desert agricultural systems at eba jawa jordan integrating archaeological and paleoenvironmental records located in the arid basalt desert of northeastern jordan the settlement of jawa is by far the largest and best preserved archaeological site in the region the early bronze age eba settlement phase of jawa 3500 3000 bce is characterized by a highly sophisticated water storage system made of a series of pools dams and canals in addition recent archaeological and geoarchaeological surveys have uncovered agricultural terrace systems in the nearby vicinity in this study four of these runoff terrace systems were investigated by detailed mapping additionally thirteen sediment profiles from inside and outside the terrace systems were recorded and sampled the examined samples were analyzed for bulk chemistry texture phytoliths diatoms and dung spherulites to supply information on the environmental and depositional conditions the terrace systems were dated using optically stimulated luminescence osl ancient terrace agriculture was practiced on slopes small plateaus and valleys close to jawa through the use of surface canals which collected and diverted floodwater from nearby wadis or runoff from adjacent slopes the terraced fields were usually arranged in cascades and comprised a system of risers canals and spillways the terrace fills investigated yield osl ages of around 3300 bce indicating that the terraces were constructed in the early bronze age the terrace fill sequences are composed of mixed unstratified fine sediments of local origin reflecting low energy fluvial deposition regimes the phytolith record is dominated by pooid grasses that include the most common near eastern cereals such as wheat and barley increased phytolith concentrations in terrace fill sediments as compared to samples from non terrace deposits nearby suggest increased plant growth and water availability within the terraces whether the terrace systems were used for growing food crops only or whether they were additionally used for grazing cannot be ascertained overall quantitative phytolith analyses in arid environments are well suited to investigate temporal and spatial distributions of plant microfossil concentrations and their relation to human activity or paleoenvironmental conditions

mode of occupation of tabun cave mt carmel israel during the mousterian period a study of the sediments and phytoliths alternative modes of occupation of tabun cave during the deposition of the mousterian levels b and c have been proposed garrod bate 1937 excavations at the wady el mughara volume 1 oxford clarendon press interpreted the archaeological record of both levels as being indicative of domestic occupational activities jelinek et al 1973 palaeorient 1 151 183 proposed that the presence of articulated limb bones of dama mesopotamica in the level b sediments below the cave chimney indicated that the cave was used as a natural game trap they also noted that the white ash layers in level c extended across the whole cave and proposed that this was due to the burning of natural vegetation in the cave this study aims at clarifying the modes of occupation during these periods level b sediments closely resemble the terra rossa soil that is common in this region burning activity is inferred from charcoal fragments seen in thin sections a minor wood ash component is present based on the preponderance of phytoliths with a variable morphology as compared to those with a consistent morphology as well as phytoliths with shapes characteristic of those formed in wood and bark of local trees thus fires were produced in the cave during this period the cave may also have been used as a game trap level c is composed of multiple layers of brown black and white sediments micromorphology mineralogy and phytolith analyses all show that these layers are mixtures of terra rossa soil and ash with the latter being abundant in the white layers the phytoliths in these layers are derived almost entirely from wood and bark and not from grasses these observations are consistent with a domestic occupational mode 1999 academic press

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

flexural plate subsidence sedimentation rates and structural development of the super deep south caspian basin abstract on a 270 km long seismic line across the west central and central parts of the south caspian basin an inverse flexural plate method is used to recover original uploaded plate parameters the original plate shows remarkable consistency of parameters determined from the 12 second deep seismic line with average rigidity d 1023 6nm bending moment m 1016n dip angle 0 14 and in line compressive stress of 1012 3n m 1 by sequentially adding the sedimentary units to the average bare basement it is shown that the geometry of the basin at jurassic time had a major downward warp and high sedimentary fill to the west leaving the eastern section open to possible erosion during early and middle cretaceous time the deep western part of the basin was then filled by sediments during late tertiary quaternary time and a new depocenter created across the central and western parts of the basin this newer depocenter was then filled during pliocene quaternary time the combined flexure of the basement plate and corresponding sediment fill behaviors with time are indicative of corresponding lithologic variations across the basin and with suspected organic rich sediments the integrated description of basement sediments and depocenter behavior points to the utility of the inverse procedure for improving our understanding of basinal evolution the value of rigidity is comparable to estimated oceanic crust values in line with the suspected tethys oceanic fragment of an island arc below the sediments the shift in depositional behavior with time from west to more northerly across the line of section is tied to the orogenic rise of the caucasus mountains to the north of the section and to the continued subduction of the talysh vandam plate fragment northward today the transpressional nature of the basin and the resolution of the in line compressive stress into components perpendicular to the great caucasus 70 and also perpendicular to the west caspian deep laid fault 25 30 are both in accord with the 25 30 km of present day sedimentary cover including the variations of thicknesses of seismic stratigraphic units along the section from azerbaijan in the west to nearly the turkmenian border in the east

