oxygen and magnesium isotope compositions of calcium aluminum rich inclusions from cr2 carbonaceous chondrites abstract we report both oxygen and magnesium isotope compositions measured in situ using a cameca ims 1280 ion microprobe in 20 of 166 cais identified in 47 polished sections of 15 cr2 renazzo type carbonaceous chondrites two additional cais were measured for oxygen isotopes only most cr2 cais are mineralogically pristine only few contain secondary phyllosilicates sodalite and carbonates most likely products of aqueous alteration on the cr2 chondrite parent asteroid spinel hibonite grossite anorthite and melilite in 18 cais have 16o rich 17o 23 3 1 9 2 error compositions and show no evidence for postcrystallization isotopic exchange commonly observed in cais from metamorphosed cv carbonaceous chondrites the inferred initial 26al 27al ratios 26al 27al 0 in 15 of 16 16o rich cais measured are consistent with the canonical value of 4 5 5 10 5 and a short duration 0 9 2 2 0 7 my eight of the 166 cr2 cais identified are associated with chondrule materials indicating that they experienced late stage incomplete melting during chondrule formation three of these cais show large variations in oxygen isotope compositions 17o ranges from 23 5 to 1 7 suggesting dilution by 16o depleted chondrule material and possibly exchange with an 16o poor 17o 5 nebular gas the low inferred 26al 27al 0 ratios of these cais 2 my after crystallization of cais with the canonical 26al 27al 0 and suggest evolution of the oxygen isotope composition of the inner solar nebula on a similar or a shorter timescale because cais in cr2 and cv chondrites appear to have originated in a similarly 16o rich reservoir and only a small number of cr2 and cv cais were affected by chondrule melting events in an 16o poor gaseous reservoir the commonly observed oxygen isotope heterogeneity in cais from metamorphosed cv chondrites is most likely due to fluid solid isotope exchange on the cv asteroidal body rather than gas melt exchange this conclusion does not preclude that some cv cais experienced oxygen isotope exchange during remelting instead it implies that such remelting is unlikely to be the dominant process responsible for oxygen isotope heterogeneity in cv cais the mineralogy oxygen and magnesium isotope compositions of cais in cr2 chondrites are different from those in the metal rich ch and cb carbonaceous chondrites providing no justification for grouping cr ch and cb chondrites into the cr clan

oxygen isotopic evolution of amoeboid olivine aggregates in the reduced cv3 chondrites efremovka vigarano and leoville amoeboid olivine aggregates aoas from the reduced cv chondrites efremovka vigarano and leoville consist of forsteritic olivine feni metal and a refractory component composed of spinel al diopside anorthite secondary ferrous olivine and alkali rich minerals nepheline and sodalite commonly observed in the oxidized cvs are rare mineralogy and chemical compositions of aoas are similar to those predicted by equilibrium thermodynamic condensation models suggesting that aoas formed primarily by gas solid condensation over a narrow temperature range slightly below the temperatures over which most ca al rich inclusions cais formed aoas in the reduced cvs preserve a 1st generation 16o rich signal 17 18o 40 similar to that observed in many cais suggesting that these refractory objects originated from a common source in the solar nebula in fact aoas and many fine grained cais may have formed by the same processes but at slightly different temperatures and can be considered a single class of refractory objects alteration of the aoas is manifested by differing extents of 16o depletion in original aoa minerals feo enrichment in olivine and formation of interstitial very fine grained na bearing phases from the six aoas and one fine grained melilite pyroxene rich cai examined in this study five distinct patterns of alteration were identified 1 one unaltered aoa from vigarano is characterized by 16o rich forsterite without feo rich rims and interstitial na bearing phases 2 weak alteration in the melilite pyroxene rich cai is characterized by incomplete 16o depletion in some melilite and precipitation of na bearing phases near the cai rim 3 oxygen isotopic composition and mineralogy are correlated in two aoas from leoville with 16o rich olivine 16o poor anorthite and a range of intermediate compositions in al diopside this pattern is consistent with model diffusion between original grains and a 16o poor reservoir during a relatively short term 60 yr high temperature 900 1100 c event 4 original forsterite has been enriched in feo but remained 16o rich in one aoa from vigarano this result is consistent with the slower rate of diffusion of o than fe and mg in olivine at least some interstitial phases are 16o rich and na bearing phases are abundant in this aoa 5 in contrast oxygen isotopic composition and fo content are correlated in two aoas from efremovka the olivine in these aoas tends to have forsteritic 16o rich cores and feo rich 16o depleted rims the general correlation between oxygen isotopic composition and fo content is difficult to model by diffusion and may have formed instead by aqueous dissolution and precipitation along the margins of preexisting olivine grains independent evidence for aqueous alteration of the efremovka aoas is provided by oh rich signals detected during ion beam sputtering of some of the 16o poor olivine elevated 16oh count rates and order of magnitude increases in 16oh detected during single analyses reflect trapping of an aqueous phase in 16o depleted olivine an elevated 16oh signal was also detected in one analysis of relatively 16o poor melilite in the melilite pyroxene cai from vigarano suggesting that this object also was altered by aqueous fluid

seismogenic sources potentially responsible for earthquakes with m 6 in the eastern southern alps thiene udine sector ne italy summary new geomorphological and structural data permitted to define the active faulting framework of the eastern southern alps ne italy all the active faults detected in the investigated area are thrust segments of the complex thrust system which has been responsible for the latest building of the eastern southalpine chain esc geomorphological investigations were performed to identify the surficial traces of recent fault activity generally represented by gentle scarps connecting uplifted palaeolandscapes of quaternary age with the flat and lower areas of the venetian and friulian plains surficial and subsurficial data the latter from reflection seismic profiles available for the investigated faults indicate that the thrusts have been responsible for the displacement of the entire wedge of quaternary deposits in the western sector of the investigated area the six recognized fault segments represent portions of a 100 km long thrust system at the boundary between the alpine relief and the plain areas in the eastern sector active tectonics is the result of parallel thrust segments located both in the alpine mountainous area and in the friulian plain the 3 d geometry of the active thrust segments has been derived from new structural surficial surveys and the interpretation of reflection seismic profiles for a total length of 1700 km on this basis we defined the geometry of 10 seismogenic sources whose dimensions are consistent with the occurrence of earthquakes with m 6 the comparison between the source geometry and the highest intensity data point distribution of large historical earthquakes has permitted to make hypotheses on the association of past seismic events to specific seismogenic sources this procedure indicated that no large historical events can be attributed to three sources montello conegliano arba ragogna medea this may indicate an elapsed time since the last activation of more than eight centuries based on the completeness of the historical catalogues the available data define therefore sources and related areas for which a high level of seismic hazard may be invoked

compound ultrarefractory cai bearing inclusions from cv3 carbonaceous chondrites two compound calcium aluminum rich inclusions cais 3n from the oxidized cv chondrite northwest africa nwa 3118 and 33e from the reduced cv chondrite efremovka contain ultrarefractory ur inclusions 3n is a forsterite bearing type b fob cai that encloses ur inclusion 3n 24 composed of zr sc y rich oxides y rich perovskite and zr sc rich al ti diopside 33e contains a fluffy type a fta cai and ur cai 33e 1 surrounded by wark lovering rim layers of spinel al diopside and forsterite and a common forsterite rich accretionary rim 33e 1 is composed of zr sc y rich oxides y rich perovskite zr sc y rich pyroxenes al ti diopside sc rich pyroxene and gehlenite 3n 24 s ur oxides and zr sc rich al ti diopsides are 16 o poor d 17 o approximately 2 to 5 spinel in 3n 24 and spinel and al diopside in the fob cai are 16 o rich d 17 o approximately 23 2 33e 1 s ur oxides and zr sc rich al ti diopsides are 16 o depleted d 17 o approximately 2 to 5 vs al ti diopside of the fta cai and spinel d 17 o approximately 23 2 and wark lovering rim al ti diopside d 17 o approximately 7 to 19 we infer that the inclusions experienced multistage formation in nebular regions with different oxygen isotope compositions 3n 24 and 33e 1 s precursors formed by evaporation condensation above 1600 c 3n and 33e s precursors formed by condensation and melting 3n only at significantly lower temperatures 3n 24 and 3n s precursors aggregated into a compound object and experienced partial melting and thermal annealing 33e 1 and 33e avoided melting prior to and after aggregation they acquired wark lovering and common forsterite rich accretionary rims probably by condensation followed by thermal annealing we suggest 3n 24 and 33e 1 originated in a 16 o rich gaseous reservoir and subsequently experienced isotope exchange in a 16 o poor gaseous reservoir mechanism and timing of oxygen isotope exchange remain unclear

whole rock 26 al 26 mg systematics of amoeboid olivine aggregates from the oxidized cv3 carbonaceous chondrite allende we report on mineralogy petrography and whole rock 26 al 26 mg systematics of eight amoeboid olivine aggregates aoas from the oxidized cv chondrite allende the aoas consist of forsteritic olivine opaque nodules and variable amounts of ca al rich inclusions cais of different types and show evidence for alteration to varying degrees melilite and anorthite are replaced by nepheline sodalite and grossular spinel is enriched in feo opaque nodules are replaced by fe ni sulfides ferroan olivine and ca fe rich pyroxenes forsteritic olivine is enriched in feo and often overgrown by ferroan olivine the aoas are surrounded by fine grained matrix like rims composed mainly of ferroan olivine and by a discontinuous layer of ca fe rich silicates these observations indicate that aoas experienced in situ elemental open system iron alkali halogen metasomatic alteration during which fe na cl and si were introduced whereas ca was removed from aoas and used to form the ca fe rich silicate rims around aoas the whole rock 26 al 26 mg systematics of the allende aoas plot above the isochron of the whole rock allende cais with a slope of 5 23 0 13 10 5 reported by jacobsen et al 2008 in contrast whole rock 26 al 26 mg isotope systematics of cais and aoas from the reduced cv chondrite efremovka define a single isochron with a slope of 5 25 0 01 10 5 larsen et al 2011 we infer that the excesses in 26 mg present in allende aoas are due to their late stage open system metasomatic alteration thus the 26 al 26 mg isotope systematics of allende cais and aoas are disturbed by parent body alteration processes and may not be suitable for high precision chronology of the early solar system events and processes

formal ratification of the quaternary system period and the pleistocene series epoch with a base at 2 58 ma in june 2009 the executive committee of the international union of geological sciences iugs formally ratified a proposal by the international commission on stratigraphy to lower the base of the quaternary system period to the global stratotype section and point gssp of the gelasian stage age at monte san nicola sicily italy the gelasian until then had been the uppermost stage of the pliocene series epoch the base of the gelasian corresponds to marine isotope stage 103 and has an astronomically tuned age of 2 58 ma a proposal that the base of the pleistocene series epoch be lowered to coincide with that of the quaternary the gelasian gssp was also accepted by the iugs executive committee the gssp at vrica calabria italy which had hitherto defined the basal boundary of both the quaternary and the pleistocene remains available as the base of the calabrian stage age now the second stage of the revised pleistocene in ratifying these proposals the iugs has acknowledged the distinctive qualities of the quaternary by reaffirming it as a full system period correctly complied with the hierarchical requirements of the geological timescale by lowering the base of the pleistocene to that of the quaternary and fully respected the historical and widespread current usage of both the terms quaternary and pleistocene copyright 2009 john wiley sons ltd

