geochemical characteristics of biotite from felsic intrusive rocks around the sisson brook w mo cu deposit west central new brunswick an indicator of halogen and oxygen fugacity of magmatic systems abstract the sisson brook w mo cu deposit was formed by hydrothermal fluids likely related to the nashwaak granites muscovite biotite granite group i and biotite granite group ii and related dykes biotite granitic dykes group iii and a feldspar biotite quartz porphyry dyke group iv chemical data obtained using epma and la icp ms data of primary magmatic biotites were used to investigate magmatic processes and associated hydrothermal fluids trace element features of biotite in the group i two mica granite suggest other magmatic processes along with a simple fractional crystallization the k rb ratios and compatible elements cr ti co v and ba in biotite from groups ii iii and iv decrease whereas incompatible elements including ta tl ga cs li and sn increase with magma fractionation no correlation of cu w and mo with k rb ratios is evident suggesting that partitioning of cu w and mo into biotite may not be entirely controlled by magma fractionation halogen fugacity of the parental magma of the nashwaak granites and related dykes calculated from zircon saturation temperature shows that group i has high f hf f cl ratios broadly higher than 0 similar to the plutons at the henderson porphyry mo deposit the f hf f cl ratios of the other groups are generally lower than 0 comparable to the santa rita porphyry cu deposit the f h 2 o f hcl and f h 2 o f hf ratios inferred from biotite in the nashwaak granites and related dykes range from 3 to 5 and from 4 to 5 respectively the inferred oxygen fugacity shows that the dyke phases groups iii and iv have the oxygen fugacity around the nickel nickel oxide buffer the plutonic phases groups i and ii have the oxygen fugacity around the quartz fayalite magnetite qfm buffer at high temperatures and oxidized to nickel nickel oxide buffer at lower temperatures this oxidation process in the plutonic phases groups i and ii could be caused by h 2 release at or near h 2 o vapor saturation at high h 2 o fe 2 the magma associated with the biotite dykes group iii is more likely the source of the hydrothermal fluids at the sisson brook deposit since it has the highest differentiation degree and seems to have formed in an oxidized setting necessary for mo to concentrate in the late stage fluids

fluid inclusion characteristics of intrusion related gold mineralization tombstone tungsten magmatic belt yukon territory canada intrusion hosted low sulfide sheeted vein systems are common within many plutons and stocks of the middle cretaceous tombstone tungsten magmatic belt yukon territory and host significant gold mineralization fluid inclusion characteristics of five such systems namely emerald lake dublin gulch scheelite dome mike lake and mactung constrain the vein forming fluid composition formation temperatures and pressures hydrothermal fluid processes and potential fluid sources the veins contain a wide range of fluid inclusion types ubiquitous type 1a and 1b inclusions are low salinity 1a xnacl 1 kbar at emerald lake and dublin gulch and 2 kbar at mactung and scheelite dome that potentially control fluid composition and evolution a variety of fluid processes may have been responsible for gold precipitation including immiscibility and or release of an evolving magmatic fluid

corrigendum central west antarctica among the most rapidly warming regions on earth nature geoscience 6 139 145 2013 published online 23 december 2012 corrected after print 23 december 2013 in our article presenting a reconstruction of the near surface temperature record at byrd station a calculation error led to an overestimation of the magnitude and statistical significance of the temperature trends in december january shown in fig

felsic magmatic phases and the role of late stage aplitic dykes in the formation of the world class cantung tungsten skarn deposit northwest territories canada abstract a field and petro chemical classification of felsic magmatic phases fmps at the world class cantung w skarn deposit was undertaken to document the evolution of magmatism and the relationships between different fmps metasomatism and mineralization early fmps include moderately differentiated zr hf 18 26 ti zr 14 15 biotite monzogranitic plutons and early biotite rich granitic dykes and compositionally similar quartz feldspar porphyry dykes late highly fractionated zr hf 8 17 ti zr 3 13 fmps sourced from a deeper monzogranitic intrusion include 1 leucocratic biotite or tourmaline bearing dykes derived from localized entrapments of residual magma and 2 sub vertical ne trending aplitic dykes derived from a larger segregation of residual fluid and incompatible element enriched magma the aplitic dykes have textures morphologies spatial associations and a pervasive calcic metasomatic mineral assemblage ca plagioclase quartz or clinozoisite indicative of syn mineralization emplacement very late stage overpressuring and initiation of sub vertical fractures into the overlying plutonic carapace and country rocks by supercritical magmatic fluid led to an interaction with calcareous country rocks that resulted in an increased aca2 in the fluid and the concurrent precipitation of w skarn residual magma also ascended with and quenched in equilibrium with the magmatic fluid to from the aplitic dykes then was metasomatized by the fluid as it interacted with calcareous country rocks overall highly fractionated and moderately to very highly undercooled fmps at cantung provide evidence for a large and evolving felsic magmatic system at depth that segregated and maintained a stable fluid and incompatible element enriched residual magma until the latest stages of crystallization the detailed study of fmps associated with magmatic hydrothermal mineral deposits allow us to refine our understanding of these mineralizing systems and better define metallogenic and exploration models for intrusion related mineralization

estimation of aqueous hcl and cl concentrations in felsic systems abstract two models are presented which can be used to make order of magnitude estimates of the concentration of hcl and cl in the magmatic volatile phase mvp one model is based primarily upon aplite chemistry and the other is based primarily on apatite chemistry the models are not entirely independent and additional information can be gained by using the models in conjunction with one another combining both methods allows for the calculation of a model bulk cl concentration of magmatic vapor both models are applied to a natural system the billy lake granite and rush creek quartz monzodiorite in the sierra nevada batholith of eastern california the bulk composition of aplite and other granitic rocks of vapor saturated near minimum melt compositions can be used to estimate maximum hcl total cl for the magmatic vapor phase the composition of the aplites in the billy lake rush creek blrc system has been used to determine model hcl kcl and hcl nacl for the vapor in equilibrium with the aplite melts both ratios are on the order of unity 1 1 these values suggest that the maximum hcl cl 1 3 corresponding to a concentration of hcl in the magmatic vapor of 0 02 molal if the magmatic system was saturated with a brine phase apatite compositions can be used to estimate the hcl concentration in the magmatic vapor as a function of temperature based on the p 2 o 5 and sio 2 concentrations in the aplites and the solubility of apatite in silicate melts apatite began to crystallize at 820 c in the aplites which also yields an estimate of 0 02 molal for the concentration of hcl for the blrc system by the apatite method within error both models produce the some result

in situ major and trace element compositions of apatite from the yangla skarn cu deposit southwest china implications for petrogenesis and mineralization abstract the yangla copper deposit is a rare triassic intrusion related cu skarn system in the central part of the jinshajiang tectonic belt central sanjiang orogenic belt southwest china major and trace element compositions of apatites from ores fertile calc alkaline intrusions and its mafic microgranular enclaves and barren calc alkaline intrusions from the yangla skarn copper deposit were measured by electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry results indicate that apatites grown within ores fertile intrusions and its enclaves show similar features but are different from that grown within barren intrusions apatite from fertile intrusions has higher ca and correspondingly lower total trace element contents which partition onto the ca sites relative to that from barren intrusions apatites from the barren intrusions have high f and low cl contents and correspondingly high f cl ratios which may have resulted from the assimilation of sediment apatites from fertile intrusions show relatively high cl and low f contents which may reflect crystallization from magmas with high water contents redox sensitive elements in apatite can be used as indicators of the oxidation state of magmas apatites from the barren intrusion have lower v and as contents higher mn fe and u contents and more pronounced negative eu anomalies than those from fertile intrusion indicating that the barren magma was more reduced consistent with its lower whole rock fe2o3 feo and zircon ce4 ce3 ratios these findings demonstrate that apatites are effective in distinguishing fertile from barren intrusions and can be used as a robust tool in mineral exploration

exsolution of magmatic volatile phases from cl enriched mineralizing granitic magmas and implications for ore metal transport abstract to understand cl dissolution in aluminosilicate liquids and the exsolution of cl rich magmatic volatile phases experiments were conducted to determine the solubility of nacl kcl and h2o in felsic liquids at 0 5 and 2 kbar the cl content of h2o poor nacl saturated and kcl saturated silicate liquids is low i e 1 3 wt to very low i e 0 2 wt and varies with changes in pressure and composition the cl concentration increases with the f concentration and the molar al na ca mg si ratio of the liquid and decreases with increasing activity of h2o in the system exsolution of a volatile phase depends on the partial pressures of all dissolved volatiles and low cl solubilities in nacl saturated and kcl saturated silicate liquids imply that exsolution of a cl bearing volatile phase will occur early in cl bearing granitic magmas i e prior to extensive melt crystallization and or at comparatively low water fugacities the solubility behavior of h2o and cl is very similar to that of co2 and h2o in felsic liquids small quantities of co2 are known to facilitate volatile phase exsolution holloway 1976 and in a similar manner volatile phases may exsolve early in cl enriched granite magmas whereas 5 to 6 wt dissolved h2o is necessary for volatile phase exsolution from a co2 free and cl free haplogranite liquid at 2 kbar and 800 c a cl rich brine will exsolve if the liquid contains only 1 wt h2o and 0 26 wt cl at the same conditions these new solubility data are interpreted in light of h2o f and cl concentrations in felsic liquids determined from silicate melt inclusions to constrain the exsolution of cl bearing magmatic volatile phases from mineralizing granitic magmas felsic magmas genetically associated with cu porphyry and mo porphyry mineralization contain sufficient h2o and cl to become saturated with respect to a hypersaline brine without strong pressure reduction boiling of the volatile phase i e exsolution of immiscible vapor and brine or strong volatile enrichment resulting from extensive crystal fractionation experiments were also conducted to investigate the solubility of mo in highly saline volatile phases coexisting with granitic liquids at 2 and 0 5 kbar the apparent partition coefficient for mo in the volatile phase s relative to silicate liquid d mo is defined as the computed concentration of mo in a volatile phase or phases the measured concentration of mo in granite glass d mo ranges from 8 to 80 as the nacl and kcl content of the volatile phase s increases from 15 to 90 wt because mo does not complex with cl in aqueous fluids it appears that mo solubility may be a strong function of the activity of na and k in alkali chloride rich volatile phases

