东昆仑造山带温泉地区超镁铁岩成因
发布时间：2018-08-16 12:13
【摘要】：东昆仑造山带位于中央造山系西段,是一个经历了多期次构造运动的复合型造山带,以原特提斯洋和古特提斯洋演化的两大洋陆构造旋回为主线,主要表现为东昆中断裂带的早古生代蛇绿岩和布青山-阿尼玛卿构造带的晚古生代蛇绿岩,且布青山地区也存在早古生代蛇绿岩。温泉超镁铁岩被认为是元古代蛇绿岩,与清水泉、乌妥等地的蛇绿岩同处于东昆中断裂带,本文通过对温泉地区超镁铁岩的矿物学、岩石学、地球化学以及年代学的研究,探讨其岩石成因、构造属性、形成时代及其对东昆仑造山带古生代构造演化的地质意义。取得以下主要进展和认识:1、温泉地区超镁铁岩由纯橄岩、异剥橄榄岩、橄榄单斜辉石岩和单斜辉石岩组成。纯橄岩中橄榄石的Fo值介于91~92,异剥橄榄岩和单斜辉石岩中橄榄石的Fo值介于80~85;铬尖晶石主要出现在异剥橄榄岩和单斜辉石岩中,Cr#值为79~91,Mg#值介于9~30,Ti O2和Al2O3的含量分别为0.09~2.11%和3.30~15.09%;异剥橄榄岩、橄榄单斜辉石岩和单斜辉石岩中的单斜辉石大部分为透辉石,Mg#值(92~98)较高。结合全岩地球化学的分析,纯橄岩属于SSZ型蛇绿岩中的变质橄榄岩,辉石岩(橄榄单斜辉石岩和单斜辉石岩)和异剥橄榄岩则属超镁铁堆晶岩,并非Alaskan-type侵入体或者层状侵入体。2、堆晶岩是由亏损地幔经过部分熔融形成高镁拉斑玄武质岩浆,然后发生了分离结晶作用和地壳混染作用形成的。异剥橄榄岩和单斜辉石岩具有包含结构和堆晶结构,橄榄石的Ni O含量和Fo值呈正相关,单斜辉石中Cr2O3含量随着Mg#值的降低而降低,各主量元素之间具有一定的相关性,表明结晶分异作用控制岩浆演化的主要过程。微量元素具有富集大离子亲石元素而相对亏损高场强元素、Nb显示负异常等特征,Ce/Nb-Th/Nb、Ta/Yb-Th/Yb以及Ti O2/Yb-La/Yb协变关系均表现为一致的正相关,且(Th/Nb)N1和Nb/La1,以上特征表明其在一定程度上受到了地壳物质的混染。3、测得单斜辉石岩的锆石U-Pb同位素年龄为331±2Ma,与布青山晚古生代蛇绿岩的年龄基本一致,说明温泉超镁铁岩与布青山蛇绿岩在成因上有一定的联系,由于所处构造位置的特殊性,温泉地区超镁铁岩可能为古特提斯洋的洋壳残留,即在东昆中断裂带也存在古特提斯洋的遗迹。
[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 卤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.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1
本文编号：2185948
[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 卤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.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.1
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