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The origin of A-type granites has been the subject of great debate, especially the enigmatic synchronous A1- and A2-type granites. Cretaceous (~125 Ma) A1- and A2-type granites are common throughout the Lower Yangtze River Belt (LYRB), eastern China. However, their genesis still remains unclear. In this study, in-situ zircon Oisotopic data and chemical compositions of the Huayuangong (HYG) A-type granites in Anhui province, provide new insights into the origin and evolution of A-type granites in the LYRB, as well as the genetic link for synchronous A1- and A2-type granites. The HYG granites include syenogranite (75.9 wt%–76.6 wt% SiO2) and quartz syenite (66.1 wt%–66.9 wt% SiO2). Both are metaluminous and belong to ferroan series. They are characterized by high alkalis (K2O + Na2O = 8.36 wt%–8.55 wt% and 11.7 wt%–11.9 wt%), high field strength elements (Zr + Nb + Ce + Y = 909 ppm–1269 ppm and 1092 ppm–1329 ppm) and high Ga/Al ratios (10,000 ∗ Ga/Al = 4.91–4.96 and 2.64–2.68). The zircon saturation thermometer results indicate high magmatic temperatures (896–964 °C and 860–882 °C). All those geochemical features show an A-type granite affinity. They can be further classified into A1-and A2-type granites, corresponding to reduced and oxidized A-type granites, respectively. Additionally, the in-situ zircon O-Hf isotope compositions are also distinctly different, with δ18O = 4.7‰–6.0‰ and eHf(t) = −1.5 to −3.6 for A1-type granites, and δ18O = 7.0‰–7.8‰ and eHf(t) = −3.3 to −6.9 for A2-type granites. The geochemical signatures and newly discovered δ18O and eHf(t)values of the two A-type granite subgroups, indicate that they were derived from different source components and under disparate physicochemical conditions (e.g.,temperature, redox state and water contents). Lithospheric mantle-like isotopic data from zircons of A1-type granites suggest fractional crystallization of reduced, anhydrous basaltic magmas resulting in the formation of A1-type granites. In contrast, A2-type granites with relatively high δ18O and negative eHf values were generated from partial melting of the lithospheric mantle which was metasomatized by slab-derived melts/fluids. The coexisting A1- and A2-type granites were formed under the extensional setting where lithospheric thinning and asthenosphere upwelling occurred.

The Lower Yangtze River Belt in eastern China preserves evidence for widespread Mesozoic magmatism. Geochronological and geochemical studies have been conducted on the magmatic rocks and their associated mineral deposits; however, the relationships and melting conditions of spatially associated I- and A-type granites remain poorly constrained. The Qingyang–Jiuhuashan granitic complex in southern Anhui Province, eastern China, comprises primarily hornblende-bearing granodiorite, monzogranite, alkali-feldspar granite, and granitic porphyry, which yield zircon U Pb ages of 142.2 ± 1.3, 134.6 ± 1.2, 126.4 ± 1.9, and 125.9 ± 1.2 Ma, respectively. Zircon grains from an enclave in the monzogranite yield an age of 134.5 ± 1.1 Ma, similar to that of the host rock. The ages are consistent with the timing of regional magmatic events in southern Anhui Province. Whole-rock geochemical compositions indicate that the granodiorite and monzogranite represent I-type granites, whereas the alkali-feldspar granite and granitic porphyry display A-type signatures. The I- and A-type granites yield similar whole-rock Sr Nd isotopic compositions, but distinct zircon δ18O values. We infer that the I-type granites were produced through water-fluxed melting of Mesoproterozoic basement during subduction of the paleo-Pacific plate. The A-type granites were generated through partial melting of the lower crust, triggered by extensional upwelling of mantle-derived magmas that provided heat and alkali-rich fluids. We identify three stages of Cretaceous tectono-magmatic activity that occurred in response to ridge subduction and subsequent slab rollback beneath eastern China.

In general, the arc magmas are oxidized, forming magnetite-series granitoids. However, there are also ilmenite-series granitoids at convergent margins. The mechanism that controls the formation of different types of granitoids remains obscure. Here we show that the temporal distributions of ilmenite-series granitoids in Japan have a good correlation with oceanic anoxic events (OAEs). The subduction of OAE sediments with high contents of organic matters releases reducing fluids/melts into the mantle wedge, leading to the formation of ilmenite-series granitoids. This is supported by sulfur isotope compositions and high concentrations of organic gas of the ilmenite-series granitoids in Japan. The temporal correlation between OAEs and Il-series granitoids suggests that the OAE sediments was predominantly distributed within short distances (

Apatite is ubiquitous in A-type granites, and can be used to elucidate the volatile contents of the silicate melt, which reflect its source characteristics. A-type granites have been recognized as a distinct group of granites. A1- and A2-type subgroups are produced under different extensional settings. However, the details of the mechanisms behind the distinctive geochemical characteristics of A1- and A2-type granites remain obscure. Belts of Cretaceous A1- and A2-type granites occur along the Lower Yangtze River Belt in eastern China. Here we investigated the major and trace element compositions of apatites from contemporary A1- and A2-type granites at different localities along the Lower Yangtze River Belt, in order to decipher their discrepant source processes. Apatites from A1- and A2-type granites show similar major and trace elements, but differ in their F and Cl concentrations. Apatites from A1-type granites in the eastern part of the Lower Yangtze River Belt have much lower F and higher Cl concentrations compared to A2-type granites in the western part. Moreover, from the east to the west, the F concentrations of apatites from A1-type granites increase, while the Cl concentrations decline. In a subducted plate, F is retained by amphibole, chlorite, serpentine and mica minerals through the amphibolite stage, and finally by phengite and lawsonite during the eclogite stage, whereas, Cl is controlled by amphibole, chlorite and serpentine. The high and varied Cl concentrations in A1 subgroup apatites, therefore, may be attributed to the breakdown of amphibole, chlorite and/or serpentine decomposition during partial melting of subducted oceanic crust releasing a large amount of Cl at shallower depth. In contrast, F is transported to deeper depths in the subducted oceanic crust, and released through breakdown of phengite and lawsonite, making an important contribution to the formation of A2-type granites. Apatites from A1- and A2-type granite samples show regular changes in LREE/HREE, LREE/MREE and MREE/HREE ratios with increasing distance from the location of the subduction zone, probably as the result of nonsynchronous dehydration of the serpentine and phengite at different stages during subduction. We propose that A1- and A2-type granites on the Lower Yangtze River Belt were derived from sources metasomatised by fluids originating from the breakdown of amphibole, chlorite and/or serpentine with higher Cl, lower F, and from phengite and/or lawsonite with relatively higher F but lower Cl, respectively.

