contemporary tectonic stress in northeastern iberia new results from borehole breakout analysis abstract in situ data on the orientation of tectonic stress in northern iberia are scarce fault slip and focal mechanism data show a variety of stress orientations difficult to interpret in terms of a general stress pattern breakout analysis performed on oriented caliper logs from 17 hydrocarbon exploration wells has provided new data on the orientation of tectonic stress in northeastern iberia the southern pyrenees the ebro basin and the northwestern valencia trough the majority of breakout data indicate a rather consistent ne sw to ene wsw directional signature of the larger horizontal principal stress orientation this orientation differs significantly from the nw western european mean stress orientation it is consistent with depth within the first 4 7 km of both the sedimentary fill and the sedimentary basins substrate and also within allochthonous thrust sheets in the southern pyrenees and in the underlying autochthonous and parautochthonous foreland basin sediments

experimental determination of the stability constants of naso4 and nab oh 40 in hydrothermal solutions using a new high temperature sodium selective glass electrode implications for boron isotopic fractionation abstract a new sodium selective glass electrode was used to measure the association constants of the sodium sulfate naso 4 and sodium borate nab oh 4 0 ion pairs at temperatures from 50 to 200 c these data were used to generate within the framework of the revised hkf model naso 4 and nab oh 4 0 equation of state parameters calculation of nab oh 4 0 association constants at temperatures up to 500 c and pressures up to 5 kbar demonstrates that this ion pair dominates boron speciation in sodium rich hydrothermal fluids at ph 8 because it has been shown that boron isotopic fractionation in natural processes is strongly affected by its aqueous speciation the formation of nab oh 4 0 complexes cannot be neglected when using boron isotopes to estimate water rock interactions occurring in the continental and oceanic crust at moderate and high temperatures

moment tensor solutions for small and moderate earthquakes in the ibero maghreb region 1 we applied time domain moment tensor inversion of local and regional waveforms to small and moderate mw 3 5 5 7 shallow earthquakes from the iberian peninsula northern morocco and northern algeria for the 6 years period from november 1995 to march 2002 and the previous network of autonomously recording seismograms nars experiment moment tensor solutions were obtained for 58 events considerably increasing the total number of available solutions in the study area for each event we performed a moment tensor inversion and a double couple grid search for simple faulting events the grid search is valuable as a quality test for its ability to reveal potential ambiguities of the solutions and to assess confidence limits of fault plane parameters or principal axes orientation the computed mechanisms show regional consistency a large part of the iberian peninsula is characterized by normal faulting mechanisms with sw ne oriented t axes thrusting and se nw compression is dominant in algeria in the alboran sea the westernmost part of the mediterranean and the transition between both regimes strike slip mechanisms dominate with approximately n s oriented p axes this pattern suggests a regional anomaly characterized by clockwise rotation of the principal horizontal stress orientations

melt inclusions in pegmatite quartz complete miscibility between silicate melts and hydrous fluids at low pressure fluorine boron and phosphorus rich pegmatites of the variscan ehrenfriedersdorf complex crystallized over a temperature range from about 700 to 500 c at a pressure of about 1 kbar pegmatite quartz crystals continuously trapped two different types of melt inclusions during cooling and growth a silicate rich h2o poor melt and a silicate poor h2o rich melt both melts were simultaneously trapped on the solvus boundaries of the silicate fluorine boron phosphorus water system the partially crystallized melt inclusions were rehomogenized at 1 kbar between 500 and 712 c in steps of 50 c by conventional rapid quench hydrothermal experiments glasses of completely rehomogenized inclusions were analyzed for h2o by raman spectroscopy and for major and some trace elements by emp electron microprobe both types of melt inclusions define a solvus boundary in an xh2o t pseudobinary system at 500 c the silicate rich melt contains about 2 5 wt h2o and the conjugate water rich melt about 47 wt h2o the solvus closes rapidly with increasing temperature at 650 c the water contents are about 10 and 32 wt respectively complete miscibility is attained at the critical point 712 c and 21 5 wt h2o many pegmatites show high concentrations of f b and p this is particularly true for those pegmatites associated with highly evolved peraluminous granites the presence of these elements dramatically reduces the critical pressure for fluid melt systems at shallow intrusion levels at t 720 c water is infinitely soluble in a f b and p rich melt simple cooling induces a separation into two coexisting melts accompanied with strong element fractionation on the water rich side of the solvus very volatile rich melts are produced that have vastly different physical properties as compared to normal silicate melts the density viscosity diffusivity and mobility of such hyper aqueous melts under these conditions are more comparable to an aqueous fluid

