Journal Sciences News
Fluid Phase Equilibria
2009
Edited by
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

2009
Copyright
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

2009
Editor's Foreword
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11 Author(s): Martin Hale
2009
Preface
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11 Author(s): E.J.M. Carranza
2009
Chapter 1: Predictive Modeling of Mineral Exploration Targets
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter explains the concepts of (1) predictive modeling, (2) the predictive modeling of geochemical anomalies and prospective areas, and (3) the application of a geographic information system (GIS) in the predictive modeling of geochemical anomalies and prospective areas in terms of data analysis, integration, and visualization. A GIS consists of computer hardware, computer software, and geographically-referenced or spatial data sets and personnel. Mineral exploration endeavours to find mineral deposits, especially those with commercially viable concentrations of minerals or metals, for mining purposes. It has four phases: (1) area selection, (2) target generation, (3) resource evaluation, and (4) reserve definition. Predictive models of either geochemical anomalies or prospective areas are generally empirical models, which depict locations where mineral deposits of the type sought plausibly exist. Such pieces of spatial geo-information are important for decision-making in mineral exploration programs. The tasks involved in the predictive modeling of significant geochemical anomalies and prospective areas, however, are tedious and complex. At every scale, from region-scale to local-scale, of exploration target generation, GIS has become a decision-making tool. The tasks involved in the modeling of geochemical anomalies and/or prospective areas at any scale of target generation are numerous, tedious, and complex. A GIS does not reduce but facilitates these tasks to allow rapid yet efficient accomplishment of the pieces of spatial geo-information of interest.
2009
Chapter 2: Spatial Data Models, Management and Operations
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter discusses the concepts of spatial data models, especially the model that is appropriate for the representation of certain types of geoscience spatial data in a geographic information system (GIS), and the concepts for capturing and organizing spatial data in a GIS database. It also discusses the various types of GIS operations for spatial data analysis. A GIS facilitates efficient capture, storage, organization, management, query, retrieval, transformation, analysis, and integration of geoscience spatial data sets used in mineral exploration. Such functionalities of a GIS, in turn, facilitate efficient modeling of spatial geo-information such as geochemical anomalies and prospective areas. The registration of spatial data to a common coordinate system, the representation of geo-objects and their data attributes as either vector or raster data models, and the organization of spatial data attributes in relational databases all contribute to the analysis and integration of various spatial data or geo-information as a series of data layers. Spatial data operations on single or multiple data layers provide efficient tools for the analysis of inter-relationships among data, which are important in the modeling of geochemical anomalies and prospective areas.
2009
Chapter 3: Exploratory Analysis of Geochemical Anomalies
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter reviews the concept and methods of exploratory data analysis (EDA) that are relevant in the modeling of uni-element geochemical anomalies and demonstrates a geographic information system (GIS)-based case study application of exploratory data analysis (EDA) in the modeling of significant geochemical anomalies. Exploration geochemical data very seldom show a normal distribution. Application of methods for geochemical anomaly recognition based on classical statistics can, thus, be misguided and potentially result in spurious anomalies. In contrast, the statistical and graphical tools of exploratory data are not based on the assumption of normal distribution of data. Careful examination of statistics and graphics in exploratory data analysis allows insight to geochemical data structure and behavior, which must be considered in the analysis of uni-element as well as multi-element geochemical anomalies. Exploratory data analysis should be favored over confirmatory data analysis in the mapping of significant geochemical anomalies. GIS supplements exploratory data analysis with tools for data manipulation, integration (of spatial data that influence the spatial variability of the geochemical landscape), and visualization in the examination and mapping of significant geochemical anomalies.
2009
Chapter 4: Fractal Analysis of Geochemical Anomalies
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter reviews the concept that geochemical landscapes have fractal properties and demonstrates geographic information system (GIS)-based applications of the concentration-area method for the fractal analysis of geochemical anomalies. In the analysis of exploration geochemical data to recognize significant anomalies, it is useful to consider that geochemical landscapes have spatial variability, geometrical properties, and scale-invariant characteristics. The concentration-area fractal method takes into account such attributes of geochemical landscapes. The concentration-area method is not, however, the only method for the fractal analysis of geochemical anomalies. There are variants of the concentration-area method, for example, a concentration-distance method and a summation method. The concentration-area method and its variants are appropriate for geochemical data analysis in the spatial domain, in which the scale-invariant characteristics of geochemical landscapes are related to the empirical density distributions, spatial variability, and geometrical patterns of geochemical data sets. Other methods for the fractal analysis of geochemical anomalies involve converting geochemical data into a function of wave numbers in the frequency domain, in which the scale-invariant characteristics of geochemical landscapes are represented by means of a power spectrum. The case study on GIS-based application of the concentration-area fractal method shows the multifractal nature of the geochemical landscape in the Aroroy district (Philippines) based on stream sediment uni-element data. The results of the case study illustrate that significant anomalies related to the epithermal gold (Au) deposit occurrences are modeled better when the geochemical landscape is represented as discrete surfaces rather than as continuous surfaces.
2009
Chapter 5: Catchment Basin Analysis of Stream Sediment Anomalies
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter discusses the techniques that can be implemented in a geographic information system (GIS) for catchment basin analysis of uni-element anomalies in stream sediments. This analysis is performed to (1) estimate local uni-element background concentrations due to lithology and (2) derive and correct uni-element residuals for downstream dilution. There are various factors that influence variation in stream sediment background uni-element concentrations. Nevertheless, a universal factor of variation in stream sediment background uni-element concentration is lithology. This chapter describes two techniques for the estimation of local uni-element background due to lithology: (1) multiple regression analysis and (2) analysis of weighted mean uni-element concentrations. To recognize anomalous sample catchment basins for certain elements, dilution corrected uni-element residuals must be subjected to analytical techniques for distinguishing between background and anomaly. A GIS supports implementation of the catchment basin analysis of stream sediment anomalies in terms of (1) creating polygons representing sample catchment basins, (2) estimating areal proportions of lithologic units in sample catchment basins, (3) estimating local background uni-element concentrations attributable to lithologic units, (4) correcting uni-element residuals for downstream dilution, and (5) classifying geochemical anomalies based on dilution-corrected uni-element residuals.
2009
Chapter 6: Analysis of Geologic Controls on Mineral Occurrence
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter discusses the techniques for the analysis of spatial associations between occurrences of mineral deposits of the type sought and certain geological features. These techniques are demonstrated by using a map of occurrences of epithermal gold (Au) deposits in the case study of Aroroy district (Philippines) to define a conceptual model of prospectivity for this type of mineral deposit in that district. Models of multi-element anomalies are examined in terms of their spatial associations with the known occurrences of epithermal Au deposits in the case study area. A conceptual model of geologic controls on mineralization forms the basis of geographic information system (GIS)-based modeling of mineral prospectivity and is usually a synthesis of exploration experience, qualitative analysis, and quantitative analyses of the spatial distributions of mineral deposit occurrences and their spatial associations with certain geological features. The representation and integration of mineral prospectivity recognition criteria as spatial evidence maps in a GIS constitute a deductive process of developing a spatial model (that is, a map) of mineral prospectivity. This can be either knowledge-driven (based on qualitative analysis) or data-driven (based on quantitative analysis).
2009
Chapter 7: Knowledge-Driven Modeling of Mineral Prospectivity
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter explains the concepts of different modeling techniques for knowledge-driven mapping of mineral prospectivity, which employ either binary or multi-class evidential maps. It demonstrates each of the modeling techniques in the mapping of prospectivity for epithermal gold (Au) deposits in the case study of Aroroy district (Philippines). The performance of knowledge-driven mineral prospectivity maps depends chiefly on the subjective nature of expert judgments that are applied in creating evidential maps and in integrating evidential maps. Therefore, depending on the technique applied, deriving an optimum knowledge-driven predictive model of mineral prospectivity entails trial-and-error or comparative analysis by the (1) adjustment of evidential scores of classes in evidential maps, (2) adjustment of evidential map weights, and (3) adjustment of inference networks for combining evidential maps. The types of geographic information system (GIS) operations used in the knowledge-driven mineral prospectivity mapping include retrieval, (re-)classification, and map overlay. The first two operations are concerned with spatial evidence representation (that is, evidential map creation), whilst the last operation is concerned with spatial evidence integration. The chapter also presents the various steps of evaluating or cross-validating a mineral prospectivity map.
