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Multistage petrogenetic evolution of Neoproterozoic serpentinized ultramafic rocks and podiform chromitites at Hagar Dungash, Eastern Desert of Egypt

Moussa, Hilmy E. and Mubarak, Heba S. and Azer, Mokhles K. and Surour, Adel A. and Asimow, Paul D. and Kabesh, Mona M. L. (2022) Multistage petrogenetic evolution of Neoproterozoic serpentinized ultramafic rocks and podiform chromitites at Hagar Dungash, Eastern Desert of Egypt. Precambrian Research, 369 . Art. No. 106507. ISSN 0301-9268. doi:10.1016/j.precamres.2021.106507. https://resolver.caltech.edu/CaltechAUTHORS:20220104-157910000

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Abstract

Podiform chromitites are found in the mantle sections of ophiolites in many places and times in the geologic record. Leading theories for their origin invoke melt-rock reaction processes involving hydrous melts in supra-subduction zone settings. Here we develop a case study of a Neoproterozoic example and a quantitative thermodynamic model of the multistage process leading to nearly monomineralic chromitite pods. We demonstrate that the Hagar Dungash ophiolite of the Eastern Desert of Egypt — despite being dismembered, incomplete, and affected by variable degrees of alteration and metamorphism — is nevertheless plainly a supra-subduction zone ophiolite containing podiform chromitite deposits. Textural, mineralogical, and chemical evidence from the serpentinized ultramafic rocks point to mantle protoliths residual to high degrees of partial melt extraction, characteristic of fore-arc ophiolites. The chromitite pods are distinguished into massive and nodular types; Cr-spinel in the massive type is almost fresh, with intermediate to high Cr# (0.60–0.85) and extremely low Fe³⁺# (nil-0.04). Cr-chlorite with up to ∼ 15 wt% Cr₂O₃ is a common interstitial mineral in the chromitites. The observations are consistent with the conceptual multistage model wherein boninitic melt develops as the end-product of melt-harzburgite reaction in the shallow upper mantle. Mixing between this boninitic melt and ascending peridotite-derived basaltic melt drives the liquid deep into the Cr-spinel stability field and precipitates nearly monomineralic chromitite. Our thermodynamic model of this mixing and precipitation process reproduces the mineral chemistry trends of the fresh chromite samples and yields an estimate of the efficiency of chromite production relative to melt flux through the system, which can be applied to development of podiform chromitites in supra-subduction systems worldwide and across geologic eras.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.precamres.2021.106507DOIArticle
ORCID:
AuthorORCID
Azer, Mokhles K.0000-0002-3711-8630
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2021 Elsevier. Received 22 March 2021, Revised 2 December 2021, Accepted 3 December 2021, Available online 28 December 2021. We acknowledge the National Research Centre (NRC), Egypt for logistical support of this work. The present manuscript is a part of the master’s thesis of Heba S. Mubarak (the second author). PDA is supported by the United States NSF, award 1947616. We are grateful to the editor, Victoria Pease, and to five anonymous reviewers for their dedicated work in helping to improve the manuscript. Credit authorship contribution statement. Hilmy E. Moussa: Investigation. Heba S. Mubarak: Investigation. Mokhles K. Azer: Conceptualization, Investigation, Visualization, Writing – original draft. Adel A. Surour: . Paul D. Asimow: Investigation, Methodology, Resources, Software, Validation, Writing – original draft. Mona M.L. Kabesh: . The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funders:
Funding AgencyGrant Number
NSFEAR-1947616
Subject Keywords:Gabal Hagar Dungash; Dismembered ophiolite; Chromitite ore; Kämmererite; Fore-arc mantle peridotite; Supra-subduction zone
DOI:10.1016/j.precamres.2021.106507
Record Number:CaltechAUTHORS:20220104-157910000
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20220104-157910000
Official Citation:Hilmy E. Moussa, Heba S. Mubarak, Mokhles K. Azer, Adel A. Surour, Paul D. Asimow, Mona M.L. Kabesh, Multistage petrogenetic evolution of Neoproterozoic serpentinized ultramafic rocks and podiform chromitites at Hagar Dungash, Eastern Desert of Egypt, Precambrian Research, Volume 369, 2022, 106507, ISSN 0301-9268, https://doi.org/10.1016/j.precamres.2021.106507.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112681
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:04 Jan 2022 22:57
Last Modified:04 Jan 2022 22:57

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