cenomanian turonian carbon isotope events recorded in terrestrial organic matter from northern japan carbon isotopic fluctuations recorded in terrestrial organic matter from the upper cretaceous cenomanian turonian succession of hokkaido japan show a remarkably similar pattern to isotopic fluctuation in carbonate carbon reported from southern england and the italian apennines chronological correlation for the cenomanian turonian section of japan is based on planktonic foraminiferal biostratigraphy with some additional data from macrofossils allowing a detailed comparison of isotope stratigraphies for japan and europe three distinct features of the isotope profile namely a positive spike near the cenomanian turonian boundary a shoulder in the lower middle turonian and a level segment in the middle upper turonian are observed in japan these features are biostratigraphically comparable and correlative with isotope profiles reported from europe the single factor influencing isotopic composition of both terrestrial organic carbon and marine carbonate carbon is isotopic change in the global co2 reservoir of the ocean atmosphere system if these three carbon isotope features are synchronous they may be inferred as having been caused by global phenomena and as providing global high resolution chemo stratigraphic markers carbon isotope stratigraphy could be an important bridge between terrestrial inland sequences and marine sequences

abundance and mineralogical association of arsenic in the suwannee limestone florida implications for arsenic release during water rock interaction arsenic as is being released from the suwannee limestone upper floridan aquifer during aquifer storage and recovery asr cycle testing with concentrations of up to 130 g l in the recovered water to determine the abundance and mineralogical association of as in the suwannee limestone matrix we have conducted a detailed mineralogical and geochemical study of 306 core samples in addition to random sampling of core material we also collected targeted samples of core material that contained organic material hydrous ferric oxide pyrite phosphate minerals and clays bulk as concentrations were determined by acid digestion followed by hydride generation atomic fluorescence spectrometry hg afs specific mineral phases were analyzed using scanning electron microscopy sem and electron probe microanalyses epma the average as concentration for all 306 samples is 3 5 ppm but only 1 7 ppm after exclusion of the targeted samples the average for the targeted samples is 9 5 ppm the detailed lithologic mineralogical and geochemical study of as in the upper floridan aquifer suwannee limestone shows that 1 arsenic is present in the suwannee limestone in low concentrations but is concentrated in minor mineral phases particularly pseudo framboidal pyrite 2 pyrite is generally as rich and can contain concentrations between 100 and 11 200 ppm as average 2300 ppm n 25 3 compared to pyrite other trace minerals contain much less as 4 pyrite is ubiquitous throughout the suwannee limestone but is most abundant in high porosity zones 5 previously suggested hydrous ferric oxide clay minerals and apatite are not an important source of as this study also provided some insight into the question whether the interaction reaction of water with an aquifer matrix that contains only a few part per million as is capable of producing high as concentrations in groundwater our findings indicate that it can be relatively easy to generate a high as groundwater despite a low bulk as concentration in the aquifer matrix a change in physico chemical conditions that selectively affects the stability of as bearing minerals is sufficient to increase as concentrations by several orders of magnitude

modeling phosphorus cycling and carbon burial during cretaceous oceanic anoxic events article i nfo in the greenhouse world of the cretaceous there were episodes of oxygen depletion in the deep ocean associated with enhanced organic carbon burial in sediments black shale formation in this study we use a box model of the oceanic phosphorus p organic carbon orgc and oxygen cycles to explore the hypothesis that variations in marine p availability control deep ocean oxygen depletion anoxia and the formation of black shales under cretaceous ocean conditions we find that for the cretaceous ocean with large continental shelves slow oceanic overturning and high sea surface temperatures oceanic anoxic events oaes can be triggered by enhanced p supply from land and that the system is particularly sensitive to oceanic mixing in our baseline scenario the deep sea becomes completely anoxic while the shelves attain only partial anoxia sedimentary burial differs between the shelves and open ocean while organic carbon burial is enhanced in both regions deep sea reactive p burial decreases dramatically under anoxia but not on the shelves where oxygen depletion is not complete furthermore our model results imply that oaes can be sustained by p recycling from sediments under low oxygen conditions ultimately however the feedbacks which result in the accumulation of atmospheric oxygen terminate the anoxic event atmospheric oxygen is modulated by land processes such as forest fires and oxidative weathering which limit the rise of atmospheric o2 our model findings are corroborated by p burial data from the geological record for oae2 approximately 94 myr bp through a sensitivity analysis we identify two necessary criteria for oaes low mixing of surface and deep waters poor ocean ventilation and enhanced sedimentary p recycling under low oxygen conditions when these criteria are met ocean anoxia is a robust result to a mild increase of continental supply of phosphorus under a wide range of environmental conditions

nutrients as the dominant control on the spread of anoxia and euxinia across the cenomanian turonian oceanic anoxic event oae2 model data comparison 1 the cenomanian turonian oceanic anoxic event oae2 is characterized by large perturbations in the oxygen and sulfur cycles of the ocean potentially resulting from changes in oxygen supply via oxygen solubility and ocean circulation and in marine productivity we assess the relative impact of these mechanisms comparing model experiments with a new compilation of observations for seafloor dysoxia anoxia and photic zone euxinia the model employed is an intermediate complexity earth system model which accounts for the main ocean dynamics and biogeochemistry of the cretaceous climate the impact of higher temperature and marine productivity is evaluated in the model as a result of higher atmospheric carbon dioxide and oceanic nutrient concentrations the model shows that temperature is not alone able to reproduce the observed patterns of oceanic redox changes associated with oae2 observations are reproduced in the model mainly via enhanced marine productivity due to higher nutrient content responsible for 85 of the change higher phosphate content could have been sustained by increased chemical weathering and phosphorus regeneration from anoxic sediments which in turn induced an enhanced nitrogen nutrient content of the ocean via nitrogen fixation the model also shows that the presence of seafloor anoxia as suggested by black shale deposition in the proto north atlantic ocean before the event might be the result of the silled shape and lack of deep water formation of this basin at the late cretaceous overall our model data comparison shows that oae2 anoxia was quasi global spreading from 5 of the ocean volume before the event to at least 50 during oae2

carbon sequestration activated by a volcanic co 2 pulse during ocean anoxic event 2 ninety four million years ago during ocean anoxic event 2 there was a marked increase in the burial of organic carbon in marine sediments measurements of stomata in fossil leaves show that the two main pulses of carbon burial were associated with a decline in atmospheric co2 levels of up to 26 the cretaceous ocean anoxic event 2 about 94 million years ago is thought to be linked to extensive volcanism which triggered a biogeochemical chain of events that eventually led to widespread marine anoxia and a remarkable increase in carbon burial in marine sediments1 2 3 it has been suggested that the event was accompanied by a substantial decrease in atmospheric co2 concentrations4 but the quantification of the drawdown remains controversial5 6 here we reconstruct atmospheric co2 concentrations throughout the ocean anoxic event from counts of the stomata in fossil leaves and use terrestrial carbon isotopes to link the reconstruction to marine records of the event7 8 we find that before the onset of ocean anoxia atmospheric co2 concentrations increased by 20 over background levels of 370 100 70 ppm this was part of a long term rise in atmospheric co2 levels presumably caused by volcanism which reached a peak of 500 400 180 ppm however two pulses of extensive carbon burial during the ocean anoxic event as indicated by positive carbon isotope excursions are associated with decreased atmospheric co2 concentrations we conclude that the sequestration of marine organic carbon led to a decrease in atmospheric co2 concentration of up to 26 during ocean anoxic event 2

tectonic and structural setting for active mesothermal gold vein systems southern alps new zealand abstract the southern alps of new zealand is an active oblique collisional mountain belt with extensive regional tectonically driven fluid flow there is no evidence for igneous activity and fluids consist of varying proportions of meteoric water and mid crustal fluid derived from dehydration reactions fluid flow is controlled by fracture porosity particularly in damage zones along faults and fault intersections gold and arsenic bearing veins exposed at the surface indicate two principal zones of gold mineralisation at depth one of these is in the highest mountains near to but not in the region of maximum uplift deformation is dominated by reverse faulting but some normal and strike slip faults occur as well the other zone of gold mineralisation is at and near the intersection of regional oblique dextral reverse faults and regional strike slip faults both zones are characterised by small discontinuous vein systems locally accompanied by ankeritic alteration of host rock veins occur in extensional and shear veins and in dilational jogs with implosion breccias gold mineralisation occurred at many structural levels between the brittle ductile transition and the near surface region the southern alps hydrothermal system represents an active roof zone to a mesothermal gold deposition system at depth as such this is a modern analogue for mesothermal gold terranes elsewhere in new zealand and around the world observations on the regional distribution of fluid flow in active orogens can give insights into fluid flow at depth where gold mineralisation is occurring now comparison of these observations with ancient gold bearing belts allows construction of three dimensional concepts of orogenic fluid flow and gold mineralisation

concentrations of reduced sulphur in inclusion fluids associated with black shale hosted quartz vein gold deposits implications for mechanisms of transport and deposition of gold and a possible exploration tool abstract analyses of reduced s and other inclusion volatiles in vein quartz from the black shale hosted clogau st davids au deposit n wales show that a relation exists between elevated inclusion s content and au grade this relation is better at discriminating between high and low grade vein material than criteria based on the other inclusion volatiles analyses of material from a similar but subeconomic vein system yields a small number of samples with an auriferous signature on the basis of either s 2 content or co 2 ch 4 ratio but application of both criteria would reject all samples the concentration of reduced s species in metamorphic fluids thought to have transported au suggests that au hs 2 was the dominant au complex thermodynamic calculations indicate that up to 8 mg au kg h 2 o may have been transported in this manner gold precipitation in the ore body resulted from destabilisation of the au hs 2 complex probably either through reduction by the black shales or as a result of flashing of h 2 s into the ch 4 rich phase which was generated during the mineralising event

some thermal and mechanical consequences of rapid uplift an example from the southern alps new zealand abstract the thermal evolution of continental crust during active collision is modeled through numerical solutions of the two dimensional heat conduction equation for a rapidly moving medium the boundary conditions used in the modeling are derived from geological and geophysical observations from the active collision zone in the south island of new zealand the problem domain over which the solutions are obtained consists of a 40 km horizontal by 25 km vertical spatial plane with a vertical discontinuity at 10 km from the western boundary to the east of this discontinuity vertical uplift rates of up to 10 mm a occur over a timespan of up to 4 ma temperature distributions are calculated at 10 ka intervals over the 4 ma duration a two dimensional high temperature region is established upon initiation of uplift of the eastern block due to the advective component carrying heat upwards more rapidly than it can be dissipated laterally from the problem domain temperatures within the upper 5 km are greater than 400 c after 2 25 ma with geothermal gradients of up to 200 c km attained within the upper 3 km at times greater than 2 5 ma the vertical temperature distribution changes little while the anomalously high temperatures spread laterally into the stationary crust using rheological equations to describe the brittle behaviour of a water saturated upper crust and the ductile behaviour of a quartz dominated lower crust together with the thermal distribution of the conduction models the mechanical evolution of a collision zone is investigated in addition to high crustal temperatures and associated high heat flow rapid uplift produces a weakening of the crust by raising of the depth of transition from brittle to ductile behaviour within the zone of most rapid uplift the brittle ductile transition rises from 13 km to less than 5 km after 1 5 ma of uplift further uplift reduces the brittle layer to 3 km thickness and causes lateral spreading of the low strength zone the reductions in crustal strength caused by the thermal weakening produce a high strain zone within the region of maximum uplift which is incapable of sustaining large differential stresses this causes horizontal and vertical stress transfer and results in shallow seismicity increases in the adjacent crust as well as in intermediate depth seismicity within the high strength upper mantle because the thermal and mechanical anomalies discussed are a function of rapid uplift all regions of active continental collision may be expected to exhibit similar behaviour some mechanical and thermal characteristics of the himalayan collision zone are briefly examined in light of the numerical modeling

diazotrophic cyanobacteria as the major photoautotrophs during mid cretaceous oceanic anoxic events nitrogen and carbon isotopic evidence from sedimentary porphyrin abstract we determined both the nitrogen and carbon isotopic compositions of nickel chelated deoxophylloerythroetioporphyrin ni dpep a major sedimentary porphyrin extracted from the livello selli and livello bonarelli black shales deposited in the western tethys sea during mid cretaceous oceanic anoxic events oaes based on empirical isotopic relationships between the tetrapyrrole nuclei of chlorophylls and photoautotroph cells we estimate that the mean nitrogen isotopic composition of the entire photoautotrophic communities during these periods ranged from 2 to 1 this result strongly suggests that n2 fixation was an important primary process in photoautotrophic production during these oaes the estimated carbon isotopic composition of the photoautotrophs was elevated between 20 and 22 relative to typical cretaceous examples indicating as much as a 5 reduction in the magnitude of carbon isotopic fractionation associated with photosynthesis during oaes in the western tethys sea this anomaly can be well explained if cyanobacteria were the dominant producers because they commonly conduct carboxylation and or active transport of carbon substrates resulting in reduced carbon isotopic fractionation we therefore conclude that diazotrophic cyanobacteria were the dominant components of primary production during oae 1a and oae 2 in the western tethys sea

