CaltechAUTHORS
  A Caltech Library Service

Evidence for low-grade metamorphism, hydrothermal alteration, and diagenesis on Mars from phyllosilicate mineral assemblages

Ehlmann, Bethany L. and Mustard, John F. and Clark, Roger N. and Swayze, Gregg A. and Murchie, Scott L. (2011) Evidence for low-grade metamorphism, hydrothermal alteration, and diagenesis on Mars from phyllosilicate mineral assemblages. Clays and Clay Minerals, 59 (4). pp. 359-377. ISSN 0009-8604. https://resolver.caltech.edu/CaltechAUTHORS:20120104-073501082

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20120104-073501082

Abstract

The enhanced spatial and spectral resolution provided by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) has led to the discovery of numerous hydrated silicate minerals on Mars, particularly in the ancient, cratered crust comprising the southern highlands. Phases recently identified using visible/near-infrared spectra include: smectite, chlorite, prehnite, high-charge phyllosilicates (illite or muscovite), the zeolite analcime, opaline silica, and serpentine. Some mineral assemblages represent the products of aqueous alteration at elevated temperatures. Geologic occurrences of these mineral assemblages are described using examples from west of the Isidis basin near the Nili Fossae and with reference to differences in implied temperature, fluid composition, and starting materials during alteration. The alteration minerals are not distributed homogeneously. Rather, certain craters host distinctive alteration assemblages: (1) prehnite-chlorite-silica, (2) analcime-silica-Fe, Mg-smectite-chlorite, (3) chlorite-illite (muscovite), and (4) serpentine, which furthermore has been found in bedrock units. These assemblages contrast with the prevalence of solely Fe, Mg-smectites in most phyllosilicate-bearing terrains on Mars, and they represent materials altered at depth then exposed by cratering. Of the minerals found to date, prehnite provides the clearest evidence for subsurface, hydrothermal/metamorphic alteration, as it forms only under highly restricted conditions (T = 200-400°C). Multiple mechanisms exist for forming the other individual minerals; however, the most likely formation mechanisms for the characteristic mineralogic assemblages observed are, for (1) and (2), low-grade metamorphism or hydrothermal (<400°C) circulation of fluids in basalt; for (3), transformation of trioctahedral smectites to chlorite and dioctahedral smectites to illite during diagenesis; and for (4), low-grade metamorphism or hydrothermal (<400°C) circulation of fluids in ultramafic rocks. Evidence for high-grade metamorphism at elevated pressures or temperatures >400°C has not been found.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1346/CCMN.2011.0590402DOIUNSPECIFIED
http://www.ingentaconnect.com/content/cms/ccm/2011/00000059/00000004/art00003PublisherUNSPECIFIED
Additional Information:© 2011 Clay Minerals Society. Received 31 March 2010; revised 11 August 2011.
Subject Keywords:Analcime, Chlorite, Craters, Diagenesis, Hydrothermal Alteration, Illite, Infrared Spectroscopy, Mars, Metamorphism, Muscovite, Phyllosilicates, Prehnite, Serpentine, Silica, Zeolites.
Issue or Number:4
Record Number:CaltechAUTHORS:20120104-073501082
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20120104-073501082
Official Citation:Evidence for low-grade metamorphism, hydrothermal alteration, and diagenesis on Mars from phyllosilicate mineral assemblages pp. 359-377(19) Authors: Ehlmann, Bethany L.; Mustard, John F.; Clark, Roger N.; Swayze, Gregg A.; Murchie, Scott L.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28637
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:04 Jan 2012 15:52
Last Modified:03 Oct 2019 03:34

Repository Staff Only: item control page