燕山山脉隆升过程的热年代学分析

Thermochronological Analysis on the Uplift Process of the Yanshan Mountains

本文应用热年代学方法,测定侵入体的热历史,进而分析燕山山脉的隆升过程。研究结果表明,燕山造山带的隆升过程在时空上具有明显非均匀性。燕山中段南部的盘山岩体约于226.48Ma侵位,在96～35Ma期间以3.45℃/Ma的速度冷却,对应于0.115mm/a的快速隆升过程;燕山中段北部的雾灵山岩体约于132Ma侵位,在86～45Ma期间以5.61℃/Ma的速度冷却,对应于0.186mm/a的快速隆升过程;燕山西段的云蒙山岩体约于143Ma侵位,在106～103.95Ma与20～0.0Ma期间分别以31.80℃/Ma、4.45℃/Ma的速度冷却,对应于1.06mm/a、0.15mm/a的快速隆升过程。燕山西段四合堂花岗片麻岩黑云母约于144.46Ma开始启动K-Ar法记年系统,在13Ma以来以7.69℃/Ma的速度冷却,对应于0.256mm/a的快速隆升过程。燕山西南缘的八达岭岩体于129Ma之前侵位,在6Ma以来以16.67℃/Ma的速度快速冷却,对应于0.556mm/a的快速隆升过程。据此笔者认为,燕山中段的快速隆升早于燕山西段,燕山西南缘隆升最晚。

Thermochronological dating is used in studying the thermal history and uplift processes of the Mesozoic plutons of the Yanshan erogenic belt. The results show that the cooling history of plutons of the Yanshan erogenic belt is complicated and the uplift process of the Yanshan Mountains is inhomogeneous. The Panshan granite of the middle Yanshan Mountains intruded in 226. 48 Ma and cooled fast during 96-35 Ma at an average rate of 3. 45℃/Ma,corresponding to a rapid uplift process at an average rate of 0. 115 mm/a. The Wulingshan alkalic complex of the middle Yanshan Mountains intruded in 132 Ma and cooled fast during 86-45 Ma at an average rate of 5. 61℃/Ma,corresponding to rapid uplift at an average rate of 0. 186 mm/a. The Yun-mengshan granite of the west Yanshan Mountains intruded in about 143 Ma and cooled fast in 106 - 103. 95 Ma and 20-0. 0 Ma at the rate of 31. 80℃/Ma and 4. 45℃/Ma, corresponding to rapid uplift at the rate of 1. 06 mm/a and 0. 15 mm/a respectively. The Sihetang gneiss granite of the west Yanshan Mountains cooled fast since 13 Ma at an average rate of 7. 69℃/Ma, corresponding to rapid uplift at an average rate of 0. 256 mm/a. The Badaling granite of the southwest Yanshan Mountains intruded in about 129 Ma and cooled fast since 6 Ma,corresponding to rapid uplift at an average rate of 0. 556 mm/a. It is concluded that the middle Yanshan Mountains uplifted earlier than the west Yanshan Mountains, followed by rapid uplift of the southwest Yanshan Mountains.