Document Type
Thesis
Abstract
I investigated 5 occurrences of ultramafic rock within the Goochland terrane, structurally bound by the Spotsylvania lineament and the Hylas fault zone. Four rock types are present: tremolite/actinolite + chlorite + talc rocks (the most dominant rock type), anthophyllite + chlorite + talc rocks, tremolite/actinolite + clinopyroxene rocks, and cummingtonite + chlorite + serpentine £ olivine rocks. Whole-rock major element and trace element compositions reveal SiO, concentrations from 40.15 to 52.67 wt. %, Mg # ranging 72.5-85.0, CaO ranging 0.83-14.41 wt. %, and Al, O3 ranging 5.24-12.90 wt. % (all on an anhydrous basis). Na2O content was typically below | wt. %. With the exception of actinolite + clinopyroxene rocks whose values are significantly lower, Cr concentrations were all above 1977 ppm and Ni concentrations were between 507 and 1248 ppm. Primitive mantle-normalized plots of transition elements reveal that tremolite/actinolite + chlorite + talc rocks are apparently similar to ultramafic rocks in the Chopawamsic terrane to the west of this study. Actinolite + clinopyroxene rocks are likely related to the Sabot amphibolite. No evidence for intrusive emplacement or granulite-facies assemblages was present in the rocks investigated.
Date Awarded
2002
Department
Geology
Advisor 1
Brent E. Owens
Recommended Citation
MacCarthy, Jonathan, "Field, Mineralogical, and Geochemical Coonstraints on the Origin and Significance of Ultramafic Rocks, Goochland Terrane, VA" (2002). Geology Senior Theses. William & Mary. Paper 99.
https://scholarworks.wm.edu/geologyseniors/99
