阿尔金曼特里克地区亚干布阳花岗质片麻岩地球化学特征及其成因

Geochemistry and Petrogenesis of Yaganbuyang Granitic Gneiss in Mantelike Area of Altun,China

为了解阿尔金南缘在新元古代早期的构造-岩浆事件,选取曼特里克地区亚干布阳花岗质片麻岩进行详细的岩石学、同位素年代学和地球化学研究。结果表明:亚干布阳花岗质片麻岩形成于新元古代青白口纪,锆石U-Pb年龄为(880.3±3.4)Ma;岩石属过铝质、钙碱性系列的镁质花岗岩,轻、重稀土元素分馏明显,Nb、Ta、Zr、Hf等高场强元素亏损,具有典型的地壳重熔型花岗岩特征,其岩浆来源于下地壳角闪岩相基性岩类的部分熔融,形成于同碰撞花岗岩区;阿尔金南缘新元古代早期的构造-岩浆事件可能对应于新元古代Rodinia超大陆汇聚事件,说明塔里木板块和柴达木板块之间在新元古代早期曾经存在板块的汇聚碰撞。

In order to understand the tectono-magma events in the southern margin of Altun in Early Neoproterozoic,the Yaganbuyang granitic gneiss in Mantelike area was selected for detailed studies of petrology,isotope chronology and petrochemistry.The results show that Yaganbuyang granitic gneiss is formed in Neoproterozoic Qingbaikou period,and the zircon U-Pb age is(880.3±3.4)Ma;the rock with obvious fractional distillation of LREE and HREE and the loss of HFSEs such as Nb,Ta,Zr and Hf,is magnesian granite in the peraluminous and calc-alkaline series,and has the characteristics of crustal remelting granite,which originates from the partial melting of base rock in the amphibolite facies of the lower crust and forms in the syn-collisional granite zone.It is suggested that the tectono-magma events in the southern margin of Altun has the possiblity of matching to the assemblage events of Rodinia supercontinent in Neoproterozoic,indicating that assemblage collision occurs between Tarim and Qaidam plates at the early time.