Assessment of rock slope stability along the proposed Ankara–Pozantı autoroad in Turkey

 The main objective of this study is the determination of the slope stability and excavatability category of discontinuous rock exposed between 53+000 and 58+000 km of the proposed Ankara–Pozantı autoroad in Turkey to provide secure access. The study area is mostly in the outcrops of highly jointed sandstone with minor layers of marl. This Maastrichtian–Eocene Group also contains conglomerate and limestone bands of flysch character called the Pas˙ada* Group. Quaternary alluvial deposits occur throughout the site. The area was divided into four design sectors based on cut slope locations. Rock slope stability was assessed kinematically as well as through utilizing limit equilibrium analyses. The excavation category was determined to range from hard to extremely hard ripping. Remedial measures for unstable rock slopes are discussed. Received: 22 July 1997 · Accepted: 14 April 1998     

Mineralogy and textures of the Lahanos and Kızılkaya massive sulphide deposits,northeastern Turkey,and their similarity to Kuroko ores

A distinct vertical zonation very similar to that described for the Kuroko deposits of Japan, is displayed by both mineralogy and textures of sulphides from the Lahanos and Kzlkaya massive sulphide deposits of northeastern Turkey. A deeper erosional level is exposed at the Kzlkaya deposit, so that only remnants of the massive sulphide ore zone are present. The zonation is from an upper zone of massive Cu and Zn sulphides (black and yellow ore) with fine-grained, colloform, banded, framboidal, and spherulitic textures, downwards through an intermediate zone of low Cu-Zn massive pyrite with transitional textures, to a lower zone of stockwork and impregnated pyrite displaying euhedral, zoned textures. The fine-grained and colloform pyrite of the upper zones is progressively overgrown by, and recrystallized to, the massive and euhedral pyrite of lower zones. The original textures of these deposits are best preserved by pyrite. The previous interpretation of these textures, of sulphide deposition from colloidal solutions ponded by an impermeable pyroclastic horizon, is reexamined in the light of present observations. Although ultra-fine-grained sulphides, framboids, and radially-cracked spherules could have formed by replacement of pre-existing minerals by a colloidal solution, the colloform and banded textures are indicative of growth in open spaces. It thus seems likely that the fine-grained colloform sulphides, including chalcopyrite, sphalerite, and tennantite as well as pyrite, were initially deposited on or near the surface of the sea-floor. Additional evidence for this interpretation is seen in the progressive recrystallization of the sulphide textures to massive, much coarser, pyrite in the lower zones. This recrystallization may in part be due to diagenetic and hydrothermal processes operating after formation of the original layered sulphides. These conclusions are in agreement with those reached for the similar, but larger Madenköy deposit 100 km to the east.     

Hydrogeological and geochemical assessments of the Gediz Graben geothermal areas, western Anatolia, Turkey

Gediz Graben is an important area for geothermal activity in Turkey. Menderes Massif rocks consisting of gneisses, schists, marbles and granodiorite, comprise the aquifers of the geothermal systems. Neogene terrestrial sediments made up mainly of sandy and clayey conglomerates cap the systems. Gediz Graben geothermal areas are physically divided into seven main groups: Turgutlu-Urganl, Sart-Çamur, Caferbeyli, Üfürük, Kurunlu, Kavakldere-Sazdere and Alaehir geothermal areas. The third highest aquifer in Turkey temperature (182 ^°C) after Kzldere (242 ^°C) and Germencik (232 ^°C) was discovered in the Kavakldere-Sazdere area. The thermomineral waters of the Gediz Graben geothermal areas have outlet temperatures of 25^–95 ^°C and an electrical conductivity of 874–6020 S/cm. Mineralization is mostly dominated by Na⁺ (188–2027 ppm) and HCO₃^– (544–2950 ppm). Kavakldere-Sazdere area shows the highest boron content among the entire geothermal aquifers of Turkey. Major geochemical processes for thermomineral waters are carbonate and silicate dissolution and mixing.     

Estimation of environmental impacts on the water quality of the Tahtalıdam watershed in İzmir, Turkey

Water pollution is a widespread problem in different areas of the world. Some of these problems originated from point contamination sources and widespread contaminant outlet sources which are observed in every country. The major elements and chemical loads of surface water have been dominated by constituents derived directly or indirectly from human activities and/or industrial practices that have increased additives in the last several decades. The point sources of contamination may result from the direct wastewater discharges to the dam sites, which are considered to be the most commonly encountered water pollution problems. One of these problems is the eutrophication process which usually occurs in the static water mass of lakes and other surface water reservoirs. This process may be caused by the continuous increase of nitrogen and phosphorus contents and decrease of O₂ level in water causing an anaerobic condition which may stimulate algae-growth flow in these water bodies, consequently reducing the quality of water. Of course, there are many research methods for determining the various kinds of water pollution. In this research, the hydrochemical parameters were evaluated to estimate the types of pollution sources, the level of pollution, and its environmental impacts on the Tahtal dam reservoir.     

