crystal poor rhyolites and rhyodacites from volcan tepetiltic mexico evidence for melt formation crystallization and eruption over short timescales abstract a detailed petrologic study is presented for six rhyolite and rhyodacite pumices that erupted from volcan tepetiltic in western mexico to determine the pre eruptive conditions of the magma reservoir as the volcano exited a 180 kya hiatus of activity rhyolite pumices are crystal poor 6 7 and minimally saturated in seven mineral phases plagioclase titanomagnetite ilmenite apatite quartz orthopyroxene clinopyroxene hornblende zircon in all samples plagioclase is the most abundant phenocryst phase and spans a range of composition of 20 30 mol an in each sample pre eruptive temperatures determined from two fe ti oxide geo thermometry range from 703 to 857 c maximum pre eruptive h2o contents determined from plagioclase hygrometry range from 5 0 8 9 wt where the most calcic plagioclase compositions correspond to the highest water contents comparison of compositions textures and sr and ba concentrations in plagioclase are used to determine phenocrysts from xenocrysts through comparison with experiments xenocrysts are identified in one sample comp 48 comparison of plagioclase abundances textures and sizes with those grown in the run products of experiments from the literature reveals that 1 the pumices were all likely super heated prior to crystallization 2 they experienced a low degree of undercooling induced by either degassing or cooling and 3 four of the pumices those with

simulation of igneous differentiation processes one of the primary goals of igneous petrology is the definition and evaluation of the roles of the processes responsible for chemical differentiation quantitative simulation of these processes not only requires an understanding of the systematics of mineral liquid equilibria in natural systems but also some understanding of how different processes interact the programs presented here consist of empirically calibrated expressions of mineral melt equilibria that are built around a thermodynamic framework the framework of the programs which are designed to model phase equilibria based igneous differentiation have been published in earlier works nielsen and dungan 1983 nielsen 1985 nielsen 1988 a b nielsen et al 1988 this presentation is to show how modeling can be used to gain otherwise unobtainable insights into the mechanics of igneous differentiation in particular for processes that are difficult to simulate in the laboratory in this chapter we will simulate the major differentiation processes that are characteristic of shallow igneous magma chambers these processes include crystallization recharge assimilation and eruption in each example we will examine how observations of natural systems can be converted into the mathematical constraints necessary for the construction of computer based models since our primary goal is to model natural igneous systems the examples show how phase equilibria modeling can be used to help solve problems related to interpretation of the chemical and mineralogic diversity of suites of natural lavas

geochemistry of late palaeocene and early eocene tephras from the north sea basin the late palaeocene to early eocene balder and sele formations of the north sea basin contain over 200 air fall water lain tephras these occur over the entire north sea area extending onshore into denmark nw germany the netherlands and se england they have also been recorded in the bay of biscay and goban spur areas of the ne atlantic and offshore mid norway results from cores drilled in two widely separated areas of the north sea have been integrated with earlier work on the northern north sea and danish sequences to demonstrate that the stratigraphic and geochemical development of the tephra sequence is regionally consistent this indicates that a single source or group of sources was responsible rather than a number of geographically separated intrabasinal volcanoes for which little geophysical evidence can be found the sequence comprises a lower group of sporadic thin tephras of variable composition including tholeiitic alkalic trachytic trachyandesitic and peralkaline varieties and an upper group of thicker more abundant tephras almost exclusively of fe ti tholeiitic composition general thickness trends and geochemical evidence indicates that the source volcanoes lay on the proto greenland scotland ridge with the tephras showing several features that ally them to the early palaeogene faeroe greenland igneous province the reasons behind the highly explosive nature of the basaltic magmatism remain enigmatic

sedimentary trace element constraints on the role of north atlantic igneous province volcanism in late paleocene early eocene environmental change abstract a growing body of geologic evidence suggests that emplacement of the north atlantic igneous province naip played a major role in global warming during the early paleogene as well as in the transient paleocene eocene thermal maximum petm event a 5 million year record of major and trace element abundances spanning 56 to 51 ma at deep sea drilling project sites 401 and 549 confirms that the majority of naip volcanism occurred as subaerial flows thus the trace element records provide constraints on the nature and scope of the environmental impact of the naip during the late paleocene early eocene interval subaerial volcanism would have injected mantle co2 directly into the atmosphere resulting in a more immediate increase in atmospheric greenhouse gas abundances than co2 input through submarine volcanism the lack of significant hydrothermalism contradicts recently proposed mechanisms for thermally destabilizing methane hydrate reservoirs during the petm any connection between naip volcanism and petm warming had to occur through the atmosphere

pyroclastic deposits within the east greenland tertiary flood basalts stratigraphic geochemical and mineralogical characterization of pyroclastic deposits on the gronau west nunatak of east greenland indicates that both alkaline and basaltic tephras occurred during the eruption of flood basalts associated with the opening of the north atlantic ocean in the early tertiary within the exposed section of gronau west nunatak c 1 km thick representing c 1 6 ma 17 of the horizons are phreatomagmatic basaltic tephras near the top of the section an alkaline tuff was dated at 53 8 0 3 ma by 40 ar 39 ar method this tuff contains a distinctive mineralogy sanidine mg katophorite aegirine and geochemistry melt inclusion compositions and trace and rare earth element abundances that indicate it was erupted from the gardiner melanephelinite carbonatite volcanic complex located 175 km to the se which was active from c 55 to 52 ma the alkaline tuff can be correlated to age equivalent compositionally similar alkaline pyroclastic horizons reported in north atlantic sediment cores and in outcrops in northern europe making it an important regional time stratigraphic marker this study indicates that north atlantic explosive volcanic events were prevalent regionally widespread and originated in east greenland during continental rifting suggesting the need for reappraisal of the impact of north atlantic volcanism on climate change during the early tertiary

sulfur isotope geochemistry of gypsiferous aridisols from central iran abstract gypsum accumulation is one of the prominent pedogenic processes occurring in many and regions of the world gypsiferous soils occur in large areas of the iranian central plateau the origin of gypsum in the aridisols of central iran and its distribution in different landscapes were studied using sulfur and oxygen isotopic composition of both solid and dissolved sulfates the results strongly support the hypothesis that the area was cut off from the tethys seaway at the end of the mesozoic era and as a result the lower cretaceous sulfate has controlled the s geochemistry of the younger sediments including the soils studied the mean values of 34 s and 18 o of the soil gypsum and of dissolved sulfate match with the average isotopic values of the marine sediments which are the most common soil parent materials the results also confirm that s and o in dissolved so 4 and so 4 in gypsum have not undergone any reduction and re oxidation reactions dissolution and reprecipitation appear to be the possible mechanisms responsible for the observed minimal isotope fractionation both 34 s and 18 o values of the soil gypsum decrease slightly with decreasing elevation in the study area these findings are important for understanding the landform evolution in this arid region

introduction to special section maurice ewing symposium on applications of trace substance measurements to oceanographic problems on october 16 20 1995 a maurice ewing symposium on applications of trace substance measurements to oceanographic problems was held at biosphere 2 in oracle arizona the objectives of this symposium were 1 to review the status of tracer methodology for oceanographic research technological advances and progress in applications 2 to evaluate the potential of the individual tracers for regional and global studies of water mass formation and circulation in the ocean and 3 to outline the role of tracers in calibration and improvement of global circulation models trace substances of natural and anthropogenic origin have been used to study circulation and mixing in the ocean for roughly the past 4 decades in such studies the penetration and subsequent spreading of anthropogenic trace substances released to the ocean are observed and evaluated in terms of flow paths and mean transit and residence times of specific water masses these studies are basically regional or global dye experiments additionally the radioactive character of several natural tracers is used to determine the mean residence times of deep waters

