petrology and geochemistry of potassic and ultrapotassic volcanism in central italy petrogenesis and inferences on the evolution of the mantle sources major trace element sr isotopic and mineral chemical data are reported for mafic volcanic rocks mg value 65 from the northern central sector of the potassic volcanic belt of central italy the rocks investigated range from potassic series ks and high k series hks to lamproitic lmp and kamafugitic kam through a transitional series trans thus covering the entire compositional spectrum of potassic and ultrapotassic magmas kam rocks are strongly silica undersaturated and compared with the other rock series have low sio2 al2o3 na2o sc and v and high cao k na na k al ks and hks have high al2o3 cao and variable enrichment in k2o and incompatible elements lmp rocks are saturated in silica and have high sio2 k2o k2o na2 mgo ni and cr and low al2o3 cao na2o sc and v trans rocks display intermediate compositional characteristics between lmp and ks all the rocks under study have fractionated hygromagmaphile element patterns with high lil hfs element values and negative anomalies of ti ta nb and ba negative sr anomalies are observed in the lmp and trans rocks lil elements show overall positive correlations with k2o whereas different trends of sr and hfse vs k2o are defined by lmp trans and ks hks kam 87sr 86sr range from about 0 710 to 0 716 ks hks and kam rocks have similar 87sr 86sr values clustering around 0 710 lmp and trans rocks have the highest 87sr 86sr values geochemical and isotopic data reported for the most primitive italian potassic and ultrapotassic rocks support the hypothesis that the interaction between crustal and mantle reservoirs was a main process in the genesis of italian potassic magmatism simple mass balance calculations exclude however an important role of crustal assimilation during ascent of subcrustal magmas to the surface and indicate that the sources of central italy volcanics underwent contamination with fluids and or melts released by upper crustal material previously brought into the mantle by subduction processes different trends of incompatible elements vs k2o observed in the studied rocks suggest distinct metasomatic processes for the sources of the investigated magmas liquids derived by bulk melting of pelitic sediments are believed to be the most likely contaminants of the source of lmp rocks fluids or melts rich in ca sr and with high lile hfse value and sr isotopic composition around 0 710 are the most likely contaminant of the source region of ks hks and kam volcanics variations in cao na2o and ferromagnesian element abundances and ratios suggest that in some zones the mantle source of potassic magmas experienced partial melting with extraction of basaltic liquids prior to metasomatism

a record of holocene climate change in the guanzhong basin china based on optical dating of a loess palaeosol sequence optical dating was used to obtain a chronology for a loess palaeosol sequence in the guanzhong basin on the loess plateau in china the sedimentary sequence recorded two dry episodes 3 7 2 4 ka and 1 2 0 8 ka ago in the holocene as shown by the presence of two layers of loess within the holocene deposits these two arid events are consistent with records of global climate change in the holocene and also coincident with major historic events in china this finding suggests that loess paleosol sequences in china can record global climate changes and implies that rapid climate change affected the progress of human civilization in addition changes in the sedimentation rate through the section suggest that agricultural expansion may have accelerated the rate of dust accumulation

a comparison of osl ages derived from silt sized quartz and polymineral grains from chinese loess abstract recent work watanuki et al submitted has shown by comparison with independent age control that silt sized quartz grains extracted from japanese loess can be used for optically stimulated luminescence osl dating for equivalent doses of up to 425 gy 500 ka at these sites further comparison with infrared ir stimulated and post ir blue stimulated osl showed that the latter signal gave accurate ages and was probably dominated by quartz whereas the former systematically underestimated ages in the range 30 600 ka and showed fading in laboratory tests the main source of the loess deposits in japan is the chinese mainland in eastern asia loess is widely distributed by the prevailing westerly winds and one of the main sources is in the western desert areas of china unfortunately independent age control is very unusual in loess deposits in china and there is little evidence for the accuracy of existing luminescence ages from this material as an alternative approach this study builds on the japanese results by using loess from two chinese sites and examining the relationship between single aliquot regeneration dose ir and post ir blue stimulated luminescence ages from polymineral samples and blue stimulated quartz luminescence ages the normalized blue stimulated osl intensity from quartz from the eastern site was about 10 times that from the west suggesting either a different source of material or less likely an increase in quartz sensitivity with transport distance by comparison with quartz results we conclude that in our samples of chinese loess the post ir blue stimulated osl is the more reliable polymineral signal when compared with the ir signal it may nevertheless include a feldspar component and this should be tested for using laboratory fading experiments

genesis and evolution of hco3 rich and so4 rich groundwaters of quaternary sediments pinawa canada abstract groundwaters collected from sediments at aecl research whiteshell laboratories include ca mg na hco3 na mg ca hco3 and ca mg na so4 hco3 water types the type produced is determined by the reactive phases encountered during migration through the enclosing sediments these include calcite gypsum and a clay substrate on which cation exchange occurs co2 charged soil waters undergo cation exchange reactions with solids of the enclosing sediments and dissolve calcite to saturation yielding ca mg hco3 groundwaters containing up to 700 mg l 1 total dissolved solids tds more saline sulphate rich groundwaters 1100 3000 mg l 1 tds are produced through combined reaction with gypsum calcite and a mg rich exchange substrate the type of groundwater produced is critically dependent upon the proportions of exchangeable cations on the bulk exchange substrate dissolution of gypsum increases so4 of the solutions but much of the released ca is taken onto the exchange substrate displacing na k first then mg continued gypsum dissolution causes precipitation of calcite and a decrease in solution ph the resulting saline waters are enriched in mg and na relative to ca compared with most groundwaters and are enriched in so4 relative to hco3 many sulphate rich groundwaters common to the northern north american prairies may have similar origins three solid phases exchange substrate calcite and gypsum are needed to model successfully these waters but interactions among them are complex calcite for example dissolves initially but is subsequently precipitated during evolution of sulphate rich waters consequently changes to major dissolved constituents and carbon isotopic ratios are difficult to predict without a comprehensive understanding of the geochemical evolution of these waters

implementation of a multivariate data assimilation scheme for isopycnic coordinate ocean models application to a 1993 1996 hindcast of the north atlantic ocean circulation 1 a 1993 1996 hindcast of the north atlantic circulation is presented and analyzed multivariate satellite observations sea surface height and sea surface temperature are assimilated into an isopycnic coordinate ocean model miami isopycnic coordinate ocean model micom using a reduced order kalman filter the seek filter the objective is to validate the assimilation system in hindcast mode before running a near real time exercise as part of the european diadem project the analysis scheme is upgraded to make the statistical parameterization as realistic as possible and this is shown to be particularly important as soon as a multivariate data set is used second the paper describes the modifications to the seek filter that are necessary to meet the requirements of a layered model and to benefit from the advantages of the isopycnic coordinate in particular the need for an initialization procedure is explained and this dynamical adjustment is shown to be more natural and robust in the context of the isopycnic coordinate the hindcast experiment is validated by comparisons with observations by studying innovation statistics and by comparing the results with independent observations expendable bathythermograph xbt profiles

helium 3 anomalies and crust mantle interaction in italy abstract the distribution of primordial 3he in the crust of italy has been investigated through a survey of groundwaters hot springs exploration and production geothermal wells the mantle derived component varies from 0 to 60 and reaches a maximum at vulcano in the eolian islands 3he anomalies occur where the conductive heat flow is relatively high but the relationships between heat flow and anomaly are uncertain the distribution of 3he in the main reservoir and cap rock to the larderello geothermal system shows that the mantle derived 3he varies from 5 to 40 of total he and reaches a maximum in fluids extracted from a depth of ca 3 km within the basement bomb produced tritiogenic 3he appears to make a near negligible contribution well 107 at larderello has been monitored over a period of 17 months and the 3 he 4 he ratio r varies from 1 4 to 1 6 times the atmospheric ratio ra whilst he ne varies from 9 to 160 a model is proposed for the larderello geothermal system whereby mantle derived heat and volatiles are advected to shallow 6 8 km depths in association with melts and released into the main geothermal reservoir at larderello in a non uniform manner possibly associated with fracturing isotopic and elemental equilibrium of gaseous species c o h appears to have taken place in the basement to the main reservoir from where fluid with r ra 3 2 has been extracted

