Fluid inclusions in diamonds from the Diavik mine, Canada and the evolution of diamond-forming fluids

Klein-BenDavid, Ofra; Izraeli, Elad S.; Hauri, E. H.; Navon, O.

doi:10.1016/j.gca.2006.10.008

Cited by 239 publications

(122 citation statements)

References 87 publications

(168 reference statements)

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“…The analysis of melt and fluid inclusions in diamonds and other minerals found in kimberlites generated deep in the mantle (van Achterbergh et al 2003;Kamenetsky et al 2004;Korsakov and Hermann 2006;Tomlinson et al 2006;Klein-BenDavid et al 2007;Guzmics et al 2008) yielded compositions very similar to our experimental alkaline carbonatites. These inclusions are extremely rich in alkalis, with generally K 2 O [ Na 2 O, and also in volatiles (Cl, H 2 O and CO 2 ), and show a strong affinity to the cationic composition of our melts, especially the carbonate-rich end members (Fig.…”

Section: Evidence For Subducted Carbonates and K-rich Metasomatism Insupporting

confidence: 79%

“…The pelite-derived carbonatites are extremely alkali-rich (up to 26 wt%) and SiO 2 ? Al 2 O 3 -poor (\15 wt%) to 400°C above the solidus and plot in the same area as carbonate-rich melt/fluid inclusions found in diamonds (Klein-BenDavid et al 2007, grey field), which however are in part also Cl-rich. The different trends reflect the melting behaviour of the alkali-rich phases at different pressures and the differences in bulk composition.…”

Section: Melting Reactionsmentioning

confidence: 72%

“…The absence of any evidence for an accumulation of this kind of melts at the base of the lithosphere, where temperatures would be low enough for complete crystallization of the carbonatite melts, suggests that a redox reaction with the reduced mantle (Frost and McCammon 2008;Rohrbach et al 2009) immobilizes these carbonatites. In fact, diamond crystallization has been shown to be favored by the catalytic behaviour of K 2 CO 3 -rich melt and fluid (Taniguchi et al 1996;Palyanov et al 2007;Klein-BenDavid et al 2007).…”

Section: Evidence For Subducted Carbonates and K-rich Metasomatism Inmentioning

confidence: 99%

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Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Grassi

Schmidt

2010

Contrib Mineral Petrol

104

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The melting behaviour of three carbonated pelites containing 0-1 wt% water was studied at 8 and 13 GPa, 900-1,850°C to define conditions of melting, melt compositions and melting reactions. At 8 GPa, the fluidabsent and dry carbonated pelite solidi locate at 950 and 1,075°C, respectively; [100°C lower than in carbonated basalts and 150-300°C lower than the mantle adiabat. From 8 to 13 GPa, the fluid-present and dry solidi temperatures then increase to 1,150 and 1,325°C for the 1.1 wt% H 2 O and the dry composition, respectively. The melting behaviour in the 1.1 wt% H 2 O composition changes from fluid-absent at 8 GPa to fluid-present at 13 GPa with the pressure breakdown of phengite and the absence of other hydrous minerals. Melting reactions are controlled by carbonates, and the potassium and hydrous phases present in the subsolidus. The first melts, which composition has been determined by reverse sandwich experiments, are potassium-rich Ca-FeMg-carbonatites, with extreme K 2 O/Na 2 O wt ratios of up to 42 at 8 GPa. Na is compatible in clinopyroxene with D cpx=carbonatite Na ¼ 10À18 at the solidus at 8 GPa. The melt K 2 O/Na 2 O slightly decreases with increasing temperature and degree of melting but strongly decreases from 8 to 13 GPa when K-hollandite extends its stability field to 200°C above the solidus. The compositional array of the sediment-derived carbonatites is congruent with alkali-and CO 2 -rich melt or fluid inclusions found in diamonds. The fluid-absent melting of carbonated pelites at 8 GPa contrasts that at B5 GPa where silicate melts form at lower temperatures than carbonatites. Comparison of our melting temperatures with typical subduction and mantle geotherms shows that melting of carbonated pelites to 400-km depth is only feasible for extremely hot subduction. Nevertheless, melting may occur when subduction slows down or stops and thermal relaxation sets in. Our experiments show that CO 2 -metasomatism originating from subducted crust is intimately linked with K-metasomatism at depth of [200 km. As long as the mantle remains adiabatic, lowviscosity carbonatites will rise into the mantle and percolate upwards. In cold subcontinental lithospheric mantle keels, the potassic Ca-Fe-Mg-carbonatites may freeze when reacting with the surrounding mantle leading to potassium-, carbonate/diamond-and incompatible element enriched metasomatized zones, which are most likely at the origin of ultrapotassic magmas such as group II kimberlites.

