Zeolitic Alteration

GEOTHERMAL ENERGY

Zeolitic Alteration:

Hydrothermal alterations in which minerals from the zeolite group are introduced

Other definitions:Wikipedia Reegle

Relict Geothermal Features

Typical list of modern geothermal features

• Hydrothermally Deposited Rock

• Silica Deposition
• Carbonate Deposition
• Alunite
• Other Hydrothermal Deposits

• Hydrothermally Altered Rock

• Silicification
• Argillic-Advanced Argillic Alteration
• Zeolitic Alteration
• Leach Capping
• Other Hydrothermal Alteration Products

Epistilbite, a mineral in the zeolite group. This photo shows epistilbite in hydrothermally altered basalt from the Puu O Ehu quarry, Lanakai Hills, Kailua,Oahu, Hawaii. http://www.iza-online.org/natural/Datasheets/Epistilbite/epistilbite.htm

Zeolite minerals, including mordenite and clinoptilolite, have been identified in a number of caldera systems. These and other zeolite minerals are regionally extensive, and their formation is associated with late stage degassing of magmatic fluids and mixing with meteoric water.

Examples

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CSV

Geothermal Resource Area	Geothermal Region	Control Structure	Host Rock Age	Host Rock Lithology	Mean Capacity	Mean Reservoir Temp
Valles Caldera - Redondo Geothermal Area	Rio Grande Rift	Caldera Rim Margins Fault Intersection Stratigraphic Boundaries	Mississippian-Pennsylvanian; Pleistocene, 1.6 to 1.25 Ma	Limestone-Madera Formation “MIPu”; Rhyolitic tuff-Intracaldera Bandelier Tuff (upper Tshirege “Qbt” and lower Otowi “Qbo” members); Caldera Fill Rhyolite (shallow)
Valles Caldera - Sulphur Springs Geothermal Area	Rio Grande Rift	Caldera Rim Margins Fault Intersection Stratigraphic Boundaries	Precambrian; Mississippian-Pennsylvanian; Pleistocene, 1.6 to 1.25 Ma; Pliocene; Miocene	Crystalline basement “pCu”; Limestone-Madera Formation “MIPu”; Rhyolitic tuff-Bandelier Tuff (upper Tshirege “Qbt” and lower Otowi “Qbo” members); Caldera Fill Rhyolite (shallow); Dacitic/Andesitic to Rhyolitic lavas and tuffs-Keres Group Volcanics (shallow); Santa Fe Group volcaniclastics “Tsf”