摘要:中天山卡瓦布拉克地区中-基性侵入岩由石英闪长岩、斜长岩和橄榄辉长岩组成。锆石LA-ICP-MS U-Pb同位素分析结果表明，石英闪长岩形成于412.2±3.2 Ma，斜长岩形成于297.1±3.1 Ma，分别代表晚古生代早期和晚期的岩浆活动。石英闪长岩的εHf（t）值介于为+0.3～+15.4，对应的二阶段模式年龄TDM2 = 1 381～427 Ma。斜长岩的εHf（t）值为+6.4～+11.3，对应的单阶段模式年龄TDM = 678～498 Ma。地球化学分析结果显示，它们均富集轻稀土和大离子亲石元素、亏损高场强元素。基于野外地质、岩相学和地球化学特征，并结合区域地质资料认为，石英闪长岩形成于早泥盆世南天山洋北向俯冲于中天山地块之下的活动大陆边缘环境，是幔源岩浆和壳源岩浆混合的产物；斜长岩和橄榄辉长岩形成于伸展环境，其母岩浆来自被俯冲带流/熔体交代过的年轻岩石圈地幔。橄榄辉长岩中的多期捕获锆石年龄揭示中天山基底经历了长期多期次构造热事件，其中最老的年龄（2 767～2 663 Ma）能否说明中天山存在太古代基底有待于进一步研究。
关键词: 卡瓦布拉克/
中-基性侵入岩/
锆石U-Pb年龄/
Hf同位素/
岩石成因
Abstract:The intermediate-mafic intrusive rocks from Kawabulak area in Central Tianshan are composed of quartz diorite, anorthosite and olivine gabbro. LA-ICP-MS zircon dating shows that the quartz diorite and anorthosite formed at 412.2±3.2 Ma and 297.1±3.1 Ma, respectively. εHf（t）values of quartz diorite vary between +0.3～+15.4 with corresponding TDM2 ages of 1 381～427 Ma, while?εHf（t）values of anorthosite change between +6.4～+11.3 with corresponding TDM2 ages of 678～498 Ma. Geochemical data show that, intermediate-mafic rocks enriched in light rare earth elements（LREEs）and large ion lithophile elements（LILEs）, depleted in high field strength elements（HFSEs）. On the base of field investigation, petrographical and geochemical analysis, integrated with regional data, we propose that quartz diorite was formed by magma mixing process in an active continental margin environment in which the South Tianshan Ocean subducted northward beneath the Central Tianshan. Anorthosite and olivine gabbro were formed in an extensional setting, parent magma of which originated from a juvenile lithospheric mantle that was previously metasomatized by subduction zone fluids/melts. The inherited zircons from olivine gabbro indicate that central Tianshan experienced multiphase tectonic thermal events, whether the oldest group（2 767～2 663 Ma）of which can represent the Central Tianshan Archean basement remains to be further study.
Key words:Kawabulak/
Intermediate-mafic intrusive rocks/
Zircon LA-ICP-MS U-Pb dating/
Hf isotopes/
Petrogenesis
PDF全文下载地址:
http://www.dzkx.org/data/article/export-pdf?id=geology_11591
