geochemistry and stratigraphic correlations application to the investigation of geothermal and mineral resources of tuscany italy contribution to the knowledge of the ore deposits of tuscany ii abstract major element geochemistry 364 analyses is used to obtain quantitative information on the initial mineralogical composition and the depositional environment of paleozoic more or less metamorphic rocks from tuscany and elba furthermore this method can be used to improve stratigraphic correlations by comparing the chemical compositions of the metamorphic rocks and their possible non metamorphic counterparts of known stratigraphic position the stratigraphic units were divided into two sets the first includes the units of known stratigraphic or tectonic position taken as reference groups permian red porphyries carboniferous rocks buti group l s porphyritic schists porphyroids lower phyllites and metabasites from the apuan alps and elba the second set comprises the units of uncertain position metapelites and metapsammites from outcrops mines and boreholes from the boccheggiano niccioleta area calamita schists and metabasites associated with these two units micaschists gneisses and associated amphibolites the main results are 1 1 the porphyroids and porphyritic schists differ strongly from the permian red porphyries thus confirming that they belong to two different volcanic episodes 2 2 all the reference units consist of shales sandstones s s or graywackes differing by their degree of maturity increasing from the lower phyllites to the buti group and to the carboniferous formations 3 3 the carboniferous rocks the buti group and the lower phyllites have distinct chemical compositions 4 4 the boccheggiano formation l s and the calamita schists are similar and include rocks chemically equivalent to the lower phyllites the buti group and the carboniferous formations 5 5 the micaschists and gneisses derive from shales and graywackes respectively and chemically recall the lower phyllites 6 6 the metabasites from the apuan alps and from niccioleta are within plate basalts whereas the amphibolites interlayered within the micaschists and gneisses seem ocean floor basalts

oolitic ironstones and contrasting ordovician and jurassic paleogeography distribution of abundant ordovician and jurassic oolitic ironstones provides a test for current ideas about factors controlling their origin these include warm climate and deep weathering dispersed continents and highstand of global sea level most of the jurassic ironstones developed in middle northern latitudes on the unstable european part of assembled laurasia at a time of low global sea level mild moist climate and abundant vegetation most of the ordovician ironstones accumulated around the northwestern margin of assembled gondwana and armorica during highstand of sea level and an absence of land plants and in high southern latitudes that supported an ice cap by the end of the period these contrasts demonstrate that neither dispersed continents nor major highstand of sea level was a necessary factor moreover requisite weathering in ordovician time may have been induced by adequate soil air co 2 pressure maintained by elevated atmospheric p co 2 in tne absence of land plants

carbonate platforms of passive extensional continental margins types characteristics and evolution abstract carbonate platforms of extensional margins may be grouped into several major categories homoclinal ramps have gentle slopes into deep water may have skeletal or ooid pellet sand shoal complexes that grade without break in slope into deep ramp nodular limestone and then into pelagic hemipelagic basin facies they generally lack significant slump and sediment gravity flow deposits in the deeper water facies distally steepened ramps differ from the above in having a marked increase in slope at the seaward edge of the deep ramp and abundant slumps slope breccias and turbidites however clasts of shallow platform margin facies are generally absent from breccias rimmed shelves have linear trends of shelf edge lime sands and reefs a marked increase in slope into deep water and foreslope and slope sands breccias with clasts of platform margin rocks and turbidites grading seaward into basin hemipelagic pelagic muds they may be divided into accretionary bypass and erosional margins isolated platforms are broad flat topped shallow platforms surrounded by deeper water few hundred meters to 4 km deep many are bypass margins but accretionary and erosional margins also occur finally incipiently to completely drowned or open platforms may develop by rapid submergence of ramps shelves or isolated platforms shallow platform margin facies are shifted landward and the earlier shallow water platform is covered with transgressive lags and deeper water blankets of hemipelagic or pelagic facies or open marine whole fossil wackestone the carbonate prisms commonly develop above a basal clastic phase ramps develop early and evolve into rimmed shelves however with drowning rimmed shelves may evolve up into ramps rimmed shelves may also develop into ramps where miogeoclinal faces prograde into filling marginal basins carbonate miogeocline deposition terminates when the shelf becomes a prograding clastic shelf or where it becomes part of a collisional orogen the various platform types may be recognized from continental margin sequences ranging from proterozoic to holocene in age

evidence for li rich brines and early magmatic fluid rock interactionin the larderello geothermal system abstract the geochemical features of fluids accompanying the first stages of geothermal activity linked to magmatic intrusions have been documented for the larderello geothermal system italy deep drilling has provided samples which preserve evidence of this early geothermal activity four wells san pompeo 2 monteverdi 7 sasso 22 and serrazzano vc 11 penetrated the deeper parts of the larderello system located in a metamorphic basement underlying the tertiary nappe complex which constitutes the main aquifer at larderello the drill holes terminated close to the inferred roof of a granitic complex thought to be responsible for geothermal activity fluid inclusion data were obtained from recrystallized quartz lenses and quartz veins in samples displaying high temperature assemblages plagioclase actinolite biotite tourmaline clinopyroxene andradite wollastonite and also from magmatic quartz in a leucogranite dike the inclusions are mainly secondary in origin oriented in fluid inclusion planes fip related to hydrothermal circulation in the larderello system several generations of high temperature fluids were trapped and include 1 1 h2o co2 dominated vapors displaying variable but significant contents of ch4 and n2 2 2 aqueous vapors containing licl with variable salinity 3 3 aqueous licl brine often oversaturated with respect to halite at room temperature 4 4 complex brine always oversaturated at room temperature with respect to two halite and sylvite or more n 4 salts the presence of licl was confirmed by identification of the salt hydrate licl 5h2o at very low temperature using raman spectroscopy bulk salinities could be roughly estimated at around 30 wt eq licl for the licl brine geometric and chronologic relationships between fip reveal close relationships and mutual contamination between the h2o co2 vapors and licl brine indicating synchronism in their trapping these fluids were generated and trapped at pressures of 100 130 mpa nearly 23 mpa above the estimated present day lithostatic pressure this implies a denudation rate between 0 2 and 0 5 mrn a 1 since the onset of hydrothermal activity compatible with the setting of larderello in a young tortonian collision belt fluid inclusion trapping temperatures 425 650 c show a monotonous increase towards the inferred granite and are around 100 200 c higher than the highest present day temperatures the results are interpreted as recording the interaction between magmatic and contact metamorphic fluids in the early larderello system the h2o co2 vapors resulted from the reheating of the basement metamorphic series often c rich under relatively high temperatures during contact metamorphism lirich fluids expelled from an underlying li rich leucogranite migrated through the metamorphic series and the already cooled granite dikes and experienced local boiling the fluid inclusion data demonstrate the involvement of magmatic fluids during the initial development of this high energy geothermal field

phase relationships of sursassite and other mn silicates in highly oxidized low grade high pressure metamorphic rocks from evvia and andros islands greece high pressure low temperature metamorphic mn rich quartzites from andros and evvia euboea islands greece situated in the eocene blueschist belt of the hellenides reveal different mn al ca mg silicate assemblages in response to variable metamorphic grade on evvia piemontite and or braunite rich quartzites which are associated with low grade blueschists t 8 kbar show the principle mineral assemblage quartz montite sursassite braunite mg chlorite hematite rutile titanite the mn al silicate sursassite basically mn2 ca 4 al2 al fe3 mn3 mg 4si6o21 oh 7 thus far reported as a rare mineral locally occurs as a rockforming mineral in cm to m thick layers on andros higher grade quartzites t 450 500 c p 10 kbar of similar composition contain the assemblage quartz piemontite spessartine braunite mg chlorite hematite phengite phlogopite rutile rare sursassite is present only as a relict phase additional mostly accessory minerals in quartzites from evvia and andros are ardennite na amphibole acmitic clinopyroxene albite apatite and tourmaline the chemical composition of the main phases is characterized in detail

dating of deformation phases using k ar and 40ar 39ar techniques results from the northern apennines abstract paleozoic to oligocene metasedimentary rocks present in the alpi apuane region of the northern apennines italy have been sequentially deformed during a tertiary progressive deformation in an attempt to date the individual deformation episodes over 50 conventional k ar and 1140 ar 39ar incremental gas release analyses have been carried out on fine grained white micas separated from samples whose structural settings were well known mineralogy x ray diffractometry and thin section analyses indicate that the constituent muscovite and phengite formed under metamorphic conditions of 3 4 kbars and 300 400 c during all deformational phases pre existing micas were variably crenulated during each subsequent deformational phase both k ar and 40ar 39ar analyses were carried out on 0 6 2 m 2 6 m and 6 20 m size separates of the phengitic white mica although the k ar apparent ages range from 11 to 27 ma and are consistent with available stratigraphic constraints the 40ar 39ar age spectra display variable internal discordancy these isotopic data indicate that 1 both the k ar and 40ar 39ar total gas ages decrease as the degree of crenulation increases 2 the k ar and 40ar 39ar total gas ages decrease as grain size decreases 3 for each sample characteristics of the 40ar 39ar age spectra depend upon grain size with fine sizes yielding discordant patterns which systematically increase in apparent age from low to high temperature and 4 phengitic micas associated with earliest structures yield generally older ages than micas associated with later structures the isotopic results are interpreted to indicate that the major deformation phase d1 occurred at approximately 27 ma with subsequent pulses ending by c 10 ma these results may be combined with finite strain data to suggest that the region was deformed at strain rates between 10 15 and 10 14 s 1 a 27 ma age indicates mid oligocene initiation of plate tectonic activity in the western mediterranean and concomitant deformation in the northern apennines

