terrestrial and marine extinction at the triassic jurassic boundary synchronized with major carbon cycle perturbation a link to initiation of massive volcanism mass extinction at the triassic jurassic tr j boundary occurred about the same time 200 ma as one of the largest volcanic eruptive events known that which characterized the central atlantic magmatic province organic carbon isotope data from the uk and greenland demonstrate that changes in flora and fauna from terrestrial and marine environments occurred synchronously with a light carbon isotope excursion and that this happened earlier than the tr j boundary marked by ammonites in the uk the results also point toward synchronicity between extinctions and eruption of the first central atlantic magmatic province lavas suggesting a causal link between loss of taxa and the very earliest eruptive phases the initial isotopic excursion potentially provides a widely correlatable marker for the base of the jurassic a temporary return to heavier values followed but relatively light carbon dominated the shallow oceanic and atmospheric reservoirs for at least 600 k y

morphology internal architecture and emplacement mechanisms of lava flows from the central atlantic magmatic province camp of argana basin morocco abstract the morphology internal architecture and emplacement mechanisms of the central atlantic magmatic province camp lava flows of argana basin in morocco are presented the volcanic pile was produced by two volcanic pulses the first represented by the tasguint formation corresponds to a succession of 3 13 individual flows created by 1 8 eruptions the second alemzi formation is composed of 2 7 individual flows formed by 1 4 eruptions these formations geochemically distinct are separated by thin silty or sandy horizons or by palaeosols they include compound pahoehoe flows and simple flows the first type is almost exclusive of the lower formation while the second type dominates the upper formation the lava flows show clear evidence of endogenous growth or inflation the characteristics of the volcanic pile suggest slow emplacement during sustained eruptive episodes and are compatible with a continental basaltic succession facies model

vein stratigraphy mineralogy and metal zonation of the kencana low sulfidation epithermal au ag deposit gosowong goldfield halmahera island indonesia

the effect of inertial accelerations on the higher frequency components of the signal from spring gravimeters summary experimental and theoretical studies have shown that due to the magma gas dynamics in the upper part of a volcano s plumbing system gravity changes can develop over periods between a few tens of seconds and several hours the mass transport implied by certain fast evolving volcanic processes also constitute the source mechanism of seismic waves with frequencies over the lower limit of the seismic band these seismic waves could affect the measuring system of spring gravimeters that are increasingly used as continuously running devices to monitor and study active volcanoes as a consequence under some circumstances the signal from a continuously running spring gravimeter will be the combination of the gravity field component and the inertial acceleration component the latter due to the ground motion in such cases the inertial acceleration must be separated from the gravity signal to assess the amount of mass redistributed during the studied process to achieve this separation the frequency response curve of the spring gravimeter to inertial accelerations must be calculated since it is not supplied by manufacturers in this paper we present a method to retrieve the above curve using simultaneous recordings during the transit of teleseismic waves of a lacoste romberg d gravimeter and a nanometrics trillium 40 broad band seismometer whose frequency response curve to ground acceleration is known ap riori the use of teleseismic waves is particularly useful for our purpose since teleseisms are not associated with a local mass redistribution the gravimeter will thus be affected only by the ground motion making the above calculation possible our results show that because of the instrumental damping the effect of the inertial acceleration is reduced in the output signal from the gravimeter to 0 5 and 0 1 of its original value at frequencies between 0 02 and 0 07 hz respectively the robustness of the calculated frequency response curve is proven using independent simultaneous signals from gravimeter and broad band seismometer

geochronology of the tumpangpitu porphyry au cu mo and high sulfidation epithermal au ag cu deposit evidence for pre and postmineralization diatremes in the tujuh bukit district southeast java indonesia the tumpangpitu porphyry and high intermediate sulfidation epithermal deposit is the largest deposit in the tujuh bukit district southeast java indonesia the porphyry resource contains 1 9 billion tonnes 0 45 cu and 0 45 g t au for 28 1 moz au and 19 billion lbs of cu there are an additional 2 1 moz au and 72 9 moz of ag in oxidized high sulfidation epithermal mineralization tumpangpitu is located along a nw striking structural corridor covering an area of 12 5 km that hosts several cu au mo mineralized tonalitic porphyries each with varying degrees of metal enrichment at least eight discrete intrusions spanning the alteration mineralization sequence have been identified at tumpangpitu what is unusual however is the presence of both a premineralization relatively dry volcanic breccia pipe tanjung jahe and a late mineralization diatreme complex associated with a significant large magmatic hydrothermal system tumpangpitu in the same district magmatism mineralization and alteration at tumpangpitu occurred in response to north directed subduction of the indo australian plate beneath the asian continental plate margin the tujuh bukit district is floored by early to late miocene sedimentary and andesitic volcanic rocks volcanic hydrothermal activity at tujuh bukit began with the formation of the weakly altered tanjung jahe diatreme complex u pbzircon ages of 8 78 0 22 8 52 0 21 ma mineralization at tumpangpitu was preceded by the intrusion of a large equigranular dioritic batholith 5 81 0 20 5 18 0 27 ma hydrothermal activity associated with mineralization has been constrained by u pb age determinations from syn to late mineralization porphyries that were emplaced in the early pliocene from 5 40 0 46 to 3 94 0 69 ma high and intermediate sulfidation au ag cu mineralization and associated advanced argillic alteration part of a district scale lithocap has overprinted and significantly upgraded the top of the porphyry orebody ar ar dating of alunite 4 385 0 049 ma and re os dating of molybdenite 4 303 0 018 ma have defined a short time period between the high sulfidation epithermal and porphyry mineralization events this suggests extreme rates of uplift exhumation and erosion in the vicinity of the sunda banda magmatic arc volcanic hydrothermal activity associated with the tumpangpitu diatreme occurred during epithermal mineralization breccia matrix zircon age of 2 7 1 0 ma with systematic errors clasts of high sulfidation state mineralized rocks are a minor but significant component of the diatreme and late stage epithermal veins cutting the diatreme demonstrate an intermineralization timing with respect to epithermal activity in the district implying that epithermal mineralization continued intermittently for 1 to 1 5 m y after porphyry mineralization ceased at tumpangpitu

mass mortality and its environmental and evolutionary consequences the latest mesozoic and earliest tertiary sediments at deep sea drilling project site 524 provide an amplified record of environmental and biostratographic changes at the end of cretaceous closely spaced samples representing time intervals as short as 102 or 103 years were analyzed for their bulk carbonate and trace metal compositions and for oxygen and carbon isotopic compositions the data indicate that at the end of cretaceous when a high proportion of the ocean9s planktic organisms were eliminated an associated reduction in productivity led to a partial transfer of dissolved carbon dioxide from the oceans to the atmosphere this resulted in a large increase of the atmospheric carbon dioxide during the next 50 000 years which is believed to have caused a temperature rise revealed by the oxygen isotope data the lowermost tertiary sediments at site 524 include fossils with cretaceous affinities which may include both reworked individuals and some forms that survived for a while after the catastrophe our data indicate that many of the cretaceous pelagic organisms became extinct over a period of a few tens of thousands of years and do not contradict the scenario of cometary impact as a cause of mass mortality in the oceans as suggested by an iridium anomaly at the cretaceous tertiary boundary

geochronology and geochemistry of the frieda river prospect area papua new guinea the frieda river prospect is located between the frieda and lagaip fault zones two major structural features of the new guinea mobile belt in the west sepik district papua new guinea the prospect can be subdivided into three spatially and geologically different areas frieda complex mianmin area and nena diorite area the frieda complex is the remnant volcanic edifice of an island stratovolcano interstratified in the mid miocene wogamush formation intrusive and volcanic units in the complex are texturally similar andesitic hornblende plagioclase porphyries and are probably comagmatic pyritic replacement copper gold and porphyry copper deposits are associated with early and late phases respectively of extensive district scale advanced argillic alteration along the central axis of the frieda complex the mianmin area is a separate unmineralized volcanic center that contains igneous rocks similar to those of the frieda complex the nena diorite a composite holocrystalline intermediate to mafic body intrudes upper cretaceous to eocene age basement rocks it is located north of and separated from the frieda complex by the frieda fault igneous activity in the frieda river prospect extended over an interval of at least 4 m y on the basis of field relations and k ar ages this igneous activity is subdivided into early intrusion 17 3 to 16 8 m y ago main intrusion 16 3 to 13 1 m y ago and late alteration about 12 8 to 11 2 m y ago events k ar ages on alunite appear to be too young to be those of formation of this mineral and the oldest 13 0 or 0 4 m y is interpreted as a minimum age for the nena pyritic replacement copper gold deposit geothermal activity which caused district scale alteration extended from earlier than 14 0 or 0 4 m y until about 11 2 or 0 2 m y ago the discordance of about 2 m y between k ar ages of coexisting hornblende and biotite in two diorites is thought to register the cooling history of the hydrothermal system a k ar age of 13 6 or 0 4 m y was obtained on hornblende from a sample of horse microdiorite regarded as the progenitor of porphyry copper mineralization this age is interpreted as near that of emplacement and provides an older limit for the age of vein controlled transitional alteration associated with most porphyry copper mineralization the primary biotite apparent k ar age of 11 5 or 0 2 m y from the same sample is accepted as a younger limit for the age of porphyry copper mineralization k ar ages from the mianmin area and the nena diorite area are very similar to those found for dioritic intrusions in the frieda complex intrusive and volcanic rocks of the frieda river prospect exhibit limited compositional variation they are all of andesitic composition and belong to a normal k calc alkaline suite the three geologically distinct areas of the prospect are distinguishable on the basis of rock and mineral chemical differences textural and chemical features of the freida complex and mianmin area igneous rocks are compatible with much of their diversity in lithology and dispersion in chemistry being due to their representing cumulate melt mixtures they are thought to have crystallized from hot 900 degrees c oxidized magmas which were emplaced at a shallow level in the crust p total

duration of and decoupling between carbon isotope excursions during the end triassic mass extinction and central atlantic magmatic province emplacement abstract changes in 13 c carb and 13 c org from marine strata occur globally in association with the end triassic mass extinction and the emplacement of the central atlantic magmatic province camp during the break up of pangea as is typical in deep time the timing and duration of these isotopic excursions has remained elusive hampering attempts to link carbon cycle perturbations to specific processes here we report 13 c carb and 13 c org from late triassic and early jurassic strata near levanto peru where intercalated dated ash beds permit temporal calibration of the carbon isotope record both 13 c carb and 13 c org exhibit a broad positive excursion through the latest triassic into the earliest jurassic the first order positive excursion in 13 c org is interrupted by a negative shift noted in many sections around the world coincident with the extinction horizon our data indicate that the negative excursion lasts 85 25 kyrs longer than inferred by previous studies based on cyclostratigraphy a 260 80 kyr positive 13 c org shift follows during which the first jurassic ammonites appear the overall excursion culminates in a return to pre perturbation carbon isotopic values over the next 1090 70 kyrs via chronologic isotopic and biostratigraphic correlation to other successions we find that 13 c carb and 13 c org return to pre perturbation values as camp volcanism ceases and in association with the recovery of pelagic and benthic biota however the initiation of the carbon isotope excursion at levanto predates the well dated camp sills from north america indicating that camp may have started earlier than thought based on these exposures or that the onset of carbon cycle perturbations was not related to camp

