Exploration Strategies For Skarn Deposits – Examples From Ertsberg, Antamina, And Other Giant Deposits

Lawrence D. Meinert

Department of Geology
Smith College
Northampton, MA 01063, USA
 

Skarn deposits are one of the more abundant ore types in the earth's crust, and form in rocks of almost all ages. Skarn is a relatively simple rock type defined by a mineralogy usually dominated by calc-silicate minerals such as garnet and pyroxene. Although the majority of skarns are found in lithologies containing at least some limestone, they can form in almost any rock type during regional or contact metamorphism and from a variety of metasomatic processes involving fluids of magmatic, metamorphic, meteoric, and/or marine origin. Although most are found adjacent to plutons, they also can occur along faults and major shear zones, in shallow geothermal systems, on the seafloor, and at lower crustal depths in deeply buried metamorphic terranes. Thus, neither a pluton nor limestone is necessarily required to form skarn. Most skarn deposits are zoned, and the general pattern is proximal garnet, distal pyroxene, and minerals like wollastonite, vesuvianite, or massive sulfides/oxides near the marble front. Recognition of distal alteration features such as bleaching, fluid escape structures, and isotopic halos can be critically important in exploration. Because most economic skarn deposits are related to magmatism, details of igneous petrogenesis and tectonic setting form a framework for exploration and classification.