biomarkers as proxies for plant inputs to peats an example from a sub boreal ombrotrophic bog lipid distributions in modern peat forming plants were determined and compared to biomarkers recovered from a ca 2800 year old peat deposited in a dutch ombrotrophic bog the peat section spans a well constrained shift in local hydrology and vegetation and potential molecular proxies for plant inputs were directly tested against the macrofossil record based on the analyses of modern plants low molecular weight lmw n alkanes c23 c25 and high molecular weight n alkanes c33 are proposed as potential biomarkers for sphagnum and non sphagnum inputs respectively consistent with this in the bargerveen peat core lmw n alkane abundances increase and hmw n alkane abundances decrease coincident with the shift to sphagnum dominated peat additional potential proxies include the abundances of c22 alkanedioic acid and phytenyl phytenoate as sphagnum indicators and the abundances of the triterpenoids taraxer 14 ene and taraxast 20 ene as biomarkers for ericaceae rootlets

experimental determination of the compositional limits of immiscibility in the system cacl2h2oco2 at high temperatures and pressures using synthetic fluid inclusions abstract using the synthetic fluid inclusion method the temperature pressure and compositional limits of fluid immiscibility in the binary system cacl 2 h 2 o have been determined at 600 and 700 c at pressures between 1 and 2 kbar the limits of the immiscible regions were determined by observation of two different inclusion types in the samples and by measurements of the depression of ice melting temperatures the region of immiscibility in this system extends to much higher pressures than that of the nacl h 2 o system with similar compositional ranges a similar study was done on the cacl 2 h 2 o co 2 system at 500 600 and 700 c at pressures of 1 1 5 2 and 3 kbar in the ternary system the presence of two different inclusion types and the measurement of clathrate melting temperatures were used to delineate the compositional regions of immiscibility the presence of co 2 extends the regions of immiscibility shown in the binary system study to much higher pressures tie lines in the two phase regions were determined by measuring the homogenization temperatures of co 2 vapor and liquid phases and the volume ratios of inclusion bubble to total inclusion in vapor rich type inclusions the locations of these tie lines indicate that the cacl 2 is heavily partitioned towards the more liquid rich phase the experimental results show that with even relatively small amounts of a divalent salt such as cacl 2 immiscibility can exist to very high temperatures and pressures from these results immiscibility should be a very common phenomenon in geologic processes ranging from sedimentary to quite high grade metamorphic environments and that it should have a very important effect on reactions between hydrothermal fluids and rocks and the resulting mineral assemblages

synthetic fluid inclusions vii re equilibration of fluid inclusions in quartz during laboratory simulated metamorphic burial and uplift p t conditions inferred from fluid inclusions in metamorphic rocks often disagree with the values predicted from mineral equilibria calculations these observations suggest that inclusions formed during early stages of regional metamorphism continue to re equilibrate during burial and subsequent uplift in response to differential pressure p t conditions accompanying burial and uplift were experimentally simulated by initially forming pure h2o inclusions in quartz at elevated temperatures and pressures and then re equilibrating the inclusions in the presence of a 20 wt nacl solution such that final confining pressures ranged from 5 kbar above to 4 kbar below the initial internal pressure of the inclusions at the temperature of re equilibration in all samples re equilibrated at confining pressures below the internal pressure some inclusions were formed that had compositions of 20 wt nacl and densities in accord with the final p t conditions additionally some inclusions were observed to contain fluids of intermediate salinities between 0 and 20 wt nacl densities of these inclusions were also consistent with formation at the re equilibration p t conditions the remainder of the fluid inclusions observed in these samples contained pure h2o and their homogenization temperatures corresponded to densities intermediate between the initial and final p t conditions in short term experiments 7 days where the initial internal overpressure exceeded 1 kbar no inclusions were found that contained the original density and none were found to have totally re equilibrated instead most h2o inclusions re equilibrated until their internal pressures were between 750 and 1500 bars above the confining pressure regardless of the initial pressure differential in a long term experiment 52 days inclusions re equilibrated at a lower confining pressure than the initial internal pressure displayed homogenization temperatures corresponding to a range in final internal pressures between 0 kbar i e total re equilibration and 1 2 kbar above the confining pressure in experiments where the confining pressure during re equilibration exceeded the initial internal pressure densities of pure h2o inclusions increased to values intermediate between the initial and final p t conditions additionally these inclusions were generally surrounded by a three dimensional halo of smaller inclusions also of intermediate density resulting in a texture similar to that previously ascribed to decrepitation from internal overpressure in extreme cases where confining pressures were 4 5 kbar above the initial pressure the parent inclusion almost completely closed leaving only the three dimensional array of small 5 m inclusions the outline of which may be several times the volume of the original inclusion groups of such inclusions closely resemble textures commonly observed in medium to high grade metamorphic rocks inclusions containing 10 and 42 wt nacl solutions trapped at 600 c and 3 kbar were re equilibrated at 600 c and 1 kbar for 5 days in dry argon to evaluate the importance of h2o diffusion as a mechanism of lowering the inclusion bulk density salinities of re equilibrated inclusions obtained from freezing point depressions and halite dissolution temperatures indicate that original compositions were preserved density changes similar to those previously described were noted in these experiments in inclusions showing no visible microfractures therefore density variations observed in inclusions in this study re equilibrated under rapid deformation conditions are considered to result from a change in the inclusion volume without significant loss of contents by diffusion or leakage