Noril’sk–Talnakh Cu–Ni–PGE deposits: a revised tectonic model

The Norilsk mining district is located at the northwest margin of the Tunguska basin, in the centre of the 3,000×4,000 km Siberian continental flood basalt (CFB) province. This CFB province was formed at the Permo-Triassic boundary from a superplume that ascended into the geometric centre of the Laurasian continent, which was surrounded by subducting slabs of oceanic crust. We suggest that these slabs could have reached the core–mantle boundary, and they may have controlled the geometric focus of the superplume. The resulting voluminous magma intruded and erupted in continental rifts and related extensive flood basalt events over a 2–4 Ma period. Cu–Ni–PGE sulfide mineralization is found in olivine-bearing differentiated mafic intrusions beneath the flood basalts at the northwestern margin of the Siberian craton and also in the Taimyr Peninsula, some 300 km east of a triple junction of continental rifts, now buried beneath the Mesozoic–Cenozoic sedimentary basin of western Siberia. The Norilsk-I and Talnakh-Oktyabrsky deposits occur in the Norilsk–Kharaelakh trough of the Tunguska CFB basin. The Cu–Ni–PGE-bearing mineralized intrusions are 2–3 km-wide and 20 km-long differentiated chonoliths. Previous studies suggested that parts of the magma remained in intermediate-level crustal chambers where sulfide saturation and accumulation took place before emplacement. The 5–7-km-thick Neoproterozoic to Palaeozoic country rocks, containing sedimentary Cu mineralization and evaporites, may have contributed additional metal and sulfur to this magma. Classic tectonomagmatic models for these deposits proposed that subvertical crustal faults, such as the northeast-trending Norilsk–Kharaelakh fault, were major trough-parallel conduits providing access for magmas to the final chambers. However, geological maps of the Norilsk region show that the Norilsk–Kharaelakh fault offsets the mineralization, which was deformed into folds and offset by related reverse faults, indicating compressional deformation after mineralization in the Late Triassic to Early Jurassic. In addition, most of the intrusions are sills, not dykes as should be expected if the vertical faults were major conduits. A revised tectonic model for the Norilsk region takes into account the fold structure and sill morphology of the dominant intrusions, indicating a lateral rather than vertical emplacement direction for the magma into final chambers. Taking into account the fold structure of the country rocks, the present distribution of the differentiated intrusions hosting the Norilsk-I and Talnakh–Oktyabrsky deposits may represent the remnants of a single, >60 km long, deformed and eroded palm-shaped cluster of mineralized intrusions, which are perceived as separate intrusions at the present erosional level. The original direction of sill emplacement may have been controlled by a northeast-trending paleo-rise, which we suggest is present at the southeastern border of the Norilsk–Kharaelakh trough based on analysis of the unconformity at the base of the CFB. The mineralized intrusions extend along this rise, which we interpret as a structure that formed above the extensionally tilted block in the metamorphic basement. Geophysical data indicate the presence of an intermediate magma chamber that could be linked with the Talnakh intrusion. In turn, this T-shaped flat chamber may link with the Yenisei–Khatanga rift along the northwest-trending Pyasina transform fault, which may have served as the principal magma conduit to the intermediate chamber. It then produced the differentiated mineralized intrusions that melted through the evaporites with in situ precipitation of massive, disseminated, and copper sulfide ore. The Norilsk–Kharaelakh crustal fault may not relate to mineralization and possibly formed in response to late Mesozoic spreading in the Arctic Ocean.Editorial handling: P. Lightfoot     

Analysis of Meteorological and Terrain Features Leading to the Izmir Flash Flood, 3–4 November 1995

Flash floods associated with heavy precipitation has become a hazardous phenomenon along the Mediterranean coasts of Turkey in recent years. During 3 and 4 November 1995 heavy and intense rainstorm activity over the Aegean coast led to flash flooding in the city of zmir. Damage exceeded $50 million and 61 people died as a result of the flood. The Karyaka district suffered the most severe damage. This study presents an analysis of the meteorological settings that led to the development of these intense storms and describes the role of the terrain features involved in the zmir flood.The important mesoscale features which initiated the severe weather outbreak included pronounced low-level advection, positive vorticity and strong upper level divergence. A surface low centered over the Aegean Sea enhanced the advection of warm and moist unstable air masses coming from the southwest over the Mediterranean Sea along a southwesterly low level jet (LLJ). A squall line oriented NE-SW over the Aegean Sea also contributed to the storm development, and intensity of the storms was further enhanced by the orographic effect. The presence of a frontal system, the stability indices associated with the event, and other meteorological features are all reminiscent of the synoptic type flash floods identified by Maddox. While the pressure and moisture patterns were favorable for severe storm activity, nonmeteorological factors including the topography, geomporphology, and and land-use contributed to the flooding to a great extent. Settling in the flood-prone zone, insufficient floodwater structures, and the lack of channel improvements in the creeks enhanced flood damage to the city. Many of the deaths occurred in the settlements located in the flood-prone zone of the Ilca and Dallk creeks.     

