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Explanation: From Lakange Mo (Cu) deposit to Jiama Cu polymetallic deposit to Bangpu Mo mineralization to Qulong Cu-Mo deposit to Bangpu Cu mineralization, the Cl contents in apatite gradually increase, but the F contents in apatite gradually decrease, and the S content is similar but variation. It indicates that the Mo-dominated porphyry deposit formed from F-S-rich magma, whereas the Cu-dominated porphyry deposit formed from Cl-S-rich magma. [Display omitted] • There are two different magmatic-hydrothermal systems that formed the Bangpu Mo-Cu deposit. • Cu and Mo mineralization contain zircon and apatite with different geochemical features. • Cu mineralization was related to Cl-rich porphyry system, whereas Mo-mineralization was related to F-rich porphyry system. The Bangpu deposit, located in the eastern part of the Gangdese Porphyry Copper Belt, Tibet, is a porphyry Mo-Cu deposit in a continental collisional orogenic belt. Cu and Mo mineralization occurred separately in the Bangpu deposit. Mo (Cu) mineralization occurred mainly in the monzogranite porphyry (MP), while Cu (Mo) mineralization occurred mainly in the diorite porphyry (DP). The cause of such spatial differences in Cu and Mo mineralization in the Bangpu deposit remains unclear. In this study, the mineral chemistry of apatite and zircon was investigated to reveal the differences in the nature of ore-forming magma between Cu (Mo) and Mo (Cu) mineralization in the Bangpu deposit. The chondrite-normalized REE patterns of the apatite grains from the MP were enriched in LREEs with negative Eu anomalies, whereas those from the DP and biotite monzonitic granite (BM) had strong negative Eu anomalies with no obvious differentiation between LREEs and HREEs. The DP, MP, and BM have a low T TiZ range from 657 °C to 917 °C and a high AST range from 687 °C to 1079 °C. The zircon grains from the DP and MP had different Th/U ratios and T TiZ values, indicating that these porphyry samples probably experienced different magma crystallization or crystal fractionation histories. The zircon Ce4+/Ce3+ and Eu/Eu* ratios indicate that the ore-bearing DP and MP have higher oxygen fugacity than the BM. The F, Cl, and S contents in the apatite showed that the DP magmas were Cl- and S- rich, whereas the MP magmas magmas were F- and S- rich. The Bangpu porphyry Mo-Cu deposit results from two superimposed magmatic-hydrothermal systems. Mo was mainly partitioned into the F-rich magmatic-hydrothermal system released from the MP, and Cu was mainly partitioned into the Cl-rich magmatic-hydrothermal system released from the DP. Our results show that zircon and apatite geochemistry can be used to explain the spatial distribution of Cu and Mo mineralization in porphyry Cu-Mo systems. [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 coexistence of aqueous fluid inclusions and silicate melt inclusions in quartz phenocrysts from porphyrites at the Bangpu porphyry Mo–Cu deposit, Tibet, China were examined to characterize the immiscibility processes during the magmatic to hydrothermal transition. The physical and chemical environment during crystallization of the magmas has been reconstructed on the basis of microthermometric experiments and trace element microanalysis. Compositions of melt and brine fluid phases are determined using Synchrotron radiation X-ray fluorescence analysis, SEM–EDS and Laser Raman spectroscopy analyses. Brine fluids were directly exsolved by a crystallizing melt, and the simultaneous entrapment of volatile-rich (brine fluid) and volatile-poor immiscible phases (silicate melt) occurred at 670–700 °C and 1.6–1.95 kbar when the magma had H 2 O contents between 5 and 6 wt% and crystal contents of 60–80%. A later low-density fluid with a higher Mo concentration exsolved after about 80–90% crystallization had occurred. This fluid contained significant concentrations of Cl, Na, K, Ca, Fe, Cu, Zn, Rb, and small amounts of Mn, Br and Pb. Immiscibility of magmatic fluids can lead to different metal partitioning behaviors between residual melt and volatile phases, which generate variable metal ratios. Copper was partitioned preferentially into the brine phase, in contrast to the behavior observed in other porphyry Cu deposits. Ore deposition by a dense brine could explain the partially deep Cu mineralization. Condensation of brine from a later low-density parental fluid could be an efficient mechanism to concentrate shallow Cu mineralization and broadly distributed Mo mineralization. The source of the Mo mineralizing fluids probably was a particularly large magma chamber that crystallized and fractionated at depth greater than upper continental crust level. [ABSTRACT FROM AUTHOR]

The Leqingla and Xin'gaguo deposits are two representative skarn Pb–Zn polymetallic deposits of the Gangdese Pb–Zn polymetallic belt, Tibet, China. LA-ICP-MS zircon U–Pb dating of the mineralization-related biotite granites from both the Leqingla and Xin'gaguo deposits yielded weighted mean ages of 60.8 Ma and 56.5 Ma, respectively, which can be inferred as their mineralization ages. The Leqingla biotite granite is characterized by high Al 2 O 3 , total Fe, Na 2 O, and low K 2 O. In comparison, the Xin'gaguo biotite granite is characterized by relative higher K 2 O but lower Al 2 O 3 , total Fe, and Na 2 O. Geochemical and mineralogical characteristics indicate that the Leqingla and Xin'gaguo biotite granites are calc-alkaline I-type granite and High K calc-alkaline I-type granite, respectively. Both the Leqingla and Xin'gaguo biotite granites are enrichment in LREE and LILEs and depletion in HFSEs, and they were formed at the India–Asia collision stage. δ 18 O and δD values for the Leqingla and Xin'gaguo deposits are −8.8‰ to 5.3‰ and −140.4‰ to −90.1‰, −4.5‰ to 7.0‰ and −117.3‰ to −81.0‰, respectively, indicating magma fluids mixed with meteoric water in ore-forming fluids. δ 34 S values (−11.6‰ to −0.3‰) of ore sulfides from the Leqingla deposit show characteristics of biogenetic sulfur isotope compositions, suggesting sulfur for the Leqingla deposit were sourced from wall rocks of the Mengla and Luobadui Formation, which are rich in organic materials. δ 34 S values of ore sulfides from the Xin'gaguo deposits show bimodal distribution (−5.0‰ to −1.6‰ and 1.6–2.1‰), indicating sulfur in the Xin'gaguo deposit were derived from both wall rocks and magma. In the Leqingla deposit, most ore sulfides have the similar Pb isotopic compositions with that of the mineralization-related biotite granite, suggesting the biotite granite supplied most of the ore-forming metals. Pb isotopic compositions of ore sulfides and Hf isotopic compositions of biotite granite show that the majority of ore-forming metals are derived from mantle components of partial melting of the Neo-Tethys Ocean slab, with some upper crust materials of the Lhasa terrane. Pb isotopic compositions of ore sulfides from the Xin'gaguo deposit are similar to that of the Leqingla deposit, indicating they have the similar sources of ore-forming metals. [ABSTRACT FROM AUTHOR]

Highlights: [•] Chalcopyrite, bornite, pyrite and pyrrhotite are not low-level highly radiogenic. [•] No Re–Os isochron age of these sulfides is geologically meaningful. [•] Re–Os isotope system is sensitive and disturbed due to hydrothermal alteration. [ABSTRACT FROM AUTHOR]