collapse of the thickened variscan crust in the french massif central mont pilat extensional shear zone and st etienne late carboniferous basin abstract a large scale extensional shear zone is described from the mont pilat area in the northeastern part of the french massif central this shear zone is about 2 km thick and is characterized by well developed n dipping foliation and stretching lineations deformation occurred under conditions of retrograde metamorphism from high temperature conditions to greenschist facies it is superimposed on a composite foliation related to the earlier variscan 380 350 ma compressional events associated with southward emplacement of nappes and hp mt metamorphism regional n s lineations and shear criteria observed at a regional scale indicate a northward displacement of the hanging wall during extension large strains locally recorded in thick mylonitic zones suggest that displacement was substantial some tens of kilometres late superimposed extensional brittle deformation and pseudotachylites show that northward displacement on normal faults continued at a shallower depth a large granitic pluton granite du velay intruded late in the the variscan orogeny was associated with extension some small leucogranitic syntectonic melts were emplaced within the shear zone and are strongly deformed geochronological rb sr data on these leucogranite bodies give an age of 320 ma and 40 ar 39 ar dating of synkinematic biotites from gneissose rocks in the shear zone yields a plateau age of 313 ma these data show that extensional ductile deformation and magmatism were still active during the latest late carboniferous thus extension occurred immediately after the well known late palaeozoic collision type compressional tectonics which had significantly thickened the crust we propose that the extensional tectonism described here is due to the gravitational collapse of the initially thick variscan crust the stephanian intracontinental sedimentary basin of st etienne was formed along the hanging wall of the normal shear zone during the late stages of this post orogenic crustal extension

simulations of low level convergence lines over north eastern australia we describe high resolution numerical model simulations of low level convergence lines over north eastern australia using the pennsylvania state university national center for atmospheric research mesoscale model mm5 the simulations are for selected events that were documented during the gulf lines experiment held in september october 2002 the calculations provide further insights into the dynamics of the convergence lines and the mechanisms involved in their formation in particular they show two clearly distinct convergence lines one that corresponds to the morning glory and one which corresponds to the north australian cloud line the former originates from the east coast sea breeze over cape york peninsula south of about 14 s while the latter originates from the east coast sea breeze north of this latitude they support also a recently proposed conceptual model for the generation of southerly morning glories and show for the first time the separation of a bore like disturbance following the collision of a nocturnal cold front to the south of the inland trough with a sea breeze front to the north of the trough moreover they show the progressive transition of the east coast sea breeze front and the inland cold front from gravity current like flows to bore like disturbances overnight to form north easterly and southerly morning glories respectively copyright 2006 royal meteorological society

petrological constraints and pt path of devonian collapse tectonics within the scandian mountain belt western gneiss region norway in norway post caledonian extension controlled the formation and sedimentation of middle devonian sedimentary basins these collapse basins were deposited along a low angle extensional detachment fault on top of caledonian high grade metamorphic rocks of the western gneiss region this paper concerns the petrological analysis of eclogite and high pressure micaschist collected within the extensional shear zone study of gneisses and micaschists surrounding these high pressure rocks allows description of the complete pt path which characterized this area application of appropriate geothermometers and geobarometers confirms that the retrograde evolution following high pressure conditions ll 15kbar at 500 600 c was characterized by nearly isothermal decompression followed by amphibolite facies metamorphism the shape of the pt path is compared with theoretical models of thermal evolution of continental orogenic crust during uplift we can observe an increase in temperature during the first stages of decompression smaller than predicted by the models considering the evidence for extensional tectonic in the study area we propose to explain such a small increase in temperature during the decompression by the intervention of extension which accelerates the collapse process and reduces the late orogenic heating of the caledonian thickened crust

eastward propagating undular bores over cape york peninsula abstract the existence of eastward propagating bores over cape york peninsula is shown from data obtained during the gulf lines experiment glex conducted during september and october 2002 and from numerical modeling experiments the disturbances were detected regularly at two stations observable on 24 days during the 40 day experiment the passage of a typical disturbance exhibits a sudden increase in pressure of around 1 hpa often accompanied by undulations and a change in the wind speed and direction from an easterly to a westerly flow disturbances were not observed during days of strong easterly flow a two dimensional nonhydrostatic mesoscale model is used to examine the formation of these disturbances it is shown that the west coast sea breeze is shallow and does not penetrate far inland because of the opposing low level easterly flow in contrast the east coast sea breeze is deeper and is less stable because it is modified by daytime convective mixing as it crosses the peninsula as the east

shrimp zircon geochronology and geochemical characteristics of metaplutonic rocks from the south western gyeonggi block korea implications for paleoproterozoic to mesozoic tectonic links between the korean peninsula and eastern china abstract the hongseong area in the south western gyeonggi block of the korean peninsula consists of several precambrian complexes that were regionally metamorphosed during the triassic collision between the north and south china blocks paleoproterozoic and neoproterozoic magmatism and triassic regional metamorphism in the hongseong area suggest a possible tectonic link with the yangtze craton in the south china block the early magmatism in the western hongseong area was neoproterozoic while that in the eastern hongseong area was paleoproterozoic sensitive high resolution ion microprobe shrimp u pb dating of zircon indicates that the neoproterozoic igneous activity occurred at ca 850 830 ma u pb ages of zircon cores and first metamorphic overgrowths in the paleoproterozoic gneisses are indistinguishable 1 88 1 86 ga indicating that the igneous activity and early metamorphism occurred in relatively rapid succession the geochemical signatures indicate an arc tectonic setting for both the paleoproterozoic and neoproterozoic rocks the age and geochemical signatures of the neoproterozoic magmatism can be matched with the neoproterozoic magmatism at the margin of the yangtze craton before amalgamation of the rodinian supercontitnent the paleoproterozoic igneous and metamorphic events may be related to the assembly of the columbian supercontinent both the neoproterozoic igneous rocks and the paleoproterozoic orthogneisses in the hongseong area were regionally metamorphosed in the triassic at ca 235 ma this regional metamorphism is well correlated with metamorphism at the northern margin of the yangtze craton where the qinling dabie sulu uhp metamorphic belt formed due to the triassic collision between the yangtze craton and north china blocks similarities in the overall age distribution and the geographic resemblance between the hongseong area and the northern margin of the yangtze craton show that the hongseong area in the south western gyeonggi block was tectonically linked with the yangtze craton at least since the time of rodinia

collapse of the luzon volcanic arc during onset of arc continent collision evidence from a miocene pliocene unconformity eastern taiwan a regional miocene pliocene unconformity in the coastal range of eastern taiwan provides information about vertical motions that affected the colliding volcanic arc during initiation of arc continent collision the unconformity separates precollisional volcanic and volcaniclastic rocks of the miocene luzon arc and forearc basin from an overlying thick sequence of syncollisional pliocene pleistocene sedimentary rocks derived from the metasedimentary accretionary wedge of taiwan the duration of time represented by the unconformity averages 1 2 m y and locally ranges up to 4 m y the basal unit of the younger syncollisional sequence consists of bathyal mega slump folded mudstone pebbly mudstone and thin bedded turbidites sharp stratigraphic juxtaposition of these deep marine deposits directly above shallow marine limestone and epiclastic rocks upper part of the older arc sequence requires extremely rapid subsidence during initiation of the collisional basin the coastal range unconformity is interpreted to represent a period of latest miocene nondeposition and or erosion in the luzon arc that was related to initial subduction of the eurasian continental margin along the manila trench this period was followed in pliocene time by very rapid subsidence or collapse of the arc platform to 1 2 km water depth there are two dissimilar mechanisms of basin subsidence that may have controlled initiation of the collisional basin 1 extension rifting and crustal thinning in the luzon arc massif to form a series of small rift or pull apart subbasins or 2 flexural subsidence of oceanic lithosphere in a foreland style basin due to crustal loading in the expanding accretionary wedge of proto taiwan although data are insufficient to provide a unique solution the flexural subsidence model is supported by systematic younging of the initial subsidence event from west to east which may record eastward migration of an outer flexural bulge notable differences between the unconformity and paleogeography of the early collisional basin and analogous present day basins in the offshore region to the south suggest that arc continent collision and basin development in eastern taiwan have experienced secular change since late pliocene time

uplift of deep crust during orogenic extensional collapse a model based on field studies in the sogn sunnfjord region of western norway the western gneiss region wgr in norway experienced high pressure metamorphism during silurian devonian continent continent collision the eclogite bearing lower crust is separated from the middle and upper crust by major detachment zones formed during extensional collapse of the orogen formation of the devonian basins is related to the extension the footwall of the detachment zones comprises three structural and metamorphic zones the upper zone zone 1 is characterized by penetrative homogeneous down to the west simple shear developed under retrograde greenschist facies metamorphism zone 2 suffered inhomogeneous simple shear of the same polarity petrography and mineral chemistry data from the lower zone zone 3 show a record of initial eclogite facies metamorphism at 600 c and 16 kbar which was decompressed almost isothermally to amphibolite facies conditions at 550 c and 10 12 kbar both the eclogite and amphibolite facies metamorphism developed in a regime of pure shear with vertical shortening the rapid decompression records an approach of approximately 20 km to the surface related to uplift that was probably the result of the removal of a thickened thermal boundary layer in the mantle lithosphere the pure shear regime which developed initially in the lower crust was truncated by zones of simple shear as the lower crust was uplifted to middle and upper crustal levels extension by simple shear in the upper crust was rooted in the lower crust where extension occurred by pure shear the shear zones in zones 1 and 2 did not penetrate the pure shear regime of the lower crust a considerable amount of tectonic stripping of the orogenic welt predates deposition of the devonian sedimentary basins

collapse basin a new type of extensional sedimentary basin from the devonian of norway pure shear and simple shear models provide interpretations of sedimentary basins formed by extension of crust and lithosphere of normal thickness devonian basins of western norway developed during collapse of the thickened caledonian crust and return to a crust and lithosphere of normal thickness because extension did not thin the lithosphere to less than its normal thickness no thermal subsidence phase followed the initial subsidence

variscan vs alpine tectonothermal evolution of the southern carpathian orogen constraints from 40ar 39ar ages abstract 40 ar 39 ar hornblende and muscovite ages indicate that basement units exposed within all major alpine nappes of the southern carpathian orogen were penetratively deformed and metamorphosed during late variscan carboniferous tectonothermal events subsequent exhumation resulted in cooling from ca 500 c hornblende k ar retention temperature to ca 375 c muscovite k ar retention temperature between ca 320 and 295 ma late variscan exhumation of middle crustal levels is interpreted to have resulted from intracontinental contraction and regional uplift subsequent to variscan continental collision between gondwana derived tectonic elements e g africa and laurussia muscovite ages within mylonite zones suggest that late variscan shear zones were probably associated with a regional shear system that developed along the southern margins of laurussia alpine metamorphic effects within the southern carpathians are generally nonpenetrative and are only significant within narrow zones of retrogression that are interpreted to have formed during initial attenuation of variscan crust associated with formation of the jurassic severin rift

age of the camaguey gold silver district cuba tectonic evolution and preservation of epithermal mineralization in volcanic arcs epithermal precious metal deposits commonly form in middle to late cenozoic volcanic arcs several kilometers above the level at which batholiths are emplaced this relationship has led to the guideline that epithermal deposits should not be sought in volcanic arcs where batholiths are widely exposed the camaguey district in central cuba violates this tenet and provides important insights into arc forming processes that create and expose epithermal deposits the camaguey district hosts the jacinto and florencia low sulfidation vein deposits and the deseada and golden hill high sulfidation prospects all of which are within a few kilometers of the large camaguey batholith some of the deposits such as jacinto lie immediately below a local paleosurface that exposes the batholith and probably formed when rhyolite domes were emplaced onto this surface a second group of deposits such as the deseada high sulfidation system is hosted by volcanic rocks that overlie the camaguey batholith and stand above the paleosurface new ar ar age measurements indicate that jacinto type deposits and prospects cooled through ar ar closure temperatures for adularia and muscovite at about 71 ma and are slightly younger than the widespread granodiorite facies of the camaguey batholith in contrast deseada type deposits and mineralized zones cooled through roughly similar closure temperatures for sericite illite and alunite at about 80 ma which is older than the age of the immediately underlying camaguey batholith these ages are best explained if the camaguey batholith and surrounding volcanic rocks underwent rapid uplift probably by tectonic unroofing to form the paleosurface below which jacinto type deposits formed and if the older deseada type deposits were thrust into place over this surface this tectonic unroofing probably took place in an extensional regime generated during oblique convergence of cuba with yucatan as the greater antilles arc moved north into the caribbean region during late cretaceous time thrusting probably accompanied late stages of this convergence and or later collision with the bahamas bank in eocene time all of the epithermal deposits were covered by late cretaceous eocene sedimentary rocks that have been removed only recently by erosion thus accounting for the preservation of these unusually old epithermal deposits extensional events causing tectonic unroofing are probably common in arcs that undergo oblique convergence and could be an important agent for formation of epithermal deposits in other parts of the world preservation of these deposits might be aided by deposition and later erosion of sedimentary cover related to later collisions

