation. The primary igneous apatite from both the ore-unrelated granite and ore-related granite shows negligible hydrothermal alteration. Fractional crystallization of feldspar (∼20%) and allanite (< 0.3%) led to higher HREE contents and HREE/LREE ratios, lower Sr contents, and a more pronounced negative Eu anomaly in the apatite from the ore-related granite. This study highlights that the magma evolution via mineral fractional crystallization could achieve the relatively high HREE contents and HREE/LREE ratios in the granites, and favors the formation of exclusive ion-adsorption HREE deposits in South China. • The ore-unrelated and ore-related granites are cogenetic Jurassic granites. • ∼20% feldspar and < 0.3% allanite fractionation crystallization occurred. • The igneous apatite without hydrothermal alteration records the HREE enrichment. • High HREE/LREE ratios achieved by magmatic differentiation. [ABSTRACT FROM AUTHOR]

Abstract: Zircons can retain a grain-scale record of granitoid compositional evolution that is accessible through microanalysis. In situ U–Pb, Hf and O isotope data yield new insights into the petrogenesis and evolution of the Neoproterozoic strongly peraluminous granitoids of the Jiangnan orogen (JO), southern China. A negative correlation of Th/U versus δ18O is found for most analyses. Some zircons from eastern JO granitoids show δ18O variations of 3–6‰ from core to rim, indicating a dramatic shift toward higher oxygen isotope values by voluminous partial melting of supracrustal rocks and signaling a transition from I-type-like to S-type-like magmas during the later stage of magmatic evolution. This mechanism provides a reasonable explanation why some granitoids have intermediate geochemical features between S-type and I-type granites. Hf isotope trends indicate that a larger proportion of mature continental crust was incorporated into the magma sources of the western JO granitoids, whereas more juvenile arc crust was incorporated into the eastern JO magmas. No significant depleted mantle-derived mafic magma was injected into the JO granitoid magmas. Instead, radiogenic Hf and Nd signatures in JO granitoids reflect incorporated juvenile arc crust and document crustal growth in southern China during the Early Neoproterozoic (ca. 900Ma). Thus, our zircon data suggest that strongly peraluminous granitoids, which are widely regarded as the products of orogenesis that primarily recycle evolved crust, can also record important information about early crustal growth. [Copyright &y& Elsevier]

The Taohekou Formation is a volcanic-sedimentary terrane formed in the early Silurian in the northern Daba Mountains, China. The volcanic rocks, with dominant alkali basalts and minor mantle xenoliths, are enriched in clinopyroxene phenocrysts. Geochemical analysis shows that the composition of clinopyroxenes from different lithofacies has a close affinity. There is a liner correlation present in composition of clinopyroxenes (including phenocryst, microcrystal and xenocryst) from coarse porphyritic basalts, pillow or fine porphyritic basalts to amygdaloidal basalts. All the clinopyroxenes, except the clinopyroxenes in mantle xenoliths, show a similar pattern of trace elements and REE, which indicates that they are likely products of successive fractional crystallization from cognate magma. Clinopyroxenes in mantle xenoliths, however, are mantle xenocrysts. The crystallization pressure of clinopyroxenes gradually decreases from mantle xenolith, deep-seated xenocryst, coarse porphritic basalts, pillow or fine porphritic basalts, to amygdaloidal basalts, which are 1.92-4.41 GPa, 1.18-2.36 GPa, 1.13-2.05 GPa, 0.44-0.62 GPa and 0.14-0.28 GPa respectively. Calculation results suggest that the primary magma originated from a mantle region deeper than 68 km and stagnates in intervals of 37-68 km, 15-20 km and 5-9 km during its ascent. The alkali basalts are characterized by increasing concentrations of Si and alkaline with the magmatic evolution. Meanwhile, they are markedly enriched in LREE, and the patterns of trace elements and REE are similar to those of oceanic island basalts. [ABSTRACT FROM AUTHOR]

