undersea longwall mining subsidence with special reference to geological and water occurrence criteria in the north east of england coalfield abstract to date the use of classical statistical techniques for the identification and analysis of parameters which control the occurrence of water on longwall panels has proved inconclusive an alternative and potentially more meaningful approach is to examine the interaction between the tensile strain induced by mining and the geological and hydrogeological environment surrounding the workings after a brief description of the geology and hydrogeology of the north east of england coalfield the paper examines in detail the water yield predicted tensile strain and geological strain water relationship occurring at four collieries with extensive undersea workings blackhall horden dawdon and westoe in each case water occurrences can be correlated with either faces worked in the vicinity of a major fault where aquifer horizons are displaced against coal measures strata overlying the working horizon or areas where the amount of cover to the base of the major aquifer horizon thins appreciably or a well developed potentially water bearing sandstone horizon exists within the intervening coal measures strata

the susceptibility of uk groundwaters to acidic deposition the weathering of minerals at shallow depths provides much of the sink for acidic atmospheric deposition the geology of the uk has been divided into four classes according to the extent to which the bedrock is likely to provide buffering and possibly give rise to acidic surface or groundwaters other modifying factors including soils superficial deposits and land use are also considered the likely sources and sinks of h in shallow groundwater systems are also reviewed most available groundwater data are derived from major aquifers often in carbonate bearing lithologies which afford excellent buffering and which are unlikely ever to be adversely affected by acidic deposition relatively few data exist for shallow groundwaters widely used for domestic supplies in rural areas especially in western and northern britain where groundwaters might be most affected acidic groundwaters and or surface waters are defined on the basis of their alkalinity and calcite saturation index si c acidic groundwaters are most likely to occur where 1 acid soils are found and glacial drift is thin or absent 2 the source of acidic inputs is high 3 carbonate minerals are absent 4 the residence time of water is short low alkalinity groundwater is found in many sandstone lithologies including the sherwood sandstone a major uk aquifer many lower palaeozoic strata and granites however existing data for susceptible areas are insufficient to show whether or not there have been significant long term changes in groundwater acidity or alkalinity

water supply to britain s eastern coastal defences in the 18th century and the work of sir thomas hyde page 1746 1821

gold deposits and hydrothermal eruption breccias associated with a maar volcano at wau papua new guinea emplacement of endogenous domes and eruption of pyroclastic flows in the morobe goldfield took place in the interval from 4 to 2 4 m y ago during the later part of this time interval following tilting of the ignimbrite pile a maar was generated at wau the subjacent diatreme is believed to extend downward for about 1 km to a regional dip slip fault zone which hosts deeper level gold mineralization at the nearby ribroaster mine following initial maar formation hydrothermal brecciation and gold deposition were controlled by low angle extensional faults which developed during incipient subsidence of a wedge of poorly supported rock between the regional fault zone and the ring fault delimiting the maar epiclastic sedimentation was widespread in the maar volatile depleted magma reached the surface around the perimeter of the maar during active sedimentation and constructed two principal endogenous domes one dacitic and the other andesitic the dacitic dome dated previously at 2 4 m y gave rise to an apron of crumble breccia along the northwestern edge of the maar accumulation of the intramaar sequence was accompanied and followed by widespread subsidence and slumping which resulted in steep dips and locally overturned beds the regional drainage system eventually breached the crater rim and resulted in deposition of channel conglomerates and fluviolacustrine beds all carrying alluvial gold radiocarbon dating of wood from this unit showed that it accumulated 42 000 years ago the most recent events at wau are believed to be a series of hydrothermal eruptions which constructed a composite breccia apron at koranga crater on the southeastern edge of the maar the most recent eruption is tentatively inferred to have taken place in 1967 modified journal abstract

basement hydrogeology and fortification of the channel islands legacies of british and german military engineering the islands of jersey guernsey alderney and sark lie close to the normandy coast of france they expose a largely precambrian crystalline basement of metamorphic and igneous rocks jersey and alderney also expose some early palaeozoic clastic sediments and all have a thin but widespread quaternary sedimentary cover the three largest islands were progressively fortified by the british between the early 13th and mid 19th centuries and by german forces during occupation in world war ii a legacy illustrated by the castles forts and numerous german coastal fortifications that still adorn them a german military geologist based on jersey from mid 1941 to mid 1944 and a military geological team on guernsey and alderney during 1942 generated hydrogeological maps and reports that were then in advance of understanding of crystalline basement aquifers elsewhere in the british isles all the major documents have now been found in germany the usa and uk although none survived on the islands themselves geological mapping and hydrogeological studies postwar under the auspices of the british geological survey were completed without access to german data however german and british data together now facilitate an appraisal of the heavily stressed aquifers on these small hard rock islands over an unusually long 65 year timespan

