nucleosynthetic osmium isotope anomalies in acid leachates of the murchison meteorite abstract we present osmium isotopic results obtained by sequential leaching of the murchison meteorite which reveal the existence of very large internal anomalies of nucleosynthetic origin e 184 os from 108 to 460 e 186 os from 14 1 to 12 6 e 188 os from 2 6 to 1 6 e 190 os from 1 7 to 1 1 despite these large variations the isotopic composition of the total leachable osmium weighted average of the leachates is close to that of bulk chondrites this is consistent with efficient large scale mixing of os isotopic anomalies in the protosolar nebula the os isotopic anomalies are correlated and can be explained by the variable contributions of components derived from the s r and p processes of nucleosynthesis surprisingly much of the s process rich osmium is released by relatively mild leaching suggesting the existence of an easily leachable s process rich presolar phase or alternatively of a chemically resistant r process rich phase taken together with previous evidence for a highly insoluble s process rich carrier such as sic these results argue for the presence of several presolar phases with anomalous nucleosynthetic compositions in the murchison meteorite the s process composition of os released by mild leaching diverges slightly from that released by aggressive digestion techniques perhaps suggesting that the presolar phases attacked by these differing procedures condensed in different stellar environments the correlation between e 190 os and e 188 os can be used to constrain the s process 190 os 188 os ratio to be 1 275 0 043 such a ratio can be reproduced in a nuclear reaction network for a macs value for 190 os of 200 22 mbarn at 30 kev more generally these results can help refine predictions of the s process in the os mass region which can be used in turn to constrain the amount of cosmoradiogenic 187 os in the solar system and hence the age of the galaxy we also present evidence for extensive internal variation of 184 os abundances in the murchison meteorite a steep anti correlation is observed between e 184 os and e 188 os since 184 os is formed uniquely by the p process this anti correlation cannot be explained by variable addition or subtraction of s process os to average solar system material instead this suggests that p process rich presolar grains e g supernova condensates may be present in meteorites in sufficient quantities to influence the os isotopic compositions of the leachates nevertheless 184 os is a low abundance isotope and we cannot exclude the possibility that the measured anomalies for this isotope reflect unappreciated analytical artifacts

stratigraphy composition and form of the deccan basalts western ghats india in the western ghats between latitudes 18 20 n and 19 15 n 7000 km2 of deccan basalt have been mapped with the primary objective of establishing a flow stratigraphy as a guide to the volcanic history of the flood basalts using over 70 measured vertical sections major and trace element analyses of nearly 1200 samples and rare earth and87sr 86sr determinations for over 60 samples we divide the basalt into three subgroups and ten formations in this paper we describe the seven principal formations in the area and the most prominent individual flows

nucleosynthetic isotope variations of siderophile and chalcophile elements in the solar system numerous investigations have been devoted to understanding how the materials that contributed to the solar system formed were incorporated into the precursor molecular cloud and the protoplanetary disk and ultimately evolved into the building blocks of planetesimals and planets chemical and isotopic analyses of extraterrestrial materials have played a central role in decoding the signatures of individual processes that led to their formation among the elements studied the siderophile and chalcophile elements are crucial for considering a range of formational and evolutionary processes consequently over the past 60 years considerable effort has been focused on the development of abundance and isotopic analyses of these elements in terrestrial and extraterrestrial materials e g shirey and walker 1995 birck et al 1997 reisberg and meisel 2002 meisel and horan 2016 this volume in this review we consider nucleosynthetic isotopic variability of siderophile and chalcophile elements in meteorites chapter 4 provides a review for siderophile and chalcophile elements in planetary materials in general day et al 2016 this volume in many cases such variability is denoted as an isotopic anomaly however the term can be ambiguous because several pre and post solar system formation processes can lead to variability of isotopic compositions as recorded in meteorites here we strictly define the term isotopic anomaly as referring to an isotopic deviation from the terrestrial composition resulting from the incorporation of varying proportions of elements with diverse nucleosynthetic origins into a meteorite component or parent body the term will not be used here to refer to isotopic variations that result from mass dependent isotopic fractionation radioactive decay in the solar system or spallation effects based on astronomical observations and physical modelling the formation of the solar system has generally been thought to have initiated by the collapse of a dense molecular cloud

the meteoritical bulletin no 85 2001 september meteoritical bulletin no 85 lists information for 1376 newly classified meteorites comprising 658 from antarctica 409 from africa 265 from asia 262 of which are from oman 31 from north america 7 from south america 3 from australia and 3 from europe information is provided for 11 falls dergaon dunbogan gujba independence itqiy moravka oued el hadjar sayama sologne valera and worden noteworthy non antarctic specimens include 5 martian meteorites dar al gani 876 northwest africa 480 and 817 and sayh al uhaymir 051 and 094 6 lunar meteorites dhofar 081 280 and 287 and northwest africa 479 482 and 773 an ungrouped enstatite rich meteorite itqiy a bencubbin like meteorite gujba 9 iron meteorites and a wide variety of other interesting stony meteorites including ch ck cm co cr cv r enstatite and unequilibrated ordinary chondrites primitive achondrites hed achondrites and ureilites