testing optically stimulated luminescence dating of sand sized quartz and feldspar from fluvial deposits abstract we apply single aliquot optically stimulated luminescence osl dating to quartz and feldspar rich extracts from fluvial channel deposits of the rhine meuse system in the netherlands the time of deposition of these deposits is tightly constrained by radiocarbon dating or historical sources this allows us to compare osl ages obtained on quartz and infrared osl ir osl ages obtained on potassium rich feldspar with independent ages over the range of 0 3 13 ka we show that the quartz osl ages are in good agreement with the expected age using ir osl dating of feldspar we find a slight age overestimate for the youngest sample whereas for older samples the age is significantly underestimated we also apply osl dating to older fluvial and estuarine channel deposits with limited independent chronological constraints comparison of feldspar ir osl ages with the quartz osl ages up to 200 ka shows a clear trend where the former severely underestimates the latter this trend is similar to that found for the samples with independent age control indicating that the feldspar ir osl ages are erroneously young for the entire age range in the youngest samples incomplete resetting of the ir osl signal prior to deposition probably masks the age underestimation we show that the ir osl age underestimation is partly caused by changes in trapping probability due to preheating correction for this phenomenon improves the ir osl ages slightly but does not provide a complete solution to the discrepancy we suggest that in the light of the problems encountered in the ir osl dating of feldspar quartz is the mineral of choice for osl dating of these deposits however feldspar dating should continue to be investigated because it has potential application to longer time scales

optical dating of romanian loess a comparison between silt sized and sand sized quartz abstract the loess palaeosol sequence near mircea vod dobrogea se romania is thought to comprise at least five glacial interglacial cycles it is considered as one of the most significant records of late quaternary environmental and climatic change in the region age information for the sequence was previously obtained through time depth modeling of magnetic susceptibility data and optically stimulated luminescence dating osl of fine silt sized 4 11 m quartz this study documents the granulometric properties of the sequence and compares the osl characteristics and age of fine sand sized 63 90 m quartz to those of silt sized quartz osl signals from both sand and silt sized quartz are dominated by a thermally stable fast decaying component a suite of laboratory test confirms that the single aliquot regenerative dose sar protocol is suitable for these samples each grain size fraction yields a set of optical ages that is consistent with the stratigraphic position of the samples the ages obtained using sand sized grains however are up to 70 higher than those obtained using silt sized quartz the discrepancy in age results is not understood as according to procedural tests the osl signal from both fractions should be suitable for dating the deposits as such it cannot be established whether the uppermost weakly developed palaeosol was formed during mis3 or mis5 and if the rate of loess accumulation varied during the last glacial only by using standard sar osl techniques both sets of ages do confirm however that the first well developed palaeosol s1 is of last interglacial age

re os isotopic records in pleistocene loess paleosol sequences from the yili basin northwestern china abstract the re os isotope system is a potentially powerful tool for obtaining information on source regions and transportation processes of aerosols such as mineral dust re os isotopic systematics were studied in two pleistocene loess paleosols exposed at kuerdenengbulake and zeketai in the yili basin northwestern china in the late pleistocene malan loess 187os 188os ratios 0 90 1 45 varied inversely with os abundances 28 61 pg g in the middle pleistocene lishi loess section fluctuations in os abundances 25 50 pg g were accompanied by a limited range of variation in 187os 188os ratios generally 1 21 1 40 four samples of malan loess from the kuerdenengbulake section had higher os concentrations and less radiogenic 187os 188os coupled with higher zoisite tourmaline ratios but uncorrelated with abundances of other minerals paleomagnetic parameters grain size characteristics major element composition or rb sr and sm nd isotopic systematics the correlation between os and zoisite tourmaline ratio suggests that the source material of the loess changed when these samples were deposited but this change was not evident in the other data in this study depth profiles show how re os isotopic compositions varied with age of deposition by characterizing os abundances and 187os 188os ratios of late pleistocene loess paleosol samples in the yili basin local paleoclimatic changes occurring over intervals of several thousand years could be identified that had not been found by traditional paleoclimatic proxies when the 143nd 144nd ratio alone cannot distinguish the provenance of global eolian sediments a combination of 143nd 144nd and 187os 188os can sometimes be effective however for the yili basin s loess paleosol the range of 187os 188os overlapped with ratios in eolian sediments from other areas offering no improvement over 143nd 144nd alone in this respect

distribution provenance and onset of the xiashu loess in southeast china with paleoclimatic implications abstract loess deposits are important archives of past climate change in subtropical china where long term terrestrial records are scarce however only a few long term records with reliable dating were reported in jiangsu province where loess deposits in southeastern china were first discovered and designated as the xiashu loess moreover the provenance of the xiashu loess is still controversial this study presents the magnetostratigraphy and detrital zircon u pb age results of loess deposits at zhoujiashan in nanjing jiangsu province to date this section with basal age of approximately 0 88 ma may be the oldest loess deposits discovered in southeastern china based on the detrital zircon u pb ages of the zhoujiashan section together with published results of geochemistry geomorphology sedimentology and meteorology we propose that the xiashu loess has two mixed sources local materials derived from the yangtze river basin including exposed river lake beds floodplains and mountains served as a major contributor the distal eolian dust that originated from the arid areas of north china including deserts piedmont alluvial fans and drylands played a minor role in the formation process of the xiashu loess the nearly synchronous onset age approximately 0 88 0 85 ma of the xiashu loess was attributed to a regional environmental event during the middle pleistocene transition

an upwelling case study on florida s west coast using a combination of satellite sea surface temperature imagery in situ currents temperature and sea level data and a numerical circulation model we describe an upwelling event observed along florida s west coast although ubiquitous features of continental shelves descriptions of coastal upwellings or downwellings are generally complicated by the continuum of processes in which they occur for the case study presented the winds were light and the baroclinic background currents were steady for several days prior to the event these conditions allow the evolution of a specific winddriven upwelling event to be viewed as an initial value problem the data and the numerical model analysis show that the route of adjustment by the sea level and currents is a classical ekman geostrophic one sea level drops due to an offshore ekman transport causing a geostrophic alongshore jet and the associated onshore flow within the bottom ekman layer accounts for the appearance of cold water at the surface this surface manifestation occurs as an elongated feature centered about the 25 m isobath that spans roughly half of the florida peninsula from just north of tampa bay to key west the coldest water is observed offshore from tampa bay and we explain this region of locally maximum upwelling on the basis of the coastline and isobath geometries

sr ca mg ca ratios and sr and stable isotopes of biogenic carbonates from the late miocene velona basin central apennines italy provide evidence of unusual non marine messinian conditions abstract the sr ca and mg ca ratios of fossil ostracod and mollusc shells from a late miocene early messinian lacustrine sequence in the velona basin central apennines italy were used to calculate the sr ca and mg ca of waters in which these taxa lived sr ca of these waters were always higher than the sr ca calculated for the messinian seawater despite the broad salinity ranges fresh water oligo mesohaline inferred from the paleontological analyses the estimated mg ca water from the velona samples are below the mg ca value for coeval seawater even though they represent relatively high values when compared with many non marine waters the salinity variations of the velona lacustrine system recorded by changes in faunal assemblages are linked to variable inputs of na cl from deep groundwaters and are not reflected in significant changes in sr ca and mg ca of the waters calculated from shell chemistry the combination of 18 o signatures and sr isotopic ratios from molluscs from the velona basin suggests a non marine environment during some episodes of the lake history given the saline inputs the waters in the lake would attain a large solute concentration oligo to mesohaline although they retained the meteoric 18 o signature we compare the paleohydrochemical inferences from the studied sequence with other messinian records and we show the importance of combining paleoecological and geochemical proxies to obtain consistent paleoenvironmental reconstructions

east asian summer monsoon intensity inferred from iron oxide mineralogy in the xiashu loess in southern china abstract the xiashu loess in comparison to the well studied loess sequences in the chinese loess plateau clp provides a good opportunity for studying east asian monsoon variations from a southern china perspective here we present a study of the iron oxide mineralogy of the xiashu loess using integrated geochemical and diffuse reflectance spectroscopy drs measurements as well as magnetic data our results show that the free iron oxide fe d to total iron fe t ratio fe d fe t hematite hm to goethite gt ratio hm gt and saturation isothermal remanent magnetization sirm to magnetic susceptibility ratio sirm all indicate particularly strong summer monsoons during the formation of paleosols ps5 and ps4 equivalent to marine isotope stage 13 and 11 respectively however magnetic susceptibility and fe d fe t are not consistently reliable indicators of summer monsoon intensity for the whole section our results indicate that a multi proxy approach can give a more reliable summer monsoon intensity reconstruction the summer monsoon shows a cooling trend and a declining of precipitation from 0 5 to 0 3 ma after which it becomes warmer and wetter towards the top of paleosol ps1 equivalent to mis 5 however ps1 was formed under a relatively cooler temperature and wetter soil conditions in comparison to ps5 and ps4 such supra orbital variations in the east asian summer monsoon superimposed on the effects of glacial interglacial cycles in southern china are also reflected in the 0 4 0 5 ma cycle of marine carbon isotopes in the global ocean possibly indicating a strong link between terrestrial weathering and the global carbon cycle

