replenishment crystal accumulation and floor aggradation in the megacrystic kameruka suite australia detailed field evidence indicates that the kameruka suite plutons of the bega batholith eastern australia grew by crystal accumulation on the floor of a magma chamber depositional features in the plutons including mafic enclave channels asymmetric enclave pillows and exotic rafts load casts and flame structures and graded and trough cross beds indicate that the pluton built progressively upward the general eastward dip of depositional features in the main pluton implies a lower western and upper eastern contact consistent with a basal granite migmatite contact in the west and a sharp hornfelsic sidewall contact in the east mafic felsic and composite dykes most common near and below the basal western contact are interpreted as conduits for magma chamber replenishment and imply open system behaviour during pluton construction textural relations are also consistent with an open system cumulate origin typically centimetre scale grains of quartz plagioclase and megacrystic alkali feldspar form a touching framework with interstices filled with smaller biotite flakes and smaller intercumulus quartz and feldspar crystals alkali feldspar megacrysts vary from euhedral and unzoned to mantled and partially replaced by plagioclase to ovoid and completely pseudomorphed by quartz albite aggregates the common occurrence of mantled and pseudomorphed alkali feldspar in mafic enclaves and in hybrid tonalitic rocks forming the matrix to enclave swarms suggests that replacement or resorption of granitic primocrysts was associated with mafic replenishments the occurrence of all megacryst types at outcrop scale implies extended alkali feldspar crystallization in different parts of the chamber thorough stirring during or after periodic replenishment and final settling in a cumulate mush the bulk composition of the cumulate mush represented by granodiorite cannot represent the emplaced magma compositional variation can be modelled by variable degrees of crystal accumulation from a parental silica rich melt represented by the silicic dykes as dykes periodically fed the magma chamber crystals accumulated on the floor and more evolved melts probably erupted from its roof thus the average composition of the magma and the cumulus minerals may have remained relatively constant and the sublinear chemical trends that typify the kameruka suite simply reflect differing proportions of melt and cumulate material sublinear chemical trends can also be explained by a restite model however the distinctive ba light rare earth element and zr spikes at high silica can be explained only by a cumulate model which also explains why the low silica granites of the suite share the same chemical characteristics as the high silica granites

microgranitoid enclave swarms in granitic plutons central sierra nevada california abstract microgranitoid enclaves are common in granitic plutons worldwide occurring individually and in homogeneous or heterogeneous swarms three plutons in the central sierra nevada batholith contain swarms with mostly heterogeneous suites of enclaves in the intermediate composition range and occur in a number of two dimensional shapes specifically as dikes small rafts lenses pipe vortices and large massive shapes swarms are characterized by various features including the nature of their boundary with the host their planar or non planar character internal geometry density of enclave packing presence or absence of schlieren and crystal aggregates and axial ratios and degree of preferred alignment of enclaves we propose that heterogeneous enclave swarms form by one or some combination of the following mechanisms 1 velocity gradient sorting parallel or normal to the flow 2 gravitational sorting or 3 break up of heterogeneous dikes common sites where enclave swarms form include pluton margins or internal viscosity walls within fractures and near the pluton roof

graphical analysis of enthalpy composition relationships in mixed magmas enthalpy composition diagrams h x calculated from existing temperature composition t x phase diagrams and thermodynamic data provide a simple and effective means for evaluating the enthalpy temperature effects of magma mixing if athermal mixing is assumed adiabatic mixing lines on h x diagrams are straight lines because enthalpy unlike temperature is an extensive property of a system comparison of binary t x diagrams with their derivative h x diagrams shows that incorrect predictions can be obtained when t x diagrams are used to analyze mixing problems an h x diagram calculated using experimentally determined phase equilibria for anhydrous basalt rhyolite mixtures predicts that adiabatic mixing of basalt and rhyolite at their respective liquidus temperatures will result in small amounts of crystallization 2 wt because the phase equilibria of hydrous basalt rhyolite mixtures have not yet been determined an h x diagram for such mixtures cannot be constructed however existing hydrous phase equilibria can be used to predict whether adiabatic mixtures of anhydrous basalt and hydrous rhyolite will be super or subliquidus calculations at ptotal 200 mpa show that on an h x diagram a mixing chord drawn between anhydrous basalt and water saturated rhyolite at their respective liquidus temperatures lies below the enthalpy values calculated for a paricutin andesite and mt st helens dacite at their estimated liquidus temperatures this indicates that the liquidus for mixtures of anhydrous basalt and water saturated rhyolite is noticeably convex upward suggesting that larger amounts of crystallization will occur than in the anhydrous case

thresholds of aeolian sand transport establishing suitable values this paper assesses the practical use and applicability of the time fraction equivalence method tfem stout zobeck 1996 of calculating a wind speed threshold for sand grain entrainment in field situations a modification of the original method is used and is applied to 1 hz measurements of wind speed and sand transport on a beach surface calculated grain entrainment thresholds are tested in terms of the percentage of sand transport events that they explain it was found that the calculated thresholds offered a poor representation of the occurrence of saltation activity explaining only about 50 of the measured transport events results are discussed in terms of system response time wind speed measurement height undetected events and sampling period a shear velocity threshold for grain entrainment was also calculated but this also failed to explain a high proportion of the sand transport events the best results 67 91 of transport events explained were found by calculating a threshold based on time averaged 40 s wind velocity measurements the applicability of a single threshold to a natural grain population is discussed a natural surface is likely to possess a range of thresholds varying over short time scales in response to parameters such as grain rearrangement and changes in moisture conditions the results show that calculated thresholds based on 40 s time averaged data consistently explain a high proportion of the recorded sand transport events this is because such a time averaged approach accounts for higher frequency variability inherent in the sand transport system

soil temperatures in an atlantic high mountain environment the forcadona buried ice patch picos de europa nw spain the present study focuses on the analysis of the ground and near rock surface air thermal conditions at the forcadona glacial cirque 2227 m a s l located in the western massif of the picos de europa spain temperatures have been monitored in three distinct geomorphological and topographical sites in the forcadona area over the period 2006 11 the forcadona buried ice patch is the remnant of a little ice age glacier located in the bottom of a glacial cirque its location in a deep cirque determines abundant snow accumulation with snow cover between 8 and 12 months the presence of snow favours stable soil temperatures and geomorphic stability similarly to other cantabrian mountains the annual thermal regime of the soil is defined by two seasonal periods continuous thaw with daily oscillations and isothermal regime as well as two short transition periods however the results showed evidence of a significantly different annual thermal regime at the ground and near rock surface air relatively stable soil thermal regimes were observed at the moraine and talus sites while a more dynamic pattern was recorded at the rock wall site here a higher interannual variability in the number of freeze thaw days was also detected which showed evidence of the important role of the snow cover as a ground surface insulator in the area seasonal frost conditions are widespread today in the high lands of the massif no permafrost regime was detected in the area though mean temperatures measured at 0 5 m depth at the forcadona buried ice patch during 2006 07 0 1 c suggest that permanent negative values may be reached at deeper layers

isotopic variation in the tuolumne intrusive suite central sierra nevada california granitoid rocks of the compositionally zoned late cretaceous toulumne intrusive suite in the central sierra nevada california have initial87sr 86sr values sri and143nd 144nd values ndi that vary from 0 7057 to 0 7067 and from 0 51239 to 0 51211 respectively the observed variation of both sri and ndi and of chemical composition in rocks of the suite cannot be due to crystal fractionation of magma solely under closed system conditons the largest variation in chemistry ndi and sri is present in the outer most equigranular units of the tuolumne intrusive suite sri varies positively with sio2 na2o k2o and rb concentrations and negatively with ndi al2o3 fe2o3 mgo feo cao mno p2o5 tio2 and sr concentrations this covariation of sri ndi and chemistry can be modeled by a process of simple mixing of basaltic and granitic magmas having weight percent sio2 of 48 0 and 73 3 respectively isotopic characteristic of the mafic magma are sri 0 7047 ndi 0 51269 and 18o 6 0 and of the felsic magma are sri 0 7068 ndi 0 51212 and 18o 8 9 the rocks sampled contain from 50 to 80 of the felsic component an aplite in the outer equigranular unit of the tuolumne intrusive suite apparently was derived by fractional crystallization of plagioclase and hornblende from magma with granudiorite composition that was a product of mixing of the magmas described above siliceous magmas derived from the lower crust having a maximum of 15 percent mantle derived mafic component are represented by the inner prophyritic units of the tuolumne intrusive suite

