青海巴颜喀拉山隆升的热年代学研究

Thermochronology of the uplift of the Bayan Har Mountains, Qinghai, China

对巴颜喀拉山年宝玉则花岗岩岩体样品的锆石、磷灰石进行了裂变径迹(FT)分析。结果显示该区的隆升可以分为三大阶段:①从低绿片岩相到锆石时钟启动:从200MaBP到105.57MaBP,去顶量约为2km,样品埋深上升到距地表约6km深度,去顶速率约为0.02mm/a;②从锆石时钟启动到磷灰石时钟启动:由于磷灰石在此时已抬升到距地表约6km的深度,由此到达时钟启动需距地表约3km时,去顶量应为3km,此阶段的持续时间为101.53MaBP,去顶速率约为0.03mm/a;③从磷灰石时钟启动至达到地表(至今):由于磷灰石在前一阶段也已抬升到距地表约3km的深度,即去顶量为3km,此阶段的持续时间为4.04MaBP,去顶速率约为0.74mm/a。

The results of zircon and apatite fission track dating of samples from the Baoyuze granite in the Bayan Har Mountains show that the uplift in the area progressed through three stages： （1） the stage from the low greenschist facies to starting age of the clock within zircons; （2） the stage from the starting age of the zircon clock to that of the apatite clock; and （3） the stage from the starting age of the apatite clock to the surface （present）. In the first stage from 200 to 105.57 Ma BP,～2 km thick materials were unroofed and samples went up to～6 km below the surface with an unroofing rate of～0.02 mm/a. In the second stage, as the apatites had risen to ～6 krn from the surface, unroofing of～3 km thick materials was needed for the starting of the clock and this stage of unroofing continued for 101.53 million years and the rate of unroofing was ～0.03 mm/a. In the third stage, because the apatite had already been uplifted to a depth of ～3 km below the surface, 3 km thick materials needed to be removed; the duration for this unroofing was 4.04 million years and the unroofing rate was ～0.74 mm/a.