active crustal deformation from the azores triple junction to the middle east the co seismic crustal deformation along the africa eurasia eurasia arabia plate boundary from the azores triple junction 30 w up to the karliova triple junction 41 e is examined based on the moment tensor summation of mainly post 1964 earthquakes with ms 5 0 strain rates range from 10 8 yr to 10 6 yr while values exceeding 10 7 yr were calculated for the back arc aegean area and for the north anatolian fault zone a remarkable stability in the azimuth of the component of compression and of extension is observed in the area that extends west of italy 17 e up to the azores triple junction along this region the deformation is taken up by compression along a mean direction of n140 with rates from 1 1 to 2 8 mm yr and by extension along a mean direction of n50 with rates from 2 4 to 12 0 mm yr at the gloria fault and in the surrounding area dextral strike slip motion occurs at a rate of 11 mm yr from sicily up to the eastern end of the hellenic arc the crust is compressed at azimuths in the range n20 n31 with an average value of 26 5 this compression is occurring at a rate of 1 21 mm yr with an average value of 9 8 mm yr in the back arc aegean area extension is occurring along a mean azimuth of n156 with a rate of 5 2 3 8 mm yr the average shortening rate along the convex side of the hellenic arc is 12 mm yr from the eastern end of the north anatolian fault 41 e up to the northern aegean trough extension along n68 n179 and compression along n158 n89 occurs which results in dextral strike slip motion the rate of extension reduces from east to west from 30 mm yr to 5 mm yr while the rate of compression reduces from 17 mm yr to 5 mm yr the northwards motion of arabia results in a n31 trending compression at a rate of 7 mm yr along the east anatolian fault zone

neogene patterns of relative plate motion for africa europe some implications for recent central mediterranean tectonics a detailed relative motion picture for the neogene africa europe plate kinematics is presented the kinematic reconstruction was carried out using the finite difference solution between the rotation parameters determined for anomalies 7 to 2 in the africa north america europe plate motion circuit the analysis shows a motion of africa with respect to europe which is nne directed during late oligocene to burdigalian times becoming nnw trending from the langhian to the early tortonian from upper tortonian times onward the motion changes to a clear north west directed convergence major late neogene tectonic features of the central mediterranean region can to a large extent be explained within the context of the reconstructed major plate motions late tortonian to recent africa europe slip vectors are compatible with a variety of geological phenomenoa such as north west directed subduction beneath calabria south east translation of calabria and extension in the tyrrhenian sea north west trending slip vectors from thrust earthquakes between gibraltar and sicily and dextral strike slip across the north african margin

an example of intraplate neotectonic activity vilarica basin northeast portugal the vilarica tectonic basin nw iberian peninsula is presented as an example of intraplate neotectonic activity the regional geological setting is first introduced then followed by a brief view on the neotectonic activity in portugal the basin consists of an elongated depression approximately 20 km long and 2 to 3 km wide trending nne ssw it is located astride a late variscan strike slip fault the manteigas braganca fault suggesting that it might correspond to a structural depression related to reactivation movements on that fault mapping of neogene and quaternary cover deposits preserved in the basin and its vicinity was accomplished and numerous evidence of tectonic deformation tilting and faulting affecting the sediments were found other geomorphological criteria are discussed showing the structural origin of the vilarica basin and its neotectonic activity attending to its location on the manteigas braganca fault the vilarica depression is interpreted as a pull apart basin resulting from left lateral strike slip displacement on that fault in the quaternary average fault slip rates are estimated with values comprised between 0 2 mm yr and 0 5 mm yr these slip rates are typical of moderate to moderately high degrees of fault activity and are compatible with the regional faulting geomorphic expression and the relatively important historical and instrumental seismicity affecting the vilarica region finally a geodynamical model is proposed and the studied area is presented in the geodynamic framework

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

inversion of moment tensor focal mechanisms for active stresses around the microcontinent iberia tectonic implications the iberian microcontinent and its connected oceanic crust are affected by deformations related to the eurasian african plate boundary active stress inversions from populations of moment tensor focal mechanisms have been performed around and inside the iberian peninsula using a total of 213 moment tensor estimates main results are 1 the tensorial solutions show better consistency and lower misfits compared to those obtained previously from first p arrival focal mechanisms 2 along the eurasia africa western boundary the type of active stresses progressively changes easternwards from triaxial extension to uniaxial compression along the terceira ridge the gloria fault zone and the gulf of cadiz 3 in the betics alboran rif zone uniaxial extension predominates with shmax n155oe trending 4 in n algeria uniaxial compression reappears 5 the iberian foreland is currently under strike slip to uniaxial extension tensorial conditions

