quantitative mineralogy of surface sediments on the iceland shelf and application to down core studies of holocene ice rafted sediments abstract quantitative x ray diffraction analyses on the 2 mm sediment fraction from the iceland shelves are reported for subglacial diamictons seafloor surface sediments and the last 2000 cal yr bp from two cores the overall goal of the paper is to characterize the spatial variability of the mineralogy of the present day surface sediments 18 non clay minerals and 7 clay minerals compare that with largely in situ erosional products typified by the composition of subglacial diamictons and finally examine the late holocene temporal variability in mineral composition using multi mineral compositions the subglacial diamictons are dominated in the non clay mineral fraction by the plagioclase feldspars and pyroxene with 36 7 6 1 and 17 9 3 5 wt respectively with smectites being the dominant clay minerals the surface seafloor sediments have similar compositions although there are substantial amounts of calcite plus there is a distinct band of sites from nw to n central iceland that contain 1 6 wt of quartz this latter distribution mimics the modern and historic pattern of drift ice in iceland waters principal component analysis of the transformed wt log ratio non clay minerals is used to compare the subglacial surface and down core mineral compositions fifty eight percent of the variance is explained by the first two axes with dolomite microcline and quartz being important foreign species these analyses indicate that today the nw n central iceland shelf is affected by the import of exotic minerals which are transported and released from drift ice the down core mineralogy indicates that this is a process that has varied over the last 2000 cal yr bp

two high levels of continental waters in the southern tunisian chotts at about 90 and 150 ka uranium and thorium content and activity ratios were measured on 20 samples 19 molluscs and 1 calcareous concretion from the great chotts in southern tunisia results were studied by the isochron method and by age frequency histograms they suggest that two major flood episodes took place about 150 and 90 ka uranium activity ratios indicate a ground water supply of continental origin in agreement with biological indicators which show large variations in salinity from fresh to marine like conditions the existence of a lacustrine phase radiocarbon dated to 17 40 ka as previously suggested for the northern sahara is highly questionable

mineralogical analysis of coals as an aid to seam correlation in the gloucester basin new south wales australia abstract quantitative mineralogical analysis using a rietveld based x ray diffraction method has been carried out on a succession of permian coal seams and associated strata in a small but structurally complex area of the gloucester basin new south wales to identify criteria that will assist stratigraphic correlation the coals are relatively rich in mineral matter which is dominated by quartz illite and interstratified illite smectite of detrital and pyroclastic origin however the mineral matter in the coals typically contains higher proportions of kaolinite and lesser proportions of illite than the associated noncoal strata suggesting at least some leaching and reprecipitation of aluminosilicates in the original peat swamp when considered on a quantitative basis several of the seams contain distinctive assemblages in their mineral matter that can assist recognition of the seams in subsurface studies these include an increased abundance of pyrite and feldspar in the marine influenced upper glenview seam an increased abundance of well ordered kaolinite in the upper bowens road seam and a higher proportion of quartz in the lower avon seam the roseville seam also contains measurable proportions of phosphate minerals which are not detected in the other coal beds used in conjunction with other factors quantitative mineralogical studies using xrd thus appear to be sufficiently sensitive to allow discrimination between individual seams in a sequence even though the coals contain an abundant overprint of detrital and pyroclastic mineral components

paleohydrology of southwestern texas current statistical methods may be unable to accurately predict recurrence intervals of rare large magnitude floods especially in semiarid regions having positively skewed annual flood distributions great hydrologic variability and widely spaced gaging stations current approaches rely on historical data but catastrophic floods may have recurrence intervals far greater than the length of historical records in the lower pecos and devils rivers of southwestern texas paleoflood discharge and frequency estimates are extended over 10 000 years by the study of slack water flood sediments slack water deposits are typically fine grained sand and silt that accumulate during floods in areas where current velocity is reduced i e in back flooded tributary mouths channel expansions downstream from bedrock spurs and or slump blocks and in shallow caves along bedrock walls radiocarbon dating of organic detritus in slack water deposits establishes the flood chronology while paleoflood discharges can be estimated by slope area techniques paleoflood information extracted from slack water sediments can greatly extend flood records these floods may be weighted like historical data in log pearson type 3 calculations of flood frequency our morphostratigraphic approach combines recorded data with geomorphic evidence to derive estimates of flood frequency this technique offers an inexpensive and rapid way to assess catastrophic flood risk

