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Jeffrey C. Wynn

Publications and source records attributed to Jeffrey C. Wynn.

At least 19 recordsLinked to original sources
USGS2008

Preliminary model of porphyry copper deposits

The U.S. Geological Survey (USGS) Mineral Resources Program develops mineral-deposit models for application in USGS mineral-resource assessments and other mineral resource-related activities within the USGS as well as for nongovernmental applications. Periodic updates of models are published in order to incorporate new concepts and findings on the occurrence, nature, and origin of specific mineral deposit types. This update is a preliminary model of porphyry copper deposits that begins an update process of porphyry copper models published in USGS Bulletin 1693 in 1986. This update includes a greater variety of deposit attributes than were included in the 1986 model as well as more information about each attribute. It also includes an expanded discussion of geophysical and remote sensing attributes and tools useful in resource evaluations, a summary of current theoretical concepts of porphyry copper deposit genesis, and a summary of the environmental attributes of unmined and mined deposits.

Open-File Report↗
USGS2000

A ground electromagnetic survey used to map sulfides and acid sulfate ground waters at the abandoned Cabin Branch Mine, Prince William Forest Park, northern Virginia gold-pyrite belt

INTRODUCTION AND BACKGROUND: Prince William Forest Park is situated at the northeastern end of the Virginia Gold-Pyrite belt northwest of the town of Dumfries, VA. The U. S. Marine Corps Reservation at Quantico borders the park on the west and south, and occupies part of the same watershed. Two abandoned mines are found within the park: the Cabin Branch pyrite mine, a historic source of acid mine drainage, and the Greenwood gold mine, a source of mercury contamination. Both are within the watershed of Quantico Creek (Fig.1). The Cabin Branch mine (also known as the Dumfries mine) lies about 2.4 km northwest of the town of Dumfries. It exploited a 300 meter-long, lens-shaped body of massive sulfide ore hosted by metamorphosed volcanic rocks; during its history over 200,000 tons of ore were extracted and processed locally. The site became part of the National Capitol Region of the National Park Service in 1940 and is currently managed by the National Park Service. In 1995 the National Park Service, in cooperation with the Virginia Department of Mines, Minerals, and Energy reclaimed the Cabin Branch site. The Virginia Gold-Pyrite belt, also known as the central Virginia volcanic-plutonic belt, is host to numerous abandoned metal mines (Pavlides and others, 1982), including the Cabin Branch deposit. The belt itself extends from its northern terminus near Cabin Branch, about 50 km south of Washington, D.C., approximately 175 km to the southwest into central Virginia. It is underlain by metamorphosed volcanic and clastic (non-carbonate) sedimentary rocks, originally deposited approximately 460 million years ago during the Ordovician Period (Horton and others, 1998). Three kinds of deposits are found in the belt: volcanic-associated massive sulfide deposits, low-sulfide quartz-gold vein deposits, and gold placer deposits. The massive sulfide deposits such as Cabin Branch were historically mined for their sulfur, copper, zinc, and lead contents, but also yielded byproduct gold and silver. The environmental impact of massive sulfide deposits can be substantial. These deposits are characterized by high concentrations of heavy-metal sulfide minerals, hosted by silicate rocks. Thus, weathering of these deposits and their mine wastes has the potential to generate heavy-metal laden sulfuric acid that can have negative impacts on aquatic ecosystems. In addition, lead associated with solid mine wastes has the potential for human health impacts through ingestion. The heavy metals that are encountered in these deposits and are most likely to cause environmental impacts include copper, zinc, lead, cadmium, and arsenic. In addition, the weathering of pyrite releases large amounts of iron, and the acid generated attacks the country rocks and causes the release of large amounts of aluminum, which also can severely impact aquatic ecosystems. A reclamation attempt was made at the site in 1995, including construction of storm-water diversion trenches around the abandoned mine area, grading tailings away from the stream bank, addition of pulverized limestone and topsoil, and revegetation. The post-reclamation chemistry of shallow groundwaters (<3 meters deep) shows a neutral pH on the southwestern bank of the stream but pH of 4.1 to 4.5 on the northeastern bank. The dominant ions are Fe2+ and SO42- (Seal, Haffner, Meier, and Pollio, 1999) A ground electromagnetic survey was conducted over the site in 1999 as part of a wider study ( Seal, Haffner, and Meier, 1998a,b, 1999). It was hoped that a 3-D map of the soil conductivity derived from the survey could provide insight into the distribution of the mobilized sulfides present under the ground.

