vegetation and fire history during the last 30 000 years based on phytolith and macroscopic charcoal records in the eastern and western areas of aso volcano japan abstract vegetation and fire history during the last 30 000 years has been reconstructed using phytolith and macroscopic charcoal records obtained from two tephra sections around aso caldera southwestern japan phytolith assemblages from both sites revealed that grassland vegetation dominated by gramineae consistently occurred for more than 30 000 years prior to 13 5 ka vegetation both east and west of aso caldera was composed mainly of sasa cool temperate dwarf bamboo although the vegetation east of the caldera considerably declined by intense volcanic activity between 30 and 13 5 ka in the holocene miscanthus pampas grass grassland was established and continued consistently to the present in the eastern area whereas sasa and pleioblastus warm temperate dwarf bamboo grassland has existed in the western area of the volcano the difference of grassland vegetation transition in the holocene between the eastern and western regions can be explained as difference of fire regime between both areas inferred from macroscopic charcoal records prior to 13 5 ka fire activity was infrequent east of aso caldera whereas fire events moderately occurred west of the caldera fire frequency in the eastern region rose abruptly at 13 5 ka and fire activity was most frequent in the last 5 ka while holocene fire frequency in the western area was similar to that of 32 30 ka the consistent presence of miscanthus grassland in combination with high fire activity east of aso caldera after 13 5 ka suggests that the miscanthus grassland was attributed to burning as a consequence of anthropogenic activities

gold speciation and transport in geological fluids insights from experiments and physical chemical modelling this contribution provides an overview of available experimental thermodynamic and molecular data on au aqueous speciation solubility and partitioning in major types of geological fluids in the earth s crust from low temperature aqueous solution to supercritical hydrothermal magmatic fluids vapours and silicate melts critical revisions of these data allow generation of a set of thermodynamic properties of the auoh aucl 2 auhs and au hs 2 complexes dominant in aqueous hydrothermal solutions however other complexes involving different sulphur forms chloride and alkali metals may operate in high temperature sulphur rich fluids vapours and melts the large affinity of au for reduced sulphur is responsible for au enrichment in s rich vapours and sulphide melts which are important gold sources for hydrothermal deposits thermo dynamic speciation and partitioning data and their comparison with au and s contents in natural fluid inclusions from magmatic hydrothermal gold deposits provide new constraints on the major physical chemical parameters temperature pressure salinity acidity redox and ubiquitous fluid components sulphur carbon dioxide arsenic affecting au concentration transport precipitation and fractionation from other metals in the crust the availability and speciation of sulphur and their changes with the fluid and melt evolution are the key factors controlling gold behaviour in most geological situations

zircon petrochronology reveals the temporal link between porphyry systems and the magmatic evolution of their hidden plutonic roots the eocene coroccohuayco deposit peru abstract we present zircon geochronologic la icpms and id tims trace element and hf isotopic evidence for a complex evolution of the plutonic roots of the eocene coroccohuayco porphyry system southern peru la icpms u pb dating has initially been carried out to optimize grain selection for subsequent high precision id tims dating and to characterize crustal assimilation xenocrystic cores this combined in situ and whole grain u pb dating of the same grains has been further exploited to derive a robust temporal interpretation of the complex magmatic system associated with the coroccohuayco porphyry skarn deposit our data reveal that a heterogeneous gabbrodioritic complex was emplaced at ca 40 4 ma and was followed by a nearly 5 ma long magmatic lull until the emplacement of dacitic porphyry stocks and dykes associated with the mineralizing event at ca 35 6 ma however at the sample scale zircons from the porphyries provide insight into a 2 ma long lived hidden magmatism probably at 4 9 km paleodepth prior to porphyry intrusion and mineralization for which no other evidence can be found on the surface today these dates together with zircon trace element analysis and hf isotopes argue for the development of a long lived magmatic system dominated by amphibole fractionation with an increasing amount of crustal assimilation and the development of a large and sustained thermal anomaly the system was probably rejuvenated at an increasing rate from 37 5 to 35 6 ma with injection of fresh and oxidized magma from the lower crust which caused cannibalism and remelting of proto plutons the porphyry intrusions at coroccohuayco were emplaced at the peak thermal conditions of this upper crustal magma chamber which subsequently cooled and expelled ore fluids zircon xenocrysts and hf isotopes in the porphyritic rocks suggest that this large upper crustal system evolved at stratigraphic levels corresponding to triassic sediments similar to the mitu group that may be present below the district using the zircon ce anomaly as a proxy for oxidation state of the magma through time we show that the high oxidation state of the porphyries is not the result of upper crustal processes but is rather controlled by magmatic processes occurring at deeper levels a comparison of our data with available high precision geochronologic data at other porphyry systems suggests that such deposits may form when injection rate volume and heat of their long lived upper crustal magmatic system reach their peaks these features might be diagnostic of a productive deposit

siderophile interelement variations in the cretaceous tertiary boundary sediments from caravaca spain a detailed profile of the siderophiles fe co ni pd re os ir pt and au from the cretaceous tertiary boundary at caravaca spain indicates that the major fractionation mechanisms are local redistribution reworking and diagenetic mobilization large fractions of the fe co and re and perhaps a small amount of pd and au appear to be terrestrially derived but nearly all of the ni os ir and pt must be derived from an extraterrestrial source only the basal layers at caravaca and stevns klint denmark are representative of the initial fallout and integrated ir fluences across entire sections can be misleading these suggest a concentration oft 120mg g projectile in the fallout and a global fluence of chondritic matter oft 140mg cm 2

the fate of magmatic sulfides during intrusion or eruption bingham and tintic districts utah magmatic sulfides in 97 samples of volcanic and intrusive rocks from the tertiary bingham cu au mo and tintic ag pb zn cu au districts utah were examined to help better understand the fate of magmatic sulfides during intrusion and eruption our findings show that shallowly emplaced dikes and sills have erratic but locally high concentrations of sulfides volcanic rocks and large porphyry intrusions from these districts typically have at least two orders of magnitude fewer sulfides than the dikes sulfide concentrations vary dramatically across these dikes and sills for example in one sill in castro gulch bingham district sulfide abundance increases from 9 ppm by volume in the center to more than 2 000 ppm near the margin chalcophile metals show corresponding changes in abundance for example the whole rock copper content of the sill ranges from 23 ppm in the center to 35 ppm along the margins the textures of sulfide grains interpreted to reflect recrystallization resorption and degassing even in the most sulfide rich samples commonly have been modified suggesting that no sample preserves all of its original magmatic sulfide content immiscible liquids of monosulfide solid solution crystallized as pyrrhotite pyrrhotite and chalcopyrite or pyrite and chalcopyrite with declining temperature and pressure these locally recrystallized to pyrite and chalcopyrite or to pyrite and an fe oxide as they are oxidized the alteration and preservation textures change from subspherical sulfide blebs near the margins of dikes and sills to partially altered sulfides farther in to complete absence of sulfides in the vast majority of intrusions except where small sulfides are completely enclosed by phenocrysts sulfide concentrations appear to vary according to cooling rate and inferred pressure at the time of quenching or crystallization of the matrix most of the sulfides along the quenched margins of these dikes and sills are in the matrix slower cooling coupled with removal of magmatic volatiles including sulfurous gases e g h2s so2 allows the resorption or oxidation of magmatic sulfides to occur during final crystallization of a magma together these processes remove greater than 90 percent of the original endowment of magmatic sulfides this probably explains the low magmatic sulfide abundances of slowly cooled large porphyritic intrusions and most importantly allows metals and sulfur to participate in the formation of porphyry deposits the relative abundances of base metals lost from the center of the sill are similar to the relative abundances of the metals in the bingham deposit production and reserves suggesting that these processes also may have operated at a larger scale

magmatic sulphides in quaternary ecuadorian arc magmas abstract new petrographic and geochemical data on magmatic sulphide inclusions msis are presented and discussed for 15 quaternary volcanic centers of the ecuadorian frontal main and back volcanic arc msis occur mostly in fe ti oxides magnetite and or magnetite ilmenite pair and to a lesser extent in silicate minerals amphibole plagioclase and pyroxene msis are present in all volcanic centers ranging in composition from basalt to dacite sio2 50 67 wt indicating that sulphide saturation occurs at various stages of magmatic evolution and independently from the volcano location along the volcanic arc msis also occur in dioritic gabbroic and hornblenditic magmatic enclaves of the volcanic rocks msis display variable sizes 1 30 m and shapes globular ellipsoidal angular irregular and occur mostly as polymineralic inclusions composed of fe rich and cu poor pyrrhotite and cu rich mostly chalcopyrite phases aerial sulphide relative abundances range from 0 3 to 7 ppm in volcanic host rocks and from 13 to 24 ppm in magmatic enclaves electron microprobe analyses of msis indicate maximum metal contents of cu 65 7 wt fe 65 2 wt ni 10 1 wt for those hosted in the volcanic rocks and of cu 57 7 wt fe 60 9 wt ni 5 1 wt for those hosted in magmatic enclaves relationships of the sulphide chemistry to the host whole rock chemistry show that with magmatic differentiation e g increasing sio2 the cu and ni content of sulphides decrease whereas the fe and s contents increase the opposite behavior is observed with the increase of cu in the whole rock because the latter is anti correlated with the sio2 whole rock content laser ablation icp ms analyses of msis returned maximum values of pges and noble metals of pd 30 ppm rh 8 1 ppm ag 92 8 ppm and au 0 6 ppm and pd 43 ppm rh 22 6 ppm ag 89 ppm and au 1 ppm for those hosted in volcanic rocks and magmatic enclaves respectively these pge contents display a different range of values with respect to those in previously investigated magmatic sulphides msis that are cu and pge cu rich are found in less evolved rocks i e lower sio2 contents that also display a lower amount of sulphide inclusions cu rich sulphide phases chalcopyrite bornite are mostly hosted by magnetite whereas pge rich ones consist of a cu poor phase pyrrhotite hosted by plagioclase however no systematic changes in the chemistry of the host silicate mineral are observed in coincidence with the occurrence of msis we use the results of our study to draw some implications on cu and other chalcophile elements behavior during arc magmatic processes potentially associated with the formation of porphyry type deposits

ru ir ratios at the cretaceous tertiary boundary implications for pge source and fractionation within the ejecta cloud abstract ruthenium and ir are the least mobile platinum group elements pges within the cretaceous tertiary k t boundary clay the ru ir ratio is therefore the most useful pge interelement parameter for distinguishing terrestrial and extraterrestrial contributions to the boundary clay the ru ir ratio of european marine k t sections 1 67 0 38 is statistically different from that of the north american continental sections 0 76 0 26 it is unlikely that this difference is due to secondary pge remobilization pge input to the boundary clay during multiple impacts or volcanic emissions the global difference in ru ir ratios in the boundary clay may therefore be primary the positive correlation between distance from the chicxulub impact structure yucatan mexico and ru ir ratio and the more than 1000 c difference in the condensation temperatures of these elements lead us to propose that fractionation of ru from ir during condensation from the ejecta cloud may have occurred resulting in the global difference in ru ir ratios

skarn metallogeny through zircon record an example from the daye cu au fe mo district eastern china abstract the daye district in eastern china hosts more than 50 fe cu au mo porphyry skarn deposits that are associated with intermediate to felsic rocks of early cretaceous ages the origin of these ore related granitoids has been intensively investigated but the petrogenetic factors controlling variable metal associations e g fe cu mo or cu au fe in different skarn deposits remain not well understood here we present hf isotope and trace element data of zircons from ore related intrusions of four representative skarn deposits i e the lingxiang and chengchao fe skarn the tonglushan cu au fe skarn and the tongshankou cu mo porphyry skarn deposits to better understand controls of the source oxidation state and fractionation degree of the magmas on the polymetallic metallogeny in the daye district zircons from the ore related granodiorite at tongshankou quartz diorite at tonglushan and diorite at lingxiang have comparable ehf t values ranging from 11 3 to 1 1 which are similar to values of the early cretaceous mafic rocks ehf t 11 9 to 1 2 in the daye district and adjacent areas this similarity suggests that these ore related intrusions were largely derived from an enriched lithospheric mantle source in comparison zircons from the ore related diorite and quartz monzonite associated with the chengchao fe skarn have much lower ehf t values 11 6 to 25 3 indicating larger degrees of crustal contribution on average zircons from the cu related intrusions at tongshankou and tonglushan have higher ce ce 1100 method of zhong et al 2019 and ce4 ce3 170 method of ballard et al 2002 ratios which are interpreted reflecting higher oxidation state for the magmas in contrast zircons from fe related intrusions at chengchao and lingxiang have much lower average values of ce ce preliminary results presented here further reveal that zircon eu eu ratio can be a useful discrimination for intrusions associated with the various metal associations in the daye district zircon eu eu of 0 45 broadly separates the fe skarns and cu bearing skarns while eu eu of 0 65 can further distinguish the cu au fe skarn from the cu mo variety this study highlights zircon chemistry as a useful indicator for the nature evolution and metallogeny of the ore related intrusions

