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Ronald G. Worl

Publications and source records attributed to Ronald G. Worl.

16 recordsLinked to original sources
USGS2001

Vein deposits hosted by plutonic rocks in the Croesus Stock and Hailey gold belt mineralized areas, Blaine County, Idaho

Mineral deposits in the Croesus and Hailey gold belt mineralized areas in Blaine County, south-central Idaho, are preciousand base-metal quartz veins that are part of a family of vein deposits spatially and temporally associated with the Idaho batholith. Historic production from these veins has been mainly gold and silver. Host rocks are older border phase plutons of the Idaho batholith that are characterized by more potassium and less sodium as compared to rocks from the main body of the batholith to the west. Host structures are reverse faults that have moderate to shallow dips to the northeast and high-angle normal faults that also strike northwest. The veins are characterized by several generations of quartz and generally sparse sulfide minerals; gold is associated with late-stage comb quartz. The precious-metal ore bodies are in a series of shoots, each of which is as much as 8 ft in width, 400 ft in breadth, and 1,000 ft in pitch length.

Bulletin↗
USGS2001

Geology and mineral deposits of the Minnie Moore and Bullion mineralized areas, Blaine County, Idaho

In the early 1880?s the discovery of rich ores in the Minnie Moore and Bullion mineralized areas sparked a rush to settle and develop the Wood River valley. Silver and lead discoveries in these areas spurred the boom in mining after completion of the Oregon Short Line Railroad to Hailey in 1883. In both areas the ore comprises galena, sphalerite, and tetrahedrite in a gangue of siderite, calcite, or quartz. Minor goldbearing quartz veins are also present. The ore is in fissure and replacement veins along fracture systems that formed in Late Cretaceous time, after intrusion of nearby granodiorite or quartz diorite stocks. The ore formed under mesothermal conditions and heat was supplied by the nearby plutons. In the Minnie Moore area, the mineralized veins are cut by low-angle normal faults that are of probable Eocene age. In the Minnie Moore mineralized area, the host rock is the middle part of the Devonian Milligen Formation, (the informal Lucky Coin limestone and Triumph argillite), which is the same stratigraphic level as the host ore in the rich Triumph mine northeast of Hailey. In the Bullion mineralized area, the ore is hosted by the lower member of the Middle Pennsylvanian to Lower Permian Dollarhide Formation. Rich ore was mined in several tunnels that reached the Mayflower vein, a northwest-striking mineralized shear zone. The deposits are thought to be mainly mesothermal veins that formed in association with Cretaceous magmatism. The syngenetic stratiform model of ore formation has often been applied to these deposits, however, no evidence of syngenetic mineralization was found in this study. Faulting has displaced most of the major orebodies and thus has made mining these deposits a challenge.

Bulletin↗
USGS1983

Biogeochemical sampling in the Mahd Adh Dhahab District, Kingdom of Saudi Arabia

A biogeochemical reconnaissance of the Mahd adh Dhahab district, Kingdom of Saudi Arabia, confirms the ability of deep-rooted Acacia trees to reflect bedrock concentrations of some trace elements. The analytical values for lead, zinc, selenium, and cadmium in ash of tree branches are significantly higher in samples from areas of known mineralization (13 sites) than in samples from areas of no known mineralization (12 sites). Geometric mean concentrations of these elements in the two areas (mineralized; nonmineralized), quoted as parts per million in ash, are lead (122; 28), zinc (713; 443), selenium (1.2; 0.6), and cadmium (1.4; 0.5). The range of molybdenum values in ash from the two areas is similar, but a cluster of four sites in an area classified as nonmineralized corresponds to an area where the U.S. Geological Survey reported anomalous molybdenum values in rock in 1965. Results for other elements were either equivocal (mercury, tellurium, silver) or showed no correspondence to the two areas. Mean values for barium, manganese, potassium, and sodium are significantly higher in areas of no known mineralization, but we conclude that this reflects a difference in country rock major-element chemistry rather than the effect of ore-forming processes. The pattern of trace-metal values in Acacia ash is present whether the sampled tree grows on bedrock, on talus, or on residual or modern alluvium. This fact suggests that the trace-element chemistry of the trees reflects bedrock geochemistry and implies that Acacia biogeochemistry could be applied as a prospecting tool in areas where bedrock is not well exposed.

