摘要
泰国Ｋｈｏｒａｔ盆地西部的晚二叠世石灰岩的古地磁研究表明磁铁矿为稳定剩磁的主要载体多组分磁分量分离技术揭示了高温磁组分（或高矫顽力）具有呈对分布的正、反极性．但是，应用逐渐展平岩层法可以发现各采样点的平均特征磁化方向在岩层展平至３０％时．磁化方向最为集中．这一发现表明二叠纪石灰岩中所揭示出的磁化方向很可能形成于褶皱（期）过程中．野外观察表明，二叠纪石灰岩在印支期发生强烈褶皱并被晚三叠世湖相石灰岩角度不整合覆盖．所以二叠纪石灰岩的重磁化很可能发生在中、晚三叠世的印支期．这些石灰岩样品切片后经显微镜、扫描电镜和电子探针分析，次生磁铁矿多数与方解石微晶和铁质碳酸钙粒共生，且多分布在方解石脉附近．重磁化很可能是由于印支期造山运动时，铁质碳酸钙受碳水化合物流体的蚀变作用所引起的。
The stable magnetization with both reversed and normal Polarities from the relatively higher temperature or coercivity has been isolated by stepwise thermal or alternative field demagnetization Acquisition of isothermal remanence and thermal demagnetization of the Permian limestone indicate that the main magnetic carrier is relative pure magnetite(saturated in a lower coercivity about 0.3 Tesla, unblocking temperature around 510℃). The occurrence of precision parameter k-peak of site-mean direction from nine sites during incremental unfolding suggests that the ChRM of the Permian limestone in the Cham-Phae areas was acquired during early to middle Triassic folding time. The remagnetization in the Permian limestone is therefore suggested occur in the early to middle Trassic. The combination of observation in the polished thin section under microscopy,microprobe analyses and SEM observation reveals secondary diagenic magetites were present in the remagnetized Permian limestone. The presence of the secondary diagenic magnetites intergrowth with calcite microlites and also the several calcareous oozes in the micro-fissures was related closely to the hydrocarbon alaeration from the ironic calcareous oozes(or nordulars). The synfolding feature and the discordance between the Upper Trassic and Permian limestone suggest the remagnetization are related to coeval hydrocarbon fluid during Indosinian Orogeny.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
1996年第S1期173-181,共9页
Chinese Journal of Geophysics
关键词
二叠纪灰岩
重磁化
Khorat盆地
Permian limestone,Remagnetization,Khorat basin,Indosinian Orogeny.
