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Minerals & deposits

Find USGS publications on mineral resources and deposits. Search commodities and geographic names, then check source reports for geology and assessment methods.

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At least 955 records · Page 53Linked to original sources

USGS1988

COEXISTING GALENA, PbS//S//S AND SULFOSALTS: EVIDENCE FOR MULTIPLE EPISODES OF MINERALIZATION IN THE ROUND MOUNTAIN AND MANHATTAN GOLD DISTRICTS, NEVADA.

Studies of galena and Pb-Bi-Ag-Cu(Hg) sulfosalts of varied compositions in the Round Mountain and Manhattan gold districts of Nevada corroborate the occurrence of several distinct mineralized systems characterized by different mineral compositions and assemblages. The different episodes of mineralization are related to different Cretaceous and Tertiary magmatic-hydrothermal events, although the assignment of specific mineral compositions and associations with dated mineralized systems is still incomplete. At the Fairview mine, galena associated with Pb-Bi-Ag sulfosalts and simple sulfides occurs as intergrowths of discretely different composition controlled by silver and bismuth content. A galena-type phase (Pbs//s//s) with solid solution toward matildite, AgBiS//2(composition Gal//6//0Mat//4//0) was found. If silver and, to a lasser extent, bismuth are absent, the galena formed will be almost pure PbS. Some minor antimony may substitute for bismuth. This study confirms a linear relationship between a cell edge and Ag-Bi(Sb) content for galena containing less than about 15 wt. percent Ag and Bi(Sb).

Canadian Mineralogist↗

USGS1987

ECONOMICS AND THE SEARCH FOR OFFSHORE HEAVY MINERAL DEPOSITS.

This paper examines the relative importance, in terms of a deposit's commercial status, of physical characteristics of onshore titanium-bearing heavy-mineral placer deposits, and applies these findings to the search for and evaluation of offshore deposits. Results obtained by applying statistical discriminant analysis show that the characteristics most useful for predicting a deposit's commercial status are the grades of the constituent titanium minerals and the size of the deposit. Heavy-mineral grade or even the combined grades of all titanium-bearing minerals (without information and constituent mineral grades) are inferior predictors of a deposit's commercial status. When data from homogeneous regions are analyzed separately, the ability to accurately predict the deposit's commerical status improves.

Marine Mining↗

USGS1990

Oxygen and carbon isotope ratios of hydrothermal minerals from Yellowstone drill cores

Oxygen and carbon isotope ratios were measured for hydrothermal minerals (silica, clay and calcite) from fractures and vugs in altered rhyolite, located between 28 and 129 m below surface (in situ temperatures ranging from 81 to 199??C) in Yellowstone drill holes. The purpose of this study was to investigate the mechanism of formation of these minerals. The ??18O values of the thirty-two analyzed silica samples (quartz, chalcedony, ??-cristobalite, and ??-cristobalite) range from -7.5 to +2.8???. About one third of the silica 7samples have ??18O values that are consistent with isotopic equilibrium with present thermal waters; most of the other silica samples appear to have precipitated from water enriched in 18O (up to 4.7???) relative to present thermal water, assuming precipitation at present in situ temperatures. Available data on fluid-inclusion homogenization temperatures in hydrothermal quartz indicate that silica precipitation occurred mostly at temperatures above those measured during drilling and imply that 15O enrichments in water during silica precipitation were generally larger than those estimated from present conditions. Similarly, clay minerals (celadonite and smectite) have ??18O values higher (by 3.5 to 7.9???) than equilibrium values under present conditions. In contrast, all eight analyzed calcite samples are close to isotopic equilibrium with present thermal waters. The frequent incidence of apparent 18O enrichment in thermal water from which the hydrothermal minerals precipitated may indicate that a higher proportion of strongly 18O-enriched deep hydrothermal fluid once circulated through shallow portions of the Yellowstone system, or that a recurring transient 18O-enrichment effect occurs at shallow depths and is caused either by sudden decompressional boiling or by isotopic exchange at low water/rock ratios in new fractures. The mineralogy and apparent 18O enrichments of hydrothermal fracture-filling minerals are consistent with deposition during transient boiling or rock-water exchange (fracturing) events. ?? 1990.

