MESOTHERMAL, OROGENIC GOLD MINERALIZATION IN GUATEMALA

Mesothermal, orogenic gold mineralization is represented by gold-arsenic (+/- antimony) quartz (+/- feldspar) veins occurring in the Jurassic-Cretaceous Tambor Formation in central Guatemala. The ophiolitic Tambor Formation, including sea-floor basalt, chert, graphitic shale, siltstone, and limestone, that have been variably metamorphosed to greenstone, phyllite, and marble, has been subjected to multiple phases of ductile and brittle deformation. These rocks crops out in a >100 km long by 20 km wide zone between the Motagua and Jocotán faults. The Tambor Formation is interpreted as part of an orogenic belt formed by the oblique collision of the Chortís and Maya blocks in the late Cretaceous to early Tertiary. Mineralized quartz veins appear to post-date ductile deformation. Veins are interpreted as mesothermal based on textural evidence, lack of obvious vertical zonation, and fluid inclusion studies. The mesothermal veins may be further classified as orogenic gold deposits, comparable in style to Reefton, New Zealand; Victoria Gold Fields, Australia.