analyzing earthquake clustering features by using stochastic reconstruction 1 on the basis of the epidemic type aftershock sequence etas model and the thinning procedure this paper gives the method about how to classify the earthquakes in a given catalogue into different clusters stochastically the key points of this method are the probabilities of one event being triggered by another previous event and being a background event making use of these probabilities we can reconstruct the functions associated with the characteristics of earthquake clusters to test a number of important hypotheses about the earthquake clustering phenomena we applied this reconstruction method to the shallow seismic data in japan and also to a simulated catalogue the results show the following assertions 1 the functions for each component in the formulation of the space time etas model are good enough as a first order approximation for describing earthquake clusters 2 a background event triggers less offspring in expectation than a triggered event of the same magnitude 3 the magnitude distribution of the triggered event depends on the magnitude of its direct ancestor 4 the diffusion of the aftershock sequence is mainly caused by cascades of individual triggering processes while no evidence shows that each individual triggering process is diffusive and 5 the scale of the triggering region is still an exponential law as formulated in the model but not the same one for the expected number of offspring

statistical modeling and characterization of induced seismicity within the western canada sedimentary basin in western canada there has been an increase in seismic activity linked to anthropogenic energy related operations including conventional hydrocarbon production wastewater fluid injection and mor

microprobe monazite geochronology understanding geologic processes by integrating composition and chronology abstractmonazite is a light rare earth element lree bearing phosphate mineral that is present in a wide variety of rock types has an extremely variable composition reflecting host rock conditions and is a robust geochronometer that can preserve crystallization ages through a long history of geological events monazite crystals typically contain distinct compositional domains that represent successive generations of monazite which in turn can provide a detailed record of the geologic history of its host rocks the electron microprobe can be used to characterize the geometry of compositional domains analyze the composition of each domain and when carefully configured determine the u th total pb age for domains as small as 5 m in width these data allow the monazite to be linked with and place timing constraints on silicate processes in the host rocks current applications span a broad range of geologic processes in igneous metamorphic hydrothermal and sedimentary rocks

paleo and neoproterozoic magmatic and tectonometamorphic evolution of the isla cristalina de rivera nico perez terrane uruguay the isla cristalina de rivera crystalline complex in northeastern uruguay underwent a multistage magmatic and metamorphic evolution based on shrimp u pb zircon th u pb monazite chime epma method and k ar age data from key units several events can be recognized 1 multistage magmatism at 2 171 2 114 ma recorded on zircon of the granulitic orthogneisses and their 2 093 2 077 ma overgrowths 2 a distinct amphibolite facies metamorphism at 1 980 ma recorded by monazite 3 greenschist facies reworking and shearing at ca 606 ma monazite and k ar on muscovite along the rivera shear zone and finally 4 intrusion of the post tectonic sobresaliente and las flores granites at around 585 ma lithological similarities geographic proximity and coeval magmatic and metamorphic events indicate a similar tectonometamorphic evolution for the isla cristalina de rivera the valentines block in uruguay and the santa maria chico granulitic complex in southern brazil since at least 2 1 ga

experimental resetting of the u th pb systems in monazite abraded fragments 200 400 m of a large chemically homogeneous and non metamict brazilian monazite crystal characterised by a concordant u pb ages of 474 1 ma 208pb 206pb 19 5 were hydrothermally treated at varying temperatures with solutions of different compositions product monazites were analysed with scanning electron microscope sem electron microprobe emp secondary ion mass spectrometer sims and isotope dilution thermal ionisation mass spectrometer id tims experiments with pure water over a temperature range of 800 1200 c at 700 mpa and durations ranging from 5 to 60 days showed that even at 1200 c any dissolution and recrystallization of new monazite is confined to the outermost surface of the grain neither pb diffusion at the emp scale nor significant discordancy were observed we performed experiments at 800 and 1000 c for different durations using different fluid compositions at quartz saturation a 10 wt cacl2 fluid a 10 wt srcl2 fluid a 10 wt nacl fluid and a fluid containing nbs 982 pb standard 208pb 206pb 1 for all runs emp traverses revealed no pb diffusion profiles significant overgrowths of newly formed monazite are documented by sem analyses they occurred only in the 1000 c experiments when either cacl2 or pb bearing fluids were present in the cacl2 experiment two zones could be distinguished within the crystal a core possessing the initial monazite composition and a rim consisting of newly formed monazite produced by dissolution precipitation which was enriched in ca and pb free id tims dating of single grains treated with srcl2 and cacl2 solutions at 1000 c are significantly discordant experiments employing the nbs pb standard produced sub concordant monazite for which the 207pb 206pb apparent age has become older than prior to the experiment 544 ma at 800 c and 495 ma at 1000 c the newly grown monazite rim had obviously incorporated pb from the fluid none of our reaction products contained a detectable diffusion profile the only resetting mechanism we detected involved dissolution precipitation the extent of the dissolution precipitation process depends on fluid composition and is a more efficient mechanism than diffusion for controlling the resetting of monazite in natural rocks

on the development of electron microprobe zircon fission track geochronology abstract the fission track method has been applied for decades to quantify rates and timing of processes in the shallow crust the most widely used approach the external detector method involves counting fission tracks a decay product resulting from the spontaneous fission of 238 u and a paired set of induced tracks parent proxy from the thermal neutron irradiation of 235 u we propose an alternate method of dating zircons that utilizes an electron microprobe to directly measure uranium concentration u and image the number of spontaneous fission tracks or etch figures that intersect the surface of the crystal using an electron backscatter detector the electron microprobe fission track ep ft method is used to date six zircon samples four of which are widely used as standards fish canyon tuff peach springs tuff buluk member of the bakata formation tuff tardee rhyolite mt dromedary complex hypabyssal granite and browns park formation tuff all samples yield ages that overlap within two standard deviations of published reference ages determined using other radiometric techniques i e k ar 40 ar 39 ar and u pb and also by the traditional fission track external detector method to correct for poorly constrained parameters such as the spontaneous fission decay constant weight to volume percent conversions etching efficiency and selection bias we calculate a preliminary z proportionality factor of 4469 661 1 the ep ft technique avoids the hazard and expense of thermal neutron irradiation allows simultaneous chemical compositions to be determined removes the step of counting an external detector manually and will likely allow much higher track densities to be counted than would be normally possible with optical microscopy the technique is ideal for dating moderate to high u zircons 100 ppm u

two dimensional water flood and mudflow simulation flo 2d is a two dimensional finite difference model that simulates clear water flood hazards mudflows and debris flows on alluvial fans and urban floodplains interactive flood or mudflow routing between channel street and floodplain flow is performed using a uniform grid system to describe complex floodplain topography a quadratic rheological model developed from field and laboratory mudflow data enables appropriate simulations of flooding conditions ranging from clear water to hyperconcentrated sediment flows computer aided design cad graphics of predicted time sequenced flood depths automates the delineation of flood hazards replication of the 1983 rudd creek mudflow in utah demonstrates the capability of the model

high spatial resolution dating of monazite and zircon reveals the timing of subduction exhumation of the vaimok lens in the seve nappe complex scandinavian caledonides in situ monazite th u total pb dating and zircon la icp ms depth profiling was applied to metasedimentary rocks from the vaimok lens in the seve nappe complex snc scandinavian caledonides results of monazite th u total pb dating coupled with major and trace element mapping of monazite revealed 603 16 ma neoproterozoic cores surrounded by rims that formed at 498 10 ma monazite rim formation was facilitated via dissolution reprecipitation of neoproterozoic monazite the monazite rims record garnet growth as they are depleted in y2o3 with respect to the neoproterozoic cores rims are also characterized by relatively high sro with respect to the cores results of the zircon depth profiling revealed igneous zircon cores with crystallization ages typical for snc metasediments multiple zircon grains also exhibit rims formed by dissolution reprecipitation that are defined by enrichment of light rare earth elements u th p y and sr rims also have subdued eu anomalies eu eu 0 6 1 2 with respect to the cores the age of zircon rim formation was calculated from three metasedimentary rocks 480 22 ma 475 26 ma and 479 38 ma these results show that both monazite and zircon experienced dissolution reprecipitation under high pressure conditions caledonian monazite formed coeval with garnet growth during subduction of the vaimok lens whereas zircon rim formation coincided with monazite breakdown to apatite allanite and clinozoisite during initial exhumation