from present rivers to old terrigenous sediments the evolution of the drainage system in the eastern southern alps terra nova 22 218 226 2010 abstract the eastern southern alps are presently dominated by southward drainage systems feeding the venetian friulian plain confined to the south of the insubric lineament following the assumption that river sediments reflect in the first instance the rocks outcropping in their catchments the comparison between present fluvial and old terrigenous sediments lets us to evaluate changes in provenance since the late miocene when the basement exhumation along the valsugana thrust system took place as indicated by apatite fission track data this tectonic event determined the onset of the main drainage systems the evolution of which has been depicted tracking the petrographic signatures from the present back to the late miocene provenance data show important episodes of stream piracy and watershed migration in response to tectonic uplift in the southern alps as well as to the messinian salinity crisis and the quaternary glaciations terra nova 00 1 9 2010

dark inclusions in allende leoville and vigarano evidence for nebular oxidation of cv3 constituents dark lithic inclusions are known to occur in several cv3 chondrites we report petrologic chemical and oxygen isotopic data on examples from allende leoville and vigarano the allende inclusions comprise a petrographic sequence ranging from a type which contains chondrules and refractory inclusions and resembles cv3 or co3 chondrites to a type which contains porous aggregates of iron rich olivine oxygen isotopic compositions correlate with the sequence chondrule rich inclusions have compositions similar to the host meteorite bulk values whereas olivine aggregate rich inclusions have more 16o depleted compositions chemical compositions on the other hand do not correlate with the petrographic sequence the dark inclusions are all systematically enriched in iron and depleted in potassium and sodium relative to their host meteorites the inclusions appear to be fragments of cv3 parent bodies which were processed to different degrees prior to their incorporation as clasts into allende leoville and vigarano the processing homogenized olivine compositions presumably through heating and also involved oxygen exchange with 16o poorer surroundings either parent body metamorphism or nebular heating might have produced the petrographic and isotopic sequences however the most 16o depleted inclusions also have layered silicate rims surrounding them which are better attributed to gas solid reactions than parent body processes in particular andradite is abundant in the rims which implies that the rims grew under conditions significantly more oxidizing than those likely to have occurred on a cv3 parent body at least part of the processing therefore appears to have taken place prior to final accumulation of the material when the fragments were dispersed in the nebula the evidence for coupled oxidation and 16o depletion in the nebula suggests that other features of the cv3 group such as the oxidized and reduced subgroups ferrous rims on forsteritic olivines and coarse grained rims on chondrules may have been established by similar gas solid reactions prior to the final assembly of the meteorites

vertical extrusion and horizontal channel flow of orogenic lower crust key exhumation mechanisms in large hot orogens a large database of structural geochronological and petrological data combined with a bouguer anomaly map is used to develop a two stage exhumation model of deep seated rocks in the eastern sector of the variscan belt an early sub vertical fabric developed in the orogenic lower and middle crust during intracrustal folding followed by the vertical extrusion of the lower crustal rocks these events were responsible for exhumation of the orogenic lower crust from depths equivalent to 18 20 kbar to depths equivalent to 8 10 kbar and for coeval burial of upper crustal rocks to depths equivalent to 8 9 kbar following the folding and vertical extrusion event sub horizontal fabrics developed at medium to low pressure in the orogenic lower and middle crust during vertical shortening fabrics that record the early vertical extrusion originated between 350 and 340 ma during building of an orogenic root in response to se directed saxothuringian continental subduction fabrics that record the later sub horizontal exhumation event relate to an eastern promontory of the brunia continent indenting into the rheologically weaker rocks of the orogenic root indentation initiated thrusting or flow of the orogenic crust over the brunia continent in a north directed sub horizontal channel this sub horizontal flow operated between 330 and 325 ma and was responsible for a heterogeneous mixing of blocks and boudins of lower and middle crustal rocks and for their progressive thermal re equilibration the erosion depth as well as the degree of reworking decreases from south to north pointing to an outflow of lower crustal material to the surface which was subsequently eroded and deposited in a foreland basin indentation by the brunia continental promontory was highly noncoaxial with respect to the se oriented saxothuringian continental subduction in the early visean suggesting a major switch of plate configuration during the middle to late visean

coarse grained chondrule rims in type 3 chondrites abstract relatively coarse grained rims occur around all types of chondrules in type 3 carbonaceous and ordinary chondrites those in h l ll3 chondrites are composed primarily of olivine and low ca pyroxene those in cv3 chondrites contain much less low ca pyroxene average grain sizes range from 4 m in h l ll3 chondrites to 10 m in cv3 chondrites such rims surround 50 10 and 1 of chondrules in cv3 h l ll3 and co3 chondrites respectively but are rare 1 around cv3 ca al rich inclusions rim thicknesses average 150 m in h l ll3 chondrites and 400 m in cv3 chondrites the rims in h l ll3 chondrites are composed of material very similar to that which comprises darkzoned chondrules and recrysiallized matrix dark zoned chondrules and coarse grained rims probably formed in the solar nebula from clumps of opaque matrix material heated to sub solidus to sub liquidus temperatures during chondrule formation mechanisms capable of completely melting some material while only sintering other material require steep thermal gradients suitable processes are lightning reconnecting magnetic field lines and possibly aerodynamic drag heating cv chondrites may have formed in a region where the chondrule formation mechanism was less efficient probably at greater solar distances than the ordinary chondrites the lesser efficiency of heating could be responsible for the greater abundance of coarse grained rims around cv chondrules alternatively cv chondrules may have suffered fewer particle collisions prior to agglomeration

accretionary rims on inclusions in the allende meteorite abstract many inclusions in allende particularly those with irregular shapes are surrounded by a sequence of thin layers which differ from one another in texture mineralogy and mineral chemistry the layer underlying all others contains either ia pyroxene needles olivine clumps of hedenbergite and andradite ib olivine doughnuts or ic rectangular olivine crystals the next layer outward ii contains tiny

quantitative analysis of detrital modes statistically rigorous confidence regions in ternary diagrams and their use in sedimentary petrology abstract detrital modes are the basic type of quantitative data used in sedimentary petrology they represent estimates of the petrographic framework composition of sand or sandstone obtained by point counting of thin sections at present geological inferences from analysis of these numerical data are semi quantitative only because many of the data processing methods employed in sedimentary petrology lack a firm theoretical basis a review of existing methods reveals a number of fundamental statistical problems associated with the use of univariate statistics and the construction of so called hexagonal fields of compositional variation it is shown that these problems can be overcome by using multivariate methods that honour the non negativity and unit sum constraints on compositional data and incorporate the covariance structure spread in compositional data can be modelled on two levels 1 by regarding the grain as unit of observation and the total point count as a sample from a multinomial distribution 2 by regarding the total count as unit of observation and a set of counts as a sample from an additive logistic normal distribution numerical methods are presented for constructing statistically rigorous confidence regions in ternary diagrams by inversion of significance tests for these two distributions statistical analyses of the framework composition and heavy mineral assemblages of modern beach and river sands illustrate their use the case histories are followed by a brief overview of popular multivariate methods for reconstructing sediment provenance

early middle miocene paleodrainage and tectonics in the pakistan himalaya the 18 14 ma kamlial formation himalayan foreland basin sedimentary rocks in the chinji village region potwar plateau pakistan are characterized by 1 lithofacies indicative of deposition by a large river 2 a dominant magmatic arc provenance completely unlike the recycled orogen foreland basin deposits stratigraphically below above or coeval with these rocks and 3 subordinate contribution from a rapidly exhuming source interpreted as either the nanga parbat haramosh massif or the southern margin of the asian crust the start of kamlial formation deposition at this locality at 18 ma marks a major break with the older murree formation rocks which were deposited by rivers draining predominantly the himalayan thrust stack south of the arc we interpret this change as the result of diversion of the paleo indus river to its present position which crosses the kohistan arc and himalayas and debouches into the foreland if the rapidly exhuming subordinate source region were the nanga parbat haramosh massif then initiation of its uplift would have resulted in significant arc detritus to the basin as the overlying arc carapace was exhumed as the carapace was progressively breached arc material would have become a less substantial component of detritus to the basin consistent with the reported petrography of the overlying siwalik deposits

petrofacies and provenance of late mesozoic forearc basin northern and central california data from the great valley group sequence represent the most complete information regarding sandstone petrology of sediment derived from a magmatic arc this information is useful in documenting tectonic and magmatic events within the arc and related terranes and forms the basis for the establishment of petrostratigraphic units for mapping and correlation sandstone and conglomerate compositions are controlled by changes in provenance many of which were basinwide and synchronous clay mineral composition is controlled primarily by burial metamorphism careful attention to sample collection sample preparation and petrographic techniques is essential for uniform results seven petrographic parameters p f lv l m qp q q f and l listed in decreasing importance to petrofacies discrimination define eight petrofacies stony creek platina lodoga grabast boxer cortina los gatos and rumsey listed in approximate order of decreasing age the upper jurassic lower cretaceous petrofacies stony creek platina and lodoga contain higher lithic contents supracrustal sources whereas the upper cretaceous petrofacies especially the rumsey contain higher proportions of plutoniclastic components quartz feldspar and micas the proportion of potassium feldspar increases from near zero in the upper jurassic to nearly 50 of all feldspars in the uppermost cretaceous the lower part of the great valley group upper jurassic and lower cretaceous contains significant quantities of sedimentaclastic and metamorphiclastic material eroded from accreted and deformed terranes tectonic highlands formed by the arc arc collision nevadan orogeny that occurred prior to initiation of the franciscan great valley sierra nevada arc trench system the klamath mountains area provided a major proportion of this detritus ophiolite and serpentinite detritus was deposited locally near the base of the great valley group as a result of deformation along the east side of the growing franciscan subduction complex volcaniclastic detritus was fed into the entire forearc basin as magmatism increased in the sierra nevada area during the cretaceous as the volcanic cover was stripped off plutoniclastic and metamorphiclastic detritus from the underlying batholithic terranes was provided in abundance to the forearc basin crustal components were more continental in the southern sierra nevada and more oceanic in the northern sierra nevada as demonstrated by the higher proportions of metamorphiclastic detritus and by the more felsic nature of volcaniclastic detritus to the south by the middle of the late cretaceous extensive batholithic terranes provided potassium feldspar rich arkosic detritus to the entire forearc basin by the paleogene arc magmatism had migrated eastward sufficiently that deeper levels of the california part of the arc were exposed by erosion tectonic activity decreased in the forearc basin and the basin was filled to sea leve in most parts

matrix material in type 3 chondrites occurrence heterogeneity and relationship with chondrules abstract matrix material in type 3 chondrites forms rims on chondrules metal sulfide aggregates ca al rich inclusions and chondritic clasts it also forms lumps up to a millimeter in size which may contain coarser silicates chondrules of all types were found with internal matrix lumps that appear to have entered the chondrules before the latter had crystallized mean concentrations of mg na al and ca in matrix occurrences show up to fivefold variations in a single chondrite variations between mean matrix compositions of individual type 3 ordinary chondrites are almost as large and partly reflect systematic differences between h l and ll matrices such variations are probably a result of nebular separation of feldspathic material and ferromagnesian silicates compositions of chondrules and their matrix rims are normally unrelated although rim compositions are correlated with those of matrix lumps inside chondrules a single chondrule was found with a composition nearly identical to that of its internal matrix lump suggesting that some chondrules may have formed from matrix material matrix lumps are as heterogeneous as chondrules but mean chondrule and matrix compositions differ even allowing for possible loss of metallic fe ni during chondrule formation since bulk compositions of matrix lumps and rims have probably not changed significantly since their formation except for fe mg exchange our matrix samples cannot represent typical chondrule precursor materials

