petroleum formation by fischer tropsch synthesis in plate tectonics a somewhat speculative hypothesis of petroleum genesis in the upper lithosphere is proposed based on fischer tropsch synthesis this hypothesis is distinct from both the organic biogenic model and the inorganic model of hydrocarbon degassing from the earth s interior fischer tropsch synthesis is a well known industrial process whereby millions of tons of hydrocarbon oil resembling petroleum are produced annually from carbon monoxide or carbon dioxide and hydrogen gases reacting on a metallic iron or iron oxide catalyst like natural petroleum this synthetic oil consists of gas gasoline diesel oil and wax fractions all rich in saturated aliphatic hydrocarbons and enriched in the light 12c isotope the hypothesis presented in this paper proposes that petroleum liquids form by fischer tropsch synthesis on magnetite and hematite catalysts when carbon dioxide derived by massive metamorphic or igneous decarbonation of subducted sedimentary carbonates reacts with hydrogen generated by the serpentinization in the absence of air of shallow mantle lithosphere and ophiolite thrust sheets oblique plate movements may favor hydrocarbon formation by creating deep faults that aid fluid flow and serpentinization the world s richest oil provinces including those of the middle east may be tentatively interpreted to have formed by this mechanism

hydrogen and carbon isotopic composition of methane as evidence for biogenic origin of natural gases from the green tuff basin japan abstract hydrogen and carbon isotopic analyses of methane were carried out to investigate the origin of natural gases commercially produced from volcanic rocks in the green tuff basin of northeast japan whose high 3he 4he ratios have been interpreted as an indication of their abiogenic origin methane isotopic signatures 13c 32 to 67 d 163 to 202 respectively suggest that these are thermogenic gases or mixtures of thermogenic gases with bacterial gases the correlations of methane d vs 13c for the gases from specific fields are consistent with a mixing model between bacterial and thermogenic end members which was previously proposed on the basis of 13c contents of c1 to c4 hydrocarbons sakata 1991 berner and faber 1996 the green tuff basin gases are isotopically distinct from well known abiogenic methanes e g geothermal methane from the east pacific rise a significant contribution of abiogenic methane would therefore be unlikely for these gases

light hydrocarbon gases in guaymas basin hydrothermal fluids thermogenic versus abiogenic origin light hydrocarbon gases methane through pentane in high temperature hydrothermal fluids of the guaymas basin gulf of california are predominantly derived from thermocatalysis of organic carbon in sediments intruded by mid ocean ridge volcanic rocks the spectrum of c1 c5 gases in guaymas basin hydrothermal fluids is characterized by a preponderance of alkanes with essentially no alkenes present comparison with high temperature fluids from 21 n on the east pacific rise where geochemical evidence indicates a distinct lack of thermogenic gas and where methane is derived abiogenically from the basalts shows that the 21 n hydrocarbon gases are characterized by a prominent ethylene signature stable isotope compositions of guaymas basin m thane differ from 21 n gas guaymas basin has dgr13c values of 43 to 51 pmil vs pdb compared to 21 n where values as high as 15 pmil have been measured these differences reflect the different origins of light hydrocarbon gases in the two systems with guaymas methane being overwhelmingly of an organic thermogenic derivation and showing no evidence of the abiogenic basalt derived gas that characterizes the 21 n environment carbon isotope analyses of dissolved inorganic carbon in guaymas basin hydrothermal fluids indicate that high temperature hydrocarbon oxidation may be an important process acting in conjunction with high temperature thermocatalytic hydrocarbon generation

fluid inclusion and stable isotope c o and s constraints on the genesis of the high grade langdu cu skarn deposit in yunnan sw china abstract the langdu cu skarn deposit is the highest grade cu deposit average 6 49 cu in the zhongdian polymetallic district in sw china skarns and ore bodies occur primarily in the contact zone of upper triassic qugasi formation fm and late triassic ca 217 ma intrusions disseminated massive stockwork and vein like sulfide ores occur in the skarn quartz calcite veins porphyry and marble skarn minerals include pyroxene garnet actinolite and epidote four types six subtypes of fluid inclusions fis are identified in the sulfide bearing quartz veins type i liquid rich two phase fis have varying vapor liquid ratios and yielded homogenization temperatures of 110 338 c and salinities of 1 7 29 5 wt nacl eqv type ii vapor rich fis contain ch4 n2 bubbles and homogenized to vapor at 262 425 c type iii fis are single phase at room temperature 20 c a vapor phase is present at below 120 c and the fis homogenized at 117 to 114 c type iv daughter mineral bearing fis homogenized by halite disappearance at 295 392 c and have salinities of 37 8 46 6 wt nacl eqv such characteristics suggest that fis were trapped by fluid immiscibility and phase separation the 34scdt values of chalcopyrite and pyrrhotite are of 5 3 to 0 7 on the 34s histogram all langdu data show a cluster of 32s rich 34scdt 5 3 to 4 6 and a cluster of 34s rich 34scdt 1 1 to 0 7 type i calcite in skarn and type ii calcite in quartz sulfide vein have 13cpdb and 18osmow values of 8 4 to 7 8 6 3 to 6 1 and 10 1 to 12 3 and 12 0 to 13 0 respectively type iii calcite from calcite sulfide veins has 13cpdb 5 6 to 0 2 and 18osmow 12 5 to 16 3 biotite garnet and pyroxene syn ore quartz and chlorite yielded 18osmow values of 6 9 4 1 5 13 2 15 3 and 6 8 respectively sulfur carbon and oxygen isotopic features of these hydrothermal minerals and the fis microthermometric data suggest that the ore forming fluids were magmatic sourced and contaminated by meteoric formation water during ascent and or fluid wallrock interactions low 34s 5 3 to 4 6 in sulfides and the ch4 in the fis are interpreted to reflect the reaction between the magmatic fluids and the carbonaceous slate in qugasi fm the methane likely expanded the vapor liquid immiscibility field and reduced the sulfates so42 to sulfides s2 and extensive water rock reaction and fluid mixing may have occurred leading to the high grade cu mineralization at langdu

methane flux and origin in the othrys ophiolite hyperalkaline springs greece abstract the occurrence and origin of methane ch4 generated by serpentinization of ultramafic rocks is of current timely interest in planetary geology astrobiology and energy resource exploration as it may contribute in particular to decipher the source of methane on mars the origin of life and the potential of abiotic hydrocarbon synthesis methane of dominant abiotic origin in serpentinized peridotites on continents ophiolites or igneous intrusions has been documented so far with complete carbon and hydrogen isotope composition in six countries in the philippines turkey oman new zealand japan and italy we report the discovery of two new sites in greece at archani and ekkara located in the othrys ophiolite massif portable sensors based on fourier transform infrared spectrometry ftir and tunable diode laser absorption spectroscopy tdlas allowed to realize that out of 21 ophiolitic springs methane is released only by four hyperalkaline ph from 10 7 to 11 3 and calcium hydroxide ca oh type waters all other 17 springs with ph

ore metal redistribution by hydrocarbon brine and hydrocarbon halide melt phases north range footwall of the sudbury igneous complex ontario canada we report methane dominant hydrocarbon fluid inclusions ch4 c2h6 c2h2 c3h8 coexisting with primary brine inclusions and secondary halide melt solid nacl inclusions in au pt rich quartz sulfide epidote alteration veins associated with the footwall style cu pge platinum group element au deposits at the fraser mine north range of the sudbury igneous complex evidence for coentrapment of immiscible hydrocarbon brine and hydrocarbon halide melt mixtures is demonstrated a primary ch4 brine assemblage was trapped during quartz growth at relatively low t min ttrapping 145 315 c and p max ptrapping 500 bar prior to the crystallization of sulfide minerals in the veins secondary inclusions contain solid halite and a mixture of ch4 c2h6 c2h2 and c3h8 and were trapped at a minimum t of 710 c the halite inclusions may represent halide melt that exsolved from crystallizing sulfide ores that texturally postdate by replacement early alteration quartz hosting the primary lower t brine ch4 assemblage laser ablation icp ms analyses show that the brine hydrocarbon and halide melt inclusions contain significant concentrations of cu 0 1 1 wt range au bi ag and pt all 0 1 10 ppm range cu pt and cu au ratios in the inclusions are significantly up to 4 log units lower than in the host alteration veins and adjacent massive sulfide ore veins suggesting either 1 early cu loss from the volatiles by chalcopyrite precipitation or 2 enhanced au and pt solubilities relative to cu at the temperatures of entrapment concentration ratios between coexisting brine and ch4 inclusions c rm elem rm brine c rm elem rm ch 4 are lower for cu au bi and ag than for other elements na ca fe mn zn pb indicating that during interaction with the brine the hydrocarbon phase was enriched in ore metals the high concentrations of ore metals in hydrocarbon brine and halide melt phases confirm that both aqueous and non aqueous volatiles were carriers of precious metals in the sudbury environment over a wide range of temperatures volatile evolution and magmatic sulfide differentiation were clearly part of a single continuous process in the sudbury footwall the exsolution of h2o poor volatiles from fractionated sulfide liquid may have been a principal mechanism controlling the final distribution of pge and au in the footwall ore systems the study reports the first measurements of precious metal concentrations in fluid inclusions from a magmatic ni cu pge environment the sudbury district

hydrocarbon composition of authigenic inclusions application to elucidation of petroleum reservoir filling history abstract geochemical analysis of petroleum inclusions trapped in authigenic feldspar and quartz in the ula formation in the north sea ula oil field revealed a petroleum of markedly different composition than the oil presently in the reservoir using microthermometry and the burial history as a dating tools it is concluded that the petroleum in the k feldspar inclusions was present in the more porous and permeable parts of the ula formation as early as 45 75 my bp when the field was at a depth of about 1 0 1 5 km as compared with the current depth of 3 4 km this early petroleum which was trapped as inclusions in authigenic k feldspar shows a distinctly different distribution of tricyclic terpanes and pentacyclic triterpanes from that of the current petroleum charge in the ula formation which was derived from the mandal formation source rock in late neogene time molecular parameters show that the oil in the k feldspar inclusions is significantly less mature than the crude oil in the present reservoir the approximate 90 c temperature increase occurring after entrapment of the early petroleum in kfeldspar the field is currently at 143 c appears not to have reset the low maturity signature of the oil in the k feldspar inclusions this could suggest that the temperature in the inclusions is too low for isomerization selective thermal degradation to occur lack of catalysts or that there are other controls on the ratio of some of these parameters still parameters like the ratio of c21 to c28 triaromatic steroids and those based on dimethyl and trimethyl naphthalenes are comparatively similar in both the inclusions and in the reservoir crude the oil inclusions in authigenic quartz and albite formed from about 10 my bp burial depth 2 5 km until the present burial depth 3 4 km are interpreted as representing a palaeo petroleum charge having a composition intermediate between the oil found in k feldspar inclusions and the oil charge in the present reservoir our data suggest strongly that the petroleum trapped in the inclusions in quartz and plagioclase represents progressive dilution of the early reservoired oil now found only in k feldspar inclusions with oil from the mandal formation analysis of solution gas in these inclusions suggests that the first petroleum associated gas to arrive at the trap from the progressively maturing mandal formation had a much wetter composition than the current reservoir solution gas to explain the present comparatively drier and isotopically lighter reservoir solution gas composition the inference is made that there has been a recent during formation of k feldspar inclusions 45 75 my bp maturation of the upper jurassic mandal formation the main source rock in this region was limited possibly to the graben axis this suggests that the petroleum found in the k feldspar inclusions was most likely derived from a deeper post caledonian palaeozoic formation

hydrocarbon behavior at nanoscale interfaces throughout earth s crust and upper mantle fluids play the dominant role in transporting and concentrating earth s energy and mineral resources liebscher and heinrich 2007 furthermore the flux of fluids which act as both reaction media and reactants strongly influences the genesis and evolution of many different kinds of rocks among many different types of fluids those containing volatile carbon hydrogen and oxygen c h o species tend to dominate in the lithosphere along with various electrolytes and silica these fluids commonly contain methane as both a major constituent and an important energy source conventional natural gas deposits reside in sedimentary basins where fluid overpressure often results in brittle failure of the confining rocks industry exploration and exploitation of shale gas e g the marcellus utica and barnett formations has refocused attention on understanding the fundamental behavior of volatile hydrocarbon rock interactions recent observations of hydrocarbons emanating from non sedimentary systems abiogenic such as mid ocean ridge hydrothermal systems or occurring within some crystalline rock dominated precambrian shield environments have challenged the view that organic rich sediments provide the only significant source of crustal hydrocarbons potter and konnerup madsen 2003 sleep et al 2004 sherwood lollar et al 2006 mccollom 2013 sephton and hazen 2013 geopressured geothermal regimes contain c h o fluids with vast energy potential in the form of methane and hot water at high pressure even fluid inclusions from both metamorphic and igneous terrains record the presence of methane bearing fluids reflecting reduced redox state conditions of formation the consequences of coupled reactive transport processes common to most geological environments depend on the properties and reactivity of these crustal fluids over broad ranges of temperature pressure and fluid composition the relative strengths of complex molecular scale interactions in geologic fluids and the changes in those interactions with temperature pressure and fluid composition are the fundamental basis for observed

