新疆哈尔里克山石城子地区钠铁闪石花岗斑岩岩墙的发现及构造背景示踪  

Arfvedsonite Granitic Porphyry Dykes Discovered in the Shichengzi Area of Harlik Mountain,Xinjiang and Their Tectonic Significance

作　　者：南云[1] 柳益群[1] 周鼎武[2] 周小虎[1] 焦鑫[1] 李哲萱 NAN Yun;LIU Yiqun;ZHOU Dingwu;ZHOU Xiaohu;JIAO Xin;LI Zhexuan(State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi＇an 710069, China;College of Geological Sciences ＆ Engineering, Shandong University of Science and Technology, Qingdao 266510, China)

机构地区：[1]西北大学地质学系,大陆动力学国家重点实验室,西安710069 [2]山东科技大学地质科学与工程学院,青岛266510

出　　处：《地质学报》2018年第6期1240-1263,共24页Acta Geologica Sinica

基　　金：国家自然科学基金(41272116); 教育部科技发展中心高等学校博导基金(20106101110020); 西北大学研究生创新教育项目(YZZ13008)联合资助的成果

摘　　要：在新疆哈尔里克山石城子地区新发现了一套侵位于晚古生代后碰撞二长花岗岩中的钠铁闪石花岗斑岩岩墙群。该类岩墙具斑状,斑晶以条纹长石和反条纹长石为主,基质矿物组成为正长石、钠长石、石英、钠铁闪石和霓石,为钠铁闪石花岗斑岩。主量元素特征显示为高硅、高碱,低铝、低镁和低钙;稀土元素总量较高,轻重稀土分馏明显,显著富集轻稀土元素;稀土元素配分模式曲线呈明显右倾的"V"型,Eu亏损强烈;微量元素特征显示为高10~4 Ga/Al、Zr和Zr+Nb+Ce+Y,强烈亏损Ba、Sr、P、Ti,富集Th、U、Zr和Hf;岩石学、地球化学特征显示其为碱性A型花岗岩。正ε_(Nd)(t)(4.13~4.75)和年轻的Nd模式年龄(t_(DM2)),指示其源区为亏损地幔来源的新生陆壳物质。LA-ICP-MS锆石U-Pb年龄结果显示岩墙的结晶年龄为晚二叠世(259.7±4.5Ma),围岩中捕获的老锆石年龄集中在2168~2635Ma和1677~1973Ma两个峰期,说明哈尔里克山地区可能存在前寒武纪古老基底,但已被新生陆壳物质改造。结合区域地质背景认为,哈尔里克山地区晚石炭世-早二叠世,为后碰撞伸展阶段;晚二叠世,进入陆内伸展阶段。One set of the arfvedsonite granitic porphyry dykes exposed widely in the Shichengzi area of Harlik Mountain,Xinjiang,NW China,was discovered.The dykes intrude into Late Paleozoic monzonitic granite plutons.The dykes are of porphyritic texture and massive structure.Phenocrysts consist dominantly of perthite and antiperthite,with matrix composed of albite,orthoclase,quartz,arfvedsonite and aegirine.The main elements analysis shows that arfvedsonite granitic porphyry has high contents of SiO2 and Na2O＋K2O,and low contents of Al2O3,MgO and CaO.These samples have a high ∑REE value and distinct fractionation between LREE and HREE,especially enrichment in LREE.The chondrite-normalized REE patterns show obvious right-leaning pattern with strong Eu negative anomaly.In addition,the primitive mantle-normalized trace elements pattern shows show high 104 Ga/Al,Zr and（Zr＋Nb＋Ce＋Y）values,and the depletion of Ba,Sr,P,and Ti and enrichment of Th,U,Zr,and Hf.The petrographic and geochemical data above indicate that the arfvedsonite granitic porphyry dykes are A-type granite.Positive ε（Nd）（t）（4.13-4.75）values and young Nd model ages（t（DM2））indicate that arfvedsonite granitic porphyry was derived from juvenile crust.LA-ICP-MS zircon U-Pb dating suggests that the dykes emplaced at Late Permian（259.7±4.5 Ma）.The ages of two old zircons in country rocks concentrate around two peaks（2168 to 2635 Ma and 1677 to 1973 Ma）,respectively,which indicate the existence of Precambrian basement in Harlik Mountain,but was reformed by juvenile crust.Combined with regional geologic background,the Harlik Mountain area was in tectonic setting of post-collision during Carboniferous and early Permian and then entered the intracontinental extension during Late Permian.

关 键 词：钠铁闪石 花岗斑岩岩墙 地球化学特征 石城子地区 哈尔里克山 

分 类 号：P534.4[天文地球—古生物学与地层学] P588.121[天文地球—地质学]