滇东地区寒武系第三阶沉积岩磁组构研究及其对古水流方向的启示  

Magnetic fabric study of the Cambrian Stage 3 sedimentary rocks in Eastern Yunnan and its implications for paleocurrent direction

作　　者：张冬孟 程鑫[1] 卫弼天 幸龙云 刘非凡 彭晓霞 邓晓红 边紫薇 李腾 兰书琪 周亚楠[1] 吴汉宁[1] ZHANG Dongmeng;CHENG Xin;WEI Bitian;XING Longyun;LIU Feifan;PENG Xiaoxia;DENG Xiaohong;BIAN Ziwei;LI Teng;LAN Shuqi;ZHOU Yanan;WU Hanning(Department of Geology/State Key Laborary of Continental Dynamics,Northwest University,Xi’an 710069,China)

机构地区：[1]西北大学地质学系/大陆动力学国家重点实验室,陕西西安710069

出　　处：《西北大学学报（自然科学版）》2023年第4期655-670,共16页Journal of Northwest University（Natural Science Edition）

基　　金：国家自然科学基金(42130206,42274097,91855211)。

摘　　要：以滇东地区朱家箐剖面和古莲村剖面为例,对滇东地区寒武系第二阶石岩头组、第三阶玉案山组和红井哨组共计42个采点(319个样品)开展了岩石磁学和磁化率各向异性研究。结果表明,样品中载磁矿物包括磁铁矿、赤铁矿以及少量的针铁矿,而AMS主要由顺磁性矿物携带;两个剖面样品的磁面理均较为发育,各向异性度较低,表现出典型的沉积特征,但结合地层走向与椭球体主轴的分布情况,认为朱家箐剖面反映了后期近E—W向挤压应力作用造成的初始变形组构,古莲村剖面的样品则保留了原生的叠瓦状沉积组构,包括流动组构和横向组构。对古莲村剖面样品的形状因子q和叠瓦角β的进一步分析发现,自玉案山组到红井哨组沉积的数百万年间,水动力条件逐渐增强,古水流方向没有显著变化,均为SW—NE向,其物源应该来自于西侧的康滇古陆。In this paper,a total of 42 sites from the Early Cambrian Shiyantou Formation,Yulingshan Formation and Hongjingshao Formation were collected in Zhujiaqing section and Guliancun section for the study of rock magnetism and anisotropy of magnetic susceptibility.The experimental results show that the magnetic minerals in the samples include magnetite,hematite and a small amount of goethite,while paramagneticminerals are the main contributors to the AMS.In both sections,the magnetic foliation is relatively developed and the degree of anisotropy is low,showing typical sedimentary characteristics.However,considered the relationship between bedding strike and the distribution of AMS ellipsoid principal axis,the AMS results of Zhujiaqing section reflect the initial deformation fabrics under the late compressive stress near E-W direction,while the AMS results of Guliancun section retain the primary imbricated sedimentary fabrics,including flow fabrics and transverse fabrics.Through further analysis of shape factor(q)and imbricated angle(β)of samples in Guliancun section,it is found that during several million years of deposition from Yuanshan to Hongjingshao Formation,the hydrodynamic conditions gradually increased,and the paleocurrentic direction was SW-NE without significant change,and the sedimentary source area may be the Kangdian old land to the west.

关 键 词：滇东地区 寒武系第三阶 岩石磁学 磁组构 古水流方向 

分 类 号：P318[天文地球—固体地球物理学]