intercalibration of the hb3gr 40ar 39ar dating standard abstract the 40 ar 39 ar dating technique is based on the knowledge of the age of neutron fluence monitors standards recent investigations have improved the accuracy and precision of the ages of most of the phanerozoic aged standards e g fish canyon tuff sanidine fcs alder creek sanidine ga1550 biotite and lp 6 biotite however no specific study has been undertaken on the older standards i e hb3gr hornblende and nl 25 hornblende generally used to date precambrian high ca k and or meteoritic rocks in this study we show that hb3gr hornblende is relatively homogenous in age composition ca k and atmospheric contamination at the single grain level the mean standard deviation of the 40 ar 39 ar k f value derived from this study is 0 49 comparable to the most homogeneous standards the intercalibration factor which allows direct comparison between standards between hb3gr and fcs is r fcs hb3gr 51 945 0 167 using an age of 28 02 ma for fcs the age of hb3gr derived from the r value is 1073 6 5 3 ma 1 internal error only and 8 8 ma including all sources of error this age is indistinguishable within uncertainty from the k ar age previously reported at 1072 11 ma turner g huneke j c podosek f a wasserburg g j 1971 40 ar 39 ar ages and cosmic ray exposure ages of apollo 14 samples earth planet sci lett 12 19 35 the r value determined in this study can also be used to intercalibrate fcs if we consider the k ar date of 1072 ma as a reference age for hb3gr we derive an age of 27 95 0 19 ma 1 internal error only for fcs which is in agreement with the previous determinations altogether this shows that hb3gr is a suitable standard for 40 ar 39 ar geochronology

geology geochemistry and 40ar 39ar ages of the cerro millo epithermal high sulfidation gold prospect southern peru abstract the high sulfidation system of cerro millo is hosted in a late miocene andesitic paleo stratovolcano in the high andes of southern peru very pronounced advanced argillic alunite silicic and argillic kaolinite and smectite alteration characterizes the central part of the hydrothermal system propylitic alteration is developed in a 3 to 4 km wide outer halo abundant alunite occurs as hypogene acicular crystals and very fine grained aggregates the latter formed during near surface steam heated overprinting hypogene alunite has an ar ar plateau age of 10 8 0 9 ma 2 and is synchronous with the andesitic volcanism ar ar on biotite 11 0 0 5 ma a second ill defined alunite age plateau of 8 0 0 9 ma is probably related to steam heated overprint and points to major erosion in between both hydrothermal events telescoping is also evident by a series of silicified horizons which mark the paleo groundwater table these units have elevated mercury antimony and arsenic levels late phase barite occurs in some structurally controlled advanced argillic altered envelopes the hypogene alteration mineralogy points to temperatures at 250 c hydraulic fracturing and steam heated overprinting suggest a shallow boiling environment slight gold enrichment is observed in the lowermost exposed parts of the system

geochemistry and deposition of 7be in river estuarine and coastal waters the atmospheric flux of cosmogenic 7be 53 3 day half life and the mode of 7be deposition in river estuarine and coastal environments have been examined the atmospheric flux of 7be commonly supports inventories ranging from 1 0 to 2 0 pci cm2 1 pci 0 037 bq beryllium 7 concentrations in water phase samples collected across salinity gradients in several estuaries along the eastern coastline of the united states range from 0 03 to 0 53 pci l and primarily reflect variations in 7be supply and sorption kinetics the major process controlling the concentration of 7be on estuarine suspended particles appears to be the length of time that these particles remain in the water column field particle to water distribution coefficients for 7be have a median value of about 4 104 but range over an order of magnitude reflecting short term variations in 7be input particle dynamics and particulate iron content rather than equilibrium sorption desorption responses to changes in water salinity or particle type residence times of 7be in the water column range from a few days in estuarine areas of rapid fine particle deposition to several weeks in high energy environments where pronounced sediment resuspension reintroduces deposited 7be back into the water column inventories of 7be in sediments range from nondetectable to 3 3 pci cm2 with the highest inventories in areas where fine particles are accumulating rapidly such sites are also major repositories for other particle reactive substances a 7be budget for the james estuary indicates that less than 5 of the expected 7be input is in the water column and that the short term estuarine trapping efficiency for atmospherically derived 7be is somewhere between 50 and 100

