hydroacoustic events located at the intersection of the atlantis 30 n and kane 23 40 n transform faults with the mid atlantic ridge we investigate the characteristics of t phase events located at the ends of two segments of the mid atlantic ridge our motivations for the study were to understand whether t phase locations represent earthquake epicenters and thus whether accurate geological inferences can be made from their spatial patterns and to understand further the relationship between t phase event characteristics and earthquake properties we examine the characteristics of 158 t phase events with respect to both event location water depth and source to receiver distance the propagation paths of the t phases are also modeled to study the effects of encountering seafloor topography we find that existing models for t phase excitation and propagation cannot explain adequately all of our observations the amplitudes received levels of t phases at the hydrophones show no dependence on event water depths in contrast to current excitation models which predict a decrease in event magnitude with increasing water depth the received levels are observed to decrease with increasing source to receiver distance and events from the two study areas exhibit different trends in relative received levels between hydrophones once attenuation is taken into account our acoustic ray trace model is able to reproduce similar trends in relative amplitudes at the hydrophones based on 1 d topography between the event and each hydrophone but the variances in both the observed data and model are high we observe a pattern of short t phase onset times for shallow water events and long onset times for deep water events where onset time is defined as the time interval between the appearance of the t phase envelope above the ambient noise and its first peak this suggests that the onset time may be a function of several variables including efficiency of energy conversion based on local topography efficiency of propagation based on event water depth and hypocentral depth in the crust the results of this study underscore the complexity of t phase excitation and propagation and argue that current models of t phase excitation and propagation need to be improved to explain the observed characteristics of t phase data

synthesis of earthquake generated t waves t phases excited by earthquakes propagate with low transmission loss along the ocean sound channel and are characterized by long duration wavetrains often having multiple peaks associated with bathymetric highs in the source region although t waves were first identified almost fifty years ago their activation has not been adequately explained in this paper we show that for continental margin earthquakes realistic t phase coda can be computed by expressing the acoustic energy in terms of several low order modes excited by point sources distributed uniformly over the seafloor the conversion of seismic energy to acoustic energy is thus consistent with seafloor scattering

on the mechanism of conversion of seismic waves to and from t waves in the vicinity of island shores high frequency seismic records from the polynesian seismic network are used to investigate in detail the processes of conversion of acoustic t wave energy from and to seismic waves at island shores on the source side we study the seismic to acoustic conversion based on t phases from hawaiian events recorded at polynesian stations located on the coral platter on the receiver side we study the acoustic to seismic conversion based on t phases from marine sources recorded across the polynesian islands in both instances our results underline the importance of steep slopes typically 50 in allowing an efficient conversion between p waves in the island structure and t waves in the water column these slopes can be coral reefs or the heads of young presumably unconsolidated basalt flows under this geometry modeling based on raytracing indicates that the seismic record of the t phase consists of a p wave at distances from the conversion point greater than 9 km at shorter distances s waves and surface waves are generated in the absence of a steep slope only surface waves are present these models can be used to compute precise and predictable travel time station corrections allowing the use of seismometers located inland to exploit the superb detection and location capabilities of t waves

observations of biological choruses in the southern california bight a chorus at midfrequencies this paper describes the characteristics of an underwater biological chorus recorded in the midfrequency band 1 10khz in the southern california bight the recordings were made in july 2002 by a large vertical aperture 131 element 2d billboard array the chorus observed predominantly on two consecutive nights during the 8 day experiment is composed of two bands of energy centered around 1 5khz and between 4 and 5khz it causes a complete reversal in the vertical directional characteristics of the mid frequency ambient sound field between day and nighttime periods whereas the vertical structure during the day shows a notch in the horizontal direction with levels more than 10db below those at higher angles the nighttime levels in the horizontal can exceed those at other vertical angles by more than 10db these nighttime sounds also are strongly anisotropic in azimuth they appear to come mainly from a popular southern california fishing spot where the water depths exceed 75m vertical beam to beam

