experimental characterization of diffusive and soret isotopic fractionation of sulfur in a reduced anhydrous basaltic melt abstract the diffusivity of isotopes of a given element in magmas can be significantly different leading to observable effects on isotope ratios similarly the soret effect or thermal diffusion can also lead to considerable isotopic fractionations seeking to characterize isotope effects accompanying sulfur diffusion in basaltic melts we conducted experiments involving separately both chemical and thermal diffusion at 1350 1500 c and 1 1 5 gpa in contrast to the isotopes of most elements investigated previously ca li mg fe cl no significant isotope fractionations beyond analytical precision were found for sulfur isotope system 32s 33s 34s and 36s in response to thermal or chemical concentration gradients analysis of our run products by secondary ion mass spectrometry sims reveals a near unity minimum diffusivity ratio for 34s 32s 0 in anhydrous basaltic melt at conditions where sulfide species predominate these results suggest that s isotope fractionations by diffusive processes are not important in basaltic melts and therefore need not be considered when interpreting s isotope signatures however we also report potential soret fractionations as large as approximately 1 for 33s 2 1 for 34s 3 8 for 36s and 40 ppm for elemental s with enrichments of s and its heavier isotopes at the colder ends of the thermal gradients

lithium behaviour and isotope fractionation during fluid rock interactions in variscan oceanic suture zones limousin ophiolite and ile de groix high pressure terrane france

a lithium isotopic study of sub greenschist to greenschist facies metamorphism in an accretionary prism new zealand article i nfo to investigate the behavior of li during low grade metamorphism and fluid flux in an accretionary prism we

silicon isotopes in granulite xenoliths insights into isotopic fractionation during igneous processes and the composition of the deep continental crust the silicon si cycle is of great current interest but the isotopic composition of the continental crust has not been determined magmatic differentiation generates liquids with heavier si and the lower crust thought to be dominated by cumulates and restites is predicted to have a light isotopic composition this is borne out by the composition of many types of granite which appear to have relative light si for their silica content here we report the si isotopic compositions of two granulite facies xenolith suites from the chudleigh and mcbride volcanic provinces australia providing new constraints on deep crustal processes and the average composition of the deep continental crust the xenoliths display a range of isotopic compositions 30si 0 43 to 0 15 comparable to that measured previously for igneous rocks the isotopic compositions of the mcbride xenoliths reflect assimilation and fractional crystallisation afc and or partial melting processes silicon and o isotopes are correlated in the mcbride suite and can be explained by afc of various evolved parent melts in contrast the chudleigh xenoliths have si isotope compositions predominantly controlled by the specific mineralogy of individual cumulates using the xenolith data and a number of weighting methods the si isotope compositions of the lower and middle crust are calculated to be 30si 0 29 0 04 95 s e and 0 23 0 04 95 s e respectively these values are almost identical to the composition of the bulk silicate earth implying minimal isotope fractionation associated with continent formation and no light lower crustal reservoir

light elements and li isotopes across the northern portion of the central american subduction zone 1 quaternary mafic rocks have been erupted from volcanoes both on and behind the volcanic front in southeastern guatemala and western el salvador behind the front volcanism extends almost continuously some 110 km from the front b and li contents as well as b nb and li yb ratios are generally higher in the mafic volcanic rocks of the volcanic front and lower in those behind the front beryllium concentrations show the opposite relationships with generally higher values behind the front in addition many behind the front samples have lower 7li 2 3 versus 4 6 for the volcanic front guatemalan volcanic rocks in general have lower 7li than those found along the remainder of the central american margin the light element variations across northern central america clearly indicate that the volcanic front receives a much more pronounced fluid contribution from dehydrating subducting cocos lithosphere than the behind the front region this dehydration pulse occurs at slab depths between 85 and 105 km and selective enrichments of b cs and cl in volcanic rocks of the volcanic front suggest that the source of this pulse is dehydrating serpentinite in addition the dehydration pulse from subducted serpentinite is likely superimposed on a continuous dehydration signal provided by subducting oceanic crust which continues behind the volcanic front to slab depths 200 km the enhanced fluid contributions at the front produce higher degrees of wedge melting thus explaining the lower be contents of front samples there are two possible explanations of the lower 7li of many behind the front volcanic rocks from southeastern guatemala western el salvador selective loss of 7li during progressive dehydration of subducting cocos lithosphere or diffusive fractionation accompanying late stage selective crustal contamination since the slightly lower 7li of guatemalan volcanic rocks in general is consistent with a minor crustal overprint the second explanation is favored and could be relevant to the few subduction zones where lower li isotopic values characterize back arc regions light element variation across southeastern guatemala and western el salvador is consistent with the operation of decompression melting behind the volcanic front be zr ratios across the northern portion of the central american subduction zone may indicate some mobility of be

the boron isotopic evolution of the little three pegmatites ramona ca abstract tourmaline mica hambergite danburite and axinite from three pegmatite dikes named main swamp and spessartine at the little three mine near ramona california have been analyzed by secondary ion mass spectrometry sims for their boron isotopic compositions 11b tourmaline is the sole host of b in the massive footwall and hanging wall sections of the dikes and the principal sink for b in the miarolitic cavities in the thinner spessartine and swamp dikes the pocket mineralogy includes foitite spessartine muscovite axinite danburite and rare beryl the thicker main dike culminates in cavities containing topaz elbaite lepidolite boromuscovite hambergite and rare stibiotantalite values of 11btur from the little three pegmatites are strikingly heavy 0 1 to 13 8 compared to other pegmatitic tourmaline 27 to 9 which is best explained by inheritance from an 11b enriched source material such as altered oceanic crust flat patterns of 11btur from margin to core of each pegmatite attest to a negligible fractionation of boron isotopes between tourmaline granitic melt and granitic melt aqueous fluid tourmaline samples from intermediate zones and miarolitic cavities have identical boron isotopic compositions except for miarolitic cavities that contain axinite and danburite whose b is in 4 fold structural coordination in these cavities the 11b of tourmaline increases relative to tourmaline from the intermediate zone interpretations of 11btur from margin to core in these and other pegmatites are hampered by uncertainties in the boron isotopic fractionation factors for melt aqueous fluid and for tourmaline granitic melt based on modeled cooling and crystallization of these dikes the growth of tourmaline should have been fast relative to the diffusivity of b through granitic melt hence an equilibrium distribution of 11b and 10b between tourmaline bulk melt and an aqueous solution i e rayleigh fractionation process is unlikely the negligible isotopic fractionation of boron in tourmaline from margins to center therefore probably records only the bulk isotopic composition of the pegmatite forming melts

determination of 88sr 86sr mass dependent isotopic fractionation and radiogenic isotope variation of 87sr 86sr in the neoproterozoic doushantuo formation abstract we measured both mass dependent isotope fractionation of 88sr 88sr 86sr and radiogenic isotopic variation of sr 87sr 86sr for the neoproterozoic doushantuo formation that deposited as a cap carbonate immediately above the marinoan related nantuo tillite the 88sr and 87sr 86sr compositions showed three remarkable characteristics 1 high radiogenic 87sr 86sr values and gradual decrease in the 87sr 86sr ratios 2 anomalously low 88sr values at the lower part cap carbonate and 3 a clear correlation between 87sr 86sr and 88sr values these isotopic signatures can be explained by assuming an extreme greenhouse condition after the marinoan glaciation surface seawater mixed with a large amount of freshwater from continental crusts with high 87sr 86sr and lighter 88sr ratios was formed during the extreme global warming after the glacial event high atmospheric co2 content caused sudden precipitation of cap carbonate from the surface seawater with high 87sr 86sr and lighter 88sr ratios subsequently the mixing of the underlying seawater with unradiogenic sr isotope compositions and normal 88sr ratios probably caused gradual decrease of the 87sr 86sr ratios of the seawater and deposition of carbonate with normal 88sr ratios the combination of 87sr 86sr and 88sr isotope systematics gives us new insights on the surface evolution after the snowball earth

