longitudinal variability of low latitude total electron content tidal influences 1 recently nighttime ultraviolet uv observations obtained by image fuv and timed guvi instruments have revealed a longitudinal wave number four pattern in the nighttime airglow intensity and in the position of the equatorial anomalies during equinox and high solar flux conditions in the present study we have extended this work and determined the longitudinal variability of the low latitude total electron content tec climatology during different geophysical conditions with a special emphasis on the longitudinal wave number four structure in the low latitude ionosphere we have used more than 5 million low latitude topex tec observations covering the entire 13 years of topex tec data from august 1992 until october 2005 this data set was used to determine the local time seasonal solar cycle and geomagnetic activity dependence of the longitudinal variability of tec at equatorial and low latitudes and in particular to address the existence and evolution of the wave number four longitudinal pattern under these conditions our study shows that the wave number four pattern is created during the daytime hours at equinox and june solstice but is absent or washed out by other processes during december solstice during equinox the wave number four pattern is created around noon with well defined longitudinal enhancements in the low latitude tec these enhancements which are symmetric about the geomagnetic equator during this season last for many hours and can be clearly seen past midnight the longitudinal patterns are found to be nearly identical between the vernal march april and autumnal september october equinoxes and largely independent of the solar cycle conditions the wave number four pattern is also observed during geomagnetically active conditions indicating that the processes that create this pattern are also present during active times the variations between the well defined longitudinal maxima and minima are of the order of 20 during june solstice the wave number four pattern is also observed in the afternoon hours but in contrast to the equinox cases it exhibits a strong hemispheric asymmetry and is not observed during the night the low latitude tec exhibits clear longitudinal variations during december solstice with large daytime enhancements over the east asian and pacific regions and a third enhancement emerging in the afternoon over the atlantic ocean but a clear wave number four pattern is not observed during this season although the equatorial and low latitude tec values exhibit clear longitudinal patterns during all seasons a significant amount of scatter remains in the tec data that is not accounted for by changes in the solar cycle the season or the local time or by the longitudinal variability this remaining scatter is largest near the poleward edges of the anomalies and is of the order of 40

daytime zonal drifts in the ionospheric 150 km and e regions estimated using ear observations multi beam observations of the 150 km echoes made using the equatorial atmosphere radar ear located at kototabang indonesia provide unique opportunity to study both vertical and zonal exb plasma drifts in the equatorial ionosphere in this paper we focus on estimating daytime zonal drifts at the 150 km 140 160 km and e 100 110 km regions using multi beam observations of 150 km and e region echoes made using the ear and study the daytime zonal drifts covering all seasons not studied before from kototabang zonal drifts in the 150 km and e regions are found to be westward and mostly below 80 m s 1 and 60 m s 1 respectively while the zonal drifts in the 150 km and e regions do not go hand in hand on a case by case basis the seasonal mean drifts in the two height regions are found to be in good agreement with each other zonal drifts at the 150 km region show seasonal variations with three maxima peaking around may september and january the zonal drifts at the 150 km region are found to be smaller than the f region drifts obtained from cindi onboard c nofs by about 25 m s 1 consistent with the height variations of f region zonal drifts observed by the jicamarca radar these results constitute the first comprehensive study of zonal drifts at the 150 km and e regions from kototabang indonesia and the results are discussed in the light of current understanding on the low latitude electrodynamics and coupling

surface deformation in a crustal setting with a long surfaced non uniformity abstract many heterogeneous zones in the crust which lie at the surface can be approximated geometrically as long horizontal cylinders of half elliptical cross section with depth for example these include alluvially filled valleys and formerly active fault zones a two dimensional elastic model giving the quasi static surface deformation for this class of crustal rigidity profiles is developed the applied stress is assumed to be a remotely applied uniform shear calculations using this model show local strain and deformation excursions from expected data assuming the conventional uniform rigidity half space model the magnitude of these anomalies can be quite large depending on the values of the heterogeneous zone s compliance and dimensions the anomalies were found to be local since the horizontal extent of their pertubation field was at most only a few times the depth of the heterogeneity

evidence for syngenetic precious metal enrichment in an appalachian volcanogenic massive sulfide system the 1806 zone ming mine newfoundland canada the ming deposit baie verte newfoundland canada is an early ordovician bimodal mafic cu au zn ag volcanogenic massive sulfide vms deposit the deposit consists of a number of ore lenses that are stacked in the uppermost part of the rambler rhyolite one of the uppermost lenses the 1806 zone is enriched in au and ag the deposit has been affected by silurian devonian greenschist to amphibolite grade metamorphism and polyphase deformation and this has led to debates as to whether the au ag enrichment in the deposit is syngenetic or a product of a later metamorphic and structural overprint the 1806 zone consists predominantly of discordant sulfide stringer stratabound semimassive to massive sulfides and a weakly mineralized silicified cap zone the ore is largely hosted within the footwall rambler rhyolite that is strongly altered to quartz sericite green mica with sporadic chlorite biotite base and precious metal zoning is developed from the down plunge portion cu au to the up plunge portion cu zn au ag pb of the 1806 zone the ore mineralogy and mineral chemistry are complex and are interpreted to be of an intermediate sulfidation type pyrite and chalcopyrite are the dominant sulfide species with minor to accessory sphalerite galena pyrrhotite and arsenopyrite sulfosalts including ag bearing tennantite tetrahedrite stannite boulangerite and loellingite and precious metal rich phases are common throughout the deposit precious metals occur as 1 mercurian electrum 7 93 20 57 wt hg and 2 various ag phases miargyrite pyrargyrite mercurian stephanite unnamed agcufes phase ag hg au alloys that are more abundant in the up plunge portion of the 1806 zone tellurides and bismuthides are present in trace amounts oxides cassiterite and magnetite are present exclusively in the down plunge portion of the 1806 zone the deposit geometry metals distribution complex ore assemblages abundant sulfosalts and the significant concentration of the epithermal suite of elements e g au ag as hg sb bi in the ore strongly contrast with those of orogenic au deposits and support a syngenetic or synvolcanic origin for precious metals in the ming vms deposit including a possible magmatic input into the 1806 zone ore forming system evidence for a late syndeformation precious metal emplacement via orogenic overprinting is lacking at the 1806 zone and all data point to a syngenetic origin for precious metal enrichment indicating that ordovician appalachian vms deposits are favorable targets for au nevertheless silurian devonian metamorphism and deformation have resulted in textural recrystallization and local remobilization of precious metals and the main fabrics largely control the current geometry of the host succession and of the ming orebody

images of transequatorial f region bubbles in 630 and 777 nm emissions compared with satellite measurements images of transequatorial f region bubbles were obtained from magnetic field aligned airglow observations from haleakala hawaii for 9 nights in august 1988 bubbles of scale size 10 100 km were recorded with an intensified ccd detector attached to a filter wheel imager and sequential images were made in the plasma recombination emissions at 630 nm and 777 nm and in the background emissions the observations also yield information on the large scale structure of the ionosphere in the northern appleton anomaly region particularly on the latitude variations of plasma concentration and layer height measurements from the dmsp f8 and f9 satellites extend this to include the southern anomaly region the dmsp satellites were near 830 km in altitude and in near polar orbits at about 1800 and 2120 hours local time a comparison of the bubble images and the dmsp results with plasma concentration and drift velocities obtained from the san marco satellite allows us to put the measurements along the san marco track into the larger ionospheric context one to one correspondence is found between the presence of the optical bubbles and the presence of plasma depletions measured from the san marco satellite allowing identification on consecutive orbits of the same depletions this extends for up to 5 hours of the satellite measured information for individual depletions that is their vertical and horizontal drift velocities and the plasma concentration variations the images show the shapes of the depletions in apex height and longitude and their evolution horizontal drift velocities of the bubbles were determined by a correlation analysis bubble occurrence is compared with day to day changes in the equatorial fountain electric fields and transequatorial asymmetries caused by neutral winds and with measurements of radar backscatter from centimeter scale irregularities associated with bubbles in the kwajalein sector the development of 10 100 km scale size bubbles at a given time and location is clearly a consequence of the presence of even larger wavelike corrugations in the f layer provided there is also at least a moderately strong equatorial fountain

low latitude zonal and vertical ion drifts seen by de 2 horizontal and vertical ion drift data from the de 2 spacecraft have been used to determine average zonal and vertical plasma flow electric field characteristics in the plus minus 26 degree dip latitude region during a time of high solar activity the data base consists of over 800 equatorial passes horizontal ion drift data were projected along magnetic field lines to the magnetic equator using a dipole model to yield their apex height dependence the average data local time profile for an apex height bin centered at 400 km indicates westward plasma flow from 0600 to 1900 solar local time slt with a maximum westward velocity of 80 m s in the early afternoon there is a sharp change to eastward flow at approximately 1900 hours with an early evening peak of 170 m s a secondary nighttime maximum exists a 0430 slt preceeding the reversal to westward flow this profile is in good agreement with jicamarca radar measurements made under similar solar maximum conditions harmonic analysis indicates a net superrotation which is strongest at lower apex altitudes the diurnal term is dominant but higher order terms through th quatradiurnal are significant vertical ion data taken at low plus minus 5 degree dip latitudes while possessing greatermore scatter generally agree wtih jicamarca values copyright american geophysical union 1989 less

equatorial zonal plasma drifts measured by the c nofs satellite during the 2008 2011 solar minimum 1 we use the measurements by the vector electric field investigation vefi on board the communication navigation outage forecasting system c nofs satellite to study the local time and seasonal and longitudinal dependent climatology of equatorial f region zonal plasma drifts during 2008 2011 these drifts are essentially westward during the day and eastward at night over jicamarca radio observatory the satellite measurements are in good agreement with incoherent scatter radar drifts our data show strong longitudinal variations particularly in the south american sector during the solstices the equinoctial data exhibit short lived and largely enhanced westward drifts near sunrise and wave 4 structures from the early afternoon to late night equinoctial periods the nighttime eastward drifts are largest near the western american sector at all seasons the june solstice postmidnight eastward drifts decrease sharply at longitudes of about 310 and have much smaller values in the entire eastern hemisphere we also briefly discuss the relationship between the longitude dependent vertical and zonal plasma drifts

the multi instrumented studies of equatorial thermosphere aeronomy scintillation system climatology of zonal drifts a spaced antenna scintillation system was installed at ancon peru in may 1994 to measure scintillation of 250 mhz signals from a geostationary satellite by three antennas spaced in the magnetic east west direction these measurements were used to establish the climatology of the zonal drift of the irregularities which cause equatorial scintillations the major objective of this study is to compare this drift climatology to the climatology of zonal neutral wind which is the driver of the equatorial electrodynamics a comparison of these two climatologies in conjunction with scintillation statistics may provide some clues regarding factors which help or hinder the formation of equatorial spread f esf with these objectives in mind the first year s drift and scintillation statistics have been presented as a function of local time season and magnetic activity and compared with the statistics of ion drift published earlier from incoherent scatter radar observations the scintillation drift is in good agreement with the jicamarca radar observations except for the fact that the local time dependence of our drift observations exhibit a broader maximum the broad maximum may be attributed to lower ion drag experienced in the presence of esf due to sustained uplifting of the ionosphere during magnetically active periods the scintillation drift often exhibits east to west reversals presumably because of the disturbance dynamo effects the westward drifts during such reversals may be as large as 100 m s we have also modeled the zonal drifts as a seasonal basis by using hedin s neutral wind model and anderson s fully analytical ionospheric model the modeled zonal drifts present good quantitative agreement with the drifts obtained with the scintillation technique

comparison of zonal neutral winds with equatorial plasma bubble and plasma drift velocities 1 a one year dataset spanning march 2011 to march 2012 of coincident observations of nighttime thermospheric zonal neutral winds equatorial plasma bubble epb velocities and zonal plasma drifts is used to examine the relationship between the thermosphere and the ionosphere near the geomagnetic equator over peru thermospheric neutral winds are determined by using a bistatic fabry perot interferometer fpi experiment located at merihill and nazca in peru the ambient plasma drift velocities were obtained using the incoherent scatter radar at the jicamarca radio observatory in peru the epb zonal velocities were estimated utilizing images of the oi 630 0 nm emission recorded by a narrow field optical imaging system at the cerro tololo inter american observatory in chile the joint analysis of these datasets illustrates that the nighttime and night to night variations in the zonal neutral winds epb velocities and plasma drifts are well correlated this consistent result of the local time variations of the neutral winds with that of epb and plasma drifts illustrates that the f region dynamo is in general fully activated however at times the magnitude of the epb velocities and the plasma drifts are different from the neutral winds it is plausible that such a difference is due either to the effect of polarization electric fields developed inside the epb or due to the latitudinal gradient of the neutral winds and epb velocity measurements since the epb velocities are estimated at a higher latitude corresponding to an apex altitude of 400 km than the wind estimates which derive from an apex altitude of 250 km

