zr bearing minerals as indicators for the polymetamorphic evolution of the eastern lower austroalpine nappes stubenberg granite contact aureole styria eastern alps austria abstract contact metamorphism during emplacement of the permian stubenberg granite has led to the formation of the assemblage forsterite calcite titanian clinohumite phlogopite chlorite in the adjacent marbles during intrusion of the granite veins rich in ti zr ree and actinides u th formed these veins show a distinct mineralogical zoning sequence with four zones going from the center of the vein to the margin these zones include the assemblages 1 geikielite baddeleyite zirconolite apatite calcite chlorite magnetite pyrrhotite assemblage 2 calcite chlorite 3 forsterite titanian clinohumite chlorite calcite phlogopite and 4 calcite forsterite baddeleyite is always replaced by zirconolite possibly via the model reaction baddeleyite 2 geikielite 3 calcite co 2 zirconolite 2 dolomite zirconolite zirc i shows a strong internal oscillatory zoning and distinct overgrowths zirc ii which have a different chemical composition the chemical variation between the cores zirc i and the rims zirc ii can be explained by using the substitutions me 5 me 2 ti 4 me 3 and ree 3 me 5 me 2 ca 2 2ti 4 in contrast to zirconolite from metacarbonates associated with contact aureoles these analyses show elevated nb contents of up to 4 5 wt nb 2 o 5 and unusually high w contents of 1 2 wt wo 3 a strong eo alpine metamorphic overprint led locally to the formation of the assemblage chlorite dolomite calcite ilmenite zirconolite ii geikielite fe sulfides late zircon grew locally presumably as the last zr bearing mineral in the carbonates which formed during permian contact metamorphism the zr mineral sequence baddeleyite zirconolite zircon implies an increasing a sio 2 and f co 2 during the growth of these minerals electron microprobe dating of zirconolite zirc i yields a weighted average age of 263 16 ma and indicates that the hfse and ree rich assemblages formed during the permian emplacement of the stubenberg granite as a result of the subsequent high p eo alpine metamorphic overprint 111 15 ma hfse and ree were locally re mobilized leading to dissolution of zirc i and reprecipitation of the ree and nb rich overgrowths of zirc ii

assessment of grain scale homogeneity and equilibration of carbon and oxygen isotope compositions of minerals in carbonate bearing metamorphic rocks by ion microprobe abstract nineteen samples of metamorphosed carbonate bearing rocks were analyzed for carbon and oxygen isotope ratios by ion microprobe with a 5 15 m spot three from a regional terrain and 16 from five different contact aureoles contact metamorphic rocks further represent four groups calc silicate marble and hornfels 6 brucite marble 2 samples that contain a reaction front 4 and samples with a pervasive distribution of reactants and products of a decarbonation reaction 4 the average spot to spot reproducibility of standard calcite analyses is 0 37 2 standard deviations sd for 18 o and 0 71 for 13 c ten or more measurements of a mineral in a sample that has uniform isotope composition within error of measurement can routinely return a weighted mean with a 95 confidence interval of 0 09 0 16 for 18 o and 0 10 0 29 for 13 c using a difference of 6sd as the criterion only four of 19 analyzed samples exhibit significant intracrystalline and or intercrystalline inhomogeneity in 13 c at the 100 500 m scale with differences within individual grains up to 3 7 measurements are consistent with carbon isotope exchange equilibrium between calcite and dolomite in five of six analyzed samples at the same scale because of relatively slow carbon isotope diffusion in calcite and dolomite differences in 13 c can survive intracrystalline homogenization by diffusion during cooling after peak metamorphism and likely represent the effects of prograde decarbonation and infiltration all but 2 of 11 analyzed samples exhibit intracrystalline differences in 18 o up to 9 4 intercrystalline inhomogeneity in 18 o up to 12 5 and or disequilibrium oxygen isotope fractionations among calcite dolomite calcite quartz and calcite forsterite pairs at the 100 500 m scale inhomogeneities in 18 o and 13 c are poorly correlated with only a single mineral dolomite in a single sample exhibiting both because of relatively rapid oxygen isotope diffusion in calcite intracrystalline inhomogeneities in 18 o likely represent partial equilibration between calcite and fluid during retrograde metamorphism calcite is in oxygen isotope exchange equilibrium with forsterite in one of four analyzed samples in equilibrium with dolomite in none of six analyzed samples and in equilibrium with quartz in neither of two analyzed samples there are no samples of contact metamorphic rock with analyzed reactants and products of an arrested metamorphic reaction that are in oxygen isotope equilibrium with each other the degree of departure from equilibrium in analyzed samples is variable and is often related at least in part to alteration of 18 o of calcite during retrograde fluid rock reaction in situ sub grain scale carbon and oxygen isotope analyses of minerals are advisable in the common applications of stable isotope geochemistry to metamorphic petrology correlation of sub mm scale stable isotope data with imaging will lead to improved understanding of reaction kinetics reactive fluid flow and thermal histories during metamorphism

