【摘要】：東喜馬拉雅構(gòu)造結(jié)南迦巴瓦雜巖由多種類型的高級變質(zhì)巖組成,包括片巖、片麻巖、大理巖、石榴角閃巖和基性麻粒巖。石榴角閃巖呈透鏡狀產(chǎn)出在片麻巖中,可見不連續(xù)分布的規(guī)模不等的淺色體。石榴角閃巖由石榴石、角閃石、黑云母、斜長石、石英、金紅石、鈦鐵礦和榍石組成,石榴石變斑晶可見由淺色礦物組成的"白眼圈"。巖相學(xué)、礦物化學(xué)和相平衡模擬表明石榴角閃巖經(jīng)歷了一條順時針型的P-T演化軌跡,可劃分為兩個階段:(Ⅰ)升溫升壓的進(jìn)變質(zhì)階段,由石榴石和斜長石斑晶記錄,峰期礦物組合為石榴石+角閃石+黑云母+斜長石+石英+金紅石+鈦鐵礦。運(yùn)用石榴石變斑晶邊部和斜長石變斑晶邊部成分在視剖面圖上的投點確定出峰期溫壓條件為~11.5kbar、790℃,達(dá)到了高壓麻粒巖相條件,并經(jīng)歷了部分熔融,產(chǎn)生至少9%的熔體;(Ⅱ)降溫降壓的退變質(zhì)階段,由石榴石邊部"白眼圈"冠狀體記錄。運(yùn)用平均溫壓法計算冠狀體中黑云母+斜長石+角閃石+石榴石組合的形成溫壓條件為~7kbar、~750℃。該階段金紅石消失,熔體結(jié)晶,并與早期礦物發(fā)生回反應(yīng)。在石榴石角閃巖的鋯石中獲得了從29.2Ma到10.2Ma的連續(xù)變質(zhì)年齡。由于鋯石通常在熔體結(jié)晶過程中生長,因此確定該組年齡代表石榴石角閃巖退變質(zhì)年齡。本文和以前的研究結(jié)果表明,南迦巴瓦雜巖中的高溫和中溫麻粒巖相亞單元具有相似的降溫降壓P-T軌跡,但高溫單元具有較高的變質(zhì)壓力條件,表明其俯沖到了更大的深度。
[Abstract]:The Nanjiabahua complex of the eastern Himalayan tectonic complex consists of various types of high-grade metamorphic rocks, including schist, gneiss, marble, pomegranate amphibolite and basic granulite. Pomegranate hornblende occurs in gneisses in lenticular form with discontinuously distributed light-colored bodies of varying sizes. Garnet amphibolite is composed of garnet, amphibolite, biotite, plagioclase, quartz, rutile, ilmenite and sphene. Petrographic, mineral chemistry and phase equilibrium simulations show that pomegranate hornblende has undergone an isochronous pin-type evolution track of Pxt, which can be divided into two stages: (I) the progressive metamorphism stage of rising temperature and pressure, recorded by garnet and plagioclase porphyry. The peak mineral assemblage is garnet hornblende biotite plagioclase quartz rutile ilmenite. Using the input points of garnet porphyry edge and plagioclase porphyry edge on the view profile, the peak temperature and pressure conditions are determined to be ~ 11.5kbar, 790 鈩，

本文編號：2465627