MWH Global

Enviroscan Ukrainian Institute of Speleology and Karstology


Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/template/toolbar_left.php on line 5
Community news

Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That pore velocity is see velocity, average interstitial.?

Checkout all 2699 terms in the KarstBase Glossary of Karst and Cave Terms


Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/template/toolbar_right.php on line 7
What is Karstbase?

Search KARSTBASE:

keyword
author

Browse Speleogenesis Issues:

KarstBase a bibliography database in karst and cave science.

Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
See all featured articles
Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
See all featured articles from other geoscience journals

Search in KarstBase

Your search for hydrothermal (Keyword) returned 221 results for the whole karstbase:
Showing 16 to 30 of 221
Strontium geochemical evidence for the origin of the barite deposits from Sardinia, Italy, 1984,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Barbieri M, Masi U, Tolomeo L,
Sr content of 137 samples of barite, 81 samples of fluorite, and 65 samples of calcite from 27 post-Cambrian karst and hydrothermal deposits. Karst calcites have an average Sr content of 26 ppm, quite similar to that of the hydrothermal calcites. Hydrothermal fluorites show an average content of 56 ppm. Forty-five percent of the karst barites have an Sr content over 6,000 ppm, while as much as 83.8 percent of the hydrothermal barites contain more than 6,000 ppm Sr. The Sr isotope composition of the Cambrian stratiform barites (0.70867 or - 3) is similar to that of Cambrian seawater, suggesting that the bulk of the Sr was provided by this source. The Sr isotope ratios of the karst barite (average 87 Sr/ 86 Sr = 0.70947 or - 1) indicate that Sr was not only derived by recycling of the stratiform barite but was also provided by the noncarbonate fraction of the Cambrian wall rocks. The Sr isotope composition of the hydrothermal barites ranges from 0.70990 or - 4 to 0.71837 or - 4, suggesting that the Sr derived mainly from a high 87 Sr/ 86 Sr ratio source.--Modified journal abstract

Morphologie et volution des cavernes et formes superficielles dans les quartzites du Roraima, 1988,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Galan C. , Lagarde J.
MORPHOGENESIS OF CAVES AND LANDFORMS IN THE PRECAMBRIAN QUARTZITE OF RORAIMA GROUP (VENEZUELA) - This paper describes caves and landforms developed in the Precambrian quartzite of the Roraima Group (1600-1800 My) in the Gran Sabana of Venezuela (cf. Pouyllau and Seurin, in Karstologia, 1985, n 5). High plateaus (Tepuys) are remnants of old erosional surfaces of Secondary-Tertiary age. The weathering of quartzite is produced in fissures by means of the dissolution of the intergranular siliceous cement. Depressions, fields of blocks and small towers, deep fissures characterise the edges of tepuys. Underground passages could be formed by dissolution, arenisation and piping from the fractures which dissect the tepuys. The part of hydrothermalism in speleogenesis is not proved.

Paleokarst - a Systematic and Regional Review, 1989,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943

Description
Prepared by some of the world's leading experts in the field, this book is the first summarizing work on the origin, importance and exploitation of paleokarst. It offers an extensive regional survey, mainly concerning the Northern Hemisphere, as well as a thorough analysis of the problems of research into paleokarst phenomena, with particular emphasis on theoretical contributions and practical exploitation. By concentrating on phenomena which have appeared in the course of geological history, the book represents a substantial development in the general theory of paleokarst and demonstrates the advantages of a comprehensive approach to the problem. Considerable emphasis is put on the economic importance of paleokarst phenomena, from the point of view of exploiting significant deposits of mineral raw materials, as well as from a civil engineering and hydrological point of view. Since the publication deals with a boundary scientific discipline, it is intended for specialists from various branches of science: geologists, paleontologists, economic geologists, geographers, mining engineers and hydrogeologists.

Contents
List of Contributors. Foreword.