geochemistry of water and gas discharges from the mt amiata silicic complex and surrounding areas central italy abstract the mt amiata volcano in central italy is intimately related to the post orogenic magmatic activity which started in pliocene times major trace elements and isotopic composition of thermal and cold spring waters and gas manifestations indicate the occurrence of three main reservoir of the thermal and cold waters in the mt amiata region the deepest one is located in an extensive carbonate reservoir buried by thick sequences of low permeability allochthonous and neo autochthonous formations thermal spring waters discharging from this aquifer have a neutral ca so4 composition due to the presence of anhydrite layers at the base of the carbonate series and possibly to absorption of deep derived h2s with subsequent oxidation to so42 in a system where ph is buffered by the calcite anhydrite pair marini and chiodini 1994 isotopic signature of these springs and n2 rich composition of associated gas phases suggest a clear local meteoric origin of the feeding waters and atmospheric o2 may be responsible for the oxidation of h2s the two shallower aquifers have different chemical features one is ca hco3 in composition and located in several sedimentary formations above the mesozoic carbonates the other one has a na cl composition and is hosted in marine sediments filling many post orogenic nw se trending basins strontium ba f and br contents have been used to group waters associated with each aquifer although circulating to some extent in the same carbonate reservoir the deep geothermal fluids at latera and mt amiata and thermal springs discharging from their outcropping areas have different composition na cl and ca so4 type respectively considering the high permeability of the reservoir rock the meteoric origin of thermal springs and the two different composition of the thermal waters self sealed barriers must be present at the boundaries of the geothermal systems the complex hydrology of the reservoir rocks greatly affects the reliability of geothermometers in liquid phase which understimate the real temperatures of the discovered geothermal fields more reliable temperatures are envisaged by using gas composition based geothermometers bulk composition of the 67 gas samples studied seems to be the result of a continuous mixing between a n2 rich component of meteoric origin related to the ca so4 aquifer and a deep co2 rich component rising largely along the boundaries of the geothermal systems nitrogen rich gas samples have nearly atmospheric n2 ar 83 and 15 n 14 n 0 ratios whereas co2 rich samples show anomalously high 15n values up to 6 13 likely related to n2 from metamorphic schists lying below the carbonate formations on the basis of average 13 c 12 c isotopic ratio 13c around 0 co2 seems to originate mainly from thermometamorphic reactions in the carbonate reservoir and or in carbonate layers embedded in the underlying metamorphic basement distribution of 3 he 4 he isotopic ratios indicates a radiogenic origin of helium in a tectonic environment that in spite of the presence of many post orogenic basins and mantle derived magmatics can presently be considered in a compressive phase

the larderello geothermal field a review abstract this paper reviews published geological geophysical petrological and geochemical data together with reservoir engineering parameters of the larderello geothermal reservoir of southern tuscany italy some theories are proposed on the deep origin evolution in time and natural state of this geothermal field prior to its exploitation the interaction between the vapor dominated reservoir and surrounding aquifers is discussed analysis of hydrogeochemical data suggests that meteoric waters from shallow external aquifers contribute little to the production of steam the vapor dominated system and the cold external aquifers are separated by areas of very low permeability where physical conditions change greatly over short distances the presence and significance of liquid phases in the peripheral areas of the vapor dominated reservoir are interpreted as being due to steam condensation the latter is a consequence of a low permeability conditions in the deep buried parts of the carbonate reservoir formations in the north northwestern sector of the field and b by the mixing of ascending superheated steam from depth with cold caso4 meteoric waters circulating in unconfined shallow aquifers within the outcrops of the carbonate reservoir formations in the south southeastern parts of the field the presence of steam below these liquid dominated sectors of the reservoir seems possible the limited natural recharge of the system the constant steam production rate for geothermal power generation 3000 t h 1 since 1951 the persistence of natural thermal features and the fact that reinjection has had little effect on the characteristics of the fluid discharged seem to indicate a steady state for the larderello field the main contribution to production seems to be from superheated steam ascending from depth and the in situ evaporation of water stored in the small pores of the rocks present in larderello in a system that is much larger than the one known at present

modeling the dynamics of a geothermal reservoir fed by gravity driven flow through overstanding saturated rocks abstract we formulate a mathematical model for a geothermal basin with an idealized geometry characterized by 1 radial symmetry around an extracting well or a cluster of wells 2 a relatively thin horizontal fractured layer lying underneath a low permeability low porosity rock layer saturated with water vaporization is allowed only at the boundary of the extracting well or well cluster the model is based on the assumption that the flow from the reservoir to the well is fed by a gravity driven flow through the overstanding rocks despite the various simplifying assumptions the resulting mathematical problem is considerably difficult also because we consider the effect of thermal expansion and thermal variation of viscosity though there is no evidence that the assumed configuration of the basin approaches the structure of a known geothermal field the results obtained match with surprising accuracy the data of a specific field in the mt amiata area data kindly provided by enel green power through tuscany region

luminescence dating of the zeketai loess section in the ili basin northwestern china methodological considerations abstract loess deposits in xinjiang northwestern china are ideal archives for past environmental changes in the westerlies dominated central asia among previous luminescence dating studies of loess in xinjiang few have attempted to systematically investigate the methodological aspects in this study we report results of a multiple procedure luminescence dating of the zeketai loess section in the ili basin central xinjiang optically stimulated luminescence osl and post infrared infrared stimulated luminescence pirir signals were used for quartz and polymineral grains of different sizes the pirir ages obtained with two protocols agree well with each other and constrain the loess deposition between 50 ka and 88 ka the osl ages of fine grained quartz are in stratigraphic order and range from 37 ka to 61 ka but are 30 younger than the pirir295 ages of both fine and medium grained polyminerals although the causes of the discrepancy between the ages derived from different luminescence dating protocols are still to be understood we stress that the quartz osl ages of loess in this region are likely to be underestimated especially for samples older than 40 ka the polymineral or potassium feldspar pirir signal is recommended for dating loess in the ili basin at least as an internal check

thermal modelling of the larderello geothermal field tuscany italy we present a 3 d thermal model of the larderello geothermal field tuscany to evaluate 1 the extent and contribution of the heat transfer mechanisms conduction vs convection at the intermediate upper crust levels 2 the variability of the heat and mass fluxes entering from below and 3 the crucial role of the formation permeability the model composed by three main layers considers the upper 10 km of the crust to better constrain the simulations with experimental data from borehole fluid inclusion studies and hypocentral distributions several sets of simulations were carried out with different bottom boundary temperatures and different formation permeabilities for the two deeper layers the results indicate that the present temperature t and pressure distributions in the larderello field require deep reservoir rocks with higher permeability than the overlying capping units and underlying intermediate crust permeability values of 1 mdarcy for the reservoir rocks are enough to allow fluid convection if the temperature at 10 km depth is as high as 500 50 c the presence of localized zones with formation permeability 50 100 times higher than the surrounding rocks strongly favours the migration of over pressurized fluids which episodically break through the overburden feeding the presently exploited geothermal fields

new osl dating of uk loess indications of two phases of late glacial dust accretion in se england and climate implications windblown dust deposits or loess locally known in the uk as brickearth blanket many parts of southern england outside the limits of the british and irish ice sheet the best studied loess exposures occur in kent southeast england where the deposits are believed to be late glacial in age new sedimentological evidence is presented for phases of accretion with two distinct units a calcareous brickearth exhibiting periglacial cryoturbation and a non calcareous massive brickearth optically stimulated luminescence osl dating has been applied to chemically isolated modal quartz silts to derive a chronology for sediment accretion and to better understand the palaeoclimatic significance of these deposits

evolution of the latera geothermal system ii metamorphic hydrothermal mineral assemblages and fluid chemistry abstract the latera field vulsini volcanic complex latium italy is one of the geothermal areas of the peri tyrrhenian belt along which a regional high thermal anomaly has been detected so far nine deep wells have been drilled within the latera caldera and four of them have been productive the geothermal reservoir is located within the fractured carbonatic rocks of the tuscan nappe the overlying volcanic units sealed by hydrothermal minerals mainly calcite and anhydrite act as an impervious cover the fluid produced by the wells comes from a deep aquifer about 1000 1500 m depth which at present is not connected with the shallow aquifer in the volcanoclastic units fluid temperatures range between 200 and 230 c in hole temperatures as high as 343 c at 2775 m depth have been measured in dry wells the study of the newly formed mineral assemblages from both volcanic and sedimentary units as sampled from the geothermal wells can be used to reconstruct the thermal evolution of the geothermal field the intrusion of a syenitic melt up to a depth of about 2000 m dated 0 86 ma represents the major thermal event for the units in the area and is assumed to represent the first step in the geothermal evolution of the latera system the above mentioned newly formed mineral assemblages can be divided into three groups a contact metasomatic calcite anhydrite diopsidic pyroxene grossularitic garnet phlogopite wollastonite or monticellite b high temperature hydrothermal calcite anhydrite k feldspar vesuvianite melanitic garnet tourmaline amphibole epidote sulphides c low temperature hydrothermal calcite anhydrite k feldspar clay minerals sulphides group a minerals are now relics part of b and all of c group are still in equilibrium with the existing conditions in different parts of the geothermal system thermodynamic calculations on the observed mineral assemblages permitted estimates of the p t conditions and gas fugacities

