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High-temperature Hydrothermal Systems Heat Sources Above 3,5 Km Depth

High-temperature Hydrothermal Systems Heat Sources Above 3,5 Km Depth. Gudmundur Omar Fridleifsson. Contact metamorphic hornfels. Sanidinte facies :. T : 800-1100 °C P : < 0, 5 Kbar. The inner contact aureole: Sanidinite Facies Hornfels. Formed at 800-1100 °C

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High-temperature Hydrothermal Systems Heat Sources Above 3,5 Km Depth

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  1. High-temperature Hydrothermal SystemsHeat Sources Above 3,5 Km Depth Gudmundur Omar Fridleifsson

  2. Contact metamorphic hornfels Sanidinte facies : T : 800-1100 °C P : < 0, 5 Kbar

  3. The inner contact aureole:Sanidinite Facies Hornfels • Formed at 800-1100 °C • augite -An44 - ore in metamorphosed lava • augite-salite-An30 in amygdales • miarolitic veins formed by gasrich high-Pressure metasomatic fluid. Veins partly filled by: • ferroaugite-hedenbergite-gt-act-sp-ap • crosscut by unchilled felsite veins (~900-1000°C)

  4. Johannsenite Contact metamorphic skarn 400-600 °C Andradite Grosular Hedenbergite Diopside

  5. The outer contact aureole:skarn minerals in lava vesicles • hedenbergitess-andradite garnet-magnetite • Mn-enriched garnets with inclusions of px • Anisotropic garnets • Redox reactions hematite to magnetite • Metasomatism around vesicles leads to well developed chlorite-albite halos suggesting extensive leaching of Ca2+ in particular, at high water/rock ratio

  6. Contact metamorphic skarn Stability field for coexisting hedenbergite-andradite is stippled

  7. Sequence of events above 3,5 km: • Pfluid near gabbro intrusions approaches Plith • Fluids at supercritical-T exist for some time • Pressure drops to hydrostatic-P with time and fluid temperature passes through the superheated steam field before adjusting to hydrotstatic temperatures • Evidently the time concept is of funda-mental importance with respect to possible exploitation in active hydrothermal systems

  8. Cooling time of the Geitafell gabbro 2A = 2,5 km 2B = 1,0 km 2C = 0,5 km T1 = 1225°C Depth to the centre of the gabbro intrusion is 1250 m • Thermal gradient : T2 • °C/km 75°C • °C/km 125°C • 140 °C/km 175°C • 180 °C/km 225°C Model of rectangular intrusion

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  10. Magma chamber

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