geochemical and geological characteristics of the es3l lacustrine shale in the bonan sag bohai bay basin china abstract although extensive studies have been conducted on unconventional shale oil resources in recent years little work has been performed on the resource potential of lacustrine shales the es3l lower sub member of the third member of the eocene shahejie formation shale of the bonan sag a set of thick lacustrine deposited sediments offers a good example for furthering the understanding of these rocks geochemical and mineralogical investigations were carried out on a large sample set from the 220 m thick sequence of well luo69 in total 200 core samples were analyzed for total organic carbon toc and rock eval pyrolysis and 421 core samples were analyzed for mineral compositions the es3l shales have a very high toc content with type i lacustrine oil prone kerogen in the early oil generation stage rock eval tmax suppression is evident in the lower part of the es3l member associated with a rise in pi production index with respect to fracability or brittleness the content of brittle minerals in the es3l shale is generally higher than that of marine shales in the usa with higher calcite mineral averaging 51 82 wt and lower clay content averaging 18 86 wt interparticle pores in minerals grains or clay aggregates intraparticle pores intercrystalline dolomite and pyrite framboid and four types of fractures tectonic fractures abnormal pressure fractures clay shrinkage fractures and inter laminar fractures are developed in the es3l shale organic matter pores are not present in the studied samples probably due to lower maturity tectonic fracture may play an important role in hydrocarbon migration and accumulation the results of this study suggest that the es3l shale in the bonan sag has very good shale oil potential especially in the lower section

platinum group minerals in the skouries cu au pd pt te porphyry deposit the skouries deposit is a platinum group element pge enriched cu au porphyry system located in the chalkidiki peninsula greece with associated ag bi and te enrichment the deposit is hosted by multiple porphyritic monzonite and syenite intrusions which originated from a magma chamber at depth an initial quartz monzonite porphyritic intrusion contains a quartz magnetite chalcopyrite pyrite vein stockwork with intense potassic alteration the quartz monzonite intrusion is cross cut by a set of syenite and mafic porphyry dykes and quartz chalcopyrite bornite magnetite veins which host the majority of the cu and au mineralisation late stage quartz pyrite veins with associated phyllic alteration crosscut all previous vein generations electron microprobe and scanning electron microscopy shows that the pge are hosted by platinum group minerals pgm in the quartz chalcopyrite bornite magnetite veins and within potassic alteration assemblages the pge mineralisation in skouries is therefore part of the main high temperature hypogene mineralisation event platinum group minerals at skouries include sopcheite ag4pd3te4 merenskyite pd pt te bi 2 and kotulskite pd te bi with rare telargpalite pd ag 3te isomertieite pd11sb2as2 naldrettite pd2sb testibiopalladite pdte sb te and sobolevskite pdbi the most common platinum group mineral is sopcheite the pgm in skouries are small 52 m2 on average and occur as spherical grains on the boundaries between sulphides and silicates and as inclusions within hydrothermal quartz and sulphides these observations support a semi metal collector model whereby an immiscible bi te melt acts as a collector for pge and other precious metals in high temperature hydrothermal fluids this mechanism would allow the formation of pgm in porphyries without pt and pd fluid saturation

organic molecules formed in a primordial womb primordial organic molecules may have evolved in seafloor hydrothermal systems by mineral catalysis most organic compounds decompose in 300 c vent fluid however we show that smectite type clays can protect and promote development of diverse organic compounds that may be precursors to biomolecules smectite provides a safe haven for the synthesis of organic molecules essentially like a primordial womb our experiments simulated seafloor hydrothermal conditions 300 c 100 mpa and reacted common clays montmorillonite saponite illite with dilute methanol as a source of c montmorillonite reacts under these conditions to illite while the other clays do not change we observed increased organic synthesis over time with montmorillonite during mineralogical reaction approaching equilibrium smectite contracts and organic molecules are expelled organic compounds unstable in hot fluid where the smectite reacts may survive in cooler waters outside the vent

clay organic association as a control on hydrocarbon generation in shale abstract programmed pyrolysis experiments investigating the influence of the mineral matrix on hydrocarbon generation from organic compounds have shown inconclusive results in past studies this study tests the hypothesis that the inhibitory vs catalytic influence of clay minerals is dependent on the physical association of the mineral matrix with organic compounds by comparing natural samples from two shale formations with different mineral organic associations samples from the miocene monterey formation have a greater area of surface contact between organic matter and mineral surfaces when compared to the more particulate texture and discrete nature of the organic matter in the samples from the permian stuart range formation comparison of kerogen extracts to the whole rock containing mineral and organic matter samples during programmed pyrolysis shows higher hydrocarbon generation from isolated kerogen compared to the whole rock sample it was extracted from in both the monterey and the stuart range formation samples the difference between extracted kerogen and whole rock samples is greater and more variable 56 210 mghc gtoc in the stuart range than the monterey formation 85 142 mghc gtoc implying greater hydrocarbon retention by the free mineral surfaces the temperature of maximum hydrocarbon generation rock eval t max is greater in whole rock than kerogen isolates 20 c mean in the monterey formation samples but shows negligible difference 2 c mean in the samples from the stuart range formation standard kerogen typing using rock eval pyrolysis data places the same kerogen as type ii to type iii on a modified van krevelen diagram depending whether it is isolated or pyrolysed with its mineral host this study identifies that not only the bulk mineralogy and kerogen type but also the degree of surface contact of the phases influence hydrocarbon generation

the largest au deposits in the st ives goldfield yilgarn craton western australia may be located in a major neoarchean volcano sedimentary depo centre the largest neoarchean gold deposits in the world class st ives goldfield western australia occur in an area known as the argo junction region e g junction argo and athena why this region is so well endowed with large deposits compared with other parts of the st ives goldfield is currently unclear because gold deposits at st ives are hosted by a variety of lithologic units and were formed during at least three different deformational events this paper presents an investigation into the stratigraphic architecture and evolution of the argo junction region to assess its implications for gold metallogenesis the results show that the region s stratigraphy may be subdivided into five regionally correlatable packages mafic lavas of the paringa basalt contemporaneously resedimented feldspar rich pyroclastic debris of the early black flag group coarse polymictic volcanic debris of the late black flag group thick piles of mafic lavas and sub volcanic sills of the athena basalt and condenser dolerite and the voluminous quartz rich sedimentary successions of the early merougil group in the argo junction region these units have an interpreted maximum thickness of at least 7 130 m and thus represent an unusually thick accumulation of the neoarchean volcano sedimentary successions it is postulated that major basin forming structures that were active during deposition and emplacement of the voluminous successions later acted as important conduits during mineralisation therefore a correlation exists between the location of the largest gold deposits in the st ives goldfield and the thickest parts of the stratigraphy recognition of this association has important implications for camp scale exploration

modeling deep water renewal in lake baikal temperature dissolved oxygen nutrients and chlorofluorocarbon 12 data obtained from lake baikal are used to describe deep water renewal in a deep temperate latitude lake observations are used to propose the physical mechanism governing convection and to formulate a model of deep ventilation the key physical mechanism governing deep water renewal is the so called thermobaric instability because the temperature of maximum density decreases with depth a lake can become conditionally unstable if the base of the cold mixed layer is displaced to a depth at which its temperature matches the local temperature of maximum density thereby resulting in sinking plumes an important consequence of this phenomenon is that deep temperate lakes such as baikal do not completely mix twice yearly instead deep ventilation is episodic a two dimensional model of a wind and buoyancy driven lake shows many strong mixing events and a fairly realistic seasonal cycle indicating that the hypothesis is physically realizable a filling box model is used to deduce the annually averaged fluxes necessary to produce a steady vertical distribution of tracers as observed good fits are obtained to oxygen and chlorofluorocarbon distributions by this model about 50 of the world s liquid freshwater is contained in the large deep lakes located in the temperate latitudes between 45 and 65 n see hutchinson 1957 of fundamental importance to such lakes is their ventilation time the time scale associated with renewal of deep water for it is the deep convection process that most strongly controls the internal redistribution of scalar properties such as dissolved oxygen nutrients and anthropogenic pollutants see wiiest et al 1988 however surprisingly few attempts to study and quantify ventilation in deep

metallogenic efficiency from deposit to region a case study in western zhejiang province southeastern china abstract metallogenic ore efficiency can be defined as the ratio of metal reserves to its total supply and we expanded a typical efficiency calculation model available at the single mineral scale to the regional scale a new cell based model was developed by analogy and by taking some other influences into account i a thicker sedimentary cover ii regional ore and rock controlling structures and their intersections iii the crustal heterogeneity unrelated and related to ores and iv metallic geochemical anomalies finally a regional contour map of weighted efficiency which is essential to metallogenic prediction was obtained it shows that the efficiency anomalies can provide a much better target area for ore positioning than do metallic content anomalies and greater ore efficiency may indicate the likelihood of occurrence of mineral deposits that are larger in size reserves taking northwestern zhejiang province as a case study in which the geochemistry of mesozoic porphyries plausibly show considerable mineralized potential we found that due to the lower magmatic temperature delayed exsolution of the hydrothermal solution and very thick sedimentary cover the cu polymetal ore efficiency associated with granitic plutons in this area is generally low the relatively higher ore productivity efficiency appears mainly in and around small rock bodies rock margins and the contacting zone between different lithologies most ore spots no matter their size fall into areas with nonzero efficiency values there seems to be no interdependence between most ore spots of smaller size and ore efficiency whereas efficiency is essential to regional small and medium scaled metallogensis

