episodic fluid migration in the fennoscandian shield recorded by stable isotopes rare earth elements and fluid inclusions in fracture minerals at forsmark sweden abstract drilling through the palaeoproterozoic bedrock at forsmark central sweden during the site investigation for a potential geological repository of highly radioactive nuclear waste has provided high quality drill core material from the upper 1 km of the fennoscandian shield analyses of stable isotopes 13c 18o 34s 87sr 86sr rare earth elements and fluid inclusions in fracture filling calcite and pyrite from these drill cores have resulted in the discrimination of several episodes of fracture mineralisations these events represent migration of fluids during a wide range of conditions ranging from high temperature hydrothermal to present day groundwater circulation four major events have been distinguished 1 precipitation of epidote chlorite and quartz under hydrothermal conditions t 150 200 c during the proterozoic sometime between 1 8 and 1 1 ga 2 hydrothermal circulation at temperatures close to 200 c with precipitation of adularia albite prehnite laumontite calcite and chlorite most of these minerals precipitated during a tectonothermal event between 1 1 and 1 0 ga possibly in response to far field effects of the sveconorwegian orogeny 3 precipitation of mainly quartz calcite pyrite and asphaltite occurred during the palaeozoic at temperatures between 60 and 190 c mainly at

comparing clays from mars and earth implications for martian habitability griffithite from miocene volcanic and sedimentary rocks in griffith park los angeles is described by treiman et al in this issue this is a ferrian trioctahedral saponite with all the fe 3 in a distorted octahedral site it is a close analog of the saponite identified by mars science laboratory at gale crater the martian saponite is likely diagenetic rather than clastic and thus may represent the presence of a once habitable fluvio lacustrine environment on mars

alteration assemblages in the nakhlites variation with depth on mars secondary mineral assemblages in the nakhlite meteorites lafayette governador valadares gv nakhla yamato y 000593 y 000749 have been studied using scanning electron microscopy transmission electron microscopy and electron probe micro analysis the different nakhlites have distinctive secondary assemblages in their olivine grains and mesostases showing compositional fractionation correlated with their relative depths below the martian surface fracture filled veins in lafayette at the bottom of the pile consist of a siderite phyllosilicate fe oxide hydrated silicate gel assemblage corresponding veins in nakhla and gv further up the pile are predominantly a siderite gel assemblage with additional evaporites including gypsum y 000593 y 000749 veins are dominated by gel the gel s mg mg fe ratio decreases from lafayette 0 37 to gv 0 32 nakhla 0 24 and y 000593 0 15 we suggest that hydrothermal fluid flowed up this depth profile initiated by melting of buried h2o co2 ice our results show a complex mix of fe rich phyllosilicate within the veins and mesostasis of lafayette with d spacings of 0 7 1 1 nm suggesting a mixture of smectite and serpentine the phyllosilicate formed at close to neutral ph 150 c we also suggest that water rock ratios w r of 1 10 occurred in lafayette with smaller values for the other nakhlites this is reflected in the volume of alteration minerals 10 of olivine in lafayette to 3 in nakhla textural evidence of rapid cooling together with the w r and likely fluid velocities suggest that the secondary assemblages formed quickly e g within months a model is proposed in which the secondary assemblages formed in an impact induced hydrothermal system terminated by precipitation of the gel and evaporation of soluble salts

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

paleokarst in the lower ordovician beekmantown group ottawa embayment structural control inboard of the appalachian orogen two paleokarsts different in age character and origin occur in dolostones of the lower ordovician beekmantown group of eastern ontario well within the interior of the laurentian paleoplatform surficial to shallow subsurface p co 2 and h 2 s concentrations arising from mixing of continentally derived pore waters with brines derived from dissolution of beekmantown evaporites compared to the region9s geologic history a pre late paleozoic age for formation of the regional paleokarst and mineralization is likely the two platform interior paleokarsts demonstrate unexpected links between tectonism changes in paleohydrological patterns and porosity development well inboard of the appalachian orogen

ferrian saponite from the santa monica mountains california u s a earth characterization as an analog for clay minerals on mars with application to yellowknife bay in gale crater ferrian saponite from the eastern santa monica mountain near griffith park los angeles california was investigated as a mineralogical analog to smectites discovered on mars by the chemin x ray diffraction instrument onboard the mars science laboratory msl rover the martian clay minerals occur in sediment of basaltic composition and have 02 l diffraction bands peaking at 4 59 a consistent with tri octahedral smectites the griffith saponite occurs in basalts as pseudomorphs after olivine and mesostasis glass and as fillings of vesicles and cracks and has 02 l diffraction bands at that same position we obtained chemical compositions by electron microprobe x ray diffraction patterns with a lab version of the chemin instrument mossbauer spectra and visible and near ir reflectance vnir spectra on several samples from that locality the griffith saponite is magnesian mg mg fe 65 70 lacks tetrahedral fe 3 and octahedral al 3 and has fe 3 fe from 64 to 93 its chemical composition is consistent with a fully tri octahedral smectite but the abundance of fe 3 gives a nominal excess charge of 1 to 2 per formula unit the excess charge is likely compensated by substitution of o 2 for oh causing distortion of octahedral sites as inferred from mossbauer spectra we hypothesize that the griffith saponite was initially deposited with all its iron as fe 2 and was oxidized later x ray diffraction shows a sharp 001 peak at 15 a 00 l peaks and a 02 l diffraction band at the same position 4 59 a and shape as those of the martian samples indicating that the martian saponite is not fully oxidized vnir spectra of the griffith saponite show distinct absorptions at 1 40 1 90 2 30 2 32 and 2 40 m arising from h 2 o and hydroxyl groups in various settings the position of the 2 31 m spectral feature varies systematically with the redox state of the octahedrally coordinated fe this correlation may permit surface oxidation state to be inferred in some cases from vnir spectra of mars obtained from orbit and in any case ferrian saponite is a viable assignment for spectral detections in the range 2 30 2 32 m

multi tracer and hydrogeophysical investigation of the hydraulic connectivity between coal seam gas formations shallow groundwater and stream network in a faulted sedimentary basin abstract characterization of geological fault networks in sedimentary basins targeted for coal seam gas development typically use deep penetrating seismic data such methods can reveal the presence of numerous fault zones at depths greater than 100 m but not necessarily show if these extend to the surface or provide a significant degree of hydraulic connectivity between deep and shallower geological formations our combined multi tracer and hydrogeophysical study used transient electromagnetic surveys to image the subsurface in a sedimentary coal seam gas basin gloucester basin nsw australia and indicated that deep faults greater than 200 m from seismic analysis may extend to within metres of the ground surface analysis of environmental tracers in surface water and groundwater samples near fault traces showed the presence of hotspots of deeper groundwater from the coal seams discharging into the stream network via the alluvial aquifer the isotopic composition of methane was extremely variable in groundwater 13c ch4 from 81 6 to 29 2 v pdb and surface water 13c ch4 from 56 0 to 19 9 v pdb suggesting several sources of methane being recycled in the connected alluvial aquifer and stream network a 4he hotspot 1 67 10 6 cm3 stp g 1 in the alluvial aquifer close to a fault line showed high methane 463 g l 1 with a thermogenic signature 13c ch4 of 62 4 and 2h ch4 of 174 7 the gloucester basin which has experienced multiple episodes of complex restructuring displays high dilation tendency of fractures close to fault damage zones with fracture orientations parallel to the orientation of maximum horizontal stress as a result there is increased permeability for wells close to the fault damage zone and with increasing depth these findings resulted in a robust hydrogeological conceptual model of a faulted basin which can be used in a monitoring and modelling framework for improved evaluation of risk associated with unconventional gas developments

