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Bhilangana granitoid is a batholithic size body exposed in Bhilangana Valley and later thrusted over rocks of Lesser Himalaya. It comprises mylonitized porphyritic granite gneiss, psammitic gneiss, and its variants, containing primary biotite and muscovite, and S-type in nature. Bhilangana granitoid is intruded by basic intrusive. The variation in chemical signatures and associated petrogenetic issues of Bhilangana granitoid are dealt with detailed petrographic, geochemical and mineral chemical study. In the vicinity of basic intrusive, the porphyritic granite gneiss shows enrichment of MgO, whereas its evolved part, psammitic gneiss shows more boron enrichment with the presence of tourmaline nodules surrounded by quartzo-feldspathic rim. The major mineral assemblage in Bhilangana granitoid is quartz–K-feldspar–plagioclase–biotite–muscovite with tourmaline, epidote, zircon, ilmenite, apatite and monazite. The granite is peraluminous with ASI values always >1. Biotite shows variation from Fe-rich siderophyllitic to Mg-rich eastonitic composition, indicating involvement of both Al-rich crustal and Mg-rich mafic sources, inferring source heterogeneity or mixing of felsic-mafic magma. Granitoid melt was buffered below QFM to NNO and partly above HM, indicating a strong reducing to the oxidizing condition of melt. The melt was saturated with the presence of 3.3–6.8 wt.% H2O content. The crystallization temperature of Bhilangana granitoid (TZr) ranges between 697° and 807°C with a solidification pressure of about 2.92–4.31 kbar, implying crystallization at a depth of 8.76–13 km. The presence of greisens assemblage of quartz–mica–tourmaline–epidote, along with the presence of fluorite, is a representative greisens assemblage for Sn–W mineralization. Thus, the Bhilangana granitoid represents the fertile nature and potentiality of Sn–W minerals. Research highlights: Bhilangana granitoid is S-type, peraluminous granitoid, formed by anatexis of crustal material The biotite chemistry reveals the variation in the redox condition and modification in the oxidation state, preserved in the different variant of granite representing the magma mixing or source heterogeneity in protolith. The Bhilangana granitoid has attended the crystallization temperature (TZr) of 697–807 °C under pressure of about 2.92–4.31 kb implying the depth of crystallization of 8.76–13 km. The presence of greisenization favours the potential of Sn–W minerals. The geochemical results shows abnormal enrichment of W and Sn in the Bhilangana granitoid. The Bhilangana granitoid appears to have fertile nature for Sn–W mineral potential. [ABSTRACT FROM AUTHOR]

Occurrence of "ferrian chromites" have earlier been reported from the Mesoarchean chromite deposits in the Boula-Nuasahi ultramafic complex (BNUC) of India. We have investigated the chromitite bodies in the southern part of the BNUC (i.e., Bangur area) with respect to the mode of occurrence, petrography, chemistry and structure of the chromite types. Although morphologically five varieties of chromite ore were found, chemically only three types of chromite can be distinguished based on EPMA analysis. These are: 1) Type I: magnesiochromite [high Cr2O3 (57–65 wt.%), low iron (FeO: 13–17 wt.%), XFe3+: < 0.1 apfu]; 2) Type II: ferrian chromite [moderate Cr2O3 (43–53 wt.%), high iron (FeO: 27–30 wt.%), XFe3+: 0.1 to 0.5 apfu]; and 3) Type III: ferrichromite [low Cr2O3 (19–29 wt.%), very high iron (FeO: 55–67 wt.%), XFe3+: 0.5 to 1.0 apfu]. Stoichiometrically calculated Fe2O3 content is very high in some grains (maximum 47 wt.%). Geochemical discrimination diagrams for the Type I pristine magnesiochromite suggest a dominantly boninitic parental magma. Trace element data obtained from LA-ICP-MS indicate that the Type II chromite has formed from a more evolved magma and is richer in trace elements such as V, Mn, Co, Cu, Pb, Ga, and Nb whereas the Type III ferrichromite shows unusually high Ti and erratic high concentrations of trace elements. Alterations in chromite is noticed in two different thermal regimes: 1) 100–200 °C related to serpentinization of dunite and peridotite rocks where chromite grains show an unaltered core, an intermediate ferrian chromite rim and an outer magnetite rim; 2) 500–600 °C where the entire chromite grain is converted to ferrichromite which can be linked to later intrusion of the Bangur gabbro. While HR-TEM study reveals that all three chromite-types have face-centered cubic structure, Raman spectroscopy indicates that there is a gradual transition of the structural state from normal spinel structure (Type I) through Type II to a fully inverse spinel structure in case of ferrichromite. [ABSTRACT FROM AUTHOR]

Martian poikilitic shergottites are cumulate rocks that can help advance the understanding of magmatic evolution from near the base of the crust (∼10 kbar) to near-surface conditions. Through a comprehensive petrographic and geochemical study, we aim to better understand poikilitic shergottite formation and the evolution in the martian interior. A suite of poikilitic shergottites, including Northwest Africa (NWA) 7755, NWA 11043, NWA 11065, NWA 10618 and Alan Hills (ALHA) 77005, were investigated for their major, minor, and trace element compositions of olivine-hosted melt inclusions (MI). The MI occur within both the early-evolutional stage textural and late-evolution stage textural domains in olivine. Major element compositions of MI indicate fractional crystallization between the early and late-crystallizing domains. Calculated parental melt compositions from these MI data yielded results that also petrogenetically link the poikilitic shergottites with the olivine-phyric shergottite subgroup. Trace element compositions of MI show that the later-crystallizing MI could have undergone open-system processes, such as fluid exsolution. Lutetium-Hf and Sm-Nd isotopic analyses were performed on NWA 7755 and NWA 11043 to constrain their age and source isotopic compositions. Northwest Africa 7755 shows a 176Lu/177Hf crystallization age of 223 ± 46 Ma, which fits into the expected range for enriched shergottites of ∼165 Ma to 225 Ma. A similar crystallization age and 176Lu/177Hf and 147Sm/144Nd source composition of NWA 7755 to the other enriched shergottites suggest that this specimen likely shares a long-lived geochemical source with these samples that has lasted for at least 60 Ma. Northwest Africa 11043 shows scatter throughout the Lu-Hf and Sm-Nd isotopic data, suggesting that this sample is not in isotopic equilibrium. This sample was possibly inherited from high-temperature processes, such as incomplete magmas mixing from a similar, but distinct, source. We conducted in situ U-Th-Pb isotope analyses of Ca-phosphate minerals for NWA 11043 and found an unreliable crystallization age of 59.2 ± 138.4 Ma: phosphates are likely recording the period of shock metamorphism related to the ejection event. Consistent crystallization ages and magmatic histories support previous work that suggest there is a common magmatic system on Mars that is responsible for the formation of enriched shergottites. [ABSTRACT FROM AUTHOR]

Diamondiferous kimberlites occur in the Wafangdian area in the eastern part of the North China Craton (NCC). In order to better constrain their magmatic source and emplacement time, we have investigated apatite from two kimberlites, i.e., the #110 dike kimberlite and the #50 root-zone kimberlite by measuring in situ their U–Pb and Sr–Nd isotopic compositions. The crystallization ages of the #110 and #50 apatites are 460.9 ± 16.8 Ma and 455.4 ± 19.3 Ma, respectively. For the #50 apatite, 87Sr/86Sr = 0.70453–0.70613 and εNd(t) = −2.74 to −4.52. For the #110 apatite, 87Sr/86Sr = 0.70394–0.70478 and εNd(t) = −3.46 to −5.65. Based on the similar distribution patterns of the rare earth elements (REEs) and the similar Sr-Nd isotope compositions of the apatite, it is believed that the #110 and #50 kimberlites have the same source region and the kimberlite magmas in Wafangdian were derived from an enriched mantle source (EMI). The primary magmatic composition has little effect on the emplacement pattern. It is more likely that the geological environment played an important role in controlling the retention and removal of volatile components (H2O and CO2). This led to the different evolutionary paths of the kimberlite magma in the later period, resulting in differences in the major element compositions of the apatite. High Sr concentrations may be associated with hydrothermal (H2O-rich fluid) overprinting events in the later magmatic period; the higher light rare earth element (LREE) concentration of the #50 apatite reflects the involvement of the REE3+ + SiO44− ⇔ Ca2+ + PO43− replacement mechanism. Two emplacement patterns of the #110 dike kimberlite (#110 apatite, low Sr, and high Si) and the #50 root-zone (#50 apatite, high Sr, and low Si) kimberlites were identified via major element analysis of the #110 apatite and #50 apatite. [ABSTRACT FROM AUTHOR]

