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东天山星星峡缝合带早古生代强过铝质花岗岩的研究及其地质意义
  • 期刊名称:地质科学
  • 时间:0
  • 页码:41-56
  • 语言:中文
  • 分类:P597[天文地球—地球化学;天文地球—地质学] P588[天文地球—岩石学;天文地球—地质学]
  • 作者机构:[1]中国科学院地质与地球物理研究所岩石圈构造演化国家重点实验室,北京100029, [2]北京矿产地质研究院,北京100012, [3]香港大学地球科学系,香港薄扶林道, [4]中国科学院地球化学研究所,广州510640
  • 相关基金:国家重点基础研究发展规划项目(编号:2007CB411307)、国家杰出青年基金项目(编号:40725009)和国家科技支撑计划重点项目(编号:2006BAB07B04-01)联合资助.
  • 相关项目:大地构造学
中文摘要:

铅炉子过铝质花岗岩带发育于中天山岛弧带南缘的星星峡缝合带内,为一长条形的二云母花岗岩。岩体地球化学特征是高Si、Al和K,低Mg、Fe的组份,全碱含量中等,σ=1.74~1.9,K2O〉Na2O,A/CNK〉1.1,属于高钾钙碱性过铝质花岗岩类(SP)。岩体的CaO/Na2O和Al2O3/TiO2比值都相对较低,分别为(0.06~0.07)和(48.9~55.3);REE、Nb、Y含量和Rb/Sr、Rb/Ba比值相对较高;Rb、Th和LREE相对富集,Ba、Si、Eu、Ti、P和HREE相对亏损;εHf=-2.3~+1.6表明岩体还具有较高的锆石同位素特征,T2DM变化范围为1573~1329Ma。这些地质学和地球化学研究表明铅炉子二云母花岗岩形成于后碰撞的伸展环境中,是在高温、中低压条件卜发生重熔形成的,其源岩为古老的地壳物质和年轻的增生物质通过物理风化作用形成泥质岩。本文通过测年获得二云母花岗岩锆石LA-ICPMS年龄为444.5±2.2Ma,表明铅炉子过铝质花岗岩形成于晚奥陶世,是中天山岛弧带和公婆泉岛弧带的碰撞时间的上限,它也是中天山岛弧带与公婆泉岛弧带碰撞造山作用的产物,是中亚增生造山带的增生方式之一。

英文摘要:

The Qianluzi granite intruded along the Xingxingxia fault at the south margin of the central Tianshan Mountains. The granite is characterized by high absolute Si,A1 and K,whereas low Mg, Fe contents, K2O 〉 Na2 O, A/CNK 〉 1. 1, is high K calc-alkaline peraluminous granite (SP). The rocks also are characterized by relatively low CaO/Na20(0.06 -0.07)and AI/O3/TiO/ (48.9 - 55.3 ) ratios ; high REE, Nb and Y abundance, enriched LREE and LILE ( Rb, U, Th, K); strongly depleted Ba,Sr P,Ti,Eu and HREE; relatively high zircon Hf isotopic(εHf(t)= -2. 3 - +1. 6)o These characters indicate the Qianluzi granite is the post-collision granite; the source rocks are mud-rocks which are the mixtures matters that origin from the whethering of the growth crust and the old crust; is recycle of the accretionary crust. In the post-collision strike-extension setting, the mantle raised along the fault and lead partial-melting of the mud rocks. The Zircon U-Pb dating by LA-ICPMS shows that its crystallization age is 444.5 ± 2.2 Ma,in the late Ordovician,limits the collision time of the central Tianshan tarrane and the Gongpoquan arc. Summary,the Qianluzi peraluminous granite(SP) is the result of the collision between the central Tianshan terrane and the Gongpoquan Tarrane,and is the one of the results of the crustal growth in the Central Asian Orogeny Belt.

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