CAJ | 학술논문

一般认为磁组构能有效地反映岩石所经历的应变特征.为了研究不同类型的磁组构和不同期次应变之间的关系,对来自华南地块两个地区的早三叠世灰岩样品进行了岩石磁学、磁组构以及应变特征的对比分析.来自湖北通山县的样品经历了三期构造变形,这为解析磁组构和多期次应变提供了理想的机会.岩石磁学结果显示携磁矿物主要为磁铁矿.磁化率各向异性(AMS)和非磁滞剩磁各向异性(AAR)结果显示其最小轴与层面垂直,最大轴和中间轴分布于层面内,反映了沉积和压实作用产生的应变,而后期构造应变在磁组构中没有体现.来自广东连县的样品发育有渗透性压溶缝面理和方解石脉,说明经历了构造应变.AMS结果没有显示占优势的组构方向.AAR结果显示三轴组构,其最大轴分布于最大应力方位,与构造应变特征吻合,最初的压实组构被构造应变组构所代替.上述结果表明:(1)AAR可以很好地反映渗透性应变的特征,而AMS有时会失效;(2)应变的尺度要小于样品的尺度,磁组构才能有效地反映应变.
일반인위자조구능유효지반영암석소경력적응변특정.위료연구불동류형적자조구화불동기차응변지간적관계,대래자화남지괴량개지구적조삼첩세회암양품진행료암석자학、자조구이급응변특정적대비분석.래자호북통산현적양품경력료삼기구조변형,저위해석자조구화다기차응변제공료이상적궤회.암석자학결과현시휴자광물주요위자철광.자화솔각향이성(AMS)화비자체잉자각향이성(AAR)결과현시기최소축여층면수직,최대축화중간축분포우층면내,반영료침적화압실작용산생적응변,이후기구조응변재자조구중몰유체현.래자엄동련현적양품발육유삼투성압용봉면리화방해석맥,설명경력료구조응변.AMS결과몰유현시점우세적조구방향.AAR결과현시삼축조구,기최대축분포우최대응력방위,여구조응변특정문합,최초적압실조구피구조응변조구소대체.상술결과표명:(1)AAR가이흔호지반영삼투성응변적특정,이AMS유시회실효;(2)응변적척도요소우양품적척도,자조구재능유효지반영응변.
It is generally regarded that magnetic fabrics can effectively reveal strain in rocks. In order to investigate the relationship between different magnetic fabric types and different stages of strain, we conducted a combined analysis of rock magnetics, magnetic fabrics and mesoscopic deformation features for Early Triassic limestones from two areas in the South China Block. Samples from the Tongshan county, Hubei province underwent three stages of deformation, which provided an ideal opportunity to test the relationship between magnetic fabric and multiple deformations. The minimum axes of AMS and AAR ellipsoids are normal to the bedding and the intermediate and maximum axes lie within the bedding, indicating deposition and compaction fabrics having not been affected by tectonic strain. Samples from the Lian county, Guangdong province experienced tectonic strain as evidenced by pervasive pressure solution seams and calcite veins. The principal directions of AMS are scattered, but those of AAR are well clustered, showing a triaxial fabric. The maximum axes of AAR are distributed around the maximum stress direction indicated by the geometry of calcite veins. The initial compaction fabric was replaced by tectonic strain. These results suggest: (1) AAR can better reflect pervasive strain than AMS; (2) Only under the condition that the scope of strain is less than that of the sample can magnetic fabric effectively reveal strain.