characterization and quantification of inorganic constituents of tropical peats and organic rich deposits from tasek bera peninsular malaysia implications for coals abstract since the carboniferous tropical latitudes have been the site of formation of many economic coal deposits most of which have a restricted range of mineralogical composition as a result of their depositional environment climatic conditions and diagenesis mineralogical and microscopic investigations of tropical peats from tasek bera peninsular malaysia were performed in order to better understand some of these factors controlling the nature distribution and association of inorganic matter in peat forming environments distribution and nature of the inorganic fraction of peat deposits give insight into the weathering conditions and detrital input into the mire system because the inorganic composition of peat deposits is determined by plant communities height of water table and climate the results of the quantitative and qualitative analysis can be used to reconstruct palaeoclimatic conditions tasek bera is a peat accumulating basin in humid tropical malaysia with organic deposits of low to high ash yield and thus representative of many ancient peat forming environments clay minerals dominate the mineralogical composition of the peat and organic rich sediments while quartz and clays dominate the underlying siliciclastic deposits kaolinite is the most abundant clay mineral in the organic deposits with minor amounts of illite and vermiculite particle size analyses indicate that 50 of the inorganic detrital fraction is 75 of the ash constituents as a consequence the vegetational communities make an important contribution to the inorganic and overall ash composition of peats and coals the ash content of the often inundated peat consists on average of 10 opaline silica from diatoms and sponge spicules while the ash of the top deposits may have up to 50 biogenic silica hence al and si hydroxides and the opaline silica from diatoms and sponges represent a large repository of al and si which may form the basis of mineral transformation neoformation and alteration processes during coalification of the peat deposits as a result most coal deposits from paleotropical environments are anticipated to have little to no biogenic inorganic material but high amounts of secondary clays such as kaolinite detrital kaolinite resilisified kaolinite or desilisified gibbsite or illite and various amounts of detrital and authigenetic quartz

determination of sediment provenance by unmixing the mineralogy of source area sediments the sedunmix program abstract along the margins of areas such as greenland and baffin bay sediment composition reflects a complex mixture of sources associated with the transport of sediment in sea ice icebergs melt water and turbidite plumes similar situations arise in many contexts associated with sediment transport and with the mixing of sediments from different source areas the question is can contributions from discrete sediment bedrock sources be distinguished in a mixed sediment by using mineralogy and if so how accurately to solve this problem four end member source sediments were mixed in various proportions to form eleven artificial mixtures two of the end member sediments are felsic and the other two have more mafic compositions end member and mixed sediment mineralogies were measured for the

digital rendering of sedimentary relief peels implications for clastic facies characterization and fluid flow abstract a new technique is presented for generating high resolution digital models of natural sedimentary deposits for quantitative analyses the traditional technique of 2d sedimentary relief peels of unconsolidated clastic deposits is combined with modern digital laser scanning and 3d microscopy techniques to represent spatially varying rock properties related to sedimentary fabrics at native resolution millimeter to meter scale peel topography relief is documented to correlate with changes in mean grain diameter and standard deviation so that the topography can be used as a proxy inferred for spatially varying rock properties related to grain sizes and sorting e g permeability threshold pressure to provide an applied example of the value of such investigation and to illustrate the influence that sedimentary structures can have on fluid migration peel topography is used to populate a threshold pressure 2d continuum for invasion percolation ip simulations ip is typically used for hydrocarbon migration and is being explored to investigate co2 migration in sequestration contexts simulation results for a 3 1 million cell model 0 5 0 25 m of a ripple laminated peel from a modern fluvial point bar suggest that sedimentary fabrics can strongly modify saturation via local capillary trapping the technique datasets and analysis presented are broadly applicable and expand quantitative characterization capabilities for a variety of geologic studies