optical dating of abrupt shifts in the late pleistocene east asian monsoon chinese loess is regarded as one of the most detailed and complete terrestrial archives of late cenozoic climate change however high resolution optically stimulated luminescence osl dates presented here reveal that the suborbital chronological framework of chinese loess used in many previous climate reconstructions requires reassessment chronological uncertainty of as much as 10 15 k y for the late pleistocene is largely a result of the widespread use of nonradiometric dating techniques that fail to account for site specific depositional conditions associated with loess emplacement and diagenesis osl based age models that account for these processes are used to examine detailed records of past sedimentation as well as grain size and magnetic susceptibility proxies for late pleistocene east asian monsoon variation abrupt shifts in monsoon proxies occur over 10 2 10 3 yr time scales potentially forced by a variety of factors and influenced by site location and site specific changes in sedimentation

fluid mixing in carbonate aquifers near rapolano central italy chemical and isotopic constraints chemical major and trace elements and isotopic compositions dd and d 18 o in waters and d 13 ci n co 2 and 3 he 4 he in gases of natural thermal 11 and cold 39 fluids spring waters and gases discharging from a tectonic window of mesozoic limestones in central italy have proved to be the result of mixing processes inside the limestone formations the limestones provide a preferential route for subsurface fluid migration and they gather both descending cold ca hco3 b depleted groundwaters and rising convective ca so4 hco3 co2 saturated b rich thermal waters atmospherically derived descending gas components n2 ne he dissolved in rainfall that infiltrates the limestone system mix with n2 ne he depleted hot rising waters boron in the liquid phase and n2 and ne in the gas phase are the most useful elements to trace the mixing process the deeper gas samples recognised in the area are associated with the hotter waters emerging in the area in spite of being depleted in ne and he and light hydrocarbons they have the higher measured 3 he 4 he ratios suggesting a contribution of mantle 3 he to the gas phase this contrasts with deep circulation in the crust which would lead to increased concentration of 4 he in the deeper gases paradoxically there is more relative concentration of 4 he in the more air contaminated gas samples than in the deeper gas samples a similar paradox exists when the d 13 co f co 2 in the deeper gas samples is considered the shallower air contaminated gas samples although they should be affected by the addition of soil 13 c depleted organic c have d 13 ci n co 2 more positive than the deeper gas samples recognized since any deep hydrothermal source of co2 should generate co2 with more positive values of d 13 c than those measured at surface a multiple single calcite precipitation process from hydrothermal solutions with c isotopic fractionation along the rising path inside the mesozoic limestone formations is proposed 2002 elsevier science ltd all rights reserved

chemical composition of thermal springs cold springs streams and gas vents in the mt amiata geothermal region tuscany italy abstract a geochemical study of thermal and cold springs stream waters and gas emissions has been carried out in the mt amiata geothermal region the cold springs and stream waters do not seem to have received significant contribution from hot deep fluids on the contrary the thermal springs present complex and not clearly quantifiable interactions with the hot fluids of the main geothermal reservoir the liquid dominated systems in the mt amiata area like most of the high enthalpy geothermal fields in the world are characterized by saline nacl fluids the nature of the reservoir rock carbonatic and anhydritic and its widespread occurrence in central italy favor a regional circulation of ca sulfate thermal waters which discharge from its outcrop areas waters of this kind which have been considered recharge waters of the known geothermal fields dilute disperse and react with the deep geothermal fluids in the mt amiata area preventing the use of the main chemical geothermometers for prospecting purposes the temperatures obtained from the chemical geothermometers vary widely and are generally cooler than temperatures measured in producing wells other thermal anomalies in central italy apart from those already known might be masked by the above mentioned circulation a better knowledge of deep fluid chemistry could contribute to the calibration of specific geothermometers for waters from reservoirs in carbonatic rocks

assimilation of surface velocity data into a primitive equation coastal ocean model summer of 1998 are 0 42 and 0 78 respectively demonstrating the effectiveness of the das our estimates of the error covariances are shown to be appropriate through a series of objective statistical tests analysis of the term balances of the model equations show that the dominant modeled dynamical balances are preserved by the das and that uncertainties in the spatial variability of the wind forcing are likely to be one source of model error by varying the relative magnitudes of the estimated forecast and observation error covariances the das is shown to be most effective when approximately 80 of the analysis is made up of the model solution index terms 4263 oceanography general ocean prediction 4219 oceanography general continental shelf processes 4255 oceanography general numerical modeling 3337 meteorology and atmospheric dynamics numerical modeling and data assimilation 4516 oceanography physical eastern boundary currents 4594 oceanography physical instruments and techniques keywords practical data assimilation numerical modeling upwelling highfrequency radar data

fluid geochemistry and geothermometry in the western sector of the sabatini volcanic district and the tolfa mountains central italy abstract a geochemical survey of 197 fluid discharges cold and thermal waters and bubbling pools and 15 gas emissions from the western sector of the sabatini volcanic district and the tolfa mountains latium central italy was carried out in 2007 2008 the chemical and isotopic compositions of the fluid discharges indicate the occurrence of two main sources 1 relatively shallow aquifers with ca na k hco 3 and ca mg hco 3 compositions when trapped in volcanic and sedimentary formations respectively and 2 a deep reservoir which is hosted in the mesozoic carbonate sequence rich in co 2 and having a ca so 4 hco 3 composition dissolution of a co 2 rich gas phase into the shallow aquifers produces high tds and high pco 2 cold waters while oxidation of deep derived h 2 s to so 4 2 generates low ph the 13 c co 2 values for gas emissions from 2 8 to 2 7 vs vpdb suggest that the origin of co 2 associated with the deep fluids is mainly related to thermo metamorphic reactions within the carbonate reservoir although significant mantle contribution may also occur however r r a values 0 37 0 62 indicate that he is mainly produced by a crustal source with a minor component from a crust contaminated mantle on the basis of the 13 c ch 4 and d ch 4 values from 25 7 to 19 5 vs vpdb and from 152 to 93 4 vs vsmow respectively ch 4 production is associated with thermogenic processes possibly related to abiogenic co 2 reduction within the carbonate reservoir the 34 s h 2 s values from 9 3 to 10 4 vs vcdt are consistent with the hypothesis of a sedimentary source of sulfur from thermogenic reduction of triassic sulfates geothermometric evaluations based on chemical equilibria co 2 ch 4 and separately h 2 s suggest that the reservoir equilibrium temperature is up to 300 c the d and 18 o data indicate that water recharging both the shallow and deep aquifers has a meteoric origin fluid geochemistry coupled with gravimetric data and tectonic lineaments supports the idea that significant contributions from a deep seated geothermal brine are present in the stigliano thermal fluid discharges exploration surveys investigated this area during 70 s 90 s for geothermal purposes nevertheless presently the area is still under exploited the presence of thermal waters and anomalous heat flow together with the demographic growth of the last years makes this site a suitable location for direct applications of the geothermal resource

distribution of ammonium in minerals of metamorphic and granitic rocks abstract sixty nine analyses are given for nh4 in minerals of metamorphic and granitic rocks mostly from the ryoke belt japan the distribution of nh4 in coexisting minerals is quite systematic suggesting that nh4 is one of the stable geochemical components in high temperature processes biotite has the highest content of nh4 followed by muscovite k feldspar and plagioclase pure quartz is almost free from nh4 calcic plagioclase contains less nh4 than does sodic plagioclase the partition coefficients d pl bi d kf bi and d kf bi are on the average 0 11 0 38 and 0 43 respectively the fractionation of nh4 in these minerals is quite similar to that of rb but much smaller than that of cs distribution of nh4 as well as those of rb and cs appears to be explained by its ionic radius and the shortest cation o distances in alkali positions of minerals

assimilation of high frequency radar currents in a nested model of the west florida shelf 1 high frequency radar currents are assimilated in a west florida shelf wfs model based on the regional ocean model system roms which is nested in the atlantic hybrid coordinate ocean model hycom for the purpose of including both local and deep ocean forcing particularly the gulf of mexico loop current tides are not included in this model an ensemble simulation of the wfs model is carried out under different wind forcings in order to estimate the error covariance of the model state vector and the covariance between ocean currents and winds radial currents measured by high frequency radar antennas near saint petersburg and venice florida usa are assimilated using this ensemble based error covariance different assimilation techniques using a time average ensemble a filter to reduce surface gravity waves and an extended state vector including wind stress were tested results of the wfs model assimilating surface currents show an improvement of the model currents not only at the surface but also at depth

