Diamondiferous garnet harzburgites from the Finsch kimberlite,Northern Cape,South Africa |
| |
Authors: | K S Viljoen P M Swash M L Otter D J Schulze P J Lawless |
| |
Institution: | (1) Anglo American Research Laboratories, Crown Mines, P.O. Box 106, 2025, South Africa;(2) Department of Geochemistry, University of Cape Town, Rondebosch, 7700, South Africa;(3) Department of Geology, University of Toronto, Erindale College, L5L1C6 Mississauga, Ontario, Canada;(4) Geology Department, Finsch Mine, 8140 Lime Acres, South Africa;(5) Present address: Bernard Price Institute for Geophysical Research, University of the Witwatersrand, WITS 2050 Johannesburg, South Africa |
| |
Abstract: | Two xenoliths of garnet harzburgite from the Finsch kimberlite, South Africa, have been found to contain diamond. One of the xenoliths has mineral compositions typical of low-T coarse textured garned peridotites, whereas minerals in the other are similar but not identical to most peridotite-suite minerals included in diamonds, especially in the low-CaO content of garnet. Geothermobarometric calculations show both xenoliths equilibrated at temperatures above 1,100°C and pressures>55 kbar, which is near the low-pressure end of the range of equilibration conditions for diamond-free garnet lherzolites and garnet harzburgites from Finsch. The chemistries of the minerals in the two rocks are distinctly different to most of the mineral inclusions in Finsch diamonds. This, as well as the different 13C compositions between xenolith diamonds (-2.8 to-4.6 ) and diamonds in the kimberlite (generally<-4.3 ) suggest different origins or sources for the diamonds. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|