hydrothermal alteration and mineralization of the galore creek alkalic cu au porphyry deposit northwestern british columbia canada the late triassic galore creek porphyry district is the largest accumulation of cu au prospects in british columbia canada in terms of contained metal the principal economic resource is the central zone deposit it comprises three high grade centers the au rich north and south gold lenses and the cu dominated central replacement zone alteration footprints ore shells and porphyry intrusions in these centers dip 45 to 60 to the west in the north gold lens and southwest in the south gold lens and central replacement zone indicative of significant postmineral tilting this inclination created an oblique vertical expression of the central zone at surface and at depth providing a 700 m depth profile through the deposit galore creek is considered to be the end member of the silica undersaturated class of alkalic porphyry cu au deposits it displays a unique hydrothermal alteration footprint generally devoid of quartz veining despite the lack of crosscutting veins a paragenetic sequence of several discrete potassic and calcic alteration events has been established during main stage alteration two mineralization events occurred that formed the economic resource in the central zone highly oxidizing fluids derived from porphyritic syenite to monzonite intrusions produced initial potassic alteration and sulfide mineralization in the north gold lens and south gold lens cu au ore shells are characterized by a gold rich core dominated by bornite associated with hematite dusted orthoclase specular hematite and anhydrite the second period of hydrothermal activity caused brecciation and calcic alteration in the central replacement zone the calcic fluids formed hydrothermal cement grading from ti rich andraditic to grossularitic garnet in the core of the breccia to a diopside and magnetite dominated assemblage at the margins calcic alteration also formed in the surrounding host rock this alteration event was followed by potassic alteration and mineralization characterized by biotite anhydrite and chalcopyrite in the cu rich ore shell of the central replacement zone most of the au is hosted in bornite that is spatially associated with oxidized reddened rock units dominated by an alteration assemblage of orthoclase hematite specular hematite garnet anhydrite high grade cu in the central zone is related to abundant chalcopyrite that has commonly replaced an assemblage of biotite magnetite diopside this distinct spatial separation strongly suggests that the local redox environment within the wall rocks governed sulfide and gold distributions the switch from early au rich mineralization to late stage cu dominated mineralization appears to have been controlled by varying redox conditions within the magma the change from more oxidized alteration assemblages fe3 fe2 to more reduced assemblages fe3 fe2 is indicative of a change in oxidation potential that may have propelled sulfide saturation in the magma and thus the subsequent depletion of most of the au

genesis and exploration implications of epithermal gold mineralization and porphyry style alteration at the endeavour 41 prospect cowal district new south wales australia endeavour 41 is a deep level structurally controlled epithermal gold deposit hosted by early ordovician subaqueous volcanosedimentary rocks calc alkalic to shoshonitic mafic to intermediate sills dikes and stocks intruded the volcanosedimentary units in the middle ordovician the most felsic intrusions together with pyroxene bearing dikes are temporally related to gold mineralization postmineralization intrusions are exclusively of mafic character endeavour 41 evolved from early high temperature porphyry style veins and alteration to lower temperature epithermal style gold mineralization early magnetite and garnet bearing veins stage 1 and 2 respectively associated with actinolite magnetite and biotite bearing alteration assemblages have been cut by gold bearing veins and associated alteration assemblages there were two main epithermal style gold mineralizing events 1 quartz pyrite calcite adularia chlorite veins stage 3 and 2 carbonate base metal sulfide veins calcite ankerite quartz pyrite sphalerite galena chalcopyrite ag tellurides arsenopyrite apatite hematite illite muscovite and chlorite stage 4 gold occurs principally as a refractory phase in pyrite it also occurs as grains of au ag tellurides and as inclusions of free gold in pyrite sphalerite and chalcopyrite hydrothermal alteration associated with gold mineralized veins produced early epidote and k feldspar epidote bearing alteration halos and later stage illite muscovite k feldspar and calcite rich alteration halos the highest gold grades are associated with muscovite and illite alteration stable isotope analyses and fluid inclusion data provide evidence of a magmatic hydrothermal component to the mineralizing fluids fluid inclusion data suggest that gold precipitated from boiling saline waters 9 0 wt nacl at temperatures of about 310 c stage 3 veins are estimated to have formed approximately 1 km below the paleosurface at hydrostatic pressure 90 bars stage 4 illite formed at temperatures below 280 c stage 3 calcite has 13 c calcite and 18 o calcite values that range from 5 2 to 4 6 and from 11 6 to 12 1 respectively calculated fluids for these mineral values at 300 c 13 c fluid 3 18 o fluid 6 are consistent with a magmatic hydrothermal source of carbon and oxygen during stage 3 a component of meteoric waters is inferred for stage 4 because 13 c carbonate and 18 o carbonate values range from 6 9 to 0 5 and from 10 9 to 30 1 respectively corresponding to 13 c fluid and 18 o fluid values of 5 and 2 at 200 to 250 c the 34 s sulfide values for early vein stages range between 4 9 and 0 5 stage 3 has 34 s sulfide values ranging from 5 2 to 0 8 with the most 34 s enriched values deposited away from the mineralized center stage 4 sulfides have isotopic compositions from 7 5 to 2 5 the negative isotopic values are consistent with oxidized sulfate predominant magmatic hydrothermal fluids sulfur isotopic zonation patterns show that the most negative 34 s values correlate with gold enriched domains and also with areas that contain high temperature porphyry style alteration facies the negative sulfur isotope values define zones of upflow for the mineralizing magmatic hydrothermal fluids the paragenetic history of endeavour 41 records a transition from deep level to shallow level magmatic hydrothermal activity this transition implies erosion and unroofing of the system synchronous with mineralization high temperature assemblages e g actinolite magnetite biotite and k feldspar epidote indicate that epithermal mineralization occurred proximal to a magmatic hydrothermal center and that there is potential for the discovery of porphyry copper gold mineralization below the current level of diamond drilling

porphyry gold copper mineralisation in the cadia district eastern lachlan fold belt new south wales and its relationship to shoshonitic magmatism the cadia porphyry gold copper district is the largest hydrothermal intrusion related gold deposit in eastern australia discovered in 1992 by newcrest mining limited pre mine resources in the district were in excess of 585 t au and 2 35 mt cu the cadia district lies within shoshonitic subaqueous volcanic rocks of the late ordovician molong volcanic belt in the eastern lachlan fold belt lfb of new south wales an island arc tectonic setting is envisaged for the formation of these volcanic rocks but the nature of the arc basement and geometry of the subduction zone s is debated mineralisation occurs in four principal porphyry deposits cadia hill cadia ridgeway cadia east cadia far east and cadia quarry as sheeted and stockwork quartz sulfide veins and locally as broadly stratabound disseminated mineralisation cadia east and skarn big cadia and little cadia all of the porphyry deposits show a close spatial association with shoshonitic monzodiorite to quartz monzonite dykes and stocks of the cadia intrusive complex cic gold copper mineralisation is hosted by these intrusions and also by the enclosing forest reefs volcanics frv wall rocks hydrothermal alteration associated with mineralisation is potassic which is overprinted by selectively pervasive propylitic and silica albite assemblages petrological studies and major and trace element analysis of rocks of the cic and frv as well as of other intrusions in the cadia district that appear unrelated to mineralisation have been conducted unaltered samples from the cic are characterised by high k2o contents up to 6 5 wt and molecular k na ratios consistently 1 confirming the alkalic and shoshonitic nature of the complex the cic samples also fall just within the shoshonite field on ce yb ta yb and th yb ta yb plots although immediately adjacent to the calc alkaline field the frv are geochemically similar to the cic although lower in p2o5 and ce lree dacitic and hornblende porphyry intrusions from within the district but spatially unrelated to mineralisation have a distinctive geochemical signature and are not shoshonitic in composition the close spatial association between gold copper mineralisation and the shoshonitic monzonitic cic argues strongly for a genetic link between the two a similar association occurs at the economic goonumbla porphyry gold copper deposits in the eastern lfb while sub economic gold copper mineralisation at cargo and copper hill is associated with calc alkaline quartz diorite and dacitic intrusions the cadia district is considered to be an excellent example of the association of alkaline potassic magmas and gold copper porphyry style mineralisation

subepithermal au pd mineralization associated with an alkalic porphyry cu au deposit mount milligan quesnel terrane british columbia canada at the mount milligan cu au porphyry deposit quesnel terrane british columbia canada barren and weakly mineralized late stage hydrothermal veins occur in volcanic rocks adjacent to zones of cu au porphyry mineralization and have overprinted the porphyry stage veins the earliest of the late stage hydrothermal veins are barren and consist of quartz pyrite carbonate chlorite tourmaline these veins are similar to transitional to late stage hydrothermal veins in other alkaline porphyry cu au deposits and we consider these to be the equivalent of transitional post porphyry pre epithermal quartz sericite pyrite veins in calc alkaline porphyry environments a later generation of volumetrically minor mineralized veins are composed of pyrite hg and as bearing quartz carbonate chlorite and contain early electrum arsenopyrite tetra hedrite tennantite platinum group element pge tellurides galena sphalerite barite and chalcopyrite as inclusions in pyrite and a later assemblage of electrum pge tellurides arsenides and antimonides galena sphalerite chalcopyrite and various au ag te bi minerals in annealed fractures and open space infillings in quartz and pyrite metal precipitation in these veins was temporally and spatially associated with the deposition and later recrystallization of pyrite primary fluid inclusions in quartz in the barren and weakly mineralized veins are two phase l v homogenize to liquid over a narrow range in t 170 270 c n 96 12 veins and show a wide range in salinity 4 2 wt nacl equiv to 28 7 wt cacl2 equiv when all samples are considered however individual veins show narrow ranges in salinity and homogenization temperature la icp ms analyses indicate that the fluids were highly enriched in as to 2 260 ppm sb to 230 ppm b to 5 400 ppm au 1 2 ppm and pd 0 5 1 ppm but depleted in cu 80 ppm compared to typical porphyry stage fluids metal ratios in the fluids overlap with bulk rock metal ratios in the mineralized veins the inclusions are interpreted to contain a contracted magmatic vapor produced by boiling that lost cu during the formation of porphyry stage veins at depth fluids show decreasing b as sb and increasing sr ca and salinity with time stable c o and h isotope analyses of vein minerals indicate that mixing of this magmatic fluid with meteoric water was not responsible for metal deposition rather metal precipitation was possibly the result of mixing of the magmatic derived fluid with a heated saline groundwater the precious and accessory metal mineralogy of the hydrothermal veins is similar to that found in low to intermediate sulfidation epithermal systems fluid inclusion microthermometry and chlorite thermometry constrain the approximate formation conditions of the veins between 200 and 1 500 bars and 240 and 280 c after the formation of the mineralized veins circulation of low salinity metal depleted fluids occurred these latest stage fluids may have formed by mixing of the saline magmatic fluid groundwater hybrid with meteoric water the results of this study suggest a genetic link between porphyry stage events and the deposition of au and pge in late stage veins in an alkalic igneous environment recognition of hydrothermal processes involving the transport of au pge as sb bi te b rich fluids in the subepithermal regimes implies that low sulfidation epithermal au deposits may have been present in the shallower parts of the magmatic hydrothermal complex and that there is potential for the discovery of pge rich epithermal veins in less deeply exhumed terranes on the other hand the formation of high grade low sulfidation epithermal au pge deposits may be prohibited if porphyry epithermal transitional fluids precipitate ore metals through mixing with groundwater prior to reaching the level where meteoric water mixing and epithermal boiling normally occur

