Тезисы международной конференции
Abstracts of International conference
Astrophyllite-group minerals from Azov region, Ukraine
Kryvdik S.G.*, Sharygin V.V.**, Morgun V.G.*
* N.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation NAS of Ukraine, Kyiv, Ukraine; ** V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia
At present day within the Azov region minerals of the astrophyllite group (astrophyllite, kupletskite, niobokupletskite and zircophyllite) were found and well described in alkaline magmatic rocks the Oktyabrsky Massif (mariupolite, peralkaline phonolite) [Valter et al., 1965; Sharygin, 2009; Sharygin et al., 2009] and in alkaline metasomatites of the Dmitrovka village (northeast from the the Oktyabrsky Massif) [Litvin et al., 1987; Pekov, 2005; Khomenko, Vyshnevskii, 2010]. In addition within the Azov region astrophyllite was identified by optical and X-ray methods in rocks of the Mala Tersa Massif, namely in veined aegirine-hedenbergite-albite syenite intersected gabbro [Krivdik, Tkachuk, 1990], and in aegirine syenite from the northwest remote area of the Oktyabrsky Massif in association with aenigmatite (X-ray data).
Kupletskite (FeO - 7.8; MnO - 19.7 wt.%) from the Oktyabrsky veined mariupolite intersected pyroxenite are strongly rich in MgO (6.9 wt.%) [Valter et al., 1965], what is seems to be mobilized from hosted pyroxenite (mafic minerals in mariupolites are high in Fe). Nevertheless, we do not exclude that high concentration of Mg and Al (5.5 wt.% Al2O3) is owing to admixture of lepidomelane (weight chemical analysis). Zn-kupletskite from peralkaline phonolites of the Kamennaya gully is characterized by broad compositional spectrum (ZnO - 4-8; MnO - 27.3-29.7; FeO - 0.1-0.9 wt.%) [Sharygin, 2009; Sharygin et al., 2009]. It should be noted that Zn-kupletskite from the Oktyabrsky phonolites shows a pronounced zoning. The increasing of Nb2О5 (from 1.0 to 7.6 wt.%) and ZrО2 (from 0.7 to 6.6 wt..%) was observed from the core to rim of grains, and outermost zones already belong to niobokupletskite and/or zircophyllite in chemical composition.
Astrophyllites-kupletskites from the Dmitrovka alkaline albite and microcline-albite metasomatites show strong diversity. According to our recent data (Table) and publications of other authors these minerals are characterized by variable ratio of FeO and MnO аs well as variable ZrO2, Nb2O5 and ZnO. According to published data essential or negligible predominance of FeO over MnO or their equal ratio is common of astrophyllite [Litvin et al., 1987; Pekov, 2005; Khomenko, Vyshnevskii, 2010], whereas kupletskite has approximately equal concentrations of MnO (19.6) and FeO (15.3 wt.%) [Pekov, 2005]. All these astrophyllites and kupletskites show appreciable ZrO2 (up to 4.9), Nb2O5 (up to 4.2 wt. %) and negligible ZnO.
Table. Chemical composition (wt.%) of the astrophyllite-group minerals from the Dmitrovka apogranite metasomatites.
EMPA - microprobe data; SEM - scanning microscope data; Ta2O5 and Cr2O3 are below detection limits; n - average; c, r - core-rim of grain; gap - not analyzed.
Our recent unpublished data (microprobe, scanning microscopy) revealed that these minerals from the Dmitrovka alkaline metasomatites show broader variations (Table). Three rock samples containing astrophyllite and kupletskite were under study. Mineral composition of studied aegirine albitites is sometimes diverse in the suite of some minor phases (arfvedsonite, fluorphlogopite, annite, ilmenite-pyrophanite-ecandrewsite) [Kryvdik et al., 2010; Sharygin, Kryvdik, 2010].
