multistage pyrites in the nibao disseminated gold deposit southwestern guizhou province china insights into the origin of au from textures in situ trace elements and sulfur isotope analyses abstract nibao is a unique thrust fault controlled and strata bound disseminated gold deposit in southwestern guizhou province china in nibao pyrite is the major sulfide mineral and au is structurally bound au within the pyrite lattice in this study we conducted detailed analyses of the pyrite chemistry and s isotope composition in nibao using laser ablation inductively coupled plasma mass spectrometry la icp ms and laser ablation multi collector inductively coupled plasma mass spectrometry la mc icp ms respectively through petrographic and pyrite chemical studies four pyrite generations py1 py4 were distinguished framboidal pyrite py1 pre ore sedimentary stage clean pyrite overgrowing framboidal pyrite py2 pre ore diagenetic stage spongy pyrite py3 early ore stage and overgrowth of narrow pyrite rims surrounding py2 py3 and disseminated pyrite associated with arsenopyrite py4 main ore stage among these py2 and py4 are the most abundant the trace element content in py2 is characterized by a wide range of as cu sb and pb concentrations 2480 58100 ppm 55 4 1610 ppm 29 1 232 ppm and 24 1 376 ppm respectively while py4 has the highest au as cu and se contents 70 ppm 4200 1630 ppm and 38 3 ppm respectively the 34s values of pre ore pyrites measured by la mc icp ms in this study and the available data in the literature range broadly from 53 3 to 114 8 indicating that they were most likely generated by bacterial reduction from marine sulfate during sedimentation diagenesis meanwhile the 34s values of ore pyrites have relative narrow 34s values mostly varying from 5 to 5 and indicating that the s was derived either from the average of sedimentary rocks or from a magmatic source since igneous rocks are scarce in the region and the exposed 77 99 ma are clearly younger than the mineralization age of the nibao gold deposit 141 ma a magmatic source is unlikely in nibao all pyrites in this study show a positive correlation r2 0 71 between co and ni and the co ni and zn ni ratios of main stage py4 are close to or within the range defined for a sedimentary diagenetic origin suggesting a sedimentary source is more likely in nibao

textural control on gold distribution in as free pyrite from the dongping huangtuliang and hougou gold deposits north china craton hebei province china article i nfo pyrite from the dongping huangtuliang and hougou gold deposits hebei province china was investigated using a combination of ore microscopy including back scattered imaging and in situ laser ablation inductively coupled plasma mass spectroscopy la icp ms a range of elements including au te ag pb bi cu co ni and as was analyzed with the aim to constrain the textural controls and influence of superimposed deformation on the distribution of invisible gold in as free pyrite thedatasetshowsexcellentcorrespondence betweenmeasuredhighgoldvaluesandthreekeytexturalcriteria i areasofclusteredtellurideinclusions especiallyindongping ii microshearingandfracturing brecciation dongping and huangtuliang and iii pyrite recrystallization huangtuliang invisible gold is only at trace levels in the hougou and gold bearing telluride minerals are not observed this is considered to result from larger scale remobilization of gold during advanced brecciation and recrystallization of pyrite pyrite grains containing clustered inclusions have by far the highest gold concentrations up to 1 wt with consistent values of thousands of ppm au interpretation of textures and la icp ms data infers that in these areas the distribution of telluride inclusions extends pervasively from micron to nanoscale i e as fields of nanoparticles local employment of coupled dissolution reprecipitation reaction between pyrite and fluids driving the k metasomatic alteration dated at 150 ma is invoked to explain such patterns syn deformational grain scale mobilization of gold and other elements took place leading to a portion of the gold being recrystallized within fractures and microshears the deformational event leads to gold enrichment in the huangtuliang pyrite where brittle fracturing brecciation has been followed by a resorption and recrystallization in the latter case foam textured pyrites again without as can contain up to hundreds of ppm gold theinterpreted sequenceof pyritepost depositional eventsis inaccordancewith the protracted magmaticevolution of the area starting with variscan alkaline intrusions 390 ma and reactivated during the yanshanian orogeny 150 ma thestudyshows i thatas freepyritecanreadilycontainsignificantamountsofinvisiblegold bothasnanoparticles

robust multi proxy data integration using late cretaceous paleotemperature records as a case study abstract in paleoclimate studies multiple temperature records are often compared and combined to evaluate temperature trends yet no standardized approach for integrating proxy derived paleotemperature records exists in addition paleotemperature data are often reported without uncertainty estimates prediction errors and raw data are not always available this complicates the quantification of for example temperature trends and the magnitude of warming events here we propose a robust quantitative approach for multi proxy analysis in paleoclimate studies to demonstrate this we study the latest maastrichtian warming event lmwe in the odp 174ax bass river core new jersey and integrate five independent paleotemperature proxies covering the last million years of the cretaceous our integrated temperature reconstruction suggests that after a climatically stable period a latest cretaceous warming of 3 9 1 1 c occurred between 450 and 100 kyr before the k pg boundary the error on this reconstructed temperature should be considered the absolute minimum error as poorly constrained or unknown uncertainties cannot be fully propagated the warming event was followed by a gradual cooling to pre warming conditions towards the end of the cretaceous furthermore the record suggests multiple warming pulses during the lmwe the results of this integrated approach are consistent with other latest cretaceous temperature records suggesting that the trend described here represents a global signal

evidence from sulfur isotope and trace elements in pyrites for their multiple post depositional processes in uranium ores at the stanleigh mine elliot lake ontario canada

effects of diagenesis on the isotopic record of late paleogene tropical sea surface temperatures abstract oxygen isotope records of planktonic foraminifera indicate that late eocene and oligocene tropical sea surface temperatures were as much as 8 c lower than present at a time when high latitude sea surface temperatures were higher than present using a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate the effects of diagenesis on bulk carbonate 18 o records for the cenozoic are quantified for four tropical sites most of the observed variations in measured 18 o values at all sites can be accounted for by diagenetic effects there are no systematic trends that support substantial variations in tropical sea surface temperatures beyond diagenetic effects with the possible exception of the early eocene for which the data are consistent with slightly higher sea surface temperatures reconstructions based on oxygen isotope records of planktonic foraminifera which indicate cooler tropical sea surface temperatures for the eocene and oligocene may be artifacts of diagenetic recrystallization as such records are particularly sensitive to diagenetic effects

the end cretaceous in the southwestern tethys elles tunisia orbital calibration of paleoenvironmental events before the mass extinction an integrated study of magnetic mass susceptibility ms bulk stable isotopes and calcareous nannofossil paleoecological changes is undertaken on the late maastrichtian of the elles section tunisia spanning the last ca 1 myr of the cretaceous a cyclostratigraphic analysis reveals the presence of milankovitch frequencies and is used for proposal of two distinct orbital age models and to provide ages of important stratigraphic horizons relative to the age of the cretaceous paleogene boundary k pgb principal component analysis pca performed on the nannofossil assemblage reveal two main factors pca1 mostly representing fluctuations of d rotatorius p stoveri lithraphidites spp retecapsa spp staurolithites spp micula spp and pca2 mostly representing fluctuations of a regularis c ehrenbergii micula spp rhagodiscus spp w barnesiae and zeugrhabdotus spp variations in pca1 and pca2 match changes in bulk 13c and 18o respectively and suggest changes in surface water fertility and temperatures and associated stress the variations in abundances of high latitude taxa and the warm water species micula murus and in bulk 18o delineate fast changes in sea surface paleotemperatures as in many other sites an end maastrichtian greenhouse warming is highlighted followed by a short cooling and an additional warm pulse in the last 30 kyr of the maastrichtian which has rarely been documented so far orbital tuning of the delineated climatic events is proposed following the two different age models calcareous nannofossil assemblages highlight a decrease in surface water nutriency but their species richness remains high through the latest maastrichtian indicating in tunisia a weak impact of deccan volcanism on calcareous nannoplankton diversity before the mass extinction

geochemistry and textures of gold bearing arsenian pyrite twin creeks nevada implications for deposition of gold in carlin type deposits this study relates morphology size texture and chemistry of arsenian pyrite in the twin creeks carlin type gold deposits to the chemical position and amount of gold that it contains arsenian pyrite is confirmed as the most important gold hosting mineral and four types of gold bearing arsenian pyrite are recognized among these four types the lowest amount of gold and arsenic 1 wt as 17 60 ppm au is contained in arsenian pyrite with relatively large grain sizes 10 30 mu m it formed at relatively high temperatures 250 degrees c and k super h super ratios adularia stable probably relatively slowly the largest amount of gold and arsenic 1 05 2 43 wt as 595 1 465 ppm au is contained in arsenian pyrite with small grain sizes up to 2 mu m that formed at low temperatures 120 degrees 200 degrees c and moderate k super h super ratios illite stable probably by relatively rapid deposition xanes exafs and sims analyses show that gold in arsenian pyrite is both structurally bound au i and in submicroscopic inclusions of free gold au highest amounts of structurally bound gold were observed in the relatively coarse grained arsenian pyrite noted above whereas most inclusions of free gold were observed in fine grained arsenian pyrite in general there is a good correlation between gold and arsenic in arsenian pyrite although au as ratios vary from one pyrite to another it is suggested that gold in arsenian pyrite was deposited by direct deposition of native gold and by adsorption of au i from hydrothermal solutions adsorption of gold by arsenian pyrite can take place from solutions that are not saturated with respect to native gold relative volumes of gold bearing pyrite from different paragenetic stages at twin creeks suggest that as much as 50 percent of the total gold in the deposit could have formed from solutions that were not saturated with respect to native gold because both au and au i are found together in arsenian pyrite it is likely that they were deposited by the same process consideration of possible depositional reactions suggests that a decrease in the activity of reduced sulfur is most likely to cause gold deposition

a stable isotopic record of the maastrichtian ocean climate system south atlantic dsdp site 528 abstract the upper maastrichtian interval of mid latitude south atlantic deep sea drilling project site 528 spans approximately the last 4 million years of the cretaceous the isotopic record of this sequence indicates that relatively large 0 5 1 0 late maastrichtian oxygen and carbon isotopic shifts occurred on geologically short time scales less than 100 500 kyr comparison with previous oxygen isotopic data suggests that in high and mid latitude southern oceans the multimillion year maastrichtian cooling trend largely resulted from geologically rapid climatic steps coincidence of the largest carbon and oxygen isotopic excursions suggests that relatively large and geologically rapid changes in marine and atmospheric carbon content may have directly contributed to the long term cooling of the late cretaceous greenhouse

decoupled geochemical behavior of as and cu in hydrothermal systems cu rich and as rich growth zones in pyrite provide new insights into the composition of late stage magmatic fluids and their host hydrothermal ore deposits the pyrite is from the pueblo viejo dominican republic and yanacocha peru high sulfidation gold silver deposits which are thought to form from hydrothermal systems that interacted with magmatic vapor plumes electron microprobe analysis secondary ion mass spectrometry and elemental maps show that pyrite the most common sulfide mineral in both deposits contains three different types of growth zones 1 as rich zones that are enriched in au ag sb te and pb 2 cu rich zones with significantly lower concentrations of these elements and 3 barren pyrite zones with no other elements these zones are interpreted to result from mixing between the pyrite forming fluid and vapors that invaded the main hydrothermal system episodically comparison to experimental studies of elemental partitioning and analyses of fumaroles and fluid inclusions from magmatic hydrothermal systems suggests that the as rich vapor formed at high and possibly magmatic temperatures whereas the cu rich vapor formed at lower temperatures possibly during migration of the original magmatic vapor the presence of finely spaced multiple growth zones in pyrite suggests that the composition of at least high sulfidation hydrothermal systems can be affected intermittently and repetitively by vapors probably from underlying magmas