Phlogopite is a crucial indicator for effectively constraining the magmatic evolution and emplacement mechanism of kimberlite. In this study, samples were collected from the No. 110 kimberlite pipe within diamond belt I and the No. 50 kimberlite pipe within diamond belt II in the southern Liaoning diamond mining area in the eastern North China Craton (NCC). Zonation is highly developed in the phlogopite; the major and trace element compositions of the phlogopite zonation in the samples were analyzed. In this study, phlogopite from the No. 50 pipe kimberlite (#50 phlogopite) zonation is divided into the following components: (1) The cores, low Ti-Cr xenocryst, average Mg# = 90.6, has a resorption structure, the presence of serpentine and talc minerals in low Ti-Cr cores (xenocrysts) can be used as evidence for hydrothermal metasomatism; (2) cores/inner rims (between core and outer rim), high Ti-Cr, it is thought to be related to the assimilation of mantle materials by deep kimberlite magma, average Mg# = 88.2; (3) outer rims, low-Cr/Cr-poor, average Mg# = 82.4, Fe, Al and Ba contents increased, and there was a trend of evolution to biotite composition believed to be related to the metasomatic metamorphism of melt and wall rock during the late magmatic evolution or ascent; (4) rinds, it is characterized by re-enrichment of Mg, rind I (low-Ti-Cr, average Mg# = 88.4), rind II (high-Ti-Cr, Mg# = 88.6), rind II may be formed earlier than rind I. Rind is very rare and has been reported for the first time in southern Liaoning kimberlite. This study was only accidentally found in the outermost part of #50 phlogopite, the Mg-rich feature represents an environment in which oxygen fugacity has increased. The phlogopite in samples from pipe No. 110 (#110 phlogopite) exhibits relatively homogeneous characteristics across different zones and is more enriched in Al and Ba, which is likely the result of mantle metasomatism. Due to its euhedral characteristics and limited composition variation, it is considered that #110 phlogopite is more likely to be derived from direct crystallization from magma than from xenocrysts. In addition, based on the simultaneous enrichment of Al and Fe in phlogopite from the core to the outer rim, pipe No. 50 was determined to be a micaceous kimberlite, while pipe No. 110 more closely resembles group I kimberlites. This paper proposes that successive pulses of kimberlite magma emplacement gradually metasomatized the conduit, and subsequent kimberlite magma ascended along the metasomatized conduit, thereby minimizing the interaction between the later magma and the surrounding mantle lithosphere. [ABSTRACT FROM AUTHOR]

Although the evolution of residual melts in magmatic systems controls their eruptability and ore-forming potential, their compositions are obscured in plutonic rocks by a protracted near-solidus evolution and the absence of interstitial glass. Here, we trace the evolution of residual melt compositions in rocks from the Strontian Intrusive Complex, Scotland, using the trace element chemistry of amphiboles, and titanites which are intergrown with amphibole rims. Laser ablation mapping reveals an abrupt change in certain trace elements in the amphibole rims, with sharp increases in Eu/Eu* and Sr/Y, and decreases in rare earth elements, Ta, Nb, and Ta/Nb ratios. Core-rim variations in these elements in titanite show the same variations as in amphibole, but are more gradual. By reconstructing the crystallisation sequence of the Strontian magmas using textural observations and thermobarometric estimates, we determine that amphibole cores crystallised prior to titanite saturation, but amphibole rims crystallised simultaneously with titanite. Using the trace element composition of the mineral phases and their modal abundance in the rock, with comparison to the whole-rock chemistry, we determine that titanite hosts the majority of the rare earth and high field strength element budget of the rocks. We therefore propose that the onset of titanite crystallisation had a profound effect on the trace element composition of late-stage residual melts at Strontian, which were inherited by the amphibole rims and subsequent titanites. This is supported by Rayleigh fractional crystallisation modelling, which demonstrates that the composition of amphibole rims cannot be explained without the influence of titanite. We therefore show that the saturation of trace element-rich phases in magmas represents a significant geochemical event in the petrogenesis of intermediate to silicic magmas. This has implications for provenance studies that attempt to reconstruct bulk rock compositions from mineral compositions, as the residual melts from which those minerals crystallise can be driven to significantly different compositions from the host magma by late-stage accessory phase crystallisation. [ABSTRACT FROM AUTHOR]

Rubidium is a moderately volatile element with high incompatibility and fluid mobility. Its stable isotopes have great potential in tracing various geological processes. For example, lunar rocks are isotopically heavier than terrestrial ones, suggesting volatile loss by evaporation during or following the formation of the Moon. However, these studies rely on a poorly constrained estimate for the composition of the Earth's mantle and a poor understanding of high-temperature processes which may act to fractionate stable Rb isotopes. It is therefore important to precisely characterize different rock types that sample the Earth's mantle as well as to evaluate the importance of key isotopic fractionation processes. In order to address these issues, we established a high precision analytical method for Rb isotopic measurements using the Nu Sapphire CC-MC-ICP-MS (collision-cell multi-collector inductively coupled plasma mass spectrometer). In addition, we present a series of Rb isotopic data of volcanic rocks from Hekla volcano (Iceland) and MORB (mid-ocean ridge basalt) samples. We show that our method returns a high Rb sensitivity (∼500 V/μg·g−1 for 85Rb) and a long-term reproducibility of 0.03‰ on δ87Rb (the permil deviation of the 87Rb/85Rb ratio from the SRM 984 standard). This method uses a 2 ng/g Rb solution for analyses, allowing us to consume about 10 times less Rb to achieve similar or better precision than previous studies. Using this method, seven geostandards and one synthetic standard return Rb isotopic data consistent with previous work. Twenty-one Hekla volcanic rocks, spanning compositions from basalt to rhyolite, show limited Rb isotopic variation, with δ87Rb values varying from −0.17‰ to −0.07‰, demonstrating that magmatic evolution has an insignificant effect on Rb isotope ratios. A set of MORB samples (n = 15) from different mid-ocean ridges also span a limited Rb isotopic variation, displaying a range similar to the Hekla rock suite (−0.19 to −0.02‰). Combining our new data together with previously reported OIB data gives an average δ87Rb value of −0.12 ± 0.08‰ (2SD, n = 25), representing the current best estimate of the mantle's isotopic composition. Considering the δ87Rb values of the upper continental crust (−0.14 ± 0.01‰, 2SE, n = 73), as inferred from recent measurements of granites, loess and sediments, and assuming this value represents the whole crust, the revised Rb isotopic composition of the bulk silicate Earth (and by extension the bulk Earth, assuming no Rb partitioned into the core) is −0.13 ± 0.06‰ (2SD). [ABSTRACT FROM AUTHOR]

Phlogopite is a crucial indicator for effectively constraining the magmatic evolution and emplacement mechanism of kimberlite. In this study, samples were collected from the No. 110 kimberlite pipe within diamond belt I and the No. 50 kimberlite pipe within diamond belt II in the southern Liaoning diamond mining area in the eastern North China Craton (NCC). Zonation is highly developed in the phlogopite; the major and trace element compositions of the phlogopite zonation in the samples were analyzed. In this study, phlogopite from the No. 50 pipe kimberlite (#50 phlogopite) zonation is divided into the following components: (1) The cores, low Ti-Cr xenocryst, average Mg# = 90.6, has a resorption structure, the presence of serpentine and talc minerals in low Ti-Cr cores (xenocrysts) can be used as evidence for hydrothermal metasomatism; (2) cores/inner rims (between core and outer rim), high Ti-Cr, it is thought to be related to the assimilation of mantle materials by deep kimberlite magma, average Mg# = 88.2; (3) outer rims, low-Cr/Cr-poor, average Mg# = 82.4, Fe, Al and Ba contents increased, and there was a trend of evolution to biotite composition believed to be related to the metasomatic metamorphism of melt and wall rock during the late magmatic evolution or ascent; (4) rinds, it is characterized by re-enrichment of Mg, rind I (low-Ti-Cr, average Mg# = 88.4), rind II (high-Ti-Cr, Mg# = 88.6), rind II may be formed earlier than rind I. Rind is very rare and has been reported for the first time in southern Liaoning kimberlite. This study was only accidentally found in the outermost part of #50 phlogopite, the Mg-rich feature represents an environment in which oxygen fugacity has increased. The phlogopite in samples from pipe No. 110 (#110 phlogopite) exhibits relatively homogeneous characteristics across different zones and is more enriched in Al and Ba, which is likely the result of mantle metasomatism. Due to its euhedral characteristics and limited composition variation, it is considered that #110 phlogopite is more likely to be derived from direct crystallization from magma than from xenocrysts. In addition, based on the simultaneous enrichment of Al and Fe in phlogopite from the core to the outer rim, pipe No. 50 was determined to be a micaceous kimberlite, while pipe No. 110 more closely resembles group I kimberlites. This paper proposes that successive pulses of kimberlite magma emplacement gradually metasomatized the conduit, and subsequent kimberlite magma ascended along the metasomatized conduit, thereby minimizing the interaction between the later magma and the surrounding mantle lithosphere.