variscan geodynamic evolution of the carnic alps austria italy the south alpine carnic alps are part of the southern flank of the european variscides and display a continuous sedimentary record from late ordovician to devonian times followed by carboniferous s directed nappe stacking and late carboniferous to early permian post collisional collapse the tectonometamorphic and sedimentary evolution of the carnic alps resembles a continuous process where pre and syn orogenic volcanism syn orogenic flysch sedimentation deformation including nappe stacking metamorphism and tectonic collapse shift in age from internal zones in the n towards external zones in the s new structural petrological and sedimentological data are presented concerning the tectonometamorphic history of the carnic alps we distinguish three thrust sheets or tectonic nappes differing in their stratigraphic sedimentological deformational and metamorphic histories which were thrust over each other in carboniferous times our data lead to a new geodynamic model showing an evolution from rifting or back arc spreading in the late ordovician to the establishment of a mature passive continental margin in the late devonian early carboniferous flysch sedimentation in an active continental margin setting during the visean namurian and finally collision during the late carboniferous between the northern margin of gondwana and a microcontinent to the n

quantitative provenance analysis of sediments review and outlook provenance analysis of sediments is aimed at reconstructing the parent rock assemblages of sediments and the climaticphysiographic conditions under which sediments formed inferring sediment provenance from the final product a basin fill is anything but straightforward because the detrital spectrum evolves as the sediment is transported along the pathway from source to basin successful provenance analysis requires that the nature and extent of compositional and textural modifications to the detrital spectrum be recognised if not quantified the history of quantification in sediment provenance studies is summarised and illustrated by tracking two fundamental ideas the concept of the sediment petrological province or petrofacies and the relation between sandstone composition and plate tectonic environment progress in sedimentary provenance analysis has been closely linked with advancements in measurement technology a brief survey of modern data acquisition tools illustrates the possibilities and limitations of modern provenance research an operational definition of quantitative provenance analysis qpa is presented in which the central role of mass balance is acknowledged extension of this definition to include quantitative predictions obtained by forward modelling computer simulation of sediment production as well as methodological improvements in data acquisition and processing is needed to cover likely future developments in qpa the contributions to the special issue quantitative provenance analysis of sediments illustrate the intrinsic multidisciplinarity and rapid expansion of qpa d 2004 elsevier b v all rights reserved

forsterite rich accretionary rims around calcium aluminum rich inclusions from the reduced cv3 chondrite efremovka it was suggested that multilayered accretionary rims composed of ferrous olivine andradite wollastonite salite hedenbergitic pyroxenes nepheline and ni rich sulfides around allende calcium aluminum rich inclusions cais are aggregates of gas solid condensates which reflect significant fluctuations in physico chemical conditions in the slowly cooling solar nebula and grain gas separation processes in order to test this model we studied the mineralogy of accretionary rims around one type a cai e104 and one type b cai e48 from the reduced cv3 chondrite efremovka which is less altered than allende in contrast to the allende accretionary rims those in efremovka consist of coarse grained 20 40 mum anhedral forsterite fa 1 8 fe ni metal nodules amoeboid olivine aggregates aoas and fine grained cais composed of al diopside anorthite and spinel forsterite although the fine grained cais aoas and host cais are virtually unaltered a hibonite spinel perovskite cai in the e48 accretionary rim experienced extensive alteration which resulted in the formation of fe rich zn bearing spinel and a ca al si hydrous mineral forsterites in the accretionary rims typically show an aggregational nature and consist of small olivine grains with numerous pores and tiny inclusions of al rich minerals no evidence for the replacement of forsterite by enstatite was found no chondrule fragments were identified in the accretionary rims

anorthite rich chondrules in cr and ch carbonaceous chondrites genetic link between ca al rich inclusions and ferromagnesian chondrules anorthite rich chondrules in cr and ch carbonaceous chondrites consist of magnesian low ca pyroxene and forsterite phenocrysts feni metal nodules interstitial anorthite al ti cr rich low ca and high ca pyroxenes and crystalline mesostasis composed of silica anorthite and high ca pyroxene three anorthite rich chondrules contain relic ca al rich inclusions composed of anorthite spinel al diopside and forsterite a few chondrules contain regions which are texturally and mineralogically similar to magnesian type i chondrules and consist of forsterite low ca pyroxene and abundant feni metal nodules anorthite rich chondrules in cr and ch chondrites are mineralogically similar to those in cv and co carbonaceous chondrites but contain no secondary nepheline sodalite or ferrosilite relatively high abundances of moderately volatile elements such as cr mn and si in the anorthite rich chondrules suggest that these chondrules could not have been produced by volatilization of the ferromagnesian chondrule precursors or by melting of the refractory materials only we infer instead that anorthite rich chondrules in carbonaceous chondrites formed by melting of the reduced chondrule precursors olivine pyroxenes feni metal mixed with the refractory materials including relic cais composed of anorthite spinel high ca pyroxene and forsterite the observed mineralogical and textural similarities of the anorthite rich chondrules in several carbonaceous chondrite groups cv co ch cr may indicate that these chondrules formed in the region s intermediate between the regions where cais and ferromagnesian chondrules originated this may explain the relative enrichment of anorthite rich chondrules in 16o compared to typical ferromagnesian chondrules russell et al 2000

granoblastic olivine aggregates in magnesian chondrules planetesimal fragments or thermally annealed solar nebula condensates abstract granoblastic olivine aggregates goa have been discovered in some type i magnesian chondrules within carbonaceous chondrites by libourel and krot libourel g krot a n 2007 evidence for the presence of planetesimal material among the precursors of magnesian chondrules of nebular origin earth planet sci lett 254 1 8 who proposed an origin from pre existing planetesimals amoeboid olivine aggregates aoa generally considered as aggregates of solar nebula condensates and found within similar carbonaceous chondrites display similar equilibrium texture though on a finer scale for these reasons we conducted experiments to determine if annealing of olivine required time scales appropriate to planetesimal or nebular heating pressed 88 4 was isothermally heated at temperatures ranging from 1350 1550 c for 1 100 h the 100 h runs yield olivine aggregates with well developed granoblastic texture at all temperatures manifest as a network of randomly oriented and sutured olivine grains with 120 triple junctions individual olivine grains are 4 6 sided and polygonal by 1450 c and equigranular texture is developed at high temperature 1500 1550 c melting of olivine commences at 1450 1500 c and aids in ripening and suturing grain coarsening and grain boundary migration textural equilibrium is clearly met at 1550 c a planetesimal origin cannot be ruled out however the experimental evidence reveals that granoblastic texture can be reproduced in an interval not inconsistent with heating times for nebular objects goa may have experienced higher degrees of thermal processing than the finer grained aoa if the precursors were the same grain coarsening would have to be accompanied by modification to bulk and isotopic compositions however the precursors could have been olivine condensates formed later than aoa annealing may have been a widespread process operating in the primordial solar nebula responsible for thermal processing and formation of goa prior to their incorporation into chondrules

the buried shape of an alpine valley from gravity surveys seismic and ambient noise analysis summary it has long been observed that damage due to earthquakes depends greatly on local geological conditions alpine valleys represent a typical populated environment where large amplifications can take place owing to the presence of surface soils with poor mechanical properties combined to complex topography of the rock basin in the framework of the eu interreg iiib sismovalp project seismic hazard and alpine valley response analysis a stretch of the tagliamento river valley trv located in the north western part of the friuli region italy and close to the epicentre of the 1976 mw 6 4 earthquake has been investigated with the aim to define the buried shape of the valley itself two non invasive low cost independent geophysical methods were used i detailed gravity survey and ii h v spectral ratio hvsr of microtremors because of structural geological complexity and active tectonics of the friuli region an irregular valley shape was expected in this area the independent analysis performed by gravity and passive noise and complemented with refraction seismic velocity profiles confirms this hypothesis and leads to two models that were consistent but for some small scale details the maximum depth estimated is about 400 450 m in the southern part of the valley while a mean value of 150 180 m is estimated in the northern part the sediment thickness obtained for this stretch of the trv is quite large if compared to eastern alps plio quaternary rates therefore the valley shape imaged by this study better corresponds to the top of carbonate rocks finally on the basis of the obtained morphology and some direct measurements we conclude that the trv features an overall 1 d seismic response i e the resonance is related only to the sediment thickness rather than to the cross section shape but in its deepest part some limited 2 d effects could take place

magnetostratigraphic dating of an intensification of glacial activity in the southern italian alps during marine isotope stage 22 abstract we applied magnetostratigraphy and mammal biostratigraphy to date climate sensitive pollen cycles and lithostratigraphic units of the pliocene pleistocene leffe sedimentary succession from the southern alps italy the leffe section was correlated to additional sections casnigo fornaci di ranica and pianengo to construct a stratigraphic network along a common fluviatile system the serio river sourced in the southern alps and flowing southward into the po river basin we obtained a coherent scenario of climate variability for the last 2 myr at leffe lacustrine deposition commenced during the olduvai normal subchron 1 94 1 78 ma and lasted up to a chronologic level compatible with marine isotope stage mis 22 0 87 ma pollen analysis revealed that climate varied cyclically from warm temperate to cool during this time interval but never as cold as during glacial intervals at around mis 22 climate cooled globally gravels attributed to high energy braided river systems fed locally by alluvial fans prograded from the serio river catchment area over the leffe basin and toward the po plain in response to a generalized event of vegetation withdrawal and enhanced physical erosion at this time alpine valley glaciers reached their first maximum southward expansion with glacier fronts located at only 5 km upstream from leffe

origin and chronology of chondritic components a review abstract mineralogical observations chemical and oxygen isotope compositions absolute 207pb 206pb ages and short lived isotope systematics 7be 7li 10be 10b 26al 26mg 36cl 36s 41ca 41k 53mn 53cr 60fe 60ni 182hf 182w of refractory inclusions ca al rich inclusions cais and amoeboid olivine aggregates aoas chondrules and matrices from primitive unmetamorphosed chondrites are reviewed in an attempt to test i the x wind model vs the shock wave model of the origin of chondritic components and ii irradiation vs stellar origin of short lived radionuclides the data reviewed are consistent with an external stellar origin for most short lived radionuclides 7be 10be and 36cl are important exceptions and a shock wave model for chondrule formation and provide a sound basis for early solar system chronology they are inconsistent with the x wind model for the origin of chondritic components and a local irradiation origin of 26al 41ca and 53mn 10be is heterogeneously distributed among cais indicating its formation by local irradiation and precluding its use for the early solar system chronology 41ca 41k and 60fe 60ni systematics are important for understanding the astrophysical setting of solar system formation and origin of short lived radionuclides but so far have limited implications for the chronology of chondritic components the chronological significance of oxygen isotope compositions of chondritic components is limited the following general picture of formation of chondritic components is inferred cais and aoas were the first solids formed in the solar nebula 4567 4568 myr ago possibly within a period of 10 and have 26al 27al 0 similar to those in chondrules 5 nebular gas the majority of chondrules within a chondrite group may have formed over a much shorter period of time

