Mineralization in Layered Mafic-Ultramafic Intrusions

Abstract

Layered mafic-ultramafic intrusions (LMI) host a variety of metal deposits including chromium in chromitites; titanium and vanadium in magnetitites; scandium in clinopyroxene; and precious metals such as the platinum-group elements (PGE) and gold, and some base metals (nickel, cobalt and copper) associated with sulfide minerals. They also contain important resources of magnesium-silicate minerals (olivine, serpentine and talc) that are likely to become particularly important for the decarbonisation of our industries, economy and our daily lives. Many of these resources have real scope to become widely used for carbon capture and greenhouse gas reduction from our atmosphere in the imminent future. A range of geological processes govern how and where these elements and minerals become concentrated, or mineralized, into potentially economic deposits. In LMI, these are largely controlled by magmatic differentiation processes such as partial melting, crystallization, contamination and liquid immiscibility, and may be thought of as the culmination of four key factors: source, pathway, agent and deposition. In this chapter, we outline the current thinking behind the mineralization processes that operate in LMI and provide a synopsis of the grades, tonnages and characteristics of ore deposits in these intrusions.