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The Baishan molybdenum deposit is located in the eastern section of the Jueluotage tectonic belt, Eastern Tianshan. There is a granite porphyry intrusion beneath the Baishan Mo ore bodies discovered by recent exploration drilling, and the Cu–Mo minerals are widely distributed in the porphyry. The zircon LA-ICPMS U–Pb age of the granite porphyry intrusion is 228.1 ± 8.0 Ma, which is in coincidence with the age of Mo mineralization (227.7 ± 4.3 Ma). The granite porphyry intrusion is calc-alkaline and peraluminous. The magma was derived from a lower crustal source, it experienced distinct crystal fraction during its evolution, and the magma intruded in a Triassic compressional background, and was probably influenced by far-field effects of the Tethys system to the south. Based on the geological, geochemical and geochronological characteristics of the granite porphyry intrusion, we propose that there is probably a porphyry Cu deposit beneath the Baishan high-Re Mo deposit. [ABSTRACT FROM AUTHOR]

Voluminous Late Mesozoic granitoids and the world’s largest Mo deposits occur in the East Qinling. This paper presents the results of Nd–Hf isotopic mapping for the Late Mesozoic granitoids (155–105 Ma) and demonstrates their constraint on the basements and distribution of the Mo deposits in the East Qinling. This isotopic map, made by 98 (21 new and 77 published) whole-rock Nd isotopic and 29 (7 new and 22 published) average zircon Hf isotopic data, shows large variations of whole-rock ε Nd ( t ) values from −22.1 to −1.5, and the correspondingly Nd model ages ( T DM(Nd) ) from 2.83 to 0.79 Ga, and zircon ε Hf ( t ) values from −26.3 to +0.1 and two-stage Hf model ages ( T DM2(Hf) ) from 2.86 to 0.96 Ga. Three regions of variations have been identified from north to south: (a) ε Nd ( t ) values range from −22.1 to −10.9 with T DM(Nd) of 2.82–1.47 Ga, and ε Hf ( t ) values 26.3 to −13.5 with T DM2(Hf) 2.86–2.04 Ga; (b) ε Nd ( t ) values −13.9 to −1.5 with T DM(Nd) 2.02–0.79 Ga, and ε Hf ( t ) values −16.2 to +0.1 with T DM2(Hf) 1.96–0.96 Ga; and (c) ε Nd ( t ) values −6.3 to −4.5 with T DM(Nd) 1.28–1.12 Ga, and ε Hf ( t ) values −1.0 to −0.3 with T DM2(Hf) 1.25–1.22 Ga, respectively. The three regions approximately correspond to the three different terranes, the southern margin of the North China Block (NCB), the North Qinling Belt (NQB) and the South Qinling Belt (SQB), respectively. These demonstrate that the granitoids in the different terranes have distinct sources and their sources change from old to more juvenile from the north (southern margin of the NCB) to the south (SQB). These also reveal the distinct basements for the terranes in Late Mesozoic. The southern margin of the NCB contains widespread Neoarchaean to Paleoproterozoic basement, the NQB comprises Archaean to Neoproterozic basement and the SQB Mesoproterozic to Neoproterozic basement. All these suggest that the three terranes underwent different tectonic evolution and the continental crust of the East Qinling were mainly formed during Archaean to Neoproterozic, different from a typical accretion orogen. The old sources of the granitoids and basements of the terranes constrain the distribution, scale and number of the Mo mineralization and deposits. Mo mineralization is closely related to the small granitic bodies with old continental component sources and Mo deposits are mainly hosted by the terranes with oldest basement. The scale and number of the Mo mineralization and deposits decreased from the southern margin of the NCB to SQB. [ABSTRACT FROM AUTHOR]

