@article{ZiemannFoersterHarlovetal.2005, author = {Ziemann, Martin Andreas and F{\"o}rster, Hans-J{\"u}rgen and Harlov, Daniel E. and Frei, Dirk}, title = {Origin of fluorapatite-monazite assemblages in a metamorphosed, sillimanite-bearing pegmatoid, Reinbolt Hills, East Antarctica}, issn = {0935-1221}, year = {2005}, abstract = {Thermobarometrical and mineral-chemical investigations by electron microprobe and LA-ICP-MS on a sillimanite- bearing pegmatoid from the Reinbolt Hills provide important constraints on the P-T-X-age relations of part of East Antarctica during Pan-African tectonism. U-Th-total Pb ages of monazite imply that the pegmatoid of originally Grenvillan age (zircon U-Pb age of ca. 900 Ma) underwent a major, late Pan-African (Cambrian) regional, granulite-facies metamorphism between 500 and 550 Ma. Most of the monazite formed during this event, as result of apatite metasomatism owing to infiltration of high-grade metamorphic fluids. Apatite-biotite and other mineral thermobarometers define the peak metamorphic temperatures and pressures with 850-950 degrees C and 0.8-1.0 GPa. The F-Cl-OH relations in apatite, and biotite, the chemistry of fluid inclusions and the presence of K-feldspar microveins suggest that the metasomatising fluid was a CO2-bearing, diluted KCl brine. The pegmatoid is the first record of monazite-(Ce) formed from fluorapatite that is rich in U (up to 2.6 Wt\% UO2) and possesses Th/U ratios <1 (0.09 on average). These chemical signatures are direct reflection of the U and Th concentration patterns in the parental fluorapatite}, language = {en} } @article{WebsterThomasFoersteretal.2004, author = {Webster, J. D. and Thomas, R. and F{\"o}rster, Hans-J{\"u}rgen and Seltmann, R. and Tappen, C.}, title = {Geochemical evolution of halogen-enriched granite magmas and mineralizing fluids of the Zinnwald tin-tungsten mining district, Erzgebirge, Germany}, issn = {0026-4598}, year = {2004}, abstract = {We remelted and analyzed crystallized silicate melt inclusions in quartz from a porphyritic albitezinnwaldite microgranite dike to determine the composition of highly evolved, shallowly intruded, Li- and F-rich granitic magma and to investigate the role of crystal fractionation and aqueous fluid exsolution in causing the extreme extent of magma differentiation. This dike is intimately associated with tin- and tungsten-mineralized granites of Zinnwald, Erzgebirge, Germany. Prior research on Zinnwald granite geochemistry was limited by the effects of strong and pervasive greisenization and alkali-feldspar metasomatism of the rocks. These melt inclusions, however, provide important new constraints on magmatic and mineralizing processes in Zinnwald magmas. The mildly peraluminous granitic melt inclusions are strongly depleted in CAFEMIC constituents (e.g., CaO, FeO, MgO, TiO2), highly enriched in lithophile trace elements, and highly but variably enriched in F and Cl. The melt inclusions contain up to several thousand ppm Cl and nearly 3 wt\% F, on average; several inclusions contain more than 5 wt\% F. The melt inclusions are geochemically similar to the corresponding whole-rock sample, except that the former contain much more F and less CaO, FeO, Zr, Nb, Sr, and Ba. The Sr and Ba abundances are very low implying the melt inclusions represent magma that was more evolved than that represented by the bulk rock. Relationships involving melt constituents reflect increasing lithophile-element and halogen abundances in residual melt with progressive magma differentiation. Modeling demonstrates that differentiation was dominated by crystal fractionation involving quartz and feldspar and significant quantities of topaz and F-rich zinnwaldite. The computed abundances of the latter phases greatly exceed their abundances in the rocks, suggesting that the residual melt was separated physically from phenocrysts during magma movement and evolution. Interactions of aqueous fluids with silicate melt were also critical to magma evolution. To better understand the role of halogen-charged, aqueous fluids in magmatic differentiation and in subsequent mineralization and metasomatism of the Zinnwald granites, Cl-partitioning experiments were conducted with a F-enriched silicate melt and aqueous fluids at 2,000 bar (200 MPa). The results of the experimentally determined partition coefficients for Cl and F, the compositions of fluid inclusions in quartz and other phenocrysts, and associated geochemical modeling point to an important role of magmatic-hydrothermal fluids in influencing magma geochemistry and evolution. The exsolution of halogen-charged fluids from the Li- and F- enriched Zinnwald granitic magma modified the Cl, alkali, and F contents of the residual melt, and may have also sequestered Li, Sri, and