luminescence dating of loess profiles in poland abstract numerical dating using luminescence methods is widely applicable in geology geomorphology paleogeography and in archaeology for establishing ages of sediments and archaeological artefacts their popularity and versatility come from the fact that quartz and feldspar are ubiquitous minerals in the natural environment both of the luminescence methods thermoluminescence tl and optically stimulated luminescence osl have been widely used for dating loess in the past in poland although osl has certain advantages over tl dating in sedimentary environments such as loess this method has been widely applied only in recent years tl results obtained for polish loess sections allowed creation of the polish loess chronology in the 1980s all luminescence dating results from laboratory intercomparison for loess profiles are presented here

hf radar data assimilation in the monterey bay area 1 the utility of high frequency hf radar data for improving numerical circulation model predictions is evaluated comparisons of the statistical properties of the codar type hf radar data and the observed wind indicate a strong correlation between the dominant alongshore upwelling favoring wind forcing and hf radar derived surface currents along the central california coastline because inadequate knowledge of the wind stress is probably a significant source of error in the model solutions the idea of using hf radar data to provide corrections to the model wind forcing is promising different hf radar data assimilation schemes are compared and judged based on the correlations observed between model currents and independent observations from two mooring sites analysis of correlation maps between model predicted and observed currents indicates a spatial and temporal shift between modeled and observed features however the impact of hf radar data assimilation reduces these spatial and temporal shifts a significant improvement in the correlation between the model and observed subsurface currents is achieved when an ekman layer projection of the corrections is included in this approach assimilation of hf radar data produces additional ekman pumping vertical velocity based on the horizontal pattern of model observed velocity mismatch at the surface

structure and late cenozoic evolution of the upper lithosphere in southwest tuscany italy abstract geological and geophysical data on southwest tuscany are reviewed in order to define the structure and evolution of the upper lithosphere from the miocene to the quaternary petrologic studies reveal the existence below all of tuscany of hercynian and older polyphased metamorphic rocks and of hercynian granite whose top is an important seismic reflecting horizon the basement is characterized by ne sw trending structures in contrast with the main nw se alpine structures of the uppermost levels the heat flow map shows two broad areas with values higher than 80 mw m2 reaching maximum values of 10 5 and 15 h f u in the geothermal areas which are also characterized by negative bouguer anomalies a landsat study revealed a ne sw band of subcircular structures passing through larderello and coinciding with a regional fault system and a steep rise in the moho petrologic geochemical and radiometric data on the tuscan igneous rocks show that partial melting took place in the tuscan crust at different levels and to varying degrees from the miocene to quaternary producing a continuous alpine granitic layer the known tuscan intrusive bodies and two batholiths below the larderello and mt amiata geothermal fields represent culminations of the alpine granite the rise of the tuscan magmas was closely correlated to a post tortonian tensional tectonics and followed its n e migration tensional tectonics started after the last compressional phase 10 11 ma b p as a consequence of the anticlockwise rotation of italy the opening of the tyrrhenian sea and the swelling of the mantle below southwest tuscany

reinterpreting climate proxy records from late quaternary chinese loess a detailed osl investigation abstract numerous authors have utilised physical properties of chinese loess and red clay deposits to develop apparently detailed and continuous past climate records from the miocene into the holocene many of these studies have further suggested that the principal climatic agent responsible for the aeolian emplacement and diagenesis of chinese loess the east asian monsoon has fluctuated rapidly on millennial to sub millennial timescales in concert with dramatic changes in the north atlantic dansgaard oeschger cycles and heinrich events and the western pacific el nino southern oscillation much of this evidence is based on reconstructions and age models that are tied to assumptions concerning the nature of loess sedimentation and diagenesis for example the belief that loess sedimentation can be viewed as essentially continuous some authors have however cast doubt on these assumptions and suggest that the application of radiometric techniques may be required to determine their validity recent studies utilising optically stimulated luminescence osl methods have reinforced these doubts and here osl dates obtained at 10 cm intervals from three sites along a transect across the chinese loess plateau have been used in combination with climate proxy evidence to test the existing assumptions that underpin many palaeoclimatic reconstructions from loess in this way the first time continuous and independently dated late quaternary climate reconstruction is developed from loess the data indicate that sedimentation is episodic and that once emplaced loess is prone to pedogenic disturbance diagenetic modification and in some cases erosion the relationships between proxies and sedimentation rates are also assessed and climatic interpretations based on different age models compared the implications of these findings for reconstructions of climate from loess are explored and comparisons are made between the developed palaeoclimate records and evidence from ice and ocean cores this exercise also highlights important information concerning the relative influence of forcing mechanisms behind east asian monsoon change over the late quaternary

behaviour of trace elements during magmatic processes in the crust application to acidic volcanic rocks of tuscany italy abstract plio quaternary acidic rock suites from three volcanic centres of tuscany italy san vincenzo roccastrada and monte amiata are composed predominantly of rhyolitic and rhyodacitic ignimbrites the rocks are characterized by distinct enrichments particularly of k and rb and display considerable compositional differences among the various volcanic centres the volcanic rocks of roccastrada and most of s vincenzo were probably generated by partial melting of metapelitic rocks from the paleozoic basement of tuscany leaving a residue composed of biotite cordierite and quartz and sometimes plagioclase or garnet the enrichment of k and related elements can be attributed to selective contamination by fluids the other volcanic rocks including trachytes of mt amiata have also been affected by interaction with an upper mantle component probably k rich basaltic rocks a similar petrogenetic model can be applied to the granodiorite pluton of mt capanne elba which belongs to the same magmatic cycle since the variation trends observed in the tuscany volcanic rocks are similar to those reported from many acidic plutons it appears that crustal anatexis accompanied by interaction with upper mantle components has frequently played an important role in the genesis of the granitic rocks

improving the quality of satellite altimetry data over continental shelves 1 satellite altimetry has proven to be a useful tool to study oceanic processes in the deep ocean over continental shelves however the aliasing of unresolved high frequency signals of tidal and wind induced origin is the source of long wavelength errors that corrupt altimetry measurements and limit their use in shallow waters in 2005 ssalto duacs performed a complete reanalysis of altimeter data to accommodate the latest tidal model got2000 and a correction for the aliased high frequency signals using a hydrodynamic model mog2d g this paper examines the quality and the performance of the newly released altimetry data over the northwest european shelf this region is known for complex tides and for frequent storm surges the newly corrected maps of sea level anomalies were compared with a previous altimetry product residual tidal aliasing was analyzed and the impact of mog2d g and got2000 models was assessed altimeter records were compared with tide gauge measurements this research showed a significant reduction in the contamination of data by high frequency aliasing achieved through the use of the aforementioned models however aliased shallow water tidal constituents pose a serious problem and it is obvious that future tidal corrections should feature local tides nonaliased physical sea level variability was also studied focusing on interannual seasonal and intra annual periods from 20 days to 1 year modes the magnitudes and the contributions of each mode to the total variance were estimated it was demonstrated that the newly corrected data can successfully be used to study the variability of sea level over continental shelves

helium isotopes in alpine regions abstract the isotopic composition of helium has been determined for a variety of groundwaters from springs and boreholes in the alps and adjacent regions the main alpine block in france italy switzerland and austria is characterized by a virtual absence of mantle derived 3he in near surface groundwaters in contrast adjacent areas where crust has been thinned by extension to the west in the rhone valley and ardeche to the north in the rhine valley and to the east in the vienna and pannonian basins mantle derived helium is clearly identified helium and undoubtedly other gases are introduced by melts whose generation is associated with crustal thinning however the surface distribution of mantle helium covers a much larger than that of associated surface volcanics this probably results from the dispersion of helium following its solution in groundwaters the po and the molasse neogene sedimentary basins developing by loading on the south and the north sides of the alps respectively have helium with typical crustal composition and a mantle component cannot be resolved these results clearly indicate the control of tectonics on the distribution of helium isotopes in the alpine regions

west florida shelf response to local wind forcing april 1998 we compare west florida shelf velocity and sea level data with a model simulation for april 1998 responses for three upwelling and three downwelling favorable wind events are documented along shelf jets accompanied by oppositely directed upper and lower layer across shelf flows with connecting vertical velocity comprise the fully three dimensional inner shelf responses which are sensitive to stratification with an initial density field representative of april 1998 the model simulates velocity and sea level variations in general agreement with the observations whereas substantial mismatches occur without stratification despite the winds being the primary motive agent for the inner shelf the stratification dependence requires that model density fields be maintained through a combination of adequate initial conditions surface offshore and land derived buoyancy inputs and data assimilation dynamical analyses define the inner shelf as the region where the surface and bottom boundary layers are important in the momentum balance kinematically this is where surface ekman layer divergence fed by the bottom ekman layer convergence or conversely sets up the across shelf pressure gradient stratification causes a response asymmetry wherein the offshore scale and magnitude of the upwelling responses are larger than those for the downwelling responses this asymmetry is attributed to thermal wind effects across the bottom ekman layer buoyancy torque by isopycnals bending into the bottom adds constructively destructively with planetary vorticity tilting under upwelling downwelling favorable winds and this may have important implications for nutrients and other material property distributions on the shelf

