eddy resolving observation of the north pacific subtropical mode water abstracthydrographic data obtained by high resolution shipboard observations and argo profiling floats have been analyzed to study the mesoscale structure and circulation of the north pacific subtropical mode water stmw the float data show that in the late winter of 2008 stmw having a temperature of approximately 18 8 17 7 and 16 6 c formed west of 140 e at 140 150 e and east of 150 e respectively in the recirculation gyre south of the kuroshio extension after spring the newly formed stmw gradually shift southward decreasing in thickness simultaneously the stmws of 16 6 and 17 7 c are gradually stirred and then mixed in terms of properties in late fall they seem to be integrated to form a single group of stmws having a temperature centered at 17 2 c such stmw circulation in 2008 is much more turbulent than that in 2006 which was investigated in a previous study the difference between the two years is attributed to the more variable state of the kuroshio extension in 2008 associate

high efficiency of natural lamellar remanent magnetisation in single grains of ilmeno hematite calculated using mossbauer spectroscopy rocks from large remanent magnetic anomalies on earth have been found to contain exsolved rhombohedral oxides which also have been proposed as earth analogues for the rocks creating the observed large remanent anomalies on mars theoretical considerations and previous case studies of natural rocks have shown that the natural magnetisation is carried by lamellar magnetism due to uncompensated moments at the interface between antiferromagnetic hematite and paramagnetic ilmenite here single grains 250 m of titanohematite with ferri ilmenite exsolution lamellae from mesoproterozoic metamorphic rock samples in southwest sweden and the adirondack mountains usa are studied using room temperature mossbauer spectroscopy to identify possible characteristic magnetic signatures of lamellar magnetism mossbauer spectra of synthetic samples of titanohematite fe0 95ti0 05o3 and fe0 9ti0 1o3 were collected for comparison and showed a dominant six line magnetic spectrum due to fe3 in titanohematite with a weak sextet due to fe2 fe3 charge transfer mossbauer spectra of the natural ilmeno hematite grains are similar to those for synthetic titanohematite but contain additionally two paramagnetic doublets corresponding to fe2 and fe3 in ilmenite however several grains also contain an additional weak broad magnetic component that we assign to iron in contact layers according to the lamellar magnetism model similar to the previous mossbauer results for natural hemo ilmenite there is no evidence for superparamagnetic behaviour of the nanoscale titanohematite lamellae contained within coarser ferri ilmenite lamellae and no evidence for single domain or superparamagnetic magnetite the compositions of titanohematite and ferri ilmenite in the individual ilmeno hematite grains calculated from the mossbauer area ratios show that compositions are closer to end member values than the compositions inferred from electron microprobe and transmission electron microscopy on the same grains consistent with observations that lamella thicknesses are as small as a few nm bulk compositions of ilmeno hematite grains calculated from the mossbauer data confirm that the swedish samples are significantly more ilmenite rich than the adirondack samples and agree with an estimation of bulk composition through point counting of electron backscatter images the mossbauer data allow a quantitative estimation of contact layer abundance which is used to determine the efficiency of lamellar natural remanent magnetisation acquisition because minerals with a high natural remanent magnetisation efficiency are expected to create larger remanent magnetic anomalies contact layer abundance determination by mossbauer spectroscopy provides a valuable new tool for mineral based magnetic anomaly interpretation on earth and other planetary bodies

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

impact of aleutian low activity on the stmw formation in the kuroshio recirculation gyre region 1 to understand the formation of north pacific subtropical mode water stmw in the kuroshio recirculation gyre region the cause of stmw thickness variation is investigated using temperature profiles in a historically archived data set the thickness variation is predominantly controlled by the main thermocline depth mtd when the main thermocline deepens shoals the wintertime mixed layer depth can develop not develop and consequently thicker thinner stmw is observed in summer the large scale atmospheric forcing controlling the mtd is explored using a wind driven hindcast ocean model the mtd variation stems primarily from a baroclinic response in the ocean to the aleutian low al activity especially the meridional movement of the al exerts a remarkable influence

