modern sedimentary processes in the wilmington canyon area u s east coast abstract sedimentary processes active in the wilmington canyon area during the past century are documented from geochronologic sedimentologic and radiographic analysis of sediment cores collected using primarily d s r v alvin site selection for the alvin dives and for collection of box and kasten cores was achieved using sea marc and seabeam data allowing accurate sampling of numerous subenvironments from this extensively dissected area of the continental margin 210 pb sediment accumulation rates from intercanyon areas are highest on the upper slope 1 7 mm yr 140 mg cm 2 yr and decrease with water depth to about 0 4 mm yr 36 mg cm 2 yr on the upper rise within submarine canyons accumulation rates vary dramatically from a maximum of 6 mm yr 500 mg cm 2 yr to less than 0 3 mm yr 22 mg cm 2 yr higher accumulation rates in canyons occur as a result of additional supply of older sediment probably from bioerosion of the canyon walls this is supported by observations from d s r v alvin reduced 210 pb activities and indurated mud clasts observed in several canyon cores extremely low accumulation rates in wilmington and south wilmington canyons are probably the result of strong episodic boundary currents non steady state 210 pb profiles and sedimentologic data indicate small scale mass wasting in south heyes canyon and on the lower slope and rise just north of wilmington canyon

hydrogeochemical factors effecting the scaling problem in balcova geothermal field izmir turkey reservoir fluid compositions have been assessed from analytical data on water samples collected from thermal and cold waters in balcova geothermal field the results of mineral equilibrium modelling indicate that the waters with some exceptions are systematically supersaturated with respect to calcite aragonite dolomite chalcedony and quartz but undersaturated with respect to amorphous silica celestite anhydrite and gypsum and undersaturated or supersaturated with respect to barite low albite k feldspar gibbsite and fe oh 3 a calculation of mineral saturation states and geochemical analyses of scale and field observations show that carbonate minerals calcite aragonite and dolomite are most likely to be precipitated as a scale type besides carbonates scale formation risk of amorphous silica fe oh 3 a anhydrite barite and celestite minerals should be taken into account in some wells and surface equipment most of the waters with some exceptions have carbonate scaling risk at all temperatures whereas the other scaling risks only exist over a limited temperature range while silica fe oh 3 a and barite show a scaling tendency at low temperatures anhydrite and celestite scaling occurs at higher temperatures

cycling of fallout pu 241am 137cs and natural u th 210pb radionuclides in washington continental slope sediments abstract we report activity profiles of pu isotopes 241am 137cs 210pb u and th isotopes in washington continental slope sediments from 332 1415 m water identify major processes responsible for them and compare results with those previously reported for washington shelf sediments specific activities of all nuclides but 137cs are higher in slope surface sediments than shelf surface sediments these higher specific activities which are due to more efficient scavenging by finer grained particles and higher concentrations of dissolved nuclides in slope waters do not cause proportionally higher slope sediment radionuclide inventories because they are counterbalanced by 5 10 fold lower sediment accumulation rates on the slope profiles of natural u and th series isotopes reveal that fallout nuclide profiles are not markedly affected by greater exchange of pore and overlying waters but they are dependent upon rate and depth of solid phase mixing 239 240pu activities inventories in slope sediments correlate with those of excess 210pb as in shelf sediments but with higher ratios of 210 pb pu in slope deposits 241 am 239 240 pu activity and inventory ratios in slope sediments average twice ratios in shelf sediments due primarily to greater particle affinity and preferential downward transport of 241am am pu activity ratios change little with depth in slope sediments suggesting insignificant separation of the two nuclides during diagenesis 239 240 pu 137 cs ratios are 2 3 times greater in slope than shelf sediments due to a combination of preferential scavenging of pu and greater 137cs loss by decay and desorption pu cs activity ratios decrease with depth in more porous slope sediments due to downward migration of 137cs 137cs is found in slope sediments from all water depths even though it is barely detectable below about 700 m in north pacific waters

budgets and behaviors of uranium and thorium series isotopes in santa monica basin sediments abstract nine natural decay series isotopes were measured in six box cores collected from a transect across the santa monica basin the 210 pb derived sedimentation rate decreases from 80 mg cm 2 yr at the slope to 20 mg cm 2 yr in the deep central basin sediment mixing prevails in sites underlying oxic waters but is subdued in the anoxic deep basin below the sill depth uranium contents in sediments are controlled by levels of authigenic u which are higher in the more reduced condition in the deep basin most of the authigenic u results from precipitation within the sediments the 232 th 228 th disequilibrium in sediments indicates that 228 ra is lost from the sediments from a depth of 10 cm upward modelling the distribution of excess 228 th and 234 th in the surficial layers of the deep basin sediments results in a mean sediment mixing coefficient of 0 2 cm 2 yr and a sedimentation rate close to that based on 210 pb there is no evidence of changing sedimentation rate in the central basin during the past century fluxes of excess 210 pb 230 th and 231 pa to the central santa monica basin sediments are much higher than what can be predicted from local supply advective input of open ocean waters coupled with enhanced scavenging of these reactive nuclides at the ocean margin is considered to be the primary cause

geothermometry and circulation depth of groundwater in semnan thermal springs northern iran semnan thermal springs with high tds and moderate temperature are located northwest of semnan the northern part of iran the spatial and temporal variations of physicochemical characteristics of the thermal and cold springs were investigated for the recognition of origin and dominant hydrogeochemical processes results show that the thermal springs have the same origin but due to different ascending flow paths and different conductive cooling mechanism their temperatures vary the chemical composition of thermal waters is controlled by dolomite halite and sulfate minerals dissolution and calcite precipitation and bacterial sulfate reduction the concentration of major and trace elements in the thermal springs does not change in wet and dry seasons notably because they are derived from old groundwater with deep circulation and high temperature seasonal change in the concentration of some trace elements is due to the seasonal variation of ph eh temperature and dilution by shallow waters decreasing so4 and carbonate saturation index and increasing na cl ratios and ca content in the dry season show dilution effect caused by the previous heavy rainfall events the temperature of the heating reservoir based on k mg chalcedony quartz and chemical equilibrium approach was approximately estimated in the range of 60 80 c hydrogeologically a conceptual model was suggested for the thermal springs the general groundwater flow direction is probably from the dolomite lar formation in chenaran anticline toward the adjacent syncline in a confined condition and then a thrust fault acts as a conduit and redirects the thermal water to the emerging springs at the surface

hydrogeochemical and isotopic characteristics of the ilica geothermal system erzurum turkey in this paper the hydrochemical isotopic characteristics of samples collected from geothermal springs in the ilica geothermal field eastern anatolia of turkey are examined and described low temperature geothermal system of ilica erzurum turkey located along the eastern anatolian fault zone was investigated for hydrogeochemical and isotopic characteristics the study of ionic and isotopic contents shows that the thermal water of ilica is mainly locally fed by groundwater which changes chemically and isotopically during its circulation within the major fault zone reaching depths the thermal spring has a temperature of 29 39 c with electrical conductivity ranging from 4 000 to 7 510 s cm and the thermal water is of na hco3 cl water type the chemical geothermometers applied in the ilica geothermal waters yielded a maximum reservoir temperature of 142 c according to the silica geothermometers the thermal waters are undersaturated with respect to gypsum anhydrite and halite and oversaturated with respect to dolomite the dolomite mineral possibly caused scaling when obtaining the thermal waters in the study area according to the enthalpy chloride mixing model cold water to the thermal water mixing ratio is changing between 69 8 and 75 the 18o 2h compositions obviously indicate meteoric origin of the waters thermal water springs derived from continental precipitation falling on to higher elevations in the study area the 13c ratio for dissolved inorganic carbonate in the waters lies between 4 63 and 6 48 in low temperature waters carbon is considered as originating from volcanic mantle co2

hydrogeology and hydrogeochemistry of a coastal low temperature geothermal field a case study from the datca peninsula sw turkey the thermal springs at the golbasi geothermal field located in the southwest coastal region of turkey discharge from the mesozoic aged fissured carbonate aquifer the temperature specific electrical conductivity and ph values of the thermal waters are respectively 21 6 29 4 c 4020 57 200 s cm and 6 85 7 35 thermal waters are na cl type brackish to saline waters the golbasi geothermal system is fed by meteoric waters and local seawater the waters are heated at depth by high geothermal gradient caused by the recent tectonic activity in the deep and ascend to the surface through fractures and faults by convection and emerge as thermal springs the thermal waters mix in different proportions with seawater 5 58 and fresh cold waters during the moving up to the surface isotope data 18o 2h and tritium show that the thermal waters are of meteoric origin and the residence time at the reservoir is at least 50 years almost all the waters are saturated with respect to ca montmorillonite gibbsite k mica illite kaolinite fe oh 3 a calcite dolomite and barite minerals the most expected minerals that cause scaling at outlet conditions during the production and utilization of golbasi geothermal waters are calcite dolomite and some barite various chemical geothermometers na k mg ternary diagram and mineral equilibrium diagrams suggest that the reservoir temperature is around 50 100 c

the mathematics of early diagenesis from worms to waves the changes that sediments undergo after deposition are collectively known as diagenesis diagenesis is not widely recognized as a source for mathematical ideas however the myriad processes responsible for these changes lead to a wide variety of mathematical models in fact most of the classical models and methods of applied mathematics emerge naturally from quantification of diagenesis for example small scale sediment mixing by bottom dwelling animals can be described by the diffusion equation the dissolution of biogenic opal in sediments leads to sets of coupled nonlinear ordinary differential equations and modeling organisms that eat at depth in the sediment and defecate at the surface suggests the one dimensional wave equation while the effect of waves on pore waters is governed by the two or three dimensional wave equation diagenetic modeling however is not restricted to classical methods diagenetic problems of concern to modern mathematics exist in abundance these include free boundary problems that predict the depth of biological mixing or the penetration of o2 into sediments algebraic differential equations that result from the fast reversible reactions that regulate ph in pore waters inverse calculations of input functions histories and the determination of the optimum choice in a hierarchy of possible diagenetic models this review highlights and explores these topics with the hope of encouraging further modeling and analysis of diagenetic phenomena

hydrochemistry of the cesme geothermal area in western turkey abstract hydrochemical characterization of thermal waters discharged from springs and wells in the cesme geothermal area show that there are two groups one is of thermal waters from a lower aquifer composed of triassic karst limestones which are the main potential reservoir of the area they are of na cl type and between 37 and 62 c and have total dissolved solids tds with around 35 000 mg l the other group are thermal waters derived from an upper aquifer formed by neogene terrestrial sediments these have lower discharge temperatures 37 40 c and lower tds values due to their having mixed with local groundwater before emerging the isotopic and chemical data shows that the initial aqueous solution is a mixture of modern seawater and meteoric water in various proportions enrichment in 18o and d values and tritium contents 8 1 tu of thermal waters reflect a rapid circulation and the contribution of modern seawater the thermal waters are undersaturated with respect to gypsum but oversaturated or around equilibrium with respect to dolomite and calcite several chemical geothermometry techniques applied to cesme geothermal waters gave estimated reservoir temperatures of around 85 100 c

