Abstract:

With the statistic results about a total of 392 geothermal gradient values and 234 heat flow values, the geothermal gradients range from 2.94℃/hm to 5.22℃/hm with an average of 3.91±0.74℃/hm, and the heat flow values vary from 24.2 mW/m² to 121 mW/m² with an average of 77.5±14.8 mW/m² in the deep-water area of the northern South China Sea. The present geothermal field in the deep-water area of the northern South China Sea is characterized with "hot basin". The heat flow value increases from continental shelf to continental slope against the trend of the crust thickness, its distribution is also characterized with prominent local anomalies. The "hot basin" in the deep-water area of the northern South China Sea might be a result of the combination of the Cenozoic lithospheric thinning with the magma activities and faulting during the Neotectonic event. The variation trend of heat flow value was controlled by the magnitude of the lithospheric thinning. The magma activities and faulting during the Neotectonic period might be the main factors for the existence of the local anomaly of heat flow value.

Key words: northern South China Sea, deep-water area, geothermal gradient, heat flow value, lithospheric, magma activity, faulting

摘要：

对392个地温梯度数据和234个大地热流数据的统计结果显示:南海北部深水区地温梯度为2.94～5.22℃/hm,平均为3.91±0.74℃/hm;大地热流值为24.2～121mW/m²,平均为77.5±14.8mW/m²。南海北部地区现今地温场具"热盆"属性,且深水区比浅水区更"热"。大地热流总体变化趋势为:从陆架到陆坡(从北到南)逐渐增高,且增高趋势与地壳减薄趋势一致,同时,平面上存在显著的局部异常点。新生代岩石圈拉张减薄以及新构造运动引发的岩浆、断裂活动是南海北部深水区具"热盆"特征的根本原因,南北向岩石圈减薄程度控制了大地热流总体变化趋势,新构造运动引发的岩浆与断裂活动则是局部热流异常形成的根本原因。

关键词: 南海北部, 深水区, 地温梯度, 大地热流值, 岩石圈, 岩浆活动, 断裂活动