Anatomy of a chromitite dyke in the mantle/crust transition zone of the Oman ophiolite

Zagrtdenov, Nail R.; Ceuleneer, Georges; Rospabé, Mathieu; Borisova, Anastassia Y.; Toplis, Michael J.; Benoît, Mathieu; Abily, Bénédicte

doi:10.1016/j.lithos.2018.05.012

Cited by 18 publications

(28 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Evenly, the TiO 2 content of the stratiform chromite is typically high (0.25-0.54 wt%), a characteristic shared by most chromitites and scattered chromites in dunites from the Maqsad area and contrasting with widespread lower values observed in almost all other massifs of the Oman ophiolite. This is a major evidence for the MORB kindred of the parent melt of the various igneous products issued from the Maqsad diapir (Clénet et al, 2010;Python et al, 2008), including chromitites (Borisova et al, 2012;Leblanc and Ceuleneer, 1991;Zagrtdenov et al, 2018).…”

Section: Chemistry Of the Stratiform Ore Bodymentioning

confidence: 85%

“…This offers a unique opportunity to study the details of magmatic processes related to chromite ore genesis (e.g. Borisova et al, 2012;Leblanc and Ceuleneer, 1991;Rollinson and Adetunji, 2013;Zagrtdenov et al, 2018).…”

Section: The Maqsad Area Of the Oman Ophiolitementioning

confidence: 99%

“…The Maqsad area is characterized by a high abundance of podiform chromitites (Borisova et al, 2012;Ceuleneer and Nicolas, 1985;Leblanc and Ceuleneer, 1991;Rollinson and Adetunji, 2013;Rollinson et al, 2018;Zagrtdenov et al, 2018), defining one of the most important chromitiferous district in the Oman ophiolite. The ore deposits occurring within the dunitic mantle-crust transition zone at the top of the Maqsad diapir, including the studied stratiform chromitite ore body, developed during the last stage of the upwelling of the asthenospheric mantle diapir.…”

Section: Structure and Petrology Of The Stratiform Ore Bodymentioning

confidence: 99%

See 2 more Smart Citations

Multi-scale development of a stratiform chromite ore body at the base of the dunitic mantle-crust transition zone (Maqsad diapir, Oman ophiolite): The role of repeated melt and fluid influxes

Rospabé

Ceuleneer

Granier

et al. 2019

Lithos

Self Cite

View full text Add to dashboard Cite

A stratiform chromite ore body crops out in the lower part of the dunitic mantle-crust transition zone (DTZ) that developed at the top of a mantle diapir in the Maqsad area in the Oman ophiolite. It is made of layers ranging in thickness from a few mm to a maximum of 3 m, and in modal composition from massive to antinodular and disseminated ore. The ore body is about 50 m thick and its lateral extent does not exceed several hundred meters. The layering dips gently to the southeast, parallel to that of the overlying gabbroic cumulates. The chromite composition is typical of a MORB kindred-moderate XCr (100 × Cr/(Cr + Al) atomic ratio), ranging from 48 to 60, and relatively high TiO 2 content, ranging from about 0.3 to 0.5 wt%-, a characteristic shared by most lithologies issued from the igneous activity of the Maqsad diapir. The silicate matrix is essentially made of slightly serpentinized olivine with minor clinopyroxene and rare pargasitic amphibole, orthopyroxene and garnet. This strongly contrasts with the nature of the mineral inclusions mostly made of the assemblage amphibole-orthopyroxene-mica, enclosed in the chromite grains and represented in abundance all along the ore body whatever the ore grade. The inclusions demonstrate the involvement of a silica-and water-rich melt and/or fluid, in addition to MORB, in the early stages of chromite crystallization. The chemical composition of chromite, silicate matrix, together with the one of silicate inclusions display well-defined evolutions vertically along the stratiform chromitite. At the scale of the ore body, the compositional trends are independent of the ore concentration but the major kinks in these trends are well-correlated with levels of magmatic breccias. This shows that abrupt chemical changes can be attributed to sudden melt +/-fluids injection events followed mainly by melt-fluid-rock interaction and in a lesser extent by quieter evolution by fractional crystallization. At the thin section scale, second order chemical variations, essentially in the Mg# (100 × Mg/(Mg + Fe 2+) atomic ratio) of chromite and Fo of olivine, are clearly attributable to re-equilibration between these two solid phases, possibly in the presence of an interstitial melt/fluid.

show abstract

Section: Chemistry Of the Stratiform Ore Bodymentioning

confidence: 85%

Section: The Maqsad Area Of the Oman Ophiolitementioning

confidence: 99%

Section: Structure and Petrology Of The Stratiform Ore Bodymentioning

confidence: 99%

See 1 more Smart Citation

Multi-scale development of a stratiform chromite ore body at the base of the dunitic mantle-crust transition zone (Maqsad diapir, Oman ophiolite): The role of repeated melt and fluid influxes

