Juraj Butek , Sébastien Fabre , Stéphanie Duchene , Ján Spišiak , Michel Grégoire
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引用次数: 0
Abstract
Rodingite is a Ca-rich and Si-poor metasomatic rock commonly occurring in association with serpentinites. This rock is characterized by specific mineral assemblages consisting of hydrated garnet, diopside, vesuvianite, epidote-zoisite, chlorite, or prehnite. However, natural rodingites are significantly heterogeneous in mineral composition and vesuvianite occurs only in some extensively rodingitized rocks. Major factors controlling the mineral diversity as well as details on fluid-rock interactions leading to the evolution of mineral and chemical composition during rodingitization have not yet been fully constrained. In this work, we use PHREEQC software to present a geochemical model for the transformation of a mafic rock into vesuvianite-bearing rodingite at a temperature of 300 °C. Through these simulations, we investigate the effect of fluid composition and progress of the metasomatic process on rodingite formation. Our results show that rodingitization requires an open system with a high input of hydrothermal fluid. Additionally, a decrease in the Si/Ca ratio in the metasomatized rock is correlated to an increase in the volume of incoming fluid. Whole rock chemical and mineral composition in natural rodingites are well reproduced by the model. Furthermore, the diversity of mineral parageneses results mainly from different degrees of transformation and only to a lesser extent to the chemical composition of hydrothermal fluid or protolith. The hydrothermal fluid doesn't need to be especially rich in calcium to transform a mafic rock into rodingite, but it must be low in magnesium, silicon, and have a high pH, which is naturally controlled by serpentinization of surrounding ultramafic rocks.
期刊介绍：
Chemical Geology is an international journal that publishes original research papers on isotopic and elemental geochemistry, geochronology and cosmochemistry.
The Journal focuses on chemical processes in igneous, metamorphic, and sedimentary petrology, low- and high-temperature aqueous solutions, biogeochemistry, the environment and cosmochemistry.
Papers that are field, experimentally, or computationally based are appropriate if they are of broad international interest. The Journal generally does not publish papers that are primarily of regional or local interest, or which are primarily focused on remediation and applied geochemistry.
The Journal also welcomes innovative papers dealing with significant analytical advances that are of wide interest in the community and extend significantly beyond the scope of what would be included in the methods section of a standard research paper.
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