Thermal structure beneath Far Eastern Russia inferred from geothermobarometric analyses of mantle xenoliths: Direct evidence for high geothermal gradient in backarc lithosphere
Thermal structure beneath Far Eastern Russia inferred from geothermobarometric analyses of mantle xenoliths: Direct evidence for high geothermal gradient in backarc lithosphere
复制标题
DOI：
10.1016/j.tecto.2012.06.005
复制
发表时间：
2012-07
期刊：
影响因子：
2.9
通讯作者：
J. Yamamoto;K. Nishimura;H. Ishibashi;H. Kagi;S. Arai;V. Prikhod'ko
中科院分区：
文献类型：
--
作者：
J. Yamamoto;K. Nishimura;H. Ishibashi;H. Kagi;S. Arai;V. Prikhod'ko
本文根据幔源包体的压力和温度信息，描述了位于亚洲东部火山链弧后的俄罗斯远东地区的地热。地幔捕虏体中含有丰富的CO2流体包裹体。准确测定CO2流体包裹体的内压，可对地幔捕虏体的深部物源进行估算。从五个地幔捕虏体获得的深度物源与使用地质温度计估计的平衡温度进行了相关。假设该相关性反映了该地区的地热，则其对应的热流约为100 mW/m2，与火山弧的地表热流相当。如此高的热流值意味着岩石圈较薄，浅部上地幔温度较高。弧后地区普遍具有高地表热流和近期火山活动的特点。此外，在弧后上地幔浅部，特别是亚洲东部，普遍存在低地震速度异常。现今捕虏体地温表明，地震异常是由浅部上地幔高温引起的。这将是岩石圈地幔变暖和随后的岩石圈减薄的直接证据，这可能是由于软流圈上涌。
Based on pressure and temperature (P–T) information of mantle-derived xenoliths, this report describes a geotherm in Far Eastern Russia, which is situated in the backarc of volcanic chains in eastern Asia. The mantle xenoliths have abundant CO2fluid inclusions. Accurate determination of the internal pressure of the CO2fluid inclusions enables estimation of the depth provenance of the mantle xenoliths. The depth provenances obtained from five mantle xenoliths are correlated with equilibrium temperatures estimated using a geothermometer. Assuming that the correlation reflects the geotherm in this region, it corresponds to heat flow of around 100mW/m2, which is comparable to the surface heat flow in the volcanic arc. Such high heat flow implies a thin lithosphere and high temperature of the shallower upper mantle. Backarc areas are universally characterized by both high surface heat flow and the occurrence of recent volcanic activities. Furthermore low seismic velocity anomaly is widely observed in the shallower upper mantle in the backarc, especially in eastern Asia. The present xenolith geotherm suggests that the seismic anomaly arises from high temperature of the shallower upper mantle. It would be direct evidence for warming of the lithospheric mantle and subsequent lithospheric thinning, which is likely attributable to asthenospheric upwelling.