A mathematical model of trace element and isotopic behavior during simultaneous assimilation and imperfect fractional crystallization

作者：Nishimura Koshi^*

来源：Contributions to Mineralogy and Petrology, 2012, 164(3): 427-440.

DOI：10.1007/s00410-012-0745-5

• AFC
• Imperfect fractional crystallization
• Crystal isotope stratigraphy
• Geochemical modeling
• Sr isotopes

The process of coupled assimilation and fractional crystallization (AFC) is one of the most popular petrogenetic concepts that explains magmatic differentiation. Conventional geochemical models for this process assume that crystals are removed instantaneously from the magma body as they are produced; however, recent advances in isotopic microanalysis have clarified that the crystals are suspended within the magma body for a certain period, affecting the whole-rock composition in response to the intra-grain isotopic zoning. This study develops a mass balance model for simultaneous assimilation and imperfect fractional crystallization (AIFC) to describe the effects of suspended crystals on the path of magma evolution. The mass balance differential equations for the liquid and suspended crystals are solved simultaneously. The analytical solution of the AIFC equations gives a quantitative account of the evolution paths of trace elements and isotopes within bulk crystals, liquid, and magma (crystals plus liquid). The chemical path of the magma differs markedly from that predicted by the conventional AFC model.

• 出版日期2012-9