intense ch4 plumes generated by serpentinization of ultramafic rocks at the intersection of the 15 20 n fracture zone and the mid atlantic ridge abstract as part of the fara french us program designed to study the mid atlantic ridge mar between 15 n and the azores twenty three dives with the submersible nautile were conducted during the french us faranaut 15n cruise on the eastern and western parts of the 15 20 n fracture zone ridge axis intersection south of the eastern ridge transform fault intersection nine nautile dives were made within the rift valley and along the western rift valley wall ch4 concentrations in the bottom waters reach 53 2 nmol kg along faulted zones on top and on the east flank of the ultramafic inner corner high 15 05 n 44 59 w where serpentinized rocks outcrop no 3he anomaly is associated with methane ruling out any primary mantle component fourteen dives were also made in the rift valley to the north close to the western intersection of the 15 20 n transform high ch4 anomalies up to 22 nmol kg are also present in the bottom waters of the rift valley northern segment on both the western and eastern valley walls and on the inner high adjacent to the eastern wall where ultramafic rocks outcrop seven vertical hydrocasts carried out in the axial valley 4500 m deep show an intense ch4 anomaly with a maximum 35 8 nmol kg at 3200 m depth this ch4 concentration is among the highest found along the mid atlantic ridge charlou and donval 1993 charlou et al 1997 ch4 concentrations of 9 9 14 9 nmol kg are also present on the western wall along the 3200 m isobath the high ch4 concentrations correspond to only weak 3he anomalies this ch4 rich plume is also associated with active fault zones that expose peridotite rocks ch4 output from ultramafic outcrops on the western and eastern intersections of the 15 20 n fracture zone with the mar is believed to reflect ongoing serpentinization these results associated with many other ch4 anomalies measured in the water column above ultramafic outcrops found between 12 n and the azores most likely reflect serpentinization processes extending along the whole slow spreading mid atlantic ridge

abiogenic hydrocarbon isotopic signatures in granitic rocks identifying pathways of formation abstract the stability and isotopic composition of hydrocarbons formed in the mantle are controversial subjects knowing the range in isotopic compositions of abiogenically derived hydrocarbons is important for recognising biological signatures in ancient and extra terrestrial materials in an effort to enhance this database stable isotope results are reported here for hydrocarbon bearing fluid inclusions hosted in two peralkaline igneous complexes from lovozero russia and strange lake canada based on the distribution of isotopic compositions we propose three pathways for abiogenically generated hydrocarbons type 1 13cch4 13cco2 and 13cc2 represents mantle derived hydrocarbons generated in equilibrium with hyperagpaitic magmas in the upper mantle and suggests that mantle ch4 and c2h6 13c and 2h could have values of 5 3 and 112 and 10 8 and 162 respectively type 2 13cco2 13cch4 13cc2 represents fischer tropsch type hydrocarbon generation in quartz bearing peralkaline rocks with co2 as the initial magmatic gas phase for type 2 13cco2 values are 2 whereas 13cch4 and 2hch4 values range from 32 to 20 and 170 and 160 respectively the 13cc2h6 values are slightly lower than associated 13cch4 values type 3 13cco2 13cch4

carbon spherules in ni cu pge sulphide deposits in the sudbury impact structure canada abstract the formation of sudbury s economically important magmatic ni cu pge sulphide deposits is attributed to superheating of crustal rocks following meteorite impact at 1 85 ga crustal contamination of magmatic sulphide deposits is thought to be important in the mineralization process and this paper documents the first occurrence of sedimentary carbon in the sudbury ni cu pge sulphides near the base of the sudbury igneous complex sic spherules of graphitic and more disordered carbon inclusions were found in chalcopyrite crystals suggesting that carbon has behaved as a chalcophilic element in the impact melt samples from the impact structure have been subjected to carbon isotopic analysis and raman microspectroscopy in order to investigate the relationship between carbonaceous strata of the huronian basement the crater fill impact breccias and the mineral deposits associated with the sudbury impact carbonaceous material occurs in the impact breccias of the onaping formation and this study presents stratigraphically constrained carbon isotopic analysis of the impact breccias sulphides from the hydrothermal zn pb cu vermilion errington deposits 1 5 km above the sic were found to contain both carbon spherules and larger irregular carbonaceous flakes suggesting a genetic link between the ni cu pge deposits and the hydrothermal zn pb cu mineralization a shared source of carbon for the vermilion errington mineralization and the cross cutting anthraxolite veins 100m above the deposits in post impact carbonaceous shales of the onwatin formation is indicated by the similarity in their raman spectra this is considered to be carbon remobilized by metamorphic hydrothermal fluids preferentially scavenging disordered carbon from within the onaping formation breccias the occurrence of carbon in the sudbury ni cu pge massive sulphide deposits indicates that carbon from the target rocks played a role in the mineralization process hitherto unrecognized

association of gold with uraninite and pyrobitumen in the metavolcanic rock hosted hydrothermal au u mineralisation at rompas perapohja schist belt northern finland the perapohja schist belt comprises a supracrustal sequence of quartzites mafic volcanics and volcaniclastics carbonate rocks black shales mica schists and greywackes which were deposited from ca 2 44 to 1 91 ga during the rifting of the archaean basement in the eastern part of the fennoscandian shield metamorphism and multiple folding of the basin fill took place during the svecofennian orogeny 1 9 1 8 ga followed by intrusions of late orogenic 1 84 1 80 ga and post orogenic granitoids 1 79 1 76 ga the rompas au u mineralisation is hosted by deformed calcsilicate veins in mafic volcanic rocks and locally contains very high grade 10 000 g t au gold pockets with strict spatial association of gold minerals to uraninite and pyrobitumen chemical ages from the unaltered domains in the structure of uraninite indicate a 1 95 1 90 ga age for the deposition of the primary high temperature e g u th 100 in uraninite hydrothermal uranium mineralisation these data are in agreement with the results of previous u pb dating of uraninite by sims textural evidence suggests that metamorphic recrystallisation of the uraninite bearing quartz dolomite veins into calcsilicate mineral assemblages during the svecofennian orogeny 1 9 1 8 ga was followed by a hydrocarbon bearing fluid flow event and radiolytic polymerisation of hydrocarbons around grains of uraninite gold precipitated during a subsequent hydrothermal process in the fractures of uraninite as well as in the cracks and on the botryoidal surfaces of uraninite pyrobitumen nodules remobilisation and redeposition of uranium by these hydrothermal events produced secondary uraninite grains with chemical ages between 1 85 and 1 65 ga native gold is associated with galena altaite hunchunite nickeline and rare cobaltite pb bearing maldonite pyrite pyrrhotite chalcopyrite molybdenite and titanite raman spectra show disordered structure of undeformed pyrobitumen nodules in contrast with the well ordered graphite in calcsilicate veins mean random reflectance data for pyrobitumen indicate 270 340 c maximum temperature of thermal maturation this temperature range is also considered as the temperature of gold deposition results of multiple sulphur isotope analyses of organic material pyrite and acid volatile bound sulphur show distinct ranges of 34s values for sorg and scrs in uraninite pyrobitumen from 6 99 to 3 55 and from 10 02 to 4 41 respectively and uraninite pyrobitumen native gold mineral associations from 1 36 to 6 87 and from 0 42 to 9 7 respectively 33s data indicate local occurrence of nonmass dependent sulphur isotope fractionation owing to interaction of fluids with organic material concentration of lead in uraninite is depleted along the gold mineral filled fractures whereas the uranogenic lead isotope contents of galena altaite and hunchuite deposited in the same fractures are extremely high suggesting that the dominant source of lead for the crystallisation of these minerals was the radiogenic lead content of uraninite taking into account this source of radiogenic lead the calculated pb pb model ages for the lead minerals are between 1 75 and 1 70 ga sulphur and tellurium removal from the fluid by reaction with radiogenic lead released by uraninite appears to be an important mechanism in the strongly localised deposition of gold minerals scavenging of sulphur by pyrobitumen nodules from gold transporting fluids was an additional process triggering precipitation of gold carbon particles and organic functional groups in pyrobitumen probably acted as nucleation and adsorption centres for gold minerals

hydrocarbons and inorganic gases in the gravberg 1 well siljan ring sweden abstract hydrocarbons and inorganic gases have been analyzed in the drilling fluid of the gravberg 1 well siljan ring sweden which represents the first commercial exploration for mantle derived methane hydrocarbons detected to a depth of 6 6 km have been in trace amounts dissolved in the drilling fluid low concentrations of hydrocarbons from granite intervals are rich in unsaturated hydrocarbons and may result from abiogenic synthesis from inorganic carbon species in the granite or may be synthesized during drilling operations from organic precursors in the drilling fluid below 5 km higher hydrocarbon concentrations in granite intervals are correlated with two different lubricants added to the drilling fluid these gases are characterized by distinctive suites of hydrocarbons especially in the c4 c6 range the effects of hydrocarbon production from these and other additives are particularly pronounced in this well due to the low concentration of indigenous hydrocarbons the highest concentrations of methane were enriched in 13c 13 c 26 and were associated with several dolerite intrusions in the granite rocks this methane was present in both a core and cuttings and is similar to methane isolated from dolerite in a well recently drilled in massachusetts u s a the methane may have a deep upper mantle origin or may be a product of abiogenic synthesis in crustal rocks significant quantities of h2 and he occurring deeper than 6 km appear to have a low temperature crustal origin there is no evidence of significant amounts of upper mantle he in the gravberg 1 gases

different tdm ch4 hydrothermal plume signatures tag site at 26 n and serpentinized ultrabasic diapir at 15 05 n on the mid atlantic ridge as a part of the 1988 noaa vents program ch4 and mn tracers were used to identify and compare hydrothermal plumes found above the tag field 26 n and in the rift valley at 15 n close to the eastern intersection of the ridge axis with the 15 20 n fracture zone at the mid atlantic ridge mar active hydrothermal venting was confirmed at tag based on elevated concentrations of total dissolved mn tdm up to 30 nmol kg high ch4 concentrations up to 200 nl l and elevated nephelometry signals plumes of a different composition were identified at 15 n with high ch4 concentrations up to 400 nl l low total dissolved mn concentrations tdm 1 nmol kg and no significant nephelometry signal the different properties of these tracers and the different tracer ratios can be used to deduce vent fluid characteristics and compare one hydrothermal area to another tdm ch4 and nephel ch4 ratios at tag are of the same order of magnitude as those observed at other spreading axis hydrothermal fields at 15 n the low tdm ch4 ratio provides evidence of fluid circulation into ultrabasic rocks and offers a potentially useful and single method of exploring for hydrothermal activity associated with serpentinization mantle degassing through hydrothermal activity associated with serpentinization is an important process with respect to chemical and thermal exchanges between the upper mantle and the ocean different ratios of hydrothermal tracers i e tdm ch4 provide a useful framework for identifying subseafloor processes along mid oceanic ridges

genesis of the vein type tungsten mineralization at nyakabingo rwanda in the karagwe ankole belt central africa the vein type tungsten deposit at nyakabingo in the central tungsten belt of rwanda is located in the eastern flank of the complex bumbogo anticlinal structure the host rock is composed of alternating sequences of sandstones quartzites and black pyritiferous metapelitic rocks two types of w mineralized quartz veins have been observed bedding parallel and quartz veins that are at high angle to the bedding which are termed crosscutting veins both vein types have been interpreted to have been formed in a late stage of a compressional deformation event both vein types are associated with small alteration zones comprising silicification tourmalinization and muscovitization dating of muscovite crystals at the border of the veins resulted in a maximum age of 992 4 1 5 ma this age is within error similar to the ages obtained for the specialized g4 granites i e 986 10 ma the w bearing minerals formed during two different phases the first phase is characterized by scheelite and massive wolframite while the second phase is formed by ferberite pseudomorphs after scheelite these minerals occur late in the evolution of the massive quartz veins sometimes even in fractures that crosscut the veins the ore minerals precipitated from a h2o co2 ch4 n2 nacl kcl fluid with low to moderate salinity 0 6 13 8 eq wt nacl and minimal trapping temperatures between 247 and 344 c the quartz veins have been crosscut by sulfide rich veins based on the similar setting mineralogy stable isotope and fluid composition it is considered that both types of w mineralized quartz veins formed during the same mineralizing event given the overlap in age between the g4 granites and the mineralized quartz veins and the typical association of the w deposits in rwanda but also worldwide with granite intrusions w originated from the geochemically specialized g4 granites intense water rock interaction and mixing with metamorphic fluids largely overprinted the original magmatic hydrothermal signature

