岩石磁组构对剩磁稳定性的制约探讨:以印支地块中生代碎屑岩和拉萨林周盆地设兴组红层为例  

Reconnaissance on the constraint of rock magnetic fabrics on the reliability of remanent magnetization:A case study for Mesozoic detrital rocks from the Indochian Block and red beds from the Shexing Formation of the Linzhou Basin,Lhasa

作　　者：贾舒斐 黄宝春[1] 鲁洪亮 赵千 闫永刚 梁雅伦 易治宇 JIA ShuFei;HUANG BaoChun;LU HongLiang;ZHAO Qian;YAN YongGang;LIANG YaLun;YI ZhiYu(Key Laboratory of Orogenic Belts and Crustal Evolution,Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871,China;National Park Research Center,School of Economics and Management,Sanming University,Sanming Fujian 365004,China;Guangdong Provincial Key Laboratory of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai Guangdong 519000,China;Planetary Environmental and Astrobiological Research Laboratory(PEARL),School of Atmospheric Sciences,Sun Yat-sen University,Zhuhai Guangdong 519000,China)

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 [2]三明学院经济与管理学院,国家公园研究中心,福建三明365004 [3]中山大学地球科学与工程学院,广东省地球动力作用与地质灾害重点实验室,广东珠海519000 [4]中山大学大气科学学院,行星环境与天体生物学研究实验室,广东珠海519000

出　　处：《地球物理学报》2023年第1期301-313,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41774074,92055205)资助.

摘　　要：岩石磁组构因能提供磁性矿物晶体形状、排列方式等赋存信息而被广泛应用于判别岩石剩磁是否受到了后期构造应力的显著影响;但常规岩石磁化率各向异性(AMS)是否能够准确限定岩石剩磁的稳定性,目前尚无深入探讨.本文以印支地块Nakhon Thai盆地中生代Nam Phong、Phu Kradung和Phra Wihan组三套碎屑岩样品及拉萨地块林周盆地设兴组红层样品为例,通过岩石磁化率组构和剩磁组构的对比分析发现,尽管Nam Phong组绝大多数样品和Phu Kradung组全部样品的AMS组构显示其具有铅笔状至强劈理过渡型构造变形组构特征,但高场等温剩磁各向异性(hf-AIR)显示其高矫顽力赤铁矿所携带的特征剩磁组构仍具有典型沉积组构特征,表明其以赤铁矿为主的载磁矿物未遭受后期构造应力的显著影响,仍然能够准确记录岩石形成时期的古地球磁场方向.另一方面发现有且仅有剩磁组构才是判别碎屑沉积岩特征剩磁是否遭受了后期构造应力影响的充分必要条件.也就是说,如果岩石剩磁组构(如以赤铁矿为主要载磁矿物的岩石hf-AIR组构)指示其原始沉积组构已被构造组构显著叠加或取代,则必然说明该岩石剩磁方向已受到构造应力的作用而发生了显著偏转,因而不能直接用于构造演化和古地理重建等块体运动学研究.The magnetic fabrics is widely used to determine whether remanent magnetization vector recorded in the rock is significantly affected by tectonic stress because it can provide information such as the shape and arrangement of magnetic mineral crystals;however,whether the conventional anisotropy of magnetic susceptibility(AMS)can accurately define the stability of remanence preserved in the rock has not been studied thoroughly.Accordingly,we conduct a combined AMS and anisotropy of remanent magnetization study on three sets of clastic rock samples from Mesozoic Nam Phong,Phu Kradung and Phra Wihan formations in the Nakhon Thai Basin of the Indochina Block and the red bed samples of the Shixing Formation from the Linzhou Basin of the Lhasa Terrane.The AMS analyses of the majority of the samples of the Nam Phong Formation and all the samples of the Phu Kradung Formation show pencil structure to strong cleavage transitional deformational fabrics.However,the anisotropy of high-field isothermal remanent magnetization(hf-AIR)shows that the magnetic fabrics of characteristic remanent magnetization(ChRM),carried by high coercivity hematite,still appears in typical sedimentary fabrics.This indicates that the ChRM has not been significantly biased by syn-depositional and/or post-depositional tectonic stress,and then can still accurately record paleo-direction of the geomagnetic field during formation of the rocks.On the other hand,it is found that only the anisotropy of remanent magnetization is the sufficient and necessary conditions to determine whether the ChRM of the clastic rocks has been affected by syn-depositional and/or post-depositional tectonic stresses.That is to say,if the magnetic fabrics of remanent magnetization,such as the hf-AIR fabrics of the clastic rock with hematite as the main magnetic carrying mineral,indicates that its original sedimentary fabrics has been significantly superimposed or replaced by the deformational fabrics,it must indicate that the ChRM direction has been significantly deflected by t

关 键 词：磁化率各向异性 剩磁各向异性 沉积组构 过渡型构造变形组构 印支地块 

分 类 号：P318[天文地球—固体地球物理学]