藏东南迦巴瓦地区雅鲁藏布江蛇绿混杂岩中玻安岩的地球化学特征和地质意义

Geochemical characteristics and geological significance of Boninite in Yaluzangbujiang ophiolitic mélanges in Najiabawa

对南迦巴瓦地区雅鲁藏布江蛇绿混杂岩带内旁辛蛇绿岩中变基性岩的地球化学特征进行研究后,发现该基性岩为玻安岩,具有SiO2>53%,镁指数(Mg#)>0.6,难熔元素(Cr、Co和Ni)明显富集,而高场强元素(Nb、Zr、Ti和Y)亏损等玻安岩所具有的典型地球化学特征。旁辛蛇绿岩中玻安岩的主要地球化学特征不仅能与世界著名的玻安岩进行对比,而且也能与雅鲁藏布江蛇绿岩带的日喀则和得几蛇绿岩中的玻安岩进行对比。因此,可以认为南迦巴瓦地区雅鲁藏布江蛇绿混杂岩形成于岛弧环境。

The boninite is recognized from Pangxin ophiolite based on geochemical criteria that are SiO 2 >53%,Mg # >0.6,high concentrations of refractory elements,such as Cr ,Co Ni ,low concentrations of high-field-strength ions.The main geochemical characteristics of sample are similar to not only boninites' from well known location but also boninites' from Rikaze and Deji ophiolite.The Pangxin ophiolite occurred in the arc setting.