isotopically uniform 16o depleted calcium aluminum rich inclusions in ch and cb carbonaceous chondrites abstract in situ oxygen isotope measurements of calcium aluminum rich inclusions cais from the metal rich carbonaceous chondrites isheyevo ch cb like acfer 214 paired with acfer 182 ch que 94411 paired with que 94627 cbb and hammadah al hamra 237 cbb revealed the presence of a common population of igneous isotopically uniform 16o depleted inclusions 17o average 2 standard deviations 7 4 6 5 and 8 3 respectively all cais from cbs and a significant fraction of those from chs and isheyevo are 16o depleted most of the 16o depleted cais consist of ti poor al diopside spinel melilite and forsterite and surrounded by a single and double layered rim of forsterite diopside the 16o depleted cais composed of hibonite grossite melilite and spinel and surrounded by the multilayered melilite diopside forsterite rims are less common some of the 16o depleted refractory igneous inclusions composed of al diopside forsterite and spinel have chondrule like textures skeletal or barred they are mineralogically most similar to al diopside rich chondrules found in metal rich carbonaceous chondrites and composed of al diopside forsterite al rich low ca pyroxene glassy mesostasis and spinel suggesting there is a continuum between these objects we suggest that i most of the isotopically uniform and 16o depleted cais resulted from remelting of pre existing possibly 16o rich refractory inclusions the remelting may have occurred during formation of the magnesian non porphyritic cryptocrystalline and skeletal chondrules in chs cbs and isheyevo either by an unspecified late single stage highly energetic event or in an impact generated plume previously hypothesized for their origin both mechanisms probably occurred in the solar nebula i e in the presence of the nebula gas the forsterite pyroxene rims around 16o depleted cais may have resulted from evaporation recondensation of silicon and magnesium during this event some of the al diopside rich cais may have formed by evaporation of the al rich chondrule melts ii in addition to these components the chs and isheyevo contain a high abundance of chondrules and refractory inclusions formed by the commonly inferred nebular processes evaporation condensation and incomplete melting of dust aggregates during multiple transient heating events these include 16o rich cais amoeboid olivine aggregates and ferromagnesian and aluminum rich chondrules with porphyritic textures such components are also present in cb chondrites but they are exceptionally rare these observations indicate that there are multiple generations of cais in metal rich carbonaceous chondrites iii because the isotopically uniform 16o depleted igneous cais and the magnesian cryptocrystalline and skeletal olivine pyroxene chondrules are found almost exclusively in metal rich carbonaceous chondrites the hypothesized impact plume mechanism of chondrule formation and recycling of cais are not common processes

post collisional sediment budget history of the alps tectonic versus climatic control based on the sediment budget of the eastern swiss and western alps since the oligocene the regional tectonic evolution has been identified as the dominant factor it is superimposed on the influence of both regional and global climate change and global sea level change during late pliocene and pleistocene times climate became the dominant factor because of cyclic glaciations the early post collisional history of the alps is characterized by a doubling of sediment discharge rates around the rupelian chattian boundary this increase is attributed to isostatic re adjustment either after large scale thermal reorganization of the lithosphere related to slab break off or to crustal thickening as continental crust became subducted from middle oligocene to late miocene times the overall trend of sediment discharge rates in the entire alps was modified only during relatively short lived phases these are characterized by an increase in aquitanian ca 23 21 ma and late burdigalian times ca 18 16 4 ma and a decrease in early to middle burdigalian 21 19 ma and langhian to serravalian times 16 4 12 ma an important still ongoing period of uplift reflected by rapidly increasing sediment discharge rates started in latest miocene times in the swiss and western alps and affected the eastern alps some 2 million years later the reason for this uplift is not clear but deep seated lithospheric processes appear to be likely

progressive alteration in cv3 chondrites more evidence for asteroidal alteration abstract the oxidized cv3 chondrites can be divided into two major subgroups or lithologies bali like cv3oxb and allende like cv3oxa in which chondrules calcium aluminum rich inclusions cais and matrices show characteristic alteration features weisberg et al 1997 krot et al 1997d kimura and ikeda 1997 the cv3oxb lithology is present in bali kaba parts of the mokoia breccia and possibly in grosnaja and allan hills alh 85006 it is characterized by the presence of the secondary low ca phyllosilicates saponite and sodium phlogopite magnetite ni rich sulfides fayalite fa 90 ca fe rich pyroxenes fs10 50wo45 50 and andradite phyllosilicates replace primary ca rich minerals in chondrules and cais which suggests mobilization of ca during aqueous alteration magnetite nodules are replaced to various degrees by fayalite ca fe rich pyroxenes and minor andradite fayalite veins crosscut fine grained rims around chondrules and extend into the matrix thermodynamic analysis of the observed reactions indicates that they could have occurred at relatively low temperatures 300 c in the presence of aqueous solutions oxygen isotopic compositions of the coexisting magnetite and fayalite plot close to the terrestrial fractionation line with large 18ofayalite magnetite fractionation 20 we infer that phyllosilicates magnetite fayalite ca fe rich pyroxenes and andradite formed at relatively low temperatures 300 c by fluid rock interaction in an asteroidal environment secondary fayalite and phyllosilicates are virtually absent in chondrules and cais in the cv3oxa lithology which is present in allende and its dark inclusions axtell alha81258 alh 84028 lewis cliff lew 86006 and parts of the mokoia and vigarano breccias instead secondary nepheline sodalite and fayalitic olivine are common fayalitic olivine in chondrules replaces low ca pyroxenes and rims and veins forsterite grains it also forms coarse lath shaped grains in matrix secondary ca fe rich pyroxenes are abundant we infer that the cv3oxa lithology experienced alteration at higher temperatures than the cv3oxb lithology the presence of the reduced and cv3oxa lithologies in the vigarano breccia and cv3oxa and cv3oxb lithologies in the mokoia breccia indicates that all cv3 chondrites came from one heterogeneously altered asteroid the metamorphosed clasts in mokoia krot and hutcheon 1997 may be rare samples of the hotter interior of the cv asteroid we conclude that the alteration features observed in the oxidized cv3 chondrites resulted from the fluid rock interaction in an asteroid during progressive metamorphism of a heterogeneous mixture of ices and anhydrous materials mineralogically similar to the reduced cv3 chondrites

petrologic study of sj101 a new forsterite bearing cai from the allende cv3 chondrite abstract the forsterite bearing type b fob cai sj101 consists of three major structural units 1 light patches of sector zoned poikilitic al rich clinopyroxene cpx with numerous inclusions of small spinel grains and aggregates and subordinate amounts of mg rich melilite mel and anorthite an sp cpx lithology 2 dark sinuous bands of al rich clinopyroxene with large up to 300 60 m poikilitically enclosed euhedral forsterite fo crystals fo cpx lithology and 3 the external cpx sp an rim overlying the entire inclusion the two major lithologies are always separated by a transition zone of clinopyroxene poikilitically enclosing both forsterite and spinel the patches of the sp cpx lithology exhibit significant textural and mineralogical variability that is size dependent small patches typically consist of cpx and spinel with minor remnants of melilite and or its alteration products large patches contain mel an rich cores with either equigranular ophitic subophitic or lacy textures reminiscent of those in types b or c cais respectively all silicates poikilitically enclose numerous spinel grains of identical habit both melilite and anorthite gradually disappear toward the boundary with the fo cpx lithology neither the evaporation mantle of al rich melilite typical of other fobs nor the wark lovering rim is present secondary minerals include grossular monticellite magnetite and a few grains of wollastonite andradite and nepheline being a rather typical fob mineralogically and chemically texturally sj101 differs from other fobs in displaying the nearly complete segregation of forsterite from spinel which occur only in the fo cpx and sp cpx lithologies respectively the complex convoluted internal structure of sj101 suggests that the coarse grained sp an mel cpx cores and fo cpx lithology represent the precursor materials of fobs proto cais and fo rich accretionary rims while the inferred chemistry and mineralogy of the fo rich rims are fairly typical the high ak content in sj101 melilite 78 7 82 3 mol implies that the sj101 proto cais represent a new type of cais that has not been sampled before this type of cais might have formed by remelting of spinel rich condensates the group ii ree pattern slightly negative 29 si and 25 mg values and nearly solar ratios of the major elements in the bulk sj101 suggest that its precursors proto cais and fo rich rims could have formed by a non equilibrium condensation in a closed system of solar composition somewhat depleted in a super refractory evaporation residue the proposed formation scenario of sj101 invokes a non steady cooling and condensation of the nebular gas interrupted by at least two distinct melting episodes required to account for the igneous textures of the mel an cpx rich cores proto cais and the fo cpx lithology

mineralogy and petrography of amoeboid olivine aggregates from the reduced cv3 chondrites efremovka leoville and vigarano products of nebular condensation accretion and annealing amoeboid olivine aggregates aoas from the reduced cv chondrites efremovka leoville and vigarano are irregularly shaped objects up to 5 mm in size composed of forsteritic olivine fa 50 melting we infer that aoas are aggregates of high temperature nebular condensates which formed in cai forming regions and that they were absent from chondrule forming regions at the time of chondrule formation the absence of low ca pyroxene and depletion in moderately volatile elements mn cr na k suggest that aoas were either removed from cai forming regions prior to condensation of these elements and low ca pyroxene or gas solid condensation of low ca pyroxene was kinetically inhibited

calcium aluminum rich inclusions in enstatite chondrites i mineralogy and textures abstract like calcium aluminum rich inclusions cais from carbonaceous and ordinary chondrites enstatite chondrite cais are composed of refractory minerals such as spinel perovskite al ti diopside melilite hibonite and anorthitic plagioclase which may be partially to completely surrounded by halos of na cl rich minerals porous aggregate and compact textures of the refractory cores in enstatite chondrite cais and rare wark lovering rims are also similar to cais from other chondrite groups however the small size 100 m low abundance 1 by mode in thin section occurrence of only spinel or hibonite rich types and presence of primary ti v oxides and secondary geikelite and ti fe sulfides distinguish the assemblage of enstatite chondrite cais from other groups the primary mineral assemblage in enstatite chondrite cais is devoid of indicators e g oldhamite osbornite of low o fugacities thus high temperature processing of the cais did not occur under the reducing conditions characteristic of enstatite chondrites implying that either 1 the cais are foreign to enstatite chondrite forming regions or 2 o fugacities fluctuated within the enstatite chondrite forming region in contrast secondary geikelite and ti fe sulfide which replace perovskite indicate that alteration of perovskite occurred under reducing conditions distinct from cais in the other chondrite groups we have not ascertained whether the reduced alteration of enstatite chondrite cais occurred in a nebular or parent body setting we conclude that each chondrite group is correlated with a unique assemblage of cais indicating spatial or temporal variations in physical conditions during production or dispersal of cais

petrology and origin of amoeboid olivine aggregates in cr chondrites amoeboid olivine aggregates aoas are irregularly shaped fine grained aggregates of olivine and ca al rich minerals and are important primitive components of cr chondrites the aoas in cr chondrites contain feni metal and some aoas contain mn rich forsterite with up to 0 7 mno and mn fe ratios greater than one additionally aoas in the cr chondrites do not contain secondary phases nepheline and fayalitic olivine that are found in aoas in some cv chondrites the aoas in cr chondrites record a complex petrogenetic history that included nebular gas solid condensation reaction of minerals with the nebular gas small degrees of melting and sintering of the assemblage a condensation origin for the mn rich forsterite is proposed the mn rich forsterite found in idps unequilibrated ordinary chondrite matrix and aoas in cr chondrites may have had a similar origin a type a calcium aluminum rich inclusion cai with an aoa attached to its wark lovering rim is also described this discovery reveals a temporal relationship between aoas and type a inclusions additionally a thin layer of forsterite is present as part of the wark lovering rim revealing the crystallization of olivine at the end stages of the wark lovering rim formation the ca al rich nodules in the aoas may be petrogenetically related to the ca al rich minerals in wark lovering rims on type a cais aoas are chondrite components that condensed during the final stage of wark lovering rim formation but in general were temporally spatially or kinetically isolated from reacting with the nebula vapor during condensation of the lower temperature minerals that were commonly present as chondrule precursors

oxygen and magnesium isotope compositions of calcium aluminum rich inclusions from rumuruti r chondrites abstract we report oxygen and magnesium isotope compositions of ca al rich inclusions cais from several rumuruti r chondrites measured in situ using a cameca ims 1280 ion microprobe on a three isotope oxygen diagram 17o vs 18o compositions of individual minerals in most r cais analyzed fall along a slope 1 line based on the variations of 17o values 17o 17o 0 52 18o within individual inclusions the r cais are divided into i 16o rich 17o 23 26 ii uniformly 16o depleted 17o 2 and iii isotopically heterogeneous 17o ranges from 25 to 5 one of the hibonite rich cais h030 l has an intermediate 17o value of 12 and a highly fractionated composition 18o 47 we infer that like most cais in other chondrite groups the r cais formed in an 16o rich gaseous reservoir the uniformly 16o depleted and isotopically heterogeneous cais subsequently experienced oxygen isotope exchange during remelting in an 16o depleted nebular gas possibly during r chondrite chondrule formation and or during fluid assisted thermal metamorphism on the r chondrite parent asteroid three hibonite bearing cais and one spinel plagioclase rich inclusion were analyzed for magnesium isotope compositions the cai with the highly fractionated oxygen isotopes h030 l shows a resolvable excess of 26mg 26mg corresponding to an initial 26al 27al ratio of 7 10 7 three other cais show no resolvable excess of 26mg 26mg the absence of 26mg in the spinel plagioclase rich cai from a metamorphosed r chondrite nwa 753 r3 9 could have resulted from metamorphic resetting two other hibonite bearing cais occur in the r chondrites nwa 1476 and nwa 2446 which appear to have experienced only minor degrees of thermal metamorphism these inclusions could have formed from precursors with lower than canonical 26al 27al ratio

calcium aluminum rich inclusions in enstatite chondrites ii oxygen isotopes abstract ln situ ion microprobe analyses of spinel in refractory calcium aluminium rich inclusions cais from type 3 eh chondrites yield 160 rich compositions dl80 and 6170 about 40 0 spinel and feldspar in a cai from an el3 chondrite have significantly heavier isotopic compositions dl80 and 6170 about 5 0 a regression through the data results in a line with slope 1 o on a three isotope plot similar to isotopic results from unaltered minerals in cais from carbonaceous chondrites the existence of cais with 160 rich and 16o poor compositions in carbonaceous as well as enstatite chondrites indicates that cais formed in at least two temporally or spatially distinct oxygen reservoirs general similarities in oxygen isotopic compositions of cais from enstatite carbonaceous and ordinary chondrites indicate a common nebular mechanism or locale for the production of most cais introduction refractory calcium aluminium rich inclusions cais in chondritic meteorites preserve a record of high temperature processing in the early solar nebula including condensation evaporation and melting macpherson

chemical and oxygen isotopic compositions of accretionary rim and matrix olivine in cv chondrites constraints on the evolution of nebular dust abstract a correlation of petrography mineral chemistry and in situ oxygen isotopic compositions of fine grained olivine from the matrix and of fine and coarse grained olivine from accretionary rims around ca al rich inclusions cais and chondrules in cv chondrites is used here to constrain the processes that occurred in the solar nebula and on the cv parent asteroid the accretionary rims around leoville vigarano and allende cais exhibit a layered structure the inner layer consists of coarse grained forsteritic and 16o rich olivine fa1 40 and 17o 24 to 5 the higher values are always found in the outer part of the layer and only in the most porous meteorites whereas the middle and the outer layers contain finer grained olivines that are more fayalitic and 16o depleted fa15 50 and 17o 18 to 1 the cv matrices and accretionary rims around chondrules have olivine grains of textures chemical and isotopic compositions similar to those in the outer layers of accretionary rims around cais there is a correlation between local sample porosity and olivine chemical and isotopic compositions the more compact regions the inner accretionary rim layer have the most mgo and 16o rich compositions whereas the more porous regions outer rim layers around cais accretionary rims around chondrules and matrices have the most mgo and 16o poor compositions in addition there is a negative correlation of olivine grain size with fayalite contents and 17o values however not all fine grained olivines are feo rich and 16o poor some small 20 olivine grains in the outer layers of the cai accretionary rims and in the matrix show significant enrichments in 16o 17o 20 to 10 we infer that the inner layer of the accretionary rims around cais and at least some olivine grains in the finer portions of accretionary rims and cv matrices formed in an 16o rich gaseous reservoir probably in the cai forming region grains in the outer layers of the cai accretionary rims and in the rims around chondrules as well as matrix may have also originated as 16o rich olivine however these olivines must have exchanged o isotopes to variable extents in the presence of an 16o poor reservoir possibly the nebular gas in the chondrule forming region s and or fluids in the parent body the observed trend in isotopic compositions may arise from mixtures of 16o rich forsterites with grain overgrowths or newly formed grains of 16o poor fayalitic olivines formed during parent body metamorphism however the observed correlations of chemical and isotopic compositions of olivine with grain size and local porosity of the host meteorite suggest that olivine accreted as a single population of 16o rich forsterite and subsequently exchanged fe mg and o isotopes in situ in the presence of aqueous solutions i e fluid assisted thermal metamorphism

are the oroclines of the variscan belt related to late variscan strike slip tectonics terra nova 23 241 247 2011 abstract early variscan structures and magnetic anomalies delineate four oroclines along the variscan belt the arcs bend the lithostratigraphic zones of the autochthon and the allochthonous terranes which include ophiolites of the rheic suture and units of gondwanan derivation subducted on both sides of the rheic ocean a transcurrent model dominated by right lateral motion explains the genesis and evolution of the oroclines and a simple plate tectonics scenario links late variscan dextral strike slip movements in the variscides to a broad intracontinental shear zone kinematically equivalent to a transform fault terra nova 00 1 7 2011

emplacement kinematics of a granite diapir the chindamora batholith zimbabwe the geometric features of a large 50 40 km granitic batholith and its surrounding greenstone belt envelope are described the batholith is made up of several intrusive components and an intrusion sequence based on contact relations and xenoliths has been established the igneous rocks show a local foliation s fabric and preferred orientation of minerals the intensity of this fabric accords with the finite strain determined from xenolith shape analysis when the strain variations are analysed in detail it appears that the batholith was built up by a succession of magmatic pulses each of which led to a stretching of the previously consolidated igneous material so called balloon tectonics evidence is presented that xenolith deformation commences only when the surrounding igneous material has crystallized and a method is suggested whereby the position of the surface separating crystal supported phase plastic behaviour from melt supported phase liquid behaviour at different stages in the plutonic history can be determined ductile shear zones are present and their geometry accords well with the shape changes necessary to allow the outer parts of the pluton to stretch

fluffy type a ca al rich inclusions in the allende meteorite abstract allende fluffy type a s fta s are a distinct sub group of ca al rich inclusions whose primary mineral assemblage consists of al rich melilite ak 0 33 spinel that is commonly very v rich perovskite and frequently hibonite some contain relatively coarse grained melilite up to 1 5 mm that is intensely kink banded and commonly reversely zoned hibonite and v rich spinel others contain much finer grained and strain free melilite 50 m and have not been found to contain hibonite or v rich spinel some fta s contain both coarser and finer grained melilite and textural relationships indicate that the latter is replacing the former fta s are characterized by extremely irregular shapes and 60 75 volume per cent of fine grained secondary alteration products many are aggregates of innumerable nodules each of which is surrounded by a wark lovering type rim sequence these nodules are frequently separated from one another by matrix like clastic rim material other fta s do not have nodular structure structural and mineralogical characteristics of their wark lovering rims suggest that fta s did not achieve their shapes by deformation of a liquid or a hot plastic solid in contrast to those in type b inclusions formation of reverse zoning in the coarser grained melilite crystals in fta s cannot be understood in terms of crystallization from a liquid but are readily explainable by condensation from a solar nebular gas during a period of falling pressure further evidence against a liquid origin is the wide range of spinel compositions within individual coarser grained fta s the fact that the reversely zoned melilite crystals cannot have been produced in any kind of sublimation or distillation process precludes formation of these inclusions as volatilization residues fta s are aggregates in some of which are preserved vapor solid condensate grains that formed at high temperature in the solar nebula

reconstruction of tertiary palaeovalleys in the south alpine foreland basin of france eocene oligocene of the castellane arc abstract the dynamics of depositional environments and the spatial deformation of drainage networks in foreland basins reflect the tectonic and erosional dynamics associated with the development of mountain belts the spatial and temporal organization of the eocene oligocene 40 25 ma sedimentation in the external part of the south alpine foreland basin of france was reconstructed using an integrated cartographic sedimentological and petrographic analysis of the tertiary sedimentary successions the depositional geometries and variations in facies and thickness of the palaeogene nummulitic succession as well as the observed flow directions in various continental and marine sediments suggest that the barreme blieux and taulanne synclines were present as palaeovalleys since the eocene the sedimentological analysis of the nummulitic succession allows the identification of three depositional sequences separated by transgressive surfaces that are recognized in the barreme blieux and taulanne synclines correlation of these sequences between the three synclines suggests that these palaeovalleys were connected by a local valley network that recorded the same sea level fluctuations during the marine nummulitic sedimentation the palaeovalley network was structurally controlled by the east west axes of the blieux and taulanne synclines and the north south axis of the barreme syncline formed during the pyrenean provencal late cretaceous middle eocene shortening and the first stage of the alpine history middle eocene respectively later on the westward alpine compression since the early oligocene induced local depocenter migration and reversal in flow direction however compared to the modern river pattern the palaeovalley orientation highlights a geometrical stability since their formation about 40 ma suggesting a long term stability of the early structures in the foreland basin this constancy can be explained by the location of the study area in a piggy back basin transported at the top of the provencal thrust sheet that facilitated the preservation of the overall axis orientation of the palaeovalleys

a jurassic tongue of the ocean infilled with oolitic sands the belluno trough venetian alps italy abstract the belluno trough is a narrow and elongate basin on the northwestern corner of the apulian plate continental margin it acquired topographic identity in early liassic time during the breakup of a widespread upper triassic carbonate shelf at the beginning liassic the belluno trough was a starved depression accumulating euxinic mudstone and bounded by two shallow water carbonate banks trento and friuli platforms this typical bahamian physiography lasted until late liassic time when the shallow water trento platform collapsed tectonically and suddenly drowned tilting northward and breaking along an old tectonic line it became therefore a submerged pelagic plateau in the meantime the western edge of the friuli platform now the windward margin of an oceanic platform turned into a prolific super producing oolite factory quite soon the oolite sands of the friuli margin started to flow down the slope reaching the basin through numerous entry points and gradually building a complex of coalescent deep sea fans which prograding westward infilled the belluno trough the fans terminated westward against the faulted edge of the trento plateau on which above a karst like surface locally encrusted with manganese red nodular ammonitic limestone was slowly accumulating northward where the topographic relief decreased the oolite fans could spill over the escarpment onto the edge of the plateau by the end of middle jurassic time the belluno trough was no longer a submarine depression but a gentle slope connecting the friuli platform to the deep pelagic trento plateau in callovian time probably because of a short drop in sea level large parts of the friuli platform were exposed to subaerial diagenesis during the subsequent oxfordian transgression the resulting rocky bottom became the substratum for an extensive growth of reefal organisms hydrozoans corals rudists which fringed the friuli platform for the whole malm and cretaceous times