crystallization and hybridism in microgranitoid enclave magmas microstructural evidence microstructural evidence indicates that many microgranitoid enclaves mafic inclusions in granitoids crystallize from globules of magma that have undergone previous magma mixing hybridism the evidence includes 1 rounded xenocrysts ocelli of quartz rimmed with fine grained aggregates of early formed minerals especially mafic minerals 2 k feldspar megacrysts commonly rimmed with plagioclase rapakivi structure and 3 corroded cores dendritic overgrowths and calcic spikes in plagioclase initial quenching of a magma globule in felsic magma involves rapid temperature equilibration which causes a high rate of nucleation of minerals precipitating from the enclave magma at the time followed by a period of slow cooling during which the nucleation and growth rates of later crystallizing minerals are similar to the much slower rates prevailing in the granitic melt this may result in markedly poikilitic microstructures involving inclusion of the earlier formed finer grained minerals in quartz and or k feldspar which are common in microgranitoid enclaves

long term soil temperature dynamics in the sierra nevada spain abstract soil temperatures play a key role on the dynamics of geomorphological processes in periglacial environments however little is known about soil thermal dynamics in periglacial environments of semiarid mid latitude mountains where seasonal frost is dominant from september 2006 to august 2012 we have monitored soil temperatures at different depths 2 10 20 50 and 100 cm in a solifluction landform located at 3005 m a s l in the summit area of the sierra nevada south spain mean annual temperatures in the first meter of the soil ranged from 3 6 to 3 9 c while the mean annual air temperature at the nearby veleta peak was 0 08 c therefore these data point out the inexistence of widespread permafrost conditions today in this massif seasonal frost controls the geomorphodynamics even in the highest lands climate conditions have shown a large interannual variability as it is characteristic in a high mountainous mediterranean environment these variations are reflected in the patterns of soil thermal dynamics the depth and duration of the frozen layer are strongly conditioned by the thickness of the snow cover the date of the first significant snowfalls conditioned the beginning and rhythm of freezing of the soil wet years resulted in a thick snow cover which insulated the ground from external climate oscillations and favored a shallow frost layer 2008 2009 2009 2010 and 2010 2011 on the other hand years with low precipitations promoted deeper freezing of the soil down to 60 70 cm extending until late may or early june 2006 2007 2007 2008 and 2011 2012 when snow melted a high increase of temperatures of 10 12 c in few weeks was recorded at all depths at this time of the year periglacial activity is enhanced due to higher water availability and the existence of freeze thaw cycles these were recorded mostly in spring and autumn in the first 50 cm depth of the soil ranging from 9 8 days at 2 cm to 3 7 days at 50 cm however the inactivity of solifluction landforms suggests that the combination of present day soil temperatures together with moisture conditions is not favorable to promote solifluction activity in the periglacial belt of the sierra nevada future climate scenarios point to a temperature increase and precipitation decrease in the area which would entail deeper but shorter frozen soil layers these conditions would not be favorable for active periglacial slope processes in the sierra nevada

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

surface dynamic of a protalus lobe in the temperate high mountain western maladeta pyrenees abstract the maladeta protalus lobe is located in the maladetas massif central pyrenees a detailed geomorphologic map rtk gps techniques bottom temperature of the winter snowcover bts technique and datalogger to monitor the ground thermal regime were used to reveal the present day activity of the protalus lobe and its location in a mountain permafrost environment systematic monitoring using differential gps at eight fixed points throughout the surface of the protalus lobe shows vertical and horizontal displacements during the field surveys of 2008 2009 2010 2011 2012 and 2013 the recorded dynamic defines a periglacial landform with low activity and rapid interannual variations in a thermal imbalance state the location of protalus lobe in marginal periglacial environments of the temperate high mountain makes it an effective morphoclimatic geoindicator

isotopic disequilibrium among commingled hybrid magmas evidence for a two stage magma mixing commingling process in the mt perkins pluton arizona this is the publisher s version also available electronically from http www jstor org stable 30070774 seq 1 page scan tab contents

new geochronological results and structural evolution of the pataz gold mining district implications for the timing and origin of the batholith hosted veins abstract the paleozoic pataz parcoy gold mining area is located in a right stepping jog on the regional cordillera blanca fault in northern peru most of the 8 million ounces of gold production from this area has come from quartz carbonate sulfide veins hosted by the pataz batholith despite a subduction zone setting since at least the cambrian the area records several periods of extension and its present structure is that of a rift and graben terrain the pataz district the northern part of the pataz parcoy area is dominated structurally by northwest to north northwest striking nw nnw faults and northeast to east northeast striking ne ene lineaments both of which have been active periodically since at least the mississippian early carboniferous nw nnw faults control the margins of a central horst that exposes basement schist and the pataz batholith and step across ne ene lineaments the lavasen graben to the east of the central horst contains the lavasen volcanics and the chagual graben to the west contains an allochthonous sedimentary sequence derived from the western andean cordillera new shrimp zircon geochronological data indicate emplacement of the pataz batholith during the middle mississippian at around 338 336 ma approximately 10 ma earlier than previous estimates based on 40 ar 39 ar geochronology the calc alkaline i type batholith comprises diorite and granodiorite the latter being the major component of the batholith and was emplaced as a sill complex within the moderately ne dipping sequence of the eastern andean cordillera moderate to high temperature ductile deformation took place on the batholith contacts during or shortly after emplacement following emplacement of the batholith differential uplift occurred along nw nnw faults forming the lavasen graben into which the lavasen volcanics were deposited shrimp u pb in zircon ages for the lavasen volcanics and the esperanza subvolcanic complex which was intruded into the western margin of the graben are within error of one another at ca 334 ma the ductile batholith contacts were cut by renewed movement on nw nnw faults such that the margins of the batholith are now controlled by these steep brittle ductile faults the nw nnw faults were oriented normal to the principal axis of regional shortening ene wsw during formation of the batholith hosted gold bearing quartz carbonate sulfide veins the misoriented faults were unable to accommodate significant displacement leading to high fluid pressures vertical extension in the competent batholith and formation of gold bearing veins brittle failure of the batholith was most extensive in the northern pataz district where the fault controlled western contact of the batholith is offset by a swarm of ne ene lineaments the timing of vein formation is not established despite published 40 ar 39 ar ages of 312 to 314 ma for metasomatic white mica which are interpreted as minimum ages of formation gold bearing veins formed during or shortly after uplift of the pataz batholith and formation of the lavasen graben they were therefore broadly coeval with deposition of the lavasen volcanics and emplacement of the esperanza subvolcanic complex these k rich weakly alkalic ferroan a type magmas may provide a viable source for the ore fluid that deposited gold in the pataz batholith

progressive hybridisation between late devonian mafic intermediate and felsic magmas in the meguma zone of nova scotia canada two felsic plutons of late devonian 385 370 ma age in the meguma zone of southwestern nova scotia contain three circa 376 ma synplutonic mafic intermediate intrusions that collectively record progressive stages of in situ hybridisation a 5 m wide spessartite dyke in the port mouton pluton probably underwent rapid cooling and crystallisation immediately after intrusion which heated and coarsened the adjacent tonalite an 85 m long sheet of pillowed kersantite also in tonalite of the port mouton pluton presumably contained residual magma after quenching and obtained k p ba rb more radiogenic sr zr nb and light ree from the tonalite during magma mingling the third synplutonic body a 100 m wide diorite sheet intrudes granodiorite of the adjacent shelburne pluton and has a circa 45 m wide gradational contact of metaluminous hornblende tonalite this tonalite dominantly records magma mixing by the transfer of ti mg fe ca and v in hornblende biotite plagioclase and at least in part apatite xenocrysts derived from dioritic pillows that were originally disaggregated in the granodiorite probably in response to convection scattered data points unusual concave down variation trends for al2o3 p2o5 and sr and non hyperbolic sr nd isotopic characteristics in the tonalite apparently reflect syn or post mixing fractionation and accumulation of xenocrysts from residual magma phosphorus may have assisted diffusion of sr zr nb and light ree and caused premature quenching of the hybrids at mcleods cove and birchtown during magma mingling and mixing

the initiation of particle movement by wind when air blows across the surface of dry loose sand a critical shear velocity fluid threshold ut must be achieved to initiate motion however since most natural sediments consist of a range of grain sizes fluid threshold for any sediment cannot be defined by a finite value but should be viewed as a threshold range which is a function of the size shape sorting and packing of the surface sediment in order to investigate the initiation of particle movement by wind a series of wind tunnel tests was carried out on a range of pre screened fluvial sands and commercially available glass beads with differing mean sizes and sorting characteristics a sensitive laser monitoring system was used in conjunction with a high speed counter to detect initial grain motion and to count individual grain movements test results indicate that when velocity is slowly increased over the sediment surface the smaller or more exposed grains are first entrained by the fluid drag and lift forces either in surface creep rolling or in saltation bouncing or hopping downwind as velocity continues to rise larger or less exposed grains may also be moved by fluid drag on striking the surface saltating grains impart momentum to stationary grains this impact may result in the rebound of the original grain as well as the ejection of one or more stationary grains into the air stream at shear velocities lower than that required to entrain a stationary particle by direct fluid pressure as a result there is a cascade effect with a few grains of varying size initially moving over a range of shear velocities the fluid threshold range and setting in motion a rapidly increasing number of grains results of the tests showed that the progression from fluid to dynamic threshold based on grain movement can be characterized by a power function the coefficients of which are directly related to the mean size and sorting characteristics of the sediment

