LITHOPROBE, Canada's national research project in the earth sciences, is investigating the tectonic evolution of northern North America through its multidisciplinary scientific program within ten study areas across Canada. Such studies primarily represent fundamental scientific research, but they also benefit the mining industry by providing a well-constrained regional framework and better understanding of tectonic processes which lead to the development of ore deposits. In cooperation with mining companies, LITHOPROBE also has pioneered the use and demonstrated the value of high resolution seismic reflection investigations to determine subsurface geology in mining camps. These studies have proven effective in imaging shallow to moderately dipping lithologic contacts as well as structural features, and in some cases have been used for the direct detection of ore bodies.
During the 1990s, LITHOPROBE activities focused on Precambrian regions, many of which host major mineral deposits. In Quebec, structure and evolution of the Abitibi greenstone belt was targeted. In the northern Abitibi belt, seismic reflection surveys in the Matagami VMS base metal camp identified structures associated with the mineralization and produced the first reflection image of an ore deposit. In Ontario, the Sudbury Structure, host to world-scale, massive sulfide nickel deposits, was confirmed as due to a meteorite impact with its elongate structure the result of extensive, post-impact, compressive deformation. Two-dimensional reflection surveys imaged the footwall contact of the norite/gabbro sublayer, which hosts the ore, to depths of 5 km. This led to a 3-d reflection experiment, the first of its kind in the world, which successfully imaged the contact and mineralization at a depth of ~2000 m. In Manitoba, the Thompson Belt is the reworked boundary zone between the Archean Superior craton and the Paleoproterozoic Trans-Hudson Orogen, and is the locale of the Thompson nickel deposits. Regional studies established the structure and evolution of the boundary zone. A combined reflection and electromagnetic survey aided in identifying the subsurface extent of the ore-bearing metasedimentary unit enclosed within Archean basement gneisses.
The role of syn-convergence extension and related structural phenomena in the exhumation of mid-and lower crustal rocks are becoming more apparent in the Earths mountain belts. Because of the increasing research on the spatial relationships between compressional and extensional structures and the improving resolution of isotopic dating techniques, it is possible to define, in detail, the temporal relationships of these periods to the geodynamic history of an orogen. Research in the southern Balkan and Aegean region has shown that the history of an orogen can not simply be subdivided into a phase of compression and a late stage of extension (e.g. the post-orogenic extensional collapse). A recently completed integration of detailed structural and kinematic analyses with 40Ar/39Ar laserprobe dating (Lips, 1998) has resolved that the development of the orogen is characterized by an interplay of compressional and extensional tectonics, which alternately build up and destabilize the orogen. The competition of the different tectonic processes has resulted in the occurrence of synchronous and diachronous tectonic events which both operated at a local and regional scale. It is now clear that some Neogene ore deposit formations in the Balkan region may be associated with the regional extension during the final collapse of the orogen, possibly by slab detachment, in the Miocene to post-Miocene (de Boorder et al., in press). The identification of events of local and/or of regional extension which affected the developing, and still immature, orogenic wedge in the pre-Miocene history provide a working platform for the characterization of the geodynamic control on the Late Cretaceous and Paleogene ore deposits, and accompanying or preceding magmatic activity, which formed throughout the Carpathian and Balkan area.
De Boorder H, Spakman W, White SH & Wortel MJR, EPSL, in press
Lips ALW, PhD thesis, Geologica Ultraiectina, 166, 224 p, (1998).
Alpine mineralizations in the region are related to the following geotectonic settings:
Intracontinental rifting in the Mesozoic, resulting in formation of alkaline mafic magmatics connected mainly with volcano-sedimentary stratiform deposits of iron, manganese, base metal, copper and igneous magnetite as well as exhalation type antimony and mercury deposits. These deposits, hosted mainly in platform carbonates can be related with crustal thinning and high heat flows generating hydrothermal systems in the Dinarides and Carpatho-Balkan area.
Ocean-floor spreading-rifting in the Jurassic resulted in formation of chromite, magnetite and massive sulphide copper deposits and stratiform Fe-Mn, as well as Ni-Cu-Co and PGE-mineralizations in the Dinaride-Vardar zone.
Subduction during the late Jurassic-Cretaceous time resulted in the formation of calc-alkaline magmatics in Rhodope, Serbo-Macedonian and Pelagonian Massifs where granitoids host quartz-molybdenum and porphyry copper-molybdenum, while the Laramian sheet-shape intrusives are associated with quartz-scheelite-molybdenite and Au-As-Pb-Zn-sulfosalts together with porphyry-molybdenum-copper, precious metal and gold copper massive sulphide mineralizations in the Banat area and Srednogorje. Late Cretaceous high sulphidation Au-Cu and porphyry Cu deposits are hosted in calc-alkaline, mainly andesitic intrusives, pyroclastics, tectonic and hydrothermal breccias or carbonates and are controlled by volcanic structures and deep faults. Vein type, disseminated and stockwerk type mineralizations are common in Banat, Bor-Majdanpek and Srednogorje area. Paleogene volcanics host high sulphidation epithermal Au-Cu, porphyry Cu, metasomatic and skarn type Cu-Zn-Pb mineralizations. Convergent motion continued during the middle Miocene in the Carpathian region and related magmatic activity produced calc-alkaline subvolcanic bodies and stratovolcanic sequences ranging in composition from rhyolitic to basaltic. These rocks host vein type, epithermal Au-Ag-bearing base metal, porphyry Cu, skarn and metasomatic, as well as hot spring type mineralizations.
Collision related Jurassic-Palaeocene granite intrusives and rift related magmatics host porphyry copper, porphyry molybdenite copper, tungstene-molybdenum, iron-skarn, low-, and high-sulphidation epithermal, massive sulphide and stratiform deposits in eastern Serbia, Apuseni and Srednogorje Mts. The late Oligocene-early Miocene collision induced andesite-latite-rhyolite host small Mo, Fe, Cu, Zn and Au- deposits in the S-Balkan.
Post-collision events resulted in extension behind the thrusted, folded and uplifted areas. The Tertiary calc-alkaline granitoid intrusives, andesite-rhyolite volcanics in the Balkan host relevant low- and high sulphidation epithermal, precious- and base metal, porphyry-copper, iron skarn, molybdenum-tungsten skarn, vein- and metasomatic type uranium deposits. Their ages seem to be late Oligocene and Neogene. Some types of deposits are associated with caldera structures or are located along the contact of Vardar zone and Serbo-Macedonian Massif. Placer deposits also are characteristic for this stage.
