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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.

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.

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.

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.

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.

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.

Many intrusions with adakite-like affinities in collisional zones have obviously higher K2O contents and K2O/Na2O ratios compared with counterparts in subduction zones. A suite of Eocene post-collisional high-K2O adakite-like intrusions, mafic microgranular enclaves, and potassic–ultrapotassic lamprophyres in the Machangqing complex are associated with the Indian–Asian collision within the western Yangtze Craton, southeastern Tibet. The potassic–ultrapotassic lamprophyres, with a zircon U–Pb age of 34·1 ± 0·2 Ma, have high K2O and MgO contents, are enriched in light rare earth elements and large ion lithophile elements, and display high Rb/Sr, and low Ba/Rb and Nb/U ratios. They show enriched isotopic compositions [i.e. (87Sr/86Sr)i = 0·7070–0·7082, εNd(t) = −3·2 to −2·8], and zircon εHf(t) values (−1·6 to +2·6). Their parental magmas are inferred to have been derived from partial melting of an enriched lithospheric mantle, metasomatized by subduction-related fluids. The adakite-like intrusions, with zircon U–Pb ages of 35·4 ± 0·4 and 35·2 ± 0·3 Ma, are characterized by high SiO2 (68·8–71·1 wt%) and Al2O3 (14·0–15·3 wt%) contents, high Sr/Y (41–118) ratios, and low Y (5·3–14·7 ppm) contents. They show low contents of compatible elements (e.g. Ni = 9·5–36·2 ppm) and total REE, and lower Mg# values than the lamprophyres and mafic microgranular enclaves. The adakite-like intrusions have positive large ion lithophile element anomalies, especially potassium, negative high field strength element anomalies, negative εNd(t) (−5·5 to −3·3), and high (87Sr/86Sr)i (0·7064–0·7070) and zircon εHf(t) values (0·0 to +2·7), indicating that they were formed by partial melting of the juvenile lower crust. Mafic microgranular enclaves hosted in the adakite-like intrusions, with U–Pb ages similar to the lamprophyre of c. 34 Ma, exhibit disequilibrium textures, and some of them contain phlogopite. They exhibit potassic–ultrapotassic affinity, and relatively high compatible element contents. They are also characterized by enriched isotopic compositions with (87Sr/86Sr)i = 0·7063–0·7074, εNd(t) = −6·6 to −4·1, and variable zircon εHf(t) values (−0·6 to +3·2). Petrological and geochemical evidence suggests that the mafic microgranular enclaves were formed by magma mixing between potassic–ultrapotassic and pristine adakite-like melts. We propose a magma mixing model for the origin of the high-K2O adakite-like intrusions from the Machangqing complex. In this model, the formation of high-K2O adakite-like intrusions occurred in three stages: (1) partial melting of metasomatized lithospheric mantle generated potassic–ultrapotassic mafic melts; (2) underplating of these mafic melts beneath thickened juvenile lower crust resulted in partial melting of juvenile mafic lower crust and the generation of adakite-like melts; (3) magma mixing involved 80 % pristine adakite-like melts and 20 % potassic–ultrapotassic melts. This leads to the enrichment of K2O in these adakite-like intrusions, and magma differentiation further promotes K2O enrichment. These results are applicable to compositionally similar adakite-like rocks produced in other collisional zones, such as the Tibet, Sulu–Dabie and Zagros orogenic belts. From which we conclude that in continental collision zones, the post-collisional mantle-derived magmas characterized by potassic–ultrapotassic affinities are spatially associated with coeval collision-related adakite-like intrusions that originated from lower crustal melting. The emplacement of adakite-like and potassic–ultrapotassic rocks is controlled by the same fault systems, which increases the possibility of interaction between these two magma suites.