shallow water sediment layer structure and composition effects on range dependent acoustic propagation at the atlantic generating station ags site effects of shallow water sediment layers on acoustic propagation over a broad band of frequencies are examined using simulations and measured experimental data accurate geoacoustic data from the new jersey shelf ags site have provided profiles of compressional and shear sound speed attenuation and density along with the detailed bathymetry and ctd data these profiles are used for input to transmission loss and wave number calculations in order to examine range dependent effects of geoacoustic properties and geological structures in this region on acoustic wave propagation parabolic equation pe models are employed for frequencies ranging from 75 to 1200 hz sensitivities to variations in sediment structure and characteristics are determined to show their acoustic influences uncertainties in geoacoustic parameters and sensitivities to required vertical resolution of modeled geoacoustic data are displayed comparisons of elastic pe simulations illustrate the influence of shear effects discussion o

apatite chemical composition determined by electron microprobe and laser ablation inductively coupled plasma mass spectrometry as a probe into granite petrogenesis abstract major minor and trace element abundances in apatites from various i and s type igneous and sedimentary granites of the lachlan fold belt have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometer the results show that apatite can accommodate many minor and trace elements whose concentrations and ratios are relatively sensitive to factors controlling many of the fundamental differences between i and s type granites apatites from s type granites generally have higher f but lower cl contents than those from i type granites which is ascribed mainly to the loss of cl during the weathering processes forming the source rocks of s type granites although fractional crystallisation can cause significant enrichment in f as well high mn and fe contents in apatites from s type granites and high s and as abundances in apatites from mafic i type granites result from different oxygen fugacities and degrees of al saturation or aluminosity between metaluminous mafic i type magmas and peraluminous s type and felsic i type magmas there are systematic and distinctive differences in absolute rare earth element ree abundances ree distribution patterns and element ratios e g la y sm nd etc between apatites from different types of granite the strong eu depletion that characterises apatites from s and felsic i type granites is interpreted here to be a result of the uniqueness of crystal chemistry of apatite and high eu2 eu3 ratios in s type and felsic i type magmas which are more reduced and peraluminous than mafic i type magmas strong ree la to eu and th enrichment in apatites from mafic i type granites and marked nd depletion in apatites from most s type and felsic i type granites are caused by the precipitation and fractionation of monazite in the parental magmas of the latter rocks substitution mechanisms are responsible for high na in apatites from s type and felsic i type granites and for high si in apatites from mafic i type granites and may also have important effects on ree partitioning between apatite and melt thus apatite chemistry can be used as an excellent indicator of granite petrogenesis the results have important implications for identifying different types of granite and are potentially significant for determining the provenance of sedimentary rocks

the influence of oxygen fugacity on tungsten and molybdenum partitioning between silicate melts and ilmenite the partitioning of molybdenum and tungsten between ilmenite ilm and silicic melts has been determined at 800 degrees c 1 kbar of pressure and at two oxygen fugacities at the oxygen fugacity of the graphite methane water buffer d super ilm melt mo 0 42 and d super ilm melt w 0 39 near the nickel nickel oxide buffer d super ilm melt mo 0 22 and d super ilm melt w 0 5 the variations in the partition coefficients with f sub o 2 are significant at the 0 06 and 0 33 levels for molybdenum and tungsten respectively the observed variation with oxygen fugacity is tentatively extrapolated to more complex systems and implies that the oxygen fugacity which prevails during magmatic crystallization may play a role in determining the mo w ratio in porphyry skarn or other hydrothermal mineral deposits examination of the literature on molybdenum and tungsten bearing mineral deposits indicates that systems with high w mo ratios are rather reduced and exhibit high ch 4 co 2 ratios in fluid inclusions low fe super 3 fe super 2 ratios in iron bearing minerals and low oxygen fugacities in associated igneous rocks on the other hand deposits with high mo w ratios are associated with rather oxidized magmatic systems we suggest that f sub o 2 dependent sequestration of molybdenum and tungsten in ferromagnesian phases during plutonic consolidation exerts a control on the relative efficiencies of removal of these metals from magmas into ore forming fluids

magmatic petrogenesis and the evolution of f cl oh fluid composition in barren and tungsten skarn associated plutons using apatite and biotite compositions case studies from the northern canadian cordillera abstract a detailed study of apatite and biotite compositions in multiple intrusive phases from five composite plutons in the northern canadian cordillera was undertaken with the aim of determining the composition of magmatic fluids relative to f cl oh for several plutons both barren and mineralizing and for specific intrusive phases from each pluton that may be related to nearby tungsten skarns magmatic apatite and biotite compositions are consistent with a crustal source of magma either derived from predominantly supracrustal rocks and or derived from predominantly infracrustal rocks and fractionated to felsic compositions increasing mno feo and xf xcl with decreasing cao in apatite broadly correlates with an increasing degree of magmatic differentiation although fe vs total aluminum in biotite is a better indicator of inter and intra plutonic differentiation anomalously iron rich biotites occur in highly fractionated and or wallrock contaminated phases of plutons associated with tungsten skarns estimates of magmatic fluid composition calculated as the activity ratios log a hcl a hf and log a hoh a hf from apatite and biotite compositions show several trends with respect to magmatic differentiation two barren plutons demonstrate that fluids in silicic magmas become hf enriched relative to hcl with increasing differentiation although re equilibration with late stage sub solidus or hydrothermal fluids may obscure this trend the three intrusions with associated tungsten skarn mineralization including the world class cantung deposit also become hf enriched with magmatic evolution however magmatic apatite and biotite in individual intrusive phases that are the most closely associated with mineralization have equilibrated with compositionally distinct fluids in these particular intrusive phases apatite appears to have equilibrated with an earlier hcl and h 2 o rich magmatic fluid and biotite appears to have equilibrated with a later hcl and a particularly h 2 o rich magmatic fluid the fluid in these magmas apparently evolved to a h 2 o rich or less saline composition as the temperature of the magma decreased none of the other intrusive phases from either the barren or tungsten associated plutons have apatite and biotite activity ratios that are suggestive of equilibration with such an hcl hf and h 2 o hf rich fluid instead the activity ratios calculated from apatite and biotite in intrusive phases that are not as closely associated with mineralization are well coupled and unremarkable although small variations are common which would suggest that both minerals equilibrated with similar fluids these intrusive phases do not appear to have produced a large quantity of saline hydrous fluid capable of seggregating and transporting tungsten the identification of intrusive phases that did produce magmatic fluids that were anomalously enriched in hcl and h 2 o could therefore be a predictor of nearby tungsten skarn mineralization

transport and concentration of molybdenum in granite molybdenite systems effects of fluorine and sulfur to investigate the effects of f and s on the transport and concentration of mo in granite molybdenite deposits we prepared four synthetic granite compositions with mo s and f each composition was run at 1000 c and 100 mpa with 6 wt h 2 o to stabilize the phase assemblage liquid aqueous vapor in all compositions mo is partitioned into the vapor phase and deposited on the capsule walls in vapor bubbles in the quenched glasses or in silica rich spherules f and s do not affect the partitioning of mo however s plays a critical role in the deposition of mo from the vapor phase thus the initial water content of the magma which controls the timing of vapor phase evolution and the presence of s are primary controls on mo ore deposition in these deposits

evolution of hf and hcl activity in magmatic volatiles of the gold mineralized emerald lake pluton yukon territory canada we examine the halogen contents of biotite amphibole and apatite from four magmatic phases of the emerald lake pluton to document the evolution in composition of magmatic volatiles in this system and to determine if this evolution is consistent with the nature and distribution of weak gold mineralization in the pluton in general the variations in halogen compositions of hydrous minerals are greater between magmatic phases than within single magma batches and the abundance of chlorine decreases and fluorine increases in hydrous minerals during the evolution of the emerald lake pluton by applying the internally consistent thermodynamic database and mineral activity composition relationships that account for coupled site substitution we further employ biotite and apatite compositions as independent monitors of fluid composition most analyzed biotite exhibits textural and or compositional features characteristic of late subsolidus halogen exchange with fluid however we have identified biotite that appears to retain halogen contents indicative of magmatic conditions fluorine contents of these biotites range from around 1 5 syenite and monzonite to greater than 2 2 wt in a late stage pegmatite dike chlorine by contrast shows a more restricted range of values and typically falls between 1 0 syenite and monzonite and 0 6 wt pegmatite apatite inclusions within anhydrous phenocrysts have fluorine contents of around 3 3 syenite to greater than 3 7 wt granite while chlorine contents fall from 0 5 to 0 1 wt with evolution from syenite to granite phases of the pluton the fluid a hcl a hf conditions recorded by biotite and apatite are in close agreement these two independent measures of hcl and hf both show a modest decrease in hcl hf as the system evolves the highest log a hcl a hf values 0 6 to 0 3 are associated with magmatic volatiles of syenite the first phase to intrude at emerald lake activity ratios recorded from the second phase monzonite show a slight fall to 0 4 to 0 1 a similar drop is recorded in the transition to hydrothermal activity recorded in biotite from a late pegmatite dike 0 1 to 0 1 a decrease in log a hcl a hf is consistent with a loss of chlorine and residual enrichment of fluorine in the magma due to progressive release of a chlorine bearing metalliferous fluid the relatively small variation in inferred fluid hcl and hf activity suggests that the magmatic volatiles present during crystallization were relatively homogeneous and argues against both the incursion of external fluids and of substantial temporal variation in fluid composition from the magma source furthermore if magmatic volatiles are the source of the gold mineralization found across all phases of the emerald lake pluton as advocated by other workers our data would suggest that the mineralizing fluids were remarkably homogeneous and distributed throughout the pluton the disseminated and low grade nature of mineralization may be at least in part a consequence

