剑川-兰坪盆地古近纪沉积-构造变革及其区域构造意义

发布时间：2018-06-07 17:23

本文选题：青藏高原东南缘 + 剑川-兰坪盆地　；参考：《大地构造与成矿学》2017年01期

【摘要】：滇西新生代兰坪盆地和剑川盆地分别位于哀牢山红河断裂带两侧,青藏高原东构造结内,其沉积过程和构造变形对青藏高原东南缘的构造演化有重要的启示意义。通过对这两个盆地古近纪沉积和构造过程的研究,我们发现兰坪盆地和剑川盆地及邻区的构造变形分为三期:始新世早期的强烈挤压变形、始新世中晚期的伸展变形、渐新世的走滑变形。始新世早期的挤压变形主要表现为兰坪地区的褶皱冲断系统、哀牢山-红河断裂的逆冲活动和剑川盆地的宽缓褶皱。沉积方面,古新统勐野井组(E_1m)较为稳定的细粒滨湖相沉积转变为始新统宝相寺组(E_2b)较粗的具有前陆盆地性质的河流相沉积,特别是宝相寺组底部发育的一套快速堆积的磨拉石建造,可能是对始新世强烈挤压环境下的沉积响应。始新世中晚期伸展变形体现在盆地的构造环境由早期的挤压环境变为伸展环境和该时期大量富钾岩体和岩脉的侵入,沉积学上,下始新统宝相寺组的河流相转变为中始新统金丝厂组(E_2j)具有快速堆积磨拉石特征的曲流河沉积,极可能是对构造体制变革的沉积响应。渐新世的走滑变形则体现在渐新统的缺失和哀牢山红河断裂的早期左行走滑。因此,我们认为剑川兰坪地区在始新世中期和渐新世均发生了显著的运动学转换,这一认识也得到了始新世中期兰坪和剑川盆地物源明显变化的支持。结合青藏高原东南部始新世中晚期岩浆的活动,渐新世大型剪切带(崇山剪切带、高黎贡剪切带)的强烈走滑和保山块体的旋转,我们推测青藏高原东南缘古近纪的构造演化为古新世-始新世早期的挤压、始新世中晚期的伸展、渐新世的转换压缩。
[Abstract]:The Cenozoic Lanping basin and Jianchuan basin in western Yunnan are located on both sides of the Ailaoshan Zhanghong River fault zone and within the eastern tectonic junction of the Qinghai-Tibet Plateau. The sedimentary process and tectonic deformation of the basin have important implications for the tectonic evolution of the southeast margin of the Qinghai-Xizang Plateau. By studying the paleogene sedimentary and tectonic processes of these two basins, we find that the tectonic deformation of Lanping basin and Jianchuan basin and its adjacent areas can be divided into three periods: strong compression deformation in the early Eocene, extensional deformation in the middle and late Eocene. The strike-slip deformation of Oligocene. The early Eocene compressional deformation was mainly manifested in the fold thrust system of Lanping area, the thrust activity of Ailaoshan-Honghe fault and the wide and gentle fold in Jianchuan basin. In terms of sedimentation, the relatively stable fine-grained lacustrine facies deposited in the Mengye well formation of the Paleocene has been transformed into the fluvial facies with the characteristics of the Foreland basin, which is relatively coarse in the Baoxisi formation of the Eocene. In particular, a set of rapidly accumulated molars formed at the bottom of the Baoxangsi formation may be a response to the deposition in the strongly squeezed environment of the Eocene. The extensional deformation in the middle and late Eocene is reflected in the tectonic environment of the basin from the early compressional environment to the extensional environment and the intrusion and sedimentology of a large number of K-rich rock bodies and veins during this period. The fluvial facies of the Baoxangsi formation of the Lower Eocene is transformed into the EJ _ 2J _ 2J _ 2 of the Jinshichang formation of the Middle Eocene, which is characterized by rapid accumulation and grinding of stones, which is probably a sedimentary response to the structural system change. The strike-slip deformation of Oligocene is reflected in the absence of the Oligocene and the early left strike-slip of the Ailaoshan fault. Therefore, we believe that there was a significant kinematic transition between the middle Eocene and Oligocene in the Jianchuan Zilanping area, which was supported by the obvious changes in the provenance of the Lanping and Jianchuan basins in the middle Eocene. Combined with the magmatic activity in the southeast of the Qinghai-Xizang Plateau, the strong strike-slip of the Oligocene large-scale shear zone (Chongshan shear zone, Goligon shear zone) and the rotation of the Baoshan block, We speculate that the Paleogene tectonic evolution in the southeastern margin of the Qinghai-Xizang Plateau is the compression of the Paleocene to the early Eocene, the extension of the middle and late Eocene, and the transformation and compression of the Oligocene.
【作者单位】：中国地质大学(武汉)地球科学学院;广西壮族自治区地质调查院;中国地质大学(武汉)地质过程与矿产资源国家重点实验室全球构造研究中心;中国地质大学(武汉)生物地质与环境地质国家重点实验室;
【基金】：国家自然科学基金(41672195) 中国地质调查局项目“青藏高原新近纪隆升过程与地质事件群研究”(1212011121261) 国家青年科学基金(41202144)联合资助
【分类号】：P548

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