laser ablation icpms study of trace element partitioning between plagioclase and basaltic melts an experimental approach plagioclase melt partition coefficients d for 34 trace elements at natural concentration levels were determined experimentally in a natural morb composition at atmospheric pressure using thin pt wire loops experiments were carried out at three tempera tures 1 220 1 200 and 1 180 c and at three different oxygen fugacities fo2 iw qfm air in order to assess the effect of fo2 on the partitioning of elements with multiple valence fe eu cr run products were analyzed by laser ablation icp ms most trace element ds increase slightly as temperature decreases except for dzr dfe deu and dcr that vary systematically with fo2 applying the lattice strain model to our data suggests the presence of fe 2 entirely in the octahedral

the occurrence and interpretation of carbonate and sulfate minerals in a sequence of vertisols in new caledonia abstract in the tamoa valley on the western coast of new caledonia a vertisol sequence shows a downslope transition from calcimagnesic vertisols containing gypsum aragonite and magnesium calcite derived from flysch colluvium to hypermagnesic vertisols rich in dolomite and magnesite and derived from peridotite and serpentinite alluvium deposited by the tamoa river gypsum magnesium calcite and magnesite were probably formed during the dry period of the last glaciation between 30 000 and 17 000 yr b p magnesite nodules seem to be allochtonous and were formed upstream by the weathering of serpentinite during the more humid period of last flandrian transgression 5000 yr b p floods of the magnesium rich waters of the tamoa river over the alluvial plain brought magnesium to the soils and lead to fluctuations of the water table these conditions favoured the formation of manganese deposits as mangans calcite pseudomorphs after lenticular gypsum crystallization of authigenic barite in calcimagnesic vertisols and dolomite formation in magnesic and hypermagnesic vertisols during the recent period apparently drier aragonite is forming in the lower part of calcimagnesic vertisols

on the elusive isotopic composition of lunar pb highly radiogenic pb isotope compositions determined for volcanic glass beads from the apollo 14 soil sample 14163 are similar to those commonly determined for mare basalts and are correlated with chemical variations observed in the beads this indicates that pb unsupported by in situ u decay has a similar origin in both glass beads and mare basalt samples and is likely to reflect variations of 238u 204pb in the lunar mantle an alternative explanation that this pb is a result of late equilibration with the radiogenic pb present in soil is less likely as it would imply that all other characteristics of glass beads such as their chemistry must also be a consequence of equilibration near the lunar surface regardless of the origin of unsupported pb observed variations of pb isotope compositions in the glass beads and mare basalts appear to be a result of two component mixing between a primitive reservoir with a value similar to the earth s mantle and kreep with a value in excess of several thousand this range cannot be explained by the fractionation of major rock forming minerals from the crystallising lunar magma ocean and instead requires substantial extraction of sulphide late in the crystallisation sequence the proportion of sulphide required to produce the inferred range places limits on the starting of the moon prior to differentiation demanding a relatively high value of about 100 200 low indicated by several basalt samples and previously analysed volcanic glass beads can be explained by the preservation of an early but post ferroan anorthosite sulphide rich reservoir in the lunar mantle while a complete range of pb isotope compositions observed in the glass beads and mare basalts can be interpreted as mixing between this sulphide rich reservoir and kreep

sulfur isotope composition of soils and fertilizers differences between northern and southern hemispheres abstract the sulfur isotope composition 34s of available su lfate was measured for 44 soils developed on volcanic ashes and basaltic terrains in japan hawaii australia new zealand brazil and chile native soil sulfates are a mixture of seaspray 34 s 20 and anthropogenic around 5 on average sulfates the isotopic values are generally higher in areas of the southern hemisphere than in the northern hemisphere such a hemispheric difference is due to differences in the relative contribution of sulfur from marine aerosols and human activity native japanese soil samples collected at the sites more than 16 km inland from the coastal line tend to show lower 34s values 1 7 to 8 9 compared to those from the coastal regions 10 9 to 17 5 dominance of anthropogenic sulfur in the japanese islands apparently existed as early as the early 1950 s application of chemical fertilizers rich in sulfur has modified the sulfur isotope composition of native soils ammonium sulfate and single superphosphate from the current market in japan have relatively low 34s values 4 9 to 10 2 which reflect sulfur sources from crude oils and ore sulfides in contrast sulfur in fertilizers commonly used in new zealand and elemental sulfur in sulfur fortified single superphosphate from australia gave higher 34s values 15 7 to 20 7 extensive application of sulfur in the form of fertilizers as in japan and new zealand affects the sulfur isotope composition of arable soils

element partitioning between minerals and melt melt composition and melt structure abstract mineral melt trace element partition coefficients d i mineral melt concentration ratio mineral melt can vary by up to two orders of magnitude in the melt composition range of natural magmatic liquids as most geochemically interesting minor and trace elements are network modifiers in silicate melts one would expect as observed positive correlation between mineral melt partition coefficients d i mineral melt and the degree of polymerization of the silicate melt nbo t linear relationships between d i mineral melt and nbo t sometimes exist over restricted nbo t ranges where the type of q n species in the melt does not change and their abundance does not vary greatly other experimental d i mineral melt vs nbo t data suggest log linear or log log relations in some cases whereas in other studies there are no simple relationships between d i mineral melt and nbo t of the melt when relating mineral melt partition coefficients to degree of melt polymerization nbo t it is assumed that a principal melt structural control on d i mineral melt is the activity of nonbridging oxygen in the melt a nbo the a nbo is related to nbo t the nbo t is not however a quantitative measure of a nbo because the nonbridging oxygens in coexisting q n species in melts are energetically non equivalent this is evident in relationships between activity coefficient ratios of melt network modifying cations i j where the ionization potentials of i and j differ and nbo t of the melt such relationships are parabolic with minima or maxima at nbo t near 1 and resemble the relations of abundance ratio x q3 x q2 vs nbo t of the melt interestingly this nbo t value is near that of natural basalt melt these observations suggest that i nbo q 3 and j nbo q 2 bond characteristics differ from one another govern trace element solution behavior in silicate melts and therefore control the effect of melt composition on mineral melt partitioning in silicate systems

upper palaeocene and lower eocene interval in the dieppe hampshire basin biostratigraphic analysis based on pyritized diatoms

numerical simulation of the filchner overflow the plume of ice shelf water isw flowing into the weddell sea over the filchner sill contributes to the formation of antarctic bottom water the filchner overflow is simulated using a hydrostatic primitive equation three dimensional ocean model with a 0 5 2 sv isw influx above the filchner sill the best fit to mooring temperature observations is found with influxes of 0 5 and 1 sv below a previous estimate of 1 6 0 5 sv based on sparse mooring velocities the plume first moves north over the continental shelf and then turns west along slope of the continental shelf break where it breaks up into subplumes and domes some of which then move downslope other subplumes run into the eastern submarine ridge and propagate along the ridge downslope in a chaotic manner the next western ridge is crossed by the plume through several paths despite a number of discrepancies with observational data the model reproduces many attributes of the flow in particular we argue that the temporal variability shown by the observations can largely be attributed to the unstable structure of the flow where the temperature fluctuations are determined by the motion of the domes past the moorings our sensitivity studies show that while thermobaricity plays a role its effect is small for the flows considered smoothing the ridges out demonstrate that their presence strongly affects the plume shape around the ridges an increase in the bottom drag or viscosity leads to slowing down and hence thickening and widening of the plume