the geochemistry of phosphorus in granite rocks and the effect of aluminium phosphorus has been shown to have a profound influence on the evolution of silicate melt systems it also controls the geochemical behavior of rare earths uranium thorium strontium and other elements through the relationships between melt and accessory phosphates based on experimental data harrison and watson 1984 proposed a model of saturation behavior of apatite in crustal melts as a function of temperature and silica content subaluminous granites fit in well with such a model but departures are evident in the case of peraluminous granites a systematic study of the distribution of p2o5 in granitoids from all over the world shows that there are two modes to describe phosphorus enrichment in peraluminous granitic rocks 1 the hoyos type trend which is parallel to the one in harrison and watson s hw model but with higher p2o5 concentrations at the same silica contents and 2 the pedrobernardo type trend implying an increase in phosphorus in the most sio2 rich differentiates of strongly peraluminous low ca granites pedrobernardo type leucogranites are characterized by the presence of rare phosphates or p rich feld spars since they have excess p2o5 over cao to form normative apatite we here propose the term perphosphorous granites high phosphorus contents appear to be due to elevated apatite solubility in peraluminous granitic melts rather than to high amounts of restitic apatite both the hoyos and pedrobernardo type departures from the hw model can be corrected by using the expression p2o5corrected p2o5hw efactor where p2o5hw is the prediction according to the hw model and factor is asi 1 6429t asi being the al2o3 cao na2o k2o molar ratio we suggest that such departures could be caused by a decrease in the ca activity in the melt as a result of increased peraluminousity the pedrobernardo type trend is a limiting case in which ca activity in the melt is nearly zero and calcium instead of phosphorus becomes the essential structural constituent esc of the apatite when this happens phosphorus starts behaving as an incompatible element that is concentrated in late fluids high p2o5 contents are more characteristic of s than other granite types no significant departures from the hw model have been found for i a or m type granites in central iberia granites associated with u sn and w mineralizations usually have high phosphorus contents values of p2o50 5 wt at sio270 wt are good indicators of economic mineralization

little ice age cold interval in west antarctica evidence from borehole temperature at the west antarctic ice sheet wais divide 1 the largest climate anomaly of the last 1000 years in the northern hemisphere was the little ice age lia from 1400 1850 c e but little is known about the signature of this event in the southern hemisphere especially in antarctica we present temperature data from a 300 m borehole at the west antarctic ice sheet wais divide results show that wais divide was colder than the last 1000 year average from 1300 to 1800 c e the temperature in the time period 1400 1800 c e was on average 0 52 0 28 c colder than the last 100 year average this amplitude is about half of that seen at greenland summit grip this result is consistent with the idea that the lia was a global event probably caused by a change in solar and volcanic forcing and was not simply a seesaw type redistribution of heat between the hemispheres as would be predicted by some ocean circulation hypotheses the difference in the magnitude of the lia between greenland and west antarctica suggests that the feedbacks amplifying the radiative forcing may not operate in the same way in both regions

geochronology geochemical and sr nd hf pb isotopic compositions of the granitoids in the yemaquan orefield east kunlun orogenic belt northern qinghai tibet plateau implications for magmatic fractional crystallization and sub solidus hydrothermal alteration abstract a general consensus has emerged that high field strength elements hfse can mobile to some extent in a hydrothermal fluid however there are hot debates on whether sub solidus hydrothermal alteration can lower the nb ta ratio in evolved melts in this study we present petrography geochronology and geochemistry of the barren and mineralized rocks in the yemaquan skarn iron deposit northern qinghai tibet plateau to probe magmatic hydrothermal transition the barren rocks consist of diorites granodiorites granites and syenogranites whereas the porphyritic granodiorites are associated with mineralization for an excellent consistency between the magmatic zircon u pb age 225 2 ma and the hydrothermal phlogopite 40 ar 39 ar age 225 1 5 ma the sr nd hf pb isotopic data demonstrate that the yemaquan granitoids are originated from a relatively homogenous enriched mantle with different degrees of crust contamination assimilation fractional crystallization afc trace elements signatures indicate that the porphyritic granodiorites related to mineralization display amphibole crystallization for high water contents whereas the barren granites have gone through biotite crystallization due to potassium enrichment by continuous upper crust contamination both of which are responsible for their nb ta ratios respectively modeling results suggest that a basaltic melt with nb ta ratio of 15 3 can reach a minimum nb ta ratio of 12 in the producing granodioritic melt by amphibole fractional crystallization based on partition coefficients of nb and ta between amphibole and melts from previous experiments this may explain the average nb ta ratio 13 7 of the barren granodiorites while it cannot account for the average nb ta ratio 8 4 of the mineralized porphyritic granodiorites and it is even lower than that of the granites 10 3 with biotite fractional crystallization exsolution of a magmatic hydrothermal fluid is inevitable when a water saturated magma emplaced in shallow crust leading to a transportation of certain chemical components from the magmatic melts to exsolved fluids because nb seems more mobile than ta in fluorine bearing fluids we contend that a preferentially transport nb over ta by sub solidus hydrothermal alteration can further lower the nb ta ratios of the mineralized porphyritic granodiorites which may also result in a broad range of hfse contents and their ratios in the altered porphyritic granodiorites formed in a post magmatic process

fluorine as a tool in the petrogenesis of quartz bearing magmatic associations applications of an improved f oh biotite apatite thermometer grid abstract fluorine contents of whole rock and biotites allow to discriminate quartz bearing magmatic associations through the nature of protoliths and petrogenetic processes f and rb are used to discriminate crustal and mantle derived melts with the exception of calcalkaline association in which mantle contribution may be significant the other quartz bearing associations are essentially derived from crustal melting by biotite and or amphibole vapor absent reactions based on experimental data and on an improved biotite apatite thermometer grid closure temperatures from near liquidus to near solidus conditions as well as fh2o fhf evolution during cooling are determined for the different magmatic associations it appears that the liquidus temperature and fh2o fhf decreases in the order high silica alkaline high k calcalkaline and calcalkaline associations while the solidus temperature follows an inverse order the fh2o fhf values for the peraluminous associations vary over a wide range and overlap the fh2o fhf values of the high k calcalkaline and calcalkaline associations

halogen elements as indicator of deep seated orebodies in the chadong as ag au deposit western guangdong china abstract halogen elements play an important role in the metallogenesis of metallic ore deposits and are involved in the whole process of remobilization transport and precipitation of metallic elements however with the exception of fluorine which as a component of fluorite and mica minerals can be occasionally concentrated in ores cl br and i are hard to enrich in the ores investigations have found that the halogen elements tend to diffuse toward country rocks with the development of hydrothermal alteration in the process of their involvement in metallogenesis especially during the post ore stage when extensive halogen diffusion halos over orebodies would be formed such halogen element diffusion halos over the chadong as ag au deposit extend as widely as 200 m the largest diffusion extent is for i and the diffusion halos of br are most noticeable 50 130 m away from the orebodies in areas of ore exposure and the strongly altered zone the cl br and i contents are close to those of the strata with a v shaped distribution pattern in the periphery of the mining district comparatively speaking in going away from the altered zone the major metallic elements au and ag in the deposit tend to decrease suddenly to their normal contents in the strata this variation feature of halogen elements can be used as geochemical indicators for exploring concealed orebodies at depth in the chadong ore deposit halogen element anomalies can be used to predict concealed orebodies at the depth range of 0 200 m

the origin of granite the role and source of water in the evolution of granitic magmas temperature and water content are the two most important parameters in the formation of granitic magmas evidence from volcanic and plutonic lithologies suggests that water contents of 2 to 4 wt are present in most silicic magmas calculations based on the stability of biotite yield water fugacities within the melt phase from about 500 to 2 000 bars although these calculations determine the log f h 2 o and the effective uncertainty of 0 5 log units yields a large absolute uncertainty comparison with crystallization experiments demonstrates that less than 2 water would require significant percentages of crystallization at temperatures above 900 c with liquidus temperatures about 1000 c water contents greatly in excess of 4 wt would mean that the magma would become vapor saturated at high pressures and would tend to crystallize during ascent to a fine grained granite before reaching shallow depths the main sources of water for magma generation are the dehydration of hydrous silicates within the crust and volatiles transported into the crust from subducted oceanic crust and upper mantle in the form of hydrous basalts and andesites dehydration reactions of muscovite biotite and horn blende are of particular significance anatectic granites may be partially classified in terms of the probable dehydration reaction responsible for their generation melts generated from muscovite dehydration are relatively cool peraluminous in composition high in k na ratio and generally high in initial 87 sr 86 sr and delta 18 o biotite generated melts tend to be higher in temperatures peraluminous to meta aluminous in composition moderately high in k na ratio and relatively high in strontium and oxygen ratios both types may contain metasedimentary enclaves granitoids generated by hornblende dehydration would be much higher in initial temperature peralka line to meta aluminous in composition and lower in k na ratio and in general would have lower strontium and oxygen ratios volatiles deposited in hydrothermally altered oceanic crust and upper mantle will be released during subduction in the form of hydrous basalts and andesites these melts are important energy transfer mechanisms to drive anatexis within the crust if these melts encounter a silicic magma chamber when intruding the crust they will be trapped below the lower density granitic melt while partially quenching against the cooler melt they may release volatiles and heat which will aid in the melting process granites generated in this way will vary in their geochemical properties depending on the relative importance of crustal versus mantle magma systems in general they will have moderate to high initial temperatures be meta aluminous in composition be variable but somewhat low in k na ratio and have lower initial strontium and delta 18 o ratios than will melts derived completely from the crust the fact that most terrestrial spreading centers are subaqueous thus may aid in the formation of a thick granitic continental crust

