No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Geochemische und petrographische Untersuchungen der Fichtelgebirgsgranite
... There are metamorphic magmatic and sedimentary rocks which as opposed to the Moldanubian Zone did not reach the high-grade level of the Moldanubian zone but were submitted only to low grade -to very low-grade metamorphic conditions. The Late Paleozoic Variscan deformation grinded these metamorphic processes in both geodynamic zones to a halt while in the aftermath a series of undeformed felsic to intermediate intrusions were emplaced into the Saxothuringian and Moldanubian zones (Richter and Stettner, 1979;Tischendorf et al., 1995;Holub et al., 1995Holub et al., , 1997Breiter, 1998;Konopásek and Schulmann, 2005;Ackerman et al., 2007;Kozłowski and Sachanbiński, 2007;Schaaf et al., 2008;Novák and Gadas, 2010;Kryza et al., 2012). The widely investigated granitic and pegmatitic rocks in the German, Czech and Polish part of the Bohemian Massif form the basis for the radiometric dating of landform series due to their abnormally high background U contents. ...
... In the epicontinental foreland basin, sedimentation which is predominantly of siliciclastic derivation lasted from the Late Permian to the Quaternary (McCann, 2008b). The Mesozoic stratigraphic units dissected by the Steinach and Main Rivers on their way towards the Rhein are listed in Table 2 (Stettner, 1977;Richter and Stettner, 1979;Hornung and Aigner, 2002;Popov et al., 2005;Voigt et al., 2008;Bachmann et al., 2010) (Fig. 1a, b). The Mesozoic basin fill is low in U outside the few uranium mineralizations a fact which is accountable for scarce U/Pb age data in the foreland. ...
... igneous rocks as compared with the crustal average (2 ppm U) and the overall suite of magmatic rocks which are arranged in order of increasing SiO 2 contents from ultrabasic to felsic: Dunite 0.02 ppm U, pyroxenite 0.70 ppm U, gabbro 0.90 ppm U, diorite 2.00 ppm U, granodiorite 2.60 ppm U, granite 4.00 ppm U. The Rudolfstein supergene U mineralization is a role model and resides in a highly fractionated granite with 14 ppm U (Table 1) (Richter and Stettner, 1979). In metamorphic rocks the U contents decrease with increasing metamorphic grade (greenschist facies 3.45 ppm U → high grade granulite facies 0.39 ppm U), whereas sandstones commonly have moderate contents averaging 0.45 ppm U (Wedepohl, 1969). ...
The quadripartite/ orthogonal and domal Central European Watershed (CEW) at the NW edge of the Bohemian Massif has been studied by a terrain analysis (fluvial, colluvial, cryogenic, aeolian landforms) combined with geochronological dating (hydraulic correlation) of landforms and the resultant hydrographic correlation of relief generations. It resulted in a morphostratigraphic review (subdivided into a protostage- creating the terrestrial platform, prestages - controlling the physical and chemical regime of the landform series, and stages- fine-tuning of the modern landscape) of the Late Cretaceous to Quaternary relief generations that lead to the creation of the “3 + 1” model of the CEW. The term “3 + 1” refers to a triple junction supplemented with a fourth branch. The characteristic land-form type of the CEW is called the “intermediate sediment trap”, a wetland caused by structural or impact-related damming processes. The evolution of the CEW is discussed by a set of four different drivers:
The endogenous 1st order drivers are activities along lineamentary fault zones which demarcate the watershed systems.
The 2nd order endogenous driver is the alkaline volcanic activity from the Late Cretaceous to the Holocene which contributed to dome-and starlike geomorphological expression.
The 3rd order impact-related driver of the Ries Meteorite impact provoked a deflection and damming of channels thereby leading to one of the intermediate sediment traps.
The 4th exogenous driver is the climate change. It is accountable for the transition from fluvial incision during the Late Cretaceous and Paleogene (humid-tropical climate zone) to a planation during the Neogene (tropical wet and dry paleoclimate zone). The Quaternary humid mid-latitude, dry continental, and (peri)glacial climate zones put the final touch on the CEW's geomorphological outward appearance.
The influence of mining, metallurgy, and mineral processing on the landscape debated in the final stage 8 heralds the onset of the Anthropocene in the CEW.
This review of the evolution of the CEW also lends support to the idea that an advanced terrain analysis can be an efficient tool for mineral exploration.
... With an area of about 350 km 2 , granites comprise about 40 % of the Variscan basement rocks in the Fichtelgebirge in Northern Bavaria (Richter & Stettner 1979, Peterek & Rohrmüller 2010. Geophysical data give evidence that this granitic terrain continues into the western foreland, where the basement is buried under a cover of Permo-Mesozoic sediments (Heinrichs et al. 1994, Schäfer et al. 2000, Bleibinhaus et al. 2003, Hofmann et al. 2003. ...
... G2, "Rand Granite" porphyric, fine-to medium-grained two-mica granite 298.5 ± 3.9 3) YIC-1e 4) G3, "Kern Granite" medium-to coarse-grained two-mica-granite 291.2 ± 6.4 3) YIC-1e 4) G4, "Zinn Granite" medium-to coarse-grained two-mica granite 298.2 ± 1.6 3) YIC-2e 4) G2*, "Rand Granite" porphyric, fine-to medium-grained two-mica granite 289 ± 2 1) YIC-2p 4) G2K, "Kösseine Granite" medium-grained, weak porphyric biotite granite 287 ± 3 1) YIC-2k 4) G3K, "Kösseine Kern Granite" coarse grained, garnet and cordierite-bearing biotite granite 286 ± 26 1) it is used to get constraints on potassium (K), uranium (U) and thorium (Th) content for the different granite types described and subdivided in earlier studies (Richter & Stettner 1979, Hecht & Vigneresse 1999, Irber et al. 1997, Schödlbauer et al. 1997, Förster et al. 2008. The Fichtelgebirge granites can be divided into two intrusion complexes, the Older Intrusive Complex (OIC) with intrusion ages between 326 and 324 Ma, and the Younger Intrusive Complex (YIC) with intrusion ages between 298 and 286 Ma ( Table 1). ...
... The Fichtelgebirge/Smrčiny region as part of the Saxothuringian Zone of the Variscan belt ( Fig. 1a) contains large amounts of Late-Variscan granites of different petrogenesis, composition and age (Richter & Stettner 1979, Siebel et al. 1997, Förster et al. 2008, Förster & Romer 2010. Host rocks of the granites are lowgrade metamorphic Palaeozoic shelf sediments, now transformed into schists, phyllites and quartzites and locally marble bands (Linnemann 2008, Linnemann & Romer 2010. ...
Granites constitute a major part of the Variscan basement exposed in N Bavaria. It can be assumed that this granitic terrain continues west of the Franconian Fault and forms the basement of the Permo-Mesozoic sedimentary platform (Franconian basin). This region bears a distinct geothermal anomaly and is currently evaluated for its geothermal potential. Granites are heat producing bodies in the earth’s crust due to radioactive decay of enriched elements and buried granitic bodies are specified as targets for geothermal prospection.
In order to assess the natural gamma ray emissions and to infer element concentrations of radioelements in situ measurements are conducted on outcrops in the Fichtelgebirge (with 302 single measurements in total) using a portable measurement device. Here, two granite complexes of different ages are exposed which are regarded as possible analogues for buried granites in the Franconian basin. The older intrusive complex (OIC) with intrusion ages around 325 Ma (“Weißenstadt-Marktleuthen Massif”) has a root zone in its eastern part; a younger intrusive complex (YIC) with intrusion ages around 295 Ma and a root zone near the Franconian Line. Furthermore spectral gamma ray logs down to 1390 m from a 1835 m deep drillhole near Weißenstadt were analyzed. The granites of the Fichtelgebirge show definite differences in their U and Th concentrations, between and within the two complexes (OIC, YIC). One influencing factor is the differentiation of the magma with a general decrease in the thorium concentration and increase in the uranium concentrations. Th/U ratios of biotite-granite from the upper section (<928 m) of the Weißenstadt borehole correlates well with the G1 of the OIC. In the lower part of the borehole (> 928 m) the Th/U ratio shows best correlation with the G3 granite of the YIC exposed in outcrops of the Ochsenkopf and Waldstein and Kornberg Granites .
The calculated heat production of the granites ranges between 4.4 to 7.6 µW/m³. Granites of the Fichtelgebirge can therefore be ranked as “moderately heat producing”. The need for further studies to estimate the potential increase in heat flow for the Franconian basin for assumed bodies of heat producing granite in the covered basement is highlighted.
... Fichtelgebirge Krušné hory-Erzgebirge Stone and Exley (1985) Richter and Stettner (1979) Štemprok (1986) Štipská and Schullann (1994) based on Franke (1989) with the marked location of the SW England and Krušnné hory -Erzgebirge, Fichtelgebirge-Smrčiny metallogenic provinces (boxes). ...
... Later these were classified as Older (OIC) and Younger (YIC) Intrusive Complexes (Lange et al, 1972(Lange et al, , Štemprok, 1986. In the Fichtelgebirge more recent work by Richter and Stettner (1979) presented a modern petrological classification differentiating 4 granite groups (G1 to G4) and a number of more mafic precursors. Such granitoid precursors were identified among the granites of the Slavkovský les where the separation of the granites into two contrasting series has been considerably modified by Fiala (1968). ...
... The evolution of granites within the batholiths can be followed from geochemical (Lange et al. 1972, Tischendorf andFörster, 1990, mainly for the German part of the province; Fiala 1969, Štemprok, 1986and Breiter et al., 1991 for the Czech part). The geochemistry of the Fichtelgebirge-Smrčiny granite pluton was characterized by Richter and Stettner (1979) and Štemprok (1992). The general geochemical characteristics of the Cornubian granites were presented by Stone and Exley (1985) and by Darbyshire and Shepherd (1985). ...
The mining regions of the Krusne hory-Erzgebirge and of SW England are components of the northern branch of the European Variscides. They both have complex metallogenesis associated with grantie batholiths of approximately similar size formed from the multiple injection of magma pulses at a high crustal level. Whereas the Krusne hory-Erzgebirge batholith and the Fichtelgebirge pluton include more primitive members, the Cornubian batholith is composed almost exclusively of more evolved granites with Rb over 300 ppm and low Sr. The chronometric interval of granite emplacement in the Krusne hory-Erzgebirge (KE) is broader, from about 330 to 290 ma, than that of the Cornish granites between 300 and 275 ma. The Cornubian metallogenic province has been more productive of tin and copper than the KE province which produced more uranium and silver and, in recent years, much fluorite. However, the overall metallogeny characterized by Sn-W-Cu-As-Zn-Pb granite-related assemblages and epithermal Pb-Ag-U-Mn associations is similar in both the provinces. -from Author
... d. Sketch map of the geological setting and the position of pegmatites and aplites of the Hagendorf-Pleystein pegmatite province, modified from Forster (1965), Richter & Stettner (1979) and Breiter & Siebel (1995). S-F: Steinwald-Friedenfels granite, LB: Leuchtenberg granite, FA: Falkenberg granite, FL: Flossenbürg granite, B: Bärnau granite, R: Rozvadov granite. ...
... dling the Czech-German border (Richter & Stettner 1979, Wendt et al. 1994, Breiter & Siebel 1995. The second-order maxima, also located within the aplites, lies at sample 488. ...
... The variation of Na and K reveals that the individual dikes of aplite and pegmatite are sodium-dominant. Boron, which is a common element in many felsic intrusive rocks in northeastern Bavaria, is depleted in the aplites and pegmatites relative to the metamorphic country-rocks, owing to some kind of dilution (Table 12) (Richter & Stettner 1979). ...