the early metamorphic history of the haast schists and related rocks of new zealand rare but widespread relics of sodic amphibole occur in metabasites and metacherts of the haast schists and related caples terrane rocks present main stage metamorphic assemblages are frequently chemically equivalent to earlier sodic amphibole bearing assemblages indicating that these rocks underwent an earlier higher p tmetamorphism prior to formation of the present pumpellyite actinolite and greenschist facies assemblages the earlier assemblages were stable during and after early isoclinal folding but were replaced by the present moderate p t assemblages prior to the last major fabric forming deformation the change in conditions was due to thermal relaxation probably accompanied by uplift and erosion and peak metamorphic temperatures were about 350 370 c in the pumpellyite actinolite zone of the caples terrane and near 390 c in the greenschist facies chlorite zone near queenstown according to henley 1975 these greenschist facies rocks attained a pressure of at least 6 4 0 4 kb during their history but a pressure of 4 6 0 6 kb has been estimated for a chlorite zone rock from middlemarch and so the 6 4 kb estimate probably refers to the maximum pressure attained during the earlier higher p t metamorphism similar changes in metamorphic facies series with time occur in some older and more complex metamorphic belts such as the caledonides and this study suggests that it may be possible to interpret particular elements in the metamorphic development of such belts in terms of specific circum pacific analogues

volume loss model for trace element enrichments in mylonites mylonites from three widely separated localities along the fries ductile deformation zone in the blue ridge province show substantial enrichments in trace and minor elements tio sub 2 p sub 2 o sub 5 zr y and v and depletions in rb and sr relative to the protolith two end member hypotheses can explain the enrichments one involves partitioning to and from an infiltrating fluid and assumes that all the elements were mobile the second hypothesis assumes the high field strength cations were largely immobile and that their enrichment is due to large volume losses in the mylonites modeling indicates that ti is immobile for fluid rock ratios as high as 10 sup 4 and petrographic and modal data support a volume loss mechanism volume loss was accommodated by loss of sio sub 2 and alkalies during feldspar dissolution calculated fluid rock volume ratios required to produce the observed sio sub 2 losses assuming ti mobility range from 70 to 600 variable enrichments in p zr y and v are attributed to selective mobility of these elements during fluid infiltration

metamorphic and post metamorphic fluid flow in the low grade rocks of the harlech dome north wales a combination of fluid inclusion stable isotope and geochemical techniques has been used to study the nature of fluids present and their behaviour during caledonian low grade metamorphism of the harlech dome north wales fluid inclusion studies show that in most of the metasedimentary sequence the peak metamorphic fluid was an aqueous na k cl brine but in the graphitic clogau formation and in parts of the overlying maentwrog formation immiscible h2o rich and ch4 rich fluids coexisted late stage inclusions are of calcium rich brine and a dilute aqueous fluid the chemical composition of chlorite in metamorphic veins and rocks varies between different formations and quartz oxygen isotopic compositions show considerable variation between different units both of these features are taken to indicate that there was little or no pervasive movement of fluid between different units at the peak of metamorphism after the metamorphic peak there was focused flow of fluid upward through the sequence along fractures in response to end caledonian uplift and unloading where the migrating fluid crossed the graphitic shales interaction between the fluid and the shales gave rise to the formation of the auriferous veins of the dolgellau gold belt subsequent to this mineralizing event there was widespread development of 18o enriched calcites and micas in the case of vein minerals it is possible that these crystallized directly from late stage fluids at lower temperature than the quartz in the same veins alternatively the original vein minerals may have re equilibrated with later 18o enriched or cooler fluid in the case of muscovites in the rock matrix it is proposed that the isotopically heavy compositions are the result of re equilibration of initially light grains with an introduced fluid requiring considerable influx of fluid this event may relate to either of two late stage fluids observed as inclusions

ca isotope stratigraphy across the cenomanian turonian oae 2 links between volcanism seawater geochemistry and the carbonate fractionation factor abstract the ca isotope composition of marine carbonate rocks offers potential to reconstruct drivers of environmental change in the geologic past this study reports new high precision ca isotope records ca 44 40 2 sd 0 04 for three sections spanning a major perturbation to the cretaceous ocean climate system known as ocean anoxic event 2 oae 2 central colorado usa portland 1 core southeastern france pont d issole and hokkaido japan oyubari yezo group in addition we generated new data for selected samples from eastbourne england english chalk where a previous ca isotope study was completed using different methodology blattler et al 2011 strata of the yezo group contain little carbonate 1 wt on average and accordingly did not yield a clear ca 44 40 signal the portland core and the pont d issole section display comparable ca 44 40 values which increase by 0 10 0 15 at the onset of oae 2 and then decrease to near initial values across the event the eastbourne ca 44 40 values are higher than previously reported they are also higher than the ca 44 40 values for the portland core and the pont d issole section but define a similar pattern according to a numerical model of the marine ca cycle elevated hydrothermal inputs have little impact on seawater ca 44 40 values elevated riverine chemical weathering inputs produce a transient negative isotope excursion which significantly differs from the positive isotope excursions observed in the portland pont d issole and eastbourne records a decrease in the magnitude of the carbonate fractionation factor provides the best explanation for a positive shift in ca 44 40 values especially given the rapid nature of the excursion because a decrease in the fractionation factor corresponds to an increase in the ca co3 ratio of seawater we tentatively attribute the positive ca isotope excursion to transient ocean acidification i e a reduction in the concentration of co 3 2 during co2 uptake recent studies utilizing a variety of isotope proxies e g nd os and pb implicate eruption of the caribbean large igneous province as a likely source of increased co2 moreover integration of c ca and os isotope data reveals new information about the timing of events during the onset of oae 2

origin of the torlesse terrane and coeval rocks south island new zealand the carboniferous to lower cretaceous torlesse terrane and haast schist derivatives constitute the major part of the complexly deformed facies of the eastern province of new zealand strata consist mainly of quartzofeldspathic graywacke and mudstone intercalated with minor but widely distributed conglomerate and volcanics with associated chert and limestone clastic rocks were deposited largely by sediment gravity flow mechanisms in a deep marine environment also present are a few highly fossiliferous shallow marine and terrestrial deposits of limited areal extent which rest unconformably on or in fault contact with torlesse flysch several periods of deformation are recognized and melange is present on both local and regional scales metamorphism ranges from zeolite to greenschist facies the bulk of the rocks fall into five areally extensive and mutually exclusive fossil zones of the following ages permian atomodesma middle triassic early late triassic torlessia late triassic monotis and late jurassic early cretaceous contacts between major fossil zones are mainly tectonic petrographic analysis permits subdivision of torlesse sandstones into five major petrofacies that correspond in age to the five major fossil zones the sandstone petrofacies mainly arkosic together with the composition of conglomerate clasts mainly indurated torlesse rocks indicate that the source terrane was a continental volcano plutonic arc probably part of gondwanaland coupled with autocannibalistic reworking of older uplifted torlesse rocks in contrast to the quartzofeldspathic nature of the torlesse coeval sedimentary rocks of the eastern province are volcanogenic they are thought to represent related forearc basin maitai murihiku terranes and trench complex caples terrane deposits derived from a volcanic island arc brook street terrane three petrofacies are established for maitai murihiku and caples sandstones the petrofacies indicate a common evolving immature to submature volcanic island arc source for these terranes a reconstruction of new zealand s eastern and western provinces is proposed in permian and triassic times the torlesse was deposited in trench slope or borderland basins along a trench transform margin fronting a continental volcano plutonic arc source western province gondwanaland deposition was spasmodic but voluminous and was accompanied by concurrent deformation and accretion resulting in parallel belts of torlesse rock younging outward from the gondwanaland margin at the same time the brook street terrane volcanic arc and associated terranes were forming to the west of the torlesse site separated from gondwanaland by a marginal sea in latest triassic or early jurassic times the torlesse was rafted into the volcanic arc system via transform faulting approximately parallel to the gondwana margin the collision event resulted in tectonic thickening of torlesse and caples rocks at the plate interface and metamorphism to haast schist the source was then dominated by older partly metamorphosed torlesse terrane newly uplifted along the collision front closing of the marginal sea behind the brook street terrane in late jurassic early cretaceous times resulted in juxtapositioning with the western province gondwanaland along the median tectonic line

vapour loss boiling as a mechanism for fluid evolution in metamorphic rocks the calculation of fluid evolution paths during reaction progress is considered for multicomponent systems and the results applied to the ternary system co2 h2o nacl fluid evolution paths are considered for systems in which a co2 rich phase of lesser density vapour is preferentially removed from the system leaving behind a saline aqueous phase liquid such boiling leads to enrichment of the residual aqueous phase in dissolved components and for certain reaction stoichiometries to eventual saturation of the fluids in salt components distinctive textures particularly radiating growths of prismatic minerals such as tremolite or diopside are associated with saline fluid inclusions and solid syngenetic salt inclusions at a number of field localities the most thoroughly studied of these localities is campolungo switzerland where metasomatic rocks have developed in association with fractures and veins at 500 c and 2 000 bars of pressure the petrography of these rocks suggests that fluid phase separation into liquid and vapour has been an important process during metasomatism fracture systems with fluids at pressure less than lithostatic may facilitate the loss of the less dense vapour phase to conditions of the amphibolite facies

carbonate systems along nutrient and temperature gradients some sedimentological and geochemical constraints research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems changes in climate ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry including carbonate saturation state and nutrient availability and thereby have determined boundary conditions for the biota that form carbonate platforms in turn the biota determine accumulation rates and facies zonations thus controlling platform geometry and facies dynamics in the first section of this paper we examine how nutrient availability influences carbonate facies associations we first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations then we discuss how carbonate sedimentation can be characterized along nutrient gradients in the second section we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems we highlight the variety of existing proxies and their limitations and suggest that multiple lines of evidence are needed for valid interpretations our short review discusses sedimentological biogenic and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations however it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs nutrient supplies changes and facies in ancient carbonate sequences

continuous metamorphic gradient documented by graphitization and k ar age southeast otago new zealand the chrystalls beach brighton coastal section southwest of dunedin new zealand exposes otago schist including the weakly metamorphosed triassic accretionary melange of the chrystalls beach complex and higher grade rocks of a largely felsic arc derived provenance melange zones contain pelagic sediments some of which are manganiferous and metabasites the grade of metamorphism increases progressively from southwest to northeast four mineral zones are recognized largely on the basis of mineral assemblages in psammitic and semipelitic rocks pumpellyite chlorite pumpellyite actinolite epidote actinolite and biotite d 002 data for carbonaceous material b 0 values for phengite and metamorphic phengite k ar ages are reported for 32 pelitic and semipelitic samples remarkably tight correlations are revealed between d 002 for progressively graphitized carbonaceous material k ar ages that range from 184 6 to 138 7 ma and linear distance along the section both the d 002 values and the k ar ages decrease progressively toward the northeast through the four mineral zones and with progressive textural changes all rocks cropping out in the section have undergone a coherent episode of progressive metamorphism associated with terrane collision and have not been disturbed by any later major displacements a convex trend for phengite b 0 values plotted against advancing graphitization suggests p t conditions during metamorphism as in the high pressure intermediate facies series the age of the metamorphic peak is inferred to be 175 155 ma middle to late jurassic with cooling to the mica closure temperature at 155 135 ma late jurassic to early cretaceous unloading denudation and cooling were accompanied by localized hydrothermal events the oldest covering strata were deposited at ca 100 ma and denudation was completed by ca 75 80 ma middle triassic radiolarian nodules in melange zones are dated as preceding the metamorphic peak by about 65 ma associated turbidites contain suspected late middle to early late triassic tube fossils

enhanced productivity led to increased organic carbon burial in the euxinic north atlantic basin during the late cenomanian oceanic anoxic event 1 three cenomanian turonian c t 93 5 ma black shale sections along a northeast southwest transect in the southern part of the proto north atlantic ocean were correlated by stable carbon isotope stratigraphy using the characteristic excursion in 13c values of both bulk organic matter om and molecular fossils of algal chlorophyll and steroids all three sites show an increase in marine organic carbon oc accumulation rates during the c t oceanic anoxic event oae the occurrence of molecular fossils of anoxygenic photosynthetic green sulfur bacteria lack of bioturbation and high abundance of redox sensitive trace metals indicate sulfidic conditions periodically reaching up into the photic zone before as well as during the c t oae during the c t oae there was a significant rise of the chemocline as indicated by the increase in concentrations of molecular fossils of green sulfur bacteria and mo al ratios the presence of molecular fossils of the green strain of green sulfur bacteria indicates that euxinic conditions periodically even occurred at very shallow water depths of 15 m or less during the c t oae however bottom water conditions did not dramatically change as indicated by more or less constant v al and zn al ratios at site 367 this suggests that the increase in oc burial rates resulted from enhanced primary productivity rather than increased anoxia which is supported by stable carbon isotopic evidence and a large increase in ba al ratios during the c t oae the occurrence of the productivity event during a period of globally enhanced organic carbon burial rates i e the c t oae points to a common cause possibly related to the formation of a deep water connection between north and south atlantic basins

