eutectic metal troilite fe mn na phosphate al free chromite assemblage in shock produced chondritic melt of the yanzhuang chondrite an assemblage with feni metal troilite fe mn na phosphate and al free chromite was identified in the metal troilite eutectic nodules in the shock produced chondritic melt of the yanzhuang h6 meteorite electron microprobe and raman spectroscopic analyses show that a few phosphate globules have the composition of na bearing graftonite fe mn na 3 po4 2 whereas most others correspond to mn bearing galileiite na fe mn 4 po4 3 and a possible new phosphate phase of na2 fe mn 17 po4 12 composition the yanzhuang meteorite was shocked to a peak pressure of 50 gpa and a peak temperature of approximately 2000 c all minerals were melted after pressure release to form a chondritic melt due to very high postshock heat that brought the chondrite material above its liquidus the volatile elements p and na released from whitlockite and plagioclase along with elements cr and mn released from chromite are concentrated into the shock produced fe ni s o melt at high temperatures during cooling microcrystalline olivine and pyroxene first crystallized from the chondritic melt metal troilite eutectic intergrowths and silicate melt glass finally solidified at about 950 1000 c on the other hand p mn and na in the fe ni s o melt combined with fe and crystallized as fe mn na phosphates within troilite while cr combined with fe and crystallized as al free chromite also within troilite

the distinct morphological and petrological features of shock melt veins in the suizhou l6 chondrite the morphology and petrology of distinct melt veins in the suizhou l6 chondrite have been investigated using scanning electron microscopy electron microprobe analyses and raman spectroscopy synchrotron energy dispersive diffraction and transmission electron microscopy it is found that the melt veins in the suizhou meteorite morphologically are the simplest straightest and thinnest among all shock veins known from meteorites at first glance these veins look like fine fractures but petrologically they are solid melt veins of chondritic composition and consist of fully crystalline materials of two distinct lithological assemblages with no glassy material remaining the suizhou melt veins contain the most abundant high pressure mineral species when compared with all other veins known in chondrites thus these veins in suizhou are classified as shock veins all rock forming and almost all accessory minerals in the suizhou shock veins have been transformed to their high pressure polymorphs and no fragments of the precursor minerals remain in the veins among the 11 high pressure mineral phases identified in the suizhou veins three are new high pressure minerals namely tuite after whitlockite xieite and the cf phase after chromite on the basis of transformation of plagioclase into maskelynite it is estimated that the suizhou meteorite experienced shock pressures andmore shock temperatures up to 22 gpa and 1000 c respectively shearing and friction along shock veins raised the temperature up to 1900 2000 c and the pressure up to 24 gpa within the veins hence phase transition and crystallization of high pressure minerals took place only in the suizhou shock veins fast cooling of the extremely thin shock veins is regarded as the main reason that up to 11 shock induced high pressure mineral phases could be preserved in these veins less

fractional crystallization of olivine melt inclusion in shock induced chondritic melt vein abstract the formation of ringwoodite wadsleyite and majorite from their parental low pressure polymorphs in melt veins in chondritic meteorites is usually interpreted to be the result of shock induced solid state phase transformation formation and survival of individual mineral melt enclaves in the chondritic high pressure melt was not considered a viable possibility we report evidence for melting of individual large olivine fragments entrained in melt veins their survival as melt enclaves in the chondritic melts and their subsequent fractional crystallization at high pressures and temperatures the fractionally crystallized olivine melt enclaves appear to be ubiquitous in chondrites in contrast ca poor pyroxene fragments in the same veins and ca poor pyroxene in chondrules entrained do not show any sign of melting texture and compositions of olivine fragments are indicative of fractional crystallization from individual olivine melts alone fragments of original unzoned olivine fa 24 26 melted and melts subsequently fractionally crystallized to mg rich wadsleyite fa 6 10 and mg poor ringwoodite fa 28 33 with a compositional gap of 26 mol fayalite in contrast compositions of ringwoodite and wadsleyite that emerged from solid sate phase transformations are identical to that of parental olivine thus erasing any source of enigma the olivine monomineralic melts barely show any signs of mixing with the chondritic liquid prior to or during their individual fractional crystallization our findings demonstrate that the formation of high pressure minerals during shock events in asteroids also results from melting and fractional crystallization from some individual mineral melts that barely mixed with the chondritic melt host a mechanism previously not recognized or accepted

stability of the seaward slope of berm breakwaters abstract an extensive research on stability of statically and dynamically stable rock slopes and gravel beaches was reanalysed and focussed on berm breakwaters berm breakwaters are initially dynamically stable under severe wave attack but become more or less statically stable after reshaping the effects on the seaward profile of wave height period storm duration spectral shape initial slope rock size rock shape and grading water depth and angle of wave attack are described in a qualitative way relationships between these variables and the profile parameters are described leading to a computer program this program was verified with independent data of berm breakwaters from various international institutes the program showed to give a good prediction of the behaviour of the seaward slope of berm breakwaters and can therefore be used as a conceptual design tool

a new formula for front slope recession of berm breakwaters the front slope stability of breakwaters with a homogeneous berm was studied in a large number of two dimensional model tests at aalborg university denmark the results are presented together with a new formula for prediction of the berm recession which is the most important parameter for describing the reshaping the formula has also been calibrated and validated against model test data from other researchers the significance of the new design formula is that it predicts berm recession much better than the existing methods especially in case of more stable structures

