活动海岭俯冲与岛弧火山活动的热模拟研究

THERMAL MODELING OF ACTIVE RIDGE SUBDUCTION AND ARC VOLCANISM

为解释活动海岭的俯冲会造成岛弧火山活动的间断这一现象，本文采用有限单元法对活动海岭俯冲的热演化过程进行了模拟计算．一般情况下，摩擦剪切生热使岛弧下100km左右深度形成地温反转，俯冲板片海洋地壳内角门岩等含水矿物脱水，释放的水进入其上覆板块，降低了地幔岩石的熔点，使热的地幔楔状体内发生部分熔融，形成岛弧火山活动．高温的活动海岭俯冲时不再出现这种温度反转，俯冲板片在较浅深度达到较高温度而脱水，水进入上覆相对较冷的地幔楔状体不能造成熔融，因此岛弧火山活动会中断．

In order to explain the cessation of arc volcanism during subduction of activeridges, we make finite element modeling on its thermal evolution. It is found that innormal cases frictional heating may produce inveded geotherms at 100 km depth,water released from amphibolite in subducted oceanic slab diffuses up to the overiyinghot mantle wedge, reduces the solidus, and results in partial melting for arcvolcanism .However, such inverted geotherm does not appear when hot active ridge issuboucted, the subducting slab dehydrates at shallower depth, but the ovenidingmantle wedge is at cooler temperature lower than the solidus, partial melting isprevented and volcanism stops during the active ridge subduction.