Due to routine maintenance, access to the Library Open Repository will be interrupted on the morning of Friday 12th February.
We apologise for any inconvenience.

Library Open Repository

Kimberlite melts rich in alkali chlorides and carbonates: A potent metasomatic agent in the mantle

Downloads

Downloads per month over past year

Kamenetsky, MB and Sobolev, AV and Kamenetsky, VS and Maas, R and Danyushevsky, LV and Thomas, R and Pokhilenko, NP and Sobolev, NV (2004) Kimberlite melts rich in alkali chlorides and carbonates: A potent metasomatic agent in the mantle. Geology, 32 (10). pp. 845-848.

[img] PDF
Geology-Kimberl...pdf | Request a copy
Full text restricted
Available under University of Tasmania Standard License.

Abstract

Kimberlite magmas, as the deepest probe into Earth's mantle (>150 km), can supply unique information about volatile components (hydrogen, carbon, chlorine, sulfur) in mantle-derived melts and fluids. All known kimberlite rocks are not suitable for studies of mantle volatiles because of their pervasive postmagmatic alteration; however, this study discusses an exceptionally fresh group I kimberlites (<0.5 wt% H2O) from the Udachnaya-East diamondiferous pipe in Siberia. Kimberlite groundmass, in addition to euhedral olivine and calcite, is extremely enriched (at least 8 wt%) in water-soluble alkali chlorides, alkali carbonates, and sulfates (ratio 5:3:1), and often shows immiscibility textures. A primary magmatic origin of alkali chlorides and alkali carbonates is confirmed by the study of strontium isotopes in the water- and dilute acid-leachates of the groundmass (Sr-87/Sr-86 = 0.7069 and 0.7050) that contrast with much more radiogenic isotope composition of the Cambrian platform sedimentary rocks and the Udachnaya-East mine-site brines. Melt inclusions in groundmass olivine, composed of halite, sylvite, alkali-Ca carbonates, phlogopite, olivine, and CO2 fluid, were used to determine the composition and evolution of the kimberlite melt prior to emplacement. Melt inclusions show immiscibility between chloride and carbonate liquids at <600oC in heating stage experiments. The chloride and carbonate enrichment in the kimberlite parental magma suggests the presence of a powerful agent for chemical modifications (metasomatism) in the mantle and crust.

Item Type: Article
Keywords: kimberlite; mantle volatiles; chlorine; carbonate; metasomatism; melt inclusions; immiscibility; oldoinyo-lengai; peridotite xenoliths; lithospheric mantle
Journal or Publication Title: Geology
Page Range: pp. 845-848
Date Deposited: 10 Aug 2006
Last Modified: 18 Nov 2014 03:11
Item Statistics: View statistics for this item

Repository Staff Only (login required)

Item Control Page Item Control Page