Interaction between mantle-derived magma and lower arc crust: quantitative reactive melt flow modelling using STyx

• Published in: Geological Society special publication 2019-01, Vol.478 (1), p.65-87
• Main Authors: Riel, Nicolas, Bouilhol, Pierre, van Hunen, Jeroen, Cornet, Julien, Magni, Valentina, Grigorova, Vili, Velic, Mirko
• Format: Article
• Language: English
• Subjects: Earth Sciences; Exploration & Geophysics; Geology; Mining Engineering & Extractive Metallurgy
• ISSN: 0305-8719; 2041-4927
• DOI: 10.1144/SP478.6

The magmatic processes occurring in the lowermost arc crust play a major role in the evolution of mantle-wedge-derived melt. Geological evidence indicates that mantle-derived magmas and in-situ products of lower crust partial melting are reacting in a pervasive melt system and are eventually extracted towards higher levels of the crust. Resolving the relative contribution of mantle-derived magma and partial melting products of pre-existing crust is essential to: (1) quantify crustal growth rate; (2) better understand the compositional range of arc magmatic series; and (3) constrain the chemical differentiation of the lower crust. In this study, we present STyx, a new modelling tool, coupling melt and heat flow with petrology to explore the dynamics of storage, transfer and hybridization of melts in complex liquid/rock systems. We perform three models representing a magmatic event affecting an amphibolitic lower arc crust in order to quantify the relative contribution between partial melting of the pre-existing crust and fractional crystallization from mantle-derived hydrous-magma. Our models demonstrate that most of the differentiated arc crust is juvenile, deriving from the differentiation of mantle melts, and that pre-existing crust does not significantly contribute to the total thickness of magmatic products.