Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with rollback, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calclkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions, diatreme, lava lake) for various types of K- and Na-alkalic and ultra-potassic magmatism. Finally, we provide a summary of the eruptive history and distribution of volcanic forms in the CPR using several sub-region schemes.     

Niobium-tantalum oxide minerals in the Jezuitsk�� Lesy granitic pegmatite, Bratislava Massif, Slovakia: Ta to Nb and Fe to Mn evolutionary trends in a narrow Be,Cs-rich and Li,B-poor dike

A complex assemblage of Nb-Ta-(Sn) oxide minerals occur in a relatively narrow (~1?2 m thick) extensively albitized, Hercynian granitic pegmatite dike intruding biotite granodiorites near Bratislava, SW Slovakia. The dike shows enrichment in beryl (locally Cs-rich) but absence of Li- and B-rich phases. Compositions and textural relationships indicate complex evolutions of Nb-Ta oxide phases with several generations presenting distinct textural and compositional features. The first generation of the Nb-Ta minerals from the quartz-microcline-muscovite zone show Ta,Fe-rich compositions with Ta# [Ta/(Ta + Nb)]?=?0.52?0.70 (Ct I columbite-tantalite), 0.88?0.90 (Tap I ferrotapiolite) and 0.73?0.86 (Fw I ferrowodginite); Mn# [Mn/(Mn + Fe)]?=?0.32?0.49 (Ct I), 0.06?0.10 (Tap I) and 0.33?0.41 (Fw I). The 2nd generation is represented by ferrocolumbite to ferrotantalite (Ct II) in saccharoidal albite zone, replacement zones of Ct II in Ct I, and irregular overgrowths of ferrotapiolite (Tap II) and ferrowodginite (Fw II) on Tap I grains. The minerals of the 2nd generation show decreasing of Ta# in comparison to the 1st group: 0.10?0.60 (Ct II), 0.85?0.87 (Tap II) and 0.73?0.77 (Fw II); Mn# attains 0.30?0.45 (Ct II), 0.06?0.09 (Tap II) and 0.26?0.37 (Fw II). The 3rd generation includes fissure fillings, overgrowths and replacement zones of manganocolumbite and manganotantalite (Ct III), ferrotapiolite (Tap III) and ferrowodginite (Fw III) on the older Nb-Ta phases (Ct I, Tap I, Fw I, Fw II), in the coarse-grained unit. The 3rd population displays distinct Mn# increasing (Ct III: 0.51?0.69, Tap III: 0.11?0.24, Fw III: 0.40?0.41), Ta# values reach 0.16?0.79 (Ct III), 0.88?0.92 (Tap III) and 0.80?0.81 (Fw III). The latest, 4th generation of the Nb-Ta phases represents irregular veinlets and patches of fluorcalciomicrolite, replacing Ct I, Tap I, Fw I, Ct II and Tap III. Decrease of Ta/(Ta + Nb) values in Ct II from the saccharoidal albite unit can be explained by crystallization from the albite-rich melt, which was significantly impoverished in Ta with respect to Nb, after crystallization of Ta-rich phases from the 1st generation (ferrotapiolite I, ferrowodginite I).     

Palygorskite from cave sediments: case study from Wadi Haqil,United Arab Emirates

The x-ray powder diffraction identification of clay minerals both in bulk samples and in separated clay fraction confirmed the presence of palygorskite in samples of cave sediments from Wadi Haqil (the western slopes of Musandam Mountains; Ras Al-Khaimah Emirate, UAE). Samples contain quartz, gypsum, smectite, kaolinite, calcite, and palygorskite, some of them chlorite, illite, feldspars, and goethite. Calcite dominates in most samples; smectite prevails in clay fraction. After heating, the 001 reflection of chlorite shifts to higher diffraction angles and its intensity decreases; these features indicate that the chlorite represent a Fe-dominant species. Unit-cell dimensions of major phases as refined by the Rietveld method are in agreement with literature data. Chemical composition of palygorskite was derived from unit-cell dimensions as follows: MgO content is 11–14 wt% and Al₂O₃ 10–13 wt%. Clay mineralogy is only hard to ascertain from the scanning electron microscope (SEM) images even after being combined with the energy-dispersive spectrometer data. The SEM was also used to characterize gypsum grains; they often display flow deformation features. Studied cave sediments represent palygorskite-bearing weathering products and desert soils re-deposited from the cave surroundings by slope processes and wind and/or surface runoff. The mixture with other clay minerals, quartz, feldspars, etc. supports this interpretation. Fine-grained quartz fraction is probably wind-blown. Gypsum and calcite are the precipitates (crusts and/or cements), although gypsum can also be re-deposited from omnipresent gypsum-cemented surface sediments.     

