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Shift in Global Tantalum Mine Production, 2000–2014

Introduction Tantalum has a unique set of properties that make it useful in a number of diverse applications. The ability of the metal to store and release electrical energy makes it ideally suited for use in certain types of capacitors that are widely used in modern electronics. Approximately 60 percent of global tantalum consumption is in the electronics industry. The ductility and corrosion resistance of the metal lends itself to application in the chemical processing industry, and its high melting point and high strength retention at elevated temperatures make it an important component of super alloys used in aircraft engines. As a major industrialized nation, the United States is a leading consumer of tantalum and tantalum-containing products. Domestic deposits typically are of low grade, and no tantalum has been recovered from mining activities in the United States since 1959. Consequently, the United States is nearly completely reliant on imports to meet its domestic consumption of tantalum for economic and national security needs. The recovery of tantalum from mine production is economically viable in only a few countries. Although developed countries dominated tantalum mine production in the early 2000s, production today is dominated by countries in the Great Lakes Region of Africa. There is concern that the sales of minerals, including columbite-tantalite or “coltan,” a mineral from which tantalum is derived, have helped finance rebel groups accused of violating human rights as part of the continuing armed conflict in the Democratic Republic of the Congo (DRC) and neighboring countries. These accusations have prompted the passage of legislation in the United States to curb the procurement of these mineral commodities, referred to as “conflict minerals,” from the DRC. Specifically, section 1502 of the 2010 Dodd-Frank Wall Street Reform and Consumer Protection Act (Public Law 111–203, 124 Stat. 2213–2218) requires companies that source tantalum, tin, tungsten, and gold (3TG) to perform due diligence on their supply chains to determine if the materials they use originate from the DRC or adjoining countries (defined as sharing a border with the DRC). The DRC, Rwanda, and surrounding countries are not globally significant sources of tin, tungsten, or gold, accounting for only about 2 percent of the mined world supply for each of these elements. The region has, however, evolved to become the world’s largest producer of mined tantalum. A further complication of the production of tantalum stems from the opacity of the tantalum market. Unlike most base and precious metals, tantalum concentrates are not publicly traded through commodities exchanges but are bought and sold through networks of dealers and on contract between producers and consumers, some of whom may not provide accurate statistical data concerning the amounts, origins, and destination of the concentrates. Some price data can be found in trade journals or in other publications; however, there are no recognized official set exchange prices for either concentrate or tantalum metal. Because price is determined by negotiation between buyer and seller, published prices for concentrate are probably not representative of global prices paid for concentrate. The development of a mine-to-market supply-chain analysis is complicated and difficult because many of the industry participants that produce, trade, and consume tantalum do not publish statistical information, contracts are long term between miners and buyers, and much of the industry is vertically integrated. As a result of these and other considerations, tantalum is considered by many to be a “critical” commodity. This fact sheet identifies and addresses the major geographic shifts in the source of mine production of tantalum which have occurred over the past 15 years, some of the factors that drove this shift, and some of the related consequences. One of the activities of the U.S. Geological Survey National Minerals Information Center (USGS-NMIC) is to analyze global supply chains and characterize major components of mineral and material flows from ore extraction through processing to first tier products. These analyses support the core mission of the USGS-NMIC as the Federal entity responsible for the collection, analysis, and dissemination of objective, unbiased, factual information on minerals essential to the U.S. economy and national security.

Fact Sheet↗

Utica/Point Pleasant brine isotopic compositions (δ7Li, δ11B, δ138Ba) elucidate mechanisms of lithium enrichment in the Appalachian Basin

Global Li production will require a ~500 % increase to meet 2050 projected energy storage demands. One potential source is oil and gas wastewater (i.e., produced water or brine), which naturally has high total dissolved solids (TDS) concentrations, that can also be enriched in Li (>100 mg/L). Understanding the sources and mechanisms responsible for high naturally-occurring Li concentrations can aid in efficient targeting of these brines. The isotopic composition (δ 7 Li, δ 11 B, δ 138 Ba) of produced water and core samples from the Utica Shale and Point Pleasant Formation (UPP) in the Appalachian Basin, USA indicates that depth-dependent thermal maturity and water-rock interaction, including diagenetic clay mineral transformations, likely control Li concentrations. A survey of Li content in produced waters throughout the USA indicates that Appalachian Basin brines from the Marcellus Shale to the UPP have the potential for economic resource recovery.