earthquake clusters in southern california i identification and stability 1 we use recent results on statistical analysis of seismicity to present a robust method for comprehensive detection and analysis of earthquake clusters the method is based on nearest neighbor distances of events in space time energy domain the method is applied to a 1981 2011 relocated seismicity catalog of southern california having 111 981 events with magnitudes m 2 and corresponding synthetic catalogs produced by the epidemic type aftershock sequence etas model analysis of the etas model demonstrates that the cluster detection results are accurate and stable with respect to 1 three numerical parameters of the method 2 variations of the minimal reported magnitude 3 catalog incompleteness and 4 location errors application of the method to the observed catalog separates the 111 981 examined earthquakes into 41 393 statistically significant clusters comprised of foreshocks mainshocks and aftershocks the results reproduce the essential known statistical properties of earthquake clusters which provide overall support for the proposed technique in addition systematic analysis with our method allows us to detect several new features of seismicity that include 1 existence of a significant population of single event clusters 2 existence of foreshock activity in natural seismicity that exceeds expectation based on the etas model and 3 dependence of all cluster properties except area on the magnitude difference of events from mainshocks but not on their absolute values the classification of detected clusters into several major types generally corresponding to singles burst like and swarm like sequences and correlations between different cluster types and geographic locations is addressed in a companion paper

earthquake clusters in southern california ii classification and relation to physical properties of the crust 1 this is a second paper in a study of statistical identification and classification of earthquake clusters using a relocated catalog of 1981 2011 seismicity in southern california and synthetic catalogs produced by the epidemic type aftershock sequence model here we focus on classification of event families statistically significant clusters composed of foreshocks mainshocks and aftershocks that are detected with the methodology discussed in part i of the study the families are analyzed using their representation as time oriented tree graphs the results 1 demonstrate that the clustering associated with the largest earthquakes m 7 is statistically different from that of small to medium earthquakes 2 establish the existence of two dominant types of small to medium magnitude earthquake families burst like and swarm like sequences and a variety of intermediate cluster forms obtained as a mixture of the two dominant types 3 suggest a simple new quantitative measure for identifying the cluster type based on its topological structure 4 demonstrate systematic spatial variability of the cluster characteristics on a scale of tens of kilometers in relation to heat flow and other properties governing the effective viscosity of a region and 5 establish correlation between the family topological structure and a dozen of metric properties traditionally considered in the literature number of aftershocks duration spatial properties b value parameters of omori utsu and bath law etc the burst like clusters likely reflect highly brittle failures in relatively cold regions while the swarm like clusters are likely associated with mixed brittle ductile failures in regions with relatively high temperature and or fluid content the results of this and paper i may be used to develop improved region specific hazard estimates and earthquake forecasts

numerical modelling of entrainment deposition in rock and debris avalanches abstract rock and debris avalanches as well as debris flows are characterized by peculiar behaviour influenced by geometry of the initial failure surface topography involved materials involved and water content during their motion rock avalanches can entrain large volumes of sediments both in a dry and in a saturated state entrained dry material has generally the consequence to reduce the total landslide runout whereas entrainment of almost saturated material can have more complex consequences we use a finite element code to simulate the motion of a moving landslide mass on materials with different properties and along very sharp topographies erosion and deposition can be modelled as well as interaction with obstacles of different characteristics we present two examples of the modelling problems and capabilities we simulated the runout of a rock avalanche on a ground formed by alluvial material under dry and saturated conditions this material can be entrained and plowed by the impacting and running rock avalanche material sensitivity of the erosion and transport mechanisms has been analysed by performing different analyses the simulated case study is the 6 10 5 m 3 arvel rock avalanche 1922 switzerland for which a reliable set of pre and post failure observations is available final geometry mass redistribution velocities and runup are used to validate the model capabilities and study the effects of different material properties

monazite geochronology of uhp and hp metamorphism deformation and exhumation nordoyane western gneiss region norway u th pb monazite geochronology is combined with previous structural analysis and quantitative estimates of metamorphic conditions to date the thermotectonic evolution of uhp and hp plates 820 c 39 kbar 780 c 18 kbar metamorphosed during the late silurian early devonian collision between baltica and laurentia the upper plate contains a microdiamond bearing kyanite garnet graphite gneiss and associated kyanite eclogites independently indicating probable diamond forming conditions in situ dating of monazite in the microdiamond sample using the shrimp ii at the geological survey of canada yielded ages of 415 6 8 ma for those included in garnet and 398 6 ma for those in the matrix these ages compare to 408 0 5 6 and 397 5 4 4 ma determined using the electron microprobe at the university of massachusetts both methods also identified complexly zoned detrital cores up to 150 micrometers in diameter with ages of 1100 950 ma and scattered grains with ages of 900 500 ma but no ages of 1680 1650 ma equivalent to the local baltica basement were found agreement between the two techniques allowed evaluation of monazite age domains 198 analyses from the microdiamond rock and a kyanite garnet sillimanite mylonite produced from it using a combination of high resolution element imaging and trace element analysis of u th pb and y this comparison yielded three mean ages of 407 0 2 1 ma 394 8 2 3 ma and 374 6 2 7 ma combining this geochronology with previous p t estimates we propose that the uhp unit reached its maximum depth of 125 km at a maximum age of 407 ma when monazite was included in garnet and experienced 65 km of exhumation at an average rate of 10 9 mm year during top southeast thrusting that brought it into contact with the hp unit following these events both units were exhumed together at an average rate of 3 8 mm year until reaching a depth of 37 km at 395 ma where these rocks experienced extensive re equilibration and top west and left lateral shearing after 395 ma these units continued to be exhumed at an average rate of 0 8 to 1 4 mm year until 375 ma the time of last equilibration of asymmetric monazite porphyroclasts in the mylonite the exhumation histories of these units record a change in mechanism from syncollisional exhumation through late to post orogenic collapse that was a consequence of plate reorganization

a perturbation solution for bingham plastic mudflows an analytical solution is proposed for laminar mudflows and debris flows that can be modeled by a bingham plastic law two dimensional unsteady nonuniform bingham flows released from a point source or a source of finite size dam break problem or mudslide problem on a steep slope are considered the method of matched asymptotic expansions was implemented to get a first order solution for the dam break problem the proposed model is found to be valid when the shock wave has advanced three reservoir lengths downstream also it is found that the bingham flow only propagates a finite distance downstream with the shock depth asymptotically approaching the yield depth and the shock velocity asymptotically falling to zero the hydrograph produced by a bingham flow is seen to have a slower and lower flood peak and a longer and higher flow tail than that produced by newtonian flow having the same dynamic viscosity comparison of the model predictions with laboratory observations shows reasonable agreement

1d numerical model of muddy subaqueous and subaerial debris flows a 1d numerical model of the downslope flow and deposition of muddy subaerial and subaqueous debris flows is presented the model incorporates the herschel bulkley and bilinear rheologies of viscoplastic fluid the more familiar bingham model is integrated into the herschel bulkley rheological model the conservation equations of mass and momentum of single phase laminar debris flow are layer integrated using the slender flow approximation they are then expressed in a lagrangian framework and solved numerically using an explicit finite difference scheme starting from a given initial shape a debris flow is allowed to collapse and propagate over a specified topography comparison between the model predictions and laboratory experiments shows reasonable agreement the model is used to study the effect of the ambient fluid density initial shape of the failed mass and rheological model on the simulated propagation of the front and runout characteristics of muddy debris flows it is found that initial failure shape influences the front velocity but has little bearing on the final deposit shape in the bingham model the excess of shear stress above the yield strength is proportional to the strain rate to the first power this exponent is free to vary in the herschel bulkley model when it is set at a value lower than unity the resulting final deposits are thicker and shorter than in the case of the bingham rheology the final deposit resulting from the bilinear model is longer and thinner than that from the bingham model due to the fact that the debris flow is allowed to act as a newtonian fluid at low shear rate in the bilinear model

inter event times of fluid induced earthquakes suggest their poisson nature 1 we analyze the inter event time distribution of fluid injection induced earthquakes for six catalogs collected at geothermal injection sites at soultz sous forets and basel we find that the distribution of waiting times during phases of constant seismicity rate coincides with the exponential distribution of the homogeneous poisson process hpp we analyze the waiting times for the complete event catalogs and find that as for naturally occurring earthquakes injection induced earthquakes are distributed according to a non homogeneous poisson process in time moreover the process of event occurrence in the injection volume domain is a hpp these results indicate that fluid injection induced earthquakes are directly triggered by the loading induced by the fluid injection we also consider the spatial distance between events and perform a nearest neighbor analysis in the time space magnitude domain our analysis including a comparison to a synthetic catalog created according to the etas model reveals no signs of causal relationships between events therefore coupling effects between events are very weak the poisson model seems to be a very good approximation of fluid induced seismicity

