seismicity of an andesitic volcano during block lava effusion volcan de colima mexico november 1998 january 1999 the block lava effusion at volcan de colima mexico began on november 20 1998 after 12 months of seismic activity and ended about 80 days later three types of seismic events were observed during the lava effusion volcano tectonic earthquakes occurred mainly at the very beginning and after the termination of lava effusion explosion earthquakes occurred frequently during the period of the maximum rate in lava effusion the remainder of the seismic signals were associated with pyroclastic flows and rockfalls from the lava dome these latter signals increased sharply in number at the onset of lava effusion the rate of occurrence remained high when the lava discharge rate decreased but gradually decreased after the termination of lava effusion maximum daily durations of seismic signals are proportional to the daily volumetric output of lava indicating the dependence of the number of pyroclastic flows on the rate of lava output a log log plot of seismic signal duration vs number of events with this duration displays a linear relationship the short period seismic signals can be divided into three categories based on duration short events with durations less than 100 s intermediate events with durations between 100 and 250 s and long events with durations longer than 250 s we infer that long events correspond to pyroclastic flows with mean deposit volume 2 105 m3 and intermediate events represent pyroclastic flows with mean deposit volume 1 103 m3

the annual cycle in equatorial convection and sea surface temperature abstract the coupled atmosphere ocean system in the equatorial eastern pacific and atlantic exhibits a distinct annual cycle that is reflected in contrasting conditions at the times of the two equinoxes the contrasts are so strong that they dominate the annual march of zonally averaged outgoing longwave radiation for the equatorial belt the march equinox corresponds to the warm season when the equatorial cold tongues in the eastern pacific and atlantic are absent with the onset of summer monsoon convection over colombia central america and west africa in may june northward surface winds strengthen over the eastern pacific and atlantic the equatorial cold tongues reappear and the marine convection shifts from the equatorial belt to the intertropical convergence zones itczs along 8 n as the northern summer program the itczs remain strong and shift northward to new 10 n while sea surface temperature sst continues to drop over the cold tongues and the southern tropics perhaps in response to the

lead isotopic patterns of galena in the piedmont and blue ridge ore deposits southern appalachians massive sulfide deposits of the southern appalachians form two distinct groups of lead isotope ratios which correlate with their geologic settings piedmont massive sulfides are associated with volcanic rocks of predominantly cambrian age they have model lead ages which are too young an effect of u pb enrichment of source rocks lead isotope ratios of piedmont massive sulfide define a trend of decreasingly radiogenic values from the mineral district virginia to the stone hill deposit alabama which probably reflects decreasingly ensialic volcanism from northeast to southwest a regression through the data has a slope which corresponds to a secondary isochron age of about 3 7 b y the line is proposed to represent mixing between variable amounts of upper crustal lead decreasing to the southwest with lead from a source relatively depleted in u pb which has however experienced either continuous or episodic enrichment of uranium relative to lead the occurrence of a similar trend in galenas from kings mountain belt ores is further evidence for such a source massive sulfides of the blue ridge geologic province occur in upper precambrian metasedimentary sequences and are typically low in lead content lead isotope ratios of galenas from ducktown and the gossan lead are highly enriched in 206 pb compared to amounts expected for deposits of that age the anomalously radiogenic component is probably the result of lead derived from the predominantly clastic sediments of the host sequences the radiogenic component of the 206 pb coupled with the narrow range of 207 pb 204 pb at ducktown indicates that much older continental crustal rocks were not involved in the ore forming process galenas from a vein in the hamme tungsten district north carolina form a tight grouping which is similar to lead in k feldspars from postorogenic approximately 300 m y old granitic plutons the mineralized veins of the virginia gold pyrite belt have galenas with a wide spread of radiogenic lead isotope ratios and do not appear to be related to massive sulfide deposits of the central virginia piedmont

self sustained oscillations at volcan de colima mexico inferred by independent component analysis we have analyzed long period lp seismic events of volcan de colima mexico recorded by four three component broad band seismometers during january 2006 frequency domain analysis shows spectra mainly peaked in the range 0 3 2 hz and characterized by a monotonic decreasing envelope as those produced in a cylindrically symmetric self oscillating cavity interacting with a confined jet independent component analysis a time series decomposition method extracts two or three nonlinear oscillation modes depending on the station with the fundamental one peaked at 0 4 0 5 hz these decomposed waves have a well defined spectral content and are self sustained oscillations with low dimensionality as shown by dynamic system reconstruction methods moreover they show radial polarization in near field and transverse polarization in far field in north west south east direction finally we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another

geochemistry and tectonic setting of the volcanics of the carolina slate belt the carolina slate belt consists of precambrian cambrian metamorphosed mafic to felsic flows volcaniclastics and derived sediments which filled in a volcanic trough presumed to have formed along the leading edge of the north american continent during the early closing of the proto atlantic ocean within the slate belt in central north carolina south carolina and on the south carolina georgia line there are volcanigenic massive sulfide deposits of kuroko affinities and their metamorphically remobilized sulfide and au quartz deposits a total of 296 chemical analyses of volcanic rocks and associated dikes of which 227 are in unpublished theses dissertation and reports are plotted on alkali sio 2 k 2 o na 2 o afm and na 2 o k 2 o cao diagrams in addition selected subsets are compared with standard discriminant plots such as tio 2 sio 2 mgo feo total al 2 o 3 and y zr ti generally speaking the volcanics of the slate belt define a bimodal suite of calc alkaline to tholeiitic rocks with strong affinities to volcanic suites described in the lesser antilles and with the volcanics of the coastal volcanic belt of maine a subduction related orogenic environment is most probable in addition the major element analyses strongly suggest that a pervasive postdepositional alteration process has taken place in general this alteration appears to have affected the fine grained matrix of the volcaniclastics but flows and dikes were not immune an overall alkali depletion and mgo enrichment is characteristic with significant but variable mobility of na 2 o k 2 o cao and sio 2 thus characterization of the magmatogenesis by major element composition alone is not easily done alteration associated with massive sulfide mineralization in the gold hill district north carolina and the lincolnton mccormick district south carolina georgia is similar to but more intense than the pervasive secondary alteration strong silicification alkali addition or subtraction and mgo enrichment is characteristic in general a significant proportion of the mineralization associated alteration falls outside the normal range of compositional variability of typical slate belt suites and thus has a notable signature

u pb and th pb whole rock isochrons from metavolcanic rocks of the carolina slate belt felsic volcaniclastic rocks and massive pyrite of a part of the carolina slate belt in south carolina referred to as the haile brewer block seem to have remained closed systems with respect to u th and pb since 465 ma u pb and th pb whole rock isochrons indicate ages of 466 40 2 and 462 53 ma respectively the pb pb secondary isochron age of the volcaniclastic rocks is 455 ma because of the divergent ways in which u th and pb have behaved during the various alteration events that have affected the haile brewer block metamorphism post tectonic intrusion weathering the isochronous relationships most likely represent the emplacement age of the rocks the preservation of u pb and th pb isochrons is thought to be due to the originally glassy nature of the volcaniclastic rocks and to the relatively impermeable character of the rocks which may have been aided by the sealing of pore space by infiltration of penecon temporaneous silica rich hydrothermal fluids the u pb and th pb whole rock ages are considerably younger than the 550 ma age inferred from u pb zircon ages and ediacaran fossil assemblages for the slate belt in north carolina the younger ages agree however with the presence of sponge spicules no older than middle cambrian in the haile brewer block the younger age of the haile brewer block with respect to other parts of the carolina slate belt indicates that the belt is more complex than has been thought

late pleistocene granodiorite beneath crater lake caldera oregon dated by ion microprobe variably melted granodiorite blocks ejected during the holocene caldera forming eruption of mount mazama were plucked from the walls of the climactic magma chamber at 5 km depth ion microprobe u pb dating of zircons from two unmelted granodiorite blocks with shrimp rg sensitive high resolution ion microprobe reverse geometry gives a nominal 238 u 206 pb age of 100 78 80 ka or 174 89 115 ka when adjusted for an initial 230 th deficit shrimp rg u th measurements on a subset of the zircons yield a 230 th 238 u isochron age of 112 24 ka considered to be the best estimate of the time of solidification of the pluton these results suggest that the granodiorite is related to andesite and dacite of mount mazama and not to magmas of the climactic eruption the unexposed granodiorite has an area of at least 28 km 2 this young shallow pluton was emplaced in virtually the same location where a similarly large magma body accumulated and powered violent explosive eruptions 7700 yr ago resulting in collapse of crater lake caldera

very long period oscillations of mount erebus volcano as the signal decays vlp scalar moments up to 5 10 11 n m exceed sp moments by an order of magnitude or more suggesting distinct though genetically related sp and vlp source mechanisms we conclude that vlp signals arise from excitation of a quasi linear resonator that is intimately associated with the conduit system and is excited by gravity and inertial forces associated with gas slug ascent eruption and magma recharge vlp signal stability across hundreds of eruptions spanning 5 years the persistence of the lava lake and the rapid posteruptive lava lake recovery indicate a stable near summit magma reservoir and vlp source process index terms 4544 oceanography physical internal and inertial waves 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms 8419 volcanology eruption monitoring 7280 keywords strombolian very long period volcano seismology

remnant colloform pyrite at the haile gold deposit south carolina a textural key to genesis auriferous iron sulfide bearing deposits of the carolina slate belt have distinctive mineralogical and textural features traits that provide a basis to construct models of ore deposition our identification of paragenetically early types of pyrite especially remnant colloform crustiform and layered growth textures of pyrite containing electrum and pyrrhotite establishes unequivocally that gold mineralization was coeval with deposition of host rocks and not solely related to paleozoic tectonic events ore horizons at the haile deposit south carolina contain many remnants of early pyrite 1 fine grained cubic pyrite disseminated along bedding 2 fine grained spongy rounded masses of pyrite that may envelop or drape over pyrite cubes 3 fragments of botryoidally and crustiform layered pyrite and 4 pyritic infilling of vesicles and pumice detailed mineral chemistry by petrography microprobe sem and eds analysis of replaced pumice and colloform structures containing both arsenic compositional banding and electrum points to coeval deposition of gold and the volcanic host rocks and thus confirms a syngenetic origin for the gold deposits early pyrite textures are present in other major deposits of the carolina slate belt such as ridgeway and barite hill and these provide strong evidence for models whereby the sulfide ores formed prior to tectonism the role of paleozoic metamorphism was to remobilize and concentrate gold and other minerals in structurally prepared sites recognizing the significance of paragenetically early pyrite and gold textures can play an important role in distinguishing sulfide ores that form in volcanic and sedimentary environments from those formed solely by metamorphic processes exploration strategies applied to the carolina slate belt and correlative rocks in the eastern united states in the avalonian basement will benefit from using syngenetic models for gold mineralization

whole rock and sulfide lead isotope data from the hydrothermal jade field in the okinawa back arc trough the mineralization of the active hydrothermal jade field resembles in many aspects the kuroko type mineralization the jade field is located in a back arc graben and is associated with a bimodal volcanism lead isotope data from igneous rocks sediments and ores further emphasize the similarities with the kuroko ores and suggest that both sediments and volcanic rocks contributed comparable amounts of lead to the deposit when compared to the sediments a much larger volume of volcanic rocks must have contributed lead to the deposit because of the considerably lower lead concentration of volcanic rocks in contrast to the crustal type lead of the jade field and the kuroko type sulfide deposits the lead isotope signatures of vms type deposits at mid ocean ridges is distinctly different in the absence of a sedimentary cover it reflects the composition of the mantle source whereas in the presence of a sedimentary cover it is either a mixture of mantle and sedimentary lead or it may even be completely dominated by the latter

overview of the 1997 2000 activity of volcan de colima mexico abstract this overview of the 1997 2000 activity of volcan de colima is designed to serve as an introduction to the special issue and a summary of the detailed studies that follow new andesitic block lava was first sighted from a helicopter on the morning of 20 november 1998 forming a rapidly growing dome in the summit crater numerous antecedents to the appearance of the dome were recognized starting more than a year in advance including 1 pronounced increases in s cl and d values at summit fumaroles in mid 1997 2 five earthquake swarms between november december 1997 and october november 1998 with hypocenters that ranged down to 8 km beneath the summit and became shallower as the eruption approached 3 steady inflation of the volcano reflected in shortening of geodetic survey line lengths beginning in november december 1997 and continuing until the start of the eruption 4 air borne correlation spectrometer measurements of so2 that increased from the background values of