high pressure polymorphs in yamato 790729 l6 chondrite and their significance for collisional conditions shock pressure recorded in yamato y 790729 classified as l6 type ordinary chondrite was evaluated based on high pressure polymorph assemblages and cathodoluminescence cl spectra of maskelynite the host rock of y 790729 consists mainly of olivine low ca pyroxene plagioclase metallic fe ni and iron sulfide with minor amounts of phosphate and chromite a shock melt vein was observed in the hostrock ringwoodite majorite akimotoite lingunite tuite and xieite occurred in and around the shock melt vein the shock pressure in the shock melt vein is about 14 23 gpa based on the phase equilibrium diagrams of high pressure polymorphs some plagioclase portions in the host rock occurred as maskelynite sixteen different cl spectra of maskelynite portions were deconvolved using three assigned emission components centered at 2 95 3 26 and 3 88 ev the intensity of emission component at 2 95 ev was selected as a calibrated barometer to estimate shock pressure and the results indicate pressures of about 11 19 gpa the difference in pressure between the shock melt vein and host rock might suggest heterogeneous shock conditions assuming an average shock pressure of 18 gpa the impact velocity of the parent body of y 790729 is calculated to be 1 90 km s 1 the parent body would be at least 10 km in size based on the incoherent formation mechanism of ringwoodite in y 790729

natural cati2o4 structured fecr2o4 polymorph in the suizhou meteorite and its significance in mantle mineralogy abstract the first natural occurrence of a high pressure polymorph of chromite has been discovered in the shock metamorphosed suizhou meteorite the composition of this high pressure polymorph is identical to that of the precursor chromite the raman spectrum of this polymorph is distinct from that of chromite synchrotron x ray diffraction analysis revealed that this polymorph has an orthorhombic cati2o4 type structure the cell parameters are a 9 462 6 a b 9 562 9 a c 2 916 1 a v 263 8 4 a3 z 4 space group bbmm and the density 5 63 g cm3 the numbers in parentheses are standard deviations on the last significant digits this polymorph is 11 5 denser than chromite the p t conditions for the phase transformation from chromite to the cati2o4 structured polymorph are estimated at 20 23 gpa and 1800 to 2000 c respectively this dense cati2o4 structured fecr2o4 phase could be a host phase for cr al fe mg and mn and other metallic elements in the deep earth

high pressure minerals in shocked meteorites heavily shocked meteorites contain various types of high pressure polymorphs of major minerals olivine pyroxene feldspar and quartz and accessory minerals chromite and ca phosphate these high pressure minerals are micron to submicron sized and occur within and in the vicinity of shock induced melt veins and melt pockets in chondrites and lunar howardite eucrite diogenite hed and martian meteorites their occurrence suggests two types of formation mechanisms 1 solid state high pressure transformation of the host rock minerals into monomineralic polycrystalline aggregates and 2 crystallization of chondritic or monomineralic melts under high pressure based on experimentally determined phase relations their formation pressures are limited to the pressure range up to 25 gpa textural crystallographic and chemical characteristics of high pressure minerals provide clues about the impact events of meteorite parent bodies including their size and mutual collision velocities and about the mineralogy of deep planetary interiors the aim of this article is to review and summarize the findings on natural high pressure minerals in shocked meteorites that have been reported over the past 50 years

re os dating of molybdenite from the pueblo viejo au ag cu and douvray cu au districts hispaniola re os dating of three samples of hydrothermal molybdenite collected from the pueblo viejo au ag cu district 5 5 moz gold past production 16 2 moz proven plus probable gold ore reserves yields ages of 112 1 0 4 112 0 0 4 and 111 5 0 4 ma these re os dates confirm an early cretaceous age for mineralization coeval with tholeiitic intraoceanic island arc volcanism and in particular with an episode of felsic magmatism and extension across the early cretaceous arc 110 118 ma re os dating of a sample of hydrothermal molybdenite collected from the douvray porphyry cu mo deposit with inferred resources of 1 257 mlb cu 0 276 moz au 6 84 moz ag and 4 367 tons mo yields an age of 93 3 0 3 ma coeval with calc alkaline magmatism along the greater antilles island arc

annama h chondrite mineralogy physical properties cosmic ray exposure and parent body history the fall of the annama meteorite occurred early morning local time on april 19 2014 on the kola peninsula russia based on mineralogy and physical properties annama is a typical h chondrite it has a high ar ar age of 4 4 ga its cosmic ray exposure history is atypical as it is not part of the large group of h chondrites with a prominent 7 8 ma peak in the exposure age histograms instead its exposure age is within uncertainty of a smaller peak at 30 4 ma the results from short lived radionuclides are compatible with an atmospheric pre entry radius of 30 40 cm however based on noble gas and cosmogenic radionuclide data annama must have been part of a larger body radius 65 cm for a large part of its cosmic ray exposure history the 10be concentration indicates a recent 3 5 ma breakup which may be responsible for the annama parent body size reduction to 30 35 cm pre entry radius

high pressure phases in an ultramafic rock from mars abstract shock induced melt pockets in the martian meteorite chassigny are completely transformed into a set of high pressure mineral phases previously unknown from ultramafic rocks the major constituents of the earth s mantle ferropericlase amorphous mg fe sio 3 perovskite ringwoodite wadsleyite high pressure phosphate ca 3 po 4 2 and cati 2 o 4 structured chromite were formed by solid state transformation and fractional crystallization upon pressure release from 23 to 10 gpa during shock pressure release the temperatures in the melt pocket dropped to timescales of 10 2 to 10 3 s to allow preservation of the high pressure phases formation and preservation of these phases in chassigny depend on the duration of shock compression which increases with the pre impact burial depth of the meteorite below the martian surface the estimated burial depth of 25 to 250 m is in agreement with the sampling depth of potential source craters for the chassigny meteorite

