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Topic: Komatiite

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	Komatiite - Wikipedia, the free encyclopedia
		The youngest komatiites are from the island of Gorgona on the Caribbean oceanic plateau.
		Komatiitic magmas are considered to be a source for spatially associated tholeiite basalts based on a study linking the two rock types in the Karelian greenstone belt of northwest Russia.
		Komatiites are composed of forsteritic olivine (Fo90 and upwards), calcic and often chromian pyroxene, anorthite (An85 an upwards) and chromite.
	en.wikipedia.org /wiki/Komatiite (948 words)

	B.I.Malyuk - Shortcut of the Doctor Sciences Dissertation
		Komatiite magmatism attenuated in proportion to the reduction of the permeability of crust due to thermal remobilisation, whereas in the association with the transitional basaltic chambers appeared the crustal foci of magma generation, and also, as a result - stratified basalt-rhyodacite chambers.
		Malyuk, B.I. and Sivoronov, A.A., On the classification of komatiites.
		Malyuk, B.I., Sivoronov, A.A., Classification, petrology and metallogeny of komatiites.
	www.geofuel.lviv.net /PETGF/MAVTO/avtoe.htm (10025 words)

	Journal of the Geological Society: Vesicles in thick komatiite lava flows, Kambalda, Western Australia (Site not responding. Last check: 2007-10-11)
		Traditionally, vesicles have been considered to be rare in komatiites, however, field studies at Kambalda, Western Australia, and critical literature examination suggest that vesicle presence and content in komatiites are grossly underestimated.
		Komatiite lavas are commonly divided into an upper spinifex or A zone, and a lower B zone, which consists of predominantly cumulus olivine.
		Vesicle diapirs are associated with vesicle-rich horizons in komatiite lavas at Kambalda.
	www.findarticles.com /p/articles/mi_qa3721/is_200001/ai_n8889034 (1100 words)

	Komatiite
		The Komatiites are known to host nickel deposits in Australia and gold deposits in Australia, South Africa and elsewhere in the world.
		Guyana Komatiites are at least 1.9 billion years old and must have tapped their magnas from great depth.
		Komatiite extends over several hundreds of hectares and Guyanor hopes to find parts where larger diamonds may occur in economic quantities.
	www.gempulse.com /diamondpulse/komatiite-diamond.asp (434 words)

	Hawaiian lava flows help in the study of 3-billion-year-old lava flows
		Named komatiite (koh-mat-tee-ite) after the Komati River in South Africa where first described, these lava flows have never been observed erupting, and their volcanic nature has been deduced from the properties and textures of the rocks.
		Second, komatiite lavas erupted much hotter, at a temperature around 1,600 degrees C (2,900 degrees F) rather than at 1,150 degrees C (2,100 degrees F), the temperature typical for Hawaiian eruptions.
		Komatiite flows seem to be extensive, but because of their limited exposure (remember the squeezing, folding, and cracking), none have ever been completely traced from one edge to the other or from the vent to the flow's toe.
	hvo.wr.usgs.gov /volcanowatch/2000/00_09_28.html (898 words)

	shetland catpund
		This and major element analysis of the rock have led to the conclusion that these rocks were originally laid down as a sequence of komatiite lava flows.
		Thus komatiites are extremely rare in rocks as young as these (Lower Ordovician) as most are found in much older Archean rocks, so must be due to much deeper fracturing of the Earth’s crust than is normal in crustal extension events of this age.
		The deep fracture that produced these komatiite lavas may been the splitting of the crust to form a constructive plate margin in an intra-continental basin related to the creation of a new ocean, the Iapetus.
	www.fettes.com /shetland/Geology_Shetlland/catpund.htm (930 words)

	Nickel 2000, Module 1A - Deposit Descriptions
		The komatiitic interval is up to 2500 m thick while the individual komatiite bands can be correlated for more than 100 km along strike.
		Three west facing komatiite units, the Eastern, Central and Western ultramafic units and a thin early flow are identified at Mt Keith.
		Further east is a felsic unit of volcanics and sediments and intermittent komatiites and fl sulphidic graphitic shales.
	www.portergeo.com.au /tours/nickel2000/m1a.asp (2406 words)

