oxygen and carbon isotope variations in gold bearing hydrothermal veins in the kushikino mining area southern kyushu japan the kushikino mine is located in the tertiary gold mining areas of southern kyushu japan the ore deposits occur in andesitic volcanics as fissure filling epithermal veins consisting of gold and silver bearing quartz and calcite with minor amounts of adularia sericite and sulfides quartz and calcite are dominant throughout the mineralization three major stages of mineral deposition are recognized as follows i first opening of fractures and deposition of translucent quartz ii repeated fracturing and the main stage of the au ag mineralization with deposition of milky quartz and calcite and iii deposition of barren calcite oxygen and carbon isotope compositions were determined for quartz and calcite from the kushikino 1 the champion vein and the arakawa 4 veins the ranges of the isotopic compositions of the minerals are as follows numbers of determination are given in parentheses vein mineral delta 18 o smow ppm delta 13 c pdb ppm kushikino 1 quartz 5 5 to 9 7 29 calcite 2 3 to 8 5 13 11 2 to 8 3 13 arakawa 4 quartz 8 4 to 10 7 8 calcite 5 6 to 9 9 5 9 7 to 8 9 5 no distinct difference in oxygen isotope compositions is observed between the stage i translucent quartz and the stage ii milky quartz in stage ii both quartz and calcite have wide ranges in delta 18 o values extending for the entire compositional ranges of the veins mentioned above the stage iii calcite has higher delta 18 o values than does the stage ii calcite the wide range in the delta 18 o values of the stage ii minerals corresponds to a temperature decrease from 220 degrees to 140 degrees c the isotopic data can be interpreted to indicate a mixing of deep hydrothermal fluid and low temperature meteoric ground water if the deep hydrothermal water was unexchanged or partially exchanged meteoric water with a limited range of delta 18 o values lower than 3ppm at 300 degrees c incorporation of a large quantity of high delta 18 o thermal waters is not plausible the delta 13 c delta 18 o trend of calcite is interpreted to show a temperature decrease and a change in the carbon species of the fluid calcite crystallized in equilibrium with a fluid in which h 2 co 3 was dominant at temperatures higher than 140 degrees or 150 degrees c whereas hco super 3 was dominant at lower temperatures this accords with inferences based on phase equilibria the stage iii calcite crystallized in a lower temperature range of the hco super 3 dominant field judging from fluid inclusion data and mineral assemblages changes in pressure or ph of the fluid were not so important in stage ii the quartz calcite deposition and au ag mineralization in stage ii may have taken place as a result of rapid cooling of the fluid due to mixing mixing of two fluids both of which were saturated with calcite but which had different temperatures caused supersaturation of the calcite and thus deposition of it along with a temperature decrease deposition of a large quantity of calcite in stage iii would be due to a pressure decrease caused by the opening of fractures at shallow depths a subsequent decrease in ph of the fluid may have caused the kaolinite alteration near the surface

chemically induced grain boundary migration in calcite temperature dependence phenomenology and possible applications to geologic systems chemically induced grain boundary migration cigm is a solid state reaction mechanism which involves grain boundary migration initially straight grain boundaries in calcite bicrystals exhibit cigm when exposed to a srco3 or baco3 rich melt at temperatures of 680 840 c in a 1 bar co2 atmosphere under these conditions cigm is apparently a much more efficient way to form solid solutions than lattice diffusion the maximum observed rate of migration 1 10 9 m s occurred at about 760 c below that temperature migration was thermally activated but above it the process was thermally inhibited some portions of the boundary swept through a given crystal volume more than once in the ca sr co3 system the solute concentrations incorporated during a single pass of the boundary were far less than values expected at chemical equilibrium and departed further from equilibrium at higher temperatures cigm may be geologically important when the distances characteristic of grain boundary migration and diffusion are much larger than those characteristic of lattice diffusion the great similarity between results in ionic calcite and metals systems suggests cigm is a very general process which may be expected to occur in a large number of geologic systems

oxygen and carbon isotopic compositions of carbonates from the neogene epithermal vein type deposits of japan implication for evolution of terrestrial geothermal activity abstract carbonates from the neogene epithermal vein type deposits in japan can be divided into two types type a which precipitated abundantly at the main stage of mineralization and type b which precipitated in small amounts at a later stage 18 o values of type a carbonate 0 to 14 are lower than those of type b carbonate 5 to 24 estimated 18 o values of type a and b ore fluids are 10 to 0 and 0 to 10 respectively 18 o of type a carbonate can be explained by meteoric water rock interaction but that of type b carbonate cannot be explained by this process rayleigh type boiling could account for the relatively high 18 o of type b carbonate

paleohydrogeology of the canadian rockies and origins of brines pb zn deposits and dolomitization in the western canada sedimentary basin results of stable isotopic and fluid inclusion studies of cambrian carbonate units in the southern canadian rockies indicate that during the late devonian or early mississippian a warm brine migrated from miogeoclinal shales in the western part of the western canada sedimentary basin into the eastern carbonate sequences this fluid had a temperature of 150 25 c salinity values of 20 to 25 equivalent wt nacl and isotopic values of 18 o 7 to 0 13 c 1 2 d 70 19 and 87 sr 86 sr 0 710 the fluids formed large bodies of coarse sparry dolomite as well as pb zn magnesite and talc mineralizations in the cambrian units it is probable that this event was also responsible for the development of pb zn mineralization specifically pine point in the devonian units as well as a component of the present day basinal brines in the basin

understanding the lunar surface and space moon interactions the surface of the moon is a critical boundary that shapes our understanding of the moon as a whole all geologic mapping and remote sensing techniques utilize only the outermost portion of the moon before leaving the moon for study in our laboratories all lunar samples that have been studied existed at or very near the surface with the exception of the deeply probing geophysical techniques our understanding of the interior of the moon is derived from surficial but not superficial information coupled with boundary of the lunar crust it is the lower boundary layer of the tenuous lunar atmosphere and constitutes both a source and a sink for atmospheric gases the surface is also where the moon interacts with the space environment causing changes in the physical nature of lunar materials and provides a laboratory for the study of processes that occur on all airless bodies the data obtained remotely by the galileo clementine and lunar prospector missions as well as data derived from lunar meteorites have resulted in major changes to our understanding of global distributions of chemistry and rocks this chapter summarizes the current understanding of this critical interface the surface of the moon in its role as the lower boundary of the lunar atmosphere the upper boundary of the crust and the window through which we view through remote sensing the composition of the crust and the history of the moon in this post lunar prospector time the view of the moon has changed lending new perspectives to lunar samples and lunar processes but the new view will likely remain in flux as we continue to digest the results from these recent space missions and move forward to a new era of lunar exploration despite the freshness of our perspective this is an important moment to capture

epigenetic sulfide mineralization associated with pennsylvanian paleokarst in eastern iowa u s a abstract paleokarst associated sulfide bearing mineral deposits are wide spread in the paleozoic carbonate rocks of eastern iowa minerals occur in nodules enclosed in karst filling mudstones as sandstone cements and as surface coatings on and fracture fillings in foundered carbonate rock clasts mineralogy and paragenetic sequence vary among the occurrences sulfur isotopic compositions exhibit wide variations within and among deposits 34 s 33 8 to 35 1 oxygen isotopic compositions of fracture filling calcite spars 18 o 8 41 to 3 60 are similar to the isotopic compositions of their carbonate rock hosts calcite spars are somewhat depleted in 13 c relative to host rock 13 c spars 5 66 to 0 24 vs 1 54 to 1 21 host rock results of mineralogic paragenetic and isotopic investigations suggest that 1 minerals are products of multiple events operating on a local rather than a regional scale 2 spatially disjunct fracture filling mineral deposits exposed in the same quarries are probably not cogenetic with paleokarst associated deposits 3 paleokarst filling calcite spars formed at near surface temperatures and 4 paleokarst associated deposits are probably not cogenetic with upper mississippi valley zn pb pitch flat deposits

geochemical and carbon isotopic studies of crude oil destruction bitumen precipitation and sulfate reduction in the deep smackover formation abstract crude oil generated by the lower smackover source facies migrated to upper smackover reservoirs where slow thermal cracking of crude oil resulted in the formation of gas condensate and late solid bitumen ultimately only pyrobitumen methane and nonhydrocarbon gases including hydrogen sulfide persist in the deepest smackover reservoirs the carbon isotopic compositions of crude oils became heavier during crude oil destruction the carbon isotopic compositions of asphaltenes nso compounds and saturated hydrocarbons in late solid bitumen and the lower smackover source facies became isotopically lighter during crude oil destruction it is suggested that some isotopically light components from crude oils were incorporated in late solid bitumen by reactions involving thermochemical sulfate reduction thermochemical sulfate reduction and crude oil destruction occurred over a long span of geologic time at temperatures in the 120 150 c range

