on the possibility of determining rates of removal of uranium from crystalline igneous rocks using u series disequilibria 2 applicability of a u leach model to mineral separates abstract preliminary u series data are presented on the disequilibria of mineral separates of surface samples from the eye dashwa lakes granite canada most analyses of the ferromagnesian quartz plus feldspar and zircon plus sphene grains show that leaching of u has taken place such that 234 u 239 u 1 and 230 th 234 u 1 the simple leach model presented in a companion paper was used to explain these characteristic ratios it is suggested that the leach model may be used on zircon and sphere grains to estimate u leach rates and this is relevant to the suggestion of using sphene like hosts as the primary barrier in the safe disposal of nuclear waste a full analysis of u mobility within a given rock volume was not possible due to our limited data base and to our inability to monitor labile u directly

what do kinematic models imply about the constitutive properties of rocks deformed in flat ramp flat folds kinematic theories of flat ramp flat folds relate fault angles to stratal dips in a way that allows prediction of structural geometries in areas of economic or scientific interest however these geometric descriptions imply constitutive properties of rocks that might be discordant with field and laboratory measurements in this study we compare deformation resulting from kinematic and mechanical models of flat ramp flat folds with identical geometries to determine the conditions over which kinematic models may be reasonably applied to folded rocks results show that most mechanical models do not conform to the geometries predicted by the kinematic models and only low basal friction 0 1 and shallow ramps ramp angle 10 produce geometries consistent with kinematic predictions this implies that the kinematic models might be appropriate for a narrow set of geometric and basal fault friction parameters

determination of recent 238u 234u and 230th mobility in granitic rocks application of a natural analogue to the high level waste repository environment abstract the isotope activity ratios 234u 238u and 230th 234u have been investigated in drill core samples up to 1300 m depth in three granitoids from australia to identify the nature of possible recent 1 0 which has generated excess 230th these enriched ground waters do not appear to have penetrated below 530 m depth and 230th excess indicates bulk loss of u the observed disequilibria indicate that significant radionuclide mobilisation has occurred in these rocks during the recent past

applications of uthpb isotope systematics to the problems of radioactive waste disposal abstract concentrations of u th and pb and the isotopic composition of pb for whole rock samples of granitoids show 1 that open system behavior is nearly universal in the surface and near surface environment and 2 that elemental mobility is possible to depths of several hundred meters several identified or at least postulated factors that control u and or pb mobility include 1 the mineralogical sites for u and its daughter products 2 access of groundwater to these sites 3 the volume of circulating water and 4 the chemistry of the groundwater studies of granitic samples from peralkaline complexes in the arabian shield have shown that most samples lost less than 20 of their u during recent exposure to the near surface environment most of the u in these samples appears to be firmly bound in zircons in contrast most surface and shallow drill core samples of the granite of lankin dome granite mountains wyoming have lost 70 of their u most of the u in these samples is weakly bound in biotite and epidote family minerals the granite recovered during the illinois deep drill hole project stephenson county illinois is mineralogically similar to the granite of lankin dome but this granite lost radiogenic pb rather than u probably as a result of exposure to groundwater that had a markedly different chemistry from that in the granite mountains studies of the sherman granite wyoming and the gotemar granite southeastern sweden have shown that u and or pb mobility is greatest in and near fractured rock the greater mobility is interpreted to be the result of both a larger water rock ratio in the fractured rock and exposure to water over an increased surface area and consequently a greater number of uranium sites several types of geochemical and mineralogic data can be used to identify rock water interaction in granites however if rock samples have favorable radiogenic to common pb ratios both the amount and approximate timing of u or pb mobility can be obtained through the use of isotopic studies such information can be extremely important in the search for favorable hosts for containment of radioactive waste rocks such as the gotemar granite have undergone considerable rock water interaction most of which occurred 400 myr ago and little in recent times thus a search for zones that have experienced only a little interaction with water may provide a misleading prediction as to the ability of such zones to shield radioactive wastes from the modern biosphere from an isotopic point of view an ideal candidate for evaluation as a host rock for radioactive wastes would have the following characteristics 1 a high ratio 2 of radiogenic to common pb in order to optimize precision of the results 2 a simple two stage geologic history so that results could be interpreted without multiple working hypotheses and 3 an originally high percentage 50 of labile u so that the results would be highly sensitive to even small amount of rock water interaction these characteristics should produce rocks with marked radioactive disequilibrium in surface samples the disequilibrium should grade to radioactive equilibrium with increasing depth until zones in which water has not circulated are found extensive regions of such zones must exist because u th pb systematics of most analyzed granitoids demonstrate closed system behavior for almost all of their history except for their recent history in the near surface environment

distribution of uranium thorium and rare earth elements in the eye dashwa lakes pluton a study of some analogue elements abstract the distribution of u th and rare earth elements ree s in the eye dashwa lakes pluton near atikokan ontario is examined materials analysed include a unaltered granite b altered granite c highly altered granite adjacent to open fractures and d fracture filling minerals distinct distribution patterns are noted for u and some ree s among the four types of samples th shows higher concentrations in materials c and d compared with unaltered and altered granite the highly altered granite and some fracture fillings have greater concentrations of u th and ree s the large concentrations of u th and ree s in these materials are due to both sorption on selective materials and precipitation as mineral phases containing these elements the occurrence of uraninite bastnaesite and thorogummite coatings on fracture fillings are examples of this precipitation

active faulting within a megacity the geometry and slip rate of the pardisan thrust in central tehran iran geological survey of iran christ church college oxford natural environment research council economic and social research council

introduction to the illinois deep hole project commonwealth edison recently drilled 3 engineering test holes in n w illinois the 3 holes uph 1 2 and 3 were 0 6 1 6 and 1 6 km deep respectively and the latter 2 penetrated nearly one kilometer of precambrian granitic basement in 1980 continuous core from all 3 holes and access to uph 3 were made available for scientific investigations through the illinois deep hole project the principal study of these holes was an integrated investigation of surface and in hole experiments plus detailed petrologic geochemical and physical property studies of the core samples 50 references

considerations for u series dating of sediments insights from the flinders ranges south australia abstract uranium isotope ratios have been determined for the fine grained detrital fraction of pleistocene wilkawillina valley fill sediments four local proterozoic bedrock samples and fine grained aeolian material from a sand dune deposit of the flinders ranges south australia the aim was to quantify the comminution age i e the time elapsed since physical weathering of the bedrock and residence time of the valley fill sediments and to place tighter constraints on input parameters for the comminution age calculation despite using two independent approaches for determination of the recoil lost fraction of 234 u from the sediment weighted geometric and surface area estimates samples fail to produce realistic comminution ages and hence residence times the issues involved in the ability to determine sediment comminution ages are discussed the 234 u 238 u activity ratio of the local bedrock is not in secular equilibrium despite the bedrock being much older than 1 ma i e the timeframe for 234 u and 238 u to reach secular equilibrium in a closed system using the average flinders ranges bedrock 234 u 238 u ratio instead of an assumed 234 u 238 u activity ratio of unity for the source would significantly reduce calculated residence times this result warrants concern for future studies using the comminution approach for which a secular equilibrium source 234 u 238 u activity ratio is assumed significant input of aeolian material may modify the measured 234 u 238 u activity ratios such input may be more tightly constrained in future studies using rare earth element and radiogenic isotopic data future comminution studies would benefit from further consideration of the importance of 1 leaching lost 234 u from source rock and bulk sediment samples 2 wind deposition of fine grained material and 3 the appropriateness and robustness of sample pre treatment procedures

the erosion response to quaternary climate change quantified using uranium isotopes and in situ produced cosmogenic nuclides abstract studying how catchment erosion has responded to past climate change can help us better understand not only how landscape evolution operates but also predict the consequences of future climate change on soil resource availability recent years have seen the development of tools that allow a quantitative assessment of past changes in catchment erosion this work reviews the principles of the application of in situ produced cosmogenic nuclides and uranium isotopes to quantifying past erosion rates results highlight the role of periglacial processes and mass wasting in dictating how catchment erosion responds to climatic variability at the 10 kyr scale at the million year scale it is more difficult to untangle the role of climate and tectonics a strong coupling exists at the 10 kyr to 100 kyr scales between climatic cycles and the transfer time of regolith from source to sink this coupling reflects changes in sediment source that are either set by changes in vegetation cover at the catchment scale or by the storage of sediments on continental shelves at a larger scale although further analytical developments are required for these tools to reach their full potential existing works suggest that in the near future they will provide unprecedented quantitative insights on how soil and fluvial systems adapt to external perturbations climatic tectonic and or anthropic

microseismicity and seismotectonics around the mosha fault central alborz iran abstract we present the results of a microearthquake study conducted during 5 months of 2006 with 44 portable seismological stations around the mosha fault the most prominent structure located east of tehran where several major earthquakes occurred during the historical time in the central alborz iran we recorded 538 earthquakes at more than 4 stations among these earthquakes 148 were located with statistical uncertainties erh and erz less than 3 km a gap less than 180 and rms less than 0 3 s we also present the seismicity recorded by the institute of geophysics of the university of tehran from may 1996 to july 2008 igtu recorded almost 13 000 events during this time 4428 were recorded in more than 4 stations and 599 with the same criteria as for the temporary network most earthquakes are located along the mosha fault at depths ranging between 0 km and 20 km with a maximum between 10 and 15 km as it does at most of the other faults in central alborz cross sections clearly show the mosha fault in its central part dipping northward at an angle of 70 we computed also 51 focal mechanisms most of them show left lateral strike slip motion associated with the mosha fault a few mechanisms located south of the mosha fault are consistent with normal faulting

paleoearthquakes of the past 30 000 years along the north tehran fault iran the north tehran fault ntf is located at the southernmost piedmont of central alborz and crosses the northern suburbs of the tehran metropolis and adjacent cities where 15 million people live extending over a length of about 110 km the ntf stands out as a major active fault and represents an important seismic hazard for the iranian capital after historical seismicity in order to characterize the activity of the ntf in terms of kinematics magnitude and recurrence intervals of earthquakes we carried out a first paleoseismological study of the fault within its central part between tehran and karaj cities we opened a trench across a 3 m high fault scarp affecting quaternary deposits our study shows that the scarp is the result of repeated events along a main n115 e trending shallow dipping thrust fault associated with secondary ruptures from the trench analysis and infrared stimulated luminescence irsl dating of fault related sediments we interpreted between 6 and 7 surface rupturing events that occurred during the past 30 kyrs their magnitudes estimated from the displacements along the faults are comprised between 6 1 and 7 2 the two last events the largest occurred during the past 7 9 1 2 ka which yields a holocene slip rate of 0 3 mm yr the 7 earthquakes scenario suggests a regular periodicity with a mean recurrence interval of 3 8 kyrs however the two most recent events could correspond to the two largest historical earthquakes recorded in the area in 312 280 b c and 1177 a d and therefore suggest that the ntf activity is not regular

a large scale landslide and related mechanism a case study in the qazvin rasht freeway iran the manjil landslide occurred after the slope cutting and the removal of the toe buttress 8 july 2013 between 41 400 and 42 200 km section of manjil radbar in the qazvin rasht freeway gilan province iran the occurrences of landslide led to blockage of the freeway a cutting was designed with a width and height of 4 and 6 m respectively and a 5 to 6 m excavation depth within a 120 m line along the slope toe based on the site investigations the landslide was characterized as a complex deep seated landslide displaying composite rotational debris flow moreover extensive field survey subsurface investigation laboratory and in situ tests show that although the landslide was triggered by an inappropriate cutting geostructural geological engineering properties and hydrology have also played a key role in its initiation and further aggravation therefore the western and eastern boundaries of the landslide coincide with the two faults f1 and f2 in addition landslide sinisterly movement is controlled by a left lateral strike slip fault f2 it was observed that the scarp follows the n130 75 direction of bedding rocks the presence of marls and shale implies a high swelling under wet conditions thus providing lubricating sliding surfaces in addition alteration and weathering of andesite basalt tuffite and tuff have been reduced the shear strength of the slope engineering geological map egm of the landslide was prepared on the basis of aerial interpretations the orientation of ground cracks and fissures geomaterial geostructural and hydrology based on ground cracks and fissures the displacement vectors are also determined and shown on the map the relationship between the displacement vectors estimated from ground cracks and fissures with gps observation and slickness slip surface is coherent

palaeoseismic evidence for a medieval earthquake and preliminary estimate of late pleistocene slip rate on the firouzkuh strike slip fault in the central alborz region of iran the 55 km long firouzkuh fault is located in the central alborz mountains of iran it is a left lateral fault which dips to the south and possesses a small dip slip component of motion that we interpret to result from extension the ratio of horizontal to vertical displacement across the fault calculated from the cumulative displacement of landscape features is 7 6 we provide constraints on the timing of the last earthquake on the firouzkuh fault from two trenches t1 and t2 across the fault zone excavated in 2004 and located east of firouzkuh city the trenches expose faulted sedimentary deposits two optically stimulated luminescence osl ages from sediments in the lower part of trench t1 date from the late pleistocene 15 9 0 9 ka and 27 1 1 7 ka the younger of the two dated units in t1 is displaced vertically across the fault by 2 2 4 4 m from which we estimate a strike slip displacement of 18 2 33 4 m and hence a average horizontal slip rate of 1 1 2 2 mm yr the sediments exposed in t1 do not yield constraints on the most recent earthquake history in trench t2 however human skeletal remains of a middle aged male which yield a radiocarbon age of 1159 28 bp corresponding to a mean calendar age of 791 ad were found within a faulted alluvial layer at a depth of 60 70 cm from the surface the existence of these medieval human places shows that a surface rupturing earthquake occurred at some time after 1159 28 bp the amount of slip in each earthquake on the firouzkuh fault is difficult to estimate but assuming the entire 55 km fault length ruptures in each event they will have had a maximum magnitude of 7 1 at our estimated late quaternary slip rate of 1 1 2 2 mm yr magnitude 7 1 earthquakes involving 1 2 m average displacement would be expected to occur every 1100 540 years as the last earthquake on the firouzkuh fault may be up to 700 years in age we suggest that the firouzkuh fault is a major hazard for earthquakes in the near future

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

gps and gravity constraints on continental deformation in the alborz mountain range iran a network of 54 survey gps sites 28 continuous gps stations and three absolute gravity ag observation sites have been set up in the alborz mountain range to quantify the present day kinematics of the range our results allow us to accurately estimate the motion of the south caspian block scb for the first time and indicate rotation of the scb relative to eurasia accounting for the left lateral motion in the alborz range in light of these new results it clearly appears that deformation rates vary along the range the eastern part accommodating mainly left lateral strike slip 2 mm yr 1 south of the range and 5 mm yr 1 north of the range with a very low range normal shortening rate on the khazar thrust fault similar to 2 mm yr 1 and the western part accommodating range normal shortening similar to 6 mm yr 1 on the khazar thrust fault with a left lateral component of similar to 2 mm yr 1 north of the range and 1 mm yr 1 south of the range these present day kinematics agree with geomorphologic estimated slip rates but not the long term deformation corroborating the idea that the kinematics of the range have changed recently due to the change of scb motion modelling of the interseismic deformation suggests a deep locking depth on the central western segment of the khazar fault similar to 30 km in agreement with the baladeh earthquake rupture and aftershock ranging between 10 and 30 km given this unusual deep locking depth and the 34 degrees dip of the thrust a large part of the alborz range is located above the seismically coupled part of the fault based on our ag measurements this part of the range seems to uplift at a rate of 1 5 mm yr 1 in agreement with terrace uplift

kinematic links between the eastern mosha fault and the north tehran fault alborz range northern iran kinematic interaction of faults is an important issue for detailed seismic hazard assessments in seismically active regions the eastern mosha fault emf and the north tehran fault ntf are two major active faults of the southern central alborz mountains located in proximity of tehran population similar to 9 million we used field geomorphological and paleoseismological data to explore the kinematic transition between the faults and compare their short term and long term history of activity we introduce the niknamdeh segment of the ntf along which the strike slip kinematics of emf is transferred onto the ntf and which is also responsible for the development of a pull apart basin between the eastern segments of the ntf the ira trench site at the linkage zone between the two faults reveals the history of interaction between rock avalanches active faulting and sag pond development the kinematic continuity between the emf and ntf requires updating of seismic hazard models for the ntf the most active fault adjacent to the tehran metropolis study of offsets of large scale morphological features along the emf and comparison with estimated slip rates along the fault indicates that the emf has started its left lateral kinematics between 3 2 and 4 7 ma according to our paleoseismological data and the morphology of the nearby emf and ntf we suggest minimum and maximum values of about 1 8 and 3 0 mm year for the left lateral kinematics on the two faults in their linkage zone averaged over holocene time scales our study provides a partial interpretation based on available data for the fault activity in northeastern tehran region which may be completed with studies of other active faults of the region to evaluate a more realistic seismic hazard analysis for this heavily populated major city c 2014 elsevier b v all rights reserved

characterizing the present day activity of the tunka and sayan faults within their relay zone western baikal rift system russia the sayan and tunka faults are located at the boundary between the northernmost mountain belt of central asia the sayan baikal ranges and the siberian platform these prominent crustal structures were involved in the opening of the southern baikal rift system since the beginning of the cenozoic and define large scale sharp morphotectonic features despite low instrumental seismic activity late pleistocene holocene morphotectonic features along the two faults indicate that the faults are active and have the capacity to produce strong earthquakes a careful mapping of the most recent trace of activity within the southeastern parts of the two faults where they merge within a relay zone demonstrates that they correspond now to left lateral reverse faults suggesting a recent inversion of their vertical component we also show that the two faults are now structurally connected via a young surface rupture and that no obvious post last glacial maximum ruptures are observed along the central part of the sayan fault beyond its junction zone with the tunka fault this suggests that the left lateral strike slip deformation is transferred from the eastern sayan fault to the tunka fault a detailed morphotectonic study along the southeastern sayan fault allows estimating a left lateral slip rate between 1 3 min and 3 9 mm year max finally a critical review of russian paleoseismic data combined with our paleoseismological investigations allows us to propose that the mean recurrence time along the two faults is on the order of 4 kyr and that they may have either ruptured together or during seismic clusters

the chemical and isotopic record of rock water interaction in the sherman granite wyoming and colorado chemical isotopic radiographic and rock leaching data are combined to describe the effects of rock water interactions in core samples of petrographically fresh 1 43 b y old sherman granite the data serve to identify sensitive indicators of incipient alteration and to estimate the degree pathways and timing of element mobilization unfractured core samples of sherman granite are remarkably fresh by most chemical or isotopic criteria but incipient alteration is indicated by the abundance and distribution of uranium and the degree of radioactive equilibration of uranium with its decay products uranium abundances which are out of equilibrium with lead decay products indicate remobilization of a portion 3 to 60 percent of original uranium in late phanerozoic time association of uranium with minor but pervasive secondary alteration products also indicates some remobilization the amount of apparent uranium mobility in unfractured sherman granite 3 to 60 percent is small compared to the results of similar studies of archean granites from nearby localities chemical and isotopic data evaluated as a function of core sample depth suggest a uranium migrational pathway involving near surface leaching and reconcentration at depth movement of solutions through the upper 200 ft 60 m of sherman granite is fracture controlled and brecciated granite shows more obvious petrographic chemical and isotopic evidence of alteration and multi element redistribution laboratory experiments using freshly crushed sherman granite confirm that uranium is leached in preference to elements such as si mg ca and k and that leachable uranium is situated close to the solid liquid interface perhaps as uranium along grain boundaries in crystal defects or on cleavage traces of minerals that exclude uranium from their structure

active transtension inside central alborz a new insight into northern iran southern caspian geodynamics the tectonic activity in the alborz mountain range northern iran is due both to the northward convergence of central iran toward eurasia and to the northwestward motion of the south caspian basin with respect to eurasia inducing a left lateral wrenching along this range these two mechanisms give rise to a nne ssw transpressional regime which is believed to have affected the entire range for the last 5 6 2 m y in this paper we show that the internal domain of central alborz is not affected by a transpressional regime but by an active transtension with a wnw ese extensional axis we show that this transten sion is young middle pleistocene it postdates an earlier n s compression and may have been initiated when the south caspian basin started moving consequently our results suggest that the south caspian basin motion may have taken place more recently than previously proposed

evaluation of relative tectonic activity in the tehran basin central alborz northern iran abstract recent deformations in the area studied control structural expansions influenced by tectonic activities causing transformations of geologic features and morphological landforms the tehran basin is located at the southern edge of the central alborz and is the result of the arabian eurasian convergence and clockwise rotation of the south caspian basin with respect to eurasia hence assessment of the drainage pattern permutations and mountain fronts appears necessary we used six significant morphometric indices for this evaluation stream length gradient sl drainage basin asymmetry af hypsometric integral hi ratio of valley floor width to valley height vf drainage basin shape bs and mountain front sinuosity smf the combined analyzed indices represented the relative active tectonics iat the study area was divided into four regions according to the values of iat these classes include class 1 very high activity class 2 high class 3 moderate and class 4 low the regions with high relative tectonic activity mostly correspond with the active structures in the basin the tectonic activity classes 1 and 2 coincide with the fault mountain fronts in the southern edge of the central alborz especially the north tehran fault the parts of the central mosha fault and the regions in the east the southeast and the west of the basin indicate the moderate class of tectonic activity class 3 the low elevation plain in the south and southwest of the area shows the lowest relative tectonic activity class 4

evaluation of pleistocene groundwater flow through fractured tuffs using a u series disequilibrium approach pahute mesa nevada usa abstract groundwater flow through fractured felsic tuffs and lavas at the nevada national security site represents the most likely mechanism for transport of radionuclides away from underground nuclear tests at pahute mesa to help evaluate fracture flow and matrix water exchange we have determined u series isotopic compositions on more than 40 drill core samples from 5 boreholes that represent discrete fracture surfaces breccia zones and interiors of unfractured core the u series approach relies on the disruption of radioactive secular equilibrium between isotopes in the uranium series decay chain due to preferential mobilization of 234 u relative to 238 u and u relative to th samples from discrete fractures were obtained by milling fracture surfaces containing thin secondary mineral coatings of clays silica fe mn oxyhydroxides and zeolite intact core interiors and breccia fragments were sampled in bulk in addition profiles of rock matrix extending 15 to 44 mm away from several fractures that show evidence of recent flow were analyzed to investigate the extent of fracture matrix water exchange samples of rock matrix have 234 u 238 u and 230 th 238 u activity ratios ar closest to radioactive secular equilibrium indicating only small amounts of groundwater penetrated unfractured matrix greater u mobility was observed in welded tuff matrix with elevated porosity and in zeolitized bedded tuff samples of brecciated core were also in secular equilibrium implying a lack of long range hydraulic connectivity in these cases samples of discrete fracture surfaces typically but not always were in radioactive disequilibrium many fractures had isotopic compositions plotting near the 230 th 234 u 1 1 line indicating a steady state balance between u input and removal along with radioactive decay numerical simulations of u series isotope evolution indicate that 0 5 to 1 million years are required to reach steady state compositions once attained disequilibrium 234 u 238 u and 230 th 238 u ar values can be maintained indefinitely as long as hydrological and geochemical processes remain stable therefore many pahute mesa fractures represent stable hydrologic pathways over million year timescales a smaller number of samples have non steady state compositions indicating transient conditions in the last several hundred thousand years in these cases u mobility is dominated by overall gains rather than losses of u

infilling history of a neoproterozoic intracratonic basin nd isotope provenance studies of the uinta mountain group western united states abstract neodymium isotope and selected trace element concentration data were obtained from 27 samples of shales and arkosic sandstones comprising the neoproterozoic uinta mountain group umg in north eastern utah and northwestern colorado to determine the provenance of siliciclastic detritus deposited in this region and to reconstruct aspects of the proterozoic geologic history of the southern margin of the archean wyoming province in the east lobe of the uinta mountains coarse grained components of the jesse ewing canyon formation the oldest recognized formation of the umg have measured nd values of 23 to 28 and were most probably derived from archean basement of the wyoming province to the north fine grained sediment in the southern portions of the jesse ewing canyon formation and shales and quartz arenites from overlying undifferentiated umg all contain at least a component of detritus derived from proterozoic crust in the west lobe the oldest members of the umg the red castle lake gilbert peak and moosehorn lake formations and arkosic arenite comprising the northern portions of the overlying mount watson formation were also derived exclusively from archean sources however as in the east lobe the more mature sandstones that dominate the southern sections of the mount watson formation have isotopic compositions that require a significant proterozoic crust derived detrital component our data support a model in which sedimentary rocks with an archean provenance represent the preserved remnants of alluvial fans marking the northern margin of the basin in which the umg was deposited a source for these sediments within the archean wyoming province is consistent with the high light rare earth element lree and th abundances of finegrained low nd sedimentary rocks given that late archean granitic rocks within the wyoming province have similar trace element characteristics sediments with proterozoic components in both the east and west lobes were apparently deposited from a fluvial system that transported sediment along the basin axis the proterozoic detrital component in these sediments originated either through direct erosion of the colorado province in the neoproterozoic or through erosion of mixed archean and proterozoic crust located to the east of the umg basin that originally formed during the paleoproterozoic accretion of the colorado province to the southern margin of the wyoming craton

patterns of historical earthquake rupture in the iranian plateau the iranian plateau accommodates the 35 mrn yr convergence rate be tween the eurasian and arabian plates by strike slip and reverse faults with relatively low slip rates in a zone 1000 km across although these faults have only locally been the subject of paleoseismological studies a rich historical and archeological record spans several thousand years long enough to establish recurrence intervals of 1000 to 5000 yr on individual fault segments several clusters of earthquakes provide evidence of interaction among reverse and strike slip faults probably due to adjacent faults being loaded by individual earthquakes the dasht e bayaz sequence of 1936 to 1997 includes earthquakes on left lateral right lateral and reverse faults the neyshabur sequence of four earthquakes between 1209 and 1405 respected the seg ment boundary between the neyshabur and binalud reverse fault systems the two pairs of earthquakes may have ruptured different faults in each segment similar to the 1971 and 1994 san fernando california earthquakes the 1978 tabas reverse fault earthquake was preceded by the 1968 ferdows earthquake part of the dasht e bayaz sequence the north tabriz fault system ruptured from southeast to north west in three earthquakes from 1721 to 1786 a previous cluster may have struck this region in 855 to 958 the mosha fault north of tehran ruptured in three earthquakes in 958 1665 and 1830 five large earthquakes struck the tehran region from 743 to 1177 but only two that large have struck the area since 1177 other earthquakes occurred in pairs in the talesh mountains near the caspian sea 1863 1896 the iran turkey border 1840 1843 and the nayband gowk fault system both 1981 other historical events did not occur as parts of sequences the historic seismic moment release in iran accounts for only a small part of the plate convergence rate which may be due to aseismic slip or to the iranian historical record long as it is being too short to sample long term deformation across the plateau no historic earthquakes of m 8 have struck iran however several long straight strike slip faults doruneh west neh east neh and nayband have not sustained large historical earthquakes raising the possibility that these long faults could produce earthquakes of m 8 thereby removing at least part of the apparent slip deficit an increased understanding of iran s seismic hazard could be obtained by an extensive paleoseismology program and space geodetic arrays supplementing the abundant historical and archaeological record

oroclinal bending in the alborz mountains northern iran new constraints on the age of south caspian subduction and extrusion tectonics abstract in this study we report an extensive paleomagnetic study 76 sites carried out in the alborz mts northern iran with the aim of reconstructing the rotation history and the origin of curvature of this orogenic chain the analyzed deposits are the sedimentary successions of the upper red formation miocene lower red formation oligocene and eocene clastic units paleomagnetic results indicate that the alborz mts can be considered a secondary arc that originated as a linear mountain belt that progressively acquired its present day curvature through opposite vertical axis rotations along its strike the curvature of the arc was entirely acquired after the middle late miocene which is the age of the youngest investigated sediments upper red formation overall our paleomagnetic data indicate that the alborz mts can be considered an orocline our results define for the first time the rotational history of the entire alborz curved mountain belt and enable us to reconstruct the paleogeographic and tectonic evolution of northern iran in the framework of arabia eurasia continental deformation the kinematics inferred by the pattern of paleomagnetic rotations is at odds with the present day kinematics of northern iran characterized by the westward extrusion of the south caspian block and by a left lateral shear between central iran and the central and western sectors of the alborz mts by integrating paleomagnetic data with stratigraphic thermochronological structural and gps information we propose that the initiation of south caspian subduction and the activation of westward extrusion of south caspian block occurred diachronously and that the initiation of the present day kinematics of northern iran was quite recent lower pleistocene

history of actinide and minor element mobility in an archean granitic batholith in manitoba canada abstract surface and borehole core samples from the lac du bonnet granite manitoba canada have been analysed for major element concentrations fe 3 fe total ratios rare earth element ree content and actinide isotopic abundances this work forms part of the geological investigations of the canadian nuclear fuel waste management program performed by atomic energy of canada limited aecl the study attempts to understand the history of and processes governing mobilisation of elements and naturally occurring radionuclides during high and low temperature alteration events in fluid bearing fractures in the granite one surface sample and two core samples from 150 m and 730 m are each in contact with fractures in the granite and show evidence of alteration events that penetrated the rock matrix over distances of at least 3 cm loss of ca and na is seen in cores from a depth of 150 m from the highly altered hematite rich rock adjacent to sub horizontal fracture zones at the underground research laboratory url of aecl near lac du bonnet in contrast k fe fe 3 fe and u concentrations increase towards the fracture surface due to formation of illite and association of u with hematite and the illite at the fracture surface u continues to increase but fe and thefe 3 fe ratio decrease indicating fe removal by reduction the ree also show some enrichment in more altered rock at intermediate depths but the total ree concentration is lower than in the surface and deep core samples no clear trends are visible for parent and fracture surface ree in surface and deep core samples however disequilibrium values of 234 u 238 u and 230 th 234 u ratios in surface and intermediate depth core samples indicate that u has been mobilised in recent geological time the last ma but th has remained relatively immobile high th u and 230 th 234 u ratios in surface samples are indicative of rapid leaching of u but little isotopic fractionation probably within the last 10 5 a apparently unaltered rock several centimetres distant from the fracture in surface and intermediate depth samples has lost appreciable u but evidence from u series disequilibrium studies suggests that this process occurred more than one million years ago perhaps during deuteric or hydrothermal alteration core from a fracture at depth in the granite shows little hematite or clay formation and lacks evidence of ree and recent or ancient actinide mobilisation the u series results are correlated with the observed concentrations and isotope activity ratios of u in groundwaters sampled from the same or adjacent fractures analyses of samples of highly altered rubble recovered from centre portions of fracture zones at the url show both excesses and deficiencies of 234 u and 230 th in neighbouring locations possibly due to the presence of a redox front whose position is controlled by modern groundwater composition the implications of these results are discussed for the concept of disposal of nuclear fuel waste at depth in plutonic rock on the canadian shield

on the possibility of determining rates of removal of uranium from crystalline igneous rocks using u series disequilibria 1 a u leach model and its applicability to whole rock data the removal of u from granitic rocks is characterised by234u 238u 1 and 230th 234u 1 it is notable from weathered eye dashwa lakes canada granite samples and from the published data that230th 234u ratios seldom exceed a limiting value of about 2 a u leach model is discussed in detail which may account for these observations the model assumes that 230th is practically immobile and that the removal of u can then be measured against the decay rate of the unsupported230th a property of the model is that the isotope ratios reach constant values reflecting a kind of secular equilibrium and this implies that u is seldom removed faster than the decay of230th if the limited230th 234u ratios from the data correspond to secular equilibrium ratios then this allows simple calculation of u leach rates from any given subsurface sample a test for the model using235u 231pa ratios is suggested a comparison of leach rates derivable from u th pb systematics of colorado and wyoming granite samples with the corresponding estimates from the model shows that the latter are high by a factor of 10 50 data from rapidly weathered surface rinds suggests that the presence of labile u restricts the application of the model to subsurface low weathered zones

morphological and palaeoseismological analysis along the taleghan fault central alborz iran summary the taleghan fault tf is a major active fault of the central alborz mountain range in iran located 50 km northwestwards of tehran this 80 km long fault represents one of the major structures threatening 15 million people living in the capital of iran and the surrounding cities e g karaj the tf could be the source of some of the strongest historical earthquakes recorded in the tehran region notably the 958 ad event estimated magnitude m 7 7 to characterize the kinematics and activity of the fault we carried out a detailed morphological and palaeoseismological study combining aerial photographs digital elevation models and fieldwork we show that unliked described so far the tf is not a reverse fault but a left lateral strike slip fault with a normal component its strike dip and rake within its eastern part are 105 60 and 20 40 respectively our palaeoseismological analysis shows that a sequence of 2 3 events with magnitudes mw 7 occurred during the past 5300 years if we consider a three event scenario the average recurrence interval is 2000 years and the most recent event is younger than 80 ad if we consider a two event scenario the time interval between the second and the first events ranges between 3760 and 830 years and the elapsed time since the last event ranges between 3529 and 1599 years combined with morphotectonics data our palaeoseismological analysis allows estimating a minimum horizontal slip rate of 0 6 1 6 mm yr 1 and a minimum vertical slip rate of 0 5 mm yr 1 taking the 450 m total vertical displacement observed across the fault we conclude that the kinematical change along the tf from reverse to left lateral normal occurred 1m a

isotopic composition of uranium and thorium in crystalline rocks the 238u 234u 230th 232th system has been investigated in 84 silicic crystalline rocks obtained from drill cores surface and near surface samples in california wyoming colorado and illinois results of these analyses displayed on ternary diagrams with apexes for 238u 234u and 230th indicate five predominant geochemical processes that affected uranium in the rock 1 bulk uranium leaching where 238u and 234u were removed with little or no fractionation 2 preferential 234u leaching by alpha recoil displacement 234u recoil loss with lesser 238u loss 3 234u recoil loss with little or no 238u loss 4 uranium assimilation where both 238u and 234u were added with present day 234u 238u activity ratios varying from 0 8 to 1 2 and 5 addition of 234u and 230th by daughter emplacement processes 234u 230th recoil gain evidence for the existence of 234u and 230th recoil gain in rocks is the most important finding of this investigation radioactive disequilibrium occurs in the majority of rocks analyzed where 234u recoil loss is the predominant process associated with incipient weathering u assimilation and 234u 230th recoil gain occur under conditions of substantial water penetration along fractures and into weathered zones in the rocks relatively unfractured and petrographically fresh rocks from the uph 3 drill hole in northern illinois are closest to being in radioactive equilibrium for any suite of rocks included in this study and they demonstrate that equilibrium during the last 0 5 m y can be maintained over a substantial vertical distance where there has been little or no movement of water in the basement rock the 238u 234u 230th system can be a sensitive indicator of geologically recent u mobility and rock water interaction both in petrographically fresh core samples and in sealed fracture zones

estimating slip rates and recurrence intervals for strong earthquakes along an intracontinental fault example of the pambak sevan sunik fault armenia north of the arabian plate active tectonics is characterised by both n s compression and e w extension associated with strike slip faults the pambak sevan sunik fault pssf zone in armenia is one of the major active structures of the region the fault is comprised of four main segments and it displays morphological evidence for dextral movement during the holocene however no large earthquake m 7 has occurred in the northern or central parts of the fault during the last 2000 years we undertook a geomorphological and paleoseismological investigation along the pambak sevan sunik fault with the aim of estimating the long term slip rate and recurrence interval of strong earthquakes trenches were excavated at three sites detailed studies of trench cross sections and dating radiocarbon and ceramics show three faulting events that occurred in the vanadzor artanih segment fioletovo and semionovka areas whereas a single event took place in the artanish sunik segment khonarhasar area in both areas we estimated the average slip rate using i the offset of rivers along the vanadzor artanish segment 2 24 0 96 mm year over an interval of 120 300 ka and ii the offset of volcanic cones along the artanish sunik segment 0 53 0 04 mm year over an interval of 1 4 ma these results suggest that a greater slip rate characterises the vanadzor artanish segment fioletovo site from the artanish sunik khonarhasar site segment division of the pambak sevan sunik fault zone into two main branches east of the artanish peninsula sevan lake could explain the difference in slip rate in addition to its segmented seismic behaviour the pambak sevan sunik fault is a well documented example of a fault that generates strong earthquakes with long recurrence time intervals about 3000 4000 years d 2001 elsevier science b v all rights reserved

the role of active strike slip faults and opposite vertical axis rotations in accommodating eurasia arabia shortening in central iran abstract in central iran most of the late cenozoic to present shortening has been accomplished in the zagros in the alborz and kopeh dagh mountain ranges between these active mountain belts a minor amount of shortening is observed and the deformation style is characterized by active strike slip faults that bound relatively aseismic blocks two main strike slip fault systems are presently active in different regions of central iran south of latitude 34 n active deformation is accommodated on n s oriented right lateral strike slip faults and north of latitude 34 n e w left lateral strike slip faults prevail in this work we investigated two different structures representative of the two different strike slip systems occurring in central iran the yazd fold system located in an area dominated by the occurrence of nnw sse oriented right lateral strike slip faults and the ferdows fold system that developed at the western termination of the e w left lateral strike slip dasht e bayaz fault paleomagnetic results show opposite vertical axis rotations related to the different orientation and sense of movement of strike slip fault systems suggesting that in central iran the n s oriented right lateral and e w oriented left lateral strike slip faults play significant roles in accommodating the arabia eurasia convergence by rotating counterclockwise and clockwise in the horizontal plane respectively

quantitative analysis of seismicity in iran we use historical and recent major earthquakes and gps geodetic data to compute seismic strain rate geodetic slip deficit static stress drop the parameters of the magnitude frequency distribution and geodetic strain rate in the iranian plateau to identify seismically mature fault segments and regions our analysis suggests that 11 fault segments are in the mature stage of the earthquake cycle with the possibility of generating major earthquakes these faults primarily are located in the north and the east of iran four seismically mature regions in southern iran with the potential for damaging strong earthquakes are also identified we also delineate four additional fault segments in iran that can generate major earthquakes without robust clues to their maturity the most important fault segment in this study is the strike slip system near the capital city of tehran with the potential to cause more than one million fatalities

the 2004 may 28 baladeh earthquake mw 6 2 in the alborz iran overthrusting the south caspian basin margin partitioning of oblique convergence and the seismic hazard of tehran we use teleseismic waveform analysis and locally recorded aftershock data to investigate the source processes of the 2004 baladeh earthquake which is the only substantial earthquake to have occurred in the central alborz mountains of iran in the modern instrumental era the earthquake involved slip at 10 30 km depth with a south dipping aftershock zone also restricted to the range 10 30 km which is unusually deep for iran these observations are consistent with co seismic slip on a south dipping thrust that projects to the surface at the sharp topographic front on the north side of the alborz this line is often called the khazar fault and is assumed to be a south dipping thrust which bounds the north side of the alborz range and the south side of the south caspian basin though its actual structure and significance are not well understood the lack of shallower aftershocks may be due to the thick pile of saturated overpressured sediments in the south caspian basin that are being overthrust by the alborz a well determined earthquake slip vector in a direction different from the overall shortening direction across the range determined by gps confirms a spatial separation partitioning of left lateral strike slip and thrust faulting in the alborz these strike slip and thrust fault systems do not intersect within the seismogenic layer on the north side though they may do so on the south the earthquake affected the capital tehran and reveals a seismic threat posed by earthquakes north of the alborz located on south dipping thrusts as well as by earthquakes on the south side of the range closer to the city

long term fault slip rates distributed deformation rates and forecast of seismicity in the iranian plateau in this paper the long term crustal flow of the iranian plateau is computed using a kinematic finite element model neokinema software based on the iterated weighted least squares method the models are fitted to the newest data set of iran including updated fault traces geologic fault offset rates geodetic benchmark velocities principal stress directions and velocity boundary conditions we are successful to find the best kinematic model in which geological slip rates geodetic velocities and interpolated stress directions are fitted at levels of 0 35 1 0 and 1 0 datum standard deviation respectively the best fitted model for the first time provides long term fault slip rates velocity and anelastic strain rate field in the iranian plateau from all available kinematic data in order to verify the model the estimates of fault slip rates are compared to slip rates from merely analyzing geodetic benchmark velocities or paleoseismological studies or published geological rates which have not been used in the model our estimated rates are all in the range of geodetic rates and are even more consistent with geological rates than previous gps based estimates using the selected model long term average seismicity maps and long term moment rates are produced on the basis of the shift hypothesis and previous global calibrations our kinematic model also provides a new constraint on ratio of seismic deformation to total deformation for different seismic zones of iran the resulting slip rates and the proposed seismic fraction of deformation provide the necessary input data for future time dependent hazard studies in iran moreover spatial distribution and total number of strong m 6 and major m 7 earthquakes which dominate the seismic hazard are all compatible with the regional seismic catalog

sediment residence times constrained by uranium series isotopes a critical appraisal of the comminution approach abstract quantifying the rates of landscape evolution in response to climate change is inhibited by the difficulty of dating the formation of continental detrital sediments we present uranium isotope data for cooper creek palaeochannel sediments from the lake eyre basin in semi arid south australia in order to attempt to determine the formation ages and hence residence times of the sediments to calculate the amount of recoil loss of 234u a key input parameter used in the comminution approach we use two suggested methods weighted geometric and surface area measurement with an incorporated fractal correction and typical assumed input parameter values found in the literature the calculated recoil loss factors and comminution ages are highly dependent on the method of recoil loss factor determination used and the chosen assumptions to appraise the ramifications of the assumptions inherent in the comminution age approach and determine individual and combined comminution age uncertainties associated to each variable monte carlo simulations were conducted for a synthetic sediment sample using a reasonable associated uncertainty for each input factor and including variations in the source rock and measured 234u 238u ratios the total combined uncertainty on comminution age in our simulation for both methods of recoil loss factor estimation can amount to 220 280 ka the modelling shows that small changes in assumed input values translate into large effects on absolute comminution age to improve the accuracy of the technique and provide meaningful absolute comminution ages much tighter constraints are required on the assumptions for input factors such as the fraction of recoil lost 234th and the initial 234u 238u ratio of the source material in order to be able to directly compare calculated comminution ages produced by different research groups the standardisation of pre treatment procedures recoil loss factor estimation and assumed input parameter values is required we suggest a set of input parameter values for such a purpose additional considerations for calculating comminution ages of sediments deposited within large semi arid drainage basins are discussed

the zandjan fault system morphological and tectonic evidences of a new active fault network in the nw of iran abstract the zandjan province is situated in the nw of iran at the junction between the southern termination of the tabriz right lateral strike slip fault and the western end of the alborz active mountain range despite this key location in terms of active tectonics there is no destructive earthquake reported in available historical seismicity catalogues even if a few low magnitude instrumental earthquakes have been recorded indicating that this area is actively deforming the zandjan region can be considered as a seismic gap based on detailed field investigations digital elevation models dems satellite image and aerial photo interpretations we have identified a major active fault network affecting this regions it is mainly constituted by several west and est verging thrust faults trending nw se to n s that clearly cut late quaternary to holocene deposits evidences in the morphology indicate also that they accommodate some right lateral slip component this fault network can be divided into four major fault zones affecting zandjan city present day population over 500 000 and part of the zandjan mianeh basin more to the west based on fault geometrical characteristics fault length segmentation and kinematics the zandjan fault system is certainly capable to produce moderate to large earthquakes mw 6 5 7 0 and serious damages in the zandjan city and surrounding areas the study of these faults is then of major interest for seismic hazard assessment in zandjan province where total population exceed 1 5 million but also to better understand present day geodynamic of nw iran

226ra 238u and 228th 228ra disequilibrium as weathering indices in beach sand sediments associated with granitoids from cyclades greece abstract radioactive secular disequilibrium measured as the absolute difference from 1 of the 226ra 238u and 228ra 228th ratios have been used to determine weathering extent twenty eight samples from beach sands of cyclades islands all of them being the weathering products of the local granitic plutons are studied for their secular disequilibrium in both 238u and 232th series 226ra 238u and 228th 228ra respectively the results are compared to weathering indices already in use worldwide and suggest a significant linear correlation of u series disequilibrium with wip alkaline and alkaline earth element leaching and pwi silica leaching for the beach sands studied and significant non linear correlations with cia chemical index of alteration and pia plagioclase index of alteration considering only the heavy mineral enriched samples significant correlations exist between u series disequilibrium and cia ciw chemical index of weathering and pia therefore with an appropriate choice of the weathering index and samples both u series and weathering index can recover the extent of chemical weathering on the other hand the use of th series disequilibrium as a weathering index is limited due to 228th and 228ra geochemistry and especially due to their short radionuclide half lives u series disequilibrium can therefore be used as a relatively sensitive weathering index in sediments consistent with cia ciw and pia indices however the mineralogical composition must be considered more specifically the mineral content of the sediments should involve considerable amounts of sensitive to weathering minerals e g fe mg minerals as well as feldspars

the migration of radionuclides in granite a review based on natural analogues abstract the characterization of a geological formation for nuclear waste disposal should be carried out on a site by site basis however the study of analogous granitic formations all around the world gives a few general guidelines for a better understanding of elemental migration processes in this review focused on mineralogical petrological and geochemical phenomena it is shown that fractures should play a dominant role in transport through granites moreover mineralogical transformations as well as their textural and petrophysical consequences e g permeability changes should be reliably predicted finally this review confirms that water rock interactions do mobilize many elements including analogues of actinides u th ree however most alteration minerals of granite e g clay minerals carbonates exhibit a high capability for efficiently trapping these heavy elements it is concluded that natural analogues are very useful for specifying the appropriate approach for the characterization of a geological site they have also proved essential for developing and validating geochemical models of mass transfers around a repository in granite

the possible bearing of the granite of the uph deep drill holes northern illinois on the origin of mississippi valley ore deposits the pb pb th pb and u pb systems of whole rock drill core samples of the granite of uph record at least one postcrystallization event treatment of the data on a concordia plot indicate the timing of this disturbance was probably 260 35 m y ago and probably no older than 400 m y ago the upper intercept age on concordia is 1416 20 m y and the pb pb isochron age for the four least disturbed rocks plus the four potassium feldspars is 1451 19 m y these ages are in close agreement with rb sr whole rock and u pb zircon ages determined by others and should be the age of granite formation considerable pb loss is indicated for many of the shallower samples that have a more red rather than pink color probably to a factor of two to three or more as a result of the disturbance although the granite remains pb rich today 40 80 ppm in some other studies of disturbed u th pb systems the radiogenic lead has been taken up by potassium feldspars however the pb for most samples seems to have been lost from the system for the granite of uph one sample with an unusually high pb content of about 195 ppm has the most radiogenic pb of any sample but normal values of th u this sample has obviously gained radiogenic pb by more than a factor of four and confirms that pb was indeed mobilized in parts of the system within the limits of the uncertainties equal amounts of pb were lost or gained in both the u pb and th pb systems which is compatible with mobilization being restricted to lead there is some tendency however for the more affected samples to have lower th u values and higher u contents a complex model in which u is gained pb lost and 208pb lost preferentially to 207pb and 206pb cannot be ruled out u and th have somewhat different crystallographic locations and decay energies so that 208pb might be in more accessible sites than the other pb isotopes fission track mapping of the samples indicates most of the u today is located in submicroscopic sites along edges and cleavages of biotite and iron oxides so u is readily available for remobilization lead extraction with only minor u or th removal may have been accomplished by chloride rich brines lead isotope data on the granite of uph indicates that some of the pb in the ore in the nearby upper mississippi valley lead zinc district may have been derived from these granites an even better match is made with the ores of southeastern missouri although a granite like that of uph would only be one end member most likely the radiogenic end member of a mixed source curiously similar aged and heavy metal rich granites from southeastern missouri are not a good match for theckn nearby ores basement rocks such as the granite of uph must be reconsidered as an important contributor to the ores of the mississippi valley but it is unlikely that they constitute the sole source

contribution of archaeological data to studies of earthquake history in the iranian plateau we use archaeological evidence to identify ancient earthquakes in the vicinity of large 20th century events in the iranian plateau two large earthquakes on the zagros main recent fault were preceded by historical earthquakes in ad 1008 and ad 1107 and by earthquakes in the intervals ad 224 459 and 1650 1600 bc giving return times of 1800 2100 500 800 and 850 950 years the ad 1962 ms 7 2 bo in zahra earthquake on the ipak fault in north central iran was preceded by an earthquake in 2000 1500 bc recorded at the sagzabad mound a return time of 3500 4000 years if there are no missing events the ad 1990 ms 7 3 rudbar tarom earthquake in the western alborz mountains was preceded by an earthquake in 1000 800 bc recorded at the marlik mound a return time of 2800 3000 years the ad 1948 ms 7 2 kopeh dagh earthquake that destroyed ashkabad capital of turkmenistan was preceded by an earthquake in 10 bc ad 10 recorded at mithradatkert nesa mound and by an earthquake in 2000 bc recorded at ak tapeh mound assuming no missing earthquakes this region has an earthquake return time of about 2000 years in khorasan province which was struck by a sequence of large earthquakes from ad 1936 to 1997 a mosque at qa en was destroyed in the mid 11th century ad probably the historical earthquake of ad1066 in the absence of palaeoseismic investigations archaeology offers the promise of recording earthquakes through more than one seismic cycle in different regions of iran q 2001 elsevier science ltd all rights reserved

comparisons of the kinematics and deep structures of the zagros and himalaya and of the iranian and tibetan plateaus and geodynamic implications 1 we compare the geologic histories the deep structures and the present day kinematics of deformation of the himalaya and the adjacent tibetan plateau with those of the zagros and iranian plateau to test geodynamic processes of continental collision shortly after india and arabia collided with eurasia horizontal shortening manifested itself by folding and thrust faulting of sedimentary rock detached from india s and arabia s underlying crystalline basement subsequently slip on thrust faults stacked slices of india s basement to build the himalaya on india s northern margin such faulting has not yet developed in the zagros where collision is more recent and arabia penetrates into eurasia more slowly than india does so that postcollision convergence with eurasia is less the greater elevation thicker crust and more marked heterogeneity of the upper mantle beneath the tibetan than beneath the iranian plateau also reflect a more advanced stage of development moreover while thrust or reverse faulting and crustal shortening continue on the margins of both plateaus normal faulting suggesting horizontal extension and crustal thinning occurs within tibet but not in iran hence the balance of forces that built the high tibetan plateau must have changed apparently some time since 15 ma removal of tibetan mantle lithosphere could have altered that balance if mantle lithosphere beneath the iranian plateau has been removed however the change in force balance has been too small to initiate normal faulting low seismic wave speeds in the uppermost mantle just beneath the moho of both plateaus suggest to us that lithosphere beneath both is thin consistent with late cenozoic removal of it but alternative explanations might account for these low speeds despite its apparently thin and hence presumably weak mantle lithosphere much of central iran undergoes little deformation it illustrates how a crustal block can behave rigidly not necessarily because it is strong but because deviatoric stresses can be small whereas differences between the two regions clearly depend on the amount that arabia and india have penetrated into eurasia which scales with both the dates of collision and rates of convergence we see no differences in the operative processes that depend on the present day rates of convergence

active tectonics within the nw and se extensions of the pambak sevan syunik fault implications for the present geodynamics of armenia this study analyzes the active tectonics within the northwestern and southeastern extensions of the pambak sevan syunik fault pssf a major right lateral strike slip fault cutting through armenia quantifying the deformations in terms of geometry kinematics slip rates and earthquake activity using cosmogenic 3he osl irsl and radiocarbon dating techniques reveal different behaviors between the two regions within the northwestern extension in the region of amasia the pssf bends to the west and splits into two main wnw ese trending reverse faults defining a compressional pop up structure we estimate an uplift rate and a shortening rate of 0 5 0 1 mm y and 1 4 0 6 mm y respectively this suggests that most of the 2 mm y right lateral movement of the pssf seems to be absorbed within the amasia pop structure within the southeastern extension the pssf shows signs of dying out within the tsghuk volcano region at the southernmost tip of the syunik graben there the tectonic activity is characterized by a very slow ns trending normal faulting associated with a slight right lateral movement slip rates analyses i e vertical slip rate ew stretching rate at 90 to the fault and right lateral slip rate of 0 2 mm y 0 1 mm y and 0 05 mm y respectively lead to the conclusion that the right lateral movement observed further north along the pssf is mainly transferred within other active faults further west within the karabagh hagari fault or other structures further northwestwards comparing our slip rates with those estimated from gps data suggests that most of the deformation is localized and seismic at least within the tsghuk region the geometrical and kinematic pattern observed within the two terminations of the pssf suggests that the fault and its surrounding crustal blocks are presently rotating anticlockwise as also observed within the gps velocity field this is consistent with the recent kinematic models proposed for the caucasus kura south caspian region and brings a new insight into the present geodynamics of armenia

geochemical baselines for the radioelements k u and th in the campania region italy a comparison of stream sediment geochemistry and gamma ray surveys abstract this paper presents new data on the baseline concentrations of u th and k in 2389 stream sediments over the whole campania region these data based on systematic sampling and analysis are compared with those obtained by gamma ray spectrometry surveys variations in the u th and k concentration in the surficial environment of the campania region appear to be related to bedrock lithology generally high u th and k values in stream sediments correspond well with the occurrence of volcanic rocks in the central western part of the region whereas low values are found in areas characterized by silico clastic and carbonate deposits occurring mostly in the southern and eastern part of the region gamma ray spectrometry maps show a similar pattern although the distribution of the highest radioactivity levels define more restricted areas than the ones resulting from mapping stream sediment geochemistry particularly high 40k radioactivity levels delimit all the known eruptive centers roccamonfina campi flegrei and somma vesuvius including the fissural sources of campania ignimbrites much better than u and th radioactivity one of the concerns for human health in the campania region is the total gamma radiation and rn potential related mostly to alkaline volcanics of the neapolitan volcanological province in particular geothermal activity occurring in all the campanian volcanic areas represents a potential hazard for rn gas

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

dating of archean basement in northeastern wyoming and southern montana rb sr whole rock and u pb zircon ages of granite and gneiss cores from three deep drill holes extend known occurrences of archean rocks in the subsurface of northeastern wyoming and southern montana rb sr and k ar mineral ages are discordant and reflect early or middle proterozoic disturbance highly altered rocks occur in a thin zone immediately below the sub cambrian unconformity samples from a few metres deeper in the basement are much fresher but show the effects of this alteration in filled fractures and thin adjacent alteration haloes whole rock rb sr systems have retained a fair degree of integrity in spite of increased susceptibility to modification because of the disturbed mineral systems interaction of the rocks with water a few metres below the sub cambrian unconformity probably occurred for only a relatively short time fractures filled rapidly with secondary minerals such as chlorite anhydrite and carbonate to maintain a relatively impermeable crystalline basement in which the silicates and their contained isotopic systems were preserved ages of cores from two wells extend the archean basement to the nacp anomaly a possible suture related to early proterozoic tectonism these and published ages limit a possible ensimatic mobile belt to a zone 300 km wide beneath the williston basin however the possibility remains that archean crust was continuous between the wyoming age province and the superior province

u th pb systematics of morphologically characterized zircon and allanite a high resolution isotopic study of the alpine rensen pluton northern italy abstract the rensen pluton is a typical member of the tertiary calc alkaline plutonic suite structurally connected to the periadriatic lineament it intrudes the austroalpine polymetamorphic basement of the eastern alps southwest of the tauern window northern italy zircons and allanites from tonalitic quartz dioritic and monzogranitic lithologies were studied systematically on the basis of refined grain by grain microanalytical techniques high resolution isotope analyses show that morphology and u pb systematics of zircon are highly correlated with magma evolution zircons from the main tonalitic part of the intrusion display a gradual increase of u content from early stage s type morphology to late stage g1 type morphology most of the zircon crystals include premagmatic seeds derived from old crustal sources unevolved s type zircons contain inherited components of late proterozoic early paleozoic apparent age whereas late stage g1 type zircons show inheritance of early proterozoic apparent age both types of inherited components are present in zircons from a fine grained tonalitic domain located at the center of the pluton which shows restitic structures the crustal affinity of this rock is corroborated by its relatively low e nd value 6 0 as compared to values obtained for the main tonalite 3 9 and the quartz diorite 3 5 the accuracy of cainozoic zircon ages is affected by initial radioactive disequilibrium in the u pb decay chains particularly uncertain is the fractionation behavior of protactinium which could be enriched in zircon due to the high stability of the pa 5 oxidation state because the th pb system is devoid of long lived intermediate radioactive nuclides the best approximation to the emplacement age of the rensen pluton is given by allanite th pb ages of 31 70 0 25ma 95 c l for the main tonalite and by a slightly younger age of 31 09 0 32ma for quartz diorite

tectonic magnetic lineation and oroclinal bending of the alborz range implications on the iran southern caspian geodynamics in this study we use the anisotropy of magnetic susceptibility ams and paleomagnetic data for deciphering the origin of magnetic lineation in weakly deformed sedimentary rocks and for evaluating oroclinal processes within the arabia eurasia collision zone in particular we have analyzed the miocene upper red formation urf from the outer curved front of the southern central alborz mountains of north iran to test for the first time with paleomagnetic data the origin primary versus secondary of this orogenic arc ams data document the existence of a magnetic lineation parallel to the orientation of the major tectonic structures which vary along strike from wnw to ene these directions are highly oblique to the paleoflow directions and hence suggest that the magnetic lineation in the urf was produced by compressional deformation during layer parallel shortening in addition our paleomagnetic data document clockwise and anticlockwise rotations along vertical axis for the western and eastern sectors of the central alborz mountains respectively combined our results suggest that the orogen represents an orocline which formed not earlier than circa 7 6 ma most likely through bending processes caused by the relative motion between the rigid crustal blocks of the collision zone moreover our study provides new insights into the iran southern caspian basin kinematic evolution suggesting that the present day sw motion of the south caspian basin with respect to central iran postdates oroclinal bending and hence cannot be as old as late miocene to early pliocene but a rather recent configuration i e 3 to 1 ma

representative uranium deposits and occurrences exclusive of sandstone impregnations and quartz conglomerates abstract all the known non sandstone and non quartz conglomerate types of uranium deposits and occurrences were reviewed to focus on geologic environments from which unknown large economic types might be expected one or more representative examples of each type was selected and its major occurrence characteristics identified following a new limited genetic classification potential significance was judged by capacity of the mineralization process to produce large deposits rather than by the size and grade of known examples the precedent for this approach is set by uranium exploration history exploration occurred in spurts stimulated by demand beyond the capability of known deposits and distinguished by recognition of new types of larger richer deposits which could supply the demand stagnation in the 1960 s and 1970 s of the discovery rate for conventional sandstone impregnations and quartz pebble conglomerates which contributed the bulk of uranium production illustrated the need for another innovative spurt the study encompassed the then unconventional types of uranium deposits however during the investigation exploration discovered so many large rich unconventional deposits that the connotation conventional on the production basis embraced them this included the rossing late magmatic replacement dissemination and a number of impregnation replacement masses related to proterozoic unconformities in canada and australia these types were included in the original project and are retained in this discussion but their inclusion reduces the significance precision and impact originally intended by designating the entire range of considered deposit types as unconventional accordingly the designation conventional unconventional has been removed or subdued however the principle that surprising discoveries introduce new economic types of deposits which were subtly evidenced in known occurrences and shift the designation of conventional was emphatically confirmed by both this project and concurrent exploration recognition of this principle lends potential significance to the remaining unconventional deposits and occurrences discussed their occurrence parameters may contain clues to yet other unknown types of large rich deposits however little effort was made in this paper to identify specific potentially economic exploration targets

active tectonics of the east alborz mountains ne iran rupture of the left lateral astaneh fault system during the great 856 a d qumis earthquake the 856 a d qumis earthquake m7 9 is the most destructive earthquake to have occurred in iran killing more than 200 000 people and destroying the cities of damghan and the old parthian capital of shahr i qumis hecatompylos this study combines evidence of historical seismicity with observations of the geomorphology and paleoseismology to provide the first detailed description of active faulting in the damghan region of the east alborz mountains iran regional left lateral shear is accommodated on the astaneh damghan and north damghan faults quaternary alluvial fans have been displaced along the astaneh fault with 15 20 m stream offsets recording the cumulative displacement over the last two to five earthquakes a paleoseismology study from a single trench along a 5 10 km segment of the astaneh fault reveals a rupture prior to 1300 a d and significantly later than 600 b c despite the limitations of a single trench in documenting the spatial and temporal evolution of the fault over the late quaternary we are nevertheless able to bracket the last event to a time period consistent with the 856 a d earthquake two older earthquakes were also identified during the holocene occurring between 600 b c and 4600 b c and between 4600 b c and 9600 b c the location of our trench within a bend on the astaneh fault which could act as a barrier to rupture propagation means the three earthquakes recovered from our trench over the holocene may represent a minimum further trenching will reveal how the astaneh fault ruptures over repeated earthquakes and consequently the magnitude and extent of slip during the 856 a d earthquake

distinguishing between fault scarps and shorelines the question of the nature of the kahrizak north rey and south rey features in the tehran plain iran terra nova 22 227 237 2010 abstract tehran is one of the largest cities in the world 12 million people facing seismic hazard standing at the foothills of alborz mountains the capital of iran is exposed to potential earthquakes associated with several nearby active faults classically mentioned as active features the kahrizak the north rey and the south rey scarps cross the town itself and would be the sources of several destructive historical earthquakes however the nature of these topographic scarps remains uncertain to assess whether these features correspond to active faults we carried out a morphological and stratigraphic study our results show that the three scarps define horizontal scarp lines that follow contour lines matching ancient shorelines further east this point associated with other morphological characteristics such as the flatness of the upper and the lower surfaces the long and regular streams that incised the upslope upper surfaces and the fact that the deposits are horizontal and without deformations suggests in fact that the kahrizak the north rey and the south rey scarps correspond most likely to ancient shore lines and are not fault scarps

left lateral active deformation along the mosha north tehran fault system iran morphotectonics and paleoseismological investigations abstract the mosha and north tehran faults correspond to the nearest seismic sources for the northern part of the tehran megacity the present day structural relationships and the kinematics of these two faults especially at their junction in lavasanat region is still a matter of debate in this paper we present the results of a morphotectonic analysis aerial photos and field investigations within the central part of the mosha and eastern part of the north tehran faults between the mosha valley and tehran city our investigations show that generally the traces of activity do not follow the older traces corresponding to previous long term dip slip thrusting movements the recent faulting mainly occurs on new traces trending e w to ene wsw affecting quaternary features streams ridges risers and young glacial markers and cutting straight through the topography often defining en echelon patterns right and left stepping these new traces correspond to steep faults with either north or south dipping directions along which clear evidences for left lateral strike slip motion are found at their junction zone the two sinistral faults display a left stepping en echelon pattern defining a positive flower structure system clearly visible near ira village further west the left lateral strike slip motion is transferred along the ene wsw trending niavaran fault and other faults the cumulative offsets associated with this left lateral deformation is small compared with the topography associated with the previous late tertiary thrusting motion showing that it corresponds to a recent change of kinematics

tectonic setting and provenance of the neoproterozoic uinta mountain and big cottonwood groups northern utah constraints from geochemistry nd isotopes and detrital modes abstract the neoproterozoic uinta mountain group was deposited in an east trending intracratonic rift bounded on the north by an active fault system and opening into a shallow sea on the west where the big cottonwood group was deposited in an estuary although this rift may have been associated with the early stages in the breakup of rodinia it was not an aulacogen geochemical nd isotope and detrital mode studies indicate that uinta mountain group sediments were derived from mixed archean and paleoproterozoic sources with the former dominating big cottonwood group sediments appear to have been derived predominantly from paleoproterozoic sources the archean sediment source is the wyoming craton and source rocks comprised dominantly granites enriched in th u y zr hf and ree the relative abundance of enriched granite implied by sedimentary rocks of the uinta mountain group indicates that the wyoming craton is anomalous compared to other archean cratons cia values and a cn k relationships in shales of the uinta mountain and big cottonwood groups indicate high degrees of weathering of sources probably in subtropical to tropical climates supporting a near equatorial location for southwestern laurentia at about 800 ma differences in the nd isotopic composition between the big cottonwood group and neoproterozoic sedimentary rocks in western utah and northeast nevada suggest a northwest striking uplift in northwest utah possibly ancestral to the paleozoic toole uinta arch

sediment residence times in catchments draining to the gulf of carpentaria northern australia inferred by uranium comminution dating abstract uranium u isotopes are useful for constraining the timescales of weathering and erosion processes the 234u 238u activity ratio parentheses denote activity ratio of fine grained detrital minerals is proposed to record the time elapsed since mineral grains were reduced to

234u 238u evidence for local recharge and patterns of ground water flow in the vicinity of yucca mountain nevada usa uranium concentrations and 234u 238u ratios in saturated zone and perched ground water were used to investigate hydrologic flow and downgradient dilution and dispersion in the vicinity of yucca mountain a potential high level radioactive waste disposal site the u data were obtained by thermal ionization mass spectrometry on more than 280 samples from the death valley regional flow system large variations in both u concentrations commonly 0 6 10 g l 1 and 234u 238u activity ratios commonly 1 5 6 are present on both local and regional scales however ground water with 234u 238u activity ratios from 7 up to 8 06 is restricted largely to samples from yucca mountain data from ground water in the tertiary volcanic and quaternary alluvial aquifers at and adjacent to yucca mountain plot in 3 distinct fields of reciprocal u concentration versus 234u 238u activity ratio correlated to different geographic areas ground water to the west of yucca mountain has large u concentrations and moderate 234u 238u whereas ground water to the east in the fortymile flow system has similar 234u 238u but distinctly smaller u concentrations ground water beneath the central part of yucca mountain has intermediate u concentrations but distinctive 234u 238u activity ratios of about 7 8 perched water from the lower part of the unsaturated zone at yucca mountain has similarly large values of 234u 238u these u data imply that the tertiary volcanic aquifer beneath the central part of yucca mountain is isolated from north south regional flow the similarity of 234u 238u in both saturated and unsaturated zone ground water at yucca mountain further indicates that saturated zone ground water beneath yucca mountain is dominated by local recharge rather than regional flow the distinctive 234u 238u signatures also provide a natural tracer of downgradient flow elevated 234u 238u in ground water from two water supply wells east of yucca mountain are interpreted as the result of induced flow from 40 a of ground water withdrawal elevated 234u 238u in a borehole south of yucca mountain is interpreted as evidence that natural downgradient flow is more likely to follow southerly paths in the structurally anisotropic tertiary volcanic aquifer where it becomes diluted by regional flow in the fortymile system

use of u isotopes in exploring groundwater flow and inter aquifer leakage in the south western margin of the great artesian basin and arckaringa basin central australia abstract the distribution of uranium isotopes 238u and 234u in groundwaters of the south western margin of the great artesian basin gab australia and underlying arckaringa basin were examined using groundwater samples and a sequential extraction of aquifer sediments rock weathering the geochemical environment and recoil of daughter products control the 238u and 234u isotope distributions giving rise to large spatial variations generally the shallowest aquifer j aquifer contains groundwater with higher 238u activity concentrations and 234u 238u activity ratios close to secular equilibrium however the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238u activity concentrations other locations in the j aquifer that receive little or no recharge contain higher 238u activity concentrations because uranium from localised uranium rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution the geochemical conditions of the deeper aquifers generally result in lower 238u activity concentrations in the groundwater accompanied by higher 234u 238u activity ratios the sequential extraction of aquifer sediments showed that recoil of 234u from the solid mineral phases into the groundwater rather than dissolution of or exchange with the groundwater accessible minerals in the aquifer caused enrichment of groundwater 234u 238u activity ratios in the boorthanna formation decay of 238u in uranium rich coatings on j aquifer sediments caused resistant phase 234u 238u activity ratio enrichment the groundwater 234u 238u activity ratio is dependent on groundwater residence time or flow rate depending on the flow path trajectory thus uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers however spatial heterogeneity and the lack of clear regional correlations made it difficult to identify recharge and inter aquifer leakage