petrologic and stable isotope constraints on the source and evolution of skarn forming fluids at pine creek california a detailed geochemical analysis of the well exposed multistage pine creek california tungsten deposit has constrained the roles of magmatic metamorphic and meteoric fluids in the development of the zoned scheelite ore and calc silicate skarn metamorphic conditions of p 2 kb t 600 degrees c and x sub co 2 0 25 are recorded in the metasedimentary rocks of the septum metamorphism yielded calcite diopside graphite and calcite dolomite periclase brucite forsterite assemblages in the variably dolomitic siliceous carbonate rocks of the pine creek septurn following intrusion of the morgan creek quartz monzonite metasomatism developed the zoned endoskarn exoskarn at the contact the massive garnet andradite sub 20 50 pyroxene hedenbergite sub 20 80 or quartz skarn assemblage carries most of the scheelite calculated t x sub co 2 equilibria corrected for solid solution effects restrict skarn formation to x sub co 2 0 2 at t 500 degrees or 50 degrees c calculated f sub o 2 f sub f 2 f sub s 2 diagrams indicate f sub o 2 values near quartz fayalite magnetite and f sub s 2 values well below pyrrhotite pyrite during skarn formation slightly falling temperatures were accompanied by increased f sub s 2 and hydration of the skarn assemblages stable isotope data for calcites show a mixing trend from unaltered marble delta 18 o 24ppm delta 13 c 3 5 degrees to values in equilibrium with magmatic fluids delta 18 o 8ppm delta 13 c 6ppm biotite quartz thermometry for the quartz monzonite yields temperatures of 410 degrees to 460 degrees c well below the solidus and suggesting later reequilibration pyroxene quartz analyses suggest that these minerals equilibrated at temperatures of 460 degrees to 560 degrees c the delta 18 o values measured for garnets suggest disequilibrium for the garnet quartz and garnet pyroxene pairs d h results for epidote and biotite suggest that meteoric water influx became more important with time sulfur isotope data are consistent with a reduced magmatic source

characteristics and origin of the zhulazhaga gold deposit in inner mongolia china abstract the zhulazhaga gold deposit in the northern margin of the north china craton ncc is a large tonnage hydrothermal deposit with a reserve of about 50 t at about 4 g t au the deposit is characterized by an epigenetic style of mineralization in metasedimentary rocks dominated by slates low grade metamorphic clastic rocks and minor volcanic rocks gold mineralization is dominantly controlled by structures manifested by stratabound orebodies located immediately to the east and west of a major n s trending fault and associated extensional fractures and ne trending fault zones the mineralization is also preferentially located in the fourth sub member of first member of the agulugou formation there are many auriferous quartz veins parallel to the bedding of the host rocks which contain the orebodies and high grade ore preferentially occurs near to these quartz veins the structures provided pathways for transportation of gold bearing fluids within the formation that appears to form a particularly favorable host rock and depositional setting hydrogen and oxygen isotope data indicate that ore forming fluids were dominated by magmatic water mixed with minor meteoric water sulfur and lead isotope data indicate that some sulfur and lead came from the magmatic fluid the metallogenic age 280 ma of this deposit and the crystallization age 280 290 ma of the granite porphyry in the district indicate a link between the hercynian magmatism and gold mineralization the hercynian tectono magmatism and associated hydrothermal activity remobilized gold and drove ore forming fluids to the favorable depositional environment the northern margin of the ncc is prospective for gold mineralization hosted in metasedimentary rocks which may be one of the most important deposit types for future gold exploration in northern china

re os geochronology of the hitachi volcanogenic massive sulfide deposit the oldest ore deposit in japan the hitachi volcanogenic massive sulfide vms deposit in the hitachi belt is one of the largest cu zn sulfide deposits in japan however its primary formation age has not been precisely determined because regional and contact metamorphism have disturbed some radiometric isotope systems e g k ar ages on wall rocks further metamorphism has greatly reduced the fossil record which has limited the use of biostratigraphy to establish the ore deposit age we applied re os isotope dating to samples from two representative sulfide deposits of the greater hitachi vms deposit the fudotaki and fujimi deposits re os isotope data from the fudotaki deposit yields a model 3 age of 533 13 ma with an initial 187 os 188 os ratio of 0 35 0 20 in contrast re os isotope data from the fujimi sulfide ore did not exhibit a linear correlation suggesting that the re os isotope system there has been disturbed by regional metamorphism of higher grade than the fudotaki deposit as well as contact metamorphism during intrusion of cretaceous granitic rocks although the fudotaki sulfide ores have been metamorphosed to lower epidote amphibolite facies the well defined re os isochron allowed us to interpret the timing of primary sulfide deposition on the paleoseafloor some orebodies of the greater hitachi vms deposit have been estimated to be early carboniferous based on the scarce fossil records and considered to be distributed in the daioin formation but our results revealed that the fudotaki deposit were formed during the cambrian and occurs in the upper akazawa formation which strongly supports the idea that the cambrian beds are widely distributed in the hitachi belt and that a significant unconformity exists between the cambrian and early carboniferous above the fudotaki deposit the cambrian re os date classifies the hitachi vms deposit as the oldest dated ore deposit in japan and in turn provides an insight to understand the geologic framework and genesis of the proto japanese islands and the east asian region

phyllosilicate poor palagonitic dust from mauna kea volcano hawaii a mineralogical analogue for magnetic martian dust the mineralogical and elemental composition of dust size fractions 2 and 5 m of eight samples of phyllosilicate poor palagonitic tephra from the upper slopes of mauna kea volcano hawaii were studied by x ray diffraction xrd x ray fluorescence xrf visible and near ir reflectance spectroscopy mossbauer spectroscopy magnetic properties methods and transmission electron microscopy tem the palagonitic dust samples are spectral analogues of martian bright regions at visible and near ir wavelengths the crystalline phases in the palagonitic dust are in variable proportions plagioclase feldspar ti containing magnetite minor pyroxene and trace hematite no basal reflections resulting from crystalline phyllosilicates were detected in xrd data weak broad xrd peaks corresponding to x ray amorphous phases allophane nanophase ferric oxide possibly ferrihydrite and for two samples hisingerite were detected as oxidative alteration products of the glass residual unaltered glass was also present mossbauer spectroscopy showed that the iron bearing phases are nanophase ferric oxide magnetite titanomagnetite hematite and minor glass and ferrous silicates direct observation by tem showed that the crystalline and x ray amorphous phases observed by xrd and mossbauer are normally present together in composite particles and not normally present as discrete single phase particles ti bearing magnetite occurs predominantly as 5 150 nm particles embedded in noncrystalline matrix material and most likely formed by crystallization from silicate liquids under conditions of rapid cooling during eruption and deposition of glassy tephra and prior to palagonitization of glass rare spheroidal halloysite was observed in the two samples that also had xrd evidence for hisingerite the saturation magnetization js and low field magnetic susceptibility for bulk dust range from 0 19 to 0 68 am2 kg and 3 4 10 6 to 15 5 10 6 m3 kg at 293 k respectively simulation of the mars pathfinder magnet array ma experiment was performed on mauna kea volcano in areas with phyllosilicate poor palagonitic dust and with copies of the pathfinder ma on the basis of the magnetic properties of dust collected by all five ma magnets and the observation that the pathfinder mas collected dust on the four strongest magnets the value for the saturation magnetization of martian dust collected in the ma experiments is revised downward from 4 2 am2 kg to 2 5 1 5 am2 kg the revised value corresponds to 2 7 1 6 wt magnetite if the magnetic mineral is magnetite using js 92 am2 kg for pure magnetite fe3o4 or to 5 0 3 0 to 3 4 2 0 wt maghemite if the magnetic mineral is pure maghemite using js 50 to 74 am2 kg for pure maghemite fe2o3 comparison of the magnetic properties of bulk mauna kea palagonitic dust to those for dust collected by ma magnets shows that the ma magnets extracted culled a subset 25 34 wt of composite magnetic particles from bulk dust the extent of culling of martian dust is not well constrained because the mauna kea palagonitic dust satisfies the essential constraints of the pathfinder magnetic properties experiment composite and magnetic particles capable of being collected by five ma magnets a working hypothesis for the strongly magnetic mineral present in martian dust and soil is magnetite possibly ti bearing formed by rapid crystallization from silicate liquids having volcanic and or impact origins subsequent palagonitization of the glass produces the nanophase ferric oxide phases that dominate the spectral properties of martian bright regions at visible and near ir wavelengths magnetic and phyllosilicate poor palagonitic dust from mauna kea volcano is thus a spectral and magnetic analogue for magnetic martian dust

alteration of hyaloclastites in the hsdp 2 phase 1 drill core 1 description and paragenesis this is the publisher s version copyright 2003 by chinese geophysical society all rights reserved

