past present and future of thermochronology in one form or another geochronologists have been practicing thermochronology 1 the use of radioisotopic dating to constrain thermal histories of rocks and minerals for over 40 years building from lessons learned over these four decades thermochronology continues to evolve due to technical developments increasingly sophisticated theoretical models and an expanding range of applications in geologic and planetary science most recently interest in earth surface processes and interactions between tectonics erosion and climate has drawn attention to techniques that can address the timing and rates of processes operating at temperatures below about 300 c the purpose of this rimg volume is to assess the current state of thermochronology as of circa 2005 which is coincidentally the 100th anniversary of the first radioisotopic date rutherford 1905 1906 excellent review papers and books on specific topics within this field have been published but no single volume has yet provided a comprehensive review of current practices basic theory and illustrative examples the motivation for this volume stems from these considerations knowing that in a fast developing field a book like this can quickly become dated we tried to include sufficient review of fundamentals and the literature to offer students and new users a useful introduction to thermochronology that may have some staying power in this chapter we first review the salient points of thermochronology s history before assessing our current capabilities and challenges and then taking the risk of suggesting where the field is headed we do not provide a comprehensive history of the method that does full justice to the work of the large and growing cohort of thermochronologists in this short space we instead opted to give our perspectives on where the intellectual and technological roots of the discipline lie which run deeper and go back farther than is sometimes appreciated

temperature limits for preservation of primary calcite clumped isotope paleotemperatures abstract solid state reordering of c o bonds in the calcite lattice can alter the clumped isotope composition of paleotemperature archives such as fossil brachiopod shells without inducing significant changes in shell microstructure and trace element concentrations metrics commonly used to gauge preservation quality to correctly interpret the paleoenvironmental significance of clumped isotope derived paleotemperatures it is necessary to understand the temperature time domain in which solid state c o bond reordering is important we address this question using a combination of laboratory and natural geological experiments on paleozoic brachiopod shells the laboratory experiments involve heating fossil brachiopod calcite at different temperatures and times to directly observe rates of 13 c 18 o bond reordering the resulting arrhenius parameters are indistinguishable from values previously determined for an optical calcite with similar trace element compositions we develop an alternative kinetic model for reordering that accounts for non first order reaction progress observed during the initial several hundred minutes of laboratory heating experiments and show that the simplified first order approximation model passey and henkes 2012 predicts reaction progress equally well for temperatures and timescales relevant to sedimentary basins we evaluate our laboratory based rate predictions by studying brachiopod calcite from several sedimentary basins with independently constrained burial temperature histories specifically we use the laboratory derived arrhenius parameters to predict the evolution of brachiopod calcite clumped isotope compositions during successive one million year time steps reflecting the burial and exhumation temperature paths of each basin while this exercise is limited by the relatively large uncertainties in the temperature histories of these basins we find general correspondence within error between predicted and observed clumped isotope values we present simplified temperature time diagrams for calcite showing domains where primary clumped isotope compositions will be preserved partially reordered and fully reordered in conclusion calcite samples dwelling at 100 c or lower for 10 6 10 8 year timescales should not be affected by solid state c o bond reordering

strong sea forcing and warmer winter during solar minima 2765 yr b p recorded in the growth bands of crassostrea sp from the confluence of river ganges eastern india abstract long term variation of solar activity plays a key role in controlling climatic oscillations during glacial interglacial cycles the records of such climatic shifts can be retrieved from sedimentary archives in overbank deposits found in the estuary regions of major rivers in the tropics which are fed by glaciers in this study we have shown the effect of solar variability on regional climate by altering the river discharge and incursion of warm water pool into the region adjoining bay of bengal during seasonal dry period the incremental growth bands present in the modern day meretrix sp and late holocene crassostrea sp were examined for reconstruction of temperature and water composition at the head bay region of the river ganges the conventional c14 techniques on fossil oyster yielded age of 2765 130 yr b p which coincides with a solar minima analysis of clumped isotope thermometry on the growth bands provided temperature estimates for the growth of shells the temperature estimates for the modern shell suggesting range of values showed a range between 13 and 42 c close to the observed temperatures recorded in the climatological data while the fossil shell had a range of values between 22 and 38 c the 18o measured in the aragonite together with the estimated temperature were used to deduce the water composition during growth at equilibrium condition the water 18o varied between 4 8 and 1 2 for the modern sample close to the observed values of water measured near this locality while the range in water composition inferred for the paleo samples was from 2 37 to 0 82 suggesting a stronger influence of sea water throughout the year the results are consistent with the argument of infiltration of water from neighbouring warm water pool into the estuary a similar approach can be extended to evaluate the effects of climate variability due to differential action of river discharge into the sea at seasonal time scales based on available mollusc shells in the sedimentary successions from the region

oxygen isotope analysis of the eyes of pelagic trilobites testing the application of sea temperature proxies for the ordovician the oxygen isotope composition of well preserved trilobite eye calcite retaining its original optical properties represents a possible source of information on paleozoic sea temperatures species of the epipelagic telephinid genera carolinites and opipeuterella from strata of early to middle ordovician age in spitsbergen and australia were analyzed and compared with benthic asaphid species scanning electron microscope sem cathodoluminescence cl electron microprobe and electron backscatter diffraction ebsd techniques were used to assess eye preservation prior to isotope analysis some apparently well preserved eyes are identified from the valhallfonna spitsbergen and emanuel australia formations the eyes show a wide variation in 18o values 6 2 to 9 8 for the valhallfonna formation 3 2 to 10 4 for the emanuel formation and 3 6 to 7 4 for the horn valley siltstone australia intra eye secondary ion mass spectrometry sims isotope results reveal an even larger range in 18o in some specimens 18o of 2 4 to 10 4 suggesting that the trilobite eyes have undergone cryptic recrystallization a sub set of trilobite cuticle from the three formations were analyzed for their carbonate clumped isotope compositions 47 and yielded crystallization temperatures above 50 c consistent with diagenetic alteration the sims and 47 results suggest that classic preservation assessment protocols for the stable isotope study of deep time carbonate samples may be insufficient especially for these techniques there is a need for extensive microstructural characterization of lower paleozoic biogenic carbonates by techniques including ebsd sims and 47 before their stable isotope signatures can be used with certainty in paleoclimate studies

diagenesis of phosphatic hardgrounds in the monterey formation a perspective from bulk and clumped isotope geochemistry understanding the authigenesis of carbon ate fluorapatite through isotopic geochem istry can yield important information on fundamental geologic processes occurring on continental margins around the world this is particularly true for phosphatic hardgrounds which are often found in regions of upwell ing but of which questions remain about the initial formation and subsequent diagen esis here we apply standard isotopes 13 c 18 o alongside the novel clumped isotope 47 used in this study for the first time to reconstruct the temperature of formation of carbonate ions within the lattice of sedimen tary carbonate fluorapatite we investigated phosphatic hardgrounds of miocene age 12 7 10 8 ma sampled at el capitan state beach in the monterey formation the range of isotopic signatures observed is between 1 5 and 8 0 for 13 c relative to the vienna peedee belemnite vpdb standard and 9 5 and 6 0 vpdb for 18 o and val ues range between 0 599 and 0 615 for 47 the enriched 13 c and depleted 18 o signa tures are suggestive of recrystallization within the methanogenic zone clumped isotope geo chemistry further constrains this transforma tion as having taken place at a temperature of 61 66 c 5 c in line with previous esti mates for maximum burial of the monterey formation based on the silica phase transi tion the calculated 18 o for the connate fluid shows an expected range for seawater composition for the miocene suggesting only minor contribution of silica derived oxygen to the 18 o of carbonate fluorapatite the combined conventional and clumped isotope data set also points out that methanogenesis took place deeper within the sediment in the middle miocene than at present day within the santa barbara basin this study fur thers our understanding of phosphogenesis and potential links to burial processes in the monterey formation and it shows for the first time that the clumped isotope paleother mometer could be used to under stand funda mental geochemical processes in authigenic sedimentary phosphates