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

peatlands of the western siberian lowlands current knowledge on zonation carbon content and late quaternary history the western siberian lowlands wsl are the world s largest high latitude wetland and possess over 900 000 km 2 of peatlands the peatlands of the wsl are of major importance to high latitude hydrology carbon storage and environmental history analysis of the existing russian data suggests that the mean depth of peat accumulation in the wsl is 256 cm and the total amount of carbon stored there may exceed 53 836 million metric tons a synthesis of published and unpublished radiocarbon dates indicates that the peatlands first developed at the end of the last glacial with a rapid phase of initiation between 11 000 and 10 000 cal yr bp initiation slowed after 8000 cal yr bp and reached a nadir at 4000 cal yr bp there has been renewed initiation particularly south of 621n following 4000 cal yr bp the initial development of peatlands in the wsl corresponds with the warming at the close of the pleistocene cooling after 4000 cal yr bp has likely led to increased permafrost and increased peatland development particularly in central and southern regions cold and dry conditions in the far north may have inhibited peatland formation in the late holocene r 2002 elsevier science ltd all rights reserved

reconstruction of late glacial and holocene climate evolution in southern china from geolipids and pollen in the dingnan peat sequence we have carried out a multi proxy analysis of a radiocarbon dated peat core that records the history of paleoclimate change dating from 18 ka in the dingnan region of southern china fatty acid and hydrocarbon distributions total organic carbon toc concentrations pollen assemblages and sediment lithology reveal a succession of three major paleoclimate intervals plant waxes are the predominant origin of the n alkanoic acid and n alkane compositions of this sedimentary sequence contributions of these geolipid components vary relative to toc and with changes in lithology and help to refine a pollen based reconstruction of local paleoclimate evolution a period of cool and fairly wet climate 15 630 10 450 cal abp follows accumulation of coarse fluvial sediments under relatively dry deglacial conditions the second period 10 450 6040 cal abp experienced the warmest climate and the highest precipitation indicated by a minimum c18 1 c18 0 ratio together with the low cpi values of n alkanes and high acl values the third time interval 6040 3800 cal abp was a moderately dry and cool period the climate record of the most recent period 3800 cal abp is obscured by agricultural disturbance the younger dryas 12 900 11 600 cal abp appears in this record as a period of variable and very wet climate during the interval 10 450 6040 cal abp both temperature and the precipitation evaporation ratio maximized therefore we consider this period to represent the holocene optimum which coincides with that of the northern hemisphere moreover our results do not fit the spatially asynchronous pattern of the east asian monsoon holocene optimum in china suggested by previous studies they instead parallel the pattern of global paleoclimate change and consequently show that the evolution of holocene paleoclimate in southern china is consistent with changes in northern hemisphere solar radiation