2009
Chapter 8: Data-Driven Modeling of Mineral Prospectivity
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

This chapter discusses the techniques addressing the issues of objective selection of a suitable unit cell size for data-driven modeling mineral prospectivity; selection of coherent deposit-type locations for data-driven modeling of mineral prospectivity; and cross-validation of data-driven mineral prospectivity models. These three issues are vital to the application of any bivariate or multivariate technique of geographic information system (GIS)-based data-driven modeling of mineral prospectivity. The experiments of data-driven modeling of mineral prospectivity presented in the chapter show that using coherent deposit-type (or proxy deposit-type) locations results in better predictive models than using just any or randomly-selected deposit-type (or proxy deposit-type) locations. The results of the experiments also show that using not just any but coherent proxy deposit-type locations (that is, unit cells immediately surrounding a unit cell representing a deposit-type location) is useful in cases where the number of occurrences of mineral deposits is considered or found insufficient to derive a proper data-driven model of mineral prospectivity. The experiments were tested through a combination of Nn and deposit-type classification strategies for the cross-validation of the predictive models of mineral prospectivity.
2009
References
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

2009
Online Sources
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

2009
Author Index
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

2008
Subject Index
Publication date: 2009
Source:Handbook of Exploration and Environmental Geochemistry, Volume 11

2008
Preface
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer
2008
Series Editor's Foreword
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Martin Hale
2008
About the Authors
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer
2008
The Indian Ocean Nodule Field
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer This chapter discusses the indian ocean nodule field (IONF). The Indian Ocean constitutes about one-seventh of the earth's surface and is the world's third largest water body. This ocean covers an area of 73.6 million km2, and is separated from the Atlantic and the Pacific oceans by roughly 20°E and 147°E, respectively. The plate boundaries of various types in the world oceans, such as divergent, convergent, transitional, and diffused are shown in this chapter. These four types of plate boundaries can be found in the India Ocean. The most spectacular geological features within and in the neighborhood of the IONF (including its flanks), which have a direct or indirect bearing on the formation, distribution, and economics of its mineral resources, are briefly described in the chapter. The physical, chemical, and biological characteristics of the sediment and water column in the IONF appear to have influenced the formation and growth of its mineral resources. The chapter outlines the physical, chemical, and biological characteristics of sediments and water column in details. Much of the physical oceanographic data from the IONF were systematically collected and analyzed under the environmental impact assessment (INDEX) programme of India's deep-sea mineral venture.
2008
Tectonics and Geomorphology
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer This chapter focuses on the tectonic and geomorphological characteristics of indian ocean nodule field (IONF). The ridge-normal structural lineaments in the IONF are largely oriented N-S to NNE-SSW, and lay perpendicular to the present-day southeast indian ridge (SEIR). Among the ridge-normal lineaments, the Vishnu FZ (along 73°E), Indrani FZ (along 79°E), and Indira FZ (along 83°E) are important. Although located outside the IONF, the influence of Indira FZ on dynamics and resource potential of the field has been considerable, and hence included in the chapter for discussion. The average depth of the IONF increases from west to east and the nodule field can be broadly divided longitudinally into three bathymetric areas. Bathymetric variations in the IONF is influenced by the rate and direction of spreading at the ridge axis as well as plate reorganization events, stress relating to intra-plate deformation at the plate boundaries between Indian and Australian (IAPB), and Australian and Capricorn (ACPB) sediment thickness, midplate volcanism, and seamount formation. Two types of faults are encountered in the IONF— that is, those having their planes facing northward away from the spreading ridge axis, from which these have been generated, and those having their planes facing southwards towards the ridge axis. The north-facing faults are normal faults. The IONF hosts several seamounts of variable dimensions that occur either in linear chains or as isolated entities. The study of these seamounts, which are essentially topographically elevated surface manifestations of mantle upwelling, provides a better understanding of crustal and mantle processes. The mode and type of emplacement of seamounts through the geological ages are generally deduced from the underlying magnetic anomalies, style of disposition, morphology, and chemistry. Magnetization of a seamount, normal or reversed, may yield constraints on the timing of seamount volcanism, particularly if a seamount is magnetized in the opposite direction to the underlying crust.
2008
Volcanics
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer Volcanic activity generally forms a complementary component contributing toward the structural and morphotectonic features on the seafloor. The central eruptions are mainly confined to the bottom of ocean basins, and largely create abyssal hills and seamounts, while K-poor tholeiitic normal mid-ocean ridge basalt (NMORB) erupts along the fissures. This chapter discusses the different types of volcanics, their distribution, and the origin of the major volcanics. The mechanisms that control the formation of basalts among others are: the cooling rate, the fluid flow, the composition of the liquid, the nucleation site, the growth rate, and the density of crystals. Ferrobasalts or FeTi basalts (i.e. enriched in Fe and Ti) are significant because of their paragenetic relation with the intensity of magnetic values of the seafloor that formed the basis for the concept of magnetic telechemistry. Ferrobasalts occur either at propagating rifts, high-amplitude magnetic zones (HAM), fast-spreading ridges, or in combination of all these. Volcanic-hydrothermal materials (VHM), discovered in the Indian Ocean Nodule Field (IONF), has important implications on the structural and volcanic histories of the field. Coarse fractions from surface and sediment column from various sedimentary regimes were investigated for VHM. Radiolarians and diatoms were identified from the various subsamples of the VHM-hosted sediments so as to determine a possible age. The two radiolarian zones, Buccinosphaera invaginata and Collosphaera tuberosa, are present with a distinct boundary between them at 30cm down core. Low-temperature alteration of deep-sea volcanics is a ubiquitous process that produces various authigenic minerals. Such alterations involve a precursor, one or more processes, and the end products. The IONF basalts are most commonly altered to palagonite, clay minerals (montmorillonite and smectite), zeolites, and iron oxides and hydroxides.
2008
Sediments
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer Sediments are formed from disintegrated rocks as a result of physical and chemical weathering. The action of various agents, like ice, wind, water, and variable temperature, helps fragment the rocks into smaller particles and leach the more soluble minerals. Weathering also results from the reaction of seawater with basalt, erupting at the crests of the mid-oceanic ridges and at other submarine volcanic features, contributing considerable amounts of materials to seawater in the process. Transported either in a dissolved or suspended state, all these materials ultimately form four types of sediment: biogenous and hydrogenous through precipitation, and lithogenous and cosmogenous in a clastic detrital state. This chapter discusses the distribution and sources of sediments. The nature and distribution of seafloor sediments in the Indian Ocean are principally controlled by five interrelated factors: (1) climatic and current pattern, (2) nutrient and organic production in surface waters, (3) relative solubility of calcite and silica, (4) submarine topography, and (5) detrital input. Based on their interactions, the four major types of sediments that occur are: terrigenous, calcareous, siliceous, and pelagic. The distribution of various clay minerals in the sediments of the Central Indian Ocean Basin (CIOB) can be used to determine the source of the sediments. Detailed study of clay minerals of different grain sizes in the surface as well as subsurface layers of sediment from 140 locations in the CIOB was made. The inter- and intra-oceanic variables that generally control the sedimentation pattern in deep-sea environments are: (1) sediment type and grain size; (2) eustatic and local sea-level changes; (3) tectonics; (4) rates of sediment supply and accumulation; (5) geometry and size of receiving basin; and (6) ocean current circulation patterns, governed in part by the coriolis effect.
