Isotope and Chemical Methods for Mineral and Geoenvironmental Assessments and Support of USGS Science Strategy
The Project objective is to facilitate the full potential of stable isotope (C,H,N,O,S), noble gas isotope (He, Ar, Ne, Ar, Kr, Xe), active gas geochemistry (CO2, H2S, SO2, CH4, HF, HCl, N2, H2, organics, light hydrocarbons), and solute geochemistry measurements of minerals and fluids (including single fluid inclusions) in multidisciplinary studies of fundamental processes that affect mineral deposits throughout their life cycles.
Science Issue and Relevance
The Mineral Resources Program is mandated to inform planners and decision-makers on matters related to mineral resources on the Nation’s lands, including the consequences of mining and natural weathering. Fulfillment of these functions requires that genetic and geoenvironmental models be developed based on the current scientific understanding of the various types of ore deposits. Stable isotope, noble gas isotope, active gas chemistry, solute chemistry, and single fluid inclusion techniques are exceptionally powerful tools in the study of fundamental processes affecting ore deposits throughout their life cycles. There is a need for integrating several geochemical techniques such that a broad array of geochemical tools is available to investigators for application to individual deposits, areas, or districts, or to topical problems in mineral deposit life cycles.
Methods to Address Issue
The project provides the Mineral Resources Program with state-of-the-art capabilities in stable isotopes and related fields of geochemistry that advance the understanding of the Nation's endowment of mineral resources. The overall goal is to provide the impartial information to policy makers related to:
- opportunities for mine development,
- domestic availability of minerals critical to modern technology and manufacturing, and
- environmental protection in areas of past, present or future mining.
These capabilities, both individually and integrated, are applied to studies of processes that are important for mineral resources from their genesis through exploration and discovery, exploitation by mining, recycling of the mined materials, disposal of those materials, and final reclamation of the mined site. The knowledge acquired is continually integrated with USGS efforts to develop and refine genetic and geoenvironmental models of ore deposits. Study results, and the models they support, are critical for the assessment of the Nation's mineral wealth and the environmental consequences of natural weathering or mining it. Knowledge gained in Project studies can also be applied more broadly to a wide spectrum of societally-relevant issues that represent high priorities in USGS investigations in the biological, hydrological, and geological sciences. This Project succeeds a similar Project that was summarized in U.S. Geological Survey Circular 1343.
Stable isotope and chemical studies of the genesis of ore deposits
Stable isotope geochemistry involves isotopic analysis of carbon, hydrogen, nitrogen, oxygen, and sulfur. These elements are abundant in common minerals and rocks, and they are the building blocks of most geologic fluids (surface waters, magmatic waters, hydrocarbon fluids, and others) and most biological compounds. Geologic metal deposits are in most cases precipitates from hot fluids. Stable isotope measurements can help to determine the source of the fluids, the sources of dissolved constituents, physicochemical parameters of ore formation such as temperature, and the trigger for metal precipitation. Stable isotope analysis can also reveal the broader geologic environment of ore formation, an essential part of any mineral deposit model.
Stable isotope and chemical studies of the natural and anthropogenic degradation of mineral deposits and the environment
Mineral resource development and utilization can adversely affect natural environments and natural ecosystems. To consider mineral resource development among other land-use options, land managers must anticipate environmental and ecosystem impacts as realistically as possible in order to provide for mitigation and maximize the sustainability of ecosystems in the long term. Predictions of ecosystem and environmental effects are based on geoenvironmental models of the various types of mineral deposits. Current geoenvironmental models are uneven in their ability to predict ecosystem and environmental impacts and some models require additional empirical studies to strengthen them.
Stable isotope methods can help advance the understanding of the environmental and
ecosystem impacts of mineral deposits and other earth resources. Isotopic analyses of the elements carbon, hydrogen, nitrogen, oxygen, and sulfur can provide information on the sources of contaminants in surface- or ground waters, the air, plants, and animals. Isotopic analyses can also reveal the chemical and biological pathways by which contaminants originate, move through ecosystems, and are degraded or otherwise lost from the ecosystem. Isotope studies will be carried out as parts of larger collaborative projects focusing on specific processes or specific sites. Isotope methods are equally applicable to environmental and ecosystem impacts of the development of other resources. To obtain the benefits of more widely integrated studies of complex natural ecosystems, this task will also support studies of environmental impacts related to other types of development including extraction and utilization of energy resources, development of agricultural resources, and urbanization.
