新疆塔里木北缘新元古代最晚期岩浆事件

摘要

报道了塔里木库鲁克塔格地区新元古代晚期花岗闪长岩和钾长花岗岩的锆石U-Pb年龄和Hf同位素组成。花岗闪长岩锆石U-Pb谐和年龄为630.1±1.3Ma，钾长花岗岩锆石U-Pb谐和年龄为630.6±1.3Ma。Hf同位素组成表明，这2种岩石主要来自古老（中）基性地壳的重熔，可能有部分地幔物质的加入。结合已有的研究表明，650~615Ma期间的岩浆活动代表了塔里木地块新元古代最晚期的岩浆活动，是Rodinia超大陆解体过程中的产物，与泛非造山事件无关。塔里木地块自新元古代中期到早寒武世，持续接受了被动大陆边缘沉积，表明在这一时期塔里木为冈瓦那大陆之外独立的大陆块体，或是位于冈瓦那大陆最边缘的稳定大陆块体。%Zircon U-Pb dating reveals that the K-feldspar granite and granodiorite in Quruqtagh on the northern margin of the Tarim block crystallized at 630.1 ± 1.3Ma and 630.6 ± 1.3Ma, respectively. Zircon Hf isotopes indicate that these granitic rocks were mainly derived from partial melting of old andestic-basic crust with possible involvement of basaltic magma from mantle sources. Based on a comprehensive analysis of the Neoproterozoic igneous activities in Tarim, the authors argue that the 650~615Ma igneous rocks in Quruqtagh were the latest phase of the Neoproterozoic igneous activities and genetically related to the breakup of the Rodin-ia suppercontinent, i.e., they had nothing to do with the Pan-Africa orogeny. From Neoproterozoic to Cambrian, sedimentary se-quences in Quruqtagh exhibited typical sedimentation features on a passive continental margin, which indicates that the Tarim block had never incorporated into the Gondwana Land.