basaltic explosive volcanism but no comet impact at the paleocene eocene boundary high resolution chemical and isotopic records from egypt spain and denmark in the search for a triggering mechanism for the paleocene eocene p e boundary event 55 ma centimeter resolution chemical e g ir os pt and isotope e g os o 187 os 188 he 3 he 4 sr 87 sr 86 records across this boundary have been established for six uplifted marine sections in egypt spain and denmark the sections studied represent some of the stratigraphically most complete records across the onset of the carbon isotopic excursion cie and associated benthic foraminifera extinctions that mark the paleocene eocene boundary high sensitivity analyses failed to uncover evidence of extraterrestrial element or isotope enrichments in the six sections refuting the hypothesis of a major comet impact at the boundary preliminary searches for other impact indicative features such as spherules or shocked quartz also gave negative results in the danish section studied three basaltic ir rich ash layers occur at the paleocene eocene boundary but no similar ashes were found in egypt or spain the three ashes represent the earliest known manifestation of an unusual i to 2 million year long phase of explosive basaltic volcanism in the faero greenland region this volcanism is synchronous with major flood basalt effusions in east greenland and is associated with prominent paleogeographic changes in the high latitude north atlantic region discharge of mantle derived os to seawater during this volcanism may explain a small decrease in os o 187 os o 188 ratio at the paleocene eocene boundary in the zumaya section in spain the environmental perturbations at the paleocene eocene boundary appear to have been triggered by basaltic volcanism but any model for the detailed causal relation remains speculative c 2004 elsevier b v all rights reserved less

volcanic sources and diagenetic alteration of permian triassic boundary k bentonites in guizhou province south china abstract terrestrial permian triassic boundary ptb sequences in south china usually contain one to three ash beds k bentonites which provide evidence of a possible trigger for the terrestrial mass extinction and are useful as a distinct marker for correlation of the ptb boundary interval from terrestrial to marine areas here we investigate the clay mineralogy and geochemistry of ash beds in the zhejue and jiucaichong sections representing paludal and lacustrine environments respectively in order to better understand the source s and preservation of these ash beds the two zhejue k bentonites exhibit similar compositions that are distinctly different from that of the jiucaichong k bentonite the former contain mainly clay minerals with minor quartz anatase and lepidocrocite and the clay minerals in these layers are mainly r1 and r3 mixed layer illite smectite i s and well crystallized to poorly crystallized kaolinite whereas the latter consists mainly of r3 i s with minor quartz feldspars and anatase the former have higher cia values 92 2 and 93 8 than the latter 79 4 indicating more intense chemical weathering that may have been related to deposition in a paludal setting with high organic acid concentrations in pore fluids these k bentonites also exhibit differences in major element chemistry mgo and k2o contents are higher at jiucaichong due to lesser weathering intensity and possibly early diagenetic uptake from pore fluids ree chemistry jiucaichong exhibits a larger eu anomaly and nd isotopic compositions zhejue k bentonites have 143nd 144nd ratios of 0 512436 and 0 512400 higher than the 0 512190 ratio for jiucaichong although some of these compositional differences may be related to the dissimilar chemical environments in which diagenesis occurred i e paludal vs lacustrine the differences in eu anomalies and nd isotopic compositions imply heterogeneous volcanic ash sources the source of these k bentonites was probably a continental volcanic arc located on the paleo southern margin of the south china craton within which multiple volcanic vents may have been active concurrently

evidence of chemical heterogeneity within lunar anorthosite parental magmas abstract lunar anorthosites are known for displaying a limited range of plagioclase an content an 94 to 98 here we demonstrate that plagioclase trace element variations from apollo ferroan anorthosites fan samples collected by the apollo 15 and 16 missions display more significant chemical heterogeneity e g chondrite normalized la sm 0 33 5 42 than previously reported we report mineral plagioclase pyroxene and olivine major and trace element abundances for a suite of apollo fan samples in addition to anorthositic clasts within apollo 16 regolith breccias this suite of data extends the compositional range currently reported for apollo anorthosites and for anorthositic clasts previously found within lunar meteorites petrological classifications of the regolith breccia clasts e g anorthosite versus noritic anorthosites cannot always be accurately assessed due to the limited size

genesis of gypsum enriched soils in north west isfahan iran abstract most of gypsum enriched soils in isfahan and neighboring provinces occur on alluvial fans dissected flood plains old dissected alluvium and piedmont plains herein we investigate the processes of formation and alteration of gypsic horizons and their pedofeatures we described and sampled representative pedons on a transect from the mountain to the piedmont plain in the study area different gypsic pedofeatures have various kinds of internal lenticular cryslalitic fabrics micromorphologic observations confirmed that gypsic horizons have an evolutionary sequence across the different geomorphic surfaces from the upper fan to the piedmont plain in primary stages upper fan gypsum crystals occur individually in the soil groundmass or as clusters in voids with idiotopic or xenotopic fabrics eventually they form internal coatings or infillings and pendants in middle and lower fans in the more developed horizons dissected flood plains or plateaus the fibrous gypsum crystals are banded and perpendicularly distributed with reference to the gravels and soil surface these loosely compacted fibers constitute the bulk of the soil materials leaving non gypsic particles as islands between crystals in these pedofeatures perpendicularly oriented fibrous crystals with their lateral inter connections give rise to a continuous three dimensional firm structure the fabric of these lenticular gypsum crystals is xenotopic or hyp idiotopic in the piedmont plain the idiotopic crystals have no preferred orientation and have random distribution internal fabric of these pedofeatures is porphyrotopic this study indicates that physical environment plays a great role in formation of different gypsic pedofeatures

tracing the source of gypsum in new caledonian soils by ree contents and ssr isotopic compositions gypsum minerals forming in pedogenic environments in new caledonia were examined for their s and sr isotope compositions and ree distributions three possible sources were identified volcanic soil derived and marine however differentiation based only on the ree contents and normalized patterns was not possible but the best preserved volcanic sample yields a negative eueu anomaly and the lowest gdnybn ratio due to the high content of organic matter mixing calculations of the 34s values and 87sr86sr ratios confirmed that the marine gypsum has a 34s value close to 21 and an 87sr86sr ratio close to 0 70912 and that the volcanic gypsum has a 34s value of 0 and an 87sr86sr ratio of about 0 70331 the soil derived gypsum samples yield intermediate values as a result of a mixing between the marine and volcanic end members negative 34s values for the volcanic gypsum are explained by low fo2 of the source rocks while high 87sr86sr ratios for the same gypsum are explained by probable atmospheric input the data confirm also that biological fractionation of 34s if any is limited

investigating the origin of anorthitic plagioclase through a combination of experiments and natural observations abstract the origin of anorthitic plagioclase in volcanic rocks worldwide remains an enigma arenal volcano costa rica provides a good example of the problem up to an 96 plagioclase are found within moderately evolved basaltic andesites we follow up a recent suggestion lundstrom c c boudreau a pertermann m 2005 diffusion reaction in a thermal gradient implications for the genesis of anorthitic plagioclase high alumina basalt and igneous mineral layering earth planet sci lett 237 829 854 that diffusion reaction processes occurring between ascending magmas and gabbroic wall rocks might provide a means of producing anorthitic plagioclase without requiring exotic ultra calcic melt compositions by integrating observations from three analytical methods 1 laboratory diffusion reaction experiments in the diopside albite anorthite daa system 2 transmission electron microscopy tem of plagioclase grains from both a diffusion reaction experiment and an arenal lava and 3 sr isotope microstratigraphy of phenocrysts and megacrysts from natural lavas from the current eruption at arenal two plagioclase saturated daa melts juxtaposed in experiments at either 1 bar pressure anhydrous or at 0 5 gpa pressure hydrous for 3 5 days at 1244 or 1125 c illustrate the dramatic effect of h 2 o on facilitating plagioclase reaction in the presence of wet melt enrichment in anorthitic plagioclase occurs at the material interface while in the presence of the dry 1 bar melt plagioclase shows no reaction tem analyses of a homogeneous anorthitic plagioclase from a diffusion reaction experiment indicates heterogeneous columns of more anorthite rich plagioclase at the 87 sr 86 sr occur within three plagioclase phenocrysts from both 1968 and 1999 arenal lavas although core compositions vary widely 0 7038 0 7052 all three phenocrysts have similar 87 sr 86 sr rim compositions 0 7043 the variability in 87 sr 86 sr at the phenocryst scale but homogeneity in 87 sr 86 sr at the bulk scale in arenal lavas ryder c h gill j b tepley iii f j ramos f reagan m this volume closed to open differentiation at arenal volcano 1968 2003 j volcanol geotherm res could be explained by erupted lavas representing a near steady state balance between ascending magmas and a flux derived from diffusion reaction processes occurring with surrounding crustal gabbros

