Results 91 to 100 of about 141 (134)

Petrogenesis of Kaapvaal lamproites (aka orangeites) constrained by the composition of olivine and similarities with kimberlites and other diamondiferous lamproites

Lithos, 2021
Abstract Kaapvaal lamproites, also known as orangeites, are H2O-rich, diamondiferous, highly micaceous, ultrapotassic rocks. Olivines in kimberlites have been shown to be extremely useful in tracking melt evolution, highlighting the importance of the chemical effects of SCLM assimilation on asthenosphere-derived melts. Kaapvaal lamproites are derived
Geoffrey H. Howarth, Thendo Nembambula
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Sublithospheric melt input in cratonic lamproites

Geology, 2022
AbstractCratonic lamproites are diamondiferous ultrapotassic rocks that are emplaced through thick continental lithosphere and thought to derive from melting of metasomatized (i.e., geochemically enriched) regions of the subcontinental lithospheric mantle (SCLM).
Sarkar, Soumendu, Giuliani, Andrea; id_orcid0000-0002-6823-2807, Phillips, David, Howarth, Geoffrey H., Ghosh, Sujoy, Dalton, Hayden   +5 more
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Potassic Rocks and the Lamproite Clan

1991
Sorenson (1974, p.7), in a review of the varied definitions proposed for alkaline rocks, concludes that the term has been used by so many petrologists in so many different ways and usually so vaguely that “it is hard to know what is covered by the term.” Alkalinity implies enrichment in the alkali elements, sodium and potassium, but this in turn can be
Roger H. Mitchell, Steven C. Bergman
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Smoky Butte lamproite, Montana

1989
exaly   +2 more sources

Lamproites and Kimberlites in India

Journal of the Geological Society of India, 1989
Abstract New petrographic and mineral chemistry data are presented to show that the Majhgawan and Hinota pipes are olivine lamproite lapilli tuffs and not kimberlites as suggested elsewhere. These bodies, therefore, comprise a newly recognized province of diamondiferous olivine lamproites.
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Tectonic Framework of Lamproite Genesis

1991
Lamproites are temporally and spatially widespread; however, they form only volumetrically minor igneous occurrences relative to most, if not all, other mantle-derived alkaline rocks. In fact, all presently known lamproite bodies comprise an aggregate volume of merely 75 km3, corresponding to a sphere with a radius of under 3 km or a 20-m-thick layer ...
Roger H. Mitchell, Steven C. Bergman
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Lamproites in North Vietnam? A Re-Examination of Cocites

The Journal of Geology, 1986
The term "cocite" was coined by Lacroix for rocks that share with lamproites a number of characteristics, among them the presence of K-rich minerals and high MgO and $$K_{2}O$$. A re-examination of the type specimens indicates the absence of Ti-rich oxides and K-richterite, but the presence of Ti-rich phlogopites, in addition to previously recognized ...
Wagner, Christiane, Velde, Danielle
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Melting experiments on SiO 2 -rich lamproites to 6.4 GPa and their bearing on the sources of lamproite magmas

Mineralogy and Petrology, 2002
Supra-solidus phase relations at temperatures and pressures ranging from 800 to 1700 °C and 2 to 6.4 GPa have been determined experimentally for three silica-rich lamproites: hyalo-leucite phlogopite lamproite (Oscar, West Kimberley); sanidine richterite lamproite (Cancarix, Murcia-Almeria); and phlogopite transitional madupitic lamproite (Middle Table
R. H. Mitchell, A. D. Edgar
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Paleomagnetism of some Indian kimberlites and lamproites

Precambrian Research, 1994
Abstract Consistent vectors have been isolated by AF demagnetization of 22 cores from two sites in Proterozoic kimberlites in the Wajrakarur district of the Dharwar Craton ( N =2, D =156, I =−71, K =1596, α =6.3, Pole WAJ 45.4°S, 121.5°W), and 12 cores from two sites from the mine at Majhgawan in the Panna district in the Aravalli craton ( N =2,
K.C. Miller, R.B. Hargraves
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The oxidation state of lamproitic magmas

TMPM Tschermaks Mineralogische und Petrographische Mitteilungen, 1985
Olivine leucitites from the Gaussberg volcano, Antarctica are primitive members of the lamproite group of ultrapotassic rocks. They are glass rich, have an Mg number of around 70, and carry spinel lherzolite xenoliths. Liquidus phase fields and compositions were studied experimentally at atmospheric pressure with controlled oxygen fugacities.
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