mobilization of gold as a polymetallic melt during pelite anatexis at the challenger deposit south australia a metamorphosed archean gold deposit the challenger gold deposit in south australia is hosted by pelitic migmatites that underwent peak metamorphism at 7 5 1 5 kbars and at least 800 c nd model ages suggest a protolith age of 2900 ma zircon u pb and garnet sm nd dating indicates that peak metamorphism occurred at 2440 ma and that garnet was present during this event at this time in situ vapor absent melting affected the pelitic host rock indicating that peak metamorphism occurred without introduction of a foreign fluid or melt thus evidence indicating the presence of ore minerals during peak metamorphism implies a prepeak mineralization event this evidence includes the occurrence of invisible gold in lollingite but not in adjacent arsenopyrite and the presence of spherical gold sulfide inclusions in peak metamorphic garnet and other silicates textures developed between pyrrhotite lollingite arsenopyrite and gold the lack of silicate alteration minerals supports this conclusion experimental evidence is presented to support our interpretation that a gold rich polymetallic melt was mobilized into leucosomes synchronously with silicate melt during peak metamorphism visible gold is restricted to migmatitic leucosomes and to a lesser extent melanosomes large inclusions of gold with coexisting arsenopyrite pyrrhotite and bismuth are hosted within peak metamorphic silicate minerals and at grain boundaries trails of micrometric spherical inclusions of predominantly gold and bismuth propagate along annealed fractures from these larger inclusions we show that these gold sulfide inclusions represent the crystallized products of an immiscible polymetallic melt metamorphism of the challenger deposit resulted in partial melting of the pelitic host rock and formation of this gold rich melt these two melts were synchronously redistributed to accumulate as leucosomes during development of a stromatic migmatite formation of a polymetallic melt thereby enabled extensive mobilization of gold producing leucosomes enriched in gold this occurred because the immiscible metallic melt was physically entrained rather than chemically dissolved within the silicate melt gold rich shoots at challenger parallel the plunge of ptygmatically folded leucosomes that are shown to be parasitic to a larger scale fold geometry which appears to be structurally related to the ore shoots it is interpreted that concurrent migration of polymetallic and silicate melt allowed concentration of gold into a series of dilational structures which developed within the larger scale fold geometry challenger represents a new deposit type other deposits around the world such as renco and griffins find are hosted in granulite facies rocks but challenger is the first reported example of leucosome hosted gold in migmatites

mineralogy and mineral chemistry of bi minerals constraints on ore genesis of the beiya giant porphyry skarn gold deposit southwestern china abstract the beiya deposit located in the sanjiang tethyan tectonic domain sw china is the third largest au deposit in china 323 t au 2 47 g t as a porphyry skarn deposit beiya is related to cenozoic himalayan alkaline porphyries abundant bi minerals have been recognized from both the porphyry and skarn ores comprising bismuthinite bi cu sulfosalts emplectite wittichenite bi pb sulfosalts galenobismutite cosalite bi ag sulfosalt matildite bi cu pb sulfosalts bismuthinite derivatives bi pb ag sulfosalts lillianite homologs galena matildite series and bi chalcogenides tsumoite the unnamed bi 2 te the unnamed ag 4 bi 3 te 3 tetradymite and the unnamed bi pb 3 te s 4 native bismuth and maldonite are also found in the skarn ores the arsenopyrite geothermometer reveals that the porphyry au mineralization took place at temperatures in the range of 350 450 c and at log f s 2 in the range of 8 0 to 5 5 respectively in contrast the beiya bi mineral assemblages indicate that the skarn ore forming fluids had minimum temperatures of 230 175 c prevailing temperatures exceeding 271 c and fluctuating f s 2 f te 2 conditions we also model a prolonged skarn au mineralization history at beiya including at least two episodes of bi melts scavenging au we thus suggest that this process was among the most effective au enrichment mechanisms at beiya

geodetic methods for detecting volcanic unrest a theoretical approach in this paper we study the application of different geodetic techniques to volcanic activity monitoring using theoretical analysis this methodology is very useful for obtaining an idea of the most appropriate and efficient monitoring method mainly when there are no records of geodetic changes previous to volcanic activity the analysis takes into account the crustal structure of the area its geology and its known volcanic activity to estimate the deformation and gravity changes that might precede eruptions the deformation model used includes the existing gravity field and vertical changes in the crustal properties both factors can have a considerable effect on computed deformation and gravity changes topography should be considered when there is a steep slope greater than 10 the case study of teide stratovolcano tenerife canary islands for which no deformation or gravity changes are available is used as a test to avoid considering topography we worked at the lowest level of las canadas and examined a smaller area than the whole caldera or island therefore the results are only a first approach to the most adequate geodetic monitoring system the methodology can also be applied to active areas where volcanic risk is not associated with a stratovolcano but instead with monogenetic scattered centers especially when sites must be chosen in terms of detection efficiency or existing facilities the canary islands provide a good example of this type of active volcanic areas and we apply our model to the island of lanzarote to evaluate the efficiency of the monitoring system installed at the existing geodynamic station on this island topography is not important the results of our study show clearly that the most appropriate geodetic volcano monitoring system is not the same for all different volcanic zones and types and the particular properties of each volcano zone must be taken into account when designing each system

magma supply dynamics at westdahl volcano alaska modeled from satellite radar interferometry 1 a group of satellite radar interferograms that span the time period from 1991 to 2000 shows that westdahl volcano alaska deflated during its 1991 1992 eruption and is reinflating at a rate that could produce another eruption within the next several years the rates of inflation and deflation are approximated by exponential decay functions having time constants of about 6 years and a few days respectively this behavior is consistent with a deep constant pressure magma source connected to a shallow reservoir by a magma filled conduit an elastic deformation model indicates that the reservoir is located about 6 km below sea level and beneath westdahl peak we propose that the magma flow rate through the conduit is governed by the pressure gradient between the deep source and the reservoir the pressure gradient and hence the flow rate are greatest immediately after eruptions pressurization of the reservoir decreases both the pressure gradient and the flow rate but eventually the reservoir ruptures and an eruption or intrusion ensues the eruption rate is controlled partly by the pressure gradient between the reservoir and surface and therefore it too decreases with time when the supply of eruptible magma is exhausted the eruption stops the reservoir begins to repressurize at a high rate and the cycle repeats this model might also be appropriate for other frequently active volcanoes with stable magma sources and relatively simple magma storage systems

tin metallogenesis associated with granitoids in the southwestern sanjiang tethyan domain nature deposit types and tectonic setting article i nfo tin mineralization in the southwestern sanjiang tethys sn metallogenic domain extends from the southeast asia tin belt in the south the eastern part of the domain does not contain significant sn deposits whereas the central part of the domain composed of the changning menglian sn belt and related to ca 239 178 ma s type granitoids generated by the collision between tengchong baoshan and simao blocks carries wide spread the hydrothermal vein type mineralization the western part of the domain composed of the tengchong baoshan sn metallogenic belt is related to both 136 113 ma and 89 52 ma s type granitoids the former granitoids resulted from the collision between western burma and tengchong baoshan blocks and generated skarn type tin deposits the younger groups correspond to the india asia continental collision and are associated with the xiaolonghe and lailishan greisen type sn deposits

practical approaches to identifying sealed and open fractures for one essential ingredient of permeable fracture networks degree of fracture pore space preservation in large fractures i show how the characterization challenge presented by sparse fracture sampling can be overcome by measuring a surrogate the abundance of rock mass cement that precipitated after fractures ceased opening sampling limitations are overcome because the surrogate is readily measured in small rock samples including sidewall cores and cuttings permitting site specific diagnosis of the capacity of fractures to transmit fluid over a wider range of sample depths than conventional methods allow a diverse core database shows that this surrogate correctly predicts where large fractures are sealed information on timing of fracture opening relative to cement sequence can be obtained in two ways first evidence of fracture movement history and cement sequences in sparse large fractures can be extrapolated to areas having only cement data alternately evidence of fracture timing can be acquired from sealed micrometer scale fractures distribution of porosity reducing cement is commonly heterogeneous from bed to bed and location to location in siliciclastic and carbonate rocks however because patterns of sealed or open fractures cannot be delineated using fracture observations alone surrogates have practical value for production fairway mapping and other applications in which identifying open fractures is essential this study highlights the vital interplay among structural and diagenetic processes for fracture porosity preservation or destruction

decorrelation in interferometric radar echoes a radar interferometric technique for topographic mapping of surfaces implemented utilizing a single synthetic aperture radar sar system in a nearly repeating orbit is discussed the authors characterize the various sources contributing to the echo correlation statistics and isolate the term which most closely describes surficial change they then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time it is found that there is decorrelation increasing with time but that digital terrain model generation remains feasible the authors present such a map of a forested area in oregon which also includes some nearly unvegetated lava flows such a technique could provide a global digital terrain map