rapid bioturbation in equatorial pacific sediments evidence from excess 234th measurements in order to evaluate bioturbation in equatorial pacific sediments profiles of excess 234th were measured in cores collected during november and december 1992 at six abyssal sites along the jgofs equatorial pacific 140 w transect from 5 s to 9 n excess 234th half life 24 1 days was detected at all sites mean inventories ranged from a low of 0 25 dpm cm 2 at 9 n to a high of 2 6 dpm cm 2 at 2 n eddy diffusive models of the excess 234th profiles suggest that on 100 day timescales particle mixing is slow at 5 s and 2 s eddy diffusion coefficient db 0 4 cm2 year 1 faster at 0 and 2 n db 0 34 4 8 cm2 year 1 and fastest at 5 n db 4 7 11 cm2 year 1 at 9 n 234th is found almost entirely in the upper 5 mm of the seabed and db values are 0 1 cm2 year 1 db values generally increase as poc flux increases although the linear relationship r2 0 334 p 0 365 displays considerable scatter however if the only sites included in the regression are those where 234th profiles were measured in at least two core sets i e 0 2 n 5 n and 9 n the linear regression improves substantially r2 0 754 p 0 0012 these results suggest that measurements on a single core may not fully characterize the sediment mixing regime in a particular region and highlight the need for multiple samples from an individual site thorium 234 db values at 5 s 2 s and 9 n are in rough agreement with published db values calculated from the profiles of intermediate half life radioisotopes such as 210pb and 137cs in open ocean abyssal sediments however at 0 2 n and 5 n 234th db values are as much as an order of magnitude greater than published 210pb db values this phenomenon has been observed in other marine environments and may result from age dependent mixing non steady state mixing or a combination of the two processes particle mixing in cores collected at 5 s and 5 n appears to be best described as a largely eddy diffusive process however in cores collected at 2 s 0 2 n and 9 n non local mixing processes appear to affect 15 30 of the excess 234th inventory at these sites non local mixing appears to transport recently deposited material at least 3 4 cm below the sediment water interface within 100 days of its arrival at the seafloor the combination of rapid biodiffusive mixing and non local transport allows recently deposited reactive biogenic debris to be rapidly mixed into the seabed this may affect a wide range of diagenetic processes including oxygen consumption dissolution of biogenic debris and organic carbon remineralization models of early diagenesis in deep sea sediments may need to incorporate both non diffusive transport terms and rapid biodiffusive mixing of recently deposited particles

water geochemistry of the seferihisar geothermal area izmir turkey abstract the na cl thermal waters of seferihisar have measured temperatures of 30 153 c and conductivities of 7400 55200 s cm they issue from upper cretaceous to paleocene bornova melange rocks which are made up of sandstone shale intercalations conglomerate mafic submarine volcanics limestone lenses serpentinite and limestone bodies and their complexes through the intersection of faults the clay rich zones of the overlying neogene terrestrial sediments cap the system the heat source is the high geothermal gradient caused by graben tectonics of the area na and cl ions mainly dominate the chemistry of thermal waters thus thermal waters of the seferihisar area appear to be mixtures of groundwaters and seawater the seawater contribution in thermal waters varies from 10 to 80 assessments from empirical chemical geothermometers mineral equilibria and silica mixing model applied on the thermal waters of the seferihisar geothermal area suggest that the temperatures of the reservoir systems vary between 60 and 180 c the seferihisar geothermal area has been physically divided into five main groups and estimated reservoir temperatures provided by the entire methods give the increase as doganbey burnu karakoc spa doganbey tuzla and cumali spa areas in ascending order of reservoir temperature hydrogeochemical assessments indicate that thermal waters were mixed with cold waters before and or after heating at depth in different proportions the results of mineral equilibrium modeling indicate that the thermal waters of seferihisar are undersaturated with respect to gypsum and amorphous silica oversaturated with respect to calcite dolomite and aragonite and undersaturated or oversaturated with respect to quartz chalcedony and anhydrite

hydrochemical and isotopic 2h 18o and 37cl constraints on evolution of geothermal water in coastal plain of southwestern guangdong province china abstract geothermal energy is abundant in guangdong province of china however majority of it is still unexploited to take full advantage of this energy it is essential to know the information of geothermal system here physical parameters such as ph and temperature major ion na ca2 mg2 cl so42 and hco3 trace elements br sr2 li and b3 and stable isotopes 2h 18o and 37cl in geothermal water non geothermal water river water cold groundwater and seawater were used to identify the origin and evolution of geothermal water in coastal plain of southwest of guangdong two separate groups of geothermal water have been identified in study area group a located in inland of study area is characterized by na and hco3 group b located in coastal area is characterized by na and cl the relationships of components vs cl for different water samples clearly suggest the hydrochemical differences caused by mixing with seawater and water rock interactions it s evident that water rock interactions under high temperature make a significant contribution to hydrochemistry of geothermal water for both group a and group b besides seawater also plays an important role during geothermal water evolution for group b mixing ratios of seawater with geothermal water for group b are calculated by cl and br binary diagram the estimated results show that about

sedimentary processes in the inner new york bight evidence from excess210pb and239 240pu abstract particle reactive radionuclides were determined in sediments from the inner new york bight to trace transport and storage of fine grained sediments and associated reactive materials seven sediment cores 20 50 cm in length were analyzed for water content loss on ignition loi and excess 210 pb three of these were also analyzed for 239 240 pu excepting some depth horizons in a core from a dredge spoil dumpsite every sample analyzed contained excess 210 pb variations in the concentration of excess 210 pb with depth in the sediment at all stations correlated strongly with loi which apparently traces that fraction of the sediment which is active in removing reactive elements from the water column in the cores analyzed for 239 240 pu every sample contained finite pu and pu concentrations correlated strongly with excess 210 pb the radionuclide distributions may be simply viewed as products of steady state sediment accumulation or of mixing geochemically reasonable accumulation rates are very high 0 5 2 6 g cm 2 y and could probably only be sustained by offshore transport of dumped materials at the other extreme the relationships between excess 210 pb and loi are compatible with rapid mixing of a 210 pb carrier phase traced by loi into the pre existing substrate with little or no actual accumulation other non steady state processes such as sediment gravity flow could also explain the observed distributions measured sediment inventories dpm cm 2 of excess 210 pb and pu at these stations are greatly in excess of those supportable by direct atmospheric deposition lateral supply is required incorporation of sedimentary fines into the sand substrate could make the inner new york bight an important repository of reactive materials

geochemical assessment of mineral scaling in kizildere geothermal field turkey the mineral scaling problems in the kizildere geothermal field along with hydrogeological and geochemical properties of this field were studied in this content chemical analyses for 26 water samples from 12 water points and an additional seven geochemical analyses and six xrd analyses of the scale samples were performed measured reservoir temperatures of wells vary from 196 in the well kd 13 to 242 c in the well r 1 geothermal reservoir waters show the water types of na hco3 and na hco3 so4 estimated mineral saturations suggest that calcite aragonite strontianite dolomite amorphous silica and barite are likely to precipitate as scales these are confirmed by the results of the geochemical and xrd data of the scale samples reservoir chemistry calculations show a fluid richer in steam and acid gases with lower concentrations in the nonvolatile constituents i e cl sio2 na etc at the reservoir geochemical modeling shows that caco3 calcite and aragonite and strontianite precipitations are inevitable for production and re injection wells and surface equipment amorphous silica scaling is the important risk of re injection wells precipitations of the minerals barite anhydrite dolomite and celestite are also possible determinations of the scaling minerals and the safety temperatures to avoid or minimize the scaling problem are the most important parts of this study it was concluded that cold injection 50 c is favored or inhibitors should be used if any mineral deposition is to be prevented or reduced in injection wells

three dimensional vp and vs structural models associated with the active subduction and collision tectonics in the taiwan region summary 3 d vp and vs models for the crust and upper mantle beneath the taiwan area have been determined using selected high resolution earthquake data from an island wide seismic network and two local seismic arrays lateral structural variations in the upper crust as also evident from surface geology are responsible for the observed large traveltime residuals or station corrections prior shallow velocity information inferred from traveltime residuals and joint hypocentral determination jhd station corrections for the uppermost crust is essential to facilitate a reliable tomographic inversion a finite difference method that is efficient and accurate for a highly heterogeneous velocity structure is applied to calculate p and s wave traveltimes from the source to receiving stations all earthquakes in the taiwan central weather bureau s catalogue are then relocated using the resultant 3 d vp and vs models the depth of the moho varies significantly especially along the east west direction in the western coastal plain and western foothills the depth of the moho is around 35 km which deepens gradually eastward reaches a maximum depth of 55 km beneath the eastern central mountain range shallows up rapidly beneath the longitudinal valley and coastal range and merges with the thin philippine sea plate offshore of eastern taiwan in central taiwan the central mountain range is bounded to the east and west by two steeply westward dipping active faults from the upper crust to a depth of about 30 km therefore the uplifted and thickened central mountain range serves as a backstop for the converging eurasian and philippine sea plates the crust beneath the central mountain range is characterized by a brittle high velocity and seismically active upper crust 15 km and a ductile low velocity and aseismic mid to lower crust below 15 km most probably due to the high geothermal activity from the excess heat supplied from the hot upper mantle beneath the thin oceanic crust to the east from the surrounding hotter upper mantle beneath the thickened continental crust and from shear heating during active collision the collision zone in eastern taiwan is characterized by an active and steeply eastward dipping seismic zone along a region of low vp and high vp vs ratio near the taitung region in southeastern taiwan it transforms into an active westward steeply dipping seismic zone along a transition zone between the high vp and vs oceanic crust and the low vp and vs continental crust near hualien region in central eastern taiwan there is no apparent seismicity within many sedimentary basins imaged from the tomographic inversion however af ew basins are either bounded on one side by an active fault or are characterized by blind faults beneath the geometry of the subduction zone in northeastern taiwan can be clearly imaged from the relocated earthquake locations behind the subduction a region of low vp and high vp vs ratio at depths of 5 to 10 km can be identified beneath the tatun chilung volcano group indicating a potential magma reservoir two steeply dipping linear seismic zones in the volcano region may mark the upward escape paths of the magmatic materials in the region

plutonium and210pb distributions in northeast atlantic sediments subsurface anomalies caused by non local mixing abstract the depth distributions of 210 pb and 239 240 pu measured in a suite of box cores collected from water depths of 4000 5000 m in the northeast atlantic ocean exhibit pronounced subsurface maxima caused by sediment reworking by benthic infauna small scale spatial heterogeneity in bioturbation rates is indicated by large differences in tracer profiles from duplicate cores separated only by a few centimeters 210 pb and 239 240 pu activity distributions from each subcore exhibit a high degree of correlation and most tracer profiles exhibit one or more subsurface maxima one dimensional biodiffusion analogue models do not adequately simulate the principal features of this data set however an inverse conveyer belt mixing model which simulates subsurface egestion or a functionally equivalent process of surficial material which is enriched both in organic debris and radioactive tracers can reproduce the subsurface tracer maxima single event and continuous subsurface egestion models have been formulated and solved for different feeding rates and background biodiffusive fields the single event model provides a better fit to the data and in particular ensures the observed high degree of correlation between the 210 pb and 239 240 pu activity profiles regardless of the different tracer input functions the most likely candidate responsible for subsurface tracer egestion is a large infaunal worm of the phylum sipunculida which dominates the biomass below a depth of 3 cm

