bismuth selenides from st andreasberg germany an oxidised five element style of mineralisation and its relation to post variscan vein type deposits of central europe carbonate veinlets at roter bar a former underground mine in the polymetallic st andreasberg vein district of the harz mountains germany host selenide minerals that are characterised as bi ag bearing clausthalite pbse tiemannite hgse guanajuatite bi2se3 and a number of selenides of bi zn cu ag and pd an unnamed bi pb ag selenide species with some hg and cu ideally bi4pb3ag2se10 is reported here specular hematite is disseminated within the clausthalite at the marginal zones of which other selenide minerals are located the occurrence of bohdanowiczite agbise2 and umangite cu3se2 constrains the formation temperature to 120 c and the selenide hematite assemblage plus barite in the carbonate gangue identifies highly oxidised conditions selenide assemblages of pb bi ag with and without co and ni occur in many parts of the variscan basement of central europe harz erzgebirge schwarzwald and bohemian massif and represent a high oxidation variety of five element ag as bi co ni veins

peridotite derived detrital pyropes versus high pressure felsic granulite derived pyrope almandine garnets from the lower triassic deposits of the ne foreland of the bohemian massif s poland central europe

near real time mapping of peak ground acceleration and peak ground velocity following a strong earthquake during a disastrous earthquake the early assessment and timely reporting of the peak ground acceleration pga and peak ground velocity pgv maps will be crucial in an effective emergency response operation in this study we first derive an empirical relationship between m l and m w the pga and pgv attenuation relationships are deduced with data from the taiwan strong motion instrumentation program tsmip and the taiwan rapid earthquake information release system treirs site corrections of the attenuation relationships for shallow and large earthquakes in taiwan region are also obtained peak values of earthquake strong ground motion can be well determined in taiwan as soon as the earthquake location is determined and magnitudes are calculated by the treirs this peak ground motion value information can be immediately turned into the calculated pga and pgv maps that can be issued within two minutes of the earthquake origin time during any disastrous earthquake these maps are found to be very useful for immediate seismic damage assessment and dispatching of emergency response missions manuscript received 1 december 2000

paleomagnetism of the cu zn pb bearing kupferschiefer black shale upper permian at sangerhausen germany syngenetic diagenetic and epigenetic models have been proposed for the cu zn pb kupferschiefer mineralization at sangerhausen germany paleomagnetic and rock magnetic measurements have been made on 205 specimens from mine workings on the margin of the sangerhausen syncline the mineralization is richest in the 0 5 m thick upper permian 258 2 ma kupferschiefer black marly shale nine sites and dies out over 0 2 m in the underlying weisliegend sandstones three sites and overlying zechstein carbonates two sites except for one site of fault zone gypsum characteristic remanent magnetization directions were isolated for all 14 sites using alternating field and thermal step demagnetization these directions provide a negative fold test indicating that the remanence postdates jurassic fault block tilting rock magnetic measurements show that the kupferschiefer shale marks a redox front between the oxidized weissliegend sandstones and non oxidized zechstein carbonates the 14 site directions give a late jurassic paleopole at 149 3 ma it is significantly different from the paleopole reported by e c jowett and others for primary or early diagenetic rote faule alteration that gives an age of 254 6 ma on the current apparent polar wander path and is associated with kupferschiefer mineralization we suggest that the late jurassic extensional tectonic event that formed the nearby north german basin also reactivated variscan basement faults and extended them up through the overlying strata thereby allowing hydrothermal basement fluids to ascend and epigenetically mineralize the kupferschiefer shale the possibility of a 53 3 ma mineralization age is also considered

variations in exhumation level and uplift rate along the obliqu slip alpine fault central southern alps new zealand we use geophysical and geological data from the southern alps to explore the relationship between plate motions and crustal structure on the geomorphology exhumation state and deformation style of rocks uplifted along amajor oblique slip fault a 50 km long segment of the southern alps has a higher uplift rate more relief deeper exhumation and a narrower width than surrounding regions there the delaminated east tilted crust of the pacific plate yields the youngest late cenozoic thermochronometric ages contours for fission track ar ar and k ar ages on several different minerals define an asymmetrically nested pattern of ages that increase away from the western side of the central southern alps eleven new 4 0 ar 3 9 ar samples of hornblende from the hanging wall of the alpine fault indicate that lower crustal rocks exhumed from 500 c in the late cenozoic are confined to a 20 km long culmination at the southern end of the central southern alps ages as low as 3 5 ma imply time integrated vertical exhumation rates as high as 6 9 mm yr this is the only part of this 5 8 ma range that may have achieved exhumational steady state remnant plugs of the original crustal hanging wall ramp are apparently preserved outside the central alps implying 70 km of fault convergence there 4 0 ar 3 9 ar age trends for hornblende near the alpine fault suggest that horizontal surfaces in the lower crust in the pacific plate have been overturned by reverse slip ductile shearing across a zone of distributed deformation that extends 2 km beyond the 1 km thick basal mylonite zone at the broadest orogen scale higher uplift rates throughout the central southern alps may be related to a rheologically controlled increase in the convergent velocity of points to the east of the alpine fault associated with a strengthening of the pacific crust at a more local scale maximum rates of uplift are inferred to occur near franz josef and fox glaciers because the alpine fault steepens at depth structural data suggests that its footwall ramp is curved and that the fault s dip steepens by 15 20 relative to its attitude farther to the south this 10 20 km long restraining bend may enhance local rates of rock uplift near franz josef and fox glaciers contemporary normal stress and shear resistance may also be increased on this part of the alpine fault helping to explain the central region s quiet historic seismicity and apparently strongly locked nature

dehydration and incipient charnockite formation a phase equilibria and fluid inclusion study from south india a 3 m traverse across a charnockite lens in a biotite garnet graphite gneiss quarry from southern india has provided mineral equilibria that indicate charnockite formation occurred under fluid conditions of x h 2 o 0 2 to 0 3 at p 5 5 pm 1 9 kb and t 700 to 750 c dehydration of biotite loss of garnet and growth of orthopyroxene are related to a decrease in x h 2 o in the fluid phase within the charnockite lens isotopic analysis of the fluid entrapped in quartz from the charnockite indicates delta 13 c 8 2 0 3 0 heavier than delta 13 c values from smaller volumes of co 2 entrapped in quartz from the gneiss although the increase in fluid inclusion abundance in the charnockite can be related to oxidation of graphite without influx of co 2 an external source of co 2 is required in order to account for the shift to heavier carbon isotope values observed in both graphite and entrapped co 2 within the charnockite carbon isotope data across the gne

products and timing of diagenetic processes in upper rotliegend sandstones from bebertal north german basin parchim formation flechtingen high germany aeolian fluvial upper rotliegend sandstones from bebertal outcrops flechtingen high north germany are an analogue for deeply buried permian gas reservoir sandstones of the north german basin ngb we present a paragenetic sequence as well as thermochronological constraints to reconstruct the diagenetic evolution and to identify periods of enhanced mesodiagenetic fluid rock reactions in sandstones from the southern flank of the ngb bebertal sandstones show comparatively high concentrations of mesodiagenetically formed k feldspar but low concentrations of illite cements illite rich grain rims were found to occur preferentially directly below sedimentary bounding surfaces i e aeolian superimposition surfaces and indicate the lowest intergranular volume illite grain rims also indicate sandstone sections with low quartz and feldspar cement concentrations but high loss of intergranular volume due to compaction 40ar 39ar age determination of pronounced k feldspar grain overgrowths and replacements of detrital grains indicates two generations an early triassic and a late jurassic generation the latter age range is similar to published diagenetic illite ages from buried rotliegend reservoir sandstones the first generation suggests an early intense mesodiagenetic fluid flow with remarkably high k activity synchronous with fast burial of proximal initial graben sediments on the southern flank of the ngb accordingly zircon fission track data indicate that the strata already reached the zircon partial annealing zone of approximately 200 c during early mesodiagenesis zircon u th he ages 92 12 ma as well as apatite fission track ages 71 75 ma indicate the termination of mesodiagenetic processes caused by rapid exhumation of the flechtingen high during late cretaceous basin inversion

extremely high density pure co2 fluid inclusions in a garnet granulite from southern india abstract a late archean 2 4 2 7 ga garnet granulite from the southern margin of the south indian craton preserves fluid inclusions with the highest density co2 yet reported from lower crustal rocks the rock comprises garnet clinopyroxene salite plagioclase amphibole pargasite orthopyroxene hypersthene biotite scapolite and quartz with accessory k feldspar ilmenite apatite and ankerite pressure temperature estimates of 9 11 kbar and 740 800 c are computed from electron microprobe data on equilibrium assemblages we report here detailed inclusion petrography and microthermometric data on fluids trapped in garnet feldspar and quartz from the granulite the dominant category in all these minerals are composed of monophase carbonic inclusions with melting temperatures close to 56 6 c indicating a co2 rich composition for the fluid laser raman microscopic studies confirm that the fluid is pure co2 with no traces of impurities such as n2 and or ch4 the inclusions homogenize into the l

deep structure and evolution of the harz mountains results of three dimensional gravity and finite element modeling a new bouguer anomaly map is presented for the region of the entire harz mountains based on more than 60 000 gravity values the various gravity anomalies are discussed and interpretation is carried out by high resolution 3 d gravity modeling one of the main subjects of interest in the investigation is the northern boundary fault zone of the harz mountains separating the mesozoic sediments in the north from the palaeozoic rocks of the harz in the south dip and vertical displacement are determined for this fault zone mean values are 3400 m and 70 respectively gravity modeling shows that the brocken and the ramberg granites are distinctly different the brocken granite is shallow whereas the ramberg granite has a maximum depth of 8 5 km and a n s dimension of 37 km the prominent benneckenstein gravity high is explained by two different models one based on a granodioritic intrusion 2900 kg m3 with a center depth of 14 km and the other based on phyllites 2740 kg m3 on a depth of 3 4 km studies on the geodynamic evolution of the harz mountains are carried out using the finite element method on the basis of a 3 d model vertical displacements that can be related to horizontal forces are computed for the period of the variscan orogeny an uplift of 600 m in the harz area is calculated for late cretaceous and tertiary 400 m are determined the total amount of 1000 m is about 12 of the vertical displacement of the northern boundary fault zone of the harz mountains shown by the gravity modeling these results do not contradict geological ideas

