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1.
 Mineral and thermal waters occur at Kalinciakovo, Santovka, Dudince, Slatina and Turovce, in the inner side of the Western Carpathian arc, the south-western margin of the Central Slovak Neovolcanics, and on the so-called Levice spring line. They are important sources of mineral waters for Slovakia, which are used for different purposes (bathing therapy, bottling, recreation). The mineral and thermal waters of Dudince have an extraordinary position among them. The mineral water with its physico-chemical composition and content of gasses enables its wide use for bathing therapy and it occupies a special position among the mineral waters of the Carpathian arc. Received: 9 November 1998 · Accepted: 2 March 1999  相似文献   

2.
 The giant Mercosul aquifer system consists of Triassic-Jurassic eolian-fluvio-lacustrine sandstones confined by Cretaceous basalt flows, and it covers about 1,195,500 km2 (461,583 miles2) in South America. The aquifer system encompasses all of the Paraná Basin and part of the Chaco-Paraná Basin and is one of the world's largest. The eolian Botucatu Sandstone and its equivalents form an important part of this system. Maps of structure, thickness of overlying rocks, and water temperature, and a potentiometric map, all based on 322 wells, define hydrogeologic characteristics and provide the basis for establishing guidelines for the long-term equilibrium use of this important multinational aquifer system. The Mercosul aquifer system is divided into two domains – the larger and better understood Paraná Basin and the smaller and less well understood Chaco-Paraná Basin. Most of the northern part of the Paraná Basin has axially-directed groundwater flow, whereas the southern part of the aquifer discharges mostly to the southwest into the Corrientes Province of Argentina, with negligible discharge into the Atlantic Ocean. The Mercosul aquifer system is conservatively estimated to have been flushed at least 180 times since deposition. Various factors are responsible for this flushing, including appreciable rainfall since the end of the Cretaceous Period, probable uplift of the basins' borders in Late Cretaceous time, simple basin geometry, long-term riverine and groundwater flow to the southwest (ancestral and present Paraná River Systems), and stable cratonic setting. Key hydraulic properties of the Mercosul aquifer system are compared to those of the eolian Jurassic Navajo-Nugget System of the western United States. The results demonstrate the importance of tectonics and climate on the evolution of sub-continental aquifer systems. Received, September 1997 / Revised, December 1998 / Accepted, January 1999  相似文献   

3.
The Paraná River is one of the largest drainage systems in the Americas. Its hydrology is characterized by an active teleconnection with the ENSO, and by a significant discharge increase trend, evident since the mid-1970s. An Eh–pH data set collected in the Paraná’s middle stretch suggests that large flood events, such as the one triggered by the 1982–1983 ENSO, are discernible in the plot, probably due to the influx of water draining flood plain water bodies. The total (particulate + dissolved) concentration of a set of heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb) was determined in a downriver survey of the middle stretch. With the exception of Cu, Cd, and Pb, the metals exhibit a significantly increasing concentration trend towards the river mouth. The slopes of the regression lines imply that Zn and Ni, on one hand, and Mn and Cr, on the other would have common controlling sources. Another set of analyses were performed during the 1982–1983 flooding event; besides an increased variability observable during the flood arrival, most elements, with the only exception of Pb, did not show a variability coherent with the discharge series.  相似文献   

4.
U-Mo and Cu mineralization occurs in horizons as well as in veins in the Permian formations near Novoveská Huta. Ore mineralization is represented by uraninite, U-Ti oxides, coffinite, molybdenite, chalcopyrite, tennantite and pyrite. The isotopic composition of S and C displays a larger variability in the stratiform ores (34S from –32.7 to +2.7 and 13C from –27.1 to — 0.5) These data suggest mixing of meteoric solutions with fluids of volcanic origin and a complex history. There is a narrower range of 34S from –18.8 to –4.6 and 13C from –6.3 to –2.5% in quartz-carbonate veins with Cu mineralization suggesting a deep source of ore-bearing solutions. The Permian volcanics were a significant source of ore elements.Their contents of U, Mo, Cu and Y are from two to eight times higher than in sedimentary rocks. Accumulations of ore elements in the horizons were formed by the reduction and adsorption processes 240 ± 30 Ma ago according to U-Pb isotopic dating. Due to Alpine tectonism, these low-grade ores (U<0.1 wt%) were remobilized and higher-grade U-Mo ores (U>0.1 wt%) were formed 130 ± 20 Ma ago at temperatures ranging from 110 to 120° C, according to fluid inclusions. Younger veins with Cu mineralization were formed 115 ± 10 Ma according to the model age of Pb at temperatures ranging from 95 to 190°C.  相似文献   