tectonics and geology of porphyry cu au deposits along the eastern sunda magmatic arc indonesia the discovery of the world class cu au deposit at tumpangpitu east java 1 9 gt 0 45 cu 0 45 g t au has reinforced the eastern sunda arc as a significant metallogenic belt that is highly promising for the discovery of major porphyry deposits the arc hosts three premier porphyry cu au deposits at batu hijau elang and tumpangpitu 300 t au and 5 mt cu these giant porphyry deposits are confined to the eastern segment of the eastern sunda arc eastern java to sumbawa constructed on island arc crust where the roo rise is being subducted by contrast major epithermal low sulfidation dominant deposits associated with poorly endowed porphyry prospects occur along the western segment of the arc western java developed on thick continental crust on the southern margin of sundaland associated with subduction of typically thin indian oceanic crust porphyry cu au deposits of the eastern sunda arc are spatially associated with small nested dioritic to tonalitic intrusive complexes with low k calc alkaline to weakly alkaline signatures hypogene alteration and mineralization developed during three main temporally and spatially overlapping events termed early transitional and late the hypogene cu au mineralized zone of the giant deposits forms a bell shaped body of 0 3 cu shell greater than 1 km in both diameter and vertical extent that is centered on multiphase elongate pencil like tonalite intrusions 200 to 1 200 m in diameter and 2 km vertical extent large 20 km 2 lithocaps associated with high sulfidation epithermal systems and postporphyry mineralization diatreme breccias characterize productive porphyry districts at batu hijau elang and tumpangpitu the known porphyry deposits with metal content exceeding 300 t au and 5 mt cu all formed later than 5 ma suggesting an important change in the metallogeny of the arc at this time these giant porphyry deposits formed relatively rapidly typically over a period of 30 to 860 k y during the pliocene pleistocene between 5 and 2 5 ma porphyry deposits along the eastern sunda arc display characteristic geologic features similar to porphyry deposits elsewhere significant differences include low k systems dominance of hydrothermal biotite over k feldspar early intense actinolite alteration associated with ore widespread shreddy chlorite after secondary biotite narrow quartz sericite pyrite alteration zones lack of development of chalcopyrite veins large overlying lithocaps and abundant chalcocite bornite covellite veinlets associated with late overprinting epithermal systems hydrothermal oligoclase is also more abundant than k feldspar in the central biotite magnetite zones

segmentation of the caledonian orogenic infrastructure and exhumation of the western gneiss region during transtensional collapse the ultra high pressure western gneiss region of the norwegian caledonides represents an archetypical orogenic infrastructure of a continent continent collision zone to test established exhumation models we synthesize the geochronology and structures of major basement windows and provide new ages from poorly dated areas migmatite u pb zircon samples date melt crystallization at c 405 ma in the oygarden complex expanding the spatial extent of devonian migmatization micas from shear zones in the oygarden and gulen domes yield 40ar 39ar ages mostly between 405 and 398 ma recording the exhumation of metamorphic core complexes on a larger scale the youngest ages of various geochronometers in different segments of the western gneiss region show abrupt breaks 10 30 myr across low angle detachments and sinistral transfer zones which also correspond to metamorphic and structural discontinuities we explain the segmentation of the orogenic infrastructure by partitioned post orogenic transtension due to lateral and vertical rheological contrasts in the orogenic edifice strong cratonic foreland and orogenic wedge v soft infrastructure differential crustal stretching dragged out deep levels of the orogenic crust below low angle detachments and became progressively dominated by sinistral transfer zones collapse obliterated the syn collisional structure of the orogenic root and resulted in the diachronous exhumation of distinct infrastructure segments supplementary material complete analytical results are available at https doi org 10 6084 m9 figshare c 5241710

reply to comment by p olivier on preorogenic exhumation of the north pyrenean agly massif eastern pyrenees france we make this reply to philippe oliver s comments on the deformation of the mesozoic cover of the northern agly massif

geology and geochemistry of gunung subang gold deposit tanggeung cianjur west java indonesia abstract the gunung subang gold deposit is located in the sunda arc volcanic belt in west java indonesia the ore bodies are associated with volcanic rocks from the miocene koleberes and bentang formation to constrain the significance of the ore genesis and mineralization this study was carried out with the aim of examining the deposit using methods such as detailed field observation petrography petrochemistry zircon u pb dating hf isotope fluid inclusion analysis and sulfur and in situ pb isotope analyses the results suggest the following 1 the volcanic rocks in gunung subang belong to the basalt andesite group with 48 66 79 17 average 61 04 sio2 the trace element patterns of the volcanic rocks exhibit relatively low hree content flat hree patterns and weak negative or positive eu anomalies which are similar to those of typical arc magmatic rocks 2 most zircons selected from the volcanic rocks are magmatic and only a few are inherited the magmatic zircons have a weighted mean u pb age of 17 0 0 4 ma and the inherited zircons are from the precambrian dated at 887 2379 ma the magmatic zircons have ehf t values ranging from 1 24 to 13 59 indicating that the magmatism may be contaminated predominantly with juvenile crust but also with a small percentage of ancient crust 3 the sulfur isotopic compositions are fairly uniform and the 34s values of pyrite galena and sphalerite range from 0 53 to 2 97 suggesting a magmatic origin 4 the pb isotopic compositions of pyrite and galena are clustered and some include relatively high amounts of radiogenic lead the mean ratios of 206pb 204pb 207pb 204pb and 208pb 204pb are 18 59 0 007 15 65 0 007 and 38 89 0 017 respectively indicating that the ore forming material is highly related to miocene to pliocene volcanic rocks 5 fluid inclusions in the quartz from the ores are liquid and vapor liquid phases with components of the nacl h2o system with homogenization temperatures of 240 320 c and salinities of 0 2 6 2 wt nacl the coexistence of vapor and liquid rich fluid inclusions suggests that boiling occurred throughout the deposition of the ore 6 the results of electron probe microanalysis epma indicate that pyrite is the major au bearing mineral combined with the observation of scanning electron microscope sem gold is primarily present as au ag telluride minerals and there may also be native gold au0 finally we consider the gunung subang is an epithermal gold deposit related to the mid miocene magmatism

the evolution of the hornelen basin detachment system western norway implications for the style of late orogenic extension in the southern scandinavian caledonides abstract the geology of the devonian hornelen basin and the surrounding western gneiss region wgr western norway has been examined in detail structural clast provenance and geothermobarometric data have been combined to reconstruct the motion history of part of a major late orogenic extensional shear zone in the southern scandinavian caledonides the nordfjord sogn detachment nsd the nsd in the hornelen basin area is a zone of mylonites 4 6 km thick tectonostratigraphically constrained within the lower and middle allochthons lma and the uppermost part of the wgr it separates eclogite bearing gneisses of the wgr from greenschist and amphibolite facies rocks of the middle and upper allochthons marking a profound metamorphic break and indicating major excision of crustal section kinematic indicators give a consistent top to the west shear sense indicating a reversal of the movement sense of the scandian nappes with the ductile strain being distributed through the entire lma section the wgr was exhumed from depths of up to 100 km in the footwall of the shear zone partly aided by pure shear vertical flattening below the nsd and extension and erosion of the hanging wall the majority of the movements on the nsd in the hornelen basin area occurred under amphibolite facies conditions prior to 410 ma subsequent shear caused limited greenschist retrogression along extensional crenulation cleavages depending on interpretation of mica 40 ar 39 ar ages this lower grade shearing may be due to a continuation of movements or renewal of motion associated with opening of the hornelen basin at about 385 ma the lack of clear evidence of penetrative greenschist facies mylonites in the hornelen area may be due to the faulted omission of tectonites of this grade following scandian a subduction and eclogite facies metamorphism at 425 ma the p t t path of the wgr shows very rapid decompression associated with early slip on the extensional detachment horizons unroofing was initially near isothermal followed by a phase of rapid near isobaric cooling after 410 ma decompression and cooling slowed as slip on the nsd slowed or even ceased by the middle devonian the wgr lay at about 10 15 km depth and the crust had almost returned to isostatic equilibrium at this time a brittle fault splaying from the nsd ramped upwards through the upper allochthon opening a scoop shaped west facing half graben the hornelen basin a further 50 km of heave on the nsd occurred during alluvial infilling of the basin subsequently the basin fill was folded by late devonian n s compression and the basin margins were modified by mesozoic faulting these features are consistent with an orogenic collapse model for southern scandinavia that involves large scale backsliding of the scandinavian caledonides within tectonostratigraphic units by this mechanism the baltic shield could have been efficiently unloaded with tectonic translations producing significant metamorphic breaks within a seemingly preserved tectonostratigraphic sequence the model favours orogenic collapse driven by an external pull rather than internal body forces

low sulfidation epithermal gold deposits in java indonesia characteristics and linkage to the volcano tectonic setting abstract java island a part of the eastern sunda magmatic arc is becoming an emerging part of the region for gold and copper endowment a total of 15 4 of 1044 tons of java gold endowment is originated from low sulfidation ls epithermal deposit type as a matter of fact the mineralization type that has given a significant credit to the gold endowment of java is intriguing to be geologically evaluated this paper is aimed to document some data information and summarizing the characteristics of selected 10 ls epithermal gold deposits in java including cibaliung kerta cisoka cikidang pongkor gunung peti cihar cijaringao petungkriyono and dalang turu as well as discussing their relationship with the volcano tectonic setting the formation of 10 ls epithermal deposits took place in the time span between early miocene and pleistocene which is coincident with the mio pliocene magmatic arc activities and even probably continue on to pleistocene all deposits show typical ls epithermal characteristics i e quartz veins with crustiform colloform textures relatively high au ag au ratio the cibaliung veins seem to have genetic linkage with the dioritic intrusion and diatreme phreatomagmatic breccias as well as with rhyolitic domes in kerta the veins exhibit close relationship with the rhyolitic rhyodacitic plugs the pongkor and cisoka veins are genetically related to rhyodacite dome plugs within caldera setting which is controlled by extensional structures cikidang and gunung peti may be related with the andesitic sub volcanic plugs cihar and cijaringao might be related to andesite dykes petungkriyono is linked with andesite and dacite plugs as well as diatreme breccia formed in an extensional basin with few calderas developed the dalang turu has been considered having a close linkage with andesite plug at extensional structures in relation to the volcano tectonic setting six deposits cibaliung kerta pongkor cisoka cikidang and gunung peti are obviously emplaced in bogor trough a back arc rift basin related to the mio pliocene arc the presence of rhyolitic to dacitic magmatism that could be related with caldera systems e g in kerta pongkor cisoka and the common association with subvolcanic plugs e g kerta are evidences of their linkage to the back arc rift basin setting the basaltic rocks in close proximity with the rhyolite rhyodacite as identified in cibaliung and kerta suggest the bimodal volcanism which is commonly occurred in the back arc rifting environment exploration for ls epithermal prospects therefore should be targeted along the back arc rifting basins e g bogor trough preferably over the areas with bimodal magmatism the bogor trough is reported extending to east java as kendeng trough basin which is also reasonably targeted for exploration

two stage rifting in the north viking graben area north sea inferences from a new three dimensional subsidence analysis abstract backstripping software from the ifp subtec was used to realize a three dimensional subsidence analysis of the norwegian part of the north viking graben for each considered epoch the software produces restored depth maps of the selected stratigraphic horizons as well as tectonic subsidence maps that allows in addition to classical subsidence curve analysis an overview of the spatial evolution of the studied basin the three dimensional data set consists of maps representing the present day geometry of the graben for this study these maps have been established on the basis of a new interpretation of available seismic lines taking into account new information on the time depth conversion and on the age of the different seismic markers data from wells give detailed information on lateral lithological variations sedimentological information and analysis of the geometry of the seismic markers have allowed palaeobathymetry and eroded thickness maps to be established and discussed with a reasonable confidence computed tectonic subsidence maps define three major events and allow discussion of their origin the lower jurassic thermal subsidence in relation to the previous triassic rifting event the jurassic rifting phase and the subsequent cretaceous post rift thermal subsidence and finally a rapid subsidence event at the beginning of the palaeocene thermal modelling provides theoretical subsidence curves the comparison with the observed curves allows testing of and discrimination between several hypotheses about two parameters the age of the first rifting event permo triassic and its relative amplitude with regard to the jurassic event the corresponding stretching factors were compared with the crustal stretching values observed along the nsdp1 seismic profile it appears that the first extensional phase is clearly triassic beginning about 240 ma and that it is characterized by higher stretching factors than the following jurassic phase the ability of different geological processes to produce both the palaeocene subsidence observed in the graben and the contemporaneous uplift of the basin margins is discussed the preferred interpretation involves buckling of the lithosphere in response to the onset of a compressional stress regime at the end of the cretaceous a simple method assuming uniform stretching is proposed for computing maps of stretching factors for both the jurassic and triassic events

