东昆仑东段早泥盆世“A”型花岗岩的确定——来自乌兰东地区都南哑合黑云母花岗岩锆石U-Pb年代学、元素地球化学证据  

Determination of Early Devonian A-type Granites in the Eastern Segment of East Kunlun--Evidences from Zircon U-Pb Geochronology and Elemental Geochemistry of Dunanyahe Biotite Granite in East of Wulan Area

作　　者：曹锦山 王国良[1] 刘建栋[1] 李五福[1] Cao Jinshan;Wang Guoliang;Liu Jiandong;Li Wufu(Key Laboratory of Geological Process and Mineral Resources in Northern Qinhai-Tibet Plateau,Qinghai Institute of Geological Survey,Xining,Qinghai,810012,China)

机构地区：[1]青海省青藏高原北部地质过程与矿产资源重点实验室,青海省地质调查院,青海西宁810012

出　　处：《新疆地质》2023年第2期167-177,共11页Xinjiang Geology

基　　金：中国地质调查局商丹-大柴旦地区区域地质调查青海省海西州察汉诺地区J47E018009等五幅1∶5万专项地质调查项目(0617-1911FZ0469)资助。

摘　　要：都南哑合岩体位于东昆仑东段乌兰东呼德生地区,通过对岩体锆石U-Pb定年和岩石地球化学进行研究,分析该岩体成因及构造背景。结果表明:都南哑合岩体主要为黑云母花岗岩,锆石^(206)Pb/^(238)U加权平均年龄为(413.3±2.1)Ma,岩体结晶年龄为早泥盆世;岩石属准铝质-过铝质高钾钙碱性系列,具高硅,SiO_(2)=71.13%~74.67%、富碱,Na_(2)O+K_(2)O=8.3%~9.26%,低铝,Al_(2)O_(3)=12.28%~13.56%、贫钛,0.15%~0.31%、贫镁,0.22%~0.34%及富钾特征。K_(2)O/Na_(2)O=0.69~1.64,平均1.36;稀土元素分布曲线呈强负铕,δEu=0.18~0.42,平均0.26,异常轻稀土富集的右倾型;富集大离子亲石元素Rb,K和高场强元素Th,La,Ce,Nd。Ba相对亏损,Sr强亏损;明显亏损高场强元素P,Ti,弱富集Nb,Ta,Sm,Zr,Hf,Y,Yb,整体具“A”型花岗岩特征。结合区域地质资料及判别图解认为,都南哑合岩体形成于后碰撞伸展构造环境,为中-下地壳物质的部分熔融及后期的分离结晶作用形成。The Dunanyahe pluton is located in east of wulan area,eastern section of East Kunlun.Based on zircon U-Pb dating and petrogeochemistry,the petrogenesis and tectonic setting of the pluton are discussed.The results show that the Dunanyahe pluton is mainly composed of biotite granite,and the weighted average age of zircon ^(206)Pb/^(238)U is(413.3±2.1)Ma,indicating the crystallization age of the pluton is early Devonian.The rocks belong to the peraluminous high-k calc-alka-line series,with high silicon(SiO_(2)=71.13%~74.67%),rich alkali(Na_(2)O+K_(2)O=8.3%~9.26%),low aluminum(Al_(2)O_(3)=12.28%~13.56%),Low in titanium(0.15%~0.31%),magnesium(0.22%~0.34%)and rich in potassium(K_(2)O/Na_(2)O=0.69~1.64,average 1.36).The ree distribution curves show a right-leaning pattern with strong negative Europium(δEu=0.18~0.42,average 0.26)and abnormal LREE enrichment.Enriched large ion lithophile elements Rb,K and high field strength elements Th,La,Ce,Nd,Ba are relatively depleted,while Sr is strongly depleted.However,P and Ti are deplet-ed and Nb,Ta,Sm,Zr,Hf,Y and Yb are weakly enriched,showing the characteristics of A-type granite.Based on region-al geological data and various discriminant diagrams,it is concluded that the duman matte body was formed by partial melting of middle and lower crust materials and subsequent separation crystallization in post-collision tensional tectonic environment.

关 键 词：都南哑合 黑云母花岗岩 岩石地球化学 “A”型花岗岩 后碰撞 

分 类 号：P619.222[天文地球—矿床学]