evaluation of scale effects in hydraulic models by analysis of laminar and turbulent flows abstract the paper presents an analysis of laminar and turbulent flow in porous stone material in order to evaluate the order of magnitude of scale effects in hydraulic models hydraulic model tests such as for example breakwater model tests are normally carried out at such small scales that the flow through the various layers of the breakwater is not completely turbulent for this reason scale effects occur a well known method to compensate for the scale effects is to use larger stones than calculated by froude s model law in certain regions of the model the paper presents formulae for the calculation of the compensated stone sizes based on earlier work by engelund further an evaluation of the energy dissipation in hydraulic models is made in order to determine the scale effect due to laminar flow

an experimental study on the hydraulic stability of icelandic type berm breakwaters abstract one of the key aspects of breakwater design and safety assessment is their stability evaluation in the present paper hydraulic stability of a multi layer berm breakwater mlbb has been studied through varying the parameter of eroded area to this end a 2 d experimental model has been carried out in the wave flume of tarbiat modares university using irregular waves with a jonswap spectrum a total of 150 tests have been performed to cover a wide range of sea state conditions and geometrical parameters such as wave height wave period water depth berm width berm elevation stone class i height front slope and nominal diameter of stone class i in this study a new dimensionless parameter is introduced to indicate that the wave breaking type plays a fundamental role in stability of mlbbs eventually a new formula is derived to estimate the damage of mlbbs based on different sea state conditions and various geometrical parameters comparisons are made between the estimated damage parameter of mlbbs by the proposed formula and those estimated by existing formulae the results denote that the present formula not only performs well for mlbbs experimental data but also indicates a reliable performance for some of lykke andersen s 2006 data in statically homogenous berm breakwaters hbbs outside the range of given formula furthermore an innovative approach is presented to examine the eroded area based on the berm recession and the intersection point of reshaped and initial profile from swl which performs faultlessly rather than the existing one

armor stability of hardly or partly reshaping berm breakwaters abstract this paper deals with stability of hardly or partly reshaping berm breakwaters a simple physical argument is used to derive a new stability formula based on the assumption that the maximum wave force causing damage of armor layer is proportional to the maximum wave momentum flux near the structure toe the main goal of the present paper is to provide an estimation technique based on this physical principle to predict the deformation of the front slope in terms of the eroded area the proposed method is verified by comparison with model test data it is found that by using the maximum wave momentum flux approach the damage to the front slope eroded area can be very well predicted moreover a simple method to estimate the eroded area based on measured or calculated berm recession rec and depth of intersection of reshaped and initial profile h f is presented the performance of the simple method based on measured data of rec and h f is better than the presented stability equation based on wave momentum flux parameter when using the best prediction formulae for recession and depth of intersection the simple method and the momentum flux stability equation provide similar uncertainty

an experimental study on the parameterization of reshaped seaward profile of berm breakwaters abstract berm breakwaters are rubble mound structures in which the seaward slope of the initial profile may be reshaped to become more stable under severe wave attack the stones in the seaward slope move from the initial slope to an equilibrium profile a 2d experimental study has been carried out in a wave flume at a hydraulic laboratory of tarbiat modares university to study the effects of sea state and structural parameters on the reshaped profile parameters of such breakwaters a series of 287 tests have been performed to cover the effect of various sea state conditions such as wave height wave period number of waves and water depth at the toe of the structure and structural parameters such as berm width berm elevation above still water level and armor stone size all the tests have been done employing irregular waves with a jonswap spectrum in this paper first the reshaped profiles are schematized and then the key parameters of the reshaped seaward profiles such as step height step length and depth of intersection point of initial and reshaped profile are investigated using results of this experimental work eventually formulae that include some sea state and structural parameters are derived for estimation of the reshaped profile parameters to assess the validity of the proposed formulae comparisons are made between the estimated parameters of reshaped profiles by these formulae and earlier formulae given by other researchers the comparisons show that the estimation procedure foretells reshaping parameters well and with less scatter according to the present data and also other experimental results within the range of parameters tested

