【摘要】 根据均衡原理制约的地热计算得到中国东部岩石圈的温度分布状态,以40、70、100km和莫霍面深度等温线图以及600°C、1100°C等温面深度的形式表示。同时计算了以1350°C等温面深度表示的中国东部的热岩石圈厚度。结果显示:在扬子克拉通西部四川盆地之下存在160～200km厚的岩石圈根,但在整个华北克拉通之下缺失岩石圈根。特别是华北克拉通西部的鄂尔多斯地区的岩石圈厚度仅130～140km,表明该地区不存在岩石圈根。在大兴安岭-太行山-武陵山重力梯度带以东地区不存在地幔柱,不支持某些学者提出的所谓"大陆根-柱构造"。本研究地热模拟计算结果与地震层析研究结果相符合得很好。中国东北部地区岩石圈减薄可能与新生代太平洋板块深俯冲导致的流体释放作用有关。采用湿的上地幔流变学模型的计算结果表明,中国东部多数地区的岩石圈流变学强度模型为"奶油蛋糕(crème brlée)"型,其强度剖面显示强地壳而弱地幔的特点。四川盆地和华北克拉通的东北部和东南部地区的岩石圈流变学强度模型为"果冻三明治(jelly sandwich)"型,其强度剖面为强地壳与强地幔。更多还原

【Abstract】 Lithospheric temperatures beneath the eastern China were estimated by local isostasy equilibrium constrained geothermal calculation in this study. Maps of the lateral temperature variation at depths of 40,70,100km and Moho boundary are presented for the eastern China,and the 600℃ and 1100℃ isotherm depth maps are also given. Meanwhile,the thermal thickness of the lithosphere is calculated as the depth of 1350℃ isotherm depth. The results show that the lithospheric root of 160~180km thick exists under Sichuan basin in the western part of Yangtze platform,but absent beneath the entire North China craton. It is notable that the lithospheric thickness is only 130~140km beneath Ordos region in the western part of North China craton; accordingly,there is no lithospheric root beneath Ordos block. Furthermore,no "mantle plumes" exist in the region east of the Daxing’anling-Taihangshan-Wulingshan Gravity Gradient Belt. These facts do not support the "continental roots-plume tectonics" argued by some scholars. These geothermal modeling results are in good agreement with those of seismic tomography and author’s previous geothermal studies. Lithospheric thinning beneath the northeastern part of China mainland (including North China craton) may be related to the volatile infiltration by dehydration of deep subducted Pacific slab; therefore,we favor the thermo-chemical erosion mechanism for the North China craton lithosphere destruction during Meso-Cenozoic. The temperatures in lower crust of the North China craton estimated are in range of 500~600℃. Accordingly,the lower crust composition of the North China craton should be more mafic than that of previously estimated based on much cooler geotherms. Using the wet mantle rheology to represent the mechanical behaviour of upper mantle,we found that the "crème brlée" model can approximate the lithospheric rheology for the most regions of eastern part of China,which is represented by strong crust portion but weak lithospheric mantle portion in vertical strength profile. On the other hand,the "jelly sandwich" model demonstrates the mechanical strength of Sichuan basin and that of northeastern and southeastern portions of the North China craton,which exhibits strong crust and strong lithospheric mantle portions in vertical strength profile.更多还原