Carbonatite melt–peridotite interaction at 5.5–7.0 GPa: Implications for metasomatism in lithospheric mantle

Sokol, Alexander G.; Kruk, Alexey N.; Чеботарев, Д. А.; Palyanov, Yury N.

doi:10.1016/j.lithos.2016.01.013

Cited by 53 publications

(21 citation statements)

References 74 publications

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“…It has been suggested that this assimilation process might be instrumental in driving the ascent of kimberlite magmas, whereby CO 2 exsolution in response to the assimilation of orthopyroxene enhances magma buoyancy (7). Although some experiments have confirmed an increase in melt SiO 2 due to orthopyroxene dissolution (9,11), other experiments indicate that the solubility of silicate minerals in carbonate melts is low at high pressure (>3.5 GPa) and temperature [≥1200°C; (9,12)]. Therefore, a fundamental, as yet unanswered, question is to what extent the assimilation of mantle material has influenced the com-positional variability of kimberlite and other carbonate-rich melts that reach Earth's surface.…”

Section: Introductionmentioning

confidence: 99%

Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

et al. 2020

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Quantifying the compositional evolution of mantle-derived melts from source to surface is fundamental for constraining the nature of primary melts and deep Earth composition. Despite abundant evidence for interaction between carbonate-rich melts, including diamondiferous kimberlites, and mantle wall rocks en route to surface, the effects of this interaction on melt compositions are poorly constrained. Here, we demonstrate a robust linear correlation between the Mg/Si ratios of kimberlites and their entrained mantle components and between Mg/Fe ratios of mantle-derived olivine cores and magmatic olivine rims in kimberlites worldwide. Combined with numerical modeling, these findings indicate that kimberlite melts with highly variable composition were broadly similar before lithosphere assimilation. This implies that kimberlites worldwide originated by partial melting of compositionally similar convective mantle sources under comparable physical conditions. We conclude that mantle assimilation markedly alters the major element composition of carbonate-rich melts and is a major process in the evolution of mantle-derived magmas.

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Section: Introductionmentioning

confidence: 99%

Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

et al. 2020

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“…However, so far attention has focused on opx dissolution as a dominant process in kimberlite magma evolution and eruption from the base of the lithosphere, although this has not yet been validated through experiments at upper mantle conditions (e.g., Stone and Luth 2016;Sokol et al 2016), and could be reproduced only for a limited pressure range (Kamenetsky and Yaxley 2015). Here, we focus on the reaction of early high-pressure kimberlite melt with clinopyroxene (cpx) and garnet (grt), manifest as solidified melt inclusions within kimberlite-hosted xenocrysts from the Lac de Gras kimberlite field (including the Diavik and Ekati Diamond Mines).…”

Section: Introductionmentioning

confidence: 99%

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

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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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“…The pelite-derived melt has Ca# 62-68, and contains about 32-37 mol % K 2 CO 3 (Figure 8b). Infiltration of this melt into lherzolite or harzburgite yields wehrlitization in accordance with the following exchange reaction [22]:…”

Section: The Compositional Trend Of Carbonate Melts During Upward Permentioning

confidence: 83%

“…Inclusions of such melts were found in "fibrous" [13][14][15][16][17][18][19] and gem-quality diamonds [20] worldwide, carried out by kimberlites from the base of subcontinental lithospheric mantle. It was also shown experimentally that these K-rich dolomitic melts can coexist with peridotite under geothermal conditions corresponding to the base of the continental lithospheric mantle [21][22][23], and could be responsible for the diamond formation as a solvent-catalyst and carbon source [24,25].…”

Section: Introductionmentioning

confidence: 95%

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The System K2CO3–CaCO3–MgCO3 at 3 GPa: Implications for Carbonatite Melt Compositions in the Shallow Continental Lithosphere

et al. 2019

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Potassic dolomitic melts are believed to be responsible for the metasomatic alteration of the shallow continental lithosphere. However, the temperature stability and range of compositions of these melts are poorly understood. In this regard, we performed experiments on phase relationships in the system K2CO3–CaCO3–MgCO3 at 3 GPa and at 750–1100 °C. At 750 and 800 °C, the system has five intermediate compounds: Dolomite, Ca0.8Mg0.2CO3 Ca-dolomite, K2(Ca≥0.84Mg≤0.16)2(CO3)3, K2(Ca≥0.70Mg≤0.30)(CO3)2 bütschliite, and K2(Mg≥0.78Ca≤0.22)(CO3)2. At 850 °C, an additional intermediate compound, K2(Ca≥0.96Mg≤0.04)3CO3)4, appears. The K2Mg(CO3)2 compound disappears near 900 °C via incongruent melting, to produce magnesite and a liquid. K2Ca(CO3)2 bütschliite melts incongruently at 1000 °C to produce K2Ca2(CO3)3 and a liquid. K2Ca2(CO3)3 and K2Ca3(CO3)4 remain stable in the whole studied temperature range. The liquidus projection of the studied ternary system is divided into nine regions representing equilibrium between the liquid and one of the primary solid phases, including magnesite, dolomite, Ca-dolomite, calcite-dolomite solid solutions, K2Ca3(CO3)4, K2Ca2(CO3)3, K2Ca(CO3)2 bütschliite, K2Mg(CO3)2, and K2CO3 solid solutions containing up to 24 mol % CaCO3 and less than 2 mol % MgCO3. The system has six ternary peritectic reaction points and one minimum on the liquidus at 825 ± 25 °C and 53K2CO3∙47Ca0.4Mg0.6CO3. The minimum point resembles a eutectic controlled by a four-phase reaction, by which, on cooling, the liquid transforms into three solid phases: K2(Mg0.78Ca0.22)(CO3)2, K2(Ca0.70Mg0.30)(CO3)2 bütschliite, and a K1.70Ca0.23Mg0.07CO3 solid solution. Since, at 3 GPa, the system has a single eutectic, there is no thermal barrier for liquid fractionation from alkali-poor toward K-rich dolomitic compositions, more alkaline than bütschliite. Based on the present results we suggest that the K–Ca–Mg carbonate melt containing ~45 mol % K2CO3 with a ratio Ca/(Ca + Mg) = 0.3–0.4 is thermodynamically stable at thermal conditions of the continental lithosphere (~850 °C), and at a depth of 100 km.

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Carbonatite melt–peridotite interaction at 5.5–7.0 GPa: Implications for metasomatism in lithospheric mantle

Cited by 53 publications

References 74 publications

Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

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 System K2CO3–CaCO3–MgCO3 at 3 GPa: Implications for Carbonatite Melt Compositions in the Shallow Continental Lithosphere

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