华北地块北缘晚古生代-中生代花岗岩体侵位深度及其构造意义

运用斜长石-角闪石温压计对华北地块北缘内蒙古隆起及燕山褶断带内不同时期花岗质侵入岩的结晶压力及侵位深度进行了估算。结果表明,晚古生代—早中生代期间,在内蒙古隆起及燕山褶断带之间,存在有强烈的差异性隆升及剥露过程,但这种差异性隆升及剥露在早侏罗世以来的表现则不明显。晚古生代—早中生代差异性隆升及剥露可能是导致内蒙古隆起上大量基底岩石出露、中—新元古代及古生代沉积盖层缺失及燕山褶断带中—新元古代及古生代沉积盖层大量保留的主要原因。内蒙古隆起强烈的隆升及剥露过程发生在晚石炭世—早侏罗世期间,其东部的剥露幅度比中东部明显偏小。晚古生代-早中生代期间内蒙古隆起的强烈剥露及其与燕山褶断带之间的差异性隆升可能与古亚洲洋板块向华北地块的俯冲、消减、碰撞及华北北缘区域性断裂(如平泉-古北口-赤城-尚义断裂、赤峰-围场-多伦断裂)的活动有关。燕山褶断带的强烈隆升与剥露发生则在晚侏罗世—早白垩世之后。晚体罗世—早白垩世以来,华北地块北缘南北两侧均有一次明显的剥露过程,这一剥露可能与本区及中国东部地壳强烈伸展有关。

Emplacement depths of the Late Paleozoic -Mesozoic granitoid intrusions from the northern North China block and their tectonic implications

Application of aluminum-in-hornblende geobarometry to different granitoid intrusions from the northern part (the Inner Mongolian Paleo-uplift,IMPU) and the southern part (Yanshan fold-and-thrust belt) of the northern margin of North China block (NCB) provides much useful information on the uplift and exhumation processes of this area since the Late Paleozoic.Emplacement depths estimated from aluminum-in-hornblende geobarometry indicate that the differential uplift and exhumation between the IMPU and the Yanshan fold-and-thrust belt was distinct during the Late Paleozoic to Early Mesozoic,but not distinct since the Early Jurassic.The exhumation of the basement crystalline rocks and absence of the Meso-Neoproterozoic and Paleozoic sedimentary rocks in the IMPU and widely distribution of the Meso-Neoproterozoic and Paleozoic sedimentary rocks in the Yanshan fold-and-thrust belt are likely a result of these strong differential uplift and exhumation during the Late Paleozoic to Early Mesozoic.The strong uplift and exhumation of the IMPU were achieved during the Late Paleozoic to Early Mesozoic,and its central-eastern part likely underwent more uplift and exhumation than its eastern part.The strong uplift and exhumation of the IMPU and the differential uplift and exhumation between the IMPU and the Yanshan fold and thrust belt were likely related to the southward subduction of the Paleo-Asian oceanic plate beneath the NCB,collision between the Mongolian arc terranes and the NCB,and movement of the regional faults such as the Pingquan-Gubeikou- Chicheng-Shangyi fault and the Chifeng-Weichang-Duolun fault during this period.The strong uplift and exhumation of the Yanshan fold-and-thrust has been achieved since the Late Jurassic-Early Cretaceous.Since this period,both southern and northern parts of the northern NCB have undergone distinct uplift and exhumation,which was likely related to the strong crustal extension of the northern NCB and the eastern China.