nucleation crystal growth and the thermal regime of cooling magmas crystallization at the margin of a quiet cooling magma has been studied numerically taking into account the kinetics of crystallization the variables are the latent heat value the growth and nucleation functions the initial magma temperature and the thermal contrast between magma and country rock we have investigated a wide range of values for these parameters corresponding to natural conditions we show that after a highly transient stage crystallization tends toward an equilibrium between heat production latent heat release and heat loss given the small diffusivity of country rocks latent heat release is the main factor controlling the temperature evolution in order to minimize the latent heat release crystallization occurs at a temperature where nucleation is small this can be close to either the liquidus or the solidus depending on the initial conditions the main process controlling crystallization is nucleation and not crystal growth nucleation occurs as a series of sharp pulses followed by longer periods of crystal growth the nucleation pulses give birth to thermal oscillations these oscillations can be sustained if the interior magma temperature is above the liquidus independently of the heat loss mechanism we show that the phenomenon occurs on the scale of a few centimeters which corresponds to the inch scale layering of many ultrabasic complexes the model allows us to calculate crystal sizes which are in good agreement with geological observations the crucial parameters which determine crystal size variations near the margins of igneous bodies are the initial thermal conditions as well as the nucleation and growth functions in the main cooling regime close to the liquidus significant size variations can be created by small thermal disturbances

relocation and assessment of seismicity in the iran region summary more than 2000 instrumentally recorded earthquakes occurring in the iran region during the period 1918 2004 have been relocated and reassessed with special attention to focal depth using an advanced technique for 1 d earthquake location a careful review of starting depths association of teleseismic depth phases and the effects of reading errors on these phases are made and when necessary waveforms have been examined to better constrain ehb focal depths uncertainties in ehb epicentres are on the order of 10 15 km in the iran region owing to the earth s lateral heterogeneity and uneven station distribution uncertainties of reviewed ehb focal depth estimates are on the order of 10 km as compared to about 4 km for long period p and sh body waveform inversions nevertheless these ehb depth estimates are sufficiently accurate to resolve robust differences in focal depth distribution throughout the iran region and within their errors show patterns that are in agreement with the smaller number of earthquakes whose depths have been confirmed by body wave modelling or local seismic networks the importance of this result is that future earthquakes with apparently anomalous depths can easily be identified and checked if necessary most earthquakes in the iranian continental lithosphere occur in the upper crust with the crustal shortening produced by continental collision accommodated entirely by thickening and distributed deformation in the zagros mountains nearly all earthquakes are confined to the upper crust depths 20 km and there is no evidence for a seismically active subducted slab dipping ne beneath central iran by contrast in southeastern iran where the arabian seafloor is being subducted beneath the makran coast low level earthquake activity occurs in the upper crust as well as to depths of at least 150 km within a northward dipping subducting slab near the oman line a region transitional between the zagros and the makran seismicity extends to depths of up to 30 45 km in the crust consistent with low angle thrusting of arabian basement beneath central iran in north central iran along the alborz mountain belt seismic activity occurs primarily in the upper crust but with some infrequent events in the lower crust particularly in the western part of the belt the talesh where the south caspian basin underthrusts nw iran earthquakes that occur in a band across the central caspian following the apscheron balkhan sill between azerbaijan and turkmenistan have depths in the range 30 100 km deepening northwards these are thought to be connected with either incipient or remnant northeast subduction of the south caspian basin basement beneath the east west trending apscheron balkhan sill curiously in this region of genuine mantle seismicity there is no evidence for earthquakes shallower than 30 km

automated composite depth scale construction and estimates of sediment core extension 1 a composite section which reconstructs a continuous stratigraphic record from cores of multiple nearby holes and its associated composite depth scale are important tools for analyzing sediment recovered from a drilling site however the standard technique for creating composite depth scales on drilling cruises does not correct for depth distortion within each core additionally the splicing technique used to create composite sections often results in a 10 15 offset between composite depths and measured drill depths we present a new automated compositing technique that better aligns stratigraphy across holes corrects depth offsets and could be performed aboard ship by analyzing 618 cores from seven ocean drilling program odp sites we estimate that 80 of the depth offset in traditional composite depth scales results from core extension during drilling and extraction average rates of extension are 12 4 1 5 for calcareous and siliceous cores from odp leg 138 and 8 1 1 1 for calcareous and clay rich cores from odp leg 154 also average extension decreases as a function of depth in the sediment column suggesting that elastic rebound is not the dominant extension mechanism

land subsidence pattern controlled by old alpine basement faults in the kashmar valley northeast iran results from insar and levelling summary fluid storage systems such as oil gas magma or water reservoirs are often controlled by the host rock structure and faulted terrain in sedimentary basins where no direct information about underlying structure is available the pattern of ground deformation may allow us to assess the buried fault arrangement we provide an example in the semi arid area of iran in the kashmar valley a region subject to land subsidence due to water overexploitation geodetically determined subsidence rates in the kashmar valley exceed 15 30 cm yr 1 the pattern of surface deformation is strongly non uniform and displays ne sw elongated bowls of subsidence the trend resembles old cretaceous to tertiary faults that evolved during early alpine tectonic deformation although these early alpine structures are considered tectonically inactive in the present day the observed land subsidence pattern indicates significant structural control on the geometry of the aquifer basin and its deformation during reservoir drainage

a quantitative assessment of dinsar measurements of interseismic deformation the southern san andreas fault case study we investigate the capabilities and limitations of the differential interferometric synthetic aperture radar dinsar techniques in particular of the small baseline subset sbas approach to measure surface deformation in active seismogenetic areas the dinsar analysis of low amplitude long wavelength deformation such as that due to interseismic strain accumulation is limited by intrinsic trade offs between deformation signals and orbital uncertainties of sar platforms in their contributions to the interferometric phases the latter being typically well approximated by phase ramps such trade offs can be substantially reduced by employing auxiliary measurements of the long wavelength velocity field we use continuous global positioning system gps measurements from a properly distributed set of stations to perform a pre filtering operation of the available dinsar interferograms in particular the gps measurements are used to estimate the secular velocity signal approximated by a spatial ramp within the azimuth range radar imaging plane the phase ramps derived from the gps data are then subtracted from the available set of dinsar interferograms this pre filtering step allows us to compensate for the major component of the long wavelength range change that within the sbas procedure might be wrongly interpreted and filtered out as orbital phase ramps with this correction the final results are obtained by simply adding the pre filtered long wavelength deformation signal to the sbas retrieved time series the proposed approach has been applied to a set of ers 1 2 sar data acquired during the 1992 2006 time interval over a 200 200 km area around the coachella valley section of the san andreas fault in southern california usa we present results of the comparison between the sbas and the line of sight los projected gps time series of the usgc pbo network as well as the mean los velocity fields derived using sbas gps and stacking techniques our analysis demonstrates the effectiveness of the presented approach and provides a quantitative assessment of the accuracy of dinsar measurements of interseismic deformation in a tectonically active area

interseismic strain accumulation and the earthquake potential on the southern san andreas fault system the southern section of the san andreas fault is the only part of the fault that hasn t ruptured in historic times for this reason it is believed to pose the largest seismic risk in california although whether tectonic stress is actually accumulating there is a topic of heated debate using data from radar interferometry satellites yuri fialko has produced a detailed map of surface deformation in the area that shows that elastic stress is accumulating at a fairly high rate during the past 300 years a displacement of 6 to 9 metres has built up this suggests that the southern san andreas fault is nearing the end of the interseismic phase of the earthquake cycle and that increased seismic activity of some kind can be expected the san andreas fault in california is a mature continental transform fault that accommodates a significant fraction of motion between the north american and pacific plates the two most recent great earthquakes on this fault ruptured its northern and central sections in 1906 and 1857 respectively the southern section of the fault however has not produced a great earthquake in historic times for at least 250 years assuming the average slip rate of a few centimetres per year typical of the rest of the san andreas fault the minimum amount of slip deficit accrued on the southern section is of the order of 7 10 metres comparable to the maximum co seismic offset ever documented on the fault1 2 here i present high resolution measurements of interseismic deformation across the southern san andreas fault system using a well populated catalogue of space borne synthetic aperture radar data the data reveal a nearly equal partitioning of deformation between the southern san andreas and san jacinto faults with a pronounced asymmetry in strain accumulation with respect to the geologically mapped fault traces the observed strain rates confirm that the southern section of the san andreas fault may be approaching the end of the interseismic phase of the earthquake cycle

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

magmatic processes revealed by textural and compositional trends in merapi dome lavas syn eruptive degassing of volcanoes may lead to syn eruptive crystallization of groundmass phases we have investigated this process using textural and compositional analysis of dome material from merapi volcano central java indonesia samples included dome lavas from the 1986 88 1992 93 1994 and 1995 effusive periods as well as pyroclastic material deposited by the november 1994 dome collapse with total crystallinities commonly in excess of 70 phenocrysts 1 microlites the liquids present in merapi andesites are highly evolved rhyolitic at the time of eruption feldspar microlites in dome rocks consist of plagioclase cores ab63an29or8 surrounded by alkali feldspar rims ab53an5or42 compositional pairs which are not in equilibrium a change in the phase relations of the ternary feldspar system caused by degassing best explains the observed transition in feldspar composition a small proportion of highly vesicular airfall tephra grains from the 1994 collapse have less evolved glass compositions than typical dome material and contain rimless plagioclase microlites suggesting that the 1994 collapse event incorporated less degassed partially liquid magma in addition to fully solidified dome rock as decompression drives volatile exsolution rates of degassing and resultant microlite crystallization may be governed by magma ascent rate microlite crystallinity is nearly identical among the 1995 dome samples an indication that similar microlite growth conditions ph2 o and temperature were achieved throughout this extrusive period however microlite number density varied by more than a factor of four in these samples and generally increased with distance from the vent low vent ward microlite number densities and greater microlite concentrations down flow probably reflect progressively decreasing rates of undercooling at the time of crystal nucleation during extrusion of the 1995 dome comparison between dome extrusion episodes indicates a correlation between lava effusion rate and microlite number density suggesting that extrusion slowed during 1995 crystal textures and compositions in the 1992 93 and 1994 domes share the range exhibited by the 1995 dome suggesting that transitions in crystallization conditions i e rates of undercooling determined by effusion rate are cyclic q 2000 elsevier science b v all rights reserved

crystal size distribution in magmatic rocks proposition of a synthetic theoretical model the crystal size distribution csd corresponds to the number of crystals of a mineral per unit volume within a series of defined size intervals many crystal size distributions in igneous systems are straight lines when plotted on the classical diagram of ln population density versus size other common csds are concave down on such graphs for the low size values the effect of growth rate on csds seems to be small and nucleation apparently increases exponentially with time although magmatic systems are always multiphase only a few csd studies deal with several phases on the basis of the few available published examples it seems that the parallelism defined as y spacing constancy of the normalized csds i e where the crystal lengths are normalized to the greatest length for each phase is a common feature in igneous systems the aim of our modelling is to propose a mathematical framework to unify the csd typology to explain the common occurrence of straight lines on the classical csd diagram and the y spacing constancy of the normalized csds for multiphase rocks and also to provide a convenient tool to easily test petrogenetic scenarios through efficient computer simulations the bulk balance modelling is based on a square matrix having for coefficients the number of nuclei of one phase by the crystallized volume of another phase this interaction matrix is the mainspring of our csd modelling which requires straightforward assumptions about the uniformity of crystal shape and growth 1 at each time every crystal of a phase has the same shape and 2 the one dimensional growth rate of a crystal is independent of its size consequently the values of the normalized csd are linked together by means of an integral equation for the most part the behaviour of the csds theoretically obtained with a constant matrix may also be observed in computer simulations of more general cases this extended approach makes feasible the application of the model to natural cases concave down shapes for the lowest size are classically interpreted as a consequence of the ending of crystallization by roughly taking into account crystal interactions during the growth process through the concept of mean clutter we successfully simulate such concave down csds

geochemical and strontium isotopic characteristics of parental aleutian arc magmas evidence from the basaltic lavas of atka eighteen flows from a basal stratigraphic sequence on the aleutian island of atka were analyzed for major elements trace elements and initial 87sr 86sr ratios petrographically these lavas contain abundant plagioclase 24 45 and lesser amounts of olivine 7 magnetite and clinopyroxene phenocrysts compositionally the lavas are high alumina 20wt basalts 48 51 wt sio2 with low tio2 1 and mgo 5 within the section compositional variations for all major elements are quite small while mgo content correlates with olivine phenocryst contents no such relationship exists between the other oxides and phenocryst content these lavas are characterized by 8 10 ppm rb high sr 610 669 ppm 308 348 ppm ba and very constant zr 23 29 ppm and sc 23 29 ppm abundances ni and cr display extremely large compositional ranges 12 118 ppm and 12 213 ppm respectively no correlation exists between trace element concentrations and phenocryst contents strontium isotopic ratios show a small but significant range 0 70314 0 70345 and are slightly elevated with respect to typical morb no systematic correlation between stratigraphic position and petrography or geochemistry is evident ree abundances measured on six samples are lree enriched la yb n 2 20 2 81 and display similar chondrite normalized patterns one sample has a slight positive eu anomaly but the other lavas do not compared to other aleutian basalts of similar silica content these lavas are less lree enriched and have lower overall abundances the geochemical characteristics of these basalts suggest they represent true liquid compositions despite their highly porphyritic nature published phase relations indicate fractionation of a more mgo rich magma could not have produced these lavas the high al2o3 and low mgo and compatible element abundances suggest a predominantly oceanic crustal source for parental high alumina basalts

equatorial pacific seismic reflectors as indicators of global oceanographic events the origin of a series of regionally correlatable seismic horizons in the neogene sediments of the central equatorial pacific is examined through seismic modeling and the detailed analyses of stratigraphic and physical property relationships in deep sea drilling project cores these regionally traceable reflectors are synchronous the younger reflectors are the direct result of carbonate dissolution events the older ones of stratigraphically selective diagenetic processes the changes in ocean chemistry associated with these events appear to be linked to global reorganizations of surface and bottom water circulation patterns the most dramatic of which are associated with reorganizations of north atlantic bottom waters these deepwater seismic horizons appear to correlate with the major events on the relative sea level curve of vail et al for the neogene

slip rate estimate and past earthquakes on the doruneh fault eastern iran summary the doruneh fault with a length of 600 km is one of the longest and most prominent faults in iran it performs an important role in the regional tectonics but has no record of large earthquakes the geomorphology of the doruneh fault contains numerous indications of cumulative left lateral slip over various scales we describe three sites where late quaternary landforms are displaced by the fault a an incised alluvial fan near the village of uch palang is displaced by 800 850 m b the kuh e teagh ahmad fold is composed of folded quaternary gravels and is displaced by 200 400 m c a sequence of three terraces of the shesh taraz river are displaced left laterally by a maximum of 25 m infrared stimulated luminescence irsl dating of the uppermost shesh taraz river terrace gives a deposition age of 10 ka which correlates with changes in global climate 10 12 ka ago and provides a provisional slip rate estimate of 2 4 0 3 mm yr 1 no major recent or historical earthquakes are recorded on the doruneh fault relatively fresh scarps and partially infilled fractures appear to be the preserved surface ruptures from an earthquake event of unknown age a series of small streams showing left lateral displacements of 3 to 5 5 m with an average slip of 4 7 m record the possible magnitude of slip during this earthquake which from scaling relationships would have had an m w of 7 5 and ruptured the fault over a length of 100 km at the estimated slip rate of 2 5 mm yr 1 the average recurrence time between large magnitude earthquakes on the doruneh fault is 2000 yr

calculation of time dependent nucleation and growth rates from quantitative textural data inversion of crystal size distribution magmatictexturesprovideaninsufficientlyexploredtooltointerpretphysical processes and environmental variables that drive differenti ation and crystallization in magma chambers we derive a newmethod which utilizes the crystal size distribution csd to re trieve the ratesof nucleation and growth from natural igneous rocks however a single csd resultsfrom an arbitrary numberofcombin ations of nucleation and growth rates ifadditional parameters suchas crystallinity evolution are employed the solution for rates becomesunique interpretation of representative log linear csd trendsshows that the nucleation rates are sensitive to even minor featuresof the csd whereas the growth rate functions are mainly related tothe crystallinity evolution the reconstructed growth rates becomeminimal at intermediate crystallinities but diverge to very highvalues at the beginning and the end of crystallization this generalresult is related to the small effective area of the solid liquid inter face close to the liquidus few small grains and near the solidus largely solidified with diminishing melt pools assuming thatgrowth rate is related to environmental variables such as magmaundercooling these results suggest that the solid fraction in manymagmas increases in a sigmoidal manner over their crystallizationinterval and indicate the tendency for largest undercooling at the be ginning and at the end of crystallization for crystallization timesconstrained by conductive cooling models thegrowth ratescalculatedfor representative csds are of the order of10

groundmass crystallization of mount st helens dacite 1980 1986 a tool for interpreting shallow magmatic processes the 1980 1986 eruption of mount st helens volcano provides an unprecedented opportunity to observe the evolution of a silicic magma system over a short time scale groundmass plagioclase size measurements are coupled with measured changes in matrix glass plagioclase and fe ti oxide chemistry to document increasing groundmass crystallinity and thus to better constrain proposed physical models of the post may 18 1980 magmatic reservoir measurements of plagioclase microlite and microphenocryst sizes demonstrate that relatively rapid growth approximately 10 9 cm s of groundmass plagioclase occurred immediately subsequent to may 18 relatively rapid plagioclase growth continued through the end of 1980 at an average rate of 3x10 11 cm s plagioclase growth rates then decreased to 1x10 11 cm s through 1986 changes in groundmass crystallinity are reflected in changes in both matrix glass and plagioclase microphenocryst rim chemistry although the matrix glass composition appears to have remained approximately constant from 1981 1986 after a rapid compositional change from may 18 until the end of 1980 plagioclase microphenocrysts show increasingly more complex zoning patterns with time microphenocryst core compositions are commonly positively correlated with crystal size both of these observations indicate continuous groundmass plagioclase growth through 1986 magmatic temperatures estimated from fe ti oxide pairs are approximately constant through 1981 at eruption temperatures of 930 c and at log fo2 of 10 8 by 1985 1986 oxide temperatures decreased to 870 c chemical and textural changes can be explained by 1 rapid degassing and crystallization in response to the intrusion of magma into a shallow 4 5 km reservoir toward the end of the may 18 1980 eruption 2 continued crystallization at a much reduced rate through 1986 due to slow cooling of the shallow magma reservoir growth rates and consequent chemical changes appear to decrease at the end of 1980 this is coincident with the change in eruption style from explosive eruptions sometimes followed by dome growth to solely extrusive dome building events and can be explained by the expected viscosity increase of both degassing and increasing crystallinity the model of twostage crystallization of magma in a shallow reservoir is consistent with conclusions from gas studies casadevall et al 1983 gerlach and casadevall 1986 a b patterns of crater deformation chadwkck et al 1988 and post 1980 seismicity endo et al 1990 although it does not explain the experimental data of hill and rutherford 1989 on the growth rate of amphibole reaction rims textural measurements on mount st helens dacite can also be used to evaluate crystallization kinetics in silicic magmas systems for which experimental data is almost non existent plagioclase growth rates are 5 10 times slower than estimated plagioclase growth rates in basaltic systems a result consistent with the higher viscosity of a more silicic melt furthermore patterns of textural change both average crystal size and number density are similar to those observed during the 1984 mauna loa eruption by lipman and banks 1987 suggesting that the only modification to the crystallization behavior of plagioclase required in extrapolation from basaltic systems is a moderate decrease in rates such that the rate of crystallization scales with the melt viscosity

nature of sub volcanic magma chambers deccan province india evidence from quantitative textural analysis of plagioclase megacrysts in the giant plagioclase basalts sub volcanic magma chambers might be a widespread component of flood basalt provinces and their presence can be revealed in some cases by plagioclase megacrystic basalts in at least four levels within the deccan flood basalt sequence the generally low abundance of small plagioclase crystals increases to 5 25 with some as large as 30 mm long these giant plagioclase basalt gpb flows were formed by mixing of megacryst rich and megacryst poor magmas the crystal size distributions csd of these megacrysts mostly plot as almost straight lines on a classic csd diagram for a plagioclase growth rate of 10 10 mm s steady state magma chamber models and simple continuous growth suggest residence times of 500 1500 years however the lack of crystals smaller than 2 mm suggests that coarsening may have been involved and crystal shape can help define the environment where this happened plagioclase megacrysts are very tabular and commonly form clusters of sub parallel crystals characteristics that are also found in the plagioclase of anorthosites formed by flotation at the top of shallow magma chambers and crystallization in a high peclet number regime e g skaergaard sept iles a possible history is as follows 1 plagioclase megacrysts crystallize in a convecting magma chamber just below the lava pile 2 currents sweep the crystals to the top of the chamber where they accumulate as a result of their buoyancy the crystals coarsen in response to the continuous supply of hot magma 3 new magma sweeps through the plagioclase mush mingles and mixes then erupts to form the gpbs the residence time recorded by the megacrysts in the gpbs is that of the magma chamber where the megacrysts formed not that of the magmas that make up the megacryst poor part of the gpbs or the other megacryst poor lavas lavas with megacrysts similar to the gpbs are uncommon but widespread galapagos surtsey etc and suggest the presence of sub volcanic magma chambers elsewhere

insar slip rate determination on the altyn tagh fault northern tibet in the presence of topographically correlated atmospheric delays 1 the interseismic strain across the altyn tagh fault at 85 e has been measured using 59 interferograms from 26 ers 1 2 sar acquisitions on a single track for the period 1993 2000 using an atmospheric delay correction that scales linearly with height we estimate the left lateral strike slip motion to be 11 1 5 mm yr assuming no relative vertical motion and a 15 km fault locking depth this is in agreement with sparse gps measurements the atmospheric delay corrections agree well with coarse contemporaneous modelled weather data reinforcing the importance of correcting for atmospheric delays in insar studies of interseismic strain accumulation particularly in areas of high topographic relief that strongly correlate with the expected tectonic signal we also find that in addition to the tropospheric water vapour wet delay the hydrostatic dry delay makes a significant contribution to the signal

the significance of intergranular diffusion to the mechanisms and kinetics of porphyroblast crystallization the spatial disposition compositional zoning profiles and size distributions of garnet crystals in 11 specimens of pelitic schist from the picuris range of new mexico usa demonstrate that the kinetics of intergranular diffusion controlled the nucleation and growth mechanisms of porphyroblasts in these rocks an ordered disposition of garnet centers and a significant correlation between crystal radius and near neighbor distances manifest suppressed nucleation of new crystals in diffusionally depleted zones surrounding pre existing crystals compositional zoning profiles require diffusionally controlled growth the rate of which increases exponentially as temperature increases with time an acceleration factor for growth rate can be estimated from a comparison of compositional profiles for crystals of different sizes in each specimen crystal size distributions are interpreted as the result of nucleation rates that accelerate exponentially with increasing temperature early in the crystallization process but decline in the later stages because of suppression effects in the vicinity of earlier formed nuclei simulations of porphyroblast crystallization based upon thermally accelerated diffusionally influenced nucleation kinetics and diffusionally controlled growth kinetics quantitatively replicate textural relations in the rocks the simulations employ only two variable parameters which are evaluated by fitting of crystal size distributions both have physical significance the first is an acceleration factor for nucleation with a magnitude reflecting the prograde increase during the nucleation interval of the chemical affinity for the reaction in undepleted regions of the rock the second is a measure of the relative sizes of the porphyroblast and the diffusionally depleted zone surrounding it crystal size distributions for the picuris range garnets correspond very closely to those in the literature from a variety of other localities for garnet and other minerals the same kinetic model accounts quantitatively for crystal size distributions of porphyroblastic garnet phlogopite sphene and pyroxene in rocks from both regional and contact metamorphic occurrences these commonalities indicate that intergranular diffusion may be the dominant kinetic factor in the crystallization of porphyroblasts in a wide variety of metamorphic environments

geomorphic and structural variations along the doruneh fault system central iran 1 this paper focuses on the analysis of geomorphic structural and behavioral characteristics along the doruneh fault system dfs east of longitude 56 45 e detailed geomorphic and structural analyses of different scale satellite images and digital topographic data accompanied with field surveys allowed us to establish a fault segmentation model in which three discrete fault zones have been recognized 1 the western fault zone wfz characterized by reverse left lateral mechanism with left handed step over geometry 2 the central fault zone cfz which is pure left lateral strike slip and comprises nearly parallel faults and 3 the eastern fault zone efz that is a trailing imbricate fan fault termination characterized by reverse faulting and fault related folding each fault zone shows discrete geometry and kinematics implying that deformation is not uniformly accommodated along the dfs we propose a new kinematic model to explain how the dfs accommodate the arabia eurasia convergence normal to the overall fault orientation according to this model the dfs takes up the northward motion between central iran lut block relative to eurasia by a complex kinematics varying from pure reverse to pure left lateral strike slip faulting the kinematics of the wfz and efz corresponds to the direction of the ne trending regional compression while the partitioning of slip into strike slip and reverse component of faulting on parallel faults strain partitioning allows the cfz to remain pure left lateral strike slip such a model propose a way to explain how large strike slip faults such as the dfs accommodate tectonic block motions perpendicular to strike of the faults

crystalmom a new model for the evolution of crystal size distributions in magmas with the quadrature based method of moments nucleation and growth of crystals and the resulting crystal size distribution play a fundamental role in controlling the physical properties of magmas and consequently the dynamics of the eruptions in the past decades laboratory experiments demonstrated that size and shape of crystals strongly control the physical properties of magma and lava additionally natural and experimental samples are usually characterized in terms of their crystal size distribution to link it with physical processes that are not directly observable such as cooling or decompression mechanisms in this paper we present crystalmom a new predictive model based on the quadrature based method of moments developed for studying the kinetic of crystallization in volcanic systems the quadrature based method of moments well established in the field of chemical engineering represents a mesoscale modelling approach that rigorously simulates the space time evolution of a distribution of particles by considering its moments the method is applied here for the first time for studying the equilibrium disequilibrium crystallization in magma modelling the temporal evolution of the moments of a crystal size distribution the model verified against numerical and experimental data represents a valuable tool to infer the cooling and decompression rates from the crystal size distribution observed in natural samples

origin of megacrysts in granitoids by textural coarsening a crystal size distribution csd study of microcline in the cathedral peak granodiorite sierra nevada california microcline megacrysts in the cathedral peak granodiorite and other parts of the tuolumne intrusive suite were formed by textural coarsening ostwald ripening of earlier formed crystals the early formed crystals nucleated and grew in an environment of increasing undercooling probably during the ascent of the magma emplacement of the magma into warm host rocks promoted textural coarsening crystals smaller than a certain size the critical size dissolved in the interstitial melt whilst large crystals grew microcline was most sensitive to this effect as the magma temperature was buffered close to its liquidus for a long period by the release of latent heat of crystallization positive feedback between textural coarsening and magma permeability channelled the flow of interstitial melt to produce a heterogeneous distribution of megacrysts megacryst growth was halted when cooling resumed at the end of the intrusive cycle k feldspar nucleation was then renewed and k feldspar crystals grew to form part of the groundmass it was the particular thermal history of this pluton that promoted textural coarsening chemically similar plutons that lack megacrysts probably did not have the pause during cooling that was necessary for the development of this texture

modeling of crystal size distributions csds in sills abstract a new model for the generation of crystal size distributions csds in igneous rocks is presented here synthetic or numerically simulated csds are generated with a growth rate that is proportional to the amount of precipitating solids and inversely related to the second moment of the csd total surface area and with the log nucleation rate i vs log cooling rate relationship of cashman cashman k v 1993 relationship between plagioclase crystallization and cooling rate in basaltic melts contrib mineral petrol v 113 pp 126 142 for crystal nucleation the resultant csds resemble those observed in natural rocks in the new model growth rate is constrained by a mass balance and crystal population systematics it is not calculated as a function of cooling rate or undercooling the development of the numerical model was motivated in part by the failure of analytical modeling of crystal populations based solely on cooling rate to generate csds similar to those observed naturally the new model is used to create a suite of csds from various positions within a sill cooling and solidification of the sill are calculated numerically the model reproduces many features observed in the csds of natural rocks such as linear csds in plots of ln population density vs crystal size d shaped mean crystal size profiles and decreasing csd intercept and slope magnitude i e slope with distance from the sill wallrock contact and the csd intercept vs slope relationship the model suggests the use of inversion to more accurately determine residence time from a natural csd

extraction of high resolution carbonate data for palaeoclimate reconstruction temporal variations in the calcium carbonate content of deepsea sediments provide direct stratigraphic as well as important palaeoenvironmental information relating to the global carbon cycle here i present an algorithm that allows carbonate content and porosity to be accurately predicted from saturated bulk density in equatorial pelagic carbonates applying the algorithm to continuous laboratory measurements of density made on dsdp and oop cores yields a nearly continuous carbonate record for the upper 200 m of the sediment section long ultra high resolution carbonate curves of this type should yield new insight into the evolution of the carbon chemistry of the oceans as well as the role of external milankovitch forcing in the development of the carbonate system the algorithm can also be applied to quantitative high resolution seismic data thereby enabling detailed carbonate records to be extracted from remotely derived geophysical data

u th baddeleyite geochronology and its significance to date the emplacement of silica undersaturated magmas baddeleyite is a frequently found accessory mineral in silica undersaturated lavas because it is typically enriched in uranium while having low initial lead baddeleyite has long been a prime target for u pb geochronology of mafic rocks the difficulties in retrieving small baddeleyite grains from volcanic samples and the lack of a detailed understanding of baddeleyite occurrence however have limited baddeleyite chronology largely to coarse grained mafic intrusive rocks here the development of u th in situ baddeleyite analysis using secondary ionization mass spectrometry sims is presented together with an assessment of baddeleyite occurrence in quaternary silica undersaturated lavas from campi flegrei naples italy samples studied comprise the pre and post campanian ignimbrite ca 40 ka lava domes of cuma and punta marmolite and astroni and accademia respectively the in situ sample preparation required initial identification of baddeleyite crystals from sawed and polished rock billets using scanning electron microscope sem backscatter imaging and energy dispersive x ray analysis u th baddeleyite isochron ages for intra caldera astroni and accademia lava domes are 5 01 2 61 2 55 ka mswd 2 0 n 17 and 4 36 1 13 1 12 ka mswd 2 9 n 24 respectively the ages for punta marmolite 62 4 3 9 3 8 ka mswd 1 2 n 11 and cuma 45 9 3 6 3 5 ka mswd 2 2 n 11 predate the campanian ignimbrite rapid baddeleyite crystallization at the time of emplacement is supported by petrologic observations that 50 of the baddeleyite crystals documented in this study occur either in vesicles or in vesicle rich regions of the host lavas whose textures developed over timescales of a few years to a few decades based on microlite crystal size distribution csd analysis radiometric u th baddeleyite ages are mostly in agreement with previously determined k ar eruption ages except for the punta marmolite lava dome whose u th baddeleyite age predates the k ar age by ca 15 ka baddeleyite thus records eruptive emplacement with little evidence for significant pre eruptive crystal residence and has potential as an eruption chronometer for quaternary silica undersaturated volcanic rocks

experimental constraints on magma ascent rate for the crater flat volcanic zone hawaiite phase equilibria and isothermal constant rate decompression experiments conducted on a hawaiite from the crater flat volcanic zone near yucca mountain nevada provide insight into the dynamics of magma transport for this magmatic province h 2 o contents up to 4 6 wt in melt inclusions the lack of plagioclase phenocrysts and the presence of amphibole all suggest that phenocrysts and melt in the crater flat volcanic zone were equilibrated at near water saturated conditions during ascent comparison of decompression induced crystallization of plagioclase microlites in experiments with natural tephra implies that magma ascent rates for the region are 0 04 m s if the magmas are water saturated estimates of minimum ascent rates increase if the magmas are water undersaturated a two stage process is needed to generate reaction rims found on natural amphibole suggesting that small batches of magma were briefly stored 3 5 days at depths as shallow as 800 m prior to eruption

do geochemical estimates of sediment focusing pass the sediment test in the equatorial pacific 1 the paleoceanographic recording fidelity of pelagic sediments is limited by chemical diagenesis and physical mixing bioturbation and horizontal sediment transport diagenesis and bioturbation are relatively well studied but the effects of physical sedimentation have been largely ignored modeling u series isotopes e g 230th can potentially quantify horizontal sediment movement but model horizontal sediment focusing often equals or exceeds the vertical particle rain we find no evidence of this level of sediment focusing in the equatorial pacific from geophysical data or sediment core comparisons the overestimate of sediment focusing by 230th is probably caused by poor model assumptions that sediment does not fractionate does not sort according to size during transport and that 230th cannot leak from slowly accumulating sediments both assumptions are weak u series methods do hold promise to quantify sediment focusing if properly calibrated with calibration the trade offs between seeking high sedimentation rates for better time resolution and the blurring by horizontal sediment focusing can be better assessed

the post eocene evolution of the doruneh fault region central iran the intraplate response to the reorganization of the arabia eurasia collision zone

tectonic reversal of the western doruneh fault system implications for central asian tectonics the left lateral doruneh fault system dfs bounds the north margin of the central iranian microplate cim and has played an important role in the structural evolution of the turkish iranian plateau the western termination of the dfs is a sinistral synthetic branch fault array that shows clear kinematic evidence of having undergone recent slip sense inversion from a dextral array to a sinistral array in the latest neogene or earliest quaternary similarly kinematic evidence from the anarak metamorphic complex suggests that this complex initially developed at a transpressive left stepping termination of the dfs and that it was inverted in the latest neogene to a transtensional fault termination the recognition that the dfs and other faults in ne iran were inverted from dextral to sinistral strike slip in the latest neogene and the likely connection between the dfs and the herat fault of afghanistan suggests that prior to the latest miocene all of the north iranian and northern afghan ranges were part of a distributed dextral fault network that extended from the west himalayan syntaxes to the western alborz also the recognition that regional slip sense inversion occurred across northern and northeastern iran after the latest miocene invalidates tectonic models that extrapolate pleistocene to recent fault slip kinematics and rates back beyond this time

multi interferogram method for measuring interseismic deformation denali fault alaska summary studies of interseismic strain accumulation are crucial to our understanding of continental deformation the earthquake cycle and seismic hazard by mapping small amounts of ground deformation over large spatial areas insar has the potential to produce continental scale maps of strain accumulation on active faults however most insar studies to date have focused on areas where the coherence is relatively good e g california tibet and turkey and most analysis techniques stacking small baseline subset algorithm permanent scatterers etc only include information from pixels which are coherent throughout the time span of the study in some areas such as alaska where the deformation rate is small and coherence very variable it is necessary to include information from pixels which are coherent in some but not all interferograms we use a three stage iterative algorithm based on distributed scatterer interferometry we validate our method using synthetic data created using realistic parameters from a test site on the denali fault alaska and present a preliminary result of 10 5 5 0 mm yr 1 for the slip rate on the denali fault based on a single track of radar data from ers1 2

kinetics of crystallization of igneous rocks the geochemistry of igneous rocks is discussed with the primary objectives of bringing together the theories underlying the kinetics of crystallization of igneous rocks and illustrating the use of these theories in understanding experimental and observational data the primary purpose of the chapter is to introduce current thinking about the kinetics of igneous rocks and to provide a basis for understanding other work a basic assumption made in the discussion is that the rate of any chemical reaction including the crystallization of igneous rocks is zero at equilibrium and proceeds at a finite rate only at a finite deviation from equilibrium as such an understanding of the processes operating in igneous rocks requires an understanding of how deviation from equilibrium affects the rates and mechanisms of the processes occurring during crystallization these processes are detailed with special emphasis given to nucleation and crystal growth jmt

combining quantitative textural and geochemical studies to understand the solidification processes of a granite porphyry shanggusi east qinling china igneous rock textures reflect the cooling history of the parental magma combined with chemical data they can provide physical and chemical information about the evolution of a magma body the petrographic textures and chemical compositions of 21 coarse and fine grained granite samples along an 250 m horizontal outcrop of the shanggusi granite porphyry are presented in this case study the coarse grained granite porphyry is an early intrusion and the fine grained granite dykes mostly intruded into the granite porphyry are later intrusions the studied samples have nearly homogeneous major element bulk rock and mineral compositions but show large variations in their trace element compositions and textural characteristics the trace element data suggest the influence of hydrous fluids possibly enriched in co2 f and cl in the evolution of the plutonic body textural analysis of the coarse grained granite porphyry indicates that the crystal size distribution csd slopes intercepts and total numbers of groundmass decrease from the center to the margin of the intrusion in contrast to the maximum diameter of the crystals lmax average length of the four largest quartz crystals for each sample however most fine grained samples and the groundmass of the coarse grained samples show concave down csds indicating textural coarsening quartz csds in the coarse grained samples are kinked with a steep sloped log linear section representing small crystals 5 1mm and a shallow sloped log linear section representing large crystals 4 1mm these two crystal populations are interpreted as resulting from a shift in cooling regime the straight csds of two fine grained samples may be due to a different cooling history in general the spatial variation of the csd patterns can be attributed to various degrees of overgrowth and mechanical compaction the quartz phenocrysts in several coarse grained samples exhibit a high degree of alignment which may be the result of magmatic flow by integrating the field geology geochemistry and quantitative textural data from the horizontal profile of the shanggusi granite porphyry it is suggested that hydrous fluids at the top of the intrusion not only controlled the fractionation of elements but also affected its cooling history fluid migration controlled undercooling can explain the solidification processes in the shanggusi intrusion and may also be prevalent in other fluid rich shallow intrusions quantitative integration of textural and geochemical data for igneous rocks can contribute to our understanding of the relationships between physical and chemical processes in a magma system and provide relatively comprehensive insights into the petrogenesis of granites

experimental quantification of plagioclase crystal size distribution during cooling of a basaltic liquid an experimental study has been conducted to constrain how thermal history controls crystal size distribution csd of plagioclase in cooling basalts data from all experiments are dominated by a log linear segment of decreasing number density with increasing crystal size consistent with observations in many natural rocks the slope of the csd is found to be a function of cooling rate faster cooling leading to greater slopes at constant cooling rate the csds flatten as temperature decreases and are sometimes kinked characteristics consistent with independent textural observations that crystal agglomeration contributes significantly to crystal growth a downturn is observed toward small size which suggests ostwald ripening furthermore we find that thermal history above the liquidus has a major influence on csds and on the temperatures of phase appearance we conclude that near the liquidus heterogeneous nucleation typically dominates

origin of anorthosite by textural coarsening quantitative measurements of a natural sequence of textural development the textures of plagioclase crystals within large olivine oikocrysts preserve the sequence of the formation of anorthosite such textures have been quantified in a troctolite anorthosite from the proterozoic lac st jean anorthosite complex canada crystal size distributions csds indicate that initially plagioclase nucleated and grew in an introduction environment of linearly increasing undercooling producing a straight the textures of plutonic rocks are one of their most line csd during this phase latent heat of crystallization was striking aspects but they have been little used to elucidate largely removed by circulation of magma through the porous crystal petrological processes as compared with chemical and mush by about 25 solidification the crystallinity was such that isotopic methods where used discussion has tended it reduced but did not eliminate the circulation of magma resulting to be qualitative in contrast to quantitative chemical in the retention of more latent heat within the crystal pile the methods hence reducing the weight of this approach temperature rose until it was buvered by the solution of plagioclase indeed it is not possible to verify physical models if close to the liquidus temperature of plagioclase nucleation of quantitative data are not available quantitative textural plagioclase was inhibited and conditions were suitable for textural studies of volcanic rocks are becoming more common coarsening of both plagioclase and olivine to occur ostwald and these methods are applied here to the development ripening in this process small crystals were resorbed whereas of anorthosite larger crystals grew from both material recycled by the resorption of quantitative textural studies of plutonic rocks really crystals smaller than the critical size and new material brought in started with jackson s studies of the stillwater complex by the circulating magmatic fluid the results of this process resemble in 1961 jackson 1961 he measured crystal size disthose of high temperature metasomatism but there is no necessity for tributions but did not record the area that he measured a magmatic fluid with a diverent composition the shapes of the hence his data cannot be completely compared with plagioclase csds fit better the communicating neighbours equation of modern data his pioneering work was not really followed textural coarsening rather than the classic lifshitz slyozov wagner up and since then most studies have looked only at equation as do other examples drawn from the literature if olivine average or typical crystal sizes these data are much started to nucleate at a higher temperature than plagioclase then less revealing of petrological processes than crystal size during the textural coarsening phase olivine would have been more distributions partly because they only give one parameter undercooled than plagioclase and would have had a higher maximum for each sample the few existing studies of crystal size growth rate in these conditions olivine would coarsen more rapidly distributions in plutonic rocks have not treated than plagioclase and engulf it hence the order of crystallization plagioclase determined from the textures would be the reverse of the order of one problem especially pertinent to quantitative texfirst nucleation of the two phases from equilibrium phase diagrams tural studies is the way that many igneous petrologists maintenance of the temperature near the plagioclase liquidus may look at rocks they commonly try to reconstruct how a rock has formed by examining the final fully crystallized also inhibit the nucleation and growth of other phases

crystal size distribution systematics and the determination of magma storage times the 1959 eruption of kilauea volcano hawaii abstract the theory of crystal size distribution csd theory is based on a steady state population balance that monitors the flux of crystals growing into and out of specificed size categories in precipitating solutions the conservation equation describing this balance permits crystal growth and nucleation rates to be determined directly from crystal size distribution data in this investigation it is shown that csd analysis can alternatively be used to calculate the residence time of crystals in the system or in volcanologic terms the magma storage time prior to eruption if the characteristic crystal growth rate can be independently determined or estimated the crystal size data needed for storage time determinations are easily obtained from thin sections of glassy eruption samples and the mathematical calculations are relatively simple analysis of the errors inherent in this new technique predicts storage estimates accurate to within an order of magnitude

the formation of columnar joints produced by cooling in basalt at staffa scotland columnar jointing in basaltic lava flows on the island of staffa nw scotland was studied using a combination of field mapping and measurement of column dimensions sample petrology and measurements of plagioclase crystal size distributions csds interpreted using theoretical models of cooling four different lava flow units were measured and column ordering was assessed using the hexagonality index and relative standard deviations of column side length top area and internal angle upper and lower colonnades consist of dominantly 5 6 and 7 sided columns with a hexagonality index value very similar to that of giant s causeway and other basaltic columnar jointed localities csds from samples at different heights within one colonnade were used to infer the propagation of the solidus isotherm which was consistent with a convective cooling mechanism within the colonnade interior sample petrology and csd measurements suggest that entablature can form both by the interaction of propagating joint sets and flooding of the flow surface by water and the most widely exposed unit on staffa shows evidence of both mechanisms operating on the same flow crystal size distribution measurements can provide a useful tool for field interpretation of lava flow cooling mechanisms

crystal size distribution analysis of plagioclase in experimentally decompressed hydrous rhyodacite magma article i nfo this study presents crystal size distributions csd of plagioclase forming during decompression experiments of hydrous rhyodacite magma samples were annealed at 130 mpa subjected to continuous decompression at either 2 mpa h 1 or 0 5 mpa h 1 and then quenched along their respective decompression paths at 20 mpa intervals samples display concave up curved csd plots which result from a combination of two crystal populations those which formed during the anneal period and those which formed during decompression the csds also display a decrease in crystal number density at 3 7 m a size range that is easily resolvable with the imaging strategy employed the downturn at small sizes is presumably due to insufficient compensation for the intersection probability effect in converting 2d measurements to 3d size distributions crystal nucleation and growth rates derived from csds using standard assumptions are compared with values obtained using 2d measurements of bulk crystal populations batch methods csd calculated nucleation rates are substantially low relative to the batch values in fact csd derived volumetric nucleation rates may underestimate actual nucleation rates by up to two orders of magnitude in contrast growth rates from csds are consistently higher than batch rates although plagioclase growth rates are relatively constant during decompression at a given rate the average growth rate in the rapidly decompressed series is approximately five times faster than the crystal growth rate in the slowly decompressed series because crystal growth rate depends on decompression rate csds are incapable of revealing decompression timescales or magma ascent rates without independent knowledge of crystal growth rate published by elsevier b v

crystal size distribution csd in rocks and the kinetics and dynamics of crystallization ii makaopuhi lava lake crystal size distribution csd theory has been applied to drill core samples from makaopuhi lava lake kilauea volcano hawaii plagioclase and fe ti oxide size distribution spectra were measured and population densities n were calculated and analyzed using a steady state crystal population balance equation n n0 exp l g slopes on ln n versus crystal size l plots determine the parameter g a product of average crystal growth rate g and average crystal growth time the intercept is j g where j is nucleation rate known temperature depth distributions for the lava lake provide an estimate of effective growth time allowing nucleation and growth rates to be determined that are independent of any kinetic model plagioclase growth rates decrease with increasing crystallinity 9 9 5 4 10 11 cm s as do plagioclase nucleation rates 33 9 1 6 10 3 cm3 s ilmenite growth and nucleation rates also decrease with increasing crystallinity 4 9 3 4 10 10 cm s and 15 2 2 10 3 cm3 s respectively magnetite growth and nucleation rates are also estimated from the one sample collected below the magnetite liquidus g 2 9 10 10 cm s j 7 6 10 2 cm3 s moments of the population density function were used to examine the change in crystallization rates with time preliminary results suggest that total crystal volume increases approximately linearly with time after 50 crystallization a more complete set of samples is needed for material with 50 crystals to define the entire crystallization history comparisons of calculated crystallization rates with experimental data suggests that crystallization in the lava lake occurred at very small values of undercooling this interpretation is consistent with proposed thermal models of magmatic cooling where heat loss is balanced by latent heat production to maintain equilibrium cooling

relationship between plagioclase crystallization and cooling rate in basaltic melts rock textures commonly preserve a record of the near surface crystallization history of volcanic rocks under conditions of simple cooling without convection or mixing textures will reflect sample cooling rate the temperature at which crystallization was initiated and the distribution of mineral phase precipitation across the crystallization interval compilation of plagioclase size and number density data on natural dike sill and lava lake and experimental samples suggests that 1 growth and nucleation rates of plagioclase in natural basaltic samples are a predictable function of cooling rate and 2 the observed crystallization rate dependence on cooling rate is similar to that observed in experiments initiated at subliquidus temperatures comparison of natural and experimental samples thus suggests that most basalts crystallize under conditions of heterogeneous nucleation with the number density of preexisting nucleii partially controlling textural responses to cooling rate changes time scales of crystallization and cooling in magmatic systems are intimately linked through a balance between heat removal from the system and heat evolved through crystallization evaluation of textural data in the context of recent numerical models of crystallization in simple one and two component systems provides new insight into regularities in the crystallization behavior of basaltic magmas for example the rate of change in crystal size and number density as dictated by mass balance has been used as a measure of the relative importance of time scales of crystallization and cooling in numerical models of crystallizing systems in natural samples plagioclase size scales with the length scale of cooling such that a logarithmic plot of grain size as a function of normalized distance across the dike has a slope that appears approximately independent of dike width solidification time comparison with available textural data for other phenocryst phases suggests that the same may be true for pyroxene and magnetite crystallization with each phase having a characteristic slope probably controlled by the thermodynamic properties of the crystallizing phase measured crystal size distributions are unimodal and show maximum frequencies in the smaller size classes distributions broaden and the grain size at peak frequency increases with increasing crystallization times decreasing cooling rates in contrast partially crystallized makaopuhi lava lake samples have crystal size distributions that decrease exponentially with increasing crystal size measured size distributions in dikes can be explained by late stage modification of makaopuhi type distributions through loss of small crystals possibly the consequence of growth without nucleation finally this compilation of the textural response of basaltic magmas to changes in cooling rate suggests that empirical calibrations of crystallization rate dependence on cooling rate from natural samples provide a reasonable model for plagioclase crystallization in near surface basaltic systems predicted growth rates will be slow and relatively constant 10 10 10 11 cm s for crystallization times expected in most shallow volcanic systems 1000 years

resolving vertical tectonics in the san francisco bay area from permanent scatterer insar and gps analysis using a combination of gps measured horizontal velocities of 200 sites and 115 487 range change rates determined with the permanent scatterer interferometric synthetic aperture radar insar method in the san francisco bay area we resolve vertical motions in the region at sub mm yr precision the highest displacement rates are due to nontectonic processes such as active landslides subsidence and rebound over aquifers and rapid settling of unconsolidated sediments along the bay margins residual displacement rates are determined by removing the contribution of the gps derived horizontal velocity field from the insar range change rates to isolate vertical tectonic rates we use only those insar measurements made on material that was not quaternary substrate which is susceptible to nontectonic and seasonally varying ground motions the insar residuals indicate significant uplift over the southern foothills of the active mount diablo anticlinorium the mission hills stepover region of the hayward and calaveras faults and the central and southern santa cruz mountains located along a restraining bend of the san andreas fault

postseismic displacement of the 1999 athens earthquake retrieved by the differential interferometry by synthetic aperture radar time series 1 in september 1999 a moderate mw 5 9 earthquake struck the attica plain causing unexpected and extensive damage to athens and its population in this work we exploit the potential of multitemporal differential interferometry by synthetic aperture radar dinsar analysis using about a hundred european remote sensing ers 1 2 images to calculate the displacement time series from 1992 to 2002 this analysis allows us to clearly separate a strictly coseismic signal from a postseismic gradual subsidence reaching a maximum value of about 3 cm in the following 2 5 years we model this signal in terms of afterslip on the seismogenic fault the afterslip distribution retrieved by linear inversion reflects the coseismic slip distribution and occurs mainly downdip of the area that ruptured during the main shock the analysis of the static stress transfer suggests that the afterslip was triggered by the main shock then it propagated aseismically through the fault plane a partial overlap between the coseismic and aseismic slip area at the hypocentral region indicates that the 1999 rupture surface was not healed at least until the date of the last postseismic image april 2002 the results obtained with a time series approach for this moderate magnitude earthquake suggest that multitemporal dinsar analysis should become an important methodology for the study of large earthquake ruptures

magma rheology variations in sheet intrusions of the ardnamurchan central complex scotland inferred from gabbro inclusion characteristics entrainment of xenoliths and their consequent assimilation are key processes in modifying the crystallization kinetics and magma dynamics of conduit systems here an integrated textural and mineral chemical study of the evolution of a suite of gabbroic inclusions within a set of sheet intrusions from the ardnamurchan central complex nw scotland is presented the key findings are as follows 1 the host magma sheets and inclusions are not cognate 2 there are microstructural and mineral chemical similarities between the gabbroic inclusions and the textures and mineralogy of the major hypersthene gabbro on ardnamurchan 3 orientations of magnetic fabrics within the host sheet groundmass and within the gabbroic inclusions are virtually identical field observations suggest that the inclusions were derived from the hypersthene gabbro and were entrained in a few laterally restricted magma segments that subsequently coalesced with inclusion free segments into continuous sheets using stokes law and adaptations thereof we calculate that the magma within the inclusion free segments behaved as a newtonian fluid with a potential settling velocity of50 028 m s in contrast the presence of gabbro inclusions probably modified the magma dynamics to bingham like behaviour we infer that this variation in the magma rheology of separate segments continued after coalescence and internally partitioned the magma sheet preventing lateral mixing and inclusion transport

crystallization kinetics of rhyolitic melts using oxygen isotope ratios crystals provide themeans to understand igneous systems but natural constraints on crystallization kinetics are rare because thermal conditions and crystallization timescales are typically unknown oxygen isotope ratios in quartz and alkali feldspar crystals in spherulites provide a natural record of the temperature interval of crystallization and crystal growth rates in rhyolitic melts oxygen isotope compositions in both phases change progressively with position from the spherulite core to rim quartz o increases from 5 0 0 3 in the core to 5 6 0 3 at the rims whereas alkali feldspar decreases from 3 7 0 4 in the core to 2 7 0 9 at the rims fractionation therefore increases from 1 3 0 7 in the cores to 2 9 1 1 at the rims oxygen isotope thermometry tracks crystallization temperature with position spherulites nucleate at 578 160 c and continue to grow until 301 88 c the in situ analyses demonstrate that spherulites self contain a record of their thermal history and that of the host lava

magma dynamics beneath kameni volcano thera greece as revealed by crystal size and shape measurements size distributions of plagioclase crystals in series of recent porphyritic dacite lavas from kameni volcano greece can be modelled by mixing two populations of crystals each with overlapping linear crystal size distributions csd termed microlites and megacrysts the magmas bearing the microlites and megacrysts started to crystallise 6 13 and 24 96 years respectively before each eruption the dates of initiation of crystallisation of the megacrysts indicate that they are left overs of earlier injections of new magma into a shallow chamber some magma remains after each eruption and continues to crystallise new magma with few or no crystals is then introduced and the microlites crystallise from the mixed magma eruption followed 6 13 years after mixing such a model would suggest that some porphyritic magmas are products of a shallow magma chamber that is never completely emptied just topped up from time to time

new kinematic constraints of the western doruneh fault northeastern iran from interseismic deformation analysis summary we used the sbas dinsar analysis technique to estimate the interseismic deformation along the western part of the doruneh fault system dfs northeastern iran we processed 90 envisat images from four different frames from ascending and descending orbits three of the ground velocity maps show a significant interseismic signal using a simple dislocation approach we model 2 d velocity profiles concerning three insar data set relative to the western part of the dfs obtaining a goodfit to the observations the resulting model indicates that a slip rate of 5mmyr 1 accumulates on the fault below 10km depth and that in its western sector the doruneh fault is not purely strike slip left lateral as in its central part but shows a significant thrust component based on published geological observations and assuming that all interseismic deformation is recovered with a single event we can estimate a characteristic recurrence interval between 630 and 1400yr

quantitative analysis of crystal grain sizes and their distributions in 2d and 3d abstract we review methods to estimate the average crystal grain size and the crystal grain size distribution in solid rocks average grain sizes often provide the base for stress estimates or rheological calculations requiring the quantification of grain sizes in a rock s microstructure the primary data for grain size data are either 1d i e line intercept methods 2d area analysis or 3d e g computed tomography serial sectioning these data have been used for different data treatments over the years whereas several studies assume a certain probability function e g logarithm square root to calculate statistical parameters as the mean median mode or the skewness of a crystal size distribution the finally calculated average grain sizes have to be compatible between the different grain size estimation approaches in order to be properly applied for example in paleo piezometers or grain size sensitive flow laws such compatibility is tested for different data treatments using one and two dimensional measurements we propose an empirical conversion matrix for different datasets these conversion factors provide the option to make different datasets compatible with each other although the primary calculations were obtained in different ways in order to present an average grain size we propose to use the area weighted and volume weighted mean in the case of unimodal grain size distributions respectively for 2d and 3d measurements the shape of the crystal size distribution is important for studies of nucleation and growth of minerals the shape of the crystal size distribution of garnet populations is compared between different 2d and 3d measurements which are serial sectioning and computed tomography the comparison of different direct measured 3d data stereological data and direct presented 2d data show the problems of the quality of the smallest grain sizes and the overestimation of small grain sizes in stereological tools depending on the type of csd

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

quartz crystal size distribution of the ordovician millbrig k bentonite abstract crystal size distribution csd analysis has been applied to quartz crystals of the ordovician millbrig k bentonite which represents one of the largest known fallout ash deposits in the phanerozoic era to establish crystal growth histories and conditions in the magma chamber prior to eruption specific csds were examined for crystal growth conditions all millbrig samples exhibit lognormal concave down shapes in agreement with previously reported csds on large silicic systems but in contrast to more mafic systems characterized by linear csds concave down csds are possibly an intrinsic property of phenocryst growth in large volume silicic magmas as documented in the literature bindeman i n 2003 crystal sizes in evolving silicic magma chambers geology 31 367 370 quartz crystals of the millbrig must have been produced by surface controlled size dependent growth with a minor ostwald ripening component which could have easily changed to supply controlled growth due to a limited supply of nutrients as the crystals grew larger csds were also used to examine the possible origin of multiple ash beds in the millbrig these ash beds appear to be a product of a series of separate eruptions that represent separate magma layers or batches each with slightly different crystal growth conditions

crystal size distributions derived from 3d datasets sample size versus uncertainties crystal size distributions csd are the most commonly studied character in quantitative textural investigations of igneous rocks the quality of csd depends fundamentally on the sample size i e total number of crystals here we use 3d x ray tomographic datasets of two early erupted bishop tuff pumice clasts comprising 849 and 446 quartz crystals to investigate the effect of sample size on the quality of the quartz size distributions because csd are obtained using a counting procedure uncertainties related to counting statistics can be used as minimum estimates of error given that most natural samples are characterized by a decreasing number of crystals with increasing crystal size uncertainties tend to increase markedly with crystal size and the number of small crystals to be counted grows very quickly with increasing sample size accordingly with as few as 100 crystals in total it is possible to properly estimate the population densities for small size bins 20 80mm however to obtain meaningful estimates across four bin sizes 20 320mm at least 250 crystals but preferably 400 crystals are needed to minimize the total number of crystals counted and keep the uncertainties on the larger size ranges within reasonable values it becomes necessary to study multiple volumes at variable spatial resolution

the effects of undercooling and deformation rates on the crystallization kinetics of stromboli and etna basalts we have investigated the effect of undercooling and deformation on the evolution of the texture and the crystallization kinetics of remelted basaltic material from stromboli pumice from the march 15 2007 paroxysmal eruption and etna 1992 lava flow isothermal crystallization experiments were conducted at different degrees of undercooling and different applied strain rate t 1 157 1 187 c and dot gamma i 4 26 s 1 for stromboli t 1 131 1 182 c and dot gamma i 0 53 s 1 for etna melt viscosity increased due to the decrease in temperature and the increase in crystal content the mineralogical assemblage comprises sp plg dominant cpx with an overall crystal fraction between 0 06 and 0 27 increasing with undercooling and flow conditions both degree of undercooling and deformation rate deeply affect the kinetics of the crystallization process plagioclase nucleation incubation time strongly decreases with increasing t and flow while slow diffusion limited growth characterizes low t low deformation rate experiments both stromboli high strain rate and etna low strain rate plagioclase growth rates g display relative small variations with stromboli showing higher values 4 8 1 9 10 9 m s 1 compared to etna 2 1 1 6 10 9 m s 1 plagioclase average nucleation rates j continuously increase with undercooling from 1 4 106 to 6 7 106 m 3 s 1 for stromboli and from 3 6 104 to 4 0 106 m 3 s 1 for etna the extremely low value of 3 6 104 m 3 s 1 recorded at the lowest undercooling experiment for etna t 20 c indicates that the crystallization process is growth dominated and that possible effects of textural coarsening occur g values obtained in this paper are generally one or two orders of magnitude higher compared to those obtained in the literature for equivalent undercooling conditions stirring of the melt simulating magma flow or convective conditions facilitates nucleation and growth of crystals via mechanical transportation of matter resulting in the higher j and g observed any modeling pertaining to magma dynamics in the conduit e g ascent rate and lava flow emplacement e g flow rate p hoehoe a transition should therefore take the effects of dynamic crystallization into account

downhole logging as a paeoceanographic tool on ocean drilling program leg 138 interface between high resolution stratigraphy and regional syntheses on ocean drilling program odp leg 138 standard shipboard procedures were modified to allow for the real time monitoring of several laboratory core scanning systems that provide centimeter scale measurements of saturated bulk density magnetic susceptibility and digital color reflectance these continuous high resolution data sets were used to ensure the proper offset of multiple holes and to splice together complete sedimentary sections typically the spliced continuous sediment sections were found to be about 10 longer than the section drilled as measured by the length of the drill string while the source of this elongation is not yet fully understood it must be compensated for in order to property determine sediment fluxes and mass accumulation rates downhole logging in conjunction with inverse correlation techniques provided a means to determine where the distortion occurred and to correct back to true in situ depths downhole logging also provides a means through the generation of synthetic seismograms of precisely relating the paleoceanographic events found in the core record to the high resolution seismic record once correlated to the seismic record the spatial and temporal extent of paleoceanographic events can be traced well beyond the borehole most seismic events in the equatorial pacific are related to rapid changes in carbonate content that in turn are related to both productivity events often expressed as monospecific laminated diatom oozes and times of enhanced dissolution while many of these events may have oceanwide extent others like the absence of carbonate in the late miocene to recent in the guatemala basin have been shown to be regional and confined to only the deeper portions of the guatemala basin as we identify and trace specific paleoceanographic events in the seismic record we can begin to explore the response of the ocean through gradients of latitude productivity and depth

steady state volcanism paleoeffusion rates and magma system volume inferred from plagioclase crystal size distributions in mafic lavas dome mountain nevada abstract the dome mountain dm lavas located in the moat of the timber mountain caldera of the sw nevada volcanic field cap a thick sequence of welded tuffs massive and bedded tuffs and mafic and rhyolitic lava flows these 10 9 m y old flows comprise a pile of some twenty flows with a total thickness of about 300 m individual flows range in thickness from 3 to 20 m and are characterized by a basal vesicular zone a massive central region and an upper vesicular region containing in most cases cooling fractures the flows dip gently away from the summit of dm a prominent topographic feature of the region with an elevation of 2065 m silica contents range from 48 8 wt at the base of the pile to 59 4 wt at the top although most of the flows are andesitic crystal size distributions csds for plagioclase in these comagmatic lavas have been determined to provide information on magma storage times these times when coupled with phase equilibria can be used to infer cooling rates which are indicative of the relative dimensions of magmatic bodies and the vigor of various magmatic cooling processes most of the csds show no sign of crystal fractionation or accumulation assuming a growth rate of 10 10 cm s calculated mean crystal residence times for most lavas cluster in the range of 1 5 to 4 years two of the lower lavas have residence times in the range of 4 to 9 years the residence times correlate inversely with nucleation density and broadly correlate inversely with silica content high residence time low silica lavas occur at the base of the pile whereas low residence time high silica lavas occur at the top of the pile one interpretation of the residence time data is that the lavas are from an open system of more or less constant residence time but varying spatially in system locations e g a magma chamber in which steady state recharge and eruption may have been reached alternatively these lavas may represent small samples closely spaced in time of a slowly cooling large batch or reservoir of magma the greater residence times associated with the lower flows may indicate the increased amount of time necessary to form the conduit of the magma volcano system by the oldest magma or simply that part of the system with the highest liquidus temperature a minimum volume of 1 4 to 2 5 km 3 for the magma chamber is estimated for the dm system using the estimated residence times in a simplified cooling model of a sheet of aspect ratio r the actual system volume depends on r which is strictly unknown and thus the actual system volume may be much larger e g 200 km 3 a mean paleoeffusion rate of 0 05 km 3 yr is obtained for the lavas by assuming that the residence time of each lava corresponds to the amount of time elapsed since the eruption of the underlying flow

crystal size distributions and scaling laws in the quantification of igneous textures this study demonstrates the value of the combined use of scaling of the chemical evolution of cooling magmas have investigated the detailed relationships between temanalysis and crystal size distribution csd measurements in the interpretation of igneous textures and outlines applications of these perature phase abundance and phase composition the reaction series bowen 1922 and the cipw norm cross methods to other fundamentally important problems theoretical calculations and measurements of natural samples are used to et al 1903 have been supplemented by modern thermodynamic models that predict the compositions and abundcharacterize the relationship between igneous texture and cooling history the total number nt and mean length l of crystals ances of minerals in equilibrium with melt of a given composition and temperature e g ariskin et al 1993 in a sample are correlated through a scaling relationship of the form n t l this proportionality depends on the mineralogy ghiorso sack 1995 although there are a few areas of uncertainty the chemistry of igneous petrogenesis is of the rock and so a modal normalization factor c is introduced the csd slope s and intercept ln n are uniquely related to fairly well understood but chemical models cannot address the central probeach other through the equation ln n 4ln s ln c where s l this overall relationship allows the texture of a rock lem of igneous crystallization which is the physical process of generating a set of crystals from magma two to be related to the local duration of cooling through an arbitrary crystal growth model quantification of the link between the texture magmas with the same composition will normally produce the same minerals in the same proportions however of a rock and its cooling history makes it possible to predict spatial variations in texture we show an example of this method using depending on their thermal histories these two magmas can solidify into rocks with drastically different physical the sudbury igneous complex canada additional applications include relating the textures of volcanic rocks to spatial and temporal appearances e g basalt and gabbro the set of minerals is the same but what distinguishes them is the abundance variations in the magma chamber and extracting kinetic parameters from suites of comagmatic rocks and size of the constituent crystals the fine grained rocks in the chilled margins of most basic intrusions cooled rapidly and the coarse grained rocks in the interiors of plutons cooled slowly this has

plagioclase crystal size distribution in some tholeiitic mafic dykes in cabo frio buzios rio de janeiro brazil abstract crystal size distribution csd has been constrained in plagioclase in two mafic dykes of the conchas beach and one at the lagoinha beach in the cabo frio buzios ne trending dyke swarm at contact with the metamorphic basement the texture is fine grained and microporphyritic and intergranular at the center of the larger dykes samples were collected at the margins and at the center of the dykes the plagioclase average characteristic size c varies from 0 07 to 0 13 mm at the margins of the narrow dykes and from 0 09 to 0 20 mm at the margins of the larger dyke at the center of the lagoinha and conchas dykes c varies from 0 19 0 02 mm and 0 60 0 07 mm respectively the csds at the dyke margins are concave up at the center of the larger conchas dyke 8 2 m the csd is log linear consistent with simple steady state crystallization pattern from the mineralogy the plagioclase phenocrysts have a high an content bytownite labradorite than the groundmass grains labradorite andesine at the margins olivine is richer in fo than at the center and respectively pyroxene is richer in ca these results indicate that the chilled margin is more mafic than the center suggesting a normal chemical evolution in a cooling magma that ascended upward from depths by newtonian to pseudoplastic flow the concave up csds probably depict heterogeneous crystallization rates possibly induced by depressurization during the magma ascent followed by rapid cooling the log linear csd pattern at the center of the conchas dyke 8 2 m width is attributed to a higher residence time of the magma which favors the processes of chemical diffusion and textural re equilibration from the calculated cooling rates the larger conchas dyke 8 2 m in width would be completely crystallized at 900 c in about 2 years

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

exploring the moon s surface for remnants of the lunar mantle 1 dunite xenoliths in mare basalts a crustal or mantle origin remotely sensed observations from recent missions e g grail kaguya chandrayaan 1 have been interpreted as indicating that the deep crust and upper mantle are close to or at the lunar surface in many large impact basins e g crisium apollo moscoviense if this is correct the capability of either impact or volcanic processes to transport mantle lithologies to the lunar surface should be enhanced in these regions somewhat problematic to these observations and interpretations is that examples of mantle lithologies in the lunar sample collection apollo program luna program lunar meteorites are at best ambiguous dunite xenoliths in high ti mare basalt 74275 are one of these ambiguous examples in this high ti mare basalt olivine occurs in three generations olivine associated with dunite xenoliths olivine megacrysts and olivine microphenocrysts the dunite xenoliths are anhedral in shape and are generally greater than 800 m in diameter the interior of the xenoliths are fairly homogeneous with regard to many divalent cations for example the mg mg mg fe 100 ranges from 82 to 83 in their interiors and decreases from 82 to 68 over the 10 30 m wide outer rim titanium and phosphorus x ray maps of the xenolith illustrate that these slow diffusing elements preserve primary cumulate zoning textures these textures indicate that the xenoliths consist of many individual olivine grains approximately 150 200 m in diameter with low ti al and p cores these highly incompatible elements are enriched in the outer fe rich rims of the xenoliths and slightly enriched in the rims of the individual olivine grains highly compatible elements in olivine such as ni exhibit a decrease in the rim surrounding the xenolith an increase in the incompatible element depleted cores of the individual olivine grains and a slight decrease in the interior rims of the individual olivine grains inferred melt composition liquid lines of descent and zoning profiles enable the reconstruction of the petrogenesis of the dunite xenoliths preservation of primary magmatic zoning ti p al and lack of textures similar to high pressure mineral assemblages exhibited by the mg suite shearer et al 2015 indicate that these xenoliths do not represent deep crustal or shallow mantle lithologies further they are chemically and mineralogically distinct from mg suite dunites identified from the apollo 17 site more likely they represent olivine cumulates that crystallized from a low ti mare basalt at intermediate to shallow crustal levels the parent basalt to the dunite xenolith lithology was more primitive than low ti basalts thus far returned from the moon furthermore this parental magma and its more evolved daughter magmas are not represented in the basalt sample suite returned from the taurus littrow valley by the apollo 17 mission the dunite xenolith records several episodes of crystallization and re equilibration during the last episode of re equilibration the dunite cumulate was sampled by the 74275 high ti basalt and transported over a period of 30 70 days to the lunar surface

origin of lunar very high potassium vhk basalts a combination of endogenous and exogenous processes abstract very high potassium or vhk basalts have been described from the apollo 14 landing site at fra mauro on the lunar near side many of the known samples are clasts in polymict breccias with a few as new work completed on fourteen vhk basalts include crystal size distributions csds and in situ chemical analyses and element maps collected by electron probe microanalysis epma csds completed on three vhk basalt samples indicate that these basalts are not impact melts and represent endogenous melts of the lunar interior potassium k element maps reveal the spatial relationship between the k rich material and the basalt clasts with attached breccia matrix if present in situ epma analyses have identified two distinct types of k rich material k feldspar and k rich glass with these new data an additional mechanism for an exogenic petrogenesis of vhk basalts is proposed that involves the impact process vhk basalts can be divided into two groups based on density and viscosity vhk 1 basalts formed when a hot impact ejecta covered the granite felsite rich matrix material containing high al basalt clasts heat from the impact ejecta partially melted and possibly evaporated nearby k bearing materials which then infiltrated and contaminated the high al clasts vhk 2 basalts are consistent with the hypothesis of granite assimilation by a high al magma as seen in the higher abundances of network forming elements