crystal size distribution of periclase in contact metamorphic dolomite marbles from the southern adamello massif italy crystal size distributions csd of periclase in contact metamorphic dolomite marbles are presented for two profiles near the cima uzza summit in the southern adamello massif italy the database was combined with geochemical and petrological information to deduce the controls on the periclase forming reaction the contact metamorphic dolomite marbles are exposed at the contact of mafic intrusive rocks and are partially surrounded by them brucite is retrograde and pseudomorphs spherical periclase crystals prograde periclase growth is the consequence of limited infiltration of waterrich fluid at t near 6058c stable isotope data show depletion in 13 c and 18 o over a narrow region 40 cm near the magmatic contact whereas the periclase forming reaction front extends up to 4 m from the contact csd analyses along the two profiles show that the median grain size of the periclase crystals does not change but that there is a progressively greater distribution of grain sizes including a greater proportion of larger grains with increasing distance from the contact a qualitative model based on the textural and geochemical data attributes these variations in grain size to changing reaction affinities along a kinetically dispersed infiltration front this study highlights the need to invoke disequilibrium processes for metamorphic mineral growth and expands the use of csds to systems of mineral formation driven by fluid infiltration

prograde and retrograde fluid flow during contact metamorphism of siliceous carbonate rocks from the ballachulish aureole scotland siliceous dolomites and limestones contain abundant retrograde minerals produced by hydration carbonation reactions as the aureole cooled marbles that contained periclase at the peak of metamorphism bear secondary brucite dolomite and serpentine forsterite dolomite marbles have retrograde tremolite and serpentine wollastonite limestones contain secondary calcite and quartz and wollastonite free limestones have retrograde tremolite secondary tremolite never appears in marbles where brucite has replaced periclase or in wollastonite bearing limestones a model for infiltration of siliceous carbonates by co2 h2o fluid that assumes a vertical upwardly directed flow b fluid flux proportional to cooling rate and c flow and reaction under conditions of local equilibrium between peak temperatures and 400 c reproduces the modes of altered carbonate rocks observed reaction textures and the incompatibility between tremolite and brucite and between tremolite and wollastonite except for samples from a dolomite xenolith retrograde time integrated flux recorded by reaction progress is on the order of 1000 mol fluid cm2 rock local focusing of flow near the contact is indicated by samples from the xenolith that record values an order of magnitude greater formation of periclase forsterite and wollastonite at the peak of metamorphism also required infiltration with prograde time integrated flux approximately 100 1000 mol cm2 the comparatively small values of prograde and retrograde time integrated flux are consistent with lack of stable isotope alteration of the carbonates and with the success of conductive thermal models in reproducing peak metamorphic temperatures recorded by mineral equilibria although isobaric univariant assemblages are ubiquitous in the carbonates most formed during retrograde metamorphism isobaric univariant assemblages observed in metacarbonates from contact aureoles may not record physical conditions at the peak of metamorphism as is commonly assumed

geikielite exsolution in spinel euhedral crystals of purple spinel are associated with calcite and forsterite in the central zone of composite metasomatic veins of the adamello contact aureole northern italy in thin section spinel is generally colorless but exhibits concentric zones of dark brown color these zones are aligned parallel to prominent crystal faces and contain abundant anisotropic lath shaped inclusions with their long axis oriented in the six directions of spinel this orientation results from the alignment of 001 geik and the 111 sp crystallographic planes the small up to approximately 20 1 m inclusions were identified as geikielite by means of element distribution maps micro raman spectroscopy and transmission electron microscopy electron microprobe data revealed that spinel consists mainly of mgal2o4 with only minor amounts of other components the overall chemical variation within individual crystals is characterized by a continuous increase in feotot and zno from center to rim 0 6 2 1 wt and 0 1 1 0 wt respectively whereas v2o3 is relatively constant 0 15 wt the bulk tio2 concentration analysis spot 20 m diameter increases in general from center 0 12 wt to rim 1 2 wt this variation however is marked by several discontinuities that correspond to the zones containing geikielite inclusions where geikielite occurs the spinel matrix is depleted in ti relative to the inclusion free zones geikielite was analyzed by analytical electron microscopy and has the formula mg0 83fe0 15mn0 02 ti0 99fe0 01 o3 the textural relationships between geikielite inclusions and spinel matrix combined with the analytical data suggest that geikielite laths represent exsolution features thus a miscibility gap exists between mg al spinel and geikielite the purple color results from scattering of light by the geikielite inclusions spinel with similar features was also observed in metasomatic veins of the bergell contact aureole italy and in granulite facies marbles of southern india

applications of diffusion data to high temperature earth systems diffusion in general is such a widespread phenomenon in nature that a basic knowledge can serve very effectively to address well known applications not only to thermochronology and petrology but also to environmental geology e g paleoclimate sedimentology and applied geosciences e g assessing contamination of gas stations indeed the list of potential applications of diffusion phenomena is so long that an exhaustive treatment would quickly exceed the scope of this review the reader is therefore referred to reviews covering various aspects of diffusion in the earth sciences including diffusion in melts watson 1994 chakraborty 1995 diffusion processes during diagenesis berner 1980 krom and berner 1980 boudreau 2000 and diffusion phenomena in general e g lasaga 1998 ganguly 2002 watson and baxter 2007 zhang 2008 all of these treatments are based on the same general concepts of diffusion which do not need restating here in great detail applications of diffusion profiles in igneous systems have been thoroughly reviewed a recent reviews in mineralogy and geochemistry volume rimg 69 putirka and tepley 2008 and there is also an excellent volume on low temperature thermochronology rimg 58 reiners and ehlers 2005 describing the impact and application of diffusion theory for age and thermal history determination with these precedents in mind we focus the present review on the application of diffusion in high temperature regimes i e systems at t 500 c both igneous and metamorphic systems are addressed but because of the recent precedents noted above we emphasize recent developments and challenges in metamorphic studies in a broad sense diffusion describes the statistical non directional movement of molecules or heat through a medium of interest as independent theories of diffusion were developed in the early 19th century and compared with the principles of statistical variance it was