late ordovician global warming the boda event there is substantial evidence for mid ashgillian global warming before the latest ordovician hirnantian glaciation as shown by the movement of previously lower latitude benthic faunas such as trilobites and brachiopods to progressively higher latitudes and by an increase in endemic faunas at low latitudes this is shown by faunal dynamics on several paleocontinents and endorsed by published evidence of warmer water sediments from gondwana and elsewhere we term this global warming the boda event

observations of high frequency scattered waves using dense arrays at teide volcano abstract a study of the seismic coda of seven small earthquakes recorded on the teide volcano canary islands spain was carried out using a temporary small aperture 12 station seismic array the purpose was to measure backazimuth apparent velocity and the type of waves that compose the coda in the frequency range 4 to 6 hz we used the zero lag cross correlation zlc method to obtain the components of the wave vector and three component analysis techniques based on the covariance matrix of the signal in the time domain to investigate the polarization properties of the signals the results show that a great part of the coda signals in the analyzed frequency range are almost uncorrelated while a low number of isolated correlated arrivals show an apparent slowness between 2 10 3 and 2 5 10 4 sec m and an almost random distribution of backazimuths the correlated arrivals have been interpreted as generated by strong scatterers probably related to the presence in the study area of surface topography irregularities the volcanic cone and the caldera rim the wave type varies from pure s type waves to mixed surface waves with some rayleigh components

geology of the barite hill gold silver deposit in the southern carolina slate belt barite hill is a stratiform gold silver deposit associated with base metal sulfides and barite in greenschist facies rocks the deposit southernmost of four recently mined gold deposits in the carolina slate belt is located in the lincolnton mccormick district of georgia and south carolina which includes several known gold silver and base metal deposits in a kuroko type geologic setting along with deposits of kyanite and manganese approximately 1 835 000 g of gold was produced mainly from oxidized ores in the main and rainsford pits from 1990 until their closing in 1994 ore is hosted by sericitically altered felsic metavolcanic and metasedimentary rocks of the late proterozoic persimmon fork formation the deposit is stratigraphically below an overturned contact between upper and lower pyroclastic units which overlie the lincolnton metarhyolite an intrusive extrusive unit gold silver rich zones in the main pit are partly coincident with lenses of siliceous barite rock but not confined to them and occur more commonly in pyrite quartz altered fragmental rock the main pit ore is stratigraphically overlain by a zone of base metal and barite enrichment which is in turn overlain by a talc tremolite alteration zone locally siliceous barite zones are absent in the rainsford pit and gold silver minerals are associated with silicified rocks and chert the barite hill deposit is interpreted to be the result of kuroko type volcanogenic base metal sulfide mineralization followed by gold silver mineralization under epithermal conditions with the following stages of evolution 1 massive sulfides barite and fine grained siliceous exhalites were deposited during late proterozoic to cambrian submarine volcanism which was related to plate convergence and subduction in a microcontinental or island arc setting distant from the north american continental plate 2 au ag te and base and precious metal te se bi minerals were deposited either during waning stages of hydrothermal activity in a failed massive sulfide system or in a separate event 3 sulfides and silica barite rock recrystallized during regional deformation and greenschist facies metamorphism related to the middle to late ordovician collision of the carolina terrane with the north american continental plate 4 quartz barite and gold were remobilized and formed veins that cut across cleavage 5 orebodies were offset along high angle faults and 6 during weathering base metal sulfides and barite dissolved and reprecipitated as supergene euhedral barite crystals that line ferric iron oxide hydroxide gossans

source mechanism of vulcanian degassing at popocatepetl volcano mexico determined from waveform inversions of very long period signals 1 the source mechanism of very long period vlp signals accompanying volcanic degassing bursts at popocatepetl is analyzed in the 15 70 s band by minimizing the residual error between data and synthetics calculated for a point source embedded in a homogeneous medium the waveforms of two eruptions 23 april and 23 may 2000 representative of mild vulcanian activity are well reproduced by our inversion which takes into account volcano topography the source centroid is positioned 1500 m below the western perimeter of the summit crater and the modeled source is composed of a shallow dipping crack sill with easterly dip of 10 intersecting a steeply dipping crack northeast striking dike dipping 83 northwest whose surface extension bisects the vent both cracks undergo a similar sequence of inflation deflation and reinflation reflecting a cycle of pressurization depressurization and repressurization within a time interval of 3 5 min the largest moment release occurs in the sill showing a maximum volume change of 500 1000 m3 pressure drop of 3 5 mpa and amplitude of recovered pressure equal to 1 2 times the amplitude of the pressure drop in contrast the maximum volume change in the dike is less 200 300 m3 with a corresponding pressure drop of 1 2 mpa and pressure recovery equal to the pressure drop accompanying these volumetric sources are single force components with magnitudes of 108 n consistent with melt advection in response to pressure transients the source time histories of the volumetric components of the source indicate that significant mass movement starts within the sill and triggers a mass movement response in the dike within a few seconds such source behavior is consistent with the opening of a pathway for escape of pent up gases from slow pressurization of the sill driven by magma crystallization the opening of this pathway and associated rapid evacuation of volcanic gases induces the pressure drop pressure recovery in the magma filling the sill is driven by diffusion of gases from the resulting supersaturated melt into bubbles assuming a penny shaped crack at ambient pressure of 40 mpa the observed pressure and volume variations can be modeled with the following attributes crack radius 100 m crack aperture 5 m bubble number density 1010 1012 m 3 initial bubble radius 10 6 m final bubble radius 10 5 m and net decrease of gas concentration in the melt 0 01 wt

paleoproterozoic high sulfidation mineralization in the tapajos gold province amazonian craton brazil geology mineralogy alunite argon age and stable isotope constraints the brazilian tapajos gold province contains the first evidence of high sulfidation gold mineralization in the amazonian craton the mineralization appears to be in large nested calderas the tapajos parima or ventuari tapajos geological province consists of a metamorphic igneous and sedimentary sequence formed during a 2 10 to 1 87 ga ocean continent orogeny the high sulfidation mineralization with magmatic hydrothermal alunite is related to hydrothermal breccias hosted in a rhyolitic volcanic ring complex that contains granitic stocks ranging in age from 1 89 to 1 87 ga cone shaped hydrothermal breccias which flare upward contain vuggy silica and have an overlying brecciated cap of massive silica the deposits are located in the uppermost part of a ring structure volcanic cone drill cores of one of the hydrothermal breccias contain alunite natroalunite pyrophyllite andalusite quartz rutile diaspore woodhouseite svanbergite kaolinite and pyrite along with inclusions of enargite luzonite chalcopyrite bornite and covellite the siliceous core of this alteration center is surrounded by advanced argillic and argillic alteration zones that grade outward into large areas of propylitically altered rocks with sericitic alteration assemblages at depth several occurrences and generations of alunite are observed alunite is disseminated in the advanced argillic haloes that envelop massive and vuggy silica or that underlie the brecciated silica cap coarse grained alunite also occurs in branching veins and locally is partly replaced by a later generation of fine grained alunite silicified hydrothermal breccias associated with the alunite contain an estimated reserve of 30 tonnes of gold in rock that grades up to 4 5 g t 1 au seven alunite samples gave 40ar 39ar ages of 1 869 to 1 846 ga with various degrees of apparent minor ar loss stable isotopic data require a magmatic hydrothermal origin for the alunite typical for high sulfidation mineralization the 34s values of most samples of alunite range from 14 0 to 36 9 sulfur isotopic alunite pyrite and oxygen isotopic alunite so4 oh temperatures range from 130 to 420 c the dh2o and 18oh2o values for alunite forming hydrothermal fluids suggest a predominance of magmatic water with a small meteoric contribution a rare sample of supergene alunite has a 34s value of 4 1 and an 40ar 39ar age of 51 3 0 1 ma other than local foliation in the volcanic rocks and recrystallization of alunite near faults the mineralization and associated alteration appears to have been remarkably undisturbed by later metamorphism and by supergene alteration the au mineralization was preserved because of burial by sediments and tuffs in taphrogenic basins that probably developed shortly after mineralization and were probably first exhumed at about 60 ma because high sulfidation mineralization forms at relatively shallow crustal levels the discoveries in tapajos province provide new perspectives for mineral exploration for the amazonian and perhaps for other precambrian cratons

nd isotopic evidence for juvenile crust in the carolina terrane southern appalachians nd isotopic analyses of whole rock samples from the older portion of the carolina terrane one of the largest terranes in the appalachian orogen demonstrate that part of this terrane is composed of juvenile mantle derived crust these data suggest that the terrane may not have originally been built upon old evolved basement material but rather may have been built upon oceanic crust a recent study by other workers demonstrates a more crustally evolved nd isotopic signature for younger components of the carolina terrane these data may indicate that the terrane interacted with evolved crust at a later time possibly by amalgamation with a more evolved crustal fragment before final accretion to laurentia rather than indicating a primary old basement a juvenile nature for the older portion of the terrane contrasts with models that suggest it is an evolved crustal fragment that formed in a continental margin setting a scenario proposed to explain the high proportion of felsic volcanic rocks within the terrane it is herein suggested that carolina is a chemically evolved but isotopically juvenile crustal fragment because it remained in an oceanic setting for an unusually long time in this regard the carolina terrane is similar to some of the large accreted terranes in the canadian cordillera such as wrangellia and alexander the presence of juvenile crust in the carolina terrane documents that at least part of the southern appalachian orogen is not composed solely of reactivated pre existing continental crust the importance of this part of the orogen in terms of the volume of juvenile phanerozoic crustal material in north america may be larger than previously thought however until additional major appalachian terranes have been isotopically characterized the volume of juvenile crust in the whole orogen remains unknown the isotopic make up of a terrane can be an important aspect of terrane analysis as different terranes may have significantly different isotopic compositions while even widespread pieces of a single terrane should have very similar isotopic characteristics the nd isotopic data for the carolina terrane form the beginning of an isotope database for terranes in the southern appalachians

coordinated biotic and abiotic change during the great ordovician biodiversification event darriwilian assembly of early paleozoic building blocks abstract the ordovician period records an extraordinary biodiversity increase known as the great ordovician biodiversification event gobe which coincided with a series of environmental changes to the earth system notably a cooling global ocean increased oxygenation and increased nutrient supply from volcanism and continental weathering the co evolution of earth and its biota during this interval has been studied in various contexts on multiple paleocontinents emerging patterns depend on the lens of investigation here we summarize the current state of understanding by reviewing and synthesizing the fossil and sedimentary records recent paleontological studies mainly focused on rhynchonelliform articulated brachiopods bryozoa cephalopods trilobites graptolites echinoderms and reef organisms have documented details of diversification body size increase development of ecosystem complexity and intensification of inter continental dispersal from the late cambrian through late ordovician biomass increased markedly between the early and middle ordovician furthermore diversification rates increase statistically during the mid darriwilian age both globally and regionally coincident with these biotic changes geochemical proxies record significant changes to earth s physical system oceanic temperatures decreased and atmospheric oxygen levels increased to near modern levels in concert with the middle ordovician diversification of shelly fauna anoxic pulses ceased and evidence for deep ocean ventilation prevails in middle ordovician strata furthermore a major middle late ordovician change in oceanic strontium isotopic composition indicates increased weathering of juvenile volcanic rocks and delivery of nutrients to marine settings this multi proxy dataset records near simultaneous changes in fossil rich shallow marine environments during exactly the interval of greatest diversification by integrating biotic and geochemical datasets a clear picture of the co evolution of earth and its biota emerges indicating that the darriwilian was the critical interval facilitating increased capacity of ecosystems we therefore recommend restricting the term gobe to indicate this short interval of rapid diversification and ecosystem change and using ordovician radiation when referencing the sum of diversifications that occurred throughout the ordovician period

time dependent features in tremor spectra abstract harmonic spectral peaks are observed in the tremor spectra of many different volcanoes and in some cases these spectral lines have been seen to change with time this has also been observed for the tremor at the soufriere hills volcano on montserrat west indies where the spectral lines are sometimes seen to glide apart before an explosion we propose a model of repeated triggering of low frequency earthquakes to explain these gliding lines using the relationship t 1 where t and are time and frequency spacing respectively and investigate factors which can affect the observation of these spectral peaks noise and amplitude variation are shown to have little effect on the spectral peaks however the time gap between events must be nearly constant over several events an error with a standard deviation of 2 or less is required for the spectral lines to be observed in the frequency range 0 5 10 hz we can reproduce the gliding spectral lines from a specific tremor episode preceding an explosion by changing t from 1 to 0 31 s over a time period of 12 min using this relationship and an automated event classification analysis program aecap we can monitor t over a long time period the aecap also extracts other seismic parameters such as energy duration and spectral characteristics an initial comparison between low frequency seismic energy and cyclic tilt shows a correlation between the two but this does not hold for later cycles

