site amplification scattering and intrinsic attenuation in the mississippi embayment from coda waves we estimate site amplification intrinsic q q i and scattering q q s values from three component coda of broadband data recorded by cooperative new madrid sesimic network stations for center frequencies 0 2 0 5 1 0 2 0 and 5 0 hz near 0 5 and 1 0 hz site amplification factors for the transverse component recorded by stations in the mississippi embayment are between 1 7 and 18 compared with stations outside the embayment the amplification factor becomes smaller at frequencies lower than 0 5 hz and higher at those greater than 1 0 hz the radial component shows a similar amplification however the vertical component shows relatively less amplification q i and q s are estimated from coda using an energy flux model for two time windows after the direct s wave and at 0 5 and 1 0 hz center frequencies the two time windows include coda up to and after twice the s wave travel time at each station coda parameters change with the time window and are attributed to a mixture of incoherent coda with coherent s wave reverberations directly after the s wave q i and q s inferred from stations outside of the embayment have higher values than those from stations within the embayment a plane wave model qualitatively explains the lack of coda amplification at high frequencies compared with a low frequency without recourse to anelastic attenuation arguments however the plane wave model cannot explain the very large observed coda amplifications at 1 and 0 5 hz seen in the data suggesting that other wave scattering effects must be occurring in the embayment velocity structure this is consistent with the relatively low q s values inferred from the energy flux model for stations within the embayment in addition to coda amplification we performed a synoptic noise study that revealed that pre event ambient background noise behaves in a similar manner to the coda for stations within and outside of the embayment the presence of large lateral velocity heterogeneities in the embayment may cause q s values to be low there

a comparison and test of various site response estimation techniques including three that are not reference site dependent abstract we compare various site response estimation techniques using after shock data of the 1989 loma prieta earthquake collected in oakland california because of recent interest in comparing results from weak and strong motion to infer any nonlinearity and between direct s and coda waves we pay particular attention to the uncertainties first sediment to bedrock spectral ratio estimates between pairs of sites are compared with those obtained from various generalized inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously we find that the site amplification factors are very similar among these approaches but that the uncertainties can be significantly different depending on how the data are weighted we also examine and test three site response estimation techniques that do not rely on a reference site to estimate source and path effects the first involves a parameterized source and path effects inversion even when the bedrock data are excluded from consideration this approach is found to reveal the frequency dependence of site response at each of the sediment sites the second technique involves taking horizontal to vertical component spectral ratios receiver function type estimates of shear wave aftershock data these are also found to reveal the frequency dependence of site response at the sediment sites and the results for the bedrock site are relatively flat and near unity the third estimate is formed by taking horizontal to vertical component ratios of ambient seismic noise and these are shown to reveal the fundamental resonant frequency of the sediment sites unfortunately discrepancies exist among all of the site response estimates and with one dimensional predictions with respect to a frequency independent scaling factor nevertheless the highly frequency dependent character of site response is well constrained and the fact that non reference site dependent methods are capable of revealing this is promising for site specific hazard assessments in regions that lack adequate reference sites

building a three dimensional model of the active plio quaternary basin of argostoli cephalonia island greece an integrated geophysical and geological approach abstract this work is a multidisciplinary approach from geological and geophysical surveys to build a 3d geological model of argostoli basin cephalonia island greece aiming to be used for computational 3d simulation of seismic motion cephalonia island is located at the north western end of the aegean subduction frontal thrust that is linked to the dextral cephalonia transform fault west of cephalonia where the seismic hazard is high in terms of earthquake frequency and magnitude the plio quaternary koutavos argostoli basin site was selected within the french research agency pia sinaps project www institut seism fr projets sinaps last accessed on november 25th 2019 to host a vertical accelerometer array the long term goal is to validate three dimensional nonlinear numerical simulation codes to assess the site specific amplification and nonlinearity herein the geological and geophysical surveys carried out from 2011 to 2017 are presented and in particular the complementary investigations that led to the identification of the main stratigraphic units and their structures in addition coral debris sampled from the vertical array deep borehole cores were used for 230th 234u measurements which confirmed the pleistocene age of the koutavos basin the characterization of the three dimensional structure of the stratigraphic units was achieved by coupling geological cross sections i e depth geometry and geophysical surveys based of surface wave analysis

geology genesis and exploration implications of the footwall and hanging wall alteration associated with the hellyer volcanic hosted massive sulfide deposit tasmania australia hellyer is a large 16 2 million metric tons high grade 13 9 zn 7 1 pb 0 4 cu 168 g t ag 2 5 g t au sea floor mound style polymetallic volcanic hosted massive sulfide vhms deposit located in the mount read volcanics of western tasmania the deposit is hosted by the que hellyer volcanics a sequence of late middle cambrian mafic to felsic coherent volcanics and polymict volcaniclastics hydrothermal alteration occurs in the regional footwall immediate footwall and hanging wall alteration in the regional footwall is confined to patchy quartz albite and chlorite with minor sericite epidote and hematite underlying hellyer is a zoned alteration pipe with a central siliceous core quartz sericite which passes into zones of chlorite chlorite carbonate sericite chlorite and finally sericite quartz stringer envelope zone on the margin overlying the central part of the deposit within the hanging wall basalt is a distinctive and zoned alteration plume five alteration zones have been identified fuchsite chlorite carbonate quartzalbite and sericite fuchsite dominated alteration occupies the central portion of the hanging wall alteration plume chlorite and carbonate alteration surrounds the fuchsite zone with carbonate zones forming near to the ore deposit and chlorite zones extending above and lateral to the carbonate outward is quartz ablite alteration which extends laterally into distal sericite alteration mass change calculations for the footwall and hanging wall indicate that in general the footwall alteration zones are depleted in cao na2o la sr ni cr and v but have enrichments of fe2o3 mno mgo k2o s and most metals compared to the host basalt the hanging wall alteration has gained cao k2o na2o co2 s in rb ba ag as mo sb cs and tl while fe2o3 mno mgo p2o5 la sr pb zn th u cd and nd are depleted cao na2o cr v and ni are depleted in the footwall andesite but enriched in the hanging wall alteration plume this relationship suggests that these elements were sourced from the breakdown of feldspars pyroxenes and andesitic groundmass of the footwall lithologies and transported in the hydrothermal fluid into the overlying basalt and precipitated as albite calcite and white micas in the hanging wall alteration the development of alteration associated with the hellyer vhms deposit occurred in three stages stage 1 regional footwall alteration was formed by unfocused hydrothermal convection of seawater down into the recently deposited volcanic pile at temperatures between approximately 250 degrees celsius and 200 degrees celsius and at low to moderate water rock ratios stage 2 alteration formed by structurally controlled fluid flow from a deep intensifying hydrothermal convection system and created the footwall alteration pipe decreasing water rock ratios and temperatures over a range of 350 degrees celsius to less than 200 degrees celsius led to the development of the concentric alteration pipe mineral zones based on modeling of whole rock d18ofr values geochemical modeling and mineral assemblages the siliceous core is interpreted to have formed at temperatures near 350 degrees celsius the chlorite rich alteration zone at 300 degrees celsius to 250 degrees celsius and the outer sericite rich alteration at temperatures of 250 degrees celsius to 150 degrees celsius the final synmineralization fluid flow event stage 3 created the hanging wall alteration plume after rapid burial of the deposit by basalt continuation of upward hydrothermal fluid flow created the zoned hanging wall alteration distribution of hanging wall alteration assemblages suggests a temperature gradient from approximately 250 degrees celsius for the fuchsite zone to lower temperatures 150 degrees celsius for the distal quartz albite and sericite alteration zones alteration mineralogy mineral chemistry lithogeochemistry and stable isotope characteristics of the footwall and hanging wall alteration have been combined into a comprehensive set of vectors which can be used in exploration for vhms deposits in similar geologic settings

geothermometry geochronology and mass transfer associated with hydrothermal alteration of a rhyolitic hyaloclastite from ponza island italy abstract a rhyolitic hyaloclastite from ponza island italy was hydrothermally altered producing four distinct alteration zones based on x ray diffraction mineralogy and field textures 1 nonpervasive argillic zone 2 propylitic zone 3 silicic zone and 4 sericitic zone the unaltered hyaloclastite is volcanic breccia with clasts of vesiculated obsidian in a matrix of predominantly pumice lapilli incomplete alteration of the hyaloclastite resulted in the nonpervasive argillic zone characterized by smectite and disordered opal ct the other three zones exhibit more complete alteration of the hyaloclastite the propylitic zone is characterized by mixed layer illite smectite i s with 10 to 85 i mordenite opal c and authigenic k feldspar akspar the silicic zone is characterized by i s with 90 i pure illite quartz akspar and occasional albite the sericitic zone consists primarily of i s with 66 i pure illite quartz and minor akspar and pyrite k ar dates of i s indicate hydrothermal alteration occurred at 3 38 0 08 ma oxygen isotope compositions of i s systematically decrease from zones 1 to 4 in the argillic zone smectite has 18o values of 21 7 to 22 0 and i s from the propylitic silicic and sericitic zones ranges from 14 5 to 16 3 12 5 to 14 0 and 8 6 to 11 9 respectively 18o values for quartz from the silicic and sericitic zones range from 12 6 to 15 9 by use of isotope fractionation equations and data from authigenic quartz hosted primary fluid inclusions alteration temperatures ranged from 50 to 65 c for the argillic zone 85 to 125 c for the propylitic zone 110 to 210 c for the silicic zone and 145 to 225 c for the sericitic zone fluid inclusion data and calculated 18owater values indicate that hydrothermal fluids were seawater dominated mass transfer calculations indicate that hydrothermal alteration proceeded in a relatively open chemical system and alteration in the sericitic zone involved the most extensive loss of chemical species especially si systematic gains in mg occur in all alteration zones as a result of i s clay mineral formation and systematic losses of na ca and k occur in most zones with the exception of ca calculations of mass transfer associated with hydrothermal alteration on ponza agree with chemical fluxes observed in laboratory experiments involving hydrothermal reactions of rhyolite and seawater the anomalous ca loss at ponza may be due to hydrothermal formation of anhydrite and later low temperature dissolution on the basis of mg enrichments derived from circulating seawater we estimate the following minimum water rock ratios 9 3 6 and 9 for the argillic propylitic silicic and sericitic zones respectively hydrothermal fluid ph for the propylitic and silicic zones was neutral to slightly basic and relatively acidic for the sericitic zone as a result of condensation of carbonic and perhaps other acids

mineralogy petrography and whole rock geochemistry of the tertiary granitic intrusions in the eastern pontides turkey abstract granitic intrusions in eocene and post eocene volcanic rocks outcrop in the northern and southern zones of the eastern pontides ne turkey intrusions in the northern zone extend nw se whereas those in the southern zone are nearly e w orientated the contacts of the intrusions with the volcanic rocks are sharp epidotized and include volcanic xenoliths the margins of southern zone intrusions often contain abundant angular mafic microgranular enclaves of diorite to quartz diorite composition the rocks also show evidence of mingling and mixing between coeval mafic and felsic magmas field observations suggest a stopping type of ascent and emplacement style for the intrusions petrographically intrusions show variations in both colour and mineralogy with fine to medium granular monzonitic poikilitic rapakivi anti rapakivi and graphic textures based on modal mineralogy the northern rocks are monzonite quartz monzonite monzodiorite and quartz monzodiorite whereas the southern samples are monzogranite and granodiorite the rocks are generally calc alkaline to mildly alkaline transitional and metaluminous and show a cafemic trend the northern zone intrusions form a post collisional a type alkaline monzonitic association and southern zone intrusions form a post collisional i type granodioritic calc alkaline transitional association whole rock compositional data indicate that differentiation occurred via fractional crystallisation with or without magma mixing incompatible and rare earth element patterns indicate that both the northern and the southern zone intrusions were derived from melting of a mantle region enriched by subduction related fluids but evolved differently during ascent and emplacement u pb zircon dating in the southern zone yields an intrusion age of 44 4 0 3 ma regional geodynamics indicates post collisional extensional tectonics in the region crustal involvement and the level of emplacement may have been important for magmatic evolution especially for the southern zone intrusions after the cessation of subduction and subsequent crustal thickening

