Thermal Modeling Applied to the Evolution of Contact Metamorphic Aureoles

提出了用计算机算法进行接触变质光晕的传导热模拟，包括侵入物热演化的数值（有限差分）模拟。我们将在此建模中考虑的变量包括：侵入体的形状（二维和三维建模），侵入体和岩石的初始温度，岩浆结晶的潜热，岩浆对流，岩石的热扩散率，以及发生在光圈内的吸热变质反应。含有变质岩岩性的接触光晕是研究这些热过程的绝佳地点，因为这些岩石中的矿物温度计提供了对温度场的良好约束。我们提出的研究的一个主要推力是将我们的传导模型应用于接触光圈的热发展，并将我们的结果与侵入物和光圈岩石的独立测温结果进行整合和比较。我们对缅因州渥太华和cup - suptic光圈的初步二维传导模型表明，我们提出的研究将对侵入物和周围热光圈的性质产生相当大的见解。例如，我们对这些光晕的建模提供了最初出现在侵入物中的晶体百分比的限制。英格兰湖区的斯基多光圈为评估侵入岩顶部的接触变质作用提供了极好的机会。我们对这个光圈的建模可以为我们提供对对流流体循环在侵入体上方接触光圈热演化中的作用的额外重要见解。提出的苏格兰南部斯特朗田光环的建模不仅可以分析变质岩覆盖的“蘑菇状”侵入体周围接触变质作用的热演化，而且还可以加深对Lasaga（1986）对斯特朗田光环中第二个硅线岩等格拉德的激动性动力学解释的理解。

It is proposed to carry out conduction thermal modeling of contact metamorphic aureoles with computer algorithms involving numerical (finite difference) simulations of the thermal evolu- tion of intrusives. Variables that we will be considered in this modeling include: shapes of intrusions (both two- dimensional and three-dimensional modeling), initial temperature of the intrusion and country rocks, latent heat of crystalliza- tion of the magma, magma convection, thermal diffusivities of the rocks, and endothermic metamorphic reactions occurring within the aureoles. Contact aureoles containing metapelitic lithologies serve as excellent locales to investigate these thermal processes because mineral thermometers in these rocks provide good constraints on the temperature field. A primary thrust of our proposed research is to apply our conduction modeling to the thermal development of contact aureoles, and to integrate and compare our results with independent thermometry of the intru- sives and aureole rocks. Our preliminary two-dimensional conduction modeling of the Ottawa and Cupsuptic aureoles in Maine shows that our proposed research will yield considerable insight into the nature of intrusives and the surrounding thermal aureoles. For example, our modeling of these aureoles provides constraints on the percentage of crystals initially present in the intrusives. The Skiddaw aureole in the Lake District of England provides an excellent opportunity to evaluate contact metamorphism overlying the roof of an intrusive. Our modeling of this aureole may provide us with additional important insight into the role of convective fluid circulation in he thermal evolution of contact aureoles above intrusives. The proposed modeling of the Strontian aureole in southern Scotland will provide not only an analysis of the thermal evolution of contact metamorphism around a "mushroom-shaped" intrusion floored by metamorphic rocks, but also improved insight into Lasaga's (1986) provocative kinetic interpretation of the second sillimanite isograd in the Strontian aureole.