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. R.A. Howie A. Woolley 1968 The role of titanium and the effect of TiO 2 on the cell-size, refractive index and specific gravity in the andradite
mineral names are shown in Chapter Analytical methods, TiO 2 -1-2: identifiers in Supp. Table 1 Several different compositional phases of ilmenite can be observed on the BSE images of Sample 784
The heavy mineral assemblages and chemistry of detrital spinel grains from the Senonian basin of the Transdanubian Range (TR) were examined and compared with previous results from Jurassic and Lower Cretaceous successions of the Gerecse Mountains of the Transdanubian Range Unit. The heavy minerals recorded that in the area of Transdanubian Range the sedimentary cover, low-grade metamorphic and granitic rocks of the continental crust were eroded in the Coniacian and Santonian. Detritus of high-grade metamorphics was transported to the bathyal basin during Campanian time. The ophiolitic source area indicated by the presence of chrome spinel, ilmenite and magnetite still existed and persisted through the Late Cretaceous. Compared to the low TiO2 content (lower than 0.2 wt%) of detrital spinels from Jurassic and Lower Cretaceous sediments of the Gerecse Mountains, the most characteristic features of spinels in the Senonian sediments are as follows: exceptionally high TiO2 content (about 0.5-4.7 wt%), relatively high amount of Cr2O3 (about 33-50.8 wt%) and high total iron (sumFeO=15-36 wt%). The data on detrital spinels from the Ajka Coal and Csehbánya Formations suggests that xenoliths (mainly dunites), which previously enclosed the spinel grains, may have been formed from alkalic-tholeiitic magma as crystal accumulates. This was the potential source rock of high TiO2-bearing spinel grains.
Abstract
In this paper we present sedimentological and geochemical data for a section of fluvial deposits from SE Hungary covering the period from about 20 to 5 ky BP. Major and trace element geochemistry of bulk sediments as well as stable C and O isotope compositions of the carbonate content indicate significant changes in depositional facies and/or sediment provenance as well as climate conditions. Variations in bulk sediment Sr, TiO2 and P2O5 concentrations were correlated with major climate change events following the Late Glacial Maximum that support the age model established on the basis of AMS 14C age data. Bulk sediment Sr concentrations and stable C and O isotope compositions of bulk sediment carbonate were determined by changes in denudation of carbonate rocks in the recharge area. The Sr and C-O isotope patterns show correlations with global temperature changes during the Pleistocene-Holocene transition. However, TiO2 and P2O5 contents show correspondence with humidity changes, suggesting variations in chemical weathering. In addition to the sedimentological effects, C and O isotope compositions of Unio crassus shell fragments show strong changes at the Pleistocene-Holocene transition, indicating that the bivalve shells can reflect climate conditions. On the other hand, shorter climate change events were difficult to track in the isotope records due to the competing fractionation processes. The combined evaluation of chemical and isotopic compositions revealed that beside the globally important Younger Dryas and Bølling/Allerød periods, the Ságvár-Lascaux interstadial was of local importance, in accordance with earlier studies.
In this paper, results of a bulk-rock geochemical study of silty and albitic claystone samples selected from the Upper Permian Boda Siltstone Formation (BSF) in the western part of the Mecsek Mountains (Tisza Mega-unit, Hungary) are presented. The high Na2O and P2O5 contents, relative to the post-Archean Australian average shale (PAAS) and the average Russian Paleozoic shale compositions, are the most striking features of the geochemistry of the Boda sediments. The samples studied are depleted in SiO2, TiO2 and Al2O3, and they are enriched in Fe2O3, MgO, CaO and K2O relative to the PAAS. The major element relations clearly show that the geochemistry of the BSF is strongly affected by post-depositional modification, corresponding to large-scale dispersal or addition of components. On the other hand, relatively high La content, low concentrations of V, Cr, Cu and Ni, and the result of the TiO2 versus Ni plot reflect a relatively felsic provenance of the BSF. By comparison with detrital mineralogy of the heteropic Cserdi alluvial fan system deposits, the authors assume that the Boda playa lake deposits had a similar immature primary composition consisting of quartz, plagioclase, K-feldspar, muscovite, biotite, chlorite and clay minerals. During weathering and transport in a semi-arid to arid climate, detrital mafic minerals were altered to yield chlorite and clay minerals plus Fe and Mg, and trace metals in solution. Mg was built into the structure of chlorite and of secondary carbonates such as dolomite and Mg-rich calcite. Based on previous geochemical studies, the BSF contains particularly sodic sedimentary rocks (up to 8 wt%) which may represent an addition of sodium in authigenic silicates from alkaline brine and/or evaporites in the playa deposits. In claystone, after albite formed, Na-depleted, Ca, K-enriched waters reacted with the clay minerals such as smectite and kaolinite to yield K-rich illitic sediments, Ca precipitated in calcite cement. P2O5 is enriched in some samples due to phosphorus mobilization during diagenesis.