Part I. Introduction.
Introduction (P. Bosák et al.). Paleokarst as a problem (J. Głazek, P. Bosák, D.C. Ford). Terminology (P. Bosák, D.C. Ford, J. Głazek).

Part II. Regional Review.
Paleokarst of Belgium (Y. Quinif). Paleokarst of Britain (T.D. Ford). Paleokarst of Norway (S.-E. Lauritzen). Paleokarst of Poland (J. Głazek). Paleokarst of Czechoslovakia (P. Bosák, I. Horáček, V. Panoš). Paleokarst of Hungary (G. Bárdossy, L. Kordos). Hydrothermal paleokarst of Hungary (P. Müller). Paleokarst of Italy. Selected examples from Cambrian to Miocene (M. Boni, B. D'Argenio). Paleokarst-related ore deposits of the Maghreb, North Africa (Y. Fuchs, B. Touahri). Paleokarst of Yugoslavia (D. Gavrilović). Paleokarst of Bulgaria (I. Stanev, S. Trashliev). Paleokarst of Romania (M. Bleahu). Paleokarst of the Union of Soviet Socialist Republics (R.A. Tsykin). Paleokarst of China (Zhang Shouyue). Paleokarst of Canada (D.C. Ford). Paleokarst of the United States (M.V. Palmer, A.N. Palmer).

Part III. Mineral Deposits Connected With Karst.
An introduction to karst-related mineral deposits (P. Bosák). Pb-Zn ores (S. Dżułyński, M. Sass-Gustkiewicz). Bauxites (G. Bárdossy). Iron ore deposits in paleokarst (G. Bárdossy, Y. Fuchs, J. Głazek). Clays and sands in paleokarst (P. Bosák). The oceanic karst: modern bauxite and phosphate ore deposits on the high carbonate islands (so-called ``Uplifted Atolls'') of the Pacific Ocean (F.G. Bourrouilh-le Jan). Paleokarst-related uranium deposits (Y. Fuchs).

Part IV. Hydrogeology and Engineering Hazards in Paleokarst Areas.
Paleokarst as an important hydrogeological factor (J. Zötl). Hydrogeological problems of opencast and underground mining of mineral deposits encountered during their exploration, development and exploitation stages (P. Bosák). Hydrogeological problems of the Cracow-Silesia Zn-Pb ore deposits (Z. Wilk). Hydrogeological problems of Hungarian bauxite and coal deposits (T. Böcker, B. Vizy). Paleokarst in civil engineering (A. Eraso). Interaction between engineering and environment in the presence of paleokarst: some case histories (J. Głazek).

Part V. Paleokarst as a Scientific Subject.
Special characteristics of paleokarst studies (I. Horáček, P. Bosák). Tectonic conditions for karst origin and preservation (J. Głazek). Problems of the origin and fossilization of karst forms (P. Bosák). Biostratigraphic investigations in paleokarst (I. Horáček, L. Kordos).

Part VI. Conclusions. Part VII. References. Part VIII. Indexes.
Author Index. Geographical Index. Subject Index.

Bibliographic & ordering Information
Hardbound, ISBN: 0-444-98874-2, 726 pages, publication date: 1989
Imprint: ELSEVIER


The results of research into caves of hydrothermal origin, 1989,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Takcsbolner K. , Kraus S.

On Hydrothermal Phases During Later Stages of the Evolution of Cup Coutunn Cave System, Turkmenia, USSR, 1990,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Maltsev Vladimir A. , Malishevsky Dmitry I.

Regularities of the formation and modelling of hydrothermal karst, 1990,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Dubljansky Ju. V.

Stable isotopic composition of the hydrothermal fluids responsible for the Nanisivik Zn-Pb deposits, Northwest Territories, Canada, 1991,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Ghazban F. , Schwarcz H. P. , Ford D. C.

