on the association between veining and index mineral distributions in barrow s metamorphic zones glen esk scotland the concept of index mineral based metamorphic zones was first introduced by george barrow in 1912 and the barrovian metamorphic zones continue to be used as a framework for describing regional met

paleoenvironmental application of taxodium macrofossil biomarkers from the bobov dol coal formation bulgaria abstract this study correlates paleobotanical observations with chemical tracers and geological interpretation for bulgarian coals two samples were studied i e clay sediment with embedded twigs paleobotanically assigned to taxodium dubium and plant material scraped off from the leaf imprint of a macrofossil an assignment of the geological age is presented by considering the biomarker assemblage and paleobotanical data in comparison with information already available for taxodium dubium the geochemical data with paleobotanical and geological observations indicate a late oligocene geological age for the bobov dol coal the following points support this assignment i triterpenoids were completely altered to des a lupane or chrysene derivatives and ii diterpenoids were diagenetically converted to their aromatized end products

analysis origin and significance of mineral matter in coal an updated review abstract the material classed as mineral matter in coal embraces crystalline mineral materials as well as a range of inorganic elements that occur in non crystalline form this review outlines the methods that may be used to evaluate the percentage of mineral matter for a coal sample as opposed to the ash yield and to identify the minerals their individual percentages and their modes of occurrence within the coal the principal techniques include low temperature oxygen plasma ashing quantitative evaluation of x ray diffraction data observation using optical microscopy and a combination of observation chemical analysis and in some cases mapping based on scanning electron microscopy and related methods a range of other techniques may also be used to provide additional information on particular mineral matter components processes responsible for mineral matter formation include detrital input biogenic activity and authigenic precipitation at different stages of the coal s depositional and post depositional history differential migration of non mineral inorganic elements may also occur in lower rank coals and expulsion of non mineral inorganics may take place with rank advance knowledge of the mineral matter may be of assistance in understanding the modes of trace element occurrence with implications for assessing possible environmental impacts and also the potential for recovery of economic products from coal the behaviour of different mineral matter components at high temperatures is also discussed as well as methods for mineralogical analysis of ashes and other coal utilization products information from mineral matter studies may provide an improved basis for understanding coal formation and for evaluating the response of particular coals to different combustion gasification and coking processes

a classification scheme for mantle derived garnets in kimberlite a tool for investigating the mantle and exploring for diamonds abstract a new empirical method has been devised for classification of mantle derived garnets in kimberlite simple chemical screens have been developed to distinguish between garnets from different parageneses based on mg fe ca cr ti and na values of published analyses of garnets from 2000 ultramafic xenoliths in kimberlite although crustal garnets are typically uncommon as xenocrysts in kimberlite the first step in the classification is to screen these from the mantle population using data from 600 garnet bearing crustal rocks such a screen may also prove useful in evaluating the source crust vs mantle of garnet in kimberlite exploration samples subsequent steps divide mantle garnets into eclogite peridotite and cr poor megacryst groupings and sub groups of the peridotite lherzolite harzburgite wehrlite and eclogite groups i and ii and a b c and grospydite populations important features of this classification include the fact that it is based on distinctions between groups of fundamental geological significance e g peridotite vs eclogite and it is based on a large well documented and well understood xenolith database as it utilizes oxide values and molar ratios of major and minor elements the rationale for the screens is readily understood and it is simple to use

a late tournaisian synmetamorphic folding and thrusting event in the eastern variscan foreland 40 ar 39 ar evidence from the phyllites of the wolsztyn leszno high western poland a variscan foreland in western poland comprises two nw trending basement highs which are concealed under carboniferous through triassic strata of the fore sudetic monocline fsm both highs consist of multiply deformed quartz sericite albite chlorite phyllites of unknown protolith age 40ar 39ar laser probe dating of white micas in up to 0 5 mm thick mica layers which form the s2 axial plane foliation in phyllites of the wolsztyn leszno high yielded an age of 340 1 2 6 ma for the lower greenschists facies metamorphism and probably also for the f2 folding this deformation was associated and followed by thrusting which brought about the basement highs the latter delivered clasts to overlying late visean early namurian flysch basin that was mainly sourced from the saxothuringian sudetes in which most of the deformation occurred between 345 335 ma the fsm basement may represent an independent terrane referred to as the wielkopolska terrane belonging to the armorican terrane assemblage

