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We have investigated a suite of natural diamonds from the kimberlite pipe of the Changma Kimberlite Belt, Mengyin County, Shandong Province, China, with the aim of constraining pressures and temperatures of formation. Here we report the non-destructive investigation of an olivine inclusion still entrapped within a lithospheric diamond by single-crystal X-ray diffraction. We were able to refine anisotropically its crystal structure to R1= 1.42 % using ionized scattering curves; this allows estimation of the composition of the olivine as Mg1.82Fe0.18SiO4. This composition corresponds to a calculated unit-cell volume equal to V= 292.70 Å3 at room temperature and pressure. We have validated the above-calculated composition and unit-cell volume by releasing the inclusion from the diamond host, resulting in a consistent composition calculated using non-destructive methods of Mg1.84Fe0.16SiO4 and V= 292.80 ± 0.07 Å3. Considering that the unit-cell volume of the olivine still inside its diamond host is V= 289.7 ± 0.2 Å3, we calculated a residual pressure Pinc= 1.4 ± 0.1 GPa with respect to the released crystal and Pinc= 1.3 ± 0.2 GPa with respect to the volume calculated from the “composition” indirectly retrieved by the structure refinement under ambient conditions. The two values of Pinc overlap within experimental uncertainty. We performed Fourier transform infrared (FTIR) analysis on the diamond host in order to calculate its mantle residence temperature, Tres, which resulted in a value of 1189 ∘C (for an assumed diamond age of 3 Ga) and 1218 ∘C (for an age of 1 Ga), with an average Tres equal to 1204 ± 15 ∘C. Using the most up-to-date pressure–volume–temperature equations of state for olivine and diamond, the residual pressure Pinc= 1.4 ± 0.1 GPa and average residence temperature of the diamond host Tres= 1204 ∘C, we retrieved a pressure of entrapment Ptrap= 6.3 ± 0.4 GPa. Using the non-destructive approach and relative Pinc = 1.3 GPa, we obtained a perfectly overlapping Ptrap= 6.2 GPa, within experimental uncertainty. This entrapment pressure corresponds to depths of about 190 ± 12 km. These results demonstrate that for high-quality crystal structure data measured on inclusions still trapped within diamond hosts, even a non-destructive approach can be used to calculate the depth of formation of diamond–olivine pairs. In terms of geological implications, the results from this work show that Changma diamonds formed under a conductive geotherm lying between 35 and 40 mW m−2, at a depth of about 190 km. This value lies within the recently reported upper limit of the average depth of formation of worldwide lithospheric diamonds, which is 175 ± 15 km and is in agreement with P–T data obtained in the literature from kimberlite xenoliths.

Methodology, supporting maps and diagrams (Figs. S1–S6), and primitive data tables (Tables S1–S2).

Carbonatite intrusions host the world’s most important light rare earth element (LREE) deposits, and their formation generally requires extraordinary fertile sources, magmatic evolution, and hydrothermal events. However, carbonatitic magma evolution, particularly the role of fractional crystallization and contamination from silicate rocks in REE enrichment, remains enigmatic. The Maoniuping world-class REE deposit in southwestern China, is an ideal target to decipher magmatic evolution and related REE enrichment as it shows continuous textual evolution from medium- to coarse-grained calcite carbonatite (carbonatite I) at depth, to progressively pegmatoidal calcite carbonatite (carbonatite II) at shallow levels. In both types of calcite carbonatites, four generations of calcite can be classified according to petrographic and geochemical characteristics. Early-crystalizing calcite (Cal-I and Cal-II) are found in carbonatite I and exhibit equigranular and a polygonal mosaic textures, while late calcites (Cal-III and Cal-IV) in carbonatite II are large-size oikocrysts (>0.5 mm in length) with strain-induced undulatory extinction and bent twinning lamellae. All these generations of calcite yield similar, near-chondritic, Y/Ho ratios (26.6−28.1) and are inferred to be of magmatic origin. Remarkably, gradual enrichment of MgO, FeO and MnO from Cal-I to Cal-IV is coupled with a significant increase in REE contents (~800 to 2000 ppm), with LREE-rich and gentle-to-steep chondrite-normalized REE patterns ((La/Yb)N = 3.1–26.8 and (La/Sm)N = 0.9–3.9, respectively). Such significant REE enrichment is ascribed to protracted magma fractional crystallization with initial low degree of fractional crystallization (fraction of melt remining (F) = ~0.95) evolving to late stage (F = 0.5–0.6) by formation of abundant calcite cumulates. Differential LREE and HREE behavior during magma evolution largely depend on separation of phlogopite, amphibole, and clinopyroxene from the carbonatitic melt, which is indicated by progressively elevated (La/Yb)N ratios ranging from 3.1 to 26.8. The four generations of calcite have significantly different C and Sr isotopic compositions with δ13CV-PDB decreasing from –3.28 to –9.97 ‰ and 87Sr/86Sr increasing from 0.70613 to 0.70670. According to spatial relations and petrographic observations, the relative enrichment of δ13C and depletion in 87Sr/86Sr ratios of Cal-I and Cal-II show primary isotopic characteristics inherited from initial carbonatitic magma. By contrast, the variable Sr and C isotopic compositions of Cal-III and Cal-IV are interpreted as the results of contamination by components derived from silicate wall rocks and loss of CO2 by decarbonation reactions. To model such contamination processes, Raleigh volatilization and Monte Carlo simulation have been invoked and the model results reveal that carbonatitic melt-wall rock interaction requires 40% radiogenic Sr contamination from silicate rocks and 35% CO2 degassing from carbonatitic melt. Moreover, positive correlations between decreasing δ13C values and increasing REE contents, together with bastnäsite-(Ce) precipitation, indicate further REE accumulation during the contamination processes. In summary, alongside REE-rich magma sources, the extent of fractional crystallization and contamination during carbonatitic magma evolution are inferred to be important mechanisms in terms of REE enrichment and mineralization in carbonatite-related REE deposits worldwide.

