TY - JOUR A1 - Weber, Michael H. A1 - Abu-Ayyash, Khalil A1 - Abueladas, Abdel-Rahman A1 - Agnon, Amotz A1 - Al-Amoush, H. A1 - Babeyko, Andrey A1 - Bartov, Yosef A1 - Baumann, M. A1 - Ben-Avraham, Zvi A1 - Bock, Günter A1 - Bribach, Jens A1 - El-Kelani, R. A1 - Forster, A. A1 - Förster, Hans-Jürgen A1 - Frieslander, U. A1 - Garfunkel, Zvi A1 - Grunewald, Steffen A1 - Gotze, Hans-Jürgen A1 - Haak, Volker A1 - Haberland, Christian A1 - Hassouneh, Mohammed A1 - Helwig, S. A1 - Hofstetter, Alfons A1 - Jackel, K. H. A1 - Kesten, Dagmar A1 - Kind, Rainer A1 - Maercklin, Nils A1 - Mechie, James A1 - Mohsen, Amjad A1 - Neubauer, F. M. A1 - Oberhänsli, Roland A1 - Qabbani, I. A1 - Ritter, O. A1 - Rumpker, G. A1 - Rybakov, M. A1 - Ryberg, Trond A1 - Scherbaum, Frank A1 - Schmidt, J. A1 - Schulze, A. A1 - Sobolev, Stephan Vladimir A1 - Stiller, M. A1 - Th, T1 - The crustal structure of the Dead Sea Transform N2 - 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 Y1 - 2004 ER - TY - JOUR A1 - Fuchs, Sven A1 - Förster, Hans-Jürgen A1 - Braune, K. A1 - Förster, A. T1 - Calculation of Thermal Conductivity of Low-Porous, Isotropic Plutonic Rocks of the Crust at Ambient Conditions From Modal Mineralogy and Porosity BT - a Viable Alternative for Direct Measurement? JF - Journal of geophysical research : Solid earth N2 - Thermal conductivity (lambda) is an essential physical property of minerals and rocks and fundamental in constraining the thermal field of the lithosphere. In case that adequate samples to measure lambda are not available, it could be indirectly inferred from calculation. One of the most widely applied indirect methods for rocks involve modal mineralogy and porosity as parameters that are incorporated into mathematical mean or mixing models. Robust inferences from these approaches for crystalline rocks were impeded by a small number of studied samples or restriction to certain rock types. We employ this method and examine its applicability to low-porosity plutonic rocks by calculating bulk thermal conductivity lambda(b) for 45 samples covering the entire range from gabbro/diorite to granite. We show that the use of the harmonic-mean model for both rock matrix and porosity provided a good match between lambda(b.meas) and lambda(b.calc) of <10% deviation (2 sigma), with relative and absolute errors amounting to 1.49.7% and 4.44.9%, respectively. The results of our study constitute a big step forward to a robust conclusion on the overall applicability of the harmonic-mean model for inferring lambda(b) of isotropic, low-porosity, mafic to silicic plutonic and metamorphic rocks with an acceptable magnitude of error. Drill cuttings and enclaves form particularly interesting objects for application of this method, as they are poorly suited for direct measurement. Well-derived lambda values for those rocks would permit to calculate heat flow and to model more profoundly the thermal state of the deeper lithosphere. Y1 - 2018 U6 - https://doi.org/10.1029/2018JB016287 SN - 2169-9313 SN - 2169-9356 VL - 123 IS - 10 SP - 8602 EP - 8614 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Förster, Hans-Jürgen A1 - Förster, Andrea A1 - Oberhänsli, Roland A1 - Stromeyer, Dietrich T1 - Lithospheric composition and thermal structure of the Arabian Shield in Jordan N2 - In this paper, a unique set of samples from the uppermost crust down to the lithospheric mantle of Jordan is analyzed for composition and petrophysical properties (density. thermal conductivity, radiogenic heat production) These data, covering a vertical section of almost 65 km. are used in conjunction with surface heat flow to generate a detailed and comprehensive lithospheric thermal model that reflects the conditions of the Arabian Shield (AS) prior to the post- Oligocene onset of lithosphere thinning and Voluminous basaltic volcanism. The pre-Miocene model geotherms, based on conductive surface heat flows of 55 and 60 mW m(-2). (a) meet the range of lithosphere-asthenosphere boundary depths of 110-160 km known from seismology, (b) conform to results of thermomechanical models on the on.