四川康定偏岩子造山型金矿床成因:石英微量元素和硫化物S同位素证据  

Genesis of the Pianyanzi orogenic gold deposit in Kangding,Sichuan:Evidence from quartz trace elements and sulfide S isotopes

作　　者：宋明伟 彭义伟 陈友良[1] 刘畅 田建吉[2] 赵鹤森[1] 王琦 王智 周钰昌 吴锋 SONG Mingwei;PENG Yiwei;CHEN Youliang;LIU Chang;TIAN Jianji;ZHAO Hesen;WANG Qi;WANG Zhi;ZHOU Yuchang;WU Feng(College of Earth and Planetery Sciences,Chengdu University of Technology,Chengdu 610059,China;Division of Geology and Mineral Resources,Beijing Research Institute of Uranium Geology,Beijing 100029,China;Inner Mongolia No.7 Geological and Mineral Exploration and Development Co.,Ltd.,Hohhot 010010,China;Northwest Geological Exploration Institute of China Metallurgical Geology Bureau,Xi’an 101399,China)

机构地区：[1]成都理工大学地球与行星科学学院,成都610059 [2]核工业北京地质研究院地质矿产研究所,北京100029 [3]内蒙古第七地质矿产勘查开发有限责任公司,呼和浩特010010 [4]中国冶金地质总局西北地质勘查院,西安101399

出　　处：《成都理工大学学报（自然科学版）》2024年第4期596-613,共18页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：中国核工业地质局地勘费项目(地GT2201);国家自然科学基金项目(41702081);油气藏地质及开发工程国家重点实验室开放基金(PLC20210208)。

摘　　要：大渡河金矿带是中国重要的金矿化富集区,发育一系列造山型金矿床。偏岩子金矿床位于大渡河南段的康定地区,矿体赋存于震旦系灯影组白云岩中。金成矿过程分为金-黄铁矿-石英阶段、金-氟镁石阶段、金-硫化物-氟镁石-石英阶段和黄铁矿-白云石-白云母阶段4个成矿阶段。通过石英中微量元素和硫化物S同位素的原位分析,旨在约束成矿流体性质、成矿物质来源和矿床成因。石英中Li,B,Na,Al,P和K相对富集,主要以Al^(3+)^(+)(Li^(+),Na^(+),K^(+),H^(+))Si^(4+)和Al^(3+)^(+)P 5^(+)2Si^(4+)的替换机制进入石英晶格。石英中Al与Li呈明显正相关关系,指示其形成温度较低。围岩中硫化物的δ^(34) S值介于-22.3‰~-13.1‰之间,表明S来源于海相硫酸盐的细菌还原作用;矿石中硫化物的δ^(34) S值范围为5.4‰~7.0‰,与交代岩石圈地幔的硫同位素值一致。综合矿床地质特征、石英微量元素和硫化物硫同位素组成,研究认为偏岩子属于造山型金矿床。成矿流体在上升过程中与赋矿白云岩接触,发生水-岩反应,导致自然金、含金硫化物、氟镁石和萤石的沉淀结晶。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 Al^(3+)^(+)(Li^(+),Na^(+),K^(+),H^(+))Si^(4+)and Al^(3+)^(+)P 5^(+)2Si^(4+)entering the quartz crystal lattice.The positive correlation between Al and Li in quartz suggested a low crystallization temperature.Theδ^(34) 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 ofδ^(34) 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.

关 键 词：氟镁石 石英微量元素 原位S同位素 造山型金矿床 偏岩子 

分 类 号：P618.41[天文地球—矿床学] P597[天文地球—地质学]