retrogression by deep infiltration of meteoric fluids into thrust zones during late orogenic rapid unroofing hypersaline na ca cl fluids are associated with late stage quartz veining and retrogression of garnet kyanite and other high p t phases in the vicinity of thrusts and major lithological boundaries in the scandian nappes of the troms ofoten region northern norway they record early devonian fluid infiltration during rapid exhumation in the final stages of caledonian orogenesis the d18o and dd characteristics of these late fluids provide compelling evidence for deep circulation of meteoric fluids the sub greenschist to low greenschist facies retrogression p 2 1 kbar t 300 350 c suggests infiltration to depths of 7 9 km in a regime of supra hydrostatic fluid pressure peak metamorphic quartz veins and associated fluids have dd and d18o characteristics consistent with a metamorphic origin dd 47 to 75 d18o 8 6 to 17 4 however late quartz veins and associated fluids show a broad spread of dd from 42 to 148 interpreted in terms of meteoric fluid infiltration such negative dd values are only recorded in present day high latitude or high altitude settings and since north norway was in an equatorial setting 10 s in the early devonian a high altitude origin is deduced by calculation and by comparison with modern examples the early devonian mountains of the north norwegian caledonides are interpreted to have had a topography in excess of 5 km the deep circulation of surface waters is interpreted in terms of topographically driven flow linked with a hydrothermal system induced by elevated geothermal gradients due to rapid uplift whilst the case for deep penetration of surface derived fluids has been promoted for mesozoic and younger mountain belts this study represents one of the first documented examples for a palaeozoic orogenic belt it suggests that many of the fundamental processes operating during the exhumation of mountain belts are similar irrespective of age

momentum transports associated with tropical cyclone recurvature abstract this study attempts to investigate the linear momentum budget responsible for tropical cyclone tc recurvature using the operational analyses from the u k meteorological office global model the environmental flow associated with recurving tcs over the western north pacific for the years 1991 95 is composited in general the dominant features include an eastward retreating subtropical ridge str and an approaching westerly trough during the recurvature while the southeasterly flow associated with the str changes to southerly in the northeast quadrant of the tc in the mid to upper troposphere the southwesterly flow associated with the trough penetrates into the northwest quadrant of the tc especially in the upper troposphere these changes of the environmental flow throughout the recurvature alter the linear momentum of the tc from southeasterly to southwesterly to understand the dynamical processes responsible for the linear momentum changes individual momentum tendency terms are calcu

reply to comments on near surface stress and displacement in a layered elastic crust and stress in a stratified crust overlying a buried screw dislocation by p c leary

mesozoic tertiary structural evolution of an extensional gneiss dome the kesebir kardamos dome eastern rhodope bulgaria greece the tectonic evolution of the rhodope massif involves mid cretaceous contractional deformation and protracted oligocene and miocene extension we present structural kinematic and strain data on the kesebir kardamos dome in eastern rhodope which document early tertiary extension the dome consists of three superposed crustal units bounded by a low angle nne dipping detachment on its northern flank in bulgaria the detachment separates footwall gneiss and migmatite in a lower unit from intermediate metamorphic and overlying upper sedimentary units in the hanging wall the high grade metamorphic rocks of the footwall have recorded isothermal decompression direct juxtaposition of the sedimentary unit onto footwall rocks is due to local extensional omission of the intermediate unit structural analysis and deformational metamorphic relationships give evidence for several events the earliest event corresponds to top to the sse ductile shearing within the intermediate unit interpreted as reflecting mid late cretaceous crustal thickening and nappe stacking late cretaceous palaeocene eocene late tectonic to post tectonic granitoids that intruded into the intermediate unit between 70 and 53 ma constrain at least pre latest late cretaceous age for the crustal stacking event subsequent extension related deformation caused pervasive mylonitisation of the footwall with top to the nne ductile then brittle shear ductile flow was dominated by non coaxial deformation indicated by quartz c axis fabrics but was nearly coaxial in the dome core latest events relate to brittle faulting that accommodated extension at shallow crustal levels on high angle normal faults and additional movement along strike slip faults radiometric and stratigraphic constraints bracket the ductile then brittle extensional events at the kesebir kardamos dome between 55 and 35 ma extension began in paleocene early eocene time and displacement on the detachment led to unroofing of the intermediate unit which supplied material for the syn detachment deposits in supra detachment basin subsequent cooling and exhumation of the footwall unit from beneath the detachment occurred between 42 and 37 ma as indicated by mica cooling ages in footwall rocks and extension proceeded at brittle levels with high angle faulting constrained at 35 ma by the age of hydrothermal adularia crystallized in open spaces created along the faults this was followed by late eocene oligocene post detachment overlap successions and volcanic activity crustal extension described herein is contemporaneous with the closure of the vardar ocean to the southwest it has accommodated an earlier hinterland directed unroofing of the rhodope nappe complex and may be pre cursor of and or make a transition to the aegean back arc extension that further contributed to its exhumation during the late miocene this study underlines the importance of crustal extension at the scale of the rhodope massif in particular in the eastern rhodope region as it recognizes an early tertiary extension that should be considered in future tectonic models of the rhodope and north aegean regions

