spatio temporal structure of the pentadecadal variability over the north pacific abstract using a multi taper frequency domain singular value decomposition mtm svd a pentadecadal oscillation was detected in the winter spring sea level pressure slp field over the north pacific and surface air temperature in north america which was significant at the 95 confidence level the mtm svd captured the different slp and air temperature distributions between the winter and spring seasons in a consistent manner the pentadecadal slp signature in the spring season is centered nearer the west coast of north america than in the winter season this zonal displacement is consistent with the prominent springtime pentadecadal air temperature variability in mid latitude western north america a wavelet analysis of the pacific decadal oscillation index pdoi showed that the regime shifts in the 1920s 1940s and 1970s involved simultaneous phase reversals of the bidecadal and pentadecadal variations the two interdecadal variations are synchronized with one another such that a half period of the pentadecadal oscillation one epoch of an individual regime corresponds to one and half periods of the bidecadal oscillation these results are consistent with the wavelet analysis of the north pacific index npi similar resonance between the bidecadal and pentadecadal variations is evident in air temperatures over alaska the bidecadal and pentadecadal signals have different seasonality in these time series suggesting that although the two interdecadal variations arise from two different physical mechanisms they interact with each other the most distinct seasonal difference was observed in mid latitude western north america where the bidecadal variation prevails only in the winter season and the pentadecadal variation only in the spring season alaska air temperatures in the winter and winter spring of 1999 were the coldest since 1977 as were springtime air temperatures in mid latitude western north america in contrast to the warm anomalies that prevailed in this region during 1977 98 the npi and pdoi also exhibited an opposite polarity in 1999 to the respective regime mean polarities these anomalous conditions in winter and spring seasons of 1999 may signify a major regime shift in 1998 1999 in order to verify whether or not a regime shift did occur in 1998 1999 a careful examination of additional data in coming ten or so years will be necessary

trace element geochemistry of martian iddingsite in the lafayette meteorite the lafayette meteorite contains abundant iddingsite a fine grained intergrowth of smectite clay ferrihydrite and ionic salt minerals both the meteorite and iddingsite formed on mars samples of iddingsite olivine and augite pyroxene were extracted from lafayette and analyzed for trace elements by instrumental neutron activation our results are comparable to independent analyses by electron and ion microbeam methods abundances of most elements in the iddingsite do not covary significantly the iddingsite is extremely rich in hg which is probably terrestrial contamination for the elements si ai fe mn ni co and zn the composition of the iddingsite is close to a mixture of 50 lafayette olivine 40 lafayette siliceous glass 10 water concordant behavior among these elements is not compatible with element fractionations between smectite and water but the hydrous nature and petrographic setting of the iddingsite clearly suggest an aqueous origin these inferences are both consistent however with deposition of the iddingsite originally as a silicate gel which then crystallized neoformed nearly isochemically the iddingsite contains significantly more magnesium than implied by the model which may suggest that the altering solutions were rich in mg 2

effect of mineralogy and pedoclimatic variations on ni and cr distribution in serpentine soils under temperate climate abstract part of the soils occurring in the serpentinite szklary massif sw poland have developed in quaternary under temperate climate on the parent rock not affected by chemical weathering in studied parent ultrabasite ni occurs in cr magnetite up to 0 96 wt of nio forsterite up to 0 55 wt of nio iddingsite up to 0 99 wt of nio and serpentine up to 0 55 wt of nio while cr is bounded with cr magnetites up to 21 77 wt of cr 2 o 3 and clinochlores up to 1 68 wt of cr 2 o 3 cr magnetites are highly resistant to weathering while other primary minerals more susceptible to weathering release parts of ni and cr which are trapped in authigenic phases the latter however contain less ni and cr than corresponding primary minerals clayous matrix 0 37 wt of nio and 0 08 wt of cr 2 o 3 smectites 0 30 wt of nio and 0 07 wt of cr 2 o 3 and mixture of oxy hydroxides and clay minerals 0 36 wt of nio and 0 14 wt of cr 2 o 3 at the mineral scale smectite plays an important role in the trapping of ni at the profile scale ni and cr are moderately diluted upwards the soil profile and cr is generally less mobile than ni the soil formed in szklary is chemically different than the analogous serpentine soils occurring more to the south in europe french massif central vosges mountains and ligurian apennines nw italy the difference is due to participation of fluvioglacial material produced by quaternary continental glaciacion in poland however similar vertical relative variations of ni and cr were found in all compared soils in spite of differences in parent rock composition allogenic contaminations and degree of soil development comparison with other well drained pedons located in similar uphill positions shows a climatic control of the cr and ni vertical distribution in serpentine soils humid mountainous variant of temperate climate induces leaching of mg and subsequent lack in smectite neoformation which lead to the release of ni ni is less mobile in the colder and dryer climate of poland moreover some primary minerals which are generally considered as not stable under soil conditions olivine serpentine and chlorite are still present even in the a horizon of the studied polish pedon their resistance is due to slower rates of weathering related to the climate but also due to former hydrothermal processes affecting the parent rock fabric

intraseasonal teleconnection between north american and western north pacific monsoons with 20 day time scale abstract based on a recently released high resolution reanalysis dataset for the north american region the intraseasonal variability isv with a time scale of about 20 days of the north american monsoon nam is examined the rainfall signals associated with this phenomenon first emerge near the gulf of mexico and eastern pacific at about 20 n they subsequently migrate to the southwestern united states along the slope of the sierra madre occidental the rainfall quickly dissipates upon arrival at the desert region of arizona and new mexico aznm the enhanced rainfall over aznm is accompanied by strong southeasterly low level flow along the gulf of california this pattern bears strong resemblance to the circulation related to gulf surge events as documented by many studies the southeasterly flow is associated with an anomalous low vortex over the subtropical eastern pacific ocean off california and a midlatitude anticyclone over the central united states in the lower troposphere this flow pat

symplectic exsolution in olivine from the nakhla martian meteorite abstract the nakhla meteorite commonly accepted to have originated from mars is a cumulus clinopyroxenite with 10 vol of fe rich olivine almost all olivine grains in nakhla contain dark lamellar inclusions less than 2 3 m wide high resolution scanning and transmission electron microscopy revealed that the inclusions are complex intergrowths of augite and magnetite such a symplectic intergrowth of augite and magnetite in olivine was known in some terrestrial rocks lunar rocks and a few meteorites the inclusion in nakhla olivine is the first symplectite found in a martian rock apparently the presence of fe3 in olivine under an oxidizing condition on mars caused symplectic exsolution at high temperature 900 c during cooling

a transition phase teleconnection of the pacific quasi decadal oscillation the atmospheric circulation patterns associated with the pacific quasi decadal oscillation qdo are investigated using available observational data from 1948 to 2007 previous studies indicate that the pacific qdo is characterized by a distinct lifecycle in the form of sea surface temperature sst patterns in the warm and cool phases of the pacific qdo the sst patterns resemble those associated with the el nino southern oscillation enso during the warm cool and cool warm transitions of the pacific qdo recurrent sst patterns are also clearly visible the rotated empirical orthogonal function analysis on the 10 15 year filtered data shows that the evolutions of sst and atmospheric circulation are well coupled while the warm cool phase pacific qdo generates an enso like circulation pattern the transition phases form a distinct short wave train emanating from southeast asia towards north america this short wave train is particularly robust in the streamfunction of water vapor flux diagnostic analyses of the heat budget the stationary wave flux and a barotropic model indicate that this short wave train is thermodynamically maintained and is likely forced by diabatic heating near southeast asia additional modulations of forcing sources in the western and eastern tropical pacific on this short wave teleconnection are also discussed

terrestrial alteration mineral assemblages in the nwa 10416 olivine phyric shergottite abstract we report on the alteration history of the olivine phyric highly depleted hd shergottite northwest africa nwa 10416 paying particular attention to the origin of the aqueous alteration seen affecting the meteorite s olivine megacrysts the rock s interior displays 1 mm zoned altered olivine megacrysts set in a groundmass of clinopyroxene unzoned olivine and interstitial plagioclase and maskelynite synchrotron micro x ray diffraction xrd and transmission electron microscopy tem show that plagioclase and maskelynite have been partially replaced by kaolinite the relict olivine megacryst cores display a unique concentric colouration for martian meteorites having central amber coloured zones surrounded by a brown mantle zone with the rims remaining clear and unaltered this colouration is a result of fluid alteration and partial replacement with hydration tem analysis revealed the 200 nm scale banded and largely amorphous nature of the alteration but with some 20 relict crystalline olivine patches although the coloured olivine zones show cation and anion site vacancies compared to stoichiometric olivine a relict igneous compositional trend is preserved in the megacrysts from mg rich altered cores mg 76 to unaltered stoichiometric rims fo53 synchrotron fe k x ray absorption near edge structure xanes analysis revealed that the coloured zones of the megacryst have different fe oxidation values high ferric contents are present in the brown mantle zones fe3 fe 0 92 and the amber zones fe3 fe 0 30 whereas the clear rims are ferrous this suggests alteration occurred in an oxidising environment and that the sharp contrast in colour of the megacryst brown to clear is a record of a relict fluid reaction front in order to test the terrestrial or extraterrestrial origin of the alteration olivine material from a shock melt vein was analysed by tem the analysis revealed 0 952 nm curved d spacing s from clay alteration undisturbed by any shock effects strongly suggesting a terrestrial origin the d spacing values most likely represent a collapsed saponite or vermiculite showing that in some places olivine has been replaced by crystalline clay oxygen isotope analysis of bulk 17o 0 309 0 009 2 and amber coloured megacryst material 0 271 0 002 2 are also consistent with terrestrial alteration we propose a model in which during the meteorite s time in northwest africa low temperature likely acidic groundwater exploited fractures the fluid altered the olivine megacrysts in a way that was controlled by the pre existing igneous compositional zonation with mg rich olivine being more susceptible to alteration in this fluid environment the plagioclase and maskelynite were also altered to a high degree after the alteration event it is likely that nwa 10416 had a significant residence time in northwest africa accounting for terrestrial calcite and the dehydration of some clay phases