2008
Ferromanganese Deposits
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer This chapter discusses the distribution, the grade, and the processes of formation of ferromanganese deposits (both nodules and crusts) during the last 5-10 million years. Acoustic and physical properties of indian ocean nodule field (IONF) nodules are studied in detail, in both dry and wet conditions. The non-destructive sound (acoustic) propagation method provides useful information on the nature of nodules. A pair of longitudinally and transversely oscillating transducers was used to measure compressional (Vp) and transverse (Vs) wave speeds through the nodules, respectively, following pulse transmit time method. Attenuation can be measured by determining the loss of acoustic pulse per unit length during the propagation through the nodules. The mineralogy of ferromanganese nodules is discussed in this chapter. The factor influencing the ferromanganese nodules formation includes: topography, availability of nucleating material, sedimentation rate, biological productivity, bottom sediment type, supply of metals, influence of bottom currents, and physico-chemical (oxidizing) environment, etc. The nodule formation in the IONF involves the source, the age, and the processes of the formation. The occurrence of nodules at the sediment–water interface would readily suggest that the bottom water and the sediment pore water (i.e. interstitial water) are the two very likely sources of elements for the accumulation around a nucleus to form nodule. The three distinct nodule growth processes are: (1) early diagenetic, (2) hydrogenetic, and (3) mixed genetic process. Ferromanganese encrustations have regularly been recovered from the deep sea along with the nodules. The inter-relationship from different ocean basins and their sum effect on the formation of various combinations of nodule types are described as: (1) tectonics and volcanisms, and (2) sediment, seawater, and chemical environment.
2008
Resource Management
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10 Author(s): Ranadhir Mukhopadhyay, Anil K. Ghosh, Sridhar D. Iyer Resources need to be mined and used in a continuous and sustainable manner without causing any (or least possible) harm to the environment, biota and human life. This chapter describes the equipment used for exploration, different mining methods, and assesses the environmental implications concerning mining. It discusses the metallurgical techniques, and converse on international legal constraints on exploration and exploitation of the nodules. The identification of ferromanganese resources is carried out by the detailed exploration and close-grid sampling of the possible resource areas, and is followed by determining the distribution and extent of the resources (i.e. resource mapping), and the evaluation of the metal content of the deposit(s) for possible economic exploitation. With the development of newer technologies and instrumentation that can successfully sustain high water pressure, the exploration strategy had undergone major modifications. The principal methods employed in the indian ocean nodule field (IONF) for manganese nodule exploration is outlined in the chapter. The impact of mining in terms of sedimentary processes, biogeochemistry, productivity, and maintenance of marine life, particularly of the benthic communities, appear to be considerable. The selection of an appropriate technique to extract economically important metals, such as nickel, copper, and cobalt, from mined manganese nodules constitutes an important stage to determine the commercial viability of the resources. For extraction of metals from manganese nodules, two distinct process routes have been recognized: hydrometallurgy (low-temperature aqueous processing) and pyrometallurgy (high-temperature smelting process).
2008
References
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10

2008
Author Index
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10

2007
Subject Index
Publication date: 2008
Source:Handbook of Exploration and Environmental Geochemistry, Volume 10

2004
Biogeochemistry in Mineral Exploration
Publication date: 2007
Source:Handbook of Exploration and Environmental Geochemistry, Volume 9 Author(s): Colin E. Dunn
2004
Preface
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): James R. Hein US Geological Survey (USGS) scientists have studied the Phosphoria Formation in the Western United States Phosphate Field throughout much of the twentieth century. In response to a request by the US Bureau of Land Management (BLM), a new series of geologic, geoenvironmental, and resource studies was initiated in 1997. This program followed three earlier USGS field programs that took place in 1909–1916, 1941–1944, and 1947–1952. The latest program (1997–2002) consisted of integrated, multiagency, multidisciplinary research with emphasis in four areas—(1) geological and geochemical baseline characterization of the Meade Peak Phosphatic Shale Member and related rocks of the Permian Phosphoria Formation; (2) delineation, assessment, and spatial analysis of phosphate resources and lands disturbed by mining; (3) contaminant residence, reaction pathways, and environmental fate associated with the occurrence, development, and use of phosphate rock; and (4) depositional origin and evolution of the Phosphoria Formation and geoenvironmental and deposit modeling. The objective of this latest research program was science in support of land management.
2004
List of contributors
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8

This chapter lists the contributors of “Life Cycle of the Phosphoria Formation.” The contributors include—(1) Michael C. Amacher who received a BSc in chemistry, MSc in chemistry, and a PhD in soil chemistry from Pennsylvania State University; (2) Kenneth J Bird who joined the US Geological Survey in 1974. His research focused initially on the petroleum potential of carbonate rocks in northern Alaska; and (3) Kevin J. Buhl who received a BA in biology from St. Mary's College, Winona, Minnesota and an MA in biology from the University of South Dakota, Vermillion.
2004
Chapter 1 The permian earth
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): J.R. Hein The Permian (about 290–250 Ma) was a time of immense global change and unique paleogeographic configurations. Climate conditions evolved from a glacial icehouse Earth to a hothouse Earth. Land masses were assembled into one great continent of Pangea that extended from pole to pole and the mega-ocean Panthalassa dominated the Earth's surface. Climatic and oceanic conditions were favorable for the formation of vast quantities of energy resources and mineral deposits, such as petroleum, coal, phosphorite, and evaporites. During the Late Permian, central northern Pangea was rocked by the outpouring of voluminous volcanic eruptions that produced the Siberian traps. The Permian ended with the greatest mass extinction of biota recorded in Earth history. The International Union of Geological Science's (IUGS) International Commission on Stratigraphy (ICS) has adopted a subdivision of the Permian that includes three Epochs that are divided into nine Stages—four Stages, three Stages, and two Stages for the Cisuralian, Guadalupian, and Lopingian Epochs, respectively.
2004
Chapter 2 Evolution of thought concerning the origin of the phosphoria formation, western us phosphate field
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): J.R. Hein, R.B. Perkins, B.R. McIntyre The Phosphoria Formation has been the subject of intensive study for nearly 100 years. Most work during the first half of the twentieth century on the Phosphoria Formation fell under three US Geological Survey (USGS) programs. The first program, from 1909 to 1916, was concerned with mapping the extent of phosphate rock within the western United States, the so-called Western Phosphate Field. Many of the basic features concern- ing the distribution, structure, and composition of the Phosphoria were determined during that time. The work of Blackwelder was especially critical in delineating geochemical con- ditions of the depositional basin, the Phosphoria sea. An important process in the formation of the Phosphoria Formation, coastal upwelling, was not understood in those earlier works. A detailed understanding of the processes involved in coastal upwelling was first developed by Kazakov in the late 1930s and those processes were later applied to the Phosphoria Formation in the late 1940s by McKelvey and co-workers. The second USGS program began in 1941 and involved detailed sampling and analyses of Phosphoria rocks to deline- ate vanadium-rich zones, which were discovered during the earlier USGS program. This sampling and analysis program also identified zinc- and uranium-rich strata within the Phosphoria Formation. The discovery of uranium, along with an increasing demand for phosphate, led to the third large USGS program headed by McKelvey, which began in 1947. From 1947 to 1952, hundreds of stratigraphic sections were measured, described, and sam- pled from 200 locations in Montana, Wyoming, Idaho, and Utah. From this work, a com- prehensive genetic model was developed for the sedimentary and oceanographic conditions that promoted phosphorite deposition. Delineation of regional facies changes, thickness changes, and chemical and petrologic changes also provided criteria for regional correla- tions of rock units. The cyclic nature of deposition of Phosphoria Formation strata was emphasized. Succeeding studies in the 1960s and 1970s established the characteristics of regional and local depositional environments and paleogeographic and paleoclimatic con- ditions of the Phosphoria sea and surrounding areas. The Phosphoria Formation was placed into a more restrictive Middle Permian time frame than had been used by previous workers. From the 1980s to the present, investigations focused on the details of phosphogenesis and the use of sequence stratigraphy to understand the role that sea level played in the evolution of the Phosphoria sea and in the cyclic deposition of the Phosphoria sequence.