mineral distribution in contact metamorphosed siliceous dolomite at ubehebe peak california based on airborne imaging spectrometer data visible and near infrared reflectance spectra of minerals in the cao mgo sio 2 h 2 o co 2 system and airborne imaging spectrometer data with a spatial resolution of 3 6 m were used to map the distribution of dolomite calcite tremolite serpentine brucite and related minerals in the ubehebe peak contact aureole the results are entirely consistent with previously mapped isograds but the high spatial resolution imagery offers a more accurate representation of the complex distribution of metamorphic minerals and serves to highlight critical relationships between mineralogy and controlling factors such as stratigraphy structure and fluid infiltration rocks in the aureole are predominantly quartz poor dolomite and limestone and these are classified as pure dolomite or calcite accordingly tremolite and serpentine after forsterite are largely restricted to stratigraphic units that contain siliceous dolomite quartzite or chert in one area however tremolite and serpentine delineate a zone of retrograde hydration attributed to fluid flow along a fault wall rocks within 200 m of the contact and inliers of marble in the pluton contain brucite after periclase which documents sites of focused infiltration of h 2 o rich fluid in addition the imagery reveals local metasomatic zones marked by grossular rich skarn and epidote alteration of the adjacent quartz monzonite as well as large scale patterns of bleaching interpreted to define the maximum extent of fluid flow the degree of bleaching and the intensity of plastic deformation are closely coupled both effects increase abruptly at the forsterite isograd which appears to represent a fundamental discontinuity with respect to chemical physical and mechanical processes in the aureole

patterns of mineral occurrence in metamorphic rocks patterns in the occurrence of minerals in metamorphic rocks suggest additional opportunities for investigating chemical and physical processes during metamorphism three such patterns are reviewed first trace minerals in metamorphic rocks commonly occur with regular distributions indicating their participation in prograde reactions that can be mapped as isograds examples include the distribution of allanite and monazite in pelitic rocks and of zircon and baddeleyite in siliceous dolomites recognition of these isograds points to the potential for developing a chronology of specific chemical reactions during metamorphism and for defining the p t conditions of those reactions second the mineralogical products of retrograde metamorphism in many cases occur in distinctive associations that are consistent with partial mineral fluid equilibrium examples include the distribution of retrograde calcite quartz and tremolite in siliceous limestones and of retrograde tremolite dolomite brucite and serpentine in siliceous dolomites from contact aureoles among other things application of partial equilibrium to retrograde metamorphic rocks leads to constraints on the amount and direction of fluid flow in contact aureoles as they cool third pseudomorphs are typically absent from prograde metamorphic rocks but are common in retrograde metamorphic rocks the distribution may be explained by the effect of force of crystallization the pattern of occurrence of pseudomorphs thus suggests novel phenomena during metamorphism that develop from an interplay between chemical and mechanical processes

the effect of fluid salinity on infiltration driven contact metamorphism of carbonate rocks calculated phase equilibria involving minerals and h2o co2 nacl fluid lead to predictions of how infiltration of rock by h2o nacl fluids with xnacl in the range 0 0 3 0 58 wt nacl drives the reactions calcite quartz wollastonite co2 and dolomite periclase calcite co2 calculations focus on metamorphism in four aureoles that together are representative of the normal p t conditions and processes of infiltration driven contact metamorphic reactions the effect of salinity on the spatial extent of oxygen isotope alteration was also computed the time integrated input fluid flux q that displaces the mineral reaction front an increment of distance along the flow path always increases with increasing xnacl for input fluids with salinity up to approximately five times that of seawater xnacl 0 05 values of q required to explain the spatial extent of decarbonation reaction are no more than 1 1 1 5 times that computed assuming the input fluid was pure h2o for more saline fluids values of q may be up to 1 4 7 9 times that for pure h2o except for reaction in the presence of halite and vapor v infiltration of h2o nacl fluids expands the region of oxygen isotope alteration relative to the size of the region of mineral reaction the expansion is significant only for saline fluids with xnacl 0 1 immiscible fluid phase separation and differential loss of the liquid l or v phase from the mineral reaction site increases the amount of reactive fluid required to advance the mineral reaction front compared to conditions under which equilibration of minerals and fluid is attained with no loss of l or v decarbonation reactions driven by infiltration of fluids with even modest seawater like salinity can explain the occurrence of salt saturated fluid and solid halide inclusions in contact metamorphosed carbonate rocks

