three dimensional architecture of shelf building sediment drifts in the offshore canterbury basin new zealand abstract a grid of high resolution multichannel seismic profiles from the offshore canterbury basin new zealand reveals that at least 11 large up to 1000 m thick 50 km long along strike and 20 km wide down dip elongate sediment drifts developed within the lower miocene to recent shelf slope sediment prism the drifts overlie a condensed section of late eocene to late oligocene limestone and cover an area of 5000 km2 the drifts were deposited in water depths of 300 750 m probably by a northward flowing contour current and aggraded to shelf depths the drifts exhibit mounded morphologies with channel like moats along their landward flanks erosion of the landward flanks creates prominent unconformities these unconformities are diachronous and therefore not sequence boundaries the internal architecture of the drifts defines two end members of elongate drift which we describe as simple and complex early early to middle miocene simple drifts are small 50 km long and up to 20 km wide and occur in the northeastern part of the survey area these late simple elongate drifts are subdivided into three parts base core and crest based on seismic facies these facies form in response to progressive confinement of current flow within the moat complex drifts may be multi crested or multistage multi crested drifts form in response to rapid lateral shifts in position of the moat perhaps associated with relative sea level change modulated by paleoslope inclination and orientation such drifts together with the observation that several drifts were often active simultaneously indicate that flow patterns were complex and involved multiple pathways multistage drifts comprise superimposed subdrifts whose retrogradational and progradational stacking patterns indicate fluctuations in the rate of sediment supply complex drift formation may require intermediate shelf relief high enough to sustain drift development during changes in sea level and rate of sediment supply but low enough so that such changes are still able to influence moat position in addition coeval climatic cooling may amplify changes in sea level current intensity and sediment supply thereby contributing to complex drift formation

lithologic succession in the path fork coal bed breathitt formation middle pennsylvanian southeastern kentucky abstract the path fork coal bed breathitt formation middle pennsylvanian westphalian b on the pine mountain thrust sheet in southeastern kentucky and adjacent portions of virginia exhibits a lithologic succession which is traceable for about 25 km lateral continuity of lithotypes within the bed can be demonstrated using organic petrography palynology and ash geochemistry the lithologic continuity is a consequence of the initial levelling of the pre peat topography and the interaction of the peat with growing anticlines and synclines

three s type volcanic suites from the lachlan fold belt southeast australia the concept that granitoids of the lachlan fold belt in southeast australia are derived from either igneous or sedimentary source rocks i or s type can be extended to volcanic rocks of the same age three suites of late silurian s type volcanics are described two of which can be matched quite closely with plutonic equivalents a large part of the paleozoic continental margin volcanic activity in southeast australia consisted of the magmatic recycling of old metasedimentary crust probably of late proterozoic age the three volcanic suites are moderately to strongly peraluminous with the corresponding presence of al rich minerals variation within the volcanic suites is ascribed chiefly to progressive removal of restite or source material residual from partial melting the most mafic suite the hawkins suite contains plagioclase cordierite orthopyroxene biotite and quartz as restite components with less abundant almandine these rocks are chemically equivalent to mafic biotite rich and cordierite bearing granitoids from parts of the berridale and murrumbidgee batholiths garnet is absent from the goobarragandra suite volcanics which are a little more felsic and close in compositon to granitoids of the young and maragle batholiths the s type character of the laidlaw suite is less pronounced although a sedimentary source seems to be established such a source would be less mature than those for the other two volcanic suites the laidlaw suite resembles but cannot be closely identified with felsic s type granitoids of the murrumbidgee and berridale batholiths low grade regional metamorphism in most of the volcanic rocks has resulted in much mineralogical alteration and mobility of alkali and alkaline earth elements despite this alteration unaltered rocks are present in all three suites compositional data for the phenocryst phases within the unaltered rocks has allowed estimation of some intensive parameters hawkins suite volcanics were extruded directly from their source region and preserve phenocryst equilibria established at 5 6 kbar at 800 c the laidlaw and goobarragandra suites reequilibrated at lower pressures than their source before extrusion the laidlaw suite reequilibrated at estimated temperatures of 725 730 c o2 of 10 15 5 to 10 14 bars and h2o of 2 to 2 5 kbar differing mineral compositions in the three suites are related to differing source rock compositons and oxygen fugacities relative biotite and orthopyroxene mg is possibly pressure dependent

a numerical study of the upwelling circulation off central chile we present a modeling study of the upwelling ocean circulation off central chile 34 40 s using a primitive equation model we make a numerical simulation of the ocean circulation for summer of 1993 a year characterized by moderate but persistent equatorward winds the results indicate the formation of an eastern boundary current system that shows classical ekman and geostrophic dynamics a strong equatorward coastal jet develops during intense upwelling activity induced by the prevailing equatorward winds the spatial and temporal variability of the upwelling favorable winds strongly controls the variability in the oceanic circulation upwelling activity in the coastal areas occurs during periods of growth peak and decay the circulation in the region is divided into two distinct dynamical areas that extend north and south of a prominent cape punta lavapie located in the center of the model domain during the peak upwelling stage the equatorward jet separates from the coast at punta lavapie and remains separated in the northern region this detachment is followed by the formation of cyclonic eddies and decreased upwelling during periods of wind relaxation the northern area is affected by advection processes and weaker local winds in contrast the equatorward flows in the southern region are persistently attached to the coastline and are more coherent with the stronger local winds

chemical differentiation of the bishop tuff and other high silica magmas through crystallization processes re examination of petrochemical data for high silica ash flow tuffs suggests that crystal liquid fractionation plays a major role in the differentiation of high silica magmas for the high silica bishop tuff the enrichment and depletion of 27 major and trace elements correlates with the bulk crystal liquid partition coefficients calculated from the data of hildreth in ways that are consistent with crystal fractionation comparison of the bishop tuff with other high silica tuffs and rhyolites with different compositional variations and different phenocryst assemblages shows the correspondence of chemical gradients with mineralogy crystal zoning studies in the cordillera paine granite in southern chile suggest that the evolution of differentiated liquids similar to those in the bishop tuff results from crystal fractionation the physical mechanisms of separation of liquid and crystals for the paine granite and bishop tuff were quite different however differentiation of the high silica ash flows might result from advection of a less dense liquid from a crystallizing boundary into the top of the magma chamber

control of relative sea level and climate on coal character in the westphalian c atokan four corners formation central appalachian basin u s a abstract peat successions preserved as coal seams preserve high resolution records of ancient terrestrial water table base level fluctuations that are driven by changes in relative sea level and or paleoclimatic change the aim of this study is to establish the roles of relative sea level and climate in controlling water table fluctuations within coal seams from the fluviodeltaic westphalian c bolsovian atokan four corners formation of the central appalachian basin usa comparison of the characteristics of 10 coals in the four corners formation with accommodation trends identified from analysis of intra coal clastic strata indicates that their thickness and vitrinite inertinite ratio correlate readily with the accommodation setting of the depositional sequence in which they occur coals that accumulated in relatively high accommodation fourth order sequences are high in vitrinite thin and overlain by or intercalated with marine and lacustrine sediments the coals have simple internal organization suggesting that they span parts of single high resolution accommodation cycles coals that accumulated in lower accommodation fourth order sequences are high in inertinite thick and overlain by or intercalated with terrestrial sediments the coals have composite internal organizations typified by multiple high resolution accommodation cycles and characteristic abrupt discontinuities of coal facies representing periods of depositional hiatus the correlations between the composition and thickness of the coals and the magnitude of associated marine transgression imply that relative sea level change was the principal control governing bulk accommodation in these mires landward of the paleoshoreline high frequency accommodation cycles within the coals reflect water table fluctuations in the original mires and were driven by high frequency sea level and or climate change the results of this study provide considerable insight into the manner in which coal composition and stratigraphy at a single locality vary over time in response to changing accommodation and provide a means to predict coal seam quality in an established sequence stratigraphic framework

the upper hance coal bed in southeastern kentucky palynologic geochemical and petrographic evidence for environmental succession the upper hance coal bed in bell county eastern kentucky exhibits considerable variation in depositional setting on a mine scale palynology and geochemistry of the coal are examined in order to supplement previous petrographic examinations the various depositional settings of the upper hance mire progress from the pioneer possibly partially allochthonous settings at the mire margins and base to the well developed planar to domed main body of the mire and finally to the terminal events of flooding clastic influx and temporary reestablishment of mires now seen as the thin rider coals palynologic diversity generally decreases upwards from the basal lithotype through the main body of the coal bed the cannel and rider lithologies represent distinct depositional events

palynologic and petrographic intervals in the upper pennsylvanian mcleansboro group western kentucky abstract the mcleansboro group formerly the sturgis formation in the western kentucky coal field spans the upper desmoinesian westphalian d and the missourian and virgilian series stephanian extensive drilling has demonstrated the lateral continuity of major and minor beds in the group making it possible to study vertical and lateral changes in palynology and petrology significant features of the mcleansboro group are the marine zones over most of the coals and paleochannels which are the only disruptions to the continuity of other lithologies the desmoinesian baker no 13 and wheatcroft no 13a coal beds were included in the study but the primary emphasis is on the missourian and virgilian coals patoka formation lower missourian coals are dominated by tree fern spores with lesser amounts of sphenopsids ferns and cordaites spores this is in marked contrast to the arborescent lycopod dominated desmoinesian coals only the no 15 coal bed exceeds 80 vitrinite the vitrinite content of the no 16 coal bed is less than 72 the lowest of any western kentucky humic coal the bond formation upper missourian represents a distinct floristic interval with a greater diversity of plant groups than in the patoka formation herbaceous lycopod spores which are relatively minor contributors to the patoka coals are common in the bond formation the coals generally exceed 80 vitrinite the mattoon formation virgillian coals have a variety of palynomorph assemblages the low sulfur geiger lake coal bed is dominated by tree fern spores with important contributions from other ferns and sphenopsids similar to the underlying tree fern interval vitrinite contents are less than 80 the uppermost mattoon coals are dominated by tree ferns and are notable in being the only coals more than 1 m thick in the stephanian portion of the section with the top coal being 4 3 m thick the uppermost coals generally contain more than 80 vitrinite the permian mauzy formation overlies the mcleansboro group the palynologic petrographic intervals appear to represent fluctuating dry low vitrinite and wet intervals within the stephanian which was itself drier than the westphalian d

