Magma flow inferred from magnetic fabrics in Wanning gabbro pluton and diabase dykes, Hainan  

作　　者：PAN XiaoQing SHEN ZhongYue DONG ChuanWan CHEN HanLin CHENG XiaoGan YANG ShuFeng ZHANG ZhiLiang 

机构地区：[1]Department of Earth Sciences,Zhejiang University,Hangzhou 310027,China

出　　处：《Chinese Science Bulletin》2012年第16期1982-1989,共8页

基　　金：supported by the National Basic Research Program of China(2007CB411706);the National Natural Science Foundation of China(40274014)

摘　　要：Measurements of anisotropy of magnetic susceptibility (AMS) were performed on a gabbro pluton and 7 diabase dykes in the Wanning area, southeast Hainan Island. Rock magnetism showed that pseudo-single domain (PSD) to multidomain (MD) Ti-poor magnetite carries the magnetic fabric in the gabbro pluton whereas MD Ti-poor magnetite carries the magnetic fabric in the diabase dykes. The corrected anisotropy degree (Pj ) in most specimens was found to be less than 1.2 which is indicative of a possible flow-related magnetic fabric. The AMS eigenvectors within each site are generally well grouped. The maximum susceptibility axes (K1 ) of the gabbro pluton are inclined towards the north at low angles (< 30°). K1 axes of the diabase dykes are inclined towards the NNW and SSE with dip angles of ≤ 30°. From this study, it appears that the emplacement mode of the gabbro pluton was characterized by intrusion from the north to the south at a low angle whereas the diabase dykes were emplaced from the NNW to the SSE at low to moderate angles. This was verified by comparison of the rock fabric to the magnetic fabric. All of this evidence leads to the conclusion that the Wanning gabbro pluton and diabase dykes were the products of pulsative intrusion from the same magma chamber in the area far to the north of Wanning, which suggests that basic rocks may exist beneath the Indosin- ian granite in the area to the north of Wanning.Measurements of anisotropy of magnetic susceptibility （AMS） were performed on a gabbro pluton and 7 diabase dykes in the Wanning area, southeast Hainan Island. Rock magnetism showed that pseudo-single domain （PSD） to multidomain （MD） Ti-poor magnetite carries the magnetic fabric in the gabbro pluton whereas MD Ti-poor magnetite carries the magnetic fabric in the diabase dykes. The corrected anisotropy degree （Pj ） in most specimens was found to be less than 1.2 which is indicative of a possible flow-related magnetic fabric. The AMS eigenvectors within each site are generally well grouped. The maximum susceptibility axes （K1 ） of the gabbro pluton are inclined towards the north at low angles （〈 30°）. K1 axes of the diabase dykes are inclined towards the NNW and SSE with dip angles of ≤ 30°. From this study, it appears that the emplacement mode of the gabbro pluton was characterized by intrusion from the north to the south at a low angle whereas the diabase dykes were emplaced from the NNW to the SSE at low to moderate angles. This was verified by comparison of the rock fabric to the magnetic fabric. All of this evidence leads to the conclusion that the Wanning gabbro pluton and diabase dykes were the products of pulsative intrusion from the same magma chamber in the area far to the north of Wanning, which suggests that basic rocks may exist beneath the Indosin- ian granite in the area to the north of Wanning.

关 键 词：辉长岩体 辉绿岩 岩浆流 海南岛 面料 磁化率各向异性 磁性 岩石磁学 

分 类 号：P588.125[天文地球—岩石学]