progressive metamorphism of pelitic rocks from protolith to granulite facies dutchess county new york usa constraints on the timing of fluid infiltration during regional metamorphism a complete barrovian sequence ranging from unmetamorphosed shales to sillimanite k feldspar zone metapelitic gneisses crops out in a region extending from the hudson river in south eastern new york state usa to the high grade core of the taconic range in western connecticut nne trending subparallel biotite garnet staurolite kyanite sillimanite and sillimanite k feldspar isograds have been identified although the assignment of barrovian zones in the high grade rocks is complicated by the appearance of fibrolitic sillimanite at the kyanite isograd thermobarometric results and reaction textures are used to characterize the metamorphic history of the sequence pressure temperature estimates indicate maximum metamorphic conditions of 475 c c 3 4 kbar in the garnet zone to 720 c c 5 6 kbar in the highest grade rocks exposed some samples in the kyanite zone record anomalous low peak conditions because garnet composition has been modified by fluid assisted reactions there is abundant petrographic and mineral chemical information indicating that the sequence with the possible exception of the granulite facies zone was infiltrated by a water rich fluid after garnet growth was nearly completed the truncation of fluid inclusion trails in garnet by rim growth or recrystallization however indicates that metamorphic reactions involving garnet continued subsequent to initial infiltration the presence of these textures in some zones of a well constrained barrovian sequence allows determination of the timing of fluid infiltration relative to the p t paths thermobarometric results obtained using garnet compositions at the boundary between fluid inclusion rich and inclusion free regions of the garnet are interpreted to represent peak metamorphic conditions whereas rim compositions record slightly lower pressures and temperatures assuming that garnet grew during a single metamorphic event infiltration must have occurred at or slightly after the peak of metamorphism i e 4 5 kbar and a temperature of c 525 550 c for staurolite and kyanite zone rocks

mineralogy and geochemistry of a superhigh organic sulfur coal yanshan coalfield yunnan china evidence for a volcanic ash component and influence by submarine exhalation abstract the mineralogy and geochemistry of a superhigh organic sulfur shos coal of late permian age from the yanshan coalfield yunnan province southwestern china have been studied using optical microscope low temperature ashing plus x ray diffraction analysis scanning electron microscope equipped with energy dispersive x ray spectrometer a sequential chemical extraction procedure and inductively coupled plasma mass spectrometry the m9 coal from the yanshan coalfield is a shos coal that has a total sulfur content of 10 12 11 30 and an organic sulfur content of 8 77 10 30 the minerals in the coal consist mainly of high temperature quartz sanidine albite muscovite illite pyrite and trace amounts of kaolinite plagioclase akermanite rutile and dawsonite as compared with ordinary worldwide bituminous coals and anthracite and chinese coals the m9 coal is remarkably enriched in b 268 g g f 841 g g v 567 g g cr 329 g g ni 73 9 g g mo 204 g g and u 153 g g in addition elements including se 25 2 g g zr 262 g g nb 20 1 g g cd 2 07 g g and tl 2 03 g g are also enriched in the coal occurrence of high temperature quartz sanidine muscovite and illite in the m9 coal is evidence that there is a volcanic ash component in the coal that was derived from acid volcanic ashes fallen into the swamp during peat accumulation occurrence of albite and dawsonite in the coal and strong enrichment of some elements including f s v cr ni mo and u are attributed to the influence by submarine exhalation which invaded along with seawater into the anoxic peat swamp abundances of lithophile elements including rare earth elements nb y zr and tio2 indicate that the silicate minerals in the coal were derived from the northern vietnam upland to the south of the basin

modification of garnet by fluid infiltration during regional metamorphism in garnet through sillimanite zone rocks dutchess county new york metapelitic rocks from a progressive metamorphic sequence in dutchess county new york record evidence for reaction between garnet and fluids associated with quartz plagioclase veins and for net transfer among garnet interiors mineral inclusions and fluid garnet fluid reaction resulted in modification of preexisting garnet textures compositions and growth zoning patterns the textural and compositional record of garnet fluid interaction varies with grade and with proximity of garnet to quartz veins garnet zone rocks do not contain evidence for extensive reaction with vein forming fluids in upper stauroliteand kyanite zone rocks garnet that is crosscut by quartz veins contains a fluid inclusion filled region near the garnet vein interface this region truncates growth zoning patterns and quartz inclusions fluid inclusions in garnet decrease in abundance away from quartz veins in some rocks lacking quartz veins fluid inclusions are concentrated in garnet interiors and in particular near fractures and are notably lacking around mineral inclusions in garnet inferences from textural and compositional features combined with thermobarometric results indicate that preexisting garnet grains were modified at t 525 550 c and 4 kbar by one or more reactions involving fluids the fluid pathways included foliationparallel channels in the rock as well as microcracks in mineral grains