Maryland, Ohio, Pennsylvania, West Virginia↗

Global tellurium supply potential from electrolytic copper refining

The transition towards renewable energy requires increasing quantities of nonfuel mineral commodities, including tellurium used in certain photovoltaics. While demand for tellurium may increase markedly, the potential to increase tellurium supply is not well-understood. In this analysis, we estimate the quantity of tellurium contained in anode slimes generated by electrolytic copper refining by country between 1986 and 2018, including uncertainties. For 2018, the results indicate that 1930 (1500-2700, 95% confidence interval) metric tons of tellurium were contained in anode slimes globally. This is nearly quadruple the reported tellurium production for that year. China has the greatest potential to increase tellurium supplies. However, most of the tellurium potentially recoverable by Chinese refineries appears to come from copper mined elsewhere. Further research into the business decisions associated with tellurium recovery may help translate the physical availability of tellurium into economic availability. The methodology presented here can be applied to other byproduct elements.

Resources, Conservation & Recycling↗

Materials flow of indium in the United States in 2008 and 2009

Indium is a material that has many applications. It is used by anyone who watches television or views a computer screen. It is found in solar energy arrays and in soldering applications that are required to be lead free. In 2009, about 550 metric tons (t) of indium metal was produced from primary sources world-wide; it was estimated that the United States consumed about 110 t of indium metal (20 percent of world primary production). However, when imports of consumer products that contain indium are considered, the United States consumed about 200 t of indium (36 percent of world primary production). When one considers the recovery from the low-efficiency sputtering process that coats indium-tin oxide onto glass and other surfaces, the recycling rate (within the manufacturing process that uses indium-tin oxide in flat panel displays approaches 36 percent. However, indium recovery from old scrap generated from end-of-life consumer products is not sufficiently economic to add significantly to secondary production. Between 1988 and 2010, indium prices averaged $381 per kilogram (in constant 2000 dollars). However, prices have been quite volatile (deviating from the average of $381 per kilogram by ±$199 per kilogram, a 52 percent difference from the average), reflecting short-term disequilibrium of supply and demand but also responsiveness of supply to demand. The dynamics of zinc smelting govern the primary supply of indium because indium is a byproduct of zinc smelting. Secondary indium supply, which accounts for about one-half of total indium supply, is governed by indium prices and technological advances in recovery. Indium demand is expected to grow because the number and volume of cutting edge technology applications that depend on indium are expected to grow.

Circular↗

Climate change may impair electricity generation and economic viability of future Amazon hydropower

Numerous hydropower facilities are under construction or planned in tropical and subtropical rivers worldwide. While dams are typically designed considering historic river discharge regimes, climate change may induce large-scale alterations in river hydrology. Here we analyze how future climate change will affect river hydrology, electricity generation, and economic viability of > 350 potential hydropower dams across the Amazon, Earth’s largest river basin and a global hotspot for future hydropower development. Midcentury projections for the RCP 4.5 and 8.5 climate change scenarios show basin-wide reductions of river discharge (means, 13 and 16%, respectively) and hydropower generation (19 and 27%). Declines are sharper for dams in Brazil, which harbors 60% of the proposed projects. Climate change will cause more frequent low-discharge interruption of hydropower generation and less frequent full-capacity operation. Consequently, the minimum electricity sale price for projects to break even more than doubles at many proposed dams, rendering much of future Amazon hydropower less competitive than increasingly lower cost renewable sources such as wind and solar. Climate-smart power systems will be fundamental to support environmentally and financially sustainable energy development in hydropower-dependent regions.

Global Environmental Change↗

A framework for quantitative assessment of impacts related to energy and mineral resource development

Natural resource planning at all scales demands methods for assessing the impacts of resource development and use, and in particular it requires standardized methods that yield robust and unbiased results. Building from existing probabilistic methods for assessing the volumes of energy and mineral resources, we provide an algorithm for consistent, reproducible, quantitative assessment of resource development impacts. The approach combines probabilistic input data with Monte Carlo statistical methods to determine probabilistic outputs that convey the uncertainties inherent in the data. For example, one can utilize our algorithm to combine data from a natural gas resource assessment with maps of sage grouse leks and piñon-juniper woodlands in the same area to estimate possible future habitat impacts due to possible future gas development. As another example: one could combine geochemical data and maps of lynx habitat with data from a mineral deposit assessment in the same area to determine possible future mining impacts on water resources and lynx habitat. The approach can be applied to a broad range of positive and negative resource development impacts, such as water quantity or quality, economic benefits, or air quality, limited only by the availability of necessary input data and quantified relationships among geologic resources, development alternatives, and impacts. The framework enables quantitative evaluation of the trade-offs inherent in resource management decision-making, including cumulative impacts, to address societal concerns and policy aspects of resource development.