imaging spread f structures using gps observations at alcântara brazil during october 1994 a dual frequency gps receiver was operated in alc ntara brazil at the same site where the cornell university portable radar interferometer cupri was performing spread f measurements for an ongoing rocket campaign we present data for two nights during which several spread f plumes drifted through the field of view of cupri fluctuations in the total electron content tec measured with the gps receiver were correlated with those plumes we define a roughness measure from a specialized high frequency filter plots of roughness in a magnetic longitude versus time space show initially low activity followed by regions of dramatic localized onsets and a slower subsequent decline features in the roughness image are well correlated with plumes in the cupri backscatter power map

laser microprobe sulphur isotope analysis of arsenopyrite experimental calibration and application to the boliden au cu as massive sulphide deposit abstract metamorphic remobilization of arsenopyrite rich ores is a globally important process which can lead to significant concentrations of gold in order to understand this and related processes relations of sulphur isotopes can give a number of important clues to resolve such relations in detail we have successfully calibrated and applied a laser combustion system for in situ analysis of sulphur isotopic compositions of arsenopyrite experimental calibration of the laser fractionation factor 0 4 was obtained by using compositionally and isotopically homogeneous natural samples from ore deposits at boliden sweden and freiberg germany subsequent to detailed microscopic study the s isotope ratios of these samples were measured by conventional and laser combustion techniques the present application to different types of arsenopyrite in the palaeoproterozoic metamorphosed vhms ores of the boliden au cu as deposit skellefte district northern sweden shows that the sulphur isotope composition of arsenopyrite is essentially unmodified during medium grade metamorphic recrystallization and remobilization here massive arsenopyrite ore is crosscut by later veins that carry a complex quartz sulphosalt sulphide assemblage the latter ore type is markedly au rich compared to the host ore and thus of significant economic interest we find that both ore types exhibit very similar sulphur isotope compositions ca 2 to 3 v cdt which is similar to most massive sulphide deposits in the skellefte district thus the crosscutting au rich vein ore has inherited the sulphur isotope composition from sulphur liberated by metamorphic reactions affecting the massive ore and most likely also inherited the au through this mechanism the latter finding clearly has important implications both for the general discussion on and the prospecting for similar high grade au ores in this world class mining region

ionospheric conditions affecting the evolution of equatorial plasma depletions model studies have been carried out to specify the ionospheric conditions and electrodynamical processes required to describe the geometry of westward tilting and bifurcating equatorial plasma depletions inferred from airglow imaging measurements taken on ascension island in early 1981 the results indicate that if the westward tilts are to be associated with eastward plasma drifts that decrease with altitude above the f peak this shear must be set up by a zonal wind pattern of decreasing speed at increasing distances from the equator below the peak calculations of flux tube integrated pedersen conductivity including both e and f region contributions are in agreement with the simulations of zalesak et al 1982 that show bifurcated depletions to be associated with a mild gradient in the bottomside conductivity profile

disturbance dynamo effects over low latitude f region a study by network of vhf spaced receivers generation of equatorial spread f esf irregularities resulting from magnetic disturbance is known for past few decades however better prediction models for this phenomenon are still lacking magnetic storms also affects the f region plasma drifts in this work we examined variability in i occurrence of such freshly generated esf and ii low latitude f region zonal plasma drifts over indian longitude for this purpose simultaneous observations of amplitude scintillations on 251 mhz signal recorded by a network of spaced receivers located at low latitude stations are utilized observational stations are situated such that it longitudinally latitudinally covers an area of 5 6 13 here effect of disturbance dynamo dd electric field at low latitude f region and its variability are studied for three magnetic storms occurring in 2011 these magnetic storms are having nearly similar type characteristics except their start time we find that as time difference i e t between local sunset and start of magnetic activity decreases the dd effects seen at low latitude f region zonal irregularity drift around midnight becomes stronger for a given magnetic storm the dd effect on f region zonal irregularity drifts is found to be only marginally stronger at dip equator in comparison to off equatorial stations although effect of dd on f region zonal irregularity drifts are felt simultaneously generation of fresh esf is variable within a smaller longitudinal belt of 5 6 it is attributed to the presence of lsws at the bottomside of f region as initiation of esf is highly likely unlikely in the vicinity of crest trough of such lsws

comparison of nighttime zonal neutral winds and equatorial plasma bubble drift velocities over brazil 1 we present results from the first extended period of coincident observations of thermospheric zonal neutral winds and equatorial plasma bubble epb zonal drift velocities over northeastern brazil during the october to december months of 2009 and 2010 the epb zonal drift velocities are estimated utilizing images of the o i 630 0 nm emissions recorded by a wide angle imaging system at cajazeiras thermospheric neutral wind estimates are based upon common volume observations made by a bistatic fabry perot interferometer fpi experiment using fpis located at cajazeiras and cariri in brazil observing the doppler shift of the o i 630 0 nm emission the results illustrate a similar pattern of nighttime and night to night variations in the zonal neutral winds and epb zonal drift velocities in general the geomagnetic zonal neutral winds and the epb velocities show an excellent agreement illustrating that the f region dynamo is fully developed however in the early evening hours the epb zonal speed is slower than that of the background winds on several occasions we conclude that this indicates that during the bubble evolution period in the early evening the f region dynamo is not fully activated

geochronology isotopic chemistry and gold mineralization of the black slate hosted haoyaoerhudong gold deposit northern north china craton abstract the haoyaoerhudong gold deposit is the largest gold deposit in the north margin of the north china craton gold province and contains over 7 moz of gold at an average grade of 0 62 g t the deposit is hosted in the carbonaceous and pyritic slate phyllite and schist and is controlled by a tight syncline and shear zones the high grade orebodies contains abundant pyrite veins and pyrite quartz veins three stages of pyrite have been identified including the diagenetic disseminated pyrite pyrite veins caused by peak matamorphism and pyrite quartz veins forming during post peak metamorphism native gold has been observed in pyrite veins and pyrite quartz veins the 40ar 39ar plateau age of a biotite separate from a tails of boudinaged pyrite quartz veins is 260 1 2 9 ma combined with previously published 40ar 39ar mica age data and low closure temperature of mica these results suggest that pyrite veins and pyrite quartz veins were formed during the peak to post peak metamorphism during 285 260 ma respectively the lower limit of the formation age of sedimentary disseminated pyrites has constrained to 1670 1560 ma by the intruded mafic ultramafic dikes disseminated pyrite separates have 34s values ranging from 39 40 to 17 85 206pb 204pb of 19 144 21 892 207pb 204pb of 15 681 15 864 and 208pb 204pb of 37 502 38 925 suggesting they were formed from seawater sulfate and has experienced strong sulfur isotopic fractionation in contrast hydrothermal pyrites from pyrite veins and pyrite quartz veins have 34s values ranging from 6 8 to 16 47 206pb 204pb of 18 566 18 922 207pb 204pb of 15 645 15 684 and 208pb 204pb of 38 924 38 983 which may reflect dissolution reprecipitation of disseminated sulfides from the pre existing organic rich sediments the mineral paragenetic geometric and cross cutting relationships of pyrite veins and pyrite quartz veins at haoyaoerhudong suggest that gold was most likely introduced into pyrite accompanying sedimentation of the organic rich shales and then became enriched during diagenesis subsequently the hydrothermal fluids following metamorphism and shear zone activity make dissolution of the gold in the diagenetic pyrite and precipitated in the intersection of shear zone and tight syncline

hemispheric asymmetries in the longitudinal structure of the low latitude nighttime ionosphere 1 observations performed with the low resolution airglow and aurora spectrograph loraas which flew aboard the advanced research and global observation satellite argos show evidence of wave number four longitudinal variations in the nighttime equatorial anomaly during march 2001 and march 2002 loraas limb scans of o i 135 6 nm emission features are used to reconstruct electron density profiles from which maps of the monthly average peak f region electron densities and heights at 0230 lt are generated the longitudinal structure is nearly identical in both years the locations of the longitudinal maxima in the northern hemisphere match that of previous studies but the loraas data show a pronounced hemispheric asymmetry in the locations of the maxima in the southern hemisphere the loraas results are compared with the international reference ionosphere iri 90 to show the derived electron densities and peak altitudes are consistent with the climatology but that the observed longitudinal structure is not a physics based model of the ionosphere sami is another model of the ionosphere sami2 is used to study the role of thermospheric neutral winds in generating the observed longitudinal pattern it is demonstrated that longitudinally varying f region winds along with effects due to the offset of the geographic and magnetic equator are the plausible cause of the hemispheric asymmetry together the effects enhance the observed wave number four pattern in the nighttime ionosphere

seasonal variations in the equatorial thermospheric wind measured at arequipa peru studies have been carried out at arequipa peru of the seasonal variations in the thermospheric winds at moderate solar flux levels and low geomagnetic activity fabry perot interferometer measurements of the doppler shifts in the 630 0 nm nightglow emission line from march to august 1983 and from april to october 1988 have yielded monthly average meridional winds that are nearly zero 50 m s and possibly fluctuating in direction through much of the night but develop a southward flow at 50 100 m s in the early and the late night from may onward the average zonal winds are eastward throughout the night reaching peak velocities before local midnight and then decreasing the peak velocities increase to a maximum around the june solstice the winds are generally stronger in 1988 than in 1983 even though the solar euv fluxes are comparable for both years comparison of the present results with earlier satellite measurements as embodied in the horizontal wind model of hedin et al reveals generally satisfactory agreement at the equinox and june solstice except for the june 1988 period killeen et al s vector spherical harmonic form of the ncar thermospheric general circulation model calculated for similar solar flux levels yields meridional and zonal wind variations which exhibit the same temporal behaviors but generally smaller values than the present measurements the present wind patterns are also compared with those measured during the same years at arecibo puerto rico one finds oppositely directed meridional flows and similar eastward zonal flows at the two locations as expected from a consideration of solar euv heating as the principal driving force

displacements on late cenozoic strike slip faults of the central mojave desert california field studies demonstrate that displacements on northwest striking wrench faults of the central mojave desert are too small to support hypotheses suggesting large interior translations and associated rotation of the province during late cenozoic time the margin of an early miocene structural belt provides the marker with which to establish lateral displacement on individual faults displacement values for faults are as follows lenwood fault 1 5 3 km camp rock fault 1 6 4 0 km calico fault 8 2 km and rodman pisgah faults 6 4 14 4 km cumulative displacement on all the major northwest striking faults of the mojave desert is about 26 7 38 4 km most if not all regionally distributed right shear presumably related to pacific north american plate interaction developed in the central mojave desert after 20 m y b p right shear was preceded by significant amounts of kinematically unrelated northeast southwest crustal extension

measurements of coseismic deformation in southern california 1972 1982 since 1972 a number of static strain changes have been measured at pinon flat observatory southern california as a result of regional faulting as recorded by a collection of long baselength strainmeters and tiltmeters these signals are in good quantitative agreement with the deformation calculated for a dislocation in an elastic half space in contrast colocated short baselength sensors are found to produce spurious results whose size is much larger than expected theoretically and well correlated with peak site acceleration calculations show that the root mean square rms of the coseismic signals from several different instruments at one site or from several sites at known hypocentral distances provide a good estimate of the seismic moment a result confirmed by the observations static moment estimates for the four largest events in this period are imperial valley 1979 m0 9 0 1018nm mexicali valley 1980 m0 6 1 1018nm westmorland 1981 m0 5 3 1017nm and brawley 1979 m0 2 3 1017 nm these estimated moments generally exceed those determined seismically by about 25 which is as expected since they include some postseismic deformation results from the mexicali valley earthquake are particularly interesting indicating an average fault strike approximately 9 different from the historic fault trace several small to moderate earthquakes ml 3 7 5 2 were also well enough recorded to estimate source parameters for the only other detectable events in the period 1972 1982 a total of three others for which the strain change erms was greater than 0 4 ne high accelerations caused most of the instruments at the site to malfunction no precursory signals were evident for any of the earthquakes recorded at this site

