Field characteristics and petrography of the advanced rifting-related Triassic submarine basaltic blocks in the Jurassic mélange of the Darnó Unit

Abstract The Darnó Unit in NE Hungary contains basalt and associated sediments related to the advanced rifting stage of Triassic age in the Neotethys. A detailed field study of five key outcrops and two deep wells revealed that only distal facies of basaltic lava flows of submarine volcanoes occur as blocks in the Jurassic mélange; the central and the most distal facies are missing. The advanced rifting-related Triassic and oceanic stage-related Jurassic basalt flows of the same mélange can be distinguished on the basis of lithostratigraphic, structural and textural features. The paper contains for the first time the detailed description of the key outcrops of peperitic facies consisting of a mixture of basalt and red micritic limestone. The occurrence of this facies is the principle key feature for discrimination in the field between Triassic and Jurassic basalt. In addition, four types of Triassic basalt were recognized: the Báj-patak-type, the Mély Valley-type, the Nagy-Rézoldal-type and the Reszél Hill-type. The observed peculiarities of advanced rift-related basalt are also compared to characteristics of volcanics encountered in wells drilled in the Darnó Unit. This comparison solves many problems of earlier interpretations of the studied wellbore sections

Environmental geochemistry of the polymetallic ore deposits: Case studies from the Rude and the Sv. Jakob historical mining sites, NW Croatia

This paper presents the results of the sampling surveys carried out in order to evaluate the environmental impact of the Rude and the Sv. Jakob historical mining sites, NW Croatia. The studied polymetallic ore deposits are differing in the mineralogical and geochemical features as well as in the host rock lithology. The Rude Fe-Cu-Pb-Zn-Ba deposit is hosted by Permian siliciclastic sediments. Siderite, hematite, galena, sphalerite, chalcopyrite, pyrite, barite and gypsum are the major ore minerals, whereas quartz is the principal gangue mineral. The Sv. Jakob Pb-Zn-Ag deposit occurs in the Middle Triassic dolostone. The most abundant ore minerals are galena, sphalerite and pyrite. Calcite and quartz represent the principal gangue minerals. Although the deposits represent the potential sources of numerous toxic metals, the pollution of the drainage streams and associated stream sediments was not recorded. The studied mining sites are characterized by the high carbonate/sulfide ratios responsible for the alkaline character of the drainage streams. Consequently, the mining sites have very low potential for generation of acid mine drainage as well as very low potential for leaching of heavy metals into the drainage systems. Furthermore, the presented study revealed that the populated areas (stream waters with decreased redox potential, increased organic matter content, high NO3-, NH4+ and PO43- concentrations; stream sediments enriched in exchangeable Pb and Zn) and the Sava river alluvium (overflowing streams enriched in Hg) represent bigger environmental threat than the investigated polymetallic ore deposits. </span

Origin and K-Ar age of the phreatomagmatic breccia at the Trepča Pb-Zn-Ag skarn deposit, Kosovo: Implications for ore-forming processes