detailed structures of the subducted philippine sea plate beneath northeast taiwan a new type of double seismic zone we studied the detailed structure of the subducted philippine sea plate beneath northeast taiwan where oblique subduction regional collision and back arc opening are all actively occurring simultaneous inversion for velocity structure and earthquake hypocenters are performed using the vast high quality data recorded by the taiwan seismic network we further supplement the inversion results with earthquake source parameters determined from inversion of teleseismic p and sh waveforms a critical step to define the position of plate interface and the state of strain within the subducted slab the most interesting feature is that relocated hypocenters tend to occur along a two layered structure the upper layer is located immediately below the plate interface and extends down to 70 80 km at a dip of 40 50 below approximately 100 km the dip increases dramatically to 70 80 the lower layer commences at 45 50 km and stays approximately parallel to the upper layer with a separation of 15 5 km in between down to 70 80 km below that the separation decreases and the two layers seem to gradually merge into one wadati benioff zone we propose to term the classic double seismic zones observed beneath japan and kuril as type i and that we observed as type ii respectively a global survey indicates that type ii double seismic zones are also observed in new zealand near the southernmost north island cascadia just north of the mendocino triple junction and the cook inlet area of alaska all of them are located near the termini of subducted slabs in a tectonic setting of oblique subduction we interpret the seismogenesis of type ii double seismic zones as reflecting the lateral compressive stress between the subducted plate and the adjacent lithosphere originating from oblique subduction and the downdip extension from slab pulling force the upper seismic layer represents seismicity occurring in the upper crust of a subducted plate and or along the plate interface whereas the lower layer is associated with events in the uppermost mantle

kinematic analysis of the taiwan slate belt the taiwan slate belt can be subdivided into two structural domains based on fold and cleavage geometries and finite and incremental strain histories the two belts correspond generally to two topographic ranges in taiwan the hsuehshan range and the backbone range rocks in the hsuehshan range are characterized by upright symmetric folds and a steeply se dipping axial planar pressure solution cleavage synkinematic fibers in pressure shadows are typically straight parallel to cleavage and plunge downdip indicating that the rocks experienced a coaxial strain history in contrast rocks in the backbone range are characterized by inclined asymmetric folds that verge toward the foreland and display a moderately se dipping axial planar pressure solution cleavage synkinematic fibers are straight and parallel to the downdip stretching lineation in xy sections in xz sections however the fibers typically display a clockwise curvature viewed to the ne indicating a noncoaxial strain history we propose that the different strain histories are due at least in part to differences in the original tectonostratigraphic settings of the strata in the two ranges strata in the hsuehshan range are interpreted to have been deposited in a half graben associated with an east dipping normal fault the strata of the backbone range in contrast are considered to have been deposited on the unfaulted chinese continental margin we suggest that the basement horst on the east side of the half graben functioned as a steep faced rigid backstop that concentrated pure shear deformation throughout most of the hsuehshan range shear strains were apparently limited to zones near the base of the sedimentary sequence and adjacent to the backstop the noncoaxial strains characteristic of the backbone range are interpreted to be the result of a regional scale shear zone that formed as chinese basement and its sedimentary cover were underthrust southeastward beneath the luzon arc

the chemistry of geothermal waters in iceland iii chemical geothermometry in geothermal investigations abstract new data from geothermal wells in iceland have permitted empirical calibration of the chalcedony and na k geothermometers in the range of 25 180 c and 25 250 c respectively the temperature functions are t c 1112 4 91 log sio 2 273 15 t c 933 0 993 log na k 273 15 concentrations are expressed in ppm these temperature functions correspond well with the chalcedony solubility data of fournier 1973 and the thermodynamic data for low albite microcline solution equilibria of heloeson 1969 a new co2 geothermometer is proposed which is considered to be useful in estimating underground temperatures in fumarolic geothermal fields its application involves analysis of co2 concentrations in the fumarole steam the temperature function which applies in the range 180 300 c is logco2 37 43 73192 t 11829 103 t2 0 18923t 86 187 logt where t is in k and co2 in moles per kg of steam

mixing sedimentation rates and age dating for sediment cores abstract analytic solutions to the advection diffusion equation useful as a guide for the interpretation of mixing sedimentation rate and age dating effects in sediment cores have been derived various simplified mixing models appropriate to 14 c and 210 pb measurements have been considered the emphasis has been on a discussion of the various interrelations and dependencies among the mixing coefficient sedimentation rate and radioactive decay constant parameters in determining the 14 c and 210 pb concentrations as a function of depth porosity variations within the sediment column are also considered and the transformed advection diffusion equation including porosity effects is derived

constraints on average taiwan reference moho discontinuity model receiver function analysis using bats data summary by analysing teleseismic waveform data we propose a large scale taiwan reference moho discontinuity model trmdm through coherent stacking and h analysis of receiver functions rfs tectonic structural features are determined from accurate crustal thickness h and reliable vp vs ratio consequently poisson s ratio estimations for taiwan the best estimated regional average moho depth is 33 5 2 9 km noted is a westward crustal thinning from 39 3 0 km in eastern taiwan to 30 1 5 km in southeastern china the averaged moho depth is 23 0 2 5 km in northern taiwan and increases to 33 5 2 0 km in the south the markedly thin crust and high vp vs ratio in northern taiwan are mainly associated with backarc opening and magmatic activities based on h estimations and associated seismicity patterns beneath suang long sslb and adjacent four stations we propose two moho reference models that exhibit distinctive crustal thickening in central taiwan the spatial variations of crustal thickness models show strong lateral change in the moho topography the thick crust in the south thin crust in the north and transition in central taiwan mark the different tectonic units between the subduction wedge and the collision prism onshore in view of the following list of constraints thicker crust in the south than in the north eastward crust thickening significant moho depth changes clear 9 11 s subcrustal boundaries from five stations the compelling thickening of crust and upper mantle beneath the central mountain belt seismicity patterns with the absence of mantle earthquake in the wadatibenioff zone regional geological features the occurrence of the inland chi chi earthquake the compelling low at yulb 1 58 0 13 that may extend to central taiwan at sslb 1 59 0 23 relatively thick crust at yulb 39 5 1 6 km and sslb 40 5 1 3 km or 52 5 1 5 km and finally the apparent horizontal offset between highest yu shan mountain and the deepest moho at sslb we are able to suggest that the initial subduction of the eurasian plate occurred in southern taiwan and most likely extended to the transition zone in central taiwan although the current rf study is limited by large interstation distance our analysis provides more notable constraints than previous studies to explicitly determine the characteristic features of moho discontinuity this detailed approach means that rather than treating the tectonic framework as a whole heterogeneous lithospheric feature clear moho boundary geometry variations indicate that active orogenic processes and differential tectonic stress loading create separate and complex crustal and subcrustal to upper mantle structural features caused by the arc continent collision

mineral saturation and scaling tendencies of waters discharged from wells 150 sc in geothermal areas of turkey aqueous species distribution was calculated from the chemical composition of water discharges from 27 selected production wells with reservoir temperatures 150 sc in seven geothermal areas including kizildere salavatli germencik kavaklidere sazdere salihli caferbeyli simav and tuzla twenty five of the water compositions are relatively dilute with electroconductivity values of 1826 to 7200 s cm and are dominated by na 410 to 2027 mg kg cl 45 to 1882 mg kg and alkalinity co2 491 to 2312 mg kg two water samples from tuzla are highly saline connate waters with cl of 35 273 to 44 140 mg kg and na of 18 200 to 22 250 mg kg mineral equilibrium modeling indicates that the aquifer waters in these selected geothermal wells with some exceptions are oversaturated with respect to calcite aragonite and celestite but undersaturated with respect to gypsum anhydrite fluorite ca montmorillonite anorthite albite low gibbsite illite kaolinite and k feldspar the waters are at near saturation with respect to chalcedony quartz amorphous silica dolomite and strontianite calculation of mineral saturation states geochemical studies and field observations show that carbonate minerals calcite aragonite and dolomite amorphous silica and sulfate minerals celestite and anhydrite are most likely to be precipitated as scales in geothermal wells assessment of calcite and amorphous silica scaling tendencies for selected well waters indicates that hot injection is favorable for tuzla well t 2 50 170 sc and for kizildere wells r 1 and kd 6 around 100 sc for the other wells cold injection 50 sc is favored if calcite and amorphous silica accumulation is to be avoided in injection wells

the deep structure of south central taiwan illuminated by seismic tomography and earthquake hypocenter data abstract the taiwan mountain belt is generally thought to develop above a through going basal thrust confined to within the sedimentary cover of the eurasian continental margin surface geology magnetotelluric earthquake hypocenter and seismic tomography data suggest however that crustal levels below this basal thrust are also currently being involved in the deformation here we combine seismic tomography and earthquake hypocenter data to investigate the deformation that is taking place at depth beneath south central taiwan in this paper we define the basement as any pre eocene rifting rocks and use a p wave velocity of 5 2 km s as a reference for the interface between these rocks and their sedimentary cover we found that beneath the coastal plain and the western foothills clustering of hypocenters near the basement cover interface suggests that this interface is acting as a detachment this detachment is located below the basal thrust proposed from surface geology for this part of the mountain belt inherited basement faults appear to determine the geometry of this detachment and their inversion in the alishan area result in the development of a basement uplift and a lateral structure in the thrust system above them however across the shuilikeng and the chaochou faults earthquake hypocenters define steeply dipping clusters that extend to greater than 20 km depth above which higher velocity basement rocks are uplifted beneath the hsuehshan and central ranges we interpret these clusters to form a deeply penetrating east dipping ramp that joins westward with the detachment at the basement cover interface it is not possible to define a basal thrust to the east beneath the central range

source of arsenic based on geological and hydrogeochemical properties of geothermal systems in western turkey abstract turkey is an area of complex geology with active tectonics and high geothermal potential especially the western part of turkey is a region of abundant geothermal activity faults accommodating the deep circulation of hydrothermal fluids of meteoric origin are the primary means by which of geothermal systems are controlled in this region many of the thermal activities are related to the improved dilation on the e w strikes of the graben faults this situation serves as a suitable environment for the presence of high levels of arsenic in geothermal water resources the highest concentrations of naturally occurring aqueous arsenic as are found in certain types of geothermal waters generally those related to major graben faults in this regard high arsenic concentrations in geothermal resources have been detected in western turkey including but not limited to biga peninsulla gediz graben kucuk and buyuk menderes graben with values ranging from 1 to 1419 ppb in geothermal fluids the thermal waters have surface temperatures of up to 100 c and reservoir temperatures range from 150 to 248 c in the menderes graben from 120 to 287 c in the gediz graben and from 153 to 174 c in biga peninsula hydrogeochemically the menderes graben and gediz graben thermal waters are of the na hco 3 ca hco 3 and na so 4 types whereas some geothermal fluids such as those of tuzla and kestanbol in the biga peninsula cesme and urla are of the na cl type

a model for particle selective transport of tracers in sediments with conveyor belt deposit feeders conveyor belt deposit feeding organisms prevalent in both marine and freshwater systems have a profound effect on sediment properties and transport processes these organisms ingest sediments over a range of depths while depositing gut contents from tails protruding above the sediment surface this action results in particle selective transfer of buried materials to the sediment surface and imposes an accelerated rate of sediment and pore water burial within the feeding zone most previous efforts to combine sediment diagenesis with the effects of biogenic reworking characterize mixing as exclusively diffusive and ignore such major advective effects here a model is developed based on fundamental diagenetic equations for transport and reaction for the distribution of tracers in accumulating sediments subject to compaction and diffusive as well as advective redistribution by benthic organisms conveyor belt cb feeding is characterized as a first order process with a depth dependent rate constant which is either localized gaussian or distributed integrated gaussian biogenic diffusivity of bulk sediments is allowed these alternative depth dependences as well the model assumes simple linear adsorption of the tracer between solid and solution phases and uses a time dependent flux at x 0 which is a combination of that originating externally and the depth integrated contributions from feeding particle selectivity is introduced by applying mass conservation separately to transport of the tracer and bulk sediments properties of the model are illustrated for tracers in nondispersive systems strongly bound to sediment solids cb recycling gives rise to transient reflections on passage of a tracer pulse through the zone of bioturbation reflections readily disappear in the presence of various integrative processes the system time resolution is defined in terms of the downward propagation of dual tracer pulses and shown to be systematically degraded by intensified feeding and selective transport a simple expression is developed for estimating the magnitude of particle selective changes in steady state surface concentrations in terms of the particle selectivity factor and the efficiency of sediment reworking unrecognized particle selectivity can lead to false inferences about changes in the rate of delivery of tracers to sediments selective cb recycling can cause a tracer such as 210pb to be retained largely within the bioturbation zone so that relatively little activity reaches the region of sediment useful for geochronological interpretation increased selectivity accentuates the sensitivity of the profile to details of the reworking process the model applied to previous studies of cb deposit feeders in tracer labeled freshwater microcosms shows the need to include particle diffusion as well as advection in the treatment of cb transport