W from the melt. Many of these fluids contained strongly elevated F concentrations that were equivalent to or greater than their Cl abundances. The exsolution of F-, Cl-, Li-, +/- W- and Sn-bearing hydrothermal fluids from Zinnwald granite magmas was important in effecting the greisenizing and alkali-feldspathizing metasomatism of the granites and the concomitant mineralization}, language = {en} } @article{WeberAbuAyyashAbueladasetal.2009, author = {Weber, Michael H. and Abu-Ayyash, Khalil and Abueladas, Abdel-Rahman and Agnon, Amotz and Alasonati-Taš{\´a}rov{\´a}, Zuzana and Al-Zubi, Hashim and Babeyko, Andrey and Bartov, Yuval and Bauer, Klaus and Becken, Michael and Bedrosian, Paul A. and Ben-Avraham, Zvi and Bock, G{\"u}nter and Bohnhoff, Marco and Bribach, Jens and Dulski, Peter and Ebbing, Joerg and El-Kelani, Radwan J. and Foerster, Andrea and F{\"o}rster, Hans-J{\"u}rgen and Frieslander, Uri and Garfunkel, Zvi and G{\"o}tze, Hans-J{\"u}rgen and Haak, Volker and Haberland, Christian and Hassouneh, Mohammed and Helwig, Stefan L. and Hofstetter, Alfons and Hoffmann-Rothe, Arne and Jaeckel, Karl-Heinz and Janssen, Christoph and Jaser, Darweesh and Kesten, Dagmar and Khatib, Mohammed Ghiath and Kind, Rainer and Koch, Olaf and Koulakov, Ivan and Laske, Maria Gabi and Maercklin, Nils}, title = {Anatomy of the Dead Sea transform from lithospheric to microscopic scale}, issn = {8755-1209}, doi = {10.1029/2008rg000264}, year = {2009}, abstract = {Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (similar to 20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the mu m to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.}, language = {en} } @article{WeberAbuAyyashAbueladasetal.2004, author = {Weber, Michael H. and Abu-Ayyash, Khalil and Abueladas, Abdel-Rahman and Agnon, Amotz and Al-Amoush, H. and Babeyko, Andrey and Bartov, Yosef and Baumann, M. and Ben-Avraham, Zvi and Bock, G{\"u}nter and Bribach, Jens and El-Kelani, R. and Forster, A. and F{\"o}rster, Hans-J{\"u}rgen and Frieslander, U. and Garfunkel, Zvi and Grunewald, Steffen and Gotze, Hans-J{\"u}rgen and Haak, Volker and Haberland, Christian and Hassouneh, Mohammed and Helwig, S. and Hofstetter, Alfons and Jackel, K. H. and Kesten, Dagmar and Kind, Rainer and Maercklin, Nils and Mechie, James and Mohsen, Amjad and Neubauer, F. M. and Oberh{\"a}nsli, Roland and Qabbani, I. and Ritter, O. and Rumpker, G. and Rybakov, M. and Ryberg, Trond and Scherbaum, Frank and Schmidt, J. and Schulze, A. and Sobolev, Stephan Vladimir and Stiller, M. and Th,}, title = {The crustal structure of the Dead Sea Transform}, year = {2004}, abstract = {To address one of the central questions of plate tectonics-How do large transform systems work and what are their typical features?-seismic investigations across the Dead Sea Transform (DST), the boundary between the African and Arabian plates in the Middle East, were conducted for the first time. A major component of these investigations was a combined reflection/ refraction survey across the territories of Palestine, Israel and Jordan. The main results of this study are: (1) The seismic basement is offset by 3-5 km under the DST, (2) The DST cuts through the entire crust, broadening in the lower crust, (3) Strong lower crustal reflectors are imaged only on one side of the DST, (4) The seismic velocity sections show a steady increase in the depth of the crust-mantle transition (Moho) from 26 km at the Mediterranean to 39 km under the Jordan highlands, with only a small but visible, asymmetric topography of the Moho under the DST. These observations can be linked to the left-lateral movement of 105 km of the two plates in the last 17 Myr, accompanied by strong deformation within a narrow zone cutting through the entire crust. Comparing the DST and the San Andreas Fault (SAF) system, a strong asymmetry in subhorizontal lower crustal reflectors and a deep reaching deformation zone both occur around the DST and the SAF. The fact that such lower crustal reflectors and deep deformation zones are observed in such different transform systems suggests that these structures are possibly fundamental features of large transform plate boundaries}, language = {en} } @article{TischendorfRiederFoersteretal.2004, author = {Tischendorf, Gerhard and Rieder, M. and F{\"o}rster, Hans-J{\"u}rgen and Gottesmann, B{\"a}rbel and Guidotti, C. V.