Fractal analysis and thermal‐elastic modeling of a subvolcanic magmatic breccia: The role of post‐fragmentation partial melting and thermal fracture in clast size distributions
Fractal analysis and thermal‐elastic modeling of a subvolcanic magmatic breccia: The role of post‐fragmentation partial melting and thermal fracture in clast size distributions
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次火山岩浆角砾岩的分形分析和热弹性建模：破碎后部分熔融和热断裂在碎屑尺寸分布中的作用
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发表时间：
2012
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Z.
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作者：
Samuel G. Roy;S. E. Johnson;P. Koons;Z.
本文利用分形分析和热弹性模型研究了位于花岗岩侵入体接触面沿着的次火山岩浆角砾岩的发育。角砾岩的等级从邻近未破裂主岩的碎屑支撑的角状碎屑到邻近侵入体的花岗岩基质支撑的孤立的圆形碎屑。现场观察表明，爆炸角砾岩机制，碎屑粒度分布分析得出的分形维数（Ds > 3）超过了已知的最小值，导致爆炸（Ds > 2.5）。现场观测、碎屑粒度分布数据、碎屑圆度数据和边界粗糙度分维数据表明，碎屑的尺寸和形状反映了部分熔融和热断裂引起的角砾化后的改性。采用数值模拟来探讨可能的热弹性效应对碎屑粒度分布的影响。瞬时浸泡假定为一个过热的花岗岩基质中的分形尺寸分布的变质沉积岩碎屑为不同的基质体积百分比。热分析仅限于潜热校正的传导热传递。变质沉积碎屑的部分熔融是一个有效的二次改性过程，可能是负责显着改变碎屑人口的侵入体附近的碎屑粒度分布。由于瞬时热脉冲，具有高表面积与体积比的角状碎屑优先破裂，因此展布碎屑经历了后期破裂，尽管该过程似乎并没有明显影响碎屑粒度分布。
This paper examines the development of a subvolcanic magmatic breccia located along the contact of a granitic intrusion using fractal analysis and thermal‐elastic modeling. The breccia grades from clast‐supported, angular clasts adjacent to unfractured host rock to isolated, rounded clasts supported by the granitic matrix adjacent to the intrusion. Field observations point to an explosive breccia mechanism, and clast size distribution analysis yields fractal dimensions (Ds > 3) that exceed the minimum value known to result from explosion (Ds > 2.5). Field observations, clast size distribution data, clast circularity data, and boundary roughness fractal dimension data suggest that the clast sizes and shapes reflect post‐brecciation modification by partial melting and thermal fracture. Numerical modeling is employed to explore the possible thermal‐elastic effects on the size distribution of clasts. Instantaneous immersion is assumed for metasedimentary clasts of a fractal size distribution in a superheated granitic matrix for different matrix volume percentages. Thermal analysis is restricted to conductive heat transfer corrected for latent heat. Partial melting of metasedimentary clasts is an effective secondary modification process that was probably responsible for markedly altering the clast size distribution for clast populations adjacent to the intrusion. Diabase clasts experienced late‐stage fracture due to the instantaneous thermal pulse in which angular clasts with high surface area to volume ratios were preferentially fractured, although this process does not appear to have markedly influenced the clast size distribution.