Boev B & Serafimovski T, Proceeding Stip-Dojran, 273-307, (1997).
Borcos M & Vlad S (eds), Plate tectonic and Metallogeny in the East Carpathian and Apuseni Mts. Guide book, 1-33, (1994).
Jankovic S, Mineralium Deposita, 32, 426-433, (1997).
Lexa J, Stohl J & Konecny V, In eds. :Hall, AJ, Boyce AJ, Naden J & Stanley ChJ:Mineral Deposit Studies Group Annual General Meeting incorporating AGM of IGCP 356 Carpatho-Balkan Metallogeny-University of Glasgow-Isotope Geosciences Unit Abstracts, 46, (1997).
Popov P, Proceedings of the Annual Meeting of IGCP Project 356, 1, 5-17, (1996).
Veto-Akos E & Zelenka T, Manuscript, (1998).
In the Eastern Alps ore formation is controlled by the particular geodynamic settings and remobilization of pre-existing metal concentrations during all major (pre-Variscan, Variscan, and Alpine) evolutionary stages (Frisch & Neubauer, 1989; Neubauer, 1994; Weber, 1997; Ebner, 1998).
The pre-Upper Ordovician (Cadominan/Panafrican) cycle is represented by magmatic arcs, back arc ophiolites and arc related sediments. In the Penninic Habach terrane the primary W-mineralization of Felbertal is linked to magmatic arc environments. In the Austroalpine Celtic terrane syngenetic Cu-, Fe-, Zn-, Pb-mineralizations are situated in arc-related environments within parts of the Ötztal-crystallline complex. Small-scale Cr-mineralizations are related to the ophiolitic Speik terrane which was obducted onto the Celtic terrane along the northern margin of Gondwana thus forming the basement of the Paleozoic Noric composite terrane.
The Variscan cycle is dominated by terrane accretion at the active European continental margin and final continent collision with intrusion of huge amounts of granitoids. Syngenetic formation of base metals in the Noric composite terrane is related to alkaline-basaltic volcanism linked to a Silurian/Devonian rifting stage and terrane separation from Gondwana. The genesis of siderite and magnesite deposits situated in Devonian shelf carbonates is still controversial. Post-Variscan Permocarboniferous (meta)sediments host magnesite, talc, anthracite (graphite), and U-mineralizations.
The Alpine cycle started with Permian rifting (formation of evaporites in transtensional basins), followed by the opening of Middle Triassic - Lower Cretaceous oceanic domains (Meliata, South Penninic, Ybbsitz ocean), subduction of oceanic realms (Late Jurassic - Early Tertiary), crustal thickening by thrusting, isostatic uplift of metamorphic cores, E-W extension and escape tectonics of Austroalpine units to the Pannonian realm. Syngenetic oceanic VMS Cu-Fe (Pb-, Zn-, As-) mineralizations are only known from the South Penninic domain. The Austroalpine Triassic shelf complexes are characterized by carbonate hosted Pb/Zn-mineralizations (Bleiberg type). Fluids of different origin were responsible for the formation of epigenetic/hydrothermal ores and industrial minerals (Fe, Mg, Ba, Cu, Au, As; talc, leucophyllite). The following geodynamic stages are considered relevant for fluid generation (Pohl & Belocky, 1994; Prochaska, 1998):- Permotriassic rifting with circulation of evaporitic brine derived fluids,- Cretaceous syngenetic fluids resulting from metamorphic devolatization,- Tertiary fluids generated by retrograde leaching during late to post tectonic extensional stages.
The Oligocene Periadriatic intrusive rocks are of subordinate metallogenic importance; ore mineralizations related to Tertiary volcanism are unknown. The only exception may be the Schlaining Sb-mineraliaztion which may be attributed to a hypothetic Miocene subvolcano.
Ebner F, BHM, 143, 209-214, (1998).
Frisch W & Neubauer F, Geol. Soc. Amer. Spec. Pap., 230, 91-100, (1989).
Neubauer F, Geowiss, 12, 136-140, (1994).
Pohl W & Belocky R, Mitt. Oesterr. Geol. Ges, 86, 141-152, (1994).
Prochaska W, XVI Congr. CBGA Abstr., 494, (1998).
Weber L, Arch. Lagerst. Forsch. Geol. BA, 19, 1-607, (1997).
Two large Pb-Zn deposits in the Republic Macedonia - the Sasa and the Toranica - occur in the same submeridional structural-metallogenic zone, but at different hypsometric levels: 1900-1400 m for Toranica, 1700-600 m and below for Sasa. The genetic model for these deposits accounts their hypsometric position.
The Sasa and the Toranica deposits are situated at the distance of about 20 km one from other and are hosted by metamorphic and volcanic rocks. The metamorphic rocks are represented by Precambrian gneisses varying in composition, and Paleozoic quartz-graphite and chlorite-sericite schists interbedded with limestones. The thickness of the limestones varies from a few centimeters to 1 m. Such a lithology controls mineralization. Dacitic sheets and quartz latite dikes with a K-Ar age of 20-18.5 Ma are distinguished among Tertiary volcanics. Quartz latite dikes reflect the magmatic control of mineralization. Ore bodies are located at the contact between quartz-graphite schists and gneisses, limestones, quartz latites. The length of some ore bodies varies from 150 to 1800 m.
Both the deposits belong to the metasomatic type, but the Sasa deposit is interpreted as the skarn type (600-400°C ), whereas the Toranica deposit was formed by the low temperature metasomatose (450-350°C). The different depth and temperature of ore formation caused a variation in composition of metasomatic rocks and ores.
The relations of ore-forming minerals in time and space, geochemical properties of minerals indicate the ore deposition in two stages: that of quartz-pyrrhotite-pyrite-sphalerite with prevalence of sphalerite, and that of quartz-calcite-pyrite- magnetite-sphalerite-galena with a leading role of galena. The analysis of fluid inclusions in quartz, calcite, sphalerite, as well as the isotopic analysis of S in the pair galena-sphalerite show that mineral paragenese of the 1st stage were formed under 370-320°C in high concentrations of salts, whereas parageneses of the 2nd stage reflect lover temperatures 250-190°C.
The fractionation of S, C, and O isotopes indicates a possible contribution of magmatic, metamorphic and meteoric waters to ore-forming process. Quantitative role of various fluids in the formation of Sasa and Toranica deposits was different. Thus the Sasa and Toranica deposits were formed in hydrothermal stage, where metasomatic processes played a major role. The data on isotopes of Pb point out that ore metals originated from the bordering part of the continental crust and upper mantle.