mineralogy of lignites and associated strata in the mavropigi field of the ptolemais basin northern greece the mineralogy of five lignite layers and the associated roof floor and intercalating strata has been analysed using low temperature oxygen plasma ashing and quantitative x ray diffraction techniques the lignite contains quartz kaolinite illite and smectite and in some cases small proportions of feldspar thought to represent mainly detrital minerals in the original peat deposits one sample also contains crystalline calcium oxalates with weddellite present in the raw lignite and whewellite in the low temperature ash lta of the same lignite sample minor proportions of gypsum are present in some of the raw lignite samples possibly in part derived from precipitation of dissolved ca and so4 in the pore waters on drying all the ltas however contain much higher proportions of bassanite and or gypsum compared to the other minerals present consistent with production of calcium sulphate artefacts from interaction of abundant organically associated ca and s in the lignite during the plasma ashing procedure the inorganic strata are mainly carbonate rocks consisting almost entirely of calcite with minor aragonite small proportions of illite traces of pyrite and in some cases siderite some non carbonate rocks are also associated with the lignite seams these are dominated by plagioclase feldspar and mica along with illite kaolinite and a relatively minor proportion of quartz the mineral assemblages can be related to the palaeoenvironmental conditions under which the various sediments including lignite were deposited comparison of the mineral abundances in the samples to the chemical composition of the materials shows that the quantitative xrd technique provides results consistent with ash analysis data although abundant in the associated rocks calcite does not occur in the lignite samples while part of the relatively abundant ca in the lignite occurs as either gypsum or weddellite most of it appears to be organically bound mine products that incorporate calcareous rocks of the type associated with the lignite may however contain separate calcite phases and display high carbonate co2 contents

paleo environment and flooding of the limpopo river plain mozambique between c ad 1200 2000 multi proxy analysis was performed on a radiocarbon dated core collected from a relic oxbow lake in the limpopo river plain mozambique with the aim to reconstruct paleo environment and past flooding of the lower river system over the past c 800 years an additional objective was to evaluate and investigate the potential use of different proxies as recorders of paleo flooding events and paleo environmental variability within the floodplain the proxies applied in this study were mineral magnetic properties grain size distribution organic carbon content and diatom microfossil assemblages we found that sediment grain size and mineral magnetic properties of the minerogenic fraction were the most sensitive proxies in terms of detecting signals from high intensity river discharge events in the 800 year long sequence variations in sand content magnetic susceptibility and saturation isothermal remnant magnetization suggest at least four major flooding events at the site during the reconstructed period in the mid 1200 late 1300 mid 1500 ad and during the last century the diatom proxy reflects the development of the site from an open oxbow lake to a mainly terrestrial area the diatom assemblage indicates that open lake conditions prevailed at the site between c ad 1200 1400 with periodic inundation by marine water most likely due to late holocene sea level changes from c ad 1400 and onwards diatoms were rarely deposited at the site which indicates drier conditions this was a result of soil formation and gradual in filling of the lake a process which possibly was accentuated by a regionally dry climate situation our study shows that oxbow lakes and the proxies used here have great potential for reconstructing flooding events a knowledge that is crucial for potential prediction and mitigation of flooding events in mozambique in the future although chronological uncertainties limit comparisons to other paleo environmental records it seems that the flooding events recorded at our site occurred both during regionally wet and dry periods our data infer however that flooding was probably more clearly recorded during the lake stages than during infilled stage probably as the terrestrial environment was more exposed to erosion c 2014 elsevier b v all rights reserved less

provenance of silt and clay within sandy deposits of the lithuanian coastal zone baltic sea abstract mineralogical analysis of the silt and clay fraction of sandy deposits of 37 surface samples and grain size data are used to interpret sediment sources acting in the se baltic sea along the lithuanian coast mineralogical composition was determined using x ray diffraction xrd methods grain size distribution was obtained by standard dry sieving and pipette techniques for identification of sources we combined known compositional information of possible sources with logical models for mineral combinations related to regional geological provinces and processes supported by results of correlation and factor principal component analyses between minerals grain size parameters and bathymetric features of the area the main sources supplying sediment into the area are 1 the sambian peninsula to the south 2 the nemunas river whose discharge passes through the curonian lagoon and 3 late pleistocene till erosion on the sea floor in the north and at the olando kepure shore cliffs the general pattern of spatial distribution related to the identified sources for the fine grained sediment fraction is interpreted as a shore parallel transport of suspended matter flowing northwards in the southeastern part of the baltic sea

