geodynamic implications of earthquake data in the southern tyrrhenian sea abstract data from short period seismic stations operating in calabria sicily and the aeolian islands have been used to investigate earthquake properties of the southern tyrrhenian lithosphere the results have been analyzed taking into account other geophysical and geological information available in the literature for the same region with the main purpose of contributing to the definition of local geodynamic processes space distribution and focal mechanisms of earthquakes support the hypothesis of southeastward migration of the southern tyrrhenian lithosphere shared by several authors in their tectonic modelling of the area we find that most seismicity appears to be related to two main faults crossing the aeolian island archipelago sisifo and vulcano and propose that these faults are important dislocation structures associated with the lithosphere migration process we also give a detailed picture of the seismic behaviour of the above mentioned fault systems by analyzing the earthquake depth distribution focal mechanisms seismic clustering and strain release some degree of activity was also detected at the eastern boundary of the southern tyrrhenian area calabrian arc in particular our results demonstrate that in this highly stressed zone of contact between different tectonic units tyrrhenian and ionian basins strain is released under seismic form up to depths of the order of 25 km in the crust and not just in the shallowest structures as proposed by other authors

the behavior of lithium and its isotopes in oilfield brines evidence from the heletz kokhav field israel twenty four brine samples from the heletz kokhav oilfield israel have been analyzed for chemical composition and li isotope ratios the chemical composition of the brines together with geological evidence suggests derivation from messinian seawater by evaporation that proceeded well into the gypsum stability field but failed to reach the stage of halite crystallization the present salinity of the samples 18 47 g cl l was achieved by dilution of the original evaporitic brine by local fresh waters like brines from other sedimentary basins the li cl ratios in the heletz kokhav samples show a prominent li enrichment five fold to eight fold relative to modern seawater the isotopic ratios of li expressed in the 6 li notation vary from 26 3 to 17 9 all values being significantly higher than that of modern seawater 32 irrespective of their corresponding li concentration 1 0 2 3 mg l the isotopic composition of li and the li cl ratio in the oilfield brines were acquired in two stages a the original evaporated seawater gained isotopically light li during the diagenetic interaction between the interstitial messinian brine and the basin sediments a parent brine with an elevated li cl ratio was formed the brine was later diluted in the oilfields b the 6 li values of the final brines were determined during epigenetic interaction with the heletz kokhav aquifer rocks at the same time the li cl ratio inherited from stage a remained largely unchanged this work represents the first use of lithium isotopic composition to elucidate the origin and evolution of formation waters in sedimentary basins copyright 2002 elsevier science ltd

is quartz cathodoluminescence color a reliable provenance tool a quantitative examination abstract we examined cathodoluminescence cl colors of quartz by using red 590 780 nm green 515 590 nm and blue 380 515 nm optical filters interfaced with a cathodoluminescence cl detector attached to a scanning electron microscope sem sem cl images taken through these filters were captured digitally and transferred to a computer luminescence intensities luminosities of the images were measured by using available commercial software measured luminosities of these cl images are directly related to relative intensities of red green and blue cl emissions luminosity data were then used to construct plots that display relative luminosities of the cl images acquired through the red green and blue filters an unfiltered cl image of each quartz grain generated by photons with wavelengths ranging from 200 700 nm was also acquired by subtracting the numerical luminosity values of the images acquired through the red green and blue filters from the luminosity value of the unfiltered image the contribution to total luminosity provided by cl emission in the near ultraviolet uv was calculated the cl colors of quartz from a variety of volcanic plutonic and metamorphic rocks and hydrothermal deposits were examined volcanic quartz phenocrysts have the most restricted cl color range with strongest emission intensity in the blue wavelength band cl colors of plutonic quartz overlap those of volcanic phenocrysts but extend over a broader range to include quartz that displays higher intensity of red emission cl emission in hydrothermal vein quartz is similar to that in plutonic quartz although some hydrothermal quartz exhibits stronger green cl emission than does plutonic quartz the cl colors of metamorphic quartz exhibit the widest variation overlapping the color fields of both volcanic and plutonic quartz and extending further into the red cl emission in the near uv makes a significant contribution 5 85 percent to the total luminosity of sem cl images particularly images of plutonic quartz because of overlap in the cl color ranges of volcanic plutonic metamorphic and hydrothermal quartz unambiguous identification of quartz provenance on the basis of cl color alone is problematic it is difficult to distinguish between volcanic and some plutonic quartz and between some plutonic and hydrothermal quartz or to distinguish magmatic quartz from metamorphic quartz that exhibits blue cl color only metamorphic quartz that exhibits moderately strong red emission appears distinguishable on the basis of color from quartz of other origins our work thus suggests that cl color is not a reliable indicator of quartz provenance

optically continuous silcrete quartz cements of the st peter sandstone high precision oxygen isotope analysis by ion microprobe a detailed oxygen isotope study of detrital quartz and authigenic quartz overgrowths from shallowly buried 1 km quartz arenites of the st peter sandstone in sw wisconsin constrains temperature and fluid sources during diagenesis quartz overgrowths are syntaxial optically continuous and show complex luminescent zonation by cathodoluminescence detrital quartz grains were separated from 53 rocks and analyzed for oxygen isotope ratio by laser fluorination resulting

the chemistry of quartz in granitic pegmatites of southern norway petrogenetic and economic implications trace element concentrations in quartz from 188 granitic pegmatites in the froland and evje iveland pegmatite fields southern norway have been determined to establish exploration targets for high purity quartz and to gain a better understanding of the genesis of pegmatites hosting these deposits both pegmatite fields were formed during the sveconorwegian grenvillian orogeny 1145 900 ma at the western margin of the fennoscandian shield in situ raster analyses within single quartz crystals were undertaken by laser ablation inductively coupled plasma mass spectrometry la icp ms spot size 75 m to assess levels of lattice bound impurities rather than mineral and fluid inclusions that are relatively easily removed during high purity quartz processing quartz in the froland pegmatites has relatively pure and homogeneous compositions containing 46 24 gg 1 al 8 3 gg 1 ti 1 4 0 8 gg 1 ge and 11 7 gg 1 li the ti in quartz geothermobarometer gives an average pegmatite crystallization temperature of 537 39 c temperature estimates are highest along the northwestern margin of the pegmatite field 550 c whereas the most differentiated pegmatites occur toward the northeast the area of greatest economic potential for high purity quartz lies just north of the central part of the field where individual pegmatites contain 1 million metric tons mt quartz with low average trace element contents of 67 11 gg 1 from mineral chemical criteria and a range of other geologic factors we propose that pegmatite melts in the froland field were generated by fluid present crustal melting at about 1060 ma in zones of localized high strain deformation during progressive thrusting along the porsgrunn kristiansand fault zone quartz in the evje iveland pegmatites has more variable compositions with 69 57 gg 1 al 19 11 gg 1 ti 2 3 1 8 gg 1 ge and 7 5 gg 1 li from its ti content it crystallized at temperatures of 613 70 c the regional spatial distribution of ti in quartz temperatures appears irregular mainly due to the scattered distributions of chemical evolved pegmatites with amazonite cleavelandite replacement zones which show crystallization temperatures down to 442 c quartz from the evje iveland pegmatites is unlikely to be of current economic interest due to its moderate to high trace element contents heterogeneous chemistry and low volume the evje iveland pegmatites show no apparent genetic link to a granite intrusion instead they probably formed as a result of partial melting at the depth of their amphibolite country rocks at around 910 ma this is related to a regional low pressure high temperature metamorphic event at about 930 to 920 ma

fluid geochemistry contribution to the interpretation of the 2011 2012 unrest of santorini greece in the frame of the dynamics of the aegean volcanic arc

cathodoluminescence of quartz from sandstones interpretation of the uv range by determination of trace element distributions and fluid inclusion p t x properties in authigenic quartz quartz overgrowths from keuper sandstones of the paris basin were examined using cathodoluminescence cl microscopy and spectroscopy coupled with a scanning electron microscope sem with the use of standard cold cl equipment it was observed that the emission of authigenic quartz is much less intense than that of detrital quartz grains but a reversal of intensity was observed with scanned cl in the 200 800 nm range the main cl emission band of diagenetic quartz is at 330 340 nm in the uv range with other bands in the visible range the determination of trace element distributions in authigenic quartz by in situ analyses and by sims imagery reveals the correlation of the 330 340 nm emission band with the highest al and li contents the cathodoluminescence emission of diagenetic quartz in the uv range appears to be influenced by the coupled substitution of al and li into the crystal two explanations are suggested 1 ai li or both serve as activators and 2 the incorporation of al and li causes lattice defects that lead to an enhancement of the intrinsic luminescence trace element analyses and fluid inclusion studies revealed that quartz overgrowths precipitated from a fluid that partially originated from an li enriched primary brine derived from eastern triassic evaporites of the paris basin the specific cl emission band in the uv range can be linked to the diagenetic environment the chemistry of the fluids appears to be the essential parameter whereas precipitation temperatures do not influence the occurrence of such emissions