illitization in a paleozoic peat forming environment as evidence for biogenic potassium accumulation abstract potassium enrichment is common in surface horizons of many paleosols and has been attributed to the formation of authigenic illite from smectites during burial diagenesis in such cases the presence of primary smectite is key to the illitization process which then results in potassium enrichment as a byproduct potassium enrichment in paleosols where no primary smectite was present however requires a different process of accumulation a lower pennsylvanian tropical ultisol from the southern anthracite field in pennsylvania is enriched in potassium in the surface horizon and formed in an environment unfavorable for smectite accumulation kaolinite dominates clay mineral fractions of soils that form in such highly weathering environments in the absence of primary smectite to scavenge potassium during illitization there should be no potassium enrichment during burial diagenesis however in lykens valley paleosol the pattern of potassium concentration organic matter distribution and authigenic illite growth suggests that organic matter may have provided an important source of potassium for illite formation illitization of kaolinite in the organic rich surface horizon is complete but illite coexists with kaolinite in the b horizon within the paleosol matrix illitization is more complete in areas of high organic concentration where organic fragments often have illite haloes with illite whorls growing from their edges we propose that the potassium enrichment both in the soil profile and in the overlying coal is the result of the luxury uptake of potassium by peat forming plants nutrient intake at rates exceeding metabolic requirements further potassium immobilized by adsorption on the peat provided interlayer cations for illite authigenesis to begin if as we suggest luxury nutrient uptake during peat formation sequestered sufficient potassium to promote later illite formation the pattern and extent of illitization within the paleosol profile reflects early biogenic nutrient accumulation thus illite in some paleosols may represent fossil evidence for a biological process the luxury uptake of potassium

mineralogy and geochemistry of al hydroxide oxyhydroxide mineral bearing coals of late paleozoic age from the weibei coalfield southeastern ordos basin north china abstract this paper mainly describes mineralogy and geochemistry of coals from the weibei coalfield in the southeastern ordos basin north china a number of al hydroxide oxyhydroxide minerals were detected in the late carboniferous coals nos 5 10 and 11 coals especially in the no 10 coal aluminum hydroxide oxyhydroxide minerals nordstrandite boehmite and diaspore in the no 10 coal are associated with kaolinite suggesting that these minerals are derived from the breakdown of kaolinite a model in which al hydroxide oxyhydroxide minerals form from the incongruent dissolution of kaolinite is presented nordstrandite and boehmite mainly occur as massive lenses n 2 mainly occurs within al hydroxide oxyhydroxide minerals nordstrandite boehmite and diaspore kaolinite and organic matter

late stage orogenic loading revealed by contact metamorphism in the northern appalachians new york pelitic schists from contact aureoles surrounding mafic ultramafic plutons in westchester county ny record a high p 0 8 gpa high t 790 c contact overprint on a taconic regional metamorphic assemblage 0 5 gpa the contact metamorphic assemblage of a pelitic sample in the innermost aureole of the croton falls pluton a small 10 km 2 gabbroic body consists of quartz plagioclase biotite garnet sillimanite ilmenite graphite zn rich al spinel both k feldspar and muscovite are absent and abundant biotite plagioclase sillimanite quartz and ilmenite inclusions are found within subhedral garnet crystals unusually low bulk rock na and k contents imply depletion of alkalic components and silica through anatexis and melt extraction during contact heating relative to typical metapelites outside the aureole thermobarometry on nearby samples lacking a contact overprint yields 620 640 c and 0 5 0 6 gpa in the aureole sample wds x ray chemical maps show distinct ca enriched rims on both garnet and matrix plagioclase furthermore biotite inclusions within garnet have significantly higher mg concentration than matrix biotite thermobarometry using gasp and garnet biotite mg fe exchange equilibria on inclusions and adjacent garnet host interior to the high ca rim zone yield 0 5 0 1 gpa and 620 50 c pairs in the modified garnet rim zone yield 0 9 0 1 gpa and 790 50 c thermocalc average p t calculations yield similar results for core 0 5 0 1 gpa 640 80 c and rim 0 9 0 1 gpa 800 90 c equilibria the core assemblages are interpreted to record the p t conditions of peak metamorphism during the ta conic regional event whereas the rim compositions and matrix assemblages are interpreted to record the p t conditions during the contact event the high pressures deduced for this later event are inter preted to reflect loading due to the emplacement of taconic allochthons in the northern appalachians during the waning stages of regional metamorphism after c 465 ma and before contact metamor phism c 435 ma in the absence of contact metamorphism induced recrystallization it is likely that this regional scale loading would remain cryptic or unrecorded