a special issue devoted to porphyry and epithermal deposits of the southwest pacific an introduction the southwest pacific is host to a number of mineralization styles including numerous world class porphyry cu au and epithermal au ag deposits cooke et al 2005 garwin et al 2005 the majority of the giant porphyry and epithermal au and cu deposits were formed within a series of middle to late cenozoic 25 1 ma arcs garwin et al 2005 maryono et al 2018 these arcs form a complex boundary between the eurasian pacific and indian australian tectonic plates stretching from japan in the northeast and myanmar in the northwest through the philippines indonesia new guinea and the volcanic island chains of the solomon islands new hebrides vanuatu and fiji fig 1

pliocene cu au bearing igneous intrusions of the gunung bijih ertsberg district irian jaya indonesia k ar geochronology nine distinct potassic intermediate igneous bodies have been identified during detailed surface and underground mapping of 100 km 2 in the gunung bijih erstberg cu au district in the highlands of irian jaya indonesia west new guinea fourteen biotite k ar ages range from 2 6 to 3 8 ma while another from a small isolated pluton is distinctly older at 4 4 ma these ages represent times of intrusion and crystallization which followed regional kilometer scale folding that resulted from collision at a subduction zone of the northern edge of the australian continental margin with the melanesian oceanic island arc complex the grasberg and ertsberg intrusions are cut by numerous faults with only minor hundreds of meters offset throughout the island of new guinea dated neogene igneous rocks form two clusters separated in age and location a distinct belt of miocene 20 10 ma plutons maramuni arc stretches the entire length of the northern highlands of papua new guinea and recurs in western iri

sudden productivity collapse associated with the triassic jurassic boundary mass extinction the end triassic mass extinction is one of the five most catastrophic in phanerozoic earth history here we report carbon isotope evidence of a pronounced productivity collapse at the boundary coincident with a sudden extinction among marine plankton from stratigraphic sections on the queen charlotte islands british columbia canada this signal is similar to though smaller than the carbon isotope excursions associated with the permian triassic and cretaceous tertiary events

phanerozoic atmospheric co2 change evaluating geochemical and paleobiological approaches abstract the theory and use of geochemical modeling of the long term carbon cycle and four paleo pco 2 proxies are reviewed and discussed in order to discern the best applications for each method geochemical models provide pco 2 predictions for the entire phanerozoic but most existing models present 5 10 m y means and so often do not resolve short term excursions error estimates based on sensitivity analyses range from 75 200 ppmv for the tertiary to as much as 3000 ppmv during the early paleozoic the 13 c of pedogenic carbonates provide the best proxy based pco 2 estimates for the pre tertiary with error estimates ranging from 500 1000 ppmv pre devonian estimates should be treated cautiously error estimates for tertiary reconstructions via this proxy are higher than other proxies and models 400 500 ppmv and should not be solely relied upon we also show the importance of measuring the 13 c of coexisting organic matter instead of inferring its value from marine carbonates the 13 c of the organic remains of phytoplankton from sediment cores provide high temporal resolution up to 10 3 10 4 year high precision 25 100 ppmv for the tertiary to 150 200 ppmv for the cretaceous pco 2 estimates that can be near continuous for most of the tertiary its high temporal resolution and availability of continuous sequences is advantageous for studies aiming to discern short term excursions this method however must correct for changes in growth rate and oxygen level at elevated pco 2 750 1250 ppmv this proxy loses its sensitivity and is not useful the stomatal density and stomatal index of land plants also provide high temporal resolution 2 year high precision 10 40 ppmv for the tertiary and possibly cretaceous pco 2 estimates and so also is ideal for discerning short term excursions unfortunately this proxy also loses sensitivity at some level of pco 2 above 350 ppmv which currently is largely undetermined our analysis of the recently developed 11 b technique shows that it currently is not yet well constrained most importantly it requires the assumption that the boron isotopic composition of the ocean remains nearly constant through time in addition it assumes that there are no biological or temperature effects and that diagenetic alteration of the boron isotopic composition does not occur a fifth co 2 proxy based on the redox chemistry of marine cerium has several fundamental flaws and is not discussed in detail here

tectonics and geology of porphyry cu au deposits along the eastern sunda magmatic arc indonesia the discovery of the world class cu au deposit at tumpangpitu east java 1 9 gt 0 45 cu 0 45 g t au has reinforced the eastern sunda arc as a significant metallogenic belt that is highly promising for the discovery of major porphyry deposits the arc hosts three premier porphyry cu au deposits at batu hijau elang and tumpangpitu 300 t au and 5 mt cu these giant porphyry deposits are confined to the eastern segment of the eastern sunda arc eastern java to sumbawa constructed on island arc crust where the roo rise is being subducted by contrast major epithermal low sulfidation dominant deposits associated with poorly endowed porphyry prospects occur along the western segment of the arc western java developed on thick continental crust on the southern margin of sundaland associated with subduction of typically thin indian oceanic crust porphyry cu au deposits of the eastern sunda arc are spatially associated with small nested dioritic to tonalitic intrusive complexes with low k calc alkaline to weakly alkaline signatures hypogene alteration and mineralization developed during three main temporally and spatially overlapping events termed early transitional and late the hypogene cu au mineralized zone of the giant deposits forms a bell shaped body of 0 3 cu shell greater than 1 km in both diameter and vertical extent that is centered on multiphase elongate pencil like tonalite intrusions 200 to 1 200 m in diameter and 2 km vertical extent large 20 km 2 lithocaps associated with high sulfidation epithermal systems and postporphyry mineralization diatreme breccias characterize productive porphyry districts at batu hijau elang and tumpangpitu the known porphyry deposits with metal content exceeding 300 t au and 5 mt cu all formed later than 5 ma suggesting an important change in the metallogeny of the arc at this time these giant porphyry deposits formed relatively rapidly typically over a period of 30 to 860 k y during the pliocene pleistocene between 5 and 2 5 ma porphyry deposits along the eastern sunda arc display characteristic geologic features similar to porphyry deposits elsewhere significant differences include low k systems dominance of hydrothermal biotite over k feldspar early intense actinolite alteration associated with ore widespread shreddy chlorite after secondary biotite narrow quartz sericite pyrite alteration zones lack of development of chalcopyrite veins large overlying lithocaps and abundant chalcocite bornite covellite veinlets associated with late overprinting epithermal systems hydrothermal oligoclase is also more abundant than k feldspar in the central biotite magnetite zones

time calibration of triassic jurassic microfloral turnover eastern north america abstract palynological data from the newark basin of the newark supergroup reveal a spike in the spore pollen ratio at the triassic jurassic boundary this spore spike is coincident with a 60 regional extinction of the palynoflora and approximately synchronous with terrestrial vertebrate extinctions orbitally controlled sedimentary cycles allow stratigraphic sections to be calibrated in time constraining the duration of the microfloral turnover to an interval of 21 ky the geologically brief palynofloral break is similar to cretaceous tertiary boundary fern spikes these data support a triassic jurassic boundary impact extinction scenario

long period lunar earth tides at the geographic south pole and recent models of ocean tides for many years the ocean tide models of schwiderski 1980 were the standards used by the earth tide community to interpret deviations of observed earth tides from predictions on the basis of earth models constructed by seismologists recently the topex poseidon altimeter mission provided new and improved information on pelagic ocean tides which led several research groups to generate new models of the major oceanic tides this in turn renewed our own interest in the observations of long period lunar tides at the geographic south pole that were reported many years ago with an attempt to interpret the deviation from predictions using the schwiderski models we used four different models of the fortnightly mf and monthly mm ocean tides to calculate their attraction and loading effects at the south pole and compared the results with the observed gravity tides in our earlier interpretation we did not realize that for long period ocean tides the so called greenwich phase does not refer to the phase of these tides at the latitude of greenwich but to the phase at the equator this resulted in a mistake in the relative phases of earth tide and ocean effect at the south pole for mf we now find that all models predict the phase lead of the observed versus theoretical tides within the formal uncertainties however the amplitude is still underpredicted by 1 5 2 per cent this could be due to several reasons instrument calibration errors in the body and or ocean tide models relaxation of the earth s elastic properties and the huge ice sheet of antarctica these possibilities are discussed for the mm tide the observed amplitude is well predicted within error however the uncertainties in the measurements are rather large

the relationship between epithermal and porphyry hydrothermal systems within the tavua caldera fiji the shoshonitic tavua caldera in viti levu fiji defines the volcanic center of the tavua volcano the caldera occurs at the intersection of the northeast trending viti levu lineament and a northwest trending lineament locally manifested by the nasivi shear zone fault related subsidence which contributed to the evolution of the tavua caldera the central inner caldera and the structural preparation for mineralization occurred on these two regional fault systems and local concentric normal faults a continuum of mineralization and alteration styles is evident along the nasivi shear zone caused by a northwesterly evolution and migration of intrusion and hydrothermal activity porphyry style subeconomic copper gold mineralization and associated alteration occurred at depth in the nasivi shear zone at the center of the caldera approximately contemporaneously with the development of the inner caldera acid sulfate style epithermal alteration and minor gold mineralization immediately postdated and were superimposed on this porphyry style alteration farther northwest along the nasivi shear zone transitional ac d sulfate to adularia sericite epithermal alteration and minor gold mineralization occur variation in hydrothermal style is considered to reflect an increasing distance from magmatic source combined with an increasing proportion of meteoric water mixing with the hydrothermal fluid northwest of this system at the intersection of the nasivi shear zone and the viti levu lineament the 4 4 m oz adularia sericite style epithermal emperor gold mine occurs high level epithermal mineralization and alteration occur 4 km northeast of the emperor gold mine in an area which has a demonstrable present day hydraulic connection with the mine variations in fluid inclusion homogenization temperatures from the mine indicate that fluids entered the structurally prepared mine area via the nasivi shear zone emperor epithermal mineralization postdated magmatism by approximately 0 4 ma stable isotope data the presence of albitic alteration beneath mineralization and high salinities within the mine indicate that the emperor northern prospects hydrothermal system is related to an intrusion into the nasivi shear zone beneath the mine this is consistent with a demonstrable northwesterly migration of intrusions with time along the nasivi shear zone albitic phyllic and propylitic assemblages comprise the main porphyry style alteration types in the caldera center calculated temperatures of formation of chlorite in these assemblages indicate that these three alteration facies formed in the temperature range 270 degrees to 340 degrees c in good agreement with available fluid inclusion data and the stability ranges of the mineral assemblages kubler indices of illite likewise imply that these assemblages formed at relatively high temperature epithermal lode alteration mineralization at emperor is shown by fluid inclusion data to have formed around 200 degrees c kubler indices of illite confirm that this alteration formed at significantly lower temperatures than did porphyry alteration and that chlorites in the emperor mine have calculated temperatures of formation mostly below 200 degrees c high level epithermal alteration occurring northeast of emperor is inferred to have formed at even lower temperatures

