TY - JOUR

T1 - Multi-Stage Hydrothermal Veins in Layered Gabbro of the Oman Ophiolite

T2 - Implications for Focused Fluid Circulation in the Lower Oceanic Crust

AU - Zhang, Chao

AU - Koepke, Jürgen

AU - Wolff, Paul Eric

AU - Horn, Ingo

AU - Garbe-Schönberg, Dieter

AU - Berndt, Jasper

N1 - Funding Information: We appreciate support during the fieldwork from Ali bin Masoud Al Sunaidy, Director General of Minerals at the Ministry of Commerce and Industry, Sultanate of Oman. This study was supported by the German Research Foundation (DFG) with project KO 1723/10‐1. Critical and constructive comments from Damon Teagle (guest editor) and two anonymous reviewers are gratefully acknowledged.

PY - 2021/8/16

Y1 - 2021/8/16

N2 - 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.

AB - 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.

KW - amphibole

KW - hydrothermal vein

KW - hydrous partial melting

KW - layered gabbro

KW - lower oceanic crust

KW - Oman ophiolite

UR - http://www.scopus.com/inward/record.url?scp=85113363591&partnerID=8YFLogxK

U2 - 10.1029/2021JB022349

DO - 10.1029/2021JB022349

M3 - Article

AN - SCOPUS:85113363591

VL - 126

JO - Journal of Geophysical Research: Solid Earth

JF - Journal of Geophysical Research: Solid Earth

SN - 2169-9313

IS - 8

M1 - e2021JB022349

ER -