3d subduction dynamics a first order parameter of the transition from copper to gold rich deposits in the eastern mediterranean region the natural variability of geometry and dynamics of subduction zones leads to a variety of mantle and crustal processes that may influence the genesis of ore deposits in the overriding plate these complex interactions cannot be fully represented by two dimensional 2d models but require that the spatial and temporal evolution of ore deposits be examined in a detailed 3d tectonic framework we compare and discuss the geodynamic and metallogenic evolution of the eastern mediterranean subduction zone since the late cretaceous by integrating a newly compiled metallogenic database with a recent kinematic reconstruction model the resulting paleotec tonic maps identify 1 a late cretaceous cu rich metallogenic period with large deposits formed above a linear and stable subduction zone that produced large amounts of potentially fertile magmas in a narrow magmatic arc and 2 a late eocene miocene pb zn followed by au rich metallogenic period with generally smaller deposits spread over a wide back arc basin that was opened due to subduction retreat and lateral slab tearing supported by high resolution numerical modeling the proposed dynamic arc and back arc metallogenic models emphasize 1 the influence of 3d slab dynamics and associated asthenospheric flow on ore distribution in space and time and 2 the importance of exhuming metamorphic domes in extensional back arc setting to focus metal bearing fluid circulations these models differ from collision and post collision models and may be valid on the western and eastern terminations of the whole tethyan orogenic belt i e mediterranean and southeast asia where fast 3d subduction dynamics has influenced the geodynamic and metallogenic evolution of the overriding plate

imaging shallow crustal structure in the upper mississippi embayment using local earthquake waveform data a 1d normal moveout nmo corrected and stacked pseudoprofiling method was applied to analyze the characteristic features shown on primary p and s wave coda and on sp waveforms from local microearthquakes in an attempt to image prominent reflectors and to resolve shallow crustal velocity structure 5 km in the upper mississippi embayment acoustic well log data were used to constrain the p wave velocity in the upper 5 km events at close distances and with clear p and s arrivals were selected to ensure reliable nmo correction for reflections and transmissions the observed reflections and transmissions are important controlling factors on modeling waveforms we analyzed local earthquake data recorded at all broadband and one short period station of the cooperative new madrid seismic network despite polarity differences among p s and sp waveforms consistent reflectors in the sedimentary section can be imaged across the three wave types correlation with a basement penetrating well indicates that reflectors at the base of the upper cretaceous holocene mississippi embayment supergroup the base of the cambrian ordovician knox group and the high velocity lower upper cambrian bonneterre formation are shown in pseudoprofiles among stations in the upper mississippi embayment our study finds that a one layer homogeneous velocity model of sediments in the ranges of 1 95 2 42 km s for v p and 0 60 0 73 km s for v s overlying a half space of paleozoic rocks with velocities in the ranges of 6 0 6 2 km s for v p and 3 26 3 6 km s for v s can represent shallow crustal structure in the upper mississippi embayment differential times of p ppphp and s ssshs appear linearly proportional to sediment thicknesses which best fits a one layer sediment structure with average v p 2 042 0 041 km s and v s 0 709 0 051 km s in the least squares sense predicted by the wave propagation effects online material figures illustrating seismograms process procedure imaged reflectors and resolved velocity structure for six broadband stations and one short period station

volcanic arc emplacement onto the southernmost appalachian laurentian shelf characteristics and constraints in the southernmost appalachians the hillabee greenstone an ordovician volcanic arc fragment lies directly atop the outermost laurentian devonian earliest mississip pian shelf sequence at the structural top of the greenschist facies talladega belt the frontal metamorphic allochthon along this orogenic segment the hillabee greenstone was emplaced between latest devonian and middle mississippian time it and the upper most laurentian section were later repeated together within a series of map scale imbri cate slices of a postmetamorphic dextral transpressional alleghanian thrust duplex system that placed the high grade eastern blue ridge allochthon atop the talladega belt geochemical and geochronologic u pb zircon studies indicate that the hillabee greenstone s interstratifi ed tholeiitic meta basalt and calc alkaline metadacite rhyolite formed within an extensional setting on con tinental crust ca 460 470 ma palinspastic reconstructions of the southern appalachian ordovician margin place the hillabee green stone outboard of the present position of the pine mountain terrane and suggest links to ordovician plutonism in the overlying east ern blue ridge and possibly to widespread k bentonite deposits within ordovician plat form units the tectonic evolution of the hil labee greenstone exhibits many unusual and intriguing features including 1 premeta morphic emplacement along a basal cryptic thrust which is remarkably concordant to both hanging wall and footwall sequences across its entire extent 230 km 2 forma tion transport and emplacement of the arc fragment accompanied by minimal deforma tion of the hillabee greenstone and under lying outer margin shelf rocks 3 emplace ment temporally coincident with the adjacent collision of the younger tectonically indepen dent ouachita volcanic arc with southeastern laurentia these features highlight strong contrasts in the ordovician taconian evolu tion of the southern and northern parts of the appalachian orogen

magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace element discriminant diagrams when dealing with ancient subalkaline volcanic rocks the alkali total iron magnesium afm diagram is of limited use in assigning a tholeiitic versus calc alkaline affinity because these eleme

high resolution shallow seismic experiments in sand part ii velocities in shallow unconsolidated sand we conducted a shallow high resolution seismic reflection and refraction experiment on a sandy beach the depth of investigation was about 2 m we interpret the data using the hertz mindlin contact theory combined with gassmann s equation these were used to obtain the vertical velocity profile then the profile was computed from seismic data using the turning rays approximation the normal moveout nmo velocity at the depth of 2 m matches the velocity profile as a result we developed a method to invert measured velocity from first arrivals i e velocity versus distance into velocity versus depth using only one adjustable parameter this parameter contains all the information about the internal structure and elasticity of the sand the lowest velocity observed was about 40 m s it is noteworthy that the theoretical lower bound for velocity in dry sand with air is as low as 13 m s we find that modeling sand as a quartz sphere pack does not quantitatively agree with the measured data however the the

relationship between alteration rare earth element distribution and mineralization of the murgul copper deposit northeastern turkey the murgul ore deposit belongs to the east pontic metallogenetic province and is related to a subvolcanic formation of an upper cretaceous island arc volcanism the deposit is linked to a 250 m thick felsic pyroclastic member of senonian age the murgul deposit consists of 1 a widespread disseminated ore with varying cu contents ranging from 0 2 to 0 7 percent 2 a stockworklike ore with average cu contents between 1 0 and 2 5 percent and 3 small ore lodes with cu contents from 5 0 to 10 0 percent the mineralization is spatially associated with an intense two stage alteration of the host rock an initial stage of phyllic and argillic alteration and a late stage characterized by silicification the continuation of the volcanic activity with ascending hydrothermal solutions caused an intense remobilization of the disseminated ore producing the stockworklike and vein mineralizations they consist of pyrite and chalcopyrite with minor contents of sphalerite galena and fahlore the study of the rare earth element distribution in the alteration zones supports the distinction between the two stages and reveals a close correlation between increasing wall rock alteration and depletion of the rare earth elements petrographic data indicate that the rare earth element patterns of the altered host rocks are predominantly controlled by the abundance of sericite illite montimorillonite kaolinite and dickite the formation of the two main orebodies must have been completed before an intense subaerial or intertidal erosion and weathering took place this phase is indicated by a relatively thin layer of transgressive kaolinized weathering products which are overlain by barren felsic volcanics

mineralogy and textures of the lahanos and kizilkaya massive sulphide deposits northeastern turkey and their similarity to kuroko ores a distinct vertical zonation very similar to that described for the kuroko deposits of japan is displayed by both mineralogy and textures of sulphides from the lahanos and kizilkaya massive sulphide deposits of northeastern turkey a deeper erosional level is exposed at the kizilkaya deposit so that only remnants of the massive sulphide ore zone are present the zonation is from an upper zone of massive cu and zn sulphides black and yellow ore with fine grained colloform banded framboidal and spherulitic textures downwards through an intermediate zone of low cu zn massive pyrite with transitional textures to a lower zone of stockwork and impregnated pyrite displaying euhedral zoned textures the fine grained and colloform pyrite of the upper zones is progressively overgrown by and recrystallized to the massive and euhedral pyrite of lower zones the original textures of these deposits are best preserved by pyrite the previous interpretation of these textures of sulphide deposition from colloidal solutions ponded by an impermeable pyroclastic horizon is reexamined in the light of present observations although ultra fine grained sulphides framboids and radially cracked spherules could have formed by replacement of pre existing minerals by a colloidal solution the colloform and banded textures are indicative of growth in open spaces it thus seems likely that the fine grained colloform sulphides including chalcopyrite sphalerite and tennantite as well as pyrite were initially deposited on or near the surface of the sea floor additional evidence for this interpretation is seen in the progressive recrystallization of the sulphide textures to massive much coarser pyrite in the lower zones this recrystallization may in part be due to diagenetic and hydrothermal processes operating after formation of the original layered sulphides these conclusions are in agreement with those reached for the similar but larger madenkoy deposit 100 km to the east