geochemistry and origin of piemontite bearing and associated manganiferous schists from arrow junction western otago new zealand abstract closely spaced analyses for major minor and trace elements have been made through 3 m of manganiferous quartzose schists and immediately overlying quartzofeldspathic schists at arrow junction otago new zealand chemically the quartzose schists correspond to pelagic siliceous muds or brown clays rather than to typical cherts whole rock oxidation ratios fe 3 100 fe 3 fe 2 increase from 16 to 99 with increasing mn apart from sio2 al2o3 is the most abundant oxide in these rocks al2o3 correlates negatively with sio2 and positively with all other components analysed in the manganiferous quartzose schists including fe2o3 mno tio2 mgo cao na2o k2o ba cr cu ni pb rb v y zn and zr parameters such as al 2 o 3 100 al 2 o 3 mno and fe ti indicate that the quartzose schists have a higher hydrothermal plus hydrogenous component than average pelagic clays but a larger terrigenous component than typical metalliferous sediments from the crest and proximal flanks of the east pacific rise close covariance of al2o3 with tio2 and zr results in ratios ti al 50 10 3 and zr al 2 10 3 conforming closely with average shale and average new zealand alpine schist metasediments but less closely with average andesite the data exclude basalt or rhyolite as the dominant aluminous detrital component al ti and zr are regarded as being of predominantly terrigenous origin normalized for constant al2o3 the following elements are enriched in grey green and in pink piemontite bearing arrow junction quartzose schists relative to average new zealand alpine metase dimentary rocks by average factors indicated mn 32 44 ni 15 15 cu 5 12 si 3 6 2 6 pb 2 4 zn 2 8 2 5 fe 1 8 1 9 y 1 7 1 8 ba 1 2 1 6 and sr 1 0 2 0 the metal enrichment trend can be regarded as being imposed on the products of a silica dilution trend in which al2o3 was reduced to 4 by dilution of end member terrigenous sediment with non terrigenous silica about 97 98 of the mn 93 of the ni 79 91 of the cu 73 61 of the sio2 and 43 48 of the fe is considered to be of a non terrigenous hydrothermal hydrogenous biogenic origin in the quartzose schists covariance of elements other than si with al2o3 within the single bed investigated is attributed firstly to accumulation of femn oxides at a rate essentially constant relative to that of clay minerals and other aluminous phases though diluted by varying amounts of largely biogenic silica and secondarily to the sorptive scavenging properties of the femn oxides and of clay mineral components of the sediment although the base metals may ultimately have been introduced to the ocean from submarine hydrothermal systems these sediments originated at a site relatively remote from a fast spreading ridge or other active submarine hydrothermal source

estimation of lignite reserve in the kalburcayiri field kangal basin sivas turkey abstract this paper addresses a case study on global estimation of lignite reserve in the kalburcayiri field from the sivas kangal basin which is one of the most productive lignite basins in eastern anatolia turkey the two lignite seams which were developed in a fresh water lacustrine depositional environment during the pliocene time are currently being exploited in the kalburcayiri open cast mine for feed coal to a power plant with 300 mw capacity tonnage thickness and quality parameters ash yield total sulphur content and calorific value of the lignite are variables considered in this study the global estimates of these variables together with 95 confidence limits are obtained using the approximation principle of global estimation a random stratified grid is fitted to available boreholes the variograms for thickness and lignite quality parameters are estimated and modeled the models are used in calculating estimation error variances that will later be used in constructing 95 confidence intervals for the true values

syntectonic sedimentation in a middle triassic rift northern apennines italy abstract the anatomy of the sedimentary and volcanic fill of a middle triassic continental rift at the western margin of the tethys is illustrated by the study of a 250 m thick sequence on the tyrrhenian coasts of the northern apennines this sequence contains two cycles of sedimentation 1 a the lower cycle comprises a basal transgressive sequence from continental alluvial fans to shallow marine carbonates and an upper sequence which correspond to an increasing tectonic activity submarine syntectonic facies assemblage the lower part of the last assemblage is characterized by a thick 22 m rapidly deposited sequence of coarse carbonate breccias with minor calcareous sandy turbidites this is overlain by channelized red beds of submarine fans composed of close interstratification and juxtaposition of carbonate breccias with red clastic matrix and red sandy quartz pebble conglomerates and silty sands interbedded alkaline pillow lava record penecontemporaneous submarine eruptions the lavas are capped by thin red cherty diaspri crusts the lower cycle of sedimentation ends with a karstic surface on relatively deep marine carbonate layers this suggests a rapid emersion due to the arrest and reversal of the downsinking of the initial aborted or failed rift 2 b the upper cycle of sedimentation starts with more mature fluvial red beds and changes upward into shallow marine sands and carbonates this upper cycle represents an early stage of evolution of a new major rift this second major rift led in jurassic times to the opening of an oceanic area between europe and western italy

forecasting coal resources and reserves in heterogeneous coal zones using 3d facies models as pontes basin nw spain abstract forecasting coal resources and reserves is critical for coal mine development thickness maps are commonly used for assessing coal resources and reserves however they are limited for capturing coal splitting effects in thick and heterogeneous coal zones as an alternative three dimensional geostatistical methods are used to populate facies distribution within a densely drilled heterogeneous coal zone in the as pontes basin nw spain coal distribution in this zone is mainly characterized by coal dominated areas in the central parts of the basin interfingering with terrigenous dominated alluvial fan zones at the margins the three dimensional models obtained are applied to forecast coal resources and reserves predictions using subsets of the entire dataset are also generated to understand the performance of methods under limited data constraints three dimensional facies interpolation methods tend to overestimate coal resources and reserves due to interpolation smoothing facies simulation methods yield similar resource predictions than conventional thickness map approximations reserves predicted by facies simulation methods are mainly influenced by a the specific coal proportion threshold used to determine if a block can be recovered or not and b the capability of the modelling strategy to reproduce areal trends in coal proportions and splitting between coal dominated and terrigenous dominated areas of the basin reserves predictions differ between the simulation methods even with dense conditioning datasets simulation methods can be ranked according to the correlation of their outputs with predictions from the directly interpolated coal proportion maps a with low density datasets sequential indicator simulation with trends yields the best correlation b with high density datasets sequential indicator simulation with post processing yields the best correlation because the areal trends are provided implicitly by the dense conditioning data

optimum and robust 3d facies interpolation strategies in a heterogeneous coal zone tertiary as pontes basin nw spain coal exploration and mining in extensively drilled and sampled coal zones can benefit from 3d statistical facies interpolation starting from closely spaced core descriptions and using interpolation methods a 3d optimum and robust facies distribution model was obtained for a thick heterogeneous coal zone deposited in the non marine as pontes basin oligocene early miocene nw spain several grid layering styles interpolation methods truncated inverse squared distance weighting truncated kriging truncated kriging with an areal trend indicator inverse squared distance weighting indicator kriging and indicator kriging with an areal trend and searching conditions were compared facies interpolation strategies were evaluated using visual comparison and cross validation moreover robustness of the resultant facies distribution with respect to variations in interpolation method input parameters was verified by taking into account several scenarios of uncertainty the resultant 3d facies reconstruction improves the understanding of the distribution and geometry of the coal facies furthermore since some coal quality properties e g calorific value or sulphur percentage display a good statistical correspondence with facies predicting the distribution of these properties using the reconstructed facies distribution as a template proved to be a powerful approach yielding more accurate and realistic reconstructions of these properties in the coal zone

mineralogy and geochemistry of two metamorphosed sedimentary manganese deposits sierra nevada california usa abstract laminated to massive rhodochrosite hausmannite and mn silicates from the smith prospect and manga chrome mine sierra nevada california were deposited as ocean floor sediments associated with chert and shale the principal lithologies at smith are chert argillite rhodochrosite hausmannite and chlorite rich layers and relatively uncommon layers of jacobsite the manga chrome mine also contains layers rich in manganoan calcite and caryopilite tephroite rhodonite spessartine and accessory alleghanyite and sonolite formed during metamorphism volcaniclastic components are present at manga chrome as metavolcanic clasts and as mn poor red garnet and hematite rich layers there is no evidence such as relict lithologies that mn was introduced into mn poor lithologies such as chert limestone or mudstone replacement of mn poor phases by mn rich phases is observed only in the groundmass of volcanic clasts that appear to have fallen into soft mn rich mud manganiferous samples from the smith prospect and manga chrome mine have high mn fe and low concentrations of ni cu zn co u th and the rare earth elements that are similar to concentrations reported from other ancient mn deposits found in chert greenstone complexes and from manganiferous sediments and crusts that are forming near modern sea floor vents the sierra nevada deposits formed as precipitates of mn rich sediments on the sea floor probably from mixtures of circulating hydrothermal fluids and seawater the composition of a metabasalt from the smith prospect is consistent with those of island arc tholeiites metavolcanic clasts from the manga chrome mine are compositionally distinct from the smith metabasalt and have alkaline to calc alkaline affinities a back arc basin is considered to be the most likely paleoenvironment for the formation of the mn rich lenses at the manga chrome mine and by association the smith prospect layers of rhodochrosite hausmannite and chert preserve the composition and some textures of the sedimentary protoliths at both sierra nevada deposits jacobsite rich layers probably represent a fe rich protolith caryopilite and manganoan calcite represent additional protoliths at the manga chrome mine the metamorphic assemblage prehnite chlorite epidote calcite in a metabasalt from the smith prospect constrains regional metamorphic conditions to a maximum temperature of 325 c and a pressure of 2 kbar slightly higher temperatures are indicated by the presence of actinolite in another metabasalt compositions of mn rich minerals in smith samples are consistent with these metamorphic conditions