The Angouran deposit is the second-largest Zn–Pb deposit in Iran with 4.7 Mt sulfide ore (27.7% Zn, 2.4% Pb, and 110 g/t Ag) and 14.6 Mt nonsulfide ore (28.1% Zn, 4.4% Pb). Various models have been proposed to explain the genesis of sulfide ore in this deposit. Moreover, the mineralization type of its primary sulfide ores remains controversial. The major and trace element concentrations and sulfur isotopic composition of the two stages of sphalerite have been analyzed to constrain mineralization conditions and the genesis. The Angouran deposit, which contains discordant orebodies, is hosted in a Neoproterozoic/Cambrian schist-marble sequence. Two stages of sphalerite have been distinguished: early-stage (S1) red-brown sphalerite and late-stage (S2) honey-yellow sphalerite. Our result shows that, relative to the S2 sphalerite, the S1 sphalerite has higher contents of Fe, Mn, Co, Cu, Ag, Sn, Ga, Sb and In, but lower contents of As and Tl. Time-resolved depth profiles in these sphalerites determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses indicate that Fe, Cd, Co, Hg, Mn, Ge, and In are mainly present in solid solution and that Ag, Cu, Pb, As, Ni, Ga, Tl, Sb, and Sn are present in both solid solution and mineral inclusions. Correlation analyses reveal the occurrence of direct substitution mechanisms, such as Zn2+ ↔ (Fe2+, Cd2+) and 2Zn2+ ↔ Ge4++□ (vacancy) as well as coupled substitutions, such as 2Zn2+ ↔ Cu+ + Ga3+, 2Zn2+ ↔ (Cu+, Ag+) + Sb3+, 3Zn2+ ↔ Pb2+ + Tl+ + As3+, 4Zn2+ ↔ Pb2+ + 2As3++□(vacancy) or (Zn2+, Pb2+) ↔ Tl+ + As3+, and 4Zn2+ ↔ Cu+ + (Ga3+, In3+) + Sn4++□(vacancy). Geothermometer studies suggest that sphalerite in the Angouran deposit precipitated from a low-temperature (

A recently discovered basanite dike in the Zaolin area of Jingdezhen, South China, contains mantle xenocrysts such as kink-banded olivines, olivines + orthopyroxenes assemblage, and chromites. In addition, polymorphic carbonates of the MgCO3–FeCO3 series occur as augens, either independently or interspersed with diopside and spinel in the matrix. The rock is characterized by high Cr and Ni contents, high whole-rock Mg# values (0.66–0.72), and high Ca/Al (0.72–1.03) and TFeO/MgO (1.1–1.3) ratios and is alkali-rich with Na2O > K2O. The trace-element partition patterns are similar to those of other basanites in eastern China as well as ocean island basalts. Whole-rock geochemical analyses show depleted Sr and Nd isotopic compositions (86Sr/87Sr=0.70358–0.703853, εNd=2.52–6.73). These data indicate that the rock has experienced negligible crustal contamination, should be derived from asthenospheric mantle, or mixed by the MORB with EMI/EMII mantle and have been carbonated. The calculated T–P conditions of the melt in equilibrium with xeno-olivine are 1160–1320°C at the mantle depth. The high Cr# values of the spinel xenocrysts indicate that the lithospheric mantle under the Jingdezhen area was probably relict Proterozoic mantle. The Ar–Ar plateau age and the isochron and inverse isochron ages for the matrix of the basanite are all 44 Ma. The basanite, as well as other alkaline basalt or lamprophyre dikes in southeastern China, formed in a rifting regime during the Eocene.

Current barriers hindering data-driven discoveries in deep-time Earth (DE) include: substantial volumes of DE data are not digitized; many DE databases do not adhere to FAIR (findable, accessible, interoperable and reusable) principles; we lack a systematic knowledge graph for DE; existing DE databases are geographically heterogeneous; a significant fraction of DE data is not in open-access formats; tailored tools are needed. These challenges motivate the Deep-Time Digital Earth (DDE) program initiated by the International Union of Geological Sciences and developed in cooperation with national geological surveys, professional associations, academic institutions and scientists around the world. DDE’s mission is to build on previous research to develop a systematic DE knowledge graph, a FAIR data infrastructure that links existing databases and makes dark data visible, and tailored tools for DE data, which are universally accessible. DDE aims to harmonize DE data, share global geoscience knowledge and facilitate data-driven discovery in the understanding of Earth's evolution., Deep-time Digital Earth is to promote data-driven discovery by harmonizing deep-time Earth data and creating ‘Geological Google’.