late cretaceous exhumation and uplift of the harz mountains germany a multi method thermochronological approach the harz mountains represent one of the most prominent surface expressions of late cretaceous intraplate shortening in central europe we present a comprehensive low temperature thermochronological data set zircon and apatite fission track and u th he covering the exhumed paleozoic basement of the harz mountains and the adjacent kyffhauser block as well as lower triassic sedimentary rocks of the western and southern rim of the harz mountains integration of results with sedimentological data from the syntectonic late cretaceous subhercynian basin allows for a detailed reconstruction of the timing of uplift and erosion of the harz mountains the data reveal that i tectonic reorganization and initial exhumation started at around 90 ma ii uplift and emergence caused erosion of the mesozoic sedimentary cover between 86 85 ma and 83 82 ma and iii erosion of at least 3 4 km of underlying paleozoic rocks followed and continued into the paleogene the thickness of removed overburden amounts to at least 6 km and most erosion occurred in santonian to campanian time at minimum rates of 0 5 km myr the southwestern rim of the harz has exhumed slower over a longer period of time and may record a phase of late cretaceous syntectonic sediment accumulation

site amplifications for generic rock sites seismic shear wave velocity as a function of depth for generic rock sites has been estimated from borehole data and studies of crustal velocities and these velocities have been used to compute frequency dependent amplifications for zero attenuation for use in simulations of strong ground motion we define a genetic rock site as one whose velocity at shallow depths equals the average of those from the rock sites sampled by the borehole data most of the boreholes are in populated areas for that reason the rock sites sampled are of particular engineering significance we consider two genetic rock sites rock corresponding to the bulk of the borehole data and very hard rock such as is found in glaciated regions in large areas of eastern north america or in portions of western north america the amplifications on rock sites can be in excess of 3 5 at high frequencies in contrast to the amplifications of less than 1 2 on very hard rock sites the consideration of unattenuated amplification alone is computationally convenient but what matters for ground motion estimation is the combined effect of amplification and attenuation for reasonable values of the attenuation parameter k 0 the combined effect of attenuation and amplification for rock sites peaks between about 2 and 5 hz with a maximum level of less than 1 8 the combined effect is about a factor of 1 5 at 1 hz and is less than unity for frequencies in the range of 10 to 20 hz depending on t using these amplifications we find provisional values of about ao 70 bars and k 0 0 035 sec for rock sites in western north america by fitting our empirically determined response spectra for an m 6 5 event to simulated values the borehole data yield shear velocities 033o of 618 and 306 rrdsec for rock and soil sites respectively when averaged over the upper 30 m from this we recommend that v30 equals 620 and 310 m sec for applications requiring the average velocity for rock and soil sites in western north america by combining the amplifications for rock sites and the site factors obtained from our analysis of strong motion data we derive amplifications for sites with 17 3o 520 m sec nehrp class c corresponding to a mix of rock and soil sites and v3o 310 and 255 m sec average soil and nehrp class d sites respectively for the average soil site the combined effect of amplification and attenuation exceeds a factor of 2 0 for frequencies between 0 4 and about 4 hz with a peak site effect of 2 4 the peak of the nehrp class d site effect is 2 7

crustal evolution in south india constraints from nd isotopes nd isotope analyses from a range of lithologies including charnockites metasediments and granitoids that comprise the high grade terrain of south india define contrasting age provinces north of the palghat cauvery shear zone the karnataka craton and the granulite blocks of nilgiri and madras are characterized by model nd ages from 3 4 to 2 4 ga with significant crustal growth during the late archean south of the palghat cauvery shear zone a pan african granulite facies event resulted in sm nd fractionation as observed in several incipient charnockite localities model nd age calculations that allow for sm nd fractionation at 550 ma yield ages in the range of 2 9 to 1 3 ga this range compares closely with published model nd ages from the high grade terrain of sri lanka mid proterozoic crustal growth 1 1 ga observed in the vijayan complex of sri lanka may have provided source material for metasediments characterized by young model nd ages in southern peninsular india the palghat cauvery shear z

stability assessment of sandstones from the st servatius church in quedlinburg unesco s world heritage site germany the st servatius church in quedlinburg unesco s world heritage site germany is characterised by long standing stability problems and structural damages which have been known over the last several centuries the monotonous cretaceous sandstone with its poor lithification is considered to be the main factor the sandstone is characterised by a high porosity of around 30 vol max ca 35 vol and a corresponding high w value the porosity and the degree of cementation are responsible for the very low compressive strength of around 8 mpa at maximum whereas under moisture these values are significantly reduced up to 40 the freeze thaw tests indicate a very poor resistance to frost weathering which may explain the near surface softening of the sandstone direct shear experiments with an approximate 60 angle of friction on the sandstone clearly demonstrate the safety margins initial geotechnical modelling does not favour the hypothesis that a landslide of the hill parallel to the southward dipping bedding planes i e shear failure along weak zones can occur a prominent clay layer also with a southward dip below the entire castle hill is monitored to determine the possible amount of movement with respect to the geological discontinuities e g joints fractures at present a combination of foundation problems are being considered for the stability situation at the church these include construction deficiencies due to deformation or softening of the foundation of the forerunner churches and missing or faulty connections from building additions geological factors responsible for the stability problems include the softening of the sandstone by the influence of weathering and penetrating water as well as the presence of possible shear planes and joints

structure and quantification of processes controlling the evolution of the inverted ne german basin abstract a ne sw reflection seismic transect crossing the entire ne german basin negb was investigated in detail to study the interaction between tectonics and sedimentation during the multiphase evolution of the region by restoring a geological section across the post rotliegend the kinematic evolution was reconstructed and rates of important geological processes such as erosion or basin shortening were quantified the present day structural style of the negb is the result of several major deformation events 1 regional subsidence accompanied by local thin skinned e w extension during the permo triassic jurassic was followed by basin inversions at the 2 jurassic cretaceous and at the 3 cretaceous tertiary boundary zechstein salt played an important role since mobile zechstein evaporites decoupled the supra salt from the sub salt succession and allowed the transmission of deformation over a large distance of major significance to the late cretaceous structural development was the crustal scale upthrusting of the calfoerde block along the gardelegen fault at the southern basin margin the accompanying horizontal shortening has a minimum value of 9 km and led to the development of thrusts and folds within the post zechstein succession

frequency dependent site amplifications with f 0 01 hz evaluated from velocity and density models in central taiwan the frequency dependent site amplifications at 87 free field strong motion station sites in central taiwan are evaluated from the velocity and density structures constructed from borehole data measured at shallow depths and the veloc ity models inferred from earthquake data at great depths results based on the quarter wavelength approximation method proposed by boore and joyner 1997 show that the site amplifications increase with frequency and are larger in the western plain with thick holocene alluvium than in the western foothill with pleistocene and miocene formations considering wave attenuation site amplification first increases and then decreases with increasing frequency the turning frequency ft associated with the maximum amplification varies site by site

restoration of the cretaceous uplift of the harz mountains north germany evidence for the geometry of a thick skinned thrust reverse movement on the harz northern boundary fault was responsible for the late cretaceous uplift of the harz mountains in northern germany using the known geometry of the surface position and dip of the fault and a published cross section of the base permian horizon we show that it is possible to predict the probable shape of the fault at depth down to a detachment level we use the inclined shear method with constant heave and argue that a shear angle of 30 was most likely in this case the detachment level is at a depth of ca 25 km kinematic restoration of the harz mountains using this fault geometry does not produce a flat horizon rather it results in a ca 4 km depression airy heiskanen isostatic equilibrium adjustment of the harz mountains restores the base permian horizon to the horizontal as well as raising the moho to a depth of 32 km a typical value for northern germany restoration also causes a rotation of tectonic fabrics within the harz mountains of about 11 clockwise we show that this model geometry is very good fit to the interpreted dekorp basin 9601 deep seismic profile

cordierite gneisses of southern kerala india petrology fluid inclusions and implications for crustal uplift history the cordierite bearing gneisses occurring as elongate patches in an 8 to 10 km wide zone along the achankovil fault lineament at the northern margin of the southern kerala crustal segment represent an important lithological unit in the archaean granulite terrane of south india the textural relationships in these rocks are consistent with the following main reactions 1 garnet quartz cordierite hypersthene 2 garnet sillimanite quartz cordierite 3 hypersthene sillimanite quartz cordierite 4 sillimanite spinel cordierite corundum and 5 biotite quartz sillimanite cordierite k feldspar many of the mineral associations and reaction textures including the remarkable preservation of symplectites are indicative of partial replacement of high pressure assemblages by cordierite bearing lower pressure ones during an event of rapid decompression temperature estimates from coexisting mineral phases show 710 garnet biotite 791 garnet cordierite and 788 c garnet orthopyroxene pressure estimates from mineral assemblages range from 5 4 to 7 kb detailed fluid inclusion studies in quartz associated with cordierite show high density co2 0 80 0 95 g cm3 as the dominant fluid phase with traces of probable ch4 in the sillimanite bearing rocks the isochore for the higher density fluid inclusions defines a pressure of 5 5 kb the fracture bound co2 and co2 h2o ch4 inclusions indicate simultaneous entrapment at 400 c and 1 7 kb in the cordierite hypersthene assemblage and 340 c and 1 2 kb in the cordierite sillimanite assemblage the p t path delineated from combined solid and fluid data corresponds to the piezothermic array of the gneisses and is characterized by t convex nature indicative of rapid and virtually isothermal crustal uplift probably aided by extensional tectonics

thermochronological constraints on the long term erosional history of the karkonosze mts central europe abstract a combination of zircon u th he zhe apatite fission track aft and apatite u th sm he ahe thermochronology is used to constrain the long term exhumation and erosional history of the karkonosze mts in north eastern bohemian massif by analyzing samples from the highly elevated summit planation surface zhe ages from the south eastern part of the planation surface are 285 19 295 20 and 308 21 ma indicating that the area remained at temperatures below 190 c since the permian in contrast zhe ages in the western part of the planation surface are mid cretaceous proving that this part was residing at temperatures above 190 c prior to exhumation the exhumation occurred in the late cretaceous as evidenced by aft and ahe ages ranging from 82 5 to 90 8 ma and from 77 5 to 91 6 ma respectively modelled cooling trajectories are characterized by a two stage cooling history fast cooling through the apatite partial annealing zone and helium partial retention zone to surface conditions between 90 and 75 ma and slow cooling or even thermal stagnation from 75 ma to present although our data do not allow us to resolve the age of the planation surface completely we narrowed down the number of explanatory options and propose two alternative solutions for the formation of the planation surface i the planation surface represents the remnant of a permian peneplain which was buried by mesozoic sediments of the central european basin system and was re exposed in the late cretaceous or ii the planation surface formed after 75 ma after termination of a period of massive erosion documented by thermochronological data and by the sedimentary record in adjacent basins cenozoic relief production and uplift of the planation surface evident from regional landforms and the sedimentary record is not recorded by thermochronological data this shows that erosion on the uplifted planation surface since 75 ma was less than 1 2 km

