aftsolve a program for multi kinetic modeling of apatite fission track data aftsolve is a computer program for deriving thermal history information from apatite fission track data it implements a new fission track annealing model that takes into account the known kinetic variability among different apatite species to fully utilize this model a fission track worker must obtain data that can be used to infer the kinetic characteristics of each apatite grain from which a measurement was taken such data can consist of etch figure lengths or chemical composition the benefit of this overall approach is that it allows useful information to be derived from previously unusable analyses extends the practical range of geological temperatures constrained by fission track analyses and increases overall confidence in model predictions aftsolve also incorporates the effects of fission track orientation relative to the apatite crystallographic c axis variation in initial track length and the biasing effect of 2 5 2 cf irradiation for enhancing confined horizontal track length detection aftsolve is written for windows operating systems and has a graphical interface that allows interactive input of thermal histories and real time generation of estimates for fission track length distributions and ages for up to six simultaneously modeled kinetic populations it also includes procedures for estimating the range of time temperature histories that are statistically consistent with a data set and constraints entered by the user

thermochronological investigation of fault zones abstract the timing of faulting episodes can be constrained by radiometric dating of fault zone rocks fault zone material suitable for dating is produced by tectonic processes such as 1 fragmentation of host rocks followed by grain size reduction and recrystallization to form mica and clay minerals 2 secondary heating melting of host rocks by frictional fault motions and 3 mineral vein formation as a result of fluid advection associated with the fault motions the thermal regime of fault zones consists primarily of the following three factors a regional geothermal structure across the fault zone and background thermal history of studied province bounded by fault systems b frictional heating of wall rocks by fault motions and c heating of host rocks by hot fluid advection in and around the fault zone thermochronological methods widely applied in fault zones are k ar 40ar 39ar fission track and u th methods for which methodological principles as well as analytical procedures are briefly described the thermal sensitivities of individual thermochronological systems are then reviewed which critically control the response of each method against the thermal processes based on the knowledge above representative examples as well as key issues are highlighted to date fault gouges pseudotachylytes mylonites and carbonate veins placing new constraints upon geological geomorphological and seismological frames finally the nojima fault is presented as an example for multiple applications of thermochronological methods in a complex fault zone

fission track analysis reveals character of collisional tectonics in new zealand during the late cenozoic the pacific plate has been obliquely converging with the australia plate in south island new zealand this has resulted in westward obduction of continental crust of the pacific plate and consequently a major mountain range the southern alps has formed east of the alpine fault and within the leading edge of the pacific plate we have applied the apatite and zircon fission track dating technique to a suite of outcrop samples from three transects across the southern alps starting at the alpine fault to better understand the uplift age and structure of the continental collision the results show the following 1 uplift was underway at 7 ma in the south at haast pass and by 5 ma in the north at arthur s pass 2 profiles of the total amount of late cenozoic uplift show an exponential increase toward the alpine fault adjacent to the alpine fault there has been 14 5 to 21 5 km of uplift in the vicinity of haast pass 14 5 to 21 km near mt cook and 12 5 to 15 5 km in the arthur s pass transect adjacent to the alpine fault in the mount cook region the average uplift rate from 5 5 ma to 1 ma was 2 3 to 2 5 mm yr between 1 ma and the present it has averaged 6 2 mm yr the strongly asymmetric uplift pattern is responsible for the exposure of a 13 25 km wide belt of greenschist to midamphibolite facies rocks immediately east of the alpine fault known as the alpine schists 3 late cenozoic uplift of torlesse greywackes and alpine schists was preceeded during the jurassic early cretaceous by 5 8 km of uplift the otago schist belt to the south was uplifted much more during this interval and in addition western parts of the otago schists were uplifted 5 6 km during the late cretaceous 4 the fission track data do not support the notion of significant late cenozoic shear heating about the alpine fault as previously suggested from spatial variations in k ar ages of the otago and alpine schists