geochemical modeling of the zoned footwall alteration pipe hellyer volcanic hosted massive sulfide deposit western tasmania australia the mineralogy of hydrothermal alteration assemblages siliceous core chlorite zone sericite zone in the footwall pipe of the hellyer volcanic hosted massive sulfide vhms deposit is controlled mainly by the temperature ph and redox state of the hydrothermal fluids based on the results of our numerical modeling the zoned alteration system could have formed by a combination of water rock interaction and cooling with a siliceous core predicted to form at the center of the conduit passing outward to a chlorite dominated zone a sericite rich zone and finally grading out to unaltered andesite these mineralogical changes relate to a gradual evolution of fluid chemistry water rock ratio ph and temperature from the core to the margin of the system initial temperatures were probably close to 350 degrees c and the hydrothermal fluids were reduced h2s dominated at low temperatures 200 degrees c a peripheral alteration zone consisting mostly of k feldspar chlorite sericite and hematite is predicted to form this low temperature zone has not been recognized at hellyer but elevated k2o contents and local k feldspar development have been noted at other vhms deposits suggesting that this zone might form at low temperatures and low water rock ratios in the footwall of vhms deposits if the existence of barren outer k feldspar alteration zones is confirmed the findings could have important implications for exploration specifically with regards to distinguishing ore related alteration zones from barren alteration systems

mass transfer and the path of metasomatic reactions in mesothermal gold deposits an example from flambeau lake ontario gold mineralization in the flambeau lake area is found in and adjacent to quartz carbonate albite veins surrounded by halos of intense ankerite albite alteration these features are the result of the passage of hydrothermal fluid through tension fractures and shear zones developed in response to regional dextral shearing wall rock alteration is zoned consisting of four distinct alteration assemblages distal weak isochemical alteration a transitional zone where chlorite was gradually removed and replaced by carbonates and albite a zone of mainly ankerite and albite and a rare marginal zone of mainly albite and quartz a detailed analysis of potential mass balance indicators from a single alteration halo in quartz diorite revealed that zr ti light ree u th and to some extent nb remained immobile during alteration a mass balance study of this halo shows that sio 2 al 2 o 3 fe 2 o 3 mgo and k 2 o were removed from the wall rock and that cao co 2 s and na 2 o were added these changes are attributed to the breakdown of chlorite sericite calcite and quartz and their replacement by albite and ankerite vein mineral textures show that the veins were open allowing the passage of the substantial amounts of hydrothermal fluid required to produce the alteration and to remove large amounts of sio 2 from the rock up to 30 wt the behavior of perfectly mobile elements indicates that the fluid rock ratio increased toward the vein a model is proposed in which the observed alteration is explained by the interaction of the wall rock with a quartz undersaturated alkaline co 2 bearing fluid the study emphasizes the importance of quartz undersaturation as a mechanism for the enhancement of hydrothermal alteration through porosity modification in addition it demonstrates how fluid rock reaction paths can be investigated using simple mass balance calculations

trace element geochemistry and petrogenesis of felsic volcanic rocks associated with volcanogenic massive cu zn pb sulfide deposits volcanogenic massive cu zn pb sulfide vms deposits occur primarily in subaqueous rift related environments e g oceanic fore arc arc back arc continental margin or continental are hosted primarily by bimodal mafic felsic volcanic successions and are typically associated with felsic volcanic rocks with specific geochemical characteristics fi alkalic dacites and rhyodacites despite being abundant in the rock record are typically barren some fii calc alkalic rhyodacites and rhyolites host vms deposits but most are barren fiii tholeiitic and fiv depleted rhyolites and high silica rhyolites are much less abundant in the rock record but commonly host vms deposits regardless of age and fiii rhyolites appear to host the largest deposits most petrogenetic models proposed for the formation of fii and fiii fiv felsic volcanic rocks link felsic magma genesis to fractionation processes in high level magma chambers now represented by associated subvolcanic intrusions where the magma is also interpreted to have supplied the heat and or metals required to generate and sustain the vms forming convective hydrothermal system however the relatively constant compositions of fii and fiii fiv felsic volcanic rocks within individual areas the high eruptive temperatures at or above liquidus of fiii rhyolites and the bimodality of vms hosting volcanic successions indicate that fractional crystallization within subvolcanic intrusions could not have generated or significantly modified the compositions of fii and fiii fiv magmas this coupled with detailed geological geochemical and geochronological studies indicates that many of these subvolcanic intrusions were emplaced in multiple phases and that the later most voluminous phases often cut ore associated hydrothermally altered rocks a reassessment of the physical conditions responsible for producing the geochemistry of ore associated fii and fiii fiv felsic volcanic rocks and a review of the compositions of felsic volcanic rocks associated with vms deposits that range in age from mesoarchean to cenozoic provide important constraints on models for vms associated felsic volcanic rocks and their relationship to mineralization the compositions of felsic volcanic rocks may be explained by low to moderate degrees of partial melting of mafic sources at a range of depths within rift environments where the mineralogy and composition of the source regions modes and degrees of partial melting pressure and temperature of melting and to a lesser extent subsequent fractionation processes account for the compositional variations from fi through fii to fiii fiv long lived enhanced heat flow and structural permeability of rift environments that allows partial melting to form some fii rhyolites at midcrustal levels 10 15 km and fiii fiv rhyolites at shallow crustal levels 10 km both within the zone of brittle fracture permeability are essential to sustain the high temperature convective hydrothermal systems that are required to form large vms deposits and camps rift environments contain long lived thermal magmatic and structural corridors that focus magma ascent heat flow high temperature convective hydrothermal systems and emplacement of subvolcanic intrusions that are favorable environments for the formation of vms deposits and fii and fiii fiv felsic volcanic rocks

formation of volcanogenic massive sulfide deposits the kuroko perspective abstract the main objective of this paper is to identify the geochemical hydrological igneous and tectonic processes that led to the variations in the physical size geometry and chemical mineralogy metal ratios and zoning characteristics of volcanogenic massive sulfide deposits with respect to space from a scale of mining district size area to a global scale and time from a all volcanogenic massive sulfide deposits vmsds appear to have formed in extensional tectonic settings such as at mid ocean spreading centers backarc spreading centers and intracontinental rifts and failed rifts all vmsds appear to have formed in submarine depressions by seawater that became ore forming fluids through interactions with the heated upper crustal rocks submarine depressions especially those created by submarine caldera formation and or by large scale tectonic activities e g rifting become most favorable sites for the formation of large vmsds because of hydrological physical and chemical reasons the fundamental processes leading to the formation of vmsds include the following six processes 1 1 intrusion of a heat source typically a 10 3 km size pluton into an oceanic crust or a submarine continental crust causes deep convective circulation of seawater around the pluton the radius of a circulation cell is typically 5 km the temperature of fluids that discharge on the seafloor increases with time from the ambient temperature to a typical maximum of 350 c and then decreases gradually to the ambient temperatures in a time scale of 100 to 10 000 years the majority of sulfide and sulfate mineralization occurs during the waxing stage of hydrothermal activity 2 2 reactions between low temperature t 2 4 as disseminated gypsum and anhydrite in the country rocks 3 3 reactions of the modified seawater with higher temperature rocks at depths during the waxing stage cause the transformation of the seawater to metal and h 2 s rich ore forming fluids the metals and sulfide sulfur are leached from the county rocks the previously formed gypsum and anhydrite are reduced by fe 2 bearing minerals and organic matter providing additional h 2 s the mass of high temperature rocks that provide the metals and reduced sulfur is typically 10 11 tons 40 km 3 in volume the roles of magmatic fluids or gases are minor in most massive sulfide systems except for so 2 to produce acid type alteration in some systems 4 4 reactions between the ore forming fluids and cooler rocks in the discharge zone cause alteration of rocks and precipitation of some ore minerals in the stockwork ores 5 5 mixing of the ore forming fluids with local seawater within unconsolidated sediments and or on the seafloor causes precipitation of primitive ores with the black ore mineralogy sphalerite galena pyrite barite anhydrite 6 6 reactions between the primitive ores with later and hotter hydrothermal fluids cause transformation of primitive ores to matured ores that are enriched in chalcopyrite and pyrite variations in the mineralogical and elemental characteristics the geometry and the size of submarine hydrothermal deposits are controlled by the following four parameters 1 a the chemical and physical characteristics of seawater composition temperature density which depend largely on the geographical settings e g equatorial evaporating basins 2 b the chemical and physical characteristics of the plumbing system lithology fractures 3 c the thermal structure of the plumbing system which is determined largely by the ambient geothermal gradient and the size and temperature of the intrusive and 4 d the physical characteristics of the seafloor depth basin topography for example the submarine hydrothermal deposits developed in basaltic plumbing systems are generally poor in pb and ba compared to those developed in felsic plumbing systems the lower temperature systems are generally poorer in sulfides but richer in iron oxides and sulfates the higher temperature and larger hydrothermal systems tend to produce chalcopyrite and pyrite rich ores contrasts in the metal ratios between the noranda type archean vmsds and the younger vmsds reflect the differences in the geothermal gradient of the plumbing systems the submarine hydrothermal deposits developed in the near equatorial regions tend to form large continuous bedded type ores because of the likeliness of creating large stratified basins the basic processes of submarine hydrothermal mineralization have remained essentially the same throughout the geologic history from at least 3 5 billion year ago to the present

stable isotope geochemistry of clay minerals from fossil and active hydrothermal systems southwestern hokkaido japan abstract miocene submarine to quaternary terrestrial volcanism in southwestern hokkaido japan is associated with hydrothermal clay alteration and mineralization including kuroko type deposits at kagenosawa 14 2 ma cu zn pb au and minamishiraoi 12 5 ma ba zn pb cu vein style mineralization at date 5 2 ma au ag cu pb zn and chitose 3 6 ma au ag and geothermal activity at noboribetsu 1 8 ma the d and 18 o values of mica sericite mica smectite chlorite chlorite smectite nacrite dickite kaolinite and smectite were used to deduce the type s of hydrothermal fluid at each locality calculated compositions for minamishiraoi and kagenosawa fluids suggest that seawater was dominant but some mixing with magmatic water is also indicated particularly for the polymetallic kagenosawa deposit hydrothermal fluids at date chitose and the noboribetsu geothermal area were dominated by meteoric water minor involvement of magmatic water during mineralization at date cannot be ruled out but evolution of local meteoric water along an evaporation trend and or an 18 o shift due to hydrothermal rock meteoric water interaction also could have produced appropriate fluid compositions the d and 18 o values of modern hot spring waters at noboribetsu closely parallel fluid compositions calculated for the clay alteration at date chitose and noboribetsu because relatively poor reproducibility was obtained for the d values of the swelling clays additional tests were conducted stepwise heating showed that for some smectitic clays water evolved between 200 and 300 c had anomalously high d values because of residual interlayer water this error can be minimized by sufficiently long preheating in vacuo at 200 c in vacuo tg patterns of other smectitic clays suggested gradual loss of hydroxyl groups beginning near 200 c rather than the more typical distinct separation between interlayer water at 400 c this behaviour constrains the maximum temperature that can be used for in vacuo preheating furthermore shifts to lower d values by as much as 19 were obtained when this smectite was dispersed in low d water for three weeks perhaps indicating isotopic exchange however with appropriate care d values obtained by conventional procedures including preheating to 200 c normally reproduced natural compositions of the smectitic clays with acceptable accuracy and precision