ore forming process of the huijiabao gold district southwestern guizhou province china evidence from fluid inclusions and stable isotopes abstract the huijiabao gold district is one of the major producers for carlin type gold deposits in southwestern guizhou province china including taipingdong zimudang shuiyindong bojitian and other gold deposits occurrences petrographic observation microthermometric study and laser raman spectroscopy were carried out on the fluid inclusions within representative minerals in various mineralization stages from these four gold deposits five types of fluid inclusions have been recognized in hydrothermal minerals of different ore forming stages aqueous inclusions co2 inclusions co2 h2o inclusions hydrocarbon inclusions and hydrocarbon h2o inclusions the ore forming fluids are characterized by a h2o co2 ch4 n2 system with medium to low temperature and low salinity from early mineralization stage to later ones the compositions of the ore forming fluids experienced an evolution of h2o nacl h2o nacl co2 ch4 n2 h2o nacl ch4 co2 with a slight decrease in homogenization temperature and salinity the 18o values of the main stage quartz vary from 15 2 to 24 1 while the dh2o and calculated 18oh2o values of the ore forming fluids range from 56 9 to 116 3 and from 2 12 to 12 7 respectively the 13cpdb and 18osmow values of hydrothermal calcite change in the range of 9 1 to 0 5 and 11 1 23 2 respectively stable isotopic characteristics indicate that the ore forming fluid was mainly composed of ore and hydrocarbon bearing basinal fluid the dynamic fractionation of the sulfur in the diagenetic pyrite is controlled by bacterial reduction of marine sulfates the hydrothermal sulfides and the diagenetic pyrite from the host rocks are very similar in their sulfur isotopic composition suggesting that the sulfur in the ore forming fluids was mainly derived from dissolution of diagenetic pyrite the study of fluid inclusions indicates that immiscibility of h2o nacl co2 fluids took place during the main mineralization stage and caused the precipitation and enrichment of gold

biological productivity during sapropel s5 formation in the eastern mediterranean sea evidence from stable isotopes of nitrogen and carbon we determined 15n 14n ratios in modern surface and sapropel s5 sediments of the mediterranean sea to clarify differences in the nutrient regime associated with sapropel formation in the modern situation high 15n of unused nitrate 15 20 remaining in the surface waters during the winter phytoplankton bloom evidences p limitation of biological production in winter 15n of surface sediments decrease towards the east of the basin 5 to 2 5 this is a consequence of either eastward increasing nitrogen fixation during the summer months or of particulate matter being supplied predominantly by the p limited winter bloom very low 1 1 15n values in sapropel s 5 from four locations require a very light source of nutrient n assimilated at a minimum of ten times the modern export flux because the isochronous records show no spatial gradient in 15n we exclude both ekman type upwelling and direct riverine discharge as likely sources of nutrients our data are consistent with an anti estuarine thermohaline circulation in the upper 500m during s5 time allowing for the trapping of nutrients in the eastern basin the most likely scenario for s5 is that phosphorus release from a relatively shallow redox boundary resulted in an imbalanced supply of n p 16 1 to the photic zone the result was a slow assimilation of carbon during summer stratification and extensive n2 fixation providing the majority of the export flux from a n limited system

fluid fluid interactions in magmatic hydrothermal ore formation hydrothermal ore deposits have provided some of the first geological evidence for the interaction of multiple fluids in the earth s interior including fluid mixing as well as fluid phase separation physical evidence comes from veins and breccias documenting the impact of fluids in breaking rocks and creating fracture permeability for ore formation as a result of the fluid expansion that is commonly associated with phase separation between melts and multiple fluids chemical evidence of fluid fluid interaction includes the precipitation of minerals in veins as a result of fluid boiling or mixing between chemically contrasting fluids fluid inclusions record interactions of multiple fluids especially in magmatic hydrothermal ore deposits and associated igneous rocks fig 1 in recent years fluid inclusions have contributed to a more quantitative understanding of the role of fluid fluid interactions since new microanalytical techniques allow determination of element concentrations in all types of fluids from low density vapor through aqueous and hypersaline liquids to hydrous salt melts roedder 1984 samson et al 2003 figure 1 geological evidence for fluid phase separation in ore forming magmatic hydrothermal systems a bonanza grade gold 1 wt that was precipitated together with fine grained pyrite in a fluidized breccia resulting from instantaneous boiling and expansion of magmatic fluids ascending from an underlying andesite porphyry intrusion the breccia consists of adularia sericite altered clasts of sedimentary wall rock s and nodules of originally colloidal pyrite with bright specks of gold p g both cemented by roscoelite r vanadium rich muscovite and late calcite c zone vii ore body porgera papua new guinea ronacher et al 2004 b bladed manganocalcite the characteristic habit of calcite precipitated from aqueous epithermal fluids as a result of the ph change following loss of co2 to a separating vapor phase madan bulgaria kostova et al 2004 c growth band in a euhedral quartz

sulfur isotopes track the global extent and dynamics of euxinia during cretaceous oceanic anoxic event 2 the mesozoic era is characterized by numerous oceanic anoxic events oaes that are diagnostically expressed by widespread marine organic carbon burial and coeval carbon isotope excursions here we present coupled high resolution carbon and sulfur isotope data from four european oae 2 sections spanning the cenomanian turonian boundary that show roughly parallel positive excursions significantly however the interval of peak magnitude for carbon isotopes precedes that of sulfur isotopes with an estimated offset of a few hundred thousand years based on geochemical box modeling of organic carbon and pyrite burial the sulfur isotope excursion can be generated by transiently increasing the marine burial rate of pyrite precipitated under euxinic i e anoxic and sulfidic water column conditions to replicate the observed isotopic offset the model requires that enhanced levels of organic carbon and pyrite burial continued a few hundred thousand years after peak organic carbon burial but that their isotope records responded differently due to dramatically different residence times for dissolved inorganic carbon and sulfate in seawater the significant inference is that euxinia persisted post oae but with its global extent dwindling over this time period the model further suggests that only 5 of the global seafloor area was overlain by euxinic bottom waters during oae 2 although this figure is 30 greater than the small euxinic fraction present today 0 15 the result challenges previous suggestions that one of the best documented oaes was defined by globally pervasive euxinic deep waters our results place important controls instead on local conditions and point to the difficulty in sustaining whole ocean euxinia

strontium isotope stratigraphy in the upper cenomanian shallow water carbonates of the southern apennines short term perturbations of marine 87sr 86sr during the oceanic anoxic event 2 abstract strontium isotope stratigraphy of shallow water carbonates from the southern apennines italy indicates that the late cenomanian early turonian evolution of marine 87sr 86sr is not accurately depicted by the marine reference curve using the low mg biotic calcite of well preserved rudist shells as a study material and carbon isotope stratigraphy for correlation to the standard ammonite biozonal scheme of northern europe new 87sr 86sr values are proposed for four different stratigraphic levels the middle and uppermost part of the guerangeri zone the lower and upper part of the geslinianum zone the southern apennines data suggest that a sharp positive shift at the onset of oceanic anoxic event 2 precedes the well known sr isotope negative shift the positive shift is interpreted in terms of enhanced rates of chemical weathering driven by global warming forced by volcanogenic co2 outgassing a stratified ocean is invoked to reconcile the high gradient and the short lag time of the perturbation with estimates of present day total mass and residence time of strontium in the ocean the sharp switch to the negative shift is related to the collapse of water column density gradient driven by thermal instability during a late cenomanian cool event more active ocean circulation suddenly delivered to surface waters the signal of increased submarine volcanism that had accumulated in deep waters

geographically different oceanographic responses to global warming during the cenomanian turonian interval and oceanic anoxic event 2 abstract oceanic anoxic event oae 2 coincided with the cenomanian turonian boundary 93 9 ma and was one of the two most prominent and globally significant of the major mid cretaceous oaes a confluence of global warming major large igneous province volcanism and intensified hydrologic cycling preconditioned the earth system for widespread preservation of organic matter during oae2 however the ultimate necessary ingredient was enhanced nutrient availability in oceanic surface waters here we present new cenomanian turonian interval seawater neodymium isotope data from the proto indian ocean that demonstrates increased water column stratification during the pre and post oae2 interval punctuated by a transient decrease in this stratification immediately prior to the onset of oae2 recorded at ocean drilling program site 763 the direct oceanographic responses to climate change on both longer and short term time scales observed in this region are distinct from those recorded in the northern tropical and southern atlantic basins the transient de stratification of the water column in the eastern proto indian ocean likely did not contribute to the accumulation of organic rich sediments in the region indicating that weathering and or hydrothermal inputs promoted enhanced surface water nutrient levels and hence primary productivity

on the appearance of cyanobacterial calcification in modern stromatolites abstract in august 1991 calcified magnesian calcite filamentous cyanobacteria scytonema mirabile appeared on the surface of a modern lacustrine stromatolite lake r2 rangiroa atoll tuamotu archipelago french polynesia previously the topmost photosynthetic layer of this sediment was devoid of such microbial biomineralisers the calcified cyanobacteria are accompanied by magnesian calcite grains which are evocative of bacterial precipitates although the appearance of cyanobacterial calcification might be related to environmental changes in the lake in particular a decrease in water salinity the persistence of non calcified specimens of a filamentous cyanobacteria phormidium crossbyanum which was once a dominant species of the lake benthos shows that calcification and environmental conditions might be only indirectly related thus attempts to use the fossil record of calcareous cyanobacterial skeletons to infer changes in the chemical composition of past oceans cannot be made without due regard of biological processes like the appearance of new competitors

cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode oceanic anoxic events oaes were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen deficient bottom waters oae2 occurring at the cenomanian turonian boundary about 93 5 myr ago is the most widespread and best defined oae of the mid cretaceous although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios the actual trigger mechanism corresponding closely to the onset of these episodes of increased carbon sequestration has not been clearly identified it has been postulated that large scale magmatic activity initially triggered oae2 refs 4 5 but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of oae2 has not yet been found here we report seawater osmium isotope ratios in organic rich sediments from two distant sites we find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of oae2 using a simple two component mixing equation we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin a approximately 30 50 fold increase relative to pre oae conditions furthermore the magmatic osmium isotope signal appears slightly before the oae2 as indicated by carbon isotope ratios suggesting a time lag of up to approximately 23 kyr between magmatism and the onset of significant organic carbon burial which may reflect the reaction time of the global ocean system our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of oae2 which may have triggered the subsequent deposition of large amounts of organic matter

simulating the biogeochemical effects of volcanic co2 degassing on the oxygen state of the deep ocean during the cenomanian turonian anoxic event oae2 cretaceous anoxic events may have been triggered by massive volcanic co2 degassing as large igneous provinces lips were emplaced on the seafloor here we present a comprehensive modeling study to decipher the marine biogeochemical consequences of enhanced volcanic co2 emissions a biogeochemical box model has been developed for transient model runs with time dependent volcanic co2 forcing the box model considers continental weathering processes marine export production degradation processes in the water column the rain of particles to the seafloor benthic fluxes of dissolved species across the seabed and burial of particulates in marine sediments the ocean is represented by twenty seven boxes to estimate horizontal and vertical fluxes between boxes a coupled ocean atmosphere general circulation model aogcm is run to derive the circulation patterns of the global ocean under late cretaceous boundary conditions the aogcm modeling predicts a strong thermohaline circulation and intense ventilation in the late cretaceous oceans under high pco2 values with an appropriate choice of parameter values such as the continental input of phosphorus the model produces ocean anoxia at low to mid latitudes and changes in marine 13c that are consistent with geological data such as the well established 13c curve the spread of anoxia is supported by an increase in riverine phosphorus fluxes under high pco2 and a decrease in phosphorus burial efficiency in marine sediments under low oxygen conditions in ambient bottom waters here we suggest that an additional mechanism might contribute to anoxia an increase in the c p ratio of marine plankton which is induced by high pco2 values according to our aogcm model results an intensively ventilated cretaceous ocean turns anoxic only if the c p ratio of marine organic particles exported into the deep ocean is allowed to increase under high pco2 conditions being aware of the uncertainties such as diagenesis this modeling study implies that potential changes in redfield ratios might be a strong feedback mechanism to attain ocean anoxia via enhanced co2 emissions the formation of c enriched marine organic matter may also explain the frequent occurrence of global anoxia during other geological periods characterized by high pco2 values

potassium argon age studies of a low grade progressively metamorphosed greywacke sequence dansey pass south island new zealand 39 potassium argon age determinations from a progressively metamorphosed greywacke schist sequence in southern new zealand prehnite pumpellyite to greenschist facies range from 199 to 154 ma early to late jurassic they show an inverse correlation of age with metamorphic grade concordant ages from varied lithologies at all metamorphic grades show that degassing of detrital potassium bearing minerals was completed during metamorphism the lowest grade metamorphic rocks which yield the oldest ages about 200 ma have only just exceeded the argon closure temperature and hence their ages date closely their time of metamorphism in the earliest jurassic thus it is shown that the jurassic cretaceous rangitata orogeny in new zealand commenced earlier is more complex and of longer duration than previously supposed the remaining ages from pumpellyite actinolite and lower greenschist rocks range uniformly through the jurassic and are interpreted as cooling ages from these data a long term uplift rate of 0 23 mm yr is calculated for the jurassic cretaceous

