科研成果
  当前位置:首页 > 科研成果 > 论文
Origin of middle Miocene leucogranites and rhyolites on the Tibetan Plateau: Constraints on the timing of crustal thickening and uplift of its northern boundary
作者: L. Y. Zhang, L. Ding, D. Yang, Q. Xu, F. L. Cai and D. L. Liu
期刊名称: Chinese Science Bulletin
发表年度: 2012
卷: 57
期: 5
联系作者:
页码: 511-524
学科:
外单位作者单位 :
单位代码:
全文链接: http://dx.doi.org/10.1002/hyp.7932
论文全文:
第一作者所在部门:
论文出处:
论文类别:
参与作者:
其它备注:
摘要: Leucogranites play a significant role in understanding crustal thickening, melting within continental collisional belts, and plateau uplift. Field investigations show that Miocene igneous rocks from the Hoh Xil Lake area mainly consist of two-mica leucogranites and rhyolites. We studied the Bukadaban two-mica leucogranites and the Kekao Lake, Malanshan and Hudongliang rhyolites by zircon U-Pb, muscovite and sanidine Ar-40/Ar-39 geochronology, and whole-rock geochemical and Sr-Nd isotopic analysis. Results yielded crystallization and cooling ages for the Bukadaban leucogranites of 9.7 +/- 0.2 and 6.88 +/- 0.19 Ma, respectively. Extrusive ages of the Kekao Lake and Malanshan rhyolites are 14.5 +/- 0.8 and 9.37 +/- 0.30 Ma, respectively. All rocks are enriched in SiO2 (70.99%-73.59%), Al2O3 (14.39%-15.25%) and K2O (3.78%-5.50%) but depleted in Fe2O3 (0.58%-1.56%), MgO (0.11%-0.44%) and CaO (0.59%-1.19%). The rocks are strongly peraluminous (A/CNK=1.11-1.21) S-type granites characterized by negative Eu anomalies (delta Eu=0.18-0.39). In also considering their Sr-Nd isotopic compositions (Sr-87/(86)Sri=0.7124 to 0.7143; epsilon Nd (9 Ma)=-5.5 to -7.1), we propose that these igneous rocks were generated through dehydration melting of muscovite in the thickened middle or lower crust of northern Tibet. Melting was probably triggered by localized E-W stretching decompression in the horse tails of Kunlun sinistral strike-slip faults. Reactivation of the Kunlun strike-slip faults, accompanied by emplacement of leucogranite and eruption of rhyolite in the Hoh Xil Lake area, indicates that large-scale crustal shortening and thickening in northern Tibet mainly occurred before 15 Ma. In addition, these findings suggest that the northern Tibetan Plateau attained its present elevation (similar to 5000 m) at least 15 Ma ago.
论文链接                

版权所有:中国科学院青藏高原研究所 Copyright © 2003-
通讯地址:北京市朝阳区林萃路16号院3号楼 邮政编码:100101
京ICP备05002818-1号 京公网安备110402500031号