Abstract This tour begins in Rapid City and ends in Lead. Load into vans at the Hilton Hotel parking lot. The road log will begin at the South Dakota School of Mines and Technology. Follow St Joseph Street east to the campus. The route for the morning portion of the trip is shown in Figure 1.

Marysvale, Utah, is an area of special geological interest. The district is a source of consistent uranium production where ores occur in veins related to igneous activity. Here is an unusual illustration of the nature of hydrothermal alteration in connection with vein formation. The region furnishes data on the relationship between centers of igneous invasion and the sedimentary accumulations of the Colorado Plateau. The area of uranium production lies in the vicinity of the Prospector, Freedom No. 2, Bullion Monarch, and near-by workings and constitutes a zone about a mile long by half a mile wide. Numerous prospects lie in a surrounding area about 7 miles across. Ores occur throughout a vertical distance of 1500 feet as indicated by drill holes and mine workings. Hypogene uranium occurs as pitchblende associated with black fluorite and fine pyrite in breccia and distributed veinlets along veins. Nearly vertical uranium veins range from a few inches to several feet in thickness. Veins pinch and swell, and ore shoots are either vertical or exhibit a steep west rake. Supergene uranium minerals occur near the surface. Umohoite is a new hydrous uranium molybdate first discovered in the Freedom No. 2 mine. The mineral occurs in the ore-bearing vein along with pitchblende. This occurrence at depth and associated with pitchblende rather than the oxidized uranium-molybdenum minerals ilsemanite and jordisite suggests hypogene origin. Earlier hydrothermal alteration produced numerous masses of alunite which occur in the rocks of the Bullion Canyon volcanic series; these are mostly pyroxene andesite and tuff. Radioactivity is low in these masses. Later hydrothermal alteration is associated with the uranium-bearing veins. Clay minerals occur along vein zones which cut quartz monzonite or granite and contain mixed aggregates of kaolinite, illite, halloysite, and montmorillonite. These are cut by broken bands of silicification with pitchblende either disseminated or in streaks. Chlorite occurs along vein borders, and adularia is a vein associate. Minor alunite is a late alteration product. Clay appears to diminish at depth. Near the surface some veins abut unconformably overlying rhyolite. Here clay masses may be found which contain oxidized ore that extends upwards into rhyolite fractures. The Potts fraction, Bullion Monarch open cut, and Lucky Strike ore bodies represent such accumulations. Clay zones extend beyond the ore-bearing portions of veins which constitute a small portion of the total length of clay veins in the area. On the other hand, ore is associated with alteration. Mount Belknap glassy rhyolite forms dikes, fills vents, and appears to be associated with diatremes. In places glassy dikes have been converted to masses of clay minerals by hydrothermal alteration. In the Bullion Monarch mine pitchblende is associated with glass, and ores occur in some of the argillitized dikes. The occurrence of uranium in late Tertiary alteration zones confirms Pb:U age determinations which place the age of Marysvale uranium at about 10,000,000 years. Marysvale lies along the western margin of the Colorado Plateau near the center of an igneous area of about 4000 square miles. Quartz monzonite and granite have invaded plateau strata and Bullion Canyon post-Wasatch Tertiary volcanics. All have been eroded. The eroded surface has been covered in places with Mount Belknap volcanic rocks. Rafted blocks of metamorphosed plateau sediments suspended in quartz monzonite intrusive plugs suggest that these strata underlie the exposed volcanic sequence. Several square miles of Paleozoic and Mesozoic sediments along the Deer Trail Mountain escarpment west of Marysvale indicate the character of the sediments which lie deeply buried beneath the volcanic rocks near the intrusives. The Antelope Range in which the uranium deposits are located lies in a graben between the Sevier fault on the east and the Tushar fault zone on the west. The graben has been disrupted north of the Tushar fault by the invasion of the Mount Belknap volcanic series.

Abstract Kennecott Minerals Company (KMC) operates a 15,000-ton-per-day open-pit gold mine located approximately 5 miles east of the town of Ridgeway, and 25 miles north of Columbia, South Carolina (Figure 1). The Ridgeway gold mine is one of four gold mines which were put in production in South Carolina in the 1980’s. It is currently the only operating gold mine in the Eastern United States. The Ridgeway mine produces gold bullion from two bulk-mineable, open-pit deposits located one mile apart. Low-grade oxide and sulfide ore produced from the siliceous deposits is blasted and hauled to a central mill complex. Ore is milled to minus 200 mesh, and gold is extracted by a carbon-in-pulp, electrowinning process. The mine operates 24 hours a day, and employs over 100 people. The mine began producing gold in December 1988 and total developed in order to achieve an ultimate production goal of 1.5 million ounces of gold bullion by the year 2000. The North Pit is 2,000 feet long, 1,400 feet wide, and 320 feet deep. The South Pit is 2,600 feet long, 1,500 feet wide, and 360 feet deep. The South Pit is being mined at full scale, and is expected to be mined out by June 1996. Activity in the North Pit is currently focused on the stripping of oxide ore and waste at the 420-440 level along the northern half of the pit. Future development plans for the North Pit include deepening the pit from the 120 elevation to -40 elevation. This paper