geothermometry on fluids circulating in a carbonate reservoir in north central italy the peri tyrrhenian belt of north central italy is a site of large scale fluid circulation in mesozoic carbonate anhydritic formations of thermal waters with ca sulfate composition these carbonate formations are the principal geothermal reservoir of the known italian geothermal fields owing to differences in the regional structure these carbonate rocks may have an intrinsic high or low hydraulic continuity the ca sulfate springs that surface at the periphery of these formations have circulated in the unconfined parts of the carbonate aquifer the high salinity na chloride geothermal fluids discharge from the confined parts of the same reservoir rocks these fluids are somewhat separated from fluids generated in the unconfined parts by possible barriers of low permeability they are also diluted with the ca sulfate waters and have re equilibrated at lower temperature because of these conditions the assessment of the deep reservoir temperatures cannot be made using rapidly re equilibrating geothermometers such as the sio2 geothermometer the latter reveals the temperature of the unconfined aquifer at best the study of the geohydrological nature of the reservoir rocks the composition of liquid and gas phases and the statistical behavior of the main chemical geothermometers applied to the shallow cold waters of the principal italian geothermal areas has shown that the geothermometer based on nali ratio seems to be the most reliable to evaluate the deep temperatures inside the confined parts of the carbonate reservoir

carbon dioxide degassing and thermal energy release in the monte amiata volcanic geothermal area italy abstract the quaternary volcanic complex of mount amiata is located in southern tuscany italy and represents the most recent manifestation of the tuscan magmatic province the region is characterised by a large thermal anomaly and by the presence of numerous co2 rich gas emissions and geothermal features mainly located at the periphery of the volcanic complex two geothermal systems are located at increasing depths in the carbonate and metamorphic formations beneath the volcanic complex the shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit ligurian unit a measured co2 discharge through soils of 1 8 109 mol a 1 shows that large amounts of co2 move from the deep reservoir to the surface a large range in 13ctdic 21 07 to 3 65 characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of tdic allows distinguishing a discharge of 0 3 109 mol a 1 of deeply sourced co2 in spring waters the total natural co2 discharge 2 1 109 mol a 1 is slightly less than minimum co2 output estimated by an indirect method 2 8 109 mol a 1 but present day release of 5 8 109 mol a 1 co2 from deep geothermal wells may have reduced natural co2 discharge the heat transported by groundwater computed considering the increase in temperature from the infiltration area to the discharge from springs is of the same order of magnitude or higher than the regional conductive heat flow 200 mw m 2 and reaches extremely high values up to 2700 mw m 2 in the north eastern part of the study area heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking the comparison of co2 flux heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining co2 degassing and heat transfer patterns

isotopic and chemical composition of water and steam discharges from volcanic magmatic hydrothermal systems of the guanacaste geothermal province costa rica the guanacaste geothermal province encompasses three major geothermal systems each centered on its respective volcanic structure rincon de la vieja to the nw miravalles in the center and tenorioto the se each shows corresponding sets of surface manifestations vapor discharges from fumaroles and steam heated pools at altitudes 500 m lower temperature so4cl springs on the lower slopes of the respective volcano and cooler neutral cl springs to the s of the volcanic chain at altitudes 500 m the production of hco3 rich waters is limited to a narrow belt stretching to the s of miravalles volcano chemical and isotopic evidence suggests that the neutral cl waters also discharged from deep wells are derived from a more primitive clso4 water formed by transfer of readily mobilised originally magmatic constituents to deeply circulating groundwater isotopic evidence suggests that this groundwater is derived largely from areas to the north of the volcanic chain the presence of immature waters within drillable depth is indicated by the incursion of an acid so4 water into a well at miravalles after deepening to 2000 m as the cl waters rise they start to boil the separated vapors feed the fumaroles and steam heated features at the surface the residual water travels underground to be discharged some 5 25 km to the s the uniformity in chemical and isotopic compositions of the neutral cl waters is compatible with the assumption that the individual thermal systems are linked at depth to form large contiguous geothermal reservoirs beneath the guanacaste geothermal province

a nested model study of the loop current generated variability and its impact on the west florida shelf 1 a west florida shelf model based on the regional ocean modeling system roms is nested in the north atlantic hybrid coordinate ocean model nat hycom the focus of this work is the study of the impact of the loop current on the west florida shelf in order to assess the model s accuracy it is compared quantitatively to in situ temperature and velocity measurements on the shelf a series of sensitivity experiments are conducted to determine the appropriate wind forcing sea surface temperature relaxation and mixing scheme by the inclusion of the loop current we are able to study the propagation of an anticyclonic vortex detaching from the loop current we found that the ambient gradient of potential vorticity is able to explain the vortex path and speed the statistics of such loop current generated flow features were examined by including a tracer marking loop current water this allows to track the loop current water on the west florida shelf and to quantify the amount of loop current water reaching the shelf

locating the boundary between the pleistocene and the holocene in chinese loess using luminescence a detailed chronology has been obtained for a loess section at yuanbao situated at the northwestern edge of the chinese loess plateau the ages were obtained by the measurement of the optically stimulated luminescence osl from coarse silt sized quartz grains these ages showed that deposition at this site was continuous from 17 ka to the present but that there was a decrease in the sedimentation rate from 0 60 to 0 10 m ka at 13 489 1 15 ka and this is proposed as the location of the pleistocene holocene p h boundary a change in osl sensitivity occurs at this depth the depth and sharpness of this boundary is compared with the change obtained in low field magnetic susceptibility ms measurements on 65 samples from the section the ms changes gradually over 1 9 m and thus does not provide an easily discernible boundary the new osl based sedimentation rates are used to calculate the mass accumulation rates for the holocene and the end of the pleistocene

origin of nitrogen rich natural gases in the california great valley evidence from helium carbon and nitrogen isotope ratios abstract dry natural gases produced from the sacramento and northern san joaquin basins contain up to 87 nitrogen 15n measurements for gases with n2 8 vary from 0 9 to 3 5 methane 13c values vary from 61 to 15 3 he 4 he ratios indicate the presence of mantle derived helium in addition to radiogenic crustal helium and suggest that the gases may originate from mixing between three principal components a hydrocarbon rich gas with 3 he 4 he 0 1r a derived from the microbial and thermogenic alteration of sedimentary organic matter a hydrocarbonrich gas with 3 he 4 he 2 75r a derived from the localized pyrolysis of sediments by magmatic volatiles and a nitrogenrich gas with 3 he 4 he 1r a the nitrogen rich component is characterized by methane 13c less negative than 25 and n 2 ar ratios as high as 22 000 nitrogen concentrations tend to increase towards the basement along the shallow eastern margin of the valley suggesting that the nitrogen rich component is derived from metasedimentary rocks deep within the crust the coast ranges fraciscan complex which was thrust well beneath the great valley during late mesozoic and early cenozoic subduction appears to be the most likely source

ocean current and wave effects on wind stress drag coefficient over the global ocean 1 the effects of ocean surface currents and dominant waves on the wind stress drag coefficient cd are examined over the global ocean major findings are as follows 1 the combination of both ocean wave and current speeds can result in reductions in daily cd 10 but the notable impact of the latter is only evident in the tropical pacific ocean 2 the presence of waves generally makes winds weaker and cd lower almost everywhere over the global ocean 3 strong ocean currents near the western boundaries kuroshio and gulf stream do not substantially influence cd since the winds and currents are not always aligned and 4 the change in speed used in bulk flux parameterization also causes large changes in fluxes globally the combined outcome of ocean currents and waves is to reduce cd by about 2 but spatial variations 0 to 14 do exist citation kara a b e j metzger and m a bourassa 2007 ocean current and wave effects on wind stress drag coefficient over the global ocean geophys res lett 34 l01604 doi 10 1029 2006gl027849

patterns of ocean current variability on the west florida shelf using the self organizing map 1 patterns of ocean current variability are examined on the west florida shelf by a neural network analysis based on the self organizing map som using time series of moored velocity data that span the interval october 1998 september 2001 three characteristic spatial patterns are extracted in a 3 4 som array spatially coherent southeastward and northwestward flow patterns with strong currents and a transition pattern of weak currents on the synoptic weather timescale the variations of these patterns are coherent with the local winds on the seasonal timescale the variations of the patterns are coherent with both the local winds and complementary sea surface temperature patterns the currents are predominantly southeastward during fall winter months from october to march and northwestward during summer months from june to september the spatial patterns extracted by the nonlinear som method are asymmetric a feature that is not captured by the linear empirical orthogonal function method thus we find for the synoptic weather and longer timescales that 1 southeastward currents are generally stronger than northwestward currents 2 the coastal jet axis is located further offshore for southeastward currents than for northwestward currents and 3 the velocity vector rotations with depth are larger in shallower water when the currents are southeastward relative to when the currents are northwestward