dating of deformation phases using k ar and 40ar 39ar techniques results from the northern apennines abstract paleozoic to oligocene metasedimentary rocks present in the alpi apuane region of the northern apennines italy have been sequentially deformed during a tertiary progressive deformation in an attempt to date the individual deformation episodes over 50 conventional k ar and 1140 ar 39ar incremental gas release analyses have been carried out on fine grained white micas separated from samples whose structural settings were well known mineralogy x ray diffractometry and thin section analyses indicate that the constituent muscovite and phengite formed under metamorphic conditions of 3 4 kbars and 300 400 c during all deformational phases pre existing micas were variably crenulated during each subsequent deformational phase both k ar and 40ar 39ar analyses were carried out on 0 6 2 m 2 6 m and 6 20 m size separates of the phengitic white mica although the k ar apparent ages range from 11 to 27 ma and are consistent with available stratigraphic constraints the 40ar 39ar age spectra display variable internal discordancy these isotopic data indicate that 1 both the k ar and 40ar 39ar total gas ages decrease as the degree of crenulation increases 2 the k ar and 40ar 39ar total gas ages decrease as grain size decreases 3 for each sample characteristics of the 40ar 39ar age spectra depend upon grain size with fine sizes yielding discordant patterns which systematically increase in apparent age from low to high temperature and 4 phengitic micas associated with earliest structures yield generally older ages than micas associated with later structures the isotopic results are interpreted to indicate that the major deformation phase d1 occurred at approximately 27 ma with subsequent pulses ending by c 10 ma these results may be combined with finite strain data to suggest that the region was deformed at strain rates between 10 15 and 10 14 s 1 a 27 ma age indicates mid oligocene initiation of plate tectonic activity in the western mediterranean and concomitant deformation in the northern apennines

laboratory calibration of the calcium carbonate clumped isotope thermometer in the 25 250 c temperature range abstract many fields of earth sciences benefit from the knowledge of mineral formation temperatures for example carbonates are extensively used for reconstruction of the earth s past climatic variations by determining ocean lake and soil paleotemperatures furthermore diagenetic minerals and their formation or alteration temperature may provide information about the burial history of important geological units and can have practical applications for instance for reconstructing the geochemical and thermal histories of hydrocarbon reservoirs carbonate clumped isotope thermometry is a relatively new technique that can provide the formation temperature of carbonate minerals without requiring a priori knowledge of the isotopic composition of the initial solution it is based on the temperature dependent abundance of the rare 13c 18o bonds in carbonate minerals specified as a 47 value the clumped isotope thermometer has been calibrated experimentally from 1 c to 70 c however higher temperatures that are relevant to geological processes have so far not been directly calibrated in the laboratory in order to close this calibration gap and to provide a robust basis for the application of clumped isotopes to high temperature geological processes we precipitated caco3 mainly calcite in the laboratory between 23 and 250 c we used two different precipitation techniques first minerals were precipitated from a caco3 supersaturated solution at atmospheric pressure 23 91 c and second from a solution resulting from the mixing of cacl2 and nahco3 in a pressurized reaction vessel at a pressure of up to 80 bar 25 250 c the calibration lines of both experimental approaches overlap and agree in the slopes with theoretical estimates and with other calibration experiments in which carbonates were reacted with phosphoric acid at temperatures above 70 c our study suggests a universal 47 t calibration t in k 47 in 47 0 98 0 01 3 407 10 9 t 4 2 365 10 7 t 3 2 607 10 3 t 2 5 880 t 0 293 0 004 this new 47 t calibration given in the absolute reference frame that extends the experimentally calibrated temperature range for clumped isotopes to 250 c can be applied to carbonates that grew at intermediate temperatures 20 250 c

constraints on the formation and diagenesis of phosphorites using carbonate clumped isotopes the isotopic composition of apatites from sedimentary phosphorite deposits has been used previously to reconstruct ancient conditions on the surface of the earth however questions remain as to whether these minerals retain their original isotopic composition or are modified during burial and lithification to better understand how apatites in phosphorites form and are diagenetically modified we present new isotopic measurements of 18 o values and clumped isotope based 47 temperatures of carbonate groups in apatites from phosphorites from the past 265 million years we compare these measurements to previously measured 18 o values of phosphate groups from the same apatites these results indicate that the isotopic composition of many of the apatites do not record environmental conditions during formation but instead diagenetic conditions to understand these results we construct a model that describes the consequences of diagenetic modification of phosphorites as functions of the environmental conditions i e temperature and 18 o values of the fluids during initial precipitation and subsequent diagenesis this model captures the basic features of the dataset and indicates that clumped isotope based temperatures provide additional quantitative constraints on both the formational environment of the apatites and subsequent diagenetic modification importantly the combination of the model with the data indicates that the 18 o values and clumped isotope temperatures recorded by phosphorites do not record either formation or diagenetic temperatures but rather represent an integrated history that includes both the formation and diagenetic modification of the apatites

warm not super hot temperatures in the early eocene subtropics the early eocene ca 55 48 ma encompasses one of the warmest intervals of the past 65 m y and is characterized by an unusually low equator to pole thermal gradient recent proxy studies suggest temperatures well in excess of 30 c even at high latitudes but confl icting interpretations derived from different types of data leave considerable uncertainty about actual early eocene temperatures a robust comparison among new paleotemperature proxies may provide insight into possible biases in their temperature estimates and additional detail on the spatial distribution of temperatures will further resolve the early eocene meridional temperature gradient we use a suite of paleotemperature proxies based on the chemistry of bivalve shell carbonate and associated sedimentary organic matter from the united states gulf coastal plain to constrain climate at a subtropical site during this key interval of earth history oxygen isotope and clumped isotope analyses of shell carbonate and two tetraether lipid analyses of sedimentary organic carbon all yield temperatures of 27 c high resolution intraannual oxygen isotope data reveal a consistent large range of seasonal variation but clumped isotope data suggest that seasonality is due primarily to precipitation not to temperature these paleotemperature estimates are 2 3 c warmer than the northern gulf of mexico today and generally consistent with early eocene temperature estimates from other low and mid latitude locations but are signifi cantly cooler than contemporaneous estimates from high southern latitudes