Natural Resources Research↗

Asian carp behavior in response to static water gun firing

The potential for invasion of Asian carp into the Great Lakes has ecological and socio-economic implications. If they become established, Asian carp are predicted to alter lake ecosystems and impact commercial and recreational fisheries. The Chicago Sanitary and Shipping Canal is an important biological conduit between the Mississippi River Basin, where invasive Asian carp are abundant, and the Great Lakes. Millions of dollars have been spent to erect an electric barrier defense in the canal to prevent movement of Asian carp into the Great Lakes, but the need for additional fish deterrent technologies to supplement the existing barrier is warranted. Scientists with the U.S. Geological Survey Northern Rocky Mountain Science Center are examining seismic water gun technology, formerly used in oceanic oil exploration, as a fish deterrent. The goal of the current study is to employ telemetry and sonar monitoring equipment to assess the behavioral response of Asian carp to seismic water guns and the sound energy it generates.

Illinois↗

The National integrated water availability assessment, water years 2010–20

Water availability is fundamentally important to human well-being, economic vitality, and ecosystem health. Because of its central importance, the U.S. Congress tasked the U.S. Geological Survey (USGS) and other Federal agencies with conducting regular, comprehensive assessments of water availability in the United States through the requirements under the SECURE Water Act. In response to this mandate, the USGS has developed the U.S. Geological Survey Integrated Water Availability Assessment—2010–20, which addresses aspects of water supply, quality, and use related to water availability in the United States. This is the first chapter of that report. The major climatic factors affecting water availability are also described. Multiple aspects of water availability are integrated to produce a more comprehensive analysis of water availability in the United States. This chapter enumerates the development, organization, and tools used in the USGS Integrated Water Availability Assessment. SECURE Water Act reports, developed by the Department of Energy Hydropower Climate Change Assessment and the Bureau of Reclamation West-Wide Climate and Hydrology Assessment, are also described. A distilled list of key findings from the overall report is also provided, serving as an introduction to each topic along with the most important high-level information.

conterminous United States↗

Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

Scientific Investigations Report 2016–5089 and accompanying data releases are the products of the U.S. Geological Survey (USGS) Sagebrush Mineral-Resource Assessment (SaMiRA). The assessment was done at the request of the Bureau of Land Management (BLM) to evaluate the mineral-resource potential of some 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming. The need for this assessment arose from the decision by the Secretary of the Interior to pursue the protection of large tracts of contiguous habitat for the greater sage-grouse ( Centrocercus urophasianus ) in the Western United States. One component of the Department of the Interior plan to protect the habitat areas includes withdrawing selected lands from future exploration and development of mineral and energy resources, including copper, gold, silver, rare earth elements, and other commodities used in the U.S. economy. The assessment evaluates the potential for locatable minerals such as gold, copper, and lithium and describes the nature and occurrence of leaseable and salable minerals for seven Sagebrush Focal Areas and additional lands in Nevada (“Nevada additions”) delineated by BLM. Supporting data are available in a series of USGS data releases describing mineral occurrences (the USGS Mineral Deposit Database or “USMIN”), oil and gas production and well status, previous mineral-resource assessments that covered parts of the areas studied, and a compilation of mineral-use cases based on data provided by BLM, as well as results of the locatable mineral-resource assessment in a geographic information system. The present assessment of mineral-resource potential will contribute to a better understanding of the economic and environmental trade-offs that would result from closing approximately 1 0 million acres of Federal lands to mineral entry.

