磷灰石裂变径迹研究新疆阿尔泰山南缘剥露历史及古地形再造

Apatite Fission Track Analyses of Exhumation History and Antiquated Topography Reconstruction in the Southern Margin of Altai , Xinjiang

本文应用裂变径迹技术对阿尔泰地区13个磷灰石裂变径迹样品进行分析研究,揭示了该地区的隆升剥露历史,并进行了古地形再造。热历史演化模式具有3个阶段的特征:①约120～80Ma至70Ma,温度较高,处于磷灰石裂变径迹退火带底部温度,主体高于100℃,晚白垩世末期和早第三纪初期,阿尔泰地区构造运动不明显,仅有微弱的升降运动,均夷作用显著;②从80～70Ma至30～20Ma,快速冷却,温度由85～75℃降至35～30℃,晚第三纪,自中新世起,特别是中新世中晚期,由于喜马拉雅运动的影响,块断升降运动较为加强,山区上升,盆地相对下降;③从约30～20Ma至现今,缓慢冷却,温度由35～30℃降为现在的地表温度(平均20℃)。三阶段隆升速率分别为0.025mm/a,0.027mm/a和0.02mm/a;隆升幅度分别为1.14km,1.34km和0.43km。地表隆升幅度变化于634～2394m之间。区内平均剥蚀量为2168m,平均隆升量3318m,二者之差1150m便是现在的平均高程。

Thirteen apatite samples from the Altai region were employed to reveal the history of uplifting and exhumation using fission track method and to reconstruct antiquated topography.History of cooling evolution is characterized with a model of three stages.Stage one from 120 Ma to 80 Ma or 70 Ma records the highest temperature and is in the bottom temperature of apatite fission track anneal strip ,with THE dominant temperature of higher than 100℃.During late Late Cretaceous and early Paleogene periods , the Altai region had nodistinct tectonic activity but just weak lifting and exhumation.Stage two lasting from 80～70 Ma to20 Ma records rapid cooling with temperature from 120～100℃ to35～30℃. Since mid-Palegene , especially from mid-late Miocene , Himalayan movement resulted in strong uplift and exhumation ,with mountains uplifting and basins relatively lowering.The final stage from 30 Ma to 20 Ma and to present records slow cooling process ,with temperature going down from35～30℃ to the temperature of current Earth＇s surface （ an average temperature of20℃ ） .The uplift rates of three stages are 0.025 mm/a , 0.027 mm/a and 0.02 mm/a , respectively ,while uplift magnitude of the three are correspondingly 1.14 km , 1.34 km and 0.43 km.The surface uplift ranges between 634 and 2394 m. Average values for exhumation and uplift are 2168 m and 3318 m , and the balance of them （ 1150 m ） is the average height of the mountain today.