ar ar age determinations of eclogitic clinopyroxene and garnet inclusions in diamonds from the venetia and orapa kimberlites ar ar age measurements are reported for selected eclogitic clinopyroxene and garnet inclusions in orapa diamonds and clinopyroxene inclusions in venetia diamonds laser drilling of encapsulated clinopyroxene inclusions within venetia diamonds released a maximum of 3 of the total 40ar indicating little diffusive transfer and storage of radiogenic 40ar at the diamond inclusion boundary apparent ages obtained during stepped heating of three diamonds are consistent with diamond crystallisation occurring just prior to the kimberlite eruption 520 ma ago stepped heating of three clinopyroxene bearing orapa diamonds gave ages of 906 1032 ma significantly above the eruption age but consistent with previously determined isotopic ages a few higher apparent ages hint at the presence an older generation of orapa diamonds that formed 2500 ma ago orapa garnets also contain measurable k contents and record a range of ages between 1000 and 2500 ma the old apparent ages and lack of significant interface 40ar released by the laser probe suggests that pre eruption radiogenic 40ar and mantle derived 40ar components are trapped in microinclusions within the pyroxene and garnet inclusions

relative age of cordilleran base metal lode and replacement deposits and high sulfidation au ag epithermal mineralization in the colquijirca mining district central peru at colquijirca central peru a predominantly dacitic miocene diatreme dome complex of 12 4 to 12 7 ma 40ar 39ar biotite ages is spatially related to two distinct mineralization types disseminated au ag associated with advanced argillic alteration and local vuggy silica typical of high sulfidation epithermal ores are hosted exclusively within the volcanic center at marcapunta a second economically more important mineralization type is characterized as cordilleran base metal lode and replacement deposits these ores are hosted in mesozoic and cenozoic carbonate rocks surrounding the diatreme dome complex and are zoned outward from pyrite enargite quartz alunite to pyrite chalcopyrite dickite kaolinite to pyrite sphalerite galena kaolinite siderite alunite samples related to the au ag epithermal ores have been dated by the 40ar 39ar method at 11 3 11 6 ma and those from the cordilleran base metal ores in the northern part of the district smelter and colquijirca at 10 6 10 8 ma the significant time gap 0 5 my between the ages of the two mineralization types in the colquijirca district indicates they were formed by different hydrothermal events within the same magmatic cycle the estimated time interval between the younger mineralization event base metal mineralization at 10 6 ma and the ages of 12 5 ma obtained on biotites from unmineralized dacitic domes flanking the vicinity of the diatreme vent suggest a minimum duration of the magmatic hydrothermal cycle of around 2 ma this study on the colquijirca district offers for the first time precise absolute ages indicating that the cordilleran base metal lode and replacement deposits were formed by a late hydrothermal event in an intrusive related district in this case post au ag high sulfidation epithermal mineralization

geology and hydrothermal alteration of the chapi chiara prospect and nearby targets southern peru using aster data and reflectance spectroscopy southern peru contains several small and medium sized epithermal au ag base metals deposits related to miocene pliocene metallogenetic belts specifically the characterization of the geology and mapping of hydrothermal alteration zones of the chapi chiara prospect canahuire deposit and cerro millo and san antonio de esquilache targets were done with data acquired by advanced spaceborne thermal emission and reflection radiometer aster spaceborne sensor aster mapping techniques included 1 band ratio and principal component analysis crosta technique applied to the visible and near infrared and short wave infrared bands to produce a regional hydrothermal alteration map alunite and or kaolinite illite muscovite and or smectite iron bearing minerals and 2 spectral indices and selective principal component analysis applied to the thermal infrared bands to detect quartz and carbonates bearing targets respectively these methods were used to establish a hydrothermal zoning pattern in paleostratovolcanoes where the chapi chiara cerro millo and san antonio de esquilache targets are located this zoning pattern was used to infer erosion conditions and the potential for metal deposits based on the mineralogy which was also analyzed using reflectance spectroscopy and petrography in addition aster data were used to characterize the carbonate host rocks the quartz bearing units of the yura group and the quartz poor unit associated with the phreatic and phreatomagmatic breccias in the canahuire deposit region this characterization led to the development of a favorability model for the occurrence of canahuire type deposits based on spatial analysis using the fuzzy logic technique

genesis of acid sulfate alteration and au cu ag mineralization at summitville colorado the summitville au cu ag deposit occurs within a porphyritic quartz latite primarily in a zone of vuggy silica alteration characterized by leaching of all major elements except silica and iron vuggy silica is best developed between an elevation of 3 700 and 3 500 m where it occurs in irregular pipes and lenticular pods up to 70 m wide and is enclosed by up to 30 m of intense quartz alunite alteration the vuggy silica zones diminish in size with decreasing elevation and rarely exceed a width of 2 m below an elevation of 3 400 m these deep vuggy silica zones are enclosed by quartz kaolinite alteration with little or no alunite sulfide mineralization occurs primarily within the vuggy silica the sulfide assemblage changes with decreasing elevation from covellite luzonite or native gold to chalcopyrite tennantite sulfides occur lining voids or in microveinlets and are accompanied by minor kaolinitc but not by alunite gold also occurs in a near surface barite goethite jarosite assemblage that crosscuts the vuggy silica consideration of alunite kaolinitc and pyrite stability relations and of aluminum speciation at 250 degrees c indicates that a ph of 2 or below and a log f sub o 2 of 31 or 1 at 250 degrees c were necessary to produce vuggy silica alteration the chalcopyrite tennantite mineralization occurring at depth in the vuggy silica zone is indicative of less oxidizing and less acidic conditions the covellite luzonite or gold assemblage requires conditions intermediate between those necessary for vuggy silica alteration and for deep sulfide mineralization barite gold mineralization is interpreted as a near surface assemblage produced under highly acidic oxidizing conditions these textural and geochemical relationships indicate that sulfide and gold mineralization postdate the formation of vuggy silica alteration in the deposit and are not directly related to the highly acidic solutions necessary for this early acid leaching event the change from extreme acid leaching to copper sulfide and precious metal deposition may represent a transition from a magmatic vapor dominated to a liquid dominated system leading to more reducing and less acidic conditions during sulfide deposition

