fire ecology of the carboniferous tropical zone abstract fossil charcoal fusain indicating the occurrence of wildfire is common in the carboniferous rocks of north america and europe during the carboniferous these regions lay on the southern margins of the laurasian continent and within the tropical zone this study examines the facies distribution and botanical identity of charcoal in order to investigate the influence of fire on carboniferous tropical ecology new data from charcoal bearing units in eastern canada poland and the british isles are presented and synthesised with previously published data of charcoal occurrence tournaisian visean charcoal bearing strata were deposited in volcanic lacustrine alluvial plain and coastal marine environments in these deposits charred floras are dominated by pro gymnospermous plants whilst uncharred compressed or permineralised floras are dominated by lycopsids uncharred lycopsid remains were probably derived from wetland communities growing close to the depocentres whilst charred gymnospermous remains may have been sourced from well drained extrabasinal settings based on the vertical distribution of charcoal layers in annually laminated lacustrine deposits it is estimated that fires occurred with high frequency approximately every 3 35 years palaeoclimatic analysis indicates that southern laurasia at this time was subject to a seasonal monsoonal tropical climate such environments today are characterised by tropical savannas with high fire frequencies and early carboniferous fire prone gymnospermous plant communities may have represented a comparable vegetation biome namurian stephanian charcoal bearing strata were deposited in alluvial plain coastal plain and coastal marine environments channelised sandstone units interpreted as river channel deposits contain charcoal derived from cordaitaleans and conifers this assemblage records fires in extrabasinal coniferopsid forests mudstone units containing coals are interpreted as the deposits of floodbasins and peat mires hollow uncharred lepidodendrid stumps occur in this facies and contain lepidodendrid charcoal in the stump bases and lepidodendrid pteridosperm coniferopsid and sphenopsid charcoal outside the stumps this assemblage records fires in wetland lepidodendrid dominated forests lepidodendrid trunks comprising of a spongy parenchymatous core surrounded by dense periderm became hollowed out during fire events an estimate of fire frequency based on the vertical spacing of charcoal layers in coals implies that fires occurred every 105 1085 years in the peat mires palaeoclimatic analysis indicates that southern laurasia was subject to a humid tropical climate during the late carboniferous such environments today are characterised by tropical rainforests where fires occur rarely and late carboniferous communities may have represented a comparable biome

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

the direction of fluid flow during contact metamorphism of siliceous carbonate rocks new data for the monzoni and predazzo aureoles northern italy and a global review periclase formed in siliceous dolomitic marbles during contact metamorphism in the monzoni and predazzo aureoles the dolomites northern italy by infiltration of the carbonate rocks by chemically reactive h2o rich fluids at 500 bar and 565 710 c the spatial distribution of periclase and oxygen isotope compositions is consistent with reactive fluid flow that was primarily vertical and upward in both aureoles with time integrated flux 5 000 and 300 mol fluid cm2 rock in the monzoni and predazzo aureoles respectively the new results for monzoni and predazzo are considered along with published studies of 13 other aureoles to draw general conclusions about the direction amount and controls on the geometry of reactive fluid flow during contact metamorphism of siliceous carbonate rocks flow in 12 aureoles was primarily vertically upward with and without a horizontal component directed away from the pluton fluid flow in two of the other three was primarily horizontal directed from the pluton into the aureole the direction of flow in the remaining aureole is uncertain earlier suggestions that fluid flow is often horizontal directed toward the pluton are likely explained by an erroneous assumption that widespread coexisting mineral reactants and products represent arrested prograde decarbonation reactions with the exception of three samples from one aureole time integrated fluid flux was in the range 102 104 mol cm2 both the amount and direction of fluid flow are consistent with hydrodynamic models of contact metamorphism the orientation of bedding and lithologic contacts appears to be the principal control over whether fluid flow was either primarily vertical or horizontal other pre metamorphic structures including dikes faults fold hinges and fracture zones served to channel fluid flow as well