Mehdiabad is the world’s largest Mississippi Valley-type (MVT) Zn-Pb deposit (394 million tonnes [Mt] of metal ore at 4.2% Zn, 1.6% Pb) and contains significant barite resources (>40 Mt). Such large accumulations of barite are not common in carbonate-hosted Zn-Pb deposits. Therefore, the origin of the barite and its association with the Zn-Pb mineralization is of significant interest for further investigation. Field work and petrographic studies indicate that the Zn-Pb-Ba orebodies in the Mehdiabad deposit are hosted by Lower Cretaceous carbonate units of the Taft and Abkuh Formations. Fine- to coarse-grained barite with lesser siderite formed in three stages (S1, S2, and S4), along with a quartz-sulfide stage (S3) with minor quartz, sphalerite, galena, chalcopyrite, and pyrite, and the main Zn-Pb sulfide stage (S5) with massive sphalerite and galena. The barites have δ34S values from 17.7 to 20.6‰, δ18O values from 13.2 to 16.8‰, Δ33SV-CDT values from –0.001 to 0.036‰, and initial 87Sr/86Sr ratios from 0.707327 ± 0.000008 to 0.708593 ± 0.000008 (V-CDT = Vienna-Canyon Diablo Troilite). The siderites have δ13CV-PDB values from –3.8 to –2.7‰, and δ18OV-SMOW values from 18.2 to 20.9‰ (V-PDB = Vienna-Pee Dee Belemnite, V-SMOW = Vienna-standard mean ocean water). These geochemical data, and the barite morphology, point to a diagenetic origin for all stages of barite. We suggest that S1 and S2 barite precipitated from pore fluids at the sulfate-methane transition zone in a methane-diffusion-limited environment with increasing methane content. S4 barite precipitated when the methane- and barium-bearing cold-seep fluid migrated to the shallow carbonate sediments and formed a methane-in-excess setting. For the three stages, the SO42- in barite came from the residual SO42- in pore fluids undergoing sulfate-driven anaerobic oxidation of methane, and the Ba2+ came from dissolved biogenic barite and terrigenous materials in the Taft and Sangestan Formations. Primary fluid inclusions trapped in S3 quartz have salinities of 5.6 to 8.1 wt % NaCl equiv and homogenization temperatures of 143.8° to 166.1°C. The quartz has δ18OV-SMOW values ranging from 9.8 to 22.5‰ and δ30Si values from –1.3 to –0.9‰. These data indicate hydrothermal fluid flow occurred between the diagenetic S2 and S4 events. Secondary fluid inclusions with salinities of 17.70 to 19.13 wt % NaCl equiv and homogenization temperatures of 123.0° to 134.0°C are found in the S3 quartz, too. They might represent the hydrothermal event formed by basinal brines in S5. According to the ore textures and the comparison of the sulfur isotopes between S5 Zn-Pb sulfides and the digenetic barites, the barite provided a host and a sulfur source for the later Zn-Pb mineralization. The relationship between barite and the Zn-Pb mineralization indicates that significant accumulations of sulfates may be a critical exploration target for this kind of giant deposit.