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]

We employed MC‐ICP‐MS to measure the mass‐dependent Ca isotope compositions of Vesta‐related meteorites. Eucrites and diogenites show distinct Ca isotope compositions, which is caused by crystallization of isotopically heavy orthopyroxene. The Ca isotope data support a model where the two lithologies are linked, where the diogenites, mainly composed of orthopyroxene crystallized from an eucritic melt. As normal eucrites are the main Ca reservoir on Vesta, their δ44/40Ca values (per mil 44Ca/40Ca ratios relative to NIST 915a) best represents that of bulk silicate Vesta (0.83 ± 0.04‰). This value is different from those of bulk Earth (0.94 ± 0.05‰) and Mars (1.04 ± 0.07‰), suggesting that there exists notable Ca isotope heterogeneity between inner solar system bodies. The δ44/40Ca difference between chondrules and these planets does not support the pebble accretion model as the main mechanism for planetary growth. Plain Language Summary: Calcium is a major, refractory element in solar system, and its mass‐dependent isotope fractionation effect is a robust proxy for probing planetary magmatic evolution and tracing the genetic relationships between solar system materials. We report high‐precision Ca isotope data for the howardite‐eucrite‐diogenite and mesosiderite meteorites, which potentially derive from the asteroid 4 Vesta, to better understand the origin and differentiation of Vesta. Eucrites and diogenites have different mass‐dependent Ca isotope compositions, which is caused by orthopyroxene crystallization from a magma ocean. We have modeled the Ca isotope evolution of this magma ocean and find that eucrites and diogenites can have formed from this melt. Eucrites show similar Ca stable isotope compositions to howardites and mesosiderites, consistent with a mixing model of eucrites and diogenites for howardites and the silicate portion of mesosiderites originating from Vesta. The Ca‐rich eucrites can best represent the Ca isotope composition of bulk Vesta. It shows Earth, Mars, and Vesta do not share a common Ca isotope composition, suggesting their potentially different precursor material. All these planets and asteroids possess different Ca isotope composition from the chondrules formed in the inner solar system, which does not support a chondrule‐rich model for accretion of terrestrial planets. Key Points: Eucrites possess isotopically light Ca than diogenites; the Ca isotope modeling shows they are co‐geneticEarth, Mars, and Vesta do not share a common Ca isotope reservoir, reflecting isotopic heterogeneities in the inner solar systemThe Ca stable isotopes of the planets/asteroids do not overlap those of chondrules, which does not support a chondrule‐rich model for planet accretion [ABSTRACT FROM AUTHOR]

The northern Canadian Cordillera is the most significant tungsten district in North America. Here, high-grade tungsten skarn deposits are associated with small, reduced, high-K calc-alkaline, S-type biotite granite plutons belonging to the 102–96 Ma Tungsten plutonic suite (TPS). A detailed U–Pb–Hf and morphological study of magmatic zircon from plutons in the southern half of the TPS belt was undertaken to better understand magmatic processes leading to the generation of the associated tungsten deposits. Antecrystic zircon from the TPS plutons began crystallizing during a transpressional regime ca. 117 Ma, suggesting the TPS magmas were active for up to 21 Myr prior to their upper crustal emplacement and final crystallization. This prolonged magmatic activity necessitates a magma origin in long-lived, deep crustal magma chambers. Hafnium isotopic compositions in zircon for the southern TPS as a whole form a non-radiogenic, univariate, and relatively wide ranging population (ε Hf i = −17.6 ± 4.5), but U–Pb–Hf trends become apparent when the data are sub-divided into sample groups with similar age, zircon morphology, and geographic location. These evolutionary trends in magmatic zircon are most simply explained by interactions between the parent melt and dissolving inherited zircon grains. This, along with changing zircon morphology, is consistent with gradual cooling and crystallization pathways exhibited by S-type magmas. Differing evolutionary trends in the U–Pb–Hf isotopic data between sample groups, however, suggest there were multiple magma batches that evolved independently, possibly in separate pockets within large, deep magma chambers. Zircon morphologies also suggest some grains in all sample groups were equilibrated with hotter and more alkaline magmas, although there is no textural or compositional evidence in the zircon for mixing of magmas with widely different compositions. An unconstrained inversion of local aeromagnetic data indicates reduced batholiths could be present 4–6+ km below the surface and that the plutons are apophysies to (or, higher level injections from) these deeper bodies. Although these batholiths can only be short-term holding chambers for magmas ascending from deep crustal levels, they may have been important for the segregation of mineralizing fluids. Since no single magmatic evolutionary pattern in the unaltered TPS plutons can be definitively linked to tungsten mineralization, pulses of mineralizing fluid may have been derived instead from the underlying batholiths. The 20+ Myr duration of deep magmatic activity exhibited by the TPS is similar to timeframes suggested for magmas associated with tungsten deposits in southern China, and may have allowed extended fractionation of a large volume of crustally derived magma to concentrate tungsten into late-stage melts. The emplacement of upper crustal batholiths and plutons in both regions during or following a transition to an extensional tectonic regime suggests the relaxed geodynamic regime may have been important in the ascension of metal-rich magmas and (or) fluids, ultimately resulting globally important tungsten deposits. [Display omitted] • Magmatic activity began 21 Myr prior to pluton emplacement and mineralization. • The plutons are late-stage magmas sourced from deep crustal magma chambers. • Individual intrusive phases were derived from separately evolving magmas. • Magma evolution was complex, as evidenced by the lack of systematic patterns. • No U–Pb–Hf–morphology pattern is definitive for associated mineralization. [ABSTRACT FROM AUTHOR]

Abstract We employed MC‐ICP‐MS to measure the mass‐dependent Ca isotope compositions of Vesta‐related meteorites. Eucrites and diogenites show distinct Ca isotope compositions, which is caused by crystallization of isotopically heavy orthopyroxene. The Ca isotope data support a model where the two lithologies are linked, where the diogenites, mainly composed of orthopyroxene crystallized from an eucritic melt. As normal eucrites are the main Ca reservoir on Vesta, their δ44/40Ca values (per mil 44Ca/40Ca ratios relative to NIST 915a) best represents that of bulk silicate Vesta (0.83 ± 0.04‰). This value is different from those of bulk Earth (0.94 ± 0.05‰) and Mars (1.04 ± 0.07‰), suggesting that there exists notable Ca isotope heterogeneity between inner solar system bodies. The δ44/40Ca difference between chondrules and these planets does not support the pebble accretion model as the main mechanism for planetary growth.

The Laiyuan complex in the central North China Craton (NCC) incorporating different magmatic suites offers an excellent opportunity to investigate the lithospheric evolution and cratonic destruction. However, the petrogenesis and tectonic implications of this magmatic suite remain debated due to lack of integrated studies. Here we evaluate the magmatism and tectonic setting assembling data from multidisciplinary investigations of the Laiyuan complex. The complex is composed of volcanic suites, granitoids, ultramafic-mafic intrusions, and dykes showing common features of enrichments in LREEs and LILEs and depletions in HFSEs. Detailed petrogenetic considerations suggest that crust-mantle and lithosphere-asthenosphere interactions contributed to the formation of various magmatic suites. The involvement of thickened lower crust and enriched lithospheric mantle in the source, and diverse magmatic processes including partial melting, fractional crystallization, and magma mixing have played a significant role in the petrogenesis of the Laiyuan complex. Furthermore, the lithosphere-asthenosphere interaction induced by thinning lithosphere and upwelling asthenosphere controlled the source variations from dolerites to lamprophyres. The complex formed in an extensional tectonic setting triggered by the subduction of the Paleo-Pacific Plate. The subduction, rollback, and stagnation of the Paleo-Pacific slab contributed to the modification of the lithospheric architecture of the North China Craton. A slow and gradual thermal-mechanical erosion occurred at the central North China Craton whereas the rapid and intense lithospheric delamination occurred at the eastern North China Craton contributing to different lithospheric evolution. Both of the mechanisms combined with the subduction of Paleo-Pacific slab played a significant role in the destruction of the North China Craton and the formation of various magmatic suites. An integrated model is proposed to describe the magmatic evolution of the Laiyuan complex. During Jurassic, the subduction of the Paleo-Pacific Plate reached beneath the central North China Craton. At 145–140 Ma, the fast slab rollback occurred and lead to hot asthenosphere upwelling and extensional setting in the central North China Craton inducing the crust-mantle interaction accounting for the petrogenesis for the formation of granitoids with MMEs (137–126 Ma), volcanic rocks (131–127 Ma), and felsic dykes (131–127 Ma). Through time, the lithosphere became substantially thin with the asthenospheric input increasing to form dolerite dykes at 125–117 Ma and lamprophyre dykes at 115–111 Ma.

