A review of the morphological varieties of ore bodies in the Madan Pb-Zn deposits, Central Rhodopes, Bulgaria
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Abstract:
The Madan Pb-Zn deposits are characterized by three morphogenetic types of ore bodies: veins, stockworks and replacement skarn-ore bodies. The subvertical veins and complex stockwork zones follow the tectonic boundaries of the NNW striking structures, cutting the various gneisses, amphibolites and marbles of the host metamorphic complex. Veins represent regularly-shaped, simple, steeply-dipping mineralized sections of the ore-bearing faults. Apophyses are common, generally joining the main vein in depth. Irregular in shape complex stockwork bodies are represented by sulphide veinlets and impregnations in deeper levels of the deposits and formed in zones with intensive hydrothermal alteration. Complex replacement metasomatic ore bodies are developed at the intersections of the ore-controlling faults with the marbles. Their morphological varieties include bed-like, columnar, mushroom-like or irregular, single or multilayered skarn- ore ledges, controlled by the lithological contacts of the skarns and marbles and screened by the other silicate rocks. The morphology of the replacement bodies is additionally complicated by post-depositional tectonic movements. The investigation summarizes the available data about the morphology of the ore bodies in the Madan district, taking into consideration the controlling factors. Understanding of the processes in the hydrothermal system and factors determining the deposition of rich ores can serve for the future successful exploitation of the deposits.Keywords:
Stockwork
Metasomatism
Ore genesis
Protolith
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Structural control of molybdenite-polymetallic deposits in granites is examined by means of analysis and correlation of fissured molybdenite veins, their host rocks, barren dikes, and other rocks of the area. It was found that the known ore bodies of the deposit are restricted to one system of fissures, having characteristic zonations in dip and strike, and further that mineral zonation in the ore-bearing veins may be related to the structural pattern of the molybdeniferous fissure system. V.P. Sokoloff
Molybdenite
Dike
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Background . The Novo-Uchaly copper-zinc VMS deposit in the Southern Urals (54°10΄54˝N and 59°20΄45˝E) is represented by a steeply dipping lens of Eifelian volcanics (rhyodacites and basalts), which are crumpled into a strongly compressed anticlinal fold. The ore deposit is blind and localised at the convergence of felsic (bottom) and mafic (top) rocks. The deposit is located at depths of 550 m (in the northern part) and 1050 m (in the southern part). The deposit thickness reaches 186 m. The length along the strike and along the dip equals 1250 m and 900 m, respectively. The ore body is intruded by gabbro-diorite and gabbro-diabase dikes. The main ore minerals are pyrite, sphalerite and chalcopyrite, as well as non-metallic minerals, such as quartz, barite and calcite. Unlike most of the Ural VMS deposits, this deposit is the zinc subtype (Zn >> Cu). The ores are predominantly massive and solid sulphide, being banded or brecciated in some parts. The main elements extracted are copper, zinc and sulphur, but gold, silver, cadmium, indium, cobalt, nickel, selenium and tellurium are also obtained. Aim . To clarify the morphology of the ore deposit, to study the ore mineral composition of the upper horizons of its northern part and to determine the underlying reasons for the complex lenticular structure of the sulphide reserve. Materials and methods . In the period 2017—2019, employees of the Institute of Ore Deposits, Petrography, Mineralogy and Biochemistry of the Russian Academy of Sciences (IGEM RAS) together with geologists of the Uchaly Mining and Processing Plant carried out a geological and mineralogical mapping of the deposit in the course of exploration works. Results . The ore contours and mineral composition of the northern part of the ore body were significantly clarified. A series of dikes of variable morphology was identified. A comparison was made of the results with current theories about the structure of the ore deposit. Detailed geological sections were determined and illustrate the complex lenticular structure of the ore deposit complicated by pinch and swell areas. The deposit was formed by processes of dynamic metamorphism. Conclusion . The geological and mineralogical structure of the deposit determined in the study enabled us to propose a schematic reconstruction of the conditions leading to the formation of its folded structure. The findings will help to re-assess the reserves and improve the system of operational exploration and delineation.
