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S.I. Kostrovitsky V.G. Malkovets E.M. Verichev V.K. Garanin L.V. Suvorova 《Lithos》2004,77(1-4):511-523
The megacryst suite of the Grib kimberlite pipe (Arkhangelsk province, Russia) comprises garnet, clinopyroxene, magnesian ilmenite, phlogopite and garnet-clinopyroxene intergrowths. Crystalline inclusions, mainly of clinopyroxene and picroilmenite, occur in garnet megacrysts. Ilmenite is characterized by a wide range in the contents of MgO (10.6–15.5 wt.%) and Cr2O3 (0.7–8.3 wt.%). Megacryst garnets show wide variations in Cr2O3 (1.3–9.6 wt.%) and CaO (3.6–11.0 wt.%) but relatively constant MgO (15.4–22.3 wt.%) and FeO (5.2–9.9 wt.%). The pyroxenes also show wide variations in such oxides as Cr2O3, Al2O3 and Na2O (0.56–2.95; 0.86–3.25; 1.3–3.0 wt.%, respectively). The high magnesium and chromium content of all these minerals puts them together in one paragenetic group. This conclusion was confirmed by studies of the crystalline inclusions in megacrysts, which demonstrate similar variations in composition. Low concentration of hematite in ilmenite suggests reducing conditions during crystallization. P–T estimates based on the clinopyroxene geothermobarometer (Contrib. Mineral. Petrol. 139 (2000) 541) show wide variations (624–1208 °C and 28.8–68.0 kbars), corresponding to a 40–45 mW/m2 conductive geotherm. The majority of Gar-Cpx intergrowths differ from the corresponding monomineralic megacrysts in having higher Mg contents and relatively low TiO2. The minerals from the megacryst association, as a rule, differ from the minerals of mantle xenoliths, but garnets in ilmenite-bearing peridotite xenoliths are compositionally similar to garnet megacrysts. The common features of trace element composition of megacryst minerals and kimberlite (they are poor in Zr group elements) suggest a genetic relationship. The origin of the megacrysts is proposed to be genetically connected with kimberlite magma-chamber evolution on the one hand and with associated mantle metasomatism on the other. We suggest that, depending on the primary melt composition, different paragenetic associations of macro/megacrysts can be crystallized in kimberlites. They include: (1) Fe–Ti (Mir, Udachnaya pipes); (2) high-Mg, Cr (Zagadochna, Kusova pipes); (3) high-Mg, Cr, Ti (Grib pipe). 相似文献
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A.A. Gibsher V.G. Malkovets A.V. Travin E.A. Belousova V.V. Sharygin Z. Konc 《Russian Geology and Geophysics》2012,53(8):763-775
A camptonite dike swarm (Agardag alkali-basalt complex) in the western part of the Sangilen Upland abounds in mantle xenoliths. Mineralogical, petrographic, and petrochemical studies show that the dikes are composed of lamprophyres of two groups, basic and ultrabasic. Ar/Ar dating of amphibole and phlogopite megacrysts gives an intrusion age for the dikes of 443.0 ± 1.3 Ma. 206Pb/238U dating of zircon from a glomeroporphyritic intergrowth in camptonite from one of the dikes yielded a core age of 489.0 ± 5.4 Ma. This corresponds to the time of formation of the Chzhargalanta granite–leucogranite complex (489.4 ± 2.6 Ma). The 206Pb/238U age of the zircon rim is 444.0 ± 7.5 Ma. The ages obtained by Ar/Ar dating of amphibole and biotite megacrysts and by U/Pb dating of the magmatic rim of zircon crystal from the camptonite coincide within the dating error, which indicates that the camptonite dikes formed in the Late Ordovician. These dikes are the oldest-known example of mantle-derived xenoliths in mafic volcanic rocks from an off-craton setting. These are samples of the Upper Ordovician lithospheric mantle. 相似文献
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Yakovlev I. V. Malkovets V. G. Gibsher A. A. Dymshits A. M. Kuzmin D. V. Danilovskaya V. A. Milaushkin M. V. Pokhilenko N. P. Sobolev N. V. 《Doklady Earth Sciences》2022,506(1):635-640
Doklady Earth Sciences - Novel data from mineralogical studies of the peridotite xenoliths from the Komsomol’skaya–Magnitnaya kimberlite pipe, Upper Muna field, Siberian craton, are... 相似文献
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Sharygin I. S. Golovin A. V. Dymshits A. M. Kalugina A. D. Solovev K. A. Malkovets V. G. Pokhilenko N. P. 《Doklady Earth Sciences》2021,500(2):842-847
Doklady Earth Sciences - The results of study secondary crystallized melt inclusions in olivine of a sheared peridotite xenolith from the Komsomolskaya–Magnitnaya kimberlite pipe (Upper Muna... 相似文献
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Afanasiev V. P. Pokhilenko N. P. Grinenko V. S. Kostin A. V. Malkovets V. G. Oleinikov O. B. 《Doklady Earth Sciences》2020,490(2):51-54
Doklady Earth Sciences - We have analyzed 141 grains of pyrope from Neogene sediments in a quarry of construction materials, in the Kenkeme River catchment, along its left-side tributary (Chakiya... 相似文献
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D. I. Rezvukhin V. G. Malkovets I. S. Sharygin D. V. Kuzmin K. D. Litasov A. A. Gibsher N. P. Pokhilenko N. V. Sobolev 《Doklady Earth Sciences》2016,466(2):173-176
The results of study of rutile inclusions in pyrope from the Internatsionalnaya kimberlite pipe are presented. Rutile is characterized by unusually high contents of impurities (up to 25 wt %). The presence of Cr2O3 (up to 9.75 wt %) and Nb2O5 (up to 15.57 wt %) are most typical. Rutile inclusions often occur in assemblage with Ti-rich oxides: picroilmenite and crichtonite group minerals. The Cr-pyropes with inclusions of rutile, picroilmenite, and crichtonite group minerals were formed in the lithospheric mantle beneath the Mirnyi field during their joint crystallization from melts enriched in Fe, Ti, and other incompatible elements as a result of metasomatic enrichment of the depleted lithospheric mantle. 相似文献
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D. I. Rezvukhin V. G. Malkovets I. S. Sharygin D. V. Kuzmin A. A. Gibsher K. D. Litasov N. P. Pokhilenko N. V. Sobolev 《Doklady Earth Sciences》2016,466(2):206-209
The results of study of crichtonite group minerals in pyropes from the Internatsionalnaya kimberlite pipe are reported. Most of the studied samples are characterized by high concentrations of Sr, Ca, Na, and LREEs in comparison with minerals of the LIMA series from kimberlites of South Africa, whereas the average concentrations of Ba and K are significantly lower. Crichtonite group minerals in pyropes are characterized by predomination of Na over K in most samples and by a high concentration of Al2O3 (up to 4.5 wt %). Findings of inclusions of crichtonite group minerals with high concentrations of incompatible elements provide evidence for the metasomatic origin of host chromium-rich pyropes. 相似文献
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Nikolenko E. I. Sharygin I. S. Rezvukhin D. I. Malkovets V. G. Tychkov N. S. Pokhilenko N. P. 《Doklady Earth Sciences》2021,497(2):300-304
Doklady Earth Sciences - Sulfide-bearing polymineralic inclusions in mantle-derived chromium pyrope garnets of lherzolite paragenesis from lamprophyres of the Chompolo field (Aldan shield, southern... 相似文献