origin of fe mn si layers associated with the permian volcanic hosted massive sulphide deposits in the tasik chini district peninsular malaysia abstract the volcanic hosted massive sulphide vhms deposits in the tasik chini district peninsular malaysia are hosted in permian volcano sedimentary rocks and are composed of fe mn si layers which occur stratigraphically above the ore bodies the oxide layers are 1 cm to 2 m thick and occur discontinuously throughout the bukit botol deposit whereas layer of oxides up to 10 m thick occurs continuously over a strike length of over 50 m at the bukit ketaya deposit their mineralogy is dominated by hematite quartz barite magnetite pyrite clastic components and commonly exhibit massive iron silica banding to microbreccia like textures the fe mn si layers from the bukit botol and bukit ketaya deposits generally have high si fe mn and base metals contents various proportions of al zr and ti and high levels of ba as u and v such mineralogical and geochemical concentrations and other geological suggest that the associated fe mn si layers were deposited by the mixing of mainly chemical components and to a smaller degree detrital components in a local submarine environment due to hydrothermal activity on the seafloor

age and paleoenvironment of the maastrichtian to paleocene of the mahajanga basin madagascar a multidisciplinary approach abstract lithology geochemistry stable isotopes and integrated high resolution biostratigraphy of the berivotra and amboanio sections provide new insights into the age faunal turnovers climate sea level and environmental changes of the maastrichtian to early paleocene of the mahajanga basin of madagascar in the berivotra type area the dinosaur rich fluvial lowland sediments of the anembalemba member prevailed into the earliest maastrichtian these are overlain by marginal marine and near shore clastics that deepen upwards to hemipelagic middle neritic marls by 69 6 ma accompanied by arid to seasonally cool temperate climates through the early and late maastrichtian an unconformity between the berivotra formation and betsiboka limestone marks the k t boundary and juxtaposes early danian zone plc or pld and latest maastrichtian zones cf2 cf1 micula prinsii sediments seasonally humid warm climates began near the end of the maastrichtian and prevailed into the early danian accompanied by increased volcanic activity during the late danian zones p1d p2 a change to seasonally arid climates was accompanied by deepening from middle to outer neritic depths

characterization of late campanian and maastrichtian planktonic foraminiferal depth habitats and vital activities based on stable isotopes abstract depth habitats of 56 late cretaceous planktonic foraminiferal species from cool and warm climate modes were determined based on stable isotope analyses of deep sea samples from the equatorial pacific dsdp sites 577a and 463 and south atlantic dsdp site 525a the following conclusions can be reached planoglobulina multicamerata de klasz and heterohelix rajagopalani govindan occupied the deepest plankton habitats followed by abathomphalus mayaroensis bolli globotruncanella havanensis voorwijk gublerina cuvillieri kikoine and laeviheterohelix glabrans cushman also at subthermocline depth most keeled globotruncanids and possibly globigerinelliodes and racemiguembelina species lived at or within the thermocline layer heterohelix globulosa ehrenberg and rugoglobigerina pseudotextularia and planoglobulina occupied the subsurface depth of the mixed layer and pseudoguembelina species inhabited the surface mixed layer however depth ranking of some species varied depending on warm or cool climate modes and late campanian or maastrichtian age for example most keeled globotruncanids occupied similar shallow subsurface habitats as rugoglobigerina during the warm late campanian but occupied the deeper thermocline layer during cool climatic intervals two distinct types of vital effect mechanisms reflecting photosymbiosis and respiration effects can be recognized by the exceptional 13c signals of some species 1 photosymbiosis is implied by the repetitive pattern of relatively enriched 13c values of racemiguembelina strongest planoglobulina rosita and rugoglobigerina species pseudoguembelina excolata weakest 2 enriched respiration 12c products are recognized in a mayaroensis gublerina acuta de klasz and heterohelix planata cushman isotopic trends between samples suggest that photosymbiotic activities varied between localities or during different climate modes and may have ceased under certain environmental conditions the appearance of most photosymbiotic species in the late maastrichtian suggests oligotrophic conditions associated with increased water mass stratification

the coniacian santonian sedimentary record in southern tanzania ruvuma basin east africa planktonic foraminiferal evolutionary geochemical and palaeoceanographic patterns a 101 m thick stratigraphically complete late coniacian early santonian ca 89 to 83 ma sedimentary sequence drilled in tanzania tanzania drilling project site 39 allows for the first time examination of the planktonic foraminiferal biostratigraphy and evolution the depositional history and geochemical patterns of the subtropical tropical indian ocean region the sedimentary succession corresponds to an outer shelf to upper slope setting and is dominated by calcareous clayey siltstones and mudstones the occurrences of tethyan marker species enable application of the tropical biozonation including identification of the dicarinella concavata and d asymetrica zones in addition tanzania drilling project site 39 is proposed as reference section for the coniacian santonian boundary in the indian ocean with the boundary placed at the lowest occurrence of globotruncana linneiana in agreement with the gssp stratotype spain the record at tanzania drilling project 39 provides a unique opportunity to document the planktonic foraminiferal evolution in a subtropical marginal sea environment during a key period in their evolutionary history characterized by a major radiation among the deep dwelling taxa combined documentation of lithological and geochemical changes caco3 corg 13ccarb and 18ocarb reveal a setting influenced by continental derived nutrients in the d concavata zone lindi formation with a change to higher carbonate production and reduced surface water primary productivity in the overlying d asymetrica zone nangurukuru formation planktonic foraminiferal assemblage changes mirror the depositional and geochemical trends and indicate a progressive shift from a more eutrophic to a more oligotrophic regime through time at the local scale this palaeoceanographic scenario is consistent with the deepening of coastal tanzania in response to the late cretaceous marine transgression registered in south east tanzania because the tectonic evolution and sea level rise along the east africa continental margin is superimposed on the coniacian campanian global long term sea level high this study hypothesizes that the epicontinental invasion of blue waters may have favoured radiation among deep dwelling taxa this article is protected by copyright all rights reserved

biotic effects of the chicxulub impact k t catastrophe and sea level change in texas abstract biotic effects of the chicxulub impact the k t event and sea level change upon planktic foraminifera were evaluated in a new core and outcrops along the brazos river texas about 1000 km from the chicxulub impact crater on yucatan mexico sediment deposition occurred in a middle neritic environment that shallowed to inner neritic depths near the end of the maastrichtian the sea level fall scoured submarine channels which were infilled by a sandstone complex with reworked chicxulub impact spherules and clasts with spherules near the base the original chicxulub impact ejecta layer was discovered 45 60 cm below the sandstone complex and predates the k t mass extinction by about 300 000 years results show that the chicxulub impact caused no species extinctions or any other significant biotic effects the subsequent sea level fall to inner neritic depth resulted in the disappearance of all larger 150 m deeper dwelling species creating a pseudo mass extinction and a survivor assemblage of small surface dwellers and low oxygen tolerant taxa the k t boundary and mass extinction was identified 40 80 cm above the sandstone complex where all but some heterohelicids hedbergellids and the disaster opportunistic guembelitrids went extinct coincident with the evolution of first danian species and the global 13c shift these data reveal that sea level changes profoundly influenced marine assemblages in near shore environments that the chicxulub impact and k t mass extinction are two separate and unrelated events and that the biotic effects of this impact have been vastly overestimated

paleoenvironments of the latest cretaceous oil shale sequence southern tethys israel as an integral part of the prevailing upwelling system abstract the late cretaceous succession in israel is part of an extensive high productivity upwelling regime that persisted over 20 m y in the southern margins of tethys the deposition of a 40 m thick organic rich carbonate oil shale sequence in the negev israel indicates a major change in the evolution of this high productivity regime and reorganization of the marine ecosystem during the latest campanian early maastrichtian time the main objective of this study was to reconstruct changes in surface water productivity and seafloor oxygenation during the deposition of the oil shale member osm and transitions with the underlying phosphate and overlying marl members using high resolution records of planktic and benthic foraminifera and total organic carbon toc content the updated age of the osm determined by integrating planktic foraminifera calcareous nannofossils and inoceramids suggests that this sequence spans a maximum of 1 85 m y from 71 6 to 69 85 ma with a sedimentation rate of at least 2 4 cm kyr five distinct planktic p types and benthic b type foraminiferal assemblages were distinguished in the studied sequence the change from p type 5 to p type 1 along the sequence correlates with a distinct decrease in toc content 18 0 0 1 wt and signifies an upward decline in surface productivity based on this relationship it was inferred that species of globigerinelloide s principally globigerinelloides asper are the best tracers for extreme eutrophic surface water whereas heterohelicids are associated with more mesotrophic conditions the transition in time from assemblages b types 5 to 1 mainly reflects a change from the predominance of praebuliminids and neobuliminids to a more diversified rotaliid dominated assemblage indicating an increase in bottom water aeration the appearances of planktic foraminifera coincident with the establishment of benthic rotaliid fauna at the phosphate oil shale member transition mark the most prominent change in the upwelling sequence this change probably reflects moderate weakening of the eutrophic surface water productivity and a regional sea level rise resulting in seafloor deepening and improved seafloor aeration a further step in the decrease in toc content to 5 5 8 wt occurs in the uppermost part of the osm latest campanian and corresponds to the transitions to assemblages p type 1 and b type 1 this change suggests a shift to mesotrophic conditions additional increase in bottom and pore water aeration and thus the demise of the upwelling activity in the southern tethys

compilation and time series analysis of a marine carbonate δ18o δ13c 87sr 86sr and δ34s database through earth history abstract the sr s o and c isotope database of marine carbonates contains over 55 000 published isotope values of low mg calcite from diagenetically little altered phanerozoic fossil shells as well as samples of whole rocks and calcite cements of ordovician to archean age carbon and oxygen isotope data for the shell material are divided into habitat subsets high mid low latitude and deep sea and whole rock data are separated by mineralogy into calcite dolomite subsets trend correlation wavelet and spectral analyses on gaussian filtered isotope records were applied to detect and quantify similarities and patterns in temporal records with the following results 1 oxygen isotope trends from the high latitude and deep sea habitats are almost indistinguishable through the last 115 ma consistent with the existence of the oceanic conveyor belt throughout this interval 2 all oxygen isotope habitat records show a strong coherent 30 45 ma 38 ma cyclicity throughout the cretaceous and the cenozoic 3 up to 70 of the multi million year variability in the 18o record of the last 115 ma can be simulated by the following equation 18 o 0 64 sin 2 t 120 ma 0 9 x sin 2 t 38 3 ma 1 1 with x ranging from 0 4 0 6 for the low high latitude and deep sea habitats to 0 8 for the mid latitude realm 1 a 120 20 ma cycle occurs in the paleozoic and neoproterozoic 18o record consistent with paleoclimate variability as interpreted from sedimentological and faunal records 2 the offset of 13c values between deep water and high latitude vs surficial habitats at lower latitudes is consistent with the operation of a biological pump in the oceans since at least the cretaceous 3 sr and s isotope records exhibit a 60 70 ma cyclicity throughout the phanerozoic

abrupt deep sea warming at the end of the cretaceous climatic and oceanographic variations during the last 2 m y of the maastrichtian inferred from high resolution 10 k y stable isotope analysis of the mid latitude south atlantic deep sea drilling project site 525 reveal a major warm pulse followed by rapid cooling prior to the cretaceous tertiary boundary between 66 85 and 65 52 ma cool but fluctuating temperatures average 9 9 and 15 4 c in intermediate and surface waters respectively this interval is followed by an abrupt short term warming between 65 45 and 65 11 ma which increased temperatures by 2 3 c in intermediate waters and decreased the vertical thermal gradient to an average of 2 7 c this warm pulse may be linked to increased atmospheric pco 2 increased poleward heat transport and the switch of an intermediate water source from high to lowmiddle latitudes during the last 100 k y of the maastrichtian intermediate and surface temperatures decreased by an average of 2 1 and 1 4 c respectively compared to the maximum temperature between 65 32 and 65 24 ma

