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At least 1,081 records · Page 60Linked to original sources
USGS1957

Magmatic, connate, and metamorphic waters

Some major types of water of “deep” origin are believed to be recognizable from their chemical and isotopic compositions. Oil-field brines dominated by sodium and calcium chlorides differ markedly from average ocean water. In general, the brines are believed to be connate in origin (“fossil” sea water) with a negligible to high proportion of meteoric water. Many brines, particularly in pre-Tertiary rocks, are much higher in salinity than sea water and are greatly enriched in calcium as well as sodium chloride. Brines near the salinity of sea water are generally higher, relative to sea water, in bicarbonate, iodine, boron, lithium, silica, ammonium, and water-soluble organic compounds, and lower in sulfate, potassium, and magnesium. Many changes take place after sea water is entrapped in newly deposited marine sediments: (1) Iodine, silicon, boron, nitrogen, and other elements have been selectively concentrated in organisms that decompose during and after burial in sediments. Many of the elements may redissolve in the interstitial water. (2) Bacteria are active in the sediments and reduce sulfate to sulfide and produce methane, ammonia, carbon dioxide, and other products. (3) Some elements have been selectively removed from sea water by inorganic processes, such as adsorption on clays and colloidal matter. When this matter is reconstituted by diagenetic and other changes, some components are redissolved. The abundance of lithium and possibly boron and other elements may be controlled to a considerable extent by these inorganic processes. (4) The interstitial water may react chemically with enclosing sediments and produce dolomite, reconstituted clays, and other minerals. The high loss of magnesium relative to calcium in most connate waters is probably caused by such reactions. Volcanic hot-spring waters of different compositions have been discussed in an accompanying paper (White, 1957). The most significant type is believed to be dominated by sodium chloride, and is best explained as originating from dense gases driven at high temperature and pressure from magma and containing much matter of low volatility that is in solution because of the solvent properties of high-density steam. This dense vapor is condensed in and greatly diluted by deeply circulating meteoric water. Most other types of volcanic water are believed to be derived from the sodium-chloride type. Volcanic sodium-chloride waters are similar in many respects to connate waters but are believed to be distinguishable by relatively high lithium, fluorine, silica, boron, sulfur, CO 2 , arsenic, and antimony; by relatively low calcium and magnesium; and by lack of hydrocarbons, water-soluble organic compounds, and perhaps ammonia and nitrate. Relatively high boron and combined CO 2 are alone not reliable indicators of a volcanic origin. During compaction, rocks lose most of their interstitial high-chloride water; much additional water may then be lost during progressive metamorphism, and the content changes from about 5 per cent in shale to perhaps 1 per cent in gneiss. This expelled water is here called metamorphic. Because of pressure and permeability gradients, it must normally escape upward and mix with connate and meteoric water. Even though large quantities must exist, no example of metamorphic water has been positively identified. Some thermal springs in California are high in salinity and relatively low in temperature and apparent associated heat flow. Some are clearly connate in origin. Other springs are characterized by very high combined carbon dioxide and boron, relative to chloride. Their compositions are considerably different from known connate and volcanic waters and are believed to be best explained by a metamorphic origin. Although some major types of deep water seem to be recognizable, there is much danger of oversimplifying the problems. Many waters are no doubt mixtures of different types, and some of high salinity result from dissolution of salts by meteoric water.

GSA Bulletin↗
USGS2012

Geologic models and evaluation of undiscovered conventional and continuous oil and gas resources: Upper Cretaceous Austin Chalk

The Upper Cretaceous Austin Chalk forms a low-permeability, onshore Gulf of Mexico reservoir that produces oil and gas from major fractures oriented parallel to the underlying Lower Cretaceous shelf edge. Horizontal drilling links these fracture systems to create an interconnected network that drains the reservoir. Field and well locations along the production trend are controlled by fracture networks. Highly fractured chalk is present along both regional and local fault zones. Fractures are also genetically linked to movement of the underlying Jurassic Louann Salt with tensile fractures forming downdip of salt-related structures creating the most effective reservoirs. Undiscovered accumulations should also be associated with structure-controlled fracture systems because much of the Austin that overlies the Lower Cretaceous shelf edge remains unexplored. The Upper Cretaceous Eagle Ford Shale is the primary source rock for Austin Chalk hydrocarbons. This transgressive marine shale varies in thickness and lithology across the study area and contains both oil- and gas-prone kerogen. The Eagle Ford began generating oil and gas in the early Miocene, and vertical migration through fractures was sufficient to charge the Austin reservoirs.