volatiles in a peralkaline system abiogenic hydrocarbons and f cl br systematics in the naujaite of the ilimaussaq intrusion south greenland agpaitic rocks comprise most of the exposed part of the 1 16 ga old 8 17 km large and about 1700 m thick ilimaussaq intrusion in south greenland within these more than 600 m thick sequence of sodalite rich naujaites mainly sodalite arfvedsonite alkali feldspar nepheline eudialyte aenigmatite are interpreted as a sodalite flotation cumulate sodalites show two to three different zones in cathodoluminescence cl and at least two zones in thin sections the cl zones can be related to chemical differences detectable by electron microprobe whereas relations with optical zonations are less obvious compositional trends in sodalite reflect trends in the evolution of volatile contents in the melt the sodalite at ilimaussaq is almost free of ca and closely corresponds to the pure na cl sodalite endmember with about 7 wt of cl s contents reach up to 0 9 wt cl br ratios range from 500 to 1700 raman spectroscopy shows that s is present as so4 2 in sodalite although sphalerite zns is a stable phase in naujaites peralkalinity and fo2 conditions allow s2 and so4 2 to be present contemporaneously the whole naujaite sequence is divided into two parts an upper part with low homogeneous s contents and cl br ratios in the sodalite cores and a lower part with strongly variable and higher s contents and with cl br ratios which are decreasing downwards the details of the s content and the cl br ratio evolution show that sodalite strongly influences the halogen contents of the melt by scavenging cl and br the naujaites were formed from a highly reduced halogen rich magma in equilibrium with magmatic methane at about 800 c which upon ascent cooling and fractionation exsolved an aqueous fluid phase both fluids were trapped in separate inclusions indicating their immiscibility micrometer sized aegirine crystals and primary hydrocarbon bearing inclusions are abundant in the crystal cores the inclusions were trapped at pressures up to 4 kbar although the emplacement pressure of the intrusion is about 1 kbar this indicates growth of the sodalite during melt ascent and a very effective mechanism of trace element scavenging during sodalite growth sodalite rims are devoid of aegirine or primary hydrocarbon inclusions and probably reflect the emplacement stage

the nature of orthomagmatic hydrothermal fluids in the oka carbonatite quebec canada evidence from fluid inclusions fluid inclusions in apatite monticellite and calcite from the oka carbonatite complex generally comprise either aqueous liquid vapour or aqueous liquid vapour halite some inclusions also contain a variety of trapped solids including calcite strontianite nahcolite and mirabilite microthermometry and raman spectroscopy indicate that co2 is not an important constituent of these fluids microthermometric data also indicate that the hydrothermal fluids liberated from the carbonatitic magma had a wide range of salinities 4 2 to 49 eq wt nacl and densities 0 77 to 1 26 g cm3 most of the fluids had relatively low concentrations of so42 and co32 6 wt however the nature of the trapped minerals and the phase behaviour of some inclusions indicate that some fluids may have had higher concentrations of so42 co32 and or hco3 textural relationships indicate that the crystallization sequence for the host minerals was monticellite apatite calcite which when combined with fluid inclusion data from the three minerals indicates that fluid salinity decreased and fluid density increased during progressive crystallization of the magma the density increase is thought to have been mainly caused by decreasing temperature isochoric projections indicate that the fluids were exsolved at minimum pressures of 4 to 8 kb these data provide a basis with which to assess the involvement of orthomagmatic aqueous fluids in the formation of hydrothermal rare element mineralization associated with carbonatites

a review of the occurrence form and origin of c bearing species in the khibiny alkaline igneous complex kola peninsula nw russia abstract the khibiny complex hosts a wide variety of carbon bearing species that include both oxidized and reduced varieties oxidised varieties include carbonate minerals especially in the carbonatite complex at the eastern end of the pluton and na carbonate phases reduced varieties include abiogenic hydrocarbon gases particularly methane and ethane dispersed bitumens solid organic substances and graphite the majority of the carbon in the khibiny complex is hosted in either the carbonatite complex or within the so called central arch the central arch is a ring shaped structure which separates khibinites coarse grained eudialite bearing nepheline syenites in the outer part of the complex from lyavochorrites medium grained nepheline syenites and foyaites in the inner part the central arch is petrologically diverse and hosts the major ree enriched apatite nepheline deposits for which the complex is best known it also hosts zones with elevated hydrocarbon dominantly methane gas content and zones of hydrothermally deposited na carbonate mineralisation the hydrocarbon gases are most likely the product of a series of post magmatic abiogenic reactions it is likely that the concentration of apatite nepheline deposits hydrocarbon gases and na carbonate mineralisation is a function of long lived fluid percolation through the central arch fluid migration was facilitated by stress release during cooling and uplift of the khibiny complex as a result carbon with a mantle signature was concentrated into a narrow ring shaped zone

preliminary evaluation of trace hydrocarbon speciation and abundance as an exploration tool for footwall style sulfide ores associated with the sudbury igneous complex ontario canada deposits of cu ni platinum group elements pge rich sulfides occur along the north range footwall of the sudbury igneous complex ontario canada the deposits have been modified chemically mineralogically and texturally by multiple syn to postmagmatic hydrothermal events and are hosted mainly within sudbury breccia a contact metamorphosed and hydrothermally altered impact breccia the composition of c1 to c6 unsaturated and saturated hydrocarbons in bulk fluid inclusion volatiles in the matrix of the sudbury breccia was investigated using in line rock crushing gas chromatography gc in order to compare the hydrocarbon composition of this rock type in breccia zones containing economic footwall sulfide deposits at the morrison deposit levack mine north range sudbury ontario with barren breccia zones trace hydrocarbons possibly abiogenic in origin occur throughout the sudbury igneous complex footwall and country rocks investigated however there are differences in the composition and abundance of bulk hydrocarbons released from mineralized and barren sudbury breccia when fluid inclusions are opened volatiles released from samples of sudbury breccia from sulfide mineralized and sulfide barren environments showed the following 1 higher average abundances of light saturated hydrocarbons c1 c4 and an approximately 2 higher total abundance of hydrocarbons mol g of rock basis associated with samples from the mineralized study area and 2 comparable average unsaturated hydrocarbon abundances in both settings but a larger range in unsaturated hydrocarbon abundances in the mineralized study area differences in bulk hydrocarbon abundance and composition reflect differences in the abundance and hydrocarbon content of fluid inclusions trapped in the barren and mineralized sudbury breccia zones in addition the compositional modification of circulating fluids by processes and conditions unique to the mineralized sudbury breccia environment may have occurred prior to inclusion entrapment e g modification by mineral catalysts differences in temperature and oxygen fugacity preliminary spatial analysis of the hydrocarbon distribution within and surrounding the morrison deposit shows that the total hydrocarbon abundance in the sudbury breccia does not change with orebody proximity within a single host breccia zone however volatiles trapped in the sudbury breccia matrix near the top of the footwall deposit where it is physically connected to contact style ni cu pge ores have elevated unsaturated hydrocarbon abundances e g propene compared to other parts of the same breccia zone distal to this zone of physical connection samples of the pge enriched sudbury breccia and mineralized veins containing alteration assemblages characteristic of the footwall ore styles have higher unsaturated hydrocarbon abundances and unsaturated saturated ratios compared to sudbury breccia and vein samples that are pge poor localized enrichments in unsaturated hydrocarbons in sudbury breccia zones may be the result of specific ore minerals and metal complexes involving the pge and group viii metals that acted as catalytic agents modifying the composition of initially light saturated hydrocarbon species prior to entrapment in fluid inclusions to apply the analysis of hydrocarbon compositions in trapped fluid inclusions to discriminating mineralized from barren zones of sudbury breccia samples from targeted areas were compared to samples of barren sudbury breccia background although a large data set is presented here to establish these compositional fields analysis of smaller sample subsets from each environment yields a statistically significant separation between the two environments total hydrocarbon abundance c3 c1 ratios and unsaturated saturated hydrocarbon ratios are useful indicators of sulfide ore proximity and may help delineate regions enriched in pge

archaeological significance of the palaeolithic charcoal assemblage from krems wachtberg abstract at the palaeolithic site of krems wachtberg numerous charcoal remains were excavated since 2005 they were concentrated in the living floor layer 4 4 especially in fireplaces 1 and 2 and several pits but also mixed into sediments above the living floor since 2008 vias dendrolab vienna institute for archaeological science university of vienna has been cooperating with the excavators to investigate these charcoal samples for wood species analysis dendrochronological synchronization and also to evaluate their palaeoclimatic potential the dominant wood type is pine which includes the species pinus sylvestris pinus mugo and pinus cembra sibirica two other gymnospermous wood types were found among the samples several charcoal pieces belong to picea abies larix decidua which cannot be separated by means of wood anatomy and a single specimen of abies sp was found a single angiosperm wood remain was analysed as fagus sylvatica dendrochronological investigations singled out a number of samples with very similar ring patterns which obviously had been growing at the same time as these clusters do not match each other samples were either not contemporary or grew on climatologically differing places as a result of these studies we were able to ascertain the synchronous use of fireplaces 1 and 2 in at least one phase the advanced methods of charcoal analysis described in this paper can be used for detecting and synchronizing settlement phases on many archaeological sites in particular it is possible to significantly enhance the temporal resolution achievable with 14c ages on wood charcoal

abiotic methane in continental ultramafic rock systems towards a genetic model abstract methane ch4 often in substantial quantities is reported for numerous surface manifestations seeps springs and aquifers in continental serpentinized ultramafic rocks in ophiolites peridotite massifs and intrusions frequently this gas is considered to have a dominant abiotic origin with variable though generally minor components of biotic gas thermogenic or microbial abiotic ch4 production through low temperature fischer tropsch type reactions ftt between a carbon c compound and h2 is endorsed by most of scholars but direct derivation from olivine hydration serpentinization magmatic sources and fluid inclusions have also been suggested here we review the application of ftt in geology discussing the appropriateness of several c compounds co2 co formic acid formate or elemental c as ch4 precursors and of aqueous versus gas phase reactions we examine published gas geochemical and flux data that provide clear constraints on the methane origins in the analysis we add new isotopic and gas seepage data acquired in surface gas manifestations at acquasanta in the voltri ophiolite genova italy multiple lines of evidence including a stable isotope compositions of ch4 co2 and helium b radiocarbon free ch4 c isotopic disequilibrium between ch4 and h2o d low temperatures of ch4 production based on clumped isotopes and heat flow data and e methane seepage forms and intensities suggest that ch4 is not formed directly in water or from magmatic sources or fluid inclusions rather all the lines of evidence taken together are compatible with the hypothesis of low temperature

geochemistry of reduced gas related to serpentinization of the zambales ophiolite philippines abstract methane hydrogen gas seeps with mantle like c and noble gas isotopic characteristics issue from partially serpentinized ultramafic rocks in the zambales ophiolite philippines new measurements of noble gas and 14c isotope abundances rock mixed volatile equilibrium calculations and previous chemical and isotopic data suggest that these reduced gases are products of periodotite hydration the gas seeps are produced in rock dominated zones of serpentinization and similar gases may be ubiquitous in ultramafic terranes undergoing serpentinization

