基于变参数板块模型的大洋岩石圈参数反演与岩石圈伸展成盆模拟

Inversion for oceanic lithosphere parameters and modeling of basin formation due to lithospheric stretching based on varied-parameters plate model

本文利用热导率、热容、热膨胀系数等参数随温度变化的经验表达式,在板块模型的基础上用隐式有限差分方法解非线性热传导方程,并利用北太平洋和北大西洋海底年龄与水深数据反演了大洋岩石圈厚度与底界温度等参数,结果表明大洋岩石圈的厚度在105 km左右,岩石圈底界温度在1450℃左右,这与Stein等用全球大量数据反演的结果一致.将变参数模型用到岩石圈拉张成盆的模拟中,结果表明当考虑岩石圈热参数随温度变化之后,预测的地表热沉降要大于常参数均匀伸展模型的预测量.由此我们指出:McKenzie的均匀伸展模型预测的初始沉降偏大而热沉降偏小,可能与该模型没有考虑热参数随深度(即温度)变化有关.

Based on empirical formula of heat conductivity, heat capacity and coefficient of thermal expansion varied with temperature, we adopt implicit finite difference method to calculate non-linear heat conduction equation and determine plate thickness and basal temperature of oceanic lithosphere using sea-floor ages and bathymetries of the North Pacific Ocean and the North Atlantic Ocean. The results indicate that the thickness of oceanic lithosphere is about 105km and the basal temperature is about 1450℃, which accord with the results obtained by Stein et al. When the varied-parameters plate model is applied to explore the formation mechanism of sedimentary basin due to lithospheric stretching, it can be found that the predicted subsidence derived from the varied-parameter model is greater than that derived from the original uniform stretching model. Therefore we point out that the reason for McKenzie＇s uniform stretching model to predict larger initial subsidence and smaller thermal subsidence than observed results is possibly because this model didn＇t take the dependence of lithospheric thermal parameters on depth or temperature into account.