the gold content of volcanogenic massive sulfide deposits volcanogenic massive sulfide deposits contain variable amounts of gold both in terms of average grade and total gold content with some vms deposits hosting world class gold mines with more than 100 t au previous studies have identified gold rich vms as having an average gold grade expressed in g t exceeding the total abundance of base metals expressed in wt however statistically meaningful criteria for the identification of truly anomalous deposits have not been established this paper presents a more extensive analysis of gold grades and tonnages of 513 vms deposits worldwide revealing a number of important features in the distribution of the data a large proportion of deposits are characterized by a relatively low gold grade 2 g t with a gradual decrease in frequency towards maximum gold grades defining a log normal distribution in the analysis presented in this paper the geometric mean and geometric standard deviation appear to be the simplest metric for identifying subclasses of vms deposits based on gold grade especially when comparing deposits within individual belts and districts the geometric mean gold grade of 513 vms deposits worldwide is 0 76 g t the geometric standard deviation is 2 70 g t au in this analysis deposits with more than 3 46 g t au geometric mean plus one geometric standard deviation are considered auriferous the geometric mean gold content is 4 7 t au with a geometric standard deviation of 26 3 t au deposits containing 31 t au or more geometric mean plus one geometric standard deviation are also considered to be anomalous in terms of gold content irrespective of the gold grade deposits with more than 3 46 g t au and 31 t au are considered gold rich vms a large proportion of the total gold hosted in vms worldwide is found in a relatively small number of such deposits the identification of these truly anomalous systems helps shed light on the geological parameters that control unusual enrichment of gold in vms at the district scale the gold rich deposits occupy a stratigraphic position and volcanic setting that commonly differs from other deposits of the district possibly due to a step change in the geodynamic and magmatic evolution of local volcanic complexes the gold rich vms are commonly associated with transitional to calc alkaline intermediate to felsic volcanic rocks which may reflect a particularly fertile geodynamic setting and or timing e g early arc rifting or rifting front at the deposit scale uncommon alteration assemblages e g advanced argillic aluminous strongly siliceous or potassium feldspar alteration and trace element signatures may be recognized e g au ag as sb bi hg te suggesting a direct magmatic input in some systems

mineralogy of the sulphide deposits at sulitjelma northern norway abstract the pyritic vms deposits at sulitjelma northern norway have been regionally metamorphosed at amphibolite facies during the caledonide orogen the deposits contain a wide diversity of sulphide sulphosalt and related minerals which are systematically discussed with reference to their occurrence paragenesis and mineral chemistry most of these minerals are however rare to absent within the massive deposits which are dominantly composed of pyrite with subordinate chalcopyrite sphalerite and pyrrhotite galena arsenopyrite cubanite molybdenite stannite and tetrahedrite occur in minor amounts syn metamorphic mobilisation has however resulted in the redistribution of a range of elements including cu pb sb as ni and au these elements have been reconcentrated into mobilised segregations where they have crystallised under retrograde conditions into a range of discrete phases ore mobilisation which took place along tectonically controlled pathways is however of a highly localised nature with a considerable range in mineral textures and parageneses observed in different samples typical associations within these mobilisates include a range of cu pb sb and cu pb as sulphosalts including bournonite meneghinite seligmannite and jordanite breithauptite nisbite costibite arsenopyrite and gudmundite co existing galena is characterised by elevated concentrations of ag bi and se argentian tetrahedrite 9 17 wt ag the chief ag carrier in the deposits as well as other ag bearing phases including pyrargyrite hessite and empressite are strongly enriched in the mobilisates gold as electrum 50 75 wt au and more rarely as aurostibite is also relatively enriched in the mobilisate samples over those from more massive parts of the deposits a further range of minerals including native antimony native arsenic allargentum dyscrasite argentite mckinstryite jalpaite and native silver occur as low temperature breakdown products of earlier formed minerals preserved textures do not contradict a model involving more than a one phase of mobilisation during the metamorphic evolution

gps phase fluctuations in the equatorial region during the miseta 1994 campaign in this paper we present the first coordinated use of global positioning system gps multisite and multisatellite observations with ground based radar and optical diagnostics to investigate equatorial irregularity patterns thirty second samples of total electron content tec obtained from gps phase differences between 1 2 and 1 6 ghz signals are used to study phase fluctuations at several stations comparisons were made with various types of ground measurements during the multi instrument studies of the equatorial thermosphere aeronomy miseta period depletions of 6300a airglow emission from arequipa peru correlated with phase fluctuations recorded at the same site phase fluctuations at arequipa occurred at the times when the jicamarca radar backscatter returns from plumes were noted but were also seen on other nights when there were no radar returns from plumes levels of phase fluctuations noted at arequipa varied considerably on nights when only thin layers of irregularities were observed by the jicamarca radar differences of ionospheric conditions between the two sites separated by only 5 5 geographic longitude may account for the different behavior patterns of irregularities noted similar differences in the general behavior pattern of phase fluctuations were shown when data from arequipa and fortaleza brazil were compared these stations 33 apart but at the same dip latitude had different patterns for some days during a magnetic storm a very high altitude plume was observed by the radar and by phase fluctuations noted at santiago at 18 dip latitude this correlation of high plume altitude during some periods of magnetic activity was validated by additional examples of phase fluctuations from three other magnetic storms in the solar minimum years of 1994 and 1995

lateral p velocity gradients near major strike slip faults in california the p wave velocity in shallow crystalline rock decreases systematically from a normal value of about 5 5 kilometers per second 20 kilometers or more from the garlock and san andreas faults to less than 3 kilometers per second at distances of less than 2 kilometers from these faults this lateral velocity gradient closely resembles the shear stress profile it is proposed that the velocity gradient results from increased fracturing nearer these major strike slip faults and that this fracturing dominates the response of the shallow crust to tectonic stress

a method for determining the drift velocity of plasma depletions in the equatorial ionosphere using far ultraviolet spacecraft observations received 7 february 2007 revised 12 june 2007 accepted 25 july 2007 published 27 november 2007 1 the far ultraviolet imager image fuv on board the nasa image satellite has been used to observe plasma depletions in the nightside equatorial ionosphere observations from periods around spacecraft apogee during which equatorial regions are visible for several hours have allowed the velocity of these plasma depletions to be determined a new method for determining the velocity of these depletions using an image analysis technique tracking of airglow depletions toad has been developed toad allows the objective identification and tracking of depletions the automation of this process has also allowed for the tracking of a greater number of depletions than previously achieved without requiring any human input which shows that toad is suitable for use with large data sets and for future routine monitoring of the ionosphere from space furthermore this automation allows the drift velocities of each bubble to be determined as a function of magnetic latitude which will give us the capability of retrieving geophysically important parameters such as the electric field which are believed to vary rapidly with magnetic latitude

gold enrichment in hydrothermal sulfides from the okinawa trough an in situ la icp ms study abstract we assess the distribution of gold and investigate the physicochemical controls on gold enrichment in the okinawa trough an immature back arc basin we conducted a systematic study of gold and other trace element concentrations using in situ laser ablation inductively coupled plasma mass spectrometry la icp ms for various minerals in hydrothermal sulfide samples from the iheya north knoll and the yonaguni knoll iv hydrothermal fields orpiment colloform pyrite and colloform sphalerite are relatively enriched in au mean contents of 30 60 17 48 and 8 68 ppm respectively compared with gold poor massive chalcopyrite sphalerite and pyrite based on gold budget estimation colloform pyrite is the most important au host followed by colloform sphalerite and orpiment with these three minerals containing the majority of gold in hydrothermal sulfides gold occurs as invisible in host minerals as lattice bound and submicron inclusions in colloform pyrite as homogeneously distributed lattice bound or nano inclusions in colloform sphalerite and generally as lattice bound in orpiment and tetrahedrite three sets of gold host minerals are identified with distinct ore formation temperatures colloform sulfides and orpiment incorporate the majority of gold at low temperatures whereas tetrahedrite and massive sulfides incorporate only minor or trace amounts of gold at medium and high temperatures respectively our results show that gold enrichment in si ba fe rich hydrothermal sulfides at low temperatures is a significant contributor to gold enrichment in hydrothermal sulfide deposits in the okinawa trough along with the more common zn and cu rich hydrothermal sulfides thermodynamic modeling calculations suggest that the near neutral ph of hydrothermal fluids and the dominant transport species namely au hs complexes rather than au cl complexes are likely responsible for gold enrichment in low temperature mineral assemblages in hydrothermal precipitates from the okinawa trough

implications of pyrite geochemistry for gold mineralisation and remobilisation in the jiaodong gold district northeast china abstract the jiaodong gold district of eastern china the largest gold producing district in china is located on the eastern margin of the north china craton it consists of three mineralisation belts the western zhao ye belt the middle qixia belt and the eastern muping rushan muru belt over 85 of mineralisation is hosted in the zhao ye belt which is bordered by the mantle tapping tan lu fault zone pyrite crystals from three deposits in the zhao ye belt and three deposits in the muru belt were studied using a combination of optical petrography bulk pyrite geochemistry and in situ laser ablation icp ms results show that although mineralisation is broadly similar between the two belts there are significant differences in ore and gangue mineral textures pyrite geochemistry and style of gold mineralisation texturally pyrite grains from the zhao ye belt are generally cubic and do not exhibit zoning in contrast muru pyrite grains are more often pyritohedral commonly exhibit well defined concentric zoning and display textures in ore and gangue minerals indicative of open space growth bulk pyrite geochemistry suggests a distinct enrichment in pb bi au ag and te in the zhao ye belt whereas the muru belt pyrite is significantly enriched in as cu and co in situ pyrite geochemistry indicates that au and as are variably correlated in the zhao ye belt typically only exhibiting correlation at low au concentrations most gold occurs as visible electrum along pyrite fractures and grain boundaries with a minor generation of invisible gold formed through as facilitated uptake into pyrite in the muru belt au and as have a strong correlation and there is limited occurrence of gold particles indicating that most gold in the muru belt is invisible gold contained in the crystal structure of as rich pyrite the differences in style of gold mineralisation between the belts indicates an inherent difference in timing of gold introduction in the zhao ye belt the visible electrum accounting for most of the gold endowment is formed post pyrite whereas the invisible gold in the zhao ye and muru belts is formed syn pyrite the heterogeneity in gold distribution in the jiaodong district is attributed to melting of metallogenically fertile archean crust at the base of the well endowed zhao ye belt and the lack of a similarly fertile source region beneath the muru belt

geomagnetic conjugate observations of equatorial airglow depletions 1 we report for the first time large scale equatorial f region airglow depletions extending to low midlatitudes in both hemispheres the observational sites were located at low midlatitude geomagnetic conjugate points clear depletions of 630 0 nm airglow intensity due to equatorial plasma bubbles were simultaneously observed with two all sky imagers at sata japan magnetic latitude 24 n and its geomagnetic conjugate point darwin australia magnetic latitude 22 s on the night of november 12 2001 airglow depletion regions with east west scale sizes of 40 100 km extend poleward the maximum apex altitude of the plasma bubbles is about 1 700 km over the geomagnetic equator the depletions move eastward at about 100 m s without changing their structures the darwin depletion structures mapped onto the northern hemisphere along the geomagnetic field coincide closely with structures in the sata images even for the 40 km structure these observations indicate that plasma depletions in the equatorial ionosphere elongate along the geomagnetic field lines

equatorial ionospheric zonal drift by monitoring local gps reference networks 1 the propagation of electromagnetic waves through the turbulent ionosphere produces scintillations through diffraction and understanding the physical nature of scintillations is important for engineers and technologists as well as for scientists in recent years the establishment of the global positioning system gps provided a new technique that can be used to study ionospheric scintillations the usual way of doing that is the deployment of gps receivers closely spaced in east west magnetic direction and then estimating the zonal drift velocities based on the signal power observations one of the weaknesses of this method is that high rate sampling such as 20 hz is required for close spaced stations and generally no such data are available for studying ionospheric scintillation in the past years in this research work a scintillation monitoring method based on slant tec stec observations of local gps continuously operating reference station cors network is proposed first the past research works on the equatorial ionospheric drift velocities are summarized then by comparing the scintillation pattern of the signal power and stec observations of california local gps reference network we find that the stec is a good choice for estimating the ionospheric zonal drift velocity then it is illustrated how to calculate the ionospheric scintillation velocity based on stec finally the proposed method is applied to hong kong gps reference network and several cases of the calculated ionospheric zonal velocities are given

