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Discovery of alunite in Cross crater, Terra Sirenum, Mars: Evidence for acidic, sulfurous waters
被引:52
|作者:
Ehlmann, Bethany L.
[1
,2
]
Swayze, Gregg A.
[3
]
Milliken, Ralph E.
[4
]
Mustard, John F.
[4
]
Clarks, Roger N.
[5
]
Murchie, Scott L.
[6
]
Breit, George N.
[3
]
Wray, James J.
[7
]
Gondet, Brigitte
[8
]
Poulet, Francois
[8
]
Carter, John
[8
]
Calvin, Wendy M.
[9
]
Benzel, William M.
[3
]
Seelos, Kimberly D.
[6
]
机构:
[1] CALTECH, Div Geol & Planetary Sci, Pasadena, CA 91125 USA
[2] CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA
[3] US Geol Survey, Denver, CO 80225 USA
[4] Brown Univ, Dept Earth Environm & Planetary Sci, Providence, RI 02906 USA
[5] Planetary Sci Inst, Tucson, AZ 85719 USA
[6] Johns Hopkins Univ, Appl Phys Lab, Johns Hopkins Rd, Laurel, MD 20723 USA
[7] Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA
[8] Univ Paris 11, Inst Astrophys Spatiale, F-91405 Orsay, France
[9] Univ Nevada, Dept Geol Sci, Reno, NV 89557 USA
基金:
美国国家航空航天局;
关键词:
Alunite;
phyllosilicates;
hydrothermal activity;
lakes;
groundwater;
Mars;
sediments;
infrared spectroscopy;
Invited Centennial article;
WESTERN-AUSTRALIA;
MERIDIANI-PLANUM;
REFLECTANCE SPECTROSCOPY;
IMAGING SPECTROSCOPY;
SULFATE ALTERATION;
SALINE LAKES;
BASIN LAKES;
SURFACE;
JAROSITE;
DEPOSITS;
D O I:
10.2138/am-2016-5574
中图分类号:
P3 [地球物理学];
P59 [地球化学];
学科分类号:
0708 ;
070902 ;
摘要:
Cross crater is a 65 km impact crater, located in the Noachian highlands of the Terra Sirenum region of Mars (30 degrees S, 158 degrees W), which hosts aluminum phyllosilicate deposits first detected by the Observatoire pour la Mineralogie, L'Eau, les Glaces et l'Activitie (OMEGA) imaging spectrometer on Mars Express. Using high-resolution data from the Mars Reconnaissance Orbiter, we examine Cross crater's basin-filling sedimentary deposits. Visible/shortwave infrared (VSWIR) spectra from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) show absorptions diagnostic of alunite. Combining spectral data with high-resolution images, we map a large (10 km x 5 km) alunite-bearing deposit in southwest Cross crater, widespread kaolin-bearing sediments with variable amounts of alunite that are layered in <10 m scale beds, and silica- and/or montmorillonite-bearing deposits that occupy topographically lower, heavily fractured units. The secondary minerals are found at elevations ranging from 700 to 1550 m, forming a discontinuous ring along the crater wall beneath darker capping materials. The mineralogy inside Cross crater is different from that of the surrounding terrains and other martian basins, where Fe/Mg-phyllosilicates and Ca/Mg-sulfates are commonly found. Alunite in Cross crater indicates acidic, sulfurous waters at the time of its formation. Waters in Cross crater were likely supplied by regionally upwelling groundwaters as well as through an inlet valley from a small adjacent depression to the east, perhaps occasionally forming a lake or series of shallow playa lakes in the closed basin. Like nearby Columbus crater, Cross crater exhibits evidence for acid sulfate alteration, but the alteration in Cross is more extensive/complete. The large but localized occurrence of alunite suggests a localized, high-volume source of acidic waters or vapors, possibly supplied by sulfurous (H2S- and/or SO2-bearing) waters in contact with a magmatic source, upwelling steam or fluids through fracture zones. The unique, highly aluminous nature of the Cross crater deposits relative to other martian acid sulfate deposits indicates acid waters, high water throughput during alteration, atypically glassy and/or felsic materials, or a combination of these conditions.
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页码:1527 / 1542
页数:16
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