Alabama;Arkansas;Florida;Georgia;Illinois;Kentucky↗
USGS1983

Ground-water resources in the Hood Basin, Oregon

The Hood Basin, an area of 1,035 square miles in north-central Oregon, includes the drainage basins of all tributaries of the Columbia River between Eagle Creek and Fifteenmile Creek. The physical characteristics and climate of the basin are diverse. The Wasco subarea, in the eastern half of the basin, has moderate relief, mostly intermittent streams, and semiarid climate. The Hood subarea, in the western half, has rugged topography, numerous perennial streams, and a humid climate. Water-bearing geologic units that underlie the basin include volcanic, volcaniclastic, and sedimentary rocks of Miocene to Holocene age, and unconsolidated surficial deposits of Pleistocene and Holocene age. The most important water-bearing unit, the Columbia River Basalt Group, underlies almost the entire basin. Total thickness probably exceeds 2,000 feet, but by 1980 only the upper 1,000 feet or less had been developed by wells. Wells in this unit generally yield from 15 to 1,000 gallons per minute and a few yield as much as 3,300 gallons per minute. The most productive aquifer in the Columbia River Basalt Group is The Dalles Ground Water Reservoir, a permeable zone of fractured basalt about 25 to 30 square miles in extent that underlies the city of The Dalles. During the late 1950's and mid-1960's, withdrawals of 15,000 acre-feet per year or more caused water levels in the aquifer to decline sharply. Pumpage had diminished to about 5,000 acre-feet per year in 1979 and water levels have stabilized, indicating that ground water recharge and discharge, including the pumping, are in balance. The other principal geologic units in the basin have more limited areal distribution and less saturated thickness than the Columbia River Basalt Group. Generally, these units are capable of yielding from a few to a hundred gallons per minute to wells. Most of the ground water in the basin is chemically suitable for domestic, irrigation, or other uses. Some ground water has objectionable concentrations of iron (0.3 to 6.4 milligrams per liter) and manganese (0.05 to 1.2 milligrams per liter) or is moderately hard to very hard (60 to 260 milligrams per liter as CaCO 3 ). The principal use of ground water in the Hood Basin is for irrigation of crops, with an estimated withdrawal of 7,700 acre-feet in 1979. Additional ground-water withdrawals in 1979 were estimated as: Industrial, 2,600 acre-feet; public supply, 2,100 acre-feet; and domestic and stock supply, 200 acre-feet.

Oregon↗
USGS2013

Field trial of a pulsed limestone diversion well

The use of limestone diversion wells to treat acid mine drainage (AMD) is well-known, but in many cases, acid neutralization is not as complete as would be desired. Reasons for this include channeling of the water through the limestone bed, and the slow reaction rate of the limestone gravel. A new approach to improve the performance of the diversion well was tested in the field at the Jennings Environmental Education Center, near Slippery Rock, PA. In this approach, a finer size distribution of limestone was used so as to allow fluidization of the limestone bed, thus eliminating channeling and increasing particle surface area for faster reaction rates. Also, water flow was regulated through the use of a dosing siphon, so that consistent fluidization of the limestone sand could be achieved. Testing began late in the summer of 2010, and continued through November of 2011. Initial system performance during the 2010 field season was good, with the production of net alkaline water, but hydraulic problems involving air release and limestone sand retention were observed. In the summer of 2011, a finer size of limestone sand was procured for use in the system. This material fluidized more readily, but acid neutralization tapered off after several days. Subsequent observations indicated that the hydraulics of the system was compromised by the formation of iron oxides in the pipe leading to the limestone bed, which affected water distribution and flow through the bed. Although results from the field trial were mixed, it is believed that without the formation of iron oxides and plugging of the pipe, better acid neutralization and treatment would have occurred. Further tests are being considered using a different hydraulic configuration for the limestone sand fluidized bed.

Pennsylvania↗
USGS1987

Inter-laboratory comparison of X-ray fluorescence analyses of eruptive products of El Chichón Volcano, Chiapas, Mexico

An inter-laboratory comparison has been made of X-ray fluorescence analyses of 10 samples of lava and pumices from El Chichón Volcano, Chiapas, Mexico. Some determinations of major-element constituents agree within analytical uncertainty, whereas others exchibit significant bias. Analyses carried out at the Michigan Technological University (MTU) laboratory are systematically lower in MgO (26–48%), Fe total (5–18%), CaO (4–15%) and higher in K 2 O (0–15%) than analyses made at the U.S. Geological Survey (USGS) Denver laboratory. These differences are ascribed in part to a complex combination of calibration assumptionsand mineralogical and particle-size effects inherent in the use of pressed rock-powder pellets in the analytical procedure of the MTU laboratory. Other, but as yet unknown, differences in sample preparation and/or analytical technique may also be important; effects related to natural sample inhomogeneityare believed to be insignificant. The inter-laboratory differences in the analytical data complicated accurate assessment of whether El Chichón magmas have changed composition during the past 300 000 a. Knowledge of such change is needed for understanding petrogenetic history and for such related studies as evaluation of volcanic hazards.

Applied Geochemistry↗
USGS1979

Mineral resources of the Citico Creek Wilderness Study Area, Monroe County, Tennessee

The proposed Citico Creek Wilderness comprises about 5,670 hectares (56.7 km2) in the Cherokee National Forest south of the Little Tennessee River in easternmost Monroe County, Tennessee. Principal drainages are Citico Creek and Doublecamp Creek. Rocks of the study area include greenschist-facies arkosic metasandstone, metagraywacke, slate, and metaconglomerate of the Great Smoky Group of late Precambrian age. Minor deposits of unconsolidated Quaternary alluvium locally mantle the bedrock. Deformation is shown by asymmetric and overturned folds and by several major faults. More than 500 sample s of soil, rock, and stream sediment were collected and analyzed for 31 major, minor, and trace elements by semiquantitative spectrographic, atomic absorption, and fire assay methods No significant metal anomalies were detected. Concentrations of Cu, Co, As, Pb, and Zn slightly higher than background are found within sulfidic parts of a distinctive stratigraphic unit composed of graphitic slate and metagraywacke. Pyrite and pyrrhotite are the chief sulfide minerals, with traces o f accessory sphalerite, chalcopyrite, galena, and arsenopyrite occurring as microscopic intergrowths. A reconnaissance ground radiometric survey and subsequent neutron activation analyses of selected radioactive rock samples show that the sulfidic parts of the graphitic slate unit have a relatively high content of Th and U, but are not potentially economic. No metallic mineral resources appear to exist within the Citico Creek Wilderness Study Area. Resources of slate, silica, and stone are present, but they display no special qualities to differentiate them from other such material throughout the region. Ceramic evaluation tests on selected samples of slate indicate that the slate would have only marginal use for structural clay products such as brick and tile. Minor sand and gravel deposits occur along a few streams but are present in larger quantities and are more easily recovered in other areas.

