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Graphical abstract Highlights • LA-ICP-MS and SIMS were applied to pyrites from Shapoling vein-type Mo deposit. • Textural and chemical evolution of hydrothermal pyrite was proposed. • The Mo-bearing pyrite identified in our study could be used as a possible pathfinder for the exploration of high-grade Mo mineralization. Abstract The Early Cretaceous (ca. 128 Ma) Shapoling vein-type molybdenum (Mo) mineralization, associated with the Huashan intrusion is a newly discovered deposit in the Xiong'ershan district, East Qinling, China where pyrite is a ubiquitous mineral phase. Here we present results from an integrated study on the texture, in situ trace element chemistry from laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and sulfur isotopic composition using secondary-ion mass spectrometry (SIMS), with a view to understand the geochemical variation, genesis of Mo mineralization and ore-forming process. The distinct textural patterns as revealed by petrographic observations suggest three types of pyrites: Py1 is composed of coarse-grained euhedral pyrite in the wall rock and early barren quartz vein at Stage I, Py2 is represented by subhedral-anhedral grains coexisting with molybdenite in quartz veins at Stage II, and Py3 forms irregular interstitial grains in the quartz + K-feldspar + molybdenite dominated veins at Stage III. The Mo enrichment mainly occurred in Py3 (with Co/Ni ratios >1 and δ34S values mainly <0‰). Our study shows that Mo, Au, Pb, Zn, Ag and Cu are selectively partitioned into pyrite as mineral micro/nano-inclusions, and that the siderophile and chalcophile elements (such as Co, Ni, As, Se and Te) occur substituted within different textural types of pyrite. The δ34S values of the pyrites in Py1 and Py2 range between −2.33‰ and −0.37‰, indicating a dominantly magmatic origin. The δ34S values of Py3 increase from −2.55‰ to +1.48‰. In situ δ34S analysis of pyrite from Py1, Py2 to Py3 shows a progressive and gradual change in redox conditions. The negative values indicate oxidized sulfur in the early generation of pyrite (Py1 that coexists with magnetite). Conversely, positive values represent reduced sulfur found in the later generations of pyrite (Py3), which contain higher concentrations of Cu, Pb, Zn and Ag. The Mo-bearing pyrite identified in our study could be used as a possible pathfinder for the exploration of high-grade Mo mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • Shapoling granitoids derived from a mixture of Taihua Group and mantle-derived components linked to lithospheric thinning. • The hydrothermal fluids shifted from early moderate- to low-salinity CO 2 -rich fluids, to late H 2 O-NaCl low-salinity fluids. • Formation of the Mo deposit is a result of the prolonged magmatic activity, with input of mantle-derived materials. The Shapoling deposit, located in Xiong'ershan area, East Qinling, China, is characterized by a magmatic-hydrothermal Mo vein system. We present whole-rock geochemical, zircon U-Pb-Hf-O isotopic, quartz H-O isotopic and fluid inclusion data for the Shapoling deposit. We use these data to investigate the petrogenesis of granitoids associated with Mo mineralization and the processes of magmatic-hydrothermal evolution that formed the Mo deposit. The granitoids from the Shapoling deposit are metaluminous, alkalic to calc-alkalic, shoshonitic to high-K series, and belong to highly fractionated I-type granitoids. These granitoids are strongly enriched in light rare earths (LREEs) and large ion lithophile elements (LILE), but depleted in heavy rare earths (HREEs) with negative europium anomalies and high field-strength elements (HFSE), mostly plotting in the range of the Taihua Group rocks. Most of the Shapoling granitoids show relatively lower Sr/Y and (La/Yb) N than the typical adakitic rocks, showing that the parental magmas were generated under lower pressure. Therefore, the Shapoling granitoids were generated at thin crustal levels by lithospheric thinning process linked to the tectonic transition from compression to extension. Zircon U-Pb ages of the Shapoling granitoids range from 132.9 ± 1.3 Ma to 126.5 ± 0.7 Ma. The εHf (t) values and δ18O zircon values show a variation trend from −19.1 to −8.0 and 5.33‰ to 6.30‰, which are consistent with Hf-O isotopic features of mixing of the partially melted Taihua Group with mantle-derived components. FIluid inclusion microthermometry results suggest that the hydrothermal fluids forming the Shapoling Mo deposit changed from early moderate- to low-salinity CO 2 -rich fluids in the H 2 O-NaCl-CO 2 system, to late H 2 O-NaCl low-salinity fluids. The corresponding quartzs have δD values varying from −93.3‰ to −78.2‰ and δ18O values from −5.14‰ to 0.92‰, indicating a dominant magmatic source but were diluted by meteoric water in the late stage. Fluid boiling is the key factor that controlling the precipitation of molybdenite. Our study provides insights into the formation of Mo system associated with a prolonged and active magmatic system, upwelling of hot asthenosphere and intense mantle-crust interaction. The prolonged magmatic system is steadily replenished by mantle-derived materials in the magma chamber, which feed the hydrothermal systems and govern the formation of the Shapoling Mo deposit. [ABSTRACT FROM AUTHOR]