At Rock properties I find a table that shows basalt as 0.1% to 1.0% porosity, and granite as 0.5% to 1.5% porosity; that's not very porous for either type, and the granite is more porous than the basalt.
Sandstone that's permeable enough to make decent reservoir rock for oil (and, I presume, for water) has ten times that porosity or better. And, in any case,
whatever, porosity is a bulk property of rock. The pores are between grains, where the grains, like zircons, that a geologist hand-picks to do dating on are NOT porous. And argon, yet once again, does not enter into "cationic and anionic exchange" or otherwise give a red rat's ass about chemical reactions of any sort under conditions encountered in rocks.
Like JonF said: evidence, please.
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