Noble gas isotope and active gas chemistry of mineral deposits
Helium, neon, argon, krypton, xenon, and radon are inert "gases" that have multiple isotopes. The relative abundances of the isotopes can reveal whether rock or water constituents came from the mantle, the deep crust, the shallow crust, or the atmosphere. In studies of mineral deposits, noble gas analyses are complementary to other types of chemical or isotopic analyses because they reveal how ore-forming systems fit into larger frameworks of crustal evolution and magma generation.
Active gases contained in hydrothermal minerals also give insights on ore formation. Active gases that are routinely measured include N2, CO2, CH2, H2, H2S, SO2, HCl, HF, H2O, and the light hydrocarbons. The data can reveal volatile evolution in hydrothermal systems, magma degassing histories, and fluid-rock chemical buffering.
Chemical Compositions of Single Melt and Fluid Inclusions
Inclusions trapped in hydrothermal minerals can contain remnants of the waters from which the minerals precipitated. Chemical and isotopic analysis of these miniscule inclusions provides a wealth of information on ancient hydrothermal systems and their role in the formation of mineral deposits. A variety of important parameters can be determined, including the mass of fluid required to produce the deposit, the chemical species that carried the metals, and the trigger that led to metal precipitation.
Solute chemistry of fluid inclusions
Certain cations and anions in fluid inclusions within hydrothermal minerals can be diagnostic of the source and history of the mineral-forming fluid. Particularly insightful are the abundances of the alkali metals lithium, sodium, and potassium, and the halides fluoride, chloride, bromide, and iodide. Analyses of these ions can reveal periods of evaporation, water-rock reactions within aquifers, and mixing of multiple fluids, all important inputs for mineral deposit models.
The Project objective is to facilitate the full potential of stable isotope (C,H,N,O,S), noble gas isotope (He, Ar, Ne, Ar, Kr, Xe), active gas geochemistry (CO2, H2S, SO2, CH4, HF, HCl, N2, H2, organics, light hydrocarbons), and solute geochemistry measurements of minerals and fluids (including single fluid inclusions) in multidisciplinary studies of fundamental processes that affect mineral deposits throughout their life cycles.
Science Issue and Relevance
The Mineral Resources Program is mandated to inform planners and decision-makers on matters related to mineral resources on the Nation’s lands, including the consequences of mining and natural weathering. Fulfillment of these functions requires that genetic and geoenvironmental models be developed based on the current scientific understanding of the various types of ore deposits. Stable isotope, noble gas isotope, active gas chemistry, solute chemistry, and single fluid inclusion techniques are exceptionally powerful tools in the study of fundamental processes affecting ore deposits throughout their life cycles. There is a need for integrating several geochemical techniques such that a broad array of geochemical tools is available to investigators for application to individual deposits, areas, or districts, or to topical problems in mineral deposit life cycles.
Methods to Address Issue
The project provides the Mineral Resources Program with state-of-the-art capabilities in stable isotopes and related fields of geochemistry that advance the understanding of the Nation's endowment of mineral resources. The overall goal is to provide the impartial information to policy makers related to:
- opportunities for mine development,
- domestic availability of minerals critical to modern technology and manufacturing, and
- environmental protection in areas of past, present or future mining.
These capabilities, both individually and integrated, are applied to studies of processes that are important for mineral resources from their genesis through exploration and discovery, exploitation by mining, recycling of the mined materials, disposal of those materials, and final reclamation of the mined site. The knowledge acquired is continually integrated with USGS efforts to develop and refine genetic and geoenvironmental models of ore deposits. Study results, and the models they support, are critical for the assessment of the Nation's mineral wealth and the environmental consequences of natural weathering or mining it. Knowledge gained in Project studies can also be applied more broadly to a wide spectrum of societally-relevant issues that represent high priorities in USGS investigations in the biological, hydrological, and geological sciences. This Project succeeds a similar Project that was summarized in U.S. Geological Survey Circular 1343.
