studies of burial metamorphism in the post taconic stage of the appalachian orogen southwestern gaspe illite crystallinity and organic matter reflectance techniques are applied to the evaluation of burial metamorphic conditions for lithostratigraphic groups accumulated during the post taconic stage of the appalachian orogen in the southwestern gas the results of this work show that the metamorphic grade of the paleozoic succession decreases upwards but is anomalously high in the youngest fortin group a model is proposed in which the two parts of the succession were separately buried the model envisages the lower part honorat matapedia and restigouche groups being uplifted in the south whilst deposition of the fortin group continued in the north in a basin yoked by the matapedia fault burial is interpreted to have occurred under an average oceanic geothermal gradient in the early paleozoic basin and under a high geothermal gradient in the fortin basin

chemographic relationships of biotite and cordierite in the mcgerrigle thermal aureole gaspe quebec biotite and cordierite occur in a 1 km wide zone of pelitic hornfelses around the mcgerrigle pluton these phases display systematic changes in xfe that can be attributed to continuous reactions involving chlorite or andalusite in the system kfmash through much of the zone biotite and cordierite were products of the breakdown of chlorite close to the pluton this continuous reaction was terminated by a discontinuous reaction that introduced andalusite pelites which interdigitate with apophyses of the intrusive at the pluton margin contain assemblages that record a continuous reaction between biotite cordierite andalusite muscovite and quartz or alternatively the discontinuous breakdown of muscovite and quartz to k feldspar and andalusite the mole fraction of fe in biotite and cordierite increased significantly with the progress of the first continuous reaction and apparently decreased during the second continuous reaction the kd of fe mg between the minerals decreased and apparently increased respectively during the two reactions biotite cordierite chlorite assemblages are interpreted to have been stable at temperatures between 525 c and 615 c and biotite cordierite andalusite assemblages stable at temperatures between 615 c and 635 c the confining pressure was estimated to have been 2 kbar the results of this study suggest that the kd of fe mg between biotite and cordierite is a function of temperature the fe mg exchange characteristics of the controlling continuous reaction and non ideal mixing of fe and mg

strain partitioning and progressive deformation history in a transpressive belt northern appalachians abstract syntectonic fibres within rocks of the gaspetrough a mid paleozoic slate belt within part of the acadian orogen of the canadian appalachians record the complex structural evolution of a transpressive belt the fibres occur around pyrite framboids and can be divided into five segments which record four distinct structural stages all four structural stages are related to a single progressive deformation since fibre segments can be traced continuously from the first segments to the last fibre growth patterns within the gaspetrough clearly indicate that folding occurred during coaxial deformation during the first three structural stages these structural stages are 1 layer parallel shortening 2 combined flattening and rigid body rotation and 3 cleavage development strain associated with vertical extension during these three stages accounts for approximately 50 shortening within the slate belt during the last structural stage deformation resulting from regional simple shear continued to affect the entire slate belt as local flattening within cleavage planes produced horizontal extension and brought about further tightening of folds strain recorded by the horizontal fibre increments produced during simple shear accounts for 25 shortening in this part of the appalachians oblique convergence during the acadian orogeny was partitioned in time between strike slip and reverse faulting convergence was accommodated by folding flattening and reverse faulting during the first part of the deformation and later on by flattening and dextral transcurrent faulting

tem and xrd determination of crystallite size and lattice strain as a function of illite crystallinity in pelitic rocks average crystallite size and mean square strain of illite in rock specimens and clay separates were measured independently in tem images and by single line fourier voigt method profile analysis of the c 1 nm peak of xrd patterns for a prograde sequence of pelitic rocks illite crystallinity indices 0 17 0 58 d2h from the gaspepeninsula quebec the tem determined crystallite sizes in clay separates approxi mate those determined by fourier profile analyses and those calculated from illite crystallinity indices by the scherrer equation with the exception of the diagenetic sample the crystallite sizes and mean square strains of illite in rock samples exhibit a trend similar to that determined by profile analyses but the average crystallite sizes are up to five times larger than those measured for clay separates tem images show that all rock samples have a wide range of crystallite sizes and the proportions of larger crystallites increase with metamorphic grade the diagenetic illite is defect rich fine grained mean thickness by volume c 70 nm 1m d material anchizonal illite tends to occur as separate aggregates of small 1m d and larger 2m 1 crystals c 200 nm comprising arrays of subparallel coalescing packets the epizone sample has thick c 400 nm defect free crystals of muscovite occurring in stacks of parallel layers or subhedral crystals intergrown with large angle boundaries cleaved crystals that are free of intracrystalline layer terminations are dominant in clay separates of all samples having ranges of smaller sizes with volume average thicknesses of c 43 43 and 81 nm c 14 28 67 nm by the voigt method respectively for the three zones the results suggest that illite crystallinity indices do not provide a direct measure of a single microstruc tural state of illite in rocks although they yield consistent limits for average crystallite sizes for the anchizone 23 48 nm here therefore they serve as a general parameter of the degree of recrystallization on a relative basis in part because the contributions of all peak broadening variables mixed layering size and strain decrease regularly with prograde regional metamorphism of pelites the microstructural changes caused by rock disaggregation are probably a function of those variables as well the data collectively demonstrate a trend from metastable defect rich small crystals towards a stable assemblage of larger defect free crystals through dissolution of strained crystals and neocrystallization consistent with the ostwald step rule

