本文選題：阿爾金北緣　切入點(diǎn)：磁組構(gòu)　出處：《中國(guó)地質(zhì)大學(xué)(北京)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：阿爾金北緣喀臘大灣地區(qū)位于阿爾金走滑斷裂與阿爾金北緣斷裂所夾持區(qū)域的中東段,大地構(gòu)造位置屬于敦煌地塊與中阿爾金地塊的俯沖-碰撞帶,本文著重對(duì)其在本區(qū)所產(chǎn)生的巖石變形特征進(jìn)行了詳細(xì)的研究。為了探究阿爾金北緣喀臘大灣地區(qū)的應(yīng)變型式和變形條件,在野外地質(zhì)觀測(cè)的基礎(chǔ)上,沿喀臘大灣溝構(gòu)造觀察剖面采集變形巖石定向樣品,實(shí)驗(yàn)研究本區(qū)變形巖石的磁組構(gòu)特征,并對(duì)變形強(qiáng)烈的巖石進(jìn)行鏡下顯微構(gòu)造特征和石英EBSD巖組分析。磁組構(gòu)結(jié)果顯示研究區(qū)校正磁化率各向異性度P’總體較大,反映出本區(qū)巖石變形強(qiáng)烈的特征。此外,而磁化率橢球主軸下半球赤平投影和類弗林圖解表明,整個(gè)區(qū)域受到統(tǒng)一的南北向擠壓應(yīng)力的作用,表現(xiàn)為壓扁型的應(yīng)變,而中部發(fā)育陡傾線理的部位呈現(xiàn)出拉長(zhǎng)型的應(yīng)變型式。同時(shí),變形巖石的鏡下顯微構(gòu)造特征和石英EBSD巖組,反映出喀臘大灣地區(qū)以中溫(400~500°C)條件下的柱面(10(?)0)11(?)0滑移變形為主,而研究區(qū)南部局部疊加有高溫條件(500~600℃)下的(10(?)0)0001滑移變形。此外,局部的地區(qū)還疊加有低溫條件下(300~400℃)的(0001)11(?)0滑移變形。且疊加型變形的出現(xiàn),均表現(xiàn)為由高溫型的滑移變形,向相對(duì)低溫型的滑移變形逐漸過(guò)渡轉(zhuǎn)變的現(xiàn)象�？εD大灣溝剖面中段含磁鐵礦礫石礫巖LA-ICP-MS鋯石U-Pb測(cè)年分析表明,其峰值年齡為510.22Ma,而北部礫巖的峰值年齡為456.75Ma,整體呈現(xiàn)出由北向南碎屑鋯石的年齡逐漸變老的趨勢(shì)。前人研究表明,未卷入變形的阿北花崗巖體的鋯石U-Pb SHRIMP測(cè)年結(jié)果為427~417Ma;而南部卷入變形的長(zhǎng)英質(zhì)糜棱巖鋯石U-Pb LA-ICP-MS年齡為477.6±4.9Ma,北部糜棱巖化閃長(zhǎng)巖的鋯石U-Pb LA-ICP-MS年齡為478.1±2.1Ma。這些同位素地質(zhì)年代學(xué)的資料表明本區(qū)巖石變形形成于477~427Ma,處在一個(gè)由俯沖到碰撞的連續(xù)變化的過(guò)程中。一系列的證據(jù)表明,在477~427Ma阿爾金北緣喀臘大灣地區(qū)受到敦煌地塊與中阿爾金地塊俯沖碰撞的連續(xù)影響,在本區(qū)形成以壓扁型應(yīng)變?yōu)橹鞯闹袦?400~500℃)柱面(10(?)0)11(?)0滑移變形,而由于俯沖角度的逐漸增大,以及地幔對(duì)流產(chǎn)生的拖拽力的作用下,使得研究區(qū)中部的巖石,將近于南北向的擠壓應(yīng)力轉(zhuǎn)化為沿板片陡傾的拉伸應(yīng)力,形成一系列拉長(zhǎng)型的應(yīng)變。
[Abstract]:The Kaladawan area on the northern edge of Altun is located in the middle and east segment of the zone between the Altun strike slip fault and the northern Altun fault. The tectonic location belongs to the subduction-collision zone between the Dunhuang block and the middle Altun block. In this paper, the characteristics of rock deformation produced in this area are studied in detail. In order to explore the strain patterns and deformation conditions in Kaladawan area on the northern edge of Altun, on the basis of field geological observations, Directional samples of deformed rocks were collected along the observation section of Kaladawangou structure, and the magnetic fabric characteristics of deformed rocks in this area were studied experimentally. The microscopic structural characteristics of the strongly deformed rocks and the analysis of quartz EBSD rock formation are also carried out. The results of magnetic fabric show that the corrected anisotropy of magnetic susceptibility in the study area is generally larger, which reflects the strong deformation characteristics of the rocks in this area. On the other hand, the hemispherical plain projection of the magnetic susceptibility ellipsoid axis and Flyning-like diagram show that the whole region is subjected to a unified South-North compressive stress, which is shown as flattened strain. At the same time, the microscopic structural characteristics of deformed rocks and quartz EBSD rock formation reflect the columnar area of Kaladawan area under the condition of moderate temperature 400 擄C). What is it? In the southern part of the study area, there is a local superposition of 10 ~ (10)? under the high temperature condition of 500 ~ (600 鈩，

本文編號(hào)：1623613