Żyły mineralne na Ornaku w Tatrach Zachodnich

W. Wątocki


Ore veins on Ornak in the Western Tatra Mountains

Known since long ago to exist in the crystalline rocks of the Tatra Mountains were ore-deposits containing gold and silver, thanks to which they were exploited by miners in the past ages. The first historical accounts of prospecting for ores date from the XV century, while mining on the eastern slopes of the mountain Ornak was first taken up in 1502, when ores of copper (tetrahedrite) and silver were begun to be extracted by means of the so-called Black Gallery (Czarna Sztolnia). Mining, carried out under very difficult geographic and climatic conditions, was soon interrupted on account of its small profitableness. Nevertheless, iii the course of the XVI century mining was resumed several times in these terrains and extended to the western slopes of the mountain Ornak, descending to the valley which up to the present day is called Starorobociańska from those old workings («stare roboty») just mentioned above. To the same period (c. 1531) belongs a shaft by means of which — after piercing a moraine lying in the valley — exploitation was carried on of ore-veins situated at the headwaters of the stream Kościeliski Potok, at the foot of the pass Pyszniańska Przełęcz. Finally, more intensive prospecting and mining took place in the XVIII century. During the reign of the last Polish king, Stanisław August Poniatowski, the previously abandoned shafts and adits were repaired, mills were built, and a smeltery was erected for obtaining copper. It is from these times, too, that have been pre its value. It is known in fact, from a report made by the thenacting mining-inspector Knoblauch, that a hundredweight of ore gave traces of gold, 10 ounces of silver, and 16 pounds of copper. After the year 1768 nothing is known of the subsequent history of the mines. Not until 1919 did Prof. W. Goetel and Prof. S. Kreutz organize, with the assistance of miners, an investigation of the state of preservation of the workings and of the geological conditions of the deposits. Incomplete descriptions of Tatra ore-deposits reoccur in all the older geological works pertaining to the Tatra Mountains (Hacquet, Genersich, Staszic, Zeuschner). Of the more recent studies of these ores should be quoted those on the subject of which two references have remained in literature, viz., the studies of W. Pawlica in 1916, and those of S. Kreutz in 1919. The ore samples collected by Pawlica and Kreutz, mostly on old dumps in the vicinity of adits, have been turned over to the author of this paper for chemical elaboration. II. CLASSIFICATION OF TATRA ORES All the Tatra ore-veins may be classified into two great sections: I. Veins occurring in magmatic rocks. II. Veins occurring in sedimentary rocks. Whereas the ores occurring in the crystalline part of the Tatra Mountains belong to older formations, in any case of pre-Permian age, the ores of the other section (in sedimentary rocks) are of considerably younger origin. Section I. This part of the ore deposits is composed of the following veins: a. carbonate veins, b. veins containing metal oxides, c. sulphide veins, d. barite veins. All these kinds of ore-veins contain quartz as their gangue mineral. Carbonate veins: (1) siderite veins, (2) calcite veins, 3) isomorphous mixtures of the two previous ones (ankerite). Among these three kinds of carbonate veins two groups are distinguished: a. carbonates of thermal origin, characterized by such minerals as tourmaline, and by the presence of sulphides, in the first place chalcopyrite and tetrahedrite, furthermore, pyrite; b. carbonates having their origin in the leaching of constituents from country-rocks, and not containing tetrahedrite or chalcopyrite. Veins containing metal oxides, i . Here are found: (1) haematites, (2) quartz veins (given here for the sake of clarity of the ore classification). Among haematite veins the following are distinguished: a. veins with tabular haematite (specularite), of the oldest origin; b. thick haematite veins, of hydrothermal origin, and thin haematite crusts in gneisses and granites (secondary product formed from leached Fe ). Quartz veins: a. pure quartz veins of aqueous origin; b. quartz-tourmaline veins with small quantities of mica (pegmatite injections), of pneumatolytic origin (Jamnicka Valley); c. combinations of quartz-sulphide veins with argentiferous sulphides; d. quartz-barite veins. Sulphide veins: 1. tetrahedrite veins, always with chalcopyrite; 2. pyrite veins or lenses; 3. chalcopyrite veins; 4. stibnite veins. It must be added here that pyrite occurs in quartz-pyrite veins as impregnations of amphibole-biotite-chlorite lenses, and as lenses in amphibolites. Barite veins: The following are distinguished here: 1. coarsely crystalline barites, without sulphides; 2. finely crystalline barites, containing sulphides. The former barites (1) contain c. 2% of SrO, while the latter barites (2) have c. 5—6% of SrO. III. DESCRIPTION OF THE ORES Siderite In the granite and its superjacent crystalline schists of the Western Tatra Mountains the ore-veins most frequently encountered are siderite veins. They occur either in fissures of tectonic nature, or in granite joints. The first type is represented by veins up to 40 cm. thick, composed of medium-grained siderite (ankerite). It was exploited in adits at Koziczki, Dziurawe and Baniste, and in the shaft at Kunszty. It is accompanied by barite and tetrahedrite, less frequently by chalcopyrite, and by such supergene minerals as covellite, malachite, azurite, limonite. The hypogene metal-bearing minerals, tetrahedrite and chalcopyrite, were precipitated in two stages, i. e., contemporaneously and after the crystallization of siderite. The chemical composition of the above-mentioned siderites, taken from the adits at Koziczki and Dziurawe, is