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

depleted mantle source for the ulungur river a type granites from north xinjiang china geochemistry and nd sr isotopic evidence and implications for phanerozoic crustal growth abstract the ulungur river granites from north xinjiang china display two petrological trends 1 a peralkaline trend composed of alkali amphibole and alkali pyroxene bearing granites and dykes and 2 an aluminous trend represented by alkali granites monzogranites and aluminous granite dykes within the peralkaline granites rb sr whole rock isochron dating yielded an age of 300 ma for the emplacement of the peralkaline granites and 270 ma for the aluminous granites the ulungur river granites share all the geochemical features common to a type granites of the world the ulungur river granites are post orogenic and emplaced in a post collisional extensional environment the peralkaline and aluminous rocks have indistinguishable nd isotopic compositions they have unusually positive and relatively uniform nd t values ranging from 5 1 to 6 7 for the peralkaline rocks at 300 ma and from 5 5 to 5 9 for the aluminous rocks at 270 ma the initial 87sr 86sr ratios cannot be determined precisely by the whole rock isochron technique mainly because most samples are highly radiogenic and have high rb sr ratios in addition the large variation in sr isotopic compositions can partly be explained by crustal contamination during magma differentiation the nd isotopic data clearly indicate that both the peralkaline and aluminous rocks were derived from a long lived depleted mantle reservoir the formation of the ulungur river a type granites is hypothesized as follows 1 a depleted mantle was first metasomatised then subjected to partial melting leading to the generation of basic magmas now represented by the kalatongke mafic ultramafic complex in the ulungur river area 2 the basic magmas have undergone high degrees of fractional crystallisation with separation of biotite hornblende plagioclase potassium feldspar and other accessory phases such as apatite and ilmenite with the residual magmas forming the peralkaline granites during the magmatic differentiation the liquids were probably contaminated by crustal materials as evidenced by nb depletion and nd sr isotopic systematics on the other hand the formation of aluminous granites involved a replenishment of new mantle derived magmas into the differentiating magma chamber and followed by fractional crystallisation with retention of hydrous phases hornblende and biotite the petrological evolution of the ulungur river granites is thus from peralkaline to calc alkaline and not from calc alkaline to peralkaline as more often observed elsewhere the ulungur river granites in common with the voluminous granitoids occurring in the central asian orogenic belt represent a significant juvenile addition of the continental crust in the phanerozoic

developments in monitoring and modelling small scale river bed topography recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography flow hydraulics and sediment transport although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within channel process studies less attention has been given to the accurate monitoring and terrain modelling of river channel form using three dimensional measurements however such information is useful in two distinct senses firstly it is one of the necessary boundary conditions for a physically based deterministic modelling approach in which three dimensional topography and river discharge drive within channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change secondly research has shown that an alternative means of estimating the medium term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel this paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey the availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition a detailed assessment is undertaken of the quality of the morphological information acquired this allow some general comments to be made concerning the use of more traditional methods to monitor and represent small scale river channel morphology

1 88 ga sao gabriel amcg association in the southernmost uatuma anaua domain petrological implications for post collisional a type magmatism in the amazonian craton abstract in the southernmost uatuma anaua domain central amazonian craton brazil crop out 1 98 ga basement inliers represented by meta leucosyenogranites and amphibolites igarape canoas suite 1 90 1 89 ga high k calc alkaline granitoids agua branca suite a 1 88 1 87 ga alkali calcic a type volcano plutonic system iricoume mapuera tonian sio2 satured alkaline granitoids 1 45 1 25 ga orthoderived metamorphic rocks jauaperi complex and orosirian upper triassic mafic intrusions new data on petrography multielementar geochemistry in situ zircon u pb ages and nd and hf isotopes of alkali calcic a type granites sao gabriel granite mapuera suite and related rocks are indicative of a 1 89 1 87 ga volcano plutonic system integrated to the sao gabriel amcg association its magmatic evolution was controlled by the fractional crystallization combined with magma mixing and cumulation processes nd isotope values endt values 3 71 to 0 51 and nd tdm model age 2 44 to 2 12 ga and u pb inherited zircon crystals 2115 22 ma 2206 21 ma 2377 17 ma 2385 17 ma of the sao gabriel system indicate a large participation of siderian rhyacian crust granite greenstones and granulites and small contribution of rhyacian mantelic magma ehft values 5 2 to 5 8 and hf tdm ages 3 27 2 14 ga also point to contribution of paleoarchean rhyacian crustal melts and small participation of siderian rhyacian mantle melts residual melts from the lower crust have been mixed with basaltic melts generated by partial melting of the subcontinental lithospheric mantle peridotite in a post collisional setting at 1 89 1 87 ga the mafic melts of such a mixture could have been originated through partial melting of residual ocean plate fragments eclogites which ascended onto a residual mantle wedge hornblende peridotite and melted it resulting in modified basaltic magma which by underplating led heat to the anatexis of the lower continental crust this widespread alkali calcic a type magmatism was caused by destabilization and magmatic reactivation in the ventuari tapajos and central amazonian provinces resulting from the ventuari tapajos collision periods younger igneous reactivations have been registered at 1 45 to 1 25 ga 1 0 ga and 100 ma culminating with the production of mafic and felsic alkaline magmas along of the northern border of the amazon basin

contribution of small glaciers to global sea level observed long term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers excluding those in greenland and antarctica to the oceans the average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance these data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975 although the error band is large these glaciers appear to account for a third to half of observed rise in sea level approximately that fraction not explained by thermal expansion of the ocean

interpretation of fluid inclusions in quartz deformed by weak ductile shearing reconstruction of differential stress magnitudes and pre deformation fluid properties abstract a well developed theoretical framework is available in which paleofluid properties such as chemical composition and density can be reconstructed from fluid inclusions in minerals that have undergone no ductile deformation the present study extends this framework to encompass fluid inclusions hosted by quartz that has undergone weak ductile deformation following fluid entrapment recent experiments have shown that such deformation causes inclusions to become dismembered into clusters of irregularly shaped relict inclusions surrounded by planar arrays of tiny new formed neonate inclusions comparison of the experimental samples with a naturally sheared quartz vein from grimsel pass aar massif central alps switzerland reveals striking similarities this strong concordance justifies applying the experimentally derived rules of fluid inclusion behaviour to nature thus planar arrays of dismembered inclusions defining cleavage planes in quartz may be taken as diagnostic of small amounts of intracrystalline strain deformed inclusions preserve their pre deformation concentration ratios of gases to electrolytes but their h2o contents typically have changed morphologically intact inclusions in contrast preserve the pre deformation composition and density of their originally trapped fluid the orientation of the maximum principal compressive stress 1 at the time of shear deformation can be derived from the pole to the cleavage plane within which the dismembered inclusions are aligned finally the density of neonate inclusions is commensurate with the pressure value of 1 at the temperature and time of deformation this last rule offers a means to estimate magnitudes of shear stresses from fluid inclusion studies application of this new paleopiezometer approach to the grimsel vein yields a differential stress 1 3 of 300 mpa at 390 30 c during late miocene nnw sse orogenic shortening and regional uplift of the aar massif this differential stress resulted in strain hardening of the quartz at very low total strain 5 while nearby shear zones were accommodating significant displacements further implementation of these experimentally derived rules should provide new insight into processes of fluid rock interaction in the ductile regime within the earth s crust

the pinal schist an early proterozoic quartz wacke association in southeastern arizona abstract at the type locality near globe arizona the pinal schist of early proterozoic age is comprised largely of quartz wacke turbidites which appear to have been deposited as a submarine fan sand grains are principally monocrystalline and polycrystalline quartz derived chiefly from plutonic sources with a minor contribution from low grade metamorphic sources the subrounded to rounded shapes of quartz sand and the sparsity of detrital feldspar indicate a significant pre turbidite erosional history felsic volcanic fragments also comprise variable proportions of the clasts qfl modal parameters indicate a source for pinal sediments comprised chiefly of granites and felsic volcanics representing a recycled terrane major and trace element contents of pinal sediments also suggest that they are largely quartz wackes and that none are graywackes ree elements exhibit typical phanerozoic shale patterns and reflect the importance of granite or rhyolite with negative eu anomalies in the source area high u th rb and hf contents and high rb sr la th and k na ratios also favor a source of dominantly granite and rhyolite an arc setting is clearly unacceptable for the pinal sediments geochemical and petrographic results favor either a continental ridt or collisional orogen a model is proposed in which pinal turbidites accumulate in an inundated continental rift granite and felsic volcanic sources lay to the east and represent older uplifted segments of the rift intense erosion in an intertidal zone may have rounded quartz grains and selectively removed feldspars prior to turbidity current transport

age inheritance and uplift history of the old woman piute batholith california and implications for k feldspar age spectra ion probe u pb zircon analyses yield a crystallization age of 74 pm 3 ma for both peraluminous and metaluminous plutons within the old woman piute batholith these analyses reveal that about 50 of the zircons from the peraluminous sweetwater wash granite are restitic inherited zircons from this batholith yield ages ranging from older than 1800 ma to 1100 ma and most are similar in age to proterozoic igneous rocks in the eastern mojave desert 40 ar 39 ar hornblende ages from the metaluminous granodiorite are 73 pm 2 ma and mica ages from both plutonic series are 70 pm 2 ma k feldspar age spectra yield age gradients with initial steps between 60 and 67 ma and rise to plateau ages of 70 pm 2 ma several k feldspars from the granodiorite yield elevated plateau ages after 50 39 ar released that result from excess argon uplift rates as high as 4 mm yr between 74 and 70 ma are required by the narrow age range for all minerals

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

modification of fluid inclusions in quartz by deviatoric stress i experimentally induced changes in inclusion shapes and microstructures fluid inclusions in quartz are known to modify their shapes and microstructures textures during weak plastic deformation however such changes have not been experimentally demonstrated and criteria are not available to relate them to paleostress conditions to address these issues quartz crystals containing natural co2 h2o nacl fluid inclusions have been experimentally subjected to compressive deviatoric stresses of 90 250 mpa at 700 c and 600 mpa confining pressure strains of up to 1 cause the inclusions to develop irregular shapes and to generate microcracks in crystallographic planes oriented subperpendicular to the major compression axis 1 the uniform alignment of the microcracks imparts a planar fabric to the samples the microcracks heal and form swarms of tiny satellite inclusions these new inclusions lose h2o by diffusion thereby triggering plastic deformation of the surrounding quartz via h2o weakening consequently the quartz samples deform plastically only in domains originally rich in inclusions this study shows that fluid inclusions deformed by deviatoric stresses may indeed record information on paleostress orientations and that they play a key role in facilitating crystal plastic deformation of quartz

dem quality assessment for quantification of glacier surface change photogrammetric digital elevation models dems are often used to derive and monitor surfaces in inaccessible areas they have been used to monitor the spatial and temporal change of glacier surfaces in order to assess glacier response to climate change however deriving photo grammetric dems of steep mountainous topography where the surface is often obscured by regions of deep shadow and snow is particularly difficult assessing the quality of the derived surface can also be problematic as high accuracy ground control points may be limited and poorly distributed throughout the modelled area we present a method of assessing the quality of a derived surface through a detailed sensitivity analysis of the dem collection parameters through a multiple input failure warning model mifwm the variance of a dem cell elevation is taken as an indicator of surface reliability allowing potentially unreliable areas to be excluded from further analysis this analysis allows the user to place greater confidence in the remaining dem an example of this method is presented for a small mountain glacier in svalbard and the mifwm is shown to label as unreliable more dem cells over the entire dem area but fewer over the glacier surface than other methods of data quality assessment the mifwm is shown to be an effective and easily used method for assessing dem surface quality

