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
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La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
SM18
AB6D
JC5BSM1B
SZ7
10-1B
TP10BJL23
11D
JC5A
PG4D
11C
SM 11
Field Relations of the Buck Creek and Carroll Knob Mafic/Ultramafic Complexes
AM: AmphiboliteDN: DuniteTC: Coronal Metatroctolite
EMS: Edenite- Margarite SchistDNA: Altered Dunite
MG: Mica GneissPX: Meta-PyroxenitePGA: Pale Green Amphibolite
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
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100 PG13A
SM1DTS-04CG96-6JP10CSZ8TS-12TS-06TS-08TS-10
La Ce Pr Nd Sm Eu Gd Tb Dy TmErHo Yb Lu
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La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
BC High Ti Amphibolites
"Group II" Amphibolites, Ashe Formation
CK 199CK 299LCH-gt, Lake Chatuge
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 andUltramafic rock units nearAddie, 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
Orthopyroxene/Talc-Tremolite schist layers showing boudinage: Chestnut Gap quarry, NC
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.
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 andLake 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?