gold and silver in pge cu ni and pge ores of the noril sk deposits russia gold and silver contents in noril sk ore are controlled by the amount of sulphides and bulk cu grade relative concentrations re calculated to 100 sulphide depend on type of ore they are higher for disseminated ore than for massive ore and are the highest for low sulphide platinum ore gold occurs mainly as high fineness au ag alloy in pyrrhotite rich ore whereas silver enters chalcopyrite mainly as solid solution increase in cu grade correlates with an increase in the concentration of silver in chalcopyrite gold and silver form discrete minerals such as au cu alloys au ag alloys tellurides sulphides selenides sulphobismuthides ag and ag pd chlorides in cu rich ores they also enter the structures of complex platinum group minerals the au ag mineralisation is related to the post magmatic hydrothermal stage under temperature conditions of 350 50 c silver entered crystallizing chalcopyrite in solid solution in the late magmatic stage while all of the gold and the remainder of the silver and some platinum group elements were transported predominantly as chloride and hydrosulphide complexes in hydrothermal fluids

geochemistry of the lublin formation from the lublin coal basin implications for weathering intensity palaeoclimate and provenance abstract the lublin formation upper westphalian a and westphalian b is the main coal bearing series of the lublin coal basin lcb so far few geochemical studies of the carboniferous of the lcb have been performed and there is almost no data on the geochemistry of this series this paper presents geochemical data for 118 samples from the lublin formation from the central part of the lcb major oxide concentrations al2o3 sio2 fe2o3 p2o5 k2o mgo cao na2o k2o mno tio2 cr2o3 ba were obtained using an x ray fluorescence spectrometry trace and major elements zr th sc la u cu sr rb ni fe mn ca mg k na were analysed using inductively coupled plasma mass spectrometry concentrations of the major and trace elements showed significant diversity especially in the westphalian b deposits the chemical index of alteration plagioclase index of alternation and weathering index of parker values as well as the rb sr sr cu c and th u ratios of the studied samples suggest a high degree of chemical weathering of the source rocks and a prevailing warm humid climate with some arid episodes based on indicators such as al2o3 tio2 tio2 zr and la th it is suggested that all the studied samples from the lublin formation of the lcb were derived from felsic to intermediate igneous rocks while the th sc ratio suggests a mixed source for these sediments

generation of gas and oil from coal and other terrestrial organic matter abstract late carboniferous permian sedimentary rocks contain the world s largest coal reserves which have generated and released gas but little if any oil in comparison organic matter deposited in lacustrine fluvial deltaic or brackish water sediments has sourced large quantities of waxy oils in countries such as china australia the u s a argentina venezuela and indonesia plus gas and condensate in deltas worldwide why is more oil coming from land derived organic matter disseminated in sediments than from the carboniferous permian coal beds which also are land deposits the answer appears to be in the hydrogen content and the ease of migration when organic matter and coals have high hydrogen contents relative to carbon they can form oil when the hydrogen is low mainly gas is formed most of the world s coal is low in hydrogen whereas much of the terrestrial organic matter disseminated in sediments is higher in hydrogen so it forms more oil also both gas and oil are adsorbed on coal more strongly than on the disseminated kerogen of sedimentary rocks this makes migration of oil out of the coal more difficult compared to migration from conventional shale source rocks

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

platinum enrichment at low temperatures and related microstructures with examples of hongshiite ptcu and empirical pt2hgse3 from itabira minas gerais brazil low temperature pt enrichment is illustrated with reference to two hypogene platiniferous minerals i a pd cu bearing pt2hgse3 an unnamed phase and ii hongshiite ptcu with up to 0 7 wt hg the former has patches oxidized to a pt o species with curvilinear microcracks originated by desiccation the latter displays parallel sets of cu depleted pt hg enriched patches along which microfractures occur such microstructures are interpreted to arise from two processes i oxidation and formation of a hydrated pt o compound which tends to succumb to a pt rich alloy by deoxygenation and dehydration leaving behind curvilinear desiccation cracks ii metal leaching conducive to native pt by removal of cu from hongshiite via micropores that coalesce along crystallographic planes to result in reticulated microcracks platinum enrichment either by oxidation or metal leaching ideally produces characteristic microcracks which may be indicative of the origin i e detrital vs supergene of alluvial and eluvial pt rich alloys

pyrochlores from the lueshe carbonatite complex democratic republic of congo a geochemical record of different alteration stages abstract magmatic pyrochlores from the lueshe syenite carbonatite complex from the northeastern part of democratic republic of congo ex zaire are characterized by ta nb ratios in an increasing order from pyroxenite calcite carbonatite sovite silicate xenoliths nodules to syenite substitutions involving nb ta ti and ree have been precisely described hydrothermal alteration of lueshe pyrochlore involves the substitution of na f va vy and ca o va vy va a site vacancy and vy y site vacancy in calcite carbonatite hydrothermal alteration of pyrochlore took place during and after the precipitation of ancylite ce strontianite celestite baryte and fayalite according to a fluid composition of relatively low ph a na a ca 2 and a hf and high a sr 2 and a lree 3 the supergene alteration is characterized by complete leaching of na ca and f and partial incorporation of k ba sr and ce resulting in the formation of kali bario strontio and ceriopyrochlore respectively the na poor pyrochlore may be an intermediate variety corresponding to an alteration stage between the hydrothermal and weathered pyrochlores the ir spectroscopic study has indicated that the weathered pyrochlore is a hydrated variety containing two bands of oh vibration modes at 3413 and 1630 cm 1 during hydrothermal and supergene alterations the cations at b site remain relatively constant the variable chemical compositions of the pyrochlores from the lueshe complex represent geochemical memories of the different alteration conditions including the variation in the oxidation reduction environment

solubility equilibria in basalt aquifers the columbia plateau eastern washington u s a a speciation solubility geochemical model wateq2 was used to analyse geographically diverse groundwater samples from the aquifers of the columbia plateau basalts in eastern washington the groundwater samples compute to be at equilibrium with calcite which provides both a solubility control for dissolved ca and a ph buffer amorphic ferric hydroxide fe oh 3 a is at saturation or modestly oversaturated in the few water samples with measured redox potentials most of the groundwater samples compute to be at equilibrium with amorphic silica glass and wairakite a zeolite and are saturated to oversaturated with respect to allophane an amorphic aluminosilicate the water samples are saturated to undersaturated with halloysite a clay and are variably oversaturated with regard to other secondary clay minerals equilibrium between the groundwater and amorphic silica presumably results from the dissolution of the glassy matrix of the basalt the oversaturation with respect to the clay minerals other than halloysite indicates that their rate of formation lags the dissolution rate of the basaltic glass the modeling results indicate that metastable amorphic solids limit the concentration of dissolved si and suggest the same possibility for al and fe the results also suggest that the processes of dissolution of basaltic glass and formation of metastable secondary minerals are continuing even though the basalts are of miocene age and presumably have undergone a long history of contact with groundwaters the computed solubility relations are found to agree with the known assemblages of alteration minerals in the basalt fractures and vesicles if account is taken of both the difficulty of identifying amorphic phases and the slow rate of formation of clay minerals at low temperatures because the chemical reactivity of the bedrock will influence the transport of solutes in groundwater the observed solubility equilibria are important factors with regard to chemical retention processes associated with the possible migration of nuclear waste stored in the earth s crust specifically the occurrence of secondary minerals will enhance the sorption of dissolved radionuclides speciation solubility geochemical models provide an important means of determining these solubility equilibria relationships

