Diamonds and the Geology of Mantle Carbon

Shirey, Steven B.; Cartigny, Pierre; Frost, Daniel J.; Keshav, Shantanu; Nestola, Fabrizio; Nimis, Paolo; Pearson, D. Graham; Sobolev, N. V.; Walter, Michael J.

doi:10.2138/rmg.2013.75.12

Cited by 392 publications

(200 citation statements)

References 368 publications

(489 reference statements)

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“…The fluorescence maps were used to define regions of interest in the X-ray diffraction maps. All of our specimens exhibit low levels of nitrogen-aggregation, compared to known ultra-deep diamonds (16). This suggests that our samples are rather young (implying very fast ascent) or have remained at temperatures that are low compared to the average TZ.…”

Section: Characterization By Infrared Spectroscopymentioning

confidence: 70%

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

Tschauner

Huang

Greenberg

et al. 2018

Science

189

139

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Encapsulating Earth's deep water filter Small inclusions in diamonds brought up from the mantle provide valuable clues to the mineralogy and chemistry of parts of Earth that we cannot otherwise sample. Tschauner et al. found inclusions of the high-pressure form of water called ice-VII in diamonds sourced from between 410 and 660 km depth, the part of the mantle known as the transition zone. The transition zone is a region where the stable minerals have high water storage capacity. The inclusions suggest that local aqueous pockets form at the transition zone boundary owing to the release of chemically bound water as rock cycles in and out of this region. Science , this issue p. 1136

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Section: Characterization By Infrared Spectroscopymentioning

confidence: 70%

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

Tschauner

Huang

Greenberg

et al. 2018

Science

189

139

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“…S ubduction of crustal material plays an important role in the global carbon cycle (1)(2)(3)(4)(5)(6). Depending on oxygen fugacity and pressure-temperature (P-T) conditions, carbon exists in the Earth's interior in the form of carbides, diamond, graphite, hydrocarbons, carbonates, and CO 2 (7)(8)(9)(10)(11).…”

mentioning

confidence: 99%

“…Depending on oxygen fugacity and pressure-temperature (P-T) conditions, carbon exists in the Earth's interior in the form of carbides, diamond, graphite, hydrocarbons, carbonates, and CO 2 (7)(8)(9)(10)(11). In the upper mantle, the oxygen fugacity (fO 2 ) varies from one to five log units below the fayalitemagnetite-quartz (FMQ) buffer, with a trend of a decrease with depth (6,(12)(13)(14)(15). At a depth of ∼250 km, mantle is reported to become metal saturated (16,17), which holds true for all mantle regions below, including the transition zone and lower mantle.…”

mentioning

confidence: 99%

“…At a depth of ∼250 km, mantle is reported to become metal saturated (16,17), which holds true for all mantle regions below, including the transition zone and lower mantle. The subduction of the oxidized crustal material occurs to depths greater than 600 km (4)(5)(6). The main carbon-bearing minerals of the subducted materials are carbonates, which are thermodynamically stable up to P-T conditions of the lower mantle (10,11,18).…”

mentioning

confidence: 99%

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Mantle–slab interaction and redox mechanism of diamond formation

Palyanov

Bataleva

Sokol

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

176

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Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle-slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle-slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content.carbonate-iron interaction | high-pressure experiment | mantle mineralogy | deep carbon cycle S ubduction of crustal material plays an important role in the global carbon cycle (1-6). Depending on oxygen fugacity and pressure-temperature (P-T) conditions, carbon exists in the Earth's interior in the form of carbides, diamond, graphite, hydrocarbons, carbonates, and CO 2 (7-11). In the upper mantle, the oxygen fugacity (fO 2 ) varies from one to five log units below the fayalitemagnetite-quartz (FMQ) buffer, with a trend of a decrease with depth (6,(12)(13)(14)(15). At a depth of ∼250 km, mantle is reported to become metal saturated (16, 17), which holds true for all mantle regions below, including the transition zone and lower mantle. The subduction of the oxidized crustal material occurs to depths greater than 600 km (4-6). The main carbon-bearing minerals of the subducted materials are carbonates, which are thermodynamically stable up to P-T conditions of the lower mantle (10,11,18). As evidenced by the compositions of inclusions in diamond, which vary from strongly reduced, e.g., metallic iron and carbides (19-23), to oxidized, e.g., carbonates and CO 2 (6,20,(24)(25)(26)(27)(28), carbonates may be involved in the reactions with reduced deep-seated rocks, including Fe 0 -bearing species (29-31). A scale of these reactions is determined mainly by the capacity of subducted carbonate-bearing domains. An important consequence of such an interaction is that it can produce diamond. However, studies on diamond synthesis via the reactions between oxidized and reduced phases are limited (32-35).To understand the mechanisms of the interaction of carbonbearing oxidized-and reduced-mineral assemblages, we performed high-pressure experiments with an iron-carbonate system; an approach was used that enabled the creation of an oxygen fugacity gradient in the capsules (Materials and Methods and SI Materials and Methods). Results and DiscussionThe experimental results and the phase compositions are given in Table 1 and Table S1, respectively. At temperatures of 1,000 and 1,100°C, the iron-car...

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“…They form a key part of Earth's deep carbon cycle (Shirey et al, 2013). The very slow chemical diffusion rates in diamond combined with high resistance to changes in external physical and chemical environments result in diamonds behaving like time capsules over much of Earth history.…”

Section: Introductionmentioning

confidence: 99%

FTIR thermochronometry of natural diamonds: A closer look

Kohn

Speich

Smith

et al. 2016

Lithos

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms FTIR thermochronometry of natural diamonds: a closer lookSimon C. Kohn, Laura Speich, Christopher B. Smith and Galina P. Bulanova School of Earth Sciences, University of Bristol, Queens Rd., Bristol, BS8 1RJ, U.K. AbstractFTIR is a commonly-used technique for investigating diamonds, but much of the most useful information is lost if spatially resolved measurements are not used. In this study we show examples of FTIR core-to-rim line scans, maps with high spatial resolution and maps with high spectral resolution that are fitted to extract the spatial variation of different nitrogen and hydrogen defects. Model residence temperatures are calculated from the concentration of A and B centres using known times of annealing in the mantle, and a new, two-stage aggregation model is presented that better constrains the thermal history of the diamond and that of the mantle lithosphere in which the diamond resided. The effect of heterogeneity within the analyzed FTIR volume is quantitatively assessed and errors in model temperatures that can be introduced by studying whole diamonds instead of thin plates are discussed. The spatial distribution of hydrogen associated with the 3107 cm -1 vibration does not follow the same pattern as nitrogen, and an enrichment of hydrogen at the boundary between pre-existing diamond and diamond overgrowths is observed. There are several possible explanations for this observation including a change in chemical composition of diamond forming fluid during growth or kinetically controlled uptake of hydrogen.

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Diamonds and the Geology of Mantle Carbon

Cited by 392 publications

References 368 publications

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

Mantle–slab interaction and redox mechanism of diamond formation

FTIR thermochronometry of natural diamonds: A closer look

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