deformation paths in the shallow levels of an accretionary prism the eocene shimanto belt of southwest japan detailed structural analysis of coherent turbidites in a part of the eocene shimanto belt on the muroto peninsula shikoku island japan reveals a structural evolution that is typical of the shallow levels of accretionary prisms in style and sequence of deformational fabrics but anomalous in that it includes both a marked rotation in shortening direction and a major out of sequence thrust deformation throughout a history of progressive lithification and burial was dominated by subhorizontal shortening and seaward vergent shear structures evolved from predominantly mesoscale thrusts and folds to larger more brittle faults and finally to kilometer scale amplified fault bend folds with an associated pressure solution cleavage this structural progression is consistent with increasing strength of the rocks decreasing fluid pressures and increasing temperature and pressure as the sediments were dewatered lithified and accreted to the prism in contrast to this straightforward structural evolution the prism scale deformation of the eocene shimanto belt is difficult to reconcile with simple models of prism developmentthat assume orthogonal subduction and seaward stepping imbrication a 50 counterclockwise rotation in the shortening direction and a major out of sequence or intraprism thrust are recorded by two distinct structural domains in both the earliest structures are clastic dikes and faults indicative of north south shortening one domain is characterized by east striking regional scale folds and cleavage that are transected by an east northeast trending cleavage however the other is characterized by northeast striking folds and cleavage that are transected by a slightly more north striking cleavage the different deformation histories of the two do mains require that they be separated by a major intraprism fault this fault carries tectonic melange containing blocks of pillow basalt and chert indicating that it rooted in the decollement zone beneath the prism the tectonostratigraphy and deformation histories of the two domains suggest that both before and after the out of sequence fault developed higher structural levels of the prism experienced significant subhorizontal shortening whereas lower structural levels bypassed this zone of deformation

geology geochronology and rift basin development in the central sector of the main ethiopia rift based on stratigraphic relationships and k ar dating of volcanic rocks from both of the escarpments flanking plateaus and from the rift floor of the central sector of the main ethiopian rift six major volcanic episodes are recognized in the rift9s development over a time span from the late oligocene to the quaternary using the k ar data correlation of volcanic units from the six periods of activity throughout the study area forms the basis for establishing six time stratigraphic chronozones for the central sector that are related to volcanism in the ethiopian cenozoic volcanic province the oldest basalt and rhyolite flows exposed along the rift margins of the central sector are time correlative to or older than those in river canyons for example blue nile on the adjacent northwest plateau a thinned mesozoic stratigraphic sequence along the guraghe western rift margin suggests that doming may have preceded volcanism and rifting of the cenozoic by late miocene time at least by 8 3 ma and 9 7 ma the eastern and western faulted margins respectively of the rift had formed at guraghe and at agere selam as indicated by containment of flows of that age within the rift wall during eruption a paroxysm of calc alkaline ignimbrite activity produced voluminous flows nearly fully contained within the rift during the pliocene epoch the munesa crystal tuff 3 5 ma a prominent marker tuff exposed on both rift margins is present at depth in a geothermal well beneath the rift floor and indicates a minimum of 2 km of downthrow in the central sector since its eruption structural and stratigraphic relationships in the central sector indicate a two stage rift development this is characterized by an early phase late oligocene or early miocene of a series of alternating opposed half grabens along the rift with alternating polarity such as that in the present gregory and western rifts of east africa and symmetrical rifts that evolved from these grabens in late miocene or early pliocene time thus evolution from alternating half graben to a full symmetrical graben with a medially located neovolcanic zone that is bifurcated to marginal grabens in the northern part of the study area may be a fundamental part of the rifting process the study indicates that there are major petrologic and tectonic differences between the main ethiopian rift and the gregory kenyan rift