morphogenesis and composition of native gold in the chelopech volcanic hosted au cu epithermal deposit srednogorie zone bulgaria native gold is an important economic component of the complex ores of the chelopech high sulphidation volcanic hosted epithermal au cu deposit bulgaria the ore consists of pyrite chalcedonic silica chalcopyrite enargite luzonite tennantite bornite sphalerite galena and numerous other sulphide arsenide and telluride minerals gold is paragenetically associated with most of the arsenic bearing and base metal sulphide minerals the chemistry and morphology of gold grains which were separated from disintegrated ores were systematically studied by scanning electron microscopy sem and electron probe microanalysis epma the gold is characterised by high fineness 950 and a mean composition of 94 1 wt au 5 27 wt ag 0 53 wt cu and 0 10 wt fe gold grains show variable morphology subhedral flakes irregular grains euhedral isometric crystals elongated rods wires and fine fibrous crystals 111 twins fine dendrite like formations spongy gold and polycrystalline grains the densest faces 111 are morphologically the most important morphometric measurements show a pronounced flatness of the gold particles the mean value of the corey factor a measure of flatness from 0 to 1 spherical is 0 14 and the mean length to width value is 1 64 it is suggested that crystal growth of gold took place in small voids fine cracks and intergranular space the geometry of which have controlled the highly variable grain shapes no direct correlation between the size and composition of gold grains exists but larger grains tend to be of higher fineness

trace element distributions in cu pb sb sulfosalts from the gutaishan au sb deposit south china implications for formation of high fineness native gold

understanding spaced receiver zonal velocity estimation 1 spaced receiver analysis can be used to estimate the ionospheric zonal irregularity velocity this involves first measuring the scintillation pattern velocity and then estimating the zonal irregularity velocity a straightforward technique involving projection planes has been used to derive a relationship between the satellite position and velocity the irregularities position and velocity and the scintillation pattern velocity this relationship relies on the alignment of the irregularities along the field lines but is independent of the irregularity spectrum when simplified this relationship can be used to estimate the zonal irregularity velocity using either geostationary satellites or global positioning system gps satellites this estimation is straightforward but must be performed in a careful manner an example of zonal irregularity velocity estimation using gps satellites is presented the average zonal irregularity velocity is estimated over a 3 week period in march 2002 at sao luis brazil 3 59 dip angle this hourly average velocity has been compared with the climatological radar observations from jicamarca observatory the spaced receiver zonal velocity agrees well within 8 m s with the radar s observations during postsunset hours

a comparison of high au massive sulfide ores hosted in ophiolite complexes of the balkan peninsula with modern analogues genetic significance abstract ophiolites of the balkan peninsula of upper jurassic to lower cretaceous age extend through the mirdita zone albania to the pindos and othrys complexes southern greece and host massive sulfide deposits of cu zn pb type the deposits in albania are hosted in intermediate to felsic dominated volcanic successions of considerable thickness these deposits are associated with ophiolites that were formed during the initial stages of an intra oceanic westward dipping subduction zone arc fore arc back arc setting and most closely resemble polymetallic sulfide deposits associated with felsic volcanic rocks at the modern seafloor the massive sulfide ores are comprised of pyrite chalcopyrite and lesser amounts of sphalerite and are characterized by an increasing content of au ag as se sb mo and hg from the othrys to pindos and mirdita munella ophiolites in addition the concentrations of these elements in both massive sulfide ores and fe cu ni co type ores are higher in the pindos compared to those in the othrys complex sulfide mineralization associated with these complexes differs from the majority of cyprus type deposits in terms of a host rock type b mineralogical composition i e the presence of tennantite tetrahedrite series minerals in the mirdita sulfide ores and the selenide clausthalite hosted exclusively within later stage chalcopyrite and sphalerite intergrowths in the pindos ores and c their enrichment in au gold in both pindos and mirdita ores occurs as submicroscopic gold including solid solution gold colloidal gold and surface bound gold in arsenian pyrite chalcopyrite and bornite grains and rarely as fine grained electrum the increasing au content up to 15 1 ppm with decreasing crystal size in fine intergrowths between pyrite and sphalerite may be related to remobilization and re deposition however submicroscopic gold in coarse grained pyrite of the main mineralization stage mean concentrations up to 1 01 ppm in the pindos ores and 0 22 ppm in the mirdita ones may be co precipitated into the structure of arsenian pyrite reflecting the direct involvement of magmatic volatiles to the ore forming hydrothermal system rather than recrystallization effects and in turn the precious metal endowment in the hydrothermal systems the mirdita and pindos massive sulfide ores are comparable to some modern seafloor deposits in terms of their association with andesitic pillow lavas and intermediate to felsic volcanic rocks and their bulk composition and mineralogy

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

long term fault creep observations in central california the u s geological survey usgs has been monitoring aseismic fault slip in central california for more than 10 years as part of an earthquake prediction experiment since 1968 the usgs creep network has grown from one creep meter at the cienega winery south of hollister to a 44 station network that stretches from hayward east of san francisco bay to palmdale in southern california in general the long term slip pattern is most variable on sections of the faults where several magnitude 4 and larger earthquakes occurred during the recording period e g calaveras fault near hollister and san andreas fault between san juan bautista and bear valley these fault sections are the most difficult to characterize with a single long term slip rate in contrast sections of the faults that are seismically relatively quiet e g san andreas fault between bear valley and parkfield produce the steadiest creep records and are easiest to fit with a single long term slip rate appendix is available with entire article on microfiche order from the american geophysical union 2000 florida avenue n w washington d c 20009 document j82 004 1 00 payment must accompany order

metamorphosed pb zn ag ores of the keketale vms deposit nw china evidence from ore textures fluid inclusions geochronology and pyrite compositions abstract the keketale pb zn deposit is located in the devonian volcanic sedimentary maizi basin of the altay orogenic belt the mineralization at keketale is hosted in marbles and deformed volcanic tuffs and biotite garnet chlorite schists folded into a series of overturned synclines formed in multiple deformation events keketale contains economic amounts of pb 0 89 mt 1 51 wt zn 1 94 mt 3 16 wt and ag 650 t 40 g t detailed petrographic studies have defined two main generations of sulfide development the banded pyrite of the early stage a is commonly stratiform with minor galena sphalerite and chalcopyrite stage b is characterized by a large amount of polymetallic sulfides including pyrrhotite chalcopyrite sphalerite and galena with minor pyrite hosted in quartz veins three types of fluid inclusions fis including mixed carbonic aqueous c type pure carbonic pc type and aqueous w type have been recognized in quartz of stage b the c type fis have homogenization temperatures of 150 326 c and salinities of 0 2 16 6 wt nacl equivalent the pc type fis are dominated by co2 with minor ch4 and n2 and have initial ice melting temperatures of 57 5 to 56 7 c co2 homogenization temperatures of 11 14 1 c the w type primary fis were completely homogenized at temperatures of 124 359 c with salinities of 5 0 14 6 wt nacl equivalent such co2 rich fluid inclusions are consistent with those discovered in orogenic type deposits in the altay area and elsewhere muscovite separates from the polymetallic quartz veinlets of stage b yield a well defined 40ar 39ar isotopic plateau age of 259 33 2 56 ma with an isochron age of 259 62 2 65 ma this age is coeval with the closure of the paleo asia ocean and reactivation of the ertix fault system la icp ms analyses of two generations of pyrite indicate that the banded pyrite of stage a is relatively depleted in metallic elements and contains low contents of cu 0 39 ppm ag 0 20 ppm au below the detection limits pb 17 43 ppm and zn 14 38 ppm whereas the pyrite in quartz polymetallic sulfide veinlets of the stage b is relatively rich in metallic elements e g cu 2 56 ppm ag 3 07 ppm au 0 01 ppm pb 1047 ppm and zn 1136 ppm the trace amounts of cu pb zn au and ag are interpreted to have been initially locked in the lattice of type a pyrite and then liberated and precipitated as micromineral inclusions with type b pyrite during subsequent metamorphism and deformation two key factors are considered vital to the formation of economic ores of the keketale pb zn deposit namely the original devonian banded pyrite formed in a vms system and subsequent permian deformation and metamorphic processes that liberated cu pb zn au and ag from the lattice of type a pyrite to form galena sphalerite and chalcopyrite with minor muscovite in quartz veinlets the model provides a new interpretation of vms pb zn deposit occurring in back arc basin environments followed by collision and new insights into the unique regional fe cu pb zn au mineralization in the altay orogenic belt

characteristics of gold mineralization in volcanogenic massive sulphide deposits of the notre dame bay area central newfoundland a reconnaissance study of 19 volcanogenic massive sulphide deposits in the notre dame bay area indicates au concentrations of up to 30 ppm betts cove and elevated gold contents 1 ppm au have been found in samples from 10 additional past producers and developed prospects systematic trends in the occurrence of gold are observed in two principal sulphide assemblages polymetallic pyrite sphalerite chalcopyrite galena arsenopyrite assemblages type i and pyrite chalcopyrite sphalerite pyrrhotite assemblages type ii type i assemblages occur in deposits with dominantly felsic host rocks whereas type ii assemblages are restricted to deposits in mafic dominated ophiolite sequences free gold grains were observed in samples from eight different deposits in both type i and type ii assemblages x ray emission spectra and electron microprobe analyses of the gold indicate that most grains are electrum although a au bearing telluride occurs at point leamington ion microprobe analyses indicate that

distribution and controls on silver mineralization in the hackett river main zone nunavut canada an ag and pb enriched archean volcanogenic massive sulfide deposit the 2 67 ga hackett river volcanogenic massive sulfide vms deposits located in the northeastern slave province nunavut canada are among the largest undeveloped massive sulfide resources in canada and are silver rich compared to other such deposits of similar age with ag grades up to 3 000 g t the deposits are hosted by the ignerit formation of the felsic to intermediate calc alkaline hackett river group metavolcanic rocks that are part of the province wide supracrustal yellowknife supergroup one of the most economically significant of the hackett river deposits is the hackett river main zone main zone which consists of two parts a stratigraphically lower chalcopyrite rich stringer zone and an upper massive to semimassive polymetallic sulfide lens the mineralization is subdivided into five types based on mineralogy textures and approximate stratigraphic position 1 disseminated footwall sulfides 2 copper rich stringer sulfides 3 pyrite poor sphalerite pyrrhotite chalcopyrite mineralization at the top of the stringer zone 4 mineralization in calc silicate altered calcareous tuff units and 5 sphalerite pyrite massive sulfide in type 1 mineralization disseminated pyrite pyrrhotite and sphalerite contain negligible ag and in type 2 bi ag pb sulfides ag bi se enriched galena and chalcopyrite are the dominant ag hosts within type 3 ag rich tetrahedrite freibergite and galena are the main ag hosts in type 4 ag is hosted in disseminated electrum and freibergite and within type 5 mineralization freibergite hosts 99 of the ag overall within the main zone ag rich freibergite contains 79 4 of the ag whereas chalcopyrite hosts 6 3 and galena contains 1 8 trace minerals such as electrum host the remainder of the ag and these have a limited spatial distribution zone refining is the most important control on the distribution of ag within the main zone and the principal controls on ag residence are mineralizing fluid temperature deposit scale relative redox conditions sulfidation state location of the mineralization relative to the hydrothermal conduit and the ratio of bi to sb in the mineralizing fluid available for coupled substitution within the freibergite and chalcopyrite ag directly substitutes for cu and replaces pb in galena by coupled substitution with bi and to a lesser extent sb lower temperatures ca 250 c the most reducing conditions favored incorporation in ag bi rich galena plus se and bi bearing sulfides or ag rich chalcopyrite under lesser reducing conditions