travelling waves and bores in the lower atmosphere the morning glory and related phenomena abstract observations of solitary wave and travelling bore like disturbances in the lower atmosphere are reviewed together with relevant theoretical laboratory and numerical studies concerning the structure propagation and genesis of such disturbances primary emphasis is given to a discussion of the morning glory phenomenon in northern australia the example par excellence of these types of disturbance and the best documented observationally to date observations of related phenomena elsewhere are reviewed briefly while such occurrences appear to be less frequent in any single location than in the southern gulf of carpentaria region of northern australia reported occurrences are widespread and there is mounting evidence that such disturbances are more common than is generally supposed the evidence suggests that whenever a suitable wave guide exists for the propagation of disturbances the latter can be generated as the natural response of quite general forcing mechanisms examples being the collision of two sea breezes from opposite directions on a peninsula the interaction between a thunderstorm outflow and a sea breeze front or simply the transformation of a thunderstorm or squall line outflow as it moves into a low level stable layer because of the large vertical displacements they produce the larger amplitude disturbances typically with surface pressure jumps of 1 mb or more must be considered as potential triggers for deep convection if the atmosphere is sufficiently conditionally unstable and the large low altitude wind shears associated with them present a serious hazard to low flying aircraft

metamorphism within the cokkul synform evidence for detachment faulting within the metamorphic infrastructure of the norwegian caledonides 67 30 n within the cokkul synform caledonian metamorphic rocks of the middle koli nappe complex mknc are in low angle fault contact with the basement mylonites derived from the precambrian tysfjord granite gneiss in the synform the mknc is composed of four fault bounded nappes each of which has a distinct tectonic stratigraphy composed of amphibolite facies metamorphosed pelitic and psammitic schists with minor lensoidal bodies of mafic and ultramafic rocks pelitic rocks from the three structurally lowest nappes contain the low variance afm mineral assemblages gar bio staur and staur ky bio with mu qtz ilm whereas staur and ky are absent from the highest nappe the kallakvare nappe afm mineral assemblages in the three lowest nappes indicate peak metamorphic temperatures of 610 660 c and peak pressures in excess of 600 mpa mineral assemblages from the kallakvare nappe are not as diagnostic of metamorphic grade however rocks from that nappe contain coexisting plagioclases from both sides of the peristerite gap suggesting lower grade peak p t conditions than those of the structurally lower nappes in addition biotite from the lower nappes is more ti rich than biotite from the kallakvare nappe however gar bio mu plag and gar bio ky plag qtz thermobarometry suggests that all four nappes equilibrated at approximately 525 25 c and 700 100 mpa gibbs method thermodynamic modelling of garnet zoning profiles suggests that the lower three nappes followed clockwise p t paths that involved heating and compression to a metamorphic peak of approximately 575 625 c 800 mpa followed by cooling and decompression to 525 c 700 mpa p t paths calculated for the kallakvare nappe show decompression and minor heating to a peak t of 500 525 c in the lower nappes staur and ky grew during the heating phase not seen by the highest nappe the outer parts of the paths from all four nappes are approximately parallel possibly recording the emplacement of the kallakvare nappe onto the already stacked lower three nappes at some time following the metamorphic peak these p t paths suggest that the sole fault of the kallakvare nappe is a normal fault garnet zonation thus appears to record a previously unrecognized phase of uplift and tectonic thinning of the mknc this event appears to be restricted to the mknc and to have occurred prior to the emplacement of the mknc onto the tysfjord granite gneiss basement of baltoscandia under greenschist facies conditions it may have been responsible for the uplift and cooling of the mknc from 25 30 km amphibolite facies conditions prior to its emplacement onto baltoscandia under 15 20 km greenschist facies conditions the deformation zone associated with this normal fault is relatively narrow generally less than 1 m thick if this is typical of other detachment faults in the metamorphic infrastructure of the scandinavian caledonides they may be relatively common but not often recognized due to the detailed study needed to document them

palaeogeography and geodynamic evolution of the gosau group of the northern calcareous alps late cretaceous eastern alps austria abstract the sedimentation of the late cretaceous gosau group of the northern calcareous alps records the complex geodynamic evolution of the northern part of the austroalpine microplate the tectonically controlled sedimentation and facies distribution were mainly governed by the oblique subduction of the pennic ligurian ocean below the austroalpine margin most of the gosau successions comprise two distinct sedimentary complexes the lower gosau subgroup upper turonian campanian is characterized by terrestrial to shallow marine facies associations alluvial fan and fan delta deposits shallow marine sandstones and sandy limestones and storm influenced nearshore and shelf deposits during the early santonian sea level highstand a great part of the northern calcareous alps was covered by a shallow shelf sea palaeotransport directions point to source areas situated both to the north and to the south of the northern calcareous alps the upper gosau subgroup upper santonian eocene comprises deep water hemipelagic and turbiditic deposits rapid subsidence into bathyal to abyssal depths started diachronously from the northwest santonian to the southeast maastrichtian after a short phase of deformation and erosion abyssal deposits in the northern parts of the northern calcareus alps and north directed palaeotransport indicate a tilting of the slope towards the north this subsidence pulse is attributed to an event of subcrustal tectonic erosion probably triggered by the subduction of a topographic high of the south penninic ocean the relationships of the gosau group of the austroalpine unit to late cretaceous deposits of the carpathians and southern alps are discussed in the framework of a plate tectonic model

the moho in extensional tectonic settings insights from thermo mechanical models the lithospheric memory is key for the interplay of lithospheric stresses and rheological structure of the extending lithosphere and for its later tectonic reactivation other important factors are the temporal and spatial migration of extension and the interplay of rifting and surface processes the mode of extension and the duration of the rifting phase required to lead to continental break up are to a large extent controlled by the interaction of the extending plate with slab dynamics the finite strength of the lithosphere has an important effect on the formation of extensional basins this applies both to the geometry of the basin shape as well as to the record of vertical motions during and after rifting we demonstrate a strong connection between the bulk rheological properties of europe s lithosphere and the evolution of some of europe s main rifts and back arc systems the thermo mechanical structure of the lithosphere has a major impact on continental break up and associated basin migration processes with direct relationships between rift duration and extension velocities thermal evolution and the role of mantle plumes compressional reactivation has important consequences for post rift inversion borderland uplift and denudation as illustrated by poly phase deformation of extensional back arc basins in the black sea and the pannonian basin region

epithermal gold veins in a caldera setting banska hodrusa slovakia the central zone of the large miocene stiavnica stratovolcano in the western carpathians hosts epithermal au mineralization of intermediate sulfidation type located at deep levels of the historic rozalia base metal mine at banska hodrusa the au mineralization occurs as subhorizontal veins at the base of pre caldera andesites close to the roof of a subvolcanic granodiorite intrusion the veins are dismembered by a set of quartz diorite porphyry sills and displaced by the younger steeply dipping rozalia base metal vein and parallel structures the base metal vein structures are related to resurgent horst uplift in the caldera center the au mineralization formed during two stages based on fluid inclusion evidence both stages formed from fluids of low salinity 0 3 wt nacl eq which underwent extensive boiling at moderate temperatures 280 330 c variable pressure conditions 39 95 bars neglecting the effect of co2 indicate continual opening of the system and a transition from suprahydrostatic towards hydrodynamic conditions at shallow depths 550 m the fluid inclusions of the rozalia base metal vein show homogenization temperature peaks at 285 and 187 c and salinities between 1 and 4 wt nacl eq precipitation of au is considered to be the result of prolonged boiling of fluids and associated decrease in au solubility oxygen and hydrogen isotope data for quartz and carbonate from the au veins show a relatively homogeneous fluid composition 2 7 to 1 1 18o 78 to 62 d the combined 18ofluid and dfluid values suggest a mixed character of fluids falling between the fields of typical magmatic and meteoric water influenced by 18ofluid shift due to fluid rock isotopic exchange end stages of open system boiling and fractionation could have been reached at least locally significantly lower isotopic composition of meteoric fluids associated with au mineralization compared to those associated with the intrusion related mineralizations could have resulted from changing paleoclimate and or analytical problems of extraction of water from fluid inclusions the proposed genetic model for the au deposit at rozalia mine highlights the importance of hydrothermal activity during the early stage of caldera collapse caldera subsidence established new convective fluid flow paths along marginal caldera faults which acted as infiltration zones major metal precipitation occurred within subhorizontal structures that formed as the result of a collapse related stress field a shallow differentiated magma chamber at the base of the volcano was the likely source of heat and magmatic components for the mineralizing fluids

the structure and timing of lateral escape during the scandian orogeny a combined strain and geochronological investigation in finnmark arctic norwegian caledonides abstract determining the timing duration and mechanism of tectonic events within an orogenic cycle such as ocean subduction continent continent collision or gravitational collapse is challenging especially in ancient orogenic belts variations in the tectonic transport direction however can be used as a guide to these stages of orogeny while thrust sheets within the caledonian allochthon in north norway were emplaced broadly eastwards perpendicular to the trend of the orogen many features indicate material transport in other orientations one dominant feature of the mageroy nappe sitting above and infolded with the kalak nappe complex is the development of a strong n s lineation orthogonal to the main transport direction strain measurements in part determined by a new method are used in the context of the regional structural data to identify the critical stage in orogeny when compressional forces are balanced by orogen parallel lateral escape quantitative 3 d strain estimation in the mageroy nappe indicates prolate deformation with c 50 horizontal shortening parallel to the thrusting direction e w and c 200 extension along the orogenic strike n s with c 30 vertical shortening temporal constraint on this fabric is provided by ar ar isotopic analysis of undeformed white mica in cross cutting granitic pegmatites these data show that prolate deformation occurred before the white mica cooling age of 416 4 ma while the previously determined depositional age of the hellefjord schist indicates that it occurred after 438 4 ma a granitic pegmatite that intruded the hellefjord schist after an initial deformation phase but during or prior to a later deformation has been dated at 431 2 ma by u pb zircon a previous lower age constraint on this deformation of 428 5 ma is given by metamorphic zircon overgrowths on fractured grains these results constrain the continental collision between baltica and laurentia in finnmark to the interval c 431 428 ma placed in a regional context these results indicate that lateral escape was orthogonal to the thrusting direction and occurred during the continent continent collision stage in the scandian orogeny before gravitationally driven collapse

the dinevar transtensional pull apart basin nw zagros mountains iran a geological study and comparison to 2d finite element elastic models the dinevar transtensional pull apart basin is a nw se trending basin located in the northwest part of the zagros mountains sanandaj sirjan tectonic zone iran this basin was formed by oblique extension in a strike slip fault system which was controlled by the pre existing sahneh and the mianrahan faults in addition to a field study we constructed a 2d finite element elastic model based on the major fault segments according to the field study various geological structures are formed around the pre existing fault segments including pencil structures with 13 aspect ratio 19 tight to open asymmetric folds oblique normal faults synthetic and antithetic faults normal and reverse fault drags and negative and hybrid type flower structure fe model results show that around the fault step is a zone of displacement gradient that indicates extension transtension within the overlapping zone consequently subsidence is predicted over the releasing fault step the modelled stress distributions within the fault step and around the fault segment tips are asymmetric elastic modelling shows that the mean normal stress within the step is tensional which would impede plastic yield while the region outside the step is characterised by compressive mean normal stress the mean normal stress pattern is characterised by a regional minimum localised inside the extensional step transtension zone and two local maximum and minimum couples formed at the advancing and retreating sides respectively in the fault segment tips the results show that two main subsidence regions depocentres or sub basins form along and in the proximity of the fault segment tips the imposed relative motion is entirely accommodated by creep on the faults which causes plastic strain to accumulate outside the faults mostly localised within the fault step this localised strain between fault segments could initiate connecting faults or reactivate earlier faults generally at high angles relative to the master fault segments as suggested by the stress and strain patterns the rotation and magnitude variation in the stress and strain trajectories reflects heterogeneous deformation in general the dinevar transtensional pull apart basin is characterised by an elongate rhomboidal to trapezoidal shaped geometry the modelled stress distribution and strain localisations within the basin are in general agreement with the locations of fault segments within the dinevar transtensional pull apart basin

structural development and petrofabrics of eclogite facies shear zones bergen arcs western norway implications for deep crustal deformational processes caledonian eclogite facies shear zones developed from grenvillian garnet granulite facies anorthosites and gabbros in the bergen arcs of western norway allow direct investigation of the relations between macroscopic structures and crystallographic preferred orientation cpo in lower continental crust field relations on the island of holsnoy show that the eclogites formed locally from granulite facies rocks by progressive development of 1 eclogite adjacent to fractures 2 eclogite in discrete shear zones 2 m thick 3 eclogite breccia consisting of 80 well foliated eclogite that wraps around rotated granulite blocks and 4 anastomosing subparallel eclogite facies shear zones 30 100 m thick continuous over distances 1 km within the granulite terrane these shear zones deformed under eclogite facies conditions at an estimated temperature of 670 50 c and a minimum pressure of 1460 mpa which corresponds to depths of 55 km in the continental crust detailed investigation of the major shear zones shows the development of a strong foliation defined by the shape preferred orientation of omphacite and by alternating segregations of omphacite garnet rich and kyanite zoisite rich layers a consistent lineation throughout the shear zones is defined by elongate aggregates of garnet and omphacite the cpo of omphacite determined from five axis universal stage measurements shows a strong b axis maximum normal to foliation and a c axis girdle within the foliation plane with weak maxima parallel to the lineation direction these patterns are consistent with deformation of omphacite by slip parallel to 001 and suggest glide along 010 the lineation and cpo data reveal a consistent sense of shear zone movement although the displacement was small localized faulting of high grade rocks accompanied by fluid infiltration can be an important mode of failure in the lower continental crust field relations show that granulite facies rocks can exist in a metastable state under eclogite facies conditions and imply that the lower crust can host differing metamorphic facies at the same depth deformation of granulite and partial conversion to eclogite such as is exposed on holsnoy island may be an orogenic scale process in the lowermost crust of collisional orogens