mineralogy of meteorite groups approximately 275 mineral species have been identified in meteorites reflecting diverse redox environments and in some cases unusual nebular formation conditions anhydrous ordinary carbonaceous and r chondrites contain major olivine pyroxene and plagioclase major opaque phases include metallic fe ni troilite and chromite primitive achondrites are mineralogically similar the highly reduced enstatite chondrites and achondrites contain major enstatite plagioclase free silica and kamacite as well as nitrides a silicide and ca mg mn na cr k and ti rich sulfides aqueously altered carbonaceous chondrites contain major amounts of hydrous phyllosilicates complex organic compounds magnetite various sulfates and sulfides and carbonates in addition to kamacite and taenite iron meteorites contain carbides elemental c nitrides phosphates phosphides chromite and sulfides silicate inclusions in iab iiicd and iie iron meteorites consist of mafic silicates plagioclase and various sulfides oxides and phosphates eucrites howardites and diogenites have basaltic to orthopyroxenitic compositions and consist of major pyroxene and calcic plagioclase and several accessory oxides ureilites are made up mainly of calcic chromian olivine and low ca clinopyroxene embedded in a carbonaceous matrix accessory phases include the c polymorphs graphite diamond lonsdaleite and chaoite as well as metallic fe ni troilite and halides angrites are achondrites rich in fassaitic pyroxene i e al ti diopside minor olivine with included magnesian kirschsteinite is also present martian meteorites comprise basalts lherzolites a dunite and an orthopyroxenite major phases include various pyroxenes and olivine minor to accessory phases include various sulfides magnetite chromite and ca phosphates lunar meteorites comprise mare basalts with major augite and calcic plagioclase and anorthositic breccias with major calcic plagioclase several meteoritic phases were formed by shock metamorphism martensite 2 fe ni has a distorted body centered cubic structure and formed by a shear transformation from taenite during shock reheating and rapid cooling the c polymorphs diamond lonsdaleite and chaoite formed by shock from graphite suessite formed in the north haig ureilite by reduction of fe and si possibly from olivine via reaction with carbonaceous matrix material ringwoodite the spinel form of mg fe 2sio4 and majorite a polymorph of mg fe sio3 with the garnet structure formed inside shock veins in highly shocked ordinary chondrites secondary minerals in meteorite finds that formed during terrestrial weathering include oxides and hydroxides formed directly from metallic fe ni by oxidation phosphates formed by the alteration of schreibersite and sulfates formed by alteration of troilite

postshock annealing and postannealing shock in equilibrated ordinary chondrites implications for the thermal and shock histories of chondritic asteroids abstract in addition to shock effects in olivine plagioclase orthopyroxene and ca pyroxene petrographic shock indicators in equilibrated ordinary chondrites oc include chromite veinlets chromite plagioclase assemblages polycrystalline troilite metallic cu irregularly shaped troilite grains within metallic fe ni rapidly solidified metal sulfide intergrowths martensite and various types of plessite metal sulfide veins large metal and or sulfide nodules silicate melt veins silicate darkening low ca clinopyroxene silicate melt pockets and large regions of silicate melt the presence of some of these indicators in every petrologic type 4 to 6 ordinary chondrite demonstrates that collisional events caused all equilibrated oc to reach shock stages s3 s6 those type 4 to 6 oc that are classified as shock stage s1 on the basis of sharp optical extinction in olivine underwent postshock annealing due to burial beneath materials heated by the impact event those type 4 to 6 oc that are classified s2 on the basis of undulose extinction and lack of planar fractures in olivine were shocked to stage s3 s6 annealed to stage s1 and then shocked again to stage s2 some oc were probably shocked to stage s3 after annealing it seems likely that many oc experienced multiple episodes of shock and annealing because 40ar 39ar chronological data indicate that mil 99301 ll6 s1 was annealed 4 26 ga ago presumably as a consequence of a major impact it seems reasonable to suggest that other equilibrated s1 and s2 oc which contain relict shock features were also annealed by impacts because some type 6 s1 oc e g guarena kernouve portales valley all of which contain relict shock features were annealed 4 44 4 45 ga ago during a period when impacts were prevalent and most oc were thermally metamorphosed it follows that impact induced annealing could have contributed significantly to oc thermal metamorphism

pressure induced forces and shear stresses on rubble mound breakwater armour layers in regular waves abstract this paper presents the results from an experimental investigation of the pressure induced forces in the core material below the main armour layer and shear stresses on the armour layer for a porous breakwater structure two parallel experiments were performed which both involved pore pressure measurements in the core material 1 core material with an idealized armour layer made out of spherical objects that also allowed for detailed velocity measurements between and above the armour and 2 core material with real rock armour stones the same core material was applied through the entire structure i e no additional filter layers were applied for both experiments high speed video recordings were synchronised with the pressure measurements for a detailed investigation of the coupling between the run up and run down flow processes and the measured pressure variations outward directed pressure gradients were found which exerted a lift force up to 60 of the submerged weight of the core material these maximum outward directed pressure gradients were linked to the maximum run down event and were in general situated at or slightly below the maximum run down level detailed velocity and turbulence measurements showed that the large outward directed pressure gradients in general coincide both in time and space with the maximum bed shear stresses on the armour layer based on the reynolds stresses the bed shear stresses were found to result in a shields parameter in the same order of magnitude as the critical value for movement of the armour stones

mineralogy of meteorite groups an update twenty minerals that were not included in the most recent list of meteoritic minerals have been reported as occurring in meteorites extraterrestrial anhydrous ca phosphate should be called merrillite not whitlockite

on front slope stability of berm breakwaters abstract the short communication presents application of the conventional van der meer stability formula for low crested breakwaters for the prediction of front slope erosion of statically stable berm breakwaters with relatively high berms the method is verified burcharth 2008 by comparison with the reshaping of a large norwegian breakwater exposed to the north sea waves as a motivation for applying the van der meer formula a discussion of design parameters related to berm breakwater stability formulae is given comparisons of front erosion predicted by the use of the van der meer formula with model test results including tests presented in sigurdarson and van der meer 2011 are discussed a proposal is presented for performance of new model tests with the purpose of developing more accurate formulae for the prediction of front slope erosion as a function of front slope relative berm height relative berm width method of armour stone placement and hydraulic parameters the formulae should cover the structure range from statically stable berm breakwaters to conventional double layer armoured breakwaters

