distinguishing potential sources of arsenic released to groundwater around a fault zone containing a mine site arsenic as contamination in groundwater in mineralized areas typically results from the oxidation of as rich sulfide minerals in aquifers from hydrothermal alteration of geothermal systems or as a result of anthropogenic influences such as mining activity the primary goal of this study was to determine the spatial and temporal variance in as concentrations in shallow groundwater in a mineralized area and to identify the main as source controlling the concentration patterns to this end a combination of a geostatistical technique for space time modeling of as concentrations and a numerical simulation which models the transport of as in groundwater is implemented a study site in north sulawesi sulawesi island indonesia was selected as it was suitable for investigating the importance of fault lines and metal mining on as contamination initially stable isotope analysis was used to ascertain the groundwater source and the mixing mechanism of the shallow and deep groundwater geostatistical modeling revealed consistent general patterns of as concentrations during the past 10 years with high concentrations found along a nw se axis by matching the geostatistical results with the distributions of as concentrations obtained through transport modeling the deep seated hydrothermal system along the fault zone was found to be the major as source wastewater from the mine was also observed to be a local as source another important influence on the as concentration pattern was a river which acted as a boundary to separate the groundwater systems into two regions

identifying groundwater arsenic contamination mechanisms in relation to arsenic concentrations in water and host rocks leaching and oxidation of high arsenic as host rocks tend to be induced by circulation of deep geothermal waters which increase as concentration in shallow groundwater the purpose of this study is to identify the mechanism of groundwater as contamination in relation to leaching and oxidation along the border between the south minahasa and bolaang mongondow districts north sulawesi indonesia this region contains miocene sedimentary rock hosted disseminated gold deposits associated with hydrothermal alteration in a fault zone abnormally high as concentrations were observed in hot and cold springs and in surrounding shallow groundwater for a total mineralization area of 8 10 km2 two methods were adopted in this study 1 microscopic and spectroscopic analyses of rock samples for mineral identification and 2 geostatistics for spatial modeling of as concentrations in groundwater jarosite was identified as the chief fill mineral in rock defects cracks and pores the presence of this mineral may indicate release of as into the environment as can occur as an alteration product derived from oxidation and leaching of pyrite as rich pyrite or sulfide minerals by geothermal waters moreover as concentrations in groundwater were estimated using geostatistics for spatial modeling the co kriging map identified local anomalies in groundwater as concentrations over the permissible limit 10 ppb such anomalies did not appear through ordinary kriging integration of the results indicates that as contamination in shallow groundwater probably is controlled by heterogeneous distributions of jarosite and variations in intensity and extent of hydrothermal activities

a survey of clasts and large chondrules in ordinary chondrites we report the results of a survey of clasts and large 5 mm chondrules macrochondrules within the 833 ordinary chondrites of the natural history museum collection thirty six macrochondrules and 24 clasts were identified and studied macrochondrules have textures and mineral assemblages like normal chondrules and so share a common origin clasts show evidence for fracturing from larger bodies and can be classified as either 1 chemically fractionated if they have major and trace element compositions differing substantially from most chondrules and clasts 2 impact melt clasts if they have microporphyritic textures and signs that indicate they are derived from shock melted chondritic material 3 microporhyritic clasts if they are similar to the last category but lack evidence for derivation through shock melting or 4 indeterminate clasts forming a diverse class that includes all those clasts that do not fit into the other categories

the l3 6 chondritic regolith breccia northwest africa nwa 869 ii noble gases and cosmogenic radionuclides abstract we measured cosmogenic radionuclides and noble gases in the l3 6 chondrite breccia northwest africa nwa 869 one of the largest meteorite finds from the sahara concentrations of 10be 26al and 36cl in stone and metal fractions of six fragments of nwa 869 indicate a preatmospheric radius of 2 0 2 5 m the 14c and 10be concentrations in three fragments yield a terrestrial age of 4 4 0 7 kyr whereas two fragments show evidence for a recent change in shielding most likely due to a recent impact on the nwa meteoroid approximately 105 yr ago that excavated material up to approximately 80 cm deep and exposed previously shielded material to higher cosmic ray fluxes this scenario is supported by the low cosmogenic 3he 21ne ratios in these two samples indicating recent loss of cosmogenic 3he most nwa samples except for clasts of petrologic type 4 6 contain significant amounts of solar ne and ar but are virtually free of solar helium judging from the trapped 4he 20ne ratio of approximately 7 trapped planetary type kr and xe are most clearly present in the bulk and matrix samples where abundances of 129xe from decay of now extinct 129i are highest cosmogenic 21ne varies between 0 55 and 1 92 10 8 cm3 stp g 1 with no apparent relationship between cosmogenic and solar ne contents low cosmogenic 22ne 21ne c ratios in solar gas free specimens are consistent with irradiation in a large body combined 10be and 21ne concentrations indicate that nwa 869 had a 4 cosmic ray exposure cre age of 5 1 myr whereas elevated 21ne concentrations in several clasts and bulk samples indicate a previous cre of 10 30 myr on the parent body most probably as individual components in a regolith unlike many other large chondrites nwa 869 does not show clear evidence of cre as a large boulder near the surface of its parent body radiogenic 4he concentrations in most nwa 869 samples indicate a major outgassing event approximately 2 8 gyr ago that may have also resulted in loss of solar helium

