The Rodna Mountains afford the most internal structural window into the crystalline units of the Eastern Carpathians in Romania. The Rodna Mountains consist of Variscan metamorphic nappes that were restacked in the Alpine phase of Carpathian development forming the Subbucovinian and Infrabucovinian nappes. In order to evaluate age of deformation, ten samples were taken from the zone of greenschist facies mylonitic schist that marks the Alpine tectonic boundary between the Subbucovinian and Infrabucovinian nappes and 40 Ar/ 39 Ar laser singlegrain ages determined for schistosity-forming muscovite. Microstructural assessment of quartz and muscovite distinguished two deformation events. Single-grain ages from the microstructurally most strongly reworked samples (four samples) give a tight clustering of ages at ca. 95 Ma. The least reworked schists have a broader clustering of ages spanning ca. 200-280 Ma with a late Permian peak and some samples showing outlier ages in the range 200-100 Ma. The relative development of the outliers, which correlates with evidence for increased microstructural reworking, is interpreted to mark progressive isotopic resetting. The ca. 95 Ma ages for the most reworked schists are estimates for the age of the Alpine nappe stacking. The ca. 200-280 Ma ages are similar to those of magmatism, metamorphism, and sedimentation thought to mark postVariscan-pre-Alpine rifting and ocean basin formation in parts of the Alps and may be the thermal imprint of a related event in the Eastern Carpathians.
The paper presents new different raw materials mixtures which should lead to the theoretical mineralogical compositions of sulfoaluminate belitic (SAB) clinkers. The mixtures, composed of limestone, gypsum, clay, diatomite, basaltic scoria, volcanic tuff and red mud (bauxite ore processing by-product), have been burned at 1220, 1240 and 1260 °C for one hour in an electrical laboratory furnace, then quenched in fresh air. The resulted clinker samples were studied in thin sections under a polarizing petrographic microscope for clinker structure, microtexture and mineralogical association. The mineralogical assemblage assessment by XRD analyses was completed. The sample XRD patterns (processed by Match software and pdf2 database) have been allowed a qualitative and a semiquantitative estimation (external standard method) of the main mineralogical compounds: C 2 S (belite), C 4 AF (brownmillerite), CS ̅ (anhydrite), C 4 A 3 S ̅ (sulfoaluminate), proper for sulfoaluminate belitic clinkers. The identified minor and secondary mineral phases were: alkali (Na, K, Na-K) sulfates, natroalunite (NKA 6 S ̅ H), limeite (C), periclase (M), gehlenite (C 2 (A 1x ,M x)(AS)). The following abbreviations were used: C= CaO; S = SiO 2 ; A= Al 2 O 3 ; F= Fe 2 O 3 ; S ̅ = SO 3 ; H = H 2 O; M= MgO; N(K)= Na 2 O(K 2 O).
This paper presents the results of laboratory investigations regarding the production of cements from local raw materials, such as limestone from Varghis, gypsum from Nucsoara, basaltic scoria from Racosul de Jos, volcanic tuff from Racosul de Sus, diatomite from Filia, and red mud from Oradea. The raw mixtures, based on modified Bogue calculations, contain limestone, gypsum, and one or two of the above-mentioned materials. The cements resulted from clinker grinding in a laboratory gas furnace at 1260-1300 ºC, with one hour at the peak temperatures, and were characterised for Blaine specific surface area, specific density, and mineral phases. Physico-mechanical properties, such as water content for normal consistency, setting time, soundness, and compressive strength were also determined. Results show that these cements contain belite, ferrite, calcium sulphoaluminate, anhydrite, and some minor compounds.
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