ti distribution in quartz across a heterogeneous shear zone within a granodiorite the effect of deformation mechanism and strain on ti resetting abstract the study of a heterogeneous ductile shear zone that developed at 500 c and 0 2 gpa during post magmatic cooling of a granodiorite has allowed the effect of strain and recrystallization on ti re equilibration of quartz to be assessed understanding this effect is critical for applying ti in quartz thermobarometry to mylonites differently strained quartz across the shear zone shows a heterogeneous distribution of ti concentrations ti measured by secondary ion mass spectrometry sims ranging between 2 and 45 ppm quartz cathodoluminescence cl is proven by spectral analysis to be correlated with ti allowing cl images to be calibrated as ti maps using sims measurements coarse grained weakly deformed domains consist of magmatic quartz extensively recrystallized by grain boundary migration gbm and mostly 65 75 area contain 20 38 ppm ti resetting to lower ti occurred locally i in haloes surrounding titanite and biotite inclusions ti as low as 6 ppm ii along grain boundaries and iii towards the interface of quartz domains with other mineral domains with increasing strain quartz underwent progressive grain size reduction and developed a bimodal microstructure with elongate grains 100 s m long surrounded by mantles of new grains 10 30 m in size recrystallized by subgrain rotation sgr dynamic recrystallization by sgr associated with prism slip became increasingly dominant over gbm as strain increased towards the shear zone core significant resetting of ti in quartz only occurred in high strain domains at shear strain probably 10 in the shear zone core where fine recrystallization amounts to 50 60 by area and coarser cores are strongly sub structured these domains are not compositionally homogeneous and still show a range of ti mostly between 2 and 10 ppm in all strain facies of the shear zone quartz filled pressure shadows associated with feldspar show an almost constant ti of 2 ppm the pristine ti content of the magmatic quartz mylonitized in the shear zone core is therefore significantly reset and converges asymptotically towards the equilibrium 2 ppm ti shown by new quartz precipitated in pressure shadows it is inferred that extensive recrystallization by sgr and repeated cycles of dislocation creep and rearrangement provided fluid access to quartz grain interiors promoting chemical buffering and leading to partial re equilibration to low ti these observations imply limitations on the use of the ti in quartz thermobarometry to constrain ambient conditions of ductile deformation

development of crystallographic preferred orientation and microstructure during plastic deformation of natural coarse grained quartz veins 1 the microstructure and crystallographic preferred orientation cpo of quartz were quantified in 17 samples of natural monomineralic tabular veins the veins opened and were deformed up to shear strain 15 in a small temperature window about 25 c above 500 c as established by ti in quartz thermometry the veins filled a set of fractures within the adamello tonalite southern alps italy and localized homogeneous simple shear during postmagmatic cooling the local square millimeter scale and bulk square centimeter cpo were investigated by computer integrated polarization microscopy cip and x ray texture goniometry weakly deformed veins wdv 1 consist of millimeter to centimeter sized crystals with a strong cpo showing a c axis girdle slightly inclined mostly with the shear sense to the foliation xy plane and a strong maximum close to the lineation x moderately deformed veins mdv 2 3 consist of elongated nonrecrystallized ribbon grains and most have a cpo showing a strong y maximum of c axes some with weak extension into a yz girdle strongly deformed veins sdv 4 to 15 are pervasively to completely recrystallized to fine 34 40 m grain size aggregates with a strong cpo similar to that of mdv the slip systems during plastic deformation were dominantly prism a with subordinate rhomb and basal a slip recrystallization occurred rather abruptly for 3 4 in contrast to dislocation creep experiments in quartz and other minerals a steady state recrystallized fabric is achieved at early stages of deformation 4 as there is no evidence with increasing strain of strengthening of the cpo of rotation of the fabric skeleton or of change in grain size wdv represent weakly deformed relicts of veins with an initial cpo believed to have developed during crystal growth but unsuitably oriented for prism a slip during subsequent shear mdv and sdv appear to derive from veins different from wdv where the vein crystals grew with orientation favorable for prism a slip the relationship between the initial growth cpo and the kinematic framework suggests that veins opened at a temperature close to that at which there is a switch between the activity of prism c and prism a slip with the temperature of growth causing growth of crystals well oriented for slip the initial cpo of veins from which quartz mylonites are commonly derived plays a critical role in the fabric evolution the strong growth and strain induced cpos of these sheared veins inhibited significant reworking during lower temperature stages of pluton cooling when basal a slip would have been dominant

a flow law for dislocation creep of quartz aggregates determined with the molten salt cell we have used the molten salt cell to conduct an experimental study on the rheology of a natural quartzite containing 0 15 wt water co axial deformation experiments were conducted at constant piston displacement rates approximating constant strain rates at low strain the strengths of our natural quartzite measured in the molten salt cell are approximately half those measured at the same conditions in solid media because unlike solid confining media molten salt does not contribute to the strength of the sample it reduces the friction on the moving piston and it allows clear identification of the hit point we have limited the experimental conditions to those required for dislocation creep and have used only steady state flow stresses measured during climb accommodated dislocation creep to calculate the flow law parameters two flow laws were determined one for samples containing minor amounts of melt 1 2 and one for melt free samples in both cases the power law stress exponent n is 4 0 0 9 which is greater than that previously reported in flow laws for dislocation creep of quartz aggregates determined in solid media the activation energy q is 137 34 kj mol 1 for samples with melt and 223 56 kj mol 1 for those without within the range of previously determined values for quartz aggregates containing 0 1 wt water the pre exponential term a is 1 1 10 4 2 mpa ns 1 for samples without melt and 1 8 10 8 2 mpa ns 1 for those with melt the lower strengths measured in the molten salt cell indicate that previous piezometer relations for quartz experimentally determined in solid media are not correct extrapolation of the flow law for melt free aggregates to natural strain rates predicts higher strengths than most previous quartz flow laws however accurate extrapolation requires determining the dependence of flow stress on fh2o and or ah

