bazenAbstractCold mineral and thermal waters from Tertiary aquifers in the Mura Basin mainly belong to the Ca-(Mg)-(Na)-HCO3 and Na-HCO3 hydrogeochemical facies, respectively, and the concentrations ...of yttrium (Y) and lanthanides or rare earth elements (REEs) are far below (10-2 – 10-4) the abundances in the aquifer sediments. Mineral waters are high pCO2, and the plots of concentrations of YREEs normalised to Post Archean Australian Shale (PAAS) show fractionation of Y and heavy REEs (HREEs) over light REEs (LREEs), and a significant positive europium (Eu) anomaly. Thermal water from regionally developed aquifer Thermal I (recently also termed the Mura/Ujfalu Formation aquifer) shows a similar PAAS-normalised pattern with an obvious positive Eu anomaly and the tendency of enrichment with middle REEs (MREEs). The plots of PAAS-normalised YREE concentrations in thermal waters from the underlying low-permeability aquifers with poorly developed fracture porosity and abundant CO2 are flat with insignificant positive Eu anomaly. The abundance and fractionation of YREEs in mineral and thermal waters seems to be mainly controlled by the presence of carbonate complexing ligands, permeability of the aquifers and the related time of water-rock interaction. YREEs have been used for geochemical recognition of overexploitation of the Sob-1 well that yields mixed waters from Thermal I and the underlying low-permeability aquifers. The well overexploitation has resulted in continuous 30-to-80-minute changes in hydrodynamic pressure in Thermal I, and the related change in temperature and chemical composition of abstracted water. Leakage from clayey-silty layers rich in coal and organic matter has been recognised over a several-year time scale by increased abundances of total organic carbon (TOC), YREEs, gallium (Ga), thallium (Tl) and selenium (Se). PAAS-normalised plots of YREE concentrations have shown significant positive anomalies of samarium (Sm), terbium (Tb) and holmium (Ho) and indicate the YHREE complexing ligands could be, beside carbonate species, humic and/or fulvic acids.
An eleven-year monitoring (1987/88–1999) of chemical composition of Na-HCO
3
thermal water from the wells Sob-1 and Sob-2 has shown long- and short-time scale changes occurring as a result of mixed ...character of abstracted thermal water and overexploitation of the wells. Constantly reoccurring changes of dynamic pressure induced the inflow of variable proportions of water from the most productive aquifer Thermal I and from lower-permeability aquifers in the underlying Lendava Formation which contain abundant CO
2
. The chloride ions originate from formation waters in the Lendava Formation, and for Thermal I, a local natural background is 80–85 mg/L. The fluoride ions mainly originate from waters in the Lendava Formation but do not correlate entirely with the chloride ions. It is assumed their abundance is largely controlled by interaction of CO
2
-rich waters with detritial marine carbonates and clay minerals. Temporal variations of concentrations of the bromide and iodide ions in thermal water from the Sob-1 largely correlate with variation of the chloride ions and indicate that the Lendava Formation is their major source. By overexploitation, some low-permeability aquifers in the Lendava Formation have been activated along with leakage from clayey lenses rich in organic matter and coal in the Mura Formation. The sources rich in the bromide and iodide, and iodide and chloride ions have been also recognized in the Sob-2 well at high pumping rate that amounted to 8.7 L/sec.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In Tertiary basins of NE Slovenia, Upper Oligocene volcanic activity occurred in a submarine environment that experienced contemporaneous clastic sedimentation. Pyroclastic deposits are essentially ...related to gas- and watersupported eruption-fed density currents. At Trobni Dol, the Lako Basin, an over 100 m thick deposit formed by a sigle sustained volcanic explosion that fed gas-supported pyroclastic flow. Diagnostic features are large matrixshard content, normal grading of pumice lapilli, collapsed pumice lapilli and the presence of charcoal. In the Smrekovec Volcanic Complex, several but only up to 5 m thick deposits related to eruption-fed gassupported pyroclastic flows occur. Deposits settled from water-supported eruption-fed density currents form fining- and thinning-upward sedimentary units which resemble the units of volcaniclastic turbidites. Pyroclastic deposits related to gas- and water-supported density currents occur in an up to 1000 m thick succession composed of coherent volcanics, autoclastic, pyroclastic, reworked volcaniclastic and mixed volcaniclastic-siliciclastic deposits that indicate a complex explosive and depositional history of the Smrekovec Volcanic Complex.