organic petrology mineralogy and depositional environment of the kipra lignite seam maritza west basin bulgaria abstract the aim of the present study is to provide additional information about the properties and depositional environment of the kipra lignite seam which was deposited during the regressive stage of development of the maritza west basin petrographical and mineralogical data along with ash yields and sulphur contents of 24 samples from a seam profile have been used to study the vertical variation of the depositional settings during peat accumulation and subsequent coalification the kipra lignite is characterized by high ash yields and sulphur contents it formed in a rheotrophic low lying mire with alkaline ph value vegetation with low preservation potential dominated within the palaeomire during peat formation frequent changes of the water level controlled the depositional environment during the deposition of units 1 and 2 high water energy caused the transportation of high amounts of inorganic material into the mire resulting in the formation of weakly gelified mineral rich lignite the organic matter from units 3 and 4 is characterized by enhanced gelification which probably reflects the decreasing energy of the system good positive correlation between sulphur contents and the gi values was established in units 4 indicating that the gelification of the tissues was probably mainly controlled by the bacterial activity in contrast the gelification of the samples from unit 3 of the kipra seam was probably governed by the redox conditions the organic matter deposited under relatively wet conditions in which the thermal and oxidative destruction of the tissues was limited a variety of major minor and accessory minerals are present in maritza west lignite the mineral composition is dominated mainly by pyrite gypsum and calcite and to a lesser extent limonite quartz kaolinite montmorillonite illite chlorite and plagioclase jarosite hematite halloysite mica k feldspar aragonite siderite and dolomite were also determined in very low concentrations these minerals formed syngenetically and epigenetically the syngenetic stage is characterized mainly by the formation of pyrite carbonates silicates and sulphates whereas the fe oxyhydroxides partially the carbonates and almost all silicates are of detrital origin during the epigenetic stage carbonates sulphates clay minerals pyrite and fe oxyhydroxides were formed alteration products like gypsum jarosite limonite chlorite kaolinite illite mica and calcite were generated due to the transformation of detrital and authigenic minerals

iron sulfide precipitation sequence in albian coals from the maestrazgo basin southeastern iberian range northeastern spain abstract deposition of important coal accumulations in the proximal areas of a delta estuary occurred in the maestrazgo basin during the middle albian late lower cretaceous these coals are characterized by high sulfur contents 4 18 in coal from the castellote subbasin and 7 16 in coal from the calanda subbasin dry basis a petrographic study of iron sulfide was carried out on the subject coals to deduce an iron sulfide precipitation sequence for five principal stages a early syngenetic stage b late syngenetic stage c syngenetic diagenetic stage d early epigenetic stage and e late epigenetic stage a sulfide precipitation control during the syngenetic stage carried out by different compounds liberated from organic matter during its coalification stages is deduced from the confrontation with other studies on coal differing in rank depositional environment and geographical location

mineralogy and environmental geochemistry of lagooned ashes resulted from combustion of maritza east lignite bulgaria the phase mineral composition of the feed coal fc from maritza east lignite used in the maritza east 1 thermo electric power station teps and lagooned ashes las generated from the burning of this lignite was studied the concentration and behaviour of 19 trace elements in the fc and las as well as in the soils and plants collected from the restored sites of former la disposals are also described the minerals and inorganic phases identified in the lignite include quartz kaolinite pyrite illite plagioclase gypsum calcite sulphur marcasite pyrrhotite magnetite k feldspar barite szomolnokite other fe sulphates sylvite ni carbonate or oxide hydroxide and glass the phase composition of las is represented by original lignite minerals pyrrhotite magnetite quartz kaolinite and newly formed minerals and phases generated during the combustion process pyrrhotite magnetite hematite quartz metakaolinite mullite indialite glass char or storage of las sulphur hematite fe hydroxides gypsum barite fe sulphates calcite sylvite it was found that cr cu and ti in the lignite ashes and co cr cu mn and ni in las are relatively enriched in comparison with their respective clarke values worldwide average contents for lignite and subbituminous coal ashes the concentrations of ag ba be co cu ga mo ni rb sn and ti in the soils have contents higher than their clarke values for soils the abundance of these elements plus mn v and zn in soils is probably related to some occurrence of discrete minerals and phases containing such elements the contents of be cr ga li ni pb ti and v in the plants growing on these restored la sites have concentrations higher than their clarke values for land plants dry basis the water soluble modes of occurrence of ag ba be co cr cu li mn mo ni pb sn ti and zn in soils and or las as well as the plant affinity to these elements should have a leading role for their concentration in plants the present results reveal that various trace elements with environmental concern could be potential pollutants of surface and subsoil waters soils and plants in the areas of restored la sites

mineral and inorganic chemical composition of the pernik coal bulgaria the mineral and inorganic chemical composition of five types of samples from the pernik subbituminous coals and their products generated from the pernik preparation plant were studied they include feed coal low grade coal high grade coal coal slime and host rock the mineral matter of the coals contains 44 species that belong mainly to silicates carbonates sulphates sulphides and oxides hydroxides and to a lesser extent chlorides biogenic minerals and organic minerals the detrital minerals are quartz kaolinite micas feldspars magnetite cristobalite spessartine and amphibole the authigenic minerals include various sulphides silicates oxihydroxides sulphates and carbonates several stages and substages of formation were identified during the syngenetic and epigenetic mineral precipitations of these coals the authigenic minerals show the greatest diversity of mineral species as the epigenetic mineralization mostly sulphides carbonates and sulphates dominates qualitatively and quantitatively the epigenetic mineralization was a result of complex processes occurring mostly during the late development of the pernik basin these processes indicate intensive tectonic hydrothermal and volcanic activities accompanied by a change from fresh to marine sedimentation environment thermally altered organic matter due to some of the above processes was also identified in the basin most of the trace elements in the pernik coals mo be s zr y cl ba sc ga ag v p br ni co pb ca and ti show an affinity to om and phases intimately associated with om some of the trace elements sr ti mn ba pb cu zn co cr ni as ag yb sn ga ge etc are impurities in authigenic and accessory minerals while other trace elements la ba cu ce sb bi zn pb cd nd etc occur as discrete phases elements such as sc be y ba v zr s mo ti and ga exceed clarke concentrations in all of the coal types studied it was also found that a number of elements in the pernik coals f v as pb mo li sr ti ga ni ge cr mn etc reveal mobility in water and could have some environmental concerns

