Hydrothermal alteration, fluid inclusions and stable isotope characteristics of the Shaquanzi Fe-Cu deposit, Eastern Tianshan: Implications for deposit type and metallogenesis

The Shaquanzi Fe-Cu deposit is an important Fe (-Cu) deposit in the Yamansu Fe mineralization belt, Eastern Tianshan. Five-stage (Stage I to V) hydrothermal alteration/mineralization have been recognized: The early skarn (Stage I) and late skarn (Stage II) stages are featured by extensive garnet and amphibole alteration, respectively. Magnetite mineralization stage (Stage III) is associated with pervasive K + Fe +/- Ca alteration, forming magnetite, mushketovite, K-feldspar, epidote, magnetite, pyrite and quartz. Chalcopyrite mineralization stage (Stage IV) has an ore mineral assemblage of chalcopyrite, bornite, acicular hematite and sphalerite, accompanied with broad epidote + chlorite + calcite alteration. The late veins stage (Stage V) occurs mainly as epidote + calcite veins crosscutting the host rocks and earlier-stage minerals. Stage I hydrothermal fluids have high temperatures (>600 degrees C), medium-high salinities, with magmatic delta O-1(8)fluid = +6 parts per thousand to +11.7 parts per thousand. Stage III ore-forming fluids are medium-high-temperature (ca. 470-570 degrees C) with medium salinity. Stage III minerals were formed under delta D-fluid = -45.7 parts per thousand to 24.3 parts per thousand, delta O-1(8)fluid = +5.8 parts per thousand to + 9.1 parts per thousand and delta S-34(fluid) = -1.7 parts per thousand to +4.7 parts per thousand, indicative of magmatic fluids mixed with minor seawater. In contrast, Stage IV fluids have low temperatures (ca. 160 degrees C), medium-low salinities and are Ca-rich, with isotopic compositions reflecting basinal brine mixed with meteoric water (delta C-1(3)fluid = -6.6 parts per thousand to -2.3 parts per thousand; delta O-1(8)fluid = -3.3 parts per thousand to +2.8 parts per thousand and delta(34)Sfluid (>=) +24.8 parts per thousand). The Shaquanzi diorite (zircon U-Pb age: 298 +/- 5 Ma) is broadly coeval with previous Re-Os ages of the Shaquanzi magnetite and pyrite (303 +/- 12 Ma and 295 +/- 7 Ma, respectively), indicating that the Shaquanzi Fe-Cu metallogeny may have been genetically linked to the regional magmatic-hydrothermal activities led by the Yamansu arc-backarc basin inversion. Features of hydrothermal alterations, mineral assemblages, oreforming fluids and tectonic setting all suggest that the Shaquanzi Fe-Cu deposit is an IOCG-like deposit, similar to those in the Cenozoic Central Andes. (C) 2016 Elsevier B.V. All rights reserved