5.
A combined Sr, O and C isotope study has been carried out in the Pucará basin, central Peru, to compare local isotopic trends of the San Vicente and Shalipayco Zn-Pb Mississippi Valley-type (MVT) deposits with regional geochemical patterns of the sedimentary host basin. Gypsum, limestone and regional replacement dolomite yield 87Sr/86Sr ratios that fall within or slightly below the published range of seawater 87Sr/86Sr values for the Lower Jurassic and the Upper Triassic. Our data indicate that the Sr isotopic composition of seawater between the Hettangian and the Toarcian may extend to lower 87Sr/86Sr ratios than previously published values. An 87Sr-enrichment is noted in (1) carbonate rocks from the lowermost part of the Pucará basin, and (2) different carbonate generations at the MVT deposits. This indicates that host rocks at MVT deposits and in the lower-most part of the carbonate sequence interacted with 87Srenriched fluids. The fluids acquired their radiogenic nature by interaction with lithologies underlying the carbonate rocks of the Pucará basin. The San Ramón granite, similar Permo-Triassic intrusions and their clastic derivatives in the Mitu Group are likely sources of radiogenic 87Sr. The Brazilian shield and its erosion products are an additional potential source of radiogenic 87Sr. Volcanic rocks of the Mitu Group are not a significant source for radiogenic 87Sr; however, molasse-type sedimentary rocks and volcaniclastic rocks cannot be ruled out as a possible source of radiogenic 87Sr. The marked enrichment in 87Sr of carbonates toward the lower part of the Pucará Group is accompanied by only a slight decrease in 18O values and essentially no change in 13C values, whereas replacement dolomite and sparry carbonates at the MVT deposits display a coherent trend of progressive 87Sr-enrichment, and 18O- and 13C-depletion. The depletion in 18O in carbonates from the MVT deposits are likely related to a temperature increase, possibly coupled with a 18O-enrichment of the ore-forming fluids. Progressively lower 13C values throughout the paragenetic sequence at the MVT deposits are interpreted as a gradually more important contribution from organically derived carbon. Quantitative calculations show that a single fluid-rock interaction model satisfactorily reproduces the marked 87Sr-enrichment and the slight decrease in 18O values in carbonate rocks from the lower part of the Pucará Group. By contrast, the isotopic covariation trends of the MVT deposits are better reproduced by a model combining fluid mixing and fluid-rock interaction. The modelled ore-bearing fluids have a range of compositions between a hot, saline, radiogenic brine that had interacted with lithologies underlying the Pucará sequence and cooler, dilute brines possibly representing local fluids within the Pucará sequence. The composition of the local fluids varies according to the nature of the lithologies present in the neighborhood of the different MVT deposits. The proportion of the radiogenic fluid in the modelled fluid mixtures interacting with the carbonate host rocks at the MVT deposits decreases as one moves up in the stratigraphic sequence of the Pucará Group.  相似文献   