late permian triassic magmatic evolution in the jinshajiang orogenic belt sw china and implications for orogenic processes following closure of the paleo tethys growth of continental crust involves the complex interplay of subduction zone magmatism to generate the crust followed by stabilization through crustal thickening magmatism and ultimately isolation from the active plate margin the jinshajiang orogenic belt sw china provides an exceptional record of continental development as the result of closure of the paleo tethys seaway and ensuing collision a compilation of u pb age and geochemical data for the plutonic and volcanic rocks within the southern part of the jinshajiang orogenic belt including new high precision ages for the ludian granitoid batholith of 231 to 220 ma enables us to explore the interaction between magmatism and orogeny in the context of the paleo tethys closure and continental amalgamation these age and geochemical constraints in conjunction with other geologic evidence suggest that subduction of the paleo tethys ocean dominated local tectonics prior to the triassic creating a volcano plutonic arc along the eastern margin of the qamdo simao terrane following consumption of the ocean collision zone magmatism dated at 247 to 237 ma was manifested by eruption of voluminous volcanic rocks in a suture parallel zone crustal anatexis was contemporaneous with the earliest phases of collision producing high silica rhyolites of early triassic age ca 247 246 ma between 245 and 237 ma the local tectonic regime switched from compression to extension probably due to strain partitioning caused by oblique convergence which led to the development of rift basins and extensive syn tectonic bimodal volcanism associated with deep water sediments from 234 ma to 214 ma the emplacement of high k calc alkaline granodiorites monzogranites occurred prior to or during isostatic uplift and extension probably caused by breakoff of the subducted slab the resultant exhumation brought deep seated granitoid batholiths to the surface and was contemporaneous with intrusion of ultramafic mafic melts ophiolitic melange ca 362 294 ma and collision related magmatic suites 247 214 ma are unconformably overlain by a late triassic 229 217 ma conglomerate rich sequence that represents an overlap assemblage across the qamdo simao terrane indochina and yangtze block of south china

extent of power law scaling for natural fractures in rock new data sets from natural faults and extension fractures exhibit simple power law scaling across 3 4 4 9 orders of magnitude regardless of rock type or movement mode the data show no evidence of natural gaps or scaling changes each data set consists of independent measurements made at different observational scales a power law regression to the subset of smaller fractures in each case provides an extrapolation that accurately predicts associated larger fractures consequently data representing a limited range of fracture sizes may be used to characterize a much broader spectrum of fracture sizes

patterns of wind drifted snow on the alaskan arctic slope detected with ers 1 interferometric sar we tested whether spaceborne interferometric synthetic aperture radar insar could be used to reveal patterns of redistribution of wind drifted snow in arctic alaska based on a simple geometric model we found that lateral variations in new snow assuming a density of 0 3 g cm 3 accumulation of 11 cm or redistribution of the existing snow into dunes of half this height could produce decorrelation of c band interferograms comparison of interferograms with field observations for two periods from winter 1993 94 one with wind but little new snow and the second with wind and new snow indicates the interferograms delineated areas where the snow depth had changed due to drifting striking patterns of windward scouring and leeward deposition were revealed the interferograms also showed that during one high wind event conspicuous interferometric bands a few kilometers wide and 30 km long were formed downwind of a mountain ridge we speculate that these bands were caused by large scale alterations in the concentrations of moving snow particles a finding consistent with ground observations of alternating bands of clear air and blizzard for the same area and similar to phenomena observed with the advanced very high resolution radiometer and the geodetic earth observing satellite during blizzards in north dakota and iowa u s a

potential of small baseline sar interferometry for monitoring land subsidence related to underground coal fires wuda northern china case study uncontrolled coal fires can result in massive surface displacements due to the change in volume of burning coal and thermal effects in the adjacent rock mass simultaneously the resultant surface breakings provide greater access to air and water that in turn can aggravate the problem of underground coal seam burning in this case study we have investigated the feasibility and potential of detecting the land subsidence accompanying coal fires by means of satellite insar observations three groups of small baseline insar approaches psi stacking and 2 passdinsar were applied to the wuda coalfield northern china to reveal the spatial and temporal signals of the land subsidence in the areas affected by the coal fires the interferometric results agree well with gps observations and coal fire data obtained by field investigation which demonstrates that the small baseline insar techniques have remarkable potential to detect this land subsidence of interest in particular our results show that the development of coal fires can lead to new subsiding areas and also accelerate the ongoing surface subsidence typically within the areas of mature coal fires through a comparison of the interferometric observations and the multi temporal coal fire maps this timely and reliable information on land subsidence will be useful for the detection and mapping of the coal fire affected regions and thereby assist in fighting and controlling coal seam burning

effect of injection rate on hydraulic fracturing in naturally fractured shale formations a numerical study this paper studies the effect of fluid injection rate on hydraulic fracturing in pre existing discrete fracture network dfn formations a flow stress damage coupling approach has been used in an initial attempt toward how reservoir responses to injection rate under different dfn connected configuration states the simulation results show that injection rate has an significant influence on the hydraulic fractures hf and dfn interaction and hydraulic fracturing effectiveness which can be characterized by the total interaction area stimulated dfn length stimulated hf length and leak off ratio for the sparse dfn model stimulated hf length increases with increasing injection rate and the stimulated dfn length decreases with the increasing injection rate for the medium dfn model stimulated hf and dfn length both increase with increasing of injection rate for the dense dfn model length of stimulated hf deceases with increasing injection rate however the stimulated dfn length increases with the increasing injection rate the effect of injection rate on hydraulic fracturing is closely related to formation characteristics which are strongly affected by the dfn connected configuration for the studied fracture network the sparse dfn model gets the optimal hydraulic fracturing effectiveness with lower injection rate however the dense dfn model has the best hydraulic fracturing effectiveness with higher injection rate this work strongly links the production technology and hydraulic fracturing effectiveness evaluation and aids in the understanding and optimization of hydraulic fracturing simulations in naturally fractured reservoirs

multiple causes for non eruptive seismic swarms at mt martin katmai volcanic cluster alaska 2004 2008 abstract in january 2006 the alaska volcano observatory recorded a non eruptive swarm of over 778 volcano tectonic vt earthquakes in the katmai volcanic cluster kvc alaska the swarm earthquakes have estimated hypocentral depths of 0 3 km below sea level bsl immediately below the summit of mt martin volcano in an effort to determine the cause of this swarm we calculated 134 double couple fault plane solutions fps for a pre swarm period jan 2004 dec 2005 the swarm period january 2006 and a post swarm period feb 2006 dec 2008 and examined temporal changes in fps orientations using directional statistical analysis statistical tests of uniformity indicate that fps orientations were heterogeneous during the pre swarm period and homogeneous during the 2006 swarm 3d tests on p and t axis orientation data also indicate that fps homogeneity may have persisted during the post swarm period best fit axial von mises distributions indicate a strongly preferred nne ssw p axis azimuth for swarm fps and a nw se mean p axis azimuth for the pre and post swarm period fps the nw se background p axis azimuth is approximately parallel to regional maximum compressive stress along the northern segment of the aleutian arc thus we find evidence for a temporary 90 reorientation of fps p axes during the 2006 swarm and suggest that the change in fps orientation may be indicative of intrusion of a shallow small volume magma or fluid filled dike beneath mt martin in early 2006 in contrast fps for vt earthquakes comprising minor swarms in 2007 and 2008 indicate only normal faulting suggesting a fundamentally different causative process from the major 2006 swarm our results demonstrate that the vt earthquake swarms which are a common occurrence in the kvc may be caused by several processes including magma intrusion tectonic activity and hydrothermal fluid circulation and highlight the need for increased monitoring and analysis during future periods of geophysical unrest

seismic evidence for magma in the vicinity of mt katmai alaska p wave traveltime delays of as much as 0 9 sec are consistently observed at one seismic station from local and regional earthquakes 70 to 150 km deep this station is on the southwest flank of mt trident the most recently active volcano within katmai national park alaska delays from local shallow earthquakes are typically less than 0 3 sec suggesting that most of the major delay results from anomalous material at depths of more than a few kilometers this station is located near the center of a bowlshaped low in the bouguer gravity field that is approximately 15 km in diameter and more than 25 mgals deep these anomalies suggest but do not prove the presence of considerable amounts of magma in the shallow part of the crust that could have been the source for all magma erupted in the vicinity of mt katmai and mt trident this century

petrogenesis of bismuth minerals in the dabaoshan pb zn polymetallic massive sulfide deposit northern guangdong province china abstract located in the northern guangdong province the dabaoshan pb zn polymetallic massive sulfide deposit is one of the most important regions to have produced fe cu pb zn and s in southern china while much progress has been made with respect to the geology and geochemistry of the deposit a better understanding of ore genesis is warranted this ore body contains abundant bismuth element only few studies exist on the distribution characteristics and existing states of bismuth electron microprobe study yields that native bismuth tellurides e g hedleyite and sulfide minerals are the main forms in which this element is found the occurrence and characteristics of native bismuth and its mineral assemblages are different with high t gold bearing deposits but are more similar to those of mid low temperature hydrothermal deposits our research shows that the bi te at dabaoshan derived from the late yanshanian dacite porphyry the bi te rich ore forming fluid developed during intrusion of the dacite and mineralized along fractures and overprint the earlier pb zn mineralization during the early overprinting event the ore forming fluid was rich in bi and te and poor in s under uniform mid temperature conditions as the hydrothermal fluids evolved they became enriched with ag and pb sulfur was rich in the fluid during the late overprinting event this may have been related to dissolution of sulfide the low abundances of bi te and ag in sulfide minerals e g galena and sphalerite indicate that ore genesis and the ore forming materials were different between the pb zn and bi te ag stages thus new geological and geochemical data were used to delineate the sequence ore genesis of dabaoshan pb zn mineralization

