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USGS2016

Book review: Mineral resource estimation

Mineral Resource Estimation is about estimating mineral resources at the scale of an ore deposit and is not to be mistaken with mineral resource assessment, which is undertaken at a significantly broader scale, even if similar data and geospatial/geostatistical methods are used. The book describes geological, statistical, and geostatistical tools and methodologies used in resource estimation and modeling, and presents case studies for illustration. The target audience is the expert, which includes professional mining geologists and engineers, as well as graduate-level and advanced undergraduate students. Review info: Mineral Resource Estimation . By Mario E. Rossi, Clayton V. Deutsch . 2014 . ISBN 978-1-4020-5716-8 332 pp.

Economic Geology↗
USGS2016

Book Review: Potassic igneous rocks and associated gold-copper mineralization, Fourth edition (D. Muller and D.I. Groves)

The fourth edition of this comprehensive textbook, which succeeds those published in 1995, 1997, and 2000, very nicely summarizes the geochemical and petrological characteristics of potassic igneous rock complexes and the different tectonic settings in which they occur. The authors provide an overview and a classification of these rocks and they outline the geochemical differences between barren and mineralized potassic igneous complexes. Owing to the common association of potassic igneous rocks with many gold- and copper-rich ore deposits, this book will be of interest not only to research scientists but also to those exploring for major deposits in young and ancient terranes. In fact, there was a clear attempt by the authors to provide a good mix of theoretical discussions based on experimental work, with case studies that illustrate field and applied research. Review info: Potassic Igneous Rocks and Associated Gold-Copper Mineralization , Fourth Edition. By Daniel Müller, David I. Groves. 2016. ISBN 978-3-319-23051-1. 311 p.

Economic Geology↗
USGS1979

Uranium, thorium, and mercury distribution through the evolution of the McDermitt Caldera complex

The McDermitt caldera complex developed over a period of 5 m.y. years during which ash-flow tuff sheets anomalous in mercury, uranium, and thorium were emplaced. The moat portions of the caldera complex were subsequently filled with tuffaceous sediments. Late in the caldera development near-surface intrusives and domes were emplaced along the margins of the complex and mineralized with uranium. Seven large hydrothermal systems developed at this time and formed large areas of alteration within the caldera-fill volcanics and sediments. Five of the altered zones are associated with economic concentrations of uranium, and or mercury.

Nevada, Oregon↗
USGS2023

A recently discovered trachyte-hosted rare earth element-niobium-zirconium occurrence in northern Maine, USA

Reported here are geological, geophysical, mineralogical, and geochemical data on a previously unknown trachyte-hosted rare earth element (REE)-Nb-Zr occurrence at Pennington Mountain in northern Maine, USA. This occurrence was newly discovered by a regional multiparameter, airborne radiometric survey that revealed anomalously high equivalent Th (eTh) and U (eU), confirmed by a detailed ground radiometric survey and by portable X-Ray fluorescence (pXRF) and whole-rock analyses of representative rock samples. The mineralized area occurs within an elongate trachyte body (~1.2 km 2 ) that intrudes Ordovician volcanic rocks. Geologic constraints suggest that the trachyte is also Ordovician in age. The eastern lobe (~900 × ~400 m) of the trachyte is pervasively brecciated with a matrix containing seams, lenses, and veinlets composed mainly of potassium feldspar, albite, and fine-grained zircon and monazite. Barite is locally abundant. Minor minerals within the matrix include columbite, bastnäsite, euxenite, chlorite, pyrite, sphalerite, and magnetite. The pXRF analyses of 22 samples (App. Table A1) collected from the eastern lobe demonstrate that this entire part of the trachyte is highly mineralized. Whole-rock geochemical analyses for samples from the eastern lobe document high average contents of Zr (1.17 wt %), Nb (1,656 ppm), Ba (3,132 ppm), Y (1,140 ppm), Hf (324 ppm), Ta (122 ppm), Th (124 ppm), U (36.5 ppm), Zn (689 ppm), and Sn (106 ppm). Among light REE, the highest average concentrations are shown by La (763 ppm) and Ce (1,479 ppm). For heavy REE (HREE), Dy and Er are the most abundant on average (167 and 114 ppm, respectively). No HREE-rich minerals such as xenotime have been identified; the HREE may reside chiefly in monazite and bastnäsite, and within the fine-grained zircon. Very strong positive correlations (R 2 ) of 0.92 to 0.98 exist between Th and Zr, Nb, Y, Ce, Yb, and Sn, indicating that the radiometric data for eTh are valid proxies for concentrations of these metals in the mineralized rocks.