heat flow and thermal history of the anadarko basin and the western oklahoma platform abstract the average geothermal gradient in the anadarko basin and the oklahoma platform estimated from 856 corrected bottom hole temperatures bhts is 21 c km analysis of previously published thermal maturation data indicates that the anadarko basin has undergone from 1 to 3 km of erosion starting about 40 to 50 ma the average thermal gradient at the time of maximum burial was in the range of 22 to 25 c km there is no evidence that the thermal state of the anadarko basin has changed significantly since the late paleozoic 250 ma to estimate heat flow in the anadarko basin and the oklahoma platform we made 652 thermal conductivity measurements on drill cuttings from 9 oil and gas wells all measurements were corrected for the effects of anisotropy temperature and porosity matrix conductivities perpendicular to bedding at 22 c range from 1 7 w m 1 k 1 for permian age sandstone and shale to 2 6 w m 1 k 1 for devonian silurian age limestone and shale in situ thermal conductivities vary from 1 3 w m 1 k 1 to 1 9 w m 1 k 1 estimated heat flow 20 ranges from 30 mw m2 to 42 mw m2 with a mean of 36 mw m2 we found no evidence for heat flow to increase significantly from the anadarko basin in the south to the oklahoma platform to the north these results contradict a previous study which found heat flow increases from south to north with heat flow in the oklahoma platform as much as 50 greater than heat flow in the anadarko basin at the present time we do not know if these differences are related to spatial variations or reflect methodological errors if our results are averaged with those reported in previous work mean heat flows in the anadarko basin and oklahoma platform are 39 mw m2 and 51 mw m2 respectively

siderophile rich particles in the melt rocks at the e clearwater impact structure quebec their characteristics and relationship to the impacting body the composition of the sampled melt rocks at the 22 km diameter e clearwater impact structure indicates the presence of 8 c 1 material the meteoritic component is fractionated with refractory siderophiles up to 30 times c 1 abundances concentrated in ten to hundred micron sized magnetic particles these particles consist of the ni sulphide millerite and what is assumed to be a mixture of refractory silicates and magnetite with grain sizes of 1 m the larger particles have a core rim structure with millerite and occasionally very minor galena and possibly pentlandite in the core an origin as a combination of altered meteoritic metal and condensed meteoritic silicate is favored for the origin of the siderophile rich particles if 8 meteoritic material is taken as the average meteoritic contamination in the melt then the e clearwater projectile may have impacted with a velocity of 17 km s 1 peak shock pressures would have been of the order of 300 gpa sufficient to vaporize the silicate component but only melt the metal component of the projectile as the meteoritic material was being driven down into vaporized melted target rocks during the initial stages of impact the melted fe ni metal underwent oxidation fe was removed and meteoritic silicate material recondensed on the cooler essentially ni metal as cavity excavation proceeded these ni metal silicate oxide particles were incorporated in the melt their refractory nature prevented thermal digestion and sulphur in the melt reacted with the metal to produce millerite on final equilibration if this hypothesis is correct it suggests that the e clearwater projectile was a c 2 or c 3 chondrite both of which are compatible with the trace element composition of the melt rocks clearwater lake is a twin impact structure formed by an asteroid pair it is still not clear however what type of projectile formed the 32 km diameter western structure where the surface melt rocks contain no identifiable meteoritic signature

the role of magmatic sulfides and mafic alkaline magmas in the bingham and tintic mining districts utah this paper reports the existence of abundant magmatic sulfides in introduction latite lava vitrophyres and vent facies dikes from the bingham and the eruption of sulfur rich magmas from el chichon tintic districts in central utah these dikes and flows appear to luhr et al 1984 and mt pinatubo westrich gerlach be comagmatic with the ore related monzonite intrusions in addition 1992 in recent years has attracted attention to the limited analytical data suggest that the magmatic sulfides contain most of solubility of sulfur in intermediate magmas and the factors the cu and ag present in the latites magmatic sulfides are preserved potentially responsible for the formation of magmatic only in the least oxidized and least degassed lavas and vitrophyres sulfides and anhydrite however the occurrence of magpetrography of comagmatic dikes and intrusions suggests that matic sulfides in intermediate magmas is not universal resorption and oxidation s degassing of the globules may make many volcanic suites appear to be sulfide unsaturated the metal content available to a magmatic ore fluid minette and inasmuch as magmatic sulfides may sequester chalcophile shoshonite lavas occur in subordinate amounts in the latitic volcanic metals what would their presence signify in magmatic fields associated with latite monzonite intrusions and hydrothermal systems that formed porphyry cu and mesothermal vein ore deposits of the tintic ag pb zn cu au and bingham deposits do they sequester a significant portion of the porphyry cu au mo districts utah the ages chemical and magmatic cu pb zn ag and au thereby restricting modal compositions and field relations of the mafic alkaline lavas metal availability of subsequent ore forming fluids suggest that such magmas mixed and fractionated at shallow crustal we have examined the volcanic rocks from the tintic levels to form the ore related latites and monzonites the unaltered and bingham mining districts fig 1 utah and found mafic alkaline lavas in these districts are some of the most cu rich that almost all of the volcanic units contain magmatic lavas in the great basin province sulfides some quenched dikes and intrusion margins also have preserved magmatic sulfides comparable with those in the volcanic rocks several lines of evidence indicate that the volcanic and intrusive rocks are comagmatic keith et al 1989 1991 waite 1996 the tintic district and east tintic sub district in utah have recorded over

contributions from mafic alkaline magmas to the bingham porphyry cu au mo deposit utah usa the bingham porphyry cu au mo deposit utah may only be world class because of substantial contributions of sulfur and metals from mafic alkaline magma to an otherwise unremarkable calc alkaline system volcanic mafic alkaline rocks in the district are enriched in cr ni and ba as well as cu au platinum group elements pge and s the bulk of the volcanic section that is co magmatic with ore related porphyries is dacitic to trachytic in composition but has inherited the geochemical signature of high cr ni and ba from magma mixing with the mafic alkaline rocks the volcanic section that most closely correlates in time with ore related porphyries is very heterogeneous containing clasts of scoriaceous latite latitic and minette and flows of melanephelinite shoshonite and olivine latite in addition to volumetrically dominant dacite trachyte bingham ore related porphyries show ample evidence of prior mixing with mafic alkaline magmas intrusive porphyries that have not been previously well studied have several chemical and mineralogical indications of magma mixing these mixed lithologies include the hybrid quartz monzonite porphyry biotite porphyry and minette dikes even some of the more silicic latite and monzonite porphyries retain high cr and ba contents indicative of mixing and contain trace amounts of sapphire 1 mm the heterogeneous block and ash flow deposits also contain sapphire and are permissively correlated with the intrusions based on chemical mineralogical and isotopic data magma mixing calculations suggest about 10 of the monzonitic latitic ore related magma may have been derived from mafic alkaline magma similar to the melanephelinite if the original s content of the mafic magma was about 2 000 4 000 ppm comparable with similar magmas then the mafic magma may have been responsible for contributing more than half of the s and a significant portion of the cu au and pge in the bingham deposit

sulfur speciation oxidation state and sulfur concentration in backarc magmas we have determined the fe3 fe2 ratio s content and the so2 4s2 ratio by sk x ray peak shift for a suite of twelve mid ocean ridge and backarc basin glasses these samples range in oxidation state from two orders of magnitude below to 1 5 orders of magnitude above the ni nio oxygen buffer sulfur speciation in the glasses is strongly dependent on magmatic oxidation state we propose that the solubility mechanism for s in basaltic melts changes over the o2 range which characterizes convergent margin magmas in low o2 sulfide saturated basaltic melts such as most morbs s is present largely as s2 and its concentration is controlled by sulfide melt silicate melt equilibrium and varies positively with o2 at higher o2 s where sulfide melt becomes unstable s concentration is controlled by melt vapor equilibrium and decreases with increasing o2 for the range of o2 s in the back arc basin basalts in this study nno 1 to nno 1 5 s is dissolved in the silicate in both oxidized and reduced forms for the lower o2 end of this range s2 dominates and equilibria involving reduced s species control s melt concentration at higher o2 s the proportion of oxidized s increases and melt vapor equilibria involving these species become more important because s partitions strongly into the vapor phase over the o2 range investigated magmatic degassing may be effective at stripping s from the melt the low s concentrations in island arc and backarc lavas do not necessarily reflect a low s source but rather result from higher o2 in the convergent margin environment

petrology of mariana trough and lau basin basalts the crust of actively opening back arc basins has close chemical and mineralogic similarities to normal mid ocean ridge basalts n morb but some subtle but distinctive differences exist these are largely due to differences in volatiles fe oxidation ratio abundances of large ion lithophile elements lil and some high field strength hfs elements isotope data for sr pb nd he and o are variable but broadly are morb like we present data contrasting mariana trough mtb and lau basin basalts lbb showing how they differ in certain trace element and isotopic signatures and compare both to n morb relative to n morb and lbb the mtb are enriched in alkalis alkaline earths light rare earth elements ree h2o and fe fe even for primitive samples while having morb type he 3 4 7 8 to 8 4 ra sr 87 86 mean 0 70293 and nd e 10 2 the lau basin is zoned with a central area having n morb characteristics for h2o lil ree nd e 8 1 to 9 0 and o but a depletion in hfs elements sr is more radiogenic mean 87 86 0 70347 and 3he 4he 3 4 7 2 to 11 0 ra is high relative to n morb the lau basin has a zone bordering the adjacent island arcs which is like mtb in both back arc basins relatively primitive unfractionated basalts with mg 100 mg fe 62 are found which resemble postulated primitive n morb calculated parental magmas obtained by adding xenocrystic olivine plot near or on 3 and 4 phase boundaries at 1 1 5 gpa for the ol di si system low p fractional crystallization and magma mixing explain most of the observed rock types possible explanations for differences between mtb and lbb include differences in the extent of previous melting episodes of their mantle sources and effects of source metasomatism through dehydration and partial melting of subducted lithosphere the long and complex history of mariana trough mantle sources led to a metasomatized mantle which gives rise to the distinctive mtb in contrast the lau basin is dominated by basalts derived from a source depleted in volatiles lil and hfs elements a previous melting history is implied mixing with a mantle component enriched in 87sr and 3he may be due to mantle counterflow driven by the subduction process

identification of the projectile at the brent crater and further considerations of projectile types at terrestrial craters abstract impact melt samples from drill hole b1 59 at the 3 8 km diameter brent crater ontario have been analysed for siderophile trace elements indicative of meteoritic contamination samples from the basal melt zone at 823 857 m depth are enriched in ir os pd ni co cr and se over basement with the abundance pattern suggesting a chondritic projectile for brent from a ni cr correlation of 10 melt samples an l or ll chondrite is inferred the contribution of an ultramafic country rock alnoite in the melt is too small to significantly influence its ni cr ratio glass rich breccias from the allochthonous breccias filling the crater also contain a meteoritic component interelement ratios e g ni cr are however fractionated relative to the melt zone samples this as well as the low au content of all brent samples is probably a product of alteration additional data on impact melts from the 65 km diameter crater manicouagan still did not reveal a meteoritic component as also for the mistastin crater 28 km diameter where cr analyses set an upper limit of 1 of an achondritic projectile component in the melt irghizites tektite like glasses from the zhamanshin impact structure have been found to contain high ni and co concentrations and our data show that ir is also enriched it is however not possible to define the projectile type enrichment of an ivory coast tektite in ir is confirmed there are large differences in siderophile element concentrations among tektites with otherwise similar chemical composition there are now four known craters formed by chondrites clearwater east lapparjarvi wanapitei and brent with brent being the smallest of these for smaller craters the projectiles appear to be limited to iron or stony iron meteorites because of atmospheric destruction of relatively small stony meteorites it appears however that all major classes of meteorites are represented among the projectiles at terrestrial impact craters