structure and chemistry of zircon and zircon group minerals zircon zrsio4 is a common accessory mineral in nature occurring in a wide variety of sedimentary igneous and metamorphic rocks known to incorporate an assortment of minor and trace elements zircon has the ability to retain substantial chemical and isotopic information leading to its use in a wide range of geochemical investigations including studies on the evolution of earth s crust and mantle e g hanchar et al 1994 bowring 1995 vervoort et al 1996 hoskin and schaltegger this volume valley this volume as well as age dating e g gibson and ireland 1995 bowring et al 1998 solar et al 1998 bowring and schmitz this volume ireland and williams this volume parrish et al this volume the physical and chemical durability of zircon is a major factor in it being the mineral by which many of earth s oldest known rocks have been dated bowring et al 1989 maas et al 1992 buick et al 1995 bowring and williams 1999 wilde et al 2001 and is also an important factor in zircon being proposed as a candidate waste form for the geologic disposal of excess plutonium from dismantled nuclear weapons ewing and lutze 1997 ewing 1999 burakov et al 2002 burakov et al 2003 ewing et al this volume the chemical and physical properties of zircon and its ability to incorporate and retain trace elements are largely determined by its crystal structure the zircon structure is adopted by numerous minerals and synthetic compounds with the general formula at o4 in which high field strength t site cations occupy isolated tetrahedra and a site cations occupy larger eight coordinated structural sites zircon type compounds share many physical properties as well as displaying variable degrees of solid solution among end members

the thorite mineralization in the madeira sn nb ta world class deposit pitinga brazil abstract the world class sn nb ta madeira deposit is located in the pitinga mine northern brazil the deposit is associated with the albite enriched granite facies of the a type madeira granite 1820 ma the mine commercially extracts tin cassiterite nb and ta u pb pyrochlore and columbite fluorine cryolite y ree xenotime zr zircon u u pb pyrochlore and zircon and th thorite are potential byproducts this work presents a detailed study of thorite mineralization in the albite enriched granite subfacies the albite enriched granite core the albite enriched granite border and associated pegmatites the madeira deposit is revealed in this work to be among the largest th deposits in the world with 164 mt of homogeneously dispersed ore average grade of 759 ppm tho2 in the rock and higher concentrations up to 1 8 wt tho2 in small pegmatites average of 0 51 wt tho2 thorite compositions are either close to the thorite pole or correspond to relatively limited substitutions in the thorite zircon xenotime coffinite solid solution system the concentration of fe in thorite ranges from 0 11 wt to 29 56 wt fe2o3 and in many cases is considered to be of structural nature as well as part of the content of f up to 6 02 wt f thorites of all subfacies were strongly affected by hydrothermal alteration related to f rich low temperature aqueous fluids the hydration of thorite allowed the introduction of m3 cations y ree fe and al and f and caused losses in si and th contents average of 48 wt tho2 the alteration also created a fe rich halo in thorite with associated secondary minerals likely th fe hydroxyfluorides and y th fe fluorcarbonates the th u average ratios in bulk rock are 1 85 in the albite enriched granite border 3 82 in the albite enriched granite core and 19 85 in the associated pegmatites this variation reflects a pattern of magmatic evolution with higher availability of u in earlier stages and u depletion in later stages in pitinga the th and u mineralization are divided into different minerals formed at distinct stages of magma evolution this feature is related to fluorine enrichment and high alkalinity of the magma that strongly inhibited the early crystallization of zircon as well as columbite and favored the early appearance of u pb pyrochlore when crystallization of hydrous silicates reduced alkalinity crystallization of zircon from a magma depleted in u nb ta and lree became intense accompanied by thorite and xenotime

atacamite inclusions in rock forming feldspars and copper bearing smectites from the radomiro tomic mine chile copper insoluble mineral occurrences recovery of copper from the radomiro tomic deposit in chile employs innovative large scale hydrometallurgical extraction methods with sulfuric acid used for heap leaching here we report on improvements in understanding mineral components of copper oxide ores which are insoluble in acid leach solutions in order to advance leaching technology using optical electron microprobe x ray diffraction energy dispersive spectroscopy and least squares inversion methods two different occluded mineral occurrences were discovered in oxide ores which present two distinct metallurgical challenges for heap leaching but offer important new opportunities in process mineralogy first in a high chloride to sulfate ratio feldspar stable portion of the orebody at radomiro tomic disseminated atacamite cu4cl2 oh 6 inclusions 1 to 8 m in diameter occur in microfractured feldspars and biotites these account for the acid insoluble fraction often as high as 30 percent of the total contained copper about 70 percent of the total copper occurs generally as atacamite in cracks which upon crushing is exposed along surfaces of the rock fragments and is hence soluble in contrast in more intensely hydrothermally altered feldspar destructive weak argillic alteration zones insoluble copper exists more probably within the crystal structure of well crystallized saponitic smectite clays in nonexchangeable octahedral crystallographic sites the two different forms of applied acid insoluble components are products of contrasting microchemical environments one in a reactive potassic alteration gangue and the second in a nonreactive gangue in both cases however the nature of hydrothermal alteration though pervasive was relatively weak and left intact rock mineral buffers capable of neutralizing acidic and reducing fluids hence the insoluble components with respect to the applied sulfuric acid reflect strong wall rock mineral assemblage control on the behavior of copper on all scales the macrofield zonal scale the microscale of individual crystals in cracks and the atomic scale of octahedral sites in the clay structure the metallurgical implications of these atacamite microinclusions in rock forming minerals and structurally bound copper in smectites are different in the former case exposing ore inclusions on fragment surfaces would require extremely costly grinding to a grain size well below 400 mesh secondly chemical extraction of microinclusion copper from feldspar host phases would entail high acid consumption as hydrolysis of feldspars by chemical reaction with applied acid would occur causing neutralization in the case of cu smectites since the copper occurs in structurally bound nonexchangeable sites processes to remove the copper via ion exchange or acidic leach cannot work alternatives to ion exchange could involve destroying the smectite host mineral perhaps by its conversion to kaolinite that may only incorporate copper or other divalent cations in negligible amounts

rare earth and trace element mobility in mid crustal shear zones insights from the mont blanc massif western alps the behaviour of rare earth elements ree during fluid rock interaction in mid crustal shear zones has received little attention despite their potential for mass balance calculation and isotopic tracing during deformation in this study several cases of large ree mobility during alpine fluid driven shear zone development in the pre alpine granitic basement of the mont blanc massif are considered on a regional scale the undeformed granite compositions range within 5 wt sio2 70 5 75 3 wt and magmatic chemical variations are of the order of 10 20 ascribed to minor effects of crystal fractionation major and trace element mobility observed in shear zones largely exceeds these initial variations shear zones developed a range of mineral assemblages as a result of shearing at mid crustal depths at not vert similar0 5 gpa 400 c five main shear zone assemblages involve muscovite chlorite epidote actinolite and calcite respectively as major phases in most cases selective enrichments of light or heavy ree and y ta hf are observed ree mobility is unrelated to deformation style cataclastic mylonitic the intensity of strain and to the shear zone s major metamorphic mineral assemblages instead the changes in ree concentrations are ascribed to the alteration of pre existing magmatic ree bearing minerals during deformation related fluid rock interaction and to the syntectonic precipitation of metamorphic ree bearing minerals mainly monazite bastnasite aeschynite and tombarthite minor proportions 2 of these accessory phases with grain sizes mostly 20 m account for enrichments of up to 5 1 compared to the initial granite whole rock ree budget the stability of the ree phases appears to be largely dependent on the altering fluid composition ree mobility is ascribed to changes in ph and to the availability of co32 po42 and so42 ligands in the fluid such processes are likely to influence the mobility of ree y hf and ta in shear zones

