paleoseismology along the 1980 surface rupture of the irpinia fault implications for earthquake recurrence in the southern apennines italy the irpinia fault was the source of the ms 6 9 1980 irpinia earthquake and produced the first unequivocal historical surface faulting in italy trenching of the 1980 fault scarp at piano di pecore a flat intermontane basin about 5 km south of the 1980 instrumental epicenter provides the first data on earthquake recurrence intervals slip per event and slip rate on a major normal fault in the southern apennines fault zone the trenches exposed evidence of four pre 1980 paleoearthquakes that occurred during the past 8600 years a best estimate average recurrence interval is 2150 years although the time interval between individual events varies by as much as a factor of 2 each paleo earthquake is similar to the 1980 surface rupture in amount of slip and style of deformation which suggests that the 1980 event is characteristic for the irpinia fault slip per event values average 61 cm the net vertical displacement of 2 12 2 36 m since 8600 cal year b p observed in the trenches gives a vertical slip rate of 0 25 0 35 mm yr a dip slip rate of 0 29 0 40 mm yr and an extension rate of 0 14 0 20 mm yr although fault behavior data are only available for the irpinia fault they provide a starting point for evaluating earthquake recurrence and rates of deformation in southern apennines they suggest that 1 fault specific earthquake recurrence intervals based on the historical seismic record overestimates the occurrence of large magnitude m7 earthquakes and 2 the holocene rate of extension across the apennines is 1 mm yr the 1980 earthquake and the paleoseismologic observations show that repeated and localized surface faulting occurs in southern apennines and leaves subtle but distinct geomorphic evidence that can be detected with detailed and careful investigation

fault parameters in the messina strait southern italy and relations with the seismogenic source abstract the messina strait is characterized by strong deformations in pliocene and pleistocene times but considering the historical seismicity significant uncertainity exists as to whether any of the surface fault systems reflects the location geometry and mechanisms of the seismogenic source based on field data and structural analyses the parameters length l displacement d age of activity t minimum slip rate min and total geological moment m g have been derived for all the faults exposed on the sicilian and calabrian sides of the strait the analysis of these parameters shows that the highest rates of activity pertain to interconnected faults of different orientation and length which bound the uplifted crystalline basement relative to the pliocene pleistocene foundered zones of the calabrian side the comparison between the fault slip rates and the regional uplift rates shows that each single fault contributes for a limited fraction only to the whole deformation release in the area the contribution of the whole fault population expressed as cumulative m g release is still one order of magnitude less than the seismic moment release taking into account the underestimation of the geological parameters the lack of information on the offshore faults and the role of anelastic deformation by aseismic creep the data suggest that the long term recurrence of seismic breaks is partitioned at the surface in a complex array of interconnected faults some of these faults might represent basement inherited structures repeatedly and preferentially reactivated over geological time

fluid flow triggered migration of events in the 1989 dobi earthquake sequence of central afar during the august 1989 sequence of earthquakes beneath the dobi graben in central afar principal events including 10 shocks with ml 5 5 propagated 50 km north westwards in 50 h the sequence is analyzed in terms of triggering by propagation of a critical pore pressure wave in a compressible fluid through a fractured medium the macroscopic fluid diffusion tensor d in the crust beneath the graben is estimated its principal eigenvector strikes n115 e nearly parallel to the graben axis with a value it is about 10 times larger than the other two consistent with fissure anisotropy in the graben the order of magnitude of the permeability 10 8 m is compatible with characteristic fissure widths ranging from 1 mm to 3 cm estimating such parameters in other extensional regions might help to understand better the temporal evolution of seismic swarms

abee and related eh chondrite impact melt breccias abstract the abee eh chondrite is an impact melt breccia about 80 90 of the chondrules were melted many of those that remain have been partly resorbed euhedral enstatite phenocrysts are abundant many have nucleated on the surfaces of relict chondrules and now protrude into kamacite globules euhedral laths of graphite essentially identical to those produced magmatically on earth occur throughout the rock abee experienced two episodes of impact melting with an intervening period of brecciation the first impact melting event produced a relatively homogeneous rock with abundant melt upon cooling the rock was shattered by bombarding meteoroids igneous oldhamite rich dark inclusions were introduced at this time a second impact event produced melt which engulfed the abee fragments and dark inclusions primarily digesting the small ones heat lost to the surrounding clastic debris caused the groundmass melt to quench previously described diamonds in abee containing typical solar system isotopic compositions of n and xe were probably produced from graphite by shock several other eh chondrites may also be impact melt breccias the most extensively melted of these is adhi kot which contains shocked but largely unmelted chondrule rich clasts as well as chondrule free sulfide and silica rich clasts that also appear to be impact products

normal faulting transcrustal permeability and seismogenesis in the apennines italy abstract late pliocene pleistocene tectonic evolution of the apennines is driven by progressive eastward migration of extensional downfaulting superposed onto the late miocene early pliocene compressional thrust belt this process has led to distinct structural domains that show decreasing transcrustal permeability from conditions of pervasive mixing between deep and surface fluids in the hinterland west to conditions of restricted fluid circulation and overpressuring in the foreland east at present the highest rates of normal faulting and the strongest seismicity occur in the area bounded by stretched highly permeable crust to the west and thick poorly permeable crust to the east in this area the seismogenic sources of the largest earthquakes 5 m s

the origin of the apenninic arcs abstract the apennine area is composed of a variety of arcs some of them forming the mountain chain and some of them being submerged below the po plain and the adriatic sea the structure of the apennine mountain belt is that of a succession of northeast east and southeastward directed arcs corresponding to single thrust sheets each arc is limited by n s oriented dextral transcurrent faults data from volcanology gravimetry and reflection seismic surveys show that an important section of the upper mantle is involved in these features the geodynamic reconstruction during neogene times i e the period of apenninic up building suggests that a unique arc existed from oligocene to middle miocene times as a result of the rotation of the sardo corso continental block this arc was successively disrupted in several segments which advanced and shortened differentially as a function of the resistance to the orogenic expansion opposed by the rigid adriatic foreland this new tectonic phase which is responsible for most of the apenninic features has been triggered by the differential evolution of anomalous mantle domes in the tyrrhenian area from post middle miocene times onwards

the origin of chondrules and chondrites debris from low velocity impacts between molten planetesimals we investigate the hypothesis that many chondrules are frozen droplets of spray from impact plumes launched when thin shelled largely molten planetesimals collided at low speed during accretion this scenario here dubbed splashing stems from evidence that such planetesimals intensely heated by 26al were abundant in the protoplanetary disk when chondrules were being formed approximately 2 myr after calcium aluminum rich inclusions cais and that chondrites far from sampling the earliest planetesimals are made from material that accreted later when 26al could no longer induce melting we show how splashing is reconcilable with many features of chondrules including their ages chemistry peak temperatures abundances sizes cooling rates indented shapes relict grains igneous rims and metal blebs and is also reconcilable with features that challenge the conventional view that chondrules are flash melted dust clumps particularly the high concentrations of na and feo in chondrules but also including chondrule diversity large phenocrysts macrochondrules scarcity of dust clumps and heating we speculate that type i feo poor chondrules come from planetesimals that accreted early in the reduced partially condensed hot inner nebula and that type ii feo rich chondrules come from planetesimals that accreted in a later or more distal cool nebular setting where incorporation of water ice with high 17o aided oxidation during heating we propose that multiple collisions and repeated re accretion of chondrules and other debris within restricted annular zones gave each chondrite group its distinctive properties and led to so called complementarity and metal depletion in chondrites we suggest that differentiated meteorites are numerically rare compared with chondrites because their initially plentiful molten parent bodies were mostly destroyed during chondrule formation

possible impact induced refractory lithophile fractionations in el chondrites abstract literature data show that refractory lithophile elements in most chondrite groups are unfractionated relative to ci chondrites the principal exception is the el chondrite group whose observed falls all of which are type 6 are depleted in ca and light ree in contrast literature data and our new inaa data on el3 pca 91020 el3 mac 88136 and el4 grein 002 show that some replicates of these samples have nearly flat ree patterns unlike those of el6 chondrites other replicates exhibit fractionated ree patterns similar to those of el6 chondrites petrographic examination shows that many el6 and some el3 and el4 chondrites are impact melt breccias or contain impact melted portions we suggest that the same impact processes that formed these breccias and produced melt are responsible for the observed bulk compositional fractionations in refractory lithophile elements i e el6 chondrites were produced from initially unequilibrated el3 material when large amounts of impact heat were deposited plagioclase and or oldhamite cas the major ree carriers in enstatite chondrites may have been melted and then transported appreciable 10 cm distances el6 chondrites represent the residuum that is depleted in ree particularly in lree and ca unlike the case for el chondrites our new inaa data on alh 84170 eet 87746 and sah 97096 all eh3 show some scatter but are consistent with the eh group having uniform refractory lithophile abundances

the blithfield meteorite and the origin of sulfide rich metal poor clasts and inclusions in brecciated enstatite chondrites abstract blithfield el6 is one of five known enstatite chondrite breccias it consists of troilite rich clasts 35 5vol embedded in an extremely metallic fe ni rich matrix 65 5 vol that contains metal nodules up to 17 mm in size clasts and matrix agglomerated independently in the solar nebula under conditions of high and low ps 2 po 2 ratios respectively the matrix accreted to an el chondrite planetesimal and was metamorphosed to 1000 c above the fe ni s eutectic chondrule textures were obliterated the s rich eutectic melt was lost from the matrix the matrix material was buried to a depth of at least 3 km accreting troilite rich material was incorporated into the matrix as clasts the breccia cooled through 500 c at 1000 10 000 c myr after cooling below 500 c blithfield was quenched possibly by impact excavation from depth and deposition onto the surface clasts or inclusions that are enriched in sulfide and depleted in metallic fe ni are common in brecciated enstatite chondrites variations in the ps 2 po 2 ratio in the nebular regions where these materials formed may explain many of their petrologic properties the silica rich clasts in adhi kot eh4 formed at very high ps 2 po 2 ratios 10 27 niningerite free silica and troilite were produced from the sulfurization of enstatite and metallic fe the troilite rich clasts in blithfield and atlanta el6 as well as the troilite rich regions of the hvittis el6 matrix formed at somewhat lower ps 2 po 2 ratios where sulfurization of metalic fe produced troilite the ni content of the residual metal increased forming some metal of martensitic composition the dark inclusions in abee eh 4 which contain up to 9 wt oldhamite formed at high ps 2 po 2 ratios in the presence of an additional ca rich component

palaeoseismicity in the gran sasso massif abruzzo central italy abstract the upper maone and venacquaro valleys on the northern side of the gran sasso massif apennines central italy have been studied in detail from the geological and geomorphological standpoints to date the activity of the faults that produced spectacular fault scarps in the late glacial and holocene sediments and morphological features the faults that produced the studied scarps have been active at least four times during the last 18 000 years and each time on the basis of the indications emerging from the study of the scarp heights displacements of similar size were probably produced the first faulting seems datable to a period slightly more recent than 18 000 years ago the second faulting occurred after the moraines of the second apennine stage these preceding a lacustrine deposit dated 11 760 160 bp could be put in the older portion of the period between 16 000 and 13 000 years ago the third faulting must be more recent than 6000 7000 years ago and slightly older than 5450 170 and 6110 180 bp a fourth phase is appreciably later than 3490 160 bp and older than the year 1000 a d for the venacquaro valley the size of the displacements more recent than 18 000 years ago indicated by the height of the fault scarps and by geophysical data is about 16 18 m for the val maone the size of the displacements more recent than the moraines of the second apennine stage is 10 11 m the respective slip rates are 0 88 1 mm year for the venacquaro valley and approximately 0 67 0 78 mm year for the maone valley it is very probable that the fault activity occurred during a seismic event or events that took place during a short time the intervals between the seismic events or seismic periods although these cannot be defined with precision appear longer than 2500 3000 years and shorter than 6000 7000 years it is possible that also in the gran sasso as in other parts of the abruzzo apennines seismic activity is characterized by events of great magnitude with long return periods

structural and fluid chemical properties of seismogenic normal faults abstract structures in extensional fault zones can be classified using the configuration of fault branch lines and tip lines important classes include the segment bend segment termination segment branch cross fault intersection and segment offset the effect of these structures on rupture history is not necessarily consistent neither between individual earthquakes nor between different fault zones rupture behavior is dependent on several other factors including loading conditions regional and localized rupture tip stress fields fluid mechanical processes and chemical processes fracture toughness is partly controlled by the angular discordance between slip directions on adjacent fault segments greater discordance between slip directions and intersection lines of fault segments results in greater strain incompatibility an internal fracture network generally evolves within a segment boundary to maintain compatibility and transfer slip between the segments the dimensions and structure of this fracture network may also partly control rupture propagation presumably activation of a fault network with large angular discordances between slip directions and intersection lines will generate numerous asperities as the subsidiary faults mutually interact and offset each other the geometry of a segment boundary may change with depth and the three dimensional nature of the structure may be important in controlling rupture history fluids influence rupturing via fluid pressure effects and time dependent chemical processes fracture propagation by stress corrosion may favor instability and chemical alteration may produce minerals of lower strengths allowing time dependent creep sealing and healing of fractures however may remove damage and increase strength elementary computations indicate that representative times for sealing and chemical alteration are between 1 and 1000 years for reasonable physical conditions well within the recurrence intervals of most large earthquakes time to failure for stress corrosion cracking is more highly variable and strongly sensitive to applied stress and fluid pressure