metallogenesis and the minerogenetic series in the gangdese polymetallic copper belt abstract the gangdese is a newly explored porphyry cu ore belt in china in fact except for the porphyry cu deposits there are a lot of other deposits forming a polymetallic copper belt in the southern gangdese sg i e southern lhasa terrane and gangdese back arc fault uplift belt gbafub also called lungar nyainqentanglha arc the gangdese polymetallic copper belt contains porphyry cu mo au cu au and mo cu skarn cu mo au w pb zn ag fe cu and mo w breccia type and hydrothermal vein type pb zn ag deposits the porphyry cu au mineralization occurred at the xiongcun area of sg during the middle jurassic 175 160 ma and was associated with island arc magmatism related to the northward subduction of the neo tethyan oceanic slab the cretaceous ca 112 ma skarn fe cu mineralization appeared at the nixiong area of gbafub and was generated in a back arc extensional setting related to the neo tethyan oceanic subduction beneath the lhasa terrane the paleocene eocene 65 51 ma porphyry mo cu skarn mo w and skarn pb zn ag deposits are located in the eastern part of gbafub and related to granitoids originating from the partial melting of the old crust with contributions from the mantle in contrast the paleocene eocene 60 45 ma porphyry cu skarn breccia and hydrothermal vein type pb zn ag and skarn fe cu deposits at the namling area were associated with granitoids derived from the partial melting of the mantle with some input of the old crust the oligocene 30 23 ma porphyry skarn cu mo w au mineralization occurred at the zedong area adjacent to north of the indus yarlung zangbo suture zone in a post collisional setting the intensified miocene 21 13 ma porphyry skarn cu mo au and skarn hydrothermal vein type pb zn ag deposits formed in the sg whereas the porphyry mo cu and skarn hydrothermal vein type pb zn ag deposits formed in the gbafub the porphyry mo cu mineralization have more substantial contributions from the old crust in addition to the mantle than those with porphyry cu mo au mineralization the source region of the high sr y intrusions associated with post collisional porphyry cu mo au mineralization is probably the arc magmas that were generated at the subduction stage and have remained stalled at the boundary between the crust and mantle since the neo tethyan ocean closed the early subduction of the neo tethyan oceanic lithosphere played a crucial role in the generation of ore deposits formed in collisional and post collisional settings six minerogenic series or groups can be recognized in the gangdese polymetallic copper belt 1 jurassic porphyry cu au minerogenic series related to island arc magmatism 2 cretaceous skarn fe cu minerogenic series in back arc extensional setting 3 paleocene eocene granitoids related polymetallic minerogenic series in collisional setting 4 oligocene porphyry skarn cu w mo au minerogenic series in post collisional setting 5 miocene cu mo au pb zn ag minerogenic series related to granitoids with substantial contributions from the mantle in post collisional setting and 6 miocene mo cu pb zn minerogenic series related to granitoids with significant contributions from the old crust in post collisional setting during mineralization some deposits underwent superimposed mineralization such as the jiru porphyry cu deposit where the eocene and miocene porphyry type cu mineralization occurred the minerogenic series can be applied to ore prospecting for example when either pb zn ag veins or porphyry skarn mo w cu orebodies are known in an area one of them could provide a useful exploration vector for the other

copper isotopic zonation in the northparkes porphyry cu au deposit se australia abstract significant systematic cu isotopic variations have been found in the northparkes porphyry cu au deposit nsw australia which is an orthomagmatic porphyry cu deposit copper isotope ratios have been measured in sulfide minerals chalcopyrite and bornite by both solution and laser ablation multi collector inductively coupled plasma mass spectrometry mc icp ms the results from both methods show a variation in 65cu of hypogene sulfide minerals of greater than 1 relative to nist976 significantly the results from four drill holes through two separate ore bodies show strikingly similar patterns of cu isotope variation the patterns are characterized by a sharp down hole decrease from up to 0 8 0 29 0 56 1 n 20 in the low grade peripheral alteration zones phyllic propylitic alteration zone to a low of 0 4 0 25 0 36 1 n 30 at the margins of the most mineralized zones cu grade 1 wt in the high grade cores of the systems the compositions are more consistent at around 0 2 0 19 0 14 1 n 40 the cu isotopic zonation may be explained by isotope fractionation of cu between vapor solution and sulfides at high temperature during boiling and sulfide precipitation processes sulfur isotopes also show an isotopically light shell at the margins of the high grade ore zones but these are displaced from the low 65cu shells such that there is no correlation between the cu and s isotope signatures fe isotope data do not show any discernable variation along the drill core this work demonstrates that cu isotopes show a large response to high temperature porphyry mineralizing processes and that they may act as a vector to buried mineralization

extracting modal structure from vertical array ambient noise data in shallow water measurements of the acoustic mode structure in shallow water can be inverted to determine ocean environmental acoustic parameters this modal stucture is embedded in shallow water ambient noise kuperman and ingenito j acoust soc am 67 1988 1996 1980 ambient noise measurements swellex 1 using a vertical array spanning the lower duct of a summer sound speed environment were used to extract the acoustic modal structure of a coastal water environment off southern california the experimental results derived from eigenvector processing are consistent with simulations using the measured environmental parameters