rates and mechanisms of discontinuous gully erosion in a red brown earth catchment new south wales australia rainfall runoff sediment discharge and gully expansion were measured for five years in a small 45 ha catchment in central n s w sixty per cent of the sediment produced from this catchment originated from gully erosion gully head erosion was episodic depending on pipe development cracking and soil detachment during small runoff events which prepared the heads for rapid soil movement by the infrequent large event

petroleum generation in the carboniferous strata of the lublin trough poland an integrated geochemical and numerical modelling approach abstract in the lublin trough eastern poland we analysed carboniferous claystone and mudstone rocks by rock eval bitumen composition n alkanes and methylphenathrenes composition and carbon isotopic composition to assess their potential for the generation of hydrocarbons in the lublin trough oil and gas prone type ii iii and iii kerogens occur in upper visean strata average tocav 1 8 wt whereas mainly gas prone type iii kerogen occurs in namurian tocav 1 98 wt and westphalian tocav 1 4 wt strata the carboniferous sequence displays maturity values of 0 5 1 2 ro rock eval tmax 430 460 c palaeo geothermal gradients in the past were much higher than now and locally reached values over 40 c km during the maximum burial event generated hydrocarbons probably consisted of natural gas with limited amounts of oil over most of the area hydrocarbon generation commenced in the late carboniferous mainly 25 but up to maximum 60 transformation ratio and was substantially complete by the time of the asturian inversion in the nw part of the lublin trough petroleum generation continued until the end of the cretaceous with transformation ratios never exceeding 11 at the base of the upper carboniferous mainly gas prone kerogen types and inadequate maturity suggests the discovered petroleum accumulations are derived from devonian and or lower paleozoic strata rather than carboniferous units however the quantitative significance of these source rocks needs further geochemical research

tourmaline occurrences within the penamacor monsanto granitic pluton and host rocks central portugal genetic implications of crystal chemical and isotopic features tourmalinization associated with peraluminous granitic intrusions in metapelitic host rocks has been widely recorded in the iberian peninsula given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of sn w mineralizations in the penamacor monsanto granite pluton central eastern portugal central iberian zone tourmaline occurs 1 as accessory phase in two mica granitic rocks muscovite granites and aplites 2 in quartz mica tourmaline rocks tourmalinites in several exocontact locations and 3 as a rare detrital phase in contact zone hornfels and metapelitic host rocks electron microprobe and stable isotope 18o d 11b data provide clear distinctions between tourmaline populations from these different settings a schorl oxyschorl tourmalines from granitic rocks have variable foititic component x 17 57 and mg mg fe ratios 0 19 0 50 in two mica granitic rocks and 0 05 0 19 in the more differentiated muscovite granite and aplites granitic tourmalines have constant 18o values 12 1 0 1 with wider ranging d 78 2 4 7 and 11b 10 7 to 9 0 values b vein breccia oxyschorl mg mg fe 0 31 0 44 results from late b and fe enriched magma derived fluids and is characterized by 18o 12 4 d 29 5 and 11b 9 3 while replacement tourmalines have more dravitic compositions mg mg fe 0 26 0 64 close to that of detrital tourmaline in the surrounding metapelitic rocks and yield relatively constant 18o values 13 1 13 3 though wider ranging d 58 5 to 36 5 and 11b 10 2 to 8 8 values and c detrital tourmaline in contact rocks and regional host metasediments is mainly dravite mg mg fe 0 35 0 78 and oxydravite mg mg fe 0 51 0 58 respectively boron contents of the granitic rocks are low 650 ppm compared to the minimum b contents normally required for tourmaline saturation in granitic melts implying loss of b and other volatiles to the surrounding host rocks during the late magmatic stages this process was responsible for tourmalinization at the exocontact of the penamacor monsanto pluton either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin vein breccia tourmalinites or as replacement of mafic minerals chlorite or biotite in the host rocks replacement tourmalinites along the exocontact of the granite thermometry based on 18o equilibrium fractionation between tourmaline and fluid indicates that a late b enriched magmatic aqueous fluid av 18o 12 1 at 600 c precipitated the vein breccia tourmaline 18o 12 4 at 500 550 c and later interacted with the cooler surrounding host rocks to produce tourmaline at lower temperatures 400 450 c and an average 18o 13 2 closer to the values for the host rock although b metasomatism associated with some granitic plutons in the iberian peninsula seems to be relatively confined in space extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of variscan magmatism and related mineralizations

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

kinoshitalite ba mg 3 al2si2 o10 oh f 2 a brittle mica from a manganese deposit in oman paragenesis and crystal chemistry kinoshitalite ideally ba mg 3 al 2 si 2 o 10 oh f 2 was studied in a granulite facies manganese ore associated with calcium bearing magnesian tephroite hausmannite calcite and manganoan clinochlore and in a second assemblage together with hausmannite altered tephroite manganoan diopside and calcite the metamorphic rocks occur enclosed in peridotites of the semail ophiolite sultanate of oman and were metamorphosed during ophiolite obduction single crystal x ray data collected on an inclusion free kinoshitalite of ba 0 99 k 0 06 na 0 01 mg 2 64 mn 0 31 al 2 01 si 2 03 o 10 oh 1 61 f 0 37 cl 0 02 composition yielded a c centered lattice of monoclinic symmetry with a 5 316 1 b 9 230 2 c 10 197 2 a 100 06 1 v 492 6 a 3 and z 1 characteristic of the 1 m polytype the structure was refined in two models assuming complete si al ordering in the space groups c 2 and c 1 allowing for additional twinning the data clearly suggest that in spite of the si al ratio of 1 assumption of complete si al ordering can be rejected two models both in agreement with space group c 2 m causing si al disorder are discussed three dimensional si al disorder would lead to violation of the al avoidance rule and substantial ba displacement the rather well defined ba position capped by two six membered rings of si 3 al 3 o 18 composition suggests one dimensional disorder where completely si al ordered layers exist parallel to 001 the disorder occurs perpendicular to 001 and may be interpreted as random stacking faults

oh bearing planar defects in olivine produced by the breakdown of ti rich humite minerals from dabie shan china the partial breakdown of ti chondrodite and ti clinohumite during exhumation from ultra high pressure to amphibolite facies conditions in garnet pyroxenites from dabie shan china produces coronas of olivine coexisting with ilmenite blebs fourier transform infrared ftir spectra of this newly formed olivine exhibit absorption bands in the hydroxyl stretching region two intense peaks were observed at 3 564 and 3 394 cm 1 identical in energy to peaks in ti clinohumite transmission electron microscopy tem of the same olivine domains revealed the presence of a complex 001 planar intergrowth these interlayers have a 1 35 nm repeat distance which is characteristic of clinohumite such interlayers are also enriched in ti with respect to the adjacent olivine as shown by energy dispersive spectrometry the combined evidence from ftir spectroscopy and tem indicates that oh is incorporated along ti clinohumite planar defects this study provides evidence that the nominally anhydrous phase olivine may contain oh as a humite type defect beyond the breakdown of the hydrous humite minerals and confirms earlier suggestions that ti plays a key role in oh incorporation in mantle olivine we suggest that olivine containing ti clinohumite defects is an important phase for water transport in subduction zones and for the storage of water in cold subcontinental mantle however these defects are unlikely to be stable in hotter parts of the oceanic mantle such as where basaltic magmas are generated