}, title = {A new graphical presentation and subdivision of potassium micas}, issn = {0026-461X}, year = {2004}, abstract = {A system based on variation of the octahedrally coordinated cations is proposed for graphical presentation and subdivision of tri- and dioctahedral K micas, which makes use of elemental differences (in a.p.f.u.): (Mg - Li) [= mgli] and (Fe-tot + Mn + Ti - Al-VI) [= feal]. All common true tri- and dioctahedral K micas are shown in a single polygon outlined by seven main compositional points forming its vertices. Sequentially clockwise, starting from Mg-3 (phlogopite), these points are: Mg2.5Al0.5, Al(2.167)square(0.833), Al1.75Li1.25, Li2Al (polylithionite), Fe22+Li, and Fe-3(2+) (annite). Trilithionite (Li1.5Al1.5), Li1.5Fe2+Al0.5, Fe22+Mg, and Mg2Fe2+ are also located on the perimeter of the polygon. IMA-siderophyllite (Fe22+Al) and muscovite (Al(2)square) plot inside. The classification conforms with the IMA-approved mica nomenclature and differentiates among the following mica species according to their position in a diagram consisting of nigh and feal axes plotted orthogonally; trioctahedral: phlogopite, biotite, siderophyllite, annite, zinnwaldite, lepidolite and tainiolite: dioctahedral: muscovite, phengite and celadonite. Potassium micas with [Si] <2.5 a.p.f.u. including IMA-siderophyllite, KFe22+AlAl2Si2O10(OH)(2), and IMA-eastonite, KMg2AlAl2Si2O10(OH)(2) seem not to form in nature. The proposed subdivision has several advantages. All common true, trioctahedral and dioctahedral K micas, whether Li-bearing or Li-free, are shown within one diagram, which is easy to use and gives every mica composition an unambiguously defined name. Mica analyses with Fe2+, Fe3+, Fe2+ + Fe3+, or Fe-tot can be considered, which is particularly Valuable for microprobe analyses. It facilitates easy reconstruction of evolutionary pathways of mica compositions during crystallization, a feature having key importance in petrologically oriented research. Equally important, the subdivision has great potential for understanding many of the crystal-chemistry features of the K micas. In turn this may allow one to recognize and discriminate the extent to which crystal chemistry or bulk composition controls the occurrence of some seemingly possible or hypothetical K mica}, language = {en} } @article{ThomasWebsterRhedeetal.2006, author = {Thomas, Rainer and Webster, J. D. and Rhede, Dieter and Seifert, W. and Rickers, Karen and F{\"o}rster, Hans-J{\"u}rgen and Heinrich, Wilhelm and Davidson, P.}, title = {The transition from peraluminous to peralkaline granitic melts: Evidence from melt inclusions and accessory minerals}, series = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, volume = {91}, journal = {Lithos : an international journal of mineralogy, petrology, and geochemistry}, number = {1-4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0024-4937}, doi = {10.1016/j.lithos.2006.03.013}, pages = {137 -- 149}, year = {2006}, abstract = {Fractional crystallization of peraluminous F- and H(2)O-rich granite magmas progressively enriches the remaining melt with volatiles. We show that, at saturation, the melt may separate into two immiscible conjugate melt fractions, one of the fractions shows increasing peraluminosity and the other increasing peralkalinity. These melt fractions also fractionate the incompatible elements to significantly different degrees. Coexisting melt fractions have differing chemical and physical properties and, due to their high density and viscosity contrasts, they will tend to separate readily from each other. Once separated, each melt fraction evolves independently in response to changing T/P/X conditions and further immiscibility events may occur, each generating its own conjugate pair of melt fractions. The strongly peralkaline melt fractions in particular are very reactive and commonly react until equilibrium is attained. Consequently, the peralkaline melt fraction is commonly preserved only in the isolated melt and mineral inclusions. We demonstrate that the differences between melt fractions that can be seen most clearly in differing melt inclusion compositions are also visible in the composition of the resulting ore-forming and accessory minerals, and are visible on scales from a few micrometers to hundreds of meters.}, language = {en} } @article{ThomasFoersterRickersetal.2005, author = {Thomas, R. and F{\"o}rster, Hans-J{\"u}rgen and Rickers, Karen and Webster, J. D.