2004
Chapter 3 The history of production of the western phosphate field
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): S.M. Jasinski, W.H. Lee, J.D. Causey The Western Phosphate Field of the United States contains one of the largest resources of phosphate rock in the world and it has been mined for nearly a century. Since the open- ing of the first mine in 1906, 229 million metric tons of marketable phosphate rock have been produced from 70 mines in the four states that comprise the Western Phosphate Field. Of these 70 mines, 49 were underground, 17 were surface, and seven used both methods; however, since 1993, all production has been from surface mines. Early scientific studies and changes in US mining laws have contributed to the exploration and development of this valuable resource. Cumulative production from the Western Phosphate Field represented 12% of the total phosphate rock produced in the United States and its end uses are evenly divided between fertilizer and industrial applications. Idaho has been the most significant producing state followed by Montana, Utah, and Wyoming. Currently, mining occurs only in Idaho and Utah at an average rate of 5 million tons per year.
2004
Chapter 4 The meade peak member of the phosphoria formation: Temporal and spatial variations in sediment geochemistry
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): R.B. Perkins, D.Z. Piper Variations in the geochemistry of rocks from the Meade Peak Member of the Phosphoria Formation were examined using ratios of elements associated with either the +terrigenous or marine sediment fractions. Inter-element relationships in the terrigenous fraction appear useful for chemo-stratigraphic correlation. A sharp decrease upsection in K2O/AI2O3 ratios occurs in the lower half of all but the most northeasterly section, wherein an offset is still evident in average and minimum values. These offsets correspond closely to the lower Guadalupian Series boundary as defined by conodont zonations, coincident with a change from major low-stand to transgressive conditions. The offsets are possibly the result of increased transport distances or flooding of source areas related to transgres- sion of the Phosphoria sea on the Wyoming shelf. A series of intervals displaying high Fe2O3/Al2O3, Ba/Al2O3 and Sc/Al2O3 ratios occur in the upper beds of the easternmost sections. The intervals do not appear to reflect amplified marine signals, but rather the introduction of terrigenous sediment from a secondary source, or, simply, reworking of sediments under higher energy conditions. The westernmost section, presumably repre- senting the deepest parts of the Phosphoria basin, contains intervals with high Ba/Al2O3. We suggest these horizons represent periods of low sediment accumulation during maxi- mum flooding and high-stand conditions. Inter-element relationships in the marine-derived sediment fraction indicate that bottom waters of the Phosphoria basin were dominantly denitrifying (suboxic). Ratios of Cd and Mo to Zn and Cu closely approach those in modern plankton in most of the sections, implying a major biogenic source for these elements. Exceptions occur through- out the westernmost (distal) section, possibly due to changes in the dominant plankton populations and relative nutrient uptakes, and in the upper part of the most northeasterly (shoreward, ramp) section, which we suggest is due to increased oxygen levels. Relatively thick phosphatic layers occur in basinal areas due largely to lack of terrig- enous dilution during deposition. These basinal deposits appear to have lower concentra- tions of many trace elements than more shoreward deposits. This may reflect deposition away from areas of peak primary production. Alternatively, biogenic detritus in these areas may have been derived from differing populations of primary producers with differing nutrient requirements. Both mid-shelf (middle ramp) and marginal environments were sites of accumulation of rich phosphatic units with high concentrations of trace elements. Deposits from marginal areas have the most varied geochemistry, largely because they experienced greater variability in terrigenous sediment influx. Even moderate changes in sea level may have dramatically altered energy levels, sediment mixing, and the amount of organic detritus reaching the sediment surface in these shallower marginal areas.
2004
Chapter 5 Regional analysis of spiculite faunas in the permian phosphoria basin: Implications for paleoceanography
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): B.L. Murchey The sponge spiculites of the Permian Phosphoria basin, Antler high, and eastern Havallah basin were the southernmost expression of one of the largest spiculite belts in the Earth's history. This spiculite belt extended from Nevada to the Barents Sea. In Idaho and Nevada, the spicule populations of this belt are dominated by demosponge spicules and are distinctive for their abundant rhax microscleres, large monaxons, and lithistid desmas. They form an Eastern Belt of spiculites that interfingers with spicule assemblages derived from choristid demosponges and hexactinellids that lived along the eastern margin of the deeper Havallah basin. The Havallah basin assemblages are similar to those in Permian arc terranes to the west, and together the sponge populations in this domain constitute a dis- tinct Central Belt. Radiolarians are virtually absent in the siliceous microfossil populations of the Eastern Belt, abundant in the populations of the Central Belt, and dominant in the populations of a Western Belt confined to Mesozoic accretionary complexes in the Pacific Coast States. The scattered sponge spicules in the Western Belt radiolarites were derived from hexactinellids. During the Permian, the relative abundance and apparent diversity of siliceous sponges expanded over a wide range of depths in the basins from Nevada and Idaho to the open ocean. Radiolarian preservation and apparent diversity increased in the deeper Cordilleran basins as well. In the Arctic regions, significant sponge spiculites were deposited in epicratonic basins. At the same time that siliceous sponge populations expanded along the northwestern margin of Pangea, warm-water carbonate producers disappeared. Suppression of carbonate-producing organisms along the margin was critical to the accu- mulation and preservation of both the demosponge spiculites in the Eastern Belt and the spicule-rich argillites of the Central Belt. Vigorous thermohaline circulation was the major control on the paleobiogeography of the late Early, Middle, and early Late Permian along northwest Pangea. It was driven by cold, nutrient- and oxygen-rich northern waters and it produced a coastal current that swept down the margin of the supercontinent. The upwelling associated with deposition of world-class phosphorites in the Phosphoria basin was a part of this larger oceanographic system.
2004
Chapter 6 Strain distribution and structural evolution of the meade plate, Southeastern Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): J.G. Evans The Meade thrust plate is one of seven main plates in the imbricate Sevier fold-and-thrust belt of northern Utah, southeastern Idaho, and western Wyoming and contains four of the five presently active mines in the Western Phosphate Field. The structural evolution model of the Phosphoria Formation in the Meade plate includes: (a) compaction of the Phosphoria by Triassic and Jurassic overburden; (b) additional compaction in Early Cretaceous by the tectonic overburden of a warm Putnam-Paris plate and resulting greenschist-facies metamorphism of the footwall rocks that would later comprise the upper Meade plate; (c) transfer of principal strain in the Sevier fold-and-thrust belt to the Meade thrust during Early to Late Cretaceous when rocks of the Meade plate developed a B perpendicular to B' tectonite and layered deformation styles and the strata in the upper part of the thrust plate were shortened by as much as 38%; (d) possible enlargement of part of the upper flat as the result of variable displacement involving incompetent strata and (or) basement structures; (e) additional, possibly passive piggyback, eastward transport of the Meade plate on younger thrusts; (f) burial of the western Meade plate by gravel from a rejuvenated Putnam-Paris plate; (g) left-lateral and right-lateral faulting within the Meade plate as a result of variable displacement on the Crawford, Absaroka, and possibly younger thrust faults; (h) Cretaceous faulting and (or) early Tertiary compression or extension that may have shuffled strata and disturbed Cretaceous metamorphic isograds; (i) periodic uplift and erosion that stripped much of the Putnam-Paris plate from the Meade plate and eroded much of the Meade plate; (j) mid- dle to late Tertiary extension associated with development of the north-northwest-trending Bear Lake-Blackfoot Reservoir graben and bimodal basalt-rhyolite volcanism, possibly a distal effect of the Yellowstone hotspot, and possibly implicated in disturbance of Cretaceous isograds.