exploring the impact of diagenesis on isotope geochemical and microstructural alteration features in biogenic aragonite for the quaternary and neogene aragonitic biogenic and abiogenic carbonates are frequently exploited as archives of their environment conversely pre neogene aragonite is often diagenetically altered and calcite archives are studied instead nevertheless the exact sequence of diagenetic processes and products is difficult to disclose from naturally altered material here experiments were performed to understand biogenic aragonite alteration processes and products shell subsamples of the bivalve arctica islandica were exposed to hydrothermal alteration thermal boundary conditions were set at 100 degrees c 175 degrees c and 200 degrees c these comparably high temperatures were chosen to shorten experimental durations subsamples were exposed to different o 18 depleted fluids for durations between two and twenty weeks alteration was documented using x ray diffraction cathodoluminescence fluorescence and scanning electron microscopy as well as conventional and clumped isotope analyses experiments performed at 100 degrees c show redistribution and darkening of organic matter but lack evidence for diagenetic alteration except in delta 47 which show the effects of annealing processes at 175 degrees c valves undergo significant aragonite to calcite transformation and neomorphism the delta o 18 signature supports transformation via dissolution and reprecipitation but isotopic exchange is limited by fluid migration through the subsamples individual growth increments in these subsamples exhibit bright orange luminescence at 200 degrees c valves are fully transformed to calcite and exhibit purple blue luminescence with orange bands the delta o 18 and delta 47 signatures reveal exchange with the aqueous fluid whereas delta c 13 remains unaltered in all experiments indicating a carbonate buffered system clumped isotope temperatures in high temperature experiments show compositions in broad agreement with the measured temperature experimentally induced alteration patterns are comparable with individual features present in pleistocene shells this study represents a significant step towards sequential analysis of diagenetic features in biogenic aragonites and sheds light on reaction times and threshold limits the limitations of a study restricted to a single test organism are acknowledged and call for refined follow up experiments

formation of dolomite at 40 80 c in the latemar carbonate buildup dolomites italy from clumped isotope thermometry the temperature of formation of replacement dolomite and 18 o h 2 o of dolomitizing fluid in the latemar carbonate buildup dolomites italy were estimated independently from carbonate clumped isotope thermometry dolomite formed at 42 72 9 11 c 2 standard deviations sd from fluid with 18 o h 2 o that averages 0 3 3 3 vienna standard mean ocean water 2 sd the estimated temperature and 18 o h 2 o are similar to those of modern diffuse flow fluids at mid ocean ridges the kind of fluid that has been proposed previously as the dolomitizing fluid in the latemar buildup based on the trace element compositions of dolomite calcite in limestone preserves original 18 o but records clumped isotope temperatures 44 76 9 11 c 2 sd that are higher than those at which the limestone formed temperature recorded by calcite but not 18 o was likely reset during dolomitization clumped isotope thermometry has great potential for application to studies of burial and diagenesis by retrieving independent estimates of temperature and 18 o h 2 o with uncertainties as low as 5 c 2 standard errors se and 0 75 2 se respectively from a single stable isotope analysis of a carbonate mineral

high temperature environments of human evolution in east africa based on bond ordering in paleosol carbonates many important hominid bearing fossil localities in east africa are in regions that are extremely hot and dry although humans are well adapted to such conditions it has been inferred that east african environments were cooler or more wooded during the pliocene and pleistocene when this region was a central stage of human evolution here we show that the turkana basin kenya today one of the hottest places on earth has been continually hot during the past 4 million years the distribution of 13c 18o bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 c and often in excess of 35 c similar soil temperatures are observed today in the turkana basin and reflect high air temperatures combined with solar heating of the soil surface these results are specific to periods of soil carbonate formation and we suggest that such periods composed a large fraction of integrated time in the turkana basin if correct this interpretation has implications for human thermophysiology and implies a long standing human association with marginal environments

methane derived authigenic carbonate from the lower doushantuo formation of south china implications for seawater sulfate concentration and global carbon cycle in the early ediacaran ocean authigenic carbonate associated with anaerobic oxidation of methane aom usually via microbial sulfate reduction msr or ferric iron reduction is generally characterized by extremely low 13c values 30 vpdb this has been used as one of the major diagnostic features for the recognition of hydrocarbon seep carbonate in the geological past previous reports on precambrian authigenic carbonates are rare limiting our understanding of the effects of their deposition on the earth s carbon isotopic mass balance in this study mainly based on petrographic features and pronounced negative 13c values as low as 38 1 we discovered authigenic calcite cement immediately above the cap dolostone in the basal ediacaran doushantuo formation in the jiulongwan section yangtze gorges area south china our observations not only provide direct evidence for the involvement of aom during carbonate precipitation in the early ediacaran 635 ma but also suggest that the seawater sulfate concentrations in the early ediacaran may have been higher than previously thought

stable isotopes and archaeological geology the carrara marble northern italy abstract the principal marble quarries of italy for the past 2000 years have been those of carrara in roman times the marble was exported all over the ancient world renaissance quarries were opened up in seravezza both the seravezza and the carrara quarries have been exploited until today the correct identification of carrara marble has always been a problem because it was traded so widely in roman times and was later used to fabricate broken or lost pieces of classical statuary many types of geochemical analysis have been tried in order to find distinctive signatures for the recognition of classical marbles including trace elements esr spectroscopy of mn thermoluminescence and stable isotopic ratios to date the most promising has been isotopic ratio analysis of oxygen and carbon in this study stable isotopic signatures were investigated as a means for distinguishing 1 the principal quarry areas of the carrara commune fossacava miseglia and torano and the seravezza commune 2 or merely the largely classical quarries of carrara from the renaissance quarries of seravezza 3 and most important the carrara quarries from other quarries of greece turkey italy and tunisia in the classical marble data base discriminant analysis da of the isotopic analyses showed that the three quarry areas of a carrara could not be told apart but that they could be told easily from seravezza in addition a mineralized carrara quarry at mandria with buff to yellow rather than white marble was also distinctive da also suggests that carrara can be told from those quarries with which it is presently confused paros in the aegean sea marmara in turkey and pentelikon near athens sr isotopic analysis showed a range in the carrara and other marbles of hettangian lower jurassic age from 0 70778 to 0 70810 which is very different from values found in paros and pentelikon this suggests that sr might make a good third discriminator for classical marble

carbonate clumped isotope bond reordering and geospeedometry carbonate clumped isotope thermometry is based on the preference of 13c and 18o to form bonds with each other at elevated temperatures such bond ordering is susceptible to resetting by diffusion of c and o through the solid mineral lattice this type of bond reordering has the potential to obscure primary paleoclimate information but could also provide a basis for reconstructing shallow crustal temperatures and cooling rates we determined arrhenius parameters for solid state reordering of c o bonds in two different calcites through a series of laboratory heating experiments we find that the calcites have different susceptibilities to solid state reordering reaction progress follows a first order rate law in both calcites but only after an initial period of non first order reaction that we suggest relates to annealing of nonequilibrium defects when the calcites are first heated to experimental temperature we show that the apparent equilibrium temperature equations or closure temperature equations for carbonate clumped isotope reordering are analogous dodson s equations for first order loss of daughter isotopes for each calcite the sensitivity of apparent equilibrium temperature to cooling rate is sufficiently high for inference of cooling rates within a factor of 5 or better for cooling rates ranging from tens of degrees per day to a few degrees per million years however because the calcites have different susceptibilities to reordering each calcite defines its own cooling rate apparent equilibrium temperature relationship the cooling rates of carrara marble inferred from carbonate clumped isotope geospeedometry are 10 6 10 3 degrees per annum and are in broad agreement with rates inferred from thermochronometric methods cooling rates for 13c depleted calcites from the late neoproterozoic doushantou cap carbonates in south china are on the order of 102 104 degrees per annum consistent with rapid cooling following formation of these calcites by a short lived hydrothermal event bristow et al 2011 nature v 474 p 68 71 most of the uncertainty in these estimates relates to uncertainty in arrhenius parameters for different calcites thus while the carbonate clumped isotope geospeedometer shows promise for recording cooling rates in settings and lithologies where other geospeedometers may not be applicable the uncertainty in cooling rate will be large without independent knowledge of the reordering kinetics of each study material thus the full potential of the method will only be realized if reordering kinetics can be accurately determined for each study material or predicted on the basis of mineral composition texture or other observable parameters