unusual lapilli tuff ejecta erupted at stromboli during the 15 march 2007 explosion shed light on the nature and thermal state of rocks forming the crater system of the volcano abstract textural and mineralogical study of high temperature angular blocks erupted during the stromboli explosion of 15 march 2007 was used to make inferences on the nature and thermal state of rocks forming the subsurface of the volcano summit crater terrace the studied ejecta consist of lapilli tuff that formed as a result of the transformation and high temperature induration sintering of the basaltic scoriae lapilli and ash originally accumulated as loose tephra during the current activity of the volcano the main processes leading to the tephra transformation were investigated through microstructural observations mineral and glass analyses sem eds and emp analyses investigations revealed that subsolidus reactions and partial melting of the tephra occurred at temperatures higher than 600 c and under variable fo 2 conditions from qfm to hm buffering curves in some blocks evidence of high t reheating and partial melting at the expense of secondary hydrothermal minerals was also observed in order to track the subsolidus reheating history of the basaltic pyroclasts a detailed study of the pseudomorphic phases and reactions after olivine driven by iron oxidation under high t conditions was performed the observed mineralogical transformation suggests that the lapilli tuff material originating from the burial of tephra routinely accumulated by persistent strombolian explosions within the crater terrace were in some cases altered by the circulation of acidic fluids and were in any case reheated due to isotherm rise forced by high heat flux and gas streaming delivered by the underlying magma system it is worth noting that the ejection of these unusual volcanic lithotypes was possible because a few days before the 15 march 2007 event the craters were clogged with lapilli tuff material that slid into the crater bottom between 7 and 9 march findings of this study suggest that the scattered permanently active vents and shallow conduits of stromboli are surrounded sideways and underneath the crater terrace by a fairly large volume of high temperature rocks with variable degree of compaction sintering up to partially melted such a spectrum of rock types is in good agreement with the conceptual model of prominent thermal zoning all around sideway and upwards the active magmatic system we speculate that continuous migration upwards of isotherms led to transformation and partial melting of the normal strombolian tephra

a north pacific short wave train during the extreme phases of enso abstract sea surface temperatures ssts exhibit an interannual seesaw between the eastern and western tropical pacific in concert with the el nino southern oscillation enso cycle evidence accumulated from previous studies suggests that a teleconnection link may exist between enhanced rainfall convection in the western pacific and precipitation severe weather over north america the aforementioned link could possibly be established by a teleconnection wave pattern induced by the anomalously warm cold sst anomalies in the western tropical pacific to demonstrate this possibility a fourier scale separation was introduced to divide the enso anomalous circulation into two wave regimes long wave waves 1 3 and short wave waves 4 15 the classic pacific north american teleconnection pattern is formed by the long wave regime in contrast emerging in the short wave regime is a well organized wave train that propagates from the western subtropical pacific along the north pacific rim into north america in

modal mineralogy of cm2 chondrites by x ray diffraction psd xrd part 1 total phyllosilicate abundance and the degree of aqueous alteration abstract cm carbonaceous chondrites are samples of incompletely serpentinized primitive asteroids using position sensitive detector x ray diffraction psd xrd and a pattern stripping technique we quantify the modal mineralogy of cm2 chondrites mighei murray murchison nogoya and cold bokkeveld there is a narrow range in the combined modal volume vol of the most abundant phases mg serpentine 25 33 and fe cronstedtite 43 50 cold bokkeveld is anomalous in containing more mg serpentine 49 59 than fe cronstedtite 19 27 even including cold bokkeveld the range in modal total phyllosilicate is 73 79 average 75 total phyllosilicate abundance provides a non ambiguous measure of the degree of aqueous alteration and indicates that these meteorites have all experienced essentially the same degree of aqueous alteration this reflects pervasive hydration of matrix across cm2 samples apparent differences in the alteration of chondrules observed in petrographic studies represent various stages in the progression towards complete hydration of all components but are not manifest in significant differences in modal mineralogy for all samples there is a limited range in olivine 6 9 and pyroxene 5 abundances modal abundances of the remaining identified phases also show a limited range calcite 0 1 3 gypsum 0 1 6 magnetite 1 1 2 4 pentlandite 0 2 1 and pyrrhotite 1 3 8 as expected we observe a strong negative correlation in the modal abundance of anhydrous fe mg silicates olivine pyroxene and total phyllosilicate mg serpentine fe cronstedtite consistent with the idea that phyllosilicate is forming by aqueous alteration of the anhydrous components the negative correlation in the modal abundance between mg serpentine and fe cronstedtite indicates a mineralogic transformation of fe cronstedtite to mg serpentine by fluid driven recrystallisation or b that these meteorites had different initial abundances of olivine and pyroxene the observed positive correlation in the relative proportion of mg serpentine with increasing total phyllosilicate abundance reflects the evolution of increasingly mg rich phyllosilicate during aqueous alteration fe cronstedtite is the dominant phyllosilicate while cm chondrule olivines are forsteritic and will form mg serpentine during aqueous alteration this implies that matrix olivine was more fe rich than chondrule olivine prior to aqueous alteration

alteration assemblages in the nakhlites variation with depth on mars secondary mineral assemblages in the nakhlite meteorites lafayette governador valadares gv nakhla yamato y 000593 y 000749 have been studied using scanning electron microscopy transmission electron microscopy and electron probe micro analysis the different nakhlites have distinctive secondary assemblages in their olivine grains and mesostases showing compositional fractionation correlated with their relative depths below the martian surface fracture filled veins in lafayette at the bottom of the pile consist of a siderite phyllosilicate fe oxide hydrated silicate gel assemblage corresponding veins in nakhla and gv further up the pile are predominantly a siderite gel assemblage with additional evaporites including gypsum y 000593 y 000749 veins are dominated by gel the gel s mg mg fe ratio decreases from lafayette 0 37 to gv 0 32 nakhla 0 24 and y 000593 0 15 we suggest that hydrothermal fluid flowed up this depth profile initiated by melting of buried h2o co2 ice our results show a complex mix of fe rich phyllosilicate within the veins and mesostasis of lafayette with d spacings of 0 7 1 1 nm suggesting a mixture of smectite and serpentine the phyllosilicate formed at close to neutral ph 150 c we also suggest that water rock ratios w r of 1 10 occurred in lafayette with smaller values for the other nakhlites this is reflected in the volume of alteration minerals 10 of olivine in lafayette to 3 in nakhla textural evidence of rapid cooling together with the w r and likely fluid velocities suggest that the secondary assemblages formed quickly e g within months a model is proposed in which the secondary assemblages formed in an impact induced hydrothermal system terminated by precipitation of the gel and evaporation of soluble salts

laihunite and jarosite in the yamato 00 nakhlites alteration products on mars 1 nakhlites martian clinopyroxenites are believed to have experienced aqueous alteration on the martian surface on the basis of the presence of reddish brown iddingsite on the rim and along cracks of large olivine crystals amorphous to poorly crystalline phyllosilicates smectites and carbonates are major products of aqueous alteration of the yamato 00 nakhlites the yamato 000593 nakhlite and its pair yamato 000749 contain large olivine crystals having opaque black material intimately associated with iddingsite on their rims and along cracks synchrotron radiation x ray diffraction micro raman spectroscopy and transmission electron microscopy revealed that the opaque material is the nonstoichiometric olivine type mineral laihunite 0 42 mg2 fe2 0 79fe3 0 79si1 00o4 typically formed as a high temperature oxidation product under nonequilibrium conditions because laihunite has been decomposed into a mixture of magnetite and amorphous silicate near the fusion crust it is preterrestrial in origin this is the first observation of large olivine crystals in martian meteorites being replaced by laihunite although its presence in olivine in the mesostasis of the miller range 03346 nakhlite has been suggested by micro raman spectroscopy because laihunite in the nakhlites does not form nanometer sized intergrowth with iron oxides fluid assisted high temperature oxidation may have played an important role in transporting away free fe2 cations liberated from olivine during laihunite formation although the yamato 00 nakhlites also contain jarosite we could not confirm the presence of preterrestrial jarosite based only on its occurrences

hydrochemistry weathering and weathering rates on madeira island madeira island consists of miocene to pleistocene lavas and pyroclasts major rock types are alkali basalts basanites and hawaiites principal soil types are leptosols andosols and cambisols our main objective was to link the chemistry of ground waters to weathering reactions and rates we collected 40 shallow groundwater samples remote from human activities with a few exceptions the ranges of electrical conductivities were 29 176 ms cm and of ph 5 8 8 5 the calculated pco2 was generally higher than the atmospheric value the contribution of sea salt to the water chemistry was 30 9 corrected for sea salt the cation concentrations in meq l decrease in the order ca 2 mg 2 na k the concentrations of so42 and no3 are very low we calculated that the total annual chemical denudation rate in the studied area amounts to 37 12 g m 2 consuming 0 86 0 38 mol co2 m 2 to achieve our main objective a set of mole balance equations ax b was used where a is a composite matrix of coefficients including ratios between stoichiometric coefficients as determined by the weathering reactions and coefficients accounting for unconstrained contributions b is the vector with a water composition and x is the set of mole fractions of dissolved primary minerals plus the residual concentrations of the unconstrained contributions olivine ol pyroxene py and plagioclase pl were considered to be the major primary minerals and smectite vermiculite halloysite allophane gibbsite and hematite the secondary minerals in the weathering reactions using iterative procedures whereby mixtures of secondary products as well as the composition of plagioclase are allowed to change we selected one best fit set of weathering reactions for each spring by checking all possible solutions of the mole balances against predefined boundary conditions at odds with goldich 1938 sequence our model results indicate for most best fit sets a weathering rate sequence of pl ol py but such reverse order is not unique on average the annual weathering rates in mol ha y vol mineral are 44 19 pl 29 14 ol and 22 13 py q 2003 elsevier b v all rights reserved