}, title = {Formation of extremely F-rich hydrous melt fractions and hydrothermal fluids during differentiation of highly evolved tin-granite magmas : a melt/fluid-inclusion study}, issn = {0010-7999}, year = {2005}, abstract = {Quartz crystals from topaz-zinnwaldite-albite granites from Zinnwald (Erzgebirge, Germany) contain, in addition to primary and secondary fluid inclusions (FIs), abundant crystalline silicate-melt inclusions (MIs) with diameters up to 200 mum. These MIs represent various stages of evolution of a highly evolved melt system that finally gave rise to granite-related Sn-W mineralization. The combination of special experimental techniques with confocal laser Raman- microprobe spectroscopy and EMPA permits precise measurement of elevated contents of H2O, F, and B in re-homogenized MIs. The contents of H2O and F were observed to increase from 3 to 30 and 1.9 to 6.4 wt\%, respectively, during magma differentiation. However, there is a second MI group, very rich in H2O, with values up to 55 wt\% H2O and an F concentration of approximately 3 wt\%. Ongoing enrichment of volatiles H2O, F, B, and Cl and of Cs and Rb can be explained in terms of magma differentiation triggered by fractional crystallization and thus, is suggested to reflect elemental abundances in natural magmas, and not boundary-layer melts. Partitioning between melt and cogenetic fluids has further modified the magmatic concentrations of some elements, particularly Sn. The coexistence of two types of MIs with primary FIs indicates fluid saturation early in the history of magma crystallization, connected with a continuous sequestration of Sn, F, and B. The results of this study provide additional evidence for the extraordinary importance of the interplay of H2O, F, and B in the enrichment of Sn during magma differentiation by decreasing the viscosity of and increasing the diffusivity in the melts as well as by the formation of various stable fluoride complexes in the melt and coexisting fluid}, language = {en} } @article{ThomasFoersterRickersetal.2004, author = {Thomas, R. and F{\"o}rster, Hans-J{\"u}rgen and Rickers, Karen and Webster, J. D.}, title = {Origin and evolution of extremely F-rich hydrous melt fractions and hydrothermal fluids during differentiation of highly evolved tin-granite magmas}, issn = {0016-7037}, year = {2004}, language = {en} } @article{SeifertRhedeFoersteretal.2009, author = {Seifert, Wolfgang and Rhede, Dieter and F{\"o}rster, Hans-J{\"u}rgen and Thomas, Rainer}, title = {Accessory minerals as fingerprints for the thermal history and geochronology of the Caledonian Rumburk granite}, issn = {0077-7757}, doi = {10.1127/0077-7757/2009/0147}, year = {2009}, abstract = {Accessory minerals of the Caledonian Rumburk granite are investigated to gain insight into its magmatic and post-magmatic evolution history. Recent geothermometers calibrated for trace elements in rutile (Zr), zircon (Ti), and quartz (Ti) were used to determine mineral-formation temperatures, which are compared with T data obtained from melt and fluid-inclusion Studies on quartz. Improved electron-microprobe analytical conditions allowed distinguishing several generations of rutile. Submicron-sized rutile needles included in quartz crystallized at around 739 +/- 13 degrees C and, thus, are evidently magmatic. Simultaneous crystallization of the high-T rutile and quartz is the favoured concept compared with an exsolution model for the needles. Th-U-total Pb dating of xenotime-(Y) by electron microprobe yielded a bimodal age distribution of 494 +/- 8 Ma (2 sigma; n = 44) and 311 +/- 8 Ma (2 sigma; n = 48), which is missing in monazite-(Ce). The older age correlates with the early Ordovician granite emplacement age Suggested by earlier isotopic Studies. The younger Carboniferous age also may be geologically reasonable, because the granite experienced a minor tectonothermal overprint during the Variscan orogenesis. However, whether this event has caused the resetting of the isotopic system in the xenotime is uncertain. This also holds for the age of the partial breakdown of monazite and xenotime into reaction coronas composed of fluorapatite, allanite-(Ce), epidote +/- clinozoisite. This alteration assemblage was likely produced already during autometasomatic reworking of the solidifying magma in Ordovician time, but it cannot be excluded that it relates to a Carboniferous fluid imprint connected with late-Variscan processes.}, language = {en} } @article{KeutschFoersterStanleyetal.2009, author = {Keutsch, Frank N. and F{\"o}rster, Hans-J{\"u}rgen and Stanley, Chris J. and Rhede, Dieter}, title = {The discreditation of hastite, the orthorhombic dimorph of CoSe2, and observations on trogtalite, cubic CoSe2, from the type locality}, issn = {0008-4476}, doi = {10.3749/canmin.47.4.969}, year = {2009}, abstract = {"Hastite", the orthorhombic dimorph of CoSe2, formerly considered as a valid mineral species occurring in the Trogtal quarries, Harz Mountains, Germany, is discredited as being identical with ferroselite, orthorhombic FeSe2. The discreditation has been unanimously approved by the IMA Commission on New Minerals, Nomenclature and Classification (CNMNC) (IMA No. 07-E). We also provide observations on the composition, homogeneity, and origin of trogtalite (cubic CoSe2) from its type locality.