problems in identifying the effects of structure and critical state in a soil with a transitional behaviour this work shows that some soils with an intermediate behaviour between clays and sands do not have a unique compression line as has also been pointed out by martins et al it has been shown here that a unique critical state line could not be determined for the remoulded soil although the results shown here are for a reconstituted residual soil similar behaviour in compressibility has been found in silts and mixtures of sand and kaolin however it has been found that the critical state framework can be applied using a family of parallel critical state lines depending on the initial specific volume one of the questions raised by this work is how the effects of structure can be quantified if the intrinsic properties of the remoulded material are not unique the compression and critical state lines of the remoulded material are not only non unique but also of a distinctly different gradient from the natural material

short wave infrared spectral and geochemical characteristics of hydrothermal alteration at the archean izok lake zn cu pb ag volcanogenic massive sulfide deposit nunavut canada application in exploration target vectoring short wave infrared swir field and laboratory spectra were used to identify and characterize hydrothermal alteration mineral chemical variability in host rocks proximal to the izok lake zn cu pb ag volcanogenic massive sulfide vms deposit in nunavut canada the deposit is hosted within a sequence of predominantly felsic pyroclastic rocks of archean age that are regionally metamorphosed to amphibolite facies these rocks are characterized by the muscovite biotite sillimanite and chlorite biotite cordierite mineral suite proximal to the deposit white micas are al rich to potassic muscovite and the biotite and chlorite are mg rich in areas that are immediately outboard of the proximal alteration zones rocks are altered to al poor muscovite and intermediate to fe rich biotite and chlorite outboard of this distal areas are characterized by potassic muscovite and mg rich biotite and chlorite the white micas and biotite chlorite group minerals display considerable variation in their al oh and fe oh absorption feature wavelength positions the variations in muscovite and biotite chlorite compositions as determined by the al oh and fe oh absorption feature wavelength positions broadly correlate with changes in hydrothermal alteration intensity as measured by the ishikawa and chlorite carbonate pyrite alteration indices our findings suggest that the large scale alteration intensity trends of the izok lake study area can be elucidated using the spectral properties of the hydrothermal alteration minerals

laboratory study of loose saturated and unsaturated decomposed granitic soil weathered soils are used extensively as fill materials in slope construction in tropical and subtropical cities such as hong kong the mechanical behavior of loose decomposed fill materials particularly in the unsaturated state has not often been investigated and is not yet fully understood the objective of this study was to understand the mechanical behavior of loose unsaturated decomposed granitic soil and to study the effects of the stress state the stress path and the soil suction on the stress strain relationship shear strength volume change and dilatancy via three series of stress path triaxial tests on both saturated and unsaturated specimens it was found that loose and saturated decomposed granitic soil behaves like clean sands during undrained shearing strain softening behavior is observed in loose saturated specimens in unsaturated specimens sheared at a constant water content a hardening stress strain relationship and volumetric contractions are observed in the considered range of net mean stresses the suction of the soil contributed little to the apparent cohesion the angle of friction appeared to be independent of the suction in unsaturated specimens subjected to continuous wetting suction reduction at a constant deviator stress the volumetric behavior changed from dilative to contractive with increasing net mean stress and the specimen failed at a degree of saturation far below full saturation it was revealed that the dilatancy of the unsaturated soil depends on the suction the state and the stress path

the mechanics of an italian silt an example of transitional behaviour by controlling the particle size distribution of an italian silt the influence of grading on its behaviour was investigated as the clay content was reduced the behaviour changed from a typical clay mode to a transitional form between that of clays and sands that had previously been seen only for gap graded soils emphasising that this type of behaviour is possibly much more extensive than previously thought the work has highlighted several features of transitional behaviour and in particular that unique normal compression and critical state lines do not exist that rendulic s principle does not apply and that drained and undrained tests do not reach unique ultimate states

facies architecture of mineralized submarine volcanic sequences cambrian mount read volcanics western tasmania the middle to late cambrian mount read volcanics western tasmania comprise compositionally and texturally diverse lavas and volcaniclastic rocks most of which were emplaced in submarine environments below wave base the facies architecture reflects the contrasting character and geometry of primary volcanic and volcaniclastic facies which are strongly controlled by eruption style and eraplacement processes in the northern mount read volcanics the principal volcanic facies are 1 silicic intermediate and mafic lavas 2 juvenile volcaniclastic deposits generated in association with the extrusion of lava flows or else produced by explosive eruptions and 3 synvolcanic intrusions involving silicic and mafic magmas emplaced into unconsolidated host sequences distribution and lithofacies characteristics suggest that deposits from both intrabasinal submarine and extrabasinal subaerial and or shallow marine volcanic centers are present the volcanic facies are interbedded with a sedimentary facies association comprising black mudstone and or graded bedded sandstone of mixed volcanic and precambrian basement provenance the predicted facies geometry of the principal volcanic facies has guided our approach to correlation in the mount read volcanics mass fiow emplaced pumiceous volcaniclastic facies provide the best framework for correlation because these are produced in large volumes erupted infrequently eraplaced rapidly and are widely distributed distinctive units of this type that occur near hellyer in the southwell subgroup and 40 km to the south at white spur howards road white spur formation could each be part of the same regionally extensive volcaniclastic facies association a similar volcaniclastic facies association hosts the hercules and rosebery massive sulfide deposits and clearly demonstrates that such associations are prospective for this style of mineralization