estimating average fracture spacing in subsurface rock knowledge of the spacing of fractures in reservoir rocks i e the distance between parallel fractures in a subsurface joint set can lead to a better understanding of the production characteristics of a reservoir and serve to quantify the relative degree of deformation in subsurface rocks in this paper i present a new method for estimating the spacing of subsurface fractures this new method is easy to use from the standpoint of both data collection and data analysis the average fracture spacing method can be applied with boreholes of any orientation relative to a fracture set the method is especially powerful when it is used for the relatively common case of a borehole nearly parallel to a fracture set e g vertical borehole intersecting vertical fractures average fracture spacing is estimated from an analytical solution based on observed borehole fracture intersections and observed fracture porosity the only data required are the dimensions of the core or imaged borehole and the total height of all sampled fractures because the likelihood of intersecting fractures increases when a well is deviated perpendicular to the fractures of a set fracture reservoirs commonly are candidates for deviated boreholes an informed decision on borehole deviation requires predicting the fracture intersection frequency as a function of both deviation magnitude and direction a new method based on probabilities of borehole fracture intersections uses spacing and height data from subsurface joint like fractures and the borehole diameter to predict fracture intersection frequencies for all possible well deviations fracture intersection frequency solutions are presented with respect to a conventional geographic reference frame thus simplifying even the most complex three dimentional situations

sanjiang tethyan metallogenesis in s w china tectonic setting metallogenic epochs and deposit types abstract tectonically the sanjiang tethyan metallogenic domain stmd is located within the eastern himalayan tibetan orogen in the sanjiang tethys southwestern china although this metallogenic domain was initiated in the early palaeozoic extensive metallogenesis occurred in the late palaeozoic late triassic and himalayan tertiary epochs corresponding tectonic settings and environments in the domain are an arc basin system related to the subduction of the palaeo tethyan oceanic slabs a post collision crustal extension setting caused by the lithospheric delamination or slab breakoff underneath the sanjiang tethys during the late triassic large scale strike slip faulting and thrusting systems due to the indo asian continent collision since the palaeocene in this metallogenic domain important gold copper base metals rare metals and tin ore belts incorporating a large number of giant deposits were developed the main types of deposits include 1 porphyry copper deposits controlled by a large scale strike slip fault system 2 vhms deposits mainly occurring in intra arc rift basins and post collision crustal extensional basins 3 shear zone type gold deposits in the ophiolitic melange zone along the thrusting shearing system 4 hydrothermal silver polymetallic deposits in the triassic intra continental rift basins and tertiary strike slip pull apart basins and 5 himalayan granite related greisen type tin and rare metallic deposits within the metallogenic epochs of the late palaeozoic to cenozoic the styles and types of the ore deposits changed from vhms types in the late palaeozoic through exhalative sedimentary type deposits in the late triassic to porphyry type copper deposits shear zone type gold deposits hydrothermal vein type silver polymetallic deposits greisen type tin and rare metal deposits in the cenozoic correspondingly ore forming metals also changed from a pb zn cu ag association through ag cu pb zn fe ag pb and ag au hg associations to ag cu pb zn cu mo au sn and li rb cs nb zr hf y ce sc associations

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

reduced and oxidized au cu bi iron oxide deposits of the tennant creek inlier australia an integrated geologic and chemical model iron oxide associated au cu bi deposits of the tennant creek gold field range from magnetite pyrrhotite pyrite reduced cu rich deposits through sulfide poor magnetite rich high grade au bi intermediate f o2 deposits to hematite rich high grade au oxidized deposits discordant magnetite hematite chlorite quartz ironstone bodies that host the ore formed hydrothermally during the 1840 to 1860 ma barramundi orogeny at temperatures up to 350 to 400 c and 2 5 to 5 kbars deposition of ironstone minerals was localized by dilatency that was generated during d1 reverse shearing and folding a separate au cu bi hydrothermal stage overprinted selected ironstones during d2 at or before 1825 to 1830 ma where favorable d1 structures and fluid pathways were reactivated the extremes of the reduced to oxidized deposit spectrum represent divergent chemical conditions that cannot be reconciled by the action of a single fluid we have identified both reducing and oxidizing fluids that helped to form the au cu bi deposits at the west peko deposit which represents the reduced end member subtype constraints from oxide silicate sulfide mineral stabilities fluid inclusions and chlorite thermochemistry indicate that au cu bi ore was introduced into ironstone at 300 to 340 c by a reducing pyrrhotite stable weakly acidic sulfur rich and n2 ch4 rich aqueous fluid containing 3 to 10 wt percent nacl equiv an ore fluid source outside the relatively oxidized metasedimentary host sequence warramunga formation is implied we suggest similar ore fluids for other reduced cu and sulfide rich deposits in the district chemical mass transfer modeling of reactions between reducing fluid and ironstone incorporating estimated thermodynamic properties for aqueous bismuth complexes indicates that highly efficient gold and native bi deposition was predominantly in response to desulfidation and oxidation of the fluid chalcopyrite precipitated mainly in response to increased ph gold bismuth ore in the eldorado deposit an oxidized and hematitic end member is interpreted to have involved mixing of an oxidizing hematite stable ca na cl brine with an intermediate f o2 low to moderate salinity ore fluid as well as reaction of both fluids with ironstone furthermore the mass transfer modeling suggests that mixing of reducing and oxidizing fluids in the absence of ironstones could have resulted in high grade au deposits lacking fe oxides a subtype that has received comparatively little exploration attention in the tennant creek district

are open fractures necessarily aligned with maximum horizontal stress abstract fluid flow in fractured rock is an increasingly central issue in recovering water and hydrocarbon supplies and geothermal energy in predicting flow of pollutants underground in engineering structures and in understanding large scale crustal behaviour conventional wisdom assumes that fluids prefer to flow along fractures oriented parallel or nearly parallel to modern day maximum horizontal compressive stress or s hmax the reasoning is that these fractures have the lowest normal stresses across them and therefore provide the least resistance to flow for example this view governs how geophysicists design and interpret seismic experiments to probe fracture fluid pathways in the deep subsurface contrary to these widely held views here we use core stress measurement and fluid flow data to show that s hmax does not necessarily coincide with the direction of open natural fractures in the subsurface 3 km depth consequently in situ stress direction cannot be considered to predict or control the direction of maximum permeability in rock where effective stress is compressive and fractures are expected to be closed chemical alteration dictates location of open conduits either preserving or destroying fracture flow pathways no matter their orientation

helium and argon isotope geochemistry of alkaline intrusion associated gold and copper deposits along the red river jinshajiang fault belt sw china abstract the red river jinshajiang strike slip fault zone on the eastern margin of the tibetan plateau was originally produced by the india eurasia collision 60 70 myr ago numerous post collisional mantle derived alkaline igneous rocks with ages of 40 30 ma have been intruded along this fault zone in recent years several copper and gold deposits associated with the alkaline intrusions of this region were discovered such as the yao an and beiya gold deposits and the yulong and machangqing copper deposits studied in this paper the mineralised intrusions are felsic with sio 2 ranging from 61 4 to 67 7 wt k 2 o na 2 o from 8 1 to 11 5 wt and k 2 o na 2 o 1 the deposits are located at both the exo and endo contact zones of the intrusions the mineral deposits are of hydrothermal origin with the ore forming temperatures mainly in the range 150 450 c this paper presents he and ar isotope analyses of these four deposits the concentrations of 4 he trapped in fluid inclusions of pyrites from the ores are 0 7 54 1 10 6 cm 3 stp g 1 and those of 40 ar are 0 6 7 3 10 6 cm 3 stp g 1 3 he 4 he ratios are 0 3 2 5 ra ra represents the 3 he 4 he ratio of air 1 39 10 6 40 ar 36 ar ratios are 316 1736 and 3 he 36 ar ratios are 0 2 11 2 10 3 generally the 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios for the gold deposits are higher than those for the copper deposits we suggest that the ore forming fluids of both gold and copper deposits were differentiated from the mantle derived alkaline magmas but were diluted by modified air saturated water masw that experienced intensive interaction with crustal rocks however the magmatic fluids responsible for the gold deposits were less extensively diluted by masw resulting in higher 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios than the copper deposits

the geological significance of pb bi and pb sb sulphosalts in the damajianshan tungsten polymetallic deposit yunnan province china abstract the sanjiang tethyan domain in se asia is one of the most important mineral belts in china cu pb zn ag au and sn are the most important resources in this domain while the tungsten mineralization is poorly reported in this study we report on mineralogy in recent discovered damajianshan dmjs tungsten cu as mo bi polymetallic deposit in the southern part of sanjiang tethyan domain related to triassic quartz porphyry studies have shown that besides common ore minerals such as native bismuth bismuthinite ikunolite some specific minerals of pb bi and pb sb sulphosalts e g izoklakeite bournonite cosalite and boulangerite have also been found based on paragenetic mineral assemblages fluid inclusions and thermodynamic studies the physicochemical conditions were evaluated for the entire metallogenic process the sulfur fugacity logf s2 ranges from 9 7 to 37 with ore forming temperatures between 190 c and 330 c and the oxygen fugacity logf o2 ranges from 37 5 to 38 5 when the temperature is 250 c the sulfur fugacity and oxygen fugacity show strong fluctuations with broadly negative correlation indicating that these variations in physicochemical conditions should be responsible for mineral assemblages and are one of the most significant factors leading to the formation of the dmjs deposit our mineralogical studies provide new information for tungsten mineralization and further exploration of tungsten resources in the sanjiang tethyan mineralization domain

