Fluid Evolution of the Čukaru Peki Cu-Au Porphyry System (East Serbia) inferred from a fluid inclusion study

Čukaru Peki is a recently discovered copper-gold deposit in the Bor metallogenic zone in east Serbia. Three types of mineralization can be distinguished in this ore deposit: porphyry, high-sulphidation, and transitional epithermal type. This research was focused on fluid inclusion analysis of genetically different veins from the porphyry and the transitional zones of Čukaru Peki with an aim of better understanding the fluid evolution and mineralization processes in this system. Seven types of veins were identified in the porphyry zone of Čukaru Peki and four of these veins contained transparent minerals which were suitable for fluid inclusion analysis. Eight types of inclusion assemblages were distinguished in these veins: type 1 – primary inclusions with homogenization temperatures above 550°C and high salinity, type 2a- scattered polyphase inclusions two salt crystals, type 2b-polyphase inclusions with two salt crystals in crystal growth zones, type 3- brine inclusions with one  salt crystal in crystal growth zones, type 4- vapour-rich inclusions, type 5- primary inclusions in anhydrite, and types 6 and 7- secondary low-temperature inclusions This research suggests that saline fluids (30-40% wt.% NaCl eq.) were the most important ones for the formation of porphyry-type mineralization and that the mineralization was formed at temperatures between 350 and 450°C and pressures between 100 and 500 bars. The epithermal stage was characterized by cooler low-salinity fluids with temperatures between 150-350°C, and salinity between 0 and 7 wt.% NaCl eq.</p

Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)

This paper focuses on constraining the erosion rate in the area of the Allchar Sb-As-Tl-Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long-term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L-8 CD, L1b/R, L1c/R, and L-4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo-depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo-depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo-depth values allow estimating the relative contributions of 205Pb derived from pp-neutrino and fast cosmic-ray muons, respectively, which is an important prerequisite for the LOREX experiment

Implications of the geological characteristics and genesis of the Allchar deposit for the Lorex Project

The polychronous and polygenetic Sb-As-Tl-Au Allchar deposit was formed in complex physicochemical processes occurring in a heterogeneous geological environment, in interaction of polyphase hydrothermal fluids with the surrounding magmatic, sediment and metamorphic rocks. The genesis of ore mineralization is related to the products of polyphase magmatic activity of Pliocene age (~6.5 to ~1.8 My), whereas it spatial location was controlled by magmatic, structural and lithological factors. The Allchar deposit comprises several orebodies of various shapes, textural-structural characteristics and element associations. Thallium mineralization, which is of significance for the LOREX project, has been proved in the northern (Crven Dol) and the central parts of the Allchar deposit. The present depth of ore mineralization from the present soil surface is 40–120 m, whereas the paleodepth of its formation is considerably bigger. Using the method of quantitative geomorphological analysis, the erosion rate has been established to be 30–35 m/My at the broader area of the Crven Dol locality and 27–50 m/My in the central part of the deposit. Using the AMS-measurement of 26Al in quartz from the southeastern part of the Allchar deposit, the erosion rate was established to be 50 to 70 m/My. Geological and mineralogical investigations to date, regarding lorandite, its trace elements – Pb, U and Th being the first and foremost, the quantities of lorandite in orebodies, and the geological age of Tl-mineralization, have provided positive results and indicate the feasibility of the LOREX project

East Vardar ophiolites revisited: a brief synthesis of geology and geochemical data

The study reports and synthesizes the available geological and geochemical data on the East Vardar ophiolites comprising most known occurrences from the South Apuseni Mountains in Romania to the tip of the Chalkidiki Peninsula in Greece. The summarized geological data suggest that the East Vardar ophiolites are mostly composed of the magmatic sequences, whereas the mantle rocks are very subordinate. The members of the magmatic sequences are characterized by the presence of abundant acid and intermediate volcanic and intrusive rocks. The age of these ophiolites is paleontologically and radiometrically constrained and these data suggest that the East Vardar ophiolite formed as a short-lived oceanic realm that was emplaced before the uppermost Kimmeridgian. A relatively weak adakitic affinity is shown by intra-ophiolitic acid and intermediate rocks in many East Vardar provinces. It can be taken as evidence that the subduction of the young and hot slab, most likely along the earlier spreading ridge has occurred. A paleo-tectonic reconstruction consisting of four stages is proposed. It involves: a) an early/mid-Jurassic northnortheastward subduction of the West Vardar oceanic plate; b) the formation of a mid-Jurassic volcanic arc and a narrow back-arc oceanic stripe of East Vardar behind it; c) the mid-/Upper Jurassic initiation of East Vardar subduction along the ridge axis, and d) complex and heterogeneous emplacement of the East Vardar ophiolites. So far available data allow for having relatively clear ideas about the origin and evolution of the East Vardar ophiolites. However, in order to provide better understanding of all aspects of its evolution we need to answer additional questions related to the true structural position of the East Vardar ophiolites slices in Serbia, the exact nature of subduction that caused back-arc spreading (intraoceanic vs subduction under continent?) and the full significance of the adakitic signature shown by rocks in the East Vardar provinces other than Demir Kapija

