fine grained spinel rich inclusions from the reduced cv chondrite efremovka ii oxygen isotopic compositions oxygen isotopes have been measured by ion microprobe in individual minerals spinel al ti diopside melilite and anorthite within four relatively unaltered fine grained spinel rich ca alrich inclusions cais from the reduced cv chondrite efremovka spinel is uniformly 16o rich 17o 20 in all four cais al ti diopside is similarly 16o rich in all but one cai where it has smaller 16o excesses 15 17o 10 anorthite and melilite vary widely in composition from 16orich to 16o poor 22 17o 5 two of the cais are known to have group ii volatilityfractionated rare earth element patterns which is typical of this variety of cai and which suggests formation by condensation the association of such trace element patterns with 16o enrichment in these cais suggests that they formed by gas solid condensation from an 16o rich gas they subsequently experienced thermal processing in an 16o poor reservoir resulting in partial oxygen isotope exchange within each inclusion oxygen isotope variations from mineral to mineral are consistent with solid state oxygen self diffusion at the grain to grain scale but such a model is not consistent with isotopic variations at a larger scale in two of the cais the spatial association of 16o depletions with both elevated fe contents in spinel and the presence of nepheline suggests that latestage iron alkali metasomatism played some role in modifying the isotopic patterns in some cais one of the cais is a compound object consisting of a coarse grained melilite rich type a lithology joined to a fine grained spinel rich one melilite and anorthite in the fine grained portion are mainly 16o rich whereas melilite in the type a portion ranges from 16o rich to 16o poor suggesting that oxygen isotope exchange predated the joining together of the two parts and that both 16o rich and 16o poor gaseous reservoirs existed simultaneously in the early solar nebula

crystal growth and disequilibrium distribution of oxygen isotopes in an igneous ca al rich inclusion from the allende carbonaceous chondrite abstract ts34 is a type b1 ca al rich inclusion cai from the allende cv3 chondrite consisting of spinel melilite ti al rich clinopyroxene fassaite and minor anorthite in an igneous texture oxygen and magnesium isotopic compositions were measured by secondary ion mass spectrometry in spots of known chemical composition in all major minerals in ts34 using the sequence of formation from dynamic crystallization experiments and from chemical compositions of melilite and fassaite the oxygen isotopic evolution of the cai melt was established oxygen isotopic compositions of the constituent minerals plot along the carbonaceous chondrite anhydrous mineral line the spinel grains are uniformly 16o rich 17o 22 7 1 7 2sd while the melilite grains are uniformly 16o poor 17o 2 8 1 8 irrespective of their akermanite content and thus their relative time of crystallization the fassaite crystals exhibit growth zoning overprinting poorly developed sector zoning they generally grow from ti rich to ti poor compositions the fassaite crystals also show continuous variations in 17o along the inferred directions of crystal growth from 16o poor 17o 3 to 16o rich 17o 23 covering the full range of oxygen isotopic compositions observed in ts34 the early crystallized 16o poor fassaite and the melilite are in oxygen isotope equilibrium and formed simultaneously the correlation of oxygen isotopic compositions with ti content in the fassaite imply that the oxygen isotopic composition of the cai melt evolved from 16o poor to 16o rich during fassaite crystallization presumably due to oxygen isotope exchange with a surrounding 16o rich nebular gas formation of spinel the liquidus phase in melts of this composition predates crystallization of all other phases so its 16o rich composition is a relic of an earlier stage anorthite exhibits oxygen isotopic compositions between 17o 2 and 9 within the range of those of fassaite indicating co crystallization of these two minerals during the earliest to intermediate stage of fassaite growth the melilite and fassaite yield an 26al 26mg mineral isochron with an initial value of 26al 27al 0 5 003 0 075 10 5 corresponding to a relative age of 0 05 0 02 myr from the canonical al mg age of cais these data demonstrate that both 16o rich and 16o poor reservoirs existed in the solar nebula at least 0 05 myr after the birth of the solar system

