Nature and timing of polymetamorphic, anatectic and metasomatic events in mafic granulite in Archean high-grade terranes: Scenario from Central Zone of the Limpopo Complex, southern Africa

Rajesh, H.M.; Safonov, O.G.; Belyanin, G.A.; Santosh, M.; Zhang, Z.; Tsunogae, T.; Fukuyama, M.; Vorster, C.; Gao, P.; Keeditse, M.

Авторы: Rajesh H.M., Safonov O.G., Belyanin G.A., Santosh M., Zhang Z., Tsunogae T., Fukuyama M., Vorster C., Gao P., Keeditse M.
Журнал: Precambrian Research
Том: 426
Год издания: 2025
Издательство: Elsevier BV
Местоположение издательства: Netherlands
Номер статьи: 107831
DOI: 10.1016/j.precamres.2025.107831
Аннотация: Mafic granulite in Archean high-grade terranes are highly sensitive to reworking and overprint processes. Understandingthe nature and timing of different events requires a careful approach with a combination of methods.This study presents field, petrographic, mineralogical, PERPLE_X phase equilibria modelling, U-Th-Hf-trace-REEzirconand 40Ar/39Ar-amphibole systematics on mafic granulites from the Verbaard area in Central Zone of theLimpopo Complex, southern Africa. The mafic granulites are interlayered and infolded conformably with theoldest meta-supracrustal rocks including quartzites, meta-ironstone and migmatitic metapelites and are intrudedby c.2.63–2.62 Ga granitoids. The granoblastic mafic granulites exhibit mineral assemblages representing variousmetamorphic transformations including minor partial melting during two metamorphic stages related to theNeoarchean (M1) and Paleoproterozoic (M2). The earliest M1 assemblage (Grt) + Opx + Cpx + Pl + Qz + Ilmformed at 830–850 ◦C, >6.5 kbar, and was transformed to Opx + Cpx + Amp + Pl + Qz + Ilm during theNeoarchean decompression to c.6.5 kbar and subsequent cooling. The M2 assemblage (Grt) + Opx + Cpx + Amp+ Pl + Qz + Ilm + Mag formed at < 800 ◦C, c.5.5 kbar during the Paleoproterozoic overprint. CL-image, Lu-Hfisotope and trace-REE characteristics of zircons distinguish the effect of two metamorphic events at 2618 ± 11Ma (M1) and 2057 ± 25 Ma (M2), both involving anatectic components. In contrast to the Neoarchean zirconcores, the Paleoproterozoic rims/newly grown grains show lower HREE abundance, suggesting their growth/overgrowth in equilibrium with garnet. The radiogenic Hf isotope compositions of both groups of zircons areexplained by local subsolidus mineral reactions rather than an input of the juvenile material. The rocks showeffects of late metasomatic alteration that is variably reflected in zircons in higher LREE concentrations and aflatter LREE profile. The c.1.95 Ga age is preserved in the Paleoproterozoic zircons with transgressive recrystallizationstructure, and supported by 40Ar/39Ar amphibole geochronology. The results highlight the texturaland corresponding elemental signatures to look out for delineation of multiple overprint events involvingmetamorphism, anatexis and metasomatism in Archean mafic granulites.
Добавил в систему: Сафонов Олег Геннадьевич

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Nature and timing of polymetamorphic, anatectic and metasomatic events in mafic granulite in Archean high-grade terranes: Scenario from Central Zone of the Limpopo Complex, southern Africaстатья

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