2004
Chapter 7 The effects of weathering on the mineralogy of the phosphoria formation, Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): A.C. Knudsen, M.E. Gunter The Permian Phosphoria Formation of the western United States is one of the largest phosphate deposits in the world. Despite the economic significance of this formation, its fine-grained nature has discouraged detailed mineralogical characterization and quantifi- cation studies. Recently, selenium and other potentially hazardous trace elements in mine waste rock have drawn increased attention and motivated extensive studies. Part of this effort has focused on a more detailed geological and mineralogical characterization of the rocks. This study uses powder X-ray diffraction (XRD) with Rietveld quantification soft- ware to quantify and characterize the mineralogy of samples collected from nine measured stratigraphic sections from the Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation at four active phosphate mines, all near Soda Springs, Idaho. These measured sections include four pairs of more-weathered and less-weathered sections as well as a single, deep, least-weathered section. Mineralogical analyses of samples from these nine sections reveal how weathering has affected the mineral content, identifies the minerals that host the trace elements of environmental concern, and discusses the complex variations in the composition of the carbonate fluorapatite (CFA). Carbonate minerals decrease sharply in concentration with increased weathering, as do pyrite and sphalerite. Because these sulfide minerals have been linked to trace elements such as Se, their weathering likely contributes to the geochemical cycling of these trace elements. CFA occurs in phosphorites globally, with varying amounts of carbonate substi- tuted for phosphate in the apatite structure. Analysis of the measured sections shows strong connections between the variable degree of carbonate substitution in the CFA structure and the host rock type. However, there is also evidence that weathering plays an important role in the composition and structure of the CFA, apparently breaking it down into nondif- fracting CFA-like compounds.
2004
Chapter 8 Petrogenesis and mineralogic residence of selected elements in the meade peak phosphatic shale member of the permian phosphoria formation, Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): R.I. Grauch, G.A. Desborough, G.P. Meeker, A.L. Foster, R.G. Tysdal, J.R. Herring, H.A. Lowers, B.A. Ball, R.A. Zielinski, E.A. Johnson The Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation hosts the ore mined by the phosphate industry of southeast Idaho. It also hosts environmentally sensitive elements (ESE) such as Se, As, Hg, Ni, Cd, Zn, and Cr. Primary chemistry, elemental distribution patterns, and mineralogy within the Meade Peak were modified by element migration and possibly the introduction of elements. Fluids moved within the Meade Peak throughout its history, although the passage of fluids was highly variable in space and time, resulting in small domains of different rock chemistry and different mineralogy. Timing of major events affecting the Meade Peak and mineral habit are used to differentiate among detrital, diagenetic, epigenetic, and supergene mineral assemblages. Cross-cutting relationships among minerals are too rare to provide much paragenetic infor- mation. Carbonate fluorapatite (CFA) occurs in several forms, but dominantly as pelloids, some of which may have formed in situ during diagenesis. The other volumetrically signifi- cant form of CFA is interstitial cement that formed during diagenesis. Beginning during diagenesis and continuing intermittently, multiple generations of carbonate (dolomite and calcite) formed overgrowths and texturally complex carbonate cements. Movement and precipitation of silica followed a similar pattern. The ammonium feldspar buddingtonite, which generally rims orthoclase, also formed during diagenesis. Bacteria apparently played a significant role during diagenesis as well as during supergene processes, resulting in extreme fractionation of S isotopes and the possible bacterially mediated formation of minerals such as glauconite and sphalerite. Catagenesis, apparently culminating in oil generation, was the last significant diagenetic change. Thrusting accompanied by fluid (oil and brine) migration began during catagenesis in the Late Jurassic or Cretaceous and continued into the early Eocene. Fluorite ± carbonate ± barite± bitumen veins formed as a result of brittle deformation and accompanying fluid movement. This fracturing event may have been associated with a period of extension and normal faulting (Neogene to Holocene). Passage of the Yellowstone hot spot to the north of the area during the Neogene is marked by silicic domes and basaltic flows. The enrichment of Hg in fracture coatings might be the result of deposition from warm fluids associated with the emplacement of the silicic domes or a generally elevated, regional thermal gradient associated with the volcanism. Many of the fracture systems are still open and continue to provide fluid pathways that are the primary depositional sites for a wide variety of supergene minerals (such as Se, efflorescent salts) and element associations (such as Hg, Cd-S, Fe-Cr-O) in which many of the ESE are concentrated. Native Se is the most commonly identified host of Se in the studied samples. The largest concentration of Se occurs in open-fracture systems that cross-cut waste rock and ore units. The age(s) of native Se formation is not known; how- ever, the latest period of Se mobility is the present. Direct measurement of efflorescent “salts” forming on new mine faces indicate that several ESE, including both Se and Zn, are concentrated on the faces soon after they are exposed. Zinc is present as hydrous sulfates, but the residence of Se in these “salts” is unknown.
2004
Chapter 9 Weathering of the meade peak phosphatic shale member, phosphoria formation: Observations based on uranium and its decay products
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): R.A. Zielinski, J.R. Budahn, R.I. Grauch, J.B. Paces, K.R. Simmons Variably weathered outcrop samples of the Meade Peak Phosphatic Shale Member of the Phosphoria Formation have 5-10% of the contained uranium (U) in a form readily extractable by 0.1 M sodium bicarbonate. Fission track radiography of outcrop samples and other less-weathered channel and core samples indicate that this mobile fraction of U is likely hosted by organic matter, secondary iron oxides and clay minerals, trace uraninite, and very fine-grained apatite cement. During weathering, this extractable U fraction is especially susceptible to redistribution, which produces small but measurable departures (1-15%) from radioactive (secular) equilibrium in the 238U decay-series. The most weath- ered samples show the strongest isotopic evidence for redistribution of U during the last 350 ka, but sequestration of U by alteration products limits open-system losses of U at the whole-rock scale. In less-weathered samples, isotopic evidence for minor U loss (or gain) over longer time periods (1 Ma) is consistent with relatively non-aggressive attack of phosphatic rock during weathering. Comparative extractability of selenium (Se) suggests that a larger fraction of Se (19%) is readily available for mobilization during the earliest stages of weathering.
2004
Chapter 10 Mineral affinities and distribution of selenium and other trace elements in black shale and phosphorite of the phosphoria formation
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): R.B. Perkins, A.L. Foster Mineral affinities and quantitative distributions of Se and other trace elements of envir- onmental concern in the Permian Phosphoria Formation were studied in samples from three variably weathered sections using microprobe, X-ray absorption spectroscopy (XAS), and sequential-extraction analyses. The results show a clear difference in the distribution of Cd, Cu, Ni, Se, V, and Zn between non-weathered and weathered samples. In unweathered sam- ples, sulfides (mainly pyrite and sphalerite) host the majority of Cd, Cu, Se, and Zn and a large proportion of the Ni and V Most of the non-sulfide fraction of these elements in unweathered samples is associated with organic matter and oxyhydroxides. A small fraction of Se is present in elemental form. Apatite is the primary host for U. Both apatite and organic matter may host a significant fraction of Mo. Of the elements investigated, only Cr, U, and V were found to have minimal association with organic matter in unweathered rocks. Acid-insoluble phases (assumed to be silicates and oxides) host the majority of Cr and a sig- nificant amount of V Molybdenum was the only element for which a significant fraction is easily leachable (assumed to be weakly adsorbed or in a very soluble phase). In weathered samples, acid-soluble oxyhydroxides are the primary hosts for all the aforementioned elements except Cr and U, which are associated with relatively stable phases in non-weathered samples. Organic-bound Ni, which represents a substantial part of total Ni in unweathered samples, apparently is more resistant to weathering than is organic-bound Mo, which appears to be readily lost during weathering. Despite the obvious shift in mineral residences of Se and associated trace elements upon weathering, weathered rocks may still contain high concentrations of these elements. As many of the elements of concern appear to be associated primarily with oxyhydroxides in weathered rocks, both dissolved and sorbed species released to the surface environment must be considered. Furthermore, trace elements in unweathered and minimally weathered rocks are hosted in a number of phases that have variable oxidation rates and a wide range of particle sizes. Some of these host phases occur as inclusions within phases more resist- ant to oxidative weathering, such as phosphate pellets. These factors indicate that the release of these elements to the environment will be a variable and long-term process.