Laser-ablation ICP mass-spectrometry was used to measure the major and trace element composition of individual fluid inclusions enclosed in natural quartz samples from a range of magmatic-hydrothermal ore deposits, in order to explore the behavior of ore-forming components during fluid phase separation ('boiling') in high-temperature saline fluid systems. Here we report data from 13 samples showing unambiguous textural and microthermometric evidence for coeval trapping of a liquid brine and a coexisting vapor phase of lower density and lower salinity. The microanalytical data reveal two groups of elements, which show drastically different geochemical behavior during fluid phase separation. Na, K, Fe, Mn, Zn, Rb, Cs, Pb and other trace elements (characteristically Cl-complexed) fractionate into the brine, whereas Cu, As and Au (probably as HS-complexes) selectively fractionate into the coexisting vapor phase. We suggest that the process of brine/vapor separation is the key to explain the common spatial and temporal association of porphyry-style Cu(-Au) and epithermal Au(-Cu-As) deposits. Physical separation of a buoyant vapor phase in the deeper porphyry environment segregates a fraction of the Cu, As and Au from the large excess of chalcophile elements (notably Fe) remaining in the dense brine. Vapor separation thus permits selective transport of high concentrations of bisulfide-complexed metals into the low-temperature epithermal environment, where they are precipitated by interaction with groundwater close to the earths surface.
Mesothermal gold lodes are widespread in orogenic belts of all ages. While the regional structural setting and geochronology of the deposits are fairly well documented, the geodynamic controls on their location and timing relative to orogenic processes are poorly understood. This study explores the role of Alpine continental collision in controlling the emplacement of gold-quartz veins in the NW Alps.
Previous work has shown that the hydrothermal fluids which formed the veins ascended to the deposit levels from mid-crustal depths or deeper. The ages of vein formation vary systematically from 31 Ma in the SW of the mineralized belt to 10 Ma in the NE, and at each locality these ages lag behind the local peak of metamorphism by several million years. The deposits lie within extensional faults and shear fractures, either within the hinges of regional-scale antiforms, which developed as SE-verging backfolds during uplift of the orogenic wedge, or within the mylonites of the Periadriatic Line, which developed during retro-thrusting of the wedge.
Two-dimensional numerical models of the dynamic evolution of the Alps have been used to track the evolution of backfolds, regions experiencing high shear strain, and to map the distribution of dilatancy as a potential monitor of fluid flow. Our first results, using forward models that do not allow for thermal equilibration, show uplift and backfolding of an orogenic wedge after approximately 100 km of continental convergence (at 1 cm/yr). A crustal scale shear zone develops, corresponding to the future Periadriatic Line, with geometry of the shear zone mediated by the presence of weak suture material inherited from the previous (subduction) phase. The distribution of strain rates in the uplifting wedge reveal a temporally and spatially restricted zone of dilatancy, whose presence strongly depends on the interaction between backthrusting caused by collision dynamics and the focusing of shear along the weak suture layer. Such dilatent zones could conceivably have been conduits of fluids derived from deep within the wedge. Moreover, their transient appearance and their structural position corresponds well with observations of vein distribution in the NW Alps.
The Fe-skarn deposit at Ocna de Fier (Vaskö) has been the site of mining activity for at least 2000 years. The area is widely known as a classic skarn occurrence, having a special place among skarns since many concepts about their genesis were first aired when discussing this locality. The deposit has long been known to contain numerous Bi-minerals. This paper deals with a study of textural associations of Bi-sulphosalts in the deposit. An understanding of Bi-minerals, and in particular, the microscopic intergrowths thereof, can allow constraints to be placed upon metasomatic evolution during ore genesis. Ocna de Fier is the northermost in the group of deposits in Banat. Skarnification and mineralisation is related to Laramian intrusives, mainly granodiorites, known as banatites, linked to calc-alkaline subduction-related activity. These lie along three belts, oriented almost N-S, across a distance of about 100 km on Romanian territory, also extending into Serbia. The widespread occurrence of skarn deposits relates to adjacent Mesozoic limestones; their alignment being concordant with the banatite belts. Orebodies are hosted within calcic skarns, on both margins of a synclinal limestone, at the contact with underlying crystalline units and intrusives. Virtually the whole of the skarn is mineralised; the orefield consists of more than 30 individual irregular-shaped bodies exploited for Fe, Cu, Pb, Zn. Changes in the dominant ore metals occur along the 6 km length of the orefield. Southwards, the character of the skarns becomes more Cu-rich and further south, a Pb-Zn character dominates at Dognecea. Each orebody has a distinct mineralogy and mineral association, typifying and giving an often unique character to individual orebodies. Bi-sulphosalt bearing assemblages are locally widespread in the deposit, occurring as small 'nests' within massive hematite-chalcopyrite ore. Individual Bi-sulphosalts occur typically in fine intergrowths, including skeletal, vermiform, patchy, lamellar and myrmekitic varieties. Textural study and microanalytical data on homogeneous areas and fine intergrowths allow reconstruction of cooling and crystallisation histories. Self-organisation growth processes are recognised, relating to oscillatory zoning during skarn formation. Intergrowths of lillianite homologues with galena result from breakdown of initial high-temperature crystals. Oscillatory zoning and atypical compositions relating to initial high-temperature crystallisation indicate that the Bi-minerals are an intregal part of the skarn process. Oscillatory processes are further evidenced by fluctuation between the stability fields of different Fe-oxides and -sulphides, indicating a externally buffered system, with fluctuating fO2 and/or fS2 during mineralisation. The widespread presence of tetradymite suggests redox-controlled crystallisation from the fluid at the magnetite-pyrrhotite and hematite-pyrite buffer. Bismuthinite derivatives and the pavonite and lillianite homologous series, because of their ability to accommodate compositional fluctuations via modular adjustment, are well-suited to record evidence for 'far-from-equilibrium' processes during a prolonged cooling history, entirely consistent with their crystallisation in a skarn environment.