contrasting fluids in gold bearing quartz vein systems formed progressively in a rising metamorphic belt otago schist new zealand four different quartz vein systems occur within 600 km 2 in east otago the vein systems have formed within fault systems which crosscut regional schistosity the macraes system formed from almost pure water at about 3 kbars and 350 degrees c data from fluid inclusions and arsenopyrite geothermometer the bonanza system formed from immiscible h 2 o co 2 nacl fluids at about 1 000 bars nenthorn formed under near surface conditions from boiling low salinity water with some co 2 present barewood most closely resembles macraes but is thought to have formed at slightly shallower levels the veins formed at different times during mesozoic cenozoic uplift of the otago schist belt c and o isotope data and the high co 2 content of some fluids suggest that the vein forming fluids were metamorphogenic a component of downward percolating meteoric water was probably involved in shallower vein formation vein formation is considered to be an inevitable consequence of devolatilization of uplifting metamorphic rocks with focusing of fluids into available structural features similar fluid flow has occurred within the last 1 m y in the northwestern extension of the otago schist where alpine fault uplift has induced gold mineralization on joint surfaces

origin and evolution of ore forming fluids of the larong w mo deposit eastern tibet constraints from fluid inclusions h o isotopes and scheelite geochemistry abstract the larong porphyry w mo deposit formed in the main collisional orogenic stage of lhasa and qiangtang terranes is the first discovered giant w mo deposit in the leiwuqi zogang metallogenic belt sanjiang region the w mo mineralization occurs as veins and stock works mainly hosted in the granodiorite porphyry monzogranite porphyry biotite granite porphyry and surrounding schist four types of fluid inclusions fis including pc type pure vapor co2 c type co2 h2o w type aqueous two phase and l type pure liquid h2o fis have been identified from stage i quartz scheelite alkaline feldspar veins stage ii including three sub stages quartz molybdenite pyrite chalcopyrite veins and stage iii quartz calcite pyrite veins the total homogenization temperatures of fis vary widely 187 437 c with multiple peaks indicating multistage fluid activities the ore forming fluids of the main mineralization stages are characterized by co2 enrichment high medium temperature 270 440 c and medium low salinity 2 4 14 4 wt nacl equiv the homogenization temperature of w type inclusions is obviously higher than that of c type inclusions and the salinity is relatively lower implying multiple immiscibility of fluids with continuous escape of co2 h o isotopic compositions suggest that the primary ore forming fluids dominantly originated from magma water mo concentrations and eu values in scheelite indicate a decreasing trend of redox state of ore fluids from stage i to stage ii to stage iii the relatively higher temperature co2 rich and oxidized fluids gradually evolved into relatively lower temperature co2 poor and reduced fluids here we propose that the decrease of temperature and oxygen fugacity and increase of s2 activity and ph values of the ore fluids caused by continuous fluid rock interaction and loss of co2 could account for the successive mineralization of w and mo at the larong deposit

controls on high sulfate concentrations in the upper floridan aquifer in southwest florida chemical profiles of groundwater in the upper floridan aquifer in southwest florida vary between an inland and a coastal site at the inland site sulfate concentrations increase with depth and chloride concentrations remain low at the coastal site sulfate concentrations are high and constant but chloride concentrations increase with depth the sulfate source at the inland site is gypsum dissolution whereas at the coastal site the sulfate source is predominantly gypsum dissolution overprinted by saltwater mixing mass transfer modeling in conjunction with isotopic data was used to evaluate hypothetical flow paths within the aquifer dedolomitization reactions gypsum and dolomite dissolution with calcite precipitation dominate along flow paths where sulfate concentrations increase the distribution of gypsum in the aquifer indicates that a deeply circulating flow path controls the chemical evolution of groundwater between the two sites fresh groundwater moves into deep zones in the aquifer where gypsum is found farther along the flow path in the discharge area this groundwater moves upward to shallower depths prior to the saltwater mixing zone saltwater mixing becomes more pronounced with both proximity to the coast and with increasing depth these results underscore the importance of evaluating vertical as well as lateral flow paths when quantifying geochemical reactions in a chemically stratified aquifer

depletion of 13c in cretaceous marine organic matter source diagenetic or environmental sigal geochemical studies of cretaceous strata rich in organic carbon oc from deep sea drilling project dsdp sites and several land sections reveal several consistent relationships among amount of oc hydrocarbon generating potential of kerogen measured by pyrolysis as the hydrogen index hi and the isotopic composition of the oc first there is a positive correlation between hi and oc in strata that contain more than about 1 oc second percent oc and hi often are negatively correlated with carbon isotopic composition 13c of kerogen the relationship between hi and oc indicates that as the amount of organic matter increases this organic matter tends to be more lipid rich reflecting the marine source of the organic matter cretaceous samples that contain predominantly marine organic matter tend to be isotopically lighter than those that contain predominantly terrestrial organic matter average 13c values for organic matter from most cretaceous sites are between 26 and 28 and values heavier than about 25 occur at very few sites most of the 13c values of miocene to holocene oc rich strata and modern marine plankton are between 16 to 23 values of 13c of modern terrestrial organic matter are mostly between 23 and 33 the depletion of terrestial oc in 13c relative to marine planktonic oc is the basis for numerous statements in the literature that isotopically light cretaceous organic matter is of terrestrial origin even though other organic geochemical and or optical indicators show that the organic matter is mainly of marine origin a difference of about 5 in 13c between modern and cretaceous oc rich marine strata suggests either that cretaceous marine planktonic organic matter had the same isotopic signature as modern marine plankton and that signature has been changed by diagenesis or that oc derived from cretaceous marine plankton was isotopically lighter by about 5 relative to modern plankton oc diagenesis does not produce a significant shift in 13c in miocene to holocene sediments and therefore probably did not produce the isotopically light cretaceous oc this means that cretaceous marine plankton must have had 13c values that were about 5 lighter than modern marine plankton and at least several per mil lighter than cretaceous terrestrial vegetation the reason for these lighter values however is not obvious it has been proposed that concentrations of co2 were higher during the middle cretaceous and this more available co2 may be responsible for the lighter 13c values of cretaceous marine organic matter

fluid evolution fluid immiscibility and gold deposition during cretaceous recent tectonics and uplift of the otago and alpine schist new zealand abstract the otago and alpine schist metamorphic belts have been uplifted and experienced collisional extensional transcurrent and then renewed collisional tectonics over the past 120 ma au bearing veins have been deposited in greenschist facies rocks at many different structural levels from 10 km depth to within a few hundred metres of the surface in many structural settings during this long uplift history fluids which deposited these veins have had a remarkably similar composition throughout the tectonic history veins formed near to the brittle ductile transition and in the lower parts of the brittle region were deposited by water with

distribution and mobility of geogenic molybdenum and arsenic in a limestone aquifer matrix abstract to investigate the potential of mo and as as possible geogenic contaminants three sediment cores were examined to evaluate their mineralogical association distribution and mobility the cores were described and analyzed for total organic carbon toc ca mg si al p sr as mo fe and s content except in the uppermost segment limestone was the main lithology with the occasional presence of dolomite and clay that change in lithology was also observed in the bulk chemical composition where ca mg and sr concentrations increased with depth while si al and p concentrations decreased with depth minor minerals included pyrite fes 2 powellite camoo 4 and ferrihydrite the minimum maximum median and standard deviations for all analyzed elements including as and mo were comparable for all three cores molybdenum and as however varied significantly with depth and median as and mo values were above their respective crustal averages of approximately 1 1 mg kg and 1 5 mg kg the median values for as were 1 9 mg kg in core dep 1 3 3 mg kg in dep 2 and 1 mg kg in dep 5 the median values for mo were 2 3 mg kg in core dep 1 2 5 mg kg in dep 2 and 2 5 mg kg in dep 5 maximum concentrations for as were 101 9 mg kg 47 5 mg kg and 56 2 mg kg in cores dep 1 dep 2 and dep 5 respectively maximum concentrations for mo were 880 mg kg 123 mg kg and 225 mg kg in cores dep 1 dep 2 and dep 5 respectively electron microprobe analyses of individual minerals revealed variable concentrations of as ranging from approximately 300 to 9000 mg kg in pyrite and up to 17 600 mg kg in powellite camoo 4 the mo concentration in pyrite was consistently below the detection limit of approximately 100 mg kg in powellite the mo concentration was up to 42 wt a subset of 10 samples from different stratigraphic sections and with different as and mo concentrations was further investigated to assess as and mo mobility under changing physicochemical conditions leaching the aquifer matrix with a 1 m naoac solution at a ph of 8 1 removed more than 70 mo in 8 of the 10 samples the maximum value was 97 in contrast to mo as was mobilized to a lesser degree in 8 of the samples less than 30 were removed and the maximum was only 50 molybdenum which seemed to be loosely bound to mineral and organic matter surfaces thus could easily be removed from the aquifer matrix while as on the other hand should be much less mobile because it occurred either tightly adsorbed by hydrous ferric oxide or as an impurity in pyrite thus it is advisable to include mo in the analytical program whenever elevated as concentrations are encountered in groundwater

geogenic as and mo groundwater contamination caused by an abundance of domestic supply wells abstract lacking a connection to a municipal water supply each household in the municipality of lithia approximately 30 km southeast of tampa florida usa is responsible for its own supply of drinking water causing a high density of private domestic supply wells dsw in this area there a multilayered aquifer system exists which can be subdivided into three distinct hydro stratigraphic units which are from the top down the surficial aquifer system sas the intermediate aquifer system ias and the upper floridan aquifer system ufa despite the relatively small area the geochemical and hydrogeological setting in lithia is complex consisting of i extensive cyclical pumping in a municipal well field to the west ii large seasonal changes in hydraulic head ii multiple aquifers with different hydraulic heads and iv a large density of domestic supply wells dsw within the zone of highest as concentrations there are approximately 100 wells in an area of 2 5 km 1 5 km most of these wells have large open screened intervals often open to all three aquifers allowing the downward flow of oxygenated and upward flow of anoxic groundwater a survey of groundwater quality found that as and mo concentrations in the dsw were up to 371 g l and 4740 g l respectively to obtain information about the individual aquifers 5 well clusters with 4 monitoring intervals approximately 50 m 65 m 80 m and 95 m below surface and 8 push core wells approximately 9 m below surface were installed and sampled in those wells as and mo were only elevated in a permeable layer within the ias at a depth of 50 m values were up to 195 g l for as and up to 5050 g l for mo using the tritium helium 3h 3he method the ages of those samples high in as and mo were determined to be 40 30 and 30 years respectively while all other samples had ages older than 50 years this indicated that mixing between young and old groundwater could be responsible for the high as and mo concentrations a good negative correlation for the whole data set was also observed between the concentration 3h and 18o values which together with hydrogeological modeling confirmed that the increased permeability created by the high density of dsw resulted in flow paths that permitted the perpetual mixing of shallow and deep groundwater the release of the as and mo appeared to be a consequence of changes to the physicochemical conditions in the aquifer either via the introduction of oxygen rich fluids into the ias or the mixing of different fluids in the ias or the introduction of oxygen depleted fluids into the ias while the mobilization of geogenic trace metals is often associated with pumping induced hydraulic gradient changes we found that a certain density of multi aquifer wells can be sufficient to alter hydrologic flow paths and induce the mobilization of geogenic trace metals even in the absence of significant pumping in lithia the dsw effectively increased the local scale permeability of the aquifer causing the mixing of oxygen rich surface and deeper anoxic groundwater across a confining unit because the alteration to the hydrologic flow paths was a consequence of changes to the physical structure of the aquifer system rather than due to pumping the alteration is not easily reversible thus significantly complicating site remediation our results provide a cautionary warning of the risks of undue private dsw development in rapidly growing communities

dinosaurs re write the geodynamics of the eastern mediterranean and the paleogeography of the apulia platform abstract evidence of a sizeable population of large dinosaurs on the apulia carbonate platform calls for a revision of the current paleotectonic and paleogeographic scenario of the eastern mediterranean area a review of geophysical and geological data of the ionian sea and surrounding areas leads to envisage the late jurassic early cretaceous ionian sea region as a cul de sac type basin enclosed by shallow water carbonate banks connecting the apulia carbonate platform to peloponnesus northern cyrenaica cyrene seamount and medina ridge these banks were repeatedly and periodically exposed to subaerial conditions and offered vast land areas for migration of dinosaurs as regards the nature of the mesozoic ionian basin interpretations are quite controversial the continental vs oceanic crust debate will likely be solved only when the ionian basin crust will be reached by drilling the conclusion of the present review leads to consider adria as a true african promontory and the apulia platform as a sort of florida peninsula attached to north africa cyrenaica spur subdividing the oceanic mesozoic mediterranean into a western ionian basin and an eastern levantine basin