evaluating the mechanical compaction of quartzarenites the importance of sorting llanos foreland basin colombia abstract mechanical compaction is the main porosity reducing process in sandstones including high reservoir quality rigid grain sandstones for such sandstones the extrapolation of theoretical or experimental compaction algorithms needs calibration with rocks having well constrained burial histories evaluating the compaction of these rocks is achieved by comparing current intergranular volume igv with depositional igv which is strongly dependent on sorting however because sandstone sorting is difficult to measure accurately its impact on depositional porosity and compaction state is largely underestimated we use the quartzarenites of the oligocene carbonera formation in the subsurface of the hydrostatically pressured llanos basin to illustrate the importance of sorting when evaluating the compaction of rigid grain sandstones igv and sorting were measured in core samples using a combination of transmitted light and cathodoluminescence images resulting in improved accuracy over standard procedures the compaction state of clean quartzarenites at given depths is best described using igv versus sorting plots which are used to derive compaction curves for specified sorting values the igv versus sorting trends are displaced to lower igv values with increasing burial depth the differences in igv caused by differences in sorting exceed the differences in igv resulting from 1000 m of burial illustrating the high impact of sorting when evaluating compaction contrasting with published experimental results the compaction of the llanos basin ductile grain poor quartzarenites is independent of grain size and grain rearrangement is the main compaction mechanism during the first 1 6 km of burial based on the llanos data we have generated igv versus depth curves for clean pure quartzarenites of specific sorting which can be used to predict their maximum primary porosity up to moderate burial depths differences with other published burial curves are probably related to unaccounted variations in sorting ductile grain content and framework strengthening cements however the llanos basin quartzarenites contain virtually no cements explaining their high degree of compaction relative to other rigid grain sandstones and making them ideal to isolate the effects of compaction on the igv of quartzarenites the llanos basin data suggest that below 2 5 km of depth clean well to moderately well sorted quartzarenites continue reducing their igv by mechanical compaction below the 26 limit which should apply only to extremely well sorted rigid grain uncemented sandstones

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

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

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

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

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

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

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

phytolith rich layers from the late bronze and iron ages at tel dor israel mode of formation and archaeological significance the presence of many phytolith rich layers in late bronze and iron age deposits at tel dor israel are indicative of specific locations where plants were concentrated detailed studies of six of these phytolith rich layers and associated sediments from tel dor show that the phytoliths were derived mainly from wild and domestic grasses the most common domestic grass was the cereal triticum aestivum bread wheat three of these layers have a microlaminated microstructure associated dung spherulites and phosphate nodules characteristics that all point to the phytolith rich layers having formed from dung in animal enclosures in two of the layers the microlaminated structure is absent while dung spherulites and phosphate nodules are present suggesting that these too originate from dung that was not deposited in an enclosure the sixth layer is microlaminated but does not contain spherulites we thus cannot suggest a parsimonious explanation of its observed properties concentrations of burnt phytoliths are present in three locations implying that dung was either burnt in situ or the ashes from burnt dung were redeposited the transformation of dung accumulations into phytolith rich layers involves a loss of organic material and hence a significant reduction in sediment volume which is clearly apparent in the stratigraphy of some of the locations examined the volume reduction can be observed in the macrostratigraphy and has important implications with regard to macrostratigraphic interpretation the presence of abundant phytolith rich layers on the tell has significant implications for the concept of urbanism during these periods 2007 elsevier ltd all rights reserved