petrology and palynology of the middle pennsylvanian leatherwood coal bed eastern kentucky indications for depositional environments abstract the eastern kentucky coal field is located in the central portion of the appalachian basin the pennsylvanian breathitt formation in this region is characterized by numerous sequences of bituminous coal bearing sedimentary rocks these coals have distinct maceral compositions due to variations in depositional environments coal characterization is an important method for determining conditions that influenced peat accumulation and overall depositional settings of mires this study focuses on the characterization of the maceral composition of the middle pennsylvanian age leatherwood coal bed it utilizes petrographical palynological and geochemical analyses to describe specific depositional environments and associated peat accumulation conditions petrographic analyses indicate that these coals have relatively high liptinite and varying inertinite content along with trace amounts of mineral matter vitrinite mainly in the form of collotelinite is the most dominant maceral group geochemical data reveals low ash and sulfur content ancillary palynological data shows the palynomorph assemblage to be dominated by tree fern and large lycopod tree spores with lesser amounts of small lycopod tree small fern and cordaites and calamites spores the petrographic geochemical and palynological data indicate that both domed ombrotrophic and planar rheotrophic mire conditions with limited local detrital influx contributed to the formation of the leatherwood coal

arsenic and lead concentrations in the pond creek and fire clay coal beds eastern kentucky coal field abstract the middle pennsylvanian breathitt formation westphalian b pond creek and fire clay coal beds are the 2 largest producing coal beds in eastern kentucky single channel samples from 22 localities in the pond creek coal bed were obtained from active coal mines in pike and martin countries kentucky and a total of 18 fire clay coal bed channel samples were collected from localities in the central portion of the coal field the overall objective of this study was to investigate the concentration and distribution of potentially hazardous elements in the fire clay and pond creek coal beds with particular emphasis on as and pb 2 elements that are included in the 1990 clean air act amendments as potential air toxics the 2 coals are discussed individually as the depositional histories are distinct the fire clay coal bed having more sites where relatively high s lithologies are encountered in an effort to characterize these coals 40 whole channel samples excluding 1 cm partings were analyzed for major minor and trace elements by x ray fluorescence and proton induced x ray emission spectroscopy previously analyzed samples were added to provide additional geographic coverage and lithotype samples from one site were analyzed in order to provide detail of vertical elemental trends the as and pb levels in the fire clay coal bed tend to be higher than in the pond creek coal bed one whole channel sample of the fire clay coal bed contains 1156 ppm as ash basis with a single lithotype containing 4000 ppm as ash basis most of the as and pb appears to be associated with pyrite which potentially can be removed in beneficiation particularly coarser pyrite disseminated finer pyrite may not be completely removable by cleaning in the examination of pyrite conducted in this study it does not appear that significant concentration of as or pb occurs in the finer pyrite forms the biggest potential problem of as or pb enriched pyrite is therefore one of refuse disposal

the volcanogenetic significance of garnet bearing minor intrusions within the borrowdale volcanic group eskdale area cumbria a number of garnetiferous minor intrusions have been mapped within the borrowdale volcanic group they underlie garnetiferous extrusive volcanic rocks which occur toward the top of a sequence of ignimbrite and lava the airy s bridge formation which is the product of a major caldera forming eruptive episode garnet and whole rock geochemistry indicate that most of the intrusions are indistinguishable from garnetiferous dacite forming the final eruptive unit of the airy s bridge formation a co magmatic link is therefore postulated one of the intrusions which intrudes the airy s bridge formation is distinct and may be related to the later eskdale pluton it is suggested that following the emplacement of ignimbrites forming the basal half of the airy s bridge formation caldera collapse partially sealed a fissure conduit system and degassed garnet bearing magma was intruded as dykes and sills and locally extruded as a post explosive lava dome it is also postulated that garnet crystallized in a high level magma chamber p

origin of the rhyolitic rocks of the taupo volcanic zone new zealand abstract major element rb sr ba cr and v analyses as well as 13 new rare earth element ree analyses are presented for the greywacke basement surrounding the taupo volcanic zone tvz on this basis the basement rocks are divided into a western basement of approximately andesitic composition 62 sio2 and an eastern basement of approximately granodiorite composition 75 sio2 these analyses 5 new ree analyses for the rhyolites and published data for the volcanic rocks of tvz are used to investigate the petrogenesis of rhyolitic rocks in the area least squares mixing calculations for major elements show that 88 fractional crystallisation of high alumina basalt produces a liquid of rhyolitic bulk composition but rayleigh fractionation models show that the trace element concentrations of the rhyolites are inconsistent with basalt fractionation 57 fractionation of the assemblage plagioclase 35 6 orthopyroxene 9 7 clinopyroxene 7 8 ilmenite 0 6 and magnetite 3 4 from a plagioclase pyroxene andesite can produce liquids of rhyolitic bulk composition ree concentrations produced by this model are consistent with those observed in the rhyolites but predicted ba and rb values are lower and v concentrations are higher than those in the rhyolites andesite fractionation also produces an unrealistic fractionation of the cr v ratio a non modal melting model involving 35 melting of a granulitic assemblage plagioclase quartz clinopyroxene orthopyroxene biotite magnetite cordierite with a bulk composition equivalent to the western basement can reproduce the ree pattern of the rhyolites as well as the concentrations of rb and ba sr values remain anomalously high but the cr v ratio does not indicate fractionation absolute values of cr and v are within the uncertainties of published crystal liquid partition coefficients the rhyolites have relatively flat ree patterns la yb 7 5 as do the greywackes la yb 8 2 so it is therefore unlikely that the rhyolites equilibrated with a garnet or amphibole bearing assemblage

paleoecology of the fire clay coal bed in a portion of the eastern kentucky coal field vertically continuous increment samples of the fire clay coal bed mid middle pennsylvanian late westphalian b collected from a portion of the central appalachian basin were studied palynologically petrographically and geochemically in order to partially reconstruct the paleoecology and processes associated with peat formation in the ancient fire clay paleomire results indicate that four compositional groups can be identified they are 1 a lycospora vitrinite dominant group characterized by high percentages of lycospora and vitrinite macerals and generally low but variable ash yields and sulfur contents 2 a mixed palynoflora high vitrinite group that petrographically is similar to group 1 except that it contains a more diverse palynoflora 3 a mixed palynoflora moderate low vitrinite group characterized by various admixtures of lycopsid fern and calamite miospores increased percentages of liptinite and inertinite macerals and low ash yields and sulfur contents and 4 a mixed palynoflora high ash yield group characterized by high percentages of small lycopsid fern and occasionally calamite and cordaite miospores high liptinite and inertinite contents high ash yields and moderate to high sulfur contents the fire clay coal bed contains a distinctive flint clay parting of probable volcanic origin that naturally divides the bed into two benches these two benches upper and lower are highly disparte in occurrence appearance and composition in the study area the lower bench generally is thin 0 5 m laterally discontinuous and mainly composed of dull mainly durain coal lithotypes ash yields typically are high sulfur contents generally are moderate to high compositional group 4 the mixed palynoflora high ash yield group defines all of the increments examined from the lower bench in contrast the upper bench is thick 0 75 m laterally continous and mainly comprised of bright mainly clarain coal lithotypes overall ash yields and sulfur contents for this bench are generally low although vertical variation is apparent all of the compositional groups occur in the upper bench in some columns notably those that are thick and uninterrupted by clastic partings groups 1 and 4 often occupy basal coal layers and groups 2 and 3 occur in higher layers other columns especially those taken in areas of thin 0 5 m fire clay coal are dominated by groups 1 and 4

origin and evolution of a peraluminous silicic ignimbrite suite the violet town volcanics the violet town volcanics are a 373 ma old comagmatic s type volcanic sequence mainly comprising crystal rich intracaldera ignimbrites rock types vary from rhyolites to rhyodacites all containing magmatic cordierite and garnet phenocrysts variation in the suite is primarily due to fractionation of early crystallized quartz plagioclase and biotite plus minor accessory phases in a high level magma chamber prior to eruption early magmatic crystallization occurred at around 4 kb and 850 c with melt water contents between 2 8 and 4 wt this high temperature markedly water undersaturated restite poor granitic magma was generated by partial melting reactions involving biotite breakdown in a dominantly quartzofeldspathic source terrain leaving a granulite facies residue

origin and evolution of mid cretaceous garnet bearing intermediate and silicic volcanics from canterbury new zealand abstract the mt somers volcanics are part of a suite of mid cretaceous 89 2 ma intermediate to silicic volcanics erupted onto an eroded surface of torlesse sediments rock types vary from basaltic andesite to high silica rhyolite andesites are medium to high k with phenocrysts of plagioclase orthopyroxene and pigeonite dacites are peraluminous and commonly contain granulite facies xenoliths and garnet xenocrysts equilibrium mineral assemblages indicate metamorphic pressures of close to 6 kbar at 800 c rhyolites are peraluminous with phenocrysts of quartz sanidine plagioclase biotite garnet and orthopyroxene the ferromagnesian phases show textural evidence of magmatic crystallization and are chemically distinct from xenocryst phases in dacites equilibrium assemblages indicate that early magmatic crystallization occurred at close to 7 kbar 20 km depth at above 850 c with melt water contents of less than 3 5 major element contents trace element contents and an initial 87 sr 86 sr ratio of 0 7085 indicate that the rhyolites formed by partial melting of dominantly quartzo feldspathic torlesse sediments leaving a granulite facies residue the chemical variation displayed by the rhyolites is best explained by fractional crystallization of the observed high pressure phenocryst assemblage most elements show a compositional gap between rhyolite and dacite the major element trace element and sr isotope compositions of the intermediate lavas are best explained by assimilation of lower crustal material combined with fractional crystallization in mantle derived tholeiitic magmas magmatism was the result of heat and magma flux from the mantle during the change from compressive to extensional tectonics after the culmination of the rangitata orogeny