geochemical characteristics of fluoride in groundwater of gimcheon korea lithogenic and agricultural origins the occurrence of fluoride in groundwaters can be influenced by many factors in korea the fluoride rich groundwaters are normally associated with rock types especially granite and gneiss in gimcheon high fluoride groundwaters up to a maximum of 2 15 mg l were observed with bimodal distribution of concentrations the groundwater in this area showed relatively high concentrations of anthropogenic chemicals such as nitrate chloride and sulfate statistical analysis showed that fluoride is positively correlated with ph alkalinity sodium and lithium indicating that the interaction with granite is the main cause enriching its concentration in gimcheon 18o data of groundwater showed a negative correlation with nitrate and can be used as an indicator of groundwater age the four samples of fluoride rich groundwater were plotted in the light d and 18o region showing that they were the result of long water rock reaction however other groundwater with a low fluoride concentration was evenly distributed throughout all d and 18o ranges and did not show a statistically significant correlation with nitrate indicating possible mixing with another source of fluoride considering the influence from the surface on the geochemical characteristics of groundwater in this area anthropogenic sources including phosphate fertilizer containing fluoride and pesticides may also have partly contributed to the concentrations of fluoride in the low fluoride groundwater the scattered distribution of fluoride rich groundwater and the significant correlation with lithium suggest that pegmatite is the main rock type increasing fluoride concentration in this area

investigation of fluoride contamination and its mobility in groundwater of simlapal block of bankura district west bengal india the occurrence of dental skeletal fluorosis among the people in the study area provided the motivation to assess the distribution severity and impact of fluoride contamination in groundwater of bankura district at simlapal block west bengal india to meet the desired objective groundwater samples were collected from different locations of laxmisagar machatora and kusumkanali regions of simlapal block at different depths of tube wells in both pre and post monsoon seasons geochemical results reveal that the groundwaters are mostly moderate to hard water type of total groundwater samples 37 are situated mainly in relatively higher elevated region containing fluoride above 1 5 mg l indicating that host aquifers are severely affected by fluoride contamination machatora region is highly affected by fluoride contamination with maximum elevated concentration of 12 2 mg l several symptoms of fluorosis among the different age groups of people in laxmisagar and machatora areas are indicating consumption of fluoridated water for prolonged period the groundwater samples were mainly na ca hco3 type and rock dominance indicating the dissolution of minerals taking place ion exchange between oh ion and f ion present in fluoride bearing mineral is the most dominant mechanism of fluoride leaching high concentration of na and hco3 increases the alkalinity of the water providing a favorable condition for fluoride to leach into groundwater from its host rocks and minerals

structural and fluid evolution of a young accretionary complex the hoh rock assemblage of the western olympic peninsula washington the hoh rock assemblage of the western olympic peninsula washington was deposited in eocene to miocene time and accreted deformed uplifted and eroded by the late miocene northeast dipping fault zones within the hoh are characterized by intensely deformed mud matrix melange and they range from 200 m to 1 000 m thick kinematic indicators within the matrix indicate thrusting to the west southwest both hanging wall and footwall sections are strongly folded and faulted wall rock sections are lithostratigraphically distinct with hanging walls composed of massive coarse sandstone and conglomerate and footwall sections composed of thin to medium bedded sandstone and siltstone folds within the wall rock sections are oblique to and are truncated by the later fault zone melanges indicating that the fault zones postdate folding evidence of fluid involvement in the hoh rocks includes petroliferous outcrops carbonate and clay cement and veins of carbonate and laumontite the progressive evolution of veins and cements paragenetic sequence can be interpreted in terms of crystallization under conditions of increasing consolidation decreasing salinity and changing fluid composition suppressed carbonate luminescence may reflect crystallization under reducing conditions perhaps related to the sulfate reduction zone the presence of hydrocarbons or clay dehydration although deformational features may be associated with the earliest phase of veining most of the localized grain breakage and matrix shear zones formed after the early micritic veins and before the last phase of sparitic carbonate laumontite veins laumontite occurred syn deformationally and in equilibrium with carbonate and also post deformationally the paragenetic sequences observed in all samples from the hoh rock assemblage can be correlated suggesting that the sources and processes controlling the fluid emplacement were similar across a wide region in addition the paragenetic sequence in the hoh rocks is similar to that documented in autochthonous coeval basins of southwest washington this similarity suggests that the precipitates formed during the evolution of the hoh rocks involved fluids that originated within the matrix and did not involve exotic or far traveled fluids