early to middle paleozoic arc magmatism in the korean peninsula constraints from zircon geochronology and geochemistry abstract the hongseong area of the central southwestern korean peninsula has been tectonically correlated to the qinling dabie sulu collisional belt of the central china orogenic belt here we have presented geochemical and sensitive high resolution ion microprobe shrimp u pb zircon data on the metaigneous rocks from the early to middle paleozoic gwangcheon gneiss located in the middle of the hongseong area our data show u pb ages of ca 450 ma for quartz dioritic gneiss 442 ma for metagabbro 409 407 and 402 ma for tonalitic gneiss 440 ma for intermediate dyke and 401 ma for mafic intrusive the rocks display geochemical features suggesting magma generation within late ordovician ca 450 ma to early devonian ca 401 ma subduction related volcanic arc and subsequent collapsing environment the ages and geochemical characteristics presented in this study correlate well with those of the early to middle paleozoic orogenic belts in the qinling orogenic belt our study provides further insights into the tectonic linkage among paleozoic to triassic east asian continents with evidence for a paleozoic pacific type subduction prior to the triassic alpine type collision

thermochronology constraints for the propagation sequence of the south pyrenean basement thrust system france spain 1 in this work we combined apatite fission track and biotite k feldspar 40ar 39ar ages with tectonic data in the west central part of the axial zone of the pyrenees we discuss the exhumation ages and rates of the neouvielle bordere louron and bielsa variscan granites and their relationships with the timing and sequence of south vergent basement thrusting within the pyrenean orogenic prism the 40ar 39ar ages on k feldspars from the neouvielle massif sample nv7 seem to indicate tectonic movements on the eaux chaudes thrust during the early middle eocene fission track results suggest that the exhumation of the neouvielle massif occurred around 35 ma and exhumation of the bordere louron massif around 32 ma in relation to thrusting on the gavarnie thrust the bielsa massif was exhumed from around 19 ma by out of sequence movements on the bielsa thrust we thus show that whereas most of the pyrenean basement thrust faults here the eaux chaudes gavarnie and guarga thrusts were active in sequence toward the southern foreland from the early eocene to the earliest miocene some of them here the bielsa thrust were activated out of sequence in the hinterland later than the generally accepted aquitanian age for the end of the pyrenean compression finally the apatite fission track modeling indicate a last cooling episode starting around 5 ma which is most certainly related to the pliocene reexcavation of the southern and northern flanks of the pyrenees

late cretaceous exhumation of the metamorphic gleinalm dome eastern alps kinematics cooling history and sedimentary response in a sinistral wrench corridor abstract the metamorphic gleinalm dome eastern alps was uplifted and exhumed within a releasing structure in a sinistral wrench corridor during the late cretaceous the dome is confined by a system of ductile shear zones including low angle normal faults and steep sinistral tear faults which define a large releasing structure with the metamorphic dome in its center the fabrics developed within all ductile shear zones record processes which were operating during decreasing temperatures from initial epidote amphibolite upper greenschist facies conditions with crystal plastic fabrics in quartz to temperatures below ca 300 c with predominantly cataclastic fabrics a cooling path based on 40ar 39ar amphibole 95 4 1 2 ma and muscovite ages 87 6 0 6 84 3 0 7 ma together with sphene zircon and apatite fission track data indicate cooling through ca 500 c at ca 94 ma to below ca 250 200 c at 65 ma subsidence of the adjacent late cretaceous kainach gosau basin occurred synchronously with cooling and uplift of the gleinalm dome internal depositional patterns record rapid subsidence at the time of cooling with internal synsedimentary block rotation above an intra crustal ductile normal fault the sinistral wrench corridor of the eastern alps developed by sinistral displacement of the austroalpine units against a relatively stable europe during the late cretaceous

genetic links between ash flow calderas and associated ore deposits as revealed by large scale thermo mechanical modeling abstract in addition to a number of epithermal ore deposits some porphyry type ore deposits are also hosted by ash flow calderas spatial correlation between ash flow calderas and these deposits is observed in several parts of the world but temporal correlation between the mineralization and the episode of caldera formation remains unclear especially because geochronological data indicate that the mineralization may date to several million years before or after caldera formation because caldera collapse represents only a very short event in a long time scale evolution between a silicic magma chamber and its host rocks we have developed a thermo mechanical model of upper crustal and magmatic system behavior during the pre and post caldera formation stages major petrophysical properties of ash flow caldera related rocks are incorporated into the model which accounts for brittle elasto ductile rheology and heat transfer and reproduces fault initiation and various caldera collapse scenarios large scale mechanisms of initiation of thermal and structural traps for epithermal ore deposits are described in particular we found that the outer sides of caldera border faults are associated with both anomalous heat transfer and a high fracture density the finite size of the insulating intracaldera units forces the accumulated heat excess to be laterally transferred across the border faults in most cases the model predicts y shaped fault geometry which is surprisingly similar to that of mineralized faults in the field variations in lithostatic pressure on the magma chamber roof and in the vicinity of the border faults can reach 10 to 20 mpa with deep overpressured zones close to the inner edge of the chamber corners despite the fact that hydrothermal convection and fluid geochemistry are not included in the model these thermal and mechanical results are believed to constrain the conditions for mineralization processes our results show that in the presence of regional extension the development of caldera border faults may be suppressed to the advantage of deep seated fractures clustered above the central part of the magma chamber thus favoring conditions for the formation of porphyry type ore deposits finally we demonstrate that well before the eruption the gradual emplacement of a hot and large silicic magma chamber may create significant extensional stress in the brittle upper crust resulting in breakup and pre eruptive normal faulting and thus allowing for conditions of pre caldera mineralization

the kyonggi shear zone of the central korean peninsula late orogenic imprint of the north and south china collision abstract the crustal scale kyonggi shear zone of central korea has been identified as a major boundary between the precambrian kyonggi massif in the south and the imjingang belt in the north the latter is an eastward extension of the qinling dabie sulu collisional belt of china field observations and microstructural analysis indicate that the extensional shear zone evolved from a deep crustal ductile regime to a shallow crustal brittle regime associated with a rapid uplift of the kyonggi massif following the late permian early triassic collision between the sino korean and yangtze cratons a rb sr muscovite age documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 norm

shrimp u pb zircon ages of pyroclastic rocks in the bansong group taebaeksan basin south korea and their implication for the mesozoic tectonics abstract the bansong group daedong supergroup in the korean peninsula has long been considered to be an important time marker for two well known orogenies in that it was deposited after the songnim orogeny permian triassic collision of the north and south china blocks but was deformed during the early to middle jurassic daebo tectonic event here we present a new interpretation on the origin of the bansong group and associated faults on the basis of structural and geochronological data shrimp sensitive high resolution ion microprobe u pb zircon age determination of two felsic pyroclastic rocks from the bansong group formed in the foreland basin of the gongsuweon thrust in the taebaeksan basin yielded ages of 186 3 1 5 and 187 2 1 5 ma respectively indicating the deposition of the bansong group during the late early jurassic inherited zircon component indicates ca 1 9 ga source material for the volcanic rocks agreeing with known basement ages the bansong group represents syntectonic sedimentation during the late early jurassic in a compressional regime during the daebo tectonic event the northeast trending regional folds and thrusts including the deokpori gakdong and gongsuweon thrusts with a southeast vergence developed in the taebaeksan basin this is ascribed to deformation in a continental arc setting due to the northwesterly orthogonal convergence of the izanagi plate on the asiatic margin which occurred immediately after the juxtaposition of the taebaeksan basin against the okcheon basin in the late stage of the songnim orogeny thus the deokpori thrust is not a continental transform fault between the north and south china blocks but an intracontinental thrust that developed after their juxtaposition

the age and tectonic significance of dolerite dykes in western norway coast parallel dykes in sw norway primarily of permo triassic age have been linked regionally to the early tectonic evolution of the norwegian continental shelf we demonstrate from palaeomagnetic data mean declination 206 1 inclination 30 1 a 95 11 8 that dolerite dykes in the coastal sunnfjord region of western norway and immediately west of the devonian basins are also of permian c 250 270 ma age and not lower or pre devonian as previously advocated the sunnfjord dykes appear to be contemporaneous with dykes from sw norway at sotra 262 6 ma and the oldest dykes from sunnhordland 260 280 ma and geochemical data attest to a transition from sub alkaline to alkaline magmatism at the dawn of the mesozoic the sunnfjord dykes are not simple records of e w extension and magma intrusion but instead represent significant mid late permian time markers within a complex zone of fault activation and rejuvenation late mesozoic cenozoic magnetic overprinting mean declination 348 6 inclination 68 9 a 95 12 and metamorphic alteration documented by these dykes are directly dependent upon proximity to major e w brittle faults south of the hornelen devonian basin hence some motion and related fluid activity do post date dyke intrusion the e w high angle normal or oblique slip faults can be regionally traced offshore to the oygarden fault zone onshore these faults truncate the hornelen low angle detachment which in turn cuts folded d evonian strata these observations along with evidence for permian and late jurassic cretaceous extension from the nearby dalsfjord region demonstrate important reactivation of a late to post caledonian detachment and high angle fault system in western norway

discussion a unifying model for the torridon group early neoproterozoic nw scotland product of post grenvillian extensional collapse by ge williams and j foden the torridonian succession in nw scotland is a well exposed sequence of sedimentary rocks that record the early neoproterozoic geological evolution of laurentia an excellent review by stewart 2002 summarised the observations on the three main torridonian units the stoer sleat and torridon groups the torridon group deposited between 1000 950 ma was initially interpreted as a rift basin stewart 1982 and williams 2001 but a number of studies rainbird et al 2001 kinnaird et al 2007 and krabbendam et al 2008 have now concluded that it represents a foreland basin positioned in front of the grenville orogen 1200 960 ma in a recent paper in earth science reviews williams and foden 2011 propose instead that the torridon group was deposited in an extensional collapse basin we question this conclusion and take this opportunity to highlight aspects of their new interpretation that we find equivocal

a mesozoic orogenic cycle from post collision to subduction in the southwestern korean peninsula new structural geochemical and chronological evidence abstract the early to middle mesozoic basins distributed sporadically over the korean peninsula preserve important records of the tectonic history of some of the major orogenic belts in east asia here we present a comprehensive study of the structural geochemical geochronological and paleontological features of a volcano sedimentary package belonging to the oseosan volcanic complex of the early to middle mesozoic chungnam basin within the mesozoic subduction collision orogen in the southwestern korean peninsula the zircon u pb data from rhyolitic volcanic rocks of the complex suggest early to middle jurassic emplacement age of ca 178 172 ma harmonious with plant fossil taxa found from the overlying tuffaceous sedimentary rock the geochemical data for the rhyolitic volcanic rocks are indicative of volcanic arc setting implying that the chungnam basin has experienced an intra arc subsidence during the basin expanding stage by subduction of the paleo pacific izanagi plate the jurassic arc related oseosan volcanic complex was structurally stacked by the older late triassic to early jurassic post collisional basin fill of the nampo group by the jangsan fault during basin inversion the late jurassic to early cretaceous k feldspar and illite k ar ages marked the timing of inversion tectonics contemporaneous with the magmatic quiescence in the southern korean peninsula likely due to flat lying or low angle subduction the basin evolution history preserved in the mesozoic chungnam basin reflects a mesozoic orogenic cycle from post collision to subduction in the southwestern korean peninsula this in turn provides a better understanding of the spatial and temporal changes in mesozoic tectonic environments along the east asian continental margin