petrogenetic significance of au bi te s associations the example of maldon central victorian gold province australia abstract mineralization at maldon victorian goldfields australia is part of the western lachlan foldbelt and is hosted by deformed lower ordovician metasediments intruded by the late devonian harcourt granite gold bi te s associations in the deposit include four gold bearing minerals maldonite native gold jonassonite and aurostibite and a range of sulphotellurides from the tetradymite group all of which are paragenetically tied to native bismuth the simpler phase associations involving bismuth maldonite and one or the other bi sulpho tellurides resemble the equivalents of eutectics in the system au bi te and hint at crystallisation from melts the complex associations include symplectites of gold and bismuth resulting from replacement of maldonite and are dominated by co existing sulphur bearing species joseite a joseite b an unnamed phase with bulk composition approximating to bi 3 te s 2 and jonassonite the complexity of such assemblages is also underpinned by chemical structural inhomogeneity within the unnamed phase i e nanoscale domains of bi 14 te s 9 and bi 5 te s 3 as documented from electron diffractions obtained from a fib tem foil although such lattice scale intergrowths reveal polysomatic disorder that can be associated with replacement of one telluride by another the structural modules in the overall stacking sequence indicate formation under local equilibrium conditions the mineralogical complexity of all au bi te s associations can be modelled in terms of interaction between simpler assemblages and sulphur bearing fluids three stages all involving gold minerals are recognised 1 bismuth maldonite hedleyite 2 bi sulphotellurides jonassonite and decomposition of maldonite gold bismuth and 3 bismuthinite gold from decomposition of maldonite or jonassonite the last stage is coincident with chloritisation and occurs during or following granite emplacement thermodynamic modelling of maldonite replacement by bismuthinite and gold indicates conditions to overlap with the pyrite hematite buffer at 258 c if neutral fluids are involved the general replacement model for the deposit shows that local scale reworking of maldonite and resultant gold remobilisation contributed to the apparent abundance of native gold this interpretation is consistent with the protracted geological history at maldon where granite intrusion post dates an orogenic event initial sulphur poor assemblages crystallised from melts predating granite emplacement the latest sulphidation event is attributed to retrograde fluids in the contact aureole whereas the earlier one could also have been produced during the multi stage deformation although observed assemblages and textures are the product of a complex sequence of overprinting there is no need to invoke input of gold from more than a single fluid generation

phase relations among tellurides sulfides and oxides pt ii applications to telluride bearing ore deposits data on telluride bearing mineral assemblages from various types of ore deposits are compiled and interpreted in terms of the prevailing fugacities of te 2 s 2 and the temperature during deposition in the majority of hydrothermal deposits the appearance of tellurides after initial deposition of sulfides reflects an increase in the f sub te 2 f sub s 2 ratio most likely due to input of h 2 te from a magmatic source in some vein deposits such as boulder county colorado initial deposition of native tellurium is followed by deposition of minerals with progressively lower tellurium content indicating a decrease in f sub te 2 over the course of telluride deposition this trend may reflect local isolation of early formed minerals from the hydrothermal fluids and or progressive depletion of tellurium at the source ore minerals in other deposits such as mahd adh dhahab saudi arabia reveal systematic temporal or spatial variations in mineralogy that are attributed to introduction of a tellurium rich fluid into a preexisting sulfide assemblage and subsequent buffering of f sub te 2 and f sub s 2 by reactions such as 2pbs te 2 2pbte s 2 this buffering may exert considerable control on vein minerals such as the presence and relative abundance of gold and calaverite and the presence or absence of native tellurium

deflation of mount etna monitored by spaceborne radar interferometry ground based measurements of volcano deformation can be used to assess eruptive hazard but require the costly and often hazardous installation and maintenance of an instrument network here we show that spaceborne radar interferometry which has already shown its utility in mapping earthquake related deformation1 can be used to monitor long term volcano deformation two families of synthetic aperture radar images acquired from ascending and descending orbits by the satellite ers 1 and looking at mount etna from opposite sides cover the time period from 17 may 1992 to 24 october 1993 and include the second half of etna s most recent eruption despite artefacts of the interferometric technique we can observe a volcano wide deflation which is an expected consequence of the eruption but which had not previously been appreciated we quantify it using a simple model based on the change of pressure in a sphere located in an elastic half space the modelled deformation increases linearly with time until the end of the eruption our results show that it will be possible to use this technique to detect the inflation of volcanic edifices that usually precedes eruptions

synthetic aperture radar interferometry coherence analysis over katmai volcano group alaska the feasibility of measuring volcanic deformation or monitoring deformation of active volcanoes using space borne synthetic aperture radar sar interferometry depends on the ability to maintain phase coherence over appropriate time intervals using ers 1 c band 5 66 cm sar imagery we studied the seasonal and temporal changes of the interferometric sar coherence for fresh lava weathered lava tephra with weak water reworking tephra with strong water reworking and fluvial deposits representing the range of typical volcanic surface materials in the katmai volcano group alaska for interferograms based on two passes with 35 days separation taken during the same summer season we found that coherence increases after early june reaches a peak between the middle of july and the middle of september and finally decreases until the middle of november when coherence is completely lost for all five sites fresh lava has the highest coherence followed by either weathered lava or fluvial deposits these surfaces maintain relatively high levels of coherence for periods up to the length of the summer season coherence degrades more rapidly with time for surfaces covered with tephra for images taken in different summers only the lavas maintained coherence well enough to provide useful interferometric images but we found only a small reduction in coherence after the first year for surfaces with lava measurement of volcanic deformation is possible using summer images spaced a few years apart as long as the surface is dominated by lavas our studies suggest that in order to make volcanic monitoring feasible along the aleutian arc or other regions with similar climatic conditions observation intervals of the satellite with c band sar should be at least every month from july through september every week during the late spring early summer or late fall and every 2 3 days during the winter

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

low cost gps based volcano deformation monitoring at mt papandayan indonesia abstract the global positioning system gps can be utilised to detect ground deformations of the surface of a volcano ground deformation monitoring is considered one of the most effective tools for investigating the behaviour of active volcanoes the decreasing cost of gps hardware together with the increased reliability of the technology facilitates such demanding applications gps ground deformation measurements can be continuous automatic conducted in all weather conditions and provide three dimensional positioning results higher computing power also means that the complex mathematics required to process gps baselines can be easily handled in near real time during the past few years a methodology has been developed for processing data collected by gps networks consisting of a mixed set of single frequency and dual frequency receivers the strategy is to deploy a few permanent fiducial gps stations with dual frequency geodetic grade receivers surrounding an inner network of low cost single frequency gps receivers such a configuration offers considerable flexibility and cost savings for geodynamic applications such as volcano deformation monitoring which require a dense spatial coverage of gps stations and where it is not possible to establish permanent gps networks using only expensive dual frequency instrumentation this configuration has recently been tested at the mt papandayan volcano in west java indonesia the two stage network design consists of an inner network of four single frequency canadian marconi cm gps receivers surrounded by three dual frequency leica crs1000 gps receivers the inner network logged and transmitted gps data from the slave stations located on the volcano to a base station the combined processing of the cm and leica receiver data was performed off line so as to investigate the performance of such a mixed mode system the basis of the processing methodology is to separate the dual frequency fiducial station data processing from the baseline processing involving the single frequency receivers on the volcano the data processing for the former was carried out using a modified version of the bernese software to generate a file of corrections analogous to wide area dgps correction models for the distance dependent biases primarily due to atmospheric refraction these corrections were then applied to the double differenced phase observations from the inner receivers to improve the baseline accuracies a description of the field testing and its challenges during february march 2000 together with a discussion of some of the results are presented

seismic response of the katmai volcanoes to the 6 december 1999 magnitude 7 0 karluk lake earthquake alaska a sudden increase in earthquake activity was observed beneath volcanoes in the katmai area on the alaska peninsula immediately following the 6 december 1999 magnitude m w 7 0 karluk lake earthquake beneath southern kodiak island alaska the observed increase in earthquake activity consisted of small m l 1 3 shallow z 5 0 km events these earthquakes were located beneath mount martin mount mageik trident volcano and the katmai caldera and began within the coda of the karluk lake mainshock all of these earthquakes occurred in areas and magnitude ranges that are typical for the background seismicity observed in the katmai area seismicity rates returned to background levels 8 to 13 hours after the karluk lake mainshock the close temporal relationship with the karluk lake mainshock the onset of activity within the mainshock coda and the simultaneous increase beneath four separate volcanic centers all suggest these earthquakes were remotely triggered modeling of the coulomb stress changes from the mainshock for optimally oriented faults suggests negligible change in static stress beneath the katmai volcanoes this result favors models that involve dynamic stresses as the mechanism for triggered seismicity at katmai