austral spring southern hemisphere circulation and temperature changes and links to the spcz abstractsignificant austral spring trends have previously been observed in west antarctica and antarctic peninsula temperatures and in atmospheric circulation across the southern pacific and atlantic here physical mechanisms for the observed trends are investigated through analysis of monthly circulation and temperatures from the era interim dataset and outgoing longwave radiation olr data the negative pressure trend over the south pacific during spring is strongest in september while the positive pressure trend over the south atlantic is strongest in october pressure trends in november are generally nonsignificant the authors demonstrate that a significant september trend toward increased convection reduced olr in the poleward portion of the south pacific convergence zone spcz is statistically related to rossby wave like circulation changes across the southern oceans the wave response is strongest over the south pacific in september and propagates eastward to the south atlantic in october o

the halogen geochemistry of the bushveld complex republic of south africa implications for chalcophile element distribution in the lower and critical zones solidification of the interstitial liquid the stratigraphic distribution halogen bearing minerals especially apatite are minor but ubiof s cu and the pge in the critical zone cannot readily be quitous phases throughout the bushveld complex interstitial apatite explained either by precipitation of sulfide as a cotectic phase or as is near end member chlorapatite below the merensky reef lower a function of trapped liquid abundance evidence from potholes and and critical zones and has increasingly fluorian compositions with the pge rich driekop pipe of the bushveld complex imply that increasing structural height above the reef main and upper zones migrating cl rich fluids mobilized the base and precious metal cl f variations in biotite are more limited owing to crystal chemical sulfides we suggest that the distribution of sulfide minerals and controls on halogen substitution but are also consistent with a the chalcophile elements in the lower and critical zones reflects a decrease in the cl f ratio with structural height in the complex general process of vapor refining and chromatographic separation of a detailed section of the upper lower zone to the critical zone is these elements during the evolution and migration of a metalliferous characterized by an upward decrease in sulfide mode from 0 01 cl rich fluid phase 0 1 to trace 0 001 cu tends to correlate with other incompatible elements in most samples whereas the platinum group elements pge can behave independently particularly in the critical zone the decrease in the cl f ratio of apatite in the

seasonal antarctic pressure variability during the twentieth century from spatially complete reconstructions and cam5 simulations as most permanent observations in antarctica started in the 1950s understanding antarctic climate variations throughout the twentieth century remains a challenge to address this issue the non summer multi decadal variability in pressure reconstructions poleward of 60 s is evaluated and assessed in conjunction with climate model simulations throughout the twentieth and early twenty first centuries to understand historical atmospheric circulation variability over antarctica austral autumn and winter seasons show broadly similar patterns with negative anomalies in the early twentieth century 1905 1934 positive pressure anomalies in the middle twentieth century 1950 1980 and negative pressure anomalies in the most recent period 1984 2013 consistent with concurrent trends in the sam index in autumn the anomalies are significant in the context of estimates of interannual variability and reconstruction uncertainty across most of the antarctic continent and the reconstructed patterns agree best with model generated patterns when the simulation includes the forced response to tropical sea surface temperatures and external radiative forcing in winter and spring the reconstructed anomalies are less significant and are consistent with internal atmospheric variability alone the specific role of tropical sst variability on pressure trends in these seasons is difficult to assess due to low reconstruction skill in the region of strongest tropical teleconnections the large internal atmospheric variability and uncertainty in the sst patterns themselves indirect estimates of pressure variability whether through sea ice reconstructions proxy records or improved models and data assimilation schemes will help to further constrain the magnitude of internal variability relative to the forced responses expected from sst trends and external radiative forcing

h2o and halogen f cl br behaviour during shallow magma degassing processes abstract degassing paths of silicic h2o rich magmas during explosive plinian and dome forming eruptions may be represented in simple evolution diagrams relating the residual volatile content of the melt to the volume ratio of gas over melt vg vl these parameters are measurable in erupted magma fragments they are used for interpreting the h2o and halogen contents determined in a series of variously degassed volcanic clasts from the 650 y b p eruption at mt pelee martinique fwi which is characterized by the succession of a dome extrusion and a plinian activity h2o degassing of plinian pumice clasts are modeled by an equilibrium closed system evolution which allows to calculate the partition coefficients of halogen between the aqueous fluid and the rhyolitic melt d v l i 1 for f 10 1 5 for cl and 3 7 1 for br at around 900 c the strong increase of the dv li values of cl and br during dome extrusion is explained by an open system degassing model with a simultaneous crystallization of the melt some significant br enrichments relative to cl in dome fragments are attributed to interactions with an hydrothermal fluid close to seawater in composition the models allow calculation of cl and br contents of aqueous fluids generated by the different degassing paths cl contents are 0 5 mol l for closed system evolution and vary between 0 2 and 1 mol l during open system evolutions these fluids are able to extract significant amounts of chloride complexed metals and silica from the magma during dome forming eruptions they also may generate mineralization of the wall rocks or the rising dome itself e g silica precipitation which may seal the volcanic system and be responsible for the dome explosivity and the transition from dome forming to plinian eruptive style the cl br ratio of initial melts of p1 eruption 250 is much lower than the basaltic and exospheric ratios 400 suggesting that strong cl br fractionation may occur during the production or the differentiation of subduction related magmas

deterministic and stochastic analyses of acoustic plane wave reflection from inhomogeneous porous seafloor the propagator matrix technique for the acoustic plane wave reflection in layered porous anisotropic seafloor is combined with monte carlo simulation to investigate the layering effect of the sediment statistical data from a geologically known site are processed and used as a benchmark realizations of sediment property profiles are generated using a spectral technique a deterministic analysis demonstrates that the amplitude and phase of reflection coefficient is highly dependent on the variation of porosity in a stochastic analysis the effect of randomness is examined it is found that the fluctuation of the sediment physical properties around a mean profile has a significant influence on the seabed reflectivity particularly for the incident angles near and above the critical value frequency behavior of reflectivity is strongly dependent on the correlation length of medium inhomogeneities this behavior is attributed to the interaction among different waves that propagate in the porous sediment layers suggesting the possibility of obtaining the properties using the reflection loss data

chemical composition of biotite from the casino porphyry cu au mo mineralization yukon canada evaluation of magmatic and hydrothermal fluid chemistry abstract the chemical composition of biotite has been determined for the dawson range batholith and the casino porphyry style cu au mo occurrence yukon territory canada biotite from the propylitic phyllic and potassic alteration zones of the casino occurrence possesses higher x mg al 2 o 3 sio 2 f and cl and lower tio 2 bao and mno concentrations than biotite outside these alteration zones this phenomenon is similar to that recorded for biotite of other porphyry cu deposits however the absolute concentrations of the oxides and halogens vary significantly among deposits calculated log f h 2 o f hf f h 2 o f hcl f hcl f hf ratios determined from biotite microprobe data indicate that hydrothermal fluids associated with potassic alteration at casino were similar to those associated with phyllic alteration in contrast fluids responsible for propylitic alteration had higher log f h 2 o f hf and less negative log f hf f hcl values the log f h 2 o f hcl and f hf f hcl ratios established for casino are similar to those for other porphyry cu deposits however log f h 2 o f hf values vary greatly among porphyry deposits this variation in log f h 2 o f hf values may be related to the source of the magmas and or magmatic processes assimilation fractional crystallization associated with melt on its ascent through the crust prior to the exsolution of magmatic fluids that are responsible for porphyry mineralization the biotite compositions from the dawson range batholith are either not consistent with the fe f and mg cl avoidance principles or record changes in the f cl ratio of the fluid during crystallization of the granitic body

analysis and model data comparison of broadband acoustic propagation at the atlantic generating station ags site an investigation of broadband acoustic propagation in a shallow water environment is performed by comparing experimental acoustic data badiey et al j acoust soc am 96 3593 3604 1994 with results from a frequency domain high order parabolic equation technique the principal quantity examined transmission loss versus frequency is determined for fixed source receiver positions over short ranges 0 5 km corresponding to experimental configurations high resolution geoacoustic data from extensive coring of the site along with ctd and detailed bathymetric data are used to construct accurate range dependent input for pe simulations and range varying wave number spectra calculations generally very good agreement between the pe results and data are observed range dependent mechanisms are seen to have a strong azimuthal dependence in both tl and wave number results for this site shear losses are considered by exploiting equivalent fluid relationships the effects of sediment dispersion through frequency dependent sound speed are also examined

unraveling histories of hydrothermal systems via u pb laser ablation dating of skarn garnet abstract skarns are one of the few direct genetic links between magma and base metals in ore deposits yet temporal relationships between skarns and their assumed causative plutons are rarely confirmed with radiometric formation ages skarns have been notoriously difficult to date directly due to a limited primary mineral assemblage generally garnet and pyroxene discrepancies in timescales of skarn formation versus pluton emplacement emphasize our tenuous understanding of temporal relationships between plutons and hydrothermal systems including the duration of hydrothermal activity and skarn mineral growth rates here we apply a new method for u pb dating grossular andradite grandite garnet via la icp ms and present the first comprehensive study to focus on u pb dates of primary skarn garnet we present u pb age constraints on garnets from multiple skarns within the jurassic and cretaceous arcs of the north american cordillera two case studies darwin and empire mountain skarns illustrate the effectiveness of the u pb grandite method by demonstrating that garnet u pb ages agree within error of the pluton and skarn hosted u pb zircon ages two additional study localities black rock and mojave skarns demonstrate the ability of grandite u pb ages to 1 directly identify a causative igneous event and 2 record timing of major tectonic events specifically extensional to trans tensional shifts in the jurassic mojave of california

