Genesis of the Pianyanzi orogenic gold deposit in Kangding,Sichuan:Evidence from quartz trace elements and sulfide S isotopes
The Daduhe gold belt is a well-known gold ore cluster in southwestern China that is characterized by a series of orogenic gold deposits.The Pianyanzi gold deposit is situated in the Kangding area of the northern section of the Daduhe belt.The Au orebodies are mainly hosted by dolomite from the Sinian Dengying Formation,and the Au ore-forming process comprises four stages:the gold-pyrite-quartz stage(Ⅰ),gold-sellaite stage(Ⅱ),gold-sulfide-sellaite-quartz stage(Ⅲ),and pyrite-dolomite-muscovite stage(Ⅳ).In this study,we examine trace elements of quartz from these different stages and analyze the sulfur isotopes of the sulfides in situ to investigate the sources of the metallogenic materials,ore-forming fluids,and ore genesis.Li,B,Na,Al,P and K were relatively rich in quartz,were probably mainly incorporated into the quartz crystal lattice,and were dominated by the coupled substitution of Al3++(Li+,Na+,K+,H+)↔Si4+and Al3++P5+↔2Si4+entering the quartz crystal lattice.The positive correlation between Al and Li in quartz suggested a low crystallization temperature.The δ34 S values of sulfides from the host rocks ranged from-22.3‰ to—13.1‰,indicating that the sulfur was derived from bacterial reduction of marine sulfates.Sulfides from the ores had values of δ34 S ranging from 5.4‰ to 7‰,suggesting a significant contribution from the metasomatic lithosphere mantle.The characteristics of the S isotopes and quartz trace elements suggest that the Pianyanzi deposit can be classified as an orogenic gold deposit.Auriferous fluids ascended along regional faults triggered by compressional tectonics,and reacted with dolomite to cause the precipitation and enrichment of gold,Au-bearing sulfides,fluorite and sellaite.
sellaitequartz trace elementS isotopeorogenic gold depositPianyanzi
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维普