spherules from the cretaceous tertiary boundary clay at gubbio italy the problem of outcrop contamination surficial outcrop contamination has occurred in some well known stratigraphic sections of carbonate rocks in the northern apennines a critical case involves several contaminated clay partings including the cretaceous tertiary boundary clay in the classic bottaccione section near gubbio italy these clay layers contain shiny spherules which in several recent studies have been said to consist of volcanic glass and have been used to support the hypothesis that the terminal cretaceous mass extinction was caused by widespread volcanism laboratory tests however indicate that these shiny spherules are made of hf insoluble and combustible material and are therefore of recent biological origin these objects were introduced into the cretaceous tertiary boundary clay and other clay layers from the surrounding soil along with abundant detrital contaminants derived from erosion of the middle miocene flysch exposed at the head of the bottaccione gorge they are completely different from the altered and flattened microtektitelike spheroids that are found only in the iridium rich cretaceous tertiary boundary clay and that provide strong evidence for a large impact

sulfur release from the columbia river basalts and other flood lava eruptions constrained by a model of sulfide saturation abstract a very likely cause of widespread environmental impacts of flood basalt eruptions is the emission of sulfur chlorine and possibly fluorine from the erupting magma we present new data on the s contents of rare glass inclusions and matrix glasses preserved in quenched lava selvages from lava fields of the columbia river basalt group crbg ginkgo sand hollow and sentinel gap flows wanapum basalt formation we compare these results with published data from neral and jawar formation lavas deccan traps india and the roza flow crbg crbg glass inclusions have up to 2000 ppm s and 15 16 wt feototal by contrast the deccan examples have about 1400 ppm s and 10 wt feototal several of the glass inclusions are partly degassed indicating entrapment during magma rise and matrix glasses are typically more evolved than glass inclusions due to small amounts of in situ crystallization using only the highest s inclusions and taking account of the effect of in situ crystallization and degassing on the s content of the residual matrix glasses indicates s yields of about 0 07 to 0 1 wt from deccan eruptions and about 0 15 wt from wanapum crbg eruptions the pre eruptive s contents of these magmas correlate with weight feototal in the same way as undegassed sulfide saturated mid ocean ridge basalts using oceanic basalts to define a sulfide saturation line and data on s contents of degassed basalts we propose an equation to estimate the weight s yield s from initially sulfide saturated basalt liquid without the need to find well preserved rare undegassed glass inclusions and matrix glasses s 0 0 1418 feo total 0 0 6381 0 0 2635 this compares well with independent estimates derived from the petrologic method by taking the difference in s concentration of glass inclusions and matrix glass applying our method to the aphyric grande ronde basalts of the crbg implies a total yield of about 1000 gt so2 delivered into the miocene atmosphere in intermittent bursts of

the role of early sulfide saturation in the formation of the yulong porphyry cu mo deposit evidence from mineralogy of sulfide melt inclusions and platinum group element geochemistry abstract sulfide melt inclusions enclosed in silicate minerals have been observed in many oxidized cu bearing porphyries the origin of such sulfide melt inclusions could bear critical information of metal enrichment or depletion during magma evolution of porphyry systems the giant yulong porphyry cu mo deposit in eastern tibetan plateau consists of a series of felsic intrusions among which the mineralized yulong intrusion emplaced at a late stage of the magmatic activity this study reports detailed texture and composition of sulfide melt inclusions from barren and mineralized intrusions as well as platinum group elements of these intrusions to evaluate potential role of early sulfide saturation in the porphyry mineralization system these sulfide melt inclusions occurring as globules or droplets are preserved in zircon amphibole and quartz grains most of them are composed of a major phase of pyrrhotite and minor pyrite chalcopyrite and pentlandite smooth boundaries between these phases suggest the origin of fractionation from sulfide melt upon cooling small amounts of cu and ni are heterogeneously distributed in the pyrrhotite the sulfide melt inclusions could be observed in both the pre and syn mineralization intrusions at yulong indicating that sulfide saturation had commonly occurred during magma evolution magnetite mineral inclusions could be observed in zircon and amphibole grains as well the mineral assemblage of magnetite pyrrhotite pyrite of the mineral inclusions constrains the yulong magmatic system to redox conditions near the magnetite pyrite pyrrhotite buffer and above the fayalite magnetite quartz buffer fmq high eu eu values 0 56 0 78 of the hosting zircons and high calculated nno values 0 5 of the hosting amphibole indicate highly oxidized nature of the parental magma both pre and syn mineralization intrusions have low pge contents pt 0 04 to 0 17 ppb pd 0 19 0 60 ppb with compositions plotting in the au poor porphyry cu fields in discriminating diagrams early sulfide saturation may have been reached and small amounts of sulfides have been segregated from magma most pges and au but little cu have been removed from the evolved magma because the partition coefficient of cu between sulfide and silicate melt is about two orders of magnitude lower than pge or au as a consequence the evolved magma would have high cu but very low pge and au resulting in the au poor porphyry cu mineralization at yulong

new links between the chicxulub impact structure and the cretaceous tertiary boundary the 200 km diameter chicxulub structure1 3 in northern yucatan mexico has emerged as the prime candidate for the cretaceous tertiary k t boundary impact crater3 6 concentric geophysical anomalies associated with enigmatic occurrences of upper cretaceous breccias and andesitic rocks led penfield and camargo1 to suspect that this structure was a buried impact basin more recently the discovery of shocked quartz grains in a chicxulub breccia3 and chemical similarities between chicxulub rocks and k t tektite like glasses3 6 have been advanced as evidence that the chicxulub structure is a k t impact site here we present evidence from core samples that chicxulub is indeed a k t source crater and can apparently account for all the evidence of impact distributed globally at the k t boundary without the need for simultaneous multiple impacts or comet showers shocked breccia clasts found in the cores are similar to shocked lithic fragments found worldwide in the k t boundary ejecta layer7 8 the chicxulub melt rocks that we studied contain anomalously high levels of iridium up to 13 5 parts per 109 also consistent with the iridium enriched k t boundary layer9 our best estimate of the crystallization age of these melt rocks as determined by 40ar 39ar analyses is 65 2 0 4 1 myr in good agreement with the mean plateau age of 64 98 0 05 myr recently reported10 furthermore these melt rocks acquired a remanent magnetization indicating that they cooled during an episode of reversed geomagnetic polarity the only such episode consistent with40ar 39ar constraints is chron 29r which includes the k t boundary

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

extensive ash falls in and around the sea of japan from large late quaternary eruptions abstract five widespread ashes of late quaternary age have been recognized on land and also in deep sea sediments in and around the sea of japan all are favorable for determining the magnitude and type of the great eruptions and for establishing a quaternary chronology around japan accurate determination of refractive indices of volcanic glass shards and phenocrysts together with chemical data have enabled successful characterization of the tephra layers and correlation between land and sea of the five tephras two are alkalic and are the products of major eruptions of two korean volcanoes the baegdusan tomakomai ash b tm and the ulreung oki ash u oki the b tm ash is recognized at the top of most cores in the northern part of the sea of japan and also on hokkaido and the northern part of honshu where a reliable archeological age is given around the 11th century the u oki ash occurs between the kikai akahoya and aira tn ashes in cores from adjacent to the ulreung do to central honshu where three radiocarbon ages of around 9300 yr b p were obtained the other three tephras are subalkalic and are correlated with large scale eruptions producing voluminous pyroclastic flows and calderas in kyushu the kikai akahoya k ah aira tn at and aso 4 ashes the former two have been well described already but their fallout areas are partly revised in this manuscript the at ash is the most prominent marker recognized not only on land of japan but also in cores from the whole area of the sea of japan and part of the pacific ocean the airfall aso 4 ash simultaneous with the aso 4 pyroclastic flow eruption is also described it mantles very extensive areas and serves as an important time marker about 70 000 years ago

vegetation history after the late period of the last glacial age based on phytolith records in nangodani valley basin southern part of the aso caldera japan

iridium anomaly from the acraman impact ejecta horizon impacts can produce sedimentary iridium peaks the observation of anomalously high iridium concentrations at the cretaceous tertiary k t boundary1 triggered the still unresolved debate concerning the origin of sedimentary ir anomalies several hypotheses have been presented including meteorite impacts1 2 and intense volcanism3 4 here we present data from the acraman impact ejecta horizon south australia5 which conclusively links high sedimentary iridium concentrations to a major meteoroid impact structure and its widely dispersed ejecta an ir anomaly up to 2 parts per 109 p p b ir as well as au pt pd ru and cr anomalies is present within the ejecta from the acraman impact event preserved in late precambrian 600 myr bp shales within the adelaide geosyncline the highest ir and cr concentrations within the ejecta are associated with the coarsergrained clasts of acid volcanics boulder to medium sand size suggesting that most of the ir is carried by these fragments the target rocks at the impact site are comparable acid volcanics that have very low ir au pt pd ru and cr concentrations indicating a meteoritic origin for the anomalous ir levels within the ejecta to our knowledge this is the first example in which an accepted widely dispersed impact ejecta blanket itself uniquely linked to a major terrestrial impact structure5 6 has been shown to be anomalously high in cosmogenic siderophile elements this finding strongly supports the hypothesis that ir anomalies in sediments can be produced by terrestrial meteorite impact events

h chondrites trace element clues to their origin we have analyzed 10 h chondrites for 20 trace elements using rnaa the meteorites included 4 of petrologic type 4 and 2 each of types 3 5 and 6 the data show that h chondrites are not isochemical h3 s are depleted by some 10 not only in fe dodd 1976 but also in the siderophiles os re ir ni pd au and ge moreover the abundance pattern of siderophiles varies systematically with petrologic type as similar fractionations of ree have been observed by nakamura 1974 it appears that both the proportions and compositions of the main nebular condensates varied slightly during accretion of the h chondrites thus the higher petrologic types are independent nebular products not metamorphosed descendants of lower petrologic types abundances of highly volatile elements cs br bi tl in cd ar36 correlate with petrologic type declining by 10 3 from type 3 to type 6 the trends differ from those for artificially heated type 3 s ikramuddinet al 1977b herzoget al 1979 but agree passably with theoretical curves for nebular condensation apparently the low volatile contents of higher petrologic types are a primary feature not the result of metamorphic loss the mineralogy of chondrites suggests that they accreted between 405 k absence of fe3o4 and 560 k presence of fes and the abundances of tl bi and in further restrict this interval to 420 500 k accretion at 1070 100 k as proposed by hutchisonet al 1979 1980 leads to some extraordinary problems volatiles must be injected into the parent body after cooling which requires permeation of the body by 1011 times its volume of nebular gas this process must also achieve a uniform distribution of the less volatile elements rb cu ag zn ga ge sn sb se f without freezeout in the colder outer layers factor analysis of our data shows 3 groupings siderophiles os re ir ni pd au and ge volatiles ag br in cd bi and tl and alkalis rb and cs the remaining 5 elements u zn te se and sb remain unassociated

meteoric burial diagenesis of pennsylvanian arkosic sandstones southwestern anadarko basin texas pennsylvanian arkosic sandstones at mobeetie field were deposited in fan deltas that prograded onto a shallow shelf in the southern anadarko basin the detrital minerals of the sandstones reflect the composition of the precambrian granites and granodiorites that were exposed in the nearby amarillo uplift distal margins of some fan delta lobes were reworked by marine processes and carbonate fossil fragments and oolites were mixed with terrigenous clastics the diagenetic history and hence reservoir quality of the distal marine reworked sandstones differ from those of the more proximal nonreworked sandstones the earliest diagenetic events formation of chlorite ooids and precipitation of fibrous submarine mg calcite cement took place in the depositional environment of the marine reworked sandstones on the basis of isotopic data the remainder of the diagenesis evidently occurred in fluids of meteoric origin shallow early meteoric diagenesis induced precipitation of iron poor calcite spar in reworked sandstones nonreworked sandstones lack calcite spar but contain early pore lining chlorite cement dissolution of aragonite by fresh meteoric ground water created moldic porosity within reworked sandstones as burial increased porosity in both the reworked and nonreworked fan delta sandstones was reduced by precipitation of authigenic quartz feldspar kaolinite fe calcite and ankerite oxygen isotope data suggest that these cements also precipitated from fluids of meteoric origin that became increasingly hot but remained relatively constant in isotopic composition the last diagenetic events were influenced by the overlying permian evaporites sodium rich fluids caused partial albitization of detrital plagioclase and sulfate derived from the evaporites precipitated as anhydrite and celestite