dynamic stratigraphy of an evaporite to red bed sequence gipskeuper triassic southwest german basin abstract the dynamics of evaporite accumulation are studied in the gipskeuper triassic of the southwest german epicontinental basin based on a hierarchical three level stratigraphic analysis 1 among the various stratification types the following are most important a thin carbonate intervals with marine faunas b massive sulfates with selenite indicating very shallow subaqueous gypsum precipitation c thin bedded gypsarenites with a variety of sedimentary structures suggesting clastic evaporite accumulation during high energy events gypsum tempestites d laminated gypsum with spectacular tepee structures testifying inter to supratidal settings e green grey and reddish claystones with nodular gypsum indicating evaporitic playa mudflats 2 facies sequences occur in several varieties and commonly form 1 4 m thick transgressive regressive cycles with shallowing upwards trends the long recognized carbonate marker beds represent short term trans or ingressions into the almost flat keuper basin highly disturbed tepee horizons form widely correlatable regressive peaks these sequences form evaporite equivalents to the ubiquitous shallowing upward cycles known from carbonate systems 3 the basin fill consists of a small scale cycles being vertically stacked upon each other to form the basic building block of the layer cake architecture of the gipskeuper succession the stacking of small scale cycles is superimposed onto a larger scale regressive cycle which records a general shift from restricted marginal marine to hypersaline marine to the more continental red bed deposition of the overlying keuper this hierarchy of cycles probably reflects various orders of eustatic sealevel fluctuations the gipskeuper thus exemplifies dynamics of evaporite accumulation and allows us to understand some of the processes that produce a layer cake stratigraphy its cycle hierarchy is a common motif in the entire southwest german basin fill and appears typical for epicontinental basins

germanium silicon fractionation in a tropical granitic weathering environment abstract germanium silicon ge si ratios were determined on quartz diorite bedrock saprolite soil primary and secondary minerals phytolith soil and saprolite pore waters and spring water and stream waters in an effort to understand ge si fractionation during weathering of quartz diorite in the rio icacos watershed puerto rico the ge si ratio of the bedrock is 2 mol mol with individual primary mineral phases ranging between 0 5 and 7 mol mol the ratios in the bulk saprolite are higher 3 mol mol than values measured in the bedrock the major saprolite secondary mineral kaolinite has ge si ratios ranging between 4 8 and 6 1 mol mol the high ge si ratios in the saprolite are consistent with preferential incorporation of ge during the precipitation of kaolinite bulk shallow soils have lower ratios 1 1 1 6 mol mol primarily due to the residual accumulation of ge poor quartz ge si ratios measured on saprolite and soil pore waters reflect reactions that take place during mineral transformations at discrete depths spring water and baseflow stream waters have the lowest ge si ratios 0 27 0 47 mol mol reflecting deep initial weathering reactions resulting in the precipitation of ge enriched kaolinite at the saprolite bedrock interface mass balance calculations on saprolite require significant loss of si and al even within 1 m above the saprolite bedrock interface higher pore water ge si ratios 1 2 mol mol are consistent with partial dissolution of this ge enriched kaolinite pore water ge si ratios increase up through the saprolite and into the overlying soil but never reach the high values predicted by mass balance perhaps reflecting the influence of phytolith recycling in the shallow soil

reconstruction of late paleozoic heat flows and burial histories at the rhenohercynian subvariscan boundary germany the thermal and burial history of the herzkamp syncline located in the transition zone between the variscan rhenish massif and the ruhr foreland basin western germany was reconstructed using pdi pc 1d basin modelling software ies the models were calibrated with new vitrinite reflectance data measured on palaeozoic outcrop samples high sample density and quality of the calibration data allowed a 3d reconstruction of the heat flow as well as of burial and erosion history vitrinite reflectance values range from 0 8 to 4 9 rr and generally increase with increasing stratigraphic age the coalification pattern confirms pre tectonic maturation especially in the western part of the study area a low coalification zone showing stagnating decreasing coalification with increasing stratigraphic age exists however northeast of the ennepe thrust indicating synorogenic coalification this anomaly is explained by early thrusting in the northern rhenish massif resulting in restricted burial early uplift and thus lower thermal maturity one result of numerical modelling is that palaeo heat flows during maximum burial westphalian or post westphalian decreased southwards from approximately 65 to less than 50 mw m2 maximum burial depths for the base and top of the namurian also decrease southwards from 7000 to 3600 m and 4600 to 1800 m respectively resulting in southwards decreasing coalification of the respective stratigraphic horizon eroded overburden increases southwards 3100 5700 m with the exception of the low coalification zone which is characterised by lower amounts of eroded overburden 1300 2900 m and an earlier onset of erosion i e in the westphalian b rather than westphalian d or post westphalian

internal triggering of volcanic eruptions tracking overpressure regimes for giant magma bodies abstract understanding silicic eruption triggers is paramount for deciphering explosive volcanism and its potential societal hazards here we use phase equilibria modeling to determine the potential role of internal triggering wherein magmas naturally evolve to a state in which eruption is inevitable in rhyolitic magma bodies whole rock compositions from five large to super sized rhyolitic deposits are modeled using rhyolite melts by running simulations with varying water contents we can track crystallization and bubble exsolution during magma solidification we use simulations with variable enthalpy and fixed pressure for the five compositions the interplay between bubble exsolution and crystallization can lead to an increase in the system volume which can lead to magma overpressurization we find that internal triggering is possible for high silica rhyolite magmas crystallizing at pressures below 300 mpa 50 wt which makes magma immobile high silica rhyolite eruptions from such depths would require external triggering but examples are scarce or entirely absent calculated crystallinities at which the critical overpressure threshold is reached compare favorably with observed crystal contents in natural samples for many systems suggesting that internal evolution plays a critical role in triggering eruptions systems in which fluid saturation happens late relative to crystallization or in which degassing is effective can delay or avoid internal triggering we argue that priming by crystallization and bubble exsolution is critical for magma eruption and external triggering serves simply as the final blow rather than being the driving force of explosive rhyolitic eruptions

seismotectonics of the nubia plate compressive margin in the south tyrrhenian region italy clues for subduction inception 1 seismological and structural data are used to constrain the active tectonics of the nubia plate compressive margin in southern italy in this region compressional displacements have resumed at the rear of the maghrebian orogenic wedge since about 700 500 ka and are presently accommodated along a seismic belt in the south tyrrhenian area where a passive margin has developed during late neogene quaternary times earthquake data from the south tyrrhenian belt are analyzed with bayloc a probabilistic nonlinear location method results show that the seismic belt is segmented and involves a series of ne sw and nw se elongated clusters the ne sw clusters are interpreted as high angle reverse fault zones verging toward the southeast whereas the perpendicular clusters are interpreted as possible strike slip fault zones transferring the contractional displacements to advanced segments of the belt in the southeast brittle deformations observed in the quaternary volcanic island of ustica are consistent with the geometry and kinematics of the seismic belt deduced from the seismological data the south tyrrhenian active belt may constitute an early stage of subduction of the tyrrhenian oceanic crust beneath sicily a similar scenario has been hypothesized also for the westward prolongation of the south tyrrhenian belt off the algerian coast by integrating instrumental and historical seismic data with tectonic evidences we infer that the south tyrrhenian belt is probably capable of producing earthquakes with a maximum size close to magnitude 7 the analyzed data suggest a multifault system behavior for the studied compressional belt this inference is important to estimate and mitigate the seismic and tsunamic hazards in such a densely populated region

quantification of brittle deformation in burial compaction frio and mount simon formation sandstones abstract brittle deformation together with grain rearrangement and ductile grain deformation is a key mechanism of compaction in sandstones quartz cementation by virtue of its impact on sandstone mechanical properties is expected to affect the compaction progress by these various mechanisms sandstone samples of different ages and compositions taken from two basins with contrasting burial histories are used to quantify the relationship between brittle deformation and quartz cementation in the context of burial compaction exponential trends of increasing deformation by microfracturing are observed in both the lithic rich frio formation from the gulf of mexico basin r2 0 81 and in the quartz rich mount simon formation from the illinois basin r2 0 78 the two formations contrast in terms of the observed rate of grain fracture increase with depth a larger number of quartz grains in the mount simon formation undergo fracturing at shallow burial 3 km a larger number of quartz grains are fractured in the frio sandstones cathodoluminescence cl imaging conducted on an sem shows that grain fracturing and subsequent cementation of fractures by quartz can occur before during and after normal quartz overgrowth precipitation although fracturing is generally concurrent with cementation the intensity of brittle deformation for a single fractured grain is independent of depth as illustrated by plotting the ratio of the number of particles in fractured grains versus depth r2 0 21 for frio and 0 03 for mount simon suggesting that once fractured grains do not tend to become the locus of subsequent fracturing apparent fracture apertures in the frio grains are slightly wider average 5 m than in mount simon grains average measurable aperture width 4 m quartz grains in the frio have a variety of fracture morphologies including wedge shaped apertures intense comminution at grain contacts and grains with exploded fabrics apparent fracture apertures in mount simon grains are thinner and transect grains as straight uniform traces differences in fracture intensity and pattern are attributed to the fact that cementation in the frio began at greater depth than cementation in the mount simon combining information on the degree of brittle deformation and the amount of quartz cement localized within microfractures here referred to as cf or volume of intragranular cement allows calculation of the amount that brittle deformation influences compaction in the frio formation 0 12 to 8 37 of porosity loss due to compaction can be attributed to brittle deformation whereas the values for the mount simon formation lie between 0 25 to 2 16 the larger values within both formations are affiliated with deeper samples in which a majority of grains manifest fracturing