The Miesbrunn pegmatite-aplite swarm (MPAS), part of the Hagendorf-Pleystein pegmatite province, southeastern Germany, was emplaced syn- to postkinematically relative to the Variscan tectonometamorphic processes (stage I). The MPAS developed along the contact between the autochthonous Moldanubicum and the nappes of the Bohemicum. Supercritical mobilization of REE, Zr, Mg, Zn, Li, Be and B during stage II led to a silicate-phosphate mineral association between 500 and 600 degrees C. Below 475 degrees C and a pressure of 3.8 kbar, contact-metasomatic reactions caused Mg phosphates to appear. Subsequently to the emplacement of the felsic intrusives bodies, the shear structure was reactivated and used as a conduit for fluids bearing S, As, Bi, Sb, Hg and U, from which sulfides and arsenides precipitated at 350 degrees C. Hypogene alteration during stages III and IV affected the primary phosphates at temperatures below 100 C, with fluctuating redox conditions when the MPAS was brought closer to the paleosurface as a result of strong uplift of the crystalline basement. Phosphates of Fe2+ formed during this epithermal mineralization in the pH range 5 to 10, whereas the stability field of Fe3+ phosphates extended toward lower values, below a pH of 5. The mineral assemblages of the MPAS are on one hand representative of mineralization at the deepest parts of the pegmatite, close to its root zone, and on the other, within the uppermost parts of pegmatites as they were pervasively altered by near-surface fluids. Sulfur isotopes of sulfides found in the MPAS and its wallrocks show a significant trend toward more strongly negative values away from the pegmatites and aplites. A survey of sulfides using their S isotopes may well be a useful exploration tool for "blind" pegmatites (i.e., not exposed).
... G4 granites (YIC-2) have high U concentrations with Th/U ratios <1 due to U mobilization and/or fractional crystallization, but lie on a fractionation line together with G2 and G3 granites (Figure 4a,b). Most authors also suggest that the continuous evolution in mineralogy and rock texture, as well as in whole-rock and mineral chemistry from G2&G3 towards G2*&G4 is an indicator for the rocks being related to each other (e.g., [106][107][108][109]. However, Siebel et al. [105] suggested, based on εNd(t) values, that due to a larger scatter of G4 compared to G2&G3, a more heterogeneous source or wall-rock contamination is responsible for the heterogeneity. ...
... Oberpfalz (Region 2) Based on chemical and isotopic composition the granites of Leuchtenberg and Zainhammer, are transitional between S-and I-type, whereas those of Falkenberg, Friedenfels, Steinwald and Flossenbürg are S-type granites [64]. Most intrusions display chemical characteristics, which can be explained by fractional crystallization processes [105,108,111,112]. Leuchtenberg and Zainhammer granites show, on average, higher Th/U ratios than the S-type granites, but mostly lower U concentrations (Figure 5a,b). ...
The origin and evolution of granites remain a matter of debate and several approaches have been made to distinguish between different granite types. Overall, granite classification schemes based on element concentrations and ratios, tectonic settings or the source rocks (I-, A-, S-type) are widely used, but so far, no systematic large-scale study on Th/U ratio variations in granites based on their source or tectonic setting has been carried out, even though these elements show very similar behavior during melting and subsequent processes. We therefore present a compiled study, demonstrating an easy approach to differentiate between S-, A- and I-type granites using Th and U concentrations and ratios measured with a portable gamma ray spectrometer. Th and U concentrations from 472 measurements in S- and I-type granites from the Variscan West-Bohemian Massif, Germany, and 78 measurements from Neoproterozoic A-type Malani granites, India, are evaluated. Our compendium shows significant differences in the average Th/U ratios of A-, I- and S-type granites and thus gives information about the source rock and can be used as an easy classification scheme. Considering all data from the studied A-, I- and S-type granites, Th/U ratios increase with rising Th concentrations. A-type granites have the highest Th/U ratios and high Th concentrations, followed by I-type granites. Th/U ratios in S- to I-type granites are lower than in A-type and I-type granites, but higher than in S-type granites. The variation of Th/U ratios in all three types of granite cannot be explained by fractional crystallization of monazite, zircon and other Th and U bearing minerals alone, but are mainly due to source heterogeneities and uranium mobilization processes.
... For a realistic economic geothermal prospection, the depth of the granitic body is also critical. Late-Variscan granites of different petrogenesis, composition, and age constitute large parts of the Variscan crust from northern Bavaria to southern Saxony (Richter and Stettner 1979;Hecht et al. 1997;Siebel et al. 1997Siebel et al. , 2003Förster et al. 2008;Žák et al. 2014). From the geological context, it is likely that the granitic terrain continues into the western foreland, where the basement is buried under a cover of Permo-Mesozoic sediments (Franconian Basin). ...
... 40 Ma from 323 to 286 Ma. The intrusions are commonly subdivided into an older (OIC) and a younger (YIC) granitic suite (Richter and Stettner 1979;Hecht et al. 1997). ...
FULL TEXT DOWNLOAD LINK, University Library FAU:**********
https://opus4.kobv.de/opus4-fau/frontdoor/index/index/start/0/rows/20/sortfield/score/sortorder/desc/searchtype/simple/query/k%C3%A4mmlein/docId/13245**********Exploration activities for hydrocarbons and thermal water between the 1960s and 1980s consolidated the assumption of a positive temperature anomaly in SE Germany. Cur-rently, the area is used exclusively for hydrothermal applications. However, the balneo-logical facilities are installed only around the centre of the anomaly defined by the deep well Mürsbach B6. In this well, an undisturbed formation temperature of 66.8 ° C was detected at 1,204.2 m depth, which corresponds to a significantly increased geothermal gradient of 48.9 °C km-1. However, the geological cause(s) for the elevated tempera-tures is not clear yet. So far, only a few data are available on the structure of the deeper subsurface in NE Bavaria. Furthermore, a representative dataset of the thermo-hydraulic and mineralogi-cal properties of the Permo-Triassic sedimentary cover and the Variscan basement rocks is missing. However, this is a prerequisite for the application of a variety of ad-vanced geological and geothermal methods as well as the estimation of the geothermal potential from heat flow density calculations. Within the scope of this thesis, a comprehensive thermo-hydraulic and mineralogical dataset of the Permo-Triassic rock units and the basement rocks of the Franconian Basin was established. In the first part of the study, the following methodological as-pects for the determination of precise rock thermal conductivities have been investigat-ed: • Do the particle size distribution, the mineralogical composition and the structural rock features influence the precision of thermal conductivity measurements? • Do the pore-fluid of mineralogically heterogeneous sandstones and the type of method used influence the precision of matrix thermal conductivity (λm) determina-tion? • Does the pore-fluid of sandstones influence the suitability of specific rock properties, which are used as proxies for the estimation of bulk rock thermal conductivity? The experiments on the determination of bulk thermal conductivity from rock fragments demonstrated that particle size effects are unequivocal. The accuracy of the measure-ment can be improved by consideration of suitable, lithology-specific particle size rang-es. These are primarily associated with the mineralogical composition and the porosity of the rock sample. For monomineralic limestones, the highest agreement was achieved with the thermal conductivity of the core sample when using powder samples with the smallest tested particle sizes ≤0.063 mm, whereas with argillaceous sandstones higher accuracies were achieved by using larger particles with diameters between 0.9 - 1.3 mm. The theoretical assumption that λm of sandstones always is constant - independently of the type of pore fluid - is incorrect. E.g. for specific sandstones, the λm is significantly higher, if calculated from bulk thermal conductivity measurements of air-saturated samples. One the one hand, an improved grain contact by the formation of kaolinite in the intergranular pore space, originating from the alteration of alkali feldspar, increases the λm of air-saturated sandstones. On the other hand, because of a lower thermal con-ductivity contrast between the pore fluid and the rock matrix, the precipitation of kaolin-ite has a significantly lower effect on the λm in case of water saturation. A pore fluid-related suitability test for estimation of the bulk thermal conductivity of sandstones was conducted with different sandstones properties. It proved that empirical models calibrated on air-saturated samples could not be readily transferred to water-saturated conditions. Depending on the type of pore fluid tested (air + water), the signifi-cance of the results of the regression analysis of individual rock parameters like Φ, vp or the quartz volume fraction is highly variable and the in case of both pore fluids too low for a reliable estimation of bulk thermal conductivity. Instead, a combination of pa-rameters should be used. The easily measurable parameter vp combined with other properties is regarded as a promising proxy for both pore fluid conditions tested: in combination with the vquartz/Φ ratio for air-saturated sandstones and in combination with the vquartz+dolomite for water-saturated sandstones. The second part of the thesis focuses on a refinement of the Franconian Basin temper-ature anomaly and the modelling of different heat sources scenarios discussed. Availa-ble temperature data of SE Germany/NE Bavaria were compiled, assessed, and uni-formly corrected. They serve for the calculation of equilibrium geothermal gradients (gradT) and heat flow densities to constrain the temperature distribution and geometry of the Franconian Basin anomaly and its geothermal potential. Numerical models of potential heat source scenarios focused on heat-producing granites were set up for the deep wells Obernsees 1 and Mürsbach B6. They serve to shed more light on the poten-tial causes of the temperature high and test the plausibility of various underground sce-narios discussed. The analysis and uniform correction of temperature data from deep wells in the Fran-conian Basin confirms the presence and refines the geometry of a positive temperature anomaly within an area of about 100 x 65 km2 characterised by elevated geothermal gradients of >30 - 48.9 °C km-1. In the centre of the anomaly, the elevated tempera-tures extend into the basement rocks but rapidly decrease from the centre towards its borders. The observation implies that an isolated, deep-seated heat source like a heat-producing granite or an increased mantle heat flow could be present as a local heat source in the deeper underground. The geothermal potential of the area is high, with surface heat flows excess 100 mW m-2 in 13 of the 18 wells investigated reaching a maximum of 136(±15) mW m-2 in the central part of the anomaly. The surface heat flow calculations indicate that the geothermal potential of the Franconian Basin anomaly is in the order of magnitude known from the Upper Rhine Graben Rift. Applying coupled heat transfer and fluid simulations, the following scenarios in combina-tion with a permeable fault zone of permeability 1.0 x 10-13 m2 could reproduce an equi-librium temperature log measurement of the central well Mürsbach B6: 1) an enhanced background heat flow of 0.115 W m-2 or 2) a heat-producing granite of very large cross-sectional area (300 km2) in combination with an average background heat flow of 0.070 W m-2. The assumption of a solely conductive regime can be excluded as a cause for the elevated temperatures in the centre of the anomaly. In contrast, the re-sults of conductive numerical models for the location of the deep well Obernsees 1 show that conductive heat transfer from radiogenic decay in the modelled granite body can predict the elevated gradT measured in the well. An important fact for both well locations is that high temperatures in the models were only achieved with the presence of a low conductive, insulating cover above the heat source.
... Late-Variscan granites of different petrogenesis, composition, and age constitute large parts of the Variscan crust from northern Bavaria to southern Saxony (Richter and Stettner 1979;Hecht et al. 1997;Siebel et al. 1997Siebel et al. , 2003Siebel et al. , 2010Förster et al. 2008;Žák et al. 2014). From the geological context, it is likely that the granitic terrain continues into the western foreland, where the basement is buried under a cover of Permo-Mesozoic sediments (Franconian Basin). ...
... 40 Ma from 323 to 286 Ma. The intrusions are commonly subdivided into an older (OIC) and a younger (YIC) granitic suite (Richter and Stettner 1979;Hecht et al. 1997). ...
