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Exploration models for podiform chromite in the Medford-Coos Bay quadrangles must consider the facts that (1) one deposit occurs for every 5 km 2 of ultramafic outcrop; similarly for a 5 km 3 volume, and (2) the average deposit has a tonnage of 206 tonnes, a volume of 8.9 m 3 and a grade between 43 and 51 percent Cr2O3.
Four deposits in the Wadi Bidah district of southwestern Saudi Arabia were explored during the period 1972-1974. The work consisted of geologic, geochemical, and geophysical investigations and diamond drilling in the subsurface. Thirteen holes were drilled, aggregating a length of 2,397 m. Drilling at three of the deposits, Gehab, Sha'ab El Tare, and Rabathan, indicated mineralized reserves aggregating 6,341,000 tons, the average grade of which is 0.95 percent copper. The deposits are strata-bound in volcaniclastic rocks of the Baish Group and in quartz porphyry, all of which are Precambrian in age. The bodies are lenticular in strike and dip, and are offset and broken by postmineral faults.
After expansion of the USGS (U.S. Geological Survey) uranium-thorium program in FY (fiscal year) 1975, new directions of research could be pursued, particularly in sedimentology or genetic stratigraphy, geochemistry-mineralogy, and geophysics. In a relatively short time, many of the new research projects have developed critical information on uranium habitats and improved methods of exploration. In FY 1979 a budget increase of approximately 20 percent is programmed, for a funding base of $6,600,000. The increase is scheduled for research grants and contracts outside the USGS in order to extend the basic program without additional personnel. This outside research will be designed not only to increase basic information on uranium occurrence but also to aid the USGS in its evaluation of uranium favorability in key resource areas for the NURE (National Uranium Resource Evaluation) program of DOE (U.S. Department of Energy).
Forty oil samples from across the North Slope of Alaska have been analyzed by the U.S. Bureau of Mines and the U.S. Geological Survey. Results of these analyses suggest two separate genetic oil types. The first type, the Simpson-Umiat oil type, occurs in reservoir rocks of Cretaceous and Quaternary age and includes oils from seeps in the Skull Cliff, Cape Simpson, Manning Point, and Ungoon Point areas; the Wolf Creek test well 3, and the Umiat oil field. These are higher gravity, low-sulfur oils with no, or slight, odd-numbered n-alkane predominance and pristane to phytane ratios greater than 1.5. The second type, the Barrow-Prudhoe oil type, occurs in reservoir rocks of Carboniferous to Cretaceous age and includes oils from South Barrow gas field, Prudhoe Bay oil field, and the Fish Creek test well 1. Physical properties of Barrow-Prudhoe oils are variable, but in general the oils are medium-gravity, high-sulfur oils with a slight even-numbered n-alkane predominance and pristane to phytane ratios of less than 1.5. The two types are believed to originate from different source rocks; the Barrow-Prudhoe type may have originated from a carbonate or other iron-deficient source rock, and the Simpson-Umiat type from a siliciclastic source rock. Occurrences of the two oil types, when outlined on a map, indicate at least two exploration fairways. The fairway for the Barrow-Prudhoe type is along the Barrow arch, and the fairway for the Simpson-Umiat type is the area of the best reservoir development for the Nanushuk Group.
The U.S. Geological Survey (U.S.G.S.) collected approximately 3,700 km of multichannel-seismic reflection profiles (lines TD-1 – TD-6) south of Cape Hatteras on the continental margin. Those profiles were collected between August 15 and October 30, 1977, under U.S.G.S. contract number 14-08-0001-16209 by the Teledyne Exploration Company. The released data include copies of the original records, velocity scans, track charts, and field tapes.