reconstruction of taconian and acadian paleostress regimes in the quebec and northern new brunswick appalachians a numerical analysis of fault populations was applied in the quebec and northern new brunswick appalachians to characterize paleostress fields attributed to the taconian and acadian orogenies the first brittle deformation documented in the external domain of the humber zone is associated with the thin skinned tectonics of the taconian orogen the taconian brittle deformation characterized by north south to ne sw reverse conjugated brittle faults evolved under a pure shear compressional regime vertical 3 axes with 1 axes oriented ese wnw the ene wsw dextral and nw se sinistral faults that are observed in the st lawrence lowlands are also attributed to taconian compression the first brittle deformation recognized in the dunnage zone and the gaspe belt is attributed to an ese wnw compression during the acadian orogeny in the dunnage zone of southern quebec the acadian paleostress axes are similar to the directions of 1 axes and to the pure shear compressional regime computed for the silurian and devonian rocks of the gaspe belt in the gaspe peninsula the acadian stresses are oriented ese wnw and are mechanically compatible with transpressional regimes reverse brittle faults and pure shear stress are identified along regional and secondary sets of ne sw brittle faults whereas a strike slip stress regime is reconstructed along major east west faults in the humber zone of the quebec appalachians a second compression is identified it is characterized by conjugate ene wsw dextral and nw se sinistral strike slip faults that crosscut taconian thrust faults this late deformation event is attributed to a distal expression of the acadian orogeny

expandability of anchizonal illite and chlorite significance for crystallinity development in the transition from diagenesis to metamorphism in mixed layer illite smectite containing 80 illite the presence of an expandable component and changes in its abundance are difficult or impossible to detect with the x ray diffraction xrd method using conventional polar interstratification compounds e g solvation with ethylene glycol although high grade diagenetic and very low grade metamorphic vlgm samples do not expand in response to ethylene glycol treatment the illite crystallinity ic improves significantly with increasing diagenetic metamorphic grade improvement of ic in anchizonal to epizonal samples previously was thought to be related primarily to increase in crystallite thickness and decrease in the number of stacking faults the present study reexamines the contribution of expandable components to ic in shale and slate samples from the gaspe peninsula for both the 2 m and 0 1 m size fractions in the high grade diagenetic and vlgm zone as tools we have used xrd patterns and high resolution transmission electron microscopy hrtem lattice fringe images of samples treated with n alkylammonium cations these studies reveal the presence of expandable components including r1 and r3 ordered structures and expandable illite expandable 2 1 clay minerals decrease in abundance with increasing metamorphic grade the improvement of ic with grade is due to the decrease in expandable layers and also to the decrease in the number of lattice defects and an increase in crystallite size stacking faults may be the main source of lattice distortion only when phyllosilicates consist of thick non expandable layer silicates during late diagenesis the chlorites become ordered and are stabilized they are the dominant phyllosilicate minerals present together with illites in the illite chlorite facies of the anchizone lattice fringe images and xrd patterns document the presence of a short range corrensite like r1 ordered phase and thick chlorite packets

a 40ar 39ar study of oceanic and continental deformation processes during an oblique collision taconian orogeny in the quebec reentrant of the canadian appalachians received 7 december 2006 revised 9 january 2008 accepted 10 march 2008 published 1 july 2008 1 two phases of penetrative deformation are documented in the taconian hinterland of the appalachian orogen in the gaspepeninsula d1 is associated with the obduction of the mont albert ophiolite onto the paleozoic laurentian margin whereas d2 corresponds to later transport of allochthons across the margin in the metamorphic sole s1 is a se dipping mylonitic fabric with a downdip lineation in underlying metabasalts d1 is characterized by nw overturned and recumbent folds and a subhorizontal s1 schistosity with an ene trending orogen parallel lineation d2 is characterized by a s2 steeply dipping penetrative axial planar crenulation cleavage and ne trending f2 folds the intraoceanic thrusting of ophiolite is dated at 465 ma early d1 whereas emplacement of ophiolite andsubsequentdeformationofthemarginwasrecorded by isotopic signatures between 459 and 456 ma late d1 d2 is dated at 448 ma throughout the hinterland taconian transpressive deformation is related to an oblique collision within the quebec reentrant of the canadian appalachians during the ordovician citation malo m g ruffet a pincivy and a tremblay 2008 a 40 ar 39 ar study of oceanic and continental deformation processes during an oblique collision taconian orogeny in the quebec reentrant of the canadian appalachians tectonics 27 tc4001 doi 10 1029 2006tc002094