the geochemical cycle of 9be a reconnaissance an initial survey has been made of the geochemistry of 9be in natural waters with a view to utilizing the isotope with the cosmogenic species 10be t1 2 1 5 m y in geochronological studies of sedimentary accumulation the mobility of9be in continental waters is a strong function of ph with acid streams ph 6 being strongly enriched as compared to alkaline carbonate rivers large scale scavenging of beryllium occurs in the estuaries of rivers containing more than about 200 pm of the element in alkaline systems of lower concentration the element appears to behave conservatively the net flux of beryllium to the ocean is estimated as that equivalent to an average effective river concentration of about 150 pm beryllium is strongly enriched in ridge crest hydrothermal solutions over ambient seawater the flux is approximately 70 of that from the continents the deep water concentrations of 9be vary by only 20 between the north atlantic and north pacific demonstrating that the chemical saltation produced by scavenging from the deep water column and release from the sediments predominates over simple advective concentration along flow lines isotopic homogenization of 10be and 9be is probably achieved in the ocean the situation in continental waters appears much less promising

halite karst geohazards natural and man made in the united kingdom in the united kingdom permian and triassic halite rock salt deposits have been affected by natural and artificial dissolution producing karstic landforms and subsidence brine springs from the triassic salt have been exploited since roman times or possibly earlier indicating prolonged natural dissolution medieval salt extraction in england is indicated by the names of places ending in wich indicating brine spring exploitation at northwich middlewich nantwich and droitwich later victorian brine extraction in these areas accentuated salt karst development causing severe subsidence problems which remain a legacy the salt was also mined but the mines flooded and consequent brine extraction caused the workings to collapse resulting in catastrophic surface subsidence legislation was enacted to pay for the damage and a levy is still charged for salt extraction some salt mines are still collapsing and the re establishment of the post brine extraction hydrogeological regimes means that salt springs may again flow causing further dissolution and potential collapse

hydrogeology and the bundeswehr water supply to german armed forces in somalia kosovo and afghanistan between 1993 and 2010

geologic evolution of the caylloma epithermal vein district southern peru the silver and base metal rich caylloma epithermal district in the tertiary volcanic belt of southern peru has been worked intermittently since the incaic period and has produced over 100 million ounces moz of ag intermediate sulfidation mineralization is present in veins hosted by miocene andesitic volcanic and volcaniclastic rocks with minor ore in underlying folded jurassic sedimentary basement new 40 ar 39 ar dates give a host rock age of 20 30 0 11 ma andesitic volcanic matrix a hydrothermal alteration age of 18 35 0 17 ma adularia in vein wall rock and postmineralization ages of 11 8 0 8 and 12 25 0 07 ma sanidine and biotite from a rhyolite dome gangue minerals include quartz calcite rhodonite rhodochrosite pyrite and minor adularia illite barite and helvite ore minerals include sphalerite galena chalcopyrite and tetrahedrite hydrothermal alteration is pervasive in lava flows but weak and localized near veins in volcaniclastic rocks hydrothermal alteration types include silicification quartz adularia and quartz illite and propylitization chlorite calcite illite banded veins show four stages of mineral precipitation 1 early sugary quartz chalcedony pyrite 2 manganese minerals 3 quartz sulfides and 4 late calcite quartz cyclic bands in the manganese stage early sulfides coarse to medium grained quartz late rhodonite calcite chalcedony are a few millimeters to 5 cm thick and form ore bands up to 1 m thick veins occupy dextral normal faults 020 050 45 70 se and extension fractures 060 090 70 90 se and are 1 to 25 m wide and as much as several kilometers long the veins display complex and multi episodic filling with textures characteristic of open space precipitation such as crustiform banding symmetric banding vugs breccias and cockade and comb textures we present a structural model in which the principal veins formed in subparallel northeast striking dextral normal faults and related extension fractures within a northwest striking structural corridor bounded by sinistral regional faults second and third order veins formed by bookshelf sliding related to movement on higher order dominantly strike slip faults slickenlines have low rakes 20 50 sw and fault kinematic analysis suggests the extension axis was oriented 4 330 and the shortening axis 55 234 in agreement with the strain field commonly proposed for the early middle miocene of southern peru ore grade is discontinuous with high grade ore zones having strike lengths of tens to hundreds of meters and extending about 300 m downdip ore shoots in fault hosted veins are narrow subvertical zones a few tens of meters wide measured in the plane of the vein separated by lower grade ore zones ore shoots in extension fractures are shorter downdip and horizontally more continuous some ore shoots occur as half cymoids that form along the main vein only in the hanging wall of synmineral transverse faults mineral composition and metal content are zoned horizontally and vertically silver base metals and calcite and manganese minerals increase to the northeast and downward and sulfide content increases gradually with depth shallower levels of the hydrothermal system are exposed to the west and southwest in the district evidence from sulfur isotopes and high salinity fluid inclusions is consistent with a model in which magmatic fluids played a role in the hydrothermal system introduced through channels of enhanced structural permeability the cyclic nature of mineral precipitation with abrupt changes in mineralogy textures and fluid composition leads us to postulate that cyclic injections of magma derived hydrothermal fluids occurred economic mineralization is estimated to have formed at a depth of about 650 m below the paleowater table with a temperature of formation of 270 c

