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Unformatted text preview: m Taylor 1997 as adapted from Cathles 1983; Abitibi background = +6 to +9 Wednesday, 15 August, 12 Kidd Creek δ18O in rhyolite s After Huston and Taylor (1999) Wednesday, 15 August, 12 Wednesday, 15 August, 12 Diamonds and Oxygen Isotopes http:// www.visitingdc.com/ images/hopediamond-picture.jpg Wednesday, 15 August, 12 Chapter 19: Continental Alkaline Magmatism. Kimberlites Figure 19.21. Hypothetical cross section of an Archean craton with an extinct ancient mobile belt (once associated with subduction) and a young rift. The low cratonal geotherm causes the graphite-diamond transition to rise in the central portion. Lithospheric diamonds therefore occur only in the peridotites and eclogites of the deep cratonal root, where they are then incorporated by rising magmas (mostly kimberlitic- “K”). Lithospheric orangeites (“O”) and some lamproites (“L”) may also scavenge diamonds. Melilitites (“M”) are generated by more extensive partial melting of the asthenosphere. Depending on the depth of segregation they may contain diamonds. Nephelinites (“N”) and associated carbonatites develop from extensive partial melting at shallow depths in rift areas. After Mitchell (1995) Kimberlites, Orangeites, and Related Rocks. Plenum. New York. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. Wednesday, 15 August, 12 Chapter 19: Continenta...
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This document was uploaded on 03/06/2014 for the course ES 4502 at Memorial University.

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