slow senonian and fast palaeocene early eocene uplift of the granitoids in the central eastern pontides turkey apatite fission track results abstract dating and forward modelling of the fission track data of apatite samples from the dereli ebinkarahisar region south of giresun in the eastern turkish pontides provides quantitative data on the regional tectonics resulting from the closure of neo thetys and the collision of eurasia and gondwana the age vs elevation profiles identified senonian 80 7 3 2 to 62 4 2 5 ma slow uplift and denudation interpreted as the result of the diapiric ascent of subduction related plutons above the neo tethyan subduction zone beneath the eurasian continent this was followed by rapid differential uplift during the palaeocene early eocene 57 4 2 4 to 47 8 2 4 ma which juxtaposed granitoid units of different ages compositions and emplacement levels in the crust and is thought to be related to the collision between the pontide eurasian and anatolide gondwana basements the modelling results must be interpreted with caution but appear to indicate a period of mio pliocene ca 5 ma reheating related to volcanism associated with the westward escape of the anatolian plate and uplift from the pliocene ca 3 5 ma up to the present

alteration mineralogy lithochemistry and stable isotope geochemistry of the murgul artvin ne turkey volcanic hosted massive sulfide deposit implications for the alteration age and ore forming fluids abstract the murgul artvin ne turkey massive sulfide deposit is hosted dominantly by late cretaceous calc alkaline to transitional felsic volcanics the footwall rocks are represented by dacitic flows and pyroclastics whereas the hanging wall rocks consist of epiclastic rocks chemical exhalative rocks gypsum bearing vitric tuff purple vitric tuff and dacitic flows multi element variation diagrams of the hanging wall and footwall rocks exhibit similar patterns with considerable enrichment in k rb and ba and depletion in nb sr ti and p the chondrite normalized rare earth element rees patterns of all the rocks are characterized by pronounced positive negative eu anomalies as a result of different degrees of hydrothermal alteration and the semi protected effects of plagioclase fractionation mineralogical results suggest illite illite smectite chlorite kaolinite and chlorite in the footwall rocks and illite smectite kaolinite and chlorite illite in the hanging wall rocks overall the alteration pattern is represented by silica sericite chlorite and chlorite carbonate epidote sericite and quartz albite zones increments of ishikawa alteration indexes resulting from gains in k 2 o and losses in na 2 o and the chlorite carbonate pyrite index towards to the center of the stringer zone indicate the inner parts of the alteration zones calculations of the changes in the chemical mass imply a general volume increase in the footwall rocks abnormal volume increases are explained by silica and iron enrichments and a total depletion of alkalis in silica zone relative k increments are linked to the sericitization of plagioclase and glass shards and the formation of illite smectite in the sericite zone in addition fe enrichment is always met by pyrite formation accompanied by quartz and chlorite illite is favored over chlorite smectite and kaolinite in the central part of the ore body due to the increase in the al k na ca ratio although the rees were enriched in the silicification zone light rees show depletion in the silicification zone and enrichment in the other zones in contrast to the heavy rees behavior hydrothermal alteration within the hanging wall rocks apart from the gypsum bearing vitric tuffs is primarily controlled by chloritization with proportional fe and mg enrichments and sericitization the 18 o and d values of clay minerals systematically change with increasing formation temperature from 6 6 to 8 7 and 42 to 50 for illites and 8 6 and 52 for chlorite respectively the o and h stable isotopic data imply that hydrothermal alteration processes occurred at 253 332 c for illites and 136 c for chlorite with a temperature decrease outward from the center of the deposit the positive 34 s values 20 3 to 20 4 for gypsum suggest contributions from seawater sulfate reduced by fe oxide hydroxide phases within altered volcanic units thus the hydrothermal alteration possibly formed via a dissolution precipitation mechanism that operated under acidic conditions the k ar dating 73 62 ma of the illites indicates an illitization process from the maastrichtian to early danian period

hydrothermal alteration of felsic volcanic rocks associated with massive sulphide deposition in the northern iberian pyrite belt sw spain abstract massive sulphide deposits of the northern iberian pyrite belt ipb are mainly hosted by felsic volcanic rocks of rhyolitic to dacitic composition beneath most of the massive ores of this area e g concepcion san miguel aguas tenidas este or san telmo deposits there is usually a wide hydrothermal alteration halo associated with stockwork type mineralization within these alteration envelopes there are two principal rock types 1 chlorite rich rocks linked to the inner and more intensely altered zones and dominantly comprising chlorite pyrite quartz sericite carbonate rutile zircon chalcopyrite and 2 sericite rich rocks more common in the peripheral zones and showing a dominant paragenesis of sericite quartz pyrite chlorite carbonate rutile zircon sphalerite mass balance calculations comparing altered and least altered felsic volcanic rocks suggest that sericitization was accompanied by moderate enrichment in mg fe and h 2 o with depletion in si na and k and a slight net mass loss of about 3 chloritization shows an overall pattern which is similar to that of the sericitic alteration but with large gains in fe mg and h 2 o and minor enrichment in si s and mn and a significant loss of na and k and a minor loss of ca and rb however chloritization has involved a much larger net mass change mass gain of about 28 only a few elements such as nb y zr ti p and lree appear to have remained inert during hydrothermal alteration whilst ti and al have undergone very minor mobilization the results point to the severity of the physico chemical conditions that prevailed during the waxing stage of the ore forming hydrothermal systems further mineralogical and geochemical studies of the altered footwall rocks in the studied deposits indicate that hydrothermal ore bearing fluids reacted with host rocks in a multi stage process which produced a succession of mineralogical and chemical changes as the temperature increased

late cretaceous and cenozoic geology of the new madrid seismic zone structure contour maps constructed from well seismic reflection and outcrop data of the tops of the paleozoic section upper cretaceous section paleocene midway group and eocene section illustrate the post paleozoic structure of the new madrid seismic zone region isopach maps of the late cretaceous section midway group and eocene section help constrain the timing of the structural events these maps which encompass much of the northern mississippi embayment reveal reactivation of the underlying late precambrian cambrian reelfoot rift during midway group deposition but no reactivation during late cretaceous or eocene deposition the structure contour maps also indicate a subtle south plunging depression on the tops of the paleozoic upper cretaceous and midway group along the axis of the northern mississippi embayment that we have called a trench this trench is 50 km wide has a maximum depth of 100 m and appears to have formed during the eocene the trench s western boundary coincides with the blytheville arch lake county uplift and its southeastern margin underlies memphis tennessee the blytheville arch lake county uplift is the structure responsible for the new madrid seismic zone and thus it is possible that the southeastern margin of the trench is also a fault zone northern mississippi embayment post paleozoic stratigraphy consists of sands silts and clays that thicken from 477 m at new madrid missouri to 987 m near memphis tennessee the uniformity of these sediments indicates their elastic properties and therefore seismic velocities are very similar however variations in cementation and unconformities within the section may influence seismic wave propagation manuscript received 17 june 1999

microtremor observations of deep sediment resonance in metropolitan memphis tennessee we measured site resonance periods throughout metropolitan memphis tennessee the site resonance was derived from recordings of ambient microtremor and is a direct measurement of seismic ground shaking in the memphis metropolitan area the period t0 in s is predicted by the empirical relation t0 0 39899 7 8922 10 3h 3 0634 10 6h2 350 h 1100 m where h is the thickness in m of the unconsolidated sediments that overly hard paleozoic rocks assuming that a quarter wavelength relationship governs the relationship between resonant period sediment thickness and average shear wave speed we estimate the average shear wave speed of unconsolidated sediments as a function of sediment thicknesses vs 521 15 0 37459h 350 h 1100 m the scatter in the observations and discordance with earlier work suggests that caution is warranted in applying these values of wave speed indiscriminately to sites in the absence of further detailed work

kaolinized potassium leached zones at the contacts of the garn formation haltenbanken mid norwegian continental shelf abstract the middle jurassic garn formation consists mainly of subarkosic arenite in which potassium feldspar is several times as abundant as plagioclase in cores from eight wells the top of the formation upper 6 12 m appears to have undergone relatively intense alteration of potassium feldspar to kaolinite with the resulting loss of bulk postassium content this could be explained as a result of subaerial weathering of the top of the sandstone body except for the fact that in two of the wells the same pattern of alteration is observed at the base of the formation an alternative explanation is that alteration resulted from the introduction of acid released by the maturation of organic matter in adjacent shales in all instances the altered zones display a gradual increase in kaolinite content and a decrease in the ratio of bulk rock potassium aluminium over a distance of several metres approaching the formation boundary this pattern indicates that the active species responsible for the alteration entered vertically from the formation contacts rather than being introduced by lateral flow along the sandstone bed the cores studied are tentatively interpreted as recording different stages in the following depth related sequence of diagenetic events 1 early kaolinization throughout the formation by meteoric water flushing 2 formation of additional kaolinite near the formation contacts by the influx of acid from surrounding shales at approximately 2 7 km depth below the sea floor and 3 extensive alteration of kaolinite to illite at approximately 3 7 km depth illitization has been impeded in the leached zones near the formation contacts due to a local deficiency in reactive potassium here kaolinite survives unaltered whereas kaolinite throughout the rest of the formation has been extensively replaced by illite this implies that the illitization of sandstone can occur by short range diffusion in a chemically closed system solely in response to increasing thermal exposure at greater depth

petrology and geochemistry of tertiary volcanic rocks from the ikizce ordu area ne turkey implications for the evolution of the eastern pontide paleo magmatic arc abstract tertiary volcanism in the ikizce region at the western edge of the eastern pontides paleo magmatic arc is represented by basaltic and andesitic rocks associated with sediments deposited in a shallow basin environment the basaltic rocks contain plagioclase an58 80 olivine fo82 84 clinopyroxene wo44 48en35 42fs7 17 hornblende mg 0 68 0 76 phenocrysts and magnetite microcrysts whereas the andesitic rocks include plagioclase an25 61 clinopyroxene wo46 49en38 43fs11 13 hornblende mg 0 48 0 81 biotite mg 0 48 0 60 phenocrysts titanomagnetite apatite and zircon microcrysts geochemical data indicate magmatic evolution from tholeiitic alkaline transitional to calc alkaline characteristics with medium k contents the geochemical variation in the rocks can be explained by fractionation of common mineral phases such as clinopyroxene olivine hornblende plagioclase magnetite and apatite the trace elements distributions of the volcanic rocks show similarities to those of e type morb have a shape that is typical of rocks from subduction related tectonic setting with enrichment in lile and to a lesser extent in lree but depletion in hfse the rocks evolved from a parental magma derived from an enriched source formed by subduction induced metasomatism of basaltic rocks the latter formed through clinopyroxene olivine controlled fractionation in a high level magma chamber the andesitic rocks developed through hornblende plagioclase controlled fractionation in shallow level magma chamber s