-in of the Dead Sea basin that started in Miocene time. and (c) are consistent with typical xenolith-derived geotherms for terranes of similar age and lithospheric thickness. Moho temperatures (at depths between 35 and 40 km) of the AS in pre-Miocene times were most likely in the order of 530-650 degrees C, with mantle heat flows averaging between 24 and 29 mW m(-2) Results contradict former views of the late Proterozoic/early Cambrian-stabilized AS being an anomalously cold terrane A "cold" thermal structure inferred from previously measured low surface heat flows (generally <= 45 mW m(-2)) is inconsistent with the thickness, composition, and petrophysical properties of the stable lithosphere of the shield. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00401951 U6 - https://doi.org/10.1016/j.tecto.2008.11.014 SN - 0040-1951 ER - TY - JOUR A1 - Weber, Michael H. A1 - Abu-Ayyash, Khalil A1 - Abueladas, Abdel-Rahman A1 - Agnon, Amotz A1 - Alasonati-Tašárová, Zuzana A1 - Al-Zubi, Hashim A1 - Babeyko, Andrey A1 - Bartov, Yuval A1 - Bauer, Klaus A1 - Becken, Michael A1 - Bedrosian, Paul A. A1 - Ben-Avraham, Zvi A1 - Bock, Günter A1 - Bohnhoff, Marco A1 - Bribach, Jens A1 - Dulski, Peter A1 - Ebbing, Joerg A1 - El-Kelani, Radwan J. A1 - Foerster, Andrea A1 - Förster, Hans-Jürgen A1 - Frieslander, Uri A1 - Garfunkel, Zvi A1 - Götze, Hans-Jürgen A1 - Haak, Volker A1 - Haberland, Christian A1 - Hassouneh, Mohammed A1 - Helwig, Stefan L. A1 - Hofstetter, Alfons A1 - Hoffmann-Rothe, Arne A1 - Jaeckel, Karl-Heinz A1 - Janssen, Christoph A1 - Jaser, Darweesh A1 - Kesten, Dagmar A1 - Khatib, Mohammed Ghiath A1 - Kind, Rainer A1 - Koch, Olaf A1 - Koulakov, Ivan A1 - Laske, Maria Gabi A1 - Maercklin, Nils T1 - Anatomy of the Dead Sea transform from lithospheric to microscopic scale N2 - 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. Y1 - 2009 UR - http://www.agu.org/journals/rg/ U6 - https://doi.org/10.1029/2008rg000264 SN - 8755-1209 ER - TY - JOUR A1 - Förster, Hans-Jürgen A1 - Rhede, Dieter T1 - The Be-Ta-rich granite of Seiffen (eastern Erzgebirge, Germany) BT - accessory-mineral chemistry, composition, and age of a late-Variscan Li-F granite of A-type affinity JF - Neues Jahrbuch für Mineralogie : Abhandlungen N2 - 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. KW - Li-F granite KW - Th-U-Pb monazite age KW - beryllium KW - tantalum KW - ytterbian xenotime-(Y) KW - ongonite KW - post-collisional setting Y1 - 2006 U6 - https://doi.org/10.1127/0077-7757/2006/0055 SN - 0077-7757 VL - 182 IS - 3 SP - 307 EP - 321 PB - Schweizerbart CY - Stuttgart ER - TY - JOUR A1 - Thomas, Rainer A1 - Webster, J. D. A1 - Rhede, Dieter A1 - Seifert, W. A1 - Rickers, Karen A1 - Förster, Hans-Jürgen A1 - Heinrich, Wilhelm A1 - Davidson, P. T1 - The transition from peraluminous to peralkaline granitic melts: Evidence from melt inclusions and accessory minerals JF - Lithos : an international journal of mineralogy, petrology, and geochemistry N2 - 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. KW - granite melts KW - magma evolution KW - melt inclusions KW - melt-melt immiscibility KW - peraluminosity KW - peralkalinity KW - accessory minerals Y1 - 2006 U6 - https://doi.org/10.1016/j.lithos.2006.03.013 SN - 0024-4937 VL - 91 IS - 1-4 SP - 137 EP - 149 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Harlov, Daniel E. A1 - Tropper, Peter A1 - Seifert, Wolfgang A1 - Nijland, Timo A1 - Förster, Hans-Jürgen T1 - Formation of Al-rich titanite (CaTiSiO4O-CaAlSiO4OH) reaction rims on ilmenite in metamorphic rocks as a function of fH(2)O and fO(2) N2 - 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. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00244937 U6 - https://doi.org/10.1016/j.lithos.2005.08.005 SN - 0024-4937 ER - TY - JOUR A1 - Förster, Hans-Jürgen T1 - Composition and origin of intermediate solid solutions in the system thorite-xenotime-zircon-coffinite N2 - A comprehensive survey of the accessory-mineral assemblages in Variscan granites of the German Erzgebirge and Pan-African granites from Jordan revealed the occurrence of intermediate solid solutions of the tetragonal thorite- xenotime-zircon-coffinite mineral group with partially novel compositions. These solid solutions preferentially formed in evolved and metasomatically altered, P-poor leucogranites of either I- or A-type affinity. Thorite from the Erzgebirge contained up to 18-8 Wt-% Y2O3, 16.1 wt.