Paleoproterozoic A-type granites are widely outcropped in the North China Craton (NCC), particularly in the Trans-North China Orogen. However, their genesis and tectonic significance remain obscure. Here we report systematic studies on geochronology and geochemical characteristics of A-type granite in Huayangchuan, south margin of the NCC. The samples are enriched in total alkali (K2O + Na2O > 8.97 wt%), and depleted in MgO (0.84–0.93 wt%), CaO (1.28–1.90 wt%) and P2O5 (0.18–0.20 wt%), with high FeOT/MgO (5.69–6.67). They are characterized by high Zr + Y + Nb + Ce values (1293–1392 ppm) and 10,000 × Ga/Al ratios (3.14–3.35), which are typical characteristics of A-type granite. The Huayangchuan A-type granite can be further classified as A1-type subgroup based on particular geochemical features, e.g., low Y/Nb (0.87–1.00) and Yb/Ta (0.88–1.10). High precision zircon U–Pb dating of the A-type granite by secondary ion mass spectrometry (SIMS) yields Paleoproterozoic 207Pb/206Pb ages of 1829.5 ± 2.5 Ma. The low zircon ɛHf(t) values (−6.97 to −10.45), along with zircon Hf model age of 2.7–2.9 Ga, indicate that the Huayangchuan A-type granite was derived from partial melting of the ancient continental crust with contribution of enriched mantle components. The low zircon δ18O composition (4.00 to 6.78‰) indicates that the zircons were crystallized from low δ18O magmas, which derived from the crust metasomatized by low δ18O mantle fluids or melts. The E-W trend A1-type granitic plutons in the NCC are generally outcropped in a rift tectonic regime, which is consistent with the development of the mantle plume in the Xiong'er district. The large volume of basaltic magmas, generated by mantle plume head, underplated the lower continental crust and formed the Huayangchuan A-type granite.

Serpentinites are important volatile and fluid mobile element repositories in oceanic lithosphere and subduction zones, and thus provide significant constraints on global geochemical cycles and tectonic evolution at convergent margins. In this contribution, two types of serpentinites from the Mianlue suture zone in the Qinling orogenic belt, central China, are identified on the basis of detailed mineralogical and geochemical study. Serpentinites from the Jianchaling region (Group 1) are composed of lizardite/chrysotile + magnesite + magnetite. Most of these serpentinites (Group 1a), consist of pseudomorphic orthopyroxene and olivine, and are characterized by low Al2O3/SiO2, high MgO/SiO2 and Ir-type PGEs to Pt ratios, suggesting a residual mantle origin. Meanwhile, the U-shape REE pattern and positive Eu, Sr and Ba anomalies of these serpentinites indicate that serpentinization fluids have interacted with gabbroic cumulates at moderately high temperatures or associate with the chlorinity and redox conditions of the fluid. Considering the limited mobility of U in the hydrating fluids for the Group 1a serpentinites, hydrating fluids for these serpentinites are most likely derived from the dehydrated slab, and have been in equilibrium with subducting sediments. There are also some serpentinites with low-grade metamorphic recrystallization from the Jianchaling region (Group 1b), represented by recrystallized serpentine minerals (antigorite). The trace element compositions of these Group 1b serpentinites suggest that partial dehydration of serpentinites associated with the transformation from lizardite to antigorite in subduction zone is also likely to affect the geochemistry of serpentinites. Serpentinites from the Liangyazi region (Group 2) are composed of antigorite + dolomite + spinel + magnetite. The high Cr number (0.65–0.80) and low Ti concentrations of spinels in Group 2 serpentinites indicate a refractory mantle wedge origin. Fertile major element compositions (e.g., high Al2O3 content and Al2O3/SiO2) and conjoint enrichment in light rare earth elements and high field strength elements, however, suggest melt-rock interactions before serpentinization. Combined with their geochemical affinity to “subducted serpentinites”, we conclude that their protoliths (refractory mantle wedge peridotite) experienced melt-rock interactions and then were incorporated into the subduction channel before serpentinization. Studies on these two types of serpentinites indicate that serpentinites from the orogenic belt are most likely characterized by multi-source, multi-stage and multi-genesis, further providing important constraints on subduction channel processes.

Accretionary orogens are the primary sites for continental growth, but the rate and amount of crust generation throughout its evolution are poorly constrained. In this contribution, our new results about the genesis of two intermediate-felsic plutons are combined with a compiled granitoid dataset to evaluate the amount and rate of crustal growth throughout the evolution of the Western Kunlun orogen, which is a typical accretionary orogen associated with the consumption of the Proto-Tethys during the early Paleozoic. The ca.446 Ma Sanshili pluton was formed through interactions between metasomatized mantle wedge-derived oxidized magmas and the lower arc crust, as indicated by high whole-rock Mg#, high Ce4+/Ce3+ ratios (308–861) of ca.446 Ma zircons, and the existence of inherited zircons with ages of 546–472 Ma. The Yirba dioritic to granodioritic pluton was emplaced at 474 ± 3 Ma. Samples from the Yirba pluton are characterized by high K2O content, higher Mg# (40–49) than pure crustal melts, slightly higher Y + Nb concentrations, and high Th/Nb ratios, and slightly enriched to depleted Hf–Nd isotopes. Combined with the presence of the 502–531 Ma inherited zircons, the Yirba pluton is suggested to from through differentiation of the metasomatized lithospheric mantle derived-magmas beneath the juvenile intra-oceanic arc in combination with crustal reworking during regional extensions. The Yirba pluton, together with contemporary A1-type granites, thus marks an extension event at ca. 475 Ma in the Western Kunlun orogen. The compiled dataset reveals three magmatic flare-ups at 530–500 Ma, 480–470 Ma, and 445–430 Ma, corresponding to two slab rollback events and the slab break-off after the final closure of the Proto-Tethys. The three episodes of more intensive magmatism are associated with more radiogenic Hf–Nd isotopes and increased Nb/La and Nb/Y ratios, indicating more contributions from intraplate-like sources during lithospheric extensions. Meanwhile, element ratios (La/Yb, Sm/Yb, and Sr/Y) that are sensitive to crustal thickness are also elevated. These phenomena are consistent with rapid juvenile crust generation during extensional stages of accretionary orogens. Our study has also shown that the rate of new crust production is quite uniform for different extensional events. The crustal generation rate during slab break-off is much higher than that during slab rollback, although the proportions of juvenile inputs in granitoids formed during slab rollback are relatively higher. This may reflect extra inputs from partial melting of oceanic slabs and subducting sediments like those in continental collision zones and/or rapid asthenospheric upwelling coupled with enhanced crust reworking during slab break-off.