environmental impact of mining activities on surface water and sediment qualities around murgul copper mine northeastern turkey mining activities in many countries around the world pose serious pressure on surrounding water bodies this study assesses the environmental impact of murgul mine one of the longest operated open pit copper mines in turkey a long term monitoring study was conducted on the surrounding surface water bodies to assess the degree of deterioration recovery in water quality stream water sediment and mine discharge samples were collected along the flow direction from the drainages under the influence of the mine sampling was also performed on the upgradient drainages from the mine to determine the background conditions water samples collected were analyzed for major ion and metal contents ph temperature ec and do contents of the water samples were measured in situ dissolved and total metal contents of the stream water samples and the mine discharges were also analyzed to determine the dominant transport phase of the metals negative effects of the past mining activities on murgul stream are visible on the streamside with the thick flotation deposits during monitoring study the most severe effect of the mining activities on murgul stream was observed following the leakage of tailing dam the impact of this incident was observed intensely up to the confluence of murgul stream and borcka dam reservoir and this was clearly seen in change of ph ec sulfate metal contents and water facies of murgul stream along flow direction toward borcka dam al fe mn cu zn pb and cd exhibited the highest concentration in the dissolved phase of the stream samples the impact of discharges from mine on murgul streambed was enormous and murgul stream was classified as heavily polluted water class iv according to turkish inland water quality regulations significant increase was also observed in metal contents of the stream sediments taken from the downstream from mine especially for cu s zn as ba and mo following the control of leakage prominent recovery in murgul stream quality was observed in many parameters and stream water achieved class i ii water quality results showed that metal loads transported in the suspended phase of stream were more significant than those in the dissolved phase current and past flotation slurry deposits near borcka dam reservoir may pose long term risk for aquatic life in borcka dam as a result of metal leaching and need further investigation

australian volcanic hosted massive sulfide deposits features styles and genetic models the cambro ordovician period has yielded the major development of volcanic hosted massive sulfide vhms deposits in australia resulting in about 12 million metric tons of contained metal copper lead and zinc concentrated in the mount read volcanics tasmania and the mount windsor volcanics queensland the archean 4 million metric tons of metal and the silurian 3 5 million metric tons of metal constitute the next important episodes while the devonian and permian have produced isolated deposits the deposits range from cu type to zn cu type to zn pb cu type the zn cu type deposits are restricted to the archean and silurian whereas the cu type and zn pb cu type occur sporadically throughout the time span from early archean to permian in general terms the major vhms bearing districts are calc alkaline in character and display a thick basal pile of rhyolitic volcanics 1 3 km thick including lavas epiclastics and subvolcanic intrusions which is overlain by a polymodal sequence containing various proportions of rhyolite dacite andesite basalt and sediments the major deposits are commonly located at the top contact of the rhyolite pile or within the lower part of the overlying polymodal sequence there is a wide range in variability of styles of australian vhms deposits including mounds pipes sheets layered deposits stacked deposits stockwork and disseminated deposits distal reworked deposits and cyclic layered deposits although these various styles show a range of features there is a consistent theme across the spectrum of metal zonation alteration mineralogy alteration chemistry sulfur isotopes macrotextures microtextures and host volcanic relationships which strongly suggests that they all belong to the one genetic group of ore deposit the classic mound style deposits such as hellyer have a series of key features subsets of which are represented in the other deposit styles the mound deposits are considered to form from deposition of metal sulfides on the sea floor immediately around the hydrothermal vent growth of the mound occurs by upward replacement of sulfide assemblages stable at higher fluid temperatures leading to zone refining and lead zinc silver gold enrichment in the outer and upper parts of the mound departure from the classic mound style of deposit is related principally to three key factors the chemistry of the ore fluid salinity temperature f02 and ah2s the nature permeability and chemistry of the volcanic pile and the sea hoor environment sea hoor topography and seawater depth these factors control the aspect ratio of the deposit the extent of stringer zone development the degree of subsea floor replacement mineralization the nature and spatial development of footwall alteration and the development and style of related distal mineralization sulfur isotope studies of australian vhms deposits indicate that reduced seawater sulfate is a major source of sulfur in the deposit whereas lead and strontium isotope results are compatible with the metals being derived by seawater convection and leaching from the volcanic pile and basement rocks this conclusion is supported by the application of various leaching models which demonstrate the availability of an adequate source of both base and precious metals in the footwall volcanic sequences the input of metals directly from volcanic magma chambers is not precluded by the available data and one likely scenario involves the contribution of gold and copper from a magmatic vapor plume rising to mix with convective seawater fluids which contribute lead zinc silver and gold leached from the footwall volcanics and basement rocks the relative importance of the magmatic input compared with the seawater convective input may help to explain the spectrum of deposit styles arid their spatial relationship to volcanic centers or adjacent sedimentary basins

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

geochemistry petrogenesis and tectonic setting of amphibolites from the southernmost exposure of the appalachian piedmont the uchee belt of the southern appalachian piedmont consists of a sequence of amphibolite amphibolitic gneiss and gneissic calc silicate surrounded by highly strained mylonitic rocks associated with motion along the bartletts ferry goat rock fault system amphibolites from three major localities within the belt the hudson mill rapids davis mill and lindsey creek localities have been analyzed for their major and trace element chemistry the mafic amphibolites are concluded to have been derived from intrinsically basaltic protoliths as determined by the presence of patchy zoning in relict igneous plagioclase normative mineralogy niggli trends and a variety of diagnostic geochemical criteria davis mill amphibolites are characterized by high ree abundances and flat ree pattern la yb sub n 1 3 to 2 3 similar to volcanic rocks from pacific type island arcs geochemical parameters such as high la nb and v ni ratios low ti v and ti zr ratios and discriminant trace element diagrams based on elements generally considered immobile during metamorphism indicate an island arc and back arc basin affinity for the amphibolites hudson mill rapids amphibolites characterized by a wide range of ree concentrations and strongly negative ce anomaly are interpreted as having been derived from parental basalts produced in a back arc basin by melting of a descending slabmore plus mantle wedge the chemical diversity of the amphibolites and the presence of thrusts strike slip faults and highly strained rocks are consistent with the premise that the western uchee belt is a deformed composite part of an extensive arc system less

mineralogy bulk and rare earth element geochemistry of massive sulphide associated hydrothermal sediments of the brunswick horizon bathurst mining camp new brunswick massive sulphides are spatially and temporally associated with iron formation if and other hydrothermal sedimentary rocks in the vicinity of the brunswick no 12 brunswick no 6 and austin brook deposits bathurst mining camp sulphide carbonate oxide and silicate predominant if is present carbonate predominant if is best developed in and around the brunswick no 12 deposit whereas hematite bearing if is absent here but prominent in the austin brook brunswick no 6 area the if is composed dominantly of si co2 fe mn and ca minor constituents include mg p ti al and s statistically significant interelement correlations between eu fe mn pb zn cd au ca sr ba p co2 and s indicate that these elements were precipitated from hydrothermal fluids vented onto the seafloor positive interelement correlations between si ti al mg k zr rare earth elements ree s except eu se v y yb co ni and cr reflect the presence of detrital clastic mafic and aluminosilicate minerals and

mass change calculations in altered rock series a technique is presented whereby precursors of altered rocks in a fractionated rock series can be identified and changes in chemical components mass and volume accurately calculated the procedure utilizes elements with high degrees of immobility in hydrothermal and associated interactive water rock systems igneous rock series and sedimentary and metamorphic rocks with primary continuity of chemical composition are amenable to this treatment in the procedure for igneous rocks best fit fractionation lines are established for an immobile igneous compatible incompatible element pair the latter element functioning as the fractionation monitor alteration paths are linear and pass through the origin intersections of the fractionation and alteration lines yield the immobile element concentrations in the precursors to the altered rocks mobile components are determined from fractionation lines and monitor values total mass changes are proportional to the displacement of altered samples from the fractionation line masses of other elements in an altered sample reconstructed values are recalculated to the concentration of the monitor element in the precursor chemical changes are the differences between the calculated precursor compositions and the reconstructed altered rock compositions errors are mainly a function of the positioning of the fractionation lines

alteration and lithogeochemistry in the masara gold district eastern mindanao philippines as tools for exploration targeting abstract the intermediate to low sulfidation epithermal gold deposit in masara compostela valley eastern mindanao philippines is associated with a diorite porphyry from the late miocene lamingag intrusive complex detailed mineralogical investigation of the host rocks in the deposit reveals five major alteration zones and at least two mineralizing events a potassic alteration zone characterized by stockwork magnetite veins secondary biotite and magnetite and an early stage chlorite sericite alteration composed of quartz chlorite illite sericite pyrite biotite magnetite calcite assemblages are interpreted to be linked with an earlier porphyry copper system in the area these were overprinted by late stage chlorite sericite alteration consisting of quartz chlorite illite sericite pyrite adularia magnetite epidote and sericite assemblages which generally contain quartz illite sericite pyrite these alteration overprints are inferred to be related to a younger low to intermediate sulfidation epithermal gold mineralization which involved near neutral fluids advanced argillic alteration comprising quartz kaolinite magnetite dickite illite calcite was also observed in the area isocon analysis shows that alteration zones associated with epithermal mineralization are generally characterized by enrichment in sio 2 and k 2 o and depletion of cao and na 2 o as well as additions of au cu zn and pb pearce element ratio per analysis indicates high degrees of sericitization in the altered diorite porphyry tuff and quartz diorite units at least three major alteration centers are defined based on the spatial distribution of the alteration index of surface samples calculated from the per analysis the results of this study support the use of whole rock geochemistry as a complement to traditional techniques in exploration geochemistry

comparison of metasomatic reactions between a common co 2 rich vein fluid and diverse wall rocks intensive variables mass transfers and au mineralization at alleghany california the gold deposits at alleghany california are typical of many epigenetic gold bearing hydrothermal vein systems in metamorphic terranes worldwide detailed analyses of alteration halos in serpentinite mafic amphibolite and granite wall rocks at alleghany indicate that widely contrasting deposit types ranging from fuchsite carbonate schists to pyrite albitites resulted when different wall rocks interacted with the same externally derived co 2 rich hydrothermal vein fluid patterns of element redistribution within halos and among lithologic units suggest a complex process involving fluid flow along vein fractures and diffusion or infiltration normal to the veins wall rocks locally controlled both the directions and magnitudes of chemical fluxes across vein walls vein fluids at constant temperature and pressure with relatively constant ratios of mobile species na super k super h super and co 2 h 2 s h 2 caused contrasting divergent reactions in proximal alteration zones because the wall rocks controlled the ratios of relatively immobile species al cr fe mg and fe mg and the component activities of hydrothermal mineral solid solutions thus pyrite and albite were stable with respect to the relatively pure siderite and k mica that occur sparingly in proximal granite zones but they were not stable with respect to the relatively impure siderite and k mica that characterize proximal serpentinite zones partly as a result of divergent reactions altered rocks exhibit contrasting mobile element concentration gradients e g ca ba sr rb na k c s and imply local sources and sinks and possibly short residence times for some of these components along discordant fluid flow paths calculated reaction coefficients for h super h 2 and h 2 s indicate that different wall rocks at different stages of alteration may have inhibited or promoted gold precipitation the distribution of gold and its calculated solubility are consistent with its having been precipitated from au hs 2 super complexes in response to pyritization of granite fluid desulfidation and reduction and possibly in part in response to dolomitization and sericitization of serpentinite fluid acidification strata bound disseminated orebodies may be expected in a variety of other host rocks with higher than average fe mg ratios where pyrite was stable with respect to intermediate magnesite siderite as in the granite it is proposed that the co 2 rich vein fluids approached partial equilibrium with alteration assemblages in the average or dominant rocks along their flow paths simpler but radically different proximal assemblages were then produced where the fluids encountered chemically extreme rock types fluid rock interaction equilibria can account for much of the diversity in the mineralogy and chemistry of gold deposits in heterogeneous metamorphic terranes while maintaining a simple genetic classification based on the distinctive chemistry of the hydrothermal fluids comparative studies of multicomponent phase equilibria and mass exchanges can provide both rationalizations and predictions of local wall rock effects on geochemical anomalies and the locations of ore deposits in lithologically heterogeneous terranes simultaneous consideration of contrasting high variance phase deficient assemblages along discordant veins is suggested as a general method for quantifying fluid intensive variables in metasomatic systems