quantitative provenance of silt and clay within sandy deposits of the lithuanian coastal zone baltic sea abstract a quantitative provenance approach is developed and in this study applied for the silt and clay fractions of sandy coastal deposits mineralogical composition of 37 surface samples was determined by x ray diffraction xrd grain size distributions were obtained by standard dry sieving and pipette techniques the characterization of mineralogical provenance is based upon known compositional information of possible sources logical models for mineral combinations related to regional geological provinces and processes and geographical features of the documented mineral distribution in the area of investigation these interpretations are further supported by results of correlation and principal component analyses of mineral varieties grain size parameters and bathymetric features of the area partitioning of source contributions specific for each site of deposition is derived by solving simultaneous equations then the quantified mineral composition at the initial source is reconstructed in the se baltic sea along the lithuanian coast exemplifying this new methodology for quantification of sediment sources the main sources supplying sediment to the area are 1 sambian peninsula to the south erosion of pleistocene till and blue earth paleogene sediments supplying 33 of fine grained sediment on average 2 nemunas river the discharge of which passes through curonian lagoon and supplies an average 17 of the coastal fine sediments and 3 pleistocene till eroded on the sea floor in the north and at the olando kepur shore cliff and contributing an average of 50 of the sediment although we use the mineralogy within the environmentally important fine grained fraction this mathematically simple approach could be used with any other parameters characterizing the identified sources a quantification of the separate source contributions to each individual site of accumulation studied using the stable mineralogical components of the sediment archive offers a time integrated net effect reflection of the combined processes of an entire environmental system

reflections of the geological characteristics of cyprus in soil rare earth element patterns abstract rare earth elements rees are used as indicators or proxies for a range of geological and mineralogical processes due to their unique geochemical characteristics total and aqua regia extractable concentrations of rees and 57 other elements have been determined for 5350 soil samples as part of the high sampling density geochemical atlas of cyprus the bedrock geology of cyprus is dominated by the sequence of ultramafic to mafic units formed at a spreading ridge and subsequently obducted to form the troodos ophiolite to and the surrounding carbonate rich circum troodos sedimentary sequence ctss deposited in environments ranging from deep marine to sub aerial total and aqua regia extractable ree patterns are similar for each element and are largely controlled by parent lithology soil to rock ree ratios are generally elevated in the to units 4 for lrees and 1 5 3 for hrees due to loss of more mobile elements during weathering but are close to 1 in the ctss units hrees are more elevated than lrees in soils derived from to units with upper continental crust normalised patterns indicating the main source to be pyroxenes and zircon trace element trends indicate rees in the ctss were largely derived from detrital material shedding off the to and deposited in progressively shallowing basins under largely anoxic conditions absence of ce4 anomalies with a minor contribution from seawater via adsorption onto secondary fe mn oxides or co precipitation with carbonates heavy mineral associated elements such as zr and th display a relative consistent ratio in the ctss soils peak hree concentrations occur in the mafic cumulates and intrusives where the median laucc ybucc is 0 12 whereas in ctss units the lrees are more elevated with a median laucc ybucc 0 7 due to the strong lithogeochemical controls soil ree spatial patterns reflect even subtle mineralogical variations within the various to units the location of major transform faults and other structures and areas that have been affected by hydrothermal alteration

quantification of mineral matter in the argonne premium coals using interactive rietveld based x ray diffraction abstract the mineral matter in the eight reference north american coal samples of the argonne premium coal series has been investigated on a quantitative basis using x ray diffraction xrd techniques x ray diffraction data obtained from electronic low temperature oxygen plasma ash lta residues from ashes produced by heating the coals in air at 370 c and also from the raw coals themselves were evaluated using an interactive data processing system siroquant based on rietveld interpretation methods the results from the three types of material lta 370 c ash and raw coal were compared for each sample this allowed the components present in the raw coals in crystalline form to be recognised separately from mineral artifacts produced particularly in the low rank coals from interaction of organically associated elements ca s etc during the two ashing processes after the allowance for the production of any artifacts the quantitative mineral assemblages identified from xrd of the raw coals were found to be consistent even for coals having a relatively low ash percentage around 5 with the results obtained from the respective mineral concentrates prepared by the ashing methods the effects of heating the coal to 370 c could also be distinguished relative to the raw coal or the lta through changes in components such as pyrite and the clay minerals although some areas of uncertainty exist particularly with magnesium in the low rank coals the calculated chemical compositions of the coal ash derived from the mineral mixtures identified for each coal were also found to be consistent with the results of direct chemical analysis of the respective coal ash materials