Ultramafic rocks of supposedly Early Paleozoic age in the Eastern Alps locally carry concentrations of chromian spinel. Discrete platinum-group minerals have been reported from two locations as inclusions in and interstitial to chromite (Thalhammer et al., 1990; Melcher & Mali 1998). Sixteen spinel concentrates from 5 ultramafic complexes were obtained using electric pulse disintegration and conventional mineral separation techniques. The concentrations of Os, Ir, Ru, Pt and Re were measured by isotope dilution ICPQMS from solutions obtained after dissolution in a high-pressure asher unit (HPA-S, PAAR) at 320°C and 125 bar. The results reveal considerable variations between, and also within complexes. Most chromitites are dominated by Ru (up to 1.28 ppm), as expected in podiform chromitites associated with restitic depleted mantle, and Pt/Ir ratios are lower than one. However, in 6 samples Pt concentrations are higher (up to 762 ppb) than the concentrations of IPGE (e.g., Pt/Ir = 3.4-14.5). Chondrite-normalized concentrations of Os and Ru usually are higher than those of Ir, resulting in negative Ir anomalies in normalized diagrams. Concentrations of PGE in massive chromitite from the Kraubath Complex vary by two orders of magnitude, e.g. from values as low as 0.02 times chondritic to 1.8 times chondritic for Ru. In this special complex, a correlation between PGE concentration and petrographic type of chromite is observed: chromite associated with olivine-orthopyroxenite bodies is rich in Re and Pt and low in IPGE, whereas chromite hosted by refractory dunite has high contents of IPGE and low Re and Pt. The degree of alteration of chromite grains is a factor important for the concentration of Pt, visible as Pt-(Ir, Rh) sulfarsenides and arsenides as secondary, low-temperature inclusions within altered chromite.
Chromites from the Hochgrössen complex reveal PGE patterns similar to Kraubath. Disseminated chromites separated from dunite in the Pernegg complex have overall low PGE contents (Os < 1 ppb), with prominent positive Ru anomalies. Spinel concentrates from Pennine basement units of the Tauern Window also have low concentrations of PGE and reveal flat chondrite-normalized patterns.
Ratios of 187Os/188Os were determined for 12 concentrates using NTIMS at the Department of Geology, University of Maryland. Results may be grouped into three domains: (1) 187Os/188Os 0.1245 at low Pt/Ir; (2) 187Os/188Os ranging from 0.1239 to 0.1271, showing a negative correlation with Pt/Ir; (3) variable 187Os/188Os (0.1329-0.2028) at high Pt/Ir values (>4). The latter group is characterised by elevated sulfide concentrations. 187Os/188Os values are in general higher than expected for Paleozoic depleted MORB-type mantle. In accordance with whole-rock geochemical data (REE), this is interpreted as significant contribution of a more radiogenic source. A possible scenario involves second-stage melting/depletion of MORB-type mantle in the mantle wedge above a subducting plate. During polymetamorphism, more mobile PGE (and Re) were locally redistributed.
This project is generously funded by the Austrian Science Foundation through grants P12322-CHE and P12323-CHE.
Melcher F & Mali H, Mitt. Abt. Miner. Landesmus Joanneum, 62/63, 37-46, (1998).
Thalhammer OAR, Prochaska W & Muehlhans HW, Contrib. Mineral Petrol, 105, 66-80, (1990).
Pb-Zn ores in the Drau Range (e.g. Bleiberg-Kreuth, Mezica, Topla) occur in sedimentary rocks of Middle to Upper Triassic age. The primary phase of ore formation is strongly connected with the occurrence of saddle dolomite cement, which is named clear saddle dolomite (CSD). Secondary phases of ore formation occur after the formation of CSD and are not considered here.
A distinct succession of five zones can be observed in CSD by cathodoluminescence (CL): (1) CL-zone I shows a red CL, often with a zonation of light red to dark red subzones; (2) CL-zone II exhibits no luminescence or shows a very dull red CL; (3) The luminescence of CL-zone III is light red CL, sometimes exhibiting a zonation of different light red colours; (4) CL-zone IV luminescence orange-red, often exhibiting an intensive zonation of different orange and red luminescing subzones; (5) CL-zone V reveals no luminescence. An up to 0.1 mm wide zone consisting of chlinochlorite often occurs between CL-zone II and III. This zone is named chlorite zone, but it does not exclusively consists of chlinochlorite, moreover, the occurrence of small (< 0.005 mm) pyrite crystals is frequent, also a few sphalerite and galena crystals can be observed.
The relationships between Pb-Zn ores and CSD show that ore formation occurred between CSD CL-zone I and CL-zone IV. Fluid inclusion data from CSD and sphalerite indicate formation temperatures between 122 and 201°C respectively 127 and 159°C.
The stratigraphic occurrence of CSD and the chlorite zone enables more exact dating of CSD and the Pb-Zn ores. Assuming relationships between the chlorite zone and a synsedimentary Fe/Mn crust of Upper Hettangian age (KAPPLER & ZEEH, in prep.), the formation time of the chlorite zone is Upper Hettangian. CL-zones I and II were precipitated between Norian and Upper Hettangian time, and CL-zones III and IV are Lower Sinemurian in age, as indicated by the stratigraphic occurrence of these CL-zones. The formation time of CL-zone V is Upper Jurassic to Lower Cretaceous. These formation times of CSD suggest that the Pb-Zn ores were formed in Upper Triassic/Lower Jurassic time. This is the time in which hydrothermal activities appear, resulting from the beginning of rifting in the alpine realm. It is assumed that the formation of CSD and Pb/Zn ores is related to these hydrothermal activities.
The Strassegg electrum-arsenopyrite mineralisation is located 50 km NE of Graz within the Graz Paleozoic nappe pile. The nappes contain Upper Silurian to Carboniferous volcanic and sedimentary rocks. The vein-type electrum-arsenopyrite mineralisation lies exclusively within metavolcanic rocks at the bottom of the nappe pile. An Early Cretaceous compressional event led to an internal imbrication of the Graz Paleozoic and the whole sequence was affected by Late Cretaceous extension. The metamorphic grade reached in the lower rock series greenschist facies and locally ampibolite facies. At Strassegg a typical lithological sequence of the Graz Paleozoic occurs. This is from footwall to hangingwall: Pelitic sediments and mafic within-plate volcanoclastic rocks - black shales - carbonates. This sequence is underlain by amphibolite facies metapelitic rocks of the Anger crystalline.