geochemical and petrogenetic features of mineralization in rare element granitic pegmatites in the light of current research abstract tremendous expansion of high technology applications of rare metals and specialty minerals requires periodic reassessment of their geological sources keeping in mind the long range technological potential of all hi tech materials available from a given type of deposit granitic pegmatites are a classic example of diversified sources li rb cs be ga sc y ree sn nb ta u th zr hf optical quartz and fluorite high purity feldpar petatite and refractory spodumene ceramic amblygonite e tc such rare element pegmatites can be subdivided into three principal families lct pegmatites with li rb cs be ga sn ta nb b p f nyf pegmatites with nb ta ti y ree zr th and u f pegmatites with a mixed geochemical signature the less evolved members of the lct family produce mainly only be nb ta and sn but exotic types with be ta nb f b p with li rb and cs and are also known so far no differences ini mineralization styles have been observed between the spodumene petalite and amblygonite subtypes of the complex type except the mineralogy of their substantial li contents however extensive divergence in k rb cs fractionation is observed violating the classic criteria for for example pollucite potential and economic ga concentration is recognized the lepidolite subtype is commonly enriched in y and h ree albitespodumene pegmatites have largely simple li sn nb ta be mineralization but a suprisingly broad range of alkali fractionation levels the not so common albite type seems to be typically enriched in sn nb ta ti the nyf family is much less abundant a general subdivision of these pegmatites is not yet available except for the recognition of sporadic lree enriched and much more widespread y hree enriched subtypes scandium is an element recognized recently as much more abundant than previously thought internal evolution of individual pegmatites is better understood today in terms of london s model of crystallization from highly hydrous but homogeneous melts experimental evidence does not support the jahns and burnham proposal of early separation of a fluid phase peraluminous fertile s granites generating lct pegmatites are derived by partial melting of upper middle crustal rocks undergoing their first anatexis and the pegmatites commonly show regional zoning metaluminous granites yeilding poorly zoned groups of nyf pegmatites are largely of the a type generated by second melting of short lived depleted lower crustal protoliths however a juvenile igneous or fluid component may be involved mixed nyf lct granite pegmatite suites may originate in several ways peraluminous lct sequences were traditionally regarded as orogenic in contrast to anorogenic nyf systems tectonic correlation with geochemistry is now considered secondary to the control by source lithologies it is the understanding of the association of pegmatite types with their geological setting and petrogenetic affiliation which assists in the search for selected hi tech materials

crust mantle coupling in the gulf of cadiz sw iberia 1 in the gulf of cadiz and cape st vincent region at the sw iberian margin seismic catalogues report seismicity down to 100 km depth according to structural models for the region this includes earthquakes that occur in the uppermost continental mantle we invert regional waveforms to estimate moment tensors and centroid depths for moderate earthquakes obtaining eight solutions mw 3 8 to 5 3 between 6 and 60 km depth moment tensor solutions and previous source estimates show predominately reverse and strike slip faulting style with nnw sse oriented p axes close to plate convergence between africa and eurasia we obtain similar stress tensor estimates from crustal and upper mantle earthquakes both with sub horizontal nnw 1 axes this indicates analogous deformation in both domains and that earthquakes are unrelated to any subduction process

neogene through quaternary tectonic reactivation of sw iberian passive margin southwest portugal the gulf of cadiz and morocco are under the potential threat of natural hazards linked to seismicity and tsunami generation we report the results of two multi channel seismic mcs surveys carried out in 1992 and 1998 along the continental margin and oceanic crust of sw iberia this mcs data set shows the evidence of the compressional deformation which involves both the continental and the oceanic crust of the study area the area of deformation extends from the southern border of the tagus abyssal plain to the seine abyssal plain encompassing the continental margin of sw portugal most of the structures observed are probably related to a mid miocene phase of africa europe plate convergence in this paper we discuss the recent advances on the identification of the tectonic structures that are still active and that may generate great earthquakes and tsunamis the tectonic structures identified are located respectively at the guadalquivir bank along the eastern border of the horseshoe abyssal plain and along the southern continental slope of sw portugal

stress and palaeostress in the betic rif cordilleras miocene to the present palaeostress orientation in the betic rif cordilleras can be determined for the miocene to the quaternary by analysis of brittle microstructures faults joints striated pebbles and stylolites in the central and northern south iberian domain 1 was subhorizontal and trended nw se from the early miocene to the present in the northern alboran domain from the burdigalian to the serravallian palaeostress ellipsoids were oblate with 3 subhorizontal and trending ene wsw in the southern part of the south iberian domain and in the northern part of the alboran domain betic cordillera from the tortonian to the quaternary palaeostress ellipsoids were variable in the granada region they were prolate with 1 subvertical but in the almeria region they were triaxial with 2 subvertical and 3 subhorizontal and trending ne sw to e w in the rif the alboran and african maghrebian domains were affected by palaeostresses with 1 subhorizontal varying from ne sw in tortonian times to n s in the plio quaternary a study of earthquake focal mechanisms by the right dihedra method indicates that the present day general stress field around the betic rif cordilleras is compressional with 1 subhorizontal and trending nw se in the betic rif cordilleras this general stress field is modified and the present day orientations of 1 2 and 3 are nearly the same as those of the palaeostresses in the pliocene and quaternary the distribution and evolution of stresses in the betic rif cordilleras from the miocene to the present can be correlated with the main neogene deformations extensional structures in the central and northern alboran domain and the southern part of the south iberian domain and compressional structures in the south iberian and african maghrebian domains and in the southern part of the alboran domain

an application of the slip model of brittle deformation to focal mechanism analysis in three different plate tectonic situations abstract the slip model of brittle deformation reches 1983 imposes a set of constraints on the angular relationships between faults their striations on slickensides and the type and orientation of the deformation ellipsoid in focal mechanisms of earthquakes these relationships can be used to determine which of the two nodal planes is the fault plane and then to obtain the strain ellipsoid of regional tectonic deformation controlling seismicity in this approach it is convenient to use pitch dip diagrams de vicente 1988 and p t diagrams angelier and mechler 1977 both developed for fault population analysis in this paper three regions in different plate tectonic situations are analysed using these methods these regions are a zone of intracontinental seismicity in the eastern peruvian andes a zone of continental compressional deformation in the iranian plateau and the fenwei graben of china nodal planes of focal mechanisms published in different papers about seismicity in these regions have been used the following conclusions being reached in the analysed zone of the peruvian andes three regional deformation types appear causing fault movements that range from slightly reverse strike slip to reverse strike slip in addition exclusively at depths in excess of 18 km there is a deformation of an uniaxial shortening type in all of these deformations the horizontal shortening axis is oriented from n87 to n93 in the iranian plateau two horizontal shortening directions appear n151 and n61 even showing faults that imply an uniaxial deformation ellipsoid the shortening axis of which is at n61 in the fenwei graben the ellipsoid of regional deformation has a stretching principal axis at n145 150 and a shortening axis at n55 60 the strike slip movement along faults being as important as the normal one