trace element partitioning between ilmenite armalcolite and anhydrous silicate melt implications for the formation of lunar high ti mare basalts abstract we performed a series of experiments at high pressures and temperatures to determine the partitioning of a wide range of trace elements between ilmenite ilm armalcolite arm and anhydrous lunar silicate melt to constrain geochemical models of the formation of titanium rich melts in the moon experiments were performed in graphite lined platinum capsules at pressures and temperatures ranging from 1 1 to 2 3 gpa and 1300 1400 c using a synthetic ti enriched apollo black glass composition in the cao feo mgo al2o3 tio2 sio2 system ilmenite melt and armalcolite melt partition coefficients d show highly incompatible values for the rare earth elements ree with the light ree more incompatible compared to the heavy ree d la ilm melt 0 0020 0 0010 to d lu ilm melt 0 069 0 010 for ilmenite d la arm melt 0 0048 0 0023 to d lu arm melt 0 041 0 008 for armalcolite d values for the high field strength elements vary from highly incompatible for th u and to a lesser extent w for ilmenite d th ilm melt 0 0013 0 0008 d u ilm melt 0 0035 0 0015 and d w ilm melt 0 039 0 005 and for armalcolite d th arm melt 0 008 0 003 d u arm melt 0 0048 0 0022 and d w arm melt 0 062 0 03 to mildly incompatible for nb ta zr and hf e g d hf ilm melt 0 28 0 05 and d hf arm melt 0 76 0 07 both minerals fractionate the high field strength elements with dta dnb and dhf dzr between 1 3 and 1 6 for ilmenite and 1 3 and 1 4 for armalcolite armalcolite is slightly more efficient at fractionating hf from w during lunar magma ocean crystallisation with dhf dw 12 13 compared to 6 7 7 5 for ilmenite the transition metals vary from mildly incompatible to compatible with the highest compatibilities for cr in ilmenite d 7 5 and v in armalcolite d 8 1 d values show no clear variation with pressure in the small range covered crystal lattice strain modelling of d values for di tri and tetravalent trace elements shows that in ilmenite divalent elements prefer to substitute for fe while armalcolite data suggest ree replacing mg tetravalent cations appear to preferentially substitute for ti in both minerals with the exception of th and u that likely substitute for the larger fe or mg cations crystal lattice strain modelling is also used to identify and correct for very small 0 3 wt melt contamination of trace element concentration determinations in crystals our results are used to model the lu hf ti concentrations of lunar high ti mare basalts the combination of their subchondritic lu hf ratios and high tio2 contents requires preferential dissolution of ilmenite or armalcolite from late stage lunar magma ocean cumulates into low ti partial melts of deeper pyroxene rich cumulates

the origin of gypsum in vertisols in new caledonia determined by isotopic characteristics of sulphur abstract gypsum crystals occur in vertisols on the west coast of new caledonia these soils are derived from the weathering of basic rocks that contain no gypsum the sulphur isotopic ratio 34 s 32 s was used as tracer to identify the origin of the gypsum a total of 26 measurements of 34 s were made on gypsum crystals from the vertisols and compared to those of continental sulphates and to marine gypsum in tidal flats the 34 s value of the crystals located in new caledonian vertisols decreases with increasing distance from the coast this suggests that the gypsum in the vertisols comes from two sources an oceanic source where the major part of the sulphur is introduced by atmospheric precipitation and a continental source where sulphides disseminated in various subsurface deposits are oxidized gypsum from atmospheric precipitation penetrates the vertisols through vertical cracks that probably formed in dry seasons during the last glacial period

microfossil biostratigraphy of the palaeogene succession in the davis strait offshore west greenland abstract a new microfossil based biostratigraphy of the paleocene and lower eocene sediments of the hellefisk 1 ikermiut 1 kang miut 1 nukik 1 and nukik 2 boreholes offshore west greenland has been established in general the five boreholes contain fairly well preserved diverse microfossil faunas and floras consisting mainly of foraminifera radiolaria ostracods and diatoms the studied interval was subdivided into three foraminiferid biostratigraphic intervals in ascending stratigraphic order the stensioeina beccariiformis praeglobobulimina ovata and pseudohastigerina wilcoxensis intervals and five biostratigraphic intervals based on additional microfossil groups the thalassiosiropsis wittiana fenestrella antiqua coscinodiscus morsianus ostracod aulacodiscus hirtus and cenodiscus cenosphaera intervals the intervals are more easily recognised in the two basinal boreholes ikermiut 1 and kang miut 1 than in the three more nearshore boreholes nukik 1 nukik 2 and hellefisk 1 due to a higher microfossil diversity and abundance

magma ascent and crustal accretion at ultraslow spreading ridges constraints from plagioclase ultraphyric basalts from the arctic mid ocean ridge plagioclase ultraphyric basalts pubs with up to 54 plagioclase phenocrysts were dredged in the rift valley and adjacent flanks of the ultraslow spreading mohns and knipovich ridges the pubs show large variations in crystal morphologies and zoning the large variations suggest that single basalt samples contain a mixture of plagioclase crystals that aggregated at different levels in the magma conduits resorbed crystals and repeated reverse zones suggest that the magma reservoirs were replenished and heated several times thin concentric zones with melt inclusions and sharp reductions in the anorthite content of 3 7 are common between the reverse zones these zones and skeletal crystals with distinctly lower anorthite contents than massive crystals are interpreted to be the result of rapid crystalliztion during strong undercooling the changes between short periods of cooling and longer periods with reheating are explained by multiple advances of crystal rich magma into cool regions followed by longer periods of gradual magma inflow and temperature increase the porphyritic basalts are characterizd by more depleted and more fractionated compositions than the aphyric basalts with lower la sm n k 2 oa nd mg numbers this relationship and the observation that pubs are sampled only close to segment centres along these ridges suggests that the pubs formed by higher degrees of melting and evolved in more long lived magma reservoirs we propose that the zoning patterns of plagioclase crystals and crystal morphologies of these pubs reflect the development and flow of magma through a stacked sill complex like conduit system whereas the aphyric equivalents represent later flow of magma through the conduit the formation of voluminous higher degree melts may trigger the development of the magma conduits and explain the generally depleted compositions of pub magmas

the hydrological setting occurrence and significance of gypsum in late quaternary salt lakes in south australia well exposed often laminated gypsum sequences occur in many quarternary salt lakes in southern south australia the gypsum in the salt lakes is classified by increasing grain size into gypsite gypsarenite and selenite the salt lakes are classified by age and hydrological setting into coastal salinas which are holocene sea water fed groundwater lakes and continental playas which are late pleistocene endorheic basins a study of the relationships between coastal salina hydrology and the associated gypsum deposition has shown the different types of gypsum form under distinct hydrological regimes as the hydrology above a coastal salina depositional surface changes through time so does the type of gypsum deposited application of a gypsum depositional model derived from a study of the coastal salina gypsum to those portions of a continental playa gypsum unit where deposition is no longer occurring confirms the applicability of the model to non salina gypsum deposits

magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase a new bulk silicate moon model with sub chondritic ti ba sr ba and sr al ratios abstract the compositions of host magmas of ferroan anorthosites fan host magmas were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks the evolution of the magmas was investigated by considering phase relations based on the melts algorithm and by re examining partition coefficients for trace elements between plagioclase and melts data little affected by post magmatic processes were selected by using plagioclase with relatively primitive sc and co contents the fan host magma contained 90 174 ppm sr 40 119 ppm ba and 0 5 1 3 tio2 and had sub chondritic sr ba and ti ba ratios it is difficult to account for the formation of fan host magma on the basis of magma evolution processes of previously proposed bulk silicate moon models with chondritic ratios for refractory elements at global scale therefore the source of the fan host magma must have had primordial sub chondritic sr ba and ti ba ratios the fan host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites and some very low ti mare rocks from lunar meteorites here we propose an alternative bulk silicate moon model the cbsm model which is enriched in crustal components of proto bodies relative to the present whole earth moon system

pedogenesis and clay mineralogical investigation of soils formed on gypsiferous and calcareous materials on a transect southwestern iran abstract this study examined pedogenesis as well as the clay mineralogy of soil and rock samples obtained from a transect of gypsiferous and calcareous materials the main objectives of this research were to study the relationship between clay minerals and physiographic units as well as the relative importance of key pedogenic processes in controlling clay mineralogy palygorskite chlorite illite smectite quartz and interstratified minerals were observed in both soil and rock samples using xrd tem and edx analyses illite chlorite and interstratified minerals are inherited largely from parent rocks most of the smectite is inherited from highly smectite marl formations although some may be the product of palygorskite weathering and transformation of illite particularly at the surface horizons neoformation of palygorskite as a result of calcite and gypsum precipitation seems to be a major pathway for the occurrence of this mineral especially on plateau physiographic units although inheritance has less importance gypsiferous soils showed more pedogenic palygorskite as compared to calcareous soils three morphological forms of palygorskite related to degree of weathering were identified in the studied pedons new great groups and subgroups of ustepts aridic gypsiustepts and aridic calcic gypsiustepts are suggested to be included in soil taxonomy based on the properties of some of the studied pedons dissolution and transport of anhydrite from outcrops is considered the main source of pedogenic gypsum in these soils micromorphological studies including thin section observations and sem analyses indicated variable habits of gypsum crystals suggested a dynamic soil environment

nannoplankton zonation and the palaeocene eocene boundary beds of nw europe an indirect correlation by means of volcanic ash layers correlation of early palaeogene ash layers in dsdp hole 550 leg 80 goban spur with those of the north sea basin indicates that the base of nannoplankton zone np10 approximates the base of the sele formation of the north sea area the bases of the danish ash series the german ash bearing untereozan 1 and the paris basin sparnacian and the top of the woolwich reading bottom bed of the london basin if as is now common practice the palaeocene eocene boundary is placed at the np9 np10 boundary then the units listed above would constitute the basal units of the eocene in their respective countries the cessation of large scale pyroclastic activity took place at about the middle of the zone np10 interval

coupled caal nasi diffusion in plagioclase feldspar experiments and applications to cooling rate speedometry abstract the rate of caal nasi interdiffusion in plagioclase feldspar was determined under 1 atm anhydrous conditions over the temperature range 1400 to 1000 c in calcic plagioclase an80 81 by homogenizing coherent exsolution lamellae the dependence of the average interdiffusion coefficient on temperature is given by the expression d 10 99 cm 2 sec exp 123 4 kcal mol rt t in k this value is for diffusion perpendicular to the 03 1 interface of the lamellae caal nasi interdiffusion is 4 to 5 orders of magnitude slower than oxygen diffusion in the temperature range 1400 to 1200 c and possibly 10 orders of magnitude slower at subsolidus temperatures the large differences in diffusion rates explain the apparent contradiction posed by the plagioclases of large layered intrusions e g the skaergaard which retain delicate ca na compositional zoning profiles on the micron scale but have undergone complete oxygen isotopic exchange with heated meteoric groundwater from the surrounding wall rocks caal nasi diffusion is slow the closure temperature is high within the solidus liquidus interval and ca na zoning is preserved oxygen diffusion is faster the closure temperature is lower 350 400 c and the feldspars exchange oxygen with the low temperature hydrothermal fluids the complex micron scale oscillatory zones in plagioclase can also be used as cooling rate speedometers for volcanic and plutonic plagioclase cooling histories typical of large mafic intrusions e g the stillwater are slow begin at high initial temperatures 1200 c and result in homogenization of oscillatory zones on the scale of 10 microns the oscillatory zones found in the plagioclase of granodioritic plutons are preserved because cooling is initiated at a lower temperature 1000 c limiting diffusion to submicron length scales despite the slow cooling rate of the intrusion

identification and characterisation of the oligocene miocene boundary base neogene in the eastern north sea basin based on dinocyst stratigraphy micropalaeontology and δ13c isotope data abstract for the first time a combined palynological and 13c isotope study has identified the oligocene miocene boundary and thus the base of the neogene within the north sea basin the type section the lemme carrosio section in northern italy is correlated with the frida 1 well in the eastern danish part of the north sea basin using a combination of data from a previous dinocyst stratigraphic study and new 13c isotope data the results show that the oligocene miocene boundary is located at a depth of 1440 m in the frida 1 well the frida 1 13c isotope curve further reflects the mi 1 glaciation event also recorded in the lemme carrosio section the dinocyst events bracketing the boundary in frida 1 are the last occurrence lo of distatodinium biffii at 1630 m below the boundary the lo of chiropteridium spp at 1370 m and first occurrence fo of ectosphaeropsis burdigalensis at 1330 m both above the boundary an influx of deflandrea phosphoritica is found in an interval immediately below the boundary 1532 1490 m while the genus homotryblium occurs abundantly in a broader interval 1650 1330 m encompassing the boundary hitherto unpublished data combined with new data provide a series of stratigraphically important nanno and micropalaeontological events that frame characterise the oligocene miocene boundary within the north sea basin an almost monospecific assemblage of reticulofenestra bisecta at 1630 m the lo of elphidium subnodosum at 1625 m the lo of aulacodiscus insignis quadrata diatom sp 3 of king 1983 at 1610 m the lo of karreriella seigliei at 1580 m and the lo of pararotalia canui at 1570 m all below the boundary and the fo of aulacodiscus aemulans diatom sp 5 of king 1983 at 1410 m and the lo of aulacodiscus aemulans at 1250 m both above the boundary the dinocyst nanno and micropalaeontological studies thus provide a series of bioevents and abundance variations which can be used to locate and to correlate the oligocene miocene boundary within the eastern north sea basin more precisely than was previously possible

influence of convective sedimentation on the formation of widespread tephra fall layers in the deep sea the formation of widespread volcanic ash fall layers in deep sea sediments was investigated experimentally to examine the settling behavior of tephra 20 180 m diameter as it travels from the atmosphere into water using a fallout mass flux rate that was constrained by measurements of distal fallout from the 1980 eruption of mount st helens 0 2 g cm 2 hr the experiments show that particle settling in the water column is dramatically accelerated by the formation of diffuse vertical gravity currents the currents form as a result of convective instabilities that develop in a surface boundary layer when the local particle concentration becomes large at the air water interface the settling velocity of particles drops abruptly and the concentration of particles increases because of the differential in mass flux above and below the fluid surface the implication of the experiments is that deposition of distal tephra fall layers in deep sea sediments may be dominantly controlled by diffuse vertical gravity currents as opposed to passive settling of individual particles through the water column this process greatly reduces the residence time of fine ash in the ocean and diminishes the role of ocean currents in influencing the distribution patterns of individual tephra layers support for this mechanism comes from observations of greatly accelerated tephra settling rates in the south china sea following the 1991 eruption of mount pinatubo in the philippines

