北阿尔金喀腊大湾南段二长花岗岩地球化学、SHRIMP锆石U-Pb年代学、Hf同位素特征及其对壳-幔相互作用的指示
发布时间：2018-08-07 11:42
【摘要】：喀腊大湾位于北阿尔金山的中东段,区内分布有大量早古生代中-酸性侵入岩体,这些岩体为探索北阿尔金早古生代构造-岩浆活动及其区域构造演化提供了重要依据。本文对出露在喀腊大湾南段的二长花岗岩展开了详细的锆石SHRIMP U-Pb年代学、全岩地球化学和锆石Hf同位素分析。锆石SHRIMP U-Pb定年获得二长花岗岩的成岩年龄为484.2±4.9Ma(MSDW=0.46,n=14),属早奥陶世。在地球化学组成上,二长花岗岩具有富碱(全碱8.31%~8.66%)、高钾(K_2O=3.65%~4.76%)和贫MgO(0.6%~0.9%)、P_2O_5(0.06%~0.11%)、TiO_2(0.39%~0.58%)和FeOT(1.82%~2.34%)的特征,岩石铝饱和指数(A/CNK)为0.96~1.01,属准铝质-弱过铝质高钾钙碱性Ⅰ型花岗岩。二长花岗岩具有弱的正Eu异常,明显富集大离子亲石元素(如K、Rb、Ba、Th、U)和LREE,相对亏损高场强元素(如Ti、Ta、Nb)和HREE,显示出弧岩浆岩的地球化学特征。锆石Hf同位素分析结果表明,二长花岗岩的ε_(Hf)(t)均为正值(+4.08~+8.26),且变化范围较小,对应的二阶段模式年龄(tDM2)为875~1099Ma,反映成岩过程中有显著的幔源新生地壳物质加入。综合区域地质背景及前人研究成果,认为喀腊大湾南段二长花岗岩应形成于北阿尔金洋向南侧阿中地块俯冲消减的活动大陆边缘弧环境,其岩浆源区可能起源于新生地壳和古老基底地壳构成混合地壳的部分熔融,岩体在形成过程中经历了壳幔岩浆混合作用,这些特征与北祁连早古生代形成于俯冲消减背景下的中-酸性侵入岩体相似,进而为北阿尔金曾是北祁连的西延部分提供了新的佐证。
[Abstract]:Kaladawan is located in the middle and eastern part of the northern Altun. There are a large number of early Paleozoic intermediate-acid intrusive rocks in the area, which provide an important basis for exploring the early Paleozoic tectonic-magmatic activities and their regional tectonic evolution in North Altun. In this paper, detailed zircon SHRIMP U-Pb geochronology, whole rock geochemistry and zircon HF isotopic analysis have been carried out for the monzogranites exposed in the southern segment of Kaladawan. The diagenetic age of the monzogranite obtained by zircon SHRIMP U-Pb dating is 484.2 卤4.9Ma (MSDWY 0.46NQ14), belonging to the early Ordovician. In terms of geochemical composition, the binomorphic granite is characterized by alkali-rich (total alkali 8.31 ~ 8.66%), high potassium (K _ 2O-3.65 ~ 4.76%) and poor MgO (0.6 ~ 0.9%), P _ 2O _ 5 (0.06 ~ 0.11%) and FeOT (0.390.58%) and FeOT (1.822o _ 2.34%). The saturation index (A/CNK) of the rock is 0.961.01and belongs to the quasi-aluminum-weakly peraluminous high-potassium calc-alkaline type 鈪，
本文编号：2169914
[Abstract]:Kaladawan is located in the middle and eastern part of the northern Altun. There are a large number of early Paleozoic intermediate-acid intrusive rocks in the area, which provide an important basis for exploring the early Paleozoic tectonic-magmatic activities and their regional tectonic evolution in North Altun. In this paper, detailed zircon SHRIMP U-Pb geochronology, whole rock geochemistry and zircon HF isotopic analysis have been carried out for the monzogranites exposed in the southern segment of Kaladawan. The diagenetic age of the monzogranite obtained by zircon SHRIMP U-Pb dating is 484.2 卤4.9Ma (MSDWY 0.46NQ14), belonging to the early Ordovician. In terms of geochemical composition, the binomorphic granite is characterized by alkali-rich (total alkali 8.31 ~ 8.66%), high potassium (K _ 2O-3.65 ~ 4.76%) and poor MgO (0.6 ~ 0.9%), P _ 2O _ 5 (0.06 ~ 0.11%) and FeOT (0.390.58%) and FeOT (1.822o _ 2.34%). The saturation index (A/CNK) of the rock is 0.961.01and belongs to the quasi-aluminum-weakly peraluminous high-potassium calc-alkaline type 鈪，
本文编号：2169914
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