plagioclase xenocrysts and mafic magmatic enclaves in some granitoids of the sierra nevada batholith california plagioclase phenocrysts from mafic magmatic enclaves and plagioclase crystals from host granitoids of some plutons of the central part of the sierra nevada batholith are complexly zoned and commonly divided into three neatly distinct parts an oscillatory locally patchy zoned andesine or more calcic core a ring with dusty calcic plagioclase and a normally zoned rim of sodic plagioclase although aspect of the calcic rings and width and zoning of the rims may slightly vary from the enclaves to the hosts cores of both phenocrysts and large plagioclase crystals show similar zoning and composition the andesine or more calcic cores are interpreted to have crystallized in the felsic or the mafic magma respectively and been incorporated into the coeval magma when the two magmas mixed introduction of the xenocrystic cores into a magma where they were not in equilibrium resulted in partial dissolution development of abundant patchy zoning and coating with dusty calcic plagioclase in both granitoids and mafic magmatic enclaves composition and zoning contrast between cores and rims of the plagioclase crystals reflect drastic changes in conditions of crystallization before and after the mechanical mixing event mixing of two magmas with contrasted compositions is suggested to be the major mechanism for generating complexly zoned plagioclase xenocrysts in granitoids and mafic magmatic enclaves this hypothesis is consistent with many recent models in which mixing of two contrasting components is proposed to play a fundamental part in the generation of calc alkaline granitoids and mafic magmatic enclaves of the sierra nevada batholith plagioclase xenocrysts may also provide information on the timing of the different mixing processes and on the magmatic evolution of the plutons

the pan african toro complex northern nigeria magmatic interactions and structures in a bimodal intrusion the toro complex is one of the pan african older granites of nigeria first described as a reversely zoned pluton made of a central dioritic mass surrounded by a broad granitic rim it has been thoroughly reinvestigated both from the petrographic and structural points of view with the help of systematic anisotropy of magnetic susceptibility ams measurements the granite main body is a hornblende biotite porphyritic monzogranite characterized by an early submagmatic fabric displaying a concentric pattern of foliations and west plunging lineations stage 1 this fabric is overprinted by a later one due to solid state strain along north south subvertical dextral shear zones stage 2 in the vicinity of the diorite an evengrained granite displays magmatic structures that are contemporaneous with this strike slip event the diorite granite contact is a complex zone where field petrographic and geochemical data enable recognition of the effects of mixing and mingling between a mafic and a felsic magma tonalites cropping out within this contact zone are interpreted as hybrid rocks the reverse zonation of the diorite itself is also the result of some hybridization process magmatic interactions mainly resulted from in situ infiltration of granitic liquid into the dioritic mass the detailed history of this bimodal intrusion began with the emplacement of the granitic magma acquiring a first stage fabric before full crystallization of the granitic core intrusion of the dioritic magma permitted reheating of the granitic magma that then crystallized with specific structural characters the second stage structures whether characterized by magmatic fabric near the diorite or by solid state strain features in north south shear zones elsewhere in the granite are related to late pan african dextral strike slip tectonics in the basement of northern nigeria the bimodal toro complex is therefore considered as a late pan african syntectonic pluton

a new instantaneous aeolian sand trap design for field use a new aeolian sediment trap is described which can give up to 1 hz measurement frequency in held conditions the trap adopts a circular horizontal trap design with a load cell connection to give continuous unobtrusive trap measurement of sediment flux simultaneous velocity recording is carried out using an anemometer trap construction costs are approximately pound 200 initial results in held conditions using a direct comparison of wind velocity data sampled at an equivalent frequency have given a first order relationship between sediment flux and velocity the trap enables simultaneous sampling of wind velocity and sediment flux at a sufficiently short interval to enable investigation of sediment transport dynamics under a variety of field conditions

origin of sierra nevadan granite evidence from small scale composite dikes composite dikes at hell hole meadow in the central sierra nevada contain hybrids created by small scale mixing of andesitic and rhyolitic magmas early rhyolitic injections had partially solidified when subsequent andesitic magmas arrived and mixed with small increments of remnant rhyolitic magma in major element chemistry the hybrid rocks define linear mgo variation diagrams that closely resemble those for the half dome mt givens and eagle peak granodiorites the patterns suggest that mixing of mafic and felsic magmas has been important in the evolution of these plutons

effects of magma mingling in the granites of mount desert island maine textures and compositional relationships associated with dark colored fine grained enclaves in the cadillac mountain and somesville granites mount desert island maine preserve abundant evidence for contamination of host granitic magmas by enclave liquids fine grained enclaves which apparently represent chilled magmatic droplets have affected the composition and texture of the host granites by three possible mechanisms 1 crystallization of feldspar quartz hornblende pegmatite pods from fluids of enclave origin in the granite surrounding enclaves and the disaggregation of the pods and dispersion of crystals into the granite 2 ionic exchange between enclaves and granitic magmas 3 the generation around enclaves of rinds consisting of an inner alkali feldspar quartz zone and an outer zone of hornblende enriched granite coarse grained pegmatite pods that occur outside of enclaves may result from migration of a hydrous residual fluid evolved during enclave crystallization out of the enclave

microgranitoid enclaves in granites globules of hybrid magma quenched in a plutonic environment microgranitoid enclaves autoliths cognate xenoliths mafic inclusions are common in high level granitoid plutons they have relatively fine grained igneous microgranitoid microstructures1 and many show evidence of having flowed in a magmatic condition2 these features counter interpretations that the enclaves represent transformed solid fragments of diverse wall rocks3 5 or restite6 11 an alternative interpretation is that the enclaves represent globules of mafic magma that have mingled commingled and quenched in the granitoid host magma12 16 a detailed review of the literature occurrence morphology and composition of micro granitoid enclaves strongly supports this view hut indicates that the enclave magmas range in composition from mafic to felsic and that magma mixing may be involved in their formation17 i summarize here the main features of microgranitoid enclaves and briefly outline the possible processes leading to their incorporation as magma globules in the host granitoid

in situ mid far micro ftir spectroscopy to trace pressure induced phase transitions in strontium feldspar and wadsleyite as representatives of nominally anhydrous minerals nams in the crust and mantle the pressure dependent behavior of strontium feldspar and wadsleyite containing different amounts of water was studied in a diamond anvil cell via mid and far ir spectroscopy up to 24 gpa the samples were synthesized in a piston cylinder press at 2 gpa 700 c strontium feldspar and in a multi anvil apparatus at 13 8 gpa 1000 c dry wadsleyite and 13 2 gpa 1150 c hydrous wadsleyite the water content of the samples was determined by polarized ftir and raman spectroscopy the strontium feldspar crystals up to 300 m contained about 1100 100 wt ppm water the hydrous wadsleyite crystals up to 240 m contained 12 500 900 wt ppm water the synthesis of dry wadsleyite yielded a fine grained powder a new thz fir microscope for the synchrotron source bessy was developed to conduct the diamond anvil cell measurements in the far ir region conventional in situ mid ir spectroscopy was also performed on all samples the measurements on strontium feldspar showed a phase transformation at 6 5 5 gpa space group i 2 c to p 2 1 c the wadsleyite analyses revealed a phase transition at approximately 8 4 7 gpa in the hydrous and approximately 10 0 7 gpa in the dry sample it probably represents a transition from an orthorhombic to a monoclinic structure the high amount of water incorporated in the hydrous wadsleyite shifts the transformation toward lower pressures compared to the dry one by comparison the relatively low amount of water in strontium feldspar does not change the stability relations compared to the dry one therefore water incorporation in nominally anhydrous minerals may have an effect on the pressure of phase transitions whereas the extent of that influence strongly depends on the structure of the phase and the amount of water carried within the mineral

