Paper No. 10-10
Presentation Time: 8:00 AM-12:00 PM
Rf/φ ANALYSIS ON ROCKS OF THE AUSTELL GNEISS AND NEW GEORGIA GROUP IN PROXIMITY TO THE BREVARD FAULT ZONE: IMPLICATIONS FOR THE DEFORMATION HISTORY OF THE EASTERN BLUE RIDGE IN GEORGIA
Rf/φ analysis has proven valuable in quantifying strain in ductilely-deformed rocks. While such analysis is typically performed on deformed quartz grains in metasedimentary rocks (e.g. metaconglomerate), previous studies have shown that ductilely-deformed feldspars are useful as strain markers in high temperature shear zones and under regional metamorphic conditions (e.g. middle-upper amphibolite facies). In this study, we perform strain analysis on a cross-strike transect in the vicinity of the Austell gneiss, immediately northwest of the Brevard fault zone and Chattahoochee fault in the Georgia portion of the Ashland-Wedowee-Emuckfaw belt (i.e. eastern Blue Ridge composite terrane). Similar studies in the equivalent Alabama portion of the eastern Blue Ridge suggest a general increase in strain from northwest to southeast as recorded by pre-kinematic metagranitoid bodies that intruded the predominantly metasedimentary country rock. In this study, we attempt to quantify the strain in this portion of the eastern Blue Ridge of Georgia for the purposes of comparison with strain studies farther to the southwest in Alabama; to assess the presence or absence of a strain gradient in proximity to the Brevard fault zone; and to compare strain partitioning in orthogneiss of the Austell gneiss with quartzofeldspathic paragneiss of the adjacent New Georgia Group. The results of this research have implications for the use of Rf/φ analysis in feldspathic paragneiss and orthogneiss, and provide a means of directly comparing quantitative strain data from opposite ends of the Ashland-Wedowee-Emuckfaw belt, as well as along-strike variation in ductile deformation recorded within the Brevard fault zone.