Post-collisional ultrapotassic rocks (UPRs) in the Tibetan Plateau exhibit extreme enrichment in incompatible elements and radiogenic isotopes. Such enrichment is considered to be either inherited from a mantle source or developed during crustal evolution. In this study, to solve this debate we combined mineral textures and in situ geochemical composition of clinopyroxene phenocrysts in UPRs from southern Tibet to reveal their crustal evolution, enrichment cause and constrain metasomatism in their mantle source. Results show that the UPRs experienced an array of crustal processes, i.e., fractional crystallization, mixing, and assimilation. Fractional crystallization is indicated by decreases in Mg# and Ni and enrichment in incompatible elements (e.g. rare earth element (REE), Sr, Zr) toward the rims of normally zoned clinopyroxene phenocrysts (type-I). Magma mixing is evidenced by the presence of some clinopyroxene phenocrysts (type-II, -III) showing disequilibrium textures (e.g. reversed and overgrowth zoning), but in situ Sr isotope and trace element analysis of those disequilibrium zones indicate that late-stage recharged mafic magmas are depleted (87Sr/86Sr: 0.70659–0.71977) compared with the primitive ultrapotassic magmas (87Sr/86Sr: 0.70929–0.72553). Assimilation is revealed by the common presence of crustal xenoliths in southern Tibetan UPRs. Considering the much lower 87Sr/86Sr values (0.707759–0.709718) and incompatible element contents of these crustal xenoliths relative to their host UPRs, assimilation should have resulted in geochemical depletion of southern Tibetan UPRs rather than enrichment. The diluting impact of both assimilation and mixing is also supported by the modeling results based on the EC-E′RAχFC model combining the growth history of clinopyroxene. Trace elements ratios in clinopyroxenes also imply that the mantle source of southern Tibetan UPRs suffered an enriched and carbonatite-dominated metasomatism. Thus, we conclude that enrichment of southern Tibetan UPRs was inherited from the mantle source.

The world-class Dahutang tungsten deposit is located within the Jiuling mining district of the central Jiangnan orogenic belt, Jiangxi Province, China. The deposit consists of a massive and gently dipping scheelite orebody that contains disseminated and veinlet-hosted mineralization located within a medium- to coarse-grained biotite granodiorite. The No. 1 ore block of the deposit also contains a 1.50–1.75 m thick shell-shaped pegmatoid zone that defines an inner contact zone between the mineralization-related porphyritic-like biotite granite and strongly mineralized biotite granodiorite that hosts the tungsten deposit. This pegmatoid zone contains very low concentrations of tungsten, but records the processes involved in the migration and enrichment of this element within the deposit. The pegmatoid contrasts with typical hydrothermal pegmatite-type ore in that it often contains megacrystic to giant alkali feldspar, quartz, and muscovite, and is spatially zoned in terms of unique texture and composition. The pegmatoid is zoned from a felsic aplite zone with a layered texture proximal to the intrusion through quartz–feldspar pegmatoid and feldspar–quartz pegmatoid zones to a final distal quartz-dominated zone. The quartz–feldspar pegmatoid is striped and contains megacrystic feldspars that have grown nearly perpendicular to the edge of the pegmatoid, indicating the direction of movement of early exsolved magmatic fluids. Cathodoluminescence imaging indicates that there are five types of quartz within the feldspar–quartz pegmatoid: megacrystic, large phenocrystic, small phenocrystic, matrix, and vein-hosted quartz. Each of these generations of quartz crystallized early, with the disseminated metasomatic quartz that crystallized during the middle stages of pegmatoid generation being followed by the uniform crystallization of late-stage, space-filling quartz. In situ oxygen isotopic and trace element analysis indicates that all of the quartz within the pegmatoid records accelerated growth, with the middle-stage disseminated metasomatic quartz associated with an increase in δ18Oquartz values, and the late-stage space-filling quartz associated with a decrease in δ18Oquartz values. All of this quartz contains elevated concentrations of alkali metals and has low Li/Al ratios (generally 10‰, reflecting the fact that the fluids that formed these minerals were of the peraluminous granite water (PGW). The trace element compositions of the samples analyzed during this study also indicate a drop in the pH of the pegmatoid-forming fluids over time. The quartz within the feldspar–quartz pegmatoid also contains melt and gas–liquid fluid inclusions, with the latter containing significant amounts of gas-phase CH4, indicating that the pegmatoid formed from low oxygen fugacity fluids. Our data indicate that the shell-shaped pegmatoid zone within the Dahutang No. 1 ore block formed from primary PGW exsolved from the hosting intrusion, with the pegmatoid recording the transition from magmatic to hydrothermal processes during the continuous but multi-stage evolution of the Dahutang deposit. The late-stage, high-temperature, water-rich, high δ18O, alkali-metal-rich, low oxygen fugacity, and acidic nature of the hydrothermal fluids that formed the deposit promoted the transportation and further deposition of tungsten.