coal rank trends in the central appalachian coalfield virginia west virginia and kentucky abstract coal rank determined from vitrinite maximum reflectance and from chemical rank parameters increases from high volatile c bituminous in portions of the eastern kentucky coalfield to low volatile bituminous in buchanan county virginia and mcdowell county west virginia and then decreases significantly to the dry fork anticline 20 km to the southeast the latter rank decrease as noted when rank data from individual coals is used across the fold 400 500 m structural relief can be accounted for by post tectonic coalification at a paleogeothermal gradient of about 40 45 c km reflectance gradients decrease from about 0 09 rmax 100 m in central buchanan county virginia to 0 06 rmax 100 min southeastern pike county kentucky to 0 03 max 100 m and less among the high volatile a and b coals to the nortwest of pike county the reflectance gradients are likely an indication of a decrease in paleogeothermal gradient to the northwest depth of burial may have also decreased to the northwest northward trending rank anomalies superimposed on the regional trend in kentucky may have been caused by subtle changes in the geothermal gradients associated with basement discontinuities or alternately by a depth of burial not accounted for at present perhaps under now eroded thrust sheets

geochemistry petrology and palynology of the pond creek coal bed northern pike and southern martin counties kentucky abstract the geochemistry petrology and palynology of the duckmantian age pond creek coal bed were investigated in northern pike and southern martin counties eastern kentucky the coal bed exhibits significant vertical variation in the investigated geochemical parameters with many diagenetic overprints of the original geochemistry included in the range of geochemical signatures are the presence of elements particularly tio 2 and zr suggesting the detrital influences at the time of deposition of a low vitrinite durain a high cao zone with elevated b be both suggesting marine influence in a lithotype in the middle of the coal bed and the postdepositional emplacement of pyrite in the uppermost lithotype individual lithotypes each representing distinct depositional environments all complicated to some degree by diagentic overprints comprise the complex history of the coal bed

genesis of lavas of the taupo volcanic zone north island new zealand the taupo volcanic zone forms part of the taupo hikurangi subduction system and comprises five volcanic centres tongariro taupo maroa okataina and rotorua tongariro volcanic centre is formed almost entirely of andesite while the other four centres contain predominantly rhyolitic volcanics and later fissure eruptions of high al basalt estimated total volume of each lava type are as follows 2 km3 of high al basalt 10 000 km3 of rhyolite and ignimbrite 97 4 the location of the andesites and vent alignments suggest a source from a subduction zone underlying the area however the lavas differ chemically from island arc andesites such as those of tonga in particular by having higher contents of the alkali elements light ree and sr and pb isotopes this suggests some crustal contamination and it is considered that this may occur beneath the wide accretionary prism of the subduction system amphibolite of the subduction zone will break down between 80 and 100 km and a partial melt will rise a multi stage process of magma genesis is then likely to occur high al basalts are thought to be derived from partial melting of a garnet free peridotite near the top of the mantle wedge overlying the subduction zone locations of the vents controlled largely by faults within the crust rhyolites and ignimbrites were probably derived from partial melting of mesozoic greywacke and argillite under the taupo volcanic zone initial partial melting may have been due to hydration of the base of the crust the water having come from dehydration of the downgoing slab the partial melts would rise to form granodiorite plutons and final release of the magma to form rhyolites and ignimbrites was allowed because of extension within the taupo graben dacites of the bay of plenty probably resulted from mixing of andesitic magma with small amounts of rhyolitic magma but those on the eastern side of the rotorua taupo area were more likely formed by a higher degree of partial melting of the mesozoic greywacke argillite basement this may be due to intrusion of andesite magma on this side of the taupo volcanic zone

calculated relationships between activity of alumina and phase assemblages of silica saturated igneous rocks petrogenetic implications of magmatic cordierite garnet and aluminosilicate abstract many peraluminous igneous rocks are characterized by the presence of al rich minerals such as cordierite garnet and aluminosilicate polymorphs clearly one of the important thermodynamic intensive variables controlling the stability of these minerals relative to al poor phases such as ortho and clinopyroxene must be the activity of al 2 o 3 a al 2 o 3 in the melt calculated phase relationships of anhydrous mineral assemblages in equilibrium with quartz saturated liquids show that at crustal pressures less than about 10 kbar garnet cordierite and aluminosilicate are only likely to crystallize from melts in which a al 2 o 3 is up to one order of magnitude higher than that required for orthopyroxene clinopyroxene crystallization in spite of this peraluminous granitoid liquids saturated with orthopyroxene garnet or orthopyroxene cordierite do not ordinarily contain significantly larger amounts of excess al al in excess of that required to form feldspars than peraluminous liquids saturated with orthopyroxene clinopyroxene these observations indicate that there must be profound compositional controls on the activity coefficient of al in silicic melts and the strongest of such controls appears to be the total alkali content of the melt the activity coefficient of al in silicic melts varies directly with total alkali oxide content so that alkali poor melts can become markedly peraluminous without ever becoming saturated in aluminous phases whereas alkali rich melts of similar normative corundum content can crystallize garnet cordierite or even aluminosilicate because activity of alumina in a silicic melt is not a simple function of excess al content classification schemes for silicic igneous rocks based on model mineralogical assemblages which reflect the value of the thermodynamic effective concentration of al during crystallization convey more petrologic information than those based on chemical parameters such as normative corundum content or alumina saturation index

water contents of silicic to intermediate magmas silicic to intermediate magmas have water contents that range from 1 wt to around 7 wt depending on the character and depth of the magma source type of melting reaction and the degree of differentiation the condition of water saturation is rare implying that crustal magma genesis generally takes place under fluid absent conditions or that any fluid present must contain volatile species other than h2o the source and quantity of water present during partial melting profoundly affect the types of melting reactions residues and magmas as well as subsequent magma evolution for s type granitic magmas melting reactions involving muscovite breakdown in pelites yield low temperature wet melts that form veins pockets and small plutons in regional metamorphic terranes biotite breakdown in pelites near the amphibolite granulite facies transition yields hotter magmas with variable water contents these are emplaced at medium to high levels under granulite facies conditions biotite breakdown in quartzofeld spathic rocks yields high temperature dry magmas emplaced as subvolcanic batholiths and volcanics

geochemistry of the pond creek coal bed eastern kentucky coalfield the pond creek coal bed middle pennsylvanian breathitt formation is an important low sulfur resource in pike and martin countries in the eastern kentucky coalfield the mined area is crossed by the n20 e trending belfry anticline the pond creek coal bed has a higher sulfur content on the west side of the anticline the vertical trends in the ash geochemistry also vary across the anticline the sites to the east of the anticline represent deposition of peat through periods of relative stability with slow deposition bright lithotypes interspersed with periods of relatively rapid clastic deposition dull lithotypes both generally removed from marine influence comparison of elemental trends between the lowest bright lithotype and the second bright lithotype suggest that the swamp became less acidic with time an upward decrease in minor element concentration may be related to the influx of clays and other silicates present in the bone lithotype this bone may have acted as a relatively low nutrient soil for the growth of the plants which contributed to the overlying bright lithotype the sites to the west of the anticline were subjected to a greater marine influence than the eastern sites high k2o al2o3 ratios at the bottom and top of the coal bed and a high tio2 zr dull clarain near the bottom of the coal point to clastic influences on the geochemistry the relatively high cao percentages in the middle third of the coal bed suggest deposition at near neutral ph the upper third of the coal bed was dominated by syngenetic and epigenetic pyrite emplacement

sea surface flow estimation from advanced very high resolution radiometer and coastal zone color scanner satellite imagery a verification study a refined technique for estimating surface currents from the displacement of features in sequential advanced very high resolution radiometer avhrr and coastal zone color scanner czcs images is presented it is used to calculate flow fields in two regions along the california coast and the results are compared to concurrent drifter drogue observations there is overall agreement to within approximately 6 cm s with somewhat better agreement at velocities less than 40 cm s the poorer performance of the technique at high velocities was due to difficulties in identifying and tracking features in areas of rapid flow the accuracy of the measurements is primarily affected by the analyst s precision in tracking each feature which in turn depends on how well the 2 to 6 km features preserve their identity from one image to the next a 12 to 24 hour interval yielded the best results in this study the directional component of the satellite derived flow field was representative of subsurface flow patterns down to at least 100 m although velocities obtained from avhrr infrared and czcs visible images may not always represent flow at the same depth the measurements were practically identical with the data used

petrology of the pond creek coal bed in eastern kentucky abstract the middle pennsylvanian breathitt formation pond creek coal bed was examined along two cross sections in pike and martin countries in the eastern kentucky coal field along the north south profile the sulfur content increased markedly to the top of the bed in the eastern portion of the east west profile the coal bed is marked by a high vitrinite high ash bone shaley coal lithotype within the top half of the bed and by a thin clarodurite vitrinertoliptite rich durain at the top of the bed a northeastward plunging anticline termed here the belfry anticline marks the boundary between the high sulfur coal beds in the west and the appearance of the bony horizon on the east the coal and the interval between the rider and the coal bed both thin across the anticline which was active at the time of deposition

the distribution of chlorophyll a and dominant planktonic components in the coastal transition zone off concepcion central chile during different oceanographic conditions abstract the oceanographic setting and the planktonic distribution in the coastal transition zone off concepcion 35 38 s 73 77 w an area characterized by its high biological production were assessed during two different seasons austral spring with equatorward upwelling favorable winds and austral winter with predominately northerly winds oceanographic and biological data total chlorophyll a particulate organic carbon microplankton large mesozooplankton 500 m as potential consumers of microplankton were obtained during two cruises october 1998 july 1999 together with satellite imagery for wind stress geostrophic flow surface temperature and chlorophyll a data the physical environment during the spring sampling was typical of the upwelling period in this region with a well defined density front in the shelf break area and high concentrations of surface chlorophyll a 5 mg m 3 on the shelf over the itata terrace during the winter sampling highly variable though weakly upwelling favorable winds were observed along with lower surface chlorophyll a values 100 km from the coast cyclonic and anti cyclonic eddies were evident in the flow field during both periods the former coinciding with higher chlorophyll a contents 1 mg m 3 than in the surrounding waters also a cold chlorophyll a rich filament was well defined during the spring sampling extending from the shelf out to 350 400 km offshore along a cross shelf transect the micro and meso planktonic assemblages displayed higher coastal abundances during the spring cruise but secondary peaks appeared in the oceanic area during the winter cruise coinciding with the distribution of the eddies these results suggest that the mesoscale features in this region in combination with upwelling play a role in potentially increasing the biological productivity of the coastal transition zone off concepcion

