nanoscale deformation twinning in xenotime a new shocked mineral from the santa fe impact structure new mexico usa shock microstructures in refractory accessory minerals such as zircon and monazite provide crucial evidence for deciphering impact related deformation in a wide variety of planetary materials here we describe the first occurrence of shock deformation in xenotime ypo 4 from a shocked quartz bearing shatter cone in granite at the santa fe impact structure new mexico usa backscattered electron imaging shows that shocked xenotime grains near the surface of a shatter cone contain multiple orientations of closely spaced planar fractures high resolution electron backscatter diffraction mapping reveals that some of the planar microstructures in 112 contain deformation twin lamellae that range from 50 nm to 200 nm in width on the polished surface and occur in up to three crystallographic orientations other features attributed to impact such as planar low angle boundaries and planar deformation bands record crystal plastic deformation shatter cone formation and co existing shocked quartz constrain minimum shock pressure experienced by the xenotime grains to 5 10 gpa an upper limit of 20 gpa is tentatively assigned based on the absence of ypo 4 polymorphs and shock twins in co existing zircon we propose that 112 deformation twins in xenotime constitute a diagnostic record of shock metamorphism similar to 112 twins in zircon they have not previously been reported in nature and occur in a rock with conspicuous evidence of shock deformation documentation of deformation twins in xenotime a widely applied u pb geochronometer can be used to identify hypervelocity deformation in shocked rocks detrital grains and other materials and may be particularly ideal for recording low pressure 20 gpa impact conditions that do not produce diagnostic shock microstructures in zircon

isotope systematics and shock wave metamorphism i u pb in zircon titanite and monazite shocked experimentally up to 59 gpa this study reports the first u pb isotope analyses on experimentally shocked zircon titanite and monazite extracted from proterozoic granitoid rocks in all three types of minerals shock waves produce drastic changes in the crystal lattices causing strong lowering of birefringence turbidization and decolorization of the individual grains moreover x ray patterns indicate transition of the crystals into polycrystalline aggregates of 10 5 mm block size precisely dated grains with concordant or nearly concordant ages were embedded in kbr and shocked at 35 47 5 and 59 gpa u pb isotope analyses on these grains show that shock metamorphism does not fractionate pb isotopes within the analytical precision of 0 1 as far as chemical fractionation is concerned there is no difference in degree of concordancy between shocked and unshocked monazite and small degrees 2 of relative upb fractionation in shocked zircon and titanite are due to time integrated pb loss and not to the shock experiment in consequence the data document that shock wave metamorphism alone does not measurably effect the u pb chronometer questioning the view that lower intercept ages of discordant u pb data reflect shock induced re equilibration of the chronometer in moderately to highly shocked rapidly cooling rocks

retention of u and pb in zircons from shocked granite in the siljan impact structure sweden the siljan ring structure central sweden was formed by a devonian impact the u pb zircon isotopic system of the shocked proterozoic granite basement appears to be undisturbed although the zircons were mechanically disrupted by the impact

timing of crystallization of the lunar magma ocean constrained by the oldest zircon the primitive moon was covered with a thick layer of melt known as the lunar magma ocean whose crystallization resulted in the moon s surface as it is observed today dating of the oldest zircon so far in lunar rocks indicates that much of the magma was probably crystallized within 100 million years of the moon s formation

new zircon shock phenomena and their use for dating and reconstruction of large impact structures revealed by electron nanobeam ebsd cl eds and isotopic u pb and u th he analysis of the vredefort domethis article is one of a series of papers published in this special issue on the theme of geochronology in honour of tom krogh integrated electron nanobeam ebsd cl eds and isotopic measurements u pb u th he of zircon from the collar and centre of the 80 km wide central uplift of the 2020 3 ma vredefort impact structure reveal new shock features in a microstructural progression related to impact basin formation and degree of u pb age resetting 1 planar fractures in 1k0 and 1k2 orientation during initial shock wave compression 2 curviplanar fractures in 1k1 orientation now annealed which host glassy inclusions of partial melt of the host rock 3 microtwin lamellae in an orientation of 65 about 110 attributed to shock wave rarefaction 4 nucleation of impact age crystallites possibly on microtwins during post shock heating by impact melt and 5 crystal plastic deformation linked to crater modification of the core of the central uplift planar fracturing and microtwinning 20 gpa in cold shock zircon in granitoid at a radial distance of 25 km failed to reset zircon age single grain id tims data

discovery of high pressure zrsio4 polymorph in naturally occurring shock metamorphosed zircons shock metamorphosed zircons were recovered from an upper eocene impact ejecta layer probably from the chesapeake bay impact structure found at three deep sea drilling project ocean drilling program sites 612 903 and 904 on the upper continental slope off new jersey the shocked zircons exhibit granular textures and some have planar features x ray diffraction patterns show that some of the shocked zircons contain a high pressure zrsio4 polymorph with a scheelite type structure that was first produced in laboratory experiments in 1969 the presence of the high pressure zrsio4 polymorph in some of the zircons indicates that they have been shock metamorphosed at pressures between 20 and 90 gpa the discovery of this phase in naturally occurring shocked zircons confirms previous predictions that this phase would be found in shock metamorphosed rocks from impact structures and it provides a new tool for calibrating peak shock pressures in impact structures and ejecta in addition because the high pressure zrsio4 polymorph has now been found in naturally occurring samples it can be given a mineral name

impact shocked zircons discovery of shock induced textures reflecting increasing degrees of shock metamorphism abstract textural effects specifically characteristic of shock metamorphism in zircons from impact environments have not been reported previously however planar deformation features pdf due to shock metamorphism are well documented in quartz and other mineral grains from these same environments an etching technique was developed that allows sem visualization of pdf and other probable shock induced textural features such as granular polycrystalline texture in zircons from a variety of impact shock environments these textural features in shocked zircons from k t boundary distal ejecta form a series related to increasing degrees of shock that should correlate with proportionate resetting of the u pb isotopic system

shift in the paradigm for gssp boundary definition abstract for over 200 years the use of biotic events as the basis for the establishment of chronostratigraphic boundaries has been the only approach successfully utilized for international and national chronostratigraphy the traditional biostratigraphic method provides relatively high resolution averaging 1 ma or sometimes less this biochronological evolutionary approach to the global boundary stratotype section and point gssp utilizes biotic primary markers pm with a few exceptions encompasses the integrated pm and other non pm markers as the general principles for defining gssp boundaries and is a reasonably reliable mechanism for global correlation and a relatively stable international geologic time scale igts the biotic pm s however possessed several serious restrictions the nature of biological taxonomy climatic sedimentary environmental and directly applicable within the tropics subtropics only biotic evolution and radiogenic isotopes are the only systems in geologic time that encompass the direction of time the latter possessed less restrictions than the former the recent tendency to define gssp s utilizing magnetic chrons climatic events and geochemistry may work in the cenozoic but is useless in the mesozoic and older sediments because their cyclic nature repeatedness and the need for a second directional in time index biostratigraphic or radioisotopic to place the pm in the right position within the scale i propose here to utilize volcanic ash beds as the best primary marker in geologic chronostratigraphy the u pb system is one of the most dependable of the geochronologic systems because it relies on a simple and non interpretive radioisotopic decay constant the ash bed gssp as a lithological horizon is universal for the gssp definition and can be correlated as an age in any facies marine lagoon and continental regardless of paleoclimatic zones paleoceanographic geochemical and most other geological factors even moderate level metamorphism 900 does not affect the u pb dating of zircons the gssp at the base of a volcanic ash bed primary marker could be established in a short working time and these ash beds can be integrated with the existing as well as new biostratigraphic geochemical magnetostratigraphic and astronomical data secondary markers to create a robust accurate and highly useable time scale several potential gssp s that could be established with the volcanic ash beds close to the traditional and or historical boundaries serve as examples for this approach and include devonian carboniferous moscovian kasimovian kasimovian gzhelian and sakmarian artinskian boundaries

pb pb ages of feldspathic clasts in two apollo 14 breccia samples pb pb isochron ages of ca 3 92 ga for three k feldspar rich clasts from apollo 14 breccias 14303 and 14083 were determinedusing secondary ion mass spectrometry sims these ages are interpreted t

a reevaluation of the evidence for a younger dryas climatic reversal in the tropical andes abstract a review of the evidence for a younger dryas equivalent climatic reversal in the tropical andes shows that a number of hypotheses need to be reassessed assumptions of the el abra cold and humid phase in colombia are compromised by insufficient dating control periods of glacier advance in peru and bolivia lack sufficient dating control to be correlated with the european younger dryas only glaciers on the quelccaya ice cap in peru may have advanced shortly before the onset of the european climatic reversal but even there a correlation is questionable a late glacial advance in the chimborazo area in ecuador is considerably older than previously suggested the same glacier advance has been dated to earlier than 12 000 bp in other areas of ecuador the emerging picture suggests two phases of glacier advances in the tropical andes 13 000 12 000 bp and 9000 10 000 bp both may have been caused by increasing precipitation unequivocal evidence for a cold younger dryas event in the tropical andes has yet to emerge

comparison of structures in zircons from lunar and terrestrial impactites there have been a number of reports of the presence of shock features such as planar fracturing and granulation the transformation of zircon to reidite and the breakdown of zircon to baddeleyite

variable microstructural response of baddeleyite to shock metamorphism in young basaltic shergottite nwa 5298 and improved u pb dating of solar system events abstract the accurate dating of igneous and impact events is vital for the understanding of solar system evolution but has been hampered by limited knowledge of how shock metamorphism affects mineral and whole rock isotopic systems used for geochronology baddeleyite monoclinic zro2 is a refractory mineral chronometer of great potential to date these processes due to its widespread occurrence in achondrites and robust u pb isotopic systematics but there is little understanding of shock effects on this phase here we present new nano structural measurements of baddeleyite grains in a thin section of the highly shocked basaltic shergottite northwest africa nwa 5298 using high resolution electron backscattered diffraction ebsd and scanning transmission electron microscopy stem techniques to investigate shock effects and their linkage with u pb isotopic disturbance that has previously been documented by in situ u pb isotopic analyses the shock altered state of originally igneous baddeleyite grains is highly variable across the thin section and often within single grains analyzed grains range from those that preserve primary magmatic twinning and trace element zonation baddeleyite shock group 1 to quasi amorphous zro2 group 2 and to recrystallized micro granular domains of baddeleyite group 3 these groups correlate closely with measured u pb isotope compositions primary igneous features in group 1 baddeleyites n 5 are retained in high shock impedance grain environments and an average of these grains yields a revised late amazonian magmatic crystallization age of 175 30 ma for this shergottite the youngest u pb dates occur from group 3 recrystallized nano to micro granular baddeleyite grains indicating that it is post shock heating and new mineral growth that drives much of the isotopic disturbance rather than just shock deformation and phase transitions our data demonstrate that a systematic multi stage microstructural evolution in baddeleyite results from a single cycle of shock loading heating and cooling during transit to space and that this leads to variable disturbance of the u pb isotope system furthermore by linking in situ u pb isotopic measurements with detailed micro to nano structural analyses it is possible to resolve the timing of both endogenic crustal processes and impact events in highly shocked planetary materials using baddeleyite this opens up new opportunities to refine the timing of major events across the solar system

inclusion localised crystal plasticity dynamic porosity and fast diffusion pathway generation in zircon abstract a population of oscillatory zoned igneous zircon grains in a javanese andesite contains fluid and mineral inclusions up to 10 m across trapped during zircon growth orientation contrast imaging and orientation mapping by electron backscatter diffraction reveal that crystal plastic deformation overprints growth zoning and has localized around 1 10 m pores and inclusions cumulative crystallographic misorientation of up to 25 around pores and inclusions in zircon is predominantly accommodated by low angle 010 slip a distinctly different population of sub micron pores is present along subgrain boundaries and their triple junctions these are interpreted to have formed as a geometric consequence of dislocation interaction during crystal plasticity dislocation creep microstructures are spatially related to differences in cathodoluminescence spectra that indicate variations in the abundance of cl active rare earth elements the extent of the modification suggests deformation related fast pathway diffusion distances that are over five orders of magnitude greater than expected for volume diffusion this enhanced diffusion is interpreted to represent a combination of fast diffusion pathways associated with creep cavitation dislocations and along low angle boundaries these new data indicate that ductile deformation localised around inclusions can provide fast pathways for geochemical exchange these pathways may provide links to the zircon grain boundary thus negating the widely held assumption that inclusions in fracture free zircon are geochemically armoured once they are physically enclosed

zircon u pb strain chronometry reveals deep impact triggered flow abstract large 100 km meteorite impact cratering events play important roles in surface and biosphere evolution however their potential for widespread ductile modification of the lithosphere has been difficult to assess due partly to our inability to isotopically age correlate deep mineral fabrics with surface records we have integrated benchmark u pb zircon dating methods id tims shrimp with new microstructural techniques ebsd xrd to demonstrate that crystal plastic deformation can cause rapid out diffusion of radiogenic pb and accompanying trace element alteration in crystalline zircon we have used this phenomenon to directly date fabric in archean zircons and xenoliths of the lower crust of south africa at 2023 15 million years coeval with the 2020 3 million year old vredefort cratering event at surface with extent 20 000 km 2 our findings indicate that regional exogenic fabrics similar to high temperature tectonic fabrics exist in ancient crust moreover our results establish that crystal plastic deformation in the lithosphere can now be directly dated and linked to planetary evolution by zircon u pb strain chronometry

evolution of zircon deformation mechanisms in a shear zone lanzo massif western alps abstract magmatic zircons within two sheared gabbroic dykes from the peridotitic massif of lanzo western alps italy revealed evolution of deformation from crystal plasticity to rigid body rotation during shear zone evolution this is the first time that multiple zircon grains have been analysed in a kinematic context in a shear zone zircon grains recorded crystal plastic deformation activating the commonly inferred 001 and 100 glide systems to the newly identified 110 glide system the exact selection of glide system could be dependant of deformation conditions such as pressure temperature and strain rate moreover the activation of one or several glide systems within a single grain could be favoured by the primary orientation of the grains combined with a high strain rate in these sheared gabbros the deformation mechanisms evolve from plastic deformation at low strain rate conditions to increase strain strain softening and localisation of deformation the progressive shear zone development and the softening of the matrix relative to the zircon has lead to a switch from crystal plasticity to rigid body rotation of zircon the zircon grains rigid body rotation involved that their long axes became parallel to the lineation of the shear zone causing reorientation and dispersion of the misorientation axes away from kinematic y

shock behavior of zircon phase transition to scheelite structure and decomposition abstract both single crystal and powdered specimens of zircon zrsio4 were shocked to peak pressures between 30 and 94 gpa using the gun method and specimens recovered were studied by means of x ray diffraction analysis transmission electron microscopy and infrared spectroscopy transformation to the scheelite structure started above 30 gpa and was completed above 53 gpa in the case of single crystal specimens tetragonal unit cell parameters of the scheelite type zrsio4 at room condition are measured to bea 4 7341 1 a c 10 51 1 a c a 2 219 2 andv 235 5 2 a3 which is smaller than that of the zircon type by 9 9 the recovered scheelite type zrsio4 reverts to the zircon type after rapid heating to 1200 c at room pressure this transformation from the zircon type to the scheelite type is unique in that it is fast displacive like but does not reverse tetragonal zro2 was detected as decomposition product in the single crystal specimen shocked to 94 gpa and further confirmed in a powdered specimen shocked to 53 gpa where enhancement of temperature is expected because of high porosity decomposition behavior of zircon observed in natural shock events is discussed on the basis of present experimental results

shock experiments on pre heated α and β quartz i optical and density data abstract discs of single crystal quartz unheated and pre heated to 275 c and 540 c i e quartz and 630 c i e quartz were experimentally shocked to pressures ranging from 20 to 40 gpa with the shock front propagating parallel to either 10 1 0 or 0001 refractive indices density and the orientation of planar deformation features pdfs were determined on the recovered quartz samples refractive indices of pre heated quartz are unaffected up to 25 gpa but density starts to decrease slightly up to this pressure above 25 gpa pre heating causes drastic variations refractive indices and birefringence of quartz shocked at ambient temperature decrease continuously until complete isotropization is reached at 35 gpa in quartz shocked at 630 c refractivity drops discontinuously in the interval from 25 to 26 gpa and complete transformation to diaplectic glass is reached at 26 gpa density follows the trends demonstrated by the optical parameters with higher pre shock temperatures yielding lower density at a given shock pressure these results indicate that the threshold pressure for the onset of transformation to diaplectic quartz glass is largely temperature invariant lying at 25 gpa whereas the pressure limit for complete transformation decreases with increasing pre shock temperature from 35 to 26 gpa quartz shocked parallel to 0001 always has a higher density and refractivity than that shocked parallel to 10 1 0 indicating a significant influence of the structural anisotropy this is also evident from the distribution of pdf orientations pressures 25 gpa cause in quartz shocked parallel to 10 1 0 pdfs that are predominantly oriented parallel to 10 1 2 while quartz shocked to the same pressures but parallel to 0001 contains almost exclusively pdfs parallel to 10 1 3 pdf orientations in quartz shocked at ambient temperature parallel to 10 1 0 show the following characteristics i the frequency of 10 1 3 is high at 20 gpa declines with increasing pressure and finally is totally absent at 32 gpa ii 10 1 3 begins to occur at 25 gpa increases and finally is the only remaining orientation at 32 gpa and iii 10 1 2 and 11 2 2 are only present at 20 and 25 gpa in contrast quartz shocked at 630 c parallel to 10 1 0 displays a broad pdf distribution with indistinct maxima and 10 1 3 is totally absent the small structural difference between and quartz which is reflected in the pdf distribution should allow in principle evaluation of the pre shock temperature in naturally impacted metamorphic rocks the results substantiate that formation of shock effects in quartz is dependent on i shock pressure ii pre shock temperature and iii shock wave direction so far the latter two parameters have not been considered in the application of experimental results to impact sites

shock metamorphism of quartz in nature and experiment ii significance in geoscience the occurrence of shock metamorphosed quartz is the most common petrographic criterion for the identification of terrestrial impact structures and lithologies its utility is due to its almost ubiquitous occurrence in terrestrial rocks its overall stability and the fact that a variety of shock metamorphic effects occurring over a range of shock pressures have been well documented these shock effects have been generally duplicated in shock recovery experiments and thus serve as shock pressure barometers after reviewing the general character of shock effects in quartz the differences between experimental and natural shock events and their potential effects on the shock metamorphism of quartz are explored the short pulse lengths in experiments may account for the difficulty in synthesizing the high pressure polymorphs coesite and stishovite compared to natural occurrences in addition post shock thermal effects are possible in natural events which can affect shock altered physical properties such as refractive index and cause annealing of shock damage and recrystallization the orientations of planar microstructures however are unaffected by post impact thermal events except if quartz is recrystallized and provide the best natural shock barometer in terms of utility and occurrence the nature of planar microstructures particularly planar deformation features pdfs is discussed in some detail and a scheme of variations in orientations with shock pressure is provided the effect of post impact events on pdfs is generally limited to annealing of the original glass lamellae to produce decorated pdfs resulting from the exsolution of dissolved water during recrystallization basal 0001 pdfs differ from other pdf orientations in that they are multiple mechanical brazil twins which are difficult to detect if not partially annealed and decorated the occurrence and significance of shock metamorphosed quartz and its other phases namely coesite stishovite diaplectic glass and lechatelierite are discussed for terrestrial impact structures in both crystalline non porous and sedimentary porous targets the bulk of past studies have dealt with crystalline targets where variations in recorded shock pressure in quartz have been used to constrain aspects of the cratering process and to estimate crater dimensions at eroded structures in sedimentary targets the effect of pore space results in an inhomogeneous distribution in recorded shock pressure and temperature which requires a different classification scheme for the variation of recorded shock compared to that in crystalline targets this is discussed along with examples of variations in the relative abundances of planar microstructures and their orientations which are attributed to textural variations in sedimentary target rocks examples of the shock metamorphism of quartz in distal ejecta such as at the k t boundary and from nuclear explosions are illustrated and are equivalent to that of known impact structures except with respect to characteristics that are due to long term post shock thermal effects finally the differences between the deformation and phase transformation of quartz by shock and by endogenic tectonic and volcanic processes are discussed we confirm previous conclusions that they are completely dissimilar in character due to the vastly different physical conditions and time scales typical for shock events compared to tectonic and volcanic events well characterized and documented shock effects in quartz are unequivocal indicators of impact in the natural environment

isotope systematics and shock wave metamorphism ii u pb and rb sr in naturally shocked rocks the haughton impact structure canada minerals and whole rocks from crystalline fragments collected in the allochthonous polymict breccia of the 23 ma old haughton impact crater on devon island arctic canada were analysed for u pb k and rb sr in order to constrain degrees of shock wave induced perturbations in these systems the results show that shock wave metamorphism at 50 gpa with onset of total melting does not significantly affect the u pb chronometers in monazite and zircon monazite preserved its age of crystallization during high grade metamorphism at 1928 2 2 1 2 0 ma 2 errors as dated by the upper intercept of 2 9 discordant monazites the same analyses yield a lower intercept age of 277 5 35 1 35 0 ma in the concordia diagram demonstrating that discordancy is not a direct effect of shock wave metamorphism but a product of time integrated pb diffusion prior to the impact event which occurred 23 ma ago this constrains maximal shock induced pb loss to less than 3 including possible alteration related pb diffusion from the shock damaged grains in 1903 1 1 4 1 1 ma old monazite from an unshocked reference gneiss recent pb loss also reaches 3 corroborating the occurrence of weak alteration related upb fractionation the data substantiate that u pb discordancy patterns are not a reliable chronometer to date impact events small rock fragments and a coherent block of shock stage i to iii vi consist of heterogeneous unequilibrated rb sr sub systems on the 10 m scale with drastically varying isr shock related rbsr fractionation is very limited and in the large block stage iii three biotite fractions yield an rb sr isochron age of 1791 34 ma 2 which is undistinguishable from the 1814 8 ma age of biotite in the unshocked basement gneiss in contrast to this m3 sized fragment rb sr systematics in a fist size sample of shock stage iii do not yield any reliable age information due to small scale 1 cm3 isotopic disequilibrium it appears that such small scale disequilibrium is essentially due to a take up of radiogenic 87sr in feldspar glass from biotite during shock wave passage this prevents dating of the impact events by the rb sr internal isochron method and it can be concluded that total rock melting is the first condition necessary to reset the rb sr chronometer in shocked crystalline rocks

complex history of a zircon aggregate from lunar breccia 73235 abstract results are reported of an investigation of the age and origin of the exceptional zircon aggregate in an anorthositic clast from lunar breccia 73235 cathodoluminescence and birefringence images show that the aggregate consists of numerous angular fragments of sector zoned primary zircon in a matrix of secondary zircon with an overall texture that resembles a pseudotachylite sims u pb analyses of the primary fragments and the matrix yielded two clearly defined ages an age of 4 315 0 015 ga and initial th u ratio of 0 21 0 35 for the primary zircon and an age of 4 187 0 011 ga and th u of 0 04 0 17 for the secondary zircon matrix a raman spectroscopic study the secondary matrix zircon was undertaken to investigate its structure results showed that the matrix has a zircon structure but there is also evidence for the presence of an amorphous component implications of the structural and u pb age data are discussed in terms of the origin and evolution of the aggregate and the history of lunar events it is proposed that an original single millimetre sized sector zoned zircon formed at 4 31 ga was subjected to a severe shock event at 4 18 ga this event resulted in the fracturing of the zircon the displacement and rotation of fragments the compression of the aggregate to a lensoid shape and the shock reduction of zircon to sub micron sized and amorphous granules in crush zones in the mosaic of fractures volatilisation loss of pb and the addition of u to the secondary zircon is attributed to processes activated by the extreme thermal pulse which accompanied the 4 18 ga shock event shock effects are seen in some of the primary fragments but raman spectra of the primary and secondary zircon show no evidence for pressure induced transformation of zircon to a scheelite structure the zircon u pb system has not been affected by the ca 3 95 ga thermal pulse that accompanied formation of the host breccia although this event has largely reset the k ar systems

effects of crystallographic anisotropy on fracture development and acoustic emission in quartz 1 transgranular microcracking is fundamental for the initiation and propagation of all fractures in rocks the geometry of these microcracks is primarily controlled by the interaction of the imposed stress field with the mineral elastic properties however the effects of anisotropic elastic properties of minerals on brittle fracture are not well understood this study examines the effects of elastic anisotropy of quartz on the geometry of brittle fracture and related acoustic emissions ae developed during indentation experiments on single crystals at ambient pressure and temperature a hertzian cone crack developed during blunt indentation of a single crystal of flawless brazilian quartz parallel to the c axis shows geometric deviation away from predictions based on the isotropic case consistent with trigonal symmetry the visible cone crack penetration depth varies from 3 to 5 mm and apical angle from 53 to 40 electron backscatter diffraction ebsd mapping of the crack tip shows that fracturing initiates along a 40 m wide process zone comprising damage along overlapping en echelon high index crystallographic planes shown by discrete bands of reduced electron backscatter pattern ebsp quality band contrast coalescence of these surfaces results in a stepped fracture morphology monitoring of ae during indentation reveals that the elastic anisotropy of quartz has a significant effect on ae location and focal mechanisms ninety four ae events were recorded during indentation and show an increasing frequency with increasing load they correspond to the development of subsidiary concentric cracks peripheral to the main cone crack the strong and complex anisotropy in seismic velocity 28 vp 43 vs with trigonal symmetry resulted in inaccurate and high uncertainty in ae locations using geiger location routine with an isotropic velocity model this problem was overcome by using a relative master event location algorithm that only requires a priori knowledge of the velocity structure within the source volume the ae location results correlate reasonably well to the extent of the observed cone crack decomposition of ae source mechanisms of the geiger relocated events shows dominantly end member behavior between tensile and compressive vector dipole events with some double couple dominated events and no purely tensile or compressive events the same events located by the master event algorithm yield greater percentage of vector dipole components and no double couple events indicating that ae source mechanism solutions can depend on ae location accuracy and therefore relocation routine that is utilized calculations show that the crystallographic anisotropy of quartz causes apparent deviation of the moment tensors away from double couple and pure tensile compressive sources consistent with the observations preliminary modeling of calcite anisotropy shows a response distinct from quartz indicating that the effects of anisotropy on interpreting ae are complex and require detailed further study

formation of planar deformation features pdfs in zircon during coseismic faulting and an evaluation of potential effects on u pb systematics abstract zircons from pseudotachylyte and cataclasite veins in the svarthumlevatnet metagabbro sw norway are faulted brecciated and display multiple sets of planar deformation features pdfs that we assign to coseismic deformation in the middle crust during caledonian continent collision the zircons give a u pb upper intercept age of 1507 4 ma interpreted as a minimum age of the gabbro and a lower intercept age of 968 31 ma likely indicating the time of granulite facies metamorphism but they do not record the caledonian coseismic faulting even when the fault planes are healed by thin veins of low u zircon the work indicates that pdfs are not exclusive to meteorite impacts but may also develop during seismic faulting

deformation related microstructures in magmatic zircon and implications for diffusion an undeformed glomeroporphyritic andesite from the sunda arc of java indonesia contains zoned plagioclase and amphibole glomerocrysts in a fine grained groundmass and records a complex history of adcumulate formation and subsequent magmatic disaggregation a suite of xenocrystic zircon records proterozoic and archaean dates whilst a discrete population of zoned euhedral igneous zircon yields a shrimp u pb crystallisation age of 9 3 0 2 ma quantitative microstructural analysis of zircon by electron backscatter diffraction ebsd shows no deformation in the inherited xenocrysts but intragrain orientation variations of up to 30 in 80 of the young zircon population these variations are typically accommodated by both progressive crystallographic bending and discrete low angle boundaries that overprint compositional growth zoning dispersion of crystallographic orientations are dominantly by rotation about an axis parallel to the zircon c axis 001 which is coincident with the dominant orientation of misorientation axes of adjacent analysis points in ebsd maps less common misorientation axes account for minor components of crystallographic dispersion these observations are consistent with zircon deformation by dislocation creep and the formation of tilt and twist boundaries associated with the operation of 100 and 010 slip systems the restriction of deformation microstructures to large glomerocrysts and the young magmatic zircon population and the absence of deformation within the host igneous rock and inherited zircon grains indicate that zircon deformation took place within a low melt fraction 5 melt mid lower crustal cumulate prior to fragmentation during magmatic disaggregation and entrainment of xenocrystic zircons during magmatic decompression tectonic stresses within the compressional sunda arc at the time of magmatism are considered to be the probable driver for low strain deformation of the cumulate in the late stages of initial crystallisation these results provide the first evidence of crystal plastic dislocation creep in zircon associated with magmatic crystallisation and indicate that the development of crystal plastic microstructures in zircon is not restricted to high strain rocks such microstructures have previously been shown to enhance bulk diffusion of trace elements u th and ree in zircon the development of deformation microstructures and therefore multiple diffusion pathways in zircon in the magmatic environment has significant implications for the interpretation of geochemical data from igneous zircon and the trace element budgets of melts due to the potential enhancement of bulk diffusion and dissolution rates

a record of ancient cataclysm in modern sand shock microstructures in detrital minerals from the vaal river vredefort dome south africa the record of terrestrial meteorite impacts is fragmentary because most impact structures and ejecta are removed by erosion or buried discovery of the missing impact record from hadean to present may be advanced through identifi cation of residual shocked detritus to evaluate which shocked minerals survive erosion and sedimentary transport we investigated modern sands from the vaal river in south africa where it crosses the 2 02 ga vredefort dome the largest terrestrial impact structure known to date shocked minerals were identifi ed in all sediment samples including from the vaal channel and tributaries within the structure in transmitted light detrital quartz preserves discontinuous decorated planar features previously identifi ed as brazil twins which are readily visible as bright continuous features in cathodoluminescence images detrital zircons preserve fi ve orientations of planar fractures pfs which can produce dramatically offset growth zoning and apparent rotation of subgrains other zircons contain fi lled fractures that may represent a new shock microstructure detrital monazite preserves four orientations of pfs and many grains contain oscillatoryzoned shocked zircon inclusions which thus represent shocked inclusions within shocked accessory grains zircon and monazite with granular texture were also identifi ed this study is proof of the concept that shocked minerals can be identifi ed in sediments up to 2 billion years after an impact event and it demonstrates their potential for preserving evidence of ancient impacts the recognition of a new geological repository for impact evi dence provides a means for identifying distal shocked detritus from eroded structures of any age and may be particularly relevant to early earth studies

planar microstructures in zircon from paleo seismic zones pseudotachylytes resulted from frictional melts associated with ultramylonites in high grade metapelitic rocks from the ivrea verbano zone in the southern alps northern italy were studied with focus on the deformation microstructures in zircon the aims were to investigate the characteristics of zircon deformation in seismic zones and to recognize specific microstructures generated in zircon during earthquakes which could be useful for mineral dating of paleo seismic events helps to understand how seismic energy is released at depth and interacts with metamorphic processes the interior of polished zircon grains ranging from 30 to 150 m in length were investigated with optical microscope and scanning electron microscope sem techniques including secondary electron se backscattered electron bse forward scattered electron fse cathodoluminescence cl imaging and crystallographic orientation mapping by electron backscatter diffraction analysis ebsd grains were studied in situ and as separated fractions embedded in epoxy disks among different cataclastic and crystal plastic deformation microstructures in zircon we identified characteristic planar deformation bands pdbs planar fractures pfs and curviplanar fractures cfs planar deformation bands in zircon are crystallographically controlled planar lattice volumes with misorientation from the host grain which varies from 0 4 to 2 7 pdbs are usually parallel to 100 crystallographic planes have width from 0 3 to 1 m and average spacing of 5 m in 2d sections planar deformation bands appear as contrast lamellae in orientation contrast images and in ebsd maps and in rare cases can be observed with the optical microscope pdbs form in specifically oriented grains due to high differential stresses high temperatures and high strain rates generated in seismically active environment and or due to shearing in the vicinity of frictional melts discovered structures represent a result of crystal plastic deformation of zircon grains with operating dislocations having 010 glide system and misorientation axis therefore they can be classified as a new type 4 lattice distortion pattern according to the existing classification for zircon piazolo et al 2012 kovaleva et al 2014 we have demonstrated that formation of planar fractures in zircon takes place not only during impacts but also in seismically active zones we observe at least two cases of formation of pfs with 100 orientation 1 as a result of evolution of pdbs and 2 as micro cleavage this study demonstrates that planar microstructures in terrestrial zircon do not exclusively form during impact events but also as a result of seismic events at depth due to unusually high differential stress strain rate and temperature according to the new findings pdbs in zircon from the deep crust are supposed to represent newly recognized evidence of seismicity

complex magmatic and impact history prior to 4 1 ga recorded in zircon from apollo 17 south massif aphanitic breccia 73235 abstract sample 73235 is one of several aphanitic impact melt breccias collected by the apollo 17 mission at stations 2 and 3 on the slopes of the south massif this study presents a detailed investigation of internal structures and u pb ages of large zircon grains from this breccia sample new data combined with the results of previous studies of zircon grains from the same location indicate that most zircon clasts in breccias from stations 2 and 3 formed during multiple magmatic events between 4 37 and 4 31 ga although the oldest zircon crystallized at about 4 42 ga and the youngest at 4 21 ga in addition zircons from the aphanitic breccias record several impact events prior to the 3 9 ga late heavy bombardment the results indicate that the zircons probably crystallized at different locations within the procellarum kreeep terrane and were later excavated and modified by several impacts and delivered to the same locality within separate ejecta blankets this locality became a source of material that formed the aphanitic impact melt breccias of the south massif during a 3 9 ga impact however the zircons showing old impact features are not modified by this 3 9 ga impact event suggesting that i this common source area was located at the periphery of excavation cavity and ii the 3 9 ga ages recorded by the zircon grains could date large basin forming events as significant as major later 3 9 ga collisions such as imbrium and serenitatis

uranium lead ages for lunar zircons evidence for a prolonged period of granophyre formation from 4 32 to 3 88 ga the ages of a number of small fragments of lunar granophyre have been determined by the in situ u th pb isotopic analysis of zircon using a sensitive high mass resolution ion microprobe shrimp i the zircon from lunar granophyre is characterized by consistently high u and th contents most 200 500 ppm and 100 300 ppm respectively compared to zircon from mafic lunar rocks some fragments of lunar granophyre are found to be as old as 4 32 ga supporting other evidence that the original lunar magma ocean crystallized completely within 200 ma of the formation of the moon itself other fragments are as young as 3 88 ga which is much later than the time of formation of most of the lunar crust the older lunar granophyres have rare earth element ree patterns that are similar to lunar kreep whilst the younger granophyres have bow shaped ree patterns that feature a greater relative enrichment in the heavy ree the wide range of ages of numerous lunar zircons lunar granophyres and other rocks indicates that zircon forming magmatism in the lunar highlands was most active prior to 4 3 ga but continuous until at least 3 88 ga the u pb isotopic composition of much lunar zircon is near concordant but the effects of isotopic disturbance as late as 1 0 ga are observed in some zircon both within granophyre fragments recrystallized by reheating and within fragments in which the original delicate silica k feldspar granophyric intergrowth is well preserved it is therefore essential to make multiple analyses of individual zircon grains and preferably analyses of suites of zircons from lunar igneous rocks if they are to be dated reliably by the u pb method it is possible that some of the younger lunar granophyres are the product of large scale silicate liquid immiscibility within late stage differentiates but this remains unproven until remnants of demonstrably cogenetic fe rich immiscible liquid are positively identified

mechanisms of strain accommodation in plastically deformed zircon under simple shear deformation conditions during amphibolite facies metamorphism abstract this study documents the strain accommodation mechanisms in zircon under amphibolite facies metamorphic conditions in simple shear microstructural data from undeformed fractured and crystal plastically deformed zircon crystals are described in the context of the host shear zone and evaluated in the light of zircon elastic anisotropy our work challenges the existing model of zircon evolution and shows previously undescribed rheological characteristics for this important accessory mineral crystal plastically deformed zircon grains have axis oriented parallel to the foliation plane with the majority of deformed grains having axis parallel to the lineation zircon accommodates strain by a network of stepped low angle boundaries formed by switching between tilt dislocations with the slip systems 010 and 1 10 110 and rotation axis 001 twist dislocations with the rotation axis 001 and tilt dislocations with the slip system 001 and rotation axis 010 the slip system 1 10 110 is newly described for zircon most misorientation axes in plastically deformed zircon grains are parallel to the xy plane of the sample and have 001 crystallographic direction such behaviour of strained zircon lattice is caused by elastic anisotropy that has a direct geometric control on the rheology deformation mechanisms and dominant slip systems in zircon young s modulus and p wave velocity have highest values parallel to zircon 001 axis indicating that zircon is elastically strong along this direction poisson ratio and shear modulus demonstrate that zircon is also most resistant to shearing along 001 thus 001 axis is the most common rotation axis in zircon the described zircon behaviour is important to take into account during structural and geochronological investigations of poly metamorphic terrains geometry of dislocations in zircon may help reconstructing the geometry of the host shear zone s large scale stresses in the crust and possibly the timing of deformation if the isotopic systems of deformed zircon were reset

modeling damage and deformation in impact simulations numerical modeling is a powerful tool for investigating the formation of large impact craters but is one that must be validated with observational evidence quantitative analysis of damage and deformation in the target surrounding an impact event provides a promising means of validation for numerical models of terrestrial impact craters particularly in cases where the final pristine crater morphology is ambiguous or unknown in this paper we discuss the aspects of the behavior of brittle materials important for the accurate simulation of damage and deformation surrounding an impact event and the care required to interpret the results we demonstrate this with an example simulation of an impact into a terrestrial granite target that produces a 10 km diameter transient crater the results of the simulation are shown in terms of damage a scalar quantity that reflects the totality of fragmentation and plastic strain both total plastic strain the accumulated amount of permanent shear deformation regardless of the sense of shear and net plastic strain the amount of permanent shear deformation where the sense of shear is accounted for damage and plastic strain are both greatest close to the impact site and decline with radial distance however the reversal in flow patterns from the downward and outward excavation flow to the inward and upward collapse flow implies that net plastic strains may be significantly lower than total plastic strains plastic strain in brittle rocks is very heterogeneous however continuum modeling requires that the deformation of the target during an impact event be described in terms of an average strain that applies over a large volume of rock large compared to the spacing between individual zones of sliding this paper demonstrates that model predictions of smooth average strain are entirely consistent with an actual strain concentrated along very narrow zones furthermore we suggest that model predictions of total accumulated strain should correlate with observable variations in bulk density and seismic velocity

resolution of impact related microstructures in lunar zircon a shock deformation mechanism map abstract the microstructures of lunar zircon grains from breccia samples 72215 73215 73235 and 76295 collected during the apollo 17 mission have been characterized via optical microscopy cathodoluminescence imaging and electron backscatter diffraction mapping these zircon grains preserve deformation microstructures that show a wide range in style and complexity planar deformation features pdfs are documented in lunar zircon for the first time and occur along 001 110 and 112 typically with 0 1 25 m spacing the widest pdfs associated with 112 contain microtwin lamellae with 65 misorientation relationships deformation bands parallel to 100 planes and irregular low angle misorientation axes this geometry is consistent with a dislocation glide system with 010 during dislocation creep nonplanar fractures recrystallized domains with sharp irregular interfaces and localized annealing textures along fractures are also observed no occurrences of reidite were detected shock deformation microstructures in zircon are explained in terms of elastic anisotropy of zircon pdfs form along a limited number of specific hkl planes that are perpendicular to directions of high young s modulus suggesting that pdfs are likely to be planes of longitudinal lattice damage twinned 112 pdfs also contain directions of high shear modulus a conceptual model is proposed for the development of different deformation microstructures during an impact event this shock deformation mechanism map is used to explain the relative timing conditions and complexity relationships between impact related deformation microstructures in zircon

shock metamorphosed zircon in terrestrial impact craters to ascertain the progressive stages of shock metamorphism of zircon samples from three well studied impact craters were analyzed by optical microscopy scanning electron microscopy sem and raman spectroscopy in thin section and grain separates these samples are comprised of well preserved rapidly quenched impactites from the ries crater germany strongly annealed impactites from the popigai crater siberia and altered variably quenched impactites from the chicxulub crater mexico the natural samples were compared with samples of experimentally shock metamorphosed zircon below 20 gpa zircon exhibits no distinct shock features above 20 gpa optically resolvable planar microstructures occur together with the high pressure polymorph reidite which was only retained in the ries samples decomposition of zircon to zro2 only occurs in shock stage iv melt fragments that were rapidly quenched this is not only a result of post shock temperatures in excess of 1700 c but could also be shock pressure induced which is indicated by possible relics of a high pressure polymorph of zro2 however zro2 was found to revert to zircon with a granular texture during devitrification of impact melts other granular textures represent recrystallized amorphous zrsio4 and reidite that reverted to zircon this requires annealing temperatures 1100 c a systematic study of zircons from a continuous impactite sequence of the chicxulub impact structure yields implications for the post shock temperature history of suevite like rocks until cooling below 600 c

response of cathodoluminescence to crystal plastic deformation in zircon geochemical and geochronological studies of zircon are commonly supplemented by cathodoluminescence cl imaging because it provides a means of recognizing different generations of zircon growth at high spatial resolution crystal plastic deformation of zircon can have significant effects on zircon geochemistry detailed analyses from electron backscatter diffraction mapping combined with panchromatic cl imaging and hyperspectral cl mapping of several crystal plastically deformed grains from different geological settings are used to establish the relationships between crystal plastic deformation and cl in zircon results show a strong spatial association between deformation microstructures and cl response that lead to modification of cl that commonly cross cuts primary zoning variable contributions from two fundamental deformation related processes result in a variety of cl characteristics a defect control on panchromatic cl intensity particularly at low angle subgrain boundaries and changes in spectral cl response due to deformation related modification of cl active ree geochemistry a framework is provided for the recognition of deformation related microstructures using cl and the usefulness of cl imaging in the discrimination of these microstructures is critically evaluated

experimental shock deformation in zircon a transmission electron microscopic study abstract in recent years apparently shock induced and thus impact characteristic microdeformations in the form of planar microdeformation features and so called strawberry granular texture have been observed in zircons in rocks from confirmed impact structures and from the k t boundary the nature of the planar microdeformations in this mineral is however still unknown and critical information is needed regarding the shock pressure range in which these deformation effects are produced we experimentally shock deformed two series of thin zircon zrsio 4 target plates cut perpendicular to the c axis at shock pressures of 20 40 and 60 gpa the recovered samples were characterized by optical and scanning electron microscopy in addition one sample series was studied by transmission electron microscopy tem microdeformation effects observed at 20 gpa include pervasive micro cleavage and dislocation patterns plastic deformation is indicated by a high density of straight dislocations in glide configuration the dominant glide systems are 010 micro cleavages induced by shear stresses during the compression stage occur mostly in the 100 planes the large density of dislocations at crack tips shows that plastic deformation was initiated by the micro cracking processs at 40 gpa the sample was partly transformed from the zircon z to a scheelite cawo 4 type s structure planar deformation features pdfs containing an amorphous phase of zircon composition are present in the not yet transformed zircon relics the phase with scheelite structure initiated in the 100 planes of zircon consists of thin 0 1 to several m bands that crosscut the zircon matrix the phase transformation is displacive martensitic and can be related by 100 z 112 s and 001 z s the scheelite structure phase is densely twinned with twins in the 112 plane the 60 gpa sample consists completely of the scheelite structure phase crosscutting and displacing relationships between twins and pdfs demonstrate that pdfs are formed in the zircon structure i e before the phase transformation to the scheelite structure occurred most likely at the shock front crystallographic orientations of optically visible planar features in zircon in comparison with orientations of planar defects at the tem scale suggest that the optically visible features are more likely planar microfractures than pdfs

crystal accumulation in a 4 2 ga lunar impact melt abstract the ages of lunar impact basins and the role of fractional crystallization in producing compositional heterogeneity of lunar melt sheets are long standing problems with significant implications for solar system dynamics and the petrologic evolution of the lunar crust here we document the formation of a basin scale impact on the moon at 4 20 0 07 ga based on the 147 sm 143 nd isochron age of a magnesian noritic anorthosite melt rock from lunar breccia 67955 major element compositions of plagioclase and mafic silicates in the melt rock imply a substantial component of primary mg suite cumulates or related lithologies in the pre impact crustal stratigraphy trace element compositions of the plagioclase including diagnostic ratios such as sr ba are also mostly similar to those in plagioclase from mg suite cumulates with a small number of grains trending toward compositions observed in ferroan anorthosites mineral melt distribution coefficients applied to trace element compositions of the 67955 plagioclase and pyroxene predict parental melt compositions that contrast strongly with the bulk rock compared to the whole rock parental melts calculated from the plagioclase are enriched in ree ree la yb 131 885 average 619 ppm vs 39 8 ppm and they have more fractionated ree patterns la yb n 1 2 9 8 average 4 9 vs 1 5 with deep negative eu anomalies eu eu 0 09 0 40 vs 1 36 trace element data for the pyroxenes also imply incompatible element enriched parental melts subsolidus equilibration between the plagioclase and the pyroxene apparently rotated the ree patterns but the conclusion that the parental melt was highly enriched in ree relative to the whole rock appears robust quantitative modeling shows that fractional crystallization of the 67955 whole rock composition cannot reproduce the range of ba sr ti and la concentrations measured in the 67955 plagioclase rather the models require an initial melt composition that was strongly enriched in these elements and they suggest that fractional crystallization became less efficient as crystallization proceeded the contrast between the inferred parental melt composition and the bulk rock implies formation of the 67955 noritic anorthosite as a crystal cumulate and that the cogenetic residual melt was strongly enriched in incompatible elements if so this would be the first documented example of fractional crystallization in a lunar impact melt sheet the petrological and geochemical characteristics of the 67955 noritic anorthosite suggest that it formed by an impact in the procellarum kreep terrane and was transported to the apollo 16 site as imbrium ejecta inheritance of ejecta related to this pre imbrium basin may contribute to the common occurrence of 4 2 ga 40 ar 39 ar plateau ages in breccia clasts and regolith fragments from the rim of north ray crater in that case those data may provide no constraints on the age of the nectaris basin despite its proximity to the apollo 16 site

thermal history recorded by the apollo 17 impact melt breccia 73217 abstract lunar breccia 73217 is composed of plagioclase and pyroxene clasts originating from a single gabbronorite intrusion mixed with a silica rich glass interpreted to represent an impact melt a study of accessory minerals in a thin section from this breccia 73217 52 identified three different types of zircon and anhedral grains of apatite which represent distinct generations of accessory phases and provide a unique opportunity to investigate the thermal history of the sample equant anhedral zircon grains that probably formed in the gabbronorite referred to as type 1 have consistent u pb ages of 4332 7 ma a similar age of 4335 5 ma was obtained from acicular zircon type 2 grains interpreted to have formed from impact melt a polycrystalline zircon aggregate type 3 occurs as a rim around a baddeleyite grain and has a much younger age of 3929 10 ma similar to the 3936 17 ma age of apatite grains found in the thin section a combined apatite type 3 zircon age of 3934 12 ma is proposed as the age of the serenitatis impact event and associated thermal pulse x ray mapping and electron probe analyses showed that ti is inhomogeneous in the zircon grains on the sub micrometer scale however model temperatures estimated from shrimp analyses of ti concentration in the 10 m diameter spots on the polished surfaces of type 1 and type 2 zircons range between about 1300 and 900 c respectively whereas ti concentrations determined for the type 3 zircon are higher at about 1400 1500 c a combination of u pb ages ti concentration data and detailed imaging and petrographic studies of the zircon grains shows that the gabbronorite parent of the zircon clasts formed shortly before the 4335 5 ma impact which mixed the clasts and the felsic melt and projected the sample closer to the surface where fast cooling resulted in the crystallization of acicular zircon type 2 the 3934 12 ma serenitatis event resulted in partial remelting of the glass and formation of polycrystalline zircon type 3 this event also reset the u pb system of apatite formed merrillite coronas around some apatite grains and probably re equilibrated some pyroxenes in the clasts although there have been arguments for pre 3 9 ga impacts based on other types of samples the age of the acicular zircon at 4335 5 ma provides the first evidence of impact melt significantly predating the lunar cataclysm our data combined with other chronological results demonstrate the occurrence of pre 3 9 ga impacts on the moon and suggest that the lunar impact history consisted of a series of intense bombardment episodes interspersed with relatively calm periods of low impact flux

electron backscatter diffraction analysis of zircon a systematic assessment of match unit characteristics and pattern indexing optimization quantitative microstructural analysis of zircon using electron backscatter diffraction ebsd requires a comparison of empirically collected electron backscatter patterns with theoretical patterns or match units derived from known crystallographic parameters there are 23 possible crystallographic data sets for zircon and associated match units derived from natural and synthetic zircon and from theoretical calculations over a range of pressures and different rare earth element ree compositions a systematic assessment of these match units has been undertaken by ebsd analysis of each of four zircons from a range of geological environments combined with principal components analysis and self organizing map networks comparison of the different match units shows a systematic relationship across all samples that are related to changes in unit cell dimensions associated with pressure and compositional variations systematic variations in the data generated from 96 ebsd maps each comprising 10 000 electron backscatter patterns indicate that match units associated with increasing pressure or ree dopants yield poorer quality ebsd data the match units from low pressure undoped natural zircon consistently yield the best ebsd results and are recommended for natural zircon ebsd studies irrespective of the zircon source or u content the results provide a clear strategy for optimizing the acquisition and analysis of ebsd data from zircon from both crustal and mantle sources in addition the developed approach to match unit analysis may be applied to all other crystalline materials potentially optimizing ebsd analyses from a range of materials