Tennessee↗
USGS2017

Geology and assessment of undiscovered oil and gas resources of the Timan-Pechora Basin Province, Russia, 2008

The Timan-Pechora Basin Province is a triangular area that represents the northeasternmost cratonic block of east European Russia. A 75-year history of petroleum exploration and production in the area there has led to the discovery of more than 16 billion barrels of oil (BBO) and 40 trillion cubic feet of gas (TCFG). Three geologic assessment units (AUs) were defined for assessing the potential for undiscovered oil and gas resources in the province: (1) the Northwest Izhma Depression AU, which includes all potential structures and reservoirs that formed in the northwestern part of the Izhma-Pechora Depression, although this part of the basin contains only sparse source and reservoir rocks and so was not assessed quantitatively; (2) the Main Basin Platform AU, which includes all potential structures and reservoirs that formed in the central part of the basin, where the tectonic and petroleum system evolution was complex; and (3) the Foredeep Basins AU, which includes all potential structures and reservoirs that formed within the thick sedimentary section of the foredeep basins west of the Uralian fold and thrust belt during the Permian and Triassic Uralian orogeny. For the Timan-Pechora Basin Province, the estimated means of undiscovered resources are 3.3 BBO, 17 TCFG, and 0.3 billion barrels of natural-gas liquids (BBNGL). For the AU areas north of the Arctic Circle in the province, the estimated means of undiscovered resources are 1.7 BBO, 9.0 TCFG, and 0.2 BBNGL. These assessment results indicate that exploration in the Timan-Pechora Basin Province is at a mature level.

Timan-Pechora Basin Province↗
USGS2019

Assessment of undiscovered copper resources of the world, 2015

The U.S. Geological Survey completed the first-ever global assessment of undiscovered copper resources for the two most significant sources of global copper supply: porphyry copper deposits and sediment-hosted stratabound copper deposits. The geology-based study identified 236 areas for undiscovered copper in 11 regions of the world. Estimated amounts of undiscovered copper resources are reported at different levels of probability. The results of the assessment indicate that a mean of at least 3,500 million metric tons (Mt) of undiscovered copper associated with these deposit types may exist worldwide, exceeding the 2,100 Mt of identified copper resources tabulated for these deposit types. Porphyry copper deposits contain 1,800 Mt of identified copper resources and are estimated to contain a mean of at least 3,100 Mt of undiscovered copper resources. South America is the dominant source for both identified and undiscovered porphyry copper resources. However, several regions of Asia, including China, have significant potential for undiscovered porphyry copper resources. The amount of mean undiscovered porphyry copper resources that may be economic to extract varies as a function of likely depth to a deposit and quality of local infrastructure that could support mining. Sediment-hosted stratabound copper deposits contain 310 Mt of identified copper resources and are estimated to contain a mean of at least 420 Mt of undiscovered copper resources. The sedimentary basins that may contain significant undiscovered copper resources are the Katanga Basin in central Africa, the Southern Permian Basin of Poland and Germany, the Chu-Sarysu Basin of Kazakhstan, and the Kodar-Udokan area of Russia. Sedimentary basins in the Northwest Botswana Rift in Botswana and Namibia, the Benguela and Cuanza Basins of Angola, and the Cambrian rocks of Egypt, Israel, and Jordan are recognized as having significant potential for undiscovered copper resources in sediment-hosted stratabound copper deposits; however, these areas require additional research, analysis, and evaluation before quantitative resource estimates can be made. The estimate of at least 3,500 Mt of undiscovered copper in two deposit types provides a basis for long-range planning for this important commodity. U.S. copper consumption is 2 Mt per year, world consumption is about 20 Mt per year, and global production from these two deposit types is about 12 Mt per year. Total global copper production from all deposit types from 1879 to 2012 was about 600 Mt. The world’s use of mineral resources, such as copper, will continue to increase in the foreseeable future to support a growing world population and increasing standards of living. The world has sufficient copper to last for decades. However, increases in exploration and growth in mining capacity will be necessary to identify and develop undiscovered resources to supply projected demand.

Scientific Investigations Report↗
USGS2011

Ages and sources of components of Zn-Pb, Cu, precious metal, and platinum group element deposits in the goodsprings district, Clark County, Nevada