genesis of the baiyun pyrophyllite deposit in the central taihang mountain china implications for gold mineralization in wall rocks abstract genesis of pyrophyllite alteration can provide important clues for ore prospecting due to its various relationships with metallic mineralization the baiyun pyrophyllite deposit in the central taihang mountain ctm of the north china craton ncc provides a natural case to gain insights into the genesis of pyrophyllite alteration and its relationships with gold mineralization in the wall rocks the pyrophyllite ores primarily occur as subparallel sheeted veins in fractures of the late archean meta volcanic rocks and locally as filling fractures within the meta intrusions phyllic alteration halos around the pyrophyllite orebody decline outwards where gold mineralization develops as disseminated aggregates in honeycomb like pyrites pyrophyllite ores are mostly dominated by 1tc type pyrophyllite sericite and quartz with minor kaolinite illite and albite as identified by xrd analyses zircon grains from the granitic porphyry in the ore field define a weight mean u pb age of 130 1 ma mswd 1 8 n 19 and those from the sericite quartz schist yield an upper intercepted u pb age of 2551 8 ma zircon grains from the pyrophyllite ore yield an upper intercepted u pb age of 2566 11 ma and a lower intercepted age of 136 7 ma mswd 0 99 n 20 reflecting a mesozoic magmatic hydrothermal event which could possibly be triggered by the lithospheric destruction of the ncc log o2 ph diagram suggests the fluids responsible for pyrophyllite alteration are extremely acidic ph 2 20 and under high oxygen fugacity hm 2 14 calculated h o isotopic compositions dh2o 34 to 20 oh2o 3 4 to 7 5 270 c oh2o 0 2 4 3 200 c of pyrophyllite ores display typical features of volatile dominated fluids with minor impact of meteoric water metal concentrations of pyrophyllite ores decrease with increasing contents of sio2 suggesting the fluids generating pyrophyllite alteration are not conductive to gold mineralization the results herein indicate that the baiyun pyrophyllite deposit formed as magma degassing in deep are similar to the common root zones of advanced argillic lithocaps barren shoulders from porphyry environments and probably be the signs for erosion of epithermal deposits at shallow crustal depths

the mechanics of subglacial sediment an example of new transitional behaviour a series of isotropic compression tests and drained and undrained triaxial compression tests have been performed on glacial sediment from iceland langjokull sediment which is well graded is thou

the intrinsic behaviour of a decomposed granite soil the intrinsic mechanics of a decomposed granite soil were investigated by triaxial tests at standard pressures and at high pressures up to 35 mpa to compare its behaviour in its saturated partially saturated and dry states in each case it was found that the behaviour could be described within a critical state framework with particle breakage as the principal means of plastic volumetric compression the behaviour of partially saturated samples compacted at around the optimum water content was found not to differ appreciably from that of saturated samples in contrast tests on dry samples revealed a state boundary surface for the dry soil which exists outside that of the saturated soil sieve analyses showed this to result from the fact that the soil in its dry state was subject to a smaller amount of particle breakage although the critical state friction angle is not affected by the presence of water the location of the state boundary surface at higher volumes stresses for the dry soils results in the

geochemical modeling of the zoned footwall alteration pipe hellyer volcanic hosted massive sulfide deposit western tasmania australia the mineralogy of hydrothermal alteration assemblages siliceous core chlorite zone sericite zone in the footwall pipe of the hellyer volcanic hosted massive sulfide vhms deposit is controlled mainly by the temperature ph and redox state of the hydrothermal fluids based on the results of our numerical modeling the zoned alteration system could have formed by a combination of water rock interaction and cooling with a siliceous core predicted to form at the center of the conduit passing outward to a chlorite dominated zone a sericite rich zone and finally grading out to unaltered andesite these mineralogical changes relate to a gradual evolution of fluid chemistry water rock ratio ph and temperature from the core to the margin of the system initial temperatures were probably close to 350 degrees c and the hydrothermal fluids were reduced h2s dominated at low temperatures 200 degrees c a peripheral alteration zone consisting mostly of k feldspar chlorite sericite and hematite is predicted to form this low temperature zone has not been recognized at hellyer but elevated k2o contents and local k feldspar development have been noted at other vhms deposits suggesting that this zone might form at low temperatures and low water rock ratios in the footwall of vhms deposits if the existence of barren outer k feldspar alteration zones is confirmed the findings could have important implications for exploration specifically with regards to distinguishing ore related alteration zones from barren alteration systems

influence of reconstitution method on the behaviour of completely decomposed granite reconstituting soil is common in construction yet the method used can affect the mechanical behaviour of the reconstituted soil when the soil contains a significant amount of fines a completely decomposed granite was reconstituted following different methods namely dry deposition moist tamping slurrying and reconstituting after separating fines by washing then it was tested in compression and shearing the test results highlight the sensitivity of the soil behaviour to the method of preparation used for reconstitution it was found that preparation methods involving large amounts of water such as slurrying s or reconstitution after washing the fines f can lead to a release of fines with effect to change the grading and change the mineralogy differences between dry deposited d moist tamped mt specimens and slurried s washed reconstituted f specimens were observed mainly in the volumetric response two different normal compression and critical state lines were obtained for the two main

the experimental contact behaviour of natural sands normal and tangential loading a comprehensive series of tests was carried out using an innovative three axis inter particle loading apparatus investigating the normal and shearing contact behaviour between sand particles of a

