Magmatic Evolution and Ascent History of the Aries Micaceous Kimberlite, Central Kimberley Basin, Western Australia: Evidence from Zoned Phlogopite Phenocrysts, and UV Laser 40Ar/39Ar Analysis of Phlogopite-Biotite.

Downes, P. J., Wartho, J.-A. and Griffin, B. J. (2006) Magmatic Evolution and Ascent History of the Aries Micaceous Kimberlite, Central Kimberley Basin, Western Australia: Evidence from Zoned Phlogopite Phenocrysts, and UV Laser 40Ar/39Ar Analysis of Phlogopite-Biotite. Journal of Petrology, 47 (9). pp. 1751-1783. DOI 10.1093/petrology/egl026.

[img] Text
Downes.pdf - Published Version
Restricted to Registered users only

Download (1193Kb) | Contact

Supplementary data:

Abstract

The Neoproterozoic Aries kimberlite was emplaced in the central Kimberley Basin, Western Australia, as a N–NNE-trending series of three diatremes infilled by lithic-rich kimberlite breccias. The breccias are intruded by hypabyssal macrocrystic phlogopite kimberlite dykes that exhibit differentiation to a minor, high-Na–Si, olivine–phlogopite–richterite kimberlite, and late-stage macrocrystic serpentine–diopside ultramafic dykes. Mineralogical and geochemical evidence suggests that the high-Na–Si, olivine–phlogopite–richterite kimberlite was derived from the macrocrystic phlogopite kimberlite as a residual liquid following extended phlogopite crystallization and the assimilation of country rock sandstone, and that the macrocrystic serpentine–diopside ultramafic dykes formed as mafic cumulates from a macrocrystic phlogopite kimberlite. Chemical zonation of phlogopite–biotite phenocrysts indicates a complex magmatic history for the Aries kimberlite, with the early inheritance of a range of high-Ti phlogopite–biotite xenocrysts from metasomatized mantle lithologies, followed by the crystallization of a population of high-Cr phlogopite phenocrysts within the spinel facies lithospheric mantle. A further one to two phlogopite–biotite overgrowth rims of distinct composition formed on the phlogopite phenocrysts at higher levels during ascent to the surface. Ultra-violet laser 40Ar/39Ar dating of mica grain rims yielded a kimberlite eruption age of 815·4 ± 4·3 Ma (95% confidence). 40Ar/39Ar laser profiling of one high-Ti phlogopite-biotite macrocryst revealed a radiogenic 40Ar diffusive loss profile, from which a kimberlite magma ascent duration from the spinel facies lithospheric mantle was estimated (assuming an average kimberlite magma temperature of 1000°C), yielding a value of ∼0·23–2·32 days for the north extension lobe of the Aries kimberlite.

Document Type: Article
Keywords: 40Ar/39Ar; diamond; kimberlite; mantle metasomatism; phlogopite–biotite
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1093/petrology/egl026
ISSN: 0022-3530
Date Deposited: 24 Nov 2015 12:57
Last Modified: 24 Nov 2015 12:57
URI: http://oceanrep.geomar.de/id/eprint/30252

Actions (login required)

View Item View Item

Document Downloads

More statistics for this item...