fast 3d target oriented reverse time datuming imaging of subsalt sediments is a challenge for traditional migration methods such as kirchhoff and one way waveequation migration consequently the more accurate twowaymethodofreverse timemigrationrtmispreferredfor subsalt imaging but its use can be limited by high computation cost to overcome this problem a 3d target oriented reverse time datuming rtd method is presented which can generate redatumed data economically in target areas beneath complex structures such as salt domes the redatumed datainthetargetareathencanbemigratedinexpensivelyusing a traditional migration method if the target area is much smaller than the acquisition area computation costs are reduced significantly by the use of a novel bottom up strategy to calculate the extrapolated green s functions target orientedrtdistestedon2dand3dseg eagesyntheticdata sets and a 3d field data set from the gulf of mexico results show that target oriented rtd combined with standard migration can image sediments beneath complex structures accurately with much less calculation effort than full volume rtm the requirement is that the area over the target zone is smallerthanthatoftheacquisitionsurvey

penecontemporaneous metamorphism fragmentation and reassembly of ordinary chondrite parent bodies the occurrence and proportions of petrologic types among ordinary chondrites have been explained by internal heating of three h l ll parent asteroids of 100 km radius e g miyamoto et al 1982 this conventional onion shell model predicts an inverse relation between petrologic type and metallographic cooling rate but none has been observed scott and rajan 1981 devised a metamorphosed planetesimal model to explain this discrepancy whereby metamorphism occurs in planetesimals a few kilometers in radius which then accrete to form r 100 km parent bodies metallographic cooling rates are then controlled by burial depth thermal and collisional constraints on the metamorphosed planetesimal model are examined here and the model is found to be applicable only to highly insulating 26al rich planetesimals that can accrete intact without being shattered by impact or to shattered planetesimals whose fragments are not widely dispersed over the target surface an alternative model is presented here in which onion shell parent bodies are collisionally fragmented during metamorphism and then gravitationally reassembled if reassembly times are short days then metallographic cooling rates would be determined by burial depth in the reaccreted parent body this model unlike previous ones can explain both coherent and incoherent cooling rates of breccia clasts by collisions during or after metamorphism respectively

brecciation among 2280 ordinary chondrites constraints on the evolution of their parent bodies abstract after accretion of meteorite parent bodies larger and smaller collisions have led to significant modifications of these bodies involved processes include excavation of material thermal metamorphism melting mixing of different materials re accretion and re lithification all these processes can be repeated several times in this study polished thin sections pts of 2280 chondrites 1193 h 947 l and 140 ll chondrites were investigated in order to obtain the abundance of brecciated rocks among the ordinary chondrites in addition we have determined the abundance and characteristics of shock vein bearing h l and ll chondrites and of impact melt rock clasts we also recognized xenolithic components based on o isotope studies noble gas data were considered in order to detect regolith breccias and to discuss late impact histories the investigation of 2280 samples shows that 23 276 of 1193 of the h chondrites 23 220 of 947 of the l chondrites and 79 110 of 140 of the ll chondrites are brecciated considering the heavily brecciated ll chondrites in 63 of the 140 chondrites 45 shock veins were clearly detected 57 of these 63 chondrites are brecciated rocks the investigation of the h and l chondrites has shown that about 26 310 of 1193 of the h chondrites and 40 379 of 947 of the l chondrites contain shock veins in our data set 20 of the h chondrites and 8 3 of the ll chondrites but only 3 0 of the l chondrites contain solar noble gases remarkably about 62 of all brecciated h chondrites with noble gases analyzed contain solar noble gases compared to only around 11 and 10 of the brecciated l and ll chondrites respectively the identification of xenolithic clasts e g ci cm and ureilite like lithologies in primitive type 3 chondrites indicates simultaneous accretion of clasts and chondrules these clasts must have been formed early within the first 2 ma on subsequently destroyed precursor first generation parent bodies the formation of complex breccias witnesses the collisions between asteroids of very different lithologies and heritage although the onion shell configuration of primordial parent bodies is necessary in order to form the chondrites with different degrees of metamorphic overprint petrologic types 3 6 subsequent catastrophic fragmentation and reassembly to form asteroids with a rubble pile structure are required to explain certain features discussed in this work however distinct peaks in the cosmic ray exposure age distributions indicate that not too many impacts in the last 100 ma were responsible to deliver the majority of the ordinary chondritic meteoroids to earth yet this certainly does not tell anything about the number of last generation parent bodies that exist in the asteroid belt since s type asteroids are the most abundant type of asteroid in the inner main belt and thought to be the parent bodies of ordinary chondrites