Virginia↗
USGS1999

An interpretation of the aeromagnetic and gravity data and derivative maps of the Craig and Dixon Entrance 1°x 3° quadrangles and the western edges of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska

The U.S. Geological Survey (USGS) is required by the Alaska National Interest Lands Conservation Act (ANILCA, Public Law 96-487) to survey certain Federal lands to determine their mineral resource potential. As part of continuing studies designed to fulfill this responsibility, geochemical, geological and geophysical surveys of the Craig and Dixon Entrance (CDE) 1°x3° quadrangles in southeastern Alaska were undertaken by the USGS during the summers of 1983-85, 1989, and 1991. The geochemical data have been reported by Cathrall and others (1993) and Cathrall (1994). A simplified geologic map has been compiled especially for this report based largely on the work of Eberlein and others (1983) and Gehrels (1991, 1992). Brew (1996) also produced a compilation. This report presents available magnetic and gravity data and an interpretation thereof. In this report (released on CD-ROM in 1999) we are releasing USGS-acquired geophysical data for CDE 1:250,000-scale quadrangles of southeastern Alaska. Much of the data have never appeared before in the public domain, including a simplified geologic map, the raw gravity and magnetic data, and derivative products including depth-to-source images, various grids of the data, imaging representations, rock densities, and overlays of the data. In addition, we have added a limited interpretation of what the gravity and magnetic data indicate about the underlying geology, structures, and their relationship to known and potential hidden mineral resources. This interpretation is necessarily limited in the case of the gravity data by the general sparsity of stations. For convenience, we have also included here various representations of the digital topography.

Alaska↗
USGS1999

Meteoritos en el desierto

Imagínese por un instante en medio del desierto. Anochece por el noroeste. Es un paisaje desolado donde por doquier se extienden vastas dunas móviles de arena grisácea. Ni una roca, ni un alma en 250 kilómetros a la redonda. Pese al ocaso solar, el termómetro señala 50 grados. A su espalda rugen los últimos estertores de la tormenta de la tarde. El viento dominante viene del sur, como siempre a principios de la primavera. De pronto, se enciende en el horizonte una luz brillante. Sólo una chispa, que se abre en al menos cuatro barras distintas. Apenas unos segundos, y su resplandor nos ciega. Nos quema la ropa. Pasan sigilosos esos objetos sobre nuestra cabeza. Hasta que un ruido bronco nos ensordece. Tiembla la tierra a nuestros pies y una onda de choque nos lanza a unos 50 metros. Hemos dejado atrás frentes de fuego que se elevan al firmamento, mientras vuelan por los aires grandes rocas blancas. Unas se estrellan contra la arena; otras las devora el fuego.

Investigación y Ciencia↗
USGS1997

Secrets of the Wabar craters

Focuses on the existence of craters in the Empty Quarter of Saudi Arabia created by the impact of meteors in early times. Mars Pathfinder and Mars Global Surveyor's encounter with impact craters; Elimination of craters in the Earth's surface by the action of natural elements; Impact sites' demand for careful scientific inspections; Location of the impact sites.

Al Hadida, Ar-Rub' Al-Khali (Empty Quarter)↗
USGS1994

Geologic map of the Venezuela part of the Puerto Ayacucho 2 degrees x 3 degrees Quadrangle, Amazonas Federal Territory, Venezuela

This map is one of a series of 1:500,000-scale maps that, along with several other products, stems from a cooperative agreement between the U.S. Geological Survey (USGS) and the Corporacion Venezolana de Guayana, Tecnica Minera, C.A. (TECMIN), a Venezuelan Government-owned mining and mineral exploration company. The agreement covered cooperative work carried out in the Precambrian Shield of southern Venezuela during 1987-1991 and included a geologic and mineral resource inventory, technology transfer, and scientific training (Wynn and others, in press). The Precambrian Guayana Shield (Escudo de Guyana, not to be confused with the neighboring country of Guyana) includes some of the oldest known rocks in the world (Mendoza, 1977) and also covers parts of neighboring Guyana, Surinam, French Guiana, Columbia, and Brazil. In Venezuela, it underlies most of Bolivar state and all of the Amazonas Federal Territory (see index map).

