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References Akhtar, K., 1996. Facies, sedimentation processes and environments in the Proterozoic Vindhyan Basin, India. Memoir of Geological Society of India 36, 127-136. Amorosi, A., 1997. Detecting compositional, spatial, and temporal attributes of glaucony: a tool for provenance research. Sedimentary Geology 109, 135-153. Banerjee, S., Bhattacharya, S.K. & Sarkar, S., 2006. Carbon and oxygen isotope compositions of the carbonate fa-cies in the Vindhyan Supergroup, central India. Journal of Earth Systems Science 115, 113-134. Banerjee, S., Jeevankumar, S

deposits of rare-metals in the Ukrainian Shield. Mineralogical Journal (Ukraine), 24 (2/3), 24-36. Kryvdik, S.G. (2002). Rare-metal syenites of the Ukrainian Shield. Geochemistry, 7, 707-717 (in Russian). Kryvdik, S.G., Tsymbal, S.N., & Geiko, Yu.V. (2003). Proterozoic ultrabasic magmatism of the North-Western part of the Ukrainian Shield. Mineralogical Journal (Ukraine), 25(5/6), 57-69 (in Russian). Kryvdik, S.G., & Dubyna, O.V. (2006b). Geochemical peculiarities of alkaline rocks in the Dnister-Bug region of the Ukrainian Shield. Mineralogical Journal (Ukraine), 28

Abstract

The finding of fossil freshwater diatoms in late Cretaceous chert in Mexico suggests - together with all the discoveries of fossil freshwater diatoms known from positions older than the Cretaceous - that the extinct marine Cretaceous diatom taxa cannot be considered to be the oldest.

resetting of the Rb-Sr system which resulted in highly radiogenic 87 Sr/ 86 Sr ratios. It has to be noticed however, that such an event is not detected in the U-Pb zircon data. This fact is in favour of the slow cooling model. In the Andrychów sample, the lower intercept age of 542 ± 21 Ma, obtained from zircon domains exhibiting a fine-scale oscillatory growth zonation in the CL images, is interpreted as the uppermost Proterozoic to Cambrian magmatic crystallization age of the granitic precursor of the orthogneiss. The concordant age at 2123 ± 23 Ma represents

SHRIMP U-Th-Pb zircon dating of the granitoid massifs in the Malé Karpaty Mountains (Western Carpathians): evidence of Meso-Hercynian successive S- to I-type granitic magmatism

Representative granitic rock samples from the Malé Karpaty Mountains of the Western Carpathians (Slovakia) were dated by the SHRIMP U-Th-Pb isotope method on zircons. Oscillatory zoned zircons revealed concordant Mississippian magmatic ages: 355±5 Ma in Bratislava granodiorite, and 347±4 Ma in Modra tonalite. The results document nearly synchronous, successive Meso-Hercynian plutonic events from S-type to I-type granites. The Neo-Proterozoic inherited zircon cores (590±13 Ma) were identified in the Bratislava S-type granitic rocks whereas scarce Paleo-Proterozoic inherited zircons (1984±36 Ma) were detected within the Modra I-type tonalites.

, India. Precambrian Research 84, 63-81. Mallik, L., Mazumder, R., Mazumder, B.S., Arima, M. & Chatterjee, P., 2012. Tidal rhythmite in offshore shale: a case study from Paleoproterozoic Chaibasa shale, eastern India and its implications. Marine and Petroleum Geology 30, 43-49. Mazumder, R., 2004. Implications of lunar orbital periodicities from Chaibasa tidal rhythmite of late Paleoproterozoic age. Geology 32, 841-844. Mazumder, R., 2005. Proterozoic sedimentation and volcanism in the Singhbhum crustal province, India and their implications. Sedimentary Geology

Dovyrenite Ca6Zr[Si2O7]2(OH)4 - A New Mineral from Skarned Carbonate Xenoliths in Basic-Ultrabasic Rocks of the Ioko-Dovyren Massif, Northern Baikal Region, Russia

