| 嵊泗岛辉绿岩墙群的侵位方式:来自磁组构的证据 |
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| 引用本文： | 潘小青,沈忠悦,陈宁华,张志亮,吕青,商亮节.嵊泗岛辉绿岩墙群的侵位方式:来自磁组构的证据[J].地球物理学报,2011,54(12):3269-3279. |
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| 作者姓名： | 潘小青 沈忠悦 陈宁华 张志亮 吕青 商亮节 |
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| 作者单位： | 浙江大学地球科学系, 杭州 310027 |
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| 基金项目： | 国家重点基础研究发展计划，浙江省基金委 |
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| 摘 要： | 岩墙磁组构能反映岩浆的侵位方式.中国东部嵊泗岛广泛发育了晚白垩世辉绿岩岩墙群.我们对其中8条不同走向岩墙进行了采样,沿岩墙两边部及横跨岩墙剖面获得共273个独立定向岩芯样品.岩石磁学分析表明辉绿岩的主要携磁矿物为多畴贫钛磁铁矿,可能含少量磁赤铁矿.各条岩墙的磁组构均具有低的各向异性度Pj＜1.2,且主轴的空间方位各不相...
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| 关 键 词： | 磁组构 侵位机制 辉绿岩墙群 嵊泗岛 |
| 收稿时间： | 2011-07-19 |
Emplacement mechanism of diabase dyke swarms in Shengsi Island:Evidence from magnetic anisotropies |
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| PAN Xiao-Qing
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SHEN Zhong-Yue
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CHEN Ning-Hua
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ZHANG Zhi-Liang
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L Qing
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SHANG Liang-Jie.Emplacement mechanism of diabase dyke swarms in Shengsi Island:Evidence from magnetic anisotropies[J].Chinese Journal of Geophysics,2011,54(12):3269-3279. |
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| Authors: | PAN Xiao-Qing SHEN Zhong-Yue CHEN Ning-Hua ZHANG Zhi-Liang L Qing SHANG Liang-Jie |
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| Institution: | Department of Earth Sciences, Zhejiang University, Hangzhou 310027, China |
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| Abstract: | Anisotropy of magnetic susceptibility(AMS) has been extensively used in the last two decades to determine the emplacement mechanism of volcanic dykes. Late Cretaceous diabase dyke swarms are well distributed in Shengsi Island, eastern China. AMS was performed in 8 diabase dykes with distinct strikes. Rock magnetism shows that multidomain Ti-poor titanomagnetites with trace maghemites carry the magnetic fabrics in diabase dykes. The corrected anisotropy degree (Pj) of all specimens is less than 1.2, indicating an original fabric. The dimensional orientations of three susceptibility axes of different dykes are completely different. Two types of AMS fabric are recognized: (1) ‘Normal’ fabric (7 dykes) defined by the clustering of K1-K2 axes on the dyke wall whereas K3 axis is nearly perpendicular to the wall, which is interpreted as fabrics induced by magma flow; (2) ‘Inverse’ fabric (1 dyke) defined by K2-K3 plane parallel to the dyke wall and K1 perpendicular to dyke wall. Types of AMS fabric are not changed after AF demagnetization at 100 mT. According to the analysis of the imbrications of magnetic foliations with the dyke walls, we can infer magma flow direction: (1) In Huangsha Village, the NNE-trending dyke is fed by horizontal or sub-horizontal flow from southwest to northeast, while the EW-trending dyke is laterally injected from west to east; (2) At Liujingtan, the NW-trending dyke is laterally injected from southeast to northwest while the NE-trending dyke from southwest to northeast. This emplacement mode suggests that a mafic magma source may exist in the southwestern area far away from the study area. The diabase dyke swarms at Shengsi Island are the products of strong EW-trending or NNE-trending lithosphere extensions induced by Pacific Plate subducting to Eurasian plate. |
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| Keywords: | AMS Emplacment mode Diabase dyke swarm Shengsi Island |
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