西藏冈底斯地块尼木地区新第三纪构造热史的磷灰石裂变径迹约束  

Apatite Fission Track Evidences for Neogene Tectono-Thermal History in Nimu Area,Southern Gangdese Terrane,Tibet Plateau

作　　者：袁万明[1] 董金泉[2] 保增宽[2] 朱炳玉[3] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [2]中国科学院高能物理研究所核分析重点实验室,北京100049 [3]广州地球化学研究所

出　　处：《原子能科学技术》2008年第6期570-573,共4页Atomic Energy Science and Technology

基　　金：国家自然科学基金资助项目(10175076,10475093,40072068);教育部“111计划”资助项目(B07011)

摘　　要：文章报道冈底斯地块尼木地区磷灰石裂变径迹研究新成果。获得的5个磷灰石裂变径迹年龄为(6.8±0.6)^(9.7±1.2)Ma,均属同一组年龄;径迹长度为(12.9±1.7)^(14.2±2.3)μm,具单峰分布。这与近期9~5 Ma挤压事件并导致藏北盆地快速沉积作用相一致。样品模拟揭示有3阶段地质热历史:从大于12 Ma到8 Ma,温度120~110℃,属于稳定阶段;8~4 Ma,约从110℃到15℃地表温度,是快速冷却阶段;4~0 Ma,处于地表演化阶段。受喜马拉雅碰撞作用的影响,第2阶段使本区急剧隆升剥露,形成现今的山貌特征。在8~4 Ma期间,平均隆升速率为1.41 mm/a,累计隆升量达5 940 m。The apatite fission track for 5 samples were obtained. All samples exhibit that the individual grain ages belong to a single population with a single mean age and have central ages from （6.8±0.6） Ma to （9. 7±1.2） Ma. Their mean track lengths range between （12.9±1.7） μm and （14.2±2.3） μm with a single peak. These ages well coincide with high sedimentation rates in the basin of north Tibet and resulted from a final compressional event of 9-5 Ma. Modeling identifies three stages in sample cooling history from about 12 Ma to present day. The first stage records a period of relative stability with little if any cooling taking place during more than about 12-8 Ma at the temperature of 120-110 ℃. The second stage is requirement for rapid cooling from 8 Ma to 4 Ma with temperature from about 110 ℃ to surface about 15 ℃. Final stage belonged to surface evolution since Pliocene. The second stage linked to the far field effects of the Himalayan collision and most likely generated the surface uplift and relief that define the resent-day Gangdese Mountains. The mean uplifting rate was 1.41 mm/a and the uplift reached 5 940 m during the 8-4 Ma.

关 键 词：构造 冷却隆升 热历史 裂变径迹 冈底斯地块 

分 类 号：P546[天文地球—构造地质学] P588[天文地球—地质学]