The Cullowhee Olistostromal Terrane

1
The Cullowhee Olistostromal Terrane
2
Blue Ridge Ultramafic Bodies
Lake Chatuge
3
Ultramafic Rock Occurrences in Subduction/Collisio
nal Belts
--Ophiolite Complexes
--Blocks in Accretionary Complexes
--Forearc Serpentinites
4
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

5
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
6
Geochemistry of the Buck Creek and Carroll Knob
Mafic/Ultramafic Complexes
Geochemically consistent with mafic and
ultramafic cumulate protoliths
7
Rare-Earth Element Systematics of Buck Creek
Compared to Lake Chatuge and Carroll Knob
Amphibolites (meta-gabbros)
Light rare-earth depleted, MORB-like patterns
8
NE Cullowhee Terrane Ultramafic Bodies Field
Relations
Deformed Amphibolite Block in metasedimentary
gneiss, Tathams 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.
9
Webster-Addie Ultramafic Body Structure and
Deformation
The Webster-Addie body includes Pyroxenite
lenses, often altered to tremolitetalc, 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
10
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.
11
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.
12
Metasomatic Effects Webster-Addie Ultramafic
Complex
Extensive dike intrusions and associated
hydrothermal veining are typical in the
Webster-Addie complex
13
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 --Suggestion
s of metasomatic alteration
14
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?