early fluid migration in a deep part of the larderello geothermal field a fluid inclusion study of the granite sill from well monteverdi 7 abstract metamorphic magmatic to hydrothermal fluids trapped in fluid inclusion planes fip were studied in a microfractured granite sill from a deep level 3483 3486 m b g l of the well monteverdi 7 larderello geothermal field this granite has recorded a complex succession of fluid migration through a dense set of healed microcracks nine generations of fluids trapped within specific microcrack networks are distinguished and include vapors and liquids of the c h o n s system aqueous liquids and brines with distinctive sets of cation chlorides licl nacl nacl cacl 2 and nacl detailed studies of the geometrical and chronological relationships between the fluid inclusion planes allow the establishment of a clear relative chronology with the c h o n s and licl fluids being earlier than the nacl cacl 2 and nacl aqueous liquids and brines in particular it can be shown that the c h o n s and licl fluids are strongly associated in space and time since the corresponding fluid inclusion planes display evidence of mutual contamination of inclusions within the planes significant changes in the physical chemical parameters occurred in the conditions of fluid trapping during the evolution of the larderello field all observed paleofluids have compositions differing from that encountered in the present day fluids and record a complex p t t x evolution from an early stage dominated by magmatic and metamorphic derived fluids towards a later stage dominated by more surficial waters at the early stage hydrothermal circulation occurred under lithostatic pressure at a depth of ca 4 5 km at temperatures as high as 450 500 c such conditions are very reminiscent of contact metamorphism and were probably created by the deep intrusive body detected by geophysical studies batini et al 1983 1985 the involved fluids are c h o n s vapors and liquids of metamorphic derivation and aqueous li bearing brines of probable magmatic derivation they are consistent with the hypothesis of the intrusive being a granite at the later stage physical conditions had evolved towards hydrostatic pressure at a depth close to the present 3 5 km one and temperatures of 400 350 c still higher than the present day ones early fluids were no longer present the observed fluids record the involvement of more surficial waters both meteoric and connate transient boiling events were probably occurring heralding the present day conditions vapor dominated geothermal system nevertheless no trapped fluids display similar composition and density with the present day geothermal fluids at larderello in old geothermal fields such as larderello it must be emphasized that the use of fluid inclusions in order to reconstruct past hydrothermal evolution is strongly dependent onto pressure estimation since significant temperature corrections may be needed in the larderello case failing to take in account the pressure effects would have led to seriously misleading conclusions

schorl dravite ferridravite tourmalines deposited by hydrothermal magmatic fluids during early evolution of the larderello geothermal field italy electron microprobe and petrographic data on tourmaline rich assemblages in addition to available data from fluid inclusions and geochronological studies are used to model the early stage of hydrothermal metamorphism in the larderello geothermal field italy during this early stage different hydrothermal events are characterized by deposition of tourmaline biotite calcic plagioclase k feldspar quartz and pyrrhotite at lithostatic pressures of 0 75 to 1 kbarsand temperatures in the range 400 degrees to 600 degrees c pressures exceeding hydrostatic values and inferred temperatures of 450 degrees to 460 degrees c at the bottom of well san pompeo 2 suggest a possible present day deposition of tourmaline in the deepest levels of the central and hottest part of the field hydrothermal tourmalines appear to have crystallized at temperatures in excess of 370 degrees c they show significant replacement of al by fe super 3 in the z site substitutions of al for si in the tetrahedral site and slight vacancies in the x and y sites produced by limited cation and proton deficient substitutions in the hydrothermal tourmaline nearest to the inferred granitic contact and in the tourmaline of a leucogranitic dike crossed by well vcll a negative correlation existing between mg and fe super 2 reveals significant reciprocal substitutions of these elements in the y site tschermak9s and aluminobuergerite substitutions and an increase in the molecular fractions of schorl and elbaite in the schorl dravite and schorl elbaite solid solutions were observed from rim to core of the vcll magmatic tourmalines rims and intermediate growth zones of magmatic tourmalines and most of the hydrothermal tourmalines have compositions falling in the field of metamorphic tourmalines this behavior reveals the dominant control of the host rock on fluid chemistry some growth zones and most cores have compositions that plot in the field of tourmalines from granitoids a gradual schorl or ferridravite enrichment from magmatic to hydrothermal tourmalines with increasing distance from the granite contact is also present in a microprobe traverse from the base to the tip of an acicular tourmaline four peaks of fe super 3 replacing al can be ascribed to four distinct hydrothermal events generated by episodic ascent from below of magmatic fluids that became more and more oxidized with increasing distance from the granite contact owing to an easier hydrogen leakage in the shallower and more fractured levels the studied mineral assemblages and available fluid inclusion data reveal close analogies between the deepest and hottest part of the larderello geothermal system and quartz tour maline and k silicate alteration zones of porphyry tin and copper deposits the mineralizing fluids are inferred to have been of magmatic origin and were characterized by t 400 degrees to 600 degrees c pressure varying between hydrostatic 0 2 0 35 kbars and lithostatic 0 75 1 kbars commonly near lithostatic values high f sub o 2 as inferred by the presence of hematite and anhydrite among fluid inclusion daughter minerals and very high salinities up to 50 60 equiv wt nacl

trace elements in the lower pliocene fossiliferous kangal lignites sivas turkey abstract the kangal lignite basin which is one of the most productive lignite basins in eastern anatolia turkey includes two lignite seams containing abundant gastropoda shells in the lower pliocene kalburcayiri formation the seams are currently exploited in an open cast mine in the kalburcayiri field and supply feed coal to a power plant with 300 mw capacity the average thickness of each of the two seams in this mine is about 10 m and they are separated by about 20 m of tuffaceous sedimentary rocks a 15 20 cm thick tuff bed occurs within the upper seam the purpose of the study was to understand mineralogy and trace element concentrations of the two lignite seams in the kalburcayiri formation which were affected by volcanic ashes fifty nine core samples of the lignites from seven boreholes across the basin and eight channel samples from the working lignite seams were collected and analysed by proximate analysis x ray powder diffraction xrd inductively coupled plasma mass spectrometry icp ms and scanning electron microscopy sem with energy dispersive x ray microanalysis techniques the samples show that the worked lignite seams on an as received basis contain high moisture contents 43 4 57 8 all the samples on an air dried basis have high ash yields from 19 5 to 81 7 and a broad range of total sulfur contents from 1 16 to 7 04 and calorific values 684 to 4621 kcal kg except for two samples with no temperature rise due to high ash yield the mineral matter of the studied samples is made up of calcite quartz feldspar pyrite opal ct clay minerals gypsum and traces of aragonite the trace element analyses on a whole coal dry basis indicate that most of the borehole samples showed enrichment in specific elements including zn 15 1394 g g mo 13 368 g g and u 5 5 131 g g when compared to the range of these elements for most coals in the world the contents of zn mo and u for the samples from the worked lignite seams are respectively 38 187 54 161 and 28 55 g g the sem studies show that zn is hosted mainly in micron sized zn bearing mineral sphalerite but no mo and u bearing minerals have been detected during these studies except for monazites containing th and u traces the mo and u concentrations are negatively correlated with the ash yields and these elements are contained mainly within organic matter

the end triassic bivalve extinction event one of the most important episodes of mass extinction of animal groups in the whole of the phanerozoic took place in the latter part of the triassic but the time of major faunal turnover of the vertebrates preceded that of marine invertebrates by several million years as shown by ammonites brachiopods and conodonts decline from a carnian early norian diversity peak was followed by a significant extinction episode at the end of the period this pattern is confirmed at generic and subgeneric level by the bivalve molluscs probably the most abundant and diverse macroinvertebrate group this paper analyses the bivalves in detail and attempts to seek a relationship of the extinction event to environmental changes as recorded by late triassic facies stratigraphy of the youngest triassic is briefly discussed following a recent recommendation the rhaetian stage is dropped and the upper norian sevatian subdivided into three new ammonite zones it is suggested that the classic northwest european rhaetic correlates with the kossen and zlambach beds of the alps and corresponds at least approximately with the upper two of these zones it is estimated that nearly half the existing bivalve genera and nearly all the species failed to survive the end triassic extinction event the trigonioid unionoid and hippuritoid orders were especially strongly affected but most of the pholadomyoid genera survived three major ecological categories are distinguished a shallow neritic group to which most taxa belong a euryhaline group that could tolerate marginal marine and lagoonal conditions and a deep neritic group notably halobia and monotis all groups were strongly affected by the extinction but species of the deep neritic group were apparently the most susceptible seven biogeographic regions are distinguished for the purpose of analysis and it is shown that provinciality is slight but some important taxa are endemic to the tethyan and pacific regions endemic genera prove to have been much more subject to extinction than cosmopolitans there are very few places in the world with a more or less continuous marine sequence of deposits across the triassic jurassic boundary details are given of sections in the alps northwest europe and nevada and briefer mention made of others with regard to late triassic palaeogeographic changes those involving climate were neglibible but there was a more or less progressive regression of epicontinental seas following a ladinian early carnian transgressive maximum with a corresponding shallowing in the more continuously marine tethyan region that this first order effect was due to a eustatic lowering of sea level is fairly certain but the situation is less clear for second order transgressive regressive cycles the late late norian rhaetian cycle is probably however the results of a minor eustatic event by the end of the triassic the sea had regressed substantially and the mass extinction event is though to be bound up partly with this phenomenon and partly with the phase of widespread anoxicity that occurred during the succeeding hettangian transgression

breccia hosted manganese rich minerals of alpi apuane italy a marine redox generated deposit mn rich beds occur within the brecce di seravezza formation bsfm intercalated between norian metadolostone megalodontic marble and hettangian marble in the alpi apuane italy the bsfm is a rockfall talus deposit that accumulates at the base of the footwall scarp of normal faults bordering extensional marine coastal basins the type sequence of metabreccia ends with a bed of chloritoid schist interpreted as the metamorphic equivalent of lateritic soils the four main types of mn mineral assemblages are 1 braunite piemontite and rare hausmannite 2 piemontite braunite hollandite and minor rhodochrosite and kutnahorite 3 braunite hollandite and rare piemontite the other minerals are quartz calcite muscovite phlogopite baryte and minor hematite rutile and apatite during the alpine orogeny pressures of 4 6 kb and temperatures of 350 380 c were attained mn assemblages with hematite and phlogopite indicate o2 10 8 for t 350 c and o2 10 6 when braunite appears on the mn rich rocks ti fe nb sn ta hf th ga rb pr k na nd were identified as detrital in origin and are positively correlated with al u is positively correlated with co pb bi mo the rare earth element patterns normalized to seawater show a negative slope towards the heavy rare earth elements with positive ce anomalies in some samples positive ce and eu anomalies in other samples and negative ce and positive eu anomalies in a third group the eu concentrations are nearly constant and the eu anomalies reflect differences in the concentration of other rare earth elements for ce a positive correlation with al2o3 sio2 indicate that a detrital signature prevails on that produced by duration of seawater exposure but a significant good correlation of la tm lu with mg could indicate at least for these elements a seawater signature only in some samples ba eu sr show anomalously high concentrations likely of hydrothermal origin however generally in all the chemical variation diagrams the bsfm samples fall outside the field of hydrothermal and hydrogenous deposits as defined in the literature for other mn deposits in addition metabasites and metavolcaniclastic beds are absent from the bsfm sequence and bsfm coastal basins were for the most part separated from the open ocean and related streams that must be excluded as possible mn sources owing to the arid climate of late triassic the runoff was negligible and the groundwater oxidizing and alkaline were unable to mobilize mn the bsfm basins are then the most suitable depositional environment for mn the water column was stagnant and stratified only where bottom of the basin was deeper than the oxic anoxic boundary reducing marine bottom waters percolated within the fractured basement and leached mn from disseminated minerals of metamorphic rocks and then rising along fault and fractures supplied mn to the bottom waters afterwards when tectonic uplift and sealevel drop brought the bottom into the oxic field mn precipitated and formed the mn rich matrix of the bsfm deposits

