argon and halogen geochemistry of hydrothermal fluids in the loch ainort granite isle of skye scotland highly turbid alkali feldspars from the loch ainort granite 59 ma isle of skye have been analysed using the 40ar 39ar method to obtain chronological and chemical k cl br i information concerning their origin and hydrothermal alteration three methods of gas extraction have been applied to neutron irradiated samples laser probe spot fusion of feldspars in vacuo crushing of a feldspar quartz separate and laser stepped heating of the crushed residue apparent ages obtained by laser probe spot fusion are mostly similar to the 59 ma intrusion age analyses of relatively pristine regions give some high apparent ages 59 ma indicating the presence of small amounts of 40are excess 40ar crushing releases significant amounts of 40are but is dominated by an 40ara atmospheric 40ar component 84kr 36ar values obtained by crushing are higher than air and are consistent with air equilibration with fresh water at low temperature 20 c therefore 40ara was most probably introduced as palaeoatmospheric argon dissolved in the circulating hydrothermal fluids that interacted with the granite thus supporting a meteoric origin for the fluids stepped heating gives a flat age spectrum and an age of 56 4 ma crushing and stepped heating both released significant amounts of halogens with high br cl and i cl ratios excess xe is also present as indicated by the high 132xe 36ar values it seems likely that the halogen and possibly xe enrichments resulted from interaction of the meteoric fluids with jurassic sedimentary country rocks

evolution of a metamorphic fluid and its role in lode gold mineralisation in the central lberian zone the central iberian zone of spain and portugal contains numerous gold deposits of varying size age and host lithology previous work concentrated on single deposits leading to a need to apply a range of techniques to the region as a whole to form a model for metallogenesis throughout the region with this aim a number of occurrences of gold mineralisation in the south western central iberian zone were studied the central iberian zone consists essentially of greenschist facies metasedimentary units intruded by hercynian granitoids hercynian deformation occurred in three main stages the earliest d1 being the most intense quartz veining is common throughout the region and a vein chronology was established relative to these deformation events v1 veins are pre hercynian and may predate the precambrian sardic deformation v2 veins are syndeformational d1 and associated with peak greenschist metamorphism v3 veins are late kinematic syn to post d2 v4 veins are syn to post d3 occurring in the final stages of the hercynian and often associated with or post dating granites reactivation of vein sets by later fluids was common fluid chemistry studies of samples of known chronology indicate three main sources of fluid the dominant fluid throughout the region from v2 to v4 is a dilute aqueo carbonic fluid of varying composition the combination of fluid inclusion analyses and geochemical studies of wallrock alteration indicates that the fluid was the result of devolatilisation and dehydration during prograde metamorphism at varying depths the resulting aqueo carbonic fluids flowed upwards mixing with each other and with meteoric waters contact metamorphism associated with granite intrusions during the d3 deformation released further aqueo carbonic fluids which in some cases unmixed to form separate carbonic and aqueous inclusions circulation of meteoric waters was important during later stages d3 prolonged low temperature fluid rock interaction produced highly saline aqueous fluids which post date all major quartz veining no single set of characteristics exists for gold mineralisation in the central iberian zone deposits cover a wide spectrum but three main types have been identified 1 early d1 v2 syn peak metamorphic gold quartz veins associated with an aqueo carbonic fluid with high n2 and ch4 2 late kinematic d2 v3 veins often associated with late brittle faults again the fluid present at the time of formation was aqueo carbonic but with lower n2 and ch4 3 late v4 low temperature veins formed by a mainly meteoric fluid which was also responsible for remobilisation and concentration of gold in earlier deposits the gold mineralisation in the central iberian zone supports the continuum model for lode gold deposits gold was leached from metasediments during prograde metamorphism transported to shallower crustal levels and deposited wherever suitable traps occurred channelling of fluid from deeper levels resulted in the localisation of deposits close to major shear zones depositional sites were usually dilational zones in faults and more rarely folds but locally lithological controls were important h2o co2 unmixing was common but was not necessarily related to gold deposition

origin of saline groundwaters in the carnmenellis granite cornwall england natural processes and reaction during hot dry rock reservoir circulation saline groundwaters up to 19 100 mg 1 1 total mineralisation issue in tin mines in the carnmenellis granite in cornwall u k at depths up to 800 m their stable isotope composition rules out seawater as a contributor to salinity circulation experiments carried out during hot dry rock hdr reservoir development in the same granite also produce return fluids with enhanced salinities acid hydrolysis of plagioclase and biotite are proposed as the main sources of salinity in the groundwater experimental studies carried out on biotites from a borehole used for hdr evaluation demonstrate the reactivity of the biotite and confirm the hypotheses of the field studies mg li k and silica levels in reacted solutions reflect the stoichiometric composition of the biotite chloride na and ca in solution on the other hand are enriched between 1 and 3 orders of magnitude over that of biotite reflecting the strongly incongruent nature of the reaction quartz and chalcedony saturation of the groundwaters encourages silica or silicate deposition rather than dissolution of rock forming quartz this argues against fluid inclusions as the source of salinity and suggests that new inclusions might be formed the proposed model for the genesis of saline water therefore links together or explains several processes groundwater movement convective heat transport the chemistry of the water water rock interaction secondary mineral including kaolinite formation and fluid inclusion formation and stability

lithium in waters of a polar desert abstract lithium li concentrations were measured in a series of stream and lake samples from a cold dry desert the mcmurdo dry valleys mdv in southern victoria land antarctica li geochemistry has been of great interest and utility in part because of its solubility and mobility during rockwater interactions in general the values determined for the streams and the dilute lake waters in this polar desert environment are similar to those found in temperate streams and lakes the source of li to these waters is a combination of marine aerosol and crustal weathering within the stream channels the hypersaline hypolimnion of lake bonney has extremely high concentrations of li which has been concentrated via a previous drawdown of the lake and its subsequent evapoconcentration the different distributions of li within the lakes is also due to past climatic changes and their effects on the chemical evolution of the lakes the high relative mobility of li controls its distribution within the aquatic systems of this cold desert environment

shedding light on ore deposits a review of synchrotron x ray radiation use in ore geology research abstract geology researchers commonly confront critical research questions that require microscopic and sub microscopic level observations e g distribution of chemical elements of economic interest nature of mineralising fluid in order to explain the macroscale phenomena related to the characterisation of and controls on ore mineralisation the emergence and technological evolution of fourth generation synchrotron radiation light sources render these facilities as important but still largely under utilised tools for advancing the frontiers of ore related research to this end the present contribution seeks to critically review and highlight the power and affordances of synchrotron x ray techniques specifically to the fields of fundamental and applied ore geology the review introduces a range of commonly applied synchrotron x ray techniques before comprehensively highlighting past applications of synchrotron x rays to a range of commodities and ore deposits types a synthesis of this information highlights the historical importance of synchrotron x ray techniques towards 1 understanding ore textures and chemical relationships at high m spatial resolutions 2 understanding coordination chemistry of metals in aqueous fluids at geologically relevant p t conditions 3 in situ evaluation of the chemistry and speciation of fluid inclusions 4 evaluating the coordination environment of deleterious and economic trace metal substitutions in major mineral structures and 5 understanding the biogeochemical behaviour and transformations of metals in the low temperature supergene mineralising environment these applications as well as recommendations for future work are described in the hope that a greater diversity of ore geology researchers will incorporate synchrotron x ray tools into their existing suite of analytical and experimental techniques

isotope geochemistry of fluid inclusions in permian halite with implications for the isotopic history of ocean water and the origin of saline formation waters abstract d and 18o values have been determined for fluid inclusions in 45 samples of permian halite the inclusions are enriched in 18o relative to the meteoric water line but are depleted in d relative to ocean water inclusions with the more positive values coincide with the isotopic composition expected for evaporating sea water which follows a hooked trajectory on a d 18o diagram inclusions with more negative values may represent more highly evaporated sea water but probably reflect synsedimentary or diagenetic mixing of meteoric water with evaporite brines the isotope systematics in these inclusions are sufficiently similar to those of a modern evaporite pan to indicate that permian sea water was isotopically similar to modern sea water connate evaporite brines can have negative values because of the probable hooked isotope trajectory of evaporating sea water and or synsedimentary mixing of evaporite brines with meteoric waters subsurface formation waters composed of mixtures of remnant primary evaporite brines and later meteoric waters may be more common than previous isotopic evidence has suggested

a new technique for sampling water and gas from deep drill holes a new technique for sampling water and gas from deep 500 1500 m drill holes is described the principle of the technique is to raise a continuous column of water inside a thin polyamide tube with a back pressure valve at the lower end and with shutoff valves every 50 m the equipment is easily assembled from standard parts sampling can be performed by three people without mechanical apparatus descent to 1000 m takes 2 hours and retrieval 1 hour the method makes it possible to obtain a practically undisturbed continuous water profile from a drill hole dissolved gases remaining inside the tube can be sampled at the surface to demonstrate the efficiency of the technique selected results from the deepest drill hole in finland having a vertical depth of 1100 m are presented

