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.
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--Blocks in Accretionary
MG: Mica Gneiss
PGA: Pale Green Amphibolite
DNA: Altered Dunite
Geochemically consistent with mafic and ultramafic cumulate protoliths
Light rare-earth depleted, MORB-like patterns
Deformed Amphibolite Block
in metasedimentary gneiss,
Tatham’s Creek, NC
Field Relations of Mafic and
Ultramafic rock units near
Addie, NC. (REU 2001)
--Green: Ultramafic rocks
Outcrops range from
map-scale,lenticular bodies to small lenses in the mica gneiss country rocks.
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
Chemically, the mafic and ultramafic rocks from Addie and Balsam are not consistent with a related cumulate assemblage. The Amphibolites are andesitic in composition.
Nd of Buck Creek and
Lake Chatuge: ~+5
Nd of Webster-Addie: ~-1
(Shaw and Wasserburg, 1984)
higher initial Sm/Nd than Buck Creek.
Extensive dike intrusions and associated hydrothermal veining are typical in the Webster-Addie complex
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
Cullowhee Terrane: “Enigmatic” (Raymond et al. 1989)
--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.
--Detailed Field Relations of mafic/ultramafic units
--Geochemical comparisons of amphibolites, and ultramafic bodies from Franklin, NC northeastward - do they have similar protoliths?