synthetic h2oco2 fluid inclusions in spontaneously nucleated forsterite enstatite and diopside hosts the method and applications abstract synthetic h2o co2 fluid inclusions have been produced in forsterite diopside and enstatite hosts during the spontaneous nucleation and growth of these phases at t 800 980 c and p 6100 7800 bars via the reactions 2 trem 18h 2 o 4 diopside 3 forsterite 5si oh 4 2h 2 o 1 trem 3h 2 o 2 diopside 3 enstatite si oh 4 2h 2 o 2 the inclusions are large 10 40 m abundant and commonly of regular shape making them ideal as standards for microthermometric and spectroscopic analyses the technique provides the opportunity to study fluid inclusion trapping mechanisms and their potential effect on inclusion chemistry the fluid inclusions exhibit a small degree of compositional scatter about the ambient composition deviations between the ambient and inclusion composition increase for experiments performed in the presence of low 3 8 c thermal gradients along the capsule length this observation suggests that compositional heterogeneities may develop in the absence of fluid convection in the capsule the effect on the inclusion composition however does not exceed 3 mol in xco2 for all inclusions studied the advantages of this technique are 1 it provides a means of producing fluid inclusions of known compositions in hosts other than quartz and 2 inclusion formation is relatively slow allowing ample time for the p t x fluid conditions of the run to equilibrate the disadvantages are that the small grains produced can be difficult to work with and the host producing reactions are viable over a relatively narrow range of p t x fluid conditions

replicated proxy climate signals over the last 2000 yr from two distant uk peat bogs new evidence for regional palaeoclimate teleconnections ombrotrophic peat is an established source of proxy climate data but previous records have been produced by different methods and have been difficult to compare high resolution plant macrofossil analysis has been applied to a lowland raised bog at fallahogy northern ireland and a montane blanket bog moine mhor in the cairngorms scotland although the bogs are 300 km apart and differ floristically the results demonstrate parallel responses to climatic forcing especially that of the little ice age this approach provides a powerful tool for reconstructing proxy climate records wherever suitable peat deposits exist in contrast to the ocean and ice core records these proxies are from a terrestrial source and related to climate changes on land over most of the holocene

synthetic fluid inclusions in natural quartz i compositional types synthesized and applications to experimental geochemistry synthetic fluid inclusions having a wide range of geologically applicable compositions in the c o h s na k ca cl cu fe system have been formed by healing fractures in inclusion free natural quartz and by precipitating new quartz overgrowths on an original seed crystal inclusion types synthesized include 1 1 liquid rich pure h2o inclusions of primary and secondary origin 2 2 pure h2o inclusions with the critical density 3 3 liquid rich inclusions containing undersaturated aqueous solutions of nacl or kcl or cacl2 or mixtures of the three salts 4 4 h2o nacl inclusions containing halite daughter minerals 5 5 h2o nacl kcl inclusions containing halite and sylvite daughter minerals 6 6 h2o co2 inclusions of various compositions containing liquid h2o and either co2 vapor or co2 liquid or both at 25 c 7 7 h2o co2 nacl inclusions containing an aqueous phase liquid and vapor co2 and halite at 25 c 8 8 c o h inclusions containing liquid h2o a co2 ch4 liquid phase and graphite daughter minerals at 25 c 9 9 h2o nacl inclusions that contain a chalcopyrite daughter mineral and 10 10 inclusions representing trapping of the coexisting immiscible fluids in the h2o nacl h2o co2 nacl and na c o h systems the inclusions exhibit uniform phase ratios at room temperature and the temperatures of various phase changes within individual inclusions agree with those predicted from experimental and theoretical data indicating that the inclusion fluid has the same composition and density as the parent solution these miniature autoclaves thus may be used to study various problems related to fluid inclusion research to calibrate analytical equipment used to study natural inclusions and to study phase equilibria solubility and pvt relations of a variety of chemical systems

a delayed climatic response to solar forcing at 2800 cal bp multiproxy evidence from three irish peatlands multiproxy palaeohydrological records from three raised bogs in northern ireland indicate that a major shift to wetter cooler climatic conditions postdated the rapid decrease in solar activity at 2800 cal bp by 100 years this event is bracketed by two wiggle match radiocarbon dated cryptotephra layers in each profile enabling a high degree of chronological precision these replicated data corroborate previous findings based on irish peat humification profiles and may indicate spatial complexity in the climatic response to solar activity between oceanic and continental areas

