Инд. авторы:	Shatsky V.S., Ragozin A.L., Skuzovatov S.Y., Kozmenko O.A., Yagoutz E.
Заглавие:	Isotope-Geochemical Evidence of the Nature of the Protoliths of Diamondiferous Rocks of the Kokchetav Subduction-Collision Zone (Northern Kazakhstan)
Библ. ссылка:	Shatsky V.S., Ragozin A.L., Skuzovatov S.Y., Kozmenko O.A., Yagoutz E. Isotope-Geochemical Evidence of the Nature of the Protoliths of Diamondiferous Rocks of the Kokchetav Subduction-Collision Zone (Northern Kazakhstan) // Russian Geology and Geophysics. - 2021. - Vol.62. - Iss. 5. - P.547-556. - ISSN 1068-7971. - EISSN 1878-030X.
Внешние системы:	DOI: 10.2113/RGG20204278; WoS: 000672643000003;
Реферат:	eng: The isotope-geochemical features of diamondiferous metamorphic rocks of the Kokchetav subduction-collision zone (KSCZ) show that both the basement rocks and the sediments of the Kokchetav massif were their protoliths. A whole-rock Sm-Nd isochron from the diamondiferous calc-silicate, garnet-pyroxene rocks and migmatized granite-gneisses of the western block of the KSCZ yielded an age of 1116 +/- 14 Ma, while an age of 1.2-1.1 Ga was obtained by U-Pb dating of zircons from the granite-gneiss basement of the Kokchetav microcontinent. Based on these data, we assume that the protoliths of the calc-silicate, garnet-pyroxene rocks and the granite-gneisses of the KSCZ were the basement rocks sharing an initially single Nd source, which was not influenced by high- to ultrahigh-pressure metamorphism (similar to 530 Ma). Therefore, their geochemical features are probably not directly related to ultrahigh-pressure metamorphism. The corresponding rock associations lack isotope-geochemical evidence of partial melting that would occur during ultrahigh-pressure metamorphism, which suggesting that they were metamorphosed under granulite-facies conditions. At the same time, the high-alumina diamondiferous rocks of the Barchi area (garnet-kyanite-mica schists and granofelses), which were depleted to different degrees in light rare-earth elements (REE) and K, have yielded a Sm-Nd whole-rock isochron age of 507 +/- 10 Ma indicating partial melting of these rocks during their exhumation stage. The close epsilon(Nd) (1100) values of the basement rocks and garnet-kyanite-mica schist with geochemical characteristics arguing against its depletion during high-pressure metamorphism indicate that the basement rocks were a crustal source for high-alumina sediments.
Ключевые слова:	ECLOGITES; ND; EXHUMATION; MASSIF; FOLD BELT; MELT INCLUSIONS; WESTERN TIANSHAN; CHEMICAL GEODYNAMICS; ELEMENT MOBILITY; PRESSURE METAMORPHIC ROCKS; Kokchetav subduction-collision zone; continental collision; UHP metamorphism; continental subduction; Sm-Nd isotope data;
Издано:	2021
Физ. характеристика:	с.547-556