DIAGENESIS AND MINERALIZATION PROCESSES IN DEVONIAN CARBONATE ROCKS OF THE SIDING-GUDAN LEAD-ZINC MINERAL SUBDISTRICT, GUANGXI, SOUTHWEST CHINA, 1991,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Schneider W. , Geng A. Q. , Liu X. Z. ,
The lead-zinc ore deposits of the Siding-Gudan mineral subdistrict Guangxi are part of the large Nanling district of South China, and hosted in Devonian carbonate rocks. The ore bodies occur significantly along main faults and fault zones, and concentrate up to 300 meters above the Cambrian/Devonian unconformity. Connected with hydrothermal karst, size and volume of the ore bodies increase in proximity to this unconformity. Moving from the unaffected host rocks to the center of the ore bodies, four zones can be discriminated by the mineral assemblage (pyrite, sphalerite, galena) as well as by the degree of ordering, Ca/Mg, and Fe/Mn ratios of different dolomites. Homogenization temperatures range from 80-100-degrees-C (Presqu'ile dolomite) to 230-260-degrees-C (massive sphalerite). The sulfides reveal delta-S-34 = -20 to parts per thousand, and fluid inclusions display a salinity of 5-12 wt % equivalent NaCl. The diagenetic and hydrothermal history is similar to that of classic Mississippi Valley Type (MVT) sulfide mineral deposits as, for example, Pine Point in Canada. Mineralization and remobilization of the sulfides took place during a wide time span from late Paleozoic through Mesozoic. Both processes are considered as an interaction of saline basinal brines ascended from the adjoining dewatering trough, and magmatic-hydrothermal fluids of several magmatic-tectonic events

MURUROA ATOLL (FRENCH-POLYNESIA) .1. STRUCTURE AND GEOLOGICAL EVOLUTION, 1992,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Buigues D, Gachon A, Guille G,
From a geographical point of view, the atoll of Mururoa belongs to the Tuamotu archipelago. In its largest dimension Mururoa (28 x 10 km) is oriented N080-degrees-E, a direction which is different from that of the other atolls of the Tuamotu, generally oriented parallel to the Pacific plate motion, N130-degrees-E. The atoll of Mururoa is built on a submarine plateau of 130 km long and 30 km wide. The western side of this plateau is 90 km long and N080-degrees-E oriented, the eastern one 40 km long and N095-degrees-E oriented. Three deep main structures of the atoll are revealed by strong aeromagnetic anomalies elongated and oriented once more N080-degrees-E. They represent ancient riftzones, similar to the present time Hawaiian ones. The most important of them, situated at southern end of the atoll, is the prolongation of the eastern plateau. The principal petrographic facies have been defined from the numerous drill holes bored in the upper 1,100 m. From the base to the top are represented volcanic deposits, a volcano-sedimentary serie of both carbonate and volcanic origin and finally reefal carbonates (limestones and dolomites). The volcanic facies represent successively submarine, transitional and aerial volcanic activity. They are commonly affected by early stage of hydrothermalism, due to lava-sea-water chemical interaction, and are frequently supported by differentiated dykes, occasionally interrupted by reefal limestones. The main geometrical distribution of the facies through the atoll and the radiochronology lead to the following model of formation : during early stages of the atoll building two main separate edifices emerged before joining and forming a single volcano. This double structure was similar to the present time morphology of Tahiti. The volcanic activity ceased 10.6 Ma ago, an age which perfectly suits a hot spot origin, at present located to the south-east of Pitcairn island

Late to post-Hercynian hydrothermal activity and mineralization in Southwest Sardinia (Italy), 1992,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Boni M, Iannace A, Koeppel V, Fruehgreen Gl, Hansmann W,