age of the los ranchos formation dominican republic timing and tectonic setting of primitive island arc volcanism in the caribbean region this study reports u pb ages for zircons from the los ranchos formation which is part of the primitive island arc sequence the oldest volcanic rocks in the greater antilles zircons were analyzed from three samples quartz porphyry quartz keratophyre from the lower part of the formation quita sueno member fragmental quartz porphyry from the upper part of the formation pueblo viejo member and the cotui quartz diorite stock that intrudes the lower part of the formation the lower part of the los ranchos formation represented by the quita sueno sample formed at either 113 9 0 8 or 118 6 0 5 ma depending on interpretation of the data whereas the upper part represented by the pueblo viejo sample formed ca 110 9 0 8 ma the cotui stock rd 73 601 was emplaced ca 111 8 0 6 ma or 112 9 0 9 ma depending on whether eight grains reflect subtle inheritance these results show that the los ranchos formation was emplaced during the aptian albian transition that the cotui stock could have supplied magma to the volcanic sequence and fluids to the pueblo viejo gold silver deposit in the upper part of the formation and that carbonaceous sediments in the upper part of the formation formed at the same time as ocean anoxic event 1b paquier caribbean plate tectonic models involving invasion of anomalous pacific crust into the caribbean region appear to agree best with this age because they provide a mechanism for the change from primitive island arc pia to calcalkaline magmatism and account for the restricted ocean circulation necessary to generate regional anoxic conditions

shock events in the solar system the message from minerals in terrestrial planets and asteroids impacts are central to the origin and evolution of planets of the solar system the shapes of craters which can reach up to 1 000 km in diameter on the moon provide critical information on the large scale dynamics of the impact and related shock minerals formed at high pressure and temperature found in shocked terrestrial rocks and meteorites give additional and complementary insights on the shock process at a smaller scale typically from a few micrometers to a few millimeters local flaws in rocks such as voids and mineral interfaces are the preferential sites for the formation of high pressure melts and minerals calculations based on the physics of shocks and the thermodynamics and kinetics of mineral transformations provide orders of magnitude for the duration transient pressure and prevailing temperature conditions of shock events case studies on shocked terrestrial and extraterrestrial materials illustrate the links between these parameters and impact duration many of the high pressure min

the nature of the l chondrite parent body s disruption as deduced from high pressure phases in the sixiangkou l6 chondrite the disruption of the l chondrite parent body lcpb at similar to 470ma is currently the best documented catastrophic celestial impact event based on the large number of l chondritic materials associated with this event uranium lead u pb dating of apatite and its high pressure decomposition product tuite in the sixiangkou l6 chondrite provides a temporal link to this event the u pb system of phosphates adjacent to shock melt veins was altered to varying degrees and the discordance of the u pb system correlates closely with the extent of apatite decomposition this suggests that the u pb system of apatite could be substantially disturbed by high temperature pulse during shock compression from natural impacts at least on the scale of mineral grains although many l chondrites can be temporally related to the catastrophic lcpb impact event the shock conditions experienced by each individual meteorite vary this could be due to the different geologic settings of these meteorites on their parent body the shock pressure and duration derived from most meteorites may only reflect local shock features rather than the impact conditions although they could provide lower limits to the impact conditions the sixiangkou shock duration similar to 4s estimated from high pressure transformation kinetics provides a lower limit to the high pressure pulse of the lcpb disruption impact combined with available literature data of l chondrites associated with this impact event our results suggest that the lcpb suffered a catastrophic collision with a large projectile with a diameter of at least 18 22km at a low impact velocity 5 6kms 1 this is consistent with astronomical estimates based on the dynamical evolution of l chondritic asteroids

mineralogy of the martian interior up to core mantle boundary pressures in order to determine the mineralogy of the martian interior along a high temperature areotherm multianvil experiments have been performed with a model martian mantle composition up to 23 5 gpa the dreibus and wanke 19851 martian mantle composition yields an upper mantle that consists of olivine clinopyroxene orthopyroxene garnet at pressures up to 9 gpa above 9 gpa orthopyroxene is no longer present the transition zone is marked by the appearance of spinel at 13 5 gpa up to 15 gpa clinopyroxene and majorite coexists with phase and or spinel by 17 gpa clinopyroxene is entirely replaced by majorite and the modal abundance of spinel increases at the expense of phase the dominant assemblage throughout most of the transition zone is spinel majorite two experiments completed in the perovskite stability field indicate that the lower mantle consists of mg fe silicate perovskite magnesiowustite and majorite casio 3 perovskite is not present in these experiments both the presence of a martian lower mantle i e an mg fe silicate perovskite bearing zone and the phase assemblage stable in the martian lower mantle are very sensitive to the temperature profile of the interior a low temperature profile may stabilize stishovite in the lower mantle or it may lead to the absence of the lower mantle because of the higher transition pressure required for forming perovskite at lower temperatures regardless of the temperature profile assumed the martian upper mantle and transition zone will account for a larger proportion of the planet s interior than is the case for the earth s interior because of the smaller size of mars