occurrence and hydrogeochemistry of fluoride in alluvial aquifer of weihe river china fluoride f has significant impacts on human health high fluoride groundwater up to 1 90 mg l has been found in upper confined aquifer underlying the first terrace of weihe river during a hydrogeological investigation for water supply in 2005 to reveal the occurrence and hydrogeochemistry of high f groundwater hydrogeochemical tools such as saturation index ionic ratios and correlation analysis were used in this study the study shows that the concentrations of most physiochemical parameters from phreatic water influenced by intensive evaporation and anthropogenic activities such as unregulated sewage and excreta disposal and agricultural practices in the area are higher than those of confined water the f concentration in phreatic water is within the acceptable limits set by china and the world health organization who while that of upper confined water shows a decreasing trend northwestward as the weihe river approaches with f concentration in the first terrace beyond the national and the who standards high f groundwater is observed in alkaline environment associated with high na ph hco3 and low ca2 and mg2 the enrichment of f is controlled by geologic and hydrogeological conditions fluorine bearing minerals presented in alluvial formations and their dissolution precipitation under the alkaline environment along groundwater flow ion exchange human activities and the mixing of different recharge waters may influence the enrichment of f as well

history of metamorphic fluids along outcrop scale faults in a paleogene accretionary prism sw japan implications for prism scale hydrology 1 synkinematic quartz crystals collected from late stage syn to post cleavage faults in the paleogene shimanto accretionary complex contain fluids that provide constraints on fluid flow within the accretionary wedge in particular the trapped fluids provide a glimpse of intraprism flow during a phase of widespread prism thickening carbonic ch4 co2 rich and aqueous h2o rich inclusions occur intermixed within single crystals that nucleated primarily in releasing stepovers along faults that deform well indurated and or cleaved wallrock invariably the carbonic inclusions contain an aqueous liquid as a perimeter phase and the aqueous inclusions contain a carbonic vapor phase suggesting coeval trapping of unmixed phases from a miscible parent fluid these observations are interpreted to reflect crystal growth following deformation driven dilitation and consequent unmixing of the parent fluid at one location cape oyama the occurrence of ch4 and h2o in the absence of co2 enables explicit constraints to be placed on pressure and temperature conditions during crystal growth these conditions suggest geothermal gradients of 50 c km during late stage faulting our results suggest local intraprism flow that was driven by deformation the scale of flow that is suggested is quite restricted and this leads us to hypothesize that the paleogene shimanto accretionary prism acted largely as a barrier to fluid flow during late stage deformation as a consequence the paleogene rocks probably served to focus fluid escape elsewhere most likely trenchward and arcward the combination of the elevated geothermal gradient which would have contributed to increasing the relative strength of this package of rocks and the lack of fluid pathways within it would have favored the development of new out of sequence thrust faults outboard of the paleogene prism or the reactivation of older more landward structures

hydrogeochemical study in the main ethiopian rift new insights to the source and enrichment mechanism of fluoride the central main ethiopian rift suffers a severe water quality problem characterized by an anomalously high fluoride f content that causes an endemic fluorosis disease the current study conducted in the ziway shala lakes basin indicates that the f content exceeds the permissible limit for drinking prescribed by the world health organization who 1 5 mg l in many important wells up to 20 mg l with even more extreme f concentration in hot springs and alkaline lakes up to 97 and 384 mg l respectively the groundwater and surface water from the highlands typically characterized by low total dissolved solids tds and ca mg hco3 hydrochemical facies do not show high f content the subsequent interaction of these waters with the various rocks of the rift valley induces a general increase of the tds and a variation of the chemical signature towards na hco3 compositions with a parallel enrichment of f the interacting matrixes are mainly rhyolites consisting of volcanic glass and only rare f bearing accessory minerals such as alkali amphibole comparing the abundance and the composition of the glassy groundmass with other mineral phases it appears that the former stores most of the total f budget this glassy material is extremely reactive and its weathering products i e fluvio volcano lacustrine sediments further concentrate the fluoride the interaction of these weathered reworked volcanic products with water and carbon dioxide at high ph causes the release of fluoride into the interacting water this mainly occurs by a process of base exchange softening with the neo formed clay minerals i e ca mg uptake by the aquifer matrix with release of na into the groundwater this is plausibly the main enrichment mechanism that explains the high f content of the local groundwater as evidenced by positive correlation between f ph and na and inverse correlation between f and ca mg saturation indices si have been calculated using phreeqc 2 for the different water groups highlighting that the studied waters are undersaturated in fluorite in these conditions fluoride cannot precipitate as caf2 and so mobilizes freely without forming other complexes these results have important implications for the development of new exploitation strategies and accurate planning of new drilling sites