modification of fluid inclusions in quartz by deviatoric stress iii influence of principal stresses on inclusion density and orientation extraction of useful geochemical petrologic and structural information from deformed fluid inclusions is still a challenge in rocks displaying moderate plastic strain in order to better understand the inclusion modifications induced by deviatoric stresses six deformation experiments were performed with a griggs piston cylinder apparatus natural nacl h2o inclusions in an oriented quartz crystal were subjected to differential stresses of 250 470 mpa at 700 900 c and at 700 1 000 mpa confining pressure independently of the strain rate and of the crystallographic orientation of the quartz the inclusions became dismembered and flattened within a crystallographic cleavage plane subperpendicular to 1 the neonate newly formed inclusions that result from dismemberment have densities that tend towards equilibrium with pfluid 1 at tshearing these results permit ambiguities in earlier deformation experiments on co2 h2o nacl to be resolved the results of the two studies converge indicating that density changes in neonate inclusions are promoted by high differential stresses long periods at high p and high t and fluid compositions that maximize quartz solubility neonates spawned from large precursor inclusions show greater changes in density that those spawned from small precursors these findings support the proposal that deformed fluid inclusions can serve as monitors of both the orientation and magnitude of deviatoric stresses during low strain ductile deformation of quartz bearing rocks

emplacement and tectonic implications of the mid proterozoic peralkaline flowers river igneous suite north central labrador abstract the flowers river igneous suite ca 1270 ma is composed of several discrete plutons of peralkaline granite eccentrically surrounding a circular area of felsic subaerial volcanic rocks dikes of peralkaline granite are oriented tangentially and radially to the volcanic center individual plutons which vary from ring shaped or arcuate to irregular in plan view were emplaced at or near the surface during and or following cogenetic volcanism these features coupled with a remarkable bulls eye aeromagnetic anomaly pattern imply that the flowers river igneous suite is a rudimentary ring complex individual ring dikes were substantially enlarged and modified by piecemeal stoping during emplacement preservation of the volcanic terrain from subsequent erosion appears to reflect cauldron subsidence of the roof of the largest granite pluton the flowers river igneous suite was emplaced in a stable intracratonic environment immediately following a period of substantial uplift and erosion this uplift was permanent induced isostatically by the addition of large volumes of mantle derived magmas during the mid proterozoic heat from the mantle derived magmas together with decompression during uplift and erosion caused small degrees of partial melting in the lower crust and the formation of independent pockets of a type magma these melts intruded the extended crest of the uplifted region forming isolated felsic volcanic centers including the flowers river igneous suite

sims oxygen isotopes indicate phanerozoic fluids permeated a precambrian gold deposit abstract the reef deposit is an anomalous au cu occurrence in the paleoproterozoic terranes of northern wisconsin better known as host to significant cu zn volcanogenic massive sulfide vms deposits previous work using lead isotopes and fluid inclusions has identified a protracted development of the mineralization from initial formation as the root zone veins of a vms deposit during the penokean orogeny 1 9 1 8 ga with the most recent mineralization remobilization activity associated with late paleozoic mississippi valley type mvt fluid flow haroldson et al 2018a 2018b here we use the oxygen isotope history of the reef deposit to verify and further examine the deposit s protracted development laser fluorination oxygen isotope measurements of primary mineralized quartz veins range in 18o from 6 8 to 10 0 vsmow and a trend is observed of increasing 18o values of parallel vein zones along a 400 m traverse from northwest to southeast likely from a temperature gradient during initial formation temperature estimates for a vms deposit setting 230 to 400 c are consistent with a hydrothermally shifted formation fluid using seawater 18o estimates during the penokean orogeny and evolving to higher 18o by incorporation of magmatic fluids or interaction with local crust in situ oxygen isotope measurement by secondary ion mass spectrometer sims of cross cutting quartz and carbonate range in 18o from 19 4 to 28 4 for quartz 25 3 to 28 1 for dolomite and 9 6 to 29 3 vsmow for calcite high 18o values 19 are measured in a crustiform textured quartz stockwork microveinlet in dolomite observed in late carbonate microveinlets and calcite in settings associated with the late quartz and dolomite and a separate calcite only setting directly linked with gold mineralization remobilization

rapakivi granites and related rocks an introduction abstract this article is an introductory chapter for the proceedings of the last seventh meeting of the international geological correlation programme igcp project 315 correlation of rapakivi granites and related rocks on a global scale 1991 1996 based on current knowledge progress made during the six years of the project and the seven papers published in this special issue a synthesis of the age distribution geotectonic environment petrogenesis geochemistry and metallogeny of the rapakivi granites and related rocks is presented

swell and shrinkage characterizations of unsaturated expansive clays from texas abstract expansive soils have long been recognized as problematic because they cause failure to civil structures constructed above them the main problem of these soils can be attributed to poor understanding of the volume changes caused by moisture fluctuations current swell and shrinkage characterization models are limited by both the lack of standardized tests and tests that employ volume changes in uniaxial direction in the present research a comprehensive laboratory investigation was undertaken to study the volume change related swell shrinkage behaviors of five different types of expansive clayey soils sampled from various regions in texas usa extensive experimental programs consisting of basic chemical and mineralogical soil properties were first determined three dimensional free swell and shrinkage tests were performed on all soils at various compaction moisture content conditions soil water characteristic curves swccs of all test soils were determined by studying the suction potentials of these soils over a wide range of moisture contents volume change measurements of soils showed a good correlation with soil properties including plasticity and soil compaction properties swcc results also showed a clear variation in swcc profiles of soils with respect to soil plasticity overall a large database of soil properties was developed and is presented here it includes physical and mineralogical properties as well as engineering swell shrinkage and swcc test results

petrology and age of the a type mulock granite batholith northern grenville province ontario abstract the mulock granite batholith is exposed over 530 km2 in the northern part of the grenville province 25 km north of north bay ontario the batholith has a u pb zircon emplacement age of 1244 4 3 ma two regional tectonic events affected the batholith 1 moderate grade regional metamorphism and 2 shearing and mylonitization related to the grenville front tectonic zone which slices across the northern third of the batholith a suite of fine to coarse grained pink gneissic granites containing accessory fluorite and with colour indices between 1 and 27 dominate the batholith and are cut by abundant aplite dikes anorthosite dikes cut the granites and aplite in the central part of the batholith the granites were originally alkali feldspar granite and syenogranite and the coarser grained varieties were originally hypersolvus the suite is mainly metaluminous to marginally peraluminous peralkaline varieties are rare most of the suite is subalkalic but subordinate alkalic granites enriched in biotite and ferrohastingsite are early phases the suite shows all the major and trace element compositions and elemental ratios diagnostic of a type granite suites metamorphism altered the primary distribution of some of the trace elements particulary rb and f the granites crystallized under relatively low pressures

granitic magma transport by fracture propagation granitic magmas commonly ascend tens of kilometres from their source terranes to upper crustal emplacement levels or to the earth s surface apart from its obvious bearing on the interpretation of the geology and geochemistry of felsic igneous rocks the magma ascent mechanism critically affects any modelling of the metamorphic evolution of the upper lithosphere as well as its rheology we propose that in general granitic magmas ascend via propagating fractures as dykes in extremely short time periods long distance diapiric transport of granitoid magmas through crustal sections is not viable on thermal or mechanical grounds and there is an apparent total absence of field evidence for diapiric rise of such magmas even in supposed type localities neither the shapes nor internal or external characteristics of granitic plutons necessarily reveal anything about the transport of their precursor magmas these are purely arrival phenomena dictated by local structure kinematics and stress states based on existing numerical treatments of the problem we show that granitic magmas are apparently sufficiently inviscid to travel through fractures to high crustal levels without suffering thermal death by freezing for example a 2000 km3 granitic batholith can be inflated by a 1 km 3m 20 km deep dyke system in less than 900 years the model proposed has numerous far reaching petrological and rheological consequences some of which are outlined

changes in geometry and subglacial drainage of midre lovenbreen svalbard determined from digital elevation models digital elevation models dems of the bed and surface of the polythermal midre lovenbreen svalbard are used to identify changes in glacier geometry between 1977 and 1995 the calculated mean annual mass balance 0 61 m water equivalent w e a 1 is more negative than that derived from field measurements 0 35 m w e a 1 although the error associated with this value 0 7 m a 1 suggests that the difference may be accounted for by errors however similar discrepancies between dem based and field based measurements of mass balance have been reported elsewhere in svalbard although errors may be responsible patterns of surface elevation change may also be explained in terms of patterns of ablation accumulation and dynamics the theoretical structure of the subglacial drainage system is modelled using different assumptions about subglacial water pressure in 1977 and 1995 these reconstructions are compared with the observed positions of proglacial outlet streams decreasing subglacial water pressure results in a decrease in the influence of surface morphology and an increase in the role of the bed topography on drainage routing which generally leads to more dispersed drainage long term changes in the position of proglacial outlet streams occur as a result of changes in glacier geometry but short term changes may also occur in response to early season water pressures controlled by meteorological and hydrological conditions copyright 2003 john wiley sons ltd

brine history indicated by argon krypton chlorine bromine and iodine analyses of fluid inclusions from the mississippi valley type lead fluorite barite deposits at hansonburg new mexico argon krypton chlorine bromine and iodine were measured in a homogeneous population of high salinity hydrothermal fluid inclusions from the tertiary age mississippi valley type mvt lead fluorite barite deposits at hansonburg new mexico to establish new types of evidence for the history of both the fluid and the major dissolved salts noble gases and halogens in fluid inclusions containing 10 10 10 9 l of brine cl 3 molal were analyzed by laser microprobe noble gas mass spectrometry lmngms on neutron irradiated samples the concentrations of36ar 4 7 10 8 molal and84kr1 8 10 9 molal in the fluid inclusions are equal to those of fresh surface waters in equilibrium with air at approximately20 5 the mole ratios ofbr cl 1 2 10 4 andi cl 1 2 10 6 are among the lowest measured in any natural waters similar to those of modern brines formed by dissolution of permian nacl bearing evaporites in southeast new mexico 40ar 36ar ratios 600 are twice that of air and indicate that the fluid inclusions had excess radiogenic40ar 1 4 10 5 molal when trapped the amount of excess40ar appears to be too large to have been acquired with cl by congruent dissolution of halite bearing evaporites and possibly too small to have been acquired with pb by congruent dissolution of granitic basement rocks with proterozoic kar ages from thelmngms data combined with published pb and s isotope data we infer the following sequence of events in the history of the hansonburg mvt hydrothermal brine 1 the brine originated as relatively dilute meteoric water and it did not gain or lose atmospheric ar or kr after recharge 2 the originally dilute fluid acquired the bulk of its cl and sulfate in the subsurface after recharge by dissolving halite bearing permian marine evaporites 3 the high salinity brine then acquired most of its pb and excess radiogenic40ar from interactions with aquifer rocks other than evaporites possibly clastic sedimentary rocks or basement rocks with phanerozoic kar ages and 4 the brine deposited fluorite without having boiled or degassed

quantitative estimation of clay mineralogy in fine grained soils stabilization design guidelines based on soil plasticity properties have certain limitations soils of similar plasticity properties can contain different dominant clay minerals and hence their engineering behavior can be different when stabilized with the same chemical additive and dosage it is essential to modify stabilizer design guidelines by including clay mineralogy of the soil and its interactions with chemical additives used chemical properties of a soil including cation exchange capacity cec specific surface area ssa and total potassium tp are dependent on clay mineral constituents and an attempt is made in this study to develop a rational and practical methodology to determine both clay mineralogy distribution and dominant clay mineral in a soil by using three measured chemical soil properties and their analyses this approach has been evaluated by determining and evaluating clay minerals present in artificial and natural clayey soils of known and unknown clay mineralogy a total of twenty natural and six artificial soils were considered and used in the chemical analyses test results and subsequent analyses including the development of artificial neural network ann based models are evaluated and described in this paper

