Advanced Search
Granodiorite
Field Collector: Esper Signius Larsen Jr.
Place Collected:Near Agua Tibia Ranch San Luis Rey Quadrangle, Southern California
Object number: ROC21670
DescriptionThis appears to be a gneiss because it is foliated, but the collector has identified it as a granodiorite. It is a foliated white-tan granitoid rock consisting of 15% layers of black fine-grained biotite (~1 mm thick) in between 30% light grey quartz streams (~1-3 mm thick), 30% single crystals of white plagioclase (≤ 8 mm), and 25% tan single crystals of K-feldspar that resemble augen. This rock may have formed adjacent to a fault and experienced some postkinematic (after fault) rerystallization.
In Collection(s)