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

biogeochemical constraints on the triassic jurassic boundary carbon cycle event 1 the end triassic mass extinctions represent one of the five most severe biotic crises in earth history yet remain one of the most enigmatic ongoing debate concerns the environmental effects of the central atlantic magmatic province camp eruptions and their linkage with the mass extinction event across the triassic jurassic boundary there is conflicting paleo evidence for changes in atmospheric pco2 during the extrusion of the camp basalts studies on sediments from european and pacific localities have however identified a substantial negative isotopic anomaly up to 3 5 across the tr j boundary providing an important indicator of changes in the operation of the ancient global carbon cycle we sought to explain the paleo evidence by utilizing a carbon cycle model for the hothouse world of the end triassic that emphasizes the chemical weathering of silicate and carbonate rocks and the ocean carbonate chemistry we find that volcanic co2 outgassing fails to fully account for either a sufficient rise in atmospheric pco2 indicated by the stomata of fossil leaves or the sedimentary isotopic fingerprint instead the scenario that best fits all of the geologic evidence is a positive feedback loop in which warming due to a buildup of volcanically derived co2 triggers destabilization of seafloor methane hydrates and the catastrophic release of ch4 palfy et al 2001 we calculate that this carbon cycle perturbation was huge involving the release of 8000 9000 gt c as co2 during the camp basaltic eruptions and 5000 gt c as ch4 in the model the initial isotopic excursion is assumed to take place over 70 kyr while complete reequilibration of the ocean atmosphere system with respect to co2 is accomplished over 700 1000 kyr our results thus provide a preliminary theoretical explanation for the bioevents estimated pco2 changes and isotopic excursions observed in marine and continental sediments at this time

evidence for magmatic hydrothermal fluids and ore forming processes in epithermal and porphyry deposits of the baguio district philippines the baguio district contains a diverse array of epithermal porphyry and skarn deposits together with a large broadly strata bound advanced argillic lithocap magmatism mineralization and alteration occurred in response to subduction of the south china sea plate and the scarborough ridge beneath northern luzon over the past 3 m y rapid uplift and exhumation resulted in epithermal veins overprinting several porphyry cu au deposits most of the epithermal au ag deposits of the baguio district including antamok and acupan the two largest au deposits are intermediate sulfidation state quartz carbonate adularia illite base metal sulfide veins that contain electrum and minor au ag tellurides in contrast high sulfidation mineralization at kelly includes enargite tennantite electrum and precious metal tellurides and is associated with advanced argillic alteration although the mineralizing fluids that formed the porphyry and epithermal deposits had distinct temperatures and salinities stable and radiogenic data provide evidence for direct magmatic contributions into each deposit type the epithermal mineralizing fluids were dilute generally 600 c hypersaline brines 30 to 70 wt nacl equiv and low density vapor sulfur isotope compositions of sulfides in the porphyry skarn and intermediate sulfidation epithermal veins of the southern and central baguio district are mostly between 1 and 6 per mil consistent with a predominance of h2s in the mineralizing fluids i e reducing conditions in contrast sulfides from the high sulfidation porphyry and intermediate sulfidation deposits located adjacent to the baguio lithocap mostly have negative sulfur isotope values 6 9 to 0 8 consistent with oxidizing so42 predominant mineralizing fluids intermediate sulfidation epithermal veins at acupan have crosscut a well mineralized porphyry cu au stock work at ampucao the two deposits cannot be distinguished on the basis of radiometric age determinations ampucao 0 51 0 26 ma acupan 0 65 0 07 ma and are interpreted to be cogenetic with telescoping of the two environments caused by the rapid uplift and exhumation associated with ridge subduction measured 34ssulfide 1 1 to 6 6 34ssulfate 10 4 to 31 8 values and initial strontium ratios of anhydrite 0 70378 0 70385 are consistent with identical and predominantly magmatic sources of these components for the ampucao porphyry and acupan epithermal veins helium isotopes provide further evidence of mantle derived components in the epithermal veins r ra values of 6 0 and 6 7 oxygen deuterium and carbon isotopes provide evidence for predominantly magmatic water at ampucao and for hybrid magmatic meteoric waters at acupan that precipitated precious metals due to boiling the proportion of magmatic water relative to meteoric water and precious metal grades both decreased with time during epithermal vein formation at acupan the common observation of cross cutting relationships between porphyry and epithermal veins observed throughout the baguio district imply that the evolution of porphyry style to intermediate sulfidation style mineralization was a common phenomenon in this region and contributed significantly to its rich metal endowment

ultra deep oxidation and exotic copper formation at the late pliocene boyongan and bayugo porphyry copper gold deposits surigao philippines geology mineralogy paleoaltimetry and their implications for geologic physiographic and tectonic controls the boyongan and bayugo porphyry copper gold deposits are part of an emerging belt of intrusion centered gold rich deposits in the surigao district of northeast mindanao philippines exhumation and weathering of these late pliocene age deposits has led to the development of the world s deepest known porphyry oxidation profile at boyongan 600 m and yet only a modest 30 70 m oxidation profile at adjacent bayugo debris flows volcanic rocks and fluviolacustrine sediments accumulating in the actively extending mainit graben subsequently covered the deposits and preserved the supergene profiles at boyongan and bayugo there is a vertical transition from shallower supergene copper oxide minerals malachite azurite cuprite to deeper sulfide stable assemblages chalcocite hypogene sulfides this transition provides a time integrated proxy for the position of the water table at the base of the saturated zone during supergene oxidation contours of the elevation of the paleopotentiometric surface based on this mineralogical transition show that the thickest portions of the unsaturated zone coincided with a silt sand matrix diatreme breccia complex at boyongan within the breccia complex the thickness of the unsaturated zone approached 600 m whereas outside the breccia complex e g at bayugo the thickness averaged 50 m contours of the paleopotentiometric surface suggest that during weathering groundwater flowed into the breccia complex from the north south and east and exited along a high permeability zone to the west the high relief 550 m on the elevation of the paleopotentiometric surface is consistent with an environment of high topographic relief and the outflow zone to the west of the breccia complex probably reflects proximity to a steep scarp intersecting the western breccia complex margin stable isotope paleoaltimetry has enabled estimation of the elevation of the land surface which further constrains the physiographic setting during supergene oxidation isotopic measurements of oxygen in supergene kaolinite from boyongan suggest that local paleometeoric water involved in weathering had a 18o composition of approximately 5 7 per mil at the latitude of the southern philippines this value corresponds to pleistocene rain water condensing at elevations between 750 and 1 050 m above contemporary sea level providing a maximum estimate for the surface elevation during weathering of the porphyry systems physiographic reconstructions suggest that the deep oxidation profile at boyongan formed in an environment of high topographic relief immediately east of a prominent 550 m escarpment the high permeability contrast between the breccia complex and the surrounding wall rocks coupled with the proximity of the breccia complex to the escarpment led to a depressed groundwater table and a vertically extensive unsaturated zone in the immediate vicinity of boyongan this thick vadose zone and the low hypogene pyrite copper sulfide ratios 0 6 at boyongan promoted in situ oxidation of copper sulfides with only modest 200 m supergene remobilization of copper in contrast higher hypogene pyrite chalcopyrite ratios 2 3 at bayugo led to greater acid production during weathering and more complete leaching of copper above the base of oxidation this process promoted significant 600 m lateral dispersion of copper down the paleohydraulic gradient into the diatreme breccia comple ultimately leading to the formation of an exotic copper deposit

body size trends and recovery amongst bivalves following the end triassic mass extinction abstract fossils in the immediate aftermath of mass extinctions are often of small size a phenomenon attributed to the lilliput effect temporary size reduction of surviving species there has been little attempt to study size trends during subsequent recovery intervals nor has the relationship between size diversity and environmental controls been evaluated here we examine the recovery following the end triassic mass extinction amongst bivalves of the british lower and middle lias three distinct phases of size change are seen that are independent of other recovery metrics initially bivalves are small but the lilliput effect is a minor factor the majority of small taxa belong to new species that undergo a later within species size increase the brobdingnag effect throughout the subsequent hettangian stage new species that appeared during the hettangian were also progressively larger and cope s rule size increase between successive species is seen notably amongst ammonites the size increase was reversed during the sinemurian stage when bivalves once again exhibited small body sizes during the pliensbachian stage another phase of size increase occurred with further evidence of the brobdingnag effect these three phases of size change are seen across all suspension feeding ecological guilds of bivalve but are not expressed among deposit feeders local environmental conditions explain some aspects of size patterns but factors such as temperature marine oxygenation and sea level do not correlate with the long term size trends the brobdingnag effect may reflect increased availability quality of food during the recovery interval a factor that controlled bivalve size but not evolution

use of carbon isotopes in paleosols as an indicator of the p co2 of the paleoatmosphere measurements of carbon isotopic composition of coexisting paleosol organic matter and carbonate results in improved estimates of the paleo p co2 content of the paleoatmosphere measurements from tertiary paleosols indicate that the levels of co2 in the early eocene middle and late miocene and pliocene were less than 1000 ppmv early cretaceous levels of p co2 were significantly higher of the order of 1500 to 3000 ppmv

age of jurassic continental tholeiites of french guyana surinam and guinea implications for the initial opening of the central atlantic ocean abstract a detailed 40ar 39ar study of mineral separates from the jurassic atlantic continental tholeiites jact of guyana french guyana and surinam south america and guinea west africa related to the initial opening of the central atlantic has been carried out in french guyana plateau ages of 196 0 5 7 ma and 196 1 7 5 ma were obtained on single small amphibole grains from nnw sse trending dykes in guinea single biotite grains from intrusive formations from the kakoulima and fouta djalon areas yielded plateau ages of 200 4 0 2 ma and 194 8 0 5 ma concordant with high temperature apparent ages on other biotites the bulk plagioclase samples display disturbed age spectra due to alteration and excess argon however intermediate temperature weighted mean plagioclase ages are similar in both regions of guyana and guinea ranging from 200 2 2 4 ma to 188 7 1 9 ma partly in agreement with the amphibole and biotite data these data combined with previous 40ar 39ar and u pb results from the northern part of the central atlantic margins indicate intense magmatic activity distributed over a large area from iberia to liberia ca 4500 km long for a short period of time 204 195 ma perhaps less for the bulk of the magmatism during the initial break up of pangea continent these data do not support an initiation of the magmatism from a radial volcano tectonic system centred in the south of the region as suggested by may 1 and the initial break up seems to affect the whole central atlantic during a period of 9 ma