efemcukuru b rich epithermal gold deposit izmir turkey efemcukuru located in the aegean region turkey is an example of vein type epithermal gold deposit with related stockwork and replacement mineralisation the veins are hosted by late cretaceous paleogene flysch facies rocks of the izmir ankara zone which were intruded by rhyolites from of neogene volcanism gold mineralisation is associated with late pulses of magmatic hydrothermal activity and is present in zones of hydraulic brecciation adjacent to veins or stockwork zones around a dome shaped small intrusion the intrusion and later epithermal mineralisation are both controlled by nw setrending faults and mineral deposits occur along strike with dips 60j to 80j to the northeast individual quartz veins associated with sulphide minerals and mineralised hornblende facies hornfels are other important ore bearing formations the alteration associated with mineralisation is represented mainly by rhodonite rhodochrosite axinite quartz calcite and adularia in veins and stockwork zone and chlorite sericite illite and kaolinite in the wall rock homogenisation temperatures of 200 300 jc reflect emplacement of ore distant from inferred magmatic heat in epithermal environment due to wide range in salinity of the fluids 0 9 eq wt nacl sulphide diversity in the deposit is rather rich than the low sulphidation epithermal systems the fluid inclusion data indicate that a complicated geothermal system existed both the gas data and the microthermometry data indicate that there was fluid mixing each type of mineralisation has been studied with the aim of clarifying the paragenetic relationships among the different minerals arsenopyrite pyrite marcasite sphalerite galena and chalcopyrite are the main minerals with pyrrhotite fahlore group sphene rutile and gold occurring as accessories pyrolusite limonite goethite lepidocrocite covellite chalcocite malachite and azurite are of secondary origin d 2003 elsevier science b v all rights reserved

the trinity pattern of au deposits with porphyry quartz sulfide vein and structurally controlled alteration rocks in ciemas west java indonesia the ciemas gold mining area is located in the sunda arc volcanic rock belt west java indonesia ore bodies are associated with miocene andesite dacite and quartz diorite porphyrite to constrain ore genesis and mineralization significance a detailed study was recently conducted examining these deposits which included detailed field observation petrographic study petrochemistry sulfur isotope analyses zircon u pb dating and fluid inclusion analysis the results include the following findings 1 ore types have been identified as porphyry a quartz sulfide vein and structure controlled alteration rocks 2 in host rocks zircon la icp ms u pb dating of quartz diorite porphyrite amphibole tuff breccia and andesite yield ages of 17 1 0 4 ma 17 1 0 4 ma and 17 5 0 3 ma respectively 3 fluid inclusions in the quartz from ore are given priority to liquid and gas liquid phases and their components are of the nacl h2o system with homogenization temperatures of 240 320 c salinities of 14 17 densities of 0 85 0 95 g cm3 and fluid pressure values between 4 1 and 46 8 mpa corresponding to metallogenic depths from 150 to 1730 m fluid characteristics are identified as similar to those of high sulfur epithermal deposits 4 the sulfur isotopic compositions are notably uniform the 34s values of wall rocks range from 3 71 to 3 85 and the 34s values of ores vary from 4 90 to 6 55 the sulfur isotopic composition of ores is similar to that of the wall rocks indicating a mixed origin of mantle with a sedimentary basement 5 the trace element patterns of different ore types are similar which indicates that they originate from the same source au deposits primarily occurred during the late magmatic activity finally we have set up the regional metallogenic model confirming that this gold deposit in the sunda arc volcanic rock belt belongs to a metallogenic system from porphyry to epithermal type

geochronological and geochemical implications of early to middle jurassic continental adakitic arc magmatism in the korean peninsula abstract sensitive high resolution ion microprobe shrimp zircon u pb ages and whole rock chemical compositions of early to middle jurassic plutons from the central to southern korean peninsula are reported to investigate the effect of paleo pacific plate subduction preserved along the continental margin twenty one plutonic rocks from the yeongnam massif i e sunchang and namwon plutons the okcheon belt jeongup boeun and mungyeong plutons the northeast gangreung pluton and the gyeonggi massif gonam anheung and ganghwa plutons have age ranges from ca 189 186 ma to 177 ma 177 166 ma and 177 173 ma respectively most plutonic rocks have chemical compositions similar to adakites showing high sio 2 45 62 74 96 wt low mgo 0 01 2 84 wt high na 2 o 2 65 4 83 wt high sr y and la yb low y and yb as well as low hfses nb and ta but initial sr ratios 0 7048 0 7262 k 2 o 0 50 5 88 wt and k 2 o na 2 o 0 34 2 1 were unlikely to have been formed by melting of either a thickened and or delaminated lower continental crust or an altered oceanic crust these suggest that the adakitic plutonic rocks in this region resulted from partial melting of an enriched mantle source metasomatized by dewatering from a delaminated flat slab the spatial distributions of this continental adakitic plutonic belt based on the present study together with previously reported geochronological results indicate that magmatic pulses gradually migrated toward the continent across the korean peninsula as a result of slab shallowing caused by periodic slab buckling the similar geochronological and geochemical characteristics petrogenesis and tectonic setting of the plutonic belt spanning the korean peninsula japan eastern china and eastern russia indicate a possible link to an active subduction system that existed during the early to middle jurassic although the products of the plate subduction might differ in different locations along the east asian continental margin

shear zone evolution during core complex exhumation implications for continental detachments abstract the formation of low angle detachments involves exhumation of previously ductile material and fault zone weakening to better understand this relationship we studied a deeply eroded metamorphic core complex which formed in the core of the bergen arcs w norway during caledonian post orogenic collapse multi scale structural mapping in the oygarden complex constrains three structural levels characterized by localized shear upper unit distributed deformation middle unit and a migmatite double dome lower unit all levels show retrogressive e w stretching accompanied by extension parallel recumbent folding albeit with opposing shear senses at upper and middle lower levels the systematic comparison of 23 shear zones constrains the ductile to brittle structural evolution initially high temperatures and partial melting controlled pervasive deep crustal flow and ductile doming during retrogressive shearing lithological heterogeneity controlled strain localization and channelized fluid flow causing retrograde phyllosilicate growth this established a feedback loop of fluid flow fabric weakening and progressive shear localization the interconnection of inherited and newly formed weak phyllosilicate rich layers promoted the formation of bivergent detachments that rapidly exhumed a dome of previously ductile crust retrogressive weakening in a kilometer wide ductile to brittle processing zone may be essential for the formation of continental detachments

devonian extensional tectonics versus carboniferous inversion in the northern orcadian basin the old red sandstone middle devonian orcadian basin was formed as a consequence of extensional collapse of the caledonian orogen onshore study of these collapse basins in orkney and shetland provides directions of extension during basin development the origin of folding of old red sandstone sediments that has generally been related to a carboniferous inversion phase is discussed syndepositional deformation supports a devonian age and consequently some of the folds are related to basin formation large scale folding of devonian strata results from extensional and left lateral transcurrent faulting of the underlying basement spatial variation of extension direction and distribution of extensional and transcurrent tectonics fit with a model of regional releasing overstep within a left lateral megashear in nw europe during late caledonian extensional collapse later inversion probably during the upper carboniferous is characterized by e w to ne sw contraction it induced reactivation of extensional faults as thrusts development of small scale folds and thrusts and right lateral transcurrent movement of the major faults such as the great glen and walls boundary faults

evolution and vertical structure of an undular bore observed on 20 june 2015 during pecan abstractthis study documents the evolution of an impressive largely undular bore triggered by an mcs generated density current on 20 june 2015 observed as part of the plains elevated convection at night pecan experiment the university of wyoming king air with profiling nadir and zenith viewing lidars sampled the south bound bore from the time the first bore wave emerged from the nocturnal convective cold pool and where updrafts over 10 m s 1 and turbulence in the wave s wake were encountered through the early dissipative stage in which the leading wave began to lose amplitude and speed through most of the bore s life cycle its second wave had a higher or equal amplitude relative to the leading wave striking roll clouds formed in wave crests and wave energy was detected to about 5 km agl the upstream environment indicates a negative scorer parameter region due to flow reversal at midlevels providing a wave trapping mechanism the observed bore strength of 2 4 2 9 and speed of 15 16 m s 1 agree

cretaceous paleogeography and paleoclimate and the setting of ski borehole sites in songliao basin northeast china article i nfo as a paradigm of greenhouse climate in earth s history the cretaceous provides significant rock records of global climate changes under conditions of greenhouse climate the songliao basin among the longest dura tion 85 90 m y of continental sedimentary basins provides an excellent opportunity to recover a nearly complete cretaceous terrestrial sedimentary record extensive lake deposits ten kilometers deep and cover ing an area of 260 000 km 2 of the songliao basin provide unique detailed records that can be tied to the glob al stratigraphic time scale thereby improving our understanding of the continental paleoclimate and ecological system the two coreholes at skis and skin sites were drilled into this basin and completed with a total length of 2485 89 m of recovered core that spanned the complete middle to upper cretaceous strata in the basin the unique geological setting of long term continuous subsidence within the largest cretaceous landmass in the world makes the cretaceous songliao basin of northeastern china an ideal place to study cretaceous climate change on the continent this paper reviews the literature on the paleogeography and paleoclimate of the northern east asia and the songliao basin during the cretaceous based on the climatolog ically sensitive deposits oxygen isotope studies and paleontology the climate during the cretaceous in the songliao basin was temperate and humid with relatively abundant rainfall during the period significant changes four cooling three warming and three semiarid events are generally consistent with the oxygen isotope data from east asia and the four cooling events in berriasian valanginian aptian albian early santonian and campanian maastrichtian may be related to potential glaciations in cretaceous

the continental crust contributes to magmatic hydrothermal gold deposit in ciemas west java indonesia constraints from hf isotopes of zircons and in situ pb isotopes of sulfides abstract multiple periods of arc magmatism induced by the subduction of the indian australian plate northward developed on java island and multistage porphyry epithermal metallogenic systems occurred within the late eocene early miocene and the late miocene early pleistocene magmatic belts these porphyry epithermal metallogenic systems have obvious spatial variations in west java there are large populations of low sulfidation type epithermal deposits while east java and its east are characterized by the occurrences of porphyry deposits however the newly discovered ciemas deposit in west java a middle miocene 17 ma porphyry epithermal au deposit provides an opportunity for further understanding the porphyry epithermal mineralization in java to elucidate the controlling factors of porphyry epithermal mineralization in west java we analyzed the hf isotopies of zircons from the igneous rocks and in situ pb isotopes of sulfides galena pyrite arsenopyrite in the ciemas deposit the results show that the zircons ehf t of igneous rocks are uniform with an average value of 11 5 0 39 and the peak value of tdm2 is 1500 1650 ma suggesting the middle miocene arc magmatism in ciemas suffered intense crustal contamination the pb isotopic compositions of sulfides are very uniform and have high amounts of radiogenic lead the mean ratios of 206pb 204pb 207pb 204pb and 208pb 204pb are 39 343 0 059 15 73 0 015 and 18 854 0 025 respectively indicating that the mineralization materials of the ciemas gold deposit mainly originated from ancient continental crust the multistage arc magmatism induced by the subduction of the indian australian plate northward beneath java island control the porphyry and epithermal mineralization in java the middle miocene arc magmatism in ciemas contaminated intensely by the sundaland and the ancient continental crust provides the main metal source for the ciemas deposit in west java

north australian cloud lines abstract a satellite classification and climatology of propagating mesoscale cloud fines in northern australia is presented these cloud fines range from long narrow lines of shallow convection to extensive deep convective squall lines with mesoscale stratiform rain areas these lines are the predominant weather feature during periods of easterly flow over the australian tropics

contribution of remote sensing techniques to the identification and characterization of miocene calderas lesvos island aegean sea hellas remote sensing techniques were combined with field investigations in order to locate and accurately characterize volcanic structures in the 17 my volcanic field of lesvos island which are difficult to recognize due to erosion and faulting landsat thematic mapper landsat tm and satellite pour observer la terre panchromatic spot pan satellite images as well as the digital elevation model dem of the study areas were digitally processed in order to reveal specific geological characteristics related with caldera structures such as topographic caldera rims and floors ring faults areas of hydrothermal alteration drainage networks and lava domes both internal and external to caldera structures six caldera structures have been recognized of which four have been identified for the first time and are reported here sigri mesotopos agra and skalohori calderas the calderas of stipsi and vatoussa have been previously reported in the literature but their revised geometry and dimensions are reported here

characteristics of jurassic continental arc magmatism in south korea tectonic implications abstract study of whole rock geochemical and isotope sr nd characteristics of jurassic plutons from south korea shows differences in chemical compositions that might reflect the jurassic tectonic environments of east asia these plutons are dominated by granites and granodiorites with subordinate intermediate monzodiorite to diorite phases all analyzed samples show depletions in ta nb p and ti and enrichment in large ion lithophile elements characteristic of high k calc alkaline i type granitoids of the active continental margin early jurassic plutons fall into two groups documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontc

low level convergence lines over northeastern australia part i the north australian cloud line observations of dry season north australian cloud lines nacls that form in the gulf of carpentaria region of northern australia and the sea breeze circulations that initiate them are described the observations were made during the 2002 gulf lines experiment glex and include measurements made by an instrumented research aircraft the observations are compared with numerical simulations made from a two dimensional cloud scale model particular emphasis is placed on the interaction between the east coast and west coast sea breezes near the west coast of cape york peninsula the sea breezes are highly asymmetric due to the low level easterly synoptic flow over the peninsula the west coast sea breeze is well defined with a sharp leading edge since the opposing flow limits its inland penetration keeping it close to its source of cold air in contrast the east coast sea breeze is poorly defined since it is aided by the easterly flow and becomes highly modified by daytime convective mixing as it crosses over the peninsula both the observations and the numerical model show that in the early morning hours the mature nacl forms at the leading edge of a gravity current the numerical model simulations show that this gravity current arises as a westward moving land breeze from cape york peninsula convergence at the leading edge of this land breeze is accompanied by ascent which when strong enough produces cloud observations show that the decay of the nacl is associated with a decline in the low level convergence and a weakening of the ascent

