本文關(guān)鍵詞： 超高溫麻粒巖 古元古代增生造山作用 三疊紀(jì)碰撞造山作用 蘇魯造山帶 揚(yáng)子板塊　出處：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：蘇魯造山帶是揚(yáng)子與華北板塊三疊紀(jì)俯沖-碰撞造山作用的產(chǎn)物,是研究大陸造山作用與動力學(xué)的天然實(shí)驗(yàn)室。盡管對三疊紀(jì)的大陸深俯沖及超高壓變質(zhì)作用進(jìn)行了大量的研究,并取得了大量成果,但對于造山帶核部出露的少量前寒武變質(zhì)表殼巖的長期構(gòu)造演化歷史還存在爭議。本文對蘇魯造山帶北部威海市西南的變質(zhì)表殼巖和后期侵入巖進(jìn)行了詳細(xì)的巖石學(xué)和鋯石年代學(xué)研究。結(jié)果顯示這一地區(qū)的變質(zhì)表殼巖主要是由片巖、片麻巖、大理巖、鈣硅酸鹽巖、斜長角閃巖、石英巖和麻粒巖等組成。泥質(zhì)麻粒巖(S12-06-1)由石榴石、夕線石、斜長石、條紋長石、反條紋長石、石英、黑云母、白云母和金紅石組成。黑云母和白云母呈石榴石和夕線石的冠狀體產(chǎn)出,為退變質(zhì)礦物。相平衡模擬表明,麻粒巖峰期變質(zhì)的溫度和壓力條件為≥940?C和~1.2GPa。石英的Ti溫壓計(jì)計(jì)算給出的麻粒巖峰期變質(zhì)溫度下限為~980?C。泥質(zhì)麻粒巖(S12-06-1)中鋯石近等粒狀或橢圓形,具扇狀或冷杉狀分帶,大多數(shù)具有平坦甚至虧損的重稀土配分模式,并有Eu的負(fù)異常,為泥質(zhì)巖麻粒巖相變質(zhì)過程中生長鋯石的典型特征。LA-ICP-MS鋯石U-Pb定年結(jié)果給出了1845±9Ma的207Pb/206Pb加權(quán)平均年齡。與泥質(zhì)麻粒巖伴生的斜長角閃巖(S12-06-3)的鋯石具有典型的巖漿鋯石特征,其定年結(jié)果給出了758±26Ma的206Pb/238U的加權(quán)平均年齡。與鈣硅酸鹽巖伴生的斜長角閃巖(S12-02-3)中有兩種變質(zhì)鋯石,一種CL發(fā)光較強(qiáng)、具平坦HREE配分模式的鋯石給出了230±4.7Ma的206Pb/238U的加權(quán)平均年齡,另一種發(fā)光較弱、富集HREE的鋯石給出了214±6.5Ma的206Pb/238U的加權(quán)平均年齡。表殼巖中的含榴花崗巖脈(S12-02-4)的鋯石具有核邊結(jié)構(gòu),鋯石邊部具巖漿成因特征,獲得了200±3.0Ma的206Pb/238U的加權(quán)平均年齡。基于以上成果,我們得出如下認(rèn)識:(1)研究區(qū)變質(zhì)表殼中的泥質(zhì)麻粒巖記錄了古元古代的超高溫變質(zhì)作用,其峰期變質(zhì)作用的溫、壓條件分別是≥980?C和~1.2GPa,變質(zhì)年齡為~1845Ma;(2)變質(zhì)表殼巖中的基性侵入巖(斜長角閃巖)的原巖年齡為~758Ma的新元古代;(3)變質(zhì)表殼巖和基性巖漿巖經(jīng)歷了三疊紀(jì)(~230Ma)的超高壓變質(zhì)作用和稍晚期(~214Ma)的角閃巖相退變質(zhì)作用,并被約~200Ma的含榴花崗巖脈侵入。結(jié)合現(xiàn)有的其他研究結(jié)果,我們認(rèn)為古元古代超高溫變質(zhì)作用很可能形成在揚(yáng)子板塊北緣的增生造山過程中,新元古代巖漿作用很可能與揚(yáng)子板塊北緣裂解相關(guān),而三疊紀(jì)變質(zhì)和巖漿事件形成在揚(yáng)子與華北板塊的碰撞造山過程中。
[Abstract]:The Sulu orogenic belt is the product of the Triassic subduction and collision orogeny between Yangtze and North China plate. Is a natural laboratory for the study of continental orogeny and dynamics. Although a great deal of research has been done on the Triassic continental deep subduction and ultrahigh pressure metamorphism, a great deal of results have been achieved. However, the long-term tectonic evolution history of a small amount of Precambrian metamorphic crust rocks exposed from the core of the orogenic belt is still controversial. In this paper, the metamorphic epidermal rocks and late intrusive rocks in the southwest of Weihai City, northern Sulu orogenic belt, are discussed in detail. The results show that the metamorphic crust rocks in this area are mainly composed of schist. Gneiss, marble, calcium silicate rock, amphibolite, quartzite and granulite are composed of garnet, skirite, plagioclase, striped feldspar, antistripe feldspar, quartz, biotite, etc. The composition of Muscovite and rutile. Biotite and Muscovite are coronal bodies of garnet and sillimanite, which are retrograde metamorphic minerals. The phase equilibrium simulation shows that the temperature and pressure conditions of granulite metamorphism are 鈮，

本文編號：1509601