effects of asymmetric sst distribution on straight moving typhoon ewiniar 2006 and recurving typhoon maemi 2003 abstractthe effects of asymmetric sea surface temperature sst distribution on the tropical cyclone tc motion around east asia have been examined using the weather research and forecasting model for the straight moving typhoon ewiniar 2006 and recurving typhoon maemi 2003 the sst tc motion relationships associated with the two different tcs and the physical mechanism of recurvature are investigated in the context of the potential vorticity tendency framework a zonally asymmetric sst distribution alters the tc translating direction and speed which is ascribable to the interaction between a tc and the environmental current associated with asymmetric sst forcing a north south sst gradient has an insignificant role in the tc motion it is noted that the straight moving i e northward moving tc deflects toward the region of warmer sst when sst is zonally asymmetric a contribution of the horizontal advection including asymmetric flow induced by asymmetric forcing is dominant for the deflection t

near surface stress and displacement in a layered elastic crust in situ stress measurements on the san andreas fault are modeled in terms of a solution to the equations of three dimensional elastic equilibrium in a layered medium crustal stresses are expressed in terms of surface deformations in particular vertical stress gradients are shown to be proportional to horizontal gradients of vertical surface deformation in light of constraints derived by this relation it is proposed to reinterpret the observed near surface in situ vertical stress gradients on the san andreas fault as partly a manifestation of a layered crust with vertically increasing rigidity extrapolation to depth of the revised stress gradients suggests that the san andreas fault can be regarded as a low stress phenomenon compatible with estimates of shear stress obtained from heat flow data

geologic and geochemical study of the picacho gold mine california gold in a low angle normal fault environment the picacho gold deposit located in southeasternmost california is a low grade gold deposit in a nearly flat lying denudational fault of regional extent and probable oligocene age the deposit is hosted by intensely fractured and faulted mesozoic leucogranite and by chloritic augen gneiss and schist and is overlain unconformably and in fault contact by unmineralized late oligocene quechan volcanic rocks the deposit is structurally characterized by normal and normal oblique faults of low to high dip at shallow depths in the mine merging downward with a synchronous low dipping ore stage extensional fault system the chocolate mountains gatuna fault of probable oligocene age in deeper portions of the deposit the fault system was infiltrated during much of its active life by hot dilute highly exchanged meteoric water having temperatures of 170 210 c salinity 2 wt nacl equivalent and calculated 18ofluid between 2 6 and 5 2 this main stage fluid precipitated quartz pyrite and specular hematite accompanied by silicification and sericitization auriferous ore stage pyrite was precipitated late in the fault evolution probably by mixing of reducing ore fluid with relatively oxidized main stage fluid during regional oligocene extension on the chocolate mountains gatuna fault the picacho deposit is characterized by a gold arsenic antimony geochemical signature consistent with bisulfide complexing of gold in reducing fluid in contrast with typical denudation fault hosted base metal rich deposits associated with high salinity fluids elsewhere in the southwestern united states the deposit is overprinted by miocene normal faults having a wide range of dips these postore faults are associated with red earthy hematite precipitation pyrite oxidation and supergene enrichment of gold