The giant Pulang porphyry Cu-Au district (446.8 Mt at 0.52% Cu and 0.18 g/t Au) is located in the Yidun arc, eastern Tibet. The district is hosted in an intrusive complex comprising, in order of emplacement, premineralization fine-grained quartz diorite and coarse-grained quartz diorite, intermineralization quartz monzonite, and late-mineralization diorite porphyry, which were all emplaced at ca. 216 ± 2 Ma. Mafic magmatic enclaves are found in both the coarse-grained quartz diorite and quartz monzonite. The well-preserved primary mineral crystals in such a systematic magma series (including contemporaneous relatively mafic intrusions) with well-defined timing provide an excellent opportunity to investigate upper crustal magma reservoir processes, particularly to test the role of mafic magma recharge in porphyry Cu formation. Two groups of amphibole crystals, with different aluminum contents, are observed in these four rocks. Low-Al amphibole crystals (Аl2О3 = 6.2–7.6 wt %) with crystallization temperatures of ~780°C mainly occur in the coarse-grained quartz diorite and quartz monzonite, whereas high-Al amphibole crystals (Al2O3 = 8.0–13.3 wt %) with crystallization temperatures of ~900°C mainly occur in the fine-grained quartz diorite and diorite porphyry. These characteristics, together with detailed petrographic observations and mineral chemistry studies, indicate that the coarse-grained quartz diorite and quartz monzonite probably formed by crystal fractionation in the same felsic magma reservoir, whereas the fine-grained quartz diorite and diorite porphyry formed from relatively mafic magmas sourced from different magma reservoirs. The occurrence of mafic magmatic enclaves, disequilibrium phenocryst textures, and cumulate clots indicates that the coarse-grained quartz diorite and quartz monzonite evolved in an open crustal magma storage system through a combination of crystal fractionation and repeated mafic magma recharge. Mixing with incoming batches of hotter mafic magma is indicated by the appearance of abundant microtextures, such as reverse zoning (Na andesine core with Ca-rich andesine or labradorite rim overgrowth), sharp zoning (Ca-rich andesine or labradorite core with abrupt rimward anorthite decrease) and patchy core (Ca-rich andesine or labradorite and Na andesine patches) textured plagioclase, zoned amphibole, high-Al amphibole clots, skeletal biotite, and quartz ocelli (mantled quartz xenocrysts). Using available partitioning models for apatite crystals from the coarse-grained quartz diorite, quartz monzonite, and diorite porphyry, we estimated absolute magmatic S contents to be 20–100, 25–130, and >650 ppm, respectively. Estimates of absolute magmatic Cl contents for these three rocks are 1,000 ± 600, 1,800 ± 1,100, and 1,300 ± 1,000 ppm, respectively. The slight increase in both magmatic S and Cl contents from the premineralization coarse-grained quartz diorite magma to intermineralization quartz monzonite magma was probably due to repeated recharge of the relatively mafic diorite porphyry magma with higher S but similar Cl contents. Mass balance constraints on Cu, S, and Cl were used to estimate the minimum volume of magma required to form the Pulang porphyry Cu-Au deposit. Magma volume calculated using Cu mass balance constraints implies that a minimum of 21–36 km3 (median of 27 km3) of magma was required to provide the total of 2.3 Mt of Cu at Pulang. This magma volume can explain the Cl endowment of the deposit but is unlikely to supply the sulfur required. Recharge of 5–11 km3 of diorite porphyry magma to the felsic magma reservoir is adequate to account for the additional 6.5–15 Mt of S required at Pulang. Repeated diorite porphyry magma recharge may have supplied significant amounts of S and some Cl and rejuvenated the porphyry system, thus aiding formation of the large, long-lived magma reservoir that produced the porphyry Cu-Au deposit at Pulang.

A second occurrence of bobtraillite is described from the Gejiu nepheline syenite, southwestern China. The extremely rare and complex boron-bearing zirconium silicate is associated with albite, orthoclase, jadeite, fluorite, andradite, titanite, as well as other REE and zirconium-bearing minerals, catapleiite, moxuanxueite, låvenite, eudialyte, britholite-(Ce), and calcioancylite-(La). The EMP and LA-ICP-MS analyses of the studied material give an empirical formula: (Na9.70Li0.42K0.08□1.80)Σ12.00(Sr10.61Ca1.14Fe0.07□0.18)Σ12.00(Zr12.87Ti0.53Nb0.31REE0.08Y0.06U0.02Th0.01□0.12)Σ14.00(Si42.41B5.59Al0.02)Σ48.02O132(OH)12 ⚫ 12H2O. Bobtraillite is trigonal, with space group P3¯c1, a=19.6977(6), c=9.9770(3) Å, V=3352.4(2) Å3, Z=1. Single-crystal structure refinement revealed that all sodium occupies the Na(1) and Na(2) sites; the site occupancy of these two positions is 0.835(18) and 0.15(2), respectively, suggesting that Na(1) site is Na dominant, while Na(2) is a vacancy-dominant site. The [8]-coordinated site has been assigned to Sr and Ca, with free occupancy factors, 0.874(10) and 0.126(10), respectively. These new data indicate that the ideal formula of bobtraillite could be written as (Na,□)12(□,Na)12Sr12Zr14(Si3O9)10[Si2BO7(OH)2]6 ⚫ 12H2O.

This study, via combined analysis of geophysical and geochemical data, reveals a lithospheric architecture characterized by crust–mantle decoupling and vertical heat-flow conduits that control orogenic gold mineralization in the Ailaoshan gold belt on the southeastern margin of Tibet. The mantle seismic tomography indicates that the crust–mantle decoupled deformation, defined from previous seismic anisotropy analysis, was formed by upwelling and lateral flow of the asthenosphere, driven by deep subduction of the Indian continent. Our magnetotelluric and seismic images show both a vertical conductor across the Moho and high Vp/Vs anomalies both in the uppermost mantle and lowest crust, suggesting that crust–mantle decoupling promotes ponding of mantle-derived basic melts at the base of the crust via a heat-flow conduit. Noble gas isotope and halogen ratios of gold-related ore minerals indicate a mantle source of ore fluid. A rapid decrease in Cl/F ratios of lamprophyres under conditions of 1.2 GPa and 1050°C suggests that the ore fluid was derived from degassing of the basic melts. Similar lithospheric architecture is recognized in other orogenic gold provinces, implying analogous formational controls.