geochemistry of late ordovician dalmanelloid brachiopods from laurentia testing the effects of paleolatitudinal gradient dalmanelloid brachiopod shells were collected from the upper ordovician lexington formation lower katian of kentucky sheguindah shale middle katian on manitoulin island ontario and the stony

dynamic variation of middle to late ordovician cephalopod provincialism in the northeastern peri gondwana region and its implications abstract middle to late ordovician cephalopod occurrence data from south china and adjacent terranes in the northeastern peri gondwana region are used to define biogeographic provinces several multivariate methods are adopted for biogeographic analysis including cluster analysis non metric multidimensional scaling and network analysis during the middle ordovician three biogeographic provinces in this region are recognized the australia the north china tibet sibumasu nts and the south china altun sa provinces in the late ordovician three provinces with modified geographic ranges may also be recognized as the cephalopods of the tibetan region and sibumasu terrane changed significantly and accordingly they have been included with south china altun to form a south china tarim tibet sibumasu province stts while the other two late ordovician provinces are the australia and the north china provinces the dynamic variation of cephalopod provincialism in the northeastern peri gondwana region may have been controlled by the changing palaeolatitude and differentiated movement of these plates or terranes from the middle through late ordovician

regional differences in pb isotopic compositions of feldspars in plutonic rocks of the northern appalachian mountains u s a and canada a geochemical method of terrane correlation feldspar pb isotopic compositions from paleozoic tonalitic to leucogranitic caledonian plutons from the northern appalachian mountains of the u s a and canada range from nonradiogenic to radiogenic relative to the evolution curve of stacey and kramers 1975 pb isotopic values in the feldspars are generally independent of modal and major and trace element contents of the plutons plutons with the least radiogenic pb isotopic signatures northern group have intruded allochthonous rocks closest to the north american craton and plutons with the most radiogenic pb southern group have intruded avalonian basement feldspars from plutons in the central group have intermediate pb isotopic compositions between the northern and southern groups and do not define an isotopically unique group the predominant source of the felsic magmas was the continental lithosphere as indicated by the general pb isotopic similarity of the plutonic feldspars with either grenville or chain lakes basement in the case of the northern group and with avalonian basement rocks in the case of the southern group the source region for plutons in the central group may have contained a mixture of grenvillian and avalonian components plutons in the northern appalachians are as a group more evolved in their pb isotopic compositions relative to caledonian plutons in the british isles

quantitative analysis of the tremor wavefield at etna volcano italy abstract the properties of volcanic tremor wavefield at mt etna volcano italy are investigated using data from two dense small aperture arrays of short period seismometers deployed on the north and south flank of the volcano spectral analysis shows that most of the seismic energy is associated to several narrow spectral peaks spanning the 1 5 hz frequency band analysis of simultaneous recordings evidences that most of these peaks are common to different sites thus suggesting a source effect as the origin of this energy frequency slowness analyses evidence a complex wavefield where body and surface waves alternatively dominate depending on the frequency band and component of motion taken into account surface waves are found to dominate at frequencies below 1 hz and above 3 hz conversely the 0 8 2 3 hz vertical and radial component wavefields at both arrays exhibit a nondispersive nature with apparent velocities spanning the 1 2 s km range particle motion analysis suggests these arrivals are associated to both p and sv waves inciding at shallow angles at the northern array back azimuths of these waves encompass the whole summit crater area at the southern array back azimuths are instead clustered around a direction pointing about 500 m east of the se crater at frequency around 4 hz the dominant direction of wave propagation at the southern site shifts about 30 w pointing to the bocca nuova voragine craters and concordance of location is found with the source imaged by the northern array the 0 8 2 3 hz transverse component of motion depicts velocities of about 0 5 km s a value which is about three times lower than those associated to the vertical and radial components results from polarization analyses at the two array sites depict the dominance of horizontal linear particle motion oriented transversally with respect to the source direction polarization ellipsoids at the stations of the sparse network all depict a quasi horizontal setting with two exceptions the direction of particle motion is always oriented tangentially to the summit volcanic edifice the origin of the large transverse motion observed at the two array sites is thus attributed to sh waves generated by free surface interaction of waves impinging the concave topography the correlation method is used to derive the dispersion properties of short period 0 5 5 hz rayleigh waves from which the shallow shear wave velocity structures are derived for beneath the two semicircular arrays using a probabilistic approach we invert slowness data measured at the two dense arrays for retrieving source location and extent the joint inversion of slowness data from the two arrays point to different sources this observation is interpreted in terms of ray bending associated to lateral heterogeneity and or strong topographic effects on wave propagation once the propagation effects are taken into account the most probable source locations are associated to a shallow region encompassing the summit craters and the eruptive fissures active at the time of the experiment september 1999

the dynamic evolution of the palaeozoic geography of eastern asia abstract new palaeogeographical reconstructions are presented for eleven time intervals through the palaeozoic of the eastern asia region from the middle cambrian at 510 ma to the end of the permian at 250 ma they centre on the continental blocks of north china south china and annamia indochina and their relationships with northeastern gondwana which was united to form part of pangea from the late carboniferous onwards also shown is the continent of tarim during the lower palaeozoic as well as the hutag uul songliao and khanka jiamasu bureya terranes both of which straddle the russian mongolian and chinese borders today from silurian times onwards we conclude that annamia and south china were united as a single continent throughout the lower palaeozoic and early devonian and were translocated by major strike slip faulting along the northeastern gondwana margin during that period from off afghanistan to outboard of the sibumasu and australian sectors of the superterrane they left the gondwana marginal area together during the lower devonian opening of the palaeotethys ocean but very shortly afterwards they themselves divided into the two separate continental blocks that we recognise today not to reunite until the triassic the various cambrian to permian rocks found in japan largely represent active volcanic arcs which originally lay to the southeast of south china although the carboniferous was more quiescent there the neotethys ocean opened during the permian dividing sibumasu and the tibetan terranes from gondwana and the palaeotethys ocean started to close progressively in the upper palaeozoic as most of the east asian continents and smaller terranes moved towards siberia the positions of the various continents and terranes have been deduced from a mixture of palaeomagnetic and faunal data the positions of large igneous provinces and kimberlites and the need to provide kinematic continuity between maps of successive ages however many uncertainties remain

did cooling oceans trigger ordovician biodiversification evidence from conodont thermometry the ordovician period long considered a supergreenhouse state saw one of the greatest radiations of life in earth9s history previous temperature estimates of up to 70 c have spawned controversial speculation that the oxygen isotopic composition of seawater must have evolved over geological time we present a very different global climate record determined by ion microprobe oxygen isotope analyses of early ordovician silurian conodonts this record shows a steady cooling trend through the early ordovician reaching modern equatorial temperatures that were sustained throughout the middle and late ordovician this favorable climate regime implies not only that the oxygen isotopic composition of ordovician seawater was similar to that of today but also that climate played an overarching role in promoting the unprecedented increases in biodiversity that characterized this period

geology of the hope brook mine newfoundland canada a preserved late proterozoic high sulfidation epithermal gold deposit and its implications for exploration the hope brook gold mine is a high sulfidation epithermal gold deposit hosted by late proterozoic rocks of the northern appalachian avalon zone it is located within the whittle hill sandstone which is intruded by a late proterozoic quartz feldspar porphyry sill dike complex of the roti intrusive suite the deposit 45 t au is enclosed within a zone of hydrothermal alteration 3 km long and up to 400 m wide this zone of alteration is characterized by extensive advanced argillic alteration with pyrophyllite kaolinite andalusite and alunite which is developed mostly in the structural hanging wall of the ore zone and two main stages of massive silicic alteration the first a buff colored stage of massive silicic alteration extends for or 3 km laterally away from the deposit it constitutes a barren to weakly auriferous unit and most likely results from the pervasive acid leaching of the original host s the second stage of gray massive silicic alteration is spatially coincident with gold mineralization and is characterized by vuggy quartz the mineralization consists of several percent of pyrite and lesser amounts of chalcopyrite and bornite and some tennantite with local traces of enargite in addition to au and cu there is a very limited amount of other metals in the deposit although it has anomalously high amounts of sb bi pb and as the ages of altered pre and late ore quartz feldspar porphyry and of an unaltered postore intermediate dike cutting altered rocks bracket the age of mineralization alteration between 578 and 574 ma this temporally and genetically links mineralization alteration and roti intrusive suite plutonism despite a strong spatial relationship between a major fault zone cinq cerf fault zone and gold mineralization the hope brook deposit bears no genetic relationship to major ductile deformation the deposit was formed approximately 150 m y prior to the development of this fault zone the existence of hope brook along with a few mesozoic pueblo viejo paleozoic temora neoproterozoic brewer and paleoproterozoic deposits enaasen highlights the potential for discovery of such au cu intrusion related deposits in older terranes despite their emplacement at high levels in the crust the potential for preservation of such high sulfidation deposits in older terranes may be high if tilting and or burial took place early in the geologic evolution of the host volcano plutonic arc although the nature and distribution of the initial buff silicic stage of alteration are critical indications of a large scale hydrothermal system the ore at hope brook is only localized in rocks displaying the gray colored second silicic stage of alteration consequently the recognition of the two stages of massive silicic alteration was critical in understanding the genesis of the hope brook deposit and constitutes an important exploration tool in discriminating between potentially mineralized and barren zones

controls on syntectonic replacement mineralization in parasitic antiforms haile gold mine carolina slate belt strata bound au ag mo mineralization in the haile gold mine area is hosted by several ellipsoidal pyrite quartz replacement bodies within a laminated phyllite unit that is bounded on both sides by cambrian volcaniclastic schists the orebodies occur within two east northeast trends corresponding to the highly strained limbs of an upright macroscopic f 2 synform and show opposing en echelon distributions along each trend although the orebodies are associated with strata bound and locally stratiform massive pyrite mineralization and have been heterogeneously deformed detailed textural and structural studies strongly suggest that both the silicic orebodies and massive pyrite lenses formed synchronously with early to late d 2 deformation by syntectonic replacement of parasitic doubly plunging antiformal fold hinges ore textures include massive to laminated silicified phyllites in low strain domains silicic mosaic breccias and lensoidal silicic augen within highly strained pyrite sericite schists many fragmental textures previously interpreted as primary in origin resulted from brittle ductile deformation associated with heterogeneous syntectonic alteration a four stage syn d 2 alteration paragenesis involved i fine grained quartz pyrite or k feldspar or molybdenite replacement along bedding and s 2 in some anticlinal fold hinges ii extensive development of steeply dipping thin quartz veins quartz replacement and local mosaic slab breccias along s 2 iii local replacement of quartz and pyrite by intense sericitization within high strain shear zones developed marginal to and crosscutting silicic zones and iv locally extensive medium to coarse grained pyrite or molybdenite replacement along sericitic high strain zones stages ii and iii are separated by a generation of barren massive quartz veins lowgrade gold occurs with stage i silicification but high grade gold is locally associated with stage iv pyritization some remobilization of gold occurred with pyrite dissolution during stage iii sericitization controls on fluid rock interaction at haile reflect shifting patterns of deformation partitioning at different scales where replacement dominantly occurred in progressive shortening domains and selective dissolution occurred in progressive shearing zones the mineralization events were predated by syntectonic feldspar porphyry dikes and postdated by late retrogressed lamprophyric dikes and unmetamorphosed diabase dikes mineralization resulted from hydrothermal alteration by predominantly metamorphic fluids with a possible magmatic contribution syn to postpeak greenschist facies metamorphism during the later stages of taconian orogenesis

gold mineralization in phyllonites at the haile mine south carolina gold mineralization at the haile mine is hosted by a sequence of high strain rocks phyllonites characterized by intense pressure solution reactions including conversion of chlorite to sericite and loss of original quartz the margins of these high strain zones are silicified and pyritized the high strain rocks are themselves mineralized with pyrite and minor molybdenite gold is found in close association with sulfides in both the phyllonites and the silicified zones textural features are used to show that the high strain rocks and the silicified zones arose through alteration during deformation of the hosting tuffaceous argillite the rocks hosting the mineralization are considered to have arisen through initially pure shear dominated deformation with migration of elements released through pressure solution reactions later deformation involved a component of simple shear with influx of fluids from outside the high strain zones anastomozing shear zones of the type seen at the haile mine will exhibit varying fluid flow regimes as they anastomoze with respect to the principal compressive stress some areas will be zones of fluid outflow and dominated by pressure solution whereas elsewhere dilation simple shear and fluid influx will predominate movement of fluid through rock piles in this way may represent a means of leaching and precipitating ore components the recognition that epigenetic gold deposits related to ductile shear zones occur in the southern appalachians is of great importance for exploration in the area because it highlights major fault zones as potential hosts for gold mineralization