implications of an elastic analysis of in situ stress measurements near the san andreas fault twenty nine measurements of in situ stress obtained with the hydraulic fracturing technique near palmdale california are the basis of an elastic analysis of the state of stress in the mojave desert adjacent to the san andreas fault the measurements were made at depths extending from 80 to 849 m and at distances from the fault between 2 and 34 km the elastic solution indicates a state of deviatoric stress typical for continents in that the inferred depth gradient of the maximum shear stress is about 7 9 mpa km extrapolation yields an average shear stress in the upper 14 km of the crust of about 56 mpa a result that is higher than estimates of the average shear stress on the san andreas fault based on the analysis of heat flow data this finding is consistent however with estimates of fault strength based on laboratory determinations of the coefficient of friction for samples of san andreas fault gouge if the regional state of deviatoric stress is limited by the strength of the fault zone if so then the coefficient of friction of the san andreas fault zone inferred from the stress field results is about 0 45 the state of stress does not appear to vary systematically with distance from the san andreas fault although considerable localized variation is observed the observations suggest an upper bound of about 0 1 mpa km for the horizontal gradient of the maximum shear stress in the direction perpendicular to the san andreas fault a result that implies a corresponding limit of about 1 4 mpa on the shear traction applied to the base of the seismogenic layer finally we demonstrate the potential application of in situ stress data to the direct assessment of accumulated slip which could be released in a large earthquake we show that on the basis of a model involving a locked fault extending to about 22 km the total fault slip below the locked portion is less than 13 m a more comprehensive set of stress data could permit the estimation of an even lower bound

comments on near surface stress and displacement in a layered elastic crust and stress in a stratified crust overlying a buried screw dislocation by p c leary

routine staining of drill core to determine carbonate mineralogy and distinguish carbonate alteration textures carbonate staining has long been utilized with thin sections similar techniques are also extremely useful for distinguishing the mineralogy and texture of different carbonate minerals in drill cores the simplest method for routine staining of whole drill core utilizes a dilute hydrochloric acid solution containing both alizarin red s and potassium ferricyanide this solution is painted on to the drill core to allow for the rapid identification of calcite ferroan calcite ferroan dolomite ankerite and rhodochrosite production scale staining of whole drill core rapidly provides a wealth of information on carbonate mineralogy and textural relationships in a number of deposit types examples from the irish zn pb district the mcarthur river zn pb ag district the ruby creek cu co deposit and the kansanshi copper deposit are presented to illustrate the type of information that can be gained through use of this inexpensive and rapid technique

stress in a stratified crust overlying a buried screw dislocation a haskell matrix solution to the equation of stress equilibrium is used to describe the crustal response to a screw dislocation source lying beneath a uniform elastic crust capped by a region of layered rigidity the solution is used to illustrate the effect a stratified crustal rigidity has on the near surface in situ stress field without accounting for this effect it is possible to overestimate the deep tectonic stress levels inferred from in situ vertical gradients measured in the uppermost crust