direct evidence for organic carbon preservation as clay organic nanocomposites in a devonian black shale from deposition to diagenesis abstract the burial of marine sourced organic carbon oc in continental margin sediments is most commonly linked to oceanographic regulation of bottom water oxygenation anoxia and or biological productivity here we show an additional influence in the devonian woodford shale in which oc occurs as nanometer intercalations with specific phyllosilicate minerals mixed layer illite smectite that we term organo mineral nanocomposites high resolution transmission electron microscopic hrtem images provide direct evidence of this nano scale relationship while discrete micron scale organic particles such as tasmanites algal cysts are present in some lamina a strong relation between total organic carbon toc and mineral surface area msa over a range of 15 toc indicate that the dominant association of organic carbon is with mineral surfaces and not as discrete pelagic grains consistent with hrtem images of nanocomposites where periods of oxygenation are indicated by bioturbation this relationship is modified by a shift to lower oc loading on mineral surfaces and reduced msa variability likely resulting from biological mixing and homogenization of the sediment oxidative burn down of oc and or stripping of oc from minerals in animal guts the toc msa relationship extends across a range of burial depths and thermal maturities into the oil window and persists through partial illitization where illitization occurs the loss of mineral surface area associated with the collapse of smectite interlayer space results in a systematic increase in toc msa and reorganization of organic carbon and clays into nano scale aggregates while the woodford shale is representative of black shale deposits commonly thought to record heightened marine productivity and or anoxia our results point to the importance of high surface area clay minerals for oc enrichment given that the vast majority of these clay minerals are formed in soils before being transported to continental margin settings their mineralogy and attendant preservative potential is primarily a function of continental climate and provenance making these deposits a sensitive recorder of land as well as oceanographic change

evolution of hydrothermal fluid characteristics at the santa rita new mexico porphyry copper deposit mineralogic and fluid inclusion investigations conducted in the laboratory combined with in situ observations of temporal relationships among geologic features demonstrate that systematic changes in hydrothermal fluid characteristics occurred with time during evolution of mineralization and alteration of the granodiorite stock at the santa rita porphyry copper deposit the earliest fluids to circulate are recorded in potassically altered orthoclase and biotite stable veins as vapor rich h 2 o co 2 inclusions and hypersaline 30 70 equiv wt nacl or kcl inclusions which homogenize over a wide temperature range from 240 degrees to greater than 800 degrees c the high salinity fluid inclusions are complex chloride brines with significant concentrations of sodium potassium copper iron and sulfur but sulfide minerals are not associated with the early potassic assemblage produced by this fluid oxygen isotope ratios of quartz in the orthoclase and biotite stable veins are identical to phenocryst quartz in the intrusion 8 2ppm later solutions circulated through newly formed fractures and older reopened veins and are recorded in low salinity less than 15 equiv wt nacl fluid inclusions which homogenize primarily in the temperature range of 220 degrees to 360 degrees c these hydrothermal fluids formed two distinct alteration assemblages as they reacted with potassically altered rock chlorite is the dominant silicate gangue mineral of the earlier chalcopyrite bearing orthoclase and clay stable assemblages and sericite characterizes the later phyllic alteration assemblage with quartz and pyrite oxygen isotope ratios of quartz of the later assemblages 8 6 10 4ppm are heavier than quartz of the earlier potassic assemblages it is concluded that the earliest hydrothermal fluids to circulate within the stock localizing the orebody at santa rita could have been derived by phase separations of fluids exsolved from crystallizing magma into condensed hypersaline liquids and h 2 o co 2 vapors as these fluids moved through fractures potassic alteration of rock occurred without concomitant deposition of sulfides later solutions of dominantly meteoric origin progressively formed hypogene copper mineralization associated with chlorite stable alteration and then phyllic alteration

mobility and h2o loss from fluid inclusions in natural quartz crystals petrographic observations on quartz crystals from the mole granite australia and other localities shed new light on the mechanisms of post entrapment modification of fluid inclusions these modifications include migration away from pseudosecondary trails changes in fluid salinity and density shape distortion and the formation of sweat haloes around strongly deformed inclusions increases in fluid salinity which usually are associated with inclusion migration indicate water losses of up to 50 however la icp ms analysis of unmobilized and mobilized inclusions of the same trail reveals basically unchanged ratios of major and trace element cations with the exception of li which seems to be incorporated into the crystal lattice during migration despite the fact that all these modifications are closely related to deformation processes they occur not only in mechanically deformed quartz but also in free standing crystals in the latter samples stress has been generated internally as a result of brazil twinned growth and compositional zonation these observations and their interpretation leads to a list of practical criteria that should help in differentiating between reliable and suspect fluid inclusions in other samples

platinum group minerals in the santo tomas ii philex porphyry copper gold deposit luzon island philippines mineralized quartz diorites of the santo tomas ii porphyry copper gold deposit carry high au contents average 1 8 ppm as well as 160 ppb pd and 38 ppb pt values of other platinum group elements pge and rhenium are below the analytical detection limits there is a significant positive correlation between au and cu the highest pd values were detected in the most au and cu rich rocks platinum group minerals pgm occur exclusively as inclusions in chalcopyrite and bornite potential pd and pt contents in sulphide concentrates are estimated at 1 5 g t and 0 4 g t respectively the precious metal assemblages consist of merenskyite main pgm kotulskite moncheite native gold electrum hessite and petzite polyphase fluid inclusions in quartz veinlets associated with a pgm bearing bornite chalcopyrite magnetite assemblage are characterized by high salinity 35 to 60 eq wt nacl and high trapping temperatures between 380 and 520 c they may represent primary magmatic hydrothermal fluids which have been responsible for the transport of pd pt and au as chloride complexes

precious metal mineralogy in porphyry skarn and replacement type ore deposits of the ertsberg gunung bijih district irian jaya indonesia petrographic and electron microprobe analyses of native au and a variety of sulfide minerals indicate a generally high but widely varying native au fineness and a cu fe sulfide host for most ag in the gunung bijih timur complex of cu au skarn deposits the big gossan and dom cu skarn deposits and the grasberg porphyry cu au deposit native au rims bornite in veins and forms inclusions in bornite and chalcopyrite in samples from grasberg and from the gunung bijih timur complex as well as filling open space in quartz veins in the complex skarn and quartz veins in the big gossan area host native au in association with pyrite pyrrhotite galena chalcopyrite sphalerite and arsenopyrite native au from the gunung bijih timur complex has a wide but bimodal range of fineness 920 to 990 and 340 to 820 avg 860 native au from grasberg samples is or 930 fine avg 960 fineness of big gossan au ranges from 540 to 960 avg 830 although compositional ranges are small within most individual samples native au from grasberg falls into two groups with respect to pd pd bearing or 3 500 ppm avg 1 800 ppm and with no detectable pd fire assay of grasberg ore reveals trace but detectable 10 ppb pd 500 ppb avg or 50 ppb concentrations of pd and no detectable pt native au from the gunung bijih timur complex averages twice as much cu as that from grasberg 1 7 vs 0 8 wt cu native au from big gossan has uniformly low cu contents or 1 200 ppm cu avg 300 ppm mass balance calculations and analytical data indicate that the bulk of the ag in the gunung bijih timur complex is contained by bornite indicating a partitioning of ag into bornite relative to native au or a discrete ag mineral this is supported by the consistent positive correlation of cu and ag throughout the gunung bijih timur complex as well as in grasberg and dom ag bearing galena occurs in the big gossan area but is rare in the grasberg the gunung bijih timur complex and the dom orebodies the high fineness of native au from the gunung bijih district represents the upper end of the reported range for porphyry and skarn type cu au deposits but is similar to values reported elsewhere in indonesia the fineness of native au in the gunung bijih timur complex does not appear to be controlled by depth or distance from the local intrusive contact mineral assemblage or paragenetic relationship the fineness of native au from the big gossan area shows a positive correlation with elevation suggestive of a lower temperature more distal character than in the other skarns of the district differences in pd contents may be related to acidity and redox conditions during native au deposition high cu high pd and low ag compositions of au grains in pan concentrates suggest a porphyry or cu skarn source relative to a more distal source compositional characteristics identified in this study may have applications to exploration within the ertsberg district and elsewhere

variation in peperite textures associated with differing host sediment properties peperites formed by mixing of magma and wet sediment are well exposed along punta china baja california mexico where two sills intrude a section of lava flows limestones and volcaniclastic rocks irregular lobes and dikes extend from the sills several meters into host sediments including highly comminuted flow top breccias lithic lapilli tuff breccias and shelly micrites whereas intrusive contacts with lava flows are sharp and planar where one sill intruded both coarse grained volcaniclastic rock and fine grained limestone textural differences between the hosts produced strikingly different styles of peperite blocky masses of the basaltic intrusions up to 1 m in size were dispersed for distances up to 3 m into host lithic lapilli tuff breccias the blocks consequently underwent in situ fragmentation as they were rapidly quenched the high degree of dispersion resulted from steam explosions as the magma enveloped pockets of water in the coarse grained permeable host elutriation of fine grained material from vertical pipes in tuff breccia above the lower sill provides evidence for meter scale fluidization of the host the contact zone between the basaltic magma and the shelly micrite host resembles a mixture of two viscous immiscible fluids fluidal peperite intrusion occurred behind a stable vapor film which entrained lime mud particles and carried them off grain by grain as magma advanced into the host thin section scale elutriation pipes formed microglobular peperite represents a frozen example of a fuel coolant interaction fci between basaltic magma and fluidized micrite host the intimate intermixing of magma and host at the submillimeter level is attributed to fluid instabilities developed along the magma vapor host interface such intimate intermixing of magma and water bearing fragmental debris is commonly a precursory step toward explosive hydrovolcanism

geology mineralization and fluid inclusion characteristics of the chorukh dairon w mo cu skarn deposit in the middle tien shan northern tajikistan abstract the chorukh dairon deposit is part of the metallogenic belt of w mo cu mo au w and au deposits along the late paleozoic active continental margin of the tien shan it is related to the late carboniferous multiphase pluton with successive intrusive phases of early monzogabbro through monzonite quartz monzonite to monzogranite and leucogranite and the latest lamprophyre dikes the deposit is an example of complex w mo cu magmatic hydrothermal system related to magnetite series shoshonitic igneous suite it contains zones of w cu mo oxidized prograde and retrograde skarns with abundant scapolite plagioclase k feldspar andradite garnet magnetite as well as molybdoscheelite and minor chalcopyrite and molybdenite skarns are overprinted by hydrosilicate alteration assemblages with amphibole chlorite epidote quartz calcite scapolite albite scheelite and chalcopyrite and are cut by quartz carbonate barite fluorite sulfide veins the fluid evolution included a release of high temperature 400 500 c high pressure 900 1100 to 700 800 bars high salinity magmatic hydrothermal aqueous chloride fluid with its direct separation from crystallizing magma and formation of prograde and retrograde skarns fluid enrichment in ca up to 15 22 wt cacl 2 at the retrograde skarn stage was possibly related to magmatic differentiation and provided intense molybdoscheelite deposition from a homogenous fluid in contrast hydrosilicate alteration assemblages were formed at lower temperatures 350 400 c initially from a homogenous and then from a boiling ca rich 20 22 wt cacl 2 magmatic hydrothermal fluid with the latter contributing to the most intense scheelite deposition the stable isotope data 13 c co 2 3 0 0 5 and 18 h 2 o 6 5 0 5 34 s 7 5 to 7 7 obtained for the hydrosilicate stage minerals suggest significant fluid sourcing from magmatic and meteoric waters as well as from sedimentary rocks enriched in seawater sulfate possibly evaporites although a strongly homogenous character of the isotopic composition reveals intense isotope homogenization in a magmatic chamber some light sulfur isotope enrichment of sulfides from the quartz carbonate barite fluorite sulfide veins 34 s 6 0 to 6 1 may be linked to the evolution of the magmatic source toward more mantle related sulfur species as these veins were formed after emplacement of the late mafic lamprophyre dikes