groundwater chemistry and water rock interactions at stripa groundwaters from near surface to a depth of 1232 m in the stripa granite have been sampled and analyzed for major and trace constituents the groundwater composition consists of two general types a typical recharge water of ca hco3 type 700 m depth of high ph 8 10 that reaches a maximum of 1250 mg l in total dissolved solids tds intermediate depths show mixtures of the two types that are highly fracture dependent rather than depth dependent any borehole can vary significantly and erratically in tds for either a horizontal or vertical direction the general transition from ca hco3 type to na ca cl type correlates with the depth profile for hydraulic conductivity that drops from 10 8 m s to 10 11 m s or lower thermomechanical stress from heater experiments clearly shows an effect on the groundwater composition that could be caused by changing flow paths leakage of fluid inclusions or both dissolution and precipitation of calcite fluorite and barite aluminosilicate hydrolysis and addition of a saline source possibly fluid inclusion leakage play the major roles in defining the groundwater composition the low permeability of the stripa granite has produced a groundwater composition that appears intermediate between the dilute shallow groundwaters typical of recharge in a crystalline rock terrain and the saline waters and brines typical of cratonic shield areas at depth

platinum enrichment at low temperatures and related microstructures with examples of hongshiite ptcu and empirical pt2hgse3 from itabira minas gerais brazil low temperature pt enrichment is illustrated with reference to two hypogene platiniferous minerals i a pd cu bearing pt2hgse3 an unnamed phase and ii hongshiite ptcu with up to 0 7 wt hg the former has patches oxidized to a pt o species with curvilinear microcracks originated by desiccation the latter displays parallel sets of cu depleted pt hg enriched patches along which microfractures occur such microstructures are interpreted to arise from two processes i oxidation and formation of a hydrated pt o compound which tends to succumb to a pt rich alloy by deoxygenation and dehydration leaving behind curvilinear desiccation cracks ii metal leaching conducive to native pt by removal of cu from hongshiite via micropores that coalesce along crystallographic planes to result in reticulated microcracks platinum enrichment either by oxidation or metal leaching ideally produces characteristic microcracks which may be indicative of the origin i e detrital vs supergene of alluvial and eluvial pt rich alloys

segmentation and supercycles a catalog of earthquake rupture patterns from the sumatran sunda megathrust and other well studied faults worldwide abstract after more than 100 years of earthquake research earthquake forecasting which relies on knowledge of past fault rupture patterns has become the foundation for societal defense against seismic natural disasters a concept that has come into focus more recently is that rupture segmentation and cyclicity can be complex and that a characteristic earthquake model is too simple to adequately describe much of fault behavior nevertheless recognizable patterns in earthquake recurrence emerge from long high resolution spatially distributed chronologies researchers now seek to discover the maximum minimum and typical rupture areas the distribution variability and spatial applicability of recurrence intervals and patterns of earthquake clustering in space and time the term supercycle has been used to describe repeating longer periods of elastic strain accumulation and release that involve multiple fault ruptures however this term has become very broadly applied lumping together several distinct phenomena that likely have disparate underlying causes we divide earthquake cycle behavior into four major classes that have different implications for seismic hazard and fault mechanics 1 quasi periodic similar ruptures 2 clustered similar ruptures 3 clustered complementary ruptures rupture cascades and 4 superimposed cycles segmentation is likewise an ambiguous term we identify master segments and asperities as defined by barriers to fault rupture these barriers may be persistent rarely or never traversed frequent occasionally traversed or ephemeral changing location from cycle to cycle we compile a catalog of the historical and paleoseismic evidence that currently exists for each of these types of behavior on major well studied faults worldwide due to the unique level of paleoseismic and paleogeodetic detail provided by the coral microatoll technique the sumatran sunda megathrust provides one of the most complete records over multiple earthquake rupture cycles long historical records of earthquakes along the south american and japanese subduction zones are also vital contributors to our catalog along with additional data compiled from subduction zones in cascadia alaska and middle america as well as the north anatolian and dead sea strike slip faults in the middle east we find that persistent and frequent barriers rupture cascades superimposed cycles and quasi periodic similar ruptures are common features of most major faults clustered similar ruptures do not appear to be common but broad overlap zones between neighboring segments do occur barrier regions accommodate slip through reduced interseismic coupling slow slip events and or smaller more localized ruptures and are frequently associated with structural features such as subducting seafloor relief or fault trace discontinuities this catalog of observations provides a basis for exploring and modeling root causes of rupture segmentation and cycle behavior we expect that researchers will recognize similar behavior styles on other major faults around the world

microthermometric laser raman spectroscopic and volatile ion chromatographic analysis of hydrothermal fluids in the paleozoic muruntau au bearing quartz vein ore field uzbekistan fluid inclusions in quartz and scheelite from flat steeply dipping central and stockwork type quartz veins within the muruntau au bearing quartz vein ore field have been investigated in a reconnaissance study using fluid inclusion mapping microthermometry laser raman spectroscopy and integrated gas and ion chromatography for bulk volatile and cation anion analysis muruntau central veins are dominated by inferred early co2 bearing fluid inclusions in contrast flat quartz veins contain considerable numbers of low density pure aqueous inclusions on deformation and recrystallization related microstructures fluid phase separation is indicated for samples from the muruntau central ore veins by fluid inclusion observational work as well as by microthermometry and bulk fluid geochemistry co2 ch4 co2 n2 and co2 c2 and c3 hydrocarbon ratios salinity data however in flat veins and all samples from the myutenbai deposit no evidence for fluid immiscibility could be found quartz microstructural results and fluid inclusion data suggest formation of the low grade mineralized flat veins before the main stage of hydrothermal activity and considerable variation in the geochemical conditions during fluid evolution in the muruntau and myutenbai deposits mixing of fluids from different sources in variable proportions may be inferred from halide geochemistry furthermore fluid inclusion br cl ratios differ significantly for samples from different vein types fluid phase separation is suggested as a mechanism for the precipitation of au from the hydrothermal fluid in the muruntau high grade au mineralized central veins

geochemistry and origin of saline groundwaters in the fennoscandian shield chemical and isotopic analyses of water from drill holes and mines throughout the fennoscandian shield show that distinct layers of groundwater are present an upper layer of fresh groundwater is underlain by several sharply differentiated saline layers which may differ in salinity relative abundance of solutes and o h sr and s isotope signature saline groundwater can be classified into four major groups based on geochemistry and presumed origin brackish and saline waters from 50 200 m depth in coastal areas around the baltic sea exhibit distinct marine chemical and isotopic fingerprints modified by reactions with host rocks these waters represent relict holocene seawater inland three types of saline groundwater are observed an uppermost layer of brackish and saline water from 300 900 m depth saline water and brines from 1000 2000 m depth and superdeep brines which have been observed to a depth of at least 11 km in the drill hole on the kola peninsula u s s r electrical and seismic studies in shield areas suggest that such brines are commonly present at even greater depths the salinity of all inland groundwaters is attributed predominantly to water rock interaction the main solutes are cl ca na and mg in varying proportions depending on the host rock lithology the abundance of dissolved gases increases with depth but varies from site to site the main gas components are n2 ch4 up to 87 vol and locally h2 the 13c value for methane is highly variable 25 to 46 and it is suggested that hydrothermal or metamorphic gases trapped within the surrounding rocks are the most obvious source of ch4 the uppermost saline water has meteoric oxygen hydrogen isotopic compositions whereas values from deeper water plot above the meteoric water line indicating considerably longer mean residence time and effective low temperature equilibration with host rocks geochemical and isotopic results from some localities demonstrate that the upper saline water cannot have been formed through simple mixing between fresh water and deep brines but rather is of independent origin the source of water itself has not been satisfactorily verified although superdeep brines at least may contain a significant proportion of relict precambrian hydrothermal or metamorphic fluids

near field tsunami models with rapid earthquake source inversions from land and ocean based observations the potential for forecast and warning computation of tsunami models in the region adjacent to large earthquakes immediately after rupture initiation remains a challenging problem limitations of traditional seismological instrumentation in the near field and concern by tsunami modelers regarding the nonuniqueness of source inversions and the use of indirect observations have in the past been hurdles for such efforts employing near field data from the mw 9 0 2011 tohoku oki data we test source models obtained from newly developed algorithms and multisensor data we demonstrate the ability of such source models determined from land based coseismic data from the combination of gps and strong motion sensors to forecast near source tsunamis we also demonstrate that rapid ingestion of offshore shallow water 100 1000 m wave gauge data substantially improves the earthquake source and tsunami forecast to assess the success of such tsunami models we rely on detailed comparisons to 2000 tsunami survey measurements collected after the event we argue that deployments of shallow water wave gauges coupled with land based geophysical sensors can in the future provide enough information to issue timely and accurate forecasts of tsunami intensity immediately or shortly after rupture initiation of large earthquakes