chronological study of oxygen isotope composition for the solar protoplanetary disk recorded in a fluffy type a cai from vigarano abstract fluffy type a ca al rich inclusions cais containing reversely zoned melilite crystals are suggested to be aggregates of direct condensates from solar nebular gas we conducted an investigation of 26 al 26 mg systematics of a fluffy type a cai from vigarano named v2 01 with known oxygen isotopic distributions of reversely zoned melilite crystals we also conducted oxygen isotope measurements of coexisting minerals two of six reversely zoned melilite crystals show continuous variations in magnesium isotopic composition with 25 mg decreasing along the inferred direction of crystal growth which supports the idea that they originated through condensation petrography suggests that the constituent minerals of v2 01 formed in the following order first spinel and fassaite enclosed by melilite then reversely zoned melilite crystals and spinel and diopside in the wark lovering rim the spinel enclosed by melilite has 16 o rich compositions 17 o 24 and on an al mg evolutionary diagram plots along model isochron with an initial value of 26 al 27 al 0 5 6 0 2 10 5 the fassaite enclosed by melilite crystals shows variable oxygen isotopic compositions 17 o 12 and 17 and plots on an isochron with 26 al 27 al 0 5 6 0 2 10 5 the oxygen isotopic compositions of reversely zoned melilite showed continuous variations in 17 o along the inferred direction of crystal growth suggesting that surrounding nebular gas during the formation of the reversely zoned melilite changed from 16 o poor 17 o values larger than 10 to 16 o rich 17 o 25 the six reversely zoned melilite crystals show indistinguishable initial 26 al 27 al values with an average 26 al 27 al 0 of 4 7 0 3 10 5 which is clearly distinguishable from the value of enclosed spinel and fassaite indicating a younger formation age than the enclosed spinel and fassaite the spinel and diopside from the wark lovering rim show 16 o rich compositions 17 o 23 with 26 al 27 al 0 4 5 0 4 10 5 the values of 26 al 27 al 0 are consistent with the formation sequence inferred from petrography the formation period for the v2 01 cai is estimated to be 0 18 0 07 myr from the difference in initial 26 al 27 al values these data suggest that the oxygen isotopic composition of solar nebular gas surrounding the cai changed from 16 o rich to 16 o poor and back to 16 o rich during the first 0 2 myr of solar system formation

evidence for extraneous origin of a magnesiowustite metal fremdling from the vigarano cv3 chondrite a calcium aluminum rich inclusion cai from the vigarano cv3 chondrite 477b contains three types of fremdlinge and pt rich phases 1 feni blebs 2 sub micron pt rich fe bearing nuggets and 3 pt rich fe bearing veins many of the feni fremdlinge contain grains of mgfe oxide periclase wustite series ion microprobe measurements of an unusually large 5 m per70 wu30 grain reveal isotopically light mg 4 3 amu in contrast to heavy mg 4 7 amu in adjacent spinel and melilite the oxygen isotopic composition of the periclase wustite is 17osmow 9 1 18osmow 12 5 distinct from isotopically normal oxygen in the surrounding melilite and the large 16o enrichments 16oexcess 52 in adjacent spinel the petrographic mineral chemical and isotopic properties of the magnesiowustite grain argue against in situ formation in the cai and indicate an extraneous origin from a reservoir depleted in silicon this reservoir probably had normal oxygen in contrast to the 16o rich reservoir from which the cai formed and isotopically light magnesium

a study of mg and k isotopes in allende cais implications to the time scale for the multiple heating processes the measurements of magnesium and potassium isotopic compositions of refractory minerals in allende calcium aluminum rich inclusions cais 7r 19 1 hn3 1 and egg3 were taken by secondary ion mass spectrometry sims the 7r 19 1 contains 16 o rich and 16 o poor melilite grains and define a single isochron corresponding to an initial 26 al 27 al ratio of 6 6 1 3 10 5 the al mg isochron o isotope measurements and petrography of melilite in 7r 19 1 indicate that 16 o poor melilite crystallized within 0 4 myr after crystallization of 16 o rich melilite suggesting that oxygen isotopic composition of the cai forming region changed from 16 o rich to 16 o poor within this time interval the 16 o poor melilite is highly depleted in k compared to the adjacent 16 o rich melilite indicating evaporation during remelting of 7r 19 1 we determined the isochron for 41 ca 41 k isotopic systematics in egg3 pyroxene with 4 1 2 0 10 9 2 as an initial ratio of 41 ca 40 ca which is at least two times smaller than the previous result sahijipal et al 2000 the ratio of 41 ca 40 ca in the egg3 pyroxene grain agrees within error with the value obtained by hutcheon et al 1984 no evidence for the presence of 41 k excess decay product of a short lived radionuclide 41 ca was found in 7r 19 1 and hn3 1 we infer that the cai had at least an order of magnitude lower than canonical 41 ca 40 ca ratio at the time of the cai formation

closed system oxygen isotope redistribution in igneous cais upon spinel dissolution abstract in several calcium aluminum rich inclusions cais from the cv3 chondrites allende and efremovka representative of the most common igneous cai types type a type b and fractionated with unknown nuclear isotopic anomalies fun the relationship between 16o excesses and tio2 content in pyroxene indicates that the latter commonly begins to crystallize with a near terrestrial 16o poor composition and becomes 16o enriched during crystallization reaching a near solar composition mass balance calculations were performed to investigate the contribution of spinel to this 16o enrichment it is found that a back reaction of early crystallized 16o rich spinel with a silicate partial melt having undergone a 16o depletion is consistent with the o isotopic evolution of cai minerals during magmatic crystallization dissolution of spinel explains the o isotopic composition 16o excess and extent of mass fractionation of pyroxene as well as that of primary anorthite dmisteinbergite and possibly that of the last melilite crystallizing immediately before pyroxene it requires that igneous cais behaved as closed systems relative to oxygen from nebular gas during a significant fraction of their cooling history contrary to the common assumption that cai partial melts constantly equilibrated with gas the mineralogical control on o isotopes in igneous cais is thus simply explained by a single 16o depletion during magmatic crystallization this 16o depletion occurred in an early stage of the thermal history after the crystallization of spinel i e in the temperature range for melilite crystallization partial melting and did not require multiple complex or late isotope exchange more experimental work is however required to deduce the protoplanetary disk conditions associated with this 16o depletion

