Tonalite
“The quartz-rich granite of mountain cores”
Tonalite is a coarse-grained intrusive igneous rock similar to granite but dominated by plagioclase feldspar rather than alkali feldspar, with significant quartz and dark minerals. It forms the deep roots of many major mountain belts and volcanic arcs, including vast batholiths along subduction zones.
plagioclase feldspar, quartz, hornblende, biotite, minor alkali feldspar
Tonale Pass (Italian Alps), Sierra Nevada Batholith (California, USA), Coast Range (British Columbia), Andes, Japan
6-7
Half Dome and El Capitan in Yosemite are largely tonalite and related rocks — the massive granite-family batholith that forms the Sierra Nevada is one of the largest on Earth.
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How does tonalite differ from granite in its feldspar composition?
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