application of aromatic compounds as maturity indicators in source rocks and crude oils concentration ratios of aromatic compounds such as naphthalenes phenanthrenes and dibenzothiophenes are at present attracting increasing attention as maturity indicators in sedimentary rocks and crude oils generally these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl aromatic homologues towards thermally more stable isomers a combination of both concepts in the methylphenanthrene index mpi resulted in an excellent maturity parameter as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance rm between 0 65 and 1 4 i e in the zone of oil formation in cases that rm measurements were ambiguous this empirical relationship has proved useful in the calculation of theoretical vitrinite reflectance rc values from the mpi on the other hand for potential petroleum source rocks reaching maturity at relatively low temperatures the influence of the organic matter type on the aromatic distributions cannot be neglected consequently organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils since the impact of the organic facies is strongly reduced with increasing maturity aromatic maturity parameters are particularly useful in the maturity evaluation of post mature crude oils and condensates in contrast to biological markers substantially higher concentrations of the key alkyl aromatics persist at elevated maturation levels thus aromatic maturity parameters should be considered as versatile tools in organic maturation studies and can complement established maturity indicators based on steranes and terpanes

fluorine end member micas and amphiboles the near end member minerals fluorphlogopite xf 0 96 and fluortremolite xf 0 82 have been found in grenville marbles near balmat new york these micas and amphiboles like other fluorine rich minerals reported in the literature are extremely low in iron the substitution of f for oh is partly responsible for stabilizing these minerals in the granulite facies marbles of the adirondacks fluorine rich amphiboles and micas are more common than generally recognized a literature review shows that many amphiboles and micas have more than fifty percent of the interlayer site occupied by fluorine this degree of solid solution qualifies these phases as independent minerals but they are not currently recognized by the i m a we propose that fluorbiotite fluorphlogopite fluoractinolite fluorarfvedsonite fluoredenite fluorhastingsite fluorpargasite fluorrichterite fluorriebeckite fluortremolite fluoredenitic hornblende fluorhastingsitic hornblende fluorpargasitic hornblende fluortremolitic hornblende fluorferro edenite and fluormagnesio arfvedsonite be formally applied as mineral names for these phases identification of the mineralogically and petrologically important solid solution of fluorine for hydroxyl is currently obscured by use of names that imply hydroxyl end members

rhonite in luna 24 pyroxenes first find from the moon and implications for volatiles in planetary magmas grains ofrhonite have been discovered in magmatic inclusions in augite grains of the lunar regolith from mare crisium returned to earth by the russian luna 24 spacecraft these rhonite grains are up to 8 m long pleochroic from tan to dark brown and associated with ulvospinel and silica rich glass electron microprobe analysis gives a composition near end member ferroan rhonite ca 1 9 mn 0 0 na 0 1 fe 2 4 5 mg 0 1 al 0 3 cr 0 0 ti 1 0 si 4 0 al 2 0 o 20 the raman spectrum of these grains is like those of terrestrial rhonites and distinct from titanian amphiboles compositionally rhonite plus silica plus water or halogens f cl is equivalent to titanian amphibole plus pyroxene so the presence ofrhonite in lunar basaltic rock is consistent with the known low abundance of volatiles in the moon when calibrated mineral reactions involving rhonite and titanian amphibole may provide quantitative constraints on fugacities of water f and cl in basaltic magmas from the moon and other planetary bodies

black shales in ukraine a review abstract as a result of a long lasting and complex geological history organic matter rich fine grained rocks black shales with widely varying ages can be found on ukrainian territory several of them are proven hydrocarbon source rocks and may hold a significant shale gas potential thick silurian black shales accumulated along the western margin of the east european craton in a foreland type basin by analogy with coeval organic matter rich rocks in poland high toc contents and gas window maturity can be expected however to date information on organic richness is largely missing and maturity patterns remain to be refined visean black shales with toc contents as high as 8 and a type iii ii kerogen accumulated along the axis of the dniepr donets rift basin ddb they are the likely source for conventional oil and gas oil prone serpukhovian black shales accumulated in the shallow northwestern part of the ddb similar black shales probably may be present in the lviv volyn basin western ukraine middle jurassic black shales up to 500 m thick occur beneath the carpathian foredeep they are the likely source for some heavy oil deposits toc contents up to 12 type ii have been recorded but additional investigations are needed to study the vertical and lateral variability of organic matter richness and maturity lower cretaceous black shales with a type iii ii kerogen toc 2 are widespread at the base of the carpathian flysch nappes but oligocene black shales menilite fm rich in organic matter 4 8 toc and containing a type ii kerogen are the main source rock for oil in the carpathians their thermal maturity increases from the external to the internal nappes oligocene black shales are also present in crimea maykop fm these rocks typically contain high toc contents but data from ukraine are missing

new mineral names the following new minerals are discussed in this issue langbanshyttanite pseudolyonsite and yangzhumingite these new minerals have been described in the european journal of mineralogy and are reported here n v chukanov i v pekov e jonsson n v zubkova y e filinchuk d i belakovskiy and d yu pushcharovsky 2011 langbanshyttanite a new low temperature arsenate mineral with a novel structure from langban sweden eur j mineral 23 675 681 the new mineral langbanshyttanite was discovered in a specimen from the langban mine filipstad district varmland county bergslagen ore province sweden the carbonate hosted langban deposit 59 86 n 14 27 e is together with related occurrences in the western part of the palaeoproterozoic bergslagen ore province in south central sweden characterized by anomalously pb as ba be sb rich metamorphosed stratabound fe and mn oxide ores with associated skarn units sulfide assemblages as well as abundant vein and fissure hosted mineral assemblages the name is for langbanshyttan which is the old name of both the mine mining village and smelter that in more recent times has been known plainly as langban langbanshyttan actually means langban s smelter or langban s furnace langbanshyttanite occurs as a very late low temperature species in the deposit it crystallized during the last stage of hydrothermal activity involving metal remobilization in the langban system post dating regional metamorphism of the volcanic hydrothermal ores and their host rocks based on existing evidence these minerals formed at very low temperature and pressure in this case most likely below 70 c the mineral formed in fractures and corrosion veinlets post dating calcite in a mn oxide bearing mn silicate rich rock associated late stage minerals are calcite antigorite sparse euhedral trigonite and a few microscopic aggregates of a so far unidentified as bearing mineral typically both calcite and antigorite exhibit evidence of being partly corroded away prior to langbanshyttanite formation trigonite coeval with langbanshyttanite occurs as sparse euhedral crystals the groundmass to the veinlets or fractures mainly consists

thermal histories and hydrocarbon generation example from utah wyoming thrust belt the thermal history of the utah wyoming thrust belt in the vicinity of the pineview oil and gas field is studied with a detailed thermal model the model incorporates a heterogeneous thermal conductivity structure radioactive heat generation in the crust sediment compaction variable basal heat flow through time and thermal effects of sedimentation erosion and thrust faulting the analysis is constrained by 206 corrected bottom hole temperatures 660 thermal conductivity measurements and 10 new vitrinite reflectance measurements present surface heat flow in this part of the utah wyoming thrust belt is estimated to be 60 8 mw m2 surface heat flow in the late cretaceous about 70 ma is inferred to have been 38 8 mw m2 from an lysis of vitrinite reflectance data about half of the apparent difference between ancient and present surface heat flow may be attributed to transient thermal effects of sedimentation erosion and thrusting the hypothesis of a constant background thermal state in this part of the thrust belt for the last 70 m y may not be ruled out however thermal history simulations in which the background thermal state changes through time better match constraints imposed by estimated present surface heat flow and vitrinite reflectance data application of the thermal history analysis to hydrocarbon generation is illustrated with a kinetic model of organic maturation oil and gas at the pineview field may have been generated in two stages first stage just before and during thrusting and the second stage during cenozoic warming

