3 Milliarden Jahre alter Meteoritenkrater in der Maniitsoq Region, Westgrönland

[karmaka]

3 Milliarden Jahre alter Meteoritenkrater in der Maniitsoq Region in Westgrönland

http://www.sciencedaily.com/releases/2012/06/120628164658.htm

http://maps.google.de/maps?q=65%C2%B015%E2%80%B2+N,+51%C2%B050%E2%80%B2+W&hl=de&ie=UTF8&ll=65.199164,-51.394043&spn=1.730615,3.845215&sll=65.257497,-51.836586&sspn=0.053957,0.120163&t=m&z=8

Adam A. Garde, Iain McDonald, Brendan Dyck, Nynke Keulen. Searching for giant, ancient impact structures on Earth: The Mesoarchaean Maniitsoq structure, West Greenland. Earth and Planetary Science Letters, 2012; 337-338: 197 DOI

http://www.sciencedirect.com/science/article/pii/S0012821X12001938

Abstract

A 100 km-scale, circular region in the Archaean North Atlantic Craton centred at 65°15′N, 51°50′W near Maniitsoq town in West Greenland comprises a set of highly unusual geological features that were created during a single event involving intense crushing and heating and are incompatible with crustal orogenic processes. The presently exposed features of the Maniitsoq structure were buried 20–25 km below the surface when this event occurred at c. 3 Ga, during waning convergent orogeny. These features include: a large aeromagnetic anomaly; a central 35×50 km2 large area of comminuted quartzo-feldspathic material; regional-scale circular deformation; widespread random fractures with featherlike textures; intense fracture cleavage; amphibolite–granite-matrix breccias unrelated to faulting or intrusions; formation and common fluidisation of microbreccias; abundant evidence of direct K-feldspar and plagioclase melting superimposed on already migmatised rocks; deformation of quartz by <c> slip; formation of planar elements in quartz and plagioclase; and, emplacement of crustally contaminated ultramafic intrusions and regional scale hydrothermal alteration under amphibolite-facies conditions. The diagnostic tools employed to identify impacting in the upper crust are inadequate for structures preserved deep within the continental crust. Nevertheless, the inferred scale, strain rates and temperatures necessary to create the Maniitsoq structure rule out a terrestrial origin of the structure.

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Stirred not shaken ! 


Stirred not shaken; critical evaluation of a proposed Archean meteorite impact in West Greenland

Chris Yakymchuk, Christopher L. Kirkland, Aaron J. Cavosie, Kristoffer Szilas, Julie Hollis, Nicholas J. Gardiner, Pedro Waterton, Agnete Steenfelt, Laure Martin

Earth and Planetary Science Letters
Volume 557, 1 March 2021

"Highlights

•    We evaluate the origin of the Archean Maniitsoq structure in Greenland.
•    Field relationships are inconsistent with a circular impact crater.
•    A survey of 5,587 zircon grains shows no evidence for shock metamorphism.
•    The Maniitsoq structure was produced through endogenic processes."