tracking mercury from the mine to the power plant geochemistry of the manchester coal bed clay county kentucky abstract the high volatile a bituminous manchester coal bed was sampled at five mine sites in central clay county southeastern kentucky the coal bed has a high mercury concentration at certain sites particularly in the high sulfur uppermost lithology whole coal hg contents range up to 0 52 ppm in a sample with 3 36 pyritic sulfur hg is enriched in the upper lithotype at several of the sites arsenic content exceeds 700 ppm ash basis for all of the whole channel samples and exceeds 1000 ppm for several of the lithotype samples regional geochemical trends from an area of approximately 75 60 km were determined using data from this study in combination with data published by the u s geological survey hg as pb and cl contents exhibit highs in the northwestern portion of the region within the smaller area covered by the detailed mine study the two western sites both have a high sulfur upper lithotype containing high levels of as and hg basement structures previously described in the study area could have influenced the regional coal rank and geochemistry possibly acting as conduits for mineralizing fluids

quantitative models of sediment generation and provenance state of the art and future developments abstract an overview of quantitative approaches to analysis and modelling of sediment generation and provenance is presented with an emphasis on major framework components as determined by means of petrographic techniques conceptual models of sediment provenance are shown to be consistent with two classes of numerical statistical models i e linear mixing models and compositional linear models these cannot be placed within a common mathematical framework because the former requires that sediment composition is expressed in terms of proportions whereas the latter requires that sediment composition is expressed in terms of log ratios of proportions additivity of proportions a fundamental assumption in linear mixing models cannot be readily expressed in log ratio terms linear mixing models may be used to describe compositional variability in terms of physical and conceptual un mixing models of physical un mixing are appropriate for describing compositional variation within transport invariant subpopulations of grains as a result of varying rates of supply of detritus from multiple sources conceptual un mixing governs the relations among chemical mineralogical and petrographic characteristics of sediments which represent different descriptive levels within a compositional hierarchy compositional linear process models may be used to describe compositional and or textural evolution resulting from selective modifications induced by sediment transport as well as chemical and mechanical weathering current approaches to modelling of surface processes treat the coupled evolution of source areas and sedimentary basins in terms of bulk mass transfer only and do not take into account compositional and textural sediment properties moving from the inverse modelling approach embodied in provenance research to process based forward models of sediment generation which provide detailed predictions of sediment properties meets with considerable albeit not insurmountable problems strategies for developing more advanced parameterizations of sediment properties and for simulating their evolution are proposed and expansion of current data acquisition protocols is discussed in the light of data requirements for such advanced sediment generation models inclusion of sediment generation modules in models of landscape evolution and basin filling will mark a significant step towards full fledged source to sink simulations of earth surface processes

identification of potential for methane ignition by rock friction in australian coal mines abstract the relative propensity for the different rock types in australian underground coal mines to ignite methane bearing atmospheres by frictional contact either with mining equipment or with other rock materials has been evaluated by laboratory testing using an instrumented rotating wheel apparatus a five point incendivity categorisation has been developed for the rocks tested and the results compared to petrographic composition mineralogy and related chemical properties recent experience with ignitions in new south wales collieries has also been taken into account with the progressive decline in ignitions from other sources frictional effects are now the most common source of methane ignition in modern underground coal mines conglomerates lithic or quartzose sandstones with low clay and carbonate contents and siliceous cherty tuffs appear to represent the most potentially incendive materials in roof and floor strata along with siliceous or pyritic impregnations that may occur in the coal seam itself temperatures in excess of 1500 c may be developed within less than 1 s during rock on rock contacts with ignitions emanating from the contact point or related heat trail rather than from incandescent particles sparks ejected during the friction process the average temperature and the coefficient of dynamic friction developed during rock on rock testing also appear to be related to frictional incendivity characteristics

relief peels in the study of palaeoflood slack water sediments abstract the use of slack water sediments as palaeostage indicators in palaeoflood hydrological analysis requires detailed sedimentological description conventional descriptions have relied mainly on field descriptions of slack water profiles however this method often fails to reveal important detail by employing the well established technique of relief peels modified for use in slack water sediment studies the problem of insufficient data recovery from slack water deposits was successfully overcome during a palaeoflood hydrological investigation of south african rivers the use of relief peels showed that this technique is a useful and in some cases indispensable aid in the description and interpretation of palaeoflood deposits for example relief peels have shown that slack water sediments are for the most part not massive exhibiting mainly flat lamination this indicates that slack water sedimentation was characterised by moderate rates of deposition rather than sudden or rapid rates relief peels have also shown that the base of tributary back flooded slack water sediments often contain intraformational rip up clasts this indicates that reworking of the existing slack water sediments is a common process during tributary back flooding the technique was particularly effective in enhancing sedimentary structure and in differentiating between interpalaeoflood non palaeoflood and intraflood pulses relief peels can also be stored permanently as a surface sample of the slack water sequence to be retrieved for later study