mass volume and chemical changes in the alteration zone at the norbec mine noranda quebec a funnel shaped alteration pipe in archean rhyolite and andesite below massive sulphide zn cu ores at the norbec mine in northwestern quebec was outlined from drill core samples geochemical parameters and normative alteration mineralogy the pipe has a mass of 37 9 million tonnes giving a volume of 13 106 m3 which represents volume increase of 10 relative to the unaltered host volcanic rocks a bulk chemical composition was calculated using weighting procedures for volumes of influence for the samples net mobile mass change or chemical flux for the alteration pipe was 5 8 106 tonnes inclusion of the massive ore lens yields a flux of 9 6 106 tonnes for the whole hydrothermal system the largest additions to the system in millions of tonnes were feo 4 2 sio2 3 8 s 1 8 k2o 0 55 and mgo 0 5 the only depletions were na2o 1 4 and cao 0 44 base and precious metals accounted for 3 4 of the total element flux

massive sulfide deposits of the noranda area quebec iv the mobrun mine the corbet deposit is located in the upper part of the flavrian andesite the lowest volcanic formation within cycle iii of the noranda central mine sequence the deposit consisted of one main lens of massive sulfides and several smaller lenses and contained 2 7 106 t of mineable ore at 2 92 cu 1 98 zn 20 6 g t ag and 1 0 g t au the orebody had a massive pyrrhotite chalcopyrite core which passed laterally into massive pyrite sphalerite the northwestern part of the ore body is overlain by 50 100 m of flavrian andesite whereas the southeastern portion is overlain by northwest rhyolite lavas within the flavrian andesite and the lower northwest rhyolite are low in k2o 0 5 and are partly of tholeiitic affinity and partly of transitional affinity the tholeiitic volcanic series has zr y ratios of 2 8 to 4 5 whereas the transitional series has zr y ratios of 4 5 to 7 1 the two series are also distinct in plots of nb zr yb zr nb y and the rare earth elements these data indicate that two s

mineralogical and geochemical characteristics of hydrothermal alteration of basalt in the kuroko mine area japan implications for the evolution of a back arc basin hydrothermal system abstract basalt in the furutobe district of the kuroko mine area in japan is characterized by abundant chlorite and epidote fluid inclusion studies indicate that chlorite is formed at lower temperatures 230 250 c than epidote 250 280 c the seawater basalt mass ratio for the early chlorite rich alteration was high max 40 but that for the later alteration was low 0 1 1 8 the cao na2o and sio2 of the bulk rock correlate negatively with mgo while feo and fe correlate positively with mgo these changes in the characteristic features of hydrothermal alteration from early to late are generally similar to those for a mid ocean ridge geothermal system accompanying basalt alteration the mgo feo ratios of chlorite and actinolite and the fe2o3 concentration of epidote from the basalt are greater than those of mid ocean ridge basalt probably owing to the differences in the fe2o3 feo and mgo feo ratios of the parent rocks the lower cao concentration and the higher na2o concentration of the bulk rock compared with altered mid ocean ridge basalt can be interpreted in terms of the difference in original bulk rock compositions the furutobe basalt as well as other submarine back arc basalts contains more vesicles filled with hydrothermal minerals epidote calcite quartz chlorite pyrite than do the mid ocean ridge basalts the abundance of vesicles plays an important role in controlling the secondary mineralogy and geochemistry of hydrothermally altered submarine back arc basin basalts

constraints of c o s isotope compositions and the origin of the unlupinar volcanic hosted epithermal pb zn au deposit gumushane ne turkey abstract the eastern pontide orogenic belt epob constitutes one of the best examples of the metallogenic provinces in on the alpine himalayan belt this study focuses on the genesis of the unlupinar pb zn au deposit in the southern part of the eastern pontide orogenic belt the main lithological units in the study area are the early carboniferous kurtoglu metamorphic complex the late carboniferous kose granitoid and the early middle jurassic enkoy formation the studied deposit is hosted by the enkoy formation which consists predominantly of basaltic andesitic rocks and associated pyroclastic rocks that are calc alkaline in composition silicic sulfidic argillic chloritic hematitic carbonate and limonite are the most obvious alteration types observed in the deposit site ore microscopy studies exhibit that the mineral paragenesis in deposits includes pyrite chalcopyrite sphalerite galena gold quartz and calcite electron microprobe analyses conducted on sphalerite indicate that the zn cd ratio varies between 84 and 204 and these ratios point at a hydrothermal deposit related to granitic magmas fluid inclusion studies in calcite and quartz show that the homogenization temperature of the studied deposit ranges between 90 160 c and 120 330 c respectively the values of sulfur isotope analysis of pyrite sphalerite and galena minerals vary between 1 6 and 5 7 and the results of oxygen and carbon isotope analysis range between 8 4 and 18 and 5 and 3 6 respectively the average formation temperature of the ore was calculated as 264 c with a sulfur isotope geothermometer all of the data indicate that the unlupinar deposit is an epithermal vein type mineralization that was formed depending on the granitic magmatism

intense silicification of footwall sedimentary rocks in the stockwork alteration zone beneath the brunswick no 12 massive sulphide deposit bathurst new brunswick intensely silicified volcaniclastic mudstones that underlie the brunswick no 12 massive sulphide deposit in northern new brunswick resemble silicified rocks described in the immediate footwall of many ancient and modern massive sulphide deposits the white to grey cryptocrystalline silica in the silicified rocks becomes more common with proximity to the vent and is most abundant immediately below the massive sulphide zone mass balance analysis of altered footwall sedimentary rocks on the 850 m level of the mine shows that sio2 increases up to 300 the high silica enrichment in the feeder zone is consistent with the presence of cherty silica in the massive sulphides and in associated exhalative iron formation coincident with silicification are enrichments in s feot mgo mno cao p2o5 f cl y cu co cr and ni as well as light rare earth elements and eu oxygen isotope analyses of chloritized and silicified footwall sedimentary rocks suggest that the hydrothermal fluid had a 18o composition o

regional variations in near surface shear wave velocity in the greater memphis area abstract site specific and regional analyses were conducted for an area that includes southwestern tennessee eastern arkansas and northwestern mississippi to establish characteristic shear wave velocity vs profiles based on measured profiles compiled from several researchers site specific studies were conducted at two locations near memphis tennessee to determine the uncertainty and randomness in measuring vs due to test related factors and local variability the result of this analysis was subsequently used as a criterion for establishing the range of variability for the characteristic vs profiles measured vs profiles were aggregated based on the age and type of geologic deposits in the memphis area to obtain characteristic profiles holocene alluvial deposits were found to have a fairly uniform shear wave velocity profile in the mississippi river floodplain pleistocene deposits characterized by a surficial layer of loess in the terrace regions of mississippi and tennessee were found to be more variable the average shear wave velocity in the upper 30 m was calculated for each measured profile based on the recommendations of the 1997 national earthquake hazards reduction program nehrp provisions to assess the susceptibility of a deposit to ground motion amplification the lowest and highest average near surface shear wave velocities were identified in the mississippi river alluvium and the pleistocene deposits respectively based on the nehrp site classes all deposits may be classified as d stiff soil however due to the thickness of soft soil deposits in the alluvial plain these deposits may be classified as e more than 3 m of soft clay based on the site class description rather than the shear wave velocity therefore a re evaluation of the nehrp site classes is proposed for the central us to more accurately represent the actual site conditions

titanite and zircon fission track dating resolves successive igneous episodes in the formation of the composite kackar batholith in the turkish eastern pontides the kackar batholith in the turkish eastern pontides comprises several intrusive units with distinctive textural mineralogical and geochemical characteristics their titanite and zircon fission track ages confirm that the different lithodem units result from consecutive igneous episodes establish their emplacement sequence and together with geochemical data help to relate them to their geodynamic context the camlikaya granitoid 112 4 1 6 ma was emplaced during an immature arc magmatic episode of early cretaceous age the sirtyayla 57 1 1 2 ma and marselevat 52 9 1 3 ma granitoids are late products of a late palaeocene mature arc episode the ayder granitoid 46 4 1 0 ma is the result of middle to late eocene post collisional magmatism related to slab break off the halkalitas quartz diorite 43 7 2 3 ma and the gullubag monzonite 38 1 0 9 ma document a middle to late eocene episode related to post collisional extension the data reveal the advantages of dense sampling spanning a maximum range of elevations apart from the increased precision on the mean redundant sampling allows to shift the basis for interpretation from a priori assumptions to a posteriori numerical criteria when using geochronometers with low to moderate closure temperatures including apatite titanite and zircon fission tracks but also k ar ar ar biotite muscovite and k feldspar

a preliminary investigation into the relationship between long period seismic noise and local fluctuations in the atmospheric pressure field summary the displacement response of an elastic half space to a plane pressure wave is examined in order to establish the conditions under which sources of this type can contribute significantly to the long period seismic noise field the study is restricted to pressure waves which propagate at velocities well below the seismic wave velocities characteristic of the half space the numerical studies indicate that pressure waves with amplitudes of 100 pbar or more can contribute significantly to the long period vertical background noise observed at the surface provided that the detectors are located on sections of alluvial fill or poorly to moderately indurated sandstones and shales whose thicknesses are greater than about a kilometre these same waves can also create significant tilt noise on long period horizontal seismographs located at or near the surface regardless of the rock type the seismic disturbances created by pressure waves decay rapidly away from the surface therefore it appears that it may be possible to eliminate the effects of atmospherically generated noise by placing the detectors at moderate depths

