Heat flow in northwest Pacific marginal seas

摘要

Heat flow studies in Northwest Pacific marginal seas has a more than 40 years history with more than 4000 heat flow values obtained. The regional average value is 80.4 mW/m~2, which is lower than the world's 87 mW/m~2, but higher than those of the Eurasia continent and the Pacific Ocean. This reflects the regional crust property in the area. The studies on distribution of the heat flow and contour pattern of heat flow in 1° X 1° and 2° X 2° scales in Northwest Pacific marginal seas revealed that the most high heat flow anomalies in the area were found along back-arc basins and island arc in an obviously northeasterly track. Exceptions are the Koman-doskaya Basin (KMB), the Izu-Bonin Trough (IBT) and the Mariana Trough (MT), which extend in northwest. The contours of low heat flow marked the boundaries of the continent and the ocean. The present heat flow values reflect the imprint of the last thermal event and relate closely to tectonic activity. The high heat flow gradient areas have high frequency of earthquake. Therefore, the area of faulting controlled the pattern of the heat flow anomalies. Heat flow gradient in 135° direction indicated a major lithosphere transformation ocean-ward resulting from movement of the earth's material. In this paper, we described patterns of heat flow distribution in the Northwest Pacific, heat flow value changes in horizontal and vertical directions, combining the studies of Shi (1997) on the landforms of the island arcs in east Asia and plate movement, and the results of Shi and Zhang (1998) on heat simulation of subduction of active ocean mountain and the activity of islands arc. A preliminary model of geodynamics in the Northwest Pacific and its adjacent area was put forward. There is a great lateral heat flow gradient on the surface of the mantle between ocean and continent, which indicates that the materials in asthenosphere move from continent to ocean causing movement of the crust.