combined raman microprobe spectrometry and microthermometry of fluid inclusions in minerals from igneous rocks of the gardar province south greenland abstract raman microprobe spectrometry has been applied to analysis of the gaseous phase in individual fluid inclusions in minerals from alkalic igneous rock types and associated hydrothermal veins from the gardar province south greenland quantitative analyses are given for co2 ch4 c2h6 h2 and h2s traces of co were observed in one co2 inclusion in conjunction with data from microthermometry the results permit calculation of the bulk chemical composition of entrapped fluids and evaluation of the possible pressure temperature oxygen fugacity and sulphur fugacity during entrapment of the individual fluid inclusions calculated oxygen fugacity values correspond to those of the nno and qfm buffer reactions at temperatures of 300 400 c and pressures of 0 5 1 0 kbar calculated sulphur fugacity values are within the range of normal ore forming solutions log fs2 6 to 10

fluid inclusions in marmarosh diamonds evidence for tectonic history of the folded carpathian mountains ukraine abstract fissures in the nappes of the folded carpathians contain euhedral quartz crystals known as marmarosh diamonds study of marmarosh diamonds collected from the nappes in the ukrainian part of the carpathians showed that these quartz crystals contain abundant primary syngenetic methane rich and aqueous inclusions many of the early inclusions show evidence of explosion decrepitation under conditions of internal overpressure caused by tectonic uplift of the enclosing sediments during miocene times regional mapping of morphologic and microthermometric characteristics of inclusions indicates that the decrepitated inclusions display characteristic textural features and homogenization temperature patterns within the different nappes suggesting that the various nappes have experienced significantly different burial uplift histories thus inclusions reveal an increase in depth of burial from the inner regions of the folded flysch carpathians towards the outer regions about 2 km for the marmarosh nappe 5 km for the rahiv nappe 7 km for the porculec and chornogora nappes and 10 km for the krosno zone the corresponding average geothermal gradients decreased from about 40 45 c km for the marmarosh nappe to about 20 25 c km the krosno zone it is also concluded that the marmarosh nappe followed a p t path close to the original inclusion isochore because inclusions from quartz crystals collected within this nappe show no evidence of decrepitation on the other hand inclusions in quartz from the krosno zone show very intense explosion features and the highest fluid densities that have been recorded for the region suggesting that the krosno zone was the most buried part of the ukrainian folded carpathians during formation of the inclusions

tectonic setting of the sandia pluton an orogenic 1 4 ga granite in new mexico structural studies of the circa 1 42 ga sandia pluton and its aureole document significant deformation synchronous with pluton emplacement and call into question the anorogenic label associated with this and other 1 4 ga granites in the southwestern united states the se margin of the pluton is a 1 to 2 km wide nw dipping ductile shear zone field and microstructural observations melt filled shear bands high temperature dynamic recrystallization of k feldspar megacrysts and crosscutting pegmatite dikes indicate that top to the nw normal movement in the shear zone took place in the presence of melt subparallel magmatic fabrics north of and structurally above the shear zone contain kinematic indicators consistent with top to the nw shear sense suggesting that over large regions of the pluton magmatic flow mimicked solid state strain in the northern aureole contact metamorphic aluminosilicate porphyroblasts grew during the formation of a ne striking crenulation cleavage s3 and related folds of late stage pegmatite dikes these features document the synchroneity of magma emplacement shortening and metamorphism and indicate that the sandia pluton is syntectonic not anorogenic we interpret the kinematic consistency of structural elements from the base of the pluton the interior of the pluton and the northern aureole to reflect a regional larger than the pluton strain field and suggest that the orogeny recorded in and around the sandia pluton involved a three dimensional strain field with subhorizontal extension n s and contraction e w directions n s extension is documented by the orientation of mineral lineations and movement directions in the basal shear zone and in high strain zones in the northern aureole and by the orientations of tabular pegmatite and aplite dikes in the pluton and aureole east to se shortening is documented in the northern aureole by orientations of folded pegmatite dikes and associated s3 crenulation cleavage and east to se shortening or least extension directions in the pluton proper are documented by the intersections of orthogonal dikes thus emplacement of the sandia pluton is interpreted to record a snapshot of regional strains inboard of an active plate margin rather than local strains generated by emplacement

evaluation of swell behavior of expansive clays from internal specific surface and pore size distribution abstractthe interdependency of microsoil fabric related properties and swell shrink behavior of expansive soils needs to be identified to achieve a more thorough and accurate prediction of heave of expansive soils in a recent research study two microsize related properties of a soil pore size distribution and specific surface area were identified and examined in an effort to address their synergistic effects on swelling behavior of soils to study this aspect in detail eight natural expansive clayey soils from known expansive soil regions were sampled and studied by using two test methods conventional one dimensional vertical swell tests and novel three dimensional volumetric swell strain tests microinternal structural details including pore void distribution were obtained from mercury intrusion porosimetry mip studies on compacted soil specimens specific surface area ssa details of the same soils were determined using the chemical ethylene glycol monoethyl ether egme method attempts were m

the penokean orogeny in the lake superior region abstract the penokean orogeny began at about 1880 ma when an oceanic arc now the pembine wausau terrane collided with the southern margin of the archean superior craton marking the end of a period of south directed subduction the docking of the buoyant craton to the arc resulted in a subduction jump to the south and development of back arc extension both in the initial arc and adjacent craton margin to the north a belt of volcanogenic massive sulfide deposits formed in the extending back arc rift within the arc synchronous extension and subsidence of the superior craton resulted in a broad shallow sea characterized by volcanic grabens menominee group in northern michigan the classic lake superior banded iron formations including those in the marquette gogebic mesabi and gunflint iron ranges formed in that sea the newly established subduction zone caused continued arc volcanism until about 1850 ma when a fragment of archean crust now the basement of the marshfield terrane arrived at the subduction zone the convergence of archean blocks of the superior and marshfield cratons resulted in the major contractional phase of the penokean orogeny rocks of the pembine wausau arc were thrust northward onto the superior craton causing subsidence of a foreland basin in which sedimentation began at about 1850 ma in the south baraga group rocks and 1835 ma in the north rove and virginia formations a thick succession of arc derived turbidites constitutes most of the foreland basin fill along with lesser volcanic rocks in the southern fold and thrust belt tectonic thickening resulted in high grade metamorphism of the sediments by 1830 ma at this same time a suite of post tectonic plutons intruded the deformed sedimentary sequence and accreted arc terranes marking the end of the penokean orogeny the penokean orogen was strongly overprinted by younger tectonic and thermal events some of which were previously ascribed to the penokean principal among these was a period of vertical faulting in the archean basement and overlying paleoproterozoic strata this deformation is now known to have post dated the terminal penokean plutons by at least several tens of millions of years evidence of the penokean orogen is now largely confined to the lake superior region comparisons with more recent orogens formed by similar plate tectonic processes implies that significant parts of a once more extensive penokean orogen have been removed or overprinted by younger tectonic events

geochemistry nd and sr isotopes and u pb zircon ages of granitoid and metasedimentary xenoliths from the navajo volcanic field four corners area southwestern united states abstract proterozoic granitoid xenoliths from the navajo volcanic field nvf in the southwestern united states range in composition from tonalite diorite to granite with the latter greatly dominating there is no apparent relationship between chemical or isotopic composition and age geographic location or degree of alteration or deformation of the xenoliths two of the major ages of proterozoic plutonism recognized in the southwest 1 75 1 70 yavapai and 1 45 1 41 ga anorogenic are represented by the nvf xenoliths in some instances within a single diatreme we did not find any xenoliths in the 1 65 1 62 ma mazatzal range the xenoliths are dominantly i types and both nd and sr isotopes and trace element distributions indicate juvenile arc sources approximately 1 8 ga the granite magmas may have been produced by either vapor absent partial melting or fractional crystallization of a tonalite parent juvenile sources must have been available for melting in each of the three periods of magma production and hence some juvenile 1 8 ga crust in this region must have escaped melting in the first two episodes of magmatism and deformation metasedimentary xenoliths are chiefly biotite sillimanite schists garnet biotite schists and garnet paragneisses these three groups are strikingly similar in chemical and isotopic composition suggesting similar graywacke pelite protoliths the schists appear to be limited to the far northern part of the volcanic field consistent with a possible crustal boundary in the basement compositional and thermobarometric results suggest that the biotite schist xenoliths are not restites but that the paragneisses may be mixtures of melt and restite sedimentary protoliths may have been deposited in a forearc basin and later tectonically transported to the deep crust during one or more arc continent collisions in the late paleoproterozoic

determining the extent and nature of mazatzal related overprinting of the penokean orogenic belt in the southern lake superior region north central usa abstract twenty one hornblende and mica 40ar 39ar dates from central and northwest wisconsin usa provide important information on the timing spatial extent and intensity of mazatzal age metamorphism and deformation which overprinted the paleoproterozoic 1870 1820 ma penokean orogenic belt in the southern lake superior region 1760 1750 ma mica plateau ages from bedrock beneath undeformed 1750 1630 ma quartzites are interpreted as the time of lower temperature 300 350 c cooling and crustal stabilization after the penokean orogeny six mica ages from bedrock underlying deformed paleoproterozoic quartzites cluster around 1600 ma 1576 1614 ma the complete absence of 1760 1750 ma mica ages beneath regions of deformed quartzites suggests widespread heating to temperatures above 300 350 c during mazatzal related deformation and metamorphism the 1600 ma mica ages are interpreted to date the cooling phase of this metamorphism two anomalously young biotite dates are interpreted to indicate partial resetting associated with mesoproterozoic rifting at 1100 ma ten hornblende 40ar 39ar dates obtained in this study address the higher temperature overprinting effects in the southern lake superior region one latest archean age of 2503 18 ma and two ages of 1853 and 1830 ma are interpreted as remnant evidence of archean and penokean age amphibolite metamorphic events respectively the majority of hornblende ages are younger than the penokean orogeny scattering between 1796 and 1638 ma microtextural analysis indicates that similar microstructures exist in samples yielding highly discordant hornblende ages this suggests that shearing and recrystallization did not play an important role in the retention or loss of argon the 1638 ma hornblende age is concordant with the mazatzal orogeny to the south and is interpreted as representing complete thermal or fluid related resetting associated with that event six other post penokean ages scatter over a 70 million year interval 1796 1723 ma and probably reflect variable retention of radiogenic argon they are interpreted to indicate variable degrees of partial intermediate temperature 350 500 c resetting of hornblende argon systematics at 1650 1630 ma collectively these data suggest that the effects of the mazatzal orogeny in the southern lake superior region involved 350 500 c metamorphism and penetrative deformation