interpreting carbon isotope excursions strangelove oceans large negative excursions in marine carbonate delta sup 13 c are commonly associated with period boundaries and mass extinctions explanations for these events must be consistent with limitations imposed by carbon isotope mass balance at steady state i e for excursions lasting more than 10 sup 5 yr the surface ocean delta sup 13 c is set by the organic fraction of the total carbon burial rate and the magnitude of the photosynthetic isotope effect the delta sup 13 c of the deep ocean and the surface to deep isotope gradient are set by both the organic fraction of the ocean s remineralized particulate flux and the magnitude of the isotope effect thus it is the carbon isotope composition of the deep ocean that is most reflective of internal oceanic processes the surface ocean records changes in the longer term throughput of carbon in the system the cessation of organic export from the surface ocean such as is presumed to have caused the strangelove ocean condition of the cretaceous tertiary k t boundary leads to an isotopically homogeneous ocean in decades to centuries if this condition persists the ocean s isotopic composition approaches that of the riverine weathering input in 10 sup 5 yr failure to approach this value during the k t event suggests continued production andmore burial of organic carbon dominantly in either terrestrial or shallow marine environments less

a mesozoic time scale we present an integrated geomagnetic polarity and stratigraphic time scale for the triassic jurassic and cretaceous periods of the mesozoic era with age estimates and uncertainty limits for stage boundaries the time scale uses a suite of 324 radiomenc dates including high resolution 40 ar 39 ar age estimates this framework involves the observed ties between 1 radiometric dates biozones and stage boundaries and 2 between biozones and magnetic reversals on the seafloor and in sediments interpolation techniques include maximum likelihood estimation smoothing cubic spline fitting and magnetochronology

numerical evaluation of mechanisms driving early jurassic changes in global carbon cycling the early jurassic early toarcian ca 183 ma carbon cycle perturbation is characterized by aabout 5 parts per thousand delta sup 13 c excursion in the exogenic carbon reservoirs a 1000 ppm rise in atmospheric co sub 2 and a 6 7 degrees warming two proposed explanations for this presumed global carbon cycle perturbation are the liberation of massive amounts of isotopically light ch4 from 1 gondwanan coals by heating during the intrusive eruption of the karoo ferrar large igneous province lip or 2 the thermal dissociation of gas hydrates carbon cycle modeling indicates that the release of ch4 from gondwanan coals synchronous with the eruption of the karoo ferrar lip fails to reproduce the magnitude or timing of the co sub 2 and delta sup 13 c excursions however sensitivity analyses constrained by a marine cyclostratigraphically dated delta sup 13 c record indicate that both features of geologic record can be explained with the huge input of about 15 340 24 750 gt c over about 220 k y a result possibly pointing to the involvement of hydrothermal vent complexes in the karoo basin the simulated release of 6000 gt c from gas hydrates also reproduces aspects of the early toarcian rock record but the large mass involved raises fundamental questionsmore about its formation storage and release less

sea level change and facies development across potential triassic jurassic boundary horizons sw britain the late triassic to early jurassic aged succession of sw britain the penarth and lower lias groups comprises mudstone sandstone and limestone strata deposited in a variety of marine to non marine environments faunal and floral characteristics of these successions have led to the proposal that one location in sw england st audrie9s bay should serve as the global stratotype section and point gssp for the base of the hettangian stage and thus for the triassic jurassic tr j boundary the sections of sw britain have also been used previously to infer sea level change history and relate this to potential kill mechanisms associated with the tr j boundary mass extinction chemostratigraphic biofacies and lithofacies data are used here to suggest alternative models of sea level change in relation to possible tr j boundary horizons in the sections of sw britain a sea level lowstand surface of erosion is inferred to occur within the cotham member of the lilstock formation a unit deposited in an environment that was often subaerially exposed in contrast to previous interpretations the top surface of the overlying langport member here inferred to be deposited on a carbonate ramp of depositional or tectonic origin represents a drowning event of at least regional extent all horizons regarded as plausible levels at which to place the tr j boundary based on fossil distributions lie within strata deposited during relative sea level rise however it is doubtful whether the higher horizons proposed to mark the boundary faithfully record times of true biotic change on a global scale and additionally there is no positive evidence that sea level fall had any relation to the genesis of proposed tr j marker horizons it is unlikely that sea level fall played a significant role in the tr j boundary extinctions in either a local or a global context

magma evolution leading to porphyry au cu mineralization at the ok tedi deposit papua new guinea trace element geochemistry and high precision geochronology of igneous zircon

a new data bank for tidal gravity measurements db 92 abstract tidal gravity parameters are now available in 352 permanent or temporary stations all over the world previous tentative interpretations of these data were made on the basis of a data bank created in 1980 1982 which contained all available results without any discrimination which could have appeared as arbitrary these interpretations were criticized on the basis of the different qualities of instruments null instruments or not data calibration and necessary corrections for ocean continent interactions as we agree that a careful re examination of the basic data is needed before any geophysical discussion we have built this new data bank which contains only those 211 stations where rigid control of every step in the observations calibrations and reduction could be made either because the original data are stored in the world data center c or because the published results give enough information to permit checks and revisions as a result the scattering in the tidal parameters is reduced by a factor of 2 with respect to the previous data while the mean values of the amplitude factors of the two main waves o 1 diurnal m 2 semi diurnal calculated continent by continent agree with the best available earth model it is expected that this new data bank will be used for renewed discussions of the results

floral changes across the triassic jurassic boundary linked to flood basalt volcanism one of the five largest mass extinctions of the past 600 million years occurred at the boundary of the triassic and jurassic periods 201 6 million years ago the loss of marine biodiversity at the time has been linked to extreme greenhouse warming triggered by the release of carbon dioxide from flood basalt volcanism in the central atlantic ocean in contrast the biotic turnover in terrestrial ecosystems is not well understood and cannot be readily reconciled with the effects of massive volcanism here we present pollen spore and geochemical analyses across the triassic jurassic boundary from three drill cores from germany and sweden we show that gymnosperm forests in northwest europe were transiently replaced by fern and fern associated vegetation a pioneer assemblage commonly found in disturbed ecosystems the triassic jurassic boundary is also marked by an enrichment of polycyclic aromatic hydrocarbons which in the absence of charcoal peaks we interpret as an indication of incomplete combustion of organic matter by ascending flood basalt lava we conclude that the terrestrial vegetation shift is so severe and wide ranging that it is unlikely to have been triggered by greenhouse warming alone instead we suggest that the release of pollutants such as sulphur dioxide and toxic compounds such as the polycyclic aromatic hydrocarbons may have contributed to the extinction

nitrogen isotope record of a perturbed paleoecosystem in the aftermath of the end triassic crisis doniford section sw england 1 the triassic jurassic transition tj is characterized by successive perturbations of the carbon cycle during a time of biotic disruption as recorded by the carbon isotopic composition of organic matter 13corg the nitrogen isotopic composition of sedimentary organic matter 15norg constitutes a key parameter to explore the functioning of the ecosystem during carbon cycle perturbations and biological crises because it provide information on seawater redox conditions and or nutrient cycling here we report the first continuous 15norg record across the tj transition at the doniford bay section bristol channel basin uk combined with 13corg kerogen typology and carbon 13cmin and oxygen 18omin isotopic composition of bulk carbonates the end triassic is characterized by a major negative excursion both in 13corg and 13cmin very low toc total organic carbon wt and high 15norg values associated with a sea level lowstand a second 13corg negative excursion occurs during the lower hettangian this interval is characterized by phases of carbonate production increase alternated with phases of exceptional accumulations of type i organic matter up to 12 associated with lower 15norg and 13corg this alternation likely reflects a succession of nutrient input increase to the basin leading to enhanced productivity and eutrophication which promoted a primary production driven by organic walled prokaryotic organisms the following om export increase generates anaerobic conditions within the basin these events occur between periods of relatively good seawater column ventilation and nutrient recycling boosting the carbonate producer recovery ecosystems remain perturbed in the bristol channel basin during the aftermath of the end triassic crisis

new chronology for the late paleocene thermal maximum and its environmental implications the late paleocene thermal maximum lptm is associated with a brief but intense interval of global warming and a massive perturbation of the global carbon cycle we have developed a new orbital chronology for ocean drilling program odp site 690 weddell sea southern ocean by using spectral analysis of high resolution geochemical records the lptm interval spans 11 precessional cycles yielding a duration of 210 to 220 k y the 13 c anomaly associated with the lptm has a magnitude of about 2 5 to 3 we show that about 2 of the excursion occurs within two steps that each were less than 1000 yr in duration the remainder developed through a series of steps over 52 k y the timing of these steps is consistent with a series of nearly catastrophic releases of methane from gas hydrates punctuated by intervals of relative equilibria between hydrate dissociation and carbon burial further we are able to correlate the records between odp sites 690 and 1051 western north atlantic on the scale of 21 k y cycles which demonstrates that the details of the 13 c excursion are recognizable between distant sites comparison of cycle records at sites 690 and 1051 suggests that sediment representing the interval 30 k y just prior to and at the onset of the lptm are missing in the latter location this unconformity probably resulted from slope failure accompanying methane hydrate dissociation within 10 k y of the start of the lptm

the nonmarine triassic jurassic boundary in the newark supergroup of eastern north america abstract for the last three decades the position of the triassic jurassic boundary tjb in nonmarine strata has largely been based on its palynostratigraphic placement just below the oldest basalts of the central atlantic magmatic province camp in the newark supergroup of eastern north america this boundary however is demonstrably older than the tjb as it is defined in marine strata thus the palynostratigraphic change used to place this tjb in the newark most resembles a late norian change in the european section and does not correspond to any palynological event at the marine defined tjb conchostracan biostratigraphy suggests that the tjb is in the newark extrusive zone above the oldest camp basalt and vertebrate biostratigraphy is consistent with this placement of the tjb radioisotopic ages indicate that the tjb defined in marine strata is no older than 200 ma but the oldest camp basalts of the newark supergroup consistently yield ages averaging about 201 ma magnetostratigraphic correlation of the newark section to the tjb section at st audrie s bay in england also indicates that the onset of camp volcanism in the newark supergroup is older than the marine tjb correlations based on carbon and osmium isotopes are also consistent with this correlation thus all data indicate that the tjb in the newark supergroup is above the lowest camp basalt in the newark extrusive zone correct placement of the tjb in the newark supergroup allows key nonmarine and marine events to be sequenced across the tjb indicating the following succession of events crurotarsan thecodont extinction the palynofloral turnover in the newark the first camp eruptions the extinctions of rhaetian ammonites and conodonts and the first appearance of jurassic psiloceratid ammonites