The Xishan Sn–W deposit is spatially related to K-feldspar granites in the Yangchun basin, western Guangdong Province, South China. LA-ICP-MS zircon U–Pb dating for the Xishan pluton defines an emplacement age of ~ 79 Ma (78.1 ± 0.9 Ma; 79.0 ± 1.2 Ma; 79.3 ± 0.8 Ma), consistent with the mineralization age of the Xishan Sn–W deposit constrained by molybdenite Re–Os isochron age (79.4 ± 4.5 Ma) and LA-ICP-MS cassiterite U–Pb ages (78.1 ± 0.9 Ma and 79.0 ± 1.2 Ma) for the cassiterite-quartz vein. These indicate a close genetic relationship between the granite and Sn–W mineralization. The Xishan K-feldspar granites have geochemical characteristics of A-type granites, e.g., high total alkali (Na2O + K2O = 7.88–10.07 wt.%), high Ga/Al ratios (10000*Ga/Al > 2.6) and high Zr + Nb + Ce + Y concentrations (> 350 ppm). They are further classified as A2-type granites. The whole-rock isotopic compositions of K-feldspar granites (initial 87Sr/86Sr = 0.705256–0.706181; eNd(t) = − 5.4 to − 4.8) and zircon eHf(t) values (− 7.8 to 2.0) suggest a mixed magma source. The low zircon Ce4 +/Ce3 + ratios (12–88) of K-feldspar granites suggest low oxygen fugacities, which is key for enrichment of tin in primary magmas. The K-feldspar granites have experienced strong differentiation as indicated by their high Rb/Sr and K/Rb ratios, and low Nb/Ta and Zr/Hf ratios, which play an important role in ore-forming element transportation and concentration. A-type granite characteristics of the Xishan pluton show that it formed in an extensional environment. The high F and low Cl characteristics of the K-feldspar granite are most probably attributed to slab rollback. In the Late Cretaceous, the Xishan Sn–W deposit was located near the interaction of the circum-Pacific and the Tethys tectonic realms. Late Cretaceous Sn–W deposits, including the Xishan deposit, form an EW-trending belt from Guangdong to Yunnan Province in South China. This belt is in accordance with the direction of the Neo-Tethys slab rollback in the Late Cretaceous. In addition, the NS-trending extension has been recognized in the Late Cretaceous in South China. We propose that the Xishan Sn–W deposit should be attributed to the Neo-Tethys slab rollback in the Late Cretaceous.

The Urumieh-Dokhtar magmatic belt of Central Iran runs parallel to the Zagros orogenic belt and has been resulted from Neotethys ocean subduction underneath Eurasia. The Bahr Aseman volcanic-plutonic complex (BAC), covering an area ~ 2000 km^2 in the Kerman magmatic belt (KMB) in the southern section of the Urumieh-Dokhtar belt, has long been considered as the earliest manifestation of extensive Cenozoic arc magmatism in KMB. The nature and timing of the magmatism, however, is poorly constrained. An area ~ 1000 km^2, in BAC and adjacent Razak volcaniclastic complex and Jebal Barez-type granitoids, was mapped and sampled for geochemistry and geochronology. Andesite and basaltic andesite are the main volcanic components in the study area; plutonic bodies vary from tonalite to quartz diorite, granodiorite and biotite-granite. The rocks in BAC display dominantly normal calc-alkaline character. On spider diagrams, the rocks are characterized by enrichments in LILE relative to HFSE and enrichments in LREE relative to HREE. These features suggest a subduction related setting for the BAC. La_N/Yb_N ratios for the intrusive and volcanic rocks range from 1.41 to 5.16 and 1.01 to 6.42, respectively. These values are lower than those for other known granitoids in KMB, namely the abyssal, dominantly Oligocene Jebal Barez-type (La_N/Yb_N = 1.66–9.98), and the shallow, dominantly late Miocene Kuh Panj-type (La_N/Yb_N = 12.97–36.04) granitoids. This suggests a less evolved magma source for the BAC igneous rocks. In Y vs. Nb and Th/Yb vs. La/Yb discrimination diagrams, an island-arc setting is defined for the BAC rocks. The rocks further plot in primitive island-arc domain in Nb vs. Rb/Zr and Y/Nb vs. TiO_2 diagrams. The BAC volcanic and plutonic rocks yielded zircon U–Pb ages of 78.1 to 82.7 Ma and 77.5 to 80.8 Ma, respectively. Zircon U–Pb dating of volcanic rocks and granitoids from the adjacent Razak complex and the Jebal Barez-type granitoids indicated 48.2 Ma and 26.1 Ma ages, respectively, consistent with earlier works on similar rocks elsewhere in KMB. The new data allow a revision of the chronostratigraphy/tectonic history of KMB. In Late Cretaceous, a back arc rift developed extending from Nain to Baft (NB back arc) to the northeast of the Sanandaj-Sirjan magmatic arc. Along with shrinking of the Neotethys Ocean, the dip angle of the subducting slab decreased during the Late Cretaceous, and arc magmatism moved from the Sanandaj-Sirjan zone landward. Meanwhile, Bahr Aseman volcanic-plutonic complex formed as an island-arc in NB back arc rift. Later with arc shift, due to shallowing of subducted slab, magmatism moved toward continent leading to extensive volcanism in Kerman magmatic arc during Eocene and Oligocene, represented by volcanic-sedimentary Razak and Hezar Complexes, respectively.

Adakite is a highly debated petrologic term that was originally proposed to describe igneous rocks formed by slab melting. Subsequent studies reported other ways to generate adakitic signatures such as the melting of mafic lower continental crust and fractional crystallization of basaltic magma. We studied adakitic rocks from the Taohuala Mountain at the southern margin of the Alxa Block, North China. These rocks are characterized by high Sr concentrations (300–450 ppm), high Sr/Y (20–75 ppm) and (La/Yb)N (25–67 ppm) ratios, and low Y (