lithium in tektites and impact glasses implications for sources histories and large impacts abstract lithium li abundances and isotope compositions were determined in a representative suite of tektites moldavites muong nong type tektites and an australite ivory coast tektites and bediasites impact related glasses libyan desert glass zhamanshinites and irghizites a glass fragment embedded in the suevite from the ries impact crater and sedimentary materials in order to test a possible susceptibility of li to fractionation during hypervelocity impact events and to de convolve links to their potential parental sources the overall data show a large spread in li abundance 4 7 58 ppm li and 7 li values 3 2 to 26 0 but individual groups of tektites and impact glasses have distinctive li compositions most importantly any significant high temperature li isotope fractionation can be excluded by comparing sedimentary lithologies from central europe with moldavites instead we suggest that li isotope compositions in tektites and impact related glasses are probably diagnostic of the precursor materials and their pre impact geological histories the muong nong type tektites and australite specimen are identical in terms of li concentrations and 7 li and we tentatively endorse their common origin in a single impact event evidence for low temperature rayleigh fractionation which must have operated prior to impact induced melting and solidification is provided for a subset of muong nong type tektites although li isotope variations in most tektites are broadly similar to those of the upper continental crust libyan desert glass carries high 7 li 24 7 which appears to mirror the previous fluvial history of parental material that was perhaps deposited in lacustrine environment or coastal seawater lithium isotopes in impact related glasses from the zhamanshin crater define a group distinct from all other samples and point to melting of chemically less evolved mafic lithologies which is also consistent with their major and trace element patterns extreme shock pressures and the related extreme post shock temperatures alone appear not to have any effect on the li isotope systematics therefore useful information on parental lithologies and magmatic processes may be retrieved from analyses of martian and lunar meteorites moreover lack of significant li depletion in tektites provides further constraints on the loss of moderately volatile elements during the moon forming impact

isotopic approaches for quantifying the rates of marine burial diagenesis 1 diagenetic reactions in marine sediments have the potential to alter geochemical proxy records and affect the global carbon cycle over tens of thousands to millions of years this article describes advances in the use of ca sr and u series isotopes in constraining carbonate recrystallization and silicate dissolution rates in marine systems we specifically focus on recent efforts that interpret isotope variability in marine pore fluids using reactive transport models of varying complexity such studies suggest that calcite recrystallization rates are significant over time scales 1 myr approaching exchange rates of 0 4 1 myr 1 over longer time scales isotopic data point to continued exchange between calcite and coexisting pore fluid though at lower rates than in young sediments extrapolating these recrystallization rates over tens of millions of years we quantify the extent to which geochemical climate proxies such as mg ca in calcite can be altered diagenetically in some cases such diagenetic effects significantly affect the interpretation of long term climatic trends as well as determinations of absolute paleotemperatures silicate dissolution rates in siliclastic marine sediments appear to be similar in magnitude to dissolution rates in terrestrial environments 10 7 10 6 yr 1 such estimates suggest that silicate weathering in marine sediments may play an important role in the carbon cycle at least over time scales approaching 400 500 kyr

coupled lithium and iron isotope fractionation during magmatic differentiation abstract in this study we investigated fe and li isotope fractionation between mineral separates of olivine pheno and xenocrysts including one clinopyroxyene phenocryst and their basaltic hosts samples were collected from the canary islands teneriffa la palma and some german volcanic regions vogelsberg westerwald and hegau all investigated bulk samples fall in a tight range of li and fe isotope compositions 56 fe wr 0 06 0 17 and 7 li ma 2 5 5 2 assuming 7 li of the olivine free matrix is virtually identical to that of the bulk sample for mass balance reasons in contrast olivine phenocrysts display highly variable but generally light fe and mostly light li isotope compositions compared to their respective olivine free basaltic matrix which was considered to represent the melt with 56 fe ol 0 24 to 0 14 and 7 li ol 10 5 to 6 5 respectively single olivine crystals from one sample display even a larger range of 56 fe ol between 0 7 and 0 1 one single clinopyroxene phenocryst displays the lightest li isotope composition 7 li cpx 17 7 but no fe isotope fractionation relative to melt the olivine phenocrysts show variable mg and ni correlated in most cases that range between 0 89 and 0 74 and between 300 and 3000 g g respectively these olivines likely grew by fractional crystallization in an evolving magma one sample from the vogelsberg volcano contained olivine xenocrysts mg 0 89 and ni 3000 g g in addition to olivine phenocrysts this sample displays the highest li and the second highest fe isotope fractionation between olivine and melt 7 li ol melt 13 56 fe ol melt 0 29 our data i e the variable olivine at constant whole rock and matrix isotope compositions strongly indicate disequilibrium i e kinetic fe and li isotope fractionation between olivine and melt for li also between cpx and melt during fractional crystallization 7 li ol melt is correlated with the li partitioning between olivine and melt i e with li ol li melt indicating li isotope fractionation due to preferential faster diffusion of 6 li into olivine during fractional crystallization olivine with low 7 li ol melt also have low 56 fe ol melt indicating that fe isotope fractionation is also driven by diffusion of isotopically light fe into olivine potentially as fe mg inter diffusion the lowest 56 fe ol melt 0 40 was observed in a sample from westerwald germany with abundant magnetite indicating relatively oxidizing conditions during magma differentiation this may have enhanced equilibrium fe isotope fractionation between olivine and melt or fine dispersed magnetite in the basalt matrix may have shifted its fe isotope composition towards higher 56 fe the decoupling of li and fe isotope fractionation in cpx is likely due to faster diffusion of li relative to fe in cpx implying that the large investigated cpx phenocryst resided in the magma for only a short period of time which was sufficient for li but not for fe diffusion the absence of any equilibrium fe isotope fractionation between the investigated cpx phenocryst and its basaltic host may be related to the similar fe 3 fe 2 of cpx and melt in contrast to cpx the generally light fe isotope composition of all investigated olivine separates implies the existence of equilibrium in addition to diffusion driven isotope fractionation between olivine and melt on the order of 0 1

experimental quantification of the fractionation of fe isotopes during metal segregation from a silicate melt abstract fractionation of fe isotopes between a silicate melt and metallic alloys has been quantified experimentally at 1500 c the effects of oxygen fugacity and run duration have been investigated to distinguish between kinetic and equilibrium fractionations a new experimental setup is presented in which metallic fe is produced by reduction of oxidized iron from a silicate melt due to a change of redox conditions this metallic fe is physically removed from the silicate and sequestered as a pt fe alloy bulk analyses of the silicate and metallic fractions using multi collector icp ms methods are coupled with in situ analyses using an ion microprobe experimental results indicate that significant isotopic fractionation of fe occurs during metal segregation during the early stages of the experiments we find evidence for kinetic fractionation caused by faster diffusion of 54 fe along concentration gradients in the alloy this process leads to the formation of a metallic phase which is isotopically light compared to the residual silicate metal silicate fractionation up to 2 35 a m u the data are used to quantify the difference in diffusion coefficient of each isotope of iron providing a means to predict fe isotope fractionation during fe diffusion in metallic alloys on the other hand this state of affairs is transient in nature and at superliquidus temperature the systems rapidly reach a state of isotopic equilibrium in which the metal is isotopically heavier than the silicate melt by about 0 2 0 15 a m u these results are consistent with the range of variation observed in natural samples these kinetic and equilibrium data provide an experimental framework to understand the observed variability among igneous and meteoritic materials formed at high temperature particularly for iron and pallasite meteorites