hillslope hydrochemistry and stream response on a wooded permeable bedrock the role of stemflow abstract the hillslope hydrochemical processes operating on a permeable carbonate bedrock can be linked to the hydrochemical response which a slope foot stream shows to rainfall events solute sources hydrochemical inputs and outputs and storm responses have been evaluated for a wooded hillslope section the data could not be interpreted in terms of a throughflow soil water movement mechanism storm events produced a rapid input of solute rich water to the stream by vertical percolation in the bedrock and subsequent lateral movement at depth the solute rich nature of the response implies that a displacement mechanism operates the rapid response from the hillslope may be initiated by stemflow which produces large concentrated point source inputs to the soil by passing the soil matrix baseflow runoff is produced by throughfall percolating through the soil matrix stemflow may be used to explain the different hydrochemical responses of the wooded hillslope and the non wooded upper portion of the catchment

the spectrum of ore deposit types volcanic environments alteration halos and related exploration vectors in submarine volcanic successions some examples from australia variations in shape metal content alteration mineralogy and volcanic host rocks of the ore deposits in the two major volcanic hosted massive sulfide vhms districts of eastern australia the cambrian mount read volcanics and the cambro ordovician mount windsor subprovince strongly reflect their volcanic environment conditions of ore formation and hydrothermal alteration processes lens and sheet style polymetallic zinc rich deposits such as rosebery hellyer que river and thalanga are considered to have formed in moderate to relatively deep water environments 500 1 000 m these deposits probably formed either on the sea floor e g hellyer que river or by replacement of porous volcaniclastic units directly below the sea floor e g rosebery the footwall alteration associated with these polymetallic vhms deposits was controlled by host rock permeability and porosity which are in turn related to volcanic facies type degree of fracturing and synvolcanic structural architecture focusing of hydrothermal fluids along synvolcanic structures has resulted in well zoned chlorite sericite footwall alteration pipes within footwall lavas at hellyer on the other hand diffuse fluid flow through very thick pumice breccia at rosebery and hercules has resulted in strata bound sericite dominated footwall alteration zones parallel to the paleosea floor and the ore lenses massive and disseminated pyritic cu au deposits such as those in the mount lyell field and at highway reward formed by subsea floor replacement and are associated with only minor zinc lead massive sulfide ore these deposits formed from higher temperature fluids 300 degrees c in which copper transport is enhanced and are commonly located in felsic volcanic centers dominated by shallow porphyritic intrusions e g highway reward the cu au ore lenses may be strata bound e g mount lyell or crosscutting pipes e g highway reward depending on the structure and permeability characteristics of the felsic volcanic host rocks the presence of high sulfidation alteration minerals e g pyrophyllite zunyite in some of the cu au deposits e g mount lyell field indicates that fluids were relatively acidic and suggests the possibility of magmatic fluid input into the hydrothermal system alteration zonation associated with the cu au vhms deposits is more symmetrical than that of the zn rich deposits with sericite rich alteration extending into the hanging wall in keeping with the subsurface replacement origin of these deposits synvolcanic gold rich deposits with high gold base metal ratios are less common than the cu au and zn rich vhms ore types the gold rich ores e g henty south hercules are strata bound in nature have low sulfide contents and are associated with central zones of intense silicification surrounded by envelopes of sericite pyrite and carbonate alteration volcanological and geochemical studies at henty indicate the gold rich ore formed by the replacement of particular volcanic units deposited in a relatively shallow water environment dominated by volcaniclastic facies lavas and limestones this spectrum of cu au zn rich and au only deposits in the mount read volcanics and the mount windsor subprovince is interpreted to represent a continuum from classic sea floor vhms ores toward those with features more akin to porphyry cu au and epithermal au ag deposits this spectrum relates to the interplay between factors in the submarine volcanic environment and the character of the hydrothermal fluid as follows 1 proportions of volcaniclastic lava and subvolcanic intrusive facies 2 depth of seawater 3 permeability and porosity of volcanic host rocks 4 balance between magmatic components and seawater components in the ore fluid and 5 temperature and acidity of the ore fluid mineralogical lithogeochemical and isotopic studies have revealed a range of alteration vectors useful in exploration for both the zn rich and cu au vhms deposits carbonate and white mica compositional variations are highlighted as important mineralogical vectors thallium and antimony halos may be useful trace element vectors and oxygen and sulfur provide important isotope vectors toward the center of the hydrothermal system

