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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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ultramafic rock occurrences in subduction collisional belts
Ultramafic Rock Occurrences in Subduction/Collisional Belts

--Ophiolite Complexes

--Blocks in Accretionary

Complexes

--Forearc Serpentinites

reu site research program 1997 2001
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
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
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
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
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
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
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
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
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
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 units1
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?