Idaho, Montana, Nevada, Oregon, Utah, Wyoming↗

Non-pegmatitic resources of beryllium in United States

During the period from 1948 to 1950 the U.S. Geological Survey conducted a program of field and laboratory research w determine the mode of occurrence of beryllium in non-pegmatitic rocks and mineral deposits as part of the Beryllium Program of the Division of Raw Materials of the U.S. Atomic Energy Commission. Approximately 23 man months were spent in the field collecting samples from 146 localities in 15 states; a total of 680 samples were collected and analyzed for beryllium. Additional samples collected by the Geological Survey. U.S. Bureau of Mines, various state Geological Surveys and other institutions. and private companies were analyzed for beryllium. In total, the beryllium content of 1,238 samples from about 600 localities in the United States is compiled in the final report which is being prepared for publication by the U.S. Geological Survey. The main topics discussed are: uses and properties of beryllium; methods of analysis and mineralogy of beryllium; occurrence of beryllium in igneous, sedimentary and metamorphic rocks, pyrometasomatic and related deposits, vein deposits, and hot spring deposits; the genesis of beryllium deposits; and a description of the deposits examined. This abstract and table 1 summarize the more pertinent economic data. Beryllium is more abundant than arsenic, gold, silver, and molybdenum in the lithosphere, but its chemical and physical properties prohibit its concentration in minerals which are common w large commercial vein and replacement deposits. There are 29 minerals in which beryllium is an essential constituent but of these only beryl, mined from granite pegmatites, is an ore of beryllium., Beryl also occurs disseminated in granites and high-temperature veins. The other 28 minerals occur as rare constituents in syenite and granite pegmatites, granites, and pyrometasomatic deposits. Beryllium, as a trace constituent, has been detected in 49 minerals but recovery of the beryllium requires metallurgical methods as yet unknown.

Trace Elements Investigations↗

Mapping the glacial geology of the Central Great Lakes region in three dimensions: A model for state-federal cooperation

Planners need to evaluate complex and competing public-policy options for managing water, land, and biological resources; they must ensure economic growth, meet the needs of an increasing population, assess hazards, and manage the environment in a sustainable manner. The State Geological Surveys of Illinois, Indiana, Michigan, and Ohio and the U.S. Geological Survey (USGS) receive many requests from local, State, and Federal planners and officials for geologic information. Thick and complex layers of glacial and related sediments blanket the bedrock of these States: a three-dimensional understanding of these deposits is critical to making informed resource-management and other planning decisions. At two recent forums (in Indianapolis, March 1997, and Columbus, Ohio, February 1999), more than 200 attendees from more than 60 local, State, and Federal agencies provided a clear message. They need three-dimensional geologic information to use in making decisions on the following issues: • Quality, quantity, distribution, and accessibility of surface and ground water • Aggregate sources and land-use conflicts • Energy and mineral resource management • Environmental management and mitigation of land and water contamination • Acceleration of the permitting processes of regulatory agencies • Industrial, commercial, residential, and infrastructure siting and construction • Agricultural land loss, erosion, sedimentation, and agrichemical use • Waste-disposal planning and mitigation • Habitat alteration and biodiversity • Coastal erosion, landslides, radon, floods, and earthquakes

Illinois, Indiana, Michigan, Ohio↗

Thermochemical approximations for sulfosalts

Most sulfosalts may be regarded as intermediate phases on joins between simple sulfide components (e.g., all lead sulfbismuthinides lie on the PbS-Bi 2 S 3 join). Many of the structures are characterized by subunits whose individual structures are similar to those of the component simple sulfides (e.g., galena-like and stibnite-like layers in the lead sulfantimonides). Therefore, as a first approximation one may estimate the properties of many sulfosalts in terms of mixtures of the simple sulfides.Recent work has shown that the free energy of reaction from the end-member sulfides, delta G m , for more than 20 sulfosalts is usually less negative than the hypothetical ideal free energy of mixing and that the standard free energy of formation, delta G degrees , per gram atom of sulfur in the formula may be represented as:delta G degrees = (N a delta G a degrees + . . . N i delta G i [degree) + (1.2 + or - 0.8)(N a RT ln N a + . . . N i RT ln N i )where N i is the mole fraction of the i-th simple sulfide component, R is the gas constant, and T is temperature in kelvins. The first term is far larger than the second. Estimates made for compounds in which the structural environment for the metals is quite different from that in the end-member sulfides, e.g., enargite, are subject to the greatest uncertainty.The estimated free energies may permit prediction of solubilities to a precision sufficient for many purposes, e.g., for H. C. Helgeson's computer-modeled hydrothermal systems. One may introduce some predictive capability into experimental design and anticipate some aspects of phase diagrams. This is especially true for redox reactions such as the behavior of proustite in the oxidized zone or the partial reduction of jamesonite to antimony + galena + pyrrhotite. However, other aspects, such as the prediction of the configuration of joins, e.g., PbS-As 2 S 3 , requires greater precision than the present rough estimates.

