Jp. Li et K. Jacques, Experimental study of partial melting of mantle peridotite - A discussion about the genesis of silica-rich fluids (melts), ACT GEO S-E, 73(4), 1999, pp. 395-403
Experiments on partial melting of mantle lherzolite have been realized at 0
.6 and 1.0 GPa and the chemical compositional variations of melts during di
fferent melting stages have been first discussed. The results show that the
trends of variations in SiO2, CaO, Al2O3, Na2O and TiO2 are different at d
ifferent melting stages. The melts produced at lower pressure are richer in
SiO2 than those at higher pressure. The mantle-derived silica-rich fluids
(silicate melts) are polygenetic, but the basic and intermediate-acid silic
ate melts in mantle peridotite xenoliths from the same host rocks, which ha
ve equivalent contents of volatile and alkali components and different cont
ents of other components, should result from in-situ (low-degree) partial m
elting of mantle peridotite under different conditions (e.g. at different d
epths, with introduction of C-O-H fluids or in the presence of metasomatic
minerals). The intermediate-acid melts may be the result of partial melting
(at lower pressure) Opx + Sp + K-Na-rich fluid + (Amphi) + (Phlog) = Ol melt. But the intermediate-acid magmas cannot be produced from the partial
melting of normal mantle peridotite unless the crustal materials are introd
uced to some extent.