塔里木盆地基底组成的区域差异性探讨

摘要

塔里木盆地基底组成与分布特征是认识下古生界碳酸盐岩层系油气富集规律的重要依据。本文在建立前寒武纪区域构造热事件的演化序列基础上，结合周边露头地层、航磁异常、连井剖面和地震反射特征，探讨了塔里木盆地基底组成的区域差异性。研究认为各露头地层区不同时代的基底地层组成存在一定的区别，与前寒武纪区域构造演化的区域差异性有关。钻井揭示古元古界结晶基底在塔北隆起、巴楚隆起和塔东隆起均有分布，但岩性差别较大。不同深度的磁源体分布特征暗示宽缓背景下的高异常体可能主要由震旦系、二叠系的基性岩和太古宇麻粒岩组成。地震剖面上，从片岩、片麻岩、麻粒岩到花岗岩，反射成层性和连续性逐渐减弱。多种方法综合判识结果显示塔南地区基底应为古元古界副片麻岩类，塔北地区基底以阿克苏群片岩类为主，塔东隆起及东南隆起带基底组成可能主要为太古宇(-古元古界？)基性麻粒岩和混合岩类，包括古元古代花岗岩体、青白口纪花岗岩、南华-震旦纪玄武岩和二叠纪基性岩墙群等不同时期岩浆活动导致了基底组成的复杂性。%The composition and distribution characteristics of the basement of the Tarim Basin is a foundation to recognize the oil and gas enrichment patterns of the lower Paleozoic carbonate strata. Based on the framework of the Precambrian regional tectonic evolution, and combined with the surrounding strata outcrops, the gravity and magnetic response, the drilling hole and the seismic reflection data, we discussed the regional differences of composition and distribution characteristics of basement of the Tarim Basin. We suggest that some differences exist widely in the sedimentary formations of different ages, which related to the inhomogeneous regional Precambrian tectonic evolution. Drilling reveals Lower Proterozoic crystalline basement distributed in the Tabei Uplift, Bachu uplift and Tadong uplift, but the lithology composition distinguish each other. The distribution characteristics of magnetic sources at different depths implied those high positive outliers in the relief background may be composed mainly of mafic-ultra mafic magmatic materils and the Archean granulites. On the seismic section, the degree of reflective layer and continuity decrease. from schist, gneiss, granulites to granite. The results obtained by various methods show that the basement of the southern Tarim basin should mainly be the Lower Proterozoic paragneiss, the northern Tarim basement should mainly be composed of Upper Proterozoic schist, while the basement composition of the East Tarim uplift and southeast uplift belt may be mainly Archean (-Lower Proterozoic?) mafic granulites and migmatites. In addition, different periods of magma activities, including the Paleoproterozoic granite, the Qingbaikou granite, the Nanhua-the Sinian basalt and the Permian mafic dyke swarms, led to the complexity of the basement composition.