origin of quartz cement in the tirrawarra sandstone southern cooper basin south australia abstract quartz cement is the most abundant authigenic mineral in the fluvio deltaic tirrawarra sandstone and plays an important role in controlling reservoir quality quartz cement ranges from 0 to 19 and is controlled by the original sandstone composition petrographic fluid inclusion electron microprobe and cathodoluminescence cl data from the quartz cement indicate multiple stages of cementation at different temperatures and suggest more than one silica source cl observations indicate up to six stages of quartz cement in some samples the stages of quartz cement can be classified into three zones an innermost zone of brown luminescing cement z1 a middle zone of bright blue luminescing cement z2 and an outer zone of brown luminescing cement z3 dead oil or bitumen is trapped b tween z2 and z3 indicating that z3 formed after oil migration commenced measurements of homogenization temperatures from fluid inclusions in quartz overgrowths indicate that quartz cement precipitated over a temperature range of 65 to 130 c z1 quartz cement formed between 65 and 80 c and z2 cement was precipitated between 80 c and 100 c z3 quartz cement formed later at temperatures around 130 c microprobe analysis shows a consistent variation in aluminum between each quartz cement zone the average aluminum content for z1 z2 and z3 is respectively 237 538 and 58 ppm fluid inclusion precipitation temperatures and aluminum content have been used to help identify the silica sources for different zones of cement a likely source of silica for z1 quartz cement is early alteration of feldspar grains the bright blue cl color in the z2 quartz cement is related to its high aluminum content the source of silica for this cement is likely to have been late dissolution of feldspar grains by acidic fluids generated during kerogen maturation late quartz cement z3 has the lowest aluminum content which is similar to that of detrital quartz grains in the tirrawarra sandstone consi ering the temperature of precipitation very low aluminum content and the presence of z3 cement in facies prone to stylolitization the silica source for the cement is likely to have been pressure solution of detrital quartz at stylolites and grain contacts

quartz electron spin resonance signal intensity of al and ti li centers as a provenance indicator an example from the yangtze river basin abstract the quartz electron spin resonance esr signal intensity si of the al and ti li centers in sediment samples collected from the mainstream and major tributaries of the yangtze river basin were measured to determine whether they can be used as fluvial sediment provenance indicators the results show significant spatial variation in the esr si between the bulk coarse 200 355 m and fine 75 154 m grain size fractions for all three size fractions the esr sis of sediment from the mid lower reaches of the basin were higher than those of the upper reaches demonstrating that the esr si can be used to distinguish between quartz contributed by the upper and mid lower reaches of the basin furthermore the quartz esr si of the major tributaries exhibited distinct spatial variation according to the distribution of the type of bedrock thus the quartz esr si can be used to trace the provenance of fluvial sediments even in large river systems additionally the upper yangtze river basin contributed a large amount of material to the lower mid mainstream and even the fine fraction of sediment in the lower yangtze river originated mainly from the upper yangtze river basin

submarine gas burst at panarea island southern italy on 3 november 2002 a magmatic versus hydrothermal episode 1 on 3 november 2002 fishermen observed the sudden appearance at the sea surface of three large whitish plumes 3 km offshore of panarea island aeolian islands southern italy caused by the uprising from the seafloor of huge columns of gas bubbles mixed with sediments and colloidal sulfur the degassing event partly superimposed an already existing gentle degassing fumarolic field since 12 november 2002 a discontinuous geochemical monitoring program of these new discharging fluids have been carried out the submarine emissions collected on november 2002 were an emulsion made by a co2 dominated continuous gas phase with suspended sediments colloidal sulfur and water condensate microdroplets acidified by dissolution of compounds such as so2 hcl and hf in the gas phase light unsaturated hydrocarbons also occurred possibly related to relatively high temperature and oxidizing conditions due to local input of magmatic fluids at depth whose occurrence was also supported by the relative high values of 3he 4he isotopic ratio r rair 4 62 with respect to previously measured values r rair 4 2 the flux of the submarine emissions significantly decreased in a couple of months together with the almost complete disappearance of the magmatic chemical markers and the decrease of the helium isotopic ratio thus the most striking feature of the temporal and spatial evolution in the chemical and isotopic compositions of the submarine fumaroles was the relatively rapid restoration since january 2003 of the precrisis conditions i e typical of a stationary hydrothermal system

recrystallization in quartz overgrowths quartz overgrowths are among the most volumetrically significant diagenetic phases in sandstones many combined petrographic and geochemical studies of quartz overgrowths rely heavily on the long held underlying assumption of their stability this study of sem cathodoluminescence sem cl imaging of quartz overgrowths from the jurassic khatatba formation of egypt calls this assumption into question these overgrowths preserve spectacular sem cl textures that can be interpreted as recrystallization fabrics there are three major growth zones in the overgrowths q1 to q3 in the first q1 fine sem cl zoning is preserved some with relict fibrous textures and smooth or bulging growth surfaces these textures could indicate initial precipitation as opaline silica chalcedony microquartz or some phase other than coarse quartz overgrowth in q1 there are discordant areas locally showing smooth and scalloped boundaries and filled with quartz with the sem cl character of later growth zones such textures suggest that earlier zones were crosscut by later phases of quartz the smooth and scalloped boundaries and their position in the overall framework of cements and grains are in places inconsistent with simple fracturing but are consistent with dissolution of earlier growth zones followed by filling with later quartz these features suggest that earlier growth zones were unstable and were replaced by coarsely crystalline quartz overgrowth such observations and other empirical and chemical considerations suggest that in some cases quartz overgrowths may result from recrystallization of less stable quartz and silica phases thus any study of sandstone diagenesis focused on quartz overgrowths should take this possibility into account

quantification of quartz cements using combined sem cl and image analysis quartz cement content is often difficult to quantify using conventional petrography developments in equipment and technique reported here show how excellent high contrast images of quartz cements can be produced using combined scanning electron microscopy and cathodoluminescence sem cl in most cases quartz cement can be differentiated readily from detrital quartz image analysis allows the percentage of authigenic quartz to be quantified advantages of this method are 1 it can be readily automated 2 backscatter electron bse and cl images can be compared directly and 3 images can be improved through acquiring and integrating multiple images comparison of results from conventional optical petrography with those from sem cl suggests that the percentages of quartz cement determined by conventional methods are overestimated where quartz cement is present in high proportions and are underestimated where quartz cement is less abundant by adopting a statistically rigorous approach to image collection the abundance of quartz cement can be determined by sem cl with a known accuracy

late and post variscan cooling and exhumation history of the northern rhenish massif and the southern ruhr basin new constraints from fission track analysis apatite fission track analyses were carried out on outcrop and core samples from the rhenish massif and the carboniferous ruhr basin germany in order to study the late and post variscan thermal and exhumation history apatite fission track ages range from 291 15 ma lower permian to 136 7 ma lower cretaceous and mean track lengths vary between 11 6 m and 13 9 m mostly displaying unimodal distributions with narrow standard deviations all apatite fission track ages are younger than the corresponding sample stratigraphic age indicating substantial post depositional annealing of the apatite fission tracks this agrees with results from maturity modelling which indicates 3500 7000 m eroded devonian and carboniferous sedimentary cover numerical modelling of apatite fission track data predicts onset of exhumation and cooling not earlier than 320 ma in the rhenish massif and 300 ma in the ruhr basin generally followed by late carboniferous triassic cooling to below 50 60 c rapid late variscan cooling was followed by moderate mesozoic cooling rates of 0 1 0 2 c ma converting into denudation rates of 1 mm a assuming a stable geothermal gradient of 30 c km modelling results also give evidence for some late triassic and early jurassic heating and or burial which is supported by sedimentary rocks of the same age preserved at the rim of the lower rhine basin and in the subsurface of the central and northern ruhr basin cenozoic exhumation and cooling of the rhenish massif is interpreted as an isostatic response to former erosion and major base level fall caused by the subsidence in the lower rhine basin