late maastrichtian warming in the boreal realm calcareous nannofossil evidence from denmark abstract the climate of the mid to late cretaceous was probably one of the warmest of the phanerozoic but by the late maastrichtian distinctly cool high latitude regions had developed studies from low latitude sites have demonstrated that the late maastrichtian cooling was punctuated by two pulses of warming but the response of nannoplankton to climatic fluctuation in the mid to high northern latitudes is not well documented a high resolution nannofossil study was undertaken on subsurface chalk sections of denmark which provide a stratigraphically complete record of late maastrichtian sedimentation of nannofossil ooze in an extensive mid to high latitude carbonate province the quantitative nannofossil data from cored sections through the upper maastrichtian chalk reveal subtle but significant shifts in taxa interpreted as having been sensitive to temperature fluctuations arkhangelskiella cymbiformis kamptnerius magnificus lucianorhabdus cayeuxii nephrolithus frequens and watznaueria barnesiae and indicate two late maastrichtian warming events correlatable with those of low latitude records and a decrease in surface water temperatures in the latest maastrichtian

nanoscale liquid inclusions of as fe s in arsenian pyrite a new mode of arsenic incorporation into arsenian pyrite has been discovered electron microprobe analyses and elemental maps of arsenian pyrite from pueblo viejo dominican republic show that its chemical composition varies from fe0 998as0 003 1 001s2 to fe0 963as0 050cu0 003ag0 001 1 017s2 and that arsenic is inversely correlated with fe high resolution transmission electron microscopy hrtem images show that some arsenic in this pyrite is present as nanoscale inclusions of amorphous as fe s in a matrix of arsenian pyrite the amorphous inclusions display negative facets with a cubic or rectangular morphology typical of negative inclusions of pyrite and arsenopyrite or marcarsite respectively and they are oriented parallel to the lattice fringes 100 of the arsenian pyrite matrix elemental maps collected by high angle annular dark field scanning transmission electron microscopy haadf stem show that the inclusions have a higher content of arsenic than the surrounding pyrite and tem edx analyses indicate approximate atomic proportions of 62 at s 28 at fe and 10 at as for the inclusions which are near the minimum melting temperature in the as fe s ternary these observations suggest that the inclusions were trapped as liquids during growth of the surrounding arsenian pyrite although not a new mineral this constitutes a third form for arsenian pyrite which has previously been shown to contain arsenic as either as1 or as3

thermal behavior of metal nanoparticles in geologic materials although significant progress has been made in understanding the behavior of natural nanoparticles in earth s critical zone i e surface and near surface environment little is known about nanoparticle stability in higher temperature environments where they are increasingly being found here we report the first direct observations of the thermal behavior of natural nanoparticles at near atomic scale revealing that their thermal stability is dependent on particle size and on the surrounding host mineral native au nanoparticles mean diameter 4 nm incorporated in arsenian pyrite from refractory au ores were observed under the transmission electron microscope during in situ heating to 650 c while isolated au nanoparticles melt with the melting point being a function of size we show that when incorporated in arsenian pyrite au nanoparticles become unstable unless the nanoparticle size distribution coarsens by diffusion driven solid state ostwald ripening this change in nanoparticle stability starts above 370 c setting an upper temperature and size limit for the occurrence of nanoparticulate au in refractory sulfides these findings not only provide new insights into the behavior of nanoparticulate au and other metals during geological processes and throughout their metallurgical recovery from refractory ores but also provide a new tool to define the thermal history of nanoparticle bearing geologic and planetary materials

tectonic evolution of the malay peninsula abstract the malay peninsula is characterised by three north south belts the western central and eastern belts based on distinct differences in stratigraphy structure magmatism geophysical signatures and geological evolution the western belt forms part of the sibumasu terrane derived from the nw australian gondwana margin in the late early permian the central and eastern belts represent the sukhothai arc constructed in the late carboniferous early permian on the margin of the indochina block derived from the gondwana margin in the early devonian this arc was then separated from indochina by back arc spreading in the permian the bentong raub suture zone forms the boundary between the sibumasu terrane western belt and sukhothai arc central and eastern belts and preserves remnants of the devonian permian main palaeo tethys ocean basin destroyed by subduction beneath the indochina block sukhothai arc which produced the permian triassic andesitic volcanism and i type granitoids observed in the central and eastern belts of the malay peninsula the collision between sibumasu and the sukhothai arc began in early triassic times and was completed by the late triassic triassic cherts turbidites and conglomerates of the semanggol formation were deposited in a fore deep basin constructed on the leading edge of sibumasu and the uplifted accretionary complex collisional crustal thickening coupled with slab break off and rising hot asthenosphere produced the main range late triassic earliest jurassic s type granitoids that intrude the western belt and bentong raub suture zone the sukhothai back arc basin opened in the early permian and collapsed and closed in the middle late triassic marine sedimentation ceased in the late triassic in the malay peninsula due to tectonic and isostatic uplift and jurassic cretaceous continental red beds form a cover sequence a significant late cretaceous tectono thermal event affected the peninsula with major faulting granitoid intrusion and re setting of palaeomagnetic signatures

sea surface temperature record of a late cretaceous tropical southern tethys upwelling system abstract late cretaceous sea surface temperatures ssts were reconstructed based on tex 86 data from the unique high productivity upwelling system in the southern tethys margin israel ssts were determined from two oil shale sequences of the santonian early maastrichtian 85 to 68 ma in southern efe syncline and central shefela basin israel paleo latitude 8 15 n these two sampling sites represent the inner and outer belts of the upwelling system our tex 86 data indicate a significant long term sst cooling trend from 36 0 to 29 3 c during the late santonian and the early campanian in the southern tethys margin consistent with the opening of the equatorial atlantic gateway eag based on our data from the equatorial region and literature data from the polar region we reassessed the equator to pole sst gradient to 22 c this value is closer to the modern ocean equator to pole sst gradient 30 c than suggested from previous studies furthermore the sst data suggests the presence of cooler surface water in the inner belt 27 7 c caused by the upwelling system and warmer surface water 29 2 c further seaward in the outer belt

new evidence concerning the age and biotic effects of the chicxulub impact in ne mexico abstract in the 1990s the chicxulub impact was linked to the k t boundary by impact spherules at the base of a sandstone complex that was interpreted as an impact generated tsunami deposit since that time a preponderance of evidence has failed to support this interpretation revealing long term deposition of the sandstone complex the k t boundary above it and the primary impact spherule ejecta interbedded in late maastrichtian marls below based on evidence from mexico and texas we suggested that the chicxulub impact predates the k t boundary impact tsunami proponents have challenged this evidence largely on the basis that the stratigraphically lower spherule layer in mexico represents slumps and widespread tectonic disturbance although no such evidence has been presented the decades old controversy over the cause of the k t mass extinction will never achieve consensus but careful documentation of results that are reproducible and verifiable will uncover what really happened at the end of the crectaceous this study takes an important step in that direction by showing 1 that the stratigraphically older spherule layer from el penon ne mexico represents the primary chicxulub impact spherule ejecta in tectonically undisturbed sediments and 2 that this impact caused no species extinctions

cenomanian to coniacian sea level changes in the lower benue trough nkalagu area nigeria and the eastern dahomey basin palaeontological and sedimentological evidence for eustasy and tectonism

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

mesozoic climates and oceans a tribute to hugh jenkyns and helmut weissert the study of past greenhouse climate intervals in earth history such as the mesozoic is an important relevant and dynamic area of research for many sedimentary geologists geochemists palaeontologists and climate modellers the mesozoic sedimentary record provides key insights into the mechanics of how the earth system works under warmer conditions providing examples of natural climate change and perturbations to ocean chemistry including anoxia that are of societal relevance for understanding and contextualizing ongoing and future environmental problems furthermore the deposition of widespread organic carbon rich sediments black shales during the mesozoic means that this is an era of considerable economic interest in july 2015 an international group of geoscientists attended a workshop in ascona switzerland to discuss all aspects of the mesozoic world and to celebrate the four decade long contributions to our understanding of this fascinating era in earth history made by hugh jenkyns university of oxford and helmut weissert eth zurich this volume of sedimentology arose from that meeting and contains papers inspired by and co authored by hugh and helmi here a brief introduction to the volume is provided that reviews aspects of hugh and helmi s major achievements contextualizes the papers of the thematic issue and discusses some of the outstanding questions and areas for future research this article is protected by copyright all rights reserved

pyrite composition and ore genesis in the prince lyell copper deposit mt lyell mineral field western tasmania australia the prince lyell copper gold silver deposit occurs in the late cambrian mt read volcanics at queenstown tasmania steeply plunging broadly conformable lenses of disseminated and stringer pyrite chalcopyrite mineralisation occur in quartz sericite chlorite rocks derived from intense alteration of predominantly felsic lavas and volcaniclastic rocks middle devonian deformation has substantially modified primary sulphide textures although extensively fractured pyrite grains in the ore have retained their original pre deformation internal structure and chemistry which are revealed by etching and electron microprobe analysis earliest sulphide mineralisation produced oscillatory zoned cobalt rich pyrite pyrite i coeval with chalcopyrite mineralisation cobalt rich pyrite is commonly associated with cambrian volcanic rocks in western tasmania and suggests a volcanogenic origin for the ore fluids at prince lyell pyrite i was corroded by later hydrothermal fluids and reprecipitated as unzoned trace element poor pyrite pyrite ii commonly as overgrowths on pyrite i cores minor amounts of a second cobalt rich pyrite pyrite iii occurs with pyrite ii in composite pyrite overgrowths sulphur isotope ratios from all pyrite generations fall within a small range 3 to 11 in situ isotopic analyses showed no consistent 34s variation between the various pyrite generations suggesting recycling of sulphur derived from a single cambrian volcanogenic source hematite alteration derived from oxidised fluids possibly from the adjacent hematitic owen conglomerate occurs in the structural footwall volcanics and the great lyell fault zone hematite inclusions in pyrite ii and iii indicate that these pyrite generations occurred after or during deposition of the conglomerate it is postulated that pyrite ii and iii were deposited during waning volcanism contemporaneous with owen conglomerate sedimentation in the late cambrian or early ordovician the great lyell fault would have acted as a growth fault margin between a terrestrial basin filling rapidly from the east and the volcanic terrane to the west the scenario raises the possibility that the concentration of mineral deposits and hematitic alteration along the great lyell fault resulted from the subsurface interaction of reduced volcanogenic fluids and oxidised basin waters along the growth fault contact

extinction dissolution and possible ocean acidification prior to the cretaceous paleogene k pg boundary in the tropical pacific abstract biotic perturbations and changes in ocean circulation during the maastrichtian stage of the latest cretaceous raise questions about whether the biosphere was preconditioned for the end cretaceous mass extinction of calcareous plankton a brief acme of inoceramid clams at 71 ma on shatsky rise in the tropical north pacific was followed by their extinction during the mid maastrichtian event at 70 1 ma associated with an abrupt warming of deep waters this was later followed by an interval of intense dissolution beginning 67 8 ma at odp site 1209 2387 m the late maastrichtian dissolution interval was initially gradual and is characterized by a low planktic benthic p b ratio highly fragmented planktic foraminifera mostly an absence of larger taxa low abundances of smaller taxa extremely low planktic foraminiferal numbers and low planktic foraminiferal and nannofossil species richness a partial recovery in carbonate preservation and calcareous plankton simple diversity began 250 kyr prior to the k pg boundary associated with the incursion of a younger more enriched 13c deep water mass although total abundances of planktic foraminifera in the sediment remained a tiny fraction of their earlier maastrichtian values a second brief dissolution event occurred 200 kyr before the boundary evidenced by renewed increase in planktic fragmentation but without a decrease in p b ratio our data show that changing deep water masses coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the first 1 6 myr dissolution interval while deccan traps volcanism may have caused surface ocean acidification 200 kyr prior to the k pg mass extinction event