particle mixing rates in sediments of the eastern equatorial pacific evidence from 210pb 239 240pu and 137cs distributions at manop sites abstract particle mixing rates db calculated from excess 210pb gradients in sediments of the east equatorial pacific range from 0 04 to 0 5 cm2 y with variation of a factor of 3 4 at a single site diffusion of the 236ra daughter 222rn may affect 210pb distributions under conditions of slow mixing and low 210pb flux to the seafloor as shown by a siliceous ooze clay core which contained the fallout radionuclides 239 240pu and 137cs but no excess 210pb relative to 226ra there is no clear relationship between 210pbderived mixing rates and sediment type accumulation rate or organic carbon flux to the sediments comparison of 210pb mixing rates with those calculated from 239 240pu and 137cs distributions reveals better agreement for a pulse input of the fallout radionuclides db 0 03 0 4 cm2 y than for continuous input at a constant rate db 0 1 1 6 cm2 y although the pu and 137cs data are better fit by the latter model the agreement may be fortuitous because 239 240pu and 137cs appear significantly deeper than 210pb in at least one core tracer separation could be caused by particle size selective mixing by the benthic fauna or by chemical mobilization if the fallout radionuclides are scavenged from surface waters by large organic rich particles such as fecal pellets their release and migration may result from decomposition of the carrier in surface sediments either a relatively unreactive form of pu e g oxidized pu has been released by this process or a one dimensional model is inadequate to explain its observed penetration into the sediments activity ratios of 239 240 pu 137 cs in the sediments decrease with increasing north latitude and the trend reflects higher fluxes of 239 240pu near the weapons test site at christmas island 2 n the 239 240 pu 137 cs ratios and fluxes to the sediment assuming constant input at the siliceous ooze red clay site are consistent with published sediment trap data from a nearby site thus if fallout radionuclide fluxes to the sea floor were higher in the past both 239 240pu and 137cs have been released from sinking particles

evaluation of groundwater hydrochemical characteristics and mixing behavior in the daying and qicun geothermal systems xinzhou basin this paper examines groundwater hydrochemical characteristics during mixing between thermal and non thermal groundwater in low to medium temperature geothermal fields a case study is made of daying and qicun geothermal fields in the xinzhou basin of shanxi province china the two geothermal fields have similar flow patterns with recharge sourced from precipitation in mountain areas heated through a deep cycle before flowing into overlying quaternary porous aquifers via fractures hydrochemical features of 60 ground and surface water samples were examined in the context of hydrogeologic information the average temperatures of the deep geothermal reservoirs are estimated to be 125 degrees c in daying field and 159 degrees c in qicun field based on na k mg geothermometry while slightly lower estimates are obtained using silica geothermometers hydrochemical features of thermal water are distinct from cold water thermal groundwater is mainly cl center dot so 4 na type with high tds while non thermal groundwater is mostly hcl 3 ca center dot mg and hco 3 ca type in the daying and qicun regions respectively hydrogeochemical processes are characterized by analyzing ion ratios in various waters higher contents of some minor elements in thermal waters such as f si b and sr are probably derived from extended water rock interaction and these elements can be regarded as indicators of flow paths and residence times mixing ratios between cold and thermal waters were estimated with cl na and b concentrations using a mass balance approach mixing between ascending thermal waters and overlying cold waters is extensive the proportion of water in the quaternary aquifer derived from a deep thermal source is lower in daying geothermal field than in qicun field 5 3 7 3 vs 6 3 49 3 mixing between thermal and non thermal groundwater has been accelerated by groundwater exploitation practices and is enhanced near faults shallow groundwater composition has also been affected by irrigation with low temperature thermal water c 2009 elsevier b v all rights reserved

the influence of radon diffusion on the 210pb distribution in sediments a mathematical model is presented which describes the distribution of radon 222 in sediments having a constant or variable depth distribution of radium 226 the model is extended to the distribution of lead 210 taking into account the mobility of radon the precursor of 210pb within the sediment column the 210pb model is compared at constant radium activity with the conventional approach which disregards the radon diffusion when estimating sedimentation rates by the 210pb method the ratio between apparent and real sedimentation rate s s expressed as a function of three dimensionless parameters demonstrates the importance of the radon diffusion effect this effect is particularly important for sediments with small initial excess 210pb activity small sedimentation rate large radon diffusivity or a combination of these factors applied to lake geneva the sedimentation is estimated to be larger by 30 50 than the original value by krishnaswami et al 1971 in sediments which are mixed at the surface physical mixing or bioturbation the 210pb activity in the mixed layer is diminished compared to that in the settling sediment material robbins et al 1977 and radon diffusion makes the activity difference even larger especially for low initial excess 210pb activity small sedimentation rate and large mixing intensity this result may be of importance for the balance of 210pb in an aquatic system if the calculations are based on activities measured in the sediment

hydrogeochemistry of the thermal waters from the yenice geothermal field denizli basin southwestern anatolia turkey abstract the chemical and isotopic properties of thermal waters kamara and cizmeli and cold springs from the yenice geothermal field ygf in southwestern anatolia turkey are investigated in order to establish a conceptual hydrogeochemical hydrogeological model these thermal waters derive from menderes metamorphic rocks and emerge along normal faults they are commonly used for heating of greenhouses and bathing facilities discharge temperatures of thermal waters are 32 c to 57 c mean 51 c for kamara and 35 c to 68 c mean 47 c for cizmeli whereas deep groundwaters are 15 c to 20 1 c mean 17 c and shallow groundwaters are 12 to 16 c mean 15 c kamara and cizmeli thermal waters are mostly of na ca hco3 so4 type whereas deep groundwaters are ca mg hco3 and mg ca hco3 types and shallow groundwaters are mainly mg ca so4 hco3 and ca mg hco3 types in the reservoir of the geothermal system dissolution of host rock and ion exchange reactions changes thermal water types high correlation in some ionic ratios e g na vs cl k vs cl hco3 vs cl and high concentrations of some minor elements e g as sr b cl f in thermal waters likely derive from enhanced water rock interaction water samples from ygf have not reached complete chemical re equilibrium possibly as a result mixing with groundwater during upward flow geothermal reservoir temperatures are calculated as 89 102 c for kamara and 87 102 c for cizmeli fields based on the retrograde and prograde solubilities of anhydrite and chalcedony based on the isotope and chemical data a conceptual hydrogeochemical hydrogeological model of the ygf has been constructed very negative 18o and 2h isotopic ratios kamara mean of 8 43 and 56 9 respectively and cizmeli mean of 7 96 and 53 7 respectively and low tritium values

rates of sediment reworking at the hebble site based on measurements of th 234 cs 137 and pb 210 abstract th 234 cs 137 and pb 210 measurements have been made on ten cores from the hebble site on the nova scotian continental rise th 234 mixing coefficients from hebble sediments show substantial lateral variability with values ranging from 1 to 33 cm 2 yr 1 these mixing coefficients are one to two orders of magnitude greater than values from typical continental rise and abyssal sediments because of high densities of benthic macrofauna th 234 data from hebble cores indicate that particles at the sediment water interface are mixed to depths of 1 5 cm on a 100 day time scale cs 137 and pb 210 data indicate that on time scales of 30 100 yrs surface sediments are reworked to depths ranging from 1 to 12 cm based on th 234 profiles from two hebble cores collected less than 200 m apart during consecutive years no temporal variability in mixing rate could be resolved in some hebble sediments there is good agreement between the th 234 mixing coefficient 100 day time scale and the pb 210 mixing coefficient 100 yr time scale in other hebble cores however th 234 data indicate that the pb 210 profile has not reached steady state if steady state solutions are used to model these non steady state profiles the calculated pb 210 mixing coefficient may underestimate the true mixing coefficient by as much as an order of magnitude

chemical geothermometers applied to formation waters gulf of mexico and california basins abstract twelve chemical geothermometers based on the concentrations of silica and proportions of na k ca and mg in water from hot springs and geothermal wells are used successfully to estimate the subsurface temperatures of the reservoir rocks these 12 geothermometers together with a new geothermometer based on the concentrations of li and na were used to estimate the subsurface temperatures of more than 200 formation water samples from about 40 oil and gas fields in coastal texas and louisiana and the central valley california the samples were obtained from reservoir rocks ranging in depth from less than 1 000 m to about 5 600 m quartz na k ca mg and na li geothermometers give concordant subsurface temperatures that are within 10 c of the measured values for reservoir temperatures higher than about 75 c na li chalcedony and a modified na k geothermometers give the best results for reservoir temperatures from 40 c to 75 c subsurface temperatures higher than about 75 c calculated by chemical geothermometers are at least as reliable as those obtained by conventional methods chemical and conventional methods should be used where reliable temperature data are required end of article last page 588

210pb scavenging in the north atlantic and north pacific oceans the radionuclide210pb shows significant geographic variations in the extent of its removal from the open ocean water column this texture of scavenging is defined by mapping 1 the integrated deficiency of210pb in the water column relative to its supply from the atmosphere and from in situ decay of dissolved226ra and 2 inventories of excess210pb in deep sea sediments the ratio of210pb deficiency to its supply termed the scavenging effectiveness is 20 in the north equatorial pacific and 50 in the north atlantic this variation is related to the combined effects of uptake of210pb onto sinking particles and lateral transport of210pb to areas of more intense removal sediment inventories of excess210pb normalized to the210pb deficiency in the overlying water column permit evaluation of the relative importance of these effects in the north equatorial pacific virtually all of the210pb removed from the water column is present in the underlying sediments but in the mid latitude north atlantic the sediments comprise only about 50 of the210pb removed the deficiencies of210pb in the mid latitude north atlantic sediments south of 50 n are qualitatively offset by surpluses in high latitude sediments north of 50 n higher primary productivity and new production in the surface waters of the high latitude north atlantic and north equatorial pacific relative to the oligotrophic central north atlantic may account for the greater fluxes of210pb to bottom sediments in those areas

gps observation of crustal deformation in the taiwan luzon region fifteen gps stations in the batan luzon area were surveyed three times during 1996 to 1998 in order to study crustal deformation in the taiwan luzon region the data from these annual surveys are processed together with data from 20 permanent stations in the taiwan area and igs stations in the asia pacific region we found that the chinese continental margin is moving in directions of 102 112 with rates of 11 12 mm yr relative to stable eurasia there is a significant southward increase in crustal motion with respect to eurasia along the n s trend of the luzon arc in the coastal range of taiwan the velocity is 53 mm yr in the direction 313 further south at two volcanic islands lanhsu and batan the velocities increase to 68 mm yr in the direction 306 and 81 mm yr in the direction 299 respectively in northern luzon the velocity reaches 86 mm yr in the direction 301 remarkable fault slips of 17 31 mm yr across the philippine fault system are detected