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

towards a general state variable constitutive relation to describe granular deformation triaxial compression experiments were performed on cylindrical quartz sand packs to explore the universality of statevariable constitutive relations used to describe granular deformation samples were subjected to relaxation creep experiments similar to slide hold slide tests from friction studies for relaxation creep tests a constant rate of axial shortening was interrupted by time intervals for which the applied shortening rate was set to zero during holds loadforce decayed exponentially with time and the total stress relaxation scales with the logarithm of hold time consistent with friction tests on reloading after holds stress monotonically increases to the pre hold steady state levels without displaying the restrengthening of static friction often observed from shear tests on granular layers we find that the existing rate and state variable friction laws can model the transient strength behavior during relaxation creep and subsequent reloading by using simple assumptions about the deformation of cylindrical sand packs in triaxial compression by analogy with the rate and state friction constitutive relations we propose a generalized state variable expression for granular deformation in simple and pure shear although additional experiments under a variety of load boundary geometries and load paths will be needed such a general constitutive relation may ultimately describe granular deformation under a broad range of conditions e g for large variations in loading rate shear stress normal stress mean stress and may be applicable to a variety of research problems that involve deformation within granular media d 2005 elsevier b v all rights reserved

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

implications of earthquake focal mechanism data for the active tectonics of the south caspian basin and surrounding regions summary the south caspian basin is a relatively aseismic block within the alpine himalayan belt but is surrounded by zones of high seismicity we used the focal mechanisms of 16 earthquakes whose source parameters we determined from inversion of body waves and the mechanisms of 15 other earthquakes to determine the style of faulting in the seismic belts surrounding the south caspian basin earthquakes beneath the talesh mountains of north west iran and immediately off shore in the south west caspian sea have shallow thrust mechanisms showing that the continental crust of north west iran is overthrusting the oceanic like crust of the south caspian basin earthquakes south of the caspian sea in northern iran show a mixture of focal mechanisms both high angle reverse faulting and left lateral strike slip faulting mechanisms are observed in the high alborz mountains farther south on the edge of the central iran plateau oblique left lateral reverse mechanisms are observed it appears that the ne direction of shortening between central iran and the south caspian basin is partitioned into pure left lateral strike slip and thrusting in the wnw trending high alborz but is accommodated by oblique faulting in lower elevations earthquakes in the kopet dag mountains east of the caspian sea also show a mixture of high angle reverse and strike slip faulting mechanisms and may be another example of the partitioning of oblique slip into strike slip and thrust motion normal faulting mechanisms at centroid depths of 35 50 km dominate in the belt of seismicity that extends across the central caspian sea the significance of the normal faulting earthquakes is enigmatic it is improbable that these events represent the motion between the southern caspian basin and eurasia for they imply a sense of motion that is incompatible with the observed topography and folding in the sediments two shallow earthquakes at about 12 km depth in this belt one a small event and the other a large second subevent of a multiple earthquake have thrusting mechanisms suggesting that shortening occurs as the continental crust of the northern caspian sea is thrust over the oceanic like crust of the southern caspian basin shortening is also suggested by the orientations of folds in the sedimentary cover south of the central caspian sea seismic belt we suggest that this shortening does indeed represent a nne motion of the caspian sea relative to eurasia but that the motion is slow and has not produced many earthquakes the deeper normal faulting events may be related to bending or down dip extension of the incipient subducted slab if the motion of the caspian sea relative to eurasia is indeed slow then the motion in the alborz between central iran and the south caspian basin will be almost the same as that between iran and eurasia as has previously been assumed the combined effect of the overthrusting of the south caspian basin by the talesh alborz mountains in the south and by the continental crust of the northern caspian sea in the north will lead to the eventual destruction of the south caspian basin and the possible formation of an intermediate depth dipping seismic zone within the continental interior similar to that presently observed in the hindu kush

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

blame it on the goats desertification in the near east during the holocene the degree to which desertification during the holocene resulted from climatic deterioration or alternatively from overgrazing has puzzled quaternary scientists in many arid regions of the world i