• First detailed temporal record of large igneous province mantle temperatures. • Mantle temperatures vary by 120 °C in the earliest 0.5 Ma of LIP magmatism. • A plume origin for the North Atlantic Igneous Province is supported. • Fluctuating mantle temperature impacts the dynamics of the crustal magmatic system. The generation of Large Igneous Provinces (LIPs) is a topic of vigorous debate with competing models variably invoking hot mantle plumes, insulative heating by supercontinents or edge driven convective instabilities. Mantle temperature and its temporal variation during LIP magmatism is key to distinguishing between these different models. This may have important consequences for the dynamics, evolution and tempo of volcano-magmatic systems developed during these periods of intense activity. Despite this, there are currently no detailed stratigraphically constrained studies of mantle temperature through a LIP succession. To address this, we have applied both olivine-spinel thermometry and modelling of primary magma compositions (Monte Carlo PRIMELT3) to constrain mantle potential temperature through a continuous sequence of LIP lavas formed during the earliest expression of the North Atlantic Igneous Province (the Antrim Lava Group). Mantle potential temperature derived from olivine-spinel and olivine addition methods give consistent temperature ranges of 1403–1521 °C and 1374–1472 °C, respectively. However, both temperature records indicate significant (100–120 °C) variation in melting temperature over a relatively short stratigraphic interval during petrogenesis of early magmas and much less variation in later magmas, suggesting initial instability or pulsing which stabilised with time. This supports a plume origin for LIP formation. Variability in melting temperature is mirrored by proxies for crustal and volcanic processes; olivine Ni contents are elevated (<3000 ppm) in the same stratigraphic interval as the lowest mantle temperatures, indicating mixing of primary and more evolved (MgO ∼4 %) melts, resulting from low magmatic flux into the crust during this time interval. The abundance and thickness of red weathering horizons capping lava flows is also significantly higher through the succession where mantle temperature variation is highest, indicating prolonged repose periods between eruption and a stop-start rhythm to volcanism. These unique observations indicate that volcanic, crustal and mantle systems are intrinsically linked and suggest that the tempo of volcanism, mediated via variations in melt flux, may ultimately be driven from below by changing mantle temperature. [ABSTRACT FROM AUTHOR]

Mangling granitic pluton is located between Heigou-Luanchuan fault and Qiaoduan Waxuezi fault in North Qinling. It is a magmatic complex formed by 3 stages of magmatic intrusion, including pyroxene-bearing biotite diorites, monzogranites and biotite syenogranite from early stage to late stage. Based on detailed field survey and petrographic observation, the mineralogy and Sr-Nd-Hf isotopes of the first two rocks in Mangling granitic pluton were systematically studied. The results show that Mangling granite pluton is mainly I type granite; from early stage to late stage ( pyroxene-bearing biotite diorites--+ monzogranites --+ biotite syenogranites), the petrogenetic type of granite has a tendency of changing from I type to I-A transitional type; the biotites from the first two rocks are formed in high oxygen fugacity, and their crystallization temperatures are 675 ·c -7 40 ·c and 550 ·c - 675 ·c, respectively; Mangling granite pluton is a mixture of felsic magma formed by partial melting of ancient crust and mafic magma possibly derived from mantle. [ABSTRACT FROM AUTHOR]

Enclaves constitute a key tracer guide to assess the magmatic source and evolutionary processes of Cu–Mo–Au porphyry-type deposits. In this study, four types of enclaves were identified in the Baogutu reduced Cu porphyry-type deposit, West Junggar, Northwest China: gabbroic enclaves (Type 1) and schist enclaves (Type 2) are proposed to be restites and immiscible enclaves, respectively, which confirm the contributions of mantle components and sediments in the reduced Cu porphyry-type deposit. Fine-grained dioritic enclaves (Type 3) have a similar mineral composition and texture to the dioritic host rocks, which are probably autoliths derived from inhomogeneous fractional crystallization. Tuffaceous siltstone enclaves (Type 4) with a zircon U-Pb age of 339.2 ± 7.5 Ma (MSWD = 0.55), the formation age of which is in agreement with the host early Carboniferous rock unit, indicate that these tuffaceous siltstone enclaves might have formed in a contamination process. Moreover, the schist enclaves, together with the newly discovered 2691.3 ± 12.3 Ma inherited zircon in tuffaceous siltstone enclaves, further indicate that the Baogutu arc could be a continental arc. [ABSTRACT FROM AUTHOR]

Iranian porphyry copper deposits (PCDs), resulted from the evolution of Neo–Tethys Ocean during the Mesozoic and Cenozoic, dominantly distributed in the five main tectono-magmatic belts that meanwhile the Kerman Porphyry Copper Belt (KPCB) is the most famous and important belt in the south of Iran while the Lut Block is the oldest and modern known porphyry belt in eastern Iran. PCDs of the KPCB (+Najmabad; group 1) hosting moderate to giant world-class deposits belong to the Oligocene–Miocene. On the other hand, PCDs of the Lut Block (except Najmabad; group 2) formed during the Eocene–Oligocene, are mostly subeconomic to barren. Despite the similarities in tectonic setting, host rock composition, hydrothermal alteration zones, and mineralization type, there are significant differences in geochemical characteristics (depression in MREE/HREE pattern (group 1) vs. horizontal trend (group 2), Sm/Yb greater than 2.4 (group 1) vs.

The origin of the KREEP (K, Rare Earth Element and P)-rich component of the Mg-suite rocks of the Procellarum KREEP Terrane (PKT), one of three major lunar crustal terranes, is unclear. In an attempt to determine its origin, we estimated the composition of host magmas of plutonic rocks, including Mg-suite rocks and evolved rocks, from the PKT (PKT-host magmas) by using secondary ion mass spectrometry analyses of plagioclase. Calculated partition coefficients for Sr, Ba and Ti between plagioclase and melts, taking into account the anorthite content of plagioclase, temperature and bulk rock major-element compositions, were applied to determine parental magma compositions. The PKT-host magmas contained 160–360 ppm Sr, 520–7600 ppm Ba and 1.1–7.0 wt.% TiO 2 ; most of them had higher Ti and Ba concentrations than KREEP basalts and high-K KREEP. We used phase relations based on the Rhyolite-MELTS algorithm to explore the evolution of the PKT-host magmas and KREEP basalts from two bulk silicate moon (BSM) starting compositions, a BSM with chondritic ratios of refractory elements, and a crustal-component-enriched BSM with non-chondritic ratios of refractory elements. We propose a three-stage evolution model. Stage-1: polybaric multi-step fractionation from a BSM magma to form ferroan anorthosite (FAN) crust and an evolved magma as the first KREEP-rich component (M 0). Stage-2: assimilation and fractional crystallization (AFC) of M 0 , early cumulate and FAN associated with deep mantle overturn and impact events to form the PKT-host magmas, Mg-suite rocks and an evolved magma as the second KREEP-rich component (K 0). Stage-3: further AFC cycles of K 0 , Mg-suite rocks or FAN associated with shallow mantle overturn and impact events to form KREEP basalts. This three-stage model for a crustal-component-enriched BSM with non-chondritic ratios of refractory elements (e.g., a sub-chondritic Ti/Ba ratio) reproduced the compositions of both the host magmas of FAN and the PKT-host magmas that fractionated to form the Mg-suite rocks and KREEP basalts of the PKT region. In particular, the model reproduced the high Ti and Ba contents of the PKT-host magmas we estimated from plagioclase composition. Variations of TiO 2 and Ba contents (and hence Ti/Ba ratios) of the magmas were critical controls on their evolution. [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]