microfabrics in situ trace element and sulfur isotope compositions of pyrite from the jinjiwo copper deposit in chengmenshan orefield northern yangtze block syngenetic stratabound mineralization and hydrothermal remobilization abstract the jinjiwo copper deposit is located in the jiurui ore district of the middle lower yangtze metallogenic belt the deposit has stratiform orebodies hosted by late carboniferous carbonate units pyrite is the dominant metallic mineral in the ores here we report on an integrated study on the microfabrics raman spectroscopy in situ la mc icp ms trace element and sulfur isotope of pyrite with a view to understand the geochemical variation genesis of copper mineralization and ore forming process textural observations suggested four types of pyrite corresponding to three metallogenic episodes syngenetic sedimentation pyi metamorphism or deformation pyii and skarn hydrothermal mineralization including the late skarn stage pyiii and hydrothermal stage pyiv raman spectra of pyrite reveal subtle differences in band position and widths fwhm and display the increasing formation temperature of from pyi through pyiv and pyiii to pyii colloform and laminated pyrite pyi share similarities in behavior of pairs of elements and have low co ni ratios and the former contains the highest concentrations of bi cu pb zn ag au mn that suggest rapid precipitation from highly saturated fluids pyii shows high co ni and as concentrations and co ni ratios of 0 03 to 6 19 pyiii and pyiv have greatly varying co ni ratios of 1 07 to 29 and typically low au concentrations suggesting a hydrothermal source pyiii is rich in co and se but is depleted in as cu pb zn ag and au in comparison with pyiv there are two kinds of sulfur one is that 34s values are near zero suggesting that the pyrite sulfur in the ores was derived from a mixed source in deep crust and the other is that 34s values are less than 39 1 indicating the sedimentary pyrite sulfur was originated from bacterial sulfate reduction the combined textural and compositional data of pyrite suggest that the formation of the jinjiwo copper deposit might have recorded the submarine exhalation sedimentation and the mesozoic tectonic transition deformation and hydrothermal overprint

global environmental changes preceding the cretaceous tertiary boundary early late maastrichtian transition stable carbon oxygen and strontium isotope data from maastrichtian planktic and benthic foraminifera from southern high latitude ocean drilling program sites 690 750 and 761 reveal major changes in climate and ocean chemistry during the early to late maastrichtian transition some 4 to 6 m y prior to the cretaceous tertiary k t boundary the 18o results suggest accelerated cooling resulting in the lowest marine temperatures of the late cretaceous the late maastrichtian rise in the seawater 87sr 86sr ratio begins at the time of this change and suggests increased rates of continental weathering and or runoff the 13c values show a negative shift of 0 5 followed by a positive shift of 1 these 13c fluctuations may reflect change in deep water chemistry with cooling variation in reduced carbon storage in coastal areas caused by eustatic sea level fluctuation and increased surface water productivity these findings contradict the common representation of stable and climatically equable environmental conditions in the latest cretaceous before the k t boundary event

a critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for late cretaceous global correlation abstract climate variability is driven by a complex interplay of global scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter regional correlation which in most cases cannot be obtained with biostratigraphic methods alone chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high resolution correlation over large distances but complications arise from a multitude of possible influences from local differences in biological diagenetic and physico chemical factors on individual 13c records that can mask the global signal to better assess the global versus local contribution in a 13c record it is necessary to compare numerous isotopic records on a global scale as a contribution to this objective this paper reviews bulk sediment 13ccarb records from the late cretaceous in order to identify differences and similarities in secular 13c trends that help establish a global reference 13c record for this period the study presents a global scale comparison of twenty 13c records from sections representing various palaeo latitudes in both hemispheres and different oceanic settings from the boreal tethys western interior indian ocean and pacific ocean and with various diagenetic overprinting the isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute 13c values and variation in amplitude between the sites these differences reflect the varying local influences e g from depositional settings bottom water age and diagenetic history whereas the concordant patterns in 13c shifts might represent 13c fluctuations in the global seawater dissolved inorganic carbon the latter is modulated by variations in organic matter burial relative to re mineralization in the global scale formation of authigenic carbonate and in partitioning of carbon between organic carbon and carbonate sinks these variations are mainly controlled by changes in climate and eustasy additionally some globally synchronous shifts in the bulk 13ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and thus can be globally synchronized by fluctuations in eustasy atmospheric and oceanic oxygen levels or in large scale oceanic circulation because the influence of early diagenetic cements on the bulk 13ccarb signal can but need not be synchronized chemostratigraphy should not be used as a stand alone method for trans continental correlation and especially minor isotopic shifts have to be interpreted with utmost care nevertheless the observed consistency of the 13c correlations confirms global scale applicability of bulk sediment 13c chemostratigraphy for the late cretaceous including sediments that underwent lithification and burial diagenesis such as the sediments from the himalayan and alpine sections limitations arise from increased uncertainties 1 in sediments with very low carbonate content 2 from larger 13c variability in sediments from very shallow marine environments 3 from unrecognized hiatuses or strong changes in sedimentation rates and 4 in sections with short stratigraphic coverage or with few biostratigraphic marker horizons the combination of chemostratigraphy with biostratigraphy and magnetostratigraphy substantially increases the precision and temporal resolution of inter regional correlations and helps overcome problems that arise from differences in biostratigraphic schemes facies or provincialism of key fossils by using an iterative approach to stepwise increase precision of the correlations isochroneity of first and last occurrences of marker species versus chemostratigraphy is tested which helps to improve biostratigraphic zonations to assess zonal boundary ages and to identify useful criteria for defining late cretaceous stage boundaries many of which are still not formally defined the presented correlations indicate a consistent position for most planktic foraminifer zonal boundaries relative to corresponding isotope shifts during the mid cretaceous sea level high whereas diachroneity appears to be more pronounced during the late campanian and maastrichtian global sea level fall a similar pattern is observed for trans continental consistency in the 13c shifts graphic correlation of isotopic shifts magnetostratigraphic and biostratigraphic events among the compared sections is used to detect hiatuses or relative changes sediment accumulation rates and visualizes consistency or offsets of individual biostratigraphic markers relative to chemo and magnetostratigraphy finally an attempt of a global average 13c stack is presented for the turonian through maastrichtian

southeastern tanzania depositional environments marine and terrestrial links and exceptional microfossil preservation in the warm turonian sediment cores from southeastern tanzania contain exceptionally well preserved calcareous and organic walled microfossils in numerous samples spanning from the aptian to the miocene the unusually high quality of preservation is commonly attributed to shallow burial and high clay content of the host sediments however such attributes apply to many deposits that are not characterized by exceptional preservation and thus invoking only grain size and burial depth is clearly an incomplete explanation for the exceptional microfossil preservation in an attempt to better characterize additional factors that were important in creating the tanzanian microfossil lagerstatte we integrated a wide range of paleontological geochemical and sedimentological observations to constrain the paleoenvironmental and early diagenetic conditions of a turonian interval where exceptional preservation is common planktic microfossil assemblages suggest that open ocean surface water conditions prevailed at the site but despite excellent organic matter preservation marine biomarkers are rare the sediments are dominantly composed of terrigenous silts and clays and terrestrially derived organic matter paleontological and geochemical observations record a remarkably stable interval dominated by excellent preservation through the lower middle turonian during the middle upper turonian though the preservation quality declines and this is associated with notable shifts in foraminiferal assemblages palynological species diversity carbon and sulfur isotope compositions and biomarker distributions the integrated data suggest that an increase in subsurface microbial activity and associated changes in pore water chemistry were important proximate variables that led to the decline in the quality of microfossil preservation up section within these shallowly buried turonian silty claystones from tanzania

maastrichtian climate productivity and faunal turnovers in planktic foraminifera in south atlantic dsdp sites 525a and 21 abstract stratigraphic faunal and isotopic analyses of the maastrichtian at dsdp sites 525a and 21 in the south atlantic reveal a planktic foraminiferal fauna characterized by two major events an early late maastrichtian diversification and end maastrichtian mass extinction both events are accompanied by major changes in climate and productivity the diversification event which occurred in two steps between 70 5 and 69 1 ma increased species richness by a total of 43 and coincided with the onset of major cooling in surface and bottom waters and increased surface productivity the onset of the terminal decline in maastrichtian species richness began at 67 5 ma and the first significant decline in surface productivity occurred at 66 2 ma coincident maximum cooling to 13 c in surface waters and the reduction of the surface to deep temperature gradient to less than 5 c major climatic and moderate productivity changes mark the mass extinction and the last 500 kyr of the maastrichtian between 200 and 400 kyr before the k t boundary surface and deep waters warmed rapidly by 3 4 c and cooled again during the last 100 kyr of the maastrichtian surface productivity decreased only moderately across the k t boundary species richness began to decline during the late maastrichtian cooling and by k t boundary time the mass extinction had claimed 66 of the species viewed within the context of maastrichtian climate and productivity changes the k t mass extinction could have resulted from extreme environmental stress even without the addition of an extraterrestrial impact

stable isotopes and geochemistry of a campanian maastrichtian pelagic succession mudurnu goynuk basin nw turkey implications for palaeoceanography palaeoclimate and sea level fluctuations this study focuses on the palaeoclimatic evolution and relative sea level fluctuations of the northern branch of neotethys during the late campanian early danian the studied succession ismailler section is located in the mudurnu goynuk basin nw turkey and dominated by apparently continuous pelagic muddy deposits stable isotopic and elemental compositions of the mudrocks are investigated in order to evaluate the palaeoceanographic conditions as well as broad tectonic reconstruction of the basin the mudrock geochemistry suggests a tectonic reorganization during late campanian as reflected by a distinct shift from felsic to mafic sediment provenance in the ismailler section five 13c events are identified four or which are well correlatable with major events in other records around the world such as the late campanian event lce campanian maastrictian boundary cmb and the late maastrichtian event lme the relative sea level variations in the basin typically match both short and long term global sea level fluctuations the remaining globally uncorrelatable 13c event does coincide with tectonic uplift and the abrupt negative 13c shift and is inferred to be the result of regional factors the dominance of worldwide events in the records of the relatively restricted ocean branch reflects the strength of global factors

variability in late cretaceous climate and deep waters evidence from stable isotopes abstract strong climatic and temperature fluctuations mark the late campanian and maastrichtian as indicated by stable isotope records from the equatorial pacific site 463 and middle and high latitude south atlantic sites 525 689 and 690 the first major global cooling decreased intermediate water temperatures iwt by 5 6 c between 73 70 ma at the same time sea surface temperature sst decreased by 4 5 c in middle and high latitudes intermediate waters iw temporarily warmed by 2 c in low and middle latitudes between 70 68 5 ma global cooling resumed between 68 5 65 5 ma when iwt decreased by 3 4 c and sst by 5 c in middle latitudes about 450 ka before the cretaceous tertiary boundary rapid global warming increased iwt and sst by 3 4 c though sst in the tropics changed little during the last 200 ka of the maastrichtian climate cooled rapidly with iwt and sst decreasing by 2 3 c during the global cooling at 71 70 ma and possibly at 67 65 5 ma the sources of cold intermediate waters in the equatorial pacific indo pacific and south atlantic were derived from the high latitude north pacific in contrast during the global climate warming between 65 2 65 4 ma the middle latitude south atlantic was closest to the source of iw production and implies that the low latitude tethys played a major role in global climate change climate changes sea level fluctuations and associated restricted seaways appear to be the most likely mechanisms for the alternating sources of iw production

late cretaceous oceans and the cool tropic paradox oxygen isotopic proxies of paleo sea surface temperatures ssts suggest that maastrichtian about 66 million years ago tropical ssts were lower than those of today they also demonstrate that maastrichtian latitudinal sst gradients were much lower than those of the present the low maastrichtian sst gradients indicate that meridional heat transport was much greater or latitudinal differences in the balance of radiation to and from the sea surface were much less extreme during the latest cretaceous than they are today or that both conditions were true these findings challenge traditional interpretations of greenhouse late cretaceous climates

