Abstract title
The Geosol Izabal. A different type of nickel-cobalt laterite in Central America

Authors
different type of nickel-cobalt laterite in Central America. By: Ricardo A. Valls, P. Geo., M. Sc. (Jaguar Nickel Inc.).

Summary
The Geosol Izabal is a new Stratigraphic Unit defined by the author within the Sierra Santa Cruz (SSC) ophiolitic belt which is located to the north of Lake Izabal, in the east-central portion of Guatemala, some 140 km northeast from Guatemala City. The Geosol Izabal is composed of the following five pedosols:

a. Gossan or Iron Cap (a.k.a. Ferricrete)

b. Limonitic Horizon

c. The Stone Line Horizon

d. Mottled Zone Horizon (a.k.a. Transition Zone)

e. Saprolitic Horizon.

The Saprolitic Horizon lies over a Saprock Horizon, which lies directly over a less weathered bedrock of the SSC ophiolitic belt. The most complete profiles are usually present over weathered dunites and serpentinites, while on top of the less altered pyroxenites there usually is the formation of only a limonitic zone.

The SSC ophiolitic belt overthrust the Maya Block of the North American Continental Plate during the Early Tertiary age along a flat structure that outcrops at its base. The SSC is one of the five ophiolitic belts identified to date in Central Guatemala that are related to the northern border of the Caribbean Plate, and therefore are related to the ophiolitic belts from Cuba and Dominican Republic.

The intrusives of this belt are composed by alternating layers of dunites and pyroxenites, usually strongly serpentinized. Existing data indicate that these rocks underwent fractional crystallization and probably some degree of magma mixing and contamination prior to their main tectonic event.

The Izabal Geosol represents an immature wet laterite profile, which develops mainly as large pockets controlled by tectonics and the presence of dunitic rocks. The most striking difference with the wet laterites of Cuba and the Dominican Republic is the presence of up to 30% of magnetite, which is another indication of the relative young age of these laterites. This magnetite, which carries nickel grades of 1.5 to 2%, could represent a secondary product for a plant producing ferro-nickel or steel products.

The relative complexity of the SSC ophiolitic belt explains the variety of mineral resources in the area, which include Ni-Co-Fe ores, chromites, bauxite, MgO, and has the potential for gold and PGM.