microseismicity and its time frequency characteristics of the left bank slope at the jinping first stage hydropower station during reservoir impoundment the instability risk associated with the left bank slope of the jinping first stage hydropower station in south western china may increase as a result of the initial impoundment of the reservoir and the raising and lowering of the reservoir level to improve our understanding of the rock slope stability and the real time behaviour of the composite system of rock slope and dam an existing microseismic ms monitoring system installed on may 2009 was improved in early 2014 this investigation represents the first time such a technique has been used to evaluate the stability of a high rock slope in china the safety and maintenance of the rock slope during the reservoir impoundment were investigated through the development of fast and accurate real time event location technique aimed at assessing the evolution and migration of the seismic activity and through the development of capabilities for forecasting the rock slope stability numerous ms events in the rock slope have been recorded using the ms monitoring system zones of damaged rock mass were identified based on a spatio temporal analysis of the seismic activity during the impoundment period moreover a waveform decomposition method based on the s transform was proposed for processing the seismic waveforms during the construction and impoundment periods of the left bank slope and the time frequency characteristics of seismic events during these two periods were thus compared the understanding of the relationships between the time frequency parameters variations in the seismic signals and the rock mass damage can provide a basis for evaluating the stability of similar rock slopes

the provenance formation and implications of reduced carbon phases in martian meteorites this review is intended to summarize the current observations of reduced carbon in martian meteorites differentiating between terrestrial contamination and carbon that is indigenous to mars indeed the identification of martian organic matter is among the highest priority targets for robotic spacecraft missions in the next decade including the mars science laboratory and mars 2020 organic carbon compounds are essential building blocks of terrestrial life so the occurrence and origin biotic or abiotic of organic compounds on mars is of great significance however not all forms of reduced carbon are conducive to biological systems this paper discusses the significance of reduced organic carbon including methane in martian geological and astrobiological systems specifically it summarizes current thinking on the nature sources and sinks of martian organic carbon a key component to martian habitability based on this compilation reduced organic carbon on mars including detections of methane in the martian atmosphere is best described through a combination of abiotic organic synthesis on mars and infall of extraterrestrial carbonaceous material although conclusive signs of martian life have yet to be revealed we have developed a strategy for life detection on mars that can be utilized in future life detection studies

comparison of body wave displacement with damage observations of a rockburst coeur d alene mining district idaho fault plane solutions for seismic events in the deep underground mines of the coeur d alene mining district in northern idaho have been difficult to reconcile with actual observations of mine damage examination of rockburst damage in stopes as well as measurements of slip movements on bedding planes suggests that rockbursts in the lucky friday mine are closely associated with gradual bedding plane slip this progressive slip reduces the physical dimensions of stopes and increases compressive stress resulting in sudden implosive failure of the stope margins thus much of the difficulty in evaluating seismological data arises from the implosional nature of these rockbursts making the first motion of the events difficult to interpret in the summer of 1998 we acquired several months of high quality seismic data from five stations in the vicinity of the lucky friday mine this is the first time that a network of high dynamic range three component instruments has been deployed in this mining district on 29 august 1988 at 6 09 utc a m l 2 9 event occurred at the lucky friday mine this event resulted from bedding plane slip and caused extensive damage in the mine that was carefully documented using a least squares procedure we were able to find a well constrained moment tensor solution that matches the p and s displacement amplitudes measured at the five temporary stations we derived a model of the mechanism to compare with the underground observations of bedding plane slip and damage we conclude that high quality seismological instrumentation is required if meaningful results are to be obtained for understanding the source mechanisms of shear implosional rockbursts manuscript received 1 february 2001

pb isotopic evidence for an early enriched crust on mars abstract martian meteorite nwa 7533 is a regolith breccia that compositionally resembles the martian surface measured by orbiters and landers nwa 7533 contains monzonitic clasts that have zircon with u pb ages of 4 428 ga the pb isotopic compositions of plagioclase and alkali feldspars as well as u pb isotopic compositions of chlorapatite in the monzonitic clasts of nwa 7533 have been measured by secondary ion mass spectrometry sims the u pb isotopic compositions measured from the chlorapatite in nwa 7533 yield an age of 1 357 81 ga 2 the least radiogenic pb isotopic compositions measured in plagioclase and k feldspar lie within error of the 4 428 ga geochron these data indicate that the monzonitic clasts in nwa 7533 are a product of a differentiation history that includes residence in a reservoir that formed prior to 4 428 ga with a value 238 u 204 pb of at least 13 4 1 7 2 and a value 232 th 238 u of 4 3 this value is more than three times higher than any other documented martian reservoir these results indicate either the martian mantle is significantly more heterogeneous than previously thought value of 1 14 vs 1 5 and or the monzonitic clasts formed by the melting of martian crust with a value of at least 13 4 therefore nwa 7533 may contain the first isotopic evidence for an enriched differentiated crust on mars

maskelynite hosted apatite in the chassigny meteorite insights into late stage magmatic volatile evolution in martian magmas apatite hosting maskelynite and alkali maskelynite within regions interstitial to cumulus olivine differ compositionally from that found within melt inclusions in the chassigny martian meteorite feldspar glass compositions within the interstitial regions evolve along a high temperature crystallization path within the melt inclusions feldspar glass shows evolution to low temperatures extending into the subsolidus regime coupled with these differences in maskelynite compositions are differences in volatile abundance in apatite included within the maskelynite apatite found within the large olivine hosted polyphase melt inclusions is uniformly fluorapatite whereas that interstitial to cumulus olivine is chlor fluorapatite we propose that the differences in maskelynite and apatite compositions within the melt inclusion and interstitial regions arose primarily from different crystallization conditions melt inclusion maskelynite and apatite are consistent with nearly closed system buildup of magmatic volatiles during crystallization within the melt inclusions exsolution of a cl bearing fluid phase and retention of this fluid phase within the melt inclusions into the hydrothermal regime for the interstitial regions however the higher solidus temperatures of the interstitial melts the early crystallization of feldspar with significant ternary component and the cl rich nature of the apatite all suggest open system fluid migration through the cumulus pile ingress of cl rich h2o poor brine from a hotter less evolved portion of the magma plumbing system and interaction of this cl rich fluid with melt prior to the crystallization of feldspar such processes of fluid migration through a cumulus pile have been suggested on earth in layered intrusions and apatite is the primary recorder of this process

samarium neodymium and rubidium strontium systematics of nakhlite governador valadares abstract the sm nd systematics of whole rock and mineral separate samples from nakhlite governador valadares define a good 147sm 143nd mineral isochron age of 1 37 0 02 ga this age is in excellent agreement with the 39ar 40ar and rb sr ages obtained previously for this meteorite however the rb sr isotopic data for our sample show that the isotopic system is disturbed the lack of isotopic equilibrium is probably caused by the weathering of the sample as indicated by the presence of secondary alteration phases the whole rock and acid washed mineral data yield a rb sr age of 1 20 0 05 ga which probably represents a lower limit to the crystallization age of the rock the petrographic evidence indicates that this meteorite is a clinopyroxene cumulate that probably crystallized in a subsurface sill mcsween 1994 thus the sm nd isotopic age probably represents the age of such a magmatic event the initial e143nd value determined for the rock at 1 37 ga is 17 1 indicating that the parent magma of the rock came from a light rare earth element depleted source of 147sm 144nd 0 237 based on a simple two stage evolution model results of the same model calculation for the initial 87sr 86sr ratio of the rock suggest that its source material was depleted in 87rb 86sr by 50 relative to the estimated martian value at 1 37 ga both the high sm nd and low rb sr values support a clinopyroxene rich cumulate source for the genesis of the nakhlite governador valadares furthermore our sm nd age and e143nd data and the previously published e142nd datum for the rock harper et al 1995 are consistent with early differentiation of the parent planet formation of cumulate sources 4 56 ga ago and late melting of the sources and formation of the rock 1 37 ga ago the good agreement of isotopic ages and petrographic features among governador valadares nakhla and lafayette strongly suggests that all three nakhlites have undergone similar evolutionary histories the nakhlite age data suggest that isotopic heterogeneity in the martian mantle sources existed up to 1 37 ga ago and early mantle structures probably have not been disturbed for a significant portion of martian history

ancient impactor components preserved and reworked in martian regolith breccia northwest africa 7034 abstract northwest africa nwa 7034 and paired stones represent unique samples of martian polymict regolith breccia multiple breccia subsamples characterized in this work confirm highly siderophile element hse re os ir ru pt pd contents that are consistently elevated e g os 9 3 18 4 ppb above indigenous martian igneous rocks mostly 187 os 188 os ratios of 0 119 0 136 record a wider variation than observed for all major chondrite types combined with the measured 187 re 188 os ratios of 0 154 0 994 the range in os isotope ratios indicates redistribution of re and os from originally chondritic components early in the history of the regolith commencing at 4 4 ga superimposed recent re mobility reflects exposure and weathering at or near the martian and terrestrial surfaces elevated os concentrations 38 0 and 92 6 ppb os superchondritic os hse ratios and 187 os 188 os of 0 1171 and 0 1197 measured for two subsamples of the breccia suggest the redistribution of impactor material at 1 5 1 9 ga possibly overlapping with a partial resetting event at 1 4 ga recorded by u pb isotope systematics in the breccia martian alteration of the originally chondritic hse host phases to form os ir rich nuggets and ni rich pyrite implies the influence of potentially impact driven hydrothermal systems multiple generations of impactor component admixture redistribution and alteration mark the formation and evolution of the martian regolith clasts and matrix of nwa 7034 and paired meteorites from the pre noachian until impact ejection to earth

time lapse seismic tomography of an underground mining zone abstract in this study we determined p wave tomographic images of the yongshaba deposit an underground mining zone in guizhou province china by inverting arrival time data of micro seismic events and blasts recorded by a passive seismic array consisting of 28 sensors during january to april 2014 using an event location technique and a travel time tomography method that can handle complex seismic discontinuities the damping parameter used in the damped least squares method is determined with the help of trade off curve to reveal internal p wave velocity changes of the study area under severe mining activities a time lapse data partition scheme is used to assess the human influence on the underground structure we introduce a parameter to measure the relative velocity changes in different periods the resolution of the tomographic images and the robustness of the obtained features are examined by conducting a series of checkerboard resolution tests and a restoring resolution test our tomographic results obtained from the entire data set reveal a prominent low velocity low v zone and many obvious high velocity high v zones these features match well with the geological setting and the excavation plan carried out in the mine according to in site surveys the low v zone may reflect empty volumes stress releases and rock breaking and cracking caused by mining activities whereas the high v zones are probably the consequences of local stress concentrations caused by regional stress redistribution the time lapse tomographic images may reveal the process of stress concentrations caused by rock breaking due to the continuing excavations in the entire observation period indicating that the mining activities influenced the rock property and caused complex changes of the underground structure