Polymetallic replacement deposit
Diorite
Felsic
Bornite
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The Journal of the Japanese Association of Mineralogists Petrologists and Economic Geologists (1964)
The Omine copper mine operated by Rasa Industrial Co. Ltd. is situated about 20km to east of Tono City, Iwate Prefecture, and adjoins to the west of western group of the Kamaishi iron-copper deposits. The mining district is composed of the Permian slate, calcareous slate, sandy slate, which are intruded and metamorphosed by the granodiorite and quartz-diorite. The granodiorite and quartz-diorite are considered to have invaded in the early-Cretaceous age. The ore deposit of Omine mine is genetically related to the granodiorite intrusion, and ore minerals were produced by the contact metasomatic and high temperature hydrothermal processes. The deposit consists of four ore bodies. Three ore bodies ranging from the first one to the third one occur in the breccia skarn zone, and are in network or impregnation in form. The shape of each ore body is cylindrical and inclined about 60°_??_80° to the northwest. These ore bodies produce a large amount of cubanite as well as chalcopyrite and pyrrhotite, accompanying with a small amount of pentlandite. The skarn of this mine is classified into two types, that is, “the banded skarn” and “the breccia skarn”. The banded skarn is composed of biotite hornfels and diopside-fels, very often interposing leucocratic veins. All these are parallel to the bedded plane. The breccia skarn is composed of diopside skarn and/or diopside-garnet skarn filling up the interstices of numerous breccia-like biotite hornfels. A remarkable K-felspathization (chiefly microclinization) is recognized in the breccia-like biotite hornfels scattering in the breccia zone. The present paper purports to clarify the genesis of the ore deposit of the Omine mine, and to describe the paragenesis of ore minerals. Special attention is given to the discussion of the K-felspathization and the skarnization of the hornfels in the breccia zone. The existence of the fourth ore body has been affirmed by boring. However, its details will be reported later when prospecting has advanced.
Hornfels
Breccia
Diorite
Metasomatism
Actinolite
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Morphology of ore bodies is relatively simple along the strike but characteristically intricate across the strike (table 4) in the regional type of pyrite-polymetallic ore deposit (C3-P1). Positions of the ore bodies are structurally-lithologically controlled. Historically, every aspect of the deposit's modern structure may be related to geological evolution of the region, from the Devonian sedimentation to terminations of the Upper Paleozoic tectonic movements.
Devonian
Table (database)
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“Les Mines Selbaie” is a large, generally low-grade, polymetallic (Zn, Cu, Ag, Au) “giant” volcanic-associated ore deposit in the Harricana-Turgeon belt, which is part of the northern Abitibi Subprovince of Quebec. Economically recoverable mineralization occurred in three zones: the A1 (open pit), A2, and B Zones (underground). The pre-mining resource was 54.9 Mt, including 8 Mt of sub-economic, locally silver-rich massive pyrite. In the Selbaie region, calc-alkaline andesitic volcanics form the “basement.” The Brouillan Volcanic Complex formed within an island-arc setting on this regional basement. Evolution of this complex involved the formation of a felsic magma chamber and the development of a large caldera structure over the Brouillan batholith. Second-order linear and sub-parallel faults and rifts developed as a result of back-arc rifting/extension. The edges of these rifts were feeders for linear felsic volcanism (similar to fissural volcanism). During felsic volcanism, the feeder zones acted as conduits for hydrothermal fluids with associated pervasive potassic alteration. The alteration is characterized both vertically and laterally by well-defined quartz, sericite, K-feldspar and/or, locally, biotite halos, to produce a mushroom-shaped morphology. This K-feldspar alteration is not common in most other volcanic-associated ore deposits. Mafic dikes cut all of the geological units and appear to occupy earlier synvolcanic structures. Regional green-schist-assemblage metamorphism and pervasive deformation affect all units. Thrust faults moved part of the Brouillan batholith and basement units over the Mine Sequence. Although there is no relationship between the earlier mineralizing events and these late thrust faults, the thrust faults probably played an important role in location of ore lenses. Three types of mineralization are present: 1) copper-rich veins and hydraulic breccias; 