The Franconian Basin in NE Bavaria is a region of gravity low between the Bohemian Massif in the east and the Kraichgau Terrane in the west. Borehole measurements have identified the northern part of the Franconian Basin as a regional geothermal anomaly and new heat flow calculations give values of > 100 mW/m². Distinct negative Bouguer anomalies observed in this basin are modeled as granitic intrusions in the Saxothuringian basement that underlies the Permo-Mesozoic units. The interpretation of gravity gradients, in combination with the filtering of gravity data, gives the possible depth constraints of the intrusive bodies. The resulting depths were cross-checked using microstructural studies of quartz veins in the basement rocks (at > 1341 m depth). The quartz shows structures typical for low-temperature plasticity and we infer a deformation temperature of ca. 300 °C. This indicates a considerable pre-Permian uplift of at least 7 km for parts of the Saxothuringian basement and supports depth estimates from gravity data. The heat supply of granitic intrusions by radiogenic decay is modeled considering several scenarios for the geological conditions recovered by the Obernsees borehole (model for conductive heat transfer). The 1390 m-deep drillhole is in a marginal position to the most-pronounced negative Bouguer anomaly. It could be shown that the Saxothuringian basement, including heat-producing granites (heat production rates: 4–6 μW/m³), covered by the insulating sedimentary rocks (1.35 km of Permian to Lower Jurassic units), can account for the enhanced geothermal gradient (38 °C/km) that were measured in the borehole.
... Lithotype 1: Lithotype 1 is composed of calcsilicate rocks alternating with marble horizons with thicknesses varying from 150 to 200 m and lined up along the southern exocontact of the Fichtelgebirge Pluton, where they are named collectively as "Wunsiedel Marble" after a town nearby (Table 1, Fig. 5a) (Richter and Stettner, 1979). The current lithotype is well-bedded and intercalated into mica schists, phyllites, and quartzites and can be traced over a distance of several tens of kilometers and mapped at various positions within Neoproterozoic through Cambrian units (Wurm, 1961;Hecht et al., 1999) (Fig. 5b and c). ...
... Uranium enrichment to ore grade and the emplacement of U deposits is not the result of a simple fractionation of the granites but the interplay of plutonic mobilization, sodium metasomatism, and propylitic wall rock alteration associated with a strong desilicification of the granites resultant in the formation of "episyenites" in this region (Dill, 1983). The abnormally high U values of around 14 ppm U determined in the Late Variscan Younger Granites played a paramount role as the source for supergene U mineralizations (Richter and Stettner, 1979). It was not until the Neogene (Mio-Pliocene) that the granites played a full part during the formation of "per descensum" U deposits and cast into the role of a restite, at least in their topmost zone undergoing pervasive chemical weathering under tropical to subtropical climates (Dill et al., 2010). ...
In some areas of the Variscan orogen felsic mobilizates (pegmatitic and aplitic rocks) are closely associated with stratiform and stockwork-like bodies enriched in Ca minerals (e.g. wollastonite, diopside-hedenbergite s.s.s., grossular-spessartine s.s.s., siderite..) and bodies aligned to them similar in structure but abundant in quartz,
plagioclase and mica. Geological mapping and lithochemical studies are the tools to decipher the nature of these crystalline rocks which are common to the Hagendorf-Pleystein Pegmatite Province, SE Germany, and present in many ensialic orogens elsewhere. Geological and chemical data suggest paired belts of a restite-mobilization
system. The Ca and Si metasomatites are different from calcareous metasediments and quartzites elsewhere in the SE German basement devoid of mobilizates (parent rocks: limestones and cherts). Mobilization conducive to this paired belt of metasomatites involved silica mobilized from a deep level of the crust as a result of metamorphic-metasomatic alteration of Precambrian to Early Paleozoic metagreywackes during retrograde metamorphism
from HP to LP metamorphism around 680–600 °C. The arrangement of mobilizates and restites in the field has been denominated as metamorphic differentiation sensu lato. The zone of silica mobilization is transitional into a zone of pegmatoids and aploids that overlaps with another one characterized by rocks derived from Ca metasomatism the footwall facies of which developed in the range 750–400 °C while in the hanging wall metamorphic rocks of rare-element pegmatites 570–430 °C occurred. The intensity of Ca metasomatism diminishes from the footwall to the hanging wall rocks and reflects a subcrustal impact. These investigations call
attention among exploration geologists and petrologists to an alternative origin of “metasilica” and “metacarbonate” rocks being encountered in a zoned arrangement with felsic mobilizates (pegmatitic and aplitic rocks). The current study also raises the question “Quo vadis” pegmatology? It is an amendment to the mainstream geoscientific handling of pegmatitic rocks as “..texturally complex igneous rocks” genetically linked to granitic plutons (see review of London (2018) in Ore Geology Reviews). Taking a holistic approach can give us a reality check and prevent pegmatology from converting into a one-way street (granites-only) that eventually
ends up in a dead-end street. The field evidence is the litmus test for all our models created in the laboratory and on the PC.
There is no ore geology without field geology.
To get access:
Your personalized Share Link:
https://authors.elsevier.com/a/1YVxT_3s85-rFt
... According to Finger et al. (1997), the majority of these Variscan plutons is attributed to S-type granites made up of high-K and to I-type granitoids. During their comprehensive field and laboratory studies, Richter and Stettner (1979) singled out two different groups of granitoids, each of which with a specific trend of magma differentiation. The Older Granites cover the entire range from granodiorites through aplite granites with the majority of them plotting in the field of monzogranites, whereas the younger granite suite is made up of monzogranites grading into syenogranites which make up the lion share of this magmatic suite. ...
... The age supports the K/Ar cooling age of 312.5 ± 2.5 Ma when muscovite passed the 350°C temperature isograde (Kreuzer et al., 1989). It also corresponds to the Rb/Sr whole rock age of the older granites 319 ± 3 Ma, which intruded immediately north of the Wunsiedel Marble and whose magma had a minimum temperature of 660°C (Richter and Stettner, 1979). ...
Metacarbonate rocks (marble, calcsilicate rock, skarn) hosting strata- and structurebound Fe-, As-Sb, Bi-, Ni-Co, Cu-Pb-Zn, U-, W- ore minerals as well as talc, clay minerals, barite and fluorite are widespread in the country rocks south of the collisional calc-alkaline felsic to intermediate intrusive rocks of the Fichtelgebirge Pluton, Germany. At its western rim, thrustbound and vein-type mineral assemblages with Au-As-Sb and F-Ba minerals associated with carbonate gangue minerals developed. Only recently, a calcite-hosted Sb mineralization was encountered in a deep-seated lineamentary fault zone cutting through metaultrabasic rocks along the northern edge of the granites. The same structure zone forms the loci of calcite-bearing U episyenite situated within this pluton. A composite geological, mineralogical and chemical (major and trace elements, REE, C- and O isotopes) study has been conducted to distinguish the heat and element source in subcrustal or deep-seated crustal areas and in the largely exposed granite complex. Only Sn-W skarn deposits are genetically related to the highly fractionated granitic members of the Variscan pluton. Pegmatite skarn has a strong subcrustal component as to the heat source and the provenance of rare elements and a moderate crustal one as far as the silicates are concerned. Deep-seated fault zones were active over a rather long period of time and acted as conduits venting magmas and hydrothermal fluids from the waning stages of the Variscan deformation through the Neogene. Calcsilicate and carbonate mineral assemblages are an efficacious tool to constrain the physico-chemical regime in this mineral province, covering the temperature range from 745 °C down to 53 °C in a medium to low pressure regime at strongly varying redox conditions. The major and trace elements, the REE variation, the Ce and Eu anomalies as well as carbon and oxygen isotopes of the various mineral assemblages enable us to identify the fluid sources and depict the element concentration processes, e.g., mixing of fluids, connate fluid and meteoric fluid interaction. From the economic point of view, the mineralizing system is most prospective for rare element deposits, talc, kaolinite-group minerals, iron, and uranium. Accumulations of fluorite and barite are subeconomic in mineral assemblages inside as well as outside the granites, while base metals and precious metals are only of mineralogical interest.
... Granites" along the western edge of the Bohemian Massif. The geological setting has been redrawn from Forster (1965), Richter and Stettner (1979) and Breiter and Siebel (1995). NWD = Naab-Wondreb Depression which preserved the kaolin deposits of the northern Oberpfalz from erosion. ...
... The kaolin deposits mined by Imerys Tableware GmbH are located at the southern outskirts of Tirschenreuth, SE Germany (Fig. 1c). The study area is located in the westernmost part of the Bohemian Massif, along the boundary of two prominent geotectonic units, the Saxothuringian Zone in the North and the Moldanubian Zone in the South (Breiter and Siebel, 1995;Forster, 1965;Richter and Stettner, 1979;Vrána et al., 1995;Weber and Vollbrecht, 1989) (Fig. 1a, b). It was not only the geodynamic situation that attracted the attention of the afore-mentioned geologists Weber and Vollbrecht (1989), but also the location of the kaolin deposits in the younger coarsegrained to porphyritic granites (Rohrmüller, 1998;Störr, 2002Störr, , 2006Strobel, 1969). ...
Residual kaolin deposits are operated on a worldwide basis. The majority of them is derived from chemical weathering of felsic rocks during the Cenozoic. This is true for the kaolin deposits on the western edge of the Bohemian Massif. Here this type of deposit provides industrial minerals for the ceramic industry in SE Germany. This raw material formed under tropical climatic conditions during the Miocene and Pliocene across a vast peneplain. Only within the Naab-Wondreb Depression, however, were economic accumulations preserved from erosion. Here near Tirschenreuth, kaolin has been mined since its discovery in 1830. The semi-consolidated regolith is composed of quartz and opaline material, alkaline feldspar, different types of kaolinite, muscovite–illite, a variegated spectrum of 14 Å phyllosilicates, Fe–Mn oxide–hydroxides and minor heavy minerals, mainly containing Ti. A precise determination of the mineralogical composition of the ceramic raw material has so far solely relied on laboratory techniques, e.g., XRD, XRF, and spectroscopic methods. To the contrary, this study takes a different approach, capturing digital data in the field to determine its mineralogical composition. Gamma spectrometry (K, U, Th), measuring the susceptibility of and analyzing short-wave infrared spectra, allows for an in-situ quality control of the run-of-mine raw material. It further assists in mapping the monotonous lithology and enables the authors to constrain the physico-chemical regime throughout formation of the kaolin deposit. The benefit for technical mineralogy and applied economic geology, and the strong points of capturing digital data in the field, is the easy and cost-efficient handling of the various methods; methods that were applied in this way for the first time. The in-door calibration and test measurements as well as the data acquisition during the field survey are presented and the data are correlated with the enhancing or deteriorating impacts of the inferred minerals on the firing behavior of the ceramic product.
Collecting digital data can also help constrain the physico-chemical regime during formation of the argillaceous deposit and improve further exploration through fine-tuning the genetic model of residual kaolin accumulation. The late Carboniferous granites around Tirschenreuth underwent strong supergene alteration in the pH range of 2.5–7 at log a SiO2(aq) − 2.5 to − 3.5, which resulted in a thick kaolinitic regolith. Illite formed under slightly increased pH, between 4 and 7, attests to a change from tropical to more temperate humid conditions in the area. The chlorite-group phyllosilicates and nontronitic members of the smectite group came into existence when the pH increased to a pH interval of 7 to 11. This considerable change in the pH of the meteoric solutions occurred at the end of the Neogene between 4.55 Ma and 3.99 Ma.
The different field methods compensate for each others' weak points. Neither method is successful on its own, but the current configuration can easily be expanded to include additional methods as there are neutron- and micro-resistivity and air- and space-borne approaches to cover more swiftly a larger exploration or study area.
... Country rocks consist of Late Proterozoic to Paleozoic rocks of low to medium metamorphic grade. They consist of metapellites and metapsammites (phyllites, mica schists, quartzites) affected by a low-pressure greenschist to amphibolite facies metamorphism, dated pre-Late Devonian (Richter and Stettner, 1979). ...
... The whole massif is subdivided into an Older Intrusive Complex (OIC) and a Younger Intrusive Complex (YIC), according to Richter and Stettner (1979). Both massifs consist of monzogranites and partly of syenogranites for the YIC. ...