late neoproterozoic to permian tectonic evolution of the quebec appalachians canada abstract due to the unique location of the quebec appalachians in a re entrant of the paleo north american margin and to the fact that the area largely escaped late paleozoic deformation this segment of the orogen preserves evidence of the early orogenic stages that are partly obscured elsewhere despite diachronicity both along and across strike of the orogen five tectonic events of regional significance are recognized 1 the earliest event is mainly recorded by neoproterozoic to early ordovician normal faults associated with extension of the laurentian craton and the establishment of a passive continental margin 2 the second event the ordovician taconian orogeny is marked by foreland directed deformation and corresponds to the principal deformational and metamorphic events recorded by the laurentian margin 3 the third event early salinic is early silurian it is restricted to the southern part of the quebec appalachians and consists of hinterland se directed thrusts folds and retrograde metamorphism 4 the fourth event late salinic is recorded by regional scale late silurian to early devonian normal or transtensional faults and is associated with the formation of the connecticut valley gaspe trough and 5 the last event the devonian acadian orogeny affects with variable intensity all the pre carboniferous lithologies this tectonic synthesis implies that the subdivision of the peri laurentian oceanic tracts proposed in other segments of the appalachians should be applied with caution in quebec and that the structural style the number of oceanic domains and possibly the vergence of subduction change along the strike of the orogen in particular the similarities of the thetford mines and boil mountain ophiolitic complexes and sedimentary covers and the lack of evidence for a major intervening suture are consistent with the maximum allochtony hypothesis i e the assumption that the southern quebec ophiolites are rooted east of the chain lake massif a geodynamic model involving the taconian obduction of a large ophiolitic nappe s the docking of a peri gondwanan gander medial new england terrane in early salinic the formation of large sedimentary basins connecticut valley gaspe and merrimack troughs due to trench rollback and or delamination during the late salinic event and collision at the outer margin of composite laurentia during the acadian orogeny can account for the protracted structural and metamorphic history of the quebec appalachians

time constraints for the tectono thermal evolution of the cantabrian zone in nw spain by illite k ar dating abstract contrasting sedimentary facies and tectonic structures diversely distributed and affected by diagenetic to low grade metamorphic activity form a complex pattern in the northwestern spanish cantabrian area of the variscan orogen the distribution of these metamorphic features is based on field observations clay mineralogy mineral crystallinity indices vitrinite reflectance data and observation of rock microtextures k ar dating of fine grained illite rich size fractions provides a complete set of ages for the episodic deformation and thermal overprints in the southeastern cantabrian area the usual k ar isochron plotting was combined with the bench type age distribution to unravel the successive illite crystallization episodes several tectono thermal episodes occurred in the southeastern pisuerga carrion province initially during the early permian at 293 4 ma in the ruesga line valsurvio dome and sierra del brezo area a further mid permian event was detected at 268 6 ma in the palentine nappes and during the mid triassic at 243 5 ma again in the valsurvio and sierra del brezo areas and along the ruesga line a later reactivation of the ruesga line was detected during mid jurassic time at 175 6 ma

age and composition of the ruisseau isabelle melange along the shickshock sud fault zone constraints on the timing of melanges formation in the gaspe appalachians melanges are common in the humber and dunnage zones of the quebec appalachians humber zone melanges are spatially associated with taconian nappes and believed to be of tectonic origin dunnage zone melanges are interpreted as relicts of an ordovician accretionary prism the ruisseau isabelle melange rim in the gaspe ap palachians was first interpreted as a dunnage zone melange because of its tectonic position along the baie verte brompton line and lithological components such as dark mudstone blocks of ultramafic rocks and greenish chromite bearing sandstone the rim comprises sedimentary rock assemblages composite shale black shale and chromite bearing sandstone assemblages an exotic block a pebbly mudstone assemblage and slivers of serpentinized peridotite and metamorphic tectonite most melanges of the dunnage zone in the quebec appalachians contain partly similar rocks but their age is not well constrained recent work on the rim and cap chat melange of the humber zone and new fossil finds in the rim rock assemblages allow us to conclude that previous distinction between melanges of the dunnage and humber zones on the basis of rock type associations is not valid according to the age of the rim rock assemblages melanges in the northern gaspe appalachians continued forming after the mid caradocian later than the dunnage zone melanges of southern gaspe appalachians the juxtaposition and structural features of the rim rock assemblages result from repeated faulting along the shickshock sud fault from late ordovi cian to middle devonian

vertical and fold axis parallel extension within a slate belt in a transpressive setting northern appalachians abstract an incremental and finite strain study of a mid paleozoic slate belt in a transpressive setting in gaspe canadian appalachians has been undertaken using syntectonic fibers from pyrite type pressure shadows regionally strain estimates are quite consistent and reflect only slightly higher strain in the central part of the anticlinorial structure defining the slate belt extensions of up to 160 vertically and 110 parallel to the fold axis were recorded in the slate belt combined with an estimated overall regional shortening of 80 the fibers first rotated toward the final position of the cleavage within a vertical section normal to the cleavage and then rotated from a vertical to a horizontal orientation this change in fiber orientation observed in cleavage parallel sections indicates an abrupt change in the incremental stretching direction from sub vertical to sub horizontal fold axis parallel the vertical extension is related to folding and cleavage development during coaxial flattening the horizontal extension reflects the strain imposed on the rocks during regional simple shear which produced strike slip faulting and further tightening of the folds folding cleavage development fold axis parallel extension and faulting are all related to oblique convergence during the middle devonian acadian orogeny in this part of the canadian appalachians and clearly indicate an overall transition from a pure shortening deformation to a simple shear dominant deformation in an overall transpressive setting