6.
From the Archean to the end of the Neoproterozoic the Borborema Province, northeast Brazil went through a complex polycyclic geologic evolution, ending, between 660 and 570 Ma, with the Brasiliano/Pan-African orogeny that led to West Gondwana amalgamation. Evolution of the metasedimentary covers of the Province, from the beginning of their deposition up to their involvement in the Brasiliano/Pan-African collision, is a key element in understanding formation of Gondwana and in attempts in pre-drift correlation between South America and West Africa. One of these covers, the Ceará Group, is exposed in the Ceará Central domain. Aiming to unravel the history of the Ceará Group, we carried out a geochronologic study of representative samples, combining Sm–Nd isotopic data, conventional U–Pb TIMS dating of zircon and U–Pb SHRIMP age determination of detrital zircon grains. Our results show that sedimentation of the Ceará Group started around 750 Ma, following rifting of the Archean/Paleoproterozoic basement, associated with bimodal volcanism. The interlayered basic volcanic rocks, re-crystallized into garnet amphibolites, show a concordant age of 749 ± 5 Ma interpreted as the age of crystallization. About 90% of calculated Sm–Nd TDM model ages of metasedimentary rocks are Paleoproterozoic and more than 50% of the analyzed samples have TDM between 1.95 and 2.4 Ma, with strongly negative ɛNd, consistent with provenance mainly from the Paleoproterozoic basement. Strong contrast between Paleoproterozoic TDM with negative ɛNd and young TDM (Mesoproterozoic) with slightly positive ɛNd is interpreted as a consequence of changes in detritus provenance induced by geomorphologic alterations resulting from tectonic activity during rifting. Ages of detrital zircon grains obtained by SHRIMP U–Pb analyses show three main groups: about 1800 Ma, 1000–1100 Ma and ca. 800 Ma which corresponds to the bimodal magmatism associated, respectively to the Orós-Jaguaribe domain, Cariris Velhos event and Independência Group.  相似文献   

7.
Knickzones are common features along rivers on the basaltic plateaus of the Paraná Basin. According to current conceptual models, knickpoints are formed in massive basalts that have a high density of vertical joints. Vesicular–amygdaloidal basalts and those with horizontal joints tend to form reaches of low slope due to their lower resistance to erosion. However, field surveys revealed complexities in this general relationship. The research presented here sought to verify the controls on the genesis of knickzones in this type of geological environment. We studied a 61 km-long mixed bedrock–alluvial river. The longitudinal profile of the river was surveyed on a topographic map with 5 m contour intervals. Tectonic lineaments oriented transverse to the channel and longitudinal lineaments in which the river lies were identified from maps. A detailed field survey of the lithologic characteristics of the riverbed was also performed. The results show that knickzones may form in any litho-structural zone in the flood basalts. On the other hand, low slope zones are predominantly sculpted into vesicular–amygdaloidal basalts, which are less resistant to erosion. The fracture densities of vesicular–amygdaloidal basalts are similar in low slope zones and in knickzones (4.86 and 4.93 m/m2, respectively). This indicates that knickzones in this type of basalt are not caused by higher resistance to erosion. Approximately 60% of the 18 knickzones identified are associated with tectonic lineaments, irrespective of the structural characteristics of the basalts. Vesicular–amygdaloidal basalt and/or basalt with horizontal joints allow the fastest knickzone migration and aid in the formation of convexities. Knickpoints in these basalts do not migrate, but erosion in the pools advances downstream and breaks the bedrock steps, thus increasing the slope. Massive basalt with vertical joints causes slower migration, and its presence at convexities indicates local uplift. Convex segments are only formed upstream of faults.  相似文献   

8.
Thousands of silica gossans are exposed at the top of the Lower Cretaceous basalt hills in the Paraná volcanic province, strongly indicating the presence of calcite, amethyst and agate geode deposits along with native copper mineralization. The Embrapa silica gossan in the northwestern portion of the province (Campo Grande region) is an excellent example of such novel geological structure in the continental flood basalts. This silica gossan has a size of 450 × 350 m standing out as a treeless area in the densely wooded savanna and makes part of the stratigraphy of six basalt flows of Paranapanema intermediate-Ti chemical type. The base of the volcanic column is constituted by two Pitanga types and the overlying column is Paranapanema type. Every basalt flow has a silicified sand layer or breccia at the top and these are fed by abundant sand dikes. The Anel Viário Norte (AVN) flow is the most intensely altered by hydrothermal fluids producing voluminous secondary calcite infillings in the amygdales and fractures. In this region the basalts contain higher copper content than the average of the volcanic province. The studied silica gossans display negative anomalies in gamma spectrometry as a response to K, U and Th depletion during alteration. We propose a new exploration methodology by observing GoogleEarth images complemented with field studies and geochemistry to readily locate favorable areas for amethyst and agate geode deposits and native copper mineralization.  相似文献   