the mode of occurrence and origin of minerals in the early permian high rank coals of the jimunai depression xinjiang uygur autonomous region nw china abstract this paper investigates the mineralogy of coal and non coal samples from the haerjiao exploration area in the jimunai depression xinjiang uygur autonomous region northwestern china using x ray diffraction xrd optical microscopy and scanning electron microscopy with an energy dispersive x ray spectrometer sem edx the minerals in the anthracite proximal to the igneous intrusions are represented by the occurrence of chlorite muscovite and illite which are absent in the semianthracite distal to the igneous intrusions kaolinite the dominant mineral in the semianthracite decreases in abundance or even disappears in the anthracite muscovite and illite in the anthracite are interpreted to result from the alteration of the kaolinite precursor and possibly formed by the interaction of kaolinite and elements e g k fe and mg from igneous hydrothermal solutions the formation of chlorite is the result of the transformation of kaolinite due to the interaction of kaolinite with fe mg rich solutions during the diagenetic stage and the direct epigenetic precipitation from fe mg rich igneous siliceous hydrothermal fluids calcite ankerite and sulfide minerals resulted from epigenetic precipitation from hydrothermal fluids cleat fracture mineralization indicates that the fe mg rich hydrothermal fluid from which chlorite precipitated was introduced earlier than the ca rich fluid from which calcite precipitated the injection of hydrothermal solutions that formed sulfide minerals occurred at the latest stage

maturation thermique des roches meres dans les bassins des basses terres du saint laurent et dans quelques buttes temoins au sud est du bouclier canadien caradocian source rocks belonging to the utica group occur around and overlay the southeastern part of the canadian shield from the ottawa embayment in the southwestern part of st lawrence lowlands to the anticosti island basin the kerogen of the source rocks is mainly made up of amorphous organic matter transmitted light resembling a solid bitumen framework in reflected light and contains a small portion of zooclasts graptolites and chitinozoans the kerogen is often too mature to have preserved the structure of the original constituents except those of graptolites and chitinozoans otherwise uv fluorescent colonial alga and tasmanites are observed in the eastern half of the st lawrence lowlands stratigraphic and tectonic burial is the main control of source rock thermal maturation from an area located 50 km west of quebec city the estimated vitrinite reflectance ro std of the source rock increases in both northeastern montmorency falls and southwestern st maurice river directions from ro std of 1 2 to 1 5 and 1 7 respectively the source rocks of the ottawa embayment and montreal area western half of the basin are overmature due to hydrothermal and igneous activities 2 3 ro std 2 8 in chicoutimi and lac saint jean outliers the source rocks show reflectances between 0 9 and 1 2 slightly less than reflectance values in the quebec city area ro std between 1 2 and 1 5 on anticosti island the thermal maturation is related to burial only and increases downdip of the inclined platform from the northeast toward the southwest ro std between 0 9 and 2 1 these observations suggest that the st lawrence platform and the southeastern canadian shield were buried by at least 3 5 km of paleozoic strata prior to erosion to grenville basement this implies that most potential hydrocarbon fields are presumably also lost by erosion

oxygen and carbon isotopic composition of ordovician brachiopods implications for coeval seawater one hundred and two articulate brachiopods and twenty one marine cements from ordovician strata were analyzed for oxygen and carbon isotopes these together with 200 previously published analyses of ordovician brachiopods mostly of upper ordovician age define a general trend of increasing 18o values with decreasing age from a minimum of 10 5 in the earliest ordovician to a maximum of 1 5 at the ordovician silurian boundary the 13c values show a general positive correlation with 18o and increase from 2 5 in the earliest ordovician to as high as 7 at the ordovician silurian boundary the magnitudes of ordovician excursions for both 18o and 13c are similar to those reported previously for the entire phanerozoic different genera of brachiopods from the same stratigraphie level did not yield any large differences in their isotopic compositions suggesting that vital effects did not influence decisively the isotope values of the studied skeletal parts petrographic examination and trace element analyses indicate that brachiopod shells from llandeilo to ashgill strata are well preserved and thus may have retained their primary isotopic signatures the same criteria for the tremadoc arenig and some llanvirn brachiopods suggest partial diagenetic alteration of 18o values in these samples but this does not preclude their utility as a recorder of a primary 13c signal the observed 18o trend for the well preserved portion of the record may reflect progressive cooling during ordovician perhaps complemented by a changing 18o values of seawater the latter could have been a consequence of a net increase in the rate of high temperature water rock interaction relative to its low temperature counterpart as indicated also by the large coeval decrease of marine 87sr86sr superimposed on the above long term 18o trend is a positive excursion of about 2 at the end of the ordovician probably reflecting a large expansion of polar ice caps the magnitude of this excursion indicates a degree of glaciation comparable to that at the height of the quaternary glacial episodes the secular 13c trend may reflect a progressive increase in marine organic productivity and or enhanced organic deposition in the ordovician oceans particularly noticeable at the time of the terminal ordovician glaciation

evolution of a lower paleozoic continental margin carbonate platform northern canadian appalachians the western margin of the northern appalachian orogene and adjacent craton is composed of a lower paleozoic low latitude carbonate platform which originally lay along the northern margin of iapetus ocean parts of the platform interior are now exposed in quebec much lies beneath the gulf of st lawrence and the outer shelf and deep water deposits crop out in western newfoundland the shelf break and upper slope are nowhere exposed but their nature has been determined from numerous clasts in sediment gravity flows redeposited on the lower slope and now stacked in allochthonous thrust complexes four separate phases recording platform growth and demise can be differentiated reflecting the interplay between tectonics eustasy and the evolving lower paleozoic biota phase 1 preplatform shelf reflects initial siliciclastic deposition on rifted crystalline basement followed by a short phase of carbonate sedimentation dominated by archeocyathan buildups and ooid shoals that was terminated by offlap of thick quartzarenites phase 2 narrow high energy platform is characterized by mixed siliciclastic carbonate peritidal sedimentation throughout manifest as three grand cycles contemporaneous deep water sediments comprise basal welded conglomerates overlain by quartzose carbonate turbidites phase 3 wide low energy platform is an onlap package of muddy fossiliferous subtidal and peritidal carbonates arranged inmore the form of two unconformity bounded megacycles the adjacent deep water slope was a narrow belt of debris flows and wide carbonate shale apron deposited in the lower part of an oxygen minimum zone phase 4 foundered platform documents the initial uplift faulting subsidence and fragmentation of the platform in a sequence of peritidal to subtidal to deep water carbonates reflecting the initial stages of the taconic orogeny less