early eocene volcanic ashes on greifswalder oie and their depositional environment with an overview of coeval ash bearing deposits in northern germany and denmark unconsolidated bentonites and carbonate cemented volcanic ashes occur in northern germany within the clay sequence of the lamstedt and schlieven formations documented by several wells ash bearing carbonate concretions so called cementstones are also known from glacially transported rafts and erratic boulders on the baltic sea island greifswalder oie representing the easternmost exposures of early eocene sediments in the north sea basin the ashes can be correlated with water lain ashes of the danish fur and olst formations mo clay generated during the opening of the north atlantic ocean about 55 ma ago two types of cementstones can be distinguished on the basis of the mineralogical composition sedimentary features and fossil content greifswalder oie type i contains a black up to 12 cm thick ash deposit that follows above two distinct thin grey ash layers the major ash unit has a rather homogeneous lower part only a very weak normal grading and faint lamination are discernible in the upper part however intercalations with light mudstone in part intensively bioturbated together with parallel and cross lamination suggest reworking of the ash in a shallow marine environment major and trace element compositions are used to correlate type i ashes with those of the danish positive series which represent rather uniform ferrobasalts of the danish stage 4 probably related to the emergence of proto iceland in contrast type ii ash comprises a single normally graded about 5 cm thick layer of water lain air fall tuff which is embedded in fine grained sandstone to muddy siltstone type ii ash is characterised by very high tio2 but low mgo contents exceptional ree patterns with a pronounced positive eu anomaly suggest intense leaching of the glass that hampers exact correlation with pyroclastic deposits within the north atlantic igneous province

latest on the absolute age of the paleocene eocene thermal maximum petm new insights from exact stratigraphic position of key ash layers 19 and 17 abstract we constructed a precise early eocene orbital cyclostratigraphy for dsdp site 550 leg 80 goban spur north atlantic utilizing precession related cycles as represented in a high resolution x ray fluorescence based barium core log based on counting of those cycles we constrain the exact timing of two volcanic ash layers in site 550 which correlate to ashes 19 and 17 of the fur formation in denmark the ashes relative to the onset of the paleocene eocene thermal maximum petm are offset by 862 kyr and 672 kyr respectively when combined with published absolute ages for ash 17 the absolute age for the onset of the petm is consistent with astronomically calibrated ages using the current absolute age of 28 02 ma for the fish canyon tuff fct standard for calibrating the absolute age of ash 17 is consistent with tuning option 2 in the astronomically calibrated paleocene time scale of westerhold et al 2008 westerhold t rohl u raffi i fornaciari e monechi s reale v bowles j and evans h f 2008 astronomical calibration of the paleocene time palaeogeography palaeoclimatology palaeoecology v 257 p 377 403 using the recently recalibrated absolute age of 28 201 ma for the fct standard is consistent with tuning option 3 in the astronomically calibrated paleocene time scale the new results do not support the existence of any additional 405 kyr cycle in the early paleocene astronomically tuned time scale

sulfate in modern playa settings and in ash beds in hyperarid deserts implication for the origin of 17o anomalous sulfate in an oligocene ash bed abstract a large amount of calcite pseudomorphs after gypsum were discovered in a volcanic ash bed and its underlying sand siltstone in the gering formation late oligocene northwestern ne usa the highly positive 17o anomalies in the residual sulfate indicate that the sulfate could only have come from the oxidation of sulfur gases by ozone in the atmosphere we previously proposed that it was most likely the result of an extreme tropospheric sulfate haze dry fog event that was associated with volcanic eruptions in the west to test the dry fog hypothesis we examine here two alternative scenarios that also involve atmospheric sulfate deposition but do not imply a dramatic volcanic and dry fog source 1 is it possible that some playas in arid or semiarid regions accumulate the type of atmospheric sulfate deposits as we see in the mid gering bed by the inflow of surface water or groundwater 2 could a period of hyperaridity and stability during the late oligocene have caused a significant accumulation of atmospheric background sulfate onto the mid gering ash bed surface sulfates from a variety of playa settings were collected and measured for their 17o anomalies the sulfate isotope both o and s and concentration profiles of two volcanic ash beds that are currently exposed in the central atacama desert chile and in taylor valley of the antarctica dry valleys were studied along with their sedimentary features these two ash beds were chosen for comparison because of their significant levels of atmospheric sulfate accumulated during prolonged and hyperarid climatic conditions results showed no or minimal 17o anomalies in any of the playa sulfate samples from around the world and none of the parameters in the mid gering ash profile matches those in either of the two volcanic ash profiles in modern hyperarid settings conclusion the observed 17o anomalous gypsum deposit in the mid gering ash bed is most likely the result of a series of extreme dry fogs that resulted in an intense pulse of atmospheric sulfate deposition to a semiarid playa setting

investigation into the petrogenesis of apollo 14 high al basaltic melts through crystal stratigraphy of plagioclase abstract the petrogenesis of apollo 14 high al basaltic melts was studied using crystal stratigraphy which involves textural crystal size distributions csds and chemical analyses electron microprobe and laser ablation inductively coupled plasma mass spectrometry the samples studied here include pristine basalt 14072 and basaltic clasts from breccia 14321 and impact generated crystalline samples 14073 14276 and 14310 plagioclase was the focus of this study because of its relatively high modal abundances and because it was on the liquidus for much of the melt cooling histories plagioclase crystals were analyzed core to rim compositions where possible to test and refine petrogenetic models based upon whole rock compositions groups a b and c designations and to investigate basalt 14072 and impact melt crystallization textural studies have shown that each basalt group has distinctive plagioclase csds which are in turn distinctive from those of the impact melts evolution of the individual basaltic melts was studied by comparing the equilibrium melt compositions calculated from plagioclase compositions using relevant partition coefficients to fractional crystallization fc and assimilation and fractional crystallization afc models petrogenetic modeling of trace elements in group a basalts revealed that petrogenesis continued beyond 40 total crystallization required to model whole rock compositions and that there were open system processes that affected the magma during plagioclase crystallization petrogenetic modeling of pristine high al basalts 14072 and groups a b and c using trace elements shows that the equilibrium melt compositions do not fall on a single afc or fc trajectory this is consistent with fluctuating degrees of assimilation i e variable r values and or variable assimilant compositions during petrogenesis petrogenetic modeling reveals that the impact melts experienced only closed system fractional crystallization this work demonstrates the importance of crystal stratigraphy in revealing the intricacies of lunar basalt petrogenesis

endolithic cyanobacteria in soil gypsum occurrences in atacama chile mojave united states and al jafr basin jordan deserts 1 soil sulfates are present in arid and hyperarid environments on earth and have been found to be abundant in soils on mars examination of soil gypsum from the atacama desert chile the mojave desert united states and al jafr basin jordan revealed endolithic cyanobacteria communities just below the surface of soil gypsum samples optical and scanning electron microscope observations of the colonized layers indicated that the unicellular chroococcidiopsis is the dominant cyanobacterium in all studied communities 16s rrna gene analysis revealed that in addition to chroococcidiopsis a few other cyanobacteria are present heterotrophic bacteria are also abundant in the colonized zones of the fine grained gypsum from the atacama and mojave desert but insignificant in the fibrous gypsum from the jordan desert endolithic life forms similar to these described here may exist or have existed on mars and should be targeted by the mars science laboratory and future in situ missions