impact melt products of chondritic material a large variety of objects in chondritic meteorites formed as a result of impact melting shock veins metal troilite mixtures metal and sulfide nodules melt pockets vugs agglutinates glassy and crystalline spherules and numerous types of melt rock clasts the type of object produced in an impact event is related to the interaction of the shock waves with the particular target rock impact melting has also affected large portions of several chondrite breccias many of these contain vugs and patches of silicate glass some workers have suggested that various iron meteorites including groups iab iiicd and iie as well as several ungrouped irons were formed from individual impact melt pools in chondritic regoliths the eagle station trio pallasites and several ungrouped meteorites bencubbin weatherford enon acapulco and allan hills a77081 may have formed from impact melted chondritic material it is also possible that the parent magmas of ureilites were derived from impact melted metal rich carbonaceous chondrite material

relationships between ultrapotassic and carbonate rich volcanic rocks in central italy petrogenetic and geodynamic implications the pleistocene intra apennine volcanic iav centres occurring east of the potassium rich roman comagmatic province show variable petrological and geochemical composition some rocks have a strongly undersaturated ultrapotassic kamafugitic affinity with k2o na2o 8 20 whereas the rocks from the southern center of mt vulture are still strongly undersaturated in silica but are enriched in both na2o and k2o with k na around unity carbonate rich pyroclastic rocks believed to represent carbonatitic magmas are found in the iav centers kamafugites have high abundances of lile and high lile hfse ratios and their incompatible element patterns resemble closely those of ultrapotassic rocks from the adjoining roman province the vulture volcanics also display high contents of lile but their lile hfse ratios are intermediate between intraplate alkaline rocks and kamafugites the carbonate rich rocks exhibit an exotic mineralogy and high enrichments in lile which speaks for a carbonatitic affinity however they have similar incompatible element patterns but consistently lower abundances of almost all the elements than the associated silicate volcanics these data favour the hypothesis that the iav carbonate rocks may represent mixtures of silicate magmas and geochemically depleted carbonate material the sedimentary carbonates that crop out extensively along the apennine chain may be the source of barren carbonate material overall geochemical data of iav centres and of the rocks from the roman province display strong geochemical and isotopic evidence of being generated in an upper mantle that was modified by addition of upper crustal material brought down by subduction processes a possible exception is represented by mt vulture which however occurs east of the main axis of the apennines on the western margin of the foreland adria plate the occurrence of strongly undersaturated alkaline rocks requires magma generation at high pressures and xco2 this is in agreement with the hypothesis that subduction processes under the apennines occurred by consumption of poorly hydrated thinned or delaminated continental crust

seismic moment summation for historical earthquakes in italy tectonic implications tectonic deformation rates in and around the apennine mountains of italy are studied using seismic moments estimated from macroseismic effects of historical earthquakes northeastward extension in the northern apennines north of 42 5 n accompanies shortening along their northeast flank since the seventeenth century the sparse seismicity in these two zones has included no earthquake with magnitude 6 5 or seismic moment above 6 1018 n m their spatially averaged deformation rates are only 0 3 mm yr 1 but are equal such that the extension and shortening balance with no relative motion between their external surroundings in contrast the numerous historical earthquakes in the central and southern apennines with magnitude 7 and seismic moment 20 1018 n m require northeastward relative velocity across the deforming zone up to 5 mm yr 1 matching the expected relative motion of their surroundings this relative velocity is taken up in part by extension and in part by strike slip depending on the trend of the deforming zone and is not accompanied by en echelon shortening elsewhere in italy the northern apennines thus show different senses and rates of deformation from localities farther south and are thus technically distinct at present in contrast with previous interpretations

rheology and seismotectonic regime in the northern central mediterranean abstract the connection between thermal field and mechanical properties is analysed in the northern central mediterranean region extending from the ligurian provencal basin to the adriatic foredeep as the thermal regime is still far from equilibrium in most of the tectonic units transient thermal models are used the temperature depth distribution is estimated in four areas affected by the volcanic activity which from the neogene to the present shifted from corsica to the apenninic arc in the adriatic foredeep the thermal effects of the recent thrust faulting phase in the buried sectors of the northern apennines are taken into account the general context consists of convergence involving westward subduction of the adriatic plate this process caused anti clockwise rotation of corsica and sardinia which led to formation of the ligurian marginal basin and also resulted in crustal doubling and overthrusting in the northern apennines and rifting in the northern tyrrhenian seismic activity is focused in the internal and external zones of the apenninic arc where low surface heat flux is observed and in the western margin of the ligurian provencal basin this is a consequence not only of lateral variations in the thermal field but also of the different tectonic settings regional extensional patterns in the shallow crust with minimum principal stress axes trending n60 e and e w are observed in the northern and in the southern sectors of the apenninic arc respectively a compressional regime at depths greater than 30 km is observed below the northern sector of the arc while to the south a change in the structure of the lithosphere is marked by a decrease in deeper seismic activity thrust faults and strike slip faults with a thrust component support a compressional regime along the western margin of the ligurian basin with maximum principal stress axis oriented n120 e two lithospheric cross sections across the study region are constructed based on structural thermal gravity rheological and seismic data there is clear evidence of the presence of the subducting slab of the adriatic plate corresponding to a thickening of the uppermost brittle layer the crustal seismicity cut off corresponds to temperatures of 320 390 c a brittle layer of considerable thickness is present in the uppermost mantle beneath variscan corsica and the adriatic foredeep with estimated seismic cut off temperature of about 550 50 c

the hadley rille enstatite chondrite and its agglutinate like rim impact melting during accretion to the moon hadley rille is a millimeter size eh chondrite containing euhedral and acicular enstatite grains kamacite globules and preferentially aligned silicate aggregates separated by elongated kamacite rich patches the hadley rille chondrite was significantly impact melted when it accreted to the lunar regolith at relative velocities of 3 km s 1 65 75 of the chondrules present initially were melted during the impact portions of the local regolith were melted and an agglutinate like rim formed around the chondritic projectile the rim consists of flow banded vesicular glass blebs of troilite and low ni metallic fe rock fragments glass shards and mineral grains the mineral grains include enstatite which is otherwise absent from the moon and must have been derived from the projectile and poorly characterized micrometer size phases enriched in light rare earth elements lree which probably formed during the impact several of the rock fragments contain 33 mg g cl which was probably derived through impact induced volatilization of cl from chondrule mesostases in the eh projectile

contribution of numeric dynamic modelling to the understanding of the seismotectonic regime of the northern apennines abstract in this paper we investigate the forces possibly active in the area of the northern apennines by means of two dimensional finite element modelling assuming a viscoelastic rheology the forces included in the models are related to continental convergence between africa and eurasia to negative buoyancy of the subducted adriatic lithosphere and to positive buoyancy of anomalously hot mantle material underneath tuscany model predicted stress distribution is compared with seismotectonic data available for the area of the northern apennines and with earthquakes distribution our results indicate that continental convergence cannot be the only mechanism acting in the study area since it causes insignificant subcrustal stresses in disagreement with intermediate seismicity observed under the apennines asthenospheric upwelling under tuscany back arc region is shown to play a crucial role in the present day dynamics of the tyrrhenian apennines positive buoyancy causes an upwards and eastwards flow that generates extensional bending stresses in tuscany and at the top of the slab under the apennines horizontal pushing of the slab is proposed as an alternative mechanism to slab pull to generate subcrustal stresses activation of slab pull does not result in a significant change in orientation of the principal stress axes at shallow depths with respect to the model in which only asthenospheric diapirism is active therefore the existence of a continuous gravitationally sinking slab cannot be ruled out on the basis of comparison with seismotectonic observations both models successfully reproduce extension in tuscany and compression in the outer margin of the apenninic belt but fail to reproduce extension along the inner portion of the chain our modelling highlights the importance of better constraining the lateral extent of the asthenospheric diapir in order to find out whether the extension and tectonic uplift in the apennines is caused by asthenospheric upwelling as in the area of tuscany

sulfidation of mg rich olivine and the stability of niningerite in enstatite chondrites abstract when heated with excess fe ni monosulfide and graphite in a sealed silica glass tube at 1200 c mg rich olivine fo90 is sulfidized to niningerite mg fe s and clinoenstatite by the reaction mg 2 sio 4 1 2 s 2 c mgsio 3 mgs co minor amounts of fe ni suicides and silicon sulfides are also produced the distribution coefficient for ni fe exchange between mg fe s and fe ni s is about 24 and is significantly greater than that for coexisting niningerite and troilite in eh enstatite chondrites experimental studies in the ni free system at both subsolidus and liquid iron sulfide temperatures are in good overall agreement with the calculated phase relations for niningerite the quenched experimental assemblage clinoenstatite troilite niningerite alloy suicide graphite is equivalent to the reduced mineral assemblage of eh enstatite chondrites the present phase relations suggest that niningerite in eh chondrites could have been produced by sulfidation of mg rich silicates during either accretion or metamorphism at low fugacities of co however niningerite is not stable under the anticipated conditions of recrystallization of el enstatite chondrites the assemblage olivine graphite pyrrhotite is unstable under magmatic conditions at low and moderate crustal pressures

browneite mns a new sphalerite group mineral from the zaklodzie meteorite browneite ima 2012 008 mns is a new member of the sphalerite group discovered in zaklodzie an ungrouped enstatite rich achondrite the type material occurs as one single crystal 16 m in size in contact with and surrounded by plagioclase enstatite and troilite are nearby low ni iron martensitic iron tridymite quartz cristobalite sinoite schreibersite buseckite keilite and graphite are also present in the type sample browneite is yellowish brown and translucent the mean chemical composition as determined by electron microprobe analysis of the type material is wt s 36 46 mn 62 31 fe 0 62 ca 0 10 sum 99 49 leading to an empirical formula calculated on the basis of 2 atoms of mn 0 993 fe 0 010 ca 0 002 s 0 995 electron back scatter diffraction patterns of browneite are a good match to that of synthetic mns with the f43m structure showing 5 601 a v 175 71 a 3 and z 4 browneite is a low temperature 200 c phase metastable relative to alabandite that postdates the impact melting and subsequent crystallization of an enstatite rich rock

contemporaneous extension and compression in the northern apennines from earthquake fault plane solutions summary the northern apenninic arc belongs to the deformation zones surrounding the adriatic plate which behaves as a rigid block it is a ne verging fold and thrust belt which developed since the miocene with the migration of an extensional compressional pair previous seismological data are roughly in agreement with this deformation picture although the outer compressional front was not clearly defined by the few available solutions in this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the northern apennines defining the extent of these two zones and their interim1 deformation better than was previously done this is accomplished through the analysis of 125 new focal mechanisms of earthquakes 2 6 md 4 8 recorded by the national network of the lstituto nazionale di geofisica in the period 1988 1995 the two deformation zones are clearly separated and lie very close to each other with a partial overlapping in the emilian tuscan apennines strikeslip events are scattered in most of the study area thrust faulting earthquakes are located in the internal part of the most recently active thrust front middle upper pleistocene there is a general trend of the compressional p axes of thrust fault and strike slip solutions to be perpendicular to the apenninic direction in the external zone while the tensional axes of the normal fault and strike slip solutions in the belt do not show a uniform orientation however clearly evident is the ene direction of extension in the peri tyrrhenian region consistent with the direction of shmln in the quaternary volcanoes of this region inferred from borehole breakouts and microearthquake fault plane solutions we determined the orientation of the stress tensor in the two main deformation zones by inversion of the 125 fault plane solutions determined in this study we found that the external belt is characterized by ne sw compression ol horizontal oriented n45 e while a normal faulting regime with o3 e w oriented is characteristic of the umbria tuscany back arc region

contribution of structural analysis to understanding the geodynamic evolution of the calabrian arc southern italy abstract a marked curvature of crustal structures characterizes the calabrian arc in southern italy the overall deformation of the arc seems mostly controlled by the sangineto shear zone to the north and by the mt kumeta alcantara shear zone to the south which both separate different crustal sectors other important fault systems cut the iblean foreland scicli ragusa fault zone and many others dissect the crystalline units of central calabria neotectonic structural analyses have been carried out in order to recognize the character of the plio pleistocene tectonic phases and their bearing on the present configuration of the arc after the middle miocene extensional phase an early middle pliocene compressional phase is detectable in many parts of the arc right and left lateral displacements respectively characterize the mt kumeta alcantara and sangineto shear zones and right lateral movements are also detectable within the scicli ragusa fault system finally the pleistocene tensional regime seems to have been controlled mainly by uplift the structural and neotectonic data allow us to propose a model of the recent evolution of the arc which was bent mainly as a result of opposed wrench faulting along the sangineto and mt kumeta alcantara shear zones