the 8 september 2017 tsunami triggered by the m w 8 2 intraplate earthquake chiapas mexico the 8 september 2017 mw 8 2 earthquake offshore chiapas mexico is the largest earthquake in recorded history in chiapas since 1902 it caused damage in the states of oaxaca chiapas and tabasco including more than 100 fatalities over 1 5 million people were affected and 41 000 homes were damaged in the state of chiapas alone this earthquake an intraplate event on a normal fault on the oceanic subducting plate generated a tsunami recorded at several tide gauge stations in mexico and on the pacific ocean here we report the physical effects of the tsunami on the chiapas coast and analyze the societal implications of this tsunami on the basis of our post tsunami field survey the associated tsunami waves were recorded first at huatulco tide gauge station at 5 04 gmt 12 min after the earthquake we covered ground observations along 41 km of the coast of chiapas encompassing the sites with the highest projected wave heights based on our preliminary tsunami model maximum tsunami amplitudes between 94 5 and 93 0 w runup and inundation distances were measured along eight sites the tsunami occurred at low tide the maximum runup was 3 m at boca del cielo and maximum inundation distance was 190 m in puerto arista corresponding to the coast in front of the epicenter and in the central sector of the gulf of tehuantepec tsunami scour and erosion was evident along the chiapas coast tsunami deposits mainly sand reached up to 32 cm thickness thinning landward up to 172 m distance

critical metals ree sc pge in ni laterites from cuba and the dominican republic ni laterites are considered worthy targets for critical metals cm exploration as rare earth elements ree sc and platinum group elements pge can be concentrated during weathering as a result

deep embrittlement and complete rupture of the lithosphere during the m w 8 2 tehuantepec earthquake subduction zones where two tectonic plates converge are generally dominated by large thrust earthquakes nonetheless normal faulting from extensional stresses can occur as well rare large events of this kind in the instrumental record have typically nucleated in and ruptured the top half of old and cold lithosphere that is in a state of extension driven by flexure from plate bending such earthquakes are limited to regions of the subducting slab cooler than 650 c and can be highly tsunamigenic producing tsunamis similar in amplitude to those observed during large megathrust events here we show from analyses of regional geophysical observations that normal faulting during the moment magnitude mw 8 2 tehuantepec earthquake ruptured the entire cocos slab beneath the megathrust region we find that the faulting reactivated a bend fault fabric and ruptured to a depth well below the predicted brittle ductile transition for the cocos slab including regions where temperature is expected to exceed 1 000 c our findings suggest that young oceanic lithosphere is brittle to greater depths than previously assumed and that rupture is facilitated by wholesale deviatoric tension in the subducted slab possibly due to fluid infiltration we conclude that lithosphere can sustain brittle behaviour and fail in an earthquake at greater temperatures and ages than previously considered geophysical observations of the 2017 tehuantepec earthquake suggest that oceanic lithosphere can sustain brittle behaviour and rupture in an earthquake at greater depths than previously assumed

saline groundwaters in the canadian shield a first overview abstract the chemical and isotopic compositions of saline groundwaters and brines in the canadian shield are described the occurrence of such waters is very widespread not related to any specific rock type or mineralization and generally can be expected at depths below 1 km the most saline brines have salinities exceeding 200 g l 1 dissolved solids and their chemistries tend to suggest that in the past saline waters penetrated the canadian shield the original chemistry of these solutions was subsequently modified through strong rock water interactions and it appears that their final chemical compositions are independent of the original chemistries stable isotope analyses indicate that these waters are not simple evaporated seawater sedimentary basin brines hydrothermal solutions or residual ore forming fluids although any of these could be a precursor of the brines secondary isotope exchange reactions and the hydration of primary silicates accompanied by the formation of clay minerals could have modified not only the primary isotopic composition but may have also profoundly influenced the chemistries of these brines to be effective these processes would have had to occur in closed systems

geology water geochemistry and geothermal potential of the jemez springs area canon de san diego new mexico abstract studies of the geology geochemistry of thermal waters and of one exploratory geothermal well show that two related hot spring systems discharge in canon de san diego at soda dam 48 c and jemez springs 72 c the hot springs discharge from separate strands of the jemez fault zone which trends northeastward towards the center of valles caldera exploration drilling to precambrian basement beneath jemez springs encountered a hot aquifer 68 c at the top of paleozoic limestone of appropriate temperature and composition to be the local source of the fluids in the surface hot springs at jemez springs comparisons of the soluble elements na li cl and b arguments based on isotopic evidence and chemical geothermometry indicate that the hot spring fluids are derivatives of the deep geothermal fluid within valles caldera no hot aquifer was discovered in or on top of precambrian basement it appears that low to moderate temperature geothermal reservoirs

comparison of surface aquifer and pore waters from a mesozoic basin and its underlying palaeozoic basement southeast france chemical evolution of waters and relationships between aquifers abstract as part of the deep geology of france gpf ardeche project water samples were collected along the ardeche margin of the massif central crystalline shield water is contained within various rocks including early jurassic carbonate triassic sandstone and evaporite permian continental deposits and the crystalline basement three sample types were studied surface water from streams and springs formation water sampled from fractured zones aquifers at various depths and pore water from rocks cored in the morte merie scientific borehole drilled to a depth of 980 m in 1993 as part of the ardeche project three main water chemistry signatures are associated with the three major geological groups 1 hco 3 ca mg water occurs in early jurassic carbonate and late triassic sandstone with dolomitic cement 2 ca so 4 water occurs in triassic sulphated shale and sandstone 3 na cl water occurs in permian sandstone and crystalline basement the samples enable a comparison between waters that flow on the surface those that have been in the underlying geological formations for a short time and those that have resided in closed pores of the host rock for a long time saturation indices computed for surface and formation waters show that dissolution reactions progressively increase the concentration of elements until saturation is reached surface waters were saturated for quartz and carbonate and formation waters for quartz carbonate gypsum muscovite and k feldspar saline water 12 g l tds from the permian rocks is controlled by a mineralogical assemblage of quartz calcite anhydrite muscovite k feldspar and albite at temperatures 80 90 c although equilibrium was reached for the formation waters concentrations in the pore waters reflect a general enrichment as compared to free formation waters from the fractured zones of the corresponding formation which suggests introduction of mobile elements in the solution only in permian rocks was a stable equilibrium observed since pore waters show no enrichment as compared to formation waters no water mixing was observed except along faults that form pathways for the fluid between formations each geological group generally behaves as a closed system except the permian rocks that seem to be or were exposed to circulation from the crystalline basement

plume mantle source heterogeneity through time insights from the duarte complex hispaniola northeastern caribbean 1 located in the cordillera central of hispaniola the duarte complex offers an opportunity to study an on land fragment of the caribbean colombian oceanic plateau geochemical sr nd isotope and 40ar 39ar radiometric age data combined with detailed mapping have shown that the duarte complex includes two lithostratigraphic units composed of four geochemical groups of metavolcanic rocks group ia low ti high mg basalts and group ib high ti picrites and primitive high mg basalts occur interlayered in the lowermost levels of the lower unit group ii light rare earth element lree enriched picrites ferropicrites and high mg basalts forms the main lava sequence of the lower unit and group iii lree enriched fe ti basalts is present exclusively in the upper unit nd isotope and incompatible trace element patterns are diverse in the duarte complex metavolcanics and are consistent with mantle sources related to a heterogeneous plume mantle melt modeling suggests that an early extensive melting 10 20 of shallow mantle resulted in the formation of relatively depleted group i and ii magmas whereas the late more enriched group iii magmas were the product of deeper low degree 96 ma hence an early cretaceous phase of the caribbean colombian oceanic plateau construction is recorded in hispaniola

candidate sites for future hot dry rock development in the united states generalized geologic and other data are tabulated for 24 potential hot dry rock hdr sites in the contiguous united states the data show that hdr resources occur in many geologic and tectonic settings potential reservoir rocks at each prospect are described and each system is cateogrized accoridng to inferred heat sources the fenton hill area in new mexico is discussed in detail because this region may be considered ideal for hdr development three other prospectively valuable localities are described the geysers clear lake region in california the roosevelt hot springs area in utah and the white mountains region in new hampshire these areas are singled out to illustrate the roles of significantly different geology and geophysics reservoir rocks and reservoir heat contents in possible hdr developments

a hot spring in granite of the western tianshan china the western tianshan range is a major cenozoic orogenic belt in central asia exposing predominantly paleozoic rocks including granite ongoing deformation is reflected by very rugged topography with peaks over 7000 m high active tectonic deformation is tied to an e w trending fracture and fault system that sections the mountain chain into geologically diverse blocks that extend parallel to the orogen in the muzhaerte valley upwelling hot water follows such a fault system in the muza granite about 20 l min 1 na so4 cl water with a temperature of 55 c having a total mineralization of about 1 g l 1 discharge from the hot spring the water is used in a local spa that is frequented by the people of the upper ili river area its waters are used for balneological purposes and the spa serves as a therapeutic institution the major element composition of the hot water is dominated by na and by so4 and cl ca is a minor component dissolved silica 1 04 mmol l 1 corresponds to a quartz saturation temperature of 116 c and a corresponding depth of the source of the water of about 4600 m this temperature is consistent with na k and na li geothermometry the water is saturated with respect to fluorite and contains 7 5 mg l 1 f as a consequence of the low ca concentration the water is undersaturated with respect to the primary minerals of the reservoir granite at reservoir temperature causing continued irreversible dissolution of granite the waters are oversaturated with respect to ca zeolite minerals such as stilbite and mesolite and it is expected that zeolites precipitate in the fracture pore space and in alteration zones replacing primary granite the stable isotope composition of o and h supports a meteoric origin of the water the cl br mass ratio of 1500 suggests that the salinity results from halite dissolution salts leached from powders of muza granite show the same cl br signature as the hot spring water sodium chloride is stored in fluid and solid inclusions in the granite which have been introduced to quartz by ductile shearing and faulting related to ongoing orogenesis the hot water remobilizes the salt that is continuously liberated by the tectonic deformation water granite interaction contributes a thenardite component na2so4 to the major element composition by albite dissolution in h2so4 the water rock interaction along faults and fractures transforms and alters muza granite to a low temperature epigranite