thermal springs in italy their relation to recent tectonics the large scale circulation of thermal waters in italy is reviewed from both a chemical and an isotopic point of view two main areas are recognized one in the alpine region and the other in the central southern apennine region the alps are an area of very high hydraulic heads and low thermal gradients where hot deep seated waters of meteoric origin rapidly reach the surface along active boundary fault systems the apennines in contrast are characterized by lower hydraulic heads and higher thermal gradients all thermal springs in italy including those in active volcanic areas originate essentially from meteoric waters and most follow long pathways in mesozoic carbonate anhydritic aquifers before emerging as indicated by relations among present hydrothermal activity in central southern italy deep crustal structures and pco2 content in thermal waters

optical dating of eolian deposits since the last interglacial along the northern margin of the chinese loess plateau abstract understanding the chronology of eolian sand loess paleosol sequences along the northern margin of the chinese loess plateau clp is crucial for comprehending climate change and the advance and retreat of the adjacent mu us desert in this study a sand loess soil sequence from the northern margin of the clp was studied by applying the single aliquot regenerative sar protocol to quartz grains and the multi elevated temperature post ir irsl met pirir protocol to k feldspar grains for equivalent dose de determination 63 90 m quartz and k feldspar grains were used our results indicate that the met pirir ages of k feldspar grains in this sequence range from 94 4 7 0 ka to 148 3 13 3 ka for the last interglacial paleosol s1 for the upper part of the section quartz based sar osl dating was used yielding ages spanning from 5 8 0 4 ka to 35 9 4 1 ka after cross checking these results with previously reported isochron osl and tl ages the reliability of the met pirir protocol when applied to the last interglacial paleosol was confirmed based on a new osl chronology of the shimao profile the studied eolian deposits can be broadly correlated with the last glacial interglacial cycle but their dating also points to sedimentary hiatuses occurring at 94 4 ka 35 9 ka and 5 8 ka due most probably to strong wind erosion caused by intensified cold dry winter monsoonal circulations during the last glacial maxima

chronology and the upper dating limit for loess samples from luochuan section in the chinese loess plateau using quartz osl sar protocol abstract luminescence dating of loess older than 100 ka has long been a challenge it has been recently reported that using optically stimulated luminescence osl of fine grained quartz 4 11 m extracted from loess the range of luminescence dating could be pushed to 0 6 ma with osl ages being in agreement with independent ages watanuki t murray a s tsukamoto s 2005 quartz and polymineral luminescence dating of japanese loess over the last 0 6 ma comparison with an independent chronology earth and planetary science letters 240 774 789 the aim of this study is to provide a luminescence chronology 20 samples for the standard luochuan loess section and to further examine the upper limit of quartz osl dating for chinese loess the growth curve does not saturate at 700 gy and should allow reliable equivalent dose d e determination up to at least 400 gy however when compared with independent chronological control the d e that could be treated as reliable is less than 230 gy corresponding to 70 ka in age for chinese loess and the d e larger than 230 gy should be underestimated ages for samples from the lower part of palaeosol s1 are severely underestimated with the maximum age of 95 ka for a sample from the bottom of this palaeosol much younger than the expected age of 128 ka the maximum d e obtained for sample l9 m collected from loess layer l9 which is below the matuyama brunhes b m boundary whose age is 780 ka is only 403 gy which corresponds to an age of 107 ka the cause of underestimation is not yet clear the previous results by watunuki et al 2005 on the extension of osl dating of loess to 0 6 ma is not confirmed when evaluating the validity of osl ages in s1 another possibility is to question the already established chronological frame for luochuan section which is based on the hypothesis of continuous dust deposition the assumption of an erosion hiatus between l2 and s1 could make the osl ages look reasonable however if this is the case then it is difficult to explain why the age of sample l9 m is only 107 ka which could be treated as a saturation age while the osl can provide a correct age for loess as old as 94 9 ka for sample lc22 collected from the bottom of s1 much work is required to clarify these confusions

osl dating of a holocene loess paleosol sequence in the southern loess plateau china optically stimulated luminescence osl dating of polymineral fine grained loess samples collected from the southern loess plateau of china was conducted using the single aliquot regenerative dose sar protocol a double sar procedure in which aliquots are subjected to both infrared ir and blue stimulations was used and two sets of equivalent dose d e determinations were produced these doses are assumed to be predominantly related to the feldspathic and quartz fine grain populations respectively the results revealed that the osl ages estimated by infrared stimulated luminescence irsl signals and those estimated by post ir stimulated luminescence post ir osl signals disagreed specifically the ages estimated using the irsl signals were smaller than those estimated using post ir osl signals the results of an anomalous fading test of the two types of osl signals revealed that the post ir osl signals from the etched sub sample by h2sif6 and hf and the un etched sub sample did not fade significantly however the irsl signals from the un etched sub sample showed obvious signs of fading these findings indicate that the lower age estimated by irsl is due to the anomalous fading of feldspar ir signals in the polymineral fine grains for samples collected from greater than 100 cm the estimates of their osl ages using two types of luminescence signals generally agreed with their pre estimated ages especially those of the post ir osl signals however for the three samples that were collected from a depth of less than 100 cm their osl ages were remarkably underestimated possibly due to the enhanced human activity such as soil cultivation that has occurred in the region since 3000 a b p

formation of authigenic minerals and their use as indicators of the physicochemical parameters of the fluid in the larderello travale geothermal field different authigenic mineral assemblages and mineral compositions have been found in different areas of the larderello travale geothermal field in the peripheral areas the most abundant authigenic minerals are quartz calcite chlorite and sulfides they formed in a temperature range of 150 sup 0 to 250 sup 0 c and with a p sub co2 range of 0 1 to 1 0 atm in a hotter part of the field at depths between 200 and 1 300 m where the main productive fractures are located the most important authigenic minerals are quartz chlorite calcite k feldspar and k bearing mica with which wairakite hematite anhydrite and barite are sometimes associated deposition of all these minerals occurs in a temperature range of 200 sup 0 to 300 sup 0 c under p sub co2 of about 1 atm and relatively high p sub o2 in fluids sometimes characterized by silica oversaturation below the 1 300 m depth in the hottest part of the field k feldspar chlorite epidote sulfides with minor sphene prehnite clinopyroxene and clinoamphibole are present these minerals form in a temperature range of 250 sup 0 to 350 sup 0 c under a p sub co2 of less than 1 atm and a p sub o2 ranging from 10 sup 40 to 10 sup 33 atm and reasonablymore reflect the physicochemical parameters of the geothermal fluid before exploitation evidence of an earlier hydrothermal stage characterized by higher temperatures can be seen in the occurrence of relic wollastonite and andradite less

a new osl chronology for dust accumulation in the last 130 000 yr for the chinese loess plateau abstract a sensitivity corrected multiple aliquot regenerative dose protocol has been developed for fine grained quartz osl dating of chinese loess its reliability has been assessed on the basis of the methodology and by dating reference samples of known age close to the transition from the last interglacial paleosol s 1 to the last glacial loess l 1 which corresponds to the marine oxygen isotope stage mis 5 4 transition on the basis of the fine grained quartz osl age estimates for 33 loess samples from the upper part of the luochuan profile a detailed chronostratigraphy of continuous dust accumulation in the past 130 ka has been proposed changes in the accumulation rate occurred during the last glacial period mis 4 to mis 2 unexpectedly high accumulation rates were found in the weakly developed l 1 2 s paleosol of the last interstadial mis 3 rather than in the classic l 1 1 and l 1 3 loess of the cold dry glacial condition mis 2 and 4 the osl ages show some disagreement with the previous numerical chronology for the loess paleosol sequence based on correlation of variations in grain size with sedimentation rate the latter method resulted in an almost constant accumulation rate from 72 to 12 ka

coastal ocean wind fields gauged against the performance of an ocean circulation model 1 atmosphere model derived flux fields are used to force coastal ocean models coarse resolution and incomplete boundary layer dynamics limit the accuracy of these forcing fields and hence the performance of the ocean models we address this limitation for the west florida shelf using optimal interpolation to blend winds measured in situ with winds produced by model analyses by improving the coastal wind field we improve the fidelity between currents modeled and currents observed comparisons between momentum analyses performed independently from the model and the data demonstrate the fidelity to be of a correct dynamical basis we conclude that the primary limitation to coastal ocean model performance lies with the boundary conditions