	Plumes (no frames) (Site not responding. Last check: 2007-10-11)
		Komatiites are rare after the Archaean and are especially rare in Phanerozoic greenstones.
		Campbell et al (1989) suggest basalts occur from the melting of a plume head, whereas komatiite is derived from the melting of the hot plume tail.
		This has implications for plate tectonics, but may also mean that firstly the tails of plumes were hot enough in the Archaean for komatiite melts to form from plume tails and that possibly plumes may have been more prevalent in the Archaean mantle than they are today.
	www.tad.me.uk /plumes/komatiite.htm (201 words)

	Abstract Listing - Text Format (Site not responding. Last check: 2007-10-11)
		2729 Ma horizon of peridotitic komatiite and lesser komatiitic basalt and basalt.
		However, some basalts and komatiitic basalts may be related to komatiite by crystal fractionation with little or no crustal contamination.
		Komatiite in the central belt most closely associated with metasedimentary rocks and situated at a higher stratigraphic level is strongly LREE-depleted (La/Sm The regional REE variations of parental komatiite may reflect subtle amounts of crustal interaction.
	gac.esd.mun.ca /gac_2003/search_abs/sub_program.asp?sess=98&form=10&abs_no=711 (400 words)

	Archaean MetaBasalts & MetaAndesites
		The body of a komatiite flow is composed of close packed olivines sometimes of 1 cm diameter and it is assumed they were formed from a very hot, very high degree melt magma.
		Komatiites may have 35% - 40% or more MgO and as high as 4000 ppm Ni, but this appears in some cases to be due to olivine accumulation.
		Komatiites are found at Noranda - Chibougamau as well as in the Onverwacht series of South Africa and the Yilgarn and Pilbara Cratons of West Australia and in Finland.
	www.geokem.com /archaean.html (3506 words)

	GG/HIGP Seminar Series: January 10,2003
		The resulting volcanic architecture is that of parent lava pathways flanked by a broad, complex, stratigraphic sequence of episodically-emplaced, variably-inflated lateral lobes and subsidiary flows fed by their own distributary pathways.
		The thermal regimes required to develop recurring lithological field relationships, facies variations, and internal structures of flow units which we have identified in komatiite sequences are consistent with those required by the volcanic architecture of their basaltic analogues.
		We have therefore applied the dynamic inflationary model to the evolution of komatiite flow fields and developed a broad volcanic facies classification that is commensurate with this model and results from detailed field-based studies.
	www.soest.hawaii.edu /GG/TGIF/tgif_030110.html (234 words)

	Komatiites
		Most komatiites have been shown to have source regions that were depleted by a previous melt extraction event, and so the actual amount of melting that produced the komatiites is probably lower than the numbers given above.
		O required the Barberton komatiites to be produced in a subduction zone, or whether a hydrous plume scenario was possible.
		Komatiitic crust is obducted onto continents during continent collision at the end of subduction.
	www.mantleplumes.org /Komatiites.html (4217 words)

	Geoscience Australia: Minerals Geochemistry Research and Development. Sarah E. Dowling & Robin E.T. Hill - ...
		Komatiite flow unit containing identifiable lava pathways now occupied by olivine-rich cumulates.
		Droplets of immiscible sulphide liquid or a discrete, dense, basal flow of sulphide are carried along by, and scavenge Ni, Cu and PGE from the komatiite lava and are ultimately trapped on the basal contact by a change in flow rheology, change in slope or direction of preferred lava pathway.
		Lower - Vertical sections through the regional komatiite flow field, illustrating the various volcanic facies depicted in the upper figure, showing lithological associations and the environments of accumulation of types 1 and 2 Ni deposits.
	www.ga.gov.au /about/corporate/ga_authors/ajagg_17_4/SE_Dowling_RET_Hill_ajagg174.jsp (1218 words)