phanerozoic large igneous provinces lips heatt haline euxinic acidic thermal transgression episodes and mass extinctions abstract the phanerozoic consists of three mutually exclusive climate states icehouse greenhouse and hothouse the greenhouse is the default state representing 70 of the phanerozoic it is characterized by a weak thermal mode pole driven deep water formation with little or no continental sea ice and weakly oxic cool water sinking near the poles nitrogen limitation characterizes greenhouse oceans in which ammonium may be the dominant bioavailable form of nitrogen the steady state greenhouse default must be forced to produce either of the other two states continent continent collision produces the intense chemical weathering that draws down atmospheric co2 and results in the icehouse state that comprises 20 25 of the phanerozoic icehouses have ice caps in contact with the ocean that produce icebergs and foster sea ice formation sea ice formation fills the ocean with highly oxic phosphorus limited icewater except for a thin layer of warm surface water in the tropics of the 23 most conspicuous mass extinctions of the phanerozoic including the late ediacaran 4 are associated with ice volume related regressions and 3 are problematic we suggest that the other 16 mass extinctions occurred when greenhouse climate was forced to hothouse climate large igneous provinces lips can trigger the heatt haline euxinic acidic thermal transgression mechanism which can force greenhouse climate to a hothouse climate state the rapid voluminous co2 emissions of lips cause a series of events that result in very slow but pronounced haline mode circulation mid latitude driven deep water formation that produces warm saline bottom water at very dry hot subtropical and middle latitudes this water upwells at the poles causing warm and moist equable climate hothouse development promotes deep sea anoxia that is generated in concert with co2 buildup and warming the spread of anoxia favors reduced nitrogen over nitrate and limited iron dust curtails nitrogen fixation this leads to dominance of primary productivity by primitive green algae and or cyanobacteria progression to euxinia that reaches the photic zone severely curtails primary productivity via poisoning even as availability of usable nitrogen plummets the result is eukaryotic mass extinction we suggest that the 16 phanerozoic mass extinctions referred to above resulted at least in part from the heatt process evidence for this relationship at 11 of the most severe extinctions is convincing data sets for the other 5 are strongly suggestive of heatt related mass extinction but do not yet have enough documentation to reliably characterize them as heatt episodes

a decametric scale investigation of the gravitational constant summary gravity measurements were made simultaneously at two locations at the top reservoir of the ffestiniog pumped storage power station in n wales one above and one below the water as the water level changed measurements were made for eight weeks using digital recording of lacoste romberg earth tide gravimeters fitted with electrostatic feedback the reservoir geometry was well defined the water level measured accurately and the water density known so we were observing the gravitational effect of accurately known slices of water having three effective weighted distances from the gravimeters in the range 26 94 m the gravity signal due to the moon and sun the earth tide was removed by two methods by subtracting a theoretical value and by differencing the records of the two gravimeters assuming the newtonian inverse square law the results give values for gravitational constant g differing from the laboratory value by only about 0 1 f 0 2 per cent so there is no evidence for any fifth force deviation from newtonian gravity the main contributions to the uncertainty come from the uncertainties in the gravimeter calibrations and positions and in the reservoir geometry

does large igneous province volcanism always perturb the mercury cycle comparing the records of oceanic anoxic event 2 and the end cretaceous to other mesozoic events mercury hg is increasingly being used as a sedimentary tracer of large igneous province lip volcanism and supports hypotheses of a coincidence between the formation of several lips and episodes of mass extinction and major environmental perturbation however numerous important questions remain to be answered before hg can be claimed as an unequivocal fingerprint of lip volcanism as well as an understanding of why some sedimentary records document clear hg enrichment signals whilst others do not of particular importance is evaluating the impact of different volcanic styles on the global mercury cycle as well as the role played by depositional processes in recording global hg cycle perturbations here new mercury records of cretaceous oceanic anoxic event 2 oae 2 94 ma and the latest cretaceous 67 66 0 ma are presented oae 2 is associated with the emplacement of multiple predominantly submarine lips the latest cretaceous with subaerial volcanism of the deccan traps both of these connections are strongly supported by previously published trends towards unradiogenic osmium os isotope values in globally distributed sedimentary records hg data from both events show considerable variation between different locations attributed to the effectiveness of different sediment types in registering the hg signal with lithologically homogeneous records documenting more clear hg enrichments than sections with major changes in lithology such as limestones to claystones or organic rich shales crucially there is no geographically consistent signal of sedimentary hg enrichment in stratigraphic records of either oae 2 or the latest cretaceous that matches os isotope evidence for lip emplacement indicating that volcanism did not cause a global hg perturbation throughout the entire eruptive history of the lips formed at those times it is suggested that the discrepancy between os isotope and hg trends in records of oae 2 is caused by the limited dispersal range of hg emitted from submarine volcanoes compared to the global scale distribution of os a similar lack of correlation between these two proxies in uppermost cretaceous strata indicates that although subaerial volcanism can perturb the global hg cycle not all subaerial eruptions will do so these results highlight the variable impact of different volcanogenic processes on the efficiency of hg dispersal across the globe factors that could influence the impact of lip eruptions on the global mercury cycle include submarine versus subaerial volcanism volcanic intensity or explosivity and the potential contribution of thermogenic mercury from reactions between ascending magma and surrounding organic rich sediments

laboratory calibration of lacoste romberg type gravimeters by using a heavy cylindrical ring summary a calibration device developed for lacoste romberg lcr gravimeters in the geodynamical observatory of the eotvos lorand geophysical institute of hungary is described the equipment generates gravity variations of about 112 gal with the use of a suspended cylindrical ring of mass 3200 kg a ring with an inner diameter slightly bigger than the width of the instrument to be calibrated is raised and lowered over the gravimeter installed on a column the advantages of this solution with respect to others are the gravimeter remains stationary during the calibration process the gravity variations generated by the ring have smooth extrema they are larger than variations caused by bodies with other geometry the experiment is symmetrical with respect to the gravimeter and no ground loading by the ring occurs the device allows a calibration accuracy for lcr instruments of the order of 0 1 per cent to be attained this is a considerable improvement for absolute calibrations in a very narrow range especially in the context of tidal measurements to reach such an error level the instrumental drift tidal variation the microseisms and air pressure must be removed most accurately from the measured data the position of the ring in space and time is measured with an accuracy of 0 1 mm and 1 s the tilt of the frame and of the instruments must be recorded and excluded from the experimental results calibration results obtained with the device are compared to the calibration values obtained at broad and medium ranges along two calibration lines with different ranges

co2 and the end triassic mass extinction the end of the triassic period was marked by one of the largest and most enigmatic mass extinction events in earth s history1 and with few reliable marine geochemical records terrestrial sediments offer an important means of deciphering environmental changes at this time tanner et al 2 describe an isotopic study of mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide pco2 across the triassic jurassic boundary was relatively constant within 250 p p m v but this is inconsistent with high resolution evidence from the stomatal characters of fossil leaves3 here i show that the temporal resolution of the fossil soil samples may have been inadequate for detecting a transient rise in pco2 i also show that the fossil soil data are consistent with a large increase in pco2 across the triassic jurassic boundary when variations in the stable carbon isotope denoted as 13c in terrestrial plant leaves are taken into account these factors suggest that the linkage between pco2 global warming and the end triassic mass extinction remains intact

stability of atmospheric co2 levels across the triassic jurassic boundary the triassic jurassic boundary 208 million years ago is associated with widespread extinctions in both the marine and terrestrial biota the cause of these extinctions has been widely attributed to the eruption of flood basalts of the central atlantic magmatic province this volcanic event is thought to have released significant amounts of co2 into the atmosphere which could have led to catastrophic greenhouse warming but the evidence for co2 induced extinction remains equivocal here we present the carbon isotope compositions of pedogenic calcite from palaeosol formations spanning a 20 myr period across the triassic jurassic boundary using a standard diffusion model we interpret these isotopic data to represent a rise in atmospheric co2 concentrations of about 250 p p m across the boundary as compared with previous estimates of a 2 000 4 000 p p m increase the relative stability of atmospheric co2 across this boundary suggests that environmental degradation and extinctions during the early jurassic were not caused by volcanic outgassing of co2 other volcanic effects such as the release of atmospheric aerosols or tectonically driven sea level change may have been responsible for this event

palaeoenvironmental interpretation of a triassic jurassic boundary section from western austria based on palaeoecological and geochemical data a section spanning the triassic jurassic boundary is described from near the village of loruns in the vorarlberg region of western austria at loruns the uppermost triassic is characterised by bedded carbonates of the kossen formation supporting a stenotopic fauna indicative of a shallow sub tidal environment of normal marine salinity the triassic jurassic boundary may be represented as a sequence boundary developed on top of a 1 1 m thick red mudstone of the lower schattwald shale which is interpreted to have been deposited in a marginal marine environment possibly a mud flat above the boundary beds the upper schattwald shale is characterised by thin bedded marl and dark limestone beds with an earliest hettangian macrofauna dominated by epifaunal filter feeding bivalves including ostreids mytilids and oxytomids which suggest a shallow subtidal salinity controlled environment typical of an interplatform lagoon carbonate production rejuvenated in the later early hettangian with development of the loruns oolite a shallow subtidal oolitic and oncolitic unit bearing echinoderms indicative of normal marine conditions low thu ratios from the remainder of the section are a result of reduced thorium in carbonate rich sediments and not from authigenic uranium in anoxic sediments in the boundary beds evidence for marine anoxia or dysoxia is absent where thu values determined by gamma ray spectrometry are above 5 the negative excursion in 13c and positive excursion in 18o in the boundary beds may be due to secondary geochemical effects due to organic diagenesis or the precipitation of caliche during paleosol development alternatively the excursions may reflect a primary geochemical signal recording short term decline in primary productivity comparison in 18o and 13c values between the kossen formation and lorfus oolite indicate no significant long term geochemical changes are evident in the section and suggest that any environmental perturbations were restricted to the boundary beds and possible sequence boundary

rising atmospheric co2 as a possible trigger for the end triassic mass extinction the end triassic mass extinction one of the five largest extinctions in earth history was a severe catastrophe in which 80 of all species were wiped out the cause of the extinction is controversial but any mechanism must account for mass extinction in both marine and terrestrial environments one smoking gun the eruption of the central atlantic magmatic province camp has prompted the hypothesis that co2 degassing to the atmosphere may have induced an environmental catastrophe at the end triassic in this study we use a numerical coupled ocean atmosphere climate model of the late triassic to determine environmental stresses associated with a rapid increase in atmospheric co2 a series of sensitivity experiments with co2 levels that bracket estimated end triassic pco2 estimates 2 8 pre industrial levels predict extreme environmental conditions on land increasing co2 from 2 to 8 pre industrial levels causes an increase in the number and severity of hot days and days without precipitation an exponential increase in continental area experiencing hot days and enhanced seasonal fluctuation in the ocean wind driven circulation decreases and meridional overturning diminishes by a factor of 4 leading to enhanced ocean stratification a three box model of the deep ocean predicts a decline of 85 mol l in deep ocean oxygen concentration with a 4 fold increase in atmospheric co2 consequently while terrestrial organisms would have been subject to severe heat and water stress marine fauna would have experienced oxygen deprivation additional sensitivity experiments indicate that variations in milankovitch orbital parameters may further contribute to faunal stress by intensifying continental heating and seasonal fluctuations in sum model results predict that rising atmospheric co2 would have significantly impacted both marine and continental environments providing a link between turnover on land and ocean during the late triassic