paired renazzo type cr carbonaceous chondrites from the sahara ten chondrites with chemical and mineralogical similarities to the carbonaceous chondrite renazzo were recovered at two locations of the sahara acfer 059 087 097 114 139 186 187 209 270 and el djouf 001 although the el djouf location is more than 500 km away from the acfer location all samples appear to result from a single fall based on chemical and petrographic similarities and supported by light element stable isotope geochemistry noble gas record and similar 26al contents the acfer el djouf meteorite is classified as a cr renazzo type carbonaceous chondrite this group presently comprises three non antarctic members al rais renazzo acfer el djouf and five antarctic meteorites the major lithological components of the acfer el djouf meteorite are large chondrules up to 1 cm in size mean diameter 1 0 0 6 mm chondrule and mineral fragments ca al rich inclusions feni metal about 8 10 vol and dark inclusions embedded in a fine grained fragment bearing groundmass mineral compositions of the ten acfer el djouf samples are similar to those of other cr chondrites most of the ca al rich inclusions are below 300 m in size and rich in melilite and spinel in some cais the rare phase caal4o7 is dominant fo rich cr bearing olivine fa0 4 and enstatite fs0 4 are the major phases of the chondrite the meteorite is mildly shocked with a shock stage of s2 indicating a peak shock pressure of 5 10 gpa for the bulk meteorite the oxygen isotopic compositions and carbon and nitrogen stable isotope geochemistry of the acfer el djouf samples are very similar to those of the other cr type chondrites the major element composition of the acfer el djouf meteorite is indistinguishable from cr chondrites when compared to renazzo the acfer el djouf samples however have systematically lower contents of the moderately volatile elements zn ga as au sb and se and the highly volatile elements br c and n this is thought to reflect primary differences between renazzo and the acfer el djouf meteorite

clues to the origin of metal in almahata sitta el and eh chondrites and implications for primitive e chondrite thermal histories abstract enstatite e chondrites are a group of texturally highly variable meteorites formed under strongly reducing conditions giving rise to unique mineral and chemical characteristics e g high abundances of various sulfides and si bearing metal in particular the abundant metal comprises a range of textures in e chondrites of different petrologic type but available in situ siderophile trace element data on metal are limited nine samples of e chondrites from the recent almahata sitta fall one eh3 two el3 4 two el6 two el impact melt rocks imr two eh imr were investigated in this study in addition to st mark s eh5 and grein 002 el4 5 with a focus on the nature of their metal constituents special attention was given to metal silicate intergrowths mssi that occur in many primitive e chondrites which have been interpreted as post accretionary asteroidal impact melts or primitive nebular condensates this study shows that siderophile trace element systematics in e chondrite metal are independent of petrologic type of the host rock and distinct from condensation signatures three basic types of siderophile trace element signatures can be distinguished indicating crystallization from a melt thermal equilibration upon metamorphism complete melting and exsolution of schreibersite perryite sulfide textural and mineral chemical constraints from el3 4s are used to evaluate previously proposed formation processes of mssi impact melting vs nebular condensation and elucidate which other formation scenarios are feasible it is shown that post accretionary in situ impact melting or metallic melt injection forming mssi on the thin section scale and nebular condensation are unlikely formation processes this leads to the conclusion that mssis are pre accretionary melt objects that were formed during melting processes prior to the accretion of the primitive e chondrites the same can be concluded for metal nodules in the eh3 chondrite examined the pre accretionary origin of mssis in e chondrites is consistent with a growing body of evidence for early differentiation followed by impact disruption of early formed planetesimals in all major chondrite types

geo genic arsenic contamination in the kerman cenozoic magmatic arc kerman iran implications for the source identification and regional analysis kerman cenozoic magmatic arc kcma is located in the southeastern part of the central iranian volcano plutonic copper belt arsenic contamination from geo genic source is one of the most important environmental concerns in this area the main objective of this study was to determine the role of geothermal related activities in the arsenic contamination for this purpose the old and active geological indicators of the geothermal activities were investigated through the quaternary travertine deposits and the present hydrothermal warm springs respectively results showed that arsenic is highly concentrated ranged mainly from 12 400 to 90 500 mg kg in the reddish brown deposits of the travertine rocks arsenic showed geochemical association with co cu mo sb tl se fe and mn in these samples yukonite ca7fe3 12 aso4 10 oh 2015h2o a rare ca ferric arsenate hydrous mineral was the only as bearing mineral identified in the reddish brown deposits of the travertine rocks arsenic concentration in the hydrothermal warm springs 38 c ranged from 15 900 to 30 500 g l the dominant form was as h3aso30 hydrothermal contaminated waters also were characterized by na cl type and high values of ec 11 400 s cm tds 8300 mg l b 42 700 g l li 3000 g l fe 900 g l sb 82 8 g l and si 47 000 g l and natural anomalies of cs mn mo rb se and tl the obtained hydro geochemical results are similar to those reported in the literature for worldwide hydrothermal waters although natural attenuation processes such as adsorption co precipitation or mixing dilution reduce most of the arsenic contamination from hydrothermal source but some urban and rural communities are still depending on the arsenic contaminated waters with arsenic concentrations higher than recommended values for drinking or irrigation a subject that increases the risk of arsenic related diseases in some areas of the kerman province

microchondrule bearing clast in the piancaldoli ll3 meteorite a new kind of type 3 chondrite and its relevance to the history of chondrules in the piancaldoli ll3 chondrite we found a mm sized clast containing 100 chondrules 0 2 64 m in apparent diameter much smaller than any previously reported that are all of the same textural type radial pyroxene fs1 17 this clast like other type 3 chondrites has a fine grained ferich opaque silicate matrix sharply defined chondrules abundant low ca clinopyroxene and minor troilite and si and cr bearing metallic fe ni however the very high modal matrix abundance 63 8 vol unique characteristics of the chondrules and absence of microscopically observable olivine indicate that the clast is a new kind of type 3 chondrite most chondrules have feo rich edges and chondrule size is inversely correlated with chondrule core feo concentration the first reported correlation of chondrule size and composition chondrules acquired fe by diffusion from fe rich matrix material during mild metamorphism possibly before final consolidation of the rock microchondrules those chondrules 100 m in diameter are also abundant in another new kind of type 3 chondrite clast in the rio negro l chondrite regolith breccia in other type 3 chondrite groups microchondrule abundance appears to be anticorrelated with mean chondrule size viz 0 02 0 04 vol in h and co chondrites and 0 006 vol in l ll and cv chondrites microchondrules probably formed by the same process that formed normal sized droplet chondrules melting of pre existing dustballs because most compound chondrules in the clast and other type 3 chondrites formed by collisions between chondrules of the same textural type we suggest that dust grains were mineralogically sorted in the nebula before aggregating into dustballs the sizes of compound chondrules and chondrule craters which resulted from collisions of similarly sized chondrules while they were plastic indicate that size sorting of dustballs occurred before chondrule formation probably by aerodynamic processes in the nebula we predict that other kinds of type 3 chondrites exist which contain chondrule abundances size ranges and proportions of textural types different from known chondrite groups

imaging spectroscopy earth and planetary remote sensing with the usgs tetracorder and expert systems 1 imaging spectroscopy is a tool that can be used to spectrally identify and spatially map materials based on their specific chemical bonds spectroscopic analysis requires significantly more sophistication than has been employed in conventional broadband remote sensing analysis we describe a new system that is effective at material identification and mapping a set of algorithms within an expert system decision making framework that we call tetracorder the expertise in the system has been derived from scientific knowledge of spectral identification the expert system rules are implemented in a decision tree where multiple algorithms are applied to spectral analysis additional expert rules and algorithms can be applied based on initial results and more decisions are made until spectral analysis is complete because certain spectral features are indicative of specific chemical bonds in materials the system can accurately identify and map those materials in this paper we describe the framework of the decision making process used for spectral identification describe specific spectral feature analysis algorithms and give examples of what analyses and types of maps are possible with imaging spectroscopy data we also present the expert system rules that describe which diagnostic spectral features are used in the decision making process for a set of spectra of minerals and other common materials we demonstrate the applications of tetracorder to identify and map surface minerals to detect sources of acid rock drainage and to map vegetation species ice melting snow water and water pollution all with one set of expert system rules mineral mapping can aid in geologic mapping and fault detection and can provide a better understanding of weathering mineralization hydrothermal alteration and other geologic processes environmental site assessment such as mapping source areas of acid mine drainage has resulted in the acceleration of site cleanup saving millions of dollars and years in cleanup time imaging spectroscopy data and tetracorder analysis can be used to study both terrestrial and planetary science problems imaging spectroscopy can be used to probe planetary systems including their atmospheres oceans and land surfaces

l chondrite asteroid breakup tied to ordovician meteorite shower by multiple isochron 40ar 39ar dating radiochronometry of l chondritic meteorites yields a rough age estimate for a major collision in the asteroid belt about 500 myr ago fossil meteorites from sweden indicate a highly increased influx of extraterrestrial matter in the middle ordovician 480 myr ago an association with the l chondrite parent body event was suggested but a definite link is precluded by the lack of more precise radiometric ages suggested ages range between 450 30 myr and 520 60 myr and can neither convincingly prove a single breakup event nor constrain the delivery times of meteorites from the asteroid belt to earth here we report the discovery of multiple 40ar 39ar isochrons in shocked l chondrites particularly the regolith breccia ghubara that allow the separation of radiogenic argon from multiple excess argon components this approach applied to several l chondrites yields an improved age value that indicates a single asteroid breakup event at 470 6 myr fully consistent with a refined age estimate of the middle ordovician meteorite shower at 467 3 1 6 myr according to a geologic time scale 2004 our results link these fossil meteorites directly to the l chondrite asteroid destruction rapidly transferred from the asteroid belt the increased terrestrial meteorite influx most likely involved larger projectiles that contributed to an increase in the terrestrial cratering rate which implies severe environmental stress

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

almahata sitta fragment ms ch characterization of a new chondrite type abstract among the several hundred mostly small meteorite fragments recovered within the almahata sitta strewn field one fragment ms ch weighing 5 68 g was detected that represents a new type of chondritic meteorite the detection of short lived cosmogenic radionuclides clearly indicates that this chondrite fragment results from a fresh meteorite fall consistent with the almahata sitta event in october 2008 the fundamental mineralogical characteristics of the almahata sitta fragment ms ch can be summarized as follows 1 the almost equilibrated olivine has high fa contents of about 36 mole the fragment is of petrologic type 3 8 0 1 2 the metal abundance of the rock is on the order of 2 5 vol 3 the mean chondrule size has been determined to be roughly 450 m 4 point counting and imaging indicate that the matrix abundance is approximately 45 vol 5 cr spinels have much lower tio2 concentrations than typical spinels within r chondrites 6 calcium aluminum rich inclusions are spinel rich and severely altered having abundant na and or cl rich alteration products spinel also contains significant concentrations of fe and zn 7 magnetites and platinum group element rich phases sulfides tellurides and arsenides characteristic of both r and ck chondrites were not found in fragment ms ch and 8 the mean oxygen isotope composition of three small fragments of almahata sitta ms ch is 17o 4 35 18o 4 94 and 17o 1 76 the oxygen isotopes relate ms ch to r chondrites no established chondrite group having all these characteristics exists

macrochondrules in chondrites formation by melting of mega sized dust aggregates and or by rapid collisions at high temperatures seventy four macrochondrules with sizes 3 mm were studied considering the extraordinary size of the chondrules occasionally achieving a mass of 1000 times and more the mass of a normal sized chondrule the conditions in the formation process must have been somewhat different compared with the conditions for the formation of the common chondrules macrochondrules are typically rich in olivine and texturally similar to specific chondrule types barred radial porphyritic and cryptocrystalline of normal sized chondrules however our studies show that most of the macrochondrules are fine grained or have elongated crystals mostly bo rp and c which lead to the assumption that they were once totally molten and cooled quite rapidly porphyritic chondrules belong to the least abundant types of macrochondrules this distribution of chondrule types is highly unusual and just a reverse of the distribution of chondrule types among the typical sized chondrules in most chondrite groups except for the ch and cb chondrites new chondrule subtypes like radial olivine ro or multi radial mr chondrules are defined to better describe the textures of certain large chondrules macrochondrules may have formed due to melting of huge precursor dust aggregates or due to rapid collisions of superheated melt droplets which led to the growth of large molten spherules in regions with high dust densities and high electrostatic attraction

lithification of gas rich chondrite regolith breccias by grain boundary and localized shock melting we studied the fine grained matrices 150 m of 14 gas rich ordinary chondrite regolith breccias in an attempt to decipher the nature of the lithification process that converted loose regolith material into consolidated breccias we find that there is a continuous gradation in matrix textures from nearly completely clastic class a to highly cemented class c breccias in which the remaining clasts are completely surrounded by interstitial shock melted material we conclude that this interstitial material formed by shock melting in the porous regolith in general the abundances of solar wind implanted 4he and 20ne are inversely correlated with the abundance of interstitial shock melted feldspathic material chondrites with the highest abundance of interstitial melted material class c experienced the highest shock pressures and temperatures and suffered the most extensive degassing it is this interstitial feldspathic melt that lithifies and cements the breccias together those breccias with very little interstitial melt class a are the most porous and least consolidated

asteroid 2008 tc 3 almahata sitta a spectacular breccia containing many different ureilitic and chondritic lithologies abstract asteroid 2008 tc3 impacted earth in northern sudan on october 7 2008 the meteorite named almahata sitta was classified as a polymict ureilite in this study 40 small pieces from different fragments collected in the almahata sitta strewn field were investigated and a large number of different lithologies were found some of these fragments are ureilitic in origin whereas others are clearly chondritic as all are relatively fresh w0 w0 1 and as short lived cosmogenic radioisotopes were detected within two of the chondritic fragments there is strong evidence that most if not all belong to the almahata sitta meteorite fall the fragments can roughly be subdivided into achondritic ureilitic 23 samples and chondritic lithologies 17 samples among the ureilitic rocks are at least 10 different lithologies a similar number of different chondritic lithologies also exist most chondritic fragments belong to at least seven different e chondrite rock types eh3 el3 4 el6 el breccias several different types of el and eh impact melt rocks and impact melt breccias some of the latter are shock darkened in addition two h group ordinary chondrite lithologies were identified and one sample of a chondrite type that is so far unique the latter has some affinities to r chondrites oxygen isotope compositions of 14 fragments provide further fundamental information on the lithological heterogeneity of the almahata sitta meteorite based on the findings presented in this study the reflectance spectrum of asteroid 2008 tc3 has to be evaluated in a new light

comparative planetary mineralogy implications of martian and terrestrial jarosite a crystal chemical perspective abstract the importance of the discovery of jarosite at the meridiani planum region of mars is discussed terrestrial studies demonstrate that jarosite requires a unique environment for its formation crystallizing from highly acidic ph 2 that reacted with aqueous solutions in shallow aquifers or on the martian surface this interaction forms both h 2 so 4 and h 2 s a martian oxidant must be identified to both oxidize h 2 s to produce the required acidity of the fluid and to oxidize fe 2 to fe 3 we suggest that reactions involving both sulfur and the reduction of co 2 to co may provide part of the answer the jarosite crystal structure is truly remarkable in terms of its tolerance for the substitution of a large number of different cations with different ionic radii and charges the structure accommodates hydrogen oxygen and sulfur the stable isotope systematics of which are strong recorders of low temperature fluid rock atmosphere interactions jarosite has been proven to be a robust chronometer for ar ar and k ar dating techniques and there is every reason to believe that u pb rb sr and nd sm techniques for older jarosite from mars will also be robust although the discovery of jarosite on mars alone with no other analytical measurements on the phase has given us insights to martian surficial processes the true power of jarosite can not be exploited until jarosite is sampled and returned from mars mars sample return is a long way off but until then we should be vigilant about examining martian meteorites for alteration assemblages that contain jarosite a suite of jarosite samples representing a significant time span on mars may hold the key to reading the record of martian atmospheric evolution

on the origin of shocked and unshocked cm clasts in h chondrite regolith breccias cm chondrite clasts that have experienced different degrees of aqueous alteration occur in h chondrite and hed meteorite breccias many clasts are fragments of essentially unshocked cm projectiles that accreted at low relative velocities to the regoliths of these parent bodies a few clasts were heated and dehydrated upon impact these objects most likely accreted at higher relative velocities we examined three clasts and explored alternative scenarios for their formation in the first scenario we assumed that the h and hed parent bodies had diameters of a few hundred kilometers so that their high escape velocities would effectively prevent soft landings of small cm projectiles this would imply that weakly shocked cm clasts formed on asteroidal fragments family members associated with the h and hed parent bodies in the second scenario we assumed that weakly shocked cm clasts were spall products ejected at low velocities from larger cm projectiles when they slammed into the h and hed parent bodies in both cases if most cm clasts turn out to have ancient ages e g 3 4 4 1 ga a plausible source for their progenitors would be outer main belt objects some which may have been dynamically implanted 3 9 ga ago by the events described in the so called nice model on the other hand if most cm clasts have recent ages 200 ma a plausible source location for their parent body would be the inner main belt between 2 1 2 2 au in that case the possible source of the cm clasts progenitors parent fragments would be the breakup 160 ma ago of the parent body 170 km in diameter of the baptistina asteroid family baf

arsenic contamination in surface drainage and groundwater in part of the southeast asian tin belt nakhon si thammarat province southern thailand the occurrence of human health problems resulting from arsenic contamination of domestic water supplies in ron phibun district nakhon si thammarat province southern thailand was first recognized in 1987 the area has an extensive history of bedrock and alluvial mining the waste from which is typically rich in arsenopyrite and related alteration products in 1994 a collaborative study was instigated involving thai and british government authorities to establish the distribution and geochemical form of as in surface drainage and aquifer systems in the affected area the probable sources of as contamination and the potential for problem alleviation hydrochemical analyses of surface and groundwaters have confirmed the presence of dissolved as at concentrations exceeding who potable water guidelines by up to a factor of 500 contamination of the shallow alluvial aquifer system is systematically more severe than the underlying carbonate hosted aquifer deep boreholes may therefore provide the best available potable water source for the local population the presence of up to 39 of total as as arsenite h3aso3 within the carbonate aquifer may however constitute a hidden toxicological risk not evident in the shallow groundwater in which arsenate species account for 95 of total as mineralogical investigations of as rich tailings and flotation wastes were undertaken to evaluate their likely impact on water quality the results indicate that although some flotation wastes contain up to 30 as the rate of leaching is extremely low consequently the as loading of drainage emanating from such waste is below the subregional average analyses of the silty alluvium that covers much of the central sector of the study area have highlighted as concentrations of up to 5000 mg kg 1 probably carried by disseminated arsenopyrite following sulfide dissolution the mobility of as in this material may be high with resultant contamination of shallow groundwater due to the low fe content of the soil on the basis of the data acquired a range of pollution mitigation schemes are currently under investigation including fe supplementation of alluvium and microbial degradation of disseminated arsenopyrite

what s up preservation of gravitational direction in the larkman nunatak 06299 ll impact melt breccia abstract larkman nunatak lar 06299 is a vesicular ll chondrite impact melt breccia that cooled rapidly 0 1 0 3 c s 1 during crystallization ar ar data from the literature indicate that the impact event that formed this rock occurred approximately 1 ga ago about 30 vol of the meteorite consists of a melt matrix containing faceted and intergrown mafic silicate grains mainly 4 11 m size olivine phenocrysts partially to completely surrounded by 2 20 m size patches of plagioclase suspended in the melt are 30 370 m size ellipsoidal to spheroidal metal sulfide nodules several hundred per thin section many connected to 8 600 m size ellipsoidal to spheroidal vesicles most of the metal sulfide nodules contain a large oblate metallic fe ni bleb at one end of the nodule for approximately 90 of the nodules the metal blebs are aligned on the same side of the nodules for approximately 80 of the nodules that are adjacent to vesicles the vesicles are attached to the opposite end of the nodules from the oblate metal blebs most of the oblate metal blebs themselves are flattened in a direction perpendicular to the long axis of the nodule vesicle these features result from alignment in the gravitational field on the ll parent asteroid making lar 06299 the first known chondrite to indicate gravitational direction using reasonable estimates of the cooling rate viscosity of the metal sulfide melt and asteroid density as well as the observed sizes of constituent phases in lar 06299 we obtain a lower limit of approximately 1 5 km for the radius of the lar 06299 parent body the body was probably substantially larger

sour gas hydrothermal jarosite ancient to modern acid sulfate mineralization in the southern rio grande rift abstract as many as 29 mining districts along the rio grande rift in southern new mexico contain rio grande rift type rgr deposits consisting of fluorite barite sulfide jarosite and additional rgr deposits occur to the south in the basin and range province near chihuahua mexico jarosite occurs in many of these deposits as a late stage hydrothermal mineral coprecipitated with fluorite or in veinlets that crosscut barite in these deposits many of which are limestone hosted jarosite is followed by natrojarosite and is nested within silicified or argillized wallrock and a sequence of fluorite barite sulfide and late hematite gypsum these deposits range in age from 10 to 0 4 ma on the basis of 40ar 39ar dating of jarosite there is a crude north south distribution of ages with older deposits concentrated toward the south recent deposits also occur in the south but are confined to the central axis of the rift and are associated with modern geothermal systems the duration of hydrothermal jarosite mineralization in one of the deposits was approximately 1 0 my most 18oso4 oh values indicate that jarosite precipitated between 80 and 240 c which is consistent with the range of filling temperatures of fluid inclusions in late fluorite throughout the rift and in jarosite 180 c from pena blanca chihuahua mexico these temperatures along with mineral occurrence require that the jarosite have had a hydrothermal origin in a shallow steam heated environment wherein the low ph necessary for the precipitation of jarosite was achieved by the oxidation of h2s derived from deeper hydrothermal fluids the jarosite also has high trace element contents notably as and f and the jarosite parental fluids have calculated isotopic signatures similar to those of modern geothermal waters along the southern rift isotopic values range from those typical of meteoric water to those of deep brine that has been shown to form from the dissolution of permian evaporite by deeply circulating meteoric water jarosite 34s values range from 24 to 5 overlapping the values for barite and gypsum at the high end of the range and for sulfides at the low end most 34s values for barite are 10 6 to 13 1 and many 34s values for gypsum range from 13 1 to 13 9 indicating that a component of aqueous sulfate was derived from permian evaporites 34s 12 2 the requisite h2so4 for jarosite formation was derived from oxidation of h2s which was likely largely sour gas derived from the thermochemical reduction of permian sulfate the low 34s values for the precursor h2s probably resulted from exchange deeper in the basin with the more abundant permian so42 at 150 to 200 c jarosite formed at shallow levels after the ph buffering capacity of the host rock typically limestone was neutralized by precipitation of earlier minerals some limestone hosted deposits contain caves that may have been caused by the low ph of the deep basin fluids due to the addition of deep seated hf and other magmatic gases during periods of renewed rifting caves in other deposits may be due to sulfuric acid speleogenesis as a result of h2s incursion into oxygenated groundwaters the isotopic data in these sour gas jarosite occurrences encode a record of episodic tectonic or hydrologic processes that have operated in the rift over the last 10 my