characterization of the hydrothermal systems associated with archean vms mineralization at panorama western australia using hyperspectral geochemical and geothermometric data abstract airborne hyperspectral imagery was used to study the distribution of white mica minerals in archean 3 2 ga submarine hydrothermal systems associated with volcanogenic massive sulfide mineralization in a well exposed volcanic sequence of the soansville greenstone belt in the pilbara western australia white mica mineral abundance and distribution maps were compared with published hydrothermal alteration maps and differences were interpreted using whole rock geochemistry and temperature estimates from oxygen isotope geothermometric studies of hydrothermally altered rocks three different zones were identified from the hyperspectral imagery 1 al rich white mica zones in the upper parts of the volcanic sequence which are related to recharge of unevolved seawater 2 al poor white mica zones at middle and upper levels of the volcanic sequence predominantly related to k alteration by more evolved hydrothermal fluids and 3 high to intermediate al content white mica zones in lower levels of the sequence and in cross cutting zones related to intense alteration by laterally flowing and upwelling evolved fluids the integrated study of the spatial distribution of hyperspectrally detected white mica minerals together with published maps and rock analyses allowed characterization of the hydrothermal systems and reconstruction of paleo fluid pathways

systematics of chlorite alteration at the phelps dodge massive sulfide deposit matagami quebec hydrothermal alteration at the phelps dodge archcan volcanogenic massive sulfide deposit has converted rhyodacite and rhyolite footwall rocks into the following mineral assemblages quartz chlorite albite epidote or sericite quartz chlorite or sericite chlorite or sericite and chlorite talc or stilpnomelane alteration at constant al was initiated by hydration addition of fe mg silicification and leaching of ca na which produced al saturated chlorites with a wide range of fe fe mg ratios within the assemblage quartz chlorite albite epidote or sericite with continued addition of fe and less mg combined with extensive leaching of quartz the chlorite became al undersaturated quartz chlorite talc assemblage and ultimately formed a rock composed essentially of chlorite the chlorite talc or stilpnomelane assemblage is stable in late crosscutting veinlets and in the ore zone chlorites in the si al mg fe system form a rectangular solid solution plane with limited substitution of al for si and extensive substitution of fe for mg in si al space the solid solution plane is outlined by al saturation presence of other al rich mineral and al undersaturation presence of al poor or al free mineral boundaries al iv substitution for si in the chlorites increases from 2 3 to 3 01 formula units based on 8 si al iv with fe fe mg whereas al iv occupancy decreases from 2 88 to 2 65 the valence charge balance is compensated by octahedral site vacancies or by the conversion of fe super 2 to fe super 3 the al iv content of chlorite also increases with temperature chlorites on the al saturated boundary of the solid solution field form a potentially useful geothermometer t degrees c 106 al iv 18 al iv is corrected for changes with the fe fe mg ratio as al iv corrected al iv 0 7 fe fe mg the fe fe mg ratios of bulk rock and contained chlorite correlate well birefringence colors of the chlorite change from green to brown violet and berlin blue as fe fe mg changes from 0 18 to 0 64 the fe fe mg variation apparently depends largely on the proportions of mg rich seawater and fe rich hydrothermal fluid in the altering brine

the north pacific climatology of winter mixed layer and mode waters abstract a climatology of the winter mixed layer in the north pacific ocean was constructed using hydrographic data from historical archives and recent observational programs including the world ocean circulation experiment the main aim was to provide better knowledge about source areas of upper water masses the authors have endeavored to preserve water properties near the frontal regions by keeping the smoothing scale as small as possible the resulting climatology shows considerable differences in the mixed layer depth and its water properties from those derived from the world ocean atlas woa maps of the potential vorticity field of the north pacific pycnocline are presented using the isopycnally averaged climatology hydrobase three distinct lateral minima of potential vorticity are identified as subtropical mode water stmw central mode water cmw and eastern subtropical mode water estmw in the western central and eastern parts of the subtropical gyre respectively the hydrobase isopy

subtropical mode water variation in the northwestern part of the north pacific subtropical gyre temporal variations of the north pacific subtropical mode water npstmw are studied with the proper temporal resolution for describing seasonal variation using monthly hydrographic data taken near the ogasawara islands npstmw is formed south of the kuroshio and the kuroshio extension in late winter and advected to the ogasawara site by the southwestward westward return flow of the kuroshio recirculation while npstmw is seen at the ogasawara site in almost all seasons npstmw with a higher core temperature is advected to this site in april and one with a colder core follows in and after june until january or february furthermore the npstmw core temperature shows considerable interannual variation this variation is very similar to that found in other regions away from the ogasawara site suggesting that it reflects the larger scale variation of npstmw and that this site would be suitable for monitoring the npstmw core temperature a significant correlation between the npstmw core temperature and the monsoon index which is defined as the difference in the sea level pressure between nemuro japan and irkutsk russia as an indicator of wintertime cooling indicates that npstmw contains a memory of wintertime cooling in the preceding winter

