A spectroscopic and carbon-isotope study of mixed-habit diamonds: Impurity characteristics and growth environment

Howell, D.; Griffin, William L.; Piazolo, Sandra; Say, Jana M.; Stern, Richard A.; Stachel, Thomas; Nasdala, Lutz; Rabeau, James R.; Pearson, Norman J.

doi:10.2138/am.2013.4179

Cited by 38 publications

(45 citation statements)

References 52 publications

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“…However, self-diffusion of carbon isotopes in diamond is extremely slow [24], and, once generated, this pattern should remain for a long time even at mantle conditions. Such patterns have been reported in some natural diamonds [10,11]. Galimov [25] shows~3 depletion in 13 C of cuboid diamonds in comparison with octahedral crystals from Yakutian kimberlites, which might, at least in part, have resulted from the surface-induced crystallochemical fractionation discussed here.…”

Section: Ab Initio Calculations Of Carbon Isotope Fractionationsupporting

confidence: 82%

Experimental and Theoretical Evidence for Surface-Induced Carbon and Nitrogen Fractionation during Diamond Crystallization at High Temperatures and High Pressures

et al. 2017

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Isotopic and trace element variations within single diamond crystals are widely known from both natural stones and synthetic crystals. A number of processes can produce variations in carbon isotope composition and nitrogen abundance in the course of diamond crystallization. Here, we present evidence of carbon and nitrogen fractionation related to the growing surfaces of a diamond. We document that difference in the carbon isotope composition between cubic and octahedral growth sectors is solvent-dependent and varies from 0.7 in a carbonate system to 0.4 in a metal-carbon system. Ab initio calculations suggest up to 4 instantaneous 13 C depletion of cubic faces in comparison to octahedral faces when grown simultaneously. Cubic growth sectors always have lower nitrogen abundance in comparison to octahedral sectors within synthetic diamond crystals in both carbonate and metal-carbon systems. The stability of any particular growth faces of a diamond crystal depends upon the degree of carbon association in the solution. Octahedron is the dominant form in a high-associated solution while the cube is the dominant form in a low-associated solution. Fine-scale data from natural crystals potentially can provide information on the form of carbon, which was present in the growth media.

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Section: Ab Initio Calculations Of Carbon Isotope Fractionationsupporting

confidence: 82%

Experimental and Theoretical Evidence for Surface-Induced Carbon and Nitrogen Fractionation during Diamond Crystallization at High Temperatures and High Pressures

et al. 2017

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“…One of the possible reasons of such observed interrelations of nitrogen and 13 C concentrations in natural diamonds can be a segregation of carbonate melt to form a diaper and its subsequent migration (38,58) that can lead to the formation of contrasting domains of carbon isotopes in the Earth's low mantle. Taking into account the average magnitude of the fractionation of 6.5‰ and the nitrogen behavior (see above), the redox interaction can be considered as one of the mechanisms responsible for the complex compositional heterogeneity of natural diamonds (59)(60)(61)(62)(63)(64).…”

Section: Significancementioning

confidence: 99%

Mantle–slab interaction and redox mechanism of diamond formation

Palyanov

Bataleva

Sokol

et al. 2013

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

173

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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 show the typical colorless sectors (octahedral growth) and brownish to grayish sectors (cuboid growth) in a three-fold symmetry (e.g. [14,15]). The cuboid areas contain high density of blackened graphitized disk-crack-like defects that appear black, which might be responsible for giving rise to the overall gray color of these sectors.…”

Section: Resultsmentioning

confidence: 99%

Plastic deformation in natural diamonds: Rose channels associated to mechanical twinning

Schoor

Boulliard

Gaillou

et al. 2016

Diamond and Related Materials

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Hollow channels in diamond are well acknowledged to be the result of dissolution processes.In this article we demonstrate that some hollow channels in natural diamonds are the consequence of intense plastic deformation by mechanical twinning. Two mixed-habit diamonds presenting numerous geometrical hollow tubes were studied. X-ray Laue analyses showed the presence of microtwins. At the intersection of microtwins, displacements and cracks are generated, creating the hollow channels observed. The presence of the cracks seems to have released the internal stress, as there was less to no signs of deformation at and around them. Further dissolutions are sometimes but not always seen within the cavities. Mechanical twinning, so far mostly identified in pink to purple diamonds, might be more widespread than originally thought in natural diamonds. Graphical AbstractMacroscopic voids (≥ 100 µm in diameter, and sometimes ≥ 1 mm long) are observed in some mixed-habit growth natural diamonds. The voids are created at the intersection of two twins and are interpreted as Rose channels. This figure shows cross sections of the Rose channels by scanning electron microscope imaging and their interpretation.

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A spectroscopic and carbon-isotope study of mixed-habit diamonds: Impurity characteristics and growth environment

Cited by 38 publications

References 52 publications

Experimental and Theoretical Evidence for Surface-Induced Carbon and Nitrogen Fractionation during Diamond Crystallization at High Temperatures and High Pressures

Experimental and Theoretical Evidence for Surface-Induced Carbon and Nitrogen Fractionation during Diamond Crystallization at High Temperatures and High Pressures

Mantle–slab interaction and redox mechanism of diamond formation

Plastic deformation in natural diamonds: Rose channels associated to mechanical twinning

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