fundamentals of fission track thermochronology fission track ft analysis has developed into one of the most useful techniques used throughout the geologic community to reconstruct the low temperature thermal history of rocks over geological time the ft method is based on the accumulation of narrow damage trails i e fission tracks in uranium rich mineral grains e g apatite zircon titanite and natural glasses which form as a result of spontaneous nuclear fission decay of 238u in nature price and walker 1963 fleischer et al 1975 the time elapsed since fission tracks began to accumulate is estimated by determining the density of accumulated tracks in a particular material in relation to the uranium content of that material chemical etching can be used to enlarge fission tracks that have formed within a mineral in order to make them readily observable under an ordinary optical microscope price and walker 1962 if a host rock is subjected to elevated temperatures fission tracks that have formed up to that point in time are shortened progressively and eventually erased by the thermal recovery i e annealing of the damage fleischer et al 1975 because thermal diffusion basically governs the annealing process the reduction in ft length is a function of heating time and temperature importantly fission tracks are partially annealed over different temperature intervals within different minerals this characteristic allows for the construction of time temperature paths of many different rock types by a plotting ft and other isotopic ages from different minerals versus their closure temperatures which is applicable in the case of a monotonous cooling history e g wagner et al 1977 zeilter et al 1982 and or by b the inverse modeling of observed ft age and confined track length data e g corrigan 1991 lutz and omar 1991 gallagher 1995 ketcham et al 2000 see also ketcham 2005

can fission track annealing in apatite be described by first order kinetics abstract it is becoming commonplace to suggest that fission track annealing in apatite can be described by first order kinetics that is the decrease in track density and or length with time during isothermal annealing can be described by a single exponential equation a review of the literature reveals that there is no convincing evidence for such an assertion but more than ample evidence to the contrary simple graphical analysis of available annealing data from the literature clearly shows that the single exponential fails to adequately describe the data more rigorous statistical model fitting is not attempted due to the generally inadequate specification of annealing data in the literature most published annealing data suffer from flaws in experimental design that render them of limited value in defining viable kinetic models for the annealing process consideration of the processes taking place during annealing suggests that there is no good reason why first order kinetics would be expected to describe fission track annealing and more complex models should be considered in order to provide reliable data capable of yielding practically useful kinetic models laboratory annealing experiments should be designed to meet a number of strict criteria in identifying viable models the need is for those which adequately describe the data rather than for physically meaningful models although models should preferably be kept as simple as possible

comment on alpine thermal and structural evolution of the highest external crystalline massif the mont blanc by p h leloup n arnaud e r sobel and r lacassin in this comment we discuss the approach used and the significance of ar ar dating of synkinematic phengite within low grade alpine shear zones and we comment the geodynamic models that can be derived from this method the paper by leloup et al 2005 is a good step forward in the tectonic comprehension of the mont blanc area and provides a good synthesis of preexisting data leloup et al 2005 have proposed a polyphase alpine history for the mont blanc massif west alps based on a multidisciplinary approach ar ar on biotite for the higher pressure temperature events of the mont blanc and ar ar on k feldspar fission tracks ft on zircon and apatite for its later exhumation stages however at this point of our knowledge of alpine deformation in the mont blanc range the polyphased tectonic evolution in particular the timing of thrust and back thrust events are not in agreement with recently obtained ar ar data

illite and hydrocarbon exploration illite is a general term for the dioctahedral mica like clay mineral common in sedimentary rocks especially shales illite is of interest to the petroleum industry because it can provide a k ar isotope date that constrains the timing of basin heating events it is critical to establish that hydrocarbon formation and migration occurred after the formation of the trap anticline etc that is to hold the oil illite also may precipitate in the pores of sandstone reservoirs impeding fluid flow illite in shales is a mixture of detrital mica and its weathering products with diagenetic illite formed by reaction with pore fluids during burial k ar ages are apparent ages of mixtures of detrital and diagenetic end members and what we need are the ages of the end members themselves this paper describes a methodology based on mineralogy and crystallography for interpreting the k ar ages from illites in sedimentary rocks and for estimating the ages of the end members

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

the recognition of reactivation during continental deformation reactivation involves the accommodation of geologically separable displacement events intervals 1 ma along pre existing structures the definition of a significant period of quiescence is central to this phenomenological definition and the duration of the interval chosen represents the resolution limit of reactivation criteria found in most ancient settings in neotectonic environments reactivation can be further defined as the accommodation of displacements along structures that formed prior to the onset of the current tectonic regime this mechanistic definition cannot always be applied to ancient settings due to the uncertainties in constraining relative plate motion vectors four sets of criteria may be used to recognize reactivation in the geological record stratigraphic structural geochronological and neotectonic some structural criteria may not be reliable if used in isolation to identify reactivated structures much of the previously published evidence cited to invoke structural inheritance is equivocal as it uses similarities in trend dip or three dimensional shape of structures numerous fault and shear zone processes can cause significant weakening both synchronously with deformation and in the long term and may be invoked to explain reactivation the collage of fault bounded blocks forming most continents therefore carries a long term architecture of inheritance which can explain much of the observed complexity of continental deformation zones

