Other
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p34c..01m&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P34C-01
Other
[1042] Geochemistry / Mineral And Crystal Chemistry, [3616] Mineralogy And Petrology / Hydrothermal Systems, [3617] Mineralogy And Petrology / Alteration And Weathering Processes, [3672] Mineralogy And Petrology / Planetary Mineralogy And Petrology
Scientific paper
Infrared remote sensing results from the OMEGA and CRISM experiments have revealed 1000s of exposures of Fe/Mg-rich phyllosilicates on Mars, including many smectite compositions intermediate between nontronite (Fe3+ endmember) and saponite (Mg2+ endmember). In addition, many of the deposits contain spectral evidence for putative higher temperature phases such as chlorite, chlorite-smectite, and other interlayered clays. In this work, we are exploring the mineralogy of the saponite-nontronite crystal chemical series, as well the interlayered smectite-talc, and smectite-chlorite systems. Previously collected sea-floor samples originate from the East Pacific Rise, Gulf of California, and Red Sea Southwest Basin. Bulk sample mineralogy revealed by X-ray diffraction (XRD) of randomly oriented powder-mounts shows that the Fe/Mg-clay minerals occur with various proportions of poorly crystalline Fe/MnOOH and NaCl, and minor sulfates and sulfides, which can be removed through washing or various treatments. XRD of oriented, air-dried and glycolated mounts reveals the presence of di- and trioctohedral smectites, talc with varied Fe content, interlayered talc-smectite, chlorite, chlorite-smectite, and poorly crystalline clays that could be considered proto-smectites. Mid-infrared and visible/near infrared reflectance spectra of the samples display clear evidence for chemical and structural variation among the samples, and subtle differences related to interlayering and crystallinity relevant to understanding infrared observations of Martian clays. The sea-floor clays likely formed in low-temperature hydrothermal settings, in some cases as direct precipitates close to hydrothermal vents, and in other cases as proximal sediments. Hydrated talc with low crystalline order and frequent Fe substitution is commonly found interlayered with smectites. The chemical and structural variation in these samples produces a range of spectral features in the 2.27-2.33 micron (wavelength) range that is similar to those observed at Mars - suggesting that talc could be more common on Mars than has been previously proposed. Interlayered clays in general might be the norm and not the exception in many Martian deposits. The samples display a range of variation in crystal order, but the notion of crystallinity depends greatly on the context within the technique that is being used. Certain infrared measurements are sensitive to chemical ordering within octahedral sheets only, whereas other infrared observations are sensitive to ordering in the tetrahedral sheets. XRD is sensitive to 1-, 2-, or 3-D ordering, depending on which peaks are considered. Some materials that appear poorly crystalline from their 00l x-ray peaks (highly disorder layer stack) may have well developed and chemically homogeneous octahedral domains that produce strong 0k0 peaks and IR spectral features. Other samples display poor hkl diffraction features and very sharp 00l peaks. Such considerations are important for interpreting clay formation mechanisms and will be essential for linking multiple observations of clays from existing IR instruments covering multiple wavelengths to the XRD data to be returned from Mars by the upcoming Mars Science Laboratory mission.
Cuadros Jaime
Glotch Timothy D.
Michalski Joseph R.
No associations
LandOfFree
The mineralogy of Fe/Mg-clays formed in low-temperature hydrothermal sea floor environments and possible formation mechanisms on Mars does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The mineralogy of Fe/Mg-clays formed in low-temperature hydrothermal sea floor environments and possible formation mechanisms on Mars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The mineralogy of Fe/Mg-clays formed in low-temperature hydrothermal sea floor environments and possible formation mechanisms on Mars will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-871187