variation of copper isotopes in chalcopyrite from dabu porphyry cu mo deposit in tibet and implications for mineral exploration abstract the study presents copper cu isotope data of mineral separates of chalcopyrite from four drill core samples in the miocene dabu porphyry cu mo deposit formed in a post collisional setting in the gangdese porphyry copper belt southern tibet copper isotope values in hypogene chalcopyrite range from 1 48 to 1 12 displaying a large variation of up to 2 60 which demonstrates cu isotope fractionation at high temperature during hydrothermal evolution the majority of measured chalcopyrite isotopic compositions show a gradual increasing trend from 1 48 to 1 12 with the increase of drilling depth from 130m to 483m as the alteration assemblages change from potassic to phyllic similarly the other 65 cu values 65 cu 65 cu 63 cu sample 65 cu 63 cu standard 1 1000 of the chalcopyrite show a gradual increasing trend from 1 48 to 0 59 with the decrease of drilling depth from 130 m to 57 m as the alteration assemblages change from potassic phyllic through argillic to relatively fresh these observations suggest a genetic link between cu isotope variation and silicate alteration assemblages formed at different temperatures indicative of a rayleigh precipitation process resulting in the large variation of 65 cu values at dabu in general samples closest to the center of hydrothermal system dominated by high temperature potassic alteration are isotopically lighter whereas samples dominated by low temperature phyllic alteration peripheral to the center are isotopically heavier the predicted flow pathways of hydrothermal fluids are from no 0 to no 3 exploration line and the lightest 65 cu values are the most proximal to the hydrothermal source finally we propose that the northwest side of the no 0 exploration line has high potential for hosting undiscovered orebodies the pattern of cu isotope variation in conjunction with the features of silicate alteration in porphyry system can be used to trace the hydrothermal flow direction and to guide mineral exploration

insights into ore genesis of ni cu pge sulfide deposits of the noril sk province russia evidence from copper and sulfur isotopes abstract combined cu s isotope data for ni cu pge sufides from the economic deposits hosted in the noril sk 1 talnakh and kharaelakh intrusions from the subeconomic deposits in the chernogorsk zub marksheider and vologochan intrusions and from the non economic occurrences in the nizhny talnakh intrusion in the noril sk province russia and the j m reef in the stillwater complex usa are presented for the first time most sulfide samples including the ores from the talnakh intrusion and the stillwater complex have a restricted range of 65 cu values from 1 1 to 0 whereas those from the kharaelakh and noril sk 1 intrusions have more variable 65 cu values of 2 3 to 1 0 samples from the three economic deposits in the noril sk province have distinct mean 65 cu values of 1 56 0 27 for kharaelakh 0 55 0 41 for talnakh and 0 23 0 28 for noril sk 1 consistent with those for carbonaceous chondrite and iron meteorites the variation of 65 cu values is interpreted to represent a primary signature of the ores although a magmatic fractionation of cu isotopes and or assimilation from an external source cannot be ruled out particularly in the case of the kharaelakh ores collectively the eight investigated intrusions have an overall sulfur 34 s range from 0 7 to 13 8 disseminated and massive ores of the same intrusion have similar 34 s values the disseminated and massive ores of the khraelakh intrusion have a mean 34 s value of 12 57 0 54 and 12 76 0 42 respectively which are distinctly different from those of the disseminated 10 97 0 44 and massive ores 10 88 0 77 of the talnakh intrusion the different 34 s values of the intrusions may be attributed to sulfur fractionation in deep seated magma chambers rather than at shallow levels or the present emplacement site the mean 34 s value of the disseminated ores from the subeconomic ni cu pge deposits and non economic occurrences spans over 10 5 averaging 0 39 with a standard deviation of 1 55 for the highly contaminated zub marksheider rocks 6 38 1 89 for nizhny talnakh 6 90 1 17 for vologochan and 10 86 0 43 for chernogorsk samples from the zub marksheider intrusion have mantle like s isotope signatures consistent with a deep seated origin although individual mineralized instrusions have a restricted range the overall trend they define of falling 34 s with rising 65 cu values might be a useful indicator of the economic potential of ni cu pge sulfide deposits