Stable isotope and chemical studies of the genesis of ore deposits
Stable isotope geochemistry involves isotopic analysis of carbon, hydrogen, nitrogen, oxygen, and sulfur. These elements are abundant in common minerals and rocks, and they are the building blocks of most geologic fluids (surface waters, magmatic waters, hydrocarbon fluids, and others) and most biological compounds. Geologic metal deposits are in most cases precipitates from hot fluids. Stable isotope measurements can help to determine the source of the fluids, the sources of dissolved constituents, physicochemical parameters of ore formation such as temperature, and the trigger for metal precipitation. Stable isotope analysis can also reveal the broader geologic environment of ore formation, an essential part of any mineral deposit model.
Stable isotope and chemical studies of the natural and anthropogenic degradation of mineral deposits and the environment
Mineral resource development and utilization can adversely affect natural environments and natural ecosystems. To consider mineral resource development among other land-use options, land managers must anticipate environmental and ecosystem impacts as realistically as possible in order to provide for mitigation and maximize the sustainability of ecosystems in the long term. Predictions of ecosystem and environmental effects are based on geoenvironmental models of the various types of mineral deposits. Current geoenvironmental models are uneven in their ability to predict ecosystem and environmental impacts and some models require additional empirical studies to strengthen them.
Stable isotope methods can help advance the understanding of the environmental and
ecosystem impacts of mineral deposits and other earth resources. Isotopic analyses of the elements carbon, hydrogen, nitrogen, oxygen, and sulfur can provide information on the sources of contaminants in surface- or ground waters, the air, plants, and animals. Isotopic analyses can also reveal the chemical and biological pathways by which contaminants originate, move through ecosystems, and are degraded or otherwise lost from the ecosystem. Isotope studies will be carried out as parts of larger collaborative projects focusing on specific processes or specific sites. Isotope methods are equally applicable to environmental and ecosystem impacts of the development of other resources. To obtain the benefits of more widely integrated studies of complex natural ecosystems, this task will also support studies of environmental impacts related to other types of development including extraction and utilization of energy resources, development of agricultural resources, and urbanization.
Noble gas isotope and active gas chemistry of mineral deposits
Helium, neon, argon, krypton, xenon, and radon are inert "gases" that have multiple isotopes. The relative abundances of the isotopes can reveal whether rock or water constituents came from the mantle, the deep crust, the shallow crust, or the atmosphere. In studies of mineral deposits, noble gas analyses are complementary to other types of chemical or isotopic analyses because they reveal how ore-forming systems fit into larger frameworks of crustal evolution and magma generation.
Active gases contained in hydrothermal minerals also give insights on ore formation. Active gases that are routinely measured include N2, CO2, CH2, H2, H2S, SO2, HCl, HF, H2O, and the light hydrocarbons. The data can reveal volatile evolution in hydrothermal systems, magma degassing histories, and fluid-rock chemical buffering.
Chemical Compositions of Single Melt and Fluid Inclusions
Inclusions trapped in hydrothermal minerals can contain remnants of the waters from which the minerals precipitated. Chemical and isotopic analysis of these miniscule inclusions provides a wealth of information on ancient hydrothermal systems and their role in the formation of mineral deposits. A variety of important parameters can be determined, including the mass of fluid required to produce the deposit, the chemical species that carried the metals, and the trigger that led to metal precipitation.
Solute chemistry of fluid inclusions
Certain cations and anions in fluid inclusions within hydrothermal minerals can be diagnostic of the source and history of the mineral-forming fluid. Particularly insightful are the abundances of the alkali metals lithium, sodium, and potassium, and the halides fluoride, chloride, bromide, and iodide. Analyses of these ions can reveal periods of evaporation, water-rock reactions within aquifers, and mixing of multiple fluids, all important inputs for mineral deposit models.