a calcium aluminum rich inclusion from the essebi cm2 chondrite evidence for captured spinel hibonite spherules and for an ultra refractory rimming sequence abstract an unusual refractory inclusion was discovered in the essebi cm2 chondrite the inclusion has high concentrations of refractory lithophile and siderophile elements with strong enrichments of the most refractory elements lu sc hf in one part of the inclusion the inclusion consists of a melilite rich core partially surrounded by a very refractory rim which in turn is covered by a mantle enriched in si al fe mn cl and s melilite compositions vary from ak 10 26 in the core to ak 0 12 in the rim the core contains several complex framboids consisting of spinel fassaite or spinel hibonite these framboids are probably spherules of the types reported from murchison and were possibly captured by the molten inclusion before it solidified these findings may indicate a genetic link between framboids in cai s and the spinel rich spherules in murchison the rim sequence consists of the following five layers from inside to outside 1 1 hibonite spinel melilite 2 2 hibonite perovskite spinel melilite melilite in this layer is altered to sodalite nepheline calcite 3 3 a hibonite corundum solid solution 4 4 a spinel corundum solid solution as much as 0 1 mole fraction al 2 67 o 4 5 5 sc rich fassaite as much as 6 2 wt sc 2 o 3 spinel al 2 o 3 solid solution al rich diopside pt rich metal crystals occur only in the rim some of these metal crystals contain minor amounts of zr and hf indicating that they formed under reducing conditions the bulk mineral chemistry and texture of the essebi inclusion indicates a complex history involving capture of solid spinel and spinel hibonite spherules similar to the murchison type by a refractory melt droplet solidification of the droplet without obliteration of the spherule textures transportation of the composite object to hotter regions of the solar nebula where the very refractory rim condensed alteration of melilite to sodalite nepheline minor calcite and finally burial in the essebi parent body the cl s bearing mantle probably formed by reactions between the inclusion and liquid and gaseous phases in the parent body

a new natural high pressure na ca hexaluminosilicate caxna1 x al3 xsi3 xo11 in shocked martian meteorites a ca na hexaluminosilicate whose ca end member was previously synthesized in numerous high pressure experiments has been identified by raman spectroscopy in heavily shocked martian meteorites this mineral has a structural formula close to caxna1 x al3 xsi3 xo11 and is similar to the calcium aluminum silicate phase previously synthesized in high pressure experiments performed on anorthite and rocks of basaltic composition this new mineral occurs in shock melt pockets in two distinct settings and is intimately intergrown with sio2 stishovite the first setting encountered in zagami consists of idiomorphic equant crystals overgrown by acicular stishovite that crystallized from a melt of labradorite composition the second setting contains the na ca hexaluminosilicate phase intergrown with stishovite and hollandite and was formed during partial melting at high pressures the mineralogical association na ca hexaluminosilicate stishovite was observed in shock melt pockets which have distinct bulk compositions in seven martian shergottites this new mineral represents after majorite the second natural occurrence of a silicate mineral with silicon in both four and six coordination the assemblage stishovite na ca hexalummosilicate sets constraints on the pressure and temperature conditions that prevailed during shock in some of the studied meteorites the na ca hexaluminosilicate mineral is a potential carrier of al and na during subduction of oceanic crust in the lower mantle of the earth c 2003 elsevier b v all rights reserved

physical and chemical properties of the epidote minerals an introduction epidote minerals are known since the 18th century but at that time the greenish to dark colored varieties were termed actinolite or schorl and not distinguished from the minerals to which these names apply today hauy defined the mineral species and introduced the name epidote in 1801 whereas werner in 1805 used the term pistacite quoted from hintze 1897 epidote is derived from greek epidosis to increase because the base of the rhombohedral prism has one side larger than the other and pistacite refers to its green color all references for names after luschen 1979 blackburn and dennen 1997 weinschenk 1896 proposed the name clinozoisite from its monoclinic symmetry and zoisite like composition for those monoclinic members of the epidote family that are fe poor optically positive and have low refractive indices and birefringence zoisite was probably confused with tremolite until the beginning of the 19th century in 1804 siegmund zois baron von edelstein 1747 1819 an austrian sponsor of mineral collections found and described a new mineral in a handspecimen from the saualpe mountains in carinthia that was named zoisite by werner hauy 1822 interpreted zoisite as a variety of epidote and included it in his epidote spezies weiss 1820 presented a theory of the epidote system and also discussed crystal morphological features of the epidote minerals weiss 1828 rammelsberg 1856 studied the relationship between epidote and zoisite and presented a compilation of chemical analyses of zoisite he already noticed that the relative concentrations of di tri and tetravalent cations are identical in zoisite and epidote but that the fe content in zoisite about 2 3 5 wt fe2o3 is generally less than in epidote about 9 12 wt fe2o3 piemontite see bonazzi and menchetti 2004 was probably first described in 1758 by cronstedt

the peralkaline granite related khaldzan buregtey rare metal zr nb ree deposit western mongolia the khaldzan buregtey rare metal nb zr ree etc deposit in peralkaline granitoids is located in western mongolia 45 km northeast of the town of kobdo the deposit which was discovered by the authors is composed of dome shaped stocks of rare metal peralkaline granite covering 0 85 km and represents the late plutonic phases of the devonian 380 390 ma multiphase khaldzan buregtey peralkaline granite massif the formation of the massif took place during tectonic extension as shown by the development of a major dike complex synchronous with granite emplacement the massif consists of peralkaline granitoids as well as gabbro and basalt and is characterized by a radial circular shape eight intrusive phases are recognized and consist of 1 nordmarkite 2 peralkaline granite 3 dikes of fine grained peralkaline granite 4 dikes of pantellerite 5 rare metal peralkaline granite 6 gabbroids 7 miarolitic peralkaline rare metal granite and 8 syenite and leucite basalt field relationships of the rare metal peralkaline granite bodies indicate an intrusive igneous origin the rare metal peralkaline granites consist of k na feldspar quartz albite arfvedsonite aegirine fluorite and diverse rare metal minerals ranging up to 25 vol percent ore minerals are represented by elpidite gittinsite and zircon pyrochlore nb rare metal flurocarbonate and monazite ree and polylithionite li the zirconium minerals often occur in the endocontact and apical parts of rare metal granite bodies and are reflected in the negative correlation of zr and nb contents in the seventh phase granites the rare metal peralkaline granites of the deposit differ from those of other massifs by their high and variable ca and f contents the granites are rich in zr up to 5 3 wt nb up to 0 8 wt ree up to 0 4 wt y up to 0 3 wt be sn rb and sometimes li pb zn hf and ta they are depleted in sr and ba and have an almost flat ree distribution pattern with a small negative eu anomaly the initial 87 sr 86 sr ratio of fluorite from rare metal peralkaline granite is 0 70433 or 7 the end value for these rocks at 386 ma ranges from 4 3 to 5 7