estimates of shear wave q and κ0 for unconsolidated and semiconsolidated sediments in eastern north america measured and calculated values of the effective quality factor qef and the site attenuation parameter 0 for unconsolidated and semiconsolidated sediments in eastern north america ena indicate that the latter is strongly dependent on sediment thickness estimates of 0 for national earthquake hazard reduction program nehrp bc site profiles sediment plus hard rock in the mississippi embayment and the atlantic coastal plain were found to increase from about 9 to 31 msec for sedi ment thicknesses ranging from 116 to 600 m stochastic simulations using the 175 m thick hypothetical nehrp bc site profile used to estimate ena ground motions in the nationalseismichazardmapsbytheu s geologicalsurvey usgs indicatethat 0 20 msec provides a smaller estimate of amplification that agrees more closely with the low strain short period site coefficients in the nehrp recommended provisions for seismic regulations for new buildings and other structures nehrpprovisions than the10msecvalueusedbytheusgs alinearregressionofthe 0 estimatescompiledin this study indicates that 0 20 msec corresponds to a relatively thick bc sediment thickness of 460 116 m these same stochastic simulations indicate that the rela tivelyshallowusgssiteprofileprovidesestimatesofamplificationthataresmallerthan thelow strainlong periodsitecoefficientsinthenehrpprovisions thedependenceof bothsiteattenuationandsiteamplificationonsedimentthicknesssuggeststhattheuseof a single reference site condition for hazard mapping might not be appropriate instead theseresultsimplythateitheraregionalsetofreferencesiteprofilesshouldbedeveloped or that a more uniform site condition such as hard rock should be used to define a more stable reference site condition in ena

evolution of the northeast german basin inferences from a 3d structural model and subsidence analysis abstract a 3d structural model of the northeast german basin was evaluated with special emphasis on its evolution as an intracontinental depression the study includes investigations on subsidence history and structural setting of the basin thickness evolution and calculated tectonic subsidence volumes of permian to quaternary sediments in the northeast german basin indicate that the subsidence history was related to five stages of basin evolution which differ in their subsidence mechanisms for the initial rift phase in the late carboniferous to early permian a dominant thermal event and subordinate horizontal stresses were indicated by thickness variation evolution and by structural evidence the main part of basin subsidence occurred in a nw se oriented basin in the subsequent phase of thermal relaxation with maximum subsidence from early permian rotliegend to middle triassic muschelkalk from middle triassic the thermal subsidence pattern was superposed by further tectonic events in the middle triassic regional extension led to a reconfiguration of the southern part of the basin where new nne ssw trending troughs rheinsberg and gifhorn troughs developed in the jurassic the northwestern part of the basin was uplifted while in the south the keuper subsiding areas continued to sink and nw se trending depressions related to salt margins became important differentiation continued into cretaceous times when regional compression caused uplift of the southeastern part of the basin and basin margins a final subsidence phase occurred in the cenozoic this was accompanied by intensive salt movement recent basin configuration reflects the superposition of structural elements resulting from different evolution stages the main structural characteristics of the basin are 1 a vertical tectonic zonation in a pre zechstein succession which lacks significant internal structures and a strongly deformed post zechstein succession which was decoupled due to the thick zechstein salt and 2 a marked asymmetry of the basin with a shallow northern slope and a steep bounding fault at the southern margin elbe fault system the northwestern part of the basin shows the structural properties of an intracratonic sag basin with persisting subsidence and with minor salt mobilisation in contrast initial structures in the southeastern part are strongly overprinted by younger tectonic events including middle triassic to jurassic extension late cretaceous inversion and late to post cretaceous salt movements tectonic elements that deform the whole sedimentary succession are restricted to the basin s southern eastern and northeastern margins where salt thickness decreases combined volumetric and backstripping investigations show that 2 3 of the total subsidence was induced by the sediment load and 1 3 was caused by tectonics the tectonic subsidence history varies laterally across the basin while tectonic subsidence curves in the northwestern part of the basin show fast subsidence during the permian and early triassic decreasing exponentially with time subsidence curves in the southeastern part indicate repeated tectonic activity however the tectonic subsidence volume created during permian to late triassic is significantly higher than the tectonic subsidence during younger phases of basin history

post variscan tectonic and landscape evolution of the elbe fault zone and the lusatian block based on apatite fission track data and geomorphologic constraints abstract the elbe fault zone is a continental scale nw striking structure that contains faults of different kinematics some faults were active at different times since at least the variscan orogenesis in the late carboniferous the lusatian fault lf was one of the major structures of the elbe fault zone in the late cretaceous when nw striking faults of central europe experienced basin inversion and thrusting during a short lived pulse of contraction the lf displays a curved appearance on earth surface what is not compatible with its activity at only one well defined event possibly different faults where active along strike of the lf at different times apatite fission track thermochronology can distinguish differential exhumation or burial of neighbouring fault blocks if the vertical difference comprised at least 1 2 km this study presents apatite fission track data from the footwall and the hangingwall block of the lf and some other faults in its vicinity our new data show a clear difference between the hangingwall block of the lf the lusatian block with uniform 70 85 ma apparent ages and relatively long track lengths and the footwall block of the lf with 66 173 ma apparent ages and shorter and more variable track lengths for one section of the lf we can show that the cretaceous fault is not visible geomorphologically but was substituted by a neighbouring cenozoic reverse fault with a distinct fault scarp we used thermal history modelling to determine the timing and magnitude of exhumation and burial events from apparent apatite fission track ages and track length distributions we infer that the present morphological expression of the lf consist of smaller faults of different kinematics and age and present an evolution model for this section of the lf this study establishes the existence of similar striking reverse faults in direct vicinity and partly intersecting each other in the elbe fault zone this observation emphasizes the significance of the elbe fault zone as a continental scale zone of crustal weakness it has not only been reactivated several times since the variscan orogenesis but represents a cluster of similar striking faults of different age and kinematics

late cretaceous to recent tectonic evolution of the north german basin and the transition zone to the baltic shield southwest baltic sea abstract in this study we investigate the late cretaceous to recent tectonic evolution of the southwestern baltic sea based on a dense grid of seismic reflection profiles this area covers the baltic sea sector of the salt influenced north german basin and its transition to the salt free baltic shield across the tornquist zone the upper cretaceous to recent structural evolution is discussed by means of individual seismic sections and derived high resolution time structure maps of the main horizons i e the upper cretaceous tertiary and pleistocene the upper cretaceous and tertiary layers reveal numerous significant faults throughout the study area several of these faults propagate upwards across the unconsolidated pleistocene sediments and occasionally penetrate the surface the salt influenced north german basin reveals three major fault trends nw se n s and nne ssw several of these faults are located directly above basement sub salt faults and salt pillows the majority of these faults are trending n s to nne ssw and parallel the direction of the gluckstadt graben faults in the salt free tornquist zone we identify two major shallow fault trends which are nw se and ne sw the majority of these faults are located above basement faults following the direction of the tornquist zone we conclude that generally basement tectonics controls activation and trends of shallow faults if salt is present the ductile salt layer causes a lateral shift between the sub and supra salt faults major plate reorganisation related to the africa iberia europe convergence and the subsequent alpine orogeny caused reactivation of pre existing faults and vertical salt movement in the late cretaceous the change of stress orientation from ne sw to a nw se during neogene caused another phase of fault and salt tectonic reactivation we explain that the ice sheet loading and or present day stress field may have acted in combination causing the recent tectonics and upward extension of the faults

new information on the thermal history of the southwestern lower saxony basin northern germany based on fission track analysis the southwestern part of the lower saxony basin lsb is characterized by gravity and magnetic anomalies and by an extremely high thermal maturity of organic matter this was for many years attributed to a late cretaceous intrusion but actually deep burial is being debated the complex thermal history of the area has been studied by fission track analysis zircon data provide evidence for widespread hydro thermal activity during the permian and upper jurassic lower cretaceous apatite ages indicate a major cooling event in the mid cretaceous 89 72 ma reflecting the time of inversion of the lsb during the cretaceous the cooling of the basin centre was rapid compared to the basin margins apatite fission track ages from borehole samples which are recently within the upper part of the apaz indicate a young heating of the sedimentary sequences until present

fission track thermochronology of the ruhla crystalline complex new constraints on the post variscan thermal evolution of the nw saxo bohemian massif abstract to help clarify the relative and absolute timing of post variscan cooling and exhumation processes in the ruhla crystalline complex rcc situated in the nw part of the saxo bohemian massif eight zircon and eleven apatite fission track ages and nine apatite track length measurements have been obtained zircon fission track ages support an existing model of post variscan exhumation of the rcc as three discrete blocks the eastern and western blocks show cooling from peak metamorphic conditions to below 260 30 c by ca 300 ma and exposure by 296 ma the central block shows a later cooling to below 260 30 c by ca 270 ma and exposure at the surface by ca 256 ma apatite fission track data reveal late cretaceous accelerated cooling through the apatite partial annealing zone 120 to 60 c this can be correlated with tectonic inversion at this time the apatite data also indicate that the rocks of the rcc were at temperatures above 110 10 c before ca 85 ma this requires either an anomalously high palaeo geothermal gradient of ca 60 c km 1 during the late cretaceous or that the rcc region was originally covered by up to 1400 m of now eroded jurassic and cretaceous sedimentary rocks we favour a combination of both factors with accelerated erosion of missing overburden during a period of increased heat flow initiated at ca 85 ma

crust mantle boundaries in the taiwan luzon arc continent collision system determined from local earthquake tomography and 1d models implications for the mode of subduction polarity reversal abstract in order to better understand the mode of subduction polarity reversal in the taiwan luzon arc continent collision zone we mapped its crust mantle boundaries using local earthquake tomography by contouring surfaces of constant vp 7 5 km s 1 we identified three moho discontinuities and the plate interface that juxtaposes eurasian lower crust against mantle lithosphere of the philippine sea plate the plate interface dips to the east under southeastern taiwan and steepens progressively towards north until it becomes vertical at 23 7 n from there it continues northward in a vertical orientation until the limit of the tomographic model inhibited further mapping for the moho additional depth constraints were derived from 1d models using p wave arrivals of local earthquakes the mohos of the eurasian and philippine sea plates are disconnected across the plate interface beneath southern taiwan the eurasian moho dips to the east at 50 60 following the orientation of the plate boundary and continuous with the benioff zone towards north the eurasian moho steepens into subvertical again together with the plate boundary the philippine sea plate moho exhibits a synform like crustal root interpreted as the base of the magmatic luzon arc towards the north this root deepens from 30 to 70 km underneath the ryukyu trench in northernmost taiwan the hinge of the vertically subducting eurasian slab steps westward out of the thrust belt leaving the deformation front to the east inactive and giving way to the north dipping philippine sea plate a subhorizontal moho at 30 35 km depth overlies the north dipping philippine sea slab and is interpreted as a newly formed moho established after westward rollback and delamination of the subducting eurasian slab in combination these data support a model of progressive subduction polarity reversal in which a tear within the eurasian lithosphere propagated southwestward deactivating the deformation front