The Trepča Pb-Zn-Ag skarn deposit in Kosovo is spatially and temporarily related to the phreatomagmatic breccia of Oligocene age (~23 Ma). The deposit shows features typical for skarn deposits worldwide, including a stage of isochemical metamorphism, a prograde stage of an anhydrous, low oxygen and low sulfur fugacity character and a retrograde stage characterized by an increase in the water activity as well as by an increase in oxygen and sulfur fugacities. The mineralization is hosted by the recrystallized Upper Triassic limestone. The prograde mineralization consists mainly of Ca-Fe-Mn±Mg pyroxenes. The host recrystallized limestone at the contact with the prograde (skarn) mineralization have the increased content of Fe, Mn, Mo, As, Au, Cs, Ga, REE and Y suggesting their transport by infiltrating magmatic fluids. The decreased  d13C and  d18O values reflect a contribution of magmatic CO2. The retrograde mineral assemblage comprises ilvaite, magnetite, arsenopyrite, pyrrhotite, marcasite, pyrite, Ca-Fe-Mn±Mg carbonates and quartz. Hydrothermal ore minerals, mostly galena, sphalerite and pyrite, were deposited contemporaneously with the retrograde stage of the skarn development. Syn-ore and post-ore carbonates reflect a diminishing influence of magmatic CO2. Syn-ore carbonates are enriched in Fe, Mg, Mn, many chalcophile elements, including Ag, As, Bi, Cd, Cu, Pb, Sb and Zn, as well as in Au, Y and REE. The post-ore stage accompanied the precipitation of significant amount of Ca-rich carbonates including the travertine deposits at the deposit surface. The phreatomagmatic breccia was developed along a NW dipping contact between the ore bearing recrystallized limestone and the overlying schist. It has an inverted cone shape with the vertical extension up to 800 m and diameter up to 150-m. The upper part of the diatreme (an underground segment of the phreatomagmatic breccia) is characterized by the presence of a hydrothermally altered rootless quartz-latite dike surrounded by an unsorted polymict breccia mantle. Despite the alteration processes, the dike has a preserved porphyritic texture. Partly preserved sanidine, accompanied with the mixture of muscovite and quartz, reflects a near-neutral to weakly acidic environment. The clasts of country rocks and skarn mineralization underwent intense milling and mixing due to repeated magmatic penetrations. Sericitization of the breccia matrix, locally accompanied with minor kaolinitization, point to an increased water activity under near-neutral to weakly acidic conditions. Large fragments originally composed of anhydrous skarn minerals (pyroxenes) are usually completely altered to a mixture of fibroradial magnetite, quartz and various amount of carbonates suggesting an increase in oxygen fugacity. Their pyrite rims reflect that the increase in oxygen fugacity was followed by an increase in sulfur fugacity. The clast predominantly composed of Fe-sulfides and minor Bi-sulfides point that the increase in sulfur fugacity was locally sufficient to complete sulfidation of hedenbergite to pyrrhotite and/or pyrite. Although the phreatomagmatic breccia at the Trepča Pb-Zn-Ag skarn deposit does not carry significant amounts of the ore mineralization, its formation was crucial for the ore deposition. Phreatomagmatic explosions and formation of the breccia turned the system from the lithostatic to hydrostatic regime and triggered the retrograde stage increasing the water activity and oxygen fugacity in the system. In addition, cooling and decompression of the system contributed to more effective degassing of magmatic sulfur increased the sulfur fugacity. </p

The evolution of the Čanište epidote-bearing pegmatite, Republic of Macedonia: evidence from mineralogical and geochemical features

The epidote-bearing Čanište pegmatite and adjacent Upper Carboniferous granodiorites cut Precambrian gneises, at the western slopes of the Selečka Mts., the Eastern Pelagonian zone, FYRO Macedonia. The pegmatite exhibits zonal internal structure with the following sub-units: the wall zone (amazonite microcline ± biotite, quartz), the first intermediate zone (epidote + hematite + grossular + muscovite + quartz + almandine ± zircon, beryl, microcline, quartz), the second intermediate zone (albite + quartz ± microcline) and the core (massive quartz). According to the microprobe data epidote belongs to clinozoisite subgroup with formula (Ca1.96-1.99Mn0.02-0.03Fe2+0.00-0.02)(Al2.17-2.46Fe3+0.51-0.82Ti0.00-0.01)(Si2O7)(Si0.99-1.00Al0.00-0.01O4)O(OH). The occurrences of almandine and zircon with low U, Th and REE content, are indicative to weakly evolved granitic/granodioritic rocks. The absence of aplites suggests steady pressure condition during the course of pegmatite crystallization. Microthermometric data combined by the two-feldspar geothermometer gained pressure from 4.8 to 5.6 kbar for the second intermediate zone. The wall zone, composed of amazonite microcline, crystallized at temperature between 650 and 760. Dropping of melt temperature below 550°C, under the oxygen fugacity between 10-22 and 10-19.5 bar, was the principal trigger for deposition of minerals in the first intermediate zone. The residual fluid, depleted in Ca, Fe and K, and enriched in water, Na and Si, caused deposition of the second intermediate zone (albite + quartz) at temperature between 445 and 465°C. The massive quartz core crystallized in the very last stage of the pegmatite evolution (T ≈ 400-480°C) from melt residue enriched in silica, water and CO2 content.</p