The Luobuling porphyry Cu–Mo deposit belongs to the Late Cretaceous Zijinshan Cu–Au–Mo mineralization field in southeastern China. Due to intensive hydrothermal alteration and weathering, it is very difficult to collect fresh whole rock samples for geochemical and isotopic studies in Luobuling. Zircon and apatite are accessory minerals that are resistant to hydrothermal alterations. In this study, we compared the trace element and isotope compositions of zircon and apatite from ore-bearing and barren samples to understand the formation of the Luoboling Cu–Mo deposit. Zircon U–Pb LA-ICP-MS dating shows that the Luoboling porphyries formed at ~ 100 Ma (100.3 ± 1.2 Ma, 100.6 ± 1.5 Ma and 98.6 ± 1.2 Ma), which belongs to the late stage mineralization of the Zijinshan mineralization field. Zhongliao porphyritic granodiorite has the same age as the deposit (99.5 ± 1.6 Ma). The age of barren Sifang granodiorite is slightly older (109.7 ± 0.8 Ma). All these zircon grains have high Ce4+/Ce3+ ratios, indicating high oxygen fugacities. The ore-bearing samples show variable eHf(t) of − 7.3 to 0.2, suggesting either heterogeneous sources or mixing of two different magmas. Interestingly, the Hf isotope composition of barren samples is systematically higher (eHf(t) of − 3.6 to 5.5), implying a lower contribution of crustal materials. The OH mole percent of apatite grains from barren samples (LBL22-03 and SF09-05) is ~ 0.5, which is higher than that of apatite from the ore-bearing samples (LBL20-01 LBL20-02 and LBL22-02), indicating lower F, Cl contents or higher water contents in the magma. In apatite from the ore-bearing samples, Sr is high, indicating the absence of plagioclase crystallization. In contrast, barren samples have varied and lower Sr, indicating that apatite crystallization was accompanied by plagioclase. These patterns were controlled by water contents because the crystallization of plagioclase is suppressed by high water contents in magmas. It also suggests that the lower OH of ore-bearing apatite was resulted from higher F, Cl in the magma. High oxygen fugacity and water contents of Luoboling plutons are favorable for mineralization, which also implies their close relations to plate subduction.

The Late Mesozoic Qianlishan granitic complex in the western Nanling Range, South China is associated with the Shizhuyuan giant W–Sn–Mo–Bi polymetallic deposit. It mainly consists of three phases of intrusions, P-1 porphyritic biotite granite, P-2 equigranular biotite granite and P-3 granite porphyry. All three phases of granite contain quartz, plagioclase, K-feldspar and Fe-rich biotite. They have geochemical affinities of A-type granites, e.g., high FeOT/(FeOT + MgO) ratios (0.84–0.99), total alkali (Na2O + K2O, 7.50–9.04 wt.%), high Ga/Al ratios (10,000*Ga/Al > 2.6) and high Zr + Nb + Y + Ce concentrations (> 350 ppm). High Y/Nb ratios (> 1.2) suggest that the Qianlishan complex belongs to A2-type granite. Zircon U–Pb ages indicate a short age interval decreasing from 158–157 Ma, to 158–155 Ma and to 154 Ma for the P-1, P-2 and P-3 granites, respectively. These ages are similar to the mineralization age of the Shizhuyuan tungsten polymetallic deposit, within error. The Qianlishan granites were generated at low oxygen fugacity conditions based on the low values of zircon Ce4 +/Ce3 + ratios (1.53–198) and significantly negative Eu anomalies (EuN/EuN*, 0.03–0.13) in apatite. New zircon eHf(t) values for the P-3 granite range from − 13.0 to − 4.4, similar to those previously obtained for the P-1 and P-2 granites. Both the granite and apatite grains therein are characterized by high F but low Cl concentrations, suggesting the influx of a high F/Cl component. The P-2 granites especially contain higher F contents (1840–8690 ppm) and W (7–158 ppm) and Sn (6–51 ppm) concentrations and with stronger evolution features. Positive trends between F and W and Sn of Qianlishan complex indicate that high F source is crucial for mineralization of W and Sn. We consider that the lithospheric mantle source may have been metasomatized by subduction fluids in the far end of subduction zones to produce the A2 feature of the Qianlishan granite and the fluorine was introduced through breakdown of phengite in the oceanic slab. Partial melting of the lithospheric mantle was induced by upwelling of the asthenospheric mantle as a consequence of slab rollback. Tungsten and tin have been enriched in reduced granitic magmas through fractionation enhanced by high F contents, forming the giant polymetallic deposits.

A large porphyry Cu–Au deposit associated with early Cretaceous intrusive rocks has been discovered and explored in the Shaxi area, Lower Yangtze River Belt (LYRB), eastern China. We studied two types of intrusive rocks in the Shaxi area: Cu–Au mineralization related diorites and quartz-diorites (adakitic rocks), and newly found high Sr/Y ratio biotite-gabbros. They were formed almost simultaneously with crystallization ages of ca. 130 to 129 Ma, younger than the early stage shoshonitic rocks (Longmenyuan, Zhuanqiao and Shuangmiao Fm.) in the Luzong volcanic basin, ~ 10 km south of the Shaxi area. These intrusive rocks show similar distribution patterns of trace elements (enriched in LILEs and depleted in HFSEs) and REEs (enriched in LREEs and depleted in HREEs, no Eu negative anomaly, flat HREE patterns). The diorites and quartz-diorites are adakitic rocks with calc-alkaline affinity, distinguished from other adakitic rocks in the LYRB which are high-K calc-alkaline series. The biotite-gabbros are not adakitic rocks, although they are characterized by high Sr/Y ratios. Shaxi adakitic rocks show positive zircon e Hf (t) values, which may be attributed to the contribution of subducted oceanic crust, while the e Hf (t) values of the biotite-gabbros are mostly negative, indicating the involvement of old crustal materials. Although Sr–Nd–Pb isotopes of Shaxi adakitic rocks are more depleted than those of other adakitic rocks in the LYRB, they are still slightly enriched, similar to continental arc adakites in the Andean Austral Volcanic Zone. The Shaxi adakitic rocks are characterized by high Sr contents and Sr/Y ratios, medium (La/Yb) N , MgO contents and Mg#, and low K 2 O/Na 2 O ratios, decoupling of Sr/Y and (La/Yb) N , low Th/U values, exhibiting characteristics of slab-derived adakitic rocks. They were not produced by fractional crystallization of basaltic magmas like adakitic rocks in Edong–Jiurui and Tongling but originally generated from partial melting of subducted paleo-Pacific Plate. Their enriched Sr–Nd–Pb–Hf isotopes indicate that the primary adakitic melts experienced assimilation of LYRB continental crust during ascending to the surface. While other high-K calc-alkaline “C-type” adakitic rocks in the LYRB were generated from mantle melting followed by crustal AFC processes. The Shaxi biotite-gabbros were generated from partial melting of enriched sub-continental lithosphere mantle (SCLM), which was previously metasomatized by sediment melts and adakitic slab melts. The LYRB adakitic rocks are characterized by high oxygen fugacities, thus favorable for Cu–Au mineralization.

