东西天山二叠纪基性岩墙群几何学和侵位机制探讨

发布时间：2018-10-15 13:15

【摘要】：岩墙群形成于伸展构造环境,是岩浆沿地壳裂隙灌入围岩形成的板状侵入体。基性岩墙群富含深部源区及成岩过程等动力学信息,与岩浆活动和岩浆事件紧密相关。新疆东西天山出露了大规模的二叠纪基性岩墙群,众多学者围绕岩墙群的岩石地球化学和同位素年代学做了前瞻性的研究,然而,与之相关的岩墙几何学和侵位机制研究相对较少。这些地区由于地理位置偏远,气候恶劣,并属于军事禁区,常规地质调查难以获得全面的数据资料。因此,本文利用遥感影像,以北山地区和柯坪地区岩墙群为研究对象,进行岩墙几何学及侵位机制的探讨。主要内容和结论如下：(1)基于遥感影像岩墙信息提取,在北山和柯坪地区各提取了1171条和117条岩墙,主要走向均为NNW-NNE,整体都呈现为近平行状排布。北山地区岩墙单体长0.3-21km,平均长3.3km,平均厚度为7.5m；柯坪地区岩墙单体长0.1-17.1km,平均长1.8km,平均厚度为3.8m。两个地区岩墙的长度和厚度分布都服从负指数分布。(2)对两个地区岩墙形态的研究发现,北山地区岩墙单体形态相对复杂和多样化,反映了该区岩墙可能形成于张性兼具剪性的伸展构造环境；柯坪地区岩墙单体形态相对单一,反映了该区岩墙可能主要受到张性构造控制。(3)通过对研究区地壳伸展率的估算发现,北山地区岩墙主要侵入到侵入岩体,在该类岩体中的地壳伸展率平均为7.2%,而整体地壳伸展率平均为1.9%；柯坪地区岩墙主要侵入到沉积岩,地壳伸展率平均为0.25%。(4)对研究区岩浆房深度进行估算,表明北山地区岩浆房深度主要集中于0.6-40km,少数可达70-100km；柯坪地区岩浆房深度主要集中于1-30km,少数可达80-100km。初步推断在地下80-100km深处形成初始岩浆房,岩浆侵位后,初始岩浆房通过岩浆运移会形成其它多个岩浆房。研究区出露的岩墙群很可能是多个岩浆房岩浆侵位的结果,并且可能是形成岩浆房、岩床和溢流玄武岩的主要通道。(5)通过对比岩浆房深度估算结果和岩墙侵位模式特征,初步认为北山和柯坪地区岩墙群的侵位模式是垂向和侧向侵位同时存在。
[Abstract]:The rock dike group is formed in extensional tectonic environment and is a plate-like intrusion formed by magma pouring into surrounding rock along crustal fissure. The basic dyke group is rich in dynamic information such as deep source area and diagenetic process, which is closely related to magmatic activity and magmatic event. In the eastern and western Tianshan Mountains of Xinjiang, large scale Permian basic-dyke swarms have been exposed. Many scholars have made prospective studies on the petrogeochemistry and isotopic chronology of the rock dike groups. However, There are relatively few studies on the geometry and emplacement mechanism of rock dikes. Due to their remote location, harsh climate and military exclusion zone, conventional geological surveys are difficult to obtain comprehensive data. Therefore, the geometries and emplacement mechanism of rock dikes in Beishan and Keping areas are studied by remote sensing images in this paper. The main contents and conclusions are as follows: (1) based on the information extraction of rock walls from remote sensing images, 1171 and 117 rock walls were extracted in Beishan and Keping, respectively, and the main strike was NNW-NNE,. In Beishan area, the monomer length of rock dike is 0.3-21km, the average length is 3.3km, and the average thickness is 7.5m.The monomeric dike in Keping area is 0.1-17.1 km, with an average length of 1.8km and an average thickness of 3.8m. The distribution of the length and thickness of the rock dikes in the two regions are both from the negative exponential distribution. (2) the study on the morphology of the rock dikes in the two regions shows that the individual forms of the rock dikes in the Beishan region are relatively complex and diversified. The results indicate that the rock dikes in this area may be formed in the extensional tectonic environment with both tensional and shear properties, and the single rock dikes in the Keping area are relatively single in shape. The results indicate that the rock dikes in this area may be controlled mainly by tensional tectonics. (3) through the estimation of the crustal extension rate in the study area, it is found that the intrusive rock mass is mainly invaded by the rock dikes in Beishan area. In this kind of rock mass, the average crustal extension rate is 7.2 and the overall crustal extension rate is 1.9. The rock wall in Keping area mainly intrudes into sedimentary rocks, and the average crustal extension rate is 0.25. (4) the depth of magma chamber in the study area is estimated. The results show that the depth of magma chamber is mainly 0.6-40km in Beishan area and 70-100km in a few cases, while the depth of magmatic chamber is mainly concentrated at 1-30km and 80-100km in Keping area. It is preliminarily inferred that the initial magma chamber is formed in the deep underground 80-100km, and after the magma emplacement, the initial magma chamber will form several other magma chambers through magmatic migration. It is very likely that the exposed rock dike group in the study area is the result of multiple magma chamber magma emplacement, and may be the main channel to form magma chamber, rock bed and overflow basalt. (5) by comparing the results of magmatic chamber depth estimation and the characteristics of emplacement model of rock wall, It is preliminarily considered that the emplacement model of the rock dike swarms in Beishan and Keping areas is both vertical and lateral emplacement.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.12

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