Early Cretaceous Plume–Ridge Interaction Recorded in the Band-e-Zeyarat Ophiolite (North Makran, Iran): New Constraints from Petrological, Mineral Chemistry, and Geochronological Data

Edoardo Barbero,Leila Vahedi,Michele Marroni,Morteza Delavari,Antonio Langone,Federica Zaccarini,Ashgar Dolati,Luca Pandolfi,Emilio Saccani

doi:10.3390/min10121100

Abstract

The North Makran domain (southeast Iran) is part of the Makran accretionary wedge and consists of an imbricate stack of continental and Neo-Tethyan oceanic tectonic units. Among these, the Band-e-Zeyarat ophiolite consists of (from bottom to top): ultramafic cumulates, layered gabbros, isotropic gabbros, a sheeted dyke complex, and a volcanic sequence. Sheeted dykes and volcanic rocks are mainly represented by basalts and minor andesites and rhyolites showing either normal-type (N) or enriched-type (E) mid-ocean ridge basalt affinities (MORB). These conclusions are also supported by mineral chemistry data. In addition, E-MORBs can be subdivided in distinct subtypes based on slightly different but significant light rare earth elements, Th, Nb, TiO2, and Ta contents. These chemical differences point out for different partial melting conditions of their mantle sources, in terms of source composition, partial melting degrees, and melting depths. U-Pb geochronological data on zircons from intrusive rocks gave ages ranging from 122 to 129 Ma. We suggest that the Band-e-Zeyarat ophiolite represents an Early Cretaceous chemical composite oceanic crust formed in a mid-ocean ridge setting by partial melting of a depleted suboceanic mantle variably metasomatized by plume-type components. This ophiolite records, therefore, an Early Cretaceous plume–ridge interaction in the Makran Neo-Tethys.

Highlights

Ophiolites may originate in a variety of oceanic settings such as mid-ocean ridges, supra-subduction zones, marginal basins, and ocean islands
We have shown in the petrogenetic discussion (Figures 15c and 16b–e) that the different Subtype-II rocks are compatible with different melting conditions in terms of partial melting degree and depth of melting of the enriched mantle source S2
Band-e-Zeyarat N-mid-ocean ridge basalt affinities (MORB) formed from partial melting of a depleted sub-oceanic mantle peridotite in the spinel-facies

Summary

Introduction

Ophiolites may originate in a variety of oceanic settings such as mid-ocean ridges, supra-subduction zones, marginal basins, and ocean islands. Minerals 2020, 10, 1100 information for the reconstruction of the tectono-magmatic events that occurred during the life of an oceanic basin To this purpose, the geochemistry of magmatic rocks forming an ophiolitic sequence is useful for identifying the nature of mantle sources, providing valuable insights for discriminating the geodynamic setting where the ophiolites originated [9,10]. The geochemistry of magmatic rocks forming an ophiolitic sequence is useful for identifying the nature of mantle sources, providing valuable insights for discriminating the geodynamic setting where the ophiolites originated [9,10] These data, coupled with the geochronological data, represent an effective tool for the reconstruction of the geodynamic history of oceanic basins. This oceanic basin was interpreted as either a marginal basin [15,16] or a back-arc basin related to the Neo-Tethys northward subduction [17,18,19]

Methods

Findings

Discussion

Conclusion