Abstract In Ghana, small-scale/artisanal gold mining has been on-going for more than a century. Artisanal mining has been the support for the rural people who more often than not are forced to sacrifice their farmlands and means of livelihood for large-scale mining operations. In order to reduce the activity of small scale/artisanal during the colonial era, laws were passed to bar indigenous operators from dealing in gold ore, amalgam, bullion, retorted gold, slags, concentrates and mercury. In recent years, however, under the auspices of the German non-governmental agency, Gesellschaft für Technische Zusammenarbeit (GTZ) and the World Bank, the Ghana government has undertaken a number of initiatives to formalise and regulate small-scale mining operations. Unfortunately, small-scale mining activities are characterised by lack of capital and minimum use of appropriate technology in the mining and treatment of the minerals into finished products. In addition, the industry is associated with land degradation and water pollution. This paper explores possible strategies that aim to make small-scale gold mining in Ghana more sustainable (i.e. more efficient, less destructive to the environment and more meaningful to the operators and the country as a whole). The roles of stakeholders in the small-scale mining industry in Ghana are also identified. It concludes that, for sustainable small-scale mining, a pragmatic synergistic approach must be adopted by all stakeholders in the organisation, regularisation, training and support of small-scale mining operations in Ghana. Mineable lands need to be delineated, illegal operators should be organised and brought under a responsible umbrella, small-scale mining operators should be supported with funds, technology and education, and alternative livelihood programmes must be pursued in mining communities.

Abstract A heap-leachable, open pit and underground gold reserve of about 173,000 ounces has been delineated by drilling at the America Mine, San Bernardino County, California. The reserve is contained within a 346,000 ounce geologic resource. The principal control for the gold mineralization is the ENE-striking, 20° to 40° NNW -dipping America Mine shear zone. The shear zone is up to 150 feet thick, is marked by mylonitic fabric in footwall rocks, and is overprinted by brittle fracturing and shearing. Ore-grade gold mineralization is up to 110 feet thick and occurs inN60°E- to N70°E-trending ore shoots which are up to +3000 feet long and up to 600 feet wide. These elongate ore shoots are axial-parallel to sub-horizontal flexures developed within the shear. The America Mine shear zone juxtaposes assemblages of rocks with contrasting origins and metamorphic grades, suggesting a terrain boundary. Footwall rocks are amphibolite-grade granitic gneisses with sparse marble lenses. Hanging wall rocks are metadiorite and metagabbro which intruded greenschist facies volcanic and sedimentary rocks. The shear contains tectonic slices (or is perhaps intruded by) a leucocratic granite and is intruded by a laterally extensive hypabyssal quartz-eye dacite. Both intrusives, confmed to the footwall side of the shear zone, are sheared, altered, and gold-mineralized. Post-mineral, NW -striking, NE-dipping, dacite dikes related to a regionally developed dike swarm in the Bullion Mountains, cut the shear, but are also slightly offset by the shear. Mineralization consists of micron-sized gold associated with intense quartz-sericite-pyrite alteration which overprints all shear zone lithologies. Accessory minerals include galena, sphalerite, tetrahedrite, chalcopyrite, and their oxidation products. Gold-free, carbonatebarite- pyrite fissure veins were emplaced along NNW-striking listric normal faults. The listric faults, which dip steeply west, cut, offset, tilt and rotate the ore shoots. The listric faults generally have minor offset (<200 feet), and related post-mineral rotation is estimated at 20°, consistent with the weak-tomoderate mid-Tertiary extension related to the Mojave Rift structural province. The gold deposit at the America Mine is interpreted as mesothermal mineralization hosted by ductile-brittle shearing along a late Mesozoic or early Tertiary thrust or a rotated subvertical (60°-70°) shear zone. The deposit is structurally complicated by mid-Tertiary extension and rotation, postmineral dacite dike emplacement, and Tertiary-Quaternary transpressional faulting.