Accuracy assessments of recent earth gravity models using crossover altimetry

Summary The calibrated variance-covariance matrices of the harmonic geopotential coefficients of the recent combined model JGM 2 has been tested and verified by independent crossover altimetry from TOPEX/Poseidon and ERS 1 using the Latitude Lumped Coefficients in the southern oceans area. Although orbits are not yet available for these missions with other recent models for which error matrices have been released, by comparison with JGM 2 results and field differences we also confirm that the error matrices for the satellite model GRIM 4S4p and the combined data model JGM 3 are also generally valid. Projections of these matrices for a variety of inclinations show that many unused orbits of even moderate altitude (≈ 800 km) will still yield trajectory crossover errors at a level of many tens of centimeters even with the latest orbitgeopotential models.     

Chinese tombs oriented by a compass: Evidence from paleomagnetic changes versus the age of tombs

Extant written records indicate that knowledge of an ancient type of compass in China is very old — dating back to before the Han dynasty (206 BC-220 AD) to at least the 4th century BC. Geomancy (feng shui) was practised for a long time (for millenia) and had a profound influence on the face of China’s landscape and city plans. The tombs (pyramids) near the former Chinese capital cities of Xi’an and Luoyang (together with their suburban fields and roads) show strong spatial orientations, sometimes along a basic South-North axis (relative to the geographic pole), but usually with deviations of several degrees to the East or West. The use of the compass means that the needle was directed towards the actual magnetic pole at the time of construction, or last reconstruction, of the respective tomb. However the magnetic pole, relative to the nearly ‘fixed’ geographic pole, shifts significantly over time. By matching paleomagnetic observations with modeled paleomagnetic history we have identified the date of pyramid construction in central China with the orientation relative to the magnetic pole positions at the respective time of construction. As in Mesoamerica, where according to the Fuson hypothesis the Olmécs and Maya oriented their ceremonial buildings and pyramids using a compass even before the Chinese, here in central China the same technique may have been used. We found a good agreement of trends between the paleodeclinations observed from tomb aligments and the available global geomagnetic field model CALS7K.2.     

Phenological observations made by the I. R. Bohemian Patriotic�CEconomic Society, 1828�C1847

Drought forecasting is a critical component of drought risk management. Identification of effective predictors is a major component of forecasting models. Sea surface temperature (SST) and sea level pressure (SLP) are relevant predictors for short- to long-term drought forecasts. However, these datasets are captured globally within a cell-wise network. This paper describes an approach to locate the most effective cells of the SST and SLP datasets using data mining. They are then applied as input to an adaptive neurofuzzy inference system (ANFIS) model to forecast possible droughts 3, 6, and 9?months in advance. Tehran plain was selected as the study area, and drought events are designated using the effective drought index (EDI). In another treatment, past values of the EDI time series were introduced to the ANFIS and the results compared with the previous findings. It was shown that R ² values were higher for all cases applying the SST/SLP datasets. Additionally, the performance of SST/SLP datasets and the ANFIS model was assessed according to ??drought?? or ??wet?? classification, and it was concluded that more than 90% of the time the ANFIS model detected the drought status correctly or with only a one class error.     

New data on the Neoproterozoic – Cambrian geotectonic setting of the Teplá-Barrandian volcano-sedimentary successions: geochemistry,U-Pb zircon ages,and provenance (Bohemian Massif,Czech Republic)

The Teplá-Barrandian unit (TBU) of the Bohemian Massif was a part of the Avalonian-Cadomian belt at the northern margin of Gondwana during Neoproterozoic and Early Cambrian times. New detrital zircon ages and geochemical compositions of Late Neoproterozoic siliciclastic sediments confirm a deposition of the volcano-sedimentary successions of the TBU in a back-arc basin. A change in the geotectonic regime from convergence to transtension was completed by the time of the Precambrian-Cambrian boundary. The accumulation of around 2,500 m Lower Cambrian continental siliciclastics in a Basin-and-Range-type setting was accompanied by magmatism, which shows within-plate features in a few cases, but is predominantly derived from anatectic melts displaying the inherited island arc signature of their Cadomian source rocks. The geochemistry of clastic sediments suggests a deposition in a rift or strike-slip-related basin, respectively. A marine transgression during Middle Cambrian times indicates markedly thinned crust after the Cadomian orogeny. Upper Cambrian magmatism is represented by 1,500 m of subaerial andesites and rhyolites demonstrating several geochemical characteristics of an intra-plate setting. Zircons from a rhyolite give a U-Pb-SHRIMP age of 499±4 Ma. The Cambrian sedimentary and magmatic succession of the TBU records the beginning of an important rifting event at the northern margin of Gondwana.