}, language = {en} } @article{HarlovWirthFoerster2005, author = {Harlov, Daniel E. and Wirth, R. and F{\"o}rster, Hans-J{\"u}rgen}, title = {An experimental study of dissolution-reprecipitation in fluorapatite : fluid infiltration and the formation of monazite}, issn = {0010-7999}, year = {2005}, abstract = {In a series of timed experiments, monazite inclusions are induced to form in the Durango fluorapatite using 1 and 2 N HCl and H2SO4 solutions at temperatures of 300, 600, and 900 degrees C and pressures of 500 and 1,000 MPa. The monazite inclusions form only in reacted areas, i.e. depleted in (Y+REE)+Si+Na+S+Cl. In the HCl experiments, the reaction front between the reacted and unreacted regions is sharp, whereas in the H2SO4 experiments it ranges from sharp to diffuse. In the 1 N HCl experiments, Ostwald ripening of the monazite inclusions took place both as a function of increased reaction time as well as increased temperature and pressure. Monazite growth was more sluggish in the H2SO4 experiments. Transmission electron microscopic (TEM) investigation of foils cut across the reaction boundary in a fluorapatite from the 1 N HCl experiment (600 degrees C and 500 MPa) indicate that the reacted region along the reaction front is characterized by numerous, sub-parallel, 10-20 nm diameter nano-channels. TEM investigation of foils cut from a reacted region in a fluorapatite from the 1 N H2SO4 experiment at 900 degrees C and 1,000 MPa indicates a pervasive nano- porosity, with the monazite inclusions being in direct contact with the surrounding fluorapatite. For either set of experiments, reacted areas in the fluorapatite are interpreted as replacement reactions, which proceed via a moving interface or reaction front associated with what is essentially a simultaneous dissolution-reprecipitation process. The formation of a micro- and nano-porosity in the metasomatised regions of the fluorapatite allows fluids to permeate the reacted areas. This permits rapid mass transfer in the form of fluid-aided diffusion of cations to and from the growing monazite inclusions. Nano-channels and nano-pores also serve as sites for nucleation and the subsequent growth of the monazite inclusions}, language = {en} } @article{HarlovTropperSeifertetal.2006, author = {Harlov, Daniel E. and Tropper, Peter and Seifert, Wolfgang and Nijland, Timo and F{\"o}rster, Hans-J{\"u}rgen}, title = {Formation of Al-rich titanite (CaTiSiO4O-CaAlSiO4OH) reaction rims on ilmenite in metamorphic rocks as a function of fH(2)O and fO(2)}, issn = {0024-4937}, doi = {10.1016/j.lithos.2005.08.005}, year = {2006}, abstract = {Reaction rims of titanite on ilmenite are described in samples from four terranes of amphibolite-facies metapelites and amphibolites namely the Tamil Nadu area, southern India; the Val Strona, area of the Ivrea-Verbano Zone, northern Italy, the Bamble Sector, southern Norway, and the northwestern Austroalpine Otztal Complex. The titanite rims, and hence the stability of titanite (CaTiSiO4O) and Al-OH titanite, i.e. vuaganatite (hypothetical end-member CaAlSiO4OH), are discussed in the light of fH(2)O- and fO(2)-buffered equilibria involving clinopyroxene, amphibole, biotite, ilmenite, magnetite, and quartz in the systems CaO-FeO/Fe2O3-TiO2-SiO2-H2O-O-2 (CFTSH) and CaO-FeO/Fe2O3-Al2O3- SiO2-H2O-O-2 (CFASH) present in each of the examples. Textural evidence suggests that titanite reaction rims on ilmenite in rocks from Tamil Nadu, Val Strona, and the Bamble Sector originated most likely due to hydration reactions such as clinopyroxene + ilmenite +quartz+ H2O = amphibole +titanite and oxidation reactions such as amphibole + ilmenite + O-2 = titanite + magnetite + quartz + H2O during amphibolite-facies metamorphism, or, as in the case of the Otztal Complex, during a subsequent greenschist-facies overprint. Overstepping of these reactions requires fH(2)O and fO(2) to be high for titanite formation, which is also in accordance with equilibria involving Al-OH titanite. This study shows that, in addition to P, T, bulk-rock composition and composition of the coexisting fluid, fO(2) and fH(2)O also play an important role in the formation of Al-bearing titanite during amphibolite- and greenschist-facies metamorphism.