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The caves with underground glaciations (multi-year or seasonal) represent by themselves one of the most interesting and distinct environments of cryominaragenesis. The main prerequisite of its broad occurence in caves is the elevated content of dissolved solids in cave water especially in the case of karst caves. Speleomineragenesis is a crystallization of the matter (formation of minerals) due to frosting of water solutions circulated in caves. The quantity and character of cryomineral components in cave ice depends first of all on lithological environment. In limestone caves different phases of calcite dominate, while in gypsum caves – gypsum, celestine, calcite and barite are typical. The admixtures are represented by allochthonic (mainly aerosols) and autochthonic particles. Cryomineral formations have a special (typical for them) micro-morphology allowing their identification. Cryomineral investigations are a new and interesting direction of cave mineralogy studies. There are also important for different reconstructions of cave environment, studying of chemical denudation etc.
Calcite veins and related sulphate–sulphide mineralisation are common in the Buda Hills. Also, abundant hypogenic caves are found along fractures filled with these minerals pointing to the fact that young cave-forming fluids migrated along the same fractures as the older mineralising fluids did. The studied vein-filling paragenesis consists of calcite, barite, fluorite and sulphides. The strike of fractures is consistent—NNW–SSE—concluding a latest Early Miocene maximum age for the formation of fracture-filling minerals. Calcite crystals contain coeval primary, hydrocarbon-bearing- and aqueous inclusions indicating that also hydrocarbons have migrated together with the mineralising fluids. Hydrocarbon inclusions are described here for the first time from the Buda Hills. Mixed inclusions, i.e., petroleum with ‘water-tail’, were also detected, indicating that transcrystalline water migration took place. The coexistence of aqueous and petroleum inclusions permitted to establish the entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1.7 NaCl eq. wt%) implies that hydrocarbon-bearing fluids were diluted by regional karst water. FT-IR investigations revealed that CO2 and CH4 are associated with hydrocarbons. Groundwater also contains small amounts of HC and related gases on the basin side even today. Based on the location of the paleo- and recent hydrocarbon indications, identical migration pathways were reconstructed for both systems. Hydrocarbon-bearing fluids are supposed to have migrated north-westward from the basin east to the Buda Hills from the Miocene on.
Porosity evolution of carbonates in the Buda Hills was the subject of this research. The aim was to provide an analogue for carbonate reservoirs that underwent multiphase diagenesis. Two major porosity types were recognized: 1) micro-porosity of powdered Triassic dolomites 2) cavernous and fracture porosity represented by the famous hypogenic cave system, hosted by Triassic and Paleogene carbonates. Powderization of dolomite is a general phenomenon in the Buda Hills, where its areal extent is exceptionally large compared to similar occurrences elsewhere in the world. Geochemistry and mineralogy of the dolomite remained constant throughout the disintegration. Powderization is absent at places where the Triassic dolomites are partially calcitized as a result of karst related dedolomitization. Since powderization was controlled by surface related processes and no geochemical changes were associated with it, disintegration of dolomite is interpreted as the result of sub-recent physical weathering, supposedly related to frost action.
Hypogenic caves are found along older calcite-barite-fluorite-sulphide veins, pointing to the fact that young cave-forming fluids migrated along the same fractures as the older mineralizing fluids did. Predominantly NNW–SSE strike of fractures concludes a latest Early Miocene maximum age for the fracture-filling minerals. Vein-calcite contains coeval primary, HC-bearing- and aqueous inclusions indicating that also HCs have migrated together with the mineralizing fluids. The coexistence of aqueous and HC inclusions permitted to establish the entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1.7 NaCl eq. wt%) implies that HC-bearing fluids were diluted by regional karst water. Fluid inclusion studies also revealed that aggressive gases (e.g. CO2, H2S) were associated with HCs and that these gases may have played a role in dissolution of the carbonates. Based on the location of the paleo- and recent HC indications, identical migration pathways were reconstructed for both systems. It was proved that HC-bearing fluids have migrated northwestward from the basin east to the Buda Hills from the Miocene on. Due to the uplift related intensification of groundwater circulation, the proportion of hydrothermal fluids has diminished in favour of cold meteoric fluids. Establishment of the actual porosity of the Buda Karst initiated in Miocene times and earlier diagenetic history of the carbonates affected only the powderization of dolomite, and it had no direct effect on the localization of hypogenic caves.