dating pseudotachylyte of the nojima fault using the zircon fission track method 1 the zircon fission track analysis of pseudotachylyte answered how old the nojima fault is which was activated during the 1995 kobe earthquake in japan the time of seismic fault motions at the crustal interior can be constrained by dating pseudotachylyte formation we succeeded in separating zircons from the pseudotachylyte layer of the fault as well as in dating them by the fission track method here we show that the layer has a significantly younger age 56 4 ma than the initial cooling age of the host rock suggesting that the fault was already initiated at 56 ma much older than the previous estimate based on the spatial distribution of sediments around the fault

statistical characteristics of gravity waves observed by an all sky imager at darwin australia 1 an all sky airglow imager with a cooled charge coupled device camera in place at darwin 12 4 s 131 0 e australia since october 2001 has been used to obtain two dimensional gravity wave images in the mesopause region using airglow images of the oi 557 7 nm emission altitude 96 km and oh band 720 910 nm 86 km emissions obtained for october 2001 to august 2002 we investigated the wavelengths phase velocities and propagation directions of gravity waves wave occurrence in oh images 60 90 is higher than in oi images 30 70 for all seasons the waves have wavelengths of less than 90 km peak 30 50 km and phase velocities of less than 90 m s peak 30 60 m s most of the waves propagate in the meridional direction and the directionality strongly depends on the season in winter waves propagate both poleward and equatorward while in summer almost all waves propagate poleward an examination of airglow imaging statistics at adelaide 35 s 138 e australia obtained by walterscheid et al 1999 leads us to conclude that this clear directionality is caused by the location of the wave sources and by the wave ducting processes that is poleward waves in summer come from an equatorial convective source through a thermal duct structure the effect of wind filtering on the waves is also discussed for zonal wave propagation

40ar39ar dating of very fine grained samples an encapsulated vial procedure to overcome the problem of 39ar recoil loss 40ar39ar dating of very fine grained materials is compromised by the loss of 39ar by recoil and also sometimes other ar isotopes during irradiation an encapsulated sample 40ar39ar procedure is described which overcomes this problem and which produces a k ar equivalent date measurements indicate that the procedure yields reliable and reproducible results it offers the potential for dating small amounts of material of many types for example very fine grained authigenic sheet silicates from rock cores which may suffer ar loss during irradiation

geological partial annealing zone of zircon fission track system additional constrains from the deep drilling miti nishikubiki and miti mishima abstract fission track ft analysis of zircon from rhyolite and sandstone samples of ministry of international trade and industry miti nishikubiki and miti mishima boreholes has given additional constraints on the temperature range of the zircon partial annealing zone zpaz over a geological time scale the advantages of these samples are the following 1 they have been exposed to a stable temperature for 1 million years and 2 it is possible to obtain data at successive temperatures ages and confined track lengths were measured in samples from depths of 3 5 5 6 km with a current environmental temperature of 223 c at the deepest track lengths in samples below 200 c are still long and ft ages are compatible with their sedimentary ages showing no evidence of annealing for a heating duration of 1 million years samples at 205 c seem to yield shortened tracks as a result of annealing because of a low number of zircon crystals only four track lengths were measured for the deepest sample whose mean length was shortest among analysed samples these data are consistent with previous results from ultra deep boreholes

thermobarometric data from a fossil zircon partial annealing zone in high pressure low temperature rocks of eastern and central crete greece abstract a fossil partial annealing zone of fission tracks in zircon is described from high pressure low temperature hp lt rocks of the phyllite quartzite unit pq on the island of crete greece correlation of regional trends in fission track age populations with independent thermobarometric and microstructural data and with new experimental annealing results allows a calibration of this low temperature thermochronological method to a degree hitherto not available from other field examples the zircon fission track ft ages of samples from the pq across crete range from original detrital signature through reduced to completely reset the annealing is the result of a single heating period related to the hp lt metamorphism with near peak temperatures lasting for only a few million years some time between 24 1 and 20 1 ma in eastern crete where rocks have experienced temperatures of 300 50 c and pressures of 0 8 0 3 gpa zircon ft ages range from 414 24 to 145 10 ma ages above 300 ma occur mostly near the east coast of the island in rocks which have not been heated to above ca 280 c and probably represent a pre variscan source track lengths are already indicative of a substantial annealing at this temperature most of the zircon ft ages from eastern crete scatter within error around the stratigraphic age samples with apparent zircon ft ages significantly younger than the depositional age are only observed in areas where temperatures exceeded ca 320 c towards the west a sudden decrease to very young ages ranging from 17 2 to 18 1 ma reflects a complete resetting at ca 350 c short tracks however are still observed throughout the central and western part of the island ages are consistently below 22 ma thermobarometric data for this area indicate maximum temperatures of 400 50 c and pressures of 1 0 3 gpa only samples from western crete which have been exposed to 400 50 c show exclusively long tracks consequently the high temperature limit of the zircon partial annealing zone zpaz appears to be between 350 and 400 c a significant influence of elevated confining pressure on the stability of fission tracks in zircon is ruled out by the results of annealing experiments at 0 5 gpa and at different temperatures which fit the curves previously obtained by other authors at ambient pressure

short term annealing characteristics of spontaneous fission tracks in zircon a qualitative description abstract thermal annealing behavior of fission tracks ft has not yet been documented under short term

injection induced microseismicity in colorado shales imperial oil resources limited uses cyclic steam stimulation to recover oil from their cold lake oil field in alberta this operation in particular situations can be associated with the failure of well casings in the colorado shales above the oil bearing formation a number of fluid injection operations was undertaken at this site and the associated microseismicity was detected using two three component geophones and fifteen hydrophones the purpose of this experiment was to simulate the occurrence of a casing failure determine the feasibility of monitoring in a shallow environment and characterize the microseismic activity a calibration survey provided values of 1786 108 m s for p wave velocity 643 56 mks for s wave velocity and 0 428 0 017 for poisson s ratio in the shale formation estimates of the quality factor q p were 15 for the horizontal direction and 38 for the vertical direction corroborating the evidence of velocity anisotropy calibration shots were located to within 10 m of the actual shot points using triangulation and polarization techniques several hundred microseismic events were recorded and 135 events were located the results showed that microseismic activity was confined to depths within 10 meters of the injection depth the experiment clearly established the feasibility of detecting microseismicity induced by fluid injection rates typical of casing failures in shales at distances over 100 m

alpine thermal and structural evolution of the highest external crystalline massif the mont blanc 1 the alpine structural evolution of the mont blanc highest point of the alps 4810 m and of the surrounding area has been reexamined the mont blanc and the aiguilles rouges external crystalline massifs are windows of variscan basement within the penninic and helvetic nappes new structural 40ar 39ar and fission track data combined with a compilation of earlier p t estimates and geochronological data give constraints on the amount and timing of the mont blanc and aiguilles rouges massifs exhumation alpine exhumation of the aiguilles rouges was limited to the thickness of the overlying nappes 10 km while rocks now outcropping in the mont blanc have been exhumed from 15 to 20 km depth uplift of the two massifs started 22 myr ago probably above an incipient thrust the alpine sole thrust at 12 ma the ne sw trending mont blanc shear zone mbsz initiated it is a major steep reverse fault with a dextral component whose existence has been overlooked by most authors that brings the mont blanc above the aiguilles rouges total vertical throw on the mbsz is estimated to be between 4 and 8 km fission track data suggest that relative motion between the aiguilles rouges and the mont blanc stopped 4 myr ago since that time uplift of the mont blanc has mostly taken place along the mont blanc back thrust a steep north dipping fault bounding the southern flank of the range the european roof is located where the back thrust intersects the mbsz uplift of the mont blanc and aiguilles rouges occurred toward the end of motion on the helvetic basal decollement hbd at the base of the helvetic nappes but is coeval with the jura thin skinned belt northwestward thrusting and uplift of the external crystalline massifs above the alpine sole thrust deformed the overlying helvetic nappes and formed a backstop inducing the formation of the jura arc in that part of the external alps nw se shortening with minor dextral ne sw motions appears to have been continuous from 22 ma until at least 4 ma but may be still active today a sequential history of the alpine structural evolution of the units now outcropping nw of the pennine thrust is proposed

annealing kinetics of fission tracks in zircon an experimental study a series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350 750 c for 10 1 103 hr i e 4 5 min 40 days variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from nisatai dacite the fading contours of normalized mean track length r on the arrhenius diagram showed as sets of straight lines we performed a series of model fittings called the parallel and fanning models in order to describe the decrease in r with increasing temperature or heating time the lowest temperature limit of the zircon partial annealing zone zpaz was defined as r 0 95 and the highest as r 0 4 which approximately corresponded to the total fading of surface tracks extrapolation of the results of the laboratory experiments to the geological timescale gives for a heating duration of 106 yr estimated values of the zpaz of 210 320 c 60 c 2 with the parallel model 190 350 c 50 c 2 with the fanning model critical temperature t0 and 170 390 c 50 c 2 with the fanning model t0 the temperatures of the zpaz decrease by 20 c for an annealing duration that is an order of magnitude longer because the estimated closure temperature of zircon fission track analysis approximately corresponds to the middle of the zpaz these results support the previously estimated closure temperature of 240 c by varying the etching time it was revealed that significant removal of radiation damage occurs at r 0 93

40ar39ar dating of pseudotachylite from the vredefort dome south africa a progress report abstract to date six pseudotachylite samples from the vredefort dome have been analysed by the stepheating 40ar 39ar technique the resulting ages ga 2 25 0 04 k ar 2 01 0 06 1 39 0 08 1 44 0 08 1 33 0 04 and 1 09 0 10 may be understood as suggesting several pseudotachylite forming events at vredefort this and other chronological and field evidence may be interpreted as supporting the possibility that vredefort pseudotachylite is not derived from a single catastrophic central shock event but was generated in several local high strain possibly seismic shock events diffusion calculations have shown that it is possible that several thermal spikes could have effectively degassed pseudotachylite at relatively low temperatures and during short periods of time e g at 340 c in 10000 yrs there is however no geological or isotopic evidence directly supporting the existence of these proposed temperature spikes at 2 0 1 3 1 4 and 1 1 ga in the region of the vredefort structure on the contrary field and laboratory observations can be invoked that seem to favour the formation of multiple generations of pseudotachylite in the vredefort dome and in the surrounding witwatersrand basin however it must be noted that likewise no direct geological evidence for local tectonic activity in the region of the witwatersrand basin at those times can be presented with the exception of emplacement of pilanesberg age dykes further tests on the validity of the 40ar 39ar ages on vredefort pseudotachylite are in progress and are discussed

40ar 39ar thermochronometry of k feldspar from the ktb borehole germany abstract the great depth and relatively steep geothermal gradient 29 c km of the ktb deep crustal borehole located in the bavarian region of germany provides the basis for our study of diffusive argon loss in k feldspar the observed borehole temperature at 9 km is 265 c which reaches well into the argon closure interval for k feldspar 125 350 c four microcline and two adularia samples distributed relatively evenly down the 9 1 km deep borehole were analyzed by the 40ar 39ar method the thermal histories of the shallow samples are consistent with existing thermochronologic data from the borehole after correction for chlorine correlated excess 40ar the deepest two samples result in age spectra that record zero apparent ages over the first few percent of 39ar released which is predicted by diffusion theory where a range of diffusion volumes are present inverse modeling of the argon kinetics of these two deep samples reveals that the present elevated geothermal gradient in the borehole has existed for only the last approximately one million years recent volcanism within 30 km of the borehole is likely the source of this present day thermal pulse

zircon fission track thermochronology and applications to fault studies zircon is one of the most useful minerals used to unravel the earth s history recorded in rocks after the success of etching fission tracks in zircon fleischer et al 1964 naeser 1969 krishnaswami et al 1974 early studies focused primarily on dating young volcanic horizons for stratigraphic purposes e g naeser et al 1973 hurford et al 1976 seward 1979 gleadow 1980 kowallis et al 1986 kohn et al 1992 subsequently fission track analysis of zircon has been extensively employed along with other radiometric dating methods such as u pb and u th he techniques e g davis et al 2003 reiners 2005 to understand the thermochronology of rocks in a variety of geological settings i e thermal history analysis of basement rocks for orogenic studies e g zeilter et al 1982 hurford 1986 kamp et al 1989 sorkhabi 1993 seward and mancktelow 1994 hasebe and tagami 2001 spikings et al 2001 thermochronology using detrital zircon grains in sedimentary rocks for provenance analysis and thermal history analysis in or near faults which will be highlighted below in this present chapter the thermal sensitivity of the zircon fission track thermochronometry is reviewed in the context of laboratory and field studies then laboratory procedures of the zircon fission track analysis using the external detector method are outlined as practiced in the fission track laboratory of kyoto university for basic fundamentals of these fission track analyses including data analysis and graphical displays see the chapter by tagami and o sullivan 2005 finally as an example of recent geological applications of the technique the results of zircon fission track analysis of the nojima fault zone japan are presented these rocks were the target of systematic drilling of an active fault system using five boreholes and a trench applications to other geological settings and the