petrology and geochemistry of ordovician k bentonites in new york state constraints on the nature of a volcanic arc altered volcanic ashes k bentonites in the late ordovician caradocian utica shale of new york state are the product of explosive arc volcanism most of the 30 k bentonites examined in this investigation contain fragmental crystals and rock fragments microliths up to 600 mu m in diameter that generally are neither detrital contamination from the surrounding black shale nor igneous phenocrysts the dominant phases are garnet two groups gr sub 15 20 alm sub 45 75 py sub 35 0 sp sub 2 5 gr sub 2 5 alm sub 55 85 py sub 10 40 sp sub 1 plagioclase feldspar an sub 80 10 alkali feldspar or sub 99 0 clinopyroxene wo sub 50 40 en sub 50 30 fs sub 0 30 and orthopyroxene wo sub 1 2 en sub 77 32 fs sub 32 66 accompanied by lesser quantities of hornblende aluminosilicate quartz sphene fe ti oxides apatite and zircon most of the fragmental crystals appear to be derived from the same source as the metamorphic microliths which possess minerals with similar compositions both crystals and microliths are interpreted as xenocrysts and xenoliths from the ancient continental crust on which the ordovician arc was constructed they became entrained in the volcanic plume during explosive eruptions a precambrian age acquired on k feldspars from one k bentonite using the sup 40 ar sub 39 ar method shows that these xenocrysts were derived from depths of less than 5 10 km in the microcontinent at the time of late ordovicianmore volcanism the occurrence of xenocrysts and xenoliths in these k bentonites underscores the importance of performing detailed petrology on ash layers prior to the onset of more sophisticated tasks e g isotopic age determinations regional stratigraphic correlations of k bentonites based upon chemical compositions less

pb sr nd isotopes in surficial materials at the pebble porphyry cu au mo deposit southwestern alaska can the mineralizing fingerprint be detected through cover the cretaceous pebble porphyry cu au mo deposit is covered by tundra and glacigenic sediments pb sr nd measurements were done on sediments and soils to establish baseline conditions prior to the onset of mining operations and contribute to the development of exploration methods for concealed base metal deposits of this type pebble rocks have a moderate range for 206pb 204pb 18 574 to 18 874 207pb 204pb 15 484 to 15 526 and 208pb 204pb 38 053 to 38 266 mineralized granodiorite shows a modest spread in 87sr 86sr 0 704354 0 707621 and 143nd 144nd 0 512639 0 512750 age corrected 89 ma values for the granodiorite yield relatively unradiogenic pb e g 207pb 204pb 15 52 low values of 87sr 86sr and positive values of nd 1 00 4 52 that attest to a major contribution of mantle derived source rocks pond sediments and soils have similar pb isotope signatures and 87sr 86sr and 143nd 144nd values that resemble the mineralized granodiorites glacial events have obscured the recognition of isotope signatures of mineralized rocks in the sediments and soils baseline radiogenic isotope compositions prior to the onset of mining operations reflect natural erosion transport and deposition of heterogeneous till sheets that included debris from barren rocks mineralized granodiorite and sulfides from the pebble deposit and other country rocks that pre and postdate the mineralization events isotopic variations suggest that natural weathering of the deposit is generally reflected in these surficial materials the isotope data provide geochemical constraints to glimpse through the extensive cover and together with other geochemical observations provide a vector to concealed mineralized rocks genetically linked with the pebble deposit

evolution of the taupo hikurangi subduction system abstract the present day taupo hikurangi subduction system is a southward extension of the tonga kermadec arc system into a sediment rich continental margin environment it consists of a shallow structural trench the hikurangi trough a 150 km wide imbricate thrust controlled accretionary borderland the continental slope shelf and coastal hills of eastern north island a frontal ridge the main greywacke ranges of north island and a volcanic arc and marginal basin the taupo volcanic zone structural elements become progressively more elevated and subduction more oblique towards the south the whole nne trending system is truncated at a largely strike slip transform boundary that extends along the southwestern part of the hikurangi trough and the hope fault of south island to the main alpine fault the volcanic arc is 200 270 km from the structural trench and comprises a nne trending chain of andesite dacite volcanoes extending along the eastern side of the taupo volcanic zone most of the andesites are olivine bearing and have been erupted within the last 50 000 years it is suggested the taupo hikurangi margin has evolved by rotation of accretionary elements from an original nw trending subduction system north of new zealand the older elements of the prism were associated with subduction of a re entrant of the pacific plate and perhaps the south fiji basin in mid tertiary times they subsequently became separated from their nw trending volcanic arc by dextral strike slip movement along curved faults east of the main greywacke ranges during the plio pleistocene oblique subduction and accretion intensified as the taupo hikurangi margin rotated into line with the nne trending kermadec system and a marginal basin was developed along a similar trend to form the taupo volcanic zone within the last 50 000 years olivine bearing andesite volcanism has commenced along the eastern side of the taupo volcanic zone

mining geology of the pond creek seam pikeville formation middle pennsylvanian in part of the eastern kentucky coal field usa abstract the pond creek seam is one of the leading producers of coal in the eastern kentucky coal field the geologic factors that affect mining were investigated in several underground mines and categorized in terms of coal thickness coal quality and roof control the limits of mining and thick coal are defined by splitting along the margin of the coal body within the coal body local thickness variation occurs because of 1 leader coal benches filling narrow elongated depressions 2 rider coal benches coming near to or merging with the main bench 3 overthrust coal benches being included along paleochannel margins 4 cutouts occurring beneath paleochannels and 5 very hard and unusual rock partings occurring along narrow elongated trends in the study area the coal is mostly mined as a compliance product sulfur contents are less than 1 and ash yields are less than 10 local increases in sulfur occur beneath sandstones and are inferred to represent post depositional migration of fluids through porous sands into the coal run of mine quality is also affected by several mine roof conditions and trends of densely concentrated rock partings which lead to increased in and out of seam dilution and overall ash content of the mined coal roof control is largely a function of a heterolithic facies mosaic of coastal estuarine origin regional fracture trends and unloading stress related to varying mine depth beneath the surface lateral variability of roof facies is the rule in most mines the largest falls occur beneath modern valleys and parallel fractures along paleochannel margins within tidally affected stackrock and beneath rider coals shale spalling kettlebottoms and falls within other more isolated facies also occur many of the lithofacies and falls related to bedding weaknesses within or between lithofacies occur along northeast southwest trends which can be projected in advance of mining fracture related falls occur independently of lithofacies trends along northwest southeast trends especially beneath modern valleys where overburden thickness decreases sharply differentiating roof falls related to these trends can aid in predicting roof quality in advance of mining

s chlorophyll squirts at 30 s off the chilean coast eastern south pacific feature tracking analysis 1 we describe the spatial structure and velocity fields of two seawifs derived chlorophyll squirts in the chilean coast consecutive daily l1a images were rectified and analyzed by means of a geographic information system the velocity fields were obtained through feature tracking analysis subjective method both the hammerhead shape and the spatial structure of the velocity field agree with previous conceptual models we succinctly discuss the biological consequences of squirts for the humboldt current coastal ecosystem

the significance of garnet in the permo carboniferous volcanic rocks of the pyrenees garnet occurs within rhyolitic to dacitic lavas ignimbrites and volcaniclastic sediments of the pyrenean calc alkaline permo carboniferous volcanic rocks on the basis of texture and major and trace element composition the garnet is interpreted as having a phenocrystal as opposed to a xenocrystal or restite origin the pyrenean silicic volcanics are strongly peraluminous consistent with derivation as a partial melt from a sedimentary source they were erupted contemporaneously with the hercynian thermal anomaly which produced regional granulite facies metamorphism and anatectic granites the late hercynian granodiorites were also intruded at about this time geochemical data suggest that the petrogenesis of the volcanic rocks differed from that of the granodiorites ree garnet matrix partition coefficients for garnets from a welded rhyolitic ignimbrite are similar to those reported for other phenocrystal garnets in rhyolites ree abundances imply that the garnets crystallized from a hree depleted melt and this is considered to reflect the effects of garnet in the restite experimental constraints suggest that the garnet crystallized at pressures 4 5kb implying that the rhyolites originated from 14 17km depth and were erupted rapidly from these depths in order for the garnet to survive these figures place constraints on the thermal regime prevailing in the late stages of the hercynian orogeny

tidal front around the hainan island northwest of the south china sea 1 as the coastal fronts being detected by the seawifs derived chl a concentrations and avhrr derived sst images a three dimensional primitive equation numerical model is used to study the physical mechanisms for the formation of fronts around the hainan island northwest of the south china sea several monthly averaged seawifs derived chl a concentrations indicate that higher chl a zones usually exist along the coasts of the zhanjiang peninsula the beibu gulf or the gulf of tonkin and the hainan island obvious surface chl a fronts can thus be seen narrowly adjacent to the higher chl a zones avhrr derived sst images indicate several other fronts that have a large seasonal variation the sst fronts are formed in the beibu gulf and in the northeastern area off the hainan island in winter the numerical modeling of seven major tidal constituents m2 s2 k1 o1 p1 n2 and k2 indicates that two high kinetic energy zones appear in the qiongzhou strait and near the southwestern coast of the hainan island the value of log h u3 where h is depth in meter and u is the depth mean tidal current in m s is calculated to predict the frontal position it is indicated that the locations of contour lines log h u3 2 9 3 0 are in good agreement with the frontal positions detected by the satellite observations therefore these chl a fronts can be considered to be mainly induced by the tidal mixing while the monsoon wind solar radiation and coastal dynamics may play an important role for the seasonal variation of several other fronts