resetting errorchrons and the meaning of canonical cai initial 26al 27al values abstract the difference between the precise mc icpms analyses of bulk calcium aluminum rich inclusion cai fragments e g jacobsen et al 2008 and supra canonical values obtained by micro analytical techniques e g laser ablation mc icpms young et al 2005 and sims taylor et al 2005 at face value seems to be problematic and therefore leads many to dismiss claims of the solar system 26al 27al 0 greater than 5 10 5 as spurious here we use mass balance calculations to quantify the importance of open system isotopic exchange during cai evolution and show that in situ supra canonical in situ canonical and bulk canonical measurements can all exist for an individual cai the calculations describe mechanisms of isotopic exchange that may have occurred early 100 s ka and late 1 5 ma in the solar nebula and much later 10 s ma on parent body planetesimals a range of possible modal mineralogies is modeled in order to populate the compositional space defined by in situ and bulk cai measurements in support of these simulated data we describe in situ measurements of 27al 24mg 25mg 24mg and 26mg 24mg obtained by la mc icpms comprising core to rim traverses across three cv3 cais the cais exhibit distinctive mg isotopic zoning profiles and varying abundances of daughter products of the short lived nuclide 26al that are consistent with varying amounts of open system isotope exchange

a petrologic and ion microprobe study of a vigarano type b refractory inclusion evolution by multiple stages of alteration and melting abstract usnm 1623 8 is a type b vigarano inclusion 6 mm in diameter consisting of melilite ak12 72 fassaite 17 23 a12o3 5 17 tio2 anorthite and spinel secondary alteration is negligible and consists of diopside and sparse nepheline melilite is normally zoned and contains up to 0 35 wt na2o higher than generally seen in melilite from other refractory inclusions a strong correlation between akermanite content and na2o in 1623 8 melilite suggests that the na was present during igneous crystallization rather than introduced later by diffusion anorthite in 1623 8 is coarse grained but commonly has an irregular border with neighboring melilite crystals many spinel grains enclosed within anorthite have selvages of melilite around them which in places are continuous with melilite exterior to the anorthite the anorthite appears to be replacing melilite ion microprobe analyses of anorthite in 1623 8 show that there is no detectable excess 26mg in nine anorthite crystals that have 27 al 24 mg as high as 970 implying an upper limit of 26 al 27 al 0 7 one crystal was found that has excess 26mg consistent with 26 al 27 al 0 3 10 6 melilite in the outer portion of the inclusion 27 al 24 mg 2 7 11 5 contains excess 26mg that considered together with spinel and pyroxene defines an isochron consistent with the canonical early solar system value of 26 al 27 al 0 4 5 10 5 melilite near an anorthite 27 al 24 mg 1 6 5 9 has 26mg values in excess of those predicted from 26 al 27 al 0 4 5 10 5 presumably caused by redistribution of radiogenic 26mg from adjacent anorthite the high na2o inferred to have been present in the melt suggests that the precursor solids were na bearing such as for example refractory material having an allende like overprint of feldspathoid bearing secondary alteration the melting event must have been brief in order that not all of the na was vaporized during melting the isotopic composition of the anorthite relative to melilite indicates a subsequent much later after the decay of most or all 26a1 episode of partial melting or solidstate recrystallization that did not affect the al rich melilite but reset most of the anorthite and some mg rich melilite near anorthite because the inclusion is both rimmed and slightly altered this late resetting event appears to have been a nebular one an assumption of homogeneously distributed 26a1 in the regions of the nebula where the inclusion formed and was later modified implies a several millionyear interval between condensation of the precursors and final melting of 1623 8

26al 26mg chronology and oxygen isotope distributions of multiple melting for a type c cai from allende abstract disequilibrium oxygen isotopic distributions of ca al rich inclusions cais correspond to multiple melting events in the solar nebula 26al 26mg systematics may be applicable for age differences among such melting events we have carried out a coordinated study of detailed petrographic observations and in situ oxygen and magnesium isotope measurements for a type c cai ek1 04 2 from the allende cv3 meteorite to determine the melting events and their ages the cai consists mainly of spinel anorthite olivine and pyroxene and has a core and mantle structure petrography of the core suggests that the crystallization sequence of the core minerals is from spinel anorthite olivine and to pyroxene the mantle has the same mineral assemblage as the core and shows incomplete melting and solidification textures oxygen isotopic compositions of the minerals are distributed along the carbonaceous chondrite anhydrous mineral ccam line 18o 44 to 9 which indicates to preserve a chemical disequilibrium status in the cai spinel shows a 16o rich signature 18o 43 while anorthite is 16o poor 18o 8 olivine and pyroxene in the core have the same oxygen isotopic composition 18o 15 which indicates their equilibrium olivine and pyroxene in the mantle have variable oxygen isotopic compositions and are slightly depleted in 16o 18o 13 to 4 compared with the same minerals in the core the 26al 26mg systematics is consistent with the disequilibrium status observed according to the petrography and oxygen isotopes spinel is plotted on a line of 26al 27al 0 3 5 0 2 10 5 anorthite is plotted on a line of 1 5 10 7 and olivine and pyroxene in the core are plotted on a line of 1 7 10 6 plots of olivine and pyroxene in the mantle are scattered below the isochron of these minerals in the core this study indicates that the ek1 04 2 type c cai underwent multiple heating events after the formation of its cai precursor the precursor cai was formed 0 4 myr after the formation of the solar system defined by canonical cai formation at least 1 6 myr after the precursor cai formation the cai was partially melted and the melt exchanged oxygen isotopes with surrounding 16o poor nebular gas 16o poor olivine and pyroxene in the core crystallized from the melt subsequently al rich chondrules accreted onto the cai and the cai experienced partial melting again and recrystallized to form the mantle the oxygen and magnesium isotopes in anorthite were redistributed during thermal metamorphism in the allende parent body our study reveals that the cai had been retained in the solar nebula for at least 1 6 myr and underwent multiple melting events in the nebula and oxygen and 26al 26mg systematics has been partially disturbed depending on crystal sizes by metamorphism on the parent body