hydrocarbon generation potential and miocene pliocene paleoenvironments of the kangal basin central anatolia turkey abstract this study deals with the organic geochemical characteristics hydrocarbon generative potential and miocene pliocene paleoenvironments of the kangal coal district which developed in a limnic depositional environment and contains the hamal etyemez and kalburcayiri coal fields in the southern part of the sivas basin central anatolia around kalburcayiri the average thickness of each of the two coal seams approximately 10 m are currently being exploited based on open cast methods the coal from which is used by the nearby lignite fired kangal power station an attempt was made to elucidate depositional conditions through proximate and ultimate analyses coal petrography and the geochemical characteristics of the kangal coals these coals have a huminite reflectance value of rmax 0 40 accordingly from the standpoint of coal rank this is a dull brown coal of the subbituminous c type huminite is the most widespread maceral type while gelinites are the most often encountered macerals relative to liptinites the proportion of inertinites is high on the basis of maceral composition the depositional environment of the kangal coals was determined to be either a forest swamp or a lake bottom the distributions of the c27 and c28 c29 steranes for all these coal samples are very similar c29 c27 c28 tricyclic terpanes have low concentrations in all samples of the kangal coals and are dominated by low molecular weight compounds c20 c24 with a maximum at c23 total organic carbon toc wt values of the kalburcayiri samples are 4 64 30 64 wt in the hamal samples 0 83 2 53 wt and in the etyemez samples 8 91 10 39 wt on the basis of tmax values the samples are in the immature early mature stage according to rock eval pyrolysis data the coals have hydrocarbon source rock potential but the coaly shales and other organic matter rich levels have no hydrocarbon source rock potential the high inertinite levels and high vitrinite inertinite ratios suggest that the kangal coals have more potential for gas generation than oil

geochemistry of ferromanganoan metasediments from the island of andros cycladic blueschist belt greece abstract on the island of andros cycladic blueschist belt metamorphosed ferromanganoan sediments occur in widespread lateral distribution they form concordant layers and lenses within a uniform sequence of quartz rich metapelitic schists which can be derived from pelagic siliceous mudstones three main types of ferromanganoan metasediments were geochemically investigated 1 piemontite spessartine and piemontite quartzites psq containing braunite rich lenses 2 spessartine quartzites sq and 3 napyroxene quartzites npxq textural and geochemical evidence leads to the conclusion that psq is derived from a mn nodule bearing sediment consisting of a mixture of terrigenous illitic clay with biogenic radiolarian ooze compared to recent nodule bearing sediments psq is markedly enriched in cu pb sr and as we assume that these elements were mobilized during diagenesis and or early metamorphism from the sedimentary column and were subsequently concentrated in minerals like piemontite ardennite and braunite under highly oxidizing conditions in contrast to psq sq and npxq are derived from parent sediments rich in smectite sq shows a higher al fe ratio in rock composition than npxq and may change into npxq by a decreasing content of spessartine while sq is chemically equivalent to a montmorillonitic clay mn 2 na almost spessartine free npxq can be derived from fe rich nontronitic clay na mn 2 required for the formation of sq was probably mobilized from adjacent mn nodule bearing sediments psq

chemical fluxes and origin of a manganese carbonate oxide silicate deposit in bedded chert abstract lens like rhodochrosite rich bodies within interbedded chert and shale are associated with basalt and or graywacke in ophiolitic and orogenic zones the buckeye manganese mine in the franciscan complex of the california coast ranges is associated with metagraywacke despite blueschist facies metamorphism this deposit preserves the compositions and some textural features of its sedimentary protoliths for this reason it is a suitable deposit with which to compare more intensely altered deposits or deposits originating in different paleoenvironments six mn rich and three mn poor minerals form monomineralic layers and mixtures rhodochrosite gageite mn oxides hausmannite braunite divalent mn silicates caryopilite taneyamalite chlorite quartz metachert and aegirine augite the mn rich protoliths have high mn fe combined with relatively low concentrations of ca al ti co ni cu th and ree ree patterns of various protoliths are distinct rhodochrosite and gageite layers are depleted seawater 5 104 and flat whereas patterns of metachert and the mn silicate rich layers mimic the patterns of metashale and metagraywacke seawater 106 hausmannite layers have flat patterns seawater 7 104 whereas braunite rich layers are more enriched seawater 2 105 and show a distinct positive ce anomaly factor analysis reveals components and fluxes attributed to sub seafloor fluids ni as zn sb w mn seawater mg au v mo detritus and veins ca ba sr silica is negatively correlated with the sub seafloor factor the observed variances indicate that water from the sediment column mixed with seawater that deposition occurred near the sediment seawater interface before mixtures of subsurface fluid and seawater homogenized and that the system was not entirely closed during metamorphism the variations in ree enrichment can be related to kinetics of deposition rhodochrosite and gageite were precipitated most rapidly and therefore were the protoliths that most effectively diluted the ree rich background resulting from fine clastic material derived from distal turbidites the variation of the ce anomaly and u th among diverse lithologies and the differences in mn oxidation states are consistent with progressive dilution of reduced subsurface fluids with oxidized seawater by this scheme rhodochrosite gageite and hausmannite were deposited from the most reduced fluids braunite from intermediate mixtures and mn silicates from the sub seafloor fluids most diluted with fresh seawater comparison of the buckeye with other lens like and sheet like deposits having high mn fe and containing mn3 and or mn2 suggests that each had three essential fluxes a sub seafloor source of mn a local source of very soluble silica and a source of relatively fresh oxygenated water additional fluxes such as clastics appear to be more characteristic of the paleoenvironment than the three essential fluxes

modern carbonate siliciclastic transitions humid and arid tropical examples climate and tectonic setting largely control characteristics of transitions between carbonate and siliciclastic sediments in depositional systems three examples selected from both humid and arid tropical settings are discussed order to illustrate details of these relationships the eastern shelf area of nicaragua is an area where siliciclastic and carbonate sediments actively interfinger under humid tropical conditions extremely high rainfall 4 5 m yr 1 in the southern part of coastal plain coupled with a correspondently high sediment flux to the nearshore shelf results in an inner shelf that is dominated by siliciclastics density gradients and persistent momentum provided by the trade winds force turbid coastal waters to the south and confine siliciclastic sediments to a coast parallel zone approximately 20 km wide the remainder of the broad shelf is characterized by carbonate sediments and reefs the mid shelf area has a coarse carbonate sediment cover composed largely of the calcareous green alga halimeda the outer shelf displays rugged topography associated with reef development skeletal carbonates containing abundant coral and coralline algal grains are characteristic of the seaward margin of the shelf significant amounts of siliciclastic sediment are confined to the nearshore part of the shelf and the transition from siliclastics to carbonates occurs over a distance of 20 km or less a second example from the humid tropics focuses on the living reefs of indonesia that are surrounded by fine grained siliciclastics a warm rainy climate results in rapid weathering of volcanic rocks from the indonesian archipelago and abundant sediment input to the shallow 40 70 m deep sunda shelf in the northern hemisphere winter monsoonally driven marine processes rrive water and sediment to the east down the axis of the java sea during summer the direction of transport is reversed this bidirectional process regime not only leaves its imprint in reef and carbonate platform morphology but also results in widespread distribution of siliciclastics from adjacent source areas isolated reefs as well as small and generally elongate reef rimmed carbonate platforms 0 5 10 km long rise 40 50 m above a sea floor composed largely of siliciclastic sediments in these cases facies transitions are very abrupt until environmental conditions curtail the carbonate producing communities of these platforms carbonate buildups and associated skeletal sediments will coexist with wider spread and more abundant siliciclastics a third example from a low latitude arid setting shows that facies transitions from carbonates to siliciclastics typically take place over short distances the lack of significant rainfall coupled with high relief along fault controlled basin margins promotes aperiodic but powerful episodes of siliciclastic that build directly into the marine environment high sloping and narrow coastal plains composed of overlapping fans result the steep seaward ends of these fans are maintained and protected from marine erosion by coral reefs and associated carbonates regionally siliciclastic to carbonate facies changes in these arid settings take place over very shor distances a few kilometers at most however on a local scale carbonates may be replaced by siliciclastics over distances as small as a few tens of meters

