Using LA-ICPMS Mapping and Sector Zonation to Understand Growth and Trace-Element Partitioning in Sector-Zoned Clinopyroxene Oikocrysts from the Norra Ulvö Gabbro, Sweden

• Published in: Journal of petrology Vol. 48; no. 4; pp. 711 - 728
• Main Authors: Claeson, D. T., Meurer, W. P., Hogmalm, K. J., Larson, S.-Å.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01-04-2007; Oxford Publishing Limited (England)
• Subjects: cumulate; oikocryst; trace elements; layered intrusion; sector-zoned
• ISSN: 0022-3530; 1460-2415
• DOI: 10.1093/petrology/egl079

Petrographic analysis and geochemical mapping are used to characterize sector-zoned clinopyroxene oikocrysts from the Norra Ulvö Gabbro, Sweden. The sector zones are distinguished optically and by differences in TiO2 , Al2O3 , and incompatible trace elements. The oikocrysts grew with a branching morphology as evidenced by numerous triple points in a single oikocryst. Oikocrysts grew from the center of domains outward and the growth within individual domains did not completely fill the space until the oikocryst had reached its full size. In some domains sector zones are overgrown by growth zones that lack sectors. The last crystallization infilled channels that allowed late-stage liquids to move through the oikocryst at the contacts with chadacrysts. Calculation of partitioning behavior of trace elements between adjacent sectors shows it to be regular and consistent with experimental results. The data show that the CaTiAl2O6 component greatly enhances the solubility of most incompatible elements in clinopyroxene.