transition matrix model of bioturbation and radionuclide diagenesis bioturbation rates in muddy sediments are thought to be due primarily to the reworking activities of benthic deposit feeders however current mathematical models of bioturbation do not explicitly link rates of particle mixing with realistic biological reworking mechanisms to address this problem i present a transition matrix model of bioturbation that quantitatively links the reworking activities of individual organisms and community level particlemixing rates solutions to the model are presented for two kinds of tracers particle reactive radionuclides with a constant input flux and conservative tracers added to the sediment as a pulse the model was used to predict the vertical profiles of excess 234 th and 210 pb in the field the model parameters were determined from benthic community structure data model predictions were then compared to measured profiles of these tracers on the basis of this comparison i inferred that maldanid polychaetes at the study site were collecting sediment at the sedimentwater interface and depositing it at depth this transport mechanism had a large effect on the predicted tracer profiles a sensitivity analysis of the model indicated that deposit feeding by the two most abundant species mediomastus ambiseta and nucula annulata was the most important process determining the burial rate of the tracers the model results also indicated that the combined effects of deposit feeding and sedimentation were sufficient to determine the vertical distributions of excess 234

a synthesis of the geologic evolution of taiwan abstract the island arc of taiwan is composed of cenozoic geosynclinal sediments more than 10 000 m thick lying on a pre tertiary metamorphic basement pleistocene to miocene andesitic islands surround the main island and are related mostly to arc magmatism the penghu island group in the taiwan strait is covered with pleistocene flood basalt neogene shallow marine clastic sediments are exposed mainly in the western foothills with pleistocene andesitic extrusives at the northern tip and the northeastern offshore islands a thick sequence of paleogene to miocene argillitic to slaty metaclastic rocks underlies the western central range and forms the immediate sedimentary cover on the pre tertiary metamorphic complex to the east which represents an older mesozoic arc trench system the coastal range in eastern taiwan is a neogene andesitic magmatic arc including also a large variety of volcaniclastic and turbiditic sediments cenozoic taiwan is the site of arc continent collision where the luzon arc on the philippine sea plate overrides the chinese continental margin on the eurasian plate east and northeast of taiwan the polarity of subduction changes whereby the oceanic philippine sea plate is subducting beneath the ryukyu arc system on the eurasian plate continent arc collision in taiwan island is anomalous and may occur in a broad belt of deformation rather than along a well defined plate boundary or subduction zone

statistical properties of low frequency earthquakes triggered by large earthquakes in southern taiwan abstract the recent discovery of triggered tremors tts and low frequency earthquakes lfes in various tectonic environments provides an opportunity for studying the fundamental properties and physical mechanisms of deep tectonic tremor here we quantify the relationship between tts and lfes beneath the central range in southern taiwan and their statistical properties during the teleseismic waves of six large distant earthquakes using waveforms of 11 lfes triggered by the 2005 m w 8 6 nias earthquake as templates we scan through 12 hours of waveform data around six mainshocks and identify a total of 783 lfes the lfes were mainly located in a compact region between 12 and 36 km in depth near the chaochou lishan fault most of lfes occurred within tt during the passage of large amplitude surface waves and the increase of the lfe rate during the surface waves is statistically significant the lfe rates do not follow an omori s type decay but rather abruptly return to the background rate immediately after the surface wave passage these findings suggest that lfes do not trigger any additional lfes at later times and are primarily driven by an external forcing our observations are consistent with the inference that tts consist of many reoccurring lfes

sedimentation and mixing rates of radionuclides in barents sea sediments off novaya zemlya abstract radionuclide measurements have been conducted on sediment cores collected in 1992 in the south eastern region of the barents sea known as the pechora sea cesium 137 and 239 24opu activities in surface sediments are generally less than 30 bq kg with the highest levels being measured in sediments off the southwestern coastline of the island of novaya zemlya high correlations between both 137cs and 239 24opu and the concentration of fine the 238 pu 239 240 vu activity ratio of 0 0245 in chernaya bay is equivalent to values measured in global fallout the 240 pu 239 pu atom ratio 0 0304 measured by mass spectrometry is much lower than values 0 18 typical of global fallout but is consistent with ratios measured for fallout from the early 1951 1955 series of weapons tests at the nevada test site the timing of the chernaya bay source term estimated from the 241 am 241 pu ratio is consistent with the timing of the 1955 and 1957 underwater nuclear tests relatively low initial yields of 241pu 241 pu 239 pu atom ratio 0 00 123 in these tests have resulted in relatively low 241 am 239 240 pu activity ratios 0 05 in recent sediments in chernaya bay radionuclide tracer profiles in cores from the pechora sea can be simulated using a two layer biodiffusion model with rapid near homogeneous mixing in the surface mixed layer and reduced mixing in the deep layer lead 210 profiles are consistent with a wide range of sedimentation and mixing rates in the deep sediment layer however the 137cs and 239 240pu results further constrain the model parameters and indicate that the downward transport of radionuclides in the sediments is governed primarily by sediment mixing with sediment burial playing a secondary role

210pb derived sediment accumulation and mixing rates for the greater puget sound region abstract recent sediment accumulation rates of 46 1200 mg cm2 yr are calculated from excess 210pb activity profiles in 44 sediment cores from 27 sites in the greater puget sound region rates calculated for nine stations in the deeper waters of central puget sound average 480 mg cm2 yr and are greatest between seattle and tacoma near the southern end of this region the standard error of this mean is 113 mg cm 2 yr magnitudes and geographic trends of 210pb derived accumulation rates agree with limited data on sediment inputs and transport paths their accuracy is further supported by several independent approaches including comparison with particle fluxes collected in year long series of sediment trap deployments at two sites accumulation rates are calculated assuming no mixing beneath surface mixed layers of 2 22 cm sediment mixing coefficients in these surface layers average at least 43 cm2 yr four times greater than those reported in open washington coast sediments the difference is attributed to the greater benthic biomass in puget sound sediments particle residence times in surface mixed layers vary from 1 5 to 68 years and introduce corresponding uncertainties in ages of horizons beneath the mixed layers for most of this region these residence times will cause a 20 30 year time lag in achieving an equivalent response of surface sediment chemical concentrations to changes in concentrations in freshly depositing particles for constituents whose stability and phase associations resemble those of 210pb these time lags limit the ability of sediment chemistry monitoring programs to recognize recent changes in composition and fluxes of chemicals to sediments recent fluxes calculated from the product of surface sediment chemical concentration and accumulation rates will be inaccurate for chemicals if their input concentrations have changed in the last 20 30 years

origin evolution and geothermometry of the thermal waters in the golemezli geothermal field denizli basin sw anatolia turkey abstract the golemezli geothermal field ggf is one of the best known geothermal fields in western anatolia turkey the exploited fluids are of meteoric origin mixed with deep magmatic fluids which interacted with the metamorphic rocks of the menderes massif the geothermal fluids are channeled along quaternary faults belonging to the main normal faults system delimiting the northern side of the denizli basin and their associated transfer zones in this study hydrochemical and isotopic analyses of the thermal and cold waters allow us to determine water rock interactions fluid paths and mixing processes two groups of thermal waters have been distinguished i group 1a comprising na so4 type and ca so4 type and ii group 1b only consisting ca hco3 type waters differently two groups were recognized in the cold waters i group 2a corresponding to ca hco3 type and ii group 2b including mg hco3 type their geochemical characteristics indicate interactions with the paleozoic metamorphic rocks of the menderes massif and with the neogene lacustrine sedimentary rocks dissolution of host rock and ion exchange reactions modify thermal water composition in the reservoir of the ggf high correlation in some ionic ratios and high concentrations of some minor elements suggest an enhanced water rock interaction none of the thermal waters has been reached a complete chemical re equilibrium possibly as a result of mixing with cold water during their pathways geothermal reservoir temperatures are calculated in the range of 130 210 c for the golemezli field very negative 18o and 2h isotopic ratios are respectively between 8 37 and 8 13 and 61 09 and 59 34 for the so4 rich thermal waters and ca 8 40 and 8 32 and 57 80 and 57 41 for the hco3 rich thermal waters low tritium

a model for 137cs and other tracers in lake sediments considering particle size and the inverse solution abstract a numerical model for the time dependent behavior of particle associated tracers in sediments has been developed the model is based on the advection diffusion equation for a tracer and includes a sediment density that increases with depth as a modified power function and a diffusion coefficient that follows a half gaussian function versus depth with maximal diffusivity at the sediment water interface the solution procedure is based on finite elements or finite differences the density function is developed from soil mechanics concepts and includes mixing effects through a young s modulus that is increased in the top layer according to a half gaussian function the new density function provides a better fit to 15 out of 17 sediment cores from lake michigan than a frequently used exponential expression the tracer model provides an excellent fit for the 137cs distributions in all of the 17 lake michigan cores that were investigated our fit to the 137cs profile of a southern lake michigan core that has been examined by others is significantly better than previous fits particularly near the top of the core from two different forms of the governing equation for a tracer and the resultant fits to experimental data it appears that 137cs is associated with colloidal and 210pb with settling particles a previously developed time domain method to extract the historical input record of a tracer from its sedimentary profile influenced by mixing has been further improved by including m depth and n time intervals where m n and by fitting the influx to a polynomial the improved method is demonstrated for the cd input to a northern lake michigan core nlm84b although the time resolution obtained 5 yr is better than the previous resolution 15 yr it is clear that the method needs to undergo further development in order to decrease the error of the reconstructed influx and particularly to avoid negative fluxes

structural lithological and geodynamic controls on geothermal activity in the menderes geothermal province western anatolia turkey western turkey belongs to the regions with the highest geothermal potential in the world resulting in significant electricity production from geothermal resources located predominantly in the menderes massif although geothermal exploitation is increasingly ongoing geological and physical processes leading to the emplacement of geothermal reservoirs are hitherto poorly understood several studies on the menderes massif led to different interpretations of structural controls on the location of hot springs and of the heat source origin this paper describes geological evidence showing how heat is transmitted from the abnormally hot mantle to the geothermal reservoirs on the basis of field studies we suggest that crustal scale low angle normal faults convey hot fluids to the surface and represent the first order control on geothermal systems at the basin scale connected on low angle normal faults kilometric high angle transfer faults are characterized by dilational jogs where fluids may be strongly focused in addition favourable lithologies in the basement e g karstic marble could play a critical role in the localization of geothermal reservoirs finally a compilation of geochemical data at the scale of the menderes massif suggests an important role of the large mantle thermal anomaly which is related to the hellenic subduction heat from shallow asthenospheric mantle is suggested to be conveyed toward the surface by fluid circulation through the low angle faults hence geothermal activity in the menderes massif is not of magmatic origin but rather associated with active extensional tectonics related to the aegean slab dynamics i e slab retreat and tearing

diagnosing non meteorically induced variations in the chemistry of saline springs of the vrancea seismic area romania a monitoring operation conducted over more than seven years has been addressing chemical fluctuations displayed by several cool low discharge springs located close to the highly seismic vrancea area romania those outflows compositions proved to be strongly controlled by binary essentially isochemical mixing between a deep origin brine and meteoric freshwater by taking advantage of this particular setting there have been constructed diagrams aimed at investigating how the groundwater discharges na k mg geothermometric parameters fluctuated as a function of the chloride content taken to be an estimator of the freshwater induced dilution we made use of the reciprocal algebraic relationships existing between the equations describing the na k mg geothermometric parameters na k temperature and k mg temperature on the one hand and the so called maturity index mi on the other in an accordingly derived plot of mi against the logarithm of the chloride concentration a series of data points being quite uniformly off set from the mi dilution curve constructed for an apparently regular period suggested that episodically all concerned springwaters were simultaneously subject to some similar changes in the controlling geochemical processes one such modification intervened 3 4 months before the occurrence of the strongest earthquake m text w 5 8 of the hydrochemical monitoring period the consequently derived interpretation was that then the numerical values of certain geothermometric coefficients were likely altered such a process could be consistent with changes in the alkali feldspars solubility relationships possibly in response to episodic al si complexing which might develop within a hypothesised still active exhumation channel