late holocene paleoecohydrology and carbon accumulation estimates from two boreal peat bogs in eastern canada potential and limits of multi proxy archives abstract the stratigraphy of four peat sequences collected in two peat bogs located in the eastmain river watershed 52 n 76 w james bay lowlands quebec canada was investigated to reconstruct past hydroclimatic conditions of peat accumulation and associated carbon dynamics during the late holocene analyses of macrofossils testate amoebae peat humification c n ratio and bulk density were performed at high resolution along each peat core allowing the potential of each proxy indicator under varying nutrient status and hydroclimatic conditions to be evaluated some synchronous changes were recorded both within and between peatlands suggesting the influence of allogenic factors in the development of these peatlands other reconstructed changes have highlighted autogenic succession processes related to the local geomorphic and hydrologic context highest peat carbon accumulation rates lorca were correlated with either wet conditions or high woody debris percentages suggesting that residence time of the biomass in the acrotelm and the nature of plant material can both influence carbon accumulation rates in peat bogs this study provides the first high resolution paleoecohydrological reconstructions from the mid boreal ecoregion of eastern canada a region in which peatlands occupy 30 to 60 of the land surface

synthetic fluid inclusions vi quantitative evaluation of the decrepitation behaviour of fluid inclusions in quartz at one atmosphere confining pressure the decrepitation behaviour of fluid inclusions in quartz at one atmosphere confining pressure has been evaluated using pure h2o synthetic inclusions formed by healing fractures in natural quartz three different modes of non elastic deformation referred to as stretching leakage or partial decrepitation and total decrepitation have been observed the internal pressure required to initiate non elastic deformation is inversely related to inclusion size according to the equation internal pressure kbar 4 26 d 0 423 where d is the inclusion diameter in microns regularly shaped inclusions require a higher internal pressure to initiate non elastic deformation than do irregularly shaped inclusions of similar size heating inclusions through the quartz inversion results in mechanical instability in the quartz crystal and leads to mass decrepitation of inclusions owing to structural mismatches generated by pressure gradients in the quartz around each inclusion long term heating experiments 2 years suggest that the internal pressure required to initiate non elastic deformation does not decrease significantly with time and indicates that short lived thermal fluctuations in natural systems should not alter the inclusion density and homogenization temperature inclusions that do exhibit decreased density higher homogenization temperature are however always accompanied by a change in shape from irregular to that of a negative crystal observations of this study are consistent with elasticity theory related to fracture generation and propagation around inclusions in minerals these results indicate that an inclusion will not be influenced by a neighbouring inclusion or other defect in the host phase as long as the distance between the two is 2 4 diameters of the larger of the two inclusions

biochemical evidence for minimal vegetation change in peatlands of the west siberian lowland during the medieval climate anomaly and little ice age peatland vegetation is controlled primarily by the depth of the water table making peat paleovegetation a useful climate archive we applied a biochemical approach to quantitatively estimate the plant sources of peat carbon based on 1 neutral sugar compositions of sphagnum vascular plants and lichens and 2 lignin phenol compositions of vascular plants we used these biochemical indices to characterize vegetation change over the last 2000 years in four peat cores from the west siberian lowland russia to investigate climate change during the medieval climate anomaly and little ice age the vegetation was dominated by sphagnum in all four cores but was punctuated by several rapid but transient transitions to vascular plant dominance in the two cores from the southern west siberian lowland 60 n possibly indicating permafrost development however there was no evidence for sustained vegetation change in response to either climatic event in cores from southern west siberian lowland this suggests that these climatic events were relatively mild in the southern west siberian lowland although the sensitivity of bog plant communities to climate change remains poorly understood

long term stability of permafrost in subarctic peat plateaus west central canada long term vegetation succession and permafrost dynamics in subarctic peat plateaus of west central canada have been studied through detailed plant macrofossil analysis and extensive ams radiocarbon dating of two peat profiles peatland inception at these sites occurred around 5800 5100 yr bp 6600 5900 cal bp as a result of paludification of upland forests at the northern peat plateau site located in the continuous permafrost zone palaeobotanical evidence suggests that permafrost was already present under the forested upland prior to peatland development paludification was initiated by permafrost collapse but re aggradation of permafrost occurred soon after peatland inception at the southern site located in the discontinuous permafrost zone the aggradation of permafrost occurred soon after peatland inception in the peat plateaus permafrost conditions have remained very stable until present sphagnum fuscum dominated stages have alternated with more xerophytic communities characterized by erica