The Goodsprings district, Clark County, Nevada, includes zinc-dominant carbonate replacement deposits of probable late Paleozoic age, and lead-dominant carbonate replacement deposits, copper ± precious metal-platinum group element (PGE) deposits, and gold ± silver deposits that are spatially associated with Late Triassic porphyritic intrusions. The district encompasses ~500 km 2 although the distribution of all deposits has been laterally condensed by late Mesozoic crustal contraction. Zinc, Pb, and Cu production from about 90 deposits was ~160,000 metric tons (t) (Zn > Pb >> Cu), 2.1 million ounces (Moz) Ag, 0.09 Moz Au, and small amounts of PGEs—Co, V, Hg, Sb, Ni, Mo, Mn, Ir, and U—were also recovered. Zinc-dominant carbonate replacement deposits (Zn > Pb; Ag ± Cu) resemble Mississippi Valley Type (MVT) Zn-Pb deposits in that they occur in karst and fault breccias in Mississippian limestone where the southern margin of the regional late Paleozoic foreland basin adjoins Proterozoic crystalline rocks of the craton. They consist of calcite, dolomite, sphalerite, and galena with variably positive S isotope compositions ( δ 34 S values range from 2.5–13‰), and highly radiogenic Pb isotope compositions ( 206 Pb/ 204 Pb >19), typical of MVT deposits above crystalline Precambrian basement. These deposits may have formed when southward flow of saline fluids, derived from basinal and older sedimentary rocks, encountered thinner strata and pinch-outs against the craton, forcing fluid mixing and mineral precipitation in karst and fault breccias. Lead-dominant carbonate replacement deposits (Pb > Zn, Ag ± Cu ± Au) occur among other deposit types, often near porphyritic intrusions. They generally contain higher concentrations of precious metals than zinc-dominant deposits and relatively abundant iron oxides after pyrite. They share characteristics with copper ± precious metal-PGE and gold ± silver deposits including fine-grained quartz replacement of carbonate minerals in ore breccias and relatively low S and Pb isotope values ( δ 34 S values vary from 0–~4‰; 206 Pb/ 204 Pb <18.5). Copper ± precious metal-PGE deposits (Cu, Co, Ag, Au, Pd, and Pt) consist of Cu carbonate minerals (after chalcocite and chalcopyrite) and fine-grained quartz that have replaced breccia clasts and margins of fissures in Paleozoic limestones and dolomites near porphyritic intrusions. Gold ± silver deposits occur along contacts and within small-volume stocks and dikes of feldspar porphyry, one textural variety of porphyritic intrusions. Lead isotope compositions of copper ± precious metal-PGE, gold ± silver, and lead-dominant carbonate replacement deposits are similar to those of Mojave crust plutons, indicating derivation of Pb from 1.7 Ga crystalline basement or from Late Proterozoic siliciclastic sedimentary rocks derived from 1.7 Ga crystalline basement. Four texturally and modally distinctive porphyritic intrusions are exposed largely in the central part of the district: feldspar quartz porphyry, plagioclase quartz porphyry, feldspar biotite quartz porphyry, and feldspar porphyry. Intrusions consist of 64 to 70 percent SiO 2 and variable K 2 O/Na 2 O (0.14–5.33) that reflect proportions of K-feldspar and albite phenocrysts and megacrysts as well as partial alteration to K-mica; quartz and biotite phenocrysts are present in several subtypes. Albite may have formed during emplacement of magma in brine-saturated basinal strata, whereas hydrothermal alteration of matrix, phenocrystic, and megacrystic feldspar and biotite to K-mica, pyrite, and other hydrothermal minerals occurred during and after intrusion emplacement. Small volumes of garnet-diopside-quartz and retrograde epidote-mica-amphibole skarn have replaced carbonate rocks adjacent to one intrusion subtype (feldspar-quartz porphyry), but alteration of carbonate rocks at intrusion contacts elsewhere is inconspicuous. Uranium-lead ages of igneous zircons vary inconsistently from ~ 180 to 230 Ma and are too imprecise to distinguish age differences among intrusion subtypes; most ages are 210 to 225 Ma, yielding a mean of 217 ± 1 Ma. K-Ar and 40 Ar/ 39 Ar ages of magmatic (plagioclase, biotite) and hydrothermal (K-mica) minerals span a similar range (183–227 Ma), demonstrating broadly contemporaneous intrusion emplacement and hydrothermal alteration but allowing for multiple Late Triassic magmatic-hydrothermal events. Imprecision and range of isotopic ages may have resulted from burial beneath Mesozoic and Tertiary strata and multiple intrusion of magmas, causing thermal disturbance to Ar systems and Pb loss from zircons in intrusions. Separate late Paleozoic (zinc-dominant carbonate replacement deposits) and Late Triassic (all other deposits) mineralizing events are supported by form, distribution, and host rocks of metal deposits, by hydrothermal mineral assemblages, isotope compositions, metal abundances, and metal diversity, and by small intrusion volumes. These characteristics collectively distinguish the Goodsprings district from larger intrusion related carbonate replacement districts in the western United States. They can be used to evaluate proximity to unexposed porphyritic intrusions associated with PGE and gold ± silver mineralization.

Nevada↗
USGS2005

Mudstone sedimentation at high latitudes: Ice as a transport medium for mud and supplier of nutrients

