Characteristics of the Density and Magnetic Susceptibility of Rocks in Northern Borneo and their Constraints on the Lithologic Identification of the Mesozoic Rocks in the Southern South China Sea  

作　　者：TANG Huafeng ZHAO Zhigang TIAN Zhiwen LU Baoliang TANG Wu HE Kailun ZHU Chenxi WANG Pujun 

机构地区：[1]Key Laboratory of Mineral Resources Evaluation of Northeast Asia,Ministry of Natural Resources,Changchun 130061,China [2]CNOOC Research Institute Co.,Ltd.,Beijing 100028,China [3]College of Earth Sciences,Jilin University,Changchun 130061,China [4]College of Geological Engineering and Geomatics,Chang'an University,Xi'an 710054,China

出　　处：《Acta Geologica Sinica(English Edition)》2021年第1期280-293,共14页地质学报（英文版）

基　　金：supported by the National Major Science and Technology Project of the Ministry of Science and Technology of China(2016ZX05026-004-001);the Major Program of the National Natural Science Foundation of China(41790453);the Natural Science Foundation of Jilin Province(20170101001JC);the Supported by Graduate Innovation Fund of Jilin University(101832020CX200)。

摘　　要：Based on the volume magnetic susceptibility and specific gravity measurements and mineral and lithologic identification results for 540 samples,the rock type,density,and magnetic susceptibility of rocks from northern Borneo were analyzed,and the applicability of gravity and magnetic data to the lithologic identification of the Mesozoic strata in the southern South China Sea was assessed accordingly.The results show that there are 3 types and 25 subtypes of rocks in northern Borneo,mainly intermediate-mafic igneous rocks and exogenous clastic sedimentary rocks,with small amounts of endogenous sedimentary rocks,felsic igneous rocks,and metamorphic rocks.The rocks that are very strongly-strongly magnetic and have high-medium densities are mostly igneous rocks,tuffaceous sandstones,and their metamorphic equivalents.The rocks that are weakly magnetic-non-magnetic and have medium-very low densities are mostly conglomerates,sandstones,siltstones,mudstones,and coal.The rocks that are weakly magnetic-diamagnetic and have highmedium densities are mostly limestones and siliceous rocks.The Cenozoic rocks are characterized by low densities and medium susceptibilities;the Mesozoic rocks are characterized by medium densities and medium-high susceptibilities;and the pre-Mesozoic rocks are characterized by high densities and low magnetism.Based on these results and the distribution characteristics of the various rock types,it was found that the pre-Mesozoic rocks produce weak regional gravity anomalies;the Mesozoic sedimentary rocks produce negative regional gravity anomalies;whereas the Mesozoic igneous rocks produce positive regional gravity anomalies;and the Cenozoic igneous rocks produce positive regional gravity anomalies.The regional high magnetic anomalies in the southern part of the South China Sea originate from the Mesozoic mafic igneous rocks and their metamorphic equivalents;and the regional medium magnetic anomalies may be produced by the felsic igneous rocks and their metamorphic equivalents.Accordingly,the identifi

关 键 词：DENSITY magnetic susceptibility MESOZOIC BORNEO South China Sea 

分 类 号：P736[天文地球—海洋地质]