biomarkers stratigraphy of irati formation lower permian in the southern portion of parana basin brazil abstract this study covers the application of biomarkers as stratigraphic markers in a lower permian marine section from the parana basin southern brazil the biomarker variations reveal changes in sedimentary environment that were not detected by sedimentological and paleontological methods and will contribute to high resolution stratigraphy the irati formation contains two lithostratigraphic units 1 the lower unit taquaral member is composed of shales deposited in a marine epicontinental to restricted environment and 2 the upper unit assistencia member which consists of carbonates interbedded with shales and organic rich shale intervals deposited in a restricted marine environment the biomarker differences observed in the taquaral member can be explained by two different types of organic matter the lower and upper parts are characterized by a high relative abundance of high molecular weight n alkanes c27 17 trisnorhopane c31 r homohopane high hopanes steranes ratio and low hydrogen index values this facies contains greater relative amount of terrestrial organic matter the low hopanes steranes ratio together with the high hydrogen index values and amorphous organic matter relative proportion observed in the middle part of the taquaral member indicate a more marine organic matter contribution in the assistencia member based on gammacerane c30 hopane ratio c28 20r methylcholestane c29 20r methylcholestane ratio total organic carbon hydrogen index values palynofacies and sedimentary structures it was possible to distinguish changes in salinity and redox conditions the bituminous shales intervals were deposited in an anoxic environment high total organic carbon high hydrogen index values high preserved amorphous organic matter content with lower salinity lower gammacerane c30 hopane and c28 20r methylcholestane c29 20r ethylcholestane ratios on the other hand the limestones intervals were deposited in an aerobic environment low total organic carbon low hydrogen index values high oxidized organic matter content with higher salinity higher gammacerane c30 hopane and c28 20r methylcholestane c29 20r methylcholestane ratios

oxygen isotopic and chemical zoning of melilite crystals in a type a ca al rich inclusion of efremovka cv3 chondrite abstract different oxygen isotopic reservoirs have been recognized in the early solar system fluffy type a ca al rich inclusions cais are believed to be direct condensates from a solar nebular gas and therefore have acquired oxygen from the solar nebula oxygen isotopic and chemical compositions of melilite crystals in a type a cai from efremovka cv3 chondrite were measured to reveal the temporal variation in oxygen isotopic composition of surrounding nebular gas during cai formation the cai is constructed of two domains each of which has a core mantle structure reversely zoned melilite crystals were observed in both domains melilite crystals in one domain have a homogeneous 16o poor composition on the carbonaceous chondrite anhydrous mineral ccam line of 18o 5 10 which suggests that the domain was formed in a 16o poor oxygen isotope reservoir of the solar nebula in contrast melilite crystals in the other domain have continuous variations in oxygen isotopic composition from 16o rich 18o 40 to 16o poor 18o 0 along the ccam line the oxygen isotopic composition tends to be more 16o rich toward the domain rim which suggests that the domain was formed in a variable oxygen isotope reservoir of the solar nebula each domain of the type a cai has grown in distinct oxygen isotope reservoir of the solar nebula after the domain formation domains were accumulated together in the solar nebula to form a type a cai

melt solidification and late stage evaporation in the evolution of a fun inclusion from the vigarano c3v chondrite vigarano 1623 5 is a forsterite bearing refractory inclusion in which oxygen magnesium and silicon show large degrees of mass dependent isotopic fractionation the core of 1623 5 consists of forsteritic olivine fassaite melilite ak89 and spinel all of which show isotopic mass fractionation averaging 30 6 amu for magnesium and 10 0 amu for silicon it is enclosed in a mantle consisting of aluminous melilite ak16 60 spinel perovskite and hibonite hibonite and spinel in the mantle are enriched in heavy isotopes of magnesium by 8 15 amu relative to the core 1623 5 originally formed by solidification of a magnesium rich melt the endemic isotopic mass fractionation may have been caused by evaporation of that melt or may reflect an earlier evaporation event affecting the reservoir from which the interior of 1623 5 formed later flash remelting of the outer part of the core and volatilization of sio2 and mgo from the melt so produced caused formation of a mantle that is in isotopic and petrologic disequilibrium with the core