extended planar defects and the rapid incorporation of ti 4 into olivine the formation of extended planar defects in minerals such as olivine is related to high point defect concentration and can be driven by large gradients in chemical potential where the energy of the system is lowered by the ordering of defects along specific planes in the crystal the presence of extended defects has the potential to create the apparently anomalous ionic diffu sion in olivine as reported recently spandler and o neill in contrib mineral petrol 159 6 791 818 2010 high resolution transmission electron microscopy and energy filtered imaging were done using experimental samples designed to examine the impact of atio2 and fo2 on the potential to form such defects in ferromagnesian olivine doped basalt 5 wt tio2 olivine reaction couple experiments were run at 1 atm and 1 310 and 1 410 c for 50 h at various fo2 ranging from 10 2 below to 10 2 above the quartz fayalite magnetite buffer our results show that extended planar defects in olivine parallel to 101 ol and occurring in ordered clusters with a prolate spheroid geometry 5 25 nm across and extending up to 150 nm into the olivine are present near the olivine glass inter faces in all of our experimental high tio2 basalt olivine samples increased ti content in the olivine is associated with the defects ordering of ti 4 and octahedral site vacancies leads to a two or three layer superstructure in the olivine defect nucleation and growth is driven by the large tio2 chemical potential gradient across the phase boundary at the start of the experiments which provides access to microstructures not otherwise present

etch pit size dissolution rate and time in the experimental dissolution of olivine implications for estimating olivine lifetime at the surface of mars various approaches have been used to estimate when and how long liquid water was present at the surface of mars the olivine dissolution lifetime application suggested by stopar et al 2006 and olsen and rimstidt 2007 is here adapted and tested at the scale of individual etch pits using published data from an experimental system in which the volume of mineral removed and the duration of the mineral removal episode are known different assumptions about the specific geometry of etch pits on olivine result in surface area estimates that vary by less than a factor of two from the simple hemispherical pit used in the calculations given that other sources of uncertainty in mass time relationships of silicate mineral dissolution during natural weathering can be up to four orders of magnitude the effects of differing geometric assumptions about the shapes and surface areas of the etch pits are negligible using compiled experimentally determined forsterite dissolution rates and the imaged etch pit sizes from experiments recovers the duration of the experiment that produced the imaged etch pits to within less than a factor of two this suggests that extensively etched olivine surfaces imply a dominance of the etch pit walls over the bulk surface between the etch pits during olivine corrosion the approach adopted here recovers the timescales of experimental etch pit production on olivine at stp and extreme undersaturation of the solution with respect to olivine in experiments where ph is known continued progress in understanding the fundamentals of olivine dissolution kinetics will narrow the ranges of uncertainty in mineral lifetime estimates at mars surface in support of constraining the compositions and duration of potentially habitable aqueous solutions on mars

silicate and oxide exsolution in pseudo spinifex olivine from metaultramafic rocks of the betic ophiolitic association a tem study transmission electron microscopy tem has been used to study submicroscopic particles in spinifex like textured olivine from secondary harzburgites collected from the cerro del almirez locality in the mulhacen complex betic cordillera se spain three main types of submicroscopic oxides have been identified 1 equidimensional fe rich spinel magnetite with average grain size in the order of 1 2 m 2 elongated cr bearing spinels fe chromite to cr magnetite with sizes ranging from 0 2 to 1 m long and 0 01 to 0 1 m thick and 3 equidimensional ti rich particles from 0 01 to 0 1 m and compositions ranging from ilmenite to fe cr ti oxide chromite and ilmenite particles form parallel chromite rich and ilmenite rich bands extending along the a axis of the host olivine both phases show a fixed orientation relationship with olivine with the approximately hexagonal close packed oxygen planes being parallel in both structures these textural relationships indicate that both chromite and ilmenite were formed during a common exsolution process magnetite particles also are orientated preferentially relative to the olivine but these particles are homogeneously distributed within the olivine suggesting either a primary origin or an exsolution process that was not contemporaneous with formation of chromite and ilmenite chromite particles commonly are accompanied by lamellae of talc and or enstatite both showing a consistent orientation relationship with olivine talc lamellae are twice as thick as the associated chromite crystals whereas enstatite lamellae show a greater thickness and moreover form single enstatite particles which consist of clino and orthoenstatite intergrowths talc formation may be explained by exsolution together with spinel from olivine containing oh groups probably related to incomplete dehydration of serpentine during olivine formation on the basis of these results and previously reported petrological data we have concluded that exsolution of chromite silicate and ilmenite occurred during the retrograde stage that followed the climax of the eo alpine metamorphic event

decadal fluctuations in the western pacific recorded by long precipitation records in taiwan a 110 year precipitation record in taiwan located at the western edge of the subtropical north pacific depicts a pronounced quasi decadal oscillation qdo the qdo in taiwan exhibits a fluctuating relationship with the similar decadal variations of sea surface temperature sst anomalies in the central equatorial pacific known as the pacific qdo a regime change was observed around 1960 such that the decadal variation of taiwan s precipitation became more synchronized with the pacific qdo s coupled evolutions of sst and atmospheric circulation than before while the underlying pattern of the pacific qod did not change using long term reanalysis data and cmip5 single forcing experiments the presented analysis suggests that increased sst in the subtropical western pacific and the strengthened western extension of the north pacific subtropical anticyclone may have collectively enhanced the relationship between the taiwan precipitation and the pacific qdo this finding provides possible clues to similar regime changes in quasi decadal variability observed around the western pacific rim

early solar system processes recorded in the matrices of two highly pristine cr3 carbonaceous chondrites met 00426 and que 99177 the mineralogy and bulk compositions of the matrices of the cr chondrites met 00426 and que 99177 have been studied using a combination of sem epma and tem techniques the matrices of these two chondrites are texturally chemically and mineralogically similar and are characterized by significant feo enrichments with respect to other cr chondrite matrices nearly flat refractory lithophile patterns variable volatile element patterns and a simple mineral assemblage dominated by amorphous silicate material and fe ni sulfides fine grained crystalline silicate phases such as olivine and pyroxene appear to be extremely rare in the matrices of both meteorites instead the mineralogy of matrices and fine grained rims of both meteorites consists of abundant amorphous feo rich silicate material containing nanoparticles of fe ni sulfides troilite pyrrhotite and pentlandite secondary alteration minerals that are characteristic of other cr chondrites e g renazzo and al rais such as phyllosilicates magnetite and calcite are also rare the texture and mineralogy of the matrices of met 00426 and que 99177 share many features with matrices in the primitive carbonaceous chondrites alh a77307 co3 0 and acfer 094 unique these observations show that met 00426 and que 99177 are very low petrologic type 3 chondrites that have escaped the effects of aqueous alteration unlike other cr chondrites which are typically classified as petrologic type 2 we suggest that these meteorites represent additional samples of highly primitive but extremely rare carbonaceous chondrites of petrologic type 3 00 according to the classification scheme of grossman and brearley 2005 the highly pristine nature of met 00426 and que 99177 provides important additional insights into the origins of fine grained materials in carbonaceous chondrites based on our new observations we infer that the amorphous silicate material and nanosulfide particles that dominate the matrices of these meteorites formed in the solar nebula by rapid condensation of material following high temperature events such as those that formed chondrules

formation of iddingsite veins in the martian crust by centripetal replacement of olivine evidence from the nakhlite meteorite lafayette abstract the lafayette meteorite is an olivine clinopyroxenite that crystallized on mars 1300 million years ago within a lava flow or shallow sill liquid water entered this igneous rock 700 million years later to produce a suite of secondary minerals collectively called iddingsite that occur as veins within grains of augite and olivine the deuterium hydrogen ratio of water within these secondary minerals shows that the aqueous solutions were sourced from one or more near surface reservoirs several petrographically distinct types of veins can be recognised by differences in their width shape and crystallographic orientation augite and olivine both contain veins of a very fine grained hydrous fe and mg rich silicate that are 1 2 m in width and lack any preferred crystallographic orientation these narrow veins formed by cementation of pore spaces that had been opened by fracturing and probably in response to shock the subset of olivine hosted veins whose axes lie parallel to 0 0 1 have serrated walls and formed by widening of the narrow veins by interface coupled dissolution precipitation widening started by replacement of the walls of the narrow precursor veins by fe mg silicate and a crystallographic control on the trajectory of the dissolution precipitation front created micrometre scale 1 1 1 serrations the walls of many of the finely serrated veins were subsequently replaced by siderite and the solutions responsible for carbonation of olivine also partially recrystallized the fe mg silicate smectite was the last mineral to form and grew by replacement of siderite this mineralization sequence shows that lafayette was exposed to two discrete pulses of aqueous solutions the first of which formed the fe mg silicate and the second mediated replacement of vein walls by siderite and smectite the similarity in size shape and crystallographic orientation of iddingsite veins in the lafayette meteorite and in terrestrial basalts demonstrates a common microstructural control on water mineral interaction between mars and earth and indicates that prior shock deformation was not a prerequisite for aqueous alteration of the martian crust

the spatiotemporal structure of twentieth century climate variations in observations and reanalyses part ii pacific pan decadal variability abstract the spatiotemporal structure of pacific pan decadal variability pdv is isolated in global long term surface temperature st datasets and reanalysis atmospheric parameter fields from which el nino southern oscillation enso effects have been removed empirical orthogonal function eof and combined eof analysis of the resulting time series identify pdv as one of two primary modes of long term variability the other being a global warming gw trend which is addressed in a companion paper part i in this study it is shown that one of several pdv interdecadal regime shifts occurred during the 1990s this significant change in the pacific basin is comparable but antiphase to the well known 1976 climate regime shift and is consistent with the observed changes in biosystems and ocean circulation a comprehensive picture of pdv as manifested in the troposphere and at the surface is described in general the pdv spatial patterns in different parameter fields share some similarities with the patt

