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Ehlmann - Coggle Diagram
Ehlmann
inferences
clays, salts and oxides originate from water interacting with materials such as glass, olivine, pyroxene, and feldspars
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Fe, Mg clays are prominent, and tend to be "mobile", comparative to the "immobile" minority that are aluminium clays.
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open systems can be weathered, and cause chemical fractionation where instead of clay, salts can be formed
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weathering (could be from water or wind), could have made the rocks more Al rich over time.
certain conditions require certain availabilities of water, and therefore can be used to determine conditions of the time
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using water conditions, crater counts, and other factors, approximate ages have been determined
smectites and chlorite form under anoxic, alkaline conditions
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measurements
conducted at various points, covering a large range of longitude and latitude
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observations
crustal clays by far were the most observed clays, and were spread out all across the planet.
sedimentary and stratigraphic clays, stratigraphic clays especially, were found in more localized regions, with the stratigraphics in clusters and the sedimentary forming lines.
Fe, Mg smectite phyllosilicates were the most prominent mineral in ALL types of clays, otherwise compositions were wildly different
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applied models
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proposed models
early mars
low atmospheric pressure, groundwater-heavy hydrological systems
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findings
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Fe, Mg minerals most likely from before late noach.
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Hydrothermal subsurface circulation (ground waters, surface water etc.) constant-ish until mid noach, then started decreasing until plateauing in amazonian
early-middle noachian = mostly groundwater, little surface water
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late hesperian - amazonian = very little groundwater, no surface water