The most widespread vein type lies at low angle to the bedding, folded with the bedding planes and often boudinaged. Veins and schistosity are oriented NW-SE and are both affected by semi-ductile normal faults. The mineralogy of the veins is strongly dependent on the host rocks. Within metapelitic rocks there are only quartz veins. Metapelitic intercalations within the carbonatic sequences and metavolcanic rocks (the metavolcanics contain carbonates) contain quartz - Fe-dolomite/calcite veins. The carbonate rocks contain only dolomite/calcite veins. A large number of veins are recorded in the metavolcanics and carbonates compared to metapelitic rocks. 18O and 12C measurements were done on representative rock samples and associated veins. All the rocks show primary 18O and 12C values (approx. 22 ‰ 18O for carbonatic rocks, 8 ‰ 18O for metavolcanics and 11-18 ‰ 18O for metapelites versus SMOW). The quartz and carbonate signatures in the veins are strongly dependent on the signature of matrix quartz and matrix carbonate from the host rock. Quartz from veins is slightly heavier in 18O compared to the associated matrix quartz from the host rock. Carbonates from veins in the carbonatic unit are depleted in 18O and 12C compared to the associated host rock. The structural relationships support an alpine age for the mineralisation. The 18O values of the quartz veins suggest one vein generation and a similar fluid source for the mineralised and the non-mineralised veins within the metavolcanic rocks. Throughout the unit, fluid movement was local and the material was transported from the immediate vicinity of the veins.
This work is supported by FWF-project 12180-TEC.
There is a close interrelationship between geodynamics, thermal evolution of the lithosphere and metallogenesis. Many deposits form as a result of the flow of brines related to topographic relief, compaction, thermal gradients and tectonics. In this contribution the possible effects of fluids driven by Tertiary syncollisional magmatism in the Eastern Alps are evaluated. In a conceptual model, the lithospheric crust (Austroalpine/Southalpine plate) above the subducted Penninic plate is intruded by magmatic rocks along the Peri-adriatic Lineament (slab breakoff; Blanckenburg & Davies, 1995). High heat flow caused by shallow magma chambers trigger saline ore solutions. During their ascent along strike-slip and normal faults, ore minerals precipitate in higher crustal levels. This model is tested with data from base metal deposits in vicinity to possible pathways for ore forming fluids: The widespread thermal effect of the Periadriatic magmatism is observed by anomalous coalification pattern in Mesozoic and Paleogene sediments adjacent to the Periadriatic Lineament. Geo-chemical and microthermometric data of vein type mercury and antimony mineralizations within the Kreuzeck-, Goldeck- and Gailtal-Crystalline Complexes, as well as geochemical data from the carbonate-hosted lead-zinc deposits of the structurally overlying Drau Range demonstrate that hydro-thermal mineralization both in cover and basement of the Eastern Alps can be explained by late orogenic magmatism acting during continental escape.
von Blankenburg F & Davies, JH, Tectonics, 14, 120-131, (1995).
The understanding of the tectonic evolution of the eastern part of the Alpine Europe registered a huge advance due to the application of new structural, paleomagnetic, isotopic and metamorphic petrology techniques on an area well mapped by local geologists in the previous decades. There is consensus on the models of Mesozoic-Cenozoic history of southeastern Europe and on basic steps of the tectonic evolution from the rift stage to the present double loop shape of the Carpathian-Balkan mountain belt and its western and southern hinterland. On the other hand, igneous petrology and associated metallogenetic studies of the Alpine magmatic belts from the eastern part of Alpine Europe also registered important progress from application of new instrumental techniques and concepts, leading to presentation of various models for the genesis of Triassic to Pleistocene magmatic rocks and associated ore deposits. It is now possible to use the progress of tectonic and petrologic studies for evaluating the controversial models concerning the Late Cretaceous, ore-bearing, igneous belt extending from the Carpathians and the Balkans. This is a narrow elongated belt, 280 kilometres long in Romania, that runs from the Apuseni Mountains in the north to the western part of the South Carpathians (Banat). It extends further south to the Carpathians of Eastern Serbia (Yugoslavia) and still further east to Srednogorie (Bulgaria), over 450 kilometres.
The term "banatite" is still extensively used by Romanian and Serbian geologists for acid to intermediate suites of Upper Cretaceous to Paleocene age, even if the alternative "Laramian magmatites" was also proposed. For Bulgarian geologists the more common term is "Late Cretaceous" magmatism, also now used by some Romanian authors. As recent U-Pb zircon ages of 75 Ma of the main granitoid intrusions discard the Laramian connection, the previous volcanism and this major plutonism have to be correlated with earlier tectonics; only dyke swarms of porphyry rocks intrude the post-tectonic, Maestrichtian and Paleocene sedimentary cover. Late Cretaceous Gosau-type basins from Western Romania, Eastern Serbia and Bulgaria contain volcanics, intrusions and ore deposits of Cu, Mo, W, Pb and Zn, sometimes of huge tonnage. Westward (for Romanian geologists) or eastward (for Serbian and Bulgarian geologists) directed subduction of Severin or, respectively, Vardar paleo-oceans were both considered as the source for Late Cretaceous magmatism and metallogenesis from South Carpathians and Balkans. Popov from Sofia however advocated the extensional, rift-related, post-subduction (intercollision) origin of the Banat-Srednogorie Late Cretaceous igneous and metallogenic belt; this is also obvious for the coeval belt from Apuseni Mountains.
In the Valea Morii Nova mine (Southern Apuseni Mountains) a Neogenic subvolcanic body of quartz andesite composition crops out, where relationships between the upper part of a Cu-Au porphyry system and later epithermal veins are exposed. Based on field relationships and petrography, the following sequence of veining events is inferred (from earlier to later): a) an early stage related to propylitic alteration; b) a second composite stage, characterized by the emplacement of barren centimetre-thick quartz-rich veins followed by millimetre-thick quartz-rich Cu-Au mineralized veins. The latter produce a stockwork-like structure;a later stage, mostly represented quartz ± calcite ± barite epithermal veins, carrying Au-Ag mineralization.
1) The following inclusions types have been identified: 2) Primary melt inclusions, within preserved plagioclase phenocrysts. 3) Multiphase inclusions. The solids are typically represented by halite and other unidentified phases. They occur within both barren and mineralized quartz veins in porphyry displaying phyllic alteration. 4) Liquid-rich inclusions, both in propylitic and epithermal veins. 5) Vapour-rich inclusions associated both with the multiphase inclusions in porphyry and with liquid-rich inclusions in epithermal veins.The porphyry veins are characterized by the occurrence of hypersaline inclusions (43 to > 60 wt% NaCleq) with variable Th (235 to > 500°C). Boiling in the porphyry system is suggested - but so far not proven - by the occurrence, in the same veins, of vapour-rich inclusions. Fluid inclusions in veins related with the propylitic alteration show a much lower salinity (up to 5.6 wt% NaCleq) and Th (265-310°C) and may be related to important external (meteoric l.s.) fluids circulation. Fluid inclusions in the epithermal veins show very low salinity (0.7-2.5 wt% NaCleq) and Th in the range 255-280°C. Limited measurements on primary liquid-rich and vapour-rich inclusions coexisting along growth zones in quartz give similar Th, suggesting trapping of a boiling fluid. At Valea Morii Nova the epithermal veins crop out at the same level of the middle to upper part of a pre-existing porphyry system. Preliminary fluid inclusions data suggest a magmatic derivation for the porphyry-related fluids, while epithermal fluids show an extremely dilute composition which suggests a dominantly meteoric component. The epithermal veins do not seem to be related to migration of porphyry-related fluids to shallower level, but rather to later circulation of geothermal, mainly meteoric fluids. Alternatively, justaxposition of epithermal and porphyry-type mineralizations could be related to telescoping, caused by rapid erosion during the lifespan of the hydrothermal system.