Chlorite, ordered mixed-layer chlorite-smectites, laumontite, quartz and albite are the most widespread alteration assemblage in cone-building and near-vent successions of lavas, autoclastic, ...pyroclastic and resedimented volcaniclastic deposits of the Oligocene Smrekovec Volcanic Complex, Slovenia. Randomly interstratified corrensite-chlorite with ~70–80% of corrensite layers (R0 Cr-Ch) is less common in occurrence and associated either with clinoptilolite and heulandite in fine-grained vitric tuffs, or with prehnite, laumontite, actinolite, analcime and albite in extensively altered and/or fractured host-rocks. The assemblage with clinoptilolite and heulandite indicates the temperatures of formation of <~120°C and can be regarded as intermediate in the prograde alteration process of volcanic glass that leads in progressively increasing temperature regime to the formation of chlorite, laumontite, prehnite and albite. The assemblage of R0 Cr-Ch, prehnite, laumontite and actinolite developed in different superimposed temperature regimes and/or stages of hydrothermal activity related to the emplacement and subsequent gradual cooling of the Kramarica Sill. The formation of prehnite and actinolite signifies the highest-temperature conditions attaining up to ~300°C. Laumontite and R0 Cr-Ch extensively developed during the cooling period and as a result of the incursion of alkaline Ca-Mg hydrothermal fluids that possibly evolved from deep ground-waters convecting through Triassic dolomite in the basement of the submarine Smrekovec stratovolcano-hosted hydrothermal system.
•R0 corrensite-chlorite, R1 chlorite-smectite, chlorite, prehnite and zeolites formed by hydrothermal alteration.•Several superimposed mineral assemblages developed during the emplacement (≤300°C) and cooling of the Kramarica Sill.•Laumontite and R0 corrensite-chlorite formed in coarse-grained and/or fractured rocks during the cooling of the sill.•The reacting hydrothermal fluids were possibly rich in the Mg2+ and Ca2+ ions and originated from the dolomite basement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hydrothermal zeolites (laumontite, yugawaralite, analcime, heulandite, clinoptilolite), prehnite and pumpellyite have been recognised in a succession of volcanic, autoclastic, pyroclastic, ...resedimented volcaniclastic and mixed siliciclastic–volcaniclastic deposits. In cone-building lithofacies association attaining 310m, the alteration minerals commonly change within a single normally graded depositional unit or alternate in the section on a dm- to m-scale, according to the host-rock lithofacies. Fine-grained deposits rich in juvenile glassy pyroclasts are altered to heulandite and clinoptilolite or analcime, and laumontite widely occurs in coarse-grained host-rocks (lapilli tuff, hyaloclastite breccia, volcaniclastic breccia, hyaloclastites) and fracture systems. In near-vent lithofacies association attaining 420m, prehnite–laumontite, laumontite–analcime, and laumontite–heulandite–clinoptilolite zones developed as a result of superimposed thermal regime generated by the emplacement of an over 200m thick sill.
The recognised dependence of alteration on porosity, permeability and fracturing of the host-rock is closely related to hydrological conditions in the stratovolcano-hosted hydrothermal system with convective–advective flow regime. After separation of steam and gases from convecting hydrothermal fluids, denser liquids outflowed intermittently, preferentially through steeply inclined (20–30°) high-permeability layers in the stratovolcano edifice. In low-permeability layers the flow was slow and thermal conditions were mainly attained by conduction. Zeolites developed only in coarse- and fine-grained vitroclastic tuffs, presumably by the dissolution of volcanic glass. The interstratified siliciclastic siltstones, tuffites and resedimented deposits with low content of glassy particles are devoid of zeolites and indicate compositional constraint on zeolitisation.
Lava flows, cooling in a submarine environment and undergoing disintegration and mingling with the enclosing water-saturated sediment were individual, ephemeral and spatially localised high-temperature hydrothermal systems favourable for the formation of pumpellyite, prehnite and laumontite.
