【摘要】：“仲巴微地體”位于雅魯藏布江構(gòu)造帶西段,內(nèi)部發(fā)育普遍產(chǎn)生變形變質(zhì)的奧陶系-三疊系地層,在志留-二疊系接觸部位發(fā)育一條的走向NWW的脆-韌性剪切帶,寬200-1000m,長(zhǎng)數(shù)十公里,總體傾向190°-220°,傾角在20°-40°之間,由南向北變形逐漸減弱。通過(guò)對(duì)仲巴微地體脆-韌性剪切帶野外調(diào)查及室內(nèi)顯微構(gòu)造分析,結(jié)合EBSD分析及構(gòu)造解析方法,對(duì)仲巴微地體脆-韌性剪切帶進(jìn)行了較為詳細(xì)的研究,初步得出了以下幾方面的認(rèn)識(shí):(1)發(fā)育在脆-韌性剪切帶內(nèi)的糜棱巖中面理的總體傾向朝南,剪切帶內(nèi)糜棱巖發(fā)育拉伸線理,可見(jiàn)眼球狀碎斑、壓力影、不對(duì)稱小褶皺、書(shū)斜、劈理折射等宏觀構(gòu)造;變形巖石顯微鏡下可見(jiàn)石英、方解石波狀消光,機(jī)械雙晶、眼球狀構(gòu)造、扭折等顯微構(gòu)造現(xiàn)象,石英、方解石顆粒重結(jié)晶作用明顯,多為動(dòng)態(tài)重結(jié)晶作用;以石英膨凸重結(jié)晶、亞顆粒旋轉(zhuǎn)重結(jié)晶為主,見(jiàn)少量方解石靜態(tài)重結(jié)晶;(2)在動(dòng)力學(xué)方面,通過(guò)分形法計(jì)算得出研究區(qū)脆-韌性變形溫度范圍為330℃~570℃,古應(yīng)力差值介于46.32~74.78MPa之間,應(yīng)變速率介于8.03×10-13s-1~1.41×10-11s-1之間。(3)石英、方解石EBSD組構(gòu)分析結(jié)合礦物變形溫度計(jì)可知仲巴微地體脆-韌性剪切帶中典型礦物的變形分為三個(gè)階段:由中高溫時(shí)期的右行剪切→中低溫時(shí)期的左行剪切→低溫時(shí)期的左行剪切,變形溫壓環(huán)境是從高綠片巖相到低角閃巖相的變質(zhì)環(huán)境→低綠片巖相的變質(zhì)環(huán)境。(4)根據(jù)EBSD分析結(jié)合研究區(qū)構(gòu)造背景,認(rèn)為該脆-韌性剪切帶的形成與特提斯洋向北俯沖作用相關(guān),并經(jīng)歷了印度板塊與歐亞板塊的碰撞與青藏高原差異性隆升階段,這三次大型的構(gòu)造活動(dòng)均造成了該剪切帶不同程度的剪切滑動(dòng)。由俯沖帶前緣強(qiáng)烈擠壓,側(cè)向伸展剪切形成順層剪切,導(dǎo)致了脆-韌性剪切帶的形成,在印度板塊與歐亞板塊的碰撞階段,由碰撞-陸內(nèi)繼承性收縮擠壓形成了北東-南西、近南北向擠壓,此時(shí)剪切帶滑動(dòng)性質(zhì)為擠壓型剪切滑動(dòng),之后伴隨青藏高原南部隆升,脆-韌性剪切帶的再一次滑動(dòng)。
[Abstract]:The "Zhongba micro-terrane" is located in the western section of the Yalu Zangbujiang structural belt. The Ordovician and Triassic strata are generally developed in the interior, and a brittle-ductile shear zone with strike NWW is developed in the Silurian and Permian contact area. Its width is 200-1000m, its length is tens of kilometers, the general tendency is 190 擄-220 擄, the inclination angle is between 20 擄-40 擄, and the deformation gradually weakens from south to north. The brittle-ductile shear zone of Zhongba micro-ground is studied in detail by field investigation and laboratory microstructure analysis, combined with EBSD analysis and structural analysis. The main conclusions are as follows: (1) the general tendency of the surface of mylonite developed in the brittle ductile shear zone is southward, and the mylonite in the shear zone develops stretching lines, with eyeball patches, pressure shadows, asymmetrical small folds, and diagonal. Microstructural phenomena such as cleavage refraction, quartz, calcite wave extinction, mechanical double crystal, eyeball structure, torsion and so on, quartz and calcite particles recrystallization can be seen under the deformed rock microscope. Most of them are dynamic recrystallization, quartz swelling and convex recrystallization, subparticle rotation recrystallization, and a small amount of calcite static recrystallization. (2) in kinetic aspect, the brittle ductile deformation temperature range of 330 鈩，

本文編號(hào)：2120182