the illite crystallinity technique a critical appraisal of its precision analysis of the precision of the illite crystallinity technique shows that machine errors are 0 8 it is necessary that contours should be at intervals of 0 1 2 which is equivalent to subdivision of the anchizone into upper and lower units where previous interpretations have relied upon an isocryst method of contouring at less than 0 1 2 the conclusions must be regarded as unsubstantiated centrifuge separation of clay fractions based on a stokes law application gives separations in which a significant but variable percentage of grains have long axes greater than the size calculated for the typical 2 m fraction utilized some 20 of grains lie in the 2 4 m range although the proportion is not believed to have a significant effect upon crystallinity values the formula is applicable for grain sizes down to 0 5 m illite crystallinity values on samples prepared by an ultrasonic disaggregation method show a small increase on those prepared by ball mill crushing the differences are minimal at the epi anchizone level but increase to some 10 at the anchizone diagenetic level the effect on grade determinations is again thought to be minimal and indicates that concern over unsuitability of the ultrasonic disaggregation method is unfounded

assessing interaction of active extensional faults from structural and paleoseismological analysis the teruel and concud faults eastern spain abstract the relationship of independence interaction or linkage between two neighbouring intraplate active extensional faults the teruel and concud faults are investigated from structural and paleoseismological data and the results are discussed to improve seismic hazard assessment for the region this paper provides the structural and paleoseismological characterization of the almost unknown teruel fault from detailed mapping and trench analysis and discusses its kinematic and dynamic relationships with the concud fault four individual events occurred between 76 0 ka and 9 2 ka bp have been recorded at two branches of the teruel fault unfortunately these only represent a small fraction of its overall activity during such time lapse and their time constraints do not allow correlating them with those at the concud fault the teruel and concud faults are independent structures from the geometric and kinematic point of view as evinced by their distinct i transport directions n275 e and n220 e respectively and ii average coseismic displacements 0 5 m and 1 9 m respectively these displacements are consistent with their respective lengths 9 0 km and 14 2 km and significantly smaller than those expected for a hypothetically joint concud teruel 23 km long fault however their displacement gradients close to the relay zone indicate that both faults undergo dynamic interaction thus suggesting a transient stage from independence to linkage we hypothesize that slip on both structures occurred at the scale of the seismic cycle in a broadly alternating manner which induced strain partitioning between them and allowed accommodating bulk biaxial extension in the region such deformation pattern would have increased the earthquake frequency with respect to the scenario of a hypothetically linked concud teruel fault but diminished the potential seismic magnitude

stratigraphy and tectono sedimentary evolution of the late ordovician to middle devonian gaspe belt in northern new brunswick evidence from the restigouche area the gaspe belt in the restigouche area comprises three successions separated by a late silurian salinic disconformity and an early devonian angular unconformity the lower upper ordovician to lower silurian sequence consists of siliciclastic turbidites of the boland brook and whites brook formations grog brook group overlain by calcareous turbidites of the pabos and white head formations matapedia group and slope and shelf deposits of the upsalquitch and limestone point formations lower chaleurs group above the salinic disconformity the upper chaleurs group and the dalhousie group record a transgressive regressive cycle the former comprises pridolian carbonate rocks of the west point formation and overlying pridolian to lochkovian sedimentary rocks of the indian point formation the chaleurs group is conformably overlain by lochkovian to early emsian subaerial volcanic rocks of the dalhousie group val d amour formation which is unconformably overlain by alluvial lacustrine deposits of the late emsian campbellton formation acadian orogenesis began during the emsian and is characterized by open to closed folding heterogenous cleavage development and reverse and strike slip faults the salinic orogeny is manifested in extensional block faulting within plate volcanism and uplift and deep erosion of early silurian strata early devonian high level intrusion of the matapedia group white head clasts in indian point conglomerate and thermal maturation data all indicate an extended period of late silurian early devonian uplift in parts of the restigouche area thermal maturities of west point and indian point strata are within the oil and condensate windows and suggest potential for hydrocarbons in the study area

paleogeography of the matapedia basin in the gaspe appalachians initiation of the gaspe belt successor basin the matapedia basin consists of the uppermost ordovician lowermost silurian deep water fine grained carbonate siliciclastic rocks of the honorat garin formation and matapedia groups pabos and white head formations the lower rock assemblage of the gaspe belt in the gaspe appalachians paleogeographic maps of eight time slices from the caradocian to the llandoverian are presented to better understand the tectonosedimentary evolution of the matapedia basin deposition evolved from siliciclastic garin fm to argillaceous limestones pabos fm to limestones white head fm the overall change from terrigenous garin fm to limestone facies white head fm reflects a change in the source area paleocurrent directions and composition of sandstones indicate an orogenic source area to the south for the garin formation which is believed to be the inliers of the humber and dunnage zones in the southern gaspe and new brunswick appalachians lime muds deposited by turbidity currents coming from the nor

the application of illite crystallinity organic matter reflectance and isotopic techniques to mineral exploration a case study in southwestern gaspe quebec epigenetic copper deposits paleothermal anomaly burial metamorphism to anchimetamorphic grade and were subsequently reheated hydrothermal convection systems modified journal abstract