quantifying tectonic versus erosive denudation by the sediment budget the miocene core complexes of the alps abstract the denudation budget of the alps is quantified for the main period of lateral extrusion between 22 and 12 ma the relative importance of tectonic denudation increases from w to e from 70 in the lepontine window in the swiss alps to 80 in the tauern window and to more than 95 in the rechnitz window the driving mechanism of tectonic denudation was eastward extrusion due to an unconstrained orogenic margin in the pannonian basin tectonic denudation in the alps was responsible for about 30 of the total exhumation between 22 and 12 ma

refractory inclusions in the ch cb like carbonaceous chondrite isheyevo i mineralogy and petrography the ch cb like chondrite isheyevo consists of metal rich 7090 vol fe ni metal and metal poor 720 vol fe ni metal lithologies which differ in size and relative abundance of fe nimetal and chondrules as well as proportions of porphyritic versus non porphyritic chondrules here we describe the mineralogy and petrography of ca al rich inclusions cais and amoeboid olivine aggregates aoas in these lithologies based on mineralogy refractory inclusions can be divided into hibonite rich 39 grossite rich 16 melilite rich 19 spinel rich 14 pyroxeneanorthite rich 8 fine grained spinel rich cais 1 and aoas 4 there are no systematic differences in the inclusion types or their relative abundances between the lithologies about 55 of the isheyevo cais are very refractory hibonite rich and grossite rich objects 20 240 m in size which appear to have crystallized from rapidly cooling melts these inclusions are texturally and mineralogically similar to the majority of cais in ch and cb chondrites they are distinctly different from cais in other carbonaceous chondrite groups dominated by the spinel pyroxene melilite cais and aoas the remaining 45 of inclusions are less refractory objects melilite spinel and pyroxene rich cais and aoas 40 300 m in size which are texturally and mineralogically similar to those in other chondrite groups both types of cais are found as relict objects inside porphyritic chondrules indicating recycling during chondrule formation we infer that there are at least two populations of cais in isheyevo which appear to have experienced different thermal histories all of the isheyevo cais apparently formed at an early stage prior to chondrule formation and prior to a hypothesized planetary impact that produced magnesian cryptocrystalline and skeletal chondrules and metal grains in cb and possibly ch chondrites however some of the cais appear to have undergone melting during chondrule formation and possibly during a major impact event we suggest that isheyevo as well as ch and cb chondrites consist of variable proportions of materials produced by different processes in different settings 1 by evaporation condensation and melting of dust in the protoplanetary disk porphyritic chondrules and refractory inclusions 2 by melting evaporation and condensation in an impact generated plume magnesian cryptocrystalline and skeletal chondrules and metal grains some igneous cais could have been melted during this event and 3 by aqueous alteration of pre existing planetesimals heavily hydrated lithic clasts the isheyevo lithologies formed by size sorting of similar components during accretion in the isheyevo parent body they do not represent fragments of ch and cb chondrites

post messinian drainage changes triggered by tectonic and climatic events eastern southern alps italy abstract the messinian quaternary history of tectonic and climatic control on sedimentation in the eastern southern alps northern italy was reconstructed using an integrated petrographic and sedimentological analysis of five sedimentary successions these units mainly consist of fluvial conglomerates of the tagliamento sequence deposited within the eastern southern alps since the upper miocene messinian salinity crisis at that time the closure of marine gateways between the atlantic ocean and the mediterranean sea caused a drop in sea level causing exchanged fluvial erosion and widening of the alpine catchments sediment composition in the upper miocene to lower pliocene units shows an abrupt change in the source areas from sediments characterized by carbonate rock fragments to detritus rich in low grade metamorphic grains in spite of tectonic activity within the eastern southern alps no major modifications in sediment supply took place during the pliocene early pleistocene time span in the middle pleistocene the first major expansion of the alpine glaciers triggered a change in drainage patterns and a marked increase in erosion rates predominantly climatic control on sedimentation in the tagliamento basin and the erosion of the carnic alps produced sediments rich in quartz siltstone and metamorphic rock fragments deposited in the upper pleistocene unit and in modern river sediments

two phase stratigraphic model of foreland basin sequences application of flexural models to nonmarine foreland basin evolution indicates that two different stratigraphic styles of basin fill may develop over time basin subsidence is most rapid during times of thrust load emplacement associated sedimentation is coarse grained immediately adjacent to the thrust front and grades rapidly into fine grained deposits that cover most of the basin the distal part of the basin may also contain deposits derived from streams that flow from beyond the basin toward the thrust belt subsequent removal of the thrust load by erosion and other processes results in flexural rebound of the thrust belt and adjacent foreland basin during this postorogenic phase of adjustment a regional unconformity develops in the proximal part of the foreland basin proximal deposits along with thrust derived sediment are redeposited in the distal foreland basin and beyond this two phase model of foreland sedimentation predicts that coarsening upward sequences in the proximal and distal parts of the basin have reciprocal significance the proximal sequence represents thrust belt advance whereas the distal sequence represents thrust belt cessation

large scale stratigraphic architecture eustatic variation and unsteady tectonism a theoretical evaluation we incorporate a process based depositional model with basin subsidence models to predict stratigraphic records this allows us to investigate the importance of subsidence geometry on coastal stratigraphy and thus to characterize and compare the stratigraphic architecture of two categories of tectonic basins the models demonstrate that the correlation of stratigraphic sequences to eustatic cycles is not the same in passive margin basins as in foreland basins and that in a foreland basin the record of episodic tectonism is distinct from that of eustatic sea level change in the model sediment transport is approximated by slope controlled diffusion nonmarine transport is treated as more efficient diffusion than marine transport three different subsidence and sediment supply models are examined a simple passive margin basin a simple foreland basin and then a foreland basin for which vertical motions are driven by thrust shortening that is compensated flexurally and for which sediment supply is related to relief predicted passive margin stratigraphies for cases of varying eustatic sea level are similar to those of natural basins and include progradational packages and subaerial unconformities which are used to define sequence boundaries that form during sea level fall we explore the timing relationships between stratigraphic features and a sinusoidal sea level history showing that the phase relationship depends on subsidence sediment flux efficiency of sediment transport and period and amplitude of sea level when the basic geometry of the basin is inverted placing the sediment supply on the side with maximum subsidence as is the case in foreland basins the sequence character changes markedly subaerial erosion does not generate unconformities in the models of a dynamic foreland basin sediment supply and subsidence are linked to the structure of the flanking thrust belt and are not necessarily constant for steady thrusting and variable sea level unconformities that define sequence boundaries form only on the distal or forebulge side of the basin and the ages of the sequence boundaries correlate to limes of rising sea level in cases of constant sea level but variable thrusting subaerial unconformities are cut locally on both the proximal margin of the basin and the distal margin of the basin yet the ages of the proximal margin and distal margin unconformities are out of phase in the tectonic cycle erosion is most pronounced during quiescence on the proximal side and during thrusting on the distal side

indicators of aqueous alteration and thermal metamorphism on the cv parent body microtextures of a dark inclusion from allende abstract an unusual dark clast in the allende cv3 chondrite termed allende af which was previously interpreted as a primary aggregate formed in the solar nebula kurat et al 1989 palme et al 1989 was re examined our study reveals abundant evidence suggesting that it probably experienced extensive aqueous alteration and subsequent thermal metamorphism on the meteorite parent body allende af contains numerous rounded to oval shaped inclusions embedded in a dark matrix the inclusions consisting predominantly of fine grains of fe rich olivine have internal textures suggesting that they are pseudomorphs after chondrules several inclusions appear to be replaced cais veins filled with fibrous olivine grains occur abundantly in both inclusions and matrix some veins up to 4 mm in length penetrate several inclusions providing strong evidence that aqueous alteration occurred after accretion the fibrous morphology of olivine in veins and inclusions suggests that the olivine was produced by dehydration and thermal transformation of phyllosilicate that had been formed by aqueous alteration olivine grains in the matrix contain numerous micro inclusions of fe ni sulfide which were probably incorporated during transformation from phyllosilicate allende af is probably related to the fine grained variety of dark inclusions reported from cv3 chondrites that has been described as the type containing abundant porous aggregates of fe rich olivine by johnson et al 1990 many dark inclusions previously described appear to be similar in texture and mineralogy to allende af and probably experienced similar secondary process on the meteorite parent body the wide variation in texture of dark inclusions can be explained by different degrees of aqueous alteration that preceded thermal metamorphism the size distribution of chondrule pseudomorphs and the abundance of cai pseudomorphs suggest that the precursor of allende af is a cv type chondrite probably allende itself oxygen isotopic and chemical compositions are consistent with this interpretation the cv parent body has been commonly thought to have escaped major secondary processing however allende af provides evidence that extensive aqueous alteration and thermal metamorphism have occurred locally on the cv parent body

pleistocene holocene climate change re establishment of fluvial drainage network and increase in relief in the swiss alps abstract data are presented about modern sediment discharge of the swiss rivers and related to the size of catchments the information reveals that the central alps have experienced denudation rates of 0 15 mm yr 1 in the foreland and 0 5 mm yr 1 in the alpine core mapping however indicates that modern erosion only affects 30 50 of the alpine surface and that fluvial and associated hillslope processes have focused erosion in 50 200 m deep valleys these valleys are incised into the glacial surface if this limited spatial extent of erosion is considered then effective erosion rates are significantly higher than average denudation rates these effective rates equal or locally exceed modern rates of rock uplift this implies that the modification of erosional processes related to the pleistocene holocene climate change has resulted in an increase in the relief at a local scale at a drainage basin scale however the relief appears not to change at present

shock metamorphism of carbonaceous chondrites abstract we have studied shock effects in carbonaceous chondrites using optical microscopy of thin sections and find that our petrographic classification of progressive shock metamorphism in ordinary chondrites can also be applied to carbonaceous chondrites we find that sixty nine carbonaceous chondrites can be assigned to four shock stages si to s4 largely on the basis of shock effects in olivine the least shocked chondrite groups are cm2 and co3 thirty six out of thirty eight members are classified as shock stage s1 differences between the mean shock levels of certain groups of chondrites e g co3 and cv3 are probably due to stochastic differences in the sampling of their parent bodies however there is an overall tendency for the mean shock level of carbonaceous chondrites and ordinary chondrites to increase with increasing petrologic type that may reflect real differences in the shock level of near surface materials on their parent bodies caused by intrinsic variations in the chemical and physical properties of these materials petrologic type 2 and 3 chondrites are more porous and richer in volatiles than types 4 to 6 the greater porosity of types 2 3 causes higher post shock temperatures and melting at lower pressures and the higher volatile contents ensure that strongly shocked material is more readily dispersed on release from high pressure we suggest that type 2 3 material shocked above 20 30 gpa normally escapes from the parent asteroids and forms particles that are too small to survive as meteorites in the cv3 group there is a correlation between the degree of chondrule flattening and the intensity of shock metamorphism analogous to that discovered in ordinary chondrites by sneyd et al 1988 suggesting that shock rather than static overburden pressure is responsible for chondrule flattening we infer that the correlations are due to collapse of pores under shock pressures of at least 5 10 gpa and that shock is an important process affecting many physical properties of type 2 4 chondrites

