本文選題：接觸變質(zhì)帶 + P-T視剖面　； 參考：《中國(guó)地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：北京房山巖體是華北克拉通東部燕山期中酸性鈣堿性侵入巖之一,其周緣發(fā)育中國(guó)典型的接觸變質(zhì)帶,依次為矽線石帶、石榴子石-十字石帶和紅柱石帶,疊加在早期區(qū)域變質(zhì)作用之上。由于前人得到的房山巖體的侵位深度和利用單變線得到的變質(zhì)壓力結(jié)果相差懸殊,本論文對(duì)房山巖體及其周圍的接觸變質(zhì)帶開展了綜合研究,并取得以下主要新認(rèn)識(shí)。利用角閃石全鋁壓力計(jì)得到房山巖體的結(jié)晶壓力為(0.39~0.28)±0.06GPa,根據(jù)角閃石-斜長(zhǎng)石溫度計(jì)得到其結(jié)晶溫度為655.9~733.7℃。該結(jié)果表明房山巖體在侵位過程中經(jīng)歷了變壓結(jié)晶作用,結(jié)合房山巖體各巖石單元的侵位溫度、壓力、巖石結(jié)構(gòu)特征以及鋯石U-Pb年齡,可知其在早期經(jīng)歷了緩慢的隆升剝蝕過程,而晚期的巨斑狀中細(xì)粒花崗閃長(zhǎng)巖單元遭受了快速的隆升剝蝕。根據(jù)本研究估算的侵位溫度和壓力,房山巖體的在持續(xù)侵位過程中抬升了7~8 km,平均抬升速率為2.33~2.67 km/Ma�；贙Mn FMASH(K2O-Mn O-Fe O-Mg O-Al2O3-Si O2-H2O)體系,利用Thermocalc 3.33對(duì)房山接觸變質(zhì)帶中的云母片巖進(jìn)行相平衡模擬,通過視剖面和石榴子石、黑云母等值線獲得房山接觸變質(zhì)帶的峰期條件,變質(zhì)壓力為(0.32~0.42)±0.04GPa,溫度為580~690℃,達(dá)角閃巖相變質(zhì),經(jīng)歷了先近等壓升溫再近等溫降壓的順時(shí)針P-T-t軌跡。此外,巖相學(xué)和相平衡研究還表明接觸變質(zhì)帶云母片巖中殘留區(qū)域變質(zhì)作用形成的變質(zhì)礦物藍(lán)晶石。相平衡模擬得到接觸變質(zhì)帶的峰期條件與用傳統(tǒng)溫壓計(jì)得到的房山巖體侵位條件具有良好的耦合關(guān)系,據(jù)此推測(cè)房山巖體的起源深度為15~16km,最后就位的深度為8~9km。房山巖體以巖漿底辟?gòu)?qiáng)力侵位,并在區(qū)域擠壓構(gòu)造背景下快速上升,變壓結(jié)晶作用是該持續(xù)侵位過程中的主要結(jié)晶方式。
[Abstract]:The Fangshan rock body in Beijing is one of the acidic calc-alkaline intrusive rocks in the Yanshanian period in the eastern part of the North China Craton. The contact metamorphic zones in China are developed in the periphery, followed by the Silicite belt, the pomegranate-cross stone belt and the andalusite zone. Superimposed on the early regional metamorphism. Because the emplacement depth of Fangshan rock mass and the result of metamorphic pressure obtained by single variant line are very different, this paper has carried out a comprehensive study on the Fangshan rock mass and its surrounding contact metamorphic zone, and has obtained the following main new understanding. The crystallization pressure of Fangshan rock mass is 0.39 ~ 0.28) 鹵0.06GPa. according to hornblende plagioclase thermometer, the crystallization temperature is 655.9 ~ 733.7 鈩，

本文編號(hào)：1813548