the formation of helgafell southwest iceland a monogenetic subglacial hyaloclastite ridge sedimentology hydrology and volcano ice interaction abstract helgafell a little eroded basaltic hyaloclastite ridge in southwest iceland formed in a single eruption under a pleistocene ice sheet the ice thickness at the eruption site was at least 500 m and it was probably located some 15 km from the glacier s snout the eruption created a 2 km long 0 8 km wide and initially 300 m high ridge gravity modelling indicates that helgafell has a bulk density of 1800 kg m 3 and that holocene lavas around it are 40 80 m thick this confirms that helgafell is predominantly made of hyaloclastite with pillow lavas and intrusions only making up a few percent of the total volume the southeast side is made of unsorted eruption fed hyaloclastites considered to have been piled up against an ice wall while moderately to well sorted water transported material is found on the northwest side glacier flow and meltwater drainage was towards the northwest the absence of basal pillow lavas suggests that magma fragmentation occurred from the onset of the eruption until its end the lithofacies preserved indicate a fully subglacial eruption although a final subaerial eruptive phase may have taken place through an ice chimney the volatile contents h 2 o 0 26 0 37 wt of several glass samples from the southeast side of the mountain indicate water pressures of 1 mpa throughout the eruption efficient syn eruptive drainage of meltwater coupled with rapid ice subsidence probably led to partial dynamic support of the ice causing water pressure in the vault to be much lower than the static load of the overlying ice observed lack of correlation between elevation and volatile content may be a consequence of gradual reduction in dynamic support as the eruption rate declined and the edifice grew higher helgafell demonstrates that explosive activity may occur under 500 m thick ice and it may be an analogue to the ridge formed in the gjalp eruption in 1996

a global view of martian surface compositions from mgs tes thermal emission spectrometer tes data from the mars global surveyor mgs are used to determine compositions and distributions of martian low albedo regions two surface spectral signatures are identified from low albedo regions comparisons with spectra of terrestrial rock samples and deconvolution results indicate that the two compositions are a basaltic composition dominated by plagioclase feldspar and clinopyroxene and an andesitic composition dominated by plagioclase feldspar and volcanic glass the distribution of the two compositions is split roughly along the planetary dichotomy the basaltic composition is confined to older surfaces and the more silicic composition is concentrated in the younger northern plains

origins of marslike spectral and magnetic properties of a hawaiian palagonitic soil a palagonitic soil hwmk1 from mauna kea hawaii has marslike spectral and magnetic properties reflectivity spectra of 20 m size separates resemble spectra for martian bright regions and reflectivity spectra of coarser size separates have some spectral characteristics in common with spectra for martian dark regions the bulk soil is magnetic with a saturation magnetization of 0 98 a m2 kg of sample 10 a m2 kg of fe at 296 k petrographic observations show that the soil contains separate populations of black and orange tephra particles which are relatively unaltered fragments of tachylite merocrystalline basalt and extensively weathered palagonitized fragments of sideromelane clear brown basalt glass respectively although both types of particles contain plagioclase and olivine microphenocrysts their iron oxide mineralogies are substantially different as documented by mossbauer and static magnetic measurements a strongly magnetic opaque iron oxide titanomagnetite is associated with black particles and is responsible for the magnetic nature of the soil a relatively weakly magnetic superparamagnetic ferric oxide and minor hematite are associated with orange particles and are responsible for the color the more highly weathered state higher state of oxidation of orange particles is a consequence of the faster weathering palagonitization rate for their sideromelane precursors than for tachylite increasing state of oxidation decreasing saturation magnetization and increasing near ir reflectivity with decreasing particle diameter of bulk soil are manifestations of the increasing proportions of palagonitic material as particle diameter decreases

alteration of hydrovolcanic basaltic ash observations with visible and near infrared spectrometry ash of basaltic composition that is produced by hydrovolcanic activity occurs frequently on earth and may be much more widespread on mars altered basaltic tephras from tuff rings and tuff cones across the basin and range were examined using visible and near infrared vis ir reflectance spectrometry and a variety of other techniques it was found that vis ir spectrometry is sensitive to subtle changes in the hydration and oxidation state of these tephras hydration produces an increase in overall reflectance with gradual development of water and hydroxyl absorptions at 1 4 m and 1 9 m the oxidation of basaltic tephras can be observed spectrally through changes in the position and slope of the fe3 o2 charge transfer edge inflections on that edge due to ferric oxide minerals and changes in the position and depth of the 1 m iron crystal field band significantly in the tuffs examined ferrous and ferric iron minerals produce one composite absorption feature rather than two resolvable bands different styles of alteration were noted between thinly bedded tuff ring deposits emplaced by high energy largely dry pyroclastic surge and massively bedded tuff cone deposits emplaced by wetter lower energy pyroclastic flow the former class of tephras become hydrated and only moderately oxidized with some limited development of dioctahedral smectite clay minerals and minimal palagonitization the latter class of tephras are highly palagonitized which implies a high degree of hydration and oxidation in fact in the most highly altered tephras all the fe2 that is initially in the volcanic glass is converted to fe3 within nanophase and bulk ferric oxide phases in the palagonite there is also more extensive development in the tuff cone beds of zeolite and phyllosilicate minerals the differences in reflectance spectra of altered basaltic tephras can be traced back to initial differences in the water magma ratio extant at the volcanic vent thus vis ir spectrometry holds the potential to be used as a tool for investigations into the volcanic history and paleoclimate of volcanic terrains

heat transfer in volcano ice interactions on mars synthesis of environments and implications for processes and landforms we review new advances in volcano ice interactions on mars and focus additional attention on 1 recent analyses of the mechanisms of penetration of the cryosphere by dikes and sills 2 documentation of the glacial origin of huge fan shaped deposits on the northwest margins of the tharis montes and evidence for abundant volcano ice interactions during the later amazonian period of volcanic edifice construction and 3 the circumpolar hesperian aged dorsa argentea formation interpreted as an ice sheet and displaying marginal features channels lakes and eskers indicative of significant melting and interior features interpreted to be due to volcano ice interactions e g sub glacial volcanic edifices pits basins channels and eskers in this context we describe and analyse several stages and types of volcano ice interactions 1 magmatic interactions with ice rich parts of the cryosphere 2 subglacial volcanism represented by intrusion under and into the ice and formation of dikes and moberg like ridges intrusion of sills at the glacier volcano substrate interface and their evolution into subglacial lava flows formation of subglacial edifices marginal melting and channels 3 synglacial ice contact volcanism represented by flows banking up against glacier margins chilling and forming remnant ridges and 4 post glacial volcanism and interactions with ice deposits

spectroscopic examinations of hydro and glaciovolcanic basaltic tuffs modes of alteration and relevance for mars abstract hydro and glaciovolcanism are processes that have taken place on both earth and mars the amount of materials produced by these processes that are present in the martian surface layer is unknown but may be substantial we have used mars rover analogue analysis techniques to examine altered tuff samples collected from multiple hydrovolcanic features tuff rings and tuff cones in the american west and from glaciovolcanic hyaloclastite ridges in washington state and in iceland analysis methods include vnir swir reflectance mwir thermal emissivity thin section petrography xrd xrf and mossbauer spectroscopy we distinguish three main types of tuff that differ prominently in petrography and vnir swir reflectance minimally altered sideromelane tuff gray to brown colored smectite bearing tuff and highly palagonitized tuff differences are also observed between the tuffs associated with hydrovolcanic tuff rings and tuff cones and those forming glaciovolcanic hyaloclastite ridges for the locations sampled hydrovolcanic palagonite tuffs are more smectite and zeolite rich while the palagonitized hyaloclastites from the sampled glaciovolcanic sites are largely devoid of zeolites and relatively lacking in smectites as well the gray to brown colored tuffs are only observed in the hydrovolcanic deposits and appear to represent a distinct alteration pathway with formation of smectites without associated palagonite formation this is attributed to lower temperatures and possibly longer time scale alteration altered hydro or glaciovolcanic materials might be recognized on the surface of mars with rover based instrumentation based on the results of this study

paragenesis elemental distribution and stable isotopes at the pena colorada iron skarn colima mexico the pena colorada iron skarn is located in the southern part of the guerrero terrane it contains 150 million metric tons mt with a grade of 36 percent magnetite the deposit occurs at the contact of a 68 ma equigranular diorite with mid cretaceous volcano sedimentary rocks of the tepalcatepec formation volcanic units within this formation have tholeiitic affinity and ree patterns that are compatible with a primitive arc setting the pena colorada diorite and associated voluminous aplitic phases are part of a late cretaceous calc alkaline continental arc that subsequently intruded this basin northeast vergent deformation affected the region in the late cretaceous north south and east west reverse and northwest and northeast strike slip faults localize the mineralization the alteration halo around the diorite intrusion is 500 m wide within an inner 200 m halo the volcano sedimentary section was affected by an early metamorphic event with discontinuous bands of pyroxene di 68 hd 29 jo 3 hornfels and garnet gr 61 am 36 ad 3 disseminations metasomatic pyroxene garnet and plagioclase cut the early metamorphic event preferentially replacing carbonate and volcanic units up to and including a 35 m thick marl located 200 m above the intrusion metasomatic pyroxene and garnet have average compositions of di 77 hd 21 jo 2 and ad 76 gr 20 am 2 sp 1 py 1 respectively pyroxene compositions reach di 94 hd 5 jo 1 whereas garnet exhibits intragrain compositional zoning from ad 49 gr 46 in the core to ad 100 gr 0 in the rim albitization of preexisting protoliths modified igneous plagioclase compositions from ab 67 an 32 or 1 up to ab 96 an 3 or 1 albitization is followed by abundant fracture controlled fe epidote and cl bearing chlorite cha 84 cli 14 pen 2 that extend from the marl unit outward some 300 m this association is cut by a later assemblage of epidote chlorite prehnite that affects the entire 500 m width of the alteration halo and part of the intrusion chlorite cha 54 cli 45 pen 1 from this later event is richer in mg than that from the previous association igneous hornblende in the intrusion is altered to actinolite a potassic alteration event related to a hydrothermal breccia and aplitic dikes overprints the pre existing calc silicate associations alteration minerals in the breccia and the 200 m potassic halo around it evolve from early k feldspar biotite quartz to late jasperoid fluorapatite calcite veins mg rich biotite phl 77 ann 23 and ree rich apatite contain f cl oh ratios of 1 0 3 and 1 0 0 respectively massive magnetite 36 specular hematite 7 sulfide o c s and h stable isotope determinations on minerals from the calc silicate association are consistent with an igneous source for the initial fluids which mixed outward with an increasing component of trapped seawater or evaporite however water in equilibrium with magnetite exhibits unusually enriched 18 o values relative to other coexisting mineral derived fluids a solution that equilibrated with limestone at relatively high temperature is required to explain these heavy values