microstructural and crystal fabric evolution during shear zone formation abstract the microstructures and crystal fabrics associated with the development of an amphibolite facies quartzo feldspathic mylonitic shear zone torridon nw scotland have been investigated using sem electron channelling our results illustrate a variety of microstructures and fabrics which attest to a complex shear zone deformation history microstructural variation is particularly pronounced at low shear strains significant intragranular deformation occurs via a domino faulting style process whilst mechanical incompatibilities between individual grains result in characteristic grain boundary deformation accommodation microstructures a sudden reduction in grain size defines the transition to medium shear strains but many of the boundaries inherited from the original and low shear strain regions can still be recognized and define distinctive bands oriented at low angles to the shear zone margin grains within these bands have somewhat steeper preferred dimensional orientations these domains persist into the high shear strain mylonitic region where they are oriented subparallel to the shear zone margin and consist of sub 20 m grains the microstructures suggest that the principal deformation mechanism was intracrystalline plasticity with contributions from grain size reduction via dynamic recrystallization grain boundary migration and grain boundary sliding crystal fabrics measured from the shear zone vary with position depending on the shear strain involved and are consistent with the operation of several crystal slip systems e g prism basal rhomb and acute rhomb planes in a consistent direction probably parallel to a and or m they also reveal the presence of dauphine twinning and suggest that this may be a significant process in quartz deformation a single crystal fabric evolution path linking the shear zone margin fabric with the mylonitic fabric was not observed rather the mylonitic fabric reflects the instantaneous fabric which developed at a particular location for a particular shear strain and original parental grain orientation the mature shear zone therefore consists of a series of deformed original grains stacked on top of each other in a manner which preserves original grain boundaries and intragranular features which develop during shear zone evolution the stability of some microstructures to higher shear strains the exploitation of others at lower shear strains and a continuously evolving crystal fabric mean that the strain gradient observed across many shear zones is unlikely to be equivalent to a time gradient

plastic anisotropy and fabric evolution in sheared and recrystallized quartz single crystals 1 the effect of a lattice preferred orientation on the flow strength of quartz aggregates dynamically recrystallized from single crystals of synthetic quartz was investigated using general shear experiments in a griggs apparatus experiments were conducted at shear strains up to 5 at a temperature of 900 c confining pressure of 1 5 gpa and shear strain rate of 10 5 s 1 three starting orientations of crystal were used to activate three slip systems basal a prism c and prism a although slip induced rotation of the crystal axes in the first two orientations led to the activation of additional slip systems for crystals with higher water contents basal a and prism a orientations are relatively weak and prism c orientations are stronger all three initial crystal orientations undergo dynamic recrystallization with increasing shear strain although the strain required for 100 recrystallization varies 2 for prism c slip 3 8 for basal a slip and 5 for prism a slip for all three starting orientations distinct domains of recrystallized grains develop with c axes parallel to y of the strain ellipsoid ymax replacing recrystallized grains of other orientations the ymax domains increase in size with increasing strain in addition strain markers show that strain is highly localized within the ymax domains indicating geometrical softening of up to an order of magnitude in effective viscosity

orientation analysis of localized shear deformation in quartz fibres at the brittle ductile transition abstract the crystallographic preferred orientation of fibrous quartz veins deformed under subgreenschist facies conditions along a temperature gradient from 270 to 370 c has been investigated to explore the active mechanism during deformation of the quartz fibres the complete crystallographic orientation of individual recrystallized grains and subgrains was determined by using a combination of cip computer integrated polarization microscopy ebsd electron back scatter diffraction and additional specially developed image analysis techniques it was found that the quartz fibres deformed along crystallographically controlled shear bands from inverse pole figures of normals to the shear band boundaries it is evident that these bands occur along the positive and negative rhomb planes of quartz it is suggested that they are initiated as fractures along these planes inside the shear bands small grains broken off from the host grain show passive rotation of the lattice consistent with the shear sense of the shear bands continued deformation and increasing temperature lead to different recrystallization microstructures inside and outside the shear bands and to a partial obliteration of the sharp orientation relationships

seismic structure of the lithosphere beneath nw namibia impact of the tristan da cunha mantle plume northwestern namibia at the landfall of the walvis ridge was affected by the tristan da cunha mantle plume during continental rupture between africa and south america as evidenced by the presence of the etendeka continental flood basalts here we use data from a passive source seismological network to investigate the upper mantle structure and to elucidate the cretaceous mantle plume lithosphere interaction receiver functions reveal an interface associated with a negative velocity contrast within the lithosphere at an average depth of 80 km we interpret this interface as the relic of the lithosphereasthenosphere boundary lab formed during the mesozoic by interaction of the tristan da cunha plume head with the pre existing lithosphere the velocity contrast might be explained by stagnated and frozen melts beneath an intensively depleted and dehydrated peridotitic mantle the present day lab is poorly visible with converted waves indicating a gradual impedance contrast beneath much of the study area converted phases of the 410 and 660 km mantle transition zone discontinuities arrive 1 5 s earlier than in the landward plume unaffected continental interior suggesting high velocities in the upper mantle caused by a thick lithosphere this indicates that after lithospheric thinning during continental breakup the lithosphere has increased in thickness during the last 132 myr thermal cooling of the continental lithosphere alone cannot produce the lithospheric thickness required here we propose that the remnant plume material which has a higher seismic velocity than the ambient mantle due to melt depletion and dehydration significantly contributed to the thickening of the mantle lithosphere