upper mississippian lower carboniferous carbonate stratigraphy and syndepositional faulting reveal likely ouachita flexural forebulge effects eastern kentucky u s a abstract stratigraphic analysis of late middle to early late mississippian early carboniferous late meramecian early chesterian carbonates in east central and northeastern kentucky u s a shows six unconformity bound sequences the earliest late meramecian st louis sequence shows a relatively uniform distribution and a typical eastward appalachian gradient along the ene trending outcrop belt on the western margin of the appalachian basin however abrupt uplift and exposure of deeper water st louis deposits indicated by erosional thinning and well developed exposure features at the meramecian chesterian transition signal inception of regional early chesterian uplift that intensively altered the nature and distribution of the five overlying early chesterian carbonate sequences uplift was related to the syndepositional reactivation of wnw trending basement faults that broke up the st louis platform and generated a mosaic like distribution of the overlying five sequences due to structurally related erosional incision and paleoslope change to the southwest these early chesterian events coincide with a major phase of northeast directed ouachita orogeny on the southern margin of laurussia and concomitant forebulge migration to the ene modeling of regional stress distribution as well as timing and location during bulge migration strongly indicate that a migrating ouachita bulge reactivated basement structures and generated the noted stratigraphic anomalies in eastern kentucky and nearby areas the likelihood of low amplitude flexural waves like the ouachita bulge migrating across areas where they were not previously considered has major implications for understanding structural stratigraphic and eustatic anomalies in supposedly stable cratonic areas far removed from active tectonism

geochemistry and origin of the bald knob manganese deposit north carolina geochemical and textural evidence for the submarine hydrothermal origin of the bald knob mn deposit north carolina is preserved in a mineralogically diverse suite of rocks that have experienced amphibolite facies metamorphism manganese and mn fe rich lithologies have high mn fe ratios and low concentrations of ni cu zn u th and rare earth elements that are similar to concentrations reported from other ancient manganiferous deposits and from crusts and sediments which are forming in hydrothermally active regions of the present sea floor manganese and ca rich carbonate minerals a variety of mn rich silicates including tephroite the mn humite group minerals spessartine rhodonite and pyroxmangite and the oxides galaxite and jacobsite form fine laminations that represent different bulk compositions no chemical or textural evidence for replacement of mn poor by mn rich minerals was found and in some samples the same lithologic units are repeated on the scale of a thin section consistent with a primary sedimentary origin for the layering chert which is one of the country rocks at bald knob and mn and ca rich carbonate rocks represent original sedimentary protoliths more than one detrital component may be present in the mn rich layers biogenic detritus was the probable source of at least some of the siliceous material that allowed for the formation of the mn rich silicates an aluminous detrital component which probably was derived from a continental or andesitic source is reflected in spessartine rich layers minor mn and co sulfide mineralization alabandite cattierite cobaltite was contemporaneous with deposition of the mn rich sediments the association of the manganiferous lithologies with chert and meta igneous rocks amphibolite is consistent with deposition of the sediments in a rifting environment such as a back arc basin or possibly a midocean ridge

sponge microbial mound facies in mississippian tuscumbia limestone walker county alabama a new core from the black warrior basin of alabama contains a newly discovered mound lithofacies in the tuscumbia limestone meramecian the schlumberger alabama power 1 plant gorgas well contains 37 2 m 122 ft of carbonate rock assigned to the tuscumbia this formation overlies the fort payne chert osagean which was penetrated but not cored in this well the tuscumbia underlies calcareous shale and limestone of the chesterian pride mountain formation three lithologic units have been defined in the cored part of the tuscumbia the basal 2 8 m 9 25 ft of the core consists of sponge microbial boundstone unit 1 this is overlain by 20 6 m 67 6 ft of mixed carbonate strata dominated by mixed particle grainstone which increases in abundance upward unit 2 some of the grainstone is brecciated suggesting exposure and paleokarst development following mound formation grainstone is interbedded with thin units of argillaceous cherty peloidal carbonate sponge microbial boundstone and mixed particle rudstone glauconite is common in the basal part of unit 2 unit 2 is abruptly overlain by 13 8 m 45 2 ft of bryozoan crinoid grainstone unit 3 containing breccia beds low angle cross strata and immature carbonate paleosols this unit is sharply overlain by the lewis limestone of the pride mountain formation which here consists of 0 5 m 1 7 ft of interbedded fossiliferous shale and mixed particle packstone the lewis limestone is overlain disconformably by fenestrate bryozoan rich shale the basal part of the core records growth of a sponge microbial mound in relatively shallow water below normal wave base the mound is not waulsortian stromatactis is absent and matrix material is grainy the upper contact is sharp and borings are locally abundant abundant authigenic glauconite indicates reducing pore waters the mound was buried by foreshoal grainstone much of which is brecciated upper tuscumbia bryozoan crinoid grainstone formed in a mobile shoal that quickly aggraded to sea level although the upper tuscumbia here is typical of the formation the shoal buried a mound facies not previously reported from the tuscumbia early diagenesis was dominated by marine cementation syndepositional alteration and fracturing burial diagenesis was dominated by calcite cementation dissolution of siliceous spicules stylolitization chert formation and later emplacement of hydrocarbons and their subsequent transformation to pyrobitumen today original interparticle voids are filled with a mixture of calcite cement replacive chert and solid hydrocarbons irregular nodules of chert replaced parts of the mound and the overlying heterogeneous unit dolomite partially replaced heterolithic strata of unit 2 patches of once porous rock in units 1 and 2 contain abundant solid hydrocarbons but porosity 0 7 5 6 and permeability 1 78 d are low in place heating led to gas generation and to concomitant in place solidification of liquid hydrocarbons

genetic diversity of manganese deposition in the terrestrial geological record terrestrial manganese deposits formed by hydrothermal sedimentary and supergene processes ancient analogues of modern oceanic hydrothermal deposits formed in spreading centre and subduction related settings and those deposited from terrestrial hot springs are discussed sedimentary mn oxide deposits formed in shallow water at the margins of stratified oceans above the redoxcline during sea level changes mn carbonate deposits probably formed by diagenesis through mn oxyhydroxide reduction coupled with organic matter oxidation climatic variation and basin water stratification responsible for mn concentration were manifestations of atmospheric coz content prompted by tectonism supergene manganese enrichment in continental weathering profiles was mainly dictated by climate topography and drainage systems manganese deposits of diverse genetic types occur in the terrestrial geological record roy 1981 these were produced by direct hydro thermal activity sedimentary processes and continental weathering although the processes may be interrelated each involves distinct mechanisms that place the deposits into specific genetic types some of these processes are best understood in preset day depositional sites the ancient environments were determined by the intensity and style of tectonism volcanism and hydrothermal activity the composition of the atmosphere and the hydrosphere and the development of the biosphere which all varied with time it is my intention to unfold the total panorama of the environmental evolution during different time envelopes that produced a variety of manganese deposits in the past only major deposits and those providing distinctive evidence of their environment of deposition will be considered here

contrasting mineralogical geochemical signatures of manganese oxides guides to metallogenesis manganese oxides have a strong sorption capacity for cationic species in the depositional fluid this sorption capacity is reflected in the chemistry of the oxides which is different from that for the oxides precipitated from fresh water seawater and hydrothermal fluids characteristic mineralogical geochemical enrichment and geochemical association defined statistically signatures in conjunction with several diagnostic plots can be employed to distinguish between the following different genetic types of manganese deposits supergene hydrothermal supergene marine terrestrial supergene dubhite and supergene marine hydrothermal sedimentary exhalative sedex dubhites are manganese oxides derived from the weathering of a mineralized sequence i e base and precious ore minerals and gangue hydrothermal deposits characteristically show geochemical enrichments in the assemblage as ba cu li mo pb sb sr v zn and an mn as geochemical association supergene marine deposits show na k ca mg sr and co cu ni geochemical enrichments whereas supergene terrestrial deposits tend to have very high ba contents and an mn ba association dubhites contain high levels of pb and zn show an mn pb base metal association and are composed of significant quantities of base metal bearing manganese oxides bixbyite braunite hausmannite huebnerite jacobsite and pyrochroite occur predominantly only in hydrothermal deposits whereas chalcophanite coronadite crednerite delta mno 2 groutite hollandite lithiophorite manganite nsutite quenselite ramsdellite romanechite todorokite and woodruffite are generally of supergene origin in addition to established plots presently used to identify marine sedimentary exhalative deposits the following diagnostic graphs were devised na vs mg distinguishes deposits of marine and fresh water origin co ni vs as cu mo pb v zn discriminates between hydrothermal and supergene oxides and pb vs zn can be used to recognize dubhites and therefore prospective sequences

hydrothermal mn deposits of the franciscan assemblage ii isotope and trace element geochemistry and implications for hydrothermal convection at spreading centers abstract major element trace element and sr nd pb and o isotopic data for a franciscan mn deposit suggest an origin by seafloor hydrothermal circulation based on q mode factor analysis the cherts and mn lenses of the blue jay mine formed from a combination of 4 components representing 1 biogenic 1 hydrothermal and 2 detrital sources rb sr u th pb and o isotopic systematics in the mn lenses were affected by input from the hydrothermal circulation of material leached from the underlying basalts nd isotopic compositions in both cherts and mn lenses are identical and within the range measured for pacific ocean water suggesting the ree were not mobilized by hydrothermal activity correlation of 18 o with sio 2 and mno 2 in the mn lenses implies the lenses formed by simple mixing of hydrothermally derived mn oxides with seawater and biogenic silica 18 o of the cherts is both uniform and depleted relative to dsdp jurassic cherts but similar to microquartz bearing cherts of the monterey formation this suggests that diagenetic activity exerted more control on oxygen isotope compositions then hydrothermal alteration or metamorphism finally a well defined rb sr isochron of 158 5myr was obtained for these cherts and opens the possibility of determining absolute radiometric ages for similar cherts throughout the geologic record

seam modeling and resource estimation in the coalfields of western anatolia abstract western anatolia turkey includes a number of lignite bearing neogene fields with difficult modeling and estimation problems resulting from severe tectonic movements and highly variable coal quality the paper considers the eynez soma and omerler tuncbilek coal fields and introduces a simple but effective way of defining the geological discontinuities that are vital for selective mining method after doing statistical analysis for both fields data taken from core samples of diamond drill holes are used to model fault blocks in order to establish a 3d coal seam model then block small mining unit modeling is performed for both coal fields and some coal quality parameters are estimated and assigned to the predefined blocks for estimation process a new method of wrinkling and unwrinkling is introduced and composited data is detrended each block is kriged by using the detrended data in unwrinkled space the volume of the blocks is converted into in situ tonnages based on their estimated densities in eynez the densities are derived from the mean lower calorific value of the blocks using the relationship between lower calorific value and density in omerler the block densities are estimated from the composited values of densities of the lithologic units in coal horizon by using ordinary kriging