oxygen isotope study of the kamioka zn pb skarn deposits central japan the kamioka zn pb deposits consist of clinopyroxene rich skarns replacing limestone lenses in hida gneissose rocks paleozoic metabasite early jurassic funatsu granitic rocks and late cretaceous porphyritic dikes and stocks are the known igneous rocks in the mining area oxygen isotopic compositions of eight separates each of clinopyroxene and quartz from the deposits table 1 and some minerals and rocks from the major rock units around the deposits table 2 have been analyzed the estimated oxygen isotopic ratios of the fluids responsible for the formation of the deposits range as low as 4 to 3 smow these values are considerably lower than expected from magmatic waters and demonstrate that none of the igneous rocks in the area could be a direct source of the skarn and ore forming fluids the data instead show that the deposits are formed by a huge convective circulation of solutions of meteoric water origin promoted by a hidden batholithic intrusion at the time of the late cretaceous

iron mineralogy and aqueous alteration from husband hill through home plate at gusev crater mars results from the mossbauer instrument on the spirit mars exploration rover 1 spirit s mossbauer mb instrument determined the fe mineralogy and oxidation state of 71 rocks and 43 soils during its exploration of the gusev plains and the columbia hills west spur husband hill haskin ridge northern inner basin and home plate on mars the plains are predominantly float rocks and soil derived from olivine basalts outcrops at west spur and on husband hill have experienced pervasive aqueous alteration as indicated by the presence of goethite olivine rich outcrops in a possible mafic ultramafic horizon are present on haskin ridge relatively unaltered basalt and olivine basalt float rocks occur at isolated locations throughout the columbia hills basalt and olivine basalt outcrops are found at and near home plate a putative hydrovolcanic structure at least three pyroxene compositions are indicated by mb data mb spectra of outcrops barnhill and torquas resemble palagonitic material and thus possible supergene aqueous alteration deposits of fe3 sulfate soil located at paso robles arad and tyrone are likely products of acid sulfate fumarolic and or hydrothermal activity possibly in connection with home plate volcanism hematite rich outcrops between home plate and tyrone e g montalva may also be products of this aqueous activity low water to rock ratios isochemical alteration are implied during palagonite goethite and hematite formation because bulk chemical compositions are basaltic so3 free basis high water to rock ratios leaching under acid sulfate conditions are implied for the high sio2 rock and soil in eastern valley and the float rock fuzzysmith which has possible pyrite marcasite as a hydrothermal alteration product

eruptive conditions and depositional processes of narbona pass maar volcano navajo volcanic field navajo nation new mexico usa phreatomagmatic deposits at narbona pass a mid tertiary maar in the navajo volcanic field nvf new mexico usa were characterized in order to reconstruct the evolution and dynamic conditions of the eruption our findings shed light on the temporal evolution of the eruption dominant depositional mechanisms influence of liquid water on deposit characteristics geometry and evolution of the vent efficiency of fragmentation and the relative importance of magmatic and external volatiles the basal deposits form a thick 5 20 m massive lapilli tuff to tuff breccia deposit this is overlain by alternating bedded sequences of symmetrical to antidune cross stratified tuff and lapilli tuff and diffusely stratified clast supported reversely graded lapilli tuffs that pinch and swell laterally this sequence is interpreted to reflect an initial vent clearing phase that produced concentrated pyroclastic density currents followed by a pulsating eruption that produced multiple density currents with varying particle concentrations and flow conditions to yield the well stratified deposits only minor localized soft sediment deformation was observed no accretionary lapilli were found and grain accretion occurs on the lee side of dunes this suggests that little to no liquid water existed in the density currents during deposition juvenile material is dominantly present as blocky fine ash and finely vesiculated fine to coarse lapilli pumice this indicates that phreatomagmatic fragmentation was predominant but also that the magma was volatile rich and vesiculating at the time of eruption this is the first study to document a significant magmatic volatile component in an nvf maar diatreme eruption the top of the phreatomagmatic sequence abruptly contacts the overlying minette lava flows indicating no gradual drying out period between the explosive and effusive phases the lithology of the accidental clasts is consistent throughout the vertical pyroclastic stratigraphy suggesting that the diatreme eruption did not penetrate below the base of the uppermost country rock unit a sandstone aquifer 360 m thick by comparison other nvf diatremes several tens of kilometers away were excavated to depths of 1 000 m beneath the paleosurface e g delaney pt ship rock new mexico the vent of a violent volcanic eruption in beus ss ed geological society of america centennial field guide rocky mountain section 2 411 415 1987 this can be accounted for by structurally controlled variations in aquifer thickness beneath different regions of the volcanic field variations in accidental clast composition and bedding style around the edifice are indicative of a laterally migrating or widening vent that encountered lateral variations in subsurface geology we offer reasonable evidence that this subsurface lithology controlled the availability of external water to the magma which in turn controlled characteristics of deposits and their distribution around the vent

p t x conditions origin and evolution of cu bearing fluids of the shear zone hosted huogeqi cu pb zn fe deposit northern china abstract huogeqi is a shear zone hosted epigenetic deposit within the greenschist amphibolite facies of the mesoproterozoic langshan group in the langshan district on the northern margin of the north china craton ncc copper mineralization in the huogeqi deposit was formed in two stages a main stage controlled by the shear zone and characterized by brittle ductile ore forming structures and a lower greenschist facies mineral assemblage and a late stage characterized by open space filling textures and low temperature minerals based on microthermometric and raman microprobe analysis the main stage cu bearing fluid was mesothermal low salinity and h 2 o ch 4 dominant and was generated by an interaction between a deep crustal metamorphic fluid and graphite bearing host rocks this interaction resulted in a more ch 4 rich fluid which was more amenable to be immiscible we showed that immiscibility of the h 2 o ch 4 fluid occurred due to temperature decrease prior to the main stage cu mineralization cu was finally precipitated from the resultant h 2 o rich aqueous fluid main stage cu mineralization temperature was obtained using various methods 310 370 c by intersection of isochors of coexistent ch 4 and aqueous inclusions 364 41 c on average by pressure correction of the homogenization temperatures of aqueous inclusions and 362 26 c using the chlorite geothermometer pressure during cu deposition fluctuated between lithostatic and hydrostatic at depths of ca 10 12 km but it seemingly had no effect on the mineralization process the late stage cu bearing fluid was a low temperature low salinity h 2 o of meteoric origin

authigenic clay mineral distribution lower tuscaloosa formation southwest mississippi impact on sandstone reservoir quality in the north hustler field area abstract a detailed study of relative clay mineral abundance and distribution in lower tuscaloosa cores from the north hustler field area of southwest mississippi provides insight into the original clay mineral composition of these rocks and their subsequent diagenetic history data produced by this study show that the relative percentages of authigenic clays often change across major lithofacies boundaries as a function of major changes in the depositional environment differences in the energies involved during sedimentation that resulted in substantial changes in textures mineralogical compositions and biota as well as wholesale changes in the chemistry of the waters of sedimentation in cases where continental to marine contacts or transitions occur in such cases differences in the effects produced by progressive diagenesis of the formation are to be anticipated an important conclusion from this study was that lower tuscaloosa clays may act as sensitive indicators of even subtle geologic change changes within lithofacies across very sharp discontinuities such as those which separate stacked fluvial bars can also produce shifts in clay mineral proportions with or without textural changes across the contact these shifts may reflect important aspects of reservoir heterogeneity even siltstone siltstone contacts are highlighted by dramatic shifts in the proportions of the clays for example across the contact between marine interdistributary bay deposits and those of a lower fluvial flood plain the study also established that carbonate cemented tight streaks are highlighted as much or more by shifts in clay mineral proportions than by the expected decrease in porosity

controls on palagonitization versus pedogenic weathering of basaltic tephra evidence from the consolidation and geochemistry of the keanakako i ash member kilauea volcano 1 on the summit of kilauea volcano incipient palagonitization and consolidation of vitric tephras from the 90 of the carbon is mantle derived we hypothesize that the palagonitized zones may denote the location of fossil steam vents similar to active vents exposed along circumferential faults on both the north and the south sides of the kilauea caldera elsewhere keanakako i tephras are weathering into pedogenic products that closely reflect modern environmental conditions under acidic soil conditions ph 6 0 tephra is undergoing dissolution with the development of opaline crusts on outcrop faces under more neutral soil ph 6 5 7 8 the pedogenic products reflect the degree of desilication of tephra mitigated by leaching dominantly smectite where mean annual rainfall is 50 cm yr and dominantly kaolinite allophane and or imogolite where rainfall exceeds 250 cm yr