The first specimen (DМ-8) contains astrophyllite with essential predominance of FeO (22.8-26.5 wt.%) over MnO (8-13 мас.%). This mineral is rich in ZrO2 (up to 5.1wt.%) and Rb2O (up to 1 wt.%) and poor in Nb2O5 (1.0-1.8%) and ZnO (0.7-1.3 wt.%). Contents of F are near 1 wt.%. The second sample (DМ-15) bears astrophyllite with higher content of MnO (13.1-15.7 wt.%), which increases from the core tio rim of grains, whereas concentration of FeO decreases (19.5-25.5 wt.%). The mineral is also characterized by high ZrO2 (up to 5.3 wt.%) and negligible Nb2O5 (up to 1.7) and ZnO (up to 1.0 wt.%). Fluorine content are commonly not higher than 1 wt.%, sometimes reaches 1.7 wt.%. Kupletskite with an essential predominance of MnO (24-25) over FeO (approximately 9 wt.%) was found in the third specimen (DМ-Astr). This phase contains appreciable ZrO2 (3.1-3.7), Nb2O5 (1.8-2.2), ZnO (1.4-1.8 wt.%) and F (up to 2.5 wt.%).
Thus, overview of all chemical data for the astrophyllite-group minerals from the Dmitrovka metasomatites possibly reveals positive correlation between MnO and F. However, kupletskite from the Oktyabrsky Massif peralkaline phonolites, which extremely rich in MnO, does show not high content of F (commonly near 1 wt.%, sometimes up to 1.4 wt.%) [Sharygin et al., 2009]. We suggest that immediate cause of high concentration of F and other elements in the Dmitrovka astrophyllites-kupletskites should be in the chemistry of mineral assemblages of the metasomatites, namely in the presence of other F-containing phases and in the chemistry of mafic and ore minerals (amphibole, mica, ilmenite-group minerals, rutile and others) with strongly variable composition.
Consequently, contrasted compositions of the astrophyllite-group minerals, including species with high Nb and Zr, may occur within one locality of alkaline apogranitic metasomatites (Dmitrovka open pit) and in other metasomatic localities in the Azov region. We suspect that further microprobe studies of the astrophyllite-group minerals from other above-mentioned alkaline rocks in the Azov region will clearly recognize wider chemical diversity of minerals in this group.
Khomenko V., Vyshnevskii O. Astrophyllite from alkaline metasomatized rocks (Dmytrivka, Azov region): crystal chemistry, spectroscopy, inclusions // In: Alkaline rocks: petrology, mineralogy, geochemistry. Abstracts and excursion guide of Conference dedicated to the memory of J.A.Morozewicz. Kyiv. 2010. P. 34-35.
Krivdik S.G., Tkachuk V.I. Petrology of alkaline rocks of the Ukrainian Shield. Kiev: Naukova Dumka. 1990. 408 p.
Kryvdik S.G., Morgun V.G., Sharygin V.V. Micas from fenites and alkaline metasomatites of eastern Azov region // Mineralogical Journal (Ukraine). 2010. V. 32. No. 4, P. 3-11.
Litvin A.L., Egorova L.N., Kulchetskaya A.A., Melnikov V.S., Sharkin O.P., Ostapenko S.S. Astrophyllite from the Azov region - first finding in Ukraine // Mineralogical Journal (Ukraine). 1987. V. 9. No. 6. P. 77-82.
Pekov I.V. Genetic mineralogy and crystal chemistry of trace elements in high-alkaline postmagmatic systems. Doctor of Science Dissertation. Moscow, MSU. 2005. 652 p.
Sharygin V.V. New minerals and mineral species in the Azov region: Oktyabrsky Massif // Transactions of UkrNDMI NAS Ukraine. 2009. Iss. 5. Part 2. P. 132-139.
Sharygin V.V., Kryvdik S.G., Pospelova L.N., Dubyna A.V. Zn-kupletskite and hendricksite in the agpaitic phonolites of the Oktyabrskii massif, Azov region, Ukraine // Doklady Earth Sciences. 2009. V. 425A. No. 3. P. 499-504.
Sharygin V., Kryvdik S. Behavior of Zn in late magmatic and metasomatic rocks of the Oktyabrsky alkaline massif, Azov region, Ukraine: mineralogical data // In: Alkaline rocks: petrology, mineralogy, geochemistry. Abstracts and excursion guide of Conference dedicated to the memory of J.A.Morozewicz. Kyiv. 2010. P. 58-59.
Valter A.A., Eremenko G.K., Lysenko T.A. Kupletskite from alkaline rocks of the Azov region // Mineralogical Sbornik of Lvov University. 1965. Iss. 19. No. 2. P. 246-252.