computation of t phase coda t phases result from the conversion of seismic to acoustic energy at the seafloor in the vicinity of an earthquake epicenter the time frequency characteristics of t phase coda are observed to be strongly dependent upon the bathymetry of the ocean floor in the source region thus earthquakes from the same geographic area generate similar t phase coda in this study detailed bathymetry and sound speeds computed from the levitus atlas are used to simulate the t phase amplitudes which would be recorded at distances of several thousand kilometers from these natural sound sources it is hypothesized that seismic acoustic coupling occurs over a distributed region of the ocean floor with seismic energy being scattered into low order modes in shallow water comparison with observed coda indicates that t phase onset times and durations are modeled quite accurately with this simple method the feasibility of using this method to determine accurate source times and locations for small suboceanic earthquakes given

coupled 63cu and 16o excesses in chondrites abstract recent developments in multiple collector magnetic sector icp ms inductively coupled plasma mass spectrometry have permitted the relative abundances of the two isotopes 63 and 65 of copper to be measured with unprecedented precision 40 ppm here we report cu isotopic variations among eight carbonaceous chondrites ccs from the ci cm co and cv groups and the presently ungrouped tagish lake and 10 ordinary chondrites ocs from the h l and ll groups the widest isotopic range of 0 8 per a m u is observed for the carbonaceous chondrites copper in carbonaceous chondrites becomes isotopically lighter with petrologic type in the order 1 to 3 but seems extremely homogeneous for each type the cu isotopic composition of tagish lake confirms its other characteristics that are intermediate between ci and cm in three of the groups ci cm co as well as for tagish lake 63 cu excess over terrestrial mantle abundances correlates well with 16 o excess for all four groups 63 cu excess also correlates remarkably well with elemental refractory volatile ratios e g ca mn for ordinary chondrites small differences exist between the h l and ll groups with cu becoming isotopically heavier in that order equilibrated and unequilibrated samples however exhibit the same cu isotopic signature within each group although the range of cu isotopic compositions in ordinary chondrites is smaller than in carbonaceous chondrites 63 cu excesses still correlate with 16 o excesses the observed trends of isotopic variation seem incompatible with a single stage fractionation process by either volatilization or low temperature metamorphism the correlations between 63 cu excesses and 16 o excesses suggest the presence of at least two and perhaps three isotopically distinct cu reservoirs in the early solar system 1 an earth like reservoir common to the ci and ll probably representing the main cu stock of the inner solar system 2 a reservoir present in all carbonaceous chondrites but most abundant in cv with large 63 cu and 16 o excesses this reservoir is probably hosted in refractory material and 3 possibly a third reservoir present in ordinary chondrites the oc trend may also be explained as a mixture of the first two cu reservoirs if its oxygen was first equilibrated with nebular gas the coexistence of 63 cu and 16 o excesses in the same component raises the issue of how volatile cu was preserved in refractory material a strong correlation between 63 cu 65 cu and ni cu ratios suggests that 63 cu excess may have originated as more refractory 63 ni t 1 2 100 yr upon irradiation of refractory grains by electromagnetic flares and particle bursts during the t tauri phase of the sun

energetics of the deep ocean s infrasonic sound field simultaneous measurements of infrasonic 0 5 20 hz acoustic particle velocity and acoustic pressure made by the marine physical laboratory s set of freely drifting swallow floats are analyzed in terms of the energetics of acoustic fields results from a recent deep ocean deployment indicate that the midwater column s acoustic potential and kinetic energy density spectra are equal above 1 7 hz since away from the ocean boundaries the sound field is locally spatially homogeneous near the ocean bottom the vertical spatial inhomogeneity is statistically significant between 0 6 1 4 hz and 7 20 hz in the lower band the pressure autospectrum decreases with increasing distance from the ocean bottom whereas in the upper band it increases due to the deep sound channel s ability to trap acoustic energy at the higher infrasonic frequencies for ship signals the signal to noise ratio in the active intensity magnitude spectrum is 3 6 db greater than in either of the two energy density spectra due to the vector nature of acoustic intensity although smaller than the net horizontal flux above a few hertz a statistically significant net vertical flux density of energy occurs across the whole frequency band from the ocean surface into the bottom the direction of the net horizontal flux density for various discrete sources e g a magnitude 4 1 earthquake a blue whale and commercial ships is discussed the net horizontal flux density of the background sound field between 5 and 12 hz may have been determined by the surrounding ocean bottom topography in one experiment its direction approximately coincides with the center of a topographic window however it also matches the heading toward a 4000 km distant hurricane a third possibility of an unknown broadband source cannot be eliminated with the available data