Numerical simulations and theoretical analyses predict that forearc ophiolites probably record the end of subduction followed by re-initiation. We report here the results of a field study and new geochronological data that enable identification of the Kermanshah forearc basin, SW Iran. This basin is filled with two terrestrial volcaniclastic successions separated by an Upper Cretaceous reef facies limestone. Early Late Cretaceous ocean island basalts, early Eocene incompatible element-enriched mid-ocean ridge basalts/normal-type mid-ocean ridge basalts and late Eocene arc basalts of the basin indicate that Neotethyan subduction ended during the early Late Cretaceous and then re-initiated during the late Eocene. We suggest that the Neotethyan Ocean between the Iranian and Arabian continents consisted of leading and trailing oceanic plates separated by a mid-ocean ridge (MOR). Subduction of the leading plate generated the Jurassic–Early Cretaceous Sanandaj–Sirjan arc, which was ended by MOR–trench collision. The Zagros late Early Cretaceous forearc ophiolites represent the youngest/hottest segments of the leading plate emplaced during the MOR–trench collision. Subsequently, subduction of the MOR generated the forearc basin and basalts with diverse geochemistry. After c. 60 myr, the cooled trailing plate started to subduct, generating the late Eocene arc basalts. This model has significant implications for investigating and understanding other fossil subduction zones elsewhere in the world. Supplementary material: Supplementary material is available at https://doi.org/10.6084/m9.figshare.c.6086586

The Yadong-Gulu Rift, cutting across the Gangdese belt and Himalayan terranes, is currently associated with a thermal anomaly in the mantle and crustal melting at 15–20 km depth. The rift follows the trace of a tear in the underthrusted Indian continental lithospheric slab recognized by high resolution geophysical methods. The Miocene evolution of a 400-km-wide band following the trace of the tear and the rift, records differences interpreted as indicative of a higher heat flow than its surroundings. In the Gangdese belt, this band is characterized by high-Sr/Y granitic magmatism that lasted 5 m.y. longer than elsewhere and by the highest values of εHf(i) and association with the largest porphyry Cu-Mo deposits in the Gangdese belt. Anomalously young magmatic rocks continue south along the rift in the Tethyan and Higher Himalayas. Here, a 300-km-wide belt includes some of the youngest Miocene Himalayan leucogranites; the only occurrence of mantle-derived mafic enclaves in a leucogranite; young mantle-derived lamprophyre dikes; and the youngest and hottest migmatites in the Higher Himalayas. These migmatites record a history of rapid exhumation contemporaneous with the exhumation of Miocene mafic eclogite blocks, which are unique to this region and which were both heated to >800 °C at ca. 15–13 Ma, followed by isothermal decompression. We suggest that the prominent tear in the Indian lithosphere, sub-parallel to the rift, is the most likely source for these tectono-thermal anomalies since the Miocene.

Since the beginning of the 21st century, the geoscience research has been entering a significant transitional period with the establishment of a new knowledge system as the core and with the drive of big data as the means. It is a revolutionary leap in the research of geoscience knowledge discovery from the traditional encyclopedic discipline knowledge system to the computer-understandable and operable knowledge graph. Based on adopting the graph pattern of general knowledge representation, the geoscience knowledge graph expands the unique spatiotemporal features to the Geoscience knowledge, and integrates geoscience knowledge elements, such as map, text, and number, to establish an all-domain geoscience knowledge representation model. A federated, crowd intelligence-based collaborative method of constructing the geoscience knowledge graph is developed here, which realizes the construction of high-quality professional knowledge graph in collaboration with global geo-scientists. We also develop a method for constructing a dynamic knowledge graph of multi-modal geoscience data based on in-depth text analysis, which extracts geoscience knowledge from massive geoscience literature to construct the latest and most complete dynamic geoscience knowledge graph. A comprehensive and systematic geoscience knowledge graph can not only deepen the existing geoscience big data analysis, but also advance the construction of the high-precision geological time scale driven by big data, the compilation of intelligent maps driven by rules and data, and the geoscience knowledge evolution and reasoning analysis, among others. It will further expand the new directions of geoscience research driven by both data and knowledge, break new ground where geoscience, information science, and data science converge, realize the original innovation of the geoscience research and achieve major theoretical breakthroughs in the spatiotemporal big data research.

Crustal growth is commonly associated with porphyry deposit formation whether in continental arcs or collisional orogens. The Miocene high-K calc-alkaline granitoids in the Gangdese belt in southern Tibet, associated with porphyry copper deposits, are derived from the juvenile lower crust with input from lithospheric mantle trachytic magmas, and are characterized by adakitic affinity with high-Sr/Y and La/Yb ratios as well as high Mg# and more evolved isotopic ratios. Researchers have argued, lower crust with metal fertilization was mainly formed by previous subduction-related modification. The issue is that the arc is composed of three stages of magmatism including Jurassic, Cretaceous, and Paleocene–Eocene, with peaks of activity at 200 Ma, 90 Ma, and ca. 50 Ma, respectively. All three stages of arc growth are essentially similar in terms of their whole-rock geochemistry and Sr-Nd-Hf isotopic compositions, making it difficult to distinguish Miocene magma sources. This study is based on ~430 bulk-rock Sr-Nd isotope data and ~270 zircon Lu-Hf isotope data and >800 whole-rock geochemistry analyses in a 900-km-long section of the Gangdese belt. We found large scale variations along the length of the arc where the Nd-Hf isotopic ratios of the Jurassic, Cretaceous, and Paleocene–Eocene arc rocks change differently from east to west. A significant feature is that the spatial distribution of Nd-Hf isotopic values of the Paleocene–Eocene arc magmas and the Miocene granitoids, including metallogenic ones, are “bell-shaped” from east to west, with a peak of εNd(t) and εHf(t) at ~91°E. In contrast, the Jurassic and Cretaceous arc magmas have different isotopic distribution patterns as a function of longitude. The isotopic spatial similarity of the Paleocene–Eocene and Miocene suites suggests that the lower crust source of the metallogenic Miocene magmas is composed dominantly of the Paleocene–Eocene arc rocks. This is further supported by abundant inherited zircons dominated by Paleocene–Eocene ages in the Miocene rocks. Another important discovery from the large data set is that the Miocene magmatic rocks have higher Mg# and more evolved Sr-Nd-Hf isotopic compositions than all preceding magmatic arcs. These characteristics indicate that the involvement of another different source was required to form the Miocene magmatic rocks. Hybridization of the isotopically unevolved primary magmas with isotopically evolved, lithospheric mantle-derived trachytic magmas is consistent with the geochemical, xenolith, and seismic evidence and is essential for the Miocene crustal growth and porphyry deposit formation. We recognize that the crustal growth in the collisional orogen is a two-step process, the first is the subduction stage dominated by typical magmatic arc processes leading to lower crust fertilization, the second is the collisional stage dominated by partial melting of a subduction-modified lower crust and mixing with a lithospheric mantle-derived melt at the source depth.

