Campo Morado: Jurassic/Cretaceous, Precious-and Base-Metal Volcanogenic Massive Sulphide Deposits in Guerrero, Mexico
Massive sulphide deposits occur in a north-northeast-trending, submarine, felsic volcanic ridge near the boundary of a carbonate platform to the east and a flysch basin to the west. They were formed in and near felsic domes that are surrounded by heterolithic debris and finer tuffaceous rocks that, in turn, are intercalated with sedimentary rocks. The deposits vary widely in composition, with different vertical and zonation patterns in each of five major deposits. Significant stringer mineralization zones occur in felsic domes beneath, flanking, and overlying massive sulphide deposits. Chert deposits are common above and below felsic units and massive sulphide deposits. During northeast-directed, Laramide shear deformation; rocks were folded discordantly and were compressed along two major thrust faults that truncate some of the deposits. Recent drilling in the G-9 deposit has encountered high-grade, precious- and base-metal mineralization in several basins above and bordering a small, northwest-trending felsic ridge that contains abundant, sphalerite-rich stringer zones. At G-9, relatively barren felsic domes overlie the massive sulphide deposits. Earlier exploration drill holes to the southwest were terminated in this unit and did not reach the presently interpreted target depth of the massive sulphides. This area is a major target for future exploration.