a comparative study of opaque phases in qingzhen eh3 and macalpine hills 88136 el3 representatives of eh and el parent bodies opaque minerals in the qingzhen eh3 and macalpine hills mac 88136 el3 enstatite chondrites were studied and compared with other eh and el chondrites all opaque minerals usually occur in multi sulfide metal clasts and nodules in the matrix between chondrules el goresy et al 1988 the higher abundance of opaque minerals the occurrence of niningerite and various alkali sulfides e g caswellsilverite phases a and b djerfisherite are diagnostic criteria for eh chondrites while alabandite is characteristic for el chondrites in addition eh chondrites are characterized by enrichments of si in both kamacite and perryite and alkali elements in sphalerite and chalcopyrite the mn contents of daubreelite and sphalerite are lower in eh than in el chondrites these are consistent with lower oxygen fugacity and higher h2s fugacity of eh than el chondrites in contrast the discovery of sphalerite and zn rich daubreelite in mac 88136 indicates that their absence in el6 chondrites is probably related to thermal metamorphism in the parent body schreibersite microspherules are commonly enclosed in most sulfides in qingzhen but are absent in mac 88136 they were once molten and probably predated all sulfide host phases the petrographic setting and chemical compositions of the sulfide hosts of the schreibersite microspherules in eh3 chondrites are consistent with formation by condensation the earliest sulfide condensates oldhamite and niningerite occupy the interiors of the clasts and nodules whereas the rims consist of troilite and djerfisherite in addition in qingzhen some other troilite djerfisherite and sphalerite assemblages coexist with perryite they were produced by sulfurization of metallic fe ni in the nebula in mac 88136 sulfurization of si bearing fe ni metal is less pronounced and it produced troilite schreibersite and less abundant perryite two kinds of normal zoning and a reverse zoning trends of niningerite and both normal and reverse zoning of sphalerite were found in clasts and nodules in qingzhen the coexistence of normal and reverse zoning profiles in niningerite grains in the same meteorite strongly suggests that they formed before accretion in the parent body because an asteroidal metamorphic or an impact event in the parent body would have erased these contrasting profiles and destroyed the textural settings in contrast alabandite in mac 88136 shows only normal zoning with the fes content decreasing to 9 3 mol toward troilite indicating very slow cooling at low temperature

osumilite in the sapphirine quartz terrane of enderby land antarctica implications for osumilite petrogenesis in the granulite facies

los angeles a tale of two stones we compare and contrast the mineralogy and petrology of the 2 stones of the extremely ferroan and cr poor martian meteorite los angeles the 2 stones are similar in many characteristics strongly suggesting that they originated from a single flow or shallow intrusion however stone 2 is more ferroan and enriched in late stage materials than its larger and more widely studied sibling stone 2 has a far higher abundance 25 vol than stone 1 10 vol of combined opaques meaning not only conventional opaque minerals but also and more abundantly fine grained symplectitic intergrowths of fayalite ferroan augite silica interpreted as pyroxferroite breakdown material pbm the bulk composition of the pbm is close to that of stoichiometric pyroxferroite with roughly 45 wt feo extensive zonation within the pyroxenes of both stones is consistent with origin by closed system fractional crystallization of the parent basaltic melt s however the compositional and modal disparity between the two stones suggests that they formed in an environment where at least mild multi cm scale differentiation occurred probably in both stones crystallization began from similar melts with mg 27 28 mol but during crystallization significant migration of the melt component occurred perhaps by crystal settling and or filter pressing stone 2 acquired an enhanced proportion of residual melt and thus higher proportions of late stage materials such as pbm oxides and phosphates within the pbm clinopyroxene poikiloblastically encloses fayalite and silica at least some of the pbm had already formed by decomposition of pyroxferroite before the major shock that caused the very scarce brecciation within los angeles however the low abundance of fractures within pbm in comparison to pyroxene and some other minerals may be an indication that the textures of pbm regions typically did not assume their final detailed configuration until after the last major shock the steep slope of a pyroxene mg cr correlation suggests that igneous crystallization occurred at higher fo2 in los angeles than in otherwise similar shergottites such as que 94201 shergotty and zagami

iron and aluminum hydroxysulfates from acid sulfate waters acid sulfate waters are produced mostly by the oxidation of common sulfide minerals such as pyrite chalcopyrite pyrrhotite and marcasite in rocks soils sediments and industrial wastes this spontaneous process of mineral weathering plays a fundamental role in the supergene alteration of ore deposits the formation of acid sulfate soils and the mobilization and release of acidity and metals to surface and ground waters the purely natural process of acid rock drainage is often intensified by human activities related to mining mineral processing construction soil drainage and dredging geochemical reaction rates are accelerated because physical disturbance gives greater exposure of mineral surfaces to air and water and to microbes that catalyze the reaction process large quantities of reactive sulfides are also concentrated and exposed to air as a result of mining and mineral processing acid sulfate waters produce a number of fairly insoluble hydroxysulfate and oxyhydroxide minerals that precipitate during oxidation hydrolysis and neutralization the objective of this chapter is to describe the formation properties fate and environmental implications of the nano to microphase hydroxy sulfates of fe and al that are precipitated from acid sulfate waters these minerals are commonly of poor crystallinity and difficult to characterize much remains to be learned about their occurrence formation and properties mine drainage the best known examples of acid sulfate waters are those released from mines where coal and metallic sulfide ores have been exploited ash et al 1951 barton 1978 nordstrom 1982a rose and cravotta 1998 nordstrom and alpers 1999 there may be as many as 500 000 inactive or abandoned mine sites in the united states alone lyon et al 1993 although most of these pose no immediate water quality problem kleinmann 1989 estimated that about 19 300 km of streams and more than 72 000 ha of lakes and reservoirs have been

geochemistry of oxide minerals of nb ta sn and sb in the varutrask granitic pegmatite sweden the case of an anomalous columbite tantalite trend the complex petalite subtype varutrask pegmatite in the proterozoic rocks of northern sweden is as a whole rather poor in nb and ta the pegmatite consolidated in eight units but the nb ta oxide minerals attained saturation levels only in a late albite lepidolite bearing unit under conditions of high activity of alkali fluorides consequently the compositional trends of columbite group minerals and cassiterite mimic those typically displayed in pegmatites of the lepidolite subtype from ferroan manganocolumbite with mn mn fe at of 0 35 and ta ta nb of 0 08 through near end member manganocolumbite 0 95 and 0 20 respectively to fe depleted manganotantalite 0 99 and 0 55 respectively and from fe mn nb ta bearing to mn fe ta nb enriched cassiterite to date rare occurrences of cassiterite with mn fe are restricted solely to the lepidolite enriched granitic pegmatites the degree of cation order in the varutrask columbite group minerals increases from early to late phases and with decreasing amounts of heterovalent substitutions slower cooling of initially disordered structures in late phases or their diminished compositional complexity may be responsible for the higher degree of order rare primary microinclusions of cassiterite in columbite group minerals show consistent and systematic preference for ta and fe suggesting an approach to chemical equilibrium but columbite group inclusions in cassiterite show in part a compositional scatter in contrast rare inclusions of ferrotapiolite and wodginite closely reflect the fe mn ta nb compositional features of the host cassiterite stibiotantalite shows high values of ta ta nb and mere traces of bi reflecting the relative abundance of native antimony and stibarsen in the pegmatite and the absence of bi bearing minerals rare primary microlite is ta and f rich whereas the more widespread pyrochlore microlite metasomatic after columbite group minerals reflects the ta ta nb values of the precursors as does the stibiomicrolite replacing stibiotantalite cesium is elevated in several grains of primary and metasomatic pyrochlore group phases that also are enriched in sb but not in stibiomicrolite the array of large cations in pyrochlore microlite metasomatic after columbite group minerals is quite different from that typical of stibiomicrolite suggestive of differences in the nature of the parent fluids the lepidolite subtype signature of the columbite group minerals and cassiterite in the petalite subtype varutrask pegmatite emphasizes the importance of specific conditions controlling stabilization of these minerals the restriction of the columbite group minerals to a very late lepidoliterich unit imposes a lepidolite subtype signature on the whole petalite subtype pegmatite a signature grossly different from the characteristics typical of petalite subtype pegmatites elsewhere