the overprint of the alpine tectono metamorphic evolution on the hercynian orogen an example from the apuane alps northern apennines italy abstract the apuane alps represent a tectonic window in the nappe structure of the northern apennines in its lowermost part the apuan metamorphic complex i e autochthonous auct and massa unit reveals a polyphase structural pattern as the result of two main alpine events of tertiary age the first event is responsible for intense isoclinal folding and the development of a pervasive schistosity in greenschist facies the second is connected with the subsequent late stage uplift the pre triassic rocks in the core of the main isoclinal anticlines were severely tectonized completely transposing a pre existing foliation and a greenschist pre alpine synkinematic metamorphism the traces of which are obvious and widespread hercynian structures of megascopic mesoscopic and microscopic size are outlined here

palaeoclimatic implications of the growth history and stable isotope delta o 18 and delta c 13 geochemistry of a middle to late pleistocene stalagmite from central western italy the age structure and stable isotope composition of a stalagmite cc i from an upland cave in central western italy were studied to investigate regional response to global climatic changes four growth phases are constrained by 28 thermal ionization and multi collector inductively coupled plasma mass spectrometry th u ages and reveal intermittent deposition through the period between marine isotope stage mis 11 and 3 similar to380 and similar to43 kyr most of the growth took place between similar to380 and similar to280 kyr a period punctuated briefly by a hiatus in deposition through the glacial maximum of mis 10 growth was terminated abruptly at 280 kyr just prior to the mis 8 glacial maximum with a present day chamber temperature of 7 5 degreesc the timing of hiatuses close to these glacial maxima point to freezing conditions at the time no deposition was recorded through the entirety of mis 7 and most of mis 6 whilst two minor growth phases occurred at similar to141 125 and similar to43 kyr growth at 141 kyr indicates temperatures 0 degreesc at a time when mis 6 ice volumes were close to their maximum high stable carbon isotope delta 13 c values similar to2 8parts per thousand to 3 1parts per thousand throughout the stalagmite s growth reflect a persistently low input of biogenic co2 indicating that the steep barren and alpine like recharge area of today ha s been in existence for at least the last similar to380 kyr during mis 9 the lowest delta 13 c values occur well after maximum interglacial conditions suggesting a lag in the development of post glacial soils in this high altitude karst the stable oxygen isotope delta 18 o trends match the main structural features of the major climate proxy records specmap vostok and devils hole suggesting that the delta 18 o of cc1 has responded to global scale climate changes whilst remarkable similarity exists between cc1 delta 18 o and regional sea surface temperature reconstructions from north atlantic core odp980 and southwest pacific marine core md97 2120 through the most detailed part of the cc1 record mis 9 8 the results suggest that cc1 and other stalagmites from the cave have the potential to capture a long record of regional temperature trends particularly in regards to the relative severity of pleistocene glacial stages c 2004 elsevier b v all rights reserved

petrographical properties and unusual features of kangal coals sivas turkey abstract in turkey low rank coal is used in three sectors power generation industry and household and commercial heating due to poor quality coal is suitable for thermal power generation only kangal coal is of low rank being mostly used in a thermal power station kangal coal basin located in eastern central turkey formed in a pliocene aged fresh water lacustrine depositional environment and includes kalburcayiri hamal and etyemez fields approximately 202 6 mt of coal reserve with calorific values between 1010 and 3420 kcal kg are hosted in the area kalburcayiri field is the only open pit production site in the basin fifty two channel samples were collected from different sites the composite profile samples of the seams were taken into considerations the content and depositional properties as well as some chemical and physical properties of the main coal seams are compared detailed organic petrographic and chemical analyses were applied for this study all coal samples tend to have similar coal petrographic properties and were deposited in a lacustrine basin later they were affected by faulting as a result there are variations in the properties and rank of the coal samples the most abundant maceral group is huminite and the most abundant maceral is gelinite liptinite and inertinite contents of the coal are low and the maceral assemblage of the coals show extremely unusual broken and deformed maceral contents tend to be more abundant considering the other turkish coals the maceral contents textures and the unusual appearances imply that the coals were formed as in a hypautochtonous way the reflectance measurements indicate the rank of the coals to be mostly as sub bituminous although some chemical analyses exhibit inefficient results

on the geological significance of clastic parasequences abstract parasequences recognized in clastic sedimentary successions of shallow marine origin are considered by some geologists to be the fundamental building blocks of depositional sequences even though problems in their definition and application have been identified by others who instead advocate their abandonment as formal sequence stratigraphic units to elucidate the geological significance of clastic parasequences and inform the debate on their use in stratigraphy a quantitative characterization of the geometry facies characteristics and timescale of deposition of 1163 parasequences has been undertaken based on a synthesis of data from outcrop and subsurface studies that are available in the scientific literature through a database compilation the attributes of the studied parasequences are analysed with respect to the interpreted geological origin of the units and with consideration of sources of bias and uncertainty particular emphasis is placed on assessing the following i the importance of heuristics and of data types and coverage in the recognition of parasequences ii differences in parasequence characteristics observed across deltaic and shoreface depositional systems and between the quaternary and the ancient rock record iii possible explanations for the range in timescales of deposition of parasequences and iv the role of autogenic dynamics on the development of deltaic parasequences partly based on a comparison with the recent evolution of modern deltas the results demonstrate that parasequence definition and physical correlation suffer from subjectivity and that significant variability exists in the spatio temporal and architectural attributes of clastic parasequences this gives rise to uncertainty that affects the use of parasequences as a framework for comparison of the architecture of packages of strata originating via shoreline regression this uncertainty must be considered when using analogue data for subsurface predictions or when attempting comparative studies of clastic successions

pelagic carbonate platforms in the geologic record their classification and sedimentary and paleotectonic evolution drastic differences in thickness and abrupt lateral facies changes in synrift and postrift pelagic sequences usually indicate structural control over deposition although the highs and the basins in pelagic carbonate systems have long been recognized in ancient rifted continental margins relatively little detailed information has been available on facies transitions between the two and on the geometries of pelagic sediment bodies outcrops in the umbria marche apennines central italy provide new constraints for jurassic paleogeographic reconstructions allowing for the development of models for these depositional systems pelagic carbonate platforms pcps are submarine highs that are drowned fragments of an ancestor regional peritidal carbonate platform pcps can be horsts or crests of rotated blocks the extensional regime and drowning history exert a major control over the pcp type and over the composition of sediment which fills inter pcp basins given the very low rates of pelagic sedimentation a few mm 1000 yr the effects of faulting on submarine topography are drastic block tilting is of great importance creating pelagic carbonate ramps that are the source area of most of the gravity flow deposits in half grabens excessively rapid tilts cause nondeposition in horst and graben settings on the other hand basins are sediment starved and there are comparatively only minor gravity flows ma s transport there is mostly in the form of collapse of platform margins the margins of pcps are erosional during most of pcp history becoming depositional when adjacent basins are filled stepped margins develop through fault induced reduction of the pcp area back stepping

a guide to phanerozoic cold polar climates from high latitude ice rafting in the cretaceous the high latitude extent of warm climate indicators at certain times in earth history has been considered as evidence that the globe was ice free for long intervals despite theoretical considerations and results from numerical modelling experiments1 2 indicating that this was unlikely one of the warmest periods the cretaceous displays faunal and floral evidence for cool temperate to sub tropical conditions very near to the poles however our studies of lower cretaceous mudstones of central australia that contain outsized exotic blocks have led to the conclusion that the blocks were emplaced by ice rafting implying that high latitude ice was present at sea level strata of a similar origin of mid jurassic to mid cretaceous age occur on other continents that were positioned between 65 and 78 palaeolatitude indeed there is a record of high latitude ice rafting throughout the phanerozoic suggesting that ice was present on earth for much of its history and that ice free conditions could have been at most only episodic over the past 600 myr

sequential filling of a late paleozoic foreland basin abstract through the use of an extensive data base of geophysical well logs parasequence scale subdivisions within a late paleozoic synorogenic clastic wedge resolve cycles of sequential subsidence of a foreland basin sediment progradation subsidence of a carbonate shelf edge diachronously subsiding discrete depositional centers and basinwide transgression although temporal resolution of biostratigraphic markers is less precise in paleozoic successions than in younger basins parasequence scale subdivisions provide more detailed resolution within marker defined units in paleozoic strata as an example the late paleozoic black warrior basin in the foreland of the ouachita thrust belt is filled with a synorogenic clastic wedge the lower part of which intertongues with the fringe of a cratonic carbonate facies in the distal part of the basin the stratal geometry of one tongue of the carbonate facies lower tongue of bangor limestone defines a ramp that grades basinward into a thin black shale an overlying tongue of the synorogenic clastic wedge lower tongue of parkwood formation consists of cyclic delta and delta front deposits in which parasequences are defined by marine flooding surfaces above coarsening and shallowing upward successions of mudstone and sandstone within the lower parkwood tongue two genetic stratigraphic sequences a and b are defined by parasequence offlap and downlap patterns and are bounded at the tops by basinwide maximum flooding surfaces the distribution of parasequences within sequences a and b indicates two cycles of sequential subsidence deepening and progradation suggesting subsidence during thrust advance and progradation during thrust quiescence parasequence stacking in sequences a and b also indicates diachronous differential tectonic subsidence of two discrete depositional centers within the basin the uppermost sequence c includes reworked sandstones and an overlying shallow marine limestone a vertical succession that reflects no tectonic subsidence a very minor or null sediment supply and basinwide transgression the temporal resolution at parasequence scale significantly improves the resolution of the tectonic history of the thrust belt foreland basin system