a multi sensor logger for rock cores methodology and preliminary results from the matagami mining camp canada abstract diamond drilling typically constitutes a major part of costs in advanced mineral exploration programs this generates thousands of meters of rock cores during major exploration campaigns but the cores are not currently utilized to their full potential they could supply three dimensional information on physical properties geochemistry and mineralogy such data could be used to model the geology or physical properties in 3d characterize hydrothermal alteration or provide chemo stratigraphic constraints for example but measuring all the parameters one by one at high spatial resolution by traditional methods would be impractical due to cost or time considerations and for some parameters it would destroy the core e g geochemistry in this paper we describe a multi sensor core logger and its use on rock cores from exploration diamond drill holes this semi automated system can measure near simultaneously non destructively and at high spatial resolution the following parameters 1 volumetric magnetic susceptibility 2 density using gamma ray attenuation 3 several chemical elements through energy dispersive x ray fluorescence spectrometry and 4 visible near infrared spectrometry which allows numerous minerals to be detected and characterized the logger also acquires a continuous image of the core using a line scan camera which allows the user to compare other properties with the visual aspect of the core and creates a complete virtual archive the aim of this mostly methodological paper is to describe the logger as a whole and then each instrument or sensor separately outlining the numerous tests that have been performed to assess and improve data quality we also present preliminary results from the matagami mining camp of canada a base metal district

ventilated thermocline strongly affected by a deep mixed layer a theory for subtropical countercurrent abstract the mixed layer thickness generally increases in the northward direction but its change seems to occur rather sharply in a narrow transition zone referred to as a mixed layer front here the author investigates the effects of the mixed layer front on the ventilated thermocline structure especially focusing on the generation mechanism of the subtropical countercurrent if the mixed layer front is not parallel to the surface density contour the fluid with minimum isopycnal potential vorticity is formed around the intersection of the mixed layer front and outcrop line if the mixed layer front slants northeastward and surface density is zonally uniform as seen in a numerical experiment carried out by kubokawa and inui in which the subtropical countercurrent was reproduced the minimum potential vorticity on a high density isopycnal occurs in the east while that in a low density isopycnal occurs in the west in the present study analytic solutions for a simple three layer model are presented f

near infrared spectra of muscovite tschermak substitution and metamorphic reaction progress implications for remote sensing near infrared nir spectra of precambrian metagraywacke in the black hills south dakota demonstrate that reflectance spectroscopy can be used to monitor progressive changes in mineral chemistry as a function of metamorphic grade the wavelength of a combination al o h absorption band in muscovite measured using both laboratory and field portable nir spectrometers shifts from 2217 nm in the biotite zone to 2199 nm in the sillimanite k feldspar zone the band shift corresponds to an increase in the al vi content of muscovite determined by electron microprobe and is thus a monitor of al 2 si 1 fe mg 1 tschermak exchange spectroscopic measurements such as these are useful in the case of aluminum deficient rocks which lack metamorphic index minerals or appropriate assemblages for thermobarometric studies and in low grade rocks subgarnet zone which lack quantitative indicators of metamorphic grade and are too fine grained for petrographic or microprobe studies more important spectroscopic detection of mineral chemical variations in metamorphic rocks provides petrologists with a tool to recover information on metamorphic reaction histories from high spectral resolution aircraft or satellite remote sensing data

effect of decadal kuroshio extension jet and eddy variability on the modification of north pacific intermediate water abstract salinity modifications in the north pacific intermediate water npiw core layer of 26 7 26 8 in the western north pacific ocean are investigated using temperature salinity data from available profiling float and hydrographic measurements in 2002 09 during 2002 05 when the kuroshio extension ke jet was intense and zonally elongated coherent positive salinity anomalies appeared along the inflow ke jet southeast of japan and in the downstream mixed water region east of 152 e broad scale negative salinity anomalies were detected south of the ke jet and in the upstream mixed water region west of 152 e the signs of these observed salinity anomalies were reversed in 2006 09 when the ke jet transitioned to a weakened and zonally contracted dynamic state by adopting an isopycnal advection diffusion model and conducting model runs with the time dependent advective field inferred from the eddy resolving satellite altimeter sea surface height data it is found that the observed salinity anomalie