An integration of GIS and remote sensing in groundwater investigations: A case study in Burdur, Turkey

The importance of groundwater is growing based on an increasing need and decreasing spring discharges in the Burdur area. Remote Sensing and the Geographic Information System (GIS) have been used for investigation of springs, which are an important groundwater source. The chemical composition of groundwater is not of drinking water quality in Burdur city and water in the Burdur residential area is being obtained from the Cine plain.The purpose of this study was to investigate new water sources by using remote sensing and GIS methods. Geology, lineament and land use maps of the research area were prepared using the Landsat TM satellite image composed of different analyses on the TM 7–4-1 band. In addition, contours, creeks, roads and springs were digitized using a topographic map of 1/100,000 scale to produce a drainage density map. A groundwater potential map was produced which integrated thematic maps, such as annual rainfall, geology, lineament density, land use, topography, slope and drainage density. According to this investigation, the surrounding villages of Askeriye, Bugduz, Gelincik, Taskap and Kayaalt were determined to be important from the point of view of groundwater potential in the research area.     

Geochronology and geochemistry of eclogites from the Mariánské Lázně Complex,Czech Republic: Implications for Variscan orogenesis

The Mariánské Lázn complex (MLC) is located in the Bohemian Massif along the north-western margin of the Teplá-Barrandian microplate and consists of metagabbro, amphibolite and eclogite, with subordinate amounts of serpentinite, felsic gneiss and calcsilicate rocks. The MLC is interpreted as a metaophiolite complex that marks the suture zone between the Saxothuringian rocks to the north-west and the Teplá-Barrandian microplate to the south-east. Sm-Nd geochronology of garnet-omphacite pairs from two eclogite samples yields ages of 377±7, and 367±4 Ma. Samples of eclogite and amphibolite do not define a whole rock Sm-Nd isochron, even though there is a large range in Sm/Nd ratio, implying that the suite of samples may not be cogenetic. Eclogites do not have correlated _Nd values and initial ⁸⁷Sr/⁸⁶Sr ratios. Five of the eight eclogite samples have high _Nd values (+10.2 to +7.1) consistent with derivation from a MORB-like source, but variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7059) which probably reflect hydrothermal seawater alteration. Three other eclogite samples have lower _Nd values (+ 5.4 to –0.8) and widely variable ⁸⁷Sr/⁸⁶Sr ratios (0.7033 to 0.7096). Such low _Nd values are inconsistent with derivation from a MORB, source and may reflect a subduction or oceanic island basalt component in their source. The MLC is an important petrotectonic element in the Bohemian Massif, providing evidence for Cambro-Ordovician formation of oceanic crust and interaction with seawater, Late Devonian (Frasnian-Famennian) high- and medium-pressure metamorphism related to closure of a Saxothuringian ocean basin, Early Carboniferous (Viséan) thrusting of the Teplá terrane over Saxothuringian rocks and Late Viséan extension.     

Isotope geochemistry of the Tieluping silver-lead deposit, Henan, China: A case study of orogenic silver-dominated deposits and related tectonic setting

The Tieluping silver deposit, which is sited along NE-trending faults within the high-grade metamorphic basement of the Xionger Terrane in the Qinling orogenic belt, is part of an important, recently discovered Mesozoic orogenic-type Ag-Pb belt. Ore formation includes three stages: an early barren quartz-pyrite stage (E), an intermediate polymetallic sulfide ore stage (M), and a late barren carbonate stage (L). Carbon, sulfur and lead isotope systematics indicate that the E-stage fluids are deeply sourced; the L-stage fluids are shallow-sourced meteoric water; whereas the M-stage fluids are a mix of deep-sourced and shallow-sourced fluids. Sulfur and lead isotope data show that the ore-forming fluids must have originated from a source with elevated radiogenic lead and low ³⁴S values, that differs significantly from exposed geologic units in the Xionger Terrane, the lower crust and the mantle. This supports the view that the carbonate-shale-chert sequences of the Guandaokou and Luanchuan Groups south of the Machaoying fault might be the favorable sources, although little is known about their isotopic compositions. A tectonic model that combines collisional orogeny, metallogeny and hydrothermal fluid flow is proposed to explain the formation of the Tieluping silver deposit. During the Mesozoic collision between the North China Craton and South China Block (Early-Mid Triassic Indosinian Orogeny), crustal slabs containing the carbonate-shale-chert sequences of the Guandaokou and Luanchuan Groups, locally rich in organic matter (carbonaceous shale), were thrust northwards beneath the Xionger Terrane along the Machaoying fault. Metamorphic devolatilisation of this underthrust slab probably provided the ore-forming fluids to develop the Ag-Pb ore belt, which includes the Tieluping silver deposit. Fluids and magmas were emplaced during extensional stages related to the Jurassic-Cretaceous Yanshanian Orogeny.Editorial Handling: B. Lehmann     