Late Cretaceous felsic volcanism erupted as calderas in the terminal stage of the massive Cretaceous volcanism in SE China. This paper reports comprehensive geochemical and isotopic data for high-silica rhyolites from the Shiniushan and Xiaoxiong calderas in eastern Fujian–Zhejiang provinces, SE China. Zircon U-Pb dating constrains these rhyolites eruptions to 94–92 Ma and 93–89 Ma in the sites of the two calderas. All the samples possess high-silica contents with peraluminous characteristics and are enriched in light rare earth elements (LREEs), Rb, and Th-U and depleted in Ba, Nb-Ta, Sr and Eu. These samples have high whole-rock F (114–596 ppm) but low Cl (3.3–54.8 ppm) contents. Apatite minerals separated from the high-silica rhyolites are classified as fluorapatite and show F-rich (F > 3.56 wt%), Cl-poor (Cl < 0.02 wt%), low (La/Sm) N and high (Gd/Yb) N ratios, with a negative Eu anomaly. The high-silica rhyolites yield initial (87Sr/86Sr) i ratios of 0.70405 to 0.70789, negative whole-rock ε Nd (t) (−3.3 to −6.3), negative apatite ε Nd (t) (−5.2 to −6.6) and negative zircon ε Hf (t) values (−0.1 to −9.6). Our data suggest that their primary magma was derived from modified crustal sources that could contain a mixture of ancient and juvenile components, and it then evolved, was injected into a low-pressure magma chamber, and finally erupted with the release of volatiles at the magma chamber roof. We infer that SE China was mainly under a setting of lithospheric extension from the Early to early Late Cretaceous because of slab roll-back and steepening of the subducted Paleo-Pacific Plate. [Display omitted] • High-silica rhyolites erupted on Xiaoxiong and Shiniushan calderas at 94–89 Ma. • Crustal sources were modified by magmatic underplating beneath SE China. • High-silica lavas erupted at low-pressure magma chamber with F-rich and Cl-poor. • Paleo-Pacific slab roll-back induced Late Cretaceous extension and volcanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • Permo-Triassic magmas record the process of accretion in the eastern CAOB. • Seismic tomography indicates the southward subduction of the Paleo-Asian Plate. • Terrane accretion is the driving mechanism of accretionary orogenesis in the CAOB. The amalgamation of accretionary terranes plays an important role in the evolution of ancient accretionary orogens, but the kinematic process and its driving mechanism are commonly ambiguous. Here we provide new constraints on the accretion kinematics and associated driving mechanism of the eastern Central Asian Orogenic Belt (CAOB), using seismic tomography and magmatism. Permian to Middle Triassic magmatism was linked to two distinct accretionary orogens, that existed along the northern margin of the North China Craton. The geochemistry of middle Permian to Middle Triassic igneous rocks indicates a magmatic arc origin at an active continental margin. Based on the horizontal zoning of magmatism and south-dipping stagnant oceanic slab imaged by seismic tomography, we conclude that southward subduction of the oceanic slab resulted in the accretion and collision of multiple arc systems along the continental margin. Our seismic tomographic models indicate that formation and growth of the eastern CAOB occurred as the result of the continuous accretion and amalgamation of arc assemblages with addition of crustal material. Tomographic models and previous Re-Os geochronological studies indicate the existence of a deep crustal root and ancient sub-continental lithospheric mantle in most regions of the eastern CAOB. Taking into account the magmatic evolution and sedimentary sequences, we conclude that the terrane accretion should be the driving mechanism of accretionary orogenesis in the eastern CAOB. [ABSTRACT FROM AUTHOR]

The compositional variability of ocean island basalts (OIBs) is thought to reflect partial melting of a lithologically-heterogeneous mantle source dominated by either pyroxenite or peridotite. The Pohnpei Island in Micronesia, which is associated with the Caroline hotspot, is suggested to have been generated from partial melting of a pyroxenite-rich mantle. To examine this hypothesis, we present new major- and trace-element compositions of olivine phenocrysts in basalts from the island. The olivines exhibit large systematic inter- and intra-crystalline compositional variability. In Sample DS1, olivines record compositional zonation, in which cores have relatively high Fo (77–85), Ni (550×10−6–2 392×10−6), and Fe/Mn ratios (66–82), whereas rims have lower Fo (71–78), Ni (526×10−6–1 537×10−6), and Fe/Mn ratios (51–62). By contrast, olivines within other samples preserve no clear compositional zonation, exhibiting similar or slightly lower Fo values (66–78), Ni contents (401×10−6–1 268×10−6), and Fe/Mn ratios (53–69) as the rims of zoned crystals. The distinct chemical contrast between the two different types of olivine suggests they formed in magma chambers at different depths. Analysis using forward petrological modeling and multi-element indicators (Fe/Mn, Zn/Fe, FC3MS (FeOT/CaO-(3×MgO/SiO2)), Mn/Zn, and Ni/(Mg/Fe)) of whole-rock samples and high-Fo olivines is inconsistent with a pyroxenite-rich mantle source. We suggest these inconsistencies reflect an influence on the partition coefficients of Ni and Mn between olivine and liquid during melting at variable pressures and temperatures. In addition, magma recharge and mixing within the magmatic plumbing system can change the composition of olivine. We suggest that identification of the mantle source of OIBs in volcanic islands such as the Pohnpei Island using olivine geochemistry should be treated with caution. [ABSTRACT FROM AUTHOR]

La Chinchilla granite (∼3.75 km2) is an epizonal pluton intruded during the Lower Carboniferous in Sierra de Velasco, Sierras Pampeanas, northwestern Argentina. Three facies have been distinguished in the pluton (equigranular, porphyritic and fine-grained border zone facies), being equigranular and porphyritic the main two granite types, which host abundant millimeter to < 2 m sized miarolitic pegmatites and pockets of simple granitic mineralogy (quartz + albite + microcline + micas) ± beryl. Micrometer-sized accessory magmatic species are monazite-(Ce), several high field strength element oxide species, ilmenite, cassiterite (1), fluorapatite and fluorite. Primary Li-bearing micas with variable degrees of late to postmagmatic replacement occur in abundances that range from ∼2 to 7 %. Textural evidence and mineral chemistry allow to distinguish between early granitic and late bladed miarolitic micas. The mineral chemistry composition of the primary micas shows members of the siderophyllite-polylithionite series. Replacing phases are Li-muscovite (phengite). Electron probe microanalyses of primary micas of both main granite types suggest that these are compositionally distinct intrusives. According to mica chemistry, the porphyritic unit is more enriched in Li than the equigranular granite. The equigranular unit with interconnected miarolitic texture was more intensely affected by fluid-rock interaction processes and is significantly richer in U and Be. An F–Na rich fluid phase caused strong albitization during late miarolitic stages, along with crystallization of polylithionite, fluorite, pyrochlore group species and cassiterite (2). In terms of mass balance, the phengite replacement process is characterized by the conservation of Si, Al and K, a slight gain of Na and Ba, and a systematic loss of orderly decreasing Fe > F > Li > Mn > Ti > Mg > Zn. Likely, the muscovite-forming fluid was the same simultaneously involved in the hydrothermal alteration of high field strength element accessory species, largely included in primary micas, which generated secondary U- and Nb-rich species such as carlosbarbosaite. The hydrothermal late miarolitic to postmagmatic fluid-mineral replacement of primary magmatic micas released significant amounts of Li, of which about 59 wt % of the Li 2 O content of protholithic micas (i.e., 1 to 2.4 wt % Li 2 O) was inherited by replacing Li-bearing muscovite and the remaining 41 wt % was released from the system. It is calculated that ∼1.5 km3 of La Chinchilla body would have expelled ∼0.38 million tons of Li 2 O, just considering than only 30 % of primary siderophyllite-polylithionite was muscovitized. Such a Li 2 O tonnage was likely transferred to the paleohydrological cycle during Carboniferous times, when the La Chinchilla stock was still undergoing its cooling down path. Currently, evidence of the final fate of mobilized Li is lacking. • Mineral chemistry of magmatic Li-Fe micas from two likely synmagmatic granite units suggests different melt compositions. • Phengitization of magmatic siderophyllite - polylithionite micas is an effective postmagmatic process for lithium release. • The phengitization fluid was involved in the breakdown and subsequent mobilization of HFSE from accessory species. • Neoformed phengite can take up part of the original Li 2 O content, but a significant amount is released after replacement. • About 0.38 million tons of Li 2 O were extracted from ∼ 1.5 km3 of granite, likely mobilized into the paleohydrological system. [ABSTRACT FROM AUTHOR]

The Wuhaolai mafic complex is located in the north margin of the North China Craton (NCC), Inner Mongolia. To discuss the mineralogical features, magma evolution process, and tectonic setting of the complex, we analyzed the geochemical compositions of clinopyroxene and hornblende using an electron probe. The results revealed that the parental magma of this complex belonged to the intraplate alkaline basalt series. The normal zoning texture and the relation between Mg# and FeO, Al2O3, CaO, Na2O, SiO2 and Cr2O3 suggested that the clinopyroxenes of pyroxenite and gabbro crystallized from the same parental magma. The similar CaO content of clinopyroxenes indicated that the parental magma of the Wuhaolai complex may have suffered crustal contamination. Furthermore, the characteristics of hornblende demonstrated that the magma source was modified by fluids derived from subducted slab. Based on the value of Kdcpx (0.23–0.27), the equilibrium melt with clinopyroxene exhibited a relatively low Mg# (43–53), indicating that the parental magma was derived from the lithospheric mantle and underwent crystal fractionation. The gabbro crystallization temperature and pressure was found to be lower than that of pyroxenite, indicating that gabbro was formed at a lower depth than that of pyroxenite. Combining the tectonic setting discrimination diagram of clinopyroxene with the results of previous studies on the late Paleozoic intrusions near the research area, we proposed that the Wuhaolai complex was formed in an intraplate environment. The magma source was modified by fluids derived from the subducted slab during the subduction of the Paleo-Asian Ocean (PAO). After the PAO closure, the parental magma of the Wuhaolai complex was produced by the partial melting of the enriched lithospheric mantle

