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A small and isolated hydrothermal vein-type Sb deposit is hosted by a lamprophyre dike which penetrated Neoproterozoic to early Cambrian volcanosedimentary successions near Chříč in the Teplá-Barrandian Unit, Czech Republic. Hydrothermal minerals were formed in several consecutive mineralization stages, separated by long pauses in hydrothermal fluid flow. Early Stage I is characterized by the formation of carbonates of dolomite-ankerite series (Carb I) and arsenopyrite with an imprecise Re-Os age of ~570 to 510 Ma. Stage I was followed by tectonic movements and brecciation. The second mineralization stage (Stage II) is characterized by the precipitation of quartz (Qtz I) and Sb minerals (predominantly stibnite) while the third stage (Stage III) is marked by the presence of carbonates of dolomite-ankerite series (Carb II) and quartz (Qtz II) along with Cu, Zn, Pb, Ag and Fe sulfides. Lead isotope data of galena indicate a Variscan age of Stages II-III. These stages were followed by precipitation of another generation of carbonate of dolomite-ankerite series (Carb III, Stage IV), quartz (Qtz III, Stage V) and formation of Sb supergene minerals. The earlier reported occurrence of gold was not confirmed in the studied rock samples but three types of gold particles of variable fineness, with one of them indicating a local origin, were found in the heavy mineral concentrate from a local creek. Elevated Au concentrations were found in arsenopyrite and pyrite. The ore-forming hydrothermal fluid of the mineralization stage III was of H2O-CO2 type with minor CH4 admixture, medium salinity, and temperatures in the range of 258-350 °C with an observed temperature decrease from Stage II to Stage V. Oxygen isotope data of Carb II correspond to high d18Ofluid values (~ +7.5 = VSMOW) with a decrease in the fluid d18O to later stages. An important part of the carbonate carbon was derived from decomposition of organic matter or its high-temperature reaction with hydrothermal fluid. Considering the wide variation in d34S values of sulfides and elevated Sb contents in the TBU black shales, we anticipate that the origin of the Chříč mineralization is closely associated with a metal and carbon-sulfur remobilization from the TBU volcanosedimentary successions in response to Cadomian and Variscan tectonothermal events. [ABSTRACT FROM AUTHOR]

Australasian Muong Nong-type tektites from the locality centered at 16.46150° N, 106.48917° E in Laos contain sporadic spherical heterogeneous sulfide inclusions less than 10 µm in diameter, which have been identified by electron probe microanalyzer and electron backscatter diffraction to represent a mixture of rare mineral shenzhuangite with a pyrrhotite polytype (possibly troilite). Contrary to type shenzhuangite found in the shocked L6 chondrite Suizhou, the mineral embedded in the tektite glass is nearly free of copper, making the composition close to its expected end-member that has not yet been found in nature; the empirical formula closest to ideal end-member composition based on four atoms per formula unit is Ni1.007Fe0.998Cu0.016Co0.058S1.922. The described occurrence also represents the first find of shenzhuangite in terrestrial material. Presented is the Raman spectrum for shenzhuangite with the tentative assignment of spectral bands based on the analogy with synthetic chalcopyrite-structured phases. The chemical composition of shenzhuangite close to NiFeS2 is not consistent with any stable phase in the Fe-Ni-S system up to melting temperature. Available data so far on phase relations in this system do not allow unambiguous interpretation of conditions under which the sulfide association within inclusions had formed. [ABSTRACT FROM AUTHOR]

The Ještěd Ridge (part of the Krkonoše-Jizera Crystalline Complex; northern part of the Bohemian Massif) hosts 20 known karst caves, which are developed in marbles of Devonian age. The caves are mostly relatively small and isolated, not connected into larger cave systems. The longest one, Západní (Jitravská) Cave, currently exceeds the length of 450 m. Majority of the known caves are shorter than 50 m. Formation of these cavities was initiated under morphological conditions different from those of today, in the pre-Quaternary. The caves are developed along two systems of regional faults, one striking NW-SE and the second striking SW-NE. One of the newly found caves, about 70 m long Dvoustovka Cave, was discovered in 2015 at an elevation of ca. 795 m a.s.l., close to the Ještěd ridgeline near the Pláně pod Ještědem site. The cave hosts several speleothem types including unusual, coarse-crystalline speleothems characterized by translucent calcite crystals up to 15 mm in size (so-called dogtooth spar). These speleothems developed in several small water pools located at different elevations within the cave. Fluid inclusions and C and O stable isotope studies (Table 1) do not support their deposition from thermal water and indicate formation from usual lowtemperature descending karst water. Fluid inclusions in calcite of dogtooth spar are single-phase, containing low-salinity water. The C and O isotope data lie in a range typical of usual low-temperature Quaternary speleothems of the area. The U-series dating (methods: spike addition; dissolution; chromatographic separation using TRU-resin; measurement on ICP-MS; results in Table 2) indicate an age of the coarse-crystalline speleothems fitting into the Eemian interglacial (118 ± 3 ka BP). Underground spaces of the Dvoustovka Cave are affected by numerous movements along cracks and rock collapses. While some of these movements occurred before the formation of the studied coarse-crystalline speleothems, majority of them are younger, related most probably to slope movements (mass wasting) during the last Glacial. The cave cannot keep larger stagnant pools of karst water today. [ABSTRACT FROM AUTHOR]