volatile composition of the phonolitic laacher see magma 12 900 yr bp implications for syn eruptive degassing of s f cl and h 2 o a volatile rich and chemically zoned phonolitic magma reservoir was tapped successively during the eruption of laacher see volcano ca 12 900 years bp and produced a tephra sequence consisting of phenocryst poor highly evolved phonolite at the base and phenocryst rich more mafic phonolite at the top the stratospheric volatile loading was estimated by comparing pre and post eruptive s f cl and h2o contents of undegassed glass inclusions and partially degassed matrix glasses glass inclusions 150 1490 ppm s and host matrix glasses 150 820 ppm s both document a strong s decrease during progressive magmatic differentiation which is interpreted to be partially caused by crystallization of hauyne the s6 stotal ratio of the pre eruptive melt increased with differentiation from 8 to 71 as indicated by s k wavelength shift measurements in glass inclusions sulfate rich highly evolved phonolitic magma was erupted during plinian and sulfide rich more mafic phonolitic magma during late phreatomagmatic phases f and cl became enriched during late stages of differentiation glass inclusions 690 4060 ppm f 1770 4400 ppm cl matrix glasses 680 3660 ppm f 2130 4330 ppm cl the most differentiated melts maximum 13 wt na2o occur only as matrix glass and are extremely f enriched 5080 8780 ppm but cl depleted 460 2820 ppm suggesting that f was retained in the melt whereas some cl was lost during pre and or syn eruptive degassing the h2o contents of glass inclusions increase irregularly with differentiation 2 5 5 7 wt matrix glasses are h2o depleted 0 2 2 8 wt compared to most glass inclusions showing that most h2o was released to the atmosphere by explosive degassing a mass balance calculation yields a syn eruptive volatile release of 1 9 tg stotal 6 6 tg cl and 403 tg h2o from the melt this is a minimum estimate since s and cl could have accumulated in a separate fluid phase as indicated by fluid inclusions in hauyne and pre eruption h2o contents close to saturation level at the likely pressure temperature conditions in the laacher see magma reservoir we estimate that at least ca 20 tg so2 were injected into the stratosphere causing a significant negative climate forcing as reflected by several paleoclimate proxies and as shown by recent modeling

re and os concentrations in arc basalts the roles of volatility and source region fo2 variations olivine and spinel compositions major elements including ferric and ferrous iron s re and os contents have been measured for a suite of primitive most 6 wt mgo basalts from the trans mexican volcanic belt tmvb including the western mexican volcanic belt the michoacan guanajuato volcanic field sierra chichinautzin pico de orizaba region palma sola san martin tuxtlas and the eastern alkaline province eap sulfur contents at sulfide saturation were calculated to determine whether the measured s contents are representative of sulfide saturated liquids most of the samples have s contents much lower than expected for sulfide saturation a few have higher contents than calculated perhaps due to the presence of sulfate in the measured total sulfur i e more oxidized samples comparison of the tmvb samples along with previously analyzed morb oib babb and arc samples reveals a continuum of re and os contents that is best explained by variation in oxygen fugacity and thus sulfide stability in the source region high re and os magmatic suites are best explained by derivation by melting of oxidized mantle where sulfide is no longer stable and re and os behave incompatibly whereas low re and os magmatic suites are derived from melting of relatively reduced mantle where sulfide is stable and re and os behave compatibly intermediate examples abound and arc magmas span a wide range of re and os concentrations due to variation of fo2 in the source during genesis of arc magmas low re magmatic suites are furthermore potentially affected by volatility which can lower re by a factor of 3 5

geochemistry of hydrothermal fluids from the pacmanus northeast pual and vienna woods hydrothermal fields manus basin papua new guinea abstract processes controlling the composition of seafloor hydrothermal fluids in silicic back arc or near arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic hydrothermal activity in such environments we conducted a survey of vent fluid compositions from two contrasting sites in the manus back arc basin papua new guinea to examine the influence of variations in host rock composition and magmatic inputs both a function of arc proximity on hydrothermal fluid chemistry fluid samples were collected from felsic hosted hydrothermal vent fields located on pual ridge pacmanus and northeast ne pual near the active new britain arc and a basalt hosted vent field vienna woods located farther from the arc on the manus spreading center vienna woods fluids were characterized by relatively uniform endmember temperatures 273 285 c and major element compositions low dissolved co 2 concentrations 4 4 mmol kg and high measured ph 4 2 4 9 at 25 c temperatures and compositions were highly variable at pacmanus ne pual and a large newly discovered vent area fenway was observed to be vigorously venting boiling 358 c fluid all pacmanus fluids are characterized by negative d h 2 o values in contrast to positive values at vienna woods suggesting substantial magmatic water input to circulating fluids at pual ridge low measured ph 25 c values 2 6 2 7 high endmember co 2 up to 274 mmol kg and negative 34 s h 2 s values down to 2 7 in some vent fluids are also consistent with degassing of acid volatile species from evolved magma dissolved co 2 at pacmanus is more enriched in 13 c 4 1 to 2 3 than vienna woods 5 2 to 5 7 suggesting a contribution of slab derived carbon the mobile elements e g li k rb cs and b are also greatly enriched in pacmanus fluids reflecting increased abundances in the crust there relative to the manus spreading center variations in alkali and dissolved gas abundances with cl at pacmanus and ne pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents in further contrast to vienna woods substantial modification of pacmanus ne pual fluids has taken place as a result of seawater ingress into the upflow zone consistently high measured mg concentrations as well as trends of increasingly non conservative so 4 behavior decreasing endmember ca cl and sr cl ratios with increased mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment decreased ph and endmember fe mn ratios in higher mg fluids indicate that the associated mixing cooling gives rise to sulfide deposition and secondary acidity production several low temperature 80 c fluids at pacmanus ne pual also show evidence for anhydrite dissolution and water rock interaction fixation of b subsequent to seawater entrainment hence the evolution of fluid compositions at pual ridge reflects the cumulative effects of water rock interaction admixing and reaction of fluids exsolved from silicic magma phase separation segregation and seawater ingress into upflow zones

contribution of mafic melt to porphyry copper mineralization evidence from mount pinatubo philippines and bingham canyon utah usa mount pinatubo in the philippines known for its cataclysmic eruption in 1991 hosts several porphyry copper deposits and active geothermal systems an underlying mafic melt supplied much of the sulphur for the dacitic magma and its injection into the dacitic magma chamber triggered the eruption the eruption caused purging of the sulphur rich fluid from the dacite to the atmosphere and extensive fracturing similar events took place at bingham canyon utah site of the largest copper and gold deposit in north america at 38 ma the bingham canyon mineralization took place beneath an active stratovolcano and pyroclastic flows contemporaneous with the mineralization show evidence for magma mingling ascent of mafic melt supplied sulphur and chalcophile elements to the felsic magma which consolidated to form the bingham stock and its underlying magma chamber injections of the mafic melt caused periodic eruptions of felsic magma to form the stratovolcano and deposition of sulphide minerals in highly fractured rocks in and around the stock

mo mineralized porphyries are relatively hydrous and differentiated insights from the permian triassic granitic complex in the baituyingzi mo cu district eastern inner mongolia ne china mo cu mineralization in the baituyingzi district of eastern inner mongolia occurs within a granitic complex this paper presents and discusses zircon u pb ages and whole rock geochemical and sr nd pb isotopic data from the granitic complex as potential indicators for porphyry mo fertility the u pb ages indicate that five units of the granitic complex were emplaced between 265 2 0 7 and 246 5 1 0 ma constrained by crosscutting dikes mo cu mineralization was probably related to the baituyingzi monzogranite porphyry dated at 248 2 0 64 ma the intrusions belong to high k calc alkaline to shoshonitic series that are characterized by highly fractionated rare earth element ree patterns and strong enrichments of large ion lithophile elements relative to high field strength elements apart from the 246 ma dike that shows negative end t values 14 9 to 13 1 the intrusions have end t values ranging from 3 9 to 1 0 relatively young depleted mantle model ages 811 to 1183 ma 206pb 204pb of 18 137 18 335 and 207pb 204pb of 15 591 15 625 which are consistent with a juvenile lower crustal origin among the intrusions the 248 ma porphyry and the 246 ma dike show adakite like characteristics e g sr y 44 9 185 and listric shaped ree patterns that indicate amphibole fractionation and a hydrous magma source however the porphyry exhibits a higher differentiation index 81 4 91 5 and a steeper ree profile e g lan ybn 25 6 87 0 than those of the 246 ma dike which suggests that it is highly differentiated we propose that the complex was generated by the partial melting of juvenile mafic lower crust containing minor old crustal relicts that was triggered by collision between the north china craton and siberian craton as indicated by the th nb th yb ba th and ba la ratios of the intrusions the crust may have been derived from the melting of the fertile mantle wedge that was metasomatized by various amounts of slab derived fluids or melts due to earlier subduction and was heterogeneous in terms of water cu mo and s contents and possible oxidation state the fertility of the porphyry was likely associated with the addition of earlier subduction related slab melts to the magma source leading to a hydrous and possible high oxidation state and the long time 20 ma collision tectonic setting in which it formed resulting in a highly differentiated state

cretaceous tertiary boundary of dsdp site 596 south pacific sediments from the cretaceous tertiary k t boundary at deep sea drilling project site 596 record accumulation of pelagic clays at about lat 45 s in the center of the ancestral south pacific the k t boundary in this region is characterized by oxidized thoroughly bioturbated sediments containing large amounts of ir and relict high pressure and high temperature mineral phases the net ir fluence 320 ng cm 2 is among the largest on earth and the number of shocked quartz grains 30 m in size 1800 cm 2 exceeds that in all localities outside of north america

chemostratigraphy across the cretaceous tertiary boundary and a critical assessment of the iridium anomaly the elevated concentration of iridium one of the platinum group elements pge at the cretaceous tertiary boundary is still the most generally accepted evidence that a large bolide struck the earth at the time of the end cretaceous mass extinctions new chemostratigraphic data for cross boundary sections from both hemispheres are not easily explained in terms of such an impact event for example the observation that the pge patterns show marked differences between the hemispheres the new constraints indicate that models of mantle derived pge should be seriously considered and that pge anomalies might not be as useful as previously thought as unambiguous identifiers of large impact events in the earth s history

90 000 year phytolith records from caldera rim to western foot of aso volcano japan implications for vegetation history since catastrophic eruption abstract vegetation history after the aso 4 ignimbrite eruption 89 ka has been reconstructed using phytolith records obtained from three tephra sections from caldera rim to the western foot of aso volcano southwestern japan the ca 90 000 year vegetation transitions vary between these sites and elevations at the northern caldera rim 800 900 m asl sparse vegetation composed of sasa sect crassinodi cool temperate dwarf bamboo and zoysia was considered to be established within 1000 years after the catastrophic aso 4 eruption the sasa grassland dominated by sasa sect crassinodi existed continuously at the northeastern caldera rim between 89 and 13 5 ka whereas pleioblastus sect nezasa warm temperate dwarf bamboo andropogoneae including miscanthus japanese pampas grass and zoysia existed in the sasa grassland between 66 and 30 ka although sasa grassland existed after 13 5 ka pleioblastus dwarf bamboo became a constituent of the grassland around 8 ka and continued flourishing until the present on the western slope ca 150 m asl sparse vegetation existed prior to 55 ka after a large outburst flood generated by a breach of caldera rim of intra caldera lake ca 89 72 ka the vegetation after 55 ka was dominated by grassland accompanied with moderate amounts of trees zoysia prevailed from about 55 to 40 ka although sasa was predominant during the period of 40 5 ka the sasa grassland containing andropogoneae pampas grass declined around 5 ka and pleioblastus dwarf bamboo became a constituent of the grassland the pleioblastus grassland including miscanthus japanese pampas grass paniceae and trees lauraceae etc continued to the present at the western foot of the volcano 100 m asl zoysia grassland became established after the large outburst flood the grassland gradually declined from ca 60 ka and almost disappeared around 40 ka instead sasa dwarf bamboo grassland which accompanied pleioblastus dwarf bamboo increased after 60 ka the sasa grassland accompanying sparse trees continued but decreased after 13 1 ka miscanthus grassland occurred after 29 ka and flourished especially in the last 8 ka the consistent presence of miscanthus grassland for 29 000 years may be related to frequent fire episodes due to human activities including burning at the low elevation of the western foot of aso volcano