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

geoarchaeological and palaeobotanical evidence for prehistoric cereal storage in the southern caucasus the neolithic settlement of goytepe mid 8th millennium bp this paper presents direct evidence for cereal storage by neolithic farmers in west asia storage features analyzed this study are circular clay bins that frequently occur at neolithic settlements 8th millennium cal bp in the southern caucasus we examined contexts and uses of clay bin features at the neolithic settlement of goytepe azerbaijan we analyzed biogenic microfossil evidence primarily from phytoliths and dung spherulites and the sediments of the clay bins through micromorphology in combination with their associated charred macrobotanical remains while phytoliths and charred botanical remains indicate direct remnants of stored plants mainly chaffs micromorphology and the analyses of faecal spherulites allow us to examine depositional and diagenetic processes of the archaeological sediments inside and outside these features as a result one of the clay bins was found to retain deposits at its base exhibiting high concentrations of grass phytoliths with relatively high proportions of inflorescences and low percentages of anatomically connected phytoliths in comparison with its upper fill deposits and areas outside of the bin these finds combined with the association of the two complete grinding stones inside the bottom of the bin suggest that the remains of cereal processing activities specifically dehusking may have been placed in the bin this interpretation is corroborated by the recovery of charred rachises and chaffs of wheat and barley as well as micromorphological observations that the bottommost fill of the bin consists almost entirely of grass phytoliths with few very small charcoal fragments and fine amorphous organic matter

the micromorphological identification of faecal spherulites from archaeological and modern materials abstract microscopic calcium carbonate spherulites from animal dung are now regularly found in archaeological micromorphology samples they have a particular set of morphological and optical characteristics including a fixed cross of extinction which is always pseudo uniaxial negative this paper gives details of these characteristics and provides methodologies for using them to distinguish faecal spherulites from similar materials e g coccoliths and related biominerals such as plant derived calcium oxalate druses and avian reptilian uric acid spheres simple predictions are made concerning the effect of thin section versus liquid mount preparations on maximum retardation diameter plots these are confirmed by the pattern of the real data but a discrepancy remains between the measured birefringence of the spherulite material and the expected birefringence from radial calcite using morse donnay s 1932 american journal of science 23 421 461 calculation possible reasons for this discrepancy are discussed

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

mechanical compaction of deeply buried sandstones of the north sea abstract sandstones experience mechanical compaction when the overburden load exceeds the compressive strength petrographic evidence is rarely sufficient to determine the timing of mechanical compaction it is often assumed from indirect evidence such as regional porosity depth trends that mechanical compaction is a process that occurs exclusively during shallow or intermediate burial mechanical compaction without grain fracturing may occur at depth following pervasive framework grain dissolution and or if anomalously high porosity has been preserved due to the presence of small amounts of cement we describe examples from the fulmar sandstone formation of the central graben north sea that experienced late stage mechanical compaction following sponge spicule dissolution and microcrystalline quartz cementation deep burial mechanical compaction involving grain crushing may occur if the rate of grain contact quartz dissolution and or quartz overgrowth development cannot compete with the rate of stress increase at grain contacts some rotliegendes sandstones of the southern north sea that have been buried to 4 5 km offer a good example where the suppression of chemical compaction due to the presence of grain coating clays resulted in pervasive grain fracturing mineral veins are frequently associated with sandstones that have experienced pervasive mechanical compaction during deep burial these may reflect the sudden development of overpressure resulting from the transfer of load to the fluid during collapse of the sandstone framework

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

sedimentation in a discharge dominated fluvial lacustrine system the neogene productive series of the south caspian basin azerbaijan abstract the largely lower pliocene productive series and its regional equivalents contain the major hydrocarbon reservoirs of the south caspian basin examination of outcrops in the apsheron region azerbaijan has resulted in re interpretation of the depositional environments of the productive series the lower part of the productive series consists of sandstones and mudstones interpreted as channelised and sheetflood fluvial deposits intercalated with mudstones that represent short lived lacustrine transgressions of a regional caspian lake the upper productive series pereriva and younger suites comprises sandstone prone intervals interpreted as deposition during periods of increased fluvial discharge and sediment supply and mudstone prone intervals interpreted as deposition during periods of decreased discharge and therefore coarse grained sediment starvation sand prone reservoir intervals in the pereriva and overlying balakhany suites mainly comprise amalgamated low sinuosity braided fluvial sheet sandstones mudstone rich intervals form inter and intra suite seals comprising alluvial plain and lacustrine facies the succession displays an overall fining up trend which is controlled by long term climatic cooling decreased fluvial discharge and reduced coarse clastic input the modern volga caspian system is a partial analogue for the lower productive series in the apsheron region where fluvial and lacustrine conditions alternate on a low gradient ramp without evidence for a shelf break lake eyre australia may be a modern analogue for the upper productive series where there are fewer lacustrine influences discernible in the sedimentology and the overall setting resembles a dryland river terminal fan