A new fossiliferous Upper Pleistocene section located on slopes of the Berounka River valley was found at the village of Stradonice (Beroun District, Czech Republic). The section (marked as A in the text below) lies approx. 35 m above the present-day level of the river. It consists of prevailing mixed eolian-deluvial and eolian sediments with exposed thickness of 90 cm. The finding includes fragments of a horse mandible (Equus ferus germanicus Nehring, 1804), rare mollusks (Pupilla muscorum, Pupilla triplicata, Helicopsis striata) and bones, and bone fragments of small vertebrates (Microtus gregalis/arvalis, Microtus sp.). The collagen of horse bones yielded a calibrated radiocarbon age of 29 366-28 771 BC, chronologically fitting into the Marine Isotope Stage 3 (MIS 3), a period of variable climate prior to the onset of the Last Glacial Maximum. A layer of brown-red soil with cubic to polyhedral structure which may belong to MIS 2 sits on the top of eolian deposits. The exposed section is covered by recent soil containing ceramic shards and animal bones coming from a period stretching from the Middle Ages until today (the oldest bone is 1 458-1 539 cal. AD). Another section (marked as B) lying at a distance of ca 20 m from section A, and 4 m higher, and close to the upper edge of the gorge, was identified. It consists of eolian-deluvial sediments also corresponding to MIS 3, and containing rare mollusks (Pupilla muscorum, Helicopsis striata) and seeds of yew (Taxus baccata). The age of section A can in general be compared to the occurrence of macrofauna found in nearby locality at Hýskov (2 km downstream), located at a similar height above the current river level. On the contrary, the section at Karlštejn-Altán (17 km downstream), developed at the same level, is apparently much older (probably MIS 9-7), and its lithology is also markedly different. [ABSTRACT FROM AUTHOR]

The Brdy Protected Landscape Area is built of geologically heterogeneous units with numerous rock types which locally show signs of hydrothermal alterations. This study was carried out as an additional investigation to the mapping of local forest humic soils contaminated by Hg. Results of the survey did not exactly correspond to the so far known history of Hg pollution in the area, and therefore a possible influence of bedrock with naturally elevated Hg contents was studied. Samples from seventeen lithological types, which are characteristic of the Brdy Protected Landscape Area, were analyzed (Table 1, Fig. 1). Both inorganic and organic carbon and sulfur were analyzed using a carbon/sulfur analyzer Eltra CS 530, whereas mercury was analyzed by means of AMA 254, a single-purpose atomic absorption spectrometer. The highest concentrations of Hg were detected in Carboniferous sedimentary rocks of the Mirošov Basin rich in organic carbon, for example a black coal from Záborčí with Hg content of 9 347 ppb or carbon-rich siltstone with concentration of 1 339 ppb Hg. Ore samples with sulfides showed also high contents of Hg such as an oolitic Feore from the locality of Jedová hora contained 1 017 ppb Hg, and a lens of hydrothermal ore consisting mostly of limonite and hematite confined to quartzite (Žák et al. 2014) at Přední Záběhlá showed 757 ppb Hg. Ordovician period in the Prague Basin is characterized by higher concentrations of Hg in volcanic rocks and related volcanoclastic sediments (Sattran et al. 1978). Concentrations of Hg in diabase from Jedová hora (4 158 ppb) and quartzite from the Felbabka locality (100 ppb) obviously support data mentioned above. A conglomerate of supposedly Cambrian age found at Jezevčí skála (Havlíček et al. 1986) also revealed high content of Hg (1 540 ppb). As Cambrian conglomerates from other localities of the area do not exhibit elevated Hg contents, the origin of high Hg in the Jezevčí skála conglomerates remains unclear; it may be related to some processes taking place during the Ordovician. Unusually high is also the Hg content in a sample of schist to greywacke of Neoproterozoic age (up to 4 194 ppb) which is likely to be connected with basic volcanic material contained in the sample. Another sample with remarkably high content of Hg is a Carboniferous arkose from the Záborčí Hill at Mirošov (778 ppb) that could be explained by higher content of Hg derived from eroded underlying coal bed, or due to secondary dissemination of sulfidic mineralization in the Mirošov Basin (Pešek et al. 2001). The results of this study indicate Hg to be related to Ordovician or even Neoproterozoic basic volcanism. However, in order to prove this assumption and to come to more reliable conclusions some more sampling and more detailed investigation should be carried out in future. [ABSTRACT FROM AUTHOR]