The investigation of epigenetic carbonate-hosted Pb-Zn deposits from China and Europe in the Eastern and Western orogens of the Tethyan Domain, have provided a new perspective on the range of processes operating in this deposit class globally. However, improved metallogenic models require new constraints on the timing of mineralization throughout the Domain. To address this need, we applied Re-Os pyrite dating to the world class Irankuh Zn-Pb deposit, Iran. The Irankah deposit is located in the thrust belt of the Malayer-Esfahan Pb-Zn Metallogenic Belt (MEMB) in the Zagros Orogen, Iran. Mineralization is hosted by the Goushfil Main Fault and adjacent dolomitized limestones. The hydrothermal mineral assemblage comprises sphalerite, galena, pyrite, minor chalcopyrite and sulfosalt minerals, together with dolomite, barite and abundant quartz. Pyrite associated with main-stage sphalerite mineralization has low concentrations of 3 to 37 ng/g Re and 6 to 49 pg/g Os that are typical of low-level highly radiogenic (LLHR) sulfides. Nonetheless, vein and replacement pyrites from the Goushfil orebody yielded a 5-point isochron age of 66.5 ± 1.6 Ma that is interpreted as the main Zn-Pb mineralization age. The new mineralization age confirms an epigenetic origin for the Irankuh Zn-Pb deposit and supports an early onset for compressional deformation in the Zagros Orogen. The geochronological data support textural evidence that mineralization in veins occurred during regional compression in an active tectonic environment. Therefore the possibility that magmatic fluids and/or heat contributed to the mineralizing system should be incorporated into regional exploration models. Further work is required to test the extent to which epigenetic carbonate-hosted Pb-Zn deposits in the thrust and fold belt settings of the Central and Eastern Tethys differ from those in the Western Tethys and classic Mississippi Valley Type ore deposits.

Rare earth elements (REEs) are a focus of current research due to their importance in a wide range of industries and technologies. Bayan Obo in China is the largest REE deposit in the world. Although some studies have investigated the banded REE ores in the Bayan Obo deposit, the origin and formation processes of the ores are unclear. In this study, we used X-ray powder diffraction, electron microprobe, laser ablation–inductively coupled plasma–mass spectrometry, and mass spectrometry methods to investigate the mineral assemblages and geochemical characteristics of minerals in banded ores in the Bayan Obo REE deposit. Based on petrographic observations, the early minerals that precipitated were alkali- and Fe-rich silicates, such as aegirine–augite and arfvedsonite, followed by bastnasite, fluorite, barite, calcite, and monazite in the late stage. The REE minerals in the banded REE ores are mainly monazite, bastnasite, and parisite (1–10 vol%) that overprinted gangue minerals, suggesting that REE mineralization occurred during the late hydrothermal stage. The sequence of mineral formation and their evolution caused progressive enrichment in REEs, F, Sr, and Ba. For example, fluorite in the banded REE ores has high concentrations of Sr (252–1910 ppm), Ba (1040–8230 ppm), and light REEs (1001–16,079 ppm), but is depleted in Nb and Ta. The bastnasite is enriched in Sr (885–4046 ppm), Ba (1073–80,809 ppm), and ΣREEs (99,631–158,227 ppm). The fluorite, arfvedsonite, and bastnasite in the banded REE ores have ɛNd(t) values of −3.68–1.78, −5.54, and 0.05, and initial (87Sr/86Sr)i (ISr) ratios of 0.70352–0.70478, 0.70620, and 0.70346, respectively. Based on these data, and the regional geological setting and Pb isotope data, it is proposed that fluorite and bastnasite crystallized from ferrocarbonatite and fine-grained dolomite, and the REE source was a mixture of HIMU mantle and global marine sediments. We also suggest that the carbonatite- or dolomite-hosting ores in Bayan Obo formed by melting of the subcontinental lithospheric mantle, which might have been previously metasomatized by REE- and CO2-rich fluids derived from subducted marine sediments.