a double seismic antenna experiment at teide volcano existence of local seismicity and lack of evidences of volcanic tremor data analyzed in the present work correspond to a 40 days field experiment carried out in teide volcano canary islands spain with two short period small aperture dense seismic antennas in 1994 the objective of this experiment was to detect analyze and locate the local seismicity we analyzed also the background seismic noise to investigate the possible presence of volcanic tremor from a set of 76 events we selected 21 of them in base of their good signal to noise ratio and their possibility to locate their seismic source by using the seismic antennas a visual classification based on the s p time and seismogram shape has permitted to establish three groups of events local seismicity s p time between 3 and 5 s very local earthquakes s p time smaller than 3 s and artificial explosions these earthquakes have been located by applying the zero lag crosscorrelation technique and the inverse ray tracing procedure those earthquakes that were recorded simultaneously by both seismic antennas were also located by intersecting both back azimuths the analysis of the seismicity has revealed that the amount of seismicity in teide volcano is moderate this seismicity could be distributed in three main areas inside the caldera edifice below the teide pico viejo complex in the eastern border of the caldera edifice and offshore of the island at present this activity is the only indicator of the volcano dynamics the analysis of the back ground seismic noise has revealed that at frequencies lower than 2 hz the oceanic load signal is predominant over other signals even over local earthquakes with a magnitude of 2 0 due to this although if in the teide area were present a weak volcanic tremor or other volcanic signals with predominant peaks below 2 hz to observe them would be a very difficult task q 2000 elsevier science b v all rights reserved

pore pressure embrittlement in a volcanic edifice the failure mode of porous rock in compression dilatant or compactant is largely governed by the overlying lithostatic pressure and the pressure of pore fluids within the rock wong solid earth 102 3009 3025 1997 both of which are subject to change in space and time within a volcanic edifice while lithostatic pressure will tend to increase monotonously with depth due to the progressive accumulation of erupted products pore pressures are prone to fluctuations during periods of volcanic unrest for example an increase in pore fluid pressure can result in rock fracture even at depths where the lithostatic pressure would otherwise preclude such dilatant behaviour a process termed pore fluid induced embrittlement we explore this phenomenon through a series of targeted triaxial experiments on typical edifice forming andesites from volcan de colima mexico we first show that increasing pore pressure over a range of timescales on the order of 1 min to 1 day can culminate in brittle failure of otherwise intact rock irrespective of the pore pressure increase rate we record comparable accelerations in acoustic emission and strain prior to macroscopic failure we further show that oscillating pore fluid pressures can cause iterative and cumulative damage ultimately resulting in brittle failure under relatively low effective mean stress conditions we find that macroscopic failure occurs once a critical threshold of damage is surpassed suggesting that only small increases in pore pressure may be necessary to trigger failure in previously damaged rocks finally we observe that inelastic compaction of volcanic rock as we may expect in much of the deep edifice can be overprinted by shear fractures due to this mechanism of embrittlement pore fluid induced embrittlement of edifice rock during volcanic unrest is anticipated to be highest closer to the conduit and as a result may assist in the development of a fractured halo zone surrounding the conduit potentially explaining commonly observed near conduit outgassing at many active volcanoes further rock embrittlement at depth may create transient outgassing pathways by linking fracture networks near the edifice to larger scale regional fault systems our experimental results affirm that pore pressure fluctuations associated with volcanic unrest may play a crucial role in dictating the evolution of a volcanic system

confirmation of the carolina slate belt as an exotic terrane an assemblage of middle cambrian atlantic faunal province trilobites has been found in the rocks of the carolina slate belt near batesburg south carolina geologic and paleomagnetic data suggest that the carolina slate belt and the adjacent charlotte belt constitute an exotic terrane that was accreted to north america in early to middle paleozoic time

paleo environmental changes during the middle late ordovician transition on the yangtze platform south china and their ecological implications abstract rocks of darriwilian and sandbian age middle late ordovician record the extraordinary peak of the great ordovician biodiversification event gobe and significant global environmental changes to track paleo environmental changes through this critical time we have analyzed iron speciation trace elements and total organic carbon in samples of the miaopo formation from an intra shelf basin in south china the results reveal moderate primary productivity and possible fluctuations in benthic redox upwelling during marine transgression is thought to have increased the availability of nutrients in surface waters sustaining the biological pump enhanced export of organic matter would have consumed dissolved oxygen at depth driving the system toward anoxia however it is also possible for deep water renewal events to transfer more dissolved oxygen into the bottom water those proxies suggests high primary productivity and varying sea level global and local not benthic anoxia as the driver of accumulated black shale thus the local marine ecosystem thrived in this oxic intra shelf basin challenging the preexisting paradox that the high diversity community flourished in an oxygen depleted environment

observations of loma prieta aftershocks from a dense array in sunnyvale california a small aperture 300 m four station array was deployed in sunnyvale california for 5 days to record aftershocks of the loma prieta earthquake of october 1989 the purpose of the array was to study the seismic response of the alluvium filled santa clara valley and the role of surface waves in the seismic shaking of sedimentary basins strong motion records of the loma prieta mainshock indicate that surface waves produced the peak velocities and displacements at some sites in the santa clara valley we use the recordings from the dense array to determine the apparent velocity and azimuth of propagation for various arrivals in the seismograms of four aftershocks with magnitudes between 3 6 and 4 4 apparent velocities are generally observed to decrease with increasing time after the s wave in the seismograms phases arriving less than about 8 sec after the s wave have apparent velocities comparable to the s wave and appear to be body waves multiply reflected under the receiver site or reflected by crustal interfaces for times 10 to 30 sec after the direct s wave we observe long period 1 to 6 sec arrivals with apparent velocities decreasing from 2 5 to 0 8 km sec we interpret these arrivals to be surface waves and conclude that these surface waves produce the long duration of shaking observed on the aftershock records much of the energy in the 40 sec after the s wave is coming approximately from the direction of the source although some arrivals have backazimuths as much as 60 different from the backazimuths to the epicenters two of the aftershocks show arrivals coming from 30 to 40 more easterly than the epicenters this energy may have been scattered from outcrops along the southeastern edge of the basin in contrast the deepest aftershock studied d 17 km displays later arrivals with backazimuths 30 to 40 more westerly than the epicenter a distinct arrival for one of the aftershocks propagates from the southwest possibly scattered from the western edge of the basin synthetic seismograms derived from a plane layered crustal model do not produce the long period love waves observed in the waveforms of the ml 4 4 aftershock these love waves may be generated by the conversion of incident s waves or rayleigh waves near the edge of the basin

first documentation of middle ordovician warm water carbonates in the mount jolmo lungma mount everest area southern xizang tibet china and its paleogeographic implications abstract a middle ordovician limestone succession representing part of the alai formation middle part of the chiatsun group of the himalayan orogenic belt is well exposed at jiacun section in nyalam county to the west of the mount jolmo lungma mount everest southern xizang tibet china the succession though reported previously has yet to be investigated in detail especially in the aspects of precise dating stratigraphic correlation and its paleogeographical affinities in this contribution we document for the first time the conodont biostratigraphy carbon isotope chemostratigraphy and microfacies analyses of this carbonate succession the conodont fauna indicates a middle darriwilian middle ordovician age corresponding to the histiodella holodentata biochronozone the carbon isotope records have shown minor fluctuations of 13c values with only a small negative carbon excursion in the lower part the microfacies analysis has resulted in the identification of seven microfacies including micritic limestone lithoclastic packstone non skeletal grainstone bioclastic limestone bioclastic lithoclastic limestone bioclastic lithoclastic oncoid limestone and bioclastic lithoclastic oncoid ooid limestone from thin sections fragments of crinoids brachiopods gastropods trilobites bryozoans and calcareous algae are identified abundant lithoclasts cortoids peloids oncoids and ooids together with the occurrences of dasyclad algae and hardgrounds are also recognized indicating a shallow and warm water marine environment and a likely tropical or subtropical affinity comparison of the lithofacies and faunas of this limestone succession of the alai formation with coeval strata in the zanskar spiti area northern india nepal bhutan canning basin west australia lhasa qiangtang sibumasu tarim and north china suggests that during the darriwilian these regions or terranes may have possessed a warm water marine environment and were located in low latitudinal zones it seems likely that this region of the northeastern gondwana and peri gondwana was protected from substantial influx of cool water currents derived from high latitudes at that time

array analysis using circular wave front geometry an application to locate the nearby seismo volcanic source summary the zero lag cross correlation technique used for array analysis in the hypothesis of plane waves has been modified to allow the wave front to be circular synthetic tests have been performed to check the capability of the method which returns the input test data when the source array distances are not greater than two or three times the array aperture for this distance range the method furnishes an estimate of the apparent velocity and the epicentral coordinates of the source for more distant sources the method becomes equivalent to that based on the planar wave approximation which gives an estimate of the backazimuth to the source and the apparent velocity the method has been applied to seismic data recorded at the active volcano located at deception island antarctica 35 volcanic long period events occurring in a small swarm were selected results show that the epicentres are close to the array between 0 4 and 2 km and aligned in a sw direction in agreement with one of the main directions of the fracture system of deception volcano

volcanic rock hosted gold and base metal mineralization associated with neoproterozoic early paleozoic back arc extension in the carolina terrane southern appalachian piedmont volcanogenic mineral deposits in the carolina terrane southern appalachian piedmont include kuroko type polymetallic massive sulfide deposits and disseminated gold pyrite deposits associated with propylitic silicic argillic and advanced argillic alteration host rocks are metavolcaniclastic and metaepiclastic rocks of a neoproterozoic early cambrian magmatic arc the favorable gold horizon is the transition from a lower succession of andesitic and rhyolitic pyroclastic rocks with basal mafic lavas to an upper sequence of epiclastic sedimentary units and minor lava and ash flows kuroko type deposits are associated with mafic to bimodal volcanic rocks in the upper sequence whole rock oxygen isotope analyses indicate that gold mineralization is associated with a transition from hydrothermal systems dominated by isotopically relatively light 18o 6 to 10 waters typical of high latitude subaerial systems to seawater 18o 0 plots of 18o vs sio2 of the host rocks show a compositional gap associated with mineralization at the subaerial to submarine transition values of 18o for the hydrothermal waters lithostratigraphic analyses and tectonic models of the carolina terrane demonstrate that mineralization coincided with extension in a rifted arc

the effect of the galapagos islands on the equatorial pacific cold tongue abstract a reduced gravity ocean general circulation model of the tropical pacific ocean is used to determine potential improvements to the simulated equatorial pacific cold tongue region through choices in horizontal resolution and coastline geometry in particular for the galapagos islands four simulations are performed with identical climatological forcing results are compared between model grids with and without the galapagos islands with coarse and fine resolutions it is found that properly including the galapagos islands results in the obstruction of the equatorial undercurrent euc which leads to improvements in the simulated spatial structure of the cold tongue including a basinwide warming of up to 2 c in the east central pacific the obstruction of the euc is directly related to the improvements east of the galapagos islands and for the basinwide reduction of the tropical cold bias through an equatorial dynamical adjustment the pattern of sst warming resulting from the inclusion of the

high dependence of ordovician ocean surface circulation on atmospheric co2 levels abstract life on earth radiated dramatically during the ordovician period 485 444 ma at all taxonomic levels during an evolutionary episode known as the great ordovician biodiversification event abundant scientific literature has documented the pattern of biodiversification for numerous organism groups however fully understanding this event also requires detailed knowledge about the spatial distribution of the organisms the full potential of the palaeobiodiversity patterns remains under explored due to the lack of knowledge about past ocean circulation surface circulation significantly conditions the dispersal of organisms in creating preferential ocean migration pathways or in contrast by isolating specific regions and thus establishing major physical barriers these uncertainties persist because neither direct observational data nor proxy data independent from the fossil record are available to reconstruct the ocean surface circulation here we present new maps of ordovician ocean surface circulation based on simulations using the general circulation model foam this is a coupled ocean atmosphere general circulation model and represents a methodological improvement over previously published work in addition we use the most up to date palaeogeographical reconstructions to increase compatibility with recent palaeontological databases in providing clear synthetic maps of ocean surface circulation in addition to raw model outputs we aim to facilitate data model comparison to assist in interpretation of palaeontological datasets and to promote renewed discussion about ordovician biogeography finally we investigate the sensitivity of the circulation pattern to the atmospheric co2 content which remains poorly constrained in the ordovician potentially ranging from more than 15 times the preindustrial atmospheric co2 level pal to 5 pal maps are systematically constructed for a high 16 pal medium 8 pal and low 4 pal co2 value we show that the circulation pattern is much more sensitive to co2 than previously suggested