improved methods for pca based reconstructions case study using the steig et al 2009 antarctic temperature reconstruction abstracta detailed analysis is presented of a recently published antarctic temperature reconstruction that combines satellite and ground information using a regularized expectation maximization algorithm though the general reconstruction concept has merit it is susceptible to spurious results for both temperature trends and patterns the deficiencies include the following i improper calibration of satellite data ii improper determination of spatial structure during infilling and iii suboptimal determination of regularization parameters particularly with respect to satellite principal component retention this study proposes two methods to resolve these issues one utilizes temporal relationships between the satellite and ground data the other combines ground data with only the spatial component of the satellite data both improved methods yield similar results that disagree with the previous method in several aspects rather than finding warming concentrated in west antarctica the authors fi

sulfur partition coefficient between apatite and rhyolite the role of bulk s content experimental studies have been performed to constrain sulfur behavior during apatite crystallization and to determine sulfur partition coefficient between apatite and melt kd s apatite melt at oxidizing conditions crystallization experiments have been conducted with a hydrous rhyolitic melt and different bulk sulfur contents 0 15 to 2 wt s at 900 and 1 000 c 200 mpa and log f rm o 2 nno 3 6 the sulfur content in the glass increases with increasing amount of added s anhydrite crystallizes for s added 0 75 wt 0 10 and 0 13 wt so3 in glass at 900 and 1 000 c respectively the amount of anhydrite increases and the amount of apatite decreases with increasing amount of added sulfur the sulfur exchange reaction in apatite is influenced by the bulk composition of the melt e g p content however changing melt composition has only little effect on kd s apatite melt for the investigated rhyolitic composition the kd s apatite melt does not depend directly on temperature decreases from 14 2 to 2 7 with increasing s content in glass from so3 0 03 to 0 19 wt respectively and can be predicted from the following equation ln kd 0 0025 s in melt in ppm 2 9178 the combination of experimental data obtained for rhyolitic and andesitic melts reveals that the sulfur partition coefficient tends toward a value of 2 for high sulfur content in the glass 0 2 wt so3 using s in apatite as proxy for determining s content in melt is promising but additional experimental data are needed to clarify the individual effects of t f rm s 2 and p and ca content in the melt on s partitioning

energy release in subvolcanic environments implications for breccia formation mechanical pdelta v energy is released from hydrous magmas in subvolcanic environments by the two generally sequential processes of second boiling and subsequent decompression the second boiling process h 2 o saturated melt crystals h 2 o vapor releases sufficient pdelta v energy in the model system previously established by burnham 1979 and burnham and ohmoto 1980 to cause fracture failure of even the strongest wall rocks tensile strength approximately 3 77 x 10 10 ergs kg super 1 to depths of 4 or 5 km following fracture failure moreover expansion of already exsolved h 2 o and exsolution of additional h 2 o upon decompression into the model fracture system releases additional pdelta v energy 9 7 x 10 10 ergs kg super 1 of magma sufficient to lift an equivalent mass of rock nearly 1 km in the absence of frictional resistance this latter energy although a conservative value is model dependent to the extent that it is affected by changing any one of the following six independent model parameters 1 bulk composition of the magma hornblende biotite granodiorite in the model 2 depth of emplacement of the magma body approximately 2 3 km p t 0 6 kb 3 mass fraction of h 2 o in the initial melt f o w 0 027 2 7 wt h 2 o 4 mass fraction of melt in the magma at the time of emplacement f o m 1 0 100 liquid 5 tensile strength of the wall rocks 3 77 x 10 10 ergs kg super 1 and 6 depth to the top of the fracture once formed approximately 2 3 km p f 0 3 kb although all of these parameters except the first are of major importance in the formation of hydrothermal breccias generally the mass fraction of h 2 o in the initial melt f o w is regarded as the single most important factor in the formation of breccia bodies in typical porphyry type systems f o w not only determines primarily whether or not the second boiling reaction releases enough pdelta v energy to produce fractures it also determines the magnitude of the decompressional energy released into the fractures if formed magmas in which f o w 0 02 to 0 04 at liquidus temperatures generally release sufficient pdelta v energy not only to produce extensive porphyry type fracture systems but also to produce the breccia bodies these systems commonly contain magmas in which f o w 0 02 on the other hand generally do not release sufficient energy for extensive breccia formation except in structurally weak wall rocks at depths shallower than approximately 2 km magmas in which f o w raquo 0 04 at near liquidus temperatures are incapable of emplacement in the subvolcanic environment

recent surface temperature trends in the interior of east antarctica from borehole firn temperature measurements and geophysical inverse methods 1 we use measured firn temperatures down to depths of 80 to 90 m at four locations in the interior of dronning maud land east antarctica to derive surface temperature histories spanning the past few decades using two different inverse methods we find that the mean surface temperatures near the ice divide the highest elevation ridge of east antarctic ice sheet have increased approximately 1 to 1 5 k within the past 50 years although the onset and rate of this warming vary by site histories at two locations nus07 5 78 65 s 35 64 e and nus07 7 82 07 s 54 89 e suggest that the majority of this warming took place in the past one or two decades slight cooling to no change was indicated at one location nus08 5 82 63 s 17 87 e off the divide near the recovery lakes region in the most recent decade inversion results indicate both cooler and warmer periods at different sites due to high interannual variability and relatively high resolution of the inverted surface temperature histories the overall results of our analysis fit a pattern of recent climate trends emerging from several sources of the antarctic temperature reconstructions there is a contrast in surface temperature trends possibly related to altitude in this part of east antarctica

the characteristic variability and connection to the underlying synoptic activity of the amundsen bellingshausen seas low 1 recent studies have noted an asymmetrical climate change across antarctica with significant warming in west antarctica and the antarctica peninsula and primarily insignificant trends in east antarctica due to its proximity variations in the position and intensity of the amundsen bellingshausen seas low absl are a suspected atmospheric mechanism here we investigate the absl to understand its characteristic variability and underlying synoptic scale influences based on three reanalysis data sets the absl is defined as the minimum monthly pressure in the 45 75 s 180 60 w domain using this criterion a significant north south and east west progression is noted in the climatological 1979 2001 average absl which is strongly tied to the location of the maximum cyclone system density and minimum cyclone central pressures more than 550 cyclones a year were identified in the vicinity of the absl during spring significant trends in their central pressures are noted in the ross sea the implied changes in temperature advection by these stronger systems are consistent with the warming in west antarctica the strongest cyclone events i e the ten with the deepest central pressures also demonstrate a connection to the climatological absl albeit weaker moreover these strong cyclone events are significantly linked to the southern annular mode sam particularly in their annual frequency and location steering in the summer this shows that large scale forcing such as from the sam may influence the strongest cyclones in the region and could allow for the prediction of such events

accessory mineral chemistry as a monitor of petrogenetic and metallogenetic processes a comparative study of zircon and apatite from wushan cu and zhuxiling w mo mineralization related granitoids abstract in this study we explore the chemistry of accessory apatite and zircon as tools to monitor the petrogenetic and metallogenetic processes involved in the formation of the wushan cu and zhuxiling w mo mineralization related granodiorite porphyry the wushan granitoids are metaluminous with a cnk of 0 88 1 01 and the zhuxiling intrusions are weakly peraluminous with higher a cnk values 1 02 1 12 the wushan granitoids have end t values of 4 6 to 4 7 which combined with the relatively elevated mg values 57 62 and adakitic features high sr y ratios of 51 60 indicate that they were derived from melting of a thickened lower crust of the yangtze block with addition of small amounts of mantle components compared to the wushan granitoids the zhuxiling granitoids have relatively high 87sr 86sr i 0 70945 0 70951 and low end t values 5 9 to 6 3 and zircon ehf t values 3 8 to 9 0 suggesting their derivation dominantly from partial melting of the neoproterozoic crust the apatites from the zhuxiling samples are characterized by relatively high mno and feo variable y and low ce which is consistent with the weakly peraluminous feature of whole rock chemistry these apatites show notable depletion of th and lree with a lower la sm n ratio 0 74 1 44 and la yb n ratio 6 2 17 9 relative to those of the host rock 3 04 3 61 and 19 1 23 4 respectively suggesting early crystallization of some lree and th enriched minerals such as allanite monazite before apatite crystallization the steep trend of ce sm versus yb gd ratios shown by zircons from the zhuxiling granitoids suggests that the crystallization of zircon is affected by the crystallization of titanite and apatite thus the crystallization sequence of accessory minerals in the zhuxiling intrusion is allanite apatite titanite and zircon the apatites from the wushan granitoids however show strongly lree enriched ree patterns with weak negative eu anomalies which indicate minor feldspar fractionation and mildly magmatic differentiation the flat trend of ce sm versus yb gd ratios shown by zircon from the wushan pluton indicates that its ree composition is affected by hornblende saturation zircon grains from the metaluminous wushan granitoids exhibit remarkably higher ce4 ce3 ratios and weaker eu eu anomalies than those of the peraluminous zhuxiling samples and the apatites from the wushan samples show higher eu eu 0 55 0 62 and lower ce ce 0 91 1 04 and mno 0 05 0 09 compared to those of the zhuxiling pluton with eu eu 0 41 0 50 ce ce 1 06 1 11 and mno 0 15 0 18 respectively the apatite and zircon chemistry suggest that the cu bearing granitoid formed at an oxygen fugacity higher than the w bearing granitoid which agrees with the fact that the wushan granitoids show whole rock fe3 fe2 ratios higher than the zhuxiling granitoids in addition apatites from the wushan intrusion show enrichment of cl and higher f cl ratios compared to those of the zhuxiling samples suggesting that a water rich parental magma with relatively high cl content is favourable for copper mineralization this case study shows that apatite and zircon chemistry could reflect the geochemical characteristics of their host rock and magma evolution moreover they provide insights into the oxidation state halogen fugacity and magma differentiation of the magmatic system which are key factors for mineralization our data suggest that magma associated with cu mineralization is relatively oxidizing chlorine enriched and less fractionated compared to w bearing magma