spatio temporal variability in elevation changes of two high arctic valley glaciers uncertainties in estimates of glacier and ice cap contribution to sea level rise exist in part due to poor quantification of mass balance errors particularly those resulting from extrapolation of sparse measurements centre line data are often assumed to be representative of the glacier as a whole with little attention paid to extrapolation errors or their effect on mass balance estimates here we present detailed digital elevation model dem measurements of glacier wide elevation changes over the last 40 years at two glaciers on svalbard norwegian arctic austre broggerbreen and midtre lovenbreen are shown to have lost 27 54 0 98 and 9 65 0 76 10 7 m 3 of ice respectively between 1966 and 2005 findings that we relate to trends in average summer air temperatures and winter accumulation these volume losses correspond to geodetic balances of 0 58 0 03 and 0 41 0 03 m w e a 1 respectively our analysis revealed high spatial complexity in patterns of elevation change varying between glaciers between measurement intervals and within and between elevation bins balances from extrapolated centre line geodetic data were the same within errors as those from full coverage dem differencing in the majority of comparisons yet significantly underestimated balance in three instances additionally field mass balance from centre line ablation stake data underestimated balances from full coverage geodetic measurements during three of six measurement periods these findings may support the hypothesis that field measurements under estimate svalbard glacier mass loss at least partly as a result of the failure of centre line measurements to account for glacier wide variations in ablation our results demonstrate the importance of deriving accurate interpolation functions and constraining extrapolation errors from sparse measurements

modification of fluid inclusions in quartz by deviatoric stress ii experimentally induced changes in inclusion volume and composition fluid inclusions in quartz are known to modify their densities during shear deformation modifications of chemical composition are also suspected however such changes have not been experimentally demonstrated their mechanisms remain unexplained and no criteria are available to assess whether deformed inclusions preserve information on paleofluid properties to address these issues quartz crystals containing natural co2 h2o nacl fluid inclusions have been experimentally subjected to compressive deviatoric stresses of 90 250 mpa at 700 c and 600 mpa confining pressure the resulting microcracking of the inclusions leads to expansion by up to 20 producing low fluid densities that bear no relation to physical conditions outside the sample nevertheless the chemical composition of the precursor inclusions is preserved with time the microcracks heal and form swarms of tiny satellite inclusions with a wide range of densities the highest reflecting the value of the maximum principle stress 1 these new inclusions lose h2o via diffusion thereby passively increasing their salt and gas contents and triggering plastic deformation of the surrounding quartz via h2o weakening using microstructural criteria to identify the characteristic types of modified inclusions both the pre deformation fluid composition and syn deformation maximum stress on the host mineral can be derived from microthermometric analysis and thermodynamic modelling

volatiles associated with alkaline igneous rift activity fluid inclusions in the ilimaussaq intrusion and the gardar granitic complexes south greenland abstract fluid inclusions in minerals from si oversaturated and si undersaturated alkalic igneous complexes belonging to the precambrian gardar rift province in south greenland contain distinctly different carbon bearing gases granites and quartz syenites are characterized by co2 and only minor ch4 whereas agpaitic nepheline syenites are dominated by hydrocarbons essentially ch4 and contain only insignificant amounts of co2 and or co in the alkaline ilimaussaq intrusion the hydrocarbon rich gases may well reflect equilibration with graphite at magmatic temperatures and at oxygen fugacities approaching those defined by the synthetic mw buffer reaction in general formation of hydrocarbon gases in agpaitic nepheline syenites is considered to reflect the fulfillment of three basic conditions 1 low oxygen fugacities 2 a wide temperature range of crystallization and a low temperature solidus and 3 retention of volatiles during crystallization the characteristic carbon bearing vapour associated with continental alkaline igneous activity is however considered to be co2

multiple fluid sources pathways and severe thermal gradients during formation of the jilove orogenic gold deposit bohemian massif czech republic abstract the jilove deposit in the central part of the bohemian massif represents a vein to stockwork type of orogenic type gold deposit it is hosted by neoproterozoic rocks of the jilove belt and by various magmatic dikes related to the 355 to 335 ma central bohemian plutonic complex the deposit is situated along the terrane boundary of the tepla barrandian and moldanubian units the deposit offered an exceptional opportunity to trace o c s and sr stable isotope evolution of parent fluids based on combined mineralogical and geochemical study of carbonate quartz scheelite and sulfide minerals which represent six stages of mineralization including the gold bearing event stable isotope data and mineral and isotope thermometry indicate gangue and ore mineral formation between 350 c and 18 o smow 4 2 0 5 and 13 c pdb 11 1 gold precipitation stage 5 probably started at about 300 c but the major event probably occurred at 230 30 c from a fluid with more variable isotope values 18 o smow 2 5 to 5 and 13 c pdb 9 to 13 5 the carbon speciation was characterized by predomination of dissolved co 2 h 2 co 3ap in the fluids some gold however undoubtedly precipitated from bicarbonate dominated fluids even at extreme variations in the 18 o values of carbonate minerals obtained from sampling profiles across individual veins with macroscopic gold revealed severe thermal gradients during vein formation 50 to 100 c difference of crystallization temperatures between the vein margin and core the sulfur stable isotope composition of sulfide minerals indicates the dominant role of sulfur remobilization from neoproterozoic rocks and stratiform mineralizations of the jilove belt by variscan hydrothermal fluids similarly the sr isotope composition of carbonates indicates both relatively primitive 87 sr 86 sr 0 7055 and more evolved 87 sr 86 sr 0 7090 fluid compositions probably indicating fluid exchange with the jilove belt and the central bohemian plutonic complex rocks respectively age determination of hydrothermal muscovite related to stage 2 via 40 ar 39 ar indicated an age of 339 0 1 5 ma for the quartz veins the mineralization is essentially coeval with the late intrusive phases of the central bohemian plutonic complex i e the ultrapotassic suite and with late orogenic large scale tectonic movements at the boundary between the two crustal terranes tepla barrandian and moldanubian based on evaluation of the available age data on the hydrothermal and magmatic activity within the broader area of the central bohemian plutonic complex we suggest two intervals of gold mineralization 347 to 341 ma and 340 to 337 ma the former interval overlaps with the intrusive activity of the blatna high k suite granodiorite the associated gold deposits mokrsko and petrackova hora exhibit strong affiliation to the intrusion related gold type deposit the later interval overlaps with the ultrapotassic magmatism and is associated with more or less classical orogenic gold type deposits jilove b lcice libcice deposits

tectono stratigraphic evolution of the early proterozoic wisconsin magmatic terranes of the penokean orogen the early proterozoic penokean orogen developed along the southern margin of the archean superior craton the orogen consists of a northern deformed continental margin prism overlying an archean basement and a southern assemblage of oceanic arcs the wisconsin magmatic terranes the south dipping niagara fault suture zone separates the south facing continental margin from the accreted arc terranes the suture zone contains a dismembered ophiolite the wisconsin magmatic terranes consist of two terranes that are distinguished on the basis of lithology and structure the northern pembine wausau terrane contains a major succession of tholeiitic and calc alkaline volcanic rocks deposited in the interval 1860 1889 ma and a more restricted succession of calc alkaline volcanic rocks deposited about 1835 1845 ma granitoid rocks ranging in age from about 1870 to 1760 ma intrude the volcanic rocks the older succession was generated as island arcs and or closed back arc basins above the south dipping subducti

tectonic setting of the midcontinent rift system abstract the continental lithosphere which hosts the midcontinent rift mcr system comprises a crustal assemblage ranging in age from 3 6 to 1 5 ga the most voluminous igneous activity along the mcr occurred within late archean 2 7 ga crust presumably due to magmatism associated with a rising mantle plume two major arms of the rift extend to the southeast and the southwest where rifting magmatism and sedimentation were confined to a 2000 km long rift that cuts through the various crustal provinces ranging in age from 3 6 to 1 5 ga tensional reactivation of pre existing crustal discontinuities may have influenced the location of parts of the mcr however direct cause and effect are difficult to distinguish for want of sufficient exposures the most active phases of magmatism and rifting occurred between 1109 and 1087 ma a u pb age of 1097 ma for the southern end of the mcr shows that magmatic activity was synchronous throughout its length there is evidence of rifting and magmatism prior to 1109 ma but there is little evidence of magmatism after 1087 ma rifting may have effectively ceased by that time rifting may have ceased as a result of compressional forces being exerted on the foreland during the grenville collisional event spanning 1030 970 ma and compressional reactivation of normal faults may have resulted in partial inversion of the mcr chemical data and u pb and sm nd isotopic data for igneous rocks along the rift are similar to those for mcr rocks in the lake superior area which are best explained in terms of a mantle plume model however since the distal arms of the mcr were developed in proterozoic lithosphere and did not involve nearly as much magmatism as in the lake superior area mantle plume sources may not have been as important in formation of the distal magmas data from the buried arms are also consistent with the mafic magmas being derived by decompression melting of proterozoic lithosphere during rifting

gold butte crustal section south virgin mountains nevada the gold butte block consists of a complex of proterozoic medium to high grade metamorphic and plutonic rocks unconformably overlain by steeply east dipping paleozoic sedimentary rocks on its east side this complex is one of the largest continuous exposures of crystalline rocks in the southwestern united states that lie structurally beneath a steeply tilted section of phanerozoic strata and it may represent part of an intact proterozoic miocene crustal section reaching paleodepths of approximately 15 km the section was exposed during tectonic denudation in miocene time at about 15 ma and lies directly adjacent to the colorado plateau to the east proterozoic and tertiary geological features support the hypothesis that the block represents a relatively intact crustal section a large exposure of proterozoic rapakivi granite the gold butte granite circa 1 45 ga crops out over most of the crystalline complex and displays strong zoning in phenocryst abundance which increases toward the top of a 10 to 12 km thick magma chamber the wallrocks of the granite are predominantly garnet bearing gneisses circa 1 7 ga which display increasing pressures of final equilibration westward away from the basal phanerozoic unconformity thermobarometry of gneisses immediately beneath the unconformity indicate pressures of 2 3 kbar whereas those 12 13 km west of the unconformity yield pressures of 5 6 kbar suggesting the crustal section was established by 1 7 ga the style of deformation displayed by denudation structures also varies from east to west with brittle faulting only in eastern portions of the block and retrograde metamorphism mylonitization and chlorite brecciation of the garnet gneiss observed in western areas

mid cenozoic stress evolution and magmatism in the southern cordillera texas and mexico transition from continental arc to intraplate extension orientations of dikes veins faults and slickenlines reveal the evolution of stress during eocene to miocene magmatism in the southern cordillera where most thoroughly studied by us in trans pecos texas magmatism began at about 48 ma shortly after the cessation of laramide folding dikes and veins that formed from then until about 32 ma strike dominantly east northeast this indicates that the least principal stress 3 was north northwest additional data suggest that the maximum principal stress 1 was east northeast the stress field changed to 1 vertical and 3 east northeast i e east northeast extension at least by 28 ma and probably by 31 ma dikes and veins that formed between 31 and 17 ma when all magmatism ceased in texas strike north northwest this change marks the beginning of regional basin and range extension however major normal faulting exclusively of high angle type did not begin until about 24 ma a similar stress change marked by a similar change in dike and vein orientations occurred throughout the southwestern united states and northern mexico the time of change is not well constrained in texas but available information allows it to have occurred at the same time thoughout the southern cordillera we suggest the earlier stress field is related to east northeast convergence between the farallon and north american plates the change in stress is approximately coincident with collision of the east pacific rise and paleotrench extension may be related to the change from a convergent to a transform margin along the western edge of north america the changes in the stress field are accompanied by changes in the sources and compositions of magmas erupted in texas contemporaneity of the changes in stress and magmatism indicates that they are related combined with regional age patterns paleostress and geochemical data indicate that pre 31 ma magmatism in the southern cordillera occurred in a subduction related continental volcanic arc subsequent magmatism occurred in an environment of intraplate extension of the basin and range province