Maine↗
USGS1969

Devonian laterite in Chitral state, West Pakistan

A Devonian laterite has recently been discovered near Reshun in the Mastuj valley of Chitral State, West Pakistan. It is believed to be the fourth recorded Paleozoic laterite in the world. The laterite is entirely within a thick carbonate of the Shogram Formation of Upper Devonian (Frasnian) age. A chemical analysis of the laterite shows the principal constitutents to be: Al 2 O 3 35.5%, SiO 2 , 21.7% Fe 2 O 3 16.0%, FeO 10.3%, TiO 2 , 3.5% CaO 0.97%, and MgO 0.70%. Minerals determined by X-ray analysis include hematite, boehmite, diaspore, anatase, rutile, kaolinite, pyrophyllite and what is probably chamosite.

Chitral↗
USGS1962

Borates in the United States, exclusive of Alaska and Hawaii

This map shows the location of borate deposits in the United States (exclusive of Alaska and Hawaii). Because all the known borate deposits of the United States of any historic or present economic importance occur in California, western Nevada, and southern Oregon, this map covers only the western part of the country.

Mineral Investigations Resource Map↗
USGS1962

Beryllium in the United States, exclusive of Alaska and Hawaii

This map shows most of the known occurrences of beryllium minerals and of rocks that contain 0.003 percent or more beryllium (0.01 percent Be0) in the United States (exclusive of Alaska and Hawaii). The occurrences are subdivided on the map according to genesis and size. The genetic types of deposits shown are: pegmatite, vein and replacement deposits (exclusive of tactite), tactite, disseminated beryl in granite and rhyolite, hot spring deposits, and residual materials. Deposits of each type that have a total production plus reserve greater than 24,000 lbs. of contained Be0 (equivalent to 1200 short ton units of Be0 or 190 tons of beryl) are shown by a large symbol. Names are given only for the districts that are of particular economic or scientific importance. Both published information and unpublished data gathered by the U. S. Geological Survey were used in preparing the map and text.

Mineral Investigations Resource Map↗
USGS1990

Fine-grained rutile in the Gulf of Maine: Diagenetic origin, source rocks, and sedimentary environment of deposition

The Gulf of Maine, an embayment of the New England margin, is floored by shallow, glacially scoured basins that are partly filled with late Pleistocene and Holocene silt and clay containing 0.7 to 1.0 wt percent TiO 2 , chiefly in the form of silt-size rutile. Eleven basins in the gulf are estimated to contain 479 X 10 6 metric tons of TiO 2 (to a depth of 10 m) in the U.S. exclusive economic zone and 168 X 10 6 in Canada, based on analyses of surface sediment and of cores 10 to 20 m long. The U.S. annually consumes approximately 1 X 10 6 metric tons of TiO 2 , of which 73 percent is imported. The inferred amount of fine-grained TiO 2 in the basins is large, and we interpret it to be predominantly rutile; but no attempt has been made yet to mine and beneficiate the fine-grained ore.Sedimentary rocks of Nova Scotia, New Brunswick, and northern Maine contain fine-grained rutile crystals and have been the major source of the fine-grained sediment in the Gulf of Maine basins during and after the Wisconsinan glaciation. We conclude that much of the rutile in the Gulf of Maine mud formed diagenetically in poorly cemented Carboniferous and Triassic coarse-grained sedimentary rocks of Nova Scotia and New Brunswick after the dissolution of titanium-rich detrital minerals (ilmenite, ilmenomagnetite). Another major source of rutile is the generally finer grained Paleozoic sedimentary rocks of northern Maine (and possibly northwestern New Brunswick) which contain recycled diagenetic rutile that most likely originated in sandstones. Additional Wisconsinan sources of fine-grained, diagenetic TiO 2 probably include sedimentary rocks of inferred Triassic age that underlie the Gulf of Maine.The diagenesis of rutlie in coarse sedimentary rocks (especially arkose and graywacke) followed by erosion, segregation, and deposition (and including recycling of fine-grained rutile from shales) can serve as a model for predicting and prospecting for unconsolidated deposits of fine-grained TiO 2 .Gulf of Maine mud is comparable in TiO 2 content to typical shale. A determination of whether the fine-grained TiO 2 in shales primarily occurs as detrital titanium minerals from metamorphic and igneous sources or as recycled, diagenetic titanium oxides from sedimentary sources may assist in interpreting shale provenance and environment of deposition.