By means of the "crush and leach" method the chemical characteristics of sparry carbonates (magnesites and siderites) in paleozoic series of the Eastern Alps were determined. Despite their similar ionic radii (Cl- = 1.81A, Br- = 1.96) the fractionation of these elements in evaporitic processes is quite different. At an evaporation index of > 10, halite is precipitated. Br has a very conservative behaviour and is not incorporated into the halite lattice. The cation systematics changed from an original Na preponderance to Mg and K dominated systems. Accordingly the composition of an evaporitic brine is shifting along the "evaporation trend". On the other hand fluids percolating through the crust dissolving halite are modified towards higher Cl/Br and Na/Br molar ratios and their composition is close to the "halite dissolution trend".
Permian ("Haselgebirge") magnesites and their hostdolomites clearly plot on the very end of the evaporation trend proving that these magnesites and the hostrocks were formed in an evaporitic environment. The sparry magnesite deposits of Carboniferous series of the Greywacke zone exhibit a similar evaporitic composition indicating a similar origin in a (Permian?) evaporitic environment. In contrast to the above "Haselgebirge magnesites" the Carboniferous marbles hosting the magnesites show marine compositions thus indicating epigenetic, metasomatic origin of these magnesites. In an early stage of diagenesis and closure of the evaporitic basins in (post?)Permian times the brines migrated through the underlying marine carbonates causing the formation of metasomatic bodies of coarse grained sparry magnesites.
Fluid chemistry of many different siderite mineralizations of the Greywacke zone revealed characteristics of brines produced during evapo-concentration of seawater for these mineralizations without regard to their hostrocks and stratigraphic position. Accordingly a comprehensive model for all siderite deposits of the Greywacke zone is proposed. Initial Permoscythian rifting processes of the Alpine period provided the pathways for downward movement of residual bittern brines. While conservative element ratios were not buffered by wallrock reactions (Cl-Br-Na) and still give evidence of the original nature of the fluids Fe was leached from extensive hydrothermal alteration zones. Sulfide vein type mineralizations with Fe-Mg-carbonates as gangue minerals seem to be the link between sparry magnesite deposits of the Greywacke zone formed under more oxidizing conditions and the siderite deposits.
Fluid chemistry of the magnesite and siderite mineralizations sharply contradicts models favouring marine sedimentary or Eoalpine remobilization models for the deposits in Paleozoic strata of the Greywacke zone of the Eastern Alps.
Kesler SE, Martini AM, Appold MS, Walter LM, Huston TJ & Furman FC, Geochim. Cosmochim. Acta, 60, 225-233, (1996).
Bölke JK & Irwin JJ, Geochim. Cosmochim. Acta, 56, 203-225, (1992).
The island arc settings are one of the most significant geological environments accommodating gold and other precious and rare metals that are of primary importance for the high-technology industries of today. The island arc settings and late-stage collisional processes at the active tectonic plate boundary are a notable example for the development of various types of Au and Ag bearing mineral deposits and hydrothermal products exhibiting bimodal distribution. During the Mezosoic development of the Sredna Gora island arc zone as a part of the global Tethyan-Eurasian copper belt and in the Rhodope Massif of Bulgaria a bimodal Late Cretaceous and Miocene distribution of the Au-Ag bearing mineral deposits have also been displayed. The processes of material transport by aqueous fluids and volatile components largely contribute to the chemical and mineral evolution of gold and other precious metals in the hydrothermal systems developed in the island arc and late-stage collisional environments. The study of these processess is of primary importance for understanding of the evolution of ore and mineral genesis, as a tool for mineral prospecting and exploration. The porphyry-copper and massive-sulphide deposits of Sredna Gora zone in Bulgaria are considered to be the products of island arc volcano-plutonic processes that took place during the Late Cretaceous. The base-metal and epithermal low - and high sulphidation gold deposits in the eastern part of the Rhodope massif are results of the Late Paleogene collisional stage of the development of the tectono-magmatic and hydrothermal processes during the subduction of the African under the Eurasian tectonic plate. The porphyry - copper deposits (Medet, Assarel, Tsar Assen and Elatsite) from the Sredna Gora and Balkan metallogenic zones of Bulgaria are connected to subvolcanic granodiorite and quartz-diorite porphyryt intrusions, while the volcanic hosted massive sulphide deposits Elshitsa, Radka and Chelopech are related to andesite - dacite magmatic activity that took place about 90 - 94 m. y. ago (B. Bogdanov, 1987). The vein-copper- Au deposits in Bulgaria - Bakadjik (Jambol area), Zidarovo and Vurli Briag (Burgas area) are connected to the Upper Cretaceous - Paleocene magmatic activity and are distinguished by Bi mineralization superimposed on the base-metal assemblages. Madjarovo, Spahievo, Zvezdel and Lozen base-metal Au-Ag deposits were formed during Miocene hydrothermal activity in the eastern part of the Rhodope massif. The main ore veins and lenses of galena-sphalerite-chalcopyrite are hosted by Tertiary volcano - plutonic and terrigeneous sequences. The different geodynamic scenarios and the ore-remobilisation processes during the Phanerozoic metallogeny in Bulgaria led to significant, but also different behavior of the mineral assemblages that are important Au-Ag-carriers and their isotope and fluid evolution.