Hercynian granitoid intrusions form a long (3200 km) belt comparable in size to other batholiths in the world. Six massifs have been selected which encompass Cabeza de Araya (Extremadura, Spain), Guitiriz (Galicia, Spain), Pontivy and Mortagne (Brittany, France), La Marche (Massif Central, France) and Fichtelgebirge (Bavaria, Germany). Detailed gravity surveys over these massifs and subsequent inversion provide their shape at depth. Correlation of the deeper zones with internal structures determine the place of the root zones. The shape of the massifs is examined along the strike of the chain. The emplacement of individual massifs is controlled by local tectonics. Most granites are not deeply rooted, but one massif (Cabeza de Araya, Spain) shows a root zone presently as deep as 14 km. Most have about half of their volume in the first 3 km below the present surface. Estimates of the magma volume transferred result in 1500 km3 issued from one specific feeder, yielding a total of 70,000 km3 of magma intruded all along the chain. The depth of emplacement of the granitic massifs does not show any significant trend along the strike of the chain. The shallower massifs in the French Massif Central correspond to more deeply eroded areas in the center of the chain. Their root zone, as well as the change in the dip of the walls, are presently observed at depths ranging between 4 and 6 km in Hercynian granites. Both variations are interpreted as being related to the brittle/ductile transition at the time of emplacement. Gross thermal considerations place the transition at its former place during magma emplacement, indicating that the upper crust has not been eroded by more than 6–8 km. This estimate severely contrasts with models involving a doubled crust.
... The Fichtelgebirge/Smrčiny (Germany, Czech Republic) constitutes a Saxothuringian region containing abundant late-Variscan granites of different petrogenesis, composition, and age (e.g., Richter & Stettner 1979, Carl & Wendt 1993, Hecht 1993, Irber et al. 1997, Hecht & Vigneresse 1999 (Fig. 1). These granites are subdivided into an older intrusive complex (OIC) and a younger intrusive complex (YIC). ...
... The older granites are further subdivided into two major textural facies, the porphyritic OIC-p and the equigranular OIC-e (Hecht & Vigneresse 1999). The OIC-p (the granite types G1, Porphyrgranit, and G1R, Reutgranit, of Richter & Stettner 1979) encompasses biotite (± muscovite) monzogranites (our samples 4082, 4095). The OIC-e (G1S, Selber Granit, and G1HS, Holzmühlgranit) two-mica granites range in composition from biotite-rich types (4180) through muscovite-rich types (9644) to nearly pure muscovite granites (12506b, 11389). ...
The late Variscan granites of the Fichtelgebirge form an older, Namurian intrusive complex (OIC-p and OIC-e) and a younger, post-Westphalian intrusive complex (YIC-1 and YIC-2). Both complexes have distinct radioactive accessory-mineral assemblages and compositions. The OIC-p biotite monzogranites contain monazite-(Ce) and minor thorite, but apparently lack magmatic xenotime-(Y) and uraninite. The more evolved OIC-e two-mica granites bear monazite-(Ce) occasionally rich in Th (up to 21 wt% ThO2) and U (8 wt% UO2), xenotime-(Y) of moderate U content (< 3.3 wt% UO2), and uraninite poor in Th and the REE. The most fractionated YIC Li-mica granites (YIC-2) may contain cheralite extremely high in Th (40.5 wt% ThO2) and U (8.6 wt% UO2), xenotime-(Y) rich in U (6.3 wt% UO2), and also a Th-REE-poor uraninite. Dissolution-reprecipitation processes account for the formation of huttonite-rich domains in monazite-(Ce), uraninite in U-depleted areas in zircon, and Mn-Fe-rich phosphorus minerals in fluorapatite. The accommodation of U in Th-poor uraninite made the OIC-e and YIC granites highly susceptible to U leaching. However, currently known U mineralization spatially associated with these granites is economically negligible.Electron-microprobe analyses yield a mean U-Th-total Pb monazite+xenotime age of 321 ± 8 Ma (2σ) for the OIC, which is further supported by the average age of uraninite in one of the studied OIC-e granites (323 ± 6 Ma). These results are in harmony with previous age data and imply a penecontemporaneous emplacement of the OIC-p and OIC-e granites, between about 326 and 321 Ma. The YIC-1 and YIC-2 granites display statistically indistinguishable mean ages of 294 ± 6 Ma and 296 ± 6 Ma. These age data imply formation of the YIC granites during one intrusion period and question recent models postulating their generation during two discrete magmatic episodes separated by ∼15 Ma. The mean monazite+xenotime age of 296 ± 4 Ma obtained for the emplacement of the Younger Intrusive Complex, together with the age of uraninite in one of the YIC-1 granite samples (294 ± 3 Ma), suggest intrusion of this granite assemblage at the Carboniferous/Permian boundary. The YIC postdates compositionally similar granites in the neighbouring Erzgebirge-Vogtland Zone by 20-25 Ma, which emplaced penecontemporaneously with the OIC.
... Granites of OIC are of the Upper Viséan-Westphalian age (340 Ma to 310 Ma) [20,29]. The age of the granites of YIC was estimated at 285 to 329 Ma [30][31][32][33]. Granites of YIC are often affected by greisenization [13,17,18] and connected with economically important accumulations of Sn, W, and Li. ...
... Granites of OIC are of the Upper Viséan-Westphalian age (340 Ma to 310 Ma) [20,29]. The age of the granites of YIC was estimated at 285 to 329 Ma [30][31][32][33]. Granites of YIC are often affected by greisenization [13,17,18] and connected with economically important accumulations of Sn, W, and Li. ...
The Sn-W ore deposits in the Krupka surroundings are associated with greisens, which occur in the upper parts of Late Variscan granitoid intrusions. Fluid inclusions were studied in samples of quartz, cassiterite, apatite, fluorite, and topaz in greisenized granites, greisens, and hydrothermal veins with Sn-W mineralization. The greisenization process took place at temperatures 370–490 °C and pressures 155–371 bars, and associated fluids had predominantly low salinity and a low gas (CO2, N2 and CH4) content. The post-greisenization stage was connected with the formation of (i) low-salinity (0–8 wt. % NaCl eq.) fluid inclusions with homogenization temperatures <120–295 °C and (ii) high-salinity (18 to >35 wt. % NaCl eq.) fluid inclusions with homogenization temperatures 140–370 °C, often containing trapped crystals of quartz, topaz, and sulfides, or daughter crystals of salts and carbonates, which were identified by microthermometric measurements, electron microprobe analysis, and Raman spectroscopy. Analyses of fluid inclusion leachates have shown that Na and Ca chlorides predominate in fluids. According to hydrogen stable isotopes, the source of greisenizing and post-greisenizing fluids was not only magmatogenic but also meteoric water or fluids derived from sedimentary rocks.
... The color code can also be applied to the lithological units of Fig. 1 Steinach River (= SR) incised into the western edge of the basement and exposes a series of different rocks in the Fichtelgebirge Mts. which attains a maximum altitude of 1052 m a.m.s.l at the Schneeberg summit (Stettner, 1977). Its neighbor, the granitic dome of the Ochsenkopf Mt. in the study area, is slightly lower (1024 m a.m.s.l.) and made up of the Marginal Granite G2 -No 5-and the Core Granite G3-No 6 -, respectively ( Fig. 4, Table 1) (Richter and Stettner, 1979). Both granites were intruded in the aftermaths of the Variscan Orogeny into a shallow marine series of meta-psammopelitic rocks of Cambrian and Ordovician age which subsequently underwent low-grade regional metamorphism sensu Bucher and Grapes (2011) Fig. 1). ...
Provenance analysis and terrain analysis backed by radiometric age dating have been combined for the first time and conducted as a composite in a foreland-basement transition zone with mutual benefits for both disciplines. A meticulous provenance analysis enables a fine-tuning during studies of the landscapes and relief generations, while a detailed terrain analysis is essential for the disentanglement of lithological-geodynamic processes that often are telescoped into each other by sedimentological processes. The basic drivers for the denudation, transport and deposition processes of the various clast communities (gravel, sand, clay) are the climate change from a tropical (Neogene) to a glacial/temperate Earth and the brittle neotectonics along the margin of the study area (Rhine Graben Rift N-S, Eger/Ohře Graben Rift E-W). As a result of this composite approach the landscape formation in the study area is described as follows: (1) (Paleogene)-Neogene peneplanation in the basement, (2) Quaternary straight to low sinuosity drainage in the basement, (3) Late Pleistocene to Holocene high-sinuosity drainage in the proximal foreland and (4) Holocene (to Late Pleistocene) meandering fluvial rivers evolving in the distal foreland. In additions to these geomorphological results progress can be made in the geodynamic evolution of the study/source area. Five Proterozoic to Late Paleozoic lithological units are identified: (1) Para-metamorphic rocks, (2) greenstones, (3) basic volcano-sedimentary rocks, (4) sedimentary units abundant in chert and (5) felsic volcanics. By means of these sedimentological finds a more detailed picture of the Variscan orogeny can be presented.
... The Erzgebirge and Fichtelgebirge crystalline complexes host several post-tectonic granitic plutons, which yielded ages either around 320 Ma or between 280 and 300 Ma (Siebel et al., 2010;Carl and Wendt, 1993;Richter and Stettner, 1979). Based on the composition of magmatic muscovite, the intrusion level of these granites was in the depth range of 15-20 km (around 4.3 kbar: Massonne, 1984). ...
A chloritoid-garnet-bearing micaschist from the southern part of the Elstergebirge was studied to better understand the Variscan orogenic evolution in the Saxothuringian zone of the northwestern Bohemian Massif. Based on the textural relations and compositions of minerals, especially of zoned garnet and potassic white mica, a P-T path was reconstructed using contoured P-T pseudosections. The U-Th-Pb dating of monazite in the micaschist was undertaken with the electron microprobe. The micaschist experienced P-T conditions along a clockwise path between 16 kbar at 510 °C and 5 kbar at 555 °C followed by isobaric heating to about 600 °C. Monazite ages range between 315 and 480 Ma with the most prominent maxima and side maxima at 346.0±1.1 (2σ), 357.3±2.3, and 368.3±1.7 Ma. Ages older than 380 Ma were related to detrital monazite pointing to a Devonian sedimentary protolith. Other ages around 325 Ma were assigned to the isobaric heating by nearby post-tectonic granites. The high-pressure event, being the result of the collision of Laurussia and Gondwana after closure of the Rheic Ocean, occurred in the Late Devonian. The exhumation to 15–20 km (5 kbar) ended probably in the Early Carboniferous. The high-pressure micaschists from the Fichtelgebirge to the Erzgebirge crystalline complexes are suggested to represent a single nappe within a metamorphic nappe pile. This nappe is composed of metasedimentary slices, which experienced different peak pressures rather than representing a coherent crustal section.
... The Fichtelgebirge and Oberpfalz granites (study areas 1 and 2, see Fig. 1) are peraluminous to metaluminous S-to I-type granites that formed through anatexis of metasedimentary and metaigneous rocks in the middle or lower crust. The intrusions are commonly divided into an older (OIC) and a younger (YIC) granitic suites (Richter and Stettner 1979;Hecht et al. 1997). Precursors of the granites, the redwitzites (diorites), are predominately metaluminous and interpreted as products of crystallization of a mantle-derived mafic magma (Kováříková et al. 2007). ...
... The maximum amount of Ca that could be released by apatite weathering is in the same range. According to Richter and Stettner (1979), accessory minerals sum to 0.3% of the bedrock mass. Assuming, that this is entirely due to apatite, and that the diameter of the cross sectional area where weathering was enhanced by drilling is about twice the diameter of the drilling core, and that the density is 2.5 g cm À3 , this would correspond to 8.34 kg apatite. ...