the ridgeway gold copper deposit a high grade alkalic porphyry deposit in the lachlan fold belt new south wales australia a discussion sir wilson et al 2003 in their important paper on the ridgeway au cu deposit describe hydrothermal alteration about the ridgeway porphyry ore system however their findings are substantially more valuable if taken into account with the published works on regional burial metamorphism of the district smith 1968 1969 these works described burial metamorphism of the ordovician volcanic sequences including the hosts to the ridgeway deposit based on district and regional zonation of secondary mineral assemblages this discussion briefly presents this context and focuses on the key issue of discriminating the porphyry related hydrothermal alteration from the effects of burial metamorphism because porphyry related hydrothermal minerals and later metamorphic mineral assemblages can be similar their discrimination is crucial in mapping alteration styles as vectors in exploration for concealed ore

illitizing fluids as precursors of hydrocarbon migration along transfer and boundary faults of the jeanne d arc basin offshore newfoundland canada abstract illite content in mixed layer illite smectite i s and the degree of ordering in the fine fraction

unidirectional solidification textures and their significance in determining relative ages of intrusions at the henderson mine colorado a variety of igneous textures displayed by stocks associated with the henderson molybdenite deposit are interpreted to result from unidirectional growth from the walls of magma chambers inward these igneous textures are present in layers and multilayered sequences consisting of crenulate quartz and feldspar pegmatites crenulate quartz dendritic alkali feldspar and quartz and dendritic and micrographic alkali feldspar quartz intergrowths minerals or intergrowths defining a layer within any one stock consistently terminate or branch inward away from the stock contacts the layers are separated by aplite or aplite porphyry and are most common in the apical and marginal parts of an individual stock layering generally parallels intrusive contacts differences in morphologies of phases among the various layers suggest changing conditions of growth from an undercooled melt and or aqueous solution changes in these physical and chemical conditions as the stock crystallized inward produced the observed textural and compositional layering unidirectional solidification textures can be used to determine the relative ages of individual stocks as well as the approximate orientation of stock contacts in the absence of other independent evidence unidirectional textures can also be used to indicate proximity to an intrusive contact these features are an invaluable aid in detailed mapping of multiple intrusion systems in which the units are compositionally identical or nearly identical

sulfur isotopic zonation in the cadia district southeastern australia exploration significance and implications for the genesis of alkalic porphyry gold copper deposits the alkalic porphyry gold copper deposits of the cadia district occur in the eastern lachlan fold belt of new south wales australia the district comprises four porphyry deposits ridgeway cadia quarry cadia hill and cadia east and two iron copper gold skarn deposits big cadia and little cadia almost 1 000 tonnes of contained gold and more than four million tonnes of copper have been discovered in these systems making cadia the world s largest known alkalic porphyry district in terms of contained gold porphyry gold copper ore at cadia is associated with quartz monzonite intrusive complexes and is hosted by central stockwork and sheeted quartz sulfide carbonate vein systems the cadia porphyry deposits are characterized by cores of potassic and or calc potassic alteration assemblages and peripheral halos of propylitic alteration with late stage phyllic alteration mostly restricted to fault zones hematite dusting is an important component of the propylitic alteration assemblage and has produced a distinctive reddening of feldspar minerals in the volcanic wall rocks around the mineralized centers sulfide mineralization is strongly zoned at ridgeway and cadia east with bornite rich cores surrounded by chalcopyrite rich halos and peripheral zones of pyrite mineralization the cadia hill and cadia quarry deposits have chalcopyrite rich cores and pyrite rich halos and cadia hill contains a high level bornite rich zone distinctive sulfur isotopic zonation patterns have been identified at ridgeway cadia hill and cadia east the deposit cores are characterized by low 34ssulfide values 10 to 4 consistent with sulfide precipitation from an oxidized sulfate predominant magmatic fluid at 450 to 400 c pyrite grains that occur in the propylitic alteration halos typically have 34ssulfide values near 0 there is a gradual increase in 34ssulfide values outwards from the deposit cores through the propylitic halos water rock interaction during propylitic alteration caused magmatic sulfate reduction and concomitant oxidation of ferrous iron bearing minerals resulting in enrichment of 34s in pyrite and also producing the distinctive reddened hematite rich alteration halos to the cadia deposits these results show that sulfur isotope analyses have potential applications in the exploration of alkalic porphyry style deposits with zones of depleted 34ssulfide values most prospective for high grade mineralization

distribution of fluid inclusions in igneous quartz of the capitan pluton new mexico usa abstract fluid inclusions in granites have been used extensively in studies of magmatic hydrothermal processes but few studies have documented the distribution of secondary fluid inclusions within the nonmineralized main body of an intrusion previous work on fluid inclusions in th u ree quartz fluorite vein deposits in the capitan pluton suggests that these veins resulted from high temperature high salinity magmatic fluids in fractured and brecciated zones in the cooled outer carapace of the pluton petrographic examination of phenocryst quartz in forty four thin sections of granite from the capitan pluton reveals that these same fluids are found in secondary fluid inclusions fluid inclusions with daughter minerals commonly occur in the outer granophyre and aplite zones but are usually absent in the porphyritic core microthermometric data and calculated salinities from fifty eight fluid inclusions in phenocryst quartz and thirty one fluid inclusions in miarolitic quartz both samples taken from the granophyre zone also correlate fairly well with the data from the th u ree quartz fluorite vein deposits and similar types of fluid inclusions are found in all three occurrences of quartz a major difference however is that vapor rich inclusions abundant as secondary inclusions in igneous phenocryst quartz are extremely scarce in the vein quartz liquid vapor homogenization temperatures of high salinity inclusions in phenocryst quartz range from 204 509 c with an average of 384 c halite dissolution temperatures of high salinity inclusions range from 442 583 c with an average of 525 c total homogenization temperatures are not as well documented due to decrepitation of many of the high salinity inclusions before total homogenization samples of miarolitic quartz appear to contain more low salinity fluid inclusions than the phenocryst quartz but high salinity inclusions are present as well these observations suggest that the magmatic hydrothermal fluids responsible for vein mineralization were not only concentrated in the vein systems but were also widely dispersed within the outer portions of the pluton furthermore the greater abundance of fluid inclusions in the outer textural zones of the pluton suggests that the interior of the pluton had not yet fully crystallized when these fluids exsolved from the magma

mineral systems prospectivity modelling for gold and nickel in the halls creek orogen western australia abstract geodynamic models geological geophysical interpretations and isotope analysis illustrate that there are links between the nickel and gold mineral systems in the halls creek orogen western australia whole rock nd and 40ar 39ar analysis of rocks throughout the region when compared with the geodynamic models suggest that nickel and gold mineralization in the halls creek orogen can be related to basin development and subsequent basin closure during the convergence of north australian craton and kimberley craton respectively whole rock nd analysis confirmed the input of juvenile melts in the centre of the orogen before the 1835 1805 ma halls creek orogeny supporting the upwelling of decompression mantle melts during the basin development these analyses also revealed the spatial links between nickel and gold mineralization and lithological units with positive end values spatially the link between these mineral systems appears to be related to the presence of deep seated shear zones that formed early in the history of the orogen and were later reactivated the results of geodynamic models geophysical interpretation and isotopic analysis are used to understand the critical processes in the gold and nickel mineralization which are presented by predictor maps the gis based knowledge driven fuzzy logic method used to integrate the predictor maps and create the prospectivity maps herein we show that mafic ultramafic units prospective for nickel mineralization formed by upwelling of decompression mantle melt during crustal thinning and extension during basin development and typically consist of the most juvenile magmas in the region whereas gold deposits formed during the compressional regime and basin closure and are located along a major shear zone separating two terranes this deep crustal scale shear zone is implied to be the site of multiple stages of deformation that acted as fluid migration pathways during basin closure and subsequent collision another critical element that appears to be related to gold prospectivity is the presence of lithologies with a juvenile signature in contrast to nickel analyses which are closely related to mafic ultramafic units the source component seems less influential when attempting to target orogenic gold deposits

endeavour 26 north a porphyry copper gold deposit in the late ordovician shoshonitic goonumbla volcanic complex new south wales australia endeavour 26 north is the largest of 12 pipelike porphyry cu au deposits found near parkes in central west new south wales within the late ordovician goonumbla volcanic complex the dominant volcanic rocks of the complex the goonumbla volcanics are latitic flows and volcanic breccias which are overlain by the trachytic wombin volcanics the volcanic rocks are characterized by high k 2 o and high k 2 o na 2 o ratios which are typical of the shoshonite association as well as an enrichment in large ion lithophile elements and a low concentration of high field strength elements the nelungaloo volcanics form an early ordovician nonshoshonitic volcanic substrate to the complex which initially developed in a submarine and subsequently subaerial setting the 87 sr 66 sr epsilon nd and pb isotope data indicate the magmas were derived from mantle sources the shoshonitic magmas may be products of high pressure fractionation in the subcontinental lithosphere the porphyry deposits are associated with a gravity low which is taken to reflect a subvolcanic chamber beneath the center of the complex all deposits are located within a pronounced circular feature in the aeromagnetic data that is interpreted as the margin of a collapsed caldera dioritic to monzonitic stocks which in part define the caldera rim represent a resurgent phase of magmatism the endeavour 31 stock which was part of this phase is ringed by six porphyry cu au deposits including endeavour 26 north the deposits are centered on fingerlike quartz monzonite porphyries which cut the endeavour 31 stock at depth geochemical anomalies of cu and zn in the bedrock define the size of the alteration system associated with the stock in part the distribution of the cu au deposits is controlled by the endeavour lineament in comparison to most other volcanic and intrusive rocks of the goonumbla volcanic complex the endeavour