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

a new formula for the sea state and structural parameters influencing the stability of homogeneous reshaping berm breakwaters the berm recession of a reshaping berm breakwater has a very important role for the stability of this kind of structure based on a 2d experimental modeling method in a wave flume the recession of the berm due to sea state and structural parameters has been studied irregular waves with a jonswap spectrum were used a total of 215 tests have been performed to cover the impact of sea state conditions such as wave height wave period storm duration and water depth at the toe of the structure and structural parameters such as berm elevation from still water level berm width and stone diameter on berm recession in this paper first a new dimensionless parameter is introduced to evaluate the combined effect of wave height and wave period on berm recession using results of the experimental work then a formula that includes some sea state and structural parameters is derived using the new dimensionless parameter for estimating the berm recession a comparison is made between the estimated berm recessions by this new formula and formulae given by other researchers to show the preference of using the new dimensionless parameter the comparison shows that the recession estimated by the new formula has not only a better correlation with the present experimental data but also has an improved correlation with other experimental results within the range of parameters tested outside the range of parameters tested the lykke andersen 2006 formula performed best

on berm breakwaters recession crown wall wave forces reliability abstract the paper reviews different formulae lykke andersen 2006 lykke andersen and burcharth 2010 torum 2007 and moghim et al 2011 for recession of berm breakwaters and compares calculated recession with previous and new recession test data there are differences of the results by different formulae but by and large all the formulae give reasonable results on the recession for shallow water berm breakwaters it seems that the lykke andersen 2006 formula works best for the deep water cases although the torum 2007 formula seems to work as good for the homogenous berm breakwater case the moghim et al 2011 formula was not included in the comparison for the deep water cases because the deep water cases are outside the validity of the formula results of tests on different alternative berm breakwater designs which may be considered as practical economic designs have also been included but without any comparison with any formulae simply because the formulae do not cover the specific designs wave forces from model tests on crown walls on berm breakwaters are presented and compared with an existing formula for wave forces on a crown wall on conventional rubble mound breakwaters pedersen 1995 it appears that the wave forces on a crown wall on a berm breakwater are smaller than the wave forces on a crown wall on a conventional rubble mound breakwater finally a probability of failure analysis of a site specific berm breakwater the sirevag berm breakwater norway is presented using monte carlo simulations the probability of failure analysis shows that the sirevag berm breakwater is extremely strong

a new mineral with an olivine structure and pyroxene composition in the shock induced melt veins of tenham l6 chondrite we report a new mineral that occurs in shock induced melt veins of the tenham l6 chondrite the new mineral identified by transmission electron microscopy tem occurs as acicular nanocrystals in a glassy matrix at the edge of shock induced melt veins that crystallized during rapid quench at high pressure the elongate crystals have aspect ratios up to 25 widths range from 5 to 40 nm and lengths are up to 500 nm energy dispersive x ray spectroscopy eds analyses provide the relative cation abundances that are consistent with a pyroxene like stoichiometry na 0 06 ca 0 02 mg 0 71 fe 0 20 al 0 11 si 0 94 o 3 selected area electron diffraction saed patterns from single crystal and polycrystalline aggregates indicate an olivine structure with refined cell parameters a 4 78 b 10 11 and c 5 94 a and a calculated density of 3 32 g cm 3 synchrotron x ray microdiffraction data are consistent with an olivine structure and provide similar cell parameters a 4 778 b 10 267 c 5 937 a the pyroxene composition represents a large deviation from olivine stoichiometry na 0 08 ca 0 03 mg 0 95 fe 0 26 al 0 15 si 0 25 0 28 2 si 1 o 4 with 0 28 formula units of vacancies 0 11 of na plus ca 2 and 0 25 of si 4 in octahedral sites our observations indicate that a metastable and nonstoichiometric olivine structure can crystallize from a silicate melt during rapid quench trace amounts of such defects may be present in stable olivines in the deep upper mantle

chronology of the pueblo viejo epithermal gold silver deposit dominican republic formation in an early cretaceous intra oceanic island arc and burial under ophiolite the pueblo viejo deposit production to 1996 166 t au 760 t ag is located in the dominican republic on the caribbean island of hispaniola and ranks as one of the largest high sulfidation acid sulfate epithermal deposits reserves in 2007 635 t au 3 648 t ag one of the advanced argillic ore bodies is cut by an inter mineral andesite porphyry dike which is altered to a retrograde chlorite illite assemblage but overprinted by late stage quartz pyrite sphalerite veins and associated low grade au ag zn cd hg in as se and te mineralization the precise tims u pb age 109 6 0 6 ma of the youngest zircon population in this dike confirms that the deposit is part of the early cretaceous los ranchos intra oceanic island arc intrusion related gold sulfide mineralization took place during late andesite dacite volcanism within a thick pile 200 m of carbonaceous sand and siltstones deposited in a restricted marine basin the high level deposit was shielded from erosion after burial under a late albian 109 100 ma ophiolite complex 8 km thick which was in turn covered by the volcano sedimentary successions 4 km of a late cretaceous early tertiary calc akaline magmatic arc estimates of stratigraphic thickness and published alunite illite and feldspar k ar ages and closure temperatures alunite 270 20 c illite 260 30 c k feldspar 150 c indicate a burial depth of about 12 km at 80 ma during peak burial metamorphism 300 c and 300 mpa the alteration assemblage kaolinite quartz in the deposit dehydrated to pyrophyllite temperature time relations imply that the los ranchos terrane then cooled at a rate of 3 4 c ma during slow uplift and erosion