the sediment stratigraphy of a flood event an example from the sabie river south africa abstract the geomorphic effects of river floods in various climatic settings worldwide have been extensively described but there is little information on sedimentary processes during and immediately following flood peaks here we reconstruct sedimentary processes and patterns of the 2012 flood on the sabie river in kruger national park south africa from the preserved geomorphic and sedimentary signature of this event based on a combination of geomorphic and sedimentary evidence the maximal and waning flow stages of the flood event are identified shown by cut and fill and fining up sequences within aggradational bars and organic horizons which may be buried that correspond to the period of flood peak recession the presence of organic horizons suggests a strongly seasonal flow regime typical of semi arid south african rivers it also provides an exemplar of a flood event stratigraphy that is usually poorly preserved in the geologic record

quantitative mineralogy of sandstones by x ray diffractometry and normative analysis abstract quantitative x ray diffraction normative calculation and whole rock chemical analysis have been compared for permo triassic quartz lithic to litho feldspathic sandstones from eastern australia the quantitative xrd technique provides mineralogical percentages that correlate well with the chemical composition of the sandstones and also with most of the mineral percentages derived from normative calculation the need for assumptions on potassium distribution between minerals provides a limitation on estimates of k feldspar and illite using the normative technique although these can be improved on a sample specific basis if necessary using complementary thin section observations or qualitative x ray diffractograms quantitative xrd analysis possibly indicates a small proportion of amorphous material in some of the sandstones especially materials with abundant lithic fragments or clay minerals but the proportion of any amorphous material overall is probably negligible both quantitative xrd and normative calculation avoid problems associated with sample heterogeneity or operator inconsistency that may affect point counting of thin sections they can also be used to provide quantitative information on sediments with abundant rock fragments or matrix components the actual mineralogy of which is not resolvable in conventional microscope investigations

the aftermath of the carnian carbonate platform demise a basinal perspective dolomites southern alps in the dolomites of northernmost italy the carbonate platform growth came to a standstill late in the early carnian late triassic the response to this shutdown of shallow water carbonate production in the interplatform basins is largely unknown because erosion has removed most of the soft basinal sediments giving rise to today s scenic landscape of the dolomites mapping in the central part of the dolomites and newly available core material has recently revealed a wellpreserved succession of basinal rocks within the heiligkreuz hospiz basin ital ospizio di santa croce basin in this paper the regional depositional nature of arrested carbonate platform production is reconstructed by tracing its sedimentological record across the slope and into the basin the uppermost st cassian formation the time equivalent basinal rocks to the prograding carbonate platforms is overlain by the heiligkreuz formation whose basal succession was deposited in a restricted and oxygen depleted environment immediately post dating the platform demise the succession consists mainly of mudrocks marlstones and peloidal packstones with abundant low diversity ostracod and pelecypod fauna and early diagenetic dolomite c and o isotope values of the basal heiligkreuz formation post dating platform demise average 2 ae4 and 2ae4 respectively and largely overlap the isotopic composition of st cassian carbonates a shift toward slightly lower d 13 c values in the heiligkreuz formation may reflect incorporation of isotopically depleted c released during bacterial sulphate reduction in the heiligkreuz sediments sedimentological palaeobiological and geochemical indices suggest that nearnormal marine conditions persisted long after the shutdown of shallow water carbonate platform growth although there are clear indications of severely reduced oxygen levels in the restricted heiligkreuz hospiz interplatform basin the early carnian platform demise induced a distinct switch in the locus of carbonate production from the shallow water platform and slope to the basin floor and a decrease in the availability of dissolved oxygen in the basinal waters it is inferred that anoxia extended at least temporarily to the top of the carbonate slope as indicated by the onlap of normal marine mounds by dark marlstones of the basal heiligkreuz formation

