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[Display omitted] • Pyrite and quartz geochemical analyses were conducted on the Mazhala Au-Sb deposit in South Tibet; • Trace elements and sulfur isotopes allow four types of pyrite to be recognized; • Pyrite has mixed sedimentary-diagenesis, magmatic-hydrothermal, and metamorphic origin; • H-O isotopic composition of quartz inclusions suggests a mixed magmatic and metamorphic water origin. The Mazhala deposit is a typical Au-Sb deposit in the northern Himalayan orogenic belt that has increasingly attracted worldwide attentions. However, debates remain regarding the source of ore–forming fluid and its evolutionary process. Herein, we investigate the genetic and compositional evolutionary characteristics of different types of pyrite grains in order to better constrain the ore–forming fluid source and ore–forming processes by means of Using in-situ trace and sulfur isotope data of pyrite and inclusion temperature and H-O isotope data of quartz. Based on the occurrence and morphological features of pyrite, four types of pyrite (Py0, Py1, Py2, and Py3) have been identified. The framboids of pyrite Py0 have high contents of Au, Ag, Cu, Pb, and Sb, with Co/Ni < l, and their δ34S values range from −34.0‰ to −19.3‰, indicating a sedimentary-diagenetic origin. Py1 pyrite exhibits stark core-rim structure. The contents of Sn, Ti, Be and W in Py1c are higher, with Co/Ni > 1. The δ34S of Py1c ranges from 0.30 to 3.9‰ (mean = 1.7‰), indicating a magmatic hydrothermal transformation origin. Py1r, Py2, and Py3 differ greatly in pyrite morphology and trace element contents, with Co/Ni < 1, indicating as hydrothermal sedimentary transformation origin. The δ34S values of Py1r, Py2, and Py3 vary from 1.4 to 6.50‰, interpreted as the presence of metamorphic sulfur sources. The δ34S values of Py1-Py2-Py3 firstly increases and then decreases, indicatinga fluid mixing process. The Mazhala ore–forming fluid is typical of low temperature (270–291 °C), low salinity (1.1–5.0 wt% NaCl equiv) and CO 2 -enrichment, with H-O isotopic compositions of quartz resembling magmatic and/or metamorphic water, which makes us to infer a mixture of magmatic and/or metamorphic water source for the Mazhala ore-forming fluid. The early pyrite grains were dissolved and reprecipitated under the action of fluid. In the process of multistage hydrothermal interaction, Au and other trace elements were released from the primary pyrite lattice into the fluid, forming the gold–bearing ore–forming fluid. Separation of fluid phase coupled with significant change in the pH value of fluid prompted the co-precipitation of Au and Sb to form the Mazhala Au-Sb deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biotite and apatite composition confirms the Longxianggai biotite granites are reduced, peraluminous granites. • Fractional crystallization and late fluid exsolution are recorded by biotite and apatite composition, both of which may play essential roles in Sn-polymetallic mineralization. • Biotite and apatite composition helps discriminate Sn-bearing from barren granitic rocks. Tin mineralization in the Dachang Sn-polymetallic district, South China, is inferred to be associated with the Late Cretaceous Longxianggai pluton, which is primarily composed of porphyritic and equigranular (from medium-grained, to medium- to fine-grained, and then fine-grained textures) biotite granites. However, the magmatic and post-magmatic evolution that may exert an essential role in determining metal fertility of granitic intrusions remains poorly constrained. A comprehensive investigation on chemical compositions of mica (magmatic biotite and hydrothermal muscovite) and apatite in the Longxianggai biotite granites is employed to trace magmatic-hydrothermal processes and their potential role in the formation of fertile granites and hydrothermal Sn mineralization. Magmatic biotite shows variable compositions from Fe-biotite to protolithionite in the porphyritic and equigranular granites. Increasing AlVI and Mn, and decreasing Mg and Ti with increasing X Fe in biotite from the porphyritic to medium-grained, and then medium- to fine-grained granites are consistent with compositional variation trends expected during magmatic differentiation, accompanying with progressive enrichment of Li, F, Rb, Cs, Nb, Ta, W and Sn. However, an obvious depletion of Sn, Nb and Cl occurs in magmatic biotite from the more evolved fine-grained granite, with hydrothermal muscovite containing higher Sn and lower Nb contents. Tin depletion in biotite possibly reflects preferential portioning of Sn in Cl-bearing fluids exsolved from the differentiated granitic magmas prior to biotite crystallization. Likewise, the decoupling of Nb with Ta in biotite may attribute to extraction of Nb by exsolved fluids to form secondary Nb-rich rutile and CGMs (columbite-group minerals) in the granite matrix. The relatively high mobility/solubility of Nb in fluids compared to Ta is also consistent with elevated Nb/Ta ratios in hydrothermal muscovite. Compared with apatite in the porphyritic granite, apatite in the medium- to fine-grained granite generally develops fluid inclusions and micro-fractures/pores (often filled with quartz, zircon and monazite), and possesses tetrad REE patterns with variable Eu anomalies, in favor of its crystallization in fluid-saturated fractionated melts. The mineralogical data indicate that equigranular granites have experienced a higher degree of magmatic fractionation than porphyritic granites, with fluid exsolution occurring in late stage of granite solidification. The prolonged fractional crystallization followed by late fluid exsolution may play an important role in hydrothermal mineralization in the Dachang district. A compilation of mica and apatite elemental compositions from Dachang and other Sn-W-related granites demonstrates that high Sn contents and high Fe/(Fe + Mg + Mn) ratios in magmatic biotite, and elevated F, Fe, Mn and Sn contents in apatite, could be geochemical indicators for granitic rocks with high Sn-W mineralization potential. [ABSTRACT FROM AUTHOR]

The article focuses on a research paper on the geological study of Chalapu Goldfield in South Tibet, China. Topics discussed include the nature and source of ore-forming fluids of the gold deposit, gold and sulphide mineralization and the analysis of fluid inclusions suggesting high carbon dioxide content.