the aurora volcanic field california nevada oxygen fugacity constraints on the development of andesitic magma the aurora volcanic field located along the northeastern margin of mono lake in the western great basin has erupted a diverse suite of high k and shoshonitic lava types with 48 to 76 wt sio2 o ver the last 3 6 million years there is no correlation between the age and composition of the lavas three quarters of the volcanic field consists of evolved 4 wt mgo basaltic andesite and andesite lava cones and flows the majority of which contain sparse euhedral phenocrysts that are normally zoned there is no evidence of mixed hybrid magmas the average eruption rate over this time period was 200 m 3 ykm 2 yyear which is typical of con tinental arcs and an order of magnitude lower than that for the slow spreading mid atlantic ridge all of the au rora lavas display a trace element signature common to subduction related magmas as exemplified by baynb ratios between 52 and 151 pre eruptive water contents ranged from 1 5 wt in plagioclase rich two pyroxene andesites to 6 wt in a single hornblende lamprophyre and several biotite hornblende andesites calculated oxygen fugacities fall within 0 4 and 12 4 log units of the ni nio buffer the aurora potassic suite follows a classic calc alkaline trend in a plot of feo t ymgo vs sio 2 and displays linear decreasing trends in feo t and tio2 with sio2 content suggesting a prominent role for fe ti oxides during differentiation however develop ment of the calc alkaline trend through fractional crys tallization of titanomagnetite would have caused the residual liquid to become so depleted in ferric iron that its oxygen fugacity would have fallen several log units below that of the ni nio buffer nor can fractionation of hornblende be invoked since it has the same effect as titanomagnetite in depleting the residual liquid in ferric iron together with a thermal stability limit that is lower than the eruption temperatures of several andesites 1040 10808c derived from two pyroxene ther mometry unless some progressive oxidation process occurs fractionation of titanomagnetite or hornblende cannot explain a calc alkaline trend in which all erupted lavas have oxygen fugacites the ni nio buffer in con trast to fractional crystallization closed system equi librium crystallization will produce residual liquids with an oxygen fugacity that is similar to that of the initial melt however the eruption of nearly aphryic lavas ar gues against tapping from a magma chamber during equilibrium crystallization a process that requires crys tals to remain in contact with the liquid a preferred model involves the accumulation of basaltic magmas at the mantle crust interface which solidify and are later remelted during repeated intrusion of basalt as an end member case closed system equilibrium crystallization of a basalt followed by equilibrium partial melting of the gabbro will produce a calc alkaline evolved liquid namely high sio 2 and low feo t ymgo with a relative fo2 corrected for the effect of changing temperature that is similar to that of the initial basalt differentiation of the aurora magmas by repeated partial melting of previous underplates in the lower crust rather than by crystal fractionation in large stable magma chambers is consistent with the low eruption rate at the aurora vol canic field

small scale disequilibrium in a magmatic inclusion and its more silicic host basaltic andesite inclusions and their host dacite from the purico chascon complex in northern chile are isotopically distinct textural characteristics of the inclusions are typical of those resulting from magma mingling serial sectioning across the interface of an inclusion and its host dacite complemented by microdrill sampling and detailed microprobe work has enabled us to examine the scale of mixing and chemical isotopic and trace element disequilibrium the results of this work show that 1 the composition of the inclusion is relatively homogeneous 2 the dacite host is generally higher in 87sr 86sr and lower in 143nd 144nd than the enclave but it is heterogeneous on a small scale and probably a hybrid 3 the isotopic composition in the marginal zone apparently on both host and inclusion sides of the weakly chilled interface actually shows the highest 87sr 86sr and lowest 143nd 144nd 4 large plagioclase crystals in the inclusions and host are xenocrystic with higher 87sr 86sr than any of the other samples these observations are reconciled with a model of magma evolution in a crustal magma chamber in such a scenario the mafic magma is overlain by a cap of rhyolite a partial melt of the dacitic ignimbrites which now underlie the purico chascon complex overturn of such a magma system gives rise to a hybrid dacite containing discrete mafic inclusions

on the prediction of bed load sand transport rate in air this paper discusses the parameterization of aeolian mass transport rate beginning with a critical discussion of four different forms of the prediction equation following this recent progress in understanding the physics of the aeolian system is used to suggest an alternative approach which provides some new insights into the prediction of mass flux the primary object of the paper is not to add another transport rate equation to those already present in the literature but rather to discuss the transport system in relation to the physical processes showing to some extent why reliable transport rate prediction has so far been elusive

an equilibrium relationship for shear velocity and apparent roughness lenght in aeolian saltation abstract an equilibrium relationship between shear velocity and apparent surface roughness is established for aeolian saltation velocity profiles of wind over blowing sand were digitized from eleven published data sets the 106 profiles were analyzed to obtain estimates of shear velocity and apparent surface roughness lenghts these values were used to test charnock s relationship for suitability in aeolian environments the results indicate that z 0 0 0091 u 2 g modifying charnock s model to describe wind over an equilibrium saltation field yields z 0 2d 50 30 0 0252 u u t 2 g the latter result is used to demonstrate that the focal point concept proposed by bagnold stems from the increase in apparent roughness with increased shear velocity the results demonstrate an excellent example of threshold controlled equilibrium in dynamic systems

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

magma mixing in granitic rocks of the central sierra nevada california abstract the el capitan alaskite exposed in the north american wall yosemite national park was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite comparisons of petrographic and compositional data for these dikes and alaskite with published data for sierra nevada plutons lead us to suggest that mafic magmas were important in the generation of the sierra nevada batholith specifically we conclude that 1 intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite rhyolitic magmas 2 interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements 3 most mafic inclusions in sierra nevada plutons represent chilled pillows of mafic magmas related by fractional crystallization and granitoid assimilation that dissolve into their felsic host and contaminate it to intermediate granodioritic compositions 4 vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton s domed ceiling causing the zoning mafic margins to felsic core that these plutons exhibit

environmental evolution in sierra nevada south spain since the last glaciation based on multi proxy records abstract our knowledge of the quaternary landscape evolution in the high mountain areas of the iberian peninsula has substantially improved over the last decades the sierra nevada is one of the most studied mountain ranges in southern europe regarding its environmental evolution the purpose of the present paper is to integrate and summarize all the studies focused on the reconstruction of the palaeoenvironmental history in this massif since the last glaciation research has focused both on different sedimentary records and historical sources a wide range of geomorphological sedimentological and geochronological techniques have been used to characterize the glacial periglacial wetland and lacustrine records for palaeoenvironmental purposes for the last nine centuries tens of descriptions maps and sketches describe the landscape of the summit area of the sierra nevada providing evidences of the historical environmental events based on a multi proxy approach five periods have been identified last glaciation deglaciation holocene little ice age and recent evolution recent studies have detected the maximum expansion of glaciers in the sierra nevada around 30 32 ka bp predating the global temperature minimum no data about the environmental evolution is available between 20 30 ka bp around 19 20 ka bp glaciers advanced significantly the process of deglaciation was rapid and around 14 15 ka bp the massif was almost free of ice the late glacial promoted the formation of small glaciers in the highest northern cirques and widespread active periglacial processes i e rock glaciers during the holocene there has been an alternation of colder warmer periods and changing moisture conditions periglacial processes have been generally widespread in the summit area with an increasing or decreasing activity depending on climate conditions ephemeral reappearance of small glacial cirques occurred in the highest northern cirques during the coldest and wettest phases this is the case of the little ice age as revealed by historical documents and sedimentary records since the last decades of the xix century the temperature has increased 0 93 c leading to a decrease of the intensity of periglacial processes in the high lands of the sierra nevada

potential inertial effects in aeolian sand transport preliminary results most models to predict aeolian sand transport rates incorporate a threshold shear velocity term to specify the condition when sand flux begins this term usually takes the form derived by the equation of bagnold 1936 when shear velocity falls below the threshold value the transport equations predict an immediate cessation of sediment movement however under some conditions this is not so and transport may continue for a period this paper describes field observations of an inertia like process that be considered when wind velocity fluctuates at near threshold values this study found that although wind conditions had decreased to below threshold levels transport was still taking place therefore using standard models that incorporate a threshold term an underestimation of sediment transport would occur

unusually dumbbell shaped guposhan huashan twin granite plutons in nanling range of south china discussion on their incremental emplacement and growth mechanism abstract the guposhan huashan twin plutons crop out as an unusually dumbbell shaped batholith within the middle mesozoic central nanling range granitic belt in south china the batholith was controlled by the east west striking yishan quannan deep crustal fault zone and spatially associated with two regional anticlinoria both plutons show concentric zonation patterns and are composed of two emplacement sequences separated by an approximately 9 m y magmatic lull the 160 163 ma niumiao lisong wanggao sequence and the 148 151 ma xinlu huamei sequence based on field mapping and observations geochronology and geochemistry in a proposed incremental emplacement and growth model the early magmas exploited physical discontinuities such as the contacts between rocks with contrasting competence and densities as well as saddles of regional scale anticlinoria assisted by dominant vertical heat flow and uplifting of the roofs the niumiao lisong wanggao sequence magmas were subsequently emplaced in an over accretion style as distinguishable increments during an approximately 3 m y span gravimetric data observations of field relationships as well as analysis of finite strain and country rock rheology confirm that the plutons became thickened considerably due to largely vertical assembling and growth and most of their space was created by vertical displacement of their country rocks interestingly the coeval twin plutons show contrasting development and growth modes during their assembling and thickening process the guposhan pluton was built on an outward building mode with a reverse zoning pattern while the huashan pluton on an inward building mode with a normal zoning pattern we propose that the contrasting modes largely resulted from their divergent thermal evolution path for example the incremental inward building mode helps retain thermal energy and maintain a high temperature in older units which facilitates injection of subsequent younger increment units of the same sequence within the older host units the independent newer sequence of xinlu huamei magmas however were controlled by shallow brittle faults developed in the older sequence units and emplaced as stocks and dykes by a dyke propagation mechanism