multi mode li diffusion in natural zircons evidence for diffusion in the presence of step function concentration boundaries abstract micron to submicron scale observations of li distribution and li isotope composition profiles can be used to infer the mechanisms of li diffusion in natural zircon extreme fractionation 20 30 within each single crystal studied here confirms that li diffusion commonly occurs in zircon sharp li concentration gradients frequently seen in zircons suggest that the effective diffusivity of li is significantly slower than experimentally determined cherniak and watson 2010 trail et al 2016 otherwise the crystallization metamorphic heating of these zircons would have to be unrealistically fast years to tens of years charge coupling with ree and y has been suggested as a mechanism that may considerably reduce li diffusivity in zircon ushikubo et al 2008 bouvier et al 2012 we show that li diffused in the direction of decreasing li y ratio and increasing li concentration uphill diffusion in one of the zircons demonstrating charge coupling with ree and y quantitative modeling reveals that li may diffuse in at least two modes in natural zircons one being slow and possibly coupled with ree y and the other one being fast and not coupled with ree y the partitioning of li between these two modes during its diffusion may depend on the pre diffusion substitution mechanism of ree and y in the zircon lattice based on our results sharp li concentration gradients are not indicative of limited diffusion and can be preserved at temperatures 700 c on geologic timescales finally large 7 li variations observed in the hadean jack hills zircons may record kinetic fractionation rather than a record of ancient intense weathering in the granite source materials

high temperature silicon isotope geochemistry abstract silicon si is the defining element of silicate reservoirs yet despite its dominance in major earth processes there is still no clear understanding of how much is hosted in earth s core how the enriched continental crust forms or even if the crust is isotopically different from the mantle because of a long history of weathering erosion and subduction with the advent of multiple collector inductively coupled plasma mass spectrometry it has become relatively straightforward to explore small 100 ppm level mass dependent variations in si isotopic composition resulting from high temperature fractionation and to develop new isotopic fingerprints of magmatic processes and source regions this paper reviews the technique developments the new data and the veracity of current interpretations only a small si isotopic effect is associated with basalt formation via mantle melting however there now is compelling evidence based on a considerable number of samples 100 that the silicate earth is isotopically fractionated by 100 200 ppm per amu to a heavy composition relative to that of chondrites and also all differentiated stony meteorites this could reflect variability in the circumstellar disc but this is not well supported by data for enstatite chondrites which are isotopically light the most plausible current explanation is that si is a light element in earth s core and that differences in the bond stiffness between silicate and metal hosted si resulted in substantial fractionation interestingly the moon has the same si isotope composition as earth s mantle which is hard to explain unless the moon s atoms were mainly derived from earth differentiated magmatic sequences such as those of hekla iceland display a systematic relationship between isotopic composition and si content more complex magmatic suites such as i and s type granites reveal a range of isotopic compositions not well correlated with chemical composition similar effects are found in lower crustal granulite facies xenoliths nonetheless the overall composition of the continental crust is only slightly heavy relative to the mantle in fact the effect is barely resolvable therefore the amounts of surface dissolved heavy si removed to the mantle via weathering over time have been small or these losses have been balanced by subduction of isotopically light clay

arrested kinetic li isotope fractionation at the margin of the ilimaussaq complex south greenland evidence for open system processes during final cooling of peralkaline igneous rocks li contents li and isotopic composition 7 li of mafic minerals mainly amphibole and clinopyroxene from the alkaline to peralkaline ilimaussaq plutonic complex south greenland track the behavior of li and its isotopes during magmatic differentiation and final cooling of an alkaline igneous system li in amphibole increase from b10 ppm in caamphiboles of the least differentiated unit to n3000 ppm in na amphiboles of the highly evolved units in contrast li in clinopyroxene are comparatively low b85 ppm and do not vary systematically with differentiation the distribution of li between amphibole and pyroxene is controlled by the major element composition of the minerals ca rich and na rich respectively and changes in oxygen fugacity due to li incorporation via coupled substitution with ferric iron during magmatic differentiation 7 li values of all minerals span a wide range from 17 to 8 with the different intrusive units of the complex having distinct li isotopic systematics amphiboles which dominate the li budget of whole rocks from the inner part of the complex have constant 7 li of 1 8 2 2 2 n 15 this value reflects a homogeneous melt reservoir and is consistent with their mantle derivation in agreement with published o and nd isotopic data clinopyroxenes of these samples are consistently lighter with 7 liamph cpx as large as 8 and are thus not in li isotope equilibrium these low values probably reflect late stage diffusion of li into clinopyroxene during final cooling of the rocks thus enriching the clinopyroxene in 6 li at the margin of the complex 7 li in the syenites increases systematically from 2 to high values of 14 this coupled with the observed li isotope systematics of the granitic country rocks reflects post magmatic open system processes occurring during final cooling of the intrusion although the shape and magnitude of the li isotope and elemental profiles through syenite and country rock are suggestive of diffusion driven isotope fractionation they cannot be modeled by one dimensional diffusive transport and point to circulation of a fluid having a high 7 li value possibly seawater along the chilled contact in all this study

first principles investigations of equilibrium calcium isotope fractionation between clinopyroxene and ca doped orthopyroxene equilibrium fractionation factors of ca isotopes among mantle minerals are essential for using ca isotopes as an important tracer in mantle geochemistry using the vibrational frequencies obtained by the first principles calculations based on density functional theory dft we calculated equilibrium fractionation factors of ca isotopes between two major ca bearing minerals clinopyroxene cpx and orthopyroxene opx our results show that opx has much higher 44 ca 40 ca than its co existing cpx even at high temperatures e g 1273 k agreeing with the observations on mantle peridotites in addition to the wellknown temperature effect our calculations for the first time reveal that the inter mineral ca isotope fractionation factor between opx and cpx also has a strong dependence on the chemical composition of opx i e ca content specifically it increases substantially with decreasing ca mg atomic ratio of opx when ca mgopx is lower than 1 15 such compositional effect on inter mineral ca isotope fractionation provides a convincing interpretation to the different isotope fractionations between coexisting opx and cpx observed in kilbourne hole and san carlos peridotites 2014 elsevier ltd all rights reserved

multiple hydro fracturing by boron rich fluids in the late miocene contact aureole of eastern elba island tuscany italy in eastern elba island tuscany italy a shallow crustal level felsic tourmaline bearing dyke sill swarm of late miocene age is associated with abundant tourmaline quartz hydrothermal veins and metasomatic masses development of these veins and masses in the host rocks demonstrates multiple hydro fracturing by magmatic boron rich saline fluid tourmalines in felsic dykes are schorl whereas in veins and metasomatic masses tourmaline composition ranges from schorl dravite through dravite to uvite this compositional shift is evidence for an increasing contribution to the magmatic boron rich fluids by a mg ca ti rich external component represented by biotite rich and amphibolite host rocks this system can be envisaged as an exposed proxy of the high temperature hydrothermal system presently active in the deepest part of the larderello travale geothermal field tuscany

water enhanced interdiffusion of major elements between natural shoshonite and high k rhyolite melts abstract the interdiffusion of six major elements si ti fe mg ca k between natural shoshonite and a high k rhyolite vulcano island aeolian archipelago italy has been experimentally measured by the diffusion couple technique at 1200 c pressures from 50 to 500 mpa and water contents from 0 3 nominally dry to 2 wt the experiments were carried out in an internally heated pressure vessel and major element profiles were later acquired by electron probe microanalysis the concentration distance profiles are evaluated using a concentration dependent diffusivity approach effective binary diffusion coefficients for four intermediate silica contents are obtained by the sauer freise modified boltzmann matano method at the experimental temperature and pressures the diffusivity of all studied elements notably increases with dissolved h 2 o content particularly diffusion is up to 1 4 orders of magnitude faster in a melt containing 2 wt h 2 o than in nominally dry melts this effect is slightly enhanced in the more mafic compositions uphill diffusion was observed for al while all other elements can be described by the concept of effective binary interdiffusion ti is the slowest diffusing element through all experimental conditions and compositions followed by si fe mg ca and k diffuse at similar rates but always more rapidly than si and ti this trend suggests a strong coupling between melt components since effects of composition including water content are dominant a pressure effect on diffusion cannot be clearly resolved in the experimental pressure range

