 |
| Titel |
Lacustrine Mineral Deposits and their Geologic Context at Bradbury Crater on Mars |
| VerfasserIn |
Daniela Tirsch, Gino Erkeling, Janice L. Bishop, Livio L. Tornabene, Harald Hiesinger, Ralf Jaumann  |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127219
|
| Publikation (Nr.) |
 EGU/EGU2016-7069.pdf |
|
|
|
|
|
| Zusammenfassung |
| The 60-km Bradbury Crater (85.8˚ E; 2.7˚ N) is located at the Libya Montes region at the
southern rim of the Isidis impact basin on Mars. This area is predominantly characterized by
Noachian-aged highland massifs that were heavily modified by fluvial, lacustrine, aeolian,
volcanic, and impact processes occurring in multiple recurring events. Bradbury Crater stands
out for its abundance of fluvial and lacustrine landforms, which reflect a varied history of
aqueous-related geological processes. A 2.8 by 5 km-sized fan-shaped deposit has been
interpreted to have played a significant role in the hydrologic evolution of landforms at
Bradbury Crater. This deposit is partly composed of Al-rich phyllosilicates, indicating
aqueous alteration processes. The current work is directed towards shedding light on the
origin and timing of these aqueous alteration processes. HRSC digital terrain models give
conclusive insight into the stratigraphic relationships of those sediments to each
other. Geological analyses have been performed on the basis of HRSC, CTX and
HiRISE image data in combination with HRSC and HiRISE digital elevation models.
Mineral detection has been performed by spectral analyses of targeted CRISM
images.
Fe/Mg-smectites are detected along the walls of the ancient Libya Montes bedrocks
and could be a result of Isidis impact-related hydrothermal alteration. Carbonates
intermixed with Fe/Mg-smectites occur at the base of the bedrock unit. Carbonate
formation may have been driven by the interaction of hydrous CO2rich fluids with
olivine at the paleolake site. An Al-smectite, consistent with beidellite, is exposed
within several layers of the deltaic deposit. Because beidellite forms at elevated
temperatures, its presence might either result from alteration in a warm paleolake
at this site or it could be an allochtonous sediment deposited here subsequently.
Since the strongest beidellite signatures are detected within the foreset and the
bottomset layer of the delta, in situ alteration in a warm standing body of water
is likely, but not certain. Alternatively they might be remnants of former Fe-rich
highland clays, which were leached into Al-smectites, transported and deposited
here.
Fe/Mg-smectites present in the ancient bedrock are exposed at higher elevations but are
stratigraphically lower and older than the lower lying Al-smectites. In either alteration
scenario for the Al-smectites, allochtonous or in situ, they are significantly younger than the
Fe-clays, a stratigraphic situation often observed on Mars. |
|
|
|
|
|
|