新疆西准噶尔哈图岩体地球化学特征及其地质意义  

Geochemical Characteristics of Hatu Pluton in West Junggar of Xinjiang, China and Their Geological Significance

作　　者：李永军[1,2] 李宇航 王祚鹏 LI Yong-jun;LI Yu-hang;WANG Zuo-peng(School of Earth Science and Resources,Chang'an University,Xi'an 710054,Shaanxi,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits of Ministry of Land and Resources,Xi'an 710054,Shaanxi,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]国土资源部岩浆作用成矿与找矿重点实验室,陕西西安710054

出　　处：《地球科学与环境学报》2020年第1期1-14,共14页Journal of Earth Sciences and Environment

基　　金：国家重点研发计划项目(2018YFC0604001);新疆两权价款中央留成专项资金项目(A16-1-LQ14)

摘　　要：哈图岩体侵位于西准噶尔南部早-中泥盆世海相火山-沉积地层中,主要岩性为二长花岗岩、正长花岗岩及少量碱长花岗岩,是研究西准噶尔晚石炭世构造环境的理想对象。哈图岩体花岗岩中SiO2含量(质量分数,下同)为72.06%~76.53%,全碱(Na2O+K2O)为7.80%~8.57%,CaO为0.20%~1.58%,MgO为0.07%~0.42%,明显具有高Si、富碱、贫Ca、低Mg的特征;这些花岗岩的Al2O3含量为12.55%~14.06%,A/CNK值为1.06~1.15,A/NK值为1.15~1.36,显示其为弱过铝质-强过铝质花岗岩。此外,哈图岩体具有较低的稀土元素总含量((88.14~139.53)×10-6)和高的轻、重稀土元素比值((La/Yb)N值为3.04~6.50),在球粒陨石标准化稀土元素配分模式中显示为典型的右倾"V"字形且具有强烈的负Eu异常,表明源区可能有斜长石残留或出现斜长石的分离结晶作用;在原始地幔标准化微量元素蛛网图中,这些花岗岩明显富集Rb、Th、U、K、Pb等大离子亲石元素,相对富集Zr、Hf,强烈亏损Sr、Ti、P,相对亏损Ba、Nb。以上特征及主量、微量元素特征和图解表明,哈图岩体为典型的弱过铝质-强过铝质A2型花岗岩,其形成于造山后伸展阶段,是由洋壳和岛弧组成的新生地壳受上涌的幔源物质加热,在浅部低压条件下发生部分熔融,再经分离结晶作用的产物。Hatu pluton in the southern margin of West Junggar invades into Early-Middle Devonian marine volcanic-sedimentary strata. The lithology of Hatu pluton is mainly composed of monzonitic granite, syenite granite and a small amount of alkali feldspar granite, which is an ideal object to study the tectonic setting of Late Carboniferous in West Junggar. The granites in Hatu pluton have high SiO2(72.06%-76.53%), Na2O+K2O(7.80%-8.57%) and Al2O3(12.55%-14.06%) contents, low CaO(0.20%-1.58%) and MgO(0.07%-0.42%) contents, with A/CNK(1.06-1.15) and A/NK(1.15-1.36) showing the characteristics of weakly peraluminous-strongly peraluminous granite. The granites have high total contents of REE((88.14-139.53)×10-6) and ratios of LREE/HREE((La/Yb)N is 3.04-6.50), and the chondrite-normalized REE pattern exhibits a typical right-dip "V" shape with a strong negative Eu anomaly, indicating that some plagioclases may be retained as a residue in the source area or there is the separation and crystallization of plagioclases. Meanwhile, the granites display significant enrichments of large ion lithophile elements(Rb, Th, U, K and Pb), relative enrichments of Zr and Hf, and depletions in Ba and Nb, especially Sr, Ti and P. The above characteristics demonstrate that Hatu pluton is a typical weakly peraluminous-strongly peraluminous A2-type granite. Combined with diagrams of major and trace elements, Hatu pluton in West Junggar is formed in a post-orogenic extension setting, and the petrogenesis is related to the juvenile crust that comprised both oceanic crust and island arc, which results from partial melting and fractionation under low pressure condition.

关 键 词：地球化学 弱过铝质-强过铝质 A2型花岗岩 岩石成因 晚石炭世 造山后 西准噶尔 新疆 

分 类 号：P588.12[天文地球—岩石学] P595[天文地球—地质学]