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

millisecond accurate monitoring of seismic travel times over 13 and 18 kilometer baselines using a repeatable airgun source we have monitored the travel times of several seismic phases along 13 and 18 km baselines from bouquet reservoir to boreholes on the san andreas fault near palmdale california the first arriving phases refract at a depth of 2 3 km while one later arrival is possibly a reflection from 10 km the majority of some 200 travel time determinations for the most prominent phases were made between august 1979 and march 1980 isolated measurements were made in november 1978 and march 1981 there exists ample geodetic and other evidence for significant strain changes during this period allowing for source variation due to fluctuating reservoir water levels we observed no travel time changes to the limit of our precision of 1 2 ms for the first arrivals and 3 5 ms for secondary arrivals or about 0 1 of the total travel time an earlier study which monitored rays penetrating only 500 m into the crust found that travel times varied by up to 0 3 over a period of several days the variations showed some correlation with strain changes due to local seismic activity and were not permanent to understand this different behavior of crustal rocks between 500 and 2000 m we investigate the depth dependence of their velocity strain sensitivity using measured p and s velocity profiles to gauge the rate at which confining pressure increases velocity we find that 1 bar of overpressure at 500 m can vary the p velocity by 0 1 while 1 bar at 2000 m will vary the velocity by only 0 01 applying the o connell budiansky physical model for cracked rock to the velocity depth profiles we can further characterize the local crust as having a high crack density a mobile fluid component and an average crack aspect ratio of 2 5 10 3 the combination of a mobile fluid content and high crack density suggests that fluids play a role in the transient velocity anomalies observed at a depth of 500 m and argues against significant undersaturation phenomena at seismogenic depths on the san andreas fault

transtensional origin of the ne sw simitli basin along the strouma strymon lineament sw bulgaria several depocentres have developed along the nnw sse striking strouma strymon lineament since the miocene forming the strouma strymon graben system some of these basins including the dzherman and simitli strike at high angles to the lineament the rhomboid shaped simitli basin is limited in the south by the ne sw striking seismically active kroupnik fault and contains terrestrial clastic sediments which have been deposited since the sarmatian its formation is attributed to wrench dominated transtension d b event which activated the basin9s ne sw striking boundary faults as left lateral strike slip structures during the early middle miocene this deformation was associated with nne ssw contraction and wnw ese extension and succeeded the nne ssw contraction caused by pure shear dominated transpression d a event which governed the region in late oligocene early miocene times during the middle late miocene the d b event was followed by wnw ese pure shear dominated extension d 1 event which caused further widening of the basin the transtensional origin of the simitli basin is explained by lateral extrusion of the crustal mass squeezed between the apulian adriatic microplate and the european foreland towards the north aegean sea the subduction retreat of the hellenic orogen possibly enhanced this lateral extrusion and from the late miocene onwards the ne sw oriented back arc extension balanced the continuing retreat

baroclinic dynamics of simulated tropical cyclone recurvature abstract the mechanisms associated with tropical cyclone recurvature are investigated using a five level primitive equation model and an idealized environment with characteristics observed in cyclone recurvature conditions all cyclones moved generally with the flow in the lower and middle troposphere but the precise motion occurs by a combination of divergence and of advection in both the horizontal and the vertical the horizontal advection arises from a combination of the initial environmental flow and local changes from rearrangement of the potential vorticity field by cyclone environment interaction the so called effect the balance between these mechanisms changes as the vortex recurves since the gradients of potential vorticity increase sharply poleward of the subtropical ridge this is the preferred region for development of an anticyclonic gyre this gyre is advected eastward and becomes the dominant anticyclonic system recurvature is aided by horizontal deformation of the cyclone in the v

calculation of oxygen isotope fractionation in hydroxyl bearing silicates abstract the modified increment method has been applied to the calculation of oxygen isotope fractionation factors for hydroxyl bearing silicate minerals the order of 18o enrichment obtained in common rock forming minerals is pyrophyllite kaolinite tourmaline talc prehnite topaz illite phengite lepidolite muscovite staurolite epidote glaucophane serpentine chlorite tremolite hornblende phlogopite biotite humite norbergite ilvaite hydroxyl bearing silicates are enriched in 18o relative to hydroxyl groups but depleted in 18o relative to anhydrous counterparts three sets of self consistent fractionation factors between quartz and the hydroxyl bearing silicate minerals between calcite and the silicate minerals and between the silicate minerals and water have been calculated for a temperature range of 0 1200 c the fractionation factors calculated for mineral pairs are applicable to isotopic geothermometry in igneous metamorphic and sedimentary petrology they can be used as a test of isotopic equilibrium or disequilibrium in natural mineral assemblages over all temperature ranges of geological interest the difference in oxygen isotope composition between the hydroxyl bearing mineral and the oh group is quantitatively demonstrated to be temperature dependent and therefore can be used as a single mineral geothermometer