syn deformation temperature and fossil fluid pathways along an exhumed detachment zone khao khwang fold thrust belt thailand abstract shale detachment zones their influence on deformational style and their internal mechanisms of deformation are an understudied aspect of fold thrust belts properties such as deformational temperature lithology and mineralogy are often recognized as having a key influence on the rheology and deformational style of detachment zones and overlying fold thrust belts however little work has been conducted on rock properties of known detachment zones a recently described upper level detachment zone in the exhumed khao khwang fold thrust belt of central thailand provides an ideal natural laboratory for investigation of the deformation conditions of the detachment zone and association with its complex deformational style the low grade metamorphic indicator illite crystallinty is used to broadly constrain deformational temperatures while oxygen and carbon stable isotope analysis provides insight into fluid flow history and fluid rock interaction illite crystallinity data indicate deep diagenetic to low anchizonal conditions and temperatures of 160 210 c in the shale detachment interpreted as reflecting peak metamorphic conditions during the triassic indosinian orogeny no trend between the intensity spacing complexity of structures and illite crystallinty is observed however shale shear zones of continuous style deformation and inferred higher finite strain display uniformly higher illite crystallinty than surrounding packages of discontinuously faulted shales we also note a positive association between total organic carbon content in the shales and the spacing and complexity of deformational structures data from limestones and syn tectonic vein fills detail the history of fluid rock interaction during early mesogenesis through to orogenesis the early covariant trend of increasingly negative 13 c and 18 o values is attributed to increasing burial while a divergent orogenic trend of increasingly negative 18 o values is interpreted as the result of a loss of matrix permeability and interruption of fluid rock re equilibration these hottest fluids were concentrated along large thrusts which facilitated fluid movement during orogenesis

interlaboratory standardization and calibration of day mineral crystallinity and crystallite size data clay mineral crystallinity and crystallite domain size data determined by x ray diffraction xrd are methods extensively used in the characterization of very low grade metamorphic conditions however the lack of sufficient interlaboratory standardization has made comparisons between different research groups unreliable due to significant variations in numerical results obtained a consequence of the different machine conditions measurement methods and sample preparations used during analysis a calibration approach to the standardization of data using rock chip standards is presented which allows data sets produced by different research groups to be directly and quantitatively compared a standardized scale the crystallinity index standard cis is proposed with illite crystallinity anchizonal boundary limits of 0 25d 2 and 0 42d 2 and equivalent illite crystallite sizes of 52 and 23 nm respectively determined by the warren averbach method calibrating both old and new data will enable more reliable comparisons between similar and contrasting geological environments and should improve the accuracy and reliability of correlations made between xrd data and other indicators of very low grade metamorphism hence increasing the value of such clay mineral studies

redox change in sedimentary environments of triassic bedded cherts central japan possible reflection of sea level change middle triassic radiolarian bedded cherts in the mino belt central japan include a sequence showing an abrupt facies change from the lower to the upper where grey black bedded cherts enriched in carbonaceous matter and framboidal pyrite are overlain by brick red hematitic bed ded cherts brownish yellow chert enriched in goethite and purple red chert occur at the boundary between the grey black bedded cherts and the brick red bedded cherts this facies change is in accor dance with stratigraphic variations of geochemical characteristics the lower section grey black bedded cherts compared with the upper section brick red bedded cherts are enriched in ctot and stot and are characterized by lower mno tio 2 higher feo fe 2 o 3 total iron as fe 2 o 3 and more variable fe2o3 tio2 values some of the lower section samples in addition are characterized by an enrich ment in some transition metals ni cu and zn the covariation of mineralogical and geochemical characteristics indicates that sedimentary environments and diagenetic processes were different between the lower and the upper section bedded cherts during the deposition of the lower section bedded cherts the sedimentary environment was anoxic and bacterial sulphate reduction occurred during the early diagenetic stage in contrast the upper section bedded cherts were subjected to less reducing diagenetic processes active sulphate reduction did not occur the change of sedimentary environment and diagenetic process at the site of deposition is likely to be attributed to the fluctuated concentration of dissolved oxygen in the water mass of a semi closed marginal ocean basin which was potentially caused by sea level change that occurred during middle triassic time