hydrothermal fluids during mesozoic reactivation of the st lawrence rift system canada c o sr and pb isotopic characterization calcite veins with accessory galena sphalerite barite and fluorite are abundant within the ottawa bonnechere and the charlevoix saguenay failed arms of the st lawrence rift system which developed during early paleozoic times within gneisses of the grenville province of canada the mineral assemblages paragenesis and precipitation temperatures of the veins resemble the mississippi valley deposits crosscutting relationships with carbonate rocks of the st lawrence lowlands and deformed carbonate rock slivers of the charlevoix astrobleme show that the ottawa graben and saguenay graben veins are younger than mid ordovician or post devonian respectively 18o and 13c values for vein calcite are positively correlated and range from 11 to 24 and 9 to 3 respectively 87sr86sr in calcite and barite range from 0 7129 to 0 7081 the fluids that precipitated calcite were part of a hydrothermal system dominated by meteoric water enriched in 18o by exchange with silicate minerals and deep seated carbon either from mantle outgassing deep seated brines of the canadian shield or from oxidation of reduced carbon in high grade metamorphic rocks veins cutting marbles of the grenville supergroup have lower 87sr86sr and higher 18o and 13c values than those hosted in quartzofeldspathic gneisses of the grenville province showing that the fluids were modified by interaction at depth with the marbles stable and sr isotope compositions are also correlated with layb ratios in calcite supporting the fact that the veins formed within similar hydrothermal systems in both the ottawa and saguenay grabens the pb isotopic compositions of vein galena are radiogenic 206pb204pb 18 0 19 7 207pb204pb 15 5 15 7 208pb204pb 37 9 41 0 and positively correlated in conventional pb pb diagrams pb isotope and ree data strongly suggest that the fluids leached selectively at the mineral scale gneisses of the grenville province the basinal fluids within the shelf sequence of the western appalachians had 208pb204pb ratios in the lower paleozoic significantly lower than those of vein galena this excludes the basin brine model of formation for the vein deposits like suggested for the mississippi valley deposits the veins rather formed in the mesozoic in response to the rifting of northeastern north america and the reactivation of the st lawrence rift

gas reservoir potential of the lower ordovician beekmantown group quebec lowlands canada the beekmantown group in the quebec lowlands was deposited as part of an extensive early ordovician coastal and shallow marine complex on the eastern margin of the north american craton the beekmantown is stratigraphically equivalent to the beekmantown knox arbuckle and ellenburger rocks of the united states and is subdivided into two formations the sandstone rich theresa formation and the overlying dolomite rich beauharnois dolomites of the beekmantown provide an important exploration target in both the autochthon and the overlying thrust sheets of the canadian and u s appalachians the reservoir potential of the autochthonous beekmantown group in the quebec lowlands can be determined from seismic data well logs cuttings and petrographic analyses of depositional and diagenetic textures deposition of the beekmantown occurred along the western passive margin of the iapetus ocean by the late ordovician the passive margin had been transformed into a foreland basin faulting locally positioned upper ordovician utica source rocks against the beekmantown and contributed to forming hydrocarbon reservoirs the largest beekmantown reservoir found to date is the st flavien field with 7 75 bcf of original gas methane in place in fractured and possibly karst influenced allochthonous dolomites within a thrust fault anticline the beekmantown below the thrust sheets forms a northward thinning wedge of peritidal and subtidal deposits seven major depositional units can be distinguished in cuttings and correlated with wireline logs most of these units form northward thinning sediment wedges and were deposited on a gently dipping ramp quartz sandstones dominate updip whereas shallow subtidal pelletal to skeletal limestones dominate downdip a widespread blanket of shaly dolomite is the uppermost unit of the beekmantown but is of poor reservoir quality dolomites in the beekmantown contain vuggy moldic intercrystalline and fracture porosity early porosity formed at the top of the major depositional units in peritidal dolomites however much of this porosity was later filled by late stage calcite cement after hydrocarbon migration thus a key to finding gas reservoirs in the autochthonous beekmantown is to define ordovician paleostructures in which early and continuous entrapment of hydrocarbons prevented later cementation

petrology and potential tectonic significance of a k bentonite in a taconian shale basin eastern ontario canada northern appalachians a 6 cm thick k bentonite herein defined as the russell bed occurs in an upper ordovician deep basin shale succession in eastern ontario canada forming part of the distal taconic foreland in eastern north america the bed lies within the pygmaeus graptolite biozone which is about 451 to 452 ma in age although some bentonites are reported from this interval in eastern north america we are reporting the first set of compositional data for a bentonite of this age gamma log correlation identifies a potential minimum distribution area of 5 km 2 for the k bentonite covering part of southern quebec new york state and eastern ontario the deposit coincides with the first influx of distal turbdites into this shale basin associated with taconic flysch and simultaneous abrupt ventilation of the once anoxic deep water basin which had formed initially after foundering of the upper ordovician carbonate platform concurrent intrabasinal extinction of several graptolite species suggests that change in sedimentation palaeoceanography and volcanism were linked to a regional external process compositionally the bentonite is distinct from the older ordovician platform deposits in eastern north america the deposit contains abundant titaniferous phlogopite with 1 6 bao fluoroapatite with 2 5 f and dynamically shaped glass spherules now altered to clay the spherules and clay matrix constitute 45 of the bed and compositionally define an illite 90 smectite i s structure with about 7 5 k 2 o age dating by ar ar analysis of the phlogopite crystals yielded a younger than expected 440 445 ma age this difference along with evidence of localized chloritization of phlogopite likely reflects known post ordovician hydrothermal activity within the basin on the basis of several geochemical proxies the magmatic source of the russell k bentonite falls within the trachyandesite field and was ba enriched comparison of geochemistry and mineralogy with older middle to late ordovician and younger early silurian k bentonites within the taconic orogen along eastern laurentia and baltica reveals that the potential source magma for the russell bed was more mafic more alkaline and less fractionated than sources typical of older platform bentonites instead it is more similar to the younger llandovery bentonites of scandinavia and scotland it remains uncertain if it signals local or regional compositional change in volcanic source in the northern appalachians

isotopic composition of disseminated sulfur in precambrian sedimentary rocks abstract isotopic analyses of trace sulfur in precambrian carbonates and clastic sedimentary rocks support the results of previous studies which have shown that 34s measurements of archean sedimentary sulfur cluster mostly around mantle like values and that a significant overall dispersion of 34 s 32 s ratios commenced at about 2 7 ga ago the outstanding feature of the proterozoic record is the predominance of heavy 34ssulfide values mostly in excess of 0 cdm consideration of these data in combination with the sparse 534s record for proterozoic sulfates suggests that 34ssulfide sulfide may have been smaller than was the case during the phanerozoic a possible scenario that is compatible with the above data is based on a proposition that the terrestrial exogenic sulfur cycle evolved in a tripartite manner in the archean it was coupled to and controlled by the magmatic endogenic cycle the proterozoic for the most part represents a transitional stage into a phanerozoic like exogenic cycle the latter essentially decoupled from its endogenic counterpart and its redox balance maintained and mediated by the biosphere the indication that the mean combined 34s of proterozoic sulfate and sulfide may have significantly exceeded the phanerozoic mean value of 2 cdm is enigmatic and poses problems for balance considerations

