东天山造山带黑尖山地区花岗闪长岩岩石成因及构造意义:来自岩石学、锆石U-Pb年代学、地球化学证据  

Petrogenesis and Tectonic Significance of Late Devonian Granodiorite in Heijinshan Area,Eastern Tianshan Orogenic Belt:Evidences from Petrology,Zircon U-Pb Geochronology,and Geochemistry

作　　者：何碧 赵振琯 刘海生 张文斌 陈红旗 HE Bi;ZHAO Zhen-guan;LIU Hai-sheng;ZHANG Wen-bin;CHEN Hong-qi(The Second Institute of Geology and Minerals Exploration Team,Gansu Provincial Bureau of Geology and Minerals Exploration and Development,Lanzhou 730000,China)

机构地区：[1]甘肃省地质矿产勘查开发局第二地质矿产勘查院,兰州730000

出　　处：《科学技术与工程》2024年第25期10620-10634,共15页Science Technology and Engineering

基　　金：中央返还新疆两权价款项目(T15-1-LQ10)。

摘　　要：黑尖山花岗闪长岩位于东天山造山带晚古生代弧盆系之小热泉子—大南湖古生代残留弧内,通过分析其野外地质特征、岩相学、岩石地球化学以及锆石U-Pb年代学特征,探讨了其岩石成因、构造背景,为东天山地区古洋盆闭合、碰撞造山时限等洋-陆构造格局及其演化研究提供新的基础信息。电感耦合等离子体质谱(inductively coupled plasma mass spectrometry,LA-ICP-MS)锆石U-Pb同位素定年结果显示黑尖山花岗闪长岩形成年龄为(373.0±3.0)Ma。岩石地球化学研究表明,花岗闪长岩具有高硅、准铝质、中-高钾钙碱性系列的I型花岗岩特征;稀土元素总量变化范围为112.82×10^(-6)~129.91×10^(-6),且轻/重稀土的比值变化范围为8.73~11.26(平均值为9.64),指示轻稀土相对重稀土富集,弱Eu负异常(δEu=0.77~0.85);样品富集大离子亲石元素(LILE,如Rb、Ba、K、U),亏损高场强元素(HFSE,如Ta、Nb和Ti)及P、Ta、Nb负异常明显;显示岛弧岩浆岩的特征,形成于板块俯冲的构造环境。综合区域地质特征、岩石地球化学和岩浆源区特征,黑尖山花岗闪长岩是东天山小热泉子—大南湖岛弧内晚古生代大规模中酸性岩浆侵入作用的同期产物,表明东天山黑尖山地区晚泥盆世花岗闪长岩是古大洋(古北天山洋)板片向北俯冲的岛弧背景产物;进一步说明东天山黑尖山地区泥盆纪晚期古大洋仍未闭合。The Heijianshan granodiorite is located in the Xiao Requanzi-Dananhu Paleozoic residual arc of the Late Paleozoic arc-basin system in the eastern Tianshan orogenic belt.Clues from fieldwork,petrography,geochemistry and Zircon U-Pb geochronology were integrated to provide constraints on the tectonic setting in the Late Devonian.Geochemistry data shows that the granitic amphibolite is a set of type I granite with the characteristics of high silica,quasi-aluminous,and medium-high potassium-calcium alkalinity.The total amount of rare earth elements varies from 112.82×10^(-6) to 129.91×10^(-6),and the light/heavy rare earth ratio varies from 8.73 to 11.26(mean value 9.64).Eu elements show weakly negative anomalies(δEu=0.77~0.85).The sample is enriched in large ion lithophile element(LILE,e.g.,Rb,Ba,K,U),lacking high-field strength elements(HFSE,e.g.,Ta,Nb,and Ti)and P,with significant negative anomalies in Nb and Ta.It shows the characteristics of island arc magmatic rocks.The inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb isotope dating results show that the weighted average ages of granitic amphibolites in the area are(373.0±3.0)Ma,indicating that the granodiorites were formed during the Late Devonian,and are contemporaneous products of large-scale Late Paleozoic medium-acidic magmatic intrusion in the Xiao Requanzi-Da Nanhu island arc of the east Tianshan Block.The combination of regional geological features,petrography and magma source area characteristics suggests that the Late Devonian granodiorite in the Heijinshan area of the east Tianshan block is a product of the island-arc of the northward subduction of the ancient oceanic plate.

关 键 词：东天山造山带 黑尖山地区 花岗闪长岩 地球化学 锆石U-PB年代学 晚泥盆世 

分 类 号：P581[天文地球—岩石学]