First petrological results along the traverse (sol 1 to 118)

Norbert Brügge, Germany
Dipl.-Geol.

 

 

My latest Analysis

My new analysis is based on a number of new insights into the groundmass and texture of the rocks, captured by the rover's cameras.

The photos published so far by NASA allow the conclusion that the boulders and remnants of it are all of igneous origin. The boulderss, which are chaotic deposited on the bottom and in the sandy elevations, are in a strongly varying stage of their disintegration. "Fresh" boulders are usually angular and have a dark groundmass. In the stage of disintegration  they dissolve columnar to friable. In the final stage of disintegration, the flat and brighly colored stones are in the ground, or it are remnants of total crumbled boulders.

It has been found that in holes residues of decomposed olivine can be found in various distributions in boulders, but often there are only empty holes. The stones at the rover's landing place which I originally referred as deposits of pumice are in reality remnants of rocks in last stage of disintegration. In retrospect, the "holes" in the supposedly blistered structure are empty nests of decomposed olivine. Such holes in high concentration leads to the conclusion that olivine is also part of the groundmass.

A main component of the matrix in the boulders is dark hornblende (amphibole). This explains the many reflections that emanate from the crystal surfaces when light is incident. These reflections were referred before as mysterious "bright inclusions". Another component are obviously bright-colored pyroxes (and olivine), because strong concentrations of magnesium and calcium are detected in a single spectrogram published so far.

 If the rocks are actually basalt, then is it a hornblende and olivine rich basalt. Attention: It could also be an ultramafic kimberlite magma, because the almost complete lack of silicon is noticeable.
Note: The rover  "Curiosity" found the same stones (olivine + hornblende).

 

First datasets from the Visible and InfraRed (VISIR) sensor and Raman spectrometer instruments of the SuperCam were now published. VISIR uses reflected sunlight to examine the mineral compositions of rocks and soils. The Raman spectrometer uses a green laser beam for its observations. The result: Clear peaks of Mg and Ca were found in the spectrogram from an outcropd stone in the ground (Sol 12). It could be an indication of pyroxenes.
 

Zoom with the SuperCam on a stone in the ground that is identified
as basaltic (?). Clear peaks of Mg and Ca were found in a spectrogram.

    

The different stages of the disintegration of the boulders suggest that these were included in the glacier moraine at different times. The youngest boulders (from the upper parts of the moraine) are still angular and "fresh". The oldest boulders, which are already in the final stages of disintegration, come from the lower parts of the eroded moraine.
So far is unclear what is the origin of a crust apparently adhering to the boulders, which flakes off and dissolves into rounded aggregates.
 

1.) Composition of groundmass and phenocrysts

Hornblende and Pyroxe in the groundmass

     

Published photos by the SherlocCams from the surface of unspecified stones shows some details from the groundmass, included dark areas therein. The probability that this dark areas are hornblende is high.The bright parts in the matrix could be pyroxene and olivine

Earthly hornblende


    
   


           

Reflexions on hornblende crystals when exposed to light

Olivine in the groundmass and as phenocrysts

An exposed rock (Sol-37) is described as puzzling. It has a smooth surface (almost vitreous) on which numerous rounded depressions can be seen. Upon closer inspection of the photo, I notice that some of the depressions still have a brownish (not secondary) filling. Obviously these are the typical remnants of decomposed olivine aggregates, which are already missing in most of the holes.

    

Sol-37 (Lava bomb !?)

Several holes from phenocrysts

 Ddecomposed olivine






Decomposed olivine

 Olivine between hornblende

High concentration of holes from decomposed olivine in the groundmass of debris

 

2.)  Stages of disintegration of the boulders

"Fresh" boulders

Columnar to friable disintegrated boulders






 

Boulders in the final stage of disintegration
At the moment I cannot explain the bright color of the remains of these disintegrated ultramafic boulders. (Oxidation?)

 

Boulders with adherent crust and their disintegrate products ?
But, the "crust" could be a different form of the friable disintegration of the groundmass and the small rounded parts on the ground are the final products.










 

 

New photos of "Perseverance" on the traverse to south,
showing the stages of disintegration on boulders, including their bleaching. It seems that the concentration of olivine in the rocks could been to vary.