新疆西准噶尔库鲁木苏岩基的解体、地球化学特征及构造意义

发布时间：2018-10-29 08:40

【摘要】：西准噶尔乃至整个北疆地区晚古生代期间岩浆活动异常强烈,发育大量花岗岩类。出露于乌尔喀什尔山一带的库鲁木苏岩基便是其中的代表之一,本文以库鲁木苏岩基为研究对象,从岩基宏观特征、岩石学、岩相学、年代学、岩石地球化学和岩浆演化等方面,对该岩基作了比较系统的研究,取得以下进展:1.库鲁木苏岩基为一复式岩基,可解体为晚石炭世沙雀序列和早二叠世库鲁木苏序列。库鲁木苏序列主要由二长花岗岩、细粒正长花岗岩、中粗粒正长花岗岩、碱长花岗岩和碱长花岗斑岩组成;沙雀序列主要由石英闪长岩和石英二长闪长岩组成。2.高精度LA-ICP-MS测年获得库鲁木苏序列年龄291.5±2.9 Ma和290.9±2.9 Ma,获得沙雀序列年龄304.9±2.5 Ma和304.1±2.9 Ma,表明二者是两期岩浆事件的产物。3.地球化学特征表明,库鲁木苏序列具有高硅、富碱,贫钙、镁及高FeOt/MgO值的特征。同时,稀土元素配分曲线具有明显的的负Eu异常,相对富集Rb、Th、K,强烈亏损Ba、Sr、P、Ti,为铝质A型花岗岩;沙雀序列SiO2含量57.82%~66.18%,Na2O含量4.86%~6.05%,低K2O/Na2O(K2O/Na2O=0.22~0.77),高CaO(CaO=1.75~5.8),A/CNK值为0.81~0.971.1,Rb/Sr为0.05~0.271,稀土配分曲线为右倾平滑状,有弱的负铕异常,暗色矿物主要为黑云母和角闪石,属于钙碱性准铝质I型花岗岩。4.沙雀序列可能由受俯冲流体交代的地幔楔部分熔融,并在上升侵位过程中受到地壳物质混染而形成;库鲁木苏序列是由板片断离引起软流圈地幔上涌,加热下地壳并发生部分熔融形成的。5.西准噶尔地区在晚石炭世仍然存在俯冲消减作用,在早二叠世俯冲消减作用结束,板块完成碰撞和拼贴,进入后碰撞伸展构造环境。
[Abstract]:During the late Paleozoic in West Junggar and the whole northern Xinjiang area magmatic activity was very strong and a large number of granites were developed. Among them, the Kulu Su rock base, which is exposed in the area of Urkashir Mountain, is one of the representatives. In this paper, the author takes the Kulu Su rock base as the research object, from the macroscopic characteristics of the rock base, petrology, petrography, geochronology, etc. In the aspects of rock geochemistry and magmatic evolution, a systematic study of the rock base has been made, and the following progress has been made: 1. The Kulumu rock base is a compound rock base, which can be disintegrated into the late Carboniferous Shatiao sequence and the early Permian Kuluxu sequence. The Kulu Musin sequence is mainly composed of monzogranite, fine-grained syenite, medium-coarse syenite, alkali feldspar granite and alkali-feldspar porphyry, while the Shake sequence is mainly composed of quartz diorite and quartz dicodiorite. High precision LA-ICP-MS dating obtained the ages of 291.5 卤2. 9 Ma and 290.9 卤2. 9 Ma, of the Kulumusu sequence and 304.9 卤2. 5 Ma and 304.1 卤2. 9 Ma, of the Sparrow sequence, indicating that they are the products of the two phases of magmatic events. The geochemical characteristics indicate that the Kulu Mu Su sequence has the characteristics of high silicon, alkali rich, poor calcium, magnesium and high FeOt/MgO value. At the same time, the REE partition curve has obvious negative Eu anomaly, and the relative enrichment of Rb,Th,K, strongly depleted Ba,Sr,P,Ti, is aluminous A-type granite. The SiO2 content of the Sparrow sequence was 57.82% and the content of Na2O was 4.86% and 6.05%, respectively, low K2O/Na2O (K2O/Na2O=0.22~0.77), high CaO (CaO=1.75~5.8), and A/CNK value of 0.81% 0.971.1% RbP / Sr 0.050.271, respectively, while the content of Na _ 2O was 4.86% and 6.05%, respectively, with low K2O/Na2O (K2O/Na2O=0.22~0.77) and high CaO (CaO=1.75~5.8). The REE partition curve is right-dip smooth, with weak negative europium anomaly. The dark minerals are mainly biotite and hornblende, belonging to calc-alkaline quasi-aluminous I-type granite. 4. The sandfinch sequence may be partially melted by mantle wedge metasomatized by subduction fluid and mixed with crustal materials during the process of rising emplacement. The Kulumusu sequence is caused by the plate fragment separation, resulting in the upwelling of the asthenosphere mantle, heating of the lower crust and the formation of partial melting. In the West Junggar area, subduction still exists in the late Carboniferous, and at the end of the early Permian subduction, the plates collide and collage and enter the post-collision extensional tectonic environment.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.12;P542

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