wall rock alteration and metamorphism of a volcanogenic massive sulfide deposit at que river tasmania petrology and mineralogy the rocks in the alteration halo surrounding the polymetallic massive sulfide deposit at que river preserve primary hydrothermal mineral textures and assemblages despite the imprint of later prehnite pumpellyite facies regional metamorphism their textural preservation is attributed to the mechanical strength of many of the hydrothermal minerals such as pyrite carbonates except calcite and quartz the competency of some of the host rocks and the low strain that has affected many rocks at the margin of the halo assemblages include quartz white mica carbonates albitized plagioclase pyrite and chlorite closer to the ore as intensity of alteration increases albite disappears pyrite apatite rutile and anatase become more common white mica quartz carbonates and chlorite vary in abundance and are distributed irregularly these minerals also occur in hydrothermal veins throughout the stockwork zone several generations of veins are commonly developed with each generation having its own distinctive hydrothermal assemblage both hydrothermal and metamorphic phases are compositionally variable despite some overlap there appear to be systematic differences in composition x ray diffraction and microprobe analyses show that the hydrothermal white micas are variable in composition ranging from illites or muscovites to fuchsites their metamorphic counterparts contain less pyrophyllite and more celadonite the hydrothermal carbonates are most commonly ferroan dolomite magnesian siderite and ferroan magnesite the latter two are more abundant than dolomite where alteration is intense calcite and ferroan dolomite formed during metamorphism and the composition of the hydrothermal and metamorphic carbonates may be different in individual specimens both hydrothermal and metamorphic chlorites are ferro clinochlores and magnesio chamosites metamorphic chlorites outside the halo are more fe rich and more al vi deficient than those within the hydrothermal chlorites exhibit fe mg and al iv al vi si iv mg fe vi tschermakite substitutions and contain al iv contents suggesting temperatures of crystallization of 290 degrees to 320 degrees c similar to the temperature of 280 degrees c inferred from fluid inclusions the chemistry of the hydrothermal phases varies throughout the halo overall fe and mg do not show a systematic trend toward mineralization however fe enrichment of hydrothermal phases in the ore is apparent as is mg enrichment of locally developed chlorite carbonate rocks na and celadonite in white micas and ca in carbonates on the other hand decrease with increasing alteration mg only became an important component in the fluid when seawater infiltrated into the hydrothermal system the heterogeneous distribution of the hydrothermal phases is attributed to successive influxes of hydrothermal fluids of varying composition into the alteration pipe variable water rock ratios and seawater entrainment

stratigraphic volcanic setting of massive sulfide deposits in the cambrian mount read volcanics tasmania the cambrian mount read volcanics of western tasmania host the volcanic hosted massive sulfide vhms deposits at hellyer que river rosebery hercules and mount lyell the volcanics were erupted along and partly onto the western margin of a precambrian basement terrane now represented by the tyennan region the volcanic belt is asymmetrical in section with a main eastern zone of relatively massive lava rich sequences accompanied by abundant intrusions and a broader western zone of volcano sedimentary sequences rich in volcaniclastic mass flow sandstone and breccia the rocks have been strongly deformed regionally metamorphosed to lower greenschist facies and hydrothermally altered in many areas stratigraphic and facies relationships within the highly complex volcanic belt are critically reviewed and reassessed the main volcanic zone is considered to comprise two interfingering lava rich associations the quartz feldspar porphyritic eastern sequence and the largely feldspar porphyritic central volcanic complex this lava rich zone interfingers with the western volcano sedimentary sequences herein referred to as the yolande river sequence the dundas group and the mount charter group new term recent volcanologic studies indicate that the lava rich sequences and indeed the bulk of the preserved mount read volcanics are submarine in character despite the presence of abundant ignimbritelike pumiceous deposits the early volcanism was predominantly rhyolitic dacitic in composition but was followed by a period of active andesitic basaltic volcanism during which the massive sulfide deposits at hellyer and que river and some of those at mount lyell were formed this widespread andesitic basaltic volcanism appears to coincide with a period of active extension and rifting along the belt focused to some extent on the henty fault system the rifting episode is evidenced by abundant tholeiitic dikes along the henty fault and throughout the northern central volcanic complex and by tholeiitic pillow lavas within the henty fault wedge the andesitic basaltic volcanism appears to have culminated in distinctive p 2 o 5 and light rare earth element lree enriched basalts at hellyer and similar rocks at lynch creek and howards plains near queenstown may be correlates the hellyer basalts were buried by black shale and the final volcanic phase was marked by a return to active felsic volcanism which produced widespread crystal and pumice rich mass flow deposits of the southwell subgroup and tyndall group

zonation of alteration facies at western tharsis implications for the genesis of cu au deposits mount lyell field western tasmania the western tharsis deposit located in the mount read volcanic belt of western tasmania is one of 22 mainly cu au deposits in the mount lyell district although the orebody at western tharsis is characterized mainly by disseminated pyrite chalcopyrite like most other deposits in the mount lyell district it also contains bornite rich ores characteristic of a second less common type of deposit the deposit is stratiform and occurs within intermediate and felsic volcanic rocks of the 500 ma central volcanic complex alteration is developed broadly symmetrically around the ore zone with an ore bearing core characterized by a quartz chlorite sericite assemblage the core is enveloped by a quartz pyrophyllite topaz fluorite zunyite woodhouseite assemblage with local bornite bearing ore zones this zone in turn is enveloped by a pyritic quartz sericite assemblage the outermost quartz chlorite carbonate sericite albite assemblage is only developed in the stratigraphic footwall more than 200 m below the ore position the hypogene pyrophyllite bearing assemblage is more characteristic of high sulfidation than volcanic hosted massive sulfide vhms related alteration assemblages moreover the close relationship of this alteration assemblage with the more prevalent quartz chlorite sericite assemblage associated with disseminated pyrite chalcopyrite mineralization suggests that these two types of mineralization are two stages of one mineralizing event not the two separate events suggested by previous authors e g arnold and carswell 1990 geologic relationships and radiogenic isotope data are consistent with an ordovician 460 ma timing for mount lyell cu au mineral deposits this mineralization may be related to the geologic event that formed the local haulage unconformity these observations indicate a potential new exploration model for mineralization in the mount read volcanic belt and in surrounding ordovician rocks

