Robertson River Igneous Suite - Hitt Mountain alkali feldspar syenite

Light-gray, coarse-grained to locally pegmatitic, inequigranular alkali feldspar syenite composed of microcline mesoperthite, quartz, and saussuritized plagioclase, with lesser hastingsitic amphibole, biotite, allanite, zircon, stilpnomelane, apatite, and rare garnet; locally displays cumulate and pseudocumulate texture. The syenite has been dated at 706± 2 Ma (U-Pb zircon; Tollo and Aleinikoff, in press).
State Virginia
Name Robertson River Igneous Suite - Hitt Mountain alkali feldspar syenite
Geologic age Proterozoic Z
Lithologic constituents
Major
Igneous > Plutonic > Syenitic > Alkali-feldspar-syenitealkali syenite
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 Culpeper - Greene - Madison - Rappahannock