摘要
对南昆仑缝合带中段西大滩盆北花岗岩,应用不同的年代学方法,测定岩浆结晶时代和构造热事件年龄,分析构造地貌演化过程。应用离子探针方法,测出西大滩盆北花岗岩的锆石U-Pb同位素年龄为196.4- 212.1 Ma,平均年龄204.1±2.6 Ma,代表岩浆侵位结晶时代。西大滩盆北花岗岩的黑云母K-Ar和Ar-Ar同位素年龄为134.47-145.3 Ma,指示晚期韧性剪切变形时代。应用矿物对热年代学方法,揭示出204.1-134.47 Ma、57. 67-26.0 Ma、26 Ma以来3期构造热事件,降温速率分别为6.46℃/Ma、4.91℃/Ma、3.84℃/Ma,对应的隆升速率分别为0.21 mm/a、0.16 mm/a、0.13 mm/a;说明134.47-57.67 Ma为缓慢降温和剥蚀夷平时期,对应的降温速率为0.64℃/Ma、差异隆升速率为0.02 mm/a。结合磷灰石裂变径迹测年和风火山群、五道梁群挤压缩短时代、区域伸展走滑起始年龄资料,推断昆仑山南部新生代山脉快速隆升发生于渐新世-中新世早期,估算隆升速率达0.26 mm/a。
Isotopic dating and thermo-chronological analyses were finished for the north Xidatan granite in the south Kunlun suture, giving a crystallization age of granitic magma and providing constraints on thermo-tectonic events and the tectono-geomorphic evolution history of the south Kunlun Mts. According to SHRIMP U-Pb isotopic dating, the zircon ages of the north Xidatan granite range from 196.4 to 212.1 Ma with an average of 204. 1±2. 6 Ma, representing the mineral crystallization age of the granite. And K-Ar and Ar-Ar ages of biotite from the north Xidatan granite, 134.47～145.3 Ma, indicate the ductile shearing time of the granite. The thermo-chronological diagram based on U-Pb isotopic dating and K-Ar and fission-track dating of apatite shows that the north Xidatan granite cooled at rates of 6.46℃/Ma, 4. 91℃/Ma, 3.84℃/Ma in period from 204. 1 to 134.47 Ma, from 57.67 to 26.0 Ma, from 26 Ma to the present, respectively, corresponding to the uplift rates of 0.21 mm/a, 0. 16 mm/a, 0. 13 mm/a, and the period of 134.47±57.67 Ma is a stable one characterized by very slow cooling and long-term erosion and planation. It is further inferred that the south Kunlun Mts. uplifted rapidly from the Eocene to early Miocene at a rate of 0. 26 mm/a according to thrusting and folding periods of the Fenghuoshan and Wudaoliang Groups, initial time of regional extension and strikeslip faulting and fission-track dating of apatite from the north Xidatan granite.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2005年第5期628-635,共8页
Acta Geologica Sinica
基金
国际合作INDEPTH-Ⅳ项目国家重点基础研究发展规划2001CB711001子项目部分研究成果。