magmatic sulfides in the porphyritic chondrules of eh enstatite chondrites abstract the nature and distribution of sulfides within 17 porphyritic chondrules of the sahara 97096 eh3 enstatite chondrite have been studied by backscattered electron microscopy and electron microprobe in order to investigate the role of gas melt interactions in the chondrule sulfide formation troilite fes is systematically present and is the most abundant sulfide within the eh3 chondrite chondrules it is found either poikilitically enclosed in low ca pyroxenes or scattered within the glassy mesostasis oldhamite cas and niningerite mg fe mn s are present in 60 of the chondrules studied while oldhamite is preferentially present in the mesostasis niningerite associated with silica is generally observed in contact with troilite and low ca pyroxene the sahara 97096 chondrule mesostases contain high abundances of alkali and volatile elements average na 2 o 8 7 wt k 2 o 0 8 wt cl 7100 ppm and s 3700 ppm as well as silica average sio 2 62 8 wt our data suggest that most of the sulfides found in eh3 chondrite chondrules are magmatic minerals that formed after the dissolution of s from a volatile rich gaseous environment into the molten chondrules troilite formation occurred via sulfur solubility within fe poor chondrule melts followed by sulfide saturation which causes an immiscible iron sulfide liquid to separate from the silicate melt the fes saturation started at the same time as or prior to the crystallization of low ca pyroxene during the high temperature chondrule forming event s protracted gas melt interactions under high partial pressures of s and sio led to the formation of niningerite silica associations via destabilization of the previously formed fes and low ca pyroxene we also propose that formation of the oldhamite occurred via the sulfide saturation of fe poor chondrule melts at moderate s concentration due to the high degree of polymerization and the high na content of the chondrule melts which allowed the activity of cao in the melt to be enhanced gas melt interactions thus appear to be a key process that may control the mineralogy of chondrules in the different classes of chondrite

hydrocarbon bearing submarine fan system of cellino formation central italy the cellino formation is a lower pliocene submarine fan system that forms extensive subsurface reservoir rocks the sequence consists of interbedded sandstones and shales which crop out in central italy it exhibits a definite geometric pattern of lateral fan accretion it is 60 by 20 km 37 by 12 mi elongate nnw sse and it follows the trend of previous fan systems the vertical and lateral sequences are interpreted from electric logs and supported by field observations the cellino formation consists of a series of different turbidite facies associations which includes a lower basin plain fan edge overlain by outer fan and fringe facies associations the lower part of the cellino formation here has been cut and deeply eroded in the northern part a new sequence follo s which activates the eastern migration of the fan system and deposits facies postdepositional deformation compressional faulting and folding decreases in the area in intensity eastward carbonate cements sandstone layers in the southwest part of the area associated hydrocarbons were trapped in outer fan lobes which were deformed into an anticline the thin shale beds provide the cap rocks of the turbidite reservoirs many of the depositional lobes have their individual gas water contacts

the compositional classification of chondrites ii the enstatite chondrite groups we present new data from a neutron activation analysis of four enstatite chondrites including the taxonomically important st sauveur and discuss the classification of enstatite chondrites the enstatite chondrites can be divided into two compositionally distinct sets in one set abundances of nonrefractory siderophiles and moderately volatile chalcophiles and alkalis are 1 5 2 0 higher than in the other a well resolved compositional hiatus separates these two sets the differences in composition are as great as those between the groups of ordinary chondrites and therefore it appears best to treat these sets as separate groups by analogy with the symbols used for ordinary chondrites we propose to designate the high fe high siderophile group eh and the low fe low siderophile group el known members of the eh group belong to petrologic types 4 and 5 whereas all el members are petrologic type 6 within the eh group no correlation is observed between petrologic type and abundance of nonrefractory siderophiles or moderately volatiles or alkalis two physical properties show only modest overlap between the eh and el groups cosmic ray ages for eh chondrites are 0 5 7 ma while those for el chondrites are 4 18 ma relative to bjurbole i xe formation intervals are 1 3 0 6 ma for eh chondrites and 2 9 0 5 ma for el chondrites the weight of the chemical and physical evidence indicates that the eh and el groups formed separate bodies at similar distances from the sun the available evidence for shallowater and happy canyon two strongly recrystallized silicate rich meteorites containing 40 mg g fe ni indicates that the former is an enstatite clan chondrite altered by loss of sulfide and plagioclase rich melts whereas the latter is intermediate in composition between el chondrites and the chondritic silicates in the pine river iab anomalous meteorite

stable isotope geochemistry and structural elements of the sabina region central apennines italy various tectonic features are present in the meso cenozoic basin units of the sabina region central apennines italy mio pliocene northeasterly verging thrusts are followed by plio pleistocene n s oriented right lateral strike slip faults stable isotope geochemistry and examination of meso and microstructures show that strain conditions differed through the course of tectonic history carbon and oxygen isotope analyses of the calate filled extensional fractures the sigmoidal veins present between stylolitic cleavage surfaces and fault plane surfaces with differing motion demonstrate those different geneses the c c of the older calcite filling fractures present both in the thrust and the strike slip systems suggests a deposition from shallow fresh water circulation furthermore the calcite fill of en echelon systems that occur in the southernmost plio pleistocene units is clearly the result of a more recent right lateral strike slip movement connected with shallow water circulation within mesozoic limestones the sigmoidal vein fills are derived from solid state pressure solution processes which were the result of strike slip movement the deformation pattern related to the older thrust system is similar but less intense this also demonstrates general recrystallization processes in a closed system this suggests that the total shortening of the deformed sections is lower than that obtained on the basis of solution on stylolitic planes because a sigruficant volume of dissolved carbonates remained in the system stable isotope analysis also confirms that the deformational history of strongly cleaved rocks in the sabina region took place in two phases and that extensional fractures formed before stylolithic planes as suggested by structural and field observations

microchondrule bearing clast in the piancaldoli ll3 meteorite a new kind of type 3 chondrite and its relevance to the history of chondrules in the piancaldoli ll3 chondrite we found a mm sized clast containing 100 chondrules 0 2 64 m in apparent diameter much smaller than any previously reported that are all of the same textural type radial pyroxene fs1 17 this clast like other type 3 chondrites has a fine grained ferich opaque silicate matrix sharply defined chondrules abundant low ca clinopyroxene and minor troilite and si and cr bearing metallic fe ni however the very high modal matrix abundance 63 8 vol unique characteristics of the chondrules and absence of microscopically observable olivine indicate that the clast is a new kind of type 3 chondrite most chondrules have feo rich edges and chondrule size is inversely correlated with chondrule core feo concentration the first reported correlation of chondrule size and composition chondrules acquired fe by diffusion from fe rich matrix material during mild metamorphism possibly before final consolidation of the rock microchondrules those chondrules 100 m in diameter are also abundant in another new kind of type 3 chondrite clast in the rio negro l chondrite regolith breccia in other type 3 chondrite groups microchondrule abundance appears to be anticorrelated with mean chondrule size viz 0 02 0 04 vol in h and co chondrites and 0 006 vol in l ll and cv chondrites microchondrules probably formed by the same process that formed normal sized droplet chondrules melting of pre existing dustballs because most compound chondrules in the clast and other type 3 chondrites formed by collisions between chondrules of the same textural type we suggest that dust grains were mineralogically sorted in the nebula before aggregating into dustballs the sizes of compound chondrules and chondrule craters which resulted from collisions of similarly sized chondrules while they were plastic indicate that size sorting of dustballs occurred before chondrule formation probably by aerodynamic processes in the nebula we predict that other kinds of type 3 chondrites exist which contain chondrule abundances size ranges and proportions of textural types different from known chondrite groups

normal and reverse zoning in niningerite a novel key parameter to the thermal histories of eh chondrites abstract two zoning trends have been discovered in niningerite grains in the eh chondrites abee kaidun iii south oman st marks yamato 74370 indarch yamato 691 and qingzhen 1 a a normal zoning with decreasing fe content from the core to the rim this is indicative of fe diffusion from niningerite to troilite upon cooling this trend is present in abee kaidun iii south oman st marks and yamato 74370 it may have developed either in the solar nebula or in the eh parent body 2 b a reverse zoning trend with increasing fe content from the core to the rim adjacent to troilite this trend is indicative of fe diffusion from troilite into niningerite as a result of thermal events it is encountered in indarch yamato 691 and qingzhen in qingzhen a reversibly zoned mn rich niningerite is found the composition of which deviates considerably from the average qingzhen compositions 26 0 33 6 mole mns 52 4 57 2 mole mgs and 12 6 21 0 mole fes versus 11 5 16 0 mole mns 67 5 73 6 mole mgs and 13 5 21 5 mole fes this is strongly suggestive of inhomogeneous accretion in that part of the solar nebula where eh chondrites condensed cores of niningerites in indarch contain massive troilite exsolution lamellae this could have formed by 1 1 slow cooling of a fes rich niningerite before accretion in the parent body or by 2 2 a two stage cooling process the results indicate that niningerite is a sensitive detector for reconstruction of the thermal histories of eh chondrites

epithermal precious metal deposits of italy an overview epithermal precious metal deposits have only quite recently been added to the metallogenic view of italy it was only in the late 1980s that two districts were recognized in sardinia and southern tuscany previously long known for a large variety of other commodities the sardinian epithermal precious metal district is associated with the oligocene miocene sardinian calc alkaline magmatic cycle the most relevant areas include the au deposit at furtei already in production and the osilo prospect where extensive exploration is under way the deposit at furtei contains at least six tonnes of gold metal the mineralogy of the deposit and of the alteration assemblages is typical of the acid sulfate high sulfidation class of volcanic hosted epithermal deposits fluids associated with alteration and mineralization have moderate temperatures 200 300 c and low salinities less than 6 wt nacl equivalent high temperature high salinity fluids similar to porphyry style systems also circulated at furtei at osilo a number of quartz veins containing up to several ppm au have been identified the alteration assemblage includes adularia and illite i e is typical of low sulfidation deposits fluid inclusion homogenization temperatures range from 198 to 270 c with salinities of less than 4 wt nacl equivalent

formation of niningerite by silicate sulfidation in eh3 enstatite chondrites unequilibrated eh chondrites contain silica bearing chondrules with abundant niningerite mg fe mn s and troilite fes distinguishing them from the silica bearing chondrules in ordinary and carbonaceous chondrites the conventional explanation for the origin of niningerite and oldhamite cas is that they are condensates from c rich nebular gas however models of condensation from a solar gas with an elevated c o ratio predict mineralogy that is inconsistent with petrographic observations we report petrographic and chemical evidence from 45 silica bearing chondrules from the eh3 chondrites sahara 97072 and alan hills 84170 for formation of niningerite and oldhamite by sulfidation of ferromagnesian silicates the results indicate extensive thermal processing of the chondrules including melting before during and after sulfidation bulk compositions of chondrules exhibiting varied degrees of sulfidation suggest that depletion of mg and enrichment of fe mn and na accompany the reactions sulfidation of feo bearing silicates which formed at oxidizing conditions at least iw 3 can occur with exposure to a h poor c and s rich gaseous reservoir 6 8 fo2 log units below the iw buffer at temperatures high enough for partial melting of silicates physicochemical analysis of mineral reactions inferred from sulfidized chondrules suggests a melted metal sulfide assemblage in a h poor environment is capable of generating sufficient s vapor to drive sulfidation the reaction of silicates with the s gas will result in progressive extraction of fe ca and mg into sulfides with the stoichiometric amounts of silica either reacting with olivine to form enstatite or when olivine is exhausted precipitating as free silica the sulfidation environment drastically increases mg volatility resulting in evaporative loss until saturation in the ambient gas is reached the newly formed mg rich niningerite will tend to reach equilibrium composition by losing mg and gaining fe plus mn from the ambient gas consistent with the observed chemical fractionation in the sulfidized chondrules therefore sulfidation of ferromagnesian silicates can also explain the low bulk mg si ratios of the enstatite chondrites if the sulfidizing gas was lost before accretion of the enstatite chondrite parent body

a unique omphacite amphibole and graphite bearing clast in queen alexandra range que 99177 a metamorphosed xenolith in a pristine cr3 chondrite abstract a metamorphosed unshocked chondritic clast containing approximately equal volumes of matrix and chondrules has been identified in the primitive cr3 chondrite que 99177 the most striking features of this clast are the presence of ferroan omphacitic pyroxenes amphiboles pargasite and pargasitic hornblende and coarse grained up to 70 m graphite laths the clast also contains relatively equilibrated feo rich olivine low ca pyroxene and sulfides pentlandite and troilite the clast s matrix contains coarse interlocking crystals the chondrules are extensively recrystallized contain no mesostasis or metal and present poorly defined boundaries based on its compositional and crystallographic features omphacite appears to have formed at high pressures 6 gpa amphibole formation probably postdated graphite formation and occurred by reaction of olivine clinopyroxene and omphacite in the presence of an oxidizing na rich fluid at high temperatures 700 c the absence of metal suggests that this fluid was also rich in s