changes in compressional and shear wave velocities and dynamic moduli during operation of a hot dry rock geothermal system compressional and shear wave velocities measured during cross well seismic surveys are found to decrease during operation of a hot dry rock geothermal system the relative p and s wave velocity decrease is very close to values predicted by o connell and budiansky 1974 who modeled velocities in rocks containing fluid saturated and dry cracks because our data fit their model quite well we attribute the velocity decrease to an increased density of fluid filled fractures in the reservoir fracture density parameters of o connell and budiansky range as high as 0 365 near the main heat transfer areas of the geothermal reservoir the dynamic shear and young s modulus are significantly lower near the principal heat transfer surfaces but the bulk modulus is largely unaffected these observations suggest that the velocity differences are caused by fully saturated fractures we demonstrate that the fractures inferred by this survey may have lengths as large as 70 cm these fractures may have been caused by shear failure microcracking associated with thermal drawdown or thermal stress cracking

porosity and fluid velocities in the upper continental crust 2 to 4 km inferred from injection tests at the soultz sous forets geothermal site a heat exchanger was created at the french hot dry rock geothermal site using a doublet of boreholes at a depth of 3600 3800 m after hydraulic stimulation this exchanger was tested during a long term circulation trial from july to november 1997 tracer tests were carried out during the circulation trial an analysis of the tracers indicates a connected porous volume in the range of 0 5 to 2 5 10 6 m 3 with a connected porosity of the order of 0 9 to 2 3 these values are one order of magnitude higher than values obtained by extrapolation from petrophysical investigation of the boreholes this result is interpreted as being due to the connection of the major faults to a dense network of 2 nd order structures fluid circulation velocities inferred from the tracer test are of the order of 0 25 to 0 36 m h velocities derived from observation of the migration of fresh fluids after injection into the granite during stimulation tests are of the same order of magnitude 0 02 to 0 17 m h yielding hydraulic conductivity estimates of 6 6 10 8 to 2 3 10 6 m s 1 both the pressure gradient during the circulation test and the density gradient are related to freshwater injection and can be considered as possibly equivalent to temperature and hydraulic gradients in the rhine graben at least during some specific geological events such as the alpine uplift phases thus the test shows that fluid migration can occur in the upper continental crust exhibiting reservoir properties and these should be taken into account in large scale modelling these properties are in good agreement with a proposed scenario of evolution involving active fluid migration during the eocene alpine uplift phase it also supports the hypothesis of seawater derived saline fluids stored in old fractured shield rocks which implies deep seawater circulation in the continental crust

rock water interactions in hot dry rock geothermal systems field investigations of in situ geochemical behavior abstract two hot dry rock hdr geothermal energy reservoirs have been created by hydraulic fracturing of precambrian granitic rock between two wells on the west flank of the valles caldera in the jemez mountains of northern new mexico heat is extracted by injecting water into one well flowing it through the fractured region and recovering the heated water from the second well the produced fluid is cooled on the surface and reinjected into the system the first reservoir was formed by fracturing the injection well at a depth of 2 75 km where the initial rock temperature was 185 c a heat extraction experiment conducted in this reservoir was run from january 27 to april 13 1978 a second larger reservoir was created after cementing the fracture to wellbore connections at 2 75 km in the injection well and refracturing 180 m deeper this second reservoir was tested from october 23 to november 16 1979 during each of these experiments samples of the geothermal fluids and gases were collected at regular intervals from the injection wellhead the production wellhead and at the make up pump which provided the water from storage ponds to replace the water lost downhole by permeation into the reservoir walls changes in the composition of the produced fluid provide a means for studying the reservoir behaviour under normal recirculating operating conditions certain of the dissolved species appear to be derived by displacement of an indigenous pore fluid while others appear to be derived by dissolving minerals known to be present in the reservoir rock in this paper we describe the results of the chemical analysis of the geothermal fluids and relate the fluid and gas chemistry to geochemical processes that result from the heat extraction experiments in particular the implications of the silica and na k ca geothermometers and the pore fluid displacement theory are examined for insight about the long term effects of fluid geochemistry on heat extraction from hdr reservoirs

origin of cacl brines in devonian formations western canada sedimentary basin abstract the majority of waters in devonian formations of the western canada sedimentary basin are high salinity ca cl brines this relatively rare type of brine is of economic interest because of its association with both oil and hydrothermal ore deposits these brines are important sources of ca2 mg2 and ore metals in sedimentary basins it is possible to generate the ca cl brines by modification of residual evaporite brines the evaporation of devonian sea water produced large quantities of gypsum and halite such as the prairie formation residual brines were not retained in the evaporating system quantities of dense halite saturated brine sufficient to account for the high salinity formation waters in the basin were lost syndepositionally the cl and br content of waters within devonian formations in the basin can be explained by dilution of the residual evaporite brines brine composition was modified as a result of density driven reflux to depths of several kilometers this placed concentrated brines in contact with precambrian basement rocks at elevated temperatures 100 300 c the most important reactions between the brine and basement rocks appear to involve albitization of feldspars further modification of the brines occured as cements formed in devonian carbonates volumetrically the most important of these is dolomite in addition some devonian carbonates were dolomitized during ascent along faults mg2 was lost from hot brines as dolomite formed

the role of isotope geochemistry studies in the canadian nuclear fuel waste management program abstract the objective of the canadian nuclear fuel waste management program is to develop and assess a method for the safe disposal of used nuclear fuel wastes from canadian nuclear power generating facilities the concept that is being developed involves the disposal of these wastes in a cavity mined at a depth of 500 1000 m in a plutonic rock formation both in the assessment of this concept and in any possible future site selection the geochemistry of the rock formation and of the groundwater plays a significant role isotope geochemistry studies involve the determination of the distribution and behaviour of stable and radioactive isotopes in the groundwater and in the rock matrix this information can be used to shed light on the geochemical history of the rock formation under investigation and increase the understanding of the geochemical processes that govern the evolution of these rock formations the information can in principle also be used to date the various geological events and processes that have led to the distribution of radioactive isotopes in the rock and in the groundwater

large scale lithospheric detachment of the downgoing cocos plate the 8 september 2017 earthquake mw 8 2 abstract on 8 september 2017 a great earthquake m w 8 2 took place in the mexican subduction zone in the tehuantepec gap where no large subduction earthquakes have taken place since 1902 however the 8 september earthquake did not occur on the contact between the cocos and north american plates the centroidal hypocentral depths reported by different agencies including the national seismological service range from 45 to 47 4 km placing it immediately beneath the down dip limit of the interplate locked zone the source mechanism reflects down dip tensional faulting the inversion of the fault process shows a rupture that initiated at the bottom of the lithosphere and propagated upward breaking through the entire subducted lithosphere an unusually long complex and copious aftershock sequence followed the main event the relocated aftershocks in the first 20 days following the main event delineate a 160 km long fault sub parallel to the oceanic trench immediately beneath the interplate contact the aftershocks also concentrate in secondary intraslab faults 50 km down dip from the mainshock rupture revealing that pervasive tensional stresses are present within the subducted plate this deformation pattern suggests a large scale tensional regime in the slab apparently induced by its own gravitational weight that pulls it away from the strongly coupled interplate contact other large intraplate earthquakes in the vicinity in 1931 m w 7 8 and 1999 m w 7 5 also reflect this detachment of the downgoing cocos plate that sinks into the mantle under its own gravitational weight the slab detachment suggests that the up dip segment of the plate interface near the isthmus of tehuantepec is locked and possibly primed for a megathrust earthquake such as the m w 8 6 that took place in 1787 on an adjacent segment of the mexican subduction zone

a diffusive ion flux of non marine origin in cumbrian lake sediments implications for element budgets in catchments abstract diffusion controlled concentration gradients of many elements exist in the sediments of derwentwater lake cumbria northern england which indicate hydraulic connection with a reservoir of high salinity water a widely distributed source of saline groundwater beneath cumbria with a composition that is compatible with anomalous surface water chemistry is demonstrated element and stable isotope characteristics indicate that the most likely source of enhanced salinity is from water rock interaction at depth involving the lake district granite batholith and surrounding meta sediments these results demonstrate the permeability and reactivity of basement rocks and suggest also that chloride cannot be regarded as conservative in water balance studies