petrogenesis of the ultramafic zone of the stillwater complex in north america constraints from mineral chemistry and stable isotopes of li and o to investigate the petrogenesis of cyclic units in layered intrusions we examined chromitite dunite poikilitic harzburgite and bronzitite from the ultramafic zone of the stillwater complex and measured stable isotopes of li and o in their major minerals the li isotopes in olivine range from 4 to 26 in 7li with uniform li contents of 1 3 ppm whereas orthopyroxene and clinopyroxene have li contents of 0 5 5 ppm and 4 8 ppm and 7li ranges of 13 to 7 and 14 to 6 respectively the 18o values vary from 4 91 to 5 72 in olivine from 5 11 to 5 87 in orthopyroxene and from 4 64 to 5 86 in clinopyroxene for a given sample olivine displays more variable and higher 7li but lower 18o values than orthopyroxene indicating that olivine experienced more extensive compositional modification after crystallization relative to orthopyroxene the general li and o isotopic compositions are interpreted as the result of re equilibration between interstitial liquids from which pyroxenes crystallized and cumulus minerals the inter mineral and inter sample isotopic variations correlate with mineral assemblages crystal sizes and major and trace element compositions revealing that the interstitial liquids varied compositionally mainly due to mixing between fractionated magma and newly injected primitive magma abrupt mineralogical and geochemical changes from silicate rocks to chromitites imply that hydrous fluids which collected on chromite surfaces and were later released from chromite seams played an additional critical medium of chemical exchange between minerals in the chromitites

the behavior of li and b in lunar mare basalts during crystallization shock and thermal metamorphism implications for volatile element contents of martian basalts late stage rims of magmatic pyroxenes from some martian basalts show decreases in li and b contents relative to earlier formed pyroxene cores this behavior is different than expected from their documented incompatible element behavior previous workers interpreted such depletions to reflect the loss of several wt magmatic water during basalt crystallization this interpretation has profound implications for the nature of the martian mantle and recent exchange of volatiles between the martian mantle and atmosphere to assess alternative mechanisms that may influence the behavior of li and b in the absence of aqueous fluid activity the effects of changing pyroxene composition during crystallization shock pressure and shock associated thermal metamorphism were studied lithium and b depletions are documented in late stage rims of pyroxenes from anhydrous lunar basalts indicating that mechanisms other than aqueous fluid activity must have influenced li and b partitioning in these pyroxenes depletions of li and b are most likely associated with changing pyroxene composition during crystallization and occur in lunar and martian pyroxenes with late stage fe enrichment it is interesting that pyroxenes without late stage fe enrichment show no concomitant li and b increases lithium loss may occur during breakdown of metastable pyroxferroite additionally changes in cr content may influence the substitution mechanism involved for incorporating li shock does not redistribute li or b but may facilitate subsequent thermally driven diffusion by the introduction of mechanical defects in grains thermally metamorphosed pyroxenes exhibit higher li and lower b contents relative to unheated pyroxenes it is likely therefore that li and b are redistributed through interactions between pyroxenes and surrounding zones of mesostasis during thermal metamorphism

developments in the understanding and application of lithium isotopes in the earth and planetary sciences the significant relative mass difference c 16 between the two stable isotopes of li approximately 6li 7 5 7li 92 5 coupled with broad elemental dispersion in earth and planetary materials makes this a system of considerable interest in fingerprinting geochemical processes determining mass balances and in thermometry natural mass fractionation in this system is responsible for c 6 variation among materials examined to date fig 1 although the modern era of li isotope quantification has begun there are still many questions about the li isotopic compositions of fundamental materials and the nature of fractionation by important mechanisms that are unanswered e g hoefs 1997 figure 1 summary of lithium isotopic compositions of earth and planetary materials filled bars are solid samples open bars are liquids see text for references and details the purpose of this chapter is to summarize the current understanding of li isotopes in geo and cosmochemical systems and to indicate 1 where li isotopes have a high probability of adding new understanding of these systems 2 where some of the more significant deficits in knowledge exist the small but burgeoning li isotope community has not yet compiled the volume of peer reviewed literature needed to adequately assess even that which has been studied to date as a result significant portions of this chapter are based on data reported in abstracts and as such are more than normally subject to revisions over time this chapter is anticipated to serve as a starting point for those interested in research incorporating li isotope geochemistry or in understanding the state of extant research experiments in li isotope fractionation knowledge of significant li isotopic fractionation during basic chemical processes is long standing the early experiments by taylor and urey 1938 in which li isotopes were fractionated by incomplete extraction of an aqueous solution from a zeolite exchange

melt solidification and late stage evaporation in the evolution of a fun inclusion from the vigarano c3v chondrite vigarano 1623 5 is a forsterite bearing refractory inclusion in which oxygen magnesium and silicon show large degrees of mass dependent isotopic fractionation the core of 1623 5 consists of forsteritic olivine fassaite melilite ak89 and spinel all of which show isotopic mass fractionation averaging 30 6 amu for magnesium and 10 0 amu for silicon it is enclosed in a mantle consisting of aluminous melilite ak16 60 spinel perovskite and hibonite hibonite and spinel in the mantle are enriched in heavy isotopes of magnesium by 8 15 amu relative to the core 1623 5 originally formed by solidification of a magnesium rich melt the endemic isotopic mass fractionation may have been caused by evaporation of that melt or may reflect an earlier evaporation event affecting the reservoir from which the interior of 1623 5 formed later flash remelting of the outer part of the core and volatilization of sio2 and mgo from the melt so produced caused formation of a mantle that is in isotopic and petrologic disequilibrium with the core

exploring the effect of lithium on pegmatitic textures an experimental study the effect of lithium li on the development of pegmatitic textures was evaluated experimentally at h 2 o saturated and h 2 o undersaturated conditions at 500 mpa pressure and temperatures ranging from 400 to 800 c the addition of 3700 ppm li to a starting material of common granitic composition lake county obsidian reduces the crystallization and melting temperatures by approximately 50 70 and 200 c respectively and promotes the formation of quartz feldspar graphic and granophyric intergrowths the presence of li in the hydrous granitic system lowers significantly the degree of undercooling needed for the development of graphic and granophyric intergrowths to 85 110 c in comparison with the li free systems where approximately 200 c of undercooling is necessary the feldspar crystals developed in li bearing samples can incorporate from 150 to 250 ppm li assume skeletal and spherulitic morphologies and exhibit one order of magnitude faster growth rates than crystals in li free samples the results of this study attest to the effectiveness of li as a fluxing agent and highlight the crucial role it plays in the development of pegmatitic textures leading to important implications for the conditions of formation of li bearing granitic pegmatites

degassing crystallization and eruption dynamics at stromboli trace element and lithium isotopic evidence from 2003 ashes during its 1800 year long persistent activity the stromboli volcano has erupted a highly porphyritic hp volatile poor scoriaceous magma and a low porphyritic lp volatile rich pumiceous magma the hp magma is erupted during normal strombolian explosions and lava effusions while the lp one is related to more energetic paroxysms during the march april 2003 explosive activity stromboli ejected two typologies of juvenile glassy ashes namely highly vesicular lp shards and volatile poor hp shards their textural and in situ chemical characteristics are used to unravel mutual relationships between hp and lp magmas as well as magma dynamics within the shallow plumbing system the mantle normalized trace element patterns of both ash types show the typical arc lava pattern however hp glasses possess incompatible element concentrations higher than lp glasses along with sr and eu negative anomalies hp shards are generally characterized by higher li contents to 20 ppm and lower 7li values 1 2 to 3 8 with respect to lp shards li contents of 7 14 ppm and 7li ranging between 4 6 and 0 9 fractional crystallization models based on major and trace element compositions combined with a degassing model based on open system rayleigh distillation and on the assumption that melt fluiddli 1 show that abundant 30 plagioclase precipitation and variable degrees of degassing can lead the more primitive lp magma to evolve toward a differentiated isotopically lighter hp magma ponding in the upper conduit and undergoing slow continuous degassing induced crystallization this study also evidences that in march 2003 stromboli volcano poured out a small early volume of lp magma that traveled slower within the conduit with respect to later and larger volumes of fast ascending lp magma erupted during the april 5 paroxysm the different ascent rates and cooling rates of the two lp magma batches i e pre and post paroxysm resulted in small but detectable differences in their chemical signatures finally this study highlights the high potential of in situ investigations of juvenile glassy ashes in petrologic and geochemical monitoring the volcanic activity and of li isotopes as tracers of degassing processes within the shallow plumbing system