microseismic and precursor analysis of high stress hazards in tunnels a case comparison of rockburst and fall of ground abstract in rock engineering microseismic monitoring technology has been extensively applied for the interpretation and forecast of rockburst hazards however highly stressed hard rocks could suffer dynamic geological hazards rockburst and gravity driven geological hazards fall of ground both of which have distinct developmental processes and precursory features that await comprehensive exploration hence in this study we adopted microseismic monitoring and an advanced method based on the source parameters of seismic energy seismic moment and apparent stress the ems method the source parameter space was constructed to ascertain microseismic events as stress adjusting deformation driven or energy releasing type the evolution of the event type and the microseismic path precisely revealed the characteristics of the hazard development in a case study of a deeply buried tunnel we analyzed the process by which high stress hazards occur using the proposed method and distinguished between the respective microseismic characteristics of the rockburst and fall of ground in the development and occurrence stages finally we proposed the key precursory of rockburst and fall of ground in high stress rock masses while deformation driven events increase notably in rockburst stress adjusting events are dominant in fall of ground overall this study could facilitate precise interpretation and warning about different high stress hazards and provide effective measures to curb the development of hazards

progressive mitigation method of rock bursts under complicated geological conditions abstract jingxi coalfield which is called china s geological encyclopedia has a complicated geological condition as one its representative mines muchengjian mine has witnessed nearly thirty rock bursts in the past decade considering geological structures the in situ stress state and the burst proneness of coal one typical mining area in muchengjian mine is selected for analysis where nearly one third of rock bursts occurred this analysis lays the foundation for selecting mitigation strategies results indicate that the blasting disturbance plays an important role in the intensity and the scale of these rock bursts jingxi coalfield has three types of rock burst mechanisms i high in situ stress rock burst ii high mining induced stress rock burst and iii high in situ stress plus high mining induced stress rock burst therefore we follow two guidelines for rock burst control one is to mitigate the high stress concentration and the second is to control the disturbance stress on the basis of these two guidelines we designed a progressive mitigation method of rock bursts pmmrb first the weak disturbance destress techniques e g large diameter drilling water infusion are applied to weaken the strength and the burst proneness of coal and to expand crack zones to reduce the stress concentration and second the strong disturbance destress blasting is applied if the release of stress concentration is not sufficient pmmrb is adopted in a similar mining area with a higher in situ stress which indicates that pmmrb is applicable to the control of rock bursts and the reduction of rock burst intensity

the chlorine isotopic composition of martian meteorites 1 chlorine isotope composition of martian mantle and crustal reservoirs and their interactions the martian meteorites record a wide diversity of environments processes and ages much work has been done to decipher potential mantle sources for martian magmas and their interactions with crustal and surface environments chlorine isotopes provide a unique opportunity to assess interactions between martian mantle derived magmas and the crust we have measured the cl isotopic composition of 17 samples that span the range of known ages martian environments and mantle reservoirs the 37cl of the martian mantle as represented by the olivine phyric shergottites nwa 2737 chassignite and shergotty basaltic shergottite has a low value of approximately 3 8 this value is lower than that of all other planetary bodies measured thus far the martian crust as represented by regolith breccia nwa 7034 is variably enriched in the heavy isotope of cl this enrichment is reflective of preferential loss of 35cl to space most basaltic shergottites less shergotty nakhlites chassigny and allan hills 84001 lie on a continuum between the martian mantle and crust this intermediate range is explained by mechanical mixing through impact fluid interaction and assimilation fractional crystallization

decline of giant impacts on mars by 4 48 billion years ago and an early opportunity for habitability the timing of the wane in heavy meteorite bombardment of the inner planets is debated its timing determines the onset of crustal conditions consistently below the thermal and shock pressure limits for microbiota survival and so bounds the occurrence of conditions that allow planets to be habitable here we determine this timing for mars by examining the metamorphic histories of the oldest known martian minerals 4 476 4 429 gyr old zircon and baddeleyite grains in meteorites derived from the southern highlands we use electron microscopy and atom probe tomography to show that none of these grains were exposed to the life limiting shock pressure of 78 gpa 97 of the grains exhibit weak to no shock metamorphic features and no thermal overprints from shock induced melting by contrast about 80 of the studied grains from bombarded crust on earth and the moon show such features the giant impact proposed to have created mars hemispheric dichotomy must therefore have taken place more than 4 48 gyr ago with no later cataclysmic bombardments considering thermal habitability models we conclude that portions of mars crust reached habitable pressures and temperatures by 4 2 gyr ago the onset of the martian wet period about 0 5 gyr earlier than the earliest known record of life on earth early abiogenesis by 4 2 gyr ago is now tenable for both planets the oldest known minerals from mars have no strong shock features indicating early cessation of giant impacts there according to microanalysis of zircon and baddeleyite grains in meteorites

the perils of partition difficulties in retrieving magma compositions from chemically equilibrated basaltic meteorites abstract the chemical compositions of magmas can be derived from the compositions of their equilibrium minerals through mineral magma partition coefficients this method cannot be applied safely to basaltic rocks either solidified lavas or cumulates which have chemically equilibrated or partially equilibrated at subsolidus temperatures i e in the absence of magma applying mineral melt partition coefficients to mineral compositions from such rocks will typically yield magma compositions that are strongly fractionated and unreasonably enriched in incompatible elements e g rees in the absence of magma incompatible elements must go somewhere they are forced into minerals e g pyroxenes plagioclase at abundance levels far beyond those established during normal mineral magma equilibria further using mineral magma partition coefficients with such rocks may suggest that different minerals equilibrated with different magmas and the fractionation sequence of those melts i e enrichment in incompatible elements may not be consistent with independent constraints on the order of crystallization subsolidus equilibration is a reasonable cause for incompatibleelement enriched minerals in some eucrites diogenites and martian meteorites and offers a simple alternative to petrogenetic schemes involving highly fractionated magmas or magma infiltration metasomatism

rock burst process of limestone and its acoustic emission characteristics under true triaxial unloading conditions abstract the rock failure process is associated with acoustic emission ae hence violent rock failure processes such as rock burst under different stress paths in laboratory can be studied using the ae monitoring technique in this paper single face dynamic unloading tests under true triaxial condition were carried out for paleozonic marine sedimentation limestone samples produced by blocks cored from 1140 m depth in jiahe coal mine of china frequency spectra analysis was conducted for the full wave ae data and figures showing the relationship of frequency amplitude of ae signals in rock burst stages were obtained the dynamical damage process and characteristics of limestone under the test condition are summarized it is found from the fast fourier transformation fft analysis of the ae signals that there exist two main frequency ranges i e lower 60 100 khz and higher 170 190 khz for the samples when the limestone samples are under relatively lower stress the ae signals are characterized by high frequency and low amplitude as the stress increases the ae signals tend to shift more towards a signature of high amplitude near the bursting failure of the rock samples it is observed that there are much higher amplitude and lower frequency events the ae accumulated energy release rapidly increases from the unloading state of the rock samples to its failure the dynamic unloading test facility provides a useful tool to gain an insight into the characteristics of rock bursts

mineralogical constraints on the thermal history of martian regolith breccia northwest africa 8114 abstract martian meteorite northwest africa nwa 8114 a paired stone to nwa 7034 provides an opportunity to examine the thermal history of a martian regolith and study near surface processes and ancient environmental conditions near an impact crater on mars our study reports petrographic and alteration textures and focuses on pyroxene and iron oxide grains some of the pyroxene clasts show exsolution lamellae indicating a high temperature magmatic origin and slow cooling however transmission electron microscopy reveals that other predominantly pyroxene clasts are porous and have partially re crystallised to form magnetite and a k bearing feldspathic glassy material together with relict pyroxene this breakdown event was associated with oxidation with up to 25 fe3 fe in the relict pyroxene measured using fe k xanes by comparison with previous studies this breakdown and oxidation of pyroxene is most likely to be a result of impact shock heating being held at a temperature above 700 c for at least 7 days in an oxidising regolith environment we report an approximate 40ar 39ar maximum age of 1 13 1 25 ga for an individual separated augite clast the disturbed nature of the spectra precludes precise age determination in section this clast is porous and contains iron oxide grains this shows that it has undergone the high temperature partial breakdown seen in other relict pyroxene clasts and has up to 25 fe3 fe we infer that the age corresponds to the impact shock heating event that led to the high temperature breakdown of many of the pyroxenes after consolidation of the impact ejecta blanket high temperatures above 700 c may have been maintained for long enough to remobilise and congruently partially melt some of the alkali feldspar clasts to produce the feldspar veins and aureoles that crosscut and in some cases surround the oxidised pyroxene however the veins could alternatively be the result of a hydrothermal event in the impact regolith a simple fourier cooling model suggests that a regolith of at least five metres depth would be sufficient to maintain temperatures associated with the pyroxene breakdown for over seven days low temperature hydrous alteration took place forming goethite identified via xrd xanes and ftir comparing with previous studies the goethite is likely to be terrestrial alteration pseudomorphing martian pyrite

rb sr and sm nd isotopic and ree studies of igneous components in the bulk matrix domain of martian breccia northwest africa 7034 the bulk matrix domain of the martian breccia nwa 7034 was examined petrographically and isotopically to better understand the provenance and age of the source material that make up the breccia both 147sm 143nd and 146sm 142nd age results for mineral separates from the bulk matrix portion of breccia nwa 7034 suggest that various lithological components in the breccia probably formed contemporaneously 4 44 ga ago this old age is in excellent agreement with the upper intersection ages 4 35 4 45 ga for u pb discordia and also concordia defined by zircon and baddeleyite grains in matrix and igneous textured clasts consequently we confirm an ancient age for the igneous components that make up the nwa 7034 breccia substantial disturbance in the rb sr system was detected and no age significance could be gleaned from our rb sr data the disturbance to the rb sr system may be due to a thermal event recorded by bulk rock k ar ages of 1 56 ga and u pb ages of phosphates at about 1 35 1 5 ga which suggest partial resetting from an unknown thermal event s possibly accompanying breccia formation the nwa 7034 bulk rock is lree enriched and similar to kreep rich lunar rocks which indicates that the earliest martian crust was geochemically enriched this enrichment supports the idea that the crust is one of the enriched geochemical reservoirs on mars that have been detected in studies of other martian meteorites

petrogenesis of a vitrophyre in the martian meteorite breccia nwa 7034 abstract northwest africa nwa 7034 and its paired meteorites nwa 7533 and nwa 7475 are the first recognized martian polymict breccia samples an unusual large subrounded clast in nwa 7034 shows a vitrophyric texture consisting of skeletal pyroxene and olivine with mesostasis this lithology has not been observed in the paired meteorites it crystallized under disequilibrium conditions as indicated by its olivine and pyroxene kdfe mg partitioning values as well as reversed order of crystallization and mineral compositions relative to those predicted by melts we report the highest bulk ni value 1020 ppm measured in any known martian meteorite or martian igneous rock suggesting an impact melt origin for the vitrophyre addition of 5 3 7 7 chondritic material to the target rock would account for the ni enrichment the bulk major and trace element abundances of the vitrophyre indicate that the protolith was not the host breccia nor any other martian meteorites however the clast is compositionally similar to humphrey rock in gusev crater analyzed by the spirit rover and to a texturally distinct group of clasts in the paired meteorite nwa 7533 thus we propose that the target rock was an igneous lithology similar to gusev basalts which was subsequently contaminated by a chondritic impactor

water on mars insights from apatite in regolith breccia northwest africa 7034 abstract determining the source of planetary water from the hydrogen isotope compositions of crustal samples is complicated by the overprinting of isotopically diverse source material by geologic and atmospheric processes as mars has no plate tectonics crustal material which may have isotopically exchanged with the martian atmosphere is not recycled into the mantle keeping the water reservoirs in the mantle and atmosphere mostly isolated buffered by the crust as the only known martian samples that are regolith breccias with a composition representative of the average crust of mars northwest africa nwa 7034 and its paired stones provide an important opportunity to investigate the water content and hydrogen isotope composition of the martian crust in particular apatites in distinct clasts as well as the brecciated matrix of nwa 7034 record a complex history including magmatic and impact processes and exchange with crustal fluids

the northwest africa 8159 martian meteorite expanding the martian sample suite to the early amazonian abstract northwest africa nwa 8159 is an augite rich shergottite with a mineralogy dominated by ca fe rich pyroxene plagioclase olivine and magnetite nwa 8159 crystallized from an evolved melt of basaltic composition under relatively rapid conditions of cooling likely in a surface lava flow or shallow sill redox conditions experienced by the melt shifted from relatively oxidizing with respect to known martian lithologies qfm on the liquidus to higher oxygen fugacity qfm 2 during crystallization of the groundmass and under subsolidus conditions this shift resulted in the production of orthopyroxene and magnetite replacing olivine phenocryst rims nwa 8159 contains both crystalline and shock amorphized plagioclase an50 62 often observed within a single grain based on known calibrations we bracket the peak shock pressure experienced by nwa 8159 to between 15 and 23 gpa the bulk composition of nwa 8159 is depleted in lree as observed for tissint and other depleted shergottites however nwa 8159 is distinct from all other martian lithologies in its bulk composition and oxygen fugacity we obtain a sm nd formation age of 2 37 0 25 ga for nwa 8159 which represents an interval in mars geologic time which until recently was not represented in the other martian meteorite types the bulk rock 147sm 144nd value of 0 37 0 02 is consistent with it being derived directly from its source and the high initial e143nd value indicates this source was geochemically highly depleted cr nd and w isotopic compositions further support a unique mantle source while the rock shares similarities with the 2 4 ga nwa 7635 meteorite there are notable distinctions between the two meteorites that suggest differences in mantle source compositions and conditions of crystallization nevertheless the two samples may be launch paired nwa 8159 expands the known basalt types ages and mantle sources within the mars sample suite to include a second igneous unit from the early amazonian

panel discussion workshop on induced seismicity june 18 1996 a workshop on induced seismicity was held on june 18 1996 as part of the second north american rock mechanics symposium narms 96 montreal quebec canada the success of the workshop on induced seismicity organized by art mcgarr as part of the 33rd u s symposium on rock mechanics in santa fe new mexico in june 1992 was an indication that narms 96 could be an appropriate opportunity for holding a similar workshop also the organizers thought that the timing of such a workshop would be appropriate since the ideas discussed during this workshop could be further developed during the 4th international symposium on rockbursts and seismicity in mines held august 11 14 1997 in krakow poland

microseismicity derived fault planes and their relationship to focal mechanism stress inversion and geologic data general stress and faulting trends have been retrieved through the analysis of mining induced microseismic events m 0 at two sites related to an mn 2 6 rockburst and an excavation at depth a comparison of results obtained through principal component analysis pca of seismicity focal mechanism and stress inversion with in situ measurements of stress and structural mapping data show that under stable stress conditions the p b t and stress inversion axes are consistent with in situ measurements of stresses stress inversion and pca fault planes lie within 10 to 20 of the most significant mapped features at the sites and the pca technique provides a robust approach for the determination of fault planes

geochemistry petrology and cooling history of 14161 7373 a plutonic lunar sample with textural evidence of granitic fraction separation by silicate liquid immiscibility we report new findings related to sample 14161 7373 the first analyzed lunar intrusive rock to show textural evidence for the formation of granitic material by silicate liquid immiscibility sli and geochemical evidence for separation of that material at least on a small scale from mafic residua ion microprobe analyses of rare earth element ree concentrations in silicates record the compositional evolution of this late stage assemblage for a sample whose bulk assemblage that of whitlockite monzogabbro has ree concentrations at 5 6 kreep levels the silicates have only moderately high ree concentrations the calculated ree concentrations of melt in equilibrium with pigeonite after re integration of pigeonite host and augite lamellae is approximately 2 high k kreep the high bulk ree concentrations of the assemblage are the result of a high proportion of whitlockite probably an excess i e the assemblage is a whitlockite cumulate variations in silicate ree concentrations reflect the co crystallization of whitlockite which we interpret to have begun crystallizing prior to the onset of late stage immiscibility of the felsic melt fraction calculated cooling rates based on a quantitative model of pyroxene exsolution reveal a two stage thermal history which involved initial crystallization at a minimum depth of 700 800 m during which the primary augite and pigeonite grains unmixed to form the observed host lamella pairs unusual compositional profiles close to the host lamella interface are consistent with a second stage of mild reheating followed by rapid cooling at a depth of 30 m most likely in an ejecta blanket the shallow depth of origin indicated for 14161 7373 is consistent with other studies of evolved lunar intrusive rocks supporting the interpretation that lunar qmd and granite as found among the apollo samples are late stage differentiates of high level intrusions and are not related to differentiation of deep crustal kreep reservoirs

characteristic microseismicity during the development process of intermittent rockburst in a deep railway tunnel abstract during deep tunnel excavation more than one rockburst sometimes occur in a particular area which seriously threatens construction safety in this work the characteristic microseismicity occurring during the development process of intermittent rockburst more than one rockburst occurring in a particular area and single rockburst only one rockburst occurring in a particular area and the associated mechanism of formation are studied data was collected during the construction of a railway tunnel in southwestern china microseismicity was recorded and analyzed before and after each rockburst for both intermittent and single rockbursts the schmidt number declines heavily with time the cumulative apparent volume rises sharply with time and the seismic activity is high before the rockburst however this characteristic microseismicity can also be found with no rockburst occurrence between each rockburst in an intermittent rockburst the ms events mostly have low ms energy i e whose logarithm measured in joules is smaller than 3 5 and the energy stored in the rockmass of the rockburst zone is not adequately released therefore there is likely to be another rockburst after the blast when high in situ stress is present after the last rockburst of an intermittent rockburst and the single rockburst some ms events of high ms energy i e whose logarithm measured in joules is larger than 3 5 occur in the deep surrounding rockmass and the energy stored in the rockmass of the rockburst zone is gradually released to a certain degree the stress is transferred to the deep surrounding rockmass whose stability is relatively high as a result a subsequent rockburst is hardly likely to occur again

the early differentiation of mars inferred from hf w chronometry abstract mars probably accreted within the first 10 million years of solar system formation and likely underwent magma ocean crystallization and crust formation soon thereafter to assess the nature and timescales of these large scale mantle differentiation processes we applied the short lived 182 hf 182 w and 146 sm 142 nd chronometers to a comprehensive suite of martian meteorites including several shergottites augite basalt nwa 8159 orthopyroxenite alh 84001 and polymict breccia nwa 7034 compared to previous studies the 182 w data are significantly more precise and have been obtained for a more diverse suite of martian meteorites ranging from samples from highly depleted to highly enriched mantle and crustal sources our results show that martian meteorites exhibit widespread 182 w 184 w variations that are broadly correlated with 142 nd 144 nd implying that silicate differentiation and not core formation is the main cause of the observed 182 w 184 w differences the combined 182 w 142 nd systematics are best explained by magma ocean crystallization on mars within 20 25 million years after solar system formation followed by crust formation 15 million years later these ages are indistinguishable from the i pu xe age for the formation of mars atmosphere indicating that the major differentiation of mars into mantle crust and atmosphere occurred between 20 and 40 million years after solar system formation and hence earlier than previously inferred based on sm nd chronometry alone

inversion of stress field evolution consisting of static and dynamic stresses by microseismic velocity tomography abstract in order to reveal the stress precursors of the 3 15 rockburst disaster that occurred in the no 1 working face of junde coal mine the combined stress field inversion including static and dynamic stresses was conducted by using p wave velocity tomography and the static high stress concentration regions were further designated simultaneously the evolution of dynamic stress generated by seven periodical caving events of primary roof was analyzed and the fracturing characteristics were described in detail ultimately the stress precursors of the 3 15 rockburst for early warning were clearly revealed the main conclusions are as follows 1 the micro fissures inside coal and rock mass produce the significant reflection and refraction on the propagation of microseismic ms waves and thus p wave overall characterizes with lower velocity and higher velocity gradient 2 after the slightly fracturing of primary roof on march 9 2013 the maximum stress concentration factor suddenly rises to 20 this sign can be viewed as an early warning precursor of rockburst 3 until march 12 2013 the large scale micro fractures begin to form inside primary roof and thus the corresponding high velocity gradient regions are generated this phenomenon can be regarded as an effective precursor of macroscopic fracturing of primary roof and 4 before the 3 15 rockburst the scope of p wave velocity gradient in the no 1 working face does not change significantly the above findings may put forward a certain reference for accurately warning the stress precursors of rockburst by p wave velocity tomography

partitioning in ree saturating minerals theory experiment and modelling of whitlockite apatite and evolution of lunar residual magmas we present compositions including rees determined by ion microprobe of apatite and whitlockite in lunar rock assemblages rich in incompatible trace elements total concentrations of ree oxides in whitlockites range from 9 13 wt and those in apatites range from 0 15 to 1 wt ratios of ree concentrations in whitlockite to those in coexisting apatite range from 10 to 60 the distribution of mg and fe between apatite and whitlockite is correlated to that of coexisting mafic silicates magnesium is strongly preferred by whitlockite and fe is preferred by apatite incorporation of rees in whitlockite is dominated by the coupled substitution of 2ree3 in ca b sites vacancy in ca iia for 2ca 2 in ca b sites and ca2 na in ca iia other substitutions account for only a small portion of the rees in whitlockite over the observed concentration range thus ree concentrations become partially saturated as the primary substitution approaches its stoichiometric limit of two rees per fifty six oxygens leading to reduced whitlockite melt distribution coefficients e g decreasing from twenty five to ten for nd the ree concentrations of lunar residual melts are not depleted by whitlockite crystallization in assemblages consisting mainly of other minerals in typical proportions distribution coefficients for the rees in lunar apatite appear to be low and variable e g 0 2 0 8 for nd variations in the modal ratio of whitlockite to apatite specifically the abundance of whitlockite lead to a range of ree concentrations in the phosphates and variations in the magnitude of ree concentration ratios between whitlockite and apatite if apatite crystallizes before whitlockite or in the absence of whitlockite as textures in several samples indicate then apatite zoned in rees and apatite crystals of different ree concentrations may occur in a given sample provided there is some amount of fractional crystallization and apatite does not later equilibrate this may occur because in the absence of whitlockite in the crystallizing assemblage the rees are highly incompatible relative to the crystalline assemblage so ree concentrations in lunar residual melts increase strongly during small increments of late stage crystallization once whitlockite begins to crystallize bulk distribution coefficients for the rees although still 1 are only mildly incompatible so the change in ree concentrations of residual melts with further crystallization is small consistent with the lack of ree zoning in whitlockite the ree concentrations in lunar whitlockites are modelled as resulting mainly from equilibrium crystallization of the assemblages in which they occur metasomatism or other secondary metamorphic processes are not indicated local melt pocket equilibrium at advanced stages of crystallization may lead to variable ree concentrations and variable whitlockite apatite concentration ratios within the same sample parent melts with extremely high ree concentrations are not required in order to crystallize ree rich lunar whitlockite if modal proportions of whitlockite are low

observation of mining induced faults in an intact rock mass at depth abstract stoping of a highly stressed remnant in a deep south african gold mine was accompanied by considerable seismic activity and some significant rockbursts the larger seismic events were registered some 60 km away at a world wide standard seismograph network wssn station several shear ruptures were encountered subsequently in a tunnel driven to follow the mining faces a careful study based on detailed exploration of two of these ruptures proved them to be the source of two of the larger rockbursts the ruptures were essentially planar features of considerable areal extent with shear displacements of up to 100 mm of a normal dip slip sense certain striking features were revealed by a scanning electron microscopic study of some of the fresh cataclastic rock flour which formed part of the comminuted filling of these ruptures these provided strong evidence for extremely violent fracturing phenomena in the faulting process a proper understanding of these phenomena could provide useful insight into the source mechanism of rockbursts and the control of the accompanying damage because of the many similarities in morphology of the faults and in the nature of the seismic signals it could be argued that the rockburst rupture is a microcosm of the pristine earthquake understanding of the mechanics of the rockburst shear rupture might therefore have some relevance in the study of the earthquake source

modern atmospheric signatures in 4 4 ga martian meteorite nwa 7034 the nwa 7034 martian basaltic breccia dated at 4 4 ga 4 4 ga represents an entirely new type of martian meteorite however due to the unique make up of nwa 7034 compared to other martian meteorite types including its anomalous oxygen isotope ratios noble gas analyses a key tool for martian meteorite identification are important to confirm its martian origin here we report the first noble gas results for nwa 7034 which show the presence of a trapped component that resembles the current martian atmosphere this trapped component is also similar in composition to trapped gases found in the much younger shergottites 150 600 ma 150 600 ma our formation ages for the sample suggest events at 1 6 ga k ar and 170 ma u th he which are considerably younger than those observed by rb sr 2 1 ga and sm nd 4 4 ga zircons 4 4 ga however our k ar age is similar to a disturbance in the u pb zircon data at 1 7 ga which could hint that both chronometers have been subjected to disturbance by a common process or event the u th he age of 170 ma could relate to complete loss of radiogenic 4he at this time and is a similar age to the crystallisation age of most shergottites while this may be coincidental it could indicate that a single event is responsible for both shergottite formation and nwa 7034 thermal metamorphism as for cosmic ray exposure ages our favoured age is 5 ma which is outside the ranges for other martian meteorite groups and may suggest a distinct ejection event nwa 7034 shows evidence for neutron capture on br which has caused elevations in kr isotopes 80 kr and 82 kr these elevated abundances indicate significant shielding and could relate to either a large meteoroid size and or shielding in relation to a regolithic origin we have also applied similar neutron capture corrections to ar and xe data which further refine the likelihood of a modern atmospheric component though such corrections remain speculative cosmogenic production rates and noble gas data are consistent with a meteoroid radius of 50 cm fission contributions are clear in the xe data with evidence to suggest that nwa 7034 contains both 238 u and 244 pu derived fission xe components if the gas in nwa 7034 was trapped at its ancient igneous formation this would suggest little evolution of the martian atmosphere between 4 4 ga and present day however as nwa 7034 is a regolith breccia with multiple lithologies and a strong compositional similarity to gusev soils the timing and incorporation of trapped atmospheric gases is unclear with hints of resetting events at 1 5 2 1 ga 1 5 2 1 ga the atmospheric component may have been incorporated during breccia formation possibly in the amazonian though it could also have been incorporated on ejection from the surface

petrogenetic linkages among martian basalts implications based on trace element chemistry of olivine the shergottites exhibit a range of major and trace element compositions crystallization ages and initial sr nd hf and pb isotopic compositions to constrain the physical mechanisms by which shergottites obtain their compositional characteristics we examined the major and trace element record preserved in olivine in the more primitive shergottites based on such characteristics as the mg v zoning calculated dni co the olivine in y 980459 are most likely phenocrysts many of these same characteristics indicate that the olivines in other shergottites are not in equilibrium with the adjacent melt however in most cases they are not xenocrystic but additions of olivine from the same basaltic system elephant moraine eet a79001 may be an exception with the olivine data suggesting that it is xenocrystic in this case the olivine crystallized from a reduced and lreedepleted melt and was incorporated into an oxidized and enriched basalt vanadium and cao in olivine appear to record the appearance of spinel and pyroxene on the liquidus of most of the shergottites most of the olivine shergottites represent basalts produced by melting of reduced iw to iw 1 depleted mantle sources olivine data indicate that many of the primary melts derived from this source had similar ni co and mn shergottites such as northwest africa nwa 1110 1068 and perhaps roberts massif rbt 04261 that appear to be derived from more enriched sources have distinctly different olivine in the case of nwa 1110 1068 the olivine data suggests that the enriched component was added to system prior to olivine crystallization

microcracking during triaxial deformation of porous rocks monitored by changes in rock physical properties ii pore volumometry and acoustic emission measurements on water saturated rocks abstract we report results from a series of laboratory triaxial deformation experiments performed on samples of darley dale sandstone at servo controlled constant strain rate and constant pore fluid pressure during deformation the volume of water either expelled from the samples during compaction or injected into the samples during dilatancy in order to maintain a constant pore fluid pressure was continuously monitored throughout each experiment in addition the parameters of differential axial stress axial strain and acoustic emission ae characteristics were also recorded complete ae waveforms were also captured and stored by means of a transient recorder and fourier analysis of these waveforms was subsequently carried out the reported experiments were all performed in a conventional high pressure gas medium triaxial cell but with the pore fluid pressure maintained constant using a new servo controlled fluid pressure intensifier and pore volumometer the ae and pore volumometry measurements on water saturated rocks reported in this paper are complementary to the measurements of elastic wave propagation parameters made on dry rocks and reported in a companion paper in this issue the two suites of data have been integrated to infer relations between crack density parameters calculated from elastic wave velocity measurements and the directly measured pore volume during deformation our results show a distinct positive correlation between changes in the axial crack density parameter x and changes in the pore volume during deformation once fluid expulsion due to elastic pore collapse has been corrected for these two parameters have then been combined to obtain an estimate of changes in the mean aspect ratio of propagating dilatant cracks the results suggest that under moderate confining pressures axially aligned dilatant cracks are likely to bow open elastically prior to significant crack extension and growth

146sm 142nd formation interval for the lunar mantle now extinct 146sm t1 2 103ma was present in the early solar system and lunar basalts might be expected to have inherited small anomalies in 142nd abundances from mantle sources with variable sm nd ratios established during the early global differentiation of the moon 142nd 144nd ratios were measured for several lunar basalts and values of nd142 deviations from terrestrial 142nd 144nd in parts in 104 calculated for them the nd142 values show very small variations attributable to 146sm decay neutron capture near the lunar surface also modified both the samarium and neodymium isotopic compositions of the basalt samples the calculated neutron fluences range from 0 to 7 8 1016 n cm2 both thermal and epithermal neutron fluences were calculated from the sm isotopic compositions of the basalts and used to correct the nd142 values for neutron capture by neodymium well resolved radiogenic enrichments nd142 and 0 17 0 08 2 respectively were measured for lunar meteorite asuka 881757 and apollo 17 basalt 74255 respectively for which the neutron fluences were nil basalts 70135 and 75075 which were exposed to small measureable neutron fluences of 2 5 1015 and 7 7 1015 n cm2 respectively have neutron corrected nd142 values of 0 25 0 15 and 0 29 0 11 respectively the average value of radiogenic nd142 for the three high ti basalts from apollo 17 is 0 22 0 06 neutron capture effects were greater for the other basalts but can be corrected using the measured neutron fluences derived from the samarium isotopic data the neutron corrected nd142 for apollo 12 ilmenite basalt 12056 consistent with its derivation from a highly depleted mantle source also three low ti basalts from apollo 12 and apollo 15 12038 15076 15555 have neutron corrected nd142 which are not resolved from zero and average 0 04 0 06 a fourth low ti basalt 12039 has neutron corrected nd142 but is subject to the largest neutron correction of 0 32 e units kreep basalt 14078 was exposed to only a small neutron fluence of 6 4 1015 n cm2 and has a small deficit of 142nd corresponding to nd142 the average neutron corrected nd142 of three kreep basalts is 0 05 0 04 the nd142 values of the basalts correlate with 147sm 144nd values for their source regions as calculated from their ages and initial nd142 values 147sm 143nd and 146sm 142nd systematics were combined in a three stage model yielding an isochron equation for the lunar mantle formation interval which was calculated to be 238 40 56 ma 2 sm nd ratios for the source regions also are derived from the model and compare favorably with values from conventional geochemical models of mare basalt petrogenesis if the moon were formed by impact of a large mars sized planetesimal with the earth the impact was early enough that the lunar mantle cooled to neodymium isotopic closure by 4 32 ga ago the bulk lunar moon142 evaluated from the mantle isochron at 147sm 144nd chur 0 1967 is 0 01 0 03 2 consistent with derivation of lunar and terrestrial neodymium from a common reservoir