2004
Chapter 11 The phosphoria formation: A model for forecasting global selenium sources to the environment
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): T.S. Presser, D.Z. Piper, K.J. Bird, J.P. Skorupa, S.J. Hamilton, S.J. Detwiler, M.A. Huebner Mining of the Permian Phosphoria Formation — a marine, oil-generating, phosphatic shale — provided the selenium (Se) source implicated in the recent deaths of livestock in southeast Idaho. Field studies and the geohydrologic balance of Se in southeast Idaho confirm risk to animals from exposure to Se through leaching of mined waste shale into streams, discharge of regional drainage, and impoundment of drainage in wetland areas. Forage grown to stabilize waste rock contoured into hills or used as cross-valley fill provides an additional mechanism of Se exposure for the environment (Mackowiak et al., Chapter 19). The average Se concentration of the Meade Peak Member of the Phosphoria Formation is an order of magnitude higher than those of other exploited marine shales that have been linked to incidences of Se toxicosis via oil refining and irrigation in the western United States. The Phosphoria Formation accumulated in an environment that preserved organic matter and contributed to the formation of economic-grade phosphate and oil deposits. The addition of this phosphate-mining case study enables a comprehensive approach to the identification of marine sedimentary Se sources and a more complete range of ecotoxic field studies on which to establish the conditions and anthropogenic connections that determine uptake, release, and recycling of Se in food webs. A constructed conceptual model of Se pollution indicates that ancient organic-rich depositional marine basins, unre- stricted by age, are linked to the contemporary global distribution of Se source rocks. A global plot shows (a) the areal association of major basins hosting phosphate deposits and petroleum source rocks and (b) the importance of paleo-latitudinal setting in influencing the composition of the deposits. Given the geographic patterns, Se emerges as a contami- nant within specific regions of the globe that may limit phosphate mining, oil refining, and drainage of agricultural lands because of potential ecological risks to vulnerable food webs. Selenium also may serve as a geochemical exploration tool that signals an ancient productive biological environment.
2004
Chapter 12 Lithogeochemistry of the meade peak phosphatic shale member of the phosphoria formation, Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): J.R. Herring, R.I. Grauch This study focuses on the geochemical composition of the Meade Peak Phosphatic Shale Member of the Permian Phosphoria Formation in southeast Idaho. We present the composition and distribution of elements in nine measured sections that were sampled by a continuous series of channel samples through the Meade Peak. Two sections were sampled at each of four operating phosphate mines, one close to the pre-mining ground surface and one from a deeper level. This permited comparison of near-surface, weathered sections with deeper, less-weathered sections. The Meade Peak ranges from 36 to 58 m thickness in the measured sections. The member has lower and upper phosphorite ore zones of about 12.1 and 5.1m thickness, respectively. A waste-rock unit about 24.6 m thick lies between the two ore zones. During mining, the middle waste-rock unit and other waste-rock units below and above the ore zones are removed and placed in waste-rock dumps. It is the removed rock that has led to concerns over the release of trace elements into the environment. The Meade Peak is a phosphatic black shale that is notably enriched in several trace elements compared to most other black shales and even to many other phosphatic black shales. Compared to the average world-shale composition, the Meade Peak waste-rock is exceptionally enriched in Ag, Cd, Cr, Se, U, and Zn. Concentrations of Hg and Tl, which average 0.5 and 2 ppm, respectively, are not strongly enriched over concentrations in other shale. Five principal components in the Meade Peak are carbonates, detrital minerals, quartz, phosphate, and organic carbon. The proportions of these components vary as a function of depositional processes and subsequent alteration. Weathering of near-surface strata completely removes carbonate and greatly lowers organic-carbon content while slightly elevating concentrations of phosphate and detrital minerals. Where the Meade Peak is highly altered from interaction with oxidizing groundwater, the concentrations of many elements are greatly reduced. The trace elements that are most easily removed by weathering are Hg, Ni, Se, and to a lesser extent Cr, Cu, Mo, Sb, and Zn. A few elements, notably Ag, Ba, U, V, and Zr, are slightly enriched in the highly altered rocks. Uranium is enriched less than its host carbonate fluorapatite in the altered zones which may result from partial oxidation and removal of U from phosphorite by bicarbonate-rich groundwater. Alteration has removed enormous quantities of many contaminant trace elements from the surficial Meade Peak. At a minimum, several hundred kilograms of Se and several other trace elements for each meter slice of rock along the strike of the Meade Peak have been released by weathering.
2004
Chapter 13 Rock leachate geochemistry of the meade peak phosphatic shale member of the phosphoria formation, Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): J.R. Herring The interaction between water and the Meade Peak Phosphatic Shale Member of the Phosphoria Formation has been studied in a series of laboratory leachate experiments. These experiments directly measure reactivity of rock powders with water and indicate the potential for dissolution and release of various potentially contaminant trace elements into the environment. The leachate protocol used deionized water with pH of about 5.5 as the leaching medium with a water/rock ratio of 20 by mass. The leachate experiments were conducted passively, with only a gentle initial shake to suspend the rock particles. The experiments mostly lasted 24 h, although splits of a few samples were allowed to react for shorter and longer times to study the effects of leachate time. Most leachates were reacted under the oxidizing conditions of atmospheric exposure, but a few were reacted in an argon atmosphere. The leachate rock samples were ground to 00 mesh (0.15 mm). This particle size is fine grained compared to natural or industrial processes involving these rocks. However, the leachate procedure used splits of the same powders that were used for chemical and mineralogical analyses, which provides direct comparison with data from those analyses. Near-surface strata of the Meade Peak have been highly altered by oxidative weathering, which greatly controls rock composition. Extensive alteration results in complete loss of carbonate and considerable reduction in organic-carbon content and many associated trace elements. In the leachate experiments, the highly altered rocks produced lower concentrations of Mo, Ni, Se, and Zn than the less-altered rocks; the soluble fraction of these elements as a percentage of total-element mass in the bulk rock was greatly reduced as well. In contrast, the less-altered rocks had leachate concentrations and leachate proportions that were much greater relative to of the original rock mass than did the highly weathered rocks. About 10% of the original mass of Mo, Ni, and Zn in the least-altered rocks leached into solution in 24 h, while Cd, Cu, and Se leached between 1 and 10% of the original element mass. Arsenic, Ba, Cr, U, and V exhibited less-reactive behavior with typically only about 0.1% of the original mass of each of these elements released into solution in 24 h. The rock samples consist of variable proportions of phosphatic, detrital, and organic carbon-rich phases. Leachate concentrations of several trace elements, notably Co, Ni, Cu, Zn, As, Se, Cd, and Sb, are associated with the organic-carbon content of the rock. In turn, a strong correlation exists between these element concentrations and conductivity and sulfate. This demonstrates that rocks enriched in organic matter will leach abundant concentrations of these trace elements. The detrital component of the rocks produced elevated leachate concentrations of Al, Cr, Fe, Ba, Th, and U. Molybdenum does not have a strong correlation with the major elements although it has a weak correlation with organic carbon. The phosphate-rich rocks do not have strong element correlations, although, the concentrations of soluble P and V correlate. The results show that rocks of the Meade Peak are highly reactive with water and release significant quantities of trace elements from finely ground-rock samples in periods as short as 1 h. Furthermore, the Meade Peak rocks that are least altered and organic matter-rich release the greatest amount of potentially contaminant trace elements into solution.