From a biogeochemical perspective, catchments can be regarded as reactors that transform the input of various substances via precipitation, deposition, or human activities as they pass through soils and aquifers towards receiving streams. Understanding and modeling the variability of solute concentration in catchment waters require the identification of prevailing processes, determining their respective contributions to the observed transformation of substances, their interplay with hydrological processes, and the determination of anthropogenic impacts. However, numerous biogeochemical processes often interact in a highly non-linear way and vary on temporal and spatial scales, resulting in temporally and spatially varying water chemistry in catchments. This is particularly true for riparian wetlands. Processes in this catchment area often superimpose the influence of the hill slope (and largest) area of the catchment on surface water quality. Accordingly, the first part of this thesis (Study 1 and 2), focuses on the temporal and spatial variability of biogeochemical processes at the catchment scale. Therefore, the first aim was to identify the prevailing biogeochemical processes which affect the quality of catchment waters in two forested granitic catchments. Based on these results, (i) the long-term behavior of these processes was determined (Study 1) and (ii) hot spots of these processes at the catchment scale along different flow paths were identified (Study 2). The second part (Study 3) focuses on the interplay between hydrological and biogeochemical processes in a riparian wetland, with the aim of systematically tracing back the temporal patterns of stream water chemistry to different biogeochemical processes and antecedent hydrological boundary conditions in the wetland. The third part (Study 4 and 5) focuses on weathering processes with the goal (i) of identifying the mineralogical sources of the groundwater’s buffer capacity against acid atmospheric deposition in a forested granitic catchment and (ii) determining the mineralogical sources of the high cation loads in surface water, induced by intensive agricultural activities in two agricultural granitic catchments. To reach these aims, multivariate statistical methods of dimensionality reduction (linear Principal Component Analysis, non-linear Isometric Feature Mapping), a low-pass filtering of time-series, a Cluster analysis, and major and trace element ratios and strontium isotopes were used. A small number of biogeochemical process bundles explained 94% and 89% of the variance of the data set in Study 1 and 2, respectively. In Study 1, redox and topsoil processes, road salt and sulfate contamination were identified as predominating processes influencing water chemistry in the respective catchments. Low-pass filtered time series of component scores revealed a different long-term behavior at different sampling sites in both catchments, which could be traced back to the fraction of wetland area in the respective subcatchments as well as by the varying thickness of the regolith. Study 2 revealed that the upper 1 m topsoil layer could be considered as a biogeochemical hot spot for redox processes, acid-induced podsolization, and weathering processes along different flow paths. Up to 97% of the biogeochemical transformation of the chemical composition of soil solution, groundwater and stream water in the Lehstenbach catchment was restricted to this soil layer representing less than 2% of the catchment’s regolith. Wetland stream water, mobilized in the topsoil layer being considered a biogeochemical hot spot, showed a highly dynamic temporal pattern of component scores. Study 3 revealed four different types of wetland stream water chemical status, depending on the interplay between discharge dynamics, biological activity, and the water table position in the wetland. The sequence of different stream water types roughly followed a seasonal pattern, albeit being heavily modified by the respective hydrological boundary conditions for different years. Extended periods of low groundwater level in the second half of the growing season drastically changed the chemical boundary conditions, becoming evident in a drastic reoxidation of reduced species like sulfides and corresponding effects. Weathering processes are one of the predominating biogeochemical process bundles influencing water chemistry in forested catchments. Study 4 showed that the mineralogical sources of the groundwater’s buffer capacity against acid atmospheric deposition were dominated by the release of base cations from apatite dissolution, preferential cation release from feldspars and biotite, and feldspars weathering. In Study 5, determining the mineralogical sources of the high cation loads in surface water induced by intensive agricultural activities revealed a dominant manure contribution in the topsoil, and enhanced mineral dissolution (plagioclase and biotite) by fertilizer application in subsoils, becoming the unique source of base cations in the saprolite. Stream water chemistry differed from that of soil water, suggesting that stream water chemistry was dominated by elements issued from enhanced mineral and rock weathering. Soil acidification induced by agriculture allows the mobilization of cations stored in soil layers, enhances the rock weathering and accelerates plagioclase dissolution, which can highly influence stream water quality. Numerous biogeochemical, hydrological, and anthropogenic processes were found to interact with each other, mostly with non-linear patterns, influencing catchment water chemistry. The integral approach used in this thesis would be a useful prerequisite to develop accurate and parsimonious models commonly used for water management purposes by distinguishing between short- term and long-term shifts, reducing the number of processes to the predominating ones ultimately to be included in the model, focusing on hot spots and including spatial patterns where necessary and appropriate.
... The plutons of the FC and western EC are such intrusions into the upper Saxothuringian crust (Behrmann and Tanner, 1997). Based on field relations, petrography, geochemistry and radiometrical dating (Besang et al., 1976;Carl and Wendt, 1993;Richter and Stettner, 1979;Stettner, 1958), the granites of the FC can be subdivided into two main complexes: the older intrusive complex (~320 Ma) and the younger intrusive complex (290-280 Ma). However, the intrusion of the latter complex occurred between 300 and 290 Ma according to Carl and Wendt (1993) and Siebel et al. (2010). ...
The studied micaschist from the northeastern Fichtelgebirge crystalline complex (FC) contains mm-sized garnet with a foam structure. Staurolite formed at the margin of garnet. Relics of staurolite are enclosed in mm-sized andalusite porphyroblasts. Garnet exhibits prograde concentric zonation with the pyrope component increasing from 1 to 6 mol%. Cores of potassic white-mica grains locally contain Si contents up to 3.15 per formula unit (pfu). The majority of this mica is characterized by Si contents close to 3.00 pfu. Pressure-temperature (P-T) pseudosections, calculated for the micaschist, indicate conditions of 10 kbar and 505 °C for an early metamorphic stage which was followed by a pressure decrease to 5 kbar and 535 °C. Late metamorphic P-T conditions recorded by garnet are around 4.5 kbar and 565 °C, compatible with the presence of staurolite. Andalusite might have metastably formed at this stage or somewhat lower pressures. The U-Th-Pb dating of monazite with the electron microprobe yielded subordinate ages younger than 315 Ma which were assigned to the nearby emplacement of granites in the FC. Some ages older than 395 Ma were related to detrital monazite in the sedimentary protolith of the micaschist. An age cluster at 384.5 ± 1.8 (2σ) Ma is preferentially assigned to the early high-pressure (HP) metamorphism resulting from the collision of Laurussia with a Peri-Gondwanan terrane. Exhumation to 15–20 km depths might have ended at 362.3 ± 1.0 Ma, but possibly the HP metamorphism occurred at this age and the 384.5 Ma age must be then referred to the provenance area of detrital monazite. The age cluster at 325.0 ± 0.7 Ma is related to a second collisional event that caused the overriding of the crystalline nappes of the FC onto the Laurussian crust.
... Anomalous Ba contents imply a strong subcrustal impact. Richter and Stettner (1979) found a steady decrease in Ba from the older towards the younger granites in the adjacent Fichtelgebirge Mts. Barium substitutes for K and Rb in many silicates such as feldspar and mica, many of which common to pegmatites. ...
The geology of pegmatite systems encompasses lithology, shape, and structure while the chemistry of major and trace elements is indicative of the ore composition; both are the “pillars” of the CMS classification scheme (Chemical composition-Mineral assemblage-Structural geology) for barren and rare-metal pegmatites, including their granitic affiliates. The term Variscan-type has been coined to describe a style of formation linked to the ensialic orogens and a timebound mineralization sandwiched between the Caledonides and the Alpides. The primary formation covers the time from the Neoproterozoic through the Permian and ends with a hydrothermal phase waning eventually in the supergene alteration and is subdivided into three stages: (1) from diatectic to metatectic gneisses, (2) from metapegmatites, metamorphic pegmatoids to thrusting, (3) from the crust to the mantle and from barren to rare metal pegmatites. This evolution is characterized by a retrograde metamorphism from HP/MP to LP regimes. The tabular and stock-like pegmatitic, aplitic and granitic rocks in autochthonous and allochthonous units are grouped into 8 types (A–H) based on the above qualifiers of the CMS scheme. On a large scale, felsic mobilizates are accumulated by mimetic (facsimile) crystallization in anticlines with the most effective traps encountered where the directions of great circle plunges cut each other at almost right angle (stereonet analysis). The term “mobilizates” is used to describe felsic mobile components in the crust which migrated to a different extent from the site of their formation. On a small scale, where southward-dipping planar architectural elements are cut across by deep-seated lineaments the “temperature depression” of the retrograde system occurs and rare-metal pegmatites are located. This subhorizontal plane is correlated with a gently dipping Moho and vertical lineamentary fault zones with bulges of the Moho (chemical contour map analysis). Spider diagrams whose element contents are normalized to a reference paragneiss are categorized into 4 chemical patterns: (1) circular patterns (= metamorphic mobilizates, magmatic mobilizates), (2) necking-down patterns (= different degrees of fractionation), (3) lens-shaped patterns (= wall rock alteration), (4) stellate pattern (= different degrees of fractionation and mixing of fluids). The marker assemblages among the major elements are: Si-Fe-P: metamorphic to magmatic (sub)crustal mobilizates, K-Na-Al: metamorphic mobilizates, Ti-Mg: restites of metamorphic and magmatic mobilizates, Ca: remnant in the exocontact of pegmatitic systems, Mn: marker of depth-pressure The marker assemblages among the minor elements are: As-Bi: HT hydrothermal-metamorphic fluids, Cu-Ni-Mo: hydrothermal-deep-seated +(ultra)basic sources, U-Zn: hydrothermal-deep-seated sources, Pb: LT hydrothermal, Nb-Ba-Rb: pegmatitic fractionation-Ba (early)-Rb (late), Zr: restites of metamorphic mobilization + fractionation, REE: metamorphic mobilizates. The marker to discriminate hypogene and supergene kaolinization are: (1) hypogene (Ca- Mg out, Zn-Cu-Bi-Rb-Nb in), (2) supergene (Zr-Ti in).
... A specific group of YIC granites are alkali feldspar zinnwalditebearing (Li-F) granites in small granite cupolas in the Eastern Pluton (Cínovec/Zinnwald, Krupka, Altenberg, Sadisdorf) ( Fig. 2 (Breiter and Kronz, 2004) and at Krásno in the Slavkovský les in the Karlovy Vary massif (Beran and Sejkora, 2006). Two major granite intrusive complexes were also distinguished in the Fichtelgebirge by Richter and Stettner (1979) and Hecht et al. (1997) as G1 (considered to be equivalent to OIC granites), and G2-G4 (as equivalent to YIC granites). In the geochemical classifications the OIC granites are transitional between I-and S-types while the YIC are typical S-type granites (Štemprok, 1986;Förster et al., 1999). ...
... d. Sketch map of the geological setting and the position of pegmatites and aplites of the Hagendorf–Pleystein pegmatite province modified from Forster (1965), Richter & Stettner (1979) and Breiter & Siebel (1995). S–F: Steinwald–Friedenfels granite, LB: Leuchtenberg granite, FA: Falkenberg granite, FL: Flossenbürg granite, B: Bärnau granite, Rozvadov granite. ...
Hagendorf-North is a zoned Li-Nb-P-feldspar-quartz pegmatite located W of the village of Hagendorf and about 0.5 km north of the renown Hagendorf-South deposit which once was the largest feldspar pegmatite in Central Europe. Hagendorf-North also known as Meixner Mine was much smaller in size and its minerals assemblage is less variegated than that recorded from its larger “brother”. However it was the site where mining began in 1860. But already before the onset of World War II, the pegmatite has no longer been considered an economic target and the mine was shut down. The reason for that small size in the shadow of this huge Hagendorf-South pegmatite is due to its overall role as feeder system to the Hagendorf-type stocklike pegmatites, which was truncated by the Pliocene chemical weathering and Pleistocene erosion, which however was comparatively moderate when compared with the western part of the pegmatite province. Hagendorf-North and South were both emplaced in the central parts of a first order anticline with its hinge line plunging towards the south and thereby providing much better structural, mineralogical and supergene conditions for Hagendorf-South than for Hagendorf-North in terms of accommodation space of the pegmatite body and preservation potential during Cenozoic supergene alteration. Both pegmatites resemble each other as to the temperature of formation spanning the range 500 °C to 550 °C. The lithogenic process giving rise to the Hagendorf-North pegmatite and its present-day size are as follows: (1) regional metamorphism-structural disturbances, (2) high temperature mobilization, (3) hydrothermal alteration, (4) epithermal mineralization, (5) weathering.
