Mapping Mt. Carmel Gabbro
Charleston Crossroads, Calhoun Mill, Belcher Crossroads

Descriptions are keyed to the map. Click the picture at left for a larger version, which will open in a new browser window.

1. Mulberry School: Gabbro - coarse-grained, black, igneous; pyroxene (black) and plagioclase feldspar (white); pyroxene in a thin dark vein; plagioclase in a wide vein with a suture in the middle, formed when the feldspar crystallized along the sides of a fissure and met in the middle. Mt Carmel gabbro formed as a result of back-arc spreading, solidifying underground in a small magma chamber; 400-500 myo: Ordovician)
2. Calhoun Creek: quartz and sericite (sericite is fine-grained mica, an alteration product of contact metamorphism); was ashflow tuff, intruded by basalt; mica was changed but quartz wasn’t
   2a St. Paul’s School: large pieces of quartz weathering out of soil means area is still in ashfall area…gabbro doesn’t have large quartz nodules
3. Less quartz, darker soil as you go along the road, getting closer to contact; also vegetation change from scrub to grass
4. Gabbro by stream
5. Calhoun Mill: andesite dike through gabbro
6. a Pyroclastic rock with quartz: gray, ashy (sericite)
   b Gabbro
7. a Clay, very little pelitic rock (aluminum-rich shale, from shelf sediments in between continent and island arc)
   b Gabbro
8. Hornfels with hornblende amphibole needles (contact metamorphic rock from mafic rock); Cross-section of needle is hexagonal.
9. Gabbro
10. Gabbro
11. Gabbro
12. Quartz weathering out

The Appalachians are rapidly rising at the rate of 1 to 2 mm per year, resulting in more cutting down by rivers. The rising could be due to isostasy caused by the erosion of top layers.