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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
E09S91,
doi:10.1029/2006JE002698,
2006
Alkaline volcanic rocks from the Columbia Hills, Gusev crater, Mars
H. Y. McSween
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA
S. W. Ruff
Department of Geological Sciences, Arizona State University, Tempe, Arizona, USA
R. V. Morris
NASA Johnson Space Center, Houston, Texas, USA
J. F. Bell III
Department of Astronomy, Cornell University, Ithaca, New York, USA
K. Herkenhoff
Astrogeology Branch, U.S. Geological Survey, Flagstaff, Arizona, USA
R. Gellert
Department of Physics, University of Guelph, Guelph, Canada
K. R. Stockstill
Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
L. L. Tornabene
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee, USA
S. W. Squyres
Department of Astronomy, Cornell University, Ithaca, New York, USA
J. A. Crisp
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
P. R. Christensen
Department of Geological Sciences, Arizona State University, Tempe, Arizona, USA
T. J. McCoy
Department of Mineral Sciences, Smithsonian Institution, Washington, D. C., USA
D. W. Mittlefehldt
NASA Johnson Space Center, Houston, Texas, USA
M. Schmidt
Department of Mineral Sciences, Smithsonian Institution, Washington, D. C., USA
Abstract
Irvine, Backstay, and Wishstone are the type specimens for three classes of fine-grained or fragmental, relatively unaltered
rocks with distinctive thermal emission spectra, found as float on the flanks of the Columbia Hills. Chemical analyses indicate
that these rocks are mildly alkaline basalt, trachybasalt, and tephrite, respectively. Their mineralogy consists of Na- and
K-rich feldspar(s), low- and high-Ca pyroxenes, ferroan olivine, Fe-Ti (and possibly Cr) oxides, phosphate, and possibly glass.
The texture of Wishstone is consistent with a pyroclastic origin, whereas Irvine and Backstay are lavas or possibly dike rocks.
Chemical compositions of these rocks plot on or near liquid lines of descent for most elements calculated for Adirondack class
rocks (olivine-rich basalts from the Gusev plains) at various pressures from 0.1 to 1.0 GPa. We infer that Wishstone-, Backstay-,
and Irvine-class magmas may have formed by fractionation of primitive, oxidized basaltic magma similar to Adirondack-class
rocks. The compositions of all these rocks reveal that the Gusev magmatic province is alkaline, distinct from the subalkaline
volcanic rocks thought to dominate most of the planet's surface. The fact that differentiated volcanic rocks were not encountered
on the plains prior to ascending Husband Hill may suggest a local magma source for volcanism beneath Gusev crater.
Received 3
February
2006;
accepted 7
June
2006;
published 23
September
2006.
Keywords: alkaline;
Mars;
volcanic.
Index Terms: 6230 Planetary Sciences: Solar System Objects: Martian satellites; 5480 Planetary Sciences: Solid Surface Planets: Volcanism (6063, 8148, 8450); 5475 Planetary Sciences: Solid Surface Planets: Tectonics (8149); 5410 Planetary Sciences: Solid Surface Planets: Composition (1060, 3672).
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Citation: McSween, H. Y., et al.
(2006),
Alkaline volcanic rocks from the Columbia Hills, Gusev crater, Mars,
J. Geophys. Res.,
111,
E09S91,
doi:10.1029/2006JE002698.
Copyright 2006 by the American Geophysical Union.
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