2004
Chapter 14 Rex Chert member of the permian phosphoria formation: Composition, with emphasis on elements of environmental concern
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): J.R. Hein, B.R. Mcintyre, R.B. Perkins, D.Z. Piper, J.G. Evans We present bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions, of rocks collected from three measured outcrop sections of the Rex Chert Member of the Phosphoria Formation in southeast Idaho. The three measured sec- tions were chosen from 10 outcrops of Rex Chert that were described in the field. The Rex Chert overlies the Meade Peak Phosphatic Shale Member of the Phosphoria Formation, the source of phosphate ore in the region. Rex Chert removed as overburden constitutes part of the material transferred to waste-rock piles during phosphate mining. It is also used to surface roads in the mining district. It has been proposed that the chert be used to cap and isolate waste piles, thereby inhibiting the leaching of potentially toxic elements into the environment. The rock samples studied here are from individual chert beds representative of each stratigraphic section sampled. The Cherty Shale Member of the Phosphoria Formation that overlies the Rex Chert in measured section 1 and the upper Meade Peak and the transition zone to the Rex Chert in section 7 were also described and sampled. The cherts are predominantly spiculite composed of granular and mosaic quartz, and sponge spicules, with various but minor amounts of other fossils and detrital grains. The Cherty Shale Member and transition rocks between the Meade Peak and Rex Chert are siliceous siltstones and argillaceous cherts with ghosts of sponge spicules and somewhat more detrital grains than the chert. The dominant mineral is quartz. Carbonate beds are rare in each section and are composed predominantly of calcite and dolomite in addition to quartz. Feldspar, mica, clay minerals, calcite, dolomite, and carbonate fluorapatite are minor to trace minerals in the chert. The concentration of SiO2 in the chert averages 94.6 wt.%. Organic-carbon content is generally very low, but can be as much as 1.8% in Cherty Shale Member samples and as much as 3.3% in samples from the transition between the Meade Peak and Rex Chert. Likewise, phosphate (P2O5) is generally low in the chert, but can be as much as 3.1% in individual chert beds. Selenium concentrations in Rex Chert and Cherty Shale Member samples vary from <0.2 to 138 ppm, with a mean concentration of 7.0 ppm. This mean Se content is heavily dependent on two values of 101 and 138 ppm for siliceous siltstone from the lower part of the Rex Chert, which contains rocks that are transitional in character between the Meade Peak and Rex Chert Members. Without those two samples, the mean Se concentration is < 1.0 ppm. Other elements of environmental interest, As, Cr, V, Zn, Hg, and Cd, generally occur in concentrations near or below that in average continental shale. Stratigraphic changes, equivalent to temporal changes in the depositional basin, in chem- ical composition of rocks are notable either as uniform changes through the sections or as distinct differences in the mean composition of rocks that comprise the upper and lower halves of the sections. Q-mode factors are interpreted to represent the following rock and mineral components: chert-silica component consisting of Si (±Ba); phosphorite-carbonate fluorapatite com- ponent composed of P, Ca, As, Y, V, Cr, Sr, and La (± Fe, Zn, Cu, Ni, Li, Se, Nd, Hg); shale component composed of Al, Na, Zr, K, Ba, Li, and organic C (± Ti, Mg, Se, Ni, Fe, Sr, V, Mn, Zn); carbonate component (dolomite, calcite, silicified carbonates) composed of car- bonate C, Mg, Ca, and Si (±Mn); and, tentatively, organic matter-hosted elements (and/or sulfide-sulfate phases) composed of Cu (± organic C, Zn, Mn, Si, Ni, Hg, Li). Selenium shows a dominant association with organic matter and to lesser degrees associations with other shale components and carbonate fluorapatite. Consideration of larger numbers of factors in Q-mode analysis indicates that native Se (a factor containing Se (± Ba)) may also comprise a minor component of the Se complement. Comparison of our data with those from newly exposed outcrops in active phosphate mines indicates that weathering of typical Rex Chert outcrops likely plays an important role in removing environmentally sensitive elements.
2004
Chapter 15 Gaseous selenium and other elements in Near-Surface atmospheric samples, Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): P.J. Lamothe, J.R. Herring Concentrations of selenium (Se) and other selected elements were determined in air samples taken near the Unit 4 waste-rock pile of the Wooley Valley phosphate mine in southeastern Idaho. The waste-rock pile is approximately 3 million m3 (4 million yard3) in volume. Twenty-four-hour air samples were taken in June 2000 at two locations down- stream from the waste-rock pile along Angus Creek in Little Long Valley and 48-h air sam- ples were taken in May 2001 at two locations near the toe of the waste-rock pile. The purpose of the study was to determine if Se and other environmentally significant volatile elements that are present in the waste-rock pile are also present in the nearby atmosphere. Three of the sampling sites were in wetland areas near the toe of the waste-rock pile through which drainage travels. The wetland is a candidate source for the release of volatile trace elements including Se from the soil and/or plants. The results indicate that small but measurable elevations of Se concentration (30–90 ngm3) occur in the near-ground atmosphere at the wetland compared to a nearby background location. No other trace ele- ments had elevated concentrations in the atmosphere at the wetland site.
2004
Chapter 16 Selenium loading through the Blackfoot River watershed: Linking sources to ecosystems
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): T.S. Presser, M. Hardy, M.A. Huebner, P.J. Lamothe The upper Blackfoot River watershed in southeast Idaho receives drainage from 11 of 16 phosphate mines that have extracted ore from the Phosphoria Formation, three of which are presently active. Toxic effects from selenium (Se), including death of livestock and deformity in aquatic birds, were documented locally in areas where phosphatic shales are exposed (Piper et al., 2000; Presser et al., Chapter 11). Current drainage conditions are leading to Se bioaccumulation at concentrations that pose a risk to fish in the Blackfoot River and its tributaries (Hamilton et al., Chapter 18). A gaging station on the Blackfoot River was re-activated in April 2001 to assess hydrologic conditions and concentration, load, and speciation for Se discharges on a watershed scale. The gaging-station data are considered to represent regional drainage conditions in the upper Blackfoot River water- shed because of its location near the outlet of the watershed and directly upstream of the Blackfoot Reservoir. Watershed discharges for 2001 and 2002 were below minimum hydrologic conditions for the gage as documented by the historical record. Drought emergencies were declared in the area in both 2001 and 2002. Unmonitored diversions for irrigation that routinely take place during the snowmelt season also affected conditions downstream. Annual cycles in Se concentration, load, and selenate (Se6+) reached maxima in the spring during the period of maximum flow at the gaging station. Thirty-seven to 44% of annual flow occurred dur- ing the three-month high-flow season (April through June) in 2001 and 56% of annual flow occurred during that time period in 2002. Extrapolation from historical hydrographs for average and wet years and a limited data set of regional Se concentrations for 2001 and 2002 indicated potential for a 3.6- to 7.4-fold increase in Se loading because of increased seasonal flows in the Blackfoot River watershed. Supplementation data indicate that: (a) the difference between total Se and dissolved Se, as a measure of the contribution of particulate Se, was < 10% except at the peak of con- centration when total Se was 18% more than dissolved Se; (b) selenite (Se4+) represented less than 10% of the dissolved species during all months of 2001; and (c) dissolved Se was approximately a 50:50 mixture of selenate and organic selenide (operationally defined Se2-) during summer 2001 (June through August). Ecological risk based on regional Se drainage occurred during both the high- and low-flow seasons. Seventy to 83% of the Se load occurred during the high-flow season. During early May of both years, dissolved-Se concentrations exceeded the criterion for the protection of aquatic life and the ecological threshold of 5 gL1 Se at which sub- stantive risk occurs. During the majority of the three-month high-flow season, dissolved- Se concentrations exceeded the 2 gL1 Se concern level for aquatic biota. The Se concentration in suspended material during high flow in 2002 was within the range of marginal risk to aquatic life (2-4 gg1 Se, dry weight). Selenate was the major species during peak flows, with both selenate and organic selenide being major species during relatively low-flow periods in summer. A change in speciation to reduced Se may indicate elevated biotic productivity during summer months and could result in enhanced Se uptake in food webs. In addition to the magnitude of regional Se release in the Blackfoot River watershed, Se concentrations in individual source drains and waste-rock seeps, and those predicted by experimental column leaching of proposed mining overburden materials, also indicate that drainage options that currently meet existing demands for phosphate mining cause eco- logical risk thresholds to be exceeded. At times, the drinking-water Se standard (50 g L1 Se) and the criterion for hazardous Se waste (1000 L-1 Se) (US Department of the Interior, 1998; US Environmental Protection Agency, 1987) are also exceeded. For water-years 2001 and 2002, seasonal increased input of water in the mining area resulted in increased Se transport, suggesting a mechanism of contamination that involves a significant Se reservoir. Hence, recognition and monitoring of Se loading to the envi- ronment on a mass balance basis (i.e. inputs, fluxes and storage within environmental media, and outputs) are essential to evaluating how to control Se concentrations within environmentally protective ranges (Presser and Piper, 1998). In areas where release of Se to aquatic systems is anticipated as a product of future expansion of phosphate mining, continuous monitoring of flow and development of seasonal Se loading patterns would help to model watersheds in terms of sources, flow periods, and environmental-Se con- centrations that most influence bioavailability. These data, in turn, could be linked to Se- bioaccumulation models specific to food webs and vulnerable species of the impacted areas to accurately project ecological effects. Gaging at this site on the Blackfoot River is planned to continue in order to establish a long-term (>10 year) record of hydrologic conditions.