crustal growth during back arc closure cretaceous exhumation history of cordillera darwin southern patagonia the cordillera darwin metamorphic complex is unique in the andes in exposing kyanite staurolite schist north of the beagle channel in southern patagonia garnet in amphibolite facies pelitic schists from bahia pia has patchy textures whereby some grains consist of clear grossular rich garnet with fine grained s1 inclusion trails truncated by regions of turbid spessartine pyrope rich garnet with biotite muscovite plagioclase and quartz inclusions micron scale aqueous inclusions in turbid garnet are consistent with recrystallization facilitated by fluid ingress s2 inclusion trails indicate this was broadly contemporary with the growth of kyanite and staurolite in the matrix pseudosection modelling in na2o cao k2o feo mgo al2o3 sio2 h2o tio2 fe2o3 nckfmashto is used to infer a p t path dominated by decompression from 12 to 9 kbar at t 620 c coupled with garnet mode decreasing from 5 to 1 u th pb in situ dating of s2 monazite indicates that staurolite and kyanite growth and thus exhumation was underway before 72 6 1 1 ma contact aureoles developed adjacent to late granite intrusions include sillimanite bearing migmatites formed at p 6 kbar after 72 ma metamorphism of southern cordillera darwin induced by continental underthrusting beneath the arc related to closure of the rocas verdes back arc basin was terminated by thrusting controlled exhumation with the rocks at p 9 kbar by c 73 ma and 6 kbar by c 70 ma

garnet polycrystals and the significance of clustered crystallization polycrystalline garnets are common in metamorphic rocks and may form as a result of close spacing of nuclei if clustering is early or impingement of larger grains if clustering occurs later in the growth history the timing of clustering relative to garnet growth is relevant to understanding the formation and evolution of porphyroblasts and evaluating the significance if any of clustering electron backscattered diffraction ebsd analysis of garnet bearing metamorphic rocks reveals the presence of polycrystalline garnet in nine localities examined in this study the northern appalachians vermont maine new york usa north american cordillera north cascades range washington snake range nevada usa western rocky mountains british columbia canada southern menderes massif turkey santander massif colombia and the sanandaj sirjan zone hamadan iran in some samples polycrystals comprise 20 30 of garnets analyzed and chemical and textural evidence suggests that early coalescence of garnet polycrystals is common some early coalescing polycrystals exhibit growth zoning that is concentric about the geometric center of the polycrystal in thin section these garnets may be undetectable as polycrystals based on morphology or zoning in some polycrystals zoning is unrelated to the location of internal grain boundaries in others fe mn mg zoning has a different pattern than that of ca zoning patterns may vary on the scale of a single thin section in addition some polycrystals are characterized by high angle misorientation boundaries that may be in special non random orientations an observation that indicates that these polycrystals are not random clusters of grains the presence of internal grain boundaries may affect diffusion pathways and length scales and may facilitate communication of porphyroblast interiors with matrix phases thereby influencing reaction history of the rock and the composition zoning of garnet

abundances and distribution of minerals and elements in high alumina coal fly ash from the jungar power plant inner mongolia china abstract the fly ash from the jungar power plant inner mongolia china is unique because it is highly enriched in alumina al2o3 50 the fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum quartz char calcite k feldspar clay minerals and fe bearing minerals the mullite content in fly ash is as high as 37 4 because of high boehmite and kaolinite contents in feed coal corundum is a characteristic mineral formed during the combustion of boehmite rich coal samples from the economizer were sieved into six size fractions 500 mesh and separated into magnetic mullite corundum quartz mcq and glass phases for mineralogical and chemical analysis the corundum content increases but amorphous glass decreases with decreasing particle size fractions of small particle sizes are relatively high in mullite probably because mullite was formed from fine clay mineral particles under high temperature combustion condition similarly fine corundum crystals formed in the boiler from boehmite in feed coal the magnetic phase consists of hematite magnetite magnesioferrite and mgfealo4 crystals the mcq phase is composed of 89 mullite 6 1 corundum 4 5 quartz and 0 5 k feldspar overall the fly ash from the power plant is significantly enriched in al2o3 with an average of 51 9 but poor in sio2 fe2o3 cao mgo na2o p2o5 and as arsenic tio2 th al2o3 bi la ga ni and v are high in mullite and the magnetic matter is enriched in fe2o3 cao mno tio2 cs co as cd ba ni sb mgo zn and v the remaining elements are high in the glass fraction the concentration of k2o na2o p2o5 nb cr ta u w rb and ni do not clearly vary with particle size while sio2 and hg decrease and the remaining elements clearly increase with decreasing particle size