sources of authigenic quartz in the permian tight sandstones close to gaoqing fault dongying sag bohai bay basin china abstract authigenic quartz is a significant cause of reduced porosity and permeability in the cement of the permian upper shihezi formation p2s sandstones in the gaoqing area dongying sag bohai bay basin china the sandstones are mainly quartzarenite with minor amounts of clay minerals authigenic quartz is generally the most commonly occurring cement and occurs as quartz overgrowth microfracture healing quartz pore filling quartz and microquartz in the sandstones three distinct separate phases of authigenic quartz i ii and iii were distinguished by using cathodoluminescence microscopy cl in the scanned cl images phase i quartz generally appears with light brown luminescence in the 450 670 nm range phase ii quartz is non luminescent in the 420 480 nm range and phase iii quartz appears with dark brown luminescence in the 470 650 nm range phase i quartz originating mainly from pressure solution has a composition similar to that of detrital quartz grains and was formed at approximately 79 3 104 c in the phase ii quartz li na mg2 al3 and ba2 are enriched and the homogenisation temperature of some aqueous inclusions is significantly higher than its maximum burial temperature of 130 c the eu of phase ii quartz is up to 1 42 the silica sources for phase ii quartz are dominated by hydrothermal fluids pressure solution feldspar dissolution and illitisation of smectite also provided a small amount of silica in the phase iii quartz all of the aqueous inclusions are almost higher than its maximum burial temperature al3 mg2 and rb are enriched in most of this quartz which was sourced mainly from hydrothermal fluids pressure solution also provided a very small amount of silica the hydrothermal fluids providing the silica source for phases ii and iii quartz migrated into the p2s sandstones along the adjacent gaoqing fault

rarely observed short period 5 10 s suboceanic rayleigh waves propagating across the tyrrhenian sea 1 shallow earthquakes occurring in the southern part of the tyrrhenian basin excite a long duration low frequency coda that propagates efficiently along paths crossing the tyrrhenian sea seismograms recorded at regional distances in the italian peninsula are analysed in the frequency time domain and compared with synthetics computed in simple vertically varying media based on results of our modeling we interpret the coda as short period 5 10 s suboceanic rayleigh waves their large amplitude and long duration that we emphasize here are explained as due to the influence of the tyrrhenian water layer over a fast seafloor with little s wave attenuation qs 300 a satisfactory fit of amplitude and duration of the observed waveforms is obtained assuming a young oceanic model with an average water column of 1 to 2 km and relatively high s wave velocity 2 5 km s in the shallow crust

implications of trace element composition of syntaxial quartz cements for the geochemical conditions during quartz precipitation in sandstones a petrographic investigation revealed polyphase quartz cementation in the finefrau sandstone upper carboniferous western germany and the solling sandstone lower triassic central germany three different cements could be distinguished in each sandstone based on their cathodoluminescence and trace element composition the first quartz generation is suggested to have been formed during eogenesis due to dissolution and replacement of feldspar the mesogenetic paragenesis comprises two generations of quartz and illite which are accompanied by albite in the solling sandstone sharp luminescence zoning in quartz overgrowths points to distinct episodes of cementation in both sandstones significant amounts of al li and h and traces of ge and b have been detected in the quartz overgrowths the al content of the quartz cements in the finefrau sandstones exceeds that in the quartz cements in the solling sandstone by a factor of five it is suggested that this compositional variation reflects the conditions in the pore water such as temperature and ph the al concentration is generally correlated to the li content with the exception of the latest quartz generation in the finefrau sandstones which is also most enriched in trace elements the ratio of li al varies between 0 11 and 0 25 in the two sandstones the li h ratio which ranges from 0 12 to 0 3 is controlled by the activity ratio of li and h in the pore fluid clay minerals are the most important source for li and high salinities favour the mobilization of li during diagenesis thus a relatively low salinity and low ph are responsible for the low li h ratio in the finefrau sandstone while high salinity and neutral to alkaline ph results in a high li h ratio for the solling sandstone the ge contents are generally near the average of detrital quartz and indicate that pressure dissolution is a major source for quartz cementation different chemical compositions of distinct quartz generations indicate changes in the physico chemical conditions and point to mobilization of silica from different sources for example pressure solution and clay mineral transformations

pore water evolution in oilfield sandstones constraints from oxygen isotope microanalyses of quartz cement abstract oxygen isotope microanalyses of authigenic quartz in combination with temperatures of quartz precipitation constrained by fluid inclusion microthermometry and burial history modelling are employed to trace the origin and evolution of pore waters in three distinct reservoirs of the brae formation in the miller and kingfisher fields north sea oxygen isotope ratios of quartz cements were measured in situ in nine sandstone thin sections with a cameca ims 4f ion microprobe in conjunction with quartz cement paragenesis in the reservoirs constrained from textural and cathodoluminescence cl microscopy studies pore water evolution was reconstructed from the time of deposition of the sandstones in the upper jurassic until the present cl photomicrographs of quartz overgrowths in the brae formation sandstones show three cement zones a b and c which can be related to different oxygen isotope compositions 1 the earliest and thinnest zone a homogeneous cl pattern with probable 18 o values between 23 and 26 direct measurements were not possible precipitated in the sandstones at temperatures 18 o values between 15 and 18 precipitated in the sandstones most likely between 70 and 90 c 3 the third zone c homogeneous cl pattern and directly measured 18 o values between 16 and 22 precipitated in the sandstones most likely at temperatures 90 c calculated oxygen isotope compositions of pore waters show that zone a quartz cements and enclosing concretionary calcite precipitated from a meteoric type fluid 7 during shallow burial 18 o 7 to a more 18 o enriched fluid 18 o 4 as burial continued to 3 0 km data from zone c quartz cements are consistent with further fluid evolution from 18 o 4 to basinal type fluids with 18 o similar to the present day formation water oxygen isotope composition 0 6 at 4 0 km burial a similar pore water evolution can be derived for all three reservoirs studied indicating that hydrogeologic evolution was similar across sandstones of the whole brae formation the quartz cement zones observed in the brae formation sandstones and the pore water history derived for the area studied is analogous to published petrographic and pore water evolution data from the nearby brent group reservoirs and from reservoirs located in the haltenbanken area on the atlantic margin offshore norway considering quartz cement is a major porosity occluding phase in many reservoir sandstones and because pore waters both dissolve quartz and carry the dissolved silica to cementation sites the data presented are valuable for improving the understanding and prediction of reservoir quality development in sandstones globally

early quartz cements and evolution of paleohydraulic properties of basal sandstones in three paleoproterozoic continental basins evidence from in situ δ18o analysis of quartz cements quartz cement microstratigraphy and high precision in situ 18 o values obtained by secondary ion mass spectrometry sims from m size quartz cement zones have been used here to determine the timing of cementation and to evaluate precipitation mechanisms within the basal sandstones of three economically significant paleoproterozoic basins the athabasca and thelon basins canada and the mcarthur basin australia in these examples the earliest quartz cements have the highest 18 o values up to 33 mean 26 0 v smow indicative of low temperature precipitation at depths of 0 to 1 1 km some paragenetically early cement phases however have lighter isotopic values that suggest either precipitation from isotopically depleted water or precipitation at higher temperatures subsequent generations of quartz cements have progressively lower 18 o values mean 16 1 3 consistent with precipitation at higher temperatures these data combined with petrographic observations indicate quartz cementation began in near surface vadose and phreatic zones the next stage of cementation is characterized by syntaxial burial cement overgrowths regionally and stratigraphically well sorted sandstone facies that were initially aquifers preferentially experienced early quartz cementation which resulted in cement bridged pore throats at relatively shallow depths of 0 2 km and very early in their burial history transforming these units into diagenetic aquitards as a result these units did not experience mineralization compositionally and texturally immature braided fluvial facies did not experience early addition of quartz cement but are instead marked by minor syntaxial overgrowth cement that make upb5 of the intergranular volume formed at depths of 3 5 km and were variably replaced by illite and chlorite during burial these lithologies were still open to fluid movement at critical times in the basin when u and

evidence for remotely triggered microearthquakes during salt cavern collapse summary microseismicity is a good indicator of spatio temporal evolution of physical properties of rocks prior to catastrophic events like volcanic eruptions or landslides and may be triggered by a number of causes including dynamic characteristics of processes in play or and external forces we show evidence of triggered microseismicity observed in the vicinity of an underground salt cavern prone to collapse by a remote m 7 2 earthquake which occurred 12 000 km away high dynamic range broad band records reveal the strong time correlation between a dramatic change in the rate of local high frequency microseismicity and the passage of low frequency seismic waves including body love and rayleigh surface waves pressure was lowered in the cavern by pumping operations of brine out of the cavern we demonstrate the near critical state of the cavern before the collapse by means of 2 d axisymmetric elastic finite element simulations on this basis we show that the increment of stress necessary for the failure of the dolomite layer which ensures the stability of the whole system is of the same order of magnitude as the maximum dynamic stress magnitude observed during the passage of the earthquakes waves this suggests that the stress oscillations due to the seismic waves correlated with the recorded microearthquakes induced damage of the overburden which eventually led to the collapse of the salt cavern we show that the contribution of rayleigh waves is the most efficient to trigger microseismicity at periods close to the natural fundamental frequency of the cavern system found at about 10 20 s by investigating the impulse response of the cavern overburden brine system

