GP43A-1232
Deep crust vs shallow mantle: sources of long wavelength magnetic anomalies

Thursday, 17 December 2015
Poster Hall (Moscone South)
Eric C. Ferre1, Sarah A Friedman2, Fatima El Atrassi3, James Andrew Conder4, Francois Demory5, Joshua M Feinberg6, Justin Filiberto1, Evgeniya Khakhalova6, Joseph Knafelc1, Fatima Martín-Hernández7, Clive Robert Neal8, Pierre Rochette9, Jessica L Till10 and Kevin Barry Walsh Jr1, (1)Southern Illinois University Carbondale, Carbondale, IL, United States, (2)Montana State University Billings, Department of Biological and Physical Sciences, Billings, MT, United States, (3)Université Libre de Bruxelles, Brussels, Belgium, (4)Southern Illinois University Carbondale, Geology, Carbondale, IL, United States, (5)CEREGE, Aix-en-Provence, France, (6)University of Minnesota, Minneapolis, MN, United States, (7)University of Madrid, Madrid, Spain, (8)Univ Notre Dame, Notre Dame, IN, United States, (9)CEREGE ARBOIS, Aix En Provence, France, (10)Deutsches GeoForschungsZentrum GFZ, Potsdam, Germany
Abstract:
Recent petromagnetic results on shallow mantle xenoliths suggest that the uppermost mantle is significantly more magnetic than previously thought, particularly in metasomatised or cold region. This magnetic mantle bears minute amounts of magnetite, a mineral indicative of higher oxygen fugacities. While the exact origin of this magnetite remains uncertain, its contribution to long wavelength magnetic anomalies adds to the potential contributions of crustal rocks.

Here we present a compilation of rock magnetic and paleomagnetic data enabling the quantitification of the respective contributions in distinct tectonic settings including subduction zones and stable cratons.

The magnetic properties of over 400 specimens of mantle xenoliths are compared to published data from hundreds of deep crustal xenoliths. The picture emerging from this comparison supports a layered distribution of oxidation state in the lithosphere reflecting both the tectonic setting and the degree of melt extraction.

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