preservation of elemental and isotopic source identification of sedimentary organic matter the amount and type of organic matter in the sediments of lakes and oceans contribute to their paleoenvironmental and paleoclimatological records only a small fraction of the initial aquatic organic matter survives destruction and alteration during sinking and sedimentation selective degradation modifies the character of the surviving small fraction of organic matter which becomes incorporated in bottom sediments organic matter alterations can continue to sub bottom depths of hundreds of meters corresponding to millions of years source and paleoenvironmental information nonetheless remains preserved in the molecular elemental and isotopic compositions of organic matter c n and 13c values of total organic matter in particular appear to retain paleoenvironmental information for multi myr time periods

shallow level metamorphic fluids in a high uplift rat metamorphic belt alpine schist new zealand fluids some of which are co2 rich up to 40 mol co2 and some of which are highly saline up to 18 wt nacl equivalent are trapped as fluid inclusions in quartz calcite metallic minerals veins which cross cut the pumpellyite actinolite to amphibolite facies rocks of the alpine schist fluids were commonly trapped as immiscible liquid vapour mixes in quartz and calcite showing open space growth textures fluid entrapment occurred at fluid pressures near 500 bars possibly as low as 150 bars at temperatures ranging from 260 to 330 c saline fluids may have formed by partitioning of dissolved salts into an aqueous phase on segregation of immiscible fluids from a low density co2 rich fluid calcite deposited by these fluids has 13c ranging from 8 4 to 11 5 and 18o from 4 to 13 isotopic data fluid compositions and mode of occurrence suggest that the fluids are derived from high grade metamorphic rocks fluid interaction with wall rock has caused biotite crystallization and or recrystallization in some rocks and retrogression of biotite to chlorite in other rocks fluid penetration through the rock is almost pervasive in many areas where permeability probably related to alpine fault activity has focussed fluids on a regional scale into fractured rocks the fluid flow process is made possible by high uplift rates in excess of 10 mm year bringing hot rocks near to the surface

cyanobacteria proliferation in the cenomanian turonian boundary interval of the apennine carbonate platform immediate response to the environmental perturbations associated with oae 2

gold mineralization without quartz veins in a ductile brittle shear zone macraes mine otago schist new zealand greenschist facies schist which hosts the macraes mine in east otago new zealand has been pervasively altered by post metamorphic lower greenschist facies fluids over a 120 m thick section perpendicular to foliation metamorphic titanite has been replaced by rutile and epidote has been replaced by a variety of metamorphic minerals including siderite chlorite muscovite and calcite the early stages of this alteration occurred during development of a ductile cleavage associated with kilometre scale recumbent folding the cleavage was widely overprinted by a subparallel set of spaced mm scale microshears which are locally enriched in rutile and hydrothermal graphite strain was then concentrated into narrow m scale zones where more intensely deformed portions of the rock are crossed and highly disrupted by closely spaced 100 m scale microshears the highly strained rocks show a combination of mylonitic and cataclastic microstructures including crystal plastic grain size reduction and recrystallization of micas to form a new foliation muscovite has grown at the expense of albite in the mylonitic cataclasites hydrothermal alteration was accompanied by addition of pyrite arsenopyrite and gold without development of quartz veins gold precipitated with sulphides during reduction of the fluid by hydrothermal graphite the whole altered rock sequence was later cut sporadically by mesothermal quartz veins which contain gold scheelite rutile pyrite and arsenopyrite this deposit displays a continuum of post metamorphic processes and hydrothermal fluid flow which occurred during uplift of the schist belt

marine black shale deposition and hadley cell dynamics a conceptual framework for the cretaceous atlantic ocean understanding the controls that determine the spatial distribution and internal heterogeneities of black shales in the mesozoic ocean has been a focal point of research over many decades the consensus is that atmosphere land ocean interactions influenced variations in marine biogeochemistry and sediment supply thus exerting fundamental controls on the richness and quality of sedimentary organic matter om and ultimately on petroleum source rock distribution and its generation potential internal small scale heterogeneities in black shales that have been reported from all ocean settings were often linked to orbitally driven fluctuations in continental runoff and marine upwelling the two processes are generically related under the ascending tropical and descending subtropical limbs of the palaeo hadley cells with fluctuations at variable time seasonal orbital geological and spatial shelf margin deep basin scales these dynamic variations translate into characteristic patterns of om quantity and quality best preserved near the continents where the forcing effects are strongest the expression of these orbital scale interactions are not well constrained at the basin scale however they may hold a key to better understand the distribution of heterogeneities in black shales this study presents a conceptual framework that links om quality and quantity in cretaceous atlantic sediments with the dominant processes that operated under the hadley cells using a comprehensive compilation of bulk organic geochemical data total organic carbon concentration toc hydrogen index hi oxygen index oi and kerogen type we explore how basic geochemical patterns can be used to identify the underlying generic processes we utilise published and new data from deep ocean sites of the dsdp odp program as well as one palaeo shelf setting tarfaya spanning a latitudinal transect from the outer subtropics to the palaeo equator during the albian the cenomanian turonian and the coniacian santonian this study emphasises the potential of integrating orbital scale datasets and wide spatial coverage as a predictive tool for black shale formation across ocean basins

round hill shear zone hosted gold deposit macraes flat otago new zealand evidence of a magmatic ore fluid the 0 8 moz round hill shear zone hosted gold deposit is one of several located on or near the hyde macraes shear zone macraes flat new zealand field relationships show stockwork veins are the oldest part of the hydrothermal system followed by flat and ramp veins hanging wall shear veins formed early but have been modified by late deformation fluid inclusion microthermometric results for dominant type i inclusions show that flat and ramp veins have the same average wt percent nacl equiv values 2 2 0 6 and were precipitated from the same fluid salinity data for these veins overlap with those from hanging wall veins average 1 3 0 3 and stockwork veins 1 6 0 6 for vein margins 0 9 0 3 for vein centers although both of the latter trend toward lower overall wt percent nacl equiv values suggesting mixing between relatively dilute and more saline end members all of the above veins have similar temperatures of homogenization t h ranging between 110 and 188 c fluid inclusion trapping temperatures are considered to be 300 c equating to a 10 km depth of formation carbon dioxide dissolved in the hydrothermal fluid is responsible for up to one third of fluid inclusion apparent salinities stockwork and hanging wall veins thus have true salinities of 1 wt percent nacl equiv 0 17 molal and flat and ramp veins have true salinities of fluid inclusion volatiles from round hill and other macraes deposits are dominated by h 2 o 99 02 99 69 mol with lesser co 2 0 14 0 76 mol n 2 0 03 0 32 mol and ch 4 0 06 0 17 mol noticeable concentrations of hydrocarbons occur in many of the samples fluid inclusion cation and anion data show few components of relatively low concentration are dissolved in the hydrothermal fluid consistent with co 2 corrected microthermometric measurements a range in fluid inclusion d h 2 o values obtained for the round hill deposit is coincident with the different vein types and also indicates mixing between two fluids one fluid is considered to be o isotope shifted meteoric water as trapped by the early stockwork veins and has the lowest d h 2 o values of 80 per mil the other fluid is represented by flat and or ramp and hanging wall veins that have d h 2 o values up to 40 per mil the macraes d h 2 o data show a trend toward the magmatic water end member for geothermal systems associated with convergent plate boundaries and are consistent with a 25 to 50 percent magmatic component in the macraes hydrothermal system

the gold conveyor belt large scale gold mobility in an active orogen the southern alps of new zealand are part of an active collisional orogen where metamorphism hydrothermal fluid flow and the formation of orogenic gold deposits are ongoing the southern alps are forming due to transpressional collision between continental crust fragments on the pacific and australian tectonic plates the plate tectonic rates and geometries the sources of fluid and broad scale fluid pathways in the hydrogeological system and the geochemical compositions of the torlesse terrane rock that is being advected through the orogen are well defined so that a mass balance of metal mobility during active orogenic processing in the southern alps of new zealand can be calculated advection of a 10 km wide x 5 km deep section of torlesse rock through the orogen at tectonic rates 0 01 m yr that is then metamorphosed up to amphibolite facies causes mobilisation of over 1127 t au 10 1mt as 47000 t hg 560000 t sb and 14000 mt h2o in 1 myrs the masses of elements mobilised at the same rate along the length of the southern alps 200 km for 5 myrs would be more than 100 times greater the metals were mobilised by the metamorphic fluid produced during the orogenic processing of the torlesse terrane rocks and the concentrations of au as hg and sb in this fluid are calculated to be 0 08 711 3 and 40 mg kg respectively the mobilised metals form the orogenic gold deposits that occur in the southern alps different styles of gold deposits form contemporaneously during the active orogenesis of the southern alps including those with a fluid temperature rock temperature that may appear have formed after the peak of metamorphism but are instead just the product hydrothermal fluid mineralising rocks on their retrograde metamorphic path the mass balance shows that there has been orders of magnitude more metal mobilised in the orogen than resides in the currently known deposits there is clear potential for large gold deposits occurring in the yet to be uplifted parts of the southern alps if there have been efficient enough fluid focussing and metal precipitation mechanisms occurring under the southern alps

lithium isotope evidence for enhanced weathering during oceanic anoxic event 2 the ocean anoxic event 2 oae2 about 93 5 million years ago was marked by high atmospheric co2 concentration rapid global warming and marine anoxia and euxinia the event lasted for about 440 000 years and led to habitat loss and mass extinction the marine anoxia is thought to be linked to enhanced biological productivity but it is unclear what triggered the increased production and what allowed the subsequent rapid climate recovery here we use lithium isotope measurements from carbonates spanning the interval including oae2 to assess the role of silicate weathering we find the lightest values of the li isotope ratio 7li during oae2 indicating high levels of weathering and therefore atmospheric co2 removal which we attribute to an enhanced hydrological cycle we use a geochemical model to simulate the evolution of 7li and the ca sr and os isotope tracers our simulations suggest a scenario in which the eruption of a large igneous province led to high atmospheric co2 concentrations and rapid global warming which initiated oae2 the simulated warming was accompanied by a roughly 200 000 year pulse of accelerated weathering of mafic silicate rocks which removed co2 from the atmosphere the weathering also delivered nutrients to the oceans that stimulated primary productivity we suggest that this process together with the burial of organic carbon allowed the rapid recovery and stabilization from the greenhouse state

depositional model of a cenomanian turonian extensional basin sopeira basin ne spain interplay between tectonics eustasy and biological productivity abstract the sopeira basin is a small extensional basin with a continuous record of sedimentation from the late albian to the late turonian in its early stages late albian middle cenomanian it formed a half graben bounded to the south by a low angle normal fault during this time sedimentation was limited to the downfaulted block until the emerged footwall was flooded resulting in the deposition of shallow water limestones over a vast platform the platform was exposed during the middle late cenomanian by a relative sea level fall the sedimentation up to this point was controlled by local factors extensional tectonics and influenced by eustatic sea level change subsequently the entire area was flooded by the late cenomanian transgression during the cenomanian turonian boundary interval the basinal sedimentation was characterized by calcisphaerid limestones with black cherts and organic rich shales while on the platform a hiatus was produced these sedimentary features are interpreted as having been caused by global mechanisms changes in atmospheric co 2 and temperature along with an increased rate of precipitation that caused an intense primary productivity at the water surface in the basinal sea eutrophication led initially to an unusual development of calcisphaerids and later to the development of opportunistic planktonic foraminifera whereas in the platform it affected the life of carbonate producing organisms dramatically and sedimentation ceased eutrophication of marine water is thus interpreted to be the main cause of the extinction of k strategist foraminifera and associated fauna at the end of the cenomanian

fluid evolution during uplift of the annapurna himal central nepal abstract fluid inclusions from post metamorphic quartz show that there has been considerable co 2 rich fluid flux during uplift of greenschist amphibolite facies rocks along the main central thrust mct maximum fluid co 2 content increased with metamorphic grade of the host rock ranging from 20 30 mole in the greenschist facies to both the north and south of the mct to 70 mole in the amphibolite facies the highest co 2 content is in late stage veins which cross cut uplift related schistosity in the sillimanite zone this contrasts with the syn metamorphic fluid which was probably dominantly aqueous fluid immiscibility occurred in quartz veins near the brittle ductile transition at 280 310 c and 700 300 bar fluid pressure an upper limit of 1600 bar lithostatic pressure was determined from a co 2 rich isochore the high thermal gradient implied by p t data is due to rapid uplift along the mct mct movement ceased in the miocene and the rocks have experienced slower uplift along a lower thermal gradient during this slower uplift ca na brines some with freezing point depression below 20 c have traversed the rock at first the brines mixed with co 2 then brines dominated until diluted by incursion of lowsalinity presumably meteoric water near the surface brines and co 2 may be reaching the surface today in diluted from as numerous warm and ambient springs brines were probably derived from connate fluids in the tibetan carbonate clastic sedimentary succession to the north of the mct co 2 was derived from metamorphosed equivalents of these sediments and perhaps from similar sediments beneath the mct