Controls on mudstone deposition at high latitudes are poorly known relative to low latitudes. In recent sediments deposited in these environments, ice significantly influences sediment transport and primary productivity. The products of ice transport are relatively well known in glacimarine settings, but are less well known from below melting sea ice. This latter setting is significant as today it is associated with high primary organic productivity. The aim of this study is to assess how sea ice might have controlled lithofacies variability and organic-matter distribution and preservation in an ancient marine, siliciclastic mudstone-dominated succession deposited at high latitudes. Combined sedimentary logging, optical and electron optical (back-scatte red electron imagery), geochemical, and isotopic methods were used to determine sample variability in forty-five samples collected from the Lower Cretaceous succession in the Mikkelsen Bay State #1 borehole (North Slope, Alaska). The succession overall fines upward and contains muddy sandstones and sand- and silt-bearing, clay-rich mudstones towards its base in contrast to clay-rich and clay-dominated mudstones towards its top. Some of the mudstone units exhibit thin (< 5 mm), relic-beds that fine upward weakly. In some units small (0.5 mm), bed-parallel silt-filled microburrows disrupt depositional laminae whereas in others pervasive burrowing completely obliterates original depositional textures. Many of the units are pelleted. These mudstones are unusual in that they contain minor but very striking outsize grains, composed of subrounded to rounded sand and granule-size material. In addition, they are good petroleum source rocks, with between 2.8 and 5.9 wt % total organic carbon, of predominantly Type II kerogen. The organic matter has an isotopic signature ranging from -25.4??? ??13C to -28.1??? ??13C. Thin tuffs (< 20 mm) and carbonate-cemented units are also present. Given the absence of significant polar ice in the Early Cretaceous the outsized grains are interpreted to have been deposited from a combination of melting, dirty anchor, and fast ice. The mud fraction, which forms the bulk of the sediment, is interpreted to have been deposited from melting, sediment-laden frazil ice, and fast ice. After deposition sediments were partially reworked by bottom currents generated by brine rejection during sea ice formation. Sympagic organisms, grazing on algae and bacteria both within and below the ice, pelleted the sediment. Bioturbation, which varies through the succession, indicates that sedimentation probably occurred beneath a predominantly oxic or dysoxic water column. In this setting productivity was fueled by nutrients released from melting sea ice in the marginal ice zone. The good petroleum source potential of these mudstones is attributed to high organic productivity coupled to episodic and rapid sedimentation rather than existence of bottom-water anoxia linked to upwelling. Because sea-ice rafting was probably the dominant sediment transport mechanism it is not appropriate to use sequence stratigraphic methodology to predict lithofacies variability in this environment. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).

Journal of Sedimentary Research↗
USGS1999

DBP formation of aquatic humic substances

Terrestrial vegetation commonly shed into reservoirs contains chemical precursors of DBPs. Aquatic humic substances (AHSs) in water generate potentially harmful disinfection by‐products (DBPs) such as haloacetic acids (HAAs) and trihalomethanes (THMs) during chlorination. AHSs from two Arkansas reservoirs were characterized to define source, identify meta‐dihydroxybenzene (m‐DHB) structures as probable DBP precursors, and evaluate predicted HAA and THM formation potentials. Elemental nitrogen content < 1 percent, phenol content > 0.5 μeq/mg, δ 13 C values of –27% o , and low yields of syringyl phenols found by cupric oxide (CuO) oxidation suggest a pine tree source for the AHSs found in the Maumelle and Winona reservoirs in Little Rock, Ark. CuO oxidation yielded fewer m‐DHB structures in Maumelle AHSs than in Winona AHSs. A higher 3,5‐dihydroxybenzoic acid (3,5‐DHBA) content correlated with increased HAA and THM formation potential. The 3,5‐DHBA concentration in Winona AHSs was similar to the range found in AHSs extracted from deciduous leaf litter, twigs, and grass leachates.

Journal - American Water Works Association↗
USGS1992

Organic matter diagenesis as the key to a unifying theory for the genesis of tabular uranium-vanadium deposits in the Morrison Formation, Colorado Plateau

Interstitial, epigenetic amorphous organic matter is intimately associated with uranium in the Grants uranium region on the southern part of the Colorado Plateau in northwestern New Mexico and is considered essential to genetic models for these deposits. In contrast, uranium minerals are intimately associated with authigenic vanadium chlorite and vanadium oxides in amorphous organic matter-poor ores of the Slick Rock and Henry Mountains mining districts on the northern part of the plateau, and therefore, in some genetic models amorphous organic matter is not considered crucial to the formation of these deposits. Differences in organic matter content can be explained by recognizing that amorphous organic matter-poor deposits have been subjected to more advanced stages of diagenesis than amorphous organic matter-rich deposits, during which organic compounds were broken down, solubilized, and removed during various diagenetic stages (e.g., sulfate reduction, methanogenesis, and organic acid production). Most diagenetic alterations (e.g., dissolution of framework grains and cements and precipitation of coarse-grained coffinite, vanadium clays, and vanadium oxides) characteristic of amorphous organic matter-poor deposits occurred when temperatures exceeded 80 degrees C--a temperature typical of the organic acid stage of diagenesis.Two factors combined to assure that a high percentage of the amorphous organic matter was removed from the Morrison Formation during diagenesis: the fact that the organic matter was humic (and therefore highly oxygenated), and that the juxtaposition of authigenic smectite and amorphous organic matter on grain rims facilitated clay mineral-organic catalysis reactions leading to the breakdown of large organic molecules into smaller, soluble molecules.Evidence that amorphous organic matter was involved in the genesis of organic matter-poor, as well as organic matter-rich, deposits includes the presence of leached iron-titanium oxides and strongly etched garnets (both attributed to leaching by organic acids), the gradation from organic matter-rich to organic matter-poor deposits in the Grants uranium region, the inverse correlation between the amount of amorphous organic matter and the intensity of diagenetic alteration, the ubiquitous occurrence of amorphous organic matter inclusions in coffinite, and the similarity in geometry of tabular uranium-vanadium ores and Holocene humate deposits. By recognizing that amorphous organic matter was crucial to the initial concentration of uranium (even in those deposits that presently contain little amorphous organic matter) and by recognizing the effects of the various stages of diagenesis on the ore, one genetic model may be applied to all of the sandstone-hosted, tabular-type uranium-vanadium deposits in the Morrison Formation on the Colorado Plateau.

