青藏高原北部中—新生代构造-热事件:来自柴西碎屑磷灰石裂变径迹的制约

Tectonic-Thermo Events of Northern Tibetan Plateau: Evidence from Detrital Apatite Fission Track Data in Western Qaidam Basin

柴西地区堆积了巨厚的新生界,不仅赋存有青海油田,且因紧邻阿尔金断裂和昆北断裂而蕴藏丰富的盆山耦合信息。对碎屑磷灰石的裂变径迹测试结果进行分析研究后认为,自渐新世以来,研究区经历了早期(32～3Ma或4Ma)的压陷-抬升和晚期(<3Ma或4Ma)的快速整体挤压-隆升2个时期。进一步的分析表明:柴西及其周缘山地从晚白垩世以来发生多阶段构造-热演化过程,即晚中生代(116～68Ma)、中生代—新生代之交(约68～62Ma)、始新世早中期(54～44Ma)、始新世晚期(约36Ma)、渐新世早期(约30Ma)、中新世(约22、16、12Ma)以及晚新生代(3Ma或4Ma、约1Ma)等阶段;同时揭示,在约28.4、19.52、14.21、8.76Ma时仅发生快速抬升,而在约30、21.8、16.38、7.38Ma时发生了强烈的挤压、盆缘掀斜、抬升剥蚀,对应于柴西地区逆冲断裂的多次逆冲叠覆活动。

Much thick Cenozoic were deposited in the western Qaidam basin（WQB）,in which not only Qinghai oil field located,but the sediments that close to Altyn Tagh fault and northern marginal fault of Kunlunshan also preserves many information of basin-orogen coupling.The study of detrital apatite fission-track（AFT） data suggests that studying area has experienced an early（32-3 Ma or 4 Ma） of the compress-depressive and late（3 Ma or 4 Ma） rapid compress-uplift of two periods.Farther analysis showed that these periods can be divided into poly-stages of tectonic-thermal processes in WQB and its around mountains since Late Cretaceous,in which Late Mesozoic（116-68 Ma）,Mesozoic-Cenozoic（ca 68-62 Ma）,Early-Middle Eocene（50-44 Ma）,Late Eocene（ca 36 Ma）,Early Oligocene（ca 30 Ma）,Miocene（ca 22,16,12 Ma） and Pliocene-Quaternary（3 Ma or 4 Ma,1 Ma） stages.The AFT data reveals studying area rapid uplift only at 28.4 Ma,19.52 Ma,14.21 Ma and 8.76 Ma,but compression,tilting-uplift-denudation at margin of the basin in about 30 Ma,21.8 Ma,16.38 Ma and 7.38 Ma,corresponds to multiple thrusting of thrusts in WQB.