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

properties origin and nomenclature of rodlets of the inertinite maceral group in coals of the central appalachian basin u s a abstract resin rodlets sclerenchyma strands and woody splinters which are collectively called rodlets were studied by chemical optical petrographic and scanning electron microscopic sem techniques a study was made of such rodlets from the bituminous coal beds of the central appalachian basin pennsylvanian upper carboniferous of the united states comparisons were made with rodlets from coal beds of the illinois basin the southern anthracite field of pennsylvania the st rose coal field of nova scotia and european and other coal fields in order to determine their physical and chemical properties a detailed study was made of the rodlets from the pomeroy coal bed high volatile a bituminous coal monongahela formation upper pennsylvanian of kanawha county west virginia the origin of the rodlets was determined by a comparative analysis of a medullosan seed fern stem from the herrin no 6 coal bed high volatile c bituminous coal carbondale formation from washington county illinois rodlets are commonly concentrated in fusain or carbominerite layers or lenses in bituminous coal beds of the central appalachian basin most of the rodlets examined in our study were probably derived from medullosan seed ferns the three types of rodlets are distinguished on the basis of cellularity morphology and fracture the resin rodlets studied by us are noncellular and appear to be similar in properties and origin to those found in coal beds of the middle and upper pennsylvanian of the illinois basin the resin rodlets extracted from the pomeroy coal bed exhibit high relief and high reflectance when polished and viewed in reflected light they are opaque in transmitted light in cross section the resin rodlets are oval to round and have diameters ranging from 60 to 450 m many are solid but some have vesicles canals or cavities which are commonly filled with clay probably kaolinite typically they have distinct fracture patterns kerfs in longitudinal and cross sections and many are characterized by dense probably oxidized rims the orientation and amounts of void space and mineralization of resin rodlets in coal have resulted in much confusion in their recognition and classification the resin rodlets are petrographically recognized as sclerotinites of the inertinite maceral group we here propose that resin rodlets be assigned to the maceral variety of sclerotinites termed resino sclerotinite because of their presumable resinous origin other investigators have confused some fusinitized resin rodlets with fungal masses which have different morphological properties and which probably have different chemical properties we here propose that such fungal masses be assigned to the maceral variety of sclerotinites termed fungo sclerotinite the sclerenchyma strands examined in our study are cellular thick walled and crescent shaped in cross section they exhibit high reflectance and high relief and belong to semifusinite and fusinite of the inertinite maceral group sclerenchyma strands are commonly associated with resin canals in medullosa and related seed fern genera which are common in coal balls of the illinois basin we here propose adoption of the maceral varietal terms sclerenchymo fusinite and sclerenchymo semifusinite for these bodies the woody splinters in the pomeroy coal bed are cellular and thin walled and have scattered pits as much as a few microns in diameter they are dark brown to black in transmitted light and commonly have a lower reflectance than the resino sclerotinite and sclerenchymo fusinite of the pomeroy coal the woody splinters belong to semifusinite and fusinite of the inertinite maceral group the maceral varietal terms xylemo semifusinite and xylemo fusinite are here proposed for these bodies elemental chemical data for the resin rodlets of the pomeroy coal bed of the central appalachian basin indicate that resin rodlets have significantly lower atomic h c and o c ratios than do sclerenchyma strands and woody splinters the lower atomic h c and o c ratios of the resin rodlets correlate with the highest reflectance in the coal ball medullosan seed fern stem from the herrin no 6 coal bed of the illinois basin the reflectances of the resin rodlets woody splinters and sclerenchyma strands are similar and comparable to those of associated vitrinite in the coal ball stem and in the attached coal however resin rodlets and sclerenchyma strands in the attached coal have significantly higher reflectances similar to those of the pomeroy coal

constraints on the thermal energy released from the chicxulub impactor new evidence from multi method charcoal analysis it has been suggested by various workers that an extraterrestrial impact at the k t boundary delivered sufficient thermal power to ignite globally extensive wildfires numerous models have sought to predict the amount of thermal power released by the impact but none have considered the distribution of wildfire indicators in k t rocks probably the most distinctive product from combustion of biomass is charcoal the abundance of charcoal across the k t boundary at eight non marine sites in north america stretching from colorado in the south to saskatchewan in the north is recorded using three separate methods that allow quantitative analyses of microscopic to macroscopic charcoal particles this study not only provides the first extensive study of charcoals across the k t boundary but also uses the presence or absence of charred material to predict the extent and severity of the thermal pulse released by the k t impact across the area predicted to have suffered the most extreme environmental effects the k t rocks contain on average between four and eight times according to the method used less charcoal than the cretaceous rock record and non charred plant remains are abundant in the k t rocks the below background charcoal abundance and the high proportion of noncharred material in the k t and lowermost tertiary rocks across the western interior of north america suggest that there were no significant wildfires in this area associated with the k t event although soot and polyaromatic hydrocarbons pahs have been reported in the k t rocks we suggest that the soot morphology and pah types are more consistent with a source from the vaporization of hydrocarbons rather than biomass for spontaneous ignition of vegetation temperatures 545 c are necessary whereas smouldering will begin at 325 c the below background levels of charcoal in the k t rocks allow the ground temperatures following the k t impact to be constrained to between no more than 545 c at any point and not above 325 c for any significant period this implies a maximum irradiance of 2 at the ground surface and that no more than 6 kw m 2 of thermal power was delivered to the ground for more than a few hours therefore our results show that the fossil record indicates that the impact at chixculub did not generate sufficient thermal power to ignite extensive wildfires