oxygen isotopic sims analysis in allende cai details of the very early thermal history of the solar system abstract the oxygen isotopic micro distributions within and among minerals in a coarse grained ca al rich inclusion cai 7r 19 1 from the allende meteorite were measured by in situ using secondary ion mass spectrometry sims all values of o isotopic ratios in 7r 19 1 minerals fall along the carbonaceous chondrite anhydrous mineral mixing ccam line on a 17 o smow vs 18 o smow plot major refractory minerals spinel fassaite and melilite in 7r 19 1 showed large negative anomalies of 17 o in the order spinel 21 16 o rich melilite 18 fassaite 15 to 1 16 o poor melilite 8 to 2 however the lower limit values of 17 o are similar at about 21 a value commonly observed in cais the similarity in the extreme values of the isotope anomaly anomalies suggests that crystallization of all cais started from an 16 o enrichment of 21 17 o relative to terrestrial values the order of the o isotopic anomalies observed for 7r 19 1 except for 16 o poor melilite is parallel to the crystallization sequence determined by experiment from cai liquid stolper 1982 indicating that the o isotopic exchange in 7r 19 1 occurred between cai melt and surrounding gas while 7r 19 1 was crystallizing from the 16 o enriched cai liquid 21 in 17 o in the 16 o poor solar nebula however the a single crystallization sequence during the cooling stage cannot explain the existence of 16 o poor melilite the presence of 16 o poor melilite suggests that multiple heating events occurred during cai formation the sharp contact between 16 o rich and 16 o poor melilite crystals and within 16 o rich melilite indicates that these multiple heatings occurred quickly based on the o isotopic and chemical compositions fassaite crystals were aggregates of relic crystals formed from cai melt whichthat have had various o isotopic compositions from the remelting processes the results of intra mineral distributions of o isotopes also support multiple heating events during cai formation

plagioclase rich inclusions in carbonaceous chondrite meteorites liquid condensates plagioclase rich inclusions in carbonaceous chondrites are of two types 1 mm cm sized ca al rich inclusions cais with 30 60 vol anorthite and up to 35 vol each of ti al pyroxene tpx melilite and spinel and 2 smaller 3 mm ca chondrules similar to those found in ordinary chondrites containing more sodic plagioclase pyroxene olivine and spinel the cais which were formerly named type i and thought to be intermediate between type a and type b cais are shown to be an independent type renamed type c with distinctive chemical and mineralogical compositions type c cais have group i or group ii trace element patterns low initial 26al27al ratios of 5 10 6 typical ak 35 55 melilite tpx with 2 12 tio2 and opaque grains osirrumopt alloy nuggets and fremdlinge smaller than 10 m the textures sequence of crystallization and concentric zonation indicate that they crystallized from melt droplets the texture of the anorthite ranges from coarse laths to a fine grained groundmass reflecting increasing retardation of its nucleation the few cais with the coarse laths cooled slowly 2 5 h from below the liquidus but the majority cooled faster from completely molten material as the elemental abundances in type c s are dominated by volatility the melts were not formed by planetary magmatic processes evaporative residues and remelted solid condensates are also ruled out because the compositions of naturally occurring experimentally produced and thermodynamically calculated residues and solid condensates differ from those of type c cais type c cais have compositions similar to those calculated for liquid condensates under high solar gas pressure 1 atm or in dust rich environments and are probably liquid condensates the few type c cais that crystallized from incompletely molten materials may have been reheated liquid condensates or mixed liquidsolid condensates

micro distribution of oxygen isotopes in a refractory inclusion from the allende meteorite abstract isotope ratios of oxygen have been measured on a fassaite crystal and the surrounding area of a coarse grained cai from the allende meteorite using secondary ion mass spectrometry values of 18 o smow for fassaite spinel anorthite grains and alteration products are 27 5 38 2 5 6 and 4 respectively which are consistent with the results obtained on mineral separates the o isotopic distributions are homogeneous either within individual single crystals of fassaite and anorthite or among the spinel grains within the analytical error no gradual variation in o isotopic composition was detected even at the boundary between different phases or at cracks inside a phase with a spatial resolution of 10 m these observations strongly suggest that the partial exchange of o isotopes in the minerals in the cai with the surrounding gas through diffusion is an unlikely origin for the observed inter mineral heterogeneity of o isotopes in the allende cais