paleobotanical and paleoecological constraints on models of peat formation in the late carboniferous of euramerica abstract the dominant plants of the late carboniferous lowland tropics were taxonomically and structurally distinct from those of any later time periods dominance was distributed among lycopsids ferns sphenopsids pteridosperms and cordaites and each of these groups had distinctive and different ecological preferences and amplitudes peat forming habitats were dominated by lycopsids throughout the westphalian with a significant cordaitean element in the middle westphalian during the stephanian tree ferns were dominant following major extinctions near the westphalian stephanian transition each of the major plant groups had distinctive architectures and tissue composition trees contributed up to 95 of the peat biomass and tree forms of lycopsids psaronius and medullosa lack good modern analogues the cordaites were the only woody plant group to contribute significantly to peat and then only during the mid westphalian structurally wood like lycopsid bark is the major woody tissue encountered in most westphalian coals tree ferns and pteridosperms were largely parenchymatous in construction the stigmarian root systems of lycopsids also were largely parenchymatous the tissue structure of these dominant plant suggests the need for extreme caution in the inference of mire ecological conditions or vegetational structure from coal petrographic data peat formed under arborescent ferns or pteridosperms or peat repeatedly exposed to decay and rerooting by stigmarian root systems of lycopsids would have a distinctly non woody signature and yet would have formed in a forested environment a summary is presented of the autecology and synecology of mire plants emphazing the structural framework provided by lycopsids during the westphalian certain constraints in the links between peat biomass and miospore palynology are discussed in terms of over representation under representation and non representation the formulation of smith s four phase hydroseral model is discussed and compared with more recent data available from plant paleoecology the current debate over an ombrotrophic vs rheotrophic origin of late carboniferous peats relies in large part on paleobotanical data almost entirely palynological in combination with petrographic analyses ecological studies of miospores and of coal ball and compression macrofossils and the linkage of miospores to source plants permit the re evaluation of mire successional models evidence for tree lycopsids sphenopsids pteridosperms and cordaites suggests growth mainly in rheotrophic mires tree ferns are likely candidates for growth in domed mires although evidence is ambiguous and some tree ferns clearly grew under rheotrophic conditions densospores produced by at least sporangiostrobus lycopsid subtrees have been considered diagnostic of ombrotrophic conditions abundant evidence refutes this simplistic interpretation and suggests broad ecological amplitudes for densospore producers including growth under rheotrophic conditions although plant fossils alone can not resolve most of the major debates in modern coal geology paleobotany does contribute significantly to our understanding of ancient mires an approach combining paleobotanical data with petrography sedimentology and geochemistry on a case by case basis is most likely to produce a clear picture

chlorophyll variability in eastern boundary currents the first three years of seawifs data 199 2000 provide the most complete quantification to date of chlorophyll seasonal variability along the full latitudinal ex tent of the four major eastern boundary currents ebcs comparisons to previously published chlorophyll seasonal climatologies deduced from the relatively sparse coverage provided by the coastal zone color scanner czcs show significant differences in both southern hemisphere ebcs while northern hemisphere regions are qualitatively simi lar comparisons between chlorophyll and cross shelf ek man transport seasonal cycles calculated from coincident satellite scatterometer data show seasonal maxima have similar phases over most of the california current at higher 32os latitudes in the peru chile and benguela currents 30os and at lowest latitudes 20on in the canary current latitudinal zones within which phases diverge are indicative of alternate and or more distant forcing

relaxation from upwelling in the coastal ocean dynamics experiment a relaxation of the upwelling system on the northern california shelf occurs when upwelling favorable winds decay or reverse observations from the coastal ocean dynamics experiment are used to investigate this process with emphasis on the near surface temperature evolution models of relaxation warming are tested for the surface layer 0 30 m over midshelf with the result that the surface heat flux and poleward alongshelf advection can account for the observed temperature behavior onshore advection of the upwelled isopycnal field is a relatively unimportant contribution the warming patterns that are observed and which provide the gradients for the advective process have wedgelike shapes warmest inshore and in the south of the experimental area these patterns appear to be related to a topographic influence of point reyes possibly through the generation of gradients in the wind field remote advection of warm water from as far south as san francisco occasionally occurs as well the nature of the relaxation mechanism has general implications a new warm saline nutrient rich water mass may be formed in the surface layer since the warming processes are not the reverse of the cooling an important asymmetry is present it causes time variable upwelling to generate conditions very different from steady upwelling a new upwelling front is created during each event with upwelled water seaward of it and reversed alongshelf flow contributes to the warming and exchange mechanisms the system cannot be described or understood without the irreversible processes during upwelling and relaxation or without a mixed layer

geochemistry of the blue gem coal bed knox county kentucky abstract the blue gem coal bed middle pennsylvanian westphalian b breathitt formation has low ash with some sample sites having less than 1 ash and low sulfur contents through parts of knox county kentucky most collection sites exhibit similar vertical elemental trends in ash geochemistry the relatively high ash 1 ash lower part of the bed displays enrichment in tio2 zr cr v and ni co zn rb and mn show enrichment at some sites a low ash 1 ash and a relative enrichment in sio2 k2o and rb and a relative decrease in cu ni co ba and mn when compared to the middle part of the bed principal components analysis indicates that the samples with an ash content 0 63 1 0 show associations for ni cu cr and co samples with between 1 01 2 0 ash display strong element associations that suggest increased clastic sediment contributions tio2 zr k2o rb sio2 the low ash content and the upwards decrease in trace concentrations both suggest that the blue gem peat swamp was ombrotrophic through at least a part of its geologic history

petrogenesis of the 2 1 ga lushan garnet bearing quartz monzonite on the southern margin of the north china craton and its tectonic implications abstract the lushan garnet bearing quartz monzonite was emplaced into the western taihua complex at 2134 17 ma on the southern margin of the north china craton ncc the rocks contain sio 2 contents of 56 98 59 05 wt with high k 2 o na 2 o 7 46 9 14 wt and al 2 o 3 15 87 17 58 wt and low cao 2 38 2 77 wt and mgo 1 18 1 50 wt contents and belong to an intermediate shoshonitic series magmatic garnet grains in the rocks are chemically homogeneous with relatively high cao 6 36 7 92 wt but low mno 1 45 1 94 wt and mgo 2 47 3 45 wt contents and high fe mn ratios they contain 61 94 66 39 mol almandine 18 60 23 40 mol grossular 10 06 15 11 mol pyrope and 1 09 4 32 mol spessartine similar to high pressure garnets formed from m type magma but different from those found in s type granites and metapelites phase equilibrium diagrams in combination with trace element distribution coefficients between zircon and garnet suggest whole rock zircon saturation temperatures varying from 891 c to 951 c and the mineral assemblage of garnet plagioclase amphibole or biotite in these rocks is stable at 15 kbar and 890 950 c with h 2 o t 800 c all of the rocks are enriched in lile and lree with low nb la ratios 0 24 0 61 similar to those of lithospheric mantle which has a nb la ratio of 0 5 therefore the garnet and whole rock chemical compositions indicate that the lushan quartz monzonite possibly formed by small degrees of partial melting of a phlogopite bearing lithospheric mantle the variable zircon hf t values 3 5 to 4 1 with t dm c from 2 34 ga to 2 51 ga suggest involvement of crustal materials the rocks have slightly negative nb and ta anomalies characteristics of island arc basalts iab however their high zr 598 926 ppm and zr y ratios 17 1 21 8 suggest an affinity with ocean island basalt oib hence the mixed iab and oib like geochemical signatures are indicative of continental intra plate rifting possibly related to extension and thinning of the lithosphere and upwelling of asthenosphere our study proposes that an intra continental rifting event occurred at 2 2 2 0 ga on the southern margin of the ncc after the final amalgamation of ncc

do upwelling filaments result in predictable biological distributions in coastal upwelling ecosystems abstract we used satellite sea surface temperature sst images and in situ zooplankton data collected in four summers of field sampling in the northern california current to address the question can the physical variables that indicate advective mesoscale circulation features e g upwelling filaments be used to infer biological distributions transects were selected from research cruises conducted when upwelling filaments were present in our study region and compared to transects occupied when filaments were not present the hydrography and distribution of several indicator species of copepods were examined along each transect sst in filaments ranged from 1 5 c to 3 0 c lower than the surrounding ocean water distributions of coastal and oceanic taxa reflected the sst patterns coastal taxa occurred offshore in higher abundances in cold upwelling filaments than in the surrounding warm ocean water in contrast species with oceanic and sub tropical affinities were most abundant where warm surface water was present biomass and species abundances varied substantially among cruises and locations and so could not be quantitatively predicted by sst patterns however upwelling filaments consistently expanded the across shelf region in which high zooplankton biomass occurred spreading the biomass from the continental shelf into offshore regions of the upwelling system we conclude with a discussion of the sampling strategies necessary to capture ecosystem variability caused by these dynamic circulation features

importance of melt fraction and source rock composition in crustal genesis the example of two granitic suites of northern portugal in the montalegre area northern portugal two varieties of syn to late tectonic hercynian aluminous granitoids are distinguished 1 1 muscovite rich two mica granites forming many successively emplaced bodies with little chemical variation the chemical characteristics of these units suggest partial melting of various crustal rocks under distinct p t and water saturation conditions there has been no homogenization between the different melt batches the rocks contain very few restitic minerals segregation processes may have operated either in the source rock or in an early magmatic stage 2 2 a cordierite biotite and muscovite bearing granitic body its mineralogical composition is extremely heterogeneous and it contains many xenoliths the genesis of this granite results essentially from partial melting of peraluminous orthogneisses the melt fraction was higher than the rheological critical melt percentage rcmp during anatexis the rigid framework of the source rock broke down leading to migration of both melt and residual minerals towards upper crustal levels the heterogeneity of the resulting granite is mostly related to an incomplete separation of residual crystals and melt the existence of biotite and cordierite rich samples is the result of accumulation of residual minerals during the magma emplacement this study emphasizes the role of the source rock composition which controls the degree of partial melting at given p t and water saturation conditions during crustal melting the strong geochemical differences between the two kinds of granitoids are related to the near absence of residual minerals in the muscovite rich granites and to the presence of residual minerals in the cordierite bearing granite it is suggested that the muscovite rich granites are mostly low melt fraction rcmp the presence of many residual crystals alkali feldspars and plagioclases as well as dark minerals in the cordierite granite implies a high viscosity of the melts and therefore water undersaturated melting conditions

diffusion creep and partial melting in high temperature mylonitic gneisses hope valley shear zone new england appalachians usa field petrographic microstructural and isotopic studies of mylonitic gneisses and associated pegmatites along the hope valley shear zone in southern rhode island indicate that late palaeozoic deformation c 275 ma in this zone occurred at very high temperatures 650 c high energy cuspate lobate phase boundary microstructures a predominance of equant to sub equant grains with low internal lattice strain and mixed phase distributions indicate that diffusion creep was an important and possibly predominant deformation mechanism field and petrographic evidence are consistent with the presence of an intergranular melt phase during deformation some of which collected into syntectonic pegmatites rb sr isotopic analyses of tightly sampled pegmatites and wall rocks confirm that the pegmatites were derived as partial melts of the immediately adjacent isotopically heterogeneous mylonitic gneisses the presence of syntectonic interstitial melts is inferred to have permitted a switch from dislocation creep to melt enhanced diffusion creep as the dominant mechanism in these relatively coarse grained mylonitic gneisses 200 500 lm syn deformational grain size a switch to diffusion creep would lead to significant weakening and may explain why the hope valley shear zone evolved into a major regional tectonic boundary this work identifies conditions under which diffusion creep operates in naturally deformed granitic rocks and illuminates the deformation processes involved in the development of a tectonic boundary between two distinct late proterozoic avalonian basement terranes

