【摘要】：喀臘大灣位于北阿爾金山的中東段,區(qū)內(nèi)分布有大量早古生代中-酸性侵入巖體,這些巖體為探索北阿爾金早古生代構(gòu)造-巖漿活動及其區(qū)域構(gòu)造演化提供了重要依據(jù)。本文對出露在喀臘大灣南段的二長花崗巖展開了詳細(xì)的鋯石SHRIMP U-Pb年代學(xué)、全巖地球化學(xué)和鋯石Hf同位素分析。鋯石SHRIMP U-Pb定年獲得二長花崗巖的成巖年齡為484.2±4.9Ma(MSDW=0.46,n=14),屬早奧陶世。在地球化學(xué)組成上,二長花崗巖具有富堿(全堿8.31%~8.66%)、高鉀(K_2O=3.65%~4.76%)和貧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,巖石鋁飽和指數(shù)(A/CNK)為0.96~1.01,屬準(zhǔn)鋁質(zhì)-弱過鋁質(zhì)高鉀鈣堿性Ⅰ型花崗巖。二長花崗巖具有弱的正Eu異常,明顯富集大離子親石元素(如K、Rb、Ba、Th、U)和LREE,相對虧損高場強(qiáng)元素(如Ti、Ta、Nb)和HREE,顯示出弧巖漿巖的地球化學(xué)特征。鋯石Hf同位素分析結(jié)果表明,二長花崗巖的ε_(Hf)(t)均為正值(+4.08~+8.26),且變化范圍較小,對應(yīng)的二階段模式年齡(tDM2)為875~1099Ma,反映成巖過程中有顯著的幔源新生地殼物質(zhì)加入。綜合區(qū)域地質(zhì)背景及前人研究成果,認(rèn)為喀臘大灣南段二長花崗巖應(yīng)形成于北阿爾金洋向南側(cè)阿中地塊俯沖消減的活動大陸邊緣弧環(huán)境,其巖漿源區(qū)可能起源于新生地殼和古老基底地殼構(gòu)成混合地殼的部分熔融,巖體在形成過程中經(jīng)歷了殼幔巖漿混合作用,這些特征與北祁連早古生代形成于俯沖消減背景下的中-酸性侵入巖體相似,進(jìn)而為北阿爾金曾是北祁連的西延部分提供了新的佐證。
[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 鹵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，

本文編號：2169914