shown in four complete chemical analyses, executed by the author of this paper and contained in the Polish text on page 31, 32. Secondary siderite Siderite of this type occurs in small veins, the thickness of which does not normally exceed 2—3 cm. It belongs to two varieties, a finegrained one and a coarse-grained one, of a light colour with a pinkish shade, in contradistinction to the metal-bearing siderites ranging from light-yellow to ash-grey. The only metal-bearing mineral accompanying the siderites is pyrite, contemporaneous in the succesion of genesis. Chemical analyses, executed from bo varieties of siderite, found in the talus between Wielki Ciemnosmereczański and Pośredni Ciemnosmereczański (fine-grained variety), and on Żelazne Wrota (coarsegrained variety), are included in the Polish text on page 34, 35. Tetrahedrite This mineral is known in the form of small impregnations in veins with the following chief associations: 1. quartz-tetrahedrite veins, 2. quartz-carbonate-tetrahedrite veins, 3. barite-tetrahedrite veins. Moreover, present as a constant companion of tetrahedrite is chalcopyrite, intergrowing the former, and less frequently encountered, pyrite. Tetrahedrite displays steel-grey colour, conchoidal fracture, and red-brown streak. Drawing conclusions from observations supplied by thin slides and polished surfaces, there exist two stages in the precipitation of sulphides: (1) contemporaneously, or almost so, with the separation of siderite or barite, in the form of small impregnations throughout the material of the vein; (2) after the separation of barite or siderite: quartz crystallizes and sulphides are precipitated in fissures of the vein material or in little vacuums, occasionally with small quantities of siderite. Two complete chemical analyses, the results of which are given in the Polish text on page 37, were executed by the author from tetrahedrites collected at the mine Kunszty (Pyszna). Pyrite Apart from their occurrence in veins, mainly in connection with tetrahedrite, pyrites were also found in the Starorobociańska Valley in lenses of schists, arranged in a direction accordant with the jointing in the granite. The schist material which fills both lenses is composed, among others, of amphibole, biotite, chlorite, and considerable quantities of apatite forming a matrix in which are imbedded idiomorphic crystals of pyrite. At points of contact between schist and granite the pyrite is enriched, forming portions composed of pyrite alone. Chemical analyses of this variety of pyrite are given on page 42. Stibnite Contrary to several mentions in old literature, this mineral does riot occur on the Polish side of the Tatra Mountains; on the other hand, the data concerning its occurrence on Wielki Krywań and Mały Krywań have been confirmed by the author’s own observations. Stibnite is imbedded there in quartz veins, worked already in the first half of the XV century for gold and silver. Apart from stibnite and quartz, of a characteristic yellow-red colour, into the composition of the local paragenetic association in some parts of the veins enter idiomorphic pyrite, yellow lead oxides, and the very rare malachite and azurite. Native gold and silver were not discovered. The results of the chemical analysis of the stibnite from Krywań are given in the table on page 45. Haematite Of the haematites quoted in the classification of ores, the following were studied chemically: 1. coarsely veined haematite from Hruby, 2. the oldest haematites from Koziczki, 3. the oldest crusts on gneiss from Błyszcz. The first of these varieties, the chemical analyses of which are collected in the table on page 46, occurs in veins, up to a dozen cm. thick or more, imbedded in the gneiss of Hruby. In this case the haematite is foliated, blood-red, and easily cleavable. In places it is intergrown with quartz. The haematite of the oldest origin from Koziczki is characterized by foliation, very considerable compactness, and fluidal arrangement of the scales, this being the consequence of dislocation movements. In connection with these movements there took place a disruption of the haematite vein and secondary filling of the fissures with younger siderite. The mean thickness of the haematite is 2—3 mm. In the vein walls the earlier quartz occurs together with idiomorphic haematite. An analysis of the haematite from Koziczki is given on page 47 of the Polish text of this work. Haematites forming spongy coatings on the surface of joints in gneisses and granites are undoubtedly of secondary origin, from the leaching of Fe out of minerals in country-rocks. The haematites are constantly accompanied by limonite. An analysis of this type of haematite is given on page 47. Barite Tatra barite is known in two varieties: 1. coarse-grained barite, not accompanied by sulphides; 2. barite containing sulphides. The first variety, found in gully No. 2 and in mines Nos. 2 and 3 on Ornak, is encountered in the form of veins, 8—10 cm. thick, in Strongly fissured gneiss. In vein walls limonite occurs abundantly. An analysis of the barite from gully No. 2 is given in the Polish text on page 48. The second variety of barite, known in particular from Dziurawe, occurs either in large grains displaying deformations and very frequent twinning, or else as a very fine-grained matrix surrounding, together with quartz, the larger crystals. Chalcopyrite and the rarer tetrahedrite fill small fissures in barite, or are visible as impregnations surrounded with quartz. Both ores are deprived of crystallographic forms proper to themselves and form irregular intergrowths. Chemical analyses of the sulphide-containing barite from Dziurawe are collected in the table on page 49. These analyses are distinguished by a considerable SrO content (6,83% by weight, on an average).

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