uranium series tracers of mudwave migration in the argentine basin abstract large wave like sediment structures are formed in the argentine basin where active bottom currents carry a heavy load of suspended sediments a model previously developed to explain the formation and migration of these mudwaves predicts that sediment deposition occurs on the upstream face of the wave while the downstream face experiences reduced deposition or erosion depending on the current velocity two mudwaves on the zapiola sediment drift in the argentine basin were cored to evaluate the relationship between present day currents and the migration of these particular structures 210 pb and 230 th were measured in sediments from upstream and downstream faces of each mudwave 210 pb inventories ranged from 33 to 118 dpm cm 2 among the various locations cored the general tendency is for higher inventories of 210 pb to occur on upstream faces indicating higher rates of sediment deposition there as predicted by the model over the time scale reflected by the 210 pb inventories sediments have accumulated on the downstream faces at rates at least one third to one half as high as on the upstream faces which rules out complete non deposition on the downstream faces unsupported 230 th activities of upstreamface sediments are a factor of 3 4 higher than activities of sediments on downstream faces indicating that late pleistocene sediments are being exposed by erosion on the downstream faces taken together these results suggest a situation on the downstream face of each mudwave where fresh particulate matter deposited from the water column is being worked into mixed layer sediments under conditions of net sediment erosion

transition from oblique subduction to collision in the northern luzon arc taiwan region constraints from bathymetry and seismic observations we systematically study the detailed bathymetry seismicity and source parameters of large and moderate sized earthquakes that occurred in the northern luzon arc taiwan region between 1964 and 1996 the purpose is to characterize the transition from oblique subduction to regional collision in terms of the distribution of morphological features the characteristics of seismogenic structures and the corresponding state of strain to the south of 21 5 n the existence of a subduction zone is clearly shown by both bathymetry and seismicity the subducted eurasia slab reaches a maximum depth of 200 km and the depth decreases sharply as it approaches taiwan focal mechanisms indicate that the subducted slab is in downdip extension for depths 150 km but switches to downdip compression at greater depths to the north of 23 n collision is clearly the predominant process with broad deformation on both sides of the suture in between the transition is accommodated by a distributed thrust deformation zone in the frontal portion of the accretionary prism closure of the forearc basin and the right lateral ne sw striking taitung canyon fault zone tcfz these structures resolve the differential movements between the subduction and collision zones and will repeatedly change their positions as the collision propagates southwestward the present day plate boundary follows the axis of the manila trench in the south broadens significantly in the zone of transition and finally becomes a zone of several tens of kilometers in width across eastern taiwan the deformation front on the other hand is located between the western foothills and coastal plain in taiwan then connects to the manila trench to the south seismic strain tensors indicate that the region to the north of tcfz has a compression rate 15 times larger than that to the south the northern luzon arc shows characteristics of oblique subduction but the effects of collision are not as significant within the subducted eurasian lithosphere as comparing to the subducted philippine sea plate beneath the southernmost ryukyu arc

remote triggering of non volcanic tremor around taiwan summary we perform a systematic survey of triggered deep non volcanic tremor beneath the central range cr in taiwan for 45 teleseismic earthquakes from 1998 to 2009 with mw 7 5 and epicentral distance 1000 km to the broad band station tpub triggered tremors are visually identified as bursts of high frequency 2 8 hz non impulsive and long duration seismic energy that are coherent among many seismic stations and modulated by the teleseismic surface waves out of the 45 earthquakes we identified nine teleseismic events associated with nine tremor sources in the southern and five in the northern cr most of the tremor sources are located within the depth range of 15 25 km in the lower crust above the moho we find that the amplitudes of the surface waves play an important role in determining the triggering potential and the apparent triggering threshold is 0 1 cm s 1 or 7 8 kpa however such threshold is partially controlled by the background noise level which could prevent weaker tremor triggered by surface waves with smaller amplitudes from being identified the amplitudes of the triggered tremor show a positive correlation with the amplitudes of the triggering surface waves consistent with the predictions by the clock advance model in addition to amplitudes other factors such as frequency contents and incidence angles also affect the triggering potential we find that intermediate period 30 10 s surface waves could trigger modulate tremors suggesting that long period 30 s surface waves are not always required in long range triggering tremors appear to be triggered by both love and rayleigh waves when the incidence angles are parallel to the strike of the cr all six events triggered tremor primarily during the rayleigh waves for strike normal incidence only the 2001 mw7 8 kunlun earthquake showed predominant love wave triggering this observation can be qualitatively explained by a simple coulomb failure for a left lateral shear on the low angle detachment fault beneath the southern cr

estimates of particle flux and reworking at the deep sea floor using234th 238u disequilibrium abstract because of high specific activities of excess234th t1 2 24 1 days on suspended particles in the deep sea this nuclide is potentially an extremely sensitive indicator of particle inputs and dynamics at the seafloor measurements were made at two deep sea sites in order to examine this potential inventories of excess234th at a low current hemipelagic mud site 3990 m in the panama basin were 1 5 september 81 and 2 5 june 82 dpm cm2 the steady state fluxes to the seafloor calculated from these inventories are in rough agreement with radionuclide fluxes measured in sediment traps small scale 100m spatial variability in inventories implies biologically significant heterogeneity in particle inputs sediment from the continental rise site in the northwest atlantic 2800 m a site with higher current velocities than the panama basin had an inventory of 1 9dpm cm2 this inventory is also in rough agreement with predictions made on the basis of nearby sediment trap data particle mixing coefficients of 30cm2 yr calculated at the pacific and atlantic sites are similar to those in shallow water deposits but could reflect disturbance during handling based on210pb data from the panama basin sediment from below 6cm is mixed at a rate 10 slower than the near surface sediment to a depth of at least 20 cm agreement between234th predicted mixing rates at the panama basin site with210pb profiles and in situ experiments with glass bead tracers implies that these rates are real although the diffusion of dissolved234th into deep sea sediments complicates interpretations 234thxs distributions in bottom sediments offer a useful adjunct to sediment traps for investigation of particle dynamics near the deep sea floor

hydrogeochemical characteristics and genesis of the high temperature geothermal system in the tashkorgan basin of the pamir syntax western china abstract high temperature geothermal systems in china such as those found in tenchong and tibet are common a similar system without obvious manifestations found in the tashkorgan basin in the western xinjiang autonomous region however was not expected the results from borehole measurements and predictions with geothermometers such as quartz na k and na k mg indicate that the reservoir temperature is approximately 250 260 c geothermal water is high in total dissolved solids 2 5 g l and sio 2 content 273 mg l and the water type is cl so 4 na likely resulting from water rock interactions in the granodiorite reservoirs based on isotope analysis it appears to be recharged by local precipitation and river water evidence from the relationships between major ions and the cl and molar na cl ratio suggests mixing between deep geothermal water and shallow cold groundwater during the upwelling process mixing ratios calculated by the relationship between cl and sio 2 show that the proportion from cold end members are 96 99 and 40 90 for riparian zone springs and geothermal water from boreholes respectively active regional tectonic and neo tectonic movements in the pamir syntax as well as radioactive elements in the granodiorite reservoir of the himalayan stage provide basis for the high heat flow background 150 350 mw m 2 nnw trending fault systems intersecting with overlying ne faults provide circulation conduits with high permeability for geothermal water

velocity field of gps stations in the taiwan area abstract the 131 stations of the taiwan gps network were surveyed 4 6 times from 1990 to 1995 with dual frequency geodetic receivers the standard deviation of an observed baseline length with its linear trend removed is in the range of 6 10 mm for a 3 120 km long baseline the average rates of length change for all baselines of the network and those from nine continuously monitoring permanent stations are used in a least squares adjustment to estimate the velocities of the gps stations relative to paisha penghu situated at the chinese continental margin to the south of fengping in the northern coastal range the velocity vectors of stations in lanhsu lutao and the coastal range trend in the directions of 306 322 with rates of 56 82 mm yr in contrast there is a dramatic decrease in the rates to the north of fengping this may be caused by the motion along the ne sw trending thrusts which obliquely cut the northern coastal range a discontinuity of about 30 mm yr in the rates along with a remarkable change in the directions of station velocity is observed across the longitudinal valley then the moving directions gradually shift to the west for the stations in the western foothills in the kaohsiung pingtung coastal area the station velocities are even directed toward the southwest to the north of the peikang high the velocity vectors of the stations change direction from the west gradually to the north and finally to the east and southeast significant nw se extensional deformation is found in the ilan plain and northern taiwan in general the pattern of the velocity field for gps stations in the taiwan area is quite consistent with the directions of present day tectonic stress

bioturbation and holocene sediment accumulation fluxes in the north east atlantic ocean benthic boundary layer experiment sites bioturbation and holocene sediment accumulation are quantified in the three experimental areas of the benthic boundary layer benbo programme by means of the natural radionuclides 14c and 210pb and the artificial radionuclides 137cs and 241am the holocene accumulation rates determined by the radiocarbon method are 4 4 and 6 5 cm kyr 1 at sites b rockall plateau 1100 m water depth and c feni drift 1925 m water depth respectively accumulation at site a situated between feni drift and porcupine bank at 3570 m water depth was interrupted by an erosional event in the mid holocene which removed 0 25 m or more of the uppermost sediment present at that time the estimated accumulation rate since that event is 2 1 cm kyr 1 different estimates of surficial bioturbation mixing depths at site b are returned by the 210pbexcess and 14c methods with the former indicating 10 cm and the latter unusually deep at 17 cm at site c 210pbexcess and the fallout radionuclides 137cs and 241am are present in two distinctly separated depth zones with the deepest mixing down to 15 cm similar to the 14c mixed layer depth this is ascribed to deep burrowing by sipunculid or echiuran worms at site c and similar deep mixing is inferred to be necessary at site b to produce the differences in mixed layer depths derived from the longer and shorter lived radionuclide profiles although the deep burrowing episodes must be rare 1 event per 102 yr the greater accumulation rate at site c compared with site b is produced by an enhanced flux of current driven clay and silt sized material this fine material both dilutes the caco3 content of the site c sediment and is responsible for the higher corg content observed at site c compared with site b unlike the site b and c sediments which are fine grained the coarse 63 125 m size fraction is the most abundant size class in the late holocene sediments at site a suggesting that the sediments at this location are winnowed

oceanic ridge crest processes oceanic ridge crest processes constitute a vigorous frontier of multidisciplinary research with global ramifications in the earth atmospheric and biologic sciences this deep ocean frontier is gradually opening in response to investigations which are elucidating the role of these processes in the lithosphere hydrosphere atmosphere and biosphere and the application of advanced instrumental and interpretive techniques which are increasing the quality and quantity of data these techniques include crustal drilling with borehole logging deep sea drilling project reports high resolution bathymetry sea beam etc side scan sonar seamarc i and ii gloria etc imagery with video and photography multichannel seismics determination of water column properties ctd with rosette sampler etc and submersible applications