Timing of low-temperature metamorphism and cooling of the Paleozoic and Mesozoic formations of the Bükkium,innermost Western Carpathians,Hungary

K-Ar ages of illite-muscovite and fission track ages of zircon and apatite were determined from various lithotypes of the Bükkium, which forms the innermost segment of the Western Carpathians. The stratigraphic ages of these Dinaric type formations cover a wide range from the Late Ordovician up to the Late Jurassic. The grade of the orogenic dynamo-thermal metamorphism varies from the late diagenetic zone through the anchizone up to the epizone (chlorite, maximally biotite isograd of the greenschist facies). The K-Ar system of the illite-muscovite in the < 2 m grain-size fraction approached equilibrium only in epizonal and high-temperature anchizonal conditions. The orogenic metamorphism culminated between the eo-Hellenic (160-120 Ma) phase connected to the beginning of the subduction in the Dinarides, and the Austrian (100-95 Ma) phase characterized by compressional crustal thickening. No isotope geochronological evidence was found for proving any Hercynian recrystallization. The stability field of fission tracks in zircon was approached using the thermal histories of the different tectonic units. A temperature less than 250°C and effective heating time of 20–30 Ma had only negligible effects on the tracks, whereas total annealing was reached between 250 and 300°C. Apatite fission track ages from the Paleozoic and Mesozoic formations show that the uplift of the Bükk Mountains occurred only in the Tertiary (not earlier than ca. 40 Ma ago). Thermal modeling based on apatite fission track length spectra and preserved Paleogene sediment thickness data proved that the Late Neogene burial of the recently exhumed plateau of the Bükk Mountains exceeded 1 km.     

Hydrogeochemical and isotopic investigation of the Kolan geothermal field, southeastern Turkey

The Kolan geothermal field is located 24 km northwest of the Karakoçan area of Elaz city in southeastern Turkey. The Keban crystallized limestone of Permo-Carboniferous age is the oldest unit in the area. This unit is overlain by the middle-upper Eocene Krkgeçit formation consisting of conglomerate, sandstone, limestone and marl alternations. The youngest unit in the area is the Upper Miocene-Lower Pliocene Karabakr formation consisting of basalt, andesite and tuffs. Thermal Springs in the Kolan field issue along two major fault zones. The temperature of the hot springs is between 38°C and 45°C. Thermal waters in the area are heated by the geothermal gradient. The waters are classified as hot or very hot and as brackish waters. On the basis of International Association of Hydrogeologists Classification (IAH), waters are grouped as Ca–Na-HCO₃–CO₂-bearing thermal and mineral waters. Chemical analyses indicate a chemical composition of Ca>(Na+K)>Mg - HCO₃>SO₄>Cl. Saturation calculations reveal that the waters are oversaturated with respect to calcite, dolomite and aragonite while undersaturated with respect to gypsum, anhydrite and halite minerals. On the basis of ¹⁸O, ²H and ³H isotope data, Kolan waters are of meteoric origin, recharged from high elevations and then circulated deeply.     

Radon in soil anomaly observed at Los Azufres geothermal field,Michoacan: a possible precursor of the 1985 Mexico earthquake (Ms = 8.1)

A radon anomaly in a nuclear track detector placed on a fault was detected prior to the destructive (Ms = 8.1) Mexican earthquake of 19 September 1985. The fault is a structural feature of the geothermal field Los Azufres, 260 km NE of the epicentral area. Since no other phenomenon can be found as a possible cause for the radon anomaly, it is proposed that preseismic regional stress perturbations may produce changes in the fluid transport patterns at the fault, suggesting that radon measurements in similar conditions could provide a good precursor in high seismic risk areas.     