The Qian'echong Mo deposit is a large porphyry Mo deposit located in the northwest Dabie Mountains, central China, with proven Mo reserves of 741 Mt at 0.081%. Chondrite-normalized REE patterns of most zircon from samples QEC002, 003, 004 and 011 show HREE enrichment with distinctive positive Ce and moderately negative Eu anomalies, which are typical of magmatic zircon in porphyry deposits. Zircon grains from sample QEC001 are all hydrothermal in origin, whereas there are only several hydrothermal zircons in the other samples. The Ti-in-zircon thermometer yields temperatures of 700–740 °C for the magmatic zircon. The Ce 4 + /Ce 3 + calculated from the Ce anomaly is a sensitive and robust indicator of magmatic oxidation status. Magmatic zircon have Ce 4 + /Ce 3 + and (Eu/Eu*) N ratios ranging between 10–577 and 0.2–1.3, respectively. Compared to the Shapinggou deposit (Climax type) also in the Dabie Mountains, the Qian'echong zircon has systematically lower Ce 4 + /Ce 3 + . Apatite from the Qian'echong deposit belongs to the F-apatite variety, with fluorine concentrations varying between 2.13–4.50% and Cl concentrations between 0.01–0.28%. Whole rock samples of the porphyry from the Qian'echong deposit have F contents of 360–1230 ppm. The porphyry intrusion is consistently associated with calc-alkaline granitic to granodioritic porphyries, with lower F, Nb, and Ta concentrations, and systematically lower Mo contents than the Climax-type deposits. All these characteristics are similar to other low-F porphyry Mo deposits along the eastern Pacific margin. Fluorine is mainly hosted in phengite during plate subduction, which may decompose far beneath the surface of the subduction zone. Therefore, high F deposits may be interpreted as locating the farthermost position reached by the subducting slab. Nevertheless, the F contents of the Qian'echong deposit is much higher than in adjacent barren granites, and may have incorporated additional F from the subduction slab. Given that the Qian'echong porphyry Mo deposit is only 77 km to the west of the Shapinggou Climax-type high-F porphyry Mo deposit, the dramatic difference in F contents suggests that the westward subduction of the Pacific and Izanagi plates may at least have extended to somewhere between the Shapinggou and Qian'echong deposits.

Mafic microgranular enclaves (MMEs) are commonly formed during magma mixing and usually record contrasting physicochemical diagenetic characteristics relative to their host rocks. We present a finding that some MMEs from the Cretaceous Qianjia pluton, which is believed to be the product of magma mixing, exhibit diagenetic conditions analogous to those of their host granites. Integrated calculations based on in situ compositions of minerals (e.g., zircon, titanite, amphibole, feldspar, and apatite) from the Qianjia monzonitic MMEs and their host granites indicate that they exhibit similar diagenetic temperatures (700–800 °C) and pressures (0.20–0.28 GPa), but discrepant oxygen fugacity and water activity. The MMEs have higher oxygen fugacity and water activity, as well as lower Th/U ratios, compared to the host granites, suggesting more oxidized and H2O-rich circumstances. Besides, high F concentrations and F/Cl ratios in apatites from both the MMEs and host granites and their parent magma indicate a relatively F-rich magma source that was probably derived by F-bearing mineral dehydration during plate subduction. Similar physicochemical diagenetic conditions between the MMEs and their host granites seemingly reveal their cognate features; however, slight differences in the oxygen fugacity, water activity, and chemistry of certain minerals (e.g., apatite and titanite) provide clues on magma mixing. We therefore propose that the MMEs involved might have been derived from local heterogeneous hybrid melts or by early crystallization during a post-mixing process. In this case, information about the magma mixing has been almost eliminated due to the geochemical re-equilibration. Therefore, in the case of magma-mixing derived intrusions, the MMEs could be formed not only during magma mixing but also during a post-mixing stage, in which certain minerals most likely preserved a few geochemical characteristics of magma mixing.

Serpentinite from the North Qaidam ultrahigh pressure metamorphic belt in northern Tibet is studied to provide insight into petro-geochemical evolution of serpentinite from seafloor hydration to subduction zone metamorphism. The North Qaidam serpentinite can be divided into undeformed lizardite serpentinite that was not severely overprinted during subduction and deformed antigorite serpentinite that was well recrystallized during subduction. Petrological and geochemical analyses demonstrate that the serpentinite was originally melt-percolated refractory abyssal harzburgite. Considering the local geodynamic setting, it is inferred that the serpentinite probably originated from the oceanic lithosphere that subducted before continental subduction. Relatively uniform low δ18O (4.0‰–4.5‰) of the antigorite serpentinite indicates high temperature hydrothermal alteration of protolith harzburgite by seawater. In contrast, much lower δ18O (0.6‰–2.7‰) of the lizardite serpentinite is ascribed to exchange with meteoric water at the Earth’s surface. Relict serpentinization textures are well preserved in the lizardite serpentinite, with reactions of olivine to lizardite and magnetite, pyroxenes to talc, tremolite, and lizardite, and spinel to chromite and chlorite. The replacement of lizardite by antigorite during subduction mostly initiates along grain boundaries and interconnecting veinlets, implying fluid-assisted transformation of lizardite into antigorite. Partial decomposition of antigorite produces magnesian secondary olivine in the antigorite serpentinite, while direct breakdown of metastable lizardite generates ferroan secondary olivine in the lizardite serpentinite. The serpentinite is enriched in fluid-mobile elements, with U primarily accumulated during seafloor alteration and alkalis notably introduced by sedimentary fluids at bending faults or in accretionary wedge. Infiltration by fluids equilibrated with sediments is also supported by highly elevated 87Sr/86Sr of the serpentinite. Moreover, 87Sr/86Sr of the antigorite serpentinite (0.710649–0.713996) is higher than that of the lizardite serpentinite (0.707184–0.708502), which implies more intense interaction of sedimentary fluids with the former than the latter. However, the lizardite serpentinite contains more alkalis and less U than the antigorite serpentinite, which indicates that large proportions of alkalis were lost during partial dehydration of serpentinite, while U was not released.

