Litotipi bauxitici dell\u2019isola di Krk (Ba\u161ka e Stara Ba\u161ka \u2013 Croazia)

Vengono descritti i litotipi bauxitici rinvenuti nel corso di una ricerca condotta nella parte meridionale dell\u2019isola di Krk (Dalmazia settentrionale \u2013 Croazia) nelle localit\ue0 di Ba\u161ka e Stara Ba\u161ka. Si tratta di rocce residuali, spesso compatte e di elevato peso specifi co, ricche di ossidi ed idrossidi di alluminio e ferro. La ricerca \ue8 stata condotta sul campo ed in laboratorio, al fi ne di comprendere meglio i rapporti che intercorrono con le rocce calcaree incassanti e con il fenomeno carsico presente nell\u2019area

Estudio sedimentológico preliminar y análisis de minerales pesados en la cueva Pocala

[Abstract] In 1999 two borings were performedin the area of Pocala Cave, one outside the cave and the other inside in the cave. In particular four samples of the first boring were studied.It seems that mineralogy is strictly connected with sedimentology where quartz and plagioclase are present. It could be a consequence of a periodical floods of flysch sediments during interglacial perio

Maturation stages of glauconites: A combined electron microprobe, Raman, and thermogravimetric study

Glauconite mineral is one of the most sensitive indicators of low sedimentation rate in the marine environment. The time of residence of glauconites at the sea bottom before burial is reflected by their so-called maturity that is differentiated based on their K2O content. The present work aims to investigate the evolution of glauconites during the transition toward the highly evolved level. Complementary electron microprobe, Raman, and Thermogravimetric analysis were performed on glauconitic grains from the Belluno basin (N Italy) with different K2O content in order to verify whether the level of glauconites evolution affects the results of these surveys

The Stillwater Complex chromitites : the response of chromite crystal chemistry to magma injection

Nineteen chromite crystals from the A, B, E, G, H, J and K chromitite layers of the Peridotite Zone of the Stillwater Complex (Montana, USA) have been studied by means of X-ray single crystal diffraction and microprobe analyses. The results show that samples from the basal A layer are quite different from the others showing very high oxygen positional parameter u (0.2633-0.2635) and Ti- contents (0.059-0.067apfu). Mg# values are within the range 0.21-0.23 while for the other chromites it is in the range 0.45-0.47. Moreover, for the other samples, according to the structural parameters, two groups have been identified. The first one comprises samples of layers B, E and G, the second includes H, J and K layer samples. It is supposed that high Fe2+ and Ti contents of A layer samples are due to the post-crystallization reaction with interstitial liquid. This fact allowed a very slow cooling rate as evidenced by the high u values. The fractionation of evolved magma from within the intrusion and pulse of a new magma bringing more chromium into the chamber lead to Cr- and Fe3+ -rich compositions and consequently to the increase of the cell edges. The decrease of u values seems to be related to the Cr+Fe3+ and/or Al contents

Provenance of late Republican Roman pottery from Caput Adriae revealed by non-invasive mineral chemistry of melanitic garnets and other igneous minerals

Quite rare pottery shards showing a paste rich in black sand particles, possibly igneous minerals, have been discovered in late Republican Roman sites of Trieste area (northeastern Italy) and south-western Slovenia in the Caput Adriae. Most of them belong to late Greco-Italic and Dressel 1 amphora types, in use from the end of the 3rd and the beginning of 1st centuries BC. Following a methodological procedure based on the analysis of igneous temper, proved to be particularly effective by several scholars, numerous minerals have been extracted from the surface of 16 pottery shards, without causing any visible damage to them. Microprobe analysis has allowed the identification of igneous minerals (olivine, clinopyroxene, feldspar and garnet), most likely originating from the Roman or Campanian magmatic provinces. The chemistry of garnets, indicated in the past as a possible tracer of ancient commerce but no longer used in the last decades to study Italian late Republican pottery, has proved to be a promising tool to distinguish among the two magmatic provinces. According to our study, most of the investigated garnets-bearing samples would originate from Somma-Vesuvius while some of them from Latium

Antarctic Salt-Cones: An Oasis of Microbial Life? The Example of Boulder Clay Glacier (Northern Victoria Land)