impact melting in the cumberland falls and mayo belwa aubrites abstract six chondritic clasts in the cumberland falls polymict breccia were examined four texturally resemble ordinary chondrites ocs and two are impact melt breccias containing shocked oc clasts adjacent to a melt matrix the six chondritic clasts are probably remnants of a single oc projectile that was heterogeneously shocked when it collided with the cumberland falls host mayo belwa is the first known aubrite impact melt breccia it contains coarse enstatite grains exhibiting mosaic extinction the enstatite grains are surrounded by a melt matrix composed of 3 16 m size euhedral and subhedral enstatite grains embedded in sodic plagioclase numerous vugs ranging from a few micrometers to a few millimeters in size constitute 5 vol of the meteorite they occur nearly exclusively within the mayo belwa matrix literature data show that some vugs are lined with bundles of acicular grains of the amphibole fluor richterite this phase has been reported previously in only two other enstatite meteorites abee and st sauveur both of which are eh chondrite impact melt breccias it seems likely that in mayo belwa volatiles were vaporized during an impact event and formed bubbles in the melt as the melt solidified the bubbles became cavities plagioclase and fluor richterite crystallized at the margins of these cavities via reaction of the melt with the vapor

formation of voids and veins during faulting abstract we have developed a quantitative model of void and vein development in fault zones based on observations of fault roughness and the contact characteristics of rough directionally anisotropic fractal surfaces this model includes progressive dilation of the fault during slip events and the elastic deformation of the surfaces normal to the fault plane closure as new void space develops the model predicts vein geometries that are qualitatively similar to those observed in fault controlled mineral deposits the statistics of the vein system are described and strategies for sampling of such structures by drilling are developed the results have significant implications for evaluation of ore reserves and evaluating the fluid transport properties of faults

seismotectonic zoning in east central italy deduced from an analysis of the neogene to present deformations and related stress fields this paper concerns the space time evolution of the late miocene to present contractional and extensional deformations within east central italy with an analysis of the pattern and orientation of the related stress field an insight into the cover basement relations and a discussion of the seismotectonic implications the pattern and orientation of the deformation and stress fields have remained unchanged since late miocene time and have been always characterized by the coexistence and parallelism in contiguous areas in a given time of shortening to the east and elongation to the west with time during a multistage deformation history both the contraction and the extension fields have moved eastward basement involved tectonics with a west dipping multiple detachment system would have allowed the progressive eastward shift of crustal slices corresponding at the surface to well defined tectonic domains with consequent crustal thinning in the tuscan zone and crustal thickening beneath the apennine mountain chain by comparing macroseismic epicenters hypocenters and focal mechanisms with crustal structure and independently known active faults it appears evident that the pattern frequency and distribution of the crustal seismicity are tectonically controlled and that a contraction extension pair is active also at the present time in fact along the adriatic coastline contractional deformation prevails with involvement of pleistocene layers whereas beneath the apennine range extensional deformation prevails both t axes in the inner domain and p axes in the outer domain are oriented southwest northeast or west south west east northeast and this coaxiality reflects the situation depicted by the geologic stress field on this basis we have produced a seismotectonic zoning of east central italy with three distinct domains intramountain seismic zone isz foothills seismic zone fsz and coastal seismic zone csz a plausible explanation for the genesis of the active seismic deformations of east central italy is that the locally intense extensional upper crustal seismicity of the intramountain seismic zone is confined to the hanging wall of a major west dipping active extensional discontinuity whereas the less frequent contractional seismic activity of the coastal seismic zone is within the hanging wall of an outer major active west dipping contractional discontinuity an area of overlap between these two zones is represented by the foothills seismic zone where superposed epicentral patterns from different surfaces of weakness at different depths are the predictable result of the asymmetry of the deformation

petrography mineral chemistry and origin of type i enstatite chondrites abstract optical and cathodoluminescence petrography were coupled with electron microprobe analysis to relate the textures and chemical compositions of minerals in the chondrules and matrix of the indarch kota kota adhi kot and abee type i enstatite chondrites clinoenstatites fall into two distinct chemical groups with characteristic red or blue luminescence red crystals are higher in ti al cr mn and ca and lower in na than blue ones rare forsterites in indarch and kota kota show distinct compositions associated with orange or blue luminescence the chemical ranges are indistinguishable for each color type in chondrules of all textural types and the presence of both color types in a single chondrule or a metal fragment requires mechanical aggregation of both crystals and liquids of both color types porphyritic chondrules are ascribed mainly to aggregation of existing crystals because both types of pyroxene and olivine occur in the same chondrule large crystals of one color type are surrounded by fine grained crystals of another type in some barred and radiating chondrules all types of chondrules are surrounded by fine grained rims rich in sulfide the matrix contains many broken chondrules and individual silicate grains but is rich in sulfide and metal analyses are given of albite minor elements and luminescence color vary between chondrites kamacite schreibersite oldhamite and niningerite although the mineral assemblages do not fit theoretical condensation sequences in detail the red pyroxene and orange olivine might result ultimately from near equilibrium crystallization in which early reduced condensates reacted with a gas while the blue crystals might result from fractional condensation in which early condensates were removed mechanically from a gas subsequent episodes involving mixing melting crystallization condensation fracturing and mechanical aggregation would be needed to produce the complex textures

petrologic geochemical and experimental constraints on models of chondrule formation abstract the petrologic and geochemical properties of chondrules as well as results of experimental studies provide strong constraints on chondrule formation models nebular formation is indicated by the non mass fractionated oxygen isotopic compositions of bulk chondrules chondrule formation from a melt is required by the prototypical spheroidal shapes and the presence of euhedral phenocrysts and glassy mesostases incomplete melting is indicated by the abundance of porphyritic chondrules which experiments demonstrate require relict nuclei and coarse relict grains the length of time that chondrules were hot is constrained by their retention of relict grains and moderately volatile elements rapid cooling of chondrules after formation is supported by the presence of zoned phenocrysts isotopic anomalies and dynamic crystallization experiments it is clear from the presence of relict grains enveloping compound chondrules and igneous rims that many chondrules were heated again after cooling the heating mechanism responsible for chondrule formation seems to have operated at varying intensities over large regions of the inner solar nebula for at least the time it took ambient nebular temperatures to cool from above 900 to below 600 k the chondrule formation mechanism provided a repeatable source of energy capable of highly localized melting characteristic of flash heating the occurrence of ferroan microchondrules with low melting temperatures within some chondrule rims indicates that chondrule formation did not occur exclusively in high temperature regions near the sun as required in bipolar outflow models mechanisms for forming chondrules that are consistent with the constraints include various flash heating models nebular lightning magnetic reconnection flares gas dynamic shock waves and radiative heating

late oligocene to recent episodes of magmatism in and around the tyrrhenian sea implications for the processes of opening in a young inter arc basin of intra orogenic mediterranean type abstract five episodes of magmatic activity as deduced from geochronological data affected the tyrrhenian and peri tyr rhenian areas from the late oligocene 32 ma to recent times the episodes of w e migration of magmatism from the islands of sardinia and corsica to the eolian islands and the roman comagmatic region of central italy are related to the anti clockwise drift movements of the apenninic chain and clockwise drifting of the sicilian part of the maghrebian chain magmatic activity in the tyrrhenian sea initiated in late miocene times 8 5 6 5 ma in concomitance with a significant change of the geodynamic regime from compressional to tensional the tyrrhenian bathyal plain was affected by two episodes of spreading the first episode occurred around 7 ma and the second from about 1 9 to 1 3 ma these spreading events apparently developed during times of magmatic quiescence in the peri tyrrhenian areas two subsequent episodes of volcanism of the seamount type occurred in the bathyal plain one from 5 to 1 8 and the other from 1 3 to recent they are contemporaneously with extensive manifestations in the peri tyrrhenian areas the different types of magmatism of the late miocene back arc spreading in the central bathyal plain and acidic manifestations of intra crustal anatectic origin in the northern continental platform and slope i e islands of capraia elba and montecristo and seamount vercelli are possibly related to movements of upwelling of the astenosphere which in the southern tyrrhenian sea developed with a much stronger intensity timing of the volcanism in relationship with the overall structural evolution through time in the basin and neighbouring lands is considered

boiling and fluid mixing in the chlorite zone of the larderello geothermal system abstract the geochemical features of the geothermal fluids produced within the boiling zone in the relatively shallow parts of the larderello geothermal system italy have been documented as a result of deep drilling which provided samples from 1480 to 2500 m depth four wells monteverdi 1 monteverdi 2a sasso 22 and capannoli 2b have been sampled in the intermediate parts of the larderello aquifer located in a metamorphic basement underlying the tertiary nappe complex which constitutes the shallow aquifer at larderello fluid inclusions from recrystallized quartz lenses and quartz veins in samples displaying a predominant quartz chlorite epidote adularia paragenesis have been studied by microthermometry and raman spectroscopy the inclusions are primary and pseudo secondary in origin when formed in authigenic quartz or of secondary origin when located in fluid inclusion planes related to microfracturing of metamorphic quartz lenses several generations of fluids are present and include h 2 o co 2 dominated vapours and liquids and a series of aqueous liquids for the most part of relatively low salinity the t m ice of both early and late inclusions are mostly between 0 0 and 4 5 c indicating that the salinities of the hydrothermal fluid were very low to moderate however rare fluid inclusions with lower t m ice from 4 9 to 25 0 c were also observed these inclusions may record the occasional input of saline fluids which may be derived from the interaction of the hydrothermal waters with the evaporites present in the shallow part of the larderello field at capannoli 2b earliest h 2 o co 2 liquids were trapped under minimal pressures of 610 645 bars which bracket the estimated present day lithostatic pressure 640 bars in all other samples the main stage of quartz chlorite crystallization occurs under boiling conditions attested by the presence of liquid and vapour rich inclusions that in some instances can be texturally interpreted to be coeval their trapping conditions 350 375 c 160 215 bars are higher than the present day temperatures at the same depth later fluid inclusions attest to a significant cooling of the fluids down to temperatures similar to the present day temperatures during this time pressures were close to hydrostatic conditions most fluid inclusions were trapped within the liquid field this indicating that a significant pressure drop has since affected the main aquifers or fractured zones which are at present under vaporstatic conditions

subcrustal earthquakes in the northern apennines italy evidence for a still active subduction previously unreported subcrustal earthquakes have been located up to 90 km depth beneath the northern apennines italy these earthquakes occur beneath a zone of abundant upper crustal seismicity mostly confined to the upper 20 km of the crust although there are relatively few well located subcrustal earthquakes there appears to be a general southwestward deepening of the hypocenters from the adriatic to the tyrrhenian sea consistent with other geophysical data which suggest that the adriatic lithosphere is presently subducting beneath the northern apennines

styles of back arc extension in the central mediterranean in the central mediterranean two back arc basins the liguro provencal lpb and the tyrrhenian basin tb opened progressively and consecutively from the late eocene oligocene to the present evolution in space and time of rifting and drifting processes along three different transects across these basins shows differences in the style of extension lpb opened with the formation of a narrow single rift while in the tb deformation and magmatism is spread over a wide area moreover at the northern end of the tb the locus of extension progressively migrated towards the east whereas in the southern tb the locus of extension and magmatism migrated inside the basin inducing continental break up and drifting of the previously formed older conjugate basins we propose that these different styles of back arc extension depend upon internal conditions such as prerift rheology linked with its geological heritage and external conditions e g the style of subduction

shear wave attenuation in the lithosphere beneath italy and surrounding regions tectonic implications more than 700 waveforms produced by 51 shallow earthquakes and recorded at regional distances 250 1400 km by the italian seismic network have been analyzed to characterize the amplitude and frequency contents of the crustal and uppermost mantle shear waves lg and sn respectively the crustal phase lg efficiently propagates through the relatively stable adriatic continental crust while it is not observed along propagation paths crossing major physiographic features like the apennine chain and the basinal domain of the tyrrhenian and ionian seas similar to lg efficient sn propagation is observed in the uppermost mantle beneath the po plain and the adriatic sea efficient sn transmission is also observed across the northern ionian sea and sicily and in the area between sardinia and the northern coasts of africa sn are efficiently transmitted across the sicily channel and rather efficient sn propagate beneath the ligurian sea on the contrary inefficient sn transmission characterizes the uppermost mantle beneath the apennines the western margin of the italian peninsula and the southern tyrrhenian sea shear wave attenuation suggests the presence of asthenospheric material in the uppermost mantle probably related to the present day extension along the apennine chain and in the tyrrhenian basin this interpretation is consistent with the presence of extensive neogene and quaternary volcanic activity in these areas and related high heat flow proposed lithospheric delaminatioh processes beneath the apennines and subduction beneath the tyrrhenian sea can reasonably explain the observed high attenuation zones in the uppermost mantle in contrast a high strength mantle lid is inferred to underlay the po plain the adriatic sea and the northern ionian sea the available waveforms also indicate that a continuous mantle lid is present beneath sicily and the extensional domain of the sicily channel as well as in the marine area south of sardinia