the evolution of illite to muscovite mineralogical and isotopic data from the glarus alps switzerland thirty five illite and muscovite concentrates were extracted from triassic and permian claystones shales slates and phyllites along a cross section from the diagenetic alpine foreland tabular jura and borehole samples beneath the molasse basin to the anchi and epimetamorphic helvetic zone of the central alps concentrates and thin sections were investigated by microscopic x ray infrared mossbauer thermal dta and tg wet chemical electron microprobe k ar rb sr 40ar 39ar and stable isotope methods with increasing metamorphic grade based on illite crystallinity data xrd and ir the following continuous changes are observed i the 1md 2m1 polymorph transformation is completed in the higher grade anchizone ii k2o increases from 6 8 wt diagenetic zone to 8 5 10 anchizone to 10 11 5 epizone reflecting an increase in the total negative layer charge from 1 2 to 2 0 iii a decrease of the chemical variation of the mica population with detrital muscovite surviving up to the anchizone epizone boundary iv a shift of an endothermic peak in differential thermal curves from 500 to 750 c v k ar and rb sr apparent ages of the fraction 2 m decrease from the diagenetic zone to the epizone k ar ages being generally lower than rb sr ages the critical temperature for total ar resetting is estimated to be 260 30 c k ar and rb sr ages become concordant when the anchizone epizone boundary is approached the stable isotope data on the other hand show no change with metamorphic grade but are dependent on stratigraphic age these results suggest that the prograde evolution from 1 md illite to 2m1 muscovite involves a continuous lattice restructuration without rupture of the tetrahedral and octahedral bonds and change of the hydroxyl radicals however this is not a recrystallization process this restructuration is completed approximately at the anchizone epizone boundary the isotopic data indicate significant diffusive loss of 40ar and 87sr prior to any observable lattice reorganization the restructuration progressively introduces a consistent repartition of ar and k in the mineral lattices and is outlined by the 40ar 39ar age spectra concordant k ar and rb sr ages of around 35 30 ma with concomitant concordant 40ar 39ar release spectra are representative for the main phase of alpine metamorphism calanda phase in the glarus alps a second age group between 25 and 20 ma can probably be attributed to movements along the glarus thrust ruchi phase while values down to 9 ma in regions with higher metamorphic conditions suggest thermal conditions persisting at least until the middle tortonian

palinspastic restoration of a post taconian successor basin deformed within a transpressive regime northern appalachians restoration of transpressional orogens requires a three dimensional analysis of the strain state in order to take into account both the pure shear and simple shear components of the deformation and assess their relative contribution throughout the deformation history restoration of the post taconian successor basin the gaspe belt located within the external part of the acadian orogen in the canadian appalachians was performed by using a step by step method based on the successive removal of strain increments the pure shear component contributed 70 of the total strain during the first stages of the deformation whereas the simple shear component contributed 30 of the total strain during the last stages three retrodeformation steps are defined starting with restoration of the last deformation stage and working back to the first deformation stage the first step is to restore slip along acadian strike slip faults the second step is to restore shortening related to the horizontal extension during the acadian regional simple shear event finally the third step is to restore vertical extension related to the pure shear event by removing slip along the reverse faults unfolding and removing internal strain associated with cleavage development retrodeformation of the simple shear component of the transpressive deformation during the first two steps is performed on a horizontal view of the gaspe belt basin which contains the horizontal extension direction and which is perpendicular to the acadian nw se directed compression likewise restoration of the pure shear component is performed in vertical sections which contain the vertical extension and which are perpendicular to the acadian nw se directed compression the palinspastic map presented here is a much more appropriate base map for the basin and allows for a more realistic paleogeographic interpretation of the gaspe belt

physical and chemical growth conditions of ordovician organogenic deep water dolomite concretions implications for the δ18o of early palaeozoic sea water the estimated depth of formation of authigenic dolomite concretions in the middle ordovician cloridorme formation quebec ranges from 350 mbsf 25 17 porosity in the lower ordovician levis formation outward decreasing 13cvpdb values 10 2 0 8 suggest precipitation in the methane generation zone with an increasing contribution of light carbonate derived by advection from thermocatalytic reactions at depth anomalously low 18ovpdb values centre to margin variations of 0 4 to 7 5 give reasonable temperatures for the concretion centres only if the 18o of ordovician sea water was negative 6 and the bottom water was warm 15 c the 3 5 lower values for the concretion margins compared with the centres can be explained if in addition volcanic ash alteration organic matter decomposition and or advection of 18o depleted water lowered the 18o of the pore water further by 2 0 4 0 during the first 25 200 m of burial reasonable growth temperatures for the margins of 17 20 c are compatible with a lowering of the isotopic ratios by 1 to 1 3 as a temperature effect the systematic concentric isotope zonation of the concretions suggests that the well ordered near stoichiometric dolomite is a primary feature and not the result of recrystallization diagenetic dolomite beds of the cloridorme formation appear to have formed by coalescence of concretions as shown by randomly sampled traverses that indicate formation at different subsurface depths growth of the cloridorme dolomites was probably limited by calcium availability at least 50 of which was derived from connate water and the remainder by diffusion from sea water dolomite precipitation was favoured over calcite by very high sedimentation rates the abundance of marine organic matter in the host sediment and a correspondingly thin sulphate reduction zone deep seated concretion growth in the levis formation required either internal sources for the participating ions carbonate dissolution event or porewater advection along faults