a comparison of seismicity rates and fluid injection operations in oklahoma and california implications for crustal stresses fluid injection into deep wellbores can increase pore pressure reduce effective stress and trigger earthquakes the extent of the seismogenic response to injection provides insight into how close faults are to failure in the injection affected area the seismogenic response to injection operations in hydrocarbon basins is examined in california and oklahoma changes in spatial and temporal seismicity rates are tested for significant variations and timing and location of such variations are determined based on nonparametric modeling of background seismicity rates oklahoma has experienced a recent surge of seismic events which exceeded the 95 confidence limit of poissonian background rates in c 2010 annual injection volumes in oklahoma increased systematically between 1998 and 2013 and have been connected to several earthquake sequences in california injection volumes increased monotonically between 2001 and 2009 however the seismogenic response was limited and was devoid of large scale background rate increase a detailed comparison of injection parameters in oklahoma and california included well density wellhead pressures peak and cumulative rates and injection depths no detectable difference was found that could readily explain the observed changes in seismicity rate in oklahoma and the lack thereof in california a strongly different seismogenic response to similar pressure perturbations indicates that the injection parameters considered are only of secondary influence on the resulting earthquake activity the primary controls on injection induced earthquakes might be the specific geologic setting and the stress state on nearby faults

analytical perils and progress in electron microprobe trace element analysis applied to geochronology background acquisition interferences and beam irradiation effects electron probe microanalysis epma of accessory minerals such as monazite xenotime and thorite for minor and trace element concentrations and geochronology requires consideration of beam irradiation effects increasing heat and charge as higher current densities and lengthy counting times are employed and requires careful detailed assessment of background intensities and interferences a carbon coat 250 a thickness is generally inadequate for prevention of absorbed current s uctuation and beam damage when using the high current densities applied for high precision e g 200 na focused beam beam irradiation effects include element mobility in monazite resulting in p loss relative to ree coating materials of higher electrical and thermal conductivity are indicated and use of gold 100 a is strongly suggested systematic compositional and therefore age variability can result simply from analytical effects requiring evaluation of all aspects of data acquisition the spectra relevant to measurement of y th pb and u are complex especially in ree bearing minerals acquisition of detailed spectral wavelength scans allows recognition of background and peak interferences as well as curvature background intensities can be extracted directly from scan data by regression x ray mapping allows delineation of domains guiding background acquisition and detailed quantitative analysis minor substitution or s uorescence of unexpected elements can compromise analyses one documented effect being the s uorescence of k in monazite adjacent to or hosted by k feldspar or micas this effect clearly evident within 10 micrometers from k feldspar can result in erroneous u concentrations leading to misinterpretation of rim ages as younger overgrowths absorption edges associated with th also become relevant to the measurement of u at high th concentrations because background intensity is sensitive to variation in average atomic number backgrounds must be acquired from each identi ed domain with particular attention being paid to th variation misapplication of background intensities can result in large age discrepancies for example application of backgrounds obtained from a high th domain in monazite to measurement of a low th domain 1 3 of the amount in the high th domain results in an overestimation of the um background intensity of 0 008 cps na and an overall increase in age of 70 m y

increasing seismicity in the u s midcontinent implications for earthquake hazard abstract earthquake activity in parts of the central united states has increased dramatically in recent years the space time distribution of the increased seismicity as well as numerous published case studies indicates that the increase is of anthropogenic origin principally driven by injection of wastewater coproduced with oil and gas from tight formations enhanced oil recovery and long term production also contribute to seismicity at a few locations preliminary hazard models indicate that areas experiencing the highest rate of earthquakes in 2014 have a short term one year hazard comparable to or higher than the hazard in the source region of tectonic earthquakes in the new madrid and charleston seismic zones

two stage partial melting during the variscan extensional tectonics montagne noire france one of the striking features that characterise the late stages of the variscan orogeny is the development of gneiss and migmatite domes as well a s extensional late carboniferous and permian sedimentary basins it remains a matter of debate whether the formation of domes was related to the well documented late orogenic extension or to the contractional tectonics that preceded migmatization and magmatism are expected to predate extension if the domes are compression related regional anticlines but they must both precede and be contemporaneous with extension if they are extensional core complexes in the montagne noire area s outhern french massif central where migmatization magmatism and the deformation framework are well documented the age of the extensional event was unequivocally constrained to 300 0 ma therefore dating migmatization in this area is a key point for discriminating between the two hypotheses and understanding the late palaeozoic evolution of this part of the variscan belt for this purpose a migmatite and an associated anatectic granite from the montagne noire dome were dated by la icp ms u th pb on zircon and monazite and laser probe 40 ar 39 ar k ar on muscovite although zircon did not record any variscan age unequivocally related to compression 380 330ma two age groups were identified from the monazite crystals a first event at ca 319 ma u th pb on monazite is interpreted as a first stage of migmatization and as the emplacement age of the granite respectively a second event at ca 298 295 ma recorded by monazite u th pb and by the muscovite 40 ar 39 ar system in the migmatite and in th e granite could be interpreted as a fluid induced event probably related to a second melting event identified through the syn extensional emplacement of the nearby montalet leucogranite ca 295 ma ago the age s of these two events post date the variscan compression and agree with an overall extensional context for the development of the montagne noire dome shaped massif comparison of these results with published chemical epma dating of monazite from the same rocks demonstrates that the type of statistical treatment applied to epma data is crucial in order to resolve different monazite age populations

the impact of injection on seismicity at the geysers california geothermal field water injection into geothermal systems has often become a required strategy to extend and sustain production of geothermal resources to reduce a trend of declining pressures and increasing non condensable gas concentrations in steam produced from the geysers operators have been injecting steam condensate local rain and stream waters and most recently treated wastewater piped to the field from neighboring communities if geothermal energy is to provide a significant increase in energy in the united states the us department of energy goal is 40 000 mw by 2040 injection must play a larger role in the overall strategy i e enhanced geothermal systems egs presented in this paper are the results of monitoring microseismicity during an increase in injection at the geysers field in california using data from a high density digital microearthquake array although seismicity has increased due to increased injection it has been found to be somewhat predictable thus implying that intelligent injection control may be able to control large increases in seismicity

sulphate incorporation in monazite lattice and dating the cycle of sulphur in metamorphic belts microgeochemical data and transmission electron microscope tem imaging of s rich monazite crystals demonstrate that s has been incorporated in the lattice of monazite as a clino anhydrite component via the following exchange ca2 s6 ree3 p5 and that it is now partly exsolved in nanoclusters 5 10 nm of caso4 the sample an osumilite bearing ultra high temperature granulite from rogaland norway is characterized by complexly patchy zoned monazite crystals three chemical domains are distinguished as 1 a sulphate rich core 0 45 0 72 wt so2 th incorporated as cheralite component 2 secondary sulphate bearing domains so2 0 05 wt partly clouded with solid inclusions and 3 late s free y rich domains 0 8 2 5 wt y2o3 th accommodated as the huttonite component these three domains yield distinct isotopic u pb ages of 1034 6 1005 7 and 935 7 ma respectively uranium th pb epma dating independently confirms these ages this study illustrates that it is possible to discriminate different generations of monazite based on their s contents from the petrological context we propose that sulphate rich monazite reflects high temperature fe sulphide breakdown under oxidizing conditions coeval with biotite dehydration melting monazite may therefore reveal the presence of s in anatectic melts from high grade terrains at a specific point in time and date s mobilization from a reduced to an oxidized state this property can be used to investigate the mineralization potential of a given geological event within a larger orogenic framework

estimation of the area of sediment deposition by debris flow using a physical based modeling approach abstract debris flow triggered by shallow landslides in hillslope catchments is a main geological phenomenon driving landscape changes and represents an important natural hazard numerous studies have assessed sediment transport and deposition by debris flows in hillslope catchments thus the objective of this study is a development of two dimensional debris flow model to estimate sediment transport and deposition in hillslope catchments to simulate debris flow we implemented a vertically integrated shallow water governing equation based on the voellmy rheological model and a simple entrainment model in addition we applied a quadtree grid structure to support adaptive mesh refinement where the mesh for the simulation was automatically generated as the debris flow proceeded finally a well balanced numerical scheme for wet dry transition treatment was implemented and implicit discretization of the general source terms including the rheological term was included for numerical stability the developed model was verified based on a debris flow triggered by the 2011 mt umyeon landslides in the republic of korea sediment transport was successfully generated and the sediment deposition area generally matched the field survey data well overall the simulated sediment volume was in good agreement with the survey results with an error below 1