Assessment of excavatability,abrasivity and slope stability in a sandstone quarry in Istanbul,Turkey

The Cebeci region is characterized by outcrops of Carboniferous sandstone, including diabase dykes. This region is very important area for aggregate production in Istanbul, Turkey. The aim of this study is to determine the engineering geological properties of sandstones to assess the excavatability, abrasivity and stability of cut slopes in a quarry site. Firstly, the sandstone samples were used to determine their petrographical and mineralogical characteristics. Then, physico-mechanical tests were performed on these samples. In order to determine rock mass properties, scan-line surveys were performed, and the major orientations of discontinuities were analyzed through the stereographic projection technique. Kinematical analyses were also made to determine the potential failures at the quarry site. According to the results obtained, excavatability is changed from easy ripping to hard ripping on sandstones; the carbonated sandstone is less abrasive than other sandstones. Based on the field studies and stability analyses of the cut slopes, optimum slope geometry and necessary support measures, such as wire mesh and rock fall barriers, are suggested.     

Oxygen,sulfur, and strontium isotope and fluid inclusion studies of barite deposits from the Iglesiente-Sulcis mining district,Southwestern Sardinia,Italy

This paper deals with barite from stratiform, karst, and vein deposits hosted within Lower Paleozoic rocks of the Iglesiente-Sulcis mining district in southwestern Sardinia. For comparison sulfates from mine waters are studied. Stratiform barite displays ³⁴S=28.8–32.1, ¹⁸O=12.7–15.6, and ⁸⁷Sr/⁸⁶Sr=0.7087, in keeping with an essentially Cambrian marine origin of both sulfate and strontium. Epigenetic barite from post-Hercynian karst and vein deposits is indistinguishable for both sulfur and oxygen isotopes with ³⁴S=15.3–26.4 and ¹⁸O=6.6–12.5; ⁸⁷Sr/⁸⁶Sr ratios vary 0.7094–0.7140. These results and the microthermometric and salinity data from fluid inclusions concur in suggesting that barite formed at the site of mineralization by oxidation of reduced sulfur from Cambrian-Ordovician sulfide ores in warm, sometimes hot solutions consisting of dilute water and saline brine with different ¹⁸O values. The relative proportion of the two types of water may have largely varied within a given deposit during the mineralization. In the karst barite Sr was essentially provided by carbonate host rocks, whereas both carbonate and Lower Paleozoic shale host rocks should have been important sources for Sr of the vein barite. Finally, ³⁴S data of dissolved sulfate provide further support for the mixed seawater-meteoric water composition of mine waters from the Iglesiente area.     

On the reliability of different methods of seismic hazard assessment in Greece

Historical and present century instrumental data have been used to determine seismic hazard in 35 sites of Greece by the application of Cornell's method (Cornell, 1968) and the mean value method. The macroseismic intensity has been considered as a measure of seismic hazard. Comparison of the results of the two methods showed that, in general, the mean value method gives higher values, particularly for low probabilities of exceedance. In addition, for some sites, the differences of the expected intensities resulting from the two methods, indicate that finer tuning of the seismogenic souce model is required, or suggest time dependence. Although each one of these methods has its own merits, the method based on seismic zonation (Cornell's method) has several advantages and must be preferred when an accurate zonation is possible by the use of macroseismic and instrumental seismic data, together with geological and geomorphological information. However, reliable estimates of seismic hazard at a particular site require work on a microzoning scale, incorporating historical, archaeological, and recent geological data.Paper presented at the 21st General Assembly of the European Seismological Commission held in Sofia, 1988.     

The geological and metallogenic setting of stratabound carbonate-hosted Zn-Pb mineralizations in the West Asturian Leonese Zone, NW Spain