coal facies studies in the eastern united states coals in the eastern united states east of the mississippi river have been the subject of a number of coal facies studies going back to the 19th century such studies would not necessarily fall within a strict modern classification of coal facies studies but if a study encompassed some aspects of paleobotany palynology petrology geochemistry or sedimentology we assumed that some data and interpretations may be of use in evaluations of the facies references are presented as a guide for further research with annotation in the tables

geochemistry of granitic melts produced during the incongruent melting of muscovite implications for the extraction of himalayan leucogranite magmas granites formed from the incongruent melting of muscovite preserve evidence of chemical disequilibrium both between restite and melt and within individual phases during crystallization miocene leucogranites from the himalayas exemplify melt formation from a pelitic source through muscovite breakdown trace elements rb sr and ba reside almost entirely in micas and feldspars in the protolith and therefore are appropriate for quantitative modeling equilibrium between melt and restite was established for sr under fluid phase absent conditions but some disequilibrium is suggested by rb abundances consistent with known diffusion rates for these elements abundances of zr and ce in the granites which provide essential structural constituents of the accessory phases zircon and monazite indicate that the himalayan granite melts were saturated in these elements if formed at temperatures of 670 700 c but slightly undersaturated if formed at somewhat higher temperatures ion microprobe traverses of y and heavy rare earth element abundances across single garnets from himalayan leucogranites provide evidence for disequilibrium between melt and phenocryst during garnet growth thus constraining the evolution of magmatic compositions during melt formation and crystallization in some cases progressive melting of the protolith and crystallization of garnet from the melt appear to have been concomitant indicating that minimum solidus temperatures were maintained throughout the melting event this suggests that thermal buffering rather than melt extraction provided the rate determining step in magma evolution

crust and mantle contributions to granite genesis an example from the variscan batholith of corsica france studied by trace element and ndsro isotope systematics the corsican batholith formed during the variscan orogeny was studied with particular emphasis on the respective roles played by crustal and mantle derived material in granite genesis major and trace element data identify the various types of magma and their genetic relationships the magmatic processes that gave rise to the observed rocks and the primitive liquids o sr nd isotope systematics constrain the origin of primitive liquids trace element models provide data on the various source materials and their possible geodynamic setting the evolution of two main calc alkaline plutonic associations is compared an older high mg k association u1 with both ultrapotassic mafic and silicic rocks the latter ranging from monzonite to leucosyenogranite and a younger calc alkaline composite association u2 involving a mafic cumulate sequence and granodiorite to leucomonzo granite both types of granite are accompanied by mafic units that were non cogenetic with surrounding granitic melts trace element calculations indicate that a primitive liquid of monzodioritic composition gave rise to the u1 mg k granite by fractional crystallization amphibole and titanite playing a major role which with increasing crystallization gave decreasing ree contents without a strong negative eu anomaly the u2 calc alkaline suite was formed by fractional crystallization involving feldspar and lree rich minerals i e monazite from a liquid of monzogranitic composition field and petrographical data identify magma mingling in both u1 and u2 between mafic and silicic rocks but geochemical data only indicate how magma mixing processes led to u2 granodiorite geochemical modelling shows that a single protolith of calculated graywacke composition yielded the two associations under different melting conditions the high mg k monzodiorite melt was formed after partial melting of a 30 non modal batch of granulite facies metamorphic protolith low ph2o but the calc alkaline monzogranite was formed by the same process in an amphibolite facies source of similar composition higher ph2o the primitive granite magmas of both associations show the same crustal characteristics i e sri 0 706 0 707 nd t 4 3 to 2 2 and 18o 7 to 8 this provides evidence that composition of both u1 and u2 granite melts probably was controlled by physico chemical fusion rather than protolith composition parameters the u1 ultrapotassic mafic rock is thought to be of mantle origin i e a deep source containing phlogopite garnet zone refining led to a significant increase of incompatible trace element contents during ascent of the magma mantle crust interaction lowered the la yb and 143nd144nd ratios but the 87sr86sr ratio increased nevertheless interaction with associated u1 mg k granite was not important and the crustal component is thought to be different from the associated granitic magma in u2 the mafic cumulate sequence clearly of mantle origin has e morb characteristics and seems the result of 10 non modal partial melting of a heterogeneous mantle of spinel or amphibole peridotite without garnet some interaction occurred with the associated granitic melt the e morb character of the mafic rock indicates that a large part of the batholith and at least the u2 magmatic association was generated under post collisional extensional conditions

distribution of partial melt in a felsic system the importance of surface energy the texture distribution and infiltration tendency of a quartz albite melt in equilibrium with a synthetic texturally equilibrated quartzite was examined in a series of distribution and infiltration experiments at 1 250 c and 8 kbar hydrostatic pressure wetting angle measurements from melt distribution experiments show a dihedral angle of 60 degrees implying a quartz quartz interfacial energy approximately 1 7 times the quartz melt value because of this specific relationship between interfacial energies the system can achieve its lowest surface free energy state with the melt either in pools or along grain edge intersections possibly forming some interconnected channels stability of melt in pockets and along grain edge intersections was observed in a fourteen day dispersed melt experiment yet melt pools failed to disperse into the quartzite during infiltration experiments comparison of the observed dihedral angle with previously measured surface energy values for the melt and quartz shows excellent agreement and also demonstrates that an aggregate of randomly orientated anisotropic grains acts approximately isotropically

almandine garnet phenocrysts in a 1 ga rhyolitic tuff from central india we report on the newly discovered almandine garnet phenocrysts in rhyolitic ignimbrites sukhda tuff in the precambrian churtela shale formation of the chhattisgarh supergroup in central india shrimp ages of igneous zircon from the ignimbrites range from 990 ma to 1020 ma these ignimbrites exhibit characteristic eutaxitic texture with compacted curvilinear glass shards with triple junctions quartz commonly embayed bluish cathodoluminescence and albite altered but retaining ghosts of twinning are common phenocrysts others are apatite ilmenite rutile magnetite zircon monazite and garnet there are no metamorphic or granitic xenoliths in the ignimbrites garnet grains occur as isolated broken isotropic crystals with sharp or corroded boundaries in a very fine grained groundmass of volcanic ash that consists principally of albite quartz magnetite and glass they do not have any systematically distributed inclusions a few have penetratively intergrown phenocrysts of apatite ilmenite rutile and zircon which we interpret as subophitic texture extensive sem bse imaging of more than 100 grains and electron microprobe traverses across about 30 grains showed no zoning or systematic compositional variability common metamorphic garnets are usually zoned with respect to fe mg mn and typically have mineral inclusions we infer therefore that these observed garnets are not metamorphic xenocrysts the average major oxide composition of analysed garnets from five different horizons within the sukhda tuff spanning approximately 300 m of the stratigraphic section have very small standard deviation for each element which is suggestive of a single magmatic source phenocrysts of quartz including those in contact with coexisting garnets show blue scanning electron cl indicating rapid cooling from high temperature this suggests that adjacent coexisting garnets are not slowly cooled restites we conclude on the basis of texture mineral chemistry and absence of any indicative xenoliths or xenocrysts that these almandine garnets al 78 7 py 12 3 gr 7 4 sp 1 6 are phenocrysts within the sukhda tuff almandine of such composition is stable under high pressure we infer that almandine crystallized at lower crustal depths in a magma that ascended very rapidly and may have erupted explosively

metalliferous coals of the westphalian a joggins formation cumberland basin nova scotia canada petrology geochemistry and palynology abstract five coals of westphalian a early middle pennsylvanian age were sampled from the joggins formation section exposed along chignecto bay at joggins nova scotia coal beds along the bay were mined beginning in the early 17th century yet there have been few detailed published investigation of the coal beds of this classic section the lowermost coal the upper coal 28 upper fundy is a high vitrinite coal with a spore assemblage dominated by arboreous lycopsid spores with tree ferns subdominant the upper portions of the coal bed have the highest ratio of well preserved to poorly preserved telinite of any of the coals investigated coal 19 clam coal has 88 total vitrinite but unlike the fundy coal bed the telinite has a poor preservation ratio and half the total vitrinite population comprises gelocollinite and vitrodetrinite the latter coal bed is directly overlain by a basin wide limestone bed the lower kimberly coal shows good preservation of vitrinite with relatively abundant telinite among the total vitrinite the middle kimberly coal which underlies the tetrapod bearing lycopsid trees found by lyell and dawson in 1852 exhibits an upward decrease in arboreous lycopod spores and an upward increase in the tree fern spore punctatisporites minutus telinite preservation increases upwards in the middle kimberly but overall is well below the preservation ratio of the upper fundy coal bed the coals all have high sulfur contents yielding up to 13 7 total sulfur for the lower lithotype of the upper fundy coal bed the kimberly coals are not only high in total and pyritic sulfur but also have high concentrations of chalcophile elements zinc ranging up to 15 000 ppm ash basis is present as sphalerite in fusain lumens arsenic and lead each exceed 6000 ppm ash basis in separate lithotypes of the kimberly coals together these data are consistent with elevated ph in planar mires the source of the elemental enrichment in this presumed continental section is enigmatic