little ice age glaciation and current glaciers in the iberian peninsula little ice age lia glacier advance has been registered in three of the main iberian high mountain areas pyrenees picos de europa and sierra nevada during the lia three different glacial env

the significance of mafic microgranular enclaves in the petrogenesis of the dehno complex sanandaj sirjan belt iran abstract quartz monzodioritic and granodioritic enclaves occur in the upper cretaceous paleocene dehno complex nw of isfahan iran they are hosted by hornblende granodiorite and granodiorite monzogranite respectively the presence of xenocrystic plagioclase biotite quartz magnesio hornblende occasionally with relics of clinopyroxene in quartz monzodiorites minor k feldspar and the lack of peraluminous minerals dominate the mineralogy of these rocks and suggest a metaluminous source the plagioclase in the quartz monzodioritic enclaves has higher an content than that of the respective plagioclase of their host hornblende granodiorite indicating crystallization from more mafic magma the quartz monzodioritic enclaves generally contain higher values of fe 2 o 3 mgo cao mno na 2 o transition elements ni cr co v ree and lower values of sio 2 k 2 o p 2 o 5 and zr than their host which are in consistent with occurrence of abundant ferromagnesian minerals in these rocks compare to their host the granodioritic enclaves have higher amount of fe 2 o 3 mgo mno tio 2 p 2 o 5 rb zr y ni cr co and lower concentration of sio 2 k 2 o and ba aside from hornblende granodiorite and granodiorite monzogranite the dehno complex comprises leucogranodiorite and tourmaline leuco granites geochemically the rocks of the complex are metaluminous to strongly peraluminous and are enriched in lile e g rb k sr ba and depleted in hfse e g nb ta p ti zr hf with medium to high k calc alkaline nature these geochemical features are proposed for the volcanic arc granites emplaced in an active continental margin whole rock and quartz 18 o values for all rocks are high 9 7 14 4 and 10 1 14 9 respectively suggesting the interaction of magma with crustal derived components the strongly peraluminous composition can be interpreted in terms of this hypothesis all these mineralogical and geochemical features support the idea that the granitoid rocks of the dehno complex developed through variable degrees of mixing mingling between a basic magma and a supracrustal melt during subduction of the neotethys oceanic crust beneath central iranian microcontenent the quartz monzodioritic enclaves most likely represent the nearest composition to the original more mafic magma the granodioritic enclaves result from the mixing mingling of globules basic magma with host granitic magma

structural criteria for identifying granitic cumulates abstractcumulates are igneous rocks that reflect relative concentration of crystals and or loss of melt and that therefore did not crystallize entirely from a magma of their current whole rock composition however this definition does not help to identify cumulates and so the problem is to determine whether the current whole rock composition reflects cumulate processes which is where structural criteria can be useful identification of cumulates in granitoids can be difficult especially in the absence of major whole rock compositional differences between cumulate and host structural and structural mineralogical criteria diagnostic of or at least consistent with granitic cumulates include 1 locally high concentrations of particular minerals relative to concentrations in the bulk of the intrusion 2 abundant euhedral crystals in contact at least with regard to cores that touched before any overgrowths and consequent molding of minerals about each other occurred 3 abundant antecrysts or mantle

the effect of surface slope on saltation threshold a new wind tunnel has been constructed to study the mass transport properties of wind blown sand this report on the first set of experiments in the new wind tunnel concerns the effect of slope on threshold friction speed the results of this series of static threshold experiments and one dynamic threshold experiment for a range of particle diameters and bed slope angles show that provided the effects of reynolds number variation and interparticle cohesive force are accounted for the static friction angle is independent of slope and close in value to the measured static angle of response

rock glacier dynamics in marginal periglacial environments vertical electric sounding bottom temperature of winter snowcover bts and ground thermal measurement debris surface analysis and a differential global positioning system dgps survey were performed on the posets rock glacier pyrenees between 2001 and 2008 high precision records of horizontal and vertical movements of the rock glacier were measured using a dgps on ten steel rods total and annual average displacements and thickness changes for each control point were derived from the field survey horizontal and vertical displacement rates in different sectors of the rock glacier were compared and these compared with thermal structural and morphological maps the inferred surface deformation was characterized by extensional and compressive flows in which two dynamic types were found the first type of movement is defined by the slide and flows related to the existence of an ice body over the frost body the second dynamic type involved the displacement generated by deformation of the frozen body the study attempts to understand the surface movement and dynamics of rock glaciers in marginal cold environments and their usefulness as environmental geoindicators copyright 2010 john wiley sons ltd

the kennack gneiss of the lizard peninsula cornwall sw england commingling and mixing of mafic and felsic magmas accompanying givetian continental incorporation of the lizard ophiolite the kennack gneiss comprises a suite of interlayered mafic and felsic igneous rocks that intruded the 397 ma lizard ophiolite complex cornwall at 376 4 1 7 ma u pb single zircon date and were shortly thereafter c 370 ma metamorphosed to the amphibolite facies weakly deformed examples at the type locality of kennack sands reveal net veining of the mafic by the felsic component dispersed enclaves of the former in the latter and flame like interfingering of the two features indicative of magmatic commingling and mixing the silicic components of the kennack gneiss range from granodiorite to syenogranite and from metaluminous to peraluminous the least silicic rocks being the most peraluminous they were generated through anatexis of a predominantly metasedimentary crustal source having trace element and isotopic compositions comparable to those of the devonian gramscatho group of south cornwall the mafic component of the gneiss includes members group 1 which are weakly enriched in light ree have minor negative ta nb p and ti anomalies in extended trace element plots and display primitive time corrected 143 nd 144 nd and 87 sr 86 sr values and others group 2 which are more strongly enriched in all incompatible trace elements exhibit more prominent negative ta nb p and ti anomalies and have isotopic ratios intermediate between group 1 mafic components and the associated felsic gneiss group 2 represents mixtures of group 1 and granitic melts whereas group 1 rocks are comparable to emorb and were probably generated through partial melting of a weakly enriched mantle source emplacement of two commingled magmas into the base of the lizard ophiolite one representing the products of crustal anatexis implies that the ophiolite was removed from its oceanic setting and was in the process of obduction in the givetian

magma mixing and the production of compositional variation within granite suites evidence from the granites of southeastern australia granite suites are groups of plutons possessing characteristic features that are a result of their derivation from source material of a specific composition variation within suites has been ascribed to a variety of processes magma mixing or mingling is a popular hypothesis generally proposed in terms of blending between a crustal melt and mafic material from the mantle that caused that melting when the compositions of pain of suites from the bega batholith of southeastern australia are compared any differences seen at either end of the range in composition are also seen at the other limit so that both the most mafic and mostfelsic rocks show similar relative abundances of particular elements similar relationships are seen for other granites in the region these observations are not consistent with largescale magma mixing or mingling and although those processes may operate on a small scale they cannot have been responsible for the major compositional variations likewise assimilation of country rocks had no significant role in producing variation in the granites of southeastern australia the production of variation by differential separation of melt from residual solid source material or restite must be favoured for many of the granite suites of this region

spatial distribution and morphometry of permafrost related landforms in the central pyrenees and associated paleoclimatic implications abstract present and past permafrost distribution in the pyrenees is still under discussion as in other mid latitude mountain regions rock glaciers and protalus lobes are the main indicators of permafrost conditions in this paper we examine the distribution of these landforms in aran and boi valleys formerly glaciated u shaped valleys ranging from 600 to 3000 m in the southern and northern sides of the central pyrenees respectively the spatial distribution of these landforms and their chronostratigraphic position within the valley allow a better understanding of the climatic and environmental conditions necessary for their development up to 151 permafrost related landforms were identified in the boi valley including 56 rock glaciers and 95 protalus lobes in the case of the northern aran valley 76 rock glaciers and 89 protalus lobes were cataloged corresponding to 165 landforms most of the landforms 93 for rock glaciers and 95 for protalus lobes are located inside the glacial cirques with a few distributed in the slopes of the formerly glaciated valleys the lowest elevation of rock glaciers is situated at 1744 m aran and 2007 m boi whereas the lowest protalus lobes are located at 1740 m and 2033 m respectively therefore this altitude may be indicative of the lowest level recording permafrost conditions during the period in which these landforms formed with paleotemperatures ca 7 8 c lower than present day between 60 and 70 of the protalus lobes and rock glaciers are located between 2300 and 2600 m in boi valley and 2100 and 2400 m in aran valley the aspect shows a prevailing orientation of nw n and ne for both cases of rock glaciers and protalus lobes being almost absent in the s se and sw aspects the average slope of both landforms lies between 11 and 27 with a maximum of 35 for rock glaciers and 29 for protalus lobes the amplitude length ratio reveals that rock glaciers placed at lower altitudes are more elongated the chronostratigraphic position of these landforms within the valley and with respect to the moraine complexes suggests the existence of three generations of permafrost related landforms which are associated to the massive deglaciation process between the maximum glacial advance of the last glaciation and the holocene