different modes of the late cretaceous early tertiary inversion in the north german and polish basins several selected seismic lines are used to show and compare the modes of late cretaceous early tertiary inversion within the north german and polish basins these seismic data illustrate an important difference in the allocation of major zones of basement thick skinned deformation and maximum uplift within both basins the most important inversion related uplift of the polish basin was localised in its axial part the mid polish trough whereas the basement in the axial part of the north german basin remained virtually flat the latter was uplifted along the sw and to a smaller degree the ne margins of the north german basin presently defined by the elbe fault system and the grimmen high respectively the different location of the basement inversion and uplift within the north german and polish basins is interpreted to reflect the position of major zones of crustal weakness represented by the wnw ese trending elbe fault system and by the nw se striking teisseyre tornquist zone the latter underlying the mid polish trough therefore the inversion of the polish and north german basins demonstrates the significance of an inherited basement structure regardless of its relationship to the position of the basin axis the inversion of the mid polish trough was connected with the reactivation of normal basement fault zones responsible for its permo mesozoic subsidence these faults zones inverted as reverse faults facilitated the uplift of the mid polish trough in the order of 1 3 km in contrast inversion of the north german basin rarely re used structures active during its subsidence basement inversion and uplift in the range of 3 4 km was focused at the elbe fault system which has remained quiescent in the triassic and jurassic but reproduced the direction of an earlier variscan structural grain in contrast n s oriented mesozoic grabens and troughs in the central part of the north german basin avoided significant inversion as they were oriented parallel to the direction of the inferred late cretaceous early tertiary compression the comparison of the north german and polish basins shows that inversion structures can follow an earlier subsidence pattern only under a favourable orientation of the stress field a thick zechstein salt layer in the central parts of the north german basin and the mid polish trough caused mechanical decoupling between the sub salt basement and the supra salt sedimentary cover resultant thin skinned inversion was manifested by the formation of various structures developed entirely in the supra salt mesozoic cenozoic succession the zechstein salt provided a mechanical buffer accommodating compressional stress and responding to the inversion through salt mobilisation and redistribution only in parts of the ngb and mpt characterised by either thin or missing zechstein evaporites thick skinned inversion directly controlled inversion related deformations of the sedimentary cover inversion of the permo mesozoic fill within the mid polish trough was achieved by a regional elevation above uplifted basement blocks conversely in the north german basin horizontal stress must have been transferred into the salt cover across the basin from its sw margin towards the basins centre this must be the case since compressional deformations are concentrated mostly above the salt and no significant inversion related basement faults are seismically detected apart from the basin margins this strain decoupling in the interior of the north german basin was enhanced by the presence of the elbe fault system which allowed strain localization in the basin floor due to its orientation perpendicular to the inferred late cretaceous early tertiary far field compression

late cretaceous and cenozoic intra plate compressional deformations in the alpine foreland a geodynamic model abstract the mesozoic grabens and wrench induced troughs of western and central europe developed in response to triassic early cretaceous intra plate tensional stresses which affected the arctic north atlantic and the tethys borderlands during the rifting phase preceding the opening of the respective oceans this resulted in the fragmentation of the continental crust of the alpine foreland during the late cretaceous and tertiary alpine orogeny collision related compressive stresses exerted on the foreland induced the reactivation of these fracture systems causing the inversion of mesozoic grabens and the uplifting of major basement blocks at distances up to 1300 km to the north of the present alpine deformation front the structural style of these inverted basins and basement uplifts is indicative of compressional and transpressional deformations the total amount of crustal shortening associated with these deformations is unlikely to exceed a few tens of kilometres these displacements require a coupling between the foreland and the orogen at the alpine a subduction zones and within the foreland a decoupling at intra crustal levels between the crust and mantle and or at deeper lithospheric levels the example of the alpine foreland indicates that compressive stresses inducing major deformations can be transmitted from a collisional plate boundary through continental lithosphere over distances of up to 1300 km circumstantial evidence suggests that collision related compressive stresses not large enough to give rise to significant deformations can be transmitted through continental lithosphere over even greater distances

attenuation of seismic shear wave energy in switzerland summary modelling the attenuation of shear wave energy is an important component of seismic hazard analysis previous studies have shown how attenuation particularly in the uppermost layers of the crust is regionally dependent the impact of this is that the decay of energy radiating from an earthquake will vary from place to place to quantify the regional attenuation in switzerland we model the fourier spectral amplitude of small to moderate earthquakes recorded on the local seismic networks high frequency decay is parametrized by q and while apparent geometrical spreading models account for the frequency independent decay of energy we analyse ground motion encompassing the significant duration of shaking to provide models that are useful for the purpose of seismic hazard analysis two methods are used to estimate the whole path attenuation parameter t first a simultaneous fit of the source model and attenuation effects across the entire spectral bandwidth for earthquakes with m 2 and secondly a linear fit of an attenuation model to the high frequency part of the spectrum for earthquakes with m 3 5 the t parameter is found to vary with hypocentral distance consistent with a weakly attenuating crust and strongly attenuating uppermost layer 1 d tomographic inversions indicate a profile of increasing q with depth down to the moho frequency independent decay is parametrized using a three part model which allows for the inclusion of moho reflection phases in the spectrum in the range of 20 140 km in the swiss foreland and from 70 to 140 km in the swiss alps

a reappraisal of the pressure temperature path of granulites from the kerala khondalite belt southern india abstract the kerala khondalite belt kkb of south india is a pan african ca 600 500 ma regional granulite terrain that is composed of charnockites khondalites and migmatitic leptinitic gneiss peak assemblages in the kkb are characterized by orthopyroxene garnet k feldspar magnetite biotite plagioclase quartz in felsic to intermediate rocks and by orthopyroxene cordierite plagioclase quartz or garnet cordierite sillimanite feldspars quartz in semipelites and pelites postpeak reaction textures in these assemblages often involve the production of cordierite and are consistent with a predominantly decompressional pressure temperature history at temperatures in excess of 700 c pressure temperature estimates based on garnet orthopyroxene thermobarometry are in the range of 6 5 7 5 kbar and 860 920 c for localities close to and within the achankovil shear zone a prominent high grade high strain zone on the northeastern margin of the kkb for this northeastern subarea peak t

the role of fe on the formation and diagenesis of interstratified glauconite smectite and illite smectite a case study of upper cretaceous shallow water carbonates abstract the widespread formation of interstratified glauconite smectite gl s and illite smectite i s in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral authigenesis to date however significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry temperature and reaction kinetics on the evolution of composition mineralogy and microstructure of gl s and i s herein we present a study on the reaction mechanisms and the physicochemical conditions that led to the precipitation of early diagenetic gl s and late diagenetic i s on a stable carbonate platform during the cenomanian at langenstein in the northern german basin the texture and the k ar age 95 0 1 8 ma of the green glauconitized grains revealed that green clay authigenesis progressed in initially organic rich semi confined micromilieus i e in fecal pellets and in foraminifera close to the sediment seawater interface the composition of gl s varied in the range k 0 20 0 74 na 0 0 10 ca 2 0 0 05 0 28 0 75 fe 3 0 63 1 20 fe 2 0 08 0 24 al 3 0 19 0 97 mg 2 0 29 0 52 2 01 2 12 al 3 0 09 0 35 si 4 3 65 3 91 o 10 oh 2 and depended on the rate of aqueous fe 2 and k ion diffusion the micromilieu of glauconitization and on the bulk sedimentation rate the mineralogical microstructural and chemical changes of the ongoing gl s products revealed the following reaction for green clay authigenesis at langenstein fe iii smectite reacted with monosilicic acid goethite and aqueous k mg 2 and fe 2 to form glauconite and aqueous na ca 2 and h ions this process considers complex mineral transformations commonly associated with glauconitization such as early diagenetic oxidation of organic matter and microbial catalyzed dissolution of fe oxy hydroxides carbonates and detrital silicates in contrast the k ar age of i s 68 0 1 6 ma and its compositional variability k 0 29 0 45 na 0 0 10 ca 2 0 0 06 0 30 0 55 fe 3 0 16 0 29 fe 2 0 0 10 al 3 1 37 1 68 mg 2 0 18 0 43 2 00 2 12 al 3 0 17 0 39 si 4 3 61 3 83 o 10 oh 2 indicate a burial diagenetic origin for this mineral phase rather than transformation of illitic clays into i s during weathering under warm and humid climatic conditions the results from kinetic modelling support a diagenetic origin of i s 50 60 i layers and 50 40 s layers and imply its formation by the replacement of pre existing k feldspar at high pore fluid activity k na ratios and at low fe 2 concentrations we propose that the substitution of al 3 for fe 3 fe 2 and mg 2 in the octahedral sheet shifts the stability field of the kaolinite fe al mg smectite fe al mg illite or glauconite triple point to much lower monosilicic acid activities and stabilizes the i s or gl s structure this reaction supports the idea that the bio availability of fe is the rate limiting factor for glauconitization which is not the case for the diagenetic growth of i s whereby the pore water fe 2 concentration may be limited by the competing formation of fe oxy hydroxides and or fe sulfides

tracing tectonic deformation using the sedimentary record the study of sediments and sedimentary basins in terms of their tectonic environment requires a multidisciplinary approach and has increasingly drawn both techniques and objectives from fields outside sedimentology the application of different theoretical experimental and empirical resources provided by structural geology geochemistry geophysics scale modelling and field geology complement sedimentological methods with the combined aim of achieving a deeper understanding of the origins evolution and significance of sedimentary sequences in terms of their tectonic history studies presented in this volume range across a wide spectrum from the analysis of sedimentary sequence architecture at basin scale down to the chemical properties of individual grains and include studies from a range of tectonic settings the volume will be of interest to those involved with or contemplating studies involving the linkages between tectonics and sedimentation as well as a wider audience to whom the results of such studies may provide fresh insight