whole coal versus ash basis in coal geochemistry a mathematical approach to consistent interpretations abstract several standard methods require coal to be ashed prior to geochemical analysis researchers however are commonly interested in the compositional nature of the whole coal not its ash coal geochemical data for any given sample can therefore be reported in the ash basis on which it is analyzed or the whole coal basis to which the ash basis data are back calculated basic univariate mean variance distribution etc and bivariate correlation coefficients etc measures of the same suite of samples can be very different depending which reporting basis the researcher uses these differences are not real but an artifact resulting from the compositional nature of most geochemical data the technical term for this artifact is subcompositional incoherence since compositional data are forced to a constant sum such as 100 or 1 000 000 ppm they possess curvilinear properties which make the euclidean principles on which most statistical tests rely inappropriate leading to erroneous results applying the isometric logratio ilr transformation to compositional data allows them to be represented in euclidean space and evaluated using traditional tests without fear of producing mathematically inconsistent results when applied to coal geochemical data the issues related to differences between the two reporting bases are resolved as demonstrated in this paper using major oxide and trace metal data from the pennsylvanian age pond creek coal of eastern kentucky usa following ilr transformation univariate statistics such as mean and variance still differ between the ash basis and whole coal basis but in predictable and calculated manners further the stability between two different components a bivariate measure is identical regardless of the reporting basis the application of ilr transformations addresses both the erroneous results of euclidean based measurements on compositional data as well as the inconsistencies observed on coal geochemical data reported on different bases

comparison of velocity estimates from advanced very high resolution radiometer in the coastal transition zone two methods of estimating surface velocity vectors from advanced very high resolution radiometer avhrr data were applied to the same set of images and the results were compared with in situ and altimeter measurements the first method used an automated feature tracking algorithm and the second method used an inversion of the heat equation the 11 images were from 3 days in july 1988 during the coastal transition zone field program and the in situ data included acoustic doppler current profiler adcp vectors and velocities from near surface drifters the two methods were comparable in their degree of agreement with the in situ data yielding velocity magnitudes that were 30 50 less than drifter and adcp velocities measured at 15 20 m depth with rms directional differences of about 60 these differences compared favorably with a baseline difference estimate between adcp vectors interpolated to drifter locations within a well sampled region high correlations between the avhrr estimates and the coincident geosat geostrophic velocity profiles suggested that the avhrr methods adequately resolved the important flow features the flow field was determined to consist primarily of a meandering southward flowing current interacting with several eddies including a strong anticyclonic eddy to the north of the jet incorporation of sparse altimeter data into the avhrr estimates gave a modest improvement in comparisons with in situ data

subsurface andesite lavas and plutonic rocks in the rotokawa and ngatamariki geothermal systems taupo volcanic zone new zealand abstract deep 2 km drillholes into the rotokawa and ngatamariki geothermal systems taupo volcanic zone tvz new zealand penetrate a sequence of silicic volcanic rocks and andesite lavas the latter being locally more than 1100 m thick one drillhole at ngatamariki bottoms in diorite 2200 m the first plutonic rocks reached by any well drilled into the taupo volcanic zone the rotokawa andesite lavas which occur below 1400 m depth are older than 330 ka and locally rest upon mesozoic metasedimentary basement rocks of the torlesse terrane they are typically dense jointed and where fresh contain phenocrysts of andesine labradorite augite hypersthene titanomagnetite and in places hornblende geochemically these rocks are medium k calc alkaline orogenic andesites their major and trace element contents and sr isotopic ratios show them to be chemically coherent with little lateral or vertical variation hydrothermal alteration has typically added volatiles but has been largely isochemical on a hand specimen scale mineralogical geochemical and stratigraphic evidence indicates that the rotokawa andesites are not genetically or temporally related to andesite lavas exposed at rolles peak 5 km east of rotokawa nor to andesite or diorite penetrated at ngatamariki but they have closer chemical affinities with the plagioclase pyroxene phyric lavas of the tongariro volcanic centre at the south end of the tvz the ngatamariki andesites have distinctive trace element compositions particularly ti and zr and are chemically and petrographically different from most other tvz lavas the occurrence of thick subsurface andesite sequences in the rotokawa ngatamariki area suggests that early eruptives here were of intermediate composition rather than the more silicic volcanics now so widespread both at the surface and in the shallow levels of several nearby geothermal systems

palynologic and petrographic variation in the pond creek coal bed pike county kentucky abstract recent studies of the petrology and ash geochemistry of the pond creek coal bed middle pennsylvanian breathitt formation in pike and martin countries kentucky have defined vertical and lateral trends that are related to the development of the northeast trending belfry anticline contemporaneous with the deposition of the pond creek peat to the northwest of the anticline the coal bed has a high caco3 middle zone and a high fe2o3 high sulfur upper zone to the east of the anticline particularly in the lick creek and jamboree 7 1 2 quadrangles the coal bed exhibits a distinctive petrographic zonation in the latter area the usual megascopic sequence is a basal durain followed by a bright clarain durain dull the palynology of the pond creek coal bed was investigated in six sets of bench lithotype samples from the lick creek and jamboree 7 1 2 quadrangles the low vitrinite basal durain zone 1 has a palynomorph assemblage which reflects the importance of tree ferns and herbaceous lycopods the easternmost site has a bright clarain below the durain the latter lithotype has a fair diversity of palynormph groups and also has the highest percentage of arborescent lycopod forms of any bench below the bone zone 5 the bright zone 2 above the durain has the greatest maceral group range and the greatest floral diversity of any of the lithotypes the zone 3 dull lithotype has increased amounts of herbaceous lycopods and decreased amounts of arborescent lycopods sphenopsids and tree ferns the zone 4 bright lithotypes are generally over 80 vitrinite and in general exhibit a dominance of arborescent lycopods although sphenopsid tree fern and small fern forms exhibit varying importance the high ash bone zone 5 has 71 6 77 0 vitrinite this lithotype is marked by a dominance of herbaceous lycopods at the expense of arborescent lycopods and sphenopsids the zone 6 bright clarian is marked by an increase in arborescent lycopods and a large decrease in herbaceous lycopods the low vitrinite terminal durain has an assemblage with high percentages of herbaceous lycopods and low percentages of arborescent lycopods as well as increase in tree fern spores over zone 6 in general the petrology and palynology trends are predictable dull lithotypes have abundant herbaceous lycopod representation and bright lithotypes have abundant arborescent lycopod representation the greatest deviation from this simple pattern is within the zone 4 bright lithotypes where diverse palynomorph assemblages occur among the high vitrinite benches overall the greatest floral diversity appears to have occurred near the base of the coal bed

multiple bench architecture and interpretations of original mire phases examples from the middle pennsylvanian of the central appalachian basin usa abstract coal seams often exhibit lateral and vertical variability in composition when sampled as a whole seam this variability is masked but if a seam is subdivided into correlateable components this variability can be tested and better understood herein an architectural approach is used to divide seams into intra seam components clastic splits and mineral partings as well as persistent fusain and durain layers can be used as intra seam bounding units to subdivide a seam into subdivisions called benches regional examination of lower and middle pennsylvanian age coal seams shows that many contain laterally persistent bounding surfaces that can be used to define multiple benches of coal within each seam inter bench analyses from some of the most extensively mined seams in the central appalachian basin show that individual benches often have different spatial and quality trends hence some component of whole seam variability is a function of changes in the relative contribution of these different benches to the seam as a whole many coal benches also exhibit intra bench variation in coal parameters intra bench variation can be analyzed in terms of parameters such as sulfur content and ash yield in order to address changes in coal quality for regional resource evaluation intra bench variation can also be analyzed in terms of a combination of palynologic petrographic and geochemical parameters termed compositional groups in order to better understand the development of the original mire systems compositional groups are defined by ranges of multiple criteria which are inferred to owe their origin to the mire type in which they formed vertical changes in compositional groups within coal benches can be used to infer paleo edaphic conditions during peat accumulation if seam thickness is a product of bench configuration and trends in compositional groups occur in benches then trends in quality can be marginally predicted based upon seam thickness and inferred bench architecture additionally changes in inter bench and intra bench thickness and compositional profiles can be used to infer original depositional controls such as paleotopography syndepositional structural movement and syndepositional clastic influx for more accurate reserve estimates

the origin of garnets in andesitic rocks from the northland arc new zealand and their implication for sub arc processes an unusual andesitic suite from the miocene volcanic arc in northland new zealand comprises pyroxene andesite and garnetbearing hornblende pyroxene hornblende and biotite hornblende andesites garnet crystals occur as 1 10 mm single crystals or more commonly as two or more annealed crystals and as garnetite lenses the andesitic rocks also contain enclaves of high mgo pyroxenite hornblendite and pyroxene hornblende gabbro as well as highal2o3 hornblende gabbro garnet hornblende gabbro and anorthosite garnet crystals in the andesitic volcanic rocks and in the enclaves show comparable compositional ranges zoning patterns and inclusions which indicate that they share a common petrogenetic history they can be grouped into four distinct types on the basis of mode of occurrence chemical composition and zoning patterns which leads to their interpretation as antecrysts rather than orthocrysts the compositions of the garnets as well as their included mineral assemblages reflect a petrogenetic trend from high temperature pyroxene bearing high mg garnet to low temperature fe rich garnet at relatively constant pressure well preserved zoning patterns in particular those of the caand mg rich garnets reflect processes within a deep crustal arc environment later assimilation is suggested by some zoning patterns that show decreasing ca and increasing fe and mn contents the garnets are interpreted as being derived by disintegration of discrete but closely related cumulate material that formed at pressures of 8 10 kbar the host volcanic rocks and their garnet crystals together with the enclaves thus represent a consanguineous mixture of liquid and solid components that developed where subduction related magmas ponded and interacted at or near the base of the crust together they represent a rare snapshot of the processes and components that produce arc type rocks

the origin of pyrenean hercynian volcanic rocks france spain ree and smnd isotope constraints reply abstract the hercynian orogeny of the pyrenees generated a suite of basalt to rhyolite calc alkaline volcanic rocks that were erupted subaerially these melts may either have been generated above a subduction zone or by lower crustal melting after input of mantle derived magmas in an extensional environment sm nd garnet whole rock mineral isochrons date a rhyolitic ignimbrite from the coll de oli ignimbrite member at 313 14 ma 2 mswd 0 7 and a rhyolitic lava of the coll de pi region at 320 2 ma 2 mswd 0 2 these ages suggest that some of the volcanism was synchronous with high temperature low pressure metamorphism and partial melting deep in the hercynian crust as seen in rocks now exposed in the axial and northern pyrenean zones and dated by u pb on zircon at between 309 5 and 315 5 ma the silicic volcanic rocks are peraluminous and have highly fractionated ree patterns with low abundances of the hree and la yb n 70 mineral and whole rock ree abundances suggest derivation of the silicic rocks by partial melting of a metasedimentary source in equilibrium with garnet and or garnet fractionation in melts derived from peraluminous sources nd isotope compositions of the entire volcanic rock suite mafic silicic compositions are within the same range as those of sediments metamorphosed during the hercynian orogeny and hercynian basement rocks they have mid proterozoic depleted mantle model sm nd ages and do not exhibit mixing trends with mantle sources even the most mafic of the volcanic rocks appear to have interacted extensively with the crust analysis of the chemistry of the volcanic rocks does not unequivocally constrain the hercynian tectonic setting of the pyrenees

