www.MantlePlumes.org © MantlePlumes.org Eruptive Temperatures of the Paleogene Picrites of West Greenland and Baffi n Bay
Tholeiitic picrites from West Greenland and Padloping Island on either side of Baffi n Bay have long been considered to be high-temperature eruptives from the ancestral Iceland mantle plume. Olivine-liquid FeO-MgO equilibria have been used to backtrack to calculated parental compositions, giving as...
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| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.497.4753 http://www.mantleplumes.org/WebpagePDFs/Greenland.pdf |
| Summary: | Tholeiitic picrites from West Greenland and Padloping Island on either side of Baffi n Bay have long been considered to be high-temperature eruptives from the ancestral Iceland mantle plume. Olivine-liquid FeO-MgO equilibria have been used to backtrack to calculated parental compositions, giving as much as 20.2 % MgO in the melt, and to estimate eruptive temperatures for them of close to 1500°C. Crystallization histories, however, indicate that these picrites are hybrids between olivine-charged crystal sludges and differentiated magmas that followed a low-pressure olivine-plagioclase-clinopyroxene cotectic during differentiation. The glasses give eruptive T = 1170-1220°C. Much of the olivine in the rocks, especially the very magnesian olivine (Fo92-93), was incorporated by magma mixing and likely scavenging of minerals from mantle wall rock. The rocks are thus hybrids and the olivine in them neither lies along a single olivine-controlled liquid line of descent, nor can it be linked to the host compositions, which are too high in iron. Therefore they are unsuitable for the backtrack procedure. Compositions of Cr-spinel support a mixing history for the picrites, but the procedure of Poustovetov & Roeder (2000) suggests temperatures of spinel crystallization no higher than about 1340°C, generally less than 1300°C, and MgO contents no higher than ~16 % in the most magnesian parental melt strains. |
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