The Significance of K-Ar Dates on Altered Kimberlitic Phlogopite from Riley County, Kansas

Brookins, Douglas G.

doi:10.1086/627412

Cited by 11 publications

(3 citation statements)

References 6 publications

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“…Kennedy & Nordlie (1968) note that kimberlite pipes often contain shale fragments rich in hydrocarbon which, subjected to temperatures of only 200-300°C, would have been drastically altered. Brookins (1969) notes that preemplacement K-Ar ages from altered kimberlitic phlogopite (collected from kimberlite pipes in Riley County, Kansas) are consistent with a temperature of injection as low as 100-200°C.…”

Section: Introductionmentioning

confidence: 95%

A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

McFadden

1977

Geophysical Journal International

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Seventeen wall rock samples close to the contact and seven accidental inclusions have been collected from four South African kimberlite pipes. Magnetic measurements on these samples have been analysed to determine the viscous partial thermoremanence (VPTRM) acquired by them at the time of the emplacement of the kimberlite. Numerical integration of the heat flow equation for a thermal model including convection of the emplaced material has been performed to determine an upper limit for the emplacement temperatures required to cause the observed WTRM. It is concluded that in these pipes the kimberlitic material, at least down to the levels studied, was almost certainly emplaced at a temperature of less than 35OoC. The emplacement temperature cannot have been greatly overestimated and it is suggested that the emplacement temperature was about 30OoC.

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Section: Introductionmentioning

confidence: 95%

A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

McFadden

1977

Geophysical Journal International

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“…This phenomenon was initially interpreted as being because of the presence of excess Ar, i.e. 40 Ar in excess of the 40 Ar* produced by the radioactive decay of 40 K (Lovering & Richards, 1964;Zartman et al, 1967;Brookins, 1969;Kaneoka & Aoki, 1978;Fitch & Miller, 1983;Allsopp & Roddick, 1985;Phillips & Onstott, 1986. The presence of excess Ar in the mantle phlogopites was assigned to high Ar partial pressures preceding, or coinciding with, kimberlite eruption (e.g.…”

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confidence: 99%

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

Wartho²,

Griffin

2006

Journal of Petrology

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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, olivinephlogopite-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. Ultraviolet laser 40 Ar/ 39 Ar dating of mica grain rims yielded a kimberlite eruption age of 815. 4 ± 4. 3 Ma (95% confidence). 40 Ar/ 39 Ar laser profiling of one high-Ti phlogopite-biotite macrocryst revealed a radiogenic 40 Ar 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.

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“…Zartman et al 1967;Paul et al 1975;Allsopp & Roddick 1985;Phillips et al 1998Phillips et al , 1999. However, K-Ar measurements and 40 Ar/ 39 Ar vacuum furnace step-heating on larger phlogopite grains were found to be complex and were interpreted as being contaminated by excess 40 Ar (Lovering & Richards 1964;Zartman et al 1967;Brookins 1969;Kaneoka & Aoki 1978;Fitch & Miller 1983;Allsopp & Roddick 1985;Phillips & Onstott 1986, 1988, denned as 40 Ar in excess of radiogenic 40 Ar ( 40 Ar*) produced by the radioactive decay of 40 K. The presence of excess 40 Ar in mantle xenoliths was assigned to high partial pressures of Ar (P Ar ) preceding or coinciding with kimberlite eruption (e.g. Kaneoka & Aoki 1978;Fitch & Miller 1983;Phillips 1991).…”

mentioning

confidence: 99%

⁴⁰ Ar/ ³⁹ Ar ages in mantle xenolith phlogopites: determining the ages of multiple lithospheric mantle events and diatreme ascent rates in southern Africa and Malaita, Solomon Islands

Wartho

Kelley²

2003

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Kimberlites are extraordinary natural phenomena, ascending through the Earth's lithosphere, entraining xenoliths, to erupt at the surface within hours to days of their inception deep within the lithospheric mantle. With the realization that some Ar/Ar phlogopite grain core ages may be indicative of geological events, we have undertaken high spatial resolution Ar/Ar dating of phlogopites in xenoliths and megacrysts from Kimberley, Monastery and Letseng in southern Africa, and Malaita, in the Solomon Islands, to test whether other mantle phlogopite cores may yield meaningful ages.Modelling of Ar diffusive loss profiles from phlogopite grain boundaries to cores provides information on both the eruption age and the duration of outgassing within the kimberlite magma, and hence yields estimates on diatreme ascent rates. The ascent durations are very similar for all of the southern African pipes studied, yielding durations of 0.9-6.9 days, assuming an average kimberlite magma temperature of 1000 °C. These can be compared to estimates from phlogopite xenoliths from Siberian diamond-bearing kimberlites yielding ascent durations of 2-15 hours (assuming the same magma temperature).

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The Significance of K-Ar Dates on Altered Kimberlitic Phlogopite from Riley County, Kansas

Cited by 11 publications

References 6 publications

A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

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

⁴⁰ Ar/ ³⁹ Ar ages in mantle xenolith phlogopites: determining the ages of multiple lithospheric mantle events and diatreme ascent rates in southern Africa and Malaita, Solomon Islands

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The Significance of K-Ar Dates on Altered Kimberlitic Phlogopite from Riley County, Kansas

Cited by 11 publications

References 6 publications

A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

A palaeomagnetic determination of the emplacement temperature of some South African kimberlites

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

40 Ar/ 39 Ar ages in mantle xenolith phlogopites: determining the ages of multiple lithospheric mantle events and diatreme ascent rates in southern Africa and Malaita, Solomon Islands

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⁴⁰ Ar/ ³⁹ Ar ages in mantle xenolith phlogopites: determining the ages of multiple lithospheric mantle events and diatreme ascent rates in southern Africa and Malaita, Solomon Islands