exhumed conduit records magma ascent and drain back during a strombolian eruption at tongariro volcano new zealand field evidence from a basaltic andesite dyke preserved in the eroded wall of a scoria cone at red crater tongariro volcano new zealand records a history of up conduit magma flow during a strombolian eruption subsequent drain back and final cessation of flow the dyke intrudes pre strombolian andesite lavas and the overlying proximal basaltic andesite scoria deposits associated with contemporaneous lavas which are in turn overlain by laminated lapilli tuff and large blocks textural and kinematic evidence of ductile shear recorded in basaltic andesite at the dyke margins records magma deformation imposed by bypassing movement of magma up the centre of the conduit during the eruption whereas the basaltic andesite occupying the central part of the lowermost exposures of the dyke preserves ductile flow folds with the opposite down flow shear sense the evidence indicates that the downward magma flow followed the eruption and this draining left the central part of the dyke empty unfilled at uppermost levels we discuss the kinematic constraints in the context of the criteria for up flow of mafic magma and present the factors most likely to result in a final drain back event with reference to experimental and numerical work we propose a draining model for the end of this eruption and that magmatic drain back may feature commonly during closing stages of strombolian eruptions at mafic volcanoes drain back which leaves large cavities in a volcanic edifice could result in hazardous structural instabilities

rb depletion in biotites and whole rocks across an amphibolite to granulite facies transition zone tamil nadu south india abstract relatively low concentrations of rb and high k rb ratios are characteristic of many granulite facies terranes this depletion in rb has been attributed to both the removal of a partial melt and exchange with a metamorphic fluid phase these models have been tested using rb concentrations in biotites and whole rocks from intermediate and felsic gneisses collected along a traverse from just north of krishnagiri to just north of salem in tamil nadu state south india along this traverse the northern amphibolite facies zone gives way to a clinopyroxene zone in which clinopyroxene appears in intermediate and felsic gneisses further south is the lowland charnockite zone characterised by the presence of orthopyroxene and the scarcity of clinopyroxene in intermediate to felsic gneisses the abundance of orthopyroxene increases southwards and it is the dominant ferromagnesium silicate in the highland charnockite zone there is a good correlation between rb in biotite and whole rock rb in samples collected throughout the traverse intermediate and felsic gneisses in the northern portion of this traverse have relatively high modal abundances of biotite low ti concentrations in the biotites high whole rock rb concentrations low k rb ratios and high rb concentrations within the biotites ti concentrations in the biotites increase southward into the clinopyroxene zone and then remain relatively constant high k rb ratios first appear at the southern boundary of the clinopyroxene zone in the lowland and highland charnockite zones the majority of the rocks have relatively low rb concentrations and high k rb ratios low rb concentrations in biotites at or near the detection limit of 65 ppm first appear in the lowland charnockite zone and persist into the highland charnockite zone a smaller group of rocks in the highland charnockite zone contain biotites with moderate rb concentrations most of these rocks also contain anomalously high biotite concentrations and low k rb ratios it is not possible to produce rb depleted rocks containing low rb biotites by simple equilibrium partial melting models beginning with a rock with the average composition of the amphibolite facies gneisses 70 ppm and using distribution coefficients from the literature it is possible to produce such rb depleted rocks if the melt is removed in batches however it requires large amounts of partial melting 40 low rb biotites can be produced by both equilibrium and batch melting if the original rocks have low whole rock concentrations of rb 10 20 ppm to begin with attempts to model rb depletion by exchange with a metamorphic fluid phase are hampered by a general lack of experimentally determined mineral fluid distribution coefficients recent experimentally determined exchange coefficients between phlogopite and a k rb cl rich supercritical brine at high pressure and temperature indicate that it would require a fluid rock mass ratio of approximately 0 125 to produce rb depleted rocks with low rb biotites by exchange with a kcl rich fluid alternatively biotites low in rb may have formed shortly after the peak of metamorphism in the rocks after they were depleted in rb but while they were still under relatively high grade conditions

flow of partially molten crust and the internal dynamics of a migmatite dome naxos greece 1 migmatite domes are common in metamorphic core complexes dome migmatites deform in the partially molten or magmatic state and commonly record complex form surfaces folds and fabrics while units mantling the dome display a simpler geometry typically formed by transposition during crustal extension we use field observations and magnetic fabrics in the naxos dome greece to quantify the complex flow of anatectic crust beneath an extensional detachment system the internal structure of the naxos dome is characterized by second order domes subdomes pinched synforms and curved lineation trajectories which suggest that buoyancy driven flow participated in dome evolution subdomes broadly occur within two compartments that are separated by a steep n s oriented high strain zone this pattern has been recognized in domes formed by polydiapirism and in models of isostasy dominated flow the preferred model involves a combination of buoyancy and isostasy driven processes the naxos dome may have been generated by regional n s extension that triggered convergent flow of partially molten crust at depth and the upwelling of anatectic migmatites within the dome this pattern is complicated by gravitational instabilities and or overturning of the high melt fraction crust leading to the growth of subdomes as the migmatites within the naxos dome reached a higher structural level they were affected by regional top to the nne kinematics of the detachment system dome formation therefore occurred by a combination of coeval and coupled processes upper crustal extension deep crust contraction during convergent flow of anatectic crust diapirism and or density driven crustal convection forming subdomes and north directed detachment kinematics

influence of regional structure on the development and quality of the upper elkhorn no 2 coal bed eastern kentucky abstract the upper elkhorn no 2 coal bed middle pennsylvanian breathitt formation in eastern kentucky exhibits thickness and coal quality trends which suggest that peat deposition was contemporaneous with tectonism the coal thickens and has high vitrinite and low ash and sulfur content the belfry anticline in pike country t in the vicinity of the floyd country channel a basement trough in both cases other pennsylvanian coals exhibit similar trends suggesting that the penecontemporaneous tectonism persisted at least through a portion of the carboniferous

rare earth element geochemistry and the origin of andesites and basalts of the taupo volcanic zone new zealand abstract two types of basalt a high al basalt associated with the rhyolitic centres north of taupo and a low al basalt erupted from red crater tongariro volcanic centre and five types of andesite labradorite andesite labradorite pyroxene andesite hornblende andesite pyroxene low si andesite and olivine andesite low si andesite occur in the taupo volcanic zone tvz north island new zealand rare earth abundances for both basalts and andesites are particularly enriched in light rare earth elements high al basalts are more enriched than the low al basalt and have values comparable to the andesites labradorite and labradorite pyroxene andesites all have negative eu anomalies and hornblende andesites all have negative ce anomalies the former is probably due to changing plagioclase composition during fractionation and the latter to late stage hydration of the magma least squares mixing models indicate that neither high al nor low al basalts are likely sources for labradorite labradorite pyroxene andesites high al basalts are considered to result from fractionation of olivine and clinopyroxene from a garnet free peridotite at the top of the mantle wedge labradorite labradorite pyroxene andesites are mainly associated with an older nw trending arc the source is likely to be garnet free but it is not certain whether the andesites result from partial melting of the top of the subducting plate or a hydrated lower portion of the mantle wedge pyroxene low si andesites probably result from cumulation of pyroxene and calcic plagioclase within labradorite pyroxene andesites and hornblende andesites by late stage hydration of labradorite pyroxene andesite magma olivine andesites low si andesites and low al basalts are related to the nne trending taupo hikurangi arc structure although the initial source material is different for these lavas they have probably undergone a similar history to the labradorite labradorite pyroxene andesites all lavas show evidence of crustal contamination

palynologic petrographic and geochemical characteristics of the manchester coal bed in eastern kentucky the manchester coal bed in eastern kentucky is the stratigraphically lowest coal in kentucky that is both laterally continuous and of consistent mineable thickness the manchester coal bed occurs in the lower part of the breathitt formation in an interval between the underlying corbin sandstone and the overlying betsie shale both of which are also aerially widespread units the manchester is early middle pennsylvanian in age and is equivalent with the middle morrowan of the eastern interior basin and the late westphalian a of western europe increment samples were collected from the western and eastern outcrop and mining areas of the eastern kentucky coal field and were analyzed palynologically petrographically and geochemically to compare and contrast the two areas in the western part of the eastern kentucky coal field the manchester coal bed is uniform in occurrence and composition the bed is consistently 0 61 0 92 m 2 3 ft thick and generally is devoid of inorganic partings palynologically the coal in this area is largely dominated by lycospora the dispersed spore of many of the large lycopsid trees e g lepidodendron and lepidophloios and to a lesser extent granasporites medius representing diaphorodendron and synchysidendron petrographically the coal contains high percentages of vitrinite macerals and correspondingly low percentages of liptinite and inertinite macerals most of the increments from this area studied are generally low in ash yield 5 and sulfur content 10 and occasionally sulfur 1 in the eastern part of the coal field the manchester coal bed is typically thicker 3 ft 1 m but usually occurs as a coal zone with intercalated coal beds and clastic units palynologically the coal in this area contains increased percentages of small lycopsid small seed ferns calamites and cordaites petrographically the coal is higher overall in liptinite and inertinite macerals ash yields in the eastern sample area are generally low 10 an exception being some high ash durain bands overall sulfur contents also are low typically 1 the western samples are interpreted as having formed in a well protected generally flooded mire a consistent water cover would provide a favorable environment for arboreous lycopsid growth and proliferation and also inhibit oxidation of the peat surface thus promoting the formation of a high vitrinite content coal the eastern samples are also interpreted as having formed in a mire that was well protected most of the time giving rise to thick sequences of low ash low sulfur coal intermittent inundation by extra swamp waters carrying sediment in this area resulted in the development of a multiple coal zone i e several peat forming events with intervening clastic deposition in contrast to a single peat forming event in the western area surficial peat exposure was more frequent in the eastern area which allowed for increased microbial degradation of the peat and subsequent formation of inertinite macerals upon conversion to bituminous coal this condition might also accelerate charring of the peat surface by wildfire