reconsidering the uplift history and peneplanation of the northern lhasa terrane tibet the elevation history of the tibetan plateau promises insight into the mechanisms and dynamics that develop and sustain high topography over tens of millions of years as well as the contribution of uplift related erosive flux to cenozoic global cooling the elevation history of the center and northern margin of the plateau have been historically less well constrained than the southern margin a diverse suite of techniques each with their own biases and uncertainties yield discrepant mid cenozoic elevation estimates 0 5 km we reconstruct paleogene to miocene elevations of the lunpola basin on the northern lhasa terrane the southernmost crustal block of the tibetan plateau using stable isotope paleoaltimetry and clumped isotope paleothermometry on lacustrine and pedogenic carbonates integrated with previously published compound specific n alkane derived hydrogen isotopes paleo elevation estimates for the lunpola basin 3 1 4 7 km demonstrate that the northern edge of the lhasa block attained high elevation prior to 24 ma and potentially by the early eocene

seawater paleotemperature and paleosalinity evolution in neritic environments of the mediterranean margin insights from isotope analysis of bivalve shells the first step of ice sheet build up on antarctica at the eocene oligocene boundary was followed by a phase of climate instability culminating during the miocene with a warming event called the middle miocene climate optimum mmco that ended with a marked cooling phase identified as the middle miocene climate transition mmct while numerous benthic foraminifera 18o and mg ca data have been used to capture the global climate evolution during this interval of climate and ice sheet instability geochemical records from shallow water carbonates still remain scarce yet such records are crucial to capture the diversity of regional environmental responses to global climate changes and thus to better understand the behavior of our climate system during this critical interval in this work we test the potential of a multi proxy approach 18o clumped isotope 47 strontium isotopes 87sr 86sr applied to bivalves recovered from the liguro provencal basin and rhodano provencal basin northwestern of the mediterranean sea to reconstruct the evolution of shallow seawater temperature and salinity in this region over the latest oligocene to middle miocene interval 10 myrs our results highlight a local cooling in the northwestern mediterranean sea during the mmco that contrasts with the warming observed in other regions with seawater temperatures inferred from 47 analyses in the 13 18 c range these cool seawater temperatures recorded in the studied region during the mmco are much cooler than those recorded in the open oceans but are in agreement with the proliferation of bryozoan observed in the castillon du gard area during this interval low bivalve 18o values 3 24 in average are recorded during this episode are interpreted to reflect enhanced freshwater inputs lowering local salinity and seawater 18o such enhanced freshwater inputs point to a phase of enhanced hydrological cycle in the studied region possibly linked to the global mid miocene warming event bivalve 87sr 86sr data mostly fall within the global seawater sr isotope reference curve but remain compatible with enhanced freshwater inputs during the aquitanian and during the langhian as these inputs were probably not important enough to induce a large departure from the seawater curve at a regional scale

intracrystalline site preference of oxygen isotopes in goethite a single mineral paleothermometer abstract the crystal structure of goethite feo oh has two distinct oxygen sites one with exclusively fe o bonds the other with bonds to both iron and hydrogen we developed a method to assess the oxygen isotope contrast between these sites by measuring both the bulk goethite and the oxygen released in the conversion of goethite to hematite the method involves collecting the water released by dehydroxylation fluorinating that population of extracted atoms and measuring the resulting oxygen isotope composition extracted o 18 then on a separate aliquot all structural oxygen is fluorinated and measured bulk o 18 using synthetic goethite precipitates grown under controlled environmental conditions we found significant temperature dependent fractionation e bulk extracted 5 51 0 26 10 6 t 2 44 5 2 8 t in kelvin this intracrystalline fractionation forms the basis of a single phase paleothermometer with an estimated uncertainty of 2 3 c the temperature dependence appears to be independent of the isotopic composition of the parent fluid from which the goethite formed and the ph of that fluid this intracrystalline thermometer can be used to simultaneously determine the formation temperature of a goethite and the isotopic composition of the water from which it formed natural goethites analyzed with this technique yield geologically reasonable formation temperatures of between 15 and 41 c

combined high precision 48 and 47 analysis of carbonates abstract high precision analysis of the excess abundance relative to the stochastic distribution of mass 48 isotopologues in co2 evolved from acid digestion of carbonates 48 has not been possible until recently due to the relatively low natural abundance of 18o here we show that the 253 plus gas source mass spectrometer equipped with faraday cups and 1013 resistors can perform combined 47 and 48 analyses on carbonates with external reproducibilities 1sd of 0 010 and 0 030 respectively 10 mg aliquots of five carbonate reference materials eth 1 eth 2 eth 3 eth 4 and carrara are digested with phosphoric acid at 90 c using a common acid bath the evolved co2 is purified using an automated gas preparation system including cryotraps and a gc and analyzed for its 47 and 48 compositions using the dual inlet system of a 253 plus gas source mass spectrometer raw 47 and 48 values are finally normalized to the carbon dioxide equilibrium scale cdes in 47 cdes 90 c vs 48 cdes 90 c space calcite reference materials carrara eth 3 and eth 4 agree with the equilibrium curve for calcite after adding semi empirically determined 90 c acid fractionation factors of 0 196 for 47 and 0 136 for 48 to theoretical 63 and 64 data agreement between measured and theoretically expected 48 cdes 90 c highlights the accuracy of our high precision clumped isotope analytical setup combined analysis of the abundances of mass 47 and mass 48 isotopologues in co2 evolved from acid digestion of natural carbonates has excellent potential for the determination of accurate and highly precise paleotemperatures as well as for the identification of rate limiting kinetic processes involved in biomineralization a formation temperature of 15 2 c is obtained on the 95 confidence level for the upper cretaceous chalk sample eth 3