methane rich fluids in the oceanic crust analyses of fluid inclusions in plutonic rocks recovered from the slow spreading southwest indian ridge swir record ch4 concentrations of 15 40 times those of hydrothermal vent fluids and of basalt hosted volcanic gases and provide the first direct sampling of co2 ch4 h2o h2 c bearing fluids in the oceanic crust compositional thermal and spatial analyses of these fluids are used to model the evolution of volatiles during the crystallization and cooling of mid ocean ridge magma chambers and to assess the potential importance of carbon bearing fluids in geochemical processes in the lower crustal component of hydrothermal systems results from these analyses show that the earliest fluids to be exsolved from the melts are dominated by co2 rich vapors which with progressive fractionation evolved to more h2o rich compositions these later fluids were most likely exsolved under immiscible conditions and involved the development of co2 h2o rich vapors and co2 h2o nacl brines that were trapped during mineral growth as well as during later high temperature fracturing events co2 ch4 h2o rich fluids in olivine and plagioclase minerals that contain up to 30 50 mol co2 and 33 mol ch4 may reflect respeciation of magmatic co2 during cooling and attendant graphite precipitation phase equilibria suggest that these fluids reequilibrated at 500 600 c and at fo2 s 3 log units below to close to qfm conditions alternatively the inclusions may record respeciation of magmatic fluids attendant with the inward diffusion of h2 into the inclusions and reduction of entrapped co2 during degassing and cooling of the gabbros throughout the subsolidus regime subsequent seawater reaction at minimum temperatures of 400 c with mafic rich layers within the gabbroic rocks or with ultramafic material that underlies the plutonic sequence resulted in the formation of ch4 h2o fluids that contain up to 40 mol ch4 molecular h2 and graphite daughter minerals these data provide strong evidence that the ch4 h2o rich fluids produced during serpentinization reactions were trapped under equilibrium conditions in the presence of graphite at very near to qfm conditions the ubiquitous occurrence of ch4 rich fluids in oceanic crustal layer 3 rocks from the swir indicates that these fluids may be a significant and previously unrecognized source for these volatile species in some hydrothermal systems venting on the seafloor and that the deep seated fluids most likely play an important role in the transfer of carbon from the lithosphere to the hydrosphere

the origin of ch4 rich fluids in reduced porphyry skarn cu mo au systems abstract although most of the methane on earth is of biogenic origin significant abiogenic methane has been identified in a variety of geological environments moreover the presence of methane has been reported recently in fluid inclusions from a number of reduced porphyry deposits the genesis of this methane however remains poorly understood here we present results of a study of magma exsolved ch4 rich aqueous fluid inclusions in the seleteguole reduced porphyry skarn cu mo au deposit nw china four types of fluid inclusions namely intermediate density two phase aqueous inclusions low density vapor inclusions brine inclusions and aqueous liquid inclusions have been distinguished on the basis of the phases present at room temperature the intermediate density inclusions were trapped as a single phase and contain 3 8 10 4 mol kg ch4 corresponding to an oxygen fugacity between fmq 1 and fmq 0 5 this attests to the remarkably reduced nature of the fluid the 13c value of the ch4 hosted fluid inclusions ranges from 29 4 to 19 1 pdb which distinguishes this methane from biogenic methane indeed the high homogenization temperature of the ch4 rich inclusions 400 c implies that the ch4 was exsolved directly from the magma given the environment in which the magma was likely generated i e at or immediately above a subducting plate we propose that the methane was produced by reactions involving organic matter bearing carbonate rocks in the subduction zone although cu mo and au in most porphyry systems are interpreted to have been transported under oxidizing conditions our results indicate that reduced aqueous liquids and vapors are also capable of transporting appreciable concentrations of these metals

geochemical characteristics and origin of natural gas in tarim basin china the tarim basin located in northwest china is one of the largest basins in the world that has not been well explored in recent years the large scale of petroleum exploration in the basin has led to the discovery of a series of oil and gas fields with an approximate 1 1 ratio of oil to gas resource this means that the natural gas resource is very important for the hydrocarbon resource in the tarim basin in this basin most of the discovered gases are condensate associated gas and oil associated gas research on chemical components and isotope composition of carbon and hydrogen of natural gases from the tarim basin shows that all discovered gases in this basin are thermogenic with respect to source organic matter there are two types of gases 1 oil type gas generated from sinian to lower paleozoic marine source rocks with the sapropelic organic matter with 44 5 to 33 8o oo of d13c1 42 0 to 28 1o oo of d13c2 35 4 to 28 4o oo of d13c3 and heavier than 200o oo of dd1 and 2 coal type gas generated from mesozoic terrestrial source rocks with the humic organic matter with 40 5 to 33 1o oo of d13c1 29 7 to 21 3o oo of d13c2 26 3 to 20 3o oo of d13c3 and lighter than 200o oo of dd1

a fluid inclusion study of vug minerals in dawsonite altered phonolite sills montreal quebec implications for hfse mobility ordovician limestones in the francon quarr on the island of montreal quebec are host to three sills of cretaceous age composed of phonolite that has been extensively altered to dawsonite an interesting feature of the sills is the presence of abundant vugs containing a wide variety of minerals including several in which one or more high field strength elements zr hf nb ti is a major component the most important of these latter minerals is weloganite a rare strontium zirconium hydrous carbonate first identified in the francon quarry four types of inclusions have been recognized in vug minerals aqueous aqueous carbonic carbonic and solidbearing aqueous inclusions homogenize at temperatures mainly between 70 and 170 c and between 230 and 390 c the homogenization temperatures of primary inclusions cluster around 350 c aqueous inclusions and the aqueous phase in aqueous carbonic inclusions have salinities ranging between 10 and 24 eq wt nacl equivalent primary aqueous carbonic inclusions have low xco2 0 7 carbonic inclusions are all secondary nahcolite dawsonite and weloganite occur as daughter minerals or trapped solids nahcolite and possibly natron or mirabilite appear to form in frozen inclusions analyses of fluid inclusion decrepitates detected high concentrations of na cl al s and c the extraordinarily high concentration of al in the fluid possibly exceeding 1 wt suggests a ph of approximately 10 pressure and temperature conditions estimated from stratigraphic reconstruction and the isochores of primary aqueous fluid inclusions were 450 bar and 360 to 400 c respectively the relatively high temperatures and compositions of primary fluid inclusions suggest that vug filling was the result of mineral precipitation from an orthomagmatic fluid a model is proposed in which a partially crystallized phonolite melt started exsolving a homogeneous low xco2 fluid immediately prior to or after intrusion sodium aluminium chlorine fluorine sulphur and hfse elements such as zr hf nb and ti were partitioned into the hydrous phase in the case of zr possibly to a concentration of 300 ppm the near horizontal orientation of the sills and the chilled margins produced by quenching of the magma created a tight seal that inhibited escape of the fluids as a result the phonolite stewed in its own juices long after crystallization giving rise to widespread replacement of primary igneous minerals by dawsonite and precipitation of this and other minerals in vugs once the sills had colled to temperatures between 200 and 300 c the aqueous fluid exsolved a high co2 fluid which was trapped as the secondary three phase type ii and type iii inclusions decreasing temperature is considered to have been the principal control of mineralization although in the case of the lower temperature minerals decreased bicarbonate or carbonate ion activity and a lower dielectric constant as a result of co2 exsolution may have played a role in the deposition of hfse bearing minerals

combined raman microprobe spectrometry and microthermometry of fluid inclusions in minerals from igneous rocks of the gardar province south greenland abstract raman microprobe spectrometry has been applied to analysis of the gaseous phase in individual fluid inclusions in minerals from alkalic igneous rock types and associated hydrothermal veins from the gardar province south greenland quantitative analyses are given for co2 ch4 c2h6 h2 and h2s traces of co were observed in one co2 inclusion in conjunction with data from microthermometry the results permit calculation of the bulk chemical composition of entrapped fluids and evaluation of the possible pressure temperature oxygen fugacity and sulphur fugacity during entrapment of the individual fluid inclusions calculated oxygen fugacity values correspond to those of the nno and qfm buffer reactions at temperatures of 300 400 c and pressures of 0 5 1 0 kbar calculated sulphur fugacity values are within the range of normal ore forming solutions log fs2 6 to 10

krems wachtberg excavations 2005 12 main profiles sampling stratigraphy and site formation abstract since 2005 detailed archaeological investigations have been carried out at the upper palaeolithic site of krems wachtberg in eastern austria where a well preserved gravettian find layer is embedded in an 8 m high late pleistocene loess sequence the excavations are accompanied by interdisciplinary sampling strategies applied on the main profiles entire sediment series as well as on selected locations within the archaeological context the latter include both evident anthropogenic structures an in situ occupation surface with hearths and burials and periglacial features that together determine the morphology and explain the formation of the main gravettian find horizon

a reassessment of models for hydrocarbon generation in the khibiny nepheline syenite complex kola peninsula russia although hydrocarbon bearing fluids have been known from the alkaline igneous rocks of the khibiny intrusion for many years their origin remains enigmatic a recently proposed model of post magmatic hc generation through fischer tropsch type reactions suggests a primary co2 fluid this hypothesis is based upon textural data gas bulk and isotopic composition and low entrapment temperature of fluid inclusions that indicate an abiogenic origin for the hc gases however new petrographic microthermometric laser raman bulk gas and isotope data are presented and discussed in the context of previously published work in order to reassess models of hc generation the gas phase is dominated by ch4 with only minor proportions of higher hydrocarbons no remnants of the proposed primary co2 rich fluid are found anywhere in the complex primary and secondary fluid inclusions show similar compositions and entrapment conditions the majority of the fluid inclusions are of secondary nature and trapped in healed microfractures this indicates a high fluid flux after magma crystallisation entrapment condtions for primary fluid inclusions are 450 550 c at 2 8 4 5 kbar these temperatures are too high for hc gas generation through the ft reaction chemical analyses of rims of fe rich phases suggest that they are not the result of alteration but instead represent changes in magma composition during crystallisation furthermore there is no clear relationship between the presence of fe rich minerals and fluid inclusion abundance as reported elsewhere fluid inclusion planes generally start and terminate at mineral boundaries 13c values for methane range from 22 4 to 5 4 confirming also an abiogenic origin for the gas these data support an abiogenic hc origin but are not consistent with a post magmatic ft type reaction the presence of primary ch4 dominated fluid and melt inclusions which contain a methane rich gas phase indicate that a magmatic origin is more likely an increase in methane content together with a decrease in 13c isotope values towards the intrusion margin suggest that magmatically derived abiogenic hydrocarbons may have mixed with biogenic hydrocarbons derived from the surrounding country rocks

hydrothermal gases offshore milos island greece hydrothermal fluids emerge from the seafloor of paleohori bay on milos the gases in these fluids contain mostly co2 but ch4 concentrations up to 2 are present the stable carbon isotopic composition of the co2 near 0 indicates an inorganic carbon source dissociation of underlying marine carbonates the carbon and hydrogen isotopes of most ch4 samples are enriched in the heavy species delta 13c 9 4 to 17 8 per mille sign delta d 102 to 189 per mille sign which is believed to be characteristic for an abiogenic production of ch4 by co2 reduction fischer tropsch reactions depletions in the deuterium content of three ch4 samples to 377 are probably caused by unknown subsurface rock alteration processes secondary hydrogen isotope exchange processes between methane hydrogen and water are most likely responsible for calculated unrealistic methane formation temperatures we show that excess helium slightly enriched in 3he is present in the hydrothermal fluids emerging the seafloor of paleohori bay when the isotopic ratio of the excess component is calculated a 3he 4heexcess of 3 6 10 6 is obtained this indicates that the excess component consists of about one third of mantle helium and two thirds of radiogenic helium we infer that the mantle derived component has been strongly diluted by radiogenic helium during the ascent of the fluids to the surface

statistical approach for the geochemical signature of two active normal faults in the western corinth gulf rift greece abstract soil gas measurements of different gas species were performed in two distinct areas of the corinth gulf rift greece the aigion neos erineos lambiri anel fault zone and the rion patras fault zone both zones lie in one of the most seismically active areas of the euro mediterranean region where a fast opening continental rift is located in particular the geochemical investigations were focused on fault segments and fracture systems previously inferred by geomorphological lithological and structural studies in this work the applicability of soil gas geochemistry surveys for the exploration of buried hidden faults was tested by using various statistical methods moreover a comprehensive geostatistical treatment of the collected data provided new insights into the control exerted by active structures on deep seated gas migration towards the surface in both investigated areas the highest 222rn and co2 concentration peaks correspond with zones where the interaction among fracture and fault segments was inferred by structural and morphological methods this indicates a clear correlation between the shape and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized in the two areas furthermore obtained results show that gases migrate preferentially through zones of brittle deformation by advective processes as suggested by the relatively high rate of migration needed to obtain anomalies of short lived 222rn in the soil pores