influence of organic matter on smectite illitization a comparison between red and dark mudstones from the dongying depression china interactions between organic matter om and clay minerals have received considerable attention in previous studies the influence of om on smectite illitization has been analyzed primarily in simulation experiments rather than in diagenetic studies the present study explores the influence of om on smectite illitization during diagenesis thirty red and dark mudstone samples from the dongying depression were analyzed x ray diffraction xrd analyses revealed that the illite percentages in mixed layer illite smectite i s of both types of samples were dispersive above 3100 m and more convergent below this depth the stacking mode of i s in dark mudstones above 3100 m remained primarily at r0 r0 5 ordering with the average number of layers nave dispersively distributed between 2 and 4 5 in red mudstones the i s changed from the r0 to r0 5 mode with the nave increasing from 2 to 5 over this range the smectite illitization in dark mudstones was slower than that in red mudstones below 3100 m the i s stacking mode of dark mudstones changed from r0 5 to r3 ordering with the nave increasing sharply from 4 to 8 in red mudstones the i s displayed r1 5 and r3 ordering with the nave varying between 4 5 and 6 5 over this range the smectite illitization in dark mudstones accelerated rapidly whereas the process in red mudstones was retarded additionally the red mudstone samples contained little om whereas the dark mudstone samples contained abundant total organic carbon 0 17 4 43 thermo xrd near infrared nir as well as mid infrared mir spectroscopy analyses suggested that the om in dark mudstones exhibited a significant transition at 3100 m coincident with the illitization change above 3100 m the smectite illitization in dark mudstones was delayed due to the om pillar effect in the interlayer spaces of smectite below 3100 m the interlayer om became varied and desorbed discharging organic acid this led to the dissolution of smectite structural layers consequently illitization in the dark mudstone was accelerated this study revealed that the existence and occurrence of om could influence the smectite illitization in diagenesis further study on the interactions between om and clay minerals is needed to facilitate our understanding on the mechanism of smectite illitization as well as its geological applications

critical considerations when assessing hydrocarbon plays using rock eval pyrolysis and organic petrology data data quality revisited abstract the dramatic increase in exploration for unconventional hydrocarbon resources has inherently fuelled the need for new source rock geochemical data the need for new data comes along with an increasing number of new users many of whom do not possess the background to interpret accurately and evaluate the quality of data sets generated by different geochemical screening techniques e g rock eval pyrolysis vitrinite reflectance here datasets from rock eval pyrolysis vitrinite reflectance and leco toc analyses are scrutinized and compared to show how failing to recognize good vs bad datasets can dramatically change interpretations during prospect or play appraisals detector saturation contamination of the sample with drilling fluid and suppression of both tmax and vitrinite reflectance are examples of complications that could compromise the validity of the results and the play or prospect reviews derived from them in addition misconceptions such as leco toc is better than rock eval 6 toc expressed by many users are a consequence of the lack of understanding of how different screening techniques and instrumentation work a solid understanding of these pitfalls and limitations can provide inexperienced geoscientists and engineers with the required support to improve risk maps for hydrocarbon charge analysis and source rock evaluations when using classic guidelines for interpreting results

geology mineralization alteration and structural evolution of the el teniente porphyry cu mo deposit sir the el teniente cu mo deposit in central chile is an extraordinary accumulation of cu mo ore fig 1 and we welcome the opportunity provided by skewes and stern 2007 to discuss and clarify several important issues regarding its classification and interpretation and to address several incorrect assertions that they make regarding our manuscript cannell et al 2005 we have interpreted el teniente to be a typical porphyry deposit in terms of its alteration assemblages vein and breccia styles and spatial and temporal relationships between cu mo mineralization and felsic porphyries skewes and stern 2007 dispute our claims that mineralization occurred primarily in veins and was related to felsic intrusive activity they also take issue with our interpretations of the various geochronological datasets from el teniente and our classification of el teniente as a porphyry cu mo deposit we address each of these in turn below in order to facilitate the following discussion table 1 correlates the geologic nomenclature of skewes and stern 2007 with that of cannell et al 2005 figures 1 and 2 illustrate the location of the main geologic units on underground mine level 6 at el teniente also shown on figure 1 are the approximate locations of the hypogene sulfide mineral zones figure 2 shows the block model of mo grades in the mine for more details of geologic relationships at el teniente refer to figure 4 of cannell et al 2005 and figures 4 and 5 of skewes et al 2002 although the dacite porphyry dike is shown as a single unit on figure 1 note that rojas 2002 2003 mapped multiple phases within this composite intrusive body skewes and stern 2007 criticized our use of what they assert to be an outdated map of hypogene mineralization

effect of pore structure on shale oil accumulation in the lower third member of the shahejie formation zhanhua sag eastern china evidence from gas adsorption and nuclear magnetic resonance abstract as shale oil occurs primarily in micro nano pores and fractures research about the effect of pore structure on shale oil accumulation has great significance for shale oil exploration and development the effect of pore structure on shale oil accumulation in the lower third member of the shahejie formation es 3 l zhanhua sag eastern china was investigated using gas adsorption soxhlet extraction nuclear magnetic resonance nmr analysis and field emission scanning electron microscope fe sem observation the results indicated that the samples contained a larger amount of ink bottle shaped and slit shaped pores after extraction than before extraction the pore volume and specific surface area of the samples were approximately 2 5 times larger after extraction than before extraction residual hydrocarbon occurred primarily in the free state form in pores with diameters of 10 1000 nm which can provide sufficient pore volume for free hydrocarbon accumulation therefore pores with diameters of 10 1000 nm were regarded as oil enriched pores which are effective pores for shale oil exploration whereas pores with diameters smaller than 10 nm were regarded as oil ineffective pores samples with only well developed small pores with diameters smaller than 1000 nm showed high oil saturation whereas samples with both small pores and also relatively large pores and micro fractures presented low oil saturation as the minimum pore size allowing fluid expulsion is 1000 nm pores with diameters greater than 1000 nm were considered as oil percolated pores large pores and micro fractures are generally interconnected and may even form a complex fracture mesh which greatly improves the permeability of shale reservoirs and is beneficial to fluid discharge

impact of hydrocarbon expulsion efficiency of continental shale upon shale oil accumulations in eastern china abstract core samples were taken from two formations the qingshankou formation in northern songliao basin and the third member of the shahejie formation of zhanhua sag to carry out a study of impact of hydrocarbon expulsion from continental shale upon shale oil accumulations in eastern china total organic carbon toc and pyrolysis data of these samples were used to establish an evaluation criterion with absolute and relative oil content indexes for determining oil potential of shale as a result a correspondence relationship between shale oil content and organic types was established factors that may affect oil content of shale were discussed through study of fractures pore development minerals and lithological assemblage of the samples the results show that oil content of mature petroleum source rocks is firstly controlled by fracture growth and secondly by pore development they played both negative and positive roles in hydrocarbon flow and accumulation in shale overpressure caused by hydrocarbon generation and existence of organic acid corrosion are two important factors affecting the formation of fractures and pores in shale respectively intervals with type i organic matter are not favorable shale oil exploration targets because they contain little oil shale with type i organic matter tends to generate large amount of hydrocarbon but these hydrocarbon will escape with a high efficiency through over pressurized fractures caused by hydrocarbon generation and lack of pore space which in turn is the result of absence of oxygen that is essential for forming organic acid to create secondary pores in shale on the contrary intervals with type ii organic matters are potential shale oil exploration targets for that they offered just right conditions for oil to stay inside higher content of oxygen that is helpful in forming organic acid moderate hydrocarbon generation capacity that will not cause over pressurized fractures in shale with secondary pores while intervals with type iii organic matter bear no exploration significance due to the fact that this type of kerogen produces less oil because of low hydrocarbon generation capacity and unfavorable molecular configuration shale intervals with thin sandstone interbeds provide favorable passageways for dissolved carbonate by organic acid to flow out avoiding secondary precipitation the pores left behind can be excellent space for generated hydrocarbon to linger around these interbeds are also favorable for later reservoir stimulation measures such as hydraulic fracturing shale oil exploration shall be focused on finding sweet spots with greater pores which are the main reservoir space

organic matter sequestered in potential energy fields predicted by 3 d clay microstructure model abstract transmission electron microscopy tem observations confirm theoretical predictions of the location of organic matter om sequestered in fine grained sediment organo clay micro and nanoscale fabric images validate for the first time the protective adsorption model of om preservation preservation of om against enzymatic digestion is demonstrated predominately at locations consistent with our model of the potential energy field that is developed through interactions of clay minerals the om and pore water chemistry pores observed in 2 d fabric tem images of clay muds commonly appear to be totally encapsulated however the great majority of these pores are clearly demonstrated to be open in one or more directions when observed in rotated 3 d images despite the scarcity of completely closed pores om is preserved against enzymatic attack in those locations where the predicted 3 d potential energy of interaction between clay domains and om is attractive

smectite illitization difference of source rocks developed in saline and fresh water environments and its influence on hydrocarbon generation a study from the shahejie formation dongying depression china abstract samples of argillaceous source rocks from three sub members of the shahejie formation es in the dongying depression china were collected to investigate the differences in hydrocarbon generation among the sub members which developed in fresh es32 es33 and saline es41 water environments pyrolysis xrd and thermo xrd analyses were used to compare the characteristics of organic matter om clay minerals and om occurrences total organic carbon and hydrocarbon potential proxies suggest that the samples from es33 were much better than the other two intervals which agrees with previous studies the characteristics of clay minerals suggest that the samples from es41 have the most abundant illite with a maximum illite percentage in mixed layer illite smectite i sm and the best crystallinity of i sm with a main stacking mode of r1 5 however the stacking modes of i sm in es32 and es33 were primarily r0 and r1 respectively and the crystallinity was relatively poor thus the smectite illitization process was faster in es41 than in the other two intervals and a saline environment was a primary cause for the acceleration of the process moreover om occurrence indicates that the samples from es41 had the lowest amount of interlayer om whereas es33 had the largest amount therefore the rapid illitization in es41 caused abundant interlayer om to be desorbed and discharged which in turn caused the amount of residual interlayer om in es41 to be less than that in the other two intervals thus the source rocks of es41 made a more significant contribution to hydrocarbon generation than those of the other two units in conclusion the inconsistent illitization among these intervals was a major cause of the differences in hydrocarbon generation