% ZrO2, and 23.3 Wt-% UO2. Xenotime and zircon have incorporated Th in abundances up to 36.3 wt.% and 41.8 wt.% ThO2, respectively. Extended compositional gradation with only minor gaps is confined to hydrated members of this mineral group, and is observed to exist between thorite and xenotime, thorite and coffinite, and Y-HREE-bearing thorite and zircon. Complex, hydrous solid solutions containing elevated abundances of three or more of the endmembers are subordinate. Previously reported intermediate solid solutions between anhydrous zircon and xenotime, and anhydrous zircon and thorite, are not observed and are in conflict with experimental work demonstrating very limited miscibility between anhydrous species of endmember composition. The majority of hydrous intermediate solid solutions in the Th-Y-Zr-U system are likely thermodynamically unstable. Instead, they are probably metastable responses to unusual physico-chemical conditions involving various parameters and conditions, the relative importance of which is incompletely known. Leaching and dissolution of preexisting accessory phases during interaction with F-bearing hydrous fluids enriched in Th, Y(HREE), Zr, and/or U, and common deposition of the various elements at disequilibrium (supersaturation) seems to play a key role, but other processes may be of similar importance. Experimental work involving hydrous conditions and complex systems composed of more than two endmembers are needed to shed light into the stability relations of the chemically uncommon compositions treated in this study. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00244937 U6 - https://doi.org/10.1016/j.lithos.2005.08.003 SN - 0024-4937 ER - TY - JOUR A1 - Breiter, Karel A1 - Förster, Hans-Jürgen A1 - Skoda, Radek T1 - Extreme P-, Bi-, Nb-, Sc-, U- and F-rich zircon from fractionated perphosphorous granites: the peraluminous Podlesi granite system, Czech Republic N2 - The strongly peraluminous and P-rich, protolithionite and zinnwaldite leucogranites from Podlesi, western Krusne Hory Mts., Czech Republic, contain accessory zircon with extraordinary enrichment of several elements, which constitute trace elements in common zircon. Elements showing a not yet reported anomalous enrichment include P (up to 20.2 wt.% P2O5; equivalent to 0.60 apfu, formula calculated on the basis of 4 oxygen atoms), Bi (up to 9.0 wt.% Bi2O3; 0.086 apfu), Nb (up to 6.7 wt.% Nb2O5, 0.12 apfu), Sc (up to 3.45 wt.% Sc2O3; 0.10 apfu), U (up to 14.8 wt.% UO2; 0.12 apfu) and F (up to 3.81 wt.% F; 0.42 apfu). Strong enrichment of P preferentially involved the berlinite-type substitution (2 Si4+ double left right arrow P5+ + Al3+) implying that significant Al may enter the Si position in zircon. Incorporation of other exotic elements is primarily governed by the xenotime (Si4++Zr4+ double left right arrow P5++Y3+), pretulite (Sc3++P5+ double left right arrow Zr4++Si4+), brabantite-type (Ca2++(U, Th)(4+)+2P(5+) double left right arrow 2Zr(4+)+2Si(4+)), and ximengite-type (Bi3++P5+double left right arrow Zr4++Si4+) substitution reactions. One part of the anomalous zircons formed late-magmatically, from a strongly peraluminous, P-F-U-rich hydrous residual melt that gave rise to the zinnwaldite granite. Interaction with aggressive residual fluids and metamictization have further aided in element enrichment or depletion, particularly in altered parts of zircon contained in the protolithionite granite. Most of the zircon from F-rich greisens have a composition close to endmember ZrSiO4 and are chemically distinct from zircon in its granite parent. This discrepancy implies that at Podlesi, granitic zircon became unstable and completely dissolved during greisenization. Part of the mobilized elements was reprecipitated in newly grown, hydrothermal zircon. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/00244937 U6 - https://doi.org/10.1016/j.lithos.2005.08.011 SN - 0024-4937 ER - TY - JOUR A1 - Harlov, Daniel E. A1 - Johansson, L. A1 - Van Den Kerkhof, A. A1 - Förster, Hans-Jürgen T1 - The role of advective fluid flow and diffusion during localized, solid-state dehydration : Sondrum Stenhuggeriet, Halmstad, SW Sweden N2 - 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 Y1 - 2006 SN - 0022-3530 ER -