format and philosophy for collecting compiling and reporting microprobe monazite ages microprobe monazite dating has been increasingly used to constrain the timing of deformation and metamorphism because of the potential to date very small monazite domains down to 5 m or less in structural and petrologic context this paper presents an analytical strategy presentation format and error considerations for microprobe monazite dating the strategy involves high resolution compositional mapping to delineate compositional domains within monazite crystals then for each compositional domain a series of th u and pb analyses are made and a single date and error are calculated the number of analyses in each domain is determined by the desired statistical precision of the date results from several monazite grains are typically combined and along with textural relationships are used to build an argument that the dates constrain the age of a deformation or metamorphic event the total error involves three components short term random error dominated by counting statistical uncertainty short term systematic error uncertainty in background correction conductive coating variation and calibration and long term systematic error uncertainty in standard composition mass absorption factors decay constants etc in homogeneous compositional domains short term random errors 2 of less than 10 m y can be obtained from five to ten analyses however short term systematic error mainly background estimation uncertainty would typically result in a doubling of the magnitude of random error microprobe dates are presented as a single gaussian probability distribution for each domain along with representative compositional maps it is recommended that a consistency standard be analyzed during each analytical session and the results be reported along with those from the unknown this proposed strategy and format are compatible with those of other geochronological techniques they incorporate analytical limitations associated with trace as opposed to major element microprobe analysis and will allow better comparisons to be made between labs and between different geochronological techniques

zoned monazite and zircon as monitors for the thermal history of granulite terranes an example from the central indian tectonic zone the growth and dissolution behaviour of detrital metamorphic and magmatic monazite and zircon during granulite facies anatexis in pelitic and psammo pelitic granulites and in garnetiferous granite from the southern margin of the central indian tectonic zone citz have been investigated using reconstructed metamorphic reaction history monazite electron microprobe dating and sensitive high resolution ion microprobe shrimp u pb zircon geochronology whereas the pelitic granulites record medium pressure granulite facies metamorphism bm1 stage the psammo pelitic granulite reached ultrahigh temperatures tmax 880 c at 8 7 kbar the meta psammite additionally records two stages of granulite facies recrystallization bm2 and bm3 irrespective of variations in the bulk rock compositions and peak metamorphic conditions monazite is highly reactive during the bm1 event producing complex chemically zoned crystals textural compositional and chemical ages of these grains indicate the stability of six compositional domains cd1 to cd6 in the paragenetic sequence of which cd1 represents pre metamorphic detrital cores of paleoproterozoic age cd2 and cd3 combined mean age of 1612 14 ma mark two stages of recrystallization of detrital monazite cores during prograde events rims of cd4 monazite ages between 1615 14 and 1586 14 ma on partially to completely equilibrated cores indicate melt crystallization at or immediately following peak bm1p metamorphism cd5 monazite age of 1574 7 ma is restricted to the psammo pelitic granulites and marks final melt crystallization at the solidus during post peak cooling bm1r stage where r represents retrograde metamorphism the metamorphic rim of cd6 monazite age of 1539 24 ma around partially resorbed cd5 domains is linked to the decomposition of bm1 garnet during the terminal hydration event as part of a granulite facies recrystallization event compositionally homogeneous monazite and rims of chemically zoned monazite grains in granite together record a magmatic crystallization age of 1604 9 ma shrimp u pb zircon dating of the psammo pelitic granulite and garnetiferous granite indicates detrital or inherited cores of paleo to neoarchean age 3584 3 to 2530 3 ma which have been variously recrystallized and overgrown by new zircon 1 at 1658 12 ma 2 between 1595 5 and 1590 6 ma 3 at 1574 9 ma these zircon dates are correlated with the timing of the following 1 the protoliths of precursor sediments of the metasedimentary granulites deposited between 2530 and 1658 ma 2 a short lived high grade event 65 70 myr before the culmination of the bm1 granulite facies event 3 a high t anatectic event corresponding to the peak bm1p metamorphism at tmax 900 c 4 final crystallization of anatectic melt at the solidus cf bm1r metamorphic stage these chronological constraints from monazite and zircon when integrated with the metamorphic reaction history and published geochronological data allow recognition of three episodes of granulite facies metamorphism in the citz at 1658 ma pre bm1 event between 1612 and 1574 ma bm1 event and between 1572 and 1539 ma combined bm2 and bm3 events as part of a latest paleoproterozoic to early mesoproterozoic orogenic event this orogeny is linked to the growth of the proto greater indian landmass

episodic tourmaline growth and re equilibration in mica pegmatite from the bihar mica belt india major and trace element variations under pegmatitic and hydrothermal conditions mica pegmatites from the bihar mica belt contain three distinct generations of tourmaline the major element composition substitution vectors and trajectories within each group are different which indicates that the three types of tourmalines are not a part of one evolutionary series rather the differences in their chemistries as well their mutual microtextural relations can be best explained by growth of tourmaline from pegmatitic melts followed by episodic re equilibration during discrete geological events the euhedral coarse grained brown type i tourmaline cores have relatively high ca mg x mg c 0 37 and al with correlated variation in sr sc ti zr y cr pb and rare earth elements rees they are inferred to have crystallized from pegmatitic melts monazites included within these tourmalines give chemical ages of 1290 1242 ma interpreted to date the crystallization of the pegmatitic tourmaline the bluish type ii and greyish type iii tourmalines with low ca and mg contents x mg 0 16 0 27 and high zn sn nb ta and na formed by pseudomorphic partial replacement of the pegmatitic tourmaline via fluid mediated coupled dissolution reprecipitation are ascribed to a hydrothermal origin the ages obtained from monazites included in these tourmalines indicate two alteration events at c 1100 ma and c 950 ma the correlated variation of ca mg and fe and the trace elements sr sn sc zn and ree within the tourmalines indicates that the trace element concentrations of tourmaline are controlled not only by the fluid chemistry but also by coupled substitutions with major element ions

electron microprobe dating of monazite because monazite is extremely rich in u and th radiogenic pb pb accumulates very quickly and reaches in about 100 ma a level where it is possible to analyse it with the electron probe assuming that common pb is negligible and that partial loss of pb has not occurred the simultaneous measurement of u th and pb allows to obtain a geologically meaningful age from a single electron probe analysis here we present the results of two years of systematical investigations aiming to define both the limits and potential of this method a specific statistical method to deal with the large number of data which can be obtained on a single sample is described and several guidelines illustrated by examples are suggested to optimize the method electron probe measurements carried out on samples of known age from 200 ma to 3 1 ga yield ages that always fall inside the confidence interval of the isotopically determined age demonstrating that this method is reliable the younger age limit is approximately 100 ma although it can be younger in some favourable cases in old monazites extremely high pb contents have been found up to 5 wt indicating that monazite can tolerate high radiation doses without experiencing lead loss the final precision on the age for a normal monazite is 30 50 ma for a total counting time of 600 s a complete dating procedure can be completed in less than 1 h first results indicate that old ages can be preserved in monazite either in small relict cores in crystals or by the coexistence of several generations of monazites in a sample this method has all the advantages of the electron probe it is non destructive has an excellent spatial resolution monazites as small as 5 i m can be dated and because it is possible to work on normal polished thin sections the petrographical position of the dated crystal is known this method offers a large number of geologists access to an in situ dating technique at moderate cost

morphology and sedimentology of a complex debris flow in a clay shale basin coupling morphological sedimentological and rheological studies to numerical simulations is of primary interest in defining debris flow hazard on alluvial fans in particular numerical runout models must be carefully calibrated by morphological observations this is particularly true in clay shale basins where hillslopes can provide a large quantity of poorly sorted solid materials to the torrent and thus change both the mechanics of the debris flow and its runout distance in this context a study has been completed on the faucon stream southeastern french alps with the objectives of 1 defining morphological and sedimentological characteristics of torrential watersheds located in clay shales and 2 evaluating through a case study the scouring potential of debris flows affecting a clay shale basin morphological surveys grain size distributions and petrographic analyses of the debris flow deposits demonstrate the granular character of the flow during the first hectometre and its muddy character from there to its terminus on the debris fan these observations and laboratory tests suggest that the contributing areas along the channel have supplied the bulk of the flow material copyright 2005 john wiley sons ltd

induced seismicity associated with fluid injection into a deep well in youngstown ohio 1 over 109 small earthquakes mw 0 4 3 9 were detected during january 2011 to february 2012 in the youngstown ohio area where there were no known earthquakes in the past these shocks were close to a deep fluid injection well the 14 month seismicity included six felt earthquakes and culminated with a mw 3 9 shock on 31 december 2011 among the 109 shocks 12 events greater than mw 1 8 were detected by regional network and accurately relocated whereas 97 small earthquakes 0 4 mw 1 8 were detected by the waveform correlation detector accurately located earthquakes were along a subsurface fault trending ene wsw consistent with the focal mechanism of the main shock and occurred at depths 3 5 4 0 km in the precambrian basement we conclude that the recent earthquakes in youngstown ohio were induced by the fluid injection at a deep injection well due to increased pore pressure along the preexisting subsurface faults located close to the wellbore we found that the seismicity initiated at the eastern end of the subsurface fault close to the injection point and migrated toward the west away from the wellbore indicating that the expanding high fluid pressure front increased the pore pressure along its path and progressively triggered the earthquakes we observe that several periods of quiescence of seismicity follow the minima in injection volumes and pressure which may indicate that the earthquakes were directly caused by the pressure buildup and stopped when pressure dropped