variability of the kuroshio extension jet recirculation gyre and mesoscale eddies on decadal time scales abstract twelve years of sea surface height ssh data from multiple satellite altimeters are used to investigate the low frequency changes and the interconnections of the kuroshio extension ke jet its southern recirculation gyre and their mesoscale eddy field the dominant signal is characterized by the steady weakening of the ke jet recirculation gyre from 1993 to 1996 followed by a gradual strengthening after 1997 during the weakening period of 1993 96 the ke path migrated southward in general and this path migration reversed in direction during the strengthening period of the ke jet and recirculation gyre after 1997 by hindcasting the ssh signals using linear vorticity dynamics it was found that weakening strengthening in the ke jet and recirculation gyre is consistent with westward propagation of negative positive ssh anomalies generating in the eastern north pacific and strengthening during their westward propagation when the ke jet and recirculation gyre were in a weak mode during 19

alteration of felsic volcanics hosting the thalanga massive sulfide deposit northern queensland australia and geochemical proximity indicators to ore thalanga is an early ordovician stratiform zn pb cu ag rich massive sulfide deposit in northern queensland australia with a total resource of 6 6 mt of ore the host rock succession consists of variably altered rhyolite in the footwall and a dacite dominated volcano sedimentary sequence in the hanging wall the sulfide deposit and the enclosing volcanic sequence were metamorphosed under upper greenschist conditions a laterally continuous footwall alteration zone extends beneath the entire deposit 3 000 m and to a stratigraphic depth of at least 300 m below the ore lenses the bulk of this zone is occupied by feldspar destructive muscovite biotite chlorite rich mottled alteration facies with disseminated pyrite representing the metamorphic equivalent of phyllosilicate dominated hydrothermal alteration discordant zones of intense quartz pyrite alteration represent the principal fluid pathways during mineralizing hydrothermal activity locally quartz k feldspar alteration facies exist on the fringes of the system and calcareous alteration and chlorite pyrite alteration facies exist in the upper part of footwall rhyolite proximal to sulfide lenses quartz feldspar porphyritic rhyolite laterally surrounding the footwall alteration zone and feldspar porphyritic dacite in the hanging wall are unaltered or weakly altered the compositional diversity of altered footwall rhyolite implies that hydrothermal alteration at thalanga was a complex processes this paper presents a model for the evolution of the footwall alteration zone calcareous alteration probably represents the initial phase of hydrothermal activity this was followed by diffuse upwelling of acidic seawater dominated fluids causing destruction of primary feldspar precipitation of pyrite and formation of hydrothermal sericite chlorite and clay minerals subsequent intense quartz pyrite alteration was directly associated with mineralization the thalanga footwall alteration zone has several geochemical characteristics that show systematic changes with increasing proximity to ore these include na depletion and elevated mg s alteration index ai chlorite carbonate pyrite index ccpi mo bi and as furthermore the x mg of chlorite and biotite increases systematically from values of 0 45 to 0 5 in least altered rhyolite to values 0 9 immediately below ore these geochemical features can be used in exploration for massive sulfide deposits as vectors to ore at the prospect scale and in discrimination of prospective hydrothermal from unprospective diagenetic alteration systems at the regional scale

the key tuffite matagami camp abitibi greenstone belt canada petrogenesis and implications for vms formation and exploration the key tuffite is a stratigraphic marker unit for most of the zinc rich volcanogenic massive sulfide deposits of the matagami camp in the abitibi greenstone belt this 2 to 6 m thick unit was previously interpreted as a mixture of ash fall andesitic to rhyolitic tuffaceous components and volcanogenic massive sulfide vms related chemical seafloor precipitate exhalative component previous attempts to develop geochemical exploration vectoring tools using metal content within the key tuffite were mostly inconclusive due to the complex nature of the key tuffite unit and a poor understanding of its composition origin and relationship with the vms forming hydrothermal systems detailed mapping and thorough lithogeochemistry of the key tuffite in the vicinity of the perseverance and bracemac mcleod deposits indicate that the key tuffite is a homogeneous calc alkaline andesitic tuff that was deposited before the vms deposits were formed the unit is mostly devoid of exhalative component but it is strongly hydrothermally altered close to orebodies this is characterized by a strong proximal chloritization and a distal sericitization which grades laterally into the unaltered key tuffite neither the key tuffite nor the ore was formed by seafloor exhalative processes for the two studied deposits this probably explains why previously proposed exploration models based on metal scavenging proved unsuccessful and suggests that a re evaluation of the exhalative model should be done at the scale of the mining camp however as shown in this study hydrothermal alteration can be used to vector towards ore along the key tuffite