Abstract
The Jabal Hamra (538 Ma) and Jabal Abu ad Dud plutons in northeast Saudi Arabia are epizonal bodies consisting of alkali feldspar granite and alkali feldspar syenite. Fracture-controlled zones of highly altered granites are recorded along the margins of the plutons. The granites intrude metamorphosed volcano-sedimentary successions of the Matran Formation. The rocks of the two plutons are chemically indistinguishable. They are characterized by above-average Th, Nb, Y, Ta, Hf and Zr, very low CaO, TiO2, MgO, FeO and MnO, and by high contents of rare earth elements (REE). Tectonic discrimination diagrams suggest an intra-plate environment, with many geochemical and mineralogical features resembling post-orogenic A-type granites. Numerous local and regional geologic constraints indicate that the plutons were intruded in an extension-related setting following the cessation of Neoproterozoic arc-related magmatism. Geochemical data are consistent with their derivation by partial melting of depleted crust followed by fractional crystallization of feldspars, ferromagnesian minerals and REE-rich accessory phases. The radiogenic isotope data [eNd (T) values are +3.5 to +4.2] indicate that the granite magma was generated from a ‘juvenile’ source, which is typical of the rocks making up most of the Arabian-Nubian Shield. Rare-metal mineralization is associated with the fracture-controlled alteration zones that occur at Jabal Al Hamra and Jabal Abu ad Dud. The altered rocks are characterized by higher TiO2, Fe2O3, SiO2 and lower Al2O3, CaO, Na2O, than the unaltered rocks. They show high and wide range in the total REE contents (804–15579 ppm), Ta (6–194 ppm), Nb (51–3483 ppm), Hf (13–368 ppm), Zr (394–14887 ppm), Th (16–572 ppm) and U (4–143 ppm). Field observations and further petrographic and chemical studies suggest that the altered rocks and the rare metal enrichment are the products of hydrothermal-metasomatic alteration of the quartz alkali feldspar syenite and the alkali feldspar granite. The rare-metal enrichment was explained by orthomagmatic fluid transport of these elements as fluoride complexes, and their subsequent deposition as a result of mixing with externally derived Fe-rich fluids.
-consistent thermodynamic data for minerals in the system Na2OK2O-Berman, R.G. 1988: Internally-consistent thermodynamic data for minerals in the system Na2OK2O-CaO-MgO-FeO-Fe2O3-Al2O3-TiO2-H2O-CO2. J. Petrol. , 29 , pp. 445-522. Internally
Ca 1.05 0.63 1.47 CaO Ti 0.23 0.11 0.38 TiO 2 Ti
2 vs. TiO 2 ( Shan et al., 2016 ) and the K 2 O/Al 2 O 3 vs. Na 2 O/Al 2 O 3 ( Garrels and Mackenzie, 1971 ) discrimination diagrams were used to identify the protolith of the parametamorphic and orthometamorphic rocks. All garnet
–4) pegmatite, Sukoró (2: MBFSZ-11138, 3: MBFSZ-11144, 4: MBFSZ-11149); 5) aplite, Bence Hill, Velence (MBFSZ-5304); 6) aplite, Tompos Hill, Pákozd (V3) 1 2 3 4 5 6 SiO 2 33.91 33.86 33.12 33.91 33.34 33.80 TiO 2 0.05 0.22 0.26 0.25 0.45 0.36 B 2 O 3 * 9