fine grained aggregates in l3 chondrites abstract the textures and chemical compositions of the constituent minerals of the fine grained aggregates fga s of l3 chondrites were studied by the backscattered electron image technique electron probe microanalysis and transmission electron microscopy plagioclase and glass in the interstices between fine grains of olivine and pyroxene indicate that the fga s once partly melted compositional zoning and decomposition texture of pyroxenes are similar to those observed in chondrules indicating a common cooling history of the fga s and chondrules therefore the mechanism that caused melting of the fga s is considered to be the same as for chondrules bulk compositions of the fga s are within the range of those of chondrules so some chondrules probably were produced by complete melting of the same precursor materials as those of the fga s the precursor materials must have included fine olivine and other grains that probably are condensates

the karst hosted mina grande nonsulfide zinc deposit bongara district amazonas region peru the mina grande zinc nonsulfide deposit amazonas region peru consists of several accumulations in karst cavities of zn oxide minerals derived from weathering of a mississippi valley type deposit hosted in mesozoic carbonate rocks of the condorsinga formation pucara group the karst cavities hosting the nonsulfide ores were developed in the miocene along northwest southeast faults avg 230 dip 70 dip angle associated with regional structures and locally along stratification joints avg 8 strike 278 dip and 26 dip angle thus far the mina grande zn accumulations have been partially mined in two pits named fase a and fase b and explored in a third area named fase c in 2008 the resources were as follows fase a 160 000 metric tons t 21 2 zn fase b 36 400 t 28 9 zn and fase c 116 700 t 22 5 zn the nonsulfide mineral assemblage consisting mostly of hydrozincite smithsonite and hemimorphite is associated with few remnants of the hypogene ore pyrite and sphalerite mineralogical and petrographic studies revealed several texturally distinct smithsonite and hydrozincite generations which are characterized by extremely negative 13 c compositions pointing to the prevailing contribution of an isotopically light carbon component from the oxidation of organic matter derived carbon and different 18 o isotope compositions 26 9 to 27 2 and 26 0 to 26 3 18 o vsmow for smithsonite and averages 24 6 and 23 7 18 o vsmow for hydrozincite these distinct 18 o compositions indicate that smithsonite and hydrozincite precipitated at least after two depositional stages these stages were probably related to several periods of uplift that occurred in the bongara district since at least 10 ma when the transition from the pebas to acre systems affected the amazonas foreland basin in the miocene the karst activity to which the supergene mineralization is related was restricted to the late miocene and early pliocene periods climatic conditions reconstructed from the ecosystems persisting in the region from late tertiary to recent time suggest that the mina grande supergene mineralization was associated with several weathering episodes that occurred under a climate resembling the present day climatic conditions

the cristal zinc prospect amazonas region northern peru part i new insights on the sulfide mineralization in the bongara province the cristal zn prospect consists of a mixed sulfide and nonsulfide mineralization located in the bongara province amazonas region northern peru the mineralization is hosted by carbonate rocks of the pucara group deposited in a mesozoic extensional basin on the western margin of the brazilian guyana shield zinc sulfides at cristal occur in the roots of the nonsulfide concentrations and are locally present also nearer to surface the sulfide mineralization postdates two hydrothermal dolomitization phases dol1 and dol2 and the sulfides occur mainly in veins cavity fillings or as disseminated mineralization within sparry to saddle dolomite they mostly consist of dark brown sphalerite intergrown with smaller amounts of pyrite sphalerite shows a distinct fe zonation with average ca 7 wt fe max ca 12 wt fe and is ge rich mean concentration of 142 ppm galena is rare the cristal sphalerite has sulfur isotopic compositions of 34s 14 to 15 vcdt oxygen isotopic compositions of dolomites are 18o 24 4 to 24 7 vsmow for dol1 and 18 4 to 22 for dol2 34s and 18o values of cristal sulfides and dolomites are similar to those observed in two mississippi valley type mvt deposits located ca 20 30 km south of the cristal prospect namely the florida canyon and florcita deposits this could be consistent with one or more events within a same mvt mineralizing system acting at the district scale the pb isotope compositions of sphalerite from two different areas of the prospect named cristal s s and charlita north define two distinct data point clusters centered around averages of 206pb 204pb 18 850 0 002 207pb 204pb 15 685 0 002 208pb 204pb 38 752 0 004 and 206pb 204pb 19 042 0 002 207pb 204pb 15 712 0 002 208pb 204pb 39 080 0 004 respectively this difference requires distinct metal bearing hydrothermal pulses in the mineralized area and or distinct pb sources the pb isotopic compositions of the cristal s s and charlita north sulfides are intermediate between the compositions of galena from the san vicente and shalipayco mvt deposits and record a contribution from an old crustal component the paleozoic basement which has pb isotopic ratios roughly matching those of dolomites and sulfides from cristal and charlita north areas represents the most reliable candidate to be an end member source of the metals of the cristal sulfide mineralization the second end member could be an igneous source isotopically identical to the late paleozoic to early mesozoic intrusives of the peruvian eastern cordillera or the triassic volcanic rocks occurring within the mitu group

carbon oxygen isotopic covariation in hydrothermal calcite during degassing of co 2 the effect of the outgassing of co2 from a hydrothermal fluid on the c and o isotopic compositions of calcite which is precipitated from this fluid is quantitatively modelled in terms of batch and rayleigh distillation equations both co2 degassing and calcite precipitation are considered to be the removal mechanisms for dissolved carbon species from the fluid combined degassing precipitation models are then developed by taking h2co3 and hco 3 respectively as the dominant dissolved carbon species a positive correlation array between 13c and 13o values of calcite can be yielded by the precipitation of calcite from a h2co 3 dominant fluid accompanied by a progressive decrease in temperature during co2 degassing whereas calcite precipitated from a hco 3 dominant fluid under the same conditions tends to display much smaller variation in 13c values than in 18o values the combined processes of co2 degassing and calcite precipitation result in lowering the 13c value of calcites with respect to those precipitated in a closed system simply due to temperature effect carbon and oxygen isotopic data for calcite from the kushikino gold mining area in japan illustrate the application of quantitative modelling and degassing of co2 is suggested as a more likely cause for the precipitation of the calcite and quartz in this mining area

organic maturation and ore precipitation in southeast missouri the sulfate reduction plus mixing hypotheses for the formation of mississippi valley type deposits have suffered from an inability to show a plausible mass balance between sulfate possible reductants and sulfide ores and a mechanism for mixing the reduced gas h 2 s with the metal bearing fluid both these problems are resolved by focusing on the gases mostly methane generated from the organic matter in the host carbonate rocks during thermal maturation caused by heat from the hydrothermal solutions in southeast missouri it appears that the volume of the bonneterre formation required to produce all the methane needed to reduce enough sulfate to precipitate all the ores is approximately the same as the volume of the brown rock facies which hosts most of the ore therefore it appears that metal and sulfate bearing solutions entered the bonneterre at lamotte sandstone pinchouts then followed permeability trends which coincided mainly with the oolitic grainstones associated with the stromatolite reef most of which are brown evolution of methane and other reducing compounds from the brown rock resulted in sulfate reduction and precipitation of sulfides several other regional and local factors in the geology of the area are found to be compatible with this idea

crystallization temperatures and stable isotope compositions of mississippi valley type carbonates and sulfides of the trenton limestone wyandot county ohio