Abstract: Paleocene (55–58 Ma) adakitic andesites from the Yanji area of NE China are subdivided into clinopyroxene andesites and amphibole andesites. Relative to the clinopyroxene andesites, the amphibole andesites contain higher SiO2, K2O and lower MgO, FeOT, Al2O3, CaO, TiO2, Cr, Ni, Sr, Y and Nb, and have evolved Sr–Nd–Pb isotope compositions. Compositional variation between the clinopyroxene andesites and amphibole andesites involves systematic decreases in MgO, Sr/Nd and εNd(t) accompanied by increases in 87Sr/86Sr(i) and 206Pb/204Pb(i), and suggests a role for crustal contamination. The compositional variations recorded in clinopyroxene and amphibole phenocrysts indicate that the primary mantle-derived adakitic magma experienced complex crustal-level processes, including magma mixing, fractional crystallization and crustal contamination or assimilation. The low Na2O contents and adakitic trace element features (high Sr/Y and Nd/Yb) in Mg-rich parts of clinopyroxene phenocrysts, and negative Sr and Eu anomalies in the Fe-rich clinopyroxene cores, suggest that all clinopyroxenes crystallized in equilibrium with little or no garnet, and argues against magmatic evolution involving differentiation of basaltic magmas. Combined mineralogical and geochemical data indicate that the clinopyroxene andesites were generated by magma mixing, clinopyroxene fractionation and limited degrees of crustal assimilation; whereas the amphibole andesites underwent magma mixing, fractionation of clinopyroxene + amphibole +/− plagioclase and higher degree of crustal assimilation. The difference in mineralogical assemblage between the two rock types was influenced by magma temperature, i.e., 900–950 °C for the amphibole andesites and >950 °C for the clinopyroxene andesites. Our results provide the following important constraints on high-MgO adakitic magma (or low-SiO2 adakite) petrogenesis: (1) the primary magma of such adakites is probably produced through melting of slab melt-modified mantle rather than being a slab melt variably hybridized by peridotite: (2) The complex magmatic evolution recorded in the Yanji adakitic andesites suggests that such adakitic rocks are far from melts in equilibrium with mantle, and magmatic process needs to be carefully examined before the petrogenetic or geodynamic significance can be assessed: (3) The perquisites for creating high-MgO or low-SiO2 adakites include slab melt–mantle interaction during oceanic slab subduction and melting of this metasomatized mantle, but this melting event need not necessarily be related in time to the subduction event. [Copyright &y& Elsevier]

• Three episodes of magmatism are firstly recognized in the Qianlishan Complex. • Initiation subduction contributed to the formation of the Ordos arc at 2.3–2.0 Ga. • HP metamorphism and syn -collisional magmatism occurred at 1.97–1.95 Ga. • The post-collisional extension caused UHT metamorphism and magmatism at 1.93–1.91 Ga. This study presents detailed petrology, major and trace element chemistry, Sr-Nd isotope, and in-situ zircon U-Pb dating and Hf-O isotopes on granites from the Qianlishan Complex of the Khondalite Belt in North China. Zircon SIMS U-Pb data indicate three episodes of Paleoproterozoic magmatism at ca. 2.06 Ga, 1.95 Ga and 1.92 Ga. Of those, the ca. 2.06 Ga hornblende monzogranites and fine-grained potassic granites display typical features of A-type granite, represented by metaluminous affinity, high FeOT/MgO ratios (3.29–5.63), and high Ga/Al and Zr + Nb + Ce + Y values with high zircon saturation temperatures (916–1000 °C). Moreover, they have positive zircon εHf values of +0.29 to +5.01 and homogenous δ18O values of 5.11–5.87 ‰, probably derived from the partial melting of calc-alkaline granitoids without addition of supracrustal rocks. The ca. 1.95 Ga garnet-bearing granites contain peraluminous minerals of garnet and muscovite and have high ASI index (>1.1) and δ18O values (7.14–9.18 ‰), indicating S-type granite. Their negative whole-rock εNd(t) values (−2.87 to −2.81) and zircon εHf(t) values (−4.06 to +1.29) suggest a source of ancient supracrustal rocks. The ca. 1.92 Ga coarse-grained potassic granites present metaluminous and magnesian signatures of I-type granite, including low A/CNK and FeOT/MgO ratios. Their negative εHf(t) values (−5.00 to −1.64) and homogenous δ18O values (5.20–6.00%) suggest that the original magma was derived primarily from enriched lower crust. The results, combined with regional geology and previous studies, establish a prolonged magmatic-metamorphic evolution of the Khondalite Belt from subduction to collision, involving ca. 2.3–2.0 Ga subduction-related arc magmatism, ca. 1.95 Ga syn -collisional high-pressure high-temperature crustal anatexis, and ca. 1.92 Ga post-collisional magmatism and synchronous ultrahigh temperature metamorphism. [ABSTRACT FROM AUTHOR]

