Ellisville Biotite Granodiorite

Ellisville biotite granodiorite (Pavlides, 1990). Mesocratic, coarse- to medium-grained, equigranular to porphyritic, massive to strongly foliated granodiorite. Mineralogy: quartz + plagioclase + potassium feldspar + biotite; accessories include epidote, allanite, titanite, and apatite. Porphyritic rocks contain potassium feldspar megacrysts up to 1.5 cm across; myrmekite commonly occurs adjacent to potassium feldspar. Brownish-green, strongly pleochroic biotite is associated with, and in places poikilitically encloses epidote, allanite, titanite, and apatite. Subhedral epidote locally encloses euhedral titanite. Pleochroic green amphibole and muscovite are minor constituents locally. The Ellisville has been dated at 440±8 Ma (Rb-Sr whole rock; Pavlides and others, 1982).
State Virginia
Name Ellisville Biotite Granodiorite
Geologic age Ordovician-Silurian
Lithologic constituents
Major
Igneous > Plutonic > Granitic > Granodiorite
Comments Western Piedmont (Northern)
References

Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.

Virginia Division of Mineral Resources, 2003, Digital Representation of the 1993 Geologic Map of Virginia, Publication 174, CD ROM (ISO-9660) contains image file, expanded explanation in pdf, and ESRI shapefiles, scale 1:500,000.

NGMDB product
Counties Fluvanna - Louisa - Orange - Spotsylvania