the influence of shale depositional fabric on the kinetics of hydrocarbon generation through control of mineral surface contact area on clay catalysis abstract accurately assessing the temperature and hence the depth and timing of hydrocarbon generation is a critical step in the characterization of a petroleum system clay catalysis is a potentially significant modifier of hydrocarbon generation temperature but experimental studies of clay catalysis show inconsistent or contradictory results this study tests the hypothesis that source rock fabric itself is an influence on clay mineral catalysis as it controls the extent to which organic matter and clay minerals are physically associated two endmember clay organic fabrics distinguish the source rocks studied 1 a particulate fabric where organic matter is present as discrete 5 m particles and 2 a nanocomposite fabric in which amorphous organic matter is associated with clay mineral surfaces at sub micron scale high resolution electron imaging and bulk geochemical characterisation confirm that samples of the miocene monterey formation california are representative of the nanocomposite source rock endmember whereas samples from the permian stuart range formation south australia represent the particulate source rock endmember kinetic experiments are performed on paired whole rock and kerogen isolate samples from these two formations using open system non isothermal pyrolysis at three different heating rates 0 7 2 and 5 k min to determine the effects of the different shale fabrics on hydrocarbon generation kinetics extrapolation to a modelled geological heating rate shows a 20 c reduction in the onset temperature of hydrocarbon generation in monterey formation whole rock samples relative to paired kerogen isolates this result is consistent with the monterey formations s nanocomposite fabric where clay catalysis can proceed because reactive clay minerals are intimately associated with organic matter by contrast there is no significant difference in the modelled hydrocarbon generation temperature of paired whole rock and kerogen isolates from the stuart range formation this is consistent with its particulate fabric where relatively large discrete organic particles have limited contact with the mineral matrix and the clay minerals are mainly diagenetic and physically segregated within pores while heating rate may have a control on mineral matrix effects this result shows that the extent to which organic matter and clay minerals are physically associated could have a significant effect on the timing of hydrocarbon generation and is a function of the depositional environment and detrital vs diagenetic origin of clay minerals in source rocks

the ridgeway gold copper deposit a high grade alkalic porphyry deposit in the lachlan fold belt new south wales australia ridgeway is a high grade gold copper porphyry deposit 54 mt at 2 5 g t au and 0 77 cu related to an alkalic intrusive complex of monzonitic composition the deposit occurs within the cadia district of new south wales australia which consists of a cluster of four late ordovician gold copper porphyry deposits and two iron copper gold skarn deposits with a combined gold resource in excess of 574 metric tonnes t the deposits lie on a 7 km long northwest oriented corridor of alteration and mineralization transverse to the axis of the postulated volcanic arc alteration and mineralization at ridgeway are zoned around a vertically attenuated intrusive complex of monzodioritic to quartz monzonitic composition distinct styles of veining and alteration are related to different intrusive phases of the monzonite complex with the intensity of alteration and grade of mineralization decreasing from early to late mineral intrusions early mineral intrusions are associated with intense actinolite magnetite biotite calc potassic alteration and up to four stages of high grade quartz magnetite sulfide veining bornite is the most abundant sulfide formed during early stage alteration and correlates well with gold moderate to weak intensity orthoclase biotite plus or minus magnetite potassic alteration accompanies the inter and late mineral intrusions this alteration being associated with chalcopyrite and pyrite rich quartz orthoclase veins propylitic and sodic albite pyrite alteration assemblages are peripheral to and locally overprint the potassic alteration phyllic alteration is restricted to the margins of late stage faults the fluid inclusion assemblage comprises one and two salt bearing brine inclusions in addition to aqueous liquid vapor inclusions of low to moderate salinity no low density vapor rich inclusions are present indicating that the fluids from which the quartz veins precipitated did not enter the liquid vapor field of the h2o nacl system the brine inclusions undergo final homogenization to liquid via halite dissolution this phenomenon in addition to the absence of low density vapor inclusions suggests that the mineralizing fluids at ridgeway were nonboiling hypersaline brines that exsolved directly from the crystallizing magma the presence of mineralized aplitic vein dikes and comb quartz layering are interpreted to indicate that the early and transitional stages of mineralization at ridgeway formed at the transition between magmatic and hydrothermal conditions

rapid identification of dolomite using a fourier transform infrared spectrophotometer ftir a fast method for identifying heinrich events in iodp site u1308 this study demonstrates that fourier transform infrared spectrophotometry ftir provides a quick and relatively inexpensive method for identifying and quantifying dolomite in deep marine sediments ftir is used to determine concentrations of dolomite in the top 29 m of sediments recovered at iodp site u1308 some of these dolomite peaks can be reliably correlated with heinrich events h1 through h6 thus ftir appears to provide a fast and reliable method for identifying heinrich events in deep sea sediments

adsorption of mudstone source rock for shale oil experiments model and a case study abstract inorganic minerals were separated from mudstone and shale to investigate their oil adsorption potential a conceptual model was developed to reconstruct the oil adsorption capacity of underground mudrock shale by combining adsorption and organic matter swelling data the predictions for the free hydrocarbon oversaturation sorption zones in the well ny1 profile were taken as a case study the results suggest that the best depth for the shale oil prospect of the es4s member strata lies between 3400 and 3600 m in the dongying depression hydrocarbon starvation zones occur mainly at a depth of

gold in porphyry copper deposits experimental determination of the distribution of gold in the cu fe s system at 400 to 700 c experiments in the system au cu fe s were carried out at temperatures of 400 to 700 c to determine how much gold could be accommodated by bornite and chalcopyrite the two most common ore minerals in porphyry copper gold deposits our results show that for all temperatures bornite contains one order of magnitude more gold than chalcopyrite or intermediate solid solution iss its high temperature equivalent the range of gold concentrations in bornite and chalcopyrite or iss decreases with decreasing temperature from 1 280 to 8 200 ppm au in bornite and 100 to 125 ppm au in iss at 600 c to 235 to 364 ppm au in bornite and 5 to 16 ppm au in chalcopyrite or iss at 500 c and to 13 to 80 ppm au in bornite and 2 to 4 ppm au in chalcopyrite or iss at 400 c the amount of gold in bornite is also strongly dependent on the composition of bornite being highest in stoichiometric bornite compositions cu5fes4 and decreasing toward cu rich and cu poor compositions phase equilibrium constraints for solutions with geologically reasonable reduced sulfur contents indicate that high temperature porphyry copper gold deposits will contain bornite and magnetite whereas lower temperature deposits whether primary or overprinted by phyllic alteration will contain chalcopyrite and pyrite if gold is present in the ore forming solutions more of it will be deposited in high temperature porphyry copper gold deposits where it will be closely associated with bornite coexisting magnetite in these deposits should generate magnetic anomalies lower temperature deposits will contain less gold which is hosted by pyrite as well as chalcopyrite and will lack magnetic anomalies comparison of the amount of gold hosted by natural porphyry copper gold ores to that hosted by bornite and chalcopyrite in our experiments suggests that significant amounts of gold can be lost from these deposits into surrounding hydrothermal systems

the tectonic significance of ordovician magmatism in the eastern lachlan fold belt abstract the shoshonitic rock series is a suite of igneous rocks derived from the mantle and containing high potassium plus low abundances of high field strength elements it is commonly associated with calcalkaline igneous rocks but in most modern examples a contemporary active subduction zone is not present mantle derived shoshonitic magmatism in the lachlan fold belt commenced in the early ordovician and terminated at the end of the ordovician when it was replaced by tholeiitic magmatism and the onset of wholesale melting of the lower to middle crust associated calcalkaline igneous rocks are insignificant the shoshonites are widely distributed across the eastern part of the fold belt in a series of discontinuous belts and volcanic centres the largest of which is the orange wellington belt extending from east of cowra to dubbo the broad geographical distribution is not typical of the curvilinear belts of volcanics associated with subduction zones and would be even greater if the intervening basins or troughs were unfolded all rocks analyzed to date are either clearly shoshonitic or show chemical features that indicate shoshonitic affinities prior to alteration and metamorphism in some areas lavas rich in olivine and clinopyroxene potassic trachybasalts dominate in others the more evolved plagioclase rich shoshonites are most abundant it is suggested that the ordovician magmatism was not accompanied by coeval subduction as has been generally assumed more likely the lithospheric mantle beneath the lachlan fold belt was modified during an earlier subduction event associated with the assembling of the basement blocks recognized from granite studies the cause of melting in the ordovician may be related to lithospheric heating or overturning prior to the upwelling of unmodified asthenosphere the hot 1200 c asthenosphere was the source for the silurian tholeiites and provided conductive heat for the melting of the lower to middle crust

petrography geochemistry and geochronology of the host porphyries and associated alteration at the tuwu cu deposit nw china a case for increased depositional efficiency by reaction with mafic hostrock tuwu is the largest porphyry copper deposit discovered in the eastern tianshan mountains xinjiang china a newly recognized volcanic complex in the early carboniferous qi eshan group at tuwu consists of basalt andesite and diorite porphyry the plagiogranite porphyry was emplaced into this complex at 332 8 2 5 ma u pb zircon sims determination whole rock element geochemistry shows that the volcanic complex and plagiogranite porphyry formed in the same island arc although the complex was derived by partial melting of the mantle wedge and the plagiogranite porphyry by partial melting of a subducting slab the diorite and the plagiogranite porphyries have both been subjected to intense hydrothermal alteration and associated mineralization but the productive porphyry is the plagiogranite porphyry three alteration and mineralization stages including pre syn and post ore stages have been recognized the pre ore stage formed a barren propylitic alteration which is widespread in the volcanic complex the syn ore stage is divided into three sub stages stage 1 is characterized by potassic alteration with chalcopyrite bornite chalcocite stage 2 is marked by chlorite sericite albite alteration with chalcopyrite pyrite bornite stage 3 is represented by phyllic alteration with chalcopyrite pyrite molybdenite the post ore stage produced a barren argillic alteration limited to the diorite porphyry a specific feature of the tuwu deposit is that the productive porphyry was emplaced into a very mafic package and reaction of the resulting fluids with the ferrous iron rich hostrocks was a likely reason that tuwu is the largest porphyry in the district