the age of the kaalijarv meteorite craters abstract precise radiometric age determination of the kaalijarv meteorite craters on the island of saaremaa in estonia have so far proved inconclusive here we present trace element analyses of peat cores taken several kilometers away from the kaalijarv craters that reveal a distinct ir enriched layer produced by the meteorite impact by radiocarbon dating the peat cores we have determined for the first time the precise age of the impact that generated the kaalijarv craters the calibrated date of the impact is 400 370 b c at 1

geostatistics based regional characterization of groundwater chemistry in a sedimentary rock area with faulted setting sophisticated modeling of a hydrogeological structure and the environment are crucial for underground construction this study characterizes hydrochemical properties of groundwater in a sedimentary rock area clarifying their spatial distribution and correlation with geologic structure and interpreting the groundwater source and chemical evolution water samples geological columns and well logs to 1 km depth were taken at 10 sites in horonobe of northern japan toward the objectives a 3d model of cl concentration was produced in conjunction with resistivity logging data through kriging estimation and sequential gaussian cosimulation variography shows that the dip of the main omagari fault is a control on the spatial correlation structure of cl concentration the 3d model shows that this fault and its auxiliary constitute a clear boundary between high and low saline waters and that cl concentrations tend to change in accord with sedimentary layer structures the integration of stable isotope analysis suggests that deep saline water with heavy d and 18o originated from fossilized seawater whereas shallow freshwater with light values is of meteoric water origin dilute saline water in the deep part of study area is partially attributable to dehydration of silica minerals vertical and lateral groundwater flows are estimated to prevail near the omagari fault and be general in other zones respectively difference in the depth of transition zones may be caused by the dominant flow among downward ascending and lateral consequently geostatistical techniques and data integration are useful to depict regional groundwater systems with a data set of water investigation limited by quantity and location

mineral control of arsenic content in thermal waters from volcano hosted hydrothermal systems insights from island of ischia and phlegrean fields campanian volcanic province italy this paper documents arsenic concentrations in 157 groundwater samples from the island of ischia and the phlegrean fields two of the most active volcano hosted hydrothermal systems from the campanian volcanic province southern italy in an attempt to identify the environmental conditions and mineral solution reactions governing arsenic aqueous cycling on ischia and in the phlegrean fields groundwaters range in composition from nacl brines which we interpret as the surface discharge of deep reservoir fluids to shallow depth circulating fluids the latter ranging from acid sulphate steam heated to hypothermal cold bicarbonate groundwaters arsenic concentrations range from 1 6 to 6900 g l 1 and from 2 6 to 3800 g l 1 in the phlegrean fields and on ischia respectively they increase with increasing water temperature and chlorine contents and in the sequence bicarbonate groundwatersbsteam heated groundwatersbnacl brines according to thermochemical modeling we propose that high as concentrations in nacl brines form after prolonged water rock interactions at reservoir t fo2 and fh2s conditions and under the buffering action of an arsenopyrite pyrite pyrrhotite rock assemblage on their ascent toward the surface nacl brines become diluted by as depleted meteoric derived bicarbonate groundwaters giving rise to hybrid water types with intermediate to low as contents steam heated groundwaters give their intermediate to high as concentrations to extensive rock leaching promoted by interaction with as bearing hydrothermal steam 2005 elsevier b v all rights reserved

the l3 6 chondritic regolith breccia northwest africa nwa 869 i petrology chemistry oxygen isotopes and ar ar age determinations northwest africa nwa 869 consists of thousands of individual stones with an estimated total weight of about 7 metric tons it is an l3 6 chondrite and probably represents the largest sample of the rare regolith breccias from the l chondrite asteroid it contains unequilibrated and equilibrated chondrite clasts some of which display shock darkening impact melt rocks imrs both clast free and clast poor are strongly depleted in fe ni metal and sulfides an unequilibrated microbreccia two different light inclusions and two different sio2 bearing objects were found although the matrix of this breccia appears partly clastic it is not a simple mixture of fine grained debris formed from the above lithologies but mainly represents an additional specific lithology of low petrologic type we speculate that this material stems from a region of the parent body that was only weakly consolidated one imr clast and one sio2 bearing object show 17o values similar to bulk nwa 869 suggesting that both are related to the host rock in contrast one light inclusion and one imr clast appear to be unrelated to nwa 869 suggesting that the imr clast is contaminated with impactor material 40ar 39ar analyses of a type 4 chondrite clast yield a plateau age of 4402 7 ma which is interpreted to be the result of impact heating other impact events are recorded by an imr clast at 1790 36 ma and a shock darkened clast at 2216 40 ma demonstrating that nwa 869 escaped major reset in the course of the event at approximately 470 ma that affected many l chondrites