natural fractures in the barnett shale and their importance for hydraulic fracture treatments gas production from the barnett shale relies on hydraulic fracture stimulation natural opening mode fractures reactivate during stimulation and enhance efficiency by widening the treatment zone knowledge of both the present day maximum horizontal stress which controls the direction of hydraulic fracture propagation and the geometry of the natural fracture system which we discuss here is therefore necessary for effective hydraulic fracture treatment design we characterized natural fractures in four barnett shale cores in terms of orientation size and sealing properties we measured a mechanical rock property the subcritical crack index which governs fracture pattern development natural fractures are common narrow 0 05 mm 0 002 in sealed with calcite and present in en echelon arrays individual fractures have high length width aspect ratios 1000 1 they are steep 75 and the dominant trend is west northwest other sets trend north south the narrow fractures are sealed and cannot contribute to reservoir storage or enhance permeability but the population may follow a power law size distribution where the largest fractures are open the subcritical crack index for the barnett shale is high indicating fracture clustering and we suggest that large open fractures exist in clusters spaced several hundred feet apart these fracture clusters may enhance permeability locally but they may be problematic for hydraulic fracture treatments the smaller sealed fractures act as planes of weakness and reactivate during hydraulic fracture treatments because the maximum horizontal stress trends northeast southwest and is nearly normal to the dominant natural fractures reactivation widens the treatment zone along multiple strands

bi melt formation and gold scavenging from hydrothermal fluids an experimental study abstract the role of polymetallic melts in scavenging ore components has recently been highlighted in the context of fluid poor metamorphosed ore deposits in contrast the role of polymetallic melts in systems dominated by hydrothermal fluids remains poorly understood using a simple au bi model system we explored experimentally whether such polymetallic melts can precipitate directly from a hydrothermal fluid and investigated the ability of these melts to scavenge au from the solution the experiments were conducted in custom built flow through reactors designed to reproduce a hydrothermal system where melt components are dissolved at one stage along the flow path e g bi was dissolved by placing bi minerals along the fluid path whereas melt precipitation was caused further along the flow path by fluid rock interaction bi rich melts were readily obtained by reaction with pyrrhotite graphite or amorphous fes when au was added to the system bi au melts with compositions consistent with the au bi phase diagram were obtained in the case of fluid reaction with pyrrhotite epitaxial replacement of pyrrhotite by magnetite was observed with textures consistent with an interface coupled dissolution reprecipitation reaction icdrr in this case the metallic melt precipitated as blebs that were localized at the replacement front or within the porous magnetite direct fractionation of bi au melts from a hydrothermal fluid or precipitation of a bi melt followed by partitioning of au from ambient fluid offer new pathways to the enrichment of minor ore components such as au without requiring fluid saturation with respect to a au mineral this mechanism can explain the strong geochemical affinity recognized between au and low melting point chalcophile elements such as bi in many gold deposits examples of deposits where such a model may be applicable include orogenic gold deposits and gold skarns contrary to models involving migration of polymetallic melts to explain element remobilization only small quantities ppm of polymetallic melts are required to affect the au endowment of a deposit via interaction with a hydrothermal fluid the experiments also show that micro environments can play a critical role in controlling melt occurrences for example reaction fronts developing via icdr reactions can promote melt formation as observed during the replacement of pyrrhotite by magnetite the associated transient porosity creates space for the melt and promotes melt fluid exchanges whereas the reaction front provides local geochemical conditions favorable to melt precipitation e g reduced low ah2s aq and catalytic surface

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

geochemistry mineralogy and mineral chemistry of the welatam cu mo bi au prospect northeast myanmar abstract the welatam prospect located in kachin state northeast myanmar is the first discovered bismuth gold locality within the tengchong lianghe tengliang metallogenic district two mineralization types identified in this area are related to three hydrothermal events the massive sulfide mineralization was formed during the hydrothermal activities of stage i and ii producing mainly iron sulfides e g pyrrhotite chalcopyrite pyrite arsenopyrite whereas the activity of stage iii resulted in quartz molybdenite mineralization which is characterized by the deposition of molybdenite galena and bi te au bearing phases the bi mineral assemblages suggest that at stage iii the prevailing temperatures were above 271 c fluid rock interaction that changed the ph fo2 fs2 and in particular temperature in hydrothermal fluids is important in causing the precipitation of liquid bismuth from bi3 the high correlation between bi and au r 0 782 demonstrates that liquid bismuth may have played a crucial role in gold enrichment here bi au bearing minerals commonly precipitate along the cleavages of molybdenite forming a distinctive mineral assemblage it may indicate that the cleavages besides providing spaces for the precipitation of liquid bismuth create local chemical conditions e g reducing and catalytic surfaces favorable for bi melt to scavenge au from ambient fluid the abundant bi minerals metal association e g cu bi mo au te w the restricted 34s values 7 3 to 1 9 of sulfides and the proximity with the welatam monzogranites suggest a magmatic contribution to the ore forming fluids

modeling of gold scavenging by bismuth melts coexisting with hydrothermal fluids the effect of gold scavenging by bismuth melts is investigated using equilibrium thermodynamic modeling of an aqueous solution mineral melt system the calculations for the au bi na cl s h o system performed at temperatures between 300 and 450 c demonstrate that au concentrations in the melt are several orders of magnitude higher than in the coexisting fluid indicating the possible formation of economic gold deposits from undersaturated aqueous fluids in which mineralization would not be expected in the absence of a bismuth melt the model applies to any deposit where a bi melt is stable and coexists with a hydrothermal fluid examples of such deposits are known from skarn intrusion related orogenic and volcanogenic massive sulfide vms gold systems in sulfur poor systems the partitioning curves presented here can be used directly to correlate the gold concentration in the fluid and the au grade in the ore e g escanaba trough vms deposit these results also illustrate important principles generally applicable to understanding magmatic hydrothermal and metamorphic deposits that may have contained significant volumes of more complex polymetallic melts

post collisional crustal extension setting and vhms mineralization in the jinshajiang orogenic belt southwestern china abstract the jinshajiang orogenic belt job of southwestern china located along the eastern margin of the himalayan tibetan orogen includes a collage of continental blocks joined by paleozoic ophiolitic sutures and permian volcanic arcs three major tectonic stages are recognized based on the volcanic sedimentary sequence and geochemistry of volcanic rocks in the belt westward subduction of the paleozoic jinshajiang oceanic plate at the end of permian resulted in the formation of the chubarong dongzhulin intra oceanic arc and jamda weixi volcanic arc on the eastern margin of the changdu continental block collision between the volcanic arcs and the yangtze continent block during early middle triassic caused the closing of the jinshajiang oceanic basin and the eruption of high si and al potassic rhyolitic rocks along the permian volcanic arc slab breakoff or mountain root delamination under this orogenic belt led to post collisional crustal extension at the end of the triassic forming a series of rift basins on this continental margin arc significant potential for vhms deposits occurs in the submarine volcanic districts of the job mesozoic vhms deposits occur in the post collisional extension environment and cluster in the late triassic rift basins

integrated analysis of sar interferometric and geological data for investigating long term reclamation settlement of chek lap kok airport hong kong abstract we investigated the long term reclamation settlement of chek lap kok airport hong kong one of the largest reclamation projects worldwide an advanced insar technique was applied to two independent asar data sets along ascending 25 scenes and descending 22 scenes orbits acquired between 2003 and 2008 and allowed us to generate deformation velocity maps and displacement time series for the investigated area intercomparison of deformation velocity results from the two asar data sets and their validation against leveling survey measurements were carried out in order to assess accuracy and reliability of the insar observations the intercomparison and validation results demonstrated the potential of elaborate insar processes on local scale areas to monitor and detect a long term residual settlement in such complex reclamation area the insar derived deformation velocity maps showed a fair stability in areas of the two original rocky islands of chek lap kok and lam chau and on most of the buildings at the site due to foundation on piles reaching the granite bedrock whereas a generally moderate 3 7 mm year to strong 10 mm year and spatially variable settlement trend was detected in the majority of reclamation areas of the airport the consistent relationship we found between the observed settlement pattern and the underlying geological conditions suggested that this recoded differential settlement was mainly related to the variations in thickness and soil properties of both the fill materials and the alluvial deposits below the reclamation a geological and geotechnical interpretation of the lithostratigraphy of the alluvial deposits beneath the reclamation implied that the relatively large settlement rate measured up to 2008 was resulted from a still active primary consolidation process

aggregate properties of fracture populations abstract empirical studies indicate that the individual attributes of both faults and extension fractures follow power law scaling aggregate properties of fracture populations are important in a variety of problems and can be specified in terms of the scaling parameters of individual fracture attributes development of an expression for an aggregate property requires consideration of a number of independent factors including the topologic dimension of the aggregate property the topologic dimension of sampling and the possibility of scaling changes for fractures that span some mechanically significant layer the riemann zeta function provides an alternative to integration for the analytical and numerical solution of aggregate problems previous work regarding aggregate properties of fracture populations has focused on the strain due to faulting new expressions are developed here for other aggregate properties of interest fracture surface area fracture porosity fracture permeability and shear wave anisotropy a general characteristic of these aggregate properties is that for most values of scaling exponents the aggregate properties are dependent on the size of the sampling domain this implies that the aggregate properties are scale dependent additionally it appears that fracture surface area is concentrated in the smallest fractures of many populations fracture porosity is concentrated in the largest fractures of most populations but not as strongly as fracture permeability which probably derives almost entirely from the largest fractures in populations