Olivine websterite veins cutting the Rabrovo serpentinites (South Macedonia): new evidence of the arc setting of the east Vardar ophiolites?

The study reports petrography and mineral chemistry data about an ultramafic vein that cuts the Rabrovo serpentinite (near Valandovo, Southern Macedonia). The serpentinite occurs as a block within a shearing zone of the East Vardar Zone tectonic mélange. The vein corresponds to medium-grained olivine websterite that sometimes displays cumulate-like textures. It is composed of low-Al orthopyroxene (Mg#[mol MgO*100/(MgO + FeOt)]~85, Al2O3<2 wt.%), clinopyroxene (Mg# = 82–86), olivine (Mg#~84) and spinel (Cr#[mol Cr2O3/(Cr2O3 + Al2O3)]~0.4, which, according to geothermometric calculations, equilibrated at 750–850 oC. Its pyroxene-rich modal composition suggests that this rock cannot represent a normal lithospheric mantle. Instead, it is supposed that it was formed via magmatic precipitations in the mantle lithosphere. In addition, the Rabrovo olivine websterite shows similar mineral chemical compositions to many other orthopyroxene-rich lithologies worldwide, which origin is commonly associated with subduction settings. Therefore, its presence is considered as additional evidence that the East Vardar ophiolites represent typical supra-subduction ophiolites

Quarz und Cristobalit aus Allchar als Monitore fuer kosmogenes

Allchar, Sb-As-Tl- Au Lagerstätte, befindet sich in Süd-West Teil von Mazedonien an der Grenze mit Griechenland. Wir haben eine ausführliche Untersuchungen, mit verschiedenen komparativen und komplementären Methoden (wie OM, Rö- Beugung, SEM, SEM-EDX, EPMA, ICP – MS, AMS) an den Quarz und Cristobalit aus Allchar durchgeführt. Zwei verschieden Art der Proben wurde untersucht: einmal als erz- bzw. petrographische Schliefe und nach Mineralogische Separation und mineralogisch – chemische Extraktion, als sogen. feinpulverliche stöchiometrische Minerale

Investigation of the microbial diversity of an extremely acidic, metal-rich water body (Lake Robule, Bor, Serbia)

An investigation of the microbial diversity in the extremely acidic, metal-rich Lake Robule was performed using culture-dependant and culture-independent (T-RFLP) methods. In addition, the ability of the indigenous bacteria from the lake water to leach copper from a mineral concentrate was tested. T-RFLP analysis revealed that the dominant bacteria in the lake water samples were the obligate heterotroph Acidiphilium cryptum (approximate to 50 % of the total bacteria) and the iron-oxidizing autotroph Leptospirillum ferrooxidans (approximate to 40 %) The iron/sulfur-oxidizing autotroph Acidithiobacillus ferrooxidans was reported to be the most abundant bacteria in the Lake in an earlier study, but it was not detected in the present study using T-RFLP, although it was isolated on solid media and detected in enrichment (bioleaching) cultures. The presence of the two bacterial species detected by T-RFLP (L. ferrooxidans and A. cryptum) was also confirmed by cultivation on solid media. The presence and relative abundance of the bacteria inhabiting Lake Robule was explained by the physiological characteristics of the bacteria and the physico-chemical characteristics of the lake water

Geochemical Detection of the pp-Neutrino flux with 205Tl LOREX collaboration

An indispensable goal of this proposal still remains the determination of the neutrino capture probability by 205Tl. The ratio 205Pb/205Tl in lorandite provides only the product of solar neutrino flux and neutrino capture probability into the different nuclear states of 205Pb