The evaporation of a localized, highly saline water body of the Boulder Clay debris-covered glacier, in the Northern Victoria Land, probably generated the accumulation of mirabilite (Na2SO4 × 10H2O) and thenardite (Na2SO4) in a glacier salt-cone. Such an extremely cold and salty environment resembles the conditions on Mars, so it can be considered a terrestrial analog. The study was aimed at gaining a first glimpse at the prokaryotic community associated with Antarctic mirabilite and thenardite minerals and also to find clues about the origin of the salts. For this purpose, samples were analyzed by a next generation approach to investigate the prokaryotic (Bacteria and Archaea) diversity. Phylogenetic analysis allowed the identification of Bacteroidota, Actinobacteriota, Firmicutes, and Gammaproteobacteria as the main bacterial lineages, in addition to Archaea in the phylum Halobacterota. The genera Arthrobacter, Rhodoglobus, Gillisia, Marinobacter and Psychrobacter were particularly abundant. Interestingly, several bacterial and archaeal sequences were related to halotolerant and halophilic genera, previously reported in a variety of marine environments and saline habitats, also in Antarctica. The analyzed salt community also included members that are believed to play a major role in the sulfur cycle

Polished stone axes from Varna/Nössingbühel and Castelrotto/Grondlboden, South Tyrol (Italy)

A collection of polished stone axes from a late Neolithic site and an Early Bronze Age hill fort in South Tyrol (Italy) have been analysed through a multi-analytical approach, mainly based on non-destructive techniques (i.e. Raman spectroscopy, X-ray fluorescence and prompt gamma activation analysis) to identify the raw materials used in the same area during different periods and compare them with those in use in the surrounding territories. The analytical results suggest raw material exploitation strategies based on local or close sedimentary, metamorphic and magmatic rocks. Most of the artefacts are made from antigoritic serpentinite, whose origin is probably from Hohe Tauern (Austria) or related secondary deposits. These data confirm the importance of such raw material for the production of polished stone axes during recent prehistory and integrate the present knowledge about the distribution of antigoritic artefacts in north-eastern Italy and neighbouring countries

A multi-analytical study of Bronze Age pottery from the UNESCO site of Al-Khutm (Bat, Oman)

The extensive investigation carried out in recent years at the UNESCO site of Al-Khutm (Ibri, Oman) has allowed to uncover the monumental remains of a tower dated back to the third millennium BC and to collect an abundant ceramic assemblage from the associated soil deposits. Eighteen selected pottery samples have been investigated using a multi-analytical approach including microfocus X-ray computed tomography, X-ray diffraction, optical microscopy and prompt gamma activation analysis to analyse the vessel-forming technique and to characterise their micro-structure, mineralogical and chemical composition to recognise possible local vs. non-local raw materials. The results provided new insights on ancient manufacturing processes and revealed that most of the vessels were locally produced exploiting raw materials from the surroundings of the site with the exception of a fragment of a black slipped jar. The chemical results suggest that the latter was imported from the Indus area in nowadays Pakistan. This evidence integrates our knowledge about the presence of this type of vessels in Oman and confirms the involvement of inland centres like Bat and Al-Khutm into a large-scale exchange system

Distribution of Capillary Transit Times in Isolated Lungs of Oxygen-Tolerant Rats

Rats pre-exposed to 85% O2 for 5–7 days tolerate the otherwise lethal effects of 100% O2. The objective was to evaluate the effect of rat exposure to 85% O2 for 7 days on lung capillary mean transit time (t¯c) and distribution of capillary transit times (h c(t)). This information is important for subsequent evaluation of the effect of this hyperoxia model on the redox metabolic functions of the pulmonary capillary endothelium. The venous concentration vs. time outflow curves of fluorescein isothiocyanate labeled dextran (FITC-dex), an intravascular indicator, and coenzyme Q1 hydroquinone (CoQ1H2), a compound which rapidly equilibrates between blood and tissue on passage through the pulmonary circulation, were measured following their bolus injection into the pulmonary artery of isolated perfused lungs from rats exposed to room air (normoxic) or 85% O2 for 7 days (hyperoxic). The moments (mean transit time and variance) of the measured FITC-dex and CoQ1H2 outflow curves were determined for each lung, and were then used in a mathematical model [Audi et al. J. Appl. Physiol. 77: 332–351, 1994] to estimate t¯c and the relative dispersion (RDc) of h c(t). Data analysis reveals that exposure to hyperoxia decreases lung t¯c by 42% and increases RDc, a measure h c(t) heterogeneity, by 40%