西秦岭大桥金矿区晚三叠世岩浆活动--锆石U-Pb定年及Lu-Hf同位素证据  

Late Triassic magmatic activity in the Daqiao gold deposit of West Qinling belt: Zircon U-Pb chronology and Lu-Hf isotope evidence

作　　者：陕亮[1,2] 张东明[3] 庞迎春[2] 刘家军[1] 张万益[4] 赵辛敏 张忠平[6] SHAN Liang;ZHANG Dongming;PANG Yingchun;LIU Jiajun;ZHANG Wanyi;ZHAO Xinmin;ZHANG Zhongping(Faculty of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;Wuhan Center, China Geological Survey, Wuhan 430205, Hubei, China;No.6 Detachment of Gold Headquarters, Chinese People's Armed police Force; Xining 810000, Qinghai, China;Development Research Center, China Geological Survey, Beijing 100037, China;Xi’an Center, China Geological Survey, Xi’an 710054, Shaanxi, China;Geological Investigation Institute of Gansu Province, Lanzhou 730000, Gansu, China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质调查局武汉地质调查中心,湖北武汉430205 [3]中国人民武装警察部队黄金部队二总队六支队,青海西宁810000 [4]中国地质调查局发展研究中心,北京100037 [5]中国地质调查局西安地质调查中心,陕西西安710054 [6]甘肃省地质调查院,甘肃兰州730000

出　　处：《地质通报》2016年第12期2045-2057,共13页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212011085534、1212011220924、121201009000150015);国家自然科学基金项目(批准号:41030423)

摘　　要：西秦岭是中国金矿的重要集中区之一。该区大桥金矿近年已达到超大型规模。最新矿床成因研究认为，成矿可能与矿区岩浆活动有关。矿区采集的4个花岗闪长岩样品LA-ICP-MS锆石U-Pb年龄测试结果主要集中于228Ma、206Ma两组，对应于晚三叠世。相应的Hf同位素组成基本相似，也可分为2个单元。εH（ft）主体分布在-8~0之间，TDM2主体为1300~1900Ma，推测壳源源区为古—中元古代古老地壳岩石，岩浆主要来源于下地壳古老物质重熔，成岩过程可能有少量地幔组分的参与。结合稀土和微量元素研究结果，认为矿区存在2期印支晚期岩浆活动。大桥金矿可能为西秦岭地区印支晚期晚三叠世区域岩浆活动引发成矿作用的产物。The West Qinling area is one of the important gold ore concentration areas in China. The Daqiao gold deposit, located in the middle of the West Qinling area, has become a superlarge deposit with the growing Au reserves. Recent research reveals that the metallogenic process may be associated with magmatic activity in the area. The zircons LA-ICP-MS U-Pb dating results of 4 granodiorite samples collected in the mining area are concentrated mainly at 228Ma and 206Ma, forming two groups obviously and corresponding to the Late Triassic. The corresponding Hf-isotopic compositions of zircons show similar phenomena and can also be divided into two units. The εH(f t)values are from -8 to 0, and the TDM2 values are from 1300Ma to 1900Ma. It is inferred that the source came from the old crustal rocks of the Paleoproterozoic-Proterozoic period, and most of the ancient lava was derived from remelting process of the old materials, which came from the lower crust, mixed probably with a small amount of mantle components which were involved in diagenetic process. In combination with REE and trace elements researches, the authors hold that there probably existed two phases of magmatic activity in late Indosinian period in the mining area. The Daqiao gold deposit is the product of metallogenic activity caused by regional magmatism in the late Indosinian epoch in West Qinling belt.

关 键 词：西秦岭 大桥金矿 岩浆岩 锆石U-Pb年龄 LU-HF同位素 

分 类 号：P534.51[天文地球—古生物学与地层学] P597.3[天文地球—地质学]