The Bangpu porphyry Mo–Cu deposit is a representative Mo-dominated deposit besides the Sharang porphyry Mo deposit in the Gangdese metallogenic belt. The Mo–Cu mineralization has a close relationship with the monzogranite porphyry and diorite porphyrite. We identify three stages during the ore formation: a pre-ore stage, a main-ore stage with Mo–Cu deposited dominantly, and a post-ore stage. In this study, He–Ar, H–O, S and Pb isotopic compositions of the Bangpu deposit were determined. Based on these determinations, integrated isotope geochemistry studies were performed to constrain the possible sources of the ore-forming fluids and metals. The 3 He/ 4 He and 40 Ar/ 36 Ar ratios of fluid inclusions exhibit a range of 0.12209–0.36370 Ra and 275.6–346.1, respectively. The 4 He and 40 Ar concentrations vary from 1.51 to 3.57 (10 −7 cm 3 STP g −1 ) and 0.49 to 9.31 (10 −7 cm 3 STP g −1 ), respectively. He–Ar isotopic compositions suggest dominantly crustal-derived fluid with minor amount of meteoric water in the main ore stage. The δ 18 O fluid and δD fluid values vary from −1.3‰ to 3.9‰ and −140.5‰ to −73.7‰, respectively, indicating that magma fluids mixed with meteoric water. The average δ 34 S value of the sulfides (0.3‰) in the main-ore stage is close to the ore-forming porphyries, indicating a magmatic source. The lead isotopic components of ore sulfides exhibit restricted ranges with 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, and 208 Pb/ 204 Pb ratios of 18.450–18.728, 15.602–5.672, and 38.715–39.211, respectively and μ values in the range of and 9.46–9.58, indicating ore-forming metals of primarily an upper crust source with a small amount of mantle materials. Compared to the Bangpu deposit, the ore metals derived from mantle are even greater in the Jiama and Qulong deposits, which leads to Cu being the dominant mineralization in the Jiama and Qulong deposit. [ABSTRACT FROM AUTHOR]

The Dabie orogen is among the most famous continent–continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U–Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re–Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87 Sr/ 86 Sr ratios of 0.7087–0.7096, and Pb isotopic ratios of ( 206 Pb/ 204 Pb) i = 16.599–16.704, ( 207 Pb/ 204 Pb) i = 15.170–15.618 and ( 208 Pb/ 204 Pb) i = 36.376–38.248. The granite has ε Nd ( t ) of −18.0 to −16.3 and ε Hf ( t ) values of −26.5 to −20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8–74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region. [ABSTRACT FROM AUTHOR]

The Daheishan giant porphyry Mo deposit is located at the eastern segment of the CAOB, NE China. The ore-bearing intrusion of Daheishan deposit is a Jurassic granitic complex that includes Changgangling biotite granodiorite, Qiancuoluo seriate granodiorite, and Qiancuoluo granodioritic porphyry. Mineralization consists of disseminated, breccia and veined types. The hydrothermal fluids show significant magmatic signatures, as evidenced by the hydrogen and oxygen isotopic compositions of quartz and sulfur isotopic characteristics of ores. Consistence of lead isotopic compositions of the sulfides and the Daheishan intrusive complex further indicate a close relationship between the mineralization and magma. The fluid inclusions in quartz comprise of predominant aqueous two-phase as well as gas-rich fluid inclusions and a small number of daughter mineral-bearing inclusions. The gas species in the fluid inclusions are H 2 O, CO 2 , N 2 , CH 4 , C 2 H 6 , Ar ∗ and minor H 2 S; the liquid compositions are SO 4 2 − , Cl − , Na + , K + , Ca 2+ and Mg 2+ . Raman spectroscopy on individual fluid inclusions reveals a main gaseous composition of H 2 O, minor H 2 S and CO 2 . The fluid system in Daheishan Mo deposit can be described as NaCl–KCl–H 2 O type. Fluid inclusion microthermometry reveals subsolidus homogenization temperatures for fluid inclusions in the magmatic quartz phenocrysts ( T h = 400–450 °C, salinities = ∼21 eq. wt.%), suggesting an obliteration of higher temperature history of the porphyry system by the superimposed processes. Most of the mineralization occurred at temperature range of 220–360 °C, or higher. The temperature and salinity decreased to 100–170 °C and 0–15 eq. wt.%, respectively, when the hydrothermal fluid activities were gradually ending. No distinct evolution pattern based on the homogenization temperature or stable isotopic analyses is observed among the different mineralization stages. Mineralization was supposed to be related to the multi-phased boiling of fluids, instead of the gradual cooling of fluids. Pressure may be more critical than temperature in controlling the precipitation of molybdenite. [ABSTRACT FROM AUTHOR]