processes controlling acid attenuation in the unsaturated zone of a triassic sandstone aquifer u k in the absence of carbonate minerals abstract continuous core samples were taken through the unsaturated zone at three sites on the outcrop of permo triassic sandstone in the british west midlands sample sites were chosen for lack of recent direct anthropogenic disturbance and for differing vegetation heathland birch woodland and conifer forest interstitial water was extracted and analyzed for 32 major and trace elements solid phases were analyzed for exchangeable cations and mineralogy the rate of recharge calculated using a cl mass balance method was three times greater below heathland than below afforested sites owing to higher evapotranspiration rates in the woodlands carbonate minerals were absent from the unsaturated zone at each site soil solutions were acidic and soils at the woodland sites were more acidic ph 4 0 than those at the heathland site ph 4 5 acidic interstitial water solutions were found to up to 5 0 m depth in the unsaturated zone and are partially neutralized by two aluminosilicate mineral reactions in the unsaturated zone cation exchange and k feldspar dissolution the rate at which these acid neutralizing reactions act to neutralize acidity is revealed by the rate of depletion of base cations from the unsaturated zone in recharge solutions k dissolution ca 2 mg 2 cation exchange the total base cation depletion rate was greatest below heathland this can be attributed mainly to the greater rate of so 4 assimilation by the woodland biome

geochemistry s vital contribution to solving water resource problems abstract as part of the events celebrating 40 a of iagc it is fitting to trace the modern evolution and development of hydrogeochemistry however fascination with water quality can be traced back more than 2 ka in the post war years hydrogeochemistry was influenced heavily by the advances in other disciplines including physical chemistry metallurgy and oceanography hydrological applications of isotope science also developed rapidly at this time and important advances in analytical chemistry allowed multi element and trace element applications to be made experimental studies on equilibrium processes and reaction kinetics allowed bench scale insight into water rock interaction consolidation of knowledge on processes in groundwaters and the current awareness of hydrogeochemistry by water professionals owe much to the work of robert garrels john hem and co workers in the early 1960s studies of down gradient evolution enabled a field scale understanding of groundwater quality and geochemical processes as a function of residence time dissolution and precipitation processes in carbonate and non carbonate aquifers redox processes cation exchange and salinity origins emerging water resource and water quality issues in the 1960s and 70s permitted the application of hydrogeochemistry to contaminant and related problems and this trend continues the impacts of diffuse pollution from intensive agriculture waste disposal and point source pollution from urban and industrial sources relied on geochemistry to solve questions of origin and attenuation in semi arid regions facing water scarcity geochemical approaches have been vital in the assessment of renewability and characterising palaeowaters the protection and new incoming regulation of water resources will rely increasingly on a sound geochemical basis for management