the significance of viscosity in density dependent flow of groundwater abstract many modeling studies of variable density groundwater flow have been performed in the last few decades in most of these studies fluid density is considered to vary with concentration while the variation of viscosity with concentration is neglected the consequences of this negligence is not completely known the present study uses a numerical simulation approach to investigate the density viscosity concentration relationship during groundwater flow and solute transport through a density stratified system fluid density is assumed to increase with depth from freshwater at the surface through brackish and saline waters to brines at the bottom half of the system the system mimics field observations at the atikokan research area ara in northwestern ontario canada hypothetical unit basin models consisting of recharge midline and discharge area regimes are employed simulations with the density concentration equation of state and a constant freshwater viscosity in the density stratified system causes groundwater to sink against the buoyancy forces of the system more water is recharged into the system than necessitated by the buoyancy the configurations and lengths of travel paths and travel time of conservative contaminants are inaccurately predicted accounting for concentration in the viscosity equation causes groundwater floating in agreement with the expected buoyancy physics of the system overestimation of concentration dependent density causes sinking whereas overestimation of viscosity results in overfloating and underestimation of groundwater recharge even in density stratified fluids with salinity of seawater recharge and through flow of water may be slightly overestimated if a concentration dependent depsity is used along with a constant freshwater viscosity the concentration dependence of both density and viscosity are to be analyzed carefully during groundwater flow and solute transport simulations in systems with considerable fluid density variations

a study of ground motion excitation based on the earthquake of september 8 2017 evidence that normal faults influence the stress parameter we performed a study of ground motion modeling based on multiple linear regression and random vibration theory using the earthquake sequence of september 8 2017 mw 8 2 our results show that there is high attenuation in the region of oaxaca chiapas and central mexico however the peak amplitude excitations of normal fault earthquakes are higher than those of thrust fault earthquakes the earthquake sequence involved a large number of events but not all the seismic events were aftershocks because many earthquakes had different rupture styles the thrust events follow a simple scaling relation with a constant stress parameter but the normal fault events are difficult to represent with a constant self similar model our best result consists of a q 0 240 pm 032 with a frequency dependent factor of 0 63 pm 0 05 the excitation term is well determined with a stress parameter of 80 bars for the thrust faults but for the normal faults the stress parameter is at least 180 bars with a non self similar model our results show that it is necessary to include new ground motion prediction equations in seismic hazard analysis for meganormal faults which have not previously been considered in subduction zones

the supergene origin of ruthenian hexaferrum in ni laterites for two decades the nature of fe rich oxygen bearing ru os compounds found in the supergene environment has been debated ru os fe oxides and nano intergrowths of ruthenium with magnetite have b

supergene neoformation of pt ir fe ni alloys multistage grains explain nugget formation in ni laterites ni laterites from the dominican republic host rare but extremely platinum group element pge rich chromitites up to 17 5 ppm without economic significance these chromitites occur either included in saprolite beneath the mg discontinuity or as floating chromitites within limonite above the mg discontinuity both chromitite types have similar iridium group pge ipge enriched chondrite normalized patterns however chromitites included in limonite show a pronounced positive pt anomaly investigation of heavy mineral concentrates obtained via hydroseparation techniques led to the discovery of multistage pge grains i os ru fe ir grains of porous appearance are overgrown by ii ni fe ir and ir fe ni pt phases which are overgrown by iii pt ir fe ni mineral phases whereas ir dominated overgrowths prevail in chromitites from the saprolite pt dominated overgrowths are observed within floating chromitites the following formation model for multistage pge grains is discussed i hypogene platinum group minerals pgm e g laurite are transformed to secondary pgm by desulphurization during serpentinization ii at the stages of serpentinization and or at the early stages of lateritization ir is mobilized and recrystallizes on porous surfaces of secondary pgm serving as a natural catalyst and iii at the late stages of lateritization biogenic mediated neoformation and accumulation of pt ir fe ni nanoparticles occurs the evidence presented in this work demonstrates that in situ growth of pt ir fe ni alloy nuggets of isometric symmetry is possible within ni laterites from the dominican republic

feasibility of estimating cementation rates in a brittle fault zone using sr ca partition coefficients for sedimentary diagenesis abstract cement phases such as calcite or quartz often incorporate trace elements from the parent fluids as they crystallize experimental sedimentary diagenesis indicates that trace element partition coefficients reflect rates of cementation the applicability of these findings to fault zone cementation is examined as we make a preliminary attempt to estimate calcite cementation rate in a brittle fault zone directly from the fault rock composition data samples for this study were collected from the knoxville outcrop of the saltville fault in tennessee the cementation rates for the fault rock samples range from 1 10 12 to 3 10 13 m 3 h per m in agreement with some experimental rates and the rates reported for samples from the dsdp sites when applied to a non responsive pore system model these rates result in rapid precipitation sealing indicating the influence exerted by the surface area volume ratio of the pore network we find it feasible to obtain a reasonable range of values for the cementation rate using the trace element partition method however the study also indicates the need for relatively accurate values for the trace carrier element ratio in the fault zone syntectonic pore fluid and exhumed cement

kinematic earthquake source inversion and tsunami runup prediction with regional geophysical data rapid near source earthquake source modeling relying only on strong motion data is limited by instrumental offsets and magnitude saturation adversely affecting subsequent tsunami prediction seismogeodetic displacement and velocity waveforms estimated from an optimal combination of high rate gps and strong motion data overcome these limitations supplementing land based data with offshore wave measurements by seafloor pressure sensors and gps equipped buoys can further improve the image of the earthquake source and prediction of tsunami extent inundation and runup we present a kinematic source model obtained from a retrospective real time analysis of a heterogeneous data set for the 2011 mw9 0 tohoku oki japan earthquake our model is consistent with conceptual models of subduction zones exhibiting depth dependent behavior that is quantified through frequency domain analysis of slip rate functions the stress drop distribution is found to be significantly more correlated with aftershock locations and mechanism types when off shore data are included the kinematic model parameters are then used as initial conditions in a fully nonlinear tsunami propagation analysis notably we include the horizontal advection of steeply sloping bathymetric features comparison with post event on land survey measurements demonstrates that the tsunami s inundation and runup are predicted with considerable accuracy only limited in scale by the resolution of available topography and bathymetry we conclude that it is possible to produce credible and rapid kinematic source models and tsunami predictions within minutes of earthquake onset time for near source coastal regions most susceptible to loss of life and damage to critical infrastructure regardless of earthquake magnitude

constraining the source of the m w 8 1 chiapas mexico earthquake of 8 september 2017 using teleseismic and tsunami observations the september 2017 chiapas mexico normal faulting intraplate earthquake mw 8 1 occurred within the tehuantepec seismic gap offshore mexico we constrained the finite fault slip model of this great earthquake using teleseismic and tsunami observations first teleseismic body wave inversions were conducted for both steep np 1 and low angle np 2 nodal planes for rupture velocities vr of 1 5 4 0 km s teleseismic inversion guided us to np 1 as the actual fault plane but was not conclusive about the best vr tsunami simulations also confirmed that np 1 is favored over np 2 and guided the vr 2 5 km s as the best source model our model has a maximum and average slips of 13 1 and 3 7 m respectively over a 130 km 80 km fault plane coulomb stress transfer analysis revealed that the probability for the occurrence of a future large thrust interplate earthquake at offshore of the tehuantepec seismic gap had been increased following the 2017 chiapas normal faulting intraplate earthquake

chromitites in ophiolites how where when why part i a review and new ideas on the origin and significance of platinum group minerals abstract platinum group minerals are the dominant control on the budget of platinum group elements in ophiolitic chromitites they vary widely in distribution morphology chemistry and os isotope compositions their distribution in different types of chromitites and different microstructural sites within them may reflect the role of chromite as a physical collector of the platinum group elements during crystallisation of both phases from melts the platinum group minerals show significant os isotope heterogeneity on the scale of single micrometric grains enclosed within individual chromite grains this micro scale isotopic heterogeneity and their random spatial distribution within the chromites argue strongly against an origin of the platinum group minerals via exsolution from the chromite lattice during post magmatic cooling a re interpretation of their microstructures and os isotopes analysed in situ had led us to review the traditional models and to propose several origins for the platinum group minerals in chromitites 1 the suites of platinum group minerals mainly record crystallisation during mixing of multiple different melts and physical entrapment in chromite 2 some platinum group minerals in chromitites may have been scavenged from wall rock peridotite during migration of the parental melts of the chromitite 3 other platinum group minerals may have precipitated from metasomatic fluid melts that infiltrated existing chromitites the recrystallization of pre existing platinum group minerals during polyphase metamorphism or recycling of the chromitite into deeper mantle levels can explain the presence of micrometric platinum group minerals with distinct os isotope compositions