}, language = {en} } @article{HarlovProchazkaFoerster2005, author = {Harlov, Daniel E. and Prochazka, V. and F{\"o}rster, Hans-J{\"u}rgen}, title = {Monazite-zircon-fluorapatite associations in the Melechov granite massif, Czech Republic}, issn = {0016-7037}, year = {2005}, language = {en} } @article{HarlovJohanssonVanDenKerkhofetal.2006, author = {Harlov, Daniel E. and Johansson, L. and Van Den Kerkhof, A. and F{\"o}rster, Hans-J{\"u}rgen}, title = {The role of advective fluid flow and diffusion during localized, solid-state dehydration : Sondrum Stenhuggeriet, Halmstad, SW Sweden}, issn = {0022-3530}, year = {2006}, abstract = {A localized dehydration zone, Sondrum stone quarry, Halmstad, SW Sweden, consists of a central, 1 m wide granitic pegmatoid dyke, on either side of which extends a 2.5-3 m wide dehydration zone (650-700 degrees C; 800 MPa; orthopyroxene-clinopyroxene-biotite-amphibole-garnet) overprinting a local migmatized granitic gneiss (amphibole-biotite- garnet). Whole-rock chemistry indicates that dehydration of the granitic gneiss was predominantly isochemical. Exceptions include [Y + heavy rare earth elements (HREE)], Ba, Sr, and F, which are markedly depleted throughout the dehydration zone. Systematic trends in the silicate and fluorapatite mineral chemistry across the dehydration zone include depletion in Fe, (Y + HREE), Na, K, F, and Cl, and enrichment in Mg, Mn, Ca, and Ti. Fluid inclusion chemistry is similar in all three zones and indicates the presence of a fluid containing CO2, NaCl, and H2O components. Water activities in the dehydration zone average 0.36, or XH2O = 0.25. All lines of evidence suggest that the formation of the dehydration zone was due to advective transport of a CO2-rich fluid with a minor NaCl brine component originating from a tectonic fracture. Fluid infiltration resulted in the localized partial breakdown of biotite and amphiboles to pyroxenes releasing Ti and Ca, which were partitioned into the remaining biotite and amphibole, as well as uniform depletion in (Y + HREE), Ba, Sr, Cl, and F. At some later stage, H2O-rich fluids (H2O activity > 0.8) gave rise to localized partial melting and the probable injection of a granitic melt into the tectonic fracture, which resulted in the biotite and amphibole recording a diffusion profile for F across the dehydration zone into the granitic gneiss as well as a diffusion profile in Fe, Mn, and Mg for all Fe-Mg silicate minerals within 100 cm of the pegmatoid dyke}, language = {en} } @article{GottesmannFoerster2004, author = {Gottesmann, B{\"a}rbel and F{\"o}rster, Hans-J{\"u}rgen}, title = {Sekaninaite from the Satzung granite (Erzgebirge, Germany) : magmatic or xenolithic?}, issn = {0935-1221}, year = {2004}, abstract = {In the earliest emplaced granite subintrusion of the multiphase peraluminous Satzung pluton, Erzgebirge, Germany, a mineral aggregate was observed consisting of sekaninaite (X-Fe = 0.74-0.94), Zn-rich hercynite (X-Zn = 0.03- 0.11), tri- and dioctahedral layer silicates of different composition and color, and minor quartz. Geological, textural, and compositional criteria argue that the sekaninaite, hercynite, quartz, and the brown biotite are not primary or secondary granite minerals, but are of metamorphic origin representing a xenolith uptaken from the granite melt near its level of emplacement. The metamorphic origin is supported by the occurrence of this mineral assemblage in metamorphic rocks exposed locally in the Erzgebirge basement. Reaction of the polymineralic metamorphic aggregate with the surrounding melt and subsequent interaction with alkali-, F- and LILE-rich residual fluids account for the widespread decomposition of the sekaninaite and formation of several layer silicates including green biotite, muscovite, berthierine/Fe chlorite, and sericite. The observed enrichment of the relic sekaninaite and its replacement products in elements such as Na, Li, Be, Rb, Cs, and F is result of interaction of the metamorphic fragment with the surrounding melt/fluid, in accordance with the evolved nature of the Satzung magmatic-hydrothermal system}, language = {en} } @article{FoersterTischendorfRhedeetal.2005, author = {F{\"o}rster, Hans-J{\"u}rgen and Tischendorf, Gerhard and Rhede, Dieter and Naumann, R. and Gottesmann, B{\"a}rbel and Lange, W}, title = {Cs-rich lithium micas and Mn-rich lithian siderophyllite in miarolitic NYF pegmatites of the Konigshain granite, Lausitz, Germany}, year = {2005}, abstract = {Annite and Fe-rich siderophyllite constitute the rock-forming micas in the late-Variscan composite granite pluton of Konigshain, Lausitz, Germany. This multiphase pluton is composed of three fractionated, but not chemically specialized monzogranite types, which contain lithophile elements such as Li, Rb, Cs, Sn, and F in average quantities. Abundant miarolitic pegmatites of the NYF family with a broad diversity of rare minerals occur in the apical part of the pluton. These pegmatitic cavities locally contain di- and trioctabedral micas as well as cation-deficient micas. Trioctahedral micas comprise F-rich manganoan lithian siderophyllite to manganoan zinnwaldite, zinnwaldite, and minor lepidolite. The formula [calculated on the basis of 22 anion valencies and 2 (F + OH + Cl)] of the most Mn-rich siderophyllite is (K0.85Rb0.08Na0.04)(0.97)(Al0.99Li0.91Fe0.51Mn0.42Ti0.01Zn0.01)(2.85) (Si3.21Al0.79)(4)O- 10(F1.80OH0.19Cl0.01)(2). This mica constitutes one of the most Mn-rich siderophyllite