Geologic History of a Felsic and Hydrated Mineral Suite in Syrtis Major

Details Geologic History of a Felsic and Hydrated Mineral Suite in Syrtis Major Geologic History of a Felsic and Hydrated Mineral Suite in Syrtis Major

Dec 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p53c1530s&link_type=abstract

American Geophysical Union, Fall Meeting 2010, abstract #P53C-1530

Biology

[5220] Planetary Sciences: Astrobiology / Hydrothermal Systems And Weathering On Other Planets, [5420] Planetary Sciences: Solid Surface Planets / Impact Phenomena, Cratering, [5470] Planetary Sciences: Solid Surface Planets / Surface Materials And Properties, [6225] Planetary Sciences: Solar System Objects / Mars

Scientific paper

Here we assess the ancient environments represented by the compositions of exposures within two craters near Antoniadi Crater in N. Syrtis Major, Mars (63°E, 20°N). We used both thermal (TIR) and visible/near-infrared (VNIR) spectroscopy to place constraints on the mineralogy, formation environment, and astrobiological potential. This region was chosen because of its varied and well-exposed mineralogy. It was first studied in the TIR because of its unique exposures of quartz- and feldspar-rich surfaces1, representing both the only current identification of crystalline quartz and the most felsic composition yet found on Mars. VNIR data acquired within the same region reveal a suite of hydrated minerals, including phyllosilicates, hydrated silica (opal), and the zeolite analcime2. In this study, we utilize the combined stability fields of the full suite of quartzofeldspathic and hydrated minerals - a unique mineral assemblage on Mars - to infer formation conditions: neutral-to-alkaline pH, low-to-moderate temperatures, and sustained water. These conditions have been cited as ideal for providing a habitable environment for nascent life3. We answer three main questions about the alteration history of these deposits: When did alteration occur? Alteration is thought to either pre-date the impact or occur in a post-impact hydrothermal cell. Our study suggests the former, since alteration is restricted to impact breccia blocks, indicating that altered rocks had formed and were later exhumed by impact. How are the quartzofeldspathic and hydrated minerals related? Quartzofeldspathic material exposed within these craters is always co-located with opal. Opal is metastable and will alter to chalcedony (microcrystalline quartz) in 400 Ma under martian conditions4 with sustained exposure to water5. In the TIR, species of opal are separable6, but spectra of chalcedony and quartz share a distinctive doublet between 8-9.5 μm7, and are mostly indistinguishable. However, in the VNIR, opal and chalcedony are separable due to variations in the width of features at 1.4, 1.9 and 2.2 μm, and the emergence of a new band at 2.26 μm with increased hydration of silica8. Most of the silica spectra show features that indicate greater hydration, indicating, along with TIR evidence, that the hydrated silica is likely chalcedony. What was the temperature of alteration and how long was the water present? On Earth, analcime forms in pH > 8.59 and temperatures <200°C10. Furthermore, identifications of nontronite, a smectite clay, indicate a similar pH10. Analcime is never found as a primary product of alteration; it requires a precursor zeolite to form, a reaction that takes > 200,000 years on Earth10. Due to its interesting and varied mineralogy, this unique assemblage is in a useful and powerful location for reconstructing past conditions on ancient Mars. 1. Bandfield, J.L. et al., JGR 109, 2004. 2. Ehlmann, B. et al., JGR 114, 2009. 3. Farmer, J. & D. Des Marais, JGR 104, 1999. 4. Lynne, B. et al., Sed. Geol. 179, 2005. 5. Tosca, N. & A. Knoll, EPSL 286, 2009. 6. Michalski, J. et al., GRL 30, 2003. 7. McDowell, M. et al., LPSC XL (#1419), 2009. 8. Milliken, R. et al., Geol. 36, 2008. 9. Gottardi, G. Eur. Jour. Min. 1, 1989. 10. Diagenesis, 1988.

Affiliated with

Also associated with

No associations

Rating

Geologic History of a Felsic and Hydrated Mineral Suite in Syrtis Major 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 Geologic History of a Felsic and Hydrated Mineral Suite in Syrtis Major, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Geologic History of a Felsic and Hydrated Mineral Suite in Syrtis Major will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1499275