Journal of Volcanology and Geothermal Research↗

USGS1991

Techniques and strategies for data integration in mineral resource assessment

The Geologic and the National Mapping divisions of the U.S. Geological Survey have been involved formally in cooperative research and development of computer-based geographic information systems (GISs) applied to mineral-resource assessment objectives since 1982. Experience in the Conterminous United States Mineral Assessment Program (CUSMAP) projects including the Rolla, Missouri; Dillon, Montana; Butte, Montana; and Tonopah, Nevada 1?? ?? 2?? quadrangles, has resulted in the definition of processing requirements for geographically and mineral-resource data that are common to these studies. The diverse formats of data sets collected and compiled for regional mineral-resource assessments necessitate capabilities for digitally encoding and entering data into appropriate tabular, vector, and raster subsystems of the GIS. Although many of the required data sets are either available or can be provided in a digital format suitable for direct entry, their utility is largely dependent on the original intent and consequent preprocessing of the data. In this respect, special care must be taken to ensure the digital data type, encoding, and format will meet assessment objectives. Data processing within the GIS is directed primarily toward the development and application of models that can be used to describe spatially geological, geophysical, and geochemical environments either known or inferred to be associated with specific types of mineral deposits. Consequently, capabilities to analyze spatially, aggregate, and display relations between data sets are principal processing requirements. To facilitate the development of these models within the GIS, interfaces must be developed among vector-, raster-, and tabular-based processing subsystems to reformat resident data sets for comparative analyses and multivariate display of relations.

Conference Paper↗

USGS1996

Jensenite, Cu 3 Te (super 6+) O 6 .2H 2 O, a new mineral species from the Centennial Eureka Mine, Tintic District, Juab County, Utah

Jensenite, ideally Cu 3 Te (super 6+) O 6 .2H 2 O, is monoclinic, P2 1 /n (14), with unit-cell parameters refined from powder data: a 9.204(2), b 9.170(2), c 7.584(1) Aa, beta 102.32(3) degrees , V 625.3(3) Aa 3 , a:b:c 1.0037:1:0.8270, Z = 4. The strongest six reflections of the X-ray powder-diffraction pattern [d in Aa(I)(hkl)] are: 6.428(100)(101,110), 3.217(70)(202), 2.601(40)(202), 2.530(50)(230), 2.144(35)(331) and 1.750(35)(432). The mineral is found on the dumps of the Centennial Eureka mine, Juab County, Utah, where it occurs as isolated crystals or as groups of crystals on drusy white quartz. Associated minerals are mcalpineite, xocomecatlite and unnamed Cu(Mg,Cu,Fe,Zn) 2 Te (super 6+) O 6 .6H 2 O. Individual crystals of jensenite are subhedral to euhedral, and form simple rhombs that are nearly equant. Some crystals are slightly elongate [101], with a length-to-width ratio up to 2:1. The largest crystal is approximately 0.4 mm in size; the average size is between 0.1 and 0.2 mm. Cleavage {101} fair. Forms are: {101} major; {110} medium; {100} minor; {301}, {201}, {203}, {102}, {010} very small. The mineral is transparent, emerald green, with a less intense streak of the same color and an uneven fracture. Jensenite is adamantine, brittle and nonfluorescent; H (Mohs) 3-4; D (calc.) 4.78 for the idealized formula, 4.76 g/cm 3 for the empirical formula. In a polished section, jensenite is very weakly bireflectant and nonpleochroic. In reflected plane-polarized light in air, it is a nondescript grey, and in oil, it is a much darker grey in color with a brownish tint, with ubiquitous bright green internal reflections. Anisotropy is not detectable. Measured values of reflectance, in air and in oil, are tabulated. Electron-microprobe analyses yielded CuO 50.91, ZnO 0.31, TeO 3 38.91, H 2 O (calc.) [8.00], total [98.13] wt.%. The empirical formula, derived from crystal-structure analysis and electron-microprobe analyses, is (Cu (sub 2.92) Zn (sub 0.02) ) (sub Sigma 2.94) Te (super 6+) (sub 1.01) O (sub 5.97) .2.03H 2 O, based on O = 8. The mineral name honors Martin C. Jensen, Reno, Nevada, who discovered the mineral.

