【作者】 黄明达；

【导师】 陈杰；

【作者基本信息】 中国地震局地质研究所 ， 构造地质学， 2011， 硕士

【摘要】 新疆帕米尔东北缘公格尔山拉张系为新生代构造活动最为强烈地区之一,是研究第四纪构造活动的最好地区之一。该拉张系是吸收帕米尔内部东西拉张量的主要断层之一,Robinson et al.（2010）认为公格尔山的快速冷却发生在～2Ma以来,且7Ma以来剥露速率是恒定的,为4.2mm/a。但其第四纪尤其是晚第四纪以来的剥露速率及过程没有得到很好的约束。本文试图采用具不同封闭温度的构造热年代学方法去约束第四纪尤其是晚第四纪以来公格尔山剥露速率和冷却速率的变化规律,这也是构造热年代研究的热点之一。在前人研究工作的基础上,本文选择采自公格尔山布伦口剖面海拔高度3300左右m至4800左右m的样品,对选自片麻岩的白云母、黑云母和锆石矿物分别开展了初步的⁴⁰Ar/³⁹Ar和（U-Th）/He测年。同时对片岩、片麻岩及石英脉样品开展了初步的释光测年实验研究,试图探索和检验光释光低温热年代学方法的可行性。通过这些实验研究获得以下几点初步认识:1)片麻岩黑云母⁴⁰Ar/³⁹Ar热年代学研究结果表明,其⁴⁰Ar/³⁹Ar年龄介于1.63-1.34Ma之间,由高程法计算此期间的平均剥露速率约为3.9mm/a,与Robinson et al.（2010）所认为的7-8Ma以来的剥露速率恒定为4.2mm/a是基本一致。2)该剖面片麻岩样品的锆石（U-Th）/He年龄在0.5-0.7Ma之间。由高程法计算其0.7-0.6Ma期间的平均剥露速率为4.7mm/a,0.6-0.5Ma期间的平均剥露速率为7.6mm/a。与黑云母⁴⁰Ar/³⁹Ar结果相比,剥露速率可能自第四纪中期以来增大,这与Robinson等（2010）的推论是不一致的。3)由片麻岩样品P05T75矿物对法计算在2.38-1.34Ma期间的冷却速率为31℃/Ma,1.34-0.5Ma期间的平均冷却速率为190℃/Ma;样品P05T70矿物对法计算在1.66-0.70 Ma期间的冷却速率为172℃/Ma,这表明冷却速率至少自1.66Ma以来呈现增大的趋势。4)释光热年代学的初步研究结果表明:a)石英脉无释光信号。片岩和片麻岩细颗粒石英尽管释光信号较弱,但均具有特征的石英TL峰及OSL衰减曲线;b)不同高度细颗粒石英样品的天然信号强度总体上随高程的增加而增大;c)同一样品、不同测片细颗粒石英SAR法等效剂量较分散,且SAR法循环过程中存在较为严重的信号累积问题。尽管样品天然测片比较分散,但SMAR法克服了信号累积问题;细颗粒石英样品SMAR法等效剂量随海拔高度增加而增加。d)对细颗粒混合矿物的红外释光测年实验表明,SMAR法红外释光等效剂量随海拔高度增加而增加。更多还原

【Abstract】 The Kongur Shan extensional system lies in the northeastern margin of Pamir in Xin Jiang which is the most active in tectonics and one of best areas for the Quaternary research. This system is one of the faults accommodating east-west extension in the Pamir. Robinson et al.（2010） proposed that the rapid in cooling begun at～2Ma,with a constant exhumation rate（4.2mm/a） over the last 7Ma. But the exhumation rate and its process are not constrained from the Quaternary, especially late Quaternary. The thesis attempts to make use of the different themochronology methods to constrain the variations of the exhumation rate and cooling rate of the Quaternary、especially late Quaternary in the Kongur Shan. It’s also a focused topic of tectonic thermochronology.Based on pevious work,I take the samples from～3300m to～4800m in Bulunkou Muscovite, biotite and Zircon minerals selected from the gneiss for ⁴⁰Ar/³⁹Ar and （U-Th）/He dating. I also carry out a preliminary study of luminescence dating of schist, gneiss and quartz, trying to explore and test the Quartz OSL-thermochronology.1) The results of biotite ⁴⁰Ar/³⁹Ar thermochronology in gnesis suggest that ⁴⁰Ar/³⁹Ar ages are during 1.63-1.34Ma. The average exhumation rate calculated by age-elevation relationship is about 3.9mm/a, accordant with the viewpoint of Robinson et al.（2010） that exhumation rate is constant since 7-8Ma, about 4.2mm/a.2) The ages of Zircon （U-Th）/He thermochronology are between 0.5-0.7Ma, The average exhumation rate calculated by the age-elevation relationship are 4.7mm/a during 0.7-0.6Ma,and 7.6mm/a during 0.6-0.5Ma.Compared with the biotite ⁴⁰Ar/³⁹Ar results, the exhumation rate may increase since the mid-Quaternary, which is inconsistent with Robinson et al.（2010）.3) The mineral pair results of the sample P05T75 show that the cooling rate is 31℃/Ma during 2.38-1.34Ma, and 190℃/Ma during 1.34-0.5Ma. the results of P05T70 show that the cooling rate is 172℃/Ma in1.66-0.7Ma. It indicates that the cooling rate has been an increasing trend since at least 1.66Ma.4) Thermochronology of OSL,IRSL and TL shows that: a) There is no OSL singal in quartz veins. Though the OSL signal of the fine-grained quartz of schist and gnesis is weak, they have typical TL peak and OSL decay curve of quartz; b) The natural OSL signal strength of the fine-grained quartz of the samples generally increases with elevation; c) The equivalent dose of the fine-grained quartz of the different disks in the same sample measured by SAR disperses, and there is a serious problem of signal accumulation in the SAR method cycle. But the SMAR method overcomes the problem of signal accumulation. The equivalent dose of the fine-grained quartz measured by SMAR increases with elevation; d) The results of the IRSL of fine-grained poly minerals show that IRSL equivalent dose measured by SMAR increases with elevation.更多还原