effects of igneous intrusions on thermal maturity of carbonaceous fluvial sediments a case study of the early cretaceous strzelecki group in west gippsland victoria australia abstract this study has investigated the effect of small igneous intrusions on early cretaceous carbonaceous fluvial sediments of the gippsland basin of south eastern australia based on outcrops in the onshore western part of the basin vitrinite reflectance measurements quantitative mineral phases and clay mineralogy were carried out on twenty two samples of organic rich mudstone up to 25 m east and west of a 1 m wide dyke samples of the dyke allowed classification as an alkali basalt based on its optical characteristics and major and trace element properties background vitrinite reflectance of 0 75 0 80 r max in the sediments is elevated up to 6 67 r max close to the dyke margin with slightly different patterns on each side of the intrusion analysis of seven selected organic rich mudstone samples shows that they all have very similar xrd patterns with the main minerals in all cases being quartz feldspar mainly plagioclase chlorite illite and interstratified illite smectite these observations suggest that the thermal maturity of the organic matter in the sediments was locally elevated by heating due to emplacement of the dyke but no significant changes were observed in host rock mineralogy that could be related to the heat generated by the dyke and the associated vitrinite reflectance variations

mineralogy and organic petrology of oil shales in the sangkarewang formation ombilin basin west sumatra indonesia abstract the ombilin basin is filled by late eocene to early oligocene marginal fan deposits brani formation and lacustrine shales sangkarewang formation unconformably overlain by a late oligocene to early miocene fluvial sequence sawahlunto and sawahtambang formations and capped by an early to mid miocene marine sequence ombilin formation significant oil shale deposits occur in the sangkarewang formation intercalated with thin laminated greenish grey calcareous sandstones x ray diffraction shows that the sediments consist mainly of quartz feldspar carbonates and a range of clay minerals together in some cases with minor proportions of sulphides evaporites and zeolites feldspar and non kaolinite clay minerals decrease up the sequence relative to kaolinite suggesting a changing sediment source as the basin was filled calcite thought to be mainly of authigenic origin is also more abundant in the middle and upper parts of the sequence the organic matter in the oil shales of the sequence is dominated by liptinite macerals particularly alginite mainly lamalginite and sporinite cutinite also occurs in some samples along with resinite and traces of bituminite the dominance of lamalginite in the liptinite components suggests that the material can be described as a lamosite samples from the sangkarewang formation have vitrinite reflectance values ranging between 0 37 and 0 55 these are markedly lower than the vitrinite reflectance for coal from the overlying sawahlunto formation 0 68 possibly due to suppression associated with the abundant liptinite in the oil shales fischer assay data on outcrop samples indicate that the oil yield is related to the organic carbon content correlations with xrd data show that with one exception the oil yield and organic carbon can also be correlated directly to the abundance of carbonate calcite and inversely to the abundance of quartz plus feldspar this suggests that the abundance of algal material in the lake sediments was preferentially associated with carbonate deposition high yields of oil are noted in some samples as a percentage of the organic carbon content this may indicate that partial generation of hydrocarbons from the material has already taken place in association with thermal maturation of the sangkarewang succession

use of mineralogical analysis in geotechnical assessment of rock strata for coal mining abstract the fundamental geotechnical properties of sedimentary rocks from the coal bearing sydney basin of new south wales australia including density porosity water absorption and moisture content as well as compressive strength have been related to the mineralogy of the materials as determined by quantitative x ray diffraction of powdered rock samples and processing by the rietveld based siroquant technique the results show for example that the overall proportions of clay minerals in the rocks as well as the types of clay minerals present affect properties such as water absorption and moisture content the presence of clay minerals also adds to the dry strength of silica cemented quartz sandstones however the strength of finer grained mudrocks is inversely related to the total percentage of clay minerals correlations have been established between the deterioration or slaking behaviour of mudrocks in water and their clay mineral content based on either simple immersion tests or on more sophisticated slake durability index determinations these relationships may be of significance in understanding the longer term behaviour of rock strata when exposed in different types of mining operations the propensity of different rocks to ignite methane in underground mines by frictional effects has also been shown to depend on the mineralogy of the rock materials whether determined by point counting of thin sections or by rietveld based xrd analysis abundant quartz feldspar and rock fragments in sandstones for example increase the likelihood of frictional ignitions whereas clay minerals and especially carbonates in the rock reduce the frictional ignition potential pyrite in the rocks if present also increases the ignition risk pyrite undergoes exothermic oxidation at high temperatures whereas other minerals respond by simple heating due to rock on rock or pick on rock friction processes