Several carbonate-hosted stratabound zinc-lead ores in the Ponferrada-Caurel area (NW Spain) are hosted by the Lower to Middle Cambrian Vegadeo Formation. Two clearly distinct groups of mineralizations occur in different stratigraphic positions. The stratiform disseminated ore is located in the Lower Member as irregular and millimetre-thick layers of sphalerite and galena replacing earlier pyrite. The lack of hydrothermal alteration and the heavy C., O and S isotopic signatures suggest that this ore is of premetamorphic origin, the sulphur and fluids being derived from the host carbonates. The more likely source of the sulphide is the abiogenic thermal reduction of sulphate derived from sulphate beds intercalated with the carbonates. The second group of mineralizations is located at the top of the Vegadeo Fm, always along its contact with the overlaying shales and sandstones of the Cabos Series. This group is economically more important and include three styles of strata-bound mineralizations. The more common one is the silica ore, a hydrothermal rock that traces the contact between the carbonate and the detrital rocks along more than 50 km. Locally, a carbonate-rich ore is found along the contact between the silica ore and the Vegadeo Fm. Laterally to these rocks, there are large bodies of the breccia ore, made up of sulphides and calcite in a matrix of chlorite. The ore assemblage is composed of sphalerite and galena with minor amounts of chalcopyrite and pyrite. Co-Ni-As sulphides, bismuthinite, tetrahedrite and Pb-Bi sulphosalts are also found as trace minerals. The geological relationships and the isotopic signatures suggest that the three ores are synchronous and of late Hercynian age. They are interpreted as linked with a tectonically driven fluid flow along the stratigraphic contact between the carbonate and the detrital rocks.The model of ore genesis involves the circulation of fluids in likely equilibrium with the detrital rocks that react with the Vegadeo Fm leading to the metasomatic replacement of limestones by quartz with synchronous precipitation of sulphides. The genesis of breccias is probably due to the formation of overpressured zones. The hydrothermal alteration results in a systematic depletion in both ¹⁸O and ¹³C of the carbonates due to the infiltration of fluids, of likely mixed metamorphic and surface origin. Fluid inclusions in the chloritic breccia suggest that the ore formation took place at temperatures higher than 200 °C in relationship with low salinity (up to 1.2% wt. NaCl eq.) water-rich (H₂O>99%) fluids. Sulphur isotopes suggest that most of the sulphur has a common origin with the stratiform ores, but here there is a significant but variable input from the detrital rocks. Lead isotopes of the different ores are within the Cambrian signature of the southern Hercynian Belt, with a long crustal history. However, mixing with a minor juvenile component cannot be ruled out. The geographic and stratigraphic proximity and the similar lead signatures between the premetamorphic and the Hercynian mineralizations suggest that the latter was derived from the remobilization, in a lead frozen system, of the stratiform-disseminated ones. The premetamorphic mineralizations can be interpreted as similar to the widespread Mississippi Valley-type deposits found in the southern Hercynian Belt. The second group of deposits can be defined as synto postmetamorphic stratabound, carbonate-hosted Zn-Pb deposits, broadly similar to MVT but formed in an orogenic setting. Specific features such as the presence of chlorite, the fluid composition (low saline H₂O-NaCl fluids) and the temperatures of formation (above at 200 °C) are interpreted as characteristic of this tectonic setting.     

Stable isotope (C,O, S) systematics of the mercury mineralization at Idrija,Slovenia: constraints on fluid source and alteration processes

The world-class Idrija mercury deposit (western Slovenia) is hosted by highly deformed Permocarboniferous to Middle Triassic sedimentary rocks within a complex tectonic structure at the transition between the External Dinarides and the Southern Alps. Concordant and discordant mineralization formed concomitant with Middle Triassic bimodal volcanism in an aborted rift. A multiple isotopic (C, O, S) investigation of host rocks and ore minerals was performed to put constraints on the source and composition of the fluid, and the hydrothermal alteration. The distributions of the ¹³C and ¹⁸O values of host and gangue carbonates are indicative of a fracture-controlled hydrothermal system, with locally high fluid-rock ratios. Quantitative modeling of the ¹³C and ¹⁸O covariation for host carbonates during temperature dependent fluid-rock interaction, and concomitant precipitation of void-filling dolomites points to a slightly acidic hydrothermal fluid (¹³C–4 and ¹⁸O+10), which most likely evolved during isotopic exchange with carbonates under low fluid/rock ratios. The ³⁴S values of hydrothermal and sedimentary sulfur minerals were used to re-evaluate the previously proposed magmatic and evaporitic sulfur sources for the mineralization, and to assess the importance of other possible sulfur sources such as the contemporaneous seawater sulfate, sedimentary pyrite, and organic sulfur compounds. The ³⁴S values of the sulfides show a large variation at deposit down to hand-specimen scale. They range for cinnabar and pyrite from –19.1 to +22.8, and from –22.4 to +59.6, respectively, suggesting mixing of sulfur from different sources. The peak of ³⁴S values of cinnabar and pyrite close to 0 is compatible with ore sulfur derived dominantly from a magmatic fluid and/or from hydrothermal leaching of basement rocks. The similar stratigraphic trends of the ³⁴S values of both cinnabar and pyrite suggest a minor contribution of sedimentary sulfur (pyrite and organic sulfur) to the ore formation. Some of the positive ³⁴S values are probably derived from thermochemical reduction of evaporitic and contemporaneous seawater sulfates.Editorial handling: P. Lattanzi     

Using numerical modelling to evaluate tsunami hazard near the Kuril Island

A sequence of computer experiments is used to study questions concerning the tsunami problem as a quantitative estimate of tsunami danger, detailed geographical tsunami classification, determination of the parameters of critical tsunami waves, and the conditions of their development. We call a wave critical, if its impact on the coast is most hazardous.Using the Middle Kuril Island as an example, we present the results of a computer experiment which includes determining the wavefields on the shelf and estimating the effects connected with the deep-water Bussol and Diana Straits.Numerical simulation of tsunami waves of different sources permits the assessment of the extent of tsunami danger in different areas of the coastal zone of Simushir Island, depending on the location of the focus zone and their geometry.The major singularities of the wavefield arise in the zones of the deep-water straits. The distribution of the amplification factors is determined by both the global parameters of the wavefields and the local properties of individual harbours. The results obtained for a particular harbour in the northern part of Simushir Island, formed the basis for the quantitative estimate of tsunami danger for this area.     