climate variability and vadose zone controls on damping of transient recharge abstract increasing demand on groundwater resources motivates understanding of the controls on recharge dynamics so model predictions under current and future climate may improve here we address questions about the nonlinear behavior of flux variability in the vadose zone that may explain previously reported teleconnections between global scale climate variability and fluctuations in groundwater levels we use hundreds of hydrus 1d simulations in a sensitivity analysis approach to evaluate the damping depth of transient recharge over a range of periodic boundary conditions and vadose zone geometries and hydraulic parameters that are representative of aquifer systems of the conterminous united states u s although the models were parameterized based on u s aquifers findings from this study are applicable elsewhere that have mean recharge rates between 3 65 and 730 mm yr 1 we find that mean infiltration flux period of time varying infiltration and hydraulic conductivity are statistically significant predictors of damping depth the resulting framework explains why some periodic infiltration fluxes associated with climate variability dampen with depth in the vadose zone resulting in steady state recharge while other periodic surface fluxes do not dampen with depth resulting in transient recharge we find that transient recharge in response to the climate variability patterns could be detected at the depths of water levels in most u s aquifers our findings indicate that the damping behavior of transient infiltration fluxes is linear across soil layers for a range of texture combinations the implications are that relatively simple homogeneous models of the vadose zone may provide reasonable estimates of the damping depth of climate varying transient recharge in some complex layered vadose zone profiles

a sensitive high resolution record of late holocene climatic change from a raised bog in northern england proxy climatic data in the form of plant macrofossils have been analysed from a 5 m core from bolton fell moss cumbria uk detailed analysis of peat from the upper 50 cm of this core is used to demonstrate a strong correlation between changes in the relative proportion of taxa and known climatic changes over the last 1000 years the record of changes in bog vegetation contained within the peat profile is used to reconstruct changes in bog surface wetness for the latter half of the holocene as bog surface wetness is directly controlled by the prevailing climatic conditions this reconstruction can be viewed as a proxy climate record twelve radiocarbon age estimates on the 5m core suggest that between 50 and 500 cm peat accumulated at a relatively constant rate of 12 4 yr cm 1 the regular sampling intervals thus provide a time series of past bog surface wetness spectral analyses of this series indicates that wetness changes are cyclic with a ca 800 year periodicity

replicability and variability of the recent macrofossil and proxy climate record from raised bogs field stratigraphy and macrofossil data from bolton fell moss and walton moss cumbria england replication of results is a basic tenet of science but in palaeoecology this is very time consuming and the signal is subject to noise the derivation of proxy climate signals from ombrotrophic peat was carried out originally using samples from open peat faces where the stratigraphic relationships could be easily observed now that such sections are rare and often degraded there is a need to demonstrate that data can be replicated from core profiles ten short cores taken from two adjacent bogs have been analysed for macrofossils and show a coherent series of changes which are also similar to previous profiles from the same sites it is concluded that variation between profiles is slight and less than observations of present vegetation mosaics might suggest recommendations for a standard approach to fieldwork on raised bogs that emphasises the utility of subfossil pool layers are proposed and the need for a secure chronology is stressed 1998 john wiley sons ltd

high resolution reconstruction of wetness dynamics in a southern boreal raised bog finland during the late holocene a quantitative approach a high resolution plant macrofossil analysis was applied to investigate wetness dynamics in a southern finnish boreal bog kontolanrahka during the last 5000 years the chronological control and the age depth model were based on 40 ams radiocarbon dates pollen analysis provided information on regional scale vegetation changes macrofossil analysis revealed prominent changes in vegetation assemblages during the late holocene indicating fluctuations in water table the reconstruction suggests that at the coring point which nowadays is a relatively wet lawn habitat type has repeatedly varied between transient communities similar to those currently represented in dry hummocks very wet lawns and even hollows in order to quantify historical changes in water table generalized additive models gam were used to investigate the current relationships between surface plant species and water table depth modern water table measurements and a survey of associated plant communities along moisture gradients prov