intrinsic w nucleosynthetic isotope variations in carbonaceous chondrites implications for w nucleosynthesis and nebular vs parent body processing of presolar materials abstract the progressive dissolution of the carbonaceous chondrites orgueil ci1 murchison cm2 and allende cv3 with acids of increasing strength reveals correlated w isotope variations ranging from 3 5 e182w and 6 5 e183w in the initial leachate acetic acid to 60 e182w and 40 e183w in the leachate residue the observed variations are readily explained by variable mixing of s process depleted and s process enriched components one w s process carrier is sic however the observed anomaly patterns and mass balance considerations require at least on additional s process carrier possibly a silicate or sulfide the data reveal well defined correlations which provide a test for s process nucleosynthesis models the correlations demonstrate that current models need to be revised and highlight the need for more precise w isotope data of sic grains furthermore the correlations provide a mean to disentangle nucleosynthetic and radiogenic contributions to 182w e182wcorrected e182wmeasured 1 41 0 05 e183wmeasured e182wcorrected e182wmeasured 0 12 0 06 e184wmeasured a prerequisite for the successful application of the hf w chronometer to samples with nucleosynthetic anomalies the overall magnitude of the w isotope variations decreases in the order ci1 cm2 cv3 this can be interpreted as the progressive thermal destruction of an initially homogeneous mixture of presolar grains by parent body processing however not only the magnitude but also the w anomaly patterns of the three chondrites are different in particular leach step 2 that employs nitric acid reveals a s deficit signature for murchison but a s excess for orgueil and allende this could be the result of redistribution of anomalous w into a new phase by parent body alteration or the fingerprint of dust processing in the solar nebula given that the thermal and aqueous alteration of murchison is between the ci and cv3 chondrites parent body processing is probably not the sole cause for creating the different pattern small scale nebular redistribution of anomalous w may have played a role as well similar nebular processes possibly acted differently on specific carrier phases and elements resulting in the diverse nucleosynthetic signatures observed in planetary materials today

evidence of fissiogenic cs estimated from ba isotopic deviations in an oklo natural reactor zone abstract isotopic studies of many elements from the uranium ore natural nuclear reactors at oklo provide useful information on the migration of radioactive nuclides the fissiogenic isotopic composition of ba is particularly interesting as it is an important indication in the search for fissiogenic cs in this report we detail the detection of remarkable isotopic deviations of ba in the oklo samples and estimate the geochemical behaviour of fissiogenic cs from excess ba isotopes six samples systematically collected from borehole sf84 zone 10 at the oklo uranium mine have been analyzed isotopic deviations of ba indicate the existence of fissiogenic cs and ba a good correlation between the elemental abundance of cs and isotopic abundances of excess 135 ba and 137 ba suggests that fissiogenic 135 ba and 137 ba behaved as cs rather than ba

the cosmic molybdenum ruthenium isotope correlation dauphas et al astrophys j 565 2002 640 644 reported molybdenum isotopic anomalies in differentiated and bulk primitive meteorites it is shown here that these isotopic anomalies correlate with one another in exactly the way expected from nucleosynthesis theory if different regions of the nebula received different contributions of s process matter synthesized in lowmass agb stars furthermore when bulk measurements are grouped by meteorite class the molybdenum isotopic anomalies correlate with the ruthenium isotopic anomalies recently reported by chen et al lunar planet sci xxxiv 2003 1789 again indicating a heterogeneous distribution of s process matter as molybdenum is only moderately siderophile most of the molybdenum presently in the mantle was delivered before the completion of core formation in contrast because ruthenium is highly siderophile nearly all of the mantle ruthenium was delivered by a late veneer after the end of core formation thus the fact the silicate earth lies on the mo ru cosmic correlation supports the idea that the earth accreted homogeneously stated otherwise the feeding zone of the earth did not change drastically with time as both the bulk of the earth and the late veneer accreted from material from the same mo ru isotopic reservoir d 2004 elsevier b v all rights reserved

mineralogy and geochemistry of the peterborough member oxford clay formation jurassic uk element fractionation during mudrock sedimentation x ray diffraction electron microprobe and sem analyses show that the peterborough member of the oxford clay formation is composed mainly of quartz and illite with lesser amounts of chlorite kaolinite k feldspar plagioclase very small amounts of anatase and apatite and variable amounts of calcite and subordinate siderite the geochemistry including major and a range of trace elements are used with the mineralogy to demonstrate the existence of several distinct components which have contributed to variations within the peterborough member these components are 1 quartz zircon and possibly other heavy minerals and k feldspars 2 carbonates 3 phosphatic material 4 organic material and 5 clays geochemical comparisons are made with various average shales demonstrating abnormally low ba cu co mn na and mg in the peterborough member it is suggested that the current mineral assemblage is mostly detrital material with little diagenetic alteration the demonstration of fractionation between hydrodynamically heavy and light grains even in an apparently fine grained sediment such as the oxford clay has disturbing consequences for geochemical studies of sediment source areas where small numbers of small samples are employed

heck and heckle seamounts northeast pacific ocean high extrusion rates of primitive and highly depleted mid ocean ridge basalt on off ridge seamounts we analyzed petrographically and chemically basalt from eight dredge hauls from the heck and heckle seamounts northeast pacific ocean major elements were determined for mineral glass and whole rock samples and trace and rare earth elements were determined for glass and whole rock samples the dredge hauls included hyaloclastites and fragments from sheet flows and pillows the clinkery fragments are interpreted to be deformed sheet flow tops characteristic of high effusion rates the hyaloclastites recovered are reworked deposits as indicated by the wide compositional range of the glass shards abundance of clay and calcite matrix and bedding most rocks are aphyric but the analyzed plagioclase and olivine phenocrysts and microcrysts are equilibrium compositions and show minor compositional zonation up to 7 5 an 1 fo calculated quenching temperatures range from 1228 o to 1216oc decrease with decreasing mg and are consistent with phase equilibria the seamount lavas are primitive mg 68 7 59 5 and restricted in compositional range la ce 0 65 0 77 the basalts are equivalent to highly depleted mid ocean ridge basalt la sm 0 29 0 41 and are at the depleted end of the range in composition of basalts from east pacific seamounts they are more depleted than basalts from the adjacent west valley spreading axis the lavas can be produced by partial melting of a depleted source mineralogical and geochemical evidence is consistent with rapid ascent of the heck and heckle lavas through oceanic crust with little residence time in magma chambers lavas of the heck and heckle seamount chains have a limited range of incompatible element ratios whereas the adjacent west valley segment of the juan de fuca ridge is highly heterogeneous in contrast lavas from the east pacific near ridge seamounts exhibit a wider range of incompatible element ratios than do the adjacent east pacific rise basalts on the west valley segment magma supply is less robust associated with lower spreading rates compared to the east pacific rise at 10on in contrast at fast spreading centers robust melting produces a mixed mantle signature in axial lavas while suppressed melting at the seamounts reveals the heterogeneities we suggest that at some spreading ridges more fertile portions of the mantle are preferentially melted such that the outwelled portions of the mantle tapped by the seamounts are more depleted

contributors to chromium isotope variation of meteorites we report the results of a comprehensive high precision survey of the cr isotopic compositions of primitive chondrites along with some differentiated meteorites to ensure complete dissolution of our samples they were first fused with lithium borate tetraborate at 1050 1000 c relative to the nist cr standard srm 3112a carbonaceous chondrites exhibit excesses in 54cr 52cr from 0 4 to 1 6e 1e 1 part in 10 000 and ordinary chondrites display a common 54cr 52cr deficit of 0 4e analyses of acid digestion residues of chondrites show that carbonaceous and ordinary chondrites share a common 54cr enriched carrier which is characterized by a large excess in 54cr 52cr up to 200e associated with a very small deficit in 53cr 52cr 2e we did not find 54cr anomalies in either bulk enstatite chondrites or in leachates of their acid digestion residues this either requires that the enstatite chondrite parent bodies did not incorporate the 54cr anomaly carrier phase during their accretion or the phase was destroyed by parent body metamorphism chromium in the terrestrial rocks and lunar samples analyzed here show no deviation from the nist srm 3112a cr standard the eucrite and martian meteorites studied exhibit small deficits in 54cr 52cr the 54cr 52cr variations among different meteorite classes suggest that there was a spatial and or temporal heterogeneity in the distribution of a 54cr rich component in the inner solar system we confirm the correlated excesses in 54cr 52cr and 53cr 52cr for bulk carbonaceous chondrites but the new data yield a steeper slope 6 6 than that reported in shukolyukov and lugmair 2006 the correlated excesses may affect the use of the mn cr chronometer in carbonaceous chondrites we could not confirm the bulk carbonaceous chondrite mn cr isochron reported by shukolyukov and lugmair 2006 and moynier et al 2007 mostly because we find much smaller total variations in e53cr 0 2 all bulk chondrites have small e53cr excesses up to 0 3 relative to the earth most likely reflecting the sub chondritic mn cr ratio of the earth the e53cr variations in chondrites do seem to grossly correlate with mn cr and yield an initial solar system 53mn 55mn value of 5 4 2 4 10 6 corresponding to an absolute age of 4566 4 2 2 ma nuclear interactions with cosmic rays result in coupled excesses in e54cr and e53cr with a 4 1 ratio in phases with high fe cr these are most dramatically demonstrated in the iron meteorite carbo showing excesses in e54cr of up to 140e these new results show that the mn cr chronometer should be used with caution in samples minerals with high fe cr and long cosmic ray exposure ages

analysis of controls on downstream fining along three gravel bed rivers in the band e golestan drainage basin ne iran abstract in many gravel bed rivers grain size changes exponentially downstream and is mainly related to selective deposition of clasts on the streambed according to size shape and density and abrasion crushing grinding splitting chipping cracking and sandblasting during transport most studies on the cause of downstream fining in rivers emphasize hydraulic sorting or selective transport as the dominant fining mechanism the band e golestan drainage basin with a surface area of about 320 km 2 is located southwest of mashhad in northeast iran this catchment s area consists of three subbasins mayan dehbar and jaghargh that flow toward northeast connecting to the kashafrud river grain size variation and causes for downstream fining were studied at 57 sites compositionally gravels in the study area consist of phyllite slate and a small amount of quartzite consequently these sediments are poorly sorted positively skewed and mainly platykurtic upstream most of the boulders are phyllites while in the downstream part slate makes up the framework of the gravel grain size distributions are weakly bimodality in the upstream and become strongly polymodal downstream based on our study the main factors in downstream fining of grain size in the study area are hydraulic sorting and abrasion

morphological evolution and dynamics of a large sand braid bar jamuna river bangladesh the initiation and evolution of a kilometre scale sand braid bar was monitored during a 28 month survey period from 1993 to 1996 in one of the world s largest braided rivers the jamuna river bangladesh repeated bathymetric surveys through two monsoon flood seasons combined with bar top surveys during exposure of the bar at low flow provide the most detailed chronology of braid bar growth yet compiled for a large sand bed river during rising and peak flow of the 1994 monsoon flood a 1 5 km long 0 5 km wide 12 m high symmetrical mid channel bar was deposited in the centre of a major channel downstream of a zone of flow convergence and significant bank erosion initial deposition and growth of the bar core were probably caused by amalgamation of dunes that are present in the jamuna channels at all flow stages bar top aggradation continued through downstream migration of an accretionary dune front a 3 m high angle of repose slipface that was composed of amalgamated 0 5 to 1 m high dunes at waning and low flow the mid channel bar widened by up to 1 km through the lateral accretion of dunes onto the margins of the initial bar core a low velocity zone in the sheltered wake region of the bar tail led to the accumulation of substantial volumes of silts and clays during the rising and peak flows of the next monsoon flood the mid channel bar extended its bar tail by up to 1 5 km as one of the anabranches became dominant and flow was deflected across the bar tail accretion at the bar tail generated a lobate transverse bar front with a 10 m high angle of repose avalanche face emergence of several smaller bars along this depositional front produced an overall reach morphology that more closely resembled an alternate bar rather than several mid channel bars the conversion of a mid channel bar to an alternate bar is contrary to many previous descriptions of the braiding process

chemical evolution of basalts from 23 n along the mid atlantic ridge evidence from melt inclusions the chemical compositions of melt inclusions in a primitive and an evolved basalt recovered from the mid atlantic ridge south of the kane fracture zone 23 24 n are determined the melt inclusions are primitive in composition 0 633 0 747 molar mg mg fe2 1 01 0 68 wt tio2 and are comparable to other proposed parental magmas except in having higher al2o3 and lower cao the primitive melt inclusion compositions indicate that the most primitive magmas erupted in this region are not near primary magma compositions olivine and plagioclase microphenocrysts are close to exchange equilibrium with their respective basalt glasses whose compositions are displaced toward olivine from 1 atm three phase saturation the most primitive melt inclusion compositions are close to exchange equilibrium with the anorthitic cores of zoned plagioclases an78 3 an83 1 the hosts for the melt inclusions in plagioclase and with olivines more forsteritic fo89 fo91 than the olivine microphenocrysts the hosts for the melt inclusions in olivine xenocrystic olivine analyzed is fo89 but contains no melt inclusions these observations indicate that olivines have exchanged components with the melt after melt inclusion entrapment whereas plagioclase compositions have remained the same since melt inclusion entrapment common denominator element ratio diagrams and oxide versus oxide variation diagrams show that the melt inclusion compositions which represent liquids higher along the liquid line of descent are related to the glass compositions by the fractionation of olivine plagioclase and clinopyroxene absent from the mincral assemblage probably occurring at elevated pressures a model is proposed whereby clinopyroxene segregates from the melt at elevated pressures to account for its absence in the erupted lavas that have the chemical imprint of clinopyroxene fractionation zoned plagioclases in the erupted lavas are thought to be survivors of decompressional melting during magma ascent since similar primitive melt inclusions occur in olivine microphenocrysts and in the cores of zoned plagioclases any model must account for all phases present

nucleosynthetic nd isotope anomalies in primitive enstatite chondrites abstract we carried out stepwise dissolutions of four primitive enstatite chondrites ec belonging to the eh subgroup large nd isotope anomalies are found in the most refractory phases dissolved using strong acids residues are characterized by excesses in 142nd and deficits in 145nd 148nd and 150nd isotopes the nd anomalies measured in the alha77295 residue are even greater than those measured in the murchison carbonaceous chondrite cc using a similar analytical technique qin et al 2011 once corrected for a common sm nd evolution the 142nd excess in the alha77295 residue is equal to 700 ppm relative to the terrestrial standard value the nd isotope patterns measured in ec and cc residues can be adjusted to coincide by adding a small amount of an s process rich carrier phase such as sic and 0 075 is required to fit the alha7795 residue small isotope differences still persist between these residues even if they can be considered similar within error in enstatite chondrites residues have a deficit in 150nd similar to or smaller than that measured in 148nd whereas in sic extracted from carbonaceous chondrites or in whole rock the deficit in 150nd is always greater than that in 148nd moreover in a binary 142nd 148nd diagram the best fit lines obtained for leachates and residues from carbonaceous chondrites and enstatite chondrites have slightly different slopes for the same 148nd 144nd ratio the anomalous component in an enstatite chondrite has a higher 142nd 144nd ratio compared to carbonaceous chondrites a feature already observed at the whole rock scale our results suggest that different chondrite groups sample different reservoirs of presolar grains formed in different environments assuming that the carrier of this anomalous component measured in residues of enstatite chondrites are sic our results may suggest that different meteorite parent bodies sample reservoirs of presolar sic formed in different stellar environments this could explain why alha77295 the sample which is the most enriched in presolar grains has a bulk 142nd isotope composition similar to the terrestrial value further investigation of enstatite chondrites is needed to test whether the isotope composition of the most refractory phases is similar to that measured in carbonaceous chondrites and in particular the 144sm that is a p process isotope only finally this study highlights the difficulty of interpreting the 142nd excess in terrestrial samples relative to chondrites since incomplete mixing of nucleosynthetic material in the solar nebula creates significant 142nd variation as shown by alha77295

the redistribution of copper during low grade metamorphism of the karmutsen volcanics vancouver island british columbia the karmutsen volcanics exposed on northern vancouver island are a sequence of chemically uniform tholeiitic basalts with a thickness greater than 5 km within the karmutsen a stratigraphic succession from close packed pillow lava to breccias to flows resulted from a transition from deep marine to subaerial eruption of the parent magmas all lithologies have undergone prehnite pumpellyite facies burial metamorphism which substantially redistributed cu within the flows but not within the subaqueously erupted breccias or pillow lavas there is no evidence for substantial metamorphic redistribution of cr ni ti zn and mn which vary only slightly in the three stratigraphic units like other transition elements cu abundance is confined to a restricted range 120 200 ppm in the subaqueously erupted rocks however in the flows cu is very unevenly distributed and is generally less abundant than in the subaqueously erupted rocks posteruptive redistribution of copper is evidenced by the fact that the present distribution of copper in the flows can be related to posteruptive mineral assemblages lowest copper abundances are in red flows rich in hematite which probably resulted from deuteric alteration highest copper abundances and most native copper occurrences are in green pumpellyite rich flows the initial copper content of the flows is not known for certain but is likely to have been similar to that of the subaqueously erupted rocks which are in other respects chemically similar to the flows it is believed that high f o 2 in low grade metamorphic fluids led to the dissolution of chalcopyrite and sporadic precipitation of native copper in association with amygdular prehnite intense pumpellyitization of some flows locally lowered the f o 2 and possibly also raised the ph of the metamorphic solutions thus favoring deposition of copper in these flows copper was not redistributed in the subaqueously erupted units because these lacked the appropriate deuteric fe ti oxide assemblages

trace element mobility during low grade metamorphism and silicification of basaltic rocks from saint john new brunswick upper carboniferous basaltic lavas from saint john new brunswick were metamorphosed under prehnite pumpellyite conditions and some were also affected by extensive silicification silicification le

archean metavolcanics from the rouyn noranda district abitibi greenstone belt quebec 2 mobility of trace elements and petrogenetic constraints qualitative evaluation of altered mafic pillows from the rouyn noranda district of the abitibi metavolcanic belt reveals that for low grade metamorphism the high field strength elements hfs zr y ti and the rare earth elements ree are immobile however where alteration is extreme the ree elements are leached and redeposited by carbonate rich and k rich metasomatic fluids whilst zr y and zr ti remain unchanged rubidium ba and to a lesser extent sr are mobile at all levels of alteration however provided certain filters are applied the original geochemical values of the lavas for the alkaline elements the hfs elements and the ree can be defined the geochemical variations thus identified for the volcanic series of the rouyn noranda district are ascribed to a combination of contamination and fractional crystallization of a primitive tholeiitic magma

controls on spatial and temporal variations in sand delivery to salmonid spawning riffles fine sediment infiltration into gravel interstices is known to be detrimental to incubating salmonid embryos infiltration into spawning riffles can show large spatial variations at the scale of a morphological unit and over time with significant implications for embryo survival furthermore some process based infiltration studies and incubation to emergence models assume that fines are delivered to redds via suspension rather than bedload this process based twelve month study examined spatial patterns of predominantly sand infiltration into gravels in an upland trout stream using infiltration baskets an assessment of rouse numbers for infiltrated sand indicated that it was transported predominantly as bedload at flow peaks clear temporal and spatial patterns existed with highest rates of infiltration strongly associated with higher discharges r2 0 7 p 0 05 seasonal variations in the delivery of different grain sizes were also a feature with enhanced contributions of 0 5 2 mm sediment during elevated winter flows and 0 125 0 5 mm sediment during spring and summer the latter potentially harmful to the later stages of embryo incubation clear spatial patterns were also evident across riffles with highest rates of infiltration tending to occur in areas of lower relative roughness the areas competent to transport sand for longer periods incubation to emergence models should take into consideration spatial patterns of fine sediment dynamics at the pool riffle scale to improve prediction

modelling of igneous fractionation and other processes using pearce diagrams geochemical data can be quantitatively modelled by means of pearce diagrams these are graphs of a z vs b z where a b and z are compositional abundances e g wt sio2 wt mgo and ppm la and z has the additional property of having constant absolute abundance in the terminology of igneous petrology z the common denominator variable could be an incompatible element the numerators a and b may be complex algebraic combinations of elements or even cipw normative abundances the utility of pearce diagrams lies in the fact that slopes of data distributions equal the bulk a b ratio of minerals lost or gained from a suite of cogenetic rocks there is no distortion because these plots correct for data closure terms of the form ai z0 zi where z0 is the abundance in a reference sample remove the scaling to ai caused by the abundance of a particular choice of z subtraction of these terms for different samples e g ai z0 zi aj z0 zj quantifies mineral losses and gains mathematical analysis shows that limited compatibility of the denominator variable is permitted a bulk partition value d of 0 1 introduces an error of only 10 in values of ai z0 zi and 10 in slope angle on pearce diagrams over a crystallization interval of 50 for d 0 01 the error is minimal for a crystallization interval over 90

ratio correlations and major element mobility in altered basalts and komatiites attempts have been made in the recent literature to constrain major element mobility in altered basalts and komatiites using the molecular proportion ratio mpr diagrams developed by t h pearce 1970 the method involves ratioing the molecular proportions of two oxides against a third oxide and presenting the results as an oxide oxide ratio plot the transformation appears to clean up scatter plots with low correlations and produces highly correlated ratio plots these plots have been taken to be indicative of igneous fractionation trends and thus of minimal bulk chemical change during alteration there are however inherent statistical problems in ratio correlation which have received much attention in the mathematical literature this paper explains the implications of enhanced correlations for work on altered rocks using ratio plots and suggests that extreme caution must be exercised in the interpretation of mpr diagrams

nucleosynthetic components of the early solar system inferred from ba isotopic compositions in carbonaceous chondrites abstract the ba isotopic composition of primitive meteorites is one of the more useful tracers to study nucleosynthetic processes in the early solar system because the seven stable ba isotopes consist of p r and s process nucleosynthetic components and possible decay products from presently extinct 135 cs ba isotopic analyses were performed on acid leachates from five carbonaceous chondrites murchison cm2 sayama cm2 allende cv3 isuna co3 and maralinga ck4 and one basaltic achondrite juvinas eucrite the ba isotopic data of acid treatment fractions in carbonaceous chondrites suggest the presence of independent nucleosynthetic components for s and r processes in the solar system the isotopic patterns from the acid residual fractions of two cm2 meteorites murchison and sayama show an enrichment of s process isotopes which is similar to that of presolar sic grains on the other hand their acid leachates have an excess of r process components among the ba isotopes in many cases of carbonaceous chondrites other than cm meteorites the excess of r process isotopes is too small for a detailed discussion about the nucleosynthetic contribution this may be interpreted as metamorphic destruction of presolar grains in meteorite matrices associated with petrographic type meteorites juvinas shows no isotopic anomalies of ba because the isotopic record in the early solar system was reset possibly by magmatic processes in the parent body

geochemical test for branching decay of 176lu abstract two different groups of values for the 176lu decay constant have been determined by recent high precision experiments the 176lu values of 1 86 1 87 10 11 a 1 were determined by age comparisons using terrestrial minerals of proterozoic and late archean age whereas values of 1 94 10 11 a 1 were determined in age comparison studies of meteorites a possible branched decay of 176lu could be the cause of this discrepancy the decay of 176lu to 176yb was detected in the early studies of radioactivity of 176lu with reported values of in the total 176lu ranging from less than 0 03 to 0 67 if the decay fraction is close to the upper limit of the reported values it can explain the 4 6 difference between the apparent 176lu values to get a reliable estimate for the decay of 176lu we have measured yb isotopic composition in 2 7 ga zircons with lu ybn chondrite normalized ratios of 1 40 and 1 45 in 1 0 ga xenotime with lu ybn 1 23 using yb from the 28 4 ma fish canyon tuff fct zircon and titanite as the modern reference value multiple analyses yielded the following weighted mean values 2 for the 176yb 174yb ratio 0 4022134 0 0000017 for the fct zircon and titanite 0 4022134 0 0000019 for the 1 0 ga xenotime and 0 4022124 0 0000033 for the 2 7 ga zircons these data yield 0 005 0 015 2 and establish an upper limit of 0 9 of total decays for the decay branch branching decay can therefore be eliminated as the cause of the discrepancy in 176lu decay constant estimates we discuss other possible causes of the 176lu terrestrial vs meteorite discrepancy

major element evolution of basaltic magmas a comparison of the information in cmas and alfe projections basalt petrologists disagree as to whether the commonly used projection forsterite diopside silica in the system cmas cao mgo al2o3 sio2 can adequately resolve differences in basaltic glass compositions for purposes of petrogenetic modelling here we suggest than an analogous plot the aluminium factor diagram alfe of nesbitt and cramer 1981 has greater diagnostic value than fo di sil a plot of molar al2o2 cao na2o k2o feo mgo vs feo feo mgo it produces more coherent patterns both for experimental basalt glasses and for natural lavas it is like fo di sil a projection through plagioclase but has the advantage that it monitors changes in fe fe mg in melts and associated crystalline phases and is particularly useful in assessing the timing of clinopyroxene crystallization in a suite of lavas the diagram owes its greater resolving power to the fact that the computation of its coordinates is less sensitive to analytical uncertainty than for fo di sil in the latter diagram normative quartz is calculated as a residual and thus manifests the uncertainties in all the major elements

iib trioctahedral chlorite from the barberton greenstone belt crystal structure and rock composition constraints with implications to geothermometry iib trioctahedral chlorite in the barberton greenstone belt bgb metavolcanic rocks was formed during pervasive greenschist metamorphism the chem ical composition of the chlorite is highly variable with the fe fe mg ratio ranging from 0 12 to 0 8 among 53 samples the chemical variation of the chlorite results from the chemical diversity of the host rock especially the mgo content of the rock but major details of the variation pattern of the chlorite are due to the crystal structure of the chlorite all major cation abundances in the chlorite are strongly correlated with each other sil icon increases with mg and decreases with fe while aliv and alvi decrease with mg and increase with fe2 a complex exchange vector explains over 90 of the chlorite compositional variation mg4sife2 3alvi 1 aliv 1 which has 3 parts fe mg substitution coupled with one part tschermakite substitution this ratio is required to maintain the charge and site balances and the dimensional fit between the tetrahedral and octahedral sheets the subtle change in al substitution in chlorite implies that alvi is preferentially ordered in the m 4 site and about 84 of the alvi present is in the m 4 sites when they are nearly filled with alvi based on 47 analyzed chlorite bearing rock samples chlorite chl composition is strongly correlated with the mgo content of the host rock calculated correlation coefficients are 0 91 for sio2chl mgorock 0 87 for al2o3chl mgorock 0 89 for mgochl mgorock and 0 85 for feochl mgorock only weak correlations have been found between chlorite oxides and other oxides of rock between same oxides in chlorite and rock sio2 0 67 al2o3 0 59 feo 0 41 however mgochl is saturated at about 36 wt in rocks that have mgo above 22 wt the mgochl is about 5 wt when the host rock approaches 0 wt of mgo this implies that mg substituting into the chlorite is approximately limited to 1 5 9 2 mg atoms per formula unit and 1 0 3 2 aliv chlorite geothermometers can not be applied to all bgb samples however the empirical chlorite geothermometer based on aliv of chlorite may be applicable to chlorites formed under metamorphic conditions because it can predict the chemical composition of the chlorite from basaltic and dacitic samples in this study an estimated temperature of about 320 c for the greenschist metamorphism of the greenstone belt through this geothermometer is consistent with that obtained by other geothermometers

primary fractionation and secondary alteration within an archean ultramafic lava flow fifteen samples across a 4 m thick komatiite flow from the val d or region in the southeast portion of the abitibi greenstone belt have been analysed for major oxides and trace elements including the rare earth elements ree the flow has been subjected to low grade regional metamorphism virtually all primary mineralogy olivine and clinopyroxene has been obliterated although primary textures are well preserved compositional differences between the upper spinifex textured portion and the underlying massive portion of the flow are largely consistent with the primary fractionation of approximately 30 olivine with a composition close to fo92

nucleosynthetic strontium isotope anomalies in carbonaceous chondrites abstract precise sr isotopic compositions in samples from sequential acid leaching experiments have been determined for three carbonaceous chondrites allende murchison and tagish lake together with those in the bulk aliquots of these meteorites the chondritic acid leachates and residues were characterized by sr isotope anomalies with variable 84sr values 106 relative deviation from a standard material ranging from 120 to 4700 ppm documenting multiple nucleosynthetic sources within a single meteorite in addition the 84sr patterns across leaching samples for individual chondrites differed from one another the highest 84sr values were observed for leaching step 3 hcl h2o 75 c for allende and murchison likely because of the incorporation of calcium and aluminum rich inclusions cais in contrast extremely low 84sr values were observed in the later fractions steps 6 and 7 for murchison and tagish lake suggesting the existence of s process enriched presolar sic grains derived from agb stars a 84sr 54cr diagram was prepared with the cais and bulk aliquots of carbonaceous chondrites and other meteorites noncarbonaceous that were plotted separately however they still formed a global positive correlation cais presented the highest 84sr and 54cr values whereas carbonaceous chondrites and noncarbonaceous meteorites had intermediate and the lowest 84sr and 54cr values respectively the positive trend was interpreted as resulting from global thermal processing in which sublimation of high 84sr and 54cr carriers generated the excess 84sr and 54cr signatures in cais while noncarbonaceous planetesimals accreted from materials that underwent significant thermal processing and thus had relatively low 84sr and 54cr values apart from the global trend the carbonaceous chondrites and noncarbonaceous meteorites both exhibited intrinsic variations that highlight an isotopic dichotomy similar to that observed in other isotope combinations e g 54cr 50ti 54cr 17o a plausible scenario for creation of the intrinsic variations involves local thermal processing e g flash heating for chondrule formation caused by additional selective destruction of presolar grains differently than that caused by global thermal processing the existence of such a global positive trend and local variations for two meteorite groups suggests a complicated dynamic history for the dust grains with respect to thermal processing material transportation and mixing in the protoplanetary disk prior to planetesimal formation

selective sorting and abrasion of river gravel i theory most gravel rivers show a tendency for characteristic grain size to decrease in the downstream direction over scales of tens or hundreds of kilometers it has been surmised that this downstream fining is due to some combination of selective sorting by which finer grains are preferentially transported downstream and abrasion by which individual particles are reduced in size here a framework for the simultaneous treatment of both phenomena is developed the analysis is restricted to bed load transport of gravel only abrasion due to binary collisions between moving bed load and stationary bed particles is considered the formulation includes the possibility of differential basin uplift and subsidence due to tectonism and mixtures of rock types with differing coefficients of abrasion the formulation of selective sorting is based on the concept of hiding as applied to a surface based bed load transport relation abrasion is first treated in terms of a lagrangian formulation for individual grains and t

archean mafic metavolcanics from the rouyn noranda district abitibi greenstone belt quebec 1 mobility of the major elements reply in a suite of archean mafic pillows from the rouyn noranda region of quebec s abitibi greenstone belt including both tholeiitic and calc alkaline varieties spanning the prehnite pumpellyite to upper greenschist metamorphic facies three types of alteration can be defined i chlorite epidote actinolite ii chlorite epidote and iii chlorite sericite the number of mineral phases decreases as a result of progressive hydration from type i to type iii alteration albitization resulting from substitution of in calcic plagioclase is highly variable in type i alteration but in types ii and iii the plagioclase is totally albitized and in some cases silicified chloritization is closely linked to increasing hydration and ca leaching with mgo and feo substituting for cao in ferromagnesian minerals calcium was mobilized and carried by solutions as evidenced by the variable concentration of epidote at the margins of pillows this calcium leaching generated an excess of al2o3 with respect to the combine

isotopic search for live 135cs in the early solar system and possibility of 135cs 135ba chronometer abstract here we report the isotopic excess of 135 ba studied from ba isotopic measurements of acid leachates of allende calcium aluminum rich inclusions cais and two primitive chondrites beardsley h5 and zag h6 clasts from the excess 135 ba abundances of cais after subtraction of the r process nucleosynthetic component in a model dependent manner a value for 135 cs 133 cs 4 8 0 8 10 4 is proposed as the initial ratio in the early solar system a correlation between excess 135 ba abundances and cs ba ratios observed in the beardsley and the zag meteorites reveals the possible existence of primordial 135 cs in the two meteorite parent bodies on the assumption of two cases for 135 cs 133 cs initial in the early solar system the 135 cs 135 ba isochron suggests that primitive aqueous alteration in the beardsley and zag meteorite bodies occurred at 8 2 11 9 ma and 13 9 17 6 ma after cai formation respectively our results are apparently consistent with previously reported data from pb pb model age determinations and 53 mn 53 cr chronometry for chondrites this is the first report of isotopic excess of 135 ba in meteorites which may relate to live 135 cs in the early solar system and the 135 cs 135 ba chronological application

non nucleosynthetic heterogeneity in non radiogenic stable hf isotopes implications for early solar system chronology abstract nucleosynthetic heterogeneity and secondary neutron capture reactions may have important implications for 176 lu 176 hf chronology and modelling of early planetary evolution so far the relevance of these phenomena for the lu hf system has not been explored we therefore have analyzed the non radiogenic stable hf isotope composition 177 hf 178 hf 179 hf and 180 hf of meteorites meteorite components and terrestrial rock samples to identify nucleosynthetic or neutron capture induced variations all analyzed chondrites have uniform 178 hf 177 hf and 180 hf 177 hf values that cannot be resolved from the average terrestrial composition thus there is no evidence for nucleosynthetic heterogeneity in chondrites or earth and these data support the use of a chondritic reference value for the hf isotope composition of the bulk silicate earth this homogeneity contrasts with nucleosynthetic heterogeneities found in lighter elements and provides evidence for a separate synthesis of light and heavy r process nuclei various mesosiderite samples and one lunar meteorite display coupled 178 hf 177 hf and 180 hf 177 hf anomalies that are associated with neutron capture induced deviations in 149 sm 154 sm and 150 sm 154 sm however the analyzed chondrites and an aubrite show only sm isotope anomalies and these are the result of neutron capture the hf isotope anomalies require substantial capture of epithermal neutrons whereas sm anomalies result primarily from thermal neutron capture the non radiogenic stable isotope composition of hf is thus a suitable monitor for epithermal neutron capture reactions the data reveal distinct neutron energy spectra mesosiderites are characterized by high epithermal to thermal neutron fluence ratios whereas the remaining samples show low epithermal to thermal ratios secondary neutron capture may significantly increase the measured 176 hf 177 hf in whole rock meteorite samples without causing a resolvable shift in 176 lu 177 hf thus it could potentially induce scatter in lu hf whole rock isochrons and produce spurious initial 176 hf 177 hf values however the slopes of internal i e mineral isochrons cannot be increased significantly by secondary neutron capture this process therefore cannot account for the unrealistically old 176 lu 176 hf ages e g 4 75 ga of some meteorites