application of thermal anemometry and high frequency measurement of mass flux to aeolian sediment transport research abstract recent research on sediment transport by temporally varying winds has stimulated the need for high frequency measurements of wind velocity turbulence and transport rate conventional technologies yielding only temporally averaged estimates of wind velocity and mass flux are unable to resolve the transitional and self regulating behaviour of the aeolian saltation system in unsteady winds the characteristics calibration and potential of thermal velocity probes suitable for research on aeolian transport are analysed recent developments in particle impact sensing and the use of sand trap force transducer combinations are reviewed and the design of a new optical mass flux sensor is presented an upper frequency limit of about 1 hz is shown to be essential to transport rate relations in unsteady forcing winds or during intermittent transport higher frequencies are required if reynolds stress or potentially influential flow structures and sediment fluid interactions in the saltation cloud are to be resolved armoured hot wire sensors measure u component air velocity to 1 hz in grain clouds and some less robust two dimensional thermal sensors may be used at higher frequencies to determine bed shear from reynolds stress u w during sand transport by wind grain impact devices and automated sand traps provide high frequency measurements of transport rate but they are intrusive and their output signals may be ambiguous this paper reports the design and testing of a new instrument system providing high frequency measurements of aeolian sand transport it comprises a non intrusive optical mass flux sensor synchronized to an array of armoured hot wire anemometers the sensor uses a linear image array to detect at a sampling frequency of 4 40 hz the transit of wind driven particles through a laser sheet transverse to the flow in a wind tunnel the physics of the sensor have been rigorously explored in static grain tests and calibrations to mass flux its principal advantages over existing devices are its non intrusive design and ability to measure near bed mass flux with precision at high frequency example applications demonstrate that this instrumentation is able for the first time to recover high frequency aspects of the temporal behaviour of aeolian saltation previously revealed only by numerical models

mafic injections in situ hybridization and crystal accumulation in the pyramid peak granite california located in the northern sierra nevada the middle jurassic pyramid peak granite and associated dioritic rocks display superbly exposed interlayered sheets of mafic felsic and hybrid rocks the mafic hybrid layers show a consistent asymmetry sharply chilled on one side and gradational through hybrids to granite on the other and dip to the southwest load casts and silicic pipes along the chilled mafic northeastern margins of the sheets indicate that depositional way up is to the southwest and that the adjacent mount tallac roof pendant was the original floor of the intrusion orientations of the pipes indicate that the layers were tilted after deposition and solidification we interpret the sheets to be intramagmatic flows that formed by injections of mafic magma into a silicic magma chamber followed by flow across the crystal rich base of that chamber the granitic and hybrid rocks interlayered with the mafic sheets represent material that accumulated on the chamber floor between episodes of mafic replenishment most contamination of the mafic sheets probably occurred because of flow front instabilities generated as the mafic magma entered and spread across the chamber floor the upward gradation from diorite to granite with decreasing abundance and size of mafic enclaves can best be explained by convective stirring at the upper boundaries of the dioritic replenishments the pyramid peak granite was probably initiated as a thin concordant sheet intruding into gently dipping jurassic supracrustal rocks the pluton was constructed incrementally with many replenishments of felsic and mafic magma and dominantly solidified by accumulation of crystals on the floor of the chamber the present steep dips of the layers suggest that downward warping of the chamber floor may have been a factor in accommodating the incrementally constructed pluton

rock glacier dynamics and paleoclimatic implications many rock glaciers contain massive ice that may be useful in paleoclimate studies interpreting geochemical ice core records from rock glaciers requires a thorough understanding of rock glacier structure and dynamics high precision surface velocity data were obtained for the galena creek rock glacier absaroka mountains wyoming surface velocities range from 0 to 1 00 m yr and vary across the rock glacier in a manner similar to true glaciers we used glen s flow law to calculate the thickness of the deforming ice layer the modeled ice thickness ranges from 0 to 50 m and is confirmed by direct observations this agreement shows that rock glacier movement can be entirely explained by deformation of massive ice within the rock glacier neither basal sliding nor deformation of basal debris is necessary recovered ice cores to depths of 25 m contain thin debris layers associated with summer ablation in the accumulation zone the ages of four samples of organic material removed from several debris layers inthe southern half of the rock glacier range from 200 40 to 2250 35 14c yr b p demonstrating that the rock glacier formed well before the little ice age and may contain ice dating to the middle holocene or earlier

a new model of rock glacier dynamics abstract rock glaciers have traditionally been described as periglacial landforms and thus associated genetically with the presence of permafrost and a seasonal active layer they have also been described as glacigenic in origin in which the main rock glacier body contains glacier ice at depth other rock glaciers can be considered as relict where they contain no interstitial ice and are functionally inactive although all rock glaciers are to some extent polygenic there is no clear simple test that can be used to distinguish between different rock glacier types this study proposes a simple and testable model for rock glacier classification based on their behaviour from evidence reported from the literature the study then proposes an interpretive evolutionary model describing the temporal evolution of rock glacier surface movement through the year that can inform on its dynamical controls this analysis provides an easily deployed interpretive framework for the origins of rock glaciers

late pleistocene and holocene glaciation in the pyrenees a critical review and new evidence from 10be exposure ages south central pyrenees a compilation and a critical assessment of the 14c data set available show that the chronology of glacial events in the pyrenees is not well constrained after reviewing the literature on glacial reconstruction we suggest a simplified subdivision of the pyrenean last glacial cycle record into last pleniglacial deglaciation and neoglacial to improve the numerical glacial chronology we provide 10be surface exposure ages for 5 glacial erosion surfaces 9 moraines and 2 erratics in the upper noguera ribagorcana valley south central pyrenees published corrected 14c data and new 10be exposure ages indicate that the major phase of moraine building recorded in this valley during the last pleniglacial probably occurred after 25 ka bp this age calls in question the generally accepted hypothesis of a very early deglaciation of the pyrenees ca 70 40 ka bp and strongly suggests that the pyrenees could have been in pleniglacial conditions during the last glacial maximum lgm however we do not exclude the possibility that the maximum glacier extent during the last glacial cycle had taken place much earlier than the lgm as indicated by some published u th ams 14c and osl data we suggest that pleniglacial conditions could have taken place during a longer 30 20 ka period than generally assumed and that the last pleniglacial could include several glacier fluctuations recorded irregularly in different valleys with a last major glacier readvance taking place around the lgm in addition the deglaciation is represented by a series of moraines deposited between ca 13 7 0 9 and 10 1 0 6 ka this moraine series indicates a highly variable climatic pattern that is partly correlated with greenland stadial 1 the younger dryas and suggests that the deglaciation could have continued into the early holocene

field chemical and physical constraints on mafic felsic magma interaction in the lamarck granodiorite sierra nevada california evidence of magma interactions resulting in both hybridization and mingling are preserved in a diverse suite of gabbroic to intermediate rocks associated with the compositionally zoned hornblende biotite lamarck granodiorite of the eastern sierra nevada california ellipsoidal mafic enclaves were formed by quenching of small amounts of high alumina basaltic magma upon injection into and dispersal through granodiorite magma early in its crystallization synplutonic intrusions of hornblende gabbro through hybridized mafic granodiorite represent injection of mafic magma at a later stage of crystallization of the granodiorite as they crosscut regional trends in foliation and compositional zoning in the host pluton where compositional contrasts between intrusion and host granodiorite are large contacts are sharp and abundant enclaves derived from the mafic intrusion are present in the granodiorite where the host is relatively mafic or where the local scale proportion of mafic magma is large contacts are zones of extensive hybridization that contain both enclaves and hybrid schlieren uncontaminated mafic intrusions have high alumina basaltic compositions whereas hybridized intrusions have silica contents as high as 63 5 mafic intrusions locally contain coarse grained cumulus gabbro inclusions mafic schlieren in granodiorite far from mafic intrusions represent localized accumulations of hornblende fe ti oxides and biotite from the granodiorite intrusion of late mafic dikes mobilized and entrained granitic residue from the granodiorite and formed composite dikes of aplite and pillowed diorite whether interacting magmas mix or mingle is a function of the heat contents and mass fractions of the end members calculations that account for compositions heats of fusion heat capacities of liquids and crystals and a range of initial temperatures crystallinities crystal sizes and magma water contents indicate that in most circumstances the basalt end member quenches the resulting large viscosity contrast between the end members prevents hybridization homogenization is likely only if the compositional difference between host and injected mafic magma is less than 10 sio2 or if the mass fraction of mafic magma is greater than 0 5 resulting mixtures have the composition of tonalite or mafic granodiorite thus the more silicic rocks of the granodiorite pluton must represent differentiation products rather than direct hybrids of mafic or intermediate magma and felsic magma