alongshore variability of the multiple barred coast of terschelling the netherlands abstract the alongshore variability of the behaviour of a multiple bar system in the nearshore zone along the barrier island of terschelling the netherlands is investigated using a bathymetric data set with an alongshore extent of 12 km sampled annually for 28 yr the spatial and temporal variability of bar behaviour is quantified in terms of bar crest position in relation to morphometric parameters such as bar depth height width and volume along the entire study area the bars were generated close to the shore migrated seaward and eventually degenerated at the outer margin of the nearshore the interannual migrational patterns of the nearshore sandbars are analysed in terms of time of residence migration rates and return periods within the life cycle of a bar the cross shore nearshore bar behaviour was found to vary alongshore for instance cross shore migration rates gradually increased from 35 to 70 m yr from one end of the study area to the other concurrently the duration of net seaward migration increased from 9 to 15 yr the return period and total life span of bars were however found to be alongshore uniform on the order of 10 12 yr and 22 yr respectively morphological characteristics of the nearshore bar zone such as slope and width also exhibit gradually alongshore varying patterns a strong causal association is established between nearshore slope and both bar migration rates and duration of net seaward migration it is hypothesised that alongshore increasing wave heights at the seaward end of the bar zone is coupled with a corresponding increase in nearshore slope the presence of an important updrift ebb tidal shoal is identified as key controlling factor in the variability of bar behaviour along the adjacent shoreline of terschelling

trace element and petrologic clues to the formation of forsterite bearing ca al rich inclusions in the allende meteorite this work presents new trace element and petrographic data for three forsterite bearing ca alrich inclusions from the allende meteorite te 818a and 110 a such inclusions form a continuum with type b1 and b2 ca al rich inclusions cais and we refer to them as type b3 cais textures mineral chemistries crystal chemically fractionated ree patterns and other properties suggest that type b3 crystallized from partly molten evaporative residues the concentrations of refractory lithophile elements are lower than in type b1 and type b2 in approximately inverse proportion to the higher concentrations of mg and si in the type b3 s the refractory trace element abundances of the forsterite bearing isotopically anomalous fun cais te and cg14 suggest that they formed at higher temperatures and under more oxidizing conditions than other type b cais thus strengthening the previously observed link between relatively oxidized cai compositions and fun properties we also present evidence that 818a was strongly re heated and modified in the nebula after its initial crystallization it consists of a core of coarse grained ti al pyroxene tpx forsterite spinel and metal grains and a thick surrounding mantle of melilite that has been almost totally converted to fine grained alteration products in the core the mean concentrations of refractory lithophiles and siderophiles are similar both 14 ci but in the mantle the refractory siderophiles are a factor of 2 lower 9 ci than the refractory lithophiles 18 ci because the core and mantle display similar mineralogically fractionated ree patterns both sloping up from la to lu the pre alteration mantle could not have formed during fractional crystallization of the primary cai nor as a later condensate over the core a 3 stage formation process is required for 818a 1 crystallization of the primary cai rich in tpx throughout 2 re heating and partial volatilization of mg and si from the outer portion of the cai causing an increase in the concentration of refractory lithophiles a loss of siderophiles and converting tpx to melilite 3 metasomatic alteration of the melilite rich mantle

crystallization sequences of ca al rich inclusions from allende an experimental study the equilibrium crystallization sequence at 1 atmosphere in air of a melt corresponding in composition to the average composition of type b ca al rich inclusions from the allende meteorite is spinel 1550 c melilite 1400 c ak22 anorthite 1260 c ti al rich clinopyroxene 1230 c ti fassaite the melilite becomes increasingly akermanitic with decreasing temperature the pyroxene is similar in composition to fassaites from type b inclusions preliminary results suggest that the crystallization sequence is similar at oxygen fugacities near the iron wustite buffer the results of these experiments have been integrated with available phase equilibrium data in the system cao mgo al 2o 3 sio 2tio 2 and a phase diagram for predicting the crystallization sequences of liquids with compositions of coarse grained ca al rich inclusions has been developed available bulk compositions of coarse grained inclusions form a well defined trend in terms of major elements extending from type a and bl inclusions near the spinel melilite join to more pyroxene rich type b2 inclusions the trend deviates from the expected sequence of solid condensates from a nebular gas at p 10 3 atm if pure diopside is assumed to be the clinopyroxene that condenses the type a b1 end of the trend is similar in composition to calculated equilibrium condensates at 1202 1227 c and the trend as a whole parallels the sequence of condensates expected from diopside condensation at 1170 c the trend is consistent to first order with the condensation of solid ti rich fassaite in place of pure diopside at higher temperatures than those at which pure diopside is predicted to condense partially molten condensates may be likely in this case or if the nebular pressure is higher than 10 3 atm

oxygen isotopic zoning of reversely zoned melilite crystals in a fluffy type a ca al rich inclusions from the vigarano meteorite the oxygen isotopic microdistributions within melilite measured using in situ secondary ion mass spectrometry correspond to the chemical zoning profiles in single melilite crystals of a fluffy type a ca al rich inclusions cais of reduced cv3 vigarano meteorite the melilite crystals show chemical reverse zoning within an individual single crystal from the akermanite rich core to the akermanite poor rim the composition changes continuously with the crystal growth the zoning structures suggest that the melilite grew in a hot nebular gas by condensation with decreasing pressure the oxygen isotopic composition of melilite also changes continuously from 16o poor to 16o rich with the crystal growth these observations suggest that the melilite condensation proceeded with change consistent with an astrophysical setting around the inner edge of a protoplanetary disk where both 16o rich solar coronal gas and 16o poor dense protoplanetary disk gas could coexist fluffy type a cais could have been formed around the inner edge of the protoplanetary disk surrounding the early sun