oxygen boron chromium and niobium enrichment in native au and ag grains a case study from the linglong gold deposit jiaodong eastern china quartz vein type gold mineralization in the linglong deposit constitutes one of the important sources of gold in china here we report the first finding of anomalous enrichment of boron b oxygen o chromium cr and niobium nb in native gold and ag te grains from the linglong deposit the oxygen content of gold and silver grains ranges up to 75 83 at boron up to 97 85 at chromium up to 26 23 at and tellurium up to 33 4 at the au precipitation is mainly linked to pyrite precipitation under reducing conditions the hfse enrichment including chromium cr and niobium nb in the gold and silver grains indicate that the ore forming fluids were derived from high temperature magmas sourced from depth the enrichment of low temperature te in the native gold and silver grains combined with the typical features of fluid boiling as inferred from fluid inclusion studies indicate that the ore fluids derived from depth upwelled rapidly and metal precipitation occurred through decompression at shallower levels our results suggest good prospect for gold and silver at depth in linglong

global positioning system measurements of the ionospheric zonal apparent velocity at cachoeira paulista in brazil ionospheric irregularities and their zonal apparent drift were studied using global positioning system gps measurements at cachoeira paulista 22 41 s 45 00 w 26 dip angle in brazil during november 6 19 1998 radio scintillations at the gps l1 frequency 1 575 ghz were monitored using four gps receivers spaced geomagnetically east west and north south total electron content tec was measured through the ionospheric advance of the gps l1 and l2 1 227 ghz phases strong amplitude scintillations coincided with tec fluctuations associated with spread f bubbles elongated along the magnetic field movement of the presnel scale 400 m ionospheric irregularity layers caused the scintillation to drift and their zonal apparent drift velocities were measured using a cross correlation technique our measurements show that the apparent eastward velocity varies from 200 m s to 150 m s at 2000 lt and then it decreases to 100 50 m s at midnight on a magnetically disturbed day reversal of the zonal apparent drift was observed just after midnight and the apparent westward velocities observed at early in the morning showed large variations with location in the sky from the receivers spaced in the geomagnetic north south direction we measured near zero time shifts from which we conclude that the correlation length of several hundred meter scale irregularities is much larger than 70 m separation between the north and south receivers

simultaneous global positioning system and radar observations of equatorial spread f at kwajalein gps satellites broadcast at two frequencies ll of 1575 42 mhz and l2 of 1227 6 mhz the dispersive property of the ionosphere is frequently used to correct positional measurements for ionospheric effects independent measurements at the two frequencies can also be combined to form a relative ionospheric delay and a measure of the total electron content tec which is uncertain by an additive constant in a previous paper musman et al 1990 estimates of this offset were utilized in constructing models of the time history of the equivalent zenith delay at westford massachusetts an ionospheric model composed of uniform shells whose electron density changes slowly in a typical diurnal pattern would produce relative ionospheric delays with a simple u shaped or j shaped curve most of the change in delay would be a result of changes in geometry between the observer and the satellite departures from a simple pattern are indicative of ionospheric disturbances and the influence of the protonosphere from gps data alone it is ambiguous whether these disturbances are due to spatial structures temporal changes or some combination of the two equatorial spread f esf refers to a variety of equatorial ionospheric disturbances some of which are associated with rising plasma plumes having low electron density and a high degree of turbulence this phenomenon occurs primarily between local sunset and local midnight at sites within about 15 of the magnetic equator in some seasons disturbances can occur during two out of three evenings while at other times it can be much quieter gps observations at kwajalein 9 n latitude reported here for august 14 1990 show severe ionospheric disruption two independent and simultaneous sets of radar observations confirm the presence of esf and reveal quite a bit about the spatial and temporal conditions which affect the system gps observations on august 15 1990 when no esf was present are much quieter we find that tens of minute variations in the tec correspond to the motion of large scale features across the gps field of view more severe gps effects are seen to be collocated with turbulent low density plumes which rise rapidly to high altitudes and drift west to east across the gps line of sight severe disruption can occur in moderately sophisticated gps systems during such events at least near solar maximum

antithetic behaviour of gold in the volcanogenic massive sulphide deposits of the iberian pyrite belt detailed mineralogical and geochemical studies of the volcanogenic sulphide mineralization in the spanish part of the iberian pyrite belt ipb define two geochemical mineralogical and spatial gold associations 1 the tharsis sotiel migollas type in which the gold is enriched with co bi in the stockworks and interaction zones at the base of the massive sulphide mound and 2 the rio tinto aznalcollar la zarza type in which the gold is enriched in facies with a polymetallic zn ag as tl hg signature in a distal position or blocked beneath the massive sulphides the first type is localized within a domain covering the southern half of the belt which is characterized by an abundance of sedimentary facies the paragenesis shows that the gold association formed at high temperature 300 c during the initial phases of massive sulphide genesis the gold which occurs in patches of very auriferous electrum au 75 wt was transported by chloride complexes the second type is found in the northern domain of the belt where volcanic facies are predominant the paragenesis shows that the gold association formed at lower temperature 280 c late in the massive sulphide genesis this gold was transported by bisulphide complexes au hs 2 and is contained in ag and hg rich electrum up to 61 0 and 30 5 wt respectively and or auriferous arsenopyrite mean of 280 ppm au two mineral expressions that are able to coexist it would appear that sulphur activity and oxygen fugacity were important factors in controlling the distribution of gold between the two host minerals and also in determining the ag content of the electrum this antithetic behaviour of the gold in the ipb reflects differences in the gold mineralizing fluids that may be due to the geologic environment i e either dominantly sedimentary and acting as a mechanical barrier for gold bearing fluids or dominantly volcanic and more open to seawater circulation the fact that possible complications can occur during massive sulphide genesis in response to the source and evolution of the fluids raises the question of whether one or two gold influxes are involved for example the two gold associations could derive from a single gold influx with remobilization and redistribution of the gold from the early co bi facies giving rise to the later gold paragenesis of the zn ag as tl hg facies this would not have occurred or would have been limited at the tharsis sotiel migollas type orebodies alternatively the two gold associations could reflect two separate evolutionary processes distinguished by the gold appearing either early or late in the hydrothermal fluids knowing the gold association of a massive sulphide deposit is an advantage when exploring for potential host facies

longitudinal responses of the equatorial low latitude ionosphere over the oceanic regions to geomagnetic storms of may and september 2017 this study presents the longitudinal dependence of responses of the equatorial low latitude ionosphere over the oceanic regions to geomagnetic storms of 28th may and 8th september 2017 we investigated the interplanetary origins of the storms total electron content tec data were obtained from global navigation satellite system stations located around the oceanic areas in the equatorial low latitude regions the rate of change of tec index roti was used as a proxy for ionospheric irregularities over the study locations further variations of the horizontal component of the earth s magnetic fields obtained from ground based magnetometers were studied we used ionospheric disturbance currents polar cap and auroral electrojet indices to monitor the storm time electric fields the may 2017 storm was driven by sheath and magnetic cloud fields while the september 2017 storm was driven by sheath fields we observed a comparative dominance of tec intensities over the oceans than over the landlocked areas empirically our results validated a theoretical suggestion of the existence of a dynamic ocean ionosphere coupling made by godin et al 2015 prompt penetration electric fields ppef was observed to be a key factor that controls tec responses to storms ppefs caused tec enhancements mainly over the pacific ocean longitudes during the may 2017 storm and enhanced tec over the atlantic ocean and the pacific oceans longitudes during the september 2017 storm these ppefs triggered irregularities over the pacific

ionospheric zonal velocities at conjugate points over brazil during the copex campaign experimental observations and theoretical validations 1 we analyze in detail the zonal velocities of large scale ionospheric plasma depletions over two conjugate stations inferred from oi 630 nm airglow all sky images obtained during the conjugate point equatorial experiment copex campaign carried out in brazil between october and november 2002 the conjugate stations were boa vista bv geogr 2 8n 60 7w dip angle 22 0 n and campo grande cg geogr 20 5s 54 7w dip angle 22 32 s over campo grande the zonal velocities were measured also by a system of spaced gps scintillation receivers the airglow zonal velocities at the conjugate sites were seen to agree very closely except for a slightly increased velocity over cg which we attribute to the presence of the geomagnetic anomaly the results show a high degree of alignment of the bubbles along the geomagnetic field lines during the bubble development phase and as the bubbles travel eastward thereby suggesting that the neutral zonal wind effect in the zonal plasma motion is an integrated effect along the flux tube the zonal velocities obtained from the gps technique were always larger than those calculated by the airglow technique which permitted observation of zonal plasma velocity shear between the altitudes of the airglow emitting layer and of the gps scintillation theoretical ambient plasma zonal velocities calculated using the formulations by haerendel et al 1992 and eccles 1998 are compared with the experimental results our results also reveal some degree of dependence of the zonal velocities on the solar flux f10 7 and magnetic kp indices during the copex period

first observations of sbas waas scintillations using collocated scintillation measurements and all sky images to study equatorial plasma bubbles 1 the first observations of amplitude scintillations on a space based augmentation system sbas satellite signal are presented the scintillations occurred on the signal transmitted by a wide area augmentation satellite waas on 8 9 september 2004 from 2250 0045 lt the gps receiver that measured the scintillations is located on haleakala hawaii geomagnetic 21 3 n 271 4 e with a maximum s4 0 35 corresponding to a peak to peak snr variation of 8 db the scintillations are relatively weak which is to be expected for a site poleward of the equatorial anomaly during declining solar conditions using a collocated all sky imager features of the irregularity structuring in the equatorial plasma bubbles are resolved the satellite signals scintillate when the ray path intersects the three main bubbles the scintillation intensity tends to peak near the walls and decreases slightly in the interior of the bubbles in this case the bubbles leading east walls contain smaller scale size irregularities than the trailing west walls

the prereversal enhancement of the zonal electric field in the equatorial ionosphere the electric fields in the ionospheric e and f regions near the magnetic equator often show a strong eastward enhancement shortly after sunset and before the eastward normally daytime field reverses to westward several theoretical models of the low latitude fields suggest that this enhancement is caused mainly or entirely by f region winds the f region dynamo but some authors have suggested that it could be produced solely by e region tidal winds we give here additional calculations and arguments in support of the f region source the enhancement of the eastward field for an eastward f region wind turns out to be a simple direct consequence of the fact that after sunset the ionospheric conductivity decreases far more rapidly in the e region than in the f region

geologic and geochemical controls on the mineralogy and grain size of gold bearing phases eastern australian volcanic hosted massive sulfide deposits the mineralogy and occurrence of gold varies in a systematic manner in volcanic hosted massive sulfide deposits of eastern australia in deposits where it is concentrated with zinc at or near the top of the massive sulfide deposit gold occurs in auriferous arsenopyrite and pyrite in the center of the lens and electrum of variable fineness 300 900 in the baritic top of the lens the former occurrence results from precipitation of the gold into the lattice of arsenopyrite and coprecipitation of submicroscopic gold grains in arsenic poor pyrite the latter occurrence results from direct precipitation of electrum from thio complexes owing to the decrease in a sub h 2 s caused by dilution and oxidation as hydrothermal fluids mix with seawater in deposits where gold is concentrated with copper at the base of the sulfide lens and in the stringer zones the gold occurs as electrum of high fineness 750 1 000 or as gold tellurides that are commonly associated with chalcopyrite and or pyrite this occurrence is caused by the direct precipitation of gold from chloro complexes owing to an increase in ph or a decrease in temperature as the hydrothermal fluids move up through the sulfide body gold in auriferous pyrite is readily mobilized during deformation as the pyrite fractures gold migrates via solution precipitation mechanisms to cracks and grain boundaries to form electrum by combination with silver which is released from sulfide minerals in a similar manner with increasing stress the electrum is released from pyrite to recrystallize with other easily remobilized minerals such as galena during this process electrum grain size increases thermodynamic modeling of the variation in electrum fineness shows good agreement with variations measured in massive sulfide ores for gold transported as a thio complex the predicted fineness of 190 to 990 for temperatures of 200 degrees to 300 degrees c and typical volcanogenic fluids matches the observed variation in deposits of the zn au association the very high finenesses observed in deposits of the cu au association can be modeled assuming gold chloro complex transport and high ag au ratios in the hydrothermal fluids