The Hagendorf-Pleystein province may be subdivided roughly into two sections. The western section is best described as the Pleystein subzone and the eastern as the Hagendorf subzone. The Hagendorf Zone is marked by a ratio of chemical weathering >> erosion. Newly formed Al-phosphates are widespread and Fe-phosphates indicative of reducing conditions occur to a moderate extent. Chemical weathering was pervasive during the Pliocene, whereas the erosional shaping of the pegmatitic landscape evolved during the Pleistocene. This has also some implications as to the “weathering ruins”. The Pleystein-Kreuzberg pegmatite has been depleted of its less resistant feldspar envelope and now morphologically stands out as a “quartz reef”, while the Hagendorf-North is a feeder channel system, being deprived of the entire pegmatite body that still was preserved in the Hagendorf-South pegmatite.
... Pyrite, sphalerite, chalcopyrite and galena are present in these shales. In the adjacent basement there are numerous granites and granodiorites, studied petrographically and chemically by Richter and Stettner (1978). Schnitzer (1957) first studied the translucent accessory minerals of these plutonic rocks and found a relatively monotonous association with tourmaline, zircon, monazite and apatite. ...
Apatites of SE Germany from late Palaeozoic and Triassic red bed clastic rocks (environments: alluvial fan, fluvial, lacustrine, with volcaniclastic intercalations) were investigated for their rare earths and U-Th contents, including their chondrite-normalized REE-patterns, Eu-Ce anomalies, LREE/HREE fractionation, U-Th distribution and U-Pb ages. For provenance purposes, apatite compositions were compared with published data from granites, volcanics, phosphorites and gneisses of the NE Bavarian basement. The applicability of REE contents of apatite to stratigraphic questions is restricted to areas and rock successions within the same heavy mineral province. The strong points of this method are in the fields of provenance studies (extrabasinal, intrabasinal) and, to a lesser degree, investigations of diagenetic alteration as demonstrated by the following examples.Apatites from Permian red beds of the Weiden embayment were probably derived from late Variscan granites in the adjacent basement on the basis of U-Pb age dating. The REE patterns and U-Th ratios of apatites from upper Stephanian rocks from Stockheim and from Autunian rocks of Erbendorf contrast conspicuously with this granite-derived apatite and probably originated from late Palaeozoic volcanic activity that generated volcaniclastic rocks.Despite their different ages of formation and depositional environments, diagenetic remobilisation gave rise to similar REE patterns and U-Th ratios in both Upper Triassic apicretes (= duricrusts composed of apatites) and Silurian marine phosphorites. The organic matter that surrounds the P-bearing strata has been responsible for the reducing conditions in both of these host environments and for the striking similarities of their REE data.
... Pyrite, sphalerite, chalcopyrite and galena are present in these shales. In the adjacent basement there are numerous granites and granodiorites, studied petrographically and chemically by Richter and Stettner (1978). Schnitzer (1957) first studied the translucent accessory minerals of these plutonic rocks and found a relatively monotonous association with tourmaline, zircon, monazite and apatite. ...
Apatites of SE Germany from late Palaeozoic and Triassic red bed clastic rocks (environments: alluvial fan, fluvial, lacustrine, with volcaniclastic intercalations) were investigated for their rare earths and U-Th contents, including their chondrite-normalized REE-patterns, Eu-Ce anomalies, LREE/HREE fractionation, U-Th distribution and U-Pb ages. For provenance purposes, apatite compositions were compared with published data from granites, volcanics, phosphorites and gneisses of the NE Bavarian basement. The applicability of REE contents of apatite to stratigraphic questions is restricted to areas and rock successions within the same heavy mineral province. The strong points of this method are in the fields of provenance studies (extrabasinal, intrabasinal) and, to a lesser degree, investigations of diagenetic alteration as demonstrated by the following examples. Apatites from Permian red beds of the Weiden embayment were probably derived from late Variscan granites in the adjacent basement on the basis of U-Pb age dating. The REE patterns and U-Th ratios of apatites from upper Stephanian rocks from Stockheim and from Autunian rocks of Erbendoff contrast conspicuously with this granite-derived apatite and probably originated from late Palaeozoic volcanic activity that generated volcaniclastic rocks. Despite their different ages of formation and depositional environments, diagenetic remobilisation gave rise to similar REE patterns and U-Th ratios in both Upper Triassic apicretes (= duricrusts composed of apatites) and Silurian marine phosphorites. The organic matter that surrounds the P-bearing strata has been responsible for the reducing conditions in both of these host environments and for the striking similarities of their REE data.
... As an example for its use, the three-dimensional method is applied to both zoned and unzoned monazites from the Hercynian G4 granite of the Fichtel-and thus form an ideal test case. For a discussion of the geology and geochemistry of the Fichtelgebirge granites the reader is referred to Richter and Stettner (1979). The analytical data obtained from two sampies (4194 and 91431, which represent rocks of ...
Previous theoretical considerations on the chemical U-Th-total Pb dating method failed to distinguish between thorogenic and uranogenic lead. However, it can be shown that the data points are located on a plane in the three-dimensional ThO2, PbO, UO2 space. The calculation of the best-fit plane yields a slope in the ThO2-PbO and UO2-PbO coordinate projections, and an initial PbO value. From the two slopes, Th/Pb- and U/Pb-ages can be calculated independently.The method described in this paper is applied to monazites from the Hercynian G4-granite of the Fichtelgebirge (Germany). Th/Pb- and U/Pb-ages were calculated at 323 ± 20 Ma and 304 ± 15 Ma, respectively. The intercept value close to zero indicates that no significant amounts of common lead are present in the monazites studied.
... Der Paradigmenwechsel vollzog sich nicht schlagartig. Auch wenn die Autoren des im Jahr 1979 herausgegebenen Bandes Geochemische und petrographische Untersuchungen der Fichtelgebirgsgranite die Frage nach der Entstehung der Tiefengesteinen nur am Rande ansprechen, so ist doch klar zu erkennen, dass sie zu einer Entstehung durch Granitisation neigen (RICHTER & STETTNER 1979). Etwa 20 Jahre später wurden die Granite im Zusammenhang mit der Erkundung des Umfeldes der Kontinentalen Tiefbohrung (KTB) erneut eingehend bearbeitet. ...
... Approximately 2 cm large prismatic colorless to pale blue crystals were taken from the G4 granite, a Variscan Snspecialized granite with an age of about 290 Ma, the youngest granite facies of the Fichtelgebirge (cf. RICHTER & STETTNER 1979). ...
... The maximum amount of Ca that could be released by apatite weathering is in the same range. According to Richter and Stettner (1979), accessory minerals sum to 0.3% of the bedrock mass. Assuming, that this is entirely due to apatite, and that the diameter of the cross sectional area where weathering was enhanced by drilling is about twice the diameter of the drilling core, and that the density is 2.5 g cm À3 , this would correspond to 8.34 kg apatite. ...
The role of different minerals in base cation release and thus the increase of buffering capacity of groundwater against acid deposition is controversially discussed in the literature. The ⁸⁷Sr/⁸⁶Sr ratios and base cation concentration were investigated in whole rock leachates, mineral separates, precipitation, soil solution, groundwater and stream water samples in the Lehstenbach catchment (Germany) to identify the weathering sequence of the granite bedrock. Three different approaches were followed in parallel. It was assumed that the contribution of different minerals to base cation supply of the groundwater with increasing weathering intensity would be observed by investigating (1) unweathered rock leachates, deep groundwater and shallow groundwater, (2) groundwater samples from new groundwater wells, reflecting the initial weathering of the drilled bedrock, and groundwater from wells that were drilled in 1988, (3) stream water during baseflow, dominated by deep groundwater, and stream water during high flow, being predominantly shallow groundwater. Whereas the first approach yielded consistent patterns, there was some evidence that groundwater from the new wells initially reflected contamination by the filter gravel rather than cation release in an initial stage of weathering. Time series samples of stream water and groundwater solute concentrations and isotope ratios turned out to reflect varying fractions of soil water and precipitation water at baseflow and high flow conditions rather than varying contributions of different minerals that prevail at different stages of granite weathering.
Kein anderer Granit hat vermutlich so viel Einfluss auf die Vorstellungen von der Platznahme ausgeübt wie der von Flamanville. Über Jahrzehnte hinweg galt er als Musterfall dafür, wie Magma weniger mit mechanischer Gewalt in das Nebengestein eindringt, als es Stück für Stück aufzulösen und zu verzehren.
Uranium in granitoids and hydrothermal uranium mineralization in the western part of the Bohemian Massif
The order of crystallization of minerals from melt is of prime importance for an understanding of magma fractionation and chemical differentiation from the magma chamber to the planetary scale. Determination of the crystallization sequence based on petrographic observations, however, is often ambiguous; especially in multiply saturated, nearly eutectic felsic melts. This paper presents a novel approach to estimate the order of crystallization of minerals in igneous systems based on a quantitative study of their spatial distributions. Statistical modelling of crystallization demonstrates that later crystallizing mineral phases are generally more clustered. A simple inversion model is then derived to calculate the crystallization sequence and the volume fraction of older minerals present in the system at the onset of crystallization of a later (younger) phase. Application of the model to a sample of equigranular granodiorite (Fichtelgebirge granite batholith, Germany) indicates that plagioclase was the first liquidus phase. It was followed by biotite, K-feldspar, and quartz at 41, 48, and 63 vol. % crystallized, respectively, which is in qualitative agreement with experimental phase equilibria results for moderately hydrous granitic melts. If phase equilibria for a given composition are known or assumed, the crystallization sequence thus constrains the intensive variables (e.g., water content) and their evolution during magma solidification. The model thus provides a novel and independent approach to reconstruct the magma crystallization path that would be inaccessible by other methods.
Uranium Deposits of the World, in three volumes, comprises an unprecedented compilation of data and descriptions of the uranium regions in Asia, USA, Latin America and Europe structured by countries. With this third, the Europe volume, Uranium Deposits of the World presents the most extensive data collection of the set. It covers about 140 uranium regions in more than 20 European countries with nearly 1000 mentioned uranium deposits. Each country and region receives an analytical overview followed by the geologically- and economically-relevant synopsis of the individual regions and fields. The presentations are structured in three major sections: (a) location and magnitude of uranium regions, districts, and deposits, (b) principal features of regions and districts, and (c) detailed characteristics of selected ore fields and deposits. This includes sections on geology, alteration, mineralization, shape and dimensions of deposits, isotopes data, ore control and recognition criteria, and metallogenesis. Beside the main European uranium regions, for example in the Czech Republic, Eastern Germany, France, the Iberian Peninsula or Ukraine, also small regions an districts to the point of singular occurrences of interest are considered. This by far the most comprehensive presentation of European uranium geology and mining would not be possible without the author’s access to extensive information covering the countries of the former Eastern Bloc states, which was partly not previously available. Abundantly illustrated with information-laden maps and charts throughout, this reference work is an indispensable tool for geologists, mining companies, government agencies, and others with an interest in European key natural resources. A great help for the reader’s orientation are the substantial bibliography of uranium-related publications and the indices, latter containing about 3900 entries in the geographical part alone. The three volumes of Uranium Deposits of the World are available as a set or individually. Also accessible (as a set and separate volumes) as an eReference on SpringerLink.com. The originally planned fourth volume with Australia, Oceania, and Africa will not be published after the author suddenly deceased.