the mesozoic continental rifting in the mediterranean area insights from the verrucano tectofacies of southern tuscany northern apennines italy in the alpine mediterranean region the continental redbeds and shallow marine siliciclastics related to the early depositional phases of the late permian mesozoic continental rifting are referred to as the most common representative of the verrucano tectofacies the verrucano type successions exposed in southern tuscany are diachronous spanning from triassic to earliest jurassic in age and accumulated within the tuscan domain a paleogeographic region of continental crust that due to the opening of the piedmont ligurian ocean formed part of the adria passive margin they belong to the metamorphic verrucano group and the non metamorphic pseudoverrucano fm viewed overall these verrucano type successions appear to manifest five episodes or pulses of an ongoing continental rifting with the exception of the first episode that developed entirely within a terrestrial setting each one is represented by basal verrucano type continental siliciclastics overlain by compositionally mixed marine deposits which resulted from four diachronous post middle triassic transgressions this suite of tectonic pulses produced the progressive westward widening backstepping of the tuscan domain in the rifting south tuscany area

triassic environments climates and reptile evolution abstract a consideration of all the available data on triassic vertebrate faunas and their stratigraphic location reveals a relatively sudden extinction event among the last of the mammal like reptiles and the herbivorous rhynchosaurs in the norian of the upper triassic this event was apparently quickly followed by the radiation of the dinosaurs also in the norian this conclusion suggests that competition was not the main factor in the initial success of the dinosaurs but opportunistic radiation following the extinction of major reptile groups a global review of triassic sedimentary facies shows that there were climatic and floral changes towards the end of the triassic it is envisaged that increasing aridity in the later triassic resulting from plate motions and particularly affecting gondwanaland and southwestern laurasia brought about floral changes and then the reptile extinctions with the rapid evolution of new floras of conifers and bennettitaleans the dinosaurs came to dominate all terrestrial faunas within the space of only a few million years

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

lignite resource estimations and seam modeling of thar field pakistan abstract thar lignite field in pakistan contains more than 175 billion tons thus far not exploited to date the coalfield has been divided into 12 exploration blocks and each block is studied and investigated separately by different agencies as a result of exploration programs a large exploration database containing geological and coal quality information is constructed but geostatistical studies regarding to quantify entire thar lignite resources is not available yet this paper aims to generate 3d solid model of main thar seam and to produce spatial distribution maps for various coal quality attributes by geostatistical method ordinary kriging 3d seam model has a volume of 17 71 billion m3 the resulting spatial map of ash content shows structured distribution and lcv map shows fair agreement with ash map except in block vi where high and low values of ash and lcv occur in close proximity the moisture distribution reveals higher values in northern and southern parts whereas the central portion possesses lower moisture values the sulfur content shows homogenous distribution with some higher sulfur patches at places the kriging variance maps are generated to delineate areas of higher uncertainty these maps could be helpful to devise further exploration programs blocks were checked on the basis of global averages and swath plot comparison

genetic types of manganese oxide deposits in scotland indicators of paleo ocean spreading rate and a devonian geochemical mobility boundary there are over 70 occurrences of manganese oxides throughout scotland of these only 13 are sufficiently well developed to be worthy of description the deposits are categorized on the basis of the formation processes eight are supergene ground water or soil deposits three formed by weathering and two are hydrothermal in origin the chemistry of marine sedimentary exhalative deposits can be related to the paleospreading rate of the once active ridge and under favorable conditions of stratigraphic preservation be used to estimate the halfwidth of the ancient ocean this approach yields estimates of 5 cm yr super 1 and about 1 000 km for the spreading rate and maximum half width of the ordovician iapetus ocean respectively figures which compare favorably with earlier estimates from faunal migration studies several of the scottish manganese outcrops are associated with old red sandstone devonian sediments a continental fluvial lacustrine facies in northern scotland diagenetic remobilization with subsequent oxidation and deposition of the manganese within the lacustrine sediments led to the formation of a manganese rich horizon in the uppermost sections of the old red sandstone sedimentary pile previously immobile in the pre devonian inorganic reaction dominant regime manganese mobility increased dramatically with the introduction of large quantities of organic acids following terrestrial colonization by plants climate change from arid to tropical with increased vegetation development promoted the formation of thick organic rich soils with the concomitant increase in available manganese chelating ligands organomanganese reactions fundamentally changed the pattern of manganese mobility in the postcolonization surficial environment making the devonian a stratigraphic geochemical boundary these changes in weathering processes would also affect the dispersal patterns of other metals which form organo complexes gold being an obvious example

a lone biodetrital mound in the chesterian carboniferous of alabama abstract a carbonate mound in the chesterian bangor limestone of lawrence county alabama consists chiefly of packstone and grainstone dominated by echinoderm ossicles and fragments of fenestrate bryozoans in situ colonies of the rugose coral caninia flaccida comprise about 8 of the mound by volume the exposed portion of the mound is approximately 25 m wide 1 6 m thick at the thickest point and roughly circular in plan the mound developed on top of a shallow ooid shoal that had been cemented and stabilised during an earlier episode of sub aerial exposure subsequent flooding of the exposed shoal surface permitted establishment of the mound biota lateral and vertical facies relationships suggest that the mound possessed about 45 cm of synoptic relief when fully developed rugose corals fenestrate and ramose bryozoans stalked echinoderms and sessile soft bodied organisms encrusted by foraminifera colonised the shoal forming a mound baffling resulted in deposition of mixed fossil packstone containing locally derived debris and coated grains from the surrounding sea floor strong currents within the mound are indicated by preferred orientation of corals and by coarse commonly cross stratified grainstone in channels between neighboring coral colonies corals are most abundant on the windward side of the mound where they account for about 13 of the mound compared to 6 10 in the central part of the mound and 2 4 on the leeward flank biodetrital mounds such as the one described here are uncommon in upper paleozoic strata and previously unknown in the bangor limestone of 10 carbonate buildups we examined in the bangor in alabama and tennessee only one is a biodetrital mound two are rugose coral microbial reefs one is a coral biostrome and six are dominated by microbialite the bangor shelf previously interpreted as sedimentologically simple appears to contain many small mounds of quite varied characteristics also the discovery of a biodetrital mound in the chesterian of alabama suggests that there may be more kinds of upper paleozoic mounds than commonly acknowledged

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

a ground water mixing model for the origin of the imini manganese deposit cretaceous of morocco the imini deposit just south of the atlas mountains of morocco consists of three beds of manganese oxide ore in a slightly deformed dolomite unit about 10 m thick of cenomanian turonian late cretaceous age the dolomite host is sugary textured massive and permeable dolomite occurs as nearly euhedral rhombs each ore bed is about a meter thick and consists almost entirely of intergrowths of pyrolusite and hollandite family minerals bao up to 11 and pbo up to 28 with a flattened geode structure overlying the ore beds are solution collapse breccias with dolomite clasts janggunite mn fe oxide and dolomite matrix and pyrolusite hollandite calcite cement the ore solution collapse breccia and coarsely recrystallized pure dolomite are coextensive a zone only 400 to 1 000 m wide but 25 km long and elongate east northeast west southwest diagenetic features of the deposit are recrystallized texture of the dolomite flattened geode structure of the ore solution collapse breccia and associated draped laminae of the insoluble residues fossil replacement by mn oxides and zoned chert nodules with inclusions a mineralogic paragenesis shown independently in each of these features from older to younger is 1 precursor carbonates 2 dolomite janggunite and 3 hollandite pyrolusite chert calcite diagenesis probably occurred during the late cretaceous in a mixing zone of fresh and saline ground water as similar diagenetic sequences without manganese deposits are widely reported to have formed in such environments carbon and oxygen isotope compositions of carbonates and oxygen isotope compositions of chert show that an increasing component of fresh meteoric ground water was present as diagenesis proceeded falling sea level allowed the mixing zone to occupy various positions within the carbonate unit and convert the primary calcareous carbonate rocks to dolomite with chert nodules anoxic seawater is known both worldwide and from the local depositional basin atlas gulf in the cenomanian turonian this is believed to be the key to manganese deposition because anoxic conditions greatly enhance manganese solubility two specific versions of the mixing zone model are presented for manganese deposition one in which a primary sedimentary manganese precipitate formed along margins of the anoxic basin and was recrystallized during diagenesis in the mixing zone and the other in which anoxic saline ground water brought manganese into the mixing zone where it precipitated

new evidence for enhanced preservation of organic carbon in contact with oxygen minimum zone on the western continental slope of india paropkari a l prakash babu c and mascarenhas a 1993 new evidence for enhanced preservation of organic carbon in contact with oxygen minimum zone on the western continental slope of india mar geol i 11 7 13 in order to evaluate the reason for organic enrichment on the western continental slope of india we provide rock eval pyrolysis data of 25 surficial sediment samples from this area results show that the organic matter on the slope is hydrogenrich type ii kerogen which suggests that the organic carbon there is mostly marine the low productivity of overlying waters rules out surface productivity as a possible cause of organic enrichment the association of higher hydrogen index hi values average 306 and higher organic carbon contents av 3 28 wt with the sediments of the upper slope in contact with the oxygen minimum zone omz clearly indicates enhanced preservation under reducing conditions in the anoxic waters of the omz it is suggested that the sediments of the upper slope in contact with the omz have excellent hydrocarbon generation potential and that these slope beds deserve preferential attention for hydrocarbon exploration

regional distribution of al silicates and metamorphic zonation in the low grade verrucano metasediments from the northern apennines italy abstract mineralogical and petrological studies of triassic verrucano metasediments of the northern apennines are reported the widespread occurrence of al silicates allows the delineation of four metamorphic zones with increasing metamorphic grade 1 kaolinite zone well perugia 2 umbria 2 kaolinite pyro phyllite zone monte argentario and part of the verrucano of the monticiano roccastrada area and monti leoni 3 pyrophyllite zone monti pisani iano monti leoni the monticiano roccastrada area and some wells in the larderello region 4 kyanite zone massa area and some wells in the larderello area the four metamorphic zones correspond to temperatures ranging from 300 c to about 450 c on the basis of the si content of muscovite and geological arguments pressures of between 3 and 5 kbar are estimated the metamorphic zones are located more or less parallel to the bent north west south east trending structural zonation of the northern apennines with the concave side towards the tyhrrenian sea during the alpine orogeny the verrucano metasediments underwent three folding phases each of which has produced an axial plane schistosity s1 s2 s3 during the first folding phase the verrucano sediments were buried increasingly deeply within the crust from east to west the climax of alpine metamorphism was attained prior to the second folding phase with crystallization of porphyroblasts of kyanite and chloritoid in a central area located between massa and larderello the inferred paleo temperature distribution pattern resembles an asymmetric thermal high defined by the kyanite zone and surrounded by the pyrophyllite zone a similar pattern is still present in the tuscan crust as indicated by a series of geothermal anomalies passing through the northern apennines