electron backscatter diffraction analysis to determine the mechanisms that operated during dynamic recrystallisation of quartz rich rocks abstract determination of the controlling nucleation and recrystallisation mechanisms from a samples microstructure are essential for understanding how the microstructure formed and evolved through time the aim of our research was to apply a quantified analytical approach to the identification of the controlling nucleation recrystallisation and microstructural modification mechanisms we used electron backscatter diffraction to quantify the microstructures of naturally deformed quartz rich rocks which were deformed at various temperature and pressure conditions our results show that ratios of the recrystallised grain size to the subgrain size with values less than 1 0 5 0 7 in the data presented here suggest bulge nucleation whereas ratios of 1 suggest subgrain rotation nucleation other supporting evidence for subgrain rotation nucleation is an increase in misorientation from the centre of an original protolith parent grain to the edge all samples show evidence for modification of the microstructure due to grain boundary sliding including increased misorientation angles between grains and movement of recrystallised grains between parent grains by systematically analysing sample microstructures it is possible to separate out evidence to determine the controlling nucleation and recrystallisation mechanisms as well as being able to identify microstructure modification mechanisms using microstructural quantification via ebsd allows a systematic methodology to analyse samples from any location from an objective viewpoint

numerical modelling of the growth dynamics of a simple silicic lava dome 1 two dimensional axisymmetrical computational models have been developed using finite element techniques to represent the rheological stiffening due to degassing induced crystallisation and the effects of a brittle carapace within a simple lava dome the dome is modelled numerically considering the effects of temperature pressure and rate of extrusion using these state variables the bulk viscosity is derived from empirical equations and the bulk rheology approximated using a solidification viscosity dividing the dome into solid dominated and fluid dominated domains elastoplastic equations for the solid component and fluid mechanical equations for the fluid domain are solved simultaneously allowing continuous stress across the fluid solid interface to ensure the two components move in unison we apply this model a hookean solid carapace model and a purely fluid lava dome model to the case of the october 1980 lava dome at mount st helens the results show that dynamic growth models involving a solid carapace are required to simulate this lava dome

fabric development in experimentally sheared quartzites abstract a fine grained quartzite was deformed under a combination of simple shear and axial compression to varying amounts of shear strain 1 3 to 2 9 the experiments were conducted at 800 c 1500 mpa and an axial strain rate of 10 6 s in the dislocation creep regime shear zone boundaries were oriented at 45 or 30 to the compressior axis the progressive development of deformation microstructures including planar fabrics and c axis preferred orientations was studied as a function of increasing shear strain elongate original grains define a foliation s which rotates from 45 to 0 to the shear zone boundary with increasing strain producing a sigmoidal foliation in a single shear zone a second foliation invariant in orientation is defined by elongate recrystallized grains which lie at about 30 40 to the shear zone boundaries no c surfaces parallel to the shear zone boundaries were observed however extensional crenulation cleavages c defined by parallel zones of recrystallized grains as well as impurity and melt segregations were observed even at low strain lying at approximately 30 to the shear zone boundaries and these could easily be mistaken for c surfaces c axis preferred orientations of original grains define symmetric type i crossed circle girdles at low strain 2 with the greater concentration of c axes in the direction of shear these features are very similar to those observed in natural ductile shear zones

the potential application of magnetic susceptibility as a technique for soil forensic examinations magnetic susceptibility measurement methodology its reproducibility and accuracy of analysis were tested on soil samples to evaluate its potential use in forensic applications it was observed that magnetic susceptibility can enable discrimination between soil samples measured values are reproducible over time and the analysis can be carried out on small samples however in order for this method to be used in a forensic soil investigation it is important to always adopt the same analytical protocol during analysis the evidential value of soil lies in the diversity of this material making the power to discriminate among soils equally large murray tedrow 1992 murray 2004 an important issue in a geoforensic investigation is the demonstration of whether or not variations in the soil properties result in dissimilarity between samples and a large number of analytical methods have been applied to characterize soils to test whether or not sites can be excluded magnetic parameters such as magnetic susceptibility are important in characterizing materials and detectable quantities of magnetic minerals are almost always found in soils the magnetic susceptibility of a soil is the sum of all of the contributions from the minerals present and varies owing to differences in the concentration and composition of those minerals in a forensic investigation it is important to not only obtain samples that are representative and comparable but also develop standardized protocols and frameworks of best practice to better evaluate soil properties in a representative manner several experiments on the magnetic susceptibility of soils have been conducted recently mostly related to pollution monitoring and mapping in some of the works the accuracy and precision of this analytical method on soils have been evaluated schibler et al 2002 boyko et al 2004 maier et al 2006 d emilio et al 2007 however these reported the use of magnetic susceptibility probes and in situ analysis although there are only a few reported applications of magnetic susceptibility in forensic investigations e g chen et al 2009 the importance of the use of this technique for forensic applications has been reported in work relating to forensic archaeology detecting clandestine graves and forensic searches for buried targets most of the research and applications deal with the survey application of portable magnetometers and the advantages and limitations of the technique are reported fenning donnelly 2004 hunter cox 2005 bergslien 2012 pringle et al 2012 this study is based on research and experimentation based on soil samples for forensic applications the magnetic susceptibility measurement methodology reproducibility and accuracy in analysis were tested on soil samples collected from different locations the magnetic susceptibility measurement of soils recovered from a crime scene at room temperature is non destructive therefore the same material is available for further analysis with any other technique additionally it does not require sample preparation and can be used as a simple and rapid method that is operable with small sample sizes thus it is an advantageous method for the study of soils being used as trace evidence in forensic investigations low field magnetic susceptibility low field magnetic susceptibility is a measure of the magnetic response of a material to an external magnetic field the volume susceptibility k measured in dimensionless units is defined as the from pirrie d ruffell a dawson l a eds 2013 environmental and criminal geoforensics geological society london special publications 384 65 73 first published online july 8 2013 http dx doi org 10 1144 sp384 7 the geological society of london 2013 publishing disclaimer www geolsoc org uk pub ethics by guest on november 11 2013 http sp lyellcollection org downloaded from

