【摘要】：阿爾泰造山帶是中亞造山帶(CAOB)的重要組成部分,在其南緣出露有高溫泥質(zhì)和鎂鐵質(zhì)麻粒巖,確定其P-T軌跡對于理解阿爾泰造山帶南緣在晚古生代的構(gòu)造演化歷史具有重要意義。通過對該區(qū)烏恰溝泥質(zhì)和鎂鐵質(zhì)麻粒巖樣品精細(xì)的巖相學(xué)觀察,顯示泥質(zhì)麻粒巖峰期前礦物組合(M0)為黑云母+堇青石±尖晶石+斜長石+石英+鈦鐵礦,峰期礦物組合(M1)為石榴石+堇青石+黑云母+斜長石+石英+磁鐵礦+鈦鐵礦±斜方輝石±尖晶石±鉀長石,退變質(zhì)礦物組合(M2)為黑云母+斜長石+石英±堇青石等;鎂鐵質(zhì)麻粒巖峰期前礦物(M0)主要為黑云母和斜長石等礦物,峰期礦物組合(M1)為斜方輝石+單斜輝石+角閃石+黑云母+斜長石+鉀長石+石英+鈦鐵礦+磁鐵礦,退變質(zhì)過程中形成少量角閃石和斜長石等礦物(M2)。使用傳統(tǒng)溫壓計(jì)和平均溫壓計(jì)算方法對其變質(zhì)峰期及峰期后的P-T條件進(jìn)行了計(jì)算,并利用Thermocalc軟件對其中兩個(gè)泥質(zhì)麻粒巖樣品進(jìn)行了視剖面圖模擬,確定了其峰期變質(zhì)條件為770-865℃和3.0-5.1 kbar,并得到了兩條峰期后近等壓冷卻(IBC)的P-T演化軌跡,這樣的P-T軌跡反映了一個(gè)伸展的大地構(gòu)造背景。已有年代學(xué)數(shù)據(jù)支持該區(qū)高溫變質(zhì)事件發(fā)生于二疊紀(jì)(270-280 Ma),與塔里木地幔柱活動(dòng)的時(shí)間(~275 Ma)高度一致,這說明二疊紀(jì)高溫變質(zhì)事件可能與塔里木地幔柱有著密切的成因聯(lián)系,因此,二疊紀(jì)地幔柱活動(dòng)引起的幔源巖漿底侵和加熱可能提供了阿爾泰南緣高溫-超高溫變質(zhì)作用所需的熱源。
[Abstract]:Altai orogenic belt is an important part of (CAOB) in Central Asian orogenic belt. High temperature muddy and mafic granulites are exposed in the southern margin of Altai orogenic belt. It is of great significance to determine its P / T trajectory for understanding the tectonic evolution history of the southern margin of Altai orogenic belt in the late Paleozoic. Based on the fine petrographic observation of Wuqagou muddy and mafic granulite samples in this area, it is shown that the mineral assemblage (M0) of argillaceous granulite before the peak period is biomica cordierite 鹵spinel plagioclase quartz ilmenite, and the peak mineral assemblage (M1) is garnet cordierite biotite plagioclase quartz magnetite ilmenite 鹵clinopyroxene 鹵spinel feldspar, and the peak mineral assemblage (M1) is garnet cordierite plagioclase quartz magnetite ilmenite 鹵clinopyroxene 鹵spinel feldspar. The retrogression mineral assemblage (M2) is biotite plagioclase quartz 鹵cordierite and so on. Before the peak period of mafic granulite, the minerals (M0) are mainly biotite and plagioclase, and the peak mineral assemblage (M1) is clinopyroxene hornblende plagioclase potassium feldspar quartz ilmenite magnetite. A small number of minerals such as hornblende and plagioclase (M2) are formed during retrogression. The P 鈮，

本文編號：2505912