U-Pb zircon age and Nd isotopic composition of granitoids,charnockites and supracrustal rocks from Heimefrontfjella,Antarctica

Heimefrontfjella and Mannefallknausane, in Dronning Maud Land, Antarctica, comprise an amphibolite-facies terrain and a granulite terrain, separated by a major mylonite zone. The amphibolite terrain is made up of mafic to felsic metavolcanics and metasediments, intruded by granitoid plutons: the granulite terrain has supracrustal rocks with similar lithologies, intruded by felsic plutonic rocks that crystallized as charnockites.U-Pb zircon ages (conventional and ion microprobe) demonstrate that magmatic activity was confined to a relatively short interval between 1130 and 1045 Ma and was followed in the amphibolite terrain by metamorphism around 1060 Ma. Specific ages are as follows: metarhyolite in the amphibolite terrain, 1093 ± 38 Ma; granitoids in the amphibolite terrain, 1045 ± 9 Ma to 1107 ± 16 Ma, charnockites in the granulite terrain, 1073 ± 8 Ma to 1135 ± 8 Ma, metamorphic zircons in garnet amphibolite and a post-metamorphic pegmatite, both 1060 ± 8 Ma. Older zircons were found only in a metasediment which yielded discordant zircon fractions with²⁰⁷Pb/²⁰⁶Pb ages between 1250 and 1450 Ma, and in a granulite facies metaquartzite, which contained concordant zircons with the following ages: 1104 ± 5 Ma, 1215 ± 15 Ma, 1400 Ma, 1700 Ma, 2000 Ma. The youngest age is interpreted as the age of granulite metamorphism, the older ages as those of detrital zircons.A Sm-Nd mineral isochron age of the garnet amphibolite (960 ± 120 Ma) agrees within error with the U-Pb age of metamorphic zircons (1060 ± 8 Ma). Initial _Nd values (T = 1.1 Ga) for 15 samples range from +4 to–4. The highest came from a metabasalt and two granitoids from Milorgfjella, the northern area; the lowest from the granulite-facies metasediment and from a charnockite, both from Vardeklettane, a nunatak in the south. The positive but subdued values preclude generation directly from depleted MORB-type mantle _Nd + 6 to + 7 at 1.1 Ga) and indicate generation from a source containing older crustal material.

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Zusammenfassung Die Gebiete um Heimefrontfjella und Mannefallknausane in Dronning Maud Land, Antarktis, bestehen aus amphibolith- und granulitfaziellen Grundgebirgskomplexen, die durch eine große Mylonitzone voneinander getrennt sind. Der amphibolithfazielle Komplex besteht aus mafisch bis felsischen Metavulkaniten und Metasedimenten, die von Granitplutonen intrudiert werden. Der Granulitkomplex enthält Suprakrustalgesteine ähnlicher Art, die von Charnockiten intrudiert werden.U-Pb-Alter, die mit der konventionellen Multikorn-Methode und an der Ionen-Mikrosonde an Einzelkörner bestimmt wurden, engen die magmatische Aktivität zwischen 1130 und 1045 Ma ein. Auf diese Periode folgte in dem amphibolithfaziellen Gebiet eine Regionalmetamorphose um 1060 Ma. Die Einzelalter sind wie folgt: in dem amphibolithfaziellen Komplex ergab ein Metarhyolith 1039 ± 38 Ma, während die Granitoide zwischen 1045 ± 9 Ma und 1107 ± 16 Ma variieren. In dem Granulitkomplex wurden die Charnockite auf 1073 ± 8 Ma bis 1135 ± 8 Ma datiert, während metamorphe Zirkone aus einem Granatamphibolith sowie aus einem posttektonischen Pegmatit identische Alter von 1060 ± 8 Ma ergaben. Ältere Komponenten wurden lediglich in einer Metasediment-Probe gefunden, die diskordante Zirkone mit²⁰⁷Pb/²⁰⁶Pb Altern zwischen ca. 1250 und 1450 Ma enthielt, sowie in einem granulitfaziellen Metaquarzit, in dem konkordante Zirkone die folgenden Alter ergaben: 1104 ± 5 Ma, 1215 ± 15 Ma, 1400 Ma, 1700 Ma, 2000 Ma. Das jüngste Zirkonalter aus dem Metaquarzit interpretieren wir als Zeitpunkt der Granulitmetamorphose, während die höheren Alter detritische Komponenten repräsentieren.Eine Sm-Nd Mineralisochrone für einen Granatamphibolith hat ein Alter von 960 ± 120 Ma, das innerhalb der experimentellen Fehler mit einem U-Pb-Alter von 1060 ± 8 Ma für metamorphe Zirkone übereinstimmt. Initiale _Nd-Werte (T = l.1 Ga) für 15 Proben variieren zwischen +4 und -4. Die höchsten Werte wurden für einen Metabasalt und zwei Granitoide von Milorgfjella im nördlichen Arbeitsgebiet bestimmt. Die niedrigsten Werte stammen aus dem granulitfaziellen Metaquarzit und von einem Charnockit, beide aus Vardeklettane, einem Nunatak im Süden. Die leicht positiven Werte lassen eine juvenile Bildung der Wirtsgesteine aus einem MORB-ähnlichen Mantel (_Nd + 6 bis + 7 um 1.1 Ga) nicht zu und deuten ein Ausgangsmaterial mit Komponenten älterer kontinentaler Kruste an.