interactions between a barotropic vortex and an idealized subtropical ridge part i vortex motion abstract a series of barotropic modeling experiments are used to examine the motion of a vortex in the vicinity of an idealized subtropical ridge the vortex propagation is highly correlated with the absolute vorticity gradient in the initial imposed environment the signal is degraded when radial band averages are used to calculate the environmental advection and absolute vorticity gradient components it is shown here that this is due partially to the difficulties in separating the cyclone from its environment application of the modeling results to climatological mean fields indicates that considerable variations in vortex propagation can occur

fluid immiscibility in natural processes use and misuse of fluid inclusion data abstract many occurrences of fluid immiscibility in natural geologic systems have been reported recently most often from fluid inclusion studies however the interpretation of fluid inclusion data in terms of immiscibility sometimes suffers from ambiguity of the vocabulary insufficient knowledge of the immiscibility constraints and insufficient knowledge of the topology in the tpx space of natural fluid systems for such reasons some authors have been misled to erroneous interpretations the term chemical immiscibility is unambiguously redefined as a multiphase multicomponent equilibrium the consequences of this definition are directly derived from the phase rule and concern the possible equations that relate the various parameters temperature pressure volumes compositions to each other these equations already put constraints on the topology of the phase equilibria in fluid systems a particular expression of the phase rule is proposed which takes into account the multiphase constant bulk volume constant bulk composition constraints in fluid inclusions the consequences of such an expression are of major importance in fluid inclusion studies the phase relations of some simple systems that approximate quite efficiently the natural complex fluids are then detailed h2o nacl co2 ch4 h2o co2 h2o co2 nacl the effects of these topologies and of the supplementary constraints constant bulk composition and constant bulk volume assumed for fluid inclusions isopleth isochoric systems are discussed

calcitization dedolomitization of jurassic dolostones lebanon results from petrographic and sequential geochemical analyses calcitized jurassic dolostones from central mount lebanon kesrouane formation are discussed utilizing petrographic mineralogical and geochemical data in particular two sequential extraction methods for both major trace elements and stable isotope analyses provide results that support and refine conventional bulk analyses data the new data demonstrate that the major dedolomitization phase of the investigated jurassic carbonates occurred as a result of the migration of karst related meteoric waters characterized by soil derived carbon and estimated 18ov smow composition between 7 2 and 3 4 into previously dolomitized horizons within the limestone rock during the final uplift and emergence of mount lebanon after palaeogene time the study demonstrates that in this case the mechanisms of dedolomitization and their resulting fabrics are controlled primarily by the texture of the original dolomite rock pervasively dolomitized rocks where the micritic matrix is entirely dolomitized show calcitization mainly through dissolution precipitation by contrast the rock textures that still include a considerable amount of limey micritic matrix spared from dolomitization are more prone to mole per mole and mimic replacement of the dolomite crystals by calcite

raman micro spectroscopy on diamond graphite and other carbon polymorphs from the ultrahigh pressure metamorphic kimi complex of the rhodope metamorphic province ne greece raman micro spectroscopy was applied on carbon inclusions in garnet porphyroblasts from kyanite biotite garnet schists of the rhodope metamorphic province rmp ne greece diamond and cuboids of poorly to highly ordered graphite were identified either as single phase inclusions or as polyphase inclusions along with co2 and or carbonates calcite magnesian calcite questionable raman bands that may be assigned to other c phases nanodiamond lonsdaleite a different c polymorph have been observed the presence of diamond confirms beyond any doubt the ultrahigh pressure uhp metamorphism reported by mposkos and kostopoulos 1 e mposkos d kostopoulos diamond former coesite and supersilisic garnet in metasedimentary rocks from the greek rhodope a new ultrahigh pressure metamorphic province established earth planet sci lett 192 2001 497 506 in the rmp cuboid graphite showing variable degree of disordering most probably formed after diamond the possible involvement of co2 and or c o h fluids in the formation of diamond is discussed