Geology and Evaluation of the K2 Kimberlite, Koidu Mine, Sierra Leone, West Africa

Cluster analysis of 352 garnets from kimberlites, associated xenoliths, and diamonds has allowed recognition of 12 chemically coherent groups, on the basis of $$TiO_{2}, Cr_{2}O_{3}, FeO, MgO$$, and CaO contents. A flow-sheet classification scheme was created for classification of new garnets from kimberlites. Other points discussed are: correlation between the various oxides (including MgO-FeO correlations and their meaning); the chemistry of garnets from deformed Iherzolites; and the recognition of one group of garnets that probably crystallized from the kimberlite magma, as opposed to most other kimberlite garnets which are chemically the same as those occurring in xenoliths.

Xenolith

Classification scheme

10.1086/628143

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Citations (234)

Controls on the explosive emplacement of diamondiferous kimberlites: New insights from hypabyssal and pyroclastic units in the Diavik mine, Canada

Lithos (2020)

Madeline Tovey Andrea Giuliani David Phillips S. Moss

Xenolith

10.1016/j.lithos.2020.105410

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Citations (16)

KIMBERLITE MINERALS FROM VARGEM (MINAS GERAIS) AND REDONDAO (PIAUi) DIATREMES, BRAZIL; AND GARNET LHERZOL]TE XENOLITH FROM REDONDAO DIATREME

Revista Brasileira de Geociências (1977)

SVISERO DARCY P.MEYER HBNRY O. A.

Garnet, diopside and Mg-ilmenite have been analyzed from the Vargem diatreme, near Coromandel, State of Minas Gerais, and conlirmed to be comparable to similar minerals from kimberlites in South Africa, Siberia and the United States. Similar minerals occur downstream from the Vargem kimberlite in placer deposits in which diamond is found. The Redondão diatreme in southwest State of Piaul also contairs kimberlitic garnets as well as several xenoliths of crustal and mantle rocks. One xenolith, although extensively serpentinized, was originally a garnetJherzolite comparable in texture and garnet chemistry to those from kimberlites in Southern Africa.

Diatreme

Xenolith

Ilmenite

Diopside

Country rock

10.25249/0375-7536.1977113

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Citations (8)

The geology of the Letseng Kimberlites, Lesotho.

N. P. Lock

Mining operations at the Letseng Diamond Mine in Lesotho have facilitated the study of the fresh kimberlite in the two diatremes (Main and Satellite pipes), and the included lower crustal and upper mantle nodules. The present day erosion level of these diatremes is close to the transition from diatreme to crater facies in the model of a kimberlite pipe. The two pipes contain a variety of distinctive kimberlites. The zonation of large and dense xenoliths in the Main pipe garnetiferous kimberlite is believed to reflect the near-surface emplacement by a process of fluidisation. The geochemistry, xenolith and diamond contents of the two pipes indicate diverse origins despite their close proximity. REE abundances together with strontium and neodymium isotopic evidence indicates kimberlite genesis by a small degree of partial melting of slightly depleted chondritic mantle. Kimberlite dykes, both older and younger than the pipes, indicate some chemical and mineralogical evolution of the parent magma. The peridotites are chromite and/or garnet bearing lherzolites and harzburgites similar to those from other Lesotho kimberlites. Textures vary from coarse to mosaic porphyroclastic and extreme fluidal and LAD varieties. All garnet-bearing xenoliths display coronas on the garnets resulting from retrograde reaction to spinel facies. In some cases reaction has gone to completion. Granuloblastic aluminous spinel lherzolites and garnet/spinel lherzolites are interpreted to derive from normal garnet lherzolite by a process of reaction, deformation, chemical homogenisation and re-equilibration during diapiric upwelling. Several peridotites are interpreted to show chemical disequilibrium and do not plot on a smoothly curving 'fossil geotherm'. This disequilibrium is believed to result from readjustment of primary phase compositions during diapiric upwell. A synthesis is presented of the kimberlite genesis in the upper mantle, the subsequent diapiric ascent and the surface emplacement.

Diatreme

Xenolith

Chromite

Pentlandite

Country rock

Anorthosite

Asthenosphere

Source

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Citations (2)

Diamondiferous garnet harzburgites from the Finsch kimberlite, Northern Cape, South Africa

Contributions to Mineralogy and Petrology (1992)

Fanus Viljoen P. M. Swash M Otter D. J. Schulze P. J. LAWLESS

Xenolith

Peridotite

Mineral resource classification

Phlogopite

10.1007/bf00310887

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Citations (42)

Statistical Comparison between Pyroxenes from Kimberlites and Their Associated Xenoliths

The Journal of Geology (1977)

W. E. Stephens J. B. Dawson

Cluster analysis of 458 pyroxenes from kimberlites, associated xenoliths and diamonds has allowed recognition of 5 chemically distinct orthopyroxene groups and 10 distinct clinopyroxene groups from the $$TiO_{2}, Al_{2}O_{3}, Cr_{2}O_{3}$$, FeO, MgO, CaO, and $$Na_{2}O$$ contents. Names assigned to these groups convey their distinctive chemical features. Because many groups contain cases from both kimberlite and xenoliths, some kimberlite pyroxenes may derive from fragmented xenoliths. However from size alone, large discrete orthopyroxene crystals, discrete sub-calcic diopside nodules and low-Cr diopsides intergrown with ilmenite are apparently not xenolithic; nor are the minute diopside crystals growing in the kimberlite matrix. Pyroxene inclusions in diamonds and pyroxenes coexisting with diamond in eclogite and peridotite xenoliths range widely in chemical composition.

Xenolith

Diopside

Pyroxene

Ilmenite

Peridotite

Pyrope

10.1086/628317

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Citations (59)

The geology and mineralogy of the Anuri kimberlite, Nunavut, Canada

Lithos (2004)

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