The chemistry of gabbro/amphibolite transitions in South Norway

Trace element data are presented for sixteen gabbro (hyperite)/amphibolite pairs which were collected from geological situations where it seems clear that the amphibolite formed from material similar in composition to that of the adjacent hyperite. The metamorphism of hyperite to amphibolite was not isochemical with respect to some trace elements. Cl, V and Rb were increased, as possibly was Zr. S and Zn were diminished, as possibly was Co. Sr and Ba are rather constant in the hyperites and appear to have been irregularly dispersed during the amphibolitisation. The trace element movement patterns are consistent with the known changes in the major elements, which have been reported earlier (Elliott, 1973). The introduced material was added during metamorphism under amphibolite facies conditions, by upward migration from an originally subjacent granulite facies zone. The evidence supports a hydrous fluid diffusion process for the mechanism of transfer.