Chemical classifications of granites sensu lato have been developed and revisited over decades, but no classification scheme has been universally accepted yet. The more or less known coupled reasons for this apparently impossible task are reviewed here. The main problem is that different granitoids do not fall in distinct categories with sharp boundaries, but comprise a continuous spectrum of rock types both in their chemical and modal compositions. The unifying factor is the minimum-melt nature of the granites sensu stricto, as primary and evolved melts can have a granitic composition. This minimum-melt nature has two consequences, which are the main reasons for the absence of sharp boundaries in every compositional classification system, either modal or chemical. Firstly, the chemistry of granites spreads from the minimum melt to non-minimum compositions, and thus some granites represent a rock series formed by a continuous magmatic evolution, not by discrete steps; secondly, granite series, which are generated from different sources and by several petrogenetic processes, eventually converge at the most silica-rich compositions. There is a relationship between the tectonic scenarios of formation of granites and the chemical overlap that contributes to the absence of a satisfactory chemical classification: the protracted evolution of the tectonic settings following the Wilson cycle and more complicated scenarios change the chemical and modal composition of the granite sources. The overlap in the most silica-rich compositions of the granites s.l. due to the minimum melt nature may extend to more mafic members in a granite series: the closer the sources are in their composition, the greater is the overlap, becoming a second contribution to the lack of sharp boundaries between granite types. The huge efforts to create a satisfactory chemical compositional classification system have actually led to a significant contribution to granite petrology: the discovery of the main chemical differences between granite types, the main chemical parameters (silica content, alkalinity, aluminosity, maficity or FeOt + MgO content, and the Fe/Mg and Na/K ratios) and the petrogenetic processes that cause the change in these parameters. Therefore, despite the lack of agreement over the 'perfect' classification system, the investigations have not been fruitless: they have led to the realization that non-genetic classifications are preferable to name the individual rock samples; chemical classification schemes should be left to distinguish magmatic suites and to unravel their prospective petrogenesis and geotectonic setting. [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]

Electron microprobe analysis was conducted on plagioclase from the plagioclase ultraphyric basalts (PUBs) erupted on the Southwest Indian Ridge (SWIR) (51°E) to investigate the geochemical changes in order to better understand the magmatic processes occurring under ultraslow spreading ridges and to provide insights into the thermal and dynamic regimes of the magmatic reservoirs and conduit systems. The phenocryst cores are generally calcic (An74–82) and are depleted in FeO and MgO. Whereas the phenocryst rims (An67–71) and the plagioclase in the groundmass (An58–63) are more sodic and have higher FeO and MgO contents than the phenocryst cores. The crystallization temperatures of the phenocryst cores and the calculation of the equilibrium between the phenocrysts and the matrix suggest that the plagioclase cores are unlikely to have crystallized from the host basaltic melt, but are likely to have crystallized from a more calcic melt. The enrichment in incompatible elements (FeO and MgO), as well as the higher FeO/MgO ratios of the outermost phenocryst rims and the groundmass, are the result of plagioclase-melt disequilibrium diffusion during the short residence time in which the plagioclase crystallized. Our results indicate that an evolved melt replenishing under the SWIR (51°E) drives the eruption over a short period of time. [ABSTRACT FROM AUTHOR]

Copper‐gold magmatic‐hydrothermal systems dominate in the Chibougamau area of the Neoarchean Abitibi subprovince (greenstone belt) of the Superior Province (craton), whereas orogenic gold mineralization is more common in the rest of the Abitibi. Understanding differences in metal endowment within the Abitibi greenstone belt requires insights into the geodynamic evolution of the Chibougamau area. This was addressed by imaging the crust using seismic reflection profiling acquired as part of the Metal Earth project. Seismic reflection sections display shallowly south‐dipping reflectors located within the upper crust (e.g., a possible deep continuation of the Barlow fault) and a northward‐dipping midcrust imbricated with older crust (Opatica subprovince) to the north. Multiple reflectors characterize the upper part of the midcrust, interpreted as faults superimposed on a major lithological boundary. These structures likely formed during terrane accretion prior to craton stabilization. Combining the new seismic data with known stratigraphic, structural, and magmatic records, we propose that the study area was initially a normal (i.e., thick) Archean oceanic crust that formed at or before 2.80 Ga and that evolved through terrane imbrication at 2.73–2.70 Ga. Shortening caused rapid burial, devolatilization, and partial melting of hydrated mafic rocks to produce tonalite magmas that may have mixed with mantle‐derived melts to produce the diorite‐tonalite suite associated with observed Cu‐Au magmatic‐hydrothermal mineralization. Key Points: A seismic reflection survey of the Chibougamau area, Abitibi greenstone belt, is performed by the Metal Earth projectThe Metal Earth and Lithoprobe seismic surveys reveal that the northern part of the Abitibi greenstone belt has a consistent architectureThe Chibougamau area is an Archean oceanic crust evolved through terrane imbrication and not through plume activity and subduction processes [ABSTRACT FROM AUTHOR]

According to field observation, the magmatic rocks of Lingshan island are grey-white in colour, with massive structure on the whole, and local stomatal, almond and rhyolite structures. Microscopic observation shows that they mainly have porphyritic texture. The main Phenocryst minerals include plagioclase (20 %), quartz (4 %), alkaline feldspar (3 %) and pyroxene (2 %), which are mostly semi-automorphic or heteromorphic, and the matrix is mainly glassy. The plagioclase number ranges from 23 to 35, belonging to the oligoclase-andesine series, indicating that the magmatic rocks in this area are close to intermediate. The SiO2 content of the magmatic rocks on Lingshan island is 56.54 % - 61.76 % (average: 59.63 %) which gradually increases from north to south. It also can be concluded that the lithology in the study area is a series of intermediate rocks. The analysis of trace element experimental data shows that crustal elements such as Th, Zr, U, Ba and Pb are enriched, whereas incompatible elements such as Nb and Ti are deficient, this indicates that the magmatic rocks originated from partial melting of the lower crust. The rocks have high strontium and low rubidium contents, which indicates that amphibole, garnet and a small amount of potassium feldspar remain in the source area. Finally, from detailed analysis of Nb-Y, Rb-Nb+Y, Al2O3 -TiO2 and Harker diagrams, it is concluded that the magmatic rocks are dacite formed by differentiation in the late stage of lower crust partial melting in an island arc extensional tectonic environment, not the rhyolite formed by eruption mentioned in most literature. In addition, we believe that the magmatic rocks of Lingshan island undergo obvious crystallization differentiation and assimilation-contamination during their ascent, which is based on the consolidation index (SI), n (Rb)/n (Sr), Nb/Ta and (La/Yb) N-Sr/Y maps of rock samples. [ABSTRACT FROM AUTHOR]

We conducted in situ geochemical (major-, trace-element and Nd isotope compositions) analyses on apatite, together with whole-rock geochemistry from gabbro, granodiorite and granite in the Cretaceous Pingtan intrusive complex (SE China), aiming to investigate the roles of magmatic evolution and post-crystallization hydrothermal activity during its formation. Regardless of limited range in initial Nd isotopes ranges in both bulk rock [ɛNd(t) = − 2.0 to − 0.4] and associated apatite [ɛNd(t) = − 3.8 to − 0.4] from the Pingtan igneous complex, the apatite shows wide compositional and textural variations from gabbro to granite. Apatite from the gabbro (Group 1) displays a zoning structure characterized by increasing F and Sr but decreasing Cl and LREE from the core to rim. The increase of Sr from the core to rim is attributed to plagioclase accumulation, and the decreases of LREE and Cl from the core to rim is caused by post-crystallization hydrothermal activity. The high Cl content in the primitive Group 1 apatite further suggests derivation of the mafic magma from a mantle wedge metasomatized by Cl-rich sediment. In contrast, apatite from the granite (Group 2) has the lowest Cl and Sr but the highest F and Yb contents, which can be further divided into two subgroups of Group 2A and 2B based on texture and composition. Group 2A apatite shows homogenous composition with trace elements similar to apatite from I-type granite. The positive correlation between Sr and Eu/Eu* indicates that crystallization of Group 2A apatite is co-precipitated with a feldspar-dominated fractionation. However, Group 2B apatite contains mineral inclusion of monazite and has the highest U content and F/Cl ratio, resembling apatite from S-type or highly fractionated I-type granite. These features are consistent with the influence of post-crystallization hydrothermal activity. Apatite from the granodiorite (Group 3) has an intermediate composition between Group 1 and 2A apatite and shows a homogenous texture with trace element features similar to that from I-type granite. Group 3 apatite defined a negative correlation of Sr with La/Yb, which is attributed to fractional crystallization of hornblende and plagioclase. The geochemistry of apatite indicates that the gabbro and granitic rocks of the Pingtan intrusive complex were, respectively, derived from the mantle and crustal sources with similar ɛNd(t) values. Our study, therefore, demonstrates that apatite geochemistry has a potential to monitor the magma source, magmatic evolution and post-crystallization fluid activity of an igneous complex. [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]

