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东昆仑东段东昆中构造混杂岩带长石山地区新发现一套蛇绿岩,主要由蛇纹岩、辉长岩、辉绿岩、玄武岩、含泥碳硅质岩组成。通过对蛇绿岩中辉长岩进行LA-ICP-MS锆石U-Pb同位素研究,获得年龄为(537.2±3.5)Ma,表明蛇绿岩形成于早寒武世。岩石地球化学研究显示,蛇纹岩的原岩为橄榄岩类,稀土元素配分曲线具开阔U型特征;辉长岩发育明显的堆晶结构,具不同程度的Eu正异常,轻稀土较重稀土富集,但稀土总量较低;玄武岩轻稀土相对重稀土富集,富集大离子亲石元素,高场强元素不分异,Nb轻微亏损,具E-MORB与IAB的双重特征。长石山蛇绿岩形成于弧后盆地环境,指示布青山—阿尼玛卿原特提斯洋在早寒武世((537.2±3.5)Ma)前已经开始向北俯冲,并在东昆中地区拉张形成弧后盆地。
A newly discovered ophiolite in the Changshunshan area of eastern Kunlun, eastern Kunqu, is composed of serpentinite, gabbro, diabase, basalt and muddy carbonaceous siliceous rocks. The LA-ICP-MS zircon U-Pb isotopic study of gabbro from the ophiolite shows an age of (537.2 ± 3.5) Ma, indicating that the ophiolite was formed during the Early Cambrian. The geochemical study shows that the original rock of the serpentinite is a peridotite and the distribution pattern of rare earth elements has an open U-shaped character. The gabbro is characterized by obvious grain structure, with different degrees of positive Eu anomalies, heavy rare earths Enriched, but the total amount of rare earths is relatively low. The light rare earths of basalts are enriched in heavy rare earths and enriched in large ion lithophile elements. The high field strength elements are indistinguishable and Nb is slightly depleted, with the dual characteristics of E-MORB and IAB. The Changshishan ophiolite was formed in the back-arc basin environment, indicating that the Butianshan-Animidqing original Tethyan had begun to subduct northward before the Early Cambrian (537.2 ± 3.5 Ma) The area stretched to form a back arc basin.