Garnet-biotite-clinozoisite gneiss: a new type of diamondiferous metamorphic rock from the Kokchetav Massif

Korsakov, Andrey V.; Shatsky, V. S.; Sobolev, N. V.; Zayachokovsky, Anton A.

doi:10.1127/0935-1221/2002/0014-0915

Cited by 61 publications

(51 citation statements)

References 23 publications

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“…We investigate coesite inclusions in zircon and garnet from diamondiferous clinozoisite gneisses, collected at the Barchi-Kol localities [27][28][29]. Garnet in these gneisses displays a large unzoned core and narrow rims with decreasing Ca and increasing Mg contents [28,29]. Similar zoning has been observed in some dolomitic metacarbonates [20].…”

Section: Geological Background and Sample Descriptionmentioning

confidence: 89%

“…This unit consists mainly of garnet-biotite gneisses and schists with alternating marbles, calc-silicate rocks and eclogites [17]. We investigate coesite inclusions in zircon and garnet from diamondiferous clinozoisite gneisses, collected at the Barchi-Kol localities [27][28][29]. Garnet in these gneisses displays a large unzoned core and narrow rims with decreasing Ca and increasing Mg contents [28,29].…”

Section: Geological Background and Sample Descriptionmentioning

confidence: 99%

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Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan)

Korsakov

Hutsebaut

Theunissen

et al. 2007

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Coesite inclusions occur in a wide range of lithologies and coesite is therefore a powerful ultrahigh-pressure (UHP) indicator. The transformation of coesite to quartz is evidenced by three optically well identifiable characteristics (e.g. palisade textures, radial crack patterns, polycrystalline quartz pseudomorphs). Under overpressure monomineralic coesite (on an optical basis), lacking the above transformation characteristics may survive. Raman micro-spectroscopy was applied on monomineralic coesite inclusions in garnet porphyroblasts from diamond-bearing garnet-clinozoisite-biotite gneisses of the Barchi-Kol area (Kokchetav Massif, Northern Kazakhstan). These coesite inclusions are euhedral and display a characteristic anisotropic hallo. However, Raman maps and separate spectra of these inclusions display shifted bands for coesite and quartz. Microscopically undetectable, quartz shows on the Raman map as a thin shell around coesite inclusion. Shift of the main coesite band allows to estimate their overpressure: coesite inclusions record 0-2.4 GPa in garnet and zircon. The quartz shell remains under lower pressure 0-1.6 GPa. The possible application of coesite and quartz Raman geobarometers for UHP metamorphic rocks is discussed.

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Section: Geological Background and Sample Descriptionmentioning

confidence: 89%

Section: Geological Background and Sample Descriptionmentioning

confidence: 99%

Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan)

Korsakov

Hutsebaut

Theunissen

et al. 2007

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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“…2). They have homogeneous cores whereas slight variations in their composition occur in narrow ($100 mm) external zones (Shatsky et al, 1995;Korsakov et al, 1998;Hermann et al, 2001;Korsakov et al, 2002;Korsakov & Hermann, 2006). Diamond and coesite inclusions identified in the garnet porphyroblasts point to peak metamorphic conditions of P$4-6 GPa and T$950-1000 C (Sobolev & Shatsky, 1990;Hermann et al, 2001;Korsakov et al, 2007).…”

Section: Sample B01-3mentioning

confidence: 99%

Is quartz a potential indicator of ultrahigh-pressure metamorphism? Laser Raman spectroscopy of quartz inclusions in ultrahigh-pressure garnets

Korsakov¹,

Perraki²,

Zhukov³

et al. 2010

ejm

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Laser Raman microspectroscopy was applied to quartz inclusions in coesite-and diamond-grade metapelites from the Kokchetav ultrahigh-pressure metamorphic (UHPM) complex, Northern Kazakhstan, and diamond-grade eclogite xenoliths from the Mir kimberlite pipe, Yakutiya, Russia to assess the quantitative correlation between the Raman frequency shift and metamorphic pressure. Quartz crystals sealed in garnets have a higher frequency shift than those in the matrix. Residual pressures retained by quartz inclusions depend on the metamorphic history of the garnet host. The Raman frequency shift of quartz inclusions in garnet from coesite-grade and diamond-grade metamorphic rocks shows no systematic change with increasing peak metamorphic pressures. The highest shifts of the main Raman bands of quartz were documented for monocrystalline quartz inclusions in garnets from a diamond-grade eclogite xenolith. Calibrations based on experimental work suggest that the measured Raman frequency shifts signify residual pressures of 0.1-0.6 GPa for quartz inclusions from coesite-grade metapelites from Kokchetav, 0.1-0.3 GPa for quartz inclusions from diamond-grade metapelites from Kokchetav, and 1.0-1.2 GPa for quartz inclusions from the diamondgrade eclogite xenoliths from the Mir kimberlite pipe. Normal stresses and internal (residual) pressures of quartz inclusions in garnet were numerically simulated with a 3-shell elastic model. Estimated values of residual pressures are inconsistent with the residual pressures estimated from the frequency shifts. Residual pressure slightly depends on P-T conditions at peak metamorphic stage. Laser Raman microspectroscopic analysis of quartz is a potentially powerful method for recovering an ultrahigh pressure metamorphic event. Monocrystalline quartz inclusions yielding a residual pressure greater than 2.5 GPa might indicate the presence of a former coesite.

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“…1. Details on these lithologies, their mineral assemblages and their diamond properties were published elsewhere [17,21,[23][24][25]. Besides these intragranular diamonds, diamonds in Kokchetav rocks might occur intergranular [26].…”

Section: Analytical Conditions and Sample Preparationmentioning

confidence: 99%

“…At the current state of research of the Kokchetav massif, this type of rock is the only one containing diamonds with predominantly octahedral morphology [18,25]. These microdiamonds also have much lower nitrogen content than the diamonds included in Grt-Cpx rocks [20].…”

Section: Clinozoisite Gneissesmentioning

confidence: 99%

Discrimination of metamorphic diamond populations by Raman spectroscopy (Kokchetav, Kazakhstan)

Korsakov

Vandenabeele

Theunissen

2005

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Metamorphic diamond is a powerful but frequently debated indicator for ultrahigh-pressure metamorphic (UHPM) conditions. Because of their small size, their optical identification needs confirmation. Characteristics of chemically extracted microdiamonds from Kokchetav, identified by different analytical methods, are used here for unambiguous in situ identification by Raman microspectroscopy. Differences appear in the diamond spectra and the Raman analytical method is explored as a helpful tool in the discrimination between diamond populations from four different UHPM lithologies of Kokchetav. Not considering the graphite-coated diamond, out of the reach of the laser wavelength used here, the comparison of these Kokchetav Raman spectra may provide additional information in other UHPM studies.

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Garnet-biotite-clinozoisite gneiss: a new type of diamondiferous metamorphic rock from the Kokchetav Massif

Cited by 61 publications

References 23 publications

Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan)

Raman mapping of coesite inclusions in garnet from the Kokchetav Massif (Northern Kazakhstan)

Is quartz a potential indicator of ultrahigh-pressure metamorphism? Laser Raman spectroscopy of quartz inclusions in ultrahigh-pressure garnets

Discrimination of metamorphic diamond populations by Raman spectroscopy (Kokchetav, Kazakhstan)

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