Economic Geology↗
USGS1988

International strategic minerals inventory summary report; titanium

Ilmenite and rutile are currently the most important titanium-bearing minerals, although anatase may be important in the future. Both ilmenite and rutile occur in hard-rock and placer deposits, but at present all rutile production and about half of the ilmenite production are from placer deposits. Anatase occurs in laterite deposits in Brazil, which at present are largely undeveloped. World ilmenite resources in identified deposits that are economically exploitable (R1E} are sufficient for about 150 years at current production rates, and about two-thirds of these resources are in China, the Soviet Union, and Norway. World rutile R1E resources would last about 80 years at current production rates, and some 54 percent of these resources are in Australia, the United States, and Italy. Combined R1E resources of anatase (which are all in Brazil) and rutile would last 300 years at current rutile production rates. Over 95 percent of the world's mine production of titanium-bearing minerals is used to manufacture titanium dioxide pigment for paint and other products. Most of the remaining 4 to 5 percent of production, which is largely rutile, is used for making titanium metal. Australia and Canada are the largest ilmenite producers, together supplying about half the world total; South Africa, Norway, and the Soviet Union together account for another third. Australia accounts for half the total world rutile production, with Sierra Leone and South Africa together accounting for another third. Australia and Norway are the largest exporters of titanium minerals. Unless major new deposits are discovered and developed in the traditional producing countries, the pattern of world production of both ilmenite and rutile could change substantially by 2020.

Circular↗
USGS2008

Understanding contaminants associated with mineral deposits

Interdisciplinary studies by the U.S. Geological Survey (USGS) have resulted in substantial progress in understanding the processes that control the release of metals and acidic water from inactive mines and mineralized areas, the transport of metals and acidic water to streams, and the fate and effect of metals and acidity on downstream ecosystems. The potential environmental effects associated with abandoned and inactive mines, resulting from the complex interaction of a variety of chemical and physical processes, is an area of study that is important to the USGS Mineral Resources Program. Understanding the processes contributing to the environmental effects of abandoned and inactive mines is also of interest to a wide range of stakeholders, including both those responsible for managing lands with historically mined areas and those responsible for anticipating environmental consequences of future mining operations. The recently completed (2007) USGS project entitled 'Process Studies of Contaminants Associated with Mineral Deposits' focused on abandoned and inactive mines and mineralized areas in the Rocky Mountains of Montana, Colorado, New Mexico, Utah, and Arizona, where there are thousands of abandoned mines. Results from these studies provide new information that advances our understanding of the physical and biogeochemical processes causing the mobilization, transport, reaction, and fate of potentially toxic elements (including aluminum, arsenic, cadmium, copper, iron, lead, and zinc) in mineralized near-surface systems and their effects on aquatic and riparian habitat. These interdisciplinary studies provide the basis for scientific decisionmaking and remedial action by local, State, and Federal agencies charged with minimizing the effects of potentially toxic elements on the environment. Current (2007) USGS research highlights the need to understand (1) the geologic sources of metals and acidity and the geochemical reactions that release them from their sources, (2) the pathways that facilitate transport from those sources, and (3) the processes that control the fate of the elements once released from the sources. Experts in the fields of economic geology, structural geology, mineralogy, geophysics, geochemistry, hydrology, ground-water modeling, microbiology, and toxicology came together for a series of studies that address these relationships on scales ranging from the microscopic to the watershed. This Circular presents results and highlights from the detailed, interdisciplinary studies that include investigations in both mining-affected areas and mineralized but unmined areas. The first section of the Circular describes laboratory and site-scale field investigations that primarily focus on mineralogic and biologic controls on the source and release of metals and acidity from mine-waste rock and hydrothermally altered areas. The second section describes a set of basin- to watershed-scale studies that not only investigate the source and release of metals and acidity but also the transport of these constituents away from the source areas. The third section is a summary of results from postremediation ecosystem monitoring. For more information on these and other project-related studies, please visit the project Web site at http://minerals.cr.usgs.gov/projects/contaminants/index.html. The Web site includes a complete bibliography and detailed descriptions of each interdisciplinary study.