tropical warming and intermittent cooling during the cenomanian turonian oceanic anoxic event 2 sea surface temperature records from the equatorial atlantic oceanic anoxic event 2 oae 2 occurring during the cenomanian turonian c t transition is evident from a globally recognized positive stable carbon isotopic excursion and is thought to represent one of the most extreme carbon cycle perturbations of the last 100 myr however the impact of this major perturbation on and interaction with global climate remains unclear here we report new high resolution records of sea surface temperature sst based on tex86 and 18o of excellently preserved planktic foraminifera and stable organic carbon isotopes across the c t transition from black shales located offshore suriname french guiana demerara rise ocean drilling program leg 207 site 1260 and offshore senegal cape verde basin deep sea drilling project leg 41 site 367 at site 1260 where both sst proxy records can be determined a good match between conservative sst estimates from tex86 and 18o is observed we find that late cenomanian ssts in the equatorial atlantic ocean 33 c were substantially warmer than today 27 29 c and that the onset of oae 2 coincided with a rapid shift to an even warmer 35 36 c regime within the early stages of the oae a marked 4 c cooling to temperatures lower than pre oae conditions is observed however well before the termination of oae 2 the warm regime was reestablished and persisted into the turonian our findings corroborate the view that the c t transition represents the onset of the interval of peak cretaceous warmth more importantly they are consistent with the hypotheses that mid cretaceous warmth can be attributed to high levels of atmospheric carbon dioxide co2 and that major oaes were capable of triggering global cooling through the negative feedback effect of organic carbon burial led co2 sequestration evidently however the factors that gave rise to the observed shift to a warmer climate regime at the onset of oae 2 were sufficiently powerful that they were only briefly counterbalanced by the high rates of carbon burial attained during even the most extreme interval of organic carbon burial in the last 100 myr

brittle and ductile deformation in a zone of rapid uplift central southern alps new zealand schists exposed in the central southern alps new zealand 1 5 km east of the alpine fault zone have been rapidly uplifted during the late cenozoic a regionally consistent sequence of mesoscopic structures discordant to the schistosity is recognized extending backward in time from recent brittle displacements of deglaciated surfaces through structures exhibiting brittle ductile transitional behaviour to ductile deformational features kinematic analysis of these structures gives consistent principal subhorizontal shortening directions similar to the present day principal horizontal shortening direction indicating their relation to late cenozoic uplift of the southern alps analysis of deformed veins suggests a minimum shortening strain of about 50 perpendicular to the foliation the veins crosscut upright mesoscopic to macroscopic folds which commonly develop high strain zones on their limbs within such zones a strong stretching lineation plunges gently sw approximately perpendicular to the stretching lineation in the mylonites along the alpine fault the folds and high strain zones do not appear to be related to late cenozoic uplift but may have originated during an earlier phase of dominantly strike slip motion fluid inclusion studies give depth temperature estimates of around 3 km and 285 c for the development of the brittle structures and 6 8 km at 310 350 c for the brittle ductile transition the deformed veins show evidence of extensive fluid infiltration during the later phases data from fluid inclusions and metamorphic assemblages give an estimate of 15 20 km and 400 450 c for their deformation these data combined with uplift rates determined by other studies allow the construction of a depth temperature time path which indicates nearly isothermal decompression associated with rapid uplift a shallow brittle ductile transition 6 8 km is consistent with numerical modeling of thermal and mechanical behavior of the crust during rapid uplift associated with continental collision and with the presence of high heat flow in the area because of the small temperature change over a large amount of decompression pressure may be an important factor in controlling the depth of the brittle ductile transition the marked temperature drop above the brittle ductile transition is thought to be enhanced by the influence of convection as an effective cooling mechanism

hydrothermal arsenic enrichment in an active mountain belt southern alps new zealand abstract torlesse terrane greywackes and hydrothermal calcite associated with active fault systems in the main divide fault zone of new zealand s south island exhibit anomalous as concentrations relative to background values of similar rock types mass balance analysis of greywacke compositional data from the upper wilberforce valley of the main divide region demonstrate an average mass gain of as on the order of a factor of 6 above typical torlesse greywackes wilberforce mean 35 3 ppm 31 3 ppm n 44 torlesse mean 5 6 ppm 4 4 n 31 in addition hydride generated icp ms analyses of the weak acid soluble fraction of individual calcite rich veins and fault gouges in the main divide fault zone exhibit as concentrations mean 81 2 ppm 113 ppm n 17 in excess of a factor of 100 over hydrothermal calcite from other fault systems mean 1 7 ppm 4 0 n 29 stable isotopic analyses of these calcite veins show a wide range for both oxygen 18o 9 9 to 25 6 and carbon 13c 12 to 1 1 this observation suggests that the hydrothermal fluid source of these veins was of a mixed meteoric and highly exchanged fluid over a wide range of temperatures we suggest that the presence of high as concentrations in young hydrothermal calcite veins in the main divide region results from active transport of as rich deep crustal fluids upward along the fault zone this interpretation is consistent with both fluid flow tectonic models and geophysical observations which suggest that expansion in the main divide fault zone provides a conduit for the escape of deep exchanged fluids into the upper crust

oxygen isotopic evidence for the origin and evolution of a scheelite ore forming fluid glenorchy new zealand the glenorchy lode field in the otago au w sb metallogenic province of new zealand is hosted by metasediments of pumpellyite actinolite facies to lowest greenschist facies the lodes cut schistosity at a high angle and consist of anastomosing veins of quartz scheelite calcite pyrite arsenopyrite within zones of crushed and deformed schist up to 6 m wide lode quartz delta 18 o values range from 16 0 to 17 4 per mil background schist contains quartz with delta 18 o values between 13 0 and 14 8 per mil and the alteration zone quartz delta 18 o values are gradational between the two extremes albite and muscovite also exhibit increased delta 18 o values in altered schists relative to background schists the width of the oxygen isotopic alteration aureole is dependent on schist permeability during mineralization and extends up to 10 m from the lodes oxygen isotopic equilibrium conditions were approached in the schists during metamorphism and in the lodes and immediate wall rocks during mineralization the remainder of the alteration zone is characterized by isotopic disequilibrium the quartz delta 18 o values in the alteration zone schists probably represent mixtures of hydrothermal quartz delta 18 o 17ppm and metamorphic quartz delta 18 o 13 14ppm the temperature of metamorphism was estimated by oxygen isotope geothermometry to be between 370 degrees and 445 degrees c although pumpellyite stability experiments by schiffman and liou 1977 suggest that 400 degrees c would be the upper limit oxygen isotope geothermometry gave a temperature range for mineralization of 280 degrees to 350 degrees c relative temperatures can be more reliably stated mineralization occurred after metamorphism at a temperature at least 80 degrees c less than that of metamorphism the ore forming fluid delta 18 o was in the range 7 to 10 per mil and on this evidence could have been either metamorphic or magmatic in origin but because there is no spatial association between au w sb mineralization and igneous activity in the otago area a metamorphic origin is favored a model for the origin and isotopic evolution of the ore forming fluid is proposed whereby the fluid was derived from metamorphic dehydration reactions in rocks of at least upper greenschist facies the fluid was trapped in the rocks until uplift of the schist pile led to hydraulic fracturing and release of the fluid to existing fault zones the fluid migrated rapidly upward retaining a constant delta 18 o value and deposited hydrothermal minerals which were 18 o enriched relative to those in the country rock ore forming elements w au were derived deep in the schist pile probably also from metamorphic reactions the oxygen isotope alteration aureole is probably too narrow to be of any practical use in exploration for similar lode deposits at least in the glenorchy area

first evidence for the cenomanian turonian oceanic anoxic event oae2 bonarelli event from the ionian zone western continental greece integrated biostratigraphic planktonic foraminifera calcareous nannofossils chemostratigraphic bulk c and o isotopes and compound specific organic geochemical studies of a mid cretaceous pelagic carbonate black shale succession of the ionian zone western greece provide the first evidence for the cenomanian turonian oceanic anoxic event oae2 bonarelli event in mainland greece the event is manifested by the occurrence of a relatively thin 35 cm yet exceptionally organic carbon rich 44 5 wt toc carbonate free black shale near the cenomanian turonian boundary within the vigla limestone formation berriasian turonian compared to the bonarelli black shale interval from the type locality of oae2 in marche umbria italy this black shale exhibits greatly reduced stratigraphic thickness coupled with a considerable relative enrichment in toc isotopically enriched 13c values for both bulk organic matter 22 2 and specific organic compounds are up to 5 higher than those of underlying organic rich strata of the aptian lower albian vigla shale member and thus compare very well with similar values of cenomanian turonian black shale occurrences elsewhere the relative predominance of bacterial hopanoids in the saturated apolar lipid fraction of the oae2 black shale of the ionian zone supports recent findings suggesting the abundance of n2 fixing cyanobacteria in cretaceous oceans during the cenomanian turonian and early aptian oceanic anoxic events

a comment on the distribution and mobility of geogenic molybdenum and arsenic in a limestone aquifer matrix by thomas pichler and ali mozaffari

geochemical and isotopic properties of fluids from gold bearing and barren quartz veins of the sovetskoye gold deposit siberia russia this paper reports on the comparative study of fluids trapped in inclusions in gold bearing and barren quartz veins at the sovetskoye gold deposit yeniseisky ridge siberia russia the host rocks are greenschist facies metasedimentary rocks of upper proterozoic age within the deposit some veins contain 10 to 25 ppm of au gold bearing veins others contain less than 1 ppm of au barren veins fluid inclusions trapped in barren veins are predominantly low salinity h2o 4 0 8 0 mass nacl equiv with variable contents of dissolved co2 12 5 mol ch4 1 3 mol and n2 1 7 mol homogenization temperatures vary from 200 to 410 c and the calculated pressures of entrapment are 1 5 kbars inclusion fluids trapped in the host schists are predominantly aqueous 97 6 99 3 mol h2o with co2 contents below 2 4 mol percent the fluids trapped in ore bearing quartz inclusions are different inclusions show higher homogenization temperatures up to 630 c and salinity up to 20 25 mass nacl equiv calculated pressures range from 0 7 to 2 0 kbars bulk gas chromatographic data of fluids extracted from native gold have contents of co2 that range from 29 3 to 62 0 mol percent n2 from 2 7 to 13 2 mol percent and ch4 from 0 0 to 2 8 mol percent in gold bearing quartz the contents of co2 range from 18 0 to 41 0 mol percent n2 from 0 1 to 0 2 mol percent and ch4 from 0 3 to 3 0 mol percent raman spectroscopic data of fluid from gold bearing quartz revealed co2 contents of individual inclusions as high as 98 2 mol percent n2 up to 66 4 mol percent and ch4 up to 88 7 mol percent fluids of the country rock schists which host gold bearing quartz veins are also enriched in co2 up to 49 5 mol the host rocks for both barren and gold bearing quartz veins show consistent ree patterns characterized by a negative eu anomaly fluids from barren quartz veins show similar ree patterns although with a less conspicuous negative eu anomaly whereas fluids from gold bearing quartz show a marked positive eu anomaly similar isotopic values of sulfur in pyrite pyrrhotite and arsenopyrite disseminated in country rocks 34s 14 7 21 6 and in barren 34s 12 9 19 9 and gold bearing quartz veins 34s 13 3 17 9 suggest that sulfur in sulfides was derived from the same source most likely being the adjacent country rocks co2 trapped in fluid inclusions of barren and gold bearing quartz has distinct isotopic compositions 13c 8 1 to 10 2 and 4 9 to 5 2 respectively and the 13c values are positively correlated with au contents in veins helium isotope composition of both types of quartz veins 3he 4he 0 04 0 05 ra for gold bearing veins and 3he 4he 0 02 ra for barren veins indicates a crustal provenance of mineral forming fluids the 40ar 39ar dating of sericite demonstrates that the barren veins 890 850 ma are significantly older than the gold bearing veins 830 730 ma on the basis of their ages barren veins are interpreted as synmetamorphic the age of the gold bearing veins corresponds to the age of the local granitoids 850 720 ma suggesting that the origin of the sovetskoye deposit is related to the tectonic activity syntetctonic magmatism

the behavior of nitrogen and nitrogen isotopes during metamorphism and mineralization evidence from the otago and alpine schists new zealand abstract metamorphism is a major mechanism for the re distribution of fluids and mass in the earth s crust with these processes most prominently highlighted by the occurrence of major gold resources within these terranes however although orogenic gold deposits have contributed over 20 of the global gold production their origins remain controversial the nitrogen concentration and isotopic composition of rocks and minerals are potentially powerful tracers of crustal metamorphism and mineralization but there have been few detailed applications of this approach to date although nitrogen isotopes have recently been used to elucidate the source of fluids in some neoarchean orogenic gold deposits and proterozoic to paleozoic mountain belts due to their age and geological complexity of these terranes major uncertainties as to the behavior of nitrogen remain the otago and alpine schists in the south island of new zealand comprise a large comparatively young the range of 15n values for mica and whole rock samples from the schists spans 0 2 to 7 0 and the nitrogen concentration from 23 to 3483 ppm sample provenance and rock type have minimal influence on the nitrogen concentration and isotopic value which appears to have been inherited from the original sedimentary kerogen there is no systematic variation between metamorphic temperature and 15n or n concentration in micas suggesting that there has been little discernible loss of 15n depleted fluids from silicates with increasing metamorphic temperature comparison of fluid mobile alkali element k rb and cs carbon and nitrogen whole rock concentrations indicates that for the otago and alpine schists in rocks up to upper greenschist facies significant nitrogen remains hosted in phases other than micas most likely poorly matured carbonaceous material samples from macraes flat a major gold producer have a similar range of 15n values to the host terrane but show distinctly higher nitrogen concentrations relative to unmineralized samples due to the incorporation of nitrogen from the mineralizing hydrothermal fluid this suggests that there is only a subtle metamorphic re distribution of nitrogen during mineralization albeit with minimal isotopic fractionation in the case of nitrogen at least the isotopic signatures of mineralized rocks support a metamorphic fluid source and are inconsistent with mantle or meteoric fluid reservoirs however due to the high relative abundance of nitrogen in sedimentary rocks compared to other potential reservoirs unless fluid fluxes are very large and well channeled nitrogen signatures are not sensitive recorders of fluid inputs from mantle magmatic or meteoric reservoirs conversely the absence of a sedimentary source nitrogen isotope signature similar to the host rock in an orogenic deposit would be a very strong indicator of an external exotic source for the mineralizing fluids