deformation and fluid flow of a major out of sequence thrust located at seismogenic depth in an accretionary complex nobeoka thrust in the shimanto belt kyushu japan 1 nobeoka thrust in kyushu southwest japan was investigated to understand the relationship between the seismogenic out of sequence thrust ost and fluid flow in accretionary prisms the nobeoka thrust is a fossilized ost being active at seismogenic depth the hanging wall exhibits a penetrative plastic deformation while a brittle cataclastic melange like occurrence characterizes the footwall although both of them have same shale and sandstone dominant protolith vitrinite reflectance analyses indicate that the maximum temperatures of the hanging wall and footwall are approximately 320 and 250 c respectively this thermal gap across the thrust corresponds to 8 6 14 4 km of displacement assuming a 28 47 c km geothermal gradient the brittle damage zone of the thrust is asymmetric only 2 m for hanging wall side and 100 m for footwall three types of mineral veins quartz and carbonate are well developed especially in the damaged footwall the tension crack filling vein the fault filling vein and postmelange one the first is harmonious with fabric perpendicular to the p surface fluid inclusion geothermobarometry indicates the p t of fluid in the intensively damaged zone of the footwall is 300 c 230 250 mpa higher than that from vitrinite reflectance which suggests that hydrothermal fluid flow is associated with deformation the same type vein in the lowest portion of the footwall damaged zone includes a much lower p t fluid this difference suggests that continuous underplating caused the damaged zone to propagate downward with cooling and shallowing which differs from faults characterized by shear localization and might be unique to aquiferous ost in accretionary complexes

fluoride enrichment in aquifers of the thar desert controlling factors and its geochemical modelling the groundwater is the only source of drinking water in the jaisalmer district of rajasthan india the study area is a part of the thar desert it has low and scattered population and no industries hence the possibility of anthropogenic input of fluoride is almost negligible thus the enrichment of fluoride is only possible due to geochemical processes taking place in the groundwater of the region a total of 100 groundwater samples 34 samples from jaisalmer and 66 samples from the pokharan administrative blocks were collected it was observed that the concentration of fluoride ranged from 0 08 mg l to 4 56 mg l in the groundwater of jaisalmer and from 0 56 mg l to 6 60 mg l in the samples of the pokharan block the alkaline condition average ph 7 7 0 22 and 8 01 0 25 in jaisalmer and the pokharan administrative block respectively in the region favours fluorite dissolution ion exchange dissolution of calcite semi arid climate alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area copyright 2012 john wiley sons ltd

abundance and distribution of fluoride concentrations in groundwater la ballenera catchment southeast of buenos aires province argentina high concentrations of fluoride have negative effects on human health and it is one of the most widespread contaminants in groundwater having being found in high concentrations in different countries over the entire world fluoride concentrations exceeding the drinking water levels are very frequent in the region known as pampa plain in argentina associated with loess like sediments bearing volcanic shards and calcium carbonate concretions in this study the behavior of fluoride in the catchment of la ballenera creek is performed to contribute to the understanding of the processes controlling its distribution at catchment scale the catchment is around 100 km2 mostly in a flat landscape outflowing into the atlantic ocean the concentration of major ions silica and fluoride was measured on 34 groundwater and 9 surface water samples obtained in october 2013 all the samples both streamwater and groundwater were sodium bicarbonate type with an average ph of 8 and 7 3 respectively the fluoride concentrations in groundwater ranged between 1 1 and 2 5 mg l with an average value of 1 9 mg l fluoride concentrations in streamwater were close to groundwater concentrations indicating the predominance of baseflow on surface water composition the variations in the contents of fluoride are due to two main factors one geological geomorphological and the other geochemical the first one is related to the dominance of loess like sediments formed by minerals bearing fluoride and the second one is related to the control resulting on calcite precipitation adsorbing fluoride ions