laboratory analysis of mudflow properties a rotational viscometer has been designed for laboratory measurements of the rheological properties of natural mudflow deposits in colorado the mudflow matrices comprised of silt and clay particles are sheared under temperature controlled conditions at volumetric sediment concentrations ranging from 0 10 0 45 this study stresses the importance of conducting rheological measurements at low rates of shear because 1 those are the conditions found in natural channels and 2 they avoid the slippage problems observed at large sediment concentrations at low rates of shear the bingham model is fitted to the measured rheograms and both the viscosity and yield stress increase exponentially with the sediment concentration of the fluid matrix both the yield stress and the viscosity increase by three orders of magnitude as the volumetric concentration of sediments in the fluid matrix changes from 10 to 40 the addition of sand particles does not significantly alter the rheological properties of the matrix unless the volumetric concentration of sands exceeds 0 20

electron microprobe petrochronology the term petrochronology has increasingly appeared in publications and presentations over the past decade the term has been defined in a somewhat narrow sense as the interpretation of isotopic dates in the light of complementary elemental or isotopic information from the same mineral s kylander clark et al 2013 although complementary isotopic and elementary information are certainly a central and critical part of most if not all petrochronology studies the range of recent studies that might use the term covers a much broader scope the term petrochronology might alternatively be defined as the detailed incorporation of chronometer phases into the petrologic and tectonic evolution of their host rocks in order to place direct age constraints on petrologic and structural processes as noted by kylander clark et al 2013 the linkage between geochronology and petrology can involve a variety of data including mineral textures and fabrics the distribution of mineral modes or volume proportions compositional zoning mineral inclusion relationships and certainly major element trace element and isotopic composition of the chronometer and all other phases electron probe micro analysis epma has a central and critical role to play in establishing the linkage between chronometer phases and their host assemblage the basic instrument is an electron microscope which can be used in either scanning or fixed beam modes with integrated wavelength dispersive spectrometers wds energy dispersive spectrometers eds electron detectors to image secondary and backscattered signals a light optical system and optionally cathodoluminescence cl detection the electron microprobe is used to investigate the distribution composition and compositional zonation of all mineral phases the data that underpin thermobarometric analysis and modeling of p t histories the microprobe with m scale spatial resolution can also characterize compositional zonation in very small accessory phases including monazite xenotime zircon allanite titanite apatite and others this as discussed below can be a

limitations of chemical dating of monazite abstract instrumental and spectral characteristics germane to chemical dating of monazite have been tested using the cameca sx 100 at rensselaer polytechnic institute statistical analysis demonstrates that for trace element analysis equal counting time on peak and background is required for optimal statistical precision thus rendering impractical the procedure of fitting the entire spectrum to obtain background values energy shifts require shifting the detector voltage window between peak and background positions and it is concluded that the differential auto pha mode works optimally for this analyses of pb free phosphates silicates and oxides are used to measure spectral interferences with the pbm peak and background positions backgrounds were modeled using both linear and exponential fits it was found that the difference in background counts using the two fits varies with each of the five spectrometers examined and that the high pressure 3 bar detectors show larger differences in exponential vs linear peak minus background p b values than the low pressure 1 bar detectors in addition every spectrometer requires a unique correction for every major element in monazite an analytical protocol is presented that incorporates these results this protocol was applied to several monazite standards to determine inter spectrometer variability and spectrometer reproducibility from session to session it was found that the difference in composition and age between spectrometers on identical spots exceeds the 2 sigma standard error of the mean of composition or age on either spectrometer this means that a additional sources of error beyond the counting statistics exist between spectrometers b the precision of microprobe ages cannot be continuously improved by additional counting and c the minimum realistic precision is on the order of 2 3 for monazites with around 1500 2000 ppm total pb or an additional absolute uncertainty of 20 50 ppm pb

newtonian fluid mechanics treatment of debris flows and avalanches calculations are carried out first for steady fully developed laminar flow on a slope application of this result to field data published in a previous paper by another author suggests that many debris flows are laminar then singular perturbation techniques are used to obtain first order solutions for unsteady non uniform flow from a point source on a steep slope solutions are obtained for both laminar and turbulent flows and it is found that the laminar flow model gives the best description of laboratory data obtained by a previous investigator a number of differences are observed in the behavior of the outer kinematic wave solutions for laminar and turbulent flow and it is suggested that it is probably not possible to describe all debris flows and avalanches with laminar flow models it is also suggested that more comparisons need to be made between theoretical results and field data measurements

differentiating induced and natural seismicity using space time magnitude statistics applied to the coso geothermal field a remarkable characteristic of earthquakes is their clustering in time and space displaying their self similarity it remains to be tested if natural and induced earthquakes share the same behavior we study natural and induced earthquakes comparatively in the same tectonic setting at the coso geothermal field covering the preproduction and coproduction periods from 1981 to 2013 we analyze interevent times spatial dimension and frequency size distributions for natural and induced earthquakes individually these distributions are statistically indistinguishable determining the distribution of nearest neighbor distances in a combined space time magnitude metric lets us identify clear differences between both kinds of seismicity compared to natural earthquakes induced earthquakes feature a larger population of background seismicity and nearest neighbors at large magnitude rescaled times and small magnitude rescaled distances local stress perturbations induced by field operations appear to be strong enough to drive local faults through several seismic cycles and reactivate them after time periods on the order of a year

constraints on the timing of late eburnean metamorphism gold mineralisation and regional exhumation at damang mine ghana the damang gold deposit in southwest ghana is unique among known deposits in ghana comprising gold mineralisation in two distinct styles early gold hosted in a stratigraphically controlled auriferous quartz pebble conglomerate horizon is overprinted by later gold mineralisation contained in a sub horizontal fault fracture quartz vein array a multi system geochronological study is used to constrain the timing of igneous activity regional metamorphism gold mineralisation and the thermal history at damang u pb analysis of zircons from birimian volcaniclastic and intrusive rocks constrain volcanism and associated intrusive activity at 2178 0 9 3 ma and 2164 6 8 0 ma respectively which is consistent with previous studies the age of formation of staurolite grade amphibolite facies peak metamorphic mineral assemblages at 2005 26 ma is provided by u th total pb epma analysis of metamorphic monazite grains in the tarkwa phyllite measured 40ar 39ar biotite ages range between 1980 9 ma and 1898 11 ma argon diffusion modelling with the programme diffarg suggests that this age range could be achieved by a period of rapid cooling at a rate of approximately 17 c ma followed by a prolonged period of much slower cooling at a rate of 0 15 c ma the period of rapid cooling is interpreted to represent localised exhumation of the damang host rocks during the latest stage of the eburnean orogeny at the time of hydrothermal gold mineralisation given these age constraints hydrothermal gold mineralisation is inferred to have occurred between approximately 2030 ma and 1980 ma these ages constrain metamorphism fluid flow and gold mineralisation at damang and are the youngest currently recognised in the birimian of sw ghana

comparative isotopic and chemical geochronometry of monazite with implications for u th pb dating by electron microprobe an example from metamorphic rocks of the eastern wyoming craton u s a polygenetic monazite grains in diverse precambrian crystalline rocks from the black hills south dakota have been analyzed in situ by ion and electron microprobe methods shrimp and emp to evaluate the accuracy and precision of emp ages determined using a new analytical protocol that incorporates improved background acquisition and interference corrections parallel evaluations were conducted by comparing emp chemical and shrimp isotopic ages at regional rock and grainscales the monazite data set includes 354 emp chemical analyses from 26 grains in six metamorphic rocks which resolve into 54 age composition domains and 31 shrimp isotopic ages from 13 grains in one of the rocks with six grains microanalyzed in common by the two methods the data set also includes monazite bearing garnets in two of the rocks whose isotopic compositions were analyzed using pb stepwise leaching pbsl methods both the emp and shrimp data sets reveal a continuum of apparent monazite ages spanning a 1790 1680 ma timeframe with a relatively high probability of ages at 1755 and 1715 ma that correspond spatially to core and rim domains pbsl ages of 1742 and 1734 ma obtained from monazite bearing garnet in two rocks are intermediate compared to the corresponding emp ages and are thereby interpreted as mixed ages emp data for two grains in the structurally deepest of the six rocks record 1785 and 1755 ma ages in the cores and higher y and lower th rims respectively and these results are duplicated by shrimp ages in these and or other grains from the same rock overall the emp shrimp and pbsl ages are internally consistent at the various scales of observation which serves to validate emp chemical dating as an accurate and precise method of discerning monazite age populations in polymetamorphic terrains the emp data set is interpreted geologically as res ecting multiple episodes of monazite growth that are provisionally related to known metamorphic events in the black hills taking the most precise emp data at face value it is possible to resolve the timing of the two older events at 1784 4 ma or 1786 6 ma and 1756 3 ma or 1753 4 ma with 95 con dence these events are considered to be related to sequential episodes of n directed thrusting and e w compression associated with paleoproterozoic crustal assembly in the mid continent a younger metamorphism related to granite intrusion known to have occurred at 1715 3 ma is dated independently at 1717 2 ma from the emp monazite ages