intragranular dynamic recrystallization in naturally deformed calcite marble diffusion accommodated grain boundary sliding as a result of subgrain rotation recrystallization abstract intragranular microshear zones within a greenschist facies calcite marble were studied to try to constrain better the processes of dynamic recrystallization as well as the deformation processes that occur within newly recrystallized grains intragranular recrystallized grains within large twinned calcite porphyroclasts can be related to the host from which they have recrystallized and are the focus of an electron backscatter diffraction study lattice distortions low angle boundaries and some high angle boundaries 15 in the microshears within a porphyroclast have the same misorientation axes suggesting that deformation occurred by climb accommodated dislocation creep involving subgrain rotation recrystallization changes in the ratio of host and twin domain as the deformation zone is entered show that twin boundary migration also occurred recrystallized grains have similar sizes 10 60 m to subgrains suggesting that they formed by subgrain rotation however within the intragranular microshear zones the misorientations between recrystallized grains and porphyroclasts are considerably larger than 15 and misorientation axes are randomly oriented moreover recrystallized grain orientations average around the porphyroclast orientation we suggest that the recrystallized grains once formed are able to deform partly by diffusion accommodated grain boundary sliding which is consistent with predictions made from lab flow laws

dislocation generation slip systems and dynamic recrystallization in experimentally deformed plagioclase single crystals abstract three samples of gem quality plagioclase crystals of an60 were experimentally deformed at 900 c 1 gpa confining pressure and strain rates of 7 5 8 7 10 7 s 1 the starting material is effectively dislocation free so that all observed defects were introduced during the experiments two samples were shortened normal to one of the principal slip planes 010 corresponding to a hard orientation and one sample was deformed with a schmid factor of 0 45 for the principal slip system 001 010 corresponding to a soft orientation several slip systems were activated in the soft sample dislocations of the 001 010 and 110 001 system are about equally abundant whereas 110 111 and 101 in 131 to 242 are less common in the soft sample plastic deformation is pervasive and deformation bands are abundant in the hard samples the plastic deformation is concentrated in rims along the sample boundaries deformation bands and shear fractures are common twinning occurs in close association with fracturing and the processes are clearly interrelated glissile dislocations of all observed slip systems are associated with fractures and deformation bands indicating that deformation bands and fractures are important sites of dislocation generation grain boundaries of tiny defect free grains in healed fracture zones have migrated subsequent to fracturing these grains represent former fragments of the fracture process and may act as nuclei for new grains during dynamic recrystallization nucleation via small fragments can explain a non host controlled orientation of recrystallized grains in plagioclase and possibly in other silicate materials which have been plastically deformed near the semi brittle to plastic transition

high temperature fracturing and ductile deformation during cooling of a pluton the lake edison granodiorite sierra nevada batholith california abstract in the bear creek area of the sierra nevada batholith california the high temperature postmagmatic deformation structures of the lake edison granodiorite include steeply dipping orthogneiss foliations joints and ductile shear zones that nucleated on joints and leucocratic dykes exploitation of segmented joints resulted in sharply bounded thin shear zones and in large slip gradients near the shear zone tips causing the deformation of the host rock at contractional domains the orthogneiss foliation intensifies towards the contact with the younger mono creek granite and locally defines the dextral rosy finch shear zone rfsz a major kilometre wide zone crosscutting the pluton contacts joints predominantly strike at n70 90 e over most of the lake edison pluton and are exploited as sinistral shear zones both within and outside the rfsz in a narrow 250 m thick zone at the contact with the younger mono creek granite within the rfsz the lake edison granodiorite includes different sets of dextral and sinistral shear zones joints the latter corresponding to the set that dominates over the rest of the lake edison pluton these shear zones joints potentially fit with a composite y r r shear fracture pattern associated with the rfsz or with a pattern consisting of y r shear fractures and rotated t mode i extensional fractures the mineral assemblage of shear zones and the microstructure and texture of quartz mylonites indicate that ductile deformation occurred above 500 c joints and ductile shearing alternated and developed coevally the existing kinematic models do not fully capture the structural complexity of the area or the spatial distribution of the deformation and magmatic structures future models should account more completely for the character of ductile and brittle deformation as these plutons were emplaced and cooled

the influence of grain boundary fluids on the microstructure of quartz feldspar mylonites quartz rich domains in pre alpine water deficient amphibolite facies 510 580 c 250 450 mpa pegmatite mylonites from mont mary mm western alps preserve a fine dynamically recrystallized grain size without significant annealing despite the high synkinematic temperatures and subsequent static greenschist facies alpine overprint the microstructure is dramatically different from more typical water rich amphibolite facies mylonites such as from the simplon fault zone in the central alps where the recrystallized grain size is on the millimetre scale the difference reflects the dominant strain induced recrystallization mechanism 1 progressive subgrain rotation and grain boundary bulging for the dry mm examples and 2 fast grain boundary migration for the wet simplon examples the grain boundary microstructure imaged with sem is also very different with most grain boundaries in the dry mm samples lacking porosity whereas grain boundaries in the wet samples are decorated by a multitude of pores quartz grain boundaries from both wet and dry samples are locally coated by thin 100 s of nanometres possibly amorphous silica films despite the differences in microstructure the crystallographic preferred orientations cpos of quartz rich domains from both areas are very similar water deficient conditions hinder grain boundary mobility and thereby modify the dominant recrystallization mechanism s but apparently have little influence on the intracrystalline slip systems as reflected in the cpos strong c axis y maxima in mm mylonites both k feldspar and plagioclase an33 38 dynamically recrystallize consistent with the inferred metamorphic conditions under water deficient conditions mid to lower crustal rocks can deform heterogeneously under transitional ductile brittle conditions at high differential stress for mm ca 300 500 mpa as estimated for dry mohr coulomb failure and preserve this high stress microstructure because of the low mobility of dry grain boundaries

lichen monitoring as a potential tool in environmental forensics case study of the cu smelter and former mining town of karabash russia the aim of this paper is to showcase the use of lichens in environmental forensics from an assessment of atmospheric deposition in and around the cu smelter and former mining town of karabash ural mountains of russia hypogymnia physodes was collected on its bark substrate in july 2001 from a reference site c 25 km sw of karabash and transplanted to 10 stations along an approximately 60 km ssw nne transect centred on karabash transplants were collected after 2 and 3 month exposure periods the elemental compositions of hypogymnia and potential sources of particulates in the study area smelter blast furnace and converter dusts wastes tailings road dusts metallurgical slags and top soils were determined by inductively coupled plasma optical emission spectrometry icp oes and quadrupole icp mass spectrometry icp ms and the pb isotope compositions of the lichens and smelter dusts by multicollector icp ms particulates on lichen surfaces were analysed by scanning electron microscopy with energy dispersive x ray analysis sem edx the method of lichen transplantation combined with multi element and surface particle elemental analysis high precision pb isotope ratio determinations and modelling was shown to be useful for the tracing of the smelter signal and components from different smelter processes for more than 25 km from karabash town the lichen monitoring methodology is discrete and comparatively low cost enabling atmospheric deposition from natural and anthropogenic sources to be determined over short 3 month periods and is therefore a valuable qualitative tool for environmental forensics key aspects of the nature and biology

local shear zone pattern and bulk deformation in the gran paradiso metagranite nw italian alps the gran paradiso nappe of the northwestern alps mostly consists of augen gneisses derived from the alpine deformation of permian granitoids the regional foliation of the augen gneisses developed at lower amphibolite facies conditions and is associated with a top to west sense of shear the granitoid protolith is preserved in the kilometre scale low strain domain of the piantonetto valley and mainly consists of a porphyritic metagranite including joints leucocratic dykes and biotite rich schlieren in this low strain domain the alpine deformation is mainly localized in discrete ductile shear zones within weakly foliated metagranite the shear zones mostly dip towards s se in a shallow shear zones1 to steep inclination shear zones2 the shear zones show typical features that can be explained by reactivation of pre existing joints and planar compositional heterogeneities palaeostress and strain analysis indicate that shear zones and the metagranite foliation both formed in the presence of a strong component of flattening the kinematics of individual shear zones depends on the orientation of the original heterogeneities acting as nucleation planes and by partitioning of strain components at the kilometre scale with concentration of the flattening component to the piantonetto low strain domain the strain geometry and the kinematics of individual shear zones within piantonetto are not directly connected to the top to west sense of tectonic transport observed elsewhere in the gran paradiso nappe however the bulk stress ellipsoid reconstructed for the incipient shear zone network within very weakly deformed granites is oriented consistently with the bulk direction of tectonic transport within the gran paradiso massif we conclude that the shear zone network of the piantonetto valley is representative of the incipient stages of ductile deformation of a granite nappe even if its architecture is determined by the arrangement of pre existing structural and compositional heterogeneities aspects of the large scale bulk strain can be derived from this local shear zone pattern

automated forensic soil mineral analysis testing the potential of lithotyping in the investigation of serious crimes soil can be in some cases a very valuable class of trace evidence the complexity of soil is part of the reason why it is useful as trace evidence but is also an inherent problem as there are many different parameters in a soil sample that could potentially be characterized the inorganic components of soils are dominated by minerals along with anthropogenic particulate grains thus the analysis of soil mineralogy as the main technique for inorganic forensic soil characterization is recommended typical methods that allow the bulk mineralogy to be determined such as x ray diffraction xrd do not allow the texture of the particles to be characterized however automated scanning electron microscopy sem provides both modal mineralogy and also allows particle textures to be characterized a recent advance in this technique has been the ability to report the modal mineralogy of a sample as lithotypes which are defined on the basis of a combination of mineralogy and other parameters such as grain size and mineral associations defined lithotype groups may include monominerallic grains but also importantly allow the automated quantification of rock types and other anthropogenic materials based on a simulated forensic scenario the use of lithotyping is evaluated as an aid in the analysis of soil samples this technique provides additional discrimination when comparing different soil samples

the role of dynamic recrystallization in the development of lattice preferred orientations in experimentally deformed quartz aggregates abstract experiments on coaxially deformed quartz aggregates show that when dynamic recrystallization involves grain size reduction the lattice preferred orientation lpo of the recrystallized grains depends on the recrystallization mechanism at low temperatures and fast strain rates strain induced grain boundary migration recrystallization favors growth of grains oriented poorly for slip on the basal and prism planes resulting in an lpo of c axes parallel to the 1 direction at higher temperatures or slower strain rates progressive subgrain rotation produces recrystallized grains which inherit the small circle girdle lpo of their deformed host grains and which continue to re orient by slip at even higher temperatures and slower strain rates progressive subgrain rotation is accompanied by rapid grain boundary migration which does not favor grains of any particular orientation thus the lpo is again similar to that of non recrystallized grains in contrast when dynamic recrystallization involves grain growth driven by surface energy reduction a strong lpo of c axes parallel to 1 develops during grain growth but then evolves with increasing strain toward a small circle girdle the correlation of lpos with recrystallization mechanisms has important implications for the assumption of homogeneous strain in theoretical models of lpos and for interpreting natural lpos in recrystallized rocks

simulating coseismic deformation of quartz in the middle crust and fabric evolution during postseismic stress relaxation an experimental study abstract non steady state deformation and annealing experiments on vein quartz are designed to simulate earthquake driven episodic deformation in the middle crust three types of experiments were carried out using a modified griggs type solid medium deformation apparatus all three start with high stress deformation at a temperature of 400 c and a constant strain rate of 10 4 s 1 type a some are followed by annealing in the stability field of quartz for 14 15 h at zero nominal differential stress and temperatures of 800 1000 c type a b or by annealing for 15 h at 900 c and at a residual stress type a c the quartz samples reveal a very high strength 2 gpa at a few percent of permanent strain the microstructures after short term high stress deformation type a record localized brittle and plastic deformation statisc annealing type a b results in recrystallisation restricted to the highly damaged zones the new grains aligned in strings and without crystallographic preferred orientation indicate nucleation and growth annealing at non hydrostatic conditions type a c results in shear zones that also develop from deformation bands or cracks that formed during the preceding high stress deformation in this case however the recrystallised zone is several grain diameters wide the grains are elongate and a marked crystallographic preferred orientation indicates flow by dislocation creep with dynamic recrystallisation quartz microstructures identical to those produced in type a b experiments are observed in cores recovered from long valley exploratory well in the quaternary long valley caldera california with considerable seismic activity the experiments demonstrate the behaviour of quartz at coseismic loading type a and subsequent static annealing type a b or creep at decaying stress type a c in the middle crust the experimentally produced microfabrics allow to identify similar processes and conditions in exhumed rocks

crystallographic orientation of microcracks in quartz and inferred deformation processes a study on gneisses from the german continental deep drilling project ktb abstract this study was carried out on four gneiss samples from the german continental deep drilling project ktb taken at depths between 556 and 8633 m the crystallographic orientation of microcracks in quartz was determined by a combination of the electron channelling pattern method ecp and u stage microscopy the distinct preferred crystallographic orientations of various crack generations point to different processes of crack initiation and propagation which partly seem to be depth dependent for older healed cracks a crystalplastic initiation due to dislocation pile up and related lattice distortion is indicated by cracking normal to prominent slip directions which are a at lower or c at comparatively higher temperatures in contrast younger open cracks preferentially formed on crystallographic planes with low surface energy rhombs and prisms which is interpreted in terms of pure elastic crack mechanisms because of the thermoelastic anisotropy of quartz internal stresses resulting from thermal contraction during cooling may be the main driving force for the initiation or further propagation of cracks parallel to the c axis crack propagation preferentially affects grains with crystal lattices and operating crack mechanisms being in a direction appropriate to the applied external tectonic stresses this selective cracking explains why cracks also show constant orientations with respect to geographic directions up to regional dimensions

crystallographic control and texture inheritance during mylonitization of coarse grained quartz veins abstract quartz veins within rieserferner pluton underwent deformation during post magmatic cooling at temperature around 450 c different crystallographic orientations of cm sized quartz vein crystals conditioned the evolution of microstructures and crystallographic preferred orientations cpo during vein parallel simple shear up to high shear strains 10 for glide in ribbons with c axis sub parallel to the shear zone vorticity y axis ribbons with c axis orthogonal to y xz type ribbons were stronger and hardened more quickly they show lower aspect ratios and fine grain size 10 20 m recrystallization along sets of microshear zones szs exploiting crystallographic planes distortion of xz type ribbons and recrystallization preferentially exploited the slip systems with misorientation axis close to y new grains of szs initiated by subgrain rotation recrystallization sgr and thereupon achieved high angle misorientations by a concurrent process of heterogeneous rigid grain rotation around y associated with the confined shear within the sz dauphine twinning occurred pervasively but did not play a dominant role on sz nucleation recrystallization became widespread at 2 and pervasive at 10 ultramylonitic quartz veins are fine grained 10 m similar to new grains of sz and show a cpo banding resulting in a bulk c axis cpo with a y maximum as part of a single girdle about orthogonal to the foliation and orientations at the pole figure periphery at moderate to high angle to the foliation this bulk cpo derives from steady state sgr associated with preferential activity in the different cpo bands of slip systems generating subgrain boundaries with misorientation axes close to y the cpo of individual recrystallized bands is largely inherited from the original crystallographic orientation of the ribbons and therefore vein crystals from which they derived high strain and pervasive recrystallization were not enough to reset the initial crystallographic heterogeneity and this cpo memory is explained by the dominance of sgr this contrast with experimental observation of a rapid erasure of a pristine cpo by cannibalism from grains with the most favourably oriented slip system under dominant grain boundary migration recrystallization

ground penetrating radar use in three contrasting soil textures in southern ontario 26 27 ground penetrating radar gpr is a non invasive geophysical tool which can be used 28 for the identification of clandestine graves gpr operates by detecting density differences in soil 29 by the transmission of high frequency electromagnetic em waves from an antenna domestic 30 pig sus domesticus carcasses were clothed in 100 cotton t shirts and 50 cotton 50 31 polyester briefs and buried at a consistent depth at three field sites of contrasting soil texture 32 silty clay loam fine sand and fine sandy loam in southern ontario gpr was used to detect and 33 monitor the graves for a period of 14 months post burial analysis of collected data revealed that 34 gpr had applicability in the identification of clandestine graves in silty clay loam and fine sandy 35 loam soils but was not suitable for detection in the fine sandy soil studied the results of this 36 research have applicability within forensic investigations involving decomposing remains by 37 aiding in the location of clandestine graves in loam soils in southern ontario through the use of 38 gpr 39 40

texture development of recrystallised quartz polycrystals unravelled by orientation and misorientation characteristics abstract the development of microstructures and textures i e crystallographic preferred orientations during recrystallisation of naturally deformed quartz polycrystals has been studied via electron diffraction techniques in the scanning electron microscope in the investigated sample series of quartz rich rocks originating from different deformation regimes the microstructural and textural changes in quartz have been significantly influenced by dynamic recrystallisation based on microstructural observations paired with orientation and misorientation analyses down to the scale of grains and subgrains criteria could be established which characterise the dominant recrystallisation process and its influence on texture development it is shown that the texture development during dynamic recrystallisation is controlled by a differential activation of slip systems in grains of soft and hard orientations the analyses provide further evidence that specific grain orientations are preferred during crystal plastic deformation recrystallisation and grain growth the influence of twinning after the dauphine law was also investigated observations of a progressive reduction in the population of dauphine twin boundaries during recrystallisation and a penetrative deformation in both hosts and twins indicate a generation prior to deformation and recrystallisation a mechanical origin for twinning and possible influence on texture development was therefore discarded

the recrystallized grain size piezometer for quartz d 1 0 3 56 0 27 s 1 26 0 13 with no change in slope at the regime 2 3 transition and no effect of temperature or a b stability field another experimental piezometer relation for regime 1 of hirth and tullis 1992 differs in slope suggesting that different recrystallization mechanisms require different piezometer calibrations index terms 3902 mineral physics creep and deformation 5120 physical properties of rocks plasticity diffusion and creep 8030 structural geology microstructures 8159 tectonophysics rheology crust and lithosphere 8164 tectonophysics stresses crust and lithosphere citation stipp m and j tullis the recrystallized grain size piezometer for quartz geophys res lett 30 21 2088 doi 10 1029 2003gl018444 2003

the control of precursor brittle fracture and fluid rock interaction on the development of single and paired ductile shear zones abstract ductile shear zones can occur as relatively isolated single structures as arrays or as characteristic paired zones in continuous glaciated exposures of metagranodiorites from the tauern window eastern alps the control of initial dilatant brittle fracture and associated fluid rock interaction on the geometry of subsequent ductile shear zones can be unequivocally established shearing occurred under amphibolite facies conditions fractures in weakly deformed metagranodiorites are often less than 1 mm thick but extend for tens of metres many are healed joints without shear offset others show minor mm cm discrete dextral offset such brittle faults commonly display a low angle en echelon arrangement with displacement transferred between discrete fracture segments by ductile compressive bridges the geometry of more strongly reactivated zones depends on the degree and heterogeneity of fluid rock interaction which is related to fluid infiltration and veining along the primary fractures with little fluid rock interaction reactivation produces single heterogeneous ductile shear zones centred on and immediately flanking the pre existing fracture with increased fluid rock interaction a bleached halo is developed symmetrically to either side of a central epidote quartz garnet calcite vein ductile shear zones commonly flank this bleached zone to develop a characteristic paired pattern strain is partitioned localizing in the central fracture vein and the flanking shear zones paired zones may anastomose in accordance with changes in the width of the central bleached zone but are always symmetrically spaced with regard to the central fracture vein with increasing deformation the ductile shear zones broaden into the adjacent metagranodiorite but not into the bleached zone which remains preserved as a low strain region paired shear zones can also develop to either side of aplite dykes examples of characteristic paired shear zones usually with a clear central vein are found in many areas ranging from greenschist to eclogite facies suggesting that the mechanism of their formation is quite general

environmental and criminal geoforensics an introduction many subdisciplines within the earth sciences make use of either geophysical instruments to investigate the subsurface environment or use analytical methods to determine the origin or provenance of geological materials these same instruments and analytical methods can be used either directly or adapted to suit the acquisition of data that pertain to a wide range of forensic science investigations such approaches as discussed below are generally not new but in recent years there has been a significant resurgence globally in the application of geological and geophysical methods to aid forensic investigations traditionally such methods were used in forensic investigations related to serious criminal cases such as terrorism murder abduction and serious sexual assaults and to a lesser extent in the investigation of cases of fraud and theft but with increasing concern into the environmental impact of human activity with the release of contaminants into the atmosphere hydrosphere and lithosphere and their potential uptake into the biosphere there has been an increased amount of environmental legislation in turn there has commonly been an increase in the costs associated with the legal discharge or disposal of wastes consequently it is unsurprising that the illegal discharge and disposal of wastes has also increased identifying the distribution impact and source of such waste materials can in part be addressed through the application of geological techniques in much the same way as used traditionally for example in the investigation of murder cases the diversification of the use of geological techniques into the investigation of environmental crime will potentially significantly increase the range of investigations in which geologists may be asked to assist but will also lead to a new array of research questions to be addressed hence the need for this special publication in this short introduction the aim is to place the current work into its broad historical context and summarize the key findings from the papers presented within this volume the papers within this special publication were presented at two separate conferences in 2010 the third international soil forensics conference held at long beach california usa and organized by the sfi group and a conference on environmental and criminal forensics organized by the forensic geoscience group of the geological society of london and held at burlington house london in december 2010

why allanite may swindle about its true age allanite from the tertiary rieserferner pluton austrian alps is texturally and chemically heterogeneous continuous covariation trends reflect coupled substitution of ca al vs fe ree th in allanite whereas systematic variations in la nd demonstrate the increasingly stronger depletion of lree in the melt during its crystallization allanite samples corrected for 206pbexcess from two rocks scatter in the concordia diagram and define discordias from 31 8 0 4 ma and 32 2 0 4 ma to ca 540 ma the apparent inheritance does not originate from the inclusion of older allanite or a high phase such as monazite xenotime or zircon but from the incorporation of radiogenic pb originating from a precursor since allanite requires a high enrichment of th u and lree it may form at the expense of a th lree rich precursor in metamorphic rocks or where such a phase had dissolved in melts likely precursors acquire with time radiogenic pb isotopic compositions this pb if incorporated in the product mineral may give the illusion of inheritance the allanite samples from the rieserferner pluton show a tendency from high th ucalc 30 50 in samples with an alpine age to low th ucalc 4 12 in samples with distinct inheritance this relation between extent of inheritance and apparent th ucalc indicates a lower th ucalc for a possible precursor falling into the th u range commonly encountered for monazite precursor monazite would have originated from assimilated palaeozoic rocks and give rise to localized enrichments of th and lree in the melt thus eventually enabling the growth of allanite

shear zones and magma ascent a model based on a review of the tertiary magmatism in the alps 1 the alpine oligocene plutons are spatially and temporally associated with the activity of the periadriatic fault system pfs an orogen parallel crustal scale transpressive mylonitic belt excellent three dimensional exposure combined with a wealth of structural seismic petrological geochronological geochemical and paleomagnetic data collected over the last decades help to constrain the relationships between deformation ascent and emplacement of the plutons magmas were channeled from the base of the thickened continental crust into the narrow mylonitic belt of the periadriatic fault system which was used as ascent pathway to cover vertical lengths of 20 to 40 km therefore the linear alignment of the plutons at the surface is not the expression of a linear source region at depth ascent of the melts is controlled by the mylonitic foliation of the pfs which forms the only steep anisotropy continuously traversing the entire alpine crust in contrast the flow direction is not influenced by the specific kinematics of the faults final emplacement of the plutons occurred by extrusion from the periadriatic fault system into the adjacent country rocks the transition from ascent to final emplacement is favored by partitioning of transpressive deformation

dislocation creep regimes in quartz aggregates abstract using optical and tem microscopy we have determined that three regimes of dislocation creep occur in experimentally deformed quartz aggregates depending on the relative rates of grain boundary migration dislocation climb and dislocation production within each regime a distinctive microstructure is produced due primarily to the operation of different mechanisms of dynamic recrystallization at lower temperatures and faster strain rates the rate of dislocation production is too great for diffusion controlled dislocation climb to be an effective recovery mechanism in this regime recovery is accommodated by strain induced grain boundary migration recrystallization with an increase in temperature or decrease in strain rate the rate of dislocation climb becomes sufficiently rapid to accommodate recovery in this regime dynamic recrystallization occurs by progressive subgrain rotation with a further increase in temperature or decrease in strain rate dislocation climb remains sufficiently rapid to accommodate recovery however in this regime grain boundary migration is rapid thus recrystallization occurs by both grain boundary migration and progressive subgrain rotation the identification of the three regimes of dislocation creep may have important implications for the determination of flow law parameters and the calibration of recrystallized grain size piezometers in addition the identification of a particular dislocation creep regime could be useful in helping to constrain the conditions at which a given natural deformation has occurred

low temperature intracrystalline deformation microstructures in quartz a review of numerous genetic interpretations of the individual low temperature intracrystalline deformation microstructures in quartz shows that there is no consensus concerning their formation mechanisms therefore we introduce a new purely descriptive terminology for the three categories of intracrystalline deformation microstructures formed in the low quartz stability field fine extinction bands feb wide extinction bands web and localised extinction bands leb the localised extinction bands are further subdivided into blocky bleb straight sleb and granular gleb morphological types a detailed polarised light microscopy study of vein quartz from the low grade metamorphic high ardenne slate belt belgium further reveals a series of particular geometric relationships between these newly defined intracrystalline deformation microstructures these geometric relationships are largely unrecognised or underemphasised in the literature and need to be taken into account in any future genetic interpretation based on our observations and a critical assessment of the current genetic models we argue that the interpretation of the pertinent microstructures in terms of ambient conditions and deformation history should be made with care as long as the genesis of these microstructures is not better confined