西秦岭岷礼成矿带马坞金矿致矿火成岩组合与成矿地质背景  

Igneous Assemblage and Metallogenic Background of the Mawu Gold Deposit in the Min-Li Ore Belt of the Western Qinling Orogen

作　　者：郭娜 刘翠[2] 崔龙 姚薇 李国英 甘黎明 黄勇[3] GUO Na;LIU Cui;CUI Long;YAO Wei;LI Guoying;GAN Liming;HUANG Yong(Xi’an Center of Mineral Resources Survey,China Geological Survey,Xi’an,Shaanxi 710100,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Civil Military Center of Geological Survey,China Geological Survey,Chengdu,Sichuan 611732,China)

机构地区：[1]中国地质调查局西安矿产资源调查中心,陕西西安710100 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]中国地质调查局军民融合地质调查中心,四川成都611732

出　　处：《现代地质》2020年第6期1261-1276,共16页Geoscience

基　　金：中央地质勘查基金项目(2011621039);中国地质调查局“全国陆域及海区地质图件更新与共享”项目(DD20190370)之“中国典型地区洋陆转换的火成岩记录”;中国地质调查局“显生宙重大岩浆事件调查与岩浆岩试点填图”项目(DD20160123)之“侵入岩1/5万专题地质填图试点及新方法填图”。

摘　　要：甘肃马坞金矿床位于西秦岭岷礼成矿带东段,中川岩体外接触带,属于微细浸染型金矿床,达中型规模。针对矿区发育的火成岩开展野外地质学、岩相学、年代学和地球化学等研究,以揭示致矿火成岩组合及其特征,进而探讨岩石成因及金矿形成的地质背景等。野外观察显示马坞矿区金矿脉常与煌斑岩脉、石英闪长岩脉及细晶岩脉等相伴生或相互穿切,说明金矿与上述脉岩的形成时间近乎一致,故认为该脉岩群为致矿火成岩组合。马坞矿区煌斑岩和花岗质脉岩LA-MC-ICP-MS锆石U-Pb测年结果表明其形成于(153.5±3.5)^(154.9±0.9)Ma,推测金矿可能形成于晚侏罗世。该脉岩群具有宽广的SiO2、K2O、Na2O、TFeO和MgO含量,属于不同的岩性,且来自不同的岩浆源区,因此属于宽谱系岩墙群,指示其形成于造山带岩石圈拆沉作用所引发的伸展环境中。脉岩和金矿赋存于以中川岩体为代表的花岗质岩基及其围岩,表明其形成于西秦岭造山运动后期的大规模岩浆活动及岩基隆升之后,属于岩基后成矿作用的产物。The Mawu gold deposit in Gansu Province is a medium-sized finely-disseminated gold deposit,which is located in the eastern part of the Min-Li ore belt in the Western Qinling Orogen,and in the exocontact of the Zhongchuan intrusion.A series of analyses on the fieldwork geology,petrology,geochronology,and geochemistry of the igneous rocks from the mining area were carried out to reveal the ore-causative igneous rock assemblages and their characteristics,and to explore their petrogenetic and geotectonic background as well as gold ore formation.Field observations indicate that the lamprophyre dikes/veins,aplitic dikes,and quartz diorite dikes were developed near or crosscut the gold veins,indicating that the gold ores and magmatic dikes were nearly coeval.LA-MC-ICP-MS zircon U-Pb dating of the lamprophyre and granitic dikes indicates that they were formed at about(153.5±3.5)Ma to(154.9±0.9)Ma,suggesting a Late Jurassic gold mineralization.Therefore,the work concludes that the igneous assemblage of Mawu gold deposit are dominated by dikes.The dikes have a wide composition range of SiO2,K2O,Na2O,TFeO and MgO,belonging to different igneous types and likely derived from different magma sources.The occurrence of wide spectrum dike swarm(WSDS)means that it was formed under an extensional environment caused by lithospheric delamination of the orogen.The dikes and gold orebodies intruded into the Zhongchuan granitic rocks and other wall-rocks,which indicates that they were formed after large-scale magmatic activities and batholith uplift in the late Western Qinling orogeny,and belongs to post-batholith metallogeny.

关 键 词：甘肃 马坞金矿 宽谱系岩墙群 致矿火成岩组合 岩基后成矿作用 晚侏罗世 

分 类 号：P588.1[天文地球—岩石学]