diagenetic and low grade metamorphic terranes of gaspe peninsula related to the geological structure of the taconian and acadian orogenic belts quebec appalachians illite crystallinity ic measurements determination of the proportion of 2m mica polytypes and organic matter reflectance measurements establish regional diagenetic low grade metamorphic trends for the taconian and acadian belts of gaspe peninsula ic varies as a function of many factors besides maximum burial temperature and heating time correlation between ic and 2m illite polytypes for the fortin group and temiscouata formation suggests i that the amount of high grade detrital mica in the samples is low and ii that ic can be used with some confidence as an estimator of regional thermal maturation levels correlation of these parameters with available organic reflectance values further supports this assumption the illites of the temiscouata and western fortin groups are mostly phengitic in composition whereas in the eastern outcrop belt they are more mg and fe rich celadonitic but generally also of lower grade and lower 2m content the d 060 values for illites measured on the unorientated 2 m fraction of samples fall between 1 502 and 1 503 a range 1 500 1 504 a indicating relatively low octahedral occupancy by mg and fe between one fifth and one third of the available spaces pyrophyllite and paragonite were not detected chlorites are fe rich and ripidolitic the ic map for the acadian belt of the peninsula displays general congruence between ic contours 2200 sample points and structural trends for the 27 000 km2 area the highest grades anchimetamorphic are associated with the oldest rocks honorat and matapedia groups exposed in the cores of major anticlines anchimetamorphic grades associated with the western outcrop belt of the lower devonian fortin group require 7 8 km of subsidence to accommodate sufficient thickness of overlying younger rocks on top of 4 5 km of fortin group deep water clastics to explain the grades in terms of burial metamorphism assuming a geothermal gradient of 30 c km 1 the lowest grade diagenetic rocks occupy a large area in the northeastern part of the peninsula smaller areas in the northwestern part of the acadian belt in the centre of chaleurs bay synclinorium and in the ordovician mictaw group the contact between the taconian and acadian belt is marked by a distinct maturation discontinuity the grand pabos fault juxtaposes rocks of contrasting maturation levels matapedia group against fortin group in the west but shows no maturation offset further east in the honorat group the fault zone limiting the fortin group in the north is also associated with a major ic jump

taconian and acadian transpression between the internal humber zone and the gaspe belt in the gaspe peninsula tectonic history of the shickshock sud fault zone the shickshock sud fault has a history of ordovician taconian silurian salinic and devonian acadian movements taconian deformation involving ductile dextral oblique slip faulting is recorded in cambrian rocks in the footwall of the shickshock sud fault metabasalt and metaarkose at amphibolite grade are converted into phyllonite and mylonitic schist shear bands asymmetric garnet porphyroclasts c s fabrics and mica fish textures indicate dextral shearing the regional sense of shear is top to west and southwest on generally southeast dipping shear zones hornblende of metabasalt yielded an 40ar 39ar age of 455 9 2 ma and muscovite from the mylonitic schist yielded an 40ar 39ar age of 454 3 0 9 ma which indicate metamorphism and deformation during the taconian orogeny evidence for silurian activity is indicated by the salinic unconformity to the south related to normal block faulting deformation features in the ordovician and silurian devonian rocks in the hanging wall were predominantl

along strike acadian structural variations in the quebec appalachians consequence of a collision along an irregular margin the quebec appalachians have been shaped by two major orogenies the middle to late ordovician taconian and the middle devonian acadian thrust faults and nappe structures characterized the taconian deformation throughout the quebec appalachians whereas structural styles pertaining to the acadian orogeny differ from southern quebec to the gaspe peninsula structural analysis of late ordovician to middle devonian supracrustal rocks shows two different acadian deformational regimes strike slip tectonics in the gaspe peninsula and thrust or dip slip tectonics in southern quebec in southern quebec acadian regional deformation produced folds which vary from upright to overturned and tight to isoclinal from the nw to the se major faults e g la guadeloupe are northwestward directed thrust faults marked by highly ductile shear zones outlined by mylonite in the gaspe peninsula structural trend is ne and major e w dextral strike slip faults transect this trend folds are open and upright inclined and tighter near the major faults where they have a clockwise rotation like the regional cleavage major faults e g grand pabos follow corridors delimiting high strain zones where the fabrics developed are indicative of a ductilebrittle regime of deformation in the temiscouata region major structural features of both southern quebec and the gaspe peninsula are recognized structures of this region consist of ene trending dextral strike slip faults and high angle wnw verging reverse faults parallel to major nne folds these structures reflect the transition from purely horizontal movement along major strike slip faults of the gaspe peninsula to vertical movement along thrust faults in southern quebec acadian structural variations within the quebec appalachians are interpreted in terms of a continental collision of gondwana along the irregular margin of laurentian and its taconian accreted terranes

a lost arc back arc terrane of the dunnage oceanic tract recorded in clasts from the garin formation and mccrea melange in the gaspe appalachians of quebec upper ordovician garin conglomerates base of the gaspe belt quebec appalachians contain three igneous clast populations 1 calc alkaline intermediat felsic rocks resemble exploits new brunswick maine and notre dame quebec newfoundland subzone lavas clasts monzonite rhyodacite give u pb zircon ages between 465 and 466 ma precluding correlation with exploits rocks we suggest that the suite represents peri laurentian continental arc magmas coeval with the red indian lake group of newfoundland correlation of lavas from a gaspe well with the popelogan arc implies that the red indian line passes through southern gaspe 2 mafic tholeiitic to alkaline clasts resemble new brunswick and maine exploits subzone alkaline lavas we interpret them as magmas associated with initiation of a back arc basin possibly on the laurentian margin 3 mafic intermediate tholeiitic to calc alkaline clasts have an oceanic subduction component and correlate with notre dame subzone lavas quebec newfoundland they are interpreted as products of spreading and off axis magmatism of a peri laurentian back arc basin we correlate mccrea melange lavas to the calc alkaline intermediat felsic and mafic intermediate suites and interpret them as samples of a notre dame subzone terrane coeval with the red indian lake group of newfoundland during initiation of a successor arc back arc a terrane which is no longer preserved in new brunswick and maine but that provides some evidence for possible extensions of newfoundland9s geology into the gaspe appalachians of quebec a mid ocean ridge basalt like intrusion in the mccrea melange ar ar age 471 2 11 2 ma is coeval with peri laurentian ophiolites in newfoundland and may record a back arc opening event