kinematic evolution of the lower plate during intracontinental subduction an example from the scandinavian caledonides geophysical data combined with pressure temperature time data form the basis for a reconstruction of the kinematic evolution of the scandinavian caledonides collisional orogenic belt the reconstruction suggests that the early stages of collision between baltica and laurentia involved intracontinental subduction of a minimum of 150 km of baltic continental crust to a depth of at least 100 km the subduction juxtaposed strong laurentian upper mantle rocks in the upper plate against weak baltic crustal rocks in the lower plate continued plate convergence coupled with the buoyancy of the baltic rocks resulted in thrust imbrication of a substantial portion of the lower plate and extrusion of the crustal rocks from the subduction zone thrusting also resulted in incorporation of fragments of the laurentian upper mantle into the baltic crust the reconstruction also suggests that direct interaction between the laurentian and baltic crustal rocks and the time of greatest crustal thickness in the orogen occurred after extrusion of the baltic crust from the subduction zone one implication of this suggestion is that the eclogite coesite assemblage presently exposed at the surface in the hinterland of the caledonides probably formed early in the collision sequence during subduction rather than during the time of greatest crustal thickness the reconstruction also suggests that exposure of the high pressure mineral assemblage was a two phase process involving extrusion from the subduction zone by thrusting during convergence and unroofing by a combination of extension on low angle normal faults and erosion the kinematic model derived for the scandinavian caledonides provides a possible scenario for the evolution of other collisional orogenic belts containing very high pressure mineral assemblages formed in situ in continental rocks and associated ultamafic rocks of mantle origin

adularia in epithermal veins queensland morphology structural state and origin four types of adularia i e sub rhombic rhombic tabular and pseudo acicular are recognised from examination of samples from ten epithermal vein deposits and prospects in queensland based on morphology of the individual crystals further investigation of the structural state of adularia reveals that each group has some specific features in terms of the degree of al si disordering which can be related to various crystallisation conditions and the thermal history sub rhombic adularia is commonly 2 4 mm in size and subhedral with more or less rhombic outlines and has a relatively ordered al si distribution 2t1 0 84 reflecting slow crystallisation conditions adularia of this type in association with coarse grained quartz is predominant at deep levels of epithermal systems where boiling is initiated in an environment of low permeability and the fluid is slightly supersaturated with respect to adularia and quartz tabular adularia characterised by its lath shape and disordered structure 2t1 values ranging from 0 64 to 0 74 is likely to have formed when the fluid moves up to a more permeable environment and starts boiling violently relatively high temperatures and rapidly changing conditions account for its special morphology and disordered structure rhombic adularia showing very small crystal size 0 2 mm with euhedral rhombic form has an intermediate degree of al si ordering pseudo acicular adularia is interpreted as pseudomorphs after carbonate and its high al si ordered structure is attributed to the presence of a carbonate precursor these two types of adularia commonly occur within crustiform and colloform bands in association with high grade ore and chalcedony or fine grained quartz which often displays various recrystallisation textures it is most likely that adularias of these two types are formed when extensive boiling is protracted microprobe analyses indicate the composition of all adularia types close to pure kalsi3o8 sericite and or carbonate altered adularias consistently display more ordered structures suggesting that the post crystallisation thermal regime affects the structural state of altered adularia even at temperatures as low as in epithermal environments

seismic and tectono metamorphic characters of the lower continental crust in phanerozoic areas a consequence of post thickening extension deep seismic profiles of phanerozoic continental crust commonly show a highly reflective lower crust rheological considerations suggest that the seismic fabric of the lower crust can be attributed to the tectonic transposition of various petrological heterogeneities in the main flow plane the variscan provinces of western europe have been affected during phanerozoic times by several extensional and compressional events the geometrical relationships between seismic and geological structures indicate that the layering of the lower crust was acquired during the late carboniferous to permian when the thickened variscan crust was affected by gravitational collapse petrological and geochronological analyses of deep crustal rocks xenoliths and exposed sections indicate that the lower crust has recorded a major high t medium p granulite facies metamorphism during the late variscan extension whereas on the surface upper carboniferous to permian basins were being deposited a similar scenario characterizes other phanerozoic orogenic belts in the caledonian provinces of the british islands the lower crust is seismically reflective it has undergone medium p granulitic metamorphism during the deposition of devonian sedimentary basins at the end of the caledonian orogeny in the same way collapse of the mesozoic belt in the western part of north america is responsible during the cenozoic for pervasive crustal extension whose consequence is a seismic layering of the lower crust accompanied by a low p granulite grade metamorphic event while in the mid and upper crusts low angle ductile normal faults give rise to the basin and range province therefore it is proposed that there is a genetic relationship between 1 post thickening crustal extension 2 low to medium p granulite facies metamorphism of the lower crust and 3 seismic layering of the lower crust

regional transect across the western caribbean sea based on integration of geologic seismic reflection gravity and magnetic data we analyze western caribbean structural styles and depositional controls associated with late cretaceous cenozoic deformational events using a 1600 km 994 mi long regional northwest southeast transect extending from the cayman trough in honduras to northern colombia different structural provinces defined along the transect include 1 the cayman trough and adjacent honduran borderlands marking the north american caribbean transtensional plate boundary characterized by late eocene holocene fault controlled depocenters 2 the nicaraguan rise that includes continental paleocene eocene rocks deposited in sag basins which are overlain by relatively undeformed miocene holocene carbonate and clastic shelf deposits of the northern nicaraguan rise following a late cretaceous convergent phase 3 the colombian basin that includes thick miocene clastic depocenters and the localized presence of upper cretaceous rocks overlying the basement and where much of the subsidence is likely isostatic and flexurally driven given its proximity to the subduction zone of northern colombia 4 the south caribbean deformed belt an active accretionary prism produced by the subduction of the caribbean large igneous province beneath the south american plate which has deformed the cenozoic prism and fore arc section and produced thrust fault controlled accommodation space for upper miocene holocene piggyback deposits and 5 the onshore cesar rancheria basin in northern colombia which has recorded the uplift of its bounding mountain ranges the sierra de santa marta massif to the west and perija range to the east plate reconstructions place the various crustal provinces along the transect into the context of the late cretaceous cenozoic deformation events that can be partitioned into strike slip convergent and extensional components

40ar 39ar mineral dates related to devonian extension in the southwestern scandinavian caledonides abstract middle devonian sedimentary basins exposed in west central norway formed during post caledonian extension they developed along west dipping low angle normal faults which effected ductile shearing of pre caledonian basement units of the western gneiss region wgr kinematic indicators suggest that the west vergent ductile deformation overprinted older east vergent caledonian fabric elements ductile extensional deformation led to development of a 2 km thick shear zone beneath the devonian basins five amphibole and nine muscovite concentrates from rocks within the shear zone and from unaffected gneisses of the western gneiss region have been analyzed with 40ar 39ar incremental release dating techniques in an attempt to calibrate the timing of extensional events well defined plateau ages are recorded by muscovite concentrates within the shear zone amphiboles display disturbed plateau ages clearly related to extraneous argon outside the shear zone muscovite records caledonian ages results suggest that a late tectonometamorphic event affected the rocks within the shear zone this event which not exceed ca 500 c completely rejuvenated muscovite argon systems and perturbed argon distribution within amphiboles this metamorphism is correlated with the extensional deformation which effected exhumation of the caledonian high pressure rocks and controlled formation of devonian basins

the formation of internal bores in the atmosphere a laboratory model summary recently several atmospheric observations have been interpreted as internal undular bores or internal solitary waves evolving from internal bores that propagate along low level temperature inversions it has been speculated that such disturbances are generated by some type of gravity current such as cold fronts sea breeze fronts and thunderstorm outflows interacting with an existing temperature inversion in this paper we describe a systematic laboratory study in a water channel of internal bores and their generation by the movement of gravity currents through a two layer model of the atmosphere we compare the results of our laboratory experiments with previous theories and numerical simulations and with several detailed atmospheric observations of internal bores at different stages of development

phanerozoic high pressure eclogite and intermediate pressure granulite facies metamorphism in the gyeonggi massif south korea implications for the eastward extension of the dabie sulu continental collision zone abstract petrological analysis zircon trace element analysis and shrimp zircon u pb dating of retrogressed eclogite and garnet granulite from bibong hongseong area sw gyeonggi massif south korea provide compelling evidence for triassic 231 4 3 3 ma high pressure hp eclogite facies m1 metamorphisms at a peak pressure temperature p t of ca 16 5 20 0 kb and 775 850 c this was followed by isothermal decompression itd with a sharp decrease in pressure from 20 to 10 kb and a slight temperature rise from eclogite facies m1 to granulite facies m2 followed by uplift and cooling granitic orthogneiss surrounding the baekdong garnet granulite and the ophiolite related ultramafic lenticular body near bibong records evidence for a later silurian 418 8 ma intermediate high pressure ihp granulite facies metamorphism and a prograde p t path with peak p t conditions of ca 13 5 kb and 800 c k ar ages of biotite from garnet granulites amphibolites and granitic orthogneisses in and around the bibong metabasite lenticular body are 208 219 ma recording cooling to about 310 c after the early triassic metamorphic peak neoproterozoic zircon cores in the retrogressed eclogite and granitic orthogneiss provide evidence that the protoliths of these rocks were 800 and 900 ma old respectively similar to the ages of tectonic episodes in the central orogenic belt of china this and the evidence for triassic hp uhp metamorphism in both china and korea is consistent with a regional tectonic link within northeast asia from the time of rodinia amalgamation to triassic continent continent collision between the north and south china blocks and with an eastward extension of the dabie sulu suture zone into the hongseong area of south korea

palaeomagnetic dating of fault rocks evidence for permian and mesozoic movements and brittle deformation along the extensional dalsfjord fault western norway summary palaeomagnetic and structural studies of the dalsfjord nappe western norway show that the basal ow angle detachment dalsfjord fault is a long lived fault zone and that the most important phase of faulting was of devonian extension probably nucleated on an earlier silurian scandian thrust fault rocks produced during subsequent movements indicate that the dalsfjord fault underwent periods of brittle low angle extensional reactivation during the permian 250 260 ma and upper jurassic lower cretaceous c 150 ma corresponding with stages of major extensional movements on the continental shelf palaeomagnetic studies may be of great importance for dating faults and major movement stages in long lived fault systems the particular importance of the results is that they show that low angle normal faults can operate in a brittle upper crustal regime

late cretaceous cenozoic tectonic transition from collision to transtension honduran borderlands and nicaraguan rise nw caribbean plate boundary

the life cycle of an undular bore and its interaction with a shallow intense cold front abstract the evolution of an undular bore and its associated wind shift spawned by the passage of a shallow surface cold front over the southern great plains of the united states is examined using surface and remote sensing observations along with output from a high resolution numerical model simulation observations show that a separation between the wind shift and thermodynamic properties of the front was induced by the formation of a bore over south central kansas around 0200 utc 29 november 2006 by the time the front bore complex passed through lamont oklahoma approximately 4 h later the bore had reached its maximum intensity and its associated wind shift preceded the trailing baroclinic zone by 20 min within several hours the bore decayed and a cold frontal passage characterized by a wind shift coincident with thermodynamic properties was observed at okmulgee oklahoma thus a substantial transformation in both the structural and dynamical characteristics of the bore as well as its relations

supergene alteration of primary ore assemblages from low sulfidation au ag epithermal deposits at pongkor indonesia and nazareno peru the textures and mineralogical assemblages of high grade ore samples from the low sulfidation au ag epithermal deposits of pongkor 2 ma west java indonesia and nazareno 10 ma cordillera shila southern peru were studied to investigate processes related to post depositional alteration of primary mineral parageneses both deposits are characterized by a late primary high grade base and precious metal stage composed of chalcopyrite sphalerite galena pyrite polybasite pearceite tennantite tetrahedrite electrum minerals of the polybasite pearceite series the main ag carriers were found to be transformed into acanthite acanthite was also found locally in association with native silver as a replacement product of base metal sulfides as veinlets alternating rhythmically with supergene iron oxyhydroxides replacing pyrite as well as associated with barite iron oxyhydroxides and covellite as boxwork fillings primary electrum grains with a composition of about au0 6ag0 4 are partially replaced by au ag sulfide locally identified as uytenbogaardtite ag3aus2 and or by acanthite with both of the replacing minerals commonly associated with vermicular electrum of a greater fineness up to au0 8ag0 2 the occurrence of the replacement textures near the present day surface and the associated secondary minerals strongly suggests a supergene origin for the au and ag sulfide phases the comparison of pongkor and nazareno also suggests that supergene remobilization of au and ag is geochemically significant and can occur in widely differing morphological and climatic contexts

