青藏高原西北缘祁漫塔格山中新世快速抬升的磷灰石裂变径迹证据

Apatite fission track evidence for the Miocene rapid uplift of the Qimantag Mountains on the northwestern margin of the Qinghai-Tibet Plateau

对祁漫塔格山体不同海拔高度所取的9个磷灰石样品的裂变径迹分析结果表明,东昆仑西段中新世早中期为主要的隆升期且隆升速率较高,早期隆升速率为111m/Ma,晚期隆升速率为98m/Ma,总体隆升速率为100m/Ma。样品显示出磷灰石裂变径迹长度大致分2类,一类磷灰石裂变径迹长度为(12.21±0.20)～(13.75±0.30)μm,径迹长度分布图基本上为窄而对称的正态分布,反映具有快的剥露冷却速率,未受到后期热事件的干扰。另一类磷灰石裂变径迹长度为(11.88±0.33)～(13.32±0.27)μm,较前一类具有稍慢的剥露冷却速率,并且受到了后期热事件的干扰。

Fission track analysis was performed on nine apatite samples from different altitudes of the Qimantag Mountain. The results show that： the main uplift period in the westem segment of the East Kunlun Mountains was early-middle Miocene, when the uphft rate was relatively high, with an uphft rate of 111 m/Ma in the early stage and an uplift rate of 98 m/Ma in the late stage and a general uplift rate of 100 m/Ma. Sample analysis indicates that according to the fission track lengths, apatite may be divided into two types. One type of apatite has fission track lengths of 12.21±0.20 to 13.75±0.30 μm, and its fission track lengths are in the main of narrow and symmetric normal distribution, which reflects that this type had a rapid denudation and cooling rate and was not subjected to interference of the late-stage thermal event. The other type of apatite has fission track lengths of 11.88±0.33 to 13.32±0.27 μm, suggesting that this type had a denudation and cooling rate shghtly slower than the former type and underwent the interference of the late-stage thermal event.