This paper reports zircon LA-ICP-MS U–Pb ages and Hf–O isotopic ratios, and whole-rock major and trace element data of Early Cretaceous felsic intrusive rocks from Nagqu area, the northern Lhasa subterrane, southern Tibet. LA-ICP-MS zircon U–Pb dating of biotite granites and biotite monzogranites in the area yields magmatic crystallization ages of ca. 112 Ma, which suggests that they were emplaced in the late Early Cretaceous. Both rocks show high-K calc-alkaline to shoshonitic composition and slightly–moderately peraluminous signature. They are enriched in the alkalis, Rb, Th, K, U and light rare earth elements, depleted in Nb, Ta, Ti and P, and characterized by high Al 2 O 3 contents (12–16 wt.%), high Rb/Sr ratios (1.3–33) and low Mg # values (15–39). Their magmatic zircons have negative e Hf (t) values (from − 25.9 to 0.5) and high positive δ 18 O values (from 7.9‰ to 11.5‰). All the above characteristics indicate that Nagqu biotite monzogranites and biotite granites were likely derived from hybrid melts of sediments from the continent crust with minor mantle-derived input, then experienced varied degrees of fractional crystallization. The Nagqu intrusion is a component of the late Early Cretaceous magmatic flare-up event that occurred during ~ 120–100 Ma in the northern and partly central Lhasa subterranes. This magmatic flare-up is marked with a great compositional diversity (basalt, rhyolite, adakitic rocks, dioritic enclave, biotite monzogranite and granite) that might be caused by the slab breakoff of the southward subducting Bangong–Nujiang oceanic lithosphere, or more likely by slab window opening, which may have significantly contributed to juvenile crustal growth of the northern Lhasa subterrane.

Qulong porphyry Cu deposit is the largest Cu deposit in China so far discovered, with total reserves of 10.6 Mt Cu@0.5% and 0.5 Mt Mo@0.03%. The petrogenesis of the Miocene intrusion and its genetic association with Cu mineralization have been debated. This study presents new results on whole rock major and trace elements, Sr–Nd isotopes, zircon U–Pb dating, Hf–O isotopic compositions of the Qulong ore-bearing and barren adakites. All the Qulong adakites studied here have low MgO (

Haiyang granite complex consists of K-feldspar granite and syenite, with a total exposure area of ~ 600 km2. The K-feldspar granite is metaluminous (A/CNK = 0.70 to 0.99) and the syenite is slightly peraluminous (A/CNK = 1.01 to 1.10), both of which have typical characteristics of A-type granite with high total alkali contents and FeOT/(FeOT + MgO) ratios. Zircon U–Pb age are 116.8 ± 1.7 Ma and 115.8 ± 2.2 Ma, for the K-feldspar granite and the syenite, respectively. This is consistent with field observation that the syenite intruded into the K-feldspar granite. Varied zircon O isotope (5.65–7.78‰ for K-feldspar granite and 4.68–7.08‰ for syenite) with peak values that are marginally higher than those of mantle zircon reflects important mantle contributions. These together with large variation of zircon eHf(t) values of K-feldspar granite (− 22.4 to − 15.6) and syenite (− 24.6 to − 13.5), can best be explained by the involvement of at least two components, e.g., enriched lithospheric mantle +/− subducted materials, and upwelling asthenosphere. Apatite has right decline REE pattern. The apatite from K-feldspar granite has higher Cl contents than those of syenite, implying more influence from a subduction released fluid in K-feldspar granite source. This distinction is supported by the systematically higher oxygen fugacity of K-feldspar granite as indicated by zircon Ce4 +/Ce3 + ratios. In the Yb/Ta–Y/Nb, Ce/Nb–Y/Nb diagrams, both K-feldspar granite and syenite plot in A1-type, with K-feldspar granite plotting closer to A2. In the Nb–Y–3Ga and Nb–Y–Ce charts, syenite plots near the boundary between A1 and A2, whereas some K-feldspar granite samples plot in A2 field, indicating a tendency of transition originally from A2 to A1. In general A1 granites form in intraplate settings, whereas A2 granite forms in post-collision. It is likely that mantle components metasomatized by subduction released fluids are easier to be partially melted, forming K-feldspar granite (closer to A2 type) with higher oxygen fugacity, which consequently eliminated subduction signatures, and then followed by A1 type syenite. Similar to the Lower Yangtze River belt, where both A1 and A2 group granites of similar ages outcropped in the same region, Haiyang granite complex may also be plausibly explained by a ridge subduction model, which has been proposed as the mechanism that controlled the decratonization of the North China Craton.

Granitoids near the Bayan Obo giant rare earth element (REE) deposit at the north margin of the North China Craton (NCC), the world's largest light REE (LREE) deposit, have been taken by some authors as the key factors that controlled the mineralization. In contrast, others proposed that the REE deposit has been partially destructed by these granitoids. Here we report systematic studies on geochronology and geochemical characteristics of granitoids of different distances from the orebodies, to investigate the genesis and their relationship to the giant Bayan Obo deposit. Granitoids studied here, including granites and quartz monzonites, are peraluminous with A/CNK = 0.99–1.11, LREE enriched and heavy REE (HREE) depleted, with variable REE concentrations (total REE = 54–330 ppm) and large negative Eu anomaly (δEu = 0.19–0.70). The REE patterns are distinct from those of ore-bearing dolomites. Some samples have slightly higher LREE concentrations, which may have been contaminated by the orebodies during intrusion. Trace elements of the granitoids are characterized by positive Pb anomaly, strong negative Ti anomaly and Nb, Ta and Sr anomalies. The granites exhibit negative Ba anomaly. The granitoids plot within the post-collision granite field in the Pearce diagram, which is consistent with the tectonic regime. The quartz monzonites and one granite have A-type granite characteristics and belong to the A 2 subgroup. Zircons in these granitoids have high Th/U values, which are typical for magmatic zircons. High precision U–Pb dating for these zircons by secondary ion mass spectrometry (SIMS) and laser ablation inductively coupled plasma mass spectrometry (LA–ICP-MS) yields Permian–Triassic 206 Pb/ 238 U ages ranging from 243.2 to 293.8 Ma. The formation of the granitoids is > 55 Ma later than the latest ore forming age. The zircons have low La concentrations (0.02–12 ppm), high (Sm/La) N (0.8–685) and Ce/Ce ⁎ (1.4–80). The Ti-in-zircon temperature of the granitoids ranges from 590 to 770 °C. All these evidences suggest that the granitoids have no contribution to the formation of the Bayan Obo deposit. Granitoids that are close to the orebodies had limited interaction with it and gained some LREE-enriched characteristics during magmatisms. Nevertheless, their effects to the orebodies are subtle. All the granitoids formed in a post-collisional tectonic regime at convergent margins, which is consistent with plate subduction during the closure of the Palaeo-Asian Ocean, which started in the Neoproterozoic and lasted until the Carboniferous/Permian.

