کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4677455 | 1634802 | 2012 | 14 صفحه PDF | دانلود رایگان |
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
► The Maniitsoq structure records intense circular deep-crustal crushing and heating.
► Current diagnostic tools of impacting are unfit for giant, deeply eroded structures.
► Simple structural upscaling of known large terrestrial impacts is inappropriate.
► The maniitsoq structure contains planar elements with orientations matching PDFs.
► We propose that the Maniitsoq structure is the remain of a giant, c. 3 Ga impact.
Journal: Earth and Planetary Science Letters - Volumes 337–338, 1 July 2012, Pages 197–210