mineral equilibria and geothermometry of the dalaman koycegiz thermal springs southern turkey abstract the dalaman and koycegiz thermal springs are from karstic limestones belonging to upper cretaceous to burdigalian beydaglari autochthon and carboniferous to lutetian lycian nappes they have measured temperatures of 24 41 c specific electrical conductivities of 14 310 45 600 s cm and are dominated by na 1550 8500 mg kg and cl 2725 15 320 mg kg the heat source of the geothermal systems of the area is tectonic related and the occurrence of the thermal springs is related to the young normal faults meteoric waters and seawaters recharge the reservoir rocks are heated at depth with increasing geothermal gradient and move up to the surface through the fractures and faults by convection trend and emerge as thermal springs while thermal waters move up to the surface they mix with different proportions of seawater and cold fresh waters the seawater contribution to the thermal waters varies from 24 to 78 lake waters in the area are connected with thermal waters consequently their chemical composition is influenced by the chemistry of thermal waters chemical equilibrium modelling based on measured outlet temperatures and measured ph shows that all the waters are oversaturated with respect to quartz and k mica and undersaturated with respect to al oh 3 anorthite gypsum siderite and sio2 a albite alunite aragonite ca montmorillonite calcite chalcedony chlorite dolomite fe oh 3 a fluorite gypsum illite k feldspar kaolinite and sepiolite minerals are mostly oversaturated or undersaturated mineral saturation studies of the thermal springs indicate that dolomite chalcedony and quartz are most likely to cause scaling at outlet conditions assessments from various chemical geothermometers and na k mg ternary and mineral equilibrium diagrams suggest that the reservoir temperature is around 65 90 c the temperatures obtained from quartz quartz steam loss mg li geothermometers and mineral equilibrium diagrams give the most reasonable results

isotope geochemical characterization and geothermometrical modeling of uttarakhand geothermal field india uttarakhand geothermal area located in the central belt of the himalayan geothermal province is one of the important high temperature geothermal fields in india in this study the chemical characteristics of the thermal waters are investigated to identify the main geochemical processes affecting the composition of thermal waters during its ascent toward the surface as well as to determine the subsurface temperature of the feeding reservoir the thermal waters are mainly ca mg hco3 type with moderate silica and tds concentrations mineral saturation states calculated from phreeqc geochemical code indicate that thermal waters are supersaturated with respect to calcite dolomite aragonite chalcedony quartz si 0 and undersaturated with respect to gypsum anhydrite and amorphous silica si 0 xrd study of the spring deposit samples fairly corroborates the predicted mineral saturation state of the thermal waters stable isotopes 18o 2h data confirm the meteoric origin of the thermal waters with no oxygen 18 shift the mixing phenomenon between thermal water with shallow ground water is substantiated using tritium 3h and chemical data the extent of dilution is quantified using tritium content of thermal springs and non thermal waters classical geothermometers mixing model and multicomponent fluid geothermometry modeling geot have been applied to estimate the subsurface reservoir temperature among different classical geothermometers only quartz geothermometer provide somewhat reliable estimation 96 140 c of the reservoir temperature geot modeling results suggest that thermal waters have attained simultaneous equilibrium with respect to minerals like calcite quartz chalcedony brucite tridymite cristobalite talc at the temperature 130 5 c which is in good agreement with the result obtained from the mixing model

alkenones as paleoceanographic proxies 1 alkenone derived estimates of temperature and co2 are contributing to our understanding of earth s climate history in order to increase confidence in alkenone based climate proxies we recommend the following actions first the sedimentary component or fraction containing alkenones should be identified in order to assess the impact of horizontal advection and vertical mixing on alkenone derived temperature and co2 estimates second differential mixing rates of alkenone containing particles and sand sized foraminifera should be quantified by independent dating of the two phases until that is accomplished apparent temporal offsets of climate proxies in the two phases should be interpreted cautiously third the stability of the unsaturation ratio and carbon isotopic compositions of alkenones during all phases of diagenesis should be confirmed both field and laboratory observations are required fourth future alkenone investigations should be coupled with other paleoclimate proxy measurements at high deposition rate sites in a variety of oceanographic settings in upwelling regions and in the vicinity of river plumes salinity and nutrient proxies should be measured since changes in these parameters may affect alkenone biosynthesis

hydrogeochemical outline of thermal waters and geothermometry applications in anatolia turkey abstract the chemical compositions of a total of 120 thermal water samples from four different tectonically distinct regions central north east and west anatolia of turkey are presented and assessed in terms of geothermal energy potential of each region through the use of chemical geothermometers na ca hco3 type waters are the dominant water types in all the regions except that na cl type waters are typical for the coastal areas of west anatolia and for a few inland areas of west and central anatolia where deep water circulation exists the discharge temperature of the springs ranges up to 100 c and the bottom hole temperatures in drilled wells up to 232 c geothermometry applications yield reservoir temperatures of about 125 c for central anatolia 110 c for north anatolia 136 c for east anatolia and 251 c for west anatolia the latter agreeing with some of the bottom hole temperatures measured in drilled wells the results reveal that the highest geothermal energy potential in turkey is associated with the west anatolian extensional tectonics which provides a regional deep seated heat source and a widespread graben system allowing deep circulation of waters the north anatolian region bounded to the south by the dextral north anatolian fault along which most of the geothermal sites are located has the lowest energy potential probably due to the restriction of the heat source to local magmatic activities confined to pull apart basins the east anatolian region undergoing contemporary compression and the central anatolian region where the compressional regime in the east is converted to the extensional regime in the west have moderate energy potential although the recently active volcanoes suggest the presence at depth of still cooling magma chambers that are potential heat sources the lack of well developed fault systems is probably responsible for the comparatively low energy potential of these regions almost all the thermal waters of turkey are saturated with respect to calcite and hence have a significant calcite scaling potential which is particularly high for west anatolian waters

significant crustal structural variation across the chaochou fault southern taiwan new tectonic implications for convergent plate boundary abstract the chaochou fault a major geological boundary in southern taiwan is considered to be a part of the convergent plate boundary between the eurasia plate and the philippine sea plate we applied the common conversion point stacking technique to teleseismic radial receiver functions and obtained moho variation and crustal structure across the chaochou fault in the eurasia plate to its west the moho depth is about 37 km and the crust is subducting to the east beneath the philippine sea plate with a dip angle of about 30 between the backbone belt and the tananao schist in the philippine sea plate the moho depth is about 17 km the longitudinal valley marks the collision boundary between the eurasia plate and the philippine sea plate the results suggest that the depth extent of the chaochou fault is about 30 35 km and the fault becomes a shallow angle thrust fault at depth the common conversion point image also shows several bending interfaces of velocity contrast in the crust we proposed a simple model to explain the philippine sea plate and eurasia plate collision process and the observed crustal deformations

particle mixing rates in deep sea sediments determined from excess 210pb and 32si profiles particle mixing rates have been determined for 5 south atlantic antarctic and 3 equatorial pacific deep sea cores using excess 210 pb and 32 si measurements radionuclide profiles from these siliceous calcareous and clay rich sediments have been evaluated using a steady state vertical advection diffusion model in antarctic siliceous sediments 210 pb mixing coefficients 0 04 0 16 cm 2 y are in reasonable agreement with the 32 si mixing coefficient 0 2 or 0 4 cm 2 y depending on 32 si half life in an equatorial pacific sediment core however the 210 pb mixing coefficient 0 22 cm 2 y is 3 7 times greater than the 32 si mixing coefficient 0 03 or 0 07 cm 2 y the difference in 210 pb and 32 si mixing rates in the pacific sediments results from 1 non steady state mixing and differences in characteristic time and depth scales of the two radionuclides 2 preferential mixing of fine grained clay particles containing most of the 210 pb activity relative to coarser particles large radiolaria containing the 32 si activity or 3 the supply of 222 rn from the bottom of manganese nodules which increases the measured excess 210 pb activity relative to 226 ra at depth and artificially increases the 210 pb mixing coefficient based on 32 si data and pore water silica profiles dissolution of biogenic silica in the sediment column appears to have a minor effect on the 32 si profile in the mixed layer deep sea particle mixing rates reported in this study and the literature do not correlate with sediment type sediment accumulation rate or surface productivity based on differences in mixing rate among three antarctic cores collected within 50 km of each other local variability in the intensity of deep sea mixing appears to be as important as regional differences in sediment properties

geochemical constraints for the origin of thermal waters from western turkey the combined chemical composition b and sr isotopes and the basic geologic setting of geothermal systems from the menderes massif in western turkey have been investigated to evaluate the origin of the dissolved constituents and mechanisms of water rock interaction four types of thermal water are present 1 a na cl of marine origin 2 a na hco3 type with high co2 content that is associated with metamorphic rocks of the menderes massif 3 a na so4 type that is also associated with metamorphic rocks of the menderes massif with h2s addition and 4 a ca mg hco3 so4 type that results from interactions with carbonate rocks at shallow depths the na cl waters are further subdivided based on br cl ratios water from the cumali seferihisar and bodrum karaada systems are deep circulated seawater br cl sea water whereas water from canakkale tuzla br cl sea water are from dissolution of messinian evaporites good correlations between different dissolved salts and temperature indicate that the chemical composition of the thermal waters from non marine geothermal systems is controlled by 1 temperature dependent water rock interactions 2 intensification of reactions due to high dissolved co2 and possibly hcl gasses and 3 mixing with overlying cold groundwater all of the thermal water is enriched in b the b isotopic composition 11b 2 3 to 18 7 n 6 can indicate either leaching of b from the rocks or b oh 3 degassing flux from deep sources the large ranges in b concentrations in different rock types as well as in thermal waters from different systems suggest the water rock mechanism 87sr 86sr ratios of the thermal water are used to differentiate between solutes that have interacted with metamorphic rocks 87sr 86sr ratio as high as 0 719479 and carbonate rocks low 87sr 86sr ratio of 0 707864

crustal structure across the san andreas fault southern california from teleseismic converted waves crustal structure along a 140 km long profile across the san andreas fault saf in southern california was imaged by stacking teleseismic p s converted phases recorded by a dense short period seismic array the crust mantle discontinuity moho is visible as a continuous feature at a depth around 30 km but is offset 6 to 8 km beneath the saf a small moho disruption can also be seen under the eastern california shear zone ecsz these results suggest that the saf and ecsz extend through the entire crust the moho upwarp under the san gabriel mountains indicates that the mountain ranges were lifted en masse as a result of crustal buckling under horizontal compression

radionuclides as indicators of sedimentary processes in abyssal caribbean sediments li w q guinasso jr n l cole k h richardson m d johnson j w and schink d r 1985 radionuclides as indicators of sedimentary processes in abyssal caribbean sediments in d k young and m d richardson editors benthic ecology and sedimentary processes of the venezuela basin past and present mar geol 68 187 204 concentrations of 2 pb and 23 24 pu were measured in triplicate sub cores from three different sedimentary environments of the venezuela basin 239 24 pu profiles gave bioturbation rate coefficients from 500 to 900 cm ka bioturbation rate coefficients determined from 239 240pu distributions were not consistent with those derived from a two layer mixing model applied to the 2 pb concentration data a four layer mixing model established that at two of the sites mixing was most rapid from 2 to 7 cm indicating that macrofauna at these depths are more effective bioturbators these findings are discussed with reference to the animals found at each site approximately 20 of the 239 24 pu that has fallen to the surface of caribbean sea is present in the sediments excess 2 0pb inventories varied from 30 to 110 of the estimated pb in the overlying water column sediments from the hemipelagic turbidite and pelagic carbonate sites contained 121 108 and 40 of the estimated flux of 2 pb to the sea floor higher 2 pb inventories at the hemipelagic and turbidite sites could have resulted from the recent incorporation of shelf sediments rich in 21 pb alternatively high inventories may indicate that 21 pb produced in deep waters is effectively scavenged by the cycling of reduced metals near the sediment seawater interface iron and manganese are found in reduced forms near the sediment seawater interface at these sites