9.
J. Demek  J. Kopecký 《GeoJournal》1994,32(3):231-240
The paper examines relations among geomorphological processes and the landforms of the Polická vrchovina Highland in the Bohemian Massif. Geologically, the Polická vrchovina Highland is a part of the Intra-Sudetic Basin on the boundary between Bohemia and Poland. The basin structure of the Highland developed during the neotectonic period. In the outer parts of the Highland, Mesozoic rocks dip gently to the centre of the basin to form cuestas. In the central part, layers are horizontal or subhorizontal. Mesas (Hejda and Osta Mesa) provide evidence of the erosion of the Mesozoic deposits. The relative uplift of the Highland resulted in the incision of the Metuje River and its tributaries. Unloading of rocks and erosion initiated typical geomorphological processes such as deep- seated creep, cambering, rockfalls, landslides and pseudokarst processes. These processes produced some typical forms controlled by rock properties, jointing, relative differences in height and climatic changes in the Tertiary and Quaternary.  相似文献   

10.
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11.
Mapping of erosion risk areas is an important tool for the planning of natural resources management, allowing researchers to propose the modification of land use properly and implement more sustainable long-term management strategies. The objective of this study was to assess and identify critical sub-catchments for soil conservation management using the USLE, GIS, and remote sensing techniques. The Tapacurá catchment is one of the planning units for water resource management of the Recife Metropolitan Region. Maps of the erosivity (R), erodibility (K), slope (LS), cover-management (C), and support practice (P) factors were derived from the climate database, digital elevation model, and soil and land-use maps. In order to validate the simulation process, total sediment delivery ratio was estimated. The results showed a mean sediment delivery ratio (SDR) of around 11.5?% and a calculated mean sediment yield of 0.108?t?ha?1?year?1, which is close to the observed one, 0.169?t?ha?1?year?1. The obtained soil loss map could be considered as a useful tool for environmental monitoring and water resources management. The methodology applied showed acceptable precision and allowed the identification of the most susceptible areas to soil erosion by water, constituting an important predictive tool for soil and environmental management in this region, which is highly relevant for the prediction of varying development scenarios for Tapacurá catchment. This approach can be applied to other areas for simple and reliable identification of critical areas of soil erosion in catchments.  相似文献   

12.
Upper Jurassic and Lower Cretaceous sedimentary layers are represented in the Brazilian Paraná Basin by the fluvio–aeolian Guará Formation and the Botucatu Formation palaeoerg, respectively, overlapped by the volcanic Serra Geral Formation. In Uruguay, the corresponding sedimentary units are named Batoví and Rivera Members (both from the Tacuarembó Formation), and the lava flows constitute the Arapey Formation (also in Paraná Basin). Despite the lack of body fossils in the mentioned Brazilian formations, Guará/Batoví dinosaur fauna is composed of theropod, ornithopod and wide–gauge sauropod tracks and isolated footprints, as well as theropod teeth. In turn, the Botucatu/Rivera dinosaur fauna is represented by theropod and ornithopod ichnofossils smaller than those from the underlying units. The analysis of these dinosaur ichnological records and comparisons with other global Mesozoic ichnofauna indicates that there is a size reduction in dinosaur fauna in the more arid Botucatu/Rivera environment, which is dominated by aeolian dunes. The absence of sauropod trackways in the Botucatu Sandstone fits with the increasingly arid conditions because it is difficult for heavy animals to walk on sandy dunes, as well as to obtain the required amount of food resources. This comparison between the Upper Jurassic and Lower Cretaceous dinosaur fauna in south Brazil and Uruguay demonstrates the influence of aridization on the size of animals occupying each habitat.  相似文献   

13.
《Geodinamica Acta》2000,13(2-3):119-132
The North Caribbean margin is an example of an oblique convergence zone where the currently exposed HP–LT rocks are systematically localised close to strike-slip faults. The petrological and structural study of eclogite and blueschist facies rocks of the peninsula of Samaná (Hispaniola, Dominican Republic) confirms the presence of two different metamorphic units. The former diplays low metamorphic grade (Santa Barbara unit), characterized by the assemblage albite - lawsonite (7.5 ± 2 kbar and 320 ± 80 °C). The latter (Punta Balandra unit), thrust over the first unit towards the NW, and is characterized by the occurrence of blueschist and eclogite facies assemblages (13 ± 2 kbar and 450 ± 70 °C), within oceanic metasediments. The isothermal retrograde evolution occurred in epidote-blueschist facies conditions (9 ± 2 kbar and 440 ± 60 °C). The late greenschist facies evolution is contemporaneous with conjugate NW–SE extension and E–W strike-slip faulting. This late extension is for regional dome and basin structures. According to their lithotectonic, structural and metamorphic characteristics, the metamorphic nappe stack of Samaná may be interpreted as a fragment of an accretionary wedge thrust onto the North American continental shelf. Evolution of the wedge was associated with the active subduction of the North American plate, under the Greater Antilles arc, at the level of the Puerto Rico trench. During active Late Cretaceous convergence, the HP rocks were initially exhumed, within the accretionary prism, by thrusting parallel to the NE–SW direction of convergence. Subsequently, during the Eocene collision between the Caribbean plate and the North American margin, the installation of a transtensive regime of E–W direction supports the local development of conjugate extension of NW–SE direction that facilitated the final phase of exhumation of the HP rocks.  相似文献   