stress corrosion cracking of quartz a note on the influence of chemical environment abstract tensile mode i stress corrosion growth of cracks on the a plane of quartz in a direction normal to z has been studied in de ionized water in 2n hcl and in 2n naoh solutions at 20 c the double torsion testing method was used to obtain crack velocity v stress intensity factor ki curves the stress corrosion index n where v kin was 19 3 for 2n hcl 12 8 for deionized water and 9 5 for 2n naoh the degree of influence of reagent chemistry on crack velocity was most marked at low ki values at 0 5 kic 3 orders of magnitude increase in crack velocity results from substituting 2n naoh for 2n hcl as the corrosive medium but decreased monotonically on raising ki so that close to kic there was no clearly discernible influence on crack growth rates ca 10 3 m s 1 these observations are explained in terms of a model of crack propagation in which at low ki values the chemistry of the bulk fluid environment controls the corrosion reaction the rate of crack growth is enhanced by increasing environmental oh concentration at high ki or velocity however the chemical composition of the quartz surface may control crack propagation rates through its influence on the chemistry of the crack tip fluid as the ph of natural pore fluids is likely to vary widely in different geological environments these results should be noted when invoking stress corrosion to explain geophysical phenomena

a chemical model for the devonian remobilization process in the cambrian volcanic hosted massive sulfide rosebery deposit western tasmania the rosebery deposit in western tasmania is a polymetallic massive sulfide deposit hosted in felsic volcanics of the cambrian mount read volcanic belt the deposit underwent upper greenschist facies regional metamorphism and related deformation during the devonian tabberabberan orogeny resulting in folding shearing and faulting thrusting of the ore lenses the south end of the rosebery deposit has undergone metasomatic replacement related to a postorogenic devonian granitoid pluton whose existence is inferred from geophysical gravity data metasomatic mineral assemblages related to this pluton have been recognized transgressing cambrian volcanic hosted massive sulfide minerals at the south end of the rosebery orebody cambrian volcanic hosted massive sulfide mineralization at rosebery consists of three primary zones a lowermost pyrite chalcopyrite zone overlain by a sphalerite galena pyrite zone and further overlain by a massive barite carbonate zone three major devonian replacement zones are also present 1 a magnetite biotite chalcopyrite zone 2 a pyrrhotite pyrite zone and 3 a tourmaline quartz magnetite zone minerals such as fluorite gamet and helvite are also present in the replacement zones metal zonation studies indicate that zinc occurs dominantly in a blanketlike enrichment zone in the primary sulfide lenses of the rosebery deposit gold is largely concentrated at the top of the ore lenses in the transgressive pyrrhotite pyrite replacement zone at the south end of the rosebery deposit zinc is conspicuously depleted but gold concentrations of more than 20 glt are observed in contrast the biotite magnetite and tourmalinebearing replacement zones contain low gold grades generally less than 5 0 glt au copper concentrations as high as 2 percent are observed in the biotite magnetite zone as well as in the pyrrhotite pyrite zone microthermometry and laser raman spectroscopy studies of fluid inclusions from tlle devonian replacement zone indicate that the early biotite magnetite and pyrrhotite pyrite assemblages formed from the interaction of moderate to high temperature 330 c saline 10 25 wt nacl equiv co2 bearing fluid with the original stratiform lead zinc mineralization the later stage tourmaline veining and associated replacement assemblages resulted from lower temperature 300 c less saline 10 wt nacl equiv fluid the high temperature high salinity and co2 bearing metasomatic fluid support the hypothesis of derivation of this fluid from devonian granite below the rosebery deposit during the devonian metasomatic event gold and to a lesser extent copper were most likely remobilized as chloride complexes because of the high temperature and high salinity of the fluid in comparison to copper and gold zinc and lead were dissolved and removed probably as chloride complexes

role of shale thickness on vertical connectivity of fractures application of crack bridging theory to the austin chalk texas abstract contrasting material properties of alternating chalk and shale layers control vertical connectivity of fractures our field observations within the austin chalk texas indicate that 1 the majority of vertical fractures occur in chalk layers and abut against contacts with shale layers 2 thicker shale layers have greater resistance to fracture propagation than thinner shale layers from these observations we hypothesize both the resistance of shale to fracturing and the thickness of shale layers may inhibit fracture propagation across the shale and into the next chalk layer we model crack propagation within a three layered system brittle chalk fracture resistant shale brittle chalk the modeled crack extends across the shale but closing tractions applied to the crack segment within the shale layer simulate resistance of shale to fracturing the crack tip lies a short distance within the unfractured chalk layer simulating a coplanar flaw with potential to propagate if the stress intensity factor at the flaw exceeds the chalk fracture toughness the crack propagates thereby bridging and eventually rupturing the shale layer for any chalk thickness there is a critical shale thickness above which fractures cross the shale layer and below which fractures arrest at shale finite element method fem analysis evaluates the influence of shale ductility within the chalk shale chalk system although remote and fluid pressure driven fractures produce identical stress intensity factors in elastic chalk shale systems lower driving stresses are required to propagate fluid pressure driven fractures through a system ductile shale layers than fractures under remote tension

tethys tectonic evolution and its bearing on the distribution of important mineral deposits in the sanjiang region sw china abstract the sanjiang region in se tibet plateau and nw yunnan is known to have formed by amalgamation of gondwana derived continental blocks and arc terranes as a result of oceanic subduction followed by continental collision from paleozoic to mesozoic in this paper we provide a synthesis of tectonic evolution magmatism and metallogeny in the region based on data from literatures early paleozoic ophiolites 473 439 ma in the changning menglian belt indicate the existence of a proto tethys ocean in this region two episodes of subduction related magmatism in the early paleozoic one occurred in the baoshan and tengchong blocks at 502 455 ma and the other occurred in the simao block at 421 401 ma are regarded as evidence for two different events of subduction of the proto tethys ocean at different locations the proto tethys was succeeded in early devonian by the paleo tethys which comprised the main ocean and three branches ailaoshan jinshajiang and garze litang the changning menglian main ocean existed from middle devonian to middle triassic the remnants of the oceanic crust are preserved in a few places in the longmu tso shuanghu suture as well as in the changning menglian ophiolite belt the eastward subduction of the main oceanic plate from early permian to early triassic formed a prominent arc terrane stretching 1500 km from yunnan to eastern tibet from the waning stage of subduction to post subduction numerous s type granite plutons with ages varying between 230 and 219 ma such as the lincang batholith in yunnan were emplaced at or close to the suture this event produced several hydrothermal w sn deposits in the region the tectonic evolution and associated magmatism of the jinshajiang and ailaoshan branch oceans are generally comparable to those of the main ocean however the branch oceans were subducted westward instead the garze litang branch ocean also underwent westward subduction from middle devonian to late triassic arc related high sr y porphyry intrusions and associated porphyry skarn cu mo au deposits are common in the jinshajiang ailaoshan region especially in the yidun arc which formed prior to jurassic the vms deposits in the sanjiang region formed in diverse tectonic settings including middle silurian back arc basins carboniferous oceanic islands paleozoic subduction zones and triassic post subduction rifting environments the mesozoic and early cenozoic evolution of the baoshan and tengchong blocks was largely influenced by eastward oceanic subduction of the meso and neo tethys from late permian to middle cretaceous and from late cretaceous to 50 ma respectively abundant early cretaceous granitoids and associated skarn type pb zn and sn fe deposits in the baoshan and tengchong blocks were produced in the background of the shan boundary oceanic slab subduction to the west and the break off of the nujiang bitu oceanic slab to the north the subduction of the neo tethys oceanic plate beneath the tengchong block from late cretaceous to paleogene formed abundant s type granitoids and many skarn type and greisen type sn w deposits granitoids formed at 105 to 81 ma and contemporaneous hydrothermal w mo ag and au deposits which temporally coincided with the subduction of the neo tethys are common in the yidun arc terrane

surface displacement of the 17 may 1993 eureka valley california earthquake observed by sar interferometry satellite synthetic aperture radar sar interferometry shows that the magnitude 6 1 eureka valley earthquake of 17 may 1993 produced an elongated subsidence basin oriented north northwest parallel to the trend defined by the aftershock distribution whereas the source mechanism of the earthquake implies a north northeast striking normal fault the 3 millimeter accuracy of the radar observed displacement map over short spatial scales allowed identification of the main surface rupture associated with the event these observations suggest that the rupture began at depth and propagated diagonally upward and southward on a west dipping north northeast fault plane reactivating the largest escarpment in the saline range

