Crystallization of Groundmass Spinel in Kimberlite

Roeder, P. L.; Schulze, Daniel J.

doi:10.1093/petrology/egn034

Cited by 108 publications

(67 citation statements)

References 42 publications

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“…1 Formation of a dolomitic silico-carbonatite melt via partial melting of carbonated peridotite close to the base of the lithosphere. 2 Ascending kimberlite melt infiltrates megacrysts after interaction with other mantle minerals (above 150 km) and is trapped by process of necking down (Roedder 1984) and/or decompression cracking . 3 Decarbonation reactions cause chemical exchange between inclusions and hosts during kimberlite ascent, forming spongy rims around inclusions in Crdiopside, whereas kelyphite zones around inclusions in Cr-pyrope form by decompression reactions.…”

Section: Discussionmentioning

confidence: 99%

“…A likely process for entrapment of a melt in mantle minerals is described as 'necking down' by Roedder (1984) and has been proposed in previous studies on polymineralic inclusions in megacrysts (Schulze 1985;van Achterbergh et al 2002van Achterbergh et al , 2004Araújo et al 2009). In this process, a melt enters the host crystal along fractures and cleavage planes by dissolution and recrystallization.…”

Section: Process and Timing Of Melt Entrapmentmentioning

confidence: 95%

“…2d, f). Hence, the polymineralic inclusions strictly are secondary in nature, as defined by Roedder (1984). However, although the veins occasionally connect to the host kimberlite (where preserved), the appearance of polymineralic inclusions and kimberlite is markedly different (Fig.…”

Section: Polymineralic Inclusionsmentioning

confidence: 95%

See 2 more Smart Citations

The evolution of calcite-bearing kimberlites by melt-rock reaction: evidence from polymineralic inclusions within clinopyroxene and garnet megacrysts from Lac de Gras kimberlites, Canada

Bussweiler

Stone

Pearson

et al. 2016

Contrib Mineral Petrol

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inclusion trails surround the inclusions. In Cr-pyropes, the inclusions additionally contain Al-spinel, clinopyroxene, and dolomite. The major and trace element compositions of the inclusion phases are generally consistent with the early stages of kimberlite differentiation trends. Extensive chemical exchange between the host phases and the inclusions is indicated by enrichment of the inclusions in major components of the host crystals, such as Cr 2 O 3 and Al 2 O 3 . This chemical evidence, along with phase equilibria constraints, supports the proposal that the inclusions within Cr-diopside record the decarbonation reaction: dolomitic melt + diopside → forsterite + calcite + CO 2 , yielding the observed inclusion mineralogy and producing associated (CO 2 -rich) fluid inclusions. Our study of polymineralic inclusions in megacrysts provides clear mineralogical and chemical evidence for an origin of kimberlite that involves the reaction of high-pressure dolomitic melt with diopside-bearing mantle assemblages producing a lower-pressure melt that crystallizes a calcite-dominated assemblage in the crust.

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Section: Discussionmentioning

confidence: 99%

Section: Process and Timing Of Melt Entrapmentmentioning

confidence: 95%

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The evolution of calcite-bearing kimberlites by melt-rock reaction: evidence from polymineralic inclusions within clinopyroxene and garnet megacrysts from Lac de Gras kimberlites, Canada

Bussweiler

Stone

Pearson

et al. 2016

Contrib Mineral Petrol

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“…However, even if these domains are secondary, they generally comprise only a small volume (0-15%) of the rock, and therefore the groundmass is predominantly igneous in origin. Lastly, the texture and mineralogy of the groundmass of the DCK-U kimberlite is typical of worldwide kimberlites (Shee 1984;Mitchell 1986Mitchell , 1995Mitchell , 1997Armstrong et al 2004;Caro et al 2004;Fedortchouk and Canil 2004;Roeder and Schulze 2008;van Straaten et al 2008), and comparable to those produced in experimental studies (Mitchell 1986, p.343-354;Otto and Wyllie 1993;Bellis and Canil 2007;Canil and Bellis 2008;Sparks et al 2009). …”