the role of magma mixing in the genesis of pge mineralization in the bushveld complex thermodynamic calculations and new interpretations the elegant magma mixing model for the formation of the platinum group elements pge mineralization associated with chromite and sulfide in the bushveld complex proposed by naldrett and von gruenewaldt 1989 has recently been questioned by cawthorn 1999 based on his own calculation cawthorn concluded that the concave upward sulfur solubility curve of a fractionated basaltic magma which is central to the model does not exist cawthorn 1999 pointed out that both the hanging wall and footwall sequences of the merensky reef formed from sulfide undersaturated magmas instead of sulfide saturated magmas as predicted by the model cawthorn argued that there is a mass balance problem with the model if these rocks did not contribute pge to the sulfides in the reef our thermodynamic calculations indicate that the concave upward curve of s solubility though different in detail from the original is very much in evidence our calculations also indicate that the content of s dissolved in the residual magma may fall below the s solubility curve when the rate of s increase in the magma due to the removal of silicate cumulates is less than the rate of increase in its s solubility due to the change in its temperature and composition during fractional crystallization mixing of such fractionated and yet sulfide undersaturated magma with appropriate amounts of a primitive magma is still capable of achieving sulfide oversaturation in the hybrid once the immiscible sulfides settle out of the magma the content of s dissolved in the hybrid may fall below its solubility curve again during further crystallization thus no sulfide segregation is expected in the rocks crystallized subsequently r factor assessment needs to consider the consequence of sulfide suspension in magma small quantities of sulfide droplets formed during the normal course of fractional crystallization may remain suspended in magma until the next replenishment and in this case they can be redissolved in the hybrid when the proportion of a new input is large enough because there is no early sulfide liquid segregation both the residual and new magmas will not be depleted in pge and are equally important for contributing pge to the sulfide liquid segregated during a subsequent magma mixing event

amphibole clinopyroxene and plagioclase melt partitioning of trace and economic metals in halogen bearing rhyodacitic melts

sulfur saturation and second stage melts application to the bushveld platinum metal deposits a model is presented for the formation of platinum group element ores by precipitation from sulfur deficient platinum group element rich second stage magmas numerous investigations indicate that basaltic magmas originating from undepleted or mildly depleted source regions are sulfur saturated at the time of eruption mantle derived peridotites residual from midocean ridge basalt magma genesis have pd abundances that are uniformly too high for it to have originated solely from silicate melt retained in the source region at the time of segregation they imply the presence of an accessory immiscible sulfide melt to host the platinum group elements the very high sulfide melt silicate melt partition coefficients of the platinum group elements would result in strong fractionation of these metals into the accessory sulfide component during the melting event the extreme platinum group element enrichment of this accessory sulfide component is evidenced by the discovery ofplatinoid minerals in residual mantle nodules containing pd and pt abundances at the low ppb level keays et al 1981 magmas generated by low to moderate degrees of partial melting of undepleted mantle are therefore sulfur saturated at the time of segregation these first stage magmas become impoverished in platinum group elements during the early stages of fractional crystallization because of coprecipitation of an immiscible sulfide phase e g midocean ridge basalt glasses average

concealed basalt matrix diatremes with cu au ag mo mineralized xenoliths santa cruz porphyry cu mo system pinal county arizona the santa cruz porphyry cu mo system near casa grande arizona includes the sacaton mine deposits and at least five other concealed mineralized fault blocks with an estimated minimum resource of 1 5 gt 0 6 cu the late cretaceous paleocene system has been dismembered and rotated by tertiary extension partially eroded and covered by tertiary quaternary basin fill deposits the mine and mineralized fault blocks which form an 11 km 7 miles by 1 6 km 1 mile ne sw trending alignment represent either pieces of one large deposit several deposits or pieces of several deposits the southwestern part of the known system is penetrated by three or more diatremes that consist of heterolithic breccia pipes with basalt and clastic matrices and subannular tuff ring and maar fill sedimentary deposits associated with vents the tephra and maar fill deposits which are covered by 485 to 910 m 1 600 3 000 ft of basin fill lie on a mid tertiary erosion surface of middle proterozoic granite and late cretaceous porphyry which compose most xenoliths in pipes and are the host rocks of the system some igneous xenoliths in the pipes contain bornite chalcopyrite covellite assemblages with hypogene grades 1 wt cu 0 01 ounces per ton oz t au 0 5 oz t ag and small amounts of mo 0 01 wt these xenoliths were derived from mineralized rocks that have not been encountered in drill holes and attest to additional possibly higher grade deposits within or subjacent to the known system the geometry stratigraphy and temporal relationships of pipes and tephras interpreted from drill hole spacing and intercepts multigenerational breccias and matrices reequilibrated and partially decomposed sulfide oxide mineral assemblages melted xenoliths and breccia matrix compositions show that the diatremes formed in repeated stages initial pulses of basalt magma fractured granite porphyry and other crustal rocks during intrusion transported multi sized fragments of these rocks upward and partially melted small fragments rapid decompression of magma induced catastrophic devolatilization that ruptured overlying rocks to the surface and generated fragment volatile suspensions that abraded conduits into near vertical cylindrical structures fragments entrained in suspensions were milled and sorted and ejected as basal surge pyroclastic deposits and airfall tephra that built tuff rings around vents and filled vent depressions comminuted m to mm sized fragments of wall rocks in magma and suspensions that remained in conduits solidified as heterolithic breccias subsequent pulses of basalt magma ascended through the same conduits brecciated older heterolithic breccias devolatilized and quenched leaving two or more generations of nested and mingled heterolithic breccias and internal zones of fluidized fragments tephra and maar fill deposits from later eruptions are composed of more hydrous and oxidized minerals than earlier tephras reflecting a higher proportion of water in transport fluid which based on fluid inclusion populations in mineralized xenoliths was saline water and co2 the large vertical extent 600 m 2 000 ft of basalt matrix in pipes near paleosurface matrix vesiculation and plastically deformed basalt lapilli indicates that diatreme eruptions were predominantly phreatic diatreme xenoliths represent crustal stratigraphy and as in the santa cruz system provide evidence of concealed mineral resources that can guide exploration drilling through cover vectors to the source of bornite dominant xenoliths containing 1 cu and significant au and ag could be determined by refinement of breccia pipe geometries by reassembly of mineralized fault blocks using modal chemical and temporal characteristics of hydrothermal mineral assemblages and fluid inclusions and by paleodrainage analysis

sulfur diffusion in rhyolite melts diffusion rates for sulfur in rhyolite melt have been measured at temperatures of 800 1100 c water contents of 0 7 3 wt and oxygen fugacities from the quartz fayalite magnetite buffer to air experiments involved dissolution of anhydrite or pyrrhotite into rhyolite melt over time scales of hours to days electron microprobe analysis was used to measure sulfur concentration profiles in the quenched glasses regression of the diffusion data in dry rhyolite melt gives dsulfur 0 05 exp 221 80rt which is one to two orders of magnitude slower than diffusion of other common magmatic volatiles such as h2o co2 and cl diffusion of sulfur in melt with 7 wt dissolved water is 1 5 to 2 orders of magnitude faster than diffusion in the anhydrous melt depending on temperature sulfur is known to dissolve in silicate melts as at least two different species s2 and s6 the proportions of which vary with oxygen fugacity despite this oxygen fugacity does not appear to affect sulfur diffusivity except under extremely oxidizing conditions this result suggests that diffusion of sulfur is controlled by one species over a large range in oxygen fugacity the most likely candidate for the diffusing species is the sulfide ion s2 re equilibration between s2 and s6 in oxidized melts must generally be slow compared to s2 diffusion in order to explain the observed results in a silicic melt undergoing degassing sulfur will tend to be fractionated from other volatile species which diffuse more rapidly this is consistent with analyses of tephra from the 1991 eruption of mount pinatubo philippines and from other high silica volcanic eruptions

sulfur isotopic evidence for sources of volatiles in siberian traps magmas abstract the siberian traps flood basalts transferred a large mass of volatiles from the earth s mantle and crust to the atmosphere the eruption of the large igneous province temporally overlapped with the end permian mass extinction constraints on the sources of siberian traps volatiles are critical for determining the overall volatile budget the role of crustal assimilation the genesis of noril sk ore deposits and the environmental effects of magmatism we measure sulfur isotopic ratios ranging from 10 8 to 25 3 vienna canon diablo troilite v cdt in melt inclusions from siberian traps basaltic rocks our measurements which offer a snapshot of sulfur cycling far from mid ocean ridge and arc settings suggest the 34 s of the siberian traps mantle melt source was close to that of mid ocean ridge basalts in conjunction with previously published whole rock measurements from noril sk our sulfur isotopic data indicate that crustal contamination was widespread and heterogeneous though not universal during the emplacement of the siberian traps incorporation of crustal materials likely increased the total volatile budget of the large igneous province thereby contributing to permian triassic environmental deterioration

modeling the solubility of sulfur in magmas a 50 year old geochemical challenge there are myriad reasons why we wish to understand the behavior of sulfur in magmatic systems reasons that vary from pure intellectual curiosity to possible impacts on society and its resources since ancient times sulfur has been associated with volcanic activity and the role of sulfur in the formation of ore deposits has long been recognized because of the necessity of metal ores for our modern life style e g barnes 1979 naldrett 1989 simon and ripley 2011 this volume recently the mechanisms and quantities of sulfur freed from natural magmas have become an important environmental issue due to their potential effects on global climate change for example the average annual volcanic so2 emission rate of 7 5 to 10 5 teragrams tg per year halmer et al 2002 may contribute 10 of the global atmospheric sulfur input halmer et al 2002 smith et al 2004 and individual eruptive episodes can rapidly contribute gigantic sulfur loads to the atmosphere 100 s to 1000 s of tg depending on the scale of the eruption self 2006 such sulfur emissions can produce potentially catastrophic local and global changes e g fedele et al 2003 ward 2009 courtillot and rennes 2003 correlated the timing of flood basalts with extinction events in earth s history and hypothesized a causal relation part of the kill mechanism responsible for extinction may be volcanically derived sulfur creating anoxic oceans and another part of the mechanism may be climatic changes brought about by sulfur injection into the atmosphere ward 2009 indeed erwin 2006 advocates that sulfur released from the eruption of the siberian flood basalts played a role in the end permian extinction in light of the evidence that volcanic degassing is a significant source of sulfur to the atmosphere stoiber et al 1987 symonds et al 1994 andres