South China is famous for its polymetallic deposits, with more than 50% of the world's W and Sb reserves and 20% of the Sn reserves, as well as abundant Cu–Mo–Pb–Zn–Au–Ag, Ta, Nb, HREE and U. This special issue reports recent progress on the tectonic evolution, magmatism and ore deposits of South China, which leads to a more comprehensive understanding of the Mesozoic large scale magmatism and mineralization events: (1) South China has been located in backarc settings during multiple subductions since the Paleozoic, which may have contributed to pre-enrichments of the ore-forming materials. (2) The Pacific plate subduction was a principle factor that controlled the late Mesozoic large scale magmatism and mineralization in South China, through flat subduction, ridge subduction/slab tearing and slab rollbacks.

The Tongling district in the Lower Yangtze River belt is one of the most important Cu-polymetal producers in China. Copper–Au deposits in the region are closely related to Early Cretaceous dioritic intrusions, which can be classified into three rock associations: pyroxene diorite–pyroxene monzodiorite, quartz diorite–quartz monzodiorite and granodiorite. The dioritic rock series (SiO2 = 54.6–64.5 wt.%) are calc-alkaline, with high Al2O3 (> 15.4 wt.%), Ba (Ba > 700 ppm) and Sr concentrations (~ 920 ppm in average), and low Y and Yb concentrations, all of which are typical for adakite. Geochemical characteristics suggest that the Tongling adakitic rocks are genetically related to slab melting and subsequent interaction with the mantle, likely during a ridge subduction along the Lower Yangtze River Belt in the Early Cretaceous. Geothermometers show high formation temperatures of 800–900 °C, which is consistent with interaction with the asthenosphere mantle as indicated. The relatively low eNd(t) values (− 11.2 to − 16.7) and high (87Sr/86Sr)i ratios (0.7067 to 0.7095) may be plausibly interpreted by contamination of enriched mantle materials and/or continental crust. The Tongling dioritic rocks are characterized by high radiogenic Pb isotopes with (206Pb/204Pb)i = 17.80–18.56, (207Pb/204Pb)i = 15.46–15.60, and (208Pb/204Pb)i = 37.92–38.48, which mostly plot in the field of MORB, near the intersection of EM-1 and EM-2, and are clearly different from those of the upper and lower continental crust and Dabie adakites. These exclude major contamination from the continental crust. Given that eastern China has both EM-1 and EM-2 types of enriched mantle, whereas the Tongling region is located near the transition from EM-1 to EM-2, the enriched Sr–Nd isotopic characteristics of Tongling adakites are best explained by slab melts with assimilation of enriched mantle components.

Nanling is the largest W–Sn mineralization belt in the world, the formation of which remains obscure. In contrast to most other deposits in the Nanling region, Dabaoshan is a polymetallic deposit, located in north Guangdong province, southeastern China. Porphyry Mo deposit was found in 2008 in the north part of Dabaoshan ore district. Here we report zircon and molybdenite ages and geochemistry results of zircon and apatite. Zircon U–Pb LA–ICP-MS dating shows that the porphyry Mo deposit formed at 167.0 ± 2.5 Ma (2σ), which is identical to the molybdenite Re–Os age for the ore deposit (166 ± 1 Ma) within error. These ages are marginally older than the major W–Sn mineralization event in the Nanling region (160 ± 5 Ma). Zircon grains associated with the Dabaoshan porphyry Mo deposit have high Ce(IV)/Ce(III) values (356–1300), which indicate high oxygen fugacity, likely associated with plate subduction. Apatite from the Dabaoshan porphyry has high and varied F with low Cl concentrations, suggesting that it formed in a F-enriched environment with high F/Cl components in the magma source. This is consistent with abundant high-F granites in the Nanling region. Chlorine is highly mobile at the early stage of plate subduction. In contrast, F is mainly hosted by minerals that are fairly stable at shallow depths, e.g., apatite, phengite, such that is much less mobile than Cl before phengite decomposition. Therefore, the F/Cl ratio increases with increasing distance from the subduction zone. Compared to the Dexing porphyry deposit to the northeast, the Dabaoshan porphyry has lower Ce(IV)/Ce(III) and high F/Cl. It is also about 5 Ma younger than the Dexing porphyry Cu deposits. All these phenomena can be plausibly interpreted by slab rollback of the obliquely subducted Pacific plate in the Jurassic. We propose that the subducting slab reached the Dabaoshan region before ~ 167 Ma, through a “flat” subduction regime, resulted in high oxygen fugacity in the magmas, which is followed by abrupt slab rollback. The onset of slab rollback is the most favorable event that leads to decomposition of phengite in the subducting slab because of abruptly elevated temperatures, releases F and consequently increases F/Cl in magmas. The Ti-in-zircon temperatures of the mineralized porphyry range from 608 to 641 °C, with an average of about 630±15 °C, whereas average temperature of the barren granodiorite nearby is 700 ± 9 °C. Considering that the Mo porphyry deposit appears as an egg shell surrounding the granodiorite and the geochemical behavior of Mo, we propose that the mineralization was related to the assimilation of metamorphosed sedimentary rocks by the granodiorite.

Early Cretaceous A-type granites in the Lower Yangtze River belt, central eastern China, with both A 1 and A 2 chemical subgroups, formed at 125 ± 2 Ma, after a Cretaceous ridge subduction. Remarkably, A 1 and A 2 group granites are distributed in three zones, roughly parallel to each other and to a slightly older adakite belt. In general, A 1 granites form in intraplate settings, whereas A 2 granites near paleo-convergent margins. The alternate distribution of these two subgroup A-type granites is compatible with a proposed Cretaceous ridge subduction in the region. The subduction of a dry and hot spreading ridge may have only released small amount of fluids, so that metasomatism on the overriding lithosphere was undetectable, correspondingly resulted in A 1 granites later on. In contrast, wetter and colder oceanic crust away from the spreading ridge was responsible for mantle metasomatism and consequently the formation of A 2 granites. Further away from the ridge, the subduction angle was much steeper, and dehydration of the slab had occurred earlier during the subduction, and thus dramatically reduced mantle metasomatism, corresponding to A 1 granites again. Both A 1 and A 2 granites formed within a short period of time due to slab window/rollback, after the ridge subduction. The distribution of the A 1 and A 2 granites together with the adakite belt may be taken as discrimination indice for ancient ridge subduction.