The newly discovered Triassic Erdaokan Ag-Pb-Zn deposit having an ore reserve of 2964 kt, with an average grade of 517 g/t Ag, 0.6 wt% Pb and 0.4 wt% Zn, is the only known bitumen-bearing magmatic-hydrothermal Ag-Pb-Zn deposit in the northeastern segment of the Great Xing’an Range, NE China. Its genetic relationship with organic matter remains elusive. In this contribution, we present results from detailed geochemistry, isotope and biomarker studies on bitumen and discuss the genesis of bitumen and its relationship with Ag-Pb-Zn mineralization. The carbon isotope and biomarker analyses suggest a biogenic origin for the organic matter that formed bitumen. We infer that the organic matter was most likely sourced from the carbonaceous shale and limestone belonging to Niqiuhe Formation. Significant interaction between the organic matter and ore-forming fluid is indicated. The light n-alkanes and analogs, alkali elements, vanadium and nickel in the bitumen were removed by the ore-forming fluid, and a variety of metal elements entered into the bitumen. The thermochemical oxidation of methane induced by high-valence metal oxides and thermochemical sulfate reductions were the two main interaction mechanisms between the organic matter and ore-forming fluid, which made an effective contribution to metal precipitation in the Erdaokan Ag-Pb-Zn deposit. On this basis, we propose a genetic model for the genesis of the Erdaokan Ag-Pb-Zn deposit and other hydrocarbon-bearing magmatic-hydrothermal deposits which envisages a significant role played by the organic matter sourced from the sedimentary rocks in ore concentration.

Carbonatite-related rare earth element (REE) deposits are the most significant source of REEs worldwide. The processes of REE precipitation, enrichment, and mineralization remain controversial. The Cenozoic Mianning–Dechang (MD) REE belt, located in Sichuan Province, southwestern China, comprises one giant (Maoniuping), one large (Dalucao), and two small–medium (Muluozhai and Lizhuang) deposits. These deposits provide a continuous record of fluid evolution, and thus are ideal for investigating the processes of REE mineralization in carbonatite-related REE deposits. Given that sulfate (i.e., barite and celestite) and sulfide (i.e., pyrite and galena) minerals crystallized and precipitated in the pegmatitic to hydrothermal stages, respectively, the REE minerals formed later than the sulfate minerals. However, the formation sequence of the sulfide minerals and bastnasite is unclear, although both pyrite and bastnasite formed in the late hydrothermal stage. We used S isotope data for sulfate and sulfide minerals and Fe isotope data for pyrite to investigate the composition and evolution of ore-forming fluids during the magmatic–hydrothermal stages. The sulfate minerals have positive δ34SCDT values (+3.2‰ to +8.3‰), and the sulfide minerals have negative δ34SCDT values (−13.5‰ to − 5.6‰) in the four REE deposits. In the Maoniuping deposit, δ34SCDT values for barite from the pegmatitic stage (+4.7‰ to +5.7‰) are higher than for barite from the hydrothermal stage (+4.1‰ to +4.5‰), which indicate that hydrothermal activity led to relative enrichment in isotopically light S. The δ34SCDT values for barite (+3.2‰ to +5.5‰) are lower than for celestite (+6.2‰ to +7.2‰) from the pegmatitic stage in the Dalucao deposit. The δ34SCDT values for galena (−13.5‰) are also lower than for pyrite (−13.5‰ to −7.2‰) from the hydrothermal stage in the Guangtoushan section. In general, δ34SCDT values change from positive to negative values (+8.3‰ to −16.4‰) as the fluids evolved from the pegmatitic to hydrothermal stages, which can be attributed to a decrease in oxygen fugacity (fO2) and addition of sediment containing isotopically light S. Iron isotopic compositions of pyrite from the hydrothermal stage show significant variations (δ56FeIRMM-014 = −0.03‰ to +0.65‰ for the Maoniuping deposit; −0.14‰ to 0.00‰ for the Dalucao deposit; +0.05‰ to +0.35‰ for the Lizhuang deposit), and are higher than those for the carbonatites (δ56Fe IRMM-014 = −0.47‰ to −0.17‰). These data indicate there are two sources of Fe in the MD REE belt, which are the carbonatite–nordmarkite magma and 56Fe-rich sediment. Paleozoic–Mesozoic volcanic–sedimentary and Mesozoic clastic and carbonate rocks are exposed in the MD REE belt. In general, the S–Fe isotope data, along with geological and petrographic observations, indicate that the REE minerals formed later than the sulfate minerals, and the S–Fe were derived from both carbonatite magma and sediment containing isotopically light S and heavy Fe.