entrainment in shallow rotating gravity currents a modeling study abstract the physics of shallow gravity currents passing through a rotating channel at subcritical froude number is investigated here with a series of idealized numerical experiments it is found that the combined effects of friction and rotation set up a complex transverse circulation that has some crucial implications for the entrainment process a key component of this secondary circulation is a geostrophically balanced transverse jet in the interface that laterally drains fluid from the interface this effect is shown to result in a strong cross channel asymmetry and a spatial separation of the entrainment process drained interfacial fluid is partly replaced by entrained ambient fluid on the deep side of the gravity current whereas the downward mixing of buoyant fluid occurs on the shallow side these results closely corresponding to recent measurements in a shallow channelized gravity current in the western baltic sea illustrate that the description of entrainment as a strictly vertical mixing p

elemental dispersion and stable isotope fractionation during reactive fluid flow and fluid immiscibility in the bufa del diente aureole ne mexico evidence from radiographies and li b sr nd and pb isotope systematics the 31 6 0 3 ma old bufa del diente alkali syenite ne mexico intruded a sequence of cretaceous limestones with intercalated sub horizontal chert layers the cherts acted as aquifers that facilitated transport of brines and pegmatitic melts within the shallow level 1 kbar contact metamorphic aureole fluid driven reactions between chert and marble wallrock and the influx of late melts and various fluids gave rise to distinct chemical and isotopic signatures within the aquifer and across the zones of infiltration and fluid driven reaction aqueous brines of magmatic origin produced thick wollastonite mantles around the chert layers wollastonite formation occurred at the expense of limestone and chert and generated co2 this co2 induced fluid unmixing into an aqueous brine and a low density co2 rich fluid which was lost to the overlying marble where it oxidized organic matter and caused 13c and 18o shifts in a zone some 5 10 cm wide after wollastonite formation the chert aquifers were locally intruded by pegmatite veins carrying alkali feldspar quartz aegirine augite eudialyte zircon and apatite aqueous fluids that exsolved during crystallization of the pegmatite veins escaped along late cross fractures and migrated along the inner and outer borders of the wollastonite margins chemical dispersion patterns of u al na k p s fe and ree across the chert to marble boundary and its metasomatic rims are shown by autoradiography and neutron induced radiography scavenging of cations at mineralogical contacts and cation transport into the marbles occurred only on the mm to cm scale isotopic data for pb and sr across a simple metachert marble boundary and for pb sr nd b and li across a metachert pegmatite marble sequence demonstrate the following 1 the pb and sr isotopic signature of early fluids was buffered by the carbonate wallrock only late fluids shielded from wallrock interaction by a wollastonite mantle variably preserved a memory of their initial magmatic signature 2 since the nd isotope signature of marble and chert is bound to calcite and clay minerals systematic shifts to unradiogenic nd in marble reflect loss of carbonate bound nd as the wollastonite margin is approached nd in the wollastonite margin is dominated by nd originally bound to clay minerals the later emplacement of the pegmatite which carried the nd isotope signature of its alkali syenite source had little effect on the nd isotopic composition of the wollastonite rim 3 although the li and b isotopic compositions reflect the alkali syenite source they are also affected by isotopic fractionation and partitioning between melt fluid and solids

ion microprobe survey of the grain scale oxygen isotope geochemistry of minerals in metamorphic rocks abstract the oxygen isotope compositions of calcite diopside dolomite forsterite garnet k feldspar kyanite plagioclase quartz and wollastonite were analyzed in suites of contact and regional metamorphic rocks using an ion microprobe spatial resolution was 10 m precision measured as the standard deviation of working standards averaged over the entire project was 0 13 0 18 for three carbonate standards and 0 11 0 12 for two silicate standards a total of 1176 analyses excluding standards were made of 73 minerals in 23 samples both intercrystalline and intracrystalline variability in 18 o is greater in contact than in regional metamorphic rocks of 27 minerals analyzed in contact metamorphosed rocks 70 exhibit statistically significant grain to grain variability in 18 o over areas 1 41 cm 2 with the largest range in silicates and carbonates in a single sample of 7 4 forsterite and 10 6 dolomite of 88 grains analyzed in two or more places in contact metamorphosed rocks 32 exhibit statistically significant intracrystalline variability in 18 o with the largest range in a single silicate and carbonate grain of 3 1 forsterite and 10 1 dolomite in contrast 44 of 45 minerals in regional metamorphic rocks exhibit significant grain to grain variability in 18 o over areas 1 17 cm 2 with the largest range in silicates and carbonates in a single sample of only 1 1 plagioclase and 0 9 calcite only 6 of 144 grains analyzed in two or more places in regional metamorphic rocks exhibit significant intracrystalline variability in 18 o with the largest range in a single silicate and carbonate grain of only 1 5 diopside and 0 7 calcite the difference in intercrystalline and intracrystalline variability in 18 o between contact and region metamorphic rocks is explained by the longer duration and slower reaction rates of regional metamorphism rather than to differences in temperature there is no significant difference in intercrystalline and intracrystalline variability in 18 o in regional metamorphic rocks among samples from the biotite garnet and kyanite zones calcite inclusions in forsterite and calcite and quartz inclusions in garnet either have 18 o that is statistically indistinguishable from 18 o of the same mineral occurring as nearby matrix grains or have statistically significant lower 18 o no reversed isotope fractionations were measured between coexisting mineral pairs minerals in individual samples however exhibit a wide range in the degree to which they attained and preserve oxygen isotope fractionations consistent with metamorphic temperatures recorded by mineral equilibria processes that account for grain scale departures from isotope exchange equilibrium include a overstepping of prograde mineral reactions b growth zoning in low diffusivity minerals c interaction of rocks with fluids at the peak of metamorphism and or during cooling d retrograde mineral reactions and e closed system isotope exchange between coexisting minerals during cooling this study provides new information about 1 the degree to which a variety of textural changes experienced by rocks during metamorphism are associated with changes in 18 o 2 oxygen isotope homogenization at the outcrop scale among contrasting lithologies 3 changes in 18 o with increasing grade of regional metamorphism and 4 time scales of metamorphic process

