The evolution of the crust-mantle system in the early Archean
Zusammenfassung der Projektergebnisse
Eoarchean mantle and mantle-derived rocks can provide primary information on geodynamic processes operating on the early Earth. This project has combined new petrological observations, comprehensive major and trace element data as well as Lu-Hf, Sm-Nd amd Re-Os isotope data of > 3.81 Ga ultramafic rocks from the Itsaq Gneiss Complex (IGC) in southern West Greenland. Lutetium-Hf whole rock age regression lines mainly yield Eoarchean ages of ca. 3.9 to 3.8 Ga, in good agreement with minimum ages inferred from field relationships (>3.8 Ga). Major and trace element signatures, the Lu-Hf isotope inventory as well as most major elements, MREE, HREE, and HFSE were only slightly disturbed during metamorphic overprint. Nearly flat primitive mantle-normalized REE patterns obtained for the mantle peridotites resemble those of refertilized modern abyssal peridotites and may reflect re-enrichment of initially depleted peridotite by melt-like subduction components, as also indicated by Th-HFSE-REE characteristics. We suggest that the compositions are best explained by partial hydrous melt depletion in the spinel stability field, followed by refertilization by low quantities of adakite-like melt. Altogether, the geochemical data can be put in the framework of a geodynamic model, where Eoarchean mantle underwent significant melt extraction and subsequent re-fertilization by subduction-like components. For the first time, combined platinum-group element (PGE) and Re-Os isotope data were measured on these peridotites showing that Re-depletion model ages are mostly Eoarchean, in accord with U-Pb zircon ages of crosscutting granitoid intrusives. PGE abundances and patterns are indistinguishable from those of modern depleted mantle peridotites. Abundances of Os, Ir and Ru combined with Os isotope compositions in the Greenland peridotites indicate that primitive, late-accreted material must have been efficiently mixed into the sampled mantle domains by Eoarchean time.
Projektbezogene Publikationen (Auswahl)
-
(2015): Sm-Nd and Lu-Hf isotope and trace-element systematics of Mesoarchaean amphibolites, inner Ameralik fjord, southern West Greenland. Mineralogical Magazine 79 (4): 857-876
Szilas, K., Hoffmann, J.E., Hansmeier, C., Hollis, J.A., Münker, C., Viehmann, S., Kasper, H.U.
-
(2016): Combined bulk-rock Hf- and Nd-isotope compositions ofMesoarchaean metavolcanic rocks from the Ivisaartoq SupracrustalBelt, SW Greenland: Deviations from the mantle array caused bycrustal recycling. Chemie der Erde 76: 543-554
Szilas, K., Hoffmann, J.E., Schulz, T., Hansmeier, C., Polat, A., Viehmann, S., Kasper, H.U., Münker, C.
-
(2016): Hafnium isotope constraints on the origin of Mesoarchaean andesites in southern West Greenland, North Atlantic Craton. Geological Society, London, Special Publications, 449 (1): 19-38
Szilas, K., Tusch, J., Hoffmann, J.E., Garde, A.A., Münker, C.
-
(2018): Coexistence of enriched and modern-like 142Nd signatures in Archean igneous rocks of the eastern Kaapvaal Craton, southern Africa. Earth and Planetary Science Letters 487: 54-66
Schneider, K.P., Hoffmann, J.E., Boyet, M., Münker, C., Kröner, A.
-
(2018): Earth’s oldest mantle peridotites show entire record of late accretion. Geology 46 (3): 199-202
van de Loecht, J., Hoffmann, J.E., Li, C., Wang, Z., Becker, H., Rosing, M.T., Kleinschrodt, R., Münker, C.
-
(2019): Petrogenesis of plagiogranites from the Troodos Ophiolite Complex, Cyprus. Contributions to Mineralogy and Petrology 174:35
Marien, C., Hoffmann, J.E., Garbe-Schönberg, D., Münker, C.
-
(2019): Petrogenetic evolution of metabasalts and metakomatiites of the lower Onverwacht Group, Barberton Greenstone Belt (South Africa). Chemical Geology 511: 152-177
Schneider, K.P., Hoffmann, J.E., Münker, C., Patyniak, M., Sprung, P., Roerdink, D., Garbe Schönberg, D., Kröner, A.
-
(2020): Hafnium-neodymium isotope, trace element and U-Pb zircon age constraints on the petrogenesis of the 3.44–3.46 Ga Dwalile greenstone remnant, Ancient Gneiss Complex, Swaziland. Precambrian Research 351: 105970
Hoffmann, J.E., Musese, E., Kröner, A., Schneider, K.P., Wong, J., Hofmann, A., Hegner, E., Kasper, H.U., Tusch, J., Münker, C.
-
(2020): Preservation of Eoarchean mantle processes in 3.8 Ga peridotite enclaves in the Itsaq Gneiss Complex, southern West Greenland. Geochimica et Cosmochimica Acta 280: 1-25
van de Loecht, J., Hoffmann, J.E., Rosing, M.T., Sprung, P., Münker, C.
-
(2022): Juvenile continental crust evolution in a modern oceanic arc setting: petrogenesis of Cenozoic felsic plutons in Fiji, SW Pacific, Geochimica et Cosmochimica Acta 320: 339-365
Marien, C.S., Drewes-Todd, E.K., Stork, A., Todd, E., Gill, J.B., Hoffmann, J.E., Tani, K., Allen, C.M., Münker, C.