unveiling the hydrothermal mineralogy of the chapi chiara gold prospect peru through reflectance spectroscopy geochemical and petrographic data abstract southern peru contains important epithermal au ag base metals deposits such as canahuire tucari santa rosa caylloma shila and paula the chapi chiara gold prospect is located in this region and is part of a paleo stratovolcano of the upper miocene pliocene the hydrothermal alteration of the prospect was characterized based on spectroradiometric data geochemistry and petrography the mineralogical data interpreted based on reflectance spectroscopy were spatialized using the sequential indicator simulation technique for producing probabilistic maps of alteration the inner part of the paleo stratovolcano sw sector is marked by three main cores of advanced argillic alteration aaa quartz alunite supergroup minerals kaolinite dickite topaz pyrophyllite diaspore associated with topographic highs the aaa1 core is surrounded by argillic alteration quartz illite paragonitic illite smectite pyrite and propylitic alteration quartz plagioclase chlorite calcite epidote smectite kaolinite pyrite chalcopyrite magnetite the central sector of the prospect situated in the ne flank of the paleo stratovolcano is characterized by hydrothermal breccias structured towards n65e the main mineral phases comprise quartz and abundant pyrite sometimes with traces of as anomalous geochemical values of ag as bi hg se sb and te coincide with high gold contents in this sector of the prospect jarosite and goethite are evidence of a subsequent supergene event based on the mineralogical characterization we conclude the existence of a high sulfidation epithermal system in chapi chiara hypogene minerals of higher temperature in the sw sector of the prospect such as diaspore pyrophyllite and topaz in the aaa zone and epidote in the propylitic alteration zone can reveal that the system is currently in a relatively deep erosion level suggesting its proximity in relation to the interface between a deep epithermal system and a mesothermal system

hydrogeology and hydrogeochemistry of a small hard rock island the heavily stressed aquifer of jersey abstract the fractured basement aquifer of jersey provides 30 of the total water needs of the island plus baseflow to surface catchment storage a 3 year field study has attempted to describe the groundwater resources in terms of quantity and quality borehole yields are typically less than 11s 1 the island wide estimate of transmissivity is 3 m 3 day 1 and effective aquifer thickness is 30 40 m although deeper circulation occurs in selected fracture systems it is estimated that much of the renewable resource is exploited groundwaters are predominantly derived from recent recharge most being oxidising with measurable tritium contents there is widespread pollution from agricultural nutrients but natural denitrification is apparent in some areas

groundwater residence time and movement in the maltese islands a geochemical approach the maltese islands are composed of two limestone aquifers the upper and lower coralline limestone separated by an aquitard the blue clay the lower coralline limestone is overlain in part by the poorly permeable globigerina limestone the upper perched aquifers are discontinuous and have very limited saturated thickness and a short water level response time to rainfall frequent detections of coliforms suggest a rapid route to groundwater however the unsaturated zone has a considerable thickness in places and the primary porosity of the upper coralline limestone is high so there is likely to be older recharge by slow matrix flow as well as rapid recharge from fractures measurement of sf6 from a pumping station in a deep part of one of the perched aquifers indicated a mean saturated zone age of about 15 years the main sea level aquifers msl on both malta and gozo have a large unsaturated thickness as water levels are close to sea level on malta parts of the aquifer are capped by the perched aquifers and more extensively by the globigerina limestone the limited detection of coliform bacteria suggests only some rapid recharge from the surface via fractures or karst features transmissivity is low and tritium and cfc sf6 data indicate that saturated zone travel times are in the range 15 40 years on gozo the aquifer is similar but is more extensively capped by impermeable blue clay cfc data show the saturated zone travel time is from 25 years to possibly more than 60 years groundwater age is clearly related to the extent of low permeability cover the 13c signature of groundwater is related to the geochemical processes which occur along the flowpath and is consistent with residence time ages in the sequence perched aquifers malta msl gozo msl the 18o and 2h enriched isotopic signature of post 1983 desalinated water can be seen in more modern groundwater particularly the urbanised areas of the perched and malta msl aquifers in all aquifers movement of solutes from the surface travelling slowly through the matrix provide a long term source of groundwater contaminants such as nitrate

residence times of234th and7be in lake geneva the activities of two short lived natural radionuclides 234th and7be were measured in lake geneva water suspended solids and sediments in order to obtain their removal residence times in the lake four independent methods of estimation are presented and compared the calcuated residence times of234th and7be vary from 60 to 280 days and from 60 to 1100 days respectively depending on season and the method used in general 7be residence times are significantly longer than those of234th for both nuclides the removal residence times are significantly longer than their respective radioactive mean lives as a consequence the estimates based on their water column inventories are not as reliable as the estimates obtained from the measured fluxes of these nuclides into sediment traps estimates based on the bottom sediment inventories are similar in magnitude to those obtained from flux into sediment traps but occasionally are erroneous because of small scale sediment heterogeneity