A 2.2-m-thick lake bed composed entirely of diatomite was found in the southwestern arm of the Nafud sand sea, about 67 km east of Tayma in northwestern Saudi Arabia. Its stratigraphic position above eolian sand and below a large barchanoid dune indicates deposition during an exceptional period of pluvial climate in an otherwise arid sand desert. Radiocarbon-dated carbonate lake beds found in similar stratigraphic settings in other parts of the Nafud suggest that the diatomite was deposited in the late Pleistocene epoch sometime between 32,000 and 20,000 years ago. Diatomite of the same pluvial episode has also been found in the Afar region of Ethiopia. Four samples of the diatomite were analyzed for major chemical components and 32 minor and trace elements. Two of the samples appeared to be representative of the lake bed. These samples contained about 85 percent SiO2, 2.34 percent Fe2O3, 1 4 percent Al2O3, and 8.27 percent ignition loss, with only traces of CaO, P2O5, MgO, Na2O, and TiO2. The high content of silica and low contents of alumina, iron oxide, lime, and other constituents indicate low contamination. Analyses of samples from the two atypical units indicate a small amount of contamination, probably clay or mica, in the basal unit and addition of iron oxide and carbonate by ground water in an isolated green-colored unit. Chemically the Bi'r Hayzan diatomite compares favorably with commercial deposits from other parts of the world. Low bulk densities of 0.64 g/cm3 (30-40 lbs/ft3) and an average porosity of 63 percent for five samples also suggest the deposit is of industrial grade. Further studies are recommended to determine: (1) the size and extent of the deposit and (2) the suitability of the diatomite for commercial applications. As means to these ends, electrical-resistivity surveys following winter rains are suggested to determine both the extent and thickness of the lake bed beneath the overlying sand dunes. A complete species identification of the diatom association and further laboratory testing of physical properties of the diatomite also should be made. Further exploration in the Nafud is recommended to locate other possible diatomite deposits.
Magnetic concentrates recovered readily by hand magnet from alluvial sediments or panned concentrates have been used successfully in exploration as a geochemical sample medium for Cu, Zn, Co, Cr, Mo, Ni, V, Sn, and Be, particularly in arid environments where alluvial sediments may be contaminated by aeolian debris. Opportunity for this use arose recently as chemical and spectrographic techniques were developed to determine the abundances of a variety of trace elements in Fe-rich media. The use of analytical data from magnetic concentrates was introduced as one of several anomaly-enhancement techniques based on heavy minerals and intended to identify blind ore deposits. An extensive literature, reviewed here, on the relation of the chemical composition of the mineral magnetite, a main component of magnetic concentrates, to geologic conditions of origin, facilitates the interpretation of trace-element data in the context of association with ore deposits.
From mid-1984 through mid-1985, the United States Geological Survey (USGS) engaged in an investigation of two craters formed from high-yield, near-surface nuclear bursts in the Marshall Islands at Enewetak Atoll (figures 1 and 2). Supported by the Defense Nuclear Agency (DNA), this cooperative venture is referred to by the acronym PEACE, derived from its official name, Pacific Enewetak Atoll Crater Exploration Program. The craters studied, KOA and OAK, resulted from 1.4- and 8.9-megaton, near-surface bursts detonated near the northern perimeter of the Enewetak lagoon on May 12 and June 28, 1958, respectively. At that time, Enewetak was administered by the United States Government under the auspices of the Trust Territories of the Pacific Islands (TTPI) and formed a part of the Pacific Proving Grounds (PPG). OAK and KOA are among the only high-yield nuclear craters available for studies of cratering processes and crater-related effects.
The principal part of this report is a discussion of the three monazite belts and the descriptions of the panned concentrates that justify their delineation, details that constitute an example of the use of heavy minerals in regional geologic exploration. The tenors of accessory minerals in rocks from the monazite belts in Viginia, North Carolina, South Carolina, Georgia, and Alabama are listed, and where possible these mineralogical data are translated into genetic interpretations. The origin of the monazite belts is discussed in the light of the mineralogical data, from which it is concluded that the beltlike distribution of monazite is analogous to a petrographic province.
The principal ore deposits in the Coeur d'Alene district are lead-zinc-silver replacement veins in Precambrian rocks of the Belt Supergroup. The main ore minerals are galena, tetrahedrite, and sphalerite. The host rocks are mainly quartzite, siltite, and argillite. Cretaceous quartz monzonite locally intrudes the Beltrocks. The geochemical investigations reported here were carried out to determine if geochemical methods would be useful in the search for concealed ore deposits. About 8,700 soil samples and 4,000 rock samples were collected from a 300-square-mile (780 square kilometer) area for this study. The samples were analyzed for 35 elements. Antimony, silver, lead, manganese, and copper form dispersion patterns and halos that are related to many of the ore deposits within the district, and these same elements were found to be most useful in delineating the known mineral belts that contain most of the orebodies. The dispersion patterns are probably primary, having only minor modifications due to secondary redistribution of the ore-forming elements. The mineral belts and geochemical-dispersion patterns have been laterally offset, perhaps as much as 16 miles (26 km), by postore faulting. Prefault dispersion patterns can be restored by adjusting the geochemical maps along the postore faults to match the dispersion patterns across the fault trace. The reconstructed dispersion patterns of antimony, arsenic, lead, sulfur, and the ratio of cadmium to zinc form concentric halos around the restored position of the Gem stocks. Most of the Coeur d'Alene ore has been mined from this halo. It appears that the geochemical exploration methods reported here successfully delineate the major mineral belts and indicate unexplored areas in which to search for new deposits.
