BELT, JOHN Q., and GARY K. RICE
GeoFrontiers Corporation, Dallas, TX

Abstract: Application Of Statistical Quality Control Measures To Surface Geochemical Exploration Data

The most important aspect of near-surface, geochemical exploration data is the statistical quality control (SQC) measures used in sample collection and analytical data processing.

Sample Collection:

1) Contamination - Extraneous sources contaminate samples and bias geochemical data quality. These sources and areas must be avoided. Data must be screened for contamination.
2) Sample Replicates - Replicate samples collected at the same time and location help determine data variability.
3) Base Stations - Dedicated base stations determine temporal data variability.

Analytical Data Processing:

1) Instrument Calibration - Two primary forms of calibration are external standard (ES) and internal standard (IS). Sample type and volume analyzed determines instrument calibration parameters.
2) Quality Control Charts - Two important quality control charts are the X-bar and R charts. Both charts monitor analytical equipment parameters insuring reproducible data over time.
3) Cross Plots and Correlation Coefficients - Cross plots and correlation coefficients compare two variables. Contamination, multiple sources, and degradation change this linear relationship.

The explorationist must be thoroughly familiar with these statistical quality control measures. Its is paramount to implement SQC measures during Sample collection and data processing. Poor quality geochemical data provides no beneficial information in evaluating your exploration prospect. Quality is the single most important factor in selecting a geochemical exploration tool.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas