isotopic fractionation of cu in tektites tektites are terrestrial natural glasses of up to a few centimeters in size that were produced during hypervelocity impacts on the earth s surface it is well established that the chemical and isotopic composition of tektites is generally identical to that of the upper terrestrial continental crust tektites typically have very low water content which has generally been explained by volatilization at high temperature however the exact mechanism is still debated because volatilization can fractionate isotopes comparing the isotopic composition of volatile elements in tektites with those of their source rocks may help to understand the physical conditions during tektite formation interestingly volatile chalcophile elements e g cd and zn seem to be the only elements for which isotopic fractionation is known so far in tektites here we extend this study to cu another volatile chalcophile element we have measured the cu isotopic composition for 20 tektite samples from the four known different strewn fields all of the tektites except the muong nong types are enriched in the heavy isotopes of cu 1 98 delta 61 cu 6 99 in comparison to the terrestrial crust delta 65 cu approximate to 0 with no clear distinction between the different groups the muong nong type tektites and a libyan desert glass sample are not fractionated delta 65 cu approximate to 0 in comparison to the terrestrial crust to refine the cu isotopic composition of the terrestrial crust we also present data for three geological reference materials delta 65 cu approximate to 0 an increase of delta 65 cu with decreasing cu abundance probably reflects that the isotopic fractionation occurred by evaporation during heating a simple rayleigh distillation cannot explain the cu isotopic data and we suggest that the isotopic fractionation is governed by a diffusion limited regime copper is isotopically more fractionated than the more volatile element zn delta 66 64 zn up to 2 49 parts per thousand this difference of behavior between cu and zn is predicted in a diffusion limited regime where the magnitude of the isotopic fractionation is regulated by the competition between the evaporative flux and the diffusive flux at the diffusion boundary layer due to the difference of ionic charge in silicates zn 2 vs cu cu has a diffusion coefficient that is larger than that of zn by at least two orders of magnitude therefore the larger isotopic fractionation in cu than in zn in tektites is due to the significant difference in their respective chemical diffusivity c 2009 elsevier ltd all rights reserved

copper isotope fractionation in sedimentary copper mineralization timna valley israel abstract copper isotopes 65 cu 63 cu are potentially powerful new geochemical proxies for oxidation reduction processes and metallic cycling this research presents a cu isotope study of mineralization in historically mined stratiform sediment hosted copper ssc ore deposits of the precambrian and cambrian rocks of the timna valley southern israel these deposits provide a natural laboratory for studying isotopic fractionations between cu sulphides and cu ii minerals copper carbonates hydroxides and silicates formed during sequential cycles of low temperature alteration of igneous copper porphyries marine sedimentary diagenesis and epigenetic mobilization in sandstones isotopic measurements were made using mc icp ms after ion chromatographic separation of the copper from matrix elements in accord with abiogenic experimental studies showing that there should be a negative isotopic fractionation between reduced and oxidized copper minerals 65 cu values of cu sulphides are significantly lower 3 4 to 1 2 than coexisting cu ii carbonates and hydroxides 1 2 to 0 5 cu ii silicates which should only show a very small isotopic fractionation relative to parent cu ii solutions give average 65 cu values of 0 09 0 24 consistent with the fact that the primary source of sedimentary copper was the precambrian igneous rocks isotopic zoning profiles in cu sulphides of the cambrian dolomites suggest they were formed through the interaction of small disconnected cu solution reservoirs with h 2 s formed by bacterial reduction of sulphate containing pore waters mass balance modeling based on the measured cu isotope compositions and experimental fractionation factors shows that the main copper reservoir is the cambrian sandstone shale sequence and that the cu sulphide reservoirs are relatively small thus most of the copper transport occurred in relatively oxidized conditions the calculated reservoir sizes are in agreement with field observations and confirm that copper isotopes are able to trace both the oxidation reduction cycles and mass transfer during sedimentary copper mineralization

comparative stable isotope geochemistry of ni cu zn and fe in chondrites and iron meteorites high precision ni isotopic variations are reported for the metal phase of equilibrated and unequilibrated ordinary chondrites carbonaceous chondrites iron meteorites mesosiderites and pallasites we also report new zn and cu isotopic data for some of these samples and combine them with literature fe cu and zn isotope data to constrain the fractionation history of metals during nebular vapor solid and planetary metal sulfide silicate phase changes the observed variations of the 62ni 58ni 61ni 58ni and 60ni 58ni ratios vary linearly with mass difference and define isotope fractionation lines in common with terrestrial samples this implies that ni was derived from a single homogeneous reservoir while no 60ni anomaly is detected within the analytical uncertainties ni isotopic fractionation up to 0 45 per mass difference unit is observed the isotope compositions of ni and zn in chondrites are positively correlated we suggest that in ordinary chondrites exchange between solid phases in particular metal and silicates and vapor followed by mineral sorting during accretion are the main processes controlling these isotopic variations the positive correlation between ni and zn isotope compositions contrasts with a negative correlation between ni and zn and cu isotope compositions which when taken together do not favor a simple kinetic interpretation the observed transition element similarities between different groups of chondrites and iron meteorites are consistent with the genetic relationships inferred from oxygen isotopes iiia pallasites and iva l chondrites copper is an exception which we suggest may be related to separate processing of sulfides either in the vapor or during core formation

oxygen isotope studies of achondrites abstract oxygen isotope abundances provide a powerful tool for recognizing genetic relationships among meteorites among the differentiated achondrites three isotopic groups are recognized l snc mars 2 earth and moon and 3 hed howardites eucrites diogenites the hed group also contains the mesosiderites main group pallasites and silicates from iiiab irons the angrites may be marginally resolvable from the hed group within each of these groups internal geologic processes give rise to isotopic variations along a slope 1 2 fractionation line as is well known for terrestrial materials variations of 17o from one planet to another are inherited from the inhomogeneities in the solar nebula as illustrated by the isotopic compositions of chondrites and their constituents among the undifferentiated achondrites five isotopic groups are found 1 aubrites 2 winonaites and iab iiicd irons 3 brachinites 4 acapulcoites and lodranites and 5 ureilites the isotopic compositions of aubrites coincide with the earth and moon and also with the enstatite chondrites these bodies apparently were derived from a common reservoir the isotopic composition of which was established at the chondrule scale by nebular processes isotopic similarities between chondrites and achondrites are seen only for the following instances 1 enstatite chondrites and aubrites 2 h chondrites and he irons and 3 l or ll chondrites and iva irons the isotopic data also support the following genetic associations 1 winonaites and iab iiicd irons 2 acapulcoites and lodranites and 3 ureilites and dark inclusions of c3 chondrites an attempt to reconcile the whole planet isotopic compositions of earth mars and the eucrite parent body with mixing models of their chemical compositions failed it is not possible to satisfy both the chemical and isotopic compositions of the terrestrial planets using known primitive solar system components

isotopic fractionation of germanium in iron meteorites significance for nebular condensation core formation and impact processes abstract the siderophile and volatile nature of germanium allow ge isotopes to be used to investigate the early history of planetesimals by tracing processes of core formation and impact through the study of magmatic and non magmatic iron meteorites germanium isotopic compositions were measured using a hexapole collision cell mc icpms with an external reproducibility of 0 06 amu iron meteorites display heavy ge isotopic compositions 74ge 74ge 70ge 0 27 to 1 92 with respect to a jmc ge standard which contrast with the light isotopic compositions of the studied terrestrial materials aldrich ge standard 74ge 1 68 1 72 0 22 sphalerite 74ge 0 69 all the data fall on the theoretical mass fractionation line indicating no isotopic anomalies the samples from magmatic irons iia iib iiiab iic have relatively homogeneous ge isotopic compositions of 74ge 1 77 0 22 2 for a large range of ge contents 36 189 ppm in contrast the samples of the non magmatic groups iab iie have lower and more variable ge isotopic compositions with 74ge 1 15 0 20 for iab group ge 254 493 ppm 74ge 0 27 to 0 43 for iie old group ge 63 69 ppm and 74ge 1 40 0 22 for the watson sample ge 50 ppm from the iie young group except for iie samples no within group correlation of 74ge with ir or ge contents is observed demonstrating that fractional crystallization or crystal segregation do not fractionate ge isotopes the lack of inter group correlation between the ge isotopic composition of magmatic irons and ni content an indicator of redox processes suggests that if ge isotopes are fractionated by redox induced diffusion during metal silicate segregation isotopic equilibration towards the initial composition must also occur during isotopic exchange at high temperature thus the average 74ge value of 1 77 0 22 should be representative of their parent body precursors the lack of correlation between the ge isotopic composition and ge ni ratios and the high ge ni ratio of iia samples ge ni in ci chondrites may reflect the high proportion of metal condensates present in the parent body before metal silicate differentiation these metal phases would carry the ge isotopic signature of a ge enriched gas phase of the solar nebula for the iab non magmatic group the light and homogeneous ge isotopic composition may result from condensation from a 70ge enriched vapour subsequent to partial melting within a porous parent body the origin of the heating event 26al decay or impact on the surface of the chondritic body cannot be distinguished in contrast it can be demonstrated that impact events are involved in the formation of iie irons the negative 74ge ge correlation with increasing 74ge values from the old group to the watson sample of the young group would result from non rayleigh evaporation of 70ge during impact with gas melt back reaction the high 74ge of the watson sample young group is consistent with successive impacts on the surface of the iie parent body the very light ge isotopic composition of the old less impacted iie irons compared to other studied iron meteorites suggests a light ge isotopic composition for the iie parent body

iron isotope differences between earth moon mars and vesta as possible records of contrasted accretion mechanisms the iron isotope compositions of shergotty nakhla chassigny snc meteorites thought to come from mars eucrites and diogenites assumed to sample asteroid 4 vesta and rocks from the moon and earth have been measured using high precision plasma source mass spectrometry the means of eight samples from mars and nine samples from vesta are within error identical despite a range of rock types they are lighter by 0 1 in 57fe 54fe compared to the average of 13 terrestrial mantle derived rocks the latter value is identical within uncertainty with a previously published mean of 46 igneous rocks from the earth the average for 14 lunar basalts and highland plutonic rocks covering a broad spectrum of major element composition is heavier by 0 1 in 57fe 54fe relative to our estimate for the earth s mantle and therefore 0 2 heavier than the eucrites diogenites and snc meteorites however the data scatter somewhat and the apollo 15 green glass and apollo 17 orange glass are identical to samples from mars and vesta there is no clear relationship between petrological characteristics and fe isotope composition despite a wide spectrum of samples instead contrasted planetary isotopic signatures are clearly resolved statistically after evaluating alternative scenario it appears that the most plausible explanation for the heavier fe in the earth and moon is that both objects grew via processes that involved partial vaporisation leading to kinetic iron isotope fractionation followed by minor loss this is consistent with the theory in which the moon is thought to have originated from a giant impact between the proto earth and another planet combined with numerical simulations fe isotope data can offer the potential to provide constraints on the processes that occurred in planetary accretion

oxygen isotope relationships in iron meteorites iron meteorites with oxygen bearing phases can be classified in terms of their oxygen isotopic abundances these iron meteorite classes are isotopically similar to various stony meteorite classes which may indicate a common origin the group iab and iiicd irons may be related to the winonaites group iie irons may be related to h chondrites group iva irons may be related to l or ll chondrites

volatilization induced by impacts recorded in zn isotope composition of ureilites ureilites are ultramafic achondrites formed by igneous processes early in the history of the solar system ureilites are heavily depleted in volatile elements probably by evaporation at the surface of the ureilite parent body however the moderately volatile element zn is an exception and its abundance is similar to cl volatilization can fractionate isotopes in a mass dependent manner therefore comparing the isotope composition of volatile elements in ureilites may better constrain the physical conditions during ureilite formation and the mechanism of origin of the variation of zn content for this study we measured the zn isotopic composition of 11 ureilites with a large range of zn content the elemental abundance of zn is negatively correlated with delta zn 66 which may reflect that isotopic fractionation occurred by evaporation during the heating event on the ureilite parent body simple rayleigh distillation predicts isotopic fractionations much larger than what is actually observed therefore such a model cannot account for the observed zn isotope fractionation in ureilites we propose that the observed isotopic fractionation can be produced by evaporation in a diffusion limited regime in addition the isotopic composition of zn is shown to be correlated with the shock grade of the ureilites this may indicate that the heating events responsible for the depletion in light isotopes in some ureilites were impacts c 2010 elsevier b v all rights reserved

compositional trends among iid irons their possible formation from the p rich lower magma in a two layer core group iid is the fifth largest group of iron meteorites and the fourth largest magmatic group i e that formed by fractional crystallization we report neutron activation data for 19 of 21 known iid irons these confirm earlier studies showing that the group has a relatively limited range in ir concentrations a factor of 5 this limited range is not mainly due to incomplete sampling instead it seems to indicate low solid liquid distribution coefficients reflecting very low s contents of the parental magma the same explanation responsible for the limited range in group iva despite this similarity these two groups have very different volatile patterns group iva has very low abundances of the volatile elements ga sb and ge whereas in group iid ga and sb abundances are the highest known in a magmatic group of iron meteorites and ge abundances are the second highest after group iiab group iid appears to be the only large magmatic group having high volatile abundances but low s in the volatile depleted groups iva and ivb it is plausible that s was lost as a volatile from a chondritic precursor material because group iid seems to have experienced minimal loss of volatiles we suggest that s was lost as an early melt having a composition near that of the fe fes eutectic 315 mg g s when temperatures had risen 400 500 k higher p rich melts formed became gravitationally unstable and drained through the first melt to form an inner core that was parental to the iid irons as discussed by kracher a wasson j t 1982 the role of s in the evolution of the parental cores of the iron meteorites geochim cosmochim acta46 2419 2426 it is plausible that a metal rich inner core and a s rich outer core could coexist metastably because stratification near the interface permitted only diffusional mixing the initial liquidus temperature of the inner p rich core is estimated to have been 1740 k after 60 crystallization the increase in p and the decrease in temperature may have permitted immiscibility with the s rich outer core we have not recognized samples of the outer core

copper and nickel partitioning in iron meteorites trace element analyses using proton induced x ray emission pixe and synchrotron x ray fluorescence sxrf have been made on metal and troilite from 9 iron meteorites representing 5 geochemical groups nickel and copper distribution coefficients d troilitemetal vary by factors of 600 and 20 respectively correlate positively with kamacite band width and correlate negatively with bulk nickel content meteorites with bulk ni 1 while those with ni 10 have cu depleted troilite dcu 1 since magmatic evolution and partial melting will produce cu enriched troilite only the observation of cu depleted troilite in ni rich meteorites is evidence for subsolidus re equilibration a process which reduces dcu by transfer of cu to exsolving metal elemental redistribution may have played an important role in establishing the present chemical trends in iron meteorites

a petrologic study of the iab iron meteorites constraints on the formation of the iab winonaite parent body abstract we have studied iab iron meteorites and their silicate bearing inclusions to elucidate the origin of their parent body we have divided iab irons into five categories which best describe the inclusions and other properties of the irons these are 1 sulfide rich irons such as mundrabilla that contain a significant volume fraction of troilite with or without associated silicates 2 irons with non chondritic silicate inclusions such as basaltic inclusions in caddo county 3 irons with rounded troilite and or graphite inclusions sometimes containing embedded angular silicate inclusions 4 irons with angular silicate inclusions similar to those of the winonaites where silicates may comprise up to 40 vol of the rock and 5 irons with phosphate bearing inclusions such as the brianite bearing iab san cristobal similarities in mineralogy mineral and oxygen isotopic compositions suggest that iab irons and winonaites are almost certainly from a common parent body iiicd irons may also have originated on this parent body although evidence supporting this suggestion is less convincing previous models for the origin of iab irons propose that they are either products of selective impact melting in the megaregoliths of a chondritic asteroid or products of partial melting and fractional crystallization during formation of a sulfur rich core the former model suffers from the fact that impact is incapable of causing preferential melting of metal and sulfide on a large scale and pooling of these selective melts into sizable bodies the latter model does not readily explain the occurrence of often fragmentary angular silicate clasts in a metallic fe ni host we propose a new model for the origin of iab irons that incorporates aspects of both previous models we suggest that a chondritic possibly heterogeneous parent body was heated by a non collisional heat source which caused partial but not complete melting of the body after peak temperatures were reached and cooling and crystallization had begun a major impact catastrophically fragmented this body and the debris gravitationally reassembled scrambling the parent body lithologies we suggest that the impact caused extensive mixing of molten metallic fe ni and solid silicate material resulting in the formation of iab irons with silicate inclusions whereas winonaites represent metamorphosed rocks and partial melt residues of the precursor silicate lithologies high temperatures of some of the reassembled debris and deep burial resulted in continued fractionation and formation of the 2

sr stable isotope composition of earth the moon mars vesta and meteorites abstract high precision stable sr isotopic variations 88 sr 86 sr are reported in a variety of terrestrial samples martian and lunar meteorites hed undifferentiated primitive meteorites chondrules and refractory inclusions almost all the whole rock samples are isotopically indistinguishable at a 50 parts per million ppm level the exceptions are cv and co chondrites which are isotopically light and for which we believe that their isotopic composition is controlled by the proportion of refractory material five separated chondrules and one refractory inclusion from allende are isotopically light with 88 86 sr fractionations up to 1 73 whereas the matrix is enriched in the heavy isotopes 88 86 sr 0 66 the depletion in heavy isotopes observed in chondrules and refractory inclusions could be attributed to the condensation of a material already depleted in sr however in that case more than 60 of the original material would be unaccounted we propose instead that isotopic fractionation by electromagnetic sorting of ionized heavy sr from neutral sr in the early solar system for the origin of the fractionation observed in refractory inclusions and redistribution of sr by aqueous alteration for the origin of the fractionation observed in chondrules and matrix we conclude that cv and co chondrites are not the primary building blocks for earth and mars

coupled 63cu and 16o excesses in chondrites abstract recent developments in multiple collector magnetic sector icp ms inductively coupled plasma mass spectrometry have permitted the relative abundances of the two isotopes 63 and 65 of copper to be measured with unprecedented precision 40 ppm here we report cu isotopic variations among eight carbonaceous chondrites ccs from the ci cm co and cv groups and the presently ungrouped tagish lake and 10 ordinary chondrites ocs from the h l and ll groups the widest isotopic range of 0 8 per a m u is observed for the carbonaceous chondrites copper in carbonaceous chondrites becomes isotopically lighter with petrologic type in the order 1 to 3 but seems extremely homogeneous for each type the cu isotopic composition of tagish lake confirms its other characteristics that are intermediate between ci and cm in three of the groups ci cm co as well as for tagish lake 63 cu excess over terrestrial mantle abundances correlates well with 16 o excess for all four groups 63 cu excess also correlates remarkably well with elemental refractory volatile ratios e g ca mn for ordinary chondrites small differences exist between the h l and ll groups with cu becoming isotopically heavier in that order equilibrated and unequilibrated samples however exhibit the same cu isotopic signature within each group although the range of cu isotopic compositions in ordinary chondrites is smaller than in carbonaceous chondrites 63 cu excesses still correlate with 16 o excesses the observed trends of isotopic variation seem incompatible with a single stage fractionation process by either volatilization or low temperature metamorphism the correlations between 63 cu excesses and 16 o excesses suggest the presence of at least two and perhaps three isotopically distinct cu reservoirs in the early solar system 1 an earth like reservoir common to the ci and ll probably representing the main cu stock of the inner solar system 2 a reservoir present in all carbonaceous chondrites but most abundant in cv with large 63 cu and 16 o excesses this reservoir is probably hosted in refractory material and 3 possibly a third reservoir present in ordinary chondrites the oc trend may also be explained as a mixture of the first two cu reservoirs if its oxygen was first equilibrated with nebular gas the coexistence of 63 cu and 16 o excesses in the same component raises the issue of how volatile cu was preserved in refractory material a strong correlation between 63 cu 65 cu and ni cu ratios suggests that 63 cu excess may have originated as more refractory 63 ni t 1 2 100 yr upon irradiation of refractory grains by electromagnetic flares and particle bursts during the t tauri phase of the sun

distribution of granite and possible devonian sediments in part of the east shetland platform north sea seismic data on the east shetland platform at about 59 509n 1 129e image 4 7 6 6 km of folded possibly devonian sediments partly coincident with a geophysical anomaly previously interpreted as a granite pluton at shallow depth seismic and potential field data constrain the possible distribution of granite and well data indicate that shallow lithologidly variable basement rocks may surround the deep devonian basin geology series halibut bank and bressay bank sheets it shows the depth in metres below sea level to base cretaceous and the location of the northern end of seismicline fgs 64 illustrated in fig 3 good control on the seismic reflectors down to base jurassic is provided by well3 28 1 previous work although there is a positive gravity anomaly centred upon the western margin of the east shetland platform in block 9 3 donato tully 1982 showed that there is a negative residual gravity anomaly in this area of the east shetland platform when a regional gravity field based on a model of crustal thinning beneath the viking graben and the gravity effect of the known tertiary and mesozoic strata are subtracted from the observed gravity field they modelled this negative residual gravity anomaly as a granite batholith 40 km in diameter buried beneath approximately 2 km of sediments with its centre close to seismic line fgs 64 fig 2 donato tully 1982 also described an associated horseshoe shaped positive magnetic anomaly around the margins of the negative residual gravity anomaly fig 2 they drew an analogy with chevoit granite where similar

isotopic composition of zinc copper and iron in lunar samples abstract we determined by icp ms the concentrations and isotopic ratios of fe cu and zn in the ti rich lunar basalt 74275 in the lunar orange glass 74220 and in up to 10 lunar soils namely 14163 15231 64501 66041 68841 69941 70011 72501 75081 and 76501 two analyses of zinc in lunar basalt 74275 give 66 zn 0 17 and 0 75 values within the range of those measured in terrestrial basalts copper in lunar basalt 74275 has 65 cu 1 4 which is isotopically heavier than values observed in terrestrial basalts in the orange glass we measured 56 fe 0 24 65 cu 0 42 and 66 zn 3 6 these values of are more negative than those obtained for 74275 and for typical lunar basalts but for cu comparable to those observed in terrestrial sulfides and meteorites in lunar soils we found 0 11 56 fe 0 51 2 6 65 cu 4 5 and 2 2 66 zn 6 4 insofar as we can generalize from a small sample set s fe cu zn and cd show similar trends in isotopic fractionation on the moon lunar basalts have nearly terrestrial isotopic ratios relative to the lunar basalt 74275 the pyroclastic glass 74220 is enriched in the lighter isotopes of fe cu and zn and the soils are enriched in the heavier isotopes of fe cu and zn the patterns in the basalts are likely inherited from the source material the light isotope enrichments seen in the orange glass originated during lava fountaining or less probably during partial condensation of vapor and the heavy isotope enrichments in the lunar soils were likely created by a combination of processes that included micrometeorite vaporization and sputtering in the orange glass the light isotope enrichments relative to lunar basalts of zn are larger than those of cu if these enrichments reflect accurately the isotopic composition of the gas they suggest that cu is more volatile than zn in the liquid from which the gas derived a simple model built on the known flux of micrometeorites to the lunar surface and a published estimate that micrometeorites generate 10 times their own mass of vapor predicts heavy isotope enrichments comparable to those observed in soils but only if the regolith gardening rate is set at about one twentieth of the generally accepted value of 1 cm my this discrepancy may reflect the difference in the time constants for micrometeorite milling and decimeter scale gardening or the importance of sputtering

the cu isotopic signature of granites from the lachlan fold belt se australia abstract this contribution reports our preliminary work to determine cu isotope ratios for various granite rocks and examine the cu isotope systematics within granite suites a chemical procedure modified from marechal marechal c n telouk p and albarede f 1999 precise analysis of copper and zinc isotopic compositions by plasma source mass spectrometry chemical geology 156 1 4 251 273 was used to separate cu from rock matrix quantitative recovery 100 6 1 6 with a low total procedural blank 2 65 0 66 ng for cu has been achieved allowing cu isotopic measurements on samples with as little as 10 ppm cu the cu isotope ratios 65cu relative to nist srm 976 of 32 rock samples ranging from mafic to felsic compositions from 3 batholiths 2 i type 1 s type from the lachlan fold belt in southeastern australia vary from 0 46 to 1 51 most of them cluster around zero with mean values for the i type and s type granites of 0 03 0 15 and 0 03 0 42 2 sigma respectively these data together with cu isotope ratios of two loess samples provide preliminary evidence that the baseline cu isotopic composition of the crystalline part of upper continental crust is close to zero the tight clustering of cu isotope ratios of rocks from the i type suites suggests that high temperature magmatic processes do not produce significant cu isotope fractionation however two granites with abnormally heavy cu isotope signatures up to 1 51 appears to be the result of localized hydrothermal alteration measurable variation in cu isotopic composition of the s type granite may reflect isotopic heterogeneity in the sedimentary source region as a result of redox processes or may be due to hydrothermal overprinting thus cu isotope geochemistry may be a useful tracer for studying hydrothermal alteration and source heterogeneity of granitic rocks

a nonmagmatic origin of group iie iron meteorites abstract new neutron activation data on 10 elements in 12 iie and iie related irons lead to a reclassification of several irons seymchan and lonaconing are removed from iie and leshan added four iie members are designated iie an to call attention to some anomalous properties the eight normal iie members define element ni trends generally similar to those in the nonmagmatic group iab the small negative slopes on w ni and ir ni diagrams are strongly indicative of a nonmagmatic origin of the iie irons we propose that iie irons like iab irons originated as individual pools of impact produced melt in the near surface region of a chondritic parent body the positive as ni and au ni trends are the only evidence suggesting fractional crystallization but their slopes are lower than those in magmatic group iiiab and only slightly higher than those of cu and sb in iab we suggest that the s and c contents of the iie precursor materials were much lower than those of the iab precursors thus higher temperatures were required to generate enough metallic melt to segregate into pools these higher temperatures are also reflected in the nonchondritic compositions of the silicate inclusions

copper isotope systematics of the lucky strike rainbow and logatchev sea floor hydrothermal fields on the mid atlantic ridge in this paper we present the copper isotope signatures of black smoker sulfides massive sulfides and their alteration products and provide new insights into mineralization processes and applications of copper isotope geochemistry to sea floor hydrothermal systems on the mid atlantic ridge the hydrothermal systems studied include the lucky strike field at 37 17 n on a basaltic substrate and the rainbow and logatchev fields situated on ultramafic rock copper isotope variation in the hydrothermal precipitates was examined in conjunction with s isotopes and se and co concentrations the comparison between 65cu and se contents shows that subsurface precipitation of cu rich sulfides does not control significantly the 65cu values of the hydrothermal chimneys it appears that the major cause of copper isotope fractionation in hydrothermal systems up to 3 is the sea floor oxidation of primary copper sulfides enrichment in the heavy copper isotope can be explained by processes occurring at the sea floor such as hydrothermal reworking of previously altered sulfides by high temperature fluid massive sulfides characterized by negative 65cu values have undergone extensive recrystallization in these mineralogical assemblages isotopically heavy copper typical of altered sulfides has been leached and redeposited in the external zones or incorporated in hydrothermal fluids copper isotopes are therefore a promising tool for the study of supergene processes and the recycling of previously oxidized sulfides as well as a means of characterizing the degree of hydrothermal reworking of large sulfide deposits further studies of copper isotope fractionation under controlled laboratory experimental conditions are required to identify copper isotope fractionation during sulfide alteration in particular the possible biological mediation of copper isotope fractionation during sulfide oxidation may be an important direction for further studies

origin of sulfur and crustal recycling of copper in polymetallic cu au co bi u ag iron oxide dominated systems of the great bear magmatic zone nwt canada the great bear magmatic zone in northwest canada contains numerous polymetallic mineral occurrences prospects and deposits of the iron oxide copper gold deposit iocg family the mineralization is hosted by the treasure lake group and igneous rocks of the great bear arc and was deposited concomitantly with the arc magmatism ca 1 88 to 1 87 ga in situ 34s n 48 and 65cu n 79 analyses were carried out on ore related sulfides from a number of these systems the 34s values mainly vary between 0 and 5 consistent with derivation of sulfur from the mantle lower 34s values 7 7 to 1 4 from the sue dianne breccia may indicate so2 disproportionation of a magmatic hydrothermal fluid the 65cu values vary between 1 2 and 0 3 and are lower than the igneous 65cu range of values 0 0 0 27 the s and cu isotopic data are decoupled which suggests that cu and possibly some s was dissolved and remobilized from supracrustal rocks during early stages of alteration e g sodic alteration and then precipitated by lower temperature more oxidizing fluids e g ca fe k alteration a limited fluid inclusion dataset and 13c and 18o values are also presented the 18ofluid values are consistent with a magmatic origin or a host rock equilibrated meteoric water source whereas the 13cfluid values support a marine carbonate source combined the s and cu isotopic data indicate that while the emplacement of the great bear magmatic bodies may have driven fluid convection and may be the source of fluids and sulfur metals such as cu could have been recycled from crustal sources

the cu isotopic composition of iron meteorites abstract high precision cu isotopic compositions have been measured for the metal phase of 29 iron meteorites from various groups and for four terrestrial standards the data are reported as the 65cu permil deviation of the 65cu 63cu ratio relative to the nist srm 976 standard terrestrial mantle rocks have a very narrow range of variations and scatter around zero in contrast iron meteorites show 65cu approximately 2 3 variations different groups of iron meteorites have distinct 65cu values nonmagmatic iab iiicd iron meteorites have similar 65cu 0 03 0 08 and 0 12 0 10 respectively close to terrestrial values approximately 0 the other group of nonmagmatic irons iie is isotopically distinct 0 69 0 15 ivb is the iron meteorite group with the strongest elemental depletion in cu and samples in this group are enriched in the lighter isotope 65cu down to 2 26 evaporation should have produced an enrichment in 65cu over 63cu 65cu 0 and can therefore be ruled out as a mechanism for volatile loss in ivb meteorites in silicate bearing iron meteorites 17o correlates with 65cu this correlation between nonmass dependent and mass dependent parameters suggests that the cu isotopic composition of iron meteorites has not been modified by planetary differentiation to a large extent therefore cu isotopic ratios can be used to confirm genetic links cu isotopes thus confirm genetic relationships between groups of iron meteorites e g iab and iiicd iiie and iiiab and between iron meteorites and chondrites e g iie and h chondrites several genetic connections between iron meteorites groups are confirmed by cu isotopes e g iab and iiicd iiie and iiiab and between iron meteorites and chondrites e g iie and h chondrites

copper isotope ratios in magmatic and hydrothermal ore forming environments multi collector inductively coupled plasma mass spectrometry now provides for precise and accurate measurements of cu isotope ratios copper minerals prepared by direct dissolution with and without chromatographic purification yield identical cu isotope ratios within analytic precision of about 0 04x 1r cu isotope ratios have been measured for copper minerals from worldwide magmatic and hydrothermal copper deposits and for several weathered deposits natural variations in d65cu values relative to nbs976 range over 9x chalcopyrite samples from mafic intrusions lie within a narrow range of about 1 5x and most cluster tightly between 0 10xand 0 20x this range lies within the broader black smoker chalcopyrite and iron meteorite ranges and possibly represents a bulk mantle cu isotope ratio most values for hydrothermal native copper from the michigan native copper district also show a narrow range just larger than 0 1xand suggest a common homogeneous source for cu in this large hydrothermal system later copper sulfide and arsenide minerals from this district range to values more than 2x lower than native copper ratios for chalcopyrite and bornite from moderate to high temperature porphyry skarn and replacement deposits as a group and within individual deposits exhibit a broad range of values variations of nearly 1xare observed over distances on the order of 1 m in some cases these variations may result from multiple mineralization events or copper remobilization during retrograde or later hydrothermal activity fractionations between chalcopyrite and bornite where they occur in the same sample or in related samples cluster near 0 4x suggesting equilibrium cu isotope fractionation between them at moderate temperatures in addition weathering of hydrothermal copper minerals produces a wide range of values in secondary copper phases in the supergene environment cuprite typically has higher values than associated native copper therefore redox states appear to exert a significant control over fractionation at low temperatures significant questions remain to be answered before the source of copper in hydrothermal environments can be fully addressed source reservoir cu ratios need to be determined and chemical and physical factors that control cu isotope fractionation must be quantitatively defined d 2003 elsevier b v all rights reserved

chronology of pleistocene sedimentary cycles in the carmel coastal plain of israel abstract the eastern mediterranean coastal plain of israel is composed mainly of loam and sand and gravel of pleistocene to holocene age supplemented by an upper pleistocene beach rock horizon indicating an alternation of marine coastal and continental environments owing to the complexity of the numerous exposures of aeolianites kurkar and soils hamra in the elongated ridges along the coastal plain it is difficult to set up a reliable stratigraphy a systematic luminescence dating study was carried out on loose sand kurkar and hamra deposits in the coastal plain between netanya and haifa in this study 33 samples were investigated from key sections along the carmel coast the chronological results are in excellent agreement with the geological estimates five periods of sand accumulation and kurkar formation can be distinguished at about 140 130 90 and around 60 ka and between 60 and 50 ka hamra formation took place between 140 and 130 ka around 80 65 and 60 ka and between 20 and 12 ka the beach rock is correlated with the sea level maximum during ois 5e the luminescence dating results indicate that neither kurkar nor hamra formation correlates with glacial and interglacial periods of the northern hemisphere however the chronological succession of these climate related cycles is in good agreement with marine and terrestrial archives in the eastern mediterranean

the iab iron meteorite complex a group five subgroups numerous grouplets closely related mainly formed by crystal segregation in rapidly cooling melts abstract we present new data for iron meteorites that are members of group iab or are closely related to this large group and we have also reevaluated some of our earlier data for these irons in the past it was not possible to distinguish iab and iiicd irons on the basis of their positions on element ni diagrams but we now show that plotting the new and revised data yields six sets of compact fields on element au diagrams each set corresponding to a compositional group the largest set includes the majority 70 of irons previously designated ia we christened this set the iab main group the remaining five sets we designate subgroups within the iab complex three of these subgroups have au contents similar to the main group and form parallel trends on most element ni diagrams the groups originally designated iiic and iiid are two of these subgroups they are now well resolved from each other and from the main group the other low au subgroup has ni contents just above the main group two other iab subgroups have appreciably higher au contents than the main group and show weaker compositional links to it we have named these five subgroups on the basis of their au and ni contents the three subgroups having au contents similar to the main group are the low au l subgroups the two others the high au h subgroups the ni contents are designated high h medium m or low l thus the old group iiid is now the slh subgroup the old group iiic is the slm subgroup in addition eight irons assigned to two grouplets plot between sll and slm on most element au diagrams a large number 27 of related irons plot outside these compact fields but nonetheless appear to be sufficiently related to also be included in the iab complex many of these irons contain coarse silicates having similar properties most are roughly chondritic in composition the mafic silicates show evidence of reduction during metamorphism in each case the silicate o isotopic composition is within the carbonaceous chondrite range 17o 0 3 in all but four cases these are within the so called iab range 0 30 17o 0 68 fine silicates appear to be ubiquitous in the main group and low au subgroups this requires that viscosities in the parental melt reached high values before buoyancy could separate these the well defined main group trends on element au diagrams provide constraints for evaluating possible models we find the evidence to be most consistent with a crystal segregation model in which solid and melt are essentially at equilibrium the main arguments against the main group having formed by fractional crystallization are a the small range in ir and b the evidence for rapid crystallization and a high cooling rate through the iron stability field the evidence for the latter are the small sizes of the iron crystals parental to the widmanstatten pattern and the limited thermal effects recorded in the silicates including retention of albitic plagioclase and abundant primordial rare gases in contrast crystal segregation in a cooling metallic melt and related processes such as incomplete melting and melt migration can produce the observed trends in the main group we infer that this melt was formed by impact heating on a porous chondritic body and that the melt was initially hotter than the combined mix of silicates and metal in the local region the melt cooled rapidly by heat conduction into the cooler surroundings mainly silicates we suggest that the close compositional relationships between the main group and the low au subgroups are the result of similar processes instigated by independent impact events that occurred either at separate locations on the same asteroid or on separate but compositionally similar asteroids

nickel isotope heterogeneity in the early solar system article i nfo ni of bulk iron and chondritic meteorites carbonaceous chondrites have variable positive e 62 ni 0 05 to 0 25 whereas ordinary chondrites have negative e 62 ni 0 04 to 0 09 the ni isotope compositions of iron meteorites overlap with those of chondrites and define an array with negative slope in the e 60 ni versus e 62 ni diagram the ni isotope compositions of the volatile depleted group ivb irons are similar to those of the refractory co cv carbonaceous chondrites whereas the other common magmatic iron groups have ni isotope compositions similar to ordinary chondrites only enstatite chondrites have identical ni isotope compositions to earth and so appear to represent the most appropriate terrestrial building material differences in e 62 ni reflect distinct nucleosynthetic components in precursor solids that have been variably mixed but some of the e 60 ni variability could reflect a radiogenic component from the decay of 60 fe comparison of the e 60 ni of iron and chondritic meteorites with the same e 62 ni allows us to place upper limits on the 60 fe 56 fe of planetesimals during core segregation we estimate that carbonaceous