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

characteristics and geological setting of synkinematic svecokarelian granitoids in southern finland abstract synkinematic granitoids are the predominant component of the svecokarelian crust their zircon u pb ages vary from 1900 to 1860 ma mainly 1890 1870 ma being roughly similar to those of mafic plutonic rocks and metavolcanic rocks synkinematic granitoids occur as distinct plutons in schist belts and also form the granitold complex of central finland with a total area in excess of 35 000 km2 the granitoids in schist belts occur as concordant plutons although locally they have cross cutting contacts and they crystallized soon after the peak of major regional deformation and metamorphism but before younger deformation phases they are composed of granodiorites tonalites and trondhjemites composite plutons are often zoned with gabbro diorite tonalite and or trondhjemite at their margins and with granodiorite and less commonly granite at their centres the granitoid complex of central finland is composed of a vast number of intrusions ranging in composition from gabbro to granite the granite intrusions comprising large parts of the complex coarse grained granitoids and polyphase deformation are common major minerals of the synkinematic granitoids are plagioclase potassium feldspar quartz biotite and hornblende typical accessories are sphene apatite magnetite and zircon whole rock analyses of 143 granitoids from throughout southern finland show calc alkaline characteristics with variable sio2 high na2o k2o and a cnk below 1 1 initial 87sr 86sr ratios are low the granitoid complex of central finland has higher feo mgo and k2o na2o than the granitoids in schist belts irrespective of silica content the synkinematic granitoids have the geological and geochemical characteristics of phanerozoic i type granitoids and are cogenetic with mafic plutonic rocks intrusion of these latter evidently caused major remelting in the lower crust giving rise to granitoid magmas so that a variable mixing of mantle derived and crustal magmas is probable according to nd isotopes studies archaean material was insignificant in the source of the granitoids except near the border zone of the archaean craton this indicates rapid recycling of material newly derived from the mantle geochemical features of the granitoid complex may also reflect a thicker crust in central finland than in surrounding areas during the generation of the granitoids many characteristics of the synkinematic granitoids strongly suggest a subduction related origin however the similarity in isotopic ages and lack of obvious linear trends in distribution of rock types combined with evidence for a minor older crustal component in their source indicates that the processes were not identical to those operating at modern continental margins

geochemical and nd isotopic systematics of granites from the arunta inlier central australia implications for proterozoic crustal evolution geochemical and sm nd isotopic results are reported for granites from the proterozoic arunta inlier of central australia these combined with new geochronological data for the granites zhao and bennett 1995 allow important constraints to be placed on proterozoic tectonic and crustal evolution in central australia granites from the arunta inlier can be divided into three major geochemical groups a calcalkaline trondhjemitic group cat a high heat production group hhp and a volumetrically significant main group the cat group which occurs only in the southern margin of the inlier is characterised by high na2o nak sr krb and sry and relatively low k2o rb rbsr th u ree nb and y analogous to calc alkaline suites occurring in modern convergent plate margins the hhp group which occurs mainly in the interior of the arunta inlier and is spatially associated with the main group is characterised by high k rb th u rbsr and rbzr and relatively low sr ba nak krb barb mgo cr and ni the main group which occurs throughout the arunta inlier is geochemically intermediate between the cat and hhp groups it is geochemically analogous to the 1880 1850 ma old barramundi igneous association recognised in other proterozoic terrains of central australia and can be further subdivided into four age subgroups 1820 1780 1750 1650 and 1615 1600 ma respectively all three groups show similar negative nb anomalies on the trace element normalized diagrams despite the geochemical diversity of the arunta granites no correlations between the nd isotopic and geochemical signatures are observed the ranges of initial nd values and nd depleted mantle model ages tnddm for the three groups of granites overlap with each other overall there are two groups of tnddm ages the most common ranging from 2 33 to 1 96 ga and the other from 1 83 to 1 72 ga although initial nd values of the granites show large variations there is a general trend for the nd values to increase i e become less negative with decreasing crystallization ages the large geochemical and isotopic variations of the arunta granites reflect considerable heterogeneity in the sources of the granites and do not support a uniform 2 3 2 1 ga old barramundi type underplate source for the origin of the granites the combined geochemical and nd isotopic data suggest the sources of the granites contain at least two main components an palaeoproterozoic mantle derived component and an older crustal component the older crustal component was incorporated into the source region of the granites either through magma assimilation of crustal materials at lower crustal levels or more probably via sediment subduction and mantle wedge metasomatism the increasing nd values with decreasing crystallization ages may be a result of progressively increasing proportions of newly accreted island arc materials being incorporated in the subducted sediments alternatively a juvenile mantle derived component may have been added to the source region of the younger granites it is apparent that the nd isotopic signatures in the granites has resulted from complex processes and neither simple mixing nor simple two stage protolith models can as yet satisfactorily explain the observations the petrogenesis of the three geochemical groups of granites can be interpreted in a plate tectonics scenario it is considered that the cat group was formed by fractionation of arc type magmas and or partial melting of arc related intrusions or underplates in a subduction related continental margin setting whilst the formation of the main group may involve partial melting of fractionated and or modified arc related underplates but not necessarily in a subduction environment the younger hhp group was probably generated by remelting of the coexisting main group during subsequent tectonothermal events

miocene rapakivi granites in the southern death valley region california usa abstract rapakivi granites in the southern death valley region california include the 12 4 ma granite of kingston peak the ca 10 6 ma little chief stock and the 9 8 ma shoshone pluton all of these granitic rocks are texturally zoned from a porphyritic rim facies characterized by rapakivi textures and miarolitic cavities to an equigranular aplite core these granites crystallized from anhydrous and peraluminous to metaluminous magmas that were more oxidized and less alkalic than type rapakivi granites from southern finland chemical and isotope nd sr pb data suggest that rapakivi granites of the southern death valley region were derived by partial melting of lower crustal rocks possibly including mesozoic plutonic component with some mantle input as well they were emplaced at shallow crustal levels 4 km in an actively extending orogen

strata bound fe co cu au bi y ree deposits of the idaho cobalt belt multistage hydrothermal mineralization in a magmatic related iron oxide copper gold system mineralogical and geochemical studies of strata bound fe co cu au bi y rare earth element ree deposits of the idaho cobalt belt in east central idaho provide evidence of multistage epigenetic mineralization by magmatic hydrothermal processes in an iron oxide copper gold iocg system deposits of the idaho cobalt belt comprise three types 1 strata bound sulfide lenses in the blackbird district which are cobaltite and less commonly chalcopyrite rich with locally abundant gold native bismuth bismuthinite xenotime allanite monazite and the be rich silicate gadolinite y with sparse uraninite stannite and bi tellurides in a gangue of quartz chlorite biotite muscovite garnet tourmaline chloritoid and or siderite with locally abundant fluorapatite or magnetite 2 discordant tourmalinized breccias in the blackbird district that in places have concentrations of cobaltite chalcopyrite gold and xenotime and 3 strata bound magnetite rich lenses in the iron creek area which contain cobaltiferous pyrite and locally sparse chalcopyrite or xenotime most sulfide rich deposits in the blackbird district are enclosed by strata bound lenses composed mainly of cl rich fe biotite some deposits have quartz rich envelopes whole rock analyses of 48 co and or cu rich samples show high concentrations of au up to 26 8 ppm bi up to 9 16 wt y up to 0 83 wt rees up to 2 56 wt ni up to 6 780 ppm and be up to 1 180 ppm with locally elevated u up to 124 ppm and sn up to 133 ppm zn and pb contents are uniformly low 821 and 61 ppm respectively varimax factor analysis of bulk compositions of these samples reveals geochemically distinct element groupings that reflect statistical associations of monazite allanite and xenotime biotite and gold detrital minerals chalcopyrite and sparse stannite quartz and cobaltite with sparse selenides and tellurides significantly cu is statistically separate from co and as consistent with the general lack of abundant chalcopyrite in cobaltite rich samples paragenetic relations determined by scanning electron microscopy indicate that the earliest y ree be mineralization preceded deposition of co cu au and bi allanite xenotime and gadolinite y commonly occur as intergrowths with and inclusions in cobaltite the opposite texture is rare monazite in contrast forms a poikiloblastic matrix to cobaltite and thin rims on allanite and xenotime reflecting a later metamorphic paragenesis allanite and xenotime also show evidence of late dissolution and reprecipitation forming discordant rims on older anhedral allanite and xenotime and separate euhedral crystals of each mineral textural data suggest extensive deformation of the deposits by folding and shearing and by pervasive recrystallization all during cretaceous metamorphism sensitive high resolution ion microprobe u pb geochronology by aleinikoff et al 2012 supports these paragenetic interpretations documenting contemporaneous mesoproterozoic growth of early xenotime and crystallization of megacrystic a type granite on the northern border of the district these ages are used together with mineralogical and geochemical data from the present study to support an epigenetic iocg model for fe co cu au bi y ree deposits of the idaho cobalt belt a sulfide facies variant of iocg deposits is proposed for the blackbird district in which reducing hydrothermal conditions favored deposition of sulfide minerals over iron oxides this new model includes mesoproterozoic vein mineralization and related fe cl metasomatism that formed the biotite rich lenses a predominantly felsic magmatic source for metals in the deposits given their local abundance of y rees and be and a major sedimentary component in the hydrothermal fluids based on independent sulfur isotope and boron isotope data for sulfides and ore related tourmaline respectively

proterozoic anorogenic magmatism and its orogenic connections there is a major belt of proterozoic so called anorogenic igneous rocks that extends from the baltic shield through southern greenland and eastern canada to southern usa all rocks are situated within a zone of 1 9 1 6 ga arc accretionary orogens that consist of juvenile mantle derived material especially accretionary prism sediments that provided the fertile source for abundant granitic crustal melts there were two main periods of formation of the anorogenic rocks 1 76 1 55 ga rocks are mainly rapakivi granites and rhyolites that formed about 60 200 ma after the last compressional events in the svecofennian ketilidian and penokean orogens the time lag being caused by the slow thermal relaxation of thickened lower crust that had commonly been depleted by the extraction of earlier granitic crustal melts 1 45 1 4 ga anorogenic rocks are mainly rhyolites and peraluminous granites in central southern usa and anorthosites in eastern canada that formed in the continental margin of the grenvillian ocean the subduction of which led to the grenville orogen these anorogenic igneous rocks formed in extensional regimes during the formation and breakup of a 1 5 ga supercontinent

age and origin of authigenic k feldspar in uppermost precambrian rocks in the north american midcontinent authigenic k feldspar occurs widely in the north american midcontinent in an alteration profile developed on uppermost precambrian rocks in the study areas of west central wisconsin and southeast missouri the alterationprofiles are kaolinitic and interpreted as former saprolite formed by weathering prior to deposition of upper cambrian sandstone k feldspar in granitic alteration profiles of west central wisconsin occurs either as coarse grained red crystals and veins replacing kaolinite or as overgrowths and fine grained crystals in pore space of partly altered granite in a granitic profile of southeast missouri k feldspar replaces primary feldspar and probably kaolinite in a diabasic profile k feldspar is disseminated and forms veins in saprolite and it replaces the outer 3 5 cm of core stones dating was conducted with the 4 0 ar 3 9 ar method using incremental heating observed spectral types are plateaus 6 near plateaus 3 undulatory 14 and stair step 5 undulatory patterns are attributed chiefly to recoil and integrated ages of these are usually within the error of plateau ages where present indicating a balanced enrichment depletion of 3 9 ar due to recoil stair step spectra are attributed to severe recoil plateau 4 0 ar 3 9 ar ages of 446 427 ma late ordovician and silurian were obtained from coarse grained k feldspar replacing kaolinite in wisconsin suggesting a duration of the alteration episode of 19 m y however potentially accurate nonplateau age measurements integrated and near plateau ages suggest that alteration continued for a considerable time thereafter possibly to ca 399 395 ma early devonian integrated 4 0 ar 3 9 ar ages of ca 362 ma late devonian and or early mississippian were obtained from fine grained k feldspar plateau ages of ca 450 late ordovician were obtained from k feldspar of the diabase profile in missouri duration of k feldspar alteration in this region was at least 16 m y and may have been as long as 52 m y the late devonian early mississippian k feldspar formed at temperatures of 100 c from saline fluid averaging 10 nacl equivalent and having a 1 8 o value of 3 5 this brine may have originated from the michigan basin east central iowa basin and or the illinois basin coincident with the acadian orogeny the middle ordovician to early devonian dates of k feldspar do not generally correspond in time with orogenic activity at the continental margin and the mechanism s for forming the k feldspar are uncertain fluid sources proposed for some or all of the k feldspar include the michigan basin taconic mountains reelfoot rift illinois basin and midcontinent epeiric seas middle ordovician k feldspar of missouri very likely formed at elevated temperatures but evidence of fluid temperature is lacking for other pre late devonian k feldspar

