Abstract Induced-polarization (IP) electrical surveys will give excellent and conclusive response over relatively smaller massive mineral occurrences similar to the Ore Knob deposit. Reconnaissance application of the method for such size targets is still somewhat limited by cost, but when applied with geology, geochemistry, and other methods such as self-potential, magnetics, and perhaps Afmag, then IP can and should be used at least as a tool for more detail. Results did not locate any immediate extensions to the known Ore Knob deposit, but did emphasize the essential part that geophysics can play in future discovery and development of mineral deposits in the region. Some knowledge of the manner in which geophysical methods may be applied, in this environment, was acquired.

Abstract The 300-year history of the Southeast Missouri Lead District is marked by a small number of significant events which periodically re-activated exploration and development and resulted in the district being a major factor in U.S. and world lead production. These events are: 1. galena in residual clay shown to French explorers near Mine LaMotte (−1700); 2. discovery of galena in clay near Bonne Terre (−1800); 3. introduction of diamond drill (1869); 4. recognition of the ore-knob relationship; 5. downward ore circulation concept (1860 to 1930); 6. development of written core logs (1936); 7. discovery of Indian Creek Mine (1947); 8. Geology Dept. established at St. Joe Lead Co. (1947); 9. recognition of algal reefs in Old Lead Belt; and 10. discovery of Viburnum Trend (1955).

Abstract The Money Knob deposit is a major new, bulk-tonnage, gold discovery located 110 km northwest of Fairbanks, Alaska, within the Tintina gold belt. The deposit was discovered in 2007 and by the end of 2009 contained a combined indicated and inferred resource of 389 metric tons (t) of gold at a grade of 0.85 g/t gold using a 0.5 g/t gold cutoff grade. Gold mineralization is hosted within a fold and thrust sequence of Cambrian and Devonian rocks intruded by 90 Ma dikes and sills, which are contemporaneous with the main-stage gold event. Gold mineralization occurs as shallowly dipping, east-west–trending, tabular bodies within permeable sedimentary and volcanic rocks, with higher grade zones related to north-northwest–trending crosscutting structural zones. The discovery of the Money Knob deposit evolved from a series of exploration programs conducted by eight different companies during a 30-year-long period. An examination of the successes and failures during the exploration history outlines three key concepts that were important in the discovery: (1) the need to operate with multiple, working exploration models that are driven by high-quality data and observations; (2) recognition that large mineral systems are rare and should be fully evaluated in light of potential long-term changes in commodity price, technology, and deposit characteristics; and (3) successful exploration requires a champion and a talented team with vision and perseverance.

Abstract The ore deposit at the Magmont-West mine, closed in 1994 due to ore exhaustion, exhibits many of the characteristics typical of the carbonate-hosted MVT ore deposits in the Viburnum Trend in Southeast Missouri, but also shows several features that contrast significantly with those deposits and makes it an especially interesting deposit to study for its mineralogy, paragenetic sequence, mineral zoning, and genesis. The Magmont-West deposit is located 3.2 km west of the main ore deposit at the Magmont mine. It is closely controlled by narrow fracture and breccia structures that result in angular, curving, and fish-hook plan shapes of the orebody. This deposit is more closely controlled by fault structures than perhaps any other deposit in the Viburnum Trend. The ores are stratigraphically higher than most ores in the district; they are contained largely within the upper Cambrian False Davis unit. This unit is the host for 80% of the ore at Magmont-West, and most of the remaining 20% occurs just above or below the False Davis Formation. The ores have unusually high zincdead ratios, and zinc averages 3% at Magmont-West in contrast to a district-wide average of about 1%. The deposit exhibits strong and unusual mineral and metal zoning with copper to the east, zinc in the central portion, and lead on the west. Colloform iron sulfide is locally abundant, and unusual copper-nickel-arsenic ores are locally present. The undeveloped Boss-Bixby copper-iron deposit, occurs in the Precambrian basement subjacent to the Magmont-West deposit. Study of the Magmont-West ore specimens shows that most ores are composed of galena, sphalerite, chalcopyrite, pyrite, marcasite, siegenite, dolomite, quartz, and calcite. The copper-nickel-arsenic-sulfide ores are present where an east-west fault intersects the main ore trend, and they contain additional minerals, including millerite, polydymite, gersdorffite, vaesite, bravoite, and luzonite. The general mineral paragenetic sequence is: dolomite, Cu-Ni-As sulfides (earliest), euhedral disseminated pyrite crystals, rotund disseminated sphalerite crystals, chalcopyrite, yellow brown sphalerite, main- stage octahedral galena, colloform marcasite and pyrite, red sphalerite, late stage cubic galena, quartz, and calcite. The results of the study of mineral zoning and paragenetic sequence indicate that the ore-forming fluids probably initially entered the orebody along the northern portion of the northerly-trending limb where that structure is intersected by an east-west fault. Deposition of Cu-Ni-As sulfides and early chalcopyrite mark the foci of entry of the early ore fluids. Fluids subsequently migrated southward, depositing zinc sulfide, lead sulfide, and iron sulfides. Ore fluid migration was controlled principally by the pinchout of the Cambrian Lamotte and Bonneterre Formations against the buried Precambrian knob to the west (West Dome), and the narrow linear inner breccia zone, but the fluids also traveled outward in the Bonneterre Formation forming banded replacement sulfide ores.