the nature of maskelynite in shocked meteorites not diaplectic glass but a glass quenched from shock induced dense melt at high pressures abstract maskelynite an important constituent of shocked meteorites once thought to be diaplectic plagioclase glass formed by shock induced solid state transformation our systematic investigation of shocked l chondrites and snc meteorites indicates that maskelynite does not contain inherited fractures or cleavage and shock induced fractures we found no evidence for models calling for melting that initiated in pdfs and affected the whole crystals maskelynite grains are smooth and display radiating cracks emerging from their surfaces into neighboring pyroxene this is indicative of shock induced melting and quenching of the dense melt at high pressure thus erasing the inherited and shock induced fractures this was followed by relaxation of the dense plagioclase glass which induced the expansion cracks in pyroxene and olivine enrichment in potassium deviation from stoichiometry degradation of igneous zoning the presence of offshoots of maskelynite in pyroxene the lack of vesiculation in the melt pockets melt veins and molten mesostasis are clear evidence for melting and quenching under high pressure our investigations present unequivocal evidence that maskelynite in meteorites is not diaplectic plagioclase glass formed by solid state transformation but a dense quenched glass the duration of the shock pulse in natural events can be several orders of magnitude longer than in shock experiments since kinetic effects are crucial factors in promoting phase transitions vitrification and melting experimentally induced solid state vitrification of plagioclase produced in dynamic experiments is inadequate for calibration of peak shock pressures in maskelynite bearing natural samples

uranium lead systematics of low ti basaltic meteorite dhofar 287a affinity to apollo 15 green glasses article i nfo dhofar 287 is a lunar meteorite found in oman in 2001 which consists of a major portion 95 of low ti mare basalt dho 287a and a minor attached part 5 of regolith breccia dho 287b here we report the u pb systematics of dho 287a using data collected with a sensitive high resolution ion microprobe shrimp in situ analyses of five merrillite and three apatite grains which are resistant to secondary petrologic events resulted in a total pb u isochron age of 3 34 0 20 ga in 238 u 206 pb 207 pb 206 pb 204 pb 206 pb 3 d space 95 confidence level the observed pb pb isochron of these eight phosphates coupled with four plagioclase grains alsoyieldeda 207 pb 206 pbageof3 35 0 13ga thisformationage whenconsideredasthecrystallizationageof

on berm breakwaters stability scour overtopping abstract experimental studies on the stability of multilayer berm breakwaters have been carried out two stone mass densities have been used the results have been compared with the results of homogenous berm breakwaters and with other results of multilayer berm breakwaters an equation for the berm recession for homogenous berms has been derived including the effect of stone gradation and water depth erosion at and erosion protection of berm breakwaters have been investigated as well as wave overtopping discharges

petrography and geochemistry of the enriched basaltic shergottite northwest africa 2975 we present a study of the petrology and geochemistry of basaltic shergottite northwest africa 2975 nwa 2975 nwa 2975 is a medium grained basalt with subophitic to granular texture electron microprobe emp analyses show two distinct pyroxene compositional trends and patchy compositional zoning patterns distinct from those observed in other meteorites such as shergotty or que 94201 as no bulk sample was available to us for whole rock measurements we characterized the fusion crust and its variability by secondary ion mass spectrometer sims measurements and laser ablation inductively coupled plasma spectroscopy la icp ms analyses as a best available proxy for the bulk rock composition the fusion crust major element composition is comparable to the bulk composition of other enriched basaltic shergottites placing nwa 2975 within that sample group the ci normalized ree rare earth element patterns are flat and also parallel to those of other enriched basaltic shergottites merrillite is the major ree carrier and has a flat ree pattern with slight depletion of eu parallel to ree patterns of merrillites from other basaltic shergottites the oxidation state of nwa 2975 calculated from fe ti oxide pairs is nno 1 86 close to the qfm buffer nwa 2975 represents a sample from the oxidized and enriched shergottite group and our measurements and constraints on its origin are consistent with the hypothesis of two distinct martian mantle reservoirs a reduced lree depleted reservoir and an oxidized lree enriched reservoir stishovite possibly seifertite and dense sio 2 glass were also identified in the meteorite allowing us to infer that nwa 2975 experienced a realistic shock pressure of 30 gpa

chemical composition and crystal structure of merrillite from the suizhou meteorite merrillite ideally ca9namg po4 7 is an important accessory phosphate mineral in many different groups of meteorites including martian meteorites and a major carrier of rare earth elements ree in lunar rocks by means of electron microprobe analysis single crystal x ray diffraction and raman spectroscopy we present the first structure determination of merrillite with a nearly ideal chemical composition ca9 00na0 98 mg0 95fe0 06 1 01 p1 00o4 7 from the suizhou meteorite a shock metamorphosed l6 chondrite suizhou merrillite is trigonal with space group r 3 c and unit cell parameters a 10 3444 3 c 37 0182 11 a and v 3430 5 2 a3 its crystal structure refined to r 1 0 032 is characterized by a structural unit consisting of a mg fe po4 6 16 complex anion that forms a bracelet and pinwheel arrangement such structural units are linked by interstitial complexes with a formula of ca9na po4 16 which differs from that of ca9 po3 oh 16 ca9 po3f 16 ca9 ca0 5 0 5 po4 16 or ca9 xree x na1 x x po4 16 in terrestrial whitlockite terrestrial extraterrestrial bobdownsite meteoritic ca rich merrillite or lunar ree rich merrillite respectively the suizhou merrillite is found to transform to tuite at high pressures pointing to the likelihood of finding ree bearing tuite on the moon as a result of shock events on ree merrillite