observations and experiments on the origin and formation of inertinite group macerals the inertinite group macerals include fusinite semifusinite inertodetrinite macrinite micrinite and funginite and secretinite which together replace sclerotinite the macrolithotype fusain comprises fusinite and semifusinite and is now widely accepted as charcoal formed by wildfire activity however alternative origins for fusinite and semifusinite are still claimed this paper considers the use of the terms pyrofusinite degradofusinite rank fusinite and primary fusinite misleading while the definitions of the terms funginite and secretinite are also considered problematic observations made on modern wildfire derived and volcanogenic charcoal assemblages using reflectance and scanning electron microscopy together with experimental charcoalification studies demonstrate that most if not all inertinite macerals have acquired their optical and physical characteristics through the action of elevated temperatures the criteria for the identification of charcoals produced by wildfire and volcanic activity are outlined and the role of the petrographic nomenclature system is discussed

elemental geochemistry and mineralogy of coals and associated coal mine overburden from makum coalfield northeast india the insufficient research on the nature and mode of occurrence of minerals and other inorganic elements of the northeast indian coal deposits has resulted in lack of proper utilization assessment and mitigation of environmental degradation the mineralogical and geochemical aspects of these coals were studied through the techniques such as optical microscopy low temperature quantitative x ray diffraction lta xrd scanning electron microscopy energy dispersive spectroscopy sem eds inductively coupled mass spectroscopy icp ms and chemical analysis techniques the leaching behavior of the elements including rees in presence of water was studied the high organic sulfur 75 of total sulfur and low ash yields were observed in these coals varying with seam depth the dominance of vitrinite 94 1 94 3 with an r max 0 72 0 78 in these coals along with their dominance within the lean organic fraction in the coal mine overburden ob samples was reported the major oxides present in these coals and their associated overburden samples were studied through xrf analysis various mineral phases were identified in both coal and ob samples such as dawsonite pyrite diaspore marcasite gypsum thenardite berzeliite garnet etc the sem eds analysis indicated the presence of siderite pyrite and kaolinite quartz illite etc in the coal ob and leached samples the distribution of concentrations of the 48 trace and rare earth elements rees varying with seam depth were normalized by upper continental crust ucc and found to be lower in comparison to global chinese and usa coals the statistical analysis on the trace and rare earth elements in the coals was performed to know their mutual correlations

the relationship between coal petrography and depositional environments from selected coal basins in canada abstract this paper reviews current research in canada relating to the sedimentology of coal bearing sequences and the petrographic character of contained seams from selected intermontane and foreland basin settings the intermontane cumberland and stellarton basins of nova scotia contain westphalian coal bearing strata of different character coal seams that formed in fluvial dominated depositional environments of the springhill coalfield cumberland basin commonly brighten upward and laterally display distinct areal zones a piedmont zone formed by interfingering of mire and distal fan sheetflow deposits an inner mire zone largely devoid of partings and a riverine zone with large scale seam splits about multistorey sandstone bodies maceral based groundwater influence and vegetation indices combined with miospore analyses indicate that the peat precursors of the no 3 seam of the inner mire zone accumulated from a groundwater influenced rheotrophic to mesotrophic forest mire swamp fen both the gelification of lignin derived maceral precursors and the domination of mire vegetation by lycopsid trees reflect this groundwater influence coal that formed from the frequently flooded paleomires of the stellarton basin is generally dull microbanded and mineral rich the location of mires within the basin was largely determined by basin subsidence rates when subsidence rates were high mires developed around the margin of a central basin lake coal seams that formed from these mires e g mcleod seam thicken toward basin margins and grade into sapropelic shale near the basin centre petrographic analyses of the mcleod seam suggest development from limnic to wet forest swamp conditions and a return to a limnic environment at the top of the seam thick coal e g foord seam developed near the basin centre during periods of lower subsidence rates and grades into red beds and paleosols toward the basin margin the foord seam of the basin centre is characterized by low mineral matter contents and a high proportion of degraded vitrinite macerals in the central parts of the seam interpreted to reflect prolonged peat accumulation with very limited clastic input the top and the base of the seam in contrast were subjected to significant clastic input as indicated by microbanding associated with significant amounts of detrital minerals and macerals coal seams of the lower cretaceous gates formation in the western canada basin formed in depositional settings ranging from coastal swamps strandplains to the upper delta plain strandplain coal is characterized by great lateral continuity and substantial thickness whereas coal of the upper delta plain is thin and discontinous the strandplain coal is characterized by variable lithotype sequences oscillatory brightening up dulling up maceral based facies parameters indicate a wide range of mire facies for these lithotype successions open moor forest moor herbaceous and or shrubby marshes and slightly raised mires results from megafossil and phyteral analyses suggest that the coastal plain mires were dominated by taxodiaceous conifers whereas ferns angiosperms and herbaceous lycopods are thought to have occupied the more marshy and or marginal stream lake side environments

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

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

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

charcoal in the silurian as evidence for the earliest wildfire rare basal pridoli plant fossils which resemble the rhyniophytoid hollandophyton colliculum and have exceptional three dimensional cellular anatomy are preserved as charcoal as such these fossils from ludford lane in the welsh borders are evidence of the earliest recorded wildfire and are the first documented from before the devonian the fossils represent the charred remains of a low growing low diversity in situ rhyniophytoid or cryptospore bearing plant vegetation charred during a low temperature fire