Economic Geology↗

Global mineral resource assessment

Introduction In response to the growing demand for information on the global mineral-resource base, the U.S. Geological Survey (USGS) is conducting the Quantitative Global Mineral Resource Assessment Project (GMRAP), a cooperative international project, begun in 2002, to assess the world's undiscovered nonfuel mineral resources. Primary Objectives The USGS conducts national and global assessments of resources (mineral, energy, water, biologic) to provide science in support of decisionmaking. Mineral resource assessments provide a synthesis of available information about where mineral deposits are known and suspected in the Earth’s crust, what commodities may be present, and estimates of amounts of resources that may be present in undiscovered deposits. The Global Mineral Resource Assessment Project started in 2002 as a cooperative international effort to assess the world’s undiscovered nonfuel mineral resources. Primary objectives are to: Outline the regional locations and estimate the probable amounts of the world’s undiscovered resources of copper, platinum-group elements (PGE), and potash in selected types of mineral deposits to depths of 1 to 3 kilometers below the Earth’s surface. Provide the first globally consistent and comprehensive analysis of undiscovered nonfuel mineral resources to provide all nations with a regional and global context for evaluating their mineral resources, planning for new mineral exploration and anticipating the economic, environmental, and social impacts of mineral development, and making land use decisions. The project emphasizes the most important types of mineral deposits for world supply of copper, platinum-group elements (PGE) and nickel, and potash. Go to the Quantitative Global Mineral-Resource Assessments home page for more information.

Scientific Investigations Report↗

Shifting sands: The influence of coral reefs on shoreline erosion from short-term storm protection to long-term disequilibrium

Climate change is exacerbating shoreline erosion and flooding, posing significant risks to coastal communities. Although traditional coastal defenses such as seawalls, dykes, and breakwaters offer protection from these hazards, their high environmental and economic costs are driving interest in cost-competitive nature-based solutions. Coral reef restoration is a nature-based solution that may be particularly apt to mitigate tropical coastal flooding and shoreline erosion while providing benefits to local tourism, fisheries, and nature. However, the novelty of this field requires studies demonstrating the benefits of reefs for coastal protection. While the flood protection benefits of reefs have been well-documented, their effects on shoreline erosion are comparatively less understood. Here, we investigate the effects of coral reefs on shoreline erosion by comparing tropical beach responses at short and long timescales, as well as identifying important reef structural features influencing coastal erosion rates. Our analyses leveraged two key datasets created in this study: the first derived from a literature review on short-term shoreline erosion due to storm events, and another compiling >80 years of long-term erosion rates, bathymetry, habitat, and wave energy for the Hawaiian Islands of Kauaʻi, Oʻahu, and Maui. Our analyses reveal three key findings regarding the effects of reefs on shoreline erosion. Firstly, we find evidence for the role of reefs in mitigating shoreline erosion during storm events, with coral reef-protected beaches experiencing 97 % less beach volume loss than unprotected beaches. Secondly, a linear regression analysis demonstrates that coral reef structure and wave energy are important predictors of long-term shoreline erosion rates, explaining 34 % of the variation across the Hawaiian Islands. Consistent with prior research, we find beaches protected by coral reefs with shallow reef crests, wide reef flats, calmer offshore conditions, and positioned farther from the shore exhibit lower erosion rates than others. Finally, when comparing historical erosion rates of protected and unprotected beaches in Hawai'i, we find a seemingly incongruous pattern where coral reef-protected beaches eroded up to 2x faster than beaches without reefs. While the cause of the enhanced erosion is yet to be fully understood, a combination of coral reef structural degradation and sea-level rise is likely shifting the equilibrium profiles of reef-protected beaches inshore. These results emphasize the role of coral reefs in reducing coastal erosion during storm events while revealing contrasting erosion patterns over long timescales. Future studies would ideally broaden the scope to include various regions, utilize advanced sediment transport models, and undertake field experiments to deepen our understanding of coral reef-coupled shoreline dynamics.

Nature-Based Solutions↗

Site fidelity and condition metrics suggest sequential habitat use by early juvenile snook

The common snook Centropomus undecimalis is an estuarine-dependent fish that relies on landward wetlands as nursery habitat. Despite its economic importance, portions of the snook's early life history are poorly understood. We compared habitat use of young-of-the-year (YOY) snook in 2 geomorphic mesohabitats (tidal pond and tidal creek) along an estuarine gradient (upstream vs. downstream) within a single wetland during fall recruitment. We used abundance, length, condition indices, and stable isotopes to assess ontogenetic mesohabitat use and site fidelity. We found that (1) YOY snook were more abundant within the upstream creek and ponds; (2) the smallest snook were found only in ponds; (3) snook from ponds had lower condition (Fulton's K and hepatosomatic index); (4) snook began moving from ponds to the creek at ~40 mm standard length; and (5) snook from the 2 mesohabitats were isotopically distinct, indicating high site fidelity at rather small spatial scales. Collectively, these data identified sequential use of mesohabitats, wherein seaward-spawned YOY snook moved landward and recruited to pond habitats, where they dedicated energy to growth (as length) before making an ontogenetic habitat shift to the creek. Once in the creek, YOY snook condition improved as they approached maturity and started the downstream return towards seaward locations. The wetland network that was previously viewed as generalized nursery habitat instead consists of mesohabitats that support different life stages in sequence. This represents ontogenetic habitat complementation, in which lower availability of a required mesohabitat type may limit the entire wetland's contribution to the adult population.