tectonically driven fluid flow and gold mineralisation in active collisional orogenic belts comparison between new zealand and western himalaya abstract hydrothermal activity and mesothermal styled gold mineralisation occurs near the main topographic divide of most active or young collisional mountain belts the southern alps of new zealand is used in this study as a model for the mineralising processes the collisional tectonics results in a two sided wedge shaped orogen into which rock is transported horizontally upper crustal rocks pass through the orogen and leave the orogen by erosion whereas lower crustal rocks are deformed into the mountain roots high relief drives meteoric water flow to near the brittle ductile transition lower to upper greenschist facies metamorphic reactions driven by deformation at the crustal decollement and in the root release water rich fluids that rise through the orogen intimate chemical interaction between fluid and rock results in dissolution and later precipitation of gold arsenic and sulphur fluid flow and mineralisation in the topographic divide region is facilitated by a network of steeply dipping faults and associated rock damage zones where oblique strike slip faults intersect the thrust faults that strike subparallel to the main mountain range the nanga parbat massif of the western himalaya is an example of an active collisional zone which hosts hydrothermal activity but no gold mineralisation the lack of gold mineralisation is due to the following factors co 2 dominated rising metamorphic fluid in dehydrated amphibolite granulite facies metamorphic rocks does not dissolve gold and arsenic hot up to 400 c meteoric water confined to fractures in the gneiss limits dissolution of gold and arsenic low density of hot water dry steam and low reduced sulphur content of fluid restrict solubility of gold and arsenic absence of fracture networks in the core of the massif and the small volumes of circulating fluid limit metal concentration and lack of reactive rock compositions limits chemically mediated metal deposition

nitrogen cycling during the cretaceous cenomanian turonian oceanic anoxic event ii low 15n values ranging from 1 2 to 3 9 and atomic carbon nitrogen c n ratios of 25 50 are characteristic of black shales deposited during the cenomanian turonian boundary interval and oceanic anoxic event ii oae ii an observed antithetic relationship between c n ratios and 15n could suggest a predominance of terrestrially derived organic matter or a diagenetic control on 15n variability shifting bulk 15n values lower however hydrogen indices hi generally 450 and a positive correlation of hi with c n mitigates against a significant terrestrial organic matter fraction high c n values are likely the result preferential degradation of labile n rich compounds during early diagenesis and loss of n as ammonium from sediments through time a hypothetical model that considers the degradation of a 15n enriched labile protein fraction yields only small 1 2 negative shifts in 15n however 15n depletion during diagenesis is contrary to normal isotope kinetics which should result in 15n enrichment of bulk organic matter therefore we conclude that the bulk 15n values in this study reflect primary changes in the nitrogen cycle the 15n data support the hypothesis of expanded nitrogen fixation driven by upwelling of nutrient nitrogen poor phosphorus replete waters during oae ii and from the mid cenomanian to santonian at demerara rise the low 15n values which are significantly lower than bulk 15n values in modern regions where nitrogen fixation is known to be important probably result from a more significant fraction of dissolved inorganic nitrogen being produced by nitrogen fixation during the peak of oae ii a marked shift to lower 15n values is observed this shift possibly reflects greater utilization of 15n depleted ammonium during a chemocline upward excursion cue dominance of low 15n values from other periods of more widespread marine anoxia is likely the result of similar processes

fluid infiltration into fault zones chemical isotopic and mechanical effects fluid infiltration into fault zones and their deeper level counterparts brittle ductile shear zones is examined in diverse tectonic environments in the 2 7 ga abitibi greenstone belt major tectonic discontinuities with lateral extents of hundreds of kilometres initiated as listric normal faults accommodating rift extension and acted as sites for komatiite extrusion and locally intense metasomatism during reverse motion on the structures accommodating shortening of the belt these transcrustal faults were utilised as a conduit for the ascent of trondhjemitic magmas from the base of the crust and of alkaline magmas from the asthenosphere and for the discharge of thousands of cubic kilometres of hydrothermal fluids such fluids were characterised by 18o 6 2 d 50 20 13c 4 4 and temperatures of 270 to 450 c probably derived from devolatilisation of crustal rocks undergoing prograde metamorphism hydrothermal fluids were more radiogenic 87sr 86sr 0 7010 to 0 7040 and possessed higher than did contemporaneous mantle komatiites or tholeiites and thus carried a contribution from older sialic basement a provinciality of87sr 86sr and 13c is evident signifying that fault plumbing sampled lower crust which was heterogeneous at the scale of tens of kilometres mineralised faults possess enrichments of large ion lithophile lil lil elements including k rb ba cs b and co2 and rare elements such as au ag as sb se te bi and w fluids were characterised by xco2 0 1 neutral to slightly acidic ph low salinity 3 wt k na 0 1 they carried minor ch4 co and n2 and they underwent transient effervescence of co2 during decompression clastic sediments occupy graben developed at fault flexures the40ar 39ar release spectra indicate that fault rocks experienced episodic disturbance on time scales of hundreds of millions of years

black shale deposition atmospheric co2 drawdown and cooling during the cenomanian turonian oceanic anoxic event 1 oceanic anoxic event 2 oae2 spanning the cenomanian turonian boundary ctb represents one of the largest perturbations in the global carbon cycle in the last 100 myr the 13ccarb 13corg and 18o chemostratigraphy of a black shale bearing ctb succession in the vocontian basin of france is described and correlated at high resolution to the european ctb reference section at eastbourne england and to successions in germany the equatorial and midlatitude proto north atlantic and the u s western interior seaway wis 13c offset between 13ccarb and 13corg is shown to be a good pco2 proxy that is consistent with pco2 records obtained using biomarker 13c data from atlantic black shales and leaf stomata data from wis sections boreal chalk 18o records show sea surface temperature sst changes that closely follow the 13c pco2 proxy and confirm tex86 results from deep ocean sites rising pco2 and sst during the late cenomanian is attributed to volcanic degassing pco2 and sst maxima occurred at the onset of black shale deposition followed by falling pco2 and cooling due to carbon sequestration by marine organic productivity and preservation and increased silicate weathering a marked pco2 minimum 25 fall occurred with a sst minimum plenus cold event showing 4 c of cooling in 40 kyr renewed increases in pco2 sst and 13c during latest cenomanian black shale deposition suggest that a continuing volcanogenic co2 flux overrode further drawdown effects maximum pco2 and sst followed the end of oae2 associated with a falling nutrient supply during the early turonian eustatic highstand

immiscible fluids in metamorphism implications of two phase flow for reaction history fluid immiscibility between a co 2 rich fluid and brine has been described from several medium to high grade marbles and calcsilicates here we also report evidence for ch 4 h 2 o immiscibility in low grade metamorphic rocks from wales and suggest that the flow of such immiscible fluids may be comparable to that of water oil or water gas mixtures in petroleum reservoirs this analogy implies that where one fluid is being produced by reaction it will flow out of the rock while the other remains immobile except insofar as it is soluble in the more abundant fluid phase hence extensive reaction may take place in the presence of coexisting immiscible fluids each having high activities it is proposed that this type of flow behavior not only accounts for the development of salt saturated fluids in marbles but also may be responsible for the elimination of carbonate and extensive loss of graphite from pelites in the lower part of the greenschist facies

geochemistry of syntectonic crustal fluid regimes along the lithoprobe southern canadian cordillera transect in conjunction with the lithoprobe southern canadian cordillera program an extensive examination of geochemical indicators of origins movement chemical evolution and economic significance of paleocrustal fluids was conducted the study area covers approximately 360 000 km2from the canadian rockies to vancouver island research incorporated petrological mineralogical fluid inclusion 18o d 13c and rb sr studies of samples of quartz carbonate veins and other rock types the results of the study document a variety of pre syn and postorogenic crustal fluid events in the rockies a major pre laramide hydrothermal event was identified which was comprised of a west to east migration of warm saline brines this was followed by a major circulation of meteoric water in the rockies during laramide uplift in the southern omineca extensional zone convecting surface fluids penetrated to the brittle ductile transition at 350 450 c and locally into the underlying more ductile rocks a principal c

elemental abundance anomalies in the late cenomanian extinction interval a search for the source s elemental abundances have been measured by neutron activation methods across the cenomanian turonian late cretaceous extinction interval in samples collected from sixteen sites in the western interior basin of north america and from twelve widely separated locations around the globe including six odp dsdp sites in most western interior basin sites in colombia and in western europe weaker two closely spaced elemental abundance peaks occur in the upper cenomanian 92 m y spanning the ammonite zones ofsciponoceras gracile throughneocardioceras juddii elements with anomalously high concentrations include sc ti v cr mn co ni ir pt and au the lower peak coincides with the disappearance extinction of the foraminiferrotalipora cushmani in north american sectionsr greenhornensis also disappears at or just below this horizon but in europe it disappears considerably earlier thanr cushmani a series of molluscan extinction and speciation or migration events also begins near the stratigraphic level of the lower elemental abundance peak the well documented positive 13c excursion begins just before the extinctions and the elemental anomalies and continues into the lower turonian well above the upper anomaly this carbon isotope excursion has been observed in east european sections where we find little or no evidence of the elemental anomalies suggesting that the two phenomena may not be tightly coupled elemental abundance ratios in the anomalies closely resemble those of mid atlantic ridge basalt or hawaiian lava tholeiitic but not those of c1 chondrite black shale average crustal rocks or lamproite and kimberlite of roughly similar age in southeastern kansas the excess ir and other siderophiles hint at possible large body impact s for the source however we have not located microspherules other than biogenic calcispheres or shocked mineral grains in any of our samples furthermore sc ti v and mn are not enriched in differentiated solar system bodies although the weak geochemical signal from comet impact s could be masked by the strong terrestrial like overprint these anomalies more likely resulted either from intense seafloor spreading activity or merely from increased circulation of deep metal rich water associated with the large late cenomanian through early turonian eustatic rise and deep water opening of the south atlantic the flooding of continental seaways and margins also could have contributed to the anomalies by preventing much continental detritus from diluting the normal background marine geochemical component

uplifted marine terraces along the alpine fault new zealand three types of evidence indicate that marine terraces are widespread in the southern alps of new zealand i remnants of shore platforms occur as distinct levels of notched ridge crests and flat summits degraded sea cliffs are common ii scattered quartz beach pebbles occur on 16 of 18 levels of exhumed shore platforms in the fox franz josef type area to altitudes as high as 1700 meters iii altitudinal spacings of new zealand terrace flights allow correlation with 18 dated global marine terraces at new guinea which were formed during glacio eustatic highstands of sea level within the last 336 x 10 3 years inferred uplift rates at fox franz josef increased from 3 2 to 7 8 meters per 10 3 years since about 135 x 10 3 to 140 x 10 3 years ago presumably because of increased convergence between the pacific and australian plates

does the primary deposit affect the biogeochemical transformation of placer gold and associated biofilms abstract placer gold particles derived from epithermal deposits display distinct morphological and compositional features compared with particles from mesothermal systems here it is hypothesized that the chemical composition of primary gold derived from different deposit types is a principle factor affecting the composition of resident biofilm communities as well as the transformation of placer particles gold particles were collected from placers originating from the epithermal system at the eisenberg germany s largest primary gold deposit for comparison placer gold from mesothermal sources was studied morphological differences due to mechanical transport and physical reshaping were not observed biogeochemical gold silver dissolution and gold re precipitation were evident on epithermal particles and they accentuate the silver fabrics and gold rich clusters in contrast on mesothermally derived gold particles these processes led to the development of gold rich rims via the formation of nano porous secondary gold microprobe and laser ablation mass spectrometric analyses of polished whole particle mounts confirmed differences in gold silver content distribution and trace metal content between particles from epi and mesothermal sources respectively on particles from all sites nano and micro particulate gold is associated with polymorphic layers these are composed of microbial cells extracellular polymeric substances eps and clay sized minerals multivariate statistical analyses shows a significant difference between biofilm communities from epi vs mesothermally derived particles which is linked to the chemical composition of the primary gold while a number of key species capable of gold transformation e g cupriavidus sp geobacter sp and rhodoferax sp were detected on particles from both sources higher numbers of organisms with the potential for gold solubilization precipitation and detoxification were associated with particles from the epithermal sources a range of species involved in gold transformation i e arthrobacter spp delftia sp shewanella sp and stenotrophomonas spp were detected only on epithermally derived placer gold this indicates the communities are sensitive to differences in gold silver and possibly trace metal cycling resulting from differences in their content distribution and mobilization behaviour in epi vs mesothermally derived particles ultimately this study shows that the chemical composition of the primary deposit strongly influences the biogeochemical transformation of placer gold and the composition of associated biofilms whereas physical transformations appear to be largely unaffected

