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晕的导热模拟，包括侵入体热演化的数值(有限差分)模拟。我们将在这个模拟中考虑的变量包括：侵入体的形状(包括二维和三维模拟)、侵入体和围岩的初始温度、岩浆结晶的潜热、岩浆对流、岩石的热扩散率以及在光环内发生的吸热变质反应。由于这些岩石中的矿物温度计对温度场提供了很好的约束，因此含有变质泥岩岩性的接触光环是研究这些热过程的极好场所。我们提出的研究的一个主要目的是将我们的传导模型应用于接触光环的热发展，并将我们的结果与对侵入岩和光环岩石的独立测温进行整合和比较。我们对缅因州渥太华和丘比特光环的初步二维传导模型表明，我们拟议的研究将对侵入岩和周围热晕的性质产生相当大的洞察力。例如，我们对这些光环的模拟提供了对侵入岩中最初存在的晶体百分比的限制。英格兰湖区的斯基多光环为评价侵入岩屋顶上的接触变质作用提供了一个极好的机会。我们对这个日冕的模拟可能会为我们提供更多关于对流流体循环在侵入体上方接触日冕的热演化中所起作用的重要见解。苏格兰南部Strontian光环的模拟不仅将提供对被变质岩覆盖的“蘑菇状”侵入体周围接触变质作用的热演化的分析，而且还有助于深入了解Lasaga(1986)对Strontian光环中第二个硅线石等值线的挑衅性动力学解释。

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.