holocene vegetation history from the salym yugan mire area west siberia the pollen stratigraphy of an ombrotrophic patterned ridge hollow raised bog in the salym yugan mire area in boreal west siberia 60 109n 72 509e covers the entire holocene period pollen data from three parallel peat cores suggest that contrary to previous assumptions betula forests did not spread into tundra until the boreal period 9000 10000 cal bp after 9000 cal bp pinus sylvestris and picea abies forests displaced betula forests in the area and dominated until 4100 4300 cal bp when picea decreased considerably due to a climatic change and pinus sylvestris became the most abundant tree species average pollen influx estimates during the wooded period from about 9000 cal bp onwards were 5600 6350 grains cm 2 yr 1 similar to pollen trap estimates from boreal coniferous forests

continental scale temperature variability during the past two millennia past global climate changes had strong regional expression to elucidate their spatio temporal pattern we reconstructed past temperatures for seven continental scale regions during the past one to two millennia the most coherent feature in nearly all of the regional temperature reconstructions is a long term cooling trend which ended late in the nineteenth century at multi decadal to centennial scales temperature variability shows distinctly different regional patterns with more similarity within each hemisphere than between them there were no globally synchronous multi decadal warm or cold intervals that define a worldwide medieval warm period or little ice age but all reconstructions show generally cold conditions between ad 1580 and 1880 punctuated in some regions by warm decades during the eighteenth century the transition to these colder conditions occurred earlier in the arctic europe and asia than in north america or the southern hemisphere regions recent warming reversed the long term cooling during the period ad 1971 2000 the area weighted average reconstructed temperature was higher than any other time in nearly 1 400 years

an assessment of the accuracy of isochore location techniques for h2o co2 nacl fluids at granulite facies pressure temperature conditions abstract synthetic h 2 o co 2 nacl fluid inclusions with xco 2 compositions ranging from 0 10 0 51 and relative salinities r s wt nacl wt nacl wt h 2 o of 6 to 23 9 wt have been produced in spontaneously nucleated forsterite diopside and orthopyroxene hosts molar volumes of the fluids at the pressure and temperature of formation have been calculated using microthermometric data from the fluid inclusions these p v t data are used to compare the accuracy of published methods of isochore location for h 2 o co 2 nacl fluids at elevated pressures and temperatures the results of these analyses show that isochores calculated with the mrk equation of bowers and helgeson geochim cosmochim acta vol 47 1247 1275 1983 reproduce the trapping pressures and temperatures well for fluids with xco 2 0 3 and up to 23 9 wt nacl for a fluid with xco 2 0 49 and relative salinity of 15 however the agreement is poor for these fluid compositions the observed molar volume is larger than that predicted from the mrk equation of bowers and helgeson and if not corrected will give isochores that are too low in pressure for a given temperature the ideal geometric mixing model of brown and lamb geochim cosmochim acta vol 53 1209 1221 1989 provides less satisfactory results for the fluid compositions studied

strontium diffusion kinetics in amphiboles and significance to thermal history determinations abstract strontium tracer diffusion coefficients have been determined in hornblende and tremolite single crystals using experiments conducted at a confining pressure of 200 mpa at temperatures ranging from 700 to 960 c a quasi hydrothermal experimental technique was devised to avoid solution precipitation effects depth profile analyses were made with an ion microprobe the arrhenius relation for diffusion parallel to the c crystallographic direction in the gore mountain hornblende over this temperature interval has an activation energy q 260 12 kj mol and a pre exponential factor d 0 4 9 18 1 3 10 8 m 2 s at 800 c transport rates parallel to the c axis measured in the two tremolite samples amnh 30563 and barrie township ontario are 3 2 10 21 m2 s and 2 0 10 21 m2 s respectively these values are factors of 3 and 5 slower than those observed for the hornblende sample at the same temperature transport rates parallel and perpendicular to the c axis are the same within the estimated uncertainty for all three compositions experiments that differed in o 2 by a factor of 6 107 mno mn3o4 mno and magnetite wustite mw for the hornblende gave the same strontium diffusion rates within a factor of two crystals with cleavage faces or polished with alumina or diamond gave the same d values provided the crystals were annealed prior to the diffusion experiment using a combination of closed system rb sr systematics and strontium diffusion kinetics it is now possible to determine the thermal histories of hornblende bearing igneous and metamorphic rocks since the diffusion rates for strontium in amphiboles are relatively slow hornblende will be more retentive of sr than of other species for which transport rates are known ar o h and will be a useful tool to record higher temperature portions of cooling paths