outcrop analog for cyclic shelf reservoirs san andres formation of permian basin stratigraphic framework permeability distribution geostatistics and fluid flow modeling vertical and horizontal transects were sampled from core and outcrop of the san andres formation at lawyer canyon guadalupe mountains new mexico to assess permeability variation in a geologic framework of upward shallowing carbonate cycles and to show the potential effect these variations have on viscous dominated flow behavior in analogous reservoirs these cycles occur in a ramp crest facies tract are 3 13 m 10 45 ft thick and contain both vertical and lateral variation of lithofacies thicker cycles consist of a basal dolomudstone which is overlain by burrowed dolopackstone and capped by bar flank ooid peloid dolograinstone and bar crest ooid dolograinstones in vertical transects permeability is extremely variable about the mean yet upward increasing trends coinciding with the succession of lithofacies typify a given cycle semi variance analysis shows permeability to be uncorrelated vertically at distances greater than 5 5 m 18 ft which is the average cycle thickness suggesting that the cycles may equate to a fluid flow unit in a reservoir semi variance analysis of measurements collected along a horizontal transect within bar crest dolograinstones of a single cycle shows permeability is uncorrelated at distances greater than 3 6 m 12 ft this correlation distance appears to be controlled by alternating porous and tightly cemented zones that formed during dolomitization vertical and lateral variogram models were fit to the spatial parameters to generate a variety of conditionally simulated permeability fields fluid flow simulations show viscous dominated flow behavior is compartmentalized by both the individual cycles and groups of cycles the basal dolomudstones are potential baffles to flow crossover between cycles but poorly developed cycles i e those that are mud rich and lack well developed bar flank and bar crest facies result in the greatest compartmentalization of fluid flow within a succession of cycles

diagenetic albitization of detrital k feldspars in jurassic lower cretaceous and tertiary clastic reservoir rocks from offshore norway ii formation water chemistry and kinetic considerations abstract formation waters from clastic reservoirs offshore norway are saturated or supersaturated with respect to albite deeper than 2 5 km and support the view of saigal et al 1988 that albitization of k feldspar is presently active in these sandstones thermodynamic and mass constraints show that the albitization process is more sensitive to potassium removal than sodium supply the temperature of albitization commencement coincides more or less with the estimated onset temperature of illitization of smectite 70 80 c interbedded shales seem to be the major potassium sink and source of sodium kinetic considerations indicate that at temperatures below 145 c the dissolution of k feldspar is always faster than albite growth combined with replacement constraints the kinetic data also explain the observed coarsening of growing albite crystals with increasing burial temperature

triggering of volcanic eruptions although earthquakes and volcanic eruptions are each manifestations of large scale tectonic plate and mantle motions it is usually thought that the occurrences of these events are not directly related there have been some studies however in which triggering of volcanic eruptions by earthquakes remote from the volcano has been proposed1 2 the 1992 landers southern california earthquake caused triggered seismicity at very large distances3 including the magmatically active4 long valley caldera region which also experienced a significant coincident deformation transient5 motivated by this demonstration of the ability of a distant earthquake to disturb a volcanic system and the earlier studies of specific cases of eruption triggering we examine here the historical record of eruptions and earthquakes to see if there are indeed significantly more eruptions immediately following large earthquakes we find that within a day or two of large earthquakes there are many more eruptions within a range of 750 km than would otherwise be expected additionally it is well known6 that volcanoes separated by hundreds of kilometres frequently erupt in unison the characteristics of such eruption pairs are also consistent with the hypothesis that the second eruption is triggered by earthquakes associated with the first

titaniq a titanium in quartz geothermometer titanium is one of many trace elements to substitute for silicon in the mineral quartz here we describe the temperature dependence of that substitution in the form of a new geothermometer to calibrate the titaniq thermometer we synthesized quartz in the presence of rutile and either aqueous fluid or hydrous silicate melt at temperatures ranging from 600 to 1 000 c at 1 0 gpa the ti contents of quartz in ppm by weight from 13 experiments increase exponentially with reciprocal t as described by text log left x text qtz text ti right 5 69 pm 0 02 frac 3765 pm 24 t k application of this thermometer is straightforward typically requiring analysis of only one phase quartz this can be accomplished either by epma for crystallization temperatures above 600 c or by sims for temperatures down to at least 400 resulting temperature estimates are very precise usually better than 5 c potentially allowing detailed characterization of thermal histories within individual quartz grains although calibrated for quartz crystallized in the presence of rutile the thermometer can also be applied to rutile absent systems if tio2 activity is constrained

contrasting triggering mechanisms of the 2001 and 2002 2003 eruptions of mount etna italy abstract mount etna produced two significant eruptions in 2001 and 2002 2003 which we have analysed using geological seismic and deformation data these eruptions showed some similarities such as the activating of two magmatic plumbing systems central lateral and eccentric but they differed in their triggering mechanisms while the 2001 eruption was largely the result of the emplacement of a n s eccentric dike independent from the central conduits consistent with e w regional extension the 2002 2003 eruption occurred in response to a major flank slip on the eastern and southeastern sides of the volcano this is demonstrated by the spatial and temporal distribution of seismicity and deformation preceding and accompanying the two eruptions during the months prior to the 2001 eruption most epicenters were concentrated on the southern flank at depths of 5 15 km below sea level during the 4 days before the eruption earthquake hypocenters migrated to shallower levels from 5 km bsl upward indicating the emplacement of the eccentric dike this is confirmed by the patterns of ground fracturing observed in the field and deformation documented by electronic distance measurements edm in contrast the months before the 2002 2003 eruption were characterised by shallower seismicity mainly concentrated along the active faults bordering the slipping flank sector flank slip accelerated in september 2002 and a second more vigorous acceleration of flank slip occurred on 26 27 october 2002 accompanying the opening of eruptive vents the very short 2 h seismic crisis preceding the onset of eruptive activity stands in neat contrast with the 4 days of intense seismicity before the 2001 eruption subsequently flank slip deformation extended all over the eastern and southeastern flanks of the volcano causing serious damage in this sector the events of 2001 2003 can be seen as a continuous chain of intimately interacting processes including regional tectonics magma accumulation and eruption and flank instability in this scenario the 2001 eruption led to increased flank instability that subsequently accelerated and culminated with the massive flank slip which in turn facilitated the 2002 2003 eruption this sequence of events points to a long term feedback mechanism between magmatism and flank instability at etna

dynamic fluid recycling at laguna caliente poas costa rica before and during the 2006 ongoing phreatic eruption cycle 2005 10

germanium geochemistry and mineralogy abstract germanium is enriched in the following geologic environments 1 1 iron meteorites and terrestrial iron nickel 2 2 sulfide ore deposits particularly those hosted by sedimentary rocks 3 3 iron oxide deposits 4 4 oxidized zones of ge bearing sulfide deposits 5 5 pegmatites greisens and skarns and 6 6 coal and lignitized wood in silicate melts ge is highly siderophile in the presence of native iron nickel otherwise it is highly lithophile among silicate minerals ge is concentrated in those having less polymerized silicate tetrahedra such as olivine and topaz in deposits formed from hydrothermal solutions ge tends to be enriched mostly in either sulfides or in fluorine bearing phases it is thus concentrated both in some hydrothermal sulfide deposits and in pegmatites greisens and skarns in sulfide deposits that formed from solutions having low to moderate sulfur activity ge is concentrated in sphalerite in amounts up to 3000 ppm sulfide deposits that formed from solutions having higher sulfur activity allowed ge to either form its own sulfides particularly with cu or to substitute for as sn or other metals in sulfosalts the ge in hydrothermal fluids probably derives from enrichment during the fractional crystallization of igneous fluids or is due to the incorporation of ge from the country rocks particularly from those containing organic material germanium bonds to lignin derivative organic compounds that are found in peat and lignite accounting for its common concentration in coals and related organic material germanium is precipitated from water together with iron hydroxide accounting for its concentration in some sedimentary and supergene iron oxide deposits it also is able to substitute for fe in magnetite in a variety of geologic environments in the oxidized zone of ge bearing sulfide deposits ge is concentrated in oxides hydroxides and hydroxy sulfates sometimes forming its own minerals it is particularly enriched in some iron and manganese bearing oxides and hydroxides including goethite up to 5300 ppm and hematite up to 7000 ppm

coexisting tectonic settings the example of the southern tyrrhenian sea we performed geodetic strain rate analyses in southern italy using new gps velocities two dimensional strain and rotation rate fields were estimated and results show that most of the shortening is distributed in the northern sicily offshore extension becomes more evident and comparable with shortening on the eastern side of the same margin and greater in the eastern sicily offshore principal shortening and extension rate axes are consistent with long term geological features seismic reflection profiles show both active compressive and extensional faults affecting pleistocene strata we show evidence for contemporaneous extension and transtension in the cefalu basin combining geodetic data and geological features point to the coexistence of independent geodynamic processes i e the active e w backarc spreading in the hangingwall of the apennines subduction zone and shortening along the southern margin of the tyrrhenian backarc basin operated by the nnw motion of africa relative to eurasia