Circular↗
USGS1966

Mineral exploration and soil analysis using in situ neutron activation

A feasibility study has been made to operate by remote control an unshielded portable positive-ion accelerator type neutron source to induce activities in the ground or rock by “in situ” neutron irradiation. Selective activation techniques make it possible to detect some thirty or more elements by irradiating the ground for periods of a few minutes with either 3-MeV or 14-MeV neutrons. The depth of penetration of neutrons, the effect of water content of the soil on neutron moderation, gamma ray attenuation in the soil and other problems are considered. The analysis shows that, when exploring for most elements of economic interest, the reaction 2 H(d,n) 3 He yielding ∼ 3-MeV neutrons is most practical to produce a relatively uniform flux of neutrons of less than 1 keV to a depth of 19″–20″. Irradiation with high energy neutrons (∼ 14 MeV) can also be used and may be better suited for certain problems. However, due to higher background and lower sensitivity for the heavy minerals, it is not a recommended neutron source for general exploration use. Preliminary experiments have been made which indicate that neutron activation in situ is feasible for a mineral exploration or qualititative soil analysis.

Nuclear Instruments and Methods↗
USGS2007

Effects of mother lode-type gold mineralization on 187Os/188Os and platinum group element concentrations in peridotite: Alleghany District, California

Osmium isotope compositions and concentrations of Re, platinum group elements (PGE), and Au were determined for host peridotites (serpentinites and barzburgites) and hydrothermally altered ultramafic wall rocks associated with Mother Lode-type hydrothermal gold-quartz vein mineralization in the Alleghany district, California. The host peridotites have Os isotope compositions and Re, PGE, and Au abundances typical of the upper mantle at their presumed formation age during the late Proterozoic or early Paleozoic. The hydrothermally altered rocks have highly variable initial Os isotope compositions with ??os, values (% deviation of 187OS/188OS from the chondritic average calculated for the approx. 120 Ma time of mineralization) ranging from -1.4 to -8.3. The lowest Os isotope compositions are consistent with Re depletion of a chondritic source (e.g., the upper mantle) at ca. 1.6 Ga. Most of the altered samples are enriched in Au and have depleted and fractionated abundances of Re and PGE relative to their precursor peridotites. Geoehemical characteristics of the altered samples suggest that Re and some PGE were variably removed from the ultramafic rocks during the mineralization event. In addition to Re, the Pt and Pd abundances of the most intensely altered rocks appear to have been most affected by mineralization. The 187Os-depleted isotopic compositions of some altered rocks are interpreted to be a result of preferential 187Os loss via destruction of Re-rich phases during the event. For these rocks, Os evidently is not a useful tracer of the mineralizing fluids. The results do, however, provide evidence for differential mobility of these elements, and mobility of 187Os relative to the initial bulk Os isotope composition during hydrothermal metasomatic alteration of ultramafic rocks. ?? 2007 Society of Economic Geologists, Inc.

Economic Geology↗
USGS1938

Sulphate minerals of the Comstock Lode, Nevada

Seventeen representative samples of supergene sulphates from old workings on the Comstock Lode are described. They range from simple minerals such as gypsum and epsomite to complex aggregates of four or more distinct species. All are well known species except a mineral of the copper (chalcanthite) or magnesium sulphate pentahydrate group, with about half the magnesium replaced by copper, zinc, ferrous iron, and manganese. Four new analyses of Comstock Lode mine waters are given. © 1938 Society of Economic Geologists, Inc.