petrographic and mineralogical study of new eh melt rocks and a new enstatite chondrite grouplet enstatite chondrites are classified into eh and el groups and some of them were melted once in this paper we report petrography and mineral chemistry of five new antarctic enstatite chondrites yamato 793225 is characterized by intermediate properties between the eh and el groups and probably represents a new grouplet of enstatite chondrites the three paired meteorites y 8404 y 8414 and y 86004 may have cooled rapidly near the surface of the parent body as impact eh melt rocks yamato 82189 is also classified as eh melt rock but it experienced slow cooling as did y 793225 yamato 82189 contains the first occurrence of phlogopite in enstatite meteorites

paleoseismicity of the ovindoli pezza fault central apennines italy a history including a large previously unrecorded earthquake in the middle ages 860 1300 a d geomorphic and trenching investigations along the ovindoli pezza fault show that this normal fault is one of the major seismogenic faults in the central apennines we found clear geological evidence for three holocene surface faulting earthquakes on this fault the most recent earthquake occurred in the middle ages between 860 and 1300 a d the penultimate occurred about 1900 b c or shortly after and the oldest probably occurred between 3300 and 5000 b c although the most recent surface faulting earthquake occurred during historical time no evidence for it have been found in the historical record slip per event ranges between 2 and 3 m and the length of the rupture is at least 12 20 km suggesting m 6 5 7 0 for the paleoearthquakes the dip slip rate determined from trenching is 0 7 1 2 mm yr and is consistent with the long term slip rate of 0 9 2 5 mm yr lower values preferred obtained from displaced geomorphic features trench data combined with long term slip rate estimates suggest the recurrence interval is longer than a millennium and possibly as long as 3300 years the time elapsed since the most recent earthquake is 700 1130 years the seismic behavior of the ovindoli pezza fault is consistent with other well known seismogenic faults of the central and southern apennines the lack of mention or mislocation of the most recent event on the ovindoli pezza fault in the historical record of the past two millennia should be attributed mainly to the unsettled cultural and social conditions and poor economic state that characterized the middle ages especially in thinly populated regions such as the central apennines this example highlights an intrinsic limit of the historical data and raises the possibility that other regions considered seismically quiet on the basis of a long historical record may in reality have had large earthquakes that were not recorded

silica bearing chondrules and clasts in ordinary chondrites unusual silica bearing chondrules and clasts have been observed in several unequilibrated ordinary chondrites there appear to be two distinct types i silica low ca pyroxene assemblages and ii silica fayalite intergrowths coexisting with low ca pyroxene only the former types are chondrules the bulk compositions of most of these objects can be expressed in terms of three components mgo feo and sio 2 since ca al and na are essentially trace elements secondary alteration has probably perturbed the fe mg ratios in most objects and produced ca rich pyroxenes in some type ii clasts but the silica low ca pyroxene and fayalite are hard to understand as other than primary phases such silica rich bulk compositions can be understood as an intermediate temperature condensate of a solar gas formed by the loss of refractory solid material by gas solid separation before the complete condensation of silicon alternatively the silicarich bulk compositions could have been formed by extreme reduction of normal chondritic olivine and orthopyroxene however the observed ca al depletion and the lack of ni poor metals are not explained by this model the fayalite bearing clasts can be explained by a relatively complex two stage process involving reduction followed by oxidation partial reduction of olivine in the presence of s produces mg rich pyroxene silica and fefes oxidation of metal and sulfide followed by reaction with silica forms fayalite an alternative is that the fayalite bearing clasts result from the decomposition of ferrosilite but this requires the production of metastable ferrosilite during shock or some other high pressure event the simplest unflawed alternative is that the fayalite bearing clasts result from the mixing of a partially molten silica fayalite liquid with mg rich pyroxene

palaeoseismology review of the state of the art abstract historical seismicity provides only a partial indication of the seismotectonic character i e earthquake potential of a given region even in italy where a relatively long historical record exists available catalogues are generally unsatisfactory for this purpose fortunately strong earthquakes often leave geological evidence herein referred to as seismites that are mainly related to surface faulting folding or other deformation and occasionally to secondary ground failures e g landslides liquefaction features etc these features may be preserved and therefore palaeoseismological studies may detect and date them thereby permitting extension of knowledge beyond the local historical threshold up to 2000 years in the most fortunate cases this paper provides a summary of criteria which may aid in the identification of areas suitable for palaeo earthquake investigation historical seismicity and the presence of well developed tectonic geomorphic features are recognized as the most reliable criteria for identifying active faulting however lack of these characteristics cannot be considered conclusive evidence for lack of activity palaeoseismological techniques aim at identifying not only the obvious effects of surface faulting such as offset of young geologic units but also the more subtle tectonic or non tectonic features including liquefaction structures gravity features and coseismic uplift and or subsidence finally we discuss some questions that pertain to palaeoseismicity evaluation techniques among these are the reliability of the quaternary dating techniques the evaluation of the seismic energy released minimum magnitude and principally the unequivocal identification of a seismic origin for the considered geological structures

tectono sedimentary characteristics of late miocene quaternary extensional basins of the northern apennines italy abstract extensional and compressional regimes exist at the same time in adjacent parts of the northern apennines italy and the former regime succeeded the latter at the same place as the thrust mountain front moved eastward since miocene times numerous extensional basins have developed west of the present mountain divide the westernmost ones formed over attenuated continental crust since late miocene and have been subjected to several subsidence and uplift events with rates of subsidence generally faster than rates of sedimentation they contain continental deposits overlain by gypsum bearing upper miocene marine sequences and siliciclastic marine pliocene deposits these basins were affected by shallow magmatism and are still experiencing high geothermal gradient and late to post magmatic activities such as in the renowned thermal region of larderello to the east closer to the present mountain divide the extensional basins formed later from pliocene to quaternary contain continental fluvial and lacustrine deposits and have not experienced near surface magmatic activities the sedimentary fill architecture of the apennine extensional basins is similar to that of other european american and african extensional or transtensional systems for instance a common characteristic is the prevalence of large alluvial fan deposits at the hanging wall shoulder of half grabens coarser smaller alluvial fans at the footwall shoulder and some fluvial deposits introduced longitudinally unlike the african rifts though the sedimentary facies distribution of extensional basins which developed in active orogenic zones such as in the apennines may be strongly affected by uplifting steep mountain slopes and can have large thick coarse alluvial fans also on the footwall side of the half grabens

segmentation and configuration of subducted lithosphere in italy an important control on thrust belt and foredeep basin evolution the apennine foredeep basin system located on continental crust consists of four roughly parallel basin segments each containing a flexural outer rise and an inner trough that deepens continuously toward the thrust belt flexural modeling of subsidence data across the basin indicates that this foredeep basin results mainly from deep subsurface loads acting on the subducted slab from within the subduction zone rather than from the topographic load of the apennine mountains the geometry of the four basin segments observed within the apennine foredeep is thus inferred to reflect subduction of segmented lithosphere where each lithospheric segment corresponds to a segment of the foredeep basin beneath the basin and in the foreland the lithosphere is continuous segmentation occurs only at depth beneath the thrust belt this pattern olf segmentation of the subducted lithosphere at depth is reflected in the large scale geometry of the outer part of the apennine thrust belt and appears to control it similarly the pattern of segmentation also appears to control the position of the eastern limit of back arc type extension in western italy these relations strongly suggest a genetic relation between subduction zone processes foredeep basin geometry and thrust belt evolution in which the configuration of the subducted lithosphere largely controls the large scale surface deformation observed in the apennine system

a geodynamic model of the southern apennines accretionary prism the apennines comprise a neogen quaternary accretionary prism that shows several anomalies with respect to classic alpine type mountain belts namely i low elevation ii a shallow new moho below the core of the belt iii high heat flow in the internal parts iv mainly sedimentary cover involved in the prism v a deep foredeep and vi a fully developed back arc basin the suction exerted by a relatively eastward migrating mantle can determine the eastward retreat of the subduction zone and an asthenospheric wedging at the retreating subduction hinge heat flow geochemical and seismological data support the presence of a hot mantle wedge underlying the western side of the apenninic accretionary prism a thermal model of the belt with foreland dipping isotherms fits with deepening of the seismicity toward the east mantle volatiles signatures are also widespread in springs along the apennines

application of the sphalerite cosmobarometer to the enstatite chondrites sphalerite is a minor constituent of a number of enstatite chondrites the assemblage sphalerite troilite kamacite buffers the iron content of sphalerite so that it is a function of temperature and pressure only high iron contents in sphalerite in enstatite chondrites are consistent with equilibration at low pressures if nebular conditions are assumed and pressure is taken as zero it is then possible to calculate blocking temperatures for diffusion of iron t b and cooling rates for the meteorites studied the variable degree of equilibration of eh3 chondrites is correlated with calculated pressures assuming that the least equilibrated y69001 formed at zero pressure parent body radii calculated from these pressures are probably too large however inhomogeneities and minor elements in sphalerite as well as the assumptions made in the calculation may have had an adverse effect on the calculations the eh4 chondrite indarch appears to have cooled at an extremely rapid rate and has an unreasonably high t b inhomogeneities and minor element content may again have affected results the data for the el6 chondrites are consistent with relatively slow cooling ca 773 k whereupon rapid cooling occurred cooling rates at 773 k are too fast by a factor of 102 to 103 in comparison with metallographically determined rates

restricted rifting and its coexistence with compressional structures results from the crop 3 traverse northern apennines italy a geological interpretation of the deep seismic reflection line crop 3 italian program crosta profonda deep crust profile no 3 which crosscuts the northern apennines from the tyhrrenian to the adriatic coast is presented the profile images the lithosphere up to 15 s twt and highlights several peculiarities a the lower crust is bedded by discontinuous sub parallel reflective markers which terminate at 7 s beneath the western side of the profile b in the same area a notable reflection is recognizable at 10 s and is interpreted as the top of the asthenosphere c east plunging shear zones are recognizable throughout the crust by contrast the adriatic outer side of this line shows a reflections deepening westward from 13 to 15 s twt related to the base of the crust 33 38 km depth b the absence of thick bedding of reflective markers within the lower crust and c tectonic structures affecting the basement which are different from those which deform the cover of the northern apennines geological interpretation is based on the eastward migration of ductile shear zones which have been recognized on the seismic line the bending of the outer zone crust is considered to be a consequence of the rifting process with the application of pushing forces against the adriatic lithosphere which cannot escape toward east

origin of sio2 rich components in ordinary chondrites abstract silica rich objects are common minor components in ordinary chondrites oc occurring as fragments and as chondrules their typical paragenesis is orthopyroxene sio 2 with bulk sio 2 65 wt and occasionally with additional olivine and or spinel individual silica rich components src have previously been studied in various types of ocs although there is only one comprehensive study of these objects by brigham et al brigham c a murrell m t yabuki h ouyang z el goresy a 1986 silica bearing chondrules and clasts in ordinary chondrites geochim cosmochim acta 50 1655 1666 several different explanations of how srcs formed have been published the main question is how silica enrichment was achieved because ci chondritic atomic mg si ratio is 1 07 and as a consequence only olivine and pyroxene but no free silica should be stable there are two basic possibilities for the sio 2 enrichment 1 a redox mechanism or magmatic fractionation on the parent body and 2 fractional condensation or recycling of chondrule mesostasis in the solar nebula to better constrain the origin of these objects we measured major and rare earth elements in srcs of various types of ordinary chondrites and in addition we studied silica polymorphism in these objects using an in situ micro raman technique bulk chondrule compositions define mixing lines between the compositions of olivine and pyroxene the srcs extend these lines to an sio 2 end member in contrast magmatic trends grossly deviate from these mixing lines concentrations of cao al 2 o 3 and ree in the pyroxenes of the srcs are low 0 01 to 1 ci and the ci normalized ree patterns are virtually flat typical of bulk chondrules but untypical of magmatic trends we therefore conclude that sio 2 rich objects are not of magmatic origin they are the result of fractional condensation in the solar nebula the silica in srcs occurs mainly as tridymite and sometimes as cristobalite or in very rare cases as quartz some sio 2 phases yielded a yet unknown micro raman spectrum which we were unable to identify the often chondrule like shape of srcs as well as the presence of high temperature sio 2 polymorphs lead to the following model for the origin of srcs formation of sio 2 rich precursors in the solar nebula by fractional condensation reheating to temperatures between 1140 and 1968 k thereby forming the srcs probably during the chondrule forming process followed by rapid cooling

the larderello geothermal field a review abstract this paper reviews published geological geophysical petrological and geochemical data together with reservoir engineering parameters of the larderello geothermal reservoir of southern tuscany italy some theories are proposed on the deep origin evolution in time and natural state of this geothermal field prior to its exploitation the interaction between the vapor dominated reservoir and surrounding aquifers is discussed analysis of hydrogeochemical data suggests that meteoric waters from shallow external aquifers contribute little to the production of steam the vapor dominated system and the cold external aquifers are separated by areas of very low permeability where physical conditions change greatly over short distances the presence and significance of liquid phases in the peripheral areas of the vapor dominated reservoir are interpreted as being due to steam condensation the latter is a consequence of a low permeability conditions in the deep buried parts of the carbonate reservoir formations in the north northwestern sector of the field and b by the mixing of ascending superheated steam from depth with cold caso4 meteoric waters circulating in unconfined shallow aquifers within the outcrops of the carbonate reservoir formations in the south southeastern parts of the field the presence of steam below these liquid dominated sectors of the reservoir seems possible the limited natural recharge of the system the constant steam production rate for geothermal power generation 3000 t h 1 since 1951 the persistence of natural thermal features and the fact that reinjection has had little effect on the characteristics of the fluid discharged seem to indicate a steady state for the larderello field the main contribution to production seems to be from superheated steam ascending from depth and the in situ evaporation of water stored in the small pores of the rocks present in larderello in a system that is much larger than the one known at present