Canadian Mineralogist↗

USGS2008

Hepatic minerals of white-tailed and mule deer in the southern Black Hills, South Dakota

Because there is a paucity of information on the mineral requirements of free-ranging deer, data are needed from clinically healthy deer to provide a basis for the diagnosis of mineral deficiencies. To our knowledge, no reports are available on baseline hepatic mineral concentrations from sympatric white-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus) using different habitats in the Northern Great Plains. We assessed variation in hepatic minerals of female white-tailed deer (n=42) and mule deer (n=41). Deer were collected in February and August 2002 and 2003 from study areas in Custer and Pennington Counties, South Dakota, in and adjacent to a wildfire burn. Hepatic samples were tested for levels (parts per million; ppm) of aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), boron (B), cadmium (Cd), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), magnesium (Mg), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), phosphorus (P), potassium (K), selenium (Se), sodium (Na), sulfur (S), thalium (T1), and zinc (Zn). We predicted that variability in element concentrations would occur between burned and unburned habitat due to changes in plant communities and thereby forage availability. We determined that Zn, Cu, and Ba values differed (P???0.05) between habitats. Because of the nutritional demands of gestation and lactation, we hypothesized that elemental concentrations would vary depending on reproductive status; Cd, Cu, Ca, P, Mn, Mo, Na, and Zn values differed (P???0.05) by reproductive status. We also hypothesized that, due to variation in feeding strategies and morphology between deer species, hepatic elemental concentrations would reflect dietary differences; Ca, Cu, K, Co, Mo, Se, and Zn differed (P???0.05) between species. Further research is needed to determine causes of variation in hepatic mineral levels due to habitat, reproductive status, and species. ?? Wildlife Disease Association 2008.

Journal of Wildlife Diseases↗

USGS2011

The United Nations framework classification for fossil energy and mineral reserves and resources 2009

Effective resource management in a globalizing economy requires accurate assessments of fossil energy and minerals resources. The recoverable quantities must be described and categorized in a manner that is consistent with scientific and social/economic information describing the economy as well as with the information describing the projects to recover them. A number of different standards have evolved over time in response to various professional needs Under a mandate given by the United Nations Economic and Social Council, the United Nations Economic Commission for Europe (UNECE) has cooperated with Governments, regulatory agencies, industry, international organizations, and professional organizations (including Committee for Mineral Reserves International Reporting Standards (CRIRSCO), the Society of Petroleum Engineers (SPE), the American Association of Petroleum Geologists (AAPG), and the Society of Petroleum Evaluation Engineers (SPEE)), as well as with outstanding experts, to define a global classification for extractive activities (including oil, gas, heavy oil and bitumen extraction) that reflects the principal concerns of existing petroleum and mineral classifications. The United Nations Framework Classification for Fossil Energy and Mineral Reserves and Resources-2009 (UNFC-2009) aims to serve the following four principal needs: 1. The needs in international energy and mineral studies to formulate robust and long-sighted policies. 2. The needs of governments in managing their resources accordingly, allowing market prices to be transferred to the wellhead with as little loss as possible. 3. The industries' needs for information while deploying technology, management and finance to secure energy supplies and capture value efficiently within the established frameworks to serve its host countries, shareholders and stakeholders. 4. The financial community's need for information to allocate capital appropriately, providing reduced costs and improved long-sightedness through the application of lower risk-compensated discount factors. The projects are categorised with respect to economic and social viability, project feasibility and maturity and uncertainty with respect to the quantities addressed. The categorisation of projects rather than of accumulations provides coherence with other critical management information such as production, cash flows, value and demand for various input factors. This key aspect of UNFC-2009 reflects the critical relationship between the quantities that can be recovered economically and the recovery processes (projects) that must be implemented to achieve those recoveries. It facilitates the recognition of potential wastage of resources through flaring or inefficient recovery processes and therefore also the potential for improvement. Copyright 2011, Society of Petroleum Engineers.

Conference Paper↗

USGS2005

Mineral resources and consumption in the twenty-first century

Modern societies are highly dependent upon energy and mineral resources to produce and deliver the material goods and even the services of everyday life. Although societies' dependence upon fossil fuels is evident and understood by much of the population, few people are as well informed about their dependence upon a wide variety of nonfuel minerals. This ignorance may result from two interrelated conditions. First, in contrast to fossil fuels, few people directly use nonfuel minerals in recognizable forms because most use is as part of manufactured products. Second, the value of raw ($38 billion) and even processed ($397 billion) nonfuel minerals in the United States in 2002 was small relative to the value the industries that consume these materials contribute to the economy ($1,700 billion). That is, although nonfuel mineral inputs are indispensable to construction and to the manufacture of durable and even nondurable goods (USGS 2003), their value is modest compared with the value of the final products.

