Diamond inclusions in garnets from metamorphic rocks: a new environment for diamond formation

Sobolev, N. V.; Shatsky, V. S.

doi:10.1038/343742a0

Cited by 784 publications

(348 citation statements)

References 8 publications

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“…The identical behavior has been observed for the analogous mechanism where K is involved instead of NH 4 (e.g., Luth, 1997;Harlow, 1997;Safonov et al, 2003;Harlow and Davies, 2004) and the extent of K incorporation indeed has been used as a geobarometer (e.g., Harlow and Veblen, 1991;Sobolev and Shatsky, 1990;Bindi et al, 2003). In comparison to NH 4 , much higher amounts of K are incorporated.…”

Section: Comparison With K-bearing Clinopyroxenessupporting

confidence: 51%

Ammonium-bearing clinopyroxene: A potential nitrogen reservoir in the Earth's mantle

et al. 2010

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In the pseudobinary system CaMgSi 2 O 6 − (NH 4 )M 3+ Si 2 O 6 , with M = Cr or Al, and NH 4 OH in excess, multi-anvil experiments at 9.5 to 12.8 GPa, 725 to 750 • C produced NH 4 -bearing diopside. Incorporation mainly follows the coupled substitution (Ca. Ammonium was identified and quantified by IR spectroscopy. In Cr-bearing diopside we found maximum concentrations in the range of 500 to 1000 ppm of NH 4 .The storage capacity of mantle clinopyroxenes for ammonium turns them to potential candidates for the nitrogen reservoir in the Earth's upper mantle, and this mechanism also contributes to its water budget. While nitrogen is transported into the mantle via cold slabs through NH 4 inherited from sedimentary material, and stored in K-bearing minerals and successor high-pressure phases, nitrogen output from the mantle is through degassing of N 2 . A probable mechanism for that is that nitrogen is kept as NH 4 in clinopyroxene in the Earth's mid and lower mantle, whereas in the upper part, it is lost due to oxidation to molecular nitrogen. It is most likely that clinopyroxene plays a major role in the long-time, large-scale nitrogen cycle between surface and deep mantle of the Earth.

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Section: Comparison With K-bearing Clinopyroxenessupporting

confidence: 51%

Ammonium-bearing clinopyroxene: A potential nitrogen reservoir in the Earth's mantle

et al. 2010

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“…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). Higher peak metamorphic conditions of P$6-8 GPa and T ¼ 1100 C have been reported by Ota et al (2000), Massonne (2003) and Dobrzhinetskaya et al (2006).…”

Section: Sample B01-3mentioning

confidence: 93%

“…Despite an extensive search for new UHPM indicators, coesite and diamond remain the most reliable indicators among others. Diamond inclusions are quite rare and have been identified so far only in a limited number of localities (Sobolev & Shatsky, 1990;Massonne, 1999;Mposkos & Kostopoulos, 2001;Van Roermund et al, 2002;Mposkos & Krohe, 2006;Perraki et al, 2006), whereas the presence of coesite has been confirmed for 18 complexes (Chopin, 2003). Unfortunately, the complex metamorphic history of UHPM rocks often erases the peak metamorphic assemblages and prevents reliable estimation of the peak metamorphic conditions.…”

Section: Introductionmentioning

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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“…Ultrahigh-temperature; UHT Ultrahighpressure; UHP , Sobolev and Shatsky, 1990;Caoué-Long et al, 1991;Chopin, 2003;Carswell and Compagnoni, 20032017100 1993 deep crustal metamorphism Table S1 25 4…”

Section: Fig 1 1990mentioning

confidence: 99%

Recent progress in lower crustal process:

Osanai

Nakano

Adachi

2017

Jour. Geol. Soc. Japan

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Ultrahigh-temperature (UHT) and ultrahigh-pressure metamorphism indicate extreme metamorphic conditions in regional metamorphic settings. In particular, the metamorphic temperature of UHT metamorphism is the highest limit of crustal metamorphism, exceeding °C and is equivalent to the temperature of basaltic magma. Typical UHT metamorphic rocks have Mg-Al-rich bulk chemical compositions and are easily identified by a characteristic mineral assemblage of sapphirine + quartz garnet, orthopyroxene + sillimanite quartz, or garnet + osumilite + quartz. Precise reconstruction of the metamorphic evolution of UHT metamorphic rocks on the basis of metamorphic reaction textures, mineral inclusion studies, pressure-temperature estimations, and micro-geochronological analyses is a powerful tool for understanding orogenic processes.

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Diamond inclusions in garnets from metamorphic rocks: a new environment for diamond formation

Cited by 784 publications

References 8 publications

Ammonium-bearing clinopyroxene: A potential nitrogen reservoir in the Earth's mantle

Ammonium-bearing clinopyroxene: A potential nitrogen reservoir in the Earth's mantle

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

Recent progress in lower crustal process:

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