Composition and geodynamic nature of the protoliths of diamondiferous rocks from the Kumdy-Kol deposit of the Kokchetav metamorphic belt, northern Kazakhstan

Buslov, M.M.; Vovna, G. M.

doi:10.1134/s0016702908090036

Cited by 6 publications

(18 citation statements)

References 8 publications

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“…1999) and Barchi-Kol (Stepanov et al, 2014) terranes and unmetamorphosed rocks of the Sharyk Formation sampled from the above-considered section in the Ilekty Mts. and from other formation sections (Buslov and Vovna, 2008). It is better seen that diamondiferous rocks and sandstones with carbonate-graphite cement are similar in REE patterns (samples IL-7, IL-8, and A-3-1).…”

Section: Geochemistry Of the Kumdy-kol Diamondiferous Rocks And Kokchmentioning

confidence: 75%

“…Quartzites and carbonate-silicate and carbonate rocks are subordinate. For comparison, we used graphite-containing terrigenous-carbonate and sand-shaly rocks sampled in the quarries near Alekseevka Village (40 km north of Kokchetav) and between Kokchetav and Bereznyakovka Village in the Ilekty Mts., respectively (Buslov and Vovna, 2008). Figure 5 shows the REE patterns of two main types of reconstructed metasedimentary rocks: metamorphic rocks of the Kumdy-Kol (Buslov and Vovna, 2008;Shatsky et al, Fig.…”

Section: Geochemistry Of the Kumdy-kol Diamondiferous Rocks And Kokchmentioning

confidence: 97%

“…The Precambrian continental deposits include the granitegneiss basement of the Kokchetav microcontinent, quartziteschist rocks of the continental shelf (Kokchetav Formation), and sand-shaly and carbonate-terrigenous rocks of the continental slope (Sharyk Formation) (Buslov and Vovna, 2008) and the arguments given below).…”

Section: Major Structural Elements Of Northern Kazakhstanmentioning

confidence: 99%

“…The UHP-HP rocks belong to high-pressure eclogite-schist-gneiss complexes formed from the basement Russian Geology and Geophysics 56 (2015) 64-80 rocks (granite-gneisses with basic bodies) and microcontinent cover rocks (quartzite-schist rocks and graphite-containing sand-shaly and terrigenous-carbonate rocks of the Ilekty Group, subdivided into the Kokchetav and Sharyk Formations) (Buslov and Vovna, 2008;Dobretsov et al, 1995bDobretsov et al, ,c, 2006Sobolev and Shatskii, 1987).…”

Section: Introductionmentioning

confidence: 99%

“…Based on the correlation between the bulk composition and REE distribution of the Early Cambrian diamondiferous calc-silicate rocks and gneisses of the Kumdy-Kol diamond deposit and those of the Late Precambrian weakly metamorphosed graphite-containing sedimentary rocks of the Sharyk Formation, Buslov and Vovna (2008) drew the conclusion about similar sedimentary associations formed on the continental slope.…”

Section: Introductionmentioning

confidence: 99%

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Structural location, composition, and geodynamic nature of diamond-bearing metamorphic rocks of the Kokchetav subduction–collision zone of the Central Asian Fold Belt (northern Kazakhstan)

Buslov

Dobretsov

Vovna

et al. 2015

Russian Geology and Geophysics

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We present data on different aspects of geology, mineralogy, petrology, geochemistry, and geochronology of diamond-bearing metamorphic rocks of the Kumdy-Kol terrane, which show the similarity of their protolith to the sedimentary rocks of the Kokchetav microcontinent. The structural location of the studied objects in the accretion-collision zone evidences that the subduction of the Kokchetav microcontinent beneath the Vendian-Cambrian Ishim-Selety island arc is the main mechanism of transport of graphite-bearing terrigenous-carbonate rocks to zones of their transformation into diamond-bearing metamorphic rocks. The sedimentary rocks of the Kokchetav microcontinent, which are enriched in graphite and iron sulfides and carbonates, contain all components necessary for diamond crystallization in deep-seated subduction zone. This is in agreement with the experimental data and the compositions of fluid-melt inclusions in the minerals of diamond-bearing rocks.