LATE TO POSTHERCYNIAN HYDROTHERMAL ACTIVITY AND MINERALIZATION IN SOUTHWEST SARDINIA (ITALY), 1992,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Boni M, Iannace A, Koppel V, Fruhgreen G, Hansmann W,
Several kinds of base metal deposits occur in the lower Paleozoic of southwest Sardinia (Iglesiente-Sulcis mineral district). This paper deals with those deposits which are generally referred to as Permo-Triassic, because they accompany and postdate the Hercynian orogeny and are related to magmatic activity. A large number of previously published geochemical data, integrated with additional new data (Sr, Pb, O, C, and S isotopes), are reviewed and discussed in the frame of the late to post-Hercynian geologic evolution of southwest Sardinia. According to geological and mineralogical characteristics, three types of deposits can be distinguished: (1) skarn ores related to late Hercynian leucogranitic intrusions, (2) high-temperature veins, and (3) low-temperature veins and karst filling. Pervasive epigenetic dolomitization phenomena are geochemically related to the low-temperature deposits. Sr and Pb isotopes of the first and second types (0.7097-0.7140 Sr-87/Sr-86; 17.97-18.29 Pb-206/Pb-204; 38.11-38.45 Pb-208/Pb-204) are distinctly more radiogenic than those of the third type (0.7094-0.7115 Sr-87/Sr-86; 17.86-18.05 Pb-206/Pb-204; 37.95-38.19 Pb-208/Pb-204) which, in turn, are closer to Paleozoic ores and carbonates. Fluid inclusion data indicate that the fluids responsible for mineralization of the first and second types of deposits were hot and dilute (T(h)= 370-degrees-140-degrees-C; <5 wt % NaCl equiv). In contrast, relatively colder and very saline fluids (T(h)= 140-degrees-70-degrees-C; >20 wt % NaCl equiv) were responsible for the third type of mineralization, as well for epigenetic dolomitization of the Cambrian host rocks. O isotopes measured in minerals from the first two types (deltaO-18SMOW = 12.8-18.9 parts per thousand) are O-18 depleted with respect to the third type (deltaO-18SMOW = 15.9-22.1 parts per thousand). These data, coupled with fluid inclusion formation temperatures, indicate that the fluids responsible for the first two types of mineralization were O-18 enriched with respect to those of the third type and related hydrothermal phenomena. The deltaS-34CDT in sulfides of the first two types vary between 3.7 and 10.73 per mil, whereas the values of the third type range from 12.0 to 17.9 per mil. Late to post-Hercynian mineralization is thus explained as the result of three distinct, though partly superimposed, hydrothermal systems. System 1 developed closer to the late Hercynian leucogranitic intrusions and led to the formation of the first and subsequently the second type of mineralization. The relatively hot and diluted fluids had a heated meteoric, or even partly magmatic, origin. Metals were leached from an external, radiogenic source, represented either by Hercynian leucogranites or by Paleozoic metasediments. Sulfur had a partly magmatic signature. System 2 was characterized by very saline, colder fluids which promoted dolomitization, silicification, and vein and karst mineralization. These fluids share the typical characteristics of formation waters, even though their origins remain highly speculative. The hydrothermal system was mainly rock dominated, with only a minor participation of the external radiogenic source of metals. Sulfur was derived by recirculation of pre-Hercynian strata-bound ores. System 3 records the invasion of fresh and cold meteoric waters which precipitated only minor ore and calcite gangue. It may represent the further evolution of system 2, possibly spanning a time well after the Permo-Triassic. The timing of all these phenomena is still questionable, due to the poor geologic record of the Permo-Triassic in southwest Sardinia. Nevertheless, the hypothesized scenario bears many similarities with hydrothermal processes documented throughout the Hercynian in Europe and spanning the same time interval. A comparison with the latter mineralization and hydrothermal activities leads to the hypothesis that the first two types of mineralization are linked to late Hercynian magmatic activity, whereas the third type may be related to either strike-slip or tensional tectonics which, throughout Europe mark the transition from the Hercynian orogeny to the Alpine cycle

La grotte de la Movile (Dobroudja, Roumanie) : analyses _minralogiques, 1993,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Diaconu G. , Morar M.
The authors present the results of X-ray analyses which, in the Movile cave, give evidence of the presence of a mineralogical association made up of calcite, aragonite, ankerite and quartz. They also take into consideration the conditions of a specific genesis for this cave which has been particularly affected by sulphurous thermomineral waters.