Economic Geology↗
USGS2010

Geologic map of Lassen Volcanic National Park and vicinity, California

The geologic map of Lassen Volcanic National Park (LVNP) and vicinity encompasses 1,905 km 2 at the south end of the Cascade Range in Shasta, Lassen, Tehama, and Plumas Counties, northeastern California (fig. 1, sheet 3). The park includes 430 km 2 of scenic volcanic features, glacially sculpted terrain, and the most spectacular array of thermal features in the Cascade Range. Interest in preserving the scenic wonders of the Lassen area as a national park arose in the early 1900s to protect it from commercial development and led to the establishment in 1907 of two small national monuments centered on Lassen Peak and Cinder Cone. The eruptions of Lassen Peak in 1914-15 were the first in the Cascade Range since widespread settling of the West in the late 1800s. Through the printed media, the eruptions aroused considerable public interest and inspired renewed efforts, which had languished since 1907, to establish a national park. In 1916, Lassen Volcanic National Park was established by combining the areas of the previously established national monuments and adjacent lands. The southernmost Cascade Range is bounded on the west by the Sacramento Valley and the Klamath Mountains, on the south by the Sierra Nevada, and on the east by the Basin and Range geologic provinces. Most of the map area is underlain by middle to late Pleistocene volcanic rocks; Holocene, early Pleistocene, and late Pliocene volcanic rocks (<3.5 m.y.) are less common. Paleozoic and Mesozoic rocks are inferred to underlie the volcanic deposits (Jachens and Saltus, 1983), but the nearest exposures of pre-Tertiary rocks are 15 km to the south, 9 km to the southwest, and 12 km to the west. Diller (1895) recognized the young volcanic geology and produced the first geologic map of the Lassen area. The map (sheet 1) builds on and extends geologic mapping by Williams (1932), Macdonald (1963, 1964, 1965), and Wilson (1961). The Lassen Peak area mapped by Christiansen and others (2002) and published in greater detail (1:24,000) was modified for inclusion here. Figure 2 (sheet 3) shows the mapping credit for previous work; figure 3 (sheet 3) shows locations discussed throughout the text. A CD-ROM entitled Database for the Geologic Map of Lassen Volcanic National Park and Vicinity, California accompanies the printed map (Muffler and others, 2010). The CD-ROM contains ESRI compatible geographic information system data files used to create the 1:50,000-scale geologic map, both geologic and topographic data and their associated metadata files, and printable versions of the geologic map and pamphlet as PDF formatted files. The 1:50,000-scale geologic map was compiled from 1:24,000-scale geologic maps of individual quadrangles that are also included in the CD-ROM. It also contains ancillary data that support the map including locations of rock samples selected for chemical analysis (Clynne and others, 2008) and radiometric dating, photographs of geologic features, and links to related data or web sites. Data contained in the CD-ROM are also available on this Web site. The southernmost Cascade Range consists of a regional platform of basalt and basaltic andesite, with subordinate andesite and sparse dacite. Nested within these regional rocks are 'volcanic centers', defined as large, long-lived, composite, calc-alkaline edifices erupting the full range of compositions from basalt to rhyolite, but dominated by andesite and dacite. Volcanic centers are produced by the focusing of basaltic flux from the mantle and resultant enhanced interaction of mafic magma with the crust. Collectively, volcanic centers mark the axis of the southernmost Cascade Range. The map area includes the entire Lassen Volcanic Center, parts of three older volcanic centers (Maidu, Dittmar, and Latour), and the products of regional volcanism (fig. 4, sheet 3). Terminology used for subdivision of the Lassen Volcanic Center has been modified from Clynne (1984, 1990).

California↗
USGS2011

Characteristics, distribution, origin, and significance of opaline silica observed by the Spirit rover in Gusev crater, Mars

The presence of outcrops and soil (regolith) rich in opaline silica (∼65–92 wt % SiO 2 ) in association with volcanic materials adjacent to the “Home Plate” feature in Gusev crater is evidence for hydrothermal conditions. The Spirit rover has supplied a diverse set of observations that are used here to better understand the formation of silica and the activity, abundance, and fate of water in the first hydrothermal system to be explored in situ on Mars. We apply spectral, chemical, morphological, textural, and stratigraphic observations to assess whether the silica was produced by acid sulfate leaching of precursor rocks, by precipitation from silica‐rich solutions, or by some combination. The apparent lack of S enrichment and the relatively low oxidation state of the Home Plate silica‐rich materials appear inconsistent with the originally proposed Hawaiian analog for fumarolic acid sulfate leaching. The stratiform distribution of the silica‐rich outcrops and their porous and brecciated microtextures are consistent with sinter produced by silica precipitation. There is no evidence for crystalline quartz phases among the silica occurrences, an indication of the lack of diagenetic maturation following the production of the amorphous opaline phase.

Journal of Geophysical Research E: Planets↗
USGS2013

Groundwater–surface-water exchange and the geologic setting of northern Minnesota's lakes, wetlands, and streams—Modern-day relevance of Tom Winter's legacy

Tom Winter spent nearly 50 years conducting research in earth science, and he specialized in the exchange between groundwater and surface water. Tom's highly productive career began in Minnesota. This fi eld trip revisits many of the places where Tom conducted his early research and demonstrates the continuing relevance of that research. Stops and topics include the groundwater infl uence on the record low stage of White Bear Lake, the contribution of groundwater to continually rising water levels in an abandoned open-pit iron mine, hydrogeology of the Shingobee headwaters aquatic ecosystem research site, hydrogeology of Lake Sallie, geology associated with the Pillager water gap, and the hydrogeology of Little Rock Lake.