metal fractionation between magmatic brine and vapor determined by microanalysis of fluid inclusions the major and trace element compositions of individual fluid inclusions from a range of magmatic hydrothermal ore deposits were analyzed by laser ablation inductively coupled plasma mass spectrometry to explore the behavior of ore forming components during fluid phase separation boiling in high temperature saline fluid systems data from 13 samples showing unambiguous evidence for coeval trapping of a liquid brine and a coexisting vapor phase identify two groups of elements with drastically different geochemical behavior na k fe mn zn rb cs ag sn pb and tl preferentially partition into the brine probably as cl complexes whereas cu as au probably as hs complexes and b selectively partition into the vapor fluid phase separation is probably a major previously underestimated process in the chemical differentiation that contributes to the extreme range of selective element enrichments in magmatic hydrothermal systems from deep plutons through porphyry style and greisen deposits to epithermal mineralization and volcanic fumaroles

the isotope geochemistry of carbon in groundwater at stripa the carbon isotopic composition of the total dissolved inorganic carbon in groundwater associated with a granitic pluton at stripa sweden reflects both inorganic and organic carbon sources following the uptake of soil carbon dioxide calcite dissolution dominates the geochemical evolution of shallow groundwater calcite saturation is reached at a depth of about 100 m in deeper waters geochemical release of ca and increasing ph cause calcite precipitation radiocarbon contents suggest carbon and water ages in excess of 20 000 years for waters at 300 400 m depth in deep groundwaters with enhanced salinities organic carbon is added to the dissolved inorganic carbon either through bacterial activity e g sulphate reducing bacteria or the oxidation of organic compounds such as methane the lowest radiocarbon contents were measured at the 300 400 meter levels and not in the deepest fluids the distribution of 13c in the deep groundwaters suggests the existence of well defined flowsystems with limited active hydraulic interaction isotope analyses on fracture calcites substantiate the complex geochemical history of the pluton

the cu isotopic signature of granites from the lachlan fold belt se australia abstract this contribution reports our preliminary work to determine cu isotope ratios for various granite rocks and examine the cu isotope systematics within granite suites a chemical procedure modified from marechal marechal c n telouk p and albarede f 1999 precise analysis of copper and zinc isotopic compositions by plasma source mass spectrometry chemical geology 156 1 4 251 273 was used to separate cu from rock matrix quantitative recovery 100 6 1 6 with a low total procedural blank 2 65 0 66 ng for cu has been achieved allowing cu isotopic measurements on samples with as little as 10 ppm cu the cu isotope ratios 65cu relative to nist srm 976 of 32 rock samples ranging from mafic to felsic compositions from 3 batholiths 2 i type 1 s type from the lachlan fold belt in southeastern australia vary from 0 46 to 1 51 most of them cluster around zero with mean values for the i type and s type granites of 0 03 0 15 and 0 03 0 42 2 sigma respectively these data together with cu isotope ratios of two loess samples provide preliminary evidence that the baseline cu isotopic composition of the crystalline part of upper continental crust is close to zero the tight clustering of cu isotope ratios of rocks from the i type suites suggests that high temperature magmatic processes do not produce significant cu isotope fractionation however two granites with abnormally heavy cu isotope signatures up to 1 51 appears to be the result of localized hydrothermal alteration measurable variation in cu isotopic composition of the s type granite may reflect isotopic heterogeneity in the sedimentary source region as a result of redox processes or may be due to hydrothermal overprinting thus cu isotope geochemistry may be a useful tracer for studying hydrothermal alteration and source heterogeneity of granitic rocks