CHEMICAL-REACTION PATH MODELING OF ORE DEPOSITION IN MISSISSIPPI VALLEY-TYPE PB-ZN DEPOSITS OF THE OZARK REGION UNITED-STATES MIDCONTINENT, 1994,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Plumlee G. S. , Leach D. L. , Hofstra A. H. , Landis G. P. , Rowan E. L. , Viets J. G. ,
The Ozark region of the U.S. midcontinent is host to a number of Mississippi Valley-type districts, including the world-class Viburnum Trend, Old Lead Belt, and Tri-State districts and the smaller Southeast Missouri barite, Northern Arkansas, and Central Missouri districts. There is increasing evidence that the Ozark Mississippi Valley-type districts formed locally within a large, interconnected hydrothermal system that also produced broad fringing areas of trace mineralization, extensive subtle hydrothermal alteration, broad thermal anomalies, and regional deposition of hydrothermal dolomite cement. The fluid drive was provided by gravity flow accompanying uplift of foreland thrust belts during the Late Pennsylvanian to Early Permian Ouachita orogeny. In this study, we use chemical speciation and reaction path calculations, based on quantitative chemical analyses of fluid inclusions, to constrain likely hydrothermal brine compositions and to determine which precipitation mechanisms are consistent with the hydrothermal mineral assemblages observed regionally and locally within each Mississippi Valley-type district in the Ozark region. Deposition of the regional hydrothermal dolomite cement with trace sulfides likely occurred in response to near-isothermal effervescence of CO2 from basinal brines as they migrated to shallower crustal levels and lower confining pressures. In contrast, our calculations indicate that no one depositional process can reproduce the mineral assemblages and proportions of minerals observed in each Ozark ore district; rather, individual districts require specific depositional mechanisms that reflect the local host-rock composition, structural setting, and hydrology. Both the Northern Arkansas and Tri-State districts are localized by normal faults that likely allowed brines to rise from deeper Cambrian-Ordovician dolostone aquifers into shallower carbonate sequences dominated by limestones. In the Northern Arkansas district, jasperoid preferentially replaced limestones in the mixed dolostone-limestone sedimentary packages. Modeling results indicate that the ore and alteration assemblages in the Tri-State and Northern Arkansas districts resulted from the flow of initially dolomite-saturated brines into cooler limestones. Adjacent to fluid conduits where water/rock ratios were the highest, the limestone was replaced by dolomite. As the fluids moved outward into cooler limestone, jasperoid and sulfide replaced limestone. Isothermal boiling of the ore fluids may have produced open-space filling of hydrothermal dolomite with minor sulfides in breccia and fault zones. Local mixing of the regional brine with locally derived sulfur undoubtedly played a role in the development of sulfide-rich ore runs. Sulfide ores of the Central Missouri district are largely open-space filling of sphalerite plus minor galena in dolostone karst features localized along a broad anticline. Hydrothermal solution collapse during ore deposition was a minor process, indicating dolomite was slightly undersaturated during ore deposition. No silicification and only minor hydrothermal dolomite is present in the ore deposits. The reaction path that best explains the features of the Central Missouri sulfide deposits is the near-isothermal mixing of two dolomite-saturated fluids with different H2S and metal contents. Paleokarst features may have allowed the regional brine to rise stratigraphically and mix with locally derived, H2S-rich fluids