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

multiple seismogenic processes for high frequency earthquakes at katmai national park alaska evidence from stress tensor inversions of fault plane solutions the volcanological significance of seismicity within katmai national park has been debated since the first seismograph was installed in 1963 in part because katmai seismicity consists almost entirely of high frequency earthquakes that can be caused by a wide range of processes i investigate this issue by determining 140 well constrained first motion fault plane solutions for shallow depth 9 km earthquakes occurring between 1995 and 2001 and inverting these solutions for the stress tensor in different regions within the park earthquakes removed by several kilometers from the volcanic axis occur in a stress field characterized by horizontally oriented 1 and 3 axes with 1 rotated slightly 12 relative to the nuvel1a subduction vector indicating that these earthquakes are occurring in response to regional tectonic forces on the other hand stress tensors for earthquake clusters beneath several katmai cluster volcanoes have vertically oriented 1 axes indicating that these events are occurring in response to local not regional processes at martin mageik vertically oriented 1 is most consistent with failure under edifice loading conditions in conjunction with localized pore pressure increases associated with hydrothermal circulation cells at trident novarupta it is consistent with a number of possible models including occurrence along fractures formed during the 1912 eruption that now serve as horizontal conduits for migrating fluids and or volatiles from nearby degassing and cooling magma bodies at mount katmai it is most consistent with continued seismicity along ring fracture systems created in the 1912 eruption perhaps enhanced by circulating hydrothermal fluids and or seepage from the caldera filling lake manuscript received 25 april 2002

vertical surface displacements at yellowstone caldera wyoming 1976 1986 between first order leveling surveys in 1976 and 1986 the east central floor of yellowstone caldera rose 15 4 1 4 mm yr and the west central floor rose 17 0 2 0 mm yr with respect to points on the south caldera rim the same pattern has prevailed since an initial survey in 1923 except that the western caldera rose 30 faster during 1976 1986 than during 1923 1976 the 1976 1986 uplift extends beyond the northwest caldera rim near the adjacent hebgen lake fault zone site of a magnitude 7 3 earthquake in august 1959 marginally significant displacements in the eastern caldera suggest that uplift continued during 1983 1984 stopped during 1984 1985 and reversed to subsidence during 1985 1986 thus long term uplift may accumulate episodically historical uplift is especially noteworthy because regional crustal extension and thermal contraction during cooling would cause the caldera floor to subside if other processes were not acting to warp it upward the pattern and dimensions of the uplift indicate a source in the upper crust beneath yellowstone caldera probably a reservoir of rhyolite magma within a cooling granitic pluton a simple point source model would suggest a source 10 15 km deep but the reservoir is probably lens shaped and closer to the surface uplift may be caused by basaltic intrusions near the base of the reservoir or accumulation of magmatic fluids during cooling and crystallization within the reservoir subsidence might be a response to regional tectonic extension or release of trapped magmatic fluids magmatic inflation volatile accumulation and crustal extension may culminate eventually in renewed eruptive activity but there is no evidence of an imminent volcanic hazard

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

a method to detect natural fracture strike in sandstones in siliciclastic hydrocarbon reservoir rocks economic gas and oil production may depend on the attributes of natural fractures and with the advent of horizontal drilling fractures are increasingly exploration and development targets yet reliable information on such key fracture attributes as orientation strike is sparse because few fractures intersect vertical well bores this paper describes how fracture strike can be documented on a bed by bed basis even in well bores where few or no visible fractures are directly sampled quartz lined opening mode microfractures lengths of microns to millimeters in quartz cemented sandstones commonly are not visible using standard petrographic methods but systematic mapping of these microfractures is possible using photomultiplier based electron beam induced luminescence scanned cathodoluminescence imaging as shown by observations primarily from three natural gas plays and one oil play in the united states microfracture strike is a good guide to the strike of large fractures macrofractures that formed concurrently because microfractures are widespread and small specimens can be used to get accurate fracture strike data this approach can be applied to samples obtained from wireline conveyed rotary drilled sidewall coring devices as well as to samples from full diameter core

superimposed orogenesis and metallogenesis in sanjiang tethys the sanjiang tethyan area experienced the superpoimsed transition from tethyan tectonic evolution in late paleozoic to continental collision orogeny in cenozoic resulting in the accumulation of massive multi stage mineralizations and large amounts of metallic industrial ore deposits the complex metallogenic evolution of this area finds expression in the following aspects large amounts of complex superimposed and reworked ore deposits were developed on the proterozoic substrate of rigid continental segment with special metallic associations of sn cu sn pb zn and fe cu volcanics hosted massive sulfide deposits were developed throughout the evolution of tethyan lithosphere from continental margin rift cu through initial ocean basin cu zn ocean arc cu zn pb and interarcual rift valley or back arc basin pb zn ag to rift basin caused by arc continental collision cu pb zn island type porphyry copper deposits at the tethyan stage were replaced by continental type porphyry copper deposits at the collision orogeny stage metallic ore forming belt and gigantic ore deposits of world class such as the yulong porphyry cu mo metallogenic belt the lanping zn pb cu ag metallogenic belt the ailaoshan au metallogenic belt the chuanxi ree metallogenic belt the tengchong lianghe sn metallogenic belt were generated explosively during the collision orogeny in cenozoic although successful researches on tectonic and metallogenic cheracteristics have been conducted for the sanjiang tethyan metallogenic domain many important scientific problems remain unsolved such as precise time limits and internal connections between tectonic superposition continental accretion and convergence and collision and transformation the control of geological setting over mineralization the constraint of the crust mantle interaction on the formation of ore deposit clusters and the anomalous concentration of large amounts of ore materials space time structure material structure and genetic type of ore deposits of the typical metallogenic system the development mechanism of metallogenic systems and the formation mechanism of large sized ore deposits it is obvious that the solution of these problems will be a great breakthrough in the study of the tectonic evolution and metallogenesis of the sanjiang tethyan metallogenic domain

deformation of new trident volcano measured by ers 1 sar interferometry katmai national park alaska using synthetic aperture radar sar interferometry we detect several centimeters of uplift that accumulated during two years 1993 1995 around the vent of the new trident volcano in alaska s katmai national park the areas of image coherence correspond to fresh blocky lavas while coherence is lost in ash covered areas from the uplift gradient we estimate the depth of a pressure source under new trident volcano to be approximately 0 8 2 0 km our results show that in spite of the difficult sub arctic environment of southern alaska strain build up can be monitored over a two year period showing the potential for global monitoring of volcano deformation using sar interferometry

on the absence of insar detected volcano deformation spanning the 1995 1996 and 1999 eruptions of shishaldin volcano alaska shishaldin volcano a large frequently active basaltic andesite volcano located on unimak island in the aleutian arc of alaska had a minor eruption in 1995 1996 and a vei 3 sub plinian basaltic eruption in 1999 we used 21 synthetic aperture radar images acquired by ers 1 ers 2 jers 1 and radarsat 1 satellites to construct 12 coherent interferograms that span most of the 1993 2003 time interval all interferograms lack coherence within 5 km of the summit primarily due to persistent snow and ice cover on the edifice remarkably in the 5 15 km distance range where interferograms are coherent the insar images show no intrusion or withdrawal related deformation at shishaldin during this entire time period however several insar images do show deformation associated with a shallow ml 5 2 earthquake located 14 km west of shishaldin that occurred 6 weeks before the 1999 eruption we use a theoretical model to predict deformation magnitudes due to a volumetric expansion source having a volume equivalent to the 1999 erupted volume and find that deformation magnitudes for sources shallower than 10 km are within the expected detection capabilities for interferograms generated from c band ers 1 2 and radarsat 1 synthetic aperture radar images we also find that insar images cannot resolve relatively shallow deformation sources 1 2 km below sea level due to spatial gaps in the insar images caused by lost coherence the lack of any deformation particularly for the 1999 eruption leads us to speculate that magma feeding eruptions at the summit moves rapidly at least 80m day from n10 km depth and that the intrusion eruption cycle at shishaldin does not produce significant permanent deformation at the surface published by elsevier b v

seismicity at the volcanoes of katmai national park alaska july 1995 december 1997 abstract upper crustal seismicity located within katmai national park occurs mainly within four distinct clusters originating near martin mageik mm subnet volcanoes trident volcano katmai caldera and snowy volcano analyses of earthquake frequency magnitude distributions reveal high b values beneath mm subnet 1 5 normal b values at trident volcano 1 0 and intermediate b values at katmai caldera 1 3 for all seismicity occurring between july 1995 and december 1997 detailed analyses of subsets of b values and hypocenter locations at mm subnet reveal a temporal increase in b value associated with an increase in the maximum depth of seismicity the changes occurred during a shallow earthquake swarm beneath mageik volcano between october 16 and 25 1996 and again in november december 1997 before the swarm the weighted least squares b value was 1 01 at mm subnet increased to 1 59 during the swarm and remained anomalously high until april 1997 the corresponding maximum depth of seismicity is generally less than 5 km for well located earthquakes occurring after september 18 1996 but shifted to 10 km during both the october 1996 swarm and the november december 1997 period the november december 1997 event is not associated with an increase in the rate of seismicity or the b value the october 1996 swarm had a cumulative moment release of 5 0 10 20 dyn cm and decayed from a peak rate of 110 events per day with a modified omori law p value of 1 06 0 11 modelling by the flow law with a 10 km depth limit for seismicity suggests that temperature gradients are on the order of 20 40 c km 1 in agreement with the p value estimate we infer that a simple pressurizing intrusion was not associated with the october swarm because higher stresses should increase seismicity and lower the b value the opposite of what we observed alternatively an actively degassing intrusion would reduce the effective stress and increase the b value at shallow depths while the increased stress would induce seismicity at depth surface temperature measurements taken at the mageik crater lake in july 1995 and again in july 1997 revealed an increase of about 10 c in the lake water temperature consistent with a degassing intrusive event

why is earthquake prediction research not progressing faster abstract as a physical phenomenon earthquakes must be predictable to a certain degree however the problem is difficult because the source volume inside the earth is inaccessible to direct observation and because the most important parameter the stress level cannot be measured directly also seismology is such a young science that the cause of earthquakes was discovered in the 1960s only advanced seismograph networks as well as modern techniques to measure crustal deformations such as the global positioning system gps and the synthetic aperture radar interferometry technique insar have come on line only recently and only in japan are they deployed with the densities necessary for significant advances in the understanding of the rupture initiation process in addition no real program for earthquake prediction research exists in the united states largely because funding agencies and peer reviewers shy away from a field in which unprofessional but motivated individuals are active although claims of successful predictions are often not justified a few correct predictions have been made most of these had time windows of years but some were accurate to days and allowed preparatory actions to make significant progress we must learn how to conduct rigorous science in a field where amateurs cannot be discouraged to venture leadership is necessary to raise the funding to an adequate level and to involve the best minds in this promising potentially extremely rewarding but controversial research topic

