Rhyolite

Rhyolite

Light colored fined grained volcanic rock composed of glass, quartz, K-feldspar and plagioclase, with relatively high silica (69-77 wt %). The composition reflects partial melting of continental crust. Rhyolitic volcanism is a feature of both Yellowstone (USA) and the Taupo Volcanic Zone (New Zealand) where geothermal activity is widespread.  The intrusive coarsely crystalline igneous rock equivalent is called granite.

Geothermal Glossary

Word of the Week – Adularia

Word of the Week – Adularia

Adularia Hydrothermal potassium bearing feldspar that forms in volcanic hosted geothermal reservoirs and is a favorable indicator of boiling and permeable conditions.

Word of the Week – Aquifer

Word of the Week – Aquifer

Aquifer Porous and permeable rock unit or unconsolidated layer in the subsurface in which all the pores and voids are filled with water. Water supply for wells comes from aquifers.

Word of the Week – Basalt

Word of the Week – Basalt

Basalt Dark grey fine grained volcanic rock composed of plagioclase, pyroxene and olivine, with relatively low silica (45-52 wt %). The composition reflects an upper mantle origin. Basalt is the most common type of volcanic rock on Earth, and it erupts from mid-ocean...

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