Total-count contoured aeroradiometric maps for the Coastal Plain of Virginia were used in an effort to locate economic heavy-mineral placer deposits. The principle behind this approach is that heavy- mineral suites commonly contain radioactive minerals that, if the concentration of heavy minerals is exposed at or within inches of the surface, enable the deposit to be located by use of airborne instruments because of its radiometric contrast with the host sediment. Detailed and regional geologic maps, soil maps, land-use and land- cover maps, information on fertilizer use, and ground-spectrometer data were used to study aeroradiometric anomalies for efficient exploration. Aeroradiometric anomalies in the Coastal Plain of Virginia have three general causes. First, the most intense anomalies are associated with cultural features, such as roads made of granitic material. Second, most anomalies of high to intermediate intensity are associated with land used for agricultural purposes and evidently are caused by applications of radioactive fertilizer. Third, anomalies of intermediate to low intensity are associated with heavy-mineral deposits. Results of this study show that aeroradiometric anomalies associated with heavy-mineral accumulations in the Coastal Plain of Virginia have ground radiometric spectra in which thorium is the strongest component and uranium and potassium are lesser components. Heavy-mineral accumulations found in this study by use of the aeroradiometric data are not considered to be of economic importance, mostly because of the low percentage of economic minerals in the heavy-mineral suites and also because of other factors such as the very fine grained nature of the host sediments and competing land use.
A reconnaissance hydrogeochemical study employing high-resolution/high-sensitivity inductively coupled plasma mass spectrometry analysis of stream and seep water samples ( n = 171) was conducted in an area of limited bedrock exposure on the northeastern Seward Peninsula, Alaska. Sampling was focused in drainages around four main areas—at the Anugi Pb-Zn-Ag occurrence and in streams upstream of historically and currently mined placer gold deposits in the Candle Creek, Utica, and Monument Mountain areas. The objective of the study was to determine whether distribution of elevated metal concentrations in water samples could “see” through sediment cover and provide evidence of bedrock sources for base metals and gold. Some observations include (1) elevated Ag, As, Pb, and Zn concentrations relative to the study area as a whole in stream and seep samples from over and downstream of part of the Anugi Pb-Zn-Ag prospect; (2) abrupt downstream increases in Tl and Sb ± Au concentrations coincident with the upstream termination of productive placer deposits in the Inmachuk and Old Glory Creek drainages near Utica; (3) high K, Mo, Sb, and F throughout much of the Inmachuk River drainage near Utica; and (4) elevated As ± base metals and Au at two sites along Patterson Creek near the town of Candle and three additional contiguous sites identified when an 85th percentile cut-off was employed. Molybdenum ± gold concentrations (>90th percentile) were also measured in samples from three sites on Glacier Creek near Monument Mountain. The hydrogeochemistry in some areas is consistent with limited stream-sediment data from the region, including high Pb-Zn-Ag-As concentrations associated with Anugi, as well as historical reports of arsenopyrite-bearing veins upstream of placer operations in Patterson Creek. Chemistry of samples in the Inmachuk River-Old Glory Creek area also suggest more laterally extensive stibnite- (and gold-?) bearing veining than is currently known in the Old Glory Creek drainage. Our results indicate that hydrogeochemistry can be a useful method of geochemical exploration and offer targets for follow-up rock, soil, and subsurface sampling to ascertain the presence of mineralized bedrock.
