CAJ | 학술논문

龙门山南段位于四川盆地以西，其新生代构造变形特征对于认识青藏高原东缘的变形机制具有一定的指示意义。磁组构是一种灵敏的应变指示计，在变形微弱的沉积岩地区尤为适用。在龙门山南段邛西断层转折褶皱不同构造部位选取48个采样点开展磁组构研究，分析断层转折褶皱的有限应变特征及区域构造变形机制。实验结果表明，邛西地区上白垩统中主要载磁矿物为高矫顽力的赤铁矿，背斜整体应变较弱，且存在3种类型的磁组构，以沉积磁组构和初始变形磁组构为主，铅笔状磁组构少见，主要存在于靠近褶皱中段的前翼部位，说明断层转折褶皱前翼较后翼和核部应变强，且中段地层应变较其他部位更为强烈。此外，各采样点磁线理的优势方位为近南北向（N10°E），表明邛西断层转折褶皱的形成与龙门山南段晚新生代近东西向的地壳水平缩短有关，暗示龙门山南段的最大主压应力方向在晚新生代存在转变的可能。
룡문산남단위우사천분지이서，기신생대구조변형특정대우인식청장고원동연적변형궤제구유일정적지시의의。자조구시일충령민적응변지시계，재변형미약적침적암지구우위괄용。재룡문산남단공서단층전절습추불동구조부위선취48개채양점개전자조구연구，분석단층전절습추적유한응변특정급구역구조변형궤제。실험결과표명，공서지구상백성통중주요재자광물위고교완력적적철광，배사정체응변교약，차존재3충류형적자조구，이침적자조구화초시변형자조구위주，연필상자조구소견，주요존재우고근습추중단적전익부위，설명단층전절습추전익교후익화핵부응변강，차중단지층응변교기타부위경위강렬。차외，각채양점자선리적우세방위위근남북향（N10°E），표명공서단층전절습추적형성여룡문산남단만신생대근동서향적지각수평축단유관，암시룡문산남단적최대주압응력방향재만신생대존재전변적가능。
The characteristics of Cenozoic deformation in the southern Longmen Mountain fold-thrust belt, which is located to the west of Sichuan basin, is important in recognizing the deformation regime of the eastern margin of the Tibetan Plateau. Magnetic fab-ric is a sensitive strain indicator particularly useful in weak deformed sedimentary areas. In this paper, a magnetic fabric investigation was carried out into the Qiongxi fault-bend fold, which is located to the south of Longmen Mountain fold-thrust belt on the basis of 48 sampling sites scattered in different parts so as to analyze the finite strain of the bending fold and discuss the regional deformation regime. The results show that hematite is the main magnetic carrier mineral in the upper Cretaceous of Qiongxi area, and the fold suf-fered weak strain;in addition, there exist three types of magnetic fabrics in the study area, and most of the sampling sites show sedi-mentary and initial deformation magnetic fabrics, with pencil structure magnetic fabrics only existent on the forelimb of the middle part of the fold. These phenomena indicate that the strain on the forelimb is relatively higher, and the strain on the layer of the mid-dle part is somewhat stronger than that of other parts of the fold-bend fold. In addition, the stereonet map of magnetic lineation shows that the orientation of the maximal susceptibility axial cluster is in nearly SN direction (N 10°E) , which indicates that the defor-mation of the bending fold of Qiongxi fault is related to the late Cenozoic EW-trending crustal shortening in the southern Longmen Mountain, and this may imply a change of the direction of the maximal stress in the southern Longmen Mountain in late Cenozoic.