global sst slp waves during the 20th century 1 a discrete number of global signals in covarying sea surface temperature sst and sea level pressure slp dominated climate variability from 40 s to 60 n during the 20th century they are the quasi biennial 2 2 year period interannual 3 to 7 year period band quasi decadal 11 year period and interdecadal 17 year period signals a joint frequency domain analysis of sst and slp anomalies over the global ocean finds these signals composed of mixed global standing modes and traveling waves that are similar in pattern and evolution on each period scale the global traveling wave is composed of global zonal wavenumbers 1 and 2 directed eastward with a phase speed that takes 1 to 2 cycles to traverse the global ocean between 40 s and 20 n the existence of these global traveling waves may enhance the predictability of regional climate variability

bulk mineralogical changes of hydrous micrometeorites during heating in the upper atmosphere at temperatures below 1000 c small particles 200 m in diameter from the hydrous carbonaceous chondrites orgueil ci murchison cm2 and tagish lake were experimentally heated for short durations at subsolidus temperatures under controlled ambient pressures in order to examine the bulk mineralogical changes of hydrous micrometeorites during atmospheric entry the three primitive meteorites consist mainly of various phyllosilicates and carbonates that are subject to decomposition at low temperatures and thus the brief heating up to 1000 c drastically changed the mineralogy changes included shrinkage of interlayer spacing of saponite due to loss of molecular water at 400 600 c serpentine and saponite decomposition to amorphous phases at 600 and 700 c respectively decomposition of mg fe carbonate at 600 c recrystallization of secondary olivine and fe oxide or metal at 700 800 c and recrystallization of secondary low ca pyroxene at 800 c the ambient atmospheric pressures controlled species of secondary fe phase taenite at pressures lower than 10 2 torr magnesiowstite from 10 3 to 10 1 torr and magnetite from 10 2 to 1 torr the abundance of secondary low ca pyroxene increases in the order of murchison orgueil and tagish lake and the order corresponds to saponite abundance in samples prior to heating mineralogy of the three unmelted micrometeorites f96ci024 kw740052 and kw740054 were investigated in detail in order to estimate heating conditions the results showed that they might have come from different parental objects carbonaterich tagish lake type carbonate poor tagish lake or ci type and cm type respectively and experienced different peak temperatures 600 700 and 800 900 c respectively at 60 80 km altitude upon atmospheric entry

a combined electron microprobe emp and raman spectroscopic study of the alteration products in martian meteorite mil 03346 1 we examine the secondary alteration products in mil 03346 using raman spectroscopic and electron microprobe traverses discussion focuses on the single olivine in 177 supplemented with observations from 168 and 169 traverses start at the rim and progress into the interior dark brown nearly opaque laihunite fe2 fe3 2 sio4 2 is present as overgrowths and 20 50 m veins of reddish brown stilpnomelane k na ca 4 ti0 1 al2 3 fe3 35 5 mn0 8 mg9 3 si63al9 o oh 206 n h2o occur inside the olivine stilpnomelane crosscuts and postdates the laihunite veins are in sharp contact with the host olivine but lined by 5 m films of jarosite kfe3 3 so4 2 oh 6 from a later generation of alteration an interstitial laihunite also hosts stilpnomelane the most recent secondary phases are gypsum and bassanite in our x ray maps of 168 and 169 ca sulfates were not observed in x ray maps of 177 but were detected in our raman point count all sulfates are believed to be martian the groundmass of mil indicates rapid cooling from elevated temperatures with fo2 near qfm reports of laihunite synthesis by olivine oxidation at elevated temperatures 100 800 c suggest the overgrowths formed during consolidation in terrestrial rocks stilpnomelane is a product of late diagenesis to garnet grade metamorphism in mil stilpnomelane appears to be a secondary phase formed at the lower end of this stability range at conditions akin to diagenesis raman spectra indicate that the stilpnomelane jarosite and ca sulfates are hydrated the stilpnomelane contains cl and was followed by jarosite a product of acid alteration and the deposition of ca sulfates and halide salts from more neutral chloride solutions

coupled air sea response to solar forcing in the pacific region during northern winter 1 observations since the middle of the 19th century show that the decadal solar oscillation at its peaks strengthens the major convergence zones in the tropical pacific intertropical convergence zone itcz and south pacific convergence zone spcz during northern winter through an amplifying set of coupled feedbacks a set of processes is described that link solar forcing and its response in the tropical pacific with reductions in precipitation in the northwest united states the process begins with an increase in solar forcing which results in a strengthening of the major convergence zones in the tropical pacific this then increases the precipitation in those regions and increases the southeast trade winds stronger trades increase the upwelling of colder water in the eastern equatorial pacific and extend the cold tongue westward thus reducing precipitation in the western pacific this redistribution of diabatic heating and associated convective heating anomalies thus produces anomalies in the tropical hadley north south and walker east west circulations the former weakens as subsidence in equatorial latitudes is enhanced the latter strengthens and extends westward additionally the resulting anomalous rossby wave response in the atmosphere and consequent positive sea level pressure anomalies in the eastern region of the aleutian low in the north pacific that extends to western north america is associated with reductions of precipitation in the northwest united states the response of the climate system to solar forcing is manifested as a strengthening of the climatological precipitation maxima in the tropics

spatial distributions of secondary minerals in the martian meteorite mil 03346 168 determined by raman spectroscopic imaging miller range mil 03346 is a nakhlite meteorite that has been extensively studied due to its unique complex secondary mineral phases and their potential implications for the hydrologic history of mars we conducted a set of raman spectroscopic and raman imaging studies of mil 03346 168 focusing on the secondary mineral phases and their spatial distributions with a goal to better understand the possible processes by which they were generated on mars this study revealed three types of calcium sulfates a solid solution of k na jarosite and two groups of hydrated species with low crystallinity hslc in the veins and or mesostasis areas of the meteorite the most abundant ca sulfate is bassanite that suggests two possible paths for its direct precipitation from a ca s h2o brine either having low water activity or with incomplete development producing bassanite with gypsum microcrystals on mars the second most abundant ca sulfate is soluble caso4 which raises a new question on the origins of this phase in the martian meteorite since caso4 readily hydrates in the laboratory but is apparently stable in atacama desert the close spatial relationship of k na jarosite solid solutions with rasvumite kfe2s3 magnetite hslc and fine grained low crystallinity alkali feldspar in mesostasis suggests a potential in situ formation of mesostasis jarosite from these fe k na s o h2o species

transmission electron microscopy of subsolidus oxidation and weathering of olivine olivine crystals in basaltic andesites which crop out in the abert rim south central oregon have been studied by high resolution and analytical transmission electron microscopy the observations reveal three distinct assemblages of alteration products that seem to correspond to three episodes of olivine oxidation the olivine crystals contain rare dense arrays of coherently intergrown ti free magnetite and inclusions of a phase inferred to be amorphous silica we interpret this first assemblage to be the product of an early subsolidus oxidation event in the lava the second olivine alteration assemblage contains complex ordered intergrowths on 001 of forsterite rich olivine and laihunite distorted olivine structure with fe3 charge balanced by vacancies based on experimental results for laihunite synthesis kondoh et al 1985 these intergrowths probably formed by olivine oxidation between 400 and 800 c the third episode of alteration involves the destruction of olivine by low temperature hydrothermal alteration and weathering elongate etch pits and channels in the margins of fresh olivine crystals contain semi oriented bands of smectite olivine weathers to smectite and hematite and subsequently to arrays of oriented hematite crystals the textures resemble those reported by eggleton 1984 and smith et al 1987 we find no evidence for a metastable phase intermediate between olivine and smectite m eggleton 1984 the presence of laihunite exerts a strong control on the geometry of olivine weathering single laihunite layers and laihunite forsteritic olivine intergrowths increase the resistance of crystals to weathering preferential development of channels between laihunite layers occurs where growth of laihunite produced compositional variations in olivine rather than where coherency strain is associated with laihunite olivine interfaces

examples of the horizontal propagation of quasi stationary waves abstract examples of the diagnostic of the horizontal propagation of stationary wave activity proposed by plumb are presented for a simple model of the atmospheric response to thermal forcing in the tropics for the observed southern hemisphere winter mean stationary waves and for several cases of anomalous quasi stationary waves in both the northern and southern hemispheres for the simple model the propagation of wave activity out of the tropics is clear from the observational data the apparent sources of anomalous stationary wave activity are located in the regions of the major middle latitude jets and storm tracks in both hemispheres in most cases the results suggest that midlatitude processes such as instabilities of the jet stream or interaction with transient eddies are the major mechanisms for forcing anomalous stationary waves there are indications that rossby like wave propagation from low latitudes plays a role in forcing anomalous stationary waves associated with southern oscillation ev

an aem tem study of weathering and diagenesis abert lake oregon i weathering reactions in the volcanics abstract abert lake in south central oregon provides a site suitable for the study of sequential weathering and diagenetic events in this first of two papers transmission electron microscopy was used to characterize the igneous mineralogy subsolidus alteration assemblage and the structural and chemical aspects of silicate weathering reactions that occur in the volcanic rocks basalts basaltic andesites and dacitic rhyolitic extrusive and pyroclastics that outcrop around the lake olivine and pyroxene replacement occurred topotactically whereas feldspar and glass alteration produced randomly oriented smectite in channels and cavities the tetrahedral octahedral and interlayer compositions of the weathering products largely dioctahedral smectites varied with primary mineral composition rock type and as the result of addition of elements released from adjacent reaction sites weathering of the highly evolved fe rich jug mountain complex at the north end of the lake produced a homogeneous smectite assemblage that contrasts with the heterogeneous smectite assemblage replacing the volcanics along the eastern margin of the lake the variability within and between the smectite assemblages highlights the microenvironmental diversity fluctuating redox conditions and variable solution chemistry associated with mineral weathering reactions in the surficial environment late stage exhalative and aqueous alteration of the volcanics redistributed many components and formed a variety of alkali and alkali earth carbonate chloride sulfate and fluoride minerals in vugs and cracks overall substantial mg si na ca and k are released by weathering reactions that include the almost complete destruction of the mg smectite that initially replaced olivine the leaching of these elements from the volcanics provides an important source of these constituents in the lake water the nature of subsequent diagenetic reactions resulting from the interaction between the materials transported to the lake and the solution will be described in part ii banfield et al 1991