trace metal distribution and isotope variations in low temperature calcite and groundwater in granitoid fractures down to 1 km depth abstract studies of low temperature fracture calcite in proterozoic or archaean crystalline rocks are very limited mainly because this calcite usually is first not very abundant and second very fine grained or forms rims on older and much more abundant hydrothermal calcite and is thus difficult to distinguish knowledge of chemical characteristics and the correlation with groundwater chemistry is thus scarce for low temperature calcite in these settings and consequently knowledge of the recent palaeohydrogeological history is limited boreholes drilled with triple tube technique in the upper 1 km of the palaeoproterozoic crystalline crust at laxemar se sweden have enabled preservation of fragile and potentially recently formed fracture minerals earlier investigations of these boreholes have resulted in an extensive set of groundwater chemistry data from various depths and in detailed knowledge of the fracture mineral assemblages ranging from 1 8 ga to present this has made it possible to identify and sample low temperature potentially recently formed calcite from water flowing fractures for which representative groundwater chemical data exists this in turn provides an opportunity to detailed comparisons of fracture calcite age span in the order of million years with possibility of post glacial contributes and groundwater age in the order of decades to more than a million year depending on depth in terms of both isotopic and geochemical properties giving input to the understanding of groundwater history partition coefficients derived in laboratory experiment and reliability of calcite geochemistry in terms of representing the actual source fluid composition in this study the focus is on trace elements fe mg mn and sr stable isotopes and sr isotopes and for the groundwater data set also aquatic speciation with visual minteq an optimised step by step sample specific analytical procedure was used for the collection of calcite coatings the methods used depended on the crystal homogeneity one or several calcite generations discerned by detailed sem investigations back scatter and cathodo luminescence 87sr 86sr ratios as well as 18o signatures in calcite are in the range expected for the precipitates from present day groundwater or older groundwater with similar composition except in sections with a considerable portion of glacial water where calcite definitely is older than the latest glaciation stable carbon isotopes in calcite generally show values typically associated with hco 3 originating from soil organic matter but at intermediate depth frequently with hco 3 originating from in situ microbial anaerobic oxidation of methane highly depleted 13c for one of the studied metals manganese there was a strong correlation between the sampled calcite coatings and hypothetical calcite predicted by applying laboratory based partition coefficients literature data on groundwater chemistry for sections corresponding to those where the calcites were sampled this points to temporal and spatial stability in groundwater mn ca ratios over millions of years or even more and show that it is possible to assess based on laboratory derived data on mn partitioning past groundwater mn composition from fracture calcites for other metals fe sr and mg which are expected to interact with co precipitating minerals to a higher degree than mn the correlations between measured and predicted calcite were weaker for various reasons

quantitative evaluation of minerals in coal deposits in the witbank and highveld coalfields and the potential impact on acid mine drainage abstract this study has investigated the quantitative distribution of minerals in coals and other lithological units in the coal bearing successions of the witbank and highveld coalfields in the mpumalanga province of south africa using low temperature oxygen plasma ashing lta high temperature ashing x ray diffraction and x ray fluorescence spectrometry techniques mineral matter makes up approximately 8 to 35 wt of the coal samples sio 2 concentrations in the coal vary between 0 0 and 35 0 wt al 2 o 3 between 0 5 and 16 0 wt fe 2 o 3 between 0 03 and 10 0 wt and s between 0 15 and 8 0 wt minor concentrations of cao 0 0 to 8 0 wt and mgo 0 0 to 1 0 wt are also present p 2 o 5 occurs in concentrations of 0 0 to 3 5 wt and k 2 o is in the order of 0 0 to 1 3 wt na 2 o varies between 0 0 and 0 45 wt with the highveld coals showing an enrichment in na 2 o 0 0 to 0 51 wt in comparison with the witbank coals the minerals in the coals are dominated by quartz and kaolinite with varying proportions of calcite dolomite and pyrite as well as accessory phosphate phases higher normalised k 2 o and na 2 o concentrations are present in the sandstones than in the associated siltstones and carbonaceous shales partly reflecting the presence of feldspars and clay minerals such as illite acid base accounting was used to investigate the potential of the coal and coal bearing units to produce acid mine drainage conditions according to the screening criteria all the coal and coal bearing units except the unit between the no 1 and no 2 coal seams are potentially acid generating the average net neutralising potential nnp values suggest that the no 5 coal seam the no 4 upper coal seam and the unit between the no 4 and no 2 coal seams are potentially acid generating with such techniques it is possible to predict the types of situations that might arise concerning groundwater quality and implement proper prevention or remediation programs

sulfate in brines in the crystalline rocks of the canadian shield abstract deep groundwaters in crystalline rocks typically are very saline and are characterized by a rather unique ca na cl dominated chemistry sulfate is present in variable amounts and may be linked to both the geochemical evolution of these fluids as well as to recent processes initiated through mining activities it is possible to distinguish on the basis of isotopic compositions between brine sulfate and secondary sulfate formed by oxidation of sulfides the latter is characterized by 34 s values which reflect the local mineral sulfide precursor and 18 o close to or below 0 smow the isotopic composition of the brine sulfate is characterized by 18 o and 34 s values which resemble marine isotopic compositions at some localities at others they could be explained as being of magmatic hydrothermal origin it is likely that the sulfate participated in the geochemical evolution of these brines thus its isotopic composition reflects geochemical processes rather than a primary origin no evidence for the influence of bacterial reduction was found

high resolution seismic reflection profiling of neotectonic faults in lake timiskaming timiskaming graben ontario quebec canada the timiskaming graben is a 400 km long 50 km wide north west trending morphotectonic depression within the canadian shield of eastern north america and experiences frequent intraplate earthquakes the graben extends along the border of ontario and quebec connecting southward with the nipissing and ottawa bonnechere grabens and the st lawrence rift system which includes a similar structure underlying the hudson valley of the eastern usa together they form a complex failed rift system related to regional extension of north american crust during the breakup of rodinia and later pangea the timiskaming graben lies within a belt of heightened seismic activity western quebec seismic zone with frequent moderate magnitude greater than magnitude 5 earthquakes including a magnitude 6 2 in 1935 these events threaten aging urban infrastructure built on soft glacial sediments post glacial landslides along the ottawa valley suggest earthquakes as large as magnitude 7 the inner part of the timiskaming graben is filled by lake timiskaming a large 110 km long post glacial successor to glacial lake barlow that was ponded by the laurentide ice sheet 9500 years ago the effects of frequent ground shaking on lake floor sediments was assessed by collecting more than 1000 line kilometres of high resolution chirp seismic profiles late glacial lake barlow glaciolacustrine and overlying post glacial sediments are extensively deformed by extensional faults that define prominent horsts and grabens multibeam bathymetry data suggest that faults influence the morphology of the modern lake floor despite high sedimentation rates and indicate recent neotectonic deformation the lake timiskaming area provides evidence of post glacial intracratonic faulting related to recurring earthquake activity along a weak spot within the north american plate