An intensive study of the geochemical characteristics (including the volatile elements Cl and S) of apatite associated with porphyry deposits was undertaken to address the debate about the crust- or mantle-derivation of their copper and gold and to better understand the controls on the transport of metals in magmatic fluids in post-subduction settings. New geochemical data on apatite reveal parameters to discriminate mineralized porphyry systems across Iran and western China (Tibet and Yunnan), from coeval barren localities across this post-subduction metallogenic belt. Apatites in fertile porphyries have higher Cl and S concentrations (reflecting water-rich crystallization conditions) than those from coeval barren ones. Our new isotopic data also indicate these volatiles are likely derived from pre-enriched sub-continental lithospheric mantle, metasomatized by previous oceanic subduction. This study demonstrates that refertilization of suprasubduction lithospheric mantle during previous collision events is a prerequisite for forming post-subduction fertile porphyries, providing an evidence-based alternative to current ore-enrichment models.

As an important contributor to the habitability of our planet, the oxygen cycle is interconnected with the emergence and evolution of complex life and is also the basis to establish Earth system science. Investigating the global oxygen cycle provides valuable information on the evolution of the Earth system, the habitability of our planet in the geologic past, and the future of human life. Numerous investigations have expanded our knowledge of the oxygen cycle in the fields of geology, geochemistry, geobiology, and atmospheric science. However, these studies were conducted separately, which has led to one-sided understandings of this critical scientific issue and an incomplete synthesis of the interactions between the different spheres of the Earth system. This review presents a five-sphere coupled model of the Earth system and clarifies the core position of the oxygen cycle in Earth system science. Based on previous research, this review comprehensively summarizes the evolution of the oxygen cycle in geological time, with a special focus on the Great Oxidation Event (GOE) and the mass extinctions, as well as the possible connections between the oxygen content and biological evolution. The possible links between the oxygen cycle and biodiversity in geologic history have profound implications for exploring the habitability of Earth in history and guiding the future of humanity. Since the Anthropocene, anthropogenic activities have gradually steered the Earth system away from its established trajectory and had a powerful impact on the oxygen cycle. The human-induced disturbance of the global oxygen cycle, if not controlled, could greatly reduce the habitability of our planet.

Magnesium isotopic compositions, along with new Sr–Nd–Pb isotopic data and elemental analyses, are reported for 12 Miocene tourmaline-bearing leucogranites, 15 Eocene two-mica granites and 40 metamorphic rocks to investigate magnesium isotopic behaviors during metamorphic processes and associated magmatism and constrain the tectonic-magmatic-metamorphic evolution of the Himalayan orogeny. The gneisses, granulites and amphibolites represent samples of the Indian lower crust and display large range in δ26Mg from −0.44‰ to −0.09‰ in mafic granulites, −0.44‰ to −0.10‰ in amphibolites, and −0.70‰ to −0.03‰ in granitic gneisses. The average Mg isotopic compositions of the granitic gneisses (−0.19 ± 0.34‰), mafic granulites (−0.22 ± 0.17‰) and amphibolites (−0.25 ± 0.24‰) are similar, indicating the limited Mg isotope fractionation during prograde metamorphism from granitic gneisses to mafic granulites and retrograde metamorphism from mafic granulites to amphibolites. The Eocene two-mica granites and Miocene leucogranites are characterized by large variations in elemental and Sr–Nd–Pb isotopic compositions. The leucogranites and two-mica granites have their corresponding (87Sr/86Sr)i varying from 0.7282 to 0.7860 and 0.7163 to 0.7191, (143Nd/144Nd)i from 0.511888 to 0.512040 and 0.511953 to 0.512076, 207Pb/204Pb from 15.7215 to 15.7891 and 15.7031 to 15.7317, 208Pb/204Pb from 38.8521 to 39.5286 and 39.2710 to 39.4035, and 206Pb/204Pb from 18.4748 to 19.0139 and 18.7834 to 18.9339. However, they have similar Mg isotopic compositions (−0.21‰ to +0.06‰ versus −0.24‰ to +0.09‰), which did not originate from fractional crystallization nor source heterogeneity. Based on hornblende/biotite/muscovite dehydration melting reaction and Mg isotopic variations in two-mica granites and leucogranites with the proceeding metamorphism, along with elemental discrimination diagrams, Eocene two-mica granites and Miocene leucogranites could be related to hornblende dehydration melting and muscovite dehydration melting, respectively. Mg isotopic compositions of Eocene two-mica granites become heavier compared to the source because of residues of isotopically light garnet in the source; while those of Miocene leucogranites become lighter because of entrainment of isotopically light garnet from the source region. Thus, a new model for crustal anatexis and Himalayan orogenesis was proposed based on the Mg isotope fractionation in the leucogranites and metamorphic rocks. This model emphasizes a successive process from Indian continental subduction to rapid exhumation of the Higher Himalayan Crystalline Series (HHCS). The former underwent high-temperature (HT) and high-pressure (HP) granulite-facies prograde metamorphism, which resulted in the hornblende dehydration melting and the formation of Eocene two-mica granites; while the latter experienced amphibolite-facies retrogression and decompression, which resulted in the muscovite dehydration melting and the formation of Miocene leucogranites.