seismic and strain studies on large laboratory rock samples being stressed to failure abstract large granite 700 700 700 mm and basalt 580 580 915mm samples were cyclicly loaded to failure strain and ultrasonic velocity measurements were made and acoustic emissions recorded during deformation all measurements were correlated in space and time several zones of acoustic emission sources were identified the acoustic patterns of emission activity within these zones varied greatly with increasing stress 1 a initially active then quiet 2 b initially active then quiet and active again before failure and 3 c activity increasing continuously and at accelerating rate toward failure at constant applied stress the seismic character of the acoustic emission signals was quite different in terms of frequency content and amplitude for the different zones the signals emanating from within a particular zone were very reproducible as recorded on a particular transducer but quite different from transducer to transducer the kaiser effect seems to hold up to about one half of the stress of failure i e very few acoustic emissions were detected when the sample was cycled below previously attained stress as long as was less than about one half of the eventual stress at failure as failure was approached the individual acoustic emission events became more energetic and relatively more power was recorded at lower frequencies strain and ultrasonic velocity measurements indicate large variations in dilatancy in the sample similar measurements on much smaller samples are consistent with these results

spatio temporal evolution of volcano seismicity a laboratory study we report a laboratory and microstructural study of a suite of deformation experiments in which basalt from mount etna volcano is deformed and fractured at an effective confining pressure representative of conditions under a volcanic edifice 40 mpa particular attention was paid to the formation of a fracture and damage zone with which to stimulate coupled hydro mechanical interactions that create the various types of seismicity recorded on volcanic edifices and which usually precede eruption location of ae events through time shows the formation of a fault plane during which waveforms exhibit the typical high frequency characteristics of volcano tectonic vt earthquakes we found that these vt earthquakes were particularly pronounced when generated using dry samples compared to samples saturated with a pore fluid water vt events generated during deformation of water saturated sample are characterised by a distinctive high frequency onset and a longer low frequency coda exhibiting properties often seen in the field as hybrid events we present evidence that hybrid events are in fact the common type of volcanic seismic event with either vt or low frequency lf events representing end members and whose proportion depend on pore fluid being present in the rock type being deformed as well as how close the rock is to failure we find a notable trend of reducing instances of hybrid events leading up to the failure stage in our experiments suggesting that during this stage the pore fluid present in the rock moves sufficiently quickly to provide a resonance seen as a lf coda our data supports recent modeling and field studies that postulate that hybrid events generated in volcanic areas are likely to be generated through the interaction of hydrothermal fluids moving through a combination of pre existing microcrack networks and larger faults such as those we observe in forensic post test examination

use of mining and seismological parameters as premonitors of rockbursts abstract comprising one of the deepest mines in the world the gold mining region of the kolar gold fields kgf in southern india is known to be confronted with the acute problem of rockbursts that pose a hazard to workmen and cause disruptions in the production schedule in combination with mining parameters seismological data of these rockbursts events systematically monitored over the years using a regional seismic network have been employed to examine and model premonitory characteristics of the events linear empirical relations are established relying on correlations seen between the seismic energy released due to a rockburst total tonnage of ore mined out and total number of rockbursts as well as seismic events in some shallow and deep workings currently active at kgf the deterministic model although not free from certain limitations at present has been applied to predict rockburst activity with some success

stress drops and radiated seismic energies of microearthquakes in a south african gold mine 1 we estimate stress drops and radiated seismic energies of 20 microearthquakes 0 0 mw 1 3 in a south african gold mine to investigate their rupture characteristics and scaling relationships to large earthquakes we analyze seismograms of borehole accelerometers recorded with high sampling rate 15 khz within 200 m of the hypocenters at the depth of 2650 m the waveform data have very high signal to noise ratio and no significant later phases are observed at all stations corner frequencies and quality factors of the anelastic attenuation q are estimated from spectra of velocity seismograms by assuming the omega squared model of boatwright 1978 we also investigate moment tensors for double couple solutions and volumetric components from the waveform inversion static stress drops of the 20 earthquakes calculated from the model of madariaga 1976 are from 3 2 to 88 mpa and scaled energies er mo the ratio of the radiated energy er to the seismic moment mo are from 4 2 10 6 to 1 1 10 4 we find that both the static stress drops and the scaled energies of the analyzed earthquakes are comparable to those values of larger earthquakes our results indicate that the dynamic rupture processes of these microearthquakes are similar to those of larger earthquakes

a shorter 146sm half life measured and implications for 146sm 142nd chronology in the solar system radiometric dating relies on measuring the abundance of long lived radionuclides relative to the abundance of their radiogenic decay products a process determined by the original radionuclide s half life for primordial radionuclides that decay slowly such as 146sm decaying to 142nd this method provides the timing of some of the earliest processes in solar system history using accelerator mass spectrometry kinoshita et al p 1614 1 provide a revised estimate for the 146sm half life of 68 7 million years which is 30 shorter than the previously accepted value this shorter half life suggests that reductions need to be made in the estimated ages for differentiation of earth s mantle and the solidification of the moon s magma ocean and for other more recent processes 1 lookup doi 10 1126 science 1215510

violent failure of a remnant in a deep south african gold mine abstract the violent failure of a peninsular remnant at a depth of 2300 m below surface occurred in a mine in the carletonville goldfield of south africa severely damaging a stope mining the ventersdorp contact reef vcr at the rockburst site the vcr is 1 2 m thick with a lava hangingwall and quartzite conglomerate footwall the remnant had been formed as the result of a fault and roll encountered during mining observations at the rockburst site led us to conclude that the seismic event with local magnitude of 2 1 resulted from failure of the remnant with attendant movement into the workings the event could not be explained by a single shear slip two different damage mechanisms were identified firstly the face and footwall on the east side of the remnant were violently ejected into the void between the original face and first line of timber packs following failure and dilation of the remnant and its foundation secondly the hangingwall on the south side of the remnant fragmented and collapsed when subjected to intense seismic shaking this response was due to the presence of a bedding parallel fault and calcite coated joints in the vicinity of a roll the stope support system failed to contain the seismically fragmented rock

crystal chemistry of merrillite from martian meteorites mineralogical recorders of magmatic processes and planetary differentiation merrillite is a ubiquitous accessory phase in a variety of martian meteorite lithologies the martian merrillites exhibit a positive correlation between mg and na and a negative correlation between mg and both mn and vacancies in the octahedral na site their ree patterns are varied and range from lree depleted to lree enriched the dominant cation substitutions in the martian merrillites are fe2 vi mg sitemg2 vi mg site and ca2 vi na site vi na site2na vi na site the ree substitution into the 8 fold coordinated ca site is accommodated by the coupled substitution caviii ca site na vi na site y3 ree3 viii ca site vi na site the ree substitution is significantly more prevalent in lunar merrillite and can be used as a fingerprint to distinguish lunar from martian meteorites the substitution of oh whitlockite and or f bobdownsite for o2 on one of the phosphate tetrahedrons appears to be rather insignificant the correlations among na mg mn and na site vacancies are linked to the premerrillite crystallization history of the melt and the crystal chemical behavior of the mg and na sites the former reflects the sequence and extent of plagioclase and pyroxene crystallization the differences in ree pattern shapes among the merrillites reflect source regions for the martian basalts and the shapes are not greatly perturbed by the crystallization history the occurrence of merrillite does not imply low volatile component in the martian magmas however the low whitlockite and bobdownsite contents suggest that these samples were not altered by hydrothermal fluids and therefore not reset owing to aqueous fluid interactions consequently the young ages of the shergottites are probably true igneous crystallization ages

unique meteorite from early amazonian mars water rich basaltic breccia northwest africa 7034 we report data on the martian meteorite northwest africa nwa 7034 which shares some petrologic and geochemical characteristics with known martian meteorites of the snc i e shergottite nakhlite and chassignite group but also has some unique characteristics that would exclude it from that group nwa 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent rover and orbiter missions it formed 2 089 0 081 billion years ago during the early amazonian epoch in mars9 geologic history nwa 7034 has an order of magnitude more indigenous water than most snc meteorites with up to 6000 parts per million extraterrestrial h2o released during stepped heating it also has bulk oxygen isotope values of 17o 0 58 0 05 per mil and a heat released water oxygen isotope average value of 17o 0 330 0 011 per mil suggesting the existence of multiple oxygen reservoirs on mars

early crustal building processes on the moon models for the petrogenesis of the magnesian suite abstract the plutonic rocks of the magnesian suite mg suite represent the period of lunar basaltic magmatism and crustal growth 4 46 to 4 1 ga that immediately followed the initial differentiation of the moon by magma ocean lmo formation and crystallization the volume and distribution of the mg suite and its petrogenetic relationship to latter stages of lunar magmatism mare basalts remains obscure these plutonic rocks exhibit a range of compositions and include ultramafics troctolites spinel troctolites norites and gabbronorites a distinguishing characteristic of this suite is that they contain some of the most magnesium rich phases fo95 90 that had crystallized from lunar magmas yet they also are significantly enriched in an incompatible element component referred to as kreep a late stage product of lmo crystallization containing abundant potassium k rare earth elements ree phosphorous p uranium and thorium ion microprobe analyses of individual mineral phases olivine pyroxene and plagioclase from the mg suite have shown some very unexpected characteristics that have profound implications on the origin of these basaltic magmas although the mg suite lithologies are typified by silicates with relatively high mg early liquidus phases such as olivine are fairly low in ni co and cr relative to more iron rich olivines in the younger mare basalts the high y and ti y in early phases such as olivine and orthopyroxene indicate that the parental basaltic melts were high in incompatible elements and contained an ilmenite fractionation signature however the y in olivine from many of the troctolites and ultramafic lithologies are only slightly greater than that of the olivine in the mare basalts whereas olivine in the norites gabbronorites and apollo 14 troctolites are exceedingly high the kreep component may have been added to the mg suite parent magmas by assimilation or mixing into the mantle source the volume of kreep required to be added to the parental magmas of the mg suite tends to favor the latter mechanism for kreep incorporation the extremely high abundances of kreep in the norites and gabbronorites are a product of substantial crystallization 40 to 70 of kreep enriched mg suite parental magmas basaltic magmatism associated with kreep extended for over 1 5 billion years and appears to have changed over time the early stages of this style of lunar magmatism mg suite appear to represent melting of early lmo cumulates with low abundances of ni co cr and v later stages of kreep rich basaltic magmatism seemed to clearly involve melting of a variety of lmo cumulate assemblages with higher incompatible element enrichment it appears that the heat derived from the kreep component was instrumental in at least initiating melting of the lunar mantle over this period of time