review of plausible chemical migration pathways in australian coal seam gas basins abstract coal seam gas csg or coal bed methane production has grown exponentially in australia over the last two decades with currently nearly 7000 productive wells and another 18 750 wells planned over the next five to ten years to address concerns over environmental contamination by hydraulic fracture fluids hff attributed to i incidents involving poor surface handling of hff and other fluids with potential migration pathways in soil and shallow groundwater and ii leakage pathways arising from hff injection into coal seams and unintended migration of these chemicals the national assessment of chemicals associated with coal seam gas extraction in australia the assessment was undertaken the assessment included a review of international studies on unconventional gas migration pathways to provide prior knowledge and comparison for use in the australian study the international literature highlighted that accidents with hff were mainly due to surface operations and included leaking equipment and spills contamination risks of groundwater from hydraulic fracturing itself were found to be very small based on analysis of micro seismic and groundwater hydrochemistry data geologic modelling of vertical fracture growth further reveals a low risk of leakage pathways developing in aquifers confined by deep shale formations this is due to limitations on the fracture growth vertically across aquitards often hundreds of meters thick retention within the shale of limited amounts of injected fluid and preferential fracture growth at shallow depths in the horizontal direction these arguments are broadly applicable to australian csg basins however important differences exist such as the reduced thickness in australia of the aquitards that separate the targeted gas resource from groundwater also hydraulic fracturing in australian coal seams is practised only when permeabilities are too low for gas extraction to be economical without stimulation from the nearly 10 000 csg wells drilled in the bowen and surat basins in queensland only 6 have received hydraulic fracturing to date the reduced risk of leakage pathways developing during csg production in australian basins is further corroborated by geologic criteria based on modelling and observations criteria include encountering certain favourable conditions during drilling injection i e i interfaces such as natural fractures faults and bedding planes which promote offsetting and branching or rock layers with higher fracture toughness causing the cessation or reduction in fracture growth ii narrow fractures due to a relatively higher elastic modulus leading to higher viscous flow loss iii high permeability layers and iv overlying layer s with a higher confining stress in addition to the leakage pathways considered in north american shale gas basins involving i pre existing fractures and faults or ii flow up the production well due to poor casing or cementing plausible chemical migration pathways in australian csg basins are due to iii connectivity via a fracture in or extended out of the coal seam formation between csg wells and water bores co located in the same formation and iv poor integrity water bores enhancing inter aquifer connectivity these plausible pathways are described and used in subsequent work as the basis of risk assessments for contamination at the local and regional scale

reconstructing carbonate alteration histories in orogenic sedimentary basins xigaze forearc southern tibet abstract carbonate clumped isotope thermometry t 47 and the oxygen stable isotope record 18 o provide critical constraints on the temperature of carbonate mineral formation and isotopic composition of ancient waters used in reconstructions of past climate tectonics and ecological and environmental change the robust use of these proxies requires that carbonate minerals in the rock record retain primary isotopic compositions through often complex post depositional thermal histories new carbonate clumped isotope thermometry and sedimentology data are paired with existing thermochronology and isotope exchange reaction modeling to provide unique constraints on the alteration history of the carbon and oxygen isotopes in tethyan marine carbonates jialazi fm tso jianding group of the xigaze forearc southern tibet within the framework of the textural and isotopic data the effects of early and late burial alteration on 47 and 18 o values of marine rocks that were buried to 4 km above sea level are modeled the alteration products are considered within two well studied mechanistic frameworks water rock recrystallization and solid state reordering of 13 c 18 o bonds at high temperature the proposed alteration model is as follows 1 shallow early diagenesis with water of similar composition and temperature to formation waters infills primary porespace with microspar 2 high temperature rock buffered water rock exchange and partial solid state reordering at 3 4 km depth and 3 near surface low temperature water rock exchange on the exhumation pathway the 47 heterogeneity within individual samples 0 456 to 0 721 requires significant differential alteration on the retrograde path high to low temperature low water rock ratio in which primary compositions and compositions inherited during early burial diagenesis are overprinted with modern meteoric values a low t 47 value is often assumed to record the primary temperature of the depositional environment however samples yielding low t 47 values in the jialazi fm have undergone extensive high temperature water rock alteration and therefore require a mechanism for increasing 13 c 18 o bond ordering on the retrograde pathway while preserving many primary biogenic structures and micritic textures this study highlights the potential significance of late stage low temperature alteration of carbonates derived from orogenic sedimentary basins for studies of terrestrial paleoenvironments and tectonics this study also provides an example framework for combining observational and analytical data to reconstruct a carbonate alteration history of a buried sedimentary package

the clumped isotope geochemistry of exhumed marbles from naxos greece exhumation and accompanying retrograde metamorphism alter the compositions and textures of metamorphic rocks through deformation mineral mineral reactions water rock reactions and diffusion controlled intra and inter mineral atomic mobility here we demonstrate that these processes are recorded in the clumped and single isotope 13 c and 18 o compositions of marbles which can be used to constrain retrograde metamorphic histories we collected 27 calcite and dolomite marbles along a transect from the rim to the center of the metamorphic core complex of naxos greece and analyzed their carbonate single and clumped isotope compositions the majority of 47 values of whole rock samples are consistent with exhumation controlled cooling of the metamorphic complex however the data also reveal that water rock interaction deformation driven recrystallization and thermal shock associated with hydrothermal alteration may considerably impact the overall distribution of 47 values we analyzed specific carbonate fabrics influenced by deformation and fluid rock reaction to study how these processes register in the carbonate clumped isotope system 47 values of domains drilled from a calcite marble show a bimodal distribution low 47 values correspond to an apparent temperature of 260 c and are common in static fabrics high 47 values correspond to an apparent temperature of 200 c and are common in dynamically recrystallized fabrics we suggest that the low 47 values reflect diffusion controlled isotopic reordering during cooling whereas high 47 values reflect isotopic reordering driven by dynamic recrystallization we further studied the mechanism by which dynamic recrystallization may alter 47 values by controlled heating experiments results show no significant difference between laboratory reactions rates in the static and dynamic fabrics consistent with a mineral extrinsic mechanism in which slip along crystal planes was associated with atomic scale isotopic reordering in the calcite lattice an intrinsic mechanism enhanced isotopic reordering rate in deformed minerals is contraindicated by these experiments we suggest that 47 values of dynamically recrystallized fabrics that form below the diffusion controlled blocking temperature for calcite constrain the temperature of deformation we find that 47 based temperatures of static fabrics from naxos marbles are 60 80 c higher than commonly observed in slowly cooled metamorphic rocks and would suggest cooling rates of 10 5 c myr 1 a similar thermal history is inferred for dolomite marbles from the core vicinity which preserve apparent temperatures up to 200 c higher than a typical blocking temperature 300 c this finding could be explained by a hydrothermal event driving a brief thermal pulse and locally resetting 47 values rapid cooling of the core complex region is consistent with a compilation of published cooling ages and a new apatite u th he age associating the thermal event with the emplacement of a granodiorite pluton at 12 ma

assessment of the clumped isotope composition of fossil bone carbonate as a recorder of subsurface temperatures abstract bone is susceptible to early diagenesis and its carbon and oxygen isotopic compositions have been suggested to reflect conditions in the soil environment and shallow subsurface during fossilization this implies open system recrystallization involving mass exchange of carbon and oxygen among bioapatite soil water and dic such recrystallization would also redistribute isotopic clumping including 13 c 18 o bonds leading to the possibility that the carbonate clumped isotope compositions of fossil bone record ground temperature during early diagenesis we assess this possibility by studying quaternary mammalian fossil bone from subtropical to polar latitudes if recrystallization is early and pervasive clumped isotope derived temperatures t 47 should closely mirror latitudinal gradients in ground temperature excluding results from a mummified specimen yielding t 47 38 c that is indistinguishable from mammalian body temperature we find that t 47 values are intermediate between mammalian body temperature and ground temperature suggesting partial recrystallization of bone carbonate xrd analyses show that the nature and extent of diagenesis varies among the samples and does not relate in a straightforward manner to t 47 no clear correlation exists between t 47 and mean annual temperature or mean warm season temperature furthermore bone tends to retain the 18 o enriched signature of body water suggesting incomplete oxygen isotope exchange with meteoric waters incomplete carbon and oxygen isotope exchange between bone carbonate and soil waters is also indicated for a set of late miocene bone enamel pairs from a sequence of stacked paleosols in northern china analysis of bone as old as early cretaceous shows that bone carbonate is susceptible to later diagenesis at elevated burial temperatures although t 47 does not closely conform to maximum burial temperature again suggesting partial recrystallization or recrystallization during different stages of the burial and exhumation circuit these results show that carbon oxygen and clumped isotopes in fossil bone are capable of recording aspects of early diagenesis and the subsequent burial and exhumation history but that distinguishing among different effects is challenging however clumped isotopes in bone can provide useful directional constraints on past temperatures for example t 47 values higher than body temperature necessarily place lower limits on maximum burial temperatures and those lower than body temperature place upper limits on minimum fossilization temperatures