crustal and uppermost mantle structure in italy from the inversion of p wave arrival times geodynamic implications summary in this paper we present a 3 d image of the p wave velocity structure in the crust and uppermost mantle beneath italy obtained by inverting p wave arrival times of crustal earthquakes we used about 48000 arrival times at stations close to the epicentres within 200 km to mitigate the eiects of both reading errors and intrinsic complexity for long distance ray paths due to the scale of heterogeneities in the earth structure beneath italy whereas two of the inverted layers located in the lower crust and beneath the moho are well resolved by the data the upper crustal layer has regions of relatively poor resolution beneath the central apennines due to the sparse station spacing we made several attempts varying the moho geometry to obtain reliable and stable results without introducing too complex and unconstrained ap rioriinformation one of the most important results is the discovery of low velocity anomalies at 38 km depth beneath the northern apenninic and calabrian arcs which we interpret as subducted crustal material of the adriatic and ionian lithospheres in the lower crust beneath the entire apennines a pronounced low velocitybelt is present suggesting high temperatures in front of the bent adriatic lithosphere based on our results and on those previously obtained from seismic tomography we propose amodel for the geodynamic evolution of the apenninic system in which the present day scenario re ects lateral heterogeneities in the subducting ionian oceanic and adriatic continental lithosphere

the matrices of unequilibrated ordinary chondrites implications for the origin and history of chondrites abstract the matrices of sixteen unequilibrated ordinary chondrites all witnessed falls were studied microscopically in transmitted and reflected light and analyzed by electron microprobe selected specimens were also studied by scanning electron microscopy these studies indicate that the fine grained opaque silicate matrix of type 3 unequilibrated chondrites is compositionally mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by larimer and anders 1967 1970 examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed with the alteration ranging in intensity from quite mild where the matrix has been only slightly altered to a more severe metamorphism that has completely recrystallized the opaque matrix most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules the metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves the present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed plus the subsequent metamorphic alteration it experienced

pyroxene selective impact smelting in ureilites abstract a characteristic feature of ureilite meteorites is reduction of feo but the reduction is usually confined to the rims of olivine in the lar 04315 lap 03587 and almahata sitta ureilites pyroxene was extensively reduced by impact smelting in lar 04315 the impact caused nearly all of the original pigeonite to melt or otherwise become sufficiently structurally compromised to allow smelting and yet a minor proportion of the pyroxene escaped smelting and survived with its original composition en 74 1 wo 10 2 olivine mosaicism confirms that lar 04315 experienced a major shock event the smelted pyroxenes also show a distinctive patchiness in their interference colors although each grain s basic optical continuity often including twinning is still discernible they also have reduced compositions are ubiquitously porous 15 and contain sprinklings of fe metal and felsic glass for the most part the olivine underwent only very slight reduction much of the small pyroxene component of lap 03587 shows the same oddly porous texture lar 04315 also contains large traces of silica and felsic glass with a typical composition of in wt 61 sio 2 23 al 2 o 3 11 cao 3 7 na 2 o glass these two phases together form selvages that line the walls of many of the largest voids in the rock silica is a by product of pyroxene smelting the felsic glass probably derives largely from interstitial basaltic melt that predated the impact however the comparatively stiff surrounding included silica may have promoted unusually high melt retention within lar 04315 through the smelting episode one aspect of which was a major stream out through the same large voids of co x gas the impact smelted pyroxene of lap 03587 is enigmatic because this ureilite also features little shocked euhedral graphite laths and no olivine mosaicism the fine grained ureilitic component of almahata sitta appears to have likewise formed by impact smelting but with more extensive melting of pyroxene especially a ca rich pyroxene component more pulverization and melting of olivine and more displacement of both however in places the original coarse equant ureilite texture is still discernible in relict form ordinarily an impact shock melts olivine before or at least no later than pyroxene but in the case of lar 04315 and lap 03587 the great shock event evidently occurred when the material was already anatectic or very nearly so and thus the difference in melting temperature between pyroxene and olivine 300 degrees lower for pyroxene was decisive if literature inferences of extremely fast cooling rates implying shallow burial depths are accurate the proportion of co x gas generated by ureilite smelting exceeded by a very large factor of order 10 3 but possibly much greater the volume represented as porosity in the final ureilites the outflow of so much gas may have by near surface explosive expansion and jetting enhanced the thoroughness of the impact triggered catastrophic impact disruption of the parent asteroid

chondrules in the qingzhen type 3 enstatite chondrite possible precursor components and comparison to ordinary chondrite chondrules abstract the qingzhen eh3 fall appears to be the least equilibrated enstatite chondrite mineral compositions vary widely from chondrule to chondrule and in some cases from grain to grain within individual chondrules as in ordinary chondrite oc chondrules most elements show appreciable ranges in concentration porphyritic olivine pyroxene pop chondrules are richer than porphyritic pyroxene pp and radial pyroxene rp chondrules in refractory lithophiles and siderophiles unlike oc chondrules qingzhen s rp and pp chondrules have similar bulk compositions elements in each of the following sets intercorrelate significantly probably because these elements were present in the same nebular components 1 1 fe co ni ir au 2 2 ca eu se 3 3 al sc hf 4 4 na ree 5 5 cl br several additional elements show no correlations set 1 elements were probably derived from a metal component as in oc chondrules set 3 elements which occur in higher concentrations in olivine bearing pop chondrules suggest the existence of a refractory lithophile rich olivine rich component similar to the one previously inferred for oc chondrules set 2 elements suggest a precursor component rich in oldhamite and set 4 elements suggest another refractory bearing component components 2 and 4 were not precursors of oc chondrules for some chondrules interelement ratios of refractory lithophiles such as ca al ti sc and ree are similar to ci ratios this indicates that these elements were probably derived from silicates we suggest that the earliest solid phases were refractory silicates that were sulfurized before chondrule formation some of these sulfurized components e g one rich in oldhamite were abundant in the region where the qingzhen chondrules formed

petrogenesis of acapulcoites and lodranites a shock melting model abstract acapulcoites are modeled as having formed by shock melting cr like carbonaceous chondrite precursors the degree of melting of some acapulcoites was low enough to allow the preservation of 3 6 vol relict chondrules shock effects in acapulcoites include veins of metallic fe ni and troilite polycrystalline kamacite fine grained metal troilite assemblages metallic cu and irregularly shaped troilite grains within metallic fe ni while at elevated temperatures acapulcoites experienced appreciable reduction because graphite is present in some acapulcoites and lodranites it seems likely that carbon was the principal reducing agent reduction is responsible for the low contents of olivine fa 4 14 mol and low ca pyroxene fs 3 13 mol in the acapulcoites the observation that in more than two thirds of the acapulcoites the fa value is lower than the fs value in contrast to the case for equilibrated ordinary chondrites the low feo mno ratios in acapulcoite olivine 16 18 compared to 32 38 in equilibrated h chondrites the relatively high modal orthopyroxene olivine ratios e g 1 7 in monument draw compared to 0 74 in h chondrites and reverse zoning in some mafic silicate grains lodranites formed in a similar manner to acapulcoites but suffered more extensive heating loss of plagioclase and loss of an fe ni s melt acapulcoites and lodranites experienced moderate post shock annealing presumably resulting from burial beneath material of low thermal diffusivity the annealing process repaired damaged olivine crystal lattices lending acapulcoites and lodranites the appearance of unshocked i e shock stage s1 rocks any high pressure phases that may have formed during initial shock reverted to their low pressure polymorphs during annealing some samples were subsequently shocked again several acapulcoites reached shock stage s2 levels alh 84190 reached s3 and the lodranite mac 88177 reached s5

depth and modes of pliocene pleistocene crustal extension of the apennines italy since early pliocene times the apenninic chain has been dissected by normal faults propagating towards the adriatic foreland in the tyrrhenian sea extension involved deep crustal sections whereas in the central apennines downfaulted area it affected the shallow crust the tyrrhenian back arc domain is connected to the overall flexural retreat of the adriatic apulia plate in front of the apenninic collisional wedge in the outer apenninic belt thin skinned delamination and gravitational collapse occurred in the hanging wall of a thickened wedge overthrusting the uplifted buoyant crust of the apulia foreland differential sinking velocity of the foreland plate results from the inherited competence contrast between the rigid gargano apulia carbonate platform to the south and the low competence lithology of the pelagic sequence of the adriatic basin to the north during late messinian early pliocene times this palaeogeographical boundary acted as a lithospheric tear separating segments of the apulia plate subjected to different subduction modes

additional complexity in the lunar crust petrology of sodic anorthosites and sulfur rich ferroan noritic anorthosites lunar breccia 67016 contains two suites of unusual highlands rocks sulfur rich noritic anorthosites and sodic anorthosites mineral compositions of the sulfur rich noritic anorthosites closely match those of ferroan anorthosites unusually large amounts of sulfides and sulfidation reactions involving olivine in these clasts probably reflect endogenous volatile transfer the sodic anorthosites are mafic poor with mineral compositions intermediate between those of pristine ferroan and alkali anorthosites rare examples of pristine rocks with similar mineral compositions are known and may represent a distinct class of lunar crustal rocks

early eocene leaves of northwestern india and their response to climate change abstract today the existence of tropical rainforests in the indian subcontinent is restricted to the fringes of the western ghats greater assam region and some small places in odisha however the palaeovegetation reconstruction in this study illustrates the existence of equatorial tropical forest in northwestern india bikaner rajasthan during the early eocene fossil leaves described here were collected from the gurha lignite mine of bikaner and showed affinities with holigarna grahamii anacardiaceae pterygota alata malvaceae syzygium spp s fruticosum and s cumini myrtaceae and gardenia spp g lucida and g gummiefra rubiaceae contrary to the present day dry and desertic conditions the fossil records provide strong evidence of humid tropical and paratropical evergreen forest with monsoon seasonality existing in and around the study area during the depositional period any shift in climatic conditions has drastic effects on the vegetation cover of a region in time and space this drastic change in climate has led to the extinction of tropical rain forest from this region this might be due to the northward movement of the indian subcontinent away from the equator formation of the himalayas and monsoon or changes in monsoon pattern

tectonic regime granite emplacement and crustal structure in the inner zone of the northern apennines tuscany italy a new hypothesis abstract geological and geophysical data on the inner part of the northern apennines and the deep 4 km geothermal wells contained therein have been reviewed in order to better characterize the tectonic regime of the region the area is affected by neogene quaternary igneous activity reduced crustal thickness high heat flow and active geothermal systems the available information leads to the following conclusions 1 at present part of the chain including its inner regions are undergoing extensional activity a tectonic situation in southern tuscany dating back to the late tortonian however the simple model of solely extensional tectonics cannot exhaustively account for the phenomena observed in the area as there is ample evidence of compressive events of pliocene and pleistocene ages 2 the geophysical data indicate reduced lithosphere thickness and the uprising of the asthenosphere to shallow crust levels the upper crust has been intruded by many granite bodies and the brittle ductile transition is probably very shallow an integrated geophysical model which accounts for heat flow seismic gravimetric and magnetic data indicates that a regional strong reflector rather than coinciding with the beginning of the ductile crust more likely indicates the presence of deep brines rather than a gneiss core complex and a generalized post collision extensional model cameli et al 1993 we support a more complex geodynamic framework including compressive phases of the internal zone and re activation of the thrust of the apennines as a consequence of crustal thrust emplacements from the late tortonian in the frame of a subducting delaminated lithosphere

interfering paths of deformation and development of arcs in the fold and thrust belt of the central apennines italy in the foreland fold and thrust belt of the central apennines the major thrust sheets design systems of arcs interfering with noncoaxial trends localization of shortening by thrusting and shearing appears to be controlled by the squeezing of low competence basinal units marche gran sasso monte picca and monte genzana in between the rigid blocks of the lazio abruzzi and adriatic carbonate platforms the geometrical interlocking has been resolved by differential rotations of the superposed thrust sheets as also substantiated by paleomagnetic data the structural analysis and the age of the syntectonic siliciclastic deposits suggest an irregular sequencing of superposed contractional and extensional events during late miocene middle pliocene times interfering kinematic paths characterize the arcuate belts where slip partitioning has adjusted the coeval deformation of the noncoaxially arranged tectonic units in the arcuate gran sasso monte picca thrust belt out of sequence thrusting displacement transfer on high angle strike slip faults and growth of high angle normal faults behind the most rotated blocks have resulted in the back and forth superposition of contractional and extensional structures in adjacent domains our kinematic reconstruction of the central apennines indicates that it is impossible to perform the retrodeformation of tectonic events by assuming a regular outward progression of deformation pulses in such a strongly arcuate belt the irregular trajectories of the displacement field and the complex overprinting relations between different sets of structures reflect the kinematic accommodation of blocks with contrasting rigidity and are not fitted easily within a regionally smoothed stress field