Nevada↗
USGS1988

Mineral and whole-rock compositions of seawater-dominated hydrothermal alteration at the Arctic volcanogenic massive sulfide prospect, Alaska

The Arctic volcanogenic massive sulfide prospect, located in the Ambler mineral district of northwestern Alaska, includes three types of hydrothermally altered rocks overlying, underlying, and interlayered with semimassive sulfide mineralization. Hydrothermal alteration of wall rocks and deposition of sulfide and gangue minerals were contemporaneous with Late Devonian or Early Mississippian basalt-rhyolite volcanism. Whole-rock analyses of altered rocks surrounding the prospect indicate that strong chemical gradients exist in major and minor oxides and volatiles. These were not homogenized or overprinted by Late Jurassic (?) to Middle Cretaceous greenschist to glaucophane-schist facies metamorphism. Very low alkali contents and moderate to very high contents of Ba, F, and Mg are the major chemical characteristics of the pervasively altered rocks. The strong Mg metasomatism, high Ba contents, and limited extent of altered rocks suggest a rapid influx of relatively cold seawater into a hot hydrothermal vent system. Alteration developed asymmetrically around a linear fissure, suggesting fracture control of ore fluids rather than a point source. Micro-probe analyses of phyllosilicates from the Arctic area indicate two discrete mineral populations. Magnesian chlorite, barian white mica, and barian fiuorphlogopite in hydrothermally altered rocks have compositions distinct from similar minerals (chlorite, phengite, biotite) developed during high-pressure metamorphism in metapelitic and metavolcanic lithologies. These differences in mineral chemistry are the result of differences in protolith composition caused by hydrothermal alteration-metasomatism. Without mineral composition data, the contacts between some alteration assemblages and relatively unaltered metavolcanic and metasedimentary rocks with similar mineralogy cannot be determined.

Economic Geology↗
USGS1976

Hard rock uranium potential in Alaska

Discussing the potential of "hardrock" (i.e., non-sedimentary type) uranium deposits in a 586,000 mi 2 portion of the North America Cordillera is a difficult task compounded by the fact that the remoteness of much of the region and the logistical difficulties have resulted in only reconnaissance geologic information being available for large parts of the state. Cobb (1970) has listed known occurrences of uranium and thorium minerals in the state and a somewhat modified version of his compilation showing chiefly hardrock occurrences is given in figure 1; it should be emphasized that these are occurrences only and not necessarily deposits of possible economic significance. The distribution pattern shows a concentration of occurrences in southeastern Alaska and particularly in the interior. The only production of uranium in Alaska from any type of deposit has been from a hardrock deposit, that being the roughly 120,000 tons of ore averaging about one percent U 3 0 8 from the Ross-Adams mine near Bokan Mountain on Prince of Wales Island close to the southern tip of southeastern Alaska. The Bokan Mountain uranium-thorium area includes about 71 mi 2 and is largely underlain by plutonic rocks (MacKevett, 1963). The plutonic rocks range from pyroxenite to peralkaline granite and syenite, but they consist chiefly of diorite, quartz diorite, granodiorite, and quartz monzonite. The peralkaline granite, a small pluton about 3 mi2 in area, is Late Triassic or Early Jurassic in age while the other plutonic rocks are early Paleozoic.

Alaska↗
USGS1990

Preliminary geologic map of the Wadi As Sirhan Quadrangle, sheet 30C, Kingdom of Saudi Arabia

The Wadi as Sirhan quadrangle lies in the northwestern pan of Saudi Arabia on the border with Jordan. It is located in the west-central part of the Sirhan-Turayf basin and is underlain by Silurian to Miocene-Pliocene sedimentary rocks that are partly covered by volcanic flows. The map area also contains large areas of surficial sand and gravel. The study area is mainly a structural depression formed by the Wadi as Sirhan graben complex, and it is flanked by highlands of moderate altitude. The Wadi as Sirhan graben is believed to have been formed by tensional forces associated with rifting in the Red Sea. The map area contains the Thaniyat, Ghinah, and Arqah phosphorite members, and the phosphate-bearing Sib member. Hypothetical estimates of mineral resource potential of the phosphate rock in the quadrangle are high, but most prospects are either covered with too much overburden or are too thin and of too low a grade to be considered for economic exploitation at this time. Several deep drill holes in the Wadi as Sirhan depression have penetrated thick sequences of marine rocks that are potential sources of oil and gas. Geological and geophysical conditions are favorable for the accumulation of hydrocarbons, and additional exploration is recommended.