90 000 year phytolith record from tephra section at the northeastern rim of aso caldera japan abstract vegetation history during the last 90 000 years has been reconstructed using the phytolith record obtained from a tephra section located at the northeastern rim of aso caldera southwestern japan the phytolith assemblage from the section revealed that grassland vegetation dominated by gramineae consistently occurred for 90 000 years sparse vegetation composed of sasa sect crassinodi cool temperate dwarf bamboo and zoysia lawn was considered to be established within 1000 years after the catastrophic aso 4 eruption 89 ka the sasa grassland dominated by sasa sect crassinodi existed continuously at the northeastern caldera rim between 89 and 13 5 ka the dominance of sasa sect crassinodi in the grassland suggests that the aso caldera rim during the period was under a cooler and drier climate plants other than sasa dwarf bamboo declined during the period of 75 66 ka mis4 whereas pleioblastus sect nezasa warm temperate dwarf bamboo andropogoneae pampas grass and zoysia existed in the sasa grassland between 66 and 30 ka mis3 during the period from 30 to 13 5 ka mis2 corresponding to the last glacial maximum lgm phytoliths from plants other than sasa dwarf bamboo and fern are only present in small numbers suggesting that they declined in response to a cool climate during the lgm sasa grassland which had continued since 89 ka existed after 13 5 ka at the northeastern rim of aso caldera in the earlier stage of the holocene phytoliths of sasa sect crassinodi and sasa sect sasa dominated but pleioblastus dwarf bamboo became a constituent of the grassland around 8 ka the proportion of pleioblastus dwarf bamboo mainly pleioblastus sect nezasa in the grassland increased and continued flourishing until the present although sasa gradually decreased in addition arboreal phytoliths were recognized at several holocene horizons these phenomena indicate that grassland vegetation composed mainly of sasa and pleioblastus dwarf bamboos with sparse trees dominated at the northeastern rim of the aso caldera in holocene time

holocene vegetation history based on phytolith records in asodani valley northern part of the aso caldera japan abstract vegetation history during the holocene has been reconstructed using phytolith records obtained from three tephra sections in the asodani valley basin northern part of aso caldera southwestern japan the topography of the asodani valley basin is divided into four types somma caldera rim and pyroclastic flow plateau caldera wall caldera floor and post caldera central cone slope the holocene vegetation transitions in the basin vary between these topographic types at the northern caldera rim sasa cool temperature dwarf bamboo grassland existed prior to 8 ka and thereafter pleioblastus warm temperature dwarf bamboo grassland dominated to the present at the steep caldera wall forest with understory of bambusoideae plants sasa and pleioblastus existed during the holocene and mixed forests composed of evergreen trees deciduous trees and conifers appeared after 6 ka on the post caldera central cone slope grassland vegetation composed of sasa existed prior to 10 2 ka and miscanthus pampas grass grassland with sparse trees established around 13 ka and flourished in the last 4 ka the center of the asodani valley was occupied by the last intra caldera lake prior to 8 9 ka and thereafter changed to swampy and fluvial environments phragmites occurred continuously in and around the intra caldera lake and the subsequent marshes and swamps in the last 11 4 ka the difference of vegetation transition in the holocene between topographic types can be explained as difference of human activities in and around the aso caldera grassland dominated by sasa pleioblastus and miscanthus occurred on pyroclastic flow plateau around the caldera and on the central cone slope which were strongly affected by human activities including burning for a long time and forest with understory bambusoideae plants was preserved on the caldera wall which is unapproachable because of the steep topography

platinum group element geochemistry of andesite intrusions of the kelian region east kalimantan indonesia implications of gold depletion in the intrusions associated with the kelian gold deposit nineteen andesite samples from the kelian gold mine and two adjacent prospects magerang imang and nakan in east kalimantan have been analyzed for cu re au and the platinum group elements pge the aim of the study was to use variations in pge concentrations to test whether the chalcophile elements became enriched or depleted with fractionation in the igneous suites associated with the kelian deposit when the data are plotted on mantle normalized chalcophile element diagrams the patterns for the magerang imang and nakan suites are subparallel over a range of pge concentrations of about 20 times pd ir ratios for magerang imang hornblende andesites and nakan pyroxene andesites are 15 to 54 and 60 to 129 respectively the lower pd ir ratios for the magerang imang suite are due to a reversal in the slope of the mantle normalized pattern between ir and os that is not seen in the nakan suite all pge concentrations from both the magerang imang and nakan suites decrease with increased fractionation furthermore all samples which have not been subjected to strong alteration are strongly depleted in au relative to adjacent elements on mantle normalized chalcophile element plots crosscutting relationships show that the gold mineralization at kelian is younger than the associated central and eastern andesite intrusions so they cannot be the source of the gold in the deposit the gold was probably derived from slightly younger intrusions similar in age to the adjacent magerang imang hornblende andesites which appear to be coeval with the mineralization and which are also depleted in gold the subparallel pge patterns preclude the depletion of cu au and pge by sulfide fractionation which would fractionate highly chalcophile pge from less chalcophile cu and re we suggest that the parallel cu au pge patterns are due to mixing between a relatively mafic pge rich magma and a more felsic magma with lower pge concentrations

transfer of sulfur in subduction settings an example from batan island luzon volcanic arc philippines sulfur abundances have been determined in silicic and basaltic melt inclusions in olivines from harzburgitic xenoliths and a basaltic lava sample all from batan island in mantle xenoliths olivines fo80 91 are present as neoblasts or in finely recrystallized patches the most magnesian olivines fo89 7 91 cao 85 cao 0 25 wt and their melt inclusions cao al2o3 from 0 8 to 1 15 have recorded early stages of crystallization the sulfur concentrations for these calc alkaline basaltic melts are estimated between 1720 and 3200 ppm with a mean value at 2550 ppm 1 390 and s cl ratio at nearly 1 this is in agreement with the idea that arc basaltic melts may contain high concentrations of sulfur s 2000 ppm at 1200 c however the heterogeneous distribution of s and its partitioning between silicate melts h2o rich vapor and s bearing solid phases as illustrated by the batan mantle xenoliths would result in highly variable sulfur concentrations in island arc basaltic magmas mostly controlled by fo2 and fs2

distribution of noble metals across the cretaceous tertiary boundary at gubbio italy iridium variation as a constraint on the duration and nature of cretaceous tertiary boundary events iridium pd pt and au were determined in sections from the bottaccione gorge and contessa valley gubbio italy by radiochemical neutron activation shales and limestones were sampled from 2 85 m above to 219 m below the cretaceous tertiary k t boundary metal enrichment was evaluated by comparing the boundary shale region with the lower part of the section background iridium is concentrated by 63 times in the boundary shales in comparison with the background whereas other metals are enriched by no more than 2 2 times the enrichment of ir is not confined to the boundary shales but extends approximately 2 m above and below this horizon within this ir rich region there are four distinct ir maxima in addition to the major ir enrichment in the k t boundary shales iridium maxima are stratigraphically coincident with maxima in abundances of shocked minerals characteristic of explosive volcanism limestones are much lower in noble metals than shales and their ir contents in the k t boundary region are largely accounted for by their minor clay mineral contents the time represented by the 4 m of ir rich section is at least 3 x 10 5 yr if published sedimentation rates are used to sustain an increased ir flux over this period and to account for the ir distribution near the k t boundary intense volcanic activity is a preferred alternative to impact of extraterrestrial material

geochemical characteristics of miocene fe cu pb zn granitoids associated mineralization in the chichibu skarn deposit central japan evidence for magmatic fluids generation coexisting with granitic melt

unique event plumes from a 2008 eruption on the northeast lau spreading center the creation of ocean crust by lava eruptions is a fundamental earth process involving immediate and immense transfers of heat and chemicals from crust to ocean this transfer creates event plumes megaplumes massive ellipsoidal eddies with distinctive and consistent chemical signatures here we report the discovery of unique event plumes associated with a 2008 eruption on the northeast lau spreading center instead of a large plume hundreds of meters thick we detected at least eight individual plumes each 50 m thick and apparently only 1 3 km in diameter yet still rising 200 1000 m above the eruption site low and uniform 3he heat 0 041 10 17 mol j and dissolved mn heat 0 04 nmol j ratios in water samples were diagnostic of event plumes high h2 concentrations up to 9123 nm and basalt shards confirmed extensive interactions between molten lava and event plume source fluids remote vehicle observations in 2009 mapped a new small 1 5 5 8 106 m3 lava flow our results suggest that event plumes are more variable and thus perhaps more common than previously recognized small event plumes may be preferentially associated with small or sheet flow eruptions and massive event plumes with slowly extruding pillow mounds 25 75 m thick despite this correlation and high h2 concentrations existing theory and seafloor observations argue that cooling lava cannot transfer heat fast enough to create the buoyancy flux required for event plumes the creation of event plumes under a broad range of eruption conditions provides new constraints for any theory of their formation

metal precipitation in the cretaceous tertiary boundary clay at stevns klint denmark abstract alvarez et al 1980 explained anomalous ir concentrations in the cretaceous tertiary k t boundary informal type sediment the fish clay in denmark in terms of a global fall out of extraterrestrial matter however geochemical and mineralogical analyses of the various sublayers in the clay reveal that not only ir but also elements such as ni co zn mo as se and sb are substantially enriched in the clay the enrichments may be due to precipitation of elements as sulfides at a redoxcline the facts supporting this view are 1 1 the over all chalcophile element abundance pattern in the clay 2 2 the occurrence of a redoxcline deduced from the distribution of organic matter and oxidized iron in the clay 3 3 the large amounts of small pyrite spheroids present at this redoxcline 4 4 the high concentration of trace elements in these spheroids also ni co and ir elements that have previously been presumed to have a meteoritic origin are substantially enriched in the spheroids a model is suggested in which metal bearing pore solutions lose their metals by precipitation upon passing the boundary between the oxic cretaceous chalk and the overlying anoxic and hydrogen sulnde rich fish clay the great similarity in geochemistry and lithological appearance between several strongly ir enriched clays suggest that the model may also be applied to other k t boundary clays

sulfur evolution of the 1991 pinatubo magmas based on apatite abstract using electron microprobe emp and laser ablation inductively coupled plasma mass spectrometry la icp ms to collect major and rare earth elements ree respectively from apatites from the 1991 mt pinatubo juvenile eruption products we have determined that two statistically distinct populations of apatite exist one population crystallized from the juvenile basaltic melt basalt apatites and the other population crystallized from the main dacitic magma body silicic apatites both populations contain high s apatites 0 7 wt so3 apatite has previously been shown to be a potential monitor for magmatic sulfur contents via numerous proposed coupled substitutions of p5 for s6 however simple apatite melt partitioning cannot account for high s silicic apatites which grew from a silicic melt with an apparent maximum s concentration of 80 ppm disparate apatite morphology i e skeletal and acicular for basalt apatites and euhedral for silicic apatites as well as compositional evidence reveal that high s silicic apatites were not inherited from the juvenile basalt during mingling mixing prior to eruption sulfur gain from neighboring anhydrite phenocrysts can also be ruled out as a source of high sulfur emp sulfur mapping of silicic apatites shows highly irregular patterns of sulfur enrichment that do not correspond with adjacent anhydrite and can be found within apatites hosted by other minerals e g hornblende and fe ti oxides with these data in mind we propose high s silicic apatites from pinatubo and other sulfur rich systems achieved elevated sulfur concentrations during high sulfur fluxing events that originated from underplated basalt during degassing of a so2 rich fluid phase that basalts were indeed sulfur rich and oxidized is here indicated by high s contents of apatites growing in basalt the predominant location of s rich areas of silicic apatite is crystal interiors of apatite inclusions in other mineral phases while large apatite microphenocrysts surrounded by groundmass glass have low sulfur contents this is evidence for placing sulfur fluxing periods long before events that ultimately led to the 1991 eruption

spheroids at the cretaceous tertiary boundary are altered impact droplets of basaltic composition sand size spheroids of k feldspar in the cretaceous tertiary c t boundary clay at caravaca southern spain were interpreted by smit and klaver as having solidified from a melt resulting from the impact of a large extraterrestrial body sand size spheroids of k feldspar glauconite and magnetite quartz have been found in the c t boundary clay in northern italy and spheroids of k feldspar and pyrite were found in the boundary clay at deep sea drilling project site 465a in the central pacific these spheroids have textures similar to those of rapidly crystallized feldspar and mafic silicates they are interpreted as diagenetically altered microcrystalline spherules of basaltic composition produced by the impact of a large asteroid in an ocean basin at the end of the cretaceous they are analogous to the glassy microtektites produced by impacts on more siliceous target rocks 21 references 4 figures

geochemical differences between subduction and collision related copper bearing porphyries and implications for metallogenesis abstract porphyry cu mo au deposits occur not only in continental margin arc settings subduction related porphyry cu deposits such as those along the eastern pacific rim eprim but also in continent continent collisional orogenic belts collision related porphyry cu deposits such as those in southern tibet these cu mineralized porphyries which develop in contrasting tectonic settings are characterized by some different trace element e g th and y concentrations and their ratios e g sr y and la yb suggesting that their source magmas probably developed by different processes subduction related porphyry cu mineralization on the eprim is associated with intermediate to felsic calc alkaline magmas derived from primitive basaltic magmas that pooled beneath the lower crust and underwent melting assimilation storage and homogenization mash whereas k enriched collision related porphyry cu mineralization was associated with underplating of subduction modified basaltic materials beneath the lower crust with subsequent transformation into amphibolites and eclogite amphibolites and resulted from partial melting of the newly formed thickened lower crust these different processes led to the collision related porphyry cu deposits associated with adakitic magmas enriched by the addition of melts and the subduction related porphyry cu deposits associated with magmas comprising all compositions between normal arc rocks and adakitic rocks all of which were associated with fluid dominated enrichment process in subduction related cu porphyry magmas the oxidation state fo2 the concentrations of chalcophile metals and other volatiles e g s and cl and the abundance of water were directly controlled by the composition of the primary arc basaltic magma in contrast the high cu concentrations and fo2 values of collision related cu porphyry magmas were indirectly derived from subduction modified magmas and the large amount of water and other volatiles in these magmas were controlled in part by partial melting of amphibolite derived from arc basalts that were underplated beneath the lower crust and in part by the contribution from the rising potassic and ultrapotassic magmas both subduction and collision related porphyries are enriched in potassium and were associated with crustal thickening their high k2o contents were primarily as a result of the inheritance of enriched mantle components and or mixing with contemporaneous ultrapotassic magmas

