Zircon Geochemical and Geochronological Constraints on Contaminated and Enriched Mantle Sources beneath the Arabian Shield, Saudi Arabia
Number of Authors: 3
2015 (English)In: The Journal of geology, ISSN 0022-1376, E-ISSN 1537-5269, Vol. 123, no 5, 463-489 p.Article in journal (Refereed) Published
Arabian Shield granitic zircon geochemistry provides insight into the petrogenetic processes involved in generating one of the planet's largest tracts of juvenile Neoproterozoic crust. New zircon geochemistry supports previous U-Pb and whole-rock data that defined four magmatic groups: (1) similar to 870-675 Ma island arc and synorogenic I-type granitoids (IA+Syn), (2) similar to 640-585 Ma I-and A-type granitoids from the Nabitah and Halaban Suture (NHSG), (3) similar to 610-600 Ma postorogenic perthitic (hypersolvus) A-type granitoids (POPG), and (4) similar to 600 Ma anorogenic aegirine-bearing perthitic (hypersolvus) A-type granitoids (AAPG). The low Nb (similar to 1-300 ppm) and intrasuite rare earth element variation in IA+Syn and NHSG zircons indicates that these suites are derivatives of contaminated mantle followed by fractionation. AAPG suites, however, have higher Nb content (similar to 10-400 ppm) and are derived from limited crust-enriched mantle interaction. Each of the IA, Syn, and NHSG suites have discrete granite subsuites distinguished using zircon morphology and geochemistry whose U-Pb ages in each case form three groups. The IA subgroups are similar to 867, similar to 847, and similar to 829 Ma; the Syn subgroups are similar to 730, 716, and 696 Ma; and the NHSG subgroups are similar to 636, similar to 610, and similar to 594 Ma. This apparent subevent repetition suggests some form of magmatic pulsing in the Arabian Shield. It is suggested that IA+Syn suites reflect typical volcanic arc granite settings and incremental subduction/accretion of eastward-migrating oceanic fragments of the East African Orogen. The appearance of similar to 636 Ma A-type magmatism within suture zones (NHSG) is possibly derived from a long-lived (similar to 50 m.yr.) melting, assimilation, storage, and homogenization (MASH) zone resulting from an similar to 640 Ma slab tear. These A-types are distinguished from more-enriched anorogenic (<600 Ma) A-types, possibly associated with lithospheric delamination.
Place, publisher, year, edition, pages
2015. Vol. 123, no 5, 463-489 p.
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:su:diva-123348DOI: 10.1086/683192ISI: 000363691400004OAI: oai:DiVA.org:su-123348DiVA: diva2:874052