neoarchean greenstone metamorphism in the eastern dharwar craton india constraints from monazite u th pbtotalages andptpseudosection calculations abstractthe archean hutti maski greenstone belt hmgb and the south kolar greenstone belt skgb are the two richest gold provinces in india here we present results of texturally constrained u th pbtotal chime dating of monazites and pt pseudosection analyses to understand the geochronological and metamorphic evolution of the two greenstone terrains the ages of felsic volcanism are constrained at ca 2669 22 ma in the hmgb and 2661 32 ma in the skgb the hmgb rocks underwent midamphibolite facies metamorphism at ca 2564 12 ma the inferred pt path indicates a contemporaneous pt increase of up to 6 kbar and 620 c followed by postpeak near isothermal decompression for the hmgb rocks the skgb rocks underwent a lower amphibolite facies metamorphism at ca 2546 12 ma and are characterized by a synchronous pt increase of up to 4 6 kbar and 600 c followed by decompressional cooling these results indicate a mixed arc plume setting for the evolution of both the greenstone belts as suggested by

aftershock patterns of ms 7 earthquakes in the india asia collision belt anomalous results from the muzaffarabad earthquake sequence kashmir 2005 the seismicity rate triggered by the muzaffarabad kashmir 2005 m w 7 6 m s 7 7 earthquake is above the average when analyzing the aftershock rate of the 18 m s 7 0 events in the india asia collision belt between 1973 and 2008 all 17 m s 7 0 events occurred within 10 latitude and 20 longitude distance from the 2005 muzaffarabad earthquake epicenter we determined the huge aftershock productivity for this earthquake is not driven by a specific omori law parameter this anomaly in aftershock rate value corresponds to a relatively higher rate decay as measured by the p value and a larger density value in a higher background seismicity rate setting prestress conditions than the other 17 sequences respectively after normalizing by the mainshock size and by the magnitude range of observation we resolved the anomalies with a 95 confidence level for five aftershock sequences for either the duration the productivity the density or the background seismicity rate when we did not include the local processes that drive these specific anomalies two other global results emerged for the averaged data from the 18 m s 7 0 aftershock sequences first for all sequences background seismicity and duration are anticorrelated graphic 1 within the framework of rate and state friction law this result supports the assertion that the observed background seismicity rate can be used as a proxy for the stressing rate dieterich 1994 second we robustly resolve the dependence of aftershock productivity on the mainshock faulting styles for example the aftershock productivity for strike slip mainshocks is on average four times smaller than the productivity of thrust faulting mainshocks 1 embed inline graphic 1 gif

monazite allanite phase relations in metapelites abstract calculations of the transition from allanite to monazite bearing assemblages in typical pelitic bulk compositions have been made using thermodynamic data estimated from oxide sums and inferred from natural parageneses calculations in the cfashpce and mnnckfmashpce systems place the allanite to monazite transition in the middle amphibolite facies 525 600 c for a bulk composition similar to shaw s average pelite the temperature of the transition is pressure dependent and strongly dependent on the bulk rock cao content consistent with inferences from natural parageneses the transition is also a function of the bulk al 2 o 3 content although the calculated result is opposite to that inferred from natural samples comparison with published results in the la mg system suggest that the nature of the ree phosphate does not greatly influence the conditions of the transition

seismicity declustering and hazard analysis of the oklahoma kansas regionseismicity declustering and hazard analysis of the oklahoma kansas region

electron microprobe observations of pb diffusion in metamorphosed detrital monazites electron microprobe analyses have been made on monazite grains from paragneiss samples in the andalusite sillimanite transition 620 15 c and sillimanite orthoclase 680 15 c zones of the cretaceous ryoke metamorphic belt southwest japan monazites from pelitic gneisses are of metamorphic origin euhedral to subhedral and chronologically homogeneous giving chemical th u total pb isochron chime ages of 98 8 3 3 98 0 3 2 ma two psammitic gneisses of individual metamorphic grade contain both metamorphic monazite grains and detrital ones as old as ca 1700 ma most detrital monazite grains are heterogeneous in the tho2 and uo2 concentrations and have multiple or single rims as young as ca 100 ma several detrital monazite grains are well rounded in form exhibit homogeneous th and u distributions and show a pb diffusion profile in the margin the width of the diffusion zones is approximately constant throughout grains from each psammitic gneiss 18 22 m for 620 c and 48 58 m for 680 c assuming the isothermal diffusion of pb from homogeneous monazite spheres during a 5 ma duration of peak metamorphism we obtain diffusion coefficients of 1 9 0 3 10 21 and 1 5 0 3 10 20 cm2 s at 620 c and 680 c respectively these data derive an activation energy of 2 44 2 85 1 26 105 j mol and a frequency factor of 3 4 10 7 8 5 10 12 2 2 107 cm2 s taking account of uncertainties of 15 c in the temperatures and of 20 in the diffusion coefficients the diffusion parameters obtained from natural samples in this study provide a reliable insight into the closure temperature for pb in monazite that has been poorly understood so far

decay rate of fluid induced seismicity after termination of reservoir stimulations we present a model describing the seismicity rate of fluid injection induced seismicity we put the focus on seismicity induced after termination of fluid injections here our primary objective is the identification of parameters controlling the decay rate of seismicity the particular importance of a theoretical model for postinjection seismicity is underlined by observations after stimulations of geothermal reservoirs at different locations for instance the postinjection phase is relevant for a seismic risk which up to now has been difficult to control because processes leading to postinjection events are not well understood based on the assumption of pore pressure diffusion as the governing mechanism leading to the triggering of seismic events we develop a method to calculate the seismicity rate during and after fluid injections we find that the decay rate of seismicity after termination of injection is very similar to the omori law which describes the decay rate of aftershock activity after t

the coupling of a submarine slide and the surface waves which it generates underwater landslides are a common source of small scale tsunamis in coastal areas they have been the object of only a few theoretical and experimental studies a numerical model is developed to study the coupling of a submarine landslide and the surface waves which it generates a formulation of the dynamics of the problem is presented where the landslide is treated as the laminar flow of an incompressible viscous fluid and the water motion is assumed irrotational long wave approximation is adopted for both water waves and the mudslide the resulting differential equations are solved by a finite difference method we present the numerical results which contrast the behavior of the mud flow under a fixed surface in the presence of one way coupling bottom deformations affect the free surface and with full coupling surface pressure gradients react on the mud flow it is found that three main waves are generated by a landslide starting from rest on a gentle uniform slope the first wave is a crest which propagates away from the mudslide site into deeper water this crest is followed by a trough in the form of a forced wave which propagates with the speed of the mudslide front the third wave is a relatively small trough which propagates shoreward two major parameters dominate the interaction between the slide and the waves it produces the density of sliding material and the depth of water at the mudslide site the two way interactions are significant for the cases of a smaller mud density and shallower waters for the cases of larger mud density and shallower waters the two way interactions are small but the waves generated are very large for larger initiation depth of the mudslide the interactions are weak and the waves generated are small we also examined the possibility of a resonance between the slide and the waves our numerical results indicate that a resonance is not expected in many practical cases

petrochronology based on ree minerals monazite allanite xenotime apatite ree minerals monazite xenotime and allanite are ree1 minerals sensu stricto because lanthanides la lu and yttrium are critical constituents in them apatite does not require ree but because it contains substantial ree in many rocks it is included in this review all four minerals also host unusually high radionuclide concentrations notably th and u forming the basis of their utility as geochronometers this quartet of accessory minerals is playing an increasingly important role in petrochronology because they provide ways to link robust spot ages to petrogenetic p t conditions so can lend petrogenetic context to chronology based on other minerals part i of this review assembles the basic requisites prior to integrative petrochronologic analysis individual characteristics of the four ree minerals are addressed first i e their crystal chemistry and stability relations thermobarometers and trace element geochemistry used for tracing petrogenesis are discussed next and finally their chronology is summarized part ii presents case studies to highlight the specific strengths of ree minerals used to resolve the dynamics of a broad range of processes from diagenetic to magmatic conditions finally a brief section at the end outlines a few of the current challenges and promising perspectives for future work to introduce the four ree minerals in style let us recall the origins of their names the three phosphates have well respected greek grandparents and allanite has solid scottish roots yet of all four of them show idiosyncracies in etymology or type material apatite had long puzzled naturalists as it shows great chemical and physical variability and can resemble other minerals once properly identified abraham gottlieb werner named it apatite his reasoning referred to the greek root and giving the precise latin translation decipio taken literally both mean i deceive or i mislead which sounds like an apt confession from this mineral for having fooled