biosedimentological features of major microbe metazoan transitions mmts from precambrian to cenozoic abstract biotic activities are involved in almost all sedimentation processes throughout the evolutionary history of life on our planet however deep time organism induced sedimentation and biosedimentary records remain unclear in terms of lithologic types strata stacking patterns and possible controlling factors we document biosedimentary features of major transitions from microbe dominated switching to metazoan dominated biosedimentary systems based on the global distributions of both microbial and metazoan carbonates through precambrian to phanerozoic times with emphasis on sedimentary records from china the compilation of 150 and 180 well documented metazoan and microbial reefs respectively from china reveals that metazoan reefs proliferated during the middle ordovician middle devonian and middle permian whereas microbial reefs were well developed during the cambrian late devonian and early middle triassic plus a moderate development during the early silurian these stratigraphic abundances of metazoan and microbial carbonates of china generally match the global patterns the updated variation trends of microbial and metazoan carbonates throughout the late precambrian and phanerozoic reveal that there were five major microbe metazoan transitions mmts the late ediacaran the cambrian and the aftermaths of the mass extinctions of the end ordovician late devonian and end permian the late ediacaran mmt began with microbe dominated oceans with occasional occurrences of metazoans the presence of cloudina dominated reefs in the latest ediacaran marks the completion of the switching of this microbe dominated depositional system into a metazoan dominated system the cambrian saw the expansion of skeletal microbes i e epiphyton renalcis in the oceans and the stratigraphic successions yield the most diverse biosedimentary deposits and or structures of the entire phanerozoic the cambrian mmt was the longest microbial metazoan alternation period and is marked by two metazoan occurrence peaks marked by dominance of abundant archaeocyath buildups during its epoch 2 and by maceriate and lithistid sponge reefs during the late furongian epoch the early silurian in china saw the deposition of a thick suite of organic rich black shales followed by alternations of microbe rich sediments oil shales and metazoan bearing deposits which are replaced by microbial and metazoan reefs during the late early silurian the late devonian mmt started during the late frasnian and persisted into the early mississippian and thus extended slightly longer than the aftermath of the frasnian famennian extinction interval alternating occurrences of microbial and metazoan reefs characterize this late devonian mmt almost all microbe mediated sediments structures observed in the cambrian mmt reoccurred in the aftermath of the end permian mass extinction during the early middle triassic mmt suggesting high similarities between those two mmts cambrian and early middle triassic mmts also share comparable carbon and sulfur isotopic perturbations warming regimes and generally oxygen deficient seawaters some of these environmental and climatic extremes may also occur during other mmts but they usually did not occur synchronously most mmts seem to have undergone four developmental stages they initiated as microbe dominated successions stage a and then were characterized by alternations of microbe dominated and of metazoan bearing or bioturbated successions stage b both microbial and metazoan reefs co occurred during stage c and a dominance of metazoan reefs marks the development of stage d ediacaran and cambrian mmts seem to have undergone the first three development stages whereas the three post extinction mmts experienced the full set of stages a d corresponding to metazoan survival initial recovery and full recovery the majority of volatile rich large igneous provinces lips coupled with intensive acidification events anoxia and global warming regimes took place during the mesozoic cenozoic however microbe dominated sediments were only widely deposited during the early triassic and greatly declined after that time therefore it seems that microbial abundance in mmts may not be directly related to these extreme lip events this is probably because a primary source of food for the metazoans might have shifted to phytoplankton e g coccoliths dinoflagellates and radiolarians in the marine waters since the triassic certainly the pre mesozoic oceans were not dominated by phytoplankton perturbations in the carbon isotope record characterize all mmts and thus may be reliable proxies indicating mmt biosedimentary systems

the amazon laurentian connection as viewed from the middle proterozoic rocks in the central andes western bolivia and northern chile middle proterozoic rocks underlying the andes in western bolivia western argentina and northern chile and early proterozoic rocks of the arequipa massif in southern peru form the arequipa antofalla craton these rocks are discontinuously exposed beneath mesozoic and cenozoic rocks but abundant crystalline clasts in tertiary sedimentary rocks in the western altiplano allow indirect samples of the craton near berenguela western bolivia the oligocene and miocene mauri formation contains boulders of granodiorite augen gneiss 1171 20 ma and 1158 12 ma u pb zircon quartzose gneiss and granofels that are inferred to have arkosic protoliths 1100 ma source region u pb zircon quartzofeldspathic and mafic orthogneisses that have amphibolite and granulite facies metamorphic mineral assemblages 1080 ma metamorphism u pb zircon and undeformed granitic rocks of phanerozoic age the middle proterozoic crystalline rocks from berenguela and elsewhere in western bolivia and from the middle proterozoic belen schist in northern chile generally have present day low 206pb 204pb 15 57 and elevated 208pb 204pb 37 2 to 50 7 indicative of high time averaged th u values the middle proterozoic rocks in general have higher present day 206pb 204pb values than those of the early proterozoic rocks of the arequipa massif 206pb 204pb between 16 1 and 17 1 but lower than rocks of the southern arequipa antofalla craton 206pb 204pb 18 5 a difference inferred to reflect grenvillian granulite metamorphism the pb isotopic compositions for the various proterozoic rocks lie on common pb isotopic growth curves implying that pb incorporated in rocks composing the arequipa antofalla craton was extracted from a similar evolving pb isotopic reservoir evidently the craton has been a coherent terrane since the middle proterozoic moreover the pb isotopic compositions for the arequipa antofalla craton overlap those of the amazon craton thereby supporting a link between these cratons and seemingly precluding part of the arequipa antofalla craton from being a detached fragment of another craton such as eastern laurentia which has been characterized by a different u pb history pb isotopic compositions for the arequipa antofalla craton are furthermore distinct from those of the proterozoic basement in the precordillera terrane western argentina indicating a pb isotopic and presumably a tectonic boundary between them the pb isotopic compositions for the precordillera basement are similar to those of eastern laurentia and support other data indicating that these rocks are a detached fragment of north america finally the distinct pb isotopic evolution history of the arequipa antofalla craton and eastern laurentia require minor modification to tectonic models linking eastern north america scotland to the oroclinal bend in western south america

seismovolcanic signals at deception island volcano antarctica wave field analysis and source modeling the seismovolcanic signals associated with the volcanic activity of deception island antarctica recorded during three antarctic summers 1994 1995 1995 1996 and 1996 1997 are analyzed using a dense small aperture 500 m seismic array the visual and spectral classification of the seismic events shows the existence of long period and hybrid isolated seismic events and of low frequency quasi monochromatic and spasmodic continuous tremors all spectra have the highest amplitudes in the frequency band between 1 and 4 hz while hybrids and spasmodic tremors have also significant amplitudes in the high frequency band 4 10 hz the array analysis indicates that almost all the well correlated low frequency signals share similar array parameters slowness and back azimuth and have the same source area close to the array site the polarization analysis shows that phases at high frequency are mostly composed of p waves and those phases dominated by low frequencies can be interpreted as surface waves no clear shear waves are evidenced from the energy evaluation we have found that the reduced displacement values for surface and body waves are confined in a narrow interval volcano tectonic seismicity is located close to the array at a depth shallower than 1 km the wave field properties of the seismovolcanic signals allow us to assume a unique source model a shallow resonating fluid filled crack system at a depth of some hundreds of meters all of the seismic activity is interpreted as the response of a reasonably stable stationary geothermal process the differences observed in the back azimuth between low and high frequencies are a near field effect a few episodes of the degassification process in an open conduit were observed and modeled with a simple organ pipe

destruction of a lava dome observed with photogrammetry acoustic and seismic sensors at volcan de colima mexico abstract during the period december 2016 to march 2017 the lava dome emplaced in september november 2016 at volcan de colima was partially destroyed by vulcanian explosions in particular 10 moderate large explosions were observed with heights of 2 6 8 km from the crater and with the generation of pyroclastic density currents pdcs shock waves and ballistics the acoustic and seismic energies were calculated for each event the values found are similar to other moderate large vulcanian explosions observed at other volcanoes the maximum value of seismic energy was of 1 6 109 j and for acoustic energy 7 5 108 j these values were compared with the height of the eruptive column which resulted in a poor correlation for the acoustic signals the reduced pressure was greater than that commonly reported for vulcanian explosions elsewhere using the time or arrival of the acoustic and seismic signals the depth of the acoustic seismic source was estimated at

the methodology of quantification of volcanic explosions from broad band seismic signals and its application to the 2004 2005 explosions at volcan de colima mexico summary a methodology is proposed for the quantification of volcanic explosions based on three parameters derived from broad band seismic signals the counter force of the eruption f the power of the explosion p and the duration of the upward movement of the gas slug in the conduit to the free surface of magma d this methodology was applied to the 2004 2005 sequence of

volcanic tremor and local earthquakes at copahue volcanic complex southern andes argentina abstract in the present paper we describe the results of a seismic field survey carried out at copahue volcano southern andes argentina using a small aperture dense seismic antenna copahue volcano is an active volcano that exhibited a few phreatic eruptions in the last 20 years the aim of this experiment was to record and classify the background seismic activity of this volcanic area and locate the sources of local earthquakes and volcanic tremor data consist of several volcano tectonic vt earthquakes and many samples of back ground seismic noise we use both ordinary spectral and multi spectral techniques to measure the spectral content and an array technique zero lag cross correlation technique to measure the back azimuth and apparent slowness of the signals propagating across the array we locate vt earthquakes using a procedure based on the estimate of slowness vector components and s p time vt events are located mainly along the border of the caviahue caldera lake positioned at the south east of copahue volcano in a depth interval of 1 3 km below the surface the background noise shows the presence of many transients with high correlation among the array stations in the frequency band centered at 2 5 hz these transients are superimposed to an uncorrelated background seismic signal array solutions for these transients show a predominant slowness vector pointing to the exploited geothermal field of las maquinitas and copahue village located about 6 km north of the array site we interpret this coherent signal as a tremor generated by the activity of the geothermal field

lead isotope analyses of leached feldspars constraints on the early crustal history of the grenville orogen abstract lead isotopic data on leached k feldspars plagioclases and muscovite provide constraints on the premetamorphic evolution of the grenville orogen in ontario and new york a boundary between reworked archean crust to the northwest and new mantle derived crust generated during mid proterozoic times to the southeast is identified within the northern portion of the gneiss belt of ontario the identification of juvenile mid proterozoic crust at the southeastern margin of the orogen is consistent with previous investigations based on neodymium model ages however near the grenville front lead isotopes indicate the presence of reworked archean crust rather than primary early proterozoic crust postulated on the basis of neodymium model ages this discrepancy between the lead and neodymium isotopic terranes underscores the necessity of using a multidisciplinary approach to identify possible terrane boundaries only through a combination of the lead with neodymium isotopes is it possible to distinguish between crust that formed during a single major orogenic cycle and crust that represents a mixture of old with new mantle derived material the combined neodymium and lead data imply that the grenville orogen in ontario consists essentially of reworked archean crust and juvenile mantle derived material generated around 1 5 ga the grenville orogen involved archean crust that was depleted in thorium and uranium several hundred ma before high grade metamorphism at ca 1 1 ga such a depletion may have a significant impact on the geotherm achieved during orogeny and may explain the lower metamorphic thermal gradients observed for the gneiss belt

the early middle ordovician graptolite genus azygograptus in south china new material and paleogeographic implications abstract this study presents a new analysis of three species of the ordovician graptolite genus azygograptus nicholson lapworth from the wenxiakou section in the zhongxiang area of hubei province the paleogeographic occurrences of the genus within south china were plotted on an up to date paleogeographic map based on a revised data set of graptolite occurrences from 68 localities compiled by the online geobiodiversity database gbdb the paleogeographic distribution of azygograptus follows a nearshore offshore trend and the taxonomic diversity of azygograptus is higher in nearshore high energy environments than in offshore low energy environments however graptolites also gathered in deeper water environments surrounding oldlands partly due to the high nutrient inputs and rapid deposition azygograptus is found not only in high latitude cold water regions as endemic taxa but also in low latitude regions oceanic circulation may account for the rapid dispersal of azygograptus from high latitude regions such as britain and scandinavia to low latitude regions such as south china eventually resulting in their observed paleogeographic distribution