Puerto Ayacucho↗
USGS1986

Archaeological prospection: An introduction to the Special Issue

Archaeological prospection, as the use of geophysical methods in archaeology is known in Europe, is about four decades old (seven decades, if aerial photography of archaeological sites is included). Virtually the entire range of geophysical methods, perhaps excluding only borehole techniques, has found application in the search for archaeological sites unseen or partially known. Pressures by developers, and the public's growing sensitivity toward the preservation of historic and prehistoric cultural artifacts and sites, has led to an accelerating use of high-resolution geophysical methods in the archaeological sciences. The archaeogeophysical articles in this Special Issue are reasonably representative of the development of this specialty field of geophysics.

Geophysics↗
USGS1979

Background information to accompany folio of geologic, mineral resource, geochemical, aeromagnetic, and gravity maps of the Hillsboro and San Lorenzo quadrangles, Sierra and Grant Counties, New Mexico, with sections on geochemistry and geophysics

The Hillsboro and San Lorenzo 15-minute quadrangles of southwestern New Mexico have been mapped at a 1:48,000 scale and selected mineralized areas within these quadrangles have been mapped in greater detail. This area of about 550 mi2 (1,424 km2) is within the southern part of the Black Range and includes much of the Mimbres Mountains and parts of the adjoining Black Range Primitive area. The region is highly mineralized with Laramide (75.1 ? 2.5 m.y.) and middle Tertiary (about 32 to 35 m.y.) intrusions providing the source for much of the base- and precious-metal mineralization. The porphyry copper deposit at Copper Flat is a subvolcanic Laramide quartz monzonite stock that was intruded into a thick section (>2,700 ft or >823 m) of Upper Cretaceous andesite. Numerous gold-bearing veins radiate from the central quartz monzonite stock, and locally offset a radial system of quartz latite dikes. Gold-bearing veins, chiefly along the south and east periphery of the stock, have provided the source for both gold lode and placer deposits. The middle Tertiary rhyolitic plugs, stocks, and dikes have intruded a dominantly carbonate section of Paleozoic sediments and bedding replacement deposits of zinc, lead, and copper are closely associated with tactite in the Carpenter (Swartz) mining district. The rich oxidized silver deposits of the Kingston district are largely fault controlled and a metallizing pluton is not present at the surface outcrop. Some of the silver-bearing base-metal veins in the Kingston district contain rhodochrosite, rhodonite, and alabandite and the highly oxidized parts of these veins have been mined for manganese ore. Very minor amounts of tungsten, as scheelite, occur in thin tactite zones along Tank Canyon, at the Silver Queen claims near Kingston, and at the Silver Tail group of mines along Pierce Canyon.

New Mexico↗
USGS1979

An experimental ground-magnetic and VLF-EM traverse over a buried paleochannel near Salisbury, Maryland

Since, 1963, the Maryland Geological Survey and the U.S. Geological Survey have been engaged in a study of the Pleistocene Series beneath a 230 square kilometer area around Salisbury, Maryland. (Hansen, 1966; Weigle, 1972; Zohdy and others, 1974, p.56) North of Salisbury a deep Pleistocene paleochannel was discovered; this channel was carved into an erosional plain at the top of the Miocene deposit, was filled and blanketed subsequently with deposits (mostly sand and gravel) of Pleistocene age. The channel is a prolific source of ground water, and has been outlined for a least 15 kilometers by means of power-augering and gamma-logging. A geophysical survey using ground magnetics and VLF-EM was made over the channel in an attempt to see if a more efficient method than augering could be developed to map the paleochannel at depth; the survey traverse was made over one of the better defined parts of the paleochannel (see figure 1.) where airborne magnetics and VLF studies could easily be done as a potential follow-up. We hoped to be able to map resistivity changes between aquifer and aquiclude facies with the VLF-EM, and perhaps identify other facies changes in black-sand concentrations with ground magnetics. The data is presented in Table 1 and plotted in figure 2. The traverse extended from north to south, with station spacing of 100 meters, for an over all length of 4.5 kilometers.

Maryland↗