Location & Access
Toto Range is located directly north of Gbarnga, a large township approximately 150km northeast of Monrovia on the Yekepa Highway. The area can be accessed from the southwest via the Belefenai Road off the Yekepa Highway or from the east via Foequelleh Road, which intersects the Yekepa Highway north of Gbarnga.
Toto Range covers an area of 143km2 and is dominated in the south by a low, narrow range of discontinuous hills and steep terrain which extends northeast to the international border with Guinea. A number of small towns lie within the area and two larger towns, Gbarnga and Ganta, are within a distance of 30km.
BHP Billiton conducted community consultation prior to all new access development. Where road access construction and other land disturbances impact on farmland or nurseries, the affected parties are compensated in accordance with standard crop prices set by the Ministry of Agriculture.
The Toto Range forms the southwestern part of a regional Archaean greenstone belt that extends over 50km and is characterised by variably metamorphosed mafic to ultramafic volcanic sequences along with IF and other metasediments. This belt starts northeast of Gbarnga, runs northeast into Guinea before crossing the border again to terminate in the Sanniquellie region of Nimba County, Liberia. The belt and the associated iron formation (“IF”) appear to be significantly affected by the Eburnean deformation cycles.
Toto Range is composed of poorly foliated gneiss/amphibolite to the west with a minor zone of lenticular IF, a central weakly to moderately magnetic mafic/ultramafic unit and a second gneiss/amphibolite formation to the east. A mica-tourmaline bearing pegmatite pervasively intrudes the stratigraphy. Mineral assemblages and alteration seen throughout the region are indicative of greenschist metamorphic grade.
Gneiss units are light-grey/ pink with a poorly developed foliation fabric and discontinuous pods/ lenses of mafic minerals, produced by metamorphic differentiation and are commonly sub-parallel to the foliation. Talc-carbonate alteration is pervasive throughout the stratigraphy.
Other rock types that occur at Toto Range include a white, weakly magnetic unit containing magnetite porphyroblasts; a light-green, medium-grained unit containing carbonate stringers; a moderately magnetic grey-black unit with pervasive leopard-print rosettes throughout and a strongly magnetic green-black unit that is fine-grained and massive. The composition of the latter unit is pyroxene-serpentine/actinolite-magnetite-chlorite-quartz.
Recent drilling indicates that primary source of major magnetic anomalies across the Toto Range exploration licence (“EL”) are ultramafic rocks and pegmatite intrusions.
Previous interpretation of the IF outcropping at the crest of Mount Gahn was that it formed the core of a complex, tightly-folded, upright isoclinal syncline plunging shallowly to the north. However, recent interpretation of the structural dataset combined with a lack of folding observed in drill core, opposes this theory. Instead, recent drill and mapping data indicate a steeply northwest dipping IF unit. Intense micro folding, brecciation/ mylonitisation and brittle deformation are common in proximity to banded IF.
The ultramafic package appears to be bounded by two parallel northeast–southwest trending regional structures which are distorted and complex towards Foe River in the south of the EL. The occurrence of shear zones and schistosity in drill core is thought to be related to these major structures.
The aeromagnetic survey suggests the presence of a northwest-southeast trending, late stage dyke in the south-western portion, which is seen to post-date the two parallel northeast-southwest trending structures.
At Toto Range the fresh IF is a thinly banded, fine-to-medium grained quartz-magnetite ± hematite unit. The IF is situated between gneissic bodies. Within the weathered zone, the IF consists of magnetite-goethite ±hematite and quartz; limonite and minor clays appeared as accessory minerals. IF weathering profile at Toto Range is shallow, approximately 20m, compared to that seen at the rest of the tenements. Enriched or friable IF is very scarce; very few meters of less significance were drilled and are generally associated with topographic highs.
BHP Billiton drilled 73 bore holes in order to explore the iron potential of the Toto Range tenement. Initial results were inconclusive with regard to iron ore potential, nevertheless, there are strong indications of the presence of other base and precious metals, which the company is pursuing.
Work Program 2016/ 2017
The work program for the Toto Range Exploration area will comprise of the following:
- To increase geological understanding of the Exploration Area and regional stratigraphy, including by testing of existing core;
- To confirm current interpretations and targeting methodology; it will also include;
- Selection of the best target for resource drilling and potential geology modelling; and
- Conducting a possible aerial survey, required to support internal development studies and potential mine planning.