uthpb zircon dating of the 13 8 ma dacite volcanic dome at cerro rico de potosi bolivia abstract the temporal relationship between the extrusion of the miocene dacite volcanic dome at cerro rico de potosi bolivia and the associated ag sn mineralization has an important bearing on the heat and metal sources for this world class mineral deposit the highly altered nature of the volcanic rock however has prevented previous efforts from definitively determining the emplacement age of the dome rather than subsequent episodes of alteration the present study uses u th pb dating of sparse zircon contained in the dacite to demonstrate that at most only several hundred thousand years separate dome emplacement from main stage mineralization the dacite contains a morphologically heterogeneous population of zircon with considerable variation in size shape and color preliminary analyses revealed the presence of a significant component of inherited zircon most likely as older cores that were overgrown by rims during the crystallization of the dacite magma morphological distinctions shape size color within the zircon population provided the basis for separating the zircon into fractions that reduced or enhanced the inherited component in composite grains by analyzing the tips of zircon with very large length to width ratios it was possible to constrain the crystallization age of the dacite to 13 8 0 2 ma the dispersion of data on a concordia diagram indicates at least two ages of inherited zircon one mesozoic associated with yellow grains and another proterozoic associated with colorless grains such xenocrystic components have useful petrogenetic implications for the source and travel path of the magma

pressure oxidation autoclave as an analogue for acid sulphate alteration in epithermal systems gold extraction at the macraes gold mine in new zealand involves concentration of pyrite and arsenopyrite oxidation of those sulphides then cyanidation the ore concentrate is predominantly otago schist host rock andesitic composition with up to 15 sulphides the oxidation step is conducted on ore concentrate slurry in an autoclave at 225 c and 3 800 kpa oxygen gas pressure with continuous feed the slurry takes ca 1 h to pass through the autoclave during which time the sulphides are almost completely oxidised sulphide oxidation causes strong acidification of the slurry which is maintained at ph of 1 2 by addition of caco3 scales form on walls in the autoclave with minerals reflecting progressive oxidation and alteration of the ore through the system the schist in the ore feed has mineralogy similar to propylitically altered andesite quartz albite muscovite chlorite and pyrite muscovite undergoes almost complete dissolution with associated precipitation of quartz and alunite kal3 so4 2 oh 6 other principal minerals deposited and discharged include anhydrite and or gypsum jarosite kfe3 so4 2 oh 6 hematite and or amorphous iron oxyhydroxide and amorphous arsenates dissolved ferrous iron passes right through the autoclave and variably hydrated fe2 and fe3 sulphate minerals including rozenite and szomolnokite both feso4 hydrate and ferricopiapite fe5 so4 6o oh hydrate are formed along the way the autoclave chemical system resembles acid sulphate hydrothermal activity in geothermal systems and high sulphidation epithermal mineral deposits formed in arc environments these natural acid sulphate systems are pervaded by volcanic vapours in the near surface environment where widespread dissolution of host rocks occurs and deposition of quartz alunite and anhydrite is common some of the volume loss associated with these natural systems may be due to dissolution of soluble sulphate minerals by later stage groundwater incursion

cyclic formation of debris avalanches at mount st augustine volcano volcanic debris avalanches have been seen at many volcanoes since the 1980 eruption of mount st helens but typically only one or two avalanche deposits are identified at each eruptive centre suggesting that catastrophic slope failures are rare or even unique events in the lifetime of a volcano1 4 here we present a series of radiocarbon dates from volcanic deposits showing that the summit edifice of mount st augustine a 1 220 m high active volcano on augustine island in the cook inlet area of south central alaska has repeatedly collapsed and regenerated averaging 150 200 years per cycle during the past 2 000 years the unprecedented frequency of summit edifice failure was made possible by sustained lava effusion rates over 10 times greater than is typical of plate margin volcanoes

internal vein texture and vein evolution of the epithermal shila paula district southern peru the epithermal shila paula au ag district is characterized by numerous veins hosted in tertiary volcanic rocks of the western cordillera southern peru field studies of the ore bodies reveal a systematic association of a main e w vein with secondary n55 60 w veins two directions that are also reflected by the orientation of fluid inclusion planes in quartz crystals of the host rock in areas where this pattern is not recognized such as the apacheta sector vein emplacement seems to have been guided by regional n40 e and n40 w fractures two main vein filling stages are identified stage 1 is a quartz adularia pyrite galena sphalerite chalcopyrite electrum mn silicate carbonate assemblage that fills the main e w veins stage 2 which contains most of the precious metal mineralization is divided into pre bonanza and bonanza substages the pre bonanza substage consists of a quartz adularia carbonate assemblage that is observed within the secondary n45 60 w veins in veinlets that cut the stage 1 assemblage and in final open space fillings the two latter structures are finally filled by the bonanza substage characterized by a fe poor sphalerite chalcopyrite pyrite galena tennantite tetrahedrite polybasite pearceite electrum assemblage the ore in the main veins is systematically brecciated whereas the ore in the secondary veins and geodes is characteristic of open space crystallization microthermometric measurements on sphalerite from both stages and on quartz and calcite from stage 2 indicate a salinity range of 0 to 15 5 wt nacl equivalent and homogenization temperatures bracketed between 200 and 330 c secondary co2 n2 and h2s bearing fluid inclusions are also identified the age of vein emplacement based on 40ar 39ar ages obtained on adularia of different veins is estimated at around 11 ma with some overlap between adularia of stage 1 11 4 0 4 ma and of stage 2 10 8 0 3 ma a three phase tectonic model has been constructed to explain the vein formation phase 1 corresponds to the assumed development of e w sinistral shear zones and associated n60 w cleavages under the effects of a ne sw shortening direction that is recognized at andean scale these structures contain the stage 1 ore assemblage that was brecciated during ongoing deformation phase 2 is a reactivation of earlier structures under a nw se shortening direction that allowed the reopening of the preexisting schistosity and the formation of scarce n50 e striking s2 cleavage planes filled by the stage 2 pre bonanza minerals phase 3 coincides with the bonanza ore emplacement in the secondary n45 60 w veins and also in open space in the core of the main e w veins our combined tectonic textural mineralogical fluid inclusion and geochronological study presents a complete model of vein formation in which the reactivation of previously formed tectonic structures plays a significant role in ore formation

