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MPM-01 General contributions to mineralogy
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Baghdadite from carbonate xenoliths in basite-ultrabasite rocks of Dovyren massif
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Irina Galuskina, University of Silesia (Poland)
Milen Kadiyski, University of Bern (Switzerland)
Thomas Armbruster, University of Bern (Switzerland)
Evgeny Galuskin, University of Silesia (Poland)
Nikolai Pertsev, Institute of Geology of Ore Deposits, Geochemistry, Mineralogy and Petrography (IGEM) RAS (Russian Federation)
Aleksandr Zadov, OOO "TEPLOHIM" (Russian Federation)
Evgeny Kislov, Geological Institute RAS, Siberian Branch (Russian Federation)
Janusz Janeczek, University of Silesia (Poland)
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Baghdadite was discovered in giant-grained skarns of mosaic structure built of fragments of fassaite-perovskite-apatite, monticellite-vesuvianite and vesuvianite-foshagite rocks. The anhedral baghdadite crystals (up to 1 mm in size) from vesuvianite-foshagite zones have constant composition: (Ca2.99Mg0.01)3(Zr0.95Ti0.04Hf0.01)1Si2O9. In these zones baghdadite occurs together with Zr-bearing perovskite and sheaf-like aggregates of dovyrenite. In monticellite-vesuvianite zones, baghdadite crystals with composition Ca3(Zr0.97Ti0.03)1Si2O9 usually overgrow calcirtite (Ca1.98Mg0.02Fe2+0.02)2.02Zr5.02(Ti1.89Hf0.04V3+0.04Al0.02)1.99O16 grains, replaced partially by dovyrenite (Ca5.86Mg0.02Fe2+0.02Mn2+0.01)5.91(Zr0.97Hf0.02)1Si4O13.79(OH)4.21. Baghdadite zones adjacent to calcirtite are enriched in Ti - Ca3(Zr0.83Ti0.17)1Si2O9. In the different skarn zones baghdadite occurs also as inhomogeneous pseudomorphs after calcirtite. These pseudomorphs have Ti-enriched zones with composition Ca3(Zr0.66Ti0.34)1Si2O9 with the hypothetical molecule of titanian analog of baghdadite Ca3TiSi2O9 reaching up to 34 %. The long-prismatic and acicular baghdadite crystals found in caverns of vesuvianite zones have low Ti contents - Ca3(Zr0.97Ti0.03)1Si2O9, and are associated with dovyrenite and zirconian hydrogarnet Ca3(Fe3+0.80Al0.58Ti0.34Mg0.13Zr0.09V3+0.03Cr0.01)2Si2.61O10.68(OH)1.32. Baghdadite with composition Ca3.01(Zr0.93Ti4+0.06)0.99Si2O9 occurs rarely in fassaitic zones between Zr-bearing perovskite and Zr-bearing titanian fassaitic pyroxene. The crystal structure of baghdadite from vesuvianite-foshagite zones was refined to R1=5.4% using a single-crystal X-ray diffractometer. Baghdadite belongs to the P21/c space group with unit cell parameters: a = 7.351, b = 10.176, c = 10.417 Å, b = 90.89°, V = 779.1 Å3. Raman spectra of baghdadite show strong lines (cm-1): 355, 404, 624, 669, 856, 922.
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