	The Following Was Taken From A Field Trip Guidebook
		The komatiite suite of rocks, from basalt, pyroxenitic basalt, peridotite and dunite (Arndt and Nisbet 1982) are well represented in the southern half of the Abitibi Belt, as shown on figure 1.
		The Komatiites exposed on Pyke Hill in the centre of Munro Township, Ontario (Fig.
		The presence of spinifex texture has become recognized as a diagnostic feature of komatiite flows (Nesbitt 1971; Donaldson 1982; Arndt and Nisbet 1982), and the distribution and variation in size of olivine grains in spinifex textures are commonly used to delineate flow units and to determine facing directions in sequences of flows (Pyke et al.
	millstreammines.com /AreaGeology.html (4103 words)

	Komatiite flow animation (Site not responding. Last check: 2007-10-11)
		We believe that komatiite hosted nickel sulfide deposits form by this mechanism, but only where the substrate rocks contain a high proportion of sulfides.
		Komatiite volcanology, volcanological setting and primary geochemical properties of komatiite-associated nickel deposits.
		Dowling, S.E., Hill, R.E.T., Barnes, S.J. and Thordarson, T. Decoupled hybrid boundary layers at the base of komatiite lava pathways: Omnipresent components of actively eroding lava pathways.
	www.em.csiro.au /em/commodities/nickel/research/projects/komatiite_flow.html (387 words)

	488
		The parental komatiite magmas are interpreted to have formed in equilibrium with residual majorite garnet in a deep mantle plume (Campbell and Grifiths, 1992).
		The komatiites and basalts define a well constrained Sm-Nd isochron (MSWD = 0.8) with a slope corresponding to an age of 2843±39 Ma, slightly older than a U-Pb zircon age of 2795±29 Ma from the overlying rhyolites.
		In addition to LREE, the komatiites and basalts are depleted in Zr and Th and show positive Nb-anomalies.
	www.the-conference.com /JConfAbs/1/488.html (761 words)

	SPINIFEX-KOMATIITE LAVA FLOWS, 3.5 GA KOMATI FORMATION, SOUTH AFRICA (Site not responding. Last check: 2007-10-11)
		Spinifex komatiites from the 3.5 Ga Komati Formation have lenticular and sheet-like shapes, similar to subaerial pahoehoe lava flows.
		Since 70% of the komatiites are massive flows choked with phenocrysts, a critical factor in the unhindered growth of large olivine blades in the upper spinifex zones is the ‘open space’ for crystal growth.
		This paper examines the morphology of spinifex komatiites -- the shape and distribution of flows, dike-filled fissures, glassy flow tops and breccias, and textural zoning -- and concludes that these features are best understood within the context of an inflationary mode of lava flow emplacement.
	gsa.confex.com /gsa/2004AM/finalprogram/abstract_75109.htm (431 words)

	Michel Houlé
		Komatiites are ultramafic volcanic rocks that occur mainly in Archean greenstone belts (e.g.
		The major aim of this study will be to establish the volcanic facies of komatiites in the AGB in order to constrain stratigraphic, tectonic, and metallogenic models.
		komatiitic dunite, komatiitic peridotite, olivine-phyric komatiite, komatiite and komatiitic basalt), textures (e.g.
	www.laurentian.ca /geology/grads/mhoule/mhoule-abstract.htm (881 words)

	GFD Annual Report 1999, Komatiite lava flows (Site not responding. Last check: 2007-10-11)
		As erosion of S-rich substrates by hot, metal-rich komatiite lavas is considered to be a fundamental process in the genesis of many magmatic Fe-Ni-Cu-(PGE) sulfide deposits, evaluating the role of thermo-mechanical erosion in the emplacement of komatiitic lavas is an important aspect of understanding the genesis of magmatic sulfide deposits.
		To help understand the erosional potential and mineralisation of komatiite lavas, we developed last year a mathematical model that quantifies the thermal, rheological, fluid dynamical, and geochemical evolution of channelised komatiite lava flows.
		The amount of contamination resulting from thermal erosion of gabbro by komatiitic basalt liquid is negligible (~1-2%), indicating that the observed contamination in the Katinniq Ultramafic Complex (~10%) must be attributable to thermo-mechanical erosion of sediment upstream during the late stages of erosion.
	rses.anu.edu.au /gfd/pages/AR99/Pages/komatiite.html (496 words)

