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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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?