New Mexico Geological Society Annual Spring Meeting — Abstracts

Historically, Ghana has relied mostly on gold, bauxite, and manganese as the major contributors to the domestic economy. Further investigation into other minerals to transform the mining sector in Ghana focused on detailed geologic field mapping and sampling. The Buem Formation of eastern Ghana, previously unrecognized as a potential source for ore deposits, was found to host banded iron formation. Banded Iron Formations (‘BIFs’) are chemical precipitates characterized by the presence of alternating layers of iron-rich and amorphous silica-rich layers.
The Buem Group comprises a complex series of metasedimentary, volcaniclastic, and volcanic rock units, including poorly-defined banded iron formation occurrences. This study reports our initial petrographic observations and economic assessment of the Gyamurume – Wawase Range, one of the host regions for BIF. Petrographic studies show that stratigraphic contacts between dominantly hematitic ferruginous horizons and siliceous strata are distinctly sharp and abrupt. Most hematite comprises micron-scale, irregular grains interstitial to granular, undulatory-extinction quartz; cross-cutting coarse quartz veinlets are barren of iron oxides. Although some BIF strata show former magnetite skeletal textures, even cm-scale ferruginous strata show only trace residual or relic magnetite. Initial studies of the mineralogical composition of Beum Formation BIF show that hematite is abundant, with nominal or no magnetite. No other silicate minerals are observed. Continued studies will assess the trace element contents of Beum Formation iron minerals, with emphasis on the P and Ti contents on hematite-dominant strata as a means of distinguishing low-contaminant, potentially economic horizons.