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Section: Geochemistry Of the Kumdy-kol Diamondiferous Rocks And Kokchmentioning

confidence: 75%

Section: Geochemistry Of the Kumdy-kol Diamondiferous Rocks And Kokchmentioning

confidence: 97%

Section: Major Structural Elements Of Northern Kazakhstanmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Structural location, composition, and geodynamic nature of diamond-bearing metamorphic rocks of the Kokchetav subduction–collision zone of the Central Asian Fold Belt (northern Kazakhstan)

Buslov

Dobretsov

Vovna

et al. 2015

Russian Geology and Geophysics

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Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions

Stepanov

Hermann

Korsakov

et al. 2014

Contrib Mineral Petrol

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The Kokchetav complex in Kazakhstan contains garnet-bearing gneisses that formed by partial melting of metasedimentary rocks at ultrahigh-pressure (UHP) conditions. Partial melting and melt extraction from these rocks is documented by a decrease in K 2 O and an increase in FeO ? MgO in the restites. The most characteristic trace element feature of the Kokchetav UHP restites is a strong depletion in light rare earth elements (LREE), Th and U. This is attributed to complete dissolution of monazite/ allanite in the melt and variable degree of melt extraction. In contrast, Zr concentrations remain approximately constant in all gneisses. Using experimentally determined solubilities of LREE and Zr in high-pressure melts, these data constrain the temperature of melting to *1,000 °C. Large ion lithophile elements (LILE) are only moderately depleted in the samples that have the lowest U, Th and LREE contents, indicating that phengite retains some LILE in the residue. Some restites display an increase in Nb/Ta with respect to the protolith. This further suggests the presence of phengite, which, in contrast to rutile, preferentially incorporates Nb over Ta. The trace element fractionation observed during UHP anatexis in the Kokchetav gneisses is significantly different from depletions reported in low-pressure restites, where generally no LREE and Th depletion occurs. Melting at UHP conditions resulted in an increase in the Sm/Nd ratio and a decoupling of the Sm-Nd and Lu-Hf systems in the restite. Further subduction of such restites and mixing with mantle rocks might thus lead to a distinct isotopic reservoir different from the bulk continental crust.

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Mobility of elements in a continental subduction zone: evidence from the UHP metamorphic complex of the Kokchetav massif

Shatsky

Skuzovatov

Ragozin

et al. 2015

Russian Geology and Geophysics

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We studied clastics of high-alumina garnet-kyanite-mica schists and garnet-kyanite-quartz granofelses, including diamond-bearing ones, found in the eluvial sediments near Lake Barchi. In contents of major elements the studied rocks correspond to argillaceous shales. The garnet-kyanite-quartz granofelses are poorer in K (0.49-1.35 wt.% K 2 O) than the garnet-kyanite-mica schists (4.9-2.2 wt.% K 2 O) but have the same contents of other major components. The REE patterns of most of the garnet-kyanite-phengite schists are similar to those of the Post-Archean Australian Shale (PAAS) (x _ La/Yb = 13). All garnet-kyanite-quartz rocks are much stronger depleted in LREE (x _ La/Yb = 1.4) and other incompatible elements. Our studies show that allanite and monazite are the main concentrators of LREE and Th in the garnet-kyanite-phengite rocks of the Barchi site. Monazite, occurring as inclusions in garnet, contains not only LREE but also Th, U, and Pb. Rutile of the nondepleted rocks is enriched in Fe and Nb impurities only. The garnet-kyanite-quartz granofelses bear rutile, apatite, and xenotime as accessory phases. Rutile of the depleted rocks shows wide variations in contents of Nb, Ta, and V impurities. In places, the contents of Nb and Ta reach 10.5 and 2.3 wt.%, respectively. The rutile decomposes into rutile with Nb (1.4 wt.%) and Fe (0.87 wt.%) impurities and titanium oxide rich in Fe (6.61 wt.%), Nb (up to 20.8 wt.%), and Ta (up to 2.81%) impurities. Based on the measured contents of incompatible elements in differently depleted high-alumina rocks, the following series of element mobility during UHP metamorphism has been established: Th > Ce > La > Pr > Nd > K > Ba > Rb > Cs > Sm > Eu. The contents of U, P, and Zr in the depleted rocks are similar to those in the nondepleted rocks. The studies have shown that metapelites subducted to the depths with diamond stability conditions can be depleted to different degrees. This might be either due to their exhumation from different depths of the subduction zone or to the presence of an external source of water controlling the temperature of dissolution of phengite and the formation of supercritical fluid/melt.

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Composition and geodynamic nature of the protoliths of diamondiferous rocks from the Kumdy-Kol deposit of the Kokchetav metamorphic belt, northern Kazakhstan

Cited by 6 publications

References 8 publications

Structural location, composition, and geodynamic nature of diamond-bearing metamorphic rocks of the Kokchetav subduction–collision zone of the Central Asian Fold Belt (northern Kazakhstan)

Structural location, composition, and geodynamic nature of diamond-bearing metamorphic rocks of the Kokchetav subduction–collision zone of the Central Asian Fold Belt (northern Kazakhstan)

Geochemistry of ultrahigh-pressure anatexis: fractionation of elements in the Kokchetav gneisses during melting at diamond-facies conditions

Mobility of elements in a continental subduction zone: evidence from the UHP metamorphic complex of the Kokchetav massif

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