zones of t wave excitation in the ne indian ocean mapped using variations in backazimuth over time obtained from multi channel correlation of ims hydrophone triplet data summary ground coupled hydro acoustic waves so called t waves observed at international monitoring system ims hydrophone triplet stations in the indian ocean were analysed for backazimuth and apparent wave speed by applying a progressive multi channel correlation method pmcc for t waves which propagate along topographically unblocked geodesic paths the three triplet channels generally show good signal correlation over sliding windows and various frequency bands a characteristic change in backazimuth over time in some cases combined with signs of dispersion is observed for many t waves generated by earthquakes from the margin of the indo australian plate between the sunda islands to the southeast and the andaman islands to the northwest backazimuths and arrival times of those pmcc detections are used to map point by point the areas where ground to water coupling takes place such areas are mostly linked to large gradients in the bathymetry predominantly at approximately the depth of the axis of the sound fixing and ranging sofar channel along island arcs edges of continental shelves and at comparatively small features like isolated islands or sea mountains six examples are discussed in this paper for the strongest events the area of detectable groundto water coupling often spans distances of more than 15 in one case even more than 26 and a range in backazimuths of up to 35 information on the accuracy of backazimuth determination on the average hydro acoustic wave speed along the wave path and on topographic blockage of waves can also be inferred from the results owing to the consistency and great detail of the mapped coupling zones for the study area it can be shown that it is predominantly seismic energy from p and or pn waves that couples efficiently into the sofar channel particularly for deep focus events the backazimuths determined for the highest amplitude segments of the signals can deviate considerably from the great circle azimuth between source and receiver and may therefore lead to inaccurate epicentre locations based on backazimuth measurements of t waves in some cases laterally reflected t waves are observed

empirical and numerical modeling of t phase propagation from ocean to land t phase propagation from ocean onto land is investigated by comparing data from hydrophones in the water column with data from the same events recorded on island and coastal seismometers several events located on hawaii and the emerging seamount loihi generated very large amplitude t phases that were recorded at both the preliminary ims hydrophone station at point sur and land based stations along the northern california coast we use data from seismic stations operated by u c berkeley along the coast of california and from the pg e coastal california seismic network to estimate the t phase transfer functions the transfer function and predicted signal from the loihi events are modeled with a composite technique using normal mode based numerical propagation codes to calculate the hydroacoustic pressure field and an elastic finite difference code to calculate the seismic propagation to land based stations the modal code is used to calculate the acoustic pressure and particle velocity fields in the ocean off the california coast which is used as input to the finite difference code tres to model propagation onto land we find both empirically and in the calculations that t phases observed near the conversion point consist primarily of surface waves although the t phases propagate as p waves after the surface waves attenuate surface wave conversion occurs farther offshore and over a longer region than body wave conversion which has the effect that surface waves may arrive at coastal stations before body waves we also look at the nature of t phases after conversion from ocean to land by examining far inland t phases we find that t phases propagate primarily as p waves once they are well inland from the coast and can be observed in some cases hundreds of kilometers inland t phase conversion attenuates higher frequencies however we find that high frequency energy from underwater explosion sources can still be observed at t phase stations

application of waveguide invariants to analysis of spectrograms from shallow water environments that vary in range and azimuth the waveguide invariant summarizes in a single scalar parameter the dispersive propagation characteristics for a given environment an expression is derived for the invariant in shallow water environments where the bottom bathymetry varies with range and azimuth it then is applied to the interpretation of broadband single element spectrograms collected during swellex 3 a shallow water acoustics experiment off the coast of san diego the unusual behavior of the interference patterns seen in the spectrograms from this experiment during the transmission of a 75 150 hz pseudo random noise sequence by a source towed over range varying bottom bathymetry is well matched by the model predictions work supported by onr code 321us

use of cu isotopes to distinguish primary and secondary cu mineralization in the canariaco norte porphyry copper deposit northern peru a significant proportion of the copper in the canariaco norte porphyry copper deposit in northern peru occurs in chalcocite and covellite rich veins and disseminations that exist from the surface to depths greater than 1 km the overall range of cu isotopic ratios of 42 mineral separates from canariaco varies from 8 42 to 0 61 with near surface chalcocite and fe oxides having isotopically depleted values compared to chalcocite covellite and chalcopyrite from deeper levels the majority 34 of 36 of measured cu sulfides have a typical hypogene copper isotope composition of 65cu 0 18 0 38 with no enriched isotopic signature existing in the canariaco norte sulfide data thus the copper isotope data indicate that most of the chalcocite and covellite formed from high temperature hypogene mineralization processes and that only a minor portion of the deposit is enriched by supergene processes the nonexistence of an enriched 65cu reservoir suggest the presence of an undiscovered lateral exotic cu occurrence that enriched 65cu that remained in solution during weathering regardless of the cause the comparative analysis of the cu isotope dataset reveals that little exploration potential for an extensive supergene enrichment blanket exists because the weathering history at canariaco norte was not conducive to preservation of enriched cu at depth beneath the leach cap