volcanic belts as markers of the mesozoic cenozoic active margin of eurasia discussion discussion sur l article de kazmin v g sbortshikov i m ricov l e zonenshain l p bovlin j knipper a l paru dans tectonophysics nld 1986 123 123 152

site amplification in the san fernando valley california variability of site effect estimation using the s wave coda and h v methods during the months that followed the 17 january 1994 m 6 7 northridge california earthquake portable digital seismic stations were deployed in the san fernando basin to record aftershock data and estimate site amplification factors this study analyzes data recorded on 31 three component stations from 38 aftershocks ranging from m 3 0 to m 5 1 and depths from 0 2 to 19 km site responses from the 31 stations are estimated from coda waves s waves and ratios of horizontal to vertical h v recordings for the coda and the s waves site response is estimated using both direct spectral ratios and a generalized inversion scheme results from the inversions indicate that the effect of qs can be significant especially at high frequencies site amplifications estimated from the coda of the vertical and horizontal components can be significantly different from each other depending on the choice of the reference site the difference is reduced when an average of six rock sites is used as a reference site in addition when using this multi reference site the coda amplification from rock sites is usually within a factor of 2 of the amplification determined from the direct spectral ratios and the inversion of the s waves however for nonrock sites the coda amplification can be larger by a factor of 2 or more when compared with the amplification estimated from the direct spectral ratios and the inversion of the s waves the h v method for estimating site response is found to extract the same predominant peaks as the direct spectral ratio and the inversion methods the amplifications determined from the hiv method are however different from the amplifications determined from the other methods finally the stations were grouped into classes based on two different classifications general geology and a more detailed classification using a quaternary geology map for the los angeles and san fernando areas average site response estimates using the site characterization based on the detailed geology show better correlation between amplification and surface geology than the general geology classification

shear wave velocity of the sedimentary basin in the upper mississippi embayment using s to p converted waves from mid october 1989 to august 1992 40 three component panda portable array for numerical data acquisition stations were deployed in the central new madrid seismic zone three component digital seismograms recorded by the panda stations in the region are characterized by 1 the very weak direct s arrivals on the vertical component which can be identified unambiguously from the two horizontal components and 2 at least two prominent secondary arrivals between the direct p and s arrivals one sp dominant on the vertical component and another ps with smaller amplitude on the two horizontal components travel time differences between the sp and s and between the p and ps are the same for different earthquakes recorded at the same station but are different at different stations even for the same event polarization analyses of three component seismograms and travel time measurements confirm the interpretation that these two secondary arrivals are the p to s ps and s to p sp converted waves that occur at the bottom of the sedimentary basin beneath each station since abundant well log data are available in the upper mississippi embayment the thickness of the sediments beneath each seismic station can be estimated travel time differences between the direct and the converted waves can be used to calculate average shear wave velocity for the sediments beneath each station the estimated shear wave velocities of the sediments beneath panda stations vary from 0 45 to 0 67 km sec the higher shear wave velocity associated with thicker sediments can be interpreted as a consequence of increasing compaction of unconsolidated sediments due to increasing overburden

giant pyritic base metal deposits the example of feitais aljustrel portugal detailed study of hanging wall rocks and alteration above the giant feitais orebody of aljustrel iberian pyrite belt portugal shows that cherts that constitute the immediate hanging wall to the sulfide deposit result from hydrothermal alteration of laterally equivalent fe and or mn rich jaspers textures geochemistry and lack of fossil radiolarians indicate that these jaspers are hydrothermal precipitates hydrothermal alteration of the jaspers took place concomitantly with sulfide precipitation through reaction with hot 150 c reduced fluids with replacement of hematite by magnetite pyrite and fe2 phyllosilicates on the basis of the above and considering also the results of previous studies on hydrothermal activity in the aljustrel volcanic rocks and sulfide ores we propose that sulfide precipitation may have taken place under a thin veneer of siliceous sediments present day massive sulfide formation in the guaymas basin and in the salton sea under hundreds of meters of sediments may be approximate analogues in the sense that the presence of a caprock reduces dispersion of black smoke and causes more efficient precipitation

zn pb cu massive sulfide deposits brine pool types occur in collisional orogens black smoker types occur in backarc and or arc basins volcanic hosted massive sulfide deposits of zn pb cu type were derived either from seawater dominated buoyant fluids that built mounds on the seafloor e g the ores of the hokuroku basin japan or from saline fluids that reversed buoyancy on mixing with seawater and filled basins on the seafloor e g several ores of the iberian pyrite belt and the mount read province in tasmania the hokuroku ores formed above subduction zones during protracted periods of regional extension but both the iberian pyrite belt and the mount read province formed under extensional stress during continent continent iberia or arc continent mount read collision and orogenesis in the iberian pyrite belt oblique convergence resulted in transcurrent faulting and this may also be the case for the mount read province transcurrent faulting may have allowed easy vertical access for the ore related magmas some of which were sourced in the asthenosphere as well as the blueschist and eclogitic facies emplaced in adjacent terrains and possibly also saline fluids exsolved from the magmas

array observations of microseismic noise and the nature of h v in the mississippi embayment abstract ambient ground motion data were collected using phased seismic arrays in fall 2002 and spring 2007 within the mississippi embayment and at a single station external to the embayment these data allowed us to determine the wave field composition of ambient noise for understanding wave propagation mechanisms giving rise to spectral peaks using nakamura s h v technique ambient ground motions in the frequency band of 0 1 0 33 hz 10 3 sec period were dominated by spatially localized rayleigh and love wave microseisms generated by high ocean waves along the north american seaboard in the time periods of analysis seismic waves important in forming the h v peak near 4 sec period are composed of relatively high phase velocity rayleigh and love waves that convert to propagating homogeneous shear waves in the thick unconsolidated sediments of the embayment the h v resonant period is controlled by both constructive and destructive interference of these shear waves a simple relationship for the h v peak is given using a propagator matrix formulation that predicts the resonance frequency of a layered medium for surface wave motion at the base of the system the amplitude of the observed h v peak however does not give an accurate estimate of shear wave amplification because it depends on the slowness of the incident wave the inconsistency in estimated average shear wave velocities using the h v method and differential travel times of local earthquake sp phases in the mississippi embayment may be explained by misidentification of sp wave conversion points from deeper interfaces

geochemistry and tectonic significance of the ongarbira metavolcanic rocks singhbhum district india abstract the volcanic sedimentary sequence of ongarbira occurs to the south of the singhbhum shear zone and rests uncomformably on a basement topographic low between the chakradharpur granite and the singhbhum granite structural analysis reveals that the ongarbira synform and other adjoining structures are kilometre scale first generation folds on e w striking axial planes these structures are in marked contrast with the corresponding kilometre scale first generation folds typical of the iron ore group synclinorium towards the south of the ongarbira belt the ongarbira metavolcanic rocks exhibit a limited range of tholeitic basalt compositions the basalts are grouped according to their mg and the details of their ree patterns groups i and ii are relatively unevolved and very similar to lree and lil depleted ocean ridge tholeiites the most evolved group iii with lree enrichment is most similar to lil enriched ocean floor basalts but may be contaminated with crustal materials in general the ongarbira volcanics evolve upward stratigraphically petrogenetic major element modelling of the ongarbira basalts suggests that the primary melt was generated by batch melting 30 of lherzolite at pressures of at least 1 5 gpa sequential fractionation of ol o1 cpx pl and cpx pl followed comparison of incompatible and compatible element distributions indicates a very similar batch m melting fractional crystallization sequence for ongarbira groups i and ii basalts group iii basalts may have been derived from a batch melt initially more enriched in incompatible elements trace element discrimination of the ongarbira basalts suggests that they were generated in an extensional environment primordial mantle normalized element distributions indicate that the basalts are similar to continental rift basalts but with oceanic affinities the chemical data along with the associated sediments indicate that the ongarbira basalts were probably emplaced in a mature continental rift although a back arc origin cannot be completely disregarded it is concluded that the ongarbira volcanics were emplaced as part of the same rifting event that resulted in outpourings of the proterozoic dalma and dhanjori volcanics implying that the ongarbira suite is proterozoic and not part of the archaean iron ore group the structural geometry of the ongarbira rocks is more conformable to that of the singhbhum mobile belt than to the iron ore group synclinorium in the singhbhum craton it is likely that the southern limit of the singhbhum mobile belt is defined by the interface of its e w structures with the nne structures of the iron ore group rocks thus the singhbhum shear zone does not mark the interface between the archaean singhbhum craton and the proterozoic singhbhum mobile belt in the eastern indian shield

ground motion site effect in the beijing metropolitan area abstract in the past 500 years many moderate to strong earthquakes have occurred in or near the beijing metropolitan area which is underlain by thick quaternary and tertiary sediments therefore the area is susceptible to damage associated with ground motion site effect particularly for the large number of high rise buildings in order to understand the earthquake site effect potential particularly in the context of the high rise buildings we are undertaking an effort to construct a 3 d shear velocity model of the quaternary and tertiary sediments for the beijing metropolitan area in this paper we present an integrated method of deriving shear wave velocity profiles at sites across the beijing metropolitan area using shear wave velocity and ambient noise measurements our results demonstrate that this method is practical for obtaining shear wave velocity profiles we performed 1 d site response analyses at six sites in the beijing metropolitan area the results show that the site resonant periods vary between 0 1 s at shallow sites in the west and 4 0 s for deep sites in the east moreover this range of resonant periods coincides with the fundamental periods of many buildings between one to 40 stories in other words earthquake site effect could generate a double resonance in a significant number of buildings in the beijing area results also show that the average shear wave velocity of the top 20 or 30 m vs20 or vs30 does not correlate with site resonance and is therefore not an appropriate parameter to account for site effect in earthquake engineering