The tectonic transition from subduction to collision is a fundamental process during orogenesis, yet the magmatic expression of this transition and related deep geodynamic processes remain unclear. This study focuses on a newly identified volcanic belt within the Moyun–Zaduo–Sulu area of the North Qiangtang Block and presents new zircon U-Pb data that indicate that this belt formed during the Middle Triassic (247–241 Ma), a time characterized by a regional transition from subduction to collisional tectonism. The volcanic belt is located to the south of a Permian to Early Triassic arc and is dominated by high-K calc-alkaline and peraluminous rhyolites. These rhyolites have low Mg#, Nb/Ta, and δEu values, contain low contents of Sr, have high Rb/Sr and whole-rock eNd(t) values, and show positive zircon eHf(t) values, all of which suggest that they formed from magmas generated by the dehydration melting of juvenile crustal material. The migration of Middle Triassic volcanism in this region was most likely caused by rollback of the subducting Longmucuo–Shuanghu Tethyan oceanic slab. Combining our new data with previously published results of numerical modeling of subduction–collisional processes and regional data from north-central Tibet yields insights into the magmatic expressions and related deep geodynamics of the transition from oceanic subduction to continental collision. This combination of data also suggests that variations in oxygen fugacity can be used as a proxy for the discrimination of magmatism related to subduction, the transition from subduction to collision, and collisional tectonism.

The genesis of high-silica igneous rocks is important for understanding the behavior of shallow magmatic systems. However, although many such studies have focused on the eruption of crystal-poor high-SiO2 rhyolites, the origin of high-silica granites (HSGs) has received comparatively little attention. Here, we present a detailed study of HSGs from the Narusongduo volcanic complex, Gangdese arc. Combining zircon U-Pb geochronology with stratigraphic investigations, we show that the Narusongduo magmatic system was constructed over a period of ≥3.7 Myr with or without lulls. On the basis of zircon textures and ages, diverse zircon populations, including antecrysts and autocrysts, are recognized within the HSGs and volcanic rocks. All of the igneous rocks within the Narusongduo volcanic complex have highly radiogenic Sr–Nd isotopic compositions. Our results indicate the presence of an andesitic magma reservoir in the upper crust at a paleodepth of ~8 km. Ubiquitous zircon antecrysts in the HSGs, combined with compositional similarities between the HSGs and evolved melts of the andesitic magma reservoir, indicate that the Narusongduo HSGs represent melts extracted from the shallow magma reservoir. In addition, our results suggest that magma recharge promoted the escape of high-silica melts to form the Narusongduo HSGs. This work presents an excellent case that kilometer-scale high-silica granites are the differentiated products from an upper crustal magma reservoir. It would make a contribution to contemporary debates concerning the efficiency of crystal–melt separation in upper crustal magmatic systems.

Saindak is one of the typical porphyry Cu deposits (PCDs) in the Chagai magmatic arc in Pakistan. Ore-forming porphyries at Saindak PCD are mainly composed of tonalite. Here, we use geochemistry of apatite enclosed in plagioclase phenocrysts from the ore-forming tonalite to constrain the releasing and recharging processes of S and Cl in the underlying parental magma chamber during PCD mineralization. Although apatite inclusions have homogeneous intra-grain S and Cl compositions, there is significant inter-grain S and Cl variations in apatite inclusions located from core to rim in the hosting plagioclase. Such inter-grain S and Cl variation in apatites are coupled with the core-to-rim trends of An, FeO and Mg contents of the hosting plagioclase phenocryst. It indicates that the Saindak PCD likely formed by episodic injection of primitive magmas during the growth of an underlying magma chamber, rather than by one major injection or by addition of mafic melt derived from different source region. Each primitive melt injection introduced essential ore-forming materials such as S and Cl, which were rapidly and effectively released to the coexisting fluids, causing mineralization. Once primitive melt injection stops, signaling the end of growth of underlying magma chamber, mineralization will cease quickly although the hydrothermal system can still survive for a long time. However, the later released fluids are relatively depleted in ore-forming materials, and thus have lower capability to generate mineralization. Accordingly, predominant porphyry-type mineralizations occurred during the growth rather than waning stage of a magmatic system.