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

petrographic characteristics and palaeoenvironmental setting of upper triassic olang coal deposits in northeastern iran abstract this study investigates the petrographic analysis microlithotype and palaeoenviroment of deposition of the upper triassic olang coal deposits in northeastern iran the average maceral composition of the studied coals consisted of 82 3 8 9 0 4 vol vitrinite inertinite and liptinite groups respectively vitrinite macerals include equal portions of collotelinite and collodetrinite and a small quantity of corpogelinite also is present in all coal seams semifusinite and fusinite are the most abundant inertinite macerals the ground water index gwi suggests that these coal seams have evolved in a limnic coal facies a bog palaeomire system under ombrotrophic hydrological conditions except the k 6 g coal seam which evolved a limnic coal facies a bog palaeomire system under mesotrophic hydrological conditions the vegetation index vi values are indicative of the dominance of herbaceous plants in the formation of coal seams of the olang area

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

petrogenetic evolution of metabasalts and metakomatiites of the lower onverwacht group barberton greenstone belt south africa abstract a well preserved sequence by archean standards of mantle derived metabasalts and metakomatiites forms large parts of the lower onverwacht group of the barberton greenstone belt south africa to elucidate the origin of mafic and ultramafic rocks from this 3 55 to 3 45 ga sequence we present a comprehensive geochemical dataset including major and trace elements as well as lu hf and sm nd isotope compositions for a variety of metavolcanic rocks these include metabasalts of the amphibolite facies sandspruit and theespruit formations as well as metabasalts and metakomatiites of the lower greenschist facies komati formation based on their incompatible trace element patterns the basalts of the sandspruit and theespruit formations can be subdivided into a light rare earth element lree depleted group a lree undepleted group and a lree enriched group positive ehf t and end t values of ca 3 to 4 and 0 to 2 respectively together with depletions in th and lacn ybcn indicate derivation of the lree depleted basalts from a depleted mantle source however chondritic ehf t and end t values combined with positive th and lacn ybcn of the lree enriched samples indicate a contribution from older granitoid crust in the petrogenesis of these samples trace element patterns of komatiites and basalts of the komati formation are generally flat relative to primitive mantle with slight depletions in heavy rare earth elements and th and overall positive ehf t of 2 5 3 5 2 s d and end t of 0 5 2 2 2 s d the coherence in trace element characteristics suggests a common magmatic origin for basalts and komatiites this study reveals that the two lavas were derived from the same mantle plume i e komatiites were formed by high degrees of melting of a depleted mantle source containing residual garnet and the basalts were formed by moderate degrees of partial melting in shallower regions of the mantle based on the current dataset combined with published data we propose a geodynamic model for the oldest units of the barberton greenstone belt that describes the development from a submerged continental setting for the sandspruit and theespruit formations to a submarine plateau setting for the komati formation as a consequence of continental rifting

orientation of logs in the taupo ignimbrite as an indicator of flow direction and vent position the taupo ignimbrite is an unwelded rhyolitic ignimbrite that originated about 1 820 yr ago from an eruptive vent within lake taupo in the taupo volcanic zone new zealand this ignimbrite is rich in carbonized plant matter including many logs the logs lie subhorizontally throughout all levels of the ignimbrite but are especially common in the lower half regionally the logs show a strong radial orientation indicating flow directions and position of the source vent log orientation is thus a reliable indicator of vent position

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

a major fire event recorded in the mesofossils and petrology of the late permian lower whybrow coal seam sydney basin australia abstract petrographic and mesofossil analyses of plies from the late permian lower whybrow coal new south wales australia have revealed a significant fire event in both the swamp setting and the hinterland the fire event is characterised by a change in the maceral composition the seam during this interval being dominated by inertinite especially semifusinite following the fire event the mineral matter content of the coal increases this may be the result of increased run off and erosion in the hinterland due to destruction of vegetation this major fire event is also reflected in a change in the vegetation as represented by the mesofossil content of the seam prior to the fire event the seam contains abundant bisaccate taeniate pollen sporangia and seed like bodies of possible glossopterid affinity these are lost at the ply in which the fire event is recorded though seed like bodies become important again later the fire event also corresponds to a change in the megaspore content of the coal a new species appearing perhaps as a result of hydrological change following this major fire event a mineral rich ply was deposited which contains miospore masses of spores from fern like plants possibly representing a re colonisation event by rhizomorphs after vegetation death this evidence for a major fire and its implications for the origin of inertinites leads to the conclusion that throughout this and other permian gondwana coals fire was an integral part of the temperate mid high latitude southern hemisphere swamp ecosystem