early ordovician lithistid sponge calathium reefs on the yangtze platform and their paleoceanographic implications lithistid sponge calathium microbial reefs were widespread on the yangtze platform during the early ordovician and are well studied however the biological affinity and the role of calathium in these reefs have remained unclear up to now we document lithistid sponge calathium reefs from the upper hunghuayuan formation early floian at huanghuachang in hubei south china these reefs have a three dimensional skeletal framework that is mostly produced by calathium and lithistid sponges calathium had a critical role in reef construction as demonstrated by well developed lateral outgrowths which connected individuals of the same species and with lithistid sponges bryozoans stromatoporoids and microbial components were secondary reef builders morphological constructional and functional analyses provide evidence that calathium was a sponge grade metazoan rather than a receptaculitid alga as previously thought at the dawn of the ordovician radiation these small scaled patch reefs thus represent the initial rebound of metazoan dominated reefs after the late early cambrian archaeocyath reef crisis gradual global cooling through the early ordovician may have been a key driver for the return of metazoan reefs

array analysis of the seismic wavefield of long period events and volcanic tremor at arenal volcano costa rica we use wavefield decomposition methods time domain crosscorrelation and frequency domain music to analyze seismic data recorded by a dense small aperture array located 2 km west of arenal volcano costa rica and operated during 2 5 days the recorded wavefield is dominated by harmonic tremor and includes also spasmodic tremor and long period lp events we find that the initial stages of lp events are characterized by three different wave arrivals these arrivals propagate with similar back azimuths pointing to the volcano summit 80 n and increasing apparent slownesses of 0 4 1 1 and 1 7 s km spasmodic tremors can not be regarded as coherent signals on the contrary harmonic tremors are highly coherent characterized by the stability of the apparent slowness vector estimates apparent slownesses lay in the range 1 2 s km back azimuths point in the general direction of the volcano but with a large variability 40 120 n nevertheless there are long term variations and evidences of multiple simultaneous components in the harmonic tremor wavefield these observations suggest that lp events and tremor are generated in a shallow source area near the volcano summit although they do not share exactly the same source region or source processes the tremor source is located in the shallowest part of the plumbing system beneath the lava crust this dynamic region is subject to complex fluctuations of the physical conditions degassing events at different locations of this region might generate variable seismic radiation patterns the effects of topography and heterogeneous shallow structure of the volcano may amplify these variations and produce the wide directional span observed for volcanic tremor on the other hand the lp source seems to be more repeatable lp events are likely triggered by fragmentation of the fluid flow in a slightly deeper portion of the volcanic conduits

swarms of microearthquakes associated with the 2005 vulcanian explosion sequence at volcan de colima mexico summary the swarms of microearthquakes that appeared at volcan de colima mexico before and after its large 2005 vulcanian explosions are discussed the study of 966 microearthquakes is based on the seismic records of short period seismic station ezv4 situated at a distance of 1 7 km from the crater three samples of microearthquakes were selected the seismic records associated with a single 2005 september 16 large explosion and the seismic records associated with two sequences of large explosions the 2005 march 10 and 13 explosions and the 2005 may 30 and june 2 5 and 7 explosions these explosions were seven of 15 large explosions e 1011 j that occurred during the 2005 explosive sequence the microearthquake waveforms were identified as the records of rockfalls and microexplosions the explosive microearthquakes represent from 84 to 89 per cent of the total number of microearthquakes with the readable waveforms the dominant frequencies of the explosive microearthquakes were 2 8 hz for the 2005 march explosion sequence and 2005 september 16 explosion and 1 3 2 0 and 2 8 hz for the 2005 may june explosion sequence energy of microexplosions that generated the microearthquake waveforms ranged from 104 to 7 107 j the force component corresponding to the largest microexplosive events was estimated at a level from 3 1 107 to 3 6 108 n the appearance of microearthquakes before large volcanic explosions and the sharp increase in their rate of appearance some hours before an explosion makes them a useful instrument for volcano monitoring

generation of vulcanian activity and long period seismicity at volcan de colima mexico abstract during the current episode which commenced in 1998 activity at volcan de colima has been characterised by daily vulcanian events several effusive phases and a number of larger dome destroying explosions the upper edifice comprises of an intricate array of fractures and within this system variations in the magma ascent rate rheology and volatile contents complete a complexity which controls the style of activity subtle variations in one or more of these factors can trigger a transition a model is presented of the vulcanian explosion mechanism which is reflected in the associated seismicity first the breaching of an impermeable cap and the initial gas loss after the rupture low frequency signal followed by fragmentation high frequency signal in 2005 a series of larger vulcanian explosions associated with ascending magma represent the period of activity with the highest production rate in recent years pyroclastic flows were produced by column collapse with the absence of vesicularity amongst the products pointing to a deep source of gas driving the eruption the appearance of swarms of long period lp events associated with the explosions provided a great opportunity for analysis and an insight into the processes within the fracture system which control the eruptive style cross correlation of the lp waveforms produced a series of ten families which reappeared in subsequent swarms suggesting a consistent source brittle fracture associated with the enhanced stain rate found along the conduit margins is suggested as the source of this seismicity this is supported by a linear relationship between log event rate and relative amplitude of the events within each swarm an analysis of the temporal distribution of lp events revealed a variation in conditions between swarms for some swarms the conditions within the fracture system meant that a conflict between the processes associated with magma ascent was revealed whilst for others it was a situation of failure and backup which can be interpreted as the failing and activation of different fractures within the upper edifice

late ordovician obliquity forced glacio eustasy recorded in the yangtze block south china abstract a high precision time framework is critical for improving our understanding of three major events the late ordovician mass extinction the hirnantian glaciation and the hirnantian isotopic carbon excursion hice in the present study we conducted detailed cyclostratigraphic analysis of a high resolution 1 2 cm intervals anhysteretic remanent magnetization series obtained from the wanhe section in south china covering the lower katian through hirnantian power spectra and derived average spectral misfit results show that the section records the ensemble of milankovitch cycles with 405 kyr long eccentricity 93 125 kyr short eccentricity 33 8 kyr main obliquity and 17 22 kyr precession periods the obliquity period of 33 8 0 46 kyr indicates a precession constant k of 57 19 0 53 arcsec yr a length of day of 22 37 0 12 h and an earth moon distance of 375 330 722 km vs 384 000 km today during the late ordovician 445 ma the ratios of obliquity band power to total power reveal periodicities of 1 32 myr for the s4 s3 term and 173 4 kyr for the s3 s6 term aided by the highly fluctuating magnetic susceptibility ms we recognized a series of 1 32 myr obliquity forced glacio eustatic cycles with three intervals of sea level rise and climate warming trend characterized by high ms values and two episodes of sea level fall and climate cooling trend before the hirnantian the 405 kyr and subsequent 33 8 kyr calibrations produce an 7 36 myr floating astronomical time scale fats for the studied succession indicating that the estimated durations for the hirnantian stage the worldwide hirnantian glaciation and the first and second phases of the late ordovician mass extinction were 1225 kyr 830 kyr 440 kyr and 540 kyr respectively this work provides a reliable high resolution time framework for further investigation of the major geological events occurred in the late ordovician and improves our knowledge of solar system behaviour and earth moon history during that period

relocalization and focal mechanisms of volcano tectonic events at colima volcano colima mexico colima volcano 19 51 n 103 62 w 3860 m a s l in western mexico is well known for its frequent activity along with nearby nevado de colima and cantaro volcanoes are part of a volcanic complex rising in the middle of the colima graben a structure on the margin of the jalisco block some one hundred km from the middle america trench the activity of colima volcano is varied and usually accompanied by intense seismicity mostly of volcano tectonic events to investigate several aspects of these earthquakes we analyzed events recorded by the seismological network of colima during the outbursts of 1998 1999 2005 and 2009 those periods of varying intensity lasted from several months to several weeks before and after a significant explosive event the hypocenters located with standard methods appear in a broad region around the volcanic complex to obtain a more accurate location of these events we relocated the hypocenters using the method of double differences a set of 1191 relocated events was obtained providing improved locations which show hypocenters clustered under the edifice of colima volcano and do not seem to be related to any particular geological feature and therefore represent the volume stressed by magma s intrusion the focal mechanism of the relocated events shows a variety of fault plane orientations with a majority indicating dip slip faulting

u pb zircon ages and pb isotope geochemistry of gold deposits in the carolina slate belt of south carolina volcanic rocks of the persimmon fork formation host the largest known gold mines of the carolina slate belt u pb shrimp zircon ages have been obtained from rocks closely associated with pyrite enargite gold deposits at brewer quartz topaz rhyolite breccia from the argillic alteration zone in the brewer pit and felsic ash flow tuff from the quartz sericite alteration zone from the disseminated and semimassive pyrite gold deposits at haile crystal lithic rhyolitic ash flow tuffs from the champion pit and from the ridgeway deposit felsic ash flow tuff from the stratigraphic host of the north pit gold deposit generally the zircons are fine grained fractured and contain crystal imperfections corrosion inclusions and pits 206 pb 238 u zircon spot ages for all deposits span a wide range mostly from 400 to 760 ma inclusions and cores indicative of inherited domains in the zircons were not found and only a few analyses range from 1 1 to 1 8 ga a distinct xenocrystic zircon population was not identified the 206 pb 238 u weighted age averages of zircon indicate the following crystallization dates for the volcanic and volcaniclastic rocks closely associated with the gold deposits 550 3 ma for brewer 553 2 ma for haile and 556 2 ma for the ridgeway deposit these zircon crystallization ages represent close estimates of the age of the original gold mineralizing events younger zircon spot ages can be attributed to the effects of paleozoic regional metamorphism pb isotope compositions of sulfide minerals galena pyrite enargite sphalerite chalcopyrite and molybdenite and silicate minerals k feldspar and sericite in the gold deposits help to constrain the sources of fluids and metals during the mineralizing events the deposits are pyrite rich containing multiple generations of pyrite including early crystallized pyrite that is closely associated with the original gold mineralizing event as well as recrystallized pyrite formed in response to paleozoic metamorphism pb isotope compositions of pyrite span a wide range including the most radiogenic values for the sulfides galena and k feldspar are not abundant but where present they are typically the least radiogenic minerals galena has a limited range of pb isotope compositions that are representative of the gold deposits as a group 206 pb 204 pb 18 020 18 326 207 pb 204 pb 15 550 15 639 208 pb 204 pb 37 605 38 286 values of 207 pb 204 pb straddle the average crustal pb growth curve consistent with contributions involving the mantle and continental crust whole rock pb isotope compositions of volcanic and volcaniclastic rocks of the persimmon fork formation nearly match the range for sulfides in the gold deposits subtle regional contrasts in pb isotope compositions exist among the deposits sulfide minerals from barite hill e g galena 206 pb 204 pb 206 pb 204 pb 18 169 haile 206 pb 204 pb 18 233 and brewer 206 pb 204 pb 18 311 in northern south carolina because pb isotope compositions of basement rocks from grenville massifs in the southern appalachians and sulfide minerals from the gold deposits do not match a direct genetic connection cannot be established diversity in values of 206 pb 204 pb and the relatively high values of 207 pb 204 pb suggest that the deposits evolved adjacent to or closely related to continental blocks perhaps linked to a back arc tectonic setting among potential younger analogues of the slate belt gold deposits are the sulfide deposits of the okinawa trough in the western pacific mantle derived isotopic contributions were more important at barite hill in southern south carolina the least radiogenic among the deposits where oceanic crust had developed than at brewer haile and ridgeway in northern south carolina where rifting thinned the continental crust

the jurassic danba hypozonal orogenic gold deposit western china indirect derivation from fertile mantle lithosphere metasomatized during neoproterozoic subduction the genesis of hypozonal orogenic gold deposits is highly controversial with both crustal metamorphic fluids and variously derived sub crustal fluids suggested as fluid and metal sources the lower jurassic danba gold deposit a rare phanerozoic hypozonal orogenic gold deposit on the western margin of the yangtze craton china provides an opportunity to resolve these controversies danba is characterized by biotite amphibole alteration and pyrrhotite dominant ore assemblages formed at 500 600 c the 34s values of ore related pyrrhotite range from 3 1 to 9 9 in sharp contrast to those of syn sedimentary pyrrhotite from devonian host rocks which are between 6 8 and 9 5 the pb isotope compositions of ore related pyrrhotite with 206pb 204pb 17 85 18 25 and 207pb 204pb 15 48 15 67 are less radiogenic and more variable than those of unaltered host rocks these differences combined with the hypozonal feature of the deposit indicate that ore metals and sulfur were derived from a sub crustal rather than a local crustal source the pge patterns of ore related pyrrhotites are similar to those of sulfides in baltic mantle lithosphere that was metasomatized by aqueous fluids in terms of marked enrichment of pd and ru but significantly differ from those of magmatic intrusions and related magmatic hydrothermal deposits this suggests that the metals that formed the danba deposit were transported via aqueous fluid from metasomatized mantle lithosphere rather than from a magmatic source the 18o of mantle fluid calculated from hydrothermal quartz and biotite ranges from 10 to 12 the anomalously high s and o isotope ratios and variable pb isotope ratios together with pge data support a model in which the inferred mantle lithosphere source was significantly hydrated metasomatized and fertilized by fluid derived from subducted oceanic sediments with elevated 34s and 18o values geological evidence suggests that this subduction event was neoproterozoic in age this study defines a model in which hydrated and metasomatized mantle lithosphere was formed during early subduction but it was over 500 million years later during later lower jurassic asthenosphere upwelling that metal and sulfur rich fluid was released into the crust to form the danba gold deposit