age of the grenville dyke swarm ontario quebec implications for the timing of lapetan rifting u pb baddeleyite and zircon ages for three diabase dykes from widely spaced localities within the grenville dyke swarm indicate a single age of emplacement at ma the 700 km long grenville dyke swarm located in the southeastern part of the canadian shield was emplaced syntectonically with the development of the ottawa graben this graben may represent a plume generated lapetan failed arm that developed at the onset of the breakup of laurentia other precisely dated lapetan rift related units such as the callander alkaline complex and the tibbit hill formation volcanic rocks indicate a protracted 36 ma period of rifting and magmatism prior to volcanism along this segment of the lapetan margin the age of the grenville dykes is the youngest in a progression of precisely dated mafic magmatic events from the 723 ma franklin dykes and sills to the 615 ma long range dykes along the northern and northeastern margins of laurentia respectively thus the age for these dykes represents a key time marker for

low temperature sulphate reduction biological versus abiological sulphate is considered to have been a major source of sulphide in strata bound and stratiform base metal sulphide deposits many of these deposits however appear to have been formed at moderate temperatures 200 c which poses the question by what mechanism s was sulphate reduced to sulphide two modes of reduction have been established experimentally 1 catalysis by sulphate reducing bacteria which at present is only known to occur below ca 100 c and 2 abiological reduction by ferrous iron or organic matter which has only been clearly shown above ca 250 c several attempts have been made to demonstrate abiological reduction below 200 c and some new data are presented here although the results do not exclude the possibility that such a reaction may be geochemically significant there has been no unequivocal demonstration of nett sulphide formation from sulphate at these temperatures recent studies of the microbiology of hydrothermal regions have opened up the prospect of bacterial sulp

ferric saponite and serpentine in the nakhlite martian meteorites abstract transmission electron microscopy and fe k x ray absorption spectroscopy have been used to determine structure and ferric content of the secondary phase mineral assemblages in the nakhlite martian meteorites nwa 998 lafayette nakhla gv y 000593 y 000749 mil 03346 nwa 817 and nwa 5790 the secondary phases are a rapidly cooled metastable assemblage that has preserved mg and ca fractionation related to distance from the fluid source for most of the nakhlites though one nwa 5790 appears not to have experienced a fluid pathway all nine nakhlite samples have also been analysed with scanning electron microscopy electron probe micro analysis bright field high resolution transmission electron microscopy hrtem and selected area electron diffraction by measuring the energy position of the fe k xanes 1 s 3 d pre edge transition centroid we calculate the ferric content of the minerals within the nakhlite meteorites the crystalline phyllosilicates and amorphous silicate of the hydrothermal deposits filling the olivine fractures are found to have variable fe 3 fe values ranging from 0 4 to 0 9 in lafayette the central silicate gel parts of the veins are more ferric than the phyllosilicates around it showing that the fluid became increasingly oxidised the mesostasis of lafayette and nwa 817 also have phyllosilicate which have a higher ferric content than the olivine fracture deposits with fe 3 fe values of up to 1 0 further study via tem analyses reveal the lafayette and nwa 817 olivine phyllosilicates to have 2 1 t o t lattice structure with a the d 001 spacing of 0 96 nm whereas the lafayette mesostasis phyllosilicates have 1 1 t o structure with d 001 spacings of 0 7 nm based on our analyses the phyllosilicate found within the lafayette olivine fractures is trioctahedral ferric saponite ca 0 2 k 0 1 0 3 mg 2 6 fe 2 1 3 fe 3 1 7 mn 0 1 5 7 si 6 7 al iv 0 9 fe 3 0 4 8 0 o 20 oh 4 n h 2 o and that found in the mesostasis fractures is an fe serpentine ca 0 1 mg 0 7 fe 3 1 0 al vi 0 4 2 2 si 2 o 5 oh 4 with a ferric gel of similar composition in lafayette and found as fracture fills throughout the other nakhlites

genesis and controls of hydrothermal dolomitization in sandstones of the appalachian thrust belt quebec canada implications for associated galena barite mineralization abstract the appalachian thrust belt of eastern quebec hosts six epigenetic barite galena sphalerite occurrences in interdigitated carbonate cemented sandstones carbonate clast bearing conglomerates and minor siltstones of the upper cambrian st damase formation two of these the st fabien and cap enrage deposits consist of veins and disseminations enveloped by dolomitized zones and contain ankerite as an essential gangue mineral in contrast the other occurrences consist exclusively of calcite cemented veins and are conspicuously devoid of dolomite the domains of the st fabien and cap enrage deposits are intensely fractured and contain abundant dolomite barite sulfide cemented interconnected fractures and pores whereas those of the other occurrences display relatively minor fractures and pores which are only rarely interconnected this difference in porosity leads to the conclusion that differences in paleo permeability were the most likely reasons for the presence of dolomite and disseminated mineralization in the two deposits and their absence from the vein only occurrences mass balance calculations relating altered and unaltered rock suggest that dolomitization was accompanied by large gains of cao mgo and co 2 and corresponding losses of sio 2 and k 2 o under conditions of constant volume the mass of silica removed from the altered sandstone at st fabien 14 5 g per 100 g of rock when considered in the context of quartz solubility implies a minimum water rock ratio of 2635 a similar value 2500 is indicated by the content of lead of a representative sample of the st fabien deposit and typical concentrations of lead in mississippi valley type fluids the ph of the mineralizing dolomitizing fluid was calculated from the solubility of dolomite and fluid inclusion estimates of m ca 2 m mg 2 and m co 2 to be between 3 9 and 4 6 fluid inclusion data suggest that dolomitization and mineralization at st fabien and cap enrage were the products of interactions between local sedimentary rocks and minor metabasaltic dikes with hydrothermal brines detailed x ray diffraction analysis of the phyllosilicates in the host rocks in and around the st fabien deposit mainly sandstones and minor metabasalt indicates that these brines could have acquired virtually all magnesium and all iron manganese needed for dolomite precipitation as a result of the replacement of chlorite by illite since p t conditions during deposition of the two types of mineralization were similar to each other it is concluded that these conditions did not govern the formation of dolomite