direct observation of reactant product interfaces formed in natural weathering of exsolved defective amphibole to smectite evidence for episodic isovolumetric reactions involving structural inheritance abstract high resolution transmission electron microscopy hrtem and energy dispersive x ray microanalysis eds were employed to characterize grain boundary structures in naturally weathered amphibole our observations provide insights into the submicroscopic mineralogic controls on transport of solutions to and from reaction sites finely exsolved amphibole anthophyllite gedrite in outcropping slightly weathered gedrite gneiss transforms isovolumetrically to smectite stacking faults and exsolution lamellar boundaries focus weathering reactions whereas chain width defects decrease the susceptibility of the surrounding amphibole to alteration relatively al poor anthophyllite lamellae alter slightly more readily than those of al rich gedrite large quantites of mg fe si and al are removed from reaction sites however smectite compositions directly reflect

aqueous corrosion of olivine in the mars meteorite miller range mil 03346 during antarctic weathering implications for water on mars abstract several nakhlites clinopyroxenite meteorites from mars contain olivine phenocrysts with corrosion features identical in size shape and distribution to the smaller etch pits of well characterized weathered terrestrial olivine miller range mil 03346 is an antarctic nakhlite find recovered after long exposure to antarctic conditions the distribution of discrete olivine etch pits almost exclusively within a few hundred microns of allocation mil 03346 171 s documentably exposed surface suggests that they formed by terrestrial weathering in antarctica the small size of olivine etch pits in mil 03346 171 relative to commonly much larger etch pits in even incipiently weathered terrestrial examples suggests that the duration of its exposure to weathering conditions was short or the weathering conditions to which it was exposed did not favor olivine corrosion in the form of etch pit formation or both time scales for the formation of etch pits estimated from experimentally determined dissolution rates of olivine over a range of phs are comparable to the measured terrestrial age of the meteorite and short relative to the time available for possible similar corrosion on mars etch pits of the observed size on mil 03346 olivine phenocrysts would be relatively easy to form supraglacially under brief episodic acidic antarctic conditions but the terrestrial age of mil 03346 is long enough that its olivine might have been weathered to the observed state by englacial films of alkaline antarctic water the paucity of similar etch pits in olivine from the interior of mil 03346 suggests that olivine in this mars meteorite was exposed to even less aqueous alteration after iddingsitization during its 1 3 billion years on mars than its exterior was subjected to during its pleistocene holocene exposure to antarctic weathering conditions

recent rainfall cycle in the intermountain region as a quadrature amplitude modulation from the pacific decadal oscillation 1 precipitation in the intermountain region has experienced a pronounced 10 20 yr cycle during the last four decades we present evidence of a quadrature phase coupling of these 10 20 yr cycles between the pacific decadal oscillation pdo and the intermountain rainfall the pdo has been linked to precipitation anomalies in the northwest and southwest u s while the intermountain region remains marginal during the transition phase of a 10 20 yr cycle in the pdo an anomalous circulation dipole over the gulf of alaska is formed this circulation dipole modulates the synoptic activity that produces rainfall in the intermountain region as a result the intermountain rainfall cycle has repeatedly lagged the pdo cycle by a quarter phase amounting to about 3 to 4 years future understanding of the 10 20 yr cycle embedded in the pdo and its quadrature phase modulation may help predict the intermountain climate

oriented chromite diopside symplectic inclusions in olivine from lunar regolith delivered by luna 24 mission abstract calcium chromium rich lamellae in olivine grain no 1611 from the luna 24 regolith were studied with feg empa and tem the lamellae consist of a worm like intergrowth of fecr 2 o 4 chromite chr and camgsi 2 o 6 diopside di with a chr di modal proportion of 1 3 the linear extension of the lamellae and crystallographic orientation relationships among the symplectite phases and the olivine suggest that the lamellae nucleated at deformation defects in the olivine host calcium depletion haloes surrounding the lamellae amount to about 75 m and indicate that the chromite diopside lamellae were formed by segregation of calcium and chromium from the host olivine into the lamellae without addition of calcium and or chromium from outside the olivine the segregation of calcium and chromium and consequently the growth of the symplectic lamellae were diffusion controlled the segregation of a calcium chromium component from the host olivine was associated with oxidation of divalent to trivalent chromium oxidation was facilitated by dehydrogenation which was driven by decompression and or a change in redox potential hydrogen point defects in the original olivine with h substituting for divalent cations on the m sites provided the necessary electron acceptors for the oxidation of chromium and after electron transfer left olivine as molecular h 2 the internal microstructure of the lamellae suggests that exsolution of the calcium chromium rich lamellae from the host olivine and formation of the chromite diopside symplectic intergrowth occurred simultaneously the time scale derived from diffusion modeling of the calcium depletion haloes around the lamellae indicates a thermal event on the order of several months to several hundred years at most symplectic inclusions found in olivine from lunar martian and terrestrial rocks are similar with respect to their shape crystallographic orientation relationships and internal microstructure of the spinel clinopyroxene intergrowth these features are inconsistent with dry olivine oxidation that is by the uptake of oxygen dehydrogenation of oh bearing precursor olivine is suggested as a general mechanism of oxidation accompanied by chemical segregation and phase separation resulting in symplectite formation

teleconnection mechanisms for tropical pacific descent anomalies during el nino abstract teleconnection mechanisms in relative descent zones are examined using the quasi equilibrium tropical circulation model qtcm the regions of anomalous descent neighboring the warm sea surface temperature sst anomalies in the eastern and central pacific ocean during the 1997 98 el nino are used as an example and results are verified for three other el nino warm events 1982 1987 and 1991 by analyzing the moisture and moist static energy budgets over these regions it is found that the physical processes responsible for the descent anomalies are different for each region anomalous dry advection is the dominant mechanism for the reduced precipitation to the north of the el nino warm region on the other hand the relative descent to the south of the el nino warm ssts is caused by reduced surface wind speed and reduced air sea contrast and resulting weaker than normal evaporation budget analysis based on the national aeronautics and space administration seasonal to interannual prediction p

characteristics of winter precipitation variation over northern central eurasia and their connections to sea surface temperatures over the atlantic and pacific oceans abstract this study reveals spatial and temporal characteristics of precipitation variability and their teleconnections to sea surface temperatures ssts over the atlantic and pacific oceans by analyzing 68 yr of recent precipitation records over the former soviet union in addition to a general increasing trend of about 0 4 mm yr 1 or 6 decade 1 over much of the study region three major modes of precipitation variation are identified a quasi biennial variation of 2 3 yr is found over the region surrounding the caspian and aral seas an el nino timescale precipitation variation of 4 5 yr is present over southern central siberia and is associated with eastern tropical pacific ssts a quasi decadal timescale variation of about 11 12 yr is evident over central european russia this quasi decadal precipitation variation is closely linked to a major sst anomaly pattern of alternating latitudinal belts over the atlantic and sst variations over the equatorial pacific ocean these associations to ssts are str

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

patterns of coherent decadal and interdecadal climate signals in the pacific basin during the 20th century two distinct low frequency fluctuations are suggested from a joint frequency domain analysis of the pacific ocean 30 s 60 n sea surface temperature sst and sea level pressure slp the lowest frequency signal reveals a spatially coherent interdecadal evolution in phase sst and slp anomalies are found along the subarctic frontal zone safz it is symmetric about the equator with tropical sst anomalies peaking near 15 latitudes in the eastern pacific the other low frequency signal reveals a spatially coherent decadal evolution it is primarily a low latitude phenomenon tropical sst anomalies peak in the central equatorial ocean with evidence of atmospheric teleconnections these interdecadal and decadal signals join the enso and quasi biennial signals in determining dominant patterns of pacific ocean natural climate variability relative phasing and location of the sst and slp anomalies for the decadal enso and the quasi biennial signals are similar to one another but significantly different from that of the interdecadal signal

dissolution of olivine during natural weathering abstract naturally weathered olivine occurring as phenocrysts in hawai ian volcanic rocks from several volcanic centers and regolith outcrop settings and as tectonized olivines from several metadunite bodies in the southern appalachian blue ridge are all similarly corroded by natural weathering conical funnel shaped etch pits occur as individual pits base to base pairs of cone shaped pits or en echelon arrays etch pit shapes and orientations in the smallest etch pit arrays visible in conventional scanning electron microscopy resemble even smaller features previously reported from transmission electron microscope investigations of olivine weathering etch pits occur in samples with chemical and or mineralogical evidence of weathering and or are associated with or proximal or directly connected to fractures or exposed outcrop surface and therefore are formed by weathering and not inherited from pre weathering aqueous alteration e g serpentinization iddingsitization of these parent rocks many etch pits are devoid of weathering products natural weathering of olivine is surface reaction limited similarity of corrosion forms from naturally weathered olivine from multiple igneous and metamorphic parent rock bodies suggests that olivine weathers in the same manner regardless of its specific crystallization recrystallization history eruption weathering exposure ages of the olivine s host rock and the local regolith history

aqueous alteration without a pronounced oxygen isotopic shift implications for the asteroidal processing of chondritic materials primitive meteorites exhibit certain features that are consistent with aqueous and thermal alteration on asteroids but o isotopic analyses show only a modest heavy isotope shift interpreted as indicating modification in the nebula to understand the isotopic effects of asteroidal alteration we take the l group ordinary chondrites weathered in antarctica as an analogue the data show that alteration is a two stage process with an initial phase producing only a negligible isotopic effect although surprising a possible explanation is found when we consider the alteration of terrestrial silicates numerous studies report pervasive development of channels a few to a few tens of nanometer wide in the incipient alteration of silicates we observe a similar texture alteration involves a restructuring of clay minerals along these narrow channels in which access of water is restricted the clay shows a topotactic relationship to the primary grain which suggests either epitaxial growth of the clay using the silicate as a substrate or inheritance of the original o structure by the clay our data suggests the latter with extensive inheritance of structural polymers by the weathering product the bulk o isotopic composition is comparatively unaffected this offers an explanation for the lack of an isotopic effect in the weathering of the l chondrites if substantial modification of chondritic materials may occur without a pronounced isotopic effect it also reconciles existing o analyses of cv chondrites with an asteroidal model of aqueous alteration

horizontal energy propagation in a barotropic atmosphere with meridional and zonal structure abstract to investigate how the propagation of energy away from steady sources may be influenced by the horizontal structure of the time averaged flow in the troposphere solutions to a barotropic model are displayed and interpreted the model is steady and linearized about a basic state which varies in latitude and longitude emphasis is placed on cases where the longitudinal variations are gradual many of the results can be analyzed by locally applying tools developed for zonally symmetric basic states e g ray tracing and refractive indices simple background flows are constructed which have longitudinally confined critical lines reflective surfaces wave guides and regions conducive to propagation an example is given in which longitudinal derivatives of the basic state are significant the theory of ray tracing in a two dimensional wind must be employed as an interpretive tool in this case it is concluded that zonal variations tend to enhance poleward equatorward propagation in large scale tr