morphogroups and small sized tests in pseudotextularia elegans rzehak from the late maastrichtian succession of meghalaya india as indicators of biotic response to paleoenvironmental stress abstract cretaceous paleocene shelf successions of therriaghat and mahadeo in meghalaya india preserve almost the whole of the late maastrichtian stage in which the warm water tethyan planktonic foraminifera pseudotextularia elegans rzehak occurs in the racemiguembelina fructicosa zone zone cf4 and pseudoguembelina palpebra zone zone cf2 as five distinct morphogroups a e morphogroups a c commonly occur in rocks representing the transgressive regime of the r fructicosa zone at therriaghat whereas that of p palpebra zone was conducive for morphogroup d in the deeper shelf around therriaghat and morphogroup e in the near shore shelf around mahadeo the absence of p elegans in the pseudoguembelina hariaensis zone zone cf3 is postulated due to tectonic cause whereas its absence in the plummerita hantkeninoides zone zone cf1 was due to regression analysis of growth parameters including length width thickness and angle of flaring of the tests of the species reveal that morphogroups b and c are generally larger in size than the other morphogroups and the test length of the meghalaya specimens is smallest over its world occurrences diverse morphogroups and small tests are unique in the species of meghalaya however the cause of such unusual growth is difficult to explain due to development close to the tectonically active deccan volcanic province and the assam arakan and himalayan mobile belts the meghalaya shelf had unusual biotic stress due to volcanic eruption sea level fluctuations induced by plate collision and climate warming and retreat of the neo tethys during the biozones cf4 and cf2 when vigorous deccan outbursts occurred p elegans developed diverse morphogroups and acquired small size tests to cope with the changed environments and possibly to increase its chances of avoiding by microspherule missiles

biogeographic patterns in terminal cretaceous planktonic foraminifera from tethyan and warm transitional waters abstract biogeographic patterns in terminal cretaceous planktonic foraminifera have been analyzed from their faunal compositions at a time slice spanning the upper parts of the calcareous nannofossil micula prinsii zone approximately the latest 20 60 k y of the cretaceous at dsdp sites from low 16 through middle 37 paleolatitudes in either the northern or the southern hemisphere the study is based on relative abundance data of 26 species at sites 356 516f 525a and 527 from the south atlantic ocean sites 384 and 548a from the north atlantic and sites 465a and 577a from the north pacific cretaceous tertiary k t boundary sections at site 516f and 577a are poorly preserved which prevented quantitative faunal analysis two major faunal assemblages one tethyan assemblage and one transitional assemblage are distinguished from the quantitative distribution patterns the tethyan assemblage dominating at sites 465a 356 and 384 is composed of heterohelix striata globotruncana aegyptiaca pseudoguembelina kempensis p costulata an undescribed form of heterohelix with relict apertural flanges along medium suture rugoglobigerina hexacamerata and trinitella scotti among these species p kempensis p costulata and h sp exhibit enhanced abundances at site 465a and constitute a warm tethyan subassemblage whereas r hexacamerata and t scotti which are most abundant at sites 356 and 384 represent a cool tethyan subassemblage seven species show greater relative abundances at sites 525a and 527 and are referred to a warm transitional subassemblage abathomphalus mayaroensis gublerina cuvillieri pseudotextularia elegans rugoglobigerina rugosa racemiguembelina fructicosa globotruncana arca and planoglobulina acervulinoides in addition an assemblage marked by the heterohelix glabrans h carinata complex h globulosa globigerinelloides multispina and rosita contusa may represent a shallower water subassemblage within warm transitional waters site 548a

decline of the maastrichtian pelagic ecosystem based on planktic foraminifera assemblage change implication for the terminal cretaceous faunal crisis an outer shelf upper slope tropical tethyan pelagic environment existed over southern israel during maastrichtian time planktic foraminifera in the 63 and 149 m size fractions from four sections in this area were studied quantitatively for a high resolution ecostratigraphic analysis of the pre cretaceous tertiary k t paleoenvironment during the maastrichtian 41 of the planktic foraminifera species became extinct mostly keeled globotruncanidae which also became quantitatively reduced near the end of the maastrichtian from as much as 35 to only 5 of the planktic foraminifera population evolutionary replacement of extinct species by new forms nearly ceased in that interval two major opportunistic blooms of guembelitria took place associated with reduced abundances of keeled forms and the dominant species heterohelix globulosa the first bloom occurred within the upper gansserina gansseri to lower abathomphalus mayaroensis zones and the second within the plummerita hantkeninoides zone the extinctions concomitant changes in faunal dominance and opportunist blooms indicate that the pelagic ecosystem in the negev area experienced multiple stresses during the maastrichtian the planktic foraminiferal assemblages were taxonomically impoverished and in decline prior to the k t boundary crisis

planktonic foraminifera differential dissolution and the quaternary stable isotope record in the west equatorial pacific differential dissolution affects the isotopic composition of different species of planktonic foraminifera in different ways in the two species studied here in cores from ontong java plateau the less resistant species globigerinoides sacculifer is more readily affected at a shallower depth than the more resistant species pulleniatina obliquiloculata 2 9 versus 3 4 km but shows a smaller and less predictable response to partial dissolution 0 2 to 0 3 per mil versus 0 6 to 0 7 per mil comparison of isotopic values from the last glacial period with those from the late holocene indicates that the apparent dissolution effect is considerably reduced during the last glacial presumably due to reduced dissolution intensity during glacial time a change in the level of the lysocline of about 400 m is suggested in the published isotope records from pacific cores v28 238 and v28 239 the dissolution generated difference in 18o noted previously by shackleton and opdyke 1976 is seen to describe a mid brunhes dissolution maximum between 300 and 500 thousand years ago this mid brunhes dissolution excursion is well known from the pacific and the indian ocean

textures and trace element composition of pyrite from the bukit botol volcanic hosted massive sulphide deposit peninsular malaysia abstract the bukit botol volcanic hosted massive sulphide vhms deposit is located in the central belt of peninsular malaysia the deposit occurs in a package of permian aged coherent felsic volcanic and volcaniclastic rocks which have a geochemical signature indicative of a volcanic arc tectonic setting mineralisation shows distinct ore zonation forming a stringer to massive sulphide zone at the footwall followed by barite lenses and exhalite layers fe mn ore at the top mineralogy is characterised by pyrite as the major sulphide mineral with minor chalcopyrite sphalerite and rare galena traces of gold silver and tin bearing minerals also occur in the massive sulphide and barite ores laser ablation inductively coupled plasma mass spectrometry la icp ms analysis combined with the textural characteristics of pyrite provides evidence for significant variations of trace elements in different pyrite types at bukit botol having three types of pyrite in the paragenetic sequence the concentrations of as se te cu zn and pb decrease from the early pyrite 1 to the late stage pyrite 3 and the co ni ratios vary for the three pyrite types the combined textural and compositional data of pyrite suggest that the hydrothermal fluid responsible for mineralisation evolved from an early high temperature reduced low ph and desulphurized fluid to more s rich oxidized high ph and cooler fluid available sulphur isotope data from the bukit botol deposit point to reduced seawater along with a possible magmatic contribution as the most probable sources for the ore forming fluids

in situ trace element and sulfur isotope analysis of pyrite in a paleoproterozoic gold placer deposit pardo and clement townships ontario canada extensive pyrite bearing auriferous cobble and boulder conglomerates are present in the basal 30 in of the mississagi formation in pardo and clement townships ontario canada the sedimentology of the conglomerates combined with regional geology indicates limited fluvial transport in a gravel bed braided river with local hyperconcentrated flows with material derived from a highly restricted catchment area postdepositional overprinting of the conglomerates is related to the penokean orogeny at 1 85 to 1 5 ga and alkali metasomatism at similar to 1 7 ga several pyrite varieties including detrital and postdepositional recrystallized and altered grains are present in the conglomerates detailed in situ laser ablation inductively coupled plasma mass spectrometry la icpms analysis of pyrite revealed that the gold in the deposit is intimately associated to large detrital pyrite grains as invisible au with lesser amounts of free gold postdepositional pyrite and pyrite overgrowths have very low au content elements such as pb bi sb te ag and hg together with au were mobilized during hydrothermal alteration and dissolution of detrital pyrite grains small scale transport and reprecipitation formed part of the postdepositional pyrite and free gold in immediate contact with postdepositional grains in contrast ni co and as were not mobilized external fluid infiltration is negligible and is indicated only by minor compositionally distinct late sulfide veinlets crosscutting the conglomerates sulfur isotope analysis of detrital pyrite yields generally positive delta 34 s values 0 97 9 26 0 the delta 34 s sulfur isotope composition of pyrite overgrowths and postdepositional grains overlaps the isotopic range of the detrital grains suggesting a near closed s system during postd epositional processes however the detrital pyrite tends to have slightly negative delta 33 s while the postdepositional and overgrowth pyrite are either neutral or slightly positive the s isotope composition of the detrital pyrite is compatible with an origin of s as dissolved sulfate in an ocean under a low oxygen atmosphere the potential source of the au bearing detrital pyrite appears to have been an as yet undiscovered archean deposit located within 1 to 8 kin of the placer deposit

opening the carbon isotope vital effect black box 2 quantitative model for interpreting foraminiferal carbon isotope data interpretation of carbon isotope records from late quaternary planktonic foraminifers are confounded due to the presence of a significant physiological component in the carbon isotopic signal a quantitative carbon isotope qc model is presented which relates the carbon isotopic composition of a foraminiferal shell to the physiological processes of respiration and symbiont photosynthesis and to the 13c value of seawater co2 the qc model is calibrated with physiological and stable isotopic data from laboratory experiments with living planktonic foraminifers model simulations of chamber and shell 13c values with the symbiont bearing foraminifers orbulina universa and globigerinoides sacculifer suggest 1 variations in symbiont density and photosynthetic rate light level or habitat depth are the primary physiological parameters controlling intraspecific carbon isotopic variability in these species 2 respiration has little effect on the 13c of o universa and 3 each chamber in a multichambered foraminiferal test will have a distinct 13c value depending on its position in the test whorl size 13c value relationships reported for g sacculifer from fossil assemblages can be explained as a function of increasing symbiont density during ontogenetic development

stable isotope composition of late cretaceous benthic foraminifera from the southern south atlantic biological and environmental effects abstract the stable carbon and oxygen isotope composition of different benthic foraminiferal species of the latest campanian and earliest maastrichtian from ocean drilling project hole 690c weddell sea southern south atlantic 1800 m paleowater depth have been investigated the total range of measured isotope values of all samples exceeds 4 for 13c and 1 1 for 18o carbon isotope values of proposed deep infaunal species are generally similar or only slightly lower when compared to proposed epifaunal to shallow infaunal species interspecific differences vary between samples probably reflecting temporal changes in organic carbon fluxes to the sea floor constantly lower 13c values for pullenia marssoni and pullenia reussi suggest the deepest habitat for these species the strong depletion of 13c values by up to 3 within lenticulinids may be attributed to a deep infaunal microhabitat strong vital effects or different feeding strategy when compared to other species or modern lenticulinids the mean 18o values reveal a strong separation of epifaunal to shallow infaunal and deep infaunal species epifaunal to shallow infaunal species are characterized by low 18o values deep infaunal species by higher values this result possibly reflects lower metabolic rates and longer life cycles of deep infaunal species or the operating of a pore water co32 effect on the benthic foraminiferal stable isotopes pyramidina szajnochae shows an enrichment of oxygen isotopes with test size comprising a total of 0 6 between 250 and 1250 m shell size although 13c lacks a corresponding trend these data likely represent the presence of changes in metabolic rates during ontogenesis these results demonstrate the general applicability of multi species stable isotope measurements of pristine cretaceous benthic foraminifera to reconstruct past microhabitats and to evaluate biological and environmental effects on the stable isotope composition