spatial and temporal variability of periglaciation of the iberian peninsula abstract active periglacial processes are currently marginal in the iberian peninsula spatially limited to the highest mountain ranges however a wide variety of periglacial deposits and landforms are distributed in low and mid altitude environments which shows evidence of past periods of enhanced periglacial activity the purpose of this paper is to summarize the present knowledge of past periglacial activity in the iberian peninsula the chronological framework takes four main stages into account the last glaciation deglaciation holocene and present day processes this study focuses on the highest massifs pyrenees cantabrian range nw ranges central range iberian range sierra nevada as well as other lower elevation environments namely the central iberian meseta during the last glaciation the periglacial belt extended to much lower altitudes than today reaching current sea level in the nw corner of the iberian peninsula a wide range of geomorphological landforms and sedimentary records is indicative of very active periglacial processes during that phase in some cases related to permafrost conditions i e block streams rock glaciers most of the inactive landforms and deposits in low and mid elevations in iberia are also related to this phase the massive deglaciation of the iberian massifs was caused by a gradual increase in temperatures the deglaciation phase was only interrupted by a short period with colder conditions the younger dryas that reactivated periglacial processes in the formerly glaciated cirques of the highest lands specifically with the widespread development of rock glaciers during the holocene periglacial processes have been only active in the highest ranges shifting in altitude according to temperature regimes and moisture conditions the little ice age saw the reactivation of periglacial activity in lower elevations than today currently periglacial processes are only active in elevations exceeding 2500 m in the southern ranges and above 2000 2200 m in the northern massifs higher in sierra nevada in the south of iberian peninsula

pyroxene in enclaves and syenites of the red hill complex new hampshire an ion and electron microprobe study the red hill complex new hampshire contains both silica undersaturated and silica saturated to oversaturated syenites ion microprobe analyses of pyroxene from the nepheline sodalite syenite nss and its enclaves reveal that the ree abundances increase in a systematic manner from low values in the enclave pyroxenes to higher values in the nss host rock pyroxenes this variation is interpreted to have resulted from differentiation and coupled with previously published mineral and bulk rock compositions suggests that the enclaves represent samples of nss parental liquids that intruded into residual syenitic liquids in a zoned magma chamber pyroxene analyses of the garland peak syenite gps and its enclaves indicate that the enclaves are of several populations some may be related to the gps others are not the gps itself is heterogeneous and pyroxene trace element zoning is difficult to explain by fractionation processes the silica oversaturated outer coarse syenite ocs contains pyroxenes with trace element characteristics that are distinct from the nss the low v concentrations suggest that the ocs exprienced magnetite fractionation prior to pyroxene growth it is proposed that high f o2in the ocs magma caused fe ti oxide crystallization which in turn influenced magmatic silica activity the chondrite normalized ree patterns of ocs pyroxenes are also suggestive of titanite crystallization another indication of high f o2 in contrast to the influence of magnetite crystallization the high and rimwardly increasing y and yb concentrations in both the nss and the ocs pyroxenes suggest that amphibole fractionation was not the major influence on silica activity therefore it is unlikely that the ocs was derived by amphibole fractionation from a nss precursor magma

magmatic inclusions in rhyolites of the spor mountain formation western utah limitations on compositional inferences from inclusions in granitic rocks inclusions of quenched mafic magma occur in a 21 ma rhyolite lava and precursory non welded tuff that form the spor mountain formation in west central utah the mafic inclusions are not lithic inclusions no comparable volcanic unit was present at the surface when the spor mountain formation erupted mineral and bulk compositions preclude liquid immiscibility the mafic inclusions show clear morphologic and textural effects of magma mingling shortly before eruption of the rhyolite globular inclusions from both units are vesicular phenocryst poor plagioclase sanidine clinopyroxene orthopyroxene magnetite ilmenite latites and trachytes with quench temperatures of about 1000 c although overlapping in sio2 tio2 zr and hf concentrations inclusions from the underlying tuff lack negative eu anomalies and are enriched in p2o5 k2o al2o3 sr pb cr and ni whereas those hosted in the overlying lava have small negative eu anomalies and two fold enrichments in fe2o3 mno hree y ta th rb and cs the most reasonable explanation for the differences between the two sets of inclusions lies in selective chemical exchange between the rhyolite lava and the mafic inclusions after eruption limited mechanical mixing occurred after the inclusions solidified and became chemically modified the textures of the inclusions in the lavas and the elements selectively mobilized in the inclusions imply that vapor phase transport occurred in this low pressure volcanic environment if such substantial variations in inclusion compositions can arise during what must have been a short period of time before chemical reactions were halted by rapid cooling it seems unlikely that the compositions of mafic inclusions formed by magma mingling in slowly cooled granites preserve their original compositions mineralogies or information about their ultimate sources using the compositions of such chemically modified inclusions as end members for mixing calculations may lead to erroneous results regarding the significance of magma mixing in plutonic rocks

age origin and cooling history of the coronel joao sa pluton bahia brazil received april 2 2002 accepted august 8 2004advance access publication october 22 2004in north east brazil archean and paleoproterozoic cratonic blocksare enclosed within a network of brasiliano age 0 7 0 55ga metasedimentary foldbelts the unfoliated coronel joa o sa grano diorite pluton which contains magmatic epidote and stronglyresorbed clinopyroxene intrudes the sergipano foldbelt zirconsyield a concordant u pb crystallization age of 625 2ma titanite ages are approximately 621ma discordant zircons suggestinheritance from at least two magma sources of ages 2 2ga model calculations based on diffusion parameters andrb sr isotope data from separated minerals indicate that the plutoncooled ata rate of 36 c myr whole rock element compositionsandinitialsr ndisotopic compositionsthat areheterogeneous onalllength scales suggest magma mixing trace element concentrationsand nd isotope data argue against a contribution from a contem poraneous mantle derived magma values of magmatic e

the grizzly lake complex yellowstone volcano usa mixing between basalt and rhyolite unraveled by microanalysis and x ray microtomography abstract magma mixing is a widespread petrogenetic process it has long been suspected to operate in concert with fractional crystallization and assimilation to produce chemical and temperature gradients in magmas in particular the injection of mafic magmas into felsic magma chambers is widely regarded as a key driver in the sudden triggering of what often become highly explosive volcanic eruptions understanding the mechanistic event chain leading to such hazardous events is a scientific goal of high priority here we investigate a mingling event via the evidence preserved in mingled lavas using a combination of x ray computed microtomographic and electron microprobe analyses to unravel the complex textures and attendant chemical heterogeneities of the mixed basaltic and rhyolitic eruption of grizzly lake in the norris mammoth corridor of the yellowstone plateau volcanic field yvf we observe evidence that both magmatic viscous inter fingering of magmas and disequilibrium crystallization dissolution processes occur furthermore these processes constrain the timescale of interaction between the two magmatic components prior to their eruption x ray microtomography images show variegated textural features involving vesicle and crystal distributions filament morphology the distribution of enclaves and further textural features otherwise obscured in conventional 2d observations and analyses although our central effort was applied to the determination of mixing end members analysis of the hybrid portion has led to the discovery that mixing in the grizzly lake system was also characterized by the disintegration and dissolution of mafic crystals in the rhyolitic magma the presence of mineral phases in both end member for example forsteritic olivine sanidine and quartz and their transport throughout the magmatic mass by a combination of both mixing dynamics and flow imposed by ascent of the magmatic mass and its eruption might have acted as a geometric perturbation of flow fields further fuelling mass exchange between magmas in terms of both chemical diffusion and crystal transfer these results illuminate the complexity of mixing in natural magmatic systems identifying several reaction related textural factors that must be understood more deeply in order to advance our understanding of this igneous process

