北祁连西段石鸡河地区火山岩地球化学特征及其动力学意义  

Geochemistry and Tectonic Setting of Lavas from Shijihe Area in Western North Qilian Mountains

作　　者：刘晓煌[1,2] 邓军[1] 孙兴丽[1] 刘玖芬[2] 孙柏年[3] 康洪杰[3] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]武警黄金第七支队,山东烟台264004 [3]兰州大学西部环境教育部重点实验室,甘肃兰州730000

出　　处：《地球科学（中国地质大学学报）》2010年第6期959-968,共10页Earth Science-Journal of China University of Geosciences

基　　金：高等学校学科创新引智计划资助(No.B07011);长江学者和创新团队发展计划资助(No.IRT0755)

摘　　要：石鸡河一带是近年新发现的北祁连山多金属成矿带,气侯和自然条件恶劣,研究程度很低.该区地层岩性为阳起石岩、角岩和细碧岩;岩石地球化学和Nd同位素数据显示岩石来源于亏损地幔,具有N-MORB洋脊玄武岩特征;Sr同位素特征显示地层Sr同位素组成的改变是蚀变引起,而不是由地壳物质加入引起的.Sm-Nd等时线年龄为481±20Ma.提出了石鸡河地区地层形成于早奥陶世,成岩环境为北祁连洋扩张环境,而非区域资料上显示的残留海盆封闭、大陆碰撞造山环境.Recent studies showed that the Shijihe area is an important polymetallic metallogenic belt in western part of North Qilian Mountains in China.However,geological study degree is very low due to its remoteness and poor conditions.The Lavas of Shijihe area consists of actinolitite hornstone and spilite.The geochemical characteristics of metamorphic basic lava with flat REE distribution patterns,the contents of HFSE similar to N-MORB and εNd（0）=＋9.03＋9.42（except the sample 08p1） manifest that the rocks belong to the tholeiitic basalt series.Sr isotope characteristics indicate that Sr isotopic composition of the rocks was altered because of the metamorphism of the rock instead of the interfused crust.Sm-Nd isochron age is 481±20 Ma.The metamorphic basic lavas of Shijihe area is residue of Early Ordovician.The diagenesis environment is oceanic ridge instead of continental collision with closing of ocean basin.

关 键 词：石鸡河 岩石地球化学 Rb—Sr同位素 Sm Nd等时线年龄 N—MORB洋脊玄武岩. 

分 类 号：P597.3[天文地球—地球化学] P588.34[天文地球—地质学]