Book chapter↗

USGS2015

Ocean minerals

Nearly 71 percent of the Earth is covered by ocean, yet during the entire history of societies, the mineral resources essential for nation building have been acquired solely from the continents. Deep-ocean minerals were discovered over a century ago during the Challenger expedition of 1873—1876, but only relatively recently did programs develop to determine their origin, distribution, and resource potential. Continental margin marine mineral deposits include aggregate, sand, placer minerals, and phosphorite. Aggregate, sand, and placers are detrital minerals that were transported and deposited on the shelf, whereas phosphorite is a chemical sedimentary deposit that formed in place from chemical reactions in the near-surface sediment. Seawater makes up 98.8 percent of the world's surface water and contains every element in the periodic table, mostly in trace concentrations. Fe-Mn crusts are found on rock surfaces of seamounts, ridges, and plateaus as pavements and coatings on talus in areas that remain sediment-free for millions of years.

Book chapter↗

USGS2015

Mapping surficial minerals at high latitudes: The USGS 2014 imaging spectrometer data collection in Alaska

Passive optical remote sensing of high latitude regions faces many challenges including a short acquisition season and poor illumination due to low solar elevation. Additional complications are encountered in the identification of surface minerals for mineral resource characterization because minerals of interest commonly are exposed on steep terrain, further challenging reflectance retrieval and detection of mineral signatures. On shallow slopes and flat terrain, vegetation cover can interfere with or obscure the absorption features of minerals in rock and soil. The USGS is conducting a study to examine the viability of using remote sensing techniques for identification of large-tonnage, base metal-rich deposits in Alaska.

Alaska↗

USGS2014

Mineral resource of the month: vermiculite

Vermiculite comprises a group of hydrated, laminar magnesium-aluminum-iron silicate minerals resembling mica. They are secondary minerals, typically altered biotite, iron-rich phlogopite or other micas or clay-like minerals that are themselves sometimes alteration products of amphibole, chlorite, olivine and pyroxene. Vermiculite deposits are associated with volcanic ultramafic rocks rich in magnesium silicate minerals, and flakes of the mineral range in color from black to shades of brown and yellow. The crystal structure of vermiculite contains water molecules, a property that is critical to its processing for common uses. Using a process called exfoliation-in which vermiculite flakes are heated to 900 degrees Celsius or higher, causing water within the flakes to flash to steam and expand-crude vermiculite ore is processed into particles that are eight to 20 times larger. The resulting lightweight material is chemically inert and fire resistant, with low density and low thermal conductivity. It is also odorless, has high liquid absorption capacity and catalytic properties. Because it is lightweight and thermally insulating, vermiculite is used in general building plasters and concrete products, alone or combined with other lightweight aggregates such as perlite. Special plasters, in which vermiculite is combined with binders like gypsum or portland cement, fillers or other additives, provide fire protection and soundproofing. As insulation, exfoliated vermiculite, sometimes treated with a water repellent, is used to fill pores and cavities in masonry construction and hollow blockwork to enhance acoustic properties, fire rating and insulation performance. Exfoliated vermiculite can also be used to produce refractory and insulation concretes and mortars, and to make high-temperature binders for construction materials, gaskets, specialty papers, textiles and vehicle brake linings. Finer grades of exfoliated vermiculite can be used to produce various shapes of insulation pellets, high-temperature insulation, as a primary component in cementitious coatings, and as a filler in inks, paints, plastics and other materials. Vermiculite can absorb liquids such as fertilizers, herbicides and insecticides, which can then be transported as free-flowing solids. It is used in the fertilizer and pesticide markets because of its ability to act as a bulking agent, carrier and extender. In horticulture, exfoliated vermiculite improves soil aeration and moisture retention, and when mixed with peat or other composted materials, such as pine bark, vermiculite produces a good growing medium for plants. As a soil conditioner, exfoliated vermiculite improves aeration in clay-rich soils and water retention in sandy soils, while reducing the likelihood of compaction, cracking and crusting of the soil. For more information on the commercial use of vermiculite, visit minerals.usgs.gov/minerals/ .

