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Cape York - The "Lakelands", Starting sol 2703
serpens
post Oct 5 2011, 01:51 AM
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The PS update noted that Steve Squyres mentioned that Chester Lake "has sort of a basaltic composition. It does not have a zinc enrichment like we saw at [Tisdale 2]."

The published APXS comparative graph for Tisdale 2 showed elevated Zn and Br but did not address Cu. I think that enhanced Br is consistent with basaltic glass but If Cu was also elevated it would possibly indicate past, hot hydrothermal activity. If not then possibly a cold seep or basaltic weathering (plagioclase?). Does anyone have any idea of the Cu level?
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Bill Harris
post Oct 5 2011, 01:42 PM
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QUOTE (Serpens)
If not then possibly a cold seep or basaltic weathering (plagioclase?). Does anyone have any idea of the Cu level?

I've not seen any of the details of the chemistry, but this will likely be a hot topic at the next LPSC.

The top of Tisdale which was APXS'd is either a weathered zone and/or has a inherent different chemistry or is a bedding plane/fracture which has a zone of Zn-rich material deposited in it (cold-water hydrothermal). That "weathered" unit has a distinctive light-ochre color is evident in other exposures along Shoemaker Ridge and should be examined further on the traverse to the "summit crater". I intuitively think of this yellowish colour as generally "limonitic", which could include almost anything, actually.

Remember, the original, deep crust here is from not only a warmer and wetter Mars, but a Mars with a hotter amd more mobile/active crust/mantle. The mantle of that era had more hotspots and plumes and there was extensive tectonic activity. Meridiani Planum is on the edge of the Tharsis uplift, a major feature by any measure.

This primeval crust (Ur-crust) has since been pounded, mixed and blended into an impact breccia by countless impacts, and it has, among other things, has a much higher surface:volume ratio than rock and can be much more reactive to chemical weathering, weathering in the presence of water.

In a way, this is a glimpse at what the Earth may have been like in Hadean times, with tectonic cycles starting and bio-processes just beginning.

Exciting times, then and now.

--Bill





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Phil Stooke
post Oct 5 2011, 02:10 PM
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Meridiani on the edge of the Tharsis uplift? That's a bit of a stretch!

Phil



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Juramike
post Oct 5 2011, 02:26 PM
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QUOTE
a bit of a stretch



best Mars uplift pun ever...


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Bill Harris
post Oct 5 2011, 02:42 PM
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QUOTE
Meridiani on the edge of the Tharsis uplift? That's a bit of a stretch!

Oops, you're correct-- I was thinking of something else.

--Bill


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Nix
post Oct 5 2011, 03:03 PM
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QUOTE (Juramike @ Oct 5 2011, 04:26 PM) *
best Mars uplift pun ever...


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Stu
post Oct 5 2011, 09:39 PM
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Colour view of the RAT hole...

Attached Image


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