Regional maps of phyllic and argillic hydrothermal alteration were compiled using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and logical operator algorithms. The area mapped extends from northwestern Iran to southeastern Pakistan and includes volcanic and magmatic arcs that make up the Urumieh-Dokhtar volcanic belt (UDVB), the Chagai volcanic belt (CVB), and the central part of the Alborz magmatic belt (AMB). The volcanic belts span the Zagros-Makran transform zone and the present day Baluchistan (Makran) volcanic arc. ASTER visible near infrared (VNIR) data contain three bands between 0.52 and 0.86 micrometers (μm) and the short-wave infrared (SWIR) data consist of six bands spanning 1.6 to 2.43 μm with 15-meter (m), and 30-m resolution, respectively. During the 8-year project, three different calibration methods were used to correct ASTER SWIR anomalies and produce ASTER calibrated reflectance data, which were then used to map hydrothermally altered rocks. Logical operators, used to map hydrothermally altered rocks, perform multiple band ratios and thresholds that can be applied to multiple ASTER scenes using a single algorithm, thus eliminating separate production and application of vegetation and dark pixel masks. Argillic and phyllic band ratio logical operators use band ratios that define the 2.17- and 2.20-μm absorption features to map kaolinite and alunite, typical in argillized rocks, and muscovite, which is a common mineral in phyllic alteration. Band thresholds for ratios in argillic and phyllic logical operator algorithms were determined by mapping known argillic and phyllic rocks at a calibration test site in Cuprite, Nevada, in the United States. The regional argillic and phyllic hydrothermal alteration map and geologic and deposit maps of the study area illustrate that distinct patterns of altered rocks are typically associated with certain types of mineral deposits. The central part of the UDVB contains numerous circular to elliptical patterns (1 to 5 kilometers in diameter) of mapped phyllic- and argillic-altered rocks associated with Eocene to Miocene intrusive igneous rocks, some of which host known porphyry copper deposits such as at Meiduk, Sar Cheshmeh, and Seridune in Iran. The Zagros-Makran transform zone and areas adjacent to the Saindak porphyry deposit and Taftan Volcano contain primarily phyllic-altered rocks that form linear patterns associated with extensive faulting and fractures indicative of epithermal and (or) polymetallic vein deposits. The ASTER alteration map and corresponding geologic maps were used to select circular to elliptical patterns of argillic- and phyllic-altered volcanic and intrusive rocks as potential porphyry copper sites. One hundred and seventy eight potential porphyry copper sites were mapped along the UDVB, and 23 sites were mapped along the CVB. The potential sites were selected to assist in further exploration and assessments of undiscovered porphyry copper deposits.
Global dependence on a limited number of countries for specific mineral commodities could lead to sudden supply disruptions for the United States, and barite is one such commodity. Analyses of barite supply amounts and sources for the United States are demonstrative of mineral commodities on which the country is import reliant. Mineral commodity trade flows can be analyzed more easily than import reliances for commodities in which U.S. domestic demand is primarily met by materials contained within manufactured products, as with the rare-earth elements in cellular phones and computers. Barite plays an essential role as a weighting material in drilling muds used in oil and gas drilling, primarily to prevent the explosive release of gas and oil during drilling. The Nation’s efforts to become more energy independent are based largely on the domestic oil and gas industry’s ability to explore and develop onshore and offshore fuel deposits. These activities include increased efforts by the United States to locate and recover oil and gas within unconventional deposits, such as those in the Bakken, Eagle Ford, and Marcellus Formations, using advanced drilling technologies. Domestic barite production was about 670,000 metric tons (t) in 2012, equivalent to about 20 percent of the domestic drilling industry’s barite demand. Mine production for the United States in 2012 was about one-third of what was produced in 1980. In 2012, barite imported from China was approximately 2.2 million t and comprised about 77 percent of total barite imports and about 70 percent of the barite used in domestic drilling. Barite from India (14 percent), Morocco (6 percent) and Mexico (2 percent) comprised the bulk of the remaining total import balance; drilling applications consumed nearly all barite imported from these three countries.
During 1951 a joint exploration program of the most promising uraniferous areas in the Silver Reef district was made by the U.S. Geological Survey and the u.S. Atomic Energy Commission. A U.S. Bureau of Mines drill crew, on contract to the Atomic Energy Commission, did 2,450 feet of diamond drilling under the geological supervision of the U.S. Geological Survey. The purpose of the drilling was to delineate broadly the favorable ground for commercial development of the uranium depostis. Ten drill holes were located around Pumpkin Point, which is the northeastern end of Buckeye Reef, to probe for extensions of small ore shootsmined on the Point in fine-grained sandstones of the Chinle formation. Three additional holes were located around teh Tecumseh Hill to prbe for extensions of the small showings of uranium-bearing rocks of Buckeye Reef.
