You’re not nit picking at all. The only way I could figure to find oceanic basalt that old is if it became part of a very old crust and thus never went back into the mantel. Help me out if there is another way.
You got that right. During the plate tectonics some fragemnts of the oceanic plate were folded, fractured, and elevated into positions mixed with the lighter granitic crustal plates now recognized as some of the earliest surviving continental plate cratons. Having become associated with the earliest continental plates or integrated into the continental plates, these pieces of early oceanic crust escaped subduction into the mantle and remelting. These few early pieces of oceanic crustal rock can be found in conjunction with the earliest continental plate cratons in places such as Greenland, Canada, Australia, the Easterm Mediterranean Seea, and elsewhere.
Chemosynthetic life is anaerobic and therefore predates aerobic photosynthetic lifeforms. dating from their advent about 2.2 billion years ago.