prevalence of fluorosis in the fluoride enriched groundwater in semi arid parts of eastern india geochemistry and health implications abstract fluorosis is becoming a global environmental toxicological problem and is most commonly found in water stressed regions in order to evaluate the geochemical mechanism of fluoride enrichment in groundwater and health implications in the padwakodari environs of eastern part of india a total of twenty two samples were collected and analysed for physico chemical parameters spreading across the study area geologically the area mainly comprises of phyllites granite gneiss mica schist and sandstone high fluoride concentrations found mainly in the granite gneisses which are situated central to northwestern parts of the study area the concentration of fluoride in the groundwater samples ranges from 0 3 to 11 mg l with an average of 2 mg l 64 of the groundwater samples containing fluoride concentration that exceed the who drinking water guidelines value of 1 5 mg l chronic ingestion of high doses has been linked to the development of dental fluorosis and in extreme cases skeletal fluorosis the dominant geochemical facies present in water are na ca mg hco 3 11 samples na mg ca hco 3 5 samples ca na mg hco 3 5 samples and ca mg na hco 3 1 sample sodium and bicarbonate ions being major component in majority of the water types located mostly in the granite gneiss formation has a tendency to increase fluoride concentration in groundwater by dissolving the fluoride from fluoride bearing minerals the oversaturation of half of the samples with respect to calcite and majority of samples undersaturation with respect to fluorite makes it feasible for fluoride to get released in to the groundwater decreasing ca activity downgradient recharge to discharge leads to a dominance of fluorite unsaturated conditions and consequently to mobilization of fluoride in groundwater the results indicate that the fluoride concentration in groundwater is mainly governed by high weathering of fluoride bearing minerals i e apatite and biotite in granite gneiss contains abundant fluoride alkaline hydrogeological environment high temperature low rainfall evapotranspiration and ion exchange

the spatial distribution and hydrogeological controls of fluoride in the confined and unconfined groundwater of tuoketuo county hohhot inner mongolia china insufficient or excessive intake of fluoride can create health problems for humans the objective of this study was to understand the occurrence of fluoride in groundwater as well as its spatiotemporal variation and sources in tuoketuo county hohhot inner mongolia china sixty seven water samples from 34 phreatic and 33 confined sources were collected from hand pumps dug wells and tube wells all samples were analyzed for ph electric conductivity ec total dissolved solids tds total hardness th as well as content of na k ca2 mg2 hco3 so4 2 cl and f the fluoride concentration in water samples varied from 0 40 to 7 20 2 33 1 79 and 0 06 to 12 70 1 65 2 38 mg l in phreatic and confined water respectively an analysis of the hydrogeochemical characteristic of samples indicated that the high fluoride content of groundwater was caused by the alkaline environment with high levels of hco3 na tds ec and with a ca2 deficiency the highest concentration of fluoride 5 mg l in phreatic water was located in the groundwater discharge area because this water was affected by the groundwater flow field in confined aquifers the concentration of fluoride was mainly controlled by lithology a high fluoride content 1 5 mg l was only observed in lacustrine platform zone in confined aquifers

warm fluid migration along tectonic melanges in the kodiak accretionary complex alaska analyses of methane water fluid inclusions from syntectonic quartz veins in melange boudins of the kodiak accretionary complex alaska indicate fluid temperatures ranging from 215 to 290 c at depths between 10 and 14 km these fluid temperatures are significantly higher than those predicted by conductive heat flow models of subduction zones given the available geological constraints this discrepancy is interpreted as the result of migration of warm fluids from deeper structural levels along active fault zones during subduction related underthrusting of these units this interpretation requires more careful consideration of how migrating fluids affect the general thermal structure of subduction zones