non ideal mixing in the phlogopite annite binary constraints from experimental data on mg fe partitioning and a reformulation of the biotite garnet geothermometer the existing experimental data ferry and spear 1978 perchuk and lavrent eva 1983 on mg fe partitioning between garnet and biotite are disparate the underlying assumption of ideal mg fe exchange between the minerals has been examined on the basis of recently available thermochemical data using the updated mixing parameters for the pyrope almandine asymmetric regular solution as inputs ganguly and saxena 1984 hackler and wood 1984 thermodynamic analysis points to non ideal mixing in the phlogopite annite binary in the temperature range of 550 c 950 c the non ideality can be approximated by a temperature independent one constant margules parameter the retrieved values for enthalpy of mixing for mg fe biotites and the standard state enthalpy and entropy changes of the exchange reaction were combined with existing thermochemical data on grossular pyrope and grossular almandine binaries to obtain geothermometric expressions for mg fe fractionation between biotite and garnet t in k begin gathered text t hw 20286 0 text 0193p 2080 x text mg text gt text text 2 text 6350 x text fe text gt text text 2 hfill text 13807 x text ca text gt text 1 x text mn text gt text 8540 x text fe text gt text x text mg text gt text 1 x text mn text gt text hfill text 4215 x text ca text gt text x text mg text gt text x text fe text gt text 4441 text 2x text mg text bt text 1 mathord left vphantom text 2x text mg text bt text 1 text 13 text 138 right kern nulldelimiterspace text 13 text 138 hfill text 8 text 3143 ink text d text 6 text 276 x text ca text gt text 1 x text mn text gt hfill text t gs 13538 0 text 0193p 837 x text mg text gt text 2 text 10460 x text fe text gt 2 hfill text 13807 x text ca text gt 1 text x text mn text gt text 19246 x text fe text gt text x text mg text gt text 1 x text mn text gt hfill text text 5649 x text ca text gt text x text mg text gt text x text fe text gt text 7972 2x text mg text bt text 1 mathord left vphantom text 5649 x text ca text gt text x text mg text gt text x text fe text gt text 7972 2x text mg text bt text 1 text 6 text 778 right kern nulldelimiterspace text 6 text 778 hfill text 8 text 3143ink text d text 6 text 276 x text ca text gt 1 text x text mn text gt hfill end gathered the reformulated geothermometer is an improvement over existing biotite garnet geothermometers because it reconciles the experimental data sets on fe mg partitioning between the two phases and is based on updated activity composition relationship in fe mg ca garnet solid solutions

three dimensional simulations of seismic wave propagation in the taipei basin with realistic topography based upon the spectral element method we use the spectral element method to simulate strong ground motion throughout the taipei metropolitan area mesh generation for the taipei basin poses two main challenges 1 the basin is surrounded by steep mountains and 2 the city is located on top of a shallow low wave speed sedimentary basin to accommodate the steep and rapidly varying topography we introduce a thin high resolution mesh layer near the surface the mesh for the shallow sedimentary basin is adjusted to honor its complex geometry and sharp lateral wave speed contrasts variations in moho thickness beneath northern taiwan are also incorporated in the mesh spectral element simulations show that ground motion in the taipei metropolitan region is strongly affected by the geometry of the basin and the surrounding mountains the amplification of ground motion is mainly controlled by basin depth and shallow shear wave speeds although surface topography also serves to amplify and prolong seismic shaking

palaeogeological hiatus surface mapping a tool to visualize vertical motion of the continents dynamic topography is a well established consequence of global geodynamic models of mantle convection with horizontal dimensions of 1000 km and amplitudes up to 2 km such physical models guide the interpretation of geological records on equal dimensions continent scale geological maps therefore serve as reference frames of choice to visualize erosion non deposition as a proxy for long wavelength low amplitude vertical surface motion at a resolution of systems or series such maps display conformable and unconformable time boundaries traceable over hundreds to thousands of kilometres unconformable contact surfaces define the shape and size of time gap hiatus in millions of years based on the duration of time represented by the missing systems or series hiatus for a single system or series base datum diminishes laterally to locations anchor points where it is conformable at the mapped resolution it is highly dependent upon scale a comparison of hiatus area between two successive system or series boundaries yields changes in location shape size and duration indicative of the transient nature of vertical surface motion as a single step technique it serves as a quantitative proxy for palaeotopography that can be calibrated using other geological data the tool magnifies the need for geological mapping at the temporal resolution of stages matching process rates the method has no resolving power within conformable regions basins but connects around them when applied to marine seismic sections that relate to rock record not to time biostratigraphic and radiometric data from deep wells are needed before hiatus areas that relate to time can be mapped

numerical modelling of ground motion in the taipei basin basin and source effects summary the taipei basin in northern taiwan is located in a high seismicity region and was affected by several earthquakes in the past ml 7 3 on 1909 april 15 ml 6 8 on 1986 november 15 the chi chi ml 7 3 earthquake on 1999 september 21 and ml 6 8 on 2002 march 31 the main characteristic of the taipei basin is its complex shape with a deep western and shallow eastern part the uppermost sungshan formation with its low shear wave velocities 90 200 m s 1 is also a distinct feature of the basin based on the large data base of earthquake records obtained from the taiwan strong motion instrumentation program network many studies on ground motion within the taipei basin exist however the influence of the various subsurface structures on the observed ground motions as well as the variability of ground motion with respect to earthquake location is not fully understood we apply a 3 d finite difference method to simulate wave propagation up to 1 hz for a small earthquake close to the basin in order to resolve these open questions by varying source and structural parameters we explore the variability of ground motion our study includes a subsurface model that is based on recent studies on the basin structure and on the crustal structure of taiwan from our simulations we find a good fit between simulated and observed waveforms and peak ground accelerations for the considered small earthquake near the basin we also explore the influence of fault plane orientation hypocentre location deep basin structure and soft soil surface layers of the sungshan formation by varying the subsurface structure and earthquake position our studies reveal that the basin structure produces an amplification factor of about 4 compared to hard rock conditions additionally the soft soil sungshan formation produce amplification of a factor of 2 this results in a maximum amplification of the basin structure of about 8 which is in good comparison with amplification values larger than 5 found from the analysis of observed earthquakes these values clearly exceed the amplification values of about 2 3 obtained when applying standard 1 d site effect analysis our simulations for different earthquake positions show that ground motion depends strongly on earthquake location and fault orientation therefore the application of average values of spectral amplification obtained from the analysis of recorded data from distant earthquakes with different azimuths and fault planes may significantly underestimate future ground motions of possible earthquakes on known faults close to the taipei basin the simulation of a small earthquake near the taipei basin presented in this study will help to set up adequate simulation parameters for a possible large earthquake close to the taipei basin such a simulation of a scenario earthquake close to the taipei basin would allow to significantly improve hazard assessment as no observations of strong earthquakes in the vicinity of the basin exist

post metamorphic co2 rich fluid inclusions in granulites in granulite facies samples from the adirondack mountains ny estimates of peak metamorphic co2 fugacities based on mineral equilibria are not consistent with estimates based on data for high density co2 rich fluid inclusions of the 21 adirondack samples investigated for this study all contain co2 rich inclusions inclusions occur in quartz apatite and garnet they range in size from 3 to 50 m and are without visible h2o in a few of the inclusions freezing point determinations and preliminary laser raman spectroscopy show the presence of small amounts 3 of other fluids n2 and h2s co2 liquid vapor homogenization temperatures are between 46 and 31 c corresponding to densities between 1 14 and 0 5 gm cc some of these densities are consistent with peak metamorphic entrapment 1 06 to 1 1 gm cc

provenance of cretaceous clastics in the subhercynian basin constraints to exhumation of the harz mountains and timing of inversion tectonics in central europe the harz mountains and the adjacent subhercynian cretaceous basin figure as the most prominent surface representative for late cretaceous inversion structures in central europe facies depositional architecture and provenance of the basin fill reflect mechanisms and timing of the exhumation of the harz from hauterivian to early santonian there is no evidence for detrital input from the nearby harz area sediments are mature quartzarenites derived from paleozoic basement rocks and or recycled permian to mesozoic sedimentary rocks this situation changed drastically in middle to late santonian when freshly exhumed and eroded mesozoic sedimentary cover rocks of the harz were delivered into the basin feldspar and lithoclasts reflect erosion of triassic and in places jurassic to turonian strata apatite and garnet in heavy mineral spectra are derived from largely unweathered lower triassic buntsandstein as indicated by apatite and garnet chemistry in early campanian paleozoic lithoclasts indicate erosion cutting down into the basement of the harz simultaneous strong decrease of feldspar garnet and apatite suggest an almost complete removal of the 2 3 km thick mesozoic cover of the harz within only 2 4 myr this translates into an exhumation rate of approximately 1 mm a consistent with apatite fission track data from granitoid rocks of the harz mountains

petrography and chemistry of sandstones from the swiss molasse basin an archive of the oligocene to miocene evolution of the central alps oligocene to miocene fluvial sandstones from the swiss molasse basin were analysed for sandstone framework composition heavy minerals whole rock geochemistry and detrital chrome spinel chemistry samples were taken from the proximal part of the basin close to the alpine main thrust and are chronostratigraphically calibrated between 31 and 13 ma sandstone composition allows the identification of different source rocks and their variation in time and space place constraints on the oligocene to miocene evolution of the central alps in the eastern part of the basin sandstones document a normal unroofing sequence with the downcutting from austroalpine sedimentary cover into austroalpine crystalline rocks and slightly later at 21 ma into penninic ophiolites in the central part downcutting into crystalline basement rocks occurred at 25 ma and the removal of the sedimentary cover was much more advanced than in the east this may be interpreted as a first signal from the doming of the lepontine area at 20 ma extensional tectonics in the hinterland led to the first exposure of low grade metamorphic rocks from the footwall of the simplon fault in the central alps erosion of these rocks persisted up to the youngest sediments at 13 ma in the western part of the basin a contribution from granitoid and ultra mafic rocks is documented as early as 28 ma the source for the ultra mafic detritus is penninic ophiolites from the piemonte zone of the western alps which were already exposed at the surface at that time

raman microspectrometry of fluid inclusions abstract for many kinds of fluid inclusions the coupling of microthermometry and raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions a review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation analytical conditions and methodology of the application of raman microspectrometry to gaseous aqueous and hydrocarbon inclusions and their daughter minerals