eddy mean flow interaction in the decadally modulating kuroshio extension system abstract satellite altimeter sea surface height ssh data of the past 16 years are used to investigate the decadal changes of the kuroshio extension ke system that oscillated between a stable and an unstable dynamic state during the stable state of 10 1992 06 1995 and 01 2002 12 2004 the ke jet was intense and had a northerly zonal mean path and a well defined southern recirculation gyre during the unstable state of 07 1995 12 2001 and 01 2005 present the ke jet had a reduced eastward transport and a more southerly flow path transitions between the two dynamic states are caused by the basin scale wind stress curl forcing in the eastern north pacific related to the pacific decadal oscillations pdos or the north pacific gyre oscillations npgos during the positive pdo or negative npgo phase the intensified aleutian low generates negative ssh anomalies in the eastern north pacific through ekman divergence as these wind induced negative ssh anomalies propagate to the west as baroclinic rossby waves they weaken the zonal ke jet and shift its path southward as its path is pushed southward 32 n the deep reaching ke jet has to ride over the shallow shatsky rise generating localized disturbances that lead to their subsequent development along the ke jet west of the shatsky rise the sequence opposite to that listed above occurs when the pdo npgo changes to its negative positive phase after the ke system transitions from a stable to unstable state the enhanced eddy interaction is found to strengthen both the southern recirculation gyre and quasi stationary meanders along the ke s upstream path this nonlinear eddy interaction is important in determining the amplitude of the observed decadal ke variability

the mattagami lake mine archean zn cu sulfide deposit quebec hydrothermal coprecipitation of talc and sulfides in a sea floor brine pool evidence from geochemistry 18 o 16 o and mineral chemistry orebody 2 is 21 million metric tons grading 10 5 percent zn 0 17 percent cu and 0 014 oz au plus 1 15 oz ag per short ton quartz in the orebody has a delta 18 o of 10 to 11 9 per mil or approximately 2 per mil heavier than footwall quartz signifying precipitation temperatures 250 degrees to 280 degrees c this is corroborated by filling temperatures of primary fluid inclusions within gangue quartz t f 240 degrees 270 degrees c both isotopic and fluid inclusion temperatures signify a broad thermal zonation from approximately 270 degrees c at the base to approximately 240 degrees c at the top of the orebody minimum water depths of 300 m are indicated from nonboiling hydrothermal fluids of 3 to 5 weight percent nacl equivalent at approximately 250 degrees c a approximately 50 degrees c cooling of fluids during passage from the footwall to a suggested sea floor brine pool above the ore zone may have been induced by turbulent mixing of approximately 20 percent pristine archean marine bottom water at approximately 70 degrees c downward into the brine pool chert in the overlying key tuffite has delta 18 o of 10 to 12 per mil probably representing equilibrium precipitation from brine pool fluids at 200 degrees to 250 degrees c spreading laterally across the sea floor in a gravitationally stable boundary layer modified journal abstract

a role of eddies in formation and transport of north pacific subtropical mode water 1 hydrographic data acquired during 2001 by argo profiling floats deployed in the kuroshio recirculation region are used to verify the inference that mesoscale eddies prevailing in the recirculation region play an important role in the formation and transport of north pacific subtropical mode water npstmw that is the deeper winter mixed layer is formed preferentially where the thermocline is deeper in association with anticyclonic eddies in the succeeding seasons mesoscale eddies retain npstmw during their southwestward movement from the npstmw formation region so that anticylonic eddies contribute substantially to the npstmw transportation the spatial distributions of the mixed layer depth in winter and the npstmw thickness in the succeeding seasons based on the float data suggest that they are affected by mesoscale eddies the float data also provide the statistical relations of these quantities against the thermocline depth which are consistent with our inference