visible near infrared and middle infrared spectroscopy of altered basaltic tephras spectral signatures of phyllosilicates sulfates and other aqueous alteration products with application to the mineralogy of the columbia hills of gusev crater mars 1 we studied visible to near infrared vnir 0 35 2 5 m and middle infrared mir 1800 250 cm 1 also called thermal infrared and vibrational spectra of basaltic tephras from mauna kea volcano that were altered under ambient hydrothermal hydrolytic and acid sulfate and dry heat conditions although models of mir spectra of altered tephras generally produce fits whose quality is reduced compared to deconvolutions of primary lithologies they successfully identify major alteration phases cristobalite oxide phyllosilicate and sulfate except in palagonites mir spectra of the 1 in spectra of the 500 1000 m fraction only if phyllosilicates are present although mauna kea palagonitic tephra is considered a vnir analog to martian dust comparison of mir altered tephra spectra 45 m fraction to dust spectra retrieved from mars global surveyor and mars exploration rover instruments do not provide good spectral matches the best mir match is a tephra that has a strong plagioclase feldspar transparency feature and was altered under dry high temperature oxidizing conditions this sample is not a vnir analog and is not a process analog but it emphasizes the mineralogical importance of plagioclase feldspar in martian dust no single tephra is a good spectral analog across the vnir and mir we found no evidence for substantial sulfates or phyllosilicates in mini thermal emission spectrometer mini tes spectra from gusev crater

recent advances in time lapse laboratory rock physics for the characterization and monitoring of fluid rock interactions abstractmonitoring thermo chemo mechanical processes geophysically e g fluid disposal or storage thermal and chemical stimulation of reservoirs or natural fluids simply entering a new system raises numerous concerns because of the likelihood of fluid rock chemical interactions and our limited ability to decipher the geophysical signature of coupled processes one of the missing links is understanding the evolution of seismic properties together with reactive transport because rock properties evolve as a result of chemical reactions and vice versa capturing this coupling experimentally is one of the missing elements in the existing literature this paper describes recent advances in rock physics experiments to understand the effects of dissolution induced compaction on acoustic velocity porosity and permeability this paper has a dual aim understanding the mechanisms underlying permanent modifications to the rock microstructure and providing a richer set of experimental information to inform th

microtextures microchemistry and mineralogy of basaltic glass alteration jeju island korea with implications for elemental behavior the meteoric alteration of basaltic glass in hyaloclastite 0 55 to 0 2 ma from jeju island korea was examined using high resolution electron microscopy in situ sample preparation using focused ion beam and microchemical analysis the glass particles showed a sequential development of alteration textures toward the glass interior as follows oscillatory zoning of smectite and amorphous bands hemispheres congruent dissolution of glass with smectite infilling in interparticle pore and the replacement of nanogranular amorphous aggregate naa for porous leached glass lg followed by a partial crystallization of smectite chemical compositions of lg widely varied from partial to complete leaching of almost all kinds of cations to a preferred leaching of na only the order of leaching in lg followed na mg 2 ca 2 fe 2 al 3 ti 4 leached cations were removed from the hyaloclastite water system or incorporated into secondary phases sodium was all but removed from the system magnesium was largely lost with partial incorporation into smectite calcium was significantly retained in naa partly incorporated into the smectite interlayer and partly lost iron and al were partitioned between naa and smectite titanium was mostly retained in naa and ti rich silicates the molar ratio of major cations to si was reversed from ca 2 mg 2 na in basaltic glass to na mg 2 ca 2 in groundwater the geochemical evolution of pore water was influenced by the microtextural and microchemical evolution of glass particles and vice versa systematic microtextural microchemical and mineralogical analyses of natural glass alteration are critical to understanding the long term behavior of glass alteration

pre emergent construction of a lacustrine basaltic volcano pahvant butte utah usa the subaqueous phases of an eruption initiated approximately 85 m beneath the surface of pleistocene lake bonneville produced a broad mound of tephra a variety of distinctive lithofacies allows reconstruction of the eruptive and depositional processes active prior to emergence of the volcano above lake level at the base of the volcano and very near inferred vent sites are fines poor well bedded broadly scoured beds of sideromelane tephra having local very low angle cross stratification m1 lithofacies these beds grade upward into lithofacies m3 which shows progressively better developed dunes and cross stratification upsection to its uppermost exposure approximately 10 m below syneruptive lake level both lithofacies were emplaced largely by traction from relatively dilute sediment gravity flows generated during eruption intercalated lithofacies are weakly bedded tuff and breccia m2 and nearly structureless units with coarse basal layers above strongly erosional contacts m4 the former combines products of deposition from direct fall and moderate concentration sediment gravity flows and the latter from progressively aggrading high concentration sediment gravity flows early in the eruption subaqueous tephra jetting from phreatomagmatic explosions discontinuously fed inhomogeneous unsteady dilute density currents which produced the m1 lithofacies near the vent dunes and crossbeds which are better developed upward in m3 resulted from interaction between sediment gravity flows and surface waves triggered as the explosion generated pressure waves and eruption jets impinged upon and occasionally breached the surface intermingling of a tephra emplaced after brief transport by tephra jets within a gaseous milieu and b laterally flowing tephra formed lithofacies m2 along vent margins during parts of the eruption in which episodes of continuous uprush produced localized water exclusion zones above a vent m4 comprises mass flow deposits formed by disruption and remobilization of mound tephra intermittent explosive magma water interactions occurred from the outset of the pahvant eruption with condensation entrainment of water and lateral flow marking the transformation from eruptive to sedimentary processes leading to deposition of the mound lithofacies

spectral analysis and mapping of palagonite tuffs of pavant butte millard county utah the pavant butte tuff cone in millard county utah was erupted into the waters of glacial lake bonneville the basaltic tephras that compose pavant butte are in various states of alteration from nearly pristine to fully palagonitized their level of alteration is detectable by visible and near infrared reflectance spectrometry unaltered sideromelane has a very low reflectance and is characterized by fe2 crystal field bands near 1 and 2 m with hydration the reflectance of the tephra increases water and hydroxyl absorption bands at 1 4 and 1 9 m also become prominent the most highly altered tephras are palagonite tuffs which are characterized by a relatively high reflectance deep h2o and oh absorptions and a steep fe3 absorption edge in the visible such altered basaltic tephras may also be good models for altered soils and dust on mars for which remote sensing is the primary source of data the geologic origin of these near ubiquitous martian surface materials is still undetermined hydrovolcanism is one possible source the palagonite tuff deposits at pavant butte were remotely observed by two airborne imaging spectrometers and the data used for compositional mapping the palagonite tuff was used as an endmember in a linear spectral mixing model analysis this method was also used to calibrate the remotely sensed data to reflectance reflectance spectra from the airborne systems validated the laboratory sample spectra and indicated the presence of both di and trioctahedral clay minerals within the palagonite tuff

application of the sphalerite geobarometer to some skarn type ore deposits based on the equation recently determined formation pressures of skarn type ore deposits were estimated from the composition of sphalerite coexisting with pyrite and hexagonal pyrrhotite as criteria for equilibrium among sphalerite pyrite and hexagonal pyrrhotite the following three points were carefully checked on each specimen 1 the presence of hexagonal pyrrhotite 2 no time sequences among the formation of sulfide minerals and 3 no compositional variation in sphalerite most of the cu fe skarn deposits studied were formed under pressures of more than 1 kb whereas zn pb cu fe deposits tend to have formed at relatively shallow environments namely under less than 1 kb the calculated pressures are qualitatively consistent with the depth of formation of deposits estimated from the geological evidences the sphalerite geobarometry is quite sensitive even at low pressure ranges and it is applicable to the deposits formed under shallow conditions

hydrovolcanic tuff rings and cones as indicators for phreatomagmatic explosive eruptions on mars hydrovolcanism is a common natural phenomenon on earth and should be common on mars too since its surface shows widespread evidence for volcanism and near surface water we investigate fields of pitted cones in the nephentes amenthes region at the southernmargin of the ancient impact basin utopia which were previously interpreted as mud volcanoes the cone fields contain pitted and breached cones with associated outgoing flow like landforms based on stratigraphic relations we determined ahesperian or youngermodel age we test the hypothesis of a hydro volcanic origin based on a detailed morphological and morphometrical analysis and an analysis of the regional context an igneous volcanic origin of these cones as hydrovolcanic edifices produced by phreatomagmatic eruptions is plausible several lines of evidence suggest the existence of subsurface water ice the pitted cones display well developed wide central craters with floor elevations below the preeruptive surface their morphometry and the overall appearance are analogous to terrestrial tuff cones and tuff rings mounds that are also observed in the same region resemble terrestrial lava domes the hydrovolcanic interaction between ascending magma and subsurface water and or water ice may explain the formation of the pitted cones although other scenarios such as mud volcanism cannot be ruled out together with the mounds the cones might represent effusive and explosive edifices of amonogenetic volcanic field composed of lava domes tuff rings tuff cones and possibly maars

types of phreatomagmatic volcanoes in the western snake river plain idaho usa abstract the western snake river plain graben in southwestern idaho includes a large hydrovolcanic field which was produced in late miocene to pleistocene time by the interaction of rising basaltic magmas with the waters and water saturated deposits of an enormous freshwater lake lake idaho the phreatomagmatic volcanoes in this field may be grouped into three types emergent subaqueous and subaerial emergent volcanoes which began erupting under water and built up above the lake level are relatively large and symmetrical are dominated by bedded tuffs and late magmatic deposits and are excellent indicators of water depth at the time of the eruption subaqueous volcanoes which never built up above the lake level are relatively small and asymmetrical are dominated by basal massive deposits and are potentially useful in discriminating between deep and very deep water settings subaerial volcanoes which were formed when magmas intercepted buried aquifers and interacted explosively with water are small tuff rings and maars with variable shapes are composed of subequal although variable proportions of basal massive deposits bedded tuffs and late magmatic deposits and are useful in determining the stratigraphic successions underlying them