carbonate hosted shallow submarine and burial hydrothermal mineralization in the upper mississippian big cove formation port au port peninsula western newfoundland strata bound sulfide zn pb fe and sulfate ba sr mineralization occurs in upper mississippian arundian holkerian limestone primarily bryozoan microbial mounds of the big cove formation on the port au port peninsula western newfoundland stages of host rock petrogenesis and mineralization are compared by integrating structure stratigraphy petrography and geochemistry fluid inclusions and c o s sr and pb isotopes strata bound mineralization is linked to fault controlled fluid flow through ordovician basement carbonate and into porous mississippian host rock with subsequent fluid migration bounded by stratigraphic permeability barriers mineralization is preferentially juxtaposed to deposits of mississippian gypsum the most likely source of sulfate the 87 s 86 sr ratios in calcite associated with mineralization suggest that fluids were most likely generated from or had undergone isotopic exchange with lower paleozoic strata including potentially metalliferous shale the integrated database underscores a potentially rapid mineralizing system of late mississippian 343 330 ma age evidence for isotopic exchange brings a permo pennsylvanian 250 300 ma age derived from lead isotope modeling into question minor syndepositional mineralization is characterized by fe oxide stained omission surfaces within well oxidized hyposaline lithofacies possibly documenting incipient hydrothermal activity and subsequent marcasite mineralization related to introduction of hydrothermal 60 degrees 120 degrees c brines into a very restricted hyposaline or lacustrine setting during faulting prominent zn pb sulfides sphalerite galena and subsequent ba sr sulfates barite celestite with intergrown marcasite and calcite have a shallow burial 30 m origin fluids were variably hot 110 degrees 190 degrees c mg poor brines 20 25 wt nacl equiv pyrite gossans mark a last stage of mineralization the delta 34 s values increase with the general successon of sulfide 4 to 12ppm sulfate 20 32ppm and then pyrite 32ppm mineralization similar to a rayleigh distillation process in a closed mineralizing system mineralization on the port au port peninsula is similar to mississippian hosted irish zn pb deposits there is an association with normal faults prominent epigenetic mineralization and a similar age this commonality may reflect late mississippian tectonic instability within the paleohemispheric fault system that linked eastern canada and ireland

a habitable fluvio lacustrine environment at yellowknife bay gale crater mars the curiosity rover discovered fine grained sedimentary rocks which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy this aqueous environment was characterized by neutral ph low salinity and variable redox states of both iron and sulfur species carbon hydrogen oxygen sulfur nitrogen and phosphorus were measured directly as key biogenic elements by inference phosphorus is assumed to have been available the environment probably had a minimum duration of hundreds to tens of thousands of years these results highlight the biological viability of fluvial lacustrine environments in the post noachian history of mars

character of the middle ordovician sauk tippecanoe sequence boundary in the ottawa embayment eastern ontario possible evidence for platform interior taconic tectonism in eastern ontario a middle ordovician disconformity that separates predominantly sandstone of the rockcliffe formation from underlying dolomite of the carillon formation beekmantown group has historically been considered equivalent to the sauk tippecanoe sequence boundary the character of the formation contact varies considerably and includes 1 rare serrated micropinnacles centimetres in height 2 smoothed irregular to undulose erosional bedforms along shallow 30 cm incised channels at least ten s of metres in width 3 a planar boundary with no obvious evidence of erosion 4 compaction effects across the boundary as well as within uppermost carillon and lowermost rockcliffe strata and 5 interbedding of carillon and rockcliffe like lithologies the latter two observations suggest that locally the disconformity represents a relatively minor gap in time local irregular paleotopography is interpreted as some combination of paleokarst mechanical erosion and differential sedime

characteristics genesis and parameters controlling the development of a large stratabound htd body at matienzo ramales platform basque cantabrian basin northern spain abstract at matienzo basque cantabrian basin northern spain a large stratabound htd body 4 by 2 km 2 and 80 400 m thick delimited by two parallel sinistral strike slip faults is exposed in aptian carbonates the margins of the htd body are characterised by dolomite tongues indicating that some limestone beds were more prone to dolomitisation however no clear relationship between htd occurrence and precursor limestone facies can be established massive limestone beds as found at the top of the htd body act as barriers to hydrothermal processes since no dolomite is present in or above these beds three types of dolomites have been differentiated i e 1 matrix 2 coarse crystalline and 3 zebra dolomite the distribution of the dolomite types is attributed to ascending fluid flow and changing degree of dolomite oversaturation the dolomite body was formed by two dolomitisation phases under burial conditions no indications for a synsedimentary early diagenetic dolomitisation have been observed the first dolomitisation phase is characterized by ferroan dolomite and the second by non ferroan dolomite the two htd phases are characterised by depleted 18 o values ranging between 10 and 16 v pdb 13 c values similar to the aptian albian marine signature and homogenisation temperatures of primary fluid inclusions between 120 c and 150 c the dolomitising fluid was enriched in 87 sr compared to aptian seawater excluding the latter as an unmodified fluid source for dolomitisation microthermometry of primary fluid inclusions indicates that the dolomitising fluid evolved from a moderate saline 9 7 14 0 wt nacl to a more saline 10 9 21 0 wt nacl h 2 o nacl brine the dolomitising fluid likely originated from evaporated seawater fluid circulation through the dolomitised strata is inferred to have taken place during the tectonically active period of the late albian throughout which important sinistral strike slip movements along basement faults occurred

quantitative mineralogical analysis of coals from the callide basin queensland australia using x ray diffractometry and normative interpretation abstract comparisons are presented between the results of quantitative x ray diffractometry using a rietveld based computational method siroquant on low temperature ash lta and normative calculation from chemical analysis of high temperature ash for a series of coal samples from the callide basin of queensland mineral percentages indicated by each method are also compared to the results of conventional x ray diffractometry on low temperature ash spiked with a known proportion of corundum evaluated in conjunction with detailed clay mineral analysis of the for species where direct comparison is possible the proportions of the different minerals in the crystalline fraction indicated by siroquant are similar to those indicated by normative analysis using a computational procedure referred to as sednorm more conventional xrd study of spiked lta materials with the samples studied seems to underestimate quartz and siderite content and by default overestimate kaolinite siroquant on the other hand tends to overestimate the proportion of ca bearing minerals relative to the ca content of the high temperature ash processed using the sednorm computation both the siroquant analysis and the normative evaluation of sednorm provide significantly more quantitative information on coal mineralogy than other more commonly used techniques

paleoclimate of mars as captured by the stratigraphic record in gale crater a kilometers thick sedimentary sequence in gale crater exhibits stratigraphic changes in lithology that are consistent with transitions in aqueous and climatic conditions purported to be global in scale the sequence is divided into two formations where the lower formation exhibits a net transition in mineralogy from clay sulfate to sulfate oxide assemblages and is separated from the overlying upper formation by an erosional unconformity superposition and crater counts suggest strata in the lower formation lie along the noachian hesperian time stratigraphic boundary whereas beds in the upper formation which lack signatures indicative of clay minerals or sulfates are thinner more regularly spaced and clearly younger the observed stratigraphic trends are consistent with the rocks at gale crater recording a global transition from a climate favorable to clay mineral formation to one more favorable to forming sulfates and other salts

hydrocarbons in silica pvtx properties of fluids and the genesis of diamond quartz from caravia berbes fluorite district asturias spain abstract the fluid history of diamond quartz crystals from caravia berbes fluorite district is intimately related with episodes of maturation and migration of hydrocarbons within the asturian basin probably linked to the structural activation of a mesozoic rift system these diamond quartz record the migration of hydrothermal silica rich brines and associated hydrocarbons that recorded a temperature increase outlined by fluid inclusion studies from 90 to 140 c this gradient is also recorded by a change in the organic matter species trapped in quartz from bitumen located in the inner quartz growth zones to liquid hydrocarbons trapped within the outer quartz overgrowths secondary ion mass spectrometer sims oxygen isotope microanalyses allowed to differentiate two 18oh2o values corresponding to the oil dominated zone core and the water dominated zone outer growth zone the heavier 18oh2o values in the water dominated zone do not only record a higher temperature of formation but also an increase in the 18oh2o of the parental fluid isotopic compositions of diamond quartz suggest a heterogeneous source of surficial fluids and formation waters expelled from claystones within the basin history the diamond quartz precipitation took place during early jurassic to eocene subsidence periods pressure temperature and composition ptx and 18oh2o characteristics point out a probable relationship with albian diagenetic events reported in cantabrian and north pyrenean basins

