兩廣雲開高州-雲爐地區麻粒岩相變質作用演化研究; P-T Evolution of Granulite Facies Rocks Of Gaozhou-Yunlu Area, Yunkai Mountain, Guangxi-Guangdong

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题名:	兩廣雲開高州-雲爐地區麻粒岩相變質作用演化研究;P-T Evolution of Granulite Facies Rocks Of Gaozhou-Yunlu Area, Yunkai Mountain, Guangxi-Guangdong
作者:	吳若慧;Jo-hui Wu
贡献者:	地球物理研究所
关键词:	雲開;麻粒岩;紫蘇花崗岩;矽卡岩;Yun-Kai;Granulite;Charnockite;Skarn
日期:	2008-07-03
上传时间:	2009-09-22 09:55:38 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	雲開地區地處華夏以及楊子兩大板塊的結合地帶且為華南加里東褶皺帶南段重要組成部分，其中高州—雲爐一帶所出露的麻粒岩相岩石以及紫蘇花崗岩類的演化研究則是探討中下部地殼以及造山帶深部演化中最關鍵的部份。本研究採集了麻粒岩以及紫蘇花崗岩類、矽卡岩類等標本從事光學顯微鏡岩象觀察以及電子微探儀成分分析工作，並使用地質溫壓計計算以及熱力學模擬的方式推測各岩類中所記錄到之溫度壓力演化途徑。於石榴—菫青麻粒岩中分析不同時期之礦物組合得到早期—峰期等壓增溫，峰期—後期減壓降溫的順時針溫度壓力演化歷史。而在紫蘇閃長岩及紫蘇花崗閃長岩中則都記錄了減壓降溫的抬升歷史。另外在矽卡岩類當中由岩象觀察以及斜輝石與角閃石之定性化學分析之化學成分發現後期受到糜嶺岩化以及角閃岩相以下之降級變質作用。綜合岩象觀察、礦物化學分析以及地質溫壓計與熱力學模擬結果，筆者認為雲開地區之麻粒岩相岩石在紫蘇花崗閃長岩岩岩漿入侵前可能為高壓角閃岩相或高壓麻粒岩相之變質泥岩，在紫蘇花崗岩岩漿入侵加熱後經由等壓增溫途徑進入中壓麻粒岩相以及低壓麻粒岩相，隨後與紫蘇花崗岩類以及矽卡岩類同時抬升進入角閃岩相以及綠色片岩相後繼續抬升至地表。結合前人定年結果所做出之構造演化模型，麻粒岩相變質作用是受到加里東期造山過程中紫蘇花崗岩類岩漿入侵而發生，而糜嶺岩化作用以及角閃岩相以下之變質作用過程則是受到印支期陸—陸碰撞（大陸造山帶）影響。 Yunkai orogenic belt lies between Xianggui block and Cathaysia block as an important part of south segment of Caledonia fold belt in South China. The granulite facies rocks (Granulites) and Charnockites in Gaozhou-Yunlu are also a key to understand middle to lower crust and to investigate the tectonic evolution of South China. In this Study, we take samples of Granulites, Charnockites and Skarns for mineral phase observation with microscrope and for mineral chemical composition analyses with electro-microprobe. We also use geothermobarometer calculation and thermodynamic modeling to find out the P-T evolution evidence preserved in all kinds of rocks. In different stage of mineral assemblage of Garnet-Cordierite granulite we get a clockwise P-T path which isobaric heating from the early stage to peak stage followed by decompression cooling to late stage. In Enderbite and Charno-enderbite, we both get a decompression cooling history. And in Skarns, though the observation of mineral phase and qualitative analyses with Clinopyroxene and Amphibole, we find the records of mylonitaztion and retrograde metamorphism of Amphibolite to Greenshist facies. With all the analyses and calculations,we think that the protolith of Granulites in Yunkai area were metapelites in Amphibolite facies or High-pressure granulite facies. After intrusion of Charno-enderbite magma, it went into Medium-pressure to Low-pressure granulite facies by heating. In the latter stage, Granulites uplift with Charnockites and Skarns and went though Amphibolite and Greenchist facies to the ground surface. Combine with perversely isochorne age data, we make a tectonic evolution model that the granulite facies metamorphism was caused by Charnockite magma intrusion in Caledonia movement, the mylonitization and Amphibolite to Greenshist facies retrograde metamorphism was affect by Indo-China movement.
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