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

trace element characteristics of different pyrite types in mesoarchaean to palaeoproterozoic placer deposits a comparative in situ la icp ms trace element study on pyrite from three different variably auriferous archaean to palaeoproterozoic palaeoplacer deposits in the ouro fino syncline quadrilatero ferrifero brazil the elliot lake area north of lake huron se canada and several deposits within the witwatersrand basin south africa revealed systematic differences between morphologically different pyrite types and between the various palaeoplacer deposits especially the ni and au concentrations as well as co ni and mo ni ratios were found to be systematically different in detrital compact detrital porous and post sedimentary hydrothermal pyrite grains from different source areas high co ni ratios and low au concentrations are typical of post sedimentary pyrite which is hydrothermal in origin in contrast relatively low co ni ratios and high au contents characterise detrital porous banded and concentric pyrite grains au 1 ppm which are syn sedimentary in origin in the elliot lake area and the witwatersrand basin detrital compact rounded pyrite is characterised by high co ni ratios which is in agreement with derivation from a hydrothermal source low au concentrations in this pyrite type support the contention of the gold and the pyrite in these deposits coming from different source rocks in contrast derivation from an originally diagenetic pyrite is suggested for the detrital compact pyrite in the ouro fino syncline because of low to intermediate co ni ratios high au contents may indicate a genetic relationship between pyrite and gold there systematic differences exist between the three areas with respect to au ni co mo and cu distributions in detrital pyrite which reflects differences in the provenance a predominantly mafic ultramafic source is indicated for the ouro fino a felsic source for the elliot lake and a mixed felsic mafic provenance for the witwatersrand pyrite populations independently of pyrite type the higher au endowment of the studied witwatersrand and ouro fino conglomerates are also reflected by an overall higher au concentration in the respective pyrite grains compared to the relatively au poor samples from elliot lake in general a strong positive correlation between au and pb levels in the various pyrite grains is noted analogous to pb which is well known for not being easily accommodated in the pyrite crystal lattice but occurring as discrete pbs phases au is considered to be present mainly in the form of discrete au phases in minute pores and interstices of the pyrite grains rather than within the pyrite lattice

reconstructing past sea surface temperatures correcting for diagenesis of bulk marine carbonate abstract a numerical model which describes oxygen isotope exchange during burial and recrystallization of deep sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured 18o values of bulk carbonate for diagenetic overprinting comparison of bulk carbonate and planktonic foraminiferal 18o records from odp site 677a indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and 18o at odp site 690 we calculate that diagenetic effects are small and that both bulk carbonate and planktonic foraminiferal 18o records accurately reflect paleogene warming of high latitude surface oceans biased from diagenesis by no more than 1 c the same is likely to be true for other high latitude sites where sedimentation rates are low at dsdp sites 516 and 525 the effects of diagenesis are more significant measured 18o values of eocene bulk carbonates are more than 2 lower at deeply buried site 516 than at site 525 consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate model corrections reconcile the differences in the data between the two sites the resulting paleotemperature reconstruction indicates a 4 c cooling of mid latitude surface oceans since the eocene at low latitudes the contrast in temperature between the ocean surface and bottom makes the carbonate 180 values particularly sensitive to diagenetic effects most of the observed variations in measured 18o values are accounted for by diagenetic effects rather than by sea surface temperature variations we show that the data are consistent with constant equatorial sea surface temperatures through most of the cenozoic with the possible exception of the early eocene when slightly higher temperatures are indicated we suggest that the lower equatorial sea surface temperatures for the eocene and oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting

uncloaking invisible gold use of nanosims to evaluate gold trace elements and sulfur isotopes in pyrite from carlin type gold deposits one hundred nm resolution secondary ionizing mass spectrometry nanosims was used to determine the distribution of au cu as sb and s and stable isotopes of s 34s 32s in gold bearing pyrite from two refractory carlin type gold deposits west banshee northern carlin trend and turquoise ridge getchell trend located in northern nevada nanosims maps reveal that gold occurs in two discrete episodes in each deposit elevated gold concentrations correlate with elevated concentrations of as sb cu te and lower 34s 32s ratios compared to periods when gold was not deposited precipitation of elevated gold and trace elements at west banshee was followed by precipitation of pyrite with lower gold concentrations whereas at turquoise ridge precipitation of trace element rich pyrite was followed by precipitation of late ore stage minerals these nanosims results are consistent with formation of the deposits by the episodic incursion of gold rich fluids into hydrothermal systems otherwise dominated by gold poor fluids such gold rich fluid pulses may be related to incursions of magmatic fluid which have been shown to have high concentrations of gold arsenic and copper in porphyry and high sulfidation epithermal systems

seismic velocity structures and detailed features of the d discontinuity near the core mantle boundary beneath eastern eurasia abstract shear and compressional velocity structures and features of the d discontinuity near the core mantle boundary cmb beneath eastern eurasia are studied based on forward waveform modeling and differential travel time analysis of scsh sh sscs ss pcp p and ppcp pp phases high quality differential travel time analysis reveals two high velocity patches spanning a width of 3000 km and separated by a 300 km wide normal velocity gap the maximum shear and compressional velocity perturbations reach 3 8 and 2 7 respectively seismic data indicate that the d discontinuity emerges in the high velocity patches and disappears in the normal velocity gap furthermore the features of the d discontinuity although constrained by rather sparse seismic data vary from diffusive discontinuities in the eastern patch to sharp discontinuities in the western patch the d discontinuities occur at about 270 km above the cmb in the eastern patch with a shear velocity jump of 3 0 5 0 and a transitional depth of at least 100 km and at 250 km above the cmb in the western patch with an abrupt shear velocity jump of 5 0 a diffusive p wave discontinuity is also observed in the eastern patch with the similar features of the s wave discontinuity the inferred features of the d discontinuity can be explained by the post perovskite transformation in the lower mantle the observations that the d discontinuities occur only in the high velocity patches may be due to the effect of the positive clapeyron slope of the post perovskite transition and the varying transitional depths of the d discontinuity in the high velocity regions may be caused by the compositional effects on the post perovskite transition in the presence of strong variations of composition within the high velocity anomalies the high velocity patches geographically correlate with the subduction of the pacific and indian plates in the past 30 60 ma and the normal velocity gap falls into the subduction gap between the pacific and indian plates these geographical correlations raise the possibility that the existence of the d discontinuity is intimately related to the presence of the past subduction material at the cmb and varying features of the discontinuity further suggest existence of strong variations of composition within the subduction materials at the cmb

stable isotope evidence for gradual environmental changes and species survivorship across the cretaceous tertiary boundary high resolution 13c and 18o records have been generated from analyses of the planktonic foraminiferal species heterohelix globulosa and the benthonic foraminiferal taxon lenticulina spp from 3 m of a cored section spanning the cretaceous tertiary k t boundary at brazos river texas these are the first stable isotope records across the k t boundary based on monospecific and monogeneric foraminiferal samples they show a gradual decrease in 13c values of about 2 5 permil beginning at the k t boundary as defined by the first appearance of tertiary planktonic foraminifera and continuing 17 20 cm above the boundary approximately 40 000 years later gradual 13c depletion contrasts with the sudden 13c drop at the k t boundary observed in many deep sea sections the surface to bottom 13c gradient decreased to less than zero approximately 25 000 30 000 years after the k t boundary and remained negative for at least the next 140 000 years concomitant with change in 13c values is a gradual decrease of about 2 5 permil in 18c values which has not been observed at other localities this 18o depletion suggests changes in temperature and or salinity in the earliest paleocene gulf of mexico no extinction of foraminiferal species is associated with the k t boundary or the onset of 18o and 13c depletions instead two phases of cretaceous species extinctions occur one extinction phase is below the k t boundary and below the tsunami bed of bourgeois et al 1988 and may be linked to sea level regression and environmental perturbations the second extinction phase coincides with the minimum in 13c and 18o values in the early danian zone p0 pla and appears directly related to environmental changes reflected in the isotopic record h globulosa which is commonly present in maastrichtian and danian sediments exhibits significantly lower 18o 16o and 13c 12c ratios in tertiary sediments relative to specimens from maastrichtian sediments demonstrating the survival of this important cretaceous taxon after the k t boundary event

gold upgrading in metamorphosed massive sulfide ore deposits direct evidence from laser ablation inductively coupled plasma mass spectrometry analysis of invisible gold the metamorphosed boliden volcanic hosted massive sulfide vhms ore deposit northern sweden is characterized by an abundance of massive arsenopyrite ore and unusually high gold enrichments up to 300 600 g t in crosscutting veins and fracture zones the ore textures observed record progressive recrystallization and porphyroblast growth during meta morphism we conducted a systematic laser ablation inductively coupled plasma mass spectrom etry la icp ms study on the gold distribution in fine grained massive arseno pyrite and pyrite ore partially recrystallized arsenopyrite ore and both arsenopyrite and pyrite porphyroblasts found in gold rich veins the gold concentrations in massive arseno pyrite are highest 30 50 ppm on average and systematically decrease to 0 2 7 ppm with increasing degree of recrystallization by contrast gold concentrations in pyrite ore are much lower and do not exceed 0 2 ppm the la icp ms data coupled with textural data provide the first direct conclusive evidence that gold is progressively liberated from massive sulfide ores during metamorphism and reprecipitated in veins and other low strain sites we suggest that such upgrading is the principal mechanism responsible for significant gold enrichment observed in many metamorphosed vhms deposits worldwide

interspecies variation in stable isotopic signals of maastrichtian planktonic foraminifera we measured stable isotopic signals of the largest specimens of all abundant species of planktonic foraminifera in late maastrichtian samples from three atlantic mid latitude and high latitude sites each sample is marked by a relatively small interspecies range of 18o values 1 2 to 0 8 each also exhibits an interspecies range of 13c values that resembles those of modern assemblages at similar latitudes 2 8 to 0 9 with greater ranges at lower latitudes these results indicate that late cretaceous planktonic foraminifera inhabited water masses characterized by a relatively narrow range of temperatures but may have occupied an array of niches as ecologically diverse as that of modern taxa maastrichtian taxa exhibit more complex relationships between skeletal morphology and vertical and seasonal paleohabitat affinities than previous paleoecologic models have assumed for example keeled taxa were not limited to cold or deep habitats and serial taxa appear to have occupied both warm near surface niches and the coolest or most saline habitats the isotopic differences between species indicate that apparent variation in maastrichtian stable isotopic signals strongly depends on the taxa analyzed narrowly constrained size fractions of rugoglobigerina species may provide a good estimate of relative variation in isotopic equilibria of near surface summer paleoconditions at low and middle latitudes gublerina species laeviheterohelix species and planoglobulina multicamerata appear the likeliest candidates for consistently tracking relative variation in isotopic equilibria of the coldest or most saline paleohabitats of maastrichtian planktonic foraminifera these isotopic results suggest that upper water column thermal gradients may have been only 3 to 5 c in mid latitude and high latitude regions they also suggest that the western and central atlantic mid latitude summer seasurface may have been much cooler or saltier in the maastrichtian than it is today finally they corroborate previous estimates of 10 c surface water at southern high latitudes

