四川盆地南缘中-新生代隆升作用研究

The southern Sichuan Basin located at southeastern margin of the Tibetan plateau, is one of the best favorable area and a demonstration zone for shale-gas exploration in the beginning of this century. It is thought to represent a deformation domain resulted from eastern growth of the Tibetan Plateau and NW-ward thrusting of the Xuefeng Orogen. We conduct low-temperature thermochronology dating (e.g., apatite and zircon fission track, apatite and zircon (U-He)/He) on the dense samples from two boreholes (i.e., Well JS-1 and Well XM-1), and those from three sections (e.g., Yongsan, Qilongchun and Shuanghe sections) characterized with low-relief, long-wavelength topography. Combined with geothermometer and structure etc., we could unravel time-temperature history, uplift and exhumation process and the tectono-thermal events in the southern Sichuan Basin. It should be noted that two boreholes locate in the Daloushan and Daliangshan frontier, and the three sections locate at the Daloushan, Daliangshan and their transfer zone. Thus, they could provide more details with differential uplift and exhumation across the southern Sichuan Basin, based on the comparison of the basin-mountain, the surface and subsurface, the Daloushan and Daliangshan, etc. Not only are these results significantly helpful for understanding of the Meso-Cenozoic geodynamics of the Sichuan basin (even the southeastern Tibetan Plateau), but also provide useful data for conventional and unconventional oil/gas exploration in the Sichuan basin.

四川盆地南缘地处青藏高原东侧、位于特提斯-喜马拉雅构造域和滨太平洋构造域的交接转换部位，是目前我国南方下古生界海相页岩气勘探开发最具代表性和示范性的地区之一。本项目利用四川盆地南缘盆内两口钻井（大凉山前缘金石1井和大娄山前缘西门1井）全井段样品及盆缘（大凉山、大娄山及其过渡区）地表典型（长波长、低起伏度）背斜剖面（如：大凉山雷波背斜永善剖面、大娄山桑木场背斜骑龙村剖面和二者过渡区宜宾兴文背斜双河剖面）样品的多封闭体系低温热年代学、地质温度计、构造变形等联合对比研究（如：造山带-盆地间、地表和地腹间、不同山-盆间对比），建立钻井与剖面精细热隆升史剖面与关键构造热事件，精确刻划四川盆地南缘中-新生代隆升剥蚀的阶段性时间、过程和机制，为深入理解四川大型叠合盆地动力学（如：青藏高原向东扩展和中国南方大陆陆内构造）及其常规-非常规油气富集与保存提供关键约束和科学依据。

四川盆地南缘地处青藏高原东侧，位于特提斯-喜马拉雅构造域和滨太平洋构造域的交接转换部位。基于川南地区多封闭系统低温热年代学、多期构造叠加解析、热史模拟等综合研究，揭示川南地区普遍经历三个阶段热演化过程：沉降埋深增温阶段（~80 Ma以前）、缓慢抬升冷却阶段（80~20 Ma）和快速隆升剥露阶段（~20Ma-现今）。晚中-新生代区域发生四期具不同应力场特征的构造变形事件与盆-山建造过程，第一期晚侏罗世-早白垩世近E-W向主应力场挤压变形事件，第二期晚白垩世（~80Ma）近S-N向主应力场挤压变形事件，第三期古近纪晚期（~40-20Ma）NE-SW向主应力场挤压变形事件和第四期晚新生代（~10-5Ma以来）NW-SE向主应力场抬升剥蚀事件，总体上构造缩短量和缩短率分别达20-30 km和10%-20%。尤其是，隆升剥蚀模型和地壳缩短变形模型等综合对比揭示，受控于青藏高原新生代东向扩展变形过程西昌盆地动力学过程表现为抬升高原盆地。总体上，四川盆地南缘板内渐变型盆山结构带（大凉山盆山结构带、大娄山盆山结构带）板内多期构造变形与盆-山建造是板缘和/或板内构造动力学的综合体现，共同受控于中国南方大陆晚中生代-新生代由滨太平洋构造域向特提斯-喜马拉雅构造域逐渐转换的重要过程。