deposition floral composition and sequence stratigraphy of uppermost triassic rhaetian coastal coals southern sweden abstract two uppermost triassic rhaetian coal beds a and b bed bjuv member southern sweden deposited at the margin of the danish basin were investigated in order to interpret the peat forming environments in a sequence stratigraphic context and to establish the peat forming vegetations of the precursor mires peat formed close to the coastline and was governed by base level watertable rise linked to relative sea level rise which is emphasized by rare occurrences of marine phytoplankton micrhystridium lunnomidinium scaniense and rhaetogonyaulax rhaetica in the b bed a maximum flooding surface mfs7 between the coal beds a and b shows that peat accumulation occurred as a coastal response to the continued transgression of the danish basin that culminated with deposition of the coal bearing bjuv member the lower b bed accumulated in a transgressive systems tract tst and the upper a bed in a highstand systems tract hst the b bed consists of coal and coaly mudstone intervals showing that peat formation repeatedly was outpaced by relative watertable rise the huminite rich coal intervals indicate peat formation under oxygen deficient stagnant water conditions where the peat accumulation rate balanced the watertable rise overall low ts values indicate a freshwater mire the base of coal bed b marks the start of a relative decrease in creation of accommodation space and the surface between the sediments and coal bed b represents a terrestrialisation surface tes the palynofloral composition suggests that the initial mire was characterised by dipterid dicksoniacean tree ferns and marattialean ground ferns and few canopy trees dominated by cupressacean taxodiacean wet loving conifers with subordinate bennettitalean and caytonialean trees the coal intervals in the b bed represent terrestrialisation situations characterised by a reduced ratio of accommodation rate peat accumulation rate the palynology of these intervals indicates establishment of canopy trees primarily cupressacean taxodiacean conifers accompanied by bennettitaleans and caytonialeans with an understory of marattialean ground ferns and rarer tree ferns flooding surfaces fs and accommodation reversal surfaces ars in the b bed reflect changes in the rate of watertable rise the coaly mudstone intervals represent paludification situations with an upward increasing ratio of accommodation rate peat accumulation rate in general the palynology of the b bed suggests a coal floral composition that was dominated by mid and upper canopy plants consisting of cupcressaceaen taxodiaceaen trees probably occupying areas with standing water while ginkgos cycads bennettiales and caytoniales and other seed ferns grew in less wet areas understory plants were less abundant whereas a ground cover of ferns mainly of the families marattiales and osmundales as well as lycophytes may have been pronounced the upper surface of the b bed is a give up transgressive surface guts above which peat accumulation was replaced by siliciclastic deposition the palynofloral composition suggests an open mire dominated by ground ferns and probable tree ferns with minor bennettitalean and caytonialean mid canopy trees and with hardly any upper canopy trees the a bed is considerably richer in inertinite compared to the b bed the palynofloral and petrographic change correlates with an increase in fire activity across the triassic jurassic boundary and deforestation of the early jurassic mires

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

characterization of organic matter in the fine grained siliciclastic sediments of the shemshak group upper triassic middle jurassic in the alborz range northern iran

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

mineral fluid equilibria in the system cao mgo sio2 h2o co2 nacl and the record of reactive fluid flow in contact metamorphic aureoles phase equilibria in the system cao mgo sio2 co2 h2o nacl are calculated to illustrate phase relations in metacarbonates over a wide range of p t x h2o co2 nacl conditions calculations are performed using the equation of state of duan et al geochim cosmochim acta 59 2869 2882 1995 for h2o co2 nacl fluids and the internally consistent data set of gottschalk eur j mineral 9 175 223 1997 for thermodynamic properties of solids results are presented in isothermal isobarical plots showing stable mineral assemblages as a function of fluid composition it is shown that in contact metamorphic p t regimes the presence of very small concentrations of nacl in the fluid causes almost all decarbonation reactions to proceed within the two fluid solvus of the h2o co2 nacl system

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

charcoal reflectance as a proxy for the emplacement temperature of pyroclastic flow deposits hot pyroclastic flow deposits often entomb and preserve vegetation as charcoal when studied in polished section this charcoal is highly reflective novel data from experimentally charred woods demonstrate that reflectance increases with both temperature and time at temperatures above 250 c reflectance rises rapidly for the first hour effectively stabilizing after 4 h for temperatures below 400 c however for higher temperatures reflectance only stabilizes after 24 h charcoalified woods from block and ash flow deposits generated by the soufriere hills volcano in montserrat have yielded interpreted deposit temperatures based on reflectance data of 325 525 c these temperatures compare favorably with directly measured data 365 640 c from the same deposits indicating that charcoal reflectance is useful as a temperature proxy for ancient pyroclastic flow deposits particularly where magnetic or mineral data are absent for this purpose however caution should be exercised as only a minimum temperature can be inferred where the heating duration of the deposit is unknown unlike magnetic or mineral data temperature data from charcoalified woods can be obtained from reworked deposits providing a valuable means of validating observations made about the style of eruption of volcanoes in ancient settings