redox controls on tungsten and uranium crystal silicate melt partitioning and implications for the u w and th w ratio of the lunar mantle the timing of core formation is essential for understanding the early differentiation history of the earth and the moon because hf is lithophile and w is siderophile during metal silicate segregation the decay of 182hf to 182w half life of 9 ma has proven to be a useful chronometer of core mantle differentiation events a key parameter for the interpretation of 182hf 182w data is the hf w ratio of the primitive i e undepleted mantle since w is incompatible during mantle melting its ratio relative to u and other similarly incompatible elements in basalts e g th la may be used as proxies for their mantle sources however the assumption that w and u are equally incompatible may be flawed for petrological systems that equilibrated over a large range of oxygen fugacity fo2 although w is typically perceived as being homovalent evidence suggests that u is heterovalent over the range of fo2 inferred for the silicate mantles of the earth and the moon here we report new partitioning data for w u high field strength elements hfse and th between clinopyroxene orthopyroxene olivine plagioclase and silicate melt in agreement with previous studies we show that these elements behave as homovalent elements at fo2 characteristic of earth s upper mantle however both w and u become more compatible at low fo2 indicating a change in their redox state with w becoming more compatible at progressively lower fo2 this result for w is particularly unexpected because this element was thought to be hexavalent even at very low fo2 the much higher compatibility of w4 the species inferred here at low fo2 relative to w6 means that even a small fraction of w4 will have a significant effect on the overall compatibility of w our results imply that over the range of reducing conditions in which lunar differentiation is thought to have taken place i e iw 2 to iw 0 5 w is likely to become fractionated from u when our partitioning data are applied to model the fractional crystallization of a lunar magma ocean lunar trends for u w hf w and th w are well reproduced the result of this model carries with it the implication that the hf w of the bulk silicate fractions that comprise the earth and the moon are virtually identical

gigantic volcanic eruptions and climatic change in the early eocene 23 layers of altered volcanic ash bentonites originating from the north atlantic igneous province have been recorded in early eocene deposits of the austrian alps about 1 900 km away from the source area the austrian bentonites are distal equivalents of the main ash phase in denmark and the north sea basin we have calculated the total eruption volume of this series as 21 000 km3 which occurred in 600 000 years the most powerful single eruption of this series took place 54 0 million years ago ma and ejected ca 1 200 km3 of ash material which makes it one of the largest basaltic pyroclastic eruptions in geological history the clustering of eruptions must have significantly affected the incoming solar radiation in the early eocene by the continuous production of stratospheric dust and aerosol clouds this hypothesis is corroborated by oxygen isotope values which indicate a global decrease of sea surface temperatures between 1 and 2 c during this major phase of explosive volcanism

the north atlantic igneous province stratigraphy tectonic volcanic and magmatic processes the north atlantic igneous province has been the subject of extensive scientific investigation over the past thirty years with a wide field of knowledge being accumulated recently recognition of the potential role of large igneous provinces in affecting ocean and atmosphere systems and biotic evolutionary pathways has lead to increased interest in this province this has been further stimulated by the expansion in the search for oil and gas in mesozoic and tertiary sediments along the ne atlantic margin an improved understanding of the interaction between igneous and sedimentary processes is vital for the identification of potential hydrocarbon resources the regions covered include continental margin norway east and west greenland the faroe shetland basin and the faroe islands themselves the papers in this book contain new data and interpretations of north atlantic igneous province magmatic processes rift evolution tectonics stratigraphy chemostratigraphy biostratigraphy seismic and isotope stratigraphy and sediment dispersal many of the papers adopt a multidisciplinary approach to tha analysis and interpretation of complex volcanic and sedimentary sequences these new data and the reviews and compilations of existing data provide the reader with access to current research directions in north atlantic igneous province geology

lower palaeogene stratigraphy of the northern north sea abstract the lower palaeogene stratigraphy of the northern north sea is described using wireline log and biostratigraphic data at group and formation level a close similarity can be shown with the stratigraphy defined in the outer moray firth area of the central north sea a two fold subdivision into the montrose and moray groups is recognized the montrose group consists of the maureen and lista formations while the succeeding moray group contains the sele balder dornoch and beauly formations the maureen and lista formations are dominantly argillaceous units that contain poorly defined sandstones the most laterally extensive of these is the heimdal member developed within the lista formation the dornoch and beauly formations are shelfal sandstone units that pass eastwards and northwards into the age equivalent dominantly argillaceous sele and balder formations the sele formation contains the hermod member while the balder formation contains the odin member these are massively developed sandstone units of very limited extent the lower palaeogene succession contains a number of high gamma log markers that are often associated with influxes of microfossils and microflora these are interpreted as condensed claystone horizons representing pauses in marine sedimentation during episodes of maximum transgression they can be correlated with similar marker horizons described from the outer moray firth area giving further confidence that the stratigraphy forms a regional framework that can be applied over the whole north sea area

a generalized transport theory water mass composition and age abstract a general theory to describe and understand advective and diffusive ocean transport is reported it allows any passive tracer field with an atmospheric source to be constructed by superposing sea surface contributions with a generalized green s function called the boundary propagator of the passive tracer equation the boundary propagator has the interpretation of the joint water mass and transit time distribution from the sea surface the theory thus includes the classical oceanographic idea of water mass analysis and extends it to allow for a distribution of transit times from the sea surface the joint water mass and transit time distribution contains complete information about the transport processes in the flow it captures this information in a more accessible way than using velocity and diffusivity fields however at least for the case of sequestration and transport of dissolved material by the ocean circulation the boundary propagator is thus the natural quantity to consider when discus

minor element partitioning and sector zoning in synthetic and meteoritic anorthite regular geometric apparently crystallographically controlled sector zoning has been produced in synthetic anorthite crystallized from a liquid of type b ca al rich inclusion cai composition cathodoluminescence cl provides a rapid method for observing the sectors sharp discontinuities in mg concentration always accompany sharp changes in cl intensity at sector boundaries although cl intensity anti correlates with mg concentration there is not a well defined quantitative relationship and mg concentration steps range from as little as 5 to almost a factor of 2 for different cl boundaries when measurable na also tends to anti correlate with cl brightness in a given crystal and thus correlates with mg the partition coefficients for mg and na can vary by up to a factor of 2 depending on the particular sector and thus are not constant for cai anorthite which formed by fractional crystallization in contrast ti either ti 3 or ti 4 concentration is not a function of sector zoning and thus does not affect the cl intensity the sector zoning and correlated chemical variations for synthetic anorthite are similar to those in natural anorthite from type b cais the cl intensity boundary sharpness and minor element zoning in synthetic anorthite are not affected by annealing at 850 c for three weeks overall our observations suggest that the observed cl patterns and minor element zoning in type b anorthite are igneous in origin and have not been modified by subsolidus reequilibration or alteration this leads to the conclusion that the 26 mg 26 al systematics in cais based almost entirely on anorthite have not been modified by subsolidus reequilibration or alteration