Fault zones control the locations of many ore deposits, but the ore-forming processes in such fault zones are poorly understood. We have studied the deformation and ore textures associated with fault zones that controlled the lead–zinc mineralization of the Dongmozhazhua deposit, central Tibet, ∼100 km southwest of Yushu City. Geological mapping shows that the structural framework of the Dongmozhazhua area is defined by NW–SE-trending reverse faults and superposed folds that indicate at least two stages of deformation. The first stage is characterized by tight nearly E–W-striking folds that formed during the closure of the Jinshajiang Paleo-Tethyan Ocean in the Triassic. The second stage of deformation produced NW–SE-trending reverse faults and related structures of the Fenghuoshan–Nangqian fold-and-thrust belt associated with India–Asia collision in the late Eocene to Oligocene. Scanline surveys along the ore-controlling fault zones show an internal structure that comprises a damage zone, a breccia zone with clasts that have become rounded, and a breccia zone with lenticular clasts, and this complex architecture was formed during at least two compressional substages of deformation. The Pb–Zn mineralization in the Dongmozhazhua area occurs exclusively close to NW–SE-trending reverse fault zones. Microtextural observations reveal that mineralization occurred as veinlets and disseminated blebs in limestone clasts, and as continuous bands and cements in fractured rocks. Cataclastic sulfide grains also can be seen in the matrix of some fault zones. The types of mineralization differ with structural position. The fillings of the ore-bearing veinlets typify the products of hydraulic fracture and both types of mineralization took place concurrently with regional contraction. We consider, therefore, that the ore-bearing fluids in the Dongmozhazhua deposit were concentrated in fault zones during regional compression and that the ore minerals were precipitated during hydraulic fracturing of host rocks. Subsequent fault activity pulverized some pre-existing sulfide material into cataclastic grains in the matrix of a tectonic breccia that developed in the same faults.

The Xiadan gold deposit from Jiaodong Peninsula contains more than 200 t of gold, and is one of the representative largest deposits within south part of the Zhaoping Fault zone. The gold orebodies consist of auriferous altered rocks that show disseminated and stockwork mineralization. Mineralization and alteration are structurally controlled by the NE- to NNE-striking Linglong detachment fault. Mineralization can be divided into three stages: (K-feldspar)–sericite–quartz–pyrite, quartz–gold–polymetallic sulfide, and quartz–carbonate, with the majority of the gold being produced during the middle stage. Based on a combination of petrography, microthermometry, and laser Raman spectroscopy, three types of fluid inclusion were identified in the vein mineral assemblages: NaCl–H2O (A-type), CO2–H2O–NaCl (AC-type), and pure CO2 (PC-type). Quartz crystals in veins that formed during the early stage contain mainly AC-type primary fluid inclusions, with rare PC-type inclusions. These fluid inclusions homogenize completely at temperatures of 253°C–408°C and have medium–low salinities (1.62–11.89 wt.% NaCl equivalent). Quartz crystals that formed during the middle stage contain all three types of fluid inclusion, and these fluid inclusions homogenize completely at temperatures of 176°C–335°C and have salinities of 0.70–14.73 wt.% NaCl equivalent. In contrast, quartz that formed during the last stage contains only A-type fluid inclusions; these inclusions have homogenization temperatures of 108°C–253°C and salinities of 1.73–11.60 wt.% NaCl equivalent. The above data indicate that the ore-forming system evolved from a CO2-rich mesothermal fluid into a CO2-poor fluid as a result of an influx of meteoric water. Fluid immiscibility is an essential prerequisite for metals precipitation in Xiadian. The characteristics of fluid inclusions, combined with H–O–S isotopes suggest that the ore-forming fluids might be of metamorphic origin. Based on the immiscibility of AC-type fluid inclusions, trapping pressures have been estimated at 88–339 MPa during ore formation, with a depth of metallogenesis of 8.8–12.6 km. The depth of erosion of study area has been calculated as about 10.3 km between 130 Ma and the present. Considering the gold mineralization occurred at around 130 Ma, the space with deep gold exploration is expectable at Xiadian.

