辉绿岩裂缝对其磁组构的影响  

Effect of Diabase Crevices on AMS Fabrics

作　　者：石林权[1] 沈忠悦[1] 潘小青[1] 李明月[1] 张志亮[1] 

机构地区：[1]浙江大学地球科学系,杭州310027

出　　处：《高校地质学报》2015年第2期223-233,共11页Geological Journal of China Universities

基　　金：浙江省自然科学基金项目(LY12D02002)资助

摘　　要：磁组构是由岩石中磁性矿物定向分布而产生的组构特征,因此磁组构分析是研究岩石组构常用的技术手段,它具有见效快、灵敏度高、无损样品等特点,近年来得到广泛应用。然而在磁组构研究工作中钻取定向样品或定向手标本时,常常会遇到天然样品含有裂缝且裂缝中充填大量近地表沉积物和自生矿物。本文针对辉绿岩裂缝充填物对其磁组构结果的影响程度做了详细研究,选用160个含裂缝的辉绿岩岩芯定向样品,通过对比去除裂缝充填物前后的磁组构变化,发现实验前后所有样品磁化率大小变化率平均值<1%,磁组构方向变化平均值<1°,因此认为辉绿岩裂缝物质对其磁组构影响甚微。矿物学和岩石磁学分析表明裂隙充填物主要为石英、长石,以及少量赤铁矿、黄铁矿和绿泥石等表生矿物。而辉绿岩的携磁矿物主要是亚铁磁性的磁铁矿,其磁化率强度约为同等质量裂缝填充物的30倍,致使辉绿岩中的裂隙充填物对磁组构的影响很小。As a rapid and sensitive petrofabric tool, the anisotropy of magnetic susceptibility（AMS） has been extensively used instudying rock fabrics. Sometimes it is difficult to drill an intact oriented core sample without any crevice, in which various fillingminerals can be found. To analyze the crevices＇ effect on diabase magnetic fabrics, 160 diabase samples with crevices are selected tostudy the AMS data then remove the filling minerals in the crevices in order to compare magnetic fabric characteristics of the diabasebefore and after the treatment. The data analysis shows that the average difference in the AMS intensity of all the specimens is less than1% and the difference in the average direction also falls in 〈1°. From the results, we conclude that crevices of diabase dykes hardlyhave much influence on the AMS features. Mineralogy and rock magnetic studies indicate that the main mineral constituents in thediabase crevices are quartz, feldspar, hematite, pyrite, and chlorite. The AMS intensity of these filling minerals is about one thirtieth ofdiabase that is dominanted by ferromagnetic mineral of magnetite, which makes crevices to have no much effect on the AMS results.

关 键 词：辉绿岩裂缝 磁组构 扫描电镜 显微激光拉曼分析 热磁曲线 

分 类 号：P542.3[天文地球—构造地质学]