underplated units in an accretionary complex melange of the shimanto belt of eastern shikoku southwest japan imbricated thrust stacks composed of melange and oceanic slabs occur in the shimanto belt eastern shikoku sw japan the melanges are divided into two types melange i consists of lenticular sandstone blocks surrounded by scaly shale matrix and melange ii is composed of blocks of oceanic material such as basalts cherts and red shale in a scaly matrix of shale melange ii is observed only near the boundaries between melange i and oceanic slabs the fabric of melange i indicates progressive deformation during underthrusting of originally coherent trench fill turbidites layer parallel extension characterizes early deformation and is divided into two stages an early stage formed during normal faulting and a subseguent stage formed perpendicular to the early extension the early extension is interpreted in terms of riedel shear associated with layer parallel shearing and tectonically induced loading normal to the layering the second extension is due to sticking thrust movement late deformation of melange i is represented by folding in association with layer parallel shearing this appears to be related to compression just before or during underplating of melange i beneath the accretionary prism layer parallel shear extends downward due to strain hardening of sheared sediments and then reaches to the base of the sediments subsequently the shear zone penetrates pelagic sediments and finally oceanic basement at this time melange ii is formed by the shearing an imbricated stack of melanges i ii and oceanic slabs forms duplexes during the underplating process the weak metamorphism of the melange complex in the study area suggests that underplating occurs at shallow depths where trench fill is thin

occurrence and formation of high fluoride groundwater in the hengshui area of the north china plain although high f groundwater was observed in the hengshui of the north china plain the depth dependence of groundwater f and its relation to aquifer sediments remains unknown both shallow groundwater and deep groundwater were collected for chemical and isotopic characterization sediments were taken from different depths down to 130 m for total element analysis and f form determination with sequential extraction procedure results show that f concentration ranges from 0 37 to 3 28 mg l and from 0 28 to 3 6 mg l in shallow and deep groundwater respectively high f water from shallow aquifers are of cl so4 na mg hco3 cl so4 na and so4 cl na mg types while hco3 so4 cl na and cl so4 na types are from deep aquifers high f waters are mainly found at the depths of 50 200 and 300 m along the flow path groundwater shows an increasing trend in f concentration from the northwest to the southeast isotopes of 18o and d in deep groundwater are more depleted in comparison with shallow groundwater suggesting that shallow and deep groundwater replenish through different ways with longer retention time of deep groundwater 13c of dissolved inorganic carbon are between 11 9 and 8 8 in shallow groundwater and between 10 6 and 7 5 in deep groundwater respectively which indicates that groundwater dic comes from both rock weathering and biodegradation of organic matter fluoride content in the sediment ranges from 140 to 1690 mg kg showing a decreasing trend with depth good correlations between f and al2o3 and fe2o3 are observed demonstrating that f contents in sediments are significantly influenced by the minerals containing fe2o3 and al2o3 in terms of adsorption sequential extraction procedure shows that exchangeable f form f1 and fe mn oxides bound f f3 generally decrease with depths while organic matter or sulfide bound f f4 keeps relatively stable and carbonate bound f f2 exhibits highly variable the relationships between f concentration and fe or mn imply that f in f1 is more inclined to be scavenged by fe and mn oxides hydroxides which have a stronger affinity for f although a variety of hydrogeochemical processes affected f concentrations dissolution precipitation is a vital process in the study area in comparison with shallow groundwater cation exchange may exhibit more significantly effect on f enrichment in deep groundwater competitive adsorption of hco3 and oh with f leads to the release of f from aquifer matrix into solution which increases groundwater f concentration evaporation is another control on f concentration especially in shallow groundwater

thickening of fault zones a mechanism of melange formation in accreting sediments sediments accreted at subduction zones undergo stratal disruption and form a type of melange the thickness of the disrupted zones grows with progressive deformation this suggests that initial fault surfaces are abandoned and deformation propagates into adjacent undeformed sediment factors causing the abandonment of fault surfaces during continuing deformation include 1 strengthening owing to porosity loss during consolidation 2 localized drops in fluid pressure on fault surfaces that act as dewaterinig conduits and 3 reorientation of fault surfaces the disruptive processes occurring in accretionary prisms result principally from the deformation of a consolidating sediment mass

