Mesozoicand Cenozoic Uplift-denudation Alongthe Altyn Tagh Fault, Northwestern China: Constraintsfrom Apatite Fission Track Data
详细信息
- 责任者：Zhang Zhicheng(Key Laboratory of Orogenic Belts and Crustal Evolution ; Ministry of Education ; Beijing 100871) ; Guo Zhaojie
- 刊名：Quaternary Sciences
- 出版年：2012
- 卷期：32(3)
- 页码：p.499-509
- issnNo：ISSN1001-7410
- isbnNo：CN11-2708/P
摘要
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 Altyn 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±0.7μm to 13.3±0.2μm,with standard deviations between 1.8μm and 2.9μm.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 was followed by rapid cooling at about 8Ma.We interpret that the 33Ma cooling event correlates with the onset of rapid uplift-denudation due to activating of the ATF,which was activated by the India-Asia collision.The 8Ma cooling event,which is well correlated with high sedimentation rates in the basins of the Altyn Tagh mountains,apparently represents tectonic activity in response to northward and eastward lateral growth of the Tibetan Plateau.