a preliminary study of mineralogy and geochemistry of four coal samples from northern iran abstract this study is related to four jurassic age bituminous coal 0 69 1 02 ro samples collected from coal mines from the west central and east of central alborz in northern iran geological settings played key roles in determining the geochemistry and mineralogy of coals from the central alborz region of northern iran the mineralogy of coals from the eastern part of the region is dominated by kaolinite halloysite and carbonates such as calcite dolomite ankerite and siderite the coals were deposited in a lacustrine environment in the western part of the region where the depositional setting was also lacustrine with volcanic input and tonstein deposition glass shards present the coal primarily contains kaolinite 68 and fluorapatite 26 in contrast coal from the central part of the region which was deposited in a terrestrial environment and on eroded limestone and dolomite rocks is dominated by dolomite 98 with little input by kaolinite these coals have low sulphur 0 35 0 70 wt which is mostly in the organic form 0 34 0 69 wt pyritic sulphur is detected only in one coal and in small quantities the boron contents of these coals range from 9 to 33 mg kg indicating that deposition occurred in a fresh water environment coal with higher concentrations of ba sr and p contain fluorapatite and goyazite gorceixite series baal 3 po 4 2 oh 5 h 2 o minerals which indicates volcanoclastic input compared to world coal averages these coals exhibit low concentrations of elements of environmental concern such as as 1 3 5 9 mg kg cd

stratigraphy and ammonite fauna of the upper shemshak formation toarcian aalenian at tazareh eastern alborz iran abstract with a thickness of 3900 m the tazareh section is one of the thickest developments of the shemshak formation in the alborz range it overlies with sharp and disconformable contact the limestones and dolomites of the lower middle triassic elikah formation and is topped again with a disconformable contact by the marls and limestones of the middle jurassic dalichai formation the nearly exclusively siliciclastic succession represents a range of environments from fluvial channels flood plains swamps and lake systems to storm dominated shelf and a comparatively deep marine and partly dysoxic basin the segment of the section between 2300 and 3500 m is exclusively marine and contains a moderately diverse ammonite fauna ranging from the middle toarcian to the upper aalenian the ammonite fauna comprises 21 taxa among them the new genus shahrudites with two new species shahrudites asseretoi and s stoecklini from the middle aalenian bradfordensis zone the other ammonites from the shemshak formation at tazareh as elsewhere in north and central iran are exclusively tethyan in character and closely related to faunas from western and central europe an ammonite based correlation of toarcian aalenian successions of the eastern alborz with time equivalent strata of the lut block part of the central east iranian microcontinent ca 500 km to the south suggests a strong influence of synsedimentary tectonics during the deposition of the upper shemshak formation

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

petrology rank and evidence for petroleum generation upper triassic to middle jurassic coals central alborz region northern iran abstract upper triassic to middle jurassic coals from the alborz region of northern iran were analyzed by reflected light fluorescence microscopy and rock eval 6 pyrolysis to evaluate their regional rank variation degree of hydrothermal alteration and petroleum generative potential the coal ranks in the region range from a low of 0 69 ror in the glanddeh rud area to a high of 1 02 ror in the gajereh area tmax c values rock eval 6 pyrolysis also increase progressively with increasing vitrinite ro values however tmax is suppressed lower than would be expected for each rank ranging from 428 c for the glandeeh coal to 438 c for the gajereh coal tmax suppression may be caused by maceral composition and soluble organics within the coal moderately high hydrogen indices persistent and oily exudations from the coals during uv exposure and traces of hydrocarbon fluid inclusions suggest that liquid petroleum was likely generated within some of the coals

thermal maturity of the upper triassic middle jurassic shemshak group alborz range northern iran based on organic petrography geochemistry and basin modelling implications for source rock evaluation and petroleum exploration organic petrography and geochemical analyses have been carried out on shales carbonaceous shales and coals of the shemshak group upper triassic middle jurassic from 15 localities along the alborz range of northern iran thermal maturity of organic matter om has been investigated using vitrinite reflectance rock eval pyrolysis and elemental analysis of kerogen reflectance of autochthonous vitrinite varies from 0 6 to 2 2 indicating thermally early mature to over mature om in the shemshak group in agreement with other maturity parameters used the shales of the shemshak group are characterized by poor to high residual organic carbon contents 0 13 to 5 84 and the presence of hydrogen depleted om predominantly as a consequence of oxidation of om at the time of deposition and the hydrogen loss during petroleum generation according to light reflected microscopy results vitrinite vitrinite like macerals are dominant in the kerogen concentrates from the shaly facies the coals and carbonaceous shales of the shemshak group show a wide range in organic carbon concentration 3 5 to 88 6 and composition inertinite and vitrinite rich types and thereby different petroleum potentials thermal modelling results suggest that low to moderate palaeo heat flow ranging from 47 to 79 mw m 2 57 mw m 2 on average affected the central eastern alborz basin during tertiary time the time of maximum burial of the shemshak group the maximum temperature that induced om maturation of the shemshak group seems to be related to its deep burial rather than to a very strong heat flow related to an uppermost triassic liassic rifting the interval of petroleum generation in the most deeply buried part of the shemshak group i e tazareh section corresponds to middle jurassic early cretaceous times exhumation of the alborz range during late neogene time especially along the axis of the central eastern alborz where maximum vitrinite reflectance values are recorded probably destroyed possible petroleum accumulations however on the northern flank of the central eastern alborz preservation of petroleum accumulations may be expected the northern part of the basin therefore seems the best target for petroleum exploration

