本文選題：石榴石成分環(huán)帶　切入點(diǎn)：相平衡模擬　出處：《巖石學(xué)報(bào)》2017年08期

【摘要】：秦嶺造山帶是華北板塊與華南板塊長(zhǎng)期匯聚的產(chǎn)物。該造山帶以商南-丹鳳縫合帶為界分為早古生代的北秦嶺造山帶和晚古生代-中生代的南秦嶺造山帶。武關(guān)雜巖位于南秦嶺造山帶的北緣,被認(rèn)為是一套形成于弧前盆地的雜巖,原巖沉積時(shí)代為泥盆紀(jì)-早石炭紀(jì),經(jīng)歷了晚石炭紀(jì)變質(zhì)作用。本文對(duì)武關(guān)雜巖的石榴黑云片巖進(jìn)行了巖石學(xué)研究。該巖石主要由斜長(zhǎng)石、石榴石、黑云母和石英組成,含少量白云母、金紅石和鈦鐵礦。變斑晶石榴石具有明顯的生長(zhǎng)成分環(huán)帶,其核部以MgO含量增加和MnO降低為特征,幔部FeO含量逐漸增加,MgO、CaO和MnO逐漸減少,而在邊部CaO明顯升高,MgO、FeO和MnO含量不同程度降低。相平衡模擬和溫壓計(jì)計(jì)算結(jié)果表明,石榴黑云片巖具有復(fù)雜的順時(shí)針P-T軌跡,早期進(jìn)變質(zhì)階段(M1)為升溫升壓過(guò)程,峰期條件為~695℃和~8.3kbar,變質(zhì)礦物組合為石榴石(核)和所含的黑云母、斜長(zhǎng)石、石英及鈦鐵礦包裹體;中期退變質(zhì)階段(M2)是降溫降壓過(guò)程,達(dá)到~615℃和~6.2kbar變質(zhì)條件,變質(zhì)礦物組合是石榴石(幔)和包含的黑云母、斜長(zhǎng)石、石英、白云母和鈦鐵礦包裹體;晚期是以近等溫升壓為特征的進(jìn)變質(zhì)過(guò)程(M3),達(dá)到~620℃和~9.1kbar條件,變質(zhì)礦物組合為石榴石(邊)和基質(zhì)礦物黑云母、斜長(zhǎng)石、石英、白云母和金紅石。M1和M2階段的構(gòu)造了一個(gè)"發(fā)夾狀"的順時(shí)針P-T軌跡,為俯沖帶變質(zhì)作用典型特征,表明巖石經(jīng)歷了早期俯沖和后來(lái)的折返過(guò)程。而以顯著增壓為特征的晚期進(jìn)變質(zhì)作用(M3)很可能表明巖石經(jīng)歷了又一期俯沖作用。因此,本研究表明武關(guān)雜巖中的石榴黑云片巖很可能處于俯沖通道之中,經(jīng)歷了多旋回俯沖與折返過(guò)程。
[Abstract]:The Qinling orogenic belt is the product of the convergence of North China plate and South China plate for a long time. The orogenic belt is divided into early Paleozoic North Qinling orogenic belt and late Paleozoic Mesozoic South Qinling orogenic belt. Wuguan is divided into early Paleozoic North Qinling orogenic belt and late Paleozoic Mesozoic South Qinling orogenic belt. The complex is located in the northern margin of the South Qinling orogenic belt. It is considered to be a set of complex rocks formed in the forearc basin. The sedimentary age of the original rocks was Devonian to early Carboniferous. It has undergone late Carboniferous metamorphism. The petrological study of the garnet biotite schist of Wuguan complex is carried out. The rock is mainly composed of plagioclase, garnet, biotite and quartz, and contains a small amount of Muscovite, which is mainly composed of plagioclase, garnet, biotite and quartz. Rutile and ilmenite. Metamorphic garnet is characterized by increasing MgO content and decreasing MnO content, and increasing FeO content and decreasing MnO content in the mantle. The results of phase equilibrium simulation and thermobarometer calculation show that the pomegranate black cloud schist has a complex clockwise P-T trajectory, and the early progressive metamorphic stage (M1) is a warming and increasing pressure process. The peak condition is 695 鈩，

本文編號(hào)：1693816