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
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.