germanium enrichment in supergene settings evidence from the cristal nonsulfide zn prospect bongara district northern peru supergene nonsulfide ores form from the weathering of sulfide mineralization given the geochemical affinity of ge to si4 and fe3 weathering of ge bearing sulfides could potentially lead to ge enrichments in silicate and fe oxy hydroxide minerals although bulk rock ge concentrations in supergene nonsulfide deposits are rarely reported here we present the results of an investigation into ge concentrations and deportment in the cristal supergene zn nonsulfide prospect bongara northern peru which formed from the weathering of a preexisting mississippi valley type mvt sulfide deposit material examined in this study originates from drillcore recovered from oxidized zn rich bodies 15 20 m thick containing 5 45 wt zn and ge concentrations 100 ppm microanalysis and laser ablation icp ms show that precursor sphalerite is rich in both fe mean fe 8 19 wt and ge mean ge 142 ppm using the mineral geothermometer ggimfis geothermometer for ga ge in mn and fe in sphalerite proposed by frenzel et al ore geol rev 76 52 78 2016 sphalerite trace element data from the cristal prospect suggest a possible formation temperature tggimfis of 225 50 c anomalously high for a mvt deposit germanium concentrations measured in both goethite mean values 100 to 229 ppm max 511 ppm and hemimorphite mean values 39 to 137 ppm max 258 ppm are similar to concentrations measured in hypogene sphalerite additionally the ge concentrations recorded in bulk rock analyses of sphalerite bearing and oxidized samples are also similar a persistent warm humid climate is interpreted for the region resulting in the development of an oxidation zone favoring the formation of abundant zn hydrosilicates and fe hydroxides both able to incorporate ge in their crystal structure in this scenario ge has been prevented from dispersion during the weathering of the ge bearing sulfide bodies and remains in the resultant nonsulfide ore

organic geochemistry of the san vicente zinc lead district eastern pucara basin peru abstract isotopic and chemical studies of organic matter of the san vicente mississippi valley type zn pb district hosted in the dolomitic units of the eastern pucara basin peru provide insight into the source of organic matter and of the organic matter ore relationship a large scatter exists in the 13c and 15n values of the highly mature kerogens these bulk data were combined with 13c covariations of the saturated and aromatic fractions of the rock extracts to indicate a contribution of continental higher plant lipids to the marine algal source of the organic matter disseminated in the host carbonate rocks an enrichment in 15n of the kerogens of mineralized samples compared to barren samples suggests that isotopically heavy nitrogen compounds were introduced to the ore fluid the fluid likely leached these compounds from the underlying clastic rocks and other detrital units of the pucara the extracts from mineralized samples are enriched in 13c compared to the associated kerogens this suggests that the rocks in the mineralized areas were stained by a mixture of extrinsic and indigenous bitumens by the use of novel instrumentation such as a gas chromatograph gc coupled to a stable isotope ratio mass spectrometer irms through a combustion c interface gc c irms stable carbon isotope analyses of individual hydrocarbons were also obtained both the molecular and isotopic signatures of the individual hydrocarbons are related to mineralization the variability in the organic molecular parameters and the 13c values of the individual n alkanes and isoprenoids indicate mixing of indigenous hydrocarbons with extrinsic 13c depleted microbially derived hydrocarbons the extrinsic source hydrocarbons were introduced to the mineralization site by the ore fluid or later fluids using the same porosity network oxidative alteration of the migrating hydrocarbons was involved in the thermochemical reduction of sulfate to h2s and precipitation of pyrobitumen large differences 12 in the carbon isotope compositions of long chain c20 n alkanes can be utilized in distinguishing sources of organics in the barren and mineralized samples

large scale fluid flow in the middle devonian presqu ile barrier western canada sedimentary basin saddle dolomite cements are regionally extensive in the middle devonian presqu9ile or keg river barrier and are spatially associated with mississippi valley type mineralization at pine point northwest territories from northeastern british columbia to pine point over a lateral distance of 400 km these dolomite cements show general trends of decreasing 87 sr 86 sr ratios 0 7106 to 0 7081 and homogenization temperatures 178 to 92 c with some increase in 18 o values 16 to 7 pdb these regional trends suggest that hotter and more radiogenic basinal fluids moved eastward updip along the presqu9ile barrier and mixed with cooler ambient formation waters these movements of basinal fluids were probably related to tectonic thrusting and compression sedimentary loading and tectonic uplift on the western margin of the western canada sedimentary basin which began to form during late jurassic to early cretaceous time and climaxed during the late cretaceous to paleocene the middle devonian presqu9ile barrier appears to have acted as a deeply buried regional conduit system that played an important role in focusing and channeling these basinal fluids these regional fluid flows appear to have been responsible for extensive burial dolomitization secondary migration of hydrocarbons and local mississippi valley type mineralization in the western canada sedimentary basin

tem investigations on the monomict ureilites jalanash and hammadah al hamra 064 we studied the petrography and mineralogy of two monomict ureilites hammadah al hamra 064 hh064 and jalanash by using reflected light and scanning electron microscopy quantitative analyses were performed by electron microprobe and the microstructures were investigated with transmission electron microscopy tem hh064 features two different textures a poikilitic and a typical one whereas jalanash shows only the typical ureilite texture our synergetic chemical and microstructural investigations reveal a complex cooling history for both ureilites the temperature for the first equilibrium deduced from the pigeonite augite assemblage in hh064 is 1200 c the presence of antiphase domains in low ca pyroxenes proves that they are clearly pigeonite the occurrences of tweed microstructure and orthopyroxene lamellae which are incompletely developed imply a faster cooling rate from the first equilibrium with a sudden end although both ureilites contain shock induced diamonds dislocations in silicates are rare this observation suggests that the meteorites were hot at the time of strong shock metamorphism or that they were heated after strong shock metamorphism after this event new microstructural features were generated by different cooling processes and were frozen by a final rapid decrease in temperature possibly due to excavation from the ureilite parent body or bodies

genesis of the mississippi valley type zn pb deposit of san vicente central peru geologic and isotopic sr o c s pb evidence the san vicente zn pb ore deposit is situated 300 km east of lima in central peru within the upper triassic lower jurassic carbonate platform pucara group at the western margin of the brazilian shield production during the last 20 years and present reserves exceed 12 million tons of ore assaying about 12 percent zn and 1 percent pb sphalerite and galena the only ore minerals occur as lens shaped bodies generally parallel to the bedding within the 1 400 m thick pucara sequence three ore bearing dolomite units occur the ore lenses are bound to dolomitized tidal flat and lagoon facies with cryptalgal lamination and evaporite molds and to adjacent oolithic grainstones of barrier facies strontium carbon oxygen and sulfur isotope geochemistry was carried out on consecutive crystallization generations the results obtained display systematic trends the 87 sr 86 sr ratios range between 0 7077 and 0 7084 the first generations display values very similar to those of upper triassic lower jurassic ocean water later generations are slightly enriched in radiogenic strontium the degree of enrichment in radiogenic strontium is low compared to other mississippi valley type deposits the delta 18 o values range between 6 and 10 per mil pdb and the delta 13 c values between 2 and 1 per mil pdb the late crystallization generations are enriched in the light isotopes of oxygen and carbon compared to the first generations the sulfur isotope ratios of sphalerite are relatively homogeneous ranging between 9 9 and 13 0 per mil a trend to lighter sulfur isotope ratios with advancing diagenetic stage can also be recognized the san vicente lead zinc deposit formed during burial diagenesis the temperatures indicated by sulfur isotope geothermometry 75 degrees 92 degrees c would be consistent with temperatures reached at a burial depth of about 2 to 3 km this might have been reached by the end of the jurassic a model based on abiogenic reduction of sulfates at or near the ore site and the introduction of a zinc and lead bearing basinal brine characterized by strontium isotope ratios slightly higher than contemporaneous seawater and highly radiogenic lead is favored the association of the orebodies with peritidal facies with abundant sulfate molds is important evidence favoring the existence of two separate reservoirs for sulfur and metals leaching of detrital material derived from precambrian upper crust from the brazilian shield would explain both strontium and lead isotope ratios