h2och4naclco2 inclusions from the footwall contact of the tanco granitic pegmatite estimates of internal pressure and composition from microthermometry laser raman spectroscopy and gas chromatography abstract fluid inclusions in tourmaline and quartz from the footwall contact of the tanco granitic pegmatite s e manitoba were studied using microthermometry mt laser raman spectroscopy lrs and gas chromatography gc ch 4 bearing aqueous inclusions occur in metasomatic tourmaline of the footwall amphibolite contact the internal pressures estimated from mt are lower than those obtained from lrs mean difference 54 19 bars the difference is probably due to errors in the measurement of th ch 4 v and to the presence of clathrate at th ch 4 v into which co 2 had been preferentially partitioned lrs estimates of pressure 125 184 bars are believed to be more accurate aqueous phase salinities based on lrs estimates of pressure are higher than those derived using the data from mt 10 20 eq wt nacl the composition of the inclusions determined by gc bulk analysis is 97 3 mol h 2 o 2 2 mol ch 4 0 4 mol co 2 250 ppm c 2 h 6 130 ppm n 2 33 ppm c 3 h 8 11 ppm c 2 h 4 and 3 ppm c 3 h 6 plus trace amounts of c 4 hydrocarbons the composition is broadly similar to that calculated from mt 92 h 2 o and 8 ch 4 with 7 eq wt nacl dissolved in the aqueous phase and 2 mol co 2 dissolved in the ch 4 phase as expected due to the dominance of a single generation of inclusions in the tourmaline however two important differences in composition are 1 i the ch 4 to co 2 ratio of this fluid determined by gc is 5 33 which is significantly lower than that indicated by mt 49 0 and 2 ii the h 2 o content estimated from mt is 92 mol compared to 98 mol from gc gc analyses may have been contaminated by the presence of secondary inclusions in the tourmaline however the rarity of the latter suggests that they cannot be completely responsible for the discrepancy the differences may be accounted for by the presence of clathrate during measurement of th ch 4 critical which would reduce co 2 relative to ch 4 in the residual fluid and by errors in visually estimating vol h 2 o the compositions of the primary inclusions in tourmaline are unlike any of those found within the pegmatite and indicate that the fluid was externally derived probably of metamorphic origin inclusions in quartz of the border unit of the pegmatite are secondary and are either aqueous 18 to 30 eq wt cacl 2 th total 184 14 c or carbonic tm co 2 for the carbonic inclusions ranges from 57 5 to 65 4 c and is positively correlated with th co 2 analyses of x ch 4 based on lrs agree within 5 mol of those derived from mt and together indicate a range of compositions from 5 to 50 mol ch 4 in the co 2 phase bulk analysis by gc gives 99 0 mol h 2 o 0 6 mol co 2 0 4 mol ch 4 160 ppm n 2 7 ppm c 2 h 6 4 ppm c 3 h 8 and 2 ppm c 2 h 4 with trace amounts of cos carbonyl sulphide and c 3 h 6 the level of h 2 o in the analysis is consistent with the dominance of the aqueous inclusions in these samples and the ch 4 co 2 ratios are consistent with estimates from mt and lrs the preservation of variable ratios of ch 4 co 2 in inclusions 2 diffusion out of the inclusions nor reduction of fluids leaving the pegmatite were responsible for the more oxidized chemistries of the border unit inclusions relative to those in the tourmaline of the metasomatised amphibolite the compositions of the inclusions in the quartz lie between those of the fluid trapped by the tourmaline externally derived and the measured composition of a co 2 bearing pegmatitic fluid which indicates that the secondary fluids trapped in the border unit quartz were produced by late mixing

experimental studies on stabilized clays at various leaching cycles abstractthe effectiveness of chemical stabilization and its permanency were investigated by subjecting chemically treated soils to leaching tests by internal water flushing which simulates moisture ingress digress into subsoils from rainfall events control and chemically stabilized soils from eight different locations were subjected to these leaching tests over 14 cycles in the laboratory each leaching cycle represents one pore volume of water flushed through the soil specimen leaching samples were collected after 3 5 7 and 14 cycles and were chemically analyzed to address pore fluid chemical composition changes and possible leaching of the chemical additives unconfined compressive strength tests were conducted on soil specimens after 3 7 and 14 leaching cycles to study soil strength variations the effects of soil type stabilizer type and dosages and the curing method on the leaching of stabilizers are analyzed test results and analyses indicate that leaching of stabilizer did occur but the

the pilot knob magnetite deposit in the proterozoic st francois mountains terrane southeast missouri usa a magmatic and hydrothermal replacement iron deposit abstract the pilot knob magnetite deposit is located in southeast missouri within the 1380 1480 ma st francois mountains terrane rhyolitic trachytic volcanic rocks the deposit is tabular dips about 45 and is sill like in nature being approximately parallel to the bedding in the host tuffs the deposit was uncovered by erosion and exposed to weathering in the late proterozoic and is overlain in angular unconformity by the cambrian lamotte sandstone this proterozoic weathering cycle apparently had little effect on the deposit with only the updip edge being converted to hematite textural and mineralogical features of the deposit suggest a combined magmatic and hydrothermal replacement origin the magnetite rich ores that make up the bulk of the deposit are interpreted as having crystallized from an iron rich magma and a surrounding envelope of lower to moderate grade ores where magnetite has clearly replaced the tuffaceous host rocks are interpreted as hydrothermal in origin after the development of the higher grade magnetite ores and the envelope of lower to moderate grade ores late hydrothermal minerals were deposited as cross cutting veins and breccia fill the two most abundant minerals in the higher grade portions of the deposit are magnetite and albitic plagioclase and petrologically the higher grade ores could be described as a magnetite sodic syenite the most abundant gangue mineral within the lower grade impregnated envelope of ores around the higher grade ores is k feldspar apparently relict from the rhyolites trachytes thin lenses within the higher grade ores contain calcite as a matrix mineral to the magnetite and are considered to indicate carbonatitic affinity rare earth elements are elevated in one of five whole rock chemical analyses of the ores and the ree bearing mineral ferriallanite has been identified minor portions of the deposit below the proterozoic weathering cap consist of high grade hematite ores having equilibrium textures at depth the deposit is intruded by the shepherd mountain gabbro a 120 m thick near horizontal dike which resulted in minor contact metamorphism of the ore

nagarparker granites showing rodinia remnants in the southeastern part of pakistan abstract the nagarparker area of the trans aravalli belt comprises precambrian igneous and metamorphic basement rocks predominantly granites these granites are subalkalic to alkalic a type containing riebeckite ferro richterite ferro edenite arvedsonite amphiboles and rutile zircon apatite allanite titanite titano magnetite ilmenite magnetite and fluorite accessory minerals the variations in nb y ce and ga and ga al ratios typify the granites of the area as post orogenic a2 type formed possibly by partial melting of the island arc crust in a rift related within plate tectonic setting the granites of the area yielded u th pb epma zircon and monazite radiometric ages between 1100 and 700 ma mostly concentrating around 750 ma based on petrological geochemical and geochronological resemblance of granites of the nagarparker area with those of the seychelles islands and the malani igneous suite it is inferred that being part of trans aravalli belt of the indian shield the nagarparker area might have shouldered the seychelles islands towards the western side of the rodinia before the supercontinent rifted in neoproterozoic

ore forming fluids in archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec canada archean gold bearing quartz veins at the sigma mine occur in deformed metavolcanics intruded by two generations of preore porphyries the veins were emplaced during a late compressional tectonic event and they consist primarily of quartz tourmaline carbonates pyrite and scheelite vein minerals have been deformed and are also cut by abundant healed fractures outlined by fluid inclusions in the veins gold typically occurs in late fractures and in recrystallized quartz microthermometric sem eda leachate analysis and gas chromatographic techniques were used to study fluid inclusions in quartz most fluid inclusions at sigma occur in late fractures and are secondary the fluid inclusions are commonly found in fractures parallel to or less commonly within gold bearing fractures and are genetically related to the gold three types of fluid inclusions are identified 1 high salinity na ca cl aqueous inclusions 25 34 wt salt with small amounts of co 2 some containing halite calcite and nahcolite as daughter minerals 2 co 2 rich inclusions containing small amounts of h 2 o and ch 4 and 3 low salinity h 2 o co 2 inclusions 10 equiv wt nacl with co 2 contents which are variable but commonly in the range of 15 to 30 mole percent co 2 leachate analyses show that in addition to na and ca the aqueous fluids contain minor amounts of k fe mg and li homogenization temperatures of h 2 o co 2 inclusions with constant phase ratios range from 285 degrees to 395 degrees c those of aqueous inclusions range from 60 degrees to 295 degrees c the aqueous and co 2 rich inclusions are interpreted to have trapped two coexisting fluids resulting from the unmixing of a homogeneous h 2 o co 2 parent fluid itself occasionally trapped in late fractures the ore bearing fluid is interpreted to be a low salinity 10 equiv wt nacl fluid containing 15 to 30 mole percent co 2 at minimum temperatures in the range of 285 degrees to 395 degrees c the relatively low homogenization temperatures of aqueous inclusions are interpreted to be the result of co 2 effervescence from a co 2 saturated aqueous fluid due to pressure fluctuations at the time of entrapment it is also proposed that the onset of gold deposition is related to the onset of fluid unmixing

morphological ripening of fluid inclusions and coupled zone refining in quartz crystals revealed by cathodoluminescence imaging implications for cl petrography fluid inclusion analysis and trace element geothermometry cathodoluminescence cl studies have previously shown that some secondary fluid inclusions in luminescent quartz are surrounded by dark non luminescent patches resulting from fracture sealing by late trace element poor quartz this finding has led to the tacit generalization that all dark cl patches indicate influx of low temperature late stage fluids in this study we have examined natural and synthetic hydrothermal quartz crystals using cl imaging supplemented by in situ elemental analysis the results lead us to propose that all natural liquid water bearing inclusions in quartz whether trapped on former crystal growth surfaces i e of primary origin or in healed fractures i e of pseudosecondary or secondary origin are surrounded by three dimensional non luminescent patches cross cutting relations show that the patches form after entrapment of the fluid inclusions and therefore they are not diagnostic of the timing of fluid entrapment instead the dark patches reveal the mechanism by which fluid inclusions spontaneously approach morphological equilibrium and purify their host quartz over geological time fluid inclusions that contain solvent water perpetually dissolve and reprecipitate their walls gradually adopting low energy euhedral and equant shapes defects in the host quartz constitute solubility gradients that drive physical migration of the inclusions over distances of tens of m commonly up to several mm rarely inclusions thus sequester from their walls any trace elements e g li al na ti present in excess of equilibrium concentrations thereby chemically purifying their host crystals in a process analogous to industrial zone refining non luminescent patches of quartz are left in their wake fluid inclusions that contain no liquid water as solvent e g inclusions of low density h2o vapor or other non aqueous volatiles do not undergo this process and therefore do not migrate do not modify their shapes with time and are not associated with dark cl zone refined patches this new understanding has implications for the interpretation of solids within fluid inclusions e g ti and al minerals and for the elemental analysis of hydrothermal and metamorphic quartz and its fluid inclusions by microbeam methods such as la icpms and sims as ti is a common trace element in quartz its sequestration by fluid inclusions and its depletion in zone refined patches impacts on applications of the ti in quartz geothermometer