free hydrogen hydrocarbon gases from the lovozero loparite deposit kola peninsula nw russia abstract the lovozero nepheline syenite massif in the north eastern fennoscandian shield well known to mineralogists and petrologists is also interesting with its high contents of hydrogen hydrocarbon gases in different forms of presence which is untypical of magmatic rocks the article systematizes and generalizes little known and unpublished data on the composition location character and scale intensity of the free gases fg emission within a major loparite deposit confined to the massif 4 and 2 are dominant in the fg composition the molecular weight distribution of hydrocarbon gas components corresponds to the classic anderson schulz flory distribution with a steep gradient carbon and hydrogen of the gases are characterized by rather heavy isotope compositions becoming lighter from the transition of methane to ethane the fg volume has been estimated as 0 2 1 6 m 3 of gas per 1 m 3 of undisturbed rock the gas recovery of walls in underground workings has been up to 0 2 ml min m 2 for 4 and 0 5 ml min m 2 for 2 in several years after their heading the discharge of some shot holes that characterizes the gas emission intensity 1 8 2 m deep and 40 mm in diameter is up to 300 ml min but its 1 2 orders lesser values dominate the discharge time in some sections varies from several days to 20 years the overpressure of gases towards the air mainly does not increase 100 hpa sometimes reaching 120 kpa it has been defined that fg distribute irregularly at the distance of centimeters to hundreds of meters and their composition and particularly emission intensity perform different temporal fluctuations the abiogenic origin of fg has been proposed with fg appearing as a mixture of gases in various proportions a gases remaining in microfissures at the massif s consolidation after the capture by fluid inclusions and those lost during degassing and b gases occurred in mechanic chemical reactions partial emission and concentration of occluded and diffusely scattered gases under the unstable stress strain mode of the rock mass combustible and explosive hydrogen hydrocarbon fg can accumulate in the air of underground workings and cause accidents disrupting the workflow the background for using characteristics of spatial temporal variations of the fg emission as precursors of dangerous geodynamic phenomena has been indicated

c o h n salt fluids associated with contact metamorphism mcgerrigle mountains quebec a raman spectroscopic study abstract contact metamorphism and metasomatism of a sequence of cambro ordovician pelitic calcareous and psammitic metasediments in the thermal aureole of the devonian mcgerrigle pluton has resulted in the generation of a wide variety of fluid compositions which can be described by the system c o h n salt microthermometric and raman spectroscopic data on fluid inclusions trapped in quartzsulfide veins adjacent to the intrusive contact indicate that three fluid types existed in the aureole 1 h 2 o 2 h 2 o co 2 and 3 ch 2 n 2 co 2 the aqueous fluids have salinities which range from 0 to 50 eq wt nacl cacl 2 this range in fluid compositions resulted from the progressive devolatilization of a variety of lithologies and the release of waters from the intrusion the range in salinity of the aqueous fluids is attributed to variable contributions of high salinity waters from the intrusions and lower salinity dehydration and formation waters some of the co 2 may be orthomagmatic however most of it probably came from decarbonation of calcareous and possibly carbonaceous lithologies ch 4 and n 2 were generated in pelitic units during thermal metamorphism ch 4 from reactions involving bitumen and graphite and n 2 from nh 2 in silicate minerals and possibly from bitumen the restriction of high mole fractions of ch 4 and n 2 to water free fluid inclusions can be explained by fluid immiscibility within the fracture system the partitioning of co 2 between water poor and water rich fluids was less extreme and in some cases co 2 and h 2 o may have been completely miscible

the impact of periglacial processes on palaeolithic sites the case of sorted patterned grounds during the last glaciation western europe witnessed recurrent millennial scale episodes of periglacial climates that had significant impact on palaeolithic site preservation after a review on the genesis and climatic meaning of sorted patterned grounds examples of polygons stripes and stone banked solifluction lobes taken from archaeological contexts are described sorted features in palaeolithic sites imply that caution should be taken in site patterning analysis for reconstructing past human behaviours since spatial alteration of the original anthropogenic pattern took place on low gradients artefact movements remain limited but may increase dramatically on slopes when solifluction adds to sorting processes although these features are widespread in modern periglacial environments archaeological examples remain scarce multiple factors are probably involved including lack of knowledge of periglacial processes and landforms by archaeologists leading to misinterpretation but also more or less complete obliteration of surface features by sedimentary processes upon burial however it is assumed that scarcity of clear anthropogenic patterning in french palaeolithic sites before the late glacial is due for a large part to post depositional disturbance by periglacial processes

geochemical characteristics of gases from the largest tight sand gas field sulige and shale gas field fuling in china abstract this study performed a detailed geochemical analyses of the components stable carbon isotopes of alkane gas and co2 stable hydrogen isotopes of alkane gas and helium isotopes of reproducing gas from the largest tight gas field sulige and shale gas fuling field in china the comparative study shows that tight gas from the sulige gas field in the ordos basin is of coal derived origin which is characterized by a positive carbon and hydrogen isotopic distribution pattern 13c1 13c2 13c3 13c4 2h1 2h2 2h3 i e the carbon and hydrogen isotopes increase with increasing carbon numbers carbon dioxide from this field are of biogenic origin and the helium is crust derived shale gas from the fuling shale gas field belongs to oil derived gas which has complete carbon and hydrogen isotopic reversal of secondary alteration origin 13c1

multiple origins of methane in the earth methane occurrences in the earth s crust are predominantly of biogenic origin i e their ultimate source is biologically formed organic matter methane can also form through inorganic reactions and is consequently termed abiogenic biogenic methanes can either form through bacterial or thermogenic processes bacterial processes follow a co2 reduction and or fermentation pathway the fermentation processes are quantitatively more important in recent fresh sediments and swamps methane formed by co2 reduction however is most common in older sediments and commercial gasfields temperature organic substrate and age may be the major factors controlling the relative importance of the two pathways stable isotope concentrations in thermogenic methanes seem to be controlled by the extent of conversion of organic matter the timing of gas expulsion and trapping the different character of methane in individual sedimentary basins may be a result of the geologic history geothermal methanes are most likely derived from pyrolysis of organic matter abiogenic methane occurs in hydrothermal vents and ophiolite complexes inorganic reactions either surficial or deep seated are the likely source of such methanes a uniform mantle origin of methane is not supported by the observed isotope variations in naturally occurring methanes

geochemistry of oil in fluid inclusions in a middle proterozoic igneous intrusion implications for the source of hydrocarbons in crystalline rocks abstract the ca 1280 ma dolerite sill within the mesoproterozoic roper group in the roper superbasin australia contains evidence for at least two episodes of hydrocarbon migration represented respectively by solid bitumen with a ketone rich extract and a mixture of a high maturity gas condensate and a lower maturity oil within oil bearing fluid inclusions the ketone isomers are formed by flash pyrolysis of kerogen during the intrusion of the dolerite sill org geochem 21 1994 829 and represent the first and oldest phase of hydrocarbon migration the gas condensate and oil were subsequently trapped as a mixture within fluid inclusions at diagenetic temperatures and pressures of around 110 c and 250 bars significantly after cooling of the sill and likely during the neoproterozoic reactivation of the roper superbasin either 1 these fluids migrated together and mixed in the reservoir or 2 an earlier oil charge was flushed by a later condensate charge and the oil condensate mixture was trapped within single fluid inclusions oil inclusions occur chiefly within albitised zones of labradorite laths within the dolerite matrix and within transcrystalline microfractures cutting vein calcite and rarely vein quartz oil inclusions trapped in the vein calcite are accompanied by hypersaline ca mg brines gas chromatography mass spectrometry of oil extracted from inclusions within the dolerite matrix shows that the oil is non biodegraded and was therefore trapped relatively quickly within the host minerals trace amounts of biomarkers indicate that the inclusion oil is of a biogenic origin and excludes any abiotic processes that are apparent sources of hydrocarbons in many crystalline rocks monomethylalkanes pentacyclic terpanes chiefly comprising hopanes and diahopanes and very low concentrations of steranes and diasteranes indicate input from cyanobacterial organic matter with a minor contribution from eukaryotes the hydrocarbons are likely derived from proterozoic source rocks such as the directly overlying velkerri formation and or the underlying barney creek formation from the mcarthur group the study has implications for the source of hydrocarbons in non sedimentary rocks and suggests that fluid inclusions can be used not only to distinguish between biogenic and abiogenic sources of hydrocarbons but also to provide critical information about the composition of the biomass fluid migration events and conditions under which hydrocarbons in different geological settings are trapped

development of oil formation theories and their importance for peak oil this paper reviews the historical development of both biogenic and non biogenic petroleum formation it also examines the recent claim that the so called abiotic oil formation theory undermines t

volatiles associated with alkaline igneous rift activity fluid inclusions in the ilimaussaq intrusion and the gardar granitic complexes south greenland abstract fluid inclusions in minerals from si oversaturated and si undersaturated alkalic igneous complexes belonging to the precambrian gardar rift province in south greenland contain distinctly different carbon bearing gases granites and quartz syenites are characterized by co2 and only minor ch4 whereas agpaitic nepheline syenites are dominated by hydrocarbons essentially ch4 and contain only insignificant amounts of co2 and or co in the alkaline ilimaussaq intrusion the hydrocarbon rich gases may well reflect equilibration with graphite at magmatic temperatures and at oxygen fugacities approaching those defined by the synthetic mw buffer reaction in general formation of hydrocarbon gases in agpaitic nepheline syenites is considered to reflect the fulfillment of three basic conditions 1 low oxygen fugacities 2 a wide temperature range of crystallization and a low temperature solidus and 3 retention of volatiles during crystallization the characteristic carbon bearing vapour associated with continental alkaline igneous activity is however considered to be co2

the occurrence of petroleum in sedimentary rocks of the meteor impact crater at lake siljan sweden abstract during the devonian large parts of sweden were covered by sandstones shales and limestones of precambrian to upper silurian age at the end of the devonian 360 m yr b p a meter struck causing a large impact crater at lake siljan with a diameter of 50 60 km annular depression was formed which is still preserved today this depression contains undisturbed as well as tilted paleozoic rocks numerous sedimentary occurrences of asphalts and seep oils are reported from quarries in the sedimentary rocks and some shallow boreholes contain a thin layer of free oil floatingon arterian groundwater a representative set of paleozoic shales and limestones found in the siljanarea was analyzed with respect to organic richness type and thermal maturity three intervals of organic rich and oil prone source rocks 2 10 toc were distinguished and extracts of these rocks were geomically compared with the seep oils using stable carbon isotopes and terpenoid biomarkers even though these low maturity oils were altered by biodegradation a correlation with ordovician source rocks was established all the analyzed organic rich rocks are on the verge of oil generation as determined by 20s 20r 5 h c 29 sterane ratios in addition burial history indicates insufficient overburden available for oil generation the seep oils however are more mature and within the oil window yet below peak generation levels thus it appears that the heat effect of meteor impact locally matured the source rock allowing for geologically instantaneous hydrocarbon generation and expulsion resulting in the formation of seep oils

abiogenic methanogenesis in crystalline rocks isotopically anomalous ch4 rich gas deposits are found in mining sites on both the canadian and fennoscandian shields with 13cch4 values from 22 4 to 48 5 and dch4 values from 133 to 372 these methane deposits cannot be accounted for by conventional processes of bacterial or thermogenic methanogenesis compositionally the gases are similar to other ch4 rich gas occurrences found in canadian and fennoscandian shield rocks sherwood lollar et al 1993 however the isotopically anomalous gases of this study are characterized by unexpectedly high concentrations of h2 gas ranging from several volume percent up to 30 vol the h2 gases are consistently depleted in the heavy isotope with dh2 values of 619 to 659 3h 4he ratios in the range of 0 4 10 8 to 4 4 sx 10 8 indicate that there is no resolvable component of mantle derived he in these deposits based on these results a mantle derived source for the c bearing gases is unlikely several lines of evidence support an alternative abiogenic origin for the gases from sudbury canada and juuka and pori finland the d depleted h2 gas and calculated d ch4 h2 equilibration temperatures of 110 170 c at all three sites are in good agreement with results obtained for abiogenically produced ch4 and h2 in ophiolite sequences in oman and the philippines serpentinization and the hydration of ultramafic rocks are the proposed mechanisms for ch4 and h2 production in these ophiolite sequences the widespread occurrence of serpentinized and altered ultramafic rocks at juuka and at a number of other sites in both canada and finland implies that similar mechanisms may be involved in gas production at at least three sites on the shields the origin of the gases at the remaining shield sites is discussed alternative hypothesis include 1 production of the rest of the shield gases by mixing between abiogenic endmembers and bacterially generated hydrocarbon gas such as identified elsewhere on the canadian and fennoscandian shields sherwood lollar et al 1993 and 2 production of a series of isotopically distinct abiogenic ch4 endmembers at each site due to variability in the isotopic composition of available carbon sources we cannot conclusively distinguish between the alternative scenarios based on existing data however the evidence for an abiogenic ch4 endmember at at least three sites emphasizes the need for substantial revision of current theories of methanogenesis abiogenic processes of ch4 production may be considerably more widespread than previously anticipated

