Crustal Geophysics and Geochemistry Science Center

Isotope and chemical methods for mineral and geoenvironmental assessments

Stable isotope and chemical studies of the natural and anthropogenic degradation of mineral deposits and the environment


Task Objectives

The development and utilization of mineral resources 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. The models are themselves based on empirical studies of active or historical mines and on a fundamental understanding of a number of complex geological, hydrological, and biological processes. Current geoenvironmental models are uneven in their ability to predict ecosystem and environmental impacts. Weaker models require additional empirical studies to strengthen them, and, because predicting future behavior of complex natural systems is inherently difficult, stronger models need to be updated by integrating the latest advances in understanding of ecosystem biogeochemistry.

The basic objective of this task is to use stable isotope methods to 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.

Statement of Work

The main efforts this year will be to (1) give a short course presentation on the environmental geochemistry of cyanide at the national Geological Society of America meeting, and (2) write a manuscript on this topic for the Reviews in Economic Geology volume that is associated with the short course. These are excellent opportunities to synthesize and publicize the large amount of work that our cyanide research group has done over the past decade. Additional work to be carried out is improvement of sulfate stable isotope methods, tools that are critical for case studies of acid rock drainage in mined areas and in naturallyweathered sulfide-rich watersheds. Work will focus on methods for liquid analysis by continuous flow pyrolysis-mass spectrometry so that the 18-O calibrations of internationally-distributed sulfate standards can be improved and greater accuracy can be achieved in isotopic measurements of unknowns. We will also continue to provide isotope data and advice for surface water and ground water studies at Handcart Gulch and Crested Butte in Colorado, and at sites contaminated by uranium tailings.

Products

  • Mandernack K.W., Mills C.T., Johnson C.A., Rahn T., and Kinney C., 2009, The delta 15-N and delta 18-O values of N2O produced during the co-oxidation of ammonia by methanotrophiic bacteria: Chemical Geology, v. 267, pp. 96- 107.

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Mineral Resources Program
Eastern Central GMEG Alaska Minerals Information Crustal Geophysics and Geochemistry Spatial Data