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

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

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

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

compaction of lithic sands experimental results and applications compaction experiments showed that the degree of physical compaction of a lithic sand is related to the amount and type of lithic material present these experiments produced a product that is texturally indistinguishable from natural lithic sandstones generally sedimentary lithic fragments are more ductile than metamorphic lithic fragments volcanic lithic fragments when altered to phyllosilicate minerals by weathering or diagenesis are extremely ductile mineralogy and intragranular microporosity influence ductility ratios based on weight percent of soft ductile minerals clay and micas to hard brittle minerals quartz and feldspar within the lithic fragments provides a good indication of ductility a ratio greater than 1 indicates the lithic material will be h ghly ductile microporous lithic fragments are more ductile than dense lithic fragments physical compaction models were developed based on experimental data from well sorted lithic sandstones for which the percentage of preserved porosities were functions of the effective stress the type of lithic material and the quantity of lithic material these models are derived from laboratory sandstones with at least 25 lithic grains in the following categories moderately ductile metamorphic lithic fragments highly ductile shale lithic fragments and extremely ductile altered volcanic lithic fragments application of the compaction models of the experimental compaction techniques to modern subsurface sand samples or outcrop equivalents can provide valuable estimates of the preserved porosities i e reservoir potential for lithic sandstones that may be exploratory objecti es in frontier basins examples using the models and experimental compaction techniques for exploration are given experimental data showed that precompaction cement and overpressure may be beneficial to porosity preservation an early formed partial cement can retard compaction and preserve porosity by stabilizing the sand pack a later cement does not have this beneficial effect overpressure when developed early retards compaction by reducing the effective stress of course a late developing overpressure is not effective at preserving porosity because compaction is an irreversible process

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

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

modelling approaches to understanding fold development implications for hydrocarbon reservoirs a mechanics based approach to the evolution of buckle folds is proposed existing analytic and simple numerical models are used to demonstrate that dramatic changes in layer parallel stress occur in developing folds and that the bulk effective rheology of folding rocks is strongly reduced in relation to neighbouring rocks with no folds a methodology for estimating regions of folds more or less likely to suffer fracture is set out in this methodology a simple abstraction of the natural fold is identified and the stress history during its development is calculated using linear viscosity as a proxy for competence this simple and computationally cheap approach allows all salient features of natural multilayer folds to be recreated in numerical experiments the final step in the method is to use the stress conditions for three types of fracture failure tensile failure dilatant shear failure and grain crushing to define potential functions that indicate increased or decreased probability of failure results give predictions that agree well with observation in the simple cases studied a novel method for approximating three dimensional deformations is used to model the propagation of folds in the axial direction and it is found that this occurs rapidly and allows constructive and destructive interference of propagating folds below a certain amplitude this provides a means by which perturbations may interact over a certain distance such a mechanism was an implicit requisite of classic fold theories but its identity has been obscure for three decades it is shown that many small perturbations are needed to give patches of coherent folds and that few large perturbations give single arc folds

geochemical evaluation of hydrocarbons and their potential sources in the western south caspian depression republic of azerbaijan abstract the western south caspian depression located in offshore azerbaijan contains significant accumulations of oil and gas in upper tertiary fluvial deltaic sediments the active tertiary hydrocarbon system is a product of unique paleogeographic and tectonic events that led to paleogene deposition of organic rich source rocks rapid pliocene subsidence concurrent with voluminous supply of clastic sediments and development of anticlinal traps with abundant shale diapirs molecular characterization of selected oil samples indicates most of the oils are sourced from similar organic facies the molecular characteristics are consistent with oils sourced from a tertiary slightly calcareous marine clastic facies examination of oil molecular characteristics oil oil correlations molecular characteristics of selected source rock samples maturation models and potential migration pathways suggests the oil is not syngenetic but most likely sourced from deeper miocene and older marine shales most of the oils have low to moderate organic maturities vre 0 75 0 85 relative to conventional peak generation windows significant variations in oil gravity and whole oil gas chromatogram character suggest post emplacement bacterial and fractionation alteration several oils display characteristics consistent with multiple phases of trap charging the bulk of reservoired gases examined in this study have been sourced from mixed terrestrial marine kerogen generated at organic maturities of vre 0 80 1 00 with some biogenic low maturity mixing none of the gases examined were sourced from the thermal destruction of liquid hydrocarbons we postulate multi stage hydrocarbon emplacement into evolving structural traps the first phase of emplacement occurred in the middle pliocene when tectonic movement and increased subsidence initiated early trap reservoir formation hydrocarbon generation and migration late rapid subsidence from quaternary tectonic activity produced additional hydrocarbons to replenish older depleted traps and charge newly formed traps this late tectonic activity also extensively redistributed hydrocarbon accumulations degassed some that were breached by faults and destroyed other oil pools thermal disequilibrium from the rapid subsidence delayed hydrocarbon generation and increased the minimum depth required for the onset of liquid hydrocarbon generation