alteration of al rich inclusions inside amoeboid olivine aggregates in the allende meteorite lightly altered al rich inclusions in amoeboid olivine aggregates have cores containing primary melilite fassaite spinel perovskite and no secondary alteration products in moderately altered inclusions whose cores now contain only fassaite spinel perovskite melilite was replaced by a fine grained mixture of grossular anorthite feldspathoids and perovskite was partially replaced by ilmenite in heavily altered inclusions fassaite has been replaced by a mixture of phyllosilicates ilmenite and the remaining primary phases are spinel perovskite in very heavily altered inclusions no primary phases remain the spinel having reacted to form either phyllosilicates or a mixture of olivine feldspathoids this sequence of alteration reactions may reflect successively lower solar nebular equilibration temperatures during alteration sio2 na2o k2o feo cr2o3 h2o and cl were introduced into the inclusions and cao was lost mgo may have been lost during the melilite reaction and added during formation of phyllosilicates electron microprobe analyses indicate that the phyllosilicates are a mixture of na rich phlogopite and chlorite or alrich serpentine thermodynamic calculations suggest that at a solar nebular water fugacity of 10 6 na rich phlogopite could have formed from fassaite at 470 k and chlorite from na rich phlogopite at 328 k olivine mantling al rich inclusions is not serpentinized suggesting that these objects stopped equilibrating with the nebular gas above 274 k

reorganization of the western himalayan river system after five million years ago uplift of mountains driven by tectonic forces can influence regional climate1 2 as well as regional drainage patterns which in turn control the discharge of eroded sediment to the ocean3 4 but the nature of the interactions between tectonic forces climate and drainage evolution remains contested5 6 7 here we reconstruct the erosional discharge from the indus river over the past 30 million years using seismic reflection data obtained from drill core samples from the arabian sea and neodymium isotope data we find that the source of the indus sediments was dominated by erosion within and north of the indus suture zone until five million years ago after that the river began to receive more erosional products from himalayan sources we propose that this change in the erosional pattern is caused by a rerouting of the major rivers of the punjab into the indus which flowed east into the ganges river before that time seismic reflection profiles from the indus fan suggest high mass accumulation rates during the pleistocene epoch partly driven by increased drainage to the indus river after five million years ago and partly by faster erosion linked to a stronger monsoon over the past four million years1 our isotope stratigraphy for the indus fan provides strong evidence for a significant change in the geometry of western himalayan river systems in the recent geologic past

petrology of allende dark inclusions abstract bulk compositions acquired by neutron activation analysis are reported for eight allende dark inclusions dis and compared with compositions of five dis previously reported in the literature enrichments of the elements na k br ba au and as are generally correlated with increased proportions of porous aggregates predominantly composed of fine grained platy to fibrous olivine these aggregates have been interpreted by some workers as chondrules and inclusions that first were exposed to aqueous alteration converting anhydrous silicates to phyllosilicates and later were dehydrated by thermal metamorphism converting phyllosilicates to olivine our data support this interpretation and suggest that the aqueous alteration was open system in character feldspathoid grains intergrown with platy to fibrous olivines in porous olivine rich aggregates and inclusions of sodalite nepheline pentlandite ilmenite and spinel in these olivines suggest that phyllosilicates produced during aqueous alteration could accommodate na k ni s etc and are most consistent with a mixture of both saponite and serpentine dehydration of saponite would require that the temperature of thermal metamorphism was higher than previously suggested and may have been as high as 800 900 c nonporous rims containing ca rich minerals andradite hedenbergite surrounding dark inclusions containing highest proportions of porous olivine rich aggregates and slight to moderate depletions of these clasts in ca relative to bulk allende suggest that these rims were also the result of redistribution of some elements during dehydration of these clasts caused by thermal metamorphism

magnetic fabric and modeled strain distribution in the head of a nested granite diapir the melechov pluton bohemian massif abstract the melechov pluton bohemian massif is interpreted as a mid crustal nested granitic diapir with an apical part exposed at the present day erosion level the diapir head exhibits a concentric structure defined by lithologic zoning and by the anisotropy of magnetic susceptibility ams in concert with theoretical models outward dipping margin parallel magnetic foliations are associated with oblate shapes of the susceptibility ellipsoids and higher degree of anisotropy passing inward into weaker triaxial to prolate fabric by contrast magnetic fabric in an inner granite unit is in places oriented at a high angle to internal contacts and is interpreted as recording an internal diapir circulation we use inverse modeling to calculate strain variations across the diapir from the ams data the magnetic fabric parameters and calculated strains are in agreement with strain distribution in heads of model newtonian diapirs traveling a distance of two body radii and suggest granitic magma ascent as a crystal poor suspension followed by crystallization of fabric markers and their response to strain near the final emplacement level the intrusive fabric thus formed late but though generally weak was still capable of recording incremental strain gradient in the granite diapir

neogene quaternary tectonic stratigraphy of the eastern southern alps ne italy abstract in order to reconstruct the neogene quaternary tectonic stratigraphy of the eastern southern alps the late tortonian lower pleistocene foredeep clastic sequences cropping out in the veneto and friuli piedmont areas have been extensively investigated focusing on the contractional features observed in the frequent conglomerate layers pitted pebbles the eastern southern alps is the result of a typical polyphase tectonic activity initiated in late oligocene characterised by the occurrence of several non coaxial stress regimes based on careful analyses of the pebbles surfaces shape and orientation of the indented features and following a systematic and statistical approach the mean orientation of the maximum compressive stress axis 1 has been obtained for more than 30 sites of measurements along the ca 120 km long investigated piedmont area the affected lithostratigraphic units and the orientation pre versus post tilting of the stereonets density peaks make it possible to recognize four distinct deformational events and characterize them in terms of mean 1 direction and timing late tortonian 1 313 00 late messinian early pliocene 338 04 late pliocene 314 03 and early middle pleistocene 160 03 the tectonic stratigraphy of the eastern southern alps during the last ca 10 ma shows the occurrence of several variations of the stress field characterized by a repeated oscillation of the 1 axis between an nnw sse and nw se directions twist tectonics taking also into account literature data about older deformational events chattian burdigalian and serravallian tortonian we analyse the neogene quaternary tectonic evolution in the frame of the central mediterranean realm and compare it with the convergence direction between the adria africa and europe lithospheric plates we show that compressional directions within the eastern southern alps are basically governed by the remote plate convergence though since late messinian the approaching northern apennines started to play a crucial role within the investigated area alternating short lived phases 1 2 ma of coupling and decoupling along the basal detachment of the apennines accretionary wedge probably caused temporary perturbations of the local stress field and complex accommodation structures in this region of ongoing crustal collision

detrital fission track analysis and sedimentary petrofacies as keys of alpine exhumation the example of the venetian foreland european southern alps italy sedimentary petrography and detrital apatite fission track analysis of sediments from the oligo miocene venetian foreland succession ne italy reveal a multi stage evolution of the alpine source areas during the first stage of sedimentation chattian to langhian the foreland basin was filled by sediments derived from erosion of mainly crystalline austroalpine units exhumed north of the periadriatic lineament these sediments are characterized by litharenites with mean quartz content of about 61 and by a mean detrital apatite fission track peak of about 30 ma the permian paleogene sedimentary cover of the southalpine crystalline basement dolomite region was bypassed by the sediments and made only a minor input from the serravallian onwards the foreland basin was incorporated into the southalpine thrust belt the compressional events of the valsugana phase resulted in thrusting and uplift of the southalpine domain as documented by tortonian fission track ages in the hanging wall of the major regional thrust valsugana thrust fault the southalpine crystalline basement unaffected by alpine metamorphism and its sedimentary cover became the main source of sediments as revealed by the increase in extrabasinal carbonate grains and detrital apatite grains with late triassic jurassic fission track ages during this final stage of basin evolution about 3000 m of sediments were deposited these strata subsequently have been uplifted and eroded since the pliocene indicating a southward migration of the alpine deformation front

present state of tectonic stress of the friuli area eastern southern alps stress orientations are determined for the friuli area from focal mechanisms using the inversion technique of gephart and forsyth 1984 the data consist of 244 fault plane solutions selected for the period 1988 1995 where the data coverage was poor this period was extended to 1978 1996 local magnitude ranges from 2 0 to 4 3 and the depths extend from 4 to 16 km the friuli area is subdivided into five seismotectonic zones on the basis of tectonic characteristics seismic activity and focal mechanisms and for each zone a stress tensor is determined the results show that the active tectonic stress in the friuli area is heterogeneous and conditioned by the complex structural pattern which is characterized by two indented tectonic wedges the western and central parts of the area are mainly affected by a compressional state of stress while in the eastern part a strike slip state of stress prevails the orientation of the principal stresses varies from the western to the eastern part of the area and differences are also noticeable with depth in the central part of the friuli area the maximum compressional stress is n s trending at shallow depths 10 km changing to nw se at deeper levels the maximum compressional stress is nw se oriented in the western part while in the eastern part it is n s oriented

anatomy of an allende coarse grained inclusion inclusion 5241 is a petrographically complex coarse grained cai from the allende meteorite containing a core with two petrographically and chemically distinct units the core is surrounded by a melilite mantle similar to that described for allende type b1 inclusions which consists of large millimetersized crystals the two different units of the core are 1 spinel free islands consisting of melilite fassaite and minor anorthite 2 spinel rich areas with major fassaite and reversely zoned melilite in this unit spinel occurs in fassaite melilite and in densely packed belts surrounding the spinel free islands mineral chemistries of melilite and fassaite in the spinel free islands are different from those in the spinel rich areas melilite in the spinel free islands is unzoned and displays a very narrow chemical variation 10 mol within individual crystals ranging between ak 52 and ak 68 in all islands they also contain considerable amounts of na melilite molecule as much as 2 7 mol in contrast melilite in the spinel rich areas is reversely zoned and barren of na melilite the composition varies between ak 43 and ak 62 with the lowest ak content within a zone decorated with fassaite and spinel inclusions zoning in individual melilite crystals in the mantle is not continuous as in allende type b1 inclusions but is rhythmic outwards from ak 30 to ak 35 near the core mantle boundary followed by a continuous decrease with the lowest value near the center of the melilite crystals ak 25 the ak content rises again and reaches a value of ak 28 at the rim of the inclusion fassaite in the spinel free islands is typically concentrically zoned with ti al rich cores and ti al poor rims the concentration of ti 3 in some fassaite crystals in the islands appears to be lower than in the spinelrich areas zoning of fassaite in the spinel rich areas is nonsystematic and the tio 2 variations are considerable 2 12wt bulk compositions of the spinel free islands plot inside the type b cai field but considerably below the fo an ge plane because they are spinel deficient in contrast compositions of the spinel rich areas plot outside the type b cai field close to pyroxene saturated compositions stolper 1982 textural relations and mineral chemistries in the spinel free islands spinel rich areas and melilite mantle cannot be explained by gas solid condensation simple stage crystallization from a refractory silicate liquid or evaporative loss by distillation but suggest a series of complex events including the capture of solid spinel free bodies by a refractory liquid the melilite mantle may have formed by crystallization from a liquid which enveloped the complex core