evolution of the oceanic calcium cycle during the late mesozoic evidence from δ44 40ca of marine skeletal carbonates abstract the ca isotope compositions of 37 late mesozoic skeletal carbonates belemnites and brachiopods from the tethyan realm were analyzed by thermal tims and plasma mc icp ms ionization mass spectrometry a poor correlation between 44 40 ca and 18 o values of belemnites suggests only a weak temperature dependency for the ca isotope composition of belemnites likely less than 0 02 c the 44 40 ca record of belemnites was therefore used to reconstruct the ca isotope composition of paleo seawater 44 40 ca sw based on an experimentally determined fractionation factor between seawater ca and belemnite calcite cc sw of 0 9986 the inferred 44 40 ca sw record with an average stratigraphic resolution of 1 ma shows systematic temporal variation of 0 5 with the middle late jurassic 154 ma minimum of 1 4 and a subsequent general increase to the early cretaceous 124 ma maximum of 1 9 the global nature of the 44 40 ca sw record is supported by identical ca isotope compositions of coeval kimmeridgian belemnites collected from two distinct paleogeographic regions the southern new zealand and northern germany margin of the tethys ocean the observed late mesozoic 44 40 ca sw record was simulated using a simple ca isotope mass balance model and the results indicate that the variation in 44 40 ca sw record can be explained by changes in oceanic input fluxes of ca that were independent of the carbonate ion fluxes such as the hydrothermal ca flux or the release of ca to the oceans via dolomitization of marine carbonates

geochemical precursors to volcanic activity at mount st helens usa the importance of the interplay between degassing and crystallization before and after the eruption of mount st helens washington usa in 1980 is well established here we show that degassing occurred over a period of decades to days before eruptions and that the manner of degassing as deduced from geochemical signatures within the magma was characteristic of the eruptive style trace element lithium and short lived radioactive isotope lead 210 and radium 226 data show that ascending magma stalled within the conduit leading to the accumulation of volatiles and the formation of lead 210 excesses which signals the presence of degassing magma at depth

silicon isotope fractionation during magmatic differentiation abstract the si isotopic composition of earth s mantle is thought to be homogeneous 30 si 0 29 0 08 2 s d and not greatly affected by partial melting and recycling previous analyses of evolved igneous material indicate that such rocks are isotopically heavy relative to the mantle to understand this variation it is necessary to investigate the degree of si isotopic fractionation that takes place during magmatic differentiation here we report si isotopic compositions of lavas from hekla volcano iceland which has formed in a region devoid of old geochemically diverse crust we show that si isotopic composition varies linearly as a function of silica content with more differentiated rocks possessing heavier isotopic compositions data for samples from the afar rift zone as well as various igneous usgs standards are collinear with the hekla trend providing evidence of a fundamental relationship between magmatic differentiation and si isotopes the effect of fractionation has been tested by studying cumulates from the skaergaard complex which show that olivine and pyroxene are isotopically light and plagioclase heavy relative to the si isotopic composition of the earth s mantle therefore si isotopes can be utilised to model the competing effects of mafic and felsic mineral fractionation in evolving silicate liquids and cumulates at an average sio 2 content of 60 wt the predicted 30 si value of the continental crust that should result from magmatic fractionation alone is 0 23 0 05 2 s e barely heavier than the mantle this is at most a maximum estimate as this does not take into account weathered material whose formation drives the products toward lighter 30 si values mass balance calculations suggest that removal of continental crust of this composition from the upper mantle will not affect the si isotopic composition of the mantle

astrophysics of cai formation as revealed by silicon isotope la mc icpms of an igneous cai silicon isotope ratios of a typical cai from the leoville carbonaceous chondrite obtained in situ by laser ablation mc icpms together with existing 25 mg 24 mg data reveal a detailed picture of the astrophysical setting of cai melting and subsequent heating models for the chemical and isotopic effects of evaporation of the molten cai are used to produce a univariant relationship between ph2 and time during melting the result shows that this cai was molten for a cumulative time of no more than 70 days and probably less than 15 days depending on temperature the object could have been molten for an integrated time of just a few hours if isotope ratio zoning was eliminated after melting by high subsolidus temperatures e g n1300 k for 500 yr in all cases subsolidus heating sufficient to produce diffusion limited isotope fractionation at the margin of the solidified cai is required these stable isotope data point to a two stage history for this igneous cai involving melting for a cumulative timescale of hours to months followed by subsolidus heating for years to hundreds of years the thermobarometric history deduced from combining si and mg isotope ratio data implicates thermal processing in the disk perhaps by passage through shockwaves following melting this study underscores the direct link between the meaning of stable isotope ratio zoning or lack thereof and the inferred astrophysical setting of melting and subsequent processing of cais 2007 elsevier b v all rights reserved

the effect of hydrothermal spring weathering processes and primary productivity on lithium isotopes lake myvatn iceland lithium isotopes are rapidly becoming one of the most useful tracers of silicate weathering processes but little is known on their behaviour in groundwaters and hydrothermal springs and how these sources might influence the weathering signal in surface waters this study presents lithium isotope compositions 7li for cold groundwaters 3 7 c and hydrothermal springs that were at geothermal temperatures 200 300 c but have cooled during transport 17 44 c both represent an important source of water and nutrients for lake myvatn iceland we also present a time series from the laxa river which is the single outflow from the lake the 7li values in the input springs to lake myvatn are highly variable 5 27 and correlate inversely with temperature and total dissolved solids these co variations imply that even in such waters the processes controlling 7li variations during weathering still operate that is the ratio of primary rock dissolution to secondary mineral formation where the latter preferentially incorporates 6li with a temperature dependent fractionation factor in high temperature geothermal waters 300 c secondary mineral formation is inhibited and has a low fractionation factor leading to little 7li fractionation even in waters that have cooled considerably over several months from their geothermal temperatures fractionation is still low and 7li values are similar to those reported from waters measured at 350 c in contrast cooler groundwaters promote relatively high proportions of clay formation which scavenge dissolved solids including 6li the time series on the laxa river the single outflow from lake myvatn shows little 7li variation with time over the 12 month sampling period 17 21 demonstrating that in contrast to tracers such as si isotopes li isotopes are unaffected by the significant seasonal phytoplankton blooms that occur in the lake thus these results clearly illustrate that li isotopes are ideally suited to constrain silicate weathering processes because fractionation by secondary mineral formation operates even when groundwater and hydrothermal inputs are significant and because li isotopes are demonstrably unaffected by phytoplankton or plant growth

limited lithium isotopic fractionation during progressive metamorphic dehydration in metapelites a case study from the onawa contact aureole maine the major trace element and li isotopic compositions of granodiorite and metapelites from the onawa pluton and surrounding contact aureole have been measured to document the behavior of li and its isotopes during progressive metamorphic dehydration major andtraceelementconcentrationsinmetapelitesofthecontactaureolechangelittle whilelossonignition loi decreaseswithincreasing metamorphic grade which ranges from regional chlorite zone metamorphism far removed from the pluton to partially melted rocks adjacent to the pluton lithium concentrations in metapelites from all zones correlate with loi and abundances of the main li bearing minerals chlorite biotite muscovite decreasing by a factor of two from 130 ppm far removed from the pluton to 64 ppm adjacent to thepluton incontrast liisotopiccompositionsremainrelativelyunchangedacrosstheaureole 7 li 3 5to 1 0 andarecomparable to the range observed in schists and unmetamorphosed shales compared to the surrounding metasediments the granodiorite has a lower li content 45 ppm and a comparable 7 li value of 0 2 similar to those of other granites and the average upper crust 0 2 these observations are consistent with the removal of li from metapelites via rayleigh distillation during progressive metamorphic dehydration with isotopic fractionation factors between fluids and rocks ranging between 1 001 and 1 004 these values are similar to thoseofarecentexperimentalstudyandproduceisotopicfractionationthatisbarelybeyondanalyticaluncertainty 1 fortheobserved degree ofli depletion the good correlationsbetweenli concentrations and loiwithmineralogicalabundancesreflecttheimportanceof mineralogyincontrollingliconcentrationsandisotopiccompositionsofmetamorphicrocks comparisonoftheseresultswiththosefrom a study of a contact halo around the tin mountain pegmatite suggests that the nature of the intrusion plays a critical role in controlling the behavior of li in country rocks large diffusive driven isotopic fractionation over a small scale is expected to occur when rocks are infiltrated by li rich magmatic fluids while metamorphic devolatilization results in minor isotopic fractionation on the aureole scale published by elsevier b v

