青海都兰县哈日扎多金属矿区构造活动的磷灰石裂变径迹分析

摘要

通过采集哈日扎多金属矿区不同矿带不同岩性的样品，进行磷灰石裂变径迹年代学分析，探讨矿区的构造演化特征。磷灰石裂变径迹年龄于120‒60.2 Ma变化，具体可分为120‒93 Ma、78 Ma和66‒60 Ma三个年龄组，较好地体现了该地区经历不同构造隆升剥蚀作用，120‒93 Ma和66‒60 Ma分别代表冈底斯地体、喜马拉雅地体先后于早白垩世、晚白垩世时期向北俯冲并与北侧地块碰撞‒汇聚的体现，78 Ma 是区域上低级变质作用的反映。磷灰石裂变径迹模拟结果显示，不同样品地质热历史相似，分为三个阶段：160‒90 Ma、90‒20 Ma、20 Ma 至今，三个阶段分别隆升0.28 km、1.40 km、1.00 km，总的隆升量为2.68 km，第三阶段代表青藏高原及周缘新生代重大隆升期，是印度板块与欧亚板块碰撞后持续挤压和后期拉张环境下的整体强烈隆升。%Background:Harizha polymetallic ore district is located in eastern section of east Kunlun mountains, Qinghai province and belongs to multicycle magmatic arc belt in middle of east Kunlun. A total of four large scale mineralizing zones have been discriminated in north area and mainly fall into tectonic alterated rock type.Purpose:The tectonic evolution characteristics of Harizha polymetallic ore district is discussed by analyzing the samples with different lithologies collected from different ore belts.Methods:The fission track age of apatite was used to calculate the absolute uplift rate of the plateau.Results: The apatite fission track ages range from 120 Ma to 60 Ma and could be divided into three units: 120‒93 Ma, 78 Ma and 66‒60 Ma, which reflected the various tectonic uplift denudation in this region. Units of 120‒93 Ma and 66‒60 Ma respectively represent the stages when Gangdise terrain and Himalayan terrain subducted to the north, collided and converged with the northern block in early cretaceous and late cretaceous successively. Age of 78 Ma shows the regional low-grade metamorphism.Conclusion: The simulation  results of apatite fission track reveal that different samples have the similar geological thermal history, which is divided into three stages: 160‒90 Ma, 90‒20 Ma and 20‒0 Ma. The amounts of uplift of these three stages are approximately 0.28 km, 1.40 km and 1.00 km, with 2.68 km as the total amount of uplifting. The stage of 20−0Ma represents a major cenozoic uplifting in Tibetan plateau and its periphery, which is the result of continuous pressing after the collision between Indian plate and Eurasian plate and the strong uplift under the extension environment afterwards.