the assessment of chemical weathering rates within an upland catchment in north east scotland a study has been made of weathering in glendye an upland catchement of heather moorland underlain mainly by granite with some gneiss in north east scotland the concentrations of a range of elements and ions in precipitation and river water were measured over a twelve month period the total input and output of each element or ion was calculated the resulting balances show net outputs of all species except hydrogen ion large net outputs of silicon 38 5 kg ha 1 a 1 and bicarbonate 48 kg ha 1 a 1 indicate considerable chemical weathering a large net output of chloride 32 kg ha 1 a 1 indicates the importance of dry deposition of oceanic aerosols when this is allowed for the rate of output of elements due to weathering is si ca na mg k fe al these results were compared with the abundance of elements in bedrock and differential weathering ratios calculated these are compared with data from the hubbard brook study in new hampshire in both cases calcium is by far the most mobile element the relative importance of the atmosphere and of chemical weathering as sources of each element was calculated and the results compared with those of a study at wet sleddale in the lake district similar patterns emerge in both cases

the effects of weathering on the physical and mechanical properties of a granitic saprolite less research has been carried out on the changes induced by weathering to the mechanical properties of reconstituted and intact soils that originate from chemical decomposition of rocks saprolite

short wavelength infrared swir spectral analysis of hydrothermal alteration zones associated with base metal sulfide deposits at rosebery and western tharsis tasmania and highway reward queensland spectral analysis of rock samples by short wavelength infrared swir analysis using the portable infrared mineral analyzer pima spectrometer is a relatively new field method with applications in mineral exploration the technique allows rapid field based identification of hydrothermal alteration minerals and delineation of alteration zones variations in mineral composition crystallinity and relative abundance may also be determined phyllosilicates including white mica and chlorite are particularly amenable to short wavelength infrared analysis these are prominent alteration minerals in the felsic volcanic rocks in the mount read volcanics tasmania and the mount windsor subprovince north queensland they have regional distributions as diagenetic and metamorphic products and exist locally in alteration zones associated with volcanic hosted sulfide deposits a geochemical and spectral investigation of white micas in the least altered rocks in the mount read volcanics has shown considerable background compositional variations the white micas range from phengite to moderately sodic muscovite and swir spectral measurements provide reliable estimates of their compositions chlorites also have a broad compositional range in these rocks however swir spectral analysis has proven to be unreliable in determining chlorite composition in samples where chlorite exists in low proportions relative to white mica or in mixed assemblages with epidote white micas in footwall alteration zones of the rosebery stratiform zn pb deposit tasmania are variably phengitic similar to those in regional background volcanics a unit of relatively unaltered volcaniclastic sandstone in the rosebery hanging wall sequence contains anomalous sodic muscovite in proximity to ore lenses white micas associated with the disseminated to massive pyritic cu au deposits at western tharsis tasmania and highway reward north queensland range in composition from phengite to slightly sodic muscovite in these symmetrically zoned alteration systems white micas grade in composition from phengite in peripheral zones to slightly sodic muscovite in proximal zones near ore in all three cases the white mica compositional variation is a vector to ore that is effectively measured by swir spectrometry with particular application in prospect scale exploration chlorite compositions at rosebery are not strictly spatially related to ore but tend to be most magnesian in zones of high chlorite abundance in the outer alteration zone at western tharsis there is a faint proximal trend to iron rich chlorites however it does not represent a well defined vector to ore in either case attempts at quantitative estimation of the relative abundance of white mica and chlorite in mixed samples by spectral analysis have produced results that are imprecise in comparison to geochemically derived estimates the data scatter relates to the low proportions of chlorite in the majority of the samples analyzed resulting in weak chlorite absorptions better results may be obtainable in specific alteration or lithostratigraphic domains by use of customized spectral unmixing software this investigation has shown that pima based swir spectrometry is a potent field method of mapping compositional variations in white micas that represent empirical vectors to at least some types of volcanic hosted sulfide deposits it has also highlighted its effectiveness in field identification of megascopically difficult or indeterminate alteration minerals such as pyrophyllite zunyite and topaz which may have genetic implications and exploration significance

possible submarine advanced argillic alteration at the basin lake prospect western tasmania australia the basin lake copper gold prospect lies in western tasmania s mount read volcanics and is hosted in a series of calc alkaline andesites quartz feldspar porphyries mudstones carbonates and sandstones between the tyndall group and the central volcanic complex alteration at the basin lake prospect occurs over a strike length of 1 4 km and includes thin strata bound pyrophyllite quartz paragonite kaolinite pyrite alunite alteration zones up to 12 m wide and containing up to 50 wt percent pyrophyllite with local fluorite veining these zones grade out to paragonite muscovite kaolinite quartz pyrite and muscovite carbonate chlorite alteration zones extensive propylitic alteration chlorite carbonate epidote affects most other rocks outside these zones mineralization consists of thin strata bound zones of massive and vein pyrite tennantite and chalcopyrite with trace covellite and galena hosted mainly within an intensely silicified core of the pyrophyllite quartzsericite alteration zone pyrite has 34s values of 1 4 to 6 9 per mil although marginal vein pyrite in the propylitic zone has 34s values around 12 4 per mil large silicified glacial erratic boulders at surface contain massive and vein pyrite enargite and tennantite with minor barite and trace covellite stannoidite and mawsonite pyrite and enargite have 34s values of 1 7 to 6 8 per mil barite has 34s values around 35 2 per mil with 87sr 86sr around 0 7108 the alteration and mineralization at the basin lake prospect is similar to that associated with high sulfidation copper gold systems formed by acidic relatively oxidized fluids a new geochemical vector here termed the advanced argillic alteration index aaai 100 sio2 sio2 10mgo 10cao 10na2o has been devised to help quantify the intensity of alteration the values of the aaai at basin lake are similar to those of several high sulfidation epithermal deposits the low sulfide 34s values are similar to those at other sulfide occurrences in the mount read volcanics that have previously been considered to be barren are lower than those of nearby volcanic hosted massive sulfide deposits and may indicate a magmatic fluid component however the 34s and 87sr 86sr values of basin lake barite at the assumed highest exposed level of the system and higher 34s values in pyrite from marginal veins are similar to those of cambrian volcanic hosted massive sulfide systems indicating the involvement of reduced seawater sulfate at these locations calcite carbon and oxygen isotope values silicate oxygen isotope values and the unusual abundance of carbonate close to advanced argillic alteration indicate fluid mixing and suggest that acidic magmatic fluids were likely neutralized by seawater this occurrence strengthens the case for prospecting the mount read volcanics and other similar submarine volcanic belts for copper gold and gold only deposits that formed by the actions of hyperacid oxidized fluids

