I'll consider submarine volcanism.

But I'll separate that from submarine alteration, which is it's own topic.

I've not seen anything so far which even remotely reminds me of submarine basalt. Pillows are not spherical in cross-section, they typically have a pointed bottom, where the succeeding pillow fills the lows in the surface created by the already cooled pillows.

Submarine volcanics (mafic or felsic) are can occur as "volcano-clastics"- a mix between igneous processes and sedimentary re-working. For example, what happens if there is explosive volcanism on the seafloor? The igneous material shot into the water column then acts as a sediment as it settles, creating sedimentary structures. The effects of the depth of the water column on volcano-clastic textures is still hotly discussed (see the latest Economic Geology*). Then there are slumped deposits and even turbidite like volcano-clastics. Like I said, this is debated. At any rate, all I see are stacked flood basalts, mostly massive in texture, some slightly porphyritic, some possible vesicles, and that's about it. (I don't include Wishtone in this, I don't think it is a simple basalt.) This pile may have been intruded by wishstone type rocks, but that is pure speculation.

Which brings me to alteration. Mafic volcanics in saline water are easily altered by the readily available groundwater, heated by the most recent flow or by intrusions . Mostly this results in clays, but they are typically Mg and Ca phyllosilicates, which tend to be green and black. Here's a example of typical marine alteration of basalts. Of course, when the hydrothermal cell is hot and cooking, all kinds of fun sulfide minerals get deposited. I don't see any of that here. What I see here are localized alteration areas. We are starting to see more interesting outcrops of the white material. There may be aeolean deposits here that are initially locallized basaltic dunes which are then cemented and altered in a process similar to the Opportunity Rocks. Maybe that's what they meant by "re-worked". But they are a minor part of the rock column.

Most of the crusts we've seen can be explained as long-term atmospheric weathering rinds and are not the smoking gun for a long-lived lake in Gusev.

jms

*I've not read the article, but a friend of mine was giving me a synopsis on the phone the other day. He keeps me up to date on Economic Geology articles, I fill him in on GSA publications.