Pervasive carbonation of peridotite to listvenite (Semail Ophiolite, Sultanate of Oman): clues from iron partitioning and chemical zoning

Abstract. Earth's long-term cycling of carbon is regulated from mid-ocean ridges to convergent plate boundaries by mass transfers involving mantle rocks. Here we examine the conversion peridotite listvenite (magnesite + quartz rock) during CO2 metasomatism along basal thrust Semail Ophiolite (Fanja, Sultanate Oman). At outcrop scale, this transformation defines reaction zones, serpentinized peridotites carbonated serpentinites and listvenites. Based on a detailed petrological chemical study, show that carbonation progressed through three main stages development replacive textures ascribed early stages, whilst carbonate (± quartz) veining becomes predominant in last stage. The pervasive replacement serpentine magnesite characterized formation spheroids, among which two types are identified based composition their core regions: Fe-core Mg-core spheroids. Fe zoning type feature matrix vein formed onset (Stage 1). While Fe-rich predicted form at low fluid XCO2 poorly moderately oxidized protolith, our study evidences local non-redox destabilization oxides into essential spheroids followed (over-)growth Mg-rich aggregates 2) near-equilibrium conditions response increasing XCO2. Furthermore, compositions carbonates indicate most siderophile transition elements released dissolution primary minerals locally trapped carbonation, while with chalcophile affinity likely be leached out zones.