CHARACTERIZATION OF METAMORPHIC ZONES IN THE TENNESSEE BLUE RIDGE USING GIS AND DIGITAL IMAGE PROCESSING

The origin of metamorphic zones of the Blue Ridge is attributed to various deformation events of sedimentary rocks of debated age, leading the topic to be controversial and continuously studied. The present study seeks to refine metamorphic isograds based on Barrovian index minerals in pelitic rocks and to help resolve these controversies. Methods used in the present study are supported by conventional petrography, powder X-ray diffraction, and by GIS and digital image processing.

Metamorphic isograds in the Blue Ridge have been determined mainly by identification of index minerals using a polarizing petrographic microscope. Applications of GIS and digital image processing in geologic studies are countless, but few researchers have applied these technologies to study spatial relationships among minerals in a rock. The use of GIS and digital image processing in studying these minerals could provide a more efficient and precise means of mineral identification and determining the location of metamorphic isograds.

A total of 8 samples of low- to high-grade metamorphosed pelitic rock have been collected along US HWY 64. The mineralogy of each sample was analyzed both by powder X-ray diffraction and in thin section, using a petrographic microscope. Photomicrographs were taken of each thin section under plane-polarized and cross-polarized light and were processed to study in GIS environments. Tools in ArcGIS and ERDAS Imagine software can be used to make reproducible measurements for comparison and quantification of different minerals in photomicrographs. A GIS-based algorithm to detect Barrovian index minerals is being developed to help refine the positions of isograds between the metamorphic zones. This algorithm can be developed incrementally and applied to other metamorphic rocks containing these minerals in the Blue Ridge.