hydrocarbon biomarkers in the topla mežica zinc lead deposits northern karavanke drau range slovenia paleoenvironment at the site of ore formation the mississippi valley type zinc and lead deposits at topla 250 150 metric tons t of ore grading 10 wt zn and 3 3 wt pb and me ica 19 million metric tons mt of ore grading 5 3 wt pb and 2 7 wt zn occur within the middle to upper triassic platform carbonate rocks of the northern karavanke drau range geotectonic units of the eastern alps slovenia the ore and host rocks of these deposits have been investigated by a combination of inorganic and organic geochemical methods to determine major trace and rare earth element ree concentrations hydrocarbon distribution and stable isotope ratios of carbonates kerogen extractable organic matter and individual hydrocarbons these data combined with sedimentological evidence provide insight into the paleoenvironmental conditions at the site of ore formation the carbonate isotope composition the ree patterns and the distribution of hydrocarbon biomarkers normal alkanes and steranes suggest a marine depositional environment at topla a relatively high concentration of redox sensitive trace elements v mo u in the host dolostones and ree patterns parallel to that of the north american shale composite suggest that sediments were deposited in a reducing environment anoxic conditions enhanced the preservation of organic matter and resulted in relatively higher total organic carbon contents up to 0 4 wt the isotopic composition of the kerogen 13 c kerogen 29 4 to 25 0 15 n kerogen 13 6 to 6 8 suggests that marine algae and or bacteria were the main source of organic carbon with a very minor contribution from detrital continental plants and a varying degree of alteration extractable organic matter from topla ore is generally depleted in 13 c compared to the associated kerogen which is consistent with an indigenous source of the bitumens the mineralization correlates with 15 n kerogen values around 0 per mil 13c depleted kerogen 13c enriched n heptadecane and relatively high concentrations of bacterial hydrocarbon biomarkers indicating a high cyanobacterial biomass at the site of ore formation abundant dissimilatory sulfate reducing bacteria feeding on the cyanobacterial remains led to accumulation of biogenic h 2 s in the pore water of the sediments this biogenic h 2 s was mainly incorporated into sedimentary organic matter and diagenetic pyrite higher bacterial activity at the ore site also is indicated by specific concentration ratios of hydrocarbons which are roughly correlated with total pb plus zn contents this correlation is consistent with mixing of hydrothermal metal rich fluids and local bacteriogenic sulfide sulfur the new geochemical data provide supporting evidence that topla is a low temperature mississippi valley type deposit formed in an anoxic supratidal saline to hypersaline environment a laminated cyanobacterial mat with abundant sulfate reducing bacteria was the main site of sulfate reduction

internal zonation in a carbonate hosted zn pb ag deposit nanisivik baffin island canada zn pb ag ores at nanisivik northwest baffin island are hosted by upper proterozoic laminated dolostone of the society cliffs formation sulfide orebodies containing pyrite sphalerite galena sparry dolomite and pyrite pseudomorphous after marcasite are characterized by well banded ore textures considered to have resulted from the progressive replacement of carbonate wall rock textural and mineralogical variations enable the main orebody to be divided into three vertical and four horizontal ore zones the upper lens of the main orebody may be further subdivided into six texturally distinct laterally extensive mine units in the eastern upper lens where textural variations are best developed fluid inclusions indicate that most ore mineralization took place over the temperature range of 165 degrees to 210 degrees c and involved a brine containing 20 to 38 wt percent nacl equiv the sulfur isotope compositions of main and late stage pyrite crystals range from delta 34 s 27 4 to 28 0 per mil iron contents of sphalerite vary from 14 to 0 mole percent fes corresponding to well developed color zoning and constrain the oxygen activity of the ore fluid to 10 super 46 to 10 super 41 at 200 degrees c during sphalerite precipitation interbanded primary marcasite and sparry dolomite gangue indicates that the ore fluid fluctuated around ph 5 ore formation is modeled based on processes involving in situ reduction of sulfate by hydrocarbons and minor h 2 s encountered at the site of ore deposition the location and configuration of the orebodies was probably controlled in part by the former position of a horizontal fluid interface banding is likely the result of repetitive sulfate reduction metal precipitation wall rock dissolution and dolomite recrystallization in response to the pulsatory influx of ore fluid textural and mineralogic variations probably resulted from slight variations in the availability of reduced sulfur

ore fluid geochemistry of the hehuashan pb zn deposit in the tongling ore district anhui province china evidence from ree and c h o isotopes of calcite abstract calcite is the main gangue mineral of the hehuashan lead zinc deposit which is located in the tongling ore district anhui province east china the ore bodies of the hehuashan deposit are hosted by dissolution breccia of the lower triassic carbonate sediments we report petrography rare earth elements ree and c h o isotope data of four generations of calcite recognized in the hehuashan deposit namely the pre ore stage calcite cal 1 early ore forming stage calcite cal 2 late ore forming stage calcite cal 3 and post ore stage calcite cal 4 in addition we also report c h o isotopes data of dolostone from the lower triassic carbonate sediments all four calcite generations show a low ree content 13 50 ppm on average indicating that the related ore forming fluids may not have been derived a magmatic fluid but rather be derived from the carbonate sediments or basinal brines low lree hree ratio 1 1 6 1 on average of all four calcite generations implies that no significant ree fractionation happened during the mineralizing processes the wide distribution of y ho ratios 17 70 of calcite indicates a result of fluids mixing the 13c values of calcite 1 4 to 4 2 are comparable to marine carbonates but the 18o values are lower indicating possibly a result of carbonates dissolution calculated 18o of the fluid in equilibrium with calcite vary from 3 1 to 0 1 combining the dv smow 100 to 81 implying a fluid mixing of a brine fluid and meteoric water or diagenetic pore water for the mineralization of the hehuashan deposit

the effects of stress and fracturing on permeability of coal abstract this paper examines the changes in structure and permeability of coal under the stress conditions experienced around longwall faces the effect of fracturing on permeability of coal is discussed and the stress permeability relationship for fractured coal is compared with that of non fractured coal an empirical relationship between stress and permeability for coal is derived from the experimental data which relates the stress permeability behaviour of coal to its rank through the compressibility of the coal itself

stable isotope geochemistry of carbonate fracture fills in the monterey formation california abstract carbonate minerals filling fractures in the monterey formation at four locations along the santa barbara channel coast display a 18o smow range from 20 7 to 35 7 and 13c range from 18 6 to 16 6 many fracture fills display a covariation of 18o and 13c and successive generations of carbonate have lower 18o values these isotope systematics can be interpr ted in terms of 18o values that were controlled by crystallization temperatures and the 18o of connate pore water and 13c values that were controlled by depth sequential organic matter degradation reactions each successive generation of carbonate precipitated at progressively higher burial temperatures from isotopically evolving connate pore water these carbonate filled fractures developed during burial and not during uplift using crystallization temperature estimates from fluid inclusion data the change in 18o of conate pore water with increasing temperature in the burial environment is modeled from this model the fracture fill 18o values indicate precipitation over the following temperature intervals 25 70 c carpinteria beach 7 15 c goleta slough beach 45 100 c refugio beach and 53 103 c jalama beach

geochemical constraints on the origin of the kicking horse and monarch mississippi valley type lead zinc ore deposits southeast british columbia canada two mississippi valley type mvt ore deposits kicking horse and monarch have been studied with the aim of comparing the ores at the two localities and to characterize the origin of the mineralizing fluids and the ore formation process es both deposits are hosted by the middle cambrian cathedral formation carbonate host rocks kicking horse on the north and monarch on the south flank of the kicking horse valley near field se british columbia the ore bodies are situated at the transition of western basinal to eastern shallow water strata of the paleo pacific passive margin succession in the cordilleran foreland province of the western canada sedimentary basin both deposits are related spatially to normal faults in both localities the ore minerals are dominated by pyrite sphalerite and galena dolomite minor quartz and calcite are also present in close association with the ores the salinity 21 30 wt nacl eq and homogenization temperatures 63 182 c measured in fluid inclusions in carbonate quartz and sphalerite lie within the typical range of mvt fluid conditions the good stoichiometry 50 53 mol caco3 low 18o values 21 to 14 vienna peedee belemnite and relatively high homogenization temperatures 95 c of the dolomite suggest the dolomites were formed under burial diagenesis the ore forming fluids probably interacted with siliciclastic units based on elevated li contents and 87sr 86sr ratios which are highest in the dolomite type after the main ore stage we propose that the ores formed from the mixing of a downward infiltrating sulfur bearing halite dissolution fluid with an upward migrating metal rich evaporated seawater fluid which had already undergone minor mixing with a dilute fluid

saddle dolomite as a by product of chemical compaction and thermochemical sulfate reduction petrographic stable and radiogenic isotope trace element and fluid inclusion data from the devonian nisku reef trend in the subsurface of alberta canada suggest that saddle dolomite was a by product of chemical compaction and thermochemical sulfate reduction in subsiding dolomitized rocks furthermore thermochemical sulfate reduction may be representative of other processes that increase the amount of saddle dolomite via an increase in carbonate alkalinity the data also confirm that saddle dolomite is most likely to form at elevated temperatures from hypersaline brines

