CAJ | 학술논문

南秦岭构造带位于秦岭造山带南部，在中生代时期经历了复杂的陆内变形过程。在晚中生代阶段，南秦岭构造带内发育一系列平行造山带的走滑断裂带。目前对于这些走滑断裂带不同构造位置的变形特征、变形叠加关系以及动力学机制等方面的认识并不充分。构造研究显示，南秦岭构造带内的宁陕断裂和安康断裂均发育大量平行于断裂带的 A 型褶皱群和近水平的拉伸线理，表明南秦岭构造带经历了以走滑剪切变形为主的构造阶段。运动学特征表明，宁陕断裂以左行剪切变形为主，而安康断裂则以右行变形为特征。选择典型岩石样品进行同位素测年来限定断裂活动的时代，其中：宁陕断裂带内同构造花岗岩脉的锆石 SHRIMP U Pb 定年结果为(186.0±4.0)Ma；安康断裂带内云母矿物的40 Ar 39 Ar 定年结果为161.2~173.5 Ma。虽然宁陕断裂和安康断裂的运动方向不同，但是同位素年代学研究限定了两条断裂发生走滑变形的时间都是早中侏罗世，从而共同构成了南秦岭构造带中间块体整体向东挤出的构造特征。同时也表明，相互碰撞的大陆在碰撞之后将很快转变为以平行造山带侧向挤出和走滑位移为主的陆内变形演化阶段。
남진령구조대위우진령조산대남부，재중생대시기경력료복잡적륙내변형과정。재만중생대계단，남진령구조대내발육일계렬평행조산대적주활단렬대。목전대우저사주활단렬대불동구조위치적변형특정、변형첩가관계이급동역학궤제등방면적인식병불충분。구조연구현시，남진령구조대내적저협단렬화안강단렬균발육대량평행우단렬대적 A 형습추군화근수평적랍신선리，표명남진령구조대경력료이주활전절변형위주적구조계단。운동학특정표명，저협단렬이좌행전절변형위주，이안강단렬칙이우행변형위특정。선택전형암석양품진행동위소측년래한정단렬활동적시대，기중：저협단렬대내동구조화강암맥적고석 SHRIMP U Pb 정년결과위(186.0±4.0)Ma；안강단렬대내운모광물적40 Ar 39 Ar 정년결과위161.2~173.5 Ma。수연저협단렬화안강단렬적운동방향불동，단시동위소년대학연구한정료량조단렬발생주활변형적시간도시조중주라세，종이공동구성료남진령구조대중간괴체정체향동제출적구조특정。동시야표명，상호팽당적대륙재팽당지후장흔쾌전변위이평행조산대측향제출화주활위이위주적륙내변형연화계단。
Southern Qinling belt is located in the south part of the Qinling orogen,which experienced the complex intra-continental deformation in Mesozoic.In the Late Mesozoic period,there were a series of strike-slip faults developed along the orogen in the southern Qinling belt. At present, the understanding of the deformation features,superposition relationship and dynamic mechanism for these strike-slip faults on different location is not sufficient.Structural studies show that the Ningshan fault and the Ankang fault are characterized by the A type fold and sub-horizontal stretching lineation,which indicated the southern Qinling belt underwent a tectonic stage dominated with the strike-slip shear deformation.Kinematic studies revealed the Ningshan fault was characterized by a sinistral shear deformation,while the Ankang fault by dextral characteristics.We chose the typical rock samples for isotopic dating to limit the fault activity time.The zircon SHRIMP U Pb age of the syn-tectonic granite vein in the Ningshan fault was (186.0±4.0)Ma,and the mica 40 Ar 3 9 Ar dating results in the Ankang fault are 1 61.2 173.5 Ma.Although the kinematic features are opposite between the Ningshan fault and the Ankang fault,the geochronological results defined that the deformation time of these two faults is the same,e.g.Early Middle Jurassic,both of which constitute a eastward extrusion for the central block of southern Qinling belt.This tectonic characteristic also indicated that the deformation of the orogen was soon transformed into the intra-continental deformation stage,which was dominant with the lateral extrusion and strike-slip displacement along the orogen.