阿尔金断裂带中段中新生代隆升历史分析:裂变径迹年龄制约  

MESOZOIC AND CENOZOIC UPLIFT-DENUDATION ALONG THE ALTYN TAGH FAULT,NORTHWESTERN CHINA:CONSTRAINTS FROM APATITE FISSION TRACK DATA

作　　者：张志诚[1] 郭召杰[1] 李建锋[1] 汤文豪[1] 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室；北京大学地球与空间科学学院,北京100871

出　　处：《第四纪研究》2012年第3期499-509,共11页Quaternary Sciences

基　　金：国家自然科学基金面上项目(批准号:41072148,40672130和40272085)资助

摘　　要：本文利用裂变径迹方法探讨阿尔金断裂中段吐拉-肃北之间隆升和剥露过程。古生代花岗岩和侏罗系沉积岩的磷灰石裂变径迹年龄介于107.2±9.0Ma到14.1±1.3Ma之间,明显小于其侵位年龄或者沉积年龄。自西部的吐拉到东端的肃北,磷灰石裂变径迹年龄逐渐升高,从14.1±1.3Ma增加到107.2±9.0Ma。花岗岩和侏罗系砂岩的磷灰石裂变径迹模拟结果表明,阿尔金断裂南侧地质体经历了两阶段的快速冷却过程,早期为33Ma左右,晚期为8Ma左右;阿尔金断裂北侧经历了晚白垩世开始的相对缓慢的冷却过程以及8Ma以来快速冷却事件。阿尔金断裂南北两侧的地质体的裂变径迹年龄和热历史略有差异,可能反映阿尔金断裂的影响。33Ma左右的快速冷却事件可能是阿尔金断裂活动引起的快速去顶作用的开始,这一事件对应了印度和欧亚板块碰撞。8Ma左右的冷却事件,与阿尔金山地区盆地内的快速沉积过程相一致,同时可能是青藏高原抬升与侧向生长在本区的响应。The study area lies between latitudes 37°30＇N and 40°20＇N, and longitudes 86°00＇E and 95°20＇E, along the northwest margin of Qinghai-Tibetan Plateau. We has carried out zircon and apatite fission track analysis from sixteen samples of the Jurassic sandstones, granites, rhyolite and Neogene granitic breccias, along the Ahyn Tagh Fault（ATF） between Tula and Subei. The zircon fission track ages of four Jurassic sandstone samples range from 115.6±18.3Ma to 179.4 ±19.7Ma. The zircon data show that all but one of the zircon ages represents a Jurassic cooling event. The apatite fission track ages range between 107.2±9.0Ma and 14. 1±1.3Ma,showing a general increasing trend with distance from the western part at Tula to eastern area at Subei, and all are significantly younger than their host rock formation or sediment deposition ages. The confined mean track lengths of the samples range from 11.3±0. 71μm to 13.3 ±0. 2μm,with standard deviations between 1.8μm and 2.91μm. All of the samples can also be divided into two broad groups depending on their apatite fission track ages and structural position. Group A refers to samples with apatite fission track ages lower than 50Ma, mostly structurally associated with the southern side of ATF. Group B refers to samples with apatite fission track ages about or older than 50Ma, generally associated with areas on the northern side of the ATF or/and on the block between the main and a secondary fault at the growing triple junction site. Modelling of the apatite fission track data （ Group A） from the granites and Jurassic sedimentary strata exposed on the southern side of the Altyn Tagh fault show a two-stage regional cooling history during Cenozoic. The earliest cooling phase occurred at 33Ma, and the second phase of cooling took place from about 8Ma. The thermal models of the apatite fission track （Group B）from the granite and granitic gravels on the northern side of the ATF show a period of slow cooling during the Cretaceous and early Paleogene that

关 键 词：裂变径迹定年分析 新生代 隆升剥露 阿尔金断裂 

分 类 号：P542.2[天文地球—构造地质学] P597.1[天文地球—地质学]