earthquake induced thermal anomalies at active volcanoes answering the question whether a regional earthquake can trigger or enhance volcanic activity requires a systematic measure of volcanic activity one such measure is heat fl ux the availability since a d 2000 of a satellite derived heat fl ux inventory for global volcanism allows us to explore how earthquakes and volcanic activity may be linked examination of 7 yr of global volcanic heat fl ux data reveals 37 volcanic responses to regional earthquakes each response is expressed by an increase in heat fl ux within 1 21 days of the triggering earthquake whether a volcano responds depends on earthquake magnitude distance to the epicenter and orientation of the earthquake focal mechanism in respect to the volcano the focal mechanism has to align with the responding system of the 7 global major increases of seismic energy during 2000 2006 4 were followed by a global volcanic heat fl ux increase the largest response involved a 300 increase and followed the largest earthquake in the period the 2004 sumatraandaman indonesia earthquake moment magnitude m w 9 3

late quaternary deformation history of the volcanic edifice of panarea aeolian arc italy a series of raised palaeoshorelines is documented along the emergent coastal slopes of panarea and surrounding islets at elevations of 115 palaeoshoreline ia and 100 m a s l ib 62 5 m ii 35 m iii 12 m iv 10 12 va and 5 m vb according to stratigraphic constraints and cross cutting relationships these palaeoshorelines are correlated with discrete high sea level stillstands during marine oxygen isotope stages mis 5e 5c 5a and 3 coastal elevation changes suggest the occurrence of a long term sustained uplift trend of the volcanic edifice since the last interglacial last 124 ka the uplift rates are not constant but display a progressive deceleration from maximum values of 1 5 1 58 m ka in the period between 124 and 100 ka down to the lowest values of 0 66 0 69 m ka which tend to be constant starting from 81 ka bp the long term deformation pattern of panarea suggests that a transitory volcano related component of uplift interplayed with the regional tectonic component affecting the sub volcanic basement which has undergone a persistent and widespread uplift since the mid pleistocene the volcano related component of uplift prevailing between 124 and 100 81 ka is interpreted as the result of visco elastic deformation mechanisms which characterize the progressive re equilibration of the shallow magmatic system following the incoming quiescence of the volcanic edifice the long term uplift values at panarea are higher than in the main portion of the western central aeolian arc where a mean uplift rate of 0 34 m ka was estimated since the last interglacial last 124 ka such a pattern of deformation on a regional scale may be a response to active deformation processes connected with the southeastward rollback of the subducting ionian slab which is still active only in correspondence with the eastern sector of the aeolian arc including panarea in the short term a localized submergence trend has been documented at the nearby islet of basiluzzo for the last 2 000 years likely connected to neo tectonic movements along main ne sw trending faults

methodological improvements for investigating silcrete formation petrography ft ir and oxygen isotope ratio of silcrete quartz cement lake eyre basin australia the oxygen isotopic composition 18o of the cement of a silcrete sample from the cordillo silcrete late eocene early oligocene of lake eyre basin australia was investigated the massive structure of the silcrete outcrop and the absence of pedogenic features suggest that this silcrete formed by precipitation from groundwater in order to avoid errors inherent in estimates of the cement 18o value from isotopic analyses of bulk material and mass balance considerations methodological improvements are described the silcrete cement is physically separated from the detrital phases its purity is checked using cathodoluminescence cl spectroscopy optical microscopy x ray diffraction xrd analyses and fourier transform infrared ft ir spectroscopy show the cement is made of three phases i overgrowth ii crypto crystalline quartz and iii micro crystalline quartz thus its 18o value must be interpreted as that of a mixture although the mixture consists mainly of crypto crystalline quartz as the amount of si oh exchangeable oxygen in the cement would bias the results by an amount less than the analytical error 0 09 it is unnecessary to go through an equilibration procedure prior to isotopic analysis the 18o value of the cement sample is between 24 8 and 25 8 relative to v smow assuming an eocene oligocene temperature of 15 20 c in agreement with published regional temperature estimates the inferred 18o value of the quartz forming solution was between 6 9 and 12 2 this is lower than the minimum 18o value of 6 70 estimated for the modern groundwater near the sample site a plausible paleoenvironmental scenario is that silcrete formed in a climate colder and wetter than the modern one from shallow groundwater frequently recharged in a setting of slow tectonic uplift

response of mount etna to dynamic stresses from distant earthquakes 1 influences of distant earthquakes on volcanic systems by dynamic stress transfer are well documented we analyzed seismic signals and volcanic activity at mount etna during two periods january 2006 and may 2008 that clearly showed variations coincident with distant earthquakes in the first period characterized by mild volcano activity the effect of the dynamic stress transfer caused by an earthquake in greece m 6 8 was twofold 1 banded tremor activity changed its features and almost disappeared 2 a swarm of volcano tectonic vt earthquakes took place the changes of the banded tremor were likely due to variations in rock permeability caused by fluid flows driven by dynamic strain the vt earthquake swarm probably developed as a secondary process promoted by the dynamically triggered activation of magmatic fluids the second period may 2008 showed an intense explosive activity during this interval the dynamic stress transfer associated with the arrival of the seismic waves of the sichuan earthquake m 7 9 affected the character of the seismo volcanic signals and on the following day triggered an eruption in particular we observed changes in volcanic tremor and increases of both occurrence rate and energy of long period events in this case we suggest that dynamic stress transfer caused nucleation of new bubbles in volatile rich magma bodies with consequent buildup of pressure highlighted by the increase of long period activity followed by the occurrence of an eruption we conclude that stresses from distant earthquakes are capable of modifying the state of the volcano

significance of trace elements in syntaxial quartz cement haushi group sandstones sultanate of oman abstract trace element contents and distributions in authigenic quartz cement in deeply buried 2500 4000 m haushi group sandstones from wells in oman have been investigated in order to determine the factors that control trace element uptake during precipitation scanning electron microscope cathodoluminescence images show well developed growth zones within the quartz cement which correlate with chemical zonations observed in electron microprobe al distribution maps the most abundant trace elements are al 50 3000 g g 1 li 1 100 g g 1 na 1 40 g g 1 and ge 0 3 5 g g 1 with a strong linear correlation between li and al and a weaker one between ge and al the molar concentration of li na accounts only for 15 of the charge compensation for al 3 substitution of si 4 though h was not measured in this study these data indicate a major role of h in charge balancing al 3 the samples belong to the same stratigraphic unit and have similar petrography but show considerable variability in absolute trace element concentrations between different wells this variability does not correlate with either sample depth or temperature and shows no regional pattern but seems to reflect petrophysical and tectonic differences within the sedimentary basin petrographic observations of the cogenetic mineral assemblages and hydrochemical modelling indicate that a change from the equilibrium assemblage quartz kaolinite dolomite to quartz illite dolomite reflects a decrease in the co 2 concentration and concurrent variations of the al concentration it is concluded that changes in the co 2 concentrations are responsible for fluctuations in fluid al concentrations and thus likely also in the investigated quartz cements

dynamic stresses coulomb failure and remote triggering dynamic stresses associated with crustal surface waves with 15 30 sec periods and peak amplitudes 5 km the latter is consistent with the observation that extensional or transtensional tectonic regimes are more susceptible to remote triggering by rayleigh wave dynamic stresses than compressional or transpressional regimes locally elevated pore pressures may have a role in the observed prevalence of dynamic triggering in extensional regimes and geothermal volcanic systems

trace elements in hydrothermal quartz relationships to cathodoluminescent textures and insights into vein formation high resolution electron microprobe maps show the distribution of ti al ca k and fe among quartz growth zones revealed by scanning electron microscope cathodoluminescence sem cl from 12 hydrothermal ore deposits formed between 100 and 750 c the maps clearly show the relationships between trace elements and cl intensity in quartz among all samples no single trace element consistently correlates with variations in cl intensity however in vein quartz from five porphyry cu mo au deposits cl intensity always correlates positively with ti concentrations suggesting that ti is a cl activator in quartz formed at 400 c ti concentrations in most rutile bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of 750 c using the titaniq geothermometer titanium concentrations of 10 ppm in all veins that formed at temperatures 350 c suggest a broad correlation between ti concentrations and temperature of quartz precipitation in quartz from most deposits formed at 2000 ppm but in high temperature quartz al concentrations are consistently in the range of several hundred ppm aluminum concentrations in quartz reflect the al solubility in hydrothermal fluids which is strongly dependent on ph aluminum concentrations in quartz therefore reflect fluctuations in ph that may drive metal sulfide precipitation in hydrothermal systems

new evidence for the origin of quartz cements in hydrocarbon reservoirs revealed by oxygen isotope microanalyses quartz cements degrade hydrocarbon reservoir quality by choking off fluid flow paths therefore it is important to understand the sources and timing of quartz cementation we present in situ microanalyses of oxygen isotope ratios in quartz cements from a jurassic hydrocarbon reservoir located offshore norway showing systematic variations that reveal the isotopic history of the pore fluids that precipitated the quartz earliest quartz cements have 18o values of 20 26 subsequent cements drop in 18o value as low as 13 but then increase back to 23 with increasing cement thickness this isotopic trend was observed in multiple overgrowths with temperatures constrained by fluid inclusions and the burial history of the reservoir the isotopic composition of porewaters can be estimated from the measured isotopic ratios in quartz cement results indicate that 97 of the quartz cement precipitated from negative 18o waters originally meteoric that were gradually modified by burial diagenetic reactions as temperatures increased precipitation began in the middle to late cretaceous however the rate of quartz precipitation increased dramatically in the last 3 5 ma as the reservoir was rapidly buried the data show that quartz precipitation is a continuous process during burial and that silica is derived locally from silicate reactions occurring within the sandstone reservoir the isotopic data do not record evidence of episodic cementation from convection driven hot basinal fluids

