青海玉树称多—囊谦一带岩石磁性特征研究

The Study on the characteristics of rock magnetism in Chengduo-Nangqian area of Yushu Qinghai

青海玉树称多—囊谦一带是三江北段成矿带重要地区之一。文章以区域1∶5万航磁调查项目为依托,利用实测的415处磁化率值和33块定向标本测定参数,对区内的蛇绿混杂岩、地层、岩浆岩和脉岩进行了岩石磁性特征统计分析。综合分析认为:蛇绿混杂岩中的蚀变超基性岩(蚀变橄榄岩)具有强磁性,可引起与地层走向一致的条带状较强磁异常;各时期形成的地层中火山岩的较强的磁性,能引起较强的磁异常,且剩磁普遍较高;古近纪的英安流纹斑岩和正长斑岩、三叠纪的花岗闪长岩具有较高的磁化率值,与周边地层有一定磁性差异,能引起一定的磁异常,部分岩石还有较高的天然剩磁;区内脉岩的磁化率普遍较高,其中煌斑岩的剩磁较强。这为研究区域磁场和局部磁异常的推断、解释提供了基础资料和参考依据。

The Chengduo-Nangqian area in Yushu district,Qinghai province is located at the north Sanjiang metallogenic belt.Based on regional 1：50 000 aeromagnetic survey,415 magnetic susceptibility values and the measured parameters of 33 directional specimen were collected in the field to analyze statisricaly the characteristics of rock magnetism of the strata and magmatic rocks and dykes.The result suggests that the altered ultrabasic rock（altered peridotite）in ophiolite complex is strong in magnetism and cause a stronger and higher banded magnetic anomaly coincided with the strata.Volcanic rock of various periods in stratum is strong in magnetism and higher residual magmatism.The paleogene andesitic rhyolitic porphyry and syenitic porphyry,Triassic granodiorite are higher in values of magnetic susceptibility and varied in magmatism with the surrounding strata.Also some rock has higher natural residual magmatism.The magnetic susceptibility of dykes in the area is generally higher,and the residual magnetism of the lamprophyre is stronger.The mentioned above provide important basic information and reference for regional magnetic field and local anomaly inference and interpretation.