本文選題：二長花崗巖和石英閃長巖 + 年代學(xué)��； 參考：《巖石學(xué)報(bào)》2016年06期

【摘要】：阿爾金南緣茫崖地區(qū)出露著早古生代二長花崗巖體和石英閃長巖體,測得其LA-ICP-MS鋯石U-Pb年齡為472.1±1.1Ma和458.3±6.2Ma。地球化學(xué)特征顯示,前者屬于鉀玄質(zhì)過鋁質(zhì)S型花崗巖,具高的(La/Yb)N和Sr/Y比值,低的HREE、Yb和Y值;后者為高鉀鈣堿性準(zhǔn)鋁質(zhì)-過鋁質(zhì)I型花崗巖,具低的(La/Yb)N和Sr/Y值,高的Yb和Y含量。通過巖石成因和構(gòu)造背景分析,二長花崗巖是陸殼深俯沖作用下,上地殼沉積巖(雜砂巖和少量泥質(zhì)巖)被俯沖帶入到50~80km深處,在高壓(1.5GPa)低溫(779.8~792.9℃)條件下主要由云母分解脫水而發(fā)生部分熔融,殘留相為石榴石+金紅石(無角閃石),在巖漿演化過程中發(fā)生了以斜長石為主(無角閃石)的強(qiáng)烈分離結(jié)晶作用;石英閃長巖是在陸殼深俯沖后的折返抬升作用下,上地殼變質(zhì)玄武巖被抬升至30km處,在低壓(0.8GPa)高溫(811.0~821.0℃)條件下發(fā)生部分熔融,殘留相為角閃石+斜長石(無石榴石),在巖漿演化過程中發(fā)生了以輝石、金紅石和磷灰石為主(無角閃石和斜長石)的分離結(jié)晶作用。結(jié)合前人研究成果,分析了阿爾金南緣早古生代巖漿活動特征及其形成機(jī)制,將該地區(qū)早古生代構(gòu)造-巖漿演化分為三個(gè)階段:1)505~472Ma陸-陸碰撞階段,以高壓環(huán)境下巖漿活動為特征,在陸殼深俯沖的同時(shí),存在俯沖陸殼的初步熔融拆離作用;2)467~450Ma板片拆離階段,由于俯沖板片的完全斷離,強(qiáng)大的浮力主要使上地殼發(fā)生抬升折返,以低壓高溫環(huán)境下上地殼巖漿活動為特征,同時(shí)存在幔源巖漿的底墊作用,具同折返雙峰式巖漿活動的特征;3)424~385.2Ma后碰撞伸展拉張階段,持續(xù)的應(yīng)力釋放松弛使構(gòu)造應(yīng)力從前期的垂向抬升轉(zhuǎn)換為側(cè)向伸展,存在地幔巖漿的底侵上涌作用,以低壓高溫環(huán)境下A型花崗巖巖漿活動為特征。
[Abstract]:The early Paleozoic monzogranite and quartz diorite are exposed in the southern margin of the Altun area. The LA-ICP-MS zircon U-Pb ages are 472.1 鹵1.1Ma and 458.3 鹵6.2 Ma. Geochemical characteristics show that the former belongs to K-peraluminous S-type granites with high ratios of La / YbN and Sr/Y and low values of HREEN and Y, while the latter is of high potassium calc-alkaline pseudo-alumina-peraluminous I-type granites with low La-P / YbN and Sr/Y values. High Yb and Y contents. Based on the petrogenetic and tectonic background analysis, it is found that the monzonitic granites are subducted into the 50~80km depths under the deep subduction of the continental crust, and the sedimentary rocks of the upper crust (complex sandstone and a small amount of argillaceous rocks) are subducted into the deep part of 50~80km. Under the condition of high pressure (1.5GPA) and low temperature (779.8GPa792.9 鈩，

本文編號：1776102