abiotic methane on earth 1 over the last 30 years geochemical research has demonstrated that abiotic methane ch4 formed by chemical reactions which do not directly involve organic matter occurs on earth in several specific geologic environments it can be produced by either high temperature magmatic processes in volcanic and geothermal areas or via low temperature 100 c gas water rock reactions in continental settings even at shallow depths the isotopic composition of c and h is a first step in distinguishing abiotic from biotic including either microbial or thermogenic ch4 herein we demonstrate that integrated geochemical diagnostic techniques based on molecular composition of associated gases noble gas isotopes mixing models and a detailed knowledge of the geologic and hydrogeologic context are necessary to confirm the occurrence of abiotic ch4 in natural gases which are frequently mixtures of multiple sources although it has been traditionally assumed that abiotic ch4 is mainly related to mantle derived or magmatic processes a new generation of data is showing that low temperature synthesis related to gas water rock reactions is more common than previously thought this paper reviews the major sources of abiotic ch4 and the primary approaches for differentiating abiotic from biotic ch4 including novel potential tools such as clumped isotope geochemistry a diagnostic approach for differentiation is proposed

alteration hfse mineralisation and hydrocarbon formation in peralkaline igneous systems insights from the strange lake pluton canada abstract two characteristics of peralkaline igneous rocks that are poorly understood are the extreme enrichment in hfse notably zr nb y and ree and the occurrence of fluid inclusions dominated by methane and higher hydrocarbons although much of the hfse enrichment can be explained by magmatic processes the common intense alteration of the parts of the peralkaline intrusions most enriched in these elements suggests that hydrothermal processes also play an important role in hfse enrichment likewise although the origin of the higher order hydrocarbons that occur as inclusions in these rocks is still debated there is strong evidence that at least in some cases their formation involved hydrothermal processes the issues of hfse enrichment and hydrocarbon formation in peralkaline intrusions are examined using data from the strange lake pluton a small middle proterozoic intrusion of peralkaline granite in northeast canada this pluton contains some of the highest concentrations of zr ree and y ever reported in an igneous body and is characterised by abundant hydrocarbon dominated fluid inclusions in rocks that have been hydrothermally altered including those that form a potential hfse ore zone we show that hfse at strange lake were partly concentrated to near exploitable levels as a result of their transport in a high salinity magmatic aqueous liquid and that this fluid coexisted immiscibly with a carbonic phase which reacted with hydrogen and iron oxides generated during the associated hydrothermal alteration to produce hydrocarbons via a fischer tropsch synthesis as a result hydrocarbons and hfse mineralization are intimately associated we then go on to show that hydrothermal alteration hfse mineralisation and hydrocarbons are also spatially associated in other peralkaline complexes and present a model to explain this association which we believe may be applicable to any peralkaline intrusion where hfse enrichment was accompanied by calcium metasomatism hematisation and hydrothermal fluorite we also suggest that even where these criteria are not satisfied hydrothermally enriched hfse and hydrocarbons will be intimately associated simply because they are products of the same initial magmatic fluid finally we speculate that the association of hfse and hydrocarbons may in some cases actually be genetic if as seems possible unmixing or effervescence of a reduced carbonic fluid from the original magmatic fluid caused changes in temperature ph f o 2 or the activity of volatile ligands sufficient to induce the deposition of hfse minerals

generation of compositionally atypical hydrocarbons in co2 rich geologic environments bitumen seepages from a trachyte flow on the suswa volcano east african rift are anomalously enriched in o and n heteroatomic organic compounds and depleted in aliphatics compositional and geologic data suggest that the biogenically derived bitumens were extracted and or transported by liquid or supercritical co2 rather than h2o possibly from caldera lake sediments compositionally atypical hydrocarbons and reduced carbon associated with other alkaline peralkaline igneous complexes as well as hg and au deposits may also reflect co2 fluids hydrocarbon extraction and migration in co2 rich fluids are considered realistic mechanisms in certain geologic environments

impact of coarse sediment supply from hillslopes to the channel in runoff dominated dryland fluvial systems sediment supply from hillslopes to channels is an important control on basin functioning and evolution however current theoretical frameworks do not adequately consider processes of runoff driven hillslope sediment supply which affect river channels spatially and temporally mountainous dryland basins exhibit an important manifestation of these processes because their debris mantled hillslopes produce coarse sediment and because rainfall is delivered as infrequent high intensity short duration rainstorms this paper combines field measurements and modeling to explore runoff driven coarse sediment supply from hillslopes to the channel and assesses a range of plausible storms on the longitudinal patterns of sediment load and its caliber over a dryland basin reach our results show that modeled sediment load and its grain size distribution are determined by the nonlinear interaction between rainfall characteristics and hillslope attributes resulting in longitudinal fluctuations in sediment supply the relative magnitude and location of which varies between storms results suggest that long hillslopes are most sensitive to rainfall and they exhibit large variations in supplied sediment load and grain size for different runoff characteristics short and steep hillslopes are less sensitive to rainfall variations as gradient effects dominate over the role of length in modulating runoff accumulation furthermore the signal of the median fraction d50 of modeled sediment supplied by the hillslope is preserved in the coarse fraction of the measured in channel grain sizes d90 finally we propose a simple index which provides new insights into the effectiveness of different rainstorms in terms of the impact of hillslope sediment supply on the channel

on the controls of oxygen fugacity in the generation and crystallization of peralkaline melts the formation of peralkaline melts is generally recognized to be related to enrichment of the mantle in sodium or potassium during a metasomatic event that predated magma generation the wide range in mineral assemblages mineral compositions and fluid compositions in peralkaline melts are to a large extent a function of the sodium potassium content of these mantle metasomatizing fluids which also governs redox conditions we propose that sodic fluids will reduce the mantle assemblage by depleting ferric iron from garnet to form the aegirine component in pyroxene in contrast potassic fluids would oxidize the mantle assemblage by extracting al2o3 from the garnet to make phlogopite we suggest that during differentiation of peralkaline melts once fe ti oxides have been depleted from the assemblage simple crystallization reactions of common solid phases such as aegirine or arfvedsonite control the oxygen fugacity by equilibria such as

our oldest children age constraints for the krems wachtberg site obtained from various thermoluminescence dating approaches abstract we present several approaches to directly date the prehistoric human activity of lighting a fire at the early gravettian infant burial site of krems wachtberg austria by thermoluminescence tl methods blue thermoluminescence b tl from polymineral fine grain and orange red thermoluminescence r tl from fine grained quartz separates both extracted from the baked loess immediately underlying the hearth were employed the b tl dating followed the classic multiple aliquot additive dose maad protocol for r tl dating the multiple aliquot regenerative mar and a shortened single aliquot regeneration sar protocol were tested all thermoluminescence ages obtained agree within 1 uncertainties and assign a weighted mean age of 33 9 2 3 ka to the last use of the hearth and by inference to the infant burial anomalous fading is precluded due to the agreement of results from all luminescence protocols as well as with independent dating methods the tl ages are consistent with calibrated radiocarbon ages on associated charcoal osl dating of the sediment deposition and with age estimates obtained by two magnetic dating approaches

paleoenvironmental fluctuations as recorded in the loess paleosol sequence of the upper paleolithic site krems wachtberg abstract the loess paleosol sequence of krems wachtberg is famous for its archeological findings above all its gravettian infant burials it represents a complex system of paleoclimatic fluctuations which is nearly complete and thus enables the correlation with global paleoclimatic records this sequence comprises activity phases with dominant eolian and partly erosional processes as well as stable short periods of weak pedogenesis periglacial environment with drier climate conditions and high eolian sedimentation rates characterize the upper part of the sequence and in periods with lower sedimentation rates cryosols and permafrost induced structures are developed although the krems wachtberg site is situated at a slope position intensive erosional phases events can be excluded the basal parts of the sequence show signs of decalcification bioturbation organic inclusions as well as changes in element distribution pedogenic horizons are partly overprinted by permafrost related structures and are disturbed by redepositional processes to a minor degree remarkably the archeological horizon is not affected by permafrost in contrast to the layers below and above the focus of this study is deciphering stratigraphy by a combination of paleopedological sedimentological analyses with rock magnetic analyses on the chronological scale the sequence records a timespan from 35 ka to 20 ka altogether there is evidence of five pedogenic units and one archeological layer which are correlated with the greenland interstadials gi 7 to gi 2 however an equivalent of a mis 3 interstadial soil comparable with the lohne soil or stillfried b soil could not be detected

geochemistry and accumulation of carbon dioxide gases in china we propose the following identification indicators for co2 of different origins based on data obtained from analyzing the molecular composition of 1198 gas samples the co2 carbon isotope values of 390 samples and the helium isotope composition of 256 samples collected from wells of 16 oil and gas bearing basins and gas seepages in china and reviewing literature on organic and inorganic co2 throughout the world co2 is of organic origin if co2 content 13cco22 is of inorganic origin if dgr13cco2 8 pmil or co2 60 and co2 is of either organic or inorganic origin or a mixtur of organic and inorganic origins if 10 pmil 13cco213cco2 values of organic co2 mainly range from 10 to 22 pmil in tectonically stable oil and gas bearing basins where deep faults and magmatism are undeveloped organic co2 occurs almost exclusively in tectonically active oil and gas bearing basins where active faults and magmatism are present or in areas of modern volcanic activity the dgr13cco2 values of inorganic co2 range from 2 to 8 pmil and are distributed along faults the inorganic co2 with a dgr13cco2 value of 0 3 pmil is of metamorphic origin and that with dgr13cco2 values of 6 2 pmil is mantle derived and of magmatic origin in china the dgr13cco2 values of inorganic co2 gas pools range from 3 41 to 8 44 pmil and the helium ratio r ra is 1 which indicates that these gases are typically derived from the mantle

volatile lines of descent in submarine plutonic environments insights from stable isotope and fluid inclusion analyses microthermometric and isotopic analyses of fluid inclusions in primitive olivine gabbros oxide gabbros and evolved granitic material recovered from ocean drilling program hole 735b at the southwest indian ridge provide new insights into the evolution of c o h nacl fluids in the plutonic foundation of the oceanic crust the variably altered and deformed plutonic rocks span a crustal section of over 1500 m and record a remarkably complex magma hydrothermal history magmatic fluids within this suite followed two chemically distinct paths during cooling through the subsolidus regime the first path included formation of co21ch41h2o1c fluids with up to 43 mole ch 4 the second path produced hypersaline brines that contain up to 50 nacl equivalent salinities subsequent to devolatilization respeciation of magmatic co2 attendant graphite precipitation and cooling from 800 c to 500 c promoted formation of ch 4 enriched fluids these fluids are characterized by average d 13 c ch4 values of 227 1 6 4 3 n5 45 with associated d 13 c co2 compositions ranging from 224 9 to 21 9 n539 and average dd values of exsolved vapor of 241 6 12 n523 in pods veins and lenses of highly fractionated residual material hypersaline brines formed during condensation and by direct exsolution in the absence of a conjugate vapor phase entrapped co21ch41h2o rich fluids within many oxide bearing rocks and felsic zones are significantly depleted in 13 c with d 13 c co2 values down to about 225 and contain co 2 concentrations higher than those predicted by equilibrium devolatilization models we hypothesize that lower effective pressures in high temperature shear zones promoted infiltration of highly fractionated melts and compositionally evolved volatiles into focused zones of deformation significantly weakening the rock strength in felsic rich zones volatile build up may have driven hydraulic fracturing of gabbroic wall rocks resulting in the formation of magmatic breccias comparison of isotopic compositions of fluids in plutonic rocks from 735b the mark area of the mid atlantic ridge and the mid cayman rise indicate 1 that the carbon isotope composition of the lower oceanic crust may be far more heterogeneous than previously believed and 2 that carbon bearing species in the oceanic crust and their distribution at depth are highly variable copyright 2001 elsevier science ltd

