Lithospheric diamond formation as a consequence of methane-rich volatile flooding: An example from diamondiferous eclogite xenoliths of the Karelian craton (Finland)

Smart, Katie A.; Cartigny, Pierre; Tappe, Sebastian; O’Brien, Hugh; Klemme, Stephan

doi:10.1016/j.gca.2017.03.014

Cited by 23 publications

(4 citation statements)

References 186 publications

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“…To investigate the potential conditions under which diamond can form from methane-rich fluids, we have undertaken a series of experiments at pressures and temperatures corresponding to the deeper portions of the cratonic mantle lithosphere under controlled ƒO 2 . A pressure range of 5-7 GPa is of particular interest as this is similar to the range reported for many lithospheric diamonds 21 and where no solid-phase transformation of graphite to diamond is expected (graphite has long been used as a heater for experiments at these pressures without spontaneous transformation). No diamond seed crystals were used to initiate or accelerate diamond growth 2 .…”

supporting

confidence: 52%

“…~150 km) lies well below the stability of CO 2 -rich fluids or carbonatitic melts 15 . In addition, some diamonds exhibiting negatively skewed 13 ∂C signatures 8,10,21 contain CH 4 ± H 2 -bearing fluid inclusions, as detected by Raman spectroscopy 22,23 ). These studies provide direct evidence for the role of CH 4 in the formation of some natural diamonds, including the population of very large "CLIPPIR" diamonds 24 , even so diamond synthesis from strongly reduced fluids has not yet been experimentally observed 25 .…”

mentioning

confidence: 99%

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Reduced methane-bearing fluids as a source for diamond

Matjuschkin

Woodland

Frost

et al. 2020

Sci Rep

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Diamond formation in the Earth has been extensively discussed in recent years on the basis of geochemical analysis of natural materials, high-pressure experimental studies, or theoretical aspects. Here, we demonstrate experimentally for the first time, the spontaneous crystallization of diamond from CH 4-rich fluids at pressure, temperature and redox conditions approximating those of the deeper parts of the cratonic lithospheric mantle (5-7 GPa) without using diamond seed crystals or carbides. In these experiments the fluid phase is nearly pure methane, even though the oxygen fugacity was significantly above metal saturation. We propose several previously unidentified mechanisms that may promote diamond formation under such conditions and which may also have implications for the origin of sublithospheric diamonds. These include the hydroxylation of silicate minerals like olivine and pyroxene, H 2 incorporation into these phases and the "etching" of graphite by H 2 and cH 4 and reprecipitation as diamond. This study also serves as a demonstration of our new high-pressure experimental technique for obtaining reduced fluids, which is not only relevant for diamond synthesis, but also for investigating the metasomatic origins of diamond in the upper mantle, which has further implications for the deep carbon cycle.

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confidence: 52%

mentioning

confidence: 99%

Reduced methane-bearing fluids as a source for diamond

Matjuschkin

Woodland

Frost

et al. 2020

Sci Rep

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“…There are three main ages of kimberlite magmatism in the northern East European Platform: first, the Paleoproterozoic Kimozero (1.92 Ga) and Kostomuksha (1.2 Ga) kimberlites of central Karelia in Russia [1] and the Kuhmo-Lentiira (1.2 Ga) kimberlites in Finland [2]; second, the Neoproterozoic Kuusamo (757 ± 2 Ma) and Kaavi-Kuopio (626-589 Ma) kimberlites of eastern Finland [3][4][5]; and, third, the Devonian-upper Carboniferous kimberlites of the Terskii Coast (380-360 Ma; [6]), Timan Ridge [7] and Arkhangelsk Diamondiferous Province (ADP, 390-340 Ma; [8]) in the European part of Russia ( Figure 1A,B). Most kimberlites contain low concentrations of diamonds and are currently economically unattractive.…”

Section: Introductionmentioning

confidence: 99%

Diamond Exploration Potential of the Northern East European Platform

Shchukina

Shchukin²

2018

Minerals

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Abstract:In this study, we assess the diamond exploration potential of the northern East European Platform based on aeromagnetic survey results and the morphologic and geochemical analysis of 1513 grains of kimberlite indicator minerals (KIMs), such as purple pyrope garnet, olivine, and Cr-diopside. These minerals were recovered from samples collected from modern river and stream sediments in four areas located in the north-eastern (within the Arkhangelsk Diamondiferous Province) and south-western (hundreds of kilometers outside of the Arkhangelsk Diamondiferous Province) parts of the Arkhangelsk region in the European part of Russia. All the studied areas are located within ancient cratons, including the Kola, Karelian, and Shenkursk cratons. Based on the major element compositions of the KIMs and thermobarometric calculations, this study confirms that the lithospheric mantle beneath the studied areas is suitable for the formation and preservation of diamonds. The high percentage of KIMs with primary magmatic grain surface morphologies is evidence of the presence of local kimberlite sources within all of the studied areas. The significant amount of diamond-associated KIMs indicates that the potential sources are diamondiferous. Hence, the results suggest that the studied areas can be recommended for further diamond prospecting activity with a high probability of discovering new diamondiferous kimberlites.

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“…Established models for diamond genesis are based primarily on mineralogical and geochemical studies of natural diamonds, thermodynamic modeling, and results of experiments on diamond crystallization in model systems (1)(2)(3)(4)(5)(6). Currently, most scientists recognize that diamond formation is polygenic in nature (4)(5)(6), involving various (i) carbon sources and crystallization media (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)) such as C─O─H (±N±S) fluids, carbonate melts/fluids, carbonates, and carbides or metal-carbon melts; (ii) P-T-fO 2 -pH conditions of formation (4-6, 12, 17, 18); and (iii) processes, mechanisms/driving forces of crystallization (4-6, 12, 19-21). According to broadly accepted models (2,4), diamond formation occurs in a course of mantle metasomatic processes and concomitant redox reactions resulting in the oxidation of hydrocarbons or the reduction of CO 2 to elemental carbon.…”

Section: Introductionmentioning

confidence: 99%

Diamond formation in an electric field under deep Earth conditions

et al. 2021

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Most natural diamonds are formed in Earth’s lithospheric mantle; however, the exact mechanisms behind their genesis remain debated. Given the occurrence of electrochemical processes in Earth’s mantle and the high electrical conductivity of mantle melts and fluids, we have developed a model whereby localized electric fields play a central role in diamond formation. Here, we experimentally demonstrate a diamond crystallization mechanism that operates under lithospheric mantle pressure-temperature conditions (6.3 and 7.5 gigapascals; 1300° to 1600°C) through the action of an electric potential applied across carbonate or carbonate-silicate melts. In this process, the carbonate-rich melt acts as both the carbon source and the crystallization medium for diamond, which forms in assemblage with mantle minerals near the cathode. Our results clearly demonstrate that electric fields should be considered a key additional factor influencing diamond crystallization, mantle mineral–forming processes, carbon isotope fractionation, and the global carbon cycle.

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Lithospheric diamond formation as a consequence of methane-rich volatile flooding: An example from diamondiferous eclogite xenoliths of the Karelian craton (Finland)

Cited by 23 publications

References 186 publications

Reduced methane-bearing fluids as a source for diamond

Reduced methane-bearing fluids as a source for diamond

Diamond Exploration Potential of the Northern East European Platform

Diamond formation in an electric field under deep Earth conditions

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