Apulia is located in the midst of the western Tethyan realm and for most of its Mesozoic history was surrounded by oceanic areas. Recent developments concerning the opening and closing of these oceans bring new constraints on the geodynamic evolution of Apulia. If rotated to its Permian position using the magnetic anomalies from the Atlantic since 188 Ma ago and assuming some eastward displacement between 188 and 249 Ma, we find that Apulia will rest over Iberia. Similarly, if we start from the proposed Permian position and move Apulia according to the same data, it will end up over the Dinarides and Hellenides in a present day position. The solution we propose to resolve this problem considers that the Apulian plate was the result of the welding of a Variscan element (Adria s.str.) with a Gondawana element (Apulia s.str.) in late Paleozoic following the closure of the Paleotethys. The southern Apulian element represents the western end of the Cimmerian continent. A Cimmerian phase of welding of Gondwana derived terranes and Variscan terranes is recorded in the Dinarides, Hellenides and Taurides. Through the Late Triassic/Early Jurassic opening of the Central Atlantic/Alpine Tethys ocean, Apulia s.l. became an African promontory and derived eastward in regard of Europe until Early Cretaceous. We show that Apulia was severed from its African motherland in Middle Cretacous times, a separation without which Apulia would have finished its course in the Carpathians. Since that time Apulia became a displaced terrane which in Neogene times has also been separated from the oceanic slabs to which it was attached through the procress of slab break-off.
Data for high-pressure metamorphism in the continental crust of the Rhodope massif are scarce. Chemistry and polytypism of white micas from the main rock types (metagranites, plagiogneisses and metapelites) of the Byala Reka metamorphic group, Eastern Rhodopes have been examinated and attempt has been made to relate its variations both to the fabric-forming episodes and conditions of mineral growth in these polyphase deformed metamorphic rocks. The investigated white micas are phengites to nearly pure muscovites with Si4+ content ranging from 3,54 to 3,03 p.f.u. On textural grounds 3 generations of white micas have been found in the rock types studied: early-, syn- and late kinematic, distinguished by their microstructural position and chemical composition. The early kinematic individuals are phengites with Si 3,33-3,54 p.f.u. and <epsilon>(Fe+Mg) 0,45-0,56 p.f.u., calculated on the basis of 11 oxygen atoms. The synkinematic white micas are nearly pure muscovites with low Si-content (3,05-3,19 p.f.u.) and paragonite-rich molecule (parmax 0,35). The late kinematic white micas are characterized by significant participation of phengite and ferriphengite molecule. The presence of these three distinct generations of white micas, chemical inhomogeneity in composition of the individual flakes (with phengite rich core and muscovite rich rim) as well as the availability of both 3T and 2 M1 polytypes can be used as a tool in the delineation of the P-T history of the area studied. The following clockwise P-T-t path for the metamorphism of the rocks from Byala Reka metamorphic group can be outlined: early HP/LT episode (Pmin 13 kbar and T~450°C), related to rapid crustal thickening caused by continental collision; erosional uplifting and unroofing (metamorphism MT/MP - P 9-3 kbar and T~550°C with final cooling episode of LT/LP type - P 3-2 kbar and T~ 400°C).
The Kratovo-Zletovo ore district is situated in the south-eastern parts of the Republic of Macedonia within the large Kratovo-Zletovo volcanic complex of Tertiary age. Surface manifestations of this subvolcanic-volcanic dacite-andesite magmatism are determined in an area occupying 1 200 km2. Producing polymetallic mineralization styles are established in an area of 400 km2.
The district is well endowed with vein type Pb-Zn mineralization (the Zletovo and Blizanci deposits), and Cu-Au stockwork-disseminated mineralization (Plavica, Borovik, Tursko Rudari etc.) in addition to the epithermal gold mineralization styles related primarily to silification zones along fault structures and/or structures of volcanic apparatuses. Mineralization styles of the kind are determined in the Plavica and Borovik deposits in hypsometric highest levels connected with the silification zones, but within strongly hydrothermally altered dacite-andesite volcanic rocks of Oligo-Miocene age. The most common alteration styles involve alunitization, silification, jarotization, kaolinization etc.
The results of the latest control geochemical investigations (about 30 samples) indicated epithermal gold mineralization (high sulphidation system) in an area of 2.5 km2 connected mainly with silicified parties in alterated volcanics. Silifications of the "secondary quartzite type" have noticeable lateral discontinuity. Notably, they are located along fault structures in a ring-radial form. In terms of their morphology, they are 100 to 650 meter long lenses measured along the longer axis that can be followed 100 to 120 meters to depth. They become narrow and get funnel shape with depth. Gold content ranges from 1 to 5 g/t Au, but contents of up to 17 g/t have been determined in individual samples. Besides gold, increased values of several other elements with average values such as arsenic with 2435 g/t As, mercury 0.905 g/t Hg, antimony 38.46 Sb, silver 8.950 g/t Ag, zinc 23.50 g/t Zn, lead 671.10 g/t Pb and copper 242.30 g/t Cu have also been determined.
Besides porphyry copper mineralization, several silification zones in hydrothermally altered volcanics with the presence of epithermal gold mineralization are determined in the Borovik deposit. Unlike Plavica, the silification zones in this deposit are connected solely to fault structures of various trends, the fault structures of SE-SW strike being most common. Gold content ranges from 0.12 to 0.46 g/t Au, in individual samples amounting to over 1.5 g/t Au. Investigations are in progress.
According to recent concepts (Boiadjiev, 1971; Valkov, et al., 1989) the Late-alpine evolution of the North-Western parts of the Rhodope massif was to be seen in the origination of superimposed Oligocene and Neogene grabens, result of brittle deformations of a consolidated basement. Studing the specifics of the synmetamorphic deformation in North-West Rila Mountains resulted in the concept that in fact the development of those grabens is in direct relation with the evolution of the metamorphic complex and the intruded undeformed granitoides. The contact zone between the metamorphites and the overlaying Neogene is clearly marked by a regional Late Tertiary Djerman detachment fault. The zone of the described fault is parallel to the mylonitic foliation in the metamorphites, with a gentle West-Northwest dip. The synkinematic criteria found along with the mylonitic foliation and the stretching lineation suggest the Southwest direction of the movements and determine the Djerman fault as a left normal-slip one. Analysis of the data leads to the following conclusions about the Late-alpine evolution of the South-Westernmost parts of the Rhodope massif: 1. During the Late Tertiery, the investigated region was a ground of a crust extension, which has resulted in the formation of the Djerman detachment fault. Movements along the fault have affected the pre-Neogene metamorphic core thus enabling the exhumation of parts of the ductile crust. The synmetamorphic extention processes contribute to the forming of an asymetric dome, in the core part of which is located the high uplifted and asymetric Kalin granite. The beginning of the extension has apparently taken place before the intrusion of the granite. 2. The deformations in the Djerman detachment fault zone have lasted after the intrusion of the Kalin granite, which is clearly seen south of Ovtcharci village, where it is affected by the the mylonitization. 3. The movement along the fault have caused the formation of grabens in the upper plate, where a sedimentation took place during Pliocene time. The changes in the uppermost parts of the lower plate were ductile in nature - amphibolit facies mylonites were formed. A superimposed greenschist facies mylonitization is related to the fast intrusion of the granites. At the base of the upper plate of the fault greenschist facies mylonitization has taken place, while higher in the section, autoclastic breccia were formed. 4. The Djerman detachment fault could be considered the Northernmost extension of the beginning in Northern Greece Strymon valley detachment fault (Dinter, D., L. Royden. 1993).