on ferroan a type granitoids their compositional variability and modes of origin we recognize eight types of ferroan granitoid that can be distinguished on the basis of major element chemistry these include alkalic granitoids that may be metaluminous or peralkaline alkali calcic granitoids that may be metaluminous peraluminous or peralkaline calc alkalic granitoids that may be metaluminous or peraluminous and rare calcic ferroan granitoids these granitoids may form by two distinct end member processes extreme differentiation of basaltic melts results in ferroan granitoids that are either peralkaline alkalic and alkali calcic or metaluminous alkalic alkali calcic and calc alkalic with alkalinity increasing with increasing pressure of differentiation partial melting of tonalitic to granodioritic crust produces alkali calcic to calc alkalic granitoids that are metaluminous at low pressures and peraluminous at high pressures it is likely that a combination of these two processes plays some role in the formation of most ferroan granitoids most granitoids that are referred to as ferroan however the term has become more confusing than edifying because it has been applied to a broad spectrum of granitoid compositions with varying petrogenesis for this reason we recommend that the term be discontinued and ferroan used in its stead

apatite in felsic rocks a model for the estimation of initial halogen concentrations in the bishop tuff long valley and tuolumne intrusive suite sierra nevada batholith magmas

chemical composition of rock forming minerals in gold related granitoid intrusions southwestern new brunswick canada implications for crystallization conditions volatile exsolution and fluorine chlorine activity chemical composition of rock forming miner als in appalachian siluro devonian granitoid intru sions southwestern new brunswick was systematically determined by electron microprobe the mineral chem ical data together with petrographic examination was used to test magmatic equilibration and to constrain crystallization conditions volatile exsolution and fluo rine chlorine activity of fluids associated with these intrusions mineralogical distinction between late silu rian to early devonian granodioritic to monzogranitic series gms and late devonian granitic series gs rocks is evident although both are subsolvus i type to evolved i type granitoids oxidized to reduced gms rocks consist of quartz plagioclase an 10 k feld spar biotite apatite titanite zircon monazite hornblende pyroxene magnetite ilmenite and sulfide gs rocks comprise quartz k feldspar pla gioclase an 10 mica group minerals zircon mon azite apatite sulfide ilmente magnetite topaz columbite and xenotime inter intrusion and intra intrusion variations in mineral chemistry are in terpreted to reflect petrogenetic processes e g assim ilation and fractional crystallization during granitoid evolution although magmatic equilibration among rock forming minerals are disturbed by subsolidus hy drothermal processes gms rocks appear to have higher magmatic temperatures variable levels of emplacement a range of fo2 i e reduced intrusions 10 16 7 10 13 4 and oxidized intrusions 10 14 0 10 10 5 bars and rela tively low fhf fhcl ratios 10 3 0 10 1 0 in exsolved fluids compared to gs rocks reduced gms intrusions bear higher gold potential and thus may be prospective targets for intrusion related gold systems

antarctic station based seasonal pressure reconstructions since 1905 1 reconstruction evaluation seasonal mean antarctic pressures at 17 stations are reconstructed based on the method of principal component regression employing midlatitude pressure data as predictors several reconstruction methods were performed in order to assess the stability and reliability of the reconstructions obtained including performing the reconstructions over a shorter 30 year window and withholding the remaining data for an independent validation generally there were small differences between the various approaches but typically reconstructions conducted on data with the trends still present and over the full period of observations achieved the highest skill seasonally reconstruction skill was high in austral summer across the entire antarctic continent reconstructions that employed gridded pressure data over oceans as well as the observations here termed pseudoreconstructions also performed remarkably well in austral winter spatially the reconstruction skill was highest near the antarctic peninsula in all seasons and weakest in coastal east antarctica and the antarctic interior during austral spring and autumn the spatial variability of the skill in part reflects the distance to the nearest midlatitude predictor nonetheless for nearly all seasons and locations the observed trends since 1957 were well captured by the reconstructions as was the low frequency decadal scale variability these results suggest antarctic pressure observations can be extended throughout the twentieth century with high confidence especially in summer allowing for a more precise understanding of the role and magnitude of natural atmospheric circulation variability across antarctica

the medieval climate anomaly in antarctica abstract the medieval climate anomaly mca is a well recognized climate perturbation in many parts of the world with a core period of 1000 1200 ce here we are mapping the mca across the antarctic region based on the analysis of published palaeotemperature proxy data from 60 sites in addition to the conventionally used ice core data we are integrating temperature proxy records from marine and terrestrial sediment cores as well as radiocarbon ages of glacier moraines and elephant seal colonies a generally warm mca compared to the subsequent little ice age lia was found for the subantarctic islands south of the antarctic convergence the antarctic peninsula victoria land and central west antarctica a somewhat less clear mca warm signal was detected for the majority of east antarctica mca cooling occurred in the ross ice shelf region and probably in the weddell sea and on filchner ronne ice shelf spatial distribution of mca cooling and warming follows modern dipole patterns as reflected by areas of opposing temperature trends main drivers of the multi centennial scale climate variability appear to be the southern annular mode sam and el nino southern oscillation enso which are linked to solar activity changes by nonlinear dynamics

zircon geochemistry of edong granitoids in the middle lower yangtze metallogenic belt eastern china constraints on w cu fe skarn mineralization abstract it has long been established that skarn deposits of different metals are associated with intrusions of different compositions intermediate felsic granitoids in the edong district of the middle lower yangtze metallogenic belt host skarn deposits with varying w cu fe proportions yet previous whole rock geochemical studies could not distinguish between the magmatic suites that formed the different skarn deposits in this study la icp ms zircon geochemical data are presented for the ruanjiawan w skarn 60300 t wo3 tongshankou cu skarn 0 6 mt cu tonglushan cu fe skarn 1 1 mt cu and 56 8 mt fe and jinshandian fe skarn 200 mt fe deposits in the edong district zircons from the ore forming intrusions of these skarn deposits are all characterized by heavy rare earth element hree enrichments and light rare earth element lree depletions with positive ce anomalies and slightly negative eu anomalies tungsten contents in zircons from the w ore forming intrusion 0 02 3 16 ppm w avg 1 14 ppm are generally higher than in zircons from the cu ore forming intrusion 0 00 0 24 ppm w avg 0 03 ppm copper content in zircons from the cu ore forming intrusion is higher than in those from the w ore forming intrusion fertile intrusive rocks from the four skarn deposits contain zircons with high calculated ce4 ce3 ratios ruanjiawan 71 7 tongshankou 207 5 tonglushan 263 6 jinshandian 189 0 fluorine content of the ruanjiawan intrusion is higher than the tonglushan and jinshandian intrusions followed by the tongshankou intrusion chlorine contents show the opposite trend we propose that the different source regions for the ore fertile intrusions is the critical factor that controls the metal content oxygen fugacity and volatile components our studies suggest that zircon geochemistry is a good indicator to distinguish tungsten causative intrusions from copper and iron ore related intrusions i e w content 1 14 ppm and ce4 ce3 ratios 207 5

significance of oh f and cl content in biotite during metamorphism of the western adamello contact aureole the hydroxyl o 4 site composition of biotite can in principle be used to retrieve information about fluid composition during fluid rock interaction however due to low f and cl content as well as difficulties involved with analyzing the h2o content using in situ techniques measuring these species in biotite has remained an elusive goal here we present high precision secondary ion mass spectrometry sims oh f cl measurements from biotite within metapelites from the western adamello tonalite wat contact aureole northern italy fluorine chlorine and hydrogen are analyzed on the sims sequentially by peak hopping at the same biotite spot h2o f and cl content were measured with a precision 1 0 06 50 5 e e e the compositions of isolated biotite crystals in andalusite are compared with that of biotite in the matrix documenting that halogens and h2o behave refractory in biotite during the time scale of contact metamorphism the h2o and halogen contents of biotite are mostly locked in during the prograde to peak formation of biotite and are not reset during further heating or cooling unless significant biotite recrystallization occurs it also appears that both ti content and xmg of the biotite from the western adamello contact aureole were not significantly reset during cooling the concentration of f and cl does not vary systematically with metamorphic grade which indicates that these species reflect initial compositions no significant rayleigh fractionation behavior was observed for these elements h2o variations in the biotite from samples throughout the western adamello contact aureole suggest that al oxy substitution partially controls the variations in oh content through charge balance of the type r2 vi oh al3 vi o2 h2 while the ti oxy substitution does not seem to influence the o 4 site occupation the main titanium substitution appears to be the ti vacancy text 2 text r text 2 text t text i text 4 square text vi exchange variations in h2o and halogen concentrations in biotite define sub mm scale areas of localized equilibration even for biotite recrystallized during dehydration reactions that produced large amounts of fluid chlorite or muscovite breakdown similar systematics were observed for ti4 and al3 these findings further support the increasing number of observations that kinetics control much of the mineralogical reactions occurring in contact aureoles and hence care is advised in using equilibrium thermodynamics in this environment

central west antarctica among the most rapidly warming regions on earth the west antarctic ice sheet is contributing to sea level rise but temperature trends in the region have remained uncertain a complete temperature record for byrd station in central west antarctica spanning from 1958 to 2010 establishes west antarctica as one of the fastest warming regions globally