53mn 53cr dating of fayalite formation in the cv3 chondrite mokoia evidence for asteroidal alteration fayalite grains in chondrules in the oxidized aqueously altered cv3 chondrite mokoia have large excesses of radiogenic chromium 53 these excesses indicate the in situ decay of short lived manganese 53 half life 3 7 million years and define an initial53mn 55mn ratio of 2 32 0 18 10 6 this ratio is comparable to values for carbonates in ci and cm chondrites and for several classes of differentiated meteorites mokoia fayalites formed 7 to 16 million years after allende calcium aluminum rich inclusions during hydrothermal activity on a geologically active asteroid after chondritic components had ceased forming in the solar nebula

abundance distribution and origin of 60fe in the solar protoplanetary disk abstract meteorites contain relict decay products of short lived radionuclides that were present in the protoplanetary disk when asteroids and planets formed several studies reported a high abundance of 60fe t1 2 2 62 0 04 myr in chondrites 60fe 56fe 6 10 7 suggesting that planetary materials incorporated fresh products of stellar nucleosynthesis ejected by one or several massive stars that exploded in the vicinity of the newborn sun we measured 58fe 54fe and 60ni 58ni isotope ratios in whole rocks and constituents of differentiated achondrites ureilites aubrites heds and angrites unequilibrated ordinary chondrites semarkona ll3 0 and nwa 5717 ungrouped petrologic type 3 05 metal rich carbonaceous chondrite gujba cba and several other meteorites cv el h ll chondrites iiiab iva ivb iron meteorites we derive from these measurements a much lower initial 60fe 56fe ratio of 11 5 2 6 10 9 and conclude that 60fe was homogeneously distributed among planetary bodies this low ratio is consistent with derivation of 60fe from galactic background 60fe 56fe 2 8 10 7 in the interstellar medium from ray observations and can be reconciled with high 26al 27al 5 10 5 in chondrites if solar material was contaminated through winds by outer layers of one or several massive stars e g a wolf rayet star rich in 26al and poor in 60fe we present the first chronological application of the 60fe 60ni decay system to establish the time of core formation on vesta at 3 7 1 7 2 5 myr after condensation of calcium aluminum rich inclusions cais

analysis of petrologic hypotheses with pearce element ratios pearce element ratios can test whether the members of a rock suite are comagmatic and can illustrate the causes of chemical diversity in comagmatic suites comagmatic rocks have constant ratios for elements conserved in the system during changes that led to the chemical diversity in basaltic systems the incompatible elements ti k and p are often conserved the slope of the trend on a pearce element ratio diagram is sensitive to the stoichiometry of the crystallizing and segregating phases a judicious choice of ratios as axes for the diagram provides a signature for the phases involved and estimates of their compositions in basaltic rocks diagrams with ti k vs p k can provide a test of the comagmatic hypothesis diagrams with 0 5 mg fe k vs si k have trends that are distinct for each comagmatic suite and different mineral assemblage different suites are distinguished by the intercepts in diagrams whereas mineral assemblages are recognized by the slopes of the trends for example if olivine is the sole crystallizing and segregating phase the trend will have a slope of 1 diagrams with 2ca na k vs al k distinguish plagioclase from augite assemblages and in conjunction with 0 5 mg fe k diagrams unravel the crystallization sequences of suites that have suffered three phase crystallization and segregation analyses from the uwekahuna laccolith kilauea the 1955 and 1967 68 eruptions of kilauea diamond craters volcanic field oregon and experimental data on morb glasses provide illustrations of the interpretations that can be obtained from pearce element ratios

origin of differentiated lavas at kilauea volcano hawaii implications from the 1955 eruption kilauea s 1955 eruption was the first major eruption longer than 2 days on its east rift zone in 115 years it lasted 88 days during which 108 106 m3 of lava was erupted along a discontinuous 15 km long system of fissures a wide compositional range of lavas was erupted including the most differentiated lavas 5 0 wt mgo from a historic kilauea eruption lavas from the first half of the eruption are strongly differentiated 5 0 5 7 wt mgo later lavas are weakly to moderately differentiated 6 2 6 7 wt mgo previous studies using only major element compositions invoked either crystal fractionation macdonald and eaton 1964 or magma mixing wright and fiske 1971 as models to explain the wide compositional variation in the lavas to further evaluate these models detailed petrographic mineralogical and whole rock major and trace element xrf analyses were made of the 1955 lavas plagioclase and clinopyroxene in the early and late lavas show no petrographic evidence for magma mixing olivines from both the early and late lavas show minor resorption which is typical of tholeiitic lavas with low mgo contents core to rim microprobe analyses across olivine augite and plagioclase mineral grains give no evidence of disequilibrium features related to mixing instead plots of an ab vs distance from the core d and fo vs d 4 5 generated essentially linear trends indicative of simple crystal fractionation least squares mass balance calculations for major and trace element data using observed mineral compositions yield excellent results for crystal fractionation sum of residuals squared 0 01 for major elements and 5 for trace elements magma mixing produced less satisfactory results especially for cr furthermore trace element plots of zr vs sr cr and a12o3 generate curved trends indicative of crystal fractionation processes there is no evidence that mixing occurred in the 1955 lavas instead the data are best explained by crystal fractionation involving a reservoir that extends at least 15 km along kilauea s east rift zone a dike was intruded into the rift zone from the summit reservoir eight days after the eruption started instead of causing magma mixing the dike probably acted as a hydraulic plunger forcing more of the stored magma to be erupted