comment on growth and recycling of early archaean continental crust geochemical evidence from the coonterunah and warrawoona groups pilbara craton australia by green m g et al tectonophysics 322 69 88

evolution of pennsylvanian late carboniferous peat swamps of the ruhr basin germany comparison of palynological coal petrographical and organic geochemical data abstract this study focuses on the reconstruction of the environment during peat swamp development eight coal and sedimentary organic rock bearing seam successions were examined all belonging to the duckmantian pennsylvanian late carboniferous 410 samples were analysed with coal petrographical methods 155 of these also by palynological methods in addition on 55 samples organic geochemical investigations were carried out with respect to n alkanes and iso alkanes the established coal petrographical parameters gelification index gi tissue preservation index tpi groundwater index gwi and vegetation index vi were used to characterize different periods of peat swamp development furthermore the new index wci water cover index was introduced to reflect water level conditions by using the ratio between hydrophilous hygrophilous and mesophilous plants in this study the index is based on palynological data but can be equally applied when quantitative macrofloral counts are available gi versus tpi values show two general trends of peat swamp evolution low gi and tpi values as indicator for drier swamp conditions like ombrogenous mires and high gi and tpi values which show a trend to water covered environments like topogenous mires in addition ash yields and gwi versus vi data also emphasize a general trend from topogenous to ombrogenous mires a decrease in water level towards the top of the seams and thus resulting in the development of domed mires is reflected by the newly introduced wci hence these parameters show recurrent peat swamp successions characterized by mineral and vitrinite rich coals typical for topogenous swamps and an evolution towards inertinite liptinite rich coals with low ash yield typical for ombrogenous swamps n alkane ratios like the carbon preference index cpi pristane n c17 phytane n c18 pristane phytane and the n c17 n c27 relationship indicate a strong correlation of these parameters with thermal maturity e g cpi values correlate with vitrinite reflectance sulphur organic carbon s toc ratios are quite uniform in clastic rocks with low to moderate toc contents but highly variable in coals probably reflecting variable sulphate availability during deposition of peats sphenophyll rich floral assemblages are restricted to low sulphur environments

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

late cretaceous coal overlying karstic bauxite deposits in the parnassus ghiona unit central greece coal characteristics and depositional environment abstract the pera lakkos coal located on top of bauxite deposits in the ghiona mining district central greece is the only known mesozoic late cretaceous coal in the country it was derived from herbaceous plants and algae growing in mildly brackish mires that formed behind a barrier system during a regression of the sea on a karstified limestone partly filled in with bauxitic detritus petrological mineralogical and geochemical data point to the predominance of reducing conditions and intense organic matter degradation in the palaeomires o c vs h c and oi vs hi plots based on elemental analysis and rock eval data characterize kerogen types i ii this reflects the relatively high liptinite content of the coal besides kerogen composition o c vs h c plot for the pera lakkos coals is in accordance with a catagenesis stage of maturation in contrast with vitrinite reflectance and t max from rock eval pyrolysis which indicate the onset of oil window maturation stage suppression of vitrinite reflectance should be considered and the high liptinite content corroborates this hypothesis despite some favourable aspects for petroleum generation presented by the pera lakkos coal its maximum thickness up to 50 cm points to a restricted potential for petroleum generation coal oxidation took place either during the late stage of peat formation due to wave action accompanying the subsequent marine transgression or epigenetically after the emergence of the whole sequence due to percolation of drainage waters both options are also supported by the ree shale normalized profiles which demonstrate an upwards depletion in the coal layer oxidation also affected pyrite included in the coal this led to the formation of acidic sulfate rich solutions which percolated downwards resulting in bleaching of the upper part of the underlying bauxite

