Article révisé par les pairs
| Résumé : | 110 samples from different massifs of the Rogaland igneous complex have been analyzed for whole-rock Pb isotopic compositions. These data show no evidence of rocks older than 1500 Ma. This is probably the time of extraction of the magmatic precursors from the mantle. The Pb data indicate a mantle origin for the parental magmas of the massiftype anorthosites and of the jotunitic series. Nevertheless, an origin by partial melting of mantle-derived basic material in the lower crust cannot be excluded, especially for the latter. The charnockitic rocks associated with the anorthosites could either be anatectic melts of the enclosing gneisses or residual liquids of anorthosite differentiation contaminated by slightly U-depleted lower-crustal material (although, in some cases, upper-crustal material has also contributed to the contamination). © 1986. |