implications of geochemical fronts in the notch peak contact metamorphic aureole utah usa abstract the geochemistry of the notch peak contact metamorphic aureole was examined to determine the dominant source of fluid attendant on metamorphism and to estimate fluid fluxes progressive metamorphism of calc silicate rocks is defined by phlogopite diopside and wollastonite isograds mineral assemblages at wollastonite and diopside grades indicate water rich conditions during decarbonation reactions near the intrusion the rocks are highly fractured in both the horizontal and the vertical direction the 18o values of most unmetamorphosed through diopside grade rocks range from 16 3 to 20 2 whereas in the wollastonite zone and near a pre intrusion fault the values approach the 9 5 value of the granitic stock coincident with the zone of18o depletion are zones of ba and zn enrichment consideration of solubilities of these elements in magmatic fluids and of published mineral water distribution coefficients indicates that these elements were advected from the magma model 18o profiles for up temperature flow of formation water assuming variable damko hler numbers and both static and variable thermal gradients fit poorly most data and do not reproduce the broadened front in the observed profile in contrast model profiles for radial one dimensional flow of magmatic water with variable damko hler number under static or variable thermal gradients fit the data well although the model isotopic front remains less distended that the one observed the integrated radial flux of magmatic water indicated by the position of the isotopic front is 1 8 107 mol m 2 additional broadening of the observed front and the scatter of the data suggest diffusion or hydrodynamic dispersion of oxygen regression of the data indicates an effective porosity of 12 in the inner aureole during fluid flow the porosity was largely fracture controlled and resulted from decarbonation sustained exsolution of water from the magma and up to 30 reaction produced volume loss in the high grade rocks the coincidence of the ba zn and 18o fronts suggests that bulk of the magmatic water flow was confined to the wollastontie zone the exception is the proximity of the fault where fluids emanating from an underlying part of the intrusion may also have flowed upward through lower grade rocks

contact metamorphism of layered carbonate shale sequences in the oslo rift ii migration of isotopic and reaction fronts around cooling plutons abstract intrusion of felsic plutons of permian age into lower paleozoic shale carbonate sequences caused extensive contact metamorphism in the oslo rift oxygen and carbon isotope data from both carbonates and shales are presented to demonstrate that the progress of metamorphic reactions in the contact aureole around the drammen granite was to a large extent controlled by the infiltration of water rich fluids of a magmatic oxygen and with a carbon isotope signature highly integrated fluid fluxes were confined to shale rich lithologies massive limestones were relatively impermeable to fluid flow the spatial distribution of isotopic and reaction fronts in the aureole and coupled 18 o 13 c isotope variations of carbonates from interlayered shale carbonate units fits well to a 1 d transport model with fluid flow away from the intrusive contact whereas the same isotope variations in limestones containing thin shale intercalations do not the high fluid fluxes estimated from 1 d models 2000 m 3 m 2 require either focused flow of magmatic fluids in the study area or large scale convective flow possibly involving fluids of meteoric origin limited kinetic broadening of the oxygen isotopic front indicates fluid fluxes of 8 m s fluid flow must have persisted for 10 4 yr to have moved the oxygen front 1000 m from the intrusive contact simple 2 d transport models involving dominant fluid flow along aquifers or fractures and involving diffusion as well as advection explain most of the coupled 18 o 13 c trends reported for carbonates from contact aureoles

mineralogical evidence for fluid rock interaction accompanying prograde contact metamorphism of siliceous dolomites alta stock aureole utah usa contact metamorphism of siliceous dolomite in the southern part of agrees well with the q m tiff 3 4 10 7 mol m 2 determined by the metamorphic aureole of the alta stock utah usa produced numerical simulation of the temperature and 18 o depletion profiles the prograde isograd sequence talc tc tremolite tr forsterite preserved in the southern aureole the estimates of q m tiff for the fo and periclase per calcite cc dolomite do ge forsterite and tremolite zones have much greater uncertainty but othermometry and phase equilibria define a general prograde t may indicate that fluid flux was considerably lower in these zones x co2 path of decreasing x co2 with rising temperature for than in the periclase zone given the outward down temperature the dolomite high variance assemblages typify the aureole per subhorizontal flow geometry indicated by a variety of petrologic cc and fo cc do characterize the inner aureole per and geochemical and geothermometry evidence presented here and elsefo zones and tr do cc and tc do cc are where this decrease implies that fluid has leaked from the flow widespread in the outer aureole tr and tc zones low variance system between the periclase and tremolite zones assemblages are rare and the thickness of reaction zones coexisting reactant and product minerals at the isogradic reaction fronts are narrow tens of metres or less the mineral assemblages calculated progress of isograd reactions and the prograde t x co2 path all key words alta fluid flow infiltration marble mineralogical indicate that massive dolomite was infiltrated by significant fluxes of water rich fluids during prograde metamorphism and that the fluid flow was down temperature and laterally away from the igneous contact fluid infiltration continued through at least the initial retrograde cooling of the periclase zone down t fluid flow introduction is also consistent with the results of cc do geothermometry and both mineral assemblages and stable isotopes have been patterns of 18 o depletion in this area the close spatial association