conditions of pocket formation in the oktyabrskaya tourmaline rich gem pegmatite the malkhan field central transbaikalia russia coexisting melt mi fluid melt fmi and fluid fi inclusions in quartz from the oktaybrskaya pegmatite central transbaikalia have been studied and the thermodynamic modeling of pvtx properties of aqueous orthoboric acid fluids has been carried out to define the conditions of pocket formation at room temperature fmi in early pocket quartz and in quartz from the coarse grained quartz oligoclase host pegmatite contain crystalline aggregates and an orthoboric acid fluid the portion of fmi in inclusion assemblages decreases and the volume of fluid in inclusions increases from the early to the late growth zones in the pocket quartz no fmi have been found in the late growth zones significant variations of solid fluid ratios in the neighboring fmi result from heterogeneous entrapment of coexisting melts and fluids by a host mineral raman spectroscopy sem eds and empa indicate that the crystalline aggregates in fmi are dominated by mica minerals of the boron rich muscovite nanpingite csal2 alsi3o10 oh f 2 series as well as lepidolite topaz quartz potassium feldspar and several unidentified minerals occur in much lower amounts fluid isolations in fmi and fi have similar total salinity 4 8 wt nacl eq and h3bo3 contents 12 16 wt the melt inclusions in host pegmatite quartz homogenize at 570 600 c the silicate crystalline aggregates in large inclusions in pocket quartz completely melt at 615 c however even after those inclusions were significantly overheated at 650 10 c and 2 5 kbar during 24 h they remained non homogeneous and displayed two types i glass unmelted crystals and ii fluid glass the fmi glasses contain 1 94 2 73 wt f 2 51 wt b2o3 3 64 5 20 wt cs2o 0 54 wt li2o 0 57 wt ta2o5 0 10 wt nb2o5 0 12 wt beo the h2o content of the glass could exceed 12 wt such compositions suggest that the residual melts of the latest magmatic stage were strongly enriched in h2o b f cs and contained elevated concentrations of li be ta and nb fmi microthermometry showed that those melts could have crystallized at 615 550 c crystallization of quartz feldspar pegmatite matrix leads to the formation of h2o b and f enriched residual melts and associated fluids prototypes of pockets fluids of different compositions and residual melts of different liquidus solidus p t conditions would form pockets with various internal fluid pressures during crystallization those melts release more aqueous fluids resulting in a further increase of the fluid pressure in pockets a significant overpressure and a possible pressure gradient between the neighboring pockets would induce fracturing of pockets and fluid explosions the fracturing commonly results in the crushing of pocket walls formation of new fractures connecting adjacent pockets heterogenization and mixing of pocket fluids such newly formed fluids would interact with a primary pegmatite matrix along the fractures and cause autometasomatic alteration recrystallization leaching and formation of primary secondary pockets

active faulting in the western pyrenees france paleoseismic evidence for late holocene ruptures abstract we have identified a 50 km long active fault scarp called herewith the lourdes fault between the city of lourdes and arette village in the french pyrenees this region was affected by large and moderate earthquakes in 1660 io viii ix msk 64 in 1750 io viii msk 64 and in 1967 md 5 3 io viii msk 64 most earthquakes in this area are shallow and the few available focal mechanism solutions do not indicate a consistent pattern of active deformation field investigations in active tectonics indicate an east west trending and up to 50 m high fault scarp in average made of 3 contiguous linear fault sub segments to the north the fault controls quaternary basins and shows uplifted and tilted alluvial terraces deviated and abandoned stream channels of the southern block are likely due to the successive uplift of the northern block of the fault paleoseismic investigations coupled with geomorphic studies georadar prospecting and trenching along the fault scarp illustrate the cumulative fault movements during the late holocene trenches exhibit shear contacts with flexural slip faulting and thrust ruptures showing deformed alluvial units in buried channels 14c dating of alluvial and colluvial units indicates a consistent age bracket from two different trenches and shows that the most recent fault movements occurred between 4221 bc and 2918 bc fault parameters and paleoseismic results imply that the lourdes fault and related sub segments may produce a mw 6 5 to 7 1 earthquake fault parameters imply that the lourdes fault segment corresponds to a major seismic source in the western pyrenees that may generate earthquakes possibly larger than the 1660 historical event

