Task 4: Develop Prototype Quantitative Models
The primary objectives of this task were to:
- Determine the set of variables that are effective for modeling,
- Design prototype models for at least two deposit types, as allowed by availability of data,
- Contrast the relative importance of climate, mineralogy, and human activity on the footprint of a deposit,
- Forecast model results to locations where field data are incomplete, and
- Recommend locations, quantities and or types of data to collect in the future so that future models may be improved and important societal goals met.
Quantitative approaches to environmental modeling were narrowed to a few methods applicable to this project's goals.
Incorporation of spatial characteristics with loglinear or other model types were fit to existing data and conceptual models for massive sulfides, resulting in a first-cut attempt to model trace element movement away from a deposit and into the surrounding soils snd water.
Methods for simple models of trace-element data were tested using existing available data. The models describe percentiles of trace-element occurrence (how likely is it to observe concentrations at specific levels?), given that some proportion of the data are reported as below a detection limit. Methods for handling data below detection (or reporting) limits has long been an issue in geochemical studies. A textbook providing guidance on this issue was completed and published in early 2005. Expanding and updating methods proposed by USGS in the late 1960s, the book provides procedures that will be required throughout the modeling process of this project.