geochemical variation of dolomite cement within the cambrian bonneterre formation missouri evidence for fluid mixing abstract compositionally zoned dolomite in the cambrian bonneterre formation of missouri precipitated from warm basin derived brine as evidenced by its fluid inclusion homogenization and freezing temperatures and radiogenic 87sr 86sr composition preexisting host carbonates played a major role in governing parent fluid composition during precipitation of the dolomite cement this is indicated by significant overlap in the isotopic and minor and trace element composition of the cement and host there is a decrease in 13c and 18o with succeeding dolomite cement zones suggesting that isotopically lighter cement armored the host rock progre sively isolating the fluids from preexisting dolomite 87sr 86sr values for a single cement zone zone 4 vary from 0 7086 to 0 7201 the more radiogenic values reflect a contribution of 87sr to the brine primarily through silicate reactions prior to entering the bonneterre formation the lower values overlap with preexisting replacement dolomite and limestone within the bonneterre again indicating the importance of host rock buffering possible mechanisms governing the apparent control on cement composition by preexisting replacement dolomite were evaluated using computer models which simulate fluid and cement composition in 1 a system in which a single fluid progressively interacts with host carbonate and 2 a system in which there is mixing of fluids having undergone different degrees of fluid rock interaction the predicted covariation of geochemical parameters using the mixing model matches the actual data from zone 4 cement better than that offer progressive fluid rock interaction in most cases the contrast between the predicted mixing and fluid rock interaction curves is greatest for cross plots involving mn fe and 13c which are effectivel buffered by host rock during progressive fluid rock interaction the mixing model works best for zone 4 cement data subdivided according to stratigraphic subunit and area suggesting a great deal of spatial variation in end member fluids equilibrium modelling with the speciation reaction modelling program phrqpitz suggests that dolomite supersaturation occurs when a relatively hot dolomite saturated fluid mixes with a cooler dolomite saturated fluid having similar pco2 values this is consistent with geochemical data from zone 4 cement which indicates mixing of a relatively unbuffered fluid with fluids buffered by local host rocks

zoned base metal mineralization in a porphyry system origin and evolution of mineralizing fluids in the morococha district peru porphyry related base metal vein and replacement mineralization i e cordilleran polymetallic mineralization in the morococha district central peru is part of a large magmatic hydrothermal system associated with the emplacement of several late miocene porphyry intrusions and formation of important cu mo mineralization zn pb ag cu veins overprint the giant toromocho porphyry cu mo deposit in the center of the district and display a typical concentric base metal zonation cu zn pb ag covering an area of approximately 50km2 a detailed fluid inclusion study supports the hypothesis that base metal mineralization precipitated from cooled and evolved metal rich intermediate density porphyry type fluids in early stages of cordilleran base metal vein formation fluid inclusions have low salinities of 2 to 5 wt nacl equiv co2 contents of 3 to 10mol and homogenization temperatures th of 380 to 340 c they are similar to intermediate density fluid inclusions trapped in a milky quartz vein predating cordilleran polymetallic mineralization with similar low salinities 3 0 3 8 wt nacl equiv and low co2 contents 6 5 8 mol but higher th of 420 to 410 c during cooling of the intermediate density fluids from 400 to 300 c the lithostatic pressure regime changed to a hydrostatic one the fluids underwent pressure drop as well as phase separation i e unmixing and lost most of their co2 they acquired moderate salinities in some cases intermediate up to 16 wt nacl to brine compositions however the bulk of the magmatic fluid retained low salinity while it continued to cool under open system conditions and precipitated tennantite tetrahedrite chalcopyrite enargite sphalerite and galena upon cooling below 270 c the fluids deposited abundant rhodochrosite and quartz while following the boiling curve toward lower p t conditions these data record an evolution of mineral precipitation from deep minimum depth of 2 1 5 km to shallow environments 300 800 m oxygen hydrogen and carbon stable isotope data indicate that the hydrothermal fluids have a dominantly magmatic signature and were diluted by meteoric waters during the carbonate stage copper 5 000 18 000 g g sulfur up to 12 000 g g and iron 2 100 6 000 g g concentrations in the intermediate density fluid inclusions in the milky quartz veins are approximately 5 to 10 times higher than in intermediate density inclusions of the early cordilleran base metal veins the base metals zn pb and mn have comparable concentrations between 100 and 1 000 g g for both types of fluid these findings suggest that the fluids identified in cordilleran polymetallic veins are compositionally similar to the porphyry type fluids and could have derived from the latter after precipitation of cu and fe bearing sulfides in a deeper porphyry environment the new data explain the commonly observed base and precious metal zonation patterns encountered in porphyry centered districts e g bingham butte and show that both porphyry and polymetallic mineralization can precipitate from similar magmatic hydrothermal fluid pulses

exsolution and coarsening mechanisms and kinetics in an ordered cryptoperthite series cryptoperthites from the klokken layered syenite intrusion were examined by tem to determine the role of exsolution ordering and twinning in the development of the coherent microtextures during slow cooling the stratigraphic position of the samples in the layered series giving an independent variable in determining their evolution both periodicity primary and secondary and morphology change with distance from the top of the series most samples contain low microcline in the diagonal association

constraints on the cooling rates of chondrules from the microstructure of clinopyroxene and plagioclase abstract attempts are made to quantify cooling rates of chondrules from the microstructure of clinopyroxene and ca rich plagioclase pigeonite diopside exsolution lamellae on 001 are frequently observed in allende granular olivine pyroxene chondrules cooling rates of 2 10 c h are obtained for the observed wavelengths between 25 and 33 nm from isothermal time temperature transformation diagrams modelling of lamellae growth during cooling yields similar cooling rates between 7 and 25 c h coarsening of pigeonite diopside exsolution lamellae takes place in the small temperature interval from approximately 1350 to 1200 c the occurrence of type b antiphase domains in ca rich plagioclase provides independent constraints on chondrule cooling rates isothermal time temperature transformation diagrams yield cooling rates of approximately 3 30 c h for the observed domain sizes between 10 and 30 nm cooling rates derived from antiphase domains in plagioclase are valid in approximately the same temperature range than those deduced from pigeonite diopside exsolution lamellae our estimates must be regarded as upper limits and they seem to be significantly lower than those derived from dynamic crystallization experiments 100 2000 gc h as dynamic crystallization experiments yield cooling rates at higher temperatures near the liquidus this observation may suggest nonlinear cooling the absence of orthoenstatite lamellae in clinoenstatite indicates high cooling rates on the order of 10 4 c h at temperatures around 1000 c

petroleum migration fluid mixing and halokinesis as the main ore forming processes at the peridiapiric jbel tirremi fluorite barite hydrothermal deposit northeastern morocco the jbel tirremi fluorite barite sulfide deposit in northeastern morocco is hosted in a jurassic aged structurally high carbonate platform known as the jbel tirremi dome the host rocks consist of unmetamorphosed flat lying early jurassic dolomitized limestones locally intruded by eocene lamprophyre dikes the orebodies consist mostly of fluorite and barite and occur as open space fillings and partial to massive replacement of the enclosing medium to coarse grained dolomitized limestones the ore mineralogy is dominated by fluorite of different colors and habits barite and to a lesser extent sulfides rare earth element compositions along with fluid inclusion halogen and isotopic data suggest that the fluorite barite mineralization and the spatially associated eocene alkaline magmatism are petrogenetically unrelated pointing instead to the regional circulation of hydrothermal basinal brines mixed to various degrees with meteoric water in a dominantly closed rock buffered system at progressively higher temperatures and fluid rock ratios in this respect fluid inclusion microthermometric measurements show that the ore bearing hydrothermal system developed in two separate stages of fluorite barite mineralization as also revealed by isotopic data both stages precipitated from saline fluids at shallow crustal levels i e 82 degrees c and possibly up to 218 degrees c whereas in the second stage the mineralizing fluid had a similar temperature range but lower salinities similar to 20 10 wt nacl equiv the recorded high salinities are interpreted to represent the involvement of a mixture of halite dissolution water and evaporated seawater component oxygen delta o 18 21 7 to 29 6 0 v smow and carbon delta c 13 7 9 to 0 2 0 v pdb isotope data along with strontium sr 87 sr 86 0 70300 070789 and lead pb 206 pb 204 17 961 20 96 pb 207 pb 204 15 511 15 697 pb 208 pb 204 37 784 39 993 isotope ratios suggest the involvement of a mixture of oil bearing fluids basinal brines and meteoric fluids that interacted extensively with the early jurassic host carbonates the underlying triassic salt bearing diapir associated siliciclastic rocks and the highly fractionated and greisenized hercynian granitic crystalline basement resulting in the release of fluoride metals and other constituents to form the jbel tirremi deposit petroleum bearing fluid released from overpressured portions of the guercif basin at lithostatic pressures and bittern brines dominated the first stage of mineralization mixing of saline oxidized cacl2 and sulfate rich bittern brine with oil bearing fluid resulted in fluorite precipitation of stage i conversely during the second stage of mineralization the hydrothermal system was open to the influx of oxidized meteoric water as a consequence of the upward migration of the triassic salt bearing diapir and associated pressure decrease the shift from stage i to stage ii is associated with the evolution of the system from lithostatic to mostly hydrostatic pressure conditions stage i mineralization is thought to have occurred during the late miocene in response to rapid sedimentation and high subsidence rates and subsequent hydrocarbon migration associated with the outward migration of the rif thrust front conversely stage ii mineralization occurred coevally with the uplift phase during tortonian time