2) disseminated and stringer, low-grade and high volume zinc-copper mineralization; and 3) finely laminated, massive, locally silver-rich pyrite mineralization within structural basins. At the bottom of these basins and at the contact of welded acid tuff (WAT) units, massive pyrite zones are locally enriched in zinc, and contain the possible vestiges of black smoker-like material. The ore metals were probably derived from leached basement andesitic volcanics in a hydrothermal system powered by one or more heat sources within the Brouillan Volcanic Complex. The Selbaie deposits are mainly characterized by: (1) the presence of small volcano-tectonic subsidence basins, which host chemical sediments and volcaniclastic materials; (2) pervasive potassic alteration; (3) locally high-grade silver mineralization (up to 1-2 kg/t Ag); and (4) the presence of random zones of Pb mineralization. The Selbaie deposits can be closely compared with the copper-rich Murgul deposits, which belong to the eastern Pontides metallogenetic province in Turkey. If conventional classification criteria for the volcanogenic massive sulfide deposits (e.g., Noranda, Mattabi types, and recent subsea floor deposits) are taken into account, the Selbaie deposits still exhibit many differences in terms of alteration assemblages, physical volcanology and some styles of mineralization (low-grade and large volume). Consequently, the “Selbaie” deposits belong to a new sub-type of volcanic-associated sulfide deposit, which may be used in future exploration programs.
Felsic
Batholith
Sericite
Greenstone belt
Caldera
Volcanic arc
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The Journal of the Japanese Association of Mineralogists Petrologists and Economic Geologists (1959)
The copper deposit of the Hamanaka area is located in the southern part of East Hokkaido. This ore deposit was discovered in the outer zone of Kuril arc, and is considered to be originated by the igneous activies of alkaline basic rocks. It must be a remarkable thing. The geological complex developed in the neighbourhood of this ore deposit are the Hamanaka formation with alkaline rocks of upper Cretaceous and some deposits of Quaternary age. The ore deposit is generally observed as massive or stratified bodies in the alternation member of black mudstone and tuffaceous sandstone, and these ore bodies consist of yellowish massive ore and dark gray Kuroko-like ore. The important minerals are pyrite and chalcopyrite, with minor quantities of sphalerite, galena, marcasite, quartz, and rarely calcite and barite. After all, this ore deposit is considered to be a cupriferous iron sulfide deposit from its geological situation, occurrence of ore bodies, and its distinctive character of ore. And it is an ore deposit that have been replaced by hydrothermal solutions.
Marcasite
Polymetallic replacement deposit
Ore genesis
Hypogene
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Stockwork
Breccia
Siltstone
Ore genesis
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Lithology
Devonian
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The Zn-Pb ore deposit in the vicinity of Chrzanow consists of about 90 ore bodies of varied size. Mineralization occurs within the Middle Triassic dolomites in form of bed-shape sphalerite concentrations, replacing the host rocks and various aggregates of sphalerite and galena, infilling their voids. Ore distribution within the rock massif is determined by lithology of the Triassic deposits and by tectonic structures but also an influence of paleohydrological factor on are body origin is assumed. The effect of these factors operation is the ore concentration in some beds, named “ore horizons” and resulted the tabular form of ore bodies and their position concordant with bedding of surrounding rocks. The influence of tectonic factor also determinates internal variability of are bodies, The described here deposit development could be assumed as typical for a part of the Silesian-Cracow ore province, located within the Upper Silesian Trough.
Massif
Lithology
Polymetallic replacement deposit
Prospecting
Bedding
Ore genesis
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The ore deposits are veins with pyrite, pyrrhotite, and chalcopyrite as principal primary sulfides, and quartz gangue. Ore shoots are lenticular. Host rocks are Precambrian metasediments, intensely folded, faulted, and intruded by syntectonic granites and mafic rocks (now amphibolite) and by post-tectonic mafic dikes. Ore is localized primarily in fractures along shear zones trending subparallel to the main faults of the district, and to a lesser extent by intersection zones, joints, folds, and breccia zones.
Copper ore
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Citations (29)