the origin and evolution of base metal mineralising brines and hydrothermal fluids south cornwall uk abstract a fluid inclusion geochemical study has been carried out on quartz from post variscan quartz carbonate base metal sulphide anhydrite fluorite veins hosted by palaeozoic basement porthleven menheniot cornwall and permo triassic sediments western approaches data indicate that the base metal mineralising fluids have a similar bulk chemical composition to the saline fluids found in the permo triassic basinal sequence and support the hypothesis that these basins are the source of the mineralising fluids cl and br systematics suggest that the brines were formed either by the evaporation of seawater or a seawater meteoric water mixture past the point of halite precipitation the major cation composition na ca k mg of the brines is not consistent solely with evaporation processes but may be explained by dolomitisation processes albitisation processes or both which are recognised in the basinal sequences the presence of seawater in the base metal mineralised veins suggests that the first marine incursions late triassic into the region must act as a lower age limit for the mineralisation the halogen chemistry of a second hotter 200 c more dilute 0 5 wt fluid identified in fault hosted e w trending veins in the porthleven area suggests that the chlorinity of these fluids has a magmatic origin circulation of these fluids in post variscan extensional structures was driven by the local high heat producing cornubian batholith the local high heat producing granites provided fracture permeability and a heat source that heated the base metal mineralising fluids as they entered the horst block and the dilute fluids circulating around the granites petrographic evidence suggests that both palaeohydrologic systems were active contemporaneously however each flow system was isolated in differently orientated structures and there is little evidence for fluid mixing

energy extraction from fractured geothermal reservoirs in low permeability crystalline rock two hot dry rock geothermal energy reservoirs were created by hydraulic fracturing of precambrian granitic rock on the west flank of the valles caldera a dormant volcanic complex in the jemez mountains of northern new mexico heat was extracted in a closed loop mode of operation injecting water into one well and extracting the heated water from a separate production well the first reservoir was produced by fracturing the injection well at a depth of 2 75 km where the indigenous rock temperature was 185 c the relatively rapid decline in temperature of the water produced from the first reservoir 100 c in 74 days indicated an effective fracture radius of about 60 m with an average thermal power extracted of 4 mw a second larger reservoir was created by refracturing the injection well 180 m deeper downhole measurements of water temperature at the reservoir outlet as well as temperatures inferred from chemical geothermometry showed that the thermal decline of this reservoir was negligible the effective heat transfer area of the new reservoir must be at least 45 000 m2 nearly 6 times larger than the first reservoir in addition reservoir residence time studies employing visible dye tracers indicated that the mean volume of the second reservoir is 9 times larger other measurements showed that flow impedances were low and that downhole water losses from these reservoirs should be manageable the geochemistry of the produced water was essentially benign with no scaling problems apparent moreover the level of induced seismic activity was insignificantly small

garnierites and garnierites textures mineralogy and geochemistry of garnierites in the falcondo ni laterite deposit dominican republic abstract garnierites ni mg bearing phyllosilicates are significant ore minerals in ni laterites of the hydrous silicate type in the falcondo ni laterite deposit dominican republic garnierites are found within the saprolite horizon mainly as fracture fillings and thin coatings on joints field observations indicate an important role of active brittle tectonics during garnierite precipitation different greenish colours and textures can be distinguished which correspond to different mineral phases defined according to x ray diffraction xrd and electron microprobe emp analyses a talc like 10 a type b serpentine like 7 a type c a mixture of talc and serpentine like and d sepiolite like types compositional data indicate continuous mg ni solid solution along the joins lizardite nepouite serpentine like kerolite pimelite talc like and sepiolite falcondoite sepiolite like in general talc like garnierite is dominant in falcondo ni laterite and displays higher ni contents than serpentine like garnierites emp analyses showing deviations from the stoichiometric mg ni solid solutions of serpentine and talc are best explained by talc and serpentine like mixing at the nanoscale a detailed textural study by means of quantified x ray element imaging provides a wealth of new information about the relationships between textural position sequence of crystallization and mineral composition of the studied garnierite samples these results indicate several stages of growth with variable ni content pointing to recurrent changes in the physical chemical conditions during garnierite precipitation in addition our detailed mineralogical study of the falcondo garnierites revealed that the different types identified have characteristic h 2 o content and sio 2 mgo ratios which play important roles during the pyrometallurgy process

characterisation and isotopic evolution of saline waters of the outokumpu deep drill hole finland implications for water origin and deep terrestrial biosphere abstract the isotopic composition of water and dissolved sr as well as other geochemical parameters at the 2516 m deep outokumpu deep drill hole finland were determined the drill hole is hosted by palaeoproterozoic turbiditic metasediments ophiolite derived altered ultramafic rocks and pegmatitic granitoids sodium ca cl and ca na cl rich waters total dissolved solids up to ca 70 g l 1 containing significant amounts of gas mainly ch 4 up to 32 mmol l 1 n 2 up to 10 mmol l 1 h 2 up to 3 1 mmol l 1 and he up to 1 1 mmol l 1 discharge from fracture zones into the drill hole this water is distinct from the shallow fresh groundwater of the area and has an isotopic composition typical of shield brines that have been modified during long term water rock interaction based on water stable isotopes and geochemistry the drill hole water profile can be divided into five water types each discharging from separate fracture systems and affected by the surrounding rocks the 2 h varies from 90 to 56 vsmow and 18 o from 13 5 to 10 4 vsmow plotting clearly above the global and local meteoric water lines on a 2 h vs 18 o diagram the 87 sr 86 sr ratios range between 0 72423 and 0 73668 simple two component mixing between 2 h and 18 o rich end member brine and meteoric water cannot explain the water stable isotopic composition and trends observed instead hydration of silicates by ancient groundwaters recharged under different climatic conditions warmer than at present is the most likely mechanism to have caused the variation of the 2 h and 18 o values water types correlate with changes in microbial communities implying that different ecosystems occur at different depths the different water types and microbial populations have remained isolated from each other and from the surface for long periods of time probably tens of millions of years

factors controlling groundwater quality in eastern united arab emirates a chemical and isotopic approach abstract chlorine 36 along with oxygen and hydrogen isotopes and selected major ions were used to investigate the factors controlling groundwater quality in the eastern part of the united arab emirates two main aquifers occupy the study area the eastern gravel plain aquifer that occurs near the coastal area and the inland ophiolite aquifer previous studies suggest that groundwater particularly in the eastern gravel plain aquifer is affected by seawater intrusion and evaporation samples of groundwater from the eastern gravel plain aquifer cl 1000 mg l have r 36 cl values in the range of 13 3 17 4 10 15 while those from the ophiolite aquifer cl 36 cl values in the range of 20 118 10 15 these values indicate the presence of bomb produced 36 cl and are consistent with recent post 1950 recharge of most of the samples d 18 o relationship plots on a typical evaporation line which suggests potential evaporation of the recharging waters prior to infiltration the r 36 cl values of the coastally bound eastern gravel plain aquifer are lower than the ophiolite aquifer which suggests an additional input of chloride to this aquifer moreover in most cases the chloride concentration is not balanced by the concentrations of other cations such as sodium potassium calcium or magnesium seawater intrusion is thus ruled out measurements of bromide concentrations support the contention that organically bound cl is being released into this environment agricultural practices which are extensive in this region are a possible source also sodium and silica concentrations provide evidence for the release of these elements by the weathering of host rocks

behaviour of major elements and some trace elements li rb cs sr fe mn w f in deep hot waters from granitic areas abstract analyses of selected hot springs in more than sixty areas in granites from europe are presented concentrations of major elements and of some trace elements li rb cs sr fe mn w f in high ph waters are not significantly affected by processes during uprise from the deep reservoir to the surface re equilibrations mixing with surficial waters normalized to k or na concentrations of all other elements are related to the aquifer temperature the knowledge of aquifer temperature and total electric charge of mobile elements cl s possibly f allows us to predict both major elements within 50 and trace elements within a factor 2 or 3 concentrations in alkaline waters from granites

the character and evolution of hydrothermal fluids associated with the kaolinized st austell granite sw england a complex assemblage of fluid inclusions is present in quartz from the st austell granite homogenization temperatures range from below 100 c to above 570 c and salinities vary from

exotic stable isotope compositions of saline waters and brines from the crystalline basement the overwhelming majority of groundwaters reported in literature show isotopic compositions that place them on or right of the meteoric water line mwl in a 2h vs 18o diagram a closer look to the steadily increasing data from the deeper crystalline basement reveals nevertheless that points left of the mwl are not so unusual as has been suggested during the last decades their supposed rareness seems to be due to a bias of sampling the concerned fluids develop only at greater depths and in low permeability environments which makes access to them so difficult paradoxically exotic stable isotope compositions may be the rule in a restricted depth zone in all crystalline basements with slow groundwater movements but not too high temperatures the present study takes stable isotope data on saline fluids from the deep french granitic basement as a starting point in order to situate the french data from the vienne region in a more general context a literature review has been undertaken assembling more than 1300 stable isotope analyses of waters and brines in crystalline rocks from stable cratons and mountain belts world wide the french fluids show some particular features with respect to the majority of other studies as their major ion composition close to seawater or a significant isotopic shift at relatively low salinities detailed knowledge on the hydrological and chemical history of the site allowed to develop a conceptual model of isotopic evolution by interaction of fracture fluids with fracture minerals this model considers interactions of the last fluids flushing the system marine water unaltered evaporated or diluted with previously precipitated mineral phases and the neoformation of the last generation of fracture minerals the model has been tested quantitatively for several combinations of dissolution precipitation reactions involving formation of carbonates clay minerals and fe hydroxides most of the modelled scenarios would leave the residual liquid phase depleted in 18o and either enriched or depleted in 2h and produce waters with isotopic signatures corresponding to the observed 2h vs 18o correlation it is therefore suggested that the general phenomenon of an isotopic shift in deep fissured silicate rocks which seems to be rather independent of lithology may result from a combination of different reaction mechanisms implying not solely the rock matrix but also the different generations of fracture minerals

