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| Titel |
Hydrothermal fault zones in the lower oceanic crust: An example from the
Samail ophiolite, Oman |
| VerfasserIn |
Barbara Zihlmann, Samuel Müller, Juergen Koepke, Damon Teagle |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250142879
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| Publikation (Nr.) |
 EGU/EGU2017-6552.pdf |
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| Zusammenfassung |
| Hydrothermal circulation is a key process for the exchange of chemical elements between the
oceans and the solid Earth and particularly for the extraction of heat from newly
accreted crust at mid-ocean ridges. However, due to a dearth of samples from intact
oceanic crust, or continuous samples from ophiolites, there remain major short
comings in our understanding of hydrothermal circulation in the oceanic crust,
especially in the deeper part. In particular, it is unknown whether fluid recharge
and discharge occurs pervasively or if it is mainly channeled onto discrete zones
such as faults. Here, we present a description of a hydrothermal fault zone that
crops out in the layered gabbro section, of Wadi Gideah in the Samail ophiolite in
Oman, which might be a channel of enhanced fluid flow. Field observations reveal an
approximately one meter-thick chlorite - epidote normal fault with heavily altered gabbro
clasts in the center. In places there is copper mineralization within the chlorite –
epidote zone. In both, the hanging and the footwall the gabbro is heavily altered and
veined, mainly with amphibole, epidote, prehnite and zeolite veins. Even though the
fault zone is within the layered gabbro section, and perhaps only 1 km above the
crust-mantle boundary, the gabbro around the fault zone shows highly variable
textures.
Preliminary strontium isotope whole rock data yield 87Sr/86Sr ratios of ∼ 0.7046, which are
considerably more radiogenic than “fresh" gabbro from the Oman ophiolite (87Sr/86Sr =
0.7026 – 0.7030), and similar to black smoker hydrothermal signatures based on epidote,
measured elsewhere in the ophiolite. |
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