Dinte D, Royden L, Geology, 21, 45-48, (1993).
Boiadjiev S, Tectonic map of Bulgaria, in scale 1:200 000 and 1:500 000,"Tehnica", Sofia, 52-99, (1971).
Valkov V, Antonova N, Doncheva K, Geol. Balcanica, 19, 21-54, (1989).
The Rila-Rhodopes batholith were emplaced within metamorphic sequences of the Rhodope Massif with still unclear age. Rb-Sr and U-Pb isotope investigations of the granitoids have been performed in order to generate ideas for their age, magma sources and emplacement history . Three rock types are distinguished. Type 1 is a hornblende-biotite and biotite granodiorite and rarely granite with plastic deformations (metamorphic foliation and mineral lineation). Type 2 is mainly a biotite granite and rarely a two-mica leucogranite, deformed in some parts of the bodies. The fabric peculiarities of the deformed types 1 and 2 are in line with the schistosity of the country rocks. Type 3 is a fine-grained leucocratic granite occurring as small stocks or vein-like aplitoid granitoids. Former researchers supposed Precambrian to Alpine ages for the different granitoids. First type granitoids - Grancharitsa and Belmeken bodies - are with mixed crustal-mantle magma source and represent an older synmetamorphic pluton with an age of ~80 Ma, U-Pb zircon method. Ages of 42 Ma, U-Pb zircon method, and 35-37 Ma, Rb-Sr isochrones, have been determined for the second and respectively third type granitoids. Isotope-geochemical data suggest magma generation during the late- to postorogenic Alpine extension. The granites reveal mixed crustal-mantle features, but with greater involvement of crustal component, then the Late Cretaceous bodies. Comparisons with the Tertiary Pirin plutons, believed to be mainly crust-derived, emphasize the striking peculiarity of the Rila-Rhodopes batholith with its low strontium ratios. Similar to the investigated granitoids is the Elatia pluton (Greece) showing even lower strontium isotopic characteristics and having probably higher mantle contribution. Rila-Rhodopes granitoids differ in age, isotope Rb-Sr characteristics and geochemistry from the metagranites in the Eastern Rhodopes, despite of their similar Late Alpine formation and/or deformation and metamorphism in an extension regime (Dinter, Royden, 1993; Burg et al., 1996; Ivanov, 1998).
Burg J-P, Ricou L-M, Ivanov Z, Godffriaux I, Dimov D, Klain L, Terra Nova, 8, 6-15, (1996).
Dinter D, Royden L, Geology, 21, 45-48, (1993).
Ivanov Z, Tectonic of Bulgaria. (in print), (1998).
The eastern belt of 'supra-subduction' affinity of the Mirdita ophiolite in Albania hosts - in contrast to most other ophiolites - enrichments of Pt and Pd: association of Pt, and to a lesser amount of other PGE, with chromite, e.g. in Bregu i Bibes/NE Albania and of Pd with BMS, e.g. near Krasta/Central Albania (Ohnenstetter et al., 1991; Çina et al., 1995).
The PGE in Bregu i Bibes are associated with opx-rich chromitites in the upper part of the ultramafic cumulate sequence of the Tropoja ophiolite zone. A funnel-shaped arrangement of the sequence is suggested. Calculations indicate that Pt is exclusively bound in discrete PGM (mainly Pt-Fe alloys). After textural and chemical evidence the PGM formation started with Pt3Fe and a few sulphides, e.g. PtS (represented by inclusions in chromite), and closed with the formation of PGE arsenides, sulpharsenides and tellurides in hydrothermally altered interstitial silicates. This sequence suggests Pt saturation before chromite precipitation (moderate fS2 and increasing fO2 , followed by decreasing fS2 and increasing activity of Cu, Bi, Te, As). The Cr-rich low-Ti chromites hosting the PGM do not correspond with their stratigraphic position in the cumulate sequence. Further discrepancies are indicated by the shape of chondrite-normalized REE patterns and a disequilibrium of 18O values of orthopyroxene and associated chromite. A tentative explanation traces the present position of the PGE-bearing chromitites back to transportation via filter pressing from deeper parts of the cumulate sequence.
The conspicuous similarities between the Bregu i Bibes occurrence and Alaska-type PGE mineralizations, e.g. Pt/<epsilon>PGE > 0.8, similar patterns of PGEcn and the prevailing Pt-rich Pt-Fe alloys, but also their discrepancies will be demonstrated. Moreover analogies of the Bregu i Bibes mineralization in the northern and southern extension of the Mirdita ophiolite (Yugoslavia; Greece) are presented.
The Pd enrichment in 'supra-Moho dunites' near Krasta (Bulqiza Complex, Central Albania) is associated with chromite-pentlandite assemblages. The pentlandite-rich samples with a total content of PGE up to 3 ppm (Pd up to 2 ppm) and 34S values ¾0.7 suggest a magmatic origin of sulphur. Moreover inclusions in chromite of Rh pentlandite associated with Cu sulphides indicate the initial formation of these minerals (or former 'chalcopentlandite'?) and the trapping of PGE under high-temperature conditions. However with respect to Pd, preliminary PIXE studies of Krasta pentlandites indicate that this mineral is not the main Pd carrier. Further analyses are in work and their results will be presented.
Ohnenstetter M, Karaj N, Neziraj A, Çina A,, C. R. Acad. Sci. Paris 213, II, 201-208, (1991).
Çina A, Neziraj A, Karaj N, Ostrosi B, Bishnjaku B,, Workshop on Albanian ophiolites and related mineralization IUGS/UNESCO Modelling Programme, Editions BRGM, 244,, 27-46, (1995).
Accretional and postaccretional mesozoic ore deposits are formed in the Noth-East of Russia. Accretional deposits are connected with the collision in late Jurassic-Neocomian period of the Kolyma-Omolone superterrein and the Okhotsk terrein with the edge of the North-Asian craton. At the period of the early collision a gold ore sheaz zone was formed followed by rare-metal, tin, gold, polymetal ore transpressional strike-slip zones. Postaccretional deposits of silver, gold and rare metals are associated with late mesozoic subductional processes. They are located in the formations overlapping and joining collision structures.
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