structural observations adjacent to a large scale extensional detachment zone in the hinterland of the norwegian caledonides abstract structural and lithological observations in a n s traverse across bremangerlandet western norway demonstrate that the region is separated into two plates by the e w striking s dipping ductile brittle vetvika shear zone the vetvika shear zone places caledonian high grade gneisses with a precambrian protolith age of the lower plate in tectonic contact with heterogeneous gneisses of the upper plate the vetvika shear zone is the uppermost part of the nordfjord sogn detachment zone a gently w plunging stretching lineation within the s dipping lower plate augen gneisses is interpreted as having formed within a several kilometers thick ductile w dipping extensional shear zone that has undergone later rotation around an e w axis a highly attenuated sequence of nappes occur structurally on top of a heterogeneous basement and cover quartzite of the upper plate pre caledonian structures are preserved locally in the gneissic upper plate basement the nappes at bremangerlandet are correlated with the caledonian middle and upper allochthons representing baltic suspect and exotic terranes respectively one large and several medium to small scale brittle top to the south extensional faults are superimposed on ductile contractional structures in the upper plate some of the extensional faults merge downward with the vetvika shear zone the contractional structures include e w trending folds and s directed thrusts in the cover quartzite and are superimposed on a pronounced w e stretching lineation conjugate sets of fractures and faults related to e w extension represent the youngest structures in the upper plate the old red sandstones devonian of the hornelen basin rest unconformably on top of extensionally faulted upper plate rocks on bremangerlandet the unconformity is partly faulted at bremanger and truncated by a regionally extensive late brittle fault along the basin margin further east this suggests a long lived tectonic history for the vetvika shear zone and its eastward continuation with movement pre and post dating the filling of the collapse basin possibly as an eastward migration of the break away fault

latest caledonian to present tectonomorphological development of southern norway abstract the regional resultant stress field of the northeastern north atlantic has shifted significantly throughout the phanerozoic in fennoscandian parts of the caledonian orogen mountain building which was characterized by nw se contraction reference to present north was followed by a collapse with transport both parallel and transverse to the mountain chain the late palaeozoic mesozoic saw several stages of e w to nw se extension varying in time and position local episodes of inversion are traceable in some cases particularly in connection with deep seated and long lived zones of weakness the cenozoic has to a larger degree been affected by compression including folding and basin inversion again some of the more pronounced effects of local inversion are related to pre existing fault systems neogene uplift of the western mountainous area in scandinavia can be unravelled by potential field study aft data and reflection seismic sections assuming that the region is close to isostatic equilibrium the uplifted areas must be supported at depth by substantial volumes of low density material within the crust or the mantle close to the crust mantle interface or close to the lithosphere asthenosphere interfaces a series of nw se oriented cross sections representing successive stages of development from the late caledonian to present were prepared and used to analyse the tectonomorphological development as related to the shifting stress configurations three stages are inferred stage 1 devonian late permian denudation of the caledonian mountain chain during the latest stage of closing of the iapetus ocean in early to mid devonian times the caledonian mountain chain reached its maximum elevation of perhaps as much as 8 9 km including the foreland basins to the east the average topographic gradient of the eastern flank may have been in the order of 1 3 the denudation of the caledonian mountains continued into the permian and by the end of the permian the mountain system was more or less obliterated with a gradient of the eastern flank probably continued to fall to less than 0 1 stage 2 triassic late cretaceous tectono thermal uplift of central south norway uplift of central south norway was rejuvenated in triassic times and continued throughout the jurassic and early cretaceous the gradient of the eastern flank increased to a maximum of approximately 0 15 and master structural elements like the laerdal gjende olestol fault complex again played important roles in the development stage 3 tertiary present renewed tectono thermal activity and post glacial rebound a second phase of post caledonian tectono thermal uplift of south central norway started in oligocene time again increasing the gradient of the eastern flank of south norway around 0 2

a nonclassical cold front observed during cops 91 frontal structure and the process of severe storm initiation abstract this case study addresses the issue of gravity current and bore development at surface cold fronts and the role of these phenomena in the generation of severe frontal convection the event investigated occurred on 27 april 1991 during the cooperative oklahoma profiler studies 1991 field project the development of a bore from a gravity current like structure along a cold front the subsequent propagation of the bore ahead of the front on a low level inversion and the process of severe thunderstorm development along the front are revealed by a dense network of remote sensing and other special observations evidence for the gravity current and bore is strengthened by comparisons made between the synthesized observations and theory the bore developed after a nocturnal inversion which acted as a waveguide had become established the bore and gravity current were both evident as fine lines in the radar reflectivity displays a microscale envelope of enhanced water vapor with an embedded roll cl

interaction of permo triassic and jurassic extensional fault blocks during the development of the northern north sea the main structural elements resulting from late permian early triassic extension have been resolved across the total width of the northern north sea the northern segment of the basin north of 61 n bounded to the west by the hutton fault and to the east by the norwegian mainland was occupied by four westerly tilted half grabens 25 35 km in width prior to jurassic extension the central segment of the basin 60 20 61 n exhibits a full graben beneath the jurassic horda platform flanked by half grabens tilted towards the basin margins the change in permo triassic fault block configuration defining structural domains is largely constrained by a basement discontinuity which runs diagonally ne sw across the basin maximum jurassic extension is represented by several centres of subsidence aligned nne ssw across a n s oriented and broader permo triassic basin jurassic extension was concentrated within the viking graben proper south of 60 n which in this area is represented by single westerly tilted en echelon half graben segments 20 25 km wide the area affected by jurassic extension becomes progressively wider to the north again governed by the basement discontinuity eventually encompassing the total width of the basin c 200 km north of 61 n the central segment of the northern north sea displays the greatest contrast in permo triassic and jurassic structural styles and basin geometry jurassic stretching and faulting was negligible to the east horda platform precisely the area which had been the site of maximum permo triassic stretching and fault activity it has generally been assumed that jurassic fault configuration along the eastern margin of the central segment of the viking graben to a large extent reflects the reactivation of major permo triassic faults this study demonstrates the interference of permo triassic and jurassic basin geometries in this area due to major faults of the two generations dipping in opposite directions as a consequence the e tilted oseberg fault block of jurassic origin and c 20km in width is underlain by a wider c 35 km and w tilted permo triassic fault block

prospectivity mapping for high sulfidation epithermal porphyry deposits using an integrated compositional and topographic remote sensing dataset abstract the targeting and discovery of epithermal porphyry mineral deposits can be enhanced using a structured quantitative methodology to analyse the distribution of ore deposits and model their spatial association with exploration evidence providing improved understanding on the controls of ore deposition a novel exploration tool integrating field and aster swir and tir satellite imagery has been developed which provides an enhanced means of resolving surface expressions of the residual silica core of the lithocap the alteration zones were clearly resolved by the remote sensing data and an intimate spatial relationship between high grade altered rocks and topographic highs was identified at a number of locations a mineral prospectivity modelling mpm approach parameterized by the results of the remote sensing study using a gis based weighted linear combination implementation of a multi criteria evaluation approach and utilising a fuzzy analytical hierarchy process to elucidate expert knowledge has been implemented to target high sulfidation epithermal porphyry deposits on the island of lesvos greece the results from this integrated altitudinal compositional modelling approach closely matched the hydrothermal alteration mapped in the field supporting the accuracy of this mpm approach

sedimentary record and tectonic implications of mesozoic rifting in southeast mongolia the east gobi basin of mongolia is a poorly described late jurassic early cretaceous extensional province that holds great importance for reconstructions of mesozoic tectonics and paleogeography of eastern asia extension is especially well recorded in the structure and stratigraphy of the unegt and zuunbayan subbasins southwest of saynshand mongolia where outcrop and subsurface relationships permit recognition of prerift synrift and postrift mesozoic stratigraphic megasequences within the synrift megasequence three sequences developed in response to climatic and rift related structural controls on sedimentation where best exposed along the northern margin of the unegt subbasin each of the synrift sequences is bounded by unconformities and generally fines upward from basal alluvial and fluvial conglomerate to fluvial and lacustrine sandstone and mudstone resedimented ashes and basalt flows punctuate the synrift megasequence rifting began in the unegt subbasin prior to 155 ma with coarse alluvial filling of local fault depressions subsidence generally outstripped sediment supply and fresh to saline lacustrine environments expanding southward with time dominated the unegt zuunbayan landscape for much of latest jurassic early cretaceous time episodic faulting and volcanism characterized the basin system for the balance of the early cretaceous a brief period of compressional and or transpressional basin inversion occurred at the end of the early cretaceous prior to deposition of a widespread upper cretaceous overlap sequence the driver s of late jurassic early cretaceous extension remain uncertain because southeast mongolia occupied an intraplate position by the beginning of the cretaceous extension in the east gobi basin was coeval with collapse and extension of early mesozoic contractional orogenic belts along the northern and southern borders of mongolia and probably was a linked phenomenon strike slip faulting associated with collisions on the southern asian and mongol okhotsk margins likely also played a role in late mesozoic deformation of the east gobi region perhaps partitioning the gobi from apparently coeval large magnitude contractional deformation in the yinshan yanshan orogenic belt south of the study area in inner mongolia

basin inversion and contractional reactivation of inherited normal faults a review based on previous and new experimental models abstract compressional inversion of former extensional sedimentary basins is a particularly common phenomenon given that passive margins share the same destiny of being subsequently incorporated into fold and thrust belts during basin inversion pre existing faults may concentrate stress and localise future thrust ramps or may be reactivated recording reversal of movement from extension to reverse this process has attracted attention largely because of its economic implications related to petroleum and ore deposit prospects and seismic hazard assessment since more than two decades analogue modelling has been used to indentify and or test a number of parameters relevant for the inversion process this paper aims therefore to offer a reasoned review of the analogue modelling work done on the subject coupling such previous results with those of a new experimental series inspired to the northern apennines stratigraphy and evolution past models have explored the role of main factors governing fault reactivation susceptibility such as fluid pressure fault weakness fault steepness angle of shortening and sediment loading the new models have addressed the role played by geometry and strength of a basal ductile layer during inversion two sets of sand silicone models were first extended orthogonally at different velocities to produce dissimilar pre inversion internal geometries and then shortened coaxially at different velocities to vary the brittle ductile coupling the experimental results confirm the selectiveness of fault inversion and reveal strong similarities with structural styles of tectonic inversion reported from the northern apennines and various areas worldwide the preferred geological model inferred from this modelling involves contribution of 1 syn inversion rotation of pre existing faults to shallower dip and 2 rotation of principal stress axes which could explain the invariable reactivation of only one of the two oppositely dipping graben bounding faults these factors would thus interact with the other well established parameters controlling the fault reactivation process

sedimentation of the neogene recent alasehir gediz continental graben system used to test alternative tectonic models for western aegean turkey abstract the alasehir gediz graben exemplifies clastic sedimentation in a long lived continental half graben in a semi arid setting developed within relatively incompetent metamorphic rocks early miocene to recent rift related sediments are exhumed on both flanks of the graben allowing detailed three dimensional study during the early miocene small fan delta lobes were shed northwards from the rugged menderes metamorphic massif into a bordering lacustrine basin during early to mid miocene time large alluvial fans prograded northwards into this basin through drainage to the aegean sea was established as the basin widened and filled discrete lobes of coarse alluvial fan sediments of latest miocene pliocene age also shedding northwards are likely to have been climatically influenced quaternary alluvium party infills the modern alasehir rift basin the sedimentary information can be used to test two alternative tectonic models for the alasehir graben in the first model an e w graben bounded by high angle faults was active during latest miocene recent time whereas earlier miocene sedimentation was controlled by n s faulting related to a n s compressional stress regime in the second hypothesis the alasehir graben was initiated much earlier in the early miocene and was then either continuously or episodically active until recent our results especially facies and palaeocurrent data from alluvial sediments indicate that clastic sedimentation was controlled by mainly e w faulting in a n s stress regime assuming the early miocene clastic sediments are correctly dated this supports the second long lived extension model however rather than steady state extension for ca 15 ma the sedimentary evidence and regional context are consistent with a pulsed extension model whereby initial early to mid miocene extension and related clastic sedimentation was followed by a second phase of extension in latest miocene pliocene time the driving force of initial early miocene extension was probably gravity spreading towards a south aegean subduction zone whereas the inferred second extension pulse is seen as being triggered by westward tectonic escape of anatolia towards the extending aegean back arc region

