Discovery of metamorphic diamonds in central China: an indication of a &gt; 4000‐km‐long zone of deep subduction resulting from multiple continental collisions

Yang, Jingsui; Xu, Zhiqin; Dobrzhinetskaya, L.; Green, Harry W.; Pei, Xianzhi; Shi, Rui; Wu, Cailai; Wooden, Joseph L.; Zhang, Jianxin; Wan, Yusheng; Li, Haibing

doi:10.1046/j.1365-3121.2003.00511.x

Cited by 182 publications

(118 citation statements)

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“…These are metasedimentary rocks in orogenic belts formed at convergent plate boundaries in PaleozoicMesozoic (Ϸ480-250 Ma) time. Five well confirmed diamondbearing terranes, the Kokchetav massif of Kazakhstan (3), Dabie and Quinlin in China (4,5), the Western Gneiss Region of Norway (6,7), the Erzgebirge massif of Germany (8), and the Kimi complex of the Greek Rhodope (9), are established now. In these localities the diamonds are characterized by small (1-80 m) crystals of skeletal, cuboidal, subrounded, and other imperfect morphologies (10,11).…”

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confidence: 95%

A look inside of diamond-forming media in deep subduction zones

Dobrzhinetskaya

Wirth

Green

2007

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

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Geologists have ''known'' for many years that continental crust is buoyant and cannot be subducted very deep. Microdiamonds 10 -80 m in size discovered in the 1980s within metamorphic rocks related to continental collisions clearly refute this statement, suggesting that material of continental crust has been subducted to a minimum depth of >150 km and incorporated into mountain chains during tectonic exhumation. Over the past decade, the rapidly moving technological advancement has made it possible to examine these diamonds in detail, and to learn that they contain nanometric multiphase inclusions of crystalline and fluid phases and are characterized by a ''crustal'' signature of carbon stable isotopes. Scanning and transmission electron microscopy, focused ion beam techniques, synchrotron infrared spectroscopy, and nano-secondary ion mass spectrometry studies of these diamonds provide evidence that they were crystallized from a supercritical carbon-oxygen-hydrogen fluid. These microdiamonds preserve evidence of the pathway by which carbon and water can be subducted to mantle depths and returned back to the earth's surface.crust ͉ microdiamonds ͉ fluid D iamond, built by densely packed carbon atoms, is valued as a gemstone and as a unique industrial/technological material because of its extraordinary hardness, transparency, and high thermal conductivity, and could become a semiconductor when doped with boron or other components (1, 2). With the exception of impact microdiamonds, all natural diamonds are formed in the earth's deep interior (upper mantle, mantle transition zone, and some of them even below the 660-km seismic discontinuity). They are delivered to the earth's surface by volatile-rich kimberlite or related magmas rising up through pipe-like structures together with abundant fragments of wall rocks from the base of the lithosphere. Because of its chemical inertness, diamond is a near-perfect container, stable for long geological times, for fluid and solid inclusions that are trapped during its growth. The chemistry and structure of inclusions are used to reconstruct mantle mineralogy, and conditions and compositions of diamond-forming media.A new, nonvolcanic type of diamond-bearing rocks was discovered Ͼ25 years ago but not made known to the western literature until 1990. These are metasedimentary rocks in orogenic belts formed at convergent plate boundaries in PaleozoicMesozoic (Ϸ480-250 Ma) time. Five well confirmed diamondbearing terranes, the Kokchetav massif of Kazakhstan (3), Dabie and Quinlin in China (4, 5), the Western Gneiss Region of Norway (6, 7), the Erzgebirge massif of Germany (8), and the Kimi complex of the Greek Rhodope (9), are established now. In these localities the diamonds are characterized by small (1-80 m) crystals of skeletal, cuboidal, subrounded, and other imperfect morphologies (10, 11). The nitrogen impurities in diamonds from Kazakhstan, Norway, and Germany suggest that all of them belong to the type 1b-1aA, implying a short residence time at high temperature (Ϸ900-1,10...

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confidence: 95%

A look inside of diamond-forming media in deep subduction zones

Dobrzhinetskaya

Wirth

Green

2007

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

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“…The discovery of microdiamonds in garnets and zircons from metamorphic rocks of the Kokchetav Massif (3) and subsequently in other ultrahigh-pressure (UHP) metamorphic terranes (27)(28)(29)(30)(31)(32) is taken as evidence that the crustal rocks were subducted to considerable depths. FTIR microspectroscopy has revealed fluid inclusions in metamorphic diamonds (33); bulk chemical analyses of the Kokchetav microdiamonds demonstrated high contents of K and Cl (34).…”

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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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“…Assuming that these changes in their characteristic properties should also be reflected in their Raman spectra, it is the second aim of this work to attempt to discriminate distinct diamonds from different rock types of the Kokchetav massif, by means of Raman spectroscopy. The comparison of these Kokchetav data with diamond spectra from Erzgebirge, Norway and from other diamond-bearing regions, including the recently reported occurrence in central China [22], may further document and provide complementary information on particular conditions favoring such metamorphic diamond occurrences.…”

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confidence: 84%

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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Discovery of metamorphic diamonds in central China: an indication of a > 4000‐km‐long zone of deep subduction resulting from multiple continental collisions

Cited by 182 publications

References 31 publications

A look inside of diamond-forming media in deep subduction zones

A look inside of diamond-forming media in deep subduction zones

The role of mantle ultrapotassic fluids in diamond formation

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

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