The eastern Jilin and Heilongjiang provinces in China are located at the junction between the Paleo-Asian Ocean and Circum-Pacific metallogenic domains, and have been affected by the temporal transition between these domains and their superposition, resulting in intensive and complicated mineralization events. This paper provides a progress in exploration for, and geological research into, endogenic metal deposits and related magmatite in the eastern Jilin and Heilongjiang provinces. Four richly mineralized areas are recognized: (1) the Lesser Xing'an–Zhuangguangcai Range metallogenic belt; (2) the Jiamusi–Khanka metallogenic belt; (3) the Yanbian metallogenic belt; and (4) the Wandashan metallogenic belt. Four temporal peaks in magmatism and metallogenesis are identified: (1) Hercynian orogenic Au deposits (260–250 Ma) show a close relationship with magmatism related to a transitional syn- to post-collisional tectonic setting; (2) Indosinian orthomagmatic ore deposits (230–210 Ma) show a close relationship to mafic–ultramafic magmatism in a post-collision extensional setting; (3) porphyry Mo deposits and skarn deposits of the Late Triassic to the Early Jurassic (200–170 Ma) formed in a continental arc setting, triggered by slab subduction; and (4) late Yanshanian large-scale mineralization was caused by tectonic extension at 133–106 Ma. Yanshanian felsic magmatism shows clear metallogenetic specialization; i.e. each rock type hosts a different type of deposit. [ABSTRACT FROM AUTHOR]

The Naruo porphyry Cu deposit is the third largest deposit discovered in the Duolong metallogenic district. Previous research has focused mainly on the geochemistry of the ore-bearing granodiorite porphyry; the metallogenesis remains poorly understood. In the present work, on the basis of outcrops and drilling core geological mapping, phases of early mineralization diorite, two inter-mineralization granodiorite porphyries, and late-mineralization granodiorite porphyry have been distinguished. Furthermore, the alteration zones were outlined, and the vein sequence was identified. The diorite and three porphyry phases were subjected to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (La–ICP–MS) zircon U–Pb dating and in situ Hf isotope analyses as well as bulk major element, trace element, and Sr–Nd isotopic analyses. Molybdenite Re–Os dating was also conducted. The zircon U–Pb dating results show that the diorite and porphyry intrusions were emplaced at about 120 Ma, and the molybdenite Re–Os isochron age is 118.8 ± 1.9 Ma; this indicates that the Naruo porphyry Cu deposit was formed during a continuous magmatic–hydrothermal process. All of the diorite and granodiorite porphyry samples showed arc magmatic characteristics. Moreover, the moderate (87Sr/86Sr) i ratios and low ε Nd(t) and ε Hf(t) values of the diorite and porphyry intrusions suggest the source region of the juvenile lower crust. The lower (87Sr/86Sr) i and (143Nd/144Nd) i ratios and higher ε Nd(t) values and incompatible element concentrations than those in the granodiorite porphyry samples indicate a two-stage magmatic generation process for the intrusions. The early mineralization diorite has a high Cu concentration, implying that the source is enriched in Cu. However, the slightly lower Cu content of the late-mineralization granodiorite porphyry samples might imply Cu release from magmas and deposition within the metallogenic stage. The multiple stages of intrusions and subsequent volcanism within the Duolong metallogenic district, together with high Sr/Y features, indicate persistent magmatism during the metallogenic epoch, which is necessary for maintaining the activity of magmatic–hydrothermal and mineralization processes. Thus, the high Cu content in the source region, mantle-derived melt upwelling, and multiple stages of persistent magmatism were favorable for the formation of the Naruo porphyry Cu deposit. The high Fe 2 O 3 /FeO ratios of the diorite and granodiorite porphyry intrusions show very high oxidation features, which is coincident with estimated magmatic oxidation state calculated by the zircon trace element compositions. The high oxidation facilitates sulfur and chalcophile metals to be scavenged into the magmatic–hydrothermal systems, which is crucial for the metallogenesis of the Naruo porphyry Cu deposit. Unlabelled Image • The Naruo porphyry Cu deposit was formed at around 120 Ma. • Ore-bearing intrusions were generated by partial melting of juvenile lower crust. • Large-scale magmatism, high oxidation are crucial for porphyry deposit formation. [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 Dahutang tungsten deposit, located in the Yangtze Block, South China, is one of the largest tungsten deposits in the world. Tungsten mineralization is closely related to Mesozoic granitic plutons. A drill core through a pluton in the Dalingshang ore block in the Central segment of the Dahutang tungsten deposit shows that the pluton is characterized by multi-stage intrusive phases including biotite granite, muscovite granite, and Li-mica granite. The granites are strongly peraluminous and rich in P and F. Decreasing bulk-rock (La/Yb)N ratios and total rare earth element (ΣREE) concentrations from the biotite granite to muscovite granite and Li-mica granite suggest an evolution involving the fractional crystallization of plagioclase. Bulk-rock Li, Rb, Cs, P, Sn, Nb, and Ta contents increase with decreasing Zr/Hf and Nb/Ta ratios, denoting that the muscovite granite and Li-mica granite have experienced a higher degree of magmatic fractionation than the biotite granite. In addition, the muscovite and Li-mica granites show M-type lanthanide tetrad effect, which indicates hydrothermal alteration during the post-magmatic stage. The micas are classified as lithian biotite and muscovite in the biotite granite, muscovite in the muscovite granite, and Li-muscovite and lepidolite in the Li-mica granite. The Li, F, Rb, and Cs contents of micas increase, while FeOT, MgO, and TiO2 contents decrease with increasing degree of magmatic fractionation. Micas in the muscovite granite and Li-mica granite exhibit compositional zonation in which Si, Rb, F, Fe, and Li increase, and Al decreases gradually from core to mantle, consistent with magmatic differentiation. However, the outermost rim contains much lower contents of Si, Rb, F, Fe, and Li, and higher Al than the mantle domains due to metasomatism in the presence of fluids. The variability in W contents of the micas matches the variability in Li, F, Rb, and Cs contents, indicating that both the magmatic and hydrothermal evolutions were closely associated with W mineralization in the Dahutang deposit. The chemical zoning of muscovite and Li-micas not only traces the processes of W enrichment by magmatic differentiation and volatiles but also traces the leaching of W by the fluids. Therefore, micas are indicators not only for the magmatic–hydrothermal evolution of granite, but also for tungsten mineralization. [ABSTRACT FROM AUTHOR]

The Wuhaolai mafic complex is located in the north margin of the North China Craton (NCC), Inner Mongolia. To discuss the mineralogical features, magma evolution process, and tectonic setting of the complex, we analyzed the geochemical compositions of clinopyroxene and hornblende using an electron probe. The results revealed that the parental magma of this complex belonged to the intraplate alkaline basalt series. The normal zoning texture and the relation between Mg# and FeO, Al2O3, CaO, Na2O, SiO2 and Cr2O3 suggested that the clinopyroxenes of pyroxenite and gabbro crystallized from the same parental magma. The similar CaO content of clinopyroxenes indicated that the parental magma of the Wuhaolai complex may have suffered crustal contamination. Furthermore, the characteristics of hornblende demonstrated that the magma source was modified by fluids derived from subducted slab. Based on the value of Kdcpx (0.23-0.27), the equilibrium melt with clinopyroxene exhibited a relatively low Mg# (43-53), indicating that the parental magma was derived from the lithospheric mantle and underwent crystal fractionation. The gabbro crystallization temperature and pressure was found to be lower than that of pyroxenite, indicating that gabbro was formed at a lower depth than that of pyroxenite. Combining the tectonic setting discrimination diagram of clinopyroxene with the results of previous studies on the late Paleozoic intrusions near the research area, we proposed that the Wuhaolai complex was formed in an intraplate environment. The magma source was modified by fluids derived from the subducted slab during the subduction of the Paleo-Asian Ocean (PAO). After the PAO closure, the parental magma of the Wuhaolai complex was produced by the partial melting of the enriched lithospheric mantle. [ABSTRACT FROM AUTHOR]

