摘要
巴仑台闪长岩反映的大洋俯冲信息为对比乌瓦门蛇绿岩与西侧长阿吾子和东侧库米什蛇绿岩的关系,探讨南天山洋的洋-陆演化过程具有重要意义。闪长岩具高碱和高铝特征,(Na2O+K2O)=4.14%~7.05%,Al2O3为14.62%~17.35%,为一套高钾钙碱性系列岩石,(La/Yb)N平均10.46,以富集轻稀土元素和大离子亲石元素(如K、Rb、Ba、Pb等)、亏损Nb、Ta、Ti等高场强元素为特征,形成于岛弧环境。闪长岩LA-ICP-MS锆石U-Pb年龄为(430.1±1.1)Ma,锆石εHf(t)=-12.7^-7.6,二阶段Hf模式年龄TDM2为1895~2219 Ma,指示巴仑台闪长岩为早志留世南天山洋北向俯冲,导致中天山古老结晶基底部分熔融形成。
Studies of petrology and geochemistry indicate that the Baluntai diorite is the high- K calc- alkaline diorite. The rocks,which have the data Na2O+K2O=4.14%-7.05%, Al2O3=14.62%-17.35%,(La/Yb)Nwith an average of 10.46, are characterized by enrichment of large ion lithophile elements(LILE, such as K, Rb, Ba, and Pb) and light REE but depletion of high field strong elements(HFSE, like Nb, Ta, and Ti),and were probably produced in an island arc settings. LA- ICP- MS zircon U- Pb dating shows that the Baluntai diorite was formed at(430.1 ± 1.1)Ma. In- situ zircon Hf analyses show that zircons from Baluntai dioritehave εHf(t) values from-12.7 to –7.6 and tDM2 model ages of 1895 Ma to 2219 Ma. Combined with Hf isotope analytical results and regional geological data, it is held that the Baluntai diorite resulted from partial melting of the Tianshan crystalline basement in response to northward subduction of South Tianshan Ocean during the Early Silurian. The isotopic ages of the Baluntai diorite body represent the upper age limit of the Wuwamen ophiolite.
出处
《中国地质》
CAS
CSCD
北大核心
2015年第5期1228-1241,共14页
Geology in China
基金
国土资源部公益性行业科研专项(201011034)资助