TY - JOUR

T1 - A Reference Section Through Fast-Spread Lower Oceanic Crust, Wadi Gideah, Samail Ophiolite (Sultanate of Oman)

T2 - Petrography and Petrology

AU - Koepke, J.

AU - Garbe-Schönberg, D.

AU - Müller, T.

AU - Mock, D.

AU - Müller, S.

AU - Nasir, S.

N1 - Funding Information: This work would not have been possible without the help of Adolphe Nicolas and Francoise Boudier during an initial state of the project. The authors wish to thank Otto Dietrich and J. Feige for careful thin section preparation. The friendly cooperation established in Oman with the Public Authority for Mining (Department of Geological Research, Dr. A. Al Rajhi and Dr. M. Alaraimi) is acknowledged. This study was funded by projects KO 1723/16-1, KO 1723/21-1, and KO 1723/25-1 of the Deutsche Forschungsgemeinschaft (DFG) within the priority program SPP 1006: ICDP. Open access funding enabled and organized by Projekt DEAL.

PY - 2022/1/3

Y1 - 2022/1/3

N2 - In the absence of a complete profile through fast-spreading modern oceanic crust, we established a reference profile through the whole paleo crust of the Samail ophiolite (Sultanate of Oman), which is regarded as the best analogue for fast-spreading oceanic crust on land. To establish a coherent data set, we sampled the Wadi Gideah in the Wadi-Tayin massif from the mantle section up to the sheeted dikes and performed different analytical and structural investigations on the same suite of samples. This paper reports our studies of the lower crust, a 5 km thick pile of gabbros, focusing on petrographic features and on the results of mineral analyses. Depth profiles of mineral compositions combined with petrological modeling reveal insights into the mode of magmatic formation of fast-spreading lower oceanic crust, implying a hybrid accretion mechanism. The lower two thirds of the crust, mainly consisting of layered gabbros, formed via the injection of melt sills and in situ crystallization. Here, upward moving fractionated melts mixed with more primitive melts through melt replenishments, resulting in a slight but distinct upward differentiation trend. The upper third of the gabbroic crust is significantly more differentiated, in accord with a model of downward differentiation of a primitive parental melt originated from the axial melt lens located at the top of the gabbroic crust. Our hybrid model for crustal accretion requires a system to cool the deep crust, which was established by hydrothermal fault zones, initially formed on-axis at very high temperatures.

AB - In the absence of a complete profile through fast-spreading modern oceanic crust, we established a reference profile through the whole paleo crust of the Samail ophiolite (Sultanate of Oman), which is regarded as the best analogue for fast-spreading oceanic crust on land. To establish a coherent data set, we sampled the Wadi Gideah in the Wadi-Tayin massif from the mantle section up to the sheeted dikes and performed different analytical and structural investigations on the same suite of samples. This paper reports our studies of the lower crust, a 5 km thick pile of gabbros, focusing on petrographic features and on the results of mineral analyses. Depth profiles of mineral compositions combined with petrological modeling reveal insights into the mode of magmatic formation of fast-spreading lower oceanic crust, implying a hybrid accretion mechanism. The lower two thirds of the crust, mainly consisting of layered gabbros, formed via the injection of melt sills and in situ crystallization. Here, upward moving fractionated melts mixed with more primitive melts through melt replenishments, resulting in a slight but distinct upward differentiation trend. The upper third of the gabbroic crust is significantly more differentiated, in accord with a model of downward differentiation of a primitive parental melt originated from the axial melt lens located at the top of the gabbroic crust. Our hybrid model for crustal accretion requires a system to cool the deep crust, which was established by hydrothermal fault zones, initially formed on-axis at very high temperatures.

KW - gabbro

KW - mineral analysis

KW - oceanic crust

KW - oceanic crust accretion

KW - Oman ophiolite

KW - petrology

UR - http://www.scopus.com/inward/record.url?scp=85123910644&partnerID=8YFLogxK

U2 - 10.1029/2021JB022735

DO - 10.1029/2021JB022735

M3 - Article

AN - SCOPUS:85123910644

VL - 127

JO - Journal of Geophysical Research: Solid Earth

JF - Journal of Geophysical Research: Solid Earth

SN - 2169-9313

IS - 1

M1 - e2021JB022735

ER -