14.
In the Dem?novská dolina Cave system (Slovakia) and its vicinity, 32 sampling places for regular observation (in 2-months interval) of δ18O and δ2H in water were established. This monitoring included precipitation waters, waters in the surface streams, waters of the underground hydrological system as well as the dripping seepage waters of the cave system. Altitudinal extent of the area was from 800 m a.s.l. (lowermost cave entrance) to 2024 m a.s.l. (Chopok Mt. on the top of the crystalline range). Initial results show some similarities but also differences within the analyzed water types. For precipitation, a high variability of isotopic composition was confirmed, from quite depleted up to more enriched waters (δ18O from -16.8‰ up to -5.7‰; δ2H from -121.6‰ to -32.7‰). During the recharge process and groundwater/surface water formation, precipitation water is homogenized, what is reflected in much more stable isotope content. The most depleted (δ18O ≈ -11.7‰ to -10.8‰; δ2H ≈ -78.9‰ to -73.4‰) were the waters of surface streams, running from the northern slopes of the Nízke Tatry Mts., formed by crystalline rocks, alochtonous to the under?ground hydrological system. Smaller autochtonous surface water streams (formed in the side valleys of the main karstic canyon) are slightly enriched (heavier, as δ18O ≈ -11.4‰ to -10.6‰; δ2H ≈ -78.3‰ to -71.5‰), what reflects lower altitudes of their watersheds. Interesting is the distribution of the isotope content of the underground streams in the cave system. The most depleted are the underground streams directly (visibly) communicating with surface waters (δ18O≈-11.33±0.13‰; δ2H≈-76.88±1.68‰). Extent of the relationship of underground streams to the autochtonous seepage waters (slow circulation through the fissures) is manifested by respective portion of iso?topically enriched waters–as the underground streams show different isotope composition. The combination of the alochtonous water components (from surface streams reaching the karstic area from the adjacent crystalline via swallow holes) and autochtonous water components (recharged directly in karstified limestones) is visible especially on the subsurface stream of Dem?novka. The most isotopically enriched (heaviest) of all water types are dripping seepage waters (δ18O ≈ -10.4‰ to -9.4‰; δ2H ≈ -71.6‰ to -65.0‰).  相似文献   

15.
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16.
Vázquez  R.  Macías  J. L.  Alcalá-Reygosa  J.  Arce  J. L.  Jiménez-Haro  A.  Fernández  S.  Carlón  T.  Saucedo  R.  Sánchez-Núñez  J. M. 《Natural Hazards》2022,110(2):1305-1337
Natural Hazards - Both climate and land-use changes can influence drought in different ways. Thus, to predict future drought conditions, hydrological simulations, as an ideal means, can be used to...  相似文献   

17.
The Paraná volcanic province is a window into mantle and crustal processes in the Cretaceous. The variability and complexity of this province can be determined through the study of minerals. An integrated study of zircon from Paraná lavas (one high-Ti basalt, one low-Ti andesite, one high-Ti rhyodacite and one high-Ti andesite sill) was achieved using backscattered electron imaging, sensitive high resolution ion microprobe (SHRIMP-IIe) for U-Pb geochronology, and laser ablation inductively coupled mass spectrometer (LA-ICPMS) to determine the Lu-Hf isotopes and the trace-element compositions. U-Pb-Hf and trace-element data indicate that zircon crystallized from the magma at approximately 134 Ma. This South American large igneous province originated from the mantle and was contaminated by crust either in the mantle or during ascent and crystallization of magma. Contaminant continental crust had Precambrian age. Trace elements point to a new compositional field for zircon, different from other types of provinces. Examination of volcanic zircon improves our understanding of age and contamination of the Paraná volcanics.  相似文献   