short wavelength infrared spectral characteristics of the hw horizon implications for exploration in the myra falls volcanic hosted massive sulfide camp vancouver island british columbia canada short wavelength infrared swir spectrometry has been used to identify previously unmapped hydrothermal alteration zones around volcanic hosted massive sulfide vhms orebodies at myra falls vancouver island british columbia hydrothermal alteration assemblages are uniformly dominated by fine grained white mica with poor development of mineralogical zonation swir spectrometry is an ideal exploration tool for characterizing this fine grained hydrothermal alteration at myra falls swir spectrometry has identified subtle shifts in the wavelengths of the aloh absorption feature of white mica corresponding to compositional changes in altered rhyolite distal and proximal to ore aloh absorption occurs at shorter wavelengths 2 198 nm and corresponds to lower fe fe mg and si al and higher na na k in strongly altered samples proximal to ore slightly sodic muscovites aloh absorption occurs at longer wavelengths 2 206 nm and corresponds to higher fe fe mg and si al and lower na na k in samples distal to ore nonsodic slightly phengitic muscovites white mica in siltstone within a meter of vhms ore has higher zn v fe and mg contents than white mica distal to these altered samples chlorite compositions identified by swir also show systematic changes with intensity of alteration and distance from ore the average wavelength of the feoh absorption feature for chlorite in rhyolitic samples proximal to ore is 2 241 nm intermediate mg chlorite whereas wavelengths in background samples average 2 247 nm intermediate fe chlorite similar changes are observed in footwall and hanging wall andesites with samples near the battle mine containing muscovite to phengitic muscovite average wavelength of the aloh absorption feature of 2 200 nm and mg rich chlorite average wavelength of the feoh absorption feature of 2 245 nm to regional andesite samples with phengitic muscovite average wavelengths of the aloh absorption feature of 2 209 nm and fe rich chlorite average wavelength of the feoh absorption feature of 2 249 nm in weakly altered rocks white mica compositions also vary with host lithology the aloh absorption feature occurs at longer wavelengths in white mica in dacite and andesite compared to adjacent rhyolitic rocks suggesting that higher fe and mg in the host lithology affects the composition of white mica two zones of intense hydrothermal alteration above the battle and hw orebodies have distinctive swir spectral characteristics with the aloh and feoh features occurring at shorter wavelengths 2 197 and 2 240 nm respectively small anomalous zones of alteration were also identified in the thelwood valley area where minor mineralized zones are present as broad zones of fine grained white mica sericite alteration are ubiquitous throughout the myra falls property alteration proximal to ore cannot be identified simply by visual logging of drill core alteration zonation may be determined by subtle shifts in white mica spectral characteristics this study indicates that swir analysis may be an effective field based exploration tool for quantifying the intensity of alteration associated with vhms orebodies and that trends in mineral compositions even in very fine grained rocks can be used as mine scale vectors to ore

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

observations of the subtropical mode water evolution from the kuroshio extension system study abstract properties and seasonal evolution of north pacific ocean subtropical mode water stmw within and south of the kuroshio extension recirculation gyre are analyzed from profiling float data and additional hydrographic and shipboard adcp measurements taken during 2004 the presence of an enhanced recirculation gyre and relatively low mesoscale eddy variability rendered this year favorable for the formation of stmw within the recirculation gyre stmw formed from late winter convection that reached depths greater than 450 m near the center of the gyre the lower boundary of stmw corresponding to 25 5 kg m 3 was set by the maximum depth of the late winter mixed layer properties within the deep portions of the stmw layer remained largely unchanged as the season progressed in contrast the upper boundary of the stmw layer eroded steadily as the seasonal thermocline deepened from late april to august vertical eddy diffusivity responsible for this erosion was estimated from a budget analysis of

high resolution physical properties geochemistry and alteration mineralogy for the host rocks of the archean lemoine auriferous volcanogenic massive sulfide deposit canada multiparameter data on drill cores have a range of useful applications for ore deposit modeling and mineral exploration density magnetic susceptibility eight major elements seven trace elements portable x ray fluorescence pxrf five mineral groups near infrared spectrometry and average visible light reflectance were determined on rock cores from several drill holes these are located near the archean lemoine auriferous volcanogenic massive sulfide vms deposit in the chibougamau mining district abitibi subprovince quebec canada this case study focuses on one particular drill hole that has been recently characterized in detail by conventional methods laboratory geochemistry petrography and stable isotopes this provides validation for the multisensor dataset the best variables and immobile element ratios to distinguish between different lithological units in the multiparameter data are density magnetic susceptibility ti zr al zr and zr y downhole profiles of these parameters allow the four different felsic units in lem 37 many of which are visually similar to be distinguished and geologic contacts to be positioned precisely such methods would be even more useful in environments where recognition of primary characteristics is strongly hampered by intense hydrothermal alteration and superimposed deformation or metamorphism volcanic and intrusive rocks can be placed on classic diagrams to assign them names and magmatic affinities based on the corrected pxrf data downhole profiles of major and trace elements combined with infrared mineralogy allow hydrothermal alteration to be characterized yielding results comparable to those of conventional techniques for the same drill hole but with a much tighter spacing and within potentially shorter time frames

