Robertson River Igneous Suite - Laurel Mills granite

Gray, coarse-grained, inequigranular granite composed of alkali feldspar mesoperthite, quartz, and plagioclase, with hastingsitic amphibole, biotite, stilpnomelane, zircon, apatite, ilmenite, magnetite, and titanite. Amphiboles typically are entirely to partially replaced by fine-grained intergrowths of quartz, biotite, stilpnomelane, magnetite, and titanite. Pale blue color of the quartz is locally diagnostic. The granite typically displays numerous, anastomosing, mesoscopic zones of deformation. The unit has been dated at 728±2 Ma (U-Pb zircon; Tollo and Aleinikoff, in press).
State Virginia
Name Robertson River Igneous Suite - Laurel Mills granite
Geologic age Proterozoic Z
Lithologic constituents
Major
Igneous > Plutonic > Granitic > Granite
Comments Blue Ridge Basement Complex, Late Proterozoic Igneous
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 Fauquier - Rappahannock