palaeostress evolution of the iberian peninsula late carboniferous to present day abstract three main stages can be differentiated in iberia from the upper carboniferous to the present the end of the variscan orogeny late carboniferous the permian early cretaceous rifting and the alpine orogeny late cretaceous to present in this contribution the main features of the stress fields determined in each of these stages are compiled and revised from the analysis of the brittle deformations mainly microfault population stresses are related to the development of the principal structures of each stage in the late variscan fracturing stage sinistral strike slip faults prevailed in a stress field with ne sw subhorizontal compression in the permian to early cretaceous rifting stage the extensional trends varied in each sector during the alpine orogeny primarily the margins of the iberian massif the betic and pyrenee mountain chains were deformed however numerous deformations are also identified in its interior where large mountain chains such as the central system and the iberian chain developed these deformations occurred in a complex stress field where zones of nw se to nne ssw horizontal compression prevailed albeit predominantly extensional zones existed as well at present the stress field in most of iberia has a nw se compressive trend associated with active deformations in the betic cordillera where a continental subduction developed however simultaneously there are zones in which extensional settings predominate such as the internal zones of the betic cordillera and the gulf of valencia region making for quite a complex current stress field

monitoring the crystallization of water saturated granitic melts in real time using the hydrothermal diamond anvil cell critical aspects of the crystallization dynamics of h2o saturated melts of a typical granitic composition as well as granitic melts enriched in lithium 8800 ppm were investigated in real time experiments using the hydrothermal diamond anvil cell at 480 700 c and 220 960 mpa complete crystallization of the charges was achieved within 5 118 h with average crystal growth rates ranging from 3 to 41 cm year for quartz and from 18 to 58 cm year for alkali feldspars demonstrating that crystals formed from a silicate melt in the presence of a coexisting aqueous phase crystallize rapidly the combination of substantial nucleation delays low nucleation densities and rapid growth rates for quartz and alkali feldspars led to the formation of euhedral megacrysts of these minerals in the vicinity of clusters comprised of much smaller muscovite or spodumene crystals subsolidus replacement processes initiated during crystal fluid interactions after the silicate melt was consumed were directly observed in the experiments the experimental results underscore the important role of water as a medium for the transport of essential elements such as si al na and k from the silicate melt to the newly formed crystals and provide important insights into the crystallization of miarolitic pegmatites

evidence for an active sinistral shear zone in the westeren alboran region a compilation of gravity seismicity neotectonics geology tomography and topography data from the alboran region reveals distinctive differences between the eastern and western part of the alboran region and betic cordillera calculated profiles of integrated crustal strength reveal that lateral differences in mechanical behaviour are caused by marked inherited differences in crustal make up the two domains with different tectonic behaviour are separated by a n025 trending lineament in the western alboran and central betic cordillera this lineament can be interpreted as an upper mantle lower crustal sinistral shear zone accommodating a large part of the convergence between africa and iberia

origin of miarolitic pegmatites in the konigshain granite lusatia abstract in this study we examine an interesting occurrence of miarolitic pegmatites in the konigshain granite of the lusatia region of the bohemian massif this granite is characterized by the extensive development of micro sized miarolitic pegmatites typically with diameters of 5 to 15 mm irregularly distributed through its upper levels and larger miarolitic pegmatites up to 1 m in the uppermost levels this granite also shows evidence of varied forms of transport of extremely volatile rich residual melts fluids in the form of more or less discrete inter granular melt bodies and associated magmatic quartz veins formed in tectonic fissures together these provide evidence for the origin of miarolitic pegmatites both in the specific case of konigshain and more generally our evidence suggests that miarolitic pegmatites form from volatile and alkali rich residual melts ranging from 10 to 50 h 2 o far more than typical granitic melts but far more silicate components than aqueous fluids or vapor suggested by some authors using melt inclusions in quartz from the aplitic and graphic granite zones in miarolitic pegmatites in the konigshain granite we show that two different inclusion populations are present we provide evidence that the first inclusion population are those related to the primary granite at the level of intrusion and the second were trapped during the re crystallization of the granite wall rocks by silicate rich supercritical fluids moving through the solid crystal framework with a porosity 0 see clarke et al 2013 our results show that a significant volume fraction of the miarolitic pegmatites was not created by a pegmatite forming fluid but formed in situ by re crystallization of wall rocks triggered by highly reactive volatiles exsolved from the pegmatite forming melts evidence is also presented which suggests the nature and speed of emplacement of the konigshain granite this evidence may explain the unusual form and abundance of miarolitic pegmatites in the studied area and may have application to similar occurrences thus there is a mixture of features which are applicable to miarolitic pegmatites in general and others which help separate the overriding processes from the variations produced by local or regional chemical or tectonic characteristics