estimating the horizontal and vertical direction of arrival of water borne seismic signals in the northern philippine sea conventional and adaptive plane wave beamforming with simultaneous recordings by large aperture horizontal and vertical line arrays during the 2009 philippine sea engineering test philsea09 reveal the rate of occurrence and the two dimensional arrival structure of seismic phases that couple into the deep ocean a ship deployed controlled acoustic source was used to evaluate performance of the horizontal array for a range of beamformer adaptiveness levels ninety t phases from unique azimuths were recorded between yeardays 107 to 119 t phase azimuth and s minus p phase time of arrival range estimates were validated using united states geological survey seismic monitoring network data analysis of phases from a seismic event that occurred on yearday 112 near the east coast of taiwan approximately 450 km from the arrays revealed a 22 clockwise evolution of t phase azimuth over 90 s two hypotheses to explain such evolution body wave excitation of multiple sources or in water scattering are presented bas

the role of sulfur in the formation of magmatic hydrothermal copper gold deposits abstract essential resources of many rare metals including copper zinc molybdenum silver and gold occur in natural sulfide mineral deposits understanding the origin of these metal resources has been limited by a lack of data about the geochemistry of sulfur the most important and abundant element of ore deposits we report the first directly measured sulfur concentrations in high temperature fluids together with their ore metal contents using a new method for sulfur quantification in fluid inclusions by laser ablation inductively coupled plasma mass spectrometry la icp ms co genetic brine and vapor inclusions from magmatic hydrothermal ore deposits and granitic intrusions show an excess of sulfur over ore metals as required for efficient ore mineral precipitation the results demonstrate that s cu and au are highly enriched in vapor like magmatic fluids implying that such low salinity fluids are the key agent for the formation of porphyry copper and epithermal gold deposits

copper isotope ratios in magmatic and hydrothermal ore forming environments multi collector inductively coupled plasma mass spectrometry now provides for precise and accurate measurements of cu isotope ratios copper minerals prepared by direct dissolution with and without chromatographic purification yield identical cu isotope ratios within analytic precision of about 0 04x 1r cu isotope ratios have been measured for copper minerals from worldwide magmatic and hydrothermal copper deposits and for several weathered deposits natural variations in d65cu values relative to nbs976 range over 9x chalcopyrite samples from mafic intrusions lie within a narrow range of about 1 5x and most cluster tightly between 0 10xand 0 20x this range lies within the broader black smoker chalcopyrite and iron meteorite ranges and possibly represents a bulk mantle cu isotope ratio most values for hydrothermal native copper from the michigan native copper district also show a narrow range just larger than 0 1xand suggest a common homogeneous source for cu in this large hydrothermal system later copper sulfide and arsenide minerals from this district range to values more than 2x lower than native copper ratios for chalcopyrite and bornite from moderate to high temperature porphyry skarn and replacement deposits as a group and within individual deposits exhibit a broad range of values variations of nearly 1xare observed over distances on the order of 1 m in some cases these variations may result from multiple mineralization events or copper remobilization during retrograde or later hydrothermal activity fractionations between chalcopyrite and bornite where they occur in the same sample or in related samples cluster near 0 4x suggesting equilibrium cu isotope fractionation between them at moderate temperatures in addition weathering of hydrothermal copper minerals produces a wide range of values in secondary copper phases in the supergene environment cuprite typically has higher values than associated native copper therefore redox states appear to exert a significant control over fractionation at low temperatures significant questions remain to be answered before the source of copper in hydrothermal environments can be fully addressed source reservoir cu ratios need to be determined and chemical and physical factors that control cu isotope fractionation must be quantitatively defined d 2003 elsevier b v all rights reserved