fluids in metamorphic rocks abstract basic principles for the study of fluid inclusions in metamorphic rocks are reviewed and illustrated a major problem relates to the number of inclusions possibly formed on a wide range of p t conditions having also suffered in most cases extensive changes after initial trapping the interpretation of fluid inclusion data can only be done by comparison with independent p t estimates derived from coexisting minerals but this requires a precise knowledge of the chronology of inclusion formation in respect to their mineral host the three essential steps in any fluid inclusion investigation are described observation measurements and interpretation observation with a conventional petrographic microscope leads to the identification and relative chronology of a limited number of fluid types same overall composition eventually changes in fluid density for the chronology the notion of gis group of synchronous inclusions is introduced it should serve as a systematic basis for the rest of the study microthermometry measurements completed by nondestructive analyses mostly micro raman specify the composition and density of the different fluid types the major problem of density variability can be significantly reduced by simple considerations of the shape of density histograms allowing elimination of a great number of inclusions having suffered late perturbations finally the interpretation is based on the comparison between few isochores representative of the whole inclusion population and p t mineral data essential is a clear perception of the relative chronology between the different isochores when this is possible as illustrated by the complicated case of the granulites from central kola peninsula a good interpretation of the fluid inclusion data can be done if not fluid inclusions will not tell much about the metamorphic evolution of the rocks in which they occur

attenuation of body waves in the central new madrid seismic zone abstract data from the portable array for numerical data acquisition panda deployment in the central part of the new madrid seismic zone have been used to study the attenuation of body waves the spectral decay technique is used to analyze acceleration amplitude spectra of both p and s waves in a frequency range of 5 to 25 hz in order to obtain the high frequency attenuation parameter a multiple weighted least squares method is applied to obtain the site attenuation factor 0 at each station and to get d dr which were interpreted in terms of a two layer q structure consisting of a sedimentary layer overlying the upper crust the 0 values for s waves are stable and show a positive correlation with sediment thickness the 0 values for p waves in the sediments show significant scatter which may be due to greater sensitivity of p wave attenuation to water content of the soils than that of s waves which gave more stable 0 values consistency checks on the assumptions made in obtaining the p and s values are made by studying the source spectrum of several events and the differential sp s from the spectral ratio of the converted sp to s phases the three sets of values are found to be internally consistent but our results are limited to deep sediment sites since the complete vertical distribution of q with sediment depth is not known

precise tracing of exhumation and provenance using 40ar 39ar geochronology of detrital white mica the example of the central alps

paleostress pattern and salt tectonics within a developing foreland basin north western subhercynian basin northern germany analysing the paleostress field in sedimentary basins is important for understanding tectonic processes and the planning of drilling campaigns the subhercynian basin of northern germany is a perfect natural laboratory to study the paleostress field in a developing foreland basin the simple layer cake geometry of the basin fill is dominated by several piercing and non piercing salt structures we derived the paleostress field from the orientation of fracture sets faults slickensides and stylolites on a regional scale the basin fill is characterized by a horizontal compressional paleostress vector that is mainly nne ssw oriented which reflects the late cretaceous inversion phase in central europe we show that the local paleostress field is distinctly perturbated due to the salt structures along the edge of the salt pillows the maximum horizontal paleostress vector is deflected by up to 90 from the regional trend in the case of the elm salt pillow it forms a radial pattern restoration of balanced cross sections demonstrates at least 9 of the shortening of the north western part of the subhercynian basin was achieved by folding the salt structures in the north western subhercynian basin are the result of varying stress conditions initial extension in the triassic caused first salt movements that prevailed during the jurassic and early cretaceous most important is the late cretaceous contractional phase that shortened the diapirs and led to the formation of the salt pillows between diapirs due to detachment folding we derive four main controlling factors for such salt dominated contractional basins 1 the wedge shape basin fill is the product of the dynamic load at the southern margin of the basin 2 a basal salt layer fed the diapirs and acted as a detachment horizon during the later shortening 3 detachment folding was the dominating deformation mechanism during contraction and 4 the pre existing diapirs controlled the position of the detachment folds

metamorphic p t conditions of the kerala south india khondalite belt a granulite facies supracrustal terrain the khondalite belt of southernmost india is an immense section of granulite facies metasediments of probable early proterozoic age dominant rock types are migmatized khondalites garnet sillimanite pm cordierite metapelites acid biotite garnet graphitic gneisses and charnockites quartzofeldspathic gneisses with orthopyroxene throughout much of southern kerala the biotite gneisses are in a state of arrested conversion to charnockite partially decrepitated co 2 inclusions in quartz at the ponmudi mixed biotite gneiss charnockite quarry have significant ch 4 and or n 2 and are texturally late the probable sequence of events in metasediments was 1 migmatization 2 charnockite formation 3 symplectitic cordierite formation and 4 late co 2 entrapment phase equilibrium diagrams of anatexis in aluminous systems and fe mg exchange between garnet and biotite indicate metamorphic temperatures of 650 850 c for the khondalites temperatures based on garnet orthopyroxene

first report of pan african sm nd and rb sr mineral isochron ages from regional charnockites of southern india mineral and whole rock isotope data for a massive charnockite from kottaram in the nagercoil block at the southern tip of peninsular india yield sm nd and rb sr ages of 517 26 ma and 484 15 ma respectively the nd model age calculated for the charnockite is c 2100 ma our study reports the first pan african mineral isochron ages from regional charnockites of peninsular india which are in good agreement with the recently obtained ages of incipient charnockites in the adjacent blocks as well as alkaline plutons within the same block our results indicate that the pan african tectonothermal event in the granulite blocks south of the palghat cauvery shear zone was regional with terrain wide rejuvenation these results correlate with similar pan african tectono thermal events reported from sri lanka and east antarctica and have an important bearing on gondwana reconstructions

clausthalite pbse and tiemannite hgse from the type locality new observations and implications for metallogenesis in the harz mountains germany abstract clausthalite and tiemannite from the type locality clausthal in the harz mountains germany have virtually gone undocumented since their discovery in the nineteenth century the minerals and their selenide assemblages are here documented in historical samples from the konigin charlotte mine in the former clausthal pb zn ag mining district clausthalite and tiemannite are the main selenide components naumannite is generally subordinate whereas klockmannite and eskebornite are accessory minerals the absence of inversion lamellae in naumannite constrains the formation temperature to 87 sr 86 sr values of 0 70914 and 0 71133 for two samples of tiemannite aggregates containing celestine anhydrite inclusions the clausthal selenide assemblages postdated the main sulfide bearing polymetallic vein style mineralisation of the harz mountains

fluid inclusion petrography abstract a procedure of fluid inclusion studies is proposed with emphasis on the criteria of selecting fluid inclusions for detailed microthermometry and spectroscopic analysis an overview of descriptive and genetic classifications of fluid inclusions in single crystals and in massive rocks is given with the intention of further differentiating the commonly used terms primary and secondary fluid inclusions some principles of fluid inclusion modification are explained cathodoluminescence cl studies of quartz with the optical high power cl microscope and the electron microprobe provided with a cl detector are an important help in fluid petrography cl textures are subdivided in primary growth textures and a wide variety of secondary microtextures which are in part induced by fluid inclusions the latter is grouped in textures indicative of local lower crystal order increasing defect structures and microtextures indicative of local quartz healing reduction of the defect structures microtextures showing the genetic relationship between fluid inclusions and the host mineral provide information about the possible post entrapment changes of fluid inclusions and therewith testify their geological relevance

the nagercoil granulite block southern india petrology fluid inclusions and exhumation history abstract the nagercoil granulite block ngb constitutes the southernmost domain in the high grade metamorphic terrain of southern india and dominantly comprises orthopyroxene k feldspar plagioclase quartz biotite ilmenite bearing massive charnockites where they are mixed with aluminous supracrustals the charnockites contain garnet often displaying typical decompression textures with coronal orthopyroxene and plagioclase surrounding relict garnet grains orthopyroxene is preserved in near pristine state in the charnockite suggesting low water activity garnet orthopyroxene thermometry of ngb charnockites yields temperatures of 691 934 c garnet biotite thermometry yield values that broadly overlap 538 864 c with the above estimate although some lower values indicative of retrograde fe mg exchange are also obtained the presence of mesoperthite in the rock and high fluorine content in biotites also suggest high metamorphic temperatures charnockite barometry using garnet orthopyroxene plagioclase quartz assemblage yields 4 0 6 3 kbar an overall drop in pressure by over 2 kbar correlate with the isothermal decompression history inferred from textural criteria detailed fluid inclusion petrographic microthermometric and laser raman spectroscopic data presented here allow an evaluation of the fluid evolution history of ngb charnockites we distinguish four groups of inclusions with the earliest generation characterised by co2 with variable but minor proportion of h2o subsequent generations are dominated by co2 locally ch4 and n2 occur as trace components co2 rich inclusions dominate in all minerals garnet k feldspar plagioclase and apatite homogenisation temperatures assign densities of 0 92 0 93 g cm3 for the co2 involved in charnockite formation a close correspondence of the isochores for co2 h2o and co2 inclusions with p t data derived from mineral phase equilibria suggests fluid entrapment at peak metamorphic conditions the metamorphic evolution of ngb and its exhumation path characterised by isothermal decompression are comparable with those of charnockites from pan african terrains elsewhere in east gondwana

precambrian tectonics and crustal evolution in south india about 3 4 ga ago voluminous calc alkaline magmas represented by the granitoid gneisses of southern india were emplaced into a now poorly preserved non continental crust unstable ensialic basins initiated at about 3 0 ga were filled with volcanic and sedimentary rocks up to about 2 6 ga this basement cover sequence was deformed at the close of the archaean first by northward accretion and thickening of several crustal slabs formerly separated by prisms of stable shelf sediments structures produced by this episode were refolded and dislocated by large n s strike slip shear belts to impart intense steep planar fabrics to large volumes of the crust fluids rich in co possibly derived from sedimentary material driven beneath the crustal slabs by the thickening mechanism purged the deep crust of h o to form granulites upward migration of hot h o rich fluids encouraged partial melting at intermediate crustal levels these late archaean tectonic and thermal events began soon after the close of basin f

triassic to recent tectonic evolution of a crestal collapse graben above a salt cored anticline in the gluckstadt graben north german basin abstract in this study we investigate faulting above a salt wall in the gluckstadt graben north german basin two supra salt faults are mapped from coast to coast over a distance of 6 9 km based on offshore and onshore seismic data these faults form a ca 2 km wide crestal collapse graben and pierce the seafloor salt wall evolution started in the early late triassic to early jurassic due to regional extension and resulting sub salt faulting the salt wall was eroded following exposure to costal and sub aerial erosion by the regional mid late jurassic to early cretaceous uplift late cretaceous to early paleogene compressional tectonics reactivated the vertical salt movement and shortened the salt wall creating a salt cored anticline with the crestal collapse graben above the supra salt faults were reactivated between the late eocene and middle miocene when the principal horizontal stress orientation changed from a ne sw to a nw se the present day orientation stratigraphic data indicate that these faults moved mainly in the cenozoic several observations strongly suggest that the faults continued developing during the pleistocene until today i the pleistocene unconformity is concave upwards and cut by faults ii growth strata within the marine holocene deposits above the graben imply recent tectonic movements iii onshore high resolution p wave vibroseis data of the south eastern eckernforde bay suggest about 10 m of faulted holocene strata and iv marine seismic data show the faults piercing the seafloor we suggest that the recent salt tectonics and upward propagation of supra salt faults resulted from differential ice sheet loading that effect on the salt wall stopped once ice grew over the whole structure at which time the wall subsided because of ice loading the salt wall and faults were reactivated again once the ice front retreated so that the ice loaded only one side of the structure