lakargiite cazro3 a new mineral of the perovskite group from the north caucasus kabardino balkaria russia lakargiite cazro3 the zirconium analog of perovskite pbnm a 5 556 1 b 5 715 1 c 7 960 1 a v 252 7 1 a3 z 4 was discovered as an accessory mineral in high temperature skarns in carbonate silicate rocks occurring as xenoliths in ignimbrites of the upper chegem verkhniy chegem volcanic structure the north caucasus kabardino balkaria russia lakargiite forms pseudo cubic crystals up to 30 35 m in size and aggregates up to 200 m lakargiite is associated with spurrite larnite calcio olivine calcite cuspidine rondorfite reinhardbraunsite wadalite perovskite and minerals of the ellestadite group the new perovskite mineral belongs to the ternary solid solution cazro3 catio3 casno3 with a maximum cazro3 content of ca 93 maximum catio3 content of 22 and maximum casno3 content of 20 significant impurities are sc cr fe ce la hf nb u and th raman spectra of lakargiite are similar to those of the synthetic phase ca zr ti o3 with strong bands at 352 437 446 554 and 748 cm 1 lakargiite crystallized under sanidinite facies conditions of contact metamorphism characterized by very high temperatures and low pressures

surface geochemical exploration for hydrocarbons in the area of prospective structures of the lublin trough eastern poland abstract the search for crude oil and natural gas deposits is dominated by expensive seismic methods however less expensive and faster surface methods are available which may improve the effectiveness of petroleum exploration one of these methods is the surface geochemical survey the objective of this method is to detect record and analyse the trace amounts of hydrocarbons in soil gas samples our paper presents the results of such research carried out over the prospective structures of the lublin trough in the eastern poland three hundred fifty five soil gas samples were collected from 1 2 m depth below the surface which were analysed by gas chromatographic analysis for their molecular composition sampling sites were arranged along 5 sampling lines with 200 m spacing maximum concentrations of ch4 total alkanes c2 c4 total alkenes c2 c4 h2 co2 and o2 detected in our samples were 0 16 vol 0 95 ppm 6 79 ppm 0 37 vol 5 01 vol and 21 6 vol respectively the results demonstrate that alkanes recorded in the soil gas which are heavier than methane originated from the deeper hydrocarbon accumulations these components migrated to the near surface zone due to their active microseepage along the tectonic discontinuities and cracks in the overburden weak correlation of h2 and co2 with alkanes were found which precludes the application of both components as additional prospective indicators in the study area diverse activity of partial oxidation of alkanes to alkenes perhaps due to different rate of microseepage of hydrocarbons has been determined using the c2h6 c2h4 c2 c2 ratio the presence of numerous tectonic dislocations intensifies the microseepage and increases the amplitudes of geochemical anomalies recorded at the surface normalization of concentrations of methane total alkanes c2 c4 and total alkenes c2 c4 with their of background values which were calculated for separate subsets of c2 c2 ratio values significantly reducing the ranges and the amplitudes of hydrocarbons anomalies it allowed for modification of the anomalous pattern due to diverse activity of partial oxidation of alkanes to alkenes statistical analysis of c2h6 c3h8 c2 c3 ratio values showed that in the study area accumulations of gas condensate and dry gas dominate with the strongest surface geochemical signals the surface geochemical results were integrated with the structural map of the top of devonian formations as well as we when displayed as trend integrated with geological cross sections the surface alkane anomalies generally occur along the major nw se trending chain of structural uplifts located between abramow glinnik and nasutow this zone is most prospective and indicates the highest petroleum potential changes in normalized concentrations of total alkanes c2 c4 allowed the identification of 9 anomalous zones indicating the presence of deep hydrocarbon sources the no 2 anomaly which was localized at the intersection of the b b and the e e sampling lines seems to be the most prospective the accumulations of dry gas or gas condensate likely occur in the anticline formed by devonian and or carboniferous strata this zone should be opened for confirmation by drilling the geochemical lead should now be integrated with all available geological seismic data for prospect development our study demonstrates that the results of surface geochemical surveys combined with the results of geological studies and geophysical surveys provide a valuable source of comprehensive information about the explored area

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

secondary minerals from extrapedogenic per latus acidic weathering environments at geomorphic edges eastern nebraska usa abstract acidic weathering of the sulfidic upper cretaceous carlile and pierre shales in nebraska has led to the precipitation of the al sulfate hydroxide minerals aluminite alunite basaluminite felsobanyaite e g the aluminum hydroxides gibbsite and bayerite and the rare al phosphate hydroxide vashegyite kaolinite has also been produced as a result of this acidic weathering these minerals do not appear as neoformed constituents in any extant soils in the region and their existence underscores the ability of pyrite oxidation to produce major changes in mineralogy on a holocene to recent time scale jarosite hydronium jarosite gypsum halotrichite and melanterite also appear as secondary minerals in the weathered shales acidic weathering and the formation of new minerals is extrapedogenic because it occurs well below the limit of modern soil sola these processes also occur at the edges of major landscape elements and can be considered to have a strong lateral component processes making them per latus processes in our usage

identification of source rocks on wireline logs by density resistivity and sonic transit time resistivity crossplots source rock formations generally show a lower density a lower sonic transit time and a higher resistivity than other sediments of equal compaction and comparable mineralogy this phenomenon can be used to identify source rocks on wireline logs provided the source rocks have a minimum thickness within the resolution of the sondes used and are sufficiently rich in organic matter classification rules have been established to assist in the recognition of source rocks on a combination of logs because of the low density contrast between water and organic matter the method becomes inaccurate at high water saturations i e low compaction within limits the amount of organic matter contained in a sediment can be estimated from log anomalies when source rocks become mature free oil is present in addition to kerogen and the resistivity increases by a factor of 10 or more

petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites petrology and geochemistry of d orbigny geochemistry of sahara 99555 and the origin of angrites

geology market and supply chain of niobium and tantalum a review tantalum ta and niobium nb are essential metals in modern society their use in corrosion prevention micro electronics specialty alloys and high strength low alloy hsla steel earns them a strategic designation in most industrialised countries the ta market is unstable due in part to historic influx of conflict columbite tantalite concentrate or coltan that caused ta mines in australia and canada to be placed on care and maintenance more recently the growing appetite of modern society for consumer goods made of conflict free minerals or metals has put pressure on suppliers pegmatites rare element enriched granites related placer deposits and weathered crusts overlying carbonatite and peralkaline complexes account for the majority of ta production several carbonatite related deposits e g upper fir and crevier canada are being considered for potential co production of ta and nb pyrochlore nb ta columbite tantalite nb ta wodginite ta nb and sn and microlite ta and nb are the main ore minerals approximately 40 of ta used in 2012 came from ta mines 30 from recycling 20 from tin slag refining and 10 from secondary mine concentrates due to rapid industrialisation and increased use of nb in steel making in countries such as china and india demand for nb is rising weathered crusts overlying carbonatite complexes in brazil and one hard rock carbonatite deposit in canada account for about 92 and 7 of nb world mine production respectively since the bulk of the production is geographically and politically restricted to a single country security of supply is considered at risk other prospective resources of nb beside carbonatites and associated weathered crusts are peralkaline complexes e g nechalacho where nb is considered as a potential co product of ree and zirconium economically significant deposits of ta and nb contain pyrochlore columbite tantalite fersmite loparite and struverite assuming continued elasticity of ta and nb prices and that the law of the supply and demand applies new sources of these metals can be developed in the long term there is no need to worry about ta and nb availability temporary disruptions in ta and nb supply are possible and could be difficult to cope with so new sources of supply may be developed to diversify geographic sources of supply for strategic reasons