precise determination of the isotopic composition of potassium application to terrestrial rocks and lunar soils we detail a method for the precise and accurate determination of isotopic variations in the 41k39k ratio with a precision of 0 5 2 m purified potassium is chemically extracted from rocks soils minerals or solutions by ion exchange chromatography complete chemical yields 99 8 are achieved in order to avoid laboratory induced isotopic fractionations the purified potassium is converted to a glass by melting with barium borate flux and the resultant bead is mounted for ion probe analysis the sims method utilized by the ion probe produces extremely stable k ion beams with no measurable temporal variability in the isotope ratio the instrumental fractionation is steady at about 4 and is corrected for by measurement of a standard the measurement of gravimetrically prepared isotopic standards indicates that the method is accurate at the stated level of precision and free of egregious errors analysis of terrestrial samples including peridotite basalts granites carbonatite biotite schists and seawater indicate the complete absence of isotopic variations in 41 1k among terrestrial materials at the 0 5 o level application to lunar soils and a regolith breccia confirms previously observed large isotopic fractionation effects garner et al 1975a church et al 1976 some lunar soils e g 14163 are shown to have large sample heterogeneity 7 o while others e g soils and a regolith breccia at several apollo 15 sites station 79 are homogeneous at the level of analytical precision the presence of potassium isotopic effects in bulk soils up to 12 7 in this study with magnitudes comparable to the rayleigh fractionation factor 25 indicates that volatility during micrometeorite impact melting played a large role in lunar regolith formation as much as 15 of the regolith potassium has been lost from the moon through the tenuous lunar atmosphere

combined fe mg chemical and isotopic zoning in olivine constraining magma mixing to eruption timescales for the continental arc volcano irazu costa rica and cr diffusion in olivine

a chemical and isotopic study of hibonite rich refractory inclusions in primitive meteorites the ion microprobe has been used to determine the concentrations of a number of trace elements including all 14 stable rare earth elements and the isotopic compositions of ca and mg in seven hibonite rich refractory inclusions hibonite in every inclusion analyzed shows the effect of ree partitioning with other solid or liquid phases in which hibonite is enriched in light over heavy ree compared to other coexisting phases this partitioning causes cl chondritenormalized enrichments to drop by factors of 4 to 22 from lanthanum to lutetium fractionations due to gas solid partitioning of ree are sometimes superimposed on the pattern produced by partitioning between condensed phases two inclusions hal and dh h1 show evidence for formation in extremely oxidizing environments and their ca is mass fractionated in favor of the heavy isotopes by 7 and 12 amu respectively two corundum hibonite inclusions show evidence of extremely high temperature gas solid fractionation such that the more volatile light ree are depleted as a group relative to the more refractory heavy ree these inclusions both have ca that is mass fractionated in favor of the light isotopes hibonite preserves the largest nuclear isotope anomalies in ti found to date faheyet al 1985a hintonel al 1987b but there does not seem to be a simple relationship between chemical composition isotopic mass fractionation and the sign and magnitude of nuclear isotopic anomalies in hibonite rich inclusions one possibility for producing a variety of chemical compositions and degrees of mass fractionation while preserving nuclear isotope anomalies is by multiple cycles of condensation and evaporation in a turbulent protoplanetary accretion disk morfill 1983 morfill and r n clayton 1986a b these cycles could also occur in a presolar nebula with large non axisymmetric temperature and pressure distributions boss 1988 nuclear anomalies are most likely to be preserved in hibonite because hibonite is the most refractory major phase to occur commonly in meteorites

high precision iron isotope measurements of terrestrial and lunar materials we present the analytical methods that have been developed for the first high precision fe isotope analyses that clearly identify naturally occurring mass dependent isotope fractionation a double spike approach is used which allows rigorous correction of instrumental mass fractionation based on 21 analyses of an ultra pure fe standard the external precision 1 sd for measuring the isotopic composition of fe is 0 14 mass for demonstrated reproducibility on samples this precision exceeds by at least an order of magnitude that of previous attempts to empirically control instrumentally produced mass fractionation dixon et al 1993 using the double spike method 15 terrestrial igneous rocks that range in composition from peridotite to rhyolite 5 high ti lunar basalts 5 fe mn nodules and a banded iron formation have been analyzed for their iron isotopic composition the terrestrial and lunar igneous rocks have the same isotopic compositions as the ultra pure fe standard providing a reference fe isotope composition for the earth and moon in contrast fe mn nodules and a sample of a banded iron formation have iron isotope compositions that vary over a relatively wide range from 56fe 0 9 to 1 2 this range is 15 times the analytical errors of our technique these natural isotopic fractionations are interpreted to reflect biological vital effects and illustrate the great potential fe isotope studies have for studying modern and ancient biological processes

the effect of chrysotile nanotubes on the serpentine fluid li isotopic fractionation we determined the lithium isotope fractionation between synthetic li bearing serpentine phases lizardite chrysotile antigorite and aqueous fluid in the p t range 0 2 4 0 gpa 200 500 c for experiments in the systems lizardite fluid and antigorite fluid 7li preferentially partitioned into the fluid and 7li values followed the t dependent fractionation of li bearing mica fluid wunder et al 2007 by contrast for chrysotile fluid experiments 7li weakly partitioned into chrysotile this contrasting behavior might be due to different li environments in the three serpentine varieties in lizardite and antigorite lithium is sixfold coordinated whereas in chrysotile lithium is incorporated in two ways octahedrally and as li bearing water cluster filling the nanotube cores low temperature ir spectroscopic measurements of chrysotile showed significant amounts of water whose freezing point was suppressed due to the li contents and the confined geometry of the fluid within the tubes the small inverse li isotopic fractionation for chrysotile fluid results from intra crystalline li isotope fractionation of octahedral li 6 with preference to 6li and lithium within the channels li ch of chrysotile favoring 7li the nanotubes of chrysotile possibly serve as important carrier of li and perhaps also of other fluid mobile elements in serpentinized oceanic crust this might explain higher li abundances for low t chrysotile bearing serpentinites relative to high t serpentinites isotopically heavy li bearing fluids of chrysotile nanotubes could be released at relatively shallow depths during subduction prior to complete chrysotile reactions to form antigorite during further subduction fluids produced during breakdown of serpentine phases will be depleted in 7li this behavior might explain some of the li isotopic heterogeneities observed for serpentinized peridotites

precise age determinations and petrogenetic studies using the kca method high precision mass spectrometric determination of calcium isotope ratios allows the 40k 40ca radioactive decay to be used for dating a much broader range of geologic materials than is suggested by previous work 40ca42ca is used to monitor enrichments in 40ca and can be measured to 0 01 2 using an exponential mass discrimination correction russell et al 1978 and large ion currents the earth s mantle has such a low kca 0 01 that it has retained primordial 40ca42ca 151 016 0 011 normalized to 42ca44ca 0 31221 as determined by measurements on two meteorites pyroxene from an ultramafic nodule metabasalt and carbonatite 40ca42ca ratios can be conveniently expressed relative to this value as ca in units of 10 4 to test the method for age dating a mineral isochron has been obtained on a sample of pikes peak granite which has been shown to have concordant k ar rb sr and u pb ages plagioclase k feldspar biotite and whole rock yield an age of 1041 32 m y 2 in agreement with previous age determinations k 0 5543 b y 1 k 0 8952 40k 0 01167 the initial 40ca42ca of 151 024 0 016 ca 0 5 1 0 indicates that assimilation of high k ca crust was insufficient to affect calcium isotopes measurements on two mica granite from eastern nevada indicate that the magma sources had k ca 1 similar to intermediate composition crustal rocks these results show that the k ca system can be used as a precise geochromometer for common felsic igneous and metamorphic rocks and may prove applicable to sedimentary rocks containing authigenic k minerals the relatively short half life of 40k the non volatile daughter and the fact that potassium and calcium are stoichiometric constituents of many minerals make the k ca system complementary to other dating methods and potentially applicable to a variety of geologic problems