physicochemical environments for the formation of quartz free manganese oxide ores from the early proterozoic hotazel formation kalahari manganese field south africa physicochemical environments for the formation of quartz free manganese oxide ores from the hotazel formation of the kalahari manganese field northern cape province south africa are discussed quantitatively on the basis of the phase relations in the system mn fe si o and qualitatively in the system ca mn fe si o the phase relations involve major oxide minerals of the ores namely braunite braunite ii hausmannite bixbyite jacobsite and hematite and were constructed under quartz deficient conditions using existing and estimated thermody namic data and mineral assemblages from the ores standard enthalpy delta hm 0 sub f 298 and gibbs free energy delta g 0 sub f 298 values of braunite are estimated to be 1 011 9 or 5 and 937 3 or 5 kcal mole respectively on the basis of published experimental data and predicted entropy and heat capacity the low grade diagenetic to very low grade metamorphic mamatwan type ores consisting mainly of braunite hausmannite jacobsite hematite kutnohorite and calcite are altered by hydrothermal solutions into the high grade high temperature wessels type ores consisting of braunite ii bixbyite hausmannite hematite calcite and andradite with trace amounts of braunite the peak temperature of formation of the high grade ores appears not to have exceeded about 300 degrees to 400 degrees c the ores are oxidized from oxygen fugacity levels defined by the assemblage hausmannite jacobsite hematite to that defined by the assemblage bixbyite hausmannite with increasing temperature under hydrothermal quartz deficient conditions the stability of braunite is enlarged to higher temperatures with increasing silica activity a sub sio sub 2 aq because braunite is much less abundant in the high grade wessels type ore than in the low grade mamatwan type ore the maximum a sub sio sub 2 aq in the solutions could be estimated at 10 super 4 to 10 super 3 at 300 degrees to 400 degrees c from the stable assemblage bixbyite hausmannite braunite kutnohorite and to some extent calcite was a major source of ca reacting with silica released from braunite to form braunite ii and andradite

manganese in monoclinic members of the epidote group piemontite and related minerals according to mayo 1932 who provided a brief historical review of the names used for piemontite the first researcher who described this mineral has been cronstedt in 1758 who named it rod magnesia in 1790 chevalier napione analyzed the sample described by cronstedt and termed it manganese rouge on the basis of his chemical data hauy designated the substance as manganese oxide violet silicifere in 1801 later in his traite de mineralogie hauy 1822 adopted the name proposed by cordier 1803 who first recognized the mineral as an epidote manganesifere the name piedmontite was proposed in 1853 by kenngott the basis of the type locality and more recently transformed into piemontite according to the standard guidelines for mineral nomenclature the name piemontite should be reserved to members of the ternary solid solution ca2al2 mn fe al si2o7 sio4 o oh that basically contains mn3 dominant at one site nonetheless the use of this name for any monoclinic manganiferous epidote group members showing the characteristic strong red yellow violet pleochroism is very common and probably convenient with special regard to petrographic purposes indeed the color of manganian i e mn3 bearing epidote or clinozoisite ranges to red to pinkish while manganoan i e mn2 bearing members do not exhibit the characteristic reddish hue the discredited name withamite was used to describe poorly manganiferous piemontite hutton 1938 yoshimura and momoi 1964 but corresponds on the basis of the current nomenclature to a manganian clinozoisite the name thulite sometimes erroneously used for pinkish clinozoisite should be reserved to mn3 bearing orthorhombic members in this chapter we focus on piemontite sensu stricto with the ideal formula ca2al2mn3 si2o7 sio4 o oh but also include for the reasons explained above those members of the clinozoisite epidote piemontite

formation of authigenic minerals and their use as indicators of the physicochemical parameters of the fluid in the larderello travale geothermal field different authigenic mineral assemblages and mineral compositions have been found in different areas of the larderello travale geothermal field in the peripheral areas the most abundant authigenic minerals are quartz calcite chlorite and sulfides they formed in a temperature range of 150 sup 0 to 250 sup 0 c and with a p sub co2 range of 0 1 to 1 0 atm in a hotter part of the field at depths between 200 and 1 300 m where the main productive fractures are located the most important authigenic minerals are quartz chlorite calcite k feldspar and k bearing mica with which wairakite hematite anhydrite and barite are sometimes associated deposition of all these minerals occurs in a temperature range of 200 sup 0 to 300 sup 0 c under p sub co2 of about 1 atm and relatively high p sub o2 in fluids sometimes characterized by silica oversaturation below the 1 300 m depth in the hottest part of the field k feldspar chlorite epidote sulfides with minor sphene prehnite clinopyroxene and clinoamphibole are present these minerals form in a temperature range of 250 sup 0 to 350 sup 0 c under a p sub co2 of less than 1 atm and a p sub o2 ranging from 10 sup 40 to 10 sup 33 atm and reasonablymore reflect the physicochemical parameters of the geothermal fluid before exploitation evidence of an earlier hydrothermal stage characterized by higher temperatures can be seen in the occurrence of relic wollastonite and andradite less

tectonic control on carbonate platform facies distribution and sequence development miocene gulf of suez abstract mid miocene deposition in the southwestern gulf of suez was governed by an extensional fault block topography shallow marine carbonates and clastics were deposited around the exposed block crests and in marginal half grabens of the rift while central troughs were filled by slope aprons and turbiditic and pelagic mudstones fan deltas developed at points along the fault block escarpments syn rift platform carbonates from one block crest esh el mellaha are described here the platform evolved in three stages generating three sedimentary sequences sequences 1 and 2 were separated by boundary fault reactivation sequences 2 and 3 by sea level drawdown exposure and karstification the sediments comprise six lithofacies associations la 1 6 reef la 1 fore reef la 2 and back reef embayment la 3 sediments form a small reef rimmed platform in sequence 1 at the southern end of the block fringing reefs and reef lagoon systems also developed along the footwall escarpment and on fan deltas which bridged the block bounding fault fringing reefs in sequence 2 generated a carbonate talus veneer la 4 along the whole 80 km length of the esh el mellaha fault scarp carbonate slope and reefal sediments preserved on the footwall exhibit abundant evidence of syndepositional fault movements with truncation of escarpment fringing sequences and repeated generation of reefal wedges minor drowning at the sequence 1 2 boundary caused deepening of lagoons progradation of leeward reefal margins with lagoonal patch reef development and back stepping and vertical accretion of the reefal rim platform development was followed by algal laminated dolomitic sediments la 5 in the area of the old platform interior sequence 3 much of the esh el mellaha ridge remained exposed during platform growth and shed coarse alluvial clastic sediments la 6 into the peripheral marine environments the relationships demonstrated between miocene sedimentation and structural setting have parallels in the modern environments of the zeit bay area

stratiform manganese mineralisation near inverness scotland a devonian sublacustrine hot spring deposit a stratiform manganiferous horizon up to 4 m thick but localised in aerial extent occurs 10 km south east of inverness in north east scotland it overlies precambrian grampian group schists and is itself overlain by middle old red sandstone devonian conglomerate which elsewhere rests unconformably on the schists the deposit was mined briefly in the early 1920s and is composed principally of fine grained braunite with minor bustamite lower sections of the deposit contain cavities infilled by late baryte calcite and rhodochrosite which resemble stromatactis this horizon is underlain by a hematite quartz layer thought to represent a laterite formed by pre mors weathering of the underlying schists the mineralogy and geochemistry of the manganese ore enriched in ag as ba bi pb sb sr and zn are characteristic of a hydrothermal origin such an origin when considered in conjunction with the outcrop textures mineralogy and stratigraphy of the deposit together with the palaeogeography of the region can only be explained by deposition from hot springs in a sublacustrine environment nearby baryte mineralisation may also have been deposited from the same geothermal system which had the caledonian 407 ma moy granitoid as heat source the managanese ore is enriched in gold pathfinder elements and minor detrital gold has been found in the area gold mineralisation may therefore have also been deposited in the upper sections of this devonian geothermal system

chemistry and geothermometry of brine produced from the salton sea scientific drill hole imperial valley california the december 29 30 1985 flow test of the state 2 14 well also known as the salton sea scientific drill hole produced fluid from a depth of 1865 1877 m at a reservoir temperature of 305 5 c another flow test at a depth of 3170 m produced brine contaminated by drilling fluid and diesel oil therefore we focus on the first flow test samples were collected at five different flashing pressures the brines are na ca k cl type waters with very high metal and low so4 and hco3 contents compositions of the flashed brines were normalized relative to the 25 c densities of the solutions and an ionic charge balance was achieved by adjusting the na concentration the composition of the preflashed reservoir fluid was calculated using enthalpy chloride relations applied to the normalized and charge balanced brines the calculated total dissolved solids in the preflashed reservoir fluid ranges from about 24 8 wt assuming insignificant thermal losses from the erupting fluid before sampling to 26 0 wt assuming a 10 enthalpy loss by conduction of thermal energy through casing and surface piping the preferred total dissolved solids of the reservoir fluid is 25 05 wt the calculated specific density of the preflashed reservoir fluid at 305 c and 1870 m depth ranges from 0 9980 no thermal loss prior to sampling to 1 0107 0 0023 g cm 3 10 thermal loss of the various cation geothermometers that are now in common use the na k ca method gives a temperature 310 c closest to the measured temperature 305 c in the production horizon calculated na k geothermometer temperatures using equations suggested by different investigators range from 326 to 364 c the mg k2 method gives a temperature of about 350 c mg li2 about 282 and na li 395 418 c