origins of the european regional stress field abstract we present a study of the origins of the european regional stress field intraplate stresses due to various plate boundary forces and intraplate stress sources were predicted using an elastic finite element analysis the finite element mesh consists of about 1629 nodes in a network of 3117 triangular elements which provide a spatial resolution of about 1 the study builds on the previous modelling studies through consideration of a wide range of plausible forces acting along the collisional eastern and southern plate boundaries and importantly through the inclusion of forces due to other lateral density variations within the lithosphere such as those associated with the continental margins and high topography the modelling was constrained by more than 1800 stress indicators from the world stress map project which provide information about the orientation of the observed maximum horizontal compressive stress sh the torque associated with the ridge push force is well constrained and the principal source of uncertainty relates to the boundary conditions used to represent the collisional resistance acting along the eastern and southern boundaries a gradient in the collisional resistance increasing in magnitude from west to east is assumed to act along the southern plate boundary whereas the eastern boundary is modelled as a pinned margin at 46 e the sh orientation and magnitude of the regional stress field was found to be largely invariant to the boundary conditions used to represent the tectonic forces acting along the eastern and southern margins and is characterized by a nearly uniform nw se compression with a magnitude in the range of 10 20 mpa averaged over a 100 km thick lithosphere lateral density variations within the continental areas of europe were found to reduce the magnitude of the predicted stresses but do not have a significant effect on the orientation of the regional stress field

determination of the h3bo3 concentration in fluid and melt inclusions in granite pegmatites by laser raman microprobe spectroscopy a method of determining the boric acid h3bo3 concentration in fluid inclusions and volatile rich glasses using laser raman microprobe spectroscopy is described the h3bo3 content of melt and fluid inclusions is determined with good accuracy and precision in the concentration range of 0 to 20 wt and with a minimum detection limit mdl of 0 05 wt h3bo3 the method is applicable to complex solutions that contain components such as nacl kcl rbcl or cscl which do not form stable hydrated borates with boric acid at room temperature this raman study demonstrates that boric acid is an abundant component in volatile rich melt inclusions and in genetically linked primary and pseudosecondary fluid inclusions particularly in tourmaline bearing granites and boron rich pegmatites in quenched pegmatite melt boron occurs predominantly as a trigonal coordinated b oh 3 complex the analytical method is applied to a series of melt and fluid inclusions from different localities and geological environments namely hydrothermal tin and tungsten deposits granite pegmatites and rhyolites special emphasis is given to the analysis of fluorine phosphorus and boron rich pegmatites of the variscan ehrenfriedersdorf complex central erzgebirge germany in this pegmatite system boron in combination with water fluorine and phosphorous is responsible for immiscibility of two coexisting silicate melts a silicate rich h2o poor melt and a silicate poor h2o rich melt accompanied by strong element fraction ation between the two boron fractionates into the water rich silicate melt by factors between 1 8 at 500 c and 1 0 at 712 c if at low pressure a vapor phase is additionally formed boron is partitioned into the vapor phase the utility of the developed method was also quantitatively tested by experiments with a hydrothermal diamond anvil cell

stress orientation and tectonic regime in the northwestern valencia trough from borehole data the orientation of the maximum horizontal stress sh is obtained from the analysis of borehole breakouts covering a depth range from 300 to 3415 m below sea level in twelve offshore exploration wells in the northwestern valencia trough the orientation of sh is roughly coincident with the strike of major extensional structures from n to s it changes counterclockwise from a ne sw orientation to a n s orientation estimates of the tectonic regimes indicate that the area is characterised predominantly by normal faulting with a strike slip component both the stress orientations and the tectonic regimes are consistent with neotectonic studies in the nearby catalan coastal ranges an established method of estimating the tectonic regime by moos and zoback 1990 was modified by the inclusion of a nontrivial cohesion but this changes the results insignificantly

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

evidence for a post 3 16 ma change in nubia eurasia north america plate motions we combine updated gps velocities from the nubian nu eurasian eu and north american na plates with 500 new 3 16 myr average seafloor spreading rates and nine transform fault azimuths from the northern atlantic and arctic basin seafloor spreading centers to estimate and test for changes in the relative motion between these plates the numerous new seafloor spreading rates and gps velocities improve our ability to detect recent changes in the relative motions of these plates the angular velocity vector that best fits the eu na gps velocities lies significantly north of the 3 ma average pole in accord with previously published geologic evidence that the eu na pole has migrated northward since v3 ma although we also find evidence for a significant post 3 ma change in nu na motion it is less compelling because the nubian plate gps velocity field is sparse and nu na seafloor spreading rates appear to have remained steady within the 1 mm yr 31 uncertainties if we systematically decrease the seafloor spreading rates to correct for outward displacement of seafloor spreading magnetic lineations the nu eu pole derived from gps site velocities lies more than 30 angular degrees south of the tightly constrained 3 ma average estimate and predicts significantly slower and more oblique present day nu eu convergence in the mediterranean both models for nu eu motion pass a key test for their accuracy namely they correctly predict strike slip motion along the well mapped gloria fault east of the azores the change to more oblique nu eu motion may reflect increasing difficulty in maintaining margin normal convergence within this continent continent collision zone 8 2003 published by elsevier b v

experimental evidence of three coexisting immiscible fluids in synthetic granitic pegmatite we present an experimental study of synthetic peraluminous granite doped with h2o b p and f which confirms that aluminosilicate melt hydrous fluid and hydrosaline melt high temperature brine can stably coexist at 450 900 c and 0 1 0 2 gpa in bulk compositions similar to those of natural granitic pegmatites hydrosaline melt is not quenchable unstable at room conditions and requires special techniques for synthesis and preservation raman spectroscopy and electron microprobe analyses of hydrosaline melt synthesized in our experiments show that it is composed of h3bo3 na3alf6 alpo4 h2o and aluminosilicate components aluminosilicate melt saturated in both hydrosaline liquid and hydrous fluid at 850 c and 0 2 gpa contains 3 6 wt f 4 2 wt p2o5 and 4 wt b2o3 natural hydrosaline melts have previously been found as inclusions trapped in rock forming minerals they are not restricted to granites and can be effective agents for enhanced crystal growth metasomatism and ore formation in addition hydrosaline melts may account for many characteristic features of rare element and miarolitic pegmatites such as giant size and perfect shapes of crystals in pegmatite cores diverse mineralogy and strong enrichment in rare elements