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

microthermometric evidence for the formation of permian vhms deposits in tasik chini area central belt of peninsular malaysia abstract the vhms deposits of tasik chini area are located in the pahang state of central belt peninsular malaysia the deposits occur in a package of permian volcanics within mixed volcano sedimentary sequence and have been exploited from the bukit botol and bukit ketaya deposits they have many similarities with kuroko style massive sulfide deposits the host rocks at both deposits are felsic volcanic rocks of rhyolitic to rhyodacitic composition mineralization occurs as distinct ore zonation forming a stringer to massive sulfide zone at the footwall followed by barite lenses and exhalite layers fe mn si ore at the stratigraphic top the sulfide phases are characterized by pyrite as the major sulfide mineral with subordinate chalcopyrite sphalerite and rare galena traces of gold silver and sn bearing minerals occur in the massive sulfide and barite ores primary fluid inclusions within quartz and barite occur as two types 1 type i two phase liquid vapour inclusions without daughter minerals and 2 type ii three phase liquid co2 bearing carbonic inclusions these three phase inclusions include liquid h2o liquid co2 and vapour co2 with variable co2 content and often decrepitate before complete homogenization microthermometric measurements of the type i inclusions show that the temperature of homogenization th varies between 180 c and 310 c with salinities ranging from 1 0 to 15 0 wt nacl equivalent in the quartz samples homogenization temperatures th of 190 c to 300 c and salinities between 1 0 and 13 0 wt nacl equivalent are recorded from the barite samples type ii inclusions have an initial melting temperature range of 57 1 c to 57 5 c clathrate melting temperature tmclathrate of 7 4 c to 8 0 c and co2 homogenization temperature thco2 between 30 1 c and 30 3 c and salinity ranging from 4 0 to 5 1 wt nacl equivalent densities pressure and depth of ore forming fluids range from 0 711 to 0 970 g cm3 12 to 93 bars and 1500 m depth of seawater laser raman spectroscopic analysis shows the presence of co2 in the carbonic inclusions the fluid inclusion results suggest that the main ore fluid during the formation of the tasik chini vhms deposit is a seawater dominated fluid but contribution from a modified seawater or possibly magmatic origin is also indicated by higher salinities relative to seawater 3 2 wt nacl and the presence of co2 taking into account the regional geodynamic evolution it is also concluded that the formation of vhms deposits in the tasik chini area occurred in a back arc geotectonic setting

biotic effects of late maastrichtian mantle plume volcanism implications for impacts and mass extinctions abstract during the late maastrichtian dsdp site 216 on ninetyeast ridge indian ocean passed over a mantle plume leading to volcanic eruptions islands built to sea level and catastrophic environmental conditions for planktic and benthic foraminifera the biotic effects were severe including dwarfing of all benthic and planktic species a 90 reduction in species diversity exclusion of all ecological specialists near absence of ecological generalists and dominance of the disaster opportunist guembelitria alternating with low o2 tolerant species these faunal characteristics are identical to those of the k t boundary mass extinction except that the fauna recovered after site 216 passed beyond the influence of mantle plume volcanism about 500 kyr before the k t boundary similar biotic effects have been observed in madagascar israel and egypt the direct correlation between mantle plume volcanism and biotic effects on ninetyeast ridge and the similarity to the k t mass extinction which is generally attributed to a large impact reveal that impacts and volcanism can cause similar environmental catastrophes this raises the inevitable question are mass extinctions caused by impacts or mantle plume volcanism the unequivocal correlation between intense volcanism and high stress assemblages necessitates a review of current impact and mass extinction theories

pyrite as a record of hydrothermal fluid evolution in a porphyry copper system a sims empa trace element study porphyry copper deposits are currently the world s largest source of copper and molybdenum and are also among the largest reservoirs of gold in the upper crust despite the fact that pyrite is a ubiquitous mineral phase in these deposits and secondary cu enrichment processes are commonly controlled by the abundance of this sulfide the major and trace element chemistry of pyrite from porphyry systems remains unconstrained in this study we report the first comprehensive trace element database of pyrite from the dexing deposit china s largest porphyry cu deposit by combining high spatial resolution and x ray mapping capabilities of electron microprobe analysis empa with low detection limits and depth profiling capabilities of secondary ion mass spectrometry sims in a suite of samples from the dexing deposit we show that the concentrations of precious metals e g au ag metalloids e g as sb se te and heavy metals e g cu co ni zn hg in pyrite from porphyry systems are more significant than previously thought among the elements analyzed cu as au and ni are the most abundant with concentrations that vary from sub ppm levels to a few wt i e 6 wt cu 3 wt as 0 25 wt au and 0 2 wt ni detailed wavelength dispersive spectrometry wds x ray maps and sims depth vs isotope concentration profiles reveal that pyrite from the dexing deposit is characterized by complex chemical zoning where the studied elements occur in different mineralogical forms while as occurs as a structurally bound element in pyrite cu and au can occur as both solid solution and micro to nano sized particles of chalcopyrite and native au or au tellurides respectively indicating that pyrite can control metal speciation and partitioning during porphyry cu mineralization the well developed oscillatory zoning detected in pyrite where cu rich as depleted growth zones alternate with cu depleted as rich layers indicates that cu is geochemically decoupled from as suggesting that this selective partitioning of metals into pyrite is most likely the result of changes in hydrothermal fluid composition

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

do planktic foraminifera accurately record shifts in the carbon isotopic composition of seawater σco2 abstract both the carbon isotopic composition of seawater and physiological vital effects such as respiration and symbiont photosynthesis influence the 13 c value of foraminiferal calcite the symbiont bearing planktic foraminifera orbulina universa was grown in a series of laboratory experiments to determine whether vital effects differentially obscure the 13 c signal such that changes in the 13 c of seawater co 2 cannot be quantitatively evaluated foraminifera were cultured under three different irradiance levels to elicit a full range of symbiont photosynthetic effects and in seawater with 13 c values ranging between 1 77 ambient and 5 76 power regression analysis of isotope data from individual shells plotted against culture irradiance yields three curves which are nearly parallel but are offset by the difference between the carbon isotopic composition of the culture waters when irradiance groups are combined and o universa 13 c values are plotted against seawater 13 c three parallel linear regressions are obtained with slopes ranging between 0 93 and 0 96 because the slopes are near unity it is concluded that the 13 c of o universa accurately tracks changes in the carbon isotopic composition of seawater regardless of the magnitude of its physiological vital effect o universa oxygen isotope data show that individuals maintained in the low and medium irradiance groups secrete their shells in isotopic equilibrium according to established paleotemperature equations in contrast individuals grown under high irradiance levels maximum symbiont photosynthetic rates are on average 0 35 depleted in 18 o relative to equilibrium symbiont enhanced calcification rates in the high light group may be responsible for the observed 18 o difference

permian tectonic framework and palaeogeography of se asia abstract the principal continental lithospheric terranes now comprising se asia and that existed in the permian are the south china indochina super terrane and the sibumasu simao west burma and sw borneo semitau terranes the simao terrane is here regarded a separate terrane derived from south china by back arc spreading in the lower carboniferous rather than as an extension of indochina the main palaeo tethys ocean in thailand is identified as being represented by the chiang mai and sra kaeo sutures and the eastern boundary of the sibumasu terrane is thus interpreted to lie farther west in thailand than previously inferred the nan uttaradit suture is interpreted as representing a marginal back arc basin and contiguous with the ailaoshan and jinshajiang sutures in sw china the south china indochina super terrane and the simao terrane were located within the palaeo tethys in equatorial latitudes during the permian where they together with north china exhibit cathaysian floras and faunas the sibumasu terrane was located on the nw australian margin of gondwana until the sakmarian major shifts in faunal affinities from gondwana province faunas to an independent sibumasu province and then to assimilation into the cathaysian province records the separation and rapid northward drift of sibumasu after the late sakmarian the principal permian palaeogeographic models for the region are assessed for internal consistencies and conflicts

maastrichtian north atlantic warming increasing stratification and foraminiferal paleobiology at three timescales 1 analysis of 944 single specimens of three species of late maastrichtian planktonic foraminifera racemiguembelina fructicosa contusotruncana contusa and rugoglobigerina rugosa from 38 samples spanning the last 3 myr of the cretaceous shows consistent isotopic trends through time consistent isotopic differences among taxa and high within sample isotopic variability throughout within sample variability does not change systematically through time for any taxon but average 18o values decrease by 1 5 and average 13c values diverge up section comparing taxa average 18o values are similar within most samples but average 13c values generally decrease from r fructicosa to r rugosa to c contusa in addition the within sample variability of individual 13c measurements is larger for r fructicosa than for either c contusa or r rugosa an observation which is consistent with a photosymbiotic habitat for r fructicosa in terms of maastrichtian paleoceanography the negative 18o trend of 1 5 corresponds to a temperature increase of 6 c and the divergence of 13c values up section suggests an increasingly stratified water column in the western atlantic through the late maastrichtian we suggest that these trends are best explained by increasing import of south atlantic waters into the north atlantic and an intensification of the northern hemisphere polar front

global climate change and planktic foraminiferal response in the maastrichtian 1 the lengthy warm stable climate of the cretaceous terminated in the campanian with a cooling trend interrupted in the early and latest maastrichtian by two events of global warming at 70 68 ma and at 65 78 65 57 ma these climatic oscillations had a profound effect on pelagic ecosystems especially on planktic foraminiferal populations here we compare biotic responses in the tropical subtropical tethyan open ocean and mesotrophic zin valley israel and oligotrophic tunisia slopes which correlate directly with global warming and cooling the two warming events coincide with blooms of guembelitria an extreme opportunist genus best known as the main survivor of the cretaceous paleogene k pg catastrophe in the maastrichtian guembelitria bloomed in the uppermost surface water above shelf and slope environments but failed to reach the open ocean as it did at k pg the coldest interval of the late maastrichtian 68 65 78 ma is marked by an acme of the otherwise rare species gansserina gansseri a deep dwelling keeled globotruncanid the g gansseri acme event can be traced from the deep ocean even onto the tethyan slope marking copious production and circulation of cold intermediate water this acme is abruptly terminated by extinction of the species a dramatic reversal attributed to a short term global warming episode this extinction corresponds precisely with the second bloom of guembelitria that began 300 kyr prior to the k pg event the antithetical relationship between blooming of guembelitria and the g gansseri acme reflects planktic foraminiferal sensitivity to warm cool warm cool climatic oscillations marking the end of the cretaceous

pyrite physical and chemical textures pyrite may crystallize initially in forms as diverse as framboids or cubes depending upon the temperatures and pressures fluid rich diagenesis or low grade metamorphism clearly results in thorough recrystallization and the common formation of cubes once these have formed the pyrite becomes much more refractory and retains many characteristics even in deposits which have undergone penetrative deformation this is in strong contrast to the behavior of most of the accompanying sulfides which often undergo ductile deformation solid state or chemical remobilization and annealing pyrite deforms sparingly until there is brittle failure however there may be significant pyrite corrosion and regrowth during metamorphism as the result of sulfur exchange with other minerals especially pyrrhotite pyrite fabrics may also be significantly modified by pressure solution or coble creep optical microscopic examination and electron microprobe chemical mapping of pyrites from a variety of mineral deposits including several high grade metamorphic ones reveals that the pyrites frequently contain both physical and chemical textures that may be interpreted in terms of the depositional and the post depositional history of the deposits inclusions of sulfides or other minerals reveal information on the timing of the crystallization or recrystallization of the pyrite chemical mapping of elements such as ni co and as reveals information on the relative time of transport of these elements in the ore fluids

paleoecology of the cretaceous tertiary mass extinction in planktonic foraminifera abstract paleobiogeographic patterns of the cretaceous tertiary k t mass extinction in planktonic foraminifera in tunisia spanning environments from open marine upper bathyal to shelf and shallow marginal settings indicate a surprisingly selective and environmentally mediated mass extinction this selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction including species richness ecological generalists ecological specialists surface and subsurface dwellers whether based on the number of species or the relative percent abundances of species the following conclusions can be reached for shallow to deep environments about three quarters of the species disappeared at or near the k t boundary and only ecological generalists able to tolerate wide variations in temperature nutrients salinity and oxygen survived among the ecological generalists heterohelicids guembelitrids hedbergellids and globigerinellids only surface dwellers survived ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively biserials thrived during the latest maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early danian triserials thrived only in shallow marginal marine environments or similarly stressed ecosystems during the latest maastrichtian but dominated both open marine and restricted marginal settings in the early danian this highly selective mass extinction pattern reflects dramatic changes in temperature salinity oxygen and nutrients across the k t boundary in the low latitude tethys ocean which appear to be the result of both long term environmental changes e g climate sea level volcanism and short term effects bolide impact

long term late cretaceous oxygen and carbon isotope trends and planktonic foraminiferal turnover a new record from the southern midlatitudes 2016 geological society of america the 35 m y long late cretaceous greenhouse climate has been the subject of a number of studies with emphasis on the cenomanian turonian and late campanian maastrichtian intervals by contrast far less information is available for the turonian early campanian interval even though it encompasses the transition out of the extreme warmth of the cenomanian turonian greenhouse climate optimum and includes an 3 m y long mid coniacian mid santonian interval when planktonic foraminifera underwent a large scale but poorly understood turnover this study presents 1350 18o and 13c values of wellpreserved benthic and planktonic foraminifera and of the 63 m size fraction from the exmouth plateau off australia eastern indian ocean these data provide 1 the most continuous highly resolved and stratigraphically well constrained record of longterm trends in late cretaceous oxygen and carbon isotope ratios from the southern midlatitudes and 2 new information on the paleoecological preferences of planktonic foraminiferal taxa the results indicate persistent warmth from the early turonian until the mid santonian cooling from the mid santonian through the mid campanian and short term climatic variability during the late campanian maastrichtian moreover our results suggest the cause of coniacian santonian turnover among planktonic foraminifera may have been the diversification of a temperature and or salinity tolerant genus marginotruncana and the cause of the santonian early campanian extinction of dicarinella and marginotruncana may have been surface ocean cooling and competition with globotruncanids