modeling novel stable isotope ratios in the weathering zone when rock is converted to weathering products the involved processes can be fingerprinted using the stable isotope ratios of metals for example li mg ca fe sr and metalloids b si here we construct a framework for interpreting these novel stable isotope ratios quantitatively in the compartments of the weathering zone in a geomorphic context the approach is applicable to any novel stable isotope system and is based on a simple steady state mass balance model that represents the weathering zone from the scale of a soil column to that of entire continents our model is based on the assumption that the two main processes associated with isotope fractionation are formation of secondary precipitates such as clays and uptake of nutrients by plants the model results show that the isotope composition of a given element in the weathering zone compartments depends on 1 the ratio between the release flux to water through primary mineral dissolution and the erosion flux of isotopically fractionated solid material consisting of secondary precipitates and organic matter 2 the isotope fractionation factors associated with secondary mineral precipitation and uptake by plants a relationship is established between isotope ratios isotope fractionation factors and indexes for chemical weathering such as chemical depletion fractions cdf and elemental mass transfer coefficients derived from simple elemental concentration measurements from this relationship isotope fractionation factors can be calibrated from chemical and isotope data measured on field material furthermore we show how the ratio of solid export to dissolved export of a given element from the weathering system can be estimated from the comparison of the isotope composition between bedrock water and sediment this calculation can be applied to samples from soils from rivers and from the sedimentary record and does not require knowing the isotope fractionation factors involved in the reactions finally we apply the model to the oceanic li isotope record reconstructed from marine carbonate sediments in order to discuss changes in global geomorphic regimes through the cenozoic

effects of volatile behaviour on dome collapse and resultant pyroclastic surge dynamics gunung merapi 2010 eruption in 2010 gunung merapi central java indonesia generated two violent eruption sequences on 26 october and 5 november culminating in widespread pyroclastic density currents pdcs associated with the destruction of lava domes tephra from pdc deposits were analysed to examine pre dome collapse volatile behaviour and evidence of carbonate assimilation secondary ion mass spectroscopy sims depth profiles of plagioclase phenocrysts reveal that the 7 li 30 si ratios in 26 october products are higher in the glass compared to the crystal indicating a build up of li in the groundmass not observed in the 5 november samples higher li in the groundmass suggests gas accumulation and rapid development of conduit overpressure in the shallow plumbing system prior to the initial 26 october explosion which was only captured through the behaviour of quickly diffusing li and not h 2 o following the explosion induced decompression juvenile magma rapidly ascended in great volume to generate extremely destructive pdcs following subsequent dome collapses particularly on 5 november additionally 26 october tephras contain carbonate grains in the ash component and abundant co 2 within the lava lapilli groundmass glass which supports previous studies indicating assimilation of calc silicate lithologies by the merapi magma at depth in the plumbing system prior to the onset of 2010 activity

principles of regression and transgression the nature of the interplay between accommodation and sediment supply perspectives abstract the rate of change of accommodation at the shoreline a and the rate of sediment supply s are the primary factors controlling regression and transgression in the geological record or retreat and advance of a coastal depositional system the generally accepted notion here referred to as the a s ratio concept stating that the migration of a shoreline is controlled principally by the magnitude of the ratio of a to s is insufficient and somewhat misleading partly owing to the problem of dimensional confusion the interplay of a and s inevitably results in autoretreat of the shoreline whereby the seaward advance of any shoreline is halted and is subsequently turned to landward retreat provided there is a continuous rise of relative sea l vel how effective the autoretreat process is depends for a given period of relative sea level rising upon the length of potential time period for the seaward advance of shoreline and is proportional to a2 s and a1 5 s0 5 in two and three dimensional sediment dispersal modes respectively autoretreat becomes more effective as a increases and or s decreases a functions more critically to the effectiveness than s does the a s ratio concept is only approximately applicable when autoretreat is less effective i e with very low a and or very high s in this sense the autoretreat theory and the a s ratio concept are complementary to each other the autoretreat mechanism is expected to be substantially useful not only in fluvial deltas but also in many other depositional systems e g barrier islands whose evolution has been considered in terms of the a s ratio concept

intra and intercrystalline oxygen isotope variations in minerals from basalts and peridotites igneous phenocrysts commonly exhibit zoning in major and trace element composition reflecting and potentially constraining the differentiation and or mixing histories of their parent melts to date little work has been done characterizing zonation of oxygen isotopes in minerals from mafic and ultramafic rocks we present 259 ion probe cameca ims 1280 measurements of 18 o in 34 natural magmatic and mantle olivines and pyroxenes from five hand samples from diverse igneous environments we compare 18 o variations with zonation in other elements especially p analyzed by electron microprobe analysis empa and nano secondary ionization mass spectrometry nanosims there is generally a close average within 0 1 0 2 agreement between average 18 o values of olivines measured by sims standardized against san carlos olivine and independently known values for bulk separates from the same samples measured by laser fluorination these data demonstrate that current ion microprobe techniques are not only precise but also accurate enough for study of sub per mil oxygen isotope variations in silicates within 0 2 provided samples are prepared and analyzed following strict guidelines all but one of the 34 studied grains are homogeneous in 18 o within a small multiple of analytical precision estimated 0 2 1 for most data poorer for a subset of measurements made on small 5 m spots this population of isotopically homogeneous grains includes some with oscillatory micrometer scale p banding the lack of 18 o variations suggests that whatever factors lead to this common mode of trace element zonation have no detectable effect on melt crystal partitioning of oxygen isotopes large 2 oxygen isotope variations are observed in one olivine glomerocryst from mauna kea hawaii this glomerocryst contains p rich domains that are either equant or skeletal or feathery in outline and these p rich domains are systematically low in 18 o compared with adjacent later grown p poor olivine this unusual oxygen isotope zonation pattern might reflect a kinetic fractionation during nucleation and growth of the cores of some olivine phenocrysts we tested this hypothesis through measurements of 18 o distributions in synthetic olivines grown at a range of rates and exhibiting diverse patterns of p zoning these synthetic olivines are homogeneous in 18 o within the limits of our analyses 0 3 0 4 in this case and show no connection between p zonation and oxygen isotope heterogeneity we therefore think it more plausible that unusual o isotope zonation in the mauna kea glomerocryst reflects addition of a low 18 o component to some hawaiian magmas just before nucleation of olivine more generally this study demonstrates the utility of modern sims techniques for in situ study of the subtle 1 range oxygen isotope variations characteristic of common mafic and ultramafic rocks

isotope fractionation by chemical diffusion between molten basalt and rhyolite abstract experimental diffusion couples were used to study chemical diffusion between molten rhyolite and basalt with special emphasis on the associated fractionation of calcium and lithium isotopes diffusion couples were made by juxtaposing firmly packed powders of a natural basalt suny morb and a natural rhyolite lake county obsidian and then annealing them in a piston cylinder apparatus for times ranging from 0 1 to 15 7 h temperatures of 1350 1450 c and pressures of 1 2 1 3 gpa profiles of the major elements and many trace elements were measured on the recovered quenched glasses the diffusivities of all elements except lithium were found to be remarkably similar while the diffusivity of lithium was two to three orders of magnitude larger than that of any of the other elements measured chemical diffusion of calcium from molten basalt into rhyolite was driven by a concentration ratio of 18 and produced a fractionation of 44ca from 40ca of about 6 because of the relatively low concentration of lithium in the natural starting materials a small amount of spodumene lialsi2o6 was added to the basalt in order to increase the concentration difference between basalt and rhyolite which was expected to increase the magnitude of diffusive isotopic fractionation of lithium the concentration ratio between li doped basalt and natural rhyolite was 15 and the resulting diffusion of lithium into the rhyolite fractionated 7li from 6li by about 40 we anticipate that several other major rock forming elements such as magnesium iron and potassium will also exhibit similarly larger isotopic fractionation whenever they diffuse between natural melts with sufficiently large differences in the abundance of these elements