oxygen isotopes in the early protoplanetary disk inferred from pyroxene in a classical type b cai abstract a major unanswered question in solar system formation is the origin of the oxygen isotopic dichotomy between the sun and the planets individual calcium aluminum rich inclusions cais from cv chondrites exhibit almost the full isotopic range but how their composition evolved is still unclear which prevents robust astrochemical conclusions a key issue is notably the yet unsolved origin of the 16 o rich isotopic composition of pyroxene in type b cais here i report an in situ oxygen isotope study of the archetypal type b cai usnm 3529 z from allende with emphasis on the isotopic composition of pyroxene and its isotopic and petrographic relationships with other major minerals the o isotopic composition of pyroxene is correlated with indicators of magmatic growth indicating that the pyroxene evolved from a 16 o poor composition and became progressively enriched in 16 o during its crystallization contrary to the long held assumption that pyroxene was initially 16 o rich this variation is well explained by isotopic exchange between a 16 o poor partial melt having the isotopic composition of melilite and a 16 o rich gas having the isotopic composition of spinel during pyroxene crystallization the isotopic evolution of 3529 z is consistent with formation in an initially 16 o rich environment where spinel and gehlenitic melilite crystallized followed by a 16 o depletion associated with melilite partial melting and recrystallization and finally a return to the initial 16 o rich environment before pyroxene crystallization this strongly suggests that the environment of cai formation was globally 16 o rich with local 16 o depletions systematically associated with high temperature events the al mg isotopic systematics of 3529 z further indicates that this suite of isotopic changes occurred in the first 150 000 yr of the solar system during the main cai formation period a new astrophysical setting is proposed where the 16 o depletion occurs in an optically thin surface layer of the disk and may have originated by evaporation of 16 o poor interstellar dust or non mass dependant isotopic fractionation

origin of compact type a refractory inclusions from cv3 carbonaceous chondrites compact type a cta inclusions are one of the major types of coarse grained refractory inclusions found in carbonaceous chondrites they have not been studied in a systematic fashion leading to some uncertainties and unproven assumptions about their origin to address this situation we studied a total of eight ctas from allende efremovka and axtell by scanning electron microscopic and electron and ion microprobe techniques these inclusions are very melilite rich ranging from 60 vol to nearly monomineralic also present are mg al spinel 5 20 perovskite trace 3 and in some samples ti rich 17 wt tio2tot fassaite trace 20 and rhonite 1 melilite compositions are mostly between ak15 and ak40 chondrite normalized ree abundance patterns for melilite flat at 10 ci with positive eu anomalies and fassaite slight hree enrichment relative to lree and negative eu anomalies are like those for their counterparts in once molten type b inclusions the patterns for rhonite have positive slopes from la through lu and abundances 10 ci for la and 35 60 ci for lu features of ctas that suggest that they were once molten include rounded inclusion shapes positively correlated sc and v abundances in fassaite radially oriented melilite laths at inclusion rims and the distribution of trace elements among the phases fractional crystallization models show that with one exception the ree contents of perovskite and fassaite arose by crystallization of these phases from late residual liquids that would have resulted from prior crystallization of the observed proportions of melilite and spinel from liquids having the bulk compositions of the inclusions one allende cta ts32 however has several features irregular shape reversely zoned melilite fassaite ree contents that are not readily explained by crystallization from a melt this inclusion may have undergone little melting and may be dominated by relict grains

fassaite composition trends during crystallization of allende type b refractory inclusion melts fassaite is a major phase in type b refractory inclusions and its wide compositional variability makes it an excellent recorder of crystallization induced changes in liquid composition traverses across zoned crystals with electron and ion microprobes show that ti v sc zr and hf decrease from core to rim while mg si rees and other trace elements increase fassaite liquid distribution coefficients derived from the compositions of early fassaite and calculated parent liquid compositions are higher than previously reported fassaite ds e g 0 2 0 8 vs 0 08 0 5 for the trivalent rees possibly due to the high ti and al contents of the fassaite we analyzed log log plots of concentrations of elements vs those of sc give linear relationships with slopes of dixl l 1 dscxl l 1 where dixl l is the bulk crystal liquid distribution coefficient for element i from this relationship we derive effective fassaite liquid ds of 2 8 for sc 1 5 for hf 1 1 for zr 0 52 for y 0 34 for ta 0 29 for nb and 0 31 0 48 for trivalent rees the effective ds are applicable to fassaite crystallizing from melts having the compositions and thermal histories of allende type b refractory inclusions and incorporate any equilibrium and kinetic effects that modify ds during the course of crystallization observed fassaite ree contents can be reproduced by a fractional crystallization model in which the effective ds are used ti3 is more compatible in fassaite than ti4 and without equilibration of the residual liquid with an external reducing gas ti3 titot ratios where titot ti3 ti4 should decrease from core to rim in fassaite crystals comparison of profiles of ti3 titot ratios in several crystals with those calculated for fractional crystallization suggests that the trend in one crystal was controlled by fractional crystallization alone but in two others the virtually constant ti3 titot ratios may imply that the liquids in these inclusions were able to maintain equilibrium with the solar nebular gas throughout crystallization attempts to determine the o2 of fassaite crystallization on the basis of ti3 titot ratios must be based on fassaite grains which are not zoned with respect to ti3 titot the range of observed ree abundances in subliquidus fassaite 7 800 cl for la and 30 2000 cl for lu now encompasses those in grains previously identified as relict removing a major reason for their identification as such rounded fassaite grains with fairly sharp mg rich rims and ti rich cores poikilitically enclosed in mantle melilite in ts34 are candidates for relict grains the grains are so scrich that they would require extreme prior crystallization of spinel and melilite which is inconsistent with their very low ree contents e g la at 3 7 cl we suggest that the cores of these grains are relict and were trapped with liquid during formation of the mantle