impact melt rock clasts in the hvittis enstatite chondrite breccia implications for a genetic relationship between el chondrites and aubrites the hvittis enstatite chondrite breccia contains 5 2 vol dark clasts which appear to be impact melt rocks the largest clast clast a is 2 5 cm in diameter it has an igneous texture no chondrules and is depleted in metallic fe ni and sulfide its fine grain size low ni kamacite and schreibersite and rare martensite resulted from rapid cooling the abundance of melt rock clasts in hvittis suggests that the breccia resided at its parent body surface however the apparent absence of el chondrites with solar wind implanted rare gases suggests that the el parent body was too small to develop a substantial regolith the bulk composition of clast a is very similar to that of average aubrites except for a sevenfold enrichment in s cr and mn these elements are concentrated in the sulfides it thus is possible that the clast was derived from one of the sulfide rich regions of the hvittis matrix if so then aubrites may be genetically related to el chondrites

mechanisms of thrust faulting in the gran sasso chain central apennines italy abstract the gran sasso chain in central italy is made up of an imbricate stack of eight thrust sheets which were emplaced over the upper miocene lower pliocene laga flysch the thrust sheets are numbered from 1 to 8 in order of their decreasing elevation in the tectonic stack and their basal thrusts are numbered from t 1 to t 8 accordingly on the basis of their different deformation features the major thrust faults fall into three groups 1 thrust faults marked by thick belts of incoherent gouges and breccia zones t 1 t 2 t 3 2 thrust faults characterized by a sharp plane which truncates folds that had developed in the footwall rocks t 5 t 6 and 3 thrust faults truncating folds developed in both the hangingwall and footwall units and bordered by foliated fault rocks t 7 the deformation features observed for the different faults seem to vary because of two combined factors 1 lithologic changes in the footwall and hangingwall units separated by the thrust faults and 2 increasing amounts of deformation in the deepest portions of the imbricate stack the upper thrust sheets from 1 to 6 are characterized by massive calcareous and dolomitic rocks they maintain a homoclinal setting and are truncated up section by the cataclastic thrust faults the lowermost thrust sheets 7 and 8 are characterized by a multilayer with competence contrasts which undergoes shear induced folding prior to the final emplacement of the thrust sheets bedding and axial planes of folds rotate progressively towards the t 5 t 6 t 7 and t 8 thrust boundaries and are subsequently truncated by propagation of the brittle thrust faults the maximum deformation is observed along the t 7 thrust fault consistent with horizontal displacement that increases progressively from the uppermost to the lowermost thrust sheet in the tectonic stack the axial planes of the folds developed in the hangingwall and footwall units are parallel to the t 7 thrust fault and foliated fault rocks have developed field data and petrographic analysis indicate that cleavage fabrics in the fault rocks form by a combination of cataclasis cataclastic flow and pressure solution slip associated with pervasive shearing along subtly distributed slip zones parallel to the t 7 thrust fault the development of such fabrics at upper crustal levels creates easy slip conditions in progressively thinner domains which are regions of localized flow during the thrust sheet emplacement

buseckite fe zn mn s a new mineral from the zaklodzie meteorite buseckite ima 2011 070 fe zn mn s is the fe dominant analog of wurtzite a new member of the wurtzite group discovered in zaklodzie and an ungrouped enstatite rich achondrite the type material occurs as single crystal grains 4 20 m in size in contact with two or more of enstatite plagioclase troilite tridymite quartz and sinoite low ni iron martensitic iron schreibersite keilite cristobalite and graphite which are also present in the type sample are not observed to be in contact with buseckite buseckite is black under diffuse illumination and nearly opaque grayish brown in transmitted light the mean chemical composition of buseckite as determined by electron microprobe analysis of the type material is wt s 35 84 fe 28 68 zn 23 54 mn 10 04 mg 1 18 sum 99 28 leading to an empirical formula calculated on the basis of 2 atoms of fe 0 46 zn 0 32 mn 0 16 mg 0 04 0 99 s 1 01 electron backscatter diffraction patterns of buseckite are a good match to that of synthetic zn 0 558 fe 0 442 s with the p6 3mc structure showing a 3 8357 c 6 3002 a v 80 27 a3 and z 2 buseckite is likely derived from the breakdown of high temperature pyrrhotite to form troilite and buseckite following the solidification of sulfide rich liquids produced during impact melting of an enstatite rich rock

intensive parameters of enstatite chondrite metamorphism abstract the enstatite oldhamite geothermometer eog developed by larimer and buseck 1974 makes use of the five phase assemblage kamacite quartz enstatite oldhamite troilite to determine metamorphic temperatures in enstatite chondrites a re evaluation of the thermodynamic foundation of the eog shows that several of the assumptions and approximations can be significantly improved with new thermodynamic data the geothermometer has been modified to reflect among other things the solution behavior of si in kamacite the solution behavior of a calcium silicate component in enstatite and metal sulfide fusion as a function of temperature and composition an analysis of the eog shows that the activity coefficient of si in kamacite and the ca rich component of enstatite are the model s most important parameters for si the activity coefficient data of sakao and elliot 1975 have been used the activity coefficient of a ca rich component of enstatite presents a unique problem since data on this parameter do not exist for one pyroxene systems and two pyroxene solution models do not provide unique activity coefficients in the absence of diopside the model therefore has been formulated using camgsi 2 o 6 as the ca rich component of enstatite and assumes that it behaves as a symmetric regular margules solution the margules interaction parameter w g is then used as an adjustable constant and is varied such that the resulting temperatures fall between minimum and maximum temperatures determined independently temperature minima were determined from the enstatite diopside solvus of carlson 1986 and indicate that the el6 chondrites have been metamorphosed to temperatures exceeding 900 1000 c the temperature of the enstatite plagioclase quartz eutectic 1090 c appropriate for el6 plagioclase compositions was used as the metamorphic maxima with these constraints a w g value of 52 kj mole was estimated as appropriate within the context of the model for el6 metamorphic conditions el6 temperatures determined via this method range from 981 c for yilmia to 1068 c for blithfield temperature estimates of greater than 1000 c for the highly equilibrated el6 chondrites require the formation of a metal sulfide liquid during metamorphism liquid fractionation of this predominantly fe fes liquid could explain the siderophile chalcophile and volatile element depletion in the el6 class relative to ci and eh chondrites liquid fractionation however is not required by the model and is consistent with a moderate cooling rate which is fast enough to lock in high cao contents in enstatite but slow enough to re equilibrate troilite and alabandite to low temperatures the oxygen fugacity determined in this study shows the enstatite chondrites to have equilibrated at extremely low f o 2 this as well as the activity of si that can be extracted from the eog indicates that the enstatite chondrites that contain sinoite si 2 n 2 o equilibrated under high nitrogen fugacities high f n 2 values imply that sinoite bearing e chondrites either formed in a nebula of high pressure f n 2 10 1 at 1050 c or more likely are products of planetary metamorphism

lateral variations of pn propagation in italy evidence for a high attenuation zone beneath the apennines pn phases recorded by 40 stations of the italian seismic network are analyzed using the spectral ratio technique to estimate the q structure of the uppermost mantle beneath the italian peninsula and nearby adriatic sea a total of 344 digital waveforms are analyzed from 22 earthquakes that occurred within distances of 300 to 1600 km the calculated apparent q values are grouped into two categories q 800 characterizes the adriatic side of the italian peninsula indicating that the adriatic lithosphere is very efficient in propagating pn phases through the uppermost mantle q 600 characterizes the uppermost mantle beneath the apennines and western italy indicating less efficient wave propagation the presence of asthenospheric mantle material at shallow depths beneath the apennines can explain the observed q

stress drops of the 1997 1998 colfiorito central italy earthquakes hints for a common behaviour of normal faults in the apennines stress drop estimates of moderate magnitude earthquakes in the umbria marche region in the northern apennines exhibit a large scatter for the two mw 5 7 and 6 0 main shocks of 26 september 1997 near colfiorito several papers resulted in stress drop estimates of 20 mpa but values as low as 2 3 mpa were proposed as well also for the largest aftershocks mw 4 estimates spread from 1 mpa up to values ten times larger we have critically revisited methods and data used in the literature we have specifically faced the trade off between source and propagation effects as we believe that it is responsible for a part of the large scatter to keep this trade off under control we have applied a methodology that combines the best fit of both source spectra after empirical green s function egf deconvolution and observed ground motion spectra finding that the results of the two different data sets converge independently at the same solution we have used ground motions observed in the colfiorito basin where an accelerograph and a co located seismological broad band station recorded three clusters of earthquakes in a broad magnitude interval 1 7 mw 6 0 we have found that the mainshock aftershock sequences result in stress drops of 2 5 mpa at mw 5 6 with an average tendency to decrease at smaller magnitudes where stress drop variability increases these findings confirm the source scaling recently assessed through empirical green s function deconvolution for another well monitored seismic sequence of normal faulting earthquakes which struck the city of l aquila in the central apennines in april 2009 the similar scaling law of the two areas suggests common mechanisms of stress release for the shallow normal faults in the apennines the propensity of smaller earthquakes to increase in variability with a tendency toward smaller stress drops may reflect an effect of fault strength heterogeneities for smaller size ruptures

geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy abstract serri g innocenti f and manetti p 1993 geochemical and petrological evidence of the subduction of delaminated adriatic continental lithosphere in the genesis of the neogene quaternary magmatism of central italy in m j r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 117 147 the neogene quaternary magmatism of the northern apenninic arc took place in four phases separated in space and time which become progressively younger from west to east phase i 14 ma phase ii 7 3 6 0 ma phase iii 5 1 2 2 ma phase iv 1 3 0 1 ma this magmatism is the result of the activation of three physically separate sources 1 the adriatic continental crust extracted from the mantle in the late proterozoic 2 a strongly refractory recently k enriched harzburgitic mantle located in the mechanical boundary layer mbl of the lithosphere and 3 a recently metasomatized cpx rich mantle compositionally variable from iherzolite to wehrlite clinopyroxenite interpreted as an ephemerally k enriched asthenosphere the adriatic continental crust is the dominant source of the acid plutonic and volcanic rocks of the tuscan region the acid magmatism is mostly found inside an ellipsoidal area about 150 300 km centred on giglio island here defined as the tuscan crustal dome within this area mantle derived magmas unaffected by important crustal contamination processes and mixing with crustal anatectic melts have so far not been found pure crustal magmas are rare but are represented for example by some of the san vincenzo and roccastrada rhyolites virtually all the tuscan acid centres show evidence of mixing with potassic mantle derived magmas major and trace elements as well as 87 sr 86 sr and 143 nd 144 nd data on primitive rocks mg 65 reveal two groups of mantle derived magmas these define two distinct mantle enrichment trends both essentially due to the additions of k rich components which metasomatized separate compositionally diverse upper mantle sectors in both cases the most remarkable mineralogical effect of these enrichment processes is the production of variable amount of phlogopite through reaction between fluids and or melts with the mantle the rocks of group i ol hy and q normative lamproites ultrapotassic high mg latites ultrapotassic shoshonites and shoshonites saturated trend are considered to be derived by partial melting at low pressure 87 sr 86 sr 0 717 ce sr 0 3 and k 2 o na 2 o 6 7 and low ratios of 143 nd 144 nd 0 5121 0 5120 and ba la 87 sr 86 sr 0 712 and k 2 o na 2 o 8 9 values and low 143 nd 144 nd ba la 0 10 ratios these constraints do not allow to exclude a complete identity between the k rich components which metasomatized the mantle sources of the saturated and undersaturated trend magmas the geochemical and isotopic features of the components that metasomatized the mantle sources of the northern apenninic arc magmatism can be explained by a geodynamic process which causes a large amount of crustal materials to be incorporated within the upper mantle we propose that the delamination and subduction of the adriatic continental lithosphere related to the still ongoing northern apennine continental collision provide a viable mechanism to explain the genesis and eastward discontinuous migration of the magmatism in central italy the subduction of delaminated lithospheric mantle with lower crustal slivers would have exposed uppermost mantle adriatic mbl and crustal units previously imbricated in the apennine chain to the heating advected by the upwelling of a recently and ephemerally k enriched asthenospheric mantle wedge and by the underplating of magmas derived from it we consider that the diapiric uprising of a hot crustally contaminated asthenosphere occurs in the wake left above the sinking of the adriatic delaminated subducting continental lithosphere the delamination subduction process of the adriatic lithosphere has probably started in the early middle miocene but earlier than 15 14 ma ago as indicated by the age and petrologic characteristics of the first magmatic episode sisco lamproite of the northern apennine orogenesis

