Quartz Diorite - Menlo Park, California
Posted by: 
Volcanoguy
N 37° 27.428 W 122° 10.263
10S E 573313 N 4145908
Quartz diorite blocks at the USGS Campus in Menlo Park, California.
Waymark Code: WMADH9
Location: California, United States
Date Posted: 12/31/2010
Views: 2
These quartz diorite blocks are one example of a series of large blocks of rocks from various locations, which are on display around the USGS Campus in Menlo Park. There is a self-guided tour of the campus available at the visitor center.
This group of blocks is an artists conception of California broken by faults.
Text of Sign: “The large black colums of plutonic rock engraved with the USGS seal are composed of what is commonly called ‘Black Granite’. The rock is a quartz diorite containing hypersthene, hornblende and biotite. This rock is from an active quarry located in the Academy Pluton in the western Sierra Nevada, east of Fresno. The pluton is a concentrically zoned intrusion about 20 kilometers (12 miles) in diameter that ranges in composition from gabbro to granodiorite. It was emplaced about 120 million years ago during the Early Cretaceous Period and is one of the earliest and westernmost intrusions in the Sierra Nevada batholithic complex.”
Type of Display: Geological
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