discovery mineral paragenesis and origin of wadalite in a meteorite the mineral wadalite ideal and simplified formula ca 6 al 5 si 2 o 16 cl 3 has been discovered for the first time in a meteorite specifically in coarse grained igneous type b calcium aluminum rich inclusions cais from the cv carbonaceous chondrite allende we report the results of electron microprobe scanning electron microscopy and transmission electron microscopy analyses of wadalite bearing assemblages in the allende cais and propose that wadalite formed by metamorphic reaction between akermanitic melilite and anorthite likely mediated by chlorine bearing fluids petrographic relationships support the likelihood of multistage alterations by fluids of different chemistries interspersed or coinciding with thermal metamorphic episodes on the allende parent asteroid fluid involvement in metamorphism of allende cais implies that these objects experienced open system alteration after accretion into the cv chondrite parent asteroid which may have resulted in disturbances of their oxygen and magnesium isotope systematics

rare earth element measurements and mapping of minerals in the allende cai 7r19 1 by nanosims ion microprobe we have established analytical procedures for quantitative rare earth element ree measurements by nanosims 50l ion microprobe with 2 10 m spatial resolution measurements are performed by multidetection using energy filtering under several static magnetic field settings relative sensitivity factors and ree oxide ree element secondary ion ratios that we determined for the nanosims match values previously determined for other ion microprobes ree measurements of 100 ppm ree glass standards yielded reproducibility and accuracy of 0 5 2 5 and 5 15 respectively ree measurements of minerals of an allende type a cai 7r19 1 were performed using three different methods spot analysis line profile and imaging these data are in excellent agreement with previous ree measurements of this inclusion by ims 3f ion microprobe the higher spatial resolution nanosims measurements provide additional insight into the formation process of this cai and offer a promising new tool for analysis of fine grained and complexly zoned materials

remelting of refractory inclusions in the chondrule forming regions evidence from chondrule bearing type c calcium aluminum rich inclusions from allende we describe the mineralogy petrology oxygen and magnesium isotope compositions of three coarse grained igneous anorthite rich type c ca al rich inclusions cais abc ts26 and 93 that are associated with ferromagnesian chondrule like silicate materials from the cv carbonaceous chondrite allende the cais consist of lath shaped anorthite an99 cr bearing al ti diopside al and ti contents are highly variable spinel and highly akermanitic and na rich melilite ak63 74 0 4 0 6 wt na2o ts26 and 93 lack wark lovering rim layers abc is a cai fragment missing the outermost part the peripheral portions of ts26 and abc are enriched in sio2 and depleted in tio2 and al2o3 compared to their cores and contain relict ferromagnesian chondrule fragments composed of forsteritic olivine fa6 8 and low ca pyroxene pigeonite fs1wo 1 9 the relict grains are corroded by al ti diopside of the host cais and surrounded by haloes of augite fs0 5wo 30 42 the outer portion of cai 93 enriched in spinel is overgrown by coarse grained pigeonite fs0 5 2wo 5 17 augite fs0 5wo 38 42 and anorthitic plagioclase an84 relict olivine and low ca pyroxene pigeonite in abc and ts26 and the pigeonite augite rim around 93 are 16 o poor 17 o 1 to 8 spinel and al ti diopside in cores of cais abc ts26 and 93 are 16 o enriched 17 o down to 20 whereas al ti diopside in the outer zones as well as melilite and anorthite are 16 o depleted to various degrees 17 o 11 to 2 in contrast to typical allende cais that have the canonical initial 26 al 27 al ratio of 5 10 5 abc 93 and ts26 are 26 al poor with 26 al 27 al 0 ratios of 4 7 1 4 10 6 1 5 1 8 10 6 and 1 2 10 6 respectively we conclude that abc ts26 and 93 experienced remelting with addition of ferromagnesian chondrule silicates and incomplete oxygen isotopic exchange in an 16 o poor gaseous reservoir probably in the chondrule forming region this melting episode could have reset the 26 al 26 mg systematics of the host cais suggesting it occurred 2 myr after formation of most cais these observations and the common presence of relict cais inside chondrules suggest that cais predated formation of chondrules