Development of a methodology for the characterization of mafic rocks with respect to their use for mineral carbonation: the mineralogy, petrology, and geochemistry of the Portage Lake Volcanics in the Keweenaw Peninsula, Michigan

Abstract

Mineral carbonation of basalt has been proposed by various researchers to reduce anthropogenic CO₂ output without necessitating considerable reduction of fossil fuel usage. The feasibility of any mafic rock for mineral carbonation depends on the present mineralogy, texture, grain size, and alteration. The purpose of this research is the development of a methodology for the characterization of mafic rocks regarding their susceptibility for mineral carbonation, based on samples from mine tailings in the Keweenaw Peninsula, Michigan. Samples were characterized using petrographic examination, microprobe analyses, whole rock data, and thermodynamic modeling. Thin section analyses revealed several alteration assemblages ranging from relatively fresh samples to extremely altered samples. End-members of minerals present in the study area were used for thermodynamic modeling. Based on thermodynamics, anorthite, prehnite, and diopside are the most feasible minerals for carbonation, minerals potentially viable include forsterite, enstatite, talc, clinochlore, and phengite. To determine feasible minerals for carbonation, kinetic modeling should be conducted to establish minerals with realistic reaction rates. The approach outlined in this study can be used as an inexpensive and expeditious method to determine mafic samples most feasible for mineral carbonation based on thermodynamic modeling. Not all mafic rocks should be treated as basalts, nor are all mafic rocks equally feasible for mineral carbonation.