Hydrogen isotope composition of magmatic water

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5721754

Taylor, B E ^[1]

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1. Geological Survey of Canada, Ottawa, Ontario (Canada)

Isotopic tracing of H[sub 2]O degassing in both small and very large rhyolitic magmas in continental tectonic settings (USA and New Zealand), and isotopic studies of high-temperature fumaroles (USA, Japan, and elsewhere) indicate that the hydrogen isotope compositions of magmatic waters vary primarily with the composition of source material and tectonic setting. Water from felsic magmas in volcanic arc settings has a mean [delta]D value off [minus]25 [+-] 5 permil, whereas water from volcanic and plutonic magmas in continental settings has a slightly lower mean [delta]D of [minus]40 [+-] 10 permil. These differences reflect the variation in composition of source materials: hydrated oceanic crust and marine sediments for the arc volcanoes, and largely metamorphic crust for magmas in continental settings. The isotopic record in certain ore deposits associated with felsic magmas (e.g., W skarns, Sn-W veins) and geothermal systems records the influx at critical times of magmatic water with a [delta]D value of [minus]35 to [minus]45 permil. This is best documented where isotopic contrast between magmatic and meteoric waters is large. The [delta]D of MORB H[sub 2]O presumably lies between the mean [delta]D for MORB glass ([minus]75 permil), the [delta]D of H[sub 2]O in equilibrium with this glass ([delta]D ca. [minus]35; assuming closed-system degassing).

• OSTI ID: 5721754
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152004 -- Geothermal Data & Theory-- Isotope & Trace Element Studies
58 GEOSCIENCES
580000* -- Geosciences
CHEMISTRY
DEGASSING
DEUTERIUM
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
ISOTOPE RATIO
ISOTOPES
LIGHT NUCLEI
MAGMA
MAGMATIC WATER
METEORIC WATER
NUCLEI
ODD-ODD NUCLEI
OXYGEN COMPOUNDS
SOURCE ROCKS
STABLE ISOTOPES
WATER