Dovyrenite, simplified formula Ca6Zr[Si2O7]2(OH)4, occurs as an accessory mineral in vein skarns developed in carbonate xenoliths in subvolcanic layered plagiodunite-troctolite series in the Ioko-Dovyren Massif of Proterozoic age, Northern Baikal Region, Buryatia, Russia. Dovyrenite is a late mineral of altered pyroxene and melilite-monticellite skarns. Associated minerals are Zr-bearing phases: fassaitic pyroxene, perovskite and hydrogarnets; and also monticellite, vesuvianite, diopside, foshagite, brucite, calzirtite, tazheranite, baghdadite, apatite, calcite, native bismuth, sphalerite, selenian galena, clausthalite, safflorite, rammelsbergite, pyrrhotite, pentlandite, valleriite, laitakarite, nickeline, nickel-skutterudite. The average structure of dovyrenite is orthorhombic, space group Pnnm, with subcell parameters A = 5.666(16) Å, B = 18.844(5) Å, C = 3.728(11) Å, V = 398.0(2) Å3 and Z = 1. Dovyrenite shows a new type of modular structure with stacking of the tobermorite-like and the rosenbuschite-like layers parallel to (010). Single-crystal structural data point to an incompletely occupied Ca(2) site from the rosenbuschite module which is confirmed by microprobe analyses: ZrO2 16.47, SiO2 32.83, TiO2 0.14, HfO2 0.16, Cr2O3 0.01, CaO 43.87, FeO 0.25, MgO 0.13, MnO 0.02, Nb2O3 0.03; total 99.38 wt% with calculated H2O. The empirical formula is (Ca5.73Fe0.03Mg0.02)σ5.78(Zr0.98Hf0.01Ti0.01)σ1Si4(O13.56OH0.44)σ14(OH)4. The presence of two types of OH group in the dovyrenite structure is corroborated by FTIR and Raman spectroscopy. Dovyrenite is an optically positive biaxial mineral: α 1.659(2), β 1.660(2); γ 1.676(2); 2Vz 30(5)° (measured), 28° (calculated). The coexistence of monticellite, foshagite and dovyrenite points to a narrow interval of crystallization 560-630°C under subvolcanic conditions (P < 108 Pa).

. Elizabethan Publishing Company: Lagos. [18] Adiotomre, E.E., Ejeh, O.I., Adaikoph, E.O. (2014): Temporal variation in the textural characteristics of clastic sediments from Geregu, Ajaokuta, Nigeria. International Journal of Scientific and Engineering Research, 5(8), pp. 60-65. [19] Ajibade, A.C, Woakes, M., Rahaman, M.A. (1987): Proterozoic crustal development in Pan-African regime of Nigeria. In: Proterozoic Lithospheric Evolution, Kröner, A. (ed.). American Geophysical Union: Washington; pp. 231-259. [20] Ajibade, A.C., Fitches, W.R. (1988): The Nigerian Precambrian and

-induced glaciolacustrine breccias in the Belchatow mine (central Poland). Sedimentary Geology 193, 93-104. He, Z., Song, T., Ding, X., Zhang, Q., Meng, X. & Ge, M., 2000. The early synsedimentary faulting of the Me- so-Proterozoic Yanshan rift and its influence on event sedimentation. Journal of Palaeogeography 2, 83-91 (in Chinese with English abstract). He, B., Qiao, X., Jiao, C., Xu, Z., Cai, Z., Guo, X., Zhang, Y. & Zhang, M., 2014. Paleo-earthquake events in the late Early Palaeozoic of the central Tarim Basin: evidence from deep drilling cores. Geologos 20, 105-123. Li, H

Burleigh Falls, Ontario Highway 36, Ontario. [In:] D.C. Roy (Ed.): Northeastern Section of the Geological Society of America, Geological Society of America Centennial Field Guide, 5, 337-338. Edwards, M.B., 1975. Glacial retreat sedimentation in the Smalfjord Formation, Late Precambrian, North Norway. Sedimentology 22, 75-94. Edwards, M.B., 1984. Sedimentology of the Upper Proterozoic glacial record, Vestertana Group. Finnmark, North Norway. Norges Geologiske Undersøkelse, Bulletin 394, Universitetsforlaget, Trondheim, 76 pp. Edwards, M.B., 2004. Glacial influence on