the capilla del monte pluton sierras de cordoba argentina the easternmost early carboniferous magmatism in the pre andean sw gondwana margin new geochronological geochemical and isotopic data are reported for the capilla del monte two mica granite pluton in the northeastern sierras de cordoba an early carboniferous age is established by a u pb zircon concordia 336 3 ma and a rb sr whole rock isochron 337 2 ma zircon saturation geothermometry indicates relatively high temperatures 735 800 c the granites have high average sio2 74 2 na2o k2o 7 8 and high field strength elements high k2o na2o 1 7 and feo mgo ratios 5 1 with low cao content 0 71 ree patterns with marked negative eu anomalies eu eu 0 14 0 56 indicate crystal fractionation dominantly of plagioclase and k feldspar from a peraluminous magma enriched in f isotope data 87sr 86srinitial 0 7086 e nd336 5 5 to 4 4 with t dm 1 5 ga zircon e hf336 0 8 to 6 1 mean t dm 1 5 ga suggest a mesoproterozoic continental source albeit with some younger or more juvenile material indicated by the hf data the pluton is the easternmost member of a carboniferous a type magmatic suite which shows an increase in juvenile input toward the west in this part of the pre andean margin the petrological and geochemical data strongly suggest a similar intraplate geodynamic setting to that of the nearby but much larger late devonian achala batholith although hf isotope signatures of zircon suggest a more uniformly crustal origin for the latter further studies are required to understand whether these bodies represent two independent magmatic episodes or more continuous activity

latest cretaceous a 2 type granites in the sakarya zone ne turkey partial melting of mafic lower crust in response to roll back of neo tethyan oceanic lithosphere abstract an integrated study of comprehensive geochronological geochemical and sr nd hf isotopic data was undertaken for the a type topcam pluton that intruded within the sakarya zone ne turkey with the aims of elucidating its origin and tectonic significance and gaining new insights into the generation of aluminous a type granites new la icp ms zircon u pb crystallization ages of 72 and 73 ma indicate emplacement in the late cretaceous time just after extensive metaluminous i type magmatism in the area the pluton consists mainly of alkali feldspar quartz plagioclase amphibole and biotite with accessory minerals such as magnetite apatite and zircon the outcrop is composed of granite syenite monzonite and quartz monzonite and possesses a wide range of sio2 content 57 70 wt with elevated ga al ratios and low mg mostly

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

characterization on the correlation between shear wave velocity and piezocone tip resistance of jiangsu clays the small strain shear modulus of a soil is a fundamental parameter related to the mechanical behavior used in evaluation of dynamic behavior and seismic design of geotechnical structures the jiangsu soft clay is a lightly overconsolidated and sensitive clay of high plasticity in nature a research database of piezocone penetration test cptu and shear wave velocity vs information for jiangsu soft clays has been collected to study the small strain shear modulus relationships for these soils and to examine the potential use of cptu and vs data in combination for the purposes of characterizing these soils test data for sites are based on the laboratory testing performed on thin wall tube samples and high quality block samples improvements have been suggested to existing correlations between the small strain shear modulus go or vs and index properties for these soils for better prediction of these soil properties

involvement of variably sourced fluids during the formation and later overprinting of paleoproterozoic au cu mineralization insights gained from a fluid inclusion assemblage approach abstract au cu mineralized quartz veins of the reef deposit wisconsin usa originally formed prior to or early in the paleoproterozoic penokean orogeny in central north america as either the root zone of a gold rich vms deposit or in an orogenic gold setting nearly 400 m y later magmatic hydrothermal fluids associated with a continental scale anorogenic magmatic event remobilized mineralization within the veins and still later during the paleozoic remobilization and perhaps upgrading of au and other metals occurred in response to circulation of fluids associated with mississippi valley type deposits found in overlying supracrustal rocks fluid constraints on the formation of the reef deposit and later overprinting over a 1 5 b y timeframe are examined using the fluid inclusion assemblage fia approach distinctive assemblages are examined on individual merit each offering individual stories to aid in our understanding of the protracted development of the reef deposit presumably primary fluid inclusions in au and cu bearing quartz sulfide veins that formed during the paleoproterozoic event show h2o co2 ch4 nacl compositions based on microthermometry and laser raman spectroscopy possibly primary h2o nacl and secondary h2o co2 ch4 nacl fia formed prior to regional deformation and are recognized as discrete relict and neonate clusters the intersection of isochores from the highest density neonate inclusions of either fluid composition indicates re equilibration at lower amphibolite conditions during regional deformation quartz hosted secondary fluid inclusion assemblages characterized by h2o ch4 and co2 ch4 compositions formed at high temperatures and have not been re equilibrated and are interpreted to post date regional metamorphism these fia occur along healed fractures with chalcopyrite mineralization these inclusions are likely associated with fluid circulation driven by emplacement of the adjacent wolf river batholith ca 1 45 ga that altered pyrite to pyrrhotite and remobilized or emplaced chalcopyrite at temperatures as high as 700 c this reduced fluid was in equilibrium with locally observed graphitic sediments secondary lower temperature

two early proterozoic successions in central wisconsin and their tectonic significance geological mapping of 7 500 km 2 of previously virtually unmapped precambrian rocks in central wisconsin suggests the presence of two early proterozoic sedimentary volcanic plutonic successions evidence for the two successions includes structural stratigraphic metamorphic and lithologic relations that are consistent throughout the area the older succession unconformably overlies archean rocks it is characterized by amphibolite facies metamorphism folding about west to northwest plunging isoclinal f 1 fold axes with more open coaxial f 2 folding basal quartzite and pelitic sediments of the older succession are overlain by volcanic rocks and intruded by syntectonic tonalite granodiorite and trondhjemite plutons the younger succession consists primarily of a greenschist facies calc alkaline basalt rhyolite sequence that unconformably overlies the older amphibolite facies rocks structures in the greenschist sequence trend northeasterly with fold axes that plunge easterly the plutonic rocks are dominantly syntectonic to late tectonic granites and quartz monzonites with only minor tonalite in most areas the two successions have been juxtaposed along major faults the older amphibolitic sequence may correlate with the chocolay group farther north in the lake superior region and the younger green schist rocks with the menominee and or baraga groups if this correlation is correct the deformation metamorphism and intrusion of the green schist succession would have occurred during the penokean orogeny metamorphism to amphibole rank isoclinal folding and tonalite intrusion of the older succession would be a major pre penokean erogenic event within the early proterozoic that may correlate with the post chocolay pre menominee break in northern michigan wisconsin and minnesota we suggest that this earlier event has been unrecognized and that it may be a significant part of the early proterozoic history of the lake superior region

architecture of a 1 38 1 34 ga granite rhyolite complex as revealed by geochronology and isotopic and elemental geochemistry of subsurface samples from west texas usa abstract during the evolution of laurentia a mesoproterozoic felsic igneous belt extended from fennoscandia through canada to the southwestern united states this belt referred to as the granite rhyolite province in north america forms much of the west texas and eastern new mexico basement we present data from 41 closely spaced wells in west texas that penetrated several hundred meters into the southern granite rhyolite province and provide the first opportunity to develop a three dimensional view of the basement from subsurface samples the felsic rock types include hornblende bearing quartz monzonite ignimbritic rhyolite and comagmatic granite with eutectic textures these rocks plot in the high k to ultra high k field quartz syenite which plots exclusively in the ultra high k field is the final felsic phase of magmatism all of the felsic magmas were variably oxidizing based on biotite compositions u pb chronology supports the intrusive relations established by petrography the quartz monzonite is oldest 1380 ma and is followed by the granite rhyolite sequence 1360 ma and the quartz syenite 1340 ma nd model ages range from 1520 to 1740 ma indicating involvement of older proterozoic crust in many wells thick mafic sills intrude the granite rhyolite sequence nd model ages for the mafic rocks range from 1560 to 1440 ma implying that they are mesoproterozoic in age the mafic rocks include an alkaline oib like suite which is not supportive of a subduction origin u pb ages are also reported for the mescalero well 1 in eastern new mexico in this well metasedimentary and metavolcanic rocks of the debaca sequence unconformably overlie a quartz syenite similar to the quartz syenite from the west texas wells detrital zircons from the basal meta arkose of the sequence are 1690 and 1320 ma indicating a maximum age of 1300 ma for this sequence

origin of gneisses in the aureole of the san gabriel anorthosite complex and implications for the proterozoic crustal evolution of southern california granulite facies gneisses along the southwestern margin of the san gabriel anorthosite complex include compositionally banded locally migmatitic felsic gneisses and mafic granulites with rare interlayered augen gneiss and garnet hypersthene spinel aluminous gneiss previous workers accepted a 1 4 ga age for these granulites and a 1 2 ga age for the adjacent anorthosite complex and hence that this proterozoic basement is allochthonous with respect to the southwestern united states part of the north american craton solvus geothermometry in felsic and mafic granulites yields minimum metamorphic temperatures of 900 950 c and new u pb zircon data yield a minimum metamorphic age of 1186 ma coincident with that of the adjacent anorthosite we reinterpret these rocks as a 1190 ma anorthosite complex and its granulite grade thermal aureole geochemical data suggest that the anorthosite complex intruded early proterozoic rocks correlative with the mojave crustal province representing the north american craton exposed to the northeast we conclude that these proterozoic basement rocks represent the southwestern margin of the north american craton and not an exotic terrane accreted in mesozoic or tertiary time

saline ground waters and brines in the canadian shield geochemical and isotopic evidence for a residual evaporite brine component abstract saline ca na cl type groundwaters and brines sampled in deep mines over an extensive area of the canadian precambrian shield have elevated br cl ratios which may indicate that the chlorinity of these waters was derived from the infiltration of residual evaporitic brines remnants of the great marine incursions of the paleozoic era boron concentrations in these waters are generally low i e 11 b 10 b ratios of these waters are significantly greater than the average value for continental crustal rocks with the highest values 4 19 approaching that of present day seawater 4 20 moreover the boron isotopic ratios generally trend to higher values with increasing chlorinity which supports the conclusion from the br cl relationship that most of the chloride in shield brines is of marine origin rather than a product of water rock interactions if this is correct crystalline rocks must then be sufficiently permeable on a regional scale to have allowed the brine to infiltrate to depths of several kilometers where it now resides

geochemical evolution of the chatham grenville stock quebec the chatham grenville stock is an anorogenic multiple intrusion that shows a complete gradation from early cumulate and noncumulate syenites to slightly peralkaline granites it can be divided into four units unit 1 the first unit is a noncumulate syenite with modal quartz less than 5 unit 2 has a wide range in composition from cumulate syenites no modal quartz to noncumulate syenites and quartz syenites modal quartz 20 units 3 and 4 are granites with modal quartz up to 25 and 30 respectively the parental magma of the whole complex was syenitic differentiation occurred as a result of crystal fractionation by filter pressing both at depth and in situ ba sr rb and eu abundances and major element mass balance calculations show that alkali feldspar mafic minerals and apatite were fractionated at least 79 fractionation is necessary to transform the mean composition of the first unit 1 into the mean composition of the last unit 4 the rare earth elements th ta hf and zr did not

