Postmagmátische Differentiation eines präkambrischen Granitintrusivs: Das Örö-Hamnö-Massiv in Südostschweden

Publisher Website
Google Scholar
Abstract
Based mainly on geochemical evidence, the Örö-Hamnö-Massif is divided into the following zones (from the margin towards the centre): The leucogranites show the highest K/Rb-, K/Cs-, Rb/Cs- and Ba/Cs-ratios among the granitoids of the Massif. Thus, an interpretation of the leucogranites a a late fraction of a granitic magma, or as a product of remelting, cannot be accepted. Most likely, the first granitoids intruded originally as an anatectic melt (red gneissic granites, with zone IV as contact zone). Differentiation in the solid state during the postmagmatic stage gave rise to the leocogranites (mobilizate) and the grey gneissic granites (“restite”, cf. Mehnert, 1968). A considerable loss of alkali metals seems to have been connected with the differentiation process, indicating the importance of such a process as a source of alkali in basement complexes. Attention is drawn to the possibility of using the differences in the trends of K/Rb-ratios between leucogranites formed by fractional crystallization of a melt, and by differentiation in the solid state, respectively, in order to distinguish between these processes. A minor body with granodioritic composition, showing rather “normal” behavior of the trace elements, is interpreted as an anatectic intrusion, which was emplaced subsequently to the main intrusion. Late faulting placed the granodiorites in their presents position.

This publication has 44 references indexed in Scilit: