microstructures and c axis fabrics indicative of quartz dissolution in sheared quartzites and phyllonites abstract quartzites sheared in low metamorphic grade shear zones that extend along the contact with migmatitic gneissic complexes in the quadrilatere ferifero region southeastern brazil show quartz microstructures indicating deformation by dissolution dissolution occurred adjacent to the foliation planes preferentially in quartz porphyroclasts oriented with their 0001 planes parallel to the foliation dissolution worked as an efficient mechanism to remove porphyroclast edges smoothing foliations and enabling strain accommodation both dissolution and crystal plasticity were competitive crystallographically controlled processes operating in different domains of the evolving microstructure dissolution occurred along the foliation planes while isovolume crystal plasticity and accompanying recrystallization operated essentially in the quartzose domains between folia phyllonites formed in the most strained domains of the shear zones fine grained quartz grains in phyllonites show uncommon c axis fabrics c axis oriented at low angles to the stretching lineation which were interpreted to form either by direct reprecipitation or by residual concentration of grains unfavourably orientated to undergo dissolution domainal c axis fabrics reflect a deformation partitioning path with increasing participation of solution transfer strengthening c axis maxima at low angles with the stretching lineation at the expense of crystal plastic processes during progressive phyllonitization

quartz recrystallization regimes c axis texture transitions and fluid inclusion reequilibration in a prograde greenschist to amphibolite facies mylonite zone ribeira shear zone se brazil abstract the crystal plastic behavior of quartz mylonites from the ribeira shear zone se brazil a major strike slip structure that was active during a prograde metamorphic phase related to the neoproterozoic brasiliano pan african orogeny was investigated using a multi method approach geothermobarometry results indicate deformational conditions ranging from 300 to 630 c and 500 700 mpa a strong correlation between mapped metamorphic zones and a dominance of different dynamic recrystallization mechanisms of quartz occurs within the mylonite zone bulging recrystallization blg dominates within the chlorite zone between 300 and 410 c subgrain rotation recrystallization sgr operates within the biotite zone from 410 to 520 c and grain boundary migration recrystallization gbm dominates in the garnet zone above 520 c the development of quartz c axis textures is mainly governed by temperature and dynamic recrystallization mechanisms textures from blg zone mylonites are characterized by maxima around z sgr zone mylonites display single girdles or asymmetric type i crossed girdles and gbm zone mylonites comprise maxima around y and intermediate between x and z the scarcity or absence of water bearing fluid inclusions in quartz mylonites from the sgr and gbm zones which are dominated by carbonic inclusions suggests water deficient conditions whereas blg zone mylonites are dominated by water bearing inclusions this evidence indicates that water was available in the protoliths but has been eliminated with increasing deformation and deformation temperature no effect of the water content variation on the quartz microstructural and recrystallized grain size evolution was detected and little influence on c axis texture development was observed most of the fluid inclusion densities were reequilibrated during the shear zone exhumation history recording a decompression in the range of 300 500 mpa while microstructural reequilibration effects related to the prograde metamorphism are largely preserved fluid inclusion microstructures and densities from two sgr zone samples preserved evidence for a near isothermal compression within the interior of the ribeira shear zone during the prograde metamorphism

short lived polyphase deformation during crustal thickening and exhumation of a collisional orogen ribeira belt brazil abstract the ribeira belt brazil is a neoproterozoic collisional related feature that was located in a south central position in west gondwana we present quantitative data on finite strain flow vorticity and deformation temperatures for the curitiba terrane a major segment of the southern ribeira belt six deformation phases d 1 d 6 related with crustal thickening and exhumation were recognized d 1 and d 2 related microstructures are preserved exclusively within porphyroblasts in part grown during stages of high pressure 9 12 kbar isobaric heating after crustal thickening d 3 phase was active from peak metamorphism attained in contrasting crustal levels 810 400 c to the early stage of exhumation 500 400 c as indicated by petrological microstructural and quartz c axis fabric evidence kinematic vorticity results indicate that the sl 3 mylonitic fabric resulted from a simple shear dominated deformation related with westward thrusting north verging overturned d 4 folds with e w trending subhorizontal axes derived from a pure shear dominated deformation regional d 5 open folds with subvertical axes and nne ssw trending traces were produced by indentation tectonics d 6 phase comprises retrograde orogen parallel transcurrent shear zones related with scape tectonics geochronological data indicate that d 3 d 6 phases occurred between 584 and 580 ma suggesting a fast exhumation rate of 8 mm year for the deepest rocks from the southern ribeira belt

strain path partitioning within thrust sheets microstructural and petrofabric evidence from the moine thrust zone at loch eriboll northwest scotland abstract quartz c axis fabrics and microstructures have been investigated within a suite of quartzites collected from the loch eriboll area of the moine thrust zone and are used to interpret the detailed processes involved in fabric evolution the intensity of quartz c axis fabrics is directly proportional to the calculated strain magnitude a correlation is also established between the pattern of c axis fabrics and the calculated strain symmetry two kinematic domains are recognized within one of the studied thrust sheets which outcrops immediately beneath the moine thrust within the upper and central levels of the thrust sheet coaxial deformation is indicated by conjugate mutually interfering shear bands globular low strain detrital quartz grains whose c axes are aligned sub parallel to the principal finite shortening direction z and quartz c axis fabrics which are symmetric both in terms of skeletal outline and intensity distribution with respect to mylonitic foliation and lineation non coaxial deformation is indicated within the more intensely deformed and recrystallized quartzites located near the base of the thrust sheet by single sets of shear bands and c axis fabrics which are asymmetric with respect to foliation and lineation tectonic models offering possible explanations for the presence of kinematic strain path domains within thrust sheets are considered

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

a new empirical calibration of the quartz c axis fabric opening angle deformation thermometer abstract the opening angle of quartz c axis fabrics oa is strongly temperature dependent and has proven to be a powerful deformation thermometer for natural metamorphic rocks previous considerations of empirical data have identified a linear correlation between oa and temperature between 250 and 650 c and no correlation above 650 c however possible effects of pressure have not been investigated we expanded the data set of oa versus temperature including data from rocks deformed over 300 1050 c and 2 5 15 kbar disregarding possible effects of pressure the oa temperature relationship can be described by two linear correlations for the intervals 250 650 c and 650 1050 c t c 6 9 o a degrees 48 250 c t 650 c and o a 87 t c 4 6 o a degrees 258 650 c t 1050 c and o a 87 the change on the curve slope of the oa temperature relationship correlates approximately to the low to high quartz transition and to changes in the dynamic recrystallization mechanism from subgrain rotation to grain boundary migration the available data suggest that pressure has a secondary effect accompanying the major temperature dependence of oa which is particularly important for temperatures above 650 c where the correlation between oa and temperature is less pronounced for fixed pressures the oa has logarithmic relationships with temperature over the range 250 1050 c the following thermometer equation is formulated from a multiple regression t c 410 44 ln oa degrees 14 22 p kbar 1272 an uncertainty of 50 c is inherited from the petrological temperature estimates of the natural samples the data suggest the gradual increasing importance of prism c slip relative to slip in quartz with rising temperature under conditions of average geological strain rate and water weakening prism c slip dominates for deformation above 700 c

titanium in quartz thermometry on synkinematic quartz veins in a retrograde crustal scale normal fault zone abstract previous studies have suggested that estimation of deformation temperatures in quartz mylonites by titanium in quartz geothermometry is only possible at temperatures 500 c above which efficient ti exchange is achieved via grain boundary migration recrystallization based on quartz mylonite samples collected across the simplon fault zone sfz we demonstrate that deformation temperatures of dynamic recrystallization can be obtained down to 350 c a prerequisite for such temperature estimates at the low temperature end of ductile deformation of quartz is the formation of synkinematic quartz veins and their immediate overprint either by subgrain rotation sgr or bulging recrystallization blg it is the slow growth of the synkinematically precipitating vein quartz that allows for equilibration of ti in the vein quartz this ti concentration may only slightly be modified during sgr hence ti in qtz thermometry provides a close approach to the vein formation temperature ti concentrations are partially reset during blg and resulting temperatures are thus maximum temperatures of quartz recrystallization importantly undeformed vein quartz always yield vein formation temperatures investigation of the dynamic recrystallization processes overprinting synkinematic quartz veins thus allows for a critical independent evaluation of the ti in quartz temperatures obtained for the sfz there is a decrease in recrystallized grain sizes towards the fault plane and a change in the dominant recrystallization process associated with a narrowing of the shear zone as indicated by the ti in quartz temperature estimates this strain localization correlates with cooling from 560 c in the oldest microstructures at the periphery of the shear zone down to 350 c in the youngest microstructures of the footwall near the hanging wall contact a great benefit of the approach presented here is that intermediate to low temperature plastic deformation in quartz can now also be assessed such novel temperature constraints on quartz crystallization are essential for better constraining deformation and rheology in the upper earth s crust

sense of nappe emplacement from quartz c axis fabrics an example from the betic cordilleras spain preferred crystallographic orientation patterns fabrics in zones of ductile deformation beneath nappes are a potentially useful indicator of the sense of nappe translation quartz c axis fabrics from a shear zone beneath the pile of higher betic nappes in the betic cordilleras spain have distinctly asymmetric topologies revealed by constructing a fabric skeleton these skeletons closely resemble those produced by computer simulations of quartz fabric development basedon taylor bishop hill theory the fabric asymmetry indicates a northerly sense of transport for the nappes consistent with field evidence from the same area analyses of both c and a axis fabrics based on asymmetric intensity distributions within the fabric give equivocal results and may reflect the presence of earlier preferred orientation patterns predating nappe emplacement

a fracture model for quartz ribbons in straight gneisses abstract polycrystalline composite quartz ribbons in straight gneisses of the grenville province are explained as dilatant quartz filled fractures formed parallel to a strong preexisting gneissosity the ribbons are thin 3 mm but long and continuous and have straight and truncating contacts with bordering grains of other minerals they are similar in morphology to polycrystalline ribbons interpreted in the literature as resulting from high strains in contrast little strain is required if the ribbons form as quartz filled fractures a monoclinic symmetry of the shapes of ribbons and inclusions can be explained by fracture interactions as they propagate the symmetry is consistent with a late extensional south side down sense of shearing which has been documented elsewhere in the grenville province

an optical method for the determination of a axis orientations in deformed aggregates of quartz abstract knowledge of a axis orientation is of paramount importance to the understanding of deformation mechanisms in quartz and by extension quartz rich rocks the positions of the a axis cannot be measured by standard optical u stage techniques since quartz is optically uniaxial many quartz grains however contain abundant fluid inclusions and in many instances these fluid inclusions occupy negative crystal shaped cavities for which the a axis can be optically determined this study has utilized these negative crystals to locate a axis positions using a u stage in order to test the validity of this approach a blind comparison was performed on a deformed quartz aggregate from the simplon fault zone central alps switzerland both a and c axis positions for this sample were measured using the proposed optical technique and via an x ray texture goniometer the locations for a axis maxima contoured on a schmidt net using the two techniques agree closely demonstrating that the optical technique was successful advantages of the optical technique are 1 that it is simple and requires inexpensive equipment and 2 that a axis positions can be determined on a grain by grain basis allowing for the detailed study of crystallographic orientation differences across grain boundaries in deformed aggregates of quartz

the hengshan low angle normal fault zone structural and geochronological constraints on the late mesozoic crustal extension in south china abstract we document in this paper a significant low angle normal fault namely the hengshan detachment fault which extends more than 150 km long in nne orientation and bounds an elongated early cretaceous basin in hunan province central south china detailed structural and geochronological analyses have been conducted along its southern segment where a well exposed 3 km thick flat ductile shear zone develops along the western margin of the hengshan granitic massif this zone is featured by shallow dipping foliations of varied trend from ne to nw which bear penetrative stretching lineations varying from nw to sw trend shear sense criteria indicate top to the nw and top to the sw motions along its northern and southern parts respectively quartz c axis orientations of mylonitic rocks from the shear zone exhibit asymmetric single or crossed girdle patterns and the distributions of fabric point maxima suggest a simultaneous operation of basal and prism slips indicating a deformation temperature ranging from 400 c to 550 c one zircon u pb age of the sheared albitite and three muscovite 40 ar 39 ar ages of the mylonitic rocks indicate that the ductile shearing initiated at 136 ma and lasted till 97 ma the zircon u pb dating results of five granitic samples from the hengshan granitic pluton yield two phases of crystallization ages of 232 228 ma and 150 151 ma respectively indicating two preceding magmatic events prior to the ductile shearing in the lower plate our structural and geochronological data allow defining the hengshan massif as an extensional dome rather than a metamorphic core complex as previously predicted due to the lack of syn tectonic plutonism and the origin of detachment fault associated with the reactivation of the inherited thrust this study provides crucial evidence for understanding how the mid upper crust deformed during the process of extension which testifies to a coeval occurrence of non coaxial deformation of the ductile flow in the middle crust and brittle faulting in the upper crust it also sheds new insights into the timing of the regional crustal extension in south china and permits to constrain its onset time to be ca 136 ma

atypical textures in quartz veins from the simplon fault zone abstract samples of monomineralic quartz veins from the simplon fault zone in southwest switzerland and north italy generally have asymmetric single girdle c axis patterns similar to textures measured from many other regions several samples have characteristically different textures however with a strong single c axis maximum near the intermediate specimen axis y the direction within the foliation perpendicular to the lineation x and a tendency for the other crystal directions to be weakly constrained in their orientation about this dominant c axis maximum this results in streaked pole figure patterns with an axis of rotation parallel to the c axis maximum these atypical samples also have a distinctive optical microstructure with advanced recrystallization and grain growth resulting in a strong shape fabric sb oblique to the dominant regional foliation sa whereas typical samples have a strong sa fabric outlined by very elongate only partially recrystallized ribbon grains the recrystallized grains of the atypical samples are themselves deformed and show strong undulose extinction and a core mantle recrystallization structure the streaked texture is likely to be a direct consequence of lattice bending and kinking during heterogeneous slip on the favoured first order prism 10 1 0 a system the heterogeneity itself being due to problems in maintaining coherence across grain boundaries when insufficient independent easy slip systems are available for homogeneous strain by dislocation glide such bending would be particularly prevalent in very elongate thin ribbon grains resulting in high internal strain energy and promoting recrystallization thus both the texture and the microstructure could be significantly modified by later strain increments affecting quartz grains with an already developed nearly single crystal texture

numerical analysis of x ray texture data an implementation in fortran allowing triclinic or axial specimen symmetry and most crystal symmetries abstract the use of complete descriptions of preferred orientation for studies of experimentally and naturally deformed rocks is discussed diagrammatic representations of preferred orientations are defined and conventions for coordinate systems are given methods of extracting information from the orientation distribution function are described a system of fortran programs which enables the orientation distribution function to be calculated for most suitable minerals is described

new results from physical modelling of arc continent collision in taiwan evolutionary model abstract both the analysis of the geological data and the results from 2d and 3d experimental modelling of arc continent collision in taiwan reveal the following major stages in this process 1 failure and thickening of the subducting crust of the chinese continental margin under the frontal part accretionary prism of the philippine sea plate psp since ca 6 7 ma 2 uplift squeezing and exhumation of the subducted crustal slice of the chinese margin and initiation of the central range about 5 ma ago 3 flexural buckling subsidence of the luzon arc fore arc under strong horizontal compression and sedimentary infilling of this area by the material shed from the growing and exhuming central range 4 failure of the psp along the west vergent longitudinal valley fault dipping beneath the arc and closure of the fore arc 5 subduction reversal and stoppage of continental subduction which has already occurred in northern taiwan and propagates to the south the southward propagation of the collision is not stationary currently occurring initial collision in southern taiwan and offshore to the south does not follow the same described above evolution as in central and northern taiwan the evolution of the collision in time and space should be considered in the framework of a 3d model where the psp rupture is preparing in the central and northern taiwan during a long time passing through a number of evolutionary stages once it has occurred the rupture longitudinal valley fault rapidly propagates to the south into the domain which did not undergo the pre rupture evolution the rupture front is currently located near 21 30 n

high ductility of k feldspar and development of granitic banded ultramylonite in the ryoke metamorphic belt sw japan granitic mylonites from an upper greenschist facies mylonite zone in the ryoke metamorphic belt sw japan show three types of microstructure with increasing mylonitization 1 mylonite 2 banded mylonite and 3 banded ultramylonite the banded mylonites and ultramylonites include bands of quartz biotite k feldspar plagioclase k feldspar quartz biotite and k feldspar plagioclase quartz the inequality sign indicates abundance in modal proportion within a band microstructural and textural investigations by cathodoluminescence cl scanning electron microscopy sem and electron back scatter diffraction ebsd show that the microstructural changes from mylonites to banded ultramylonites have occurred through fracturing of plagioclase porphyroclasts k feldspar replacement by myrmekite k feldspar precipitation in fractures and tails and dislocation creep of quartz and k feldspar development of the banded structure was promoted by high mobility via solution transfer of k feldspar clear spatial distribution of constituent minerals in polyphase feldspar rich bands instead of homogeneous mixing of them indicates that the grain boundary sliding was not the dominant deformation process

evolution of quartz microstructure and c axis crystallographic preferred orientation within ductilely deformed granitoids arolla unit western alps abstract we have studied quartz microstructures and the c axis crystallographic preferred orientations cpos in four granitoid samples representative of increasing ductile shear deformation from a weakly deformed granitoid stage 1 to a mylonitic granitoid stage 4 the quartz c axis cpo measured in the mylonitic granitoid has been compared with the one observed in a fully recrystallized quartz mylonite from the same area all the samples belong to the austroalpine arolla unit western alps and were deformed at greenschist facies conditions the quartz c axis cpo was analyzed using a u stage and the optical orientation imaging technique the magmatic plagioclase forming more than 50 of the volume of the granitoid is extensively replaced by a mica rich aggregate even in weakly deformed samples of stage 1 these aggregates flow to form an interconnected weak matrix with increasing deformation wrapping relatively less strained quartz grains that undergo dominantly coaxial strain recrystallization of quartz ranges from less than 1 in the weakly deformed granitoid to up to 85 in the mylonitic granitoid with average grain strain of 41 and 64 respectively with increasing strain and recrystallization quartz grains in the granitoids show a sequence of transient microstructures and cpos crystal plastic deformation is initially accomplished by dislocation glide with limited recovery and at 50 grain strain it results in a cpo consistent with dominantly basal a slip at 60 grain strain recrystallization is preferentially localized along shear bands which appear to develop along former intragranular cracks and the recrystallized grains develop a strong c axis cpo with maxima orthogonal to the shear band boundaries and independent of the host grain orientation within the granitoid mylonite at an average quartz grain strain of 64 recrystallization is extensive and the c axis cpo of new grains displays maxima overlapping the host c axis orientation and therefore unrelated to the bulk sense of shear the host controlled cpo is inferred to reflect pervasive recrystallization by progressive subgrain rotation the switch from shear band control to host control on c axis cpo occurred between 40 and 70 of recrystallization in the quartz mylonite the quartz c axis cpo develops an asymmetric single girdle consistent with the bulk sense of shear and the synkinematic greenschist facies conditions this study indicates that the cpo evolution of quartz may significantly differ in cases of polymineralic vs monomineralic rocks under the same deformation conditions if quartz in the polymineralic rock behaves as a strong phase

deformation conditions and kinematics of fault rocks in the hatagawa fault zone and the shajigami shear zone northeast japan insights from calcite and quartz microstructures abstract calcite grains are plastically deformed at lower temperatures than are quartz grains which means that investigating the microstructures of both minerals should provide useful information regarding the deformation history of faults we investigated the conditions of deformation and kinematics of fault rocks within the hatagawa fault zone and the shajigami shear zone northeast japan using deformation microstructures and crystallographic preferred orientations of quartz and calcite the hatagawa fault zone trends nnw sse and the associated foliated granite cataclasites show sinistral shear limestone mylonite samples showing sinistral shearing display girdles of calcite c axes close to the yz plane and z maximum suggesting relatively high and low temperatures of deformation respectively the shajigami shear zone trends ne sw and quartz microstructures in granodiorite mylonites of the shear zone indicate dislocation creep at temperatures of 400 500 c the limestone mylonites have z maximum patterns of calcite c axes these fault rocks were deformed during the cretaceous before the cenozoic 40 counterclockwise rotation of northeast japan in a kinematic framework characterized by a shortening direction that rotated from n s to nw se the kinematics and deformation ages of the fault rocks correspond to a change in the direction of motion of the izanagi plate at c 100 ma

an illustration of the advantages of a complete texture analysis described by the orientation distribution function odf using quartz pole figure data abstract the preferred orientation of eight crystal directions of quartz was measured with an x ray texture goniometer for selected quartz bearing tectonites with a clear pattern of c axis preferred orientation the advantages of data analysis by means of calculations of the orientation distribution function and other forms of data presentation derived from the odf are demonstrated

relationships between strain and quartz crystallographic fabrics in the roche maurice quartzites of plougastel western brittany abstract an integrated microstructural and petrofabric study of the plastically deformed and partially recrystallized roche maurice quartzites of plougastel western brittany has revealed a clear correlation between the pattern of c axis fabrics displayed by detrital quartz grains and the symmetry of the calculated strain ellipsoid in specimens with flattening k 0 strains c axes lie on a small circle girdle opening angle 28 42 centred about the principal finite shortening direction z for specimens that exhibit approximate plane strain k 1 cross girdle c axis fabrics consisting of a small circle girdle centred about z and connected through the intermediate principal extension direction y were detected within individual specimens c axis fabrics of syntectonically recrystallized new quartz grains within the matrix are similar to those of detrital quartz grains c axes of new grains located within the relatively undeformed sections of the host detrital grains are commonly orientated at angles between 10 and 40 to the host c axis and are in addition statistically orientated at a higher angle to z than their host c axes these relationships are interpreted as indicating that both host grain control and the local strain and or stress field may have influenced the process of recrystallization the relative influence of these factors is however unknown microstructural and petrofabric studies indicate that the roche maurice quartzites have been subjected to essentially coaxial strain histories the role of syntectonic recrystallization in facilitating continued plastic deformation in quartzites subjected to such strain histories is considered

microfabric memory of vein quartz for strain localization in detachment faults a case study on the simplon fault zone abstract this manuscript deals with the adaptation of quartz microfabrics to changing physical deformation conditions and discusses their preservation potential during subsequent retrograde deformation using microstructural analysis a sequence of recrystallization processes in quartz ranging from grain boundary migration recrystallization gbm over subgrain rotation recrystallization sgr to bulging nucleation blg is detected for the simplon fault zone sfz from the low strain rim towards the internal high strain part of the large scale shear zone based on i the retrograde cooling path ii estimates of deformation temperatures and iii spatial variation of dynamic recrystallization processes and different microstructural characteristics continuous strain localization with decreasing temperature is inferred in contrast to the recrystallization microstructures crystallographic preferred orientations cpo have a longer memory cpo patterns indicative of prism and rhomb glide systems in mylonitic quartz veins overprinted at low temperatures 400 c suggest inheritance of a high temperature deformation in this way microstructural textural and geochemical analyses provide information for several million years of the deformation history the reasons for such incomplete resetting of the rock texture is that strain localization is caused by change in effective viscosity contrasts related to temporal large and small scale temperature changes during the evolution of such a long lived shear zone the spatially resolved quantitative investigation of quartz microfabrics and associated recrystallization processes therefore provide great potential for an improved understanding of the geodynamics of large scale shear zones

quartz textures from the simplon fault zone southwest switzerland and north italy quartz textures measured from monomineralic veins within the simplon fault zone show very similar patterns over a strike length of some 30 km the c axes form asymmetric kinked single girdles with variably developed vestiges of crossed girdle limbs the kinking of the girdle may be controlled by the two c axis orientations where double rhomb a slip is possible a strong a maximum lies between 20 and 30 to the lineation in the xz plane which seems too large to be the angle to the bulk shear plane straight single girdle patterns may be possible for strict simple shear in natural fault zones where deformation is in general heterogeneous on all scales kinked single girdles and type i crossed girdle textures are much more common perhaps because such textures provide more freedom to accommodate a general two dimensional strain

v pull apart microstructures a new shear sense indicator abstract granitoids deformed in a low grade shear zone show conspicuous development of asymmetric pull apart microstructures in feldspars characterized by v shaped gaps between the separated fragments v pull aparts they occur beside active shear planes and result from rigid body rotation of one fragment relative to the other the shear sense in the adjacent flow surface can be easily determined through the asymmetry normally shown by v pull aparts where the fracture wall at a lower angle to the shear plane indicates which fragment has rotated synthetically to the adjacent shearing another diagnostic feature is the foliation deflection that occurs adjacent to the rotated fragment the v shaped gaps are infilled by recrystallized quartz mica aggregates showing quartz c axis patterns indicative of strong participation of crystal plastic processes in these domains evidence of crack seal by precipitation c axes parallel to the direction of separation have also been found the rigid body rotation indicated by these microstructures worked as a mechanism of removal of protruding porphyroclast edges enabling the smoothing of the shear planes rigid body rotation should operate in circumstances where other mechanisms such as dissolution or crystal plasticity did not succeed in eliminating undulations along the shear planes