内蒙古赤峰大西营子金矿区赋矿火山岩年代学与岩石地球化学特征  

Geochronology and Geochemistry Characteristics of Volcanic Rocks from the Daxiyingzi Gold Deposit in Chifeng, Inner Mongolia

作　　者：柳长峰 赵守恒 张浩然 郎海龙 张凤娟 刘文灿 LIU Changfeng;ZHAO Shouheng;ZHANG Haoran;LANG Hailong;ZHANG Fengjuan;LIU Wencan(Geological Survey Institute,China University of Geosciences,Beijing 100083,China;Anhui Tongling Mineral Resources Ltd,Tongling,Anhui244000,China)

机构地区：[1]中国地质大学(北京)地质调查院,北京100083 [2]铜陵有色集团股份有限公司,安徽铜陵244000

出　　处：《现代地质》2020年第1期27-39,共13页Geoscience

基　　金：企业委托项目“内蒙古赤峰市大西营子西金矿控矿因素及成矿规律研究(H90059)”;国家自然青年基金项目(41702054)

摘　　要：大西营子金矿区位于内蒙古赤峰地区,金矿赋存在玛尼吐组火山岩中。对大西营子金矿区赋矿围岩进行了岩石学、锆石U-Pb年代学和岩石地球化学研究。矿区火山岩主要包括安山岩、粗安岩、粗面岩和火山碎屑岩。通过锆石LA-ICP-MS U-Pb定年,获得安山岩和粗安岩年龄分别为(157.8±6.2)Ma和(156.9±7.4)Ma,应代表其形成年龄。岩石地球化学数据显示该套火山岩具有相对富碱、富铝的特征,属于高钾钙碱性和碱性岩石系列。岩石富集轻稀土元素和大离子亲石元素(Th、U、Zr、Hf),亏损重稀土元素和Nb、Ta、Ti等高场强元素。这些特征显示岩浆来自被俯冲流体交代富集的岩石圈地幔,且经历了以单斜辉石为主的结晶分异过程。结合区域地质资料,认为在大西营子金矿区火山岩形成于造山后伸展环境,与蒙古—鄂霍茨克洋闭合作用有关。The Daxiyingzi gold deposit is hosted by Manitu Formation volcanic rocks,and is located at Chifeng,Inner Mongolia.We undertake zircon U-Pb dating and whole-rock geochemical analyses of the volcanic rocks from Daxiyingzi,with the aim to constrain the formation age and tectonic evolution of the volcanic rocks.The volcanic rocks mainly consist of andesite,trachyandesite and trachyte.LA-ICP-MS U-Pb zircon dating of the andesite and trachyandesite yield Late Jurassic(~157 Ma)age.The volcanic rocks are featured by their high alkali and Al2O3 contents,and are high-K calc-alkaline to alkaline.The volcanic rocks are also characterized by their moderately-enriched light rare earth element(LREE)patterns and high abundances of Th,U,Zr,and Hf,but negative Nb,Ta,and Ti anomalies.These features indicate that the mafic rocks were likely formed by partial melting of the lithospheric mantle metasomatized by subduction,and the AFC process likely played an important role in the magmatic evolution.Combined with previous studies on the contemporaneous tectono-magmatic activities in the northern North China Craton,we suggest that the volcanic rocks were formed in a post-orogenic extensional setting,possibly related to the closure of Mongol-Okhotsk Ocean.

关 键 词：造山后 粗安岩 锆石U-PB定年 大西营子金矿 蒙古—鄂霍茨克洋 

分 类 号：P588.1[天文地球—岩石学]