The hydrogen got there thanks to slabs of water-rich oceanic basalt
forced down into the mantle along subduction zones.
The mantle plumes have produced up to 26 cubic kilometers of oceanic basalt
each year during the last 150 million years.
Mass-balance and noble-gas arguments indicate that most of the mantle is depleted but He and Ne isotopes, and convergence of Sr-Nd-Pb isotopic arrays suggest that FOZO is a somewhat primitive (unmelted) component common to all oceanic basalt
Marty, "Iron isotopic systematics of oceanic basalts
," Geochimica et Cosmochimica Acta, vol.
Geochemical fingerprinting of oceanic basalts
with applications to ophiolite classification and the search for Archean oceanic crust.
Trace element mobility during hydrothermal alteration of oceanic basalts
. Geochimica et Cosmochimica Acta, 42, 127-136.
McDonough, "Chemical and isotopic systematics of oceanic basalts
: implications for mantle composition and processes," Magmatism in the Ocean Basins, pp.
Engel, A.E.J., Engel, C.G., and Havens, R.G., 1965, Chemical characteristics of oceanic basalts
and the upper mantle: Geological Society of America Bulletin, v.
The researchers used a series of thermodynamic calculations to determine that the source material for BIFs must have come from oceanic rocks with a very low aluminum content, unlike modern oceanic basalts
that contain high levels of aluminum.
Evidence for microbial activity at the glass-alteration interface in oceanic basalts
. Earth Planet.