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

variability of natural and bomb produced radionuclide distributions in abyssal red clay sediments the nature of sedimentation and mixing are examined in abyssal red clay sediments from the north central pacific using three types of indicators 23 th 232th organic 14c and 137cs and 239 24 pu 23 th 232th analysed revealed that the clay sedimentation rate in three box cores collected within a 50 km radius was less than 1 0 ram 10 3 yr however analyses of the organic carbon in thin layers of sediment revealed that radiocarbon was present much deeper in the cores down to 20 cm than was expected from the 23 th 232th distribution in addition both the stratigraphy and inventory of radiocarbon was significantly different between box cores the distributions and inventories of 137cs and 239 24 pu were similar to that found for radiocarbon further illustrating the spatial variability of radionuclides in oligotrophic north pacific red clays these data suggest that bioturbational processes are important for transporting organic carbon down into the sediment column

volcano stratigraphy of the extension related silicic volcanism of the cubukludag graben western turkey an example of generation of pyroclastic density currents western turkey9s extension related cumaovasi volcanic rocks lower miocene 17 ma are excellent examples of silicic eruptions the sub aerial silicic volcanism at cubukludag graben between izmir and kusadasi in west central anatolia is mainly in the form of rhyolite domes lava flows and pyroclastic deposits the initial features of volcanism derived from phreatomagmatic explosive eruptions from silicic magma that came into contact with lake waters during neogene times most of the volcanic succession represents pyroclastic density currents pdcs known as the kuner ignimbrite the deposits are fine grained and laminated at the base and pass laterally and vertically into deposits displaying well developed traction structures soft sediment deformation and or erosion channels in the ne part of the region alternate deposits of massive diffusely stratified lapilli and ash are the main products of the later explosive stage massive lithic breccias forming the top of the sequences are the proximal facies of the pdcs the lava phase mainly consists of rhyolite extruded as dome and fissure eruptions of lavas aligned along ne sw trending faults as well as from extensional cracks that are nearly perpendicular to the main graben faults considering the tectono stratigraphical aspects and geochemical nature of the study area we propose that the cumaovasi silicic volcanism was produced by extension related crustal melting during the late early miocene period 17 ma

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

geostatistics based regional characterization of groundwater chemistry in a sedimentary rock area with faulted setting sophisticated modeling of a hydrogeological structure and the environment are crucial for underground construction this study characterizes hydrochemical properties of groundwater in a sedimentary rock area clarifying their spatial distribution and correlation with geologic structure and interpreting the groundwater source and chemical evolution water samples geological columns and well logs to 1 km depth were taken at 10 sites in horonobe of northern japan toward the objectives a 3d model of cl concentration was produced in conjunction with resistivity logging data through kriging estimation and sequential gaussian cosimulation variography shows that the dip of the main omagari fault is a control on the spatial correlation structure of cl concentration the 3d model shows that this fault and its auxiliary constitute a clear boundary between high and low saline waters and that cl concentrations tend to change in accord with sedimentary layer structures the integration of stable isotope analysis suggests that deep saline water with heavy d and 18o originated from fossilized seawater whereas shallow freshwater with light values is of meteoric water origin dilute saline water in the deep part of study area is partially attributable to dehydration of silica minerals vertical and lateral groundwater flows are estimated to prevail near the omagari fault and be general in other zones respectively difference in the depth of transition zones may be caused by the dominant flow among downward ascending and lateral consequently geostatistical techniques and data integration are useful to depict regional groundwater systems with a data set of water investigation limited by quantity and location

spatial temporal evolution of early aftershocks following the 2010 ml 6 4 jiashian earthquake in southern taiwan chi chia tang 1 2 cheng horng lin2 and zhigang peng3 1hubei subsurface multi scale imaging lab institute of geophysics and geomatics china university of geosciences 388 lumo rd wuhan hubei 430074 p r china e mail iori897 gmail com 2institute of earth sciences academia sinica 128 sec 2 academia rd nangang taipei 11529 taiwan 3school of earth and atmospheric sciences georgia institute of technology 311 ferst drive atlanta ga 30332 usa

the chemistry of geothermal waters in iceland i calculation of aqueous speciation from 0 to 370 c abstract a computer programme has been developed to calculate the composition and aqueous speciation of geothermal reservoir waters including ph redox potential and gas partial pressures the programme is specifically suited to handle geochemical data from wet steam wells hot water wells and boiling hot springs but it may also be used for non thermal waters solubility data for selected geothermal minerals are incorporated to facilitate the study of solution mineral equilibria the programme may also be used to study chemical changes in water chemistry accompanying boiling variable degassing and cooling and how these changes disturb solution mineral equilibria

a model for radionuclides in sediments influenced by mixing and compaction a model for the activity of radionuclides in sediments has been set up based on the one dimensional advection diffusion equation the model considers sedimentation mixing and compaction observed distributions of deposit feeding organisms and the nature of physical disturbances indicate that a gaussian diffusion coefficient may be appropriate two layer models with constant and gaussian mixing respectively in the upper layer are compared with measured pb 210 profiles for two cores from green bay lake michigan and it is found that the maximal diffusion coefficient d0 in the gaussian model is considerably greater than the constant d value e g d0 4 versus d 0 2 cm2 year if compaction effects are neglected the solution for the gaussian model is based on an approximate power series method compaction can be taken into account by using an exponential sedimentation rate or bulk sediment density by comparing with measured data for a lake ontario core it is seen that compaction alone can give an appreciable flattening of the activity curves near the top layers

the influence of inherited continental margin structures on the stress and strain fields of the south central taiwan fold and thrust belt in this paper we test whether or not structural and morphological features inherited from the eurasian continental margin are affecting the contemporary stress and strain fields in south central ta

the crust and upper mantle structure beneath southeastern china we analyzed teleseismic waveforms recorded by 44 stations in the fujian and taiwan provinces of china and obtained 5344 high quality receiver functions the crustal thickness h and average crustal vp vs ratio k beneath every station were estimated using the h k stacking method crustal thicknesses near the fujian province range from 28 3 to 32 8 km with an average of 31 1 km and the corresponding vp vs ratios vary from 1 70 to 1 84 with a mean of 1 76 from inland to offshore of the fujian province the crustal thicknesses decrease and poisson s ratios increase these may indicate decreasing sio2 and increasing calcalkaline contents in the crust the discontinuity structures such as the moho subducting slab the 410 and 660 km discontinuities hereafter we call them the 410 and the 660 are also studied using common converted point ccp stacking of receiver functions along two nw se lines of central and northern taiwan the ccp stacking results show a western dipping structure at depths above 50 km suggesting that the philippine sea plate is probably subducting beneath the eurasian continent plate near the central and northern taiwan the ccp stacking results show sharp and flat 410 and 660 km discontinuities and the transition zone thickness tzt is the same as that of ambient mantle beneath fujian and taiwan strait but thickens in the east of taiwan these results suggest that 1 the subducting eurasian continent plate is confined to the depths above 410 km beneath fujian and taiwan strait and 2 the south china sea slab may reach the transition zone beneath the east of taiwan 2007 elsevier b v all rights reserved

steady state tracer dynamics in a lattice automaton model of bioturbation the intensity of biogenic sediment mixing is often expressed as a biodiffusion coefficient db quantified by fitting a diffusive model of bioturbation to vertical profiles of particle bound radioisotopes the biodiffusion coefficient often exhibits a dependence on tracer half life short lived radioisotopes e g 234th tend to yield notably larger db values than longer lived radioisotopes e g 210pb it has been hypothesized that this is a result of differential mixing of tracers by particle selective benthos this study employs a lattice automaton model of bioturbation to explore how steady state tracers with different half lives are mixed in typical marine settings every particle in the model is tagged with the same array of radioisotopes so that all tracers experienced exactly the same degree of mixing two different estimates of the mixing intensity are calculated a tracer derived db obtained in the standard way by fitting the biodiffusion model to resulting tracer profiles and a particle tracking db derived from the statistics of particle movements the latter provides a tracer independent measure of mixing for use as a reference our simulations demonstrate that an apparent db tracer dependence results from violating the underlying assumptions of the biodiffusion model breakdown of the model is rarely apparent from tracer profiles emphasizing the need to evaluate the model s criteria from biological and ecological parameters rather than relying on obvious indications of model breakdown e g subsurface maxima simulations of various marine environments coastal slope abyssal suggest that the time scales of short lived radioisotopes such as 234th and 7be are insufficient for the tracers to be used with the biodiffusion model 210pb appears an appropriate tracer for abyssal sediments while 210pb and 228th are suitable for slope and coastal sediments

helium carbon relationships in geothermal fluids of western anatolia turkey abstract we investigate the helium carbon and oxygen hydrogen isotopic systematics and co2 3he ratios of 8 water and 6 gas samples collected from 12 geothermal fields in western anatolia turkey 3he 4he ratios of the samples r normalized to the atmospheric 3he 4he ratio ra 1 39 10 6 range from 0 27 to 1 67 and are significantly higher than the crustal production value of 0 05 fluids with relatively high r ra values are generally found in areas of significant heat potential kizildere and tuzla fields co2 3he ratios of the samples ranging from 1 6 109 to 2 3 1014 display significant variation and are mostly higher than values typical of an upper mantle source 2 109 the 13c co2 and 13c ch4 values of all fluids vary from 8 04 to 0 35 and 25 80 to 23 92 vs pdb respectively stable isotope values 18o d of the geothermal waters are conformable with the mediterranean meteoric water line and indicate a meteoric origin the temperatures calculated by gas geothermometry are significantly higher than estimates from chemical geothermometers implying that either equilibrium has not been attained for the isotope exchange reaction or that isotopic equilibration was disturbed due to gas additions en route to the surface evaluation of he co2 abundances indicates that hydrothermal degassing and calcite precipitation controlled probably by adiabatic cooling due to degassing significantly fractionate the elemental ratio co2 3he in geothermal waters such processes do not affect gas phase samples to anywhere near the same extent for the gas samples mixing between mantle and various crustal sources appears to be the main control on the observed he c systematics however crustal inputs dominate the co2 inventory considering that limestone is the main source of carbon 70 to 97 of the total carbon inventory the carbon flux from the crust is found to be at least 20 times that from the mantle as to the he inventory the mantle derived component is found to vary up to 21 of the total he content and is probably transferred to the crust by fluids degassed from deep mantle melts generated in association with the elevated geotherm and adiabatic melting accompanying current extension the range of 3he enthalpy ratios 0 000032 to 0 19 10 12 cm3 stp j of fluids in western anatolia is consistent with the release of both helium and heat from contemporary additions of mantle derived magmas to the crust the deep faults appear to have facilitated the deep circulation of the fluids and the transport of mantle volatiles and heat to the surface

seismic tomography of taiwan improved constraints from a dense network of strong motion stations in this study a large collection of 41 141 s p times from the untapped records of the taiwan strong motion instrumentation program tsmip network is combined with the p and s wave arrival times from the taiwan central weather bureau seismic network cwbsn to image the v p and v p v s structures beneath taiwan the records from the 680 tsmip stations throughout taiwan in the past 15 years enhance the path coverage and the resolution in the tomography inversions tremendously our result for the v p structure largely confirms previous studies but brings better constraint on the v p v s structure the colliding luzon volcanic arc is characterized by a belt of high v p and high v p v s with high seismicity that includes the offshore islands of lutao and lanyu and the coastal ranges in eastern taiwan at the depth between about 13 and 25 km this high v p v s belt can be traced to the subduction zone in the region between hualian and ilan in the deeper portion the shallow portions of the southwestern coastal plain and the pingtung region are also characterized by a belt of high v p v s with lower seismicity most of the events occurred at the base of the high v p v s zones we suggest that material strength in those regions may be too low to accumulate stress which may indicate water saturated young sediments finally the central range region is characterized by a low v p v s belt