br cl ratios and o h c and b isotopic constraints on the origin of saline waters from eastern canada saline groundwaters were recovered from undisturbed restigouche deposit and active brunswick 12 mine zn pb volcanogenic massive sulfide deposits in the bathurst mining camp bmc northern new brunswick canada these groundwaters along with fresh to brackish meteoric ground and surface waters from the bmc have been analyzed to determine their major trace element and stable isotopic o h c and b compositions saline groundwaters total dissolved solids 22 45 g l are characterized by relatively high na ca ratios compared to brines from the canadian shield and low na clmolar and d 11 b isotopic compositions 2 5 to 11 1 compared to seawater although saline waters from the canadian shield commonly have oxygen and hydrogen isotopic compositions that plot to the left of the global meteoric water line those from the bmc fall close to the water line fracture and vein carbonate minerals at the restigouche deposit have restricted carbon isotopic compositions of around 5 to 6 the carbon isotopic compositions of the saline waters at the restigouche deposit 12 d 13 cdic are the result of fractionation of dissolved inorganic carbon by methanogenesis we suggest that unlike previous models for shield brines the composition of saline waters in the bmc is best explained by prolonged water rock reaction with no requirement of precursor seawater we suggest that elevated br cl ratios of saline waters compared to seawater may be explained by differential uptake of br and cl during groundwater evolution through water rock reaction 2007 elsevier ltd all rights reserved

platinum group minerals pgm in the falcondo ni laterite deposit loma caribe peridotite dominican republic two ni laterite profiles from the loma caribe peridotite dominican republic have been investigated for their platinum group element pge geochemistry and mineralogy one profile loma peguera i

u th he geochronology of goethite and the origin and evolution of cangas abstract u th he geochronology of 147 grains of goethite cements extracted from ferruginous duricrusts cangas developed on banded iron formations from the quadrilatero ferrifero region minas gerais brazil records a history of protracted mineral dissolution reprecipitation that started at ca 48 1 4 8 ma and continues intermittently until the present a large majority of the samples more than 30 are younger than 2 ma revealing active mineral dissolution reprecipitation in the recent past within cangas goethite cements are younger near the surface and become progressively older towards the bottom of the weathering profile indicating that iron is more effectively cycled in the parts of the weathering profile more strongly affected by biogenic activity u th he geochronology of 14 goethite grains from saprolites in the same profiles yield results ranging from 55 3 5 5 to 25 7 2 6 ma for a single weathering profile goethite cements from cangas are invariably younger than goethite grains from the underlying saprolite indicating that the duricrust and the saprolite behave as independent and separate systems responding to different environmental controls thorium shows conservative behaviour during goethite dissolution reprecipitation and it is enriched towards the surface of the weathering profile uranium on the other hand is preferentially leached from the surface into the saprolite or out of the weathering profile recurrent goethite dissolution reprecipitation lends great textural complexities to cangas but it is also responsible for its capacity to reheal when physically disrupted this self healing property accounts for canga s role in armoring banded iron formation landscapes

geochemical study on natural gas and water discharges in the southern latium italy circulation evolution of fluids and geothermal potential in the region abstract the waters discharged in southern latium south of rome are mainly meteoric in origin two types of circulation occur in the region one infiltrates the carbonate sediments outcropping in the area and emerges from fractures along their borders the other consists of waters that infiltrate and circulate essentially within the albani volcanic rocks the first type produces either alkaline earth bicarbonate sulfate waters or if they mix with fossil marine waters or interact with recent marine sediments alkaline chloride waters on the pontina plain the chemistry of the waters produced by the second type of circulation alkaline earth bicarbonate or alkaline bicarbonate is strictly related to their gaseous phases which consist for the most part of the co 2 produced at depth silica and gas geothermometers whose results correlate well indicate that low enthalpy fluids 80 c are present throughout the study area with the exception of the northwestern part where medium enthalpy fluids 150 c also appear

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

geochemical results of a single well hydraulic injection test in an experimental hot dry rock geothermal reservoir soultz sous foreˆts alsace france abstract as part of the investigation of the hot dry rock hdr potential of the soultz test site 25 300 m 3 of fresh water were injected into borehole gpki in granite between depths 2850 and 3400 m the returned fluids were chemically monitored during the 57 h of production that followed the 21 h of shut in time and there is evidence of mixing and water rock interactions although the chemical composition of the two sampled indigenous fluids 1817 m and 3485 m depth which circulate at various levels in the granite is very similar participation of both fluids in mixing with injected water has been revealed from the slight chemical differences this test also suggests evidence for the presence of a third fluid the large volume of injected water induced greater cooling of the reservoir than in previous tests and a temperature effect on water rock interactions has been demonstrated there is release of mg and of sio 2 and f to a lesser extent whereas so 4 release is greater because it is partly related to anhydrite dissolution mixing of the injected water with the highly saline indigenous fluid conceals part of the water rock interactions because there is no evidence of the release of major elements k na however trace elements are useful for determining some dissolution reactions for example relatively high concentrations of f and relatively low 87 sr 86 sr ratios the presence of the brine also induces some chemical reactions as it increases calcite and anhydrite solubility lithium and b in the indigenous fluid are taken up during the test and adsorption reactions on solid surfaces are proposed as an explanation for this depletion chemical monitoring during this single well hydraulic test has proved relevant for determining which parts of the processes dissolution and precipitation are liable to modify the physical properties of the reservoir during fluid circulation for energy extraction particularly in the vicinity of the injection borehole

87sr 86sr values in groundwaters of the east bull lake pluton superior province ontario canada abstract the east bull lake pluton is a 2 48 ga old layered mafic intrusion located on the southern margin of the superior province precambrian shield in ontario canada the groundwaters have been studied as part of a detailed geological mapping and geochemical study of the pluton for the canadian nuclear fuel waste management program all groundwater samples are dilute the most concentrated na cl type water contains 3 1 g l total dissolved solids present day87sr 86sr values of the rock samples varies from 0 705 to 0 714 and the groundwaters from 0 711 to 0 720 the ca hco3 recharge waters show the greatest range in values in contrast to the deeper na hco3 and deep na cl waters where a narrow range of 0 712 0 713 is found fracture filling laumontite calcite and gypsum have the same isotopic signature as the deep water the ca hco3 water is the youngest component of the groundwater system and its spread in isotopic values reflects local conditions at the surface the na cl water is considered to be the oldest component and its sr isotopic ratio value indicates equilibration with silicate fracture mineral phases the isotopic data suggest that laumontite calcite and gypsum fracture phases have either crystallized from this water or are currently controlling its isotopic composition by dissolution no age can be assigned to the deep waters except that the na cl component may date from the early paleozoic based on geological arguments or more likely be 104 106 years old based on kinetic studies of rock water interaction and other isotopic data if seawater was one component of the na cl water history there is no record of this in the87sr 86sr ratios

geothermal mineral equilibria the dominant reaction determining the chemistry of fluids in a geothermal system of the new zealand type consists of the conversion of primary plagioclase by co2 to calcite and clays with log pco2 15 26 7850 t 273 2 temperature t in c subsequent reactions involving secondary minerals control relative co2 h2s contents the distribution of mineral phases throughout a geothermal system reflects the stepwise conversion of thermodynamically unstable primary phases through a series of intermediate metastable phases to a thermodynamically stable secondary assemblage the relative stabilities of these phases was evaluated on the basis of their solubilities the least soluble aluminiumsilicate representing the thermodynamically most stable phase under a given set of conditions observed assemblages of secondary minerals in geothermal systems represent indicators allowing mineral fluidinteraction conditions to be evaluated on the basis of multi component mineral stability diagrams

nanoscale constraints on the in situ transformation of ru os ir sulfides to alloys at low temperature abstract we report new results of a combined focused ion beam high resolution transmission electron microscopy fib hrtem investigation of two grains of platinum group minerals pgm corresponding to the laurite rus2 erlichmanite oss2 solid solution series the grains are included within unaltered chromite and the serpentine dominant matrix of the mantle hosted chromitite body of monte bueno in eastern cuba at the micron scale the grain hosted in unaltered chromite preserves magmatic features including a complex oscillatory zoning defined by a core of erlichmanite surrounded by alternating bands of os rich os poor laurite revealed by conventional field emission scanning electron microscopy fe sem and x ray mapping by electron microprobe analyzer epma combining high magnification hmem high angle annular dark field haadf images and the corresponding energy dispersive spectra eds the elemental mappings acquired using hrtem showed that the oscillatory zoning occurs at both the micron and nano scales a specific feature highlighted by hrtem observations is the rather complex structure of the erlichmanite core consisting of an aggregation of much smaller cores

