本文選題：高壓變質(zhì)作用　切入點：部分熔融　出處：《巖石學(xué)報》2017年08期

【摘要】：喜馬拉雅造山帶的核心由高級變質(zhì)巖系和淡色花崗巖構(gòu)成,是研究碰撞造山作用和板塊構(gòu)造的天然實驗室。本文評述了喜馬拉雅造山帶變質(zhì)作用和部分熔融研究取得的新進展和存在的爭議,主要內(nèi)容包括:(1)造山帶核部具有"三明治"結(jié)構(gòu),高級變質(zhì)和部分熔融的高喜馬拉雅系列(GHS)夾持在較低級變質(zhì)的特提斯喜馬拉雅系列(THS)和低喜馬拉雅系列(LHS)之中,GHS的變質(zhì)作用程度具有向上和向下部構(gòu)造層位降低的特征。高喜馬拉雅系列主要由高壓麻粒巖相到榴輝巖相的變質(zhì)巖組成,具有1.2~1.6GPa和700~800℃峰期變質(zhì)條件,順時針型變質(zhì)作用P-T軌跡,其進變質(zhì)以增溫增壓為特征,退變質(zhì)早期為近等溫或增溫降壓過程,晚期為降溫降壓和近等壓降溫過程;(2)在造山帶西段,緊鄰縫合帶產(chǎn)出的超高壓變質(zhì)巖具有4.4~4.8GPa和560~760℃的峰期變質(zhì)條件和順時針型P-T軌跡,并在退變質(zhì)中期出現(xiàn)加熱過程;(3)盡管造山帶的高壓和超高壓變質(zhì)巖形成在中、高溫條件下,但巖石中的石榴石都保存有明顯的主量和微量元素生長成分環(huán)帶特征;(4)造山帶變質(zhì)核下部發(fā)育反轉(zhuǎn)的中、高壓型變質(zhì)序列;(5)在造山帶核部,變泥質(zhì)和長英質(zhì)麻粒巖的強烈部分熔融主要是增壓、增溫進變質(zhì)過程中的白云母和黑云母脫水熔融,和近等溫或增溫降壓過程中的黑云母脫水熔融,可以形成花崗質(zhì)和英云閃長質(zhì)熔體。加厚下地殼的高變質(zhì)溫度足以使各種成分巖石(包括基性巖)發(fā)生深熔,而不需要外來熱源;(6)造山帶變質(zhì)核經(jīng)歷了長期的變質(zhì)演化過程,其進變質(zhì)始于~47Ma,峰期變質(zhì)發(fā)生在~25Ma,退變質(zhì)持續(xù)到~15Ma。這些巖石也記錄了持續(xù)的(超過20Myr)高溫變質(zhì)和部分熔融過程。在造山帶西段的超高壓變質(zhì)巖具有~46Ma的峰期變質(zhì)年齡和~40Ma的退變質(zhì)年齡,所以經(jīng)歷了一個快速俯沖與折返過程;(7)印度大陸西緣與島弧的碰撞(造山帶西段)和印度大陸東緣與大陸弧的碰撞時間一致,為~50Ma;(8)在造山帶西段,印度大陸的深和陡俯沖形成了超高壓變質(zhì)巖;而在造山帶中段,印度大陸的平緩俯沖形成了中高壓變質(zhì)巖;(9)構(gòu)造變質(zhì)不連續(xù)在變質(zhì)核中廣泛存在。多重有序逆沖和無序逆沖導(dǎo)致的巖片疊置控制著造山帶的地殼結(jié)構(gòu);(10)現(xiàn)有的構(gòu)造模型,包括楔形擠出、隧道流、臨界楔和構(gòu)造楔模型,都不能全面合理地解釋造山帶變質(zhì)核部的折返機制。
[Abstract]:The core of the Himalayan orogenic belt is composed of high metamorphic rocks and pale granite. It is a natural laboratory for the study of collision orogeny and plate tectonics. This paper reviews the recent advances and controversies in the study of metamorphism and partial melting of Himalayan orogenic belts. The main contents include: 1) the core of the orogenic belt has a "sandwich" structure. High grade metamorphism and partial melting high Himalayan series (GHS) entrainment in lower grade metamorphic Tethys Himalayan series (THS) and low Himalayan series (LHSs) the degree of metamorphism of GHS is reduced upward and downwards. The high Himalayan series consists mainly of metamorphic rocks from high-pressure granulite facies to eclogite facies, It has the peak metamorphic conditions of 1.2~1.6GPa and 700 鈩，

本文編號：1662477