palaeogeothermal gradients by vitrinite reflectance data and their relation to the present geothermal gradient patterns of the polish lowland abstract the paleogeothermal gradient values have been determined by vitrinite reflectance data taking the burial history into consideration the paleogeothermal gradient values are generally higher than the present measured geothermal gradients the paleogeothermal gradient and present geothermal gradient have been compared for the precambrian platform area and for the paleozoic platform area in the polish lowland region there exist high paleogeothermal gradient anomalies in the paleozoic platform and in the southeastern part of the polish lowland in the precambrian platform area where the drastic differences between the paleogeothermal gradients and the present geothermal gradient pattern occur the high paleogeothermal gradient values are most likely due to the thermal features of the variscan orogenic activities in central europe variscan and post variscan heating could play a significant role in the generation and destruction of oil deposits

the art of maturity modeling part 2 alternative models and sensitivity analysis the sensitivity of exploration decisions to variations in several input parameters for maturity modeling was examined for the miti rumoi well hokkaido japan decisions were almost completely insensitive to uncertainties about formation age and erosional removal across some unconformities but were more sensitive to changes in removal during unconformities which occurred near maximum paleotemperatures exploration decisions were not very sensitive to the choice of a particular kinetic model for hydrocarbon generation uncertainties in kerogen type and the kinetics of different kerogen types are more serious than differences among the various kinetic models results of modeling using the tti method were unsatisfactory thermal history and timing and amount of hydrocarbon generation estimated or calculated using the tti method were greatly different from those obtained using a purely kinetic model we strongly recommend use of the kinetic r o method instead of the tti method if we had lacked measured r o data subsurface temperature data or both our confidence in the modeling results would have been sharply reduced conceptual models for predicting heat flow and thermal conductivity are simply too weak at present to allow us to carry out highly meaningful modeling unless our input is constrained by measured data maturity modeling therefore requires the use of more not fewer measured temperature and maturity data the use of sensitivity analysis in maturity modeling is very important for understanding the geologic system for knowing what level of confidence to place on the results and for determining what new types of data would be most necessary to improve our confidence sensitivity analysis can be carried out easily using a rapid interactive maturity modeling program

the sandstone hosted beverley uranium deposit lake frome basin south australia mineralogy geochemistry and a time constrained model for its genesis the sandstone hosted beverley uranium deposit is located in terrestrial sediments in the lake frome basin in the north flinders ranges south australia the deposit is 13 km from the u rich mesoproterozoic basement of the mount painter inlier which is being uplifted 100 to 200 m above the basin by neotectonic activity that probably initiated in the early pliocene the mineralization was deposited mainly in organic matter poor miocene lacustrine sands and partly in the underlying reductive strata comprising organic matter rich clays and silts the bulk of the mineralization consists of coffinite and or uraninite nodules growing around co rich pyrite with an s isotope composition 34 s 1 0 0 3 suggestive of an early diagenetic lacustrine origin in contrast authigenic sulfides in the bulk of the sediments have a negative s isotope signature 34 s ranges from 26 2 to 35 5 indicative of an origin via bacterially mediated sulfate reduction minor amounts of zn bearing native copper and native lead also support the presence of specific reducing microenvironments in the ore zone small amounts of carnotite are associated with the coffinite ore and also occur beneath a paleosoil horizon overlying the uranium deposit provenance studies suggest that the host miocene sediments were derived from the reworking of early cretaceous glacial or glaciolacustrine sediments ultimately derived from paleozoic terranes in eastern australia in contrast the overlying pliocene strata were in part derived from the mesoproterozoic basement inlier mass balance and geochemical data confirm that granites of the mount painter domain were the ultimate source of u and ree at beverley u pb dating of coffinite and carnotite suggest that the u mineralization is pliocene 6 7 3 4 ma the suitability of the beverley deposit for efficient mining via in situ leaching and hence its economic value are determined by the nature of the hosting sand unit which provides the permeability and low reactivity required for high fluid flow and low chemical consumption these favorable sedimentologic and geometrical features result from a complex conjunction of factors including deposition in lacustrine shore environment reworking of angular sands of glacial origin deep pliocene weathering and proximity to an active fault exposing extremely u rich rocks

mineralogy and radiation effects of microlite from the harding pegmatite taos county new mexico microlite rangrng from crystalline to metamict is a principal accessory in several lithologic units of the harding pegmatite taos county new mexico from the sequence of lithologic units within the pegmatite crystallization of microlite from the pegmatite magma is inferred to have begun relatively late after the formation of the beryl and quartz zones and continued throughout the formation of the core zones and subsolidus replacement units over 200 chemical analyses of microlite determined by electron microprobe are reported and they are consistent with the accepted structural formula a2 b2x6y phro where principally a ca na ij mn b ta nb ti x o and y f oh o general features of microlite crystal chemistry identified include l a positive correlation between a site vacancies and the maximum y site vacancies 2 a positive correlation between na and f and 3 a negative correlation between u and f the latter is consistent with the interpretation that u at the a site in the pyrochlore structure is analogous to the uranyl group uo3 requiring o in place of f at the y site microlite compositions from four of five lithologic units examined are chemically distinct in terms of linear combinations of the variables ij fe ti bi ca ce pb f mn ba sb th ta and na the cleavelanditeunit microlites the exception not surprisingly have chemistries like those of the quartzlath spodumene zone which the cleavelandite unit in part has replaced the earliest formed microlites from the quartz lath spodumene zone have the highest ta na and f and are low in u and mn in contrast microlites from the later microcline spodumene zone and the replacement units are generally higher in ti mn and u and lower in f and na chemical changes ascribed to primary hydrothermal alteration from residual pegmatitic fluids include increases in ca mn and ti and an overall loss of a site cations alteration effects and chemical zoning within crystals analyzed in terms of simple end members identifies the following principal substitution schemes bnbbta bta bnb acayo anayf and aeye anayf for core to rim zoning in crystals and acayo anayf and acayo aey for primary alteration secondary weathering alteration results in decreases in na ca and f and increases in hro the effects of alpha recoil damage due to the decay of constituent u have been examined because of the wide variation in u content 0 1 10 wto o uor the microlites exhibit the full range of structural periodicity from completely crystalline 20 dpa based on x ray and electron ditrraction analysis the progressive structural modification of microlite udth increasing alpha dose involves 1 formation of isolated defect aggregates i e individual alpha recoil tracks up through doses of l0 4 alphas mg with no detectable effect on the materials s ability to diffract x rays or electrons 2 continued damage and overlap of these defect aggregates yielding coexisting regions of amorphous and crystalline domains at l0rs to 1016 alphas mg and 3 complete amorphization at doses greater than 10 7 alphas mg