Jinding is the third-largest known Mississippi Valley-type (MVT) Zn-Pb deposit. It is hosted by a dome containing a suite of complex breccias and sandstones with abundant gypsum and anhydrite. This study presents the results of new geologic mapping of the Jinding open pit and discusses the geology of the deposit in detail. Our new data support a previously proposed model where the deposit is hosted in an evaporite dome created by the diapiric migration of Late Triassic evaporites during Paleocene thrust loading. Nearly all of the mineralization in the deposit is hosted by evaporite diapir-related rocks, including diapiric breccias and laterally extruded material mixed with fluvial sandy sediments (limestone clast-bearing sandstones) and overlying gypsum-sand diapiric units (mainly clast-free sandstones). The new mapping determined that the currently light gray colored sandstones within the Jinding dome were originally red, with the bleaching being a response to calcite and pyrite alteration as a result of pre-ore interaction with hydrocarbons. The bleached sandstones host sphalerite and galena that replaced calcite, and Zn-Pb sulfides also occur in limestone breccias and gypsum-rich rocks as a result of replacement and open space-filling mineralizing processes. The Jinding deposit demonstrates that MVT Zn-Pb mineralization can be hosted by a variety of evaporite diapir-related rocks and indicates that dome structures and the presence of pre-ore hydrocarbons are both important for the formation of Zn-Pb mineralization.

As the world’s major source of Cu, Mo, and Au, porphyry copper deposits are magmatic-hydrothermal systems in which base and precious metals are deposited from aqueous solutions at temperatures generally >300°C. During formation of the deposits, metal-transporting fluids typically affected large volumes (up to ~100 km3) of upper crustal rocks, which has led to enormous mass redistribution and local concentration of many elements. Several critical elements, including Re, Se, and Te that are typically not found as primary ores, are locally concentrated in some porphyry copper deposits. Presently, mining and milling of porphyry copper deposits supply ~80% of the world’s Re and nearly all of the Se and Te. China has about 70 economic porphyry copper deposits, including 11 giant and 16 large deposits, with total pre-mining resources of ~78 million tonnes (Mt) Cu averaging 0.2% to 1% Cu, ~4.7 Mt Mo averaging 0.01% to 0.08% Mo, and 1400 tonnes (t) Au averaging 0.5 g/t Au. Rhenium, Se, Te, and PGE (platinum group elements) have been reported to be enriched in some porphyry copper deposits in China, but their tonnage, grade, occurrence, and resource potential remain unclear. In this study, based on a simple synthesis of critical elements in the porphyry copper deposits worldwide and geological characteristics of Chinese porphyry copper deposits, we systematically summarize these attributes of critical elements, particularly Re, in the porphyry copper deposits of China. The porphyry copper deposits in China are mainly concentrated in the following belts or districts: The Gangdese belt in southern Tibet, the Yulong belt in eastern Tibet, the Duolong district in central Tibet, the Zhongdian belt in northwestern Yunnan Province, the Central Asian orogenic belt across northern China, the Zhongtiaoshan belt in Shanxi Province, the Middle-Lower Yangtze River Valley belt, and the Dexing district in Jiangxi Province. Chinese porphyry copper deposits were formed during Paleoproterozoic, Ordovician, Carboniferous, Late Triassic to Early Cretaceous, and Eocene to Miocene, with the majority forming during the latter two time periods. Approximately 45% of the giant and ~30% of the large porphyry copper deposits in China formed in arc settings, whereas at least 35% of the giant and ~45% of the large porphyry copper deposits in China occured in post-collisional settings. The porphyry copper deposits in China typically contain ~3−313 t of Re at average grades ranging from 0.03 to 0.5 g/t Re, with ten deposits containing >50 t Re. The Re-rich porphyry copper deposits in China were mainly formed during Jurassic and Eocene to Miocene. The three largest deposits (Yulong, Jiama, and Qulong), in terms of contained Re, were formed during Eocene to Miocene and in a postcollisional setting. Rhenium in these porphyry copper deposits mainly occurs in molybdenite, and is associated with potassic and/or phyllic alteration. Average Re content in molybdenite from these deposits ranges from 30 to 1000 ppm, but shows a negative correlation with the Mo grade of the corresponding deposit. In contrast, there are only limited data on the endowment of Se, Te, and PGE for Chinese porphyry copper deposits. Similar to porphyry copper deposits worldwide, Se, Te, and PGE in Chinese porphyry copper deposits are concentrated in the sulfide minerals. The contents of Se and Te in sulfide minerals from several deposits (e.g., Bolong, Shaxi) range from ~3 to 700 ppm and are typically highest (generally >300 ppm) in Cu-bearing sulfides (e.g., bornite, chalcopyrite). Concentrations of PGE in ores of Chinese porphyry copper deposits are highly variable, with Pd+Pt contents ranging from 0.2 to 450 ppb. In summary, Chinese porphyry copper deposits, particularly those in postcollisional settings, show similar grades of Re, Se, Te, and PGE to porphyry copper deposits worldwide, indicating a large potential of these critical elements in Chinese porphyry copper deposits to meet the nation’s economic needs. To better understand the occurrence, resource potential, and enrichment processes of critical elements in the porphyry copper deposits of China, detailed case studies and regional comparisons, as well as improvements in analytical techniques, are a pressing need.

