Magmatic to Solid-State Fabric Transition in a Post-Tectonic Tonalite Pluton

岩浆房是海洋和大陆岩石圈构造的重要组成部分，它深刻地影响着地壳和地幔的热力学行为。在冷却和结晶过程中，岩浆房的力学性质发生了变化，因为变形的适应能力从岩浆流动转变为固态过程。因此，要理解岩浆房的热-力学演化，了解岩浆流和固态流的相对重要性以及两者之间转换的性质至关重要。这个项目正在调查保存在墨西哥下加利福尼亚州圣何塞岩体中的这种过渡。深部岩体晚于区域变形，因此岩浆流向固态流的转变反映了岩浆室内部的动力学。这种转变在构造后的岩体中很少观察到，我们的结果将对研究更复杂的同构造例子的人有益。详细的测绘和空间定向样品的收集工作正在沿着该岩体的四条横断面进行。利用x射线成分作图、微观结构分析和电子背散射衍射研究，跟踪变形结晶岩体的化学演化过程，评价变形机制和岩浆岩理的成因。该项目将支持一名博士生和几名缅因大学的大四本科生参加，作为他们“顶点体验”的一部分。

Johnson0087661Magma chambers are an essential component in the construction of oceanic and continental lithosphere, and profoundly influence the thermal and mechanical behavior of the crust and mantle. The mechanical properties of a magma chamber change during cooling and crystallization, as accommodation of deformation changes from magmatic flow to solid-state processes. Thus, to understand the thermo-mechanical evolution of magma chambers, it is crucial to understand the relative importance of magmatic and solid-state flow, and the nature of the transition between them. This project is investigating such a transition preserved in the San Jose pluton, Baja California, Mexico. The pluton postdates the regional deformation, and so the transition from magmatic to solid-state flow reflects internal magma-chamber dynamics. Such transitions are rarely observed in post-tectonic plutons, and our results will benefit others who are working in more complex syntectonic examples. Detailed mapping and collection of spatially oriented samples is taking place along four transects in the pluton. X-ray compositional mapping, microstructural analysis and electron backscatter diffraction studies are being employed to track the chemical evolution of the deforming and crystallizing pluton, and to evaluate deformation mechanisms and the origins of the magmatic foliations. The project is supporting a PhD student, and several senior undergraduates at the University of Maine will participate as part of their Capstone Experience.