organic and inorganic geochemistry of ljubija siderite deposits nw bosnia and herzegovina the ljubija siderite deposits hosted by a carboniferous sedimentary complex within the inner dinarides occur as stratabound replacement type ore bodies in limestone blocks and as siderite sulfides veins in shale three principal types of ore textures have been recognized including massive dark siderite and ankerite siderite with zebra texture and siderite veins the ore and host rocks have been investigated by a combination of inorganic major trace and rare earth element concen trations organic characterization of hydrocarbons includ ing biomarkers and stable isotope geochemical methods isotope ratios of carbonates sulfides sulfates kerogen and individual hydrocarbons new results indicate a marine origin of the host carbonates and a hydrothermal metasomatic origin of the fe mineralization the differ ences in ore textures e g massive siderite zebra siderite are attributed to physicochemical variations e g changes in acidity temperature and or salinity of the mineralizing fluids and to the succession and intensity of replacement of host limestone vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization the equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites around 245 c then for siderite vein around 185 c sulfur isotope ratios suggest permian seawater or permian evaporites as the main sulfur source fluid inclusion composition confirms a contribution of the permian seawater to the mineralizing fluids and accord with a permian mineralization age organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal metasomatic origin of the ljubija iron deposits

sulfur isotope evidence for thermochemical reduction of dissolved sulfate in mississippi valley type zinc lead mineralization bongara area northern peru the bongara area northern peru contains mississippi valley type mvt zn pb mineralization hosted in late triassic jurassic carbonate rocks of the pucara group mineralization is interpreted to have formed during the late cretaceous peruvian orogenic event florida canyon and florcita located within 30 km of each other in the bongara area were studied to determine the origin and possible sources of sulfur in the mineralization one hundred and two in situ sulfur isotope analyses were determined on sphalerite galena and pyrite the narrow and symmetric distributions of the sphalerite 1 34s values are consistent with sulfate reduction in an open system with regard to sulfate the 34s values of sphalerite 1 from florida canyon 13 7 to 14 2 v cdt median 1 9 v cdt are lower and more variable than those for florcita 6 2 to 19 3 v cdt median 15 9 v cdt sphalerite 2 34s 0 3 to 17 6 v cdt median 2 4 v cdt postdating sphalerite 1 probably formed in a closed system with regard to sulfate the geologic setting fluid inclusion microthermometry and 34s values indicate that thermochemical reduction of dissolved sulfate tsr was the principal h2s production mechanism for metal precipitation possible sources of sulfate include late cretaceous seawater 34s 18 to 21 and evaporitic sulfate minerals in the middle late triassic chambara condorsinga formations 34s 12 to 15 and or in the late jurassic sarayaquillo formation 13 to 18 reduced sulfur from thermal cracking of organosulfur compounds and probably also remnants of h2s formed by bacterial sulfate reduction bsr might have been present during metal precipitation in florida canyon sample scale 34s variations observed in some samples from both areas reflect variable proportions of sulfate from different sources temperature effects on isotopic fractionation from sulfate to sulfide and the addition of reduced sulfur from organic compounds sample scale 34s variations can be interpreted as evidence for in situ sulfate reduction during mineralization this study places constraints on the mineralization mechanism the nature of sulfate reduction and the source of sulfur in mvt mineralization in northern peru the observed sample scale 34s variations lend support to the conclusion that in situ thermochemical sulfate reduction can occur during mineralization in these environments

origin of dolomites in the lower cambrian xiaoerbulak formation in the tarim basin nw china implications for porosity development abstract dolomites occur pervasively in the cambrian strata in the tarim basin nw china although the cambrian strata have been deeply buried and affected by multiple phases of dolomitization some intervals in the upper part of the lower cambrian xiaoerbulak formation developed high porosity the goal of this study is to understand the origin of different types of dolomites and the formation mechanism of the porosity in the xiaoerbulak formation the geochemistry of matrix dolomites suggests that they formed from middle rare earth element mree enriched anoxic pore fluids close to or within the zone of iron reduction the similar ree y patterns and overlapping 13 c values between pore filling and matrix dolomites indicate that the fluids that were responsible for the precipitation of pore filling dolomite apparently inherited the signatures of the formation waters that were stored in the host strata low 18 o values coupled with high ba zn and rare earth element ree content of pore filling dolomites indicate that pore filling dolomites were formed at elevated temperatures the precipitation of authigenic quartz and saddle dolomites and high mn content in pore filling dolomites indicate that hydrothermal fluids that mostly originated from cambrian basinal clastic units or basement rocks were involved the mixture of formation water and external hydrothermal fluids is the most likely explanation for the formation of significant porosity and precipitation of pore filling dolomites at depth breccia dolomite zebra dolomite and saddle dolomite occur mostly in areas that are close to faults which suggests that hydrothermal fluids passed through strike slip faults in this area when these faults were activated the development of permeable layers in the upper part of the xiaoerbulak formation overlain by impermeable layers of the wusongger formation suggests a possible potential diagenetic trap when the faults were activated high pressure and high temperature fluids flowed up through faults and hit low permeability beds at the base of the wusongger formation then the hydrothermal fluids flowed laterally into permeable dolomite strata at the top of the xiaoerbulak formation and encountered the formation brines large volumes of secondary porosity formed when host dolomite was leached by the mixing fluids and pore filling dolomites and other minerals formed soon afterward both the faults and original host facies exerted important influences on the lateral extent of the dissolution

seismic monitoring and analysis of excessive gas emissions in heterogeneous coal seams abstract uncontrolled and excessive gas emissions pose a serious threat to safety in underground coal mining in a recently completed research project a suite of monitoring techniques were employed to assess the dynamic response of the coal seam being mined to longwall face advance at coal mine velenje in slovenia together with continuous monitoring of gas emissions two seismic tomography measurement campaigns and a microseismic monitoring programme were implemented at one longwall top coal caving panel over 2000 microseismic events were recorded during a period of four months over the same period there also was a recorded episode of relatively high gas emission in the same longwall district in this paper a detailed analysis of the processed microseismic data collected during the same monitoring period is presented specifically the analysis includes the spatial distribution of the microseismic events with respect to the longwall face advance the magnitude of the energy released per week and its temporal evolution examination of the spatial distribution of the recorded microseismic events has shown that most of the microseismic activity occurred ahead of the advancing face furthermore the analysis of the gas emission and microseismic monitoring data has suggested that there is a direct correlation between microseismicity and gas emission rate and that gas emission rate tends to reach a peak when seismic energy increases dramatically it is believed that localised stress concentration over a relatively strong xylite rich zone and its eventual failure which was also identified by the seismic tomography measurements may have triggered the heightened microseismic activity and the excessive gas emission episode experienced at the longwall panel monitored

clinopyroxenes from mantle related xenocrysts in alkaline basalts from hannuoba china augite pigeonite exsolutions and their thermal significance optically homogeneous augite xenocrysts closely associated with spinel peridotite nodules occur in alkali basalts from hannuoba hebei province china they were studied by electron and x ray diffraction to define the occurrence and significance of pigeonite exsolution microtextures sub calcic augite wo34 exsolved into en62 62fs25 21wo13 17 pigeonite and en46 45fs14 14wo40 42 augite as revealed by tem through diffuse coarser 001 lamellae 100 300 a and only incipient 100 thinner ones 70 a c2 c augite and p21 c pigeonite lattices measured by ccd xrd relate through a aug a pgt b aug b pgt c aug c pgt 5 278 1 vs 5 189 1 a and aug pgt 106 55 1 vs 108 55 2 cell and site volumes strongly support the hypothesis that the augite xenocrysts crystallised at mantle depth from alkaline melts after the augite xenocrysts entered the magma 001 lamellae first formed by spinodal decomposition at a tmin of about 1 100 c and coarsened during very rapid transport to the surface in a later phase possibly on cooling incipient 100 lamellae then formed