Felsic veins within the Xitieshan UHP eclogite in North Qaidam, NW China vary from 1 cm or less to several decimetres in width, exhibiting coarse granular in texture and heterogeneous distribution in mineral assemblages. They encircle or cut the deformed sub-lentoid eclogite body. Some fine veins extended into and ended in the eclogite, without visible link to their country rocks. They consist mainly of feldspar and quartz with minor amounts of muscovite, biotite and amphibole. To constrain their formation age, the conditions and source of vein-forming fluid/melt, and the relationship between the veins and host UHP eclogite, a combined study of zircon U–Pb dating and mineral inclusions was carried out on the felsic veins and their host eclogite. Zircon grains from the felsic veins are perfectly euhedral with zonations, characterized by very low Th/U ratios and steep HREE patterns without Eu anomalies. These zircons contain micro-inclusions of plagioclase, muscovite, garnet and quartz, which are consistent with mineral assemblage of the veins except for garnet captured from the host eclogite, indicating that these zircons crystallized during the veining. LA-ICPMS U–Pb dating yielded a weighted mean 206 Pb/ 238 U age of 428 ± 2 Ma, representing the formation age of veins. Zircon grains from the host eclogite are oval to round with homogeneous and/or cloudy internal-structure; residual core can be observed locally. They contain eclogite–facies micro-inclusions of garnet, omphacite, rutile and kyanite in metamorphic domains. LA-ICPMS U–Pb dating gave a metamorphic age of 458 ± 2 Ma. Geochemical analyses show that the felsic veins are tonalitic with high Na/K ratios, high Sr contents but low Y and Yb contents, and LREE-enriched patterns, consistent with partial melting of omphacite in eclogite at elevated pressures. Therefore, the felsic veins were most likely derived from partial melting of the host UHP eclogite. There is a considerable difference of about 30 Myr in zircon U–Pb age between the UHP eclogite–facies metamorphism and the felsic veining, indicating that the partial melting took place in the exhumation stage of the UHP terrain.

Voluminous Late Paleozoic igneous rocks and associated Cu–Au–Mo deposits occur in the northwestern Tianshan district, Xinjiang, west China. However, the tectonic setting and petrogenesis of these rocks remain controversial. This paper reports zircon U–Pb and Hf CUU isotopic data, major and trace elements, and Sr–Nd–Pb isotopic data for the intrusive rocks and minor dacites in the Lamasu–Dabate area of northwestern Tianshan adjacent to the Cu–Au–Mo deposits. LA-ICPMS U–Pb zircon analyses suggest that the Lamasu porphyries were formed at 366 ± 3 Ma and contain 907–738 Ma inherited zircons, the Dabate dacites were formed at 316 ± 4 Ma, and granite porphyries were formed at 289 ± 3 Ma with ~ 319 Ma inherited zircons. The Lamasu porphyries consist of plagioclase granite and granodiorite, and are geochemically similar to adakites, e.g., having high Al2O3 (14.54–19.75 wt.%) and Sr (308–641 ppm) and low Y (7.84–16.9 ppm) contents, with fractionated rare earth element (REE) patterns and slightly positive Sr anomalies. However, they have variable initial ratios of 87Sr/86Sr (0.7072–0.7076) and 206Pb/204Pb (18.139–18.450), and variable eNd(t) (− 5.6 to − 0.8) and positive eHf(t) (+ 1.4 to + 10.6) values. They also have variable Mg# (100 × Mg2+/(Mg2++ Fe2+)) (41–73) and low Th (3.13–8.09) and Th/Ce (0.14–0.28) values. We suggest that the Lamasu adakitic magmas were generated through partial melting of southward subducted Junggar oceanic crust, with subsequent melt-mantle interaction and assimilation of basement rocks. The Dabate dacites show typical arc-like geochemical characteristics (e.g., enrichment of large ion lithophile elements (LILE) and strong negative anomalies of Ta, Nb, P and Ti), with variable eNd(t) (+ 0.1 to + 3.3). They were probably generated by melting of juvenile basaltic lower crust as a result of magma underplating. The Dabate granite porphyries are geochemically similar to A2-type granites, e.g., high SiO2 (75.6–77.6 wt.%) and alkalis (Na2O + K2O = 8.27–8.70 wt.%), low CaO (0.28–0.34 wt.%) and Mg# (2–10), and obvious negative Eu, Ba and Sr anomalies. They have variable values of eNd(t) (− 1.7 to 0) and 206Pb/204Pbi (18.567–18.721) and zircon eHf(t) (+ 0.5 to + 11.1). The Dabate A-type granite porphyries contain Late Carboniferous residual zircon cores, suggesting that their source rock possibly contained Carboniferous arc igneous rocks. Taking into account all available data from Late Paleozoic magmatic rocks and Cu–Mo–Au mineralization in the northern Tianshan district, we suggest that the Dabate–Lamasu area was a continental arc during the Late Devonian–Carboniferous but had entered a post-collisional stage by the Early-Permian (~ 290 Ma).

The Baimazhai deposit in Yunnan Province is one of the largest Cu–Ni sulfide deposits hosted in mafic–ultramafic intrusions in China. Concentrations of platinum-group elements (PGE) in massive sulfide ores and host rocks from Baimazhai were determined by using inductively coupled plasma mass spectrometry (ICP-MS) following nickel sulfide fire assay pre-concentration. The results show that the total PGE (ΣPGE) are quite low, decreasing gradually from central massive ores (78.2–556 ppb) to olivine pyroxenite (0.472–67.0 ppb), gabbro (0.847 ppb) and, websterite (0.76–0.809). The intruded lamprophyre dykes also show low ΣPGE (2.98–4.07 ppb). The ΣPGE exhibit obvious positive correlations with Au, Ni and Cu contents. Primitive mantle normalized PGE patterns of the massive Cu–Ni ores are of the Pt–Pd type with relatively steep and trough-like patterns, which are similar to those of the host rocks. In addition, the Pt/Pd and Cu/Pd ratios of the massive sulfide ores are similar to those of olivine pyroxenite, gabbro and websterite. These characteristics suggest that sulfides in the massive ores are of magmatic origin, co-genetic with their host rocks. The relatively high Pt/Pd ratios of the Baimazhai massive sulfide ores (averaging 0.83) and their host rocks imply that the Baimazhai sulfides formed in a single sulfide saturation event, but not through multiple sulfide injections. High Ir contents (0.77–5.52 ppb, averaging 2.35 ppb) and dramatically variable Pd/Ir ratios (4.76–296, averaging 138) of the massive sulfide ores suggest that the Baimazhai sulfide ores might have suffered significant late stage hydrothermal alteration. The Baimazhai massive sulfide ores yield a Re–Os isochron age of 259 ± 20 Ma (MSWD = 0.025), which is the same as the major eruption stage of the Emeishan large igneous province and the Baimazhai intrusion, further supporting their magmatic origin. The initial 187Os/188Os value of 0.456 ± 0.026 indicates that crustal contamination has played an important role during mineralization. The proportion of crust-derived Os is calculated to be more than 30%.