Section: Single Unit Of Well-crystallised Coherent Kimberlitementioning

confidence: 60%

A rare occurrence of a crater-filling clastogenic extrusive coherent kimberlite, Victor Northwest (Ontario, Canada)

et al. 2011

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Kimberlite pipes can contain significant proportions of dark and dense kimberlite that have mostly been interpreted as intrusive coherent (hypabyssal) in origin. This study reports a well-documented occurrence of a fresh intra-crater clastogenic extrusive coherent kimberlite that is concluded to have formed as a result of lava fountaining. This paper focuses on a dark, dense, competent, generally crystal-rich, massive kimberlite unit within the Victor Northwest kimberlite pipe (Ontario, Canada). Using a comprehensive volcanological and petrographic analysis of all available drill cores, it is shown that this unit has a fresh well-crystallised coherent groundmass and is extrusive and pyroclastic in origin. The proposed clastogenic coherent extrusive origin is based on deposit morphology, gradational contacts to enveloping pyroclastic units, as well as the presence of remnant pyroclast outlines and angular broken olivines. This paper, and an increasing number of other studies, suggest that fragmental extrusive coherent kimberlite in intra-crater settings may be more common than previously thought. The emplacement history and volcanology of these pipes need to be reconsidered based on the emerging importance of this particular kimberlite facies.

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“…The composition of groundmass spinel is widely used as a petrogenetic indicator (Schulze 2001;Roeder and Schulze 2008). Spinel macrocrysts are extensively studied to: (i) map the vertical distribution of rock types and processes in the sub-continental lithospheric mantle (SCLM) (e.g., O'Reilly and Griffin 2006;Malkovets et al 2007), (ii) infer the nature and extent of metasomatism experienced by the underlying mantle (Haggerty 1995), and (iii) assess the diamond potential of kimberlites (Sobolev 1974;Fipke 1991;Griffin et al 1994;Gurney and Moore 1993;Kaminsky et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Diamond-facies chrome spinel from the Tokapal kimberlite, Indrāvati basin, central India and its petrological significance

et al. 2012

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Widespread and abundant spinel is the only primary mineral of petrogenetic significance preserved in the hydrothermally altered, crater-facies, Neoproterozoic (≥620 Ma) Tokapal kimberlite pipe that intruded the Indrā-vati basin, Bastar craton, Central India. Two distinct spinel populations occur: (i) finer-grained (<50 μm) microcrysts which are zoned from titaniferous magnesiochromitechromite to magnetite; and (ii) larger macrocrysts (>400 μm) with cores having distinctly chromium-rich (Cr 2 O 3 up to 63.67 wt%), and TiO 2 -poor (<0.68 wt%) compositions. Based on their morphology and chemical composition the macrocrysts are inferred to be disaggregated mantle xenocrysts and their compositional range extends well into the diamond stability field. However, the reported absence of diamond and other indicator minerals (such as pyrope garnet, chrome diopside and magnesian ilmenite) in the Tokapal pipe is intriguing since diamondiferous cratonic roots are indeed preserved in the Bastar craton, and also the kimberlite itself was derived from a similar source region(s) as that of the well-known diamondiferous Mesoproterozoic (ca. 1,100 Ma) kimberlites from Wajrakarur, Dharwar craton, southern India. Given the large areal extent (>550 ha) of kimberlite, there is a possibility that it contains diamonds but they were not recovered during the sampling. Alternately, highly oxidising conditions imparted by the metasomatic fluids/melts derived from (i) asthenosphere-lithosphere interaction, or (ii) the kimberlite itself might have played an important role in the destruction of diamond, and other indicator minerals.

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Crystallization of Groundmass Spinel in Kimberlite

Cited by 108 publications

References 42 publications

The evolution of calcite-bearing kimberlites by melt-rock reaction: evidence from polymineralic inclusions within clinopyroxene and garnet megacrysts from Lac de Gras kimberlites, Canada

The evolution of calcite-bearing kimberlites by melt-rock reaction: evidence from polymineralic inclusions within clinopyroxene and garnet megacrysts from Lac de Gras kimberlites, Canada

A rare occurrence of a crater-filling clastogenic extrusive coherent kimberlite, Victor Northwest (Ontario, Canada)

Diamond-facies chrome spinel from the Tokapal kimberlite, Indrāvati basin, central India and its petrological significance

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