dating phosphates of the strongly shocked suizhou chondrite impacts on undifferentiated asteroidal bodies provide invaluable information for understanding the solar system evolution nevertheless dating early and small scale impact events is technically challenging uranium lead u pb systematics of u bearing phases within shock induced melt veins smvs of chondrites may be significantly disturbed by localized heating thus providing opportunities to date these impact events as one of the major u hosts in chondrites apatite in the suizhou l6 chondrite has been compositionally and structurally modified to varying degrees by shock metamorphism apatite grains in the host remained largely intact during the impact and have recorded the initial thermal cooling time similar to 4550 ma on their parent body apatite grains in regions less than 100 mu m bordering the smvs or in relatively cold regions within the smvs were partly decomposed to tuite driven by the localized transient heating within the smvs their u pb systematics were disrupted to varying extents apatite in regions close to the center of the smvs has been completely transformed to tuite which yields an age of 4481 30 ma 2 sigma providing an upper limit to the impact event this study clearly demonstrates that by integrating in situ u pb isotope analysis with detailed microstructural and compositional analysis of phosphates it is possible to deduce the timing of early and small scale celestial impact events and hence create a more comprehensive understanding of the impact history of the solar system

tuite γ ca3 po4 2 formed by chlorapatite decomposition in a shock vein of the suizhou l6 chondrite tuite ca3 po4 2 was first discovered as the high pressure phase of whitlockite in shock veins of the suizhou l6 meteorite this study reports the finding of tuite in a shock vein of the same suizhou chondrite as a product of decomposition of chlorapatite where it coexists with coarse grained ringwoodite majorite lingunite fine grained majorite pyrope solid solution and magnesiowustite moreover we also successfully synthesized tuite with a multianvil apparatus from chlorapatite at 15 gpa and 1573 k over 24 h both natural and synthetic tuite crystals were examined by means of optical microscopy scanning electron microscope electron microprobe analysis x ray diffraction and raman spectroscopy our results suggest that the na2o mgo and cl contents in natural tuite may serve as good indicators for distinguishing the precursor phosphate mineral chlorapatite or whitlockite

eclogitic minerals in a shocked basaltic meteorite analytical transmission electron microscopy atem was used to characterize mineral parageneses occurring in melt veins of shock origin in the martian meteorite zagami we discovered a new ultra high pressure eclogite facies mineral assemblage consisting of omphacite stishovite and kalsi3o8 hollandite these tiny 200 300 nm high pressure minerals are embedded in silicate glass which forms the groundmass of the shock veins the microtexture of the veins and zoning of the clinopyroxene indicate the formation of minerals by crystallization from a high pressure melt using calibration data from shock and multi anvil experiments we infer that frictional melting occurred in veins at minimum temperatures of 2400 2500 c and at a pressure of ca 30 gpa subsequently the high pressure phases crystallized during decompression in the pressure interval from 25 5 gpa

rare earth element carriers in the shergotty meteorite and implications for its chronology ion probe measurements of the rare earth element ree concentrations of individual grains of the shergotty meteorite are reported phases analyzed include whitlockite apatite baddeleyite augite pigeonite maskelynite and k rich glass u concentrations of whitlockite and apatite crystals were also obtained the whole rock ree pattern is dominated by whitlockite which contains over 95 of the light rare earth elements lree ree concentrations in apatite are much lower than estimated by laulet al 1986 all the whitlockites whether intergrown with pyroxene equant or interstitial have the same relative abundances of lree i e patterns are almost flat from la to sm the observation by joneset al 1985 of a skeletal whitlockite with lree enrichment is not confirmed by analyses of the same grain pyroxene rims are not enriched in lree no leachable carrier enriched in lree and associated with pyroxene laulet al 1986 jagoutz and wanke 1986 has been found instead either a laboratory contamination or a petrographically cryptic phase such as a film on grain boundaries is suspected as the carrier of lree enrichments if a grain boundary film carries the enrichments it would not be resistant to the metamorphic resetting which has affected other isotopic reservoirs in this sample thus there is no compelling reason to consider the sm nd pyroxene leachates line jagoutz and wanke 1986 as a 360 m y isochron estimates of ree abundances in the shergotty intercumulus melt indicate that a complex petrogenesis is required in agreement with the conclusions of mckayet al 1986a pyroxene distribution coefficients measured experimentally mckayet al 1986a are compared with estimates from measured ree abundances in augite and pigeonite evolution of ree abundances in the shergotty late stage interstitial melt as inferred from analyses of whitlockite conforms with trends predicted from partitioning considerations and requires no special processes such as metasomatism the average u concentrations of whitlockite and apatite are respectively 540 and 1 550 ppb although the calcium phosphates are enriched in u they contain less than 20 of the u in shergotty

discussion of c e 2000 volcanic domes and gold mineralization in the pueblo viejo district dominican republic mineralium deposita vol 35 pp 511 525

natural high pressure polymorph of merrillite in the shock veins of the suizhou meteorite abstract a new high pressure polymorph of merrillite with the structure of trigonal ca 3 po 4 2 was found in the shock produced veins of the suizhou meteorite where it coexists with ringwoodite majorite naalsi 3 o 8 hollandite and majorite pyrope garnet the crystallographic nature of this natural ca 3 po 4 2 phase was characterized by raman spectroscopy and x ray diffraction and all data compare favorably to the same data obtained from ca 3 po 4 2 synthesized at 14 gpa and 1400 c the cell parameters of this new high pressure mineral are a 5 258 1 angstroms and c 18 727 3 angstroms space group r 3m and density 3 447 g cm 3 where the number in parentheses are standard deviations in the last significant digits the natural occurrence of the ca 3 po 4 2 phase together with other high pressure minerals constrains the pressure of the shock veins at about 23 gpa the suizhou meteorite provides the first naturally occurring example of ca 3 po 4 2 polymorph