stable isotope δ13c δ18o analysis of sulfide bearing carbonate samples using laser absorption spectrometry hydrothermally altered country rocks surrounding hydrothermal ore deposits are commonly characterized by altered 18 o and 13 c values relative to distal unaltered rocks stable isotopes have been recognized as a powerful tool to complement traditional geochemical and geophysical approaches during mineral exploration particularly in carbonate replacement and carlin type deposits however wall rock alteration and carbonate veining during ore formation is often accompanied by the precipitation of sulfide minerals complicating stable isotope analysis the classic phosphoric acid extraction technique for carbonate minerals results in the release of additional h 2 s gas interfering with isotope ratio mass spectrometry irms and laser absorption spectrometry las analysis of co 2 here we present the first results from a novel off axis integrated cavity output spectrometer oa icos instrument capable of determining the stable isotope composition 13 c 18 o of mixed co 2 h 2 s gas evolved from carbonate sulfide mixtures instrument calibration was performed by analyzing in house and commercially available caco 3 stable isotope reference materials analyses of mixed co 2 h 2 s tank gas and sulfide spiked stable isotope reference materials containing up to 40 wt chalcopyrite and sphalerite demonstrate that the method outlined here is capable of effectively analyzing previously problematic high sulfide samples the analytical capabilities together with the robust nature of the oa icos instrument may be of direct practical use for mineral exploration in carbonate hosted hydrothermal systems including ore deposits

the relationship between acoustic emission and permeability of rock under stress abstract the results of research into an assessment of the applicability of high frequency acoustic emission techniques to the prediction of gas outbursts are reported simultaneous measurements of acoustic emission and permeability under triaxial compression have been conducted on outburst prone sandstone the results show that the changes in acoustic emission activity and permeability occur together at the dilatancy stage this relationship was considered theoretically the agreement between the theoretical and experimental results shows that the high frequency acoustic emission method is very promising for predicting gas outbursts the high frequency acoustic emission measurements in the field at polish collieries have been successfully interpreted in terms of permeability changes

carbon and oxygen isotope study of hydrothermal carbonates in the zinc lead deposits of the san vicente district central peru a quantitative modeling on mixing processes and co2 degassing abstract carbon and oxygen isotope studies of the host and gangue carbonates of mississippi valley type zinc lead deposits in the san vicente district hosted in the upper triassic to lower jurassic dolostones of the pucara basin central peru were used to constrain maiels of the ore formation a mixing model between an incoming hot saline slightly acidic radiogenic pb sr fluid and the native formation water explains the overall isotopic variation 13 c 11 5 to 2 5 relative to pdb and 18 o 18 0 to 24 3 relative to smow of the carbonate generations the dolomites formed during the main ore stage show a narrower range 13 c 0 1 to 1 7 and 18 o 18 7 to 23 4 which is explained by exchange between the mineralizing fluids and the host carbonates combined with changes in temperature and pressure this model of fluid rock interaction explains the pervasive alteration of the host dolomite i and precipitation of sphalerite i the open space filling hydrothermal white sparry dolomite and the coexisting sphalerite ii formed by prolonged fluid host dolomite interaction and limited co 2 degassing late void filling dolomite iii or calcite and the associated sphalerite iii formed as the consequence of co 2 degassing and concomitant ph increase of a slightly acidic ore fluid widespread brecciation is associated to co 2 outgassing consequently pressure variability plays a major role in the ore precipitation during the late hydrothermal events in san vicente the presence of native sulfur associated with extremely carbon light calcites replacing evaporitic sulfates e g 13 c 11 5 altered native organic matter and heavier hydrothermal bitumen from 27 0 to 23 0 13 c points to thermochemical reduction of sulfate and or thiosulfate the 13 c and 18 o values of the altered host dolostone and hydrothermal carbonates and the carbon isotope composition of the associated organic matter show a strong regional homogeneity these results coupled with the strong mineralogical and petrographic similarities of the different mvt occurrences perhaps reflects the fact that the mineralizing processes were similar in the whole san vicente belt suggesting the existence of a common regional mineralizing hydrothermal system with interconnected plumbing

carbon and oxygen isotopic covariations in hydrothermal calcites isotopic covariations of carbon and oxygen in hydrothermal calcites are quantitatively modeled in terms of the following three mixing processes 1 mixing between two different fluids which leads to the precipitation of calcite 2 mixing between fluid and rock a calcite precipitation due to fluid rock interaction b secondary alteration of primary calcite by interaction with a subsequent fluid the models are derived from mass balance equations a distinction among the three mixing processes can be made on a 13c vs 18o diagram which places important constraints on the genesis of hydrothermal mineralization the variables which control the ultimate isotopic composition of hydrothermal calcites include the composition of the initial fluid and the wallrock temperature and dissolved carbon species owing to significant temperature dependent fractionation effects during equilibrium precipitation of calcite from a hydrothermal fluid the mixing processes may be distinguished by telltale patterns of isotopic data in 13c vs 18o space in particular caution must be exercised in postulating the fluid mixing as the cause for mineral deposition this is demonstrated for hydrothermal pb zn deposits in the western harz mountains germany a positive correlation between 13c and 18o values is observed for calcites from the bad grund deposit in the upper harz two sample profiles through calcite veins show similar correlations with the lowest values at the center of the veins and the highest values at the vein margins because the correlation array has a greater slope than for calcite precipitation at equilibrium in a closed system and because fluid mixing may not proceed perpendicular to the vein strike it is assumed that a fluid rock interaction is responsible for the observed correlation and thus for the precipitation of calcite a deep seated fluid is inferred with a 13c value of 7 and a 18o value of 10 as well as h2co3 as the dominant dissolved carbon species precipitation temperatures of the calcites are estimated to be about 280 170 c quite different isotopic distributions are observed for calcites from the st andreasberg deposit in the middle harz an alteration model is suggested based mainly on the isotopic distribution through a calcite vein in addition to a primary fluid which has the same isotopic composition as that in the bad grund deposit and thus seems to be responsible for the precipitation of calcite associated with sulfides an evolved hco 3 dominant subsurface fluid with 13c about 20 15 and 18o 0 is deduced to alter the primary calcite at low temperatures of 70 40 c

a salt diapir related mississippi valley type deposit the bou jaber pb zn ba f deposit tunisia fluid inclusion and isotope study the bou jaber ba f pb zn deposit is located at the edge of the bou jaber triassic salt diapir in the tunisia salt diapir province the ores are unconformity and fault controlled and occur as subvertical column shaped bodies developed in dissolution collapse breccias and in cavities within the late aptian platform carbonate rocks which are covered unconformably by impermeable shales and marls of the fahdene formation late albian cenomanian age the host rock is hydrothermally altered to ankerite proximal to and within the ore bodies quartz as fine grained bipyramidal crystals formed during hydrothermal alteration of the host rocks the ore mineral assemblage is composed of barite fluorite sphalerite and galena in decreasing abundance the ore zones outline distinct depositional events sphalerite galena barite ankerite and fluorite fluid inclusions commonly oil rich have distinct fluid salinities and homogenization temperatures for each of these events sphalerite galena 17 to 24 wt nacl eq and th from 112 to 136 c ankerite barite 11 to 17 wt nacl eq and th from 100 to 130 c fluorite 19 to 21 wt nacl eq th from 140 to 165 c the mean temperature of the ore fluids decreased from sphalerite 125 c to barite 115 c and increased during fluorite deposition 152 c then decreased to 110 c during late calcite precipitation laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of fluid inclusions in fluorite are metal rich hundreds to thousands ppm pb zn cu fe but the inclusions in barite are deficient in pb zn cu fe inclusions in fluorite have cl br and na br ratios of several thousand consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a br enriched brine derived from evaporation plus a component of halite dissolution the salinity of the barite hosted fluid inclusions is less than obtained simply by the evaporation of seawater to halite saturation and requires a dilution of more than two times by meteoric water the higher k na values in fluid inclusions from barite suggest that the brines interacted with k rich rocks in the basement or siliciclastic sediments in the basin carbonate gangue minerals ankerite and calcite have 13c and 18o values that are close to the carbonate host rock and indicate fluid equilibrium between carbonate host rocks and hydrothermal brines the 34s values for sphalerite and galena fall within a narrow range 1 to 10 with a bulk value of 7 5 indicating a homogeneous source of sulfur the 34s values of barite are also relatively homogeneous 22 with 6 higher than the 34s of local and regional triassic evaporites 15 the latter are believed to be the source of sulfate temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of triassic sulfate via hydrocarbons produced probably from late cretaceous source rocks the 87sr 86sr ratio in the bou jaber barite 0 709821 to 0 711408 together with the lead isotope values of bou jaber galena 206pb 204pb 18 699 to 18 737 207pb 204pb 15 635 to 15 708 and 208pb 204pb 38 321 to 38 947 show that metals were extracted from homogeneous crustal source s the tectonic setting of the bou jaber ore deposit the carbonate nature of the host rocks the epigenetic style of the mineralization and the mineral associations together with sulfur and oxygen isotope data and fluid inclusion data show that the bou jaber lead zinc mineralization has the major characteristics of a salt diapir related mississippi valley type mvt deposit with superimposed events of fluorite and of barite deposition field relations are consistent with mineral deposition during the eocene miocene alpine orogeny from multiple hydrothermal events 1 zn pb sulfides formed by mixing of two fluids one fluid metal rich but reduced sulfur poor and a second fluid reduced sulfur rich 2 barite precipitation involved the influx of a meteoric water component that mixed with a barium rich fluid and 3 fluorite precipitated from a highly saline fluid with higher temperatures