high elevation of jiaolai basin during the late cretaceous implication for the coastal mountains along the east asian margin abstract a large body of evidence suggests that there were extensive coastal mountains along the east asian margin during the late cretaceous however current knowledge of the paleo mountains the period range and elevation is limited therefore direct paleoaltimetry is needed to validate and evaluate the paleo mountains in east asia our study area is jiaolai basin which is located at the east asian continental margin we estimate the paleoelevation of jiaolai basin during the late cretaceous using carbonate clumped isotope paleothermometry after correcting for seasonal preference latitudinal difference and secular climate change we conclude that the paleoelevation of jiaolai basin was almost certainly 2 0 km at 80 ma combined with the evidence from stratigraphy paleogeography and paleoclimatology our results suggest that the existence of coastal mountains along east asia during the late cretaceous is likely and the model of okhotomorsk east asia collision is preferred

comparison of clumped isotope signatures of dolomite cements to fluid inclusion thermometry in the temperature range of 73 176 c abstract widespread application of the novel clumped isotope paleothermometer 47 using dolomite samples from shallow crustal settings has been hindered by a lack of adequate constraints on clumped isotope systematics in dolomites that formed at temperatures greater than 50 c consequently many high temperature applications involving diagenetic dolomites have required an assumption that the relationship between temperature and 47 in diagenetic dolomite resembles the theoretical temperature dependence for calcite here we present 47 results from dolomite cements for which precipitation temperatures were determined independently using fluid inclusion microthermometry we compare a rock based calibration for samples from the temperature range of 73 to 176 c to previously published laboratory derived calibrations for synthetic calcites this novel combination of approaches yields results that are broadly consistent with results reported from controlled laboratory experiments providing an important confirmation of the utility of clumped isotopes in real world systems our results suggest that the 47 of dolomite cements may provide key information in the reconstruction of burial and thermal histories and also in the recognition of potential petroleum reservoirs

the evolution of latitudinal temperature gradients from the latest cretaceous through the present abstract latitudinal temperature gradients are a defining characteristic of the climate system using thermometric indicators including 18o plant and animal fossils glycerol dialkyl glycerol tetraether gdgt proxies and clumped isotope estimates we document marine and terrestrial temperature gradients for the latest cretaceous late paleocene early eocene early oligocene pliocene and recent the changes in gradients reflect the transition greenhouse to icehouse conditions the evolution of latitudinal temperature gradients in marine and terrestrial realms are similar but has some distinctive differences marine temperatures are generally warmer than those on land except for the late paleocene early eocene the marine records show distinct inflection points at 30 and 50 latitude indicating the existence of frontal systems in the ocean except for the late paleocene early eocene the marine records show an increasingly steeper trend from latest cretaceous through recent being most pronounced after the early oligocene greenhouse icehouse transition this trend reflects the increasing intensity of high latitude and polar cooling as the icehouse state developed during the late paleocene early eocene the oceans were characterized by slightly warmer tropics and much warmer higher latitudes than at present the continents have generally had tropical temperatures like those of today varying by

oxygen self diffusion in calcite dependence on temperature and water fugacity oxygen self diffusion in natural calcite single crystals was studied hydrothermally at 400 800 c and 10 350 mpa confining pressure diffusion coefficients d were determined from18o concentration profiles measured with an ion microprobe at 100 mpa confining pressure the arrhenius parameters yield an activation energy q 173 6 kj mole and pre exponential factor d0 7 10 9 m2 s over the temperature range 400 800 c and there is no measurable anisotropy constant temperature experiments at 700 c indicate that there is a strong linear correlation slope 0 9 of d with water fugacity over the range 4 240 mpa consistent with the interpretation that in the presence of water the dominant oxygen bearing transport species in calcite is molecular water a sample containing 1180 ppm mn shows a marked increase in observed d values at temperatures below 600 c however when pre annealed at 700 c the d values obtained at 550 c are within a factor of four of the value obtained for the low 100 ppm mn sample the results of this study confirm that in contrast to carbon oxygen diffusion rates in calcite are greatly enhanced when water is present the difference in the effect of water on doxygen and dcarbon in calcite may provide valuable information for evaluating the role of fluids in the thermal histories of calcite bearing rocks

use of clumped isotope thermometry to constrain the crystallization temperature of diagenetic calcite we describe an approach to estimating the crystallization temperatures of diagenetic calcites using clumped isotope thermometry a paleothermometer based on the 13 c 18 o bond enrichment in carbonates application of this thermometer to calcified gastropod shells and calcite cements in an early eocene limestone from the colorado plateau reveals a record of calcite precipitation and replacement at temperatures varying from 14 to 123 c the early eocene host sediments were never deeply buried but they experienced a significant thermal pulse associated with the emplacement of a late miocene basalt flow the combination of independent constraints on thermal history with clumped isotope thermometry petrographic including cathodoluminescence observations and oxygen isotopic data provides an improved basis for estimation of the temperature and timing of diagenetic events and fluid sources the petrography and calcite 18 o values taken alone suggest that the aragonite to calcite transformation of gastropod shell material occurred simultaneously with early formation of cements and lithification of the matrix in the same sample however addition of clumped isotope thermometry demonstrates that this phase transformation of shell material occurred at temperatures of 94 123 c in a highly rock buffered microenvironment i e with the isotopic composition of fluid buffered by coexisting carbonate millions of years after lithification of the matrix and formation of initial low temperature 14 19 c calcite cements within shell body cavities clumped isotope temperatures in excess of reasonable earth surface conditions recorded by later formed cements demand that cement growth occurred in association with the lava emplacement our results illustrate the potential for clumped isotope thermometry to constrain conditions of diagenesis and guide interpretations that would not be possible on the basis of conventional stable isotopic and petrographic data alone and demonstrate how petrographic characterization of clumped isotope thermometry samples can benefit paleoclimate studies