calcium aluminum rich inclusions with fractionation and unknown nuclear effects fun cais i mineralogy petrology and oxygen isotopic compositions we present a detailed characterization of the mineralogy petrology and oxygen isotopic compositions of twelve fun cais including c1 and ek1 4 1 from allende cv that were previously shown to have large isotopic fractionation patterns for magnesium and oxygen and large isotopic anomalies of several elements the other samples show more modest patterns of isotopic fractionation and have smaller but significant isotopic anomalies all fun cais studied are coarse grained igneous inclusions type b forsterite bearing type b compact type a and hibonite rich some inclusions consist of two mineralogically distinct lithologies forsterite rich and forsterite free poor all the cv fun cais experienced postcrystallization open system iron alkali halogen metasomatic alteration resulting in the formation of secondary minerals commonly observed in non fun cais from cv chondrites the cr fun cai gg 3 shows no evidence for alteration in all samples clear evidence of oxygen isotopic fractionation was found most samples were initially 16 o rich on a three oxygen isotope diagram various minerals in each fun cai spinel forsterite hibonite dmisteinbergite most fassaite grains and melilite only in gg 3 define mass dependent fractionation lines with a similar slope of 0 5 the different inclusions have different 17 o values ranging from 25 to 16 melilite and plagioclase in the cv fun cais have 16 o poor compositions 17 o 3 and plot near the intercept of the allende cai line and the terrestrial fractionation line we infer that mass dependent fractionation effects of oxygen isotopes in fun cai minerals are due to evaporation during melt crystallization differences in 17 o values of mass dependent fractionation lines defined by minerals in individual fun cais are inferred to reflect differences in 17 o values of their precursors differences in 18 o values of minerals defining the mass dependent fractionation lines in several fun cais are consistent with their inferred crystallization sequence suggesting these minerals crystallized during melt evaporation in other fun cais no clear correlation between 18 o values of individual minerals and their inferred crystallization sequence is observed possibly indicating gas melt back reaction and oxygen isotope exchange in a 16 o rich gaseous reservoir after oxygen isotope fractionation some fun cais could have experienced partial melting and gas melt oxygen isotope exchange in a 16 o poor gaseous reservoir that resulted in crystallization of 16 o depleted fassaite melilite and plagioclase the final oxygen isotopic compositions of melilite and plagioclase in the cv fun cais may have been established on the cv parent asteroid as a result of isotope exchange with a 16 o poor fluid during hydrothermal alteration we conclude that fun cais are part of a general family of refractory inclusions showing various degrees of fractionation effects due to evaporative processes superimposed on sampling of isotopically heterogeneous material these processes have been experienced both by fun and non fun igneous cais generally the inclusions identified as fun show larger isotope fractionation effects than non fun cais there is a wide spread in un isotopic anomalies in a large number of cais not exhibiting large fractionation effects in oxygen magnesium and silicon the question of why some fun cais show more extreme un isotopic effects is attributed by us to limited sampling and not a special source of isotopically anomalous material we consider the majority of igneous cais to be the result of several stages of thermal processing evaporation condensation and melting of aggregates of solid precursors composed of incompletely isotopically homogenized materials the unknown nuclear effects in cais are common to both fun and non fun cais and are not a special characteristic of fun inclusions but represent the spectrum of results from sampling a very heterogeneous medium in the accreting solar system

mineral equilibrium in fractionated nebular systems we investigated the equilibrium mineral assemblages in chemically fractionated nebular systems using a computer routine that finds the set of minerals and gases which minimizes the gibbs free energy of a system with stipulated elemental abundances diagrams are presented showing the equilibrium mineralogy as a function of temperature 400 2300 k for unfractionated solar material and five fractionated systems the fractionated systems were defined by mixing in various proportions the following four volatility components that solar material can be divided into refractory dust carbonaceous matter ices and h2 gas dust enrichment is seen to increase temperatures of condensation evaporation and the fe2 content of mafic minerals and to permit existence of stable melt phases enrichment of dust and organic matter produces mineral assemblages that are similar in many ways to those of enstatite chondrites but with mafic minerals that are far more reduced fe2 poor than those in primitive enstatite chondrites enrichment of dust organics and ices leads to highly ferrous mineralogies even at the highest temperatures but does not predict the stability of hydrous phases above 450 k

from middle jurassic heating to neogene cooling the thermochronological evolution of the southern alps abstract the dolomite region is located in the southern alps which were affected by mesozoic extensional tectonics and by consequent thermal perturbations in this work vitrinite reflectance and apatite fission track analysis are used to estimate the thermal evolution these methodologies have been applied to the permo mesozoic succession which crops out along the transalp seismic profile the regional distribution of the organic matter maturity seems to be mainly controlled by different burials reached during the norian liassic extensional phase in connection with high heat flow values the best solutions obtained from thermal modelling of both vitrinite and fission track data suggest that peak of high heat flow occurred during bajocian bathonian ages when western tethys was characterized by intrusions of gabbros and plagiogranites and extrusion of tholeiite basalts this time coincides with the onset of the drifting phase and related thermal subsidence the following thermal relaxation occurred during continuous sedimentation and the maximum burial does not coincide with peak temperatures cooling history has been carefully analysed through apatite fission track data on samples collected close to the valsugana overthrust which document an important exhumation event at about 10 ma the related erosion has been analysed through the combined use of arenite petrography and fission track analysis on detrital samples of the veneto foredeep succession which represents the storage of detritus during tertiary these data confirm that after serravalian the southalpine domain and related covers were affected by subaerial erosion

re examining pluton emplacement processes abstract previous pluton emplacement studies have attempted to explain how space is made during pluton emplacement in fact the only means of making space during emplacement of mantle derived magmas in the crust are 1 lowering the moho or 2 outward displacement of the earth s surface other pluton emplacement mechanisms are material transfer processes mtps that do not increase the volume of the crust one frequently cited mtp for emplacement of concentrically zoned and ballooning plutons is ductile flow of wall rocks around the plutons the expected structures and total strains near such plutons are dependent on the three dimensional pluton shape the width of the deforming aureole whether the pluton is a piercing or non piercing diapir and in the latter case the number of body radii the pluton travels we have re examined a few such plutons and calculated the amount of material transfer caused by ductile flow in no case is more than 40 and in most cases only 15 35 of the required material transfer accommodated by wall rock flow the contact aureoles around these plutons are too narrow and or strains too low indicating that the plutons are predominantly discordant bodies with narrow 0 1 0 4 pluton radii concordant aureoles a comparison of strains in natural contact aureoles and those made in mechanical models of diapirs indicates that natural strains are at least an order of magnitude less than model strains we suggest that the similarities between models of diapiric ascent of spherical bodies and concentrically zoned plutons are superficial because the models are too simplistic instead we argue that the ascent and emplacement of magmas require multiple near field and far field mtps these mtps will show gradients with depth distance from the magma and with time rates of near field mtps must be rapid whereas far field rates are probably nearer to long term average rates of orogenic processes

forsterite bearing type b refractory inclusions from cv3 chondrites from aggregates to volatilized melt droplets detailed petrologic and oxygen isotopic analysis of six forsterite bearing type b calcium aluminum rich inclusions fobs from cv3 chondrites indicates that they formed by varying degrees of melting of primitive precursor material that resembled amoeboid olivine aggregates a continuous evolutionary sequence exists between those objects that experienced only slight partial melting or sintering through objects that underwent prolonged melting episodes in most cases melting was accompanied by surface evaporative loss of magnesium and silicon this loss resulted in outer margins that are very different in composition from the cores so much so that in some cases the mantles contain mineral assemblages that are petrologically incompatible with those in the cores the precursor objects for these fobs had a range of bulk compositions and must therefore have formed under varying conditions if they condensed from a solar composition gas five of the six objects show small degrees of mass dependent oxygen isotopic fractionation in pyroxene spinel and olivine consistent with the inferred melt evaporation but there are no consistent differences among the three phases forsterite spinel and pyroxene are 16 o rich with d 17 o 24 in all fobs melilite and anorthite show a range of d 17 o from 17 to 1

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

amoeboid olivine aggregates from ch carbonaceous chondrites amoeboid olivine aggregates aoas in ch carbonaceous chondrites are texturally and mineralogically similar to those in other carbonaceous chondrite groups they show no evidence for alteration and thermal metamorphism in an asteroidal setting and consist of nearly pure forsterite fa 3 in wt cao 0 1 0 8 cr2o3 0 04 0 48 mno 0 5 anorthite al diopside in wt al2o3 0 7 8 1 tio2 1 fe ni metal spinel and occasionally low ca pyroxene fs1wo2 3 and calcium aluminum rich inclusions cais the cais inside aoas are composed of hibonite grossite melilite ak13 44 spinel perovskite al ti diopside in wt al2o3 up to 19 6 tio2 up to 13 9 and anorthite the ch aoas including cais within aoas have isotopically uniform 16o rich compositions average 17o 23 4 2 3 2sd and on a three isotope oxygen diagram plot along slope 1 line the only exception is a low ca pyroxene bearing aoa 1 103 that shows a range of 17o values from 24 to 13 melilite grossite and hibonite in four cais within aoas show no evidence for radiogenic 26mg excess 26mg in contrast anorthite in five out of six aoas measured has 26mg corresponding to the inferred initial 26al 27al ratio of 4 3 0 7 10 5 4 2 0 6 10 5 4 0 0 3 10 5 1 7 0 2 10 5 and 3 0 2 6 10 6 anorthite in another aoa shows no resolvable 26mg excess an upper limit on the initial 26al 27al ratio is 5 10 6 we infer that ch aoas formed by gas solid condensation and aggregation of the solar nebula condensates forsterite and fe ni metal mixed with the previously formed cais subsequently they experienced thermal annealing and possibly melting to a small degree in a 16o rich gaseous reservoir during a brief epoch of cai formation the low ca pyroxene bearing aoa 1 103 may have experienced incomplete melting and isotope exchange in an 16o poor gaseous reservoir the lack of resolvable 26mg excess in melilite grossite and hibonite in cais within aoas reflects heterogeneous distribution of 26al in the solar nebula during this epoch the observed variations of the inferred initial 26al 27al ratios in anorthite of the mineralogically pristine and uniformly 16o rich ch aoas could have recorded i admixing of 26al in the protoplanetary disk during the earliest stages of its evolution and or ii closed system mg isotope exchange between anorthite and mg rich minerals spinel forsterite and al diopside during subsequent prolonged days to weeks thermal annealing at high temperature 1100 c and slow cooling rates 0 01 k h 1 that has not affected their o isotope systematics the proposed thermal annealing may have occurred in an impact generated plume invoked for the origin of non porphyritic magnesian chondrules and fe ni metal grains in ch and cb carbonaceous chondrites about 5 myr after formation of cv cais

polyphase metamorphism in the eastern carnic alps n italy s austria clay minerals and conodont colour alteration index evidence thermal evolution of the palaeozoic triassic sequences of the carnic alps has been characterized by b cell dimension and kubler index illite crystallinity of k white micas ki arkai index ai of chlorites clay mineral assemblages and conodont colour alteration index cai data indicate at least two metamorphic events variscan and alpine in the older event high anchizonal conditions predominated although epizonal conditions were reached over wide areas it was characterized by low intermediate pressure facies the thermal peak was mainly due to an extensional regime during the bashkirian a younger thermal overprint generated by alpine orogeny was of lower grade reaching high diagenetic anchizonal conditions characterized by high pressure facies inverted metamorphic patterns are associated with middle to late miocene thrusting hydrothermal alteration in the northern part of the region can be linked with emplacement of oligocene plutons and high heat flow along the periadratic lineament