In order to gain insights into continental arc magmatic processes, we have conducted a petrological and geochemical study of major and trace elements and Sr, Nd, and Pb isotopes of the Ampato-Sabancaya compound volcano, which belongs to the Andean Central Volcanic Zone (CVZ). Whole-rock compositions for Ampato and Sabancaya range from andesites to dacites (56.7–69.3 wt% SiO 2) and both belong to a medium- to high-K calk-alkaline magmatic series. Ampato-Sabancaya samples are characterized by high contents of large-ion lithophile elements (LILE; e.g. , K, Rb, Ba, Th), low concentrations of high field strength elements (HFSE; e.g. , Nb, Zr) and heavy rare earth elements (HREE; e.g. , Yb), with consequently high La/Yb and Sr/Y ratios. An increase in these ratios is usually interpreted as a result of magmatic differentiation in the presence of garnet in the deep crust. A detailed analysis reveals that the rocks of Ampato-Sabancaya display three different compositional groups. (1) The first, composed mainly of andesites (56.7–59.8 wt% SiO 2), corresponds to lavas from the early stage of the Ampato Basal edifice, as well as pyroclastic deposits from the Ampato Upper edifice. (2) The second group corresponds to andesitic and dacitic compositions (60.0–67.3 wt% SiO 2) from the Ampato Basal edifice (Moldepampa stage), the Ampato Upper edifice, and the Sabancaya edifice. (3) The third group corresponds to dacitic compositions (65.0–69.3 wt% SiO 2) associated with the Corinta Plinian fallout and pyroclastic flow deposits from the Ampato Upper edifice. This last group of dacites, erupted during the Ampato Upper edifice stage, have drastically different compositions from the other groups with Sr/Y (<27) and Sm/Yb (<4.7) ratios lower than other lavas and lacking evidence of amphibole and/or garnet fractionation during their genesis. As a whole, Sr, Nd, Pd isotopic ratios suggest that mantle-derived magmas are significantly affected by assimilation processes during their evolution, due to the thick (65–70 km) continental crust beneath the CVZ in southern Peru. In summary, the magmatic evolution of group 1 and 2 can be explained by a two-step model in which primitive magmas evolved in the deep crust in the so-called melting-assimilation-storage-homogenization (MASH)-type reservoirs by assimilation-fractional crystallization (AFC) processes involving garnet and/or amphibole. Then, amphibole-dominated upper crustal AFC processes and magma mixing are responsible for the geochemical diversity of the main ASCV trend. In contrats, the group 3 dacites followed an upper crustal AFC process (without amphibole) from a different primitive magma, which did not suffer the high pressure, garnet-dominated AFC processes. This evolution highlights the complexities associated to magma genesis and differentiation at continental arcs contructed on a thick crust. • Ampato-Sabancaya medium-high-K calc-alkaline suite range from andesites to dacites. • Trace elements and isotope ratios indicate crustal assimilation processes. • Geochemical modelling shows that AFC and magma mixing have controlled the evolution. • Magma evolved by lower and upper crustal differentiation. • The assimilated crust is the Arequipa Proterozoic basement. [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]

Research on seamounts provides some of the best constraints for understanding intraplate volcanism, and samples from seamounts reveal crucial evidence about the geochemical makeup of the oceanic mantle. There are still many seamounts in the West Pacific Seamount Province (WPSP) that have not been studied, meaning their ages and geochemistry remain unknown. A better understanding of these seamount trails and their evolutionary history, investigated with age and geochemistry data, will enable better understanding of the geological processes operating underneath the Pacific Ocean Plate. Here, new 40Ar/39Ar ages and trace element and Sr-Nd-Pb isotopic data for seven basalt rocks from four seamounts in the WPSP are provided. Chemically, these rocks are all Oceanic Island Alkali basalt (OIA type); analysis of olivine phenocrysts shows that the magmas experienced strong olivine fractionation and changed from olivine + plagioclase to olivine + plagioclase + clinopyroxene cotectic during their evolution. Rare earth element (REE) patterns and a spider diagram of the samples in this study show OIB (Ocean Island Basalt) like behavior. The range of 87Sr/86Sr values is from 0.704 60 to 0.706 24, the range of 206Pb/204Pb values is from 18.241 to 18.599, and the range of 143Nd/144Nd values is from 0.512 646 to 0.512 826; together, these values indicate magma sources ranging from EMI to EMII. Finally, new 40Ar/39Ar age data show that these seamounts formed at ~97 and ~106 Ma, indicating that some may have undergone the same formation processes as seamounts in the eastern part of the Magellan Seamount Trail, but other seamounts likely have different origins. [ABSTRACT FROM AUTHOR]

Abstract The Dasuji porphyry Mo deposit is located at the northern margin of North China Craton. Mo mineralization occurs mainly within the intrusions of alkali feldspar granite, granite porphyry, and quartz porphyry, which yield weighted mean 206Pb/238U ages (2σ) of 227.6 ± 1.5, 225.7 ± 1.5, and 224.3 ± 1.8 Ma, respectively. These ages are indistinguishable to the molybdenite Re Os isochron age of 223.9 ± 1.5 Ma (2σ). The Dasuji granites show the petrological, mineralogical, geochemical, and geotectonic characteristics of A-type granites. They exhibit low negative εNd(t) values (−16.7 to −12.6) with corresponding T DM2 (Nd) ages of 1705–2000 Ma, variable but mainly negative εHf(t) values (mostly −21.0 to −7.9) with corresponding T DM2 (Hf) ages of 1715–2728 Ma, and Pb isotopic compositions indicating that the primary magmas were dominantly derived from partial melting of ancient lower crust. In chondrite- and mantle-normalized trace element diagrams, all the granitic rocks show negative anomalies in Ba, Sr, and Eu, and a positive anomaly in Pb. The ratios of LREE/HREE, and (La/Yb) N and δEu values decrease from the alkali feldspar granite to the granite porphyry and quartz porphyry. These data are attributed to fractional crystallization processes. Fractionation of feldspar, biotite, and possibly K-feldspar produced the variations in major elements and Rb, Sr and Ba, and the distribution of REE are controlled mainly by fractionation of zircon, allanite, minor apatite, and possibly a small quantity of monazite. Together with the regional geology, the data infer that the Dasuji porphyry Mo deposit formed in a post-collision extensional setting during the Late Triassic. Graphical abstract Unlabelled Image Highlights • Ore-related Dasuji granites are formed between 227.6 and 224.3 Ma. • The primary magmas were derived from partial melting of ancient lower crust, with a minor mantle contribution. • The magma experienced at least two stages of fractional crystallization. • The Dasuji granites are A-type granites. [ABSTRACT FROM AUTHOR]

A new model of porphyry Cu system, which involves pre-enrichment of Cu through sulfide accumulation near the mantle-crust boundary, has been recently proposed to account for variations of Cu endowment in different magmatic arcs. To test this model and explore the possible controlling factors of porphyry Cu metallogeny, we studied the mineralogy and platinum-group elements (PGE) geochemistry of the giant Pulang porphyry Cu-Au system in the Sanjiang Region, SW China. The Late Triassic Pulang intrusive complex comprises five phase of porphyrtic stocks and dikes (ca. 217–212 Ma), which intruded a slightly older (ca. 230–218 Ma) volcanic-sedimentary sequence of the Tumugou Formation. Both the intrusive complex and the related volcanic wall rocks have similar PGE concentrations, Pd/Pt ratios and primitive mantle-normalized PGE patterns, indicating that no discernible sulfide cumulates were lost or gained during magmatic differentiation. The variation in PGE concentrations between different types of rocks at Pulang is probably ascribed to magma mixing between mafic and felsic end-members. Two types of amphibole, i.e., high-Al (Al 2 O 3  = 9.4–11.8 wt%) and low-Al (5.9–7.3 wt%) types, have been identified in the Pulang complex. It is estimated that the magma equilibrated with the high-Al amphibole may have contained up to 6.2 wt% H 2 O, and was formed under 334–538 MPa (ca. 11–18 km deep eqv.) with oxygen fugacity ( f O 2 ) between NNO + 0.2 and NNO + 1.5. In contrast, the magma that equilibrated with the low-Al amphibole was likely formed at a much shallower depth (89–202 MPa, ca. 3–7 km eqv.), and was more oxidized (NNO + 1.0–NNO + 1.7) with a low H 2 O content (4.2–4.9 wt%). High f O 2 would increase sulfur solubility in the magma, thus prohibiting early removal of metals via sulfide precipitation. In addition, the higher H 2 O content may have enhanced volatile exsolution from the evolving magmas at Pulang. We suggest that oxygen fugacity and H 2 O content of the magma are two critical factors that controlled the Pulang porphyry Cu-Au metallogeny. [ABSTRACT FROM AUTHOR]