formation and subduction of central mode water based on profiling float data 2003 08 abstract temperature and salinity data from argo profiling floats in the north pacific during 2003 08 have been analyzed to study the structure of winter mixed layer north of the kuroshio extension and the subsurface potential vorticity distribution in the subtropical gyre in relation to the formation and subduction of the central mode water cmw in late winter two zonally elongated bands of deep mixed layer extend at 33 39 and 39 43 n from the east coast of japan to 160 w these correspond to the formation region of the lighter variety of cmw l cmw and that of the denser variety of cmw d cmw and the recently identified transition region mode water trmw respectively in the western part of the l cmw and d cmw trmw formation regions west of 170 e the winter mixed layer becomes deeper and lighter to the east i e to the downstream as a result the formed mode water is reentrained into the mixed layer in the farther east in the following winter and modified to the lighter water and is thus

remote reemergence areas of winter sea surface temperature anomalies in the north pacific 1 taking account of water movement we detect pairs of formation and reemergence areas of winter sea surface temperature sst anomalies in the north pacific by analyzing various kinds of data sets two pairs of formation and reemergence areas are detected one pair is located in the northern subtropical gyre and water properties in both the formation and reemergence areas well correspond to those of north pacific central mode water npcmw another pair is found in the western to central part of the subtropical gyre the formation area corresponds well to that of north pacific subtropical water npstmw but the reemergence area is remote from the formation area examinations on upper ocean current field trace of temperature anomalies in the subsurface and change of water properties from the formation area to the reemergence area clearly indicate that waters with winter sst anomalies move from the formation area to the reemergence area in a year

a mechanism for the recurrence of wintertime midlatitude sst anomalies abstract in the early 1970s namias and born speculated that ocean temperature anomalies created over the deep mixed layer in winter could be preserved in the summer thermocline and reappear at the surface in the following fall or winter this hypothesis is examined using upper ocean temperature observations and simulations with a mixed layer model the data were collected at six ocean weather stations in the north atlantic and north pacific concurrent and lead lag correlations are used to investigate temperature variations associated with the seasonal cycle in both the observations and the model simulations concurrent correlations between the surface and subsurface temperature anomalies in both the data and the model indicate that the penetration of temperature anomalies into the ocean is closely tied to the seasonal cycle in mixed layer depth high correlations extend to relatively deep shallow depths in winter summer lead lag correlations in both the data and the model at some of the stations

a special issue on archean magmatism volcanism and ore deposits part 2 volcanogenic massive sulfide deposits preface this is the second of a two part special issue of economic geology devoted to archean ore deposits the first part of the special issue vol 107 no 5 contains six papers that discuss craton to deposit scale controls on komatiite associated ni cu pge deposits barnes and fiorentini 2012 collins et al 2012 fiorentini et al 2012 heggie et al 2012a b taranovic et al 2012 and six papers that discuss the diversity and key aspects of greenstone hosted au deposits cote mantha et al 2012 garde et al 2012 leclerc et al 2012 mercier langevin et al 2012b schneider et al 2012 sherlock et al 2012 a general introduction to the special issue and an overview of some implications for exploration for greenstone hosted au and komatiite associated ni cu pge deposits in ancient belts is given in mercier langevin et al 2012a the ten papers in this second part of the special issue discuss specific aspects of archean volcanogenic massive sulfide vms deposits the archean which represents more than one third of earth s history was a prolific period for the formation of vms deposits franklin et al 2005 most of these deposits formed within a comparatively narrow time interval between 2740 and 2690 ma in the neoarchean approximately 8 of the global vms tonnage production reserves and geologic resources is contained within deposits of archean age fig 1a given the low degree of preservation of archean crust compared to phanerozoic crust e g veizer 1988 the abundance of archean vms deposits is remarkable proterozoic vms deposits account for approximately 20 of the global vms tonnage whereas the phanerozoic deposits contain 72 of the global tonnage the latter is due in large part to giant vms deposits of the iberian pyrite belt in spain and portugal the urals in russia the rudny