formation and destruction of periclase by fluid flow in two contact aureoles periclase formed in steeply dipping marbles from the beinn an dubhaich aureole scotland and the silver star aureole montana by the reaction dolomite periclase calcite co2 equilibrium between rock and fluids with x co 2 1 requires that reaction was infiltration driven brucite pseudomorphs after periclase occur in the beinn an dubhaich aureole either as bed by bed replacement of dolomite or in a lens along the contact between dolomite and a pre metamorphic dike transport theory predicts that infiltration drove both periclase reaction and 18o depletion fronts which moved at significantly different velocities along the flow path the distributions of brucite and 18o depleted rocks are identical in surface exposures thus indicating upward flow time integrated flux q was 500 mol cm2 and the fluid source was magmatic because periclase and its hydrated equivalent brucite are unaltered to dolomite by retrograde reactions the exposure of brucite marbles accurately images the flow paths of peak metamorphic fluids in the silver star aureole brucite pseudomorphs after periclase exclusively occur in tabular bodies that are beds with elevated mg ca the spatial pattern of 18o depletion requires upward vertical fluid flow estimated prograde q 103 104 mol cm2 and the fluid source was magmatic low mg ca 18o depleted brucite free rocks pose a dilemma because the periclase reaction front should have traveled 18 times further through them than the isotope alteration front the dilemma is resolved by reaction textures that indicate periclase and brucite were destroyed in low mg ca rocks by infiltration driven retrograde carbonation reactions values of retrograde q were 103 104 mol cm2 brucite after periclase was preserved only in high mg ca layers where periclase developed in greater abundance the geometry of brucite marbles at silver star thus reflects the location of high mg ca beds rather than the geometry of fluid flow retrograde reactions must be considered before the mineralogical record of prograde fluid flow can correctly be interpreted in both aureoles fluid flow mineral reaction and isotope depletion were structurally controlled by bedding and lithologic contacts

fluid flow patterns and infiltration isograds in melilite marbles from the bufa del diente contact metamorphic aureole north east mexico in the inner aureole of the bufa del diente alkali syenite north east mexico thin calcareous argillite bands horizontally embedded in impure marbles acted as contact metamorphic aquifers for hypersaline brines of magmatic origin thick bedded marbles were largely impervious from 180 m up to the intrusion contact argillites were completely decarbonated resulting in melilite wollastonite phlogopite perovskite bearing parageneses in marbles this assemblage is confined to a narrow 7 12 m wide infiltration zone adjacent to the contact up to this distance calcite wollastonite diopside alkali feldspar titanite was stable indicating that the fluid evolution in these marbles was internally buffered brine infiltration from the metaargillite aquifer into the marbles occurred perpendicular to the marble metaargillite boundaries and was confined to a zone 4 6 cm wide above the boundaries this is documented by the three reactions cc di mel co2 1 cc kfs di h2o phl wo co2 2 cc ttn prv wo co2 3 melilites ak32 45gh13 32sm32 40 to ak52 72gh0 1sm28 48 occur as rims around diopsides and become continuously thicker towards the metaargillite beds fluid inclusion observations suggest that the infiltrating brine was hypersaline nacl kclcq 65 wt and that the reactions took place at the water rich side of the h2o co2 salts immiscibility field at about 600d c 2 3 and 660 to 680d c 1 at p 1200 bar and xco2 0 02 mass balance calculations show that the amount of brine infiltrated from the aquifer into the marble was very low and decreased continuously with increasing distance from the boundary the maximum width of brine infiltration was about 6 cm this confirms that brine flow was largely parallel to the aquifer not perpendicular to it the co2 produced by the decarbonation reactions probably escaped as an immiscible low density h2o co2 fluid of xco2 0 5 into overlying marble via grain edge flow the metaargillite marble boundary acted as a semipermeable membrane 6 cm in thickness keeping back the brine in the aquifer and losing the in situ produced low density co2 rich fluid