diagenesis and very low grade metamorphism of the antalya unit mineralogical evidence of triassic rifting alanya gazipasa central taurus belt turkey the paleozoic lower mesozoic formations of the antalya unit in southern turkey comprise diagenetic sediments shale mudstone shale siltstone sandstone and scarce spiculite together with very low grade metamorphic lithologies slate metamudstone metasiltstone metasandstone and metalimestone these diagenetic and metamorphic lithologies are dominant in the northern demirtas alanya and southern gazipasa parts of the unit respectively the main minerals of the meta sedimentary rocks are phyllosilicates 2m1 1md 1m illite ia chlorite c v c s i s quartz plagioclase calcite and dolomite the cambrian cretaceous units of the antalya unit differ from the devonian cretaceous northern bolkardagi and aladag units with respect to age lithology and phyllosilicate assemblage but show a considerable similarity to the metamorphic permian triassic mahmutlar nappe of the alanya unit in their phyllosilicate paragenesis although the antalya and precambrian tertiary geyikdagi units seem to have similar lithologies and phyllosilicate associations there are some distinct mineralogical differences such as phyllosilicate polytypes and degree of diagenetic metamorphic alteration ophiolitic fragments olistostromal lithologies phyllosilicate parageneses illite polytype variations anchi epimetamorphic illite crystallinity and relatively low b values suggest that the paleozoic lower mesozoic parts of the antalya unit were metamorphosed in anticlockwise p t t paths in a rifting associated extensional basin the grade of diagenetic metamorphic alteration increases from north to south in the antalya unit related to the higher heat flow due to the southward deepening of the basin vertical diagenetic metamorphic inversion between the lower paleozoic and triassic units is related to higher the heat flux which affected the triassic sediments rather than to thrust tectonics

calibration of the anchizone a critical comparison of illite crystallinity scales used for definition instrumental settings for determination of illite muscovite crystallinity half height width of the 10 a x ray diffraction peak and the limits of the anchimetamorphic zone adopted by various authors fall into several groups the variation in the limiting peak widths between the authors that have adopted kubler s neuch tel boundary values of 0 42 and 0 25 2 can be interpreted in terms of variation in the instrumental settings the choice of time constants higher than those given by the formula causes peak broadening this effect is particularly marked at high scan rates the peak broadening is by constant increments that are virtually independent of the absolute peak width the differences between the kubler neuch tel derived limiting values and some other scales are appreciably greater than can be accounted for by these differences in instrumental settings many of these scales are not equivalent in particular the limits adopted by dunoyer de segonzac 1969 and subsequent workers at strasbourg are too broad their anchizone represents a range of grades of metamorphism lower than that of kubler widely overlapping the latter s diagenetic zone those adopted by some other mainly french authors are too narrow the limits of the anchizone should be calibrated by inter laboratory standards and the instrumental settings should be specified in full

formation of corrensite chlorite and chlorite mica stacks by replacement of detrital biotite in low grade pelitic rocks transmission and scanning electron microscopy were utilized to investigate the nature and mechanisms of alteration of abundant detrital biotite of volcanic origin and progressive modification of phyllosilicate aggregates in a prograde sequence of pelitic rocks illite crystallinity index 0 19 0 58 a28 from the gasp6 peninsula in quebec detrital biotite has been diagenetically altered to form corrensite and chlorite through two mechanisms 1 layer by layer replacement gave rise to interstratification of packets of layers and complex mixed layering via several kinds of layer transitions between biotite and chlorite corrensite or smectite 2 dissolution transport precipitation resulted in the formation of relatively coarse grained aggregates of randomly orientated corrensite rich flakes and fine grained corrensite intergrown with chlorite and illite in the matrix the data show that stacks consisting of alternating packets of trioctahedral and dioctahedral phyllosilicates originated during early diagenesis when lenticular fissures in strained altering biotite were filled by dioctahedral clays subsequent prograde evolution of dioctahedral clays occurred through deformation dissolution and crystallization and overgrowth illite evolved to muscovite with k in part provided through biotite alteration and corrensite chlorite to homogeneous chlorite the alteration of detrital biotite is closely related to the formation of titanite and magnetite in diagenetic rocks and pyrite calcite and anatase or rutile in the higher grade rocks the observations demonstrate that detrital biotite of volcanic origin may be the principal precursor of chlorite in chlorite rich metapelites originating in marginal basins the mineral parageneses suggest that the transitions from corrensite to chlorite and illite to muscovite may be a function of local chemistry and time