post taconic tilting and acadian structural overprint of the classic barrovian metamorphic gradient in dutchess county new york field mapping and 40ar 39ar age spectrum dating of white mica across the classic metamorphic gradient in dutchess county new york indicate that post peak metamorphic and structural events complicate the interpretation of this sequence as an intact taconic metamorphic field gradient oriented samples were collected and fabrics were measured along two 7 km transects these transects extend from west of the biotite zone west of clove mountain to the sillimanite zone swamp river valley in eastern dutchess county field and petrographic analysis reveals three pervasive foliations s1 s2 and s3 s1 is folded in the lower grade rocks of the sequence but is increasingly overprinted at garnet and higher zones by a penetrative foliation s2 s2 dips steeply to the se and is axial planar to folds in s1 s2 is overgrown by porphyroblasts of biotite biotite chloritoid biotite garnet staurolite kyanite sillimanite at respective metamorphic grades that appear to approximate peak temperature conditions s1 s2 and peak temperature conditions are constrained as late taconic based on a depositional age of 460 ma potter 1972 for the walloomsac formation and a staurolite age of 454 ma lanzirotti and hanson 1997 from kyanite sillimanite grade rocks s3 is a greenschist facies foliation composed of muscovite biotite chlorite that truncates or overprints s2 in garnet through sillimanite grade rocks in the eastern part of the study area s3 dips gently to the s se and becomes more penetrative to the east such that in the garnet zone s2 is overprinted by a weakly developed spaced s3 cleavage while in many samples in the staurolite and higher metamorphic zones s2 micas are significantly overprinted by s3 micas s3 is observed wrapping around and truncating peak temperature porphyroblasts three samples of lepidoblastic white mica with varying proportions of s1 s2 and s3 from the biotite through staurolite zone all produce 40ar 39ar age spectra suggesting closure ages of 385 ma these white mica ages are interpreted to represent the time of cooling through white mica closure 350 c the 40ar 39ar ages in conjunction with field mapping and petrographic analysis suggest that s3 developed in the devonian acadian orogeny furthermore the 40ar 39ar data constrains the timing of tilting and uplift of the ordovician barrovian sequence from the middle silurian to early devonian this study suggests mid crustal wedging during the salinic orogeny as a possible mechanism for tilting the rocks of this region and exposing the taconic aged barrovian field gradient at the surface today we conclude the low grade acadian metamorphic overprint of these rocks involved deformation that produced a new third cleavage that was coincident with regional cooling from peak taconic metamorphic conditions and thus required strain but no reheating during the acadian

scandium sc geochemistry in coals siberia russian far east mongolia kazakhstan and iran abstract this research discusses new original data on the geochemistry of scandium sc in the coals of the asian region of russia mongolia kazakhstan and iran in general the studied coals are enriched in sc compared with the mean value for coals throughout the world in different regions of the studied territory coal deposits with anomalous sc concentrations up to commercially important concentrations were found and the factors that control the sc contents in those coals were revealed the composition of the rock types that surround the coal forming basins and the hydro geochemical conditions of these basins and deposits determine the levels of sc accumulation in the coals it was found that sc was redistributed and partially lost from the seams during coal metamorphism studies of the modes of sc occurrence in the coals showed the predominance of an organic mode in addition the peculiarities of the sc distribution in the deposits and coal seams indicate a predominantly hydrogenous mechanism for the accumulation of anomalous sc concentrations in coal and peat scandium in coal and peat accumulates by leaching from coal bearing strata and re deposition in coal peat beds with the participation of soil and ground water enriched with organic acids specific conditions for the formation of coal containing sc enriched rocks and for the sc leaching and transportation into coal seams are necessary for the accumulation of high sc concentrations in the coals such conditions that occur in the contemporary mire ecosystems of western siberia could also have occurred in ancient basins of peat coal accumulation