geochemistry of martian basalts with constraints on magma genesis abstract over the past decade our knowledge of the geochemical and mineralogical diversity of martian rocks has greatly increased rocks on the surface of mars are older than most martian meteorites and have a wider range in bulk chemistry higher sio 2 higher total alkalis and lower mgo contents recent martian meteorite discoveries nwa 7034 nwa 7635 and nwa 8159 are also significantly older than the shergottites and nwa 7034 contains clasts which have a similar range in chemistry of the surface basalts in this invited review i summarize what is known about the bulk chemistry major elements of martian igneous rocks and use the chemistry to constrain the formation conditions in the interior and how these conditions have changed through time the basalts at gale crater are consistent with forming from a metasomatized mantle source which affected not only the chemistry of the basalts but also the formation conditions basalts at gusev crater bounce rock at meridiani planum and those basalts not affected by metasomatism like those at gale crater have a mantle potential temperature of 1450 c for the noachian conversely martian shergottites have a much higher mantle potential temperature 1745 c which has always been problematic to explain for such young rocks new formation conditions calculations are consistent with previous models of formation by a hot mantle plume but solve the pressure of formation paradox from the previous model combining the calculations for mantle potential temperature with previous estimates for grs measurements of surface volcanics from the hesperian and amazonian i calculate a baseline cooling curve and mantle melting conditions for the martian interior through time

temporal imaging of mine induced stress change using seismic tomography abstract in an effort aimed at monitoring mining induced stress changes that may influence ground failure the us bureau of mines conducted a series of active 3 d seismic tomographic surveys at the homestake lead south dakota and lucky friday mullan idaho mines existing rock bolts were used to mount geophones and as strike points for introducing seismic energy using a 3 6 kg sledge hammer travel time measurements were recorded spanning up to 160 m between drifts at several levels the tomographic uncertainty was minimized by computing iso velocity surfaces of constant probability based on statistics from multiple reconstructions and a threshold criteria periodic imaging using tomographic velocity surfaces demonstrated that temporal and spatial changes in the local stress field occurred in response to ground failure and stope advancement at a gold and silver mine respectively

seismological and energy balance constraints on the mechanism of a catastrophic bump in the book cliffs coal mining district utah u s a on 21 january 1993 an underground mine in the book cliffs coal mining district of eastern utah experienced a m 3 6 seismic event the event coincided with the crushing out of 24 18 2 m 18 2 m 2 7 m seam height pillars encompassing an area of nearly 15 000 m seismic stations of the university of utah array bureau of reclamation arrays and other western seismic stations recorded the event digital recordings from the university of utah provided 41 waveforms for first motion polarity determinations all but three reliable polarity readings were dilatations source parameter and radiated seismic energy determinations were made using four of the university of utah three component stations attenuation corrected p wave and s wave radiated energies were determined the sum of p and s wave radiated energies is 1 5 7 1 gj depending on the attenuation model for comparison with the radiated energy the maximum possible strain energy in the crushed pillars is estimated as 4 1 gj given other energy absorbing processes involved in the damage additional sources of energy beyond the pillar strain energy are required six scenarios for the event mechanism are examined for consistency with the seismic analysis and on site damage observations this study suggests that this catastrophic coal bump was precipitated by a subsidence related fault slip with normal slip on a fault in close proximity to the mine workings published by elsevier science ltd

ion microprobe studies of trace elements in apollo 14 volcanic glass beads comparisons to apollo 14 mare basalts and petrogenesis of picritic magmas abstract the major element geochemistry of picritic lunar glass beads indicates that they represent primary basaltic liquid compositions and as such provide unique information concerning the origin of mare basalts and characteristics of the lunar interior this study used ion microprobe techniques for trace element analysis of individual glass beads representing seven compositionally distinct types of picritic glass beads from the apollo 14 site high ti glasses 17 11 tio2 red black orange intermediate ti glasses 5 4 tio2 yellow low ti glasses 2 8 tio2 lap low alkali picritic papike et al 1989 very low ti glasses ba sr 1 of these glasses are different from low ti mare basalts at other sites but are similar to crystalline basalts at the apollo 14 site the intermediate to high ti picritic glasses exhibit a flat to slightly positive lree slope and a negative hree slope the orange glass has a higher total ree abundance and a slightly larger negative eu anomaly than the red black and yellow glasses relative to the apollo 17 high ti glasses apollo 14 high ti glasses are enriched in ree lree hree y v zr sr ba and ba sr and are similar in alkali elements li rb co and sc trace element modeling within the context of liquid lines of descent and major element characteristics indicates that the picritic glass beads at the a 14 site are not related by low pressure fractional crystallization to each other or to crystalline basalts at the apollo 14 or other landing sites a possible exception is the relationship between lap and basalts of the high al basalt suite the wide range of primary magma compositions and the lack of petrogenetic linkage via crystal fractionation to crystalline basalts indicates that either a wide compositional range of evolved mare basalts has not yet been sampled or a unique mechanism is selectively tapping these picritic magmas directly from their mantle source region the wide range of major and trace element characteristics of the volcanic glass beads is consistent with derivation from mineralogically distinct sources which consist of varying proportions of olivine orthopyroxene clinopyroxene ilmenite plagioclase kreep component the evolved kreep component may have been incorporated into these primary picritic magmas by either assimilation fractional crystallization type processes afc or by hybridization of the mantle source the former appears less likely due to the general systematic increase in incompatible elements relative to ti concentration and the apparent lack of crystallization that is required in afc type models the hybridization processes may be the result of sinker mechanisms as proposed by ringwood and kesson 1976 a manifestation of original mantle inhomogeneities or a magma ocean stirred by large impacts

inventory of h2o in the ancient martian regolith from northwest africa 7034 the important role of fe oxides water rich martian regolith breccia northwest africa nwa 7034 was analyzed by fourier transform infrared spectroscopy and transmission electron microscopy to determine the inventory and phase distribution of h2o used herein to refer to both molecular h2o and oh structural components in hydrous minerals hydrous fe oxide phases hydromaghemite and an unidentified nanocrystalline fe bearing oxide phase observed with hydromaghemite and phyllosilicates saponite were identified as the primary mineralogic hosts for h2o with a minor contribution from cl rich apatite based on mass balance calculations and modal abundances of minerals constrained by powder x ray diffraction and petrography we can account for the entire 6000 ppm h2o measured in bulk rock analyses of nwa 7034 this h2o is distributed evenly between hydrous fe rich oxides and phyllosilicates indicating that fe oxides could be as important as phyllosilicates for h2o storage in martian surface material

rock mechanical analysis of a m1 4 0 seismic event induced by mining in the saar district germany summary on 2008 february 23 a 4 0 magnitude seismic event occurred in close proximity to a deep underground longwall coal mine in the german saar mining district preceding this event was a series of smaller seismic events which can be traced back to geological structures a seismic network was installed to observe and analyse the seismic events underground core drilling was performed to obtain rock samples for rock mechanical testing possible causes for the events failure of rock mass or slip on unknown faults are evaluated by numerical methods failure of rock mass is excluded as a cause since the stresses are well below the strength of the rock mass seismic events are of similar fault plane strike and are organized in several clusters associated with local and regional tectonic elements it was found from backcalculation that fault planes with friction angles as low as 8 must have been present the role of pore pressure on the fault stability is discussed and found to play no role in generating the seismic events finally the question of mining in a rock mass obviously close to failure is addressed and it was concluded that any mining activity would lead to a significant seismic response

geologic history of martian regolith breccia northwest africa 7034 evidence for hydrothermal activity and lithologic diversity in the martian crust the timing and mode of deposition for martian regolith breccia northwest africa nwa 7034 were determined by combining petrography shape analysis and thermochronology nwa 7034 is composed of igneous impact and brecciated clasts within a thermally annealed submicron matrix of pulverized crustal rocks and devitrified impact volcanic glass the brecciated clasts are likely lithified portions of martian regolith with some evidence of past hydrothermal activity represented lithologies are primarily ancient crustal materials with crystallization ages as old as 4 4 ga one ancient zircon was hosted by an alkali rich basalt clast confirming that alkalic volcanism occurred on mars very early nwa 7034 is composed of fragmented particles that do not exhibit evidence of having undergone bed load transport by wind or water the clast size distribution is similar to terrestrial pyroclastic deposits we infer that the clasts were deposited by atmospheric rainout subsequent to a pyroclastic eruption s and or impact event s although the ancient ages of igneous components favor mobilization by impact s despite ancient components the breccia has undergone a single pervasive thermal event at 500 800 c evident by groundmass texture and concordance of 1 5 ga dates for bulk rock k ar u pb in apatite and u pb in metamict zircons the 1 5 ga age is likely a thermal event that coincides with rainout breccia lithification we infer that the episodic process of regolith lithification dominated sedimentary processes during the amazonian epoch the absence of pre amazonian high temperature metamorphic events recorded in ancient zircons indicates source domains of static southern highland crust punctuated by episodic impact modification

composition and petrology of hed polymict breccias the regolith of 4 vesta the polymict breccias of the howardite eucrite and diogenite hed clan of meteorites preserve records of regolith processes that occur on vesta their putative home world these breccias howardites polymict eucrites and polymict diogenites are impact engendered mixtures of diogenites and eucrites the compositions of polymict breccias can be used to constrain the lithologic diversity of the vestan crust and the excavation depths of these materials we have done petrological and compositional studies of multiple samples of 5 polymict eucrites and 28 howardites to investigate these issues older analyses were done on samples of approx 0 5 gram mass by inaa newer analyses on samples of approx 5 gram mass by xrf and icp ms we estimate the percentage of eucritic material poem of polymict breccias by comparing their al and or ca contents to those of average basaltic eucrite and diogenite our samples have poem ranging from 28 to 98 adding two polymict diogenites from extends the range to poem 10 one hypothesis is that ancient well mixed vestan regolith has poem approx 67 and has a higher content of admixed impactor material several of our howardites have poem of 59 74 al and or ca contents 10 of poem 67 about a third have ni contents 300 micro g g suggesting they contain 2 chondritic material cm and or cr these may be regolithic howardites only one lew 85313 contains ne dominated by a solar wind sw component pca 02066 is dominated by impact melt material of polymict parentage and petrologically appears to be a mature regolith breccia yet it does not contain sw ne gro 95602 falls within the poem window contains sw ne yet has a ni content of 193 micro g g its petrologic characteristics suggest it was formed from immature regolith no polymict breccia clasts no glass trace element characteristics of the polymict breccias demonstrate the dominance of main group eucrites as the basaltic component mixing diagrams of zr nb ba hf and ta with al show no evidence for a significant contribution from stannern trend eucrites an exception is polymict eucrite lew 86001 poem 92 which is dominated by stannern trend basaltic debris howardite lap 04838 poem 84 has higher incompatible trace concentrations than other polymict breccias excluding lew 86001 and either contains a stannern trend basaltic component or has a significant contributions from evolved eucrites like nuevo laredo