the high cut parameter kappa for the near surface geology in and around the taipei basin taiwan abstract the decay parameter at the high frequency kappa value introduced by anderson and hough 1984 is measured from 54 stations situated in and around the taipei basin northern taiwan different frequency windows for the s wave amplitude spectra are used to measure the r value for each individual record the preferred r values are determined by the least squared fitting with the best correlation coefficient the site specific 0 values which are computed by removing the anelastic effect of regional geological structure by grouping r into the crustal and subduction events according to the focal depth and site classification i e class b c d and e sites are calculated to be in the range of 0 034 0 066 s we correlate the 0 values with the averaged shear wave velocity of the topmost 30 m layer v s 30 and find the independence of 0 on v s 30 in addition 28 stations lie on sediment in the taipei basin the gradient of 0 versus the sedimentary thickness to the tertiary base in the basin is calculated and then used to estimate the effective quality factor q ef of the layer q ef is 75 3 for the whole sedimentary layers above the tertiary base given one standard deviation q ef are in the 41 9 376 7 range q ef can provide an accurate referred parameter for the future ground motion simulation applications

the chemical composition of specular hematite from tilkerode harz germany implications for the genesis of hydrothermal hematite and comparison with the quadrilatero ferrifero of minas gerais brazil the black shale hosted selenide vein type deposit at tilkerode eastern harz germany has specular hematite enclosed in clausthalite pbse the specular hematite has ti and v in amounts of up to 1 wt tio2 and 3 wt v2o5 and subordinate but important contents of mo 22 372 ppm and b up to 68 ppm the tilkerode hematite serves as a reference for hydrothermal hematite formed at relatively low temperatures 150 c the composition of the tilkerode hematite is compared with that of two generations of specular hematite from itabirite hosted iron ore deposits in the quadrilatero ferrifero of minas gerais brazil the first generation of specular hematite represents an early tectonic hematitisation of dolomitic itabirite at aguas claras and occurs as fine grained crystals reconnaissance data indicate that the aguas claras hematite is poorer in ti and v relative to the tilkerode hematite but has 5 10 ppm b and 7 11 ppm li the second generation of specular hematite defines the pervasive tectonic foliation of the gongo soco iron ore this hematite has ti contents of up to 2 wt tio2 and subordinate amounts of v 62 367 ppm its b and li concentrations are mostly below 2 ppm b and 1 ppm li the presence of ti and b in the tilkerode hematite can be explained by highly saline b bearing fluids that were capable of mobilising otherwise immobile ti the mo signature of the tilkerode hematite suggests that mo was derived from the host black shale in minas gerais b and li were incorporated into the early tectonic hematite from saline fluids at relatively low temperatures aguas claras and then released during metamorphic hematite growth at higher temperatures as suggested by the foliation defining hematite without b li signature gongo soco

the age of the latest thermal overprint of tin and polymetallic deposits in the erzgebirge germany constraints from fluorite u th sm he thermochronology the erzgebirge region of germany records two major episodes of hydrothermal activity which includes a late carboniferous to early permian event associated with significant sn w mineralization that is related to late variscan granite magmatism and a mesozoic episode of polymetallic vein mineralization in contrast to the first event the age of the younger hydrothermal activity is poorly constrained for the latter various geochronological methods yielded a wide age range from permian to early tertiary here we apply fluorite u th sm he thermochronology fhe on both types of mineralization with a twofold goal 1 to investigate the sensitivity and applicability of the new fhe method evans et al 2005 and 2 to constrain the thermal history of ore deposits in the erzgebirge region two hundred and thirty three aliquots from seven mineralization localities have been dated fluorite from six deposits yielded cretaceous fhe ages between 112 to 79 ma which are independent of their paragenesis in contrast fluorite from the sadisdorf sn w deposit yielded an age of 234 ma the younger ages are interpreted as cooling ages indicating the time of the last thermal overprint including possible hydrothermal activity in the erzgebirge the oldest triassic fhe ages at sadisdorf indicate that the mesozoic thermal overprint only partially reset the u th sm he system of the late variscan mineralization thermal modeling based on fhe ages and he diffusion parameters in fluorite results in thermal histories comparable to the results from the well established apatite based thermal modeling this study emphasizes the applicability of fluorite u th sm he thermochronology which is especially suited for ore deposits where apatite is lacking

deciphering the late paleozoic to mesozoic tectono sedimentary evolution of the northern bohemian massif from detrital zircon geochronology and heavy mineral provenance from permian to late cretaceous the northern bohemian massif experienced a complex intra plate tectono sedimentary evolution involving development of at least four generations of sedimentary basins in different settings we examine this protracted evolution using stratigraphic changes in sediment provenance analyzed through heavy mineral assemblages and u pb detrital zircon geochronology by laser ablation icp ms in permian jurassic and late cretaceous successions the provenance data point to multiple temporally evolving sources ranging from local e g the west sudetic island through more distant from elsewhere in the bohemian massif to exotic likely derived from baltica the latter is interpreted as a trace of now completely eroded late jurassic to early cretaceous basin that once covered the lusatian lausitz block and received the baltica derived detritus from northerly fluvial and deltaic depositional systems we suggest that fill of this basin was recycled into the bohemian cretaceous basin during progressive unroofing of the west sudetic island a time slice reconstruction of the paleogeographic and tectono sedimentary evolution of the northern bohemian massif is then developed to show that periods of basin development and deposition early permian late early permian to early triassic middle jurassic early cretaceous and late cretaceous were interrupted by major depositional gaps middle triassic early jurassic mid cretaceous and post early campanian the mesozoic depositional episodes resulted from reactivation of major nw se strike slip fault zones due to stress transfer from the north atlantic rift during jurassic to early cretaceous overridden by the far field effect of convergence of iberia africa and europe during late cretaceous

intraplate brittle deformation and states of paleostress constrained by fault kinematics in the central german platform abstract the structural evolution of central europe reflects contrasting tectonic regimes after the variscan orogeny during mesozoic cenozoic time the brittle deformation related to each tectonic regime is localized mainly along major fault zones creating complex fracture patterns and kinematics through time with diverging interpretations on the number and succession of the causing events by contrast fracture patterns in less deformed domains often provide a pristine structural inventory we investigate the brittle deformation of a relatively stable wide area of the central german platform using fault slip data to identify the regional stress fields required to satisfy the data in a non classical approach and in order to avoid local stress variations and misinterpretations the fault slip data are scaled up throughout the study area into subsets of consistent kinematics and chronology for sedimentary cover and crystalline basement rocks direct stress tensor inversion was performed through an iterative refining process and the computed stress tensors were verified using field based observations criteria on relative tilt geometry and indicators of kinematic change suggest a succession of events which begins with a post triassic normal faulting regime with 3 axis trending ne sw the deformation then follows by strike slip and thrust faulting regimes with a change of 1 axis from n s to ne sw supposedly in the late cretaceous two younger events are characterized by cenozoic normal and oblique thrust faulting regimes with nw se trending 3 and 1 axes respectively the fracture patterns of both the cover and basement rocks appear to record the same states of stress

charnockite geobarometers based on coexisting garnet pyroxene plagioclase quartz numerous geothermometers based on compositions of coexisting minerals have been calibrated experimentally or theoretically during the past 10 yr in contrast few continuous reaction geobarometers exist which have had wide application one based on the reaction of cordierite to garnet sillimanite and quartz is limited by a relatively narrow pressure range of application and also by conflicting calibrations1 2 because the mixing relations of mg and fe and the role of h2o in cordierite3 are not understood another successful barometer uses the assemblage garnet plagioclase al2sio5 and quartz4 5 continuous geobarometers based on the reaction of orthofer rosilite to fayalite plus quartz6 and on the aluminium content of enstatite in equilibrium with garnet7 have been used to a lesser extent the former barometer is limited by rarity of the requisite assemblage and the latter by uncertain experimental calibration for crustal rocks we calibrate here two mineralogical geobarometers from measured thermodynamic data the participating minerals pyroxenes garnet plagioclase and quartz are frequently associated in high grade metamorphic rocks calculation of pressures for several terrains show that the geobarometers yield reasonable and consistent results for the entire range of crustal pressures

strong ground motion in the taipei basin from the 1999 chi chi taiwan earthquake the taipei basin located in northwest taiwan about 160 km from the epicenter of the chi chi earthquake is a shallow triangular shaped basin filled with low velocity fluvial deposits there is a strong velocity contrast across the basement interface of about 600 m sec at a depth of about 600 700 m in the deeper section of the basin suggesting that ground motion should be amplified at sites in the basin in this article the ground motion recordings are analyzed to determine the effect of the basin both in terms of amplifications expected from a 1d model of the sediments in the basin and in terms of the 3d structure of the basin residuals determined for peak acceleration from attenuation curves are more positive amplified in the basin average of 5 3 cm sec 2 compared to 24 2 cm sec 2 for those stations outside the basin and between 75 and 110 km from the surface projection of the faulted area a 40 increase in peak ground acceleration residuals for peak velocity are also significantly more positive at stations in the basin 31 8 cm sec compared to 20 0 cm sec out the correlation of peak motion with depth to basement while minor in peak acceleration is stronger in the peak velocities record sections of ground motion from stations in and around the taipei basin show that the largest long period arrival which is coherent across the region is strongest on the vertical component and has a period of about 10 12 sec this phase appears to be a rayleigh wave probably associated with rupture at the north end of the chelungpu fault records of strong motion from stations in and near the basin have an additional higher frequency signal nearest the deepest point in the basin the signal is characterized by frequencies of about 0 3 0 4 hz these frequencies are close to simple predictions using horizontal layers and the velocity structure of the basin polarizations of the s wave are mostly coherent across the array although there are significant differences along the northwest edge that may indicate large strains across that edge of the basin the length of each record after the main s wave are all longer at basin stations compared to those outside this increase in duration of ground shaking is probably caused by amplification of ground motion at basin stations although coda q 0 67 1 30 hz is slightly larger inside the basin compared to those at local stations outside the basin durations correlate with depth to basement these motions are in the range that can induce damage in buildings and may have contributed to the structural collapse of multistory buildings in the taipei basin