stress and mass changes at a wet volcano example during the 2011 2012 volcanic unrest at kawah ijen volcano indonesia since 2010 kawah ijen volcano has been equipped with seismometers and its extremely acid volcanic lake has been monitored using temperature and leveling sensors providing unprecedented time resolution of multiparametric data for an acidic volcanic lake the nature of stress and mass changes of the volcano is studied by combining seismic analyses and volcanic lake measurements that were made during the strongest unrest ever recorded by the seismic network at kawah ijen the distal vt earthquake swarm that occurred in may 2011 was the precursor of volcanic unrest in october 2011 that caused an increase in shallow earthquakes the proximal vt earthquakes opened pathways for fluids to ascend by increasing the permeability of the rock matrix the following months were characterized by two periods of strong heat and mass discharge into the lake and by the initiation of monochromatic tremor mt activity when steam gases interacted with shallow portions of the aquifer significant seismic velocity variations concurrent with water level rises in which water contained a large amount of steam gas were associated with the crises that caused an although the unrest did not affect the shallow hydrothermal system at a large scale whereas shallow vt earthquakes likely reflect a magmatic intrusion mt and relative seismic velocity changes are clearly associated with shallow hydrothermal processes these results will facilitate the forecast of future crises

pliocene and pleistocene exhumation and uplift of two key areas of the northern apennines application of different thermochronological methods to two areas of pronounced relief apuane alps and mt falterona of the northern apennines chain documents an average exhumation rate of about 0 7m m yr this result suggests that the general exhumation of the chain is driven mainly by erosion nevertheless the long term exhumation trend seems to be perturbed by shortterm events at higher exhumation rates the time of increased exhumation rates coincides with onset of intramontane sedimentation documenting a contribution of tectonics local normal faulting to the surface uplift the data indicate an eastward shifting of the onset of topographic relief early pliocene in the apuane alps and early pleistocene in the mt falterona area r 2002 elsevier science ltd and inqua all rights reserved

a 600 million year carbonate clumped isotope record from the sultanate of oman carbonate clumped isotope thermometry is a promising technique that has the potential to help decode the significance of the variability of both physical and geochemical compositions of ancient carbonate rocks this study utilizes a 600 million year record of marine carbonate rocks from the subsurface and surface of the sultanate of oman to explore how burial and exhumation affected the carbonate clumped isotope thermometer samples span 6 km of burial depth and include calcite and dolomite mineralogies and a range of carbonate rock textures we find evidence for two broad patterns in the physical and geochemical behavior of carbonate rocks during burial the first group of carbonates yield water 18 o vsmow compositions slightly enriched or equal to an expected ice free seawater composition of 1 2 and display good to fair textural preservation suggesting that cementation and lithification occurred within tens of meters of the sediment water interface temperatures from the second group sit on the present day geotherm yield highly enriched water 18 o vsmow compositions and display fair to poor textural preservation we find no evidence for solid state reordering in paired analyses of calcites and dolomites our results contribute to a growing body of work that indicates that the seawater 18 o vsmow composition has not changed significantly over 600 myr and was not 6 in the ediacaran

basin scale thermal and fluid flow histories revealed by carbonate clumped isotopes δ47 middle jurassic carbonates of the paris basin depocentre the reconstruction of past diagenetic conditions in sedimentary basins is often under constrained this results from both the analytical challenge of performing the required analyses on the minute sample amounts available from diagenetic mineral phases and the lack of tracers for some of the diagenetic parameters the carbonate clumped isotopes thermometry 47 opens new perspectives for unravelling the temperatures of diagenetic phases together with the source of their parent fluids two parameters that are otherwise impossible to constrain in the absence of exploitable fluid inclusions here is reported the study of a large number of sedimentary and diagenetic carbonate phases from middle jurassic reservoirs of the paris basin depocentre by combining detailed petrographic observations with a large number of 47 data n 45 on a well documented paragenetic sequence including calcite and dolomite burial cements the data reveal carbonate crystallization at temperatures between 29 c and 98 c from fluids with 18owater values between 7 and 2 in response to the progressive burial and uplift of the paris basin throughout 165 myr of basin evolution coupled to the time temperature evolution previously estimated from thermal maturity modelling these temperatures allow determining the timing of four successive cementation episodes the overall dataset indicates a history of complex water mixing with a significant contribution of hypersaline waters from the triassic aquifers migrated upward along faults during the cretaceous subsidence of the basin subsequent large scale infiltrations of meteoric waters induced a dilution of these pre existing brines in response to the paris basin uplift in the tertiary overall the data presented here allow proposing an integrated approach to characterize the cementation events affecting the studied carbonate reservoir units based on temperature oxygen isotope composition and salinity of the parent fluids as well as on petrographic grounds this article is protected by copyright all rights reserved

carbonate clumped isotope evidence for latitudinal seawater temperature gradients and the oxygen isotope composition of early cretaceous seas abstract in this study we investigated early cretaceous valanginian ca 135 million years ago climate from subtropical to boreal palaeolatitudes combined carbonate clumped isotope and oxygen isotope data derived from sub arctic boreal and sub tropical fossil belemnite rostra mollusca cephalopoda provide new palaeotemperature estimates as well as a constraint on the oxygen isotope composition of seawater our belemnite data reveal balmy high latitude marine temperatures ca 22 c and warm sub tropical temperatures ca 31 c supplementing our clumped isotope based temperature estimates with published tex86 data results in a conservative reconstruction of a latitudinal temperature gradient that is reduced compared to modern conditions we find that modelling efforts are close to reproducing tropical temperatures when high pco2 levels are considered warm polar temperatures imply however that data model discrepancies remain early cretaceous seawater oxygen isotope values show a modern profile and are much more positive up to 1 5 smow than typically assumed based on our findings if the positive cretaceous seawater 18o values are not considered carbonate 18o thermometry would underestimate temperatures most acute at middle and tropical latitudes

uplift of the central andes of nw argentina associated with upper crustal shortening revealed by multiproxy isotopic analyses this study contributes to the uplift history of the andes which has received increasing attention in recent years because of its implications for geodynamic models and climate feedbacks shortening resulting in crustal thickening and removal of gravitationally unstable mantle lithosphere has been proposed to control deformation and uplift of cordillera type orogenic systems such as the puna plateau of the central andes and its eastern margin the eastern cordillera we present new clumped isotope 47 18o and 2 data from carbonate nodules marlstone spring deposits and volcanic ashes from the puna plateau and eastern cordillera of nw argentina when combined with other geological evidence our data indicate that the puna plateau was near its present elevation since at least 10 ma whereas the eastern cordillera rose 1 5 km between 14 and 7 ma this history of uplift correlates with active shortening in the eastern cordillera and with incorporation of a regional foreland into the propagating orogenic wedge our study suggests that the elevation of the puna plateau changed little during the miocene pliocene whereas the margin experienced significant uplift associated with active deformation and crustal thickening

investigating the effect of burial histories on the clumped isotope thermometer an example from the green river and washakie basins wyoming abstract the 47 clumped isotope thermometer has been applied to multiple studies aimed at reconstructing the paleoelevation and paleoclimate of sedimentary basins and paleosol sequences ideally this technique directly preserves the temperature of carbonate formation avoiding any speculation on the composition of surface water from which the carbonate precipitated recently however concerns about post depositional alteration of the 47 isotope signature from the effects of burial and or diagenetic alteration have arisen potentially complicating the application of the 47 clumped isotope thermometer for determining paleo surface temperatures here we investigate the effect of burial history on mass 47 clumped isotope to this purpose we collected samples from the surface and from drill cores in two different areas of the greater green river basin the washakie basin near rock springs wyoming and the green river basin near pinedale wyoming both basins are filled with a thick sequence of eocene lacustrine strata and the thermal histories of both basins are well documented from petroleum prospecting studies clumped isotope 47 compositions were measured from lacustrine micritic limestones with a range of peak burial depths from 1 to 6 5 km for samples from the washakie basin that did not experience burial depths exceeding 2000 meters the measured 47 values vary from 0 623 to 0 684 yielding carbonate formation temperatures consistent with previously hypothesized paleocene eocene surface temperatures in contrast samples from the green river basin collected from greater burial depths demonstrate significantly lower 47 values higher temperatures the consistency of 18o values and lack of cl evidence for recrystallization suggest closed system resetting of the clumped isotope thermometer by either partial solid state re ordering or carbonate reprecipitation during burial the 47 values of the deeply buried samples have been compared to values derived from recrystallization and temperature history reordering models thrms both recrystallization and reordering models are successful at predicting 47 reordering at burial temperatures 100 c these observations from samples collected from a basin with a remarkably well constrained thermal history and geothermal gradient highlight the challenges in elucidating burial histories or diagenetic processes solely from clumped isotopic compositions