experimental determination of stability relations between monazite fluorapatite allanite and ree epidote as a function of pressure temperature and fluid composition the experimental alteration of monazite to allanite ree epidote fluorapatite and or fluorapatite britholite was investigated at 450 to 610 mpa and 450 to 500 c experiments involved monazite albite k feldspar muscovite biotite sio 2 caf 2 and variety of fluids including h 2 o kcl h 2 o nacl h 2 o cacl 2 h 2 o na 2 si 2 o 5 h 2 o 1 m hcl 2 m naoh 2 m koh 1 m ca oh 2 2 m ca oh 2 and caco 3 h 2 o the reaction products or lack thereof clearly show that the stability relations between monazite fluorapatite and allanite or ree epidote are more dependent on the fluid composition and the ratio of silicate minerals than on the p t conditions a high ca content in the fluid promotes monazite dissolution and the formation of fluorapatite and allanite or ree epidote lowering the ca content and raising the na content in the fluid decreases the solubility of monazite but promotes the formation of allanite replacing na with k in the same fluid causes fluorapatite with a britholite component to form from the monazite however allanite and ree epidote are not formed monazite is stable in the presence of nacl brines in kcl brine monazite shows a very limited reaction to fluorapatite when the fluid is na 2 si 2 o 5 h 2 o strong dissolution of monazite occurs resulting in the mobilization of rees and actinides to form fluorapatite britholite and turkestanite these experimental results are consistent with natural observations of the partial to total replacement of monazite by fluorapatite ree epidote and allanite in fluid aided reactions involving the anorthite component in plagioclase at mid to high grade metamorphic conditions in contrast an alkali bearing environment with excess na prevents the growth of allanite and eventually promotes the precipitation of secondary monazite the results from this study provide implications for geochronology and for deducing fluid compositions in metamorphic rocks

assessing debris flows using lidar differencing 18 may 2005 matata event new zealand the town of matata in the eastern bay of plenty new zealand experienced an extreme rainfall event on the 18 may 2005 this event triggered widespread landslips and large debris flows in the awatarariki and waitepuru catchments behind matata the light detection and ranging technology lidar data sets flown prior to and following this event have been differenced and used in conjunction with a detailed field study to identify the distribution of debris and major sediment pathways which from the awatarariki catchment transported at least 350 000 50 000 m3 of debris debris flows were initially confined to stream valleys and controlled by the density and hydraulic thrust of the currents before emerging onto the awatarariki debris fan where a complex system of unconfined sediment pathways developed here large boulders clasts logs and entire homes were deposited as the flows decelerated downstream from the debris fan the pre existing coastal foredune topography played a significant role in deflecting the more dilute currents that in filled lagoonal swale systems in both directions the differenced lidar data have revealed several sectors characterised by significant variation in clast size thickness and volume of debris as well as areas where post debris flow cleanup and grading operations have resulted in man made levees sediment dumps scoured channels and substantial graded areas the application of differenced lidar data to a debris flow event demonstrates the techniques potential as a precise and powerful tool for hazard mapping and assessment

discriminating characteristics of tectonic and human induced seismicity we analyze statistical features of background and clustered subpopulations of earthquakes in different regions in an effort to distinguish between human induced and natural seismicity analysis of end member areas known to be dominated by human induced earthquakes the geyser geothermal field in northern california and tautona gold mine in south africa and regular tectonic activity the san jacinto fault zone in southern california and the coso region excluding the coso geothermal field in eastern central california reveals several distinguishing characteristics induced seismicity is shown to have 1 higher rate of background events both absolute and relative to the total rate 2 faster temporal offspring decay 3 higher rate of repeating events 4 larger proportion of small clusters and 5 larger spatial separation between parent and offspring compared to regular tectonic activity these differences also successfully discriminate seismicity within the coso and salton sea geothermal fields in california before and after the expansion of geothermal production during the 1980s online material figures of examined regions earthquake epicenters and joint distributions of the time and space components of the nearest neighbor distance

field experiments and numerical modeling of mass entrainment in snow avalanches 1 snow entrainment alters the speed and hence the run out distance of avalanches yet little is known about this significant process we studied entrainment in snow avalanches using observations from 1 the swiss vallee de la sionne test site 2 the italian pizzac site 3 catastrophic avalanches that occurred during the winter 1998 1999 in switzerland and 4 a medium sized spontaneous avalanche that occurred in 2000 in davos switzerland we determined mass and energy balances for 18 avalanche events on average the mass increased by a factor of 4 the primary mode of entrainment appeared to be frontal ploughing although entrainment behind the avalanche front was also observed step entrainment where a snow cover layer fractures and is entirely consumed by the avalanche also occurred basal erosion was negligible mass availability and snow cover structure were the limiting factors governing entrainment other factors such as track topography and avalanche dimension played a secondary role using the experimental results we introduced an entrainment model into a saint venant type flow model where the internal shear deformation of the avalanche is governed by a bagnold law and the shear stress at the basal layer is treated as a voellmy fluid the model with entrainment not only improves the prediction of the velocities and flow heights in comparison to measurements but also reproduces the variations in run out distances which characterize avalanches with similar terminal velocities but different masses

multi step tims and ca tims monazite u pb geochronology abstract multi step chemical abrasion thermal ionization mass spectrometry ca tims methods were developed for monazite using six samples that vary in composition and age amelia jefferson county burke elk mountain 554 and madagascar to evaluate whether the multi step ca tims approach reveals complexities in either age or composition that might be masked by single step analysis this study presents a side by side comparison of monazite samples dated via multi step tims not annealed and ca tims annealed and measurement of rare earth element ratios for each dissolution step the data demonstrate three important contributions first annealing reduces solubility after one partial dissolution step not annealed fractions were 3 3 4 1 times more digested than the annealed fractions the difference in solubility suggests that monazite does not fully self anneal at low temperatures second multi step tims analyses yielded high precision u pb plateau ages for the burke and amelia monazites ca tims analyses yielded high precision u pb plateau ages for madagascar and amelia monazites jefferson county elk mountain and 554 yielded more complex results and no u pb plateau ages third chemical analysis of partial dissolution steps reveals heterogeneous age and compositional data for annealed samples because not annealed samples yielded more consistent age and compositional data high temperature annealing is not recommended for monazite instead optimal tims results are provided by slow partial dissolution of monazite in weak acid

the timing of metamorphism in the odenwald spessart basement mid german crystalline zone new in situ electron microprobe monazite and white mica 40ar 39ar step heating ages support the proposition that the odenwald spessart basement mid german crystalline zone consists of at least two distinct crustal terranes that experienced different geological histories prior to their juxtaposition the monazite ages constrain tectonothermal events at 430 43 ma 349 14 ma 331 16 ma and 317 12 ma 316 4 ma and the 40ar 39ar analyses provide white mica ages of 322 3 ma and 324 3 ma granulite facies metamorphism occurred in the western odenwald at c 430 and 349 ma and amphibolite facies metamorphism affected the eastern odenwald and the central spessart basements between c 324 and 316 ma we interpret these data to indicate that the otzberg michelbach fault zone which separates the eastern odenwald spessart basement from the western odenwald basement is part of the rheic suture which marks the position of a major variscan plate boundary separating gondwana and avalonia derived crustal terranes the age of the carboniferous granulite facies event in the western odenwald overlaps with the minimum age of eclogite facies metamorphism in the adjacent eastern odenwald the granulite and eclogite facies rocks experienced contrasting pressure temperature paths but occur in close spatial proximity being separated by the rheic suture as high pressure and high temperature metamorphisms are of similar age we interpret the odenwald spessart basement as a paired metamorphic belt and propose that the adjacent high pressure and high temperature rocks were metamorphosed in the same subduction zone system juxtaposition of these rocks occurred during the final stages of the variscan orogeny along the rheic suture