massive dissociation of gas hydrate during a jurassic oceanic anoxic event in the jurassic period the early toarcian oceanic anoxic event about 183 million years ago is associated with exceptionally high rates of organic carbon burial high palaeotemperatures and significant mass extinction heavy carbon isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon which is isotopically light in contrast examples of light carbon isotope values from marine organic matter of early toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12c versus 13c refs 1 2 5 6 here however we report carbon isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic biospheric and atmospheric carbon reservoirs and that this occurred despite the enhanced burial of organic carbon we propose that as has been suggested for the late palaeocene thermal maximum some 55 million years ago the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental margin sediments

geology and isotope geochemistry of the wainaulo cu au porphyry deposit namosi district fiji the late miocene calc alkalic wainaulo cu au porphyry deposit of the namosi district fiji hosts distinct styles of alteration and mineralization that overlapped to produce a substantial porphyry cu au resource the early stages produced medium grade cu low grade au and concentric calc potassic to propylitic alteration that is zoned around the early stage diorite intrusions discrete zones of high grade cu and au and calc sodic alteration were then superimposed during the intrusion of the main stage quartz diorites and the formation of quartz sulfide and epidote sulfide veins as the magmatic hydrothermal system waned lower cu and au grades with a weaker intensity of calc sodic alteration and lower density of veins were produced coincident with emplacement of subsequent quartz diorite intrusions late stage anhydrite pyrite veins and chlorite illite alteration overprinted the quartz diorite intrusive complex the final hydrothermal event consisted of argillic alteration that was concentrated in and around steeply dipping ene trending shears these structures appear to have controlled the emplacement of the quartz diorite complex and distribution of high grade cu au mineralization suggesting they were active during the pre and synmineralization stages stable and radiogenic isotopic data provide evidence for direct seawater contributions to the magmatichydrothermal system measured 34ssulfide 5 0 to 3 8 and 34ssulfate 9 0 16 8 values are consistent with a predominantly magmatic source whereas an elevated bulk sulfur composition 6 7 suggests mixing with an isotopically heavy fluid e g seawater estimates of dfluid derived from epidote 9 1 to 11 3 and 18ofluid from epidote and anhydrite 0 2 to 4 7 approach that of vienna standard mean ocean water and the initial sr isotope ratios of epidote 0 70364 0 70378 suggest a component of seawater sr ranging from 3 2 to 5 8 these results are consistent with the inferred submarine paleogeographic setting and may explain the abundance of albite and epidote rich alteration assemblages at wainaulo

porphyry and epithermal deposits and 40ar 39ar geochronology of the baguio district philippines the baguio district is located in the central cordillera of northern luzon philippines it contains numerous mineralized porphyry copper gold epithermal gold silver and skarn gold lead zinc deposits the district is floored by cretaceous eocene metavolcanic and metasedimentary rocks which are overlain by marine to terrestrial sedimentary and volcanic rocks of early miocene to pliocene ages tertiary arc magmatism related to east directed subduction of the south china sea plate along the manila trench beneath northern luzon produced a major batholith the central cordillera intrusive complex which defines the eastern boundary of the baguio district the intrusive complex was emplaced in the early miocene based on 40ar 39ar age determinations for the lucbuban gabbro 22 6 0 5 ma and virac granodiorite 20 23 0 38 and 20 2 0 7 ma recent exploration has led to the discovery of several new porphyry copper gold and skarn prospects in the western baguio district mineralization was preceded by the intrusion of a suite of hornblende megacrystic andesite dikes in the central part of the district from 4 55 0 15 to 3 45 0 19 ma porphyry copper gold and skarn deposits at black mountain and mexico on the western side of the district formed between 3 09 0 15 and 2 81 0 24 ma the santo tomas ii cu au pd porphyry deposit was emplaced into the central southern part of the district at about 1 5 ma based on secondary biotite 40ar 39ar ages of 1 48 0 05 ma and 1 47 0 05 ma on the eastern side of the district porphyry style mineralization at the hartwell and ampucao porphyry cu au prospects returned 40ar 39ar ages of 1 09 0 10 and 0 51 0 26 ma respectively quartz carbonate base metal sulfide style epithermal gold silver veins are well developed on the eastern side of the baguio district and crosscut porphyry style mineralization at the acupan baguio gold and nugget hill deposits epithermal veining is inferred to have occurred in the past million years based on a reported k ar age determination of 0 65 0 07 ma from the acupan gold mine a large advanced argillic alteration zone the baguio lithocap crops out in the northwest part of the district and formed between 1 4 and 0 9 ma based on previous k ar dating pliocene pleistocene mineralization in the baguio district was triggered by the east directed subduction of the scarborough ridge ridge subduction caused the subduction angle along the manila trench beneath northern luzon to decrease which facilitated crustal thickening and exhumation ridge subduction also promoted the development of northwest trending faults in the upper plate that interacted with major arc parallel north and arc normal northeast trending fault sets associated with the philippine fault system fertile magmas were emplaced into transtensional strike slip relay basins resulting in the accumulation of more than 35 moz of gold and several million tonnes of copper over approximately 3 m y

a u pb and 40ar 39ar time scale for the jurassic published time scales provide discrepant age estimates for jurassic stage boundaries and carry large uncer tainties the u pb or 40 ar 39 ar dating of volcaniclastic rocks with precisely known stratigraphic age is the preferred method to improve the calibration a radiometric age database consisting of fifty u pb and 40 ar 39 ar ages was com piled to construct a revised jurassic time scale accepted ages have a precision of 5 ma 2 or better and are con fined to no more than two adjacent stages the majority of these calibration points result from integrated bio and geochronologic dating in the western north american cordillera and have not been previously used in time scales di rect dates are available only for the triassic jurassic boundary and the initial boundary of the crassicosta chron and the callovian stage the chronogram method was used to estimate all early and early middle jurassic zone boundaries attempted here for the first time late middle jurassic substage boundaries and late jurassic stage boundaries signif icant improvement is achieved for the pliensbachian and toarcian where six consecutive zone boundaries are deter mined the derived zonal durations are disparate varying between 0 4 and 1 6 ma the latest jurassic isotopic database remains too sparse therefore chronogram estimates are improved using interpolation based on magnetochronology the initial boundaries of jurassic stages are proposed as follows berriasian jurassic cretaceous 1418 18

carbon addition and removal during the late palaeocene thermal maximum basic theory with a preliminary treatment of the isotope record at odp site 1051 blake nose the late palaeocene thermal maximum lptm was a brief interval at c 55 ma characterized by a 2 5 to 3 per thousand shift in the 13c of global carbon reservoirs the geochemical perturbation probably represents a massive input of 12c rich carbon to the exogenic carbon cycle largely unresolved issues concerning this carbon injection during the lptm are the rates of carbon input and removal simple expressions are developed here to describe a 13c excursion in the exogenic carbon cycle after carbon input a change in global 13c d ex dt can be explained to a first approximation by a set of parameters the initial mass and isotopic composition of the global carbon cycle mex o ex o and the fluxes and isotopic compositions of external carbon inputs outputs and injected carbon fin in fout out fadd add in general for a given exogenic carbon cycle a large fadd or low add results in a larger 13c excursion likewise for a given negative 13c excursion a large mex or low ex requires a greater input of 12c differences in fin in fout and out cause changes in the response of ex over time for a negative 13c excursion of given magnitude a greater fin requires a greater input of 12c and lessens the time for ex to return to initial conditions a decrease in out caused by an increase in the relative output of organic matter and carbonate has a similar effect variable dmadd dt produces transients in ex that are related to the source function but modified by carbon removal in theory a well dated and representative global 13c excursion could be used to derive the carbon inputs and ouputs ocean drilling program odp site 1051 has an expanded early palaeogene section and recent work at this location has provided a well dated 13c record across the lptm this 13c record contains transient variations of apparently global nature these observed transients are best explained by a pulsed injection of ch4 into an exogenic carbon cycle with a greater carbon throughput or enhanced burial of organic matter after carbon addition

physicochemical processes in the magma chamber under the black mountain porphyry cu au deposit philippines insights from mineral chemistry and implications for mineralization the black mountain porphyry cu au deposit in the baguio district northern luzon philippines is associated with late miocene to pliocene intrusive rocks that retain primary crystallization signatures providing an excellent natural laboratory to study the details of magma chamber processes each igneous phase contains disequilibrium textures including resorptive textures in plagioclase and distinct core rim textures in amphibole high crystallization temperatures and pressures in felsic 880 c and 2 8 kbar and mafic 1 030 c and 7 7 kbar rocks recorded by amphibole phenocrysts reflect crystallization in the magma chamber amphibole in felsic rocks aged 6 39 0 49 to 2 83 0 23 ma have similar crystallization temperatures and pressures suggesting a long lived and hot felsic magma chamber under the black mountain deposit four independent oxybarometers including amphibole coexisting magnetite ilmenite magmatic anhydrite and zircon consistently show a high oxidation state of nno 1 for the felsic magma and nno 0 7 for the mafic magma element profiles across phenocrystic plagioclase display repeated oscillatory variations of ca fe and sr contents with large anorthite variations and a positive correlation between cao and feo the amphibole is classified as group 1 mg hornblende to tschermakite hornblende in felsic rocks and group 2 mg hastingsite in mafic rocks the group 1 amphiboles show a variety of major and trace element variations from core to rim in disequilibrated grains and transitional compositions to group 2 mg hastingsite both mineral textures and chemistry recorded by phenocrysts of plagioclase and amphibole indicate repeated mafic magma recharge in the felsic magma chamber the common occurrence of rounded or elongated sulfide inclusions in the megacrystic amphibole from the mafic rocks 2 81 0 15 ma suggests a greater enrichment of cu in mafic rocks relative to the ore forming porphyries 2 91 2 83 ma this is also consistent with higher cu contents 3 4 0 9 ppm in the megacrystic amphibole from the mafic rocks relative to amphibole in felsic rocks 1 0 0 2 ppm and may indicate up to 3 4 times higher cu in the mafic magma relative to felsic magma therefore large scale mafic magma recharge particularly at 2 8 ma likely introduced ore forming metals to the long lived felsic magma chamber further contributing to the fertility of the felsic rocks and ultimately to cu au mineralization at the black mountain deposit

carbon isotope anomaly and other geochemical changes at the triassic jurassic boundary from a marine section in hungary most mass extinctions are linked with carbon isotope excursions implying that biotic crises are coupled with changes in the global carbon cycle the isotopic evolution during the end triassic extinction is far less documented than that for the other major phanerozoic extinctions here we report a sharp and short lived 23 5 excursion in carbon isotope values for carbonate d 13 ccarb corresponding to a 22 excursion in the isotopic composition of marine organic matter d 13 corg and other geochemical

events around the triassic jurassic boundary in northern and eastern spain a review abstract more than 20 successions containing the triassic jurassic t j boundary were studied in five of the major geological units of spain the data are from outcrop cored boreholes and interpreted well logs a consistent 3 4 13 c org isotope excursion starting in the rhaetian and continuing in the hettangian was recorded in asturias climate changes in the t j transition show a warming episode in the early hettangian other climate changes are indicated by an increase in hygrophytic miospores above the t j boundary this reflects a more humid episode at the beginning of the hettangian the messejana dyke in southeastern iberia is part of the central atlantic magmatic province camp co 2 outgassing related to extensive magmatic activity in the camp is thought to be one of the possible factors responsible for the end triassic mass extinction no major sea level changes or unconformities were recorded at the t j boundary only in the asturias area was there a well defined shallow carbonate platform during the t j transition the other areas of eastern and northern spain were occupied by coastal playas and sabkhas that developed in arid climatic conditions the biotic crisis around the t j boundary is reflected in the palynomorph record in asturias seven species do not persist beyond the late rhaetian and only six appeared in the triassic jurassic transition however 22 taxa appeared in the early hettangian