geochemical and mineralogical studies of ca 12 ma hydrothermal manganese rich rocks in the hokuroku district in japan abstract geological and geochemical studies were performed on ca 12 ma mn rich rocks in the hokuroku district in japan to constrain the origin of mn rich hydrothermal fluids and precipitation pathways of mn oxides mn rich rocks occur in hyaloclastites of rhyolite lavas in the studied areas colloform textures of mn oxides were common in those mn rich rocks carbonaceous layers uniquely alternate with mn oxides in the colloform textures the mn oxides layers in the colloform textures were composed of aggregates of nano scale todorokite birnessite and pyrolusite the carbonaceous layers also host apatite nano crystals these findings imply that the carbonaceous layers most likely represent fossilized microbial mats of mn oxidizing bacteria the close association of nano scale mn oxides with organic matter clay and silica minerals suggests that mn oxides initially precipitated near venting areas of low temperature hydrothermal fluids the early mn oxides were trapped in the hyaloclastites and experienced diagenetic modifications combined with hydrothermal alteration seawater penetration and microbial activities in the hyaloclastites such secondary processes further enriched mn in the hyaloclastites forming various mn silicates e g pennantite and shirozulite and veins made of mn ii and iii silicate and oxide silicate e g rhodonite and braunite later hydrothermal fluids also brecciated the massive mn rich rocks rhodochrosite and rhodonite occurred in such brecciated mn rich rocks or sheared hyaloclastites preferentially the carbon isotope compositions of rhodochrosite ranged from 26 7 to 20 8 vpdb the mudstone and early colloform textures in the hyaloclastites contained appreciable amounts of organic matter such organic matter was degraded by microbial processes under the influence of the later hydrothermal activities followed by the formation of rhodochrosite these findings contribute not only to understanding the formation mechanisms of hydrothermal mn rich rocks but also to future exploration of mn deposits

widespread weathered glass on the surface of mars low albedo sediments cover 10 7 km 2 in the northern lowlands of mars but the composition and origin of these widespread deposits have remained ambiguous despite many previous investigations here we use near infrared spectra acquired by the mars express omega observatoire pour la mineralogie l9eau les glaces et l9activite imaging spectrometer to show that these sediments exhibit spectral characteristics that are consistent with both high abundances of iron bearing glass and silica enriched leached rinds on glass this interpretation is supported by observations of low albedo soil grains with possible rinds at the phoenix mars lander landing site in the northern lowlands by comparison with the extensive glass rich dune fields and sand sheets of iceland we propose an explosive volcanic origin for these glass rich sediments we also propose that the glassy remnant rinds on the sediments are the result of postdepositional alteration as these rinds are commonly formed in arid terrestrial volcanic environments during water limited moderately acidic leaching these weathered glass rich deposits in the northern lowlands are also colocated with the strongest concentrations of a major global compositional surface type previously identified in mid infrared spectra suggesting that they may be representative of global processes our results provide potential confirmation of models suggesting that explosive volcanism has been widespread on mars and also raise the possibilities that glass rich volcaniclastics are a major source of eolian sand on mars and that widespread surficial aqueous alteration has occurred under amazonian climatic conditions

tracing the ore formation history of the shear zone controlled huogeqi cu pb zn deposit in inner mongolia northern china using h o s and fe isotopes abstract the original ore fluid of the huogeqi cu pb zn deposit in inner mongolia northern china was enriched in heavy oxygen isotopes with 18o values ranging from 9 9 to 11 4 per mil which is characteristic of the metamorphic devolatilization of pelitic rocks the d values determined by direct measurement of syn ore hydrothermal tremolite range from 116 to 82 per mil lying between the domains of typical metamorphic fluid and meteoric water which is in equilibrium with organic matter oxygen and hydrogen isotope ratios indicate that the ore fluid was derived from deep sourced metamorphic fluid and interacted with organic rich shale during fluid migration which is consistent with the fluid evolution history revealed by a previous fluid inclusion study sulfides in the deposit are characteristically enriched in heavy s isotopes with an average 34s value of 13 4 6 2 per mil 1 n 103 the s isotope ratios are identical to stratabound sulfides generated through the non bacterial reduction of neoproterozoic marine sulfate with 34s values of 17 per mil previous studies on lead isotopes of sulfides revealed that the ore forming metals cu pb and zn at the huogeqi deposit were also remobilized from a stratabound source this source was syngenetically elevated in its cu pb and zn sulfide content as a result of submarine hydrothermal activities forming sulfide rich layers within a rift tectonic setting the fe isotope ratios for sulfides are consistent with those of an intercalated iron formation within the ore hosting rocks suggesting that the fe in the sulfides was derived from local host rocks during sulfide precipitation and the fe rich rocks are favorable lithological units for high grade mineralization the heterogeneous sources of ore fluid s ore forming metals and fe are explained by a multistage genetic model which is supported by the geological characteristic of the deposit the enriched sulfides were subsequently remobilized and enriched by metamorphic devolatilization during the permian and triassic periods the metamorphic ore fluid ascended along a shear zone and interacted with organic rich shale sulfides eventually precipitated within the shear zone at a shallower crustal level especially where the shear zone intersected fe rich host rocks this multistage genetic model has implications for mineral exploration greenschist to amphibolite facies terranes containing thick neoproterozoic rift sequences are ideal regions for potential cu pb zn mineralization in particular intercalated volcanic rocks within the rift sequences are indicative of high heat flow and are ideal for the development of submarine hydrothermal systems the primary structures hosting mineralization and ore shoots in the huogeqi area are jogs in the shear zones in addition fe rich lithological units such as iron formations are ideal hosts for high grade ore

the rocks of gusev crater as viewed by the mini tes instrument 1 the miniature thermal emission spectrometer mini tes on board the mars exploration rover spirit is part of a payload designed to investigate whether a lake once existed in gusev crater mini tes has observed hundreds of rocks along the rover s traverse into the columbia hills yielding information on their distribution bulk mineralogy and the potential role of water at the site although dust in various forms produces contributions to the spectra we have established techniques for dealing with it all of the rocks encountered on the plains traverse from the lander to the base of the columbia hills share common spectral features consistent with an olivine rich basaltic rock known as adirondack class beginning at the base of the west spur of the columbia hills and across its length the rocks are spectrally distinct from the plains but can be grouped into a common type called clovis class these rocks some of which appear as in place outcrop are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration the northwest flank of husband hill is covered in float rocks known as wishstone class with spectral features that can be attributed uniquely to plagioclase feldspar a phase that represents more than half of the bulk mineralogy rare exceptions are three classes of basaltic exotics found scattered across husband hill that may represent impact ejecta and or float derived from local intrusions within the hills the rare outcrops observed on husband hill display distinctive spectral characteristics the outcrop called peace shows a feature attributable to molecular bound water and the outcrop that hosts the rock called watchtower displays a dominant basaltic glass component despite evidence from the rover s payload for significant alteration of some of the rocks no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by mini tes the mineralogical results supplied by mini tes provide no clear evidence that a lake once existed in gusev crater

oxygen isotope study of metamorphosed manganese deposits of the noda tamagawa mine northeast japan manganese ores of the noda tamagawa mine are metamorphosed equivalents of bedded type sedimentary manganese deposits the ore lenses are typically zoned with a central pyrochroite hausmannite zone an outer tephroite zone and an outermost rhodonite zone closest to the wall rock chert the 18 o vsmow values of 65 tephroite 32 rhodonite and eight quartz samples from the manganese ores and chert are in the ranges of 9 9 to 20 0 11 7 to 20 3 and 23 0 to 23 9 per mil respectively the overall order of 18 o enrichment corresponds to the order of equilibrium fractionation among these minerals however the temperatures calculated from quartz rhodonite and rhodonite tephroite pairs from neighboring ore zones are not consistent with those estimated from the mineral assemblages in the wall rocks the 18 o values for mnco 3 the most probable candidate of the precursor manganese mineral were calculated from the oxygen isotope mass balance among manganese silicates silica and co 2 to be 19 2 to 23 4 per mil if the mnco 3 initially precipitated from fluids of 18 o 0 0 to 2 5 per mil the temperatures of precipitation can be calculated to be between 62 and 111 c consistent with the primary mnco 3 having been precipitated by low temperature submarine hydrothermal solutions

geochemical and mineralogical analyses of palagonitic tuffs and altered rinds of pillow basalts in iceland and applications to mars samples of altered pillow lavas and hyalotuffs were collected from a volcanic tuya and hyaloclastite ridge in western iceland altered basaltic material from regions such as hloudufell tuya and thorolfsfell ridge may be similar to the surface fines on mars which are thought to contain altered basaltic components as well geochemical and mineralogical analyses have been performed on the icelandic samples in order to characterize the properties that distinguish palagonitization from other forms of low temperature alteration in this environment major elements were measured using an electron microprobe and mineralogy was determined through x ray diffraction and visible infrared reflectance spectroscopy the primary focus in this study was on the less than 2 microns size fractions of the hloudufell altered pillow and thorolfsfell palagonitic tuff samples the palagonitic tuff contained more crystalline clay minerals and has a higher al fe ratio the altered pillow lava contained higher abundances of nanophase iron oxides oxyhydroxides the extended visible region spectra of the less than 2 microns fractions of both icelandic samples are similar to bright martian soils measured by pathfinder

