The zoned Kleivan granite — an end member of the anorthosite suite in southwest Norway

The intrusive Kleivan granite, Farsund area, SW Norway, shows a gradual unilateral zonation from charnockite through hornblende granite to biotite granite. Strong geochemical fractionation includes K/Rb variation from 478 to 121 and Rb/Sr from 0.13 to 26.4, and points towards a petrogenetic relationship with anorthosite suite rocks not apparent in the more homogeneous charnockites of the area. Close geochemical and petrographic similarity between the charnockitic part of the Kleivan granite and the Farsund charnockite suggest derivation of both plutons from a common source. Quantitative trace element modelling, based on crystal fractions derived from petrographic mixing calculations relating four main rock types, suggests that the Kleivan granite zonation may result from a fractional crystallization process, involving noritic and mangeritic cumulate-kindreds. The results therefore indicate strongly that simple relationships exist between charnockite and anorthosite rock-kindreds. A partial fusion model for the Farsund charnockite is favoured, since this explains the development of an anomalous Sr-87/Sr-86 ratio (0.7128 compared with 0.7053 for the Kleivan granite) and higher Rb/Sr ratios, other trace elements being similar for the two related charnockites. The recognition of substantial amounts of acid end members to the anorthosite suite of the Rogaland province supports an origin in common with andesine-type anorthosites for this igneous province.