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

geology of the boyongan and bayugo porphyry cu au deposits an emerging porphyry district in northeast mindanao philippines the boyongan and bayugo porphyry cu au mineral deposits discovered under postmineralization cover during the previous decade are part of an emerging belt of intrusion centered au rich cu mineral deposits and prospects in the surigao district of northeast mindanao philippines since their formation in the early pleistocene exhumation and weathering of these deposits have led to the development of a 600 m thick oxidation profile at boyongan and a modest 30 70 m oxidation profile at bayugo debris flows volcanic material and fluviolacustrine sediments accumulating in the actively extending mainit graben subsequently covered the weathered deposits preserving their supergene profiles the mineral deposits formed in association with a composite diorite complex containing at least 12 discrete intrusive stages three premineralization diorite porphyry stocks and a silt sand matrix breccia complex represent early stages of magmatism and brecciation significant cu and au introduction followed these events and occurred in association with small early mineralization diorite porphyry stocks at boyongan and bayugo within the diorite complex the two mineral deposits are spatially distinct separated by approximately 1 km of premineralization diorites inter and late mineralization intrusions were emplaced as the magmatic hydrothermal system waned a characteristic progression of vein and k silicate alteration styles affected each of the synmineralization intrusions rare comb quartz unidirectional solidification textures stage 0 mark the transition from magmatic to hydrothermal conditions quartz poor wispy magnetite biotite k feldspar veinlets characterize stage 1 stage 2 veins consist of quartz with selvage and or disseminated magnetite or biotite and k feldspar halos stage 3 quartz veins have k feldspar halos but generally lack magnetite and biotite stage 4 veins consist of massive bornite chalcopyrite and chalcopyrite pyrite with k feldspar halos stage 3 quartz veins and stage 4 sulfide veins host cu au mineralization of the greatest volumetric significance reflecting the general paucity of sulfide in the earlier vein stages despite the simplicity of this sequence detailed paragenetic reconstructions reveal that this characteristic progression of veining and k silicate alteration was repeated with the emplacement of each synmineralization intrusive event revealing multiple magmatic hydrothermal cycles of alteration and mineralization at boyongan and bayugo intense and pervasive illite alteration in association with pyrite chalcopyrite and tetrahedrite tennantite developed in narrow structures crosscutting quartz k feldspar veins debris flows in the burial sequence above and adjacent to the boyongan bayugo complex also contain abundant clasts with intense pervasive illite and alunite pyrophyllite dickite kaolinite alteration assemblages that have overprinted k silicate style quartz veins in both mineral deposits cu and au are associated with intense quartz vein stockworks composed primarily of k silicate stage 3 veins despite this association not all of these quartz vein stockworks contain cu and au to the same tenor quartz vein stockworks in the eastern high grade of boyongan have been intersected over a vertical interval of 800 m having affected much of the early mineralization stock however hypogene cu grades exceed 0 5 by weight only in the upper 300 m of the stockwork in the cupola of the early mineralization stock superior grade development in high grade zones at boyongan locally exceeding 2 cu and 3 g t au developed where fertile vein stages from two or more magmatic hydrothermal cycles affected the same wall rock the documented paragenetic relationships demonstrate multiple discrete cycles of k silicate stage veining and alteration associated with each synmineralization intrusive event all such events predate formation of feldspar destructive illite smectite chlorite illite pyrite and quartz alunite clay assemblages existing geochronological constraints on the timing of magmatism and hydrothermal activity demonstrate that these repeated cycles supporting superior grade development transpired extremely rapidly in a period of less than 200 000 years 2 3 2 1 ma geologic and geochronological constraints on the life cycle of boyongan and bayugo describe an extremely dynamic history of emplacement exhumation weathering and burial over a period of 2 3 m y the study illustrates the spectrum of metallogenic processes operative over a geologically brief period and highlights some of the key elements responsible for formation of superior grades and for deposit preservation in an extensional setting

additive effects of acidification and mineralogy on calcium isotopes in triassic jurassic boundary limestones the end triassic mass extinction coincided with a negative 13c excursion consistent with release of 13c depleted co2 from the central atlantic magmatic province however the amount of carbon released and its effects on ocean chemistry are poorly constrained the coupled nature of the carbon and calcium cycles allows calcium isotopes to be used for constraining carbon cycle dynamics and vice versa we present a high resolution calcium isotope 44 40ca record from 100 m of marine limestone spanning the triassic jurassic boundary in two stratigraphic sections from northern italy immediately above the extinction horizon and the associated negative excursion in 13c 44 40ca decreases by 0 8 in 20 m of section and then recovers to preexcursion values coupled numerical models of the geological carbon and calcium cycles demonstrate that this 44 40ca excursion is too large to be explained by changes to seawater 44 40ca alone regardless of co2 injection volume and duration less than 20 of the 44 40ca excursion can be attributed to acidification the remaining 80 likely reflects a higher proportion of aragonite in the original sediment based largely on high concentrations of sr in the samples our study demonstrates that coupled models of the carbon and calcium cycles have the potential to help distinguish contributions of primary seawater isotopic changes from local or diagenetic effects on the 44 40ca of carbonate sediments differentiating between these effects is critical for constraining the impact of ocean acidification during the end triassic mass extinction as well as for interpreting other environmental events in the geologic past

a unique geochemical record at the permian triassic boundary a 330 metre core drilled through the marine permian triassic boundary in the carnic alps of austria allows closely correlated studies of geochemistry petrography and palaeontology across the boundary the isotope shifts and metal concentrations are extended multiple and complex and do not resemble those seen at the cretaceous tertiary boundary both the carbon isotope shifts and the chemical events including an indium anomaly may have causes related to a major regression of the sea

timing the end triassic mass extinction first on land then in the sea the end triassic marks one of the five biggest mass extinctions but current geologic time scales are inadequate for understanding its dynamics a tuff layer in marine sedimentary rocks encompassing the triassic jurassic transition yielded a u pb zircon age of 199 6 0 3 ma the dated level is immediately below a prominent change in radiolarian faunas and the last occurrence of conodonts additional recently obtained u pb ages integrated with ammonoid biochronology confirm that the triassic period ended ca 200 ma several million years later than suggested by previous time scales published dating of continental sections suggests that the extinction peak of terrestrial plants and vertebrates occurred before 200 6 ma the end triassic biotic crisis on land therefore appears to have preceded that in the sea by at least several hundred thousand years

isotopic imprint of climate and hydrogeochemistry on terrestrial strata of the triassic jurassic hartford and fundy rift basins abstract late triassic to early jurassic terrestrial sequences in the hartford and fundy rift basins have distinctive carbon and oxygen isotopic compositions of calcite and dolomite the isotopic data mostly reflect paleoclimatic fluctuations and hydrogeochemistry of the lacustrine playa and fluvial environments dolomites from laminae in three sequences of playa red mudstones and lacustrine gray to black mudstones in the hartford basin have variable isotopic compositions 13c 5 8 to 1 8 pdb 18o 7 2 to 0 7 pdb within any single symmetrical cycle of playa red mudstone lacustrine gray black gray mudstone playa red mudstone there is a systematic change to relatively enriched 13c compositions in dolomite in the grayish black and black mudstones in the center of the cycle these carbon isotopic data suggest that the lacustrine sequences formed as the lakes changed from well mixed with anoxic bottom waters to stratified with anoxic bottom waters where 13c depleted carbon was concentrated in organic matter that was then buried calcites from lacustrine micritic and biomicritic limestones of the scots bay formation of the fundy basin have stable isotopic compositions 13c 4 6 to 2 2 pdb 18o 6 1 to 3 0 pdb that become more enriched in 18o and 13c upward in shallowing depositional sequences these isotopic data reflect initial calcite precipitation when a high inflow of fresh water produced high lake levels followed by progressively lower inflow resulting in lower lake stands and higher salinity due to continuing evaporative loss of surface wat r the lake waters were well oxygenated at all times in the hartford basin caliche calcites in fluvial mudstones and sandstones have isotopic compositions 13c 7 3 to 3 8 pdb 18o 8 0 to 5 6 pdb that reflect paleosol processes during climatic conditions that varied from warm and dry in late triassic time to relatively cooler and probably wetter in the early jurassic isotopic compositions of caliche calcites in redbeds in the fundy basin indicate a parallel climate change from late triassic to early jurassic time but also that the climate was relatively hotter and probably drier over the entir interval as compared to the hartford basin

