Thermal regime transition in eastern North China and its tectonic implication  

作　　者：FU Mingxi HU Shengbiao WANG Jiyang 

机构地区：[1]Institute of Geology & Geophysics, Chinese Academy of Sciences, Beijing 100029, China Institute of Geology & Geophysics, Chinese Academy of Sciences, Beijing 100029, China Institute of Geology & Geophysics, Chinese Academy of Sciences, Beijing 100029, China

出　　处：《Science China Earth Sciences》2005年第6期840-848,共9页中国科学（地球科学英文版）

基　　金：the Chinese Academy of Sciences(Grant No.KZCX1-07); the National Basic Research Programme(973)(Grant No.G1999075504); the National Natural Science Foundation of China(Grant No.40172100).

摘　　要：The pre-Cenozoic formation in the Cenozoic depositon centres in eastern North China reached its maximum temperature at present, and the earlier paleo-temperature, therefore, has been overprinted, but the record of paleo-temperature by the vitrinite reflectance (Ro) has not been overprinted by the later thermal events in the pre-Cenozoic formation located in the uplift or in the Paleozoic-Mesozoic residual basins out of the Cenozoic depositon centres. The reconstruction of paleo-temperature gradient and paleo-heat flow, based on the vitrinite reflectance in the Paleozoic and the Mesozoic structural layers in boreholes, indicated that the eastern North China was characterized by much higher paleo-temperature gradient (40-55℃/km) and heat flow (>80 mW/m2) during the Middle-Late Mesozoic than those in the Early Mesozoic and at present. The higher paleo-heat flow during the Middle-Late Mesozoic implies that the thickness of the 'thermal' lithosphere at that time was just 50-55 km, it had been much thinned relative to the thickness (135-148 km) at the Early Mesozoic. The transition of near-surface thermal regime in eastern North China occurred around 110 Ma, and the corresponding deep tectonothermal processes should take place at ~160 Ma.The pre-Cenozoic formation in the Cenozoic depositon centres in eastern North China reached its maximum temperature at present, and the earlier paleo-temperature, therefore, has been overprinted, but the record of paleo-temperature by the vitrinite reflectance (Ro) has not been overprinted by the later thermal events in the pre-Cenozoic formation located in the uplift or in the Paleozoic-Mesozoic residual basins out of the Cenozoic depositon centres. The recon-struction of paleo-temperature gradient and paleo-heat flow, based on the vitrinite reflectance in the Paleozoic and the Mesozoic structural layers in boreholes, indicated that the eastern North China was characterized by much higher paleo-temperature gradient (40-55℃/km) and heat flow (>80 mW/m2) during the Middle-Late Mesozoic than those in the Early Mesozoic and at present. The higher paleo-heat flow during the Middle-Late Mesozoic implies that the thickness of the “thermal” lithosphere at that time was just 50-55 km, it had been much thinned relative to the thickness (135-148 km) at the Early Mesozoic. The transition of near-surface thermal re-gime in eastern North China occurred around 110 Ma, and the corresponding deep tectono-thermal processes should take place at ~160 Ma.

关 键 词：EASTERN North China  THERMAL regime  paleo-heat flow  "thermal" LITHOSPHERIC thickness  THINNING of litho-sphere. 

分 类 号：N[自然科学总论]