laboratory studies of two common saprolitic soils in hong kong two commonly encountered saprolitic soils in hong kong weathered volcanic tuff wt and weathered granite wg were studied using high quality intact samples the intact samples exhibited quasi preconsolidation pressure or yield stress under isotropic compression due to their bonded structures but the yield was progressive and not abrupt as the stress increased significant volumetric changes were measured these changes resembled clay type behavior the soils also exhibited anisotropic deformation under isotropic loading and unloading which was associated with the features of their parent rocks during the drained tests shearing at the in situ stress state produced peak strength and volumetric dilation undrained shearing showed complicated stress paths and dilatancy behavior in these soils phase transformation states and dilative shear failure were readily seen which resembles typical sand type behavior distinct shear band s appeared in the wt specimens during shearing whereas a bulging type of failure appeared in the wg specimens the soils ultimately approached the corresponding state guided by a unique critical state line regardless of their complex initial states in relation to the bonded structure and drainage conditions

calculation of oxygen isotope fractionation in hydroxyl bearing silicates abstract the modified increment method has been applied to the calculation of oxygen isotope fractionation factors for hydroxyl bearing silicate minerals the order of 18o enrichment obtained in common rock forming minerals is pyrophyllite kaolinite tourmaline talc prehnite topaz illite phengite lepidolite muscovite staurolite epidote glaucophane serpentine chlorite tremolite hornblende phlogopite biotite humite norbergite ilvaite hydroxyl bearing silicates are enriched in 18o relative to hydroxyl groups but depleted in 18o relative to anhydrous counterparts three sets of self consistent fractionation factors between quartz and the hydroxyl bearing silicate minerals between calcite and the silicate minerals and between the silicate minerals and water have been calculated for a temperature range of 0 1200 c the fractionation factors calculated for mineral pairs are applicable to isotopic geothermometry in igneous metamorphic and sedimentary petrology they can be used as a test of isotopic equilibrium or disequilibrium in natural mineral assemblages over all temperature ranges of geological interest the difference in oxygen isotope composition between the hydroxyl bearing mineral and the oh group is quantitatively demonstrated to be temperature dependent and therefore can be used as a single mineral geothermometer

hydrochemical budgets for a magnesian limestone catchment in lowland england a solute budget study of a magnesian limestone catchment in lowland eastern england showed that 66 of the total solute output from the catchment was derived from chemical weather with 451 302 kg yr 1 778 1 kg ha 1 yr 1 removed in solution the major solutes species produced were ca2 mg2 and hco 3 derived mainly from chemical weathering by percolating acidic rain water catchment runoff was deduced to be comprised of combined piston flow in fissures to springs and matrix seepage each had an overlapping range of ca2 mg2 ratios suggesting a similar long residence time

lithogeochemical and stable isotopic insights into submarine genesis of pyrophyllite altered facies at the boco prospect western tasmania the boco prospect is a large fault dismembered pipelike hydrothermally altered zone in the mount read volcanics of western tasmania it is a synvolcanic alteration zone hosted by felsic volcanic rocks formed in a subaqueous proximal intracaldera setting previous detailed geochemical and geophysical surveys and extensive drill testing have indicated it contains no economic metals the strong to intense pervasively quartz phyllosilicate pyrite altered northern segment of the prospect is semiconcentrically zoned short wavelength infrared swir spectral analysis has revealed that phyllosilicate assemblages grade from phengitic white mica in the least altered peripheries through normal potassic white mica to central zones containing kaolinite slightly sodic white mica and pyrophyllite mass balance calculations indicate average net mass losses in the altered facies were about 10 to 30 g 100 g mainly owing to loss of sio2 which implies very high hydrothermal water rock ratios whole rock oxygen isotope compositions of the enclosing least altered felsic rocks 18o values 8 2 11 7 are indistinguishable from those of altered facies 9 6 11 8 we attribute the former to low temperature diagenetic isotopic exchange with 0 per mil 18o seawater in the peripheral least altered zones and the latter to exchange with 3 to 6 per mil 18o hydrothermal fluids at high water rock ratios and temperatures generally greater than 220 c and locally greater than 270 c in the intensely altered facies pyrite sulfur isotope compositions in the boco altered facies 34s values 1 2 7 2 are distinctly lower than most tasmanian massive sulfide deposits 6 15 compatible with a dominantly magmatic source of sulfur the alteration mineral assemblages estimated mass changes and isotopic data show that the boco alteration system was formed by a large volume of focused acidic hydrothermal fluid which had an oxygen isotope composition of 3 to 6 per mil 18o at and temperature greater than 270 c the slightly 18o enriched fluid isotope composition suggests derivation from either mixed magmatic fluid and seawater or isotopically evolved sea water its advanced argillic altered facies place boco among a newly recognized class of southeast australian cambrian volcanic hosted prospects and deposits these include chester basin lake western tharsis and north lyell in tasmania and rhyolite creek hill 800 and mike s bluff in eastern victoria swir spectral analyses with field portable spectrometers allow early discrimination of this type of hydrothermally altered system and can potentially assist subsequent exploration in mapping facies zonation