mineralogy of gold in the elshitsa massive sulphide deposit sredna gora zone bulgaria the elshitsa volcanic hosted massive sulphide deposit occurs in the central part of the srena gora metallogenic zone in bulgaria the gold bearing massive sulphide mineralization is considered to be the product of an island arc volcano plutonic process and hydrothermal activity that took place during the late cretaceous in addition to the major gold hosted opaque minerals such as pyrite chalcopyrite sphalerite and galena there are minor phases of tennantite goldfieldite se bearing aikinite native silver and bornite in the massive sulphide lenses and stringer zones most of the sulphide minerals are se bearing all of the six mineral assemblages that were deposited during the pyrite and copper pyrite stages of mineralization are gold bearing the gold tenor as a rule is less than 1 g t native gold and electrum occur as blebs or intergranular particles in the sulphide minerals gold in the early massive pyrite is of submicroscopic type 100 m in the late gold sulphide assemblages the electrum fineness in 41 individually studied grains varies between 780 and 992 with a mean of 895 native silver was found in association with bornite cu te sb and bi are the most common trace elements in gold and electrum the cu zn pb association is most important as a au ag carrier a model for gold behaviour during sulphide deformation is proposed involving coarsening of gold grain size from the earlier to the later sulphide mineral assemblages

forecasting the evolution of seismicity in southern california animations built on earthquake stress transfer 1 we develop a forecast model to reproduce the distribution of main shocks aftershocks and surrounding seismicity observed during 1986 2003 in a 300 310 km area centered on the 1992 m 7 3 landers earthquake to parse the catalog into frames with equal numbers of aftershocks we animate seismicity in log time increments that lengthen after each main shock this reveals aftershock zone migration expansion and densification we implement a rate state algorithm that incorporates the static stress transferred by each m 6 shock and then evolves coulomb stress changes amplify the background seismicity so small stress changes produce large changes in seismicity rate in areas of high background seismicity similarly seismicity rate declines in the stress shadows are evident only in areas with previously high seismicity rates thus a key constituent of the model is the background seismicity rate which we smooth from 1981 to 1986 seismicity the mean correlation coefficient between observed and predicted m 1 4 shocks the minimum magnitude of completeness is 0 52 for 1986 2003 and 0 63 for 1992 2003 a control standard aftershock model yields 0 54 and 0 52 for the same periods four m 6 0 shocks struck during the test period three are located at sites where the expected seismicity rate falls above the 92 percentile and one is located above the 75 percentile the model thus reproduces much but certainly not all of the observed spatial and temporal seismicity from which we infer that the decaying effect of stress transferred by successive main shocks influences seismicity for decades finally we offer a m 5 earthquake forecast for 2005 2015 assigning probabilities to 324 10 10 km cells

effect of magnetic activity on the dynamics of equatorial f region irregularities 1 two different aspects of the effect of magnetic activity on the dynamics of equatorial spread f esf irregularities are studied here using spaced receiver scintillation observations the first one deals with the question of how magnetic activity affects the generation of esf irregularities for this a parameter designated the random velocity which is a measure of random changes in the irregularity drift velocity is evaluated from the data in past studies this parameter has been found to have large values in the early phase of evolution of esf irregularities during the postsunset period with a steep decline to a low value by 22 lt this behavior is attributed to the decline in the height of the f region therefore a sudden increase in the random velocity in the postmidnight period is attributed to an increase in the height of the f region due to the ionospheric zonal electric field turning from westward to eastward due to the effect of magnetic activity which may also generate fresh irregularities that produce the observed scintillations this idea has been used to suggest that for two of the magnetically active days considered in the present study the irregularities may be freshly generated in the postmidnight period the second aspect is the identification of geomagnetically disturbed plasma drifts which is generally possible only after 22 lt when the estimated irregularity drift velocities are close to that of the background plasma the pattern of the estimated drift after 22 lt 3 ut is found to be well defined for magnetically quiet days with scintillations during a period of a month this allows the identification of a superimposed westward perturbation in the drift produced by a disturbance dynamo due to magnetic activity for all the three events studied here on 19 february and 1 march 1999 the eastward drift velocities show an identical decrease of about 50 m s from the undisturbed drift at 0440 ut on 1 march the decay phase of the storm sets in later and the eastward velocity continues to decrease until 0530 ut turning westward with a maximum decrease of about 80 m s from the undisturbed drift on 22 october 1999 which was more disturbed than these two days the westward perturbation was larger causing the drift velocity to turn westward around 5 ut and a decrease of nearly 150 m s from the quiet time drift at 8 ut the results are in broad agreement with some of the recent empirical models of the evolution with storm time of equatorial disturbance dynamo electric fields

effect of geomagnetic activity on equatorial radio vhf scintillations and spread f the paper discusses the occurrence of scintillations of ats 3 137 mhz beacons recorded at huancayo on geomagnetically quiet and disturbed days during the years 1969 1976 and compares the results with the corresponding occurrence of range and frequency spread f at huancayo during the equinoctial months and the december solsticial months the geomagnetic activity reduces the equatorial scintillations during premidnight hours but increases their occurrence during the postmidnight hours these features are very similar to the effect of geomagnetic activity on the occurrence of the range type of equatorial spread f rather than on the occurrence of frequency spread which decreases for any hour of the night during geomagnetic active periods during the june solsticial months the occurrence of both scintillations and spread f is very much reduced however both the phenomena are more frequent on disturbed than on quiet days for any of the hours of the night these effects are consistently the same for any of the years within the solar cycle it is suggested that the equatorial radio scintillations at 137 mhz during the nighttime are produced primarily by the occurrence of the range type of spread f the geomagnetic effects are due to the modifications of the equatorial electric field by the geomagnetic disturbance and thereby affect the development of f region irregularities causing scintillations

equatorial ionospheric responses to high intensity long duration auroral electrojet activity hildcaa 1 the knowledge of the coupling processes between the magnetosphere and the equatorial ionosphere is of basic importance to the understanding of the near earth space weather this study focuses on observational results of such coupling processes based on data collected during the phenomenon defined as high intensity long duration continuous ae activity hildcaa which occurs outside the main phase of geomagnetic storms the fact that the responses of the equatorial low latitude ionosphere to hildcaa events have not been specifically focused so far is one of the motivations for this study ionosonde data on hmf2 h f and fof2 from three locations in brazil magnetic equatorial station sao luis sl subequatorial station fortaleza fz and low latitude station cachoeira paulista cp are analyzed together with ace satellite data on solar wind and interplanetary magnetic and electric fields during three hildcaa events that occurred in the years 2000 and 2001 the results did not indicate any presence of penetrating electric field disturbance during these events however they provided clear evidence of disturbance dynamo electric field and disturbance thermospheric winds through f layer height changes that were similar but generally less intense than those observed during a typical storm event the fof2 presented no particular disturbances that can be clearly attributed to the hildcaa event previous extensive studies carried out by the authors on ionospheric storm effects for these same three stations clearly illustrate the much more intense f layer storm disturbances compared with hildcaa events disturbances

observations of small to large scale ionospheric irregularities associated with plasma bubbles with a transequatorial hf propagation experiment and spaced gps receivers the results from simultaneous observations of the nighttime transequatorial propagation tep of hf radio waves between australia and japan and the gps scintillation measurements in south china and vietnam are presented in this paper the results showed that there was good correspondence between the nighttime eastward traveling off great circle propagation ogcp of broadcasting waves of radio australia from shepparton australia measured at oarai japan and the scintillations in gps radio waves at hainan china this shows that the nighttime eastward traveling ogcp in hf tep is caused by a large scale ionospheric structure associated with a plasma bubble the zonal drift velocities of the large scale ionospheric structure estimated by the change in the direction of arrival of the ogcp were similar to those of the small scale irregularities associated with plasma bubbles measured by the gps scintillation spaced receiver technique our results show that the hf tep measurement is quite useful for monitoring the plasma bubble occurrence over a wide area and for forecasting the arrival of the plasma bubble at places located to the east of it

global storm time plasma redistribution imaged from the ground and space 1 the bulk redistribution of plasma in the near earth space environment during the onset and main phase of a magnetic storm has been observed on a global scale with 2 minute resolution using far ultraviolet images from the nasa image satellite and ground based total electron content tec maps using global positioning satellite gps receivers the dynamic variations under the storm conditions show a redistribution of plasma away from the nominal low latitude location of the equatorial ionospheric anomalies resulting in peak nightside ionospheric densities at middle latitudes a zonal redistribution of plasma is also evident as the plasma is depleted across the atlantic sector while tec values grow in the caribbean sector to the largest values on the nightside the ground based gps measurements provide 24 hour observations of tec while the fuv measurements provide nightside observation with greater spatial resolution continuous over land and sea the complimentary observations are shown to have a very good correspondence promising new analyses of storm time plasma redistribution with high temporal and spatial resolution and greatly improved global coverage

ground deformation events preceding the homestead valley earthquakes abstract hours prior to the homestead valley sequence of earthquakes in the south central mojave desert 4 7 m l 5 2 on 15 march 1979 evidence of ground displacement was recorded at three widely separated points on the periphery of the mojave block the displacements were sensed as anomalous water levels on the two major aqueducts in southern california and as a creep step on a united states geological survey creepmeter as well as being on the periphery of the mojave block the water level sensors are immediately adjacent to small neogene faults while the creepmeter spans the 1857 break of the san andreas fault near palmdale recalling the well established geodetic anomaly on the san andreas fault near palmdale in early 1979 and the recently documented enhancement of the strike slip component of microseismic activity on this section of the fault during the same period we suggest that these events the ground deformation events discussed herein and the homestead valley earthquakes are all aspects of a blockwide strain episode

determination of low latitude plasma drift speeds from fuv images 1 thousands of images of the nighttime equatorial airglow arcs have been obtained by the far ultraviolet imager fuv on board the nasa image satellite imaging periods lasting several hours around the time of satellite apogee allow for the determination of the velocity of drifting plasma density depletions occurring within the airglow arcs these velocities reflect the e b drift of low latitude plasma under the influence of a vertical electric field a survey of several weeks of data produces information regarding the variation of drift speeds with solar 10 7 cm radio flux comparisons to previous measurements by the jicamarca radar show that the fuv determined plasma drift speeds are 10 35 greater particularly before 2100 local time this difference is attributed mainly to the different magnetic latitudes of the observations

f region east west drifts at jicamarca f region east west drifts have been measured at jicamarca for almost 10 years using incoherent scatter the drifts are westward during the day and eastward at night the daytime drift velocities are about 50 m s and change very little with season or solar cycle the evening reversal occurs at about 1600 local time throughout the solar cycle the maximum nighttime eastward drifts are about 105 and 130 m s during solar minimum and maximum respectively the daytime and nighttime drifts show very litle variation with magnetic activity these jicamarca incoherent scatter results especially the reversal times differ appreciably from results obtained using other techniques but there appear to be fairly simple explanations for the apparent disagreements

equatorial disturbance dynamo electric fields f region vertical drift data from jicamarca peru show that equatorial east west electric fields are sometimes perturbed 16 24 hours after the onset of geomagnetic storms these disturbance dynamo electric fields which must be caused primarily by the action of neutral winds at low and middle latitudes decrease and sometimes even reverse the quiet time electric field pattern during both daytime and nighttime the long delay excludes the possibility that gravity waves are responsible and suggests that the thermospheric circulation is disturbed the data also show that after some storms there are no such delayed disturbances a fact which may be due to the longitudinal structure of the disturbances at high latitudes and or that only very strong storms can produce major thermospheric perturbations that extend to middle and low latitudes

longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by image fuv 1 the far ultraviolet imager fuv on board the image satellite provides an instantaneous global view of the oi 135 6 nm nightglow with 2 min time resolution because the oi 135 6 nm emission from the nighttime ionosphere is determined by the line of sight integrated plasma density the nightglow images are useful for studying the nighttime low latitude ionosphere globally with the image fuv 135 6 nm observations from march to june 2002 we have examined the global characteristics of the nighttime equatorial anomaly ea by constructing a constant local time map lt map in which pixels within an assigned local time range are extracted from the image fuv nightglow images obtained over an observation period of 3 days or more and are put together to compose a global distribution map of emission intensities at that local time these lt maps show that the development of the ea has a significant longitudinal structure in which peaks and dips of the crest emission intensity and the crest latitude have about 90 longitudinal separation in the longitude range from 0 to 250 although there is not enough data over the american sector this result suggests that the ea longitudinal structure has a prominent zonal component of the wave number 4 the observed longitudinal structure of the nighttime ea could not be fully explained by factors such as the empirical electric field and neutral wind models the geomagnetic declination angle or the displacement of the geomagnetic equator from the geographic equator to explain the observed longitudinal structure of the ea in particular the wave number 4 feature we may need to consider other forcing for example nonmigrating tide originated from the lower atmosphere