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

sequence stratigraphy of the archaean supracrustal belts of the pilbara block western australia abstract the stratigraphic succession of the 3580 2770 m y old granite greenstone terrain of the pilbara block is re assessed by the first and second order sequence stratigraphic techniques that are the standard for phanerozic terrains with the view to testing the conformity of stratigraphic cause and response a holistic tectonostratigraphic framework is presented that pairs the supracrustal and crustal rock records the resulting sequence scheme is tested against the cause of first order sequence cycles viz global sea level responses to supercontinent breakup and assembly three first order inter regional unconformities divide the stratigraphic succession of the supracrustal belts into four units of first order megasequence status in order of decreasing age these are named the warrawoona gorge creek roebourne and mount negri megasequences a total of 17 second order supersequences are also named although some may represent supersequence sets the megasequences and or their genetic crustal equivalents represent the preserved rock record of four megacycles of forearc arc and or back arc geotectonic evolution associated with the convergent margins of a pilbara continent individual supersequences are the rock record of separate second order basins or basin phases and reflect the different geotectonic components of each megasequence the four megacycles had respective longevities from oldest to youngest of 150 m y 230 m y 160 m y and 180 m y they are identical in their stratigraphic successions and predicted first order sea level cycles to phanerozoic first order tectono eustatic cycles and are interpreted as the same response to global tectonic change the warrawoona and gorge creek megacycles and the roebourne and mount negri megacycles are tectonogenetic pairs of the east pilbara and the west pilbara megacycle sets respectively the east pilbara megacycle set evolved over a period of 380 m y from 3490 ma to 3110 ma whereas the west pilbara megacycle set evolved over a period of 340 m y from 3110 ma to 2770 ma the two megacycle sets are identical in their longevity geotectonic components and predicted sea level cycles to convergent margin wilson and supercontinent cycles and are thereby interpreted individually as the oldest established records of the supercontinent cycle the implication of this interpretation is that a steady state global tectonic regime has been in operation from early in earth s history which has important consequences for theoretical modelling of the earth s early tectonic style and secular changes in its geochemical regime

geochemical and environmental baseline of major and trace elements in zarand coals southeastern iran in order to establish a geochemical baseline for environmental impacts of coal measures in rhaeto jurassic zarand coalfields multielement geochemistry of 22 host rocks 26 coal seams and 9 coal ashes was determined by icp ms icp aes xrf pgm icp24 and cv ass methods at als chemex canada the discrimination diagrams of major trace elements show a continental margin granitoid arc provenance for coal bearing sandstones and shales compared to the crustal abundance world coals and american coals the geochemical baseline for most of the elements is within the limits of safeguard background values however higher contents of li 49 31 185 mg kg rb 71 12 131 73 mg kg cs 7 13 16 12 mg kg v 72 19 213 1 mg kg th 7 63 11 8 mg kg as 10 1 31 31 mg kg nb 5 4 15 07 mg kg ta 0 4 1 mg kg hf 1 89 mg kg ga 12 63 32 16 mg kg ce 37 31 64 28 mg kg pb 40 23 55 76 mg kg cr 48 23 133 mg kg zr 60 39 mg kg and hg 0 24 mg kg are of some environmental as well as economic concerns the low values of b 0 12 12 mg kg s 7 839 10 567 mg kg and zn 63 25 157 6 mg kg in zarand coals may indicate a fluvial freshwater environment of coal deposition au pt and pd contents are slightly higher than the crustal abundance and further studies are required for their possible environmental and economic evaluation as the mean hg value in ash 0 0075 mg kg is almost 32 times lower than the mercury content of the coal seams 0 24 mg kg it is noteworthy that much of hg is released by coal combustion to the atmosphere which has certainly a detrimental environmental impact the ce cs ga la li rb and v values are much higher than the average world and american coals and merit further investigations for being the economic by products

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

geochemical properties of coals in the lushan coalfield of iran abstract iran s coals occur in the alborz and central iran basins one of the important coalfields in the alborz basin is the lushan coalfield the focus of our investigation it is located at the northern mountain ranges of iran our goal was to determine which factors control coal quality the coal bearing shemshak formation mainly consists of sandstone shale siltstone and clay stone twenty four coal samples were collected and analyzed for major and some trace elements using x ray fluoresence spectroscopy xrf the abundance of these elements is discussed in relation to local geological conditions the correlation between the various elements is demonstrated through scatter diagrams and possible genetic associations are discussed the average concentrations of some major and trace elements such as sr ba si ca mg and mn are higher than those of most coals in the world while the others fall within global ranges

outlining of high quality coking coal by concentration volume fractal model and turning bands simulation in east parvadeh coal deposit central iran abstract this study aims at identifying the proper parts of c 1 and b 2 coking coal seams in the north block of east parvadeh coal deposit central iran using the concentration volume c v fractal modeling according to sulfur and ash values which were calculated by turning bands conditional simulation the c v log log plots were generated based on results of 100 realizations derived via turning bands simulation which show seven different geochemical populations for both sulfur and ash data in b 2 seam which has a relatively good quality for coking coal with sulfur and ash values lower than 1 548 and 6 39 respectively additionally c v log log plots indicate that there are seven and six for sulfur and ash geochemical populations in c 1 seam containing a proper coal quality with respect to sulfur and ash values less than 1 41 and 6 92 respectively high quality populations are located in the northern and western parts of the studied area which correlated with usgs standard the logratio matrix was used for the correlation between results obtained by the c v fractal modeling and geological particulars consisting of pyritic veins and ash coals based on the logratio matrix for sulfur values higher than 3 55 and 3 39 for c 1 and b 2 respectively low quality parts of the seams have good correlation with pyritic veins in the eastern and central parts of the area moreover there are high values of overall accuracy oa for correlation between parts of the seams with high values of ash which are 47 86 and 39 81 for c 1 and b 2 respectively and ash coals obtained by geological data