Title: Grain
size dependent potential for self generation of magnetic anomalies on
Mars via thermoremanent magnetic acquisition and magnetic interaction
of hematite and magnetite
Author(s): Kletetschka
G, Ness NF, Connerney JEP, Acuna MH, Wasilewski PJ
Source: PHYSICS
OF THE EARTH AND PLANETARY INTERIORS 148 (2-4): 149-156 FEB 2005
Document Type: Article
Language: English
Abstract: Early
in the history of planetary evolution portions of Martian crust became
magnetized by dynamo-generated magnetic field. A lateral distribution
of the secondary magnetic field generated by crustal remanent sources
containing magnetic carriers of certain gram size and mineralogy is
able to produce an ambient magnetic field of larger intensity than
preexisting dynamo. This ambient field is capable of magnetizing
portions of deeper crust that cools through its blocking temperatures
in an absence of dynamo. We consider both magnetite (Fe3O4) and
hematite (alpha-Fe2O3) as minerals contributing to the overall
magnetization. Analysis of magnetization of magnetic minerals of
various grain size and concentration reveals that magnetite grains less
than 0.01 nun in size, and hematite grains larger than 0.01 mm in size
can become effective magnetic source capable of magnetizing magnetic
minerals contained in surrounding volume. Preexisting crustal remanence
(for example similar to250 A/m relates to 25% of multi-domain hematite)
can trigger a self-magnetizing process that can continue in the absence
of magnetic dynamo and continue strengthening and/or weakening magnetic
anomalies on Mars. Thickness of the primary magnetic layer and
concentration of magnetic carriers allow specification of the
temperature gradient required to trigger a self-magnetization process.
(C) 2004 Elsevier B.V. All rights reserved.
Author Keywords: magnetic
mineralogy; self-magnetization; blocking temperature; Martian crust;
temperature gradient
KeyWords Plus: REMANENT
MAGNETIZATION; MULTIDOMAIN GRAINS; LAMELLAR MAGNETISM; SNC METEORITES;
IGNEOUS ROCKS; FIELD; PYRRHOTITE; TRM; SPECTROMETER; TEMPERATURE
Addresses: Kletetschka
G (reprint author), Catholic Univ Amer, Dept Phys, Washington, DC 20064
USA
Catholic Univ Amer, Dept Phys, Washington, DC 20064 USA
Acad Sci Czech Republ, Inst Geol, Prague, Czech Republic
NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
Univ Delaware, Bartol Res Inst, Newark, DE 19716 USA
Publisher: ELSEVIER
SCIENCE BV, PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
Subject Category: GEOCHEMISTRY
& GEOPHYSICS
IDS Number: 898XL
ISSN: 0031-9201