possible extension of the midcontinent rift in west texas and eastern new mexico the midcontinent rift system forms one of the most prominent gravity features in north america the recognized geophysical anomaly extends in an arc from southern oklahoma to lake superior and then into southern michigan the midcontinent rift system was active between 1185 1010 ma as indicated in the lake superior region by age determinations on intrusive igneous rocks we suggest that the period of formation of the midcontinent rift was also a time of extensive igneous activity in texas and new mexico this activity is represented by intrusions beneath the central basin platform texas and new mexico intrusions which crop out at the pajarito mountain in the sacramento mountains new mexico a basaltic debris flow in the franklin mountains texas basalt flows at van horn texas and the crosbyton geophysical anomaly east of lubbock texas these bodies and other bodies located by geophysical anomalies and wells drilled into mafic precambrian rocks may be related to the midcontinent rift system

evidence against the dorag mixing zone model for dolomitization along the wisconsin arch a case for hydrothermal diagenesis ordovician carbonates near the wisconsin arch represent the type locality in ancient rocks for the dorag or mixing zone model for dolomitization field petrographic and geochemical evidence suggests a genetic link between the pervasive dolomite trace mississippi valley type mvt minerals and potassium k silicate minerals in these rocks which preserve a regional hydrothermal signature constraints were placed on the conditions of water rock interaction using fluid inclusion methods cathodoluminescence and plane light petrography stable isotopic analyses and organic maturity data homogenization temperatures of two phase aqueous fluid inclusions in dolomite sphalerite and quartz range between 65 and 120c freezing data suggest a na ca mg cl h2o fluid with salinities between 13 and 28 wt nacl equivalent the pervasive dolomitization of paleozoic rocks on and adjacent to the wisconsin arch was the result of water rock interaction with dense brines at elevated temperatures and it was coeval with regional trace mvt mineralization and k silicate diagenesis a reevaluation of the dorag mixing zone model for dolomitization in conjunction with convincing new petrographic and geochemical evidence has ruled out the dorag model as the process responsible for pervasive dolomitization along the wisconsin arch and adds to the abundant body of literature that casts serious doubt about the viability of the dorag model in general

abiogenic fischer tropsch synthesis of hydrocarbons in alkaline igneous rocks fluid inclusion textural and isotopic evidence from the lovozero complex n w russia a detailed fluid inclusion study has been carried out on the hydrocarbon bearing fluids found in the peralkaline complex lovozero petrographic microthermometric laser raman and bulk gas data are presented and discussed in context with previously published data from lovozero and similar hydrocarbon bearing alkaline complexes in order to further understand the processes which have generated these hydrocarbons ch4 dominated inclusions have been identified in all lovozero samples they occur predominantly as secondary inclusions trapped along cleavage planes and healed fractures together with rare h2o dominant inclusions they are consistently observed in close association with either arfvedsonite crystals partially replaced by aegirine aegirine crystals or areas of zeolitization the majority of inclusions consist of a low density fluid with ch4 homogenisation temperatures between 25 and 120 c those in near surface hand specimens contain ch4 h2 up to 40 mol higher hydrocarbons however inclusions in borehole samples contain ch4 higher hydrocarbons h2 indicating that at depth higher hydrocarbons are more likely to form estimated entrapment temperatures and pressures for these inclusions are 350 c and 0 2 0 7 kbar a population of high density liquid ch4 dominant inclusions have also been recorded mainly in the borehole samples homogenising between 78 and 99 c these consist of pure ch4 trapped between 1 2 and 2 1 kbar and may represent an early ch4 bearing fluid overprinted by the low density population the microthermometric and laser raman data are in agreement with bulk gas data which have recorded significant concentrations of h2 and higher hydrocarbons up to c6h12 in these samples these data combined with published isotopic data for the gases ch4 c2h6 h2 he and ar indicate that these hydrocarbons have an abiogenic crustal origin and were generated during postmagmatic low temperature alteration reactions of the mineral assemblage this would suggest that these data favour a model for formation of hydrocarbons through fischer tropsch type reactions involving an early co2 rich fluid and h2 derived from alteration reactions this is in contrast to the late magmatic model suggested for the formation of hydrocarbons in the similar peralkaline intrusion ilimaussaq at temperatures between 400 and 500 c

structural controls on gold mineralization on the margin of the yilgarn craton albany fraser orogen the tropicana deposit western australia the tropicana gold deposit is located adjacent to the margin of the yilgarn craton in the albany fraser orogen western australia the deposit is hosted in granulite facies quartzo feldspathic gneisses of the archean tropicana gneiss ore bodies comprise biotite pyrite alteration concentrated in shear zones that formed during ne sw shortening in the late archean and clearly postdate the formation and deformation of high grade gneiss fabrics d1 and d2 the orientation of the ore bodies is controlled by the shear zones that are in turn localised by the gneissic banding mineralization also involved solution and coeval microfracturing and veining of more competent pegmatitic units the mineralizing event d3 was followed by at least two further deformations which reactivated and overprinted the biotite fabrics with sericite and chlorite created new shear zones and affected gold distribution d5 consisted of dextral shear on e w shear zones which subdivide the deposit into five major structural domains the importance of structurally controlled permeability at tropicana is similar in cratonic lode gold deposits as is the protracted deformation fluid flow history like renco mine in zimbabwe tropicana gold deposit was formed by hydrothermal fluid flow peripheral to the craton economic gold mineralization was clearly post peak metamorphism

u pb geochronology of the wolf river batholith north central wisconsin evidence for successive magmatism between 1484ma and 1468ma abstract single grain zircon u pb age determinations were completed on individual phases of the mesoproterozoic anorogenic wolf river batholith wrb of wisconsin and the nearby wausau syenite complex in order to a define the age more precisely and accurately b determine whether there is a resolvable age difference within units of the wrb and c determine whether the wausau syenite complex is coeval with any or all parts of the wrb u pb results for many individual zircon grains from the wrb plot near concordia and yield ages ranging from 1468 4 ma to 1484 2 ma plutons of the northeastern lobe of the wrb peshtigo monzonite hager porphyry belongia granite and high falls granite have a weighted average crystallization age of 1470 3 1 2 ma which is younger than the main complex plutons wolf river granite wiborgite porphyry red river granite and waupaca granite which yields a weighted average crystallization age of 1475 6 1 7 ma excluding one sample of wolf river granite from hogarty which yields an age of 1484 2 ma two samples from the main complex also contain zircons with younger apparent ages of 1470 1471 ma these younger grains may reflect late stage alteration of some zircons coeval with emplacement of the northeastern lobe the wausau syenite and the nine mile granite of the nearby wausau syenite complex 1522 ma and 1506 ma respectively are significantly older than the wrb and definitely not coeval or comagmatic the syenite complex may be a precursor to the larger wrb magmatism sm nd t dm ages for most wrb samples indicate crust formation ages from 1 8 ga to 1 9 ga compatible with formation of the magmas from late paleoproterozoic penokean crust one unit which locally intrudes archean gneiss has a small component of that older rock involved in its evolution the two wausau complex units have younger tdm ages and appear to have incorporated slightly greater amounts of juvenile constituents

a semi empirical swell prediction model formulated from clay mineralogy and unsaturated soil properties abstract swell behavior of expansive clays is an inherent property that can be better explained through its hydro mechanical volume change behavior arising from soil attributes like matric suction and clay mineralogy information previous swell related modeling studies have not incorporated these attributes for swell behavior thereby leading to poor to erroneous characterization practices both chemical and hydrological attributes of the soils are targeted in this expansive soil modeling eight natural expansive soils were collected and their swell strains were measured under different confining pressure conditions soil suction properties of expansive soils as well as soil water characteristic curves swcc s were determined using standard measurement procedures including pressure plate and filter paper techniques slope of the paths traversed by the soil specimens in a void ratio soil matric suction framework are determined and used as mechanical input parameters for the heave modeling a new parameter mechanical hydro chemical parameter mhcp is used that accounts for both matric suction and clay mineralogy information this parameter is correlated with swell property measurements and the correlations developed provided reliable and reasonable swell property predictions independent validations with other soils are still needed for further enhancement of the mhcp framework for more reliable predictions

in situ study of the shrinkage swelling of a clay soil over several cycles of drought rewetting abstract this article presents results describing the in situ behavior of clay soils pleistocene brach formation regarding shrinkage and swelling an experimental site was established different types of sensors were used to continuously measure the movements of the clay bed rock and variations in the temperature and water content of the soil these parameters were correlated with annual climatic variations as measured at an on site meteorological station the results obtained thus far represent five cycles of drought rewetting thus enabling a medium term study of the shrinkage swelling of a clay soil over time a cumulative effect of shrinkage over several cycles was observed with non negligible variations of water content to a depth of 3 m almost 1 cm of cumulative shrinkage occurred over the first three cycles of a 2 meter thick clay layer the last two cycles were marked by a stabilization of the swelling by determining the accumulated soil hydric condition over time we discovered a correlation between this parameter and the periods of shrinkage swelling the accumulated hydric condition as defined in this article is a good indicator of the behavior of soil under shrinkage and swelling

textural evolution of synthetic fluid inclusions in quartz during reequilibration with applications to tectonic reconstruction experimental reequilibration of synthetic 10 wt nacl h2o inclusions in natural quartz reveals that reequilibration textures show distinct differences depending upon the p t path followed by the inclusion after formation these differences combined with other geological information may be used to determine whether the sample rock followed a dominantly isothermal or isobaricp t path following entrapment the intensity and style of inclusion reequilibration features is related to the direction and magnitude of the departure of thep t path from the original isochore for the inclusion thus fluid inclusion reequilibration textures not only permit inclusionists to determine whether the rocks followed an isothermal or isobaric retrogradep t path but also the magnitude of departure of this path from one that is isochoric

contrasting sr and nd isotopic behaviour during magma mingling new insights from the mannum a type granite abstract the mannum granite in south australia is a classic a type granite which displays good evidence for magma mingling such as numerous syn plutonic mafic enclaves and rapakivi feldspars in both the granite and enclave study of the sr and nd isotopes show that the systems are dominantly controlled by plagioclase and titanite respectively the contrasting behaviour of these minerals during the development of a bimodal magmatic system has led to a well defined 482 ma isochron across a granite enclave boundary in the sr isotope system but not in the nd isotope system in situ techniques involving the development and production of a new titanite glass standard were developed to resolve this dichotomy inferred repeated interaction with mafic magmas has resulted in the destabilization and restabilization of plagioclase this has produced rapakivi textures and provides an effective mechanism for efficient sr isotope equilibration across the range of bulk rock compositions despite this interaction titanite in the host granite retain a range of initial nd isotope ratios indicating multiple parental magmas were assembled to produce the final pluton decoupling of the sr and nd isotope systems in other magmatic systems could be indicative of magma mixing as opposed to mingling where physical evidence e g enclaves xenocrysts etc is absent

can crystallization of olivine tholeiite give rise to potassic rhyolites an experimental investigation experiments were conducted to determine whether the rhyolites and basalts of the intraplate silica saturated potassic suites could be genetically related through crystallization extreme crystallization 96 97 of a high mgo 10 62 wt olivine tholeiite from the snake river plain with an initial bulk water content of 0 4 wt at a mid crustal pressure of 4 3 kbar generated potassic rhyolitic liquids similar in major element chemistry to those found in the quaternary rhyolite domes of the snake river plain and their plutonic equivalents in the proterozoic laramie anorthosite complex residual liquids comparable in composition to the bulk rock compositions of intermediate rocks found at the craters of the moon and cedar butte eruptive centers in the snake river plain are also generated along this crystallization path