formation of anhydrous and hydrous skarn in cu au ore deposits by magmatic fluids most skarn ore deposits are characterized by two distinctly different alteration styles an early prograde stage with anhydrous minerals such as garnet and pyroxene forms from relatively high temperature hypersaline liquid a later retrograde stage with hydrous minerals such as epidote amphibole and chlorite plus sulfide ore minerals forms from lower temperature lower salinity fluids these two alteration stages commonly have been thought to reflect a dominance of magmatic and meteoric water respectively with relevance to the source of ore metals we report data from two different skarn systems one being part of the world s largest cu au resource stable isotope compositions of anhydrous and hydrous alteration minerals from both deposits indicate a magmatic source for both the prograde and retrograde stages 18o averages 5 0 per mil for garnet range 3 4 7 2 6 5 per mil for pyroxene 4 3 8 2 and 7 1 per mil for amphibole 4 3 8 7 the d values of late amphibole are more complex with magmatic values 77 to 78 for one deposit and both magmatic and lighter values for another deposit that could be explained either by magmatic degassing or by limited mixing with meteoric water we conclude that the differences in fluid composition prograde versus retrograde stages resulted from a magmatic fluid that intersected its solvus during the early stage creating vapor and hypersaline liquid whereas in the later stage this magmatic fluid did not intersect its solvus because it followed a different cooling path this late low salinity liquid only boiled once its vapor pressure curve was reached causing sulfide ore to precipitate during the retrograde stage

thermal infrared spectral character of hawaiian basaltic glasses multispectral thermal infrared remote sensing of hawaiian basalts younger than a few hundred years old can be used to discriminate basalt lava flows that are difficult to map with visible and near infrared images laboratory thermal infrared reflectance spectra of the exposed surfaces of mauna loa and kilauea basalts show systematic changes with age fresh glass collected from active lava flows shows a broad reflectance feature between 8 and 12 m indicative of a strong degree of disorder after a few weeks of exposure to the environment the spectra of the top surfaces of samples begin to exhibit spectral features suggestive of ordering into silicate chainlike and sheetlike units with progressive aging features of apparent sheetlike structures become the preferred mode as soon as 3 years after emplacement a silica rich coating can begin to develop on the surfaces adding another spectral feature to the laboratory reflectance measurements the thermal infrared multispectral scanner tims with six channels between 8 and 12 m has been used to take advantage of these spectral differences in basalts to map flows in hawaii remote sensing instruments with increased spectral resolution in the thermal infrared would aid in further discrimination of basalts with more subtle differences in age quenching and weathering histories

spatial evolution of zn fe pb isotopes of sphalerite within a single ore body a case study from the dongshengmiao ore deposit inner mongolia china analyses of sphalerite minerals from the characteristic brecciated zn pb ores of the main ore body in the giant dongshengmiao deposit have revealed variations in 66zn from 0 17 to 0 40 and in 56fe from 1 78 to 0 35 further the investigated pyrrhotite samples have iron that is isotopically similar to that of associated sphalerite minerals the most distinctive pattern revealed by the zinc and iron isotope data is the lateral trend of increasing 66zn and 56fe values from southwest to northeast within the main ore body the lead isotopic homogeneity of ore sulfides from the main ore body suggests that there is only one significant source for metal thus precluding the mixing of multiple metal sources as the key factor controlling spatial variations of zinc and iron isotopes the most likely control on spatial variations is rayleigh fractionation during hydrothermal fluid flow with lighter zn and fe isotopes preferentially incorporated into the earliest sulfides to precipitate from fluids precipitations of sphalerite and pyrrhotite have played vital roles in the zn and fe isotopic variations respectively of the ore forming system accordingly the larger isotopic variability for fe than zn within the same hydrothermal system perhaps resulted from a larger proportion of precipitation for pyrrhotite than for sphalerite the lateral trend pattern revealed by the zinc and iron isotope data is consistent with the occurrence of a cystic shaped breccia zone which is characterized by marked elevation in cu the results further confirm that zn and fe isotopes can be used as a vectoring tool for mineral prospecting

thermodynamics and lattice vibrations of minerals 5 applications to phase equilibria isotopic fractionation and high pressure thermodynamic properties in previous papers in this series a model that uses available elastic structural and spectroscopic data on minerals has been used to predict the thermodynamic functions cv heat capacity s entropy e internal energy and f helmholtz free energy in this paper four applications to problems of current geochemical and geophysical interest are presented 1 interpretation of complex trends of calorimetric data 2 calculation of phase equilibria 3 calculation of oxygen isotopic fractionation factors and 4 estimation of the effect of pressure on thermodynamic functions the model demonstrates that trends in high temperature thermodynamic properties of silicates are determined by the position and relative numbers of high frequency modes generally antisymmetric si al o stretching modes the position of these modes varies systematically with degree of polymerization of tetrahedra and therefore high temperature calorimetric behavior is relatively systematic as a function of crystal structure and mineral composition trends at low frequency are much more complex because the low frequency optic modes that most strongly influence the low temperature thermodynamic functions depend in a complex way on the size coordination and mass of cations and various polyhedra in the minerals the heat capacity curves of kyanite andalusite and sillimanite and of quartz coesite and stishovite show crossovers that cannot be explained by debye theory which accounts only for acoustic mode behavior but can be explained by the model spectra proposed because proper account is taken of the changing low and high frequency optic modes upon polymorphic transformations the proposed model is sufficiently accurate that phase equilibrium problems can be addressed the quartz coesite stishovite equilibrium curves the kyanite andalusite sillimanite triple point and the breakdown of albite to jadeite plus quartz are cited as specific examples for each example predicted slopes of equilibrium curves agree moderately well to excellently with slopes determined experimentally the calculated slopes are sensitive to spectroscopic parameters particularly to the distribution of optic modes in the far infrared this sensitivity is discussed in detail for the albite breakdown reaction the model can be used for prediction of isotopic fractionation factors if spectra of the isotopic forms of the mineral are known or postulated a simple set of rules for generating hypothetical spectra of 18o minerals from measured spectra of the 16o forms is given reduced partition functions are calculated for 13 minerals at 298 k the model values of reduced partition function 1000 ln of these minerals decrease in the order quartz calcite albite muscovite clinoenstatite anorthite diopside pyrope grossular zircon forsterite andradite rutile in good agreement with experimental data at 1000 k the first six minerals show small crossovers so that the order becomes calcite muscovite albite quartz anorthite and clinoenstatite the differences in 1000 ln at high temperature for these minerals are so small that the model probably cannot address the deviations from experimental trends the model clearly defines the region in which the fractionation factors do not follow a 1 t trend and should be useful for extrapolation of experimental data to low temperatures finally a modified gruneisen parameter model is proposed for shift of the lattice vibrational frequencies under compression and thermodynamic properties to 1000 kbar 1000 k are given for nine minerals at 1 mbar the predicted decrease in entropy at 298 k ranges from 54 of the 1 bar value for periclase to 25 for stishovite

emission spectroscopy of clay minerals and evidence for poorly crystalline aluminosilicates on mars from thermal emission spectrometer data 1 to understand the aqueous history of mars it is critical to constrain the alteration mineralogy of the martian surface previously published analyses of thermal infrared 6 25 m remote sensing data of mars suggest that dark regions have 15 20 clay minerals however near infrared 1 3 m spectral results generally do not identify widespread clay minerals thermal infrared detections of clays on mars are difficult to interpret owing in part to the relative paucity of published spectral analyses of clay minerals and clay bearing materials using similar spectra thermal infrared emission spectra in this study we present an analysis of the thermal emission spectral features 6 25 m or 400 1650 cm 1 of a suite of clay mineral reference materials and clay bearing rocks linking their spectral features to the crystal chemical properties of the clays on the basis of this context provided by the emission spectral analysis of clay minerals and clay bearing rocks we reconsider the evidence for clay minerals on mars from thermal emission spectrometer tes results we propose that global scale clay abundances determined from tes probably represent a geologically significant surface component though they may actually correspond to poorly crystalline aluminosilicates with similar si o ratios to clay minerals 0 3 0 4 rather than well crystalline clays if clay minerals or clay like materials on mars are poorly crystalline and or dessicated they may be detectable in the thermal infrared but not easily detected with near infrared data sets