fractionation of families of major minor and trace metals across the melt vapor interface in volcanic exhalations chemical families of metals fractionate systematically as they pass from a silicate melt across the interface with the vapor phase and on into a cooled volcanic plume we measured three groups of metals in a small suite of samples collected on filters from the plumes of kilauea hawaii usa etna sicily and merapi java volcanoes these were the major minor and trace metals of the alkali and alkaline earth families k rb cs ca sr ba a group of ordinarily rare metals cd cu in pb tl that are related by their chalcophile affinities and the radon daughter nuclides 210po 210bi and 210pb the measurements show the range and some details of systematic melt vapor fractionation within and between these groups of metals in the plumes of all three volcanoes the alkali metals are much more abundant than the alkaline earth metals in the kilauea plume the alkali metals are at least six times more abundant than the alkaline earth metals relative to abundances in the melt at etna the factor is at least 300 fractionations within each family are commonly also distinctive in the kilauea plume in addition to the whole alkaline earth family being depleted the heaviest metals of the family sr ba are progressively more depleted than the light metal ca in plumes of fumaroles at merapi k cs ratios were approximately three orders of magnitude smaller than found in other earth materials this may represent the largest observed enrichment of the light ion lithophile lil metals changes in metal ratios were seen through the time of eruption in the plumes of kilauea and etna this may reflect degree of degassing of volatiles with which metals complex from the magma bodies at kilauea the changes in fractionation were seen over about three years fractionation within the alkaline earth family increased and that between the two families decreased over that time all of the ordinarily rare chalcophile metals measured are extremely abundant in volcanic plumes and cd and tl are enriched relative to the others indium is much more abundant in the plume of the hotspot volcano kilauea than in the etna plume probably non hotspot in character it may be a useful indicator of the tapping of deep mantle zones or could aid in the interpretation of reports of pt group metals in exhalations from hot spot volcanoes indium in old glacial ice strata could help assess magnitude and variability of exhalations from hotspot volcanoes in past time strong melt vapor fractionation of the alkali and alkaline earth metals may only be observed in plumes during quiescent degassing of volcanoes when large amounts of ash or spatter undifferentiated lava enter the plume its alkali and alkaline earth metal composition may approach that of the melt ratios among the chalcophile metals may not be much changed by addition of ash because their concentrations in melt are so small and masses of them in any plume may remain dominated by transfer across the melt vapor interface radon daughter nuclides give information about state of volcanic activity at time of sampling the precisely known origins ultratrace detectability decay systematics and wide variations in volatility of these species provide information about residence times degassing and travel histories and identities of melt bodies in volcanic systems

stable isotope evidence of heterogeneous fluid infiltration at the ubehebe peak contact aureole death valley national park california stable isotope ratios of carbon and oxygen are used to define quantitatively the effects of magmatic fluid infiltration in marbles contact meta morphosed by the 173 ma ubehebe peak quartz monzonite death valley national park california in previous studies of fluid infiltration quantitative interpretation of aureole wide isotopic data has been difficult due to small data sets for this study sampling strategies were developed to obtain a data set that was large and unbiased enough to be statistically representative of the carbonates north of the ubehebe peak intrusion a total of 357 samples of marble were analyzed for bulk carbonate isotopic ratios separate analyses of coexisting calcite and dolomite were also obtained for an additional 31 samples unmetamorphosed samples 1900 3000 m from the intrusion have 18 o permil smow values of 25 5 0 8 1 and 13 c permil pdb values of 0 4 0 6 1 samples in the tremolite zone 750 1900 m have 18 o values ranging from 19 4 to 27 7 permil with a median value of 25 2 permil and 13 c ranges from 5 1 to 0 5 permil with a median value of 0 9 permil forsterite zone samples 0 750 m have isotopic ratios shifted to values as low as 11 1 permil 18 o and 9 1 permil 13 c despite this shift most forsterite zone samples retain sedimentary isotopic compositions with median 18 o values of 25 0 permil and 13c values of 1 2 permil 18o values for igneous minerals show no evidence for interaction with heated meteoric or metamorphic fluids the shifts in isotopic compositions within the marbles are interpreted to be the result of magmatic infiltration the effects of this infiltration were quantified by identifying samples with isotopic alteration that can only be attributed to infiltration the results show that magmatic fluid infiltration was limited in extent and very heterogeneous there is no evidence for infiltration of isotopically reactive fluids beyond 850 m from the intrusive contact and within this 850 m zone only 28 percent of the samples have been infiltratively altered with respect to 18 o and 20 percent are depleted in 13 c compositions the isotopic data when evaluated in conjunction with geostatistical and petrologic data indicate that the geometry of the hydrothermal flow system was mainly vertical and away from the pluton infiltration was restricted to large nearly vertical tube like zones of increased permeability these higher permeability zones likely reflect an initial heterogeneity of the host rocks and show no significant evidence for reaction enhanced permeability given the heterogeneity of the system and a lack of knowledge about many basic parameters controlling fluid infiltration it is shown that the best method of calculating the amount and composition of the infiltrating fluid may be a mass balance approach fluid rock ratio the application of mass balance models is discussed and shown to be valid only under limited conditions since infiltration at ubehebe peak was largely vertical the observed isotope alteration patterns represent an infiltration side and not a front because this precludes the use of traditional mass balance calculations a new infiltration side inside model is proposed that allows the isotopic data to be evaluated the inside model uses the ratio of the areal amounts of infiltrative alteration to calculate a fluid composi tion fluid amounts cannot be obtained from this model results for the ubehebe

calcite inclusions in forsterite forsterite in metamorphosed siliceous dolomites commonly contains calcite inclusions that are significantly more magnesian than even the most magnesian calcite grains in the matrix of the same rock calcite inclusions in forsterite from dolomite bearing rocks therefore have an unexploited potential for providing more accurate estimates of the peak t of metamorphism than do matrix calcite grains some consequences for estimating fluid pressure and for the development of models of heat and fluid transport during contact metamorphism are reviewed measured compositions of calcite inclusions in forsterite from five contact aureoles indicate that significant growth of forsterite grains continues over a 50 200 c range in t after the initial nucleation and growth of the mineral during heterogeneous mineral fluid reaction the continued growth may occur by an annealing mechanism driven by reduction in interfacial free energy