sulfur abundance and its speciation in oxidized alkaline melts abstract the sulfur concentrations and the relative proportions of s2 and s6 were measured by electron microprobe in a series of melt inclusions trapped in phenocrysts from different subduction related and within plate volcanoes the melt inclusions correspond to potassic and shoshonitic primary melts to tholeiitic and hawaiitic primitive melts in the tholeiitic and the transitional basaltic melt inclusions sulfur is mainly present as s2 s 6 s total 0 03 to 0 08 and varies from 0 13 to 0 18 wt the occurrence of immiscible sulfides attests to their saturation in shoshonitic and potassic primary melts sulfur s 0 12 to 0 32 wt is dissolved as both s2 and s6 s 6 s total 0 3 to 0 7 their oxygen fugacity estimated from the s 6 s total ratios ranges from ninio to ninio 1 log unit hawaiitic melts may also dissolve up to 0 3 wt sulfur possibly because of their oxidation state close to ninio as illustrated by samples from mt etna italy variations of sulfur at constant s 6 s total ratio and temperature in both the potassic and shoshonitic primary melts indicate that these melts are undersaturated with respect to a s rich condensed phase in agreement with their relatively high oxidation state it strongly suggests that sulfur behavior in relatively oxidized primary alkaline melts is controlled by the mantle source melting conditions

primary igneous anhydrite progress since its recognition in the 1982 el chichon trachyandesite abstract primary igneous anhydrite was first identified in 1982 el chichon pumices analysis of the sulfur budget for the eruption provided compelling evidence that the pre eruptive magma contained a significant gas phase at 7 km depth in order to account for the excess gas release of 5 9 million tons of so2 to the stratosphere by the eruption primary igneous anhydrite and a larger excess gas release of 20 million tons of so2 were noted for the significantly larger eruption of mount pinatubo in 1991 for which a separate gas phase at 7 9 km depth was also required by the sulfur budget pumices from both eruptions have mineral assemblages dominated by plagioclase and hornblende with minor biotite and show evidence for co nucleation and mutual inclusions of anhydrite and apatite both magmas were also very water rich and highly oxidized with oxygen fugacities 1 log unit above the synthetic ni nio buffer furthering the similarities between these two eruptions ion microprobe analyses of sulfur isotopic compositions of anhydrites in pumices from el chichon and mount pinatubo both showed that individual crystals are isotopically homogeneous but inter crystalline variations in 34s are well beyond analytical error this study reviews the history of thought regarding primary igneous anhydrite ten volcanic and plutonic analogues to the el chichon and mount pinatubo magmas are discussed all were similarly water rich and highly oxidized magmas hornblende is the dominant mafic phenocryst in all but one plutonic example in that case so much early anhydrite precipitated that no calcium remained to form hornblende biotite is very abundant in that exceptional plutonic case and is present in six of the other examples with primary igneous anhydrite sphene is known as an indicator mineral of high magmatic oxygen fugacity it was present in the 1982 el chichon pumices and in 6 of the other anhydrite bearing samples hornblende and biotite phenocrysts are also characteristic of the intermediate to felsic plutonic rocks that typically host porphyry cu deposits such magmas are also known to be water rich and highly oxidized a close spatial and petrogenetic connection exists between magmas with primary igneous anhydrite and magmatic hydrothermal ore deposits

the magnetite crisis in the evolution of arc related magmas and the initial concentration of au ag and cu the association of large au cu ag ore deposits with convergent margins is commonly attributed to the higher content of chalcophile elements in the parental magmas generated at subduction zones compared with mid ocean ridges we present new geochemical data for arc like relatively oxidized mantle derived basalt to rhyolite magmas from the pual ridge and vicinity eastern manus basin which show that the initial abundances of base and precious metals in the parental basalts are similar to those of mid ocean ridge basalt morb the contents of au cu and ag are built up in the evolving pual ridge liquids to levels considerably in excess of those in morb because unlike morb they are not saturated in a sulfide phase which is a consequence of their being more oxidized than morb the behaviour of s during the evolution of the pual ridge magmas is obscured by late stage so2 loss during eruption but we show that it may be inferred by using se as a proxy because this element follows s closely during magmatic evolution except it is not lost during low pressure near sea floor degassing the onset of magnetite fractionation at 60 wt sio2 and an mg number of 40 is accompanied by an abrupt decrease in the contents of au cu and ag previously attributed to separation of cu au rich fluid which is also shown by se implying that magnetite fractionation triggers sulfide saturation petrological modelling reveals that the amount of magnetite fractionation involved is sufficient to convert most of the s originally dissolved in the magma as sulfate so42 to sulfide s2 triggering saturation in a cu rich sulfide phase tentatively identified as bornite cu5fes4 this sulfide phase sequesters au and ag elements with the same valence as cu in sulfides but not other potentially chalcophile elements such as ni re and pt which suggests that the phase is crystalline rather than an immiscible sulfide melt the relatively high contents of cu and au characteristic of evolved convergent margin magmas requires no enrichment from subducted material instead the association of major cu au deposits with convergent margin magmatism results specifically from the process of magmatic evolution under oxidizing conditions this same property also leads to early magnetite fractionation triggering the abrupt saturation in the cu rich sulfide hence the easily recognizable trend of magmatic evolution under oxidizing conditions i e the sharp drop in chalcophile element concentrations may be an exploration guide to economic au ag cu provinces or a crucial pre enrichment step in the formation of such deposits the decrease in p2o5 and sr at the same stage in the fractionation sequence 60 wt sio2 indicates that saturation in apatite is concomitant with magnetite sulfide saturation in the eastern manus basin

structurally bound s2 s1 s4 s6 in terrestrial apatite the redox evolution of hydrothermal fluids at the phillips mine new york usa abstract the oxidation state of sulfur s plays a critical role in the formation of igneous and hydrothermal mineral systems constraining the oxidation state of s during mineralization and alteration is a valuable tool for understanding primary versus secondary processes that affect mineral systems recent experimental studies demonstrate that apatite which is a ubiquitous accessory mineral in igneous and hydrothermal ore forming systems structurally incorporates multiple oxidation states of s i e s6 s4 s2 and that the abundance of reduced versus oxidized s in apatite is systematically related to oxygen fugacity in this study we used micro x ray absorption near edge structure xanes spectroscopy at the s k edge to measure the oxidation states of s in natural apatite from the phillips mine magnetite sulfide mineral deposit putnam county new york micro xanes transects were collected within two apatite grains starting near the edge of 1 a pyrrhotite inclusion and 2 an inclusion assemblage consisting of pyrite ferroan carbonate pyroxene and magnetite significant compositional and textural variations within the apatite were observed by electron probe micro analysis epma wavelength dispersive wds spectroscopy element mapping and cathodoluminescence cl imaging and used in combination with the xanes data to discuss the formation of the phillips mine apatite the xanes analyses reveal that apatite contains variable proportions of s6 s4 s1 and s2 with corresponding peak absorption energies of 2481 7 0 3 ev 2477 9 0 4 ev 2471 8 0 1 ev and 2469 8 0 04 ev respectively notably this marks the first observation of reduced s species s2 s1 in terrestrial apatite peak areas ratios s6 s demonstrate systematic variations in the oxidation state of s within the apatite grains elevated s6 s peak area ratios typically coincide with higher concentrations of s and rare earth elements within the apatite grains several observations including the presence of multiple oxidation states of s in apatite and monazite inclusions that record secondary fluid mediated dissolution reprecipitation of apatite indicate differences in the oxidation of s thus oxygen fugacity during primary mineralization and secondary alteration i e metasomatism we propose a model for the formation of the phillips mine apatite wherein the primary apatite grains crystallized from a reduced s bearing hydrothermal fluid characterized by a low so2 h2s ratio subsequently metasomatism of apatite in the presence of an oxidized fluid which contained an elevated so2 h2s ratio resulted in the exsolution of rare earth elements from apatite and concomitant growth of monazite and the structural incorporation of oxidized s s6 and s4 in apatite this study demonstrates that the oxidation states of s in apatite provide valuable geochemical information regarding the redox evolution of mineralized systems

an evaluation of the solubility of sulfide sulfur in silicate melts from experimental data and natural samples abstract an evaluation of the solubility of sulfur in silicate melts from experimental data obtained under a wide variety of experimental conditions has been undertaken under reducing conditions fo2 below qfm sulfur is present as sulfide ii oxidation state and precipitates as pyrrhotite or an fe s o sulfide phase when the sulfur concentration in the silicate melt is sufficiently high the basic solubility reaction is 1 2 s 2 g o 2 silicate melt 1 2 o 2 g s 2 silicate melt for silicate melts with high feo contents 10 wt feo sulfur dissolves as an fe3so2 or 2feo fes species when saturated with pyrrhotite fes sulfide melt 2feo silicate melt fe 3 so 2 silicate melt log k log x s 21ogx feo 0 8 at 1200 c 1 bar under saturated and unsaturated conditions 1 2 s 2 g 3feo silicate melt fe 3 so 2 silicate melt 1 2 o 2 g log k log x s 1 2 1og o 2 3 log x feo 1 2 log s 2 4 1 at 1200 c 1 bar log k also shows a positive pressure dependence 0 1 per kbar for silicate melts with low feo contents fes sulfide melt o 2 silicate melt feo silicate melt s 2 silicate melt log k log x s log x feo 5 8 9007ndash 1000 c 1 6 kbar for silicate melts with intermediate feo contents 1 10 wt feo the behavior of sulfur is more complex with sulfur probably present as an fes species fes sulfide melt fes silicate melt log k log x s 1 05 3000 t k 850 1200 c 1 bar 2 2 kbar the effects of temperature pressure melt composition and other experimental conditions have been assessed the ability to predict the solubility of sulfur in silicate melts has implications for the formation of ore deposits associated with igneous systems application of the results to natural systems shows that some samples have a concentration of sulfur higher than that which could have been dissolved in the silicate melt indicating that the magma carried excess sulfur and or sulfur has been added after crystallization of the magma

a 90 000 year tephrostratigraphic framework of aso volcano japan abstract a detailed 90 000 year tephrostratigraphic framework of aso volcano southwestern japan has been constructed to understand the post caldera eruptive history of the volcano post caldera central cones were initiated soon after the last caldera forming pyroclastic flow eruption 90 ka and have produced voluminous tephra and lava flows the tephrostratigraphic sequence preserved above the caldera forming stage deposits reaches a total thickness of 100 m near the eastern caldera rim the sequence is composed mainly of mafic scoria fall and ash fall deposits but 36 silicic pumice fall deposits are very useful key beds for correlation of the stratigraphic sequence explosive silicic pumice fall deposits that fell far beyond the caldera have occurred at intervals of about 2500 years in the post caldera activity three pumice fall deposits could be correlated with lava flows or an edifice in the western part of the central cones although the other silicic tephra beds were erupted at unknown vents which are probably buried by the younger products from the present central cones most of silicic eruptions produced deposits smaller than 0 1 km 3 but bulk volumes of two silicic eruptions producing the nojiri pumice 84 ka and kusasenrigahama pumice kpfa 30 ka were on the order of 1 km 3 vei 5 the largest pyroclastic eruption occurred at the kusasenrigahama crater about 30 ka this catastrophic eruption began with a dacitic lava flow and thereafter produced kpfa 2 2 km 3 total tephra volume in the past 90 000 years is estimated at about 18 1 km 3 dense rock equivalent dre whereas total volume for edifices of the post caldera central cones is calculated at about 112 km 3 which is six times greater than the former therefore the average magma discharge rate during the post caldera stage of aso volcano is estimated at about 1 5 km 3 ky which is similar to the rates of other quaternary volcanoes in japan

