弧盆成因探讨

弧前盆地和弧后盆地有着同样的成因,是俯冲洋壳2次脱水的产物。第一次是洋壳的孔隙水脱出导致弧前盆地的形成,第二次是洋壳的晶间水脱出导致弧后盆地成盆。根据物质的热胀冷缩原理,用岩石膨胀因素分析弧盆的成因,实测了6种火成岩的膨胀率。根据膨胀率,模拟计算了弧盆的三维膨胀长度、一维弦张长度和沉降幅度。讨论了脱水过程、陆陆俯冲、岛弧弧形的成因和盆地的成因等问题。认为弧盆的形成和演化是3种力作用的结果:一是岩石体积膨胀作用的三维膨胀力,二是重力沉降作用的一维弦张力,三是洋壳俯冲作用的挤压力。

Origins of the Arc Basin

Arc basin refers to the fore-arc basin and back-arc basin,these have the same origin for their formation due to two periods of dehydration of the subducted oceanic crust.In the first period,the fore-arc basin is shaped due to dehydration of the intergranular water of oceanic crust,and in the second period,the back-arc basin is shaped due to dehydration of the intercrystal water of oceanic crust.Based on the principle of thermal expansion and cold contraction of the substances,this paper presents an in-depth analysis of the factors of the arc basin’s origin with measured six types of volcanic rocks’ expansion coefficients,by which 3-D expansion length,1-D string expansion length and subsiding scope are calculated and discussion of the dehydration process,continental subduction,origins of island arc and basin,etc.It is shown that the formation and evolution of the arc basin are the consequences of three types of forces,namely,the 3-D expansion force of rock volumetric expansion action,the 1-D string tensile force of the gravitational settling action and the compressive force of the oceanic crust subduction.