	Nickel sulphide deposits: genetic understanding leading to exploration success (Overview - Research)
		Komatiites were part of a large global outpouring around 2.7 billion years ago, and are very rare in rocks less than 1.8 billion years old.
		The goal is to identify ‘haloes’ within the host rocks, and to discriminate potentially fertile komatiite flows and intrusions from those with limited potential.
		Komatiites and Nickel Sulfide Ores of the Black Swan area, Yilgarn Block, Western Australia.
	www.csiro.au /csiro/content/standard/ps32,,.html (706 words)

	GFD Annual Report 2000, Numerical models of komatiite lava flows at Perserverance, Western Australia (Site not responding. Last check: 2007-10-11)
		One of the remarkable features inferred from the compositions of Precambrian komatiite lavas is their capability for turbulent flow and thermal erosion of substrate when emplaced as channelized flows.
		To help understand the erosional potential and mineralization of komatiite lavas, we have recently developed a mathematical model that quantifies the thermal, rheological, fluid dynamical, and geochemical evolution of channelized komatiite lava flows.
		For thermo-mechanical erosion to be responsible for the formation of the ~100 m deep, concave Perseverance embayment and the highly-contaminated (~10–20%) Perseverance komatiites, the most likely scenarios require emplacement of thick (10–100m), turbulent, channelized liquidus or superheated komatiite lavas over a welded or unconsolidated submarine tuff.
	rses.anu.edu.au /gfd/pages/AR2000/Pages/numerical.html (370 words)

	Author Auteur (Site not responding. Last check: 2007-10-11)
		The timing of komatiitic volcanism and mafic-ultramafic intrusions (MUM) in the Kidd-Munro assemblage and nearby areas are investigated using U-Pb zircon and baddeleyite geochronology.
		Komatiites of the Kidd-Munro assemblage are 2717-2713 Ma, including the Dundonald and Alexo Ni deposits at 2716.8 +/-2.1 Ma, the age for a dacite/rhyolite immediately under the Ni-bearing komatiite flows.
		The upper Shaw Dome komatiites including the Langmuir #1 and #2 Ni deposits are 2708 Ma +/- 2 Ma, the age for a dacite flow that is intercalated with and cut by the Ni-bearing komatiite flow.
	www.ggl.ulaval.ca /cgi-bin/consultau.cgi?87& (436 words)

	OBSERVED AND PREDICTED CRYSTALLIZATION SEQUENCE IN BARBERTON KOMATIITE (Site not responding. Last check: 2007-10-11)
		The 3.3 Ga Weltevreden Formation of the Barberton Greenstone Belt includes massive komatiite flows that are exceptionally fresh, preserving original igneous textures, minerals, and glass.
		Such OL is in predicted equilibrium with the random spinifex layers of these flows, which have MgO 35.1 wt%, and require low pressure temperatures of 1700C.
		High temperatures for these komatiites and OL are also consistent with the minor element concentrations observed.
	gsa.confex.com /gsa/2002AM/finalprogram/abstract_38375.htm (502 words)

	[No title] (Site not responding. Last check: 2007-10-11)
		Emplacement and erosion by Archean komatiite lava flows at Kambalda: Revisited
		We have developed a mathematical model to evaluate the flow and erosional potential of submarine, channelized komatiite lavas at Kambalda, Western Australia.
		Field data from Kambalda were used to constrain the choice of important input parameters, and model results were compared with data from field studies and geochemical analyses.
	www.agu.org /pubs/abs/jb/97JB03538/97JB03538.html (204 words)

	Lava Compositions on Venus
		A high degree of partial melting within the upper mantle may give a quartz tholeiite and komatiite composition, at greater depths and pressures komatiite (enriched in iron and magnesium), olivine tholeiite, or iron-rich picrite may be produced.
		The morphology and extent of the lava flows are consistent with a basaltic composition and may be of a komatiite or carbonate rich type.
		For komatiite and basalt flows on Venus, with lava temperatures greater than Venusian surface temperatures, convective cooling causes their total heat flux to be greater than on Earth.
	www.es.ucl.ac.uk /research/planetary/undergraduate/mcmillan/venus/venus.htm (5893 words)

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