mineral matter and trace elements in coals of the gunnedah basin new south wales australia abstract the concentrations of major and trace inorganic elements in a succession of permian coals from the gunnedah basin new south wales have been determined by x ray fluorescence techniques applied to both whole coal and high temperature ash samples the results have been evaluated in the light of quantitative data on the minerals in the same coals determined from x ray diffraction study of whole coal samples using a rietveld based interpretation program siroquant to determine relationships of the trace elements in the coals to the mineral species present comparison of the chemical composition of the coal ash interpreted from the quantitative mineralogical study to the actual ash composition determined by xrf analysis shows a high degree of consistency confirming the validity of the xrd interpretations for the gunnedah basin materials quartz illite and other minerals of detrital origin dominate the coals in the upper part of the sequence whereas authigenic kaolinite is abundant in coals from the lower part of the permian succession these minerals are all reduced in abundance however and pyrite is a dominant constituent in coals formed under marine influence at several stratigraphic levels calcite and dolomite occur as cleat and fracture infillings mostly in seams near the top and bottom of the sequence the potassium bearing minerals in the detrital fraction are associated with significant concentrations of rubidium and the authigenic kaolinite with relatively high proportions of titanium zirconium is also abundant with associated p and hf in the gunnedah basin coal seams relationships exhibited by ti zr nd and y are consistent with derivation of the original sediment admixed with the seams from an acid volcanic source pyrite in the coals is associated with high concentrations of arsenic and minor proportions of thallium no other element commonly associated with sulphides in coals however appears to occur in significant proportions with the pyrite in the sample suite small concentrations of cl present in the coal are inversely related to the pyrite content and appear to represent ion exchange components associated with the organic matter strontium and barium are strongly associated with the cleat filling carbonate minerals ge and ga appear to be related to each other and to the coal s organic matter cr and v are also related to each other as are ce la nd and pr but none of these show any relationship to the organic matter or a particular mineral component

vertical movements of the crust case histories from the northern appalachian basin evidence of former deep burial of ordovician to devonian strata of the northern appalachian basin has been obtained from various techniques of study including fluid inclusion homogenization temperatures 18 o and vitrinite reflectance diagenetic minerals indicate paleotemperatures of 100 200 c maximum depths of burial were calculated from the estimated paleotemperatures a gradient of 26 c km was assumed silurian strata of the basin are interpreted to have reached maximum burial depths of 5 0 km devonian strata in the catskill mountains had former burial depths of 6 5 km lower ordovician carbonate sequences were buried to 7 km middle ordovician strata had paleodepths of 5 km and devonian carbonate strata had paleodepths from 4 5 to 5 km if these strata were buried deeper than previously thought unexpectedly large amounts of uplift and erosion ranging from 4 3 to 7 km must also have taken place to bring these strata to the present land surface the occurrence of such large scale vertical movements of the crust and lithosphere must be recognized in paleogeographic reconstructions such drastic changes represent isostatic unroofing with widespread implications for paleogeography of a kind unrecognized at present

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

precambrain fault systems as control on regional differences in relative sea level along the early ordovician platform of eastern north america abstract this study proposes that there was regional variation in early ordovician subsidence histories along eastern laurentia controlled by broad differences in the susceptibility of inherited precambrian crustal structure to reactivation with changing ocean basin tectonism two continental scale phanerozoic fault systems southern oklahoma fault system ottawa bonnechere graben extend into the craton interior from the apices of the ouachita and quebec embayments or reentrants respectively their traces identify reactivated proterozoic fault zones previous studies show that rates of subsidence for early ordovician sedimentation along the axis of the southern oklahoma fault system are elevated compared to regional rates beyond this structural corridor a similar history applies to early ordovician sedimentation within the ottawa embayment eastern ontario along the present axis of the ottawa bonnechere graben the theresa formation lower beekmantown group contains a third order peritidal siliciclastic dominated sequence evidence for local tectonism prior to and during its development within the embayment includes 1 late cambrian pre theresa preferential uplift differential erosion and subsidence along the eastern structural boundary of the embayment 2 differential intrabasinal subsidence during theresa deposition 3 an apparent offset in timing of peak flooding within the embayment to that along the st lawrence promontory 1500 km distant and 4 absence of a subaerial unconformity in the embayment that otherwise separates eustatic cycles on the promontory and defines a likely sea level fall below the shelf margin in comparison subsidence within the embayment appears to have matched at least the rate of the eustatic fall regional differences in early ordovician subsidence histories along this margin may illustrate that the precambrian fault zones were structurally more sensitive than promontories to the developing reconfiguration of oceanic lithospheric elements that would lead to the taconic orogeny

the occurrence of authigenic minerals in solid bitumens abstract solid bitumens the residues of migrating hydrocarbons may contain authigenic minerals closely comparable to those in organic rich siliciclastic rocks the minerals include quartz feldspars illite and pyrite authigenic feldspars are of orthoclase or albite composition in vanadium rich bitumens roscoelite is the dominant silicate phase the minerals are recorded in bitumens from host rocks of precambrian to tertiary age silicate inclusions are particularly developed in large bitumen veins which occupy major fluid migration pathways at a megascopic scale the bitumens appear to be pure hydrocarbon deposits but the silicates indicate a major aqueous component in the hydrocarbon bearing fluids the sulfur isotope systematics of fractionated bitumen samples are similar to those of sediments during early diagenesis composed of 34s depleted pyrite and 34s enriched organic sulfur

pb zn occurrences and their pb isotopic signatures bearing on metallogeny and mineral exploration paleozoic sedimentary rocks northern appalachians quebec galena pb isotope ratios of epithermal vein and disseminated sulfide occurrences in the taconian orogen and siluro devonian basin cluster around 17 90 18 05 for 206pb 204pb and 37 70 38 00 for 208pb 204pb the major source of pb in most if not all occurrences is a fairly common continental crust a characteristic found in published analyses of grenville feldspar pb a southwest to northeast increase in galena 206pb 204pb ratios is ascribed to the supply of several types of detritus from grenville basement during the cambro ordovician coarse grained k feldspar bearing in the southwest grading into fine grained phyllitic and relatively more highly radiogenic in the northeast emplacement i of pb zn barite veins and disseminations commonly of homogeneous crustal pb isotopic signature was late taconian ii of pb zn quartz veins of less homogeneous signature was post taconian and iii of pb zn carbonate veins relatively highly radiogenic and commonly homogeneous was late or post acadian signa

