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Spatial Data Development and Analysis - Geochemical Databases

Task Objectives

The Mineral Resources Program supports two major national geochemical databases: the National Geochemical Database (NGDB) and the National Geochemical Survey (NGS). The NGDB consists primarily of geochemical data acquired by various Mineral Resources Program projects over the years and consequently is a spatial and analytical patchwork. However, the NGDB does include all data produced as part of the National Uranium Resource Evaluation (NURE), also maintained as a separate online dataset, (http://pubs.usgs.gov/of/1997/ofr-97-0492/), and all data produced as part of the NGS. The NGS is composed of data for approximately 75,000 samples, primarily stream sediment, analyzed using a consistent analytical protocol. NGS data were acquired in a fashion designed to ensure a high level of quality control and thus represent the sole, detailed, comprehensive geochemical database for the U.S. (http://tin.er.usgs.gov/geochem/doc/home.htm). The NGDB is supported by the National Geochemical Database Project, whereas NGS development was an activity conducted within the National Surveys and Analyses Projects, which terminated in 2007. Collectively, all of these data represent a major resource for conduct of the Updated National Mineral Resource Assessment Project.

SubTask long-term goals include:

• Continue to develop and maintain the National Geochemical Survey database (NGS).
• Supply raw and derivative geochemical data,
• Improve data quality and accuracy,
• Support data integration work of the GIS Development SubTask,
• Create applied/interpretive assessment products,
• Provide nationwide (250 K or better) coverage for geochemical and modal data. Use mineralogic data along with statistical methods, in part based on the NIST results, to produce geochemical maps and baseline data insupport of mineral resource assessment activities.
• Collaborate with economic geologists preparing updated mineral deposit models (Task 2) to help define geochemical characteristics of various deposit types.
• Conduct research concerning the application of geochemical data to mineral resource assessments.
• Develop analytical methodologies for presenting and analyzing geochemical data, particularly in map format. Determine how to portray uncertainty and how to accomodate portrayal of censored data.
• Prototype use of these methodologies in a TiO² resource assessment.

Statement of Work

Continue to develop and maintain the National Geochemical Survey database (NGS) (http://tin.er.usgs.gov/geochem/doc/home.htm). These activities include continued data input for newly analyzed samples, infilling small areas for which NGS regional sample coverage is inadequate, reanalysis of selected samples from high priority areas using better, more complete analytical routines.

Continue innovative statistical analysis of NGS data in cooperation with National Institute of Standards and Technology (NIST).

Begin developing methodologies that utilize statistical results to prepare derivative, primarily elemental ratio-based, geochemical maps that also include meaningful portrayal of uncertainty and censored values.

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