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A discussion on the tectonic implications of Ediacaran late- to post-orogenic A-type granite in the northeastern Arabian Shield, Saudi Arabia
Stockholm University, Faculty of Science, Department of Geological Sciences.
Stockholm University, Faculty of Science, Department of Geological Sciences.
Number of Authors: 4
2017 (English)In: Tectonics, ISSN 0278-7407, E-ISSN 1944-9194, Vol. 36, no 3, 582-600 p.Article in journal (Refereed) Published
Abstract [en]

The transition from late-orogenic to post-orogenic magmatism following major orogenic episodes such as the Neoproterozoic to Cambrian East African Orogen (EAO) is an important, yet not well-understood geological event marking the cessation of subduction-controlled magmatism between buoyant lithospheric fragments. Forming the northern part of the EAO in the Arabian-Nubian Shield are three granitic suites that successively intruded the same northeastern area and post-date the 640Ma major orogenic episode: (1) 620-600Ma alkali feldspar (hypersolvous) granite with alkaline/ferroan/A-type geochemistry, (2) 599Ma granite cumulates (some garnet-bearing) with calc-alkaline/magnesian affinities, and (3) 584-566Ma alkali feldspar (hypersolvous) granite (aegirine-bearing) with a distinctive peralkaline/ferroan/A-type signature. Combining whole-rock geochemistry from the southern and northern Arabian Shield, suites 1 and 2 are suggested to be products of late-orogenic slab tear/rollback inducing asthenospheric mantle injection and lower crustal melting/fractionation toward A-type/ferroan geochemistry. Suite 3, however, is suggested to be produced by post-orogenic lithospheric delamination, which replaced the older mantle with new asthenospheric (rare earth element-enriched) mantle that ultimately becomes the thermal boundary layer of the new lithosphere. Major shear zones, such as the 620-540Ma Najd Fault System (NFS), are some of the last tectonic events recorded across the Arabian Shield. Data presented here suggest that the NFS is directly related to the late-orogenic (620-600Ma) slab tear/rollback in the northeastern Shield as it met with opposing subduction polarity in the southern Shield. Furthermore, this study infers that east and west Gondwana amalgamation interacted with opposing convergence reflected by the NFS.

Place, publisher, year, edition, pages
2017. Vol. 36, no 3, 582-600 p.
Keyword [en]
Arabian Shield, post-orogenic granite, lower crustal melting, asthenosphere, mantle, Najd Fault System
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-143475DOI: 10.1002/2016TC004320ISI: 000399742900010OAI: oai:DiVA.org:su-143475DiVA: diva2:1104110
Available from: 2017-05-31 Created: 2017-05-31 Last updated: 2017-05-31Bibliographically approved

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