Modeling of
Iron Oxide Concretion Formation: Complexities and Sensitivities of Fluid
Interactions on Earth and Mars
Chan, Marjorie A.1, Jens Ormö2,
Anthony Park3, Michael Stich2, Virginia Souza-Egipsy2,
Goro Komatsu4 (1) University of Utah, Salt
Lake City, UT (2) 2Centro de Astrobiología
(INTA/CSIC), Instituto Nacional
de Técnica Aeroespacial,
Madrid, Spain (3) Sienna Geodynamics & Consulting, Inc, Bloomington, IN (4)
Università d’Annunzio, Pescara, Italy
Abundant iron oxide concretions of the
Jurassic Navajo Sandstone of southern
Three numerical simulations show the
development of self-organized nucleation centers upon supersaturation.
Simulations cover 1-D models of simple diffusion that produce few nucleation
bands, to models with both diffusive and advective
mass-transfer mechanisms. Model sensitivities show that acidic conditions can
cause iron to stay in solution longer to produce nucleation centers that are
farther from the input source.
Laboratory bench tests with reactions of
FeSO4 or Fe(NO3)3
with KOH show how the precipitation of iron sulfates or iron-hydroxides may
form. Rinds may show inward growth depending on the concentration of the iron
source in relation to the surrounding fluid. Complex factors such as
concentration and flux, time, and multiple events can create banded patterns during
rind growth. The comparisons of the terrestrial examples with numerical and
laboratory models have strong implications for understanding similar hematite
concretions and the history of liquid water and, thus, the potential of similar
processes at Mars environments.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California