petrogenesis of u and mo bearing a2 type granite of the gattar batholith in the arabian nubian shield northeastern desert egypt evidence for the favorability of host rocks for the origin of associated ore deposits abstract hydrothermal ore deposits associated with granitic rocks are the result of combinations and series of successive processes events and conditions in a magma system and at post magmatic stage the metal content of a granitic magma as well as fractional crystallization metal ligand complexation emplacement mechanisms and tectonic processes influence the metal precipitation and content of a hydrothermal ore deposit the present study of the gattar batholith evaluates how these processes contribute to the generation of an ore deposit gattar batholith in the north eastern desert of egypt as part of the northern region of the arabian nubian shield ans is geographically mineralogically and geochemically divided into two distinctive areas the southern part mainly consists of syenogranite while the northern part is dominated by highly evolved alkali feldspar granite uranium and mo mineralization occurring here is mostly limited to the margin of the highly evolved alkali feldspar granites new u pb zircon geochronology within this study indicates an age of 620 600 ma although high common pb and discordant age data of many zircon grains reflect alteration by f rich fluids some zircons with distinct older u pb ages were considered to be inherited from the wall rocks representing juvenile crust of the ans the two different granitic rocks are comagmatic in origin and have a type characteristics generated by partial melting of lower juvenile crust of the ans geochemical data are in good agreement with a magmatic origin of the alkali feldspar granites suggesting fractional crystallization of a syenogranitic source as the most favorable process of their formation petrography geochemistry and geochronology studies of the gattar granites along with field observations provide evidence for multiple intrusions as a result of successive magma pulses with different chemical composition this led to the formation of reverse zoning within the intrusive complex this kind of magma emplacement promotes the escape of exsolved metal bearing volatile rich fluids into the boundary of the hammamat sedimentary rocks hsr and gattar granite at the northern part of the batholith build up of volatiles is a common phenomenon in granitic rocks and typically results in enhanced contents of f alkalis and ore metals released at subsolidus stage

quantitative models linking igneous amphibole composition with magma cl and oh content minerals of the amphibole group are found in igneous rocks on earth and other rocky bodies since the o 3 site of amphibole can contain oh o 2 f and cl amphibole composition provides important information about water and halogen contents oxidation state and other features of its formation and alteration environments however the complexity of amphibole crystal chemistry means this information is difficult to extract furthermore it has been regular practice in the era of the electron microprobe to neglect h and fe 3 analyses for amphibole critically reducing the amount of information available in amphibole analyses in the literature we have assembled models and insights from previous work to create a methodology that allows the estimation of magmatic h 2 o and cl contents from existing amphibole analyses since the methodology requires use of a cation norm we begin with a deeper investigation of the consequences of different cation normalization schemes for amphibole analyses and provide grounds for deciding which scheme best fits a given amphibole analysis we then show how the existing model of popp and coworkers can be reversed to estimate the oh and o 3 o 2 contents of amphiboles in synthesis experiments using a synthetic data set collected from the literature 39 amphibole analyses we calibrate a partitioning model for the oh cl competition on the o 3 site of igneous amphiboles k cl x cl x oh amphibole cl oh melt ln k cl 6 59 k na a 0 679 mg 0 487 f 6 e where x signifies a mole fraction of an anion on the o 3 site cl and oh signify melt mole fractions of the anion in question on a one oxygen stolper zhang basis k na a mg and 6 fe signify the amount of each component in the amphibole in atoms per amphibole formula unit with a denoting vacancies on the amphibole a site we then combine the popp et al model with our new model to link the occupancy of the amphibole o 3 site and other crystal chemical parameters to the cl and h 2 o content of melts crystallizing amphibole the competition between oh and cl for this site can be used to calculate the melt and amphibole oh h 2 o contents as well as the speciation of fe in amphibole provided that the cl content of both the amphibole and its coexisting melt is known without analyzing either phase for h or fe 3 fe 2 while the models in this paper should be recalibrated using future experimental data this work shows that considerably more information about the volatile contents of magmas can be gleaned from amphibole than previously shown and provides additional information about the crystal chemistry of amphibole and how it affects cl partitioning into minerals of this group

apatite as probe for the halogen composition of metamorphic fluids bamble sector se norway halogen composition of replaced apatite formed during a regional metasomatic event bamble sector se norway reveals information about the composition and evolution of the hydrothermal fluid infiltration and pervasive fluid flow of highly saline fluids into gabbroic bodies lead to scapolitization and amphibolitization where magmatic cl rich apatite reacts with the hydrothermal fluid to form oh and or f rich apatite apatite from highly altered samples adjacent to the shear zone has highest f up to 15 000 g g and lowest br 4 25 g g concentrations whereas apatite from least altered samples has very low f 30 200 g g and high br 30 85 g g in addition individual replaced apatite grains show a zonation in f with high concentrations along rims and cracks and low f in core regions iodine concentrations remain rather constant as low values of 0 18 0 70 g g we interpret all observed compositional features of replaced apatite to be the result of a continuous evolution of the fluid during fluid rock interaction due to its high compatibility f from the infiltrating fluid is incorporated early into recrystallized apatite close to shear zone and rims of individual apatite grains in contrast br as an incompatible halogen becomes enriched in the fluid and is highest in the most evolved fluid using experimental partition data between replaced apatite and fluid we calculated f concentrations of the evolving fluid to decrease from 60 to 1 g g and br to increase from 1200 to 5000 g g i concentrations of the fluid are constant in the order of 370 g g although cl is expected to show a similar behavior as br replaced apatite has constant cl concentrations throughout the alteration sequence 1 wt which is likely the result of a rather constant cl activity in the fluid chlorine stable isotope values of individual apatite grains are heterogeneous and range from 1 2 to 3 7 high 37cl values are generally correlated with oh rich zones of replaced apatite whereas low 37cl values are measured in f rich zones of replaced apatite and in cl apatite of probably magmatic origin though apatite 37cl values follow the general bulk trend the individual 37cl signature seems to reflect the highly localized composition of interfacial fluid at the reaction front our observations suggest that apatite can be used as a fluid probe for f br and i to detect a compositional evolution of the fluid which can be quantified by using experimentally derived partition coefficients partitioning of cl and cl stable isotopes between highly saline fluids and apatite is complex and likely controlled by more unknown factors than just the cl concentration

synoptic weather types for the ross sea region antarctica abstractsynoptic classifications over the southern ocean in the ross sea region of antarctica 50 s antarctic coast 150 e 90 w have been derived from ncep reanalysis data 1979 2011 producing a set of six synoptic types for the region these types describe realistic synoptic conditions for the region and represent the moisture bearing low pressure systems that circulate around antarctica the types are described as follows low bellingshausen amundsen l ba low l zonal z low ross l r ridge r and low amundsen l a seasonal frequencies of the synoptic types reflect the seasonal zonal shift of the amundsen sea low asl and also correlate well with the southern oscillation index soi and the southern annular mode sam variability in the occurrences of the synoptic types l r and l ba indicate a shifting of the position of the asl farther east west toward away from the antarctic peninsula during la nina el nino and positive negative sam conditions a joint linear regression of the

precambrian crust beneath the mesozoic northern canadian cordillera discovered by lithoprobe seismic reflection profiling 1 the cordillera in northern canada is underlain by westward tapering layers that can be followed from outcrops of proterozoic strata in the foreland belt to the lowermost crust of the orogenic interior a distance of as much as 500 km across strike they are interpreted as stratified proterozoic rocks including 1 8 0 7 ga supracrustal rocks and their basement the layering was discovered on two new deep seismic reflection profiles in the yukon line 3 650 km and northern british columbia line 2 1245 km in two segments that were acquired as part of the lithoprobe slave northern cordillera lithospheric evolution snorcle transect in the mackenzie mountains of the eastern yukon the layering in line 3 is visible between 5 0 and 12 0 s 15 to 36 km depth it is followed southwestward for nearly 650 km 500 km across strike and thins to less than 1 0 s 3 0 3 5 km thickness near the moho at the yukon alaska international boundary in the northern rocky mountains of british columbia the upper part of the layering on line 2 correlates with outcrops of proterozoic 1 76 1 0 ga strata in the muskwa anticlinorium at this location the layering is at least 15 km thick and is followed westward then southward into the middle and lower crust for 700 km 300 km across strike it disappears as a thin taper at the base of the crust 150 km east of the coast of the alaskan panhandle the only significant disruption in the layering occurs at the tintina fault zone a late to postorogenic strike slip fault with up to 800 km of displacement which appears as a vertical zone of little reflectivity that disrupts the continuity of the deep layering on both profiles 300 km apart the base of the layered reflection zone coincides with the moho which exhibits variable character and undulates in a series of broad arches with widths of 150 km in general the mantle appears to have few reflections however at the southwest end of line 3 near the alaska british columbia border a reflection dips eastward from 14 0 s to 21 0 s 45 to 73 km depth beneath exposed eocene magmatic rocks it is interpreted as a relict subduction surface of the kula plate our interpretation of proterozoic layered rocks beneath most of the northern cordillera suggests a much different crustal structure than previously considered 1 ancient north american crust comprising up to 25 km of metamorphosed proterozoic to paleozoic sediments plus 5 10 km of pre 1 8 ga crystalline basement projects westward beneath most of the northern canadian cordillera 2 the lateral 500 km by at least 1000 km and vertical up to 25 km extent of the proterozoic layers and their internal deformation are consistent with a long lived margin for northwestern north america with alternating episodes of extension and contraction 3 the detachments that carry deformed rocks of the mackenzie mountains and northern rocky mountains are largely confined to the upper crustal region above the layering 4 accreted terranes include thin klippen that were thrust over north american pericratonic strata e g yukon tanana and terranes such as nisling and stikinia that thicken westward as the underlying proterozoic layers taper and disappear 5 the ages of exposed rocks are not necessarily indicative of the ages of underlying crust a frequent observation in lithoprobe interpretations so that estimates of crustal growth based on surface geology may not be representative