The recently discovered Zhuxi W–Cu ore deposit is located within the Taqian–Fuchun Ore Belt in the southeastern edge of the Yangtze Block, South China. Its inferred tungsten resources, based on new exploration data, are more than 280 Mt by 2016. At least three paragenetic stages of skarn formation and ore deposition have been recognized: prograde skarn stage; retrograde stage; and hydrothermal sulfide stage. Secondly, greisenization, marmorization and hornfels formation are also observed. Scheelite and chalcopyrite are the dominant metal minerals in the Zhuxi deposit and their formation was associated with the emplacement of granite stocks and porphyry dykes intruded into the surrounding Carboniferous carbonate sediments (Huanglong and Chuanshan formations) and the Neoproterozoic slate and phyllites. The scheelite was mostly precipitated during the retrograde stage, whereas the chalcopyrite was widely precipitated during the hydrothermal sulfide stage. A muscovite 40Ar/39Ar plateau age of about 150 Ma is interpreted as the time of tungsten mineralization and molybdenite Re–Os model ages ranging from 145.9 ± 2.0 Ma to 148.7 ± 2.2 Ma (for the subsequent hydrothermal sulfide stage of activity) as the time of the copper mineralization. Our new molybdenite Re–Os and muscovite 40Ar/39Ar dating results, along with previous zircon U–Pb age data, indicate that the hydrothermal activity from the retrograde stage to the last hydrothermal sulfide stage lasted up to 5 Myr, from 150.6 ± 1.5 to 145.9 ± 1 Ma, and is approximately coeval or slightly later than the emplacement of the associated granite porphyry and biotite granite. The new ages reported here confirm that the Zhuxi tungsten deposit represents one of the Mesozoic magmatic–hydrothermal mineralization events that took place in South China in a setting of lithospheric extension during the Late Jurassic (160–150 Ma). It is suggested that mantle material played a role in producing the Zhuxi W–Cu mineralization and associated magmatism.

Understanding the geological history of the Lhasa Terrane prior to the India–Asia collision (~ 55 ± 10 Ma) is essential for improved models of syn-collisional and post-collisional processes in the southern Lhasa Terrane. The Miocene (~ 18–10 Ma) adakitic magmatism with economically significant porphyry-type mineralization has been interpreted as resulting from partial melting of the Jurassic juvenile crust, but how this juvenile crust was accreted remains poorly known. For this reason, we carried out a detailed study on the volcanic rocks of the Yeba Formation (YF) with the results offering insights into the ways in which the juvenile crust may be accreted in the southern Lhasa Terrane in the Jurassic. The YF volcanic rocks are compositionally bimodal, comprising basalt/basaltic andesite and dacite/rhyolite dated at 183–174 Ma. All these rocks have an arc-like signature with enriched large ion lithophile elements (LILEs; e.g., Rb, Ba and U) and light rare earth elements (LREEs) and depleted high field strength elements (HFSEs; e.g., Nb, Ta, Ti). They also have depleted whole-rock Sr–Nd and zircon Hf isotopic compositions, pointing to significant mantle isotopic contributions. Modeling results of trace elements and isotopes are most consistent with the basalts being derived from a mantle source metasomatized by varying enrichment of subduction components. The silicic volcanic rocks show the characteristics of transitional I–S type granites, and are best interpreted as resulting from re-melting of a mixed source of juvenile amphibole-rich lower crust with reworked crustal materials resembling metagraywackes. Importantly, our results indicate northward Neo-Tethyan seafloor subduction beneath the Lhasa Terrane with the YF volcanism being caused by the initiation of back-arc rifting. The back-arc setting is a likely site for juvenile crustal accretion in the southern Lhasa Terrane.

The deep crustal continental components and architecture of the western Central Asian Orogenic Belt (CAOB) have long been a matter of debate. This article presents an integrated study of published geochronological and Hf-in-zircon isotopic data for inherited zircons from the Palaeozoic granitoid rocks and associated felsic volcanic rocks of the Chinese Altai, East Junggar, and nearby regions. The aim is to trace the age spatial distribution of deep old crustal components. Our data set comprises 463 published age data obtained by SHRIMP and LA-ICP-MS from felsic igneous rocks in these areas. Among these samples, zircon xenocrysts were observed in 69 granitic rocks and 15 felsic volcanic rocks from the Chinese Altai and 30 granitoid rocks and five felsic volcanic rocks in the East Junggar, respectively.Three major zircon xenocrysts provinces are defined based on the distribution of these inherited zircon ages, combined with Hf-in-zircon isotopes. Province I, mainly situated in the eastern part of th...