The destruction of the North China Craton (NCC) culminated during the Early Cretaceous, inducing widespread magmatism and related mineralization in the eastern China. The Shizhuzi magmatic complex (SMC) from the Liaodong Peninsula is typical products of this event, thus could provide important insights on the destruction process. Here, we present petrological, geochronological, and elemental and isotopic geochemical data for the SMC rocks in order to reveal their magma sources, petrogenesis and the possible geodynamic process. The complex comprises quartz diorite, granodiorite, and granite, accompanied with Au, Cu and Mo mineral deposits. Zircon U Pb dating shows that the different rocks were coeval with the formation ages of 129–126 Ma, coincident with the associated mineralization. However, field relations, whole-rock major and trace element contents and isotopic compositions indicate different origin for the quartz diorites and the coeval granodiorites and granites. The quartz diorites are calc-alkaline rocks with high MgO, Mg# and low SiO 2. They are enriched in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depleted in high field strength elements (HFSEs) with significant negative Nb, Ta and Ti anomalies. These geochemical data and the highly enriched zircon Hf isotopes suggest that they were derived from partial melting of enriched subcontinental lithospheric mantle. The granodiorites and granites from the SMC have high SiO 2 and low MgO contents, suggesting that they were derived from crustal sources. These rocks are I-type rocks with high-K calc-alkaline features. Their primary magma originated from the partial melting of basaltic lower crust and experienced fractional crystallization. The ascending mantle-derived magma provided heat for the melting of the crustal rocks. Based on regional geology, the SMC was generated in the extensional setting related to the roll-back of the subducted Paleo-Pacific plate. The concurrent mantle and crustal melting in the formation of the SMC revealed the loss of stability of the cratonic lithosphere, related to the destruction of the NCC during Early Cretaceous. Besides, the emplacement of SMC might also contribute to the formation of contemporaneous Au, Mo, and Cu deposits. • The SMC was formed in the Early Cretaceous and contributed to Mo–Au–Cu mineralization. • The melting of the mantle and crust occurs simultaneously during the SMC formation. • Two stage evolution: quartz diorite (mantle influenced) to granodiorite and granite. • Hornblende, plagioclase and zircon play an important role in the fractionation. • The SMC was formed in an extensional setting related to the destruction of NCC. [ABSTRACT FROM AUTHOR]