geochemistry and origin of formation brines from the paris basin france 2 saline solutions associated with oil fields abstract oil fields from the paris basin are located in three geological levels dogger middle jurassic rhaetian and keuper upper triassic the origin of water and dissolved salts in saline solutions associated with oil is investigated using the hypothesis that cl and br are conservative in solution in a diagram of cl br ratios vs cl the points of the dogger and the keuper aquifers lie in the zone of primary brines whereas those of the rhaetian are located in the zone of secondary brines the na cl ratio is very high in all of the saline solutions suggesting either a relatively poorly evolved brine at the beginning of halite deposition or some halite dissolution all of the saline solutions especially those from the dogger aquifer are clearly diluted dilution by meteoric waters would not alter the cl br ratio high concentrations of lithium rubidium and boron are attributed to the presence of an extremely evolved brine of marine origin in mixtures of secondary brines formed by dissolution of halite and small amounts of sylvite and ca sulphate mass balance calculations of the excess of cl with respect to na k allows the fraction x of water derived from the primary brine to be calculated assumptions are that all na and k is derived from the secondary brine and that the cl content of the primary brine is constrained by bischofite saturation at 11 000 mmol kg 1 the typical proportion of water from the primary brine waters is 0 7 in the dogger formation and 2 4 in the keuper values of the concentration factor cf expressed as the ratio of the molal concentration of a conservative ion in the evolved brine to its concentration in seawater have been calculated for lithium solutions from the dogger and keuper aquifers have cfli values of 1 8 103 and of 7 7 103 respectively in the rhaetian aquifer the linear relationship between heavy isotope contents of the brine 2h and 18o and the cl content indicates a mixture of two water sources the first one is meteoric water as defined by the intersection of the formation water line with the global meteoric water line 2 h 65 18 o 9 3 the other end member is enriched in heavy isotopes and in cl and is attributed to seawater that has dissolved evaporites mainly halite however the presence of small amounts of an extremely evolved brine is required to account for the bromide lithium rubidium and boron contents of the formation brine from the rhaetian aquifer as this contribution is very limited in amount it cannot affect the heavy isotope content of the formation water mass balance equations are solved for ternary mixtures of meteoric water seawater and brine the same constraints as above no na and k supplied by the primary brine and clbrine 11 000 mmol kg 1 are applied it is also assumed that the seawater component has the same ionic contents as modern seawater and that the salt content of the meteoric component is negligible the fraction of primary brines is x 1 4 according to the cl balance this estimate agrees with that obtained from the lithium balance assuming that the primary brine component was the same as that of the keuper formation water mass balance calculations also indicate that the so42 content of the rhaetian formation water is exclusively due to the secondary brine component in the three saline solutions the very high ca2 contents and high ca 2 mg 2 ratios may be attributed to reaction of the very evolved brine free of so2 4 with gypsum or anhydrite the result is an exchange of mg2 for ca2 which causes a release of ca2 to the solution and a precipitation of secondary mg sulphate this process can also account for the high strontium contents of the analysed samples values of the ratio 87 sr 86 sr are very high in the keuper formation water due to close contact of the solutions with the granitic basement or with granite derived detrital deposits values in the rhaetian and dogger aquifers equal those of upper triassic marine deposits the stable isotope 34s and 18o content of the dissolved aqueous so2 4 indicates a triassic origin for the bulk of sulphate involved in the evolution of formation waters from the rhaetian and from the dogger all geochemical indicators thus show a vertical migration of triassic brines however aqueous so2 4 from the keuper has a permian isotopic signature suggesting a reworking in solution of salts from this period

provenance interpretation of quartz by scanning electron microscope cathodoluminescence fabric analysis we used a cathodoluminescence cl detector attached to a scanning electron microscope sem to study patterns of variable intensity cl in quartz grains from a variety of igneous metamorphic sedimentary and shock deformed meteorite impact rocks distinctive fabrics in quartz grains revealed by sem imaged differential cl include zoning healed fractures complex shears planar features shocked quartz dark cl streaks and patches indistinct mottled texture and nondifferential low contrast cl zoning is common in volcanic quartz and some plutonic quartz zoned plutonic quartz is distinguished from volcanic quartz by the presence of closed fractures and dark cl streaks and patches metamorphic quartz displays either an indistinct mottled texture or nearly uniform nondifferential cl quartz from rocks severely deformed by tectonism displays a complex pattern of multiple small scale shears quartz from meteorite impact sites and some system boundaries is characterized by intricate patterns of planar features presumably created by shock metamorphism thus the sem cl fabric analysis technique provides a rapid method for distinguishing quartz from a variety of source rocks

mineralization and petrogenesis of the qiongheba porphyry copper deposit in mengxi district east junggar china abstract the qiongheba porphyry cu deposit is characterized by geochemical features of island arc and adakitic intrusions with fractional crystallization playing a key role in the formation of the ore bearing rocks calculated sulfur concentrations in silicate melts at sulfide saturation show that two thirds of the sulfur was exsolved during the fractional crystallization process to contribute to the formation of sulfides the ore bearing rocks in the qiongheba area yielded u pb zircon ages of 414 412 ma coeval with the 412 ma re os age of molybdenite indicating that sulfide mineralization is broadly coeval with magmatic crystallization the color cathodoluminescence of quartz purple and k feldspar pink in the fibrous veins and miarolitic cavities qtz 2 and kfs 2 are the same as those qtz 1 and kfs 1 in the granitic porphyry whereas the hydrothermal quartz qtz 3 and k feldspar kfs 3 are black and green suggesting that the color cathodoluminescence can be used to unravel the paragenesis of pcd the oxygen isotopic values of qtz 1 and qtz 2 range from 9 15 to 10 1 and 8 93 to 10 4 with calculated equilibrium fluid compositions of 9 86 to 11 7 and 10 5 to 12 0 respectively indicating a magma dominated fluid composition whereas qtz 3 veins have very low oxygen isotopic values from 4 60 to 1 25 with corresponding fluid compositions of 3 51 to 0 17 implying that the fluid formed via the mixing of magmatic and meteoric water titanium in quartz thermometry constrains the magmatic crystallization to 580 627 c whereas the magmatic to hydrothermal transition occurred at 523 613 c

crustal motion along the eurasia nubia plate boundary in the calabrian arc and sicily and active extension in the messina straits from gps measurements 1 we investigate crustal deformation along the eurasia nubia plate boundary in calabria and sicily revealed by the gps velocity field obtained by the combination of continuous site velocities with previous results from episodic campaigns we recognize two distinct crustal domains characterized by different motions and styles of deformation convergence in sicily is taken up by crustal shortening along the former tyrrhenian back arc passive margin in agreement with seismological data and geological evidence of recent cessation of deformation along the plio pleistocene subduction front the analysis of the gps data and the consistency between earthquake slip vectors and convergence direction suggest that eu nu convergence in sicily does not require intermediate crustal blocks significant eurasia 3 mm yr to nne and nubia fixed 5 mm yr to ese residual velocities in calabria suggest instead the presence of an intermediate crustal block which can be interpreted as a forearc sliver or as an independent ionian block according to the first hypothesis subduction is still active in the ionian wedge although we find no evidence for active back arc spreading in the tyrrhenian sea the n115 e oriented sicily calabria gps relative motion is consistent with the extension observed during the 1908 mw 7 1 messina earthquake we suggest that up to 3 mm yr 80 of this estimated relative motion between sicily and the calabrian arc may be taken up in the messina straits

provenance analysis by single quartz grain sem cl optical microscopy abstract the integration of panchromatic scanning electron microscopy cathodoluminescence sem cl with optical microscopy analysis on single quartz grains is a new technique to interpret provenance of quartz rich sediments the combination of information gained from sem cl on textural features and cl response with information from optical microscopy allows distinction of different quartz types much more easily then with conventional microscopy or color cl analysis features visible by sem cl include zoning microcracks deformation fractures and lamellae diagenetic crushing recrystallization and strength and texture of cl response features visible by optical microscopy include embayments open fractures extinction behavior and mono poly and microcrystallinity the key is to integrate cl and optical properties of the same quartz grains in order to reduce ambiguities inherent in both techniques used on their own our technique is well suited for distinguishing between plutonic volcanic and metamorphic quartz in coarse to medium grained sand or sandstone this simple and inexpensive approach can easily be combined with other provenance techniques in this paper we outline the combined sem cl optical microscopy technique and demonstrate its application with examples from the south island of new zealand