pongkor west java indonesia a pliocene supergene enriched epithermal au ag mn deposit the pongkor gold silver epithermal deposit with reserves of at least 98 tonnes of gold and 1026 tonnes of silver average grades 16 4 g t au and 171 2 g t ag is one of the most recent and largest gold and silver discoveries in indonesia proven within a short period 1988 1991 40ar 39ar dating on adularia samples give an age of 2 05 0 05 ma the deposit is of the low sulfidation epithermal type and consists of four main mineralized quartz veins located close to the internal rim of a volcano tectonic depression caldera this resulted from an explosive ignimbritic eruption that produced pyroclastic flows and accretionary lapilli with rare intercalations of epiclastic rocks this volcanic unit unconformably overlies miocene subaqueous volcanic andesitic rocks with interbedded epiclastic rocks the mineralized bodies are thick average 4 2 m steeply dipping quartz carbonate adularia veins with a very low sulfide content 0 5 wt their genesis is related to an extensional episode within a tectonic corridor showing nw se and nne ssw conjugate strike slip faults the major vein being located on the inner rim of the caldera the vein fill reveals four successive stages of deposition marked by a specific facies 1 carbonate quartz breccia with dominant quartz and calcite and minor kutnahorite rhodochrosite and rhodonite cq facies 2 a network of banded quartz and former carbonate transformed into manganese oxides through supergene alteration moq facies 3 banded opaline milky quartz boq facies and 4 grey locally banded sulfide rich quartz breccia cutting all the other types gsq facies adularia was deposited at the same time as the quartz the mineralogy and internal structures of the veins crustiform banding vugs collapse breccia clearly indicate a dilational context which is common in low sulfidation epithermal systems gold and silver grades as well as sulfide mineral abundances increase steadily through stages 1 to 4 locally reaching 1 kg t in the gsq facies the sulfides are dominated by pyrite accompanied by common acanthite aguilarite polybasite pearceite and electrum in which the gold content ranges from 48 to 74 wt sphalerite galena chalcopyrite and hessite are fairly rare although present within the cq facies the fluid inclusions of the four facies show homogenization temperatures ranging from 150 to 382 c indicating boiling of a hydrothermal fluid with an initial temperature of around 205 c no marked difference is seen in the gsq facies which has the highest gold content salinities are low generally below 1 wt eq nacl lead isotope compositions of the associated volcanic rocks and the mineralization are very similar 206pb 204pb between 18 706 and 18 814 and between 18 744 and 18 801 respectively demonstrating a genetic link between the pliocene volcanism and the auriferous hydrothermal activity the isotopic signature suggests that the source of the mineralization and associated volcanic rocks is an underlying ancient continental crust that melted and remobilized during the pliocene volcanic and hydrothermal events these conclusions seem applicable to the entire bayah dome the existence of both a tectonic corridor and a caldera favoured channelling of the hydrothermal fluids and the deposition of primary ore in the veins late intense weathering of the ore deposit to depths of 250 m below the surface has given rise to manganese oxide layers limonite zones and silver micronuggets within the veins as well as to gold enrichment

the generation of the morning glory abstract a high resolution cloud model is used to explore in detail the generation of the morning glory a low level nonlinear atmospheric internal wave observed on the southwestern side of cape york peninsula australia the model is two dimensional and nonhydrostatic and simulates an east west cross section of the southern part of cape york peninsula at a horizontal resolution of 200 m most of the numerical experiments are initialized at sunrise with a 5 m s 1 easterly flow and a sounding taken upstream from the peninsula the sea breezes that develop over cape york peninsula are highly asymmetric with the east coast sea breeze being both deeper and warmer than its western counterpart when the sea breezes meet the east coast sea breeze rides over that from the west coast and in the process produces a series of waves that propagate on the west coast sea breeze the model calculations show that when the phase speed of these waves matches the westward propagation speed of the east coast sea breeze the

multiple deformations along the honam shear zone in southwestern korea constrained by rb sr dating of synkinematic fabrics implications for the mesozoic tectonic evolution of northeastern asia abstract the honam shear zone dextrally running along the southern margin of the ogcheon belt korea has drawn much attention in reconstructing the mesozoic tectonic framework of northeastern asia here we present rb sr data for the middle to southwestern part of the honam shear zone in an attempt to directly determine ages of deformation in the middle part the younger limit of deformation is constrained to be 162 11 ma by feldspar biotite rb sr dating of the deformed sunchang granodiorite on the other hand an early cretaceous deformation age is estimated for synkinematic fibers in ultramylonites from the southwestern part by two reproducible rb sr errorchrons at 138 4 and 139 23 ma this deformational time scale is consistent with earlier interpretations based on field evidence magnetic susceptibility data and age data for jurassic plutons within the shear zone our data demonstrate that the honam shear zone is not a permian to triassic tectonic feature related to the chinese continental collision

structure and evolution of north australian cloud lines observed during amex phase i abstract north australian clouds lines are distinctive squall line phenomena that occur in easterly flow across northern australia three basic types have been identified ranging from a long narrow line of convective clouds type 1 to a severe squall line type 3 in this paper we examine a group of type 1 lines which occurred during the first phase of the australian monsoon experiment amex the lines occurred in an ambient easterly flow with a distinct maximum near 850 hpa most of the lines developed on the western side of deep convective cells along the sea breeze front in a manner that had substantial similarities to the african squall line development described by bolton the resolvable structure resembled a shallow version of the moncrieff miller squall line

40ar 39ar geochronology of the pongkor low sulfidation epithermal gold mineralisation west java indonesia abstract the pongkor gold deposit located approximately 90 km southwest of jakarta is well known as the typical low sulfidation ls epithermal gold deposit and the largest gold vein deposit in indonesia the pongkor gold mineralisation has been the subject of several geological studies determination of the duration of gold mineralisation events however is less well understood the mineralisation events are important for understanding the genesis of ore deposits this study presents 40ar 39ar age results for four adularia samples from ciguha gold bearing quartz vein yielding plateau ages of 1 80 0 03 ma 2 33 0 32 ma and 1 88 0 02 ma plus one weighted mean age of 1 95 0 04 ma adularia from the kubang cicau gold bearing quartz veins yielded a 40ar 39ar plateau age of 2 02 0 03 ma the period of adularia growth in the ciguha vein may have extended from ca 2 07 to 1 77 ma that includes the ages of 1 95 0 04 ma and 1 88 0 02 ma the time interval indicates multiple generations of the adularia the data suggest that mineralisation of ciguha may have continued episodically or continuously the age of adularia from the kubang cicau gold bearing quartz vein 2 02 0 03 ma is within the error of the ciguha vein age and the adularia growth of kubang cicau vein reveals at the beginning of ciguha s adularia growth the data suggest that gold mineralisation in the pongkor deposit for kubang cicau and ciguha veins was initiated at the relatively similar time the 40ar 39ar adularia ages of this study are within error of the previously reported 40ar 39ar results milesi et al 1999 but significantly younger than the previously reported k ar adularia dating result kageyama 1999 in rosana and matsueda 2002

late paleozoic tectonic amalgamation of northwestern china sedimentary record of the northern tarim northwestern turpan and southern junggar basins sedimentary rocks contained in basins adjacent to the tian shan provide a long and complex record of the late paleozoic continental amalgamation of northwestern china complementing that provided by rocks preserved within the range this record which comprises dramatic changes in sedimentary facies sediment dispersal patterns sandstone provenance and basin subsidence rates broadly supports previous interpretations of a two part evolution of the tian shan late devonian to early carboniferous collision of the tarim continental block with the central tian shan followed by collision of this combined block with island arcs in the north tian shan and bogda shan in late carboniferous early permian times the first collision resulted in widespread angular unconformities within the tarim basin continued convergence following the collision created a long lived flexural foredeep along the northern margin of the tarim block which received at least 2000 m of lower carboniferous through lower permian fluvial and marine sediment derived from the interior of tarim subsequent early permian continental extension of the northern tarim basin resulted in the deposition of interbedded nonmarine siliciclastic sedimentary rocks and mafic to felsicvolcanic rocks sandstone within this interval was derived from the paleo tian shan and is composed predominantly of lithic volcanic grains similar to the rhyolite in contrast to the tarim basin calc alkaline volcanic rocks and volcanogenic sedimentary rocks dominated carboniferous and permian sedimentation in the northern turpan and northwestern junggar basins volcanic arcs remained active in the north tian shan and bogda shan through the early late carboniferous depositing a kilometers thick interval of deep marine sediment gravity flows in the northwestern junggar basin major arc magmatism ceased in the late carboniferous in response to closure of the oceanic basin between the combined tarim central tian shan block and the north tian shan bogda shan arcs upper carboniferous through lower permian rocks in the northwestern junggar basin compose the sedimentary fill of a bathymetric basin of oceanic depth on the northern side of the volcanic arcs culminating in a 1000 m thick marine regressive sequence middle to upper permian sandstones were derived from the uplifted paleo tian shan and bear the distinctive provenance imprint of granitic rocks presently exposed within the range late permian subsidence of the junggar basin accommodated 5 km of nonmarine sediments however the cause of this subsidence and its relationship to regional tectonic events remain controversial

extension parallel folding in the scandinavian caledonides implications for late orogenic processes abstract structural analyses of the devonian basins and basement rocks in the scandinavian caledonides show the existence of large scale e w oriented folds which affect the para autochthonous western gneiss region of the baltic craton these folds mostly occur in areas of widespread and intense late orogenic extension chronology based on structural relationships both within the devonian sediments and caledonian rocks shows that folding has been active from the first stages of the ductile extension and ended after devonian basin sedimentation folding evolved through time towards crustal scale transcurrent left lateral faulting in the zones of maximum deformation such an evolution is explained by progressive unloading of the western gneiss region due to extension which involved a permutation of the maximum stress from a vertical position at the onset of extension to a horizontal position in the subsequent stages folding parallel to late orogenic extension as well as left lateral translation on east to northeast trending crustal scale faults suggest the occurrence of a regional direction of compression perpendicular to the direction of extension this in turn argues for an external force triggering the late orogenic extensional process in the scandinavian caledonides

subduction tectonic erosion and late cretaceous subsidence along the northern austroalpine margin eastern alps austria abstract the late cretaceous to early tertiary subsidence history of the northern calcareous alps nca records the effect of two independent basin formation mechanisms at the northern leading margin of the austroalpine unit the terrestrial to shallow marine sediments of the lower gosau subgroup were deposited mainly within small fault bound basins during a phase of strike slip faulting from the late turonian onwards after a short period of uplift deformation and erosion of 1 to 3 ma renewed rapid subsidence followed during this period the whole nca subsided into bathyal to abyssal depths the characteristics of this second evolutionary phase are 1 a short period of uplift and erosion followed by strong subsidence of the whole nca with tectonic subsidence rates up to 700 m ma 2 sedimentation of turbidites and hemipelagites upper gosau subgroup 3 northward tilting of the depositional area 4 elimination of an accretionary wedge north of the nca as the main source for the sediments and 5 a pronounced migration of the subsidence event from the northwest to the southeast from late turonian santonian to the maastrichtian these features can be explained by a model of subduction tectonic erosion along the northern margin of the austroalpine unit a part of the adriatic microplate tectonic erosion as compared to recent analogues and fore arc modelling may be due to the collision and oblique subduction of an oceanic swell or ridge of the penninic plate beneath the overriding austroalpine unit with the nca on its leading northern margin

late visean hidden basins in the internal zones of the variscan belt u pb zircon evidence from the french massif central u pb zircon ages from volcanic rocks interbedded in two upper carboniferous basins of the variscan massif central france document the presence of an unexpected late visean sedimentary sequence zircons extracted from a fireclay at the base of the sedimentary pile in the bosmoreau basin provide an age of 332 4 ma identical to the 333 2 ma age obtained from a rhyolitic lava sampled in the decazeville basin in addition both volcanic rocks contain inherited or xenocrystic zircons reflecting the ages of the basement and or source components the bosmoreau fireclay contains a limited amount of xenocrystic zircons having ages of ca 390 400 ma whereas inheritance is much more abundant in the decazeville rhyolite which includes a mesoproterozoic source component 1 0 ga the ca 330 ma ages demonstrate that these two basins with mainly stephanian sedimentary infill were actually initiated during the late visean and are the first known upper crustal evidence of the visean westphalian extensional event recognized previously only in midcrustal plutonic bodies moreover the location of these basins in the hanging wall blocks of two major fault systems i e the argentat and sillon houiller faults suggests a genetic link between fault motion and basin opening as early as the late visean these results indicate that magmatism and associated volcanism block movement along major crustal scale faults erosion and basin opening were contemporaneous and shed new light on the visean westphalian synconvergent extension that was previously understood only as a deep seated event

shear heating in extensional detachments implications for the thermal history of the devonian basins of w norway article i nfo the supra detachment basins in western norway were formed during lower to middle devonian in the hangingwall of the extensional system of detachments known as the nordfjord sogn detachment zone nsdz the basins experienced elevated peak temperatures up to 345 c adjacent to the main detachment fault during the terminal stages of the extension in this study we show that the heat generated by the de formation of the rocks within the shear zone of the detachment also known as shear heating played a role in the thermal evolution of the entire region during the extension and could have induced the elevated peak temperatures of the supra detachment basins we numerically analyse the influence of the rheology and the deformation style within the shear zone the rate of exhumation of the footwall and the thickness of the sedimentary accumulation on the top of the system the model reproduces the elevated temperatures recorded in the supra detachment basins where locally 100 c and 25 of the total heat budget can be attrib uted to shear heating we show that this additional heat source may increase the peak temperatures of the hangingwall as far as 5 km away from the detachment