effect of mesoscale eddies on subtropical mode water variability from the kuroshio extension system study kess abstract forty eight profiling floats have been deployed in the kuroshio extension ke region since may 2004 as part of the kuroshio extension system study kess project by combining the float temperature salinity measurements with satellite altimetry data this study investigates the role played by mesoscale eddies in controlling the property changes in north pacific subtropical mode water stmw following a 3 yr period of low eddy activity in 2002 04 the ke showed a transition to a high eddy kinetic energy state in 2005 this transition is the result of delayed oceanic response to the 2002 shift in the basin scale surface wind forcing in connection with the pacific decadal oscillation the high eddy kinetic energy state of the ke is characterized by successive shedding of strong cold core rings into the recirculation gyre resulting from the interaction of the ke jet with the shatsky rise or the preexisting cutoff rings by transporting northern origin high potential vorticity pv ke water into t

the subtropical mode water circulation in the north pacific abstract historical hydrographic data are analyzed to investigate the seasonal variation of the subsurace pycnostad in the northwestern part of the north pacific and to relate it to the circulation of subtropical mode water stmw a gyre scale scheme of stmw circulation is deduced based on its observed climatological formation area and climatological geostrophic flow fields the deduced circulation is supported by climatological features of the subsurface hydrography presented separately for the non large meander period and the large meander period of the kuroshio zonal and meridional sections and isopycnal maps of potential vorticity and apparent oxygen utilization the kuroshio countercurrent composing the kuroshio recirculation system advects stmw formed in the wintertime thick mixed layer immediately off the kuroshio and the kuroshio extension during the non large meander period the recirculation system has a single anticyclonic gyre centered near 30 n 137 e and advects stmw formed off the kurosh

geochemistry of hydrothermally altered rocks at the horne mine noranda quebec low k rhyolites of the archean blake river group that host the horne volcanogenic massive sulfide deposit are altered to quartz sericite chlorite albite quartz sericite zone and chlorite or quartz chlorite zone assemblages the quartz sericite zone accounts for approximately 90 percent of the 5 km 3 of the altered hanging wall and footwall rocks chlorite zone alteration is limited to portions of the footwall and flanks of the cu rich h orebodies clusters of gold bearing chlorite quartz veinlets crosscut large volumes of the quartz sericite zone rocks alteration has added an average of 13 wt percent sio 2 2 3 wt percent k 2 o 430 ppm ba and 46 ppm rb to the system and leached 3 6 wt percent na 2 o 2 2 wt percent cao and 41 ppm sr middle and light ree were increasingly mobile from yb to la they were leached from the chlorite zone rocks and added to quartz sericite zone rocks chlorite was more fe rich fe fe mg 0 65 0 85 in the chlorite zone rocks than in other altered lithologies fe fe mg 0 2 0 5 sulfur isotope values for massive ores are in the range delta 34 s 2 1 to 1 9 per mil mineral separates from altered rocks yielded delta 18 o values of 10 2 to 12 1 per mil for quartz 7 2 to 9 5 per mil for calcite 2 2 to 3 0 per mil for chlorite and 0 1 to 1 0 per mil for magnetite oxygen and sulfur isotope fractionation between coexisting minerals suggests formation from fluids having delta 18 o 3 to 4 per mil at temperatures between 275 degrees to 380 degrees c oxygen isotope compositions of host rocks are delta 18 o 8 or 1 per mil for freshest rhyolite delta 18 o 6 6 to 11 6 per mil for quartz sericite zone rocks and delta 18 o 3 9 to 4 4 per mil for chlorite zone rocks these measured values compare closely to estimated whole rock delta 18 o values based on mass balance considerations using normative mineralogies alteration of wall rocks encompassing the massive sulfide orebodies is characterized by intense sericitization a high degree of silicification and a marked positive delta 18 o anomaly calculations based on sio 2 solubilities and probable k contents of the hydrothermal fluids suggest a water rock mass ratio of 50 to 300 during the mineralization event