fassaite composition trends during crystallization of allende type b refractory inclusion melts fassaite is a major phase in type b refractory inclusions and its wide compositional variability makes it an excellent recorder of crystallization induced changes in liquid composition traverses across zoned crystals with electron and ion microprobes show that ti v sc zr and hf decrease from core to rim while mg si rees and other trace elements increase fassaite liquid distribution coefficients derived from the compositions of early fassaite and calculated parent liquid compositions are higher than previously reported fassaite ds e g 0 2 0 8 vs 0 08 0 5 for the trivalent rees possibly due to the high ti and al contents of the fassaite we analyzed log log plots of concentrations of elements vs those of sc give linear relationships with slopes of dixl l 1 dscxl l 1 where dixl l is the bulk crystal liquid distribution coefficient for element i from this relationship we derive effective fassaite liquid ds of 2 8 for sc 1 5 for hf 1 1 for zr 0 52 for y 0 34 for ta 0 29 for nb and 0 31 0 48 for trivalent rees the effective ds are applicable to fassaite crystallizing from melts having the compositions and thermal histories of allende type b refractory inclusions and incorporate any equilibrium and kinetic effects that modify ds during the course of crystallization observed fassaite ree contents can be reproduced by a fractional crystallization model in which the effective ds are used ti3 is more compatible in fassaite than ti4 and without equilibration of the residual liquid with an external reducing gas ti3 titot ratios where titot ti3 ti4 should decrease from core to rim in fassaite crystals comparison of profiles of ti3 titot ratios in several crystals with those calculated for fractional crystallization suggests that the trend in one crystal was controlled by fractional crystallization alone but in two others the virtually constant ti3 titot ratios may imply that the liquids in these inclusions were able to maintain equilibrium with the solar nebular gas throughout crystallization attempts to determine the o2 of fassaite crystallization on the basis of ti3 titot ratios must be based on fassaite grains which are not zoned with respect to ti3 titot the range of observed ree abundances in subliquidus fassaite 7 800 cl for la and 30 2000 cl for lu now encompasses those in grains previously identified as relict removing a major reason for their identification as such rounded fassaite grains with fairly sharp mg rich rims and ti rich cores poikilitically enclosed in mantle melilite in ts34 are candidates for relict grains the grains are so scrich that they would require extreme prior crystallization of spinel and melilite which is inconsistent with their very low ree contents e g la at 3 7 cl we suggest that the cores of these grains are relict and were trapped with liquid during formation of the mantle

refractory inclusions in the prototypical cm chondrite mighei abstract refractory inclusions in the mighei cm2 meteorite are very abundant 35 being found in three thin sections of the meteorite the most common are pyroxene rimmed spinel rich inclusions that occur in a range of structural and textural types some inclusions are simple aggregates of crystals or rimmed crystals ranging from loose clusters of spinel grains to distended chains of pyroxene rimmed spinel knots others are more compact and may have experienced recrystallization or melting these include nodular spinel inclusions with polygonal granular textured spinel interiors and pyroxene rims ribbons of spinel in some cases with hibonite and or perovskite that are again rimmed by pyroxene and refractory spherules four inclusions are complex aggregates of several texturally distinct objects each collectively mighei inclusions are similar to those in murchison but appear to be somewhat more altered volatility fractionated and unfractionated trace element patterns similar to those found in refractory inclusions in other carbonaceous chondrites are represented in mighei inclusions and in addition some mighei inclusions have volatility fractionated pattern types not previously found in refractory inclusions in three of the complex aggregates fundamentally different trace element patterns are present within different portions of each inclusion meaning that these objects accreted from genetically different components that never equilibrated with one another subsequent to accretion bulk inclusion magnesium isotopic compositions show minor mass fractionation effects fmg values range from 2 3 to 7 5 but the average fmg value is indistinguishable from normal 1 8 1 2 there are no correlations between magnesium isotopic composition and textural type or trace element pattern type the diverse inclusion types in mighei represent a variety of origins and histories textures suggest that the nodular and banded inclusions may have experienced solid state recrystallization whereas the porous and chain like varieties and complex aggregates have not magnesium isotopic compositions and trace element abundances suggest that the mighei inclusions are unlikely to be evaporation residues and are more likely to be the products of condensation or recondensation processes

diffusion obstacles and opportunities in petrochronology many of the approaches in petrochronology are rooted in the assumption of equilibrium diffusion is an expression of disequilibrium the movement of mass in response to chemical potential gradients and isotopes in response to isotopic gradients it is extremely important that we be aware of how the effects of diffusion can place obstacles across our path towards petrochronologic enlightenment conversely the effects of diffusion also provide opportunities for understanding rates processes and conditions experienced by rocks the enormity of the field does not permit us to provide a comprehensive review of either the mathematics of diffusion or quantitative data that have been obtained relevant to the interpretation of diffusive processes in rocks and minerals many resources cover these topics including rimg volume 72 diffusion in minerals and melts zhang and cherniak 2010 and several textbooks crank 1975 glicksman 2000 particularly relevant to the discussion of petrochronology are summaries of the theory and controls on diffusion brady and cherniak 2010 zhang 2010 as well as diffusion rates in feldspar cherniak 2010a accessory minerals cherniak 2010b garnet ganguly 2010 mica pyroxene and amphibole cherniak and dimanov 2010 and melts zhang and ni 2010 zhang et al 2010 rather than duplicate that material our goal is to explore the obstacles and opportunities presented by the effects of diffusion as they inform the rates of petrologic processes to achieve this goal we emphasize key principles and illustrative examples quantitative interpretation of the effects of diffusion assumes predictability of numerous factors that may affect chemical or isotopic transport including temperature initial and boundary conditions water and oxygen fugacities activities of other components multiple mechanisms of diffusion and crystal chemistry coupling of the substitution of elements into different crystallographic sites additionally the extraction of meaningful ages durations of events and temperatures requires

biological control of calcium isotopic abundances in the global calcium cycle measurements of 44ca 40ca expressed as 44ca were made on igneous rocks and on shell and bone material from modern organisms to investigate the magnitude and origins of calcium isotopic fractionation in nature the results document a span of 4 in 44ca measured with the double spike technique to a precision of 0 15 volcanic rocks including basalt and rhyolite show little variability and cluster near 44ca 0 0 2 systematic analysis of biological samples indicates that biological processing of calcium discriminates against heavy isotopes and that biological fractionation is the primary generator of calcium isotopic fractionation in nature preliminary data suggest that calcium becomes isotopically lighter as it moves through food chains calcium carbonate shells of marine microorganisms and deep sea carbonate ooze have 44ca about 1 0 lower than seawater this fractionation causes seawater to be enriched in heavy calcium 44ca 0 9 relative to igneous rocks marine organisms consequently are isotopically heavier than their terrestrial counterparts at similar trophic level the calcium isotopic composition of living and fossil organisms may record information on diet and environment

calcium isotopes in igneous rocks and the origin of granite abstract the k ca radioactive parent daughter system provides a tool for tracing the origins of igneous rocks it is complementary to other isotopic systems because as stoichiometric constituents of major minerals the concentrations of k and ca and the k ca ratio in rocks are simply related to mineralogy in this paper we report the first high precision calcium isotopic analyses of continental granitic rocks island arc rocks and mid ocean ridge basalts these data show that mid ocean ridge basalts have the low 40 ca 42 ca ratios expected for the earth s mantle but that island arc rocks have slightly higher 40 ca 42 ca ratios indicative of crustal calcium in their magma sources many granitic rocks have high initial 40 ca 42 ca ratios and in conjunction with independent evidence for the age of the crustal sources these ratios provide constraints on the k ca ratios and in turn on the silica contents and residual mineralogy of the deep crustal magma sources