microbial hydrocarbon gases in the witwatersrand basin south africa implications for the deep biosphere in this study compositions and 13c and 2h isotopic values of hydrocarbon gases from 5 mines in the witwatersrand basin south africa support the widespread occurrence of microbially produced methane in millions of years old fissure waters the presence of microbial methane is to a large extent controlled by the geologic formations in which the gases are found samples from the witwatersand supergroup have the largest microbial component based on 13c and 2h signatures and ch4 c2 values based on mixing between a microbial ch4 component and a more 13c enriched and 2h depleted c2 rich end member conservative estimates of the contribution of microbial ch4 to the gas samples range from 90 microbial ch4 at beatrix masimong and merriespruit to between 5 and 80 microbial ch4 at evander and 18 microbial ch4 at kloof the witwatersrand basin s history of thermal alteration of organic rich ancient sedimentary units suggests a thermogenic origin for this 13c enriched end member alternatively the potential for an abiogenic origin similar to hydrocarbon gases produced by water rock interaction at other precambrian shield mines is discussed microbial methane is predominantly found in paleo meteoric fissure waters with 18o and 2h values that fall on the meteoric waterline and have temperatures between 30 to 40 c in contrast fissure waters with a larger component of nonmicrobial hydrocarbon gases show a trend towards more enriched 18o and 2h values that fall well above the meteoric waterline and temperatures of 45 to 60 c the enrichment in 18o and 2h in these samples and their high salinity are similar to the isotopic and compositional characteristics of saline groundwaters and brines produced by water rock interaction at precambrian shield sites elsewhere the reported 100 ma ages of fissure waters from the witwatersrand and ventersdorp formations suggest that these microbial hydrocarbon gases are the product of in situ methanogenic communities in the deep subsurface of the witswaterand basin small subunit ribosomal rna genes were amplified using archaeal specific primer sets from dna extracts derived from several of these waters fissure waters with a high proportion of microbial methane also contained sequences resembling those of known methanogens

hydrogen generation from mantle source rocks in oman hydrogen gas associated with ca2 oh rich alkaline groundwaters ph 10 12 is at present emanating from ultramafic rocks of the oman ophiolite isotopic and chemical evidence indicates that hydrogen is formed by low temperature redox reactions in a closed groundwater environment this is normally a cryptic process in the hydrosphere but is fortuitously revealed by the unusual hydrogeological conditions in oman where atmospheric oxygen is totally assimilated it is suggested that hydrogen generation in mantle source rocks at depth and in the early archaean surface environment may be more widespread than has hitherto been realised

isotope major minor and trace element geochemistry of late magmatic fluids in the peralkaline ilimaussaq intrusion south greenland abstract the persodic 1 16 ga old ilimaussaq intrusion consists of alkali granites syenites and agpaitic nepheline syenites these rocks are cut by late magmatic veins and lenses consisting of albite aegirine ussingite na2alsi3o8 oh fluorite and occasionally quartz oxygen isotope compositions of quartz indicates both orthomagmatic 18oqtz 8 5 and country rock influenced 18oqtz 10 origin while albite and aegirine do not contain fluid inclusions suitable for investigations ussingite contains secondary hydrocarbon fluid inclusions fluorite contains brine inclusions of primary and secondary origin with up to 26 3 wt naclequiv and quartz contains predominantly secondary brine inclusions with up to 29 7 wt naclequiv or ch4 h2o nacl mixtures these fluids are interpreted to reflect fluids in equilibrium with late stage melts at ilimaussaq at 450 c the carbon and hydrogen isotope composition of ch4 in ussingite 13c 6 to 3 d 121 is indicative of a magmatic abiogenic origin however the isotopic composition of ch4 in fluid inclusions in quartz veins resembles the signature of thermogenic ch4 13c 43 to 23 d 176 to 121 but the higher hydrocarbons are mostly 13c depleted in relation to ch4 up to 7 3 which is typical of abiogenically derived hydrocarbons ion chromatography of fluid inclusion leachates from the late stage veins reveals cl br ratios of 100 as such values seem to be typical of peralkaline magmatic rocks at least in the gardar province of south greenland it is suggested that this ratio is typical of gardar magmatic fluids and may be characteristic of the cl br ratio of the lithospheric mantle from which these alkaline melts are derived

luminescence based loess chronostratigraphy of the upper palaeolithic site krems wachtberg austria abstract the loess section krems wachtberg lower austria is well known for its upper palaeolithic find layer which contains a double and a single infant burial the layer containing the grave archaeological horizon ah 4 4 was dated to 26 580 160 14 c bp einwogerer et al 2006 corresponding to ca 31 ka cal bp and is embedded in an 8 m thick loess sequence in order to provide a chronostratigraphy of the entire section 38 samples for luminescence dating were taken at high resolution from below and above the find layer the samples were dated using the quartz coarse grain fraction the quartz fine grain fraction and or the polymineral fine grain fraction the resulting ages are in correct chronostratigraphic order and in case samples were measured with different protocols agree within errors with each other and with the radiocarbon age of the find layer the polymineral fine grain ages are systematically slightly lower than the quartz ages although no fading could be detected in laboratory experiments loess deposition at the site commenced ca 40 ka ago and reaches up to ca 22 ka the ages indicate nearly continuous loess sedimentation throughout this time span short breaks in sedimentation probably exist but cannot be resolved due to the uncertainties of luminescence ages

methane clumped isotopes in the songliao basin china new insights into abiotic vs biotic hydrocarbon formation abiotic hydrocarbon gas typically generated in serpentinized ultramafic rocks and crystalline shields has important implications for the deep biosphere petroleum systems the carbon cycle and astrobiology distinguishing abiotic gas produced by chemical reactions like sabatier synthesis from biotic gas produced from degradation of organic matter or microbial activity is sometimes challenging because their isotopic and molecular composition may overlap abiotic gas has been recognized in numerous locations on the earth although there are no confirmed instances where it is the dominant source of commercially valuable quantities in reservoir rocks the deep hydrocarbon reservoirs of the xujiaweizi depression in the songliao basin china have been considered to host significant amounts of abiotic methane here we report methane clumped isotope values 18 and the isotopic composition of c 1 c 3 alkanes co 2 and helium of five gas samples collected from those xujiaweizi deep reservoirs some geochemical features of these samples resemble previously suggested identifiers of abiotic gas 13 c enriched ch 4 decrease in 13 c 12 c ratio with increasing carbon number for the c1 c4 alkanes abundant apparently non biogenic co 2 and mantle derived helium however combining these constraints with new measurements of the clumped isotope composition of methane and careful consideration of the geological context suggests that the xujiaweizi depression gas is dominantly if not exclusively thermogenic and derived from over mature source rocks i e from catagenesis of buried organic matter at high temperatures methane formation temperatures suggested by clumped isotopes 167 213 c are lower than magmatic gas generation processes and consistent with the maturity of local source rocks also there are no geological conditions e g serpentinized ultramafic rocks that may lead to high production of h 2 and thus abiotic production of ch 4 via co 2 reduction we propose that the songliao gas is representative of an atypical type of thermogenic gas that can be mistaken for abiotic gas such gases may be encountered more frequently in future exploration of deep or over mature petroleum systems

magmatic fluids in the fen carbonatite complex s e norway three different types of carbonatite magma may be recognized in the cambrian fen complex s e norway 1 peralkaline calcite carbonatite magma derived from ijolitic magma 2 alkaline magnesian calcite carbonatite magma which yielded biotite amphibole sovite and dolomite carbonatite and 3 ferrocarbonatite liquids related to 2 and or to alkaline lamprophyre magma damjernite apatite formed during the pre emplacement evolution of 2 contains inclusions of calcite and dolomite devitrified mafic silicate glass and aqueous fluid all of these inclusions have a magmatic origin and were trapped during a mid crustal fractionation event p 4 kbars t 625 c where apatite and carbonates precipitated from a carbonatite magma which coexisted with a mafic silicate melt the fluid inclusions contain water dissolved ionic species mainly nacl with minor polyvalent metal salts and in some cases co2 two main groups of fluid inclusions are recognized type a co2 bearing inclusions of approximate molar composition h2o 88 90 co 27 5 nacl 5 d 0 85 0 87 g cm3 type b co2 free aqueous inclusions with salinities from 1 to 24 wt nacleq and densities betwen 0 7 and 1 0 g cm3 more strongly saline type b inclusions salinity ca 35wt d 1 0 to 1 1 g cm3 contain solid halite at room temperature and occur in overgrowths on apatite type a inclusions probably contain the most primitive fluid from which type b fluids have evolved during fractionation of the magmatic system type b inclusions define a continuous trend from low towards higher salinities and densities and formed as a result of cooling and partitioning of alkali chloride components in the carbonatite system into the fluid phase available petrological data on the carbonatites show that the fluid evolution in the fen complex leads from a regime dominated by juvenile co2 h2o fluids during the magmatic stage to groundwater derived aqueous fluids during post magmatic reequilibration

hearth side bone assemblages within the 27 ka bp krems wachtberg settlement fired ribs and the mammoth bone grease hypothesis besides two human infant burials the most important evident feature of the recent excavations at the gravettian pavlovian base camp site krems wachtberg is a multi phased hearth with a diameter of almost 1 5 m the feature is part of a compacted living floor which probably represents the interior of a dwelling the hearth contains charcoal mostly burned small bone fragments lithic artefacts in a matrix of ashy sediment and fire modified loess numerous mammoth limb bone flakes and the overall extensively fractured bone assemblages mainly from mammuthus equus rangifer and capra including a considerable portion of cancellous bone pose the question whether bone grease manufacture could have been a possible cause of these patterns the analysis of faunal remains addresses besides the most accurate determinations of species and skeletal position fragment size class proportions green bone fracture frequency the intensity of combustion and spatial distribution patterns while the most frequent species within the living floor is woolly mammoth followed by wild horse reindeer and ibex ungulate and mammoth bone counts are more balanced in the assemblages of the three distinct hearth phases a tendency toward more importance of the ungulates and more intense fragmentation can be observed in the last phase the bones which can be attributed to wild horse show a remarkably different spatial distribution than the mammoth remains generally the patterns suggest that a large part of the bones within the hearth is burned waste partly from fireside consumption for instance of rib meat in contrast abundance and concentration of green fractured mammoth and ungulate limb bones around the hearth is interpreted as primary refuse from marrow procurement strategies to counter resource fluctuations nutritional stress differential use and treatment of animal tissue including the fat within the bones are considered the most important issues for understanding gravettian settlement patterns

genetic characterization of natural gases natural gases can be characterized genetically using four properties c2 concentration carbon and hydrogen isotope variations in methane and carbon isotope variation in ethane three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters in these diagrams compositional fields have been defined for primary gases biogenic thermogenic associated and thermogenic nonassociated and for gases which result from mixing of these gases these fields are strictly empirical and comprise compositional variations found in about 500 natural gases the isotopic and compositional variations in natural gases can be described in terms of 1 processes during formation of the gases such as bacterial fermentation or maturation of organic matter and 2 processes during secondary migration mixing of primary gases is an important and common process migration of gases predominantly affects the c2 concentration whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged allowing an assessment of the origin of migrated gases and properties of their source rocks the formation of gas from humic organic matter and coals is not yet clear from published data the diagrams use data from various basins and areas interstitial gases from the gulf of california are entirely of bacterial origin traces of thermogenic gases are formed only in the vicinity of dolerite sills gases in the south german molasse basin and in the vienna basin are of bacterial mixed and thermogenic origins data from the north italian po basin provide examples for genetic characterization of migrated gases

involvement of variably sourced fluids during the formation and later overprinting of paleoproterozoic au cu mineralization insights gained from a fluid inclusion assemblage approach abstract au cu mineralized quartz veins of the reef deposit wisconsin usa originally formed prior to or early in the paleoproterozoic penokean orogeny in central north america as either the root zone of a gold rich vms deposit or in an orogenic gold setting nearly 400 m y later magmatic hydrothermal fluids associated with a continental scale anorogenic magmatic event remobilized mineralization within the veins and still later during the paleozoic remobilization and perhaps upgrading of au and other metals occurred in response to circulation of fluids associated with mississippi valley type deposits found in overlying supracrustal rocks fluid constraints on the formation of the reef deposit and later overprinting over a 1 5 b y timeframe are examined using the fluid inclusion assemblage fia approach distinctive assemblages are examined on individual merit each offering individual stories to aid in our understanding of the protracted development of the reef deposit presumably primary fluid inclusions in au and cu bearing quartz sulfide veins that formed during the paleoproterozoic event show h2o co2 ch4 nacl compositions based on microthermometry and laser raman spectroscopy possibly primary h2o nacl and secondary h2o co2 ch4 nacl fia formed prior to regional deformation and are recognized as discrete relict and neonate clusters the intersection of isochores from the highest density neonate inclusions of either fluid composition indicates re equilibration at lower amphibolite conditions during regional deformation quartz hosted secondary fluid inclusion assemblages characterized by h2o ch4 and co2 ch4 compositions formed at high temperatures and have not been re equilibrated and are interpreted to post date regional metamorphism these fia occur along healed fractures with chalcopyrite mineralization these inclusions are likely associated with fluid circulation driven by emplacement of the adjacent wolf river batholith ca 1 45 ga that altered pyrite to pyrrhotite and remobilized or emplaced chalcopyrite at temperatures as high as 700 c this reduced fluid was in equilibrium with locally observed graphitic sediments secondary lower temperature