climatology of f region zonal plasma drifts over jicamarca 1 we use extensive incoherent scatter radar observations made at the jicamarca radio observatory between 1970 and 2003 to study and model empirically the equatorial zonal plasma drifts near the f region peak using bernstein polynomials as base functions our quiet time model results confirm that the daytime drifts are westward and are nearly season and solar cycle independent the nighttime drifts are eastward have larger magnitudes and increase strongly with solar flux particularly near equinox and december solstice enhanced geomagnetic activity drives small eastward perturbation drifts during the day and much larger westward disturbance drifts at night the nighttime drift perturbations are largest near midnight and increase strongly with solar flux near equinox and december solstice but are essentially absent near june solstice the jicamarca zonal disturbance drifts can be largely accounted for by disturbance dynamo electric fields with a dominant time delay of about 3 15 hours following enhanced geomagnetic activity in the postmidnight sector there are also smaller westward disturbance drifts associated with time delays of about 15 24 hours and perhaps even longer our results strongly suggest that the longitudinal dependence of both the quiet and disturbed equatorial nighttime zonal drifts varies with season

an empirical model of the drift velocity of equatorial plasma depletions 1 the far ultraviolet imager on the image spacecraft image fuv has been used to observe o plasma depletions in the post sunset equatorial ionosphere small scale density irregularities associated with such depletions are believed to adversely affect trans ionospheric radio signals such as gps prediction of the motion of these plasma depletions is a necessary component of the ability to forecast the occurrence of such radio signal interference an automated method has recently been developed to identify and track the position and zonal drift velocity of these depletions here we use this method to create a large database of the zonal drift velocities of these depletions we present an empirical model based on these observations that describes the observed drift velocities as a function of both local time and magnetic latitude which is essential to represent their behavior a comparison of the observed drift velocities with zonal winds from both an empirical model horizontal wind model hwm07 and a first principles model the tiegcm reveals that the plasma depletions drift velocities have a latitudinal gradient that cannot be explained solely by the f region dynamo in the post sunset period at least by these climatological models this suggests that these plasma depletions may not simply drift with the background f region plasma it has previously been suggested that vertical polarization electric fields associated with the plasma depletions are responsible for their zonal drifts exceeding the background flow which may explain the previously observed discrepancy in the drift velocities and the discrepancy in their gradients reported here

observations and implications of water well and creepmeter anomalies in the mojave segment of the san andreas fault zone four years of continuous water level data from a 1 900 m deep well near the san andreas fault in southern california show a 21 month period of unusual rapid fluctuations the anomalous water level activity ceases with the occurrence of the 8 july 1986 ml 5 6 north palm springs earthquake on the san andreas fault approximately 120 km southeast of the well site the water level data correlate with signals from two san andreas fault zone strain sensors the long term water level variations are similar in shape to those recorded by a borehole dilatometer 30 km from the well site while the rapid water level fluctuations correlate in time with anomalies in the record of a fault zone creepmeter located 35 km from the water level monitor the observations are interpreted in terms of strain occurring in a horizontally and vertically heterogeneous crust tectonic deformation is concentrated along weak block bounding fault zones the blocks are sufficiently rigid to generate correlated displacement phenomena along their weak boundaries as a consequence fault zone strain events can be related over large distances as in the case of the north palm springs earthquake and the coincident creep and water level anomalies the observed creep and water level events occur in a weak aseismic shallow 3 km material overlying stronger asperities along which the fault is locked and regional strain loading occurs local failure of the fault within the weak shallow material has no far field effects and is not important in the crustal stress budget but may signal accelerated strain accumulation at depth in this context the reported observations demonstrate the possibility of joint detection of fault zone anomalies that relate to and possibly anticipate major tectonic strain events on large faults

microchemical studies of placer and lode gold in the klondike district yukon canada 1 evidence for a small gold rich orogenic hydrothermal system in the bonanza and eldorado creek area orogenic gold camps are commonly associated with placer deposits although in many cases the relationship between placer and lode source may be unclear placer gold deposits in bonanza and eldorado creeks in the northern klondike district goldfield yukon canada probably yielded more than 2 million ounces moz from a small geographic area but known occurrences of gold bearing orogenic style veins from which the placers were derived accounted for only a few thousand ounces the alloy chemistry and mineralogy of opaque mineral microinclusions microchemical signatures within these gold grains were compared to that of samples collected during a detailed placer gold sampling program collection of placer samples from the headwaters of watercourses in this unglaciated area allowed identification of microchemical signatures within gold populations from proximal sources which augmented information from lode gold sources to facilitate characterization of local gold mineralization a total of 1 163 gold grains from 18 lode sources and 2 777 grains from 27 placer localities within the bonanza and eldorado creek drainages were characterized in terms of the ag and hg content of the alloy together with the associated inclusion suite and two main compositional ranges along with several subtypes were identified type 1 gold is a simple au ag alloy but various subtypes have been identified on the basis of different ranges of ag and or specific inclusion assemblages type 2 gold is an au ag hg alloy composition the spatial arrangement of the gold types shows a systematic change in microchemical signature the lowest ag gold occurs in the lone star ridge area and the ag content increases both in the northeast and southwest the appearance of te bearing mineral inclusions in populations coincides with increasing ag and argentite inclusions are present only in high ag gold toward the periphery of study area type 2 gold is absent at lone star ridge and all localities to the east but is progressively more abundant in sample localities to the west the geographic distribution of gold types correlates well with placer abundance inferred from the production from previous mining activity and the study area is bounded by creeks and gulches in which there was insufficient placer gold for economic extraction we conclude that the lone star ridge area represents the epicenter of a single hydrothermal system in which spatial and temporal fluid evolution has generated compositional zonation variation in ag is ascribed to decrease in au ag aq following preferential au deposition in the center of the system controls on hg contents within au alloy are unclear but may be a consequence of mineralization temperature the complex but consistent signatures of placer gold samples from the eldorado creek drainage represents liberation of types 1 and 2 gold grains which coexist in some lode occurrences the different proportions of types 1 and 2 gold observed in placer and lode samples from west of lone star ridge reflect both temporal and spatial evolution of the hydrothermal system the main eldorado creek placers exhibit a signature most similar to lode gold from the buckland and nugget zones on lone star ridge placer gold in upper bonanza creek is distinguished by a relatively narrow ag range and the small but consistent presence of hessite in the inclusion suite no corresponding lode occurrence for this gold type has been identified to date this is the first time that the compositional signatures of major placer gold deposits derived from orogenic gold vein systems has been studied in this detail and the application of basic chemical principles to fluid evolution and electrum precipitation has allowed demarcation of an area in which extremely rich gold mineralization was formerly present while simultaneously identifying the most promising areas for further exploration for undiscovered lode gold

active tectonic studies in the united states 1987 1990 the techniques and instrumentation used in active tectonic studies are discussed and recent results are reviewed it is suggested that a critical mass of data on several particular regions has been accumulated making possible critical debates and attempts to assess earthquake hazards particular attention is given to studies of the pacific northwest region basin and range deformation studies and distributed deformation and hidden earthquake sources also included is a comprehensive bibliography for the period

structuring of intermediate scale equatorial spread f irregularities during intense geomagnetic storm of solar cycle 24 here we examine the structuring of equatorial plasma bubble epb during intense geomagnetic storm of solar cycle sc 24 that occurred on 17 march 2015 using spaced receiver scintillation observations on a 251 mhz radio signal recorded by a network of stations in indian region as yet this is the strongest geomagnetic storm dstmin 223nt that occurred in present sc present study reveals that the structuring of equatorial spread f esf irregularities was significantly different on 17 march as compared to quiet days of corresponding month esf irregularities of intermediate scale 100 m to few kilometers are observed at unusually higher altitudes 800 km covering wider longitudinal latitudinal belt over indian region a presence of large scale irregularity structures with stronger n at raised f peak with small scale irregularities at even higher altitudes is observed it caused strong focusing effect s4 1 that prevails throughout premidnight hours at dip equatorial station tirunelveli other observational aspect is that zonal irregularity drifts over low latitude station kolhapur exhibited a large deviation of 230 m s from their average quiet time pattern during this geomagnetic storm two southward turnings of significant strength bz 15 nt occurred at 11 4 ist indian standard time and 17 9 ist the later southward turning of interplanetary magnetic field imf bz resulted in a large eastward prompt penetration electric field ppef close to sunset hours in indian longitude estimates of ppef obtained from real time ionospheric model are too low to explain the observed large upliftment of f region in the post sunset hours possible reason for observed enhanced ppef linked effects is discussed

scintillations plasma drifts and neutral winds in the equatorial ionosphere after sunset an equatorial campaign was conducted during september 25 to october 7 1994 to investigate the neutral and plasma dynamics in the equatorial ionosphere after sunset in relation to the day to day variability of the occurrence of equatorial spread f esf the campaign was organized under the auspices of national science foundation s multi instrumented studies of the equatorial thermosphere aeronomy program miseta which included the jicamarca radar spaced antenna satellite scintillation digisonde all sky imager and fabry perot interferometer fpi measurements near the magnetic equator in peru during a part of the period september 27 to october 3 the geophysics directorate of phillips laboratory performed measurements away from the magnetic equator at aguaverde chile magnetic latitude 11 s located 800 km to the east of the jicamarca meridian using geostationary and gps satellite scintillation digisonde and all sky imager systems the incoherent scatter radar results indicate that the postsunset enhancement of upward plasma drift even though of the order of only 20 m s 1 during the solar minimum period is a necessary condition for the generation of esf in view of the extreme difficulty of determining the neutral wind speed during the early evening hours by the fpi due to low airglow intensity it was not possible to unequivocally associate the observed postsunset enhancements with strong eastward neutral winds however considering a few observations contiguous to the campaign period it appears that such a causal relationship may exist the scintillation drift measurements in peru and chile indicated that the zonal irregularity drift was smaller away from the magnetic equator implying a variation of neutral wind with latitude this is reproduced in the altitude variation of zonal drift observed by the jicamarca radar during a magnetic storm scintillation measurements indicated that eastward drifts near the magnetic equator are accompanied by westward drifts near the anomaly peak which is consistent with the effects of a disturbance dynamo the campaign results indicate that in order to resolve the variability of esf a careful probing of neutral dynamics as a function of latitude needs to be undertaken during the postsunset period

magnetospheric disturbance induced equatorial plasma bubble development and dynamics a case study in brazilian sector 1 equatorial ionospheric plasma bubble irregularity development and dynamics during the major magnetospheric storm of 26 august 1998 are investigated using the data collected by a multistation and multi instrument diagnostic network operated at equatorial and low latitude sites in brazil and auroral electrojet activity au al imf and dst indices a magnetospheric disturbance onset in the morning of 26 august 1998 was initiated by a solar wind shock and associated imf bz polarity reversals and ssc that were soon followed by a succession of substorm like auroral electrojet ae intensifications and dst development an imf bz southward turning and associated ae intensifications in the brazilian dusk sector produced intense prompt penetration eastward electric field that caused large f region vertical drift and consequently the developments of intense postsunset equatorial anomaly and a series of intense plasma bubbles the latter event lasting the entire night as observed by digital ionosondes at sao luis 2 33 s 315 8 e dip angle 5 and fortaleza 3 9 s 321 55 w dip angle 9 and an all sky imager two scanning photometers and a digisonde at the low latitude site cachoeira paulista 22 6 s 315 e dip angle 28 a notable aspect of the dynamics of the bubbles was their initially very low eastward drift velocity which turned into steadily increasing westward velocity that lasted till early morning hours the results show for the first time a relationship between the zonal drift velocities of optically observed large scale bubbles tens to hundreds of kilometers and that of the smaller scale kilometer sizes structures as observed by a digital ionosonde the results point to the dominant role of a disturbance dynamo associated westward thermospheric wind to maintain the plasma irregularity drift increasingly westward going into postmidnight hours as an important finding the results further show that significant contribution to the westward plasma bubble irregularity drift normally attributed to disturbance dynamo effect could arise from prompt penetration disturbance zonal electric field in the course of a disturbance sequence lasting several hours such effect is attributed to hall electric field arising from the primary disturbance zonal electric field under enhanced nighttime ionospheric conductivities produced possibly by storm associated particle precipitation in the brazilian longitude sector in agreement with recent evidences abdu et al 1998b