inhomogeneous distribution of ree in scheelite and dynamics of archaean hydrothermal systems mt charlotte and drysdale gold deposits western australia scheelite is a widespread accessory mineral in hydrothermal gold deposits and its rare earth element ree patterns and nd and sr isotopic compositions can be used to constrain the path and origin of the mineralising fluids and the age of the hydrothermal activity micro analyses by laser ablation high resolution inductively coupled mass spectroscopy and cathodoluminescence imaging reveal a very inhomogeneous distribution of the ree in single scheelite grains from the mt charlotte and drysdale archaean gold deposits in western australia two end member ree patterns are distinguished type i is middle ree mree enriched with no or minor positive eu anomaly whereas type ii is flat or mree depleted with a strong positive eu anomaly the chemical inhomogeneity of these scheelites is related to oscillatory zoning involving type i and type ii patterns with zone widths varying from below 1 to 200 m intra sectorial growth discontinuities syn crystallisation brittle deformation and variations in the relative growth velocities of crystallographically equivalent faces suggest a complex crystallisation history under dynamic hydraulic conditions the co existence of mree enriched and mree depleted patterns within single scheelite crystals can be explained by the precipitation of a mineral which strongly partitions mree relative to light and heavy ree scheelite itself has such characteristics as does fluorapatite which is locally abundant and has ree contents similar to that of scheelite in this context the systematic increase of the eu anomaly between type i and type ii patterns is produced by the difference between the partition coefficients of eu2 and eu3 and not by fluid mixing or redox reactions consequently the high positive eu anomaly typical of scheelite from gold ores may not necessarily be inherited from the hydrothermal fluid but may reflect processes occurring during ore deposition this case study demonstrates that in hydrothermal systems characterised by low ree concentrations in the fluid and by the precipitation of a ree rich mineral which strongly fractionates the ree the ree patterns of such a mineral will be highly sensitive to the dynamics of the hydrothermal system

three dimensional p wave velocity structure derived from local earthquakes at the katmai group of volcanoes alaska abstract the three dimensional p wave velocity structure beneath the katmai group of volcanoes is determined by inversion of more than 10 000 rays from over 1000 earthquakes recorded on a local 18 station short period network between september 1996 and may 2001 the inversion is well constrained from sea level to about 6 km below sea level and encompasses all of the katmai volcanoes martin mageik trident griggs novarupta snowy and katmai caldera the inversion reduced the average rms travel time error from 0 22 s for locations from the standard one dimensional model to 0 13 s for the best three dimensional model the final model from the 6th inversion step reveals a prominent low velocity zone 3 6 5 0 km s centered at katmai pass and extending from mageik to trident volcanoes the anomaly has values about 20 25 slower than velocities outboard of the region 5 0 6 5 km s moderately low velocities 4 5 6 0 km s are observed along the volcanic axis between martin and katmai caldera griggs volcano located about 10 km behind northwest of the volcanic axis has unremarkable velocities 5 0 5 7 km s compared to non volcanic regions the highest velocities are observed between snowy and griggs volcanoes 5 5 6 5 km s relocated hypocenters for the best 3 d model are shifted significantly relative to the standard model with clusters of seismicity at martin volcano shifting systematically deeper by about 1 km to depths of 0 to 4 km below sea level hypocenters for the katmai caldera are more tightly clustered relocating beneath the 1912 scarp walls the relocated hypocenters allow us to compare spatial frequency size distributions b values using one dimensional and three dimensional models we find that the distribution of b is significantly changed for martin volcano which was characterized by variable values 0 8 b b b b b b values indicating the robustness of the observations the strong high b value region at mageik volcano is mainly associated with an earthquake swarm in october 1996 that possibly indicates a shallow intrusion or influx of gas the new velocity and spatial b value results in conjunction with prior gravity bouguer anomalies up to 40 mgal and interferometry several cm uplift data provide strong evidence in favor of partially molten rock at shallow depths beneath the mageik katmai novarupta region moderately low velocities beneath martin and katmai suggest that old mostly solidified intrusions exist beneath these volcanoes higher relative velocities beneath the griggs and snowy vents suggest that no magma is resident in the shallow crust beneath these volcanoes

monitoring the evolution of the pasig potrero alluvial fan pinatubo volcano using a decade of remote sensing data abstract since the 1991 climactic eruption of pinatubo in the philippines various hazards have affected areas surrounding the volcano the most significant of these hazards involve the redeposition of pyroclastic flow and fall deposits as lahars deposit derived pyroclastic flows and ash falls due to phreatic explosions many of these processes occurred in areas that are inaccessible for ground observation and monitoring we describe here how sequential remote sensing data obtained over the period december 18 1991 to november 1 2001 from the spot ers radarsat sir c x sar airsar landsat 7 etm and aster sensors provide a means of monitoring the decade long development of the post eruption pinatubo landscape this method represents an efficient and safe alternative to time consuming physically demanding and risky field campaigns we apply principal component analysis image subtraction band ratioing and density slicing to these data to track the changes in the post eruption landscape estimate volumes of deposition and allow hazard vulnerability prediction along the timeline establish by the series of data sets the maps derived from the remote sensing data agree well with the field derived maps for the first 5 years 1991 1995 provide important large area coverage and show details that are unobtainable from conventional ground based mapping the volume of lahars deposited during the first 6 months following the eruption is estimated between 0 045 and 0 075 km 3 covering an area of 45 km 2 moreover changes in the settlement patterns of the local population as well as in the construction and modification of the engineering structures for controlling the lahar hazards can be identified in the multi temporal scenes spanning the entire decade of observations these types of information are crucial inputs for local decision and policy making in volcanic hazard mitigation

rapid subsidence over oil fields measured by sar interferometry the lost hills and belridge oilfields are in the san joaquin valley california the major oil reservoir is high porosity and low permeability diatomite extraction of large volumes from shallow depths causes reduction in pore pressure and subsequent compaction forming a surface subsidence bowl we measure this subsidence from space using interferometric analysis of sar synthetic aperture radar data collected by the european space agency remote sensing satellites ers 1 and ers 2 maximum subsidence rates are as high as 40 mm in 35 days or 400 mm yr measured from interferograms with time separations ranging from one day to 26 months the 8 and 26 month interferograms contain areas where the subsidence gradient exceeds the measurement possible with ers sar but shows increased detail in areas of less rapid subsidence synoptic mapping of subsidence distribution from satellite data powerfully complements ground based techniques permits measurements where access is difficult and aids identification of underlying causes

oxidation state of europium in scheelite tracking fluid rock interaction in gold deposits abstract we used xanes spectroscopy to measure the oxidation state of europium in situ at near m resolution in hydrothermal scheelite from the giant archean gold deposits of kalgoorlie western australia by combining these measurements with xrf imaging it is possible to distinguish inhomogeneities in eu2 eu3 ratios that developed during mineral precipitation from the effects of subsequent hydrothermal alteration and weathering thermodynamic analysis reveals that under the conditions typical of the formation of many au deposits the eu2 eu3 ratio in the hydrothermal fluid is highly sensitive to ph the range in ph calculated from the eu2 eu3 ratios in the analyzed scheelite corresponds to a maximum in au solubility under the ore forming conditions and suggests buffering of ph by the co2 aq rich fluid the primary heterogeneity of the karlgoorlie scheelite most likely results from ph oscillating between fluid and rock buffered conditions and reflects the dynamics of the hydrothermal system

ground deformation associated with the march 1996 earthquake swarm at akutan volcano alaska revealed by satellite radar interferometry in march 1996 an intense swarm of volcano tectonic earthquakes 3000 felt by local residents mmax 5 1 cumulative moment of 2 7 1018 n m beneath akutan island in the aleutian volcanic arc alaska produced extensive ground cracks but no eruption of akutan volcano synthetic aperture radar interferograms that span the time of the swarm reveal complex island wide deformation the western part of the island including akutan volcano moved upward while the eastern part moved downward the axis of the deformation approximately aligns with new ground cracks on the western part of the island and with holocene normal faults that were reactivated during the swarm on the eastern part of the island the axis is also roughly parallel to the direction of greatest compressional stress in the region no ground movements greater than 2 83 cm were observed outside the volcano s summit caldera for periods of 4 years before or 2 years after the swarm we modeled the deformation primarily as the emplacement of a shallow east west trending north dipping dike plus inflation of a deep mogi type magma body beneath the volcano the pattern of subsidence on the eastern part of the island is poorly constrained it might have been produced by extensional tectonic strain that both reactivated preexisting faults on the eastern part of the island and facilitated magma movement beneath the western part alternatively magma intrusion beneath the volcano might have been the cause of extension and subsidence in the eastern part of the island we attribute localized subsidence in an area of active fumaroles within the akutan caldera by as much as 10 cm during 1992 1993 and 1996 1998 to fluid withdrawal or depressurization of the shallow hydrothermal system

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