本文選題：昌寧-孟連帶 + 變質(zhì)作用��； 參考：《成都理工大學(xué)》2015年碩士論文

【摘要】：昌寧-孟連帶的演化歷史一直是中外地質(zhì)學(xué)者和專家研究的熱點(diǎn)�！巴跹艓r組”位于昌寧-孟連帶南段的西緣,其地層劃分、巖石特征及變質(zhì)特征,以及地質(zhì)演化等方面,仍有諸多存疑。通過對(duì)滇西鳳慶地區(qū)“王雅巖組”野外剖面及路線地質(zhì)調(diào)查,室內(nèi)巖石薄片研究及成分測(cè)試,經(jīng)綜合對(duì)比認(rèn)為:該套巖石的主要巖性為藍(lán)晶石石榴石十字石黑云母片巖、黑云母石英片巖,其內(nèi)部夾少量長英質(zhì)(花崗質(zhì))片巖、千糜巖,有2期花崗巖脈侵入(其中有一期與區(qū)域上印支期花崗巖同期)。巖石經(jīng)過后期變質(zhì)變形改造后發(fā)育成同質(zhì)構(gòu)造片巖、糜棱巖等,代表性礦物共生組合(泥質(zhì)巖類)為:M1:十字石(St)+鐵鋁榴石(Alm)+黑云母1(Bi)+斜長石(Pl)+石英(Q);M2:藍(lán)晶石(Ky)+鐵鋁榴石(Alm)+黑云母2(Bi)+鉀長石(K)+白云母(Mus)+石英(Q);M3:鐵鋁榴石(Alm)+黑云母3(Bi)+石英(Q),糜棱巖化出現(xiàn):石英(Q)+絹云母(Ser),總體顯示造山變質(zhì)特征。巖石化學(xué)特征表明其原巖為長英質(zhì)巖類和泥質(zhì)巖類的沉積巖。根據(jù)變質(zhì)礦物成分分析數(shù)據(jù)及其結(jié)晶化學(xué)研究:該套巖石中的藍(lán)晶石晶體化學(xué)式為(Fe0.0049-0.0189Al1.9311-1.9933)1.9453-1.9929[(Si0.95-0.9956 Al0.0046-0.05)1O4]O,AlⅣ/AlⅥ約為0.0251;十字石為(Fe0.6503-0.7006Al0.024-0.5016)0.8-1.3Al4[(Al0.1136Si1.8864)O4]2O2(OH)2,AlⅣ/AlⅥ約為0.0252,其XMg值較低,屬鐵十字石;石榴石以鐵鋁榴石為主,鎂鋁榴石(2.75%~9.29%);鈣鋁榴石(6.64%~19.63%),其晶體化學(xué)為:Ca0.2553-0.6032,Mg0.0851-0.2816,Fe1.8667-2.2495,Mn0.1370-0.4168)2.9334-2.9698Al1.869-1.997[(Al0.0008-0.0182Si0.9818-0.9992)1O4]3,AlⅣ/AlⅥ約為0.0091,其F總變化于88.87~95.97之間,顯示石榴石形成于不同壓力條件。黑云母為富鐵黑云母,成分表現(xiàn)為高Al2O3(平均為20.72%)和Fe OT(20.16%)而低Mg O(平均為9.16%),MF值介于0.408~0.540之間(較高),Ti O2質(zhì)量分?jǐn)?shù)在1.16%~2.32%之間;按其礦物特征及成因可分為三期:M1黑云母與十字石同期,被后期變形改造而呈旋斑狀;M2黑云母為長鱗片狀黑云母;M3黑云母呈單片、無定向排列。綜合研究認(rèn)為:“王雅巖組”變質(zhì)巖共經(jīng)歷了三期變質(zhì)作用:第一次變質(zhì)變形(M1-D1),也是本套巖石的初始變質(zhì)期,即十字石、石榴石的形成階段,變質(zhì)溫壓達(dá)511℃~513℃,變質(zhì)壓力達(dá)0.439GPa;為低壓相系綠簾角閃巖相;第二次變質(zhì)變形(M2-D2),即藍(lán)晶石、白云母的形成階段,變質(zhì)溫壓達(dá)553℃,變質(zhì)壓力達(dá)0.551Gpa;為中壓相系角閃巖相。第三次變質(zhì)作用(M3-D3),形成黑云母+石榴石變質(zhì)礦物組合,變質(zhì)溫壓達(dá)303℃~310℃,變質(zhì)壓力達(dá)0.09Gpa,屬低壓相系綠片巖相;其后發(fā)生變形(D4),和變形(D5),主要形成片理褶皺,伴隨有局部糜棱巖化,形成絹云母+石英組合。綜上,結(jié)合區(qū)域構(gòu)造背景可知,主變質(zhì)期(晉寧期)要早于主變形期(燕山-喜馬拉雅期)。該套巖石首先經(jīng)歷了低壓型綠簾角閃巖相到升溫升壓至中壓角閃巖相的進(jìn)變質(zhì),然后再經(jīng)歷了降溫降壓至低壓型綠片巖相的退變質(zhì)過程。
[Abstract]:The evolutionary history of the Changning-Menglian belt has been a hot spot for geologists and experts both at home and abroad. "Wangya Yan formation" is located in the western margin of the southern section of Changning-Menglian belt. Its stratigraphic division, rock characteristics and metamorphic characteristics, as well as geological evolution are still doubtful. Based on the field profile and route geological investigation of "Wangya formation" in Fengqing area, western Yunnan Province, and the laboratory study of thin rock slice and composition test, it is concluded that the main lithology of this set of rocks is the bluestone garnet cross biotite schist. Biotite quartz schist with a small amount of felsic (granitic) schist and mylonite intercalated in its interior, with two stages of granite vein intrusion (one of which coincides with the regional upper Indosinian granite). After the later metamorphic transformation, the rocks developed into homogeneous structural schist, mylonite, etc. Representative mineral symbiotic assemblages (=: M1: Stectite) Almite (Alm) biotite (1) plagioclase) Quartz (QN) M2: Kyydite) Almite (Almite) biotite (K) Musmica) Quartz QP3: Alm (Alm) biotite 3Bi) The occurrence of quartz and mylonitization: quartz Q) serine, which shows the characteristics of orogenic metamorphism in general. The petrochemical characteristics indicate that the source rocks are feldspar and argillaceous sedimentary rocks. According to the analysis data of metamorphic mineral composition and its crystallization chemistry, the crystal chemical formula of bluestone in this set of rocks is: Fe0.0049-0.0189Al1.9311-1.9933A1.9453-1.9929 [Si0.95-0.9956 Al0.0046-0.05)1O4] Ochal 鈪，

本文編號(hào)：1989446