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

olivine dissolution rates a critical review abstract the dissolution rates of olivine have been considered by a plethora of studies in part due to its potential to aid in carbon storage and the ease in obtaining pure samples for laboratory experiments due to the relative simplicity of its dissolution mechanism most of these studies provide mutually consistent results such that a comparison of their rates can provide insight into the reactivity of silicate minerals as a whole olivine dissolution is controlled by the breaking of octahedral m2 oxygen bonds at or near the surface liberating adjoining sio44 tetrahedra to the aqueous fluid aqueous species that adsorb to these bonds apparently accelerate their destruction for example the absorption of h h2o and at some conditions selected aqueous organic species will increase olivine dissolution rates nevertheless other factors can slow olivine dissolution rates notably olivine dissolution rates are slowed by lowering the surface area exposed to the reactive aqueous fluid by for example the presence and or growth on these surfaces of either microbes or secondary phases the degree to which secondary phases decelerate rates depends on their ability to limit access of the reactive aqueous fluids to the olivine surface it seems likely that these surface area limiting processes are very significant in natural systems lowering olivine surface reactivity in many environments compared to rates measured on cleaned surfaces in the laboratory a survey of the literature suggests that the major factors influencing forsteritic olivine dissolution rates are 1 ph 2 water activity 3 temperature and 4 mineral fluid interfacial surface area evidence suggests that the effects of aqueous inorganic and organic species are relatively limited and may be attributed at least in part to their influence on aqueous solution ph moreover the observed decrease in rates due to the presence of secondary mineral coatings and or the presence of microbes can be attributed to their ability to decrease olivine surface area directly exposed to the reactive aqueous fluid as the reactivity of forsterite surfaces are spatially heterogeneous its surface area normalized rates will tend to decrease as it dissolves even in the absence of a mineral or bacterial coating each of these factors limits and or influences the application of forsterite dissolution to 1 enhanced weathering efforts 2 mineral carbonation and 3 the low temperature generation of hydrogen or hydrocarbons via the oxidation of its divalent iron

a delayed action oscillator shared by biennial interannual and decadal signals in the pacific basin 1 biennial interannual and decadal signals in the pacific basin are observed to share patterns and evolution in covarying sea surface temperature sst 18 c isotherm depth z18 zonal surface wind zsw and wind stress curl wsc anomalies from 1955 to 1999 each signal has warm sst anomalies propagating slowly eastward along the equator generating westerly zsw anomalies in their wake these westerly zsw anomalies produce cyclonic wsc anomalies off the equator which pump baroclinic rossby waves in the western central tropical north pacific ocean these rossby waves propagate westward taking 6 12 and 36 months to reach the western boundary near 7 n 12 n and 18 n on biennial interannual and decadal period scales respectively there they reflect as equatorial coupled waves propagating slowly eastward in covarying sst z18 and zsw anomalies taking 6 12 and 24 months to reach the central eastern equatorial ocean these equatorial coupled waves produce a delayed negative feedback to the warm sst anomalies there the decrease in rossby wave phase speed with latitude the increase in meridional scale of equatorial sst anomalies with period scale and the associated increase in latitude of rossby wave forcing are consistent with the delayed action oscillator dao model used to explain el nino however this is not true of the western boundary reflection of rossby waves into slow equatorial coupled waves this requires modification of the extant dao model we construct a modified dao model demonstrating how the various mechanisms and the size and sources of their delays yield the resulting frequency of each signal

aqueous alteration of chondrules from the murchison cm carbonaceous chondrite replacement pore filling and the genesis of polyhedral serpentine forsterite and clinoenstatite in type iab chondrules from the murchison cm carbonaceous chondrite have been partially serpentinized and the mechanisms of their alteration reveal crystallographic and microstructural controls on the reaction of silicate minerals with parent body aqueous solutions grains of forsterite were altered in two stages narrow veinlets of fe rich serpentine formed first and by the filling of sheet pores most of these pores were oriented parallel to 010 and 001 and had been produced by earlier fracturing and or congruent dissolution in the second stage the subset of veinlets that were oriented parallel to 001 was widened accompanying the replacement of forsterite by mg fe serpentine this reaction proceeded most rapidly parallel to 001 and crystallographic controls on the trajectory of retreating vein walls created fine scale serrations murchison clinoenstatite grains have a skeletal appearance due to the presence of abundant veinlets and patches of phyllosilicate two alteration stages can again be recognized with initial water mineral interaction producing tochilinite rich veinlets by the filling of 001 parallel contraction cracks pores then formed by congruent dissolution that was guided principally by orthopyroxene lamellae and they were subsequently filled by submicrometer sized crystals of polyhedral serpentine this finding that murchison forsterite and clinoenstatite grains have been altered demonstrates that aqueous processing of magnesium silicate minerals started much earlier in cm parent body history than previously believed our results also show that the occurrence of polyhedral serpentine can be used to locate former pore spaces within the parent body

alteration of olivine in a basalt from central france abstract the belbex basalt is a miocene alkaline basalt of the kind typical of the massif central of france and of continental rift systems generally it outcrops as part of the cantal stratovolcano in the vicinity of aurillac the current cambisol overlies a relatively simple weathering profile that shows the progressive enrichment of sio2 al2o3 fe2o3 and tio2 characteristic of alteration under humid climatic conditions on the scale of individual grains olivine follows a weathering trend that conserves si and al and contrasts in this respect from an earlier path of deuteric alteration paradoxically sio2 which acts as a mobile component in the weathering macrosystem is essentially immobile within the microsystem a likely reason is that the activity of sio2 in the microsystem is buffered by the breakdown of glass the first phase to weather in the parent basalt the composition of the weathered olivine is consistent with an evolution towards a smectite goethite assemblage two of the secondary minerals found in the macrosystem

linkages between 200 mb tropical and extratropical circulation anomalies during the 1986 1989 enso cycle abstract nmc operational wind analyses have been used to document the 200 mb circulation anomalies during the solstice seasons of the 1987 1989 enso cycle using the one level vorticity balance diagnostic approach the 200 mb rossby wave anomalous source distribution was derived as departures from a three year mean for the single warm phase season january march 1987 the effective rossby wave anomaly sources were found to be generally quite small within 15 of the equator poleward of about 15 the anomalous 200 mb divergence through the planetary vorticity divergence anomaly stretching term is the dominant factor in determining the anomalous 200 mb vorticity source distribution its jfm standard deviation around 30 35 n was an order of magnitude larger than that found in the deep tropics the january march and june august 200 mb circulation differences between the warm and cold phase of the 1987 1989 enso cycle are described the enso cycle linkages between the equatorial pacific convection anomali

tree ring reconstruction of the level of great salt lake usa utah s great salt lake gsl is a closed basin remnant of the larger pleistocene age lake bonneville the modern instrumental record of the gsl level i e elevation change is strongly modulated by pacific ocean coupled ocean atmospheric oscillations at low frequency and therefore reflects the decadalscale wet dry cycles that characterize the region a within basin network of seven tree ring chronologies was developed to reconstruct the gsl water year september august level based upon the instrumental record of gsl level from 1876 to 2005 the result was a 576 year reconstruction of the gsl level that extends from 1429 to 2005 all calibration verification tests commonly used in dendroclimatology were passed the reconstruction explains 48 of the variance in the instrumental gsl level and exhibits significant periodicity at sub decadal scales over the past six centuries meanwhile predominance of multi decadal periodicity in the early half of the record shifted to quasi decadal dominance in the latter half and this is consistent with that of proxy reconstructions of the pacific decadal oscillation the gsl level reconstruction is a crucial component to improving our insight into the possible controls of coupled ocean atmosphere interactions on precipitation delivery

coherence between the great salt lake level and the pacific quasi decadal oscillation the lake level elevation of the great salt lake gsl a large closed basin lake in the arid western united states is characterized by a pronounced quasi decadal oscillation qdo the variation of the gsl elevation is very coherent with the qdo of sea surface temperature anomalies in the tropical central pacific also known as the pacific qdo however such coherence denies any direct association between the precipitation in the gsl watershed and the pacific qdo because in a given frequency the precipitation variation always leads the gsl elevation variation therefore the precipitation variation is phase shifted from the pacific qdo this study investigates the physical mechanism forming the coherence between the gsl elevation and the pacific qdo pronounced and coherent quasi decadal signals in precipitation streamflow water vapor flux and drought conditions are found throughout the great basin recurrent atmospheric circulation patterns develop over the gulf of alaska during the warm to cool and cool to warm transition phases of the pacific qdo these circulation patterns modulate the water vapor flux associated with synoptic transient activities over the western united states and in turn lead to the qdo in the hydrological cycle of the great basin as the gsl integrates the hydrological responses in the great basin the hydrological qdo is then transferred to the gsl elevation because the gsl elevation consistently lags the precipitation by a quarter phase about 3 yr in the quasidecadal time scale these processes take an average of 6 yr for the gsl elevation to eventually respond to the pacific qdo this creates a half phase delay of the gsl elevation from the pacific qdo thereby forming the inverse yet coherent relationship between them tree ring reconstructed precipitation records confirm that the quasi decadal signal in precipitation is a prominent feature in this region