surficial deposits on salt diapirs zagros mountains and persian gulf platform iran characterization evolution erosion and the influence on landscape morphology the surfaces of salt diapirs in the zagros mountains are mostly covered by surficial deposits which significantly affect erosion rates salt karst evolution land use and the density of the vegetation cover eleven salt diapirs were selected for the study of surficial deposits in order to cover variability in the geology morphology and climate in a majority of the diapirs in the zagros mountains and persian gulf platform the chemical and mineralogical compositions of 80 selected samples were studied mainly by x ray powder diffraction and x ray fluorescence changes in salinity along selected vertical profiles were studied together with the halite and gypsum distribution the subaerial residuum formed from minerals and rock detritus released from the dissolved rock salt is by far the most abundant material on the diapirs fluvial sediments derived from this type of residuum are the second most common deposits found while submarine residuum and marine sediments have only local importance the mineralogical chemical composition of surficial deposits varies amongst the three end members evaporite minerals gypsum anhydrite and minor halite carbonates dolomite and calcite and silicates oxides mainly quartz phyllosilicates and hematite based on infiltration tests on different types of surficial deposits most of the rainwater will infiltrate while overland flow predominates on rock salt exposures recharge concentration and thick accumulations of fine sediment support relatively rich vegetation cover in some places and even enable local agricultural activity the source material diapir relief climatic conditions and vegetation cover were found to be the main factors affecting the development and erosion of surficial deposits a difference was found in residuum type and landscape morphology between the relatively humid nw part of the studied area and the arid persian gulf coast in the nw the medium and thick residuum seems to be stable under current climatic conditions large sinkholes and blind valleys with sinking streams are common on other diapirs the original thick residuum is undergoing erosion and the new morphology is currently represented by salt exposures and badland like landscapes or by fields of small sinkholes developed in the thin residuum models for evolution of the subaerial residuum and the diapir landscape morphology are described in this paper while the thick residuum with vegetation has very low erosion rates the salt exposures and thin residuum are eroded rapidly during wet periods e g early holocene the diapirs rose and salt glaciers expanded as the influx of salt mass was much faster compared to erosion after the onset of an arid climate c 6 ka bp the rising of the some diapir surfaces decreased or even reversed due to acceleration of erosion thanks to vegetation degradation and changes in the residuum type and thickness

crystal accumulation in a 4 2 ga lunar impact melt abstract the ages of lunar impact basins and the role of fractional crystallization in producing compositional heterogeneity of lunar melt sheets are long standing problems with significant implications for solar system dynamics and the petrologic evolution of the lunar crust here we document the formation of a basin scale impact on the moon at 4 20 0 07 ga based on the 147 sm 143 nd isochron age of a magnesian noritic anorthosite melt rock from lunar breccia 67955 major element compositions of plagioclase and mafic silicates in the melt rock imply a substantial component of primary mg suite cumulates or related lithologies in the pre impact crustal stratigraphy trace element compositions of the plagioclase including diagnostic ratios such as sr ba are also mostly similar to those in plagioclase from mg suite cumulates with a small number of grains trending toward compositions observed in ferroan anorthosites mineral melt distribution coefficients applied to trace element compositions of the 67955 plagioclase and pyroxene predict parental melt compositions that contrast strongly with the bulk rock compared to the whole rock parental melts calculated from the plagioclase are enriched in ree ree la yb 131 885 average 619 ppm vs 39 8 ppm and they have more fractionated ree patterns la yb n 1 2 9 8 average 4 9 vs 1 5 with deep negative eu anomalies eu eu 0 09 0 40 vs 1 36 trace element data for the pyroxenes also imply incompatible element enriched parental melts subsolidus equilibration between the plagioclase and the pyroxene apparently rotated the ree patterns but the conclusion that the parental melt was highly enriched in ree relative to the whole rock appears robust quantitative modeling shows that fractional crystallization of the 67955 whole rock composition cannot reproduce the range of ba sr ti and la concentrations measured in the 67955 plagioclase rather the models require an initial melt composition that was strongly enriched in these elements and they suggest that fractional crystallization became less efficient as crystallization proceeded the contrast between the inferred parental melt composition and the bulk rock implies formation of the 67955 noritic anorthosite as a crystal cumulate and that the cogenetic residual melt was strongly enriched in incompatible elements if so this would be the first documented example of fractional crystallization in a lunar impact melt sheet the petrological and geochemical characteristics of the 67955 noritic anorthosite suggest that it formed by an impact in the procellarum kreep terrane and was transported to the apollo 16 site as imbrium ejecta inheritance of ejecta related to this pre imbrium basin may contribute to the common occurrence of 4 2 ga 40 ar 39 ar plateau ages in breccia clasts and regolith fragments from the rim of north ray crater in that case those data may provide no constraints on the age of the nectaris basin despite its proximity to the apollo 16 site

trace element partitioning between high an plagioclase and basaltic to basaltic andesite melt at 1 atmosphere pressure we determined plagioclase melt partition coefficients for 18 elements by performing controlled cooling rate 1 atmosphere experiments using both natural and synthetic basaltic 51 wt sio2 and basaltic andesite 56 wt sio2 powders in a vertical quench furnace the experiments produced an69 to an87 composition plagioclase three starting powders were gorda ridge basalt synthetic diopside 40 albite 28 anorthite 32 mixture and arenal volcano costa rica basaltic andesite the gorda and synthetic powders were doped at both low concentrations 20 200 ppm and high concentration 200 5000 ppm whereas the arenal powder was doped only at high concentrations resulting in two doped gorda powders low np and high sdp two doped diopside albite anorthite powders low dad high sdd and one doped arenal powder high ar99 2 trace elements concentrations in both glass and plagioclase were measured by secondary ion mass spectrometry sims and or by laser ablation inductively coupled plasma mass spectrometry la icp ms results for the partitioning of trace elements between plagioclase and melt at different doping levels demonstrate both adherence to henry s law and good agreement between the different analytical techniques in general plagioclase melt partition coefficients determined in the an69 73 range are similar to other published values however some of those occurring for plagioclase compositions an75 are distinctly lower than those predicted by current regression formulations we applied a two lattice melt model to these data to account for differences in melt composition and temperature and found that there were no aberrations associated with partition coefficients a new set of regression formulations is determined involving the newly determined dataset for plagioclase with an contents between 75 and 87

weathering and alteration of volcanic ashes in various depositional settings during the permian triassic transition in south china mineralogical elemental and isotopic approaches to better understand the alteration of volcanic ash in different depositional environments we measured the clay mineralogy major and trace element geochemistry and sr and nd isotopic composition of altered ashes in two permian triassic boundary ptb successions in southern china the pengda and xinmin sections in guizhou province represent different depositional settings allowing us to investigate the role of the early burial environment on authigenic clay formation the ptb ash beds in both sections consist predominantly of mixed layer illite smectite clays altered ashes in the relatively shallow pengda section contain predominantly r2 and r3 i s clays with 70 to 85 illite layers whereas their stratigraphic equivalents in the deeper xinmin section contain only r3 i s clays which are of two types with 88 and 99 illite layers respectively the two studied ash beds can be stratigraphically correlated between the pengda and xinmin sections and show similar 143nd 144nd ratios 0 511991 for pd 1 and 0 511983 for xm 1 0 512073 for pd 2 and 0 512074 for xm 2 ree distributions and immobile element cross plots are consistent in suggesting that the altered ashes may have originated via felsic volcanism altered ashes in the deep sea xinmin section have notably high 87sr 86sr ratios 0 764209 and 0 795921 relative to those from equivalent horizons in shallower environments 0 728455 and 0 749953 this difference in 87sr 86sr ratios is likely attributable to different degrees of chemical weathering elemental ratios such as sio2 al2o3 k2o al2o3 y sr and zr sr all support more intensive chemical leaching in deep water environments the altered ashes at xinmin contain substantially more k2o than those at pengda suggesting greater incorporation of k into clay minerals due to lower ph during early diagenesis clay mineral assemblages and stacking structures of i s clays in the altered ashes are consistent with a general sequence of smectite illitization during diagenesis and burial metamorphism in both sections