compositions reported to date. The lithium micas poorer in Mn are distinguished by elevated concentrations of Rb (up to 2.5 wt \% Rb2O), CS (UP to 1.2 wt \% Cs2O), and F (up to 9.6 wt \%). This fluorine content is probably consistent with the maximum possible F occupation of 2 of the (F,OH,Cl)-site. The structural formula of the most Li-rich lepidolite is (K0.83Rb0.07Cs0.03)(0.93) (Li1.62Al1.00Fe0.38)(3.00)(Si3.62Al0.38)(4) O-10(F1.91OH0.09)(2). During hydrothermal alteration, lepidolite and zinnwaldite became partially depleted in K, Li, Rb, Cs, and F and gradually transformed into cation-deficient micas (lithian phengite to illite of phengitic affinity)}, language = {en} } @article{FoersterTischendorfRhede2005, author = {F{\"o}rster, Hans-J{\"u}rgen and Tischendorf, Gerhard and Rhede, Dieter}, title = {Mineralogy of the Niederschlema-Alberoda U-Se-polymetallic deposit, Erzgebirge, Germany. v. watkinsonite, nevskite, bohdanowiczite and other bismuth minerals}, year = {2005}, abstract = {The uranium deposit at Niederschlema-Alberoda, Germany, contains a rich variety of Bi minerals deposited between the Permian and the Cretaceous; these have been studied for paragenetic relations, composition, and conditions of formation. Particular attention is given to the rare Bi selenides watkinsonite, nevskite, and cuproan bohdanowiczite. Whereas watkinsonite and nevskite only occur intergrown with clausthalite, bohdanowiczite is more widespread and also is associated with Cu selenides. Watkinsonite from this second confirmed locality worldwide has an average composition (Cu1.47Ag0.49)(Sigma 1.96)(Pb1.01Hg0.01 Fe-0.01)(Sigma 1.03)Bi-3.98(Se7.98S0.05)(Sigma 8.03), ideally (Cu,Ag)(2)PbBi4Se8. These findings suggest that the empirical formula of watkinsonite originally proposed for the type specimen from the Otish Mountains uranium deposit in Quebec [CU2+xPb1+xBi4-xSe,S,Te)(8), x approximate to 0.3] requires revision. The composition of nevskite is (Pb0.06Bi0.95)(Sigma 1.01)Se-0.99, on average. Bohdanowiczite from the Cu- selenide assemblage shows extensive substitution of Cu+ for Ag+, expressed by the crystallochemical formula (Ag1.80- 0.94CU0.16-1.05Pb0.00-0.05)(Sigma 1.97-2.07)BiSigma 1.97-2.03SeSigma 3.96-4.04. This observation seems to argue for the natural existence of CU2Bi2Se4, the Se-dominant analogue of emplectite. The Bi selenides were deposited at temperatures of about 100 degrees C, in the Jurassic. The lack of thermodynamic data for all the Bi selenides limits reliable inferences on the fugacities of selenium and sulfur that prevailed during their formation. Other Bi minerals from this locality comprise members of the bismuthinite-aikinite solid-solution series of Permian age and, more importantly, native Bi and Bi sulfides (matildite, bismuthinite, wittichinite), deposited in the Cretaceous}, language = {en} } @article{FoersterRomerGottesmannetal.2009, author = {F{\"o}rster, Hans-J{\"u}rgen and Romer, Rolf L. and Gottesmann, B{\"a}rbel and Tischendorf, Gerhard and Rhede, Dieter}, title = {Are the granites of the Aue-Schwarzenberg Zone (Erzgebirge, Germany) a major source for metalliferous ore deposits? : a geochemical, Sr-Nd-Pb isotopic, and geochronological study}, issn = {0077-7757}, doi = {10.1127/0077-7757/2009/0138}, year = {2009}, abstract = {The Aue-Schwarzenberg Granite Zone (ASGZ), in the western Erzgebirge of Germany, is composed of small, late- Variscan F-poor biotite and two-mica granites. The biotite granites (Aue granite suite, Beierfeld, Bernsbach) are weakly to mildly peraluminous (A/CNK = 1.07-1.14; 70-76 wt\% SiO2), display similar Sr-87/Sr-86 initial ratios (0.7065-0.7077; t = 325 Ma), and exhibit a narrow range in epsilon Nd-325 (-2.6 to -3.5). They are closely affiliated compositionally with the biotite granites in the distant, more voluminous Nejdek massif (Czech Republic). The two-mica granites (Schwarzenberg granite suite, Lauter) are Si-rich (74-77 wt\% SiO2) and mildly to strongly peraluminous (A/CNK = 1.17- 1.26). The granites from Schwarzenberg Lire distinctly higher in their Sr(i)ratios (0.709-0.713; t = 325 Ma) and possess lower values of epsilon Nd-325 (-4.9 to -5.2) relative to the biotite granites. The Lauter granites have a Nd-isotopic composition between -3.6 and -4.0 (t = 325 Ma). Mean Th-U-total Pb uraninite ages (Ma +/- 2 sigma) obtained for the granites from the Aue Suite (324.3 +/- 3. 1), Beierfeld (323.7 +/- 3.1), Bernsbach (320.7 +/- 2.9), Schwarzenberg (323.3 +/- 2.4), and the Kirchberg granite al Burkersdorf (322.7 +/- 3.5) indicate that magmatism in the ASGZ commenced in the Namurian and took place early within the major episode of granite formation in the Erzgebirge-Vogtland zone (327-318 Ma). Geochemical and mineralogical patterns of variably altered samples imply that the ASGZ granites are unlikely to have significantly contributed to the formation of spatially associated metalliferous ore deposits (Sn, W, Mo, Ph, Zn, Bi, Co, Ni), except for uranium. In particular the Aue granite suite should have served as major Source for U accumulated in the economically important post-granitic deposits of Schneeberg and Schlema-Alberoda.