critical assessment of geochronological data from the carajas mineral province brazil implications for metallogeny and tectonic evolution abstract the carajas domain in the amazonian craton brazil displays remarkable metallogenetic diversity containing iron oxide copper gold iocg cu au mn fe ni co pge cr and au pge mineral systems it consists of mesoarchean 2 83 3 08 ga basement granitoids and gneisses overlain by the ca 2 73 2 76 ga rift related meta volcanosedimentary units of the neoarchean carajas basin coeval ca 2 76 mafic ultramafic complexes host nickel cobalt laterite vermelho puma onca and magmatic pge cr luanga deposits unconformably overlying this is the aguas claras formation a package of fluvial to shallow marine sedimentary rocks of controversial but probable archean age based on 2 6 2 7 ga cross cutting mafic dikes this hosts manganese deposits azul small polymetallic cu au deposits breves and the serra pelada au pt pd deposit iocg deposits are located along wnw regional shear zones hosted within the itacaiunas supergroup mesoarchean basement and bimodal 2 76 2 73 ga neoarchean granitoids and gabbro geochronology supports the existence of multiple superimposed and episodic hydrothermal and mineral systems multiple mineralization ages are common within single deposits and establishing the age of primary mineralization as opposed to overprinting hydrothermal events is challenging copper mineralization formed as early as ca 2 76 ga coeval with basin formation while structurally controlled iocg deposits formed or were substantially modified during multiple hydrothermal episodes ca 2 72 2 68 ga 2 6 2 45 ga and 1 88 ga for the northern iocg deposits e g salobo and igarape bahia alemao a temporal overlap between 2 57 ga mineralization and the 2 57 ga alkaline old salobo granite is commonly used to infer a genetic link yet this geochronology s reliability is debatable younger ages exist for the old salobo granite 2 55 2 53 ga zircons are metamict and older mineralization ages have been reported suggesting a more complex history the occurrence of ages ca 2 60 2 45 ga is spatially restricted to the north and coincides with an important yet poorly understood tectono thermal event involving reactivation of the northern cinzento shear zone and amphibolite facies metamorphism whether iocg deposits formed during this tectonic event or represent substantially modified or metamorphosed older mineralization or both is contentious older mineralization ca 2 71 ga at the igarape cinzento iocg deposit in the north is coeval with the southern iocg deposits formed ca 2 72 2 68 ga sequeirinho bacaba and bacuri this does not convincingly overlap with the intrusion of widespread 2 76 2 73 ga syntectonic granitoids so a genetic link with magmatic fluids is speculative and basinal brines may play a role due to controversy regarding the timing of compression and basin closure the tectonic setting is debated mineralization either formed during rifting or synchronous with basin inversion but the latter is more supported by geochronology and ore textures in the south paleoproterozoic ca 1 88 ga iocgs the sossego curral orebodies of the sossego deposit and alvo 118 or alternatively overprinting cu au systems formed coeval with craton wide a type 1 88 ga granite magmatism this magmatic hydrothermal system is responsible for a large part of the metallogenetic diversity of carajas domain small generally

spatiotemporal distribution of oklahoma earthquakes exploring relationships using a nearest neighbor approach determining the spatio temporal characteristics of natural and induced seismic events holds the opportunity to gain new insights into why these events occur linking the seismicity characteristics with other geologic geographic natural or anthropogenic factors could help to identify the causes and suggest mitigation strategies that reduce the risk associated with such events the nearest neighbor approach utilized in this work represents a practical first step toward identifying statistically correlated clusters of recorded earthquake events detailed study of the oklahoma earthquake catalog s inherent errors empirical model parameters and model assumptions is presented we found that the cluster analysis results are stable with respect to empirical parameters e g fractal dimension but were sensitive to epicenter location errors and seismicity rates most critically we show that the patterns in the distribution of earthquake clusters in oklahoma are primarily defined by spatial relationships between events this observation is a stark contrast to california also known for induced seismicity where a comparable cluster distribution is defined by both spatial and temporal interactions between events these results highlight the difficulty in understanding the mechanisms and behavior of induced seismicity but provide insights for future work

geochronology of shear zones a review abstract shear zones play a major role in the deformation of the crust at a variety of scales as expressions of strain localization during orogeny and rifting and also as reactivated structures they influence the geometry and evolution of orogenic belts and rifts crustal rheology magma ascent and emplacement and fluid flow consequently assessing the timing of shear zone activity is crucial to reconstruct the tectonometamorphic evolution of the lithosphere the interpretation of thermochronologic data from shear zones is however not straightforward in the first place closure temperatures depend on a number of factors grain size cooling rate mineral composition and pressure among others on the other hand deformation related processes such as dynamic recrystallization neocrystallization and fluid circulation seem to be crucial for isotopic systems and thus the obtained ages cannot be solely interpreted as a function of temperature in sheared rocks for this reason geochronologic data from shear zones might not only record cooling below closure temperature conditions but may also be affected by neo or recrystallization fluid assisted deformation and inheritance of the protolith age s in order to robustly reconstruct p t e t paths of long term crustal scale shear zones structural microstructural and petrologic data from mylonites need to be integrated with ages from different thermochronometric systems in addition geochronologic data from associated intrusions and adjacent blocks can provide further irreplaceable constraints on the timing of deformation and its regional implications one of the most challenging aspects that future lines of investigation should analyze is the quantitative evaluation of so far poorly explored aspects of isotopic diffusion particularly the coupling with deformation processes based on natural theoretical and experimental data future works should also investigate the role of strain partitioning and localization processes in order to constrain the timing of deformation in different parts of a shear zone or in different branches of anastomosing shear zone networks

evidence for cool extrusion of the north indochina block along the ailao shan red river shear zone a diancang shan perspective abstractmuch debate surrounds the temporal thermal structural evolution of the 1000 km nw se trending ailao shan red river asrr shear zone this mainly reflects the contradictory interpretations of the timing and p t conditions for the occurrence of left lateral shearing event due to a diverse data set of mineral ages our new microstructural petrological and geochronological data from the southern section of the diancang shan dcs block along the west wall of the asrr support slow cooling from 300 c to 150 c from the middle eocene to the late miocene accompanied by left lateral shearing activity this conclusion is based on the following 1 the lower greenschist facies assemblages of biotite replaced by muscovite or chlorite the albitized k feldspar and the stable association of k feldspar chlorite rather than muscovite biotite are universally observed for the synkinematic sn 1 and mylonitic s c fabrics from both quartzofeldspathic and amphibolite domains 2 new 40ar 39ar data for k fe

u pb monazite geochronology of granitic rocks from maine implications for late paleozoic tectonics in the northern appalachians crystallization ages of monazites from peraluminous granites and granitic pegmatites in southwestern maine constrain the timing of final ductile motion of a major shear zone to approximately 280 ma u pb monazite ages of granite at brunswick 278 pm 2 ma and evolved granitic pegmatites in topsham 275 269 ma provide evidence that synkinematic intrusion was followed by final emplacement at the end of ductile deformation these granitic rocks were evidently generated during the final high temperature event experienced by this portion of the appalachian orogen during this time the host rocks record initial rapid cooling c 16 c m y followed by slower cooling c 4 c m y into the mesozoic the similarity of ages of granite in brunswick and pegmatites in topsham permit the rocks to be related to the same magmatic system the spatially associated sebago batholith the largest exposed pluton in new england has a concordant u pb monazite age of 293 pm 2 ma thus the sebago batholith cannot be

anthropogenic seismicity rates and operational parameters at the salton sea geothermal field geothermal power is a growing energy source however efforts to increase production are tempered by concern over induced earthquakes although increased seismicity commonly accompanies geothermal production induced earthquake rate cannot currently be forecast on the basis of fluid injection volumes or any other operational parameters we show that at the salton sea geothermal field the total volume of fluid extracted or injected tracks the long term evolution of seismicity after correcting for the aftershock rate the net fluid volume extracted injected provides the best correlation with seismicity in recent years we model the background earthquake rate with a linear combination of injection and net production rates that allows us to track the secular development of the field as the number of earthquakes per fluid volume injected decreases over time

resolving poly metamorphic paleoarchean ages by chemical dating of monazites using multi spectrometer u th and pb analyses and sub counting methodology abstract chemical u th total pb dating method is a low cost and reliable technique to estimate the age of monazites of detrital and diagenetic origin or those found in low to high t metamorphic or magmatic rocks using electron microprobe emp analyses the method has been commonly applied for age estimation in phanerozoic and proterozoic rocks and less commonly in neoarchean rocks monazite dates from the paleoarchean era are rare and the associated error of spot age 2 error absolute age 100 is high i e between 2 and 26 the errors associated with chemical dating of monazite are significantly larger compared to isotope methods which impede precise age estimation and age resolution in polygenetic monazites of neoarchean and older rocks in this study simultaneous element analyses in multiple spectrometers and the sub counting method of analyses are employed to obtain precise estimates of u th and pb concentrations in monazite using vanadinite pb 5 vo 4 3 cl as the pb standard instead of pbs the method yields an age of 3118 28 ma with mount narryer mesoarchean monazite thermal ionization mass spectrometry tims age 3132 1 ma and 516 12 ma with moacyr monazite tims age 509 1 ma emp monazite age 497 10 ma as the reference samples the modifications led to 40 reduction in spot age errors in the mount narryer sample relative to those obtained by conventional monazite dating method the reduced errors in spot ages helped in resolving statistically un mixed age populations 3152 16 ma 3322 15 ma and 3420 140 ma in polygenetic monazites within muscovite quartz schists from the singhbhum craton eastern india the significance of these dates is briefly discussed