东秦岭上宫金矿流体成矿作用:放射成因同位素地球化学研究  

HYDROTHERMAL METALLOGENY OF THE SHANGGONG GOLD DEPOSIT,EAST QINLING:RADIOGENIC ISOTOPE GEOCHEMISTRY

作　　者：陈衍景[1] 唐国军[1] Franco PIRA JNO 祁进平[1] 林治家[3] 

机构地区：[1]北京大学地质系,北京100871 [2]Geological Survey of Western Australia [3]中国科学院地球化学研究所,贵州贵阳550002

出　　处：《矿物岩石》2004年第3期22-27,共6页Mineralogy and Petrology

基　　金：自然科学基金(49972035和40352003);九五攀登(95预-39-04);教育部跨世纪人才和科学院百人计划项目

摘　　要：　赋存于东秦岭熊耳地体熊耳群陆相火山岩中的上宫金矿,是典型的断控脉状造山型金矿床,其成矿物质长期被认为来自结晶基底太华超群(所谓原生矿源层)、盖层熊耳群(所谓衍生矿源层)或燕山期花岗岩,或者下伏地壳或地幔。但是,这些观点与放射成因同位素研究结果相矛盾,因此可以认为成矿物质侧向来源于熊耳地体以南的管道口群栾川群沉积地层,后者沿马超营断裂向北陆内俯冲到熊耳地体之下,通过变质脱水导致上宫金矿成矿流体系统的发育和矿床形成。此外,成矿早阶段石英40Ar/39Ar年龄为222.8Ma±24.9Ma;成矿早、中、晚阶段矿物或岩石的Rb-Sr等时线年龄分别为242Ma±10Ma,165Ma±7Ma和113Ma±6Ma,表明成矿发生在250Ma～100Ma之间,同步于华北与扬子板块的陆陆碰撞造山作用。The Shanggong Au deposit, hosted in a continental volcanic sequence of the Xiong′er Group in the Xiong′er Terrane, East Qinling, is a fault-controlled orogenic-type lode gold deposit. In previous studies its ore-forming fluids and metals were interpreted as being originated from the crystalline basement of the Taihua Supergroup (namely, primary source-bed), the Xiong′er Group (secondary source-bed), and/or the Yanshanian (Jurassic-Cretaceous) granitoids. The lower crust and the mantle beneath the Xiong′er terrane were also suggested as the source. However, these interpretations are not spported by the radiogenic isotope data presented in this paper. Instead, the radiogenic isotope data, including Sr and Pb, show that the ore-forming fluids and metals have been sourced from a sedimentary sequence of the Guandaokou and Luanchuan Groups outcroped in the south of the ore-hosting terrane. Metamorphic devolatilization of the sedimentary sequence during its north-dipping intracontinental subduction along the Machaoying fault resulted in the development of ore-forming fluid-system and the formation of the Shanggong gold deposit. The ()^(40)Ar/()^(39)Ar dating of the early-stage quartz yields an age of 222.8 Ma±24.9 Ma. Rb/Sr isochron dating for alteration minerals or rocks formed in the early, middle and late stages yield ages of 242 Ma±10 Ma, 165 Ma±7 Ma and 113 Ma±6 Ma, respectively.This shows that the metallogenesis occurred in the period of 250 Ma^100 Ma,and was coeval with continental collision between the Yangtze and North China plates.

关 键 词：金矿 成矿流体 成矿作用 放射成因同位素 大陆碰撞 

分 类 号：P618.51[天文地球—矿床学] P597.1[天文地球—地质学]