發(fā)布時(shí)間：2018-08-16 12:13

【摘要】：東昆侖造山帶位于中央造山系西段,是一個(gè)經(jīng)歷了多期次構(gòu)造運(yùn)動(dòng)的復(fù)合型造山帶,以原特提斯洋和古特提斯洋演化的兩大洋陸構(gòu)造旋回為主線,主要表現(xiàn)為東昆中斷裂帶的早古生代蛇綠巖和布青山-阿尼瑪卿構(gòu)造帶的晚古生代蛇綠巖,且布青山地區(qū)也存在早古生代蛇綠巖。溫泉超鎂鐵巖被認(rèn)為是元古代蛇綠巖,與清水泉、烏妥等地的蛇綠巖同處于東昆中斷裂帶,本文通過(guò)對(duì)溫泉地區(qū)超鎂鐵巖的礦物學(xué)、巖石學(xué)、地球化學(xué)以及年代學(xué)的研究,探討其巖石成因、構(gòu)造屬性、形成時(shí)代及其對(duì)東昆侖造山帶古生代構(gòu)造演化的地質(zhì)意義。取得以下主要進(jìn)展和認(rèn)識(shí):1、溫泉地區(qū)超鎂鐵巖由純橄巖、異剝橄欖巖、橄欖單斜輝石巖和單斜輝石巖組成。純橄巖中橄欖石的Fo值介于91~92,異剝橄欖巖和單斜輝石巖中橄欖石的Fo值介于80~85;鉻尖晶石主要出現(xiàn)在異剝橄欖巖和單斜輝石巖中,Cr#值為79~91,Mg#值介于9~30,Ti O2和Al2O3的含量分別為0.09~2.11%和3.30~15.09%;異剝橄欖巖、橄欖單斜輝石巖和單斜輝石巖中的單斜輝石大部分為透輝石,Mg#值(92~98)較高。結(jié)合全巖地球化學(xué)的分析,純橄巖屬于SSZ型蛇綠巖中的變質(zhì)橄欖巖,輝石巖(橄欖單斜輝石巖和單斜輝石巖)和異剝橄欖巖則屬超鎂鐵堆晶巖,并非Alaskan-type侵入體或者層狀侵入體。2、堆晶巖是由虧損地幔經(jīng)過(guò)部分熔融形成高鎂拉斑玄武質(zhì)巖漿,然后發(fā)生了分離結(jié)晶作用和地殼混染作用形成的。異剝橄欖巖和單斜輝石巖具有包含結(jié)構(gòu)和堆晶結(jié)構(gòu),橄欖石的Ni O含量和Fo值呈正相關(guān),單斜輝石中Cr2O3含量隨著Mg#值的降低而降低,各主量元素之間具有一定的相關(guān)性,表明結(jié)晶分異作用控制巖漿演化的主要過(guò)程。微量元素具有富集大離子親石元素而相對(duì)虧損高場(chǎng)強(qiáng)元素、Nb顯示負(fù)異常等特征,Ce/Nb-Th/Nb、Ta/Yb-Th/Yb以及Ti O2/Yb-La/Yb協(xié)變關(guān)系均表現(xiàn)為一致的正相關(guān),且(Th/Nb)N1和Nb/La1,以上特征表明其在一定程度上受到了地殼物質(zhì)的混染。3、測(cè)得單斜輝石巖的鋯石U-Pb同位素年齡為331±2Ma,與布青山晚古生代蛇綠巖的年齡基本一致,說(shuō)明溫泉超鎂鐵巖與布青山蛇綠巖在成因上有一定的聯(lián)系,由于所處構(gòu)造位置的特殊性,溫泉地區(qū)超鎂鐵巖可能為古特提斯洋的洋殼殘留,即在東昆中斷裂帶也存在古特提斯洋的遺跡。
[Abstract]:The East Kunlun orogenic belt, located in the western part of the central orogenic system, is a composite orogenic belt that has undergone multiple tectonic movements, with the two major oceanic tectonic cycles of the original Tethys Ocean and the PaleoTethys Ocean as the main line. The main features are the early Paleozoic ophiolite and the late Paleozoic ophiolite in the Buqingshan-Animaqing tectonic belt, and the early Paleozoic ophiolite also exists in the Buqingshan area. The hot spring ultramafic rock is considered to be the Proterozoic ophiolite, and the ophiolite of Qingshuiquan and Wutuo are in the middle fault zone of Dongkun.Based on the study of mineralogy, petrology, geochemistry and geochronology of ultramafic rocks in the hot spring area, The petrogenesis, tectonic attributes, age of formation and its geological significance to the Paleozoic tectonic evolution of the East Kunlun orogenic belt are discussed. The ultramafic rocks in the hot spring area are composed of peridotite, heteroglyphic peridotite, olivine monocline and monocline pyroxenite. The Fo value of olivine in pure olivine is between 91 and 92, the Fo value of olivine in isophoric peridotite and monocline pyroxenite is between 80 and 85, and chromium spinel mainly occurs in isophoric peridotite and monocline pyroxenite. The Cr # value of olivine in isopectite and monocline pyroxenite is 79 ~ 91 and mg ~ (#) is between 930 TIO _ 2 and Al2O3. 0.09% 2.11% and 3.30% 15.09%. Most of the clinopyroxene in olivine monoclinopyroxene and monoclinopyroxene are diopside with high Mg# value (92 / 98). Based on the analysis of the whole rock geochemistry, the peridotite belongs to the metamorphic peridotite in the SSZ ophiolite, while the pyroxenite (olivine monocline and monocline pyroxenite) and the heteroglass peridotite belong to ultramafic heaps. Not Alaskan-type intrusions or layered intrusions. The heap rocks are formed by partial melting of depleted mantle to high magnesium Black Tortoise magma, and then to separate crystallization and crustal mixing. The heteropyroxene peridotite and monocline pyroxenite have the structure of inclusions and stacks, the content of nio in olivine is positively correlated with the value of Fo, the content of Cr2O3 in clinopyroxene decreases with the decrease of Mg# value, and there is a certain correlation among the main elements. The main process of magmatic evolution is controlled by crystallization differentiation. The trace elements are characterized by the enrichment of large ion lithophile elements and the relative depletion of the high field strength elements (Nb), which show negative anomalies. The covariances of ce / Nb-Thr / Nb / Nb / Yb-Thr / Yb and Ti O2/Yb-La/Yb show a consistent positive correlation. And (Th/Nb) N1 and NB / La 1, which indicate that they are contaminated by crustal materials to some extent. The zircon U-Pb isotopic age of monocline pyroxenite is 331 鹵2 Ma. which is basically the same as that of late Paleozoic ophiolite in Buqingshan. It shows that the spa ultramafic rock is related to the origin of Buqingshan ophiolite. Due to the particularity of the tectonic position, the ultramafic rock in the hot spring area may be a remnant of the oceanic crust in the PaleoTethys ocean. The ancient Tethys Ocean remains in the middle fault zone of East Kunming.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P588.1

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