四川江油马角坝地区飞仙关组磁异常地质因素讨论  

Discussion on geological factors of magnetic anomaly of the Lower Triassic Feixianguan Formation in Majiaoba area,Jiangyou,Sichuan,China

作　　者：李军[1,2] 李霞[1] 陈喻溪 简兴祥 张兵 陈进超[1] LI Jun;LI Xia;CHEN Yuxi;JIAN Xingxiang;ZHANG Bing;CHEN Jinchao(College of Geophysics,Chengdu University of Technology,Chengdu 610059,China;Key Laboratory of Earth Exploration&Information Techniques of the Ministry of Education,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地球物理学院,成都610059 [2]地球勘探与信息技术教育部重点实验室(成都理工大学),成都610059

出　　处：《成都理工大学学报（自然科学版）》2023年第2期229-239,共11页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家自然科学基金项目(42142034)。

摘　　要：为查明四川江油马角坝地区出露的古生界-中生界海相碳酸盐岩和陆相碎屑岩区域磁异常的地质因素,对研究区典型地质剖面进行了地面高精度磁法测量,通过测区岩层物性测试和基于L 0范数约束的磁测数据共轭梯度聚焦反演,获得了研究区多套地层的磁性特征和深部磁性成像结构;研究结果表明地面观测的下三叠统飞仙关组高达近1000 nT的磁异常,并非完全由其含铁质泥页岩地层所引起,最高可达近5 A/m的磁化强度成像异常揭示深部可能存在侵入的基性岩或超基性岩体。这一岩体可能与发生在扬子西缘的二叠纪末大规模岩浆事件持续活动密切相关,其岩浆活动在川西北的龙门山北段作用时间可能至少持续到了早三叠世的飞仙关期。结合区域重磁异常分布规律,认为这一岩浆事件可能在整个川西北地区并非个例存在。Surface high-precision magnetic method is used to measure the typical geological section of Lower Triassic Feixianguan Formation in Majiaoba area,Sichuan Province.The magnetic characteristics and deep magnetic imaging structure of multiple strata in the study area are obtained by using the conjugate gradient focused inversion of the lithology and physical properties test and magnetic data based on L 0 norm constraint.The geological factors of magnetic anomalies in the Paleozoic-Mesozoic marine carbonate rocks and continental clastic rocks in the study area are also identified.The results show that the magnetic anomalies of the Lower Triassic Feixianguan Formation,up to about 1000 nT observed on the ground,are not entirely caused by the iron-bearing mud shale formation,and the magnetic intensity imaging anomalies of up to about 5 A/m reveal that there may be intrusive mafic rocks or ultrabasic rocks in the depth,which may be closely related to the continuous large-scale magmatic event at the end of Permian in the western margin of the Yangtze block,and its magmatic activity may have lasted at least until the early Triassic in the northern section of Longmen Mountains,northwest of Sichuan.Combined with the distribution of regional gravity and magnetic anomalies,it is concluded that this magmatic event may not be a unique occurrence in the whole northwest Sichuan.The proposition of existence of deep intrusive rocks has deepened the understanding of geological phenomena in the study area,proposed new view of regional geology,and improved the recognition of oil and gas evolution and tectonics of early Triassic in the study area.

关 键 词：龙门山 飞仙关组 磁异常 辉绿岩 

分 类 号：P631.325[天文地球—地质矿产勘探]