羌塘盆地中央隆起带的抬升演化:构造-热年代学约束

Uplifting evolution of the Central Uplift Belt,Qiangtang:constraints from tectono-thermochronology

本文综合磷灰石裂变径迹年龄(113～43 Ma)、锆石裂变径迹年龄(169～103 Ma)、锆石U-Pb年龄(215～206 Ma)、黑云母K-Ar年龄(186～178 Ma),通过磷灰石热史模拟,TASC图谱分析和矿物封闭温度-年龄等手段,获得了中央隆起晚三叠世至今较为完整的冷却抬升历史。中央隆起主要经历了早侏罗世、晚侏罗世—早白垩世、晚白垩世—中新世早期和中新世晚期至今四期冷却事件,与南北羌塘板块后碰撞伸展、拉萨-羌塘板块碰撞、新特提斯洋板片俯冲、印度-欧亚板块碰撞以及中新世南北向走滑-伸展存在动力学联系,造成11.4km、2.85km、4.3～5km和0.85km的抬升量。中央隆起在侏罗纪相对两侧盆地抬升,随着两侧盆地经历了侏罗纪的沉积增厚,与两侧盆地高差减小,在早白垩世早期可能位于海平面附近,随后快速抬升至2～2.5km,统一接受晚白垩世红层沉积,并经历长期持续的逆冲推覆构造活动,进一步抬升至5km,随后受到中新世古大湖夷平和南北向伸展作用影响,中央隆起相对盆地发生差异抬升。

Based on our measurements of fission track ages of apatites(113-43 Ma)and zircons(169-103 Ma),U-Pb ages of zircons(215-206 Ma)and K-Ar ages of biobites(186-178 Ma)of granite samples,we performed apatite fission track thermal history modeling and track age spectra calculation(TASC)to obtain up-to-date histories of uplifting and cooling of the Qiangtang Central Uplift Belt(QCUB)since the Late Triassic.The QCUB experienced four major uplifting-cooling episodes,namely the Early Jurassic,Late Jurassic-Early Cretaceous,Late Cretaceous-early Miocene and later Miocene.The four episodes correspond to the dynamics of the post-collision stretching of the South and North Qiangtang blocks,Lhasa-South Qiangtang collision,Neo-Tethys ocean subduction,and Indo-Asian collision and N-S strike-slip movement,respectively,and experienced upliftings of 11.4,2.85,4.3-5 and 0.85 km,respectively.The QCUB probably was at sea level in the Early Cretaceous,and rapidly uplifted to 2-2.5 km in the Late Cretaceous;during 90-20 Ma,the long term thrusting systems caused further uplifting to^5 km,followed by differential surface uplifting due to the denudation effect of the Great Lakes and the south-north strike-slip action in the Miocene.