Živa u tlu i zraku kao element-indikator za boksitna ležišta u Istri - eksperimentalni istraživački model

ID order to find out a secondary dispersion halo of mercury and some other trace elements around the bauxite ore bodies, the authors sampled terra rossa along traverses over them. At the same time, mercury in air is measured and expressed by relative values (mA) using Zeeman mercury vapor analyser. Mercury in soil was determined by flameless atomic absorption method and Cd, Pb, Zn, Cu, Co and Mn by standard AA techniques. The results are equivocal since the natural vertical soil profiles are severely disturbed on traverses due to different land use, what should be taken into consideration during continuation of the survey.U radu je obrađeno istraživanje sekundarne disperzije žive i nekih drugih elemenata oko boksitnih rudnih tijela u Istri. U tu svrhu izvršeno je uzorkovanje terra rosse uzduž traversi položenih preko boksitnih rudnih tijela. Istovremeno s uzorkovanjem tla vršena su mjerenja pomoću Zeemanovog analizatora živinih para u zraku, a vrijednosti su izražavane u relativnim vrijednostima (mA). Živa u tlu je određivana pomoću metode besplamene atomske apsorpcije, a Cd, Pb, Zn, Cu, Co i Mn standardnom atomskom apsorpcijom. Rezultati ne pokazuju jednoznačnost na terenima s različitim stupnjem poremećenja prirodnog, vertikalnog profila tla (oranica, livada i Suma), što se mora uzeti u obzir prilikom nastavka istraživanja

ŽIVA U ZRAKU IZNAD URBANIH I INDUSTRIJSKIH DIJELOVA GRADA ZAGREBA

In recent years Zagreb city encounters severe pollution problems in aquatic, terrrestrial and atmospheric environment. A random or permanent monitoring of some inorganic gaseous pollutants in atmosphere has already been organized and published alsewhere. By means of a sophisticated mercury vapor analyser with a Zeeman effect background corrector, however, continuous registration along two traverses (monitoring routes) over rural, urban and industrial parts of Zagreb has been elaborated for the first lime. Data show strong anthropogenic influence in the Žitnjak industrial area. The anomaly high 105 ngm Hg, on the 22 October moved slightly to downtown by change of wind direction on the 31 October. Intensity raised as much as 155 ngm Hg, 13 times augmented in comparison to a background value on the Medvednica mountain. Explanation should be sought in denser public traffic, change of wind direction and lowering of atmospheric pressure.Posljednjih godina grad Zagreb se susreće sa značajnim ekološkim problemima zagađenja svih medija; vode, zraka i tla. Povremena i stalna praćenja koncentracije određenih anorganskih zagađivača u atmosferi izvode se već duže vrijeme, a rezultati su publicirani u znanstvenim časopisima. Međutim, prvi put u našem gradu je korišten model suvremenog živinog analizatora s korektorom analitičkih šumova, baziranom na Zeemanovon efektu, koji omogućava kontinuirano registriranje vrijednosti koncentracija žive u zraku. Mjerenja su izvedena uzduž dviju trasa koje prolaze kroz ruralne, urbane i industrijske predjele grada Zagreba, Rezultati mjerenja su omogućili izradu grube geokemij-ske karte distribucije žive i lokaciju anomalnih koncentracija u najugroženijim područjima. Anomalija od 105 ngm Hg, registrirana 21. listopada (subota), vidljivo se pomakla u smjeru prema centru grada 31. listopada (utorak). Njezin intenzitet je porastao na 155 ngm Hg, 15 puta više od prosječnih vrijednosti na Medvednici, a položaj ukazuje na značajan antropogeni utjecaj u području industrijske zone Žitnjaka. Objašnjenje ove pojave treba tražiti u pojačanom utjecaju gradskog prometa, promjeni smjera vjetra i sniženju atmosferskog pritiska kao predznaka pogoršanja vremenskih uvjeta