characterizing low temperature aqueous alteration of mars analog basalts from mauna kea at multiple scales we performed a multi scale characterization of aqueous alteration of mars analog basaltic rock from a mauna kea drill core using high resolution visible and short wave infrared vis swir spectral imaging scanning electron microscopy x ray diffraction and point vis swir spectra several types of smectites zeolites and primary minerals were identified mineral classes were mapped in cut sections extracted from the drill core and used to represent the range of alteration products seen in field data collected over 1000 m depth calvin et al 2020 ten distinct spectral end members identified in the cut sections were used to map the field point spectra trioctahedral fe and mg rich smectites were present toward the top of the zone of analysis 972 m below the surface and increased in abundance toward the bottom of the drill core 1763 m depth the mineralogy demonstrates a general trend of discontinuous alteration that increases in intensity with depth with less pervasive phyllosilicate alteration at the top several zones of different mixtures of zeolites toward the center followed by more abundant phyllosilicates in the lowest sections distinctly absent are fe mg phyllosilicates other than smectites as well as carbonates sulfates and al phyllosilicates such as kaolinite or illite furthermore hematite was only detected in two of 24 samples the suite of assemblages points to aqueous alteration at low to moderate temperatures at neutral to basic ph in low oxygen conditions with little evidence of extensive surface interaction presenting a possible analog for an early mars subsurface environment we also present a library of vis swir spectra of the analyzed cut sections including both spatial averages i e unweighted linear mixtures of spectral images of each cut section and single point spectra of the cut sections this will allow for consideration of nonlinear mixing effects in point spectra of these assemblages from natural surfaces in future terrestrial or planetary work

fluid inclusion constraints on temperatures of petroleum migration from authigenic quartz in bitumen veins abstract solid bitumens in fracture systems commonly contain microscopic crystals of authigenic quartz which were precipitated coevally with the bitumen early in the paragenesis of the fracture fillings the quartz contains primary fluid inclusions both aqueous and hydrocarbon yielding homogenization temperatures particularly in the range 95 130 c indicating minimum temperatures of entrapment during petroleum migration volumes of up to 50 entrained quartz and a predominance of aqueous inclusions indicate that the petroleum fluid had a substantial aqueous component

the geochemical record of hydrothermal mineralization and tectonism inboard of the appalachian orogen the ottawa embayment abstract the history of mineralization of the ottawa embayment includes migration of basin brines within the confines of an early paleozoic basin and cross stratal fracture flow linked to structural reactivation of an underlying neoproterozoic failed rift system paleoporosity consists of paleokarst pal in lower ordovician dolostone beekmantown group and fractures now veins that cross cut both lower paleozoic pl and precambrian pc strata a series of contrasting mineral assemblages which define changing fluid compositions fill paleokarst cavities and rare interconnected paleofractures now veins first there is an early pal succession of quartz saddle dolomite then calcite with accessory hydrocarbon as well as sulphide and sulphate minerals the quartz defines migration of saline 20 wt silica brines and hydrocarbon that spans a temperature increase defined by fluid inclusions from 13 c of the dolomite identifies strong sedimentary rock water interaction but a depleted 13 c composition 14 for the calcite illustrates that with cooling paleokarst cavities were sites of bacterially mediated sulphate reduction remaining paleokarst porosity is filled with a late pal mineral assemblage that contains low temperature mostly

elemental geochemistry of sedimentary rocks at yellowknife bay gale crater mars sedimentary rocks examined by the curiosity rover at yellowknife bay mars were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts no evidence of chemical weathering is preserved indicating arid possibly cold paleoclimates and rapid erosion and deposition the absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low temperature circumneutral ph rock dominated aqueous conditions analyses of diagenetic features including concretions raised ridges and fractures at high spatial resolution indicate that they are composed of iron and halogen rich components magnesium iron chlorine rich components and hydrated calcium sulfates respectively composition of a cross cutting dike like feature is consistent with sedimentary intrusion the geochemistry of these sedimentary rocks provides further evidence for diverse depositional and diagenetic sedimentary environments during the early history of mars

the 1982 cocrust seismic experiment across the ottawa bonnechere graben and grenville front in ontario and quebec summary during the summer of 1982 the canadian consortium for crustal reconnaissance using seismic techniques cocrust conducted a major long range seismic refraction and wide angle reflection experiment across the grenville province of the canadian shield three seismic lines each approximately 300 km in length were located i along the ottawa bonnechere graben ii perpendicular to the graben and iii perpendicular to the crenville front geological evidence indicates that the graben may have originated from a failed arm of the st lawrence rift system and the grenville front marks the boundary between the grenville province and the much older superior province other geological features of the grenville province that were traversed by the profiles were the central metasedimentary belt and the central gneiss belt analysis of the data involved conventional traveltime procedures coupled with the use of synthetic seismogram analysis using programs that were written to handle laterally heterogeneous structures results from the survey indicate a variation in near surface seismic velocity

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

mineralogy of a mudstone at yellowknife bay gale crater mars sedimentary rocks at yellowknife bay gale crater on mars include mudstone sampled by the curiosity rover the samples john klein and cumberland contain detrital basaltic minerals calcium sulfates iron oxide or hydroxides iron sulfides amorphous material and trioctahedral smectites the john klein smectite has basal spacing of similar to 10 angstroms indicating little interlayer hydration the cumberland smectite has basal spacing at both similar to 13 2 and similar to 10 angstroms the larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating h2o retention basaltic minerals in the mudstone are similar to those in nearby eolian deposits however the mudstone has far less fe forsterite possibly lost with formation of smectite plus magnetite late noachian early hesperian or younger age indicates that clay mineral formation on mars extended beyond noachian time

a new geological framework for the middle ordovician carillon formation uppermost beekmantown group ottawa embayment onset of taconic foreland deposition and tectonism within the laurentian platform interior the carillon formation underlies the ottawa embayment a craton interior extension of the regional laurentian paleoshelf defined today by the ottawa bonnechere graben facies within the embayment during the middle ordovician identify a mixed sediment carbonate siliciclastic tide influenced peritidal and schizohaline basin host to a mosaic of dolomitic tidal mudflats shallow lagoons or ponds and channels skeletal metazoans were rare but bioturbation increased with episodic influx of less saline water carrying sand and mud possibly in response to regional climate change stratigraphic analysis reveals that the formation coincides with a third order eustatic sea level cycle but higher order stratigraphic patterns show no obvious eustatic link instead a stepwise onlap geometry coincided with local faulting that produced widespread syndepositional sediment deformation in particular stages of faulting and post carillon erosion are mapped along the present day trace of a northwest southeast orie

perspectives oxygen isotopes and the origin of quartz published data indicate that in igneous rocks the delta 18 o of quartz averages about 9 per thousand in metamorphic rocks 13 to 14 per thousand in sandstones 11 per thousand in shales 19 per thousand quartz overgrowths in sandstones 20 per thousand and cherts 28 per thousand either a very large proportion of the silt and clay size quartz in shales about 90 of the total quartz in shales is secondary or the isotopic data are incomplete it is concluded that the latter interpretation is correct because published isotopic analyses of metamorphic rocks consider only the coarser grained rocks phyllites and slates whose quartz is nearly all of silt and clay size and has more positive delta 18 o values than quartz from schists and gneisses probably supplies the bulk of quartz to mudrocks