【摘要】 居里面是岩石中铁磁性矿物因温度升高达到居里点而由铁磁性变为顺磁性时的温度界面,在这个面以下的岩石由于温度超过居里点而被认为几乎无磁性。1985年中美双船地震扩展排列东剖面(ESPE)和1993年中日合作海底地震仪剖面(OBS93)均穿越南海东北部各主要构造带和盆地,获得了完整的地震及重、磁资料。通过上述剖面的磁测异常反演出其磁居里面,同时由热流探测资料计算其地温场并从中获取了热居里面(575℃等温面)数据(热居里面是笔者相对于磁居里面而提出的一个新概念,即指由海底热流探测资料经地温场模拟而获得的居里面)。研究结果表明,两种方法得到的居里面深度在很多地区并不一致,表现出显著的差异。笔者认为造成这种差异的主要原因在于,在有可能存在未知热事件的地区,计算稳态地温场的前提条件并不成立,因而由这种方法计算出来的热居里面在这些地区并不能真正反映居里面的深度,从而形成了它与磁居里面的显著差异。通过计算研究区磁及热居里面并根据其差异可以快速判定该区下部是否存在10Ma以来的热侵事件以及是否有浅层热源,这对于研究南海东北部新生代含油气盆地深部结构及沉积充填特征与烃源岩成熟生烃作用以及油气运聚成藏规律和油气资源潜力评价等,均具有重要的油气地质意义和地球科学意义。更多还原

【Abstract】 Curie point isotherm is the temperature isotherm where ferromagnetic minerals in the rocks change from ferromagnetism into paramagnetism because the temperature increases to the Curie point. Below this isotherm,the rocks are thought to be almost non-magnetism because their temperature is higher than the Curie point. Sino-US two-ship expanding spread profiles eastern transect (ESPE) in 1985 and Sino-Japan Ocean Bottom Seismography profile in 1993 (OBS93) crossed the major structural belts and basins in the northeastern South China Sea. Integral gravity,magnetic,heatflow and seismic data were acquired along these profiles. Magnetic Curie point isotherm was obtained by inversion of the magnetic anomalies,and thermal Curie point isotherm (the 575℃ isotherm) was obtained according to the geothermal temperature field calculated from the heatflow survey data. The results showed that the two Curie point isotherms derived respectively from the prior two methods were inconsistent with significant differences in many regions. After analyzing their calculation principle,the authors believed that the reason for these differences was that the prerequisite calculating the stable-state geothermal temperature filed was untenable in some areas with possible unknown underground heat events,then the thermal Curie point isotherm derived from this method would not show the actual Curie point isotherm in such areas. In order to explain these differences more clearly,the authors introduced the concept of thermal equilibrium,which showed that the two types of Curie point isotherm were consistent in thermal equilibrium region and inconsistent in thermal disequilibrium region. As a result,they could achieve the magnetic and thermal Curie point isotherm first in some areas and distinguish the unknown underground heat events from their differences,which has important instructional significance and reference value for the study on regional tectonics,oil and gas geological conditions and resource predictions.更多还原