The Chating deposit is the largest Cu--Au porphyry deposit in the Xuancheng district of the Middle-Lower Yangtze River Metallogenic Belt. It is associated with three intrusive phases, an amphibole diorite porphyry, an ore-bearing quartz diorite porphyry and a late diorite porphyry. The amphibole diorite porphyry and quartz diorite porphyry are characterized by large ion lithophile element enrichment, depleted high field strength elements, low Yb/Lu and Y/Yb ratios, low εHf(t) (−8.29 to −12.02), εNd(t) (−6.93 to −7.42), and high 87Sr/86Sr (i) (0.705723 to 0.705802), suggesting a source comprised of both subduction-modified mantle- and crust-derived materials. The zircon U--Pb ages of the amphibole diorite porphyry (138.8 ± 3.0 Ma) and quartz diorite porphyry (137.6 ± 3.0 Ma) are consistent with their cross-cutting relationships and within error of the average molybdenite Re--Os age of 136.0 ± 1.3 Ma, suggesting that the Chating porphyry mineralization belongs to the early metallogenic event in the Middle-Lower Yangtze River Metallogenic Belt. Both the amphibole diorite porphyry and quartz diorite porphyry contain high and low Al amphiboles. The high Al amphiboles from the two intrusions show similar ranges of calculated temperatures (842 to 908 °C), pressures (143 to 229 MPa; corresponding to depths of 5.2 to 8.6 km), melt H 2 O contents (2 to 4 wt%), ΔNNO values (0.12 to 0.99), and Mg# (57 to 65), suggesting coeval crystallization in the same magma chamber. The low Al amphiboles with higher Mg# (68 to 75) formed at lower temperatures (711 to 812 °C) and pressures (49 to 89.3 MPa; corresponding depth of 1.9 to 3.4 km). The core-rim textures and abrupt compositional changes of amphibole and plagioclase from the amphibole diorite porphyry suggest that mafic magma was repeatedly injected into the magma chamber. In contrast, the patchy amphiboles and oscillatory zoned plagioclases in the quartz diorite porphyry may result from continuous fractional crystallization of biotite, amphibole, and plagioclase which would have increased the metal content and f O 2 of the residual magma, and resulted in the exsolution of ore-forming fluids. Unlabelled Image • Intrusions and molybdenite in Chating yielded similar ages at ca. 137 Ma. • Both the mantle- and crust-derived magmas contributed to the magma source. • Mafic magma injection caused the emplacement of pre-ore intrusion. • Minerals fractional crystallization is critical to porphyry mineralization. [ABSTRACT FROM AUTHOR]

• Formation of Miaoya carbonatites involving both crystal fractionation and fluid immiscibility. • Both carbonatites and syenites were fractionated from carbonated syenitic magma. • REE enrichment are associated with fractionation processes of parental calcium carbonatite. Carbonatites are well known as economic resources for rare metals, such as rare earth elements (REE) and Nb. However, the origin and evolutionary processes of carbonatites and related silicate rocks as well as the relevant rare metals enrichment mechanism are highly controversial. In this study, we present detailed petrographic observations and geochemical data on the Miaoya syenite-carbonatite complex, which hosts both Nb and REE resources. The Miaoya syenites consist predominantly of K-feldspar, with minor zircon, nioboaeschynite, pyrochlore, and Fe-Ti oxides, and have positive Nb, Ta, Zr and Hf anomalies on primitive mantle-normalized patterns. There are two types of carbonatites at the Miaoya Complex: calciocarbonatites and ferrocarbonatites. Calciocarbonatites consist mainly of calcite, apatite, and biotite, together with allanite, monazite, bastnäsite(-Ce), and parisite-(Ce). Ferrocarbonatites which are the later products of the complex and occur as dykes cutting both calciocarbonatites and syenites, contain ankerite, calcite, apatite, and fluorite, bastnäsite-(Ce), and parisite-(Ce). The carbonatites have lower Nb, Ba, U, Th, and Zr, but higher P, Sr and REE concentrations than the associated syenites. However, both rock types have similar zircon U-Th-Pb ages (430–440 Ma), and nearly identical initial 87Sr/86Sr ratios (0.70325 to 0.70413) and εNd(t) values (2.5 to 3.2), implying that they were derived from a common source of carbonated silicate magmas. A genetic model of combined fractionation and immiscibility is proposed for the Miaoya complex. Fractionation of the carbonated silicate magmas lead to Nb enrichment in syenite and the immiscibility of the parental calcium carbonatite melts when the magmas reached a carbonate saturation level, together with partitioning of P, Sr, and REE into the parental carbonatite melts. During further fractionation of the carbonatite melts, REE components were elevated to economic values in the final ferrocarbonatites. This model can be widely applicable to other alkaline-carbonatite complexes and provides a reasonable explanation for extreme enrichment of rare metals in such rocks. [ABSTRACT FROM AUTHOR]