geochemical and boron oxygen and hydrogen isotopic constraints on the origin of salinity in groundwaters from the crystalline basement of the alpine foreland abstract the b isotopic composition in combination with o and h isotopes and hydrochemical tracers is utilized to constrain the evolution of basement hosted groundwaters via water rock interactions and fluid infiltration from external sedimentary reservoirs two distinct groundwater types have been identified in the central european crystalline basement n switzerland sw germany 1 fresh groundwaters characterized by low values of 11b 3 5 to 0 6 18o 12 0 to 10 0 and d 86 8 to 71 9 and 2 brackish groundwaters with distinctly heavier b o and h isotopic compositions 11b 6 4 to 17 6 18o 9 4 to 5 6 d 67 6 to 60 8 fresh groundwaters show a systematic decrease in 11b related to an increase in b concentrations and degree of total mineralization along the pathway of groundwater migration which can only be interpreted in terms of leaching of crystalline host rocks a 11b value of 3 3 is inferred for the crustal b source mainly hercynian granites involved in the leaching process in agreement with the known 11b range of granitic rocks the evolution of brackish groundwaters derived from crystalline basement reservoirs with little water circulation is more complex as indicated by b o h stable isotope and hydrochemical e g b cl na cl and br cl constraints brackish groundwaters from the study area are influenced by admixture of sediment derived fluids which infiltrated from late paleozoic permo carboniferous and early mesozoic lower triassic sedimentary strata the data presented show that b isotopes are sensitive to mixing processes of fluids derived from different crustal reservoirs and hence may be utilized as a tracer for constraining the internal autochthonous vs external allochthonous origin of salinity in basement hosted groundwaters

platinum group element and gold enrichment in soils monitored by chromium stable isotopes during weathering of ultramafic rocks abstract weathering of ultramafic rocks can lead to the formation of soil profiles with high contents of fe ni co platinum group elements pge and gold traditionally these metal rich soils are known as laterites and are formed under tropical climates and stable tectonic conditions however little is known about their possible development in cold humid regions and the factors governing pge and gold mobility and enrichment under these weathering conditions are poorly constrained in this study five soil profiles developed on serpentinized chromite bearing ultramafic rocks at la cabana located in the coastal range of south central chile 38 s were studied by combining major and trace element geochemistry with chromium stable isotope data the results show that the soils developed at la cabana have higher pge and au contents than the parent serpentinite rock with pge and au reaching up to 160 ppb and 29 ppb in a limonitic soil horizon and clay saprolite respectively most soil samples have slightly negative 53 52crsrm979 values within a range of 0 089 0 012 to 0 320 0 013 average of 0 178 and are in agreement with previous data reported for modern soils a noteworthy relation between 53 52cr data and pge au contents is observed in the studied soil horizons where isotopically lighter values of 53 52cr match the higher contents of pge and gold these results show that pedogenetic processes operating at the cold and humid la cabana area are capable of increasing the total pge and au contents of certain soil horizons such processes are complex and multivariate but are primarily modulated by chromite dissolution and the formation of secondary phases such as clay minerals and oxy hydroxide phases in the soil these findings provide evidence that important weathering and pge au supergene accumulation are not only restricted to tropical latitudes and that the chromium isotope system is a useful proxy to track surface redox process and noble metal enrichment during pedogenesis

constraining permeabilities in a large scale groundwater system through model calibration abstract the range of field estimates of permeabilities in rocks of the atikokan research area ara canada has been reduced by calibrating a groundwater flow model of the ara the flow model was calibrated to the recharge component of the water balance and to measured freshwater heads in boreholes a good match between field and simulated recharge and between measured and simulated heads was obtained with two different permeability depth distributions that differed by up to two orders of magnitude in places solute transport simulation of the distributions of total dissolved solids tds chlorides cl and oxygen 18 18 o in groundwater in the area was performed to further refine the permeability estimates vertical average linear groundwater velocities from the calibrated flow model were used in one dimensional solute transport models of the system to generate depth concentration profiles of tds cl and 18 o recharge midline and discharge area models of both the fracture zones and the rock mass were employed the midline area is the narrow zone that separates the recharge downward flow area from the discharge upward flow area groundwater flow is essentially horizontal in the midline area envelopes formed by the simulated profiles that were created with the velocities of one simulation case more tightly enclosed the field data tds cl 18 o than those of another simulation case indicating that velocities of the former simulation case better represent the hydrodynamics of the real system the models demonstrate that the scatter of tds cl and 18 o field data for the ara is consistent with the groundwater flow model predictions and can be explained by the complexity arising from different hydraulic regimes recharge midline discharge and hydrogeologic environments fracture zones rock mass of the regional flow system solute transport simulation of hydrochemical constituents can aid in refining and constraining permeabilities in large scale groundwater systems

ni phyllosilicates garnierites from the falcondo ni laterite deposit dominican republic mineralogy nanotextures and formation mechanisms by hrtem and aem ni bearing magnesium phyllosilicates garnierites are significant ni ores in ni laterites worldwide the present paper reports a detailed tem investigation of garnierites from the falcondo ni laterite deposit dominican republic different types of garnierites have been recognized usually consisting of mixtures between serpentine and talc like phases that display a wide range of textures at the nanometer scale in particular chrysotile tubes polygonal serpentine and lizardite lamellae are intergrown with less crystalline talc like lamellae samples consisting uniquely of talc like and of sepiolite falcondoite were also observed occurring as distinctive thin lamellae and long ribbon shaped fibers respectively hrtem imaging indicates that serpentine is replaced by the talc like phase whereas tem aem data show preferential concentration of ni in the talc like phase we suggest therefore that the crystallization of ni bearing phyllosilicates is associated with an increase in the silica activity of the system promoting the replacement of the ni poor serpentine by the ni enriched talc like phase these results have interesting implications in material science as garnierites are natural analogs of ni bearing phyllosilicate supported synthetic catalysts finally saed and hrtem suggest that the ni bearing talc like phase corresponds to a variety of talc with extra water showing larger d 001 than talc i e 9 2 9 7 a described as kerolite pimelite in clay mineral literature

the 2017 mexico tsunami record numerical modeling and threat assessment in costa rica an mw 8 2 earthquake and tsunami occurred offshore the pacific coast of mexico on 2017 09 08 at 04 49 utc costa rican tide gauges have registered a total of 21 local regional and far field tsunamis the quepos gauge registered 12 tsunamis between 1960 and 2014 before it was relocated inside a harbor by late 2014 where it registered two more tsunamis this paper analyzes the 2017 mexico tsunami as recorded by the quepos gauge it took 2 h for the tsunami to arrive to quepos with a first peak height of 9 35 cm and a maximum amplitude of 18 8 cm occurring about 6 h later as a decision support tool this tsunami was modeled for quepos in real time using commit community model interface for tsunami with the finer grid having a resolution of 1 arcsec 30 m however the model did not replicate the tsunami record well probably due to the lack of a finer and more accurate bathymetry in 2014 the national tsunami monitoring system of costa rica sinamot was created acting as a national tsunami warning center the occurrence of the 2017 mexico tsunami raised concerns about warning dissemination mechanisms for most coastal communities in costa rica due to its short travel time

water rock interactions during experiments within the geothermal hot dry rock borehole gpk1 soultz sous foreˆts alsace france abstract hydraulic injection backflow tests were carried out in borehole gpk1 at a site designed for geothermal hot dry rock experiments located in the rhine graben near soultz sous fore ts france the injected fresh water was in contact with granite at 137 c for a few hours through the monitoring of the chemical composition of the production fluids it was noticed that substantial mixing with the indigenous brine from the granite and chemical exchanges between the granite and the fluids release of co 2 so 4 f ba and sio 2 took place the mineralogical origin of these components is discussed it appears that at least calcite biotite sulphide minerals and feldspar were dissolved from the rock for most of the components the dissolution kinetics are very fast during the first steps of the interaction and then slow down after a few minutes sulphate concentration data indicate that the fluid entered into different fractures the chemical compositions of both the indigenous brine and the injected fresh water are relevant to determine the behaviour of the minerals

water rock interaction processes in the triassic sandstone and the granitic basement of the rhine graben geochemical investigation of a geothermal reservoir saline fluids have been collected in the rhine graben over the last two decades both from the triassic sandstone aquifer and the granitic basement down to a depth of 3500m their salinities and location are compared in order to distinguish the respective influences of temperature and host rock mineralogy in the water rock interaction processes the comparison shows that sulphates in the sedimentary formations were dissolved by the fluids which also led to br enrichment mica dissolution has strongly increased the rb and cs contents which then provide an indication of the degree of water rock interaction the sr isotopic ratios are used to compare the fluids with the granite minerals two relationships are revealed for the fluids in the sandstone and the granite one related to widespread mica dissolution which could have affected both the buntsandstein and the granite and the other to subsequent plagioclase dissolution which is observed only in the granite computations showed that 12 5g of mica and 1 658 of plagioclase per liter of fluid have been dissolved the nature of these two relationships suggests two different evolutions for the fluids and the individualization of the two reservoirs during the graben s history the cation concentrations are mainly controlled by temperature and are independent of the type of host rock equilibrium with the rock mainly caused ca and k concentration variations which has induced clear ca k and ca 18o k 18o correlations geothermometric computations indicate that with increasing depth the cations the silica and the 18o so4 geothermometers evolve towards a value close to 230 c this demonstrates the existence of a hot reservoir in the granite of the graben at a depth estimated at 4 5 5 km