recent and present day stresses in the granada basin betic cordilleras example of a late miocene present day extensional basin in a convergent plate boundary the diffuse convergent boundary between the eurasian and african plates in the western mediterranean is associated with a seismicity zone more than 300 km wide although the two plates are converging nw se the betic and rif cordilleras contain extensional structures that have been active since the miocene the extensional tectonics in the region which occurred simultaneously with the uplift of the cordillera have been analyzed in the southeastern sector of the late miocene to recent granada basin using earthquake focal mechanisms the determination of paleostresses from the study of the orientation and kinematics of microfaults and the study of the major structures both the geological surface data and the focal mechanisms indicate present day regional conditions of ne sw extension with triaxial to prolate stress ellipsoids however the stress field is heterogeneous with local variations in stress over time with different stresses sometimes even acting simultaneously in adjacent areas the most frequent changes consist of pluridirectional or ne sw extension favored by the prolate character of the stress ellipsoids and nw se subhorizontal compression favored by the regional tectonic setting strike slip faults are scarce even though they are the most likely structure to be expected in a region with sw ne extension and nw se compression seismicity is concentrated in the upper crust and may correspond to the activity of low to high angle normal faults similar to the surface faults although they can not be correlated with them the lower cutoff of this seismicity probably coincides with the 300 c isotherm and suggests a low thermal gradient for the region present day regional stresses have 1 vertical at the surface but in depth plunge toward the sw

boron isotope composition of coexisting tourmaline and hambergite in alkaline and granitic pegmatites abstract the boron isotopic composition of tourmaline and hambergite be2bo3 oh f from peraluminous n 12 peralkaline n 1 and peralkaline nepheline syenite n 16 pegmatites has been measured by secondary ion mass spectrometry for which a new hambergite reference material was developed the focus of this study is on nepheline syenite pegmatites from the larvik plutonic complex norway and one peralkaline pegmatite related to the nearby eikeren skrim complex norway where we investigate the source of boron as being from magmatic vs external fluids tourmaline hambergite mineral pairs were also analysed from peraluminous pegmatite localities russia tajikistan and pakistan to test for systematic b isotope fractionation between these two minerals tourmaline and hambergite from peraluminous granitic pegmatites have light boron ratios 11b 12 9to 1 0 associated with s type granites whereas peralkaline granitic and nepheline syenite pegmatites have boron ratios 11b 1 7 to 11 8 which we interpret is a result of heavy boron enrichment from external fluids our data show that hambergite tracks isotope variations of its geochemical setting and could therefore be used as a proxy mineral in place of tourmaline when geochemical stability favours hambergite the results suggest a slight but consistent partitioning of b isotopes between tourmaline and hambergite with 11b 11btourmaline 11bhambergite in the range of approximately 3 to 5 boron is in trigonal coordination with oxygen in both of these mineral phases as verified by nmr single crystal xrd analyses of tourmaline and hambergite reveal consistent longer distances of tourmaline relative to hambergite we attribute the boron isotopic fractionation to the longer bond lengths in tourmaline compared with hambergite

neotectonic evolution of the central betic cordilleras southern spain abstract paleostress orientations were calculated from fault slip data of 36 sites located along a traverse through the central betic cordilleras southern spain heterogeneous fault sets which are frequent in the area have been divided into homogeneous subsets by cross cutting relationships observed in the field and by a paleostress stratigraphy approach applied on each individual fault population the state of stress was sorted according to main tectonic events and a new chronology is presented of the miocene to recent deformation in the central part of the betic cordilleras the deviatoric stress tensors fall into four distinct groups that are regionally consistent and correlate with three late oligocene aquitanian to recent major tectonic events in the betic cordilleras the new chronology of the neotectonic evolution includes from oldest to youngest the following main tectonic phases 1 late oligocene aquitanian to early tortonian 1 subhorizontal n s partly e w directed 3 subvertical compressional structures thrusting of nappes large scale folding and strike slip faulting in the alboran domain and the external zone of the betic cordilleras 2 early tortonian to pliocene pleistocene 1 subvertical 3 subhorizontal nw se partly n s directed or e w directed radial extension large scale normal faulting in the central betic cordilleras and in the oldest neogene formations of the granada basin related to the gravitational collapse of the betic cordilleras and the exhumation of the intensely metamorphosed rock series of the internal zones at the same time formation of the alboran basin and intramontane basins such as the granada basin 3 pleistocene to recent 3a 1 subvertical 3 subhorizontal ne sw with prominent normal faulting but coevally 3b 1 subhorizontal nw directed 3 ne sw subhorizontal with strike slip faulting extensional structures and strike slip faulting are related to the ongoing convergence of the eurasian and african plates and coeval uplift of the betic cordilleras reactivation of pre existing fractures and faults was frequently observed phase 3 is interpreted as periodic strike slip and normal faulting events due to a permutation of the principal stress axes mainly 1 and 2