age of a eucrite clast from the bholghati howardite 39ar 40ar rb sr and sm nd investigations of the large eucrite clast 1 studied by the bholghati consortium show that it crystallized from a melt 4 51 ga ago the crystallization age is given most precisely by a sm nd internal isochron of 4 510 0 034 ga 2 error limits for 147sm 0 00654 ga 1 142nd144nd measurements show that the clast contained live 146sm at the time of crystallization a solar system initial 146sm144sm0 0 00431 0 0039 0 0026 at 4 555 ga ago can be calculated from a 146sm 142nd isochron and the age of the clast alternatively using 146sm144sm 0 0 0045 as previously reported in the literature a 146sm142nd formation interval of 0 05 0 12 0 08 ga can be calculated which is concordant with the 147sm 143nd isochron age and in agreement with pu u xe and pu nd xe formation intervals reported in a companion consortium paper the initial 143nd144nd ind of the clast was ind 0 505958 50 2 error limits normalized to 146nd 144nd 0 724140 and is consistent with the chur reference value for evolution in a source having chondritic relative ree abundances prior to magma generation however when interlaboratory bias is considered the data are also permissive of a lree depleted source as suggested in a companion consortium paper a primary rb sr isochron yields an age of 4 54 0 06 ga 2 error limits for 87rb 0 01402 ga 1 in agreement with the more precise sm nd age the initial 87sr86sr isr of the clast was isr 0 699006 21 and was the same within error limits as isr previously determined for a pristine eucrite clast from polymict eucrite y75011 compatible with a common parent body the 39ar 40ar data and some of the rb sr data show that bholghati was affected by a major thermal event 2 3 ga ago and also provide weak evidence for a minor thermal event 1 ga ago the age and isotopic systematics of the clast are consistent with those of other eucrites and support the widely held assumption of a common parent body for howardites and eucrites the isotopic investigations of polymict eucrites and howardites point to a prolonged cratering record on the howardite eucrite diogenite hed parent body and suggest that it survived the cataclysm affecting the moon 3 8 4 0 ga ago

mining induced seismicity seismic measurement using multiplet approach and numerical modeling the volume of influence of mining works is essentially determined from in situ observations field measurements particularly surface subsidence measurements as well as from numerical investigations seismic monitoring is the primary requirement for mining in rock burst environment a micro seismic network is systematically used to monitor coal extraction in the provence colliery south eastern france a significant database of seismic events is now available a further advancement in this sequence was added by the development of doublets technique or multiplet selections the technique uses with the database to identify families of seismic events and to work out the relative locations of these events the analysis of location of these multiplet families showed a particular spatial distribution locations of the epicentre follow the direction in which the coalface is advancing numerical models are used in the paper to show the overstress distribution by comparing the seismic activity and results of the numerical modeling of the advancing coalface with observations a close correlation can be established between the location of seismic activity and induced stresses in the ground surface of the working areas by combining micro seismic monitoring with the numerical modeling the volume of influence of long wall mines is determined results show that such a coupling can be an efficient way for detecting areas subjected to rock burst hazards this can also prove to be a powerful tool for assisting the planning of underground workings in complex geological and mining conditions

petrography and composition of martian regolith breccia meteorite northwest africa 7475 the northwest africa nwa 7475 meteorite is one of the several stones of paired regolith breccias from mars based on petrography oxygen isotope mineral compositions and bulk rock compositions its inventory of lithic clasts is dominated by vitrophyre impact melts that were emplaced while they were still molten other clast types include crystallized impact melt rocks evolved plutonic rocks possible basalts contact metamorphosed rocks and siltstones impact spherules and vitrophyre shards record airborne transport and accreted dust rims were sintered on most clasts presumably during residence in an ejecta plume the clast assemblage records at least three impact events one that formed an impact melt sheet on mars 4 4 ga ago a second that assembled nwa 7475 from impactites associated with the impact melt sheet at 1 7 1 4 ga and a third that launched nwa 7475 from mars 5 ma ago mildly shocked pyroxene and plagioclase constrain shock metamorphic conditions during launch to 5 and 15 gpa the mild postshock heating that resulted from these shock pressures would have been insufficient to sterilize this water bearing lithology during launch magnetite maghemite and pyrite are likely products of secondary alteration on mars textural relationships suggest that calcium carbonate and goethite are probably of terrestrial origin yet trace element chemistry indicates relatively low terrestrial alteration comparison of mars odyssey gamma ray spectrometer data with the fe and th abundances of nwa 7475 points to a provenance in the ancient southern highlands of mars gratteri crater with an age of 5 ma and an apparent diameter of 6 9 km marks one possible launch site of nwa 7475

exsolution and shock microstructures of igneous pyroxene clasts in the northwest africa 7533 martian meteorite northwest africa nwa 7533 is a martian regolith breccia this meteorite and its pairings offers a good opportunity to study near surface processes that occurred on early mars here we have conducted a transmission electron microscope study of medium and coarse grained a few tens to hundreds of micrometers ca rich pyroxene clasts in order to define their thermal and shock histories the pyroxene grains have a high temperature magmatic origin as revealed by the well developed pigeonite augite exsolution microstructure exsolution lamella characteristics composition thickness and spacing indicate a moderately slow cooling some of the pyroxene clasts display evidence for local decomposition into magnetite and silica at the submicron scale this phase decomposition may have occurred at high temperature and occurred at high oxygen fugacity at least 2 3 log units above the qfm buffer after the formation of the exsolution lamellae this corresponds to oxidizing conditions well above typical martian magmatic conditions these oxidizing conditions seem to have prevailed early and throughout most of the history of nwa 7533 the shock microstructure consists of 100 mechanical twins which have accommodated plastic deformation other pyroxene shock indicators are absent compared with snc meteorites that all suffered significant shock metamorphism nwa 7533 appears only mildly shocked the twin microstructure is similar from one clast to another suggesting that the impact which generated the 100 twins involved the compacted breccia and that the pyroxene clasts were unshocked when they were incorporated into the nwa 7533 breccia

the role of geologic structure and stress in triggering remote seismicity in creighton mine sudbury canada a study was undertaken at the creighton mine near sudbury canada to investigate the relationships between geologic structure stress and seismicity creighton mine hosts numerous families of shear zones and experiences frequent microseismic and often macroseismic events underground structural mapping as well as microstructural and kinematic analysis are used to characterize faults fault geometries are then compared to those derived from seismic event focal mechanisms focal mechanism information is next used for stress inversion to obtain estimates of in situ principal stresses for three spatial clusters of events on the 7400 foot 2256 m level fault characteristics are then integrated into a numerical discontinuum model of the 7400 foot level of the mine to examine the distribution of stresses in the study volume the synthesis of these elements is used to determine the sources of seismicity within the deepest levels of the mine the major shear zones within the mine have not been found to contribute to seismicity via fault slip but do influence the flow of stress around the main excavation an anomalous cluster of microseismic events is postulated to be a result of induced stresses from mine development on deeper levels

persistent earthquake clusters and gaps from slip on irregular faults clustering of earthquakes at various spatial scales is the result of a heterogeneous distribution of stresses and at least for intermediate magnitude earthquakes areas that are quiet at present are likely to remain so in the future

deformation forecasting and stability analysis of large scale underground powerhouse caverns from microseismic monitoring abstract to assess the stability of the underground powerhouse caverns and analyse the failure mechanism of the surrounding rock mass at the baihetan hydropower station in southwest china a high resolution microseismic ms monitoring system was implemented in the left bank underground powerhouse caverns based on the temporal and spatial distribution of ms events the correlation between ms activities and construction was established and three damage regions for the surrounding rock mass during excavation were identified ms clusters were found to occur most often in stress concentration regions of the underground powerhouse caverns and to result from various factors including excavation induced unloading and geological structure activation the seismic source parameters i e moment magnitudes and s wave to p wave energy ratios e s e p of the three ms clusters demonstrate the different failure modes and risks of the surrounding rock mass the temporospatial evolution of the ms activities apparent stress and cumulative apparent volume in localized rock mass during the period of a typical large deformation were used to develop a comprehensive analytical method for forecasting the deformation of the surrounding rock mass thus this comprehensive analytical method which incorporates ms monitoring conventional monitoring geological survey and construction is promising for identifying the damage zones and forecasting the macro deformation of the surrounding rock mass in underground powerhouse caverns subjected to excavation

evolution of the lunar crust sims study of plagioclase from ferroan anorthosites abstract the lunar crust down to a depth of 65 km is composed of older 4 5 ga ferroan anorthosites and younger 4 43 4 17 ga mg suite lithologies which include dunites troctolites and norites the anorthosites are generally inferred to represent floating cumulates in a lunar magma ocean possible depth 800 km moon s radius 1 738 km the cumulates that are inferred to be located near the base of the magma ocean are dominantly olivine and pyroxene the last dregs of the magma ocean are enriched in incompatible elements and have been named kreep k rare earth elements p kreep formed in this manner is probably concentrated near the crust mantle boundary at 70 km depth we are attempting to characterize melts parental to ferroan anorthosites and mg suite norites by analyzing rees la ce nd sm eu dy er yb and ba sr and y in their cumulus plagioclase if the cumulus grains have not been compromised by postcrystallization effects and if we know the relevant mineral melt partition coefficients ds we can invert the trace element data for plagioclase to parental melt compositions melts parental to ferroan anorthosites are estimated to contain ree at concentrations ten to fifty times chondrites melts parental to the earlier crystallizing anorthosites lower ree have virtually no eu anomaly while melts parental to later crystallizing anorthosites higher ree have small negative eu anomalies this is qualitatively consistent with the fractionation of eu relative to other ree by crystallization of plagioclase with large positive eu anomalies melts parental to the mg suite have much higher total ree and very large negative eu anomalies the characteristics of mg suite norite parental magmas may have been derived by the assimilation of kreep near the crust mantle boundary by mg rich basaltic melts formed deeper in the cumulate pile or near the contact between the lower cumulate horizons of the magma ocean and primitive unprocessed lunar mantle 800 km