determining the direction of contact metamorphic fluid flow an assessment of mineralogical and stable isotope criteria one dimensional fluid advection dispersion models predict differences in the patterns of mineralogical and oxygen isotope resetting during up and down temperature metamorphic fluid flow that may in theory be used to determine the fluid flow direction with respect to the palaeotemperature gradient under equilibrium conditions down temperature fluid flow is predicted to produce sharp reaction fronts that separate rocks with isobarically divariant mineral assemblages in contrast up temperature fluid flow may produce extensive zones of isobarically univariant mineral assemblages without sharp reaction fronts however during contact metamorphism mineral reaction rates are probably relatively slow compared with fluid velocities and distended reaction fronts may also form during down temperature fluid flow in addition uncertainties in the timing of fluid flow with respect to the thermal peak of metamorphism and the increase in the variance of mineral assemblages due to solid solutions introduce uncertainties in determining fluid flow directions equilibrium down temperature flow of magmatic fluids in contact aureoles is also predicted to produce sharp 18o fronts whereas up temperature flow of fluids derived by metamorphic devolatilization may produce gradational 18o vs distance profiles however if fluids are channelled significant kinematic dispersion occurs or isotopic equilibrium is not maintained the patterns of isotopic resetting may be difficult to interpret the one dimensional models provide a framework in which to study fluid rock interaction however when some of the complexities inherent in fluid flow systems are taken into account they may not uniquely distinguish between up and down temperature fluid flow it is probably not possible to determine the fluid flow direction using any single criterion and a range of data is required

metasomatism and self organization of dolerite dyke marble contacts beinn an dubhaich skye dolerite dykes which intrude dolomitic marble in the aureole of the beinn an dubhaich granite on the isle of skye have developed metasomatized margins close to the contact with the younger granite in the southern part of torrin quarry these margins display well defined mineralogical zones which can be divided into two groups on the basis of composition chlorite bearing margins display the sequence dolerite diopside spinel chlorite calcite magnetite olivine calcite spinel dolomite whereas phlogopite bearing sequences have a phlogopite calcite fluorapatite layer in place of the chlorite bearing layer no spatial pattern is seen in the distribution of the two margin types but textural and compositional evidence points to an importance of metasomatism by localized infiltration of magmatic fluids in the development of the phlogopite bearing sequences extensive patterning of the phlogopite bearing margins by a process of self organization during grain growth has resulted in the formation of alternating silicate only calcite only layers parallel to the dyke margin on a millimetre to centimetre scale early development of chlorite bearing sequences at the dolerite dolomite contact during contact metamorphism was followed by metasomatism controlled growth of phlogopite and patterning at or after the peak of metamorphism associated with the expulsion of aqueous fluids from the crystallizing pluton

formation of wollastonite by chemically reactive fluid flow during contact metamorphism mt morrison pendant sierra nevada california usa quartz calcite sandstones experienced the reaction calcite introduction quartz wollastonite co2 during prograde contact metaflow of chemically reactive fluid may control the minmorphism at p 1500 bars and t 560 c rocks were in eralogy stable isotope composition and trace element equilibrium during reaction with a co2 h2o fluid with xco2 chemistry of rocks during contact metamorphism e g 0 14 the transition from calcite bearing wollastonite free to labotka et al 1988 jamtveit et al 1992a 1992b nabelek wollastonite bearing calcite free rocks across the wollastonite isograd labotka 1993 bowman et al 1994 roselle et al is only several millimeters wide the wollastonite forming reaction 1999 a number of aspects of metamorphic fluid flow was driven by infiltration of quartz calcite sandstone by chemically however remain the subject of debate including the reactive h2o rich fluids and the distribution of wollastonite directly direction of flow labotka et al 1988 ferry dipple images the flow paths of reactive fluids during metamorphism the 1992 ferry 1995a hanson 1995a whether numerical mapped distribution of wollastonite and modeling of an o isotope models that assume uniform rock properties adequately profile across a lithologic contact indicate that the principal direction predict the geometry of fluid flow in aureoles that contain of flow was layer parallel directed upward with any cross layer a variety of anisotropic structural features hanson 1992 component of flow 0 1 of the layer parallel component fluid 1995b cook et al 1997 and the degree to which local flow was channeled at a scale of 1 100 m by pre metamorphic mineral fluid equilibrium is attained lasaga rye dikes thrust and strike slip faults fold hinges bedding and 1993 bolton et al 1999 lasaga et al 2000 these and stratigraphic contacts limits on the amount of fluid based on related questions were addressed in an investigation of minimum and maximum estimates for the displacement of the contact metamorphism in the mt morrison pendant wollastonite reaction front from the fluid source are 0 7 1 9 eastern sierra nevada california the location is an 10 cm fluid cm rock the sharpness of the wollastonite isograd exceptional site for the study of metamorphic fluid flow the consistency of mineral thermobarometry the uniform measured for several reasons first the mt morrison sandstone o o fractionations between quartz and calcite and model the focus of this study is ideal for application of concalculations all argue for a close approach to local mineral fluid tinuum models of coupled fluid flow and reaction because equilibrium during the wollastonite forming reaction it is unusually homogeneous in mineralogy and texture