I guessed on sulfates
From the guess that this was white based on a B/W picture. At least it does look white!
The mid ocean ridge was a jest, but continued fissure volcanism on a flooded crater floor is not.
I agree that I could not find any good pillow possibilities (story of my life!). I promote the possibility that some of these may suggest subaqueous processes involving volcanism, such as volcanic turbidites or peperites.
I dont see any high angle cross bedding to suggest anything aeolian, but there certainly are layers. The rocks at Peace look like pure precipates, not an alteration crust - they're full of holes. I think the rat ground much more than anticipated - looks like the deepest hole yet. Thanks for the opinions.