新疆托克逊可可乃克一带晚奥陶世侵入岩地球化学特征及地质意义  

Geochemistry Characteristics of Lata Ordovician Intrusive Rock from Kekenaike Area in Tuokexun Xinjiang,and Its Geological Significance

作　　者：郑勇 杨阳 杨林春 陈邦学 颜松林 梁宇轩 宁显贵 Zheng Yong;Yang Yang;Yang Lingchun;Cheng Bangxuen;Yan Songling;Liang Yunxuan;Ning Xianggui(No.11 Geological Brigade of Xinjiang Uyghur Autonomous Region Geological Bureau,Changji,Xinjiang,831100,China;No.2 Geological Brigade of Xinjiang Uyghur Autonomous Region Geological Bureau,Kashgar,Xinjiang,844800,China;Shanxi Geological Exploration Institute,General Administration of Geology and Mines of China Chemical Industry,Xi’an,Shaanxi,710000,China)

机构地区：[1]新疆维吾尔自治区地质局第十一地质大队,新疆昌吉831100 [2]新疆维吾尔自治区地质局第二地质大队,新疆喀什844800 [3]中化地质矿山总局陕西地质勘查院,陕西西安710000

出　　处：《新疆地质》2024年第4期515-525,共11页Xinjiang Geology

基　　金：新疆维吾尔自治区自然科学基金项目(2022D01A290)资助。

摘　　要：新疆托克逊县可可乃克地处可可乃克早古生代陆缘弧东段,发育片麻状花岗闪长岩、片麻状花岗岩,通过野外调查及LA-ICP-MS锆石U-Pb测年、地球化学分析,讨论其构造环境,为进一步研究北天山洋俯冲汇聚提供依据。测年结果显示:片麻状花岗岩获得(448.0±2.4)Ma年龄值,为晚奥陶世。地球化学特征表明:片麻状花岗闪长岩SiO_(2)平均64.69%,MgO平均1.18%,Al_(2)O_(3)平均14.85%,CaO平均2.78%;Na_(2)O+K_(2)O平均6.47%;K_(2)O/Na_(2)O平均1.06%,里特曼指数σ=1.88,A/CNK平均1.07;片麻状花岗岩SiO_(2)平均70.08%,MgO平均0.54%,Al_(2)O_(3)平均13.47%,CaO平均2.00%;Na_(2)O+K_(2)O平均7.02%;K_(2)O/Na_(2)O平均1.45%,里特曼指数σ=1.80,A/CNK平均1.05。为富硅,富镁,贫钙岩石。全碱含量较高,富钾,属准铝质高钾钙碱性系列岩石,属“I”、“S”型花岗岩。稀土总量较高(ΣREE=290.92×10^(-6)~436.00×10^(-6)),LREE/HREE=3.41~6.39,La_(N)/Yb_(N)=8.52~21.22,富集轻稀土,具弱的Eu负异常,δEu为0.50~0.96;大离子亲石元素Rb,K,Ba,Th,La,Ce富集,高场强元素Ta,Nb,Ti亏损,表明岩浆起源与汇聚俯冲密切相关,微量元素特征显示岩浆源具壳幔混合特征;其陆缘弧花岗岩地球化学特征表明,在可可乃克一带的片麻状花岗闪长岩、片麻状花岗岩是北天山洋于晚奥陶世向南俯冲汇聚的产物。Kekenaike area is located in the eastern part of the Kekenaike continental margin island arc of Early Paleozoic,The Late Ordovician gneiss granodiorite and gneiss granitic were discover.The tectonic environment of Kekenaike intrusive rock is discussed through field observation、LA-ICP-MS zircon U-Pb age and geochemical testing,which provides a basis for further study of subduction convergence in the North Tianshan Ocean.The age results show that the granitic gneiss is 448.0±2.4 Ma,which belong to late Ordovician.Geochemical characteristics:the granodiorite gneiss's average value of SiO_(2)is 64.69%,MgO is 1.18%,Al_(2)O_(3)is 14.85%and CaO is 2.78%,(Na_(2)O+K_(2)O)is 6.47%,K_(2)O/Na_(2)O is 1.06%,the Rittman index(σ)is 1.88,A/CNK is 1.07.;The granitic gneiss's average value of SiO_(2)is 70.08%,MgO is 0.54%,Al_(2)O_(3)is 13.47%,and CaO is 2.00%,(Na_(2)O+K_(2)O)is 7.02%,K_(2)O/Na_(2)O is 1.45%,the Rittman index(σ)is 1.80,A/CNK is 1.05.The granite is rich in Si and Mg、low in Ca.The rock is high content of(Na_(2)O+K_(2)O)and high content of K_(2)O/Na_(2)O,belongs to the high potasssium calc-alkali and metaluminous rock series,I、S-type granite.The total amount of REE is high(ΣREE=290.92~436.00×10^(-6)),LREE/HREE is 3.41~6.39,La_(N)/Yb_(N)=8.52~21.22,togerther with light rare earth,and weak negative Eu anomaly(δEu is 0.50~0.96).The Large ion lithophilic elements(Rb,K,Ba,Th,La,Ce)are relatively enriched,The high field strength elements(Ta,Nb,Ti)are deficit,which reveals that magma origin is closely related with convergence subduction,the characteristics of trace elements show that the magma source is characteristics of crust-mantle mixing.The geochemical characteristics of the continental marginal arc granites show that the gneiss granodiorites and gneiss granites in the Kekeanake area are the products of the North Tianshan Ocean subduction and convergence in the Late Ordovician.

关 键 词：可可乃克 晚奥陶世 侵入岩 地球化学特征 地质意义 

分 类 号：P534.42[天文地球—古生物学与地层学] P59[天文地球—地质学]