space time clustering of seismic events and hazard assessment in the zabrze bielszowice coal mine poland the results of the statistical analysis of seismic activity recorded in the zabrze bielszowice coal mine in poland are presented in this article the monitoring was conducted by a small network consisting of four triaxial geophones deployed in vertical holes in the roof for over 1000 seismic events recorded during the two month s experiment the location of sources was realized the seismic sources were mostly located ahead of the active face of the longwall since the first day of the monitoring cluster analysis was sequentially performed for increasing number of sources at the end of the experiment 31 clusters were identified they consisted of different numbers of events and were separated in space about 40 of the events were not included in the clusters for each large cluster hazard analysis was separately performed the hazard function evaluated for the largest cluster was compared with hypocenters of high energy tremors e 1000 j recorded by the geophones in that area for some cases recorded tremors occurred after an abrupt decrease of hazard function but only one of them was located in the vicinity of the appropriate cluster we concluded that for the analyzed cluster a correlation between evaluated hazard function and time occurrences of the high energy tremors existed except for one case there is no space correlation between analyzed clusters and high energy tremors

ancient geologic events on mars revealed by zircons and apatites from the martian regolith breccia nwa 7034

classification of igneous rocks analyzed by chemcam at gale crater mars abstract several recent studies have revealed that mars is not a simple basalt covered planet but has a more complex geological history in gale crater on mars the curiosity rover discovered 59 igneous rocks this paper focuses on their textures acquired from the cameras such as mahli and mastcam and their geochemical compositions that have been obtained using the chemcam instrument light toned crystals have been observed in most of the rocks they correspond to feldspars ranging from andesines oligoclases to anorthoclases and sanidines in the leucocratic vesiculated rocks darker crystals observed in all igneous rocks except the leucocratic vesiculated ones were analyzed by libs and mainly identified as fe rich pigeonites and fe augites iron oxides have been observed in all groups whereas f bearing minerals have been detected only in few of them from their textural analysis and their whole rock compositions all these 59 igneous rocks have been classified in five different groups from primitive rocks i e dark aphanitic basalts basanites trachybasalts tephrites and fine coarse grained gabbros norites to more evolved materials i e porphyritic trachyandesites leucocratic trachytes and quartz diorites the basalts and gabbros are found all along the traverse of the rover whereas the felsic rocks are located before the kimberley formation i e close to the peace vallis alluvial fan deposits this suggests that these alkali rocks have been transported by fluvial activity and could come from the northern rim of the crater and may correspond to deeper strata buried under basaltic regolith sautter et al 2015 some of the basaltic igneous rocks are surprisingly enriched in iron presenting low mg similar to the nakhlite parental melt that cannot be produced by direct melting of the dreibus and wanke 1986 martian primitive mantle the basaltic rocks at gale are thus different from gusev basalts they could originate from different mantle reservoirs or they could have undergone a more extensive fractional crystallization gale basaltic rocks could have been the parental magma of residual liquid extending into alkali field towards trachyte composition as magma fractionated under anhydrous condition on its way to the surface before sub adiabatic ascent

characteristics of wind blown sand on gobi mobile sand surface the characteristics of wind blown sand on gobi mobile sand surface have been investigated through field observation and wind tunnel experiments on moving sand surface the pattern of wind speed profile in sand flow follows the power function overline u az b and its power exponent is about 0 20 while on gobi surface due to collision of sand grains with gravels the structure of sand flow differs from that on moving sand surface which decreases exponentially with height the height of blown sand activities on gobi surface is mainly concentrated below 20 cm in addition the structure of sand flow can reach a peak at a certain height and increases with inlet wind velocity

microseismic frequency spectrum evolutionary rule of rockburst triggered by roof fall abstract strong rockburst disaster in deep coal mines is easily triggered by the higher static stress of mining coal seam and the dynamic stress wave disturbance generated by hard and thick roof fall revealing the frequency spectrum evolutionary rule of microseismic ms signals before and after roof fall is a very important issue for evaluating and forecasting rockburst danger by experimental tests for combined coal and rock samples rockburst failure and in situ measurements in a strong rockburst coal mine the frequency spectrum evolutionary rule and precursory characters were analyzed in detail the following conclusions were drawn 1 precursory ms signals show the elevated energy and events lower frequency and trend of spectrum moving to low frequency band 2 mainshock signals of rockburst are characterized by maximum amplitude vibration velocity wider spectrum and higher predominant frequency and 3 aftershock signals are characterized by the sudden decreasing amplitude highest predominant frequency and trend of spectrum moving to high frequency band

ground motions induced by mining seismic events with different focal mechanisms abstract it is essential to quantify the ground motions induced by seismic events with different focal mechanisms in underground mine to quantitatively calculate the induced ground motions we expressed the motions as the convolution of the seismic source and the wave propagation path using seismological method firstly we investigated the theoretical ground motion patterns using four idealized focal mechanisms results show that the pure compressional failure source and the pure tensional failure source induced the same ground motion patterns the vibrations they induced attenuate extremely fast the pure shear failure source shows closely azimuth related pattern with four quadrants around the source the pure explosive failure source induces vibrations attenuating toward all directions away from the source but the vibrations are not attenuated gradually with the increasing distance then we investigated the ground motions under complicated focal mechanisms using recorded fault slip events cavity collapse events and tensional failure events the fault slip events show a four quadrants ground motion distribution in the horizontal plane and a two quadrants distribution in the vertical plan but the cavity collapse events show a two quadrants distribution in the horizontal plane and a four quadrants distribution in the vertical plane it is concluded that the induced ground motion at a certain location is controlled by the dual effects of the azimuth and the source focal mechanism as well as the distance and the source magnitude

focal mechanism determination for microseismic events and its application to the left bank slope of the baihetan hydropower station in china determination of the focal mechanism of microseismic ms events occurring in rock engineering plays an important role in hazard evaluation and forecasting a complete moment tensor inversion strategy is proposed to analyse ms events recorded at the left bank slope of the baihetan hydropower station southwest of china a coordinate system rotation procedure is adopted to construct a reliable 1 d velocity model for the green s function calculation the layered velocities are accurately determined by inversion using the recorded blasts and geological survey results to reduce the influence of noise contamination only the waveforms in the frequency range of 60 150 hz are analysed before moment tensor inversion a relocation procedure using an eikonal solver is performed to accurately locate seismic sources a robust global optimization routine is applied to maximize the objective function thereby determining the focal mechanism the proposed method is tested using a hypothetical seismic source in the sensor network used for monitoring ms events in the rock slope the synthetic test shows that the method is robust and can provide accurate solutions when subject to location error noise contamination and velocity model disturbances the analysis results of the 12 ms events show that the moment tensors characterizing ms events present significant non double couple components and that the majority of the ms events have a strike orientation in accordance with that of the main staggered zones

heterogeneous distribution of h2o in the martian interior implications for the abundance of h2o in depleted and enriched mantle sources we conducted a petrologic study of apatite within 12 martian meteorites including 11 shergottites and one basaltic regolith breccia these data were combined with previously published data to gain a better understanding of the abundance and distribution of volatiles in the martian interior apatites in individual martian meteorites span a wide range of compositions indicating they did not form by equilibrium crystallization in fact the intrasample variation in apatite is best described by either fractional crystallization or crustal contamination with a cl rich crustal component we determined that most martian meteorites investigated here have been affected by crustal contamination and hence cannot be used to estimate volatile abundances of the martian mantle using the subset of samples that did not exhibit crustal contamination we determined that the enriched shergottite source has 36 73 ppm h2o and the depleted source has 14 23 ppm h2o this result is consistent with other observed geochemical differences between enriched and depleted shergottites and supports the idea that there are at least two geochemically distinct reservoirs in the martian mantle we also estimated the h2o cl and f content of the martian crust using known crust mantle distributions for incompatible lithophile elements we determined that the bulk martian crust has 1410 ppm h2o 450 ppm cl and 106 ppm f and cl and h2o are preferentially distributed toward the martian surface the estimate of crustal h2o results in a global equivalent surface layer gel of 229 m which can account for at least some of the surface features on mars attributed to flowing water and may be sufficient to support the past presence of a shallow sea on mars surface

record of the ancient martian hydrosphere and atmosphere preserved in zircon from a martian meteorite how the atmosphere hydrosphere and surface materials interacted on early mars is poorly understood oxygen isotopic composition of zircon grains in a martian meteorite reveals a prolonged history of exchange between martian regolith and atmosphere

regolith breccia northwest africa 7533 mineralogy and petrology with implications for early mars northwest africa 7533 a polymict martian breccia consists of fine grained clast laden melt particles and microcrystalline matrix while both melt and matrix contain medium grained noritic monzonitic material and crystal clasts the matrix also contains lithic clasts with zoned pigeonite and augite plus two feldspars microbasaltic clasts vitrophyric and microcrystalline spherules and shards the clast laden melt rocks contain clump like aggregates of orthopyroxene surrounded by aureoles of plagioclase some shards of vesicular melt rocks resemble the pyroxene plagioclase clump aureole structures submicron size matrix grains show some triple junctions but most are irregular with high intergranular porosity the noritic monzonitic rocks contain exsolved pyroxenes and perthitic intergrowths and cooled more slowly than rocks with zoned pyroxene or fine grain size noritic material contains orthopyroxene or inverted pigeonite augite calcic to intermediate plagioclase and chromite to cr bearing magnetite monzonitic clasts contain augite sodic plagioclase k feldspar ti bearing magnetite ilmenite chlorapatite and zircon these feldspathic rocks show similarities to some rocks at gale crater like black trout mara and jake m the most magnesian orthopyroxene clasts are close to alh 84001 orthopyroxene in composition all these materials are enriched in siderophile elements indicating impact melting and incorporation of a projectile component except for ni poor pyroxene clasts which are from pristine rocks clast laden melt rocks spherules shards and siderophile element contents indicate formation of nwa 7533 as a regolith breccia the zircons mainly derived from monzonitic melt rocks crystallized at 4 43 0 03 ga humayun et al 2013 and a 147sm 143nd isochron for nwa 7034 yielding 4 42 0 07 ga nyquist et al 2016 defines the crystallization age of all its igneous portions the zircon from the monzonitic rocks has a higher 17o than other martian meteorites explained in part by assimilation of regolith materials enriched during surface alteration nemchin et al 2014 this record of protolith interaction with atmosphere hydrosphere during regolith formation before melting demonstrates a thin atmosphere a wet early surface environment on mars and an evolved crust likely to have contaminated younger extrusive rocks the latest events recorded when the breccia was on mars are resetting of apatite much feldspar and some zircons at 1 35 1 4 ga bellucci et al 2015 and formation of ni bearing pyrite veins during or shortly after this disturbance lorand et al 2015

case history of a slip type rockburst first motion analyses of digital seismic records and an assessment of damage provided conclusive evidence that a fault slip source mechanism was responsible for a richter magnitude 2 that occurred at the lucky friday mine on april 13 1990 this event was the first time that movement along an argillite bed had been observed after the macroseismic monitoring system had been installed the physical evidence of a shear slip type failure established confidence in using double couple first motion analyses for the macroseismic system the u s bureau of mines is conducting this research as part of its mission to enhance safety by reducing rockburst hazards in mines