Laboratory for Crustal Petrology, Department of Geology, University of Maryland, College Park, MD 20742-4211, USA.
Philos Trans A Math Phys Eng Sci. 2010 Jan 13;368(1910):11-51. doi: 10.1098/rsta.2009.0200.
Volumetrically significant melt production requires crustal temperatures above approximately 800 °C. At the grain scale, the former presence of melt may be inferred based on various microstructures, particularly pseudomorphs of melt pores and grain-boundary melt films. In residual migmatites and granulites, evidence of melt-extraction pathways at outcrop scale is recorded by crystallized products of melt (leucosome) and residual material from which melt has drained (melanosome). These features form networks or arrays that potentially demonstrate the temporal and spatial relations between deformation and melting. As melt volume increases at sites of initial melting, the feedback between deformation and melting creates a dynamic rheological environment owing to localization and strain-rate weakening. With increasing temperature, melt volume increases to the melt connectivity transition, in the range of 2-7 vol% melt, at which point melt may escape in the first of several melt-loss events, where each event represents a batch of melt that left the source and ascended higher in the crust. Each contributing process has characteristic length and time scales, and it is the nonlinear interactions and feedback relations among them that give rise to the dissipative structures and episodicity of melt-extraction events that are recorded as variations in the spatial and temporal patterning of the crust. Focused melt flow occurs by dilatant shear failure of low-melt fraction rocks creating melt-flow networks that allow accumulation and storage of melt, and form the link for melt flow from grain boundaries to veins allowing drainage to crustal-scale ascent conduits. Preliminary indications suggest that anatectic systems are strongly self-organized from the bottom up, becoming more ordered by decreasing the number and increasing the width of ascent conduits from the anatectic zone through the overlying subsolidus crust to the ductile-to-brittle transition zone, where the melt accumulates in plutons.
大量熔体的产生需要地壳温度高于约 800°C。在颗粒尺度上，以前熔体的存在可以根据各种微观结构来推断，特别是熔体孔隙的假像和晶界熔体薄膜。在残留的混合岩和麻粒岩中，熔体提取途径的证据在露头尺度上记录为熔体的结晶产物（白体）和从其中排出熔体的残余物质（黑素体）。这些特征形成网络或阵列，可能证明了变形和熔化之间的时间和空间关系。随着初始熔化部位熔体体积的增加，变形和熔化之间的反馈会导致局部化和应变速率弱化，从而产生动态流变学环境。随着温度的升高，熔体体积增加到熔体连通性转变点，在 2-7vol%熔体范围内，此时熔体可能在第一次熔体损失事件中逸出，每次事件代表一批离开源区并在壳层中上升更高的熔体。每个贡献过程都有其特征长度和时间尺度，正是它们之间的非线性相互作用和反馈关系导致了熔体提取事件的耗散结构和间歇性，这些事件记录了地壳空间和时间格局的变化。集中的熔体流动是通过低熔体分数岩石的扩容剪切破坏发生的，形成熔体流动网络，允许熔体积累和储存，并形成从晶界到脉体的熔体流动的连接，允许熔体向壳层尺度上升管道排水。初步迹象表明，自形作用系统从底部向上强烈自组织，通过减少上升管道的数量和增加从自形作用区到上覆亚固态地壳到韧性-脆性过渡带的宽度，变得更加有序，在那里熔体积聚在侵入体中。