origin and stratigraphy of phreatomagmatic deposits at the pleistocene sinker butte volcano western snake river plain idaho abstract sinker butte is the erosional remnant of a very large basaltic tuff cone of middle pleistocene age located at the southern edge of the western snake river plain phreatomagmatic tephras are exposed in complete sections up to 100 m thick in the walls of the snake river canyon creating an unusual opportunity to study the deposits produced by this volcano through its entire sequence of explosive eruptions the main objectives of the study were to determine the overall evolution of the sinker butte volcano while focusing particularly on the tephras produced by its phreatomagmatic eruptions toward this end twenty three detailed stratigraphic sections ranging from 20 to 100 m thick were examined and measured in canyon walls exposing tephras deposited around 180 of the circumference of the volcano three main rock units are recognized in canyon walls at sinker butte a lower sequence composed of numerous thin basaltic lava flows an intermediate sequence of phreatomagmatic tephras and a capping sequence of welded basaltic spatter and more lava flows we subdivide the phreatomagmatic deposits into two main parts a series of reworked mostly subaqueously deposited tephras and a more voluminous sequence of overlying subaerial surge and fall deposits most of the reworked deposits are gray in color and exhibit features such as channel scour and fill planar stratification high and low angle cross stratification trough cross stratification and bouma turbidite sequences consistent with their being deposited in shallow standing water or in braided streams the overlying subaerial deposits are commonly brown or orange in color due to palagonitization they display a wide variety of bedding types and sedimentary structures consistent with deposition by base surges wet to dry pyroclastic fall events and water saturated debris flows proximal sections through the subaerial tephras exhibit large regressive cross strata planar bedding and bomb sags suggesting deposition by wet base surges and tephra fallout medial and distal deposits consist of a thick sequence of well bedded tephras however the cross stratified base surge deposits are thinner and interbedded within the fallout deposits the average wavelength and amplitude of the cross strata continue to decrease with distance from the vent these bedded surge and fall deposits grade upward into dominantly fall deposits containing 75 95 juvenile vesiculated clasts and localized layers of welded spatter indicating a greatly reduced water melt ratio overlying these dryer deposits are massive tuff breccias that were probably deposited as water saturated debris flows lahars the first appearance of rounded river gravels in these massive tuff breccias indicates downward coring of the diatreme and entrainment of country rock from lower in the stratigraphic section the wetter nature of these deposits suggests a renewed source of external water the massive deposits grade upward into wet fallout tephras and the phreatomagmatic sequence ends with a dry scoria fall deposit overlain by welded spatter and lava flows field observations and two new 40 ar 39 ar incremental heating dates suggest the succession of lavas and tephra deposits exposed in this part of the snake river canyon may all have been erupted from a closely related complex of vents at sinker butte we propose that initial eruptions of lava flows built a small shield edifice that dammed or disrupted the flow of the ancestral snake river the shift from effusive to explosive eruptions occurred when the surface water or rising ground water gained access to the vent as the river cut a new channel around the lava dam water levels dropped and the volcano returned to an effusive style of eruption

late pleistocene basaltic ash and volcanic eruptions in the bonneville basin utah microprobe analyses of glass and radiocarbon dating of samples associated with three basaltic volcanic ashes in the deposits of lake bonneville make the ashes useful stratigraphic markers for correlation within the bonneville basin two of the ashes were derived from tuff cones pavant butte and tabernacle hill that erupted into lake bonneville in what is now the black rock desert of south central utah near kanosh utah the pavant butte ash is interbedded with barrier beach lagoon marl that is slightly less than 16 000 yr old five radiocarbon dates on carbonate materials stratigraphically associated with the ash elsewhere in the sevier desert average 15 300 yr b p lake bonneville was in its transgressive phase about 15 m below the bonneville shoreline when the pavant butte eruption began at the tabernacle hill tuff cone a basalt flow that has pillows wave rounded cobbles and tufa on its outer margins was erupted into lake bonneville shortly after the tuff cone at or near the provo shoreline the tabernacle hill tuff cone and basalt flow are older than a radio carbon date of about 14 300 yr b p on tufa collected from the outer margin of the basalt flow but younger than the bonneville flood at about 14 500 yr b p the third ash informally termed the thiokol ash has been found interbedded with lake bonneville deposits in two exposures in northern utah and in sediment cores from the great salt lake it is about 25 000 yr old and may have been erupted from a volcanic field on the northwest shore of great salt lake or from the snake river plain microprobe analyses of glass from samples of the black rock desert ashes show them to have similar chemical compositions but glass from tabernacle hill can be distinguished from pavant butte glass by its higher concentrations of cao and p 2 o 5 systematic differences in chemical composition between samples of pavant butte glass can be explained by comagmatic processes thiokol glass has less sio 2 ai 2 o 3 mgo and na 2 o but greater total iron and p 2 o 5 than do the black rock desert glasses

mineralogical composition of sands in meridiani planum determined from mars exploration rover data and comparison to orbital measurements constraints on the mineralogical composition of low albedo low sulfur sands at meridiani planum are determined from mars exploration rover mer opportunity miniature thermal emission spectrometer mini tes mossbauer and alpha proton x ray spectrometer measurements results of this work show that the sand is olivine basaltic in composition with minor amounts of sulfate and a high silica phase glass or secondary amorphous silica measurements from all three instruments indicate that pyroxene is twice as abundant as olivine and that the pyroxene composition is dominated by the low calcium variety the volume abundance of olivine is constrained to be 10 15 results from detailed analyses of mer data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with mars global surveyor tes data tes derived mineral abundances are within 5 of those derived from mer data which is generally within the statistical errors associated with tes derived phase abundances the agreement lends support to global and regional scale variations in mineralogical composition determined from tes data in previous studies an alternative method of least squares minimization is used for modeling the tes and mini tes data the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by tes data users

oxygen isotope fractionation in quartz albite anorthite and calcite laboratory measurements of equilibrium oxygen isotope fractionation in quartz albite anorthite and calcite have been carried out by anhydrous exchange between silicates and calcite at temperatures of 600 c and above exchange in these systems is as rapid as exchange between silicates and water fractionation factors can be summarized in the following equations qc 0 38 106t 2 abc 0 57 106t 2 anc 1 59 106t 2 from which the silicate pair fractionations are readily obtained these results are compared with published theoretical estimates as well as data derived from hydrothermal experiments some significant differences are found in particular it is difficult to reconcile all of the hydrothermal data either with theoretical calculations or with the present experimental data the new experiments provide an internally consistent set of fractionation factors suitable for isotopic thermometry and for test of disequilibrium in natural systems

precipitation of gold in a low sulfidation epithermal gold deposit insights from a submillimeter scale oxygen isotope analysis of vein quartz sir we welcome the opportunity to respond to bogie and lawless discussion of our paper on the submillimeter scale oxygen isotope variation of vein quartz from the low sulfidation style gold deposit at the hishikari mine the disputed point is whether or not the bladed and fine grained quartz precipitated initially as chalcedony and recrystallized to quartz in a subsequent stage similarity of texture between chalcedony e g typically found in agate and flaky or acicular bladed quartz suggests that there is some truth in bogie and lawless idea the texture of bladed quartz suggests rapid crystallization from solutions supersaturated with respect to quartz however it is difficult to define only from the texture whether

thermally altered palagonitic tephra a spectral and process analog to the soil and dust of mars we studied six palagonitic soil samples ph 1 through ph 6 which were collected at 30 cm intervals from a lava slab on mauna kea hawaii the samples represent an alteration sequence caused by heating during emplacement of molten lava over a preexisting tephra cone they are both spectral and weathering alteration process analogs to the martian surface techniques employed included visible and near ir spectroscopy mossbauer spectroscopy and magnetic analysis the two samples collected from beyond 90 cm from the slab ph 5 and ph 6 did not see the transient heating event and are composed of coarse grained glassy basaltic hawaiitic particles some of which have been moderately palagonitized since formation of the cone in the late pleistocene the four samples closest to the slab ph 1 through ph 4 have been strongly altered in response to heating during its emplacement their iron oxide mineralogy is dominated by nanophase ferric oxide the sample adjacent to the slab ph 1 which would have seen the highest temperatures has a factor of 3 less h2o and contains crystalline hematite and magnetite in addition to nanophase ferric oxide lesser amounts of magnetite but not hematite are present in samples 30 cm ph 2 and 60 cm ph 3 from the slab the reflectivity spectra of samples ph 2 through ph 4 are similar to spectra of palagonites reported by other workers to be good mars visible to near ir spectral analogs the reflectivity spectrum of ph 1 is an even better spectral analog to mars in that it exhibits absorption features indicative of both nanophase and crystalline ferric oxides similar to several new martian telescopic data sets our sampling site may also be a process analog for mars in that heating episodes by volcanism and or impact cratering could produce crystalline ferric oxides from poorly crystalline palagonitic material thus localized thermal alteration events may provide a volumetrically important mechanism for the palagonitization of basaltic glass and the production of crystalline ferric oxides on mars

mineralogy composition and alteration of mars pathfinder rocks and soils evidence from multispectral elemental and magnetic data on terrestrial analogue snc meteorite and pathfinder samples major element multispectral and magnetic properties data were obtained at ares vallis during the mars pathfinder mission to understand the compositional mineralogical and process implications of these data we obtained major element mineralogical and magnetic data for well crystalline and nanophase ferric minerals terrestrial analogue samples with known geologic context and snc meteorites analogue samples include unaltered palagonitic and sulfatetic tephra from mauna kea volcano hydrolytic and acid sulfate alteration steam vent material from kilauea volcano hydrolytic alteration and impactites from meteor crater relithification salient results for mars pathfinder include 1 band depths bd530b and bd600 and the reflectivity ratio r800 r750 are consistent with the dominant ferric mineral being nanophase ferric oxide associated with an unknown amount of h2o and occurring in composite particles along with subordinate amounts of other ferric minerals hematite and hematite plus nanophase goethite are most consistent with the data but maghemite akaganeite schwertmannite and nanophase lepidocrocite are also possible interpretations ferric oxides that are consistently not favored by the data as sole alteration products are jarosites and well crystalline goethite and lepidocrocite 2 the strength of the ferric adsorption edge r750 r445 implies the fe3 fe2 values for pathfinder rock and soil are within the ranges 0 7 3 and 3 20 respectively 3 ferrous silicates are indicated for subsets of pathfinder rocks and soils one subset has a band minimum near 930 nm that can attributed to low ca pyroxene alternatively the band could be a second manifestation of certain ferric oxides including nanophase goethite maghemite akaganeite and schwertmannite another subset has a negative spectral slope from 800 to 1005 nm which could result from the high energy wing of a high ca pyroxene and or olivine band a mixture of bright and dark materials and for rocks thin coatings of bright dust on dark rocks 4 chemical data on pathfinder rocks and soils are consistent with two component mixtures between an andesitic rock with low mgo and so3 concentrations soil free rock and a global basaltic soil with high mgo and so3 concentrations rock free soil pathfinder rock free soil can be modeled as a chemical mixture of snc meteorites and the pathfinder soil free rock 5 pathfinder soil cannot be obtained by chemical alteration of pathfinder rocks by any of the hydrolytic and acid sulfate alteration processes we studied presumably global mixing has obscured and possibly erased the elemental signatures of chemical alteration 6 the strongly magnetic phase in palagonitic and sulfatetic tephra is titanomagnetite and possibly its oxidation product titanomaghemite fe ti spinels the saturation magnetization of the tephra samples 0 5 2 0 am2 kg is at or below the low end of the range inferred for martian dust 4 2 am2 kg implying that lithogenic fe ti spinels are a possible candidate for the martian strongly magnetic phase 7 the predominantly palagonitic spectral signature and magnetic nature of martian soil and dust are consistent with glassy precursors with imbedded fe ti spinel particles comparison with lunar glass production rates suggests that production of sufficient quantities of glassy materials on mars by volcanic and impact processes is sufficient to account for these observations