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

the recent upper miocene to quaternary and present tectonic stress distributions in the iberian peninsula a general synthesis of the recent and present stress situation and evolution in the iberian peninsula was obtained from microstructural and seismological analysis the stress evolution was deduced from 1 fault population analysis fpa from 409 sites distributed throughout the iberian peninsula 2 paleostress indicators given by 324 stations taken from the bibliography and 3 seismic data corresponding to 161 focal mechanisms evenly spread in the studied region the application of fpa together with the determination of stress tensors and focal mechanisms for the whole iberian microplate has provided two main results 1 the iberian peninsula is undergoing a nw se oriented compression except for the northeastern part pyrenees ebro basin and iberian chain where it is n s to ne sw and the gulf of cadiz where it seems to be e w and 2 the main trends of the stress field have remained almost constant since the upper miocene the analysis performed by zones suggests the presence of local heterogeneities in the stress field

european mediterranean regional centroid moment tensor catalog solutions for years 2001 and 2002 abstract we present regional centroid moment tensor rcmt solutions for 168 moderate magnitude earthquakes that occurred in the european mediterranean region during 2001 and 2002 events with moment magnitudes as low as 4 0 were successfully analyzed although this low threshold is only achievable in regions with the best azimuthal coverage and with stations at a few hundred kilometers distance earthquakes with focal depths from 10 to more than 200 km were analyzed comparison with standard harvard cmts when available shows good agreement the solutions shown in this paper represent an addition to the european mediterranean rcmt catalog that we are maintaining the rcmt catalog now spans 6 years from 1997 to 2002 and contains 420 solutions we also outline the main seismic sequences that occurred in the european mediterranean region during 2001 2002

rupture process of the 26 january 2001 mw 7 6 bhuj india earthquake from teleseismic broadband data we investigate the rupture process of the 26 january 2001 bhuj india m w 7 6 earthquake through inversion of teleseismic broadband body waves this earthquake ranks as one of the most important recent events due to its occurrence within a stable continental interior where such events are rare the bhuj earthquake occurred on a moderately dipping blind thrust fault within an ancient failed rift about 70 of the seismic moment released in the earthquake was confined to a very small area 375 km2 surrounding the hypocenter and at depths below 12 km the static stress drop of the bhuj earthquake is anomalously high 20 mpa the source time history of the event indicates very rapid onset to the moment release and most likely high slip velocities within the deep asperity this suggests that some of the damage near the epicenter may have been caused by anomalously high frequency ground motions the teleseismic data also indicate the presence of a second area of large slip in the shallow part of the bhuj fault although the depth extent of this shallow large slip area is not resolved comparisons of the predicted ground motions with observed intensities suggest that substantial slip occurred in the upper 10 km of the fault in order to explain the distribution of high intensities to the west and northwest of the fault the upper surface layers near the bhuj fault consist of unconsolidated low rigidity sediments and alluvium the upper 10 km of the bhuj fault may therefore be in a conditionally stable region that normally deforms through aseismic creep and can sustain seismic rupture only when dynamically stressed by rupture of the high strength deep asperity we suggest that this deep asperity may be related to a lithologic anomaly of ultramafic composition

regional patterns of tectonic stress in europe nearly 1500 stress orientation determinations are now available for europe the data come from earthquake focal mechanisms overcoring measurements well bore breakouts hydraulic fracturing measurements and young fault slip studies and sample the stress field from the surface to seismogenic depths three distinct regional patterns of maximum compressive horizontal stress shmax orientation can be defined from these data a consistent nw to nnw shmax stress orientation in western europe a wnw ese shmax orientation in scandinavia similar to western europe but with a larger variability of shmax orientations and a consistent e w shmax orientation and n s extension in the aegean sea and western anatolia the different stress fields can be attributed to plate driving forces acting on the boundaries of the eurasian plate locally modified by lithospheric properties in different regions on average the orientation of maximum stress in western europe is subparallel to the direction of relative plate motion between africa and europe and is rotated 17 clockwise from the direction of absolute plate motion the uniformly oriented stress field in western europe coincides with thin to medium lithospheric thickness approximately 50 90 km and high heat flow values 80 m w m2 in western europe a predominance of strike slip focal mechanisms implies that the intermediate principal stress is vertical the more irregular horizontal stress orientations in scandinavia coincide with thick continental lithosphere 110 170 km and low heat flow 50 m w m2 the cold thick lithosphere in this region may result in lower mean stresses associated with far field tectonic forces and allow the stress field to be more easily perturbed by local effects such as deglaciation flexure and topography the stress field of the aegean sea and western anatolia is consistent with n s extension in a back arc setting behind the hellenic trench subduction zone the stress field is influenced in places by regional geologic structures e g in the western alps where shmax directions show a slight tendency toward a radial stress pattern not all major geologic structures however appear to affect the shmax orientation e g in the vicinity of the rhine rift system horizontal stress orientations are continuous