GSA Field Guides↗
USGS2008

Hydrogeology and water quality of the Leetown area, West Virginia

The U.S. Geological Survey’s Leetown Science Center and the co-located U.S. Department of Agriculture’s National Center for Cool and Cold Water Aquaculture both depend on large volumes of cold clean ground water to support research operations at their facilities. Currently, ground-water demands are provided by three springs and two standby production wells used to augment supplies during periods of low spring flow. Future expansion of research operations at the Leetown Science Center is dependent on assessing the availability and quality of water to the facilities and in locating prospective sites for additional wells to augment existing water supplies. The hydrogeology of the Leetown area, West Virginia, is a structurally complex karst aquifer. Although the aquifer is a karst system, it is not typical of most highly cavernous karst systems, but is dominated by broad areas of fractured rock drained by a relatively small number of solution conduits. Characterization of the aquifer by use of fluorometric tracer tests, a common approach in most karst terranes, therefore only partly defines the hydrogeologic setting of the area. In order to fully assess the hydrogeology and water quality in the vicinity of Leetown, a multi-disciplinary approach that included both fractured rock and karst research components was needed. The U.S. Geological Survey developed this multi-disciplinary research effort to include geologic, hydrologic, geophysical, geographic, water-quality, and microbiological investigations in order to fully characterize the hydrogeology and water quality of the Leetown area, West Virginia. Detailed geologic and karst mapping provided the framework on which hydrologic investigations were based. Fracture trace and lineament analysis helped locate potential water-bearing fractures and guided installation of monitoring wells. Monitoring wells were drilled for borehole geophysical surveys, water-quality sampling, water-level measurements, and aquifer tests to characterize the quality of water and the hydraulic properties of the aquifer. Surface geophysical surveys provided a 3-dimensional view of bedrock resistivity in order to assess geologic and lithologic controls on ground-water flow. Borehole geophysical surveys were conducted in monitoring wells to assess the storage and movement of water in subsurface fractures. Numerous single-well, multi-well, and straddle packer aquifer tests and step-drawdown tests were conducted to define the hydraulic properties of the aquifer and to assess the role of bedrock fractures and solution conduits in the flow of ground water. Water samples collected from wells and springs were analyzed to assess the current quality of ground water and provide a baseline for future assessment. Microbiological sampling of wells for indicator bacteria and human and animal DNA provided an analysis of agricultural and suburban development impacts on ground-water quality. Light detection and ranging (LiDAR) data were analyzed to develop digital elevation models (DEMs) for assessing sinkhole distribution, to provide elevation data for development of a ground-water flow model, and to assess the distribution of major fractures and faults in the Leetown area. The flow of ground water in the study area is controlled by lithology and geologic structure. Bedrock, especially low permeability units such as the shale Martinsburg Formation and the Conococheague Limestone, act as barriers to water flowing down gradient and across bedding. This retardation of cross-strike flow is especially pronounced in the Leetown area, where bedding typically dips at steep angles. Highly permeable fault and fracture zones that disrupt the rocks in cross-strike directions provide avenues through which ground water can flow laterally across or through strata of low primary permeability. Significant strike parallel thrust faults and cross-strike faults typically coincide with larger solution conduits and act as drains for the more pervasive network of interconnected diffuse fractures. Results of borehole geophysical surveys indicate that although numerous fractures may intersect a borehole, only one or two of the fractures typically transmit most of the water to a well. The diffuse-flow dominated network of fractures that provides the majority of storage occupies only a small proportion of the total aquifer volume but constitutes the majority of porosity within the aquifer. Solution conduits, while occupying a relatively small volume of the overall aquifer, are especially important because they serve as primary drains for the ground-water flow system. Surface resistivity maps and cross-sectionsshow anomalous areas of low resistivities coincident with the prevailing geologic strike at N. 20º E., with major cross-strike faults, and with major springs in the region. Transmissivity derived from straddle packer tests was highly variable, and ranged over three orders of magnitude (1.8 x 10 -6 to 5.9 x 10 -3 ft 2 /d) in diffuse-flow fractures. A similar large variability in transmissivity was documented by single- and multi-well aquifer tests conducted in conduit-flow dominated portions of the aquifer (2.0 x 10 3 to 1.4 x 10 4 ft 2 /d) in lowland areas immediately adjacent to the Leetown Science Center. A stream-gaging station installed on Hopewell Run near the point where the stream exits the Leetown watershed indicates average daily streamflow for the Hopewell Run of approximately 11.2 ft 3 /s, and ranged from a minimum of 1.80 ft 3 /s on September 28, 2005, to a maximum of 73.0 ft 3 /s on December 11, 2003. Base-flow (ground-water) discharge surveys identified numerous small seeps adjacent to streams in the area. Hydrographs of the stage of Balch Spring show rapid response to individual storms. Strong correlation of the flow of Hopewell Run and Balch Spring indicates the nearby losing stream reach is partly responsible for higher fluctuations in the stage of Balch Spring. A water budget for the study period (2003-2005), based on measured precipitation and hydrograph analyses, is expressed as Precipitation (38.60 in/yr) = Surface Runoff (1.36 in/yr) + Ground-Water Discharge (17.73 in/yr) + Evapotranspiration (24.23 in/yr) – Change in storage (4.72 in/yr). Flow of ground water through the epikarst, a shallow zone of intensely weathered rock and regolith, can be rapid (on the order of days or weeks) as flow is concentrated in solution conduits. Flow within the intermediate and deeper zones is typically much slower. Eight dye-tracer tests conducted in the Leetown area found ground-water flow patterns to be divergent, with velocities ranging from about 12.5 to 610 ft/day and a median velocity of 50 ft/day. Estimates of ground-water age in carbonate rocks in the region are on the order of 15 years in the shallower portions of the aquifer to 50 years or older for deeper portions of the aquifer. Shallow springs can have a significant component of fairly young water (< 5 years in age). Ground-water samples collected from 16 sites (12 wells and 4 springs) in the Leetown area were analyzed for more than 340 constituents. Only turbidity, indicator bacteria, and radon were typically present in concentrations exceeding U.S. Environmental Protection Agency (USEPA) drinking-water or aquatic life standards.