deev jahi model of the permian triassic boundary mass extinction a case for gas hydrates as the main cause of biological crisis on earth the smoking gun revealing the secrets of the end permian mass mortality is a unique 1 2 m thick layer consisting of 5 20 cm long crystals of calcite that occurs precisely at the permian triassic boundary ptb in iran armenia turkey and china this layer is interpreted as synsedimentary abiotic seafloor cement indicative of precipitation from a highly carbonate supersaturated seawater its 13 c composition 13 c 0 pdb is 4 to 5 pdb lower than the typical upper permian values 4 to 5 pdb suggesting the involvement of massive amounts of gas hydrate ch 4 13 c 60 pdb the temporal coincidence of the cement layer with the ptb suggests that the process that promoted seafloor cementation was also responsible for the biological crisis a cementation model is developed based on accumulation dissociation cycle of gas hydrates which also explains the mass extinction at the ptb the upper permian accumulation period of gas hydrates ended abruptly adjacent to the ptb and the dissociation event began releasing 3 2 to 4 7 10 18 g ch 4 into the ocean oxidation of ch 4 in the water column created a seawater that was charged with co 2 an oceanic acid bath and had lower than normal o 2 content but not anoxic this oceanic acid bath first dissolved suspended fine grained carbonate particles and small calcareous organisms followed by extensive dissolution of platform carbonates raising ca 2 and hco 3 concentrations of seawater when the release of ch 4 declined the acid bath ocean became a soda ocean precipitating massive amount of seafloor cements observed globally at the ptb the study suggests that prior to cement precipitation the ptb ocean was charged with co 2 warm had low oxygen high ca 2 and high hco 3 concentrations these conditions collectively created stressful conditions causing the marine mass mortality the leakage of ch 4 to the atmosphere produced a super hot climate resulting in the biological devastation on land the proposed kill mechanism is developed on the basis of the physical clue the cement layer left behind by the killing process the change in ocean chemistry the accumulation dissociation cycles of gas hydrates also explain the 13 c pattern of marine carbonates and the periodicity of mass extinction events during the phanerozoic accumulation periods were long 5 to 20 my providing favorable conditions for ecosystem development pardeess phase the dissociation events were short and catastrophic 10 to 500 ky causing low oxygenation super hot climate and biological devastation doozakh phase it appears that most mass extinctions of the phanerozoic have been related to the internal working of the earth system during the phanerozoic methane has played the role of the deev jahi a female demon in persian mythology whose task is to attack the earth every so often to kill life on land and in sea

on the nature of methane gas hydrate dissociation during the toarcian and aptian oceanic anoxic events the magnitude and timing of a major rapid negative carbon isotope excursion recorded in marine and terrestrial matter through the early toarcian early jurassic and early aptian early cretaceous oceanic anoxic events oaes have been proposed to be the result of large methane gas hydrate dissociation events here we develop and evaluate a global carbon isotope mass balance approach for determining the responses of each component of the exogenic carbon cycle terrestrial biosphere atmosphere and ocean the approach includes a dynamic response of the terrestrial carbon cycle to methane related co2 increases and climatic warming our analyses support the idea that both the early toarcian and early aptian isotopic curves were indicative of large episodic methane releases 5000 and 3000 gt respectively promoting warm greenhouse conditions in the mesozoic these events are calculated to have increased the atmospheric co2 concentration by 900 and 600 ppmv respectively and land surface temperatures by 2 5 to 3 0 c however we show that much of the methane released from oceanic sediments is rapidly sequestered by terrestrial and marine components in the global carbon cycle and this effect strongly attenuated the potential for ancient methane gas hydrate dissociation events to act as major amplifiers in global warming an increase in oceanic carbon sequestration is consistent with the deposition of globally distributed black shales during these oaes our analyses point to the urgent need for high resolution marine and terrestrial carbon isotope records to better characterize the nature of the toarcian and aptian events and improve our interpretation of their consequences for the global carbon cycle

carbon isotope evidence for cam photosynthesis in the mesozoic crassulacean acid metabolism cam photosynthesis a flexible adaptation to water stress has not been shown to occur before the pleistocene despite suggestions that cam first evolved in the mesozoic or earlier here we report on multiple 7 positive organic carbon isotope excursions d 13 corg 20 i n late triassic and early jurassic c 200 ma sedimentary rocks from an arid terrestrial ecosystem in south africa these excursions are interpreted as evidence of the episodic domin ance of cam plants in response to heightened aridity in the heartland of gondwana and hint at climatic instability in a greenhouse world

carbon cycle dynamics following the end triassic mass extinction constraints from paired δ13ccarb and δ13corg records 1 constraining the carbon isotopic changes associated with the end triassic mass extinction is key to understanding the causes of the extinction and dynamics of recovery from it yet the pattern and timing of 13c variation surrounding the extinction remain poorly constrained here we present close to 1000 new 13c measurements from six newly sampled sections in italy we observe a sharp negative excursion in 13ccarb coincident with the disappearance of the triassic fauna and two positive excursions above it the negative 13ccarb excursion in these sections does not occur in 13corg suggesting a possible diagenetic origin in contrast the interval of elevated 13c occurs in both carbonate and organic carbon suggesting that it is likely to be a primary feature the positive excursions in the lombardy basin southern alps and mt cefalo southern apennines appear to be time correlative on the basis of their position above the disappearance of characteristically triassic biota however it is less certain that they are time correlative with positive excursions in other sections worldwide as few options exist that honor both bio and chemostratigraphy nonetheless similarity to other events that are interpreted as global as well as carbon cycle considerations suggest that the isotopic enrichment is best interpreted to reflect a shift in the isotope composition of the global surface carbon reservoir our data indicate that perturbation of the global carbon cycle was not confined to the immediate vicinity of the extinction interval but rather persisted for substantial length of geologic time afterwards

exploration applications of copper isotopes in the supergene environment a case study of the bayugo porphyry copper gold deposit southern philippines copper isotope compositions of secondary phases from the supergene profile of the bayugo porphyry copper gold deposit philippines show significant isotopic fractionation relative to hypogene sulfide phases and reveal systematic patterns of isotopic enrichment in the leached cap iron oxides and supergene copper sulfides thirty nine iron oxide copper oxide and copper sulfide minerals yielded 65 cu values between 3 4 and 6 9 per mil samples of hypogene sulfides have a narrow range of values near zero per mil 0 6 to 1 0 in contrast samples of supergene sulfides chalcocite and djurleite collected from the exotic and enriched copper zones define a trend of decreasing 65 cu from the enriched source area and proximal exotic zone 3 downgradient to the distal portions these findings are significant because within exotic copper zones the copper isotope values of supergene sulfides can provide an indication both of proximity and direction to the source area the technique could be applied in the search for unrecognized porphyry centers upgradient from headless exotic copper occurrences by exploring for the supergene copper phases with the highest 65 cu values independently copper isotope ratios of iron oxides in surface samples or fossil leached caps might be used to rank prospects and to focus drilling in areas with the greatest potential for mature enrichment profiles by mapping the distribution of isotopically enriched leached cap iron oxides the leached cap screening and targeting tool could enhance the iron oxide mapping techniques traditionally applied in leached cap interpretation and exploration

broad terrane jurassic flood basalts across northeastern north america early jurassic tholeiitic lavas that flowed across mesozoic basins of northeastern north america were comagmatic as shown by their geochemistry petrography paleomagnetism radiometric ages and stratigraphy the basin basalts are correlated with diabase dikes that intersect the basins but also extend far outside them if the dikes represent feeders to fissure vents a vast flood basalt province must have extended across the rifted terranes of eastern north america in early jurassic time the initial member of the basalt flood was the most uniform and widespread among present basin remnants of the basalts but subsequent flows may have covered some areas farther from the basins other younger jurassic flood basalts have been described along submarine sections of the continental shelf and shelf break and beneath cretaceous coastal plain sediments in the southeastern united states across the inland mesozoic rift terranes the initial fissure eruptions produced a temporary basaltic plain perhaps 1600 km long and 200 to 400 km wide or roughly 500000 km 2 rivaling other great continental flood basalt provinces

new geochemical evidence for the onset of volcanism in the central atlantic magmatic province and environmental change at the triassic jurassic boundary the late triassic early jurassic was a time of major global change however the fundamental processes driving these changes are less than clear we have determined the re and os abundances and os isotope compositions of marine mudrock samples that span the triassic jurassic boundary in the uk and have established that major isotopic and geochemical shifts in the composition of seawater took place in the latest triassic we argue that these shifts were caused by the sudden initiation of widespread igneous activity within the central atlantic magmatic province associated with rifting of the supercontinent pangea the os isotope composition of seawater responded rapidly to these events demonstrating that the seawater os isotope system has great potential in identifying the nature and precise timing of major environmental change

carbon isotope stratigraphy and palynostratigraphy of the triassic jurassic transition in the tiefengraben section northern calcareous alps austria abstract the end triassic is characterized by enhanced rates of biotic turnover in both the marine and terrestrial realms carbon isotope anomalies have been reported worldwide that may indicate coeval global disturbances in the biogeochemical cycles here we present the results of an integrated study of the palynomorph assemblages and the carbon isotope composition of organic matter in the tiefengraben section near st wolfgang austria carbon isotope values from bulk organic matter show significant fluctuations through the triassic jurassic t j boundary interval with two prominent negative 13 c org excursions an initial negative carbon isotope excursion occurs at the base of the kendlbach formation tiefengraben member pre planorbis beds although triassic ammonoids and conodonts have their highest occurrence at the top of the underlying kossen formation the palynomorph and calcareous microfossil assemblages indicate still a rhaetian age for the lower part of the tiefengraben member high abundance of prasinophytes during the interval of the initial carbon isotope excursion may represent a bloom of green algae that flourished as a result of the disturbance of the marine ecosystems increased spore abundance together with the disappearance of distinctive late triassic pollen types e g ovalipollis rhaetipollis indicate vegetation changes on land that are contemporaneous with the marine biotic crisis a second negative carbon isotope excursion occurs in the middle part of the tiefengraben member based on palynological evidence the t j boundary may be drawn at about this level by the lowest occurrence of cerebropollenites thiergartii the established carbon isotope curve as well as palynostratigraphic and other biostratigraphic events can be correlated with st audrie s bay england

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

evidence for late jurassic release of methane from gas hydrate four late jurassic carbonate successions deposited in the tethys atlantic ocean record a negative carbon isotope excursion of at least 2 the excursion is present in both organic and carbonate carbon records and is comparable in magnitude and duration to isotopic changes during the late paleocene thermal maximum our results indicate that during the late jurassic long considered a warm greenhouse time additional greenhouse gas was input to the atmosphere by a sudden release of methane from buried gas hydrate a potential triggering mechanism may have been the opening of an oceanic gateway through the early atlantic between the ancient tethys and pacific oceans

annual volcanic carbon dioxide emission an estimate from eruption chronologies continuing interest in the effects of carbon dioxide on climate has been promoted by the exponentially increasing anthropogenic production of co2 volcanoes are also a major source of carbon dioxide but their average input to the atmosphere is generally considered minor relative to anthropogenic input this study examines eruption chronologies to determine a new estimate of the volcanic co2 input and to test if temporal fluctuations may be resolved employing representative average values of 2 7 g cm 3 as density of erupted material 0 2 wt percent co2 in the original melt 60 percent degassing during eruption and an average volume of 0 1 km3 for each of the eruptions in the recently published eruption chronology of hirschboeck 1980 a volcanic input of about 1 5 1011 moles co2 yr 1 was determined for the period 1800 1969 the period 1800 1899 had a somewhat lower input than 1900 1969 which could well be related more to completeness of observational data than to a real increase in volcanic co2 this input is well below man s current co2 production of 4 5 1014 moles co2 yr 1