Yes, entirely possible, and there's a range of scenarios there. In fact, my segregation models for the marbles require not just that the marbles grow, but that they replace the existing rock there, or at least engulf it.

Filling of vesicles is another way, and I'm sure that there are more.

One issue is that if the marbles are either primary features, like oolites, or a secondary replacement of a primary feature, such as vesicles, we should see patterns in the distribution of the marbles within the rocks - such as marble-rich layers. I haven't noticed any yet, although I've had my eye open for them.

BTW, over on Alex's Planetary Science group, Bruce Moomaw has suggested that the talc-like mineral Pyrophyllite is a candidate for the bulk component of the pale rock.

Spurred by this, I went and did some homework:-

I needed to mug-up on pyrophyllite.
http://mineral.galleries.com/minerals/silicate/pyrophyl/pyrophyl.htm
has some interesting comments.

Note that pyrophyllite is a hydrous mineral (hear that Odyssey bell
ringing?) and that on partial or full thermal dehydration it
transforms to flaky masses of thin sheets. Which raises the question,
are we seeing true bedding? The blocky appearance of the outcrop and
its somewhat jumbled appearance at first gave the impression of
massive cross-bedding, or structural disruption due to crater
formation, but another possibility is that we are seeing sheet
silicates exfoliating.

And how would pyrophyllite behave in Mars' atmosphere? Would that of
itself lead to dehydration and exfoliation of a surface layer - therte
are certainly differential weathering effects visible in the rock
outcrop - some smooth surfaces that look recently exhumed, and some
craggy and flaky older exposures - or is this simply harder and softer
zones showing differential weathering? Again, more questions for us
poor Terrestrials...

I don't neccesarily ascribe to Bruce's theory, but it poses some
useful questions we can ask.

Is the Haematite primary, or an alteration product or weathering rind?
If the spheroids were originally pyrite, as noted in Bruce's example
and also by another correspondend citing the Mt. Tom Price mine in
Australia, then where do the Fe and S come and go. (Pyrite to
haematite sounds suspiciously like sulphate reducing bacteria!).

Alternatively, if the precursor is Goethite, its more an Fe question,
but still requiring an answer (but would explain the distribution of
"random" spheroids through a massive groundmass.)

Talc is the magnesium analogue. Ferripyrophyllite is Fe-bearing.
http://webmineral.com/data/Ferripyrophyllite.shtml

One could imagine an Fe-bearing precursor metamorphosing to massive
Fe-free pyrophyllite plus Fe spherules.

Note the association with haematite!

One problem with the dehydration-exfoliation idea - on Earth this does
not readily occur until 800 C !