摘要
青藏高原三江地区高程缓降、河流及深切峡谷发育,重建其构造-热年代时空演化为把握该地区地形地貌发育演化的内在驱动力提供科学依据。本研究以云南德钦白马雪山岩体为研究对象,开展磷灰石（U-Th）/He及裂变径迹年代学分析,结合已发表的U-Pb和Ar-Ar年代学结果来重塑该地区的构造-热演化历史和地形演化。研究表明,该地区经历了多期快速冷却事件：三叠世的岩浆侵位活动,早白垩世和中-晚始新世的快速冷却,以及中新世和上新世以来的快速剥蚀。青藏高原隆升致使全球气候变化的同时也导致其周缘地区经受强烈侵蚀：中新世以来（21～11Ma）快速冷却速率为10℃/Myr,而上新世以来（ca.5Ma）冷却速率从10℃/Myr增至15℃/Myr。假定区域现今地温梯度为25～35℃/km,河谷剖面不同位置的侵蚀速率及剥蚀量的空间分布特征进一步表明（靠近澜沧江主干道处侵蚀速率远高于其支流,且对应的年龄相对年轻）,河流下切及溯源侵蚀的多重效应导致该地区快速剥蚀、剥露,地形起伏加大的瞬态地貌演化规律。
The topographic evolution of the Three River Region in southeastern margin of the Tibetan Plateau,a region of rugged topography with well-developed drainage networks,offers a natural laboratory for investigating the effect of mountain buildings on climate,and the interactions between the two. Reconstruction of its spatial-temporal development provides constraints for a better understanding of the driving force on the topographical and tectonic evolution. Focusing on this topic,we present a synthesis of the tectonic and thermochronological evolution of the Baimaxueshan pluton since the Triassic by using apatite fission track and（ U-Th） / He dating combined with published data. The results suggest the pluton has experienced multi-stages of cooling： a short period of rapid cooling after its emplacement during Late Triassic,a long period of thermal stability,and then enhanced multiple exhumation phases during the Cenozoic times. Cooling rates increased around the Middle Miocene with a rate of 10℃ / Myr,and again enhanced at the Early Pliocene（ ca. 5Ma） up to 15℃ / Myr along the deep valley. Assuming that local geothermal gradient is 25 ～ 35℃ / km in the study area,the erosion rates and total amounts vary with different locations within the drainage network（ faster and younger near the trunk than drainage divides）. This pattern indicates the incision and headward marching of the trunk river drives the regional denudation in the Three Rivers Region,a transient state of topography with increasing local relief over time.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第5期1348-1360,共13页
Acta Petrologica Sinica
基金
国家自然科学基金项目(41172179
41425010)
国家自然科学杰出青年基金项目(412250)联合资助
关键词
白马雪山岩体
热历史
地貌演化
三江地区
青藏高原
Baimaxueshan Pluton Thermal history Geomorphic evolution Three River Region Tibetan Plateau