extensional basins in the tectonically bimodal central apennines fold thrust belt italy response to corner flow above a subducting slab in retrograde motion the apennines fold thrust belt has developed over the past 20 m y in response to southeastward retrograde migration of the adriatic trench in a region of ongoing subduction but little plate convergence the orogenic belt is characterized by a gently sloping southwestern flank in a state of regional extensional collapse and a steeply sloping northeastern flank in regional contraction in any given area in the central apennines the chronologies of thrusting and subsequent extension provide an estimate of the time required for attainment of high elevation 2 5 3 0 km the time between initial extension and eruption of local ultramafic lavas provides an estimate of the time required to collapse by regional crustal thinning these estimates suggest that the northeastern contractional flank of the range is rising at least twice as fast as the southwestern flank is collapsing we propose that the bimodal state of stress in the apennines is maintained by corner flow in the mantle wedge beneath the crest of the range

shock effects in eh6 enstatite chondrites and implications for collisional heating of the eh and el parent asteroids abstract of the six chondrites that were listed as eh6 or eh6 an during the course of this study we confirm the eh classification of y 8404 y 980211 and y 980223 and the eh an classification of y 793225 two chondrites a 882039 and y 980524 are reclassified as el the former contains ferroan alabandite and both contain kamacite with 1 wt si all of the meteorites contain euhedral enstatite grains surrounded by metal sulfide although this texture is rare in y 793225 consistent with enstatite crystallizing from a mixed melt all contain enstatite with 0 5 mg

mineralogy and petrology of the abee enstatite chondrite breccia and its dark inclusions the abee e4 enstatite chondrite breccia consists of clasts many rimmed by metallic fe ni dark inclusions and matrix the clasts and matrix were well equilibrated by thermal metamorphism as evidenced by uniform mineral compositions recrystallized chondrules low mno content of enstatite and high abundance of orthoenstatite the clasts acquired their metal rich rims prior to this metamorphic episode the occurrence in abee of relatively unmetamorphosed dark inclusions clasts with nearly random magnetic orientations and a matrix with a uniform magnetic orientation 18 19 indicates that clast and matrix metamorphism occurred prior to the agglomeration of the breccia the dark inclusions are an unusual kind of enstatite chondritic material distinguished from the clasts and matrix by their relative enrichments in ree 21 23 low relative abundances of kamacite total metallic fe ni and silica lower niningerite total sulfide ratios high relative abundances of oldhamite and martensite smaller euhedral enstatite more heterogeneous enstatite and metallic fe ni more calcic enstatite and more nickeliferous schreibersite we propose the following model for the petrogenesis of the abee breccia the maximum metamorphic temperature of breccia parent material was 840 c the minimum temperature of formation of abee niningerite and perhaps near 950 1000 c the fe ni s eutectic temperature euhedral enstatite crystals in metallic fe ni and sulfide rich areas grew at these metamorphic temperatures into pliable metal and sulfide breccia parent material was impact excavated from depth admixed with dark inclusions and rapidly cooled 700 to 200 c in about 2 hours 15 during this cooling clast and matrix material acquired thermal remanent magnetization random conglomeration of clasts and unconsolidated matrix materials caused the clasts to have random magnetic orientations and the matrix areas to have net magnetic intensities of zero due to the cancellation of numerous randomly oriented magnetic vectors of equal intensity in the matrix a subsequent ambient magnetic field imparted a uniform net magnetic orientation to the matrix and caused the magnetic orientations of the clasts to be somewhat less random the abee breccia was later consolidated possibly by shock or by shallow burial and very long period low temperature 215 c metamorphism

the adhi kot breccia and implications for the origin of chondrules and silica rich clasts in enstatite chondrites abstract the adhi kot eh4 enstatite chondrite breccia consists of silica rich clasts 12 mn 5 vol chondrule rich clasts 55 mn 10 vol and matrix 35 mn 10 vol the silica rich clasts are a new kind of enstatite chondritic material which contains more cristobalite 18 28 wt than enstatite 12 14 wt as well as abundant niningerite and troilite the bulk atomic mg si ratios of the clasts 0 22 0 40 are much lower than the average for enstatite chondrites 0 79 kamacite and martensite with 8 11 wt ni and a martensitic structure occur in all three breccia components the clasts have kamacite rich rims and kamacite rich aggregates occur in the matrix a unidirectional change in the ambient ps2 po2 ratio in the region of the solar nebula where adhi kot agglomerated can explain many of the breccia s petrologic features if this region initially had a very high ps2 po2 ratio in a gas of non cosmic composition sulfurization of enstatite and metallic fe e g mgsio3 2fe c 3h2s mgs sio2 2fes h2o ch4 may have occurred producing abundant niningerite free silica and troilite at the expense of enstatite and metallic fe the ni content of the residual metal would have increased perhaps to 8 10 wt the silica rich clasts agglomerated under these conditions a significant fraction of the originally produced niningerite was lost perhaps by aerodynamic size sorting processes lowering the clasts bulk mg si ratios the ps2 po2 ratio then decreased perhaps because of infusion of additional h2o and sulfurization of metallic fe and enstatite ceased the chondrule rich clasts agglomerated under these conditions acquiring little free silica and niningerite an episode of chondrule formation occurred at this time by melting millimeter sized agglomerates of this relatively silica poor enstatite chondrite material and concomitant fractionation of an immiscible liquid of metallic fe ni and sulfide the chondrule rich clasts agglomerated many such chondrules subsequently the matrix agglomerated acquiring the few remaining chondrules kamacite rich aggregates formed after the cessation of metal sulfurization and agglomerated with the matrix the kamacite rich clast rims were acquired at this time the components of adhi kot accreted to the eh chondrite parent body where the breccia was assembled buried beneath additional accreting material and metamorphosed at temperatures of 700 c impact excavation of the breccia and deposition onto the surface caused the formation of martensite from taenite inside the clasts and the matrix at the surface impact melting produced an albite glass spherule which was incorporated into the matrix however the absence of solar wind implanted rare gases in bulk adhi kot indicates that the breccia spent little time in a regolith

alkali differentiation in ll chondrites abstract the ll group chondrites krahenberg krbg and bhola are heterogeneous agglomerates containing a variety of lithic fragments and chondrules as well as crystal fragments the fe fe mg content of most olivine grains is uniform fa28 although a few with distinctly lower fe contents were found fa19 both meteorites contain large cm sized fragments with high enrichments of k 12 rb 45 and cs 70 relative to ll chondrites while the ree concentrations are normal except for a negative eu anomaly na and sr are depleted 0 5 and the na k weight ratio is 0 33 compared to 11 in the host however there is no difference in the sum of na k atoms also the major elements si al mg ca and fe are nearly the same in fragments as in the host material the k rich igneous lithic fragments have a microporphyritic texture of euhedral to skeletal olivines in a partly devitrified glass with 4 k2o the main pans of both krbg and bhola contain mesostasis glasses in porphyritic chondrules and lithic fragments with varying k content 0 1 8 6 k2o and na k ratios 0 2 100 crystalline plagioclase is depleted in k with an average na k ratio of 22 i e higher than that for ordinary chondritic plagioclase 8 4 olivines in the large k rich fragments and in the host meteorites have the same iron content fa28 indicating that both formed under the same oxygen fugacity and probably on the same parent body conceivable mechanisms for the formation of the k rich rocks from normal ll chondrite parent material are 1 magmatic differentiation 2 na k exchange via a vapor phase 3 silicate liquid immiscibility 4 volatilization and condensation in impact events process 2 appears most feasible for forming a rock enriched only in k and heavier alkalies and depleted in na without noticeably changing other elements including the ree

explicating the behavior of mn bearing phases during shock melting and crystallization of the abee eh chondrite impact melt breccia literature data show that among eh chondrites the abee impact melt breccia exhibits unusual mineralogical characteristics these include very low mno in enstatite 0 04 wt higher mn in troilite 0 24 wt and oldhamite 0 36 wt than in eh4 indarch and eh3 kota kota which are not impact melt breccias low mn in keilite 3 6 4 3 wt high modal abundances of keilite 11 2 wt and silica 7 wt but ranging up to 16 wt in some regions low modal abundances of total silicates 58 8 wt and troilite 5 8 wt and the presence of acicular grains of the amphibole fluor richterite these features result from abees complex history of shock melting and crystallization impact heating was responsible for the loss of mno from enstatite and the concomitant sulfidation of mn troilite and oldhamite grains that crystallized from the impact melt acquired relatively high mn contents abundant keilite and silica also crystallized from the melt these phases along with metallic fe were produced at the expense of enstatite niningerite and troilite melting of the latter two phases produced a s rich liquid with higher fe mg and fe mn ratios than in the original niningerite allowing the crystallization of keilite prior to impact melting f was distributed throughout abee perhaps in part adsorbed onto grain surfaces after impact melting most of the f that was not volatilized was incorporated into crystallizing grains of fluor richterite other eh chondrite impact melt breccias and impact melt rocks exhibit some of these mineralogical features and must have experienced broadly similar thermal histories

rate of diffuse carbon dioxide earth degassing estimated from carbon balance of regional aquifers the case of central apennine italy central italy is characterized by an anomalous flux of deeply derived co2 in the western tyrrhenian sector of central italy co2 degassing occurs mainly from focused emissions vents and strong diffuse degassing and thermal springs whereas in the eastern apennine area deep co2 is dissolved in cold groundwaters of regional aquifers hosted by mesozoic carbonate evaporite formations influx of deep co2 into 12 carbonate aquifers 12 500 km2 of the central apennine is computed through a carbon mass balance that couples aquifer geochemistry with isotopic and hydrogeological data mass balance calculations estimate that 6 5 1010 mol yr 1 of inorganic carbon are dissolved in the studied aquifers approximately 23 of this amount derives from biological sources active during the infiltration of the recharge waters 36 comes from carbonate dissolution while 41 is representative of deep carbon sources characterized by a common isotopic signature 13c 3 the calculated deep co2 influx rate ranges from 105 to 107 mol yr 1 km 2 increasing regionally from east to west in the study area

seismicity and p wave velocity image of the southern tyrrhenian subduction zone summary this paper focuses on the deep earth structure and earthquake distribution within the southern tyrrhenian subduction zone we discuss seismological observations which provide insight into the mechanics of subduction processes for an unusual compressional margin the motivation for this work derives from the recognition that little is known about one of the most intriguing geodynamic features of the italian peninsula and the fact that a large amount of information can be extracted from data collected by the istituto nazionale di geofisica national seismic network we show that the hypocentres of intermediate and deep earthquakes that have occurred since 1988 image a nw dipping plane continuous from the ionian sea to the tyrrhenian down to 450 km depth we also present a 3 d model of the deep structure beneath southern italy derived using deep earthquake seismic tomography tomographic images reveal a high velocity body dipping from the apulian and iblean forelands towards the tyrrhenian basin in the crust and upper mantle at least down to 320 km depth this high velocity body may be related to the cold subducted ionian lithosphere earthquake hypocentres are confined within the high velocity body delineating the subduction beneath the calabrian arc

si bearing metal and niningerite in almahata sitta fine grained ureilites and insights into the diversity of metal on the ureilite parent body a detailed mineralogical and chemical study of almahata sitta fine grained ureilites ms 20 ms 165 ms 168 was performed to shed light on the origin of these lithologies and their sulfide and metal the almahata sitta fine grained ureilites silicates 0 5 mn fe 0 5s with some similarities to the mineralogy of enstatite e chondrites overall metal grains show a large compositional variability in ni and si concentrations niningerite grains probably formed as a by product of smelting via sulfidation the large si ni variation in fine grained ureilite metal could be the result of variable degrees of reduction during impact smelting inherited from coarse grained ureilite precursors or a combination of both large si bearing metal grains probably formed via coalescence of existing and newly formed metal during impact smelting bulk and in situ siderophile trace element abundances indicate three distinct populations of 1 metal crystallized from partial melts in ms 20 2 metal resembling bulk chondritic compositions in ms 165 and 3 residual metal in ms 168 almahata sitta fine grained ureilites developed their distinctive mineralogy due to severe reduction during smelting despite the presence of e chondrite and ureilite stones in the almahata sitta fall a mixing relation of e chondrites or their constituents and ureilite material in almahata sitta can be ruled out based on isotopic textural and mineral chemical reasons

emplacement of foreland thrust systems emplacement driving mechanisms for thrust systems have been briefly reviewed and compared with distinctive structural styles in thrust belts a b type mode which implies a push from the rear and an elastic brittle behavior of the rock mass appears to be suitable as a general model for the emplacement of thrust sheets in thin skinned fold and thrust belts where stratal shortening of sedimentary covers and imbrication of upper level crustal rocks occur in such an environment that the mechanical behavior of the crustal section involved the mode and timing of deformation and the geometry of thrust systems are all strongly dependent upon the coupling between induced tectonic strain and transient close to lithostatic pore fluid pressure buildup over a critical areal extent the model presented here does not require a weak basal horizon for the detachment of thrust sheets and pore pressure pp does not need to be high at once under the entire length of the thrust wedge rather the transient buildup of pp and hence the spatial and temporal progressive weakening of the rock mass are directly coupled with deformation