A.I.duPont Students see geology of the Delaware Piedmont
- amphibolites
- Appalachian Piedmont
- Baltimore Gneiss
- Barley Mill Gneiss
- bedrock
- Brandywine Blue Gneiss
- Brandywine Springs
- Clinopyroxene
- Cockeysville Marble
- crystalline rocks
- deformation
- Delaware
- Enstatite (Bronzite)
- fall zone
- Fall Zone
- Faulkland Gneiss
- Garnet
- geology
- Glenarm Series
- Greenbank
- Hornblende
- Hypersthene
- igneous
- magma
- Magnetite
- mapping
- Metapyroxenite and metagabbro (undifferentiated)
- Mica
- Microcline
- Mount Cuba
- Orthoclase
- Orthopyroxene
- pegmatite
- Plagioclase
- Pyroxene
- Quartz
- Red Clay Creek
- Rockford Park Gneiss
- rocks
- Serpentinite
- Setters Formation
- Sillimanite
- Taconic Orogeny
- tectonics
- topography
- Wilmington Complex
- Wissahickon Formation
- Wooddale
- Yorklyn
- Zircon
Montchanin Metagabbro
Coarse-grained gabbroic and metagabbroic rocks, variably metamorphosed and deformed. Primary igneous minerals include olivine, clinopyroxene, orthopyroxene, and plagioclase.
Brandywine Blue Gneiss
Medium to coarse grained granulites and gneisses composed of plagioclase, quartz, orthopyroxene, clinopyroxene, brown-green hornblende, magnetite, and ilmenite. Mafic minerals vary from < 5-30 modal percent. A lineation due to a preferred orientation of quartz and mafic minerals is obvious on weathered surfaces. Unit contains thin, discontinuous fine-grained mafic layers.
Perkins Run Gabbronorite Suite
Fine- to coarse-grained gabbronorite and minor diorite with subophitic to ophitic textures, variably foliated or lineated. Plagioclase, orthopyroxene, clinopyroxene, and hornblende are major minerals; biotite and olivine locally present. Olivine typically surrounded by corona structures as described for the Bringhurst Gabbro. Contemporaneous with the Ardentown Granitic Suite.
Bringhurst Gabbro
Coarse- to very coarse-grained gabbronoite with subophitic textures. Primary minerals are plagioclase, olivine, clinopyroxene and orthopyroxene. Olivine, where present, is surrounded by an inner corona of orthopyroxene and an outer corona of pargasitic hornblende, both with spinel symplectites. The gabbronorites locally contain abundant xenoliths of mafic Brandywine Blue Gneiss.
Iron Hill Gabbro
Black to very dark green, coarse- to very coarse-grained, uralitized olivine-hypersthene gabbronorite and pyroxenite with subophitic textures. Primary minerals are calcic plagioclase, orthopyroxene, clinopyroxene, and olivine. Amphibole is secondary, a pale blue-green actinolite. Olivine, when present, is surrounded by coronas similar to those in the Bringhurst Gabbro. The gabbronorite is deeply weathered leaving a layer of iron oxides, limonite, goethite, and hematite, mixed with ferruginous jasper. The jasper contains thin seams lined with drusy quartz. Contacts with the Christianstead Gneiss are covered with sediments of the Coastal Plain.



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