controls on different mineralization styles of the dongbulage mo and taibudai cu mo porphyry deposits in the great xing an range ne china abstract the dongbulage porphyry mo dominant and taibudai cu mo deposits are located in the central southern great xing an range inner mongolia northeastern china and are associated with granite porphyry and monzogranite intrusions respectively re os isotope data for five molybdenite samples from the dongbulage mo deposit give a weighted mean model age of 164 3 1 2 ma which is in accordance with a zircon u pb age of 164 5 1 7 ma for the host granite porphyry indicating that the deposit formed at the end of the middle jurassic the zircon u pb age of the taibudai ore bearing monzogranite is 137 9 1 7 ma indicating that the deposit formed in the early cretaceous whole rock geochemical data indicate that the dongbulage granite porphyry and the taibudai monzogranite are high k calc alkaline and have ree patterned light rare earth elements lrees enriched and heavy rare earth elements hrees depleted both plutons show ba nb and ti depletions on normalized trace element diagrams and the dongbulage granite porphyry shows strongly negative eu anomalies which are absent in the taibudai intrusion the geochemical differences between the two intrusions suggest that the dongbulage granite porphyry is the result of more advanced fractional crystallization which led to the formation of a mo dominant deposit whereas the lesser degree of crystal fractionation in the taibudai monzogranitic magma resulted in the formation of a cu deposit the relatively listric shaped ree patterns of taibudai rocks suggest more hydrous parental magmas than that of dongbulage rocks therefore fractional crystallization and magma water content exert a significant control on the styles of mineralization mo versus cu dominant in the central southern great xing an range

open system degassing of sulfur from krakatau 1883 magma we present the first sulfur and oxygen isotopic data for tephra from the catastrophic 1883 eruption of krakatau sulfur isotopic ratios in unaltered krakatau tephra erupted august 26 27 1883 are markedly enriched in 34s relative to mantle sulfur high 34s values of 6 3 to 16 4 can best be explained by open system or multi stage degassing of so2 from the oxidized rhyodacitic and gray dacitic magmas with 34s enrichment of so2 4 remaining in the melt lower whole rock 34s values of 2 6 and 4 0 in two oxidized gray dacitic samples indicate more primitive subarc mantle sulfur in the 1883 magma chamber initial 34s of the rhyodacitic magma was probably in the 1 5 to 4 0 range and similar to 34s values measured in arc volcanic rocks from the mariana arc

influences of the tonga subduction zone on seafloor massive sulfide deposits along the eastern lau spreading center and valu fa ridge abstract this study investigates the morphology mineralogy and geochemistry of seafloor massive sulfide sms deposits from six back arc hydrothermal vent fields along the eastern lau spreading center elsc and valu fa ridge vfr in the context of endmember vent fluid chemistry and proximity to the tonga subduction zone to complement deposit geochemistry vent fluid analyses of cu zn ba pb and h 2 aq were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions results document southward increases in the abundance of mantle incompatible elements in hydrothermal fluids ba and pb and sms deposits ba pb as and sb which is also expressed in the abundance of barite baso 4 and galena pbs in sms deposits these increases correspond to a decrease in distance between the elsc vfr and the tonga subduction zone that correlates with a change in crustal lithology from back arc basin basalt in the north to mixed andesite rhyolite and dacite in the south barite influences deposit morphology contributing to the formation of horizontal flanges and squat terraces results are also consistent with a regional scale lowering of hydrothermal reaction zone temperatures from north to south except at the southernmost mariner vent field that leads to lower temperature higher ph vent fluids relative to mid ocean ridges of similar spreading rates mottl et al 2011 these fluids are cu and zn poor and the deposits formed from these fluids are cu poor but zn rich in contrast at the mariner vent field higher temperature and lower ph vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles mottl et al 2011 the mariner fluids are cu and zn rich and vent from sms deposits that are rich in cu but poor in zn with moderate amounts of pb thermodynamic calculations indicate that the contrasting metal contents of vent fluids and sms deposits can be accounted for by vent fluid ph wurtzite sphalerite zn fe s and galena pbs are saturated at higher temperatures in higher ph zn cu and pb poor elsc vfr vent fluids but are undersaturated at similar temperatures in low ph zn cu and pb rich vent fluids from the mariner vent field indicators of ph in the elsc and vfr sms deposits include the presence of co precipitated wurtzite and chalcopyrite along conduit linings in deposits formed from higher ph fluids and different correlations between concentrations of zn and ag in bulk geochemical analyses significant positive bulk geochemical zn ag correlations occur for deposits at vent fields where hydrothermal fluids have a minimum ph at 25 c 3 6 data show that the compositions of the mineral linings of open conduit chimneys minerals present mol fes in zn fe s that precipitate directly from hydrothermal fluids closely reflect the temperature and sulfur fugacity of sampled hydrothermal fluids these mineral lining compositions thus can be used as indicators of hydrothermal fluid temperature and composition ph metal content sulfur fugacity

chalcophile elements and ir in continental cretaceous tertiary boundary clays from the western interior of the usa abstract this study presents data for ir and the chalcophile elements as sb and zn in seventeen samples from continental k t boundary layers in the western interior of the usa the results show that in contrast to previously studied marine boundary clays the continental boundary layers show no correlation between ir and any of the chalcophile elements compared with average shale the continental boundary layers are significantly to strongly enriched in ir as and sb but show ordinary zn concentrations the ir enrichments can be attributed to fallout of extraterrestrial matter whereas as and sb enrichments can be readily explained by the close spatial association of the boundary layers with coal and the abundance in the layers of jarosite goethite and other weathering products of pyrite if compared to jarosite rich coal associated background samples the boundary layers show much higher ir concentrations but similar or possibly slightly enhanced concentrations of as sb and zn the correlation between chalcophile elements and ir in marine boundary clays and the absence of such a correlation in continental boundary clays concurs with the idea that a major fraction of the ir in extremely ir rich 30 460 ppb ir marine boundary clays has precipitated from seawater that was enriched in ir being derived from a vaporized asteroid

degassing of metals and metalloids from erupting seamount and mid ocean ridge volcanoes observations and predictions recently it has been reported that the element polonium degasses from mid ocean ridge and seamount volcanoes during eruptions published and new observations on other volatile metal and metalloid elements can also be interpreted as indicating significant degassing of magmatic vapors during submarine eruptions this process potentially plays an important role in the net transfer of chemical elements from erupting volcanoes to seawater in addition to that arising from sea floor hydrothermal systems in this paper a framework is constructed for predicting and assessing semiquantitatively the potential magnitude and chemical fingerprints in the water column of metal and metalloid degassing using 1 predictions from a summary of element volatilities during mafic subaerial volcanism worldwide and 2 limited data from submarine volcanic effusives the latter include analyses of polonium and trace metals in near volcano water masses sampled following a submarine eruption at loihi seamount hawaii 1000 m bsl in 1996 the element volatility predictions and observations show good agreement considering the limited dataset some of the highest volatility main group and transition element enrichments in seawater over loihi are predicted by the degassing mass transfer model i present when expanded to cover all submarine volcanic activity it is predicted that exit fluxes of these elements are up to 102 103 greater by degassing than by normal mor hydrothermalism in contrast mor exit fluxes of low volatility alkali and alkaline earth elements are likely 102 106 greater from hydrothermal inputs degassing inputs to the ocean are probably highly episodic occurring almost entirely during eruptions these are times of enhanced and abnormal hydrothermalism as well although major hydrothermal and degassing events may not be chemically recognizable in real water masses as wholly distinct entities it is nevertheless possible to predict to what extent each process flavors the effluents of the other degassing at mid ocean ridges may explain a variety of observations previously ascribed to complexities occurring during hydrothermal venting and or fluid ascent in the buoyant hydrothermal plumes above ridges

tectonic controls of late paleozoic subsidence in the south central united states the ouachita marathon fold and thrust belt has a foreland region in texas oklahoma new mexico and colorado which was deformed in a style reminiscent of the laramide foreland in wyoming and montana large asymmetric basins are separated by basement block uplifts which were subaerially exposed and eroded during pennsylvanian and early permian time a major previously unrecognized aspect of this deformation is the regional subsidence which resulted in burial of the uplifts analysis of the subsidence history for three basins suggests that crustal extension was not a factor in affecting regional subsidence this suggestion is in agreement with the presence of a thick crust and reverse and thrust faults in the region a model is proposed in which northward directed low angle subduction places oceanic lithosphere converted to eclogite beneath the foreland resulting isostatic adjustments would have created tectonic subsidence of the same order of magnitude as that observed in the ouachita foreland

use of platinum group elements for impactor identification terrestrial impact craters and cretaceous tertiary boundary abstract this study presents the abundances of ru ir pt pd rh and au platinum group elements pge in the ejecta layer at the cretaceous tertiary boundary and melt rocks from east clearwater lake brent new quebec and lake wanapitei impact craters all believed to have been formed by the impact of chondritic projectiles the objective was to evaluate the pure application of pge interelement ratios e g ru ir for impactor identification to compare the utility of both melt rocks and ejecta deposits for this purpose and to expand the pge database for these craters the similarity of pge interelement ratios within the chondrite and iron meteorite groups precludes their use in the fine classification of impactors of this composition introduction of indigenous pge from country rock may contaminate the original meteoritic signature in addition the extent of pge fractionation during impact and melt sheet cooling and of post sedimentary pge remobilization must be evaluated in each case for east clearwater the pge chondrite normalized plot is flat indicating a chondritic impactor based on ru ir and cr ir ratios a cl or l chondrite is most likely however variation of ratios with depth in the core makes any fine classification of the projectile tenuous for the brent and new quebec craters the flat chondrite normalized pge plot indicates a chondritic impactor but finer classification is precluded by possible post syn depositional pge fractionation at lake wanapitei ni cr and cr ir ratios indicate a ll chondrite impactor wolf et al 1980 but sparse pge data for this chondrite type does not allow further classification of the projectile a flat chondrite normalized pge plot indicates a chondritic rather than an iron impactor at lake wanapitei the global ejecta layer at the cretaceous tertiary boundary has a chondritic pge signature but only when the integrated flux of pge on a global scale is considered individual sites may not show chondritic ratios due to differential pge remobilization resulting from local differences in depositional environment continental vs marine and to vaporization and or condensation pge fractionation occurring during impact the results for melt rocks and the k t ejecta deposit indicate that pge can be used for impactor identification but primarily in combination with other siderophile chalcophile meteoritic elements and their ratios

low sulfur content in submarine lavas an unreliable indicator of subaerial eruption low s content 250 ppm has been used to identify subaerially erupted hawaiian and icelandic lavas large differences in s content of submarine erupted lavas from different tectonic settings indicate that the behavior of s is complex variations is s abundance in undegassed submarine erupted lavas can result from different source compositions different percentages of partial melting and crystal fractionation low s concentrations in highly vesicular submarine lavas suggest that partial degassing can occur despite great hydrostatic pressure these processes need to be evaluated before using s content as an indicator of eruption depth

sulfide mineral in intrusive and volcanic rocks of the bingham park city belt utah we report here the results of a reconnaissance study of sulfide inclusions in some intrusive and volcanic rocks from the bingham park city belt in central utah the study was undertaken to determine whether primary sulfides were preserved in these rocks and if so to assess their role in the geochemistry of copper in the magmas numerous samples were studied from the alta clayton peak and flagstaff stocks and a few samples were also studied from the little cottonwood last chance and soldier canyon stocks as well as from the phoenix dike and the keetley volcanics our results show that sulfides are present in unaltered intrusive and volcanic rocks although most of these inclusions lack hematite and pyrite that are typical products of degassing at least some inclusions appear to have been modified possibly by reaction with enclosing iron bearing host minerals measurements of the sizes of inclusions suggest that sulfides contain only 20 to 50 percent of the copper in the rock whereas sulfide selective analyses suggest that all of the copper in the rock is hosted by sulfides despite this uncertainty compositions of sulfides vary systematically from unit to unit the distribution of sulfide inclusions in different minerals suggests that mafic intrusions were saturated with sulfur over a longer period of time during their crystallization history than were felsic intrusions although there are exceptions chalcopyrite is most abundant in intrusions emplaced at deeper levels bornite is found in intrusions emplaced at intermediate levels and pyrrhotite is found in the shallowest intrusions and volcanic rocks finally apparently unaltered samples of the last chance soldiers canyon and phoenix bodies contain talnakhite a copper bearing sulfide mineral that was not observed in the other intrusive rocks in view of the close association of the last chance and phoenix bodies with the bingham porphyry copper deposit this relationship could be of use in evaluation of the mineral potential of felsic intrusive rocks