vermicular kaolinite relics in fly ash derived from bokaro and jharia coals jharkhand india abstract during a study of fly ash from two pulverized fuel power plants bokaro and chandrapura burning coal from the bokaro coalfield in jharkand state india glassy and vermicular mineral forms were found associated with the char a combination of optical microscopy xrd sem eds and xrf analysis has shown that this morphotype reported here for the first time originated from kaolinite that expanded during heating inside the furnace chamber under relatively low combustion temperatures the morphotype has an internal structure that resembles the fanning out structure formed during vermicular kaolinite development

fe3 distribution in oxidized olivine a synchrotron micro xanes study synchrotron micro xanes spectroscopy smx is used to examine the amount and distribution of fe super 2 and fe super 3 in five samples of fayalite previously studied by mossbauer spectroscopy rockport fayalite is homogeneous and the fe in it is completely reduced olivine from qianan is almost completely oxidized and probably contains finely intergrown silica laihunite and hematite with hematite predominating pantelleria olivine has an oxidized rim around a reduced core suggesting either a post crystallization reaction with fayalite and oxygen going to laihunite and hematite or a change in prevailing oxidation during growth the texture of olivine from the mourne mountains suggests exsolution from a fayalite laihunite solid solution based on the substitution of three fe super 3 atoms for two fe super 2 and one vacancy that was stable at high temperature laihunite from the type locality lai he village shows 1 3 mu m mottling between light and dark areas in backscatter images but these areas cannot correspond to pure fayalite and laihunite exsolution because the bulk fe super 3 sigma fe of such a combination would not correspond to the smx value of 67 fe super 3 rather the texture observed in backscatter is interpreted to represent alternating areas of magnetite rich and laihunite rich compositions with a similar i e 67 fe super 3 sigma fe extent of oxidation

quantifying carbon fixation in trace minerals from processed kimberlite a comparative study of quantitative methods using x ray powder diffraction data with applications to the diavik diamond mine northwest territories canada abstract the capacity of mine waste to trap co2 is in some cases much larger than the greenhouse gas production of a mining operation in mine tailings the presence of secondary carbonate minerals that trap co2 can therefore represent substantial fixation of this greenhouse gas the abilities of three methods of quantitative phase analysis to measure trace nesquehonite mgco3 3h2o in samples of processed kimberlite have been assessed the method of reference intensity ratios rir the internal standard method and the rietveld method with x ray powder diffraction data tests on synthetic mixtures made to resemble processed kimberlite indicate that both the rir and rietveld methods can be used accurately to quantify nesquehonite to a lower limit of approximately 0 5 wt for conditions used in the laboratory below this value estimates can be made to a limit of approximately 0 1 wt using a calibration curve according to the internal standard method the rir method becomes increasingly unreliable with decreasing abundance of nesquehonite primarily as a result of an unpredictable decline in preferred orientation of crystallites for rietveld refinements structureless pattern fitting was used to account for planar disorder in lizardite by considering it as an amorphous phase rietveld refinement of data collected from specimens that were serrated to minimize preferred orientation of crystallites gives rise to systematic overestimates of refined abundances for lizardite and underestimates for other phases the resulting pattern of misestimates may be mistaken for the effect of amorphous and or nanocrystalline material in samples this effect is mitigated by collecting data from non serrated specimens which typically give relative errors on refined abundances for major and minor phases in the range of 5 20 however relative error can increase rapidly for abundances less than 5 wt nonetheless absolute errors are sufficiently small that estimates can be made for the amount of co2 stored in secondary nesquehonite using the rir method or the rietveld method for abundances 0 5 wt and a calibration curve for abundances

generation of forsteritic olivine fo99 8 by subsolidus oxidation in basaltic flows we identify olivine grains with compositions up to fo99 8 which are found in multiple primitive basaltic lava flows from a monogenetic volcano in the big pine volcanic field california usa in this study we show that the forsterite in these basalts formed by subsolidus recrystallization in a high fo2 environment olivine compositions are bimodal with flows having either all normal compositions fo74 9 94 4 or highly forsteritic fo97 2 99 8 compositions in many grains the subhedral forsteritic olivine has a hematite and clinopyroxene rim and internal parallel oriented planes of hematite clinopyroxene and orthopyroxene results of isotopic chemical crystallographic petrographic and mineralogical analyses show that the forsterite formed through subsolidus oxidation of olivine phenocrysts the forsteritic olivines generally occur in the thinner flows we infer that a rapidly emplaced sequence of thin vesicular spatter fed flows allowed the original olivine phenocrysts to become repeatedly reheated while exposed to air our study required sampling each flow so it was difficult to avoid the altered portions of the thinner flows other studies would tend to avoid such flows which may account for why such forsteritic olivines have not been more widely recognized

multiscale variabilities in global sea surface temperatures and their relationships with tropospheric climate patterns el nino southern oscillation enso is a global phenomenon with significant phase propagation within and between basins this is captured and described in the first mode of a complex empirical orthogonal function ceof analysis of sea surface temperature anomaly ssta from the midnineteenth century through 1991 the global enso from the ssta data plus a linear trend everywhere are subsequently removed in order to consider other global modes of variability uncontaminated by the intra and interbasin effects of enso an ordinary eof analysis of the ssta residuals reveals three non enso modes of low frequency variability that are related to slow oceanic and climate signals described in the literature the first two modes have decadal to multidecadal timescales with high loadings in the pacific they bear some spatial similarities to the enso pattern but are broader more intense at high latitudes and differ in the time domain a ceof analysis confirms that they are not merely the phase related components of a single mode and that all three modes are without significant phase propagation the third mode is a multidecadal signal with maximal realization in the extratropical north atlantic southeast of greenland it is consistent with studies that have documented connections between north atlantic ssta and the tropospheric north atlantic oscillation nao all three ssta modes have midtropospheric associations related to previously classified northern hemisphere teleconnection patterns the relationships between ssta modes and tropospheric patterns are consistent with the ocean atmosphere interactions discussed in previous studies to explain low frequency climate oscillations in the north pacific and north atlantic sectors the first three leading modes of non enso ssta are most related to the tropospheric patterns of the pacific north american the north pacific and the arctic oscillations ao respectively the 500 hpa pattern associated with the third ssta mode also bears similarities to the nao in its atlantic sector this north atlantic mode has a region of high positive ssta loadings in the gulf of alaska which appear to be connected to the north atlantic ssta by a tropospheric bridge effect in the ao

pakistan s two stage monsoon and links with the recent climate change 1 meteorological conditions related to the pakistan floods of 2010 were examined in the context of monsoon dynamics and large scale circulations case and climatological analyses suggest that summer precipitation in northern pakistan comprises two distinct phases 1 a premonsoon trough phase july whose rainfall is more episodic and intense occurring prior to arrival of the monsoon trough and 2 a monsoon trough phase august whose rainfall is persistent yet less episodic driven by northward migration of the monsoon trough analyses of conditional instability moisture flux and circulation features support a persistent increase in conditional instability during the july premonsoon trough phase accompanied by increased frequency of heavy rainfall events conversely evidence does not support intensification of the august monsoon trough phase the increased convective activity during the premonsoon trough phase agrees with the projected increase in the intensity of heavy rainfall events over northern pakistan large scale circulation analysis reveals an upper level cyclonic anomaly over and to the west of pakistan a feature empirically associated with weak monsoon the analysis also suggests that the anomalous circulation in 2010 is not sporadic but rather is part of a long term trend that defies the typical linkage of strong monsoons with an anomalous anticyclone in the upper troposphere

linear simulation of the stationary eddies in a general circulation model part i the no mountain model abstract the quantitative validity of linear stationary wave theory is examined by comparing the results from a linear primitive equation model on the sphere with the stationary eddies produced by a general circulation model gcm the gcm simulated has a flat lower boundary so that the stationary eddies can be thought of as forced by heating sensible latent and radiative and time averaged transient eddy flux convergences orographic forcing is examined in the second part of this study the distribution of the diabatic heating and transient eddy flux convergences and the zonally symmetric basic state are taken directly from the gcm s climatology for northern winter djf strong rayleigh friction is included in the linear model wherever the zonal mean wind is small as well as near the surface the linear model is found to simulate the stationary eddy pattern of the gcm with considerable skin in both midlatitudes and the tropics some deficiencies include the inaccurate simulation of the upper troposp

climate and rock weathering a study of terrestrial age dated ordinary chondritic meteorites from hot desert regions abstract ordinary chondrites oc recovered from the desert areas of roosevelt county new mexico the nullarbor region of western australia and the algerian and libyan sahara for which 14c terrestrial ages have been determined were examined by 57fe mossbauer spectroscopy oc were chosen as a standard sample to investigate weathering processes as their well constrained trace and bulk element chemistry normative mineralogy and isotopic composition define a known pre weathering starting composition given that terrestrial ages are known it is possible to compare initially very similar samples that have been subsequently weathered in a range of climatic regimes from the present day to 44 ka bp in addition recently fallen equilibrated oc contain iron only as fe0 and fe2 thus the abundance of ferric iron is directly related to the level of terrestrial weathering mossbauer spectroscopy identifies two broad types of ferric alteration paramagnetic phases akaganeite lepidocrocite and goethite and magnetically ordered principally magnetite and maghemite oc finds show a range in the percentage of total fe existing as fe3 from zero to over 80 however oxidation is comparable between fragments of the same oc separated since their time of fall i e paired meteorites our results indicate several features of meteorite weathering that may result from climatic or geomorphologic conditions at the accumulation site 1 saharan samples are overall less weathered than non saharan samples which may be related to the relatively recent age ca 20 ka of the saharan accumulation surface 2 broad differences between sites in the rate of weathering arising from regional differences in climate 3 consistent differences in the weathering products between samples that fell during humid periods and those that fell during more arid periods those falling during humid periods contain a higher proportion of magnetically ordered ferric oxides 4 one region the nullarbor that shows a variation in the total amount of ferric species that closely matches the climatic record for this area of australia for the last 30 ka points 3 and 4 may be related to the identification of a rapid initial weathering phase the majority of weathering occurs in the first few hundred years after fall followed by passivation of weathering by porosity reduction porosity reduction and the associated restriction in the ability of water to penetrate the sample appears to be the mechanism whereby a weathering assemblage formed during the brief initial period of oxidation is preserved through subsequent climatic cycles over the terrestrial lifetime of the sample

