The Isabal Ophiolitic Belt in Guatemala
The Izabal area contains two ophiolite complexes, the Juan de Paz-Los Mariscos (JP) and the Sierra de Santa Cruz ophiolite complex (SSC). All the known laterite deposits are located here, to the eastern end of the Motagua Suture Zone (MSZ). The MSZ represents the NW corner of the Caribbean Plate with ages of obduction ranging from post Triassic to Tertiary in a west - east direction. The geological information of the Izabal area presented in this publication is the result of the mapping efforts of the Ministry of Energy and Mines of Guatemala. This publication includes a model of the geological evolution of the complex as well as an updated stratigraphic column for Central Guatemala completed by P. Geo. Ricardo Valls. Nickel-cobalt laterites are the most important ore resource in this area. A typical laterite profile consists of 3 to 5 meters of a "Limonitic Horizon", followed by a leached zone called the "Mottled Zone", with thickness from 0 to 1 meter. The Mottled Zone contains the "Stoneline" and is usually enriched in heavy metals like gold, chromite, and platinum group metals. The "Saprolite Horizon" is located below the Mottled Zone and ranges from 7 to 10 m thick. It overlies the "Saprock" with thickness of one to two meters. The "Saprock" grades transitionally into the unaltered bedrock. Full lateritic profiles develop only over serpentinized olivine-rich rocks. Because of their young age, Guatemalan laterites still contain large amounts of magnetite. Aeromagnetic surveys are therefore effective not only as a mapping tool, but also to locate new lateritic targets. Satellite image interpretation is another technique used for the location of laterites.