mid latitude ionospheric irregularities persisting into late morning during the magnetic storm on 19 march 2001 1 post sunrise intense ionospheric irregularities at low to mid latitudes are reported for the first time a method based on spaced receiver technique is proposed to estimate the apparent drift velocity of the irregularities by using the correlation of the slant total electron content tec from 3 gps receivers the irregularities were detected at 23 45 n by the gps earth observation network geonet of japan from 0455 lt to 1051 lt on 21 march 2001 during the recovery phase of the magnetic storm at the corresponding time spread f was observed with 3 ionosondes located meridionally at okinawa 127 8 e 26 3 n 20 7 n magnetic latitude kokubunji 139 5 e 35 7 n 30 0 n magnetic latitude and wakkanai 141 7 e 45 4 n 40 5 n magnetic latitude while an intense negative ionospheric storm was processing and propagating from mid to lower latitudes the irregularities were seen as plasma bubbles by the defense meteorological satellite program dmsp in situ measurements westward drift with the speed of 100 m s was estimated by spaced receivers from geonet and confirmed by dmsp during the evolution of the irregularities the plasma bubbles at mid latitude sustained 1 5 hour after sunrise and at the lower latitudes they survived more than 4 hours after sunrise the observations suggested that the irregularities were generated by an eastward electric field associated with the disturbance dynamo and the long time existence of the irregularities after sunrise seemed to be related to the daytime intense negative ionospheric storm on 21 march

effect of atmospheric tides on the morphology of the quiet time postsunset equatorial ionospheric anomaly longitudinal wave number four pattern in the magnetic latitude and concentration of the f region peak ion density when measured at a fixed local time in a new comparison of two data sets with observations made by the ogo 4 satellite this pattern is seen to be persistent over many days around equinox during magnetically quiet conditions close to solar maximum but can be dominated by other processes such as cross equator winds during other periods it is found that the longitudinal variability is created by a processes occurring in the dayside ionosphere a longitudinal modulation of the dayside equatorial fountainisthemostlikelydrivingmechanism throughcomparisonwithgwsm 02model it isshownthatthepredictedmodulationofthedaysidethermosphericwindsandtemperaturesat e region altitudes created by non migrating diurnal tides can explain the modulation in the dayside equatorial fountain this result highlights the importance of understanding the temporal variability of tropospheric weather systems on our understanding and possible predictability of the development of the f region ionosphere it may also provide a possible further means of testing our understanding of atmospheric tides on a global scale

native gold from the inagli pt au placer deposit the aldan shield russia geochemical characteristics and implications for possible bedrock sources the inagli alluvial pt au placer deposit in the republic of sakha yakutia russia is linked to the inagli massif one of the several uralian alaskan type alkaline ultrabasic complexes in the aldan shield gold from the placer is heterogeneous in composition and is represented by three types type 1 gold is the most abundant and is characterized by simple au ag alloys with 4 34 wt ag low cu up to 0 08 wt and negligible hg pt and pd contents and silver tellurium sulfosalts ag cu te s as compounds in the inclusion suite silicate inclusions are biotite k feldspar fe mg amphibole chlorite plagioclase fe mg pyroxene zircon and titanite distinctive features of this gold type are most similar to those derived from low sulfidation systems linked to iron oxide copper gold or iron skarn types of mineralization the bedrock source of type 1 gold could be related with monzonite to syenite intrusions surrounding the inagli massif distinctive features of type 2 gold include a wide discontinuous range of ag content 1 18 wt elevated cu up to 0 5 wt and occasional pd up to 0 3 wt levels non detectable pt and hg contents and rare inclusions of simple sulfides digenite pyrrhotite and na amphibole type 3 gold is distinguished by a narrow range in ag content 5 8 wt elevated hg 0 5 1 wt contents negligible cu pt and pd levels and au pb compounds k feldspar inclusions microchemical characteristics of type 2 and type 3 gold are interpreted as suggestive of an alkaline magmatic related fluid based on the grain morphology and microchemical signatures potential bedrock sources for both gold types could be related to the numerous alkaline veins and potassic alteration zones within the dunite core a comparison of the inagli and the kondyor placer gold allows to generate distinctive generic signatures for gold from uralian alaskan type alkaline ultrabasic complexes in the aldan shield

comparing strain events a case study for the homestead valley earthquakes we present a procedure for comparing strain events at different sites and apply it to observations for the homestead valley earthquake sequence of 15 march 1979 coseismic strain steps occurred on two laser strainmeters at pinon flat observatory pfo and on a creepmeter spanning the san andreas fault at wiebe ranch xwr the creepmeter records were studied by leary and malin 1984 the pfo coseismic strains are consistent with a source model derived from near field geodetic measurements while the xwr coseismic extension is 1200 times too large and of the wrong sign the xwr instrument showed an anomalous extension about 20 hours before the earthquake leary and malin 1984 but no such signals were detected on the pfo strainmeters at this time to compare these preseismic observations we must make some assumption about the preseismic source and we choose to assume that any precursory slip occurred on the fault plane that eventually ruptured under this assumption the preseismic xwr and pfo records cannot be reconciled unless the preseismic dislocation is left lateral or mostly thrust and the fault zone at xwr magnifies strain by a factor of 2900 or more this strain magnification implies that the fault zone shear modulus at xwr is 107 pa three orders of magnitude smaller than the shear modulus of typical crustal rocks however earth tide observations at xwr constrain the strain magnification at this site to be less than about 55 thus the preseismic extension at xwr is probably not a precursor to the homestead valley earthquake

gold in the brunswick no 12 volcanogenic massive sulfide deposit bathurst mining camp canada evidence from bulk ore analysis and laser ablation icp ms data on sulfide phases the 329 mt brunswick no 12 volcanogenic massive sulfide deposit total resource of 163 mt at 10 4 zn 4 2 pb 0 34 cu and 115 g t ag is hosted within a middle ordovician bimodal volcanic and sedimentary sequence massive sulfides are for the most part syngenetic and the bulk of the sulfide ore occurs as a zn pb rich banded sulfide facies that forms an intimate relationship with a laterally extensive algoma type iron formation and defines the brunswick horizon zone refining of stratiform sulfides is considered to have resulted in the development of a large replacement style cu rich basal sulfide facies which is generally confined between the banded sulfide facies and an underlying stringer sulfide zone complex polyphase deformation and associated lower to upper greenschist facies regional metamorphism is responsible for the present geometry of the deposit textural modification has resulted in a general increase in grain size through the development of pyrite and arsenopyrite porphyroblasts which tend to overprint primary mineral assemblages despite the heterogeneous ductile deformation primary features have locally been preserved such as fine grained colloform pyrite and base and precious metal zonation within the main zone base metal and trace element abundances in massive sulfides from the brunswick no 12 deposit indicate two distinct geochemical associations the basal sulfide facies characterized by a proximal high temperature hydrothermal signature cu co bi se contains generally low au contents averaging 0 39 ppm n 34 conversely au is enriched in the banded sulfide facies averaging 1 1 ppm au n 21 and is associated with an exhalative suite of elements zn pb as sb ag sn finely laminated sulfide lenses hosted by iron formation at the north end of the main zone are further enriched in au averaging 1 7 ppm n 41 and ranging up to 8 2 ppm laser ablation inductively coupled plasma mass spectrometry icp ms analyses of pyrite n 97 from the north end of the main zone average 2 6 ppm au and range from the detection limit 0 015 ppm to 21 ppm overall these analyses reveal a distinct au sb as ag hg mn association within pyrite grains gold is strongly enriched in large pseudo primary masses of pyrite that exhibit relict banding and fine grained cores smaller euhedral pyrite porphyroblasts and euhedral rims of metamorphic origin surrounding the pyrite masses contain much less au sb ag as and sn arsenopyrite occurring chiefly as late porphyroblasts contains less au averaging 1 0 ppm and ranging from the detection limit 0 027 ppm to 6 9 ppm depth profiles for single spot laser ablation icp ms analyses of pyrite and arsenopyrite display uniform values of au and an absence of discrete microscopic inclusions of au bearing minerals which is consistent with chemically bonded au in the sulfide structure the pervasive correlation of au with sn in the zn pb rich banded sulfide facies suggests similar hydrothermal behavior during the waxing stages of deposition on the seafloor under high temperature 350oc and moderate to low ph conditions au and sn in hydrothermal fluids would be transported as chlorocomplexes an abrupt decrease in temperature and ah2s accompanied by an increase in fo2 and ph during mixing with seawater would lead to the simultaneous destabilization of both au and sn chlorocomplexes the enrichment of au in fine grained laminated sulfides on the periphery of the deposit accompanied by sporadic occurrences of barite and fe poor sphalerite supports lower hydrothermal fluid temperatures analogous to white smoker activity on the flanks of a large volcanogenic massive sulfide system in lower temperature 350oc and mildly acidic hydrothermal fluids au would be transported by thiocomplexes which exhibit multifunctional retrograde prograde solubility and a capacity to mobilize au to the outer parts of the sulfide mound the sluggish nature of this low temperature venting together with larger variations in ambient fo2 could lead to a sharp enrichment of au towards the stratigraphic hanging wall of massive sulfide deposits

effects of solar and geomagnetic activities on the zonal drift of equatorial plasma bubbles equatorial plasma bubbles are mostly generated in the postsunset sector and then move in the zonal direction plasma bubbles can last for several hours and move over hundreds of kilometers even more than 1000 km in this study we use measurements of ion density by the communication navigation outage forecasting system satellite to determine the orbit averaged drift velocity of plasma bubbles the objective of the study is to identify the dependence of the bubble drift on the solar radio flux and geomagnetic activities in total 5463 drift velocities are derived over may 2008 to april 2014 and a statistical analysis is performed the average pattern of the bubble drift is in good agreement with the zonal drift of the equatorial f region plasma the zonal drift velocity of plasma bubbles increases with the solar radio flux however the increase shows different features at different local times geomagnetic activities cause a decrease of the eastward drift velocity of plasma bubbles equivalent to the occurrence of a westward drift through disturbance dynamo process in particular the decrease of the eastward drift velocity appears to become accelerated when the dst index is smaller than 60 nt or kp is larger than 4

metamorphic ore remobilization in the hallefors district bergslagen sweden constraints from mineralogical and small scale sulphur isotope studies the marble and metavolcanic hosted pb zn ag sb as deposits of the hallefors district located in the palaeoproterozoic bergslagen ore province south central sweden comprise both stratabound sulphides and discordant ag rich sulphide sulphosalt veins the complex sulphide sulphosalt assemblages of the alfrida jan olof mines at hallefors were investigated by a combination of ore microscopy electron microprobe analysis and in situ laser sulphur isotope analysis the massive ore is characterized by positive and homoge neous d 34 s 1 4 to 2 7 v cdt whereas vein hosted sulphides and sulphosalts exhibit similar but generally less positive to slightly negative d 34 s 0 6 to 2 0 comparison of the observed ore mineral assemblages with calculated phase equilibria in the sys tem fe as s o h and isotopic fractionation as a function of temperature oxygen fugacity and ph indi cates that the vein type mineralization was formed from relatively reduced and rather alkaline hydrothermal fluids at these reduced conditions fractionation of d 34 s via changes of fo2 is insignificant and thus the isotopic signatures of the vein minerals directly reflect the com position of the sulphur source we therefore conclude that the vein type ore essentially inherited the sulphur isotope signature from the pre existing massive sulp hides via metamorphic remobilization at approximately 300 400c and 2 3 kbar scales of remobilization observable are on the order of about 5 mm to 30 cm overall the sulphide sulphosalt assemblages from the alfrida jan olof mines exhibit d 34 s values which are comparable to a majority of metasupracrustal hosted deposits in the bergslagen province thereby suggesting a common origin from ca 1 90 1 88 ga volcanic hydro thermal processes