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•Oligocene submarine stratovolcano hosted hydrothermal system•Host-rock lithofacies and convective–advective flow regime controlled alteration.•Laumontite and prehnite are common in coarse-grained deposits.•Heulandite and clinoptilolite dominate in fine-grained vitoclastic tuffs.•Peperites were altered by the inherited heat of disintegrating lava flow.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Middle to Upper Pliocene (~
3
Ma) Grad Volcanic Field (SW Pannonian basin system) encompasses an area of about 3
km
2, of which some 1.7
km
2 belong to the outcropping volcanics. Pyroclastic and ...syn-eruptively reworked volcaniclastic deposits are the most widespread in occurrence. Remains of an autobrecciated lava flow, a residual neck and their peperites are partially reworked by a large debris flow.
Volcanic activity occurred in a continental depositional environment dominated by alluvial fan and braided river systems. Streams draining from the north-west to the south-east were infilling a rapidly subsiding Radgona Depression.
The style of volcanic activity was mainly explosive and was reinforced by hydrovolcanic processes. Three volcanic centres probably existed, and they migrated spatially and temporally from the north to the south over a distance of some 5.6
km. The rocks of the northernmost volcanic centre are fairly eroded and contain abundant, up to 10
cm sized lherzolite xenoliths.
The largest crater developed about 2.5
km to the south. From an early maar stage, a tuff-cone, and subsequently, a tuff-ring evolved. The crater was filled with eroded pyroclastic material and stream load.
A new vent became active some 500
m to the south. Initial stage was mainly magmatic and produced pyroclastic flow and fall deposits. Late-stage eruptions were predominantly hydrovolcanic (phreatomagmatic and phreatic), and built up a small tuff-cone having some 300
m in diameter.
Trachybasaltic and subordinate basanitic magmas erupting in the Grad Volcanic Field are geochemically distinguishable from the neighbouring occurrences in the South Styrian Basin and the South Burgenland Swell. Relatively lower abundance of TiO
2, MgO, Sc, V and Cu, and higher abundance of MnO, P
2O
5, Zn, Sr, Zr, Hf, Nb, Ba, Ta and U indicate somewhat different source and/or evolutionary pattern.
► The Grad Volcanic Field developed ~3 Ma ago in an active alluvial fan environment. ► Trachybasaltic and basanitic magma affinity prevailed. ► Phreatomagmatic and phreatic explosive activity occurred. ► Various fluvial-volcaniclastic deposits developed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Fresh-water, coarse-grained and detritus-dominated Mura Formation in North Eastern Slovenia includes pyroclastic and volcaniclastic deposits originating from Upper Pliocene volcanic activity of ...basaltic geochemical character. Although localized in occurrence at the hamlet Grad, these pyroclastic and volcaniclastic sediments forma distinctive depositional unit, for which the term “Grad Member” is proposed and introduced in this paper.In the Grad area no lavas or cinder cones are preserved, and the origin of volcaniclastic fragments still uncertain. For this reason, chemical composition of basaltic rock fragments from the Grad Member volcaniclastics has been studied and compared with basaltic rocks from the neighboring locations at Klöch, Kindsberg, Dölling and Neuhaus. The Grad Member pyroclastic and volcaniclastic deposits seem to be fed from the same source which is different from the occurrences in Austria. That supports the idea about the existence of a local volcanic centre in the present Grad area. The old volcanic edificeswerepossiblydestroyed by the late-stage hydrovolcanic eruptions, and pyroclastic and volcaniclastic deposits subjected to constant reworking by fluvial currents in a dynamic sedimentary environment of alluvial fan and braided river systems.
Dacitic glassy lava flow at Trlično is surrounded by a dacite – siltstone peperite and peperitic breccia that underwent alteration, recognised in two, only a few metres thick zones. In the ...higher-temperature alteration zone, albite extensively replaces volcanic glass and primary plagioclases. The siltstone components are altered to microcrystalline quartz, iron oxides and interlayered illite/smectite clay minerals. This zone developed upon thermalmetamorphosis related to the transfer of heat from the cooling lava. In the lower temperature alteration zone, analcime occurs as the replacement of volcanic glass and pore- and fissure-filling, while the primary plagioclases and poorly lithified siltstone remained fairly unchanged. This zone developed under hydrothermal conditions related to the heating, circulation and reactions of pore waters in the sediment surrounding the lava flow.
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