characteristics and genesis of gangdese porphyry copper deposits in the southern tibetan plateau preliminary geochemical and geochronological results porphyry type cu mo au deposits have been discovered along the gangdese magmatic arc in the southern tibetan plateau extensive field investigations and systematic studies of geochemistry s pb isotopic tracing together with re os and 40ar 39ar isotopic dating indicate that the mineralisation of the copper belt is genetically related to emplacement of late orogenic granitic porphyries during the post collisional crustal relaxation period of the late himalayan epoch these porphyries are petrochemically k enriched and belong to shoshonitic to high k calc alkaline series they display enrichment of large ion lithophile elements lile rb k u th sr pb and depletion of high field strength elements hfse nb ta ti and the heavy rare earth elements hree and y without eu anomalies these characteristics demonstrate that subduction played a dominant role in their petrogenesis and residual garnet was left in the magma sources pb isotope data show a linear correlation in the plumbotectonic framework diagram ranging from orogenic pb in the eastern segment of the copper belt to mantle pb in the western segment these constitute a mixing line of the indian oceanic morb with indian oceanic sediments and suggest that the porphyry magmas were dominantly derived from partial melting of subducted oceanic crusts mixed with a minor quantity of sediments and mantle wedge components the gangdese porphyry copper polymetallic belt has alteration characteristics and zonation typical of porphyry type copper deposits which include potassic alteration k feldspathisation and biotitisation silicification sericitisation and propylitisation mineralisation mainly occurs in strongly altered granitic cataclasite at the exo contact with veinlet disseminated textures the porphyries themselves are weakly mineralised with disseminated pyrite and chalcopyrite the copper deposits contain simple ore mineral associations consisting of chalcopyrite pyrite bornite molybdenite sphalerite and oxidised minerals of malachite covellite and molybdite during supergene oxidation primary ores underwent secondary enrichment to form economic orebodies with cu grade ranging from 1 to 5 ore sulphides of the copper belt display s and pb isotopic compositions identical to the ore bearing porphyries their 34s values vary between 3 8 and 2 4 and are typical of mantle sulphur the 206pb 204pb 207pb 204pb and 208pb 204pb ratios vary in the ranges 18 106 to 18 752 15 501 to 15 638 and 37 394 to 39 058 respectively and yielded radiogenetic lead enriched signatures twelve molybdenite samples from the copper belt yielded isochron ages of 14 76 0 22 ma and 13 99 0 16 ma for the nanmu and chongjiang deposits and model ages of 13 5 to 13 6 ma for the lakang e deposit meanwhile 40ar 39ar isotopic dating of two biotite phenocrysts from the chongjiang and lakang e deposits give plateau ages of 13 5 1 0 ma and 13 42 0 10 ma respectively during the geodynamic evolution of the gangdese collision orogenic belt intrusion of the ore bearing porphyries took place just before the rapid uplift and e w extension of the southern plateau and the ore forming process may have occurred simultaneously with the uplift and extension 14 0 1 ma

normal mode composition of earthquake t phases understanding the nature of the coupling between the underwater acoustic field and the land seismic field is important for evaluating the performance of the t phase stations in the international monitoring system for the comprehensive nuclear test ban treaty for upslope propagation in an ocean environment the places where underwater acoustic field energy couples into the land seismic field are determined to first approximation by the local water depth and the normal mode composition of the acoustic energy therefore the use of earthquake generated t phases as natural probes of water to land coupling characteristics is aided by knowledge of their modal composition data collected by a 200 element 3000 m aperture vertical hydrophone array during a 1989 experiment in the deep northeast pacific ocean are used to determine the mode composition of t phase arrivals from two mb 4 1 earthquakes near the w est coast of the u s one occurring offshore and the other on land results from an eigenanalysis approach and conventional mode decomposition for the two events are consistent and show that at 5 hz the offshore event s arrivals have higher order mode content compared to those from the event on land single hydrophone recordings at pt sur of two mb 4 4 hawaiian events in 1996 and 1997 one occurring offshore and the second on land display time frequency arrival structures that are explainable by the dispersion characteristics over the oceanic path although other effects due to complex source time functions and shear wave and dispersive propagation effects along the initial land path cannot be separated with these single element data differences in these two events arrival structures suggest differences in normal mode content consistent with those seen in the pair of 1989 events ocean path dispersion also appears to play a significant role in determining the i n water arrival structure from a 1995 french nuclear test at mururoa recordings of two hawaiian events in 1997 by the t phase station vib and the seismic station at berkeley illustrate that the water land coupling confuses the relative timing between normal modes resulting in apparent loss of information about the source

seismicity and velocity structure of loihi seamount from the 1996 earthquake swarm the largest earthquake swarm yet recorded on loihi submarine volcano took place in july and august of 1996 the swarm consisted of two phases of seismic activity and was associated with the formation of a pit crater and additional faulting of loihi s summit platform the first phase of activity was comprised of predomi nantly high frequency events scattered over the southern flanks of the volcano fol lowing a day of seismic quiescence the second phase of activity began consisting of lower frequency earthquakes with strong t phases the phase 2 events took place beneath loihi s summit presumably marking the formation of the pit crater pele s pit data obtained by an ocean bottom seismometer obs on loihi during the swarm help constrain a new velocity model for loihi the relocated earthquakes combined with other characteristics of the swarm enabled us to develop a model for the events leading up to the formation of pele s pit that includes 1 a prolonged eruption 2 a tectonic event beneath loihi s south flank and 3 the drainage of a shallow magma chamber