甘肃北山大山头基性杂岩体SHRIMP锆石U-Pb年龄及其地质意义  

Zircon SHRIMP U-Pb Dating of the Dashantou Basic Complex and Its Geological Significance in Beishan Area, Gansu Province

作　　者：闫海卿[1,2] 赵焕强[1] 丁瑞颖 米世好 王强[1] 贺宝林[1] 范模春[1] 任建梅[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]华东冶金地质勘查局815地质队,安徽巢湖238000 [4]陕西省地质矿产勘查开发局第三地质队,陕西宝鸡721300

出　　处：《西北地质》2012年第4期216-228,共13页Northwestern Geology

基　　金：国土资源部公益性行业基金项目(200911007;201011058);新疆东天山-北山地区铜镍矿勘查选区研究(1212011085061);中央高校基金(CHD2011TD007)联合资助

摘　　要：大山头岩体是北山地区黑山铜镍硫化物成矿带中一个较大的基性杂岩体,其地球化学特征、成岩时代、岩浆源区性质和成岩背景等问题是研究岩浆铜镍硫化物矿床成岩、成矿过程必须解决的基础科学问题。笔者首次获得大山头杂岩体SHRIMP锆石U-Pb年龄为(359.3±5.7)Ma,确定了黑山成矿带超镁铁岩带的成岩期为泥盆纪末。地球化学特征显示大山头杂岩体的原生岩浆可能为高Mg玄武岩浆,其岩浆源区为富集岩石圈地幔,并且受到强烈的洋壳俯冲流体交代和地壳物质的同化混染。构造背景研究显示红柳河-牛圈子-洗肠井早古生代古缝合带的俯冲作用可能持续到泥盆纪末。大约在359.3±5.7Ma大山头—黑山一带洋壳俯冲作用依然影响着大陆边缘初始裂谷近内的岩浆活动。Dashantou rock is a large basic complex of Heishan Cu-Ni sulfide metallogenic belt in Beishan area, of which the geochemical characteristics, petrogenic age, nature of magma source, diagenesis setting are the basic scientific problems that must be solved in studying magma Cu-Ni sulfide deposit rock-forming and ore-forming processes. A SHRIMP zircon U-Pb age of （359.3±5. 7） Ma has been first obtained in this paper, which determining diagenesis stages of Heishan metallogenic belt is in the Late Devonian. The rock geochemistry shows that primary magma of Dashantou complex may be high magnesian basaltic magma, of which the magma source belongs to the enriched mantle and has been strongly metasomasised by fluid formed in the subduction process of oceanic crust and contaminated by crustal material. The study on tectonic setting of Dashantou area suggests that the subduction of Hongliuhe-Niujuanzi-Xichangjing paleo- suture zone in the early Paleozoic continued to the end of the Devonian possibly. In about （359.3±5.7） Ma the oceanic crust subduction in Dashantou-Heishan still affected magmatism activity in initial rift of continental margin.

关 键 词：同位素年龄 地球化学特征 同化混染 源区性质 构造背景 

分 类 号：P597[天文地球—地球化学] P588.12[天文地球—地质学]