mineralogy and geochemistry of a late permian coal in the dafang coalfield guizhou china influence from siliceous and iron rich calcic hydrothermal fluids abstract this paper describes the influence of siliceous and iron rich calcic low temperature hydrothermal fluids lthf on the mineralogy and geochemistry of the late permian no 11 coal anthracitic r r 2 85 in the dafang coalfield in northwestern guizhou province china the no 11 coal has high contents of vein ankerite 10 2 vol and vein quartz 11 4 vol with formation temperatures of 85 and 180 c respectively indicating that vein ankerite and vein quartz were derived from low temperature calcic and siliceous hydrothermal fluids in two epigenetic episodes the vein quartz appears to have formed earlier than vein ankerite did and at least three distinct stages of ankerite formation with different ca sr and fe mn ratios were observed the two types of mineral veins are sources of different suites of major and trace metals scanning electron microscope and sequential extraction studies show that in addition to fe mg and ca vein ankerite is the dominant source of mn cu ni pb and zn in the coal and the contents of these five elements are as high as 0 09 and 74 0 33 6 185 and 289 g g respectively in contrast vein quartz is the main carrier mineral for platinum group elements pges pd pt and ir in the coal and the contents of pd pt and ir are 1 57 0 15 and 0 007 g g respectively sequential extraction showed a high pge content in the silicate fraction up to 10 4 g g pd 1 23 g g pt and 0 05 g g ir respectively it is concluded that the formation of ankerite and quartz and the anomalous enrichment of trace elements in the no 11 coal in the dafang coalfield guizhou result from the influx of calcic and siliceous low temperature hydrothermal fluids

minerals in bituminous coals of the sydney basin australia and the illinois basin u s a although other forms of inorganic components may be significant in lower rank coals the mineral matter in most bituminous coals is dominated by silicates carbonates sulphides phosphates and other crystalline mineral groups these may be present in various forms including thin bands and laminae intimately associated with the organic matter as well as lenticles nodules crystal aggregates and cell infillings all of which indicate approximately contemporaneous formation with the peat bed other minerals however occur as veins or cleat and fracture fillings indicating precipitation after most of the compaction and presumably after most of the rank advance ome of the penecontemporaneous mineral matter is of detrital origin representing epiclastic or pyroclastic particles washed or blown into the peat swamp other mineral matter however including much of the pyrite quartz and siderite as well as abundant well crystallized kaolinite appears to have been formed by precipitation processes either within the swamp waters or in the pores of the peat deposit pyrite largely formed by bacterial reduction of dissolved sulphate ions seems to be related in abundance to marine transgressions which allowed permeation of sea water into the swamp and through the peat bed beneath siderite appears to form in the absence of sulphate rich sea water probably from co2 released by organic decay the clay fraction of the noncoal rocks in many coal bearing sequences is typically dominated by illite or interstratified clay minerals with kaolinite chlorite and possibly montmorillonite also present to a variable though typically minor extent although perhaps modified by chemical reactions or ion exchange mechanisms in the peat swamp these clay minerals may also be present in the coal as well especially near the base of top of the seam the kaolinite in the noncoal rocks is usually poorly crystallized and typically a minor constituent but well crystallized kaolinite is characteristically present and often the dominant component in the mineral fraction of bituminous coal beds as well as in some of the lutites including underclays intimately associated with the seams a progressive upward gradation to a particularly kaolinite dominated mineral assemblage occurs in some seams of the sydney basin australia this gradation is thought to be due to either increased blockage of detrital contaminants as the swamp developed or to in situ chemical or biological leaching of the mineral fraction and reconstitution of the residues in the upper parts of the peat bed superimposition of such cycles is also noted within the seam in some instances suggesting repetition of several phases of this type during major peat accumulations

trace element abundances in major minerals of late permian coals from southwestern guizhou province china abstract fourteen samples of minerals were separated by handpicking from late permian coals in southwestern guizhou province china these 14 minerals were nodular pyrite massive recrystallized pyrite pyrite deposited from low temperature hydrothermal fluid and from ground water clay minerals and calcite deposited from low temperature hydrothermal fluid and from ground water the mineralogy elemental composition and distribution of 33 elements in these samples were studied by optical microscopy scanning electron microscope equipped with energy dispersive x ray spectrometer sem edx x ray diffraction xrd cold vapor atomic absorption spectrometry cv aas atomic fluorescence spectrometry afs inductively coupled plasma mass spectrometry icp ms and ion selective electrode ise the results show that various minerals in coal contain variable amounts of trace elements clay minerals have high concentrations of ba be cs f ga nb rb th u and zr quartz has little contribution to the concentration of trace elements in bulk coal arsenic mn and sr are in high concentrations in calcite pyrite has high concentrations of as cd hg mo sb se tl and zn different genetic types of calcite in coal can accumulate different trace elements for example ba co cr hg ni rb sn sr and zn are in higher concentrations in calcite deposited from low temperature hydrothermal fluid than in that deposited from ground water furthermore the concentrations of some trace elements are quite variable in pyrite different genetic types of pyrites py a b c d have different concentrations of trace elements and the concentrations of trace elements are also different in pyrite of low temperature hydrothermal origin collected from different locations the study shows that elemental concentration is rather uniform in a pyrite vein there are many micron and submicron mosaic pyrites in a pyrite vein which is enriched in some trace elements such as as and mo the content of trace element in pyrite vein depends upon the content of mosaic pyrite and of trace elements in it many environmentally sensitive trace elements are mainly contained in the minerals in coal and hence the physical coal cleaning techniques can remove minerals from coal and decrease the emissions of potentially hazardous trace elements