geochemical characteristics of the south tuscany italy volcanic province constraints on lava petrogenesis abstract three suites of volcanic rocks from radicofani mts cimini and mt amiata south tuscany italy were analyzed for major and trace element contents and sr isotopic composition all samples are silica saturated hypersthene normative and some are peraluminous samples from radicofani and the less evolved mts cimini samples have high mg numbers 74 5 66 3 consistent with the fosteritic rich nature of their olivine phenocrysts and high bulk rock abundances of ferromagnesian trace elements all samples are highly enriched in light ree 150 315 chondrites compared to heavy ree 9 15 chondrites and have negative eu anomalies eu eu 0 92 0 44 87 sr 86 sr ratios are high and variable radicofani 0 7137 0 7150 mts cimini 0 7128 0 7138 mt amiata 0 7119 0 7131 a distinctive feature of the radicofani samples is that with decreasing age the rocks increase in k2o content but decrease in la ce these south tuscany rocks have geochemical characteristics of the calc alkaline and alkaline series namely in addition to the high k rb cs ba and lree contents they have high ratios of incompatible elements relative to the high field strength ions such as ti zr hf nb and hree when compared to an estimated primitive mantle composition in general the geochemical characteristics of south tuscany volcanics are consistent with mixing between crustal derived material and mantle derived magma the mantle derived component was unusually rich in radiogenic sr and incompatible elements and had geochemical features similar to basic lavas of the high k series in the roman province

authigenic minerals from the paola ridge southern tyrrhenian sea evidences of episodic methane seepage abstract paola ridge along the nw calabrian margin southern tyrrhenian sea is one of the few reported deep sea sites of precipitation of authigenic carbonates in the tyrrhenian sea here the changing composition of the seeping fluids and the dynamic nature of the seepage induced the precipitation of pyrite siderite and other carbonate phases the occurrence of this array of authigenic precipitates is thought to be related to fluctuation of the sulfate methane transition zone smtz concretions of authigenic minerals formed in the near sub bottom sediments of the paola ridge were investigated for their geochemical and isotopic composition these concretions were collected in an area characterized by the presence of two alleged mud volcanoes and three mud diapirs the mud diapirs are dotted by pockmarks and dissected by normal faults and are known for having been a site of fluid seepage for at least the past 40 kyrs present day venting activity occurs alongside the two alleged mud volcanoes and is dominated by co2 rich discharging fluids this discover led us to question the hypothesis of the mud volcanoes and investigate the origin of the fluids in each different domed structure of the study area in this study we used stable isotopes carbon and oxygen of carbonates coupled with rare earth element ree composition of different carbonate and non carbonate phases for tracing fluid composition and early diagenesis of authigenic precipitates the analyses on authigenic precipitates were coupled with chemical investigation of venting gas and sea water authigenic calcite aragonite concretions from surficial sediments on diapiric structures have depleted 13c isotopic composition and slightly positive 18o values by contrast siderite concretions generally found within the first 6 m of sediments on the alleged mud volcanoes yielded positive 13c and 18o values the siderite ree pattern shows consistent lree light ree fractionation mree medium ree enrichment and positive gd and la anomalies as shown by the ree distribution the 13c depleted composition and their association with chemosymbiotic fauna calcite aragonite precipitated at time of moderate to high methane flux close to the seafloor under the influence of bottom seawater authigenic siderite on the other hand formed in the subseafloor during periods of lower gas discharges under prolonged anoxic conditions within sediments in equilibrium with 13c rich dissolved inorganic carbon dic and 18o rich water likely related to methanogenesis and intermittent venting of deep sourced co2

equivalent dose determinations for polymineralic fine grains using the sar protocol application to a holocene sequence of the chinese loess plateau abstract a single aliquot regenerative dose sar protocol involving stimulation of the same disc with an infra red laser diode followed by blue leds was applied to polymineralic fine grains infra red stimulated luminescence irsl and post ir optically stimulated luminescence osl ages are presented for a series of 19 fine grain 4 11 m samples taken from a loess section duowa in the western chinese loess plateau there are significant differences between the equivalent doses and thus the ages for the irsl and post ir osl measurements three potential explanations are investigated incomplete bleaching prior to deposition thermal transfer of charge and initial sensitivity change the question regarding which sequence of ages ir or post ir osl is correct if either is not resolved although the 19 post ir osl ages yield more consistent results it is proposed that the double sar protocol employed may not be correctly monitoring the sensitivity changes relating to either or both natural signals

a combined geochemical and isotopic study of the fluids discharged from the montecatini thermal system nw tuscany italy abstract the thermo mineral fluids discharges of montecatini terme northern apennines tuscany italy have been exploited since the roman times and despite the fact that this thermal complex is one of the biggest in europe the most recent geochemical investigations were published almost 40 years ago to fill this gap in this paper a detailed geochemical and isotopic investigation on the main thermal springs and wells from the montecatini thermal system mts is presented the chemical and isotopic features of the montecatini waters suggested that they are mainly controlled by water rock interaction processes between meteoric water permeating at depth from the surrounding reliefs up to 800 m a s l and the triassic evaporites burano formation belonging to the tuscan sedimentary series the local stratigraphic and tectonic framework favors an efficient recharge of the hydrothermal reservoir by the meteoric precipitation from a large catchment area and this aspect plays a fundamental role for the longevity of the montecatini thermal spas notwithstanding the huge amount of thermal water exploited the 3h values indicated that the thermal waters are likely related to a relatively long 50 years fluid circulation pattern approaching the surface thermal and saline waters mix with cold and low tds total dissolved solids waters hosted in short shallow aquifer s whose chemistry is dictated by the interaction of rain waters with silico clastic rocks of low solubility geothermometric estimations in the f so42 hco3 system suggested the occurrence of a main fluid reservoir at t 80 95 c and pco2 0 5 bars such co2 pressure is consistent with values estimated for other thermal springs from central southern tuscany being co2 basically supplied by a deep source nevertheless 13c co2 and 13c tdic values were lower than those expected for a mantle thermometamorphic co2 source this can be explained by i isotopic fractionation occurring during calcite precipitation and or ii mixing with biogenically derived gases occurring at relatively shallow depth

origins of methane discharging from volcanic hydrothermal geothermal and cold emissions in italy abstract we have addressed the origins of methane in fumarolic thermal and cold emissions discharging from a diversity of geological settings spread all over the italian peninsula and at panarea and pantelleria islands fluid discharges from the main geothermal systems of the peri tyrrhenian area including mt amiata larderello latera and manziana show 13c ch4 and d ch4 values 28 v pdb and 160 v smow respectively and c1 c2 concentration ratios 1000 these patterns suggest that ch4 discharged from these systems is primarily generated by abiogenic reduction of co2 and or co methane seems to have at least partially a different origin than the higher hydrocarbons that might be entirely related to the thermal decomposition of organic matter or alternatively to methane polymerization fumaroles from the volcanic systems of solfatara vesuvio panarea and pantelleria have c1 c2 concentration ratios in a wide range from 17 to 4300 but 13c ch4 and d ch4 values 21 v pdb and 120 v smow respectively such isotopic values are very similar to those reported for ch4 discharging from ultramafic hydrothermal systems in agreement with recent evidence provided for solfatara and pantelleria we therefore infer that the ch4 in the volcanic fumaroles is mainly abiogenic too the 13c ch4 from 21 6 to 36 9 v pdb and d ch4 from 113 to 164 v smow values as well as the c1 c2 concentration ratios from 19 to 2240 in the co2 rich fluid discharges located between the geothermal volcanic systems and the apennine sedimentary chain tend to decrease eastwards as the temperatures of the fluid reservoirs progressively diminish suggesting that the ch4 production is mainly related to thermogenic processes according to this general trend the ch4 dominated fluids from mud volcanoes located eastwards of the co2 rich emissions are fed by an almost pure thermogenic source the easternmost fluid discharges from the po valley and the adriatic coast where organic matter evolves at relatively shallow depths in the presence of a low geothermal gradient record the lowest 13c ch4 and d ch4 values i e as low as 69 v pdb and

high resolution luminescence chronology for xiashu loess deposits of southeastern china abstract loess deposits in xiashu are representative of such deposits in southeastern china that are mainly distributed in the middle and lower reaches of the yangtze river valley these loess paleosol sequences provide a key archive of past climate change in humid subtropical regions however the ages of the sequences are not well constrained in this study the standard quartz single aliquot regenerative sar dose optically stimulated luminescence osl and k feldspar post infrared infrared stimulated luminescence post ir irsl pirir290 methods are used to date two loess sequences in nanjing region our results show that quartz sar osl and k feldspar pirir290 ages are more or less indistinguishable from one another up to 50 ka beyond this age the k feldspar pirir ages increased systematically with deposition depth agreeing well with the expected ages as far as 200 ka on the basis of a fully independently dated timescale we are therefore able to propose for the first time a new age model for the xiashu loess deposits accumulated since the penultimate interglacial period using our newly obtained luminescence dating ages we observe a marked difference between the loess accumulation rates in the two sequences potentially forced by regional depositional processes and loess preservation