evolution of veins and sub economic ore at strassegg paleozoic of graz eastern alps austria evidence for local fluid transport during metamorphism the north eastern part of the graz paleozoic thrust sheet at strassegg austria is characterised by metamorphic assemblages that reflect increasing temperature conditions from 3008c in hangingwall to around 5508c in footwall units the main quartz andror carbonate vein generation cuts the schistosity at moderate to low angles is folded with the schistosity and is commonly boudinaged there is a correlation between vein and the host rock mineralogy additionally the d 18 o and 13 d c signatures of vein minerals quartz andror carbonates vary systematically with the isotopic signature of the host rock and its minerals within individual units d 18 o of vein quartz has a narrow range of values in contrast with a larger variation in both with d 18 o and d 13 c of carbonates at strassegg the greenschist unit hosts an as au mineralisation arsenopyrite

the size distribution of exsolution lamellae in iron free clinopyroxene the size distribution of pigeonite and diopside exsolution lamellae on 001 obtained at temperatures of 1100 1200 and 1300 c and annealing times between 2 and 4320 h was studied by transmission electron microscopy a total of 5192 pigeonite and 5286 diopside lamellae was studied at all three temperatures the size distributions of pigeonite and diopside lamellae are smaller during exsolution compared to the subsequent coarsening process the final size distributions are time invariant indicating that a steady stage distribution is reached the theory of ardell 1972a which assumes volume diffusion as rate limiting process and takes into account the non zero volume fraction of the precipitates describes the experimental size distributions quite well and also leads to the observed exponent of three in the rate law

igneous ca rich pyroxene in comet 81p wild 2 the stardust spacecraft successfully returned dust from comet 81p wild 2 to earth in january 2006 preliminary examination of the samples showed abundant crystalline silicates comparable to those found in chondritic meteorites presumably formed in the asteroid belt here we report results of a transmission electron microscopy tem study of a pyroxene bearing terminal particle which contains lamellar intergrowths of pigeonite and diopside on the 001 plane this microstructure is typical for an igneous process and formation by exsolution during cooling width and wavelength of the lamellae indicate a cooling rate within the range 10 100 c h in close agreement with those of chondrules or lava from an asteroidal igneous rock this observation shows that some stardust material experienced periods of igneous processing similar to material found in the inner early solar system this implies that igneous materials were common materials in a large region of the protoplanetary disk and were not restricted to the asteroid belt their presence in comet wild 2 also supports the favored view of large radial mixing from the inner to the outer regions before the comet s accretion

origin of late dolomite cement by co2 saturated deep basin brines evidence from the ozark region central united states studies of fluid inclusions in regionally extensive late dolomite cement ldc throughout the ozark region show that co2 effervescence was widespread during dolomite precipitation on the basis of quantitative analyses of inclusion fluids reaction path modeling shows that ldc with trace amounts of sulfides can be deposited by effervescence of a co2 saturated basin brine as it migrates to shallower levels and lower confining pressures this precipitation mechanism best explains occurrences of ldc in the ozark region and may account for ldc found in sedimentary basins worldwide

regional epigenetic dolomitization in the bonneterre dolomite cambrian southeastern missouri a dolomite bed averaging 6 m in thickness forms the base of a limestone and shale facies of the bonneterre dolomite cambrian southeastern missouri the dolomite immediately overlies the lamotte sandstone and covers an area of more than 16 600 km 2 it is proposed that this basal dolomite formed as a result of interaction with warm basin derived water circulating through the underlying lamotte sandstone and that the dolomitization event coincided with the emplacement of mississippi valley type sulfide ores in the nearby viburnum trend this hypothesis is supported by 1 petrographic evidence that suggests an origin at temperatures 50 c 2 cathodoluminescent microstratigraphy of dolomite cements which is correlative with that in gangue dolomite cements in the nearby orebodies and 3 stable oxygen and carbon isotope values that are consistent with a basinal origin of the dolomitizing water the basal dolomite bed may represent one of the most extensive epigenetic dolomites yet documented this implies that a basinal water can alter rocks over a wide area at a considerable distance from its source

transport of stable isotopes kinetics dispersive advection and the isotopic fronts of baumgartner and rumble 1988 baumgartner and rumble 1988 apply a kinetic continuum theory for stable isotope transport to unidimensional infiltration of fluid into rock their numerical applications are restricted to the simplified case of rapid isotope exchange between phases where the sharp isotope fronts of pure advection are distended by dispersive mechanisms only however kinetic limitations of isotope exchange are potentially an equally important distending mechanism and it will only rarely be possible to ascribe front gradients to diffusion dispersion alone abrupt isotopic changes at vein boundaries are more often a secondary signal of lithologic change than the expression of a retarded advective front at such boundaries diffusion and dispersion play a role that is comparable to or greater than that of advection so that the detailed shapes of isotope fronts depend upon boundary conditions for the infiltration process zerodimensional box models have legitimate if limited uses in the modelling of fluid rock interaction and are reexamined

exsolution by spinodal decomposition ii perthite formation during slow cooling of anatexites from ngoronghoro tanzania perthites in slowly cooled granulite facies rocks from the ngoronghoro structure tanzania show complex microstructures reflecting several stages of exsolution and coarsening mesoperthites with an integrated bulk composition of or26 5ab71an2 5 are comprised of lamellar intergrowth of 5 to 10 m wide orthoclase rich and albite rich lamellae spindle perthites with a bulk composition of or67ab31 5an1 5 are comprised of 2 to 10 m wide and several 109s of m long albite rich spindles in an orthoclase rich host in the mesoperthite primary exsolution occurred by spinodal decomposition whereas the spindle perthite formed by a nucleation and growth mechanism the interfaces between the exsolved phases are generally incoherent unmixing and coarsening of the mesoperthite is discussed in the light of non linear uphill diffusion the microstructure evolution and successive chemical separation of the exsolved phases during cooling are modeled based on cahn hilliard theory we find that coarsening primarily occurs during the first 20 c to 30 c of cooling after the homogeneous precursor feldspar has entered the coherent spinodal the extent of coarsening and the characteristic size of the exsolved phases depend on the cooling rate over this temperature interval for geologically relevant cooling rates on the order of 5 c ma to 50 c ma the compositions of the exsolved phases develop along the solvus down to about 480 c to 530 c and are frozen in only at lower temperatures the compositions that are finally preserved in the orthoclase rich and in the albite rich phases depend on cooling rate over this temperature interval both the characteristic lamella width of the mesoperthite as well as the compositions of the exsolved phases indicate slow cooling at 5 c ma during the coarsening stage and down to about 450 c during later stages of the cooling history the albite rich phase of the mesoperthite exsolved about the peristerite gap and the orthoclase rich host of the spindle perthite exsolved a second generation of coherent albite rich spindles the incoherent phase boundaries of the primary perthite microstructures served as passageways for fluids during late stage deuteric alteration which lead to secondary coarsening in the mesoperthite and to alteration of the albite rich precipitates in the spindle perthite finally both types of perthites were replaced by coarse grained patch perthite during deuteric alteration