ultramafic rock carbonation constraints from listvenite core bt1b oman drilling project the occurrence of the quartz carbonate alteration assemblage listvenite in ophiolites indicates that ultramafic rock represents an effective sink for dissolved co2 however the majority of earlier studies of ultramafic rock carbonation had to rely on the surface exposure of reaction textures and field relationships here we present the first observations on ultramafic rock alteration obtained from the 300 m deep bt1b drill hole icdp oman drilling project allowing for a continuous and high resolution investigation hole bt1b recovered continuous drill core intersecting surface alluvium 200 meters of altered ultramafic rock comprising mainly listvenite and minor serpentinite bands at 90 m and 180 m depth and 100 meters of the underlying metamorphic sole textural evidence suggests that the carbonation of fully serpentinized harzburgite commenced by non equilibrium growth of spheroidal carbonate characterized by sectorial zoning resulting from radially oriented low angle boundaries in the serpentinite carbonate spheroids are composed of alternating magnesite cores and dolomite rims whereas texturally similar carbonate in the listvenite is composed of fe rich magnesite cores and ca fe rich magnesite rims the distinct compositions and mineral inclusions indicate that the carbonation extent was controlled by fluid accessibility resulting in the simultaneous formation of limited carbonate in the serpentinite bands and complete carbonation in the listvenite parts of bt1b the presence of euhedral magnesite overgrowing spheroidal carbonate in the listvenite suggests near equilibrium conditions during the final stage of carbonation the carbonate clumped isotope thermometry constrains carbonate crystallization between 50 c and 250 c implying repeated infiltration of reactive fluids during ophiolite uplift and cooling

crustal extension in the northern apennines the transition from compression to extension in the alpi apuane core complex an interpretation of northern apennine geology is presented which relates the temporal and spatial occurrence of both compressional and extensional deformation features in terms of the changing dynamic evolution within an accretionary wedge after a model proposed by platt 1986 followed by the initiation and development of continental rifting during cretaceous to eocene time an accretionary wedge formed as remnant tethyan oceanic crust subducted beneath the rotating corsica sardinia microplate microplate collision during the oligocene was characterized by the rapid imbrication of buoyant continental crust of the italian continental margin the record of which is preserved within the duplex structure geometry of the alpi apuane region the overthickened wedge geometry returned to a more stable configuration by developing extensional features during the miocene both listric normal faults at upper crustal levels and shear zones indicating evidence of distributed ductile extensional strain at mid crustal levels are recorded it is proposed that large scale regional extension with associated volcanism beginning in the messinian was represented by the intrusion of asthenospheric material from the subducted plate into the already attenuated accretionary complex further rifting perhaps aided by subduction and back arc processes in the southern apennines led to the formation of the tyrrhenian sea as an oceanic basin both the apennines and north american core complexes record evidence of crustal thickening followed by crustal thinning and finally of continental rifting this suggests that the similar histories of these regions with vastly different plate tectonic settings may both be explained by processes linked to the changing internal dynamics of accretionary wedges

massive formation of early diagenetic dolomite in the ediacaran ocean constraints on the dolomite problem paleozoic and precambrian sedimentary successions frequently contain massive dolomicrite camg co3 2 units despite kinetic inhibitions to nucleation and precipitation of dolomite at earth surface temperatures 100 c thus raising doubt about the validity of these deposits as archives of earth surface environments we present a high resolution 63 my long clumped isotope temperature t 47 record of shallow marine dolomicrites from two drillcores of the ediacaran 635 to 541 ma doushantuo formation in south china our t 47 record indicates that a majority 87 of these dolostones formed at temperatures of 100 c when considering the regional thermal history modeling of the influence of solid state reordering on our t 47 record further suggests that most of the studied dolostones formed at temperatures of 60 c providing direct evidence of a low temperature origin of these dolostones furthermore calculated 18o values of diagenetic fluids rare earth element plus yttrium compositions and petrographic observations of these dolostones are consistent with an early diagenetic origin in a rock buffered environment we thus propose that a precursor precipitate from seawater was subsequently dolomitized during early diagenesis in a near surface setting to produce the large volume of dolostones in the doushantuo formation our findings suggest that the preponderance of dolomite in paleozoic and precambrian deposits likely reflects oceanic conditions specific to those eras and that dolostones can be faithful recorders of environmental conditions in the early oceans

thermochronologic evidence for the exhumational history of the alpi apuane metamorphic core complex northern apennines italy 1 the apennine range is a young convergent orogen that formed over a retreating subduction zone the alpi apuane massif in the northern apennines exposes synorogenic metamorphic rocks and provides information about exhumation processes associated with accretion and retreat u th he and fission track ages on zircon and apatite are used to resolve exhumational histories for the apuane metamorphic rocks and the structurally overlying very low grade macigno formation stratigraphic metamorphic and thermochronologic data indicate that the apuane rocks were structurally buried to 15 30 km and 400 c at about 20 ma exhumation to 240 c and 9 km depth below sea level occurred at 10 13 ma by 5 ma the apuane rocks were exhumed to 70 c and 2 km the macigno and associated tuscan nappe were also structurally buried and the macigno reached its maximum depth of 7 km at 15 to 20 ma stratigraphic evidence indicates that the apennine wedge was submarine at this time thus we infer that initial exhumation of the apuane was coeval with tectonic thickening higher in the wedge as indicated by synchronous structural burial of the tuscan nappe from 6 to 4 ma thinning at shallow depth is indicated by continued differential exhumation between the apuane and the tuscan nappe at high rates after 4 ma differential exhumation ceased and the apuane and the tuscan nappe were exhumed at similar rates 0 8 km ma which we attribute to erosion of the apennines following their emergence above sea level

clumped isotope composition of marbles from the backbone range of taiwan the clumped isotope composition of carbonates provides a new way to retrieve temperatures for ancient geological systems without knowing the isotopic compositions of co existing fluid minerals the application of this new thermometer in the past decade however has been largely restricted to low temperature 250 c geological processes in this study we present clumped isotope analyses for marbles collected from the backbone range of taiwan which has been subjected to greenschist facies metamorphism during the ongoing arc continent collision we find that the 47 temperatures either indicate temperatures of the last dynamic open system recrystallization of marbles due to tectonic movement stress or signify closed system closure temperatures during rock exhumation demonstrating that clumped information from marbles has great potential for revealing process characteristics during mountain building