"Moist MORB" axial magmatism in the Oman ophiolite: The evidence against a mid-ocean ridge origin

Geology ◽  
2013 ◽  
Vol 41 (4) ◽  
pp. 459-462 ◽  
Author(s):  
C. J. MacLeod ◽  
C. Johan Lissenberg ◽  
L. E. Bibby
Keyword(s):  
Oman Ophiolite ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

The conversion tectonics from spreading to subduction: Paleostress analysis of dike swarms during the subduction initiation in the Oman Ophiolite

2019 ◽  
Vol 132 (5-6) ◽  
pp. 1333-1343 ◽  
Author(s):  
Susumu Umino ◽  
Yuki Kusano ◽  
Atsushi Yamaji ◽  
Takahiro Fudai ◽  
Akihiro Tamura ◽  
...  
Keyword(s):  
Stress Field ◽  
Clockwise Rotation ◽  
Oman Ophiolite ◽  
Subduction Initiation ◽  
Mid Ocean Ridge ◽  
Abrupt Changes ◽  
Rift Zones ◽  
Dike Swarms ◽  
Ocean Ridge ◽  
Paleostress Analysis

Abstract We present paleostress analyses of dike swarms intruded during the subduction initiation in the northern Oman Ophiolite to understand the tectonomagmatic environment. Five swarms of subparallel dikes extending WNW-ESE are 1–5 km in width and are spaced every 5 km N-S. Each swarm has a core of 100% sheeted dikes 1–2 km in width, which emanated from the dunite-wherlite-clinopyroxenite-gabbronorite-diorite-tonalite complexes below and intruded through V1 and into V2 extrusive rocks. Individual dike strikes are varied but generally subparallel to the overall trend of the swarm. Paleostress analyses indicate subvertical σ1, ∼σ2, and subhorizontal σ3 with high magma pressures, resulted in the mutually intrusive, extensional shear dikes and abrupt changes in dike strike at high angles. These occurrences suggest intrusions under a more compressive environment compared to the extensional stress field that formed the N-S–striking sheeted dikes of V1 spreading stage. Most E-W–striking dikes possess both boninitic and tholeiitic geochemistry. The latter resemble the V1 flows and dikes with affinities of mid-ocean ridge basalt. Some tholeiitic dikes strike N-S, which are mutually intrusive to E-W–striking dikes. Tholeiitic dikes are more intensely altered than boninite, suggesting their older ages. Conversion of the stress field from a N-S–running spreading axis to inextensional E-W–running rift zones associated with the change in magma geochemistry agree with the relatively compressive V2 arc above a forced subduction zone, which originated from intraoceanic thrusting caused by the clockwise rotation of a microplate including the future northern ophiolite.

Mantle segmentation along the Oman ophiolite fossil mid-ocean ridge

Nature ◽  
2004 ◽  
Vol 432 (7014) ◽  
pp. 167-172 ◽  
Author(s):  
Laurent Le Mée ◽  
Jacques Girardeau ◽  
Christophe Monnier
Keyword(s):  
Oman Ophiolite ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

PETROGENESIS OF GABBRO FROM ARCTIC GAKKEL MID-OCEAN RIDGE

2019 ◽  
Author(s):  
Yung Ping Lee ◽  
◽  
Jonathan E. Snow ◽  
Yongjun Gao
Keyword(s):  
Mid Ocean Ridge ◽  
Ocean Ridge

scholarly journals Melt addition to mid-ocean ridge peridotites increases spinel Cr# with no significant effect on recorded oxygen fugacity

2021 ◽  
Vol 566 ◽  
pp. 116951
Author(s):  
Suzanne K. Birner ◽  
Elizabeth Cottrell ◽  
Jessica M. Warren ◽  
Katherine A. Kelley ◽  
Fred A. Davis
Keyword(s):  
Oxygen Fugacity ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

scholarly journals Sunda arc mantle source δ18O value revealed by intracrystal isotope analysis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Frances M. Deegan ◽  
Martin J. Whitehouse ◽  
Valentin R. Troll ◽  
Harri Geiger ◽  
Heejin Jeon ◽  
...  
Keyword(s):  
Mantle Source ◽  
Secondary Ion Mass Spectrometry ◽  
Isotope Composition ◽  
Isotope Analysis ◽  
Sunda Arc ◽  
Mid Ocean Ridge ◽  
Plumbing Systems ◽  
Ocean Ridge ◽  
Secondary Ion ◽  
Magma Plumbing

AbstractMagma plumbing systems underlying subduction zone volcanoes extend from the mantle through the overlying crust and facilitate protracted fractional crystallisation, assimilation, and mixing, which frequently obscures a clear view of mantle source compositions. In order to see through this crustal noise, we present intracrystal Secondary Ion Mass Spectrometry (SIMS) δ18O values in clinopyroxene from Merapi, Kelut, Batur, and Agung volcanoes in the Sunda arc, Indonesia, under which the thickness of the crust decreases from ca. 30 km at Merapi to ≤20 km at Agung. Here we show that mean clinopyroxene δ18O values decrease concomitantly with crustal thickness and that lavas from Agung possess mantle-like He-Sr-Nd-Pb isotope ratios and clinopyroxene mean equilibrium melt δ18O values of 5.7 ‰ (±0.2 1 SD) indistinguishable from the δ18O range for Mid Ocean Ridge Basalt (MORB). The oxygen isotope composition of the mantle underlying the East Sunda Arc is therefore largely unaffected by subduction-driven metasomatism and may thus represent a sediment-poor arc end-member.

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