seismic reliability of axially loaded vertical piles the reliability of single vertical pile foundations subjected to seismic loads is assessed and compared with the minimum acceptable reliability level for static load conditions mandated by the cana

tropical pacific decadal variability and the subtropical tropical cells abstract the decadal scale variability in the tropical pacific has been analyzed herein by means of observations and numerical model simulations the two leading modes of the sea surface temperature sst variability in the central western pacific are a decadal mode with a period of about 10 yr and the enso mode with a dominant period of about 4 yr the sst anomaly pattern of the decadal mode is enso like the decadal mode however explains most variance in the western equatorial pacific and off the equator a simulation with an ocean general circulation model ogcm forced by reanalysis data is used to explore the origin of the decadal mode it is found that the variability of the shallow subtropical tropical overturning cells is an important factor in driving the decadal mode this is supported by results from a multicentury integration with a coupled ocean atmosphere general circulation model cgcm that realistically simulates tropical pacific decadal variability finally the sensitivity of the shal

a mossbauer spectroscopy and x ray diffraction study of ordinary chondrites quantification of modal mineralogy and implications for redox conditions during metamorphism we present a method that combines mssbauer spectroscopy and x ray diffraction to quantify the modal mineralogy of unequilibrated ordinary chondrites uocs despite being a fundamental tool in the interpretation of geological systems there are no modal mineralogical data available for these meteorites this is due to their fine grained nature highly heterogeneous silicate mineralogy and the presence of poorly characterized phases consequently it has not been possible to obtain accurate modal mineralogy by conventional techniques such as point counting here we use mssbauer spectroscopy as a preliminary identification technique and x ray diffraction provides the quantification for a suite of recent uoc falls we find the most primitive uocs to contain a significant amount of phyllosilicate material that was converted during metamorphism to form ferromagnesian silicates a complete suite of antarctic samples is analyzed by each method to observe mineralogical trends and these are compared with trends shown by recent falls the fact that mineralogical relationships shown by finds and falls are in agreement allows us to be confident that we are observing the products of pre terrestrial alteration mssbauer spectroscopy reveals evidence of steadily increasing reduction with metamorphism in the uocs because this technique allows comparisons to be made between uocs and eocs our reduction sequence can be combined with other evidence showing progressive oxidation in the eocs this yields an integrated model of changing redox conditions on equilibrating ordinary chondrite parent bodies

mineralogy aqueous alteration and primitive textural characteristics of fine grained rims in the y 791198 cm2 carbonaceous chondrite tem observations and comparison to alha81002 abstract transmission electron microscopy tem was used to study the microtextural and mineralogical characteristics of fine grained rims in the unbrecciated cm2 chondrites y 791198 and alha81002 in an effort to provide constraints on the origins of the rims themselves our tem observations show that the rims in y 791198 are composed of two distinct types of region sulfide poor and sulfide rich that are intermixed in a complex manner at the micron to submicron level the sulfide poor regions are largely composed of amorphous silicate material or nanocrystalline serpentine but rare fibrous and coarse grained serpentine grains have also been identified no fine grained cronstedtite or tochilinite were observed although coarse grained lumps of tochilinite are present in the rims in contrast the sulfide rich regions are characterized by the presence of a myriad nanometer sized fe ni sulfide grains pentlandite with some ni rich pyrrhotite embedded within an amorphous silicate similar in composition to that of the sulfide poor regions the sulfide rich regions also contain rare phases such as olivine and fe ni metal grains with grain sizes that are always 100 nm in size z contrast scanning transmission electron microscopy stem reveals that the fine grained rims consist of a mosaic of irregularly shaped sulfide poor and sulfide rich regions with sizes of about 0 2 0 5 m that have been compacted together during parent body lithification despite aqueous alteration the distinct mineralogical characteristics of these different regions are preserved on a fine scale and probably represent primitive heterogeneity in the dust from which these rims formed serpentine is much better developed and more widespread in the fine grained rims of alha81002 than y 791198 complex mats of serpentine fibers are commonly found and cronstedtite and tochilinite are plentiful anhydrous minerals such as olivine are rare and have usually been replaced by serpentine like y 791198 all the fine grained rims studied in alha81002 show the same mineral assemblages and textural characteristics throughout and between rims the homogeneity of the mineralogy textural relationships and degree of hydration in the rims of these two chondrites is more consistent with parent body alteration than with pre accretionary alteration

pacific decadal variability the tropical pacific mode and the north pacific mode pacific decadal variability is studied in a series of coupled global ocean atmosphere simulations aided by two modeling surgery strategies partial coupling pc and partial blocking pb the pc experiments retain full ocean atmosphere coupling in selected regions but constrain ocean atmosphere coupling elsewhere by prescribing the model climatological sst to force the atmospheric component of the coupled system in pb experiments sponge walls are inserted into the ocean component of the coupled model at specified latitudinal bands to block the extratropical tropical oceanic teleconnection both modeling and observational studies suggest that pacific decadal variability is composed of two distinct modes a decadal to bidecadal tropical pacific mode tpm and a multidecadal north pacific mode npm the pc and pb experiments showed that the tropical pacific mode originates predominantly from local coupled ocean atmosphere interaction within the tropical pacific extratropical tropical teleconnections although not a necessary precondition for the genesis of the tropical decadal variability can enhance sst variations in the tropics the decadal memory in the tropics seems to be associated with tropical higher baroclinic modes the north pacific mode originates from local atmospheric stochastic processes and coupled ocean atmosphere interaction atmospheric stochastic forcing can generate a weaker npm like pattern in both the atmosphere and ocean but with no preferred timescales in contrast coupled ocean atmosphere feedback can enhance the variability substantially and generate a basin scale multidecadal mode in the north pacific the multidecadal memory in the midlatitudes seems to be associated with the delayed response of the subtropical subpolar gyre to wind stress variation in the central north pacific and the slow growing decaying of sst anomalies that propagate eastward in the kuroshio extension region oceanic dynamics particularly the advection of the mean temperature by anomalous meridional surface ekman flow and western boundary currents plays an important role in generating the north pacific mode

evidence for silicate dissolution on mars from the nakhla meteorite veins containing carbonates hydrous silicates and sulfates that occur within and between grains of augite and olivine in the nakhla meteorite are good evidence for the former presence of liquid water in the martian crust aqueous solutions gained access to grain interiors via narrow fractures and those fractures within olivine whose walls were oriented close to 001 were preferentially widened by etching along 001 this orientation selective dissolution may have been due to the presence within olivine of shock formed 001 100 and 001 110 screw dislocations the duration of etching is likely to have been brief possibly less than a year and the solutions responsible were sufficiently cool and reducing that laihunite did not form and fe liberated from the olivine was not immediately oxidized the pores within olivine were mineralized in sequence by siderite nanocrystalline smectite a fe mg phyllosilicate and then gypsum whereas only the smectite occurs within augite the nanocrystalline smectite was deposited as submicrometer thick layers on etched vein walls and solution compositions varied substantially between and sometimes during precipitation of each layer together with microcrystalline gypsum the fe mg phyllosilicate crystallized as water briefly returned to some of the veins following desiccation fracturing of the smectite these results show that etching of olivine enhanced the porosity and permeability of the nakhlite parent rock and that dissolution and secondary mineralization took place within the same near static aqueous system

the primitive matrix components of the unique carbonaceous chondrite acfer 094 a tem study the mineralogical and chemical characteristics of the fine grained matrix 53 m of the unique primitive carbonaceous chondrite acfer 094 have been investigated in detail by scanning electron microscopy sem and analytical transmission electron microscopy atem generally the fine grained matrix represents a highly unequilibrated assemblage of an amorphous material small forsteritic olivines 200 300 nm low ca pyroxenes 300 400 nm and fe ni sulfides 100 300 nm the matrix is basically unaffected by secondary processes only minor amounts of serpentine and ferrihydrite as products of hydrous alteration are present texturally the amorphous material acts as a groundmass to olivines pyroxenes and sulfides mostly exhibiting rounded or elongated morphologies only very few clastic mineral grains have been found the texture and chemical composition of the amorphous material are consistent with an origin by disequilibrium condensation in either the cooling solar nebula or a circumstellar environment as such the amorphous material may be considered as a possible precursor of matrix materials in other types of chondrites the non clastic matrix olivines fo98 99 and pyroxenes en97 100 are suggested to have formed either by condensation in the solar nebula under highly oxidizing conditions or by recrystallization from the amorphous material the formation of these grains by fragmentation of chondrule components is unlikely due to chemical and microstructural reasons rapid cooling caused the observed intergrowths of clino orthoenstatite in the mg rich matrix pyroxenes although some similarities exist comparing the fine grained matrix of acfer 094 with the matrices of the unequilibrated c03 chondrite alha77307 and the unique type 3 chondrite kakangari acfer 094 remains unique since it contains the highest measured concentrations of circumstellar sic and the second highest of diamond highest is orgueil it seems reasonable to suggested that at least parts of the amorphous material in the fine grained matrix may be of circumstellar origin

interaction of arc magmas with subvolcanic hydrothermal systems insights from compositions and metasomatic textures of olivine crystals in fresh basalts of daisen and mengameyama western honshu japan