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The southern part of the West African Craton includes the Baoulé-Mossi Domain, the world’s premier Paleoproterozoic gold province (~10,000 metric ton gold endowment). Structural, metamorphic, and geochronological data suggest gold mineralisation occurred during three episodes that span much of the Eoeburnean and Eburnean orogenic cycles. Eoeburnean orogenic and rare skarn-hosted gold deposits formed between ca. 2200 and 2135 Ma during repeated episodes of volcanism, plutonism, and shortening, which thickened the Paleoproterozoic crust. Early Eburnean orogenic and placer gold deposits formed between ca. 2110 and 2095 Ma during inversion, metamorphism, and subsequent oblique shortening of intra-orogenic basins filled after ca. 2135 Ma. This episode of mineralisation terminated when the Baoulé-Mossi Domain docked with the Archean Kénéma-Man Domain at ca. 2095 Ma. Late Eburnean orogenic and less common intrusion-related gold deposits formed between ca. 2095 and 2060 Ma during strike-slip to oblique-slip tectonics, post-collisional high-K plutonism and crustal reworking across the western and southern Baoulé-Mossi Domain. Eoeburnean gold deposits include ca. 10 % of the gold endowment of the Baoulé-Mossi Domain, whereas the Early Eburnean and Late Eburnean deposits include ca. 50–70% and 20–40%, respectively. Here, we highlight the favourable confluence of accretion-collision tectonics, involving juvenile crust formation as well as protracted magmatic, metamorphic, and deformation histories that resulted in diachronous gold events spread over at least 100 myr throughout the Baoulé-Mossi Domain.

The Higdon deposit is located on the east flank of the St. Francois Mountains, approximately 11.5 km NE of Fredericktown, MO in the Mine LaMotte-Fredericktown district of the world renown Southeast Missouri (SEMO) region of Mississippi Valley-type (MVT) deposits. It was discovered in the 1950s and an attempt to mine the deposit was made in the 1960s. In the 2000s the importance of the Higdon deposit increased after extensive exploration by The Doe Run Mining Co. revealed a larger deposit, greater Ni-Co content than initially estimated and the presence of a low grade Unconformity-type Uranium deposit, similar to those of the Athabasca Basin in Canada. The overall paragenetic sequence, stratigraphy and stratigraphic controls of the Higdon deposit resembles those present in other SEMO MVT deposits located at the east flank of the St. Francois Mountains. The stratigraphy includes the Cambrian formations: Eminence, Potosi, Derby-Doe Run, Davis, Bonneterre and Lamotte which unconformably overlies Precambrian granitic intrusions. A common feature is the presence of collapse breccias especially at the base of the Bonneterre Formation and a relatively thin Lamotte Formation. Fine-grained, disseminated sulfides of Fe, Pb, Zn, Co and Ni are hosted in the lower one third of the Bonneterre Formation and upper two thirds of the Lamotte Formation, in a series of grainstone beds, open spaces in collapse breccias, near pinch outs of the Lamotte Formation against basement highs. Disseminations and nodules of pitchblende (uraninite) occur through the entire Lamotte Formation. The Higdon deposit differs in several important ways from the deposits of the Viburnum Trend on the west flank of the St. Francois Mountains. These differences include a distinctly lower stratigraphic interval of collapse breccias and mineralization, greater abundance of Co-Ni minerals, presence of pitchblende, and a significant fault control of mineralization. Several regionally extensive high angle faults aligned parallel to the NW-striking Simms Mountain and Mine LaMotte fault systems bound the deposit, especially the high Ni-Co-U portion. Petrographic and microprobe studies at Higdon revealed a mineral paragenetic sequence of uraninite (pitchblende, within a carbon matrix), pyrite, marcasite, chalcopyrite, bravoite, siegenite, gerdorsffite, sphalerite and galena. These minerals were deposited in four different stages: (1) a U dominated stage that precipitated the pitchblende during Early Ordovician to Permian time; (2) a Fe sulfide dominated sulfide characterized by pyrite, marcasite and bravoite; (3) a Cu-Co-Ni stage dominated by chalcopyrite and siegenite, and (4) a Zn-Pb stage characterized by the precipitation of sphalerite and galena. Precambrian uraniferous granitic intrusions in the vicinity of the Higdon deposit supplied the U for the pitchblende mineralization. At Higdon the U mineralization represents an overlapping deposit in an otherwise MVT system. This required leaching by fluids migrating through the basement along high angle faults and U precipitation in a reducing environment as the fluids encountered the Lamotte Formation. The Ni and Co were possibly leached from mafic and ultramafic intrusions along the Reelfoot Rift or from the Precambrian basement and transported to the Higdon area by fluids migrating along the regional NW-trending faults. Mixing with connate Pb-Zn brines moving laterally through the Lamotte Sandstone and other permeable units may have triggered the sulfide precipitation. Finally, the Higdon deposit is anomalous in the tonnage and grade of its Ni-Co resource (0.17% Ni, 0.14% Co) with significant values contained in siegenite (30.9% Ni, 23.9% Co), bravoite (0.04% Ni, 6.3% Co), gerdorsffite (26.1% Ni, 8.0% Co) and marcasite-pyrite (0.3% Ni, 0.2% Co).