Open-File Report↗
USGS2014

Suggestions as to future research in ground‐water hydrology

Determination of the ground‐water supply available from any aquifer or in any specified area requires not merely the application of specific quantitative methods but also a broad and accurate knowledge of the geologic, hydrologlc, and geochemical factors that are involved, and consideration of the economic and legal limitations. Further research is needed as to geologic texture and structure in relation to the occurrence and movement of the water; the precise nature of specific yield, which determines the effective storage capacities of the aquifers; the molecular physics involved in the downward and upward movement of water in the zone of aeration, and quantitative evaluation of ground‐water recharge and discharge; the hydraulics of ground water, as studied by pumping test methods, with special reference to boundary conditions; studies of perennial yield of aquifers of low permeability; the genesis of the mineral contents of ground water as determined through appropriate geologic, hydrologlc, and chemical studies; and methods of geophysical exploration and well logging for determining the occurrence of ground water. Serious study is also needed as to practicable methods of implementing the recently developed principles and methods of ground‐water hydrology in the production of water supplies and the economic and legal problems involved.

Eos, Transactions, American Geophysical Union↗
USGS1989

Estimates of undiscovered conventional oil and gas resources in the United States: A part of the Nation's energy endowment

In 1987, the U.S. Geological Survey and the Minerals Management Service completed a new assessment of the undiscovered conventional resources of crude oil and natural gas in the United States. This assessment responded to a national need for such estimates, considered new geological, technologic, and economic information, and used more definitive methods of resource appraisal than previous assessments. The conventional resources assessed were (1) those considered recoverable under current technology and (2) those that could be developed and produced economically under specified price and cost relationships, excluding exploration costs. This study did not include resources from tar deposits, intractable heavy oil deposits, oil shales, gas in low-permeability (less than 0.1 millidarcy in situ) "tight" reservoirs, coal bed methane, gas in geopressured shales and brines, and natural gas hydrates (clathrates). For this study, the United States was divided into 13 regions (9 onshore and 4 offshore), including the Exclusive Economic Zone (EEZ). The 13 regions were further divided into 115 provinces (appendix A, figs. Al and A2). The resource estimates were based fundamentally upon review and analysis of petroleum geology and the exploration history of oil and gas plays in these provinces. Probability procedures were used in their derivation. Because of the uncertainty in estimating undiscovered resources, the estimated quantities are reported as a range of values that correspond to different probability levels. The undiscovered recoverable conventional resources of oil for the United States, as of January, 1, 1987, are estimated to range from 33 to 70 billion barrels, with a mean estimate of 49 billion barrels: the estimates of gas range from 307 to 507 trillion cubic feet, with a mean estimate of 399 trillion cubic feet (table 1). Range estimates correspond to 95-percent probability (19 in 20 chance) and 5-percent probability (1 in 20 chance) of there being more than those amounts, respectively. Corresponding estimates for natural gas liquids (NGL) range from 6 to 12 billion barrels, with a mean estimate of 9 billion barrels. Further, the assessed undiscovered economically recoverable oil and gas resources for the United States, as of January 1, 1987, are estimated to range from 21 to 54 billion barrels of oil and 208 to 326 trillion cubic feet of gas, corresponding to the 95-percent and 5-percent probabilities of there being more than these amounts, respectively (table 1). The mean value for oil is 35 billion barrels and for gas is 263 trillion cubic feet. Corresponding estimates for NGL range from 5 to 8 billion barrels, with a mean of 6 billion barrels. Distribution of these resources by region is shown in figure 1.

Report↗