low temperature alteration at the world class laronde penna archean au rich volcanogenic massive sulfide deposit abitibi subprovince quebec canada evidence from whole rock oxygen isotopes the oxygen isotope composition of 169 whole rock samples from the world class laronde penna au rich volcanogenic massive sulfide deposit range from 6 5 to 22 0 fractional crystallization from basalt to rhyolite accounts for a variation of approximately 2 in primary whole rock 18o values the remaining variance in whole rock 18o values found at laronde penna must therefore be ascribed to water rock exchange with hydrothermal fluids the metamorphosed hydrothermally altered host rocks have been subdivided according to mineralogical assemblages which display weak covariance with 18o values and whole rock geochemical alteration indices water rock equilibrium exchange models indicate that the high 18o values that characterize the laronde penna deposit are compatible with low temperature 150oc hydrothermal alteration at high water rock oxygen atomic ratios 1 50 zones of lower 18o values stratigraphically beneath the principal ore lens 20 north indicate local zones of higher temperature hydrothermal alteration the oxygen isotope composition of the hydrothermal fluid is estimated to have been 5 as a consequence of mixing between seawater 18o 0 and a component of magmatic water degassed from the volcanic and intrusive rocks associated with the laronde penna deposit

application of airborne laboratory and field hyperspectral methods to mineral exploration in the canadian arctic recognition and characterization of volcanogenic massive sulfide associated hydrothermal alteration in the izok lake deposit area nunavut canada we have investigated the application of ground laboratory and airborne optical remote sensing methods for the detection of hydrothermal alteration zones associated with the izok lake volcanogenic massive sulfide vms deposit in nunavut canada this bimodal felsic zn cu pb ag deposit is located above the tree line in a subarctic environment where lichens are the dominant cryptogamic species coating the rocks the immediate host rhyolitic rocks have been hydrothermally altered and contain biotite chlorite and white micas as dominant alteration minerals these minerals have spectral al oh and fe oh absorption features in the short wave infrared wavelength region that display wavelength shifts which are documented to be due to chemical compositional changes our ground spectrometer measurements indicate that there is a systematic trend in the fe oh absorption feature wavelength position of biotite chlorite with increasing distance from the vms deposit the average fe oh absorption feature wavelength position of the proximal areas 398 3 146 m from mineralization is observed at 2 254 nm and that of the distal areas 5 782 6 812 m at 2 251 nm moreover the proximal areas have an average al oh absorption feature wavelength position at 2 203 nm in contrast with the average wavelength position at 2 201 nm in the distal areas implying a spectral shift of 2 nm these findings indicate that hydrothermal alteration zones can be detected by hyperspectral remote sensing despite the presence of abundant lichen cover however the airborne results discussed in this study required the screening out of more than 99 of the pixels in the area

high sulfate concentrations in limestone springs an important factor in conduit initiation major ion concentrations in 404 springs in carbonate strata were found to exhibit a wide range in sulfate values sulfate concentrations are often much larger than would be expected from the analysis of samples from surface outcrops springs in the sierra madre oriental mexico the rocky mountains front range canada and the peak district england show similarities in sulfate concentration and in spatial distribution springs with high sulfate concentrations are found close to base level and are thermal springs with low sulfate concentration are found at higher elevations above base level and are not thermal there is a direct relationship between sulfate concentration and spring temperature and an inverse relationship with discharge the results from the three areas described support a model of local and regional flow patterns with deep regional flow providing the warm sulfate rich water the initial fracture porosity development in these aquifers may owe as much to the removal of sulfur minerals as to the removal of carbonate minerals high sulfate values are frequently found in carbonate aquifers so this model may be of widespread applicability

chemical denudation on a magnesian limestone hillslope field evidence and implications for modelling the pattern of relative denudation at the soil bedrock interface over a wooded magnesian limestone hillslope was investigated using micro weight loss bedrock tablets the resulting pattern of weight loss after emplacement for one year indicated a consistent upslope increase in solutional denudation results from tablets emplaced for two years confirmed this dye tracing and gypsum sphere weight loss results showed that water movement over the slope was by vertical percolation and not by throughflow the pattern of solutional denudation was related to changes in soil type and associated changes in soil ph continued slope development by solutional denudation will ultimately lead to slope decline comparison with a similar study suggests that a general soil chemistry based model of hillslope solutional denudation can be proposed