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Section: Evidence For Subducted Carbonates and K-rich Metasomatism Insupporting

confidence: 79%

Section: Melting Reactionsmentioning

confidence: 72%

Section: Evidence For Subducted Carbonates and K-rich Metasomatism Inmentioning

confidence: 99%

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Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Grassi

Schmidt

2010

Contrib Mineral Petrol

104

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“…Principally, more recent information has accrued from micro-and nano-inclusions in mantle-derived and metamorphic diamonds. Analysis of the composition of the inclusions in fibrous or cloudy mantle diamonds shows that, at the time of entrapment, the inclusion matter was a specific fluid whose composition belongs to one of the three main types: (i) a hydrous-silicic end-member that is rich in water, Si, Al, and K; (ii) a carbonatitic end-member that is rich in carbonate, Mg, Ca, Fe, K, and Na; and (iii) a brine (hydrous-saline end-member that is rich in Cl, K, and Na) (16)(17)(18)(19)(20)(21)(22)(23). Despite wide compositional variations, all inclusions are enriched in K (24).…”

mentioning

confidence: 99%

The role of mantle ultrapotassic fluids in diamond formation

Palyanov

Shatsky

Sobolev

et al. 2007

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

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Analysis of data on micro-and nano-inclusions in mantle-derived and metamorphic diamonds shows that, to a first approximation, diamond-forming medium can be considered as a specific ultrapotassic, carbonate/chloride/silicate/water fluid. In the present work, the processes and mechanisms of diamond crystallization were experimentally studied at 7.5 GPa, within the temperature range of 1,400 -1,800°C, with different compositions of melts and fluids in the KCl/K 2CO3/H2O/C system. It has been established that, at constant pressure, temperature, and run duration, the mechanisms of diamond nucleation, degree of graphite-to-diamond transformation, and formation of metastable graphite are governed chiefly by the composition of the fluids and melts. The experimental data suggest that the evolution of the composition of deep-seated ultrapotassic fluids/melts is a crucial factor of diamond formation in mantle and ultrahigh-pressure metamorphic processes. high-pressure experimentA n important stage in solving problems of diamond genesis is constructing a clear physical model of diamond formation (1). One of the key parameters to be modeled is the composition of the diamond crystallization medium, with a fluid being largely considered as a crucial agent in diamond formation. It is generally agreed that the mantle media of diamond crystallization were volatile-saturated melts or fluids (1-7). Carbonbearing fluids and carbonates could be sources of carbon, and the medium could have been saturated with it by redox reactions. Recent studies have been aimed at searching and examining fluid and fluid-containing inclusions in genetically different diamonds. Also, experiments have been performed to model the processes of diamond crystallization in the media compositionally corresponding to the inclusions. It is the combination of these two approaches that permits us to gain deeper insight into diamond genesis and to better understand the specific character of processes of deep-seated mineral formation.Studies of mineral inclusions in diamonds have determined the main types of diamondiferous parageneses: ultramaffic, eclogitic (4,8,9), and intermediate websterite (10) and calc-silicate types (11). Some mineral inclusions, e.g., intergrowths of phlogopite with pyroxene (8, 12, 13) and phlogopite with calcite (14), are unambiguously evidence that K and H 2 O were present in the diamond-forming medium. It is pertinent to note that, as early as 30 years ago, neutron activation analysis of diamonds without visible inclusions, taken from three South African deposits, revealed a mixture of mostly K and of other components, which was interpreted as evidence of the presence of entrapped melt (15). Principally, more recent information has accrued from micro-and nano-inclusions in mantle-derived and metamorphic diamonds. Analysis of the composition of the inclusions in fibrous or cloudy mantle diamonds shows that, at the time of entrapment, the inclusion matter was a specific fluid whose composition belongs to one of the three main types: (i) ...

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“…Dissolution-chemical annealing requires the presence of water. Diamond-forming fluids are reported to be water-rich (Klein-BenDavid et al 2007;Navon et al 1988;Schrauder and Navon 1994), and evidence for a hydrous nature for diamond #3615 is the phlogopite inclusion in the core area (Fig. 1).…”

Section: Interpretation Of the Diamond CL Halomentioning

confidence: 99%

Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions

Vries¹,

Drury

Winter

et al. 2010

Contrib Mineral Petrol

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As a step towards resolving the genesis of inclusions in diamonds, a new technique is presented. This technique combines cathodoluminescence (CL) and electron backscatter diffraction (EBSD) using a focused ion beamscanning electron microscope (FIB-SEM) instrument with the aim of determining, in detail, the three-dimensional diamond zonation adjacent to a diamond inclusion. EBSD reveals that mineral inclusions in a single diamond have similar crystallographic orientations to the host, within ±0.4°. The chromite inclusions record a systematic change in Mg# and Cr# from core to the rim of the diamond that corresponds with a *80°C decrease of their formation temperature as established by zinc thermometry. A chromite inclusion, positioned adjacent to a boundary between two major diamond growth zones, is multi-faceted with preferred octahedral and cubic faces. The chromite is surrounded by a volume of non-luminescent diamond (CL halo) that partially obscures any diamond growth structures. The CL halo has apparent crystallographic morphology with symmetrically oriented pointed features. The CL halo is enriched in *200 ppm Cr and *80 ppm Fe and is interpreted to have a secondary origin as it overprints a major primary diamond growth structure. The diamond zonation adjacent to the chromite is complex and records both syngenetic and protogenetic features based on current inclusion entrapment models. In this specific case, a syngenetic origin is favoured with the complex form of the inclusion and growth layers indicating changes of growth rates at the diamond-chromite interface. Combined EBSD and 3D-CL imaging appears an extremely useful tool in resolving the ongoing discussion about the timing of inclusion growth and the significance of diamond inclusion studies.

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Fluid inclusions in diamonds from the Diavik mine, Canada and the evolution of diamond-forming fluids

Cited by 239 publications

References 87 publications

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

The role of mantle ultrapotassic fluids in diamond formation

Three-dimensional cathodoluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions

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