Earth↗

USGS2011

Exploration case study using indicator minerals in till at the giant Pebble porphyry Cu-Au-Mo deposit, southwest Alaska, USA

The Pebble deposit in southwest Alaska (Fig. 1) contains one of the largest resources of copper and gold in the world. It includes a measured and indicated resource of 5,942 million tonnes (Mt) at 0.42% Cu, 0.35 g/t Au, and 250 ppm Mo (0.30% copper equivalent, CuEQ, cut off) and contains significant concentrations of Ag, Pd, and Re (Northern Dynasty Minerals 2011). The deposit remains open at depth. The Pebble West zone was discovered in 1989 by Cominco American. In 2005, Northern Dynasty Minerals Ltd. (NDM) discovered Pebble East, and in July 2007, NDM partnered with Anglo American to form the Pebble Limited Partnership (PLP). The U.S. Geological Survey began collaborative investigations with PLP in 2007 to identify techniques that will improve mineral exploration in covered terranes. The Pebble deposit is an ideal location for such a study because the deposit is undisturbed (except for drilling), is almost entirely concealed by post-mineral volcanic rocks and glacial deposits, and because its distribution is well constrained in the subsurface by PLP’s drill-hole geology and geochemistry. An exploration method developed by Averill (2007) that utilizes porphyry copper indicator minerals (PCIMR) in glacial till samples was applied at Pebble; samples were collected up- and down-ice (of former glaciers) from the deposit. The distribution of several PCIMs identifies the deposit, which suggests that PCIMs may be useful in exploration for other concealed porphyry deposits in the region. In this study, we compare the efficacy of PCIMs relative to that of pond and stream sediments also collected in the deposit area. The Pebble deposit is located 380 km southwest of Anchorage, in the Bristol Bay region of southwest Alaska. There is no road network and access to the study area is by helicopter. The deposit is situated in a broad glacially sculpted topographic low at the head of three drainages, Talarik Creek, North Fork Koktuli River, and the South Fork Koktuli River (Fig. 1). The study area is in a zone of discontinuous permafrost and is masked by lichen-rich tundra vegetation.

Alaska↗

USGS2014

Mineral resource of the month: Vermiculite

Earth↗

USGS2021

Beach placer mineral deposits along localized paleoshorelines of the western Interior Seaway, upper cretaceous Fox Hills sandstone, eastern Denver Basin, Colorado

Beach placers deposited within the Fox Hills Sandstone along the eastern flank of the Denver Basin contain minerals deemed critical in 2018 by the U.S. Department of the Interior. These marine beach placers, or paleoplacers, were deposited in the Late Cretaceous along the western edge of the retreating Western Interior Seaway (WIS). Preliminary investigations determined that these deposits contain potential critical mineral resources including titanium, zirconium, hafnium, and rare earth elements (REE). This report contains the results of a limited investigation conducted by the CGS in this area to provide additional information on the nature of these mineral deposits. The following tasks were completed during this investigation: review and summary of publicly available documents and publications; collection of samples and stratigraphic analysis of accessible outcrops; mineralogical analysis of select samples; and laboratory analysis of samples for select critical mineral concentrations. This report may assist with future mineral exploration efforts in this area and provide insight into the retreat of the WIS during the Late Cretaceous.

Report↗

USGS2023

Automated georeferencing and feature extraction of geologic maps and mineral sites

The predictive power of mineral prospectivity analysis depends on high quality, spatially accurate, analysis-ready datasets. Of paramount importance are geologic maps and mineral site data, but the state of readiness for utilizing these datasets remains sub-optimal for advanced computational techniques. As the U.S. Geological Survey (USGS) fulfils its mission to map the distribution of critical mineral commodities, non-georeferenced maps held within historical collections represent rich sources of input data. Through a series of machine learning challenges organized by the Defense Advanced Research Projects Agency (DARPA) in collaboration with the USGS, significant progress has been made in accelerating data ingestion, processing, and preparation tasks that enable mineral prospectivity mapping and mineral resource assessment workflows. Specifically, two tasks that previously required time-intensive human effort, 1) georeferencing map images, and 2) legend-based feature extraction from map images, are discussed.

Conference Paper↗

USGS2024

Conventional rare earth element mineral deposits: The global landscape

Four conventional mineral deposit types—carbonatite, alkaline igneous, heavy mineral sand, and regolith-hosted ion-adsorption clay deposits—currently supply global markets with the rare earth elements (REEs) and rare earth oxides (REOs) necessary to meet the technological needs of global communities. The unique properties of REEs make them useful in a wide variety of applications, such as alloys, batteries, catalysts, magnets, phosphors, and polishing compounds. Rare earth element minerals are complex in both composition and structure. Carbonate, oxide, silicate, and phosphate-type minerals contain highly variable amounts of rare earths. Most rare earth-bearing minerals contain mainly lighter rare earths, a mixture of all the rare earths, or only the heavier rare earths. Diverse technological applications require the full range of light, middle, and heavy rare earths. The production of these elements, in particular the heavy rare earths, remains highly dependent on deposits from China. Diversification of rare earth supply chains is contingent on expanded knowledge of globally distributed resources and an understanding of the degree to which those resources have been explored and evaluated. The knowledge of tectonic setting, typical rock associations, deposit morphology, and deposit genesis has led to the discovery of many conventional-type rare earth deposit types. Recent developments are anticipated to result in further discoveries that have the potential to meet the ever-expanding applications of REEs and REOs to address modern societal needs.

