Crescumulate layering in a gabbroic body on Seiland, northern Norway

• Published in: Geological Magazine
• Main Author: Robins, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1972
• Subjects: Geology; Norway; Seiland; Rognsund; Northern Norway
• Online Access: http://dx.doi.org/10.1017/s0016756800042813; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756800042813

Summary The cumulates and crescumulates in the Crescumulate Zone of the Rognsund gabbro are described. The olivine and olivine-clinopyroxene crescumulates contain large dendritic crystals of olivine due to rapid upward growth from cumulus nucleii on the temporary floor of the magma chamber. Crescumulate growth was accompanied by the bottom accumulation of primocrysts, some of which were enlarged by the normal adcumulus process. The crescumulates are thought to have originated when cumulus crystals sank from a labile environment near the roof of the body into a metastable environment on the floor.