geochemistry of the cambrian volcanic hosted massive sulfide rich mount read volcanics tasmania and some tectonic implications the cambrian mount read volcanics belt in western tasmania hosts five major gold rich massive sulfide deposits and remains the focus of intense exploration activity and geologic research a geochemical study of least altered lavas and shallow intrusions with emphasis on basaltic to andesitic compositions was carried out to determine the primary magmatic affinities and tectonic setting of eruption of the mount read volcanics to aid in internal correlations within the belt and to provide starting material estimates for mineralization related alteration studies three calc alkaline suites one extending to shoshonitic compositions and two tholeitiic suites have been distinguished within the mount read belt suite i is voluminous and includes the eastern sequence central volcanic complex tyndall group the intrusive quartz feld spar porphyries and granitoids and the andesitic lavas of the que hellyer footwall sequence suite i andesites are transitional medium to high k calc alkaline rocks la yb n 5 12 avg 8 1 and are the least light ree enriched calc alkaline lavas in the mount read volcanics suite ii comprises intrusive and extrusive often hornblende porphyritic andesites and dacites mainly from the upper part of the southern central volcanic complex they are more p 2 o 5 and light ree enriched la yb n 10 26 avg 16 7 than suite i and have high k calc alkaline affinities suite iii includes basaltic and andesitic lavas from the que hellyer hanging wall sequence in the northern part of the belt the lynch creek basalts near queenstown and intrusive basalts in the howards plains area northwest of queenstown suite iii rocks show a striking compositional range from low tio 2 0 4 0 5 low p 2 o 5 0 1 basalts with la yb n values from 8 to 12 and almost flat heavy ree patterns to low tio 2 0 4 0 8 but strongly to exceptionally p 2 o 5 and light ree enriched basalts with up to 350 times chondritic la and la yb n values up to 34 the latter are regarded as shoshonites tholeiitic pillow basalts of the henty fault wedge and the closely related dikes of the henty dike swarm constitute suite iv these have tio 2 contents from 1 0 to 1 6 percent very low nb contents 3 ppm and only slightly light ree enriched ree patterns la yb n 1 4 3 4 they are considered to be most similar to suprasubduction zone basalts erupted during the early phase of arc splitting and back arc basin development and indicate a period of tension and rifting of the mount read belt in post central volcanic complex but pre tyndall group time suite v is constituted by the miners ridge basalts and includes low tio 2 0 7 basalts with strong light ree depletion la yb n 0 5 and higher tio 2 to 2 6 lavas with only slight light ree depletion la yb n 0 9 suite v basalts are tentatively correlated with rift tholeiite sequences associated with the crimson creek formation and therefore are regarded as part of the pre mount read volcanics basement the three calc alkaline suites occur in a general stratigraphic order with suites i and ii being more or less coeval near queenstown they indicate a magmatic evolution from transitional medium to high k rocks through high k rocks to strongly enriched shoshonitic rocks closest modern analogues are postcollisional volcanics in regions of arc continent collision e g east papua and the roman province the occurrence of boninite derived chromites probably derived from the allochthonous mafic ultramafic complexes outcropping just west of the mount read belt in two sedimentary units within the mount read volcanics sequence below suite iii basalts supports a postcollisional origin for at least the major part of the mount read volcanics other similar postcollisional sequences particularly if formed in a submarine setting must be considered highly prospective for vhms deposits

some aspects of the compressibility behaviour of a clayey sand the intrinsic behaviour of a residual clayey sand derived from sandstone was investigated in one dimensional compression the data show some interesting differences when compared with other published data in that no unique normal compression line can be identified although the compressibility on first loading is similar to that for many sandy materials at states on their normal compression lines the locations of the compression curves were found to be a function of the initial voids ratio and there was no convergence at higher stresses tests on a model clay sand mixture indicated that this behaviour is common to gap graded clayey sands key words sands compressibility oedometer tests

phyllosilicate alteration mineral assemblages in the active subsea floor pacmanus hydrothermal system papua new guinea odp leg 193 pacmanus is an active submarine hydrothermal system in the manus back arc basin papua new guinea located at 1 600 to 1 700 m below sea level on the crest of a dacitic volcano it is inferred to represent a modern analogue of ancient mineralizing sea floor hydrothermal systems that produced volcanogenic polymetallic massive sulfide deposits ocean drilling program odp leg 193 drilled the subsea floor hydrothermal alteration zone of pacmanus in a high temperature discharge area roman ruins and a low temperature discharge area snowcap reaching a maximum depth of 380 m below the sea floor evidence from short wavelength infrared swir spectroscopy x ray diffraction xrd analyses calculated normative mineral abundances and electron microprobe data show that there are substantial variations in the hydrothermal phyllosilicate assemblages within the pacmanus hydrothermal system the altered dacite at roman ruins contains 10 to 25 wt percent normative chlorite smectite and up to 15 wt percent normative illite in contrast altered dacite below snowcap contains up to 50 wt percent combined normative illite paragonite chlorite smectite pyrophyllite swir data show that pyrophyllite is particularly abundant between 50 and 120 and between 220 and 270 m below sea floor indicating localized interaction of dacite with acidic hydrothermal fluids variations in the na k ratio of dioctahedral phyllosilicate determined by electron microprobe and spectral analyses confirm the presence of a paragonitic component at snowcap a model is suggested to explain the differences in the distribution of hydrothermal phyllosilicate assemblages in the two areas in terms of variations in fluid composition and changes to the subsea floor hydrology in a dynamically evolving volcanic hydrothermal environment