摘要
华北克拉通破坏存在空间上的差异性,至今其内在的动力学机制仍存在较大的争议,这种差异性在岩石圈热结构上必然有所表现.广义上岩石圈热结构包括热流结构、温度场结构和热岩石圈厚度,是揭示岩石圈演化及其内在动力学过程的重要基础.基于二维地震剖面和大地热流数据,建立二维稳态热传导有限元模型,对华北克拉通东部岩石圈热结构进行模拟计算并与西部进行对比分析,在此基础上对比热岩石圈与地震岩石圈厚度差异的变化.结果显示,华北克拉通东、西部岩石圈热结构有着较为明显的差异,地幔热流值波动范围分别在24~44/20.5~24.5mW·m^(-2),壳幔比1.61~0.70/1.84~1.51,以1300℃等温线计算得到的热岩石圈厚度变化范围在75~139km/128~162km.华北克拉通东部相对西部有着较高的深部地幔热流值和较小的地震/热岩石圈厚度差异,这可能意味着东部软流圈地幔有效黏度相比西部低,估算差异可达2~3个数量级.
Lithospheric thermal structure has important impact on its rheological,physical properties and also the characteristics of crustal deformation,geological evolution and distribution of earthquakes.As one of the most typical cases for relatively complete destruction of its Archean keel since Mesozoic,the lithospheric thermal structure of North China Craton（NCC）should have some change.Therefore,we implement a 2-D thermal modeling based on the surface heat flow and seismic profile data to investigate the thermal structure of NCC.Our model is based on the 2-D steady-state heat conduction equation by using the finite element algorithm in the frame of the space rectangular coordinates system.We obtain the surface heat flow data by Kriging interpolation,and then determine the lithospheric thermal structure by adjusting the mantle heat flow to fit the surface heat flow data until an acceptable solution is found.Different from the lithospheric thermal structure of the Ordos basin which is located in the western NCC,the mantle heat flow in the eastern NCC is estimated to be 24~44mW·m-2,Qc/Qmto be 1.61~0.70,which shows an obvious fluctuations and is higher than other cratons allover the world.The thermal lithospheric thickness along the seismic profile turns out to be 75~139km by defining the base of the thermal lithosphere as the 1300 ℃ isotherm.The thermal lithospheric thickness is thin in the east and becomes thicker to the west with a minimum thickness near the Tanlu fault zone.The temperature at Moho range 560~710 ℃ and has a similar trend as the thermal lithospheric thickness.Compared with the seismic and thermal lithospheric thickness in NCC,there exist nearly80~90km differences in Ordos,64 km in the Fenwei graben,but only 40 km in the Taihang Mountains and no more than 10 km near the Tanlu fault zone.There are also large differences in conductive heat flow at the base of lithosphere between eastern and western NCC.These huge changes could be attributed to the different viscosity of the asthenosphere.There are probably two to three orders of magnitude differences in the viscosity which could be caused by 11~35times water content differences if the effects of other factors are ignored.Differences in the viscosity of the asthenosphere and the lithospheric thermal structure between eastern and western NCC might be one of the reasons why the western NCC is in a relatively stable state but the eastern NCC is destructed.The research on the lithospheric thermal structure provides a clue for studying the evolution of lithosphere and can help us to reveal the thermal regime of thinning and destruction in the craton.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第10期3618-3626,共9页
Chinese Journal of Geophysics
基金
国家自然科学基金(41574075)
国家重点研发计划项目(2016YFC0601005)联合资助
关键词
华北克拉通
岩石圈热结构
地震岩石圈厚度
软流圈黏度
North China Craton
Lithospheric thermal structure
Seismic lithospheric thickness
Viscosity of the asthenosphere
