zankaon

January 28, 2016

Banded iron formation and plate tectonics -the former supportive of the latter?

Filed under: Letters from Ionia — Tags: , , — zankaon @ 4:49 pm

Are banded iron formation and plate tectonics commencment consistent? BIF were laid down in ocean basin sediment 2-3 billion years ago as a result of First Oxygenation. Irregardless of prior or later initation of such tectonics, wouldn’t such BIF be subducted, resulting in more homogeneous distribution than what is now found on continents?

What are other possibilities? Might such deposits be scraped off, as subduction ensues? Iron ore is found next to archean continental shields, as in northern Minnesota. Also stromatolytes are found in 1.9 billion year old Gunflint formation, not so far from above mentioned ore deposits. Are both consistent with an ancient Archean ocean lapping at the shores of Canadian continental shield?

Might one have BIF deposits from ocean basins become part of marine plateau, such as like Java Ontong, with subsequent plate motion towards a continent? Collisions can result in uplift and mountain builting, such as for sub-continent and asia, and also for Ural mountains.

Also terrains can be annealed onto the side of a continent, such as for Wranger terrain etc. for western part of Canada and Alaska. For example for a past rotated North America, centered at ~20 degrees north latitude, might terrains be considered as transported eastward, and eventually annealing with the continent? Might this be considered a model for incorporating marine sediment BIF into a continental setting, for after commencement of plate tectonics; assuming initiation of plate tectonics ~3 billion years ago?

stromatolytes

http://www.lakesuperior.com/the-lake/natural-world/192feature/

http://www.lakesuperior.com/the-lake/natural-world/243-lake-superior-basin-fiery-beginning/

Emergence of modern continental crust about 3 billion years ago. Bruno Dhuime, Andreas Wuestefeld; Chris J. Hawkesworth,
Nature Geoscience 8, 552–555 (2015) doi:10.1038/ngeo2466

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