青藏高原东南缘兰坪—思茅盆地反S型构造属性的古地磁约束

发布时间：2019-05-29 18:48

【摘要】：兰坪—思茅(盆地)内部发育的一系列褶皱和逆冲断层组成了显著的弧形构造,其中部呈现反S形构造形态。该地区地壳构造变形方式及其演化过程与青藏高原东南缘地壳物质新生代侧向挤出逃逸密切相关,对其开展地壳构造变形方式的定量分析,具有重要的意义。本文通过兰坪—思茅盆地中部反S形构造区域四条白垩纪红层剖面的岩石磁学和古地磁学研究,获得南涧牛街地区早白垩世LN-a和LN-b剖面的特征剩磁方向分别为D_s=244.7°,I_s=-47.3°,Ks=31.6,α_(95)=16.6°(K_1j~1),和D_s=245.4°,I_s=-46.4°,K_s=52.2,α_(95)=9.4°(K_1n~2),两剖面在99%置信度下通过了Mc Fadden(1990)褶皱检验;小湾镇地区早白垩世NX-a和NX-b剖面(两套地层分属轴向不同的两褶皱)特征剩磁方向分别为D_s=244.9°,I_s=-40.2°,K_s=1067.5,α_(95)=2.3°(K_1j~1)和D_s=182.6°,I_s=-42.1°,K_s=335.2,α_(95)=3.7°(K_1j~2)。结合前人在兰坪—思茅地体中部获得的可靠古地磁数据及青藏高原东南缘区域新生代断裂活动演化过程的分析,指出兰坪—思茅盆地中部弧形反S形构造的形成和演化,以及兰坪—思茅盆地构造区内部差异性旋转变形作用主要受控于新生代时期青藏高原东南缘地壳块体侧向旋转挤出过程中的相互挤压作用和临沧花岗岩基对兰坪—思茅地体侧向顺时针旋转挤出运动的阻挡等一系列构造因素。
[Abstract]:A series of folds and thrust faults developed in Lanping-Simao (basin) form a significant arc structure, and the middle part of the basin presents an anti-S-shaped structure. The crustal tectonic deformation pattern and its evolution process in this area are closely related to the Cenozoic lateral extrusion escape of crustal material in the southeast margin of Qinghai-Xizang Plateau. It is of great significance to carry out the quantitative analysis of crustal tectonic deformation mode. In this paper, the petromagnetism and paleomagnetism of four Cretaceous red bed sections in the anti-S-shaped structural area in the central Lanping-Simao Basin are studied. The characteristic remanence directions of early Cretaceous LN-a and LN-b profiles in Nanjian Niujie area are D_s=244.7 掳, I_s=-47.3 掳, Ks=31.6, 伪 _ (95) = 16.6 掳(K_1j~1) and D_s=245.4 掳, respectively. I_s=-46.4 掳, K 鈮，

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