四川西昌地区基底结构初探
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摘要
据已有地质资料分析，四川西昌地区是油气勘探很有前景的后备区，但勘探、研究程度极低，尤其缺乏深部构造和基底结构资料，为此，利用以往的重、磁力资料重新进行计算机处理，并结合已有资料对区内基底结构、岩性、断裂及构造单元划分、含油气前景等重新进行了解释与研究。研究认为：区内主要有９条基底断裂，以南北向为主，东西向为辅，特基底切割成特征各异的９个断块区；基底存在着由下元古界深变质岩系和中、上元古界浅变质岩系组成的“双层基底”，其岩性分布主要受东西向基底断裂控制；基底起伏亦受断裂控制，明显呈“东高西低”格局，甘洛、布拖以西为凹陷，以东为隆起。根据这些特征，可将区内划分为９个四级构造单元，结合己有地质、地震及遥感资料综合分析认为：米市凹陷生储盖组合较好，是油气勘探的有利区；昭觉、布拖断凹和凉山断穹虽然出露地层较老，但其深部、背斜翼部及向斜部位仍是有希望的地区。
Xichang region of Sichuan is a reserve area having good oil-gas exploration potential according to the analysis of geological data. But the exploration and research degrees are very low, especially lacking the data of deep structure and basement structure. By computing the previous and present data of gravity and magnetism, the basement structure, lithology, fracture, stractural unit division, gas-bearing potential etc. in the area are interpreted and studied. The studied result shows that there are 9 basement ruptures mainly lying in the north-south and subservienntly in the east-west, and they segregat the basement into 9 blocks with various features; There is a "bilayer basement" consisting of hypometomorphic rocks of Lower Proterozoic and epimetamorphic rocks of Upper Proterozoic and its lithology distribution is controlled by the basement ruptures in the east-west;The basement fluctuation is also controlled by the ruptures and appears high in the east and low in the west, it is sag on the west of Ganluo-Butuo and it is uplift on the east of Ganluo-Butuo. In the light of the features, 9 four-grade structural units are divided in the area. By comprehensively analysing the present data of geology, seism and remote sensing, it is considered that Mishi sag with good source-reserve-cover combination is favourable oil-gas exploration area; Although Zhaojiao fault sag,Butuo fault sag and Liangshan fault dome exposure strata remotely, their deep part, anticlinal flanks and syncline still are hopeful areas.
Xichang region of Sichuan is a reserve area having good oil-gas exploration potential according to the analysis of geological data. But the exploration and research degrees are very low, especially lacking the data of deep structure and basement structure. By computing the previous and present data of gravity and magnetism, the basement structure, lithology, fracture, stractural unit division, gas-bearing potential etc. in the area are interpreted and studied. The studied result shows that there are 9 basement ruptures mainly lying in the north-south and subservienntly in the east-west, and they segregat the basement into 9 blocks with various features; There is a "bilayer basement" consisting of hypometomorphic rocks of Lower Proterozoic and epimetamorphic rocks of Upper Proterozoic and its lithology distribution is controlled by the basement ruptures in the east-west;The basement fluctuation is also controlled by the ruptures and appears high in the east and low in the west, it is sag on the west of Ganluo-Butuo and it is uplift on the east of Ganluo-Butuo. In the light of the features, 9 four-grade structural units are divided in the area. By comprehensively analysing the present data of geology, seism and remote sensing, it is considered that Mishi sag with good source-reserve-cover combination is favourable oil-gas exploration area; Although Zhaojiao fault sag,Butuo fault sag and Liangshan fault dome exposure strata remotely, their deep part, anticlinal flanks and syncline still are hopeful areas.
引文
1王汝植等．西昌—滇中地区沉积盖层及其地史演化．重庆：重庆出版社，19882李复汉等．康滇地区的前震旦系．重庆：重庆出版社，19883刘绍裕．对川东基底性质、结构的探讨．天然气工业，1989；19（2）
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