Book chapter↗

USGS2025

Airborne geophysics for geologic mapping of critical mineral systems in the United States southern midcontinent

The increased demand for clean energy technology and a significant reliance on foreign supply chains have given impetus to understanding critical mineral systems and locating potential resources within the United States. At least thirteen critical mineral-bearing systems have been identified throughout the U.S. southern Midcontinent (Hofstra and Kreiner, 2020) but much of the region’s geologic framework is concealed by vegetation and sedimentary cover that hinder traditional geologic mapping efforts. Airborne geophysical data provide an effective way to overcome these obstacles and to provide additional insight into the deeper structures that underlie shallow mineralization. However, legacy airborne magnetic and radiometric data were collected using now-outdated instruments and methods, inconsistent survey parameters, and large flight-line spacings resulting in low-resolution data that present challenges to regional-scale study and interpretation. Over the last decade, the U.S. Geological Survey Earth Mapping Resources Initiative (EMRI) and National Cooperative Geologic Mapping Program have conducted a series of high-resolution airborne magnetic and radiometric surveys across the southern Midcontinent (Fig. 1) as part of an effort to improve understanding of the geophysical framework and natural resource potential in the region. These surveys are designed using modern survey methods and instruments with consistent parameters for flight-line spacing and flight height relative to magnetic sources. The EMRI airborne surveys are planned in collaboration with State geological surveys based on focus areas (Dicken et al., 2022) according to the presence of or potential for critical mineral deposits. High-resolution airborne magnetic and radiometric data cover focus areas such as the southeast Missouri iron metallogenic province and South-Central iron-oxide-apatite (IOA) – iron-oxide-copper-gold (IOCG) province, the Magnet Cove alkaline-carbonatite complex, the Midwest Permian ultramafic dike district, the Illinois-Kentucky fluorspar district, and several Mississippi Valley-type lead-zinc deposits and districts (Fig. 1). These focus areas represent known deposits or prospective host systems of critical minerals including rare earth elements (REEs), platinum-group elements (PGEs), cobalt, lithium, fluorspar, niobium, titanium, vanadium, lead, zinc, gallium, germanium, and many more. Other significant geologic and geophysical features covered include the Reelfoot rift, the New Madrid seismic zone, the Illinois basin, the Arkoma basin, the South-Central magnetic lineament, and the Kentucky-Tennessee magnetic anomaly (Fig. 1). This presentation focuses on new airborne magnetic and radiometric data with continuous coverage across parts of six states, preliminary interpretations, examples of geologic mapping applications, and discussion of newly discovered magnetic anomalies and follow-up investigations.

Conference Paper↗

USGS2025

Mineralization processes at Escanaba Trough

Escanaba Trough off northern California is the southernmost and only sediment covered segment of the Gorda Ridge. Hydrothermal mineralization was first discovered in Escanaba Trough in 1985, and subsequent investigations included the delineation of the NESCA (northern Escanaba) and SESCA (southern Escanaba) sections of Escanaba Trough, as well as drilling by Ocean Drilling Program (ODP) Leg 169 in 1996. Preliminary research conducted in the 1980s distinguished two classes of sulfide mineral assemblages within the Escanaba Trough: one dominated by pyrrhotite (Fe 1-x S) and one containing ‘mixed sulfides’ including chalcopyrite (CuFeS 2 ) and sphalerite (ZnS). In 2022, we conducted a research expedition to the Escanaba Trough to more thoroughly characterize mineralization processes and consider preservation of precipitated minerals throughout hydrothermally active and inactive sections of Escanaba Trough, with the specific objective of characterizing the host minerals, and processes of enrichment for specific elements which are currently listed as critical elements and can also be toxic under certain conditions (Sb, As, Ba, Co, Ga, Ge, Te). The following will include initial results from that work.

California↗