The U.S. Geological Survey explored the Spring Creek Mesa area from July 11, 1951, to August 14, 1953. During that period, 280 diamond-drill holes were completed for a total of 180,287 feet. Sedimentary rocks of Mesozoic age are exposed in and adjacent to the Spring Creek Mesa area. These rocks consist of, from oldest to youngest: the Upper Jurassic Morrison formation, the Lower Cretaceous Burro Canyon formation, and the Upper Cretaceous Dakota formation. The Morrison formation consists of two members in the Spring Creek Mesa area: the lower is the Salt Wash member and the upper is the Brusby Basin member. All of the large uranium-bearing deposits discovered by the Geological Survey drilling in the Spring Creek Mesa area are in a series of coalescing sandstone lenses in the uppermost part of the Salt Wash member of the Morrison formation. Most of the ore deposits are believed to be irregular tabular or lens-shaped masses and probably lie parallel to the bedding, although in detail, they may crosscut the bedding. Also, ore deposits that take the form of narrow elongate concretionary-like structures, locally called “rolls”, may be present in the Spring Creek Mesa area. The mineralized material consists mostly of sandstone which has been selectively impregnated and in part replaced by uranium and vanadium minerals. Also, rich concentrations of uranium and vanadium are commonly associated with thin mudstone seams, beds of mudstone pebbles, and carbonaceous material of various types. Two suites of ore minerals are present in the ore deposits - - an oxidized suite of secondary uranium and vanadium minerals and a relatively unoxidized suite of “primary” uranium and vanadium minerals. The following geologic criteria are useful as guides to ore in the Spring Creek Mesa area: 1. Large ore deposits generally occur where the “ore-bearing sandstone” is more than 40 feet thick. 2. The color of the mudstone associated with the “ore-bearing sandstone” in the vicinity of large ore deposits is commonly gray instead of the usual red. 3. The “ore-bearing sandstone” is normally a light red, but in the vicinity of oxidized ore deposits it is light brown and in the vicinity of relatively unoxidized ore deposits it is gray. 4. The “ore-bearing sandstone” in the vicinity of relatively unoxidized ore deposits commonly contains sparse to abundant disseminated pyrite. In the vicinity of oxidized deposits it commonly contains abundant limonite spots and widespread limonite staining.
The Marble exploration hole 4 was drilled to determine the chemical and physical properties of marble from the surface to depth of about 1,200 feet. The drill hole is in the north-central part of the Tippipah Spring quadrangle, approximately 40 miles north of Mercury, Nev. The collar of the hole is at an elevation of 5,490.28 feet and has the Nevada State grid coordinates of N. 904,480.13 and E. 637,758.38. The hole is accessible by a graded dirt road easily traversed by heavy construction equipment, that connects to the highway between Mercury and Groom Lake. The hole was core drilled by Minerals Engineering Company, Grand Junction, Colo., with a 2,000-foot capacity Portadrill drilling rig and conventional NX coring equipment. Drilling was started July 13, and completed August 30, 1959. The drilling fluid was water for most of the hole. At some places in the hole, where loss of drilling fluid was high, the water was thickened with bentonitic mud. At 1,103 feet, presumed caving of the hole caused the drill stem to stick so that it could not be withdrawn; subsequently about 920 feet of the drill stem was recovered. The hole was then reamed to 800 feet and cemented from 785 to 855 feet. A whipstock was emplaced at depth of 805 feet so that the hole, which was vertical to this depth, would be deflected 4° from the vertical. Core was recovered for this part of the hole from 1,088 to 1,187 feet, the total depth. Seven feet of 8-inch outside diameter casing was set from the collar. This report summarizes the information obtained during preparation of the lithologic log of the core and presents results of chemical analyses of marble samples collected from surface near the drill hole. The report was prepared by the U.S. Geological Survey on behalf of the Albuquerque Operations Office, U.S. Atomic Energy Commission. The writers acknowledge the assistance of Mr. John Foster, drilling foreman for Minerals Engineering Company and Mr. Walter A. Johnson, field engineer for Holmes and Narver, Inc., the engineering-contracting firm.
Outlaw Mesa is northeast of the Dolores River, about 10 miles southeast of Gateway, Mesa County, Colo. It is an oval-shaped area of about 17 square miles lying mostly within T. 50 N., R. 17 W«, and T. 50 No, R. 18 W., New Mexico principal meridian. The area is accessible by three unimproved roads from Colorado Highway 141. The altitude of the mesa ranges from about 5,500 feet to over 7,000 feet. Total production from Outlaw Mesa from 1914 to 1949 was about 4,000 tons of carnotite ore, having an estimated grade of about 0.50 percent U30Q and 2.5 percent V 2 O 5 . The production from 1949 to October 1951 was about 18,000 tons, having an estimated grade of about 0.35 percent U 3 O 8 and 1.6 percent V 2 O 5 . About 80 percent of the production from 1949 to October 1951 was from deposits discovered by U. S. Geological Survey diamond-drilling in public land, now leased to the Climax Uranium Co. A more complete history of mining and production OE Outlaw Mesa has been given in earlier reports. The results of Geological Survey exploration on Outlaw Mesa are summarized in this preliminary report. A final and more comprehensive report will be transmitted later. No additional drilling is planned.