Fenix Project > Geological Setting

The Fenix nickel-cobalt deposits are in lateritic weathering profiles that have formed on ophiolitic peridotites thrust into place during the early Tertiary. The laterites developed during the late Tertiary era through prolonged tropical weathering of the ultramafic bedrock.

The ultramafic rocks of the Lake Izabal region lie in the vicinity of a major transform fault zone stretching from here through Jamaica to the southern peninsula of Hispaniola. The transform fault, which is thought to have a left lateral displacement of about 1,300 km, comprises two branches, the Polochic-Chixoy fault system through Lake Izabal and the parallel Motagua fault in the large valley south the Sierra de Las Minas. These faults curve from their trans-Caribbean ENE trend into a WNW trend across the highlands of Guatemala to parallel the Americas trench off the Pacific coast. The ophiolitic rocks are in fault contact with limestones and other sedimentary rocks of the North American tectonic plate.

Lake Izabal occupies a graben in a pull-apart basin along the Polochic-Chixoy fault system, and the terraces hosting the deposits appear to represent small down-dropped blocks flanking the main structure. Some of the terraces in the La Gloria area are clearly separated from the higher terrain to the north by marked topographic lineaments that probably represent such faults. The ultramafic rocks are predominantly harzburgite (ca. 80% olivine + 20% orthopyroxene). In the mine area there are minor (<5%) small (several meter scale) bodies of dunite and pyroxenite. The ultramafic rocks are strongly jointed and are cut by zones of serpentinite matrix breccia. Most show moderate to intense serpentinization which is related to the fundamental control of the level of nickel enrichment.