青海省德令哈市东泽令沟花岗岩特征及锆石U-Pb年龄

GRANITE CHARACTERISTICS AND ZIRCON U-PB AGE IN THE EAST OF ZELINGGOU,DELINGHA CITY,QINGHAI PROVINCE

泽令沟花岗岩位于柴北缘构造带欧龙布鲁克陆块的中段,主要岩性为二长花岗岩、石英闪长岩,其SiO2含量在61~68%之间,属于中酸性岩,由钙碱性向碱性过渡,属A型花岗岩。岩体中稀土较富集,轻稀土含量更高,稀土、微量元素含量接近于火山岛弧型花岗岩。δEu<1,Eu较强亏损型,岩浆分异程度较高。岩体锆石年龄为431±12 Ma,为早中志留世,具有后造山期花岗岩的特征,推测其应该为柴达木板块向欧龙布鲁克陆块碰撞期后的岩浆活动产物。

Zelinggou granite is located in the middle part of the Oronbrook block in the northern margin of Qaidam,sandwiched between Qilian plate and Qaidam plate[1],in which the main lithology is monzogranite and quartz diorite,with SiO2 content of 61~68%.It belongs to intermediate acid rock and a type of granite with the transition from calc alkaline to alkaline,attributing to A-type of granite,in which the content of rare earth and trace elements is close to that of volcanic island arc granite,featured byδEU<1,EU strongly depleted and high magma differentiation.The zircon age of the granite rocks is 431±12 Ma,belonging to the early middle Silurian with characteristics of post orogenic granites.It is speculated that the granite rocks were formed by magmatic activity after the collision between the Qaidam plate and the Oronbrook block.