}, language = {en} } @article{FoersterRhedeTischendorf2004, author = {F{\"o}rster, Hans-J{\"u}rgen and Rhede, Dieter and Tischendorf, Gerhard}, title = {Mineralogy of the Niederschlema-Alberoda U-Se-polymetallic deposit, Erzgebirge, Germany : I. Jolliffeite, NiAsSe, the rare Se-dominant analogue of gersdorffite}, year = {2004}, abstract = {The Niederschlema-Alberoda uranium deposit, in the Erzgebirge region of Germany, contains an uncommon assemblage of metallic minerals, in particular selenides, sulfides, arsenides, tellurides, and native elements, in addition to uraninite and coffinite. The complex mineralogy resulted from the superposition of several mineralizing events over the time interval from the Permian to the Cretaceous; these events introduced and redeposited a great variety of metallic elements within the hydrothermal uranium deposit (Pb, Ag, Cu, Hg, Tl, Bi, Co, Ni, As, Sb, Se, S, Te). One of the exotic minerals is jolliffeite, an arsenoselenide with end-member composition NiAsSe, so far only known from Lake Athabasca, Saskatchewan, Canada. A single, small, anhedral grain of jolliffeite from Niederschlema-Alberoda is included and partly replaced by sulfurian eskebornite. Associated minerals comprise hematite, Ni-Co-Se-bearing lollingite, clausthalite, tiemannite, mercurian hakite-giraudite solid solutions, sulfurian berzelianite, sulfurian umangite, hessite, Ni-Co-As-bearing pyrite, and Se-rich chalcopyrite. The sulfurian jolliffeite has the empirical formula (Ni0.85Cu0.09Co0.05Fe0.02Ag0.01)Sigma(1.02)As(0.98)(Se0.77S0.23)(Sigma1. 00) and differs from type jolliffeite mainly by substantial substitution of Cu (2.6-3.3 wt.\%) for Ni and S (3.2-4.1 wt.\%) for Se. Substantial S-for-Se substitution in jolliffeite implies extensive and probably complete miscibility between NiAsSe and its S-dominant analogue, gersdorffite-Pa3 (NiAsS). We suggest that a localized accumulation of Ni and As in the Se-(S)-bearing hydrothermal fluid gave rise to the crystallization of jolliffeite at some rare locations at a late stage of formation of the Jurassic selenide assemblage}, language = {en} } @article{FoersterRhede2006, author = {F{\"o}rster, Hans-J{\"u}rgen and Rhede, Dieter}, title = {The Be-Ta-rich granite of Seiffen (eastern Erzgebirge, Germany)}, series = {Neues Jahrbuch f{\"u}r Mineralogie : Abhandlungen}, volume = {182}, journal = {Neues Jahrbuch f{\"u}r Mineralogie : Abhandlungen}, number = {3}, publisher = {Schweizerbart}, address = {Stuttgart}, issn = {0077-7757}, doi = {10.1127/0077-7757/2006/0055}, pages = {307 -- 321}, year = {2006}, abstract = {The mildly peraluminous granite of Seiffen, in the eastern Erzgebirge of Germany, is exposed by drillcores and associated with an abandoned Sri mine. The granite is of Stefanian age, with overlapping Th-U-total Pb monazite (302 +/- 4 Ma) and K-Ar siderophyllite ages (301 +/- 5 Ma). It is among the youngest granites in the Erzgebirge, emplaced in an extensional setting. The medium-grained, equigranular granite classifies as high-F, low-P Li-mica granite of A-type affinity. It is spatially associated with a high-Si rhyolitic microgranite, documenting the shallow intrusion level of this igneous association. Zircon, monazite-(Ce), and xenotime-(Y) constitute important radioactive accessory minerals in the granite, hosting the major proportions (> 80-90\%) of the bulk-rock budgets of the REE, Y, and Th. A significant percentage of U (40-50\%) may reside within unidentified phases or precipitated along grain boundaries. The most uncommon accessory phase is late-magmatic ytterbian xenotime-(Y) containing up to 11.2 wt\% Yb2O3, in addition to 7.3 wt\% Er2O3 and 7.9 wt\% Dy2O3. The Seiffen granite (epsilon(Nd(300)) = -4.6) is geochemically evolved and rich in Sri (23-63 ppm) and W (11-14 ppm). It contains elevated to high concentrations of incompatible lithophile elements such as F, Li, Ga, Rb, Y, Nb, Cs, REE, Th, and U, thus having much in common chemically with subvolcanic ongonites. The most prominent compositional feature is the strong enrichment (in ppm) in Be (51-55) and Ta (23-28). The granite exhibits flat chondrite-normalized REE patterns (La-N/Lu-N = 1.35-1.48) and a moderate negative Eu anomaly (Eu/Eu* = 0.12-0.13). Indications for alteration-induced, postmagmatic disturbances of initial elemental abundances are weak and mainly relate to the ore-forming elements Sri and U.}, language = {en} }