Open-File Report↗
USGS1979

The Jabal Ishmas-Wadi Tathlith gold belt, Kingdom of Saudi Arabia

The Jabal Ishmas-Wadi Tathlith gold belt is a north-south zone of numerous ancient gold mines in the southeastern Precambrian shield of Saudi Arabia, extending along long 43?30'E. between lat 18?N. and 21?30'N., a distance of about 390 km. The gold belt coincides with a major zone of faulting, shearing, and alteration. The fault zone and most of the gold mines occur within a belt of layered metavolcanic and metavolcaniclastic rocks that is situated between a continuous belt of gneissic rocks to the west and a discontinuous belt of gneissic rocks to the east. Layered rocks are slightly to highly metamorphosed andesitic to dacitic volcanic rocks intercalated with volcaniclastic sediments. Massive volcanic rocks predominate in the southern and very northern parts of the belt whereas medium- to fine-grained sedimentary rocks and volcaniclastic rocks, in part younger than the massive volcanic rocks, predominate in the central portions. There are five geographic groups of ancient gold mines in the belt, each of which contain deposits that are probably genetically related and are typical of that group. These deposits are hydrothermal in nature and are in or next to quartz veins, quartz breccia zones, or quartz stringer zones. A few of the deposits are spatially related to felsic dikes or small bodies of gabbro but most are in quartz veins of regional systems. In order to facilitate evaluation of individual deposits, a model was developed to determine the potential resource of each deposit. The model was developed from historical data and utilizes geologic parameters and analyses of waste dump samples to give an optimum potential resource tonnage and grade. Although these are only estimates based upon present exposures and limited analytical data, the results indicate that the deposits in the gold belt have limited economic potential. A majority of the prospects evaluated are small deposits, each estimated to contain less than 50,000 tons of gold ore. Twelve of the prospects are estimated to contain deposits ranging from 50,000 to 400,000 tons of ore at grades ranging from 7 to 32 grams per ton (g/t).

Open-File Report↗
USGS1978

Mineral exploration, Mahd adh Dhahab District, Kingdom of Saudi Arabia

Mahd adh Dhahab is the largest of numerous ancient gold mines scattered through the Precambrian shield of Saudi Arabia and the only one with recent production. During the period 1939-54, 765,768 fine ounces of gold and 1,002,029 ounces of silver were produced from the mines by the Saudi Arabian Mining Syndicate. Ore minerals at Mahd adh Dhahab include free gold and silver, tellurides, sphalerite, and chalcopyrite in and associated with a system of north-trending quartz veins and quartz veinlet stockworks. Pyrite is a common sulfide gangue mineral. Country rocks are a north dipping sequence of pyroclastic and transported pyroclastic rocks of the Hulayfah Group that are locally highly silicified and potassium-feldspathized. The prime target for this exploration program was a north-trending zone of quartz veins and breccias, faults, alteration, and metalization approximately 400 m wide and 1000 m long. The ancient and recent mine workings are located in the northern part of this zone. Although the quartz veins and alteration cut all lithologies, the major metalization is confined to the intersection of veins and agglomerate. Ten holes were diamond drilled to explore geochemical, geological, and geophysical targets in the area. A significant new zone of metalization was discovered 700 m south of the ancient and recent mine workings and within the same major zone of quartz veins, alteration, and faults. Metalization in this southern mineralized zone is at the intersection of the quartz veins and a distinctive and highly altered agglomerate. The total zone of vein and agglomerate intercept is potentially metalized and comprises a block of ground 40 m thick and 400 m wide along the strike of the agglomerate and projected downdip 250 m. Tonnage of this block is 17.2 million tons. The explored zone, approximately 25 percent of the potentially metalized rock, has a potential resource of 1.1 million tons containing 27 g/t gold and 73 g/t silver.