simultaneous magma and gas eruptions at three volcanoes in southern italy an earthquake trigger this study was partly funded by the deutsche forschungsgemeinschaft wa 1642 1 4 and protezione civile project ingv dpc v2

quartz cementation and related sedimentary architecture of the triassic solling formation reinhardswald basin germany abstract the olenekian solling formation of the reinhardswald basin was studied with the aim to examine the dependency of the degree of silica diagenesis on the sedimentary architecture the solling formation is composed of stacked sandstone clay siltstone cycles deposited by braided i e subarkoses and meandering i e subarkosic wackes river systems the sand dominated braided rivers of the lower solling formation are characterized by channels and downstream accretion whereas mixed load meandering rivers of the upper solling formation are represented by lateral accretion and laminated sands diagenetic processes which modified the sandstone siltstone successions include compaction feldspar alteration and cementation sandy clay poor successions are highly quartz cemented i e silica importers whereas clay and mica rich successions are more compacted i e silica balanced or silica exporters three quartz cement generations with a total volume of up to 18 indicate that silica from several different sources cemented the sandy fluvial architectural elements of the lower solling formation cementation includes silica supply from internal and external to the sandstone layers which are silica from grain margin dissolution from feldspar alteration silica released from clay siltstones and silica precipitated from basinal brines this cementation history is supported by cathodoluminescence observations and fluid inclusion studies and a consistent burial history was successfully modeled by simulation of the thermal subsidence in contrast to the lower solling formation the fluvial architectural elements of the mixed load systems of the upper solling formation contain only one quartz cementation phase with a total volume up to 8 the reinhardswald basin shows a dependency of the fluvial architecture and the diagenetic features for that we define the term diagenetic architecture

the 2002 2003 submarine gas eruption at panarea volcano aeolian islands italy volcanology of the seafloor and implications for the hazard scenario abstract a submarine gas eruption started in november 2002 offshore of panarea volcano aeolian islands italy the intensity of the gas emission and the considerable anomalies of the geochemical and geophysical parameters have alarmed the volcanological community and the italian civil protection agency on the possibility that this activity may represent a volcanic unrest at panarea volcano we used a high resolution marine digital terrain model mdtm with 0 5 m accuracy and detailed underwater surveys by scuba diving to study the exhalation centres and the geological morphological and structural features of the seafloor and to clarify the relationships between gas vents distribution submarine volcanological structures and the recent deformation of this area the underwater surveys revealed an exhalative field characterised by 21 main active gas vents and craters from metres to tens of metres in diameter and a pervasive exhalation from the seafloor hundreds of fossil craters associated with gas pipes and hydrothermal alteration are also present on the seafoor craters pipes and conduits are not associated with juvenile deposits and relate to a long standing history of gas exhalation and eruptions we present the first geological sketch map of the seafloor surrounding the exhalative area and establish the role of ne and nw trending fractures as the main pathways for the gas exhalation

salinization of groundwater in the north german basin results from conjoint investigation of major trace element and multi isotope distribution conjoint consideration of distribution of major rare earth elements ree and y combined to rey and of h o c s sr isotopes reveals that four types of groundwater are distinguishable by their chemical composition presented by spider patterns rey patterns indicate thermo saline deep water and two types of shallow saline groundwaters presence of connate waters is not detectable sr isotope ratios distinguish three sources of sr fast and slow weathering of biotite and k feldspar in pleistocene sediments respectively and dissolution of limestones 13c dic indicate dissolution of limestone under closed and open system conditions numerous samples show 13c dic 13 which is probably caused by incongruent dissolution of calcite and dolomite the brines from below 1 000 m represent mixtures of pre pleistocene seawater or its evaporation brines and infiltrated post pleistocene precipitation the shallow waters represent mixtures of pleistocene and recent precipitation salinized by dissolution of evaporites or by mixing with ascending brines the distribution of water types is independent on geologic units and lithologies even the tertiary rupelian aquiclude does not prevent salinization of the upper aquifer

variations in water content in opal a and opal ct from geyser discharge aprons abstract opal a sio2 nh2o and its diagenetic derivative opal ct are found in environments that range from the deep ocean floor to terrestrial spring geyser systems although the loss of water may be a critical factor in the transition from opal a to opal ct analytical difficulties in determining the distributions and quantities of molecular water h2omol and silanols h2osioh has hindered a full understanding of the processes involved with this diagenetic transition electron microprobe emp and micro fourier transform infrared ftir analyses of opal a and opal ct collected from geyser discharge aprons on iceland and the north island of new zealand produce compatible and reliable derivations of the total weight water in opal a and opal ct provided that they contain 1 wt of other elements such as al emp analyses produce excellent results where microscale variations in total water content are required but it cannot determine if that water is formed of molecular water h2omol or silanols h2osioh in contrast ftir analyses yield total water molecular water and silanol contents of the opal microscale variations however are commonly masked because the scale of ftir analysis is coarser than that for emp analyses analyses of sinters from iceland and new zealand show that the opal a contains 2 1 12 1 average 7 3 wt total water whereas the opal ct contains 1 0 8 9 average 5 5 wt total water based on ftir analyses the opal a contains 1 2 9 8 average 6 8 wt molecular water and 0 4 2 4 average 1 0 wt silanols compared to opal ct which contains 3 8 8 2 average 6 7 wt molecular water and 0 1 0 7 average 0 2 wt silanols the dual usage of emp and ftir analyses provide important information on the distribution of different types of water in opal a and opal ct irrespective of the environments where they formed

diagenesis and reservoir quality of lacustrine deep water gravity flow sandstones in the eocene shahejie formation in the dongying sag jiyang depression eastern china the lacustrine deep water gravity flow sandstone reservoirs in the middle of the third member of the shahejie formation 43 7 38 2 ma are the main exploration targets for hydrocarbons in the dongying sag jiyang depression eastern china the impact of diagenesis on reservoir quality of these sandstones has been established by a variety of methods petrographically the sandstones consist mainly of lithic arkose with 43 of quartz 33 of feldspar and 24 of lithic fragment with reservoirs having average porosity and permeability values of 17 1 and 38 1 md respectively in addition to their primary intergranular pores secondary pores are well developed from feldspar dissolution with pore throat radii ranging from 0 01 to 40 m the dissolution of feldspar and transformation of smectite to illite may be the sources of silica for the first phase of quartz overgrowth whereas illitization of kaolinite may be responsible for the second phase of quartz overgrowth in addition pressure dissolution of quartz is also an important source of silica for quartz overgrowth dissolution of feldspar has little impact on reservoir quality whereas compaction and carbonate cementation are the main factors significantly reducing reservoir quality oil charge may have retarded carbonate cementation and generated overpressure that retarded compaction thus preserving porosity precipitation of vermicular kaolinite resulting from feldspar dissolution promoted a change in the wettability of the reservoir from water wet to oil wet which is beneficial for oil entrapment the central parts of medium to thick bedded sandstones that have experienced oil charge twice appear to have the highest quality reservoirs based on petrophysical properties this work provides a new interpretation of the formation mechanism of high quality lacustrine deep water gravity flow sandstones reservoirs that have experienced multiple periods of oil charge

effusive to explosive transition during the 2003 eruption of stromboli volcano the persistent explosive activity of stromboli volcano italy ceased in december 2002 and correlated with the onset of a seven month long effusive eruption on the volcano flank from new vents that opened just below the summit craters we intensively monitored this effusive event collecting and interpreting in real time an extensive multiparametric geophysical data set the resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical strombolian activity we present a direct link between gas flux magma volume flux and seismicity supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity this insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity

a multidisciplinary approach to the evaluation of the mechanism that triggered the cerda landslide sicily italy abstract the present paper describes a multidisciplinary approach to the evaluation of a seismically triggered landslide that occurred in the cerda area italy on september 6 2002 about 1 h after an earthquake took place in the south tyrrhenian sea the study was focused on an analysis of the role of the seismic input in triggering the landslide in view of the evidence that no other mass movement was recorded in the adjacent areas despite geological and geomorphological spatial homogeneity the studied area is located on a slope of the western flank of the fiume imera settentrionale northern sicily which is made up of clayey arenitic rocks the slope inclines gently but is not uniform due to fluvial gravitative and rainwash processes field data dealing with global positioning system gps geology geomorphology geophysics vertical electrical sounding or ves and geochemistry soil gas fluxes and composition were acquired and analysed in order to investigate the cause effect relationships between the earthquake and the mass movement the gps survey allowed us to map the ground failures that have also been classified on the basis of their kinematical meaning i e compressive distensive or transcurrent structures the geological analysis revealed outcropping rocks and tectonic structures the geomorphologic survey highlighted the presence of preexisting landslide bodies the geophysical survey detected a buried surface located at a depth of about 100 m finally the geochemical survey showed that the gas released from the displaced mass came from a shallow depth and was not related to any active fault system the abovementioned information allowed us to interpret the landslide event as a partial reactivation of a preexisting landslide body that was triggered by the earthquake