mineralogy and geochemistry of bobov dol coals bulgaria abstract the mineralogy elemental composition and modes of occurrence of 49 elements in nine composite samples of bobov dol high ash coals were studied by optical microscopy scanning and transmission electron microscopy x ray diffractometry and chemical analysis the major minerals were quartz kaolinite illite plagioclase and k feldspar and the minor minerals and phases were pyrite marcasite siderite calcite dolomite gypsum muscovite montmorillonite and volcanic glass the accessory minerals include a wide variety of minerals such as galena pyrrhotite magnetite hematite goethite chromite rutile anatase corundum gibbsite biotite chlorite zircon enstatite garnet jarosite alunite barite polyhalite aragonite ankerite witherite apatite halite and sylvite the modes of occurrence and some genetic peculiarities of the above mentioned minerals are described thirty three elements occurred in concentrations higher than the respective clarke values especially s rb nb hf zn cu pb mn ti and u the concentration trends and modes of occurrence of the trace elements are also discussed in decreasing order of significance the trace elements probably occur as element organic compounds as impurities in the mineral constituents as major components in the minerals as major and impurity components in the inorganic amorphous constituents and in the fluid constituents the bobov dol coals have undergone complex syngenetic diagenetic and epigenetic mineralization processes associated with hydrothermal and volcanic activities these processes were also accompanied by intensive tectonic movements and possibly by a later change from continental to marine sedimentation in the area after burial of the coal

geochemistry of boron in bulgarian coals a set of 466 individual full channel samples coals coaly shales and partings of thirteen bulgarian coal deposits as well as vitrain lenses gagatite and coalified woods embedded in sedimentary rocks have been analyzed by atomic emission spectroscopy the deposits consist of lignites subbituminous and bituminous coals the average boron content ranges from 15 to 164 ppm in the coals the boron content of the individual coal samples ranges from 2 to 164 ppm about 86 of the samples have a b content from 2 to 110 ppm which corresponds to the most probable interval of concentration for coals worldwide the boron content is not related to rank the lignites have the lowest boron content some of the vitrain and xylain samples studied are enriched in boron in comparison with the whole coal samples boron occurs in both organic borg and inorganic binorg forms excluding one deposit the boron content in the ash correlates negatively with the ash content whereas in coals it usually slightly increases with increasing ash content organically associated b dominates in the low ash coals and in the deposits enriched in boron the coals of the burgas deposit have the highest b content which is in agreement with the geological evidence for marine influence during the early stages of coalification the distribution of b is also independent of other geological factors

multiple mechanisms of remagnetization involving sedimentary greigite fe3s4 sedimentary greigite fe3s4 is being increasingly implicated as the carrier of late diagenetic remagnetizations in fine grained marine and terrestrial sediments we have conducted detailed scanning electron microscope observations on polished sections from such sediments coupled with elemental microanalysis to identify greigite and to characterize the mode of occurrence and the relationships between the observed greigite and other authigenic and detrital mineral phases this detailed observational work in conjunction with recently published work has enabled identification of several mechanisms for remagnetization involving greigite 1 neoformation of greigite on the surfaces of early diagenetic framboidal and nodular pyrite 2 greigite growth within cleavages of detrital sheet silicate grains 3 neoformation of greigite on the surfaces of authigenic clays smectite illite 4 greigite nucleation on the surfaces of siderite 5 greigite growth on the surface of gypsum that resulted from earlier oxidation of nodular pyrite many other mechanisms for greigite neoformation are conceivable the key variables are appropriate redox conditions for generation of sulphide and availability of iron from the dissolution of a wide range of possible reactive detrital and authigenic iron bearing minerals documentation of a wide range of mechanisms for neoformation of greigite provides compelling evidence that sediments containing greigite should be routinely suspected of remagnetization which will complicate or compromise studies of environmental magnetism and geomagnetic field behaviour

calibration of a ti in muscovite geothermometer for ilmenite and al2sio5 bearing metapelites abstract the ti in muscovite geothermometer was empirically calibrated as ln t oc 7 258 0 289 ln ti 0 158 mg fe mg 0 031 ln p kbar using ilmenite and al2sio5 bearing assemblages in metapelites under p t conditions of 450 800 c and 0 1 1 4 gpa the calibration was conducted for muscovites containing ti 0 01 0 07 fe 0 03 0 16 mg 0 01 0 32 and mg fe mg 0 05 0 73 respectively on the basis of 11 oxygen per formula unit such compositional range covers more than 90 natural muscovites and the random error of this thermometer is estimated to be of 65 c the geothermometer was validated against a set of independently determined temperature conditions between different degrees in samples from different prograde inverted and contact metamorphic terranes application of this thermometer beyond the calibration conditions is not encouraged