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

implications of outcrop geology for reservoirs in the neogene productive series apsheron peninsula azerbaijan the neogene sediments of eastern azerbaijan and western turkmenistan contain significant hydrocarbon reserves in deltaic reservoirs sedimentary logging of these reservoirs at outcrop in azerbaijan has outlined four facies associations that encompass a range of paleoenvironments from alluvial braided river sandstones and conglomerates to delta front siltstones and mudstones the facies associations suggest a river dominated braid delta and are arranged into an architecture controlled by base level changes parasequences parasequence sets and sequence boundaries are key elements the facies associations and stratigraphic architecture together with outcrop observations of cementation and faulting are summarized in terms of four idealized reservoir models fluvial delta plain proximal delta front and distal delta front each reservoir model has distinctive grain size and shale distributions comparison of nearby oil fields with the studied outcrops suggests that the outcrops form good analogs from which to model reservoir architecture barriers and baffles to fluid flow reservoir heterogeneity and reservoir quality variations

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

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

structural controls on mechanical compaction within sandstones an example from the apsheron peninsula azerbaijan abstract mechanical compaction of sand rich reservoirs usually occurs during shallow burial and involves the rearrangement of framework grains and the ductile deformation of soft lithoclasts the reservoir quality porosity and permeability of some neogene sandstones of the south caspian basin has however been dramatically reduced by mechanical compaction involving extensive grain fracturing i e porosity collapse these sandstones were probably susceptible to pervasive grain fracturing because they were buried rapidly and experienced compressional deformation prior to reaching 80 c consequently they did not undergo quartz cementation and were therefore exposed to high stresses while they were extremely weak grain size and structural position are also important controls on the distribution of grain fracturing in the onshore analogue in the apsheron peninsula microstructural analysis confirms that susceptibility to distributed grain fracturing increases with increasing grain size structural position has also an important impact on the distribution of porosity collapse in particular sandstones within the hinges of folded sections have undergone much more extensive grain fracturing than within the surrounding area the increased stresses in this structural position have enhanced distributed grain fracturing and subsequent deformation band development

phytolith taphonomy in the middle to late holocene fluvial sediments of ounjougou mali west africa in semi arid ecosystems where lacustrine sediments are rare bio proxies preserved in fluvial deposits are needed to understand environmental changes in this study we evaluate the potential of phytoliths as a bio proxy in the yame river s deposits at ounjougou mali west africa covering the middle to late holocene 7790 4000 cal bp in soils phytolith assemblages result mainly from decomposition of local vegetation but in alluvial deposits the taphonomy of phytoliths is more complex depending on the type of transport and deposition in order to define the spatial origin of the phytolith assemblages either from local valley floor or regional vegetation catchment area we took the sedimentary characteristics of the deposits into account using a combination of general and index approaches phytoliths of 14 modern and 29 fossil samples from the yame valley were analyzed the predominant source area of represented phytoliths varies with the fluvial energy of transport channel deposits carried during periods of strong fluvial activity contain higher numbers of savanna grass phytoliths and display a lower ratio of dicotyledon versus poaceae phytoliths d p than those deposited in the floodplain where phytoliths from the local gallery forest are more strongly represented from the 5th millennium bp onwards higher percentages of grass short cell phytoliths gscp and lower d p values point to gradual vegetation opening due to increasing aridity high amounts of burned phytoliths show regular fire incidence in the gallery forest and attest for human impact on the landscapes of ounjougou from the 7th millennium bp onwards after 4500 cal bp there is evidence for pearl millet cultivation