2004
Chapter 17 Selenium attenuation in a wetland formed from mine drainage in the phosphoria formation, Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): L.L. Stillings, M.C. Amacher The black shale-hosted phosphorite of the Phosphoria Formation has been mined for phosphate during most of the twentieth century. Selenium (Se) occurs in high concentra- tions throughout much of the formation, leading to concerns that mining activities may enhance its release to the environment. Seepage water from waste-rock dumps has been discovered to contain up to 1800 gL1 dissolved Se. Our study focuses on the removal of Se from surface waters in a wetland located at the base of a waste-rock dump. Samples of surface water and sediment were collected from a line of seeps emerging at the base of the waste-rock pile and throughout the length of the wetland. Sediment samples (collected to a depth of 15 cm) were analyzed with selective extractions for exchangeable, carbonate, Mn oxide, Fe oxide, and organic matter + sulfide + residual fractions, with each fraction being analyzed for total bulk chemistry. Water samples were also analyzed for major, minor, and trace elements. Seepage waters are easily distinguished from background waters. Seepage waters display a Ca-SO4 chemistry compared to the Ca-HCO3 chemistry of background water. Major ions and Se occur at much higher concentrations in seepage waters, and the range of solute con- centrations is much greater in seepage waters than in background waters. Selenium concen- trations in seepage water are highly variable and depend on location and discharge volume of the seep. Although we did not quantify discharge, the high discharge at the main seep site in June 1999 contained a greater Se concentration (520 g L1) than the lower discharge in September 1999 (1123 gL1). Se concentrations were also higher during the months following a deeper snow pack (520 gL1 in June, 1999, vs. 38 gL1 in June, 2000). Se is quickly attenuated from surface water as it flows from the seeps through the wetland, and concentrations drop from a range of 11–520 gL1 at the main seep site to <5 gL1 within 50 m of the seeps. Wetland sediments within this 50 m distance show the highest con- centration of total Se, up to 693 mgkg1, and in all but one sample most of the Se is found within the non-crystalline Fe-oxide fraction of the sediment. The total bulk concentration of Se in the sediments (mg kg1) can be estimated with a linear expression: where [ncFe2O3]sed is the concentration of non-crystalline Fe oxides in the sediment (as percent Fe2O3). This expression fits the data with an r2 of 0.968 (n = 7). Wetland waters do not appear to result from simple linear mixing between seepage and background waters. Instead, we hypothesize that Se adsorption and/or coprecipitation with non-crystalline Fe oxides is the process responsible for sequestering Se from wetland waters to the sediments.
2004
Chapter 18 Selenium and other trace elements in water, sediment, aquatic plants, aquatic invertebrates, and fish from streams in se idaho near phosphate mining
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): S.J. Hamilton, K.J. Buhl, P.J. Lamothe Nine stream sites in the Blackfoot River watershed in SE Idaho were sampled in June 2000 for water, surficial sediment, aquatic plants, aquatic invertebrates, and fish. Selenium (Se) and other elements were measured in these aquatic ecosystem components and a haz- ard assessment was performed on the data. Water quality characteristics were relatively uniform among the nine sites examined. Of the aquatic components assessed, water was the least informative, especially its analysis for Se contamination because measured concentrations were substantially below the national water quality criterion of 5 gL1. In contrast, Se and several other elements were elevated in sediment, aquatic plants, and aquatic invertebrates from several sites, indicating accumulation in sediments and cycling through plants and invertebrates. Only Se in fish was elevated to concentrations of poten- tial concern. A hazard assessment of Se in the aquatic environment suggests low hazard at Trail Creek and Sheep Creek, moderate hazard at upper Slug Creek and lower Slug Creek, and high hazard at Angus Creek near the mouth, upper East Mill Creek, lower East Mill Creek, Dry Valley Creek, and lower Blackfoot River.

Chapter 19 Uptake of selenium and other contaminant elements into plants and implications for grazing animals in Southeast Idaho
Publication date: 2004
Source:Handbook of Exploration and Environmental Geochemistry, Volume 8 Author(s): C.L. Mackowiak, M.C. Amacher, J.O. Hall, J.R. Herring As part of a series of geoenvironmental studies on the mobilization and fate of selenium (Se) and other potentially toxic trace elements in southeast Idaho phosphate mining areas, trace element concentrations (mg kg1 dry mass) in plant samples collected along transects at the Wooley Valley Unit 1,3, and 4 waste-rock dumps were compared with samples collected from undisturbed sites at Dairy Syncline, Deer Creek, Dry Valley, Maybe Canyon, and Rasmussen Ridge. Additionally, trace-element concentrations in veg- etation samples collected from wetlands associated with mine waste-rock piles were compared with samples collected from a single reference wetland. In undisturbed areas, Se in vegetation growing in soils overlying and derived from Phosphoria Formation phosphatic rocks tended to be higher than vegetation in undisturbed Wells Limestone or Rex Chert soils. Vegetation growing in highly disturbed soils, such as those comprising waste-rock dumps, had the highest tissue Se. Vegetation in a wetland at the base of Wooley Valley Unit 4 waste-rock dump accumulated decreasing concentrations of Se with increasing distance away from the waste-rock dump along the wetland flow path. Iron oxides were observed coating wetland sediment surfaces and helped control Se bioavailability. Plant uptake, as well as coprecipitation and sorption of Se by iron oxides, were key processes in the natural attenuation of Se in this wetland. Legumes at the rock dumps contained higher Se (mean = 80 mg kg-1) than trees (mean = 52 mgkg1), grasses (mean = 18 mgkg1), shrubs (mean = 6 mgkg1), and forbs (mean = 3 mg kg-1). However, grasses were among the highest Se accumulators among plant lifeforms in contaminated wetlands, with a mean value of 53 mg kg1 Se. In most places, uptake of Cd, Cr, Cu, Mn, Mo, Ni, and Zn was below critical high levels for plants. However, Se, Cd, Cr, and Zn uptake by some plants may have been large enough to affect their growth. Several plant lifeforms had Se concentrations that surpassed the acute and chronic toxicity thresholds for grazing livestock and wildlife, posing a lethal risk to these animals. Forages, particularly legumes, sampled from waste-rock dumps had increased Mo concentrations, resulting in Cu/Mo ratios below 1. High Mo (above 10 mg kg1) and Cu/Mo ratios below 2 may cause molybdenosis in ruminants. There were instances where tree Zn content exceeded upper chronic intake for livestock/wildlife. This may pose some concern for browsing animals feeding upon trees, particularly in winter months. Based on the vegetation survey, possible remediation strategies via physical, chemical, and biologi- cal manipulations of the contaminated sites include removal of the most contaminated soils, capping contaminated soils and revegetating capping materials, application of selec- tive herbicides to remove legumes from reclaimed waste-rock dumps, and fencing some contaminated areas to better manage grazing.
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