Open-File Report↗
USGS1978

Ore controls at the Mahd adh Dhahab gold mine, Kingdom of Saudi Arabia

Mahd adh Dhahab is the largest of numerous ancient gold mines scattered through the Precambrian shield of Saudi Arabia and the only one with recent production. Free gold and silver, tellurides, pyrite, galena, sphalerite, and chalcopyrite are in and associated with quartz veins and quartz veinlet stockworks. Country rocks consist of a sequence of pyroclastic and transported pyroclastic rocks of the Halaban Group that are locally highly silicified and potassium-feldspathized. Two known ore zones occur in a north-trending zone of quartz veins and breccias, faults, alteration, and metallization approximately 400 m wide and 1,000 m long. The ancient and recent workings are located in the northern part of this zone, and a significant new discovery, the southern mineralized zone, is in the southern part. A potential resource of 1.1 million tons of 27 g/t Au and 73 g/t Ag ore is contained in the southern mineralized zone. Geologic setting of ore bodies is similar in both zones. Significant mineralization occurs only within altered and fractured agglomerate directly beneath a cap of fine-grained tuff and sedimentary rock where the layered rocks are cut by metalliferous quartz veins. Ore was localized by four interacting controls; depth, an impervious cap, metalliferous quartz veins and a receptive host rock.

Open-File Report↗
USGS1976

Evaluation of the Umm Al Khabath copper prospect, Jabal Ibrahim quadrangle, sheet 20/41C, Kingdom of Saudi Arabia

The Umm Al Khabath copper prospect (lat 20°10'N.; long 41°23'E.) was tested by 815 m of diamond drilling in three holes. Meager metallization of copper, zinc, gold, and silver is related to a distinct phase of quartz-pyrite veinlet stockworks and associated silicification, sericitization, and pyritization. Alteration and metallization are within a major north-trending shear zone, 10-50 m wide. Lithologies cut by the shear zone are pyroclastic agglomerate and tuff with intercalated ferruginous chert, wacke, and basalt flows, all belonging to the Precambrian Baish Group. The outcrop of the shear zone for a length of 1400 m contains scattered gossan, local zones of abundant malachite and chrysocolla veinlets, patches of malachite-rich calcrete cap, and several shallow ancient workings. Composite chip samples taken from the surface across the sheared and altered zone contain anomalous concentrations of copper and zinc in amounts greater than can be expected from the weathering of the slightly metallized rock of the sheared and altered zone.

Jabal Ibrahim quadrangle↗
USGS1975

Mineral deposits in western Saudi Arabia; a preliminary report

Mineral deposits in Saudi Arabia include a variety of deposits which were formed in many geologic environments. These include magmatic and late magmatic deposits in igneous masses, contact metamorphic deposits along the margins of igneous bodies, and stratiform sulfide deposits and veins. Notable deposits of sedimentary origin include deposits of iron oxides and phosphate. Strata-bound massive sulfide deposits containing copper, zinc, and nickel sulfides associated with pyrite and pyrrhotite in complexly deformed volcanic rocks in Saudi Arabia have been the subject of controversy. They are considered by some geologists to be of syngenetic or volcanogenic origin, and by others to be epigenetic. The principal mineral deposits in western Saudi Arabia are localized in mineral belts within tectonic zones that trend northerly, northeasterly, and northwesterly. These belts contain the exploration target areas most promising for future exploration. Noteworthy among these are: 1) the northerly-trending Bidah copper-zinc belt; 2) the Sayid copper-zinc zone; 3) the northwest-trending Nuqrah copper zinc-silver belt; and 4) the north-northwesterly-trending Al Amar belt. Gold and silver deposits are mainly localized in north-trending structural features of the Hijaz geotectonic cycle and northwest Najd trends. Saudi Arabian metal deposits known thus far contain reserves in the 2 billion dollar range. Further exploration should result in discoveries that could significantly increase this amount; Saudi Arabia may well have workable metallic and nonmetallic mineral resources for industrial developments in many parts of the Kingdom. In order to effectively carry on a search for new mineral deposits, the belts should be mapped in detail, with emphasis on the delineation of stratigraphic and structural features that control metallization. In addition, geochemical and geophysical studies should be made of promising areas to outline exploration targets. These targets could then be systematically explored.

Open-File Report↗