Rospabé

Ceuleneer

Granier

et al. 2019

Lithos

Self Cite

View full text Add to dashboard Cite

show abstract

“…Our experiments demonstrate that formation of the hybrid mid-ocean ridge basaltic melt saturated with chromite is possible at conditions of predominant proportion of basaltic melt (above 70 wt%) and, therefore, due to high melt/rock ratio (>2) at 0.2 to 1.0 GPa pressure. The main physico-chemical parameters controlling the chromite crystallization are the presence of aqueous fluid or/and hydrous basaltic melts into the reactive system (Borisova et al, 2012a;Johan et al, 2017;Zagrtdenov et al, 2018). The fluid presence at 0.2 GPa pressure is also necessary condition for the chromite concentrating by a physical, not a chemical process due to surface tension of the fluid, which is sufficient to maintain dispersed chromite crystals inside the fluid upon the chromite crystallization (Matveev & Balhaus, 2002).…”

Section: Mechanism Of the Basaltic Melt-hydrated Peridotite Reactionmentioning

confidence: 99%

“…Magmas resulting from the mixing between "asthenospheric" tholeiites and hydrated "lithospheric" melts of depleted andesitic affinity were proposed as parental for some puzzling occurrences of orthopyroxene-rich primitive cumulates along mid-ocean ridges and in ophiolites (Benoit et al, 1999;Nonnotte et al, 2005). The formation of such hybrid or/and depleted magmas due to assimilation of serpentinized mantle peridotite leads to the formation of the Moho transition zone composed by dunites and chromitites (Borisova et al, 2012a;Zagrtdenov et al, 2018;Rospabé et al, 2019a,b).…”

Section: Introductionmentioning

confidence: 99%

Hydrated Peridotite–Basaltic Melt Interaction Part II: Fast Assimilation of Serpentinized Mantle by Basaltic Magma

et al. 2020

Self Cite

View full text Add to dashboard Cite

The most abundant terrestrial lavas, mid-ocean ridge and ocean island basalt (MORB and OIB), are commonly considered to be derived from a depleted MORB-mantle component (DMM) and more specific, variably enriched mantle plume sources. However, findings of oceanic lavas and mafic cumulates issued from melts, enriched in chlorine and having a radiogenic 87 Sr/ 86 Sr ratio, can be attributed to an interaction between the asthenosphere-derived melts and lithospheric peridotite variably hydrated due to penetration of hydrothermal water down to and below Moho level. To constrain mechanisms and rates responsible for the interaction, we report results of 15 experiments of reaction between serpentinite and tholeiitic basaltic melt at 0.2 -1.0 GPa and 1250 -1300°C. Results show that the reaction proceeds via a multi-stage mechanism: (i) transformation of serpentinite into Cr-rich spinel-bearing harzburgite (Fo92-95 mol.%) containing pore fluid, (ii) partial melting and dissolution of the harzburgite assemblage with formation of interstitial hydrous melts (up to 57 -60 wt% of SiO2 contents at 0.5 GPa pressure), and (iii) final assimilation of the Cr-rich spinel-bearing harzburgite/dunite and formation of hybrid basaltic melts with 12 -13 wt.% of MgO and elevated Cr (up to ~500 ppm) and Ni (up to ~200 ppm) contents. Assimilation of serpentinite by basaltic melt may occur under elevated melt/rock ratios (>2) and may lead to chromitite formation. We show that hybrid magmas produced by the progressive assimilation of serpentinized lithospheric mantle may be recognized by high Mg-numbers and high Cr and Ni contents of olivine and pyroxenes, an excess of SiO2, H2O and halogens in the melts, and some unusual isotopic composition (e.g., radiogenic 87 Sr/ 86 Sr, non-mantle δ 18 O and low 3 He/ 4 He). Our experiments provide evidence that MORB and high-Mg-Cr orthopyroxene-rich cumulates depleted in incompatible elements can be produced from common mid-ocean ridge basaltic melts modified by reaction with hydrated lithospheric peridotite. We established that the rate of assimilation of serpentinized peridotite is controlled by silica diffusion in the reacting hydrous basaltic melt. Our study challenges 3 traditional interpretation of the variations in MORB and OIB chemical and isotopic composition in terms of deep mantle plume source heterogeneities or/and degrees of partial melting.

show abstract

Chromitites of the Kraka ophiolite (South Urals, Russia): geological, mineralogical and structural features

Saveliev

2021

Miner Deposita

View full text Add to dashboard Cite

Anatomy of a chromitite dyke in the mantle/crust transition zone of the Oman ophiolite

Cited by 18 publications

References 77 publications

Multi-scale development of a stratiform chromite ore body at the base of the dunitic mantle-crust transition zone (Maqsad diapir, Oman ophiolite): The role of repeated melt and fluid influxes

Multi-scale development of a stratiform chromite ore body at the base of the dunitic mantle-crust transition zone (Maqsad diapir, Oman ophiolite): The role of repeated melt and fluid influxes

Hydrated Peridotite–Basaltic Melt Interaction Part II: Fast Assimilation of Serpentinized Mantle by Basaltic Magma

Chromitites of the Kraka ophiolite (South Urals, Russia): geological, mineralogical and structural features

Contact Info

Product

Resources

About