tectonic evolution of the sibumasu indochina terrane collision zone in thailand and malaysia constraints from new u pb zircon chronology of se asian tin granitoids three principal granite provinces are defined across se asia as follows 1 the western thailand myanmar burma province consists of hornblende biotite i type granodiorite granites and felsic biotite k feldspar garnet tourmaline granites associated with abundant tin mineralization in greisen type veins new ion microprobe u pb dating results from phuket island show zircon core ages of 212 2 and 214 2 ma and a thermal overprint with rims of 81 2 1 2 and 85 75 ma 2 the north thailand west malaya main range province has mainly s type biotite granites and abundant tin mineralization resulting from crustal thickening following collision of the sibumasu plate with indochina during the mid triassic biotite granites around kuala lumpur contain extremely u rich zircons up to 38000 ppm that yield ages of 215 7 and 210 7 ma 3 the east malaya province consists of dominantly permian triassic i type hornblende biotite granites but with subordinate s type plutons and a type syenite gabbros biotite k feldspar granites from tioman island off the east coast of malaysia also yield a zircon age of 80 1 ma showing cretaceous magmatism in common with province 1 geological and u pb geochronological data suggest that two east dipping in present day coordinates subduction zones are required during the triassic one along the bentong raub palaeo tethyan suture and the other west of the phuket burma province 1 belt supplementary material a full description of u pb analytical methods used and data tables are available at www geolsoc org uk sup18523

gold in the brunswick no 12 volcanogenic massive sulfide deposit bathurst mining camp canada evidence from bulk ore analysis and laser ablation icp ms data on sulfide phases the 329 mt brunswick no 12 volcanogenic massive sulfide deposit total resource of 163 mt at 10 4 zn 4 2 pb 0 34 cu and 115 g t ag is hosted within a middle ordovician bimodal volcanic and sedimentary sequence massive sulfides are for the most part syngenetic and the bulk of the sulfide ore occurs as a zn pb rich banded sulfide facies that forms an intimate relationship with a laterally extensive algoma type iron formation and defines the brunswick horizon zone refining of stratiform sulfides is considered to have resulted in the development of a large replacement style cu rich basal sulfide facies which is generally confined between the banded sulfide facies and an underlying stringer sulfide zone complex polyphase deformation and associated lower to upper greenschist facies regional metamorphism is responsible for the present geometry of the deposit textural modification has resulted in a general increase in grain size through the development of pyrite and arsenopyrite porphyroblasts which tend to overprint primary mineral assemblages despite the heterogeneous ductile deformation primary features have locally been preserved such as fine grained colloform pyrite and base and precious metal zonation within the main zone base metal and trace element abundances in massive sulfides from the brunswick no 12 deposit indicate two distinct geochemical associations the basal sulfide facies characterized by a proximal high temperature hydrothermal signature cu co bi se contains generally low au contents averaging 0 39 ppm n 34 conversely au is enriched in the banded sulfide facies averaging 1 1 ppm au n 21 and is associated with an exhalative suite of elements zn pb as sb ag sn finely laminated sulfide lenses hosted by iron formation at the north end of the main zone are further enriched in au averaging 1 7 ppm n 41 and ranging up to 8 2 ppm laser ablation inductively coupled plasma mass spectrometry icp ms analyses of pyrite n 97 from the north end of the main zone average 2 6 ppm au and range from the detection limit 0 015 ppm to 21 ppm overall these analyses reveal a distinct au sb as ag hg mn association within pyrite grains gold is strongly enriched in large pseudo primary masses of pyrite that exhibit relict banding and fine grained cores smaller euhedral pyrite porphyroblasts and euhedral rims of metamorphic origin surrounding the pyrite masses contain much less au sb ag as and sn arsenopyrite occurring chiefly as late porphyroblasts contains less au averaging 1 0 ppm and ranging from the detection limit 0 027 ppm to 6 9 ppm depth profiles for single spot laser ablation icp ms analyses of pyrite and arsenopyrite display uniform values of au and an absence of discrete microscopic inclusions of au bearing minerals which is consistent with chemically bonded au in the sulfide structure the pervasive correlation of au with sn in the zn pb rich banded sulfide facies suggests similar hydrothermal behavior during the waxing stages of deposition on the seafloor under high temperature 350oc and moderate to low ph conditions au and sn in hydrothermal fluids would be transported as chlorocomplexes an abrupt decrease in temperature and ah2s accompanied by an increase in fo2 and ph during mixing with seawater would lead to the simultaneous destabilization of both au and sn chlorocomplexes the enrichment of au in fine grained laminated sulfides on the periphery of the deposit accompanied by sporadic occurrences of barite and fe poor sphalerite supports lower hydrothermal fluid temperatures analogous to white smoker activity on the flanks of a large volcanogenic massive sulfide system in lower temperature 350oc and mildly acidic hydrothermal fluids au would be transported by thiocomplexes which exhibit multifunctional retrograde prograde solubility and a capacity to mobilize au to the outer parts of the sulfide mound the sluggish nature of this low temperature venting together with larger variations in ambient fo2 could lead to a sharp enrichment of au towards the stratigraphic hanging wall of massive sulfide deposits

santonian campanian planktonic foraminifera from tanzania shatsky rise and exmouth plateau species depth ecology and paleoceanographic inferences abstract the santonian campanian interval is of particular interest as it encompasses a cooling trend after the late cretaceous greenhouse maximum warmth of the turonian as well as a possibly related major faunal turnover among planktonic foraminifera the recovery of pristinely preserved planktonic foraminifera from santonian campanian sequences in southeastern tanzania allows examination of faunal changes and documentation of species specific stable isotope 13 c and 18 o signatures these isotopic data are ideal for inferring species paleoecological preferences and for tracing major paleoceanographic changes this study reports the first 18 o and 13 c data generated on glassy specimens of marginotruncana coronata m undulata m marginata and m pseudolinneiana and sigalia carpatica additional results from shatsky rise ocean drilling program leg 198 hole 1210b and exmouth plateau odp leg 122 hole 762c provide geographic control on species habitat preferences and paleoceanographic context isotopic analyses suggest that double keeled species including globotruncana bulloides contusotruncana fornicata c plummerae and probably marginotruncanids inhabited the surface mixed layer whereas the biserial gublerina rajagopalani was a permanent thermocline dweller thus our study confirms recent suggestions that the depth distribution models based on shell morphology and analogies with modern taxa are not applicable at all the examined localities changes in planktonic foraminiferal assemblages are used to define several ecological intervals each one characterized by a distinctive taxonomic composition and or increasing decreasing species diversity combined geochemical and paleontological observations suggest that by the middle late campanian a stratified upper water column developed in tanzania while less stratified and or mesotrophic conditions prevailed at shatsky rise and exmouth plateau

the maastrichtian record from shatsky rise northwest pacific a tropical perspective on global ecological and oceanographic changes we present new isotopic and micropaleontological data from a depth transect on shatsky rise that record the response of the tropical pacific to global biotic and oceanographic shifts during the mid maastrichtian results reveal a coupling between the upper ocean characterized by a weak thermocline and low to intermediate productivity and intermediate waters during the earliest maastrichtian oxygen and neodymium isotope data suggest a significant contribution of relatively warm intermediate water from the north pacific isotopic shifts through the early maastrichtian suggest that this warmer water mass was gradually replaced by cooler waters originating in the southern ocean although the cooler water mass remained dominant through the remainder of the maastrichtian it was displaced intermittently at shallow intermediate depths by north pacific intermediate water the globally recognized mid maastrichtian event similar to 69 ma manifested by the brief appearance of abundant inoceramid bivalves over shallow portions of shatsky rise is characterized by an abrupt increase similar to 2degrees 3degrees c in sea surface temperatures a greater flux of organic matter out of the surface ocean and warmer similar to 4degrees c intermediate waters results implicate simultaneous changes in surface waters and the sources distribution patterns of intermediate water masses as an underlying cause for widespread biotic and oceanographic changes during mid maastrichtian time

origin of the triassic qilinchang pb zn deposit in the western yangtze block sw china insights from in situ trace elemental compositions of base metal sulphides abstract the qilinchang pb zn deposit 5mt of sulphide ore at mean grades of 2 3 9 2 pb and 2 7 22 5 zn is hosted in early carboniferous carbonate rocks and mainly controlled by ne ns and nw trending structural belts between the xiaojiang and zhaotong qujing buried faults ore minerals are sphalerite galena pyrite chalcopyrite and marmatite whereas gangue minerals are dolomite calcite and quartz three generations of pyrite are recognized these include fine grained anhedral pyrite py i medium grained anhedral to subhedral hydrothermal pyrite py ii and coarse grained subhedral to euhedral hydrothermal pyrite py iii while the sphalerite occurs in two forms as fine grained intergrown with galena and associated with py i and py ii laser ablation inductively coupled plasma mass spectrometry la icp ms analysis was performed to evaluate trace element compositions of pyrite and sphalerite from different generations of ores py i has relatively higher concentrations of mg mn co ni and tl py ii in cu as se mo and sb relative to pyrite of other generations the contents of trace elements in py iii are variable but significantly enriched in ti v bi ag and pb compared to py i and py ii this variation indicates that these elements occur as micro mineral inclusions of possible ag pb bearing phases sphalerite of stage i has higher concentrations of mn fe co ni cu ga ge as ag cd in sb hg and pb than stage ii these elements are homogeneously distributed in all samples analyzed the incorporation of these elements is primarily through simple substitution mechanisms e g 2zn2 cu in3 as indicated from binary plots principal component analyses pca applied to la icp ms dataset for pyrite reveal two main clusters py i enriched in ni co and as py ii and py iii high in with v mn cu zn se mo ag sb au and bi likewise the pca also confirms two clusters of elements for sphalerite ge cu as sb ag fe and cd corresponding to sph i and in sn and ga corresponding to sph ii py i has higher co ni ratio ranging from 0 04 to 1 6 compared to py ii and py iii having co ni ratios from 0 to 0 706 and 0 0 696 respectively we report that the pyrites from the qilinchang deposit have co ni ratios slightly lower than typical mississippi valley type mvt deposits 0 2 7 2 and different from iron oxide copper gold iocg and porphyry cu deposits considering these geochemical signatures it can be suggested that the qilinchang deposit was not related to magmatic activities we thus propose that the ore forming fluids responsible for the formation of the deposit were generated from a low temperature environment similar to typical mvt deposits

productivity across the cretaceous tertiary boundary in high latitudes in low and middle latitudes the cretaceous tertiary boundary is marked by a sudden and pronounced decrease in 13c values of near surface water carbonates and a reduction in the surface to bottom 13c gradient these isotopic data have been interpreted as evidence of a decline in surface water productivity that was responsible for the extinction of many planktic foraminiferal species and other marine organisms at or near the k t boundary we present planktic and benthic foraminiferal isotopic data from two almost biostratigraphically complete sections at ocean drilling program site 738 in the antarctic indian ocean and at nye klov in denmark these data suggest that planktic carbonate 13c values in high latitudes may not have decreased dramatically at the k t boundary thus surface water productivity may not have been reduced as much as in low and middle latitudes comparison of the records of site 738 with those of odp sites 690 and 750 indicates a pronounced decline in 13c values of planktic and benthic foraminifera and fine fraction bulk carbonate 200 000 yr after the k t boundary this reflects a regional shift in the carbon isotopic composition of oceanic total dissolved carbon tdc and correlates with a similar change in benthic foraminiferal 13c values at mid and low latitude deep sea drilling project sites 527 and 577 this oceanographic event was followed by the ecosystem s global recovery 500 000 yr after the k t boundary these data suggest that the environmental effects of the k t boundary may have been less severe in the high latitude oceans than in tropical and subtropical regions