Development of an igneous rock database with geologic functions: Application to Neogene bimodal igneous rocks and mineral resources in the Great Basin
Authors: Yager Douglas B. , Hofstra Albert H. , Fifarek Katheryn , Webbers Ank 
Published: September 2010

Geologists routinely use sample data (descriptive, qualitative, quantitative) to characterize a hierarchy of larger geologic features that each have their own independent attributes, use physical relationships between geologic features to establish their relative ages, combine this information with dated features to understand evolutionary histories of study areas at various scales, and produce maps to display such information in space and time relative to other features of interest. This paper demonstrates how we integrated such routine geologic functions into an existing igneous rock relational database designed to store, organize, update, query, and retrieve sample data that have well-defined locations. The resulting igneous rock database is utilized to capture information on Neogene bimodal igneous rocks in northern Nevada and the eastern Great Basin Province. The database is a useful tool that facilitates queries to generate geographical information system displays and petrologic plots that elucidate the time-space-composition relationships of volcanic centers to one another and to geophysical anomalies, structural features, and mineral deposits.

Database information is parsed into the following data tables: physical hierarchy of scale, absolute and relative age, chemistry, paleomagnetic, rock mode, image, cross section, X-ray diffraction, and igneous-related structure. Information is organized in a telescoping geologic hierarchy schema: igneous province, volcanic field, volcanic system or caldera, extrusive flow or intrusion, sample, and various subsamples. Absolute radiometric age determinations on samples from geologic features and expert interpretations of relative age relationships between different features may be captured and used together to constrain the ages of undated features. Such age information is linked to features of various scales in the hierarchy. Common attributes that are shared between the relational database and geographic information system (GIS) features include feature-identification or sample-identification, and they permit linking of geographic entities and tabular data for query, analysis, and display in GIS or derivative tables.

Relational database keys merge analytical, map, and image data across this geologic hierarchy-age-location schema to facilitate queries that address geologic problems. Data acquired at the sample scale of observation is linked to increasingly larger features that have their own independent attributes using GIS. This schema enables users to retrieve information on one or more hierarchical features for input into external software for various GIS, statistical, petrologic, and other display, analysis, or comparison purposes. Fundamental interpretations resulting from such analyses or displays, e.g., rock classification, may be used to populate additional fields in the database. The database is designed for flexibility and can accommodate information resulting from both detailed and reconnaissance studies. The geologic functions that were developed and that we added to an existing igneous rock database (Lehnert et al., 2000) for this study have wide applicability and could readily be integrated into other geoscience databases.