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A triple S-shaped compositional profile in a Karoo dolerite sill - evidence of concurrent multiple fractionation processes

Citation

Cawthorn, RG and Chistyakova, SY and Latypov, RM and Kamenetsky, VS and Danyushevsky, LV, A triple S-shaped compositional profile in a Karoo dolerite sill - evidence of concurrent multiple fractionation processes, Geology, 45, (7) pp. 603-606. ISSN 0091-7613 (2017) [Refereed Article]

Copyright Statement

Copyright 2017 Geological Society of America

DOI: doi:10.1130/G38917.1

Abstract

Thick dolerite sills show a range of vertical geochemical variation trends attributable to various processes during slow crystallization. We have identified chemical parameters in a 169-m-thick sill from the Karoo igneous province in South Africa that define three different lower crossover levels (maximum or minimum concentrations) creating S-shaped variation trends. The crossover level for wholerock MgO is at 20 m height (due to mechanical sorting of olivine); the anorthite content of plagioclase is at 52 m (due to addition of primitive magma); and that of the incompatible trace elements is at 75 m (due to different proportions of early formed grains to trapped liquid). Each process can operate independently and concurrently, leading to their maximum effects occurring at different levels in the intrusion. The independence of these processes and the triple S-shaped geochemical profiles have not been recognized before in any mafic-ultramafic sills.

Item Details

Item Type:Refereed Article
Keywords:dolerite, fractionation, Karoo, igneous, compositional profile, plagioclase
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Kamenetsky, VS (Professor Vadim Kamenetsky)
Author:Danyushevsky, LV (Professor Leonid Danyushevsky)
ID Code:117813
Year Published:2017
Deposited By:Earth Sciences
Deposited On:2017-06-28
Last Modified:2018-04-26
Downloads:0

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