origin and deposition of a graphitic schist hosted metamorphogenic au w deposit macraes east otago new zealand the macraes gold tungsten deposit occurs in a low angle thrust system in biotite grade otago schist native gold scheelite pyrite and arsenopyrite are found in and adjacent to quartz veins and silicified schist of lenticular reef zones where the thrust system cuts through graphitic pelitic schist mineralization is confined to a shear zone up to 80 m thick which is closely sub parallel to the regional schistosity chemical alteration is dominated by silicification with some addition of cr and depletion of sr and ba alteration extends only about 5 m from major veins oxygen becomes isotopically heavier away from veins due to temperature decrease as hot fluids penetrated into cooler 250 c rock graphite within the shear zone rocks has reflectance of 6 7 in oil similar to graphite in medium high grade otago schist and is presumed to be metamorphic in origin this graphite has acted as a reducing agent to cause precipitation of gold where the thrust system acting as a conduit for metamorphic fluids intersects the graphitic schist the metals were derived from the underlying schist pile which may include an over thrust oceanic assemblage containing metal enriched horizons

deep structure of the campanian lucanian arc southern apennine italy abstract recent exploration activities and successful discovery of large oil fields in the upper val d agri area southern apennine italy have encouraged the collection of large quantities of geological and geophysical data and their integration into comprehensive geological models here we present a series of structural profiles based on several hundred kilometres of seismic lines two and three dimensional and the results of many deep wells the best seismic lines have been extensively reprocessed and also tied to magnetotelluric data geological interpretations of those lines have been interactively tested and verified by gravity and magnetic modelling and structural balancing the wells and seismic data demonstrate that the fundamental tracts of the deep architecture of the orogen as it appears today were developed only at the end of the late pliocene the final closure of the ensialic shear zone responsible for the subduction of at least 150 km of continental lithosphere originally underlying the lagonegro basin can be dated as early pliocene the involvement of the inner apulian platform in the core of the belt and the activation of a new and more external left lateral oblique ensialic shear zone can be constrained to the late pliocene pleistocene the seismic profiles clearly show the underthrusting of the outer apulian platform unit beneath the inner apulian platform unit the thick skinned character of the plio pleistocene contractional structures is evident from the structural profiles this geometry is constrained by gravity magnetic data and structural considerations according to the relatively steep angle of dip about 10 of the apulian foreland beneath the chain the structural profiles depict the general architecture of the campanian lucanian arc the apennine platform and lagonegro unit are largely allochthonous and a part of the lagonegro basement could be buried below the apennine platform sole thrust the neogene plastic successions of the apennine platform and lagonegro basin were detached and now outcrop in the bradanic foredeep the inner apulian platform constitutes a huge thrust sheet structured as a wide antiform in the core of the belt its regional culmination roughly corresponds to the val d agri area extensional and transtensional structures cross cut the pre existing compressional structures as shown by the quaternary valleys of vallo di diano and val d agri the profiles shown also highlight the existing contrast between the deep structures in the core of the belt and the tectonic style of the lagonegro liguride and sicilide units these units were in fact subjected to brittle ductile deformation under metamorphic part of liguridi units and deep diagenetic to anchizonal conditions lagonegro units and were affected by a general overthrust shear directed towards the ne the inner apulian platform was on the contrary involved in the thrust belt together with its basement whereas the outer apulian platform affected by a subduction underwent a regional bending with associated normal faulting

impact of cretaceous sea level rise and anoxic events on the mesozoic carbonate platform of yugoslavia the adriatic dinaric carbonate platform of yugoslavia was influenced by rapid sea level rise and an oceanic anoxic event during the cenomanian turonian open marine biota such as planktonic foraminifera radiolarians and locally even ammonites associated with and bracketed by successions of typical shallow water carbonates indicate partial drowning of substantial areas of the platform during this time suggestive furthermore that the rate of increase of water depth was locally great enough to outpace carbonate production the presence of carbon rich and fish bearing platy limestones commonly cherty as an associated coeval facies indicates the development of anoxic or euxinic environments and the stromatolitic laminations in such rocks are attributed to the action of bacterial mats it is suggested that an extensive column of deoxygenated water developed in the neighboring marche umbrian adriatic deep water basin and was carried on to the carbonate platform during the cenomanian turonian transgression

benthic phosphorus regeneration net primary production and ocean anoxia a model of the coupled marine biogeochemical cycles of carbon and phosphorus we examine the relationships between ocean ventilation primary production water column anoxia and benthic regeneration of phosphorus using a mass balance model of the coupled marine biogeochemical cycles of carbon c and phosphorus p the elemental cycles are coupled via the redfield c p ratio of marine phytoplankton and the c p ratio of organic matter preserved in marine sediments the model assumes that on geologic timescales net primary production in the oceans is limited by the upwelling of dissolved phosphorus to the photic zone the model incorporates the dependence on bottom water oxygenation of the regeneration of nutrient phosphorus from particulate matter deposited at the water sediment interface evidence from marine and lacustrine settings modern and ancient demonstrates that sedimentary burial of phosphorus associated with organic matter and ferric oxyhydroxides decreases when bottom water anoxia dysoxia expands steady state simulations show that a reduction in the rate of thermohaline circulation or a decrease of the oxygen content of downwelling water masses intensifies water column anoxia dysoxia and at the same time increases surface water productivity the first effect reflects the declining supply of oxygen to the deeper parts of the ocean the second effect is caused by the enhanced benthic regeneration of phosphorus from organic matter and ferric oxyhydroxides sedimentary burial of organic carbon and authigenic calcium phosphate mineral francolite on the other hand is promoted by reduced ocean ventilation according to the model global scale anoxia dysoxia leads to a more efficient recycling of reactive phosphorus within the ocean system consequently higher rates of primary production and organic carbon burial can be achieved even when the continental supply of reactive phosphorus to the oceans remains unchanged

metabasalts as sources of metals in orogenic gold deposits although metabasaltic rocks have been suggested to be important source rocks for orogenic gold deposits the mobility of au and related elements as sb se and hg from these rocks during alteration and metamorphism is poorly constrained we investigate the effects of increasing metamorphic grade on the concentrations of au and related elements in a suite of metabasaltic rocks from the otago and alpine schists new zealand the metabasaltic rocks in the otago and alpine schists are of morb and wpb affinity and are interpreted to be fragments accreted from subducting oceanic crust gold concentrations are systematically lower in the higher metamorphic grade rocks average au concentrations vary little between sub greenschist 0 9 0 5 ppb and upper greenschist facies 1 0 0 5 ppb but decrease significantly in amphibolite facies samples 0 21 0 07 ppb the amount of au depleted from metabasaltic rocks during metamorphism is on a similar scale to that removed from metasedimentary rocks in otago arsenic concentrations increase with metamorphic grade with the metabasaltic rocks acting as a sink rather than a source of this element the concentrations of sb and hg decrease between sub greenschist and amphibolite facies but concentration in amphibolite facies rocks are similar to those in unaltered morb protoliths and therefore unaltered oceanic crust cannot be a net source of sb and hg in a metamorphic environment the concentrations of au as sb and hg in oceanic basalts that have become integrated into the metamorphic environment may be heavily influenced by the degree of seafloor alteration that occurred prior to metamorphism we suggest that metasedimentary rocks are much more suitable source rocks for fluids and metals in orogenic gold deposits than metabasaltic rocks as they show mobility during metamorphism of all elements commonly enriched in this style of deposit

southern alps cu au hydrothermal system westland new zealand the southern alps of new zealand is an actively rising mountain belt which displays a thermal anomaly adjacent to the alpine fault the australian pacific plate boundary extensive fluid movement occurs in this uplift zone resulting in metallic vein mineralization gold mineralization is confined to greenschist facies rocks while younger veins in amphibolite facies rocks near the alpine fault are enriched in copper transport and deposition of metals in this complex hydrothermal system is governed by interaction between rising metamorphic fluids and downward percolating meteoric fluid metamorphic fluids have equilibrated with graphitic schist country rock and are relatively reduced infiltration and mixing of meteoric water increases oxygen activity and decreases sulphur activity in the fluid oxidised meteoric water heats up and dissolves cu during downward percolation this cu is deposited as the fluid becomes more reduced hence there is a progressive increase in copper content in the middle portions of the hydrothermal system especially in the more permeable highly fractured rocks near the alpine fault

trace element abundances in the rock canyon anticline pueblo colorado marine sedimentary section and their relationship to caribbean plateau construction and oxygen anoxic event 2 1 rapid eruption of submarine lava flows during formation of the caribbean plateau correlates closely with ocean anoxic event 2 oae2 which bracketed the cenomanian turonian boundary 93 5 ma these events also correspond with a positive excursion in carbon isotopic composition of seawater hydrothermal activity associated with large scale submarine volcanism may have been responsible for this abrupt change in ocean chemistry we determined the distribution of major minor and trace element abundances in the rock canyon marine sedimentary section pueblo colorado after normalizing element concentrations to zr to remove the variable contribution of terrigenous material to these sediments we detected an interval of concentrated metal abundance anomalies that coincides with the abrupt beginning of the positive 13c isotope excursion the metal abundance anomalies indicate that intermittent hydrothermal activity in the form of both water rock exchange and magmatic degassing introduced large concentrations of trace metals into the cretaceous ocean at the same time that extinctions of benthic species turnover in plankton communities and increases in isotopically light organic carbon burial occurred the stratigraphic position of this interval of trace metal anomalies matches events associated with oae2 and indicates that intermittent hydrothermal activity on a massive scale triggered abrupt changes in carbon burial and deep ocean oxygen contents

orbital time scale and new c isotope record for cenomanian turonian boundary stratotype previous time scales for the cenomanian turonian boundary ctb interval containing oceanic anoxic event ii oae ii vary by a factor of three in this paper we present a new orbital time scale for the ctb stratotype established independently of radiometric biostratigraphic or geochemical data sets update revisions of ctb biostratigraphic zonation and provide a new detailed carbon isotopic record for the ctb study interval the orbital time scale allows an independent assessment of basal biozone ages relative to the new ctb date of 93 55 ma gts04 the d 13 corg data document the abrupt onset of oae ii significant variability in d 13 corg values and values enriched to almost 222 these new data underscore the difficulty in defining oae ii termination using the new isotope curve and time scale estimates of oae ii duration can be determined and exported to other sites based on integration of well established chemostratigraphic and biostratigraphic datums the new data will allow more accurate calculations of biogeochemical and paleobiologic rates across the ctb

the gold carbonate association source of co2 and co2 fixation reactions in archaean lode deposits abstract abundant carbonate is a ubiquitous feature of archaean lode gold deposits both in domains of alteration enveloping veins and in rocks enclosing auriferous sediments detailed studies of chemical mass balance in metabasalts progressively altered towards gold bearing quartz carbonate veins disposed within shear zones at yellowknife reveal massive additions of co2 k si and fe accompanying mineralisation with concomitant depletions of na coherent behaviour of al sc zr also v and nb provides a reference for constraining the volume relations during hydrothermal alteration in the peripheral regions of alteration depletions of ca and mg result in overall volume reduction but these elements are added to veins and their immediate alteration envelopes where there is a large positive volume change precious metals together with cr ni cu zn pb rb cd and ba have been added to the veins and altered wall rocks whereas quartz noble metals and other trace elements have been precipitated from hydrothermal fluids solution of ca mg and some fe indigenous to peripheral alteration regions combining with co2 from the mineralising reservoir appears to be the process for forming the abundant ferri dolomite gangue observations of many archaean au deposits reveals that carbonate chemistry reflects the nature of wall rocks with wall rocks donating the bivalent metal cations and hydrothermal fluids the co2 alteration reactions at yellowknife involved hydrolysis of albite accompanied by fixation of kaqueous to produce muscovite with na loss and hydrolysis of chlorite epidote with co2 fixation to form ferri dolomite studies of oxygen isotopes fe 2 fe 2 fe 3 and structure reveal that au quartz and carbonate were precipitated in the presence of fluids of probable metamorphic origin 18 o 8 9 at low redox potential and at ambient temperatures of 400 450 c during episodes of hydrofracturing the abundant co2 and k required for extensive carbonate muscovite replacement alteration could be supplied by fluids released during prograde metamorphism under greenschist or greenschist amphibolite facies conditions where the relative proportion of co 2 h 2 o is in the order of 0 2 to 0 5 and k na 1 given high co2 co in the hydrothermal reservoir these molecules may act as complexing agents for transport of au and other rare elements e g w pd ni cr