岩石圈下层塑性流动网带的剪切热效应

SHEAR-HEATING EFFECT OF PLASTIC-FLOW BELTS IN THE LOWER LITHOSPHERE

基于“网状塑性流动”大陆动力学模型和中国大陆大地热流的分布特征,文中针对网带黏性剪切热效应的平衡态,通过热力学能量方程的求解,导出网带温度异常方程等关系式,并通过与网带热流正异常的拟合分析,确定了相关的参数值。研究表明,塑性流动网带黏性剪切热的产生为温度的正异常提供了热源,并通过热传导扩展网带的影响范围,形成相应的热异常网带。作为对中东亚塑性流动网络系统平均状况的估计,网带的热异常宽度与地震带所显示的网带视宽度一致,约为65km;剪切网带的宽度为44km,约为网带热异常宽度的23;网带中线处的温度正异常约为210K,剪切网带边界处的温度正异常约为67K,至热异常带边缘处降低为零,其起伏形态与网带大地热流正异常“凸峰”相一致。文中为岩石圈下层塑性流动网络的存在及其对大地热流正异常分布的控制提供了理论依据。

Based on the ＂ Netlike plastic-flow＂ model for continental dynamics and the distribution of terrestrial heat flow in the China continent, the balanced state of viscous shear-heating effect of plastic-flow belts （PFBs） is analyzed in the paper, involving the establishment of the equations of PFB-induced temperature-anomalies by solving the energy equations of thermal dynamics and the determination of the relevant parameters by fitting the positive heat-flow-anomalies of PFBs. It is shown that the viscous shear-heating of PFB provides a thermal energy source for positive temperatureanomalies and results in the enlargement of PFB-affected width by heat conduction. It is indicated as an estimation of the average situation for the Central-Eastern Asia （CEAs） plastic-flow network system that the thermal-anomaly width of PFB is identical with the average apparent-width of PFBs manifested by seismic belts, being approximate to 65km; the shear width of PFB is equal to 44km, about 2/3 of the thermal-anomaly width ; the form of the positive temperature-anomaly distribution curve as a result of the analysis is consistent with that of the positive heat-flow anomaly ＂peak＂ controlled by PFBs ; the positive temperature anomalies at the mid line and boundary of PFB are about 210K and 67K respectively and decrease to zero at the boundary of the thermal-anomaly belt affected by PFB. The results of this study give a theoretical verification for the existence of plastic-flow network in the lower lithosphere and the effect of PFB on the positive anomalies of terrestrial heat-flow.