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

postaccumulation sandstone porosity evolution by mechanical compaction and the effect on gas saturation case study of the lower shihezi formation in the bayan aobao area ordos basin china abstract porosity evolution and reservoir quality are strongly affected by mechanical compaction however the compaction induced porosity reduction process in sandstone reservoirs during the postaccumulation period and its effect on gas saturation remain poorly understood by studying the sandstones in the bayan aobao area we were able to quantify the porosity evolution and gas saturation variations caused by mechanical compaction during the postaccumulation period through fluid inclusion analysis and mathematical modeling moreover we verified our findings by compaction experiments and geological statistics fluid inclusion microthermometry was employed to determine the hydrocarbon accumulation periods and the highest homogenization temperature of the two phase aqueous fluid inclusions coexisting with natural gas fluid inclusions i e 115 c with a corresponding geological age of 140 ma was regarded as the beginning of the postaccumulation stages with these data we constructed an inversion evolution model based on the geologic statistical model of sandstone mechanical compaction for the postaccumulation period and determined the gas saturation changes based on compaction porosity evolution the modeling results indicate that the sandstone porosity decreased greatly during postaccumulation subsidence and increased slightly during late stage uplift while the gas saturation increased with both the porosity decrease during the postaccumulation subsidence and the porosity increases during the later uplift the modeling results of subsidence are concordant with the compaction experiments which also show that the larger the initial porosity the greater the porosity reduction the uplift modeling results demonstrate that an erosion induced decrease in burial depth allowed the sandstone porosity to increase which is supported by some scholars findings e g neuzil and pollock 1983 jiang et al 2004 zhang 2013 and by the positive correlation between sandstone porosities and restored geologic unit thicknesses in the study area however the inversion modeling indicates that the reason for the porosity rebound in litharenites is that the increase in elastic porosity slightly exceeds the decrease in viscoplastic porosity which would have been different if the uplift induced erosion rate had been distinctly lower gas production test data and restored geologic unit thicknesses indicate that uplift and erosion may be able to enrich sandstone gas reservoirs to a certain extent consistent with the calculated gas saturation variation results but a full understanding of gas saturation evolution awaits further studies the inversion model can provide a powerful tool for quantitative analysis of the sandstone compaction process during the postaccumulation period which could be used for reference in other similar regions

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

domestic activities and spatial distribution in ain abū nukhayla wadi rum southern jordan the use of phytoliths and spherulites studies abstract the pre pottery neolithic b site of ayn ab nukhayla wadi rum jordan contains structural installations loci composed of inter connected oval rock walled pithouses questions that arose from their study centered on how to identify possible herding and agricultural activities and to assess any differences in how the loci were used the combined study of phytoliths and spherulites identified from different loci are presented here the results of quantitative morphologic and morphometric analyses of phytoliths and spherulites identified in the different loci are discussed cereal processing is evident in some loci by the concentration of the inflorescent parts of festucoid grass phytoliths associated with the presence of handstones and querns these loci appear to have encompassed specific areas in which domestic activities including the grinding of cereals and the preparation of other plant resources were undertaken in contrast other loci such as locus 20 seem to have been used as pens for herd animals sheep goats as indicated by very high densities of spherulites the results of this study provide new insights on plant uses herding practices and the economic diversity of early neolithic communities in the levant

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

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

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

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

phytoliths and microcharcoal at jinluojia archeological site in middle reaches of yangtze river indicative of paleoclimate and human activity during the last 3000 years a variety of phytoliths together with prolific microcharcoal particles sponge spicules and diatoms were extracted and identified in four cultural layers from an archeological site at jinluojia macheng hubei province central china the warmth iw and aridity iph indices calculated from grass phytoliths reveal warm and wet periods during the west zhou early east zhou tang and song dynasties whilst cool and dry periods occurred during the late east zhou ming and qing dynasties the paleoclimate conditions reconstructed on the basis of grass phytoliths extracted from archeological sediments are in agreement with those from natural sediments in the middle yangtze region in contrast the woody phytoliths show a positive correlation with microcharcoal particles suggesting an anthropogenic contribution to the woody phytoliths from the use of woody plants for fuel during cooking and heating two episodes of the enhanced abundance of woody phytoliths and microcharcoal particles were found to occur at east zhou dynasty and from ming and qing dynasties to the present proposed to be a consequence of the population expansion and or the frequent wars

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