SEDIMENT-HOSTED GOLD MINERALIZATION IN THE RATATOTOK DISTRICT, NORTH SULAWESI, INDONESIA, 1994,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Turner S. J. , Flindell P. A. , Hendri D. , Hardjana I. , Lauricella P. F. , Lindsay R. P. , Marpaung B. , White G. P. ,
The Ratatotok district in the Minahasa Regency of North Sulawesi, Indonesia is an area of significant gold mineralisation. Gold has been mined in the district since at least the 1850s, and intensively by the Dutch between 1900 and 1921 with a recorded production of 5,060 kg of gold. Newmont began exploring the district in 1986, and has delineated a major sediment-hosted replacement-style deposit at Mesel, and other smaller deposits in an 8 X 5 km area. A total drill-indicated resource of over 60 metric tonnes of gold ( 2 Moz) is reported for Mesel, and three of the smaller deposits. Approximately 80% of this resource is refractory. Silver grades are usually low (< 10 g/t). The Mesel deposit is similar to many Carlin-type deposits in carbonate hostrocks, alteration, geochemical signature and ore mineralogy, but is distinct in tectonic setting. The discovery of replacement-style mineralisation at Mesel, in an impure limestone within a Tertiary island arc environment, demonstrates that deposits with outward characteristics similar to Carlin-type mineralisation are not restricted to a continental setting. Carbonate sediments in the Ratatotok district were deposited in a Late Miocene restricted basin. Later compressional tectonics caused uplift that resulted in karst development in the limestone and erosion of the adjacent volcanic arc with deposition of a thick epiclastic unit. This was followed by intrusion of shallow level pre-mineral andesite into the sequence. Mineralisation at Mesel, and probably elsewhere in the district, is synchronous with the late-stage reactivation of strike-slip faults. Mineralising fluids at Mesel were focussed along steep structures sympathetic to these faults, and trapped below a relatively impermeable andesite cap rock. Hydrothermal fluids caused decalcification of the silty, more permeable carbonate units with the formation of secondary dolomite, deposition of fine arsenian pyrite, silica veinlets and gold. Volume loss due to decalcification and dolomite formation caused collapse brecciation which enhanced fluid flow and further mineralisation. This locally culminated in total decarbonation and deposition of massive silica. Late-stage stibnite occurs in structural zones within the ore deposit, whereas arsenic (as realgar and orpiment) and mercury (as cinnabar) are concentrated on the periphery. Elsewhere in the Ratatotok district, gold mineralisation is restricted to replacement-style mineralisation in permeable zones along limestone-andesite contacts, open-space-filling quartz-calcite veins and stockworks, and residual quartz-clay breccias. The residual breccias are developed in-situ, and are interpreted to form by dissolution of the wallrock limestone from around pre-existing mineralisation. This has resulted in widespread eluvial gold occurrences

DEBATE ABOUT IRONSTONE - HAS SOLUTE SUPPLY BEEN SURFICIAL WEATHERING, HYDROTHERMAL CONVECTION, OR EXHALATION OF DEEP FLUIDS, 1994,
Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/include/functions1.php on line 943
Kimberley M. M. ,
Ironstone is any chemical sedimentary rock with > 15% Fe. An iron formation is a stratigraphic unit which is composed largely of ironstone. The solutes which have precipitated to become ironstone have dissolved from the Earth's surface, from the upper crust, e.g. the basaltic layer of oceanic crust, or from deeper within the Earth. Genetic modellers generally choose between surficial weathering, e.g. soil formation, and hydrothermal fluids which have convected through the upper kilometre of oceanic crust. Most genetic modellers attribute cherty laminated iron formations to hydrothermal convection and noncherty oolitic iron formations to surficial weathering. However, both types of iron formations are attributable to the exhalation of fluids from a source region too deep for convection of seawater. Evidence for a deep source of ferriferous fluids comes from a comparison of ancient ironstone with modern ferriferous sediment in coastal Venezuela. A deep-source origin for ironstone has wide-ranging implications for the origins of other chemical sedimentary ores, e.g. phosphorite, manganostone, bedded magnesite, sedimentary uranium ore, various karst-filling ores, and even petroleum. Preliminary study of a modern oolitic iron deposit described herein suggests that the source of iron and silica to iron formations may have been even deeper than envisioned within most hydrothermal convection models

Results 16 to 30 of 221
You probably didn't submit anything to search for