a petrologic and fluid inclusion study of charnockites from the lutzow holm bay region east antarctica evidence for fluid rich metamorphism in the lower crust abstract the proterozoic terrain of lutzow holm bay in east antarctica comprises an amphibolite to granulite facies progression from north to south exposing an oblique section of the lower crust the granulite terrain is represented dominantly by orthopyroxene bearing anhydrous granulites charnockites garnet and biotite bearing gneisses leptynites and garnet sillimanite and graphite bearing aluminous metapelites khondalites thus it is petrographically identical with its gondwanian counterparts in sri lanka and southern india charnockite formation is characterized by the consumption of garnet biotite and quartz to produce orthopyroxene alkali feldspar and plagioclase under isothermal conditions and at reduced water activities a number of mineral reaction textures including orthopyroxene plagioclase symplectites around clinopyroxene relics in intermediate charnockites and spinel rims between adjacent garnet and sillimanite in khondalites suggest near isothermal conditions of equilibration mineral phase equilibria barometry traverse across the granulite terrain indicates an increase in pressure from c 5 kbar in the north to c 8 9 kbar in the south the temperature gradient of c 100 c is less pronounced fluid inclusion studies indicate abundant co 2 trapped within the charnockite minerals the systematic variation in fluid densities with a garnet feldspar quartz succession within individual samples argues against post metamorphic fluid infiltration and fits a scenario of mineral equilibration during near isothermal uplift following a clockwise pressure temperature time path along the pressure gradient the fluid densities show an increase from c 0 98 to c 1 10 g cm 3 this strengthens other evidence of a synmetamorphic entrapment of co 2 preliminary carbon isotope measurements of co 2 extracted from inclusions yield 13 c values of c 5 to 6 suggesting a sub continental mantle source the gondwanan lutzow holm bay terrain had undergone substantial extension during the late proterozoic with displacement along megafaults and emplacement of several alkaline subalkaline granite and syenite plutons and also k basalts it is therefore envisaged that the abundant co 2 in the charnockites could have been derived from an attenuated continental lithosphere and transferred through magmatic conduits

provenance of cretaceous synorogenic sandstones in the eastern alps constraints from framework petrography heavy mineral analysis and mineral chemistry abstract the detrital components of cretaceous sedimentary rocks in the northern calcareous alps reflect the early alpine geodynamic evolution of the austroalpine microplate two contrasting source areas are distinguished on the base of light and heavy mineral analysis the first source area is located at the southeastern margin of the austroalpine and is composed of palaeozoic sediments and metamorphic rocks mesozoic carbonate rocks and ultrabasic rocks derived from the suture zone of the vardar meliata ocean the second source area is located in the northwest in a lower austroalpine position near the transpressive plate margin that juxtaposes austroalpine and penninic units this source area comprises palaeozoic low grade metamorphic rocks including high pressure hp rocks late palaeozoic meta sediments mesozoic carbonate rocks and ultrabasic rocks from obducted slices of penninic oceanic crust chemical analyses of detrital white mica amphibole and garnet support the discrimination between the two source areas tourmaline chemistry calls for a significant amount of metasedimentary rocks in the source area granitoid rocks and high grade metamorphic rocks are rare blue amphibole phengite and chloritoid composition suggest the erosion of lower blueschist facies rocks in the northwestern source area we suggest a modified model of austroalpine valanginian to coniacian tectono sedimentary evolution which is based on 1 an onset of subduction of the penninic ocean no earlier than late cretaceous 2 deposition of the analyzed sedimentary rocks in piggyback basins and 3 a reconstruction of provenance as proposed in this study

frequency dependent sites amplifications evaluated from well logging data in central taiwan 1 based on the quarter wavelength approximation by boore and joyner 1997 the frequent dependent site amplifications at 87 free field strong motion stations in central taiwan from borehole data are evaluated results show that the amplifications increase with frequency and the amplification is larger at the sites in the western plain with holocene alluvium than at those in the western foothill with pleistocene and miocene formations

inversion related features along the southeastern margin of the north german basin elbe fault system abstract a seismostratigraphic approach constrained by well data is used for the interpretation of the deformation style along the central elbe fault system efs within the sedimentary succession structural analysis allows to qualify to quantify and to date tectonic events the stratigraphic interpretation is complicated by the mobilized upper permian zechstein salt and by erosional events a first order quantification of the inversion related uplift is estimated from vertical fault offsets that reach up to 4 km the main uplift occurred during the maastrichtian paleocene amounts of erosion inferred from comparing the strata thickness on top of the flechtingen high with the surrounding basinal areas range from 3 to 4 km the data indicate a changing deformation style thick skinned deformation with southwest dipping thrusts that vertically offset the pre permian basement is observed along the flechtingen high in the central part of the efs thin skinned deformation occurs in the north german basin where salt detaches the post permian cover from the barely faulted basement it is concluded that during the late cretaceous early tertiary inversion the efs responded to regional compression with uplift and formation of an internal high the flechtingen high a stress sensitive crustal weak zone beneath the efs could be the reason for the repeated strain localization in the area

magnetic fabric constraints for syn magmatic doming of the laccolithic brocken granite pluton harz mountains northern germany hyper solidus fabrics of the early permian brocken granite pluton exposed over an area of c 160 km and elongated in nne ssw direction were determined by measuring the anisotropy of magnetic susceptibility ams the brocken granite pluton consists of five petrographically distinguishable and mappable granitic varieties characterized by a generally paramagnetic behavior with primary biotite partly altered to chlorite and secondary tourmaline as the major carrier of the susceptibility whereas biotite modal content isolines roughly follow petrographic trends the tourmaline modal contents do not hence implying secondary post emplacement processes that controlled tourmaline distribution a few samples with primary and secondary magnetite show ferrimagnetic behavior and are co axial with the paramagnetic fabrics the generally low magnetic anisotropies in all granitic varieties are a distinct and challenging feature for determining magmatic flow directions ams data indicate the predominance of sub horizontal fabrics outlining an nne ssw trending dome axis interpreted to have resulted from granite sheets stacked syn magmatically in a high crustal level building up a laccolithic pluton ams fabrics together with age data and geophysical indications suggest that the emplacement and distribution of the brocken granite pluton is structurally controlled by nne ssw striking deep fault structures and only weakly influenced by wnw nw trending structures late carboniferous to early permian plutonism in the harz mountains evolved in an e w directed extensional regime and was accompanied by volcanic activity and development of nw and ne trending sedimentary basins

geochemical compositions of neoproterozoic to lower palaeozoic shales and siltstones in the volta basin ghana constraints on provenance and tectonic setting abstract many researchers have investigated the provenance and tectonic setting of the voltaian sediments using the geochemistry of sandstones in the basin the shales and siltstones in the basin have not been used much in the provenance studies in this paper the geochemistry of shales and siltstones in the kwahu group and oti group of the voltaian supergroup from agogo and environs in the southeastern section of the basin has constrained the provenance and tectonic setting trace element ratios la sc th sc and cr th and rees sensitive to average source compositions revealed sediments in the shales and siltstones may mainly be from felsic rocks though contributions from old recycled sediments and some andesitic rock sediments were identified the felsic rocks may be granites and or granodiorites some intermediate rocks of andesitic composition are also identified while the recycled sediments were probably derived from the basement metasedimentary rocks the enrichment of light ree lan ybn c 7 47 negative eu anomalies eu eu c 0 59 and flat heavy ree chondrite normalized patterns denote an upper continental crustal granitic source materials for the sediments trace element ternary discriminant diagrams reveal passive margin settings for sediments though some continental island arc settings sediments were also depicted mixing calculations based on ree concentrations and modeled chondrite normalized ree patterns suggest that the birimian basement complex may be the source of detritus in the voltaian basin rees are more associated with shales than siltstones on this basis chondrite normalized ree patterns show that shale lithostratigraphic units may be distinguished from siltstone lithostratigraphic units the significant variability in shales elemental ratios can therefore be used to distinguish between shales of the oti group from that of the kwahu group

understanding the physics of kappa κ insights from a downhole array at high frequencies the acceleration spectral amplitude decreases rapidly this has been modelled with the spectral decay factor its site component 0 is used widely today in ground motion prediction and simulation and numerous approaches have been proposed to compute it in this study we estimate for the euroseistest valley a geologically complex and seismically active region with a permanent strong motion array consisting of 14 surface and 6 downhole stations site conditions range from soft sediments to hard rock first we use the classical approach to separate local and regional attenuation and measure 0 second we take advantage of the existing knowledge of the geological profile and material properties to examine the correlation of 0 with different site characterization parameters 0 correlates well with vs30 as expected indicating a strong effect from the geological structure in the upper 30 m but it correlates equally well with the resonant frequency and depth to bedrock of the stations which indicates strong effects from the entire sedimentary column down to 400 m third we use our results to improve our physical understanding of 0 we propose a conceptual model of 0 with vs comprising two new notions on the one hand and contrary to existing correlations we observe that 0 stabilizes for high vs values this may indicate the existence of regional values for hard rock 0 if so we propose that borehole measurements almost never used up to now for 0 may be useful in determining these values on the other hand we find that material damping as expressed through travel times may not suffice to account for the total 0 measured at the surface we propose that apart from material damping additional site attenuation may be caused by scattering from small scale variability in the profile if this is so then geotechnical damping measurements may not suffice to infer the overall crustal attenuation under a site but starting with a regional value possibly from a borehole and adding damping we might define a lower bound for site specific 0 more precise estimates would necessitate seismological site instrumentation

carbonic fluid inclusions in south indian granulites evidence for entrapment during charnockite formation field evidence and fluid inclusion studies on south indian incipient charnockites suggest that charnockite formation occurred during a decompressional brittle regime following the peak of metamorphism and regional deformation the most abundant type of inclusions in quartz and garnet grains in these charnockites contain high density carbonic fluids although lower density fluids occur in younger arrays of inclusions discrete fluid inclusion generations optically are observed to decrepitate over well defined temperature intervals and quantitative measurements of co2 abundance released from these inclusions by stepped thermal decrepitation show up to a four fold increase by volume in the incipient charnockites relative to the adjacent gneisses from which they are derived studies based on optical thermometry visual decrepitation and stepped heating inclusion release together indicate that entrapment of carbonic fluids coincided with charnockite formation we confirm that an influx of carbon dioxide rich fluids is associated with the amphibolite granulite transition as recorded by the incipient charnockites the remnants of which are commonly preserved as the earliest generation of high density fluid inclusions