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Résumé Les régions de Heimefrontfjella et Mannefallknausane situées dans le Dronning Maud Land en Antartique sont formées par deux zones principales à degrés métamorphiques différents: une à faciès amphibolitique et une autre à faciès granulitiques, séparées par une zone mylonitique. Des roches métavolcaniques à composition variant de basique à felsique ainsi que des roches d'origine sédimentaire composent la zone amphibolitique. Elles sont recoupées par des plutons granitiques. La zone granulitique est formée également par des roches d'origine volcanique et sedimentaire qui sont, elles, recoupées par des charnockites.Les mesures d'U-Pb sur zircons (utilisant la méthode conventionnelle et la microsonde ionique) montrent que l'activité magmatique s'est confinée à une période relativement courte entre 1130 Ma et 1045 Ma. Elle a été suivie par un métamorphisme, il y a 1060 Ma, dans la zone amphibolitique. De façon plus détaillée, les âges sont les suivants: dans la zone amphibolitique, rhyolite datée à 1093 ± 38 Ma, granitoïdes datés à 1045 ± 9 Ma et 1107 ± 16 Ma; dans la zone granulitique, charnockites datées entre 1073 ± 8 Ma et 1135 ± 8 Ma, zircons métamorphiques provenant d'une amphibolite à grenat datés à 1060 ± 8 Ma et pegmatite postmétamorphique datée à 1060 ± 8 Ma. Deux roches ont fourni des zircons donnant des âges plus anciens: un sédiment métamorphisé et un metaquartzite. Les âges²⁰⁷Pb/²⁰⁶Pb obtenus pour les fractions discordantes des zircons du metasediment varient entre 1250 et 1450 Ma alors que le metaquartzite contient des zircons concordants avec les âges suivants: 1104±5 Ma, 1215±15Ma, 1400 Ma, 1700 Ma et 2000 Ma. L'âge le plus jeune obtenu pour le métaquartzite est interprété comme représentant l'âge du métamorphisme granulitique alors que les âges plus anciens représentent les âges de zircons détritiques.Une isochrone Sm-Nd sur minéraux a été obtenue sur une amphibolite à grenat. Elle définit un âge de 960 ± 120 Ma qui correspond, aux erreurs près, à l'âge U-Pb des zircons métamorphiques (1060 ± 8 Ma). Les _Ndinitiaux (T = 1,l Ga) obtenus pour 15 échantillons varient entre +4 et –4. Les valeurs les plus élevées ont été obtenues pour un basalte et deux granitoïdes de Milorgfjella situés dans la partie nord; les valeur _Nd les plus faibles proviennent du métasédiment dans la zone granulitique et d'une charnockite. Ces deux échantillons se situent dans le nunatak Vardeklettane dans le Sud. Les _Nd étant positifs mais toutefois plus faibles que la valeur du manteau appauvri à cette période (entre +6 et +7 à 1,1 Ma), une extraction directe du manteau ne peut être retenue et nous suggérons que la région source contenait du matériau crustal plus ancien.

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Heimfreontfjella Mannefallknausane Dronning Maud, , , . , . , ., , 1130 1045 Ma. 1060 . : — 1093±38 Ma, 1045±9 Ma 1107±16 Ma. 1073±8 Ma 1135±8 Ma, - 1060±8 Ma. , , 1250 1450 Ma. : 1104±5 Ma, 1215±15 Ma, 1400 Ma, 1700 Ma 2000 Ma. , , , . Sm-Nd, -, 960±120 Ma, , - 1060±8 Ma. Nd (T=1,1 ) 15 + 4 — 4. Milogrfjella . , Vardeklettane . , MORB (Nd + 6 + 7, 1,1 ); .