giant porphyry deposits characteristics distribution and tectonic controls more than half of the 25 largest known porphyry copper deposits defined in terms of contained copper metal formed during three time periods the paleocene to eocene eocene to oligocene and middle miocene to pliocene these giant deposits are clustered within three provinces central chile northern chile and southwest arizona northern mexico other giant deposits occur in montana utah panama peru argentina irian jaya mongolia and iran compressive tectonic environments thickened continental crust and active uplift and erosion were associated with the formation of many of these deposits calc alkalic magmas are most favorable for the formation of giant porphyry copper deposits although several of the largest systems are associated with high k calc alkalic intrusions the 25 largest gold rich porphyry deposits are concentrated in the southwest pacific and south america with other occurrences in eurasia british columbia alaska and new south wales many of the deposits formed in the last 13 m y the largest of the deposits are associated with high k calc alkalic intrusions many calc alkalic porphyritic intrusions have also produced giant gold rich porphyries in the last 20 m y the formation of giant porphyry copper molybdenum and copper gold deposits in the circum pacific region has been closely associated with subduction of aseismic ridges seamount chains and oceanic plateaus beneath oceanic island and continental arcs in several examples these tectonic perturbations have promoted flat slab subduction crustal thickening uplift and erosion and adakitic magmatism coeval with the formation of well endowed porphyry and or epithermal mineral provinces similar tectonic features are inferred to be associated with the giant porphyry copper molybdenum provinces of northern chile eocene oligocene and southwest united states cretaceous paleocene topographic and thermal anomalies on the downgoing slab appear to act as tectonic triggers for porphyry ore formation other factors such as sutures in the overriding plate permeability architecture of the upper crust efficient processes of ore transport and deposition and in some cases formation and preservation of supergene enrichment blankets are also vital for the development of high grade giant ore deposits a low grade geochemical anomaly may be the final product of mineralization if ore forming processes do not operate efficiently even in the most favorable geodynamic settings

mineralogical and chemical distribution of the es3l oil shale in the jiyang depression bohai bay basin e china implications for paleoenvironmental reconstruction and organic matter accumulation abstract the es3l lower sub member of the third member of the eocene shahejie formation shale in the jiyang depression is a set of relatively thick and widely deposited lacustrine sediments with elevated organic carbon and is considered to be one of the most important source rocks in east china we can determine the mineralogy organic and inorganic geochemistry of the es3l shale and calculate paleoclimate indexes by using multiple geochemical proxies based on organic chemistry total organic carbon toc and rock eval pyrolysis major and trace elements x ray diffraction and carbon and oxygen isotope data from key wells alongside ecs elemental capture spectroscopy well log data these indicators can be used to analyze the evolution of the paleoenvironment and provide a mechanism of organic matter om accumulation the es3l oil shale has high toc abundance most samples 3 0 and is dominated by type i kerogens additionally the organic rich shale is rich in cao and enrichment in some trace metals is present such as sr ba and u the positive 13c and negative 18o values high sr ba b ga and ca ca fe ratios and low c s ratios indicate that the es3l shales were mainly deposited in a semi closed freshwater brackish water lacustrine environment the consistently low ti al and si al ratios reflect a restricted but rather homogeneous nature for the detrital supply many redox indicators including the th u v v ni and u ratios pyrite morphology and toc ts fe diagrams suggest deposition under dysoxic to suboxic conditions subsequently the brackish saline bottom water evolved into an anoxic water body under a relatively arid environment during which organic lean marls were deposited in the early stage later an enhanced warm humid climate provided an abundant mineral nutrient supply and promoted the accumulation of algal material om input from algal blooms reached a maximum during the deposition of the organic rich calcareous shale with seasonal laminations high p ti ratios and a strongly positive relationship between the p and toc contents indicate that om accumulation in the oil shale was mainly controlled by the high primary productivity of surface waters with help from a less stratified water column factors such as the physical protection of clay minerals and the dilution of detrital influx show less influence on om enrichment

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

structural evolution of auriferous veins at the endeavour 42 gold deposit cowal mining district nsw australia polyphase veins at the low grade structurally controlled epithermal gold deposit endeavour 42 in the junee narromine volcanic belt of the ordovician to silurian macquarie arc central new south wales australia record multiple tectonically driven fluid flow events during the mid paleozoic ordovician host rocks consist of a volcano sedimentary succession intruded by trachyandesite and andesitic lavas and intrusions as well as a volumetrically significant ordovician diorite sill the entire succession was tilted and faulted prior to the emplacement of multiple mafic to intermediate dike phases commonly localized along faults gold bearing veins cut all lithologic units at the endeavour 42 deposit with the exception of rare late stage intrusions economic gold is restricted to faults fault hosted breccias and veins with two distinct populations 1 an older steeply dipping conjugate vein set cut by 2 two younger moderately dipping vein sets both steep and inclined moderately dipping vein sets contain a similar mineral assemblage implying formation during a single epithermal system veins are generally 1 to 10 mm thick commonly straight walled but locally form overlapping veins with hard linkages the steep veins reactivated two sets of older faults fault parallel fractures and dike contacts and accommodated subhorizontal extension high gold grade hydrothermally cemented breccias are associated with early gold bearing veins and localized along deposit scale faults crosscutting the early steep gold bearing vein sets are inclined gold bearing veins with moderate dips to the southwest and west these opened as a new vein set and as veins localized along and at a slight angle to westward dipping bedding planes respectively the geometry of the inclined moderately dipping veins either represents a sudden change in the far field stress state to near vertical minimum compressive stress thereby suggesting a change from an extensional to a contractional environment or it may reflect local changes in the differential stress state with subhorizontal northeast southwest tension late veins and thrust faults in the deposit indicate a postmineral contractional environment the endeavour 42 deposit underwent tectonic burial until it was exhumed in the early carboniferous as indicated by 40ar 39ar plateau ages of 362 7 2 1 356 3 1 8 and 344 5 2 1 ma toward the end of the kanimblan cycle

organic matter induced mineralogical changes in clay sized phlogopite and muscovite in alfalfa rhizosphere weathering of micaceous minerals is the major source of potassium in soils many studies have shown the beneficial effects of organic matter om on soil physical chemical biological and nutritional properties however there is no information on the effect of om on the breakdown of k rich micaceous minerals the objective of this study was to investigate the transformation of muscovite and phlogopite as influenced by added om in the rhizosphere zone of alfalfa growth medium was a mixture of quartz sand micaceous mineral muscovite or phlogopite and om 0 0 5 and 1 cocopeat on a weight basis during 120 days of alfalfa cultivation plants were irrigated with either a complete or a k free nutrient solution and distilled water as needed at the end of the experiment plants were harvested and their k uptake was measured by flame photometer following dry ash extraction micas and their weathering products were separated from the quartz sand to analyze their clay fractions using x ray diffraction xrd results showed a significant increase in total k uptake in pots containing trioctahedral mica phlogopite and om as compared with non om treatments addition of om transformed phlogopite to 2 1 expanding clays but left dioctahedral mica muscovite intact with undetectable formation of any secondary minerals root activities and om decomposition appear to have increased rhizosphere acidity which in turn facilitated k release from trioctahedral mica phlogopite and induced the formation of vermiculite and a minor quantity of smectite and hydroxy interlayered vermiculite hiv in conclusion the influence of om on the formation of expanding clays greatly depends on the type of micaceous mineral

ordovician convergent margin volcanism and tectonism in the lachlan sector of east gondwana the enigmatic early paleozoic tectonic setting of the lachlan orogen in australia has obscured reconstructions of east gondwana recognition of an intraoceanic mafic island arc in this paper establishes the presence of a convergent plate boundary in the tasmanides from the early ordovician to the early silurian this in turn facilitates the updating of supercontinent correlations

towards an understanding of the role of clay minerals in crude oil formation migration and accumulation this article reviews progress in the understanding of the role of clay minerals in crude oil formation migration and accumulation clay minerals are involved in the formation of kerogen catalytic cracking of kerogen into petroleum hydrocarbon the migration of crude oil and the continued change to hydrocarbon composition in underground petroleum reservoirs in kerogen formation clay minerals act as catalysts and sorbents to immobilize organic matter through ligand exchange hydrophobic interactions and cation bridges by the mechanisms of maillard reactions polyphenol theory selective preservation and sorptive protection clay minerals also serve as catalysts in acid catalyzed cracking of kerogen into petroleum hydrocarbon through lewis and bronsted acid sites on the clay surface the amount and type of clay mineral affect the composition of the petroleum bronsted acidity of clay minerals is affected by the presence and state of interlayer water and displacement of this water is a probable driver in crude oil migration from source rocks during crude oil migration and accumulation in reservoirs the composition of petroleum is continually modified by interaction with clay minerals the clays continue to function as sorbents and catalysts even while they are being transformed by diagenetic processes the detail of chemical interactions and reaction mechanisms between clay minerals and crude oil formation remains to be fully explained but promises to provide insights with broader application including catalytic conversion of biomass as a source of sustainable energy into the future

quartz vein emplacement mechanisms at the e26 porphyry cu au deposit new south wales porphyry cu au mo deposits are characterized by numerous fracturing events brittle fracture of mineralized intrusions and the surrounding host rocks is a consequence of hydraulic breakage caused by the interplay of the changing physiochemical properties of magmatic fluids and or the local tectonic regime we have mapped more than 1 400 quartz sulfide vein sets at the ordovician endeavour 26 north e26 deposit central new south wales in order to constrain the processes influencing fracture development around small 200 m porphyritic intrusions veins from intermediate levels in the e26 deposit define complicated patterns within 10 m of the porphyritic intrusions whereas more systematic patterns occur up to 50 m from the intrusive contact the outer parts of the ore deposit are characterized by quartz veins with orientations of 340 and subordinate orthogonal sets of bisecting veins at 240 and 290 the data show a broad range of vein orientations that define a conical distribution around a vertical axis there is a rare subset of near horizontal veins that formed early relative to the main stage of ore bearing vein emplacement many quartz veins exhibit fault displacements at both micro and macroscopic scales and fabrics including serrate fractures slickenlines and asymmetric fiber trails the distribution of veins suggests that the dominant fracture array developed perpendicular to the direction of bulk finite extension but significant vein dilation also occurred in orientations with a component of shear strain we propose a physical model that combines intrusion driven hydraulic fracturing into a preexisting fracture mesh to help explain the observed vein patterns and to better link fracture development and vein emplacement hydraulically driven deformation was important locally at e26 contributing to the formation of the irregular fracture stockwork immediately adjacent to the small intrusive bodies the more predictable vein patterns that occur away from the porphyritic intrusions require part of the hydraulically driven extension to have reactivated the existing fracture mesh parts of this more systematic geometry including the occurrence of flat veins are probably related to the emplacement of larger 10 km diameter magma bodies adjacent to e26 with doming causing the subordinate fracture arrays including the gross conical distribution fluctuating fluid pressures combined with hydraulically driven extension caused dilation of preexisting and synmineralization fractures and superposition of veins with similar orientations vein patterns suggest that the regional stress state that existed prior to or synchronously with porphyry ore deposit formation strongly influenced vein orientation to within tens of meters away from the mineralizing intrusions fractures that localized ore in the e26 porphyry deposit developed in response to the infiltration of fluid batches including magma and magmatic hydrothermal fluids into a regional deformation environment