The Tethyan metallogenic domain (TMD), as one of the three major domains in the world, extends over 10000 km from east to west, and has developed several world-class metallogenic belts, such as the Gangdese porphyry Cu belt, the Sanjiang metallogenic belt, the Iran porphyry Cu belt, the Pakistan porphyry Cu belt, the southeastern European epithermal gold deposit belt, and the Southeast Asian Sn belt. The formation and evolution of the TMD is mainly controlled by the multi-stage subduction of Tethys oceanic slabs, the opening and closing of several small ocean basins, and continent-continent collision. The Tethys oceans include the Proto-Tethys (Cambrian-Silurian), Paleo-Tethys (Carbonaceous-Triassic) and Neo-Tethys (Jurassic to Cretaceous), which in turn are formed by rifting from the Gondwana land at different times in different micro-continents. With a series of geological processes such as oceanic opening and closing, continental collision and post-collisional reworking with intraplate deformation, various types of ore deposits are developed in the TMD, including porphyry deposits, epithermal deposits, VMS deposits, chromite deposits, Sn deposits and orogenic gold deposits. The metallogenic processes of the TMD can be categorized into three stages. (1) Oceanic subduction: With the subduction of the oceanic slab and dehydration of basalt and sediments, the asthenospheric mantle was metasomatized with preliminary enrichment in metals under oxidized condition. (2) Continental subduction: Continental collision induced partial melting of the mantle wedge enriched the metals and water in mafic melts, which ascended from subarc depths to the lower crust, locally to the shallow crust for hydrothermal mineralization. (3) Post-collisional reworking: Partial melting of the mafic intrusives in the lower crust produced felsic melts under oxidized and water-rich conditions, which underwent crystal fractionation and transferred water and metals into hydrothermal fluids for mineralization. The large-scale porphyry mineralization in the TMD mainly occurs in the Miocene, which is an important scientific issue worthy of further study in the future. How is the metal enriched in the processes of gradual maturity of the crust, and how does large-scale mineralization occur in a collisional orogen where there is no subduction and dehydration of oceanic slabs anymore to supply S and Cl? These are still important questions in the study of porphyry mineralization in the Tethyan orogen. The application of hyperspectral and mineralogical studies of alteration assemblages is beneficial for prospecting and exploration in the TMD.

Amphibole fractionation during the early evolution of arc magmas has been widely inferred on the basis of distinctive geochemical fingerprints of the evolved melts, although amphibole is rarely found as a major mineral phase in arc volcanic rocks, so-called cryptic amphibole fractionation. Here, we present a detailed case study of xenoliths of amphibole-rich cumulate from the Zhazhalong intrusive suite, Gangdese arc, which enables an investigation of this differentiation process using a combination of petrological observations and in situ geochemical constraints. Evidence that the xenoliths represent fragments of igneous cumulates includes: (1) the presence of an amphibole-dominated crystal framework; (2) mineral and whole-rock Fe–Mg exchange coefficients; (3) rare-earth element patterns that are similar in the amphiboles and the xenoliths; (4) the compositions of basaltic to andesitic liquids in equilibrium with amphiboles; and (5) enrichment of the xenoliths in compatible elements and depletion in incompatible elements. The amount of trapped liquid based on La, Ce, and Dy abundances varies from ~12 to ~20%. Actinolitic cores within amphibole grains likely represent reaction between olivine precursor and hydrous melt, as evidenced by their high Cr and Ni contents. Amphibole thermometry and oxybarometry calculations indicate that crystal accumulation occurred over temperatures of 857–1014 °C, at mid-crustal pressures of 312 to 692 MPa and oxygen fugacity between 0.4 and 1.9 log units above the nickel–nickel oxide buffer. Quantification of the major-element compositions of the parent liquids indicates that the Zhazhalong amphibole cumulates crystallized from basaltic to andesitic magmas, probably with a shoshonitic affinity, and with SiO2 contents of 46.4–66.4 wt%. Appropriate partition coefficients, calculated using a parameterized lattice strain model and an empirical partitioning scheme, were employed to calculate the trace-element compositions of the liquids in equilibrium with amphibole. Our results confirm that Dy/Yb and Dy/Dy* ratios, which decrease with increasing degrees of differentiation, can be used as robust signatures of amphibole fractionation. This work presents a direct snapshot of the process of amphibole fractionation and provides a natural example of the hidden amphibole “sponge” in arc crust. In particular, this study also suggests that some appinites likely represent amphibole-rich cumulates, which may help to explain the genesis of other unusual but petrologically significant rocks.

Description, Felsic volcanism in South China with Cu, Hg, and S released exacerbated environmental changes that drove the end-Permian extinction., The Siberian Traps large igneous province (STLIP) is commonly invoked as the primary driver of global environmental changes that triggered the end-Permian mass extinction (EPME). Here, we explore the contributions of coeval felsic volcanism to end-Permian environmental changes. We report evidence of extreme Cu enrichment in the EPME interval in South China. The enrichment is associated with an increase in the light Cu isotope, melt inclusions rich in copper and sulfides, and Hg concentration spikes. The Cu and Hg elemental and isotopic signatures can be linked to S-rich vapor produced by felsic volcanism. We use these previously unknown geochemical data to estimate volcanic SO2 injections and argue that this volcanism would have produced several degrees of rapid cooling before or coincident with the more protracted global warming. Large-scale eruptions near the South China block synchronous with the EPME strengthen the case that the STLIP may not have been the sole trigger.