Der Falkenberger Granit ist ein porphyrisch ausgebildeter Zweiglimmer-Granit mit bis zu 10 cm großen Kalifeldspatidioblasten in mittel- bis grobkörniger Grundmasse. Südlich schlieSt sich der Leuchtenberger Granit und südöstlich der Flossenbürger Granit an (Abb. 10.1). Eine geochemische Untersuchung von Madel (1975), der die Verteilung der Elemente Li, Na, K, Rb, Ca, Sr, Ba, Ti und Zr mit 155 Probenpunkten und eine Untersuchung des Bayerischen Geologischen Landesamtes, bei der die Elemente U, Th, Sr, Rb und Pb mit 323 Proben flächenhaft bestimmt werden konnten, zeigt, daß nicht nur der ältere Leuchtenberger und der jüngere Flossenbürger Granit als gesonderte Einheit, sondern auch, daß der NW-Teil und der SE-Teil des Falkenberger Granits als getrennte Einheiten anzusehen sind.
Aplites and pegmatites can be correlated with their country rocks using the temporal, the compositional/chemical and physical relationships. The emplacement of pegmatitic rocks began during the early Paleozoic (470–440 Ma) which are encountered as metapegmatites in nappe units in the Bohemian Massif, proper, and in the Ötztal Massif within the Alpine Mts. Range. At the end of the MP-HT metamorphism around 370 Ma pegmatoids came into existence in the allochthonous units. From the core to the margin near the collision zone the granites and the pegmatites get younger. The belong to the Variscan heat event, but a close-up view of some of the pegmatites bear witness of an older cooling age of the muscovite from the HPPP pegmatite than the whole-rock age of the nearby Flossenbürg granite. The pegmatite show different ages as the major-rock-forming silicates and rare-element minerals, e.g. columbite are considered. Considering the element assemblage of the pegmatites and aplites in the Hagendorf-Pleystein-Pegmatite Province reveals that the element has not been derived from one source only. Intracrustal sources may be claimed for Li, F, U, Sn, B, P, As and Mn. Niobium, beryllium and bismuth (?) are of subcrustal derivation. In addition, there are subcrustal - intermediate repositories as it is the case with the Zn, REE and Y. Apart from the granitic intrusive rocks and metamorphic rocks, another group of subcrustal magmatic rocks, (meta)-lamprophyres, has not been drawn the attention to, which they deserve. If the fractionation and zonation in a pegmatite field or province is investigated and an attempt is made to compare these individual pegmatites and aplites with a nearby granite some critical points have to be considered.
Pegmatitic rocks are not randomly distributed across the Variscan/Hercynian basement in Central Europe. The evolution of pegmatites s.l. in the course of a complex orogeny of Meso-Europe took rather long, from the Devonian (419 Ma) through the Permian (252 Ma). In terms of structural geology and geodynamics, pegmatitic deposits primarily occur in ensialic Variscan-type orogens (calc-alkaline) with a thickened crust and a preponderance of thrusting and nappe stacking. In Rift-type settings (alkaline) a strong subcrustal impact is evident and as reactivated/reworked pseudopegmatites in Alpine-type orogens (calc-alkaline) these deposits developed during the initial stages when the crustal section was still rather thick. Both types pertain to the marginal ensimatic settings. They left their hallmarks to some extent also within the Central European Variscides and at its southern edge in the Alpine-Carpathian Orogen. The geodynamic units subjected to very-low-grade- to low-grade stage metamorphism at the margin of the Central European Variscides are barren with regard to pegmatites and aplites. Pegmatoids with minor B-(Li)-P-REE-U-Be mineralization occur along a suture zone extending across the present-day continents. It resulted from the late Variscan closure of the Rheic Ocean between Gondwana and Laurussia with remnants of an arc-related plutonism. Within allochthonous metamorphic complexes and nappes barren feldspar-quartz pegmatoids plus metapegmatites developed. Further south another part of this former coherent nappe also contains a small Be-Nb-P mineralization. Within the Subfluence zone, marked by continent-continent collision and thickening of the crust pegmatite, granite- pegmatite (miarolitic), pegmatite-aplite and pegmatoid abundant in B, Be, F, Li, Sn, U, P and As are encountered. Heading further to the core zone of the Variscan orogen, strong diapthoresis and shearing in the contact zone between the Saxothuringian and Moldanubian zones sensu lato favored the emplacement of pegmatite and aplite enriched in B, P, Be, Nb, As, Zr and F. High grade metamorphic rocks in an autochthonous position with a protolith mainly of Proterozoic age exist in the core zone. At the margin they are overthrusted onto adjacent geodynamic units and penetrated by multiple intrusions. The Hagendorf-Pleystein Pegmatite Province is located near the root zone for the nappe complexes thrusted onto the north-western geodynamic realms. Pegmatites and aplites with minor pegmatoids of the Hagendorf-Pleystein Pegmatite Province show the most varied concentration of rare elements in pegmatitic and aplitic rocks in this crustal section (B-P-REE-Nb/Ta-Li-Sc-Zn-Be). In some parts in core zone pegmatites can also be observed associated with skarns. Variscan lithologies were incorporated into the Alpine orogen and reactivated during the Alpine orogeny at the southern edge of the Meso-Europe. They contain granitic pegmatites, meta-pegmatites, pegmatoids and pseudo-pegmatites (B-Be-P-Nb-U-F-As-Li-Sn-REE-U). By quality this element assemblage is not very much different from that of the neighboring Variscan parent rocks. The suite of pegmatitic and aplitic mineral deposits is associated with mineral deposits of non-pegmatitic origin. They include thrustbound deposits (Au-As-Sb-(Hg)-Fe-Cu-Pb-Zn), plutonic/granite-related deposits (Sn-W-Mo-Pb-Ag-Zn-(In)-Cu-U), and unconformity-related (U-Pb-Zn-F-Ba). While the deposits can at least in parts structurally and compositionally related to the various types of pegmatites and aplites, stratabound deposits are mainly marker deposits for geodynamic units prone to aplitic or pegmatitic rocks in an ensialic orogen (SMS > > VM FeS-Cu-Zn, SEDEX Fe deposits, black-shale –hosted U-Cu-Mo-Sb-Zn-REE (low-grade-large-tonnage) and graphite). As an exception from this rule, the two last-mentioned mineralization with organic compounds can be considered (see geophysical surveys).
Repeatedly changing tectonic regimes during Late Proterozoic-Phanerozoic evolution resulted in the formation of numerous distinct plutonic-volcanic suites (Benek et al. 1973; Collective authorship 1986; Tischendorf et al. 1987b). In times of extensional tectonics, ultramafic and mafic rocks (tholeiitic basalt, ophiolite series, etc.) predominated. In stages soon after compressional movements, however, abundant intermediate to acidic magmas, in addition to subordinate mafic melts, were generated (diorite, granodiorite, monzonite, trachybasalt, lamprophyre, and particularly granitoids). Both mantle and crustal material contributed to the variety of magmatic associations (Fig. 1). Small granitoid intrusions are usually less differentiated; however, the more voluminous plutons exhibit, in most cases, a remarkable evolution from more primitive to strongly evolved and specialized magmatic members.
The crustal structure and the geotectonic development of the Variscan Belt of Europe have been controversial for al long time. Early in this century, F.E.Suess (1912), Kossmat (1927) and others had published thrust-tectonic concepts for the Variscan Belt, which are nothing less but anticipations of modern structural concepts stimulated by plate tectonics. The target area of the present KTB project served, in this early phase of research, as an outstanding example of horizontally directed tectonism. Since this time, the Variscan basement of NE Bavaria has occupied a key role in the ensuing geotectonic debate.
Pegmatitic rocks are very coarse-grained basement rocks abundant in quartz, feldspar or/and mica, in places, endowed either with mega crystals of the aforementioned rock-forming minerals or rare-element minerals. Pegmatites are treated in this study together with aplitic rocks, which are compositionally similar to pegmatites but strikingly different from them by their fine-grained texture. Rocks of the granitic suite take an intermediate position between the two and, locally, they are transitional into both end-member types, emphasized in the denomination by supplements such as aplite granite or pegmatitic granite. A similar scenario can be reported for syenitic and, less frequently, for granodioritic through dioritic rocks which are found to be associated in time and space with pegmatites and aplites.
Most of the U occurrences situated at the western edge of the Bohemian Massif show in their upper parts secondary U minerals. The immigration (P, V, As and Se) from the country rocks and the ore body, via saprolite and paleosoils into the secondary ore minerals is investigated. The P content is suggested to be closely related to hydromorphic paleosoils. From those intermediate stages it may have been brought into the upper parts of the vein structures. No laterogenic impoverishment in the wall rocks with respect to phosphorus or apatite could be determined. The arsenic distributions is also governed as at other sulfide deposits by underlying sulfides and reducing conditions of a primary hypogene ore zone, whereas vanadium content in U secondary minerals is closely related to the enclosing country rocks. Granites, on account of their low content in mafic minerals, have low V contents in U secondary minerals.
Besides the Schwarzach Area, U ore mineralisations from other U occurrences have been investigated. Some of the U deposits are certainly of “per ascensum” origin and their secondary U mineralisation can well be interpreted as having been derived from the underlying primary “black ores”.
However, some mineralisations cannot be classified with certainty as being “per ascensum”. They include some properties pointing to “per ascensum” (e. g. sulfide association) as well as characteristics typical for “per descensum” (small depth, large amounts of U-VI minerals). The mode of formation may in some cases be as follows: Variscan or Alpine ore mineralisations of no economic significance may have formed a reducing environment and caused U to be concentrated. Younger redistribution processes influenced by modern tectonics (uplifting) and the fluviatile drainage pattern have taken place and in some cases destroyed the primary deposits or enhanced the ore mineralisation. These processes roughly resemble those described from sandstone — hosted roll front deposits.
SmNd isotopic results are presented for late-and post-tectonic granitoids, comprising peraluminous granites and subordinate metaluminous dioritic rocks (redwitzites) from the Fichtelgebirge (FG) and Northern Oberpfalz (NOP), NE Bavaria. The data, combined with a number of earlier geochromological studies on these granitoids, place severe constraints on the crustal evolution of this region during the Carboniferous and pre-Carboniferous epoch.Redwitzites range in ϵNd(T) from −4 to 0 (inclusive data from P.K. Holl and coworkers). The ϵNd(T)-values of the granites s.s. are restricted to overlapping ranges of −8 to −3 (FG) and −8 to −2 (NOP). In both domains, the older granites (330-325 Ma) are characterized by ϵNd(T)-values of > −4 whilst the younger granites (315-305 and ∼290 Ma) have ϵNd(T)-values of < −4. The diversity observed in Nd isotopic characteristic is interpreted in terms of different source material. The Nd isotopic compositions of the redwitzites exhibit source heterogeneity suggesting mixing between mantle magma and crust. The Nd isotopic features of the older granites are consistent with the magmatic precursors having been generated by partial melting of pre-existing mature crust variably contaminated by mantle material or, alternatively, by melting of chemically less evolved crust resembling paragneisses of teh ZEV structural unit. The origin of the younger granites can be confidently linked to anatexis of common Moldanubian and Saxothuringian metasediments. Two-stage Nd model ages (TDM) of the granitoids are in the range 1.1–1.7 Ga. These ages provide further support of substantial involvement of pre-Phanerozoic crust in the generation of the granitoids.The Leuchtenberg granite and the G2 and G3 granites yield late Variscan SmNd isochron ages which are concordant with previous RbSr data on these granites. By contrast, the Nd isotopic data for Bärnau and Flossenbürg define pseudo-isochrons suggestive of mixing between contrasting felsic melts.
Dioritic intrusives and granites from the northwestern Bohemian Massif, West Germany were analyzed for the chemical and isotopic composition of Rb-Sr and Sm-Nd. The Marktredwitz intrusive suite and the Tirschenreuth-Mähring sill intrusions yield apparent Rb-Sr whole-rock isochron ages of 468 ± 9 Ma and 470 ± 33 Ma, respectively, while the Reuth-Erbendorf granodiorites display a scatter with an apparent age of 545 ± 16 Ma.The Rb-Sr whole-rock ages conflict with geological evidence: the diorites intruded metamorphic country rocks which experienced an Early Devonian metamorphism. Contact relationships between the diorites and porphyritic granites indicate nearly contemporary emplacement. The intrusion ages of two porphyritic granites from this area have been dated at 319 Ma and 311 Ma.The diorites display a variation in ϵNd (320 Ma) ranging from −1.0 to −4.4, whereas the two granites yield homogeneous initial ϵNd values of −3.7 and −6.6. The variations in elemental concentrations and initial isotopic ratios clearly show a mixing trend within the dioritic rock suites. The mixing partners are a presumably mantle-derived magma and crustal components of varying composition.The isotope systematics of the diorites and the concordance of their Rb-Sr whole-rock age values with Caledonian rock-forming events in Central Europe point to a pre-intrusive Caledonian event inherited in these rocks. We suggest that the diorites were formed by multistage anatectic processes.