graphite ch4 h2o co2 equilibria at low grade metamorphic conditions equilibrium calculations and published phase equilibria are used to show that at temperatures below 400 c and pressures above 300 bar the fluids coexisting with graphite in the c o h system consist either of co2 h2o mixtures or ch4 h2o mixtures bulk fluid compositions consisting of ch4 h2o will unmix to methane rich fluid and h2o rich liquid at temperatures below about 325 c compositions on the co2 h2o join will unmix only at temperatures below about 275 c oxygen fugacity in the ch4 h2o graphite three phase region is fixed at constant p and t and approximately equal to that of the quartz magnetite fayalite assemblage in the co2 h2o graphite three phase region oxygen fugacity is about three orders of magnitude greater from the end stages of diagenesis to temperatures of 300 c and possibly 400 c in salt rich systems many metamorphic rocks may contain ch4 h2o fluids rather than co2 h2o mixtures thus metamorphic reactions involving carbonate minerals would involve ch4 graphite and h2o rather than co2 the immiscibility between ch4 and h2o could result in the common occurrence of methane natural gas in low grade metamorphic terrains

subseafloor phase equilibria in high temperature hydrothermal fluids of the lucky strike seamount mid atlantic ridge 37 17 n abstract as part of an integrated study conducted at the lucky strike seamount mid atlantic ridge 37 17 n in 2008 gas tight sampling devices were used to collect high temperature 300 c hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression compared with previous observations from 1993 to 1997 the most substantial changes in vent fluid compositions are dramatically increased co2 concentrations 5 up to 133 mmol l and the observation of vent fluids enriched in dissolved chloride relative to seawater combined with an increase in 13 c co 2 values by 4 in 2008 the elevated co2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event the additional supporting fluid chemistry is however similar to that of the previous sampling intervals necessitating a reassessment of the subseafloor controls on vent fluid chemistry at lucky strike in the context of recently obtained geophysical data that provides the depth extent of a steady state magma chamber two phase behavior is indicated by the chloride variability in the vent fluids and comparison with experimental data for the associated chloride dependent partitioning of minor trace elements suggests the possibility of a similar source fluid for all the vent structures while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end members a recently calibrated fe mn geothermometer indicates minimum subseafloor equilibration temperatures of 350 385 c however constraints imposed by dissolved si cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430 475 c and pressures near the top of the axial magma chamber 410 480 bars where magmatic co2 becomes entrained in the circulating fluids the distance between the magma chamber and the seafloor at lucky strike is substantially greater than at most faster spreading ridges and we propose the resulting increased residence time in the up flow zone leads to the re equilibration of temperature sensitive transition metals at conditions less extreme than those associated with peak reaction agreement between experimental data thermodynamic model calculations and dissolved concentrations of fe cu zn h2 and h2s in the lucky strike fluids reinforce the hypothesis of ph redox equilibria for transition metals at relatively oxidizing conditions and temperatures predicted by the empirical fe mn geothermometer in situ ph measurements of the high temperature fluids exiting the seafloor are also consistent with the model calculations

abiogenic fischer tropsch synthesis of hydrocarbons in alkaline igneous rocks fluid inclusion textural and isotopic evidence from the lovozero complex n w russia a detailed fluid inclusion study has been carried out on the hydrocarbon bearing fluids found in the peralkaline complex lovozero petrographic microthermometric laser raman and bulk gas data are presented and discussed in context with previously published data from lovozero and similar hydrocarbon bearing alkaline complexes in order to further understand the processes which have generated these hydrocarbons ch4 dominated inclusions have been identified in all lovozero samples they occur predominantly as secondary inclusions trapped along cleavage planes and healed fractures together with rare h2o dominant inclusions they are consistently observed in close association with either arfvedsonite crystals partially replaced by aegirine aegirine crystals or areas of zeolitization the majority of inclusions consist of a low density fluid with ch4 homogenisation temperatures between 25 and 120 c those in near surface hand specimens contain ch4 h2 up to 40 mol higher hydrocarbons however inclusions in borehole samples contain ch4 higher hydrocarbons h2 indicating that at depth higher hydrocarbons are more likely to form estimated entrapment temperatures and pressures for these inclusions are 350 c and 0 2 0 7 kbar a population of high density liquid ch4 dominant inclusions have also been recorded mainly in the borehole samples homogenising between 78 and 99 c these consist of pure ch4 trapped between 1 2 and 2 1 kbar and may represent an early ch4 bearing fluid overprinted by the low density population the microthermometric and laser raman data are in agreement with bulk gas data which have recorded significant concentrations of h2 and higher hydrocarbons up to c6h12 in these samples these data combined with published isotopic data for the gases ch4 c2h6 h2 he and ar indicate that these hydrocarbons have an abiogenic crustal origin and were generated during postmagmatic low temperature alteration reactions of the mineral assemblage this would suggest that these data favour a model for formation of hydrocarbons through fischer tropsch type reactions involving an early co2 rich fluid and h2 derived from alteration reactions this is in contrast to the late magmatic model suggested for the formation of hydrocarbons in the similar peralkaline intrusion ilimaussaq at temperatures between 400 and 500 c

fischer tropsch synthesis of hydrocarbons during sub solidus alteration of the strange lake peralkaline granite quebec labrador canada abstract the composition of the carbonic phase s of fluid inclusions in pegmatite quartz from the strange lake peralkaline complex has been analysed by gas chromatography using online extraction of inclusion contents and a poraplot q capillary column the measured gas species are in order of abundance ch 4 h 2 c 2 h 6 co 2 n 2 ca n c 4 h 10 n c 5 h 12 c 2 h 2 i c 4 h 10 and c 2 h 4 minor amounts of i c 5 h 12 n c 6 h 14 i c 6 h 14 and neo c 6 h 14 were also detected but not quantified in some samples a suite of quartz samples from ca metasomatised pegmatites contains fluid inclusions with a similar distribution of hydrocarbons but much higher proportions of c0 2 the carbonic fluid coexisted immiscibly with a brine salvi and williams jones 1992 which on the basis of field and petrographic evidence was interpreted to have originated from the magma however thermodynamic calculations indicate that the above gas species specifically the hydrocarbons could not have coexisted at equilibrium in the proportions measured at any geologically reasonable conditions either prior to or post entrapment we propose instead that the gas compositions measured in the strange lake inclusions and in inclusions from other alkalic complexes resulted from the production of h 2 during the alteration of arfvedsonite to aegirine and the subsequent reaction of this h 2 with orthomagmatic c0 2 and co to form hydrocarbons in a magnetite catalysed fischer tropsch synthesis locally influx of an oxidised calcic brine derived externally from the pluton altered the original composition of the fluid by converting hydrocarbons to c0 2

hydrothermal hydrocarbon gases 2 application in the east african rift system hydrocarbon gases are ubiquitous in the hydrothermal systems of the east african rift system ears though often found at very low concentrations in the volcanic eastern branch as compared to the sedimentary western branch study of the chemical and isotopic compositions of these hydrocarbons from sites in kenya ethiopia djibouti and uganda reveals considerable homogeneity over hundreds of km of the various rift units consideration of c and he isotopic evidence points to a predominantly crustal thermogenic origin for the hydrocarbons there being no evidence of mantle inputs in either the morb or hotspot sectors of the ears temperature information from geothermal wells has been utilised to investigate the relationship between reservoir temperatures and ratios of ch4 to c2h6 the general c1 c2 geothermometric relationship proposed in part 1 of this study holds reasonably well and is shown to give results equal to or better than the inorganic gas geothermometers presently in use both in the wellfields and undeveloped high enthalpy geothermal areas results from low enthalpy hot spring systems are less well correlated with apparent deep temperatures but consistent with data from similar systems elsewhere in the world

transport of rare earth elements by hydrocarbon bearing brines implications for ore deposition and the use of rees as fluid source tracers abstract low temperature 100 160 c hydrocarbon bearing brines mobilize ree at concentrations up to several thousand ppm total rare earth elements ree at el hammam morocco the major element chemistry na ca mg and temperature of the fluids in this system are consistent with those of oil field brines in contrast ree concentrations in the fluid suggest a significant element input from a magmatic source spatially related lamprophyres predating the formation of el hammam share a similar trace element signature therefore hydrocarbon bearing basinal brines seem to have leached some of these elements through fluid rock interaction from the lamprophyres supporting the ability of oil field brines to mobilize not only base metals as in mississippi valley type mvt deposits but also rare earth elements the stability constants of ree aqueous complex at temperatures of 100 160 c the chemistry of oil field brines worldwide and the partitioning behavior of ree between fluorite and water at el hammam indicate that acetate carbonate and fluoride are likely to be major contributors to ree mobilization in these settings the direct implications of the low temperature transport of ree by oil bearing brines is that in systems where these kind of fluids occur the ree signature observed may not reflect the source of the fluid as much as a combination of fluid source and fluid rock interaction in addition oil field brines can efficiently scavenge transport and deposit ree leading to anomalously high accumulations such as the el hammam fluorite deposit and may also contribute to ree mobilization and concentration in other systems

the magmatic and fluid evolution of the motzfeldt intrusion in south greenland insights into the formation of agpaitic and miaskitic rocks the 1 275 ga motzfeldt intrusive complex in the gardar failed rift province in south greenland formed from six successively intruding melt batches sm1 sm6 interpreted to be derived from a common magma source at depth five units sm1 sm5 crystallized an alkaline to peralkaline miaskitic mineral assemblage of amphibole clinopyroxene feldspar nepheline fe ti oxides zircon apatite fluorite and rarely olivine the last magmatic batch sm6 is characterized by an agpaitic mineral assemblage of aegirine nepheline alkali feldspar eudialyte and rare fluorite or sodalite coexisting mafic minerals constrain the crystallization conditions of the miaskitic rocks to about 850 6008c whereas solidus temperatures below 5008c are indicated by coexisting alkali feldspars in the agpaitic rocks oxygen fugacities during the orthomagmatic stage are below the fmq fayalite magnetite quartz buffer fmq 0 5t o 2 0 whereas late hematite provides evidence of a higher relative oxygen fugacity during late stage alteration the nd and oxygen isotope compositions of amphiboles and pyroxenes are homogeneous throughout the complex and suggest a common mantle derived magma source for all six units which is comparable with other gardar intrusions the hydrogen isotopic composition of amphiboles dd 99 to 132 indicates lowtemperature fluid rock interaction with low fluid rock ratios fluid inclusion studies indicate that h2o nacl fluids present during the magmatic stages in the miaskitic units had salinities of510 wt nacl eq calcite crystals in fluid inclusions within these rocks suggest that co2 or hco3 was an important component of the original fluid phase in contrast the agpaitic unit is characterized by a ch4 h2o naclfluid the c o h isotope compositionsofthefluid inclusions in all units are consistent with mixing between a small volume of magmatic fluid and a large volume of meteoric water the chemical evolution of the motzfeldt complex is a type example of the connection of the transition from miaskitic to agpaitic mineral assemblages with redox dependent fluid solid equilibria thetransitionfromarelatively oxidized to a relatively reduced fluid is correlated with a change from a more reduced fe 2 bearing miaskitic taramite arfvedsonite zircon sm1 sm5 to a more oxidized fe 3 bearing agpaitic assemblage aegirine eudialyte sm6 we suggest that coupled fluid solid redox equilibria involving fe 2 f e 3 c o2 and ch4 in this case were simply driven by temperature decrease and an overall increase in na k in the melt this observation sheds light on the heavily debated miaskite agpaite transition the combined temperature and compositional effect stabilized fe 3 c h 4 and enhanced the solubility of zr possibly as na zr si o complexes in the latest stage melt sm6 resulting in the crystallization ofan agpaitic mineral assemblage in terms of redox conditions during crystallization the motzfeldt rocks represent an intermediate case in the gardar province between more oxidized co2dominated intrusions such as the syenite carbonatite complex of