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Multi‐Stage Hydrothermal Veins in Layered Gabbro of the Oman Ophiolite: Implications for Focused Fluid Circulation in the Lower Oceanic Crust
Author(s) -
Zhang Chao,
Koepke Jürgen,
Wolff Paul Eric,
Horn Ingo,
GarbeSchönberg Dieter,
Berndt Jasper
Publication year - 2021
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2021jb022349
Subject(s) - gabbro , geology , geochemistry , hydrothermal circulation , ophiolite , oceanic crust , metamorphic facies , amphibole , magma chamber , magma , petrology , facies , igneous rock , volcano , geomorphology , tectonics , subduction , paleontology , quartz , structural basin
An outcrop in the layered gabbro section from the Wadi Wariyah of the Oman ophiolite has been investigated to provide new insights into the hydrothermal activities that cover a large temperature range in the lower crust at fast‐spreading mid‐ocean ridges. Our observations reveal a complex veining system composed of gabbroic dikes, hydrous mineral (amphibole, epidote, and prehnite) veins and associated alteration, which strongly overprinted the layered gabbros shortly after the solidification of the gabbroic cumulates. The general strike of the veins is roughly perpendicular to the magmatic foliation of the layered gabbro. Mineral‐based geothermometry indicates a wide temperature range (ca. 1,000−250°C) of hydrothermal activities, spanning from hydrous suprasolidus stage (VHT) through amphibolite facies (HT) and epidote‐amphibolite facies (MT) down to the prehnite‐pumpellyite facies (LT), which induced significant differences in selective element depletion and enrichment as well as in exchange of Sr and O isotopes. A key observation is the omnipresence of relics from a previous temperature stage in a given hydrothermal paragenesis formed at lower temperatures, implying that the same pathways were used for hydrothermal veining in a broad temperature interval spanning about 750°C. Our observations support a model that focused fluid circulations, in the form of combined microcracking (grain boundary spacing) and macrocracking (veining), developed shortly subsequent to the complete solidification of the layered gabbros, which may have facilitated effective cooling for magma crystallization in the lower crust.