rock glacier dynamics in a marginal periglacial high mountain environment flow movement 1991 2000 and structure of the argualas rock glacier the pyrenees the argualas rock glacier is located on the southern side of the central pyrenees argualas massif vertical electric sounding debris surface analysis and a topographic survey were performed on this rock glacier between 1991 and 2000 high precision measurement records were obtained using a total station horizontal and vertical movements of the rock glacier were measured by means of sixteen steel rods horizontal and vertical angles and distances to each rod were measured from three stations on a bedrock ridge total and annual average displacements were derived from the emergence value and the horizontal displacement of each rod then the horizontal and vertical displacement rates in different sectors of the rock glacier were compared the inferred surface deformation was characterized by both extensional and compressive flows as well as thinning of the frozen body the displacement rates showed temporal variations related to atmospheric thermal changes pointing to a high sensibility of the rock glacier

literature review of sand transport by wind on a dry sand surface abstract a critical and comprehensive literature survey of sand transport by wind on a dry sand surface is made from the perspective of engineering use principal findings are 1 most predictive expressions for the sand transport rate show a cubic dependence on the shear velocity or obey a similar power law 2 some difference is found in the value of the multiplicative empirical coefficient in the various formulas and much of the scatter may be ascribed to relative trap efficiency 3 verification of predictive formulas has mainly rested on laboratory measurements and reliable but limited field verification has not been made until recently 4 the laboratory and field data indicate that both the bagnold and the kawamura formulas are applicable to a well sorted sand and can be used for estimation of wind blown sand transport on dry natural beaches modifications have been made for a widely distributed sand and for fluctuating wind velocity

partitioning of lithophile trace elements between h 2 o and h 2 o co 2 fluids and topaz rhyolite melt experiments have been conducted with h 2 o and h 2 o co 2 bearing fluids and melts of a cl f and lithophile trace element enriched vitrophyre associated with topaz rhyolite from spor mountain utah the starting material is mildly peraluminous and contains 1 25 wt percent f and 1 500 ppm cl the experiments were conducted with f sub o 2 controlled near ni nio at pressures of 0 5 to 4 kbars and at temperatures of 770 degrees to 950 degrees c fluid melt trace element distribution coefficients d i were calculated for li be b rb sr y zr nb cs ba ce th and u after ion microprobe analysis of starting material and run product glasses the concentration of element i in the fluid was calculated by mass balance and the fluid melt distribution coefficient d i was calculated as ppm by weight of i in fluid ppm by weight of i in melt the partitioning of li rb sr y nb cs and ce between aqueous fluids and melts of topaz rhyolite composition depends strongly on temperature and pressure at 0 5 kbars li rb sr y nb cs and ce concentrate in the fluid at temperatures or 900 degrees c at 2 kbars this same group of lithophile elements except for sr concentrate in the fluid at t or 900 degrees c be b and ba partition in favor of the melt at 0 5 and 2 kbars and at all temperatures of this study in the presence of co 2 free aqueous fluids at 4 kbars and at temperatures of 770 degrees to 950 degrees c all lithophile elements partition in favor of the melt this behavior for lithophile elements mimics that of published data on the partitioning of pb and zn between rhyolitic melts and cl bearing fluids previous studies have demonstrated an equivalent effect of pressure on the distribution of chalcophile trace elements between granitic melts and cl bearing aqueous fluids fluid melt distribution coefficients for the lithophile trace elements are significantly smaller for topaz rhyolite melts in equilibrium with mixed co 2 h 2 o fluids than for topaz rhyolite melts plus co 2 free aqueous fluids there is no evidence for co 2 complexing with the lithophile trace elements at pressures 6 m the data imply that the alkali elements m dissolve into the fluid as mcl 0 complexes and that ce dissolves into the fluid as a cecl 0 3 complex water saturated magmas of topaz rhyolite composition may become differentiated with respect to li cs and rb or ce y and nb if an aqueous fluid phase is evolved and moves through the magma under the influence of a temperature gradient that has a maximum temperature of at least 850 degrees to 900 degrees c

the little ice age in iberian mountains abstract the little ice age lia is known as one of the coldest stages of the holocene most records from the northern hemisphere show evidence of significantly colder conditions during the lia which in some cases had substantial socio economic consequences in this study we investigated the magnitude and timing of climate variability during the lia in the mountains of the iberian peninsula based on a wide range of natural records including from glacial periglacial and lacustrine peatland areas fluvial alluvial deposits speleothems and tree rings historical documents and early instrument data the onset of the lia commenced in approximately ce 1300 and cold conditions with alternating moisture regimes persisted until approximately ce 1850 the environmental responses ranged from rapid e g tree rings to delayed e g glaciers the colder climate of the lia was accompanied by severe droughts floods and cold heat waves that showed significant spatio temporal variation across the iberian mountains several phases within the lia have been detected including a 1300 1480 increasing cooling with moderate climate oscillations b 1480 1570 relatively warmer conditions c 1570 1620 gradual cooling d 1620 1715 coldest climate period of the lia particularly during the maunder minimum with temperatures approximately 2 c below those at present e 1715 1760 warmer temperatures and a low frequency of extreme events f 1760 1800 climate deterioration and more climate extremes i e cold and heat waves floods and droughts g 1800 1850 highly variable climate conditions alternating with stability 1800 1815 extreme events 1815 1835 and a slight trend of warming associated with intense hydrometeorological events 1835 1850 h since 1850 a gradual staggered increase in temperature of approximately 1 c post lia warming has led to substantial changes in geo ecological dynamics mainly through shrinking of the spatial domain affected by cold climate processes

the interplay between crystallization replenishment and hybridization in large felsic magma chambers abstract while hybridized granitoid magmas are readily identifiable the mechanisms of hybridization in large crustal magma chambers are so not clearly understood characteristic features of hybrid granitoids are 1 both the granitoid and included enclaves are commonly hybrids as shown by mineralogy geochemistry and isotopes 2 mixing seen in zoned plutons and synplutonic dykes and enclaves occurred early 3 zoned plagioclase phenocrysts commonly show very complex life histories of growth and dissolution 4 mafic end members in hybrids are commonly fractionated magmas and 5 stratification in subvolcanic granitoid magma chambers is not uncommon and stratification has been identified in some deeper level plutons hybridization must overcome the tendency to form a stable stratification of dense mafic magma underlying less dense felsic magma experimental work with magma analogues and theoretical considerations reveal very severe thermal rheological and dynamical limitations on mixing only very similar composition temperature magmas are likely to mix to homogeneity and only moderately silicic hybrids are likely to be produced however impossibly silicic hybrids do exist synchronous interactive fractional crystallization and hybridization may provide a mechanism for hybridization of magmas in the following manner a mafic magma intrudes into the base of a stratified felsic magma and is cooled against it crystallization of the upper boundary layer of the mafic magma yields an eventually buoyant residual melt that overturns and mixes with an adjacent stratum of the felsic magma chamber subsequently melt released by crystallization pf this now hybrid zone mixes with adjacent more felsic zones thus a suite of hybrid magmas are progressively formed density inhibitions are overcome by the generation of relatively low density residual melts as crystallization proceeds later injections are preserved as dykes and enclaves composed of hybrid magma in this process only physically adjacent and dynamically thermally similar magmas directly interact and so may mix to homogeneity finally not simply felsic and mafic endmembers mix but a whole suite of intermediate endmembers participate ranging from relatively mafic through to felsic pairs of magmas direct mixing between the primary magmas only occurs at the beginning

the role of maximum wind speed in sand transporting events abstract a sand transporting event is the minimum unit of aeolian sand transport process to understand the role of maximum wind speed in such sand transporting events wind speeds were measured at a height of 2 m above the ground in the arid menggen and semi arid taibus banner regions in north china during 2009 and 2011 the sand transport flux of each sand transporting event was calculated based on theoretical equations then the relationships between the maximum wind speed and the average wind speed the duration and sand transport flux of sand transporting events were analyzed it was found that the maximum wind speed was proportional to the average wind speed of sand transporting events with a linear model fit and was also significantly correlated with the duration of sand transporting events with a power model fit the maximum wind speed was also positively correlated with sand transport flux of sand transporting events according to a power model the maximum wind speed could therefore represent both wind speed and the duration of sand transporting events and play a decisive role in the sand transport process of these events the sand transport flux of sand transporting events can be predicted rapidly and conveniently by monitoring maximum wind speed

mid holocene glacial activity in the pyrenees radiocarbon dating of sediments from a bog at c 2100 m in the cirque de troumouse provides the first reliable dating of holocene glacier fluctuations in the pyrenees the oldest organic material in the bog provides a maximum date 5190 90 bp for moraines immediately downvalley which are either lateglacial or more probably holocene in age bracketing dates on laminated glacioacustrine sediments in the bog indicate a neoglacial event between 4955 90 and 4654 60 bp which was probably contemporaneous with moraine ridges immediately upvalley more recent neoglacial events as yet undated are indicated by younger silt rich sediments in the bog and two younger moraine sets on the cirque floor at altitudes of c 2250 2350 m little ice age events were more restricted in extent and are recorded by younger moraines at c 2360 and at c 2650 m resting on and immediately below the cirque wall