West Virginia↗
USGS2013

Crystallization of oxidized, moderately hydrous arc basalt at mid- to lower-crustal pressures: Implications for andesite genesis

This study focuses on the production of convergent margin calc-alkaline andesites by crystallization–differentiation of basaltic magmas in the lower to middle crust. Previous experimental studies show that dry, reduced, subalkaline basalts differentiate to tholeiitic (high Fe/Mg) daughter liquids, but the influences of H 2 O and oxidation on differentiation are less well established. Accordingly, we performed crystallization experiments at controlled oxidized fO 2 (Re–ReO 2 ≈ ΔNi–NiO + 2) on a relatively magnesian basalt (8.7 wt% MgO) typical of mafic magmas erupted in the Cascades near Mount Rainier, Washington. The basalt was synthesized with 2 wt% H2O and run at 900, 700, and 400 MPa and 1,200 to 950 °C. A broadly clinopyroxenitic crystallization interval dominates near the liquidus at 900 and 700 MPa, consisting of augite + olivine + orthopyroxene + Cr-spinel (in decreasing abundance). With decreasing temperature, plagioclase crystallizes, Fe–Ti-oxide replaces spinel, olivine dissolves, and finally amphibole appears, producing gabbroic and then amphibole gabbroic crystallization stages. Enhanced plagioclase stability at lower pressure narrows the clinopyroxenitic interval and brings the gabbroic interval toward the liquidus. Liquids at 900 MPa track along Miyashiro’s (Am J Sci 274(4):321–355, 1974) tholeiitic versus calc-alkaline boundary, whereas those at 700 and 400 MPa become calc-alkaline at silica contents ≥56 wt%. This difference is chiefly due to higher temperature appearance of magnetite (versus spinel) at lower pressures. Although the evolved liquids are similar in many respects to common calc-alkaline andesites, the 900 and 700 MPa liquids differ in having low CaO concentrations due to early and abundant crystallization of augite, with the result that those liquids become peraluminous (ASI: molar Al/(Na + K + 2Ca) > 1) at ≥61 wt% SiO 2 , similar to liquids reported in other studies of the high-pressure crystallization of hydrous basalts (Müntener and Ulmer in Geophys Res Lett 33(21):L21308, 2006). The lower-pressure liquids (400 MPa) have this same trait, but to a lesser extent due to more abundant near-liquidus plagioclase crystallization. A compilation of >6,500 analyses of igneous rocks from the Cascades and the Sierra Nevada batholith, representative of convergent margin (arc) magmas, shows that ASI increases continuously and linearly with SiO2 from basalts to rhyolites or granites and that arc magmas are not commonly peraluminous until SiO 2 exceeds 69 wt%. These relations are consistent with plagioclase accompanying mafic silicates over nearly all the range of crystallization (or remelting). The scarcity of natural peraluminous andesites shows that progressive crystallization–differentiation of primitive basalts in the deep crust, producing early clinopyroxenitic cumulates and evolved liquids, does not dominate the creation of intermediate arc magmas or of the continental crust. Instead, mid- to upper-crustal differentiation and/or open-system processes are critical to the production of intermediate arc magmas. Primary among the open-system processes may be extraction of highly evolved (granitic, rhyolitic) liquids at advanced degrees of basalt solidification (or incipient partial melting of predecessor gabbroic intrusions) and mixing of such liquids into replenishing basalts. Furthermore, if the andesitic-composition continents derived from basaltic sources, the arc ASI–SiO 2 relation shows that the mafic component returned to the mantle was gabbroic in composition, not pyroxenitic.

Contributions to Mineralogy and Petrology↗
USGS1975

Abundances of uranium, thorium, and potassium for some Australian crystalline rocks

This report contains a tabulation of the basic radioelement and radiogenic heat data obtained during an Australian National University (ANU) - United States Geological Survey (USGS) heat-flow project, directed jointly by J. C. Jaeger (ANU) and J. H. Sass (USGS). Most samples were collected during the periods June through September, 1971 and 1972. The measurements were made subsequently by two of us (C. M. Bunker and C. A. Bush) using the gamma-ray spec trometric techniques described by Bunker and Bush (1966, 1967). Interpreting the spectra for quantitative analyses of the radioelements was accomplished with an iterative leastsquares computer program modified from one by Schonfeld (1966). Uranium content determined by gamma-ray spectrometry is based on a measurement of the daughter products of 226 Ra. Equilibrium in the uranium-decay series was assumed for these analyses . Throughout the report, when U content is stated, radium-equivalent uranium is implied. The coefficient of variation for the accuracy of the radioelement data, when compared to ana lyses by isotope dilution and flame photometry is about 3 percent for radium-equivalent uranium and thorium and about 1 percent for potassium. These percentages are in addition to minimum standard deviations of about 0.05 ppm for U and Th, and about 0.03 percent for K.

Open-File Report↗