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The magnesium and calcium contents of sediments, especially pelites, as a function of age and degree of metamorphism


Van Moort, JC, The magnesium and calcium contents of sediments, especially pelites, as a function of age and degree of metamorphism, Chemical Geology, 12, (1) pp. 1-37. ISSN 0009-2541 (1973) [Refereed Article]

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Elsevier Scientific Publishing Company, Amsterdam

DOI: doi:10.1016/0009-2541(73)90025-9


The silicate and carbonate fraction of 98 non-metamorphic shale samples from the Australian platform and of different geological age were analysed for calcium, magnesium, ferrous iron and carbonate. Cainozoic and Mesozoic shales prove to be essentially calcitic, Cambrian and Proterozoic shales are essentially dolomitic and sideritic. A similar trend of high MgO values can be demonstrated for the silicate fraction of the old shales. Extensive literature study confirms these trends for shales and carbonate rocks from all over the world. Slates, hornfelses and schists are Mg rich and Ca poor, whether young or old.

Ronov's model of the evolution of the earth's crust ocean and atmosphere, explaining these trends, is critically reviewed but rejected because of impossible storage problems of calcium in the Proterozoic. The increased magnesium content of the old sediments is explained by calcium carbonate sweating out of the sedimentary column, magnesium introduction from altering volcanic rocks within the sedimentary pile and magnesium introduction from connate brines in sandstones. The increasing calcium content of all kinds of sediments with decreasing age is claimed to be related to preferential weathering of extrusive volcanic rocks and sweating out of calcium carbonate from the sedimentary column.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geochemistry
Research Field:Exploration geochemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Van Moort, JC (Dr Jan Van Moort)
ID Code:103632
Year Published:1973
Web of Science® Times Cited:15
Deposited By:Earth Sciences
Deposited On:2015-10-21
Last Modified:2015-11-13

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