CAJ | 학술논문

胭脂坝岩体是秦岭造山带内具典型代表性意义的晚三叠世花岗岩，已有的年代学和地球化学研究对岩体的侵位机制有着不同的认识。采用磁组构方法研究了该岩体的内部组构特征，并结合区域构造探讨了岩体的侵位机制。结果显示，胭脂坝岩体51个采点、348个样品的平均体积磁化率（K m ）值普遍小于100μSI，总体较低。磁滞回线和热磁曲线特征表明，岩体磁组构主要由顺磁性矿物控制。大部分样品的校正磁化率各向异性度（P J ）值小于1．10，平均为1．06，表现出低各向异性度的总体特征。样品磁化率椭球形态参数（T）值多大于0，磁化率椭球体以压扁椭球为主。综合分析认为，岩体的磁组构是典型的岩浆组构，记录了岩浆侵位的流动构造。岩体磁组构以东西向中低角度倾伏的磁线理和南北向倾伏的磁面理为总体特征，磁线、面理轨迹揭示出岩浆自西向东的侵位流动。这样的岩浆侵位过程应与中、浅部地壳的走滑挤压构造相关，岩体侵位时造山带处于同碰撞构造环境。
연지패암체시진령조산대내구전형대표성의의적만삼첩세화강암，이유적년대학화지구화학연구대암체적침위궤제유착불동적인식。채용자조구방법연구료해암체적내부조구특정，병결합구역구조탐토료암체적침위궤제。결과현시，연지패암체51개채점、348개양품적평균체적자화솔（K m ）치보편소우100μSI，총체교저。자체회선화열자곡선특정표명，암체자조구주요유순자성광물공제。대부분양품적교정자화솔각향이성도（P J ）치소우1．10，평균위1．06，표현출저각향이성도적총체특정。양품자화솔타구형태삼수（T）치다대우0，자화솔타구체이압편타구위주。종합분석인위，암체적자조구시전형적암장조구，기록료암장침위적류동구조。암체자조구이동서향중저각도경복적자선리화남북향경복적자면리위총체특정，자선、면리궤적게시출암장자서향동적침위류동。저양적암장침위과정응여중、천부지각적주활제압구조상관，암체침위시조산대처우동팽당구조배경。
Many geochronological and geochemical works had been done about the Yanzhiba granite pluton in South Qinling recently.However,opinions for its tectonic settings are contradictory.Internal fabrics of Yanzhiba pluton are interpreted by magnetic fabric method in order to explain the emplacement mechanism.348 samples in 51 sites were measured in the lab.The values of Km(magnetic suscep-tibility)are less than 100 μSI generally,and PJ (corrected AMS degree)values of the samples are less than 1.10(the mean value is 1.06),which are consistent with paramagnetic granite.Hysteresis loops andχ t curves show that the AMS of samples were controlled by biotite mainly.Most of the T(shape parameter)values of samples are positive,which show dominant oblate magnetic ellipsoids.It was indicated that the magnetic fabrics are associated with magma flow.Magnetic fabrics in the pluton show eastward magma flow with a NE-striking feeder zone in the western part of Yanzhiba pluton during emplacement.Such an emplacement model is accordant with the lateral extrusion tectonics in Qinling orogen during Late Triassic collision between North and South China blocks.