The Cullowhee Olistostromal Terrane

Blue Ridge Ultramafic Bodies Lake Chatuge

Ultramafic Rock Occurrences in Subduction/Collisional Belts --Ophiolite Complexes --Blocks in Accretionary Complexes --Forearc Serpentinites

REU Site Research Program, 1997-2001 48 Undergraduate Participants over 4 years Students conducted Field mapping, Petrography, Whole-rock and mineral chemistry and field geophysics Post-Summer student efforts in petrography, mineral chemistry and geochemistry

Field Relations of the Buck Creek and Carroll Knob Mafic/Ultramafic Complexes MG: Mica Gneiss PX: Meta-Pyroxenite PGA: Pale Green Amphibolite AM: Amphibolite DN: Dunite TC: Coronal Metatroctolite EMS: Edenite- Margarite Schist DNA: Altered Dunite

Geochemistry of the Buck Creek and Carroll Knob Mafic/Ultramafic Complexes Geochemically consistent with mafic and ultramafic cumulate protoliths

Rare-Earth Element Systematics of Buck Creek Compared to Lake Chatuge and Carroll Knob Amphibolites (meta-gabbros) Light rare-earth depleted, MORB-like patterns

NE Cullowhee Terrane Ultramafic Bodies: Field Relations Deformed Amphibolite Block in metasedimentary gneiss, Tatham’s Creek, NC Field Relations of Mafic and Ultramafic rock units near Addie, NC. (REU 2001) --Yellow: amphibolites --Green: Ultramafic rocks Amphibolite/ultramafic Outcrops range from map-scale,lenticular bodies to small lenses in the mica gneiss country rocks.

Webster-Addie Ultramafic Body: Structure and Deformation The Webster-Addie body includes Pyroxenite lenses, often altered to tremolite+talc, which define the local foliation. These lenses/layers may represent deformed pyroxene pods, or original pyroxenite layers. Orthopyroxene/Talc-Tremolite schist layers showing boudinage: Chestnut Gap quarry, NC

Geochemistry of the Webster-Addie and Balsam Gap Ultramafic Bodies Amphibolites Chemically, the mafic and ultramafic rocks from Addie and Balsam are not consistent with a related cumulate assemblage. The Amphibolites are andesitic in composition.

REE Comparison: NE ultramafics to the Buck Creek complex Isotopic Characteristics: Nd of Buck Creek and Lake Chatuge: ~+5 Nd of Webster-Addie: ~-1 (Shaw and Wasserburg, 1984) Webster-Addie has higher initial Sm/Nd than Buck Creek.

Metasomatic Effects: Webster-Addie Ultramafic Complex Extensive dike intrusions and associated hydrothermal veining are typical in the Webster-Addie complex

Implications of Blue Ridge Ultramafic Rock Units: SW Cullowhee Terrane: Buck Creek, Carroll Knob, Lake Chatuge --a fragmented Ophiolite Complex? NE Cullowhee Terrane: --Lenticular Mafic and Ultramafic bodies --No clear cumulate characteristics --no petrogenetic links evident between ultramafic and mafic rocks --Suggestions of metasomatic alteration

Implications of Blue Ridge Ultramafic Rock Units: Cullowhee Terrane: “Enigmatic” (Raymond et al. 1989) Possibly: --SW Cullowhee Terrane: A suture-zone assemblage, w/ the Hayesville Fault as the old suture. --NE Cullowhee Terrane: extenstion of “Melange” rocks of the Ashe Metamorphic Suite, or a different structural unit within a paleo-accretionary complex. To Test: --Detailed Field Relations of mafic/ultramafic units --Geochemical comparisons of amphibolites, and ultramafic bodies from Franklin, NC northeastward - do they have similar protoliths?