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

microtremor measurements used to map thickness of soft sediments the observations about the behavior of microtremor spectra presented here show that noise measurements can be used as a powerful tool to determine the thickness of soft cover layers the most suitable method for this determination is nakamura s technique which is the ratio of the horizontal component noise spectrum and that of the vertical component i i v spectrum the frequency of the main peak in these spectral ratios correlates well with the sediment thickness at the site using an extensive database of microtremor measurements carried out in the western lower rhine embayment germany it was possible to show that this correlation is clearly valid for a wide range of thickness namely from tens of meters to more than 1000 m a simple formula was derived that for the sediments to be found in the area investigated directly calculates the cover thickness from the frequency of the main peak in the h v spectrum a comparison with calculated resonant frequencies sug gests the relation derived from the noise measurements depending on the velocity depth function of the shear wave classical spectral ratios are shown to be strongly influenced by the noise level and are therefore less reliable in determining the res onant frequency of the subsoil the practical relevance of the investigation is illus trated by means of cross sections constructed from results of the microtremor anal yses which provide a convincing image of the surficial structure of the areas investigated

paleomagnetism of the samar ophiolite implications for the cretaceous sub equatorial position of the philippine island arc abstract samar island in the eastern part of central philippines is underlain by a complete ophiolite suite the samar ophiolite we present the first geochronological and paleomagnetic data for the samar ophiolite whole rock k ar dating of two basalt samples yielded an age of 100 2 2 7 ma and 97 9 2 8 ma thirteen sites in four localities yielded characteristic remanent magnetization with in situ direction of d 340 i 24 k 15 95 11 and tilt corrected direction of d 342 i 27 k 15 95 11 these values suggest that the ophiolitic basement rocks of samar formed in the late cretaceous at a paleolatitude of 14 s 6 the paleolatitude is several degrees south of the sub equatorial positions calculated for the three other mesozoic ophiolites of the philippine mobile belt pmb whose paleomagnetism had been previously studied the pmb ophiolites in eastern and central philippines share a common age geochemistry and paleolatitude with the halmahera ophiolite suggesting that they originated from a mesozoic supra subduction zone that spanned a few degrees north of the equator to around 15 s

microseisms observations in the santa clara valley california we have investigated ground motion amplification in the santa clara valley scv using microseisms observed during the 1998 deployment of 41 short period seismometers the santa clara valley seismic experiment scvse lindh et al 1999 fletcher et al 2003 recorded many local regional and teleseismic events in our previous work we investigated the 3d velocity structure of the scv by modeling the teleseismic p waves recorded during the scvse dolenc et al 2005 to complement these results we now focus on the microseisms that were recorded during the same period and relate these observations to local earthquake wave amplification it is found that the seismic noise is related to the ocean wave heights measured on the weather buoy west of half moon bay california the spectral ratio of the horizontal to vertical h v microseisms at each scvse site is stable with time and the period of the dominant peak in the h v ratio is related to the basin depth the results of this study show that seismic noise can be used in the assessment of the effects of deep sediments on long period earthquake ground motions

geochemical characteristics of the composite kackar batholith generated in a neo tethyan convergence system eastern pontides turkey abstract the composite kackar batholith of cretaceous to late eocene age consists of various intrusions derived from different geodynamic settings ranging from early to mature arc through collision to post collisional extension in the neo tethyan convergence system of the eastern pontides of ne turkey the intrusions were emplaced into cretaceous and middle eocene volcano sedimentary units and are unconformably overlain by late cretaceous early to middle eocene and miocene units the 10 lithological units are grouped into five geodynamic associations on the basis of geological setting and geochemical characteristics 1 early arc origin as represented by the medium k calc alkaline calk camlikaya granitoid of early cretaceous age 2 mature arc origin as represented by the medium to high k calc alkaline sirtyayla and marselevat granitoids of late cretaceous to early palaeocene age 3 syn collisional plutonism as represented by the peraluminous asniyor leucogranite of palaeocene age 4 post collisional plutonism as represented by the high k calc alkaline ayder k feldspar megacrystic granitoid and the sasmistal microgranite of middle to late eocene age 5 the extension related mildly alkaline gullubag monzonite the medium k calc alkaline to slightly tholeiitic thol halkalitas quartz diorite and the low k tholeiitic ardesen gabbro and isina diabase of late eocene age that are mainly exposed as small shallow stocks and n s ne sw nw se and e w trending veins

geochemical fluid inclusion and isotopic o h and s constraints on the origin of pb zn au vein type mineralizations in the eastern pontides orogenic belt ne turkey abstract the mineralization area altinpinar torul gumushane is situated in the southern zone of the eastern pontides orogenic belt epob which is one of the important metallogenic provinces in the alpine himalayan belt and is intruded by the late carboniferous granitic rocks gumushane granitoid an early to middle jurassic volcano sedimentary unit consisting mainly of basaltic andesitic volcanic and pyroclastic rocks enkoy formation and eocene basaltic andesitic volcanic rocks alibaba formation the studied pb zn au mineralizations are related to silica veins ranging from a few millimeters to a maximum of 40 cm in thickness and are localized within fracture zones developed along the contact between the gumushane granitoid and enkoy formation silicic sulfidic hematitic argillic intense chloritic and carbonate alteration are the most common types from the fault lines toward the outer zones cavity filling and banded structures are widely observed the mineral paragenesis comprises galena sphalerite pyrite chalcopyrite tennantite and quartz mineral chemistry studies indicate that ion exchange occurs between zn and fe in sphalerites and the zn cd ratio of sphalerites varies between 50 65 and 144 64 the homogenization temperatures measured from fluid inclusions vary between 170 c and 380 c especially between 250 c and 300 c and the wt nacl eqv salinity of ore forming fluids is between 2 4 and 7 3 4 7 on average supporting an epithermal system in their origin the values of sulfur isotopes which are obtained from pyrite and galena minerals range between 8 3 and 2 3 indicating that sulfur which enables mineral formation originates from magmatic genesis the average formation temperature of the ore is 317 c as determined with a sulfur isotope geothermometer the values of oxygen and hydrogen isotopes vary between 8 5 and 10 2 and 91 and 73 respectively with regard to the compositions of oxygen and hydrogen isotopes fluids comprising the mineralization are formed by the mixture of magmatic water and meteoric water this situation is supported by the fact that the increase in the homogenization temperature indicates dilution with surface water but depends on the increase in the salinity of fluid inclusions considering all the data it is clear that the studied mineralization is an epithermal vein type mineralization that is related to granitic magmas

broadband microtremor observation of basin resonance in the mississippi embayment central us we report systematic variations in the fundamental period of seismic site resonance within the mississippi embayment the resonance periods are revealed by peaks in horizontal to vertical h v spectral ratios of microtremor measurements and increase with the depth to the sediment basement interface the sediment depth varies slowly enough spatially that at any site it can be modeled as a one dimensional problem revealing structural details of the sedimentary column the strong impedance contrast and gentle dip of the base of the embayment sediments may trap seismic energy within the soft sediments increasing durations and amplitudes of strong ground motions broadband recordings of microtremor within the mississippi embayment provide a simple method to study the seismic response of the basin

seismic ground motions from a bolide shock wave 1 an intensely brilliant bolide accompanied by an audible sonic boom occurred on the night of 3 november 2003 2150 lt or 4 november 2003 0350 ut in northeastern arkansas the sonic boom was well recorded by 22 three component stations of the center for earthquake research and information cooperative seismic network arrival times and wave polarizations were used to reconstruct the acoustic wave front propagating across the network and to estimate trajectory parameters of the bolide a grid search location technique constrains the trajectory and gives a reference height of 50 100 km above the southern edge of the network an azimuth of propagation of 270 290 toward the northwest and a plunge of 38 48 downward the trajectory and date of the bolide event are consistent with a taurid shower meteor transient ground motions from the sonic boom were studied using plane wave cagniard dehoop and propagator matrix theory for an incident pressure pulse impinging on a layered elastic earth model general characteristics of the vertical and radial polarization and wave frequency content require acoustic coupling within a thin 10 m near surface layer with low p wave 0 25 km s and s wave 0 125 km s velocities ground motions are generally confined to this near surface layer are not sensitive to deeper earth structure within the mississippi embayment unconsolidated sediments and display both leaky mode pl a type of dispersed p type seismic wave and locked mode rayleigh wave propagation acoustic wave ground motion coupling studies may be a useful way to analyze near surface site responses to determine velocity structure in earthquake shaking hazard studies

hydrothermal alteration associated with volcanogenic massive sulfide deposits examples from turkey mineralogic and geochemical studies were carried out on hydrothermal alteration zones associated with two types of volcanogenic massive sulfide deposits in turkey the first type includes cu zn pb deposits in the eastern black sea region associated with upper cretaceous dacitic rocks the second type includes the kre pyritic cu orebodies in the western black sea region that are associated with paleo tethys ophiolites triassic lower jurassic and overlain by carbonaceous argillites and turbidites the eastern black sea deposits are characterized by clay alteration of both the footwall and hanging wall the clay zones in the hanging wall range up to 200 m in thickness and from 300 m to 2 km in lateral extent alteration beneath the deposits consists mainly of sericite quartz and pyrite with carbonate and kaolinite present in some deposits this central zone is surrounded by an illitc mica mg rich chlorite gypsum zone that grades outward into a zeolite zone kaolinite mixed layer illite smectite hematite and local chlorite occur in the hanging wall rocks carbonates comprise dolomite siderite and local calcite in the footwall rocks the crystallinity of illite shows an increase with depth similarly in the hanging wall rocks there is a sharp increase in the proportion of illite in mixed layer illite smectite and a change in the kaolin polytype from kaolinite to nacrite as the orebody is approached these variations in alteration assemblage suggest steep upward decreasing temperatures during the hydrothermal alteration of the footwall and hanging wall sequences the mineralogy chemistry and size of the alteration zones associated with the eastern black sea deposits are similar in many respects to those of the japanese kuroko deposits the alteration pipes below the kre deposits consist of chlorite quartz and sulfides with some local illite epidote calcite and siderite chlorite is fe rich and becomes increasingly so toward the massive ore relative to unaltered basaltic host rocks the pipes are enriched in fe 2 o 3 and mgo and depleted in na 2 o k 2 o and cao in the eastern black sea deposits a model involving the mixing of ascending hydrothermal fluids with cool seawater below the paleosea floor could explain the formation of the chlorite anhydrite assemblage in the outer alteration zones and the quartz sericite assemblage at high a sub k super a sub h super ratios in the inner footwall zones in some deposits decreases in a sub k super a sub h super ratio and temperature resulted in the formation of kaolin minerals

petrogenesis of the post collisional volcanic rocks from the borcka artvin area implications for the evolution of the eocene magmatism in the eastern pontides ne turkey abstract whole rock geochemistry 40 ar 39 ar data and sr nd isotopes are presented for the eocene borcka volcanic rocks on the eastern corner of the eastern pontide orogenic belt ne turkey borcka artvin volcanic rocks are divided into three suites basic dyke borcka basalt and civankoy suite these rocks contain plagioclase an 49 88 clinopyroxene wo 38 49 en 38 54 fs 8 25 hornblende mg 0 57 0 74 phenocrysts and magnetite titanomagnetite and apatite microphenocrysts 40 ar 39 ar ages on hornblendes ranging from 46 9 0 1 to 39 9 0 5 ma within the middle eocene the volcanic rocks show tholeiitic calc alkaline affinities and have low to medium k contents they are enriched in large ion lithophile lile and light rare earth elements lree with pronounced depleted high field strength elements hfse the chondrite normalized ree patterns la cn lu cn 1 19 show low to medium enrichment indicating similar sources for the rock suite initial 87 sr 86 sr values 87 sr 86 sr 46 ma vary between 0 70423 and 0 70495 while initial 143 nd 144 nd values 143 nd 144 nd 46 ma lie between 0 51263 and 0 51285 the main solidification processes involved in the evolution of the volcanics consist of fractional crystallization with minor amounts of crustal contamination all our evidences support the conclusion that the parental magma of the rocks probably derived from an enriched mantle previously metasomatized by fluids derived from subducted slab in a post collisional extension related geodynamic setting