climate driven paleolimnological change controls lacustrine mudstone depositional process and organic matter accumulation constraints from lithofacies and geochemical studies in the zhanhua depression eastern china abstract the influence of paleoclimate on the depositional process of lacustrine mudstone and organic matter accumulation is important to both paleoclimate reconstruction and hydrocarbon exploration here we study the lower third member es3l of the eocene shahejie formation in the zhanhua depression bohai bay basin eastern china in order to understand how paleoclimate influenced depositional processes and organic matter accumulation of lacustrine organic rich mudstone by combining detailed core descriptions and microscopic observations and high resolution mineralogical and geochemical analyses we identified two major lithofacies including massive calcareous mudstone and laminated calcareous mudstone from the luo 69 drilling core the sedimentologic observations and changes of geochemical proxies including detritus index ln al2o3 na2o b ga and v v ni suggest that the massive calcareous mudstone was deposited in a small shallow salt lake that was dysoxic anoxic and the paleoclimate in the lake catchment was cool and arid and the laminated calcareous mudstone was deposited in a large and deep stratified lake which has anoxic highly saline bottom and oxic less saline surface water and the lake catchment was more humid and warm the dominant lithofacies changed from laminated calcareous mudstone to massive calcareous mudstone in the studied core suggesting that the lake became shallower and smaller when the paleoclimate became cooler and drier through time such a climate trend may be a response to global cooling during the middle eocene the average total organic content toc in both lacustrine highstand and lowstand are comparable even though the lake water chemistry and amount of terrigenous input are different we infer that the accumulation of organic matter within the lacustrine highstand was controlled by the combination of primary productivity carbonate production and preservation in anoxic bottom water while accumulation within lacustrine lowstand was only controlled by primary productivity

endeavour copper gold porphyry deposits northparkes new south wales intrusive history and fluid evolution four economic porphyry copper gold deposits endeavour 22 26 27 and 48 occur within the late ordovician goonumbla volcanic complex of central west new south wales australia together these deposits have a combined ore reserve of 63 6 million metric tons mt at 1 1 percent copper and 0 5 g t gold mineralization is centered in narrow pipelike quartz monzonite porphyry qmp intrusive complexes we have recognized at least nine intrusive phases within the endeavour deposits these are in order of emplacement as follows a premineral equigranular monzodiorite early mineral equigranular to weakly porphyritic biotite quartz monzonite bqm stocks and dikes synmineral k feldspar qmp k qmp pipes and dikes late mineral augite biotite k feldspar qmp ka qmp intrusions and biotite qmp b qmp dikes and postmineral basaltic trachyandesite dikes augite monzonite porphyry dikes and basaltic dikes early stage biotite magnetite and propylitic alteration of the host volcanic rocks and k feldspar alteration of the bqm occurred at each deposit during the intrusion of the bqm stocks and early mineral b qmp dikes transitional stage unidirectional solidification textures and other related anisotropic textures formed mostly during the emplacement of k qmp and ka qmp intrusions main stage sulfide mineralization at all four deposits is spatially and temporally associated with the k qmp and to a lesser extent ka qmp intrusions and their associated k feldspar and sericite hematite alteration assemblages and is characterized by multiple generations of stockwork and sheeted quartz k feldspar bornite chalcopyrite and gold bearing veins late stage sericite quartz copper sulfide carbonate hematite alteration and vein assemblages formed prior to the emplacement of the postmineral intrusions weak to moderate postmineral propylitic alteration assemblages were the last alteration event related to the qmp intrusive complexes intrusive activity and associated biotite alteration occurred between 446 and 437 ma based on 40ar 39ar analyses of biotite and hornblende based on microthermometric analyses of fluid inclusions from early transitional main and late stage veins the endeavour deposits formed at depths between 1 000 and 1 700 m below the paleosurface with a lithostatic pressure regime prevailing throughout the early transitional and main stages and near hydrostatic pressures during the late stage sericitic events the first three stages were dominated by high temperature 460 550 c magmatic hydrothermal brines with salinities of 55 to 60 wt percent nacl kcl equiv although the late stage fluids were cooler 350 400 c and less saline 40 wt nacl equiv their compositions are consistent with the magmatic hydrothermal origin indicated by previous oxygen and hydrogen isotope studies confirming that the endeavour porphyry deposits are representatives of the orthomagmatic end member of the porphyry continuum

oyu tolgoi mongolia siluro devonian porphyry cu au mo and high sulfidation cu mineralization with a cretaceous chalcocite blanket the oyu tolgoi porphyry cu au mo deposit is located in the gobi desert of southern mongolia the deposit consists of three main mineralized zones north central and south oyu interpreted to constitute at least two separate porphyry copper centers oyu tolgoi is associated with a series of small structurally controlled stocks and dikes of monzonitic and dioritic composition which intrude a sequence of siluro devonian volcanic and sedimentary rocks country rocks consist of pillow basalt and basaltic andesite interbedded with fine grained clastic sedimentary horizons the sequence is interpreted to have formed in a subaqueous island arc volcanic environment which formed part of the extensive paleozoic tuva mongol arc these island arc rocks are covered by carboniferous terrigenous sequences and are intruded by carboniferous syenite and granite and permian alkaline granite much of the area is covered by poorly consolidated cretaceous sedimentary sequences central oyu consists of a multiple phase hydrothermal breccia crosscutting an altered fine grained feldspar porphyry containing porphyry type alteration and mineralization the breccia underwent texture destructive advanced argillic alteration characterized by several associations of quartz alunite dickite pyrophyllite sericite and zunyite plus lesser svanbergite and fluorite these associations overprint earlier formed k silicate and quartz sericite illite assemblages copper mineralization at central oyu is present in a supergene chalcocite blanket that formed at the expense of a pyrite rich hypogene chalcocite covellite tennantite arsenosul vanite sulvanite chalcopyrite bornite sulfide suite that accompanied the advanced argillic alteration event at south oyu a feldspar hornblende porphyry of monzonitic composition intrudes a sequence of fine grained andesite and basaltic andesite hypogene copper gold mineralization occurs as early magnetite rich pyrite poor quartz chalcopyrite bornite stockworks and sheeted veinlets hydrothermal alteration is composed of biotite and k feldspar with apatite and minor albite magnetite averages 7 to 10 vol percent and copper and gold grades vary sympathetically these early assemblages are overprinted by a sericite chlorite event with ore grade copper and erratic gold and molybdenum values and also by structurally controlled pyrite rich advanced argillic alteration k ar ages show that the hypogene copper gold mineralization at south oyu is latest silurian earliest devonian 411 3 ma and that the entire district was intruded by postmineralization syenite during the carboniferous 307 4 ma the supergene chalcocite blanket at central oyu formed in the early cretaceous earliest late cretaceous based on ages for supergene alunite of 117 1 and 93 1 ma which makes central oyu one of the oldest preserved chalcocite blankets in the world chalcocite blanket preservation was favored by climatic desiccation into the late cretaceous and the tertiary it is inferred that significant regional uplift took place at the silurian devonian boundary this synmineral ization uplift and erosion may have been in part responsible for the telescoping of the hydrothermal systems at oyu tolgoi including the superposition of epithermal style associations over higher temperature deeper seated assemblages typical of the porphyry environment

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

petrology of the yerington batholith nevada evidence for evolution of porphyry copper ore fluids the jurassic yerington batholith western nevada is a composite pluton that contains several centers of porphyry copper mineralization and is exposed in structural cross section at paleodepths ranging from 0 to 8 km within these exposures the mcleod hill quartz monzodiorite bear quartz monzonite and luhr hill granite form successive intrusions that are in turn volumetrically smaller approximately 75 19 and 6 vol respectively more deeply emplaced tops at 65 km 3 luhr hill granite the low cu content approximately 10 ppm of the granite would allow extraction of approximately 50 ppm cu from it during crystallization these data suggest an orthomagmatic model in which both high and low density saline aqueous fluids formed during exsolution of water from the crystallizing luhr hill granite and from which salts cu fe and s strongly partitioned into the high density ore fluid low density fluids may have risen from the magma as a vapor plume mineralization occurred when fluid overpressures caused fracturing of wall rock and upward intrusion of granite porphyry dikes and high density saline ore fluids both the f sub o 2 path during subsolidus cooling and the deposition of most s as chalcopyrite pyrite in ore suggest that reduction of magmatic s to sulfide may have been a mechanism for oxidation of magmatic ferromagnesian silicate and fe ti oxide minerals

element mobility patterns in magnetite group iocg systems the fab iocg system northwest territories canada this paper documents element mobility patterns from a magnetite group iron oxide copper gold iocg prospect in the northwest territories of canada and explores implications for space time chemical evolution of metasomatic systems hosting iocg deposits the fab system located in the great bear magmatic zone gbmz of the northwest territories canada contains numerous fe cu u showings associated with high temperature ht potassic iron alteration overprinting extensive zones of sodic to ht calcic iron alteration each hydrothermal alteration assemblage is associated with distinct element mobility patterns that record evolving physico chemical properties of the hydrothermal fluids new geochronological data constrain the alteration and iocg mineralization in the fab system to a 3 m y window between 1870 1867 ma which is broadly contemporaneous with extensive high level intrusive activity across the gbmz regional to local scale element mobility patterns characteristic of the sodic and sodic calcic iron alteration type record leaching combined with weak to strong mass losses pure sodic alteration depleted the rocks in ca co cu fe mg th u and v conversely sodic calcic iron alteration records significant depletions of nb ree ta ti th and u these element mobility patterns differ from intense ht calcic iron alteration that is enriched in ca co f fe mg mn ni and v with modest enrichments to locally significant mineralization in th u and ree ht calcic iron alteration is also characterized by substantial mass gains that translate into volume gains in stockwork zones and mass volume gains in zones of intense host rock replacement ht potassic iron alteration is characterized by enrichments in ba k ni u and v along with locally co and cu the temporal and spatial association of the fab system alteration and the emplacement of the porphyritic dacite are indicative of the predominant involvement of magmatic hydrothermal fluids the high f and cl contents of the porphyritic dacite and of the ht calcic iron alteration zones as well as nb ree ta th and ti mobility provide strong evidences of high halogen activities f and cl in the hydrothermal fluids high f and cl activities in the hydrothermal fluid are interpreted to have facilitated the mobilization of normally immobile nb ta ti th or weakly mobile elements as well as some metals e g v ni co the formation of ree fluorocarbonates and calcite in the early and incipient ht calcic iron alteration zones indicates the presence of co2 in the hydrothermal fluids weaker hfse hree and ti mobility during later ht potassic iron alteration is interpreted to reflect decreasing temperatures pressures f activities and increasing fo2 as the fluids evolved and interacted with the host rocks