18.
Numerical results are presented of surface-subsurface water modeling of a natural hillslope located in the Aburrá Valley, in the city of Medellín (Antioquia, Colombia). The integrated finite-element hydrogeological simulator HydroGeoSphere is used to conduct transient variably saturated simulations. The objective is to analyze pore-water pressure and saturation variation at shallow depths, as well as volumes of water infiltrated in the porous medium. These aspects are important in the region of study, which is highly affected by soil movements, especially during the high-rain seasons that occur twice a year. The modeling exercise considers rainfall events that occurred between October and December 2014 and a hillslope that is currently monitored because of soil instability problems. Simulation results show that rainfall temporal variability, mesh resolution, coupling length, and the conceptual model chosen to represent the heterogeneous soil, have a noticeable influence on results, particularly for high rainfall intensities. Results also indicate that surface-subsurface coupled modeling is required to avoid unrealistic increase in hydraulic heads when high rainfall intensities cause top-down saturation of soil. This work is a first effort towards fostering hydrogeological modeling expertise that may support the development of monitoring systems and early landslide warning in a country where the rainy season is often the cause of hydrogeological tragedies associated with landslides, mud flow or debris flow.  相似文献   

19.
This paper presents the tectonostratigraphic evolution of the Maimará Basin and explores the relationship between the clastic sediments and pyroclastic deposits in the basin and the evolution of the adjacent orogeny and magmatic arc. The sedimentary facies in this part of the basin include, in ascending order, an ephemeral fluvial system, a deep braided fluvial system and a medial to distal ephemeral fluvial system. We interpret that Maimará Formation accumulated in a basin that has developed two stages of accumulation. Stage 1 extended from 7 to 6.4 Ma and included accelerated tectonic uplift in the source areas, and it corresponds to the ephemeral fluvial system deposits. Stage 2, which extended from 6.4 to 4.8 Ma, corresponds to a tectonically quiescent period and included the development of the deep braided fluvial system deposits. The contact between the Maimará and Tilcara formations is always characterized by a regional unconformity and, in the study area, also shows pronounced erosion.Rare earth element and other chemical characteristics of the tuff intervals in the Maimará Formation fall into two distinct groups suggesting the tuffs were erupted from two distinct late Miocene source regions. The first and most abundant group has characteristics that best match tuffs erupted from the Guacha, Pacana and Pastos Grandes calderas, which are located 200 and 230 km west of the study area at 22º-23º30′S latitude. The members the second group are chemically most similar to the Merihuaca Ignimbrite from the Cerro Galán caldera 290 km south-southwest of the studied section. The distinctive geochemical characteristics are excellent tools to reconstruct the stratigraphic evolution of the Neogene Maimará basin from 6.4 to 4.8 Ma.  相似文献   

20.
《International Geology Review》2012,54(10):1163-1179
Native copper is widespread in the Lower Cretaceous Paraná basaltic province, southern Brazil, both as films in fractures and as massive balls in amygdules. The focus of this investigation is on the large concentration of occurrences (n = 85) that forms the Vista Alegre district in the border region of Rio Grande do Sul and Santa Catarina states. The high average of 220 ppm Cu content of the basalts resulted in ore of native copper, Cu oxides, abundant chrysocolla in the top of mineralizations, and minor malachite and azurite. Native copper is associated with dioctahedral and trioctahedral smectites, zeolites (heulandite and clinoptilonite), quartz, and calcite, typical of a low-T (100–150°C) hydrothermal alteration assembly. The PGE distribution shows enrichment in Pd in relation to Pt both in basalts and in native copper, supporting the hypothesis of hydrothermal origin of the mineralization. No evidence was found of direct precipitation of copper from the lava; based on field and petrographic evidence, integrated with BSE images, EPMA analyses, EGP contents of native copper, and bulk rock analyses, this is an epigenetic hydrothermal copper mineralization, followed by supergene enrichment.  相似文献   

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