玉龙-哈巴雪山晚第四纪隆升方式研究

The Yulong-Haba Mountains is located in the southeastern margin of the Tibetan Plateau, where the boundaries of the first order landscape unit in China, and bordered by the Sichuan Yunnan rhombic block to the east. The Yulong-Haba Mountains is famous for the lowest latitude snow mountain in China. The uplift of a mountain is related to the regional tectonic framework and the source of the main compressive stress. At present, there are two kinds of views about the uplift mode of the Yulong-Haba Mountains. One view suggest that the uplift of the Yulong-Haba Mountains is mainly due to compression effect of the lateral movement at the end of strike-slip fault. However, in another view, the uplift of the Yulong-Haba Mountains may be related to the ENE movement at the Himalayan East Syntaxis. At this application, we will focus on 1) comparing the faults activity capacity on both sides of the Yulong-Haba Mountains (especially the amount of vertical movement and rate), 2) measuring and analyzing the changes of the longitudinal phases of river terraces in Tiger-Leaping-Gorge, 3) researching the features of broad valley landscape and causes of Jinsha River sediments at the upstream of Tiger-Leaping Gorge, 4) extracting and analyzing characteristics of the regional topography, and 5) analyzing results of GPS observation and leveling, stress field and deep structure. Those studies will be used to determine the uplift mode of the Yulong-Haba Mountains (uniform or one-side uplift). Thus, further to analyze the tectonic framework of the surrounding areas of the Yulong-Haba Mountains.

玉龙-哈巴雪山位于青藏高原东南缘，中国一级地貌单元分界所在，东侧为川滇菱形块体，是我国纬度最低的雪山。山体隆升方式与区域构造框架、主压应力来源等有关。目前，关于玉龙-哈巴雪山隆升方式主要有两种观点：一种认为隆升主要是周边走滑断裂活动引起的尾端挤压作用形成；另一种则认为隆升可能与喜马拉雅东构造结向北东东方向挤压有关。本申请通过：1.对玉龙-哈巴雪山东西两侧断层活动性和活动参数（尤其是垂直活动量与速率）的研究，比较两条断裂垂直运动能力的差异；2.测量和分析虎跳峡峡谷河流阶地位相变化；3.研究虎跳峡上游金沙江宽谷地貌和巨厚江底沉积物的成因；4.提取和分析玉龙-哈巴雪山周边地形地貌分布特征；5.分析现今GPS、水准测量、应力场、深部结构等有关区域背景结果。从而确定玉龙-哈巴雪山隆升方式（整体均匀抬升还是单侧抬升），再进一步分析玉龙-哈巴雪山周边地区的构造运动框架。

玉龙-哈巴雪山位于青藏高原东南缘，是我国纬度最低的雪山。雪山的隆升方式决定了周边断层的运动特征、附近主要河流的地貌特征。为厘清玉龙-哈巴雪山晚第四纪隆升方式，通过对玉龙-哈巴雪山周边断层运动习性、金沙江河谷地貌、堆积物成因及年代学、雪山岩体低温热年代学、虎跳峡内岩石暴露年龄等研究。取得以下主要成果：中甸-大具-玉龙雪山东麓断层带是川滇菱形块体的西边界，右旋走滑兼逆冲，晚更新世以来垂直和右旋速率为2.37-3.94 mm/a和5.03-8.37 mm/a。冲江河断层晚更新世以来不再活动。丽江-小金河断层在130±25 ka, 736±81 ka和1203±199 ka有过明显的活动；建立了ESR测定玄武岩区断层带内重晶石的测年流程；白格堰塞湖溃坝洪水在石鼓形成雍水湖，相关样品测试表明，OSL和ESR都有大于100 Gy的等效剂量残留值，在河流阶地剖面OSL测年时，非正常的信号剂量值可能含有洪水事件的信息；在金沙江石鼓有约距今12 ka、奉科有约440—556 ka、涛源440-690 ka的湖相层，为沿江大型滑坡形成的堰塞湖的产物；堆积在大具盆地中哈巴雪山大规模冰水堆积物年龄为40.2-28.7 ka；虎跳峡上游石鼓一带金沙江江心州、宽谷地貌和巨厚江底堆积物，是因为下游中甸-大具-玉龙雪山东麓断层带的右旋兼逆冲活动，导致玉龙-哈巴雪山快速不均匀抬升形成的；锆石（U-Th）/He年龄表明在3 Ma左右雪山地区发生速率约为1 mm/yr的快速隆升事件；磷灰石裂变径迹（FT）表明在2.58 Ma隆升速率从0.3mm/a突然增长为2.2 mm/a；中虎跳峡暴露年龄表明其隆升速率为1.24 mm/yr, 小于玉龙雪山东麓断裂约为2.37-3.94 mm/a的逆冲速率，从东往西隆升速率在变小，为不对称隆升；玉龙-哈巴雪山的形成为来自西侧东构造节近东西向的挤压以及川滇菱形块体向西南方向运动共同作用的结果。