Parental magmas of mafic layered intrusions: Using an updated COMAGMAT model for calculations of sulfide-silicate cotectics during their crystallization

摘要

1 Introduction25 years ago we proposed a petrologic technique (called geochemical thermometry) designed to resolve inverse problems for mafic igneous rocks, including estimates of the initial temperature, trapped liquid and mineral compositions, as well as original modal proportions, as "recorded" by the whole-rock chemistry (Frenkel et al. 1988; Ariskin, 1999) . This method is based on an assumption that any crystal-liquid mush that produces a completely crystalline rock should pass through a stage when relative movements of solids and interstitial liquid have ceased, so that the system may be considered as closed. In this case, it is theoretically feasible to calculate all thermodynamic parameters for the initial system, using phase equilibria models designed for the calculation of equilibrium melting/crystallization relations in igneous rocks. In this paper we present results of applications of this approach for modeling the composition of parental magmas of several mafic layered intrusions, followed by quantification of sulfide-silicate cotectics during crystallization of these parents.