In the past few years the systematic study of caves intercepted by mine workings in southwest Sardinia has permitted us to observe morphologies due to rare speleogenetic and minerogenetic processes related to ancient hydrothermal activity. These relic morphologies are slowly being overprinted by recent speleogenetic processes that tend to obscure the hypogene origin of these caves. A combined geomorphological and mineralogical investigation has permitted a fairly detailed reconstruction of the various phases of evolution of these caves. Cave formation had already started in Cambrian times, but culminated in the Carboniferous, when most of the large voids still accessible today were formed. A key role in carbonate dissolution was played by sulphuric acid formed by the oxidation of the polymetallic ores present in the rocks since the Cambrian. During the Quaternary a variety of minerals formed inside the caves: calcite and aragonite, that yielded sequences of palaeo-environmental interest, and also barite, phosgenite, hydrozincite, hemimorphite and many others. These minerals are in part due to a phreatic thermal hypogenic cave forming phase, and in part to later epigene overprinting in an oxidizing environment rich in polymetallic ores. Massive gypsum deposits, elsewhere typical of this kind of caves, are entirely absent due to dissolution during both the phreatic cave formation and the later epigenic stage
Five hypogenic-origin caves from Southern France are presented. Investigations using XRD, SEM and Raman spectroscopy, reveal the presence of uncommon cave minerals. Oilloki Cave is a small lead ore mine-cave containing galena, cerussite, and bismuth (present as native element or as sulfide).La Baume Cave is a hydrothermal breccia-pipe, filled with colorful (red, green, white) clays. Some of the clay minerals (clinochlore se-piolite), could originate from hydrothermal weathering of clastic material. The Mala-coste Quarry, harbors a hydrothermal chimney with enlarged vugs lined with calcite spar and filled with iron oxyhydroxides poolfingers (goethite-hematite) and manganese oxides (birnessite, todorokite). Deposition of iron and manganese oxides results of the pH-Eh evolution along the hydrothermal chimney. Pigette Cave is a hydrothermal ver-tical maze with calcite lining and small iron oxyhydroxides and manganese oxides mass-es. The hydrothermal weathering of the walls deposited grains of lithiophorite, barite, and celadonite, which could originate from glauconite. Baume Galinière Cave is a small horizontal maze originating from the oxidation of sulfide masses of pyrite. Beside the common byproducts (gypsum, goethite, sulfur), the six members of the jarosite sub-group are present: jarosite, ammoniojarosite, argentojarosite, hydronium jarosite, natro-jarosite, plumbojarosite, together with fibroferrite. In these caves, three minerals are new cave minerals (bismuth, celadonite, argentojarosite); some others have been men-tioned before only in a few caves worldwide (clinochlore, lithiophorite, ammoniojaro-site, hydronium jarosite, natrojarosite, plumbojarosite, fibroferrite). The mineralogene-sis involves different processes: (i) Deposition in mixing zone from species carried by rising deep flow (barite, galena, bismuth, birnessite, todorokite, lithiophorite); (ii) Hy-drothermal weathering of clay minerals contained in host rock or present as clastic sediments (clinochlore, sepiolite, celadonite); (iii) Oxidation of sulfide masses (goethite, cerussite, jarosite subgroup minerals, fibroferrite).
n the past few years the systematic study of caves intercepted by mine workings in southwest Sardinia has permitted us to observe morphologies due to rare speleogenetic and minerogenetic processes related to ancient hydrothermal activity. These relic morphologies are slowly being overprinted by recent speleogenetic processes that tend to obscure the hypogene origin of these caves. A combined geomorphological and mineralogical investigation has permitted a fairly detailed reconstruction of the various phases of evolution of these caves. Cave formation had already started in Cambrian times, but culminated in the Carboniferous, when most of the large voids still accessible today were formed. A key role in carbonate dissolution was played by sulphuric acid formed by the oxidation of the polymetallic ores present in the rocks since the Cambrian. During the Quaternary a variety of minerals formed inside the caves: calcite and aragonite, that yielded sequences of palaeo-environmental interest, and also barite, phosgenite, hydrozincite, hemimorphite and many others. These minerals are in part due to a phreatic thermal hypogenic cave forming phase, and in part to later epigene overprinting in an oxidizing environment rich in polymetallic ores. Massive gypsum deposits, elsewhere typical of this kind of caves, are entirely absent due to dissolution during both the phreatic cave formation and the later epigenic stage.
The abundance and variety of speleothems are undoubtedly among the remarkable features of Cova des Pas de Vallgornera, the longest cave system in Mallorca Island developed in the eogenetic karst of its southern coast. Due to the monotonous carbonate lithology of the area, most of the speleothems are composed of calcite and in a few cases aragonite, although other minerals are also represented (e.g., gypsum, celestine, barite.). However, in spite of the rather common mineralogy of the speleothems, its distribution results strongly mediated by the lithologic and textural variability linked to the architecture of the Upper Miocene reefal rocks. Apart from a vast majority of speleothem typologies that are ubiquitous all along the cave system, some particular types are restricted to specific sections of the cave. In its landward inner passages, formed in the low permeability back reef facies, a great variety of speleothems associated to perched freshwater accumulations stands out, as well as some non frequent crystallizations like for example cave rims. On the other hand, the seaward part of the cave (developed in the very porous reef front facies) hosts conspicuous phreatic overgrowths on speleothems (POS), which are discussed to show their applications to constrain sea level changes. The factors controlling the distribution of speleothems found in Cova des Pas de Vallgornera are discussed along the paper, focusing the attention on the lithologic, hydrogeologic and speleogenetic conditionings; at the same time some uncommon speleothems, not found in any other cave in Mallorca, are also documented from this locality. Finally, a cognizant endeavour has been undertaken to illustrate with photographs the most remarkable speleothem types represented in the cave.
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