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

the source of fluoride toxicity in muteh area isfahan iran endemic dental fluorosis has been observed in most inhabitants of three villages of muteh area located in northwest of isfahan province with mottled enamel related to high levels of fluoride in drinking water 1 8 2 2 ppm forty seven groundwater samples from six villages were collected and fluoride concentrations along with physico chemical parameters were analyzed fluoride concentration in this area varies from 0 2 to 9 2 mg l with highest fluoride level at muteh gold mine chahkhatun mine fluoride concentration positively correlates with ph and hco3 indicating that alkaline ph provides a suitable condition for leaching of fluoride from surrounding rocks the district is mainly covered by three lithological units namely metamorphic and granite rocks alluvial sediments and carbonate rocks factor analysis shows that parameters can be classified into four components electrical conductivity ec total dissolved solids tds cl na and k ph and f so4 2 and mg2 hco3 and ca2 the groundwaters from the three geological units were compared using mann whitney u test the order of median fluoride concentration is metamorphic and granite rocks alluvial sediments carbonate rocks hence the fluoride content is most probably related to fluoride bearing minerals such as amphibole and mica group minerals in metamorphic and granitic rocks the concentration of fluoride in drinking water wells located near the metamorphic complex in muteh area is above 2 ppm

elevation change and ice flow at horseshoe valley patriot hills west antarctica patriot hills is located at 80 18 s 81 22 w at the southernmost end of the heritage range ellsworth mountains west antarctica a comparison of glacier elevation data and ice velocities obtained by the differential global positioning system in the period 1996 97 is presented ablation accumulation rates measured at a network of stakes in horseshoe valley show average accumulation of 70 kg m 2 a 1 in the central part of the valley and a maximum ablation of 170 kg m 2 a 1 at the edge of the blue ice area close to patriot hills changes in the surface elevation of the glacier measured at 81 stakes in the period 1995 97 show a mean thickening of 0 43 0 42 m a 1 which considering the uncertainties indicates that the ice sheet around patriot hills is in near steady state surface velocities in combination with ice thicknesses obtained by ground based radio echo sounding are used to compute the ice flux across the horseshoe valley transect a total outflow of 0 44 0 08 km 3 a 1 is obtained considering a catchment area for horseshoe valley of 1087 km 2 upstream from the flow transect and a net accumulation rate of 100 kg m 2 a 1 a total input of 0 11 0 04 km 3 a 1 by snow accumulation is obtained accepting a near equilibrium condition for the ice sheet the flux difference i e 0 33 km 3 a 1 must be supplied by flow from the inland ice sheet through ice cliffs located in mountain gaps in the heritage range if horseshoe valley is not in steady state but is thickening the positive mass balance could be due to increased snow accumulation or enhanced ice flow from the interior of the ice sheet new data are needed to elucidate this

early tertiary fluid flow and pressure temperature conditions in the shimanto accretionary complex of south west japan constraints from fluid inclusions the pressure and temperature history of the tertiary shimanto belt of south west japan has been elucidated by analysing fluids trapped in quartz crystals which grew syn kinematically along late stage brittle faults the samples come from three areas that span the paleogene exposures on the muroto peninsula of shikoku island applying microthermometric and laser raman microsampling techniques to coeval water rich and carbonic fluid inclusions we have constrained the pressure and temperature conditions that accompanied a widespread and kinematically distinct phase of deformation the results suggest elevated geothermal gradients during late stage deformation conditions that are in disaccord with previous plate reconstructions that have depicted old thermally mature pacific crust subducting beneath eurasia during the early to middle tertiary these conditions can most easily be accounted for by including an additional plate boundary in the western pacific during paleogene time plate reconstructions that include the kula plate in this region are therefore consistent with our findings in addition our results provide clues to the conditions that likely accompany seismogenic deformation at active convergent plate boundaries