More or less intensive supergene redeposition is displayed in the upper parts of all of the U occurrences in the basement rocks of northeastern Bavaria. The secondary U minerals formed during this redeposition — uranophane, torbernite, autunite, uranocircite and saleeite — were dated using the U/Pb and ionium-uranium methods. All of the samples yielded discordant ages. The upper intersection of the discordia with the concordia in the graph of vs. 238U/206Pb can be regarded only in some cases as the age of the primary pitchblende from which the U mineral was formed, whereas in all cases the lower intersection gives the age of the secondary U mineralization. Ages between 0.110 ± 0.006 Ma (by the ionium—uranium method) and 8.6 Ma were obtained; these can be divided into three groups: Group I comprises all of the minerals whose activity ratio was lower than 1. Assuming that there was no 230Th present at the time of mineral formation, ages between 0.110 and 0.164 Ma were calculated for three torbernite occurrences. Group II consists of those U minerals which are in a state of radioactive equilibrium (i.e. older than 0.4 Ma), but which yielded ages between 0 and 3 Ma. Owing to the limited precision of the lower intersections, more accurate dates cannot be given. Group III contains the oldest of the secondary U minerals and is characterized by well-defined ages between 5.6 and 8.4 Ma.
The Saxothuringian zone lies between the Moldanubian block (largely consolidated in late Precambrian time) to the south and the Rhenohercynian zone to the north. It is characterized by exotic blocks of relatively high-grade metamorphic rocks set among very low-grade Palaeozoic sequences. These ‘Zwischengebirge’ (Münchberg, Wildenfels, Frankenberg) were formerly interpreted as metamorphic ‘diapirs’. Recent investigations have led to a revival of the nappe concepts previously proposed by Suess, Wurm, Kossmat and others.
The Münchberg complex is a pile of later Proterozoic to early Palaeozoic volcanic and sedimentary rocks, some now at advanced states of metamophism, in which both stratigraphic sequences and metamorphic grades appear in inverted order. These rocks rest upon a Carboniferous wildflysch, which, in its turn, rests upon an autochthonous Devonian and, locally, a Lower Carboniferous sequence. The flysch material, like the nappes above, was derived from sources in the SE.
Special features of the sedimentary facies, the tectonic deformation, and the state of very low-grade metamorphism, combine with the evidence of a well-developed thrust at the base of the wildflysch sequence to suggest that this sequence should be treated as the lowest tectonic unit in the Münchberg pile of nappes.
Tectonic deformation of the Palaeozoic sequence began with the production of tight to isoclinal, recumbent, NW-facing folds, accompanied and outlasted by subhorizontal thrusting. It was at this time that the nappe-like tectonic units (already in their metamorphic state) were emplaced. An F 2 refolding produced open, upright to SE-facing folds.
A study of illite crystallinity has indicated the significance of a transverse zone, which was the locus of enhanced heat flow throughout the time of deformation, and has confirmed that a metamorphic inversion was introduced when the (relatively strongly metamorphic) wildflysch was thrust over the autochthonous Devonian and Carboniferous.
The Saxothuringian zone shows the closest approach to an alpino-type character found in the northern part of the Variscides. Basin development, deformation and metamorphism are best explained in terms of a model based on horizontal tectonism.
Hercynian S-type granites from the Hauzenberg igneous complex show a range of boron concentration from 1 to 12 ppm. The whole-rock boron data are not significantly correlated with concentrations of other trace elements (Zr, Rb, Ba, Sr, Ni, V, Co, Cu, Zn, F); neither is boron correlated with the major elements (except with sodium) or with the differentiation index (DI). The boron budget in the rock-forming minerals (plagioclase, alkali feldspar, quartz, biotite, muscovite) of the tourmaline-free granites reveals that the highest concentrations of boron occur in muscovite, whereas the greatest amount of boron is incorporated in plagioclase (57-69%) due to its high modal amount. Boron in plagioclase increases with the extent of serialization (obtained by X-ray diffractometry). Muscovite in a pegmatite contains more than 50% of the total boron. The areal distribution of boron within the complex is neither uniform nor random; an increase of boron concentrations from granodioritic to granitic rocks is indicated, whereas the late differentiates are depleted in boron.
Systematic mineralogical and geological studies have been conducted on many unconformity-type uranium deposits. Baryte vein deposits confined to the unconformity between Palaeozoic or Precambrian basement and the Permian-Triassic cover are of widespread occurrence in Central Europe. Age dating carried out on pitchblende predating and postdating baryte, indicates that baryte mineralization took place between Lower Permian and Lower Jurassic times (290 to 200 Ma). The unconformity is considered to be a first-order geohydraulic surface which favoured fluid migration via convective cells. The thermal convection may be related to Variscan granites which might have provided additional heat by the decay of U, Th and K.
This paper presents a new and simple method for the estimation of the water content in hydrous silicate melts. It uses homogenization measurements on melt inclusions in rock-forming minerals (quartz, feldspar, topaz, apatite) in granite and rhyolite rocks from the Erzgebirge, the Slavkovs14 les, the Fichtelgebirge, the Falkenberg granite (Oberpfalz) and Thuringia. The obtained H2O contents of the inclusion melts can approximate to those observed in magmatic melts. Generally, the water contents range from 2.5 to 9 wt.%.
Granitic pluton emplacement and zonation are controlled, among others, by regional deformation and the rate of magma supply. The latter has consequences for the disposition of successively emplaced, more chemically evolved, batches of magma. Our general interpretation is based on a multidisciplinary approach combining field observations, gravity data, internal structures and geochemical variations. Magma feeders are identified in the plutons as the deepest zones, inferred from gravity measurements, when they also correspond to vertical lineations. Correlation of the root zone location with compositional zoning indicate how the magma evolved during emplacement. Two case studies of Hercynian granite plutons illustrate the interpretations: the normally zoned Cabeza de Araya pluton (Spain), and the multiphase Fichtelgebirge pluton (Germany) which displays both normal and reverse zoning. It is proposed that reverse zoning reflects discontinuous magma injection due to a tectonic rate slower than the rate of magma supply. Conversely, normal zoning can occur when magma injection is continuous in time, with successive magma batches entering within not yet crystallized magma. The two case studies illustrate how the understanding of compositional zoning and emplacement of granitic plutons can be improved by multi-disciplinary approaches combining classical and modern techniques.
Uranyl phosphates (torbernite, autunite, uranocircite, saleeite) and hydrated uranyl silicates (normal and beta-uranophane) found in various erosion levels and structures in the Late Variscan granites at the western edge of the Bohemian Massif, Germany, were the target of mineralogical investigations and age dating, using conventional and more advanced techniques such as Laser-Ablation-Inductive-Coupled-Plasma Mass Spectrometry (LA-ICP-MS). Supergene U minerals have an edge over other rock-forming minerals for such studies, because of their inherent ‘clock’ and their swift response to chemical and physical environmental changes on different scales. Uraniferous phoscretes and silcretes, can be used to characterize the alkalinity/acidity of meteoric/per descensum fluids and to constrain the redox conditions during geomorphic processes. This study aims to decipher the geomorphological and palaeohydrological regime that granitic rocks of the Central European Variscides (Moldanubian and Saxothuringian zones) went through during the Neogene and Quaternary in the foreland of the rising Alpine mobile fold belt. The study provides an amendment to the current sub-division of the regolith by introducing the term “hydraulith”, made up of percolation and infiltration zones, for the supergene alteration zone in granitic terrains. It undercuts the regolith at the brink of the phreatic to vadose hydrological zones. Based upon the present geomorphological and mineralogical studies a four-stage model is proposed for the evolution of the landscape in a granitic terrain which might also be applicable to other regions of the European Variscides, considering the hydrological facies changes along with paleocurrent and paleoslope in the basement and the development of the fluvial drainage system in the foreland.
The Spessart Crystalline Complex, north-west Bavaria contains two orthogneiss units of granitic to granodioritic composition, known as the Rotgneiss and Haibach gneiss, respectively, which are structurally conformable with associated metasediments. The igneous origin of the Rotgneiss is apparent from field and textural evidence, whereas strong deformation and recrystallization in the Haibach gneiss has obscured most primary textures. New geochemical data as well as zircon morphology prove the Haibach gneiss to be derived from a granitoid precursor, which was chemically similar to the Rotgneiss protolith, thus suggesting a genetic link between those two rock units. Both gneiss types have chemical compositions typical of anatectic two-mica leucogranites. They show characteristics of both I- and S-type granites. Rb-Sr whole rock data on the Haibach gneiss provide an isochron age of 40714 Ma (IR = 0.70770.0007; MSWD 2.2), which is slightly younger than the published date for the Rotgneiss (43915 Ma; IR=0.70480.0026; MSWD 4.9). Single zircon dating of six idiomorphic grains, using the evaporation method, yielded a mean 207Pb/206Pb age of 41018 Ma for the Haibach gneiss and 41818 Ma for the Rotgneiss. Both zircon ages are within analytical error of the Rb-Sr isochron dates and are interpreted to reflect the time of protolith emplacement in Silurian times. Three xenocrystic zircon grains from the Rotgneiss yielded 207Pb/206Pb ages of 227812, 249013 and 273410 Ma, respectively, suggesting that late Archaean to early Proterozoic crust was involved in the generation of the granite from which the Rotgneiss is derived. Although it is assumed that the granitic protoliths of the two gneisses were formed through anatexis of older continental crust, the relatively low 87Sr/86Sr initial ratios of both gneisses may also indicate the admixture of a mantle component. The Rotgneiss and the Haibach gneiss thus document granitic magmatism at an active continental margin during late Silurian times.
The Rozvadov Pluton is a complex of mainly Variscan granitoid rocks situated near the Bohemian-Bavarian border between Brnau, Tachov, Rozvadov and Waidhaus, 25 km ESE of the KTB site. Five mappable units can be distinguished, which intruded as folows: (1) slightly deformed leucocratic meta-aplite/metapegmatite dykes with garnet and tourmaline; (2) a complex of cordierite-bearing granitoids, which have been divided into three facies (a) biotite granite with cordierite (at the margin of the complex), (b) biotite-cordierite granite and (c) cordierite tonalite (in the centre of the complex; (3) fine-grained biotite granite of the Rozvadov type with associated pegmatite bodies; (4) two-mica Brnau granite; and (5) geochemically specialized albite-zinnwaldite-topaz granite (Krov kmen/Kreuzstein granite) with indications of Sn-Nb-Ta mineralization and associated phosphorus-rich pegmatite cupolas. Rare earth element data suggest that meta-aplite/pegmatite dykes are the result of a batch partial melting process, whereas the compositional variation of the other rock types was mainly controlled by fractional crystallization. The genesis of the cordierite granitoid suite is best explained in terms of a batch melting of metapelitic source followed by crystallization of a cordierite-rich cumulate and K-feldspar enriched melt. The leucocratic pluton constituents — the meta-aplites and the Brnau and Kov kmen granites are rich in phosphorus (0.5–0.8%). The main carriers of phosphorus are alkali feldspars, especially K-feldspar (up to 0.8% P2O5). The presence of P-rich leucocratic granites is one of the features distinguishing the Variscan granitoids within the Moldanubian zone from the nearly contemporaneous granitoids in the Saxothuringian zone.
ResearchGate has not been able to resolve any references for this publication.