beryllium in river baseflow shallow groundwaters and major aquifers of the u k abstract beryllium is potentially a highly toxic element which may be mobilised especially under acidic conditions in natural waters results from major aquifers the unsaturated zone from shallow groundwaters and river baseflow were used to establish the naturally occurring baseline concentrations in u k waters out of 924 samples from 13 aquifer units be was detected in only 12 samples in carbonate aquifers no be was found above the detection limit of 0 05 g l the occurrence of be 0 05 g l was restricted to arenaceous aquifers where concentrations up to 1 g l be were found mainly in the carboniferous millstone grit and lower cretaceous lower greensand aquifers interstitial water profiles from the unsaturated zones of the lower greensand surrey and triassic sandstone west midlands contain be concentrations in excess of 10 g l within the top 10 m which may persist to the water table at concentrations near to 1 g l be the only major anomaly to be found in river baseflow was from the mourne mountains of northern ireland where be concentrations of up to 4 7 g l were found associated with the outcrop of the tertiary granite intrusion elsewhere be 0 22 g l was found in neutral groundwaters derived from granite feeding the acid loch fleet southern scotland in which concentrations of 0 09 g l were maintained beryllium occurrence therefore depends strongly on geology the predominant aqueous species below ph 5 5 is be 2 and above this be oh dominates the presence of high al in most waters sampled greatly suppresses the formation of bef complex ions beryllium shows close geochemical behaviour with mg across a range of ph which may have environmental consequences if be substitution for mg takes place

comparison between the fluid characteristics of the rodalquilar and two neighbouring epithermal gold deposits in spain the operating rodalquilar gold deposit and the abandoned triunfo and maria josefa gold mines are located within the sierra del cabo de gata volcanic field some 40 km east of almeria in se spain while the gold mineralization at rodalquilar is mainly controlled by caldera tectonics vein structures at triunfo and maria josefa are not wall rock alteration at triunfo and maria josefa is characterized by argillic alteration illite sericite kaolinite the alteration zonation around the gold mineralized vein structures at rodalquilar ranges from advanced argillic alteration porous quartz alunite pyrophyllite dickite over argillic alteration into a regionally developed propylitization fluid inclusion studies from all three mines indicate that gold was deposited from low salinity fluids 2 5 wt nacl equivalent between 170 and 250 c however the hydrothermal system at rodalquilar was fed by a second fluid source high salinity halite and or sylvite bearing liquid rich and vapour dominated co2 bearing fluid inclusions are assumed to be of magmatic origin high sulfidation ore mineral assemblages at depth covellite enargite tennantite and part of the advanced argillic alteration can be related to these fluids thus part of those features which attribute the rodalquilar gold deposit to the acid sulfate or high sulfidation type of epithermal gold deposits stem from magmatically derived fluids which are typical for a porphyry environment whereas gold mineralization at all three localities is associated with low salinity fluids probably of marine origin

mobilization of beryllium in the sedimentary column at convergent margins studies of be distributions in subduction zone sediments will help to understand questions regarding the enrichments of cosmogenic be 10 in arc volcanic rocks analyses of be 10 and be 9 in sediments of ocean drilling program site 808 nankai trough and be 9 in porewaters of site 808 and sites 671 and 672 barbados ridge complex show significant decreases in solid phase be 10 and large increases of porewater be 9 at the location of the decollement zone and below or at potential flow conduits these data imply the potential mobilization of be during pore fluid expulsion upon sediment burial experiments involving reaction between a decollement sediment and a synthetic nacl cacl2 solution at elevated pressure and temperatures were conducted in an attempt to mimic early subduction zone processes the results demonstrate that be is mobilized under elevated pressure and temperature with a strong ph dependence the be mobilization provides an explanation of be 10 enrichment in arc volcanic rocks and supports the argument of the importance of the fluid processes in subduction zones at convergent margins