Marine Ecology Progress Series↗

Manganese nodules

The existence of manganese (Mn) nodules (Figure 1) has been known since the late 1800s when they were collected during the Challenger expedition of 1873–1876. However, it was not until after WWII that nodules were further studied in detail for their ability to adsorb metals from seawater. Many of the early studies did not distinguish Mn nodules from Mn crusts. Economic interest in Mn nodules began in the late 1950s and early 1960s when John Mero finished his Ph.D. thesis on this subject, which was published in the journal Economic Geology (Mero, 1962) and later as a book (Mero, 1965). By the mid-1970s, large consortia had formed to search for and mine Mn nodules that occur between the Clarion and Clipperton fracture zones (CCZ) in the NE Pacific (Figure 2). This is still the area considered of greatest economic potential in the global ocean because of high nickel (Ni), copper (Cu), and Mn contents and the dense distribution of nodules in the area. While the mining of nodules was fully expected to begin in the late 1970s or early 1980s, this never occurred due to a downturn in the price of metals on the global market. Since then, many research cruises have been undertaken to study the CCZ nodules, and now 15 contracts for exploration sites have been given or are pending by the International Seabed Authority (ISA). Many books and science journal articles have been published summarizing the early work (e.g., Baturin, 1988; Halbach et al., 1988), and research has continued to the present day (e.g., ISA, 1999; ISA, 2010). Although the initial attraction for nodules was their high Ni, Cu, and Mn contents, subsequent work has shown that nodules host large quantities of other critical metals needed for high-tech, green-tech, and energy applications (Hein et al., 2013; Hein and Koschinsky, 2014).

Book chapter↗

Coupling ecological and social network models to assess “transmission” and “contagion” of an aquatic invasive species

Network analysis is used to address diverse ecological, social, economic, and epidemiological questions, but few efforts have been made to combine these field-specific analyses into interdisciplinary approaches that effectively address how complex systems are interdependent and connected to one another. Identifying and understanding these cross-boundary connections improves natural resource management and promotes proactive, rather than reactive, decisions. This research had two main objectives; first, adapt the framework and approach of infectious disease network modeling so that it may be applied to the socio-ecological problem of spreading aquatic invasive species, and second, use this new coupled model to simulate the spread of the invasive Chinese mystery snail ( Bellamya chinensis ) in a reservoir network in Southeastern Nebraska, USA. The coupled model integrates an existing social network model of how anglers move on the landscape with new reservoir-specific ecological network models. This approach allowed us to identify 1) how angler movement among reservoirs aids in the spread of B . chinensis , 2) how B . chinensis alters energy flows within individual-reservoir food webs, and 3) a new method for assessing the spread of any number of non-native or invasive species within complex, social-ecological systems.

Journal of Environmental Management↗

Solid solutions in the system Cu-Fe-S, part I: The Cu-S and CuFe-S joins

T he data of Rau (1967) on the H 2 S/H 2 ratios of gas in equilibrium with high digenite solid solutions permit the calculation of the activity of Cu 2 S as a function of temperature and composition. The activity of Cu 2 S falls to 0.5 when the mole fraction (in the system Cu 2 S-S) drops only to 0.87. These calculations also permit the estimation of the activity of S 2 -temperature curve for the hexagonal chalcocite-high digenite reaction and a revised standard free energy for covellite.New data on the variation of the activity of S 2 in equilibrium with various metal/sulfur ratios for Cu = Fe in the intermediate solid solution permit the calculation of the activity of CuFeS 2 and show that it may drop as low as 0.2 at a mole fraction of 0.90 (system CuFeS 2 -Cu 2 Fe 2 S 2 ). The behavior of the copper-bearing solid solutions closely parallels that of pyrrhotite (Toulmin and Barton, 1964) in which the activity of FeS falls to 0.4 at a mole fraction of 0.9. A phase diagram is given for the CuFe-S join between 400 degrees and 700 degrees C.

Economic Geology↗