thermal imaging and analysis of short lived vulcanian explosions at volcan de colima mexico abstract vulcanian explosions present a major hazard at many active volcanoes but they also provide useful insights into the underlying behaviour of the volcanic system and therefore require close monitoring thermal infrared cameras are an effective tool for imaging vulcanian explosion plumes since they capture detailed temperature information and can reveal the internal dynamics of the plume forming explosions high spatial resolution thermal images of 200 small to moderate sized vulcanian explosions from the summit crater of volcan de colima mexico recorded between 2006 and 2011 were analysed to distinguish different event types and develop an explosion classification scheme explosions display a broad spectrum of sizes and characteristics ranging between two typical end members large impulsive events producing rapidly ascending explosion plumes up to heights of 600 1600 m above the crater rim and small diffusive events with plumes restricted to heights 1 to 29 m s 1 a time series of thermal imagery throughout the period 2006 2011 reveals a weak relationship between apparent plume temperatures and lava dome extrusion with the highest explosion temperatures coinciding with the onset of dome growth in early 2007 temporal variations in the source locations of explosions across the summit crater are also identified and appear to show a close relationship to the patterns of lava dome growth and thermal evolution with explosion source locations associated with the highest temperature thermal features

vulcanian explosions in the process of building destruction of the lava dome of andesitic volcano insight from the seismic signals recorded at volcan de colima mexico abstract the seismic signals associated with the vulcanian explosive events at volcan de colima mexico during its 1998 2014 eruption were discriminated into three types according the waveforms of their initial phases this classification includes about 85 90 of all seismic signals associated with explosive events it was shown that the classification of the explosive seismic signals gave a useful tool for analysis of the eruption development analysis was performed for two 6 month stages of the eruption the 2003 post effusive stage culminated with large explosions and the 2007 co effusive stage during the beginning of new lava dome growth in the crater of the volcano the predominance 95 of the type 1 and 3 events with low frequency lf and high low frequency hf lf initial phases in the sample of the 2003 post effusive stage explosive events identifies the termination of the lava effusion and preparation to the stage of large explosions the high participation 37 of the type 2 events with high frequency hf initial phases in the sample of the 2007 co effusive stage explosive events indicates the process of the lava dome growth beginning the introduction of multi stage conceptual model of explosive process allows the interpretation of peculiarities of the seismic signals associated with explosive activity analysis of the spectral content of the initial lf phases of the seismic signals associated with the explosions showed that the sources of lf initial phases corresponding to the ascent of magma within the volcanic conduit above the fragmentation zone were common for post effusive and co effusive stages the source of events with the hf initial phases differed from the source of events with the lf first phases the sources of explosions at explosion level were situated at different sites during post effusive and co effusive stages

long period seismicity at shishaldin volcano alaska in 2003 2004 indications of an upward migration of the source before a minor eruption abstract we have analyzed the long period lp seismic activity at shishaldin volcano aleutians islands alaska in the period october 2003 july 2004 during which a minor eruption took place in may 2004 with ash and steam emissions thermal anomalies volcanic tremor and small explosions we have focused the attention on the time evolution of lp rate size spectra and polarization dip angle along the dataset we find an evolution toward more shallow dip angles in the polarization of the waveforms during the sequence the dip angle is a manifestation of the source location because the lp seismic sources are presumed to reflect the aggregation of gas slug or pockets within the melt we use the polarization dip at the lp onset as a proxy for the nucleation depth of the seismic events within the conduit we refer to this parameter as the nucleation dip and the position along the conduit of the gas aggregation as nucleation depth the nucleation dip changes throughout the dataset it shows a sharp decrease between the end of december 2003 and the end of january 2004 followed by a gradual increase until the onset of the eruption at the same time a general increase of the lp rate occurs we have associated the dip evolution with a sinking and a subsequent decrease of the nucleation depth which would quickly migrate up to about 8 km below the crater rim followed by a slow depth decrease which culminates in the eruption the change in the nucleation depth reflects either a pressure variation within the plumbing system which would affect the confining pressure experienced by the gas aggregations we have imputed such a pressure change to the intrusion of batches of magma from a deeper magma chamber 5 km for a cylindric conduit with rigid walls this leads to a volume of the injected new magma of 10 5 10 7 m 3 compatible with estimates in other areas suggesting that the lp process can be considered a good proxy of the thermodynamical conditions of the shallow plumbing system

geologic framework of the veladero high sulfidation epithermal deposit area cordillera frontal argentina located in the northern part of the el indio belt of chile argentina the 12 6 million ounce moz gold late miocene veladero high sulfidation epithermal deposit is hosted principally in late oligocene and middle miocene volcanic and volcaniclastic rocks and to a lesser extent in the underlying permian rhyolitic pyroclastic rocks the principal host rocks are poorly bedded volcaniclastic breccia and minor air fall tuff of the middle miocene cerro de las tortolas formation which unconformably overlies deformed and structurally interleaved late oligocene and late paleozoic rocks these latter rocks form a steeply dipping fold and thrust belt that was bevelled by the regional miocene frontera deidad paleogeomorphic surface the cerro de las tortolas formation deposited across the frontera deidad surface represents at veladero an 16 ma vent complex characterized by domes and their coeval subvolcanic equivalents infiernillo intrusive unit surrounded by coarse poorly sorted volcaniclastic breccia that grades eastward onto a volcaniclastic apron of bedded and reworked detritus with interbedded air fall tuff and local lacustrine tuffaceous sandstone and siltstone gold at veladero is hosted in a tabular north northwest elongated silicified horizon that cuts across the host stratigraphy and has a subhorizontal top that ranges between 4 200 and 4 400 m above sea level the silicified horizon lies at the approximate elevation to slightly beneath the 14 5 to 12 ma azufreras torta surface which controlled formation of the economic el indio tambo and pascua lama high sulfidation gold deposits elsewhere in the el indio belt published late miocene 40ar 39ar ages between 11 and 10 ma on alunite from the filo federico zone at veladero and from uneconomic prospects nearby indicate that advanced argillic alteration and likely gold deposition is 5 m y younger than the 16 ma host rocks the veladero deposit formed after a change in the local tectonic environment from one of shortening that preceded deposition of the host volcaniclastic sequence to one of extension localized within the vicinity of veladero that episodically disrupted the host volcanic sequences reactivated the steeply dipping thrust faults and displaced the frontera deidad and azufreras torta paleogeomorphic surfaces regional tectonic relationships suggest that this transition did not reflect a fundamental change in the overall shortening that dominates the cenozoic of the chilean argentinean andes instead local extension around veladero resulted from the inherent gravitational instability created by topography in excess of 4 000 m above sea level

decomposition of high frequency seismic wavefield of the strombolian like explosions at erebus volcano by independent component analysis summary the characteristics of the strombolian like activity at erebus volcano antarctica are evidenced by decomposing the wavefield of the explosion quakes associated with the bursting of gas slugs at the surface the decomposition is achieved by adopting a non linear technique operating in time domain that is independent component analysis although the spectral properties and polarization analysis of the recorded signals provide evidence of an overall complex volcanic structure the decomposed waves indicate well polarized phases with high rectilinearity slightly different directions in azimuth can be individuated compatible with different and close vibrating solid structures like conduits in the summit volcanic plumbing system

variscan cycling of gold into a global coal reservoir this project is in support of the nerc sos security of supply of critical elements programme under grant ne m010953 1 j johnston and j bowie provided skilled technical help the manuscript benefitted from incisive reviews by n moles y wu carmine and an anonymous reviewer whose advice is much appreciated

meganodular limestone of the pagoda formation a time specific carbonate facies in the upper ordovician of south china abstract the decimeter scale 3 d network structure of the upper ordovician pagoda formation in south china has been an enigmatic sedimentary feature and a case of non uniformitarian carbonate depositional system without modern analog the network bands are developed pervasively throughout the entire pagoda formation superficially resembling desiccation or syneresis cracks especially in bedding plane view with decimeter scale sub polygonal to irregularly sinuous patterns detailed petrographic analysis however shows that the crack like network bands have the same carbonate matrix skeletal grains and overall fabrics as the rock they surround in this study we demonstrate that the network structure is not generated by shrinkage cracks but is rather a time specific lithofacies it originated from prolonged growth of nodular carbonate controlled by the convergence of several geological and paleoclimatic factors including a a protracted sea level highstand lasting for about 5 myr b an interval of tectonic quiescence favoring the dominance of carbonate production with minimal siliciclastic input and c location of the south china paleoplate in the hurricane free paleoequatorial zone devoid of severe storm disturbances between the fairweather and maximum storm wave bases normally 15 120 m depths favoring long term uninterrupted growth of caco3 meganodules on a mid shelf substrate this study corroborates recent paleogeographic reconstructions that position the south china paleoplate on the equator during the late ordovician

suspect terranes and accretionary history of the appalachian orogen the north american connection or the grenvillian continental crust that separated from eastern north america during the initiation of the appalachian orogenic cycle is poorly defined within the present orogen a variety of terranes occur outboard of the north american miogeocline all structurally uncoupled and therefore suspect stratigraphic analysis indicates that appalachian accretion progressed from the miogeocline outward the boundaries of the earliest accreted western terranes are marked by melange and ophiolite complexes later boundaries between eastern terranes are steep mylonitic zones and brittle faults accretionary events defined by stratigraphic analysis correspond to times of major deformation plutonism and metamorphism in the history of the orogen

the effects of conduit length and acoustic velocity on conduit resonance implications for low frequency events abstract low frequency seismic events at volcanoes are modelled as the seismic wavefield from a magma filled conduit embedded in a solid country rock using a finite difference method the effects of varying the conduit length and the impedance contrast between the magma and the country rock are examined generating a range of possible signals short windowed spectrograms are used to look at the time frequency relationships within the events in detail and some of the possible variations are identified using a series of schematic spectrograms the numerical results are compared to examples of observed seismic data from soufriere hills volcano montserrat while the spectra of the observed events are often different to the spectra of the numerical results the spectrograms have similar features and show that the low frequency events from montserrat are composed of discrete subevents

resources of gold in phanerozoic epithermal deposits we have estimated earth s endowment of gold in phanerozoic epithermal deposits using a tectonic diffusion model which simulates the emplacement of deposits at a shallow crustal depth and their subsequent vertical tectonic migration in the crust the calculation was calibrated by least squares comparison of a calculated age frequency distribution to the age frequency distribution for 448 epithermal deposits of phanerozoic age results indicate that 17 percent of the epithermal deposits that formed through phanerozoic time remain in the crust today whereas 83 percent have been removed by erosion assuming a similar age distribution for all 1 181 epithermal deposits in our compilation indicates that 307 000 deposits formed throughout phanerozoic time that 63 000 of these remain in the crust and that 244 000 have been eroded grade and tonnage data of gold in 757 epithermal deposits in the compilation have an arithmetic average of 34 7 t and yield an estimate of 2 2 106 t of gold for epithermal deposits remaining in the crust using the model based vertical distribution of deposits remaining in the crust we estimate that epithermal deposits in the upper kilometer of the united states contain 2 9 104 t of gold adjusting for areas of outcropping volcanic rocks in each continent increases our estimate to 4 0 104 t these estimates are similar to the 1 7 104 t gold resource estimated by the u s geological survey using completely different methods several comparisons based on these results provide insights into the efficiency of processes that form epithermal deposits and the outlook for sustainability for instance all of the epithermal deposits that formed through phanerozoic time represent only about 0 03 percent of the gold in the crust only about 0 007 percent of crustal gold remains in epithermal deposits the rest has been eroded and recycled this is consistent with comparisons based on the flux of gold in the taupo volcanic zone which indicate that epithermal deposits trap only 0 1 to 0 2 percent of the gold that moves through convergent margin hydrothermal systems epithermal gold deposits that remain in the crust can supply current production from them for 1 400 to 5 000 years depending on success of exploration and depth of mining finally we are consuming gold from epithermal deposits about 17 000 times faster than earth is replenishing the supply