the distribution and hydrogeological controls of fluoride in the groundwater of central ethiopian rift and adjacent highlands occurrence of fluoride f in groundwater has drawn worldwide attention since it has considerable impact on human health in ethiopia high concentrations of f in groundwaters used for community water supply have resulted in extensive dental and skeletal fluorosis as a part of a broader study the distribution of f in groundwater has been investigated and compared with bedrock geology and pertinent hydrochemical variables the result indicates extreme spatial variations high f concentration is often associated with active and sub active regional thermal fields and acidic volcanics within high temperature rift floor variations in f can also be related to changes in calcium concentration resulting from dissolution of calcium minerals and mixing with waters of different chemical composition originated from variable hydrogeological environment across the rift valley the concentration of f dramatically declines from the rift towards the highlands with the exception of scattered points associated with thermal springs confined in local volcanic centers there are also interactions of f rich alkaline lakes and the surrounding groundwater meteoric waters recharging volcanic aquifers become enriched with respect to f along the groundwater flow path from highland recharge areas to rift discharge areas locally wells drilled along large rift faults acting as conduits of fresh highland waters show relatively lower f these areas are likely to be possible sources of better quality waters within the rift the result of this study has important implications on site selection for water well drilling

sources distributions of fluoride in waters and its influencing factors from an endemic fluorosis region in central guizhou china the use of high fluoride content coal caused the severe coal burning endemic fluorosis in zhijin county guizhou province china the long term mine exploitation in this region is as an important source of acid mine drainage amd and leads to the release of potential fluoride f into the surrounding waters aiming to investigate the source hydrogeochemical characteristics and influencing factors of fluoride in waters of this area a hydrogeological and geochemical research has been conducted in this study samples of various types of waters were collected and analyzed for major cations major anions and tfe al selected coal and gangue samples were analyzed for fluoride contents the f concentration in amd or amd affected waters ranged from 0 27 to 4 94 mg l and f was mainly enriched in na so4 and mg so4 waters but a relatively low f concentration was found in the ca so4 water the f concentration in the ca hco3 water without being affected by amd ranged from 0 01 to 0 20 mg l the elevated f contents were found in the amd which is mainly influenced by the local coal mining activities and it is resulted from the dissolution of fluoride bearing minerals in coal bearing clastic rocks as well as the low ph values high al and fe concentrations high total dissolved solids and high al f ratio of the amd in addition the dissolution precipitation of carbonate rocks and special hydrogeological conditions determined the f concentration in surface water meanwhile the climate is also an influencing factor that cannot be ignored to affect the f concentrations of surface water and groundwater

a rheologic model for wet crust applied to strike slip faults the strength and stability of crustal faults are not adequately addressed by the widely used two mechanism rheologic models of the crust based on byerlee s law and power law creep the models neglect the fluid assisted mechanisms of deformation that are important to strength of the crust and do not describe the variation in rate dependence of friction that governs the stability of fault slip several distinct mechanisms of frictional slip are defined on the basis of variations in frictional behavior and microfabric of simulated fault gouge in laboratory experiments state variable constitutive relations are used in a multiple mechanism formulation to describe the rate and temperature dependence of three friction mechanisms in wet quartz gouge at elevated temperatures this multimechanism description of friction is substituted for byerlee s law in the two mechanism models to generate a multimechanism rheologic model for the crust the multimechanism model is used to predict the rate and temperature dependence of crustal strength and the slip rate and depth temperature conditions over which each mechanism dominates application of the model to strike slip faults in the crust illustrates that the thickness of the actively shearing zone within faults is a critical parameter governing fault strength and stability the model predicts that frictional strength at midcrustal depths is significantly reduced relative to byerlee s law only for thick fault zones the reduction in strength is due to the operation of a strain rate sensitive friction mechanism involving combined cataclasis and solution transfer the rheologic model predicts that only very thin faults display the rate dependent characteristics necessary for initiation of seismic slip to any significant depth in the crust