Magnet Cove, Arkansas
Photos © B.L. Dutrow
|
| Field trip participants - 2005 Mineralogy class! |
| Stop 1: The (Metamorphosed) Novaculite Locality |
|
|
|
| the class with Jennifer in the lead. |
Amy, Marianne, Ashley examining the novaculite |
|
|
| Contact metamorphism ( ~440C) caused recrystallization
of grains to produce a sugary texture (no cementing material). Avg.
grain size is about 45 microns. (brookite and rutile also present) |
Nick and Mike collecting samples. |
| Stop 2: Trachytes and phonolites |
|
|
|
| In the fall leaves - holocrystalline and aphanitic
outrops. Alkali fsp, Na-plag, nepheline, analcime, diopside, bt, gar, hbl and/or aegirine. |
Flow banding, ptygmatic injection features; small
sedimentary and igneous xenoliths. |
| Stop 3: Carbonatite |
|
|
|
| Carbonatite outcrop displaying rhombohedral cleavage
of the coarse-grained calcite. Accessory minerals: carbonate-apatite, monticellite,
biotite, magnetite, pyrite, perovskite. |
A short lunch by the creek |
| Stop 5: Pseudoleucite locality: |
|
|
|
| The creek with carbonatites |
Garnet pseudoleucite syenite near contact with shale.
Pseudoleucite (form of leucite replaced by nepheline and orthoclase), alkali
fsp, melanite (garnet), aegerine, in fine grained groundmass. |
|
|
| Collecting at Stop 5 |
Stop 6: Shales along Lake Oauchita |
| Our Geo-float tour |
|
|
|
| Tour guide covering geologic features and history
of the Lake. |
"Tiger rock" - silica dissolution and ppt in fractures. |
|
|
| Angel staircases |
Its a cool evening.... |
|
|
| Mike and Jason staying warm |
The final sunset..... |