modelling the time dependent frequency content of low frequency volcanic earthquakes abstract low frequency volcanic earthquakes and tremor have been observed on seismic networks at a number of volcanoes including soufriere hills volcano on montserrat single events have well known characteristics including a long duration several seconds and harmonic spectral peaks 0 2 5 hz they are commonly observed in swarms and can be highly repetitive both in waveforms and amplitude spectra as the time delay between them decreases they merge into tremor often preceding critical volcanic events like dome collapses or explosions observed amplitude spectrograms of long period volcanic earthquake swarms may display gliding lines which reflect a time dependence in the frequency content using a magma filled dyke embedded in a solid homogeneous half space as a simplified volcanic structure we employ a 2d finite difference method to compute the propagation of seismic waves in the conduit and its vicinity we successfully replicate the seismic wave field of a single low frequency event as well as the occurrence of events in swarms their highly repetitive characteristics and the time dependence of their spectral content we use our model to demonstrate that there are two modes of conduit resonance leading to two types of interface waves which are recorded at the free surface as surface waves we also demonstrate that reflections from the top and the bottom of a conduit act as secondary sources that are recorded at the surface as repetitive low frequency events with similar waveforms we further expand our modelling to account for gradients in physical properties across the magma solid interface we also expand it to account for time dependence of magma properties which we implement by changing physical properties within the conduit during numerical computation of wave propagation we use our expanded model to investigate the amplitude and time scales required for modelling gliding lines and show that changes in magma properties particularly changes in the bubble nucleation level provide a plausible mechanism for the frequency variation in amplitude spectrograms

analysis of the seismic wavefield properties of volcanic explosions at volcan de colima mexico insights into the source mechanism summary we have investigated the wavefield properties of the seismic signals generated by the explosions of volc an de colima mwe have analysed these properties to understand the initial mechanism that triggered the explosive events our study is focused on the direct waves coming from the crater area thus we have analysed a set of moderate volcanic explosions at volc an de colima that was recorded by a small aperture seismic array over two periods october 2005 and april 2006 we can distinguish two types of explosions vulcanian and ash free events both types of explosions share the same characteristics that is a long period signal not related to any type of emission before the arrival of high frequency phases and a later high frequency signal directly related to ash or gas emission we have applied the zero lag cross correlation technique to obtain backazimuth and apparent slowness of the incoming waves we have also applied polarization analysis to the record of every detected volcanic explosion by comparing the results of both of these analyses we have been able to identify the dominant wave types that comprise the seismic wavefield and infer in time and space a possible primary source mechanism that would trigger the volcanic explosions we have observed an apparent slowness variation of the first onset of the long period lp signal with a possible upward migration of the source the depth of the source has been identified at a range between 2 6 and 3 3 km below the crater associated with the range of measured apparent velocities relative to the first onset of the lp signal

the annual warm to cold phase transition in the eastern equatorial pacific diagnosis of the role of stratus cloud top cooling abstract the forcing of the march to may southerly surface wind tendency along the equatorial south american coast which leads to the annual transition of the eastern tropical pacific basin s climate from its peak warm phase in april is explored through diagnostic modeling modeling experiments with a high resolution 18 levels 2 5 30 zonal waves steady state global linear primitive equation model that produces a striking simulation of most aspects of the march to may change in the lower tropospheric circulation over the eastern tropical pacific including the notable southerly surface wind tendency have provided unique insight into the role of various physical processes the model is forced by the 3d distribution of the residually diagnosed diabatic heating and the submonthly momentum and thermal transients all obtained from the twice daily 2 5 2 5 european centre for medium range weather forecasts uninitialized analyses for 1985 95 the principal findings are the following the initia

source location of long period seismicity at volcan de colima mexico this paper presents an analysis of seismicity associated with the volcanic activity of volcan de colima mexico and recorded in the period november 2005 april 2006 during a field survey by the istituto nazionale di geofisica e vulcanologia ingv osservatorio vesuviano the observatorio vulcanologico de colima of colima university and the instituto andaluz de geofisica university of granada three different types of volcanic earthquakes have been identified on the basis of their spectral properties type a 0 3 1 hz type b 1 5 hz and type c 3 4 hz results of polarization analysis applied to type a events show a predominance of radial motion indicating that the wavefield comprises compressional waves p and shear waves polarized in the vertical plane sv while the signal always begins with a negative polarity type a b and c earthquakes have been located using both a flat layered model and a 3d model including topography hypocentre distributions indicate that the source of type a signals is very shallow and confined to a small volume lying about 1 km below the crater in contrast the source of type b and c events is significantly deeper with most hypocentres located in a volume of about 1 km3 centred at 2 5 3 km depth a cluster analysis based on the cross correlation among the waveforms of different events recorded at the same station was applied to type a earthquakes only two clusters which include only a small percentage of events were found indicating that earthquake families were uncommon during the period of our survey

characterization of fracture systems using precise array locations of earthquake multiplets an example at deception island volcano antarctica 1 volcano tectonic earthquakes are common seismic events in active volcanic areas the stress produced by volcanic processes is released through fracturing of the shallow crust very often these earthquakes occur in multiplets with similar waveforms a fact which indicates common source characteristics in this work we introduce a method that uses array techniques to calculate precise relative locations of earthquake multiplets we use the relative slowness estimate method to determine accurately the apparent slownesses and propagation azimuths of the earthquakes relative to a selected master event we also obtain precise estimates of the s p delays this information is used to calculate precise relative locations by ray tracing in an earth model we applied this method to determine the characteristics of the fractures activated during the 1999 seismic series at the deception island volcano antarctica we selected a set of 17 earthquake multiplets initially located in a small 4 4 km region a few km ne of the array site we estimated precise locations for 14 of the clusters in most cases hypocenters were distributed in well defined planar geometries we found the best fitting planes which we interpreted as fractures in the medium for two clusters the method spatially separated the earthquakes into two subgroups thus we obtained two planes for each of these clusters resulting in a total of 16 fracture planes this is the first time that the orientations of fracture planes related to a seismic series have been obtained using a seismic array we performed several tests to check various aspects in relation to the stability of the method and concluded that the results were robust the dip angles indicate that the planes are mostly subvertical while the strike angles clearly show a nw se trend for most of the planes and a few planes with ne sw trends the geometry and position of these planes suggest that the 1999 seismic series was influenced by regional tectonics although the origin of the destabilization of the system may be related to the reactivation of a shallow magma chamber

sulfur and lead isotope geochemistry of hypogene mineralization at the barite hill gold deposit carolina slate belt southeastern united states a window into and through regional metamorphism the barite hill gold deposit at the southwestern end of the carolina slate belt in the southeastern united states is one of four gold deposits in the region that have a combined yield of 110 metric tons of gold over the past 10 years at barite hill production has dominantly come from oxidized ores sulfur isotope data from hypogene portions of the barite hill gold deposit vary systematically with pyrite barite associations and provide insights into both the pre metamorphic late proterozoic hydrothermal and the paleozoic regional metamorphic histories of the deposit the 34s values of massive barite cluster tightly between 25 0 and 28 0 which closely match the published values for late proterozoic seawater and thus support a seafloor hydrothermal origin the 34s values of massive sulfide range from 1 0 to 5 3 and fall within the range of values observed for modern and ancient seafloor hydrothermal sulfide deposits in contrast 34s values for finer grained intergrown pyrite 5 1 6 8 and barite 21 0 23 9 are higher and lower than their massive counterparts respectively calculated sulfur isotope temperatures for the latter barite pyrite pairs 15 9 17 1 range from 332 355 c and probably reflect post depositional equilibration at greenschist facies regional metamorphic conditions thus pyrite and barite occurring separately from one another provide pre metamorphic information about the hydrothermal origin of the deposit whereas pyrite and barite occurring together equilibrated to record the metamorphic conditions preliminary fluid inclusion data from sphalerite are consistent with a modified seawater source for the mineralizing fluids but data from quartz and barite may reflect later metamorphic and or more recent meteoric water input lead isotope values from pyrites range for 206pb 204pb from 18 005 18 294 for 207pb 204pb from 15 567 15 645 and for 208pb 204pb from 37 555 38 015 the data indicate derivation of the ore leads from the country rocks which themselves show evidence for contributions from relatively unradiogenic mantle like lead and more evolved or crustal lead geological relationships and stable and radiogenic isotopic data suggest that the barite hill gold deposit formed on the late proterozoic seafloor through exhalative hydrothermal processes similar to those that were responsible for the massive sulfide deposits of the kuroko district japan on the basis of similarities with other gold rich massive sulfide deposits and modern seafloor hydrothermal systems the gold at barite hill was probably introduced as an integral part of the formation of the massive sulfide deposit

deciphering the role of southern gateways and carbon dioxide on the onset of the antarctic circumpolar current 1 growth of antarctic ice sheet during the cenozoic 34 million years ago appears as a potential tipping point in the long term cooling trend that began 50 ma ago for decades the onset of the antarctic circumpolar current acc following the opening of the drake passage and of the tasman seaway has been suggested as the main driver of the continental scale antarctic glaciation however recent modeling works emphasized that the eocene oligocene atmospheric carbon dioxide co2 lowering could be the primary forcing of the antarctic glaciation questioning the acc theory here we investigate the response of the acc to changes in co2concentrations occurring from the late eocene to the late oligocene we used a fully coupled atmosphere ocean model foam with a mid oligocene geography we find that the opening of southern oceanic gateways does not trigger the onset of the acc for co2typical of the late eocene 840 ppm a cooler background climatic state such as the one prevalent at the end of the oligocene is required to simulate a well developed acc in this cold configuration the intensified sea ice development around antarctica and the resulting brine formation lead to a strong latitudinal density gradient in the southern ocean favoring the compensation of the ekman transport and consequently the acc our results imply that the acc has acted as a feedback rather than as a driver of the global cooling

application of lead isotope studies to massive sulfide and vein deposits of the carolina slate belt samples of ore leads from a number of cambrian massive sulfide and vein deposits in the carolina slate belt of the charlotte 2 degrees quadrangle north carolina have been analyzed in general these deposits are characterized by high 207 pb 204 pb ratios 15 609 to 15 646 and abnormally young model ages delta asymp 100 m y their thorogenic lead values are typical of those of other deposits of their geologic age based on the strong evidence for a syngenetic origin for the massive sulfide deposits one of two multistage processes is required to explain the data the first requires derivation of the ore leads from a basement of at least grenville age and more likely 1 7 to 2 0 b y old such basement is not known in this portion of the appalachian piedmont we favor the second process which is the derivation of the ore leads from the 10 000 m of felsic intermediate and mafic volcanic volcaniclastic and epiclastic rocks of the underlying uhwarrie formation and albemarle group mean age 600 m y with an average mu 25 the model lead ages can be reduced to delta 20 m y assuming a basinal migration of lead at a date of approximately 540 m y the vein deposits using this short term two stage model yield ages of approximately 490 m y these correlate well with the peak metamorphism in the north carolina portion of the carolina slate belt

biogeographical significance of cambrian trilobites from the carolina slate belt abundant middle middle cambrian trilobites of the ptychagnostus atavus interval zone are described from the upper asbill pond formation informal name near batesburg south carolina the fauna containing at least nine species has strong affinities with cool water faunas of both armorica and baltica but little affinity with warm water shelf faunas of laurentia this is compatible with previous conclusions that the carolina slate belt is an exotic terrane that was accreted to north america during the early or middle paleozoic further evaluation however introduces an alternative possibility that the fauna could have lived in deep cool water environments along the periphery of laurentia and subsequent displacement need not necessarily have been great combined faunal and stratigraphic components of the carolina slate belt do not precisely match those of any known region but may be closest to those of bohemia although a southpolar location in proximity to armorica baltica and gondwana seems likely a definitive placement in a reconstruction of the cambrian world is not yet possible included in the trilobite fauna are the agnostoids hypagnostus mammillatus h parvifrons peronopsis fallax ptychagnostus sp and tomagnostus fissus the polymeroids include agraulos sp paradoxides cf polonicus paradoxides sp and skreiaspis sp

probabilistic source location of explosion quakes at stromboli volcano estimated with double array data data from two dense arrays of short period seismometers are used to retrieve source locations of the explosion quakes at stromboli volcano slowness vectors estimated at both arrays with the zero lag cross correlation technique constitute the experimental data set a probabilistic approach based on a grid search spanning the volcano interior is used to calculate the probability of the source location results depict a shallow source located beneath the crater area at depths not greater than 500 m below the surface results are slightly different from but comparable to those obtained in a companion experiment carried out in the same time period using a broad band seismometer network which show a source shifted some hundreds of meters northwest of the crater area the method is revealed to be effective and useful for future studies having the purpose of real time tracking of the explosion quakes and tremor