oxygen isotopic variations in soil quartz developed on rhyolite residuum from kiso central japan abstract positive identification of the origin of fine grained quartz in highly weathered soils is not proven by routine microscopic examination the oxygen isotope composition 18 o vs smow of quartz was determined in the albic horizon of three soils developed on the cretaceous nohhi rhyolite from kiso central japan differences in the isotopic composition of quartz as a function of particle size were observed and attributed to the degree of hydrothermal alteration one soil sample developed nearby hornblende porphyrite intrusion showed systematic increases in the 18 o values with increasing particle size from 3 6 1 10 m to 9 5 500 2000 m such a trend is indicative of the higher contribution of secondary quartz precipitated from hydrothermal meteoric fluids in fine size fractions in contrast to primary magmatic quartz in coarse size fractions hydrothermal activity was inferred for another soil where no lateral intrusion is mapped the variation in the oxygen isotopic composition of quartz in different particle sizes precludes both eolian and authigenic origins for the soils the stable isotope technology provides the only rationale for positive identification of the origin of fine grained quartz in soils

athena mimos ii mossbauer spectrometer investigation 1 mossbauer spectroscopy is a powerful tool for quantitative mineralogical analysis of fe bearing materials the miniature mossbauer spectrometer mimos ii is a component of the athena science payload launched to mars in 2003 on both mars exploration rover missions the instrument has two major components 1 a rover based electronics board that contains power supplies a dedicated central processing unit memory and associated support electronics and 2 a sensor head that is mounted at the end of the instrument deployment device idd for placement of the instrument in physical contact with soil and rock the velocity transducer operates at a nominal frequency of 25 hz and is equipped with two 57co rh mossbauer sources the reference source 5 mci landed intensity reference target fe2o3 plus fe0 and pin diode detector are configured in transmission geometry and are internal to the instrument and used for its calibration the analysis mossbauer source 150 mci landed intensity irradiates martian surface materials with a beam diameter of 1 4 cm the backscatter radiation is measured by four pin diode detectors physical contact with surface materials is sensed with a switch activated contact plate the contact plate and reference target are instrumented with temperature sensors assuming 18 fe for martian surface materials experiment time is 6 12 hours during the night for quality spectra i e good counting statistics 1 2 hours is sufficient to identify and quantify the most abundant fe bearing phases data stored internal to the instrument for selectable return to earth include mossbauer and pulse height analysis spectra 512 and 256 channels respectively for each of the five detectors in up to 13 temperature intervals 65 mossbauer spectra engineering data for the velocity transducer and temperature measurements the total data volume is 150 kb the mass and power consumption are 500 g 400 g for the sensor head and 2 w respectively the scientific measurement objectives of the mossbauer investigation are to obtain for rock soil and dust 1 the mineralogical identification of iron bearing phases e g oxides silicates sulfides sulfates and carbonates 2 the quantitative measurement of the distribution of iron among these iron bearing phases e g the relative proportions of iron in olivine pyroxenes ilmenite and magnetite in a basalt 3 the quantitative measurement of the distribution of iron among its oxidation states e g fe2 fe3 and fe6 and 4 the characterization of the size distribution of magnetic particles special geologic targets of the mossbauer investigation are dust collected by the athena magnets and interior rock and soil surfaces exposed by the athena rock abrasion tool and by trenching with rover wheels

hydrothermal minerals and alteration rates at surtsey volcano iceland the volcanic island surtsey off the south coast of iceland was created by volcanic activity in 1963 1967 core from a 181 m deep hole extending 123 m below sea level shows the results of 12 yr of hydrothermal alteration of basaltic tephra the primary cause of heating of the tephra and of development of the hydrothermal system was the intrusion of dikes below sea level at present the hottest part of the hole at a maximum temperature of 150 c is cooling at 0 9 c per year palagonitization of sideromelane glass a dominant constituent of the tephra is an important alteration process that is strongly temperature dependent the rate doubling for every 12 c increase at 60 c 90 is palagonitized above 120 c olivine crystals are replaced on their edges by nontronite the thickness of clay doubles for each 8 c increase ten hydrothermal minerals have crystallized in the tephra at 25 to 150 c the dominant species are smectite nontronite analcite phillipsite and tobermorite the primary clay species of palagonite is probably nontronite other minerals are halite opal calcite chabazite xonotlite anhydrite and gypsum no major differences in mineral occurrence are noted above and below sea level but phillipsite and tobermorite tend to grow larger below sea level even at the same temperature analcite appears at lower temperature 55 c above sea level than below sea level 75 c anhydrite is most abundant deep in the hole where inflowing cool sea water precipitated sulfate due to reduced sulfate solubility at higher temperatures

manganese formations in the accretionary belts of japan implications for subduction accretion process in an active convergent margin abstract in the accretionary complexes of japan many bedded manganese and iron manganese ore deposits occur especially in the jurassic complexes such as the chichibu tamba mino ashio and northern kitakami belts the manganese ores in these jurassic accretionary complexes probably formed from manganese nodule crust bearing siliceous sediments on deep sea floor and were subsequently converted to the manganese ores by metamorphism during the subduction accretion process some of the deposits also show the signatures of younger granitic intrusions the manganese formations now incorporated within these belts are marker beds of accretionary tectonics associated with plate tectonic processes in convergent margins

precipitation rates and atmospheric heat transport during the cenomanian greenhouse warming in north america estimates from a stable isotope mass balance model stable isotope mass balance modeling results of meteoric 18o values from the cenomanian stage of the cretaceous western interior basin kwib suggest that precipitation and evaporation fluxes were greater than that of the present and significantly different from simulations of albian kwib paleohydrology sphaerosiderite meteoric 18o values have been compiled from the lower tuscaloosa formation of southwestern mississippi 25 n paleolatitude the dakota formation rose creek pit fairbury nebraska 35 n and the dunvegan formation of eastern british columbia 55 n paleolatitude these paleosol siderite 18o values define a paleolatitudinal gradient ranging from 4 2 vpdb at 25 n to 12 5 vpdb at 55 n this trend is significantly steeper and more depleted than a modern theoretical siderite gradient 25 n 1 7 65 n 5 6 vpdb and a holocene meteoric calcite trend 27 n 3 6 67 n 7 4 vpdb the cenomanian gradient is also comparatively steeper than the albian trend determined for the kwib in the mid to high latitudes the steep latitudinal trend in meteoric 18o values may be the result of increased precipitation and evaporation fluxes amount effects under a more vigorous greenhouse world hydrologic cycle a stable isotope mass balance model has been used to generate estimates of precipitation and evaporation fluxes and precipitation rates estimates of cenomanian precipitation rates based upon the mass balance modeling of the kwib range from 1400 mm yr at 25 n paleolatitude to 3600 mm yr at 45 n paleolatitude the precipitation evaporation p e flux values were used to delineate zones of moisture surplus and moisture deficit comparisons between cenomanian p e and modern theoretical siderite and holocene calcite latitudinal trends shows an amplification of low latitude moisture deficits between 5 25 n paleolatitude and moisture surpluses between 40 60 n paleolatitude the low latitude moisture deficits correlate with a mean annual average heat loss of 48 w m2 at 10 n paleolatitude present 8 w m2 at 15 n the increased precipitation flux and moisture surplus in the mid latitudes corresponds to a mean average annual heat gain of 180 w m2 at 50 n paleolatitude present 17 w m2 at 50 n the cenomanian low latitude moisture deficit is similar to that of the albian however the mid latitude 40 60 n precipitation flux values and precipitation rates are significantly higher albian 2200 mm yr at 45 n cenomanian 3600 mm yr at 45 n furthermore the heat transferred to the atmosphere via latent heat of condensation was approximately 10 6 that of the present at 50 n the intensified hydrologic cycle of the mid cretaceous greenhouse warming may have played a significant role in the poleward transfer of heat and more equable global conditions paleoclimatological reconstructions from multiple time periods during the mid cretaceous will aid in a better understanding of the dynamics of the hydrologic cycle and latent heat flux during greenhouse world conditions