factors controlling sulfur concentrations in volcanic apatite apatite crystals from two types of samples were analyzed by electron microprobe for 15 major and trace elements 1 apatite in h2o and s saturated experimental charges of the 1982 el chichon trachyandesite and 2 apatite in volcanic rocks erupted from 20 volcanoes the so3 contents of the experimental apatite increase with increasing oxygen fugacity from 0 04 wt in reduced charges buffered by fayalite magnetite quartz o2 fmq to 1 0 2 6 wt in oxidized charges buffered by manganosite hausmanite mnh or magnetite hematite mth the so3 contents of mnh and mth buffered apatite also generally increase with increasing pressure from 2 to 4 kbar and decreasing temperature from 950 to 800 8c the partition coefficient for so 3 between apatite and oxidized melt increases with decreasing temperature but appears to be independent of pressure apatites in volcanic rocks show a wide range of so3 contents 0 04 to 0 63 wt our sample set includes one group known to contain primary anhydrite and a second group inferred to have been free of primary anhydrite no systematic differences in apatite s contents are observed between these two groups our study was initiated to define the factors controlling s contents in apatite and to evaluate the hypothesis that high s contents in apatite could be characteristic of s rich anhydrite bearing magmas such as those erupted from el chichon in 1982 and pinatubo in 1991 this hypothesis is shown to be invalid probably chiefly a consequence of the slow intra crystalline diffusion that limits re equil ibration between early formed apatite and the evolving silicate melt contributing factors include early crystallization of most apatite over a relatively small temperature interval common late stage magmatic enrichment of s progressive oxidation during magmatic evolution and strong controls on s contents in apatite exerted by temperature and o2 pressure

magmatic arc asymmetry and distribution of anomalous plutonic belts in the batholiths of california effects of assimilation crustal thickness and depth of crystallization in order to better understand geologic fac tors controlling pronounced regional variations in whole rock chemistry mineralogy and mineral chemistry in the batholiths of california we calculate the magmatic intensive variables f hf f h 2 o f hf f hcl and f o 2 regional scale west to east increases in f oh in mafic silicates corresponding to the systematic i wc to i mc and i sc progression reflect orders of magnitude increase in f hf f h 2 o attending pluton crystallization low f hf f h 2 o of formation of western i wc types is consistent with their derivation from low fluorine source rocks in subducted oceanic slabs or the upper mantle in contrast higher f hf f h 2 o of crystallization of i mc and i sc types to the east implies the involvement of 1 progressively greater amounts of continental crustal source material such as biotite bearing metamorphic rocks their unweathered sedimentary derivatives retaining f rich mafic minerals or their fusion products and or 2 source materials which become more f rich toward the continental interior the regional distribution of i mc and i sc types suggests that the precambrian craton of western north america or derivative sediments may extend farther north in california and be morphologically more complex than previously thought from seemingly out of place occurrences of i wc plutons on the eastern slopes of the sierra nevada batholith we infer the existence of regions where precambrian basement was thin or absent in mesozoic time which prevented extensive cratonal contamination of subducted slab or upper mantle derived magmas new methods for estimating t f o 2 relations in the magmas demonstrate that i scr granites crystallize at oxygen fugacities as much as five orders of magnitude lower than those of i wc i mc and i sc types under conditions at or below the maximum stability limit of graphite in equilibrium with a c o h s gas phase the local scale formation of i scr granites in plutonic belts within specific wall rock terranes containing highly reducing sediments or metasediments may occur by contamination of i types with graphitic pelite or in some cases by the direct fusion of this reducing pelitic wall rock the spatial distribution of i scr granite provinces therefore is controlled simply by wall rock lithology amphibole geobarometry demonstrates a general west to east decrease in crystallization pressure across the sierra nevada batholith in contrast the peninsular ranges batholith displays a west to east crystallization pressure increase the bulk of the california batholiths crystallized at pressures less than 4 5 kb and depths less than about 15 19 km in the southern sierra nevada batholith the san gabriels and the eastern peninsular ranges however plutons crystallized at pressures exceeding 6 kb at deep crustal levels 23 km reconstruction of the pre erosion top of the batholith shows that in an east west cross section the central sierra nevada batholith was a horizontal tabular body with an aspect ratio of at least five to one

time scales of assembly and thermal history of a composite felsic pluton constraints from the emerald lake area northern canadian cordillera yukon knowledge of the time scales of emplacement and thermal history during assembly of composite felsic plutons in the shallow crust are critical to deciphering the processes of crustal growth and magma chamber development detailed petrological and chemical study of the mid cretaceous composite emerald lake pluton from the northern canadian cordillera yukon territory coupled with u pb and 40 ar 39 ar geochronology indicates that this pluton was intruded as a series of magmatic pulses intrusion of these pulses produced a strong petrological zonation from augite syenite hornblende quartz syenite and monzonite to biotite granite our data further indicate that multiple phases were emplaced and cooled to below the mineral closure temperatures over a time scale on the order of the resolution of the 40 ar 39 ar technique v1 myr and that emplacement occurred at 94 3 ma simple thermal modelling and heat conduction calculations were used to further constrain the temporal relationships within the intrusion these calculations are consistent with the geochronology and show that emplacement and cooling were complete in less than 100 kyr and probably 70 5 kyr these results demonstrate that production transport and emplacement of the different phases of the emerald lake pluton occurred essentially simultaneously and that these processes must also have been closely related in time and space by analogy these results provide insights into the assembly and petrogenesis of other complex intrusions and ultimately lead to an understanding of the processes involved in crustal development 2002 elsevier science b v all rights reserved

geoacoustic parameters in a stratified sea bottom from shallow water acoustic propagation due to the difficulty of direct measurement there is a need to develop inverse techniques for remote sensing bottom geoacoustic parameters in the lowan mode measurements are extended to extract acoustic attenuation and speed in a horizontally stratified bottom in shallow water as a function of frequency and depth the computational and experimental results show that for a limited frequency band we can find an equivalent depth profile of sea bottom acoustic attenuation with a linear frequency dependence that simulates the effect of nonlinear frequency dependence without depth structure on some field characteristics such as the attenuation rate of individual mode the frequency response of long range sound propagation and the amplitude ratio of mode 2 to mode 1 however the resultant equivalent negative gradient for the sea bottom attenuation is too strong to be accepted in light of available data the conclusion is that nonlinear frequency dependence of the acoustic attenuation in the upper sedimentary layer is required to explain many aspects of shallow water sound propagation

partitioning of fluorine and chlorine between biotite and granitic melt experimental calibration at 200 mpa h 2 o experiments from 640 to 680 c 200 mpa h2o at fo2 nno employing a natural f rich vitrophyric rhyolite from spor mountain utah assessed the effect of variable mg 100mg mg mn fe on the partitioning of fluorine and chlorine between biotite bt and melt over this temperature interval bt fluorite quartz is the sole liquidus phase partition coefficients for fluorine between biotite and glass dfbt melt show a strong dependence on the mg of bt dfbt melt varies from 1 5 to 7 2 over the range of mg from 21 to 76 a strong linear correlation between dfbt melt and mg has a slope of 9 4 and extrapolates through the origin i e dfbt melt 0 at mg 0 an annite siderophyllite solid solution in these experiments dclbt melt values 1 to 6 in the same experiments vary inversely with mg the al content of biotite does not vary with the aluminum saturation index asi molar al2o3 alkali and alkaline earth oxides of melt but two exchange mechanisms involving al appear to operate in these micas 1 alvi aliv siiv mgiv and mgiv 2aliv 2siiv iv the effects of other components such as li or other intensive parameters including fo2 have yet to be evaluated systematically at comparable mg of bt however the spor mountain rhyolite yields higher dfbt melt values than an li rich strongly peraluminous melt previously investigated the results indicate that the mg of bt exerts the principal control on halogen partitioning with asi and t as second order variables the experimental partition coefficients compare well with other experimental results but not with most volcanic rocks magmatic bt from most rhyolites records higher dfbt melt due to reequilibration with degassed h2o depleted magma and perhaps with f2o 1 exchange that may accompany oxidation fe3 o fe2 oh 1 this behavior is evident in magmatic biotite from a zoned peraluminous rhyolite complex near morococala bolivia bt is sharply zoned with f rich rims but bt core melt inclusion pairs fall on our experimental curve for dfbt melt these experimental data can be used in part to assess the preservation of magmatic volatile contents in plutonic or volcanic silicic rocks for plutonic rocks the actual f content of melt not a relative activity ratio involving hf species can be reasonably estimated if the mica has not undergone subsolidus reequilibration this information is potentially useful for some shallow level ca poor magmas that are thought to be rich in f e g a and s type granites but do not conserve f well as rocks

the interconnected global climate system a review of tropical polar teleconnections abstractthis paper summarizes advances in research on tropical polar teleconnections made roughly over the last decade elucidating el nino southern oscillation enso impacts on high latitudes has remained an important focus along different lines of inquiry tropical to polar connections have also been discovered at the intra seasonal timescale associated with madden julian oscillations mjo on the timescale of decades changes in mjo phases can result in temperature and sea ice changes in the polar regions of both hemispheres moreover the long term changes in sst of the western tropical pacific tropical atlantic and north atlantic ocean have been linked to the rapid winter warming around the antarctic peninsula while sst changes in the central tropical pacific have been linked to the warming in west antarctica rossby wave trains emanating from the tropics remain the key mechanism for tropical and polar teleconnections from intraseasonal to decadal timescales enso related tropical sst anomal

a review of shallow ore related granites textures volatiles and ore metals shallow texturally complex granites can be associated spatially introduction and temporally with hydrothermal alteration and mineralization granite related ore deposits include porphyry and skarn the formation of a granite related ore deposit represents the confluence type ores and other hydrothermal deposits that are of many chemical and physical geological factors including magma spatially and temporally associated with granitic sensu composition e g concentrations of ore metals chlorine and water lato rocks in this paper i emphasize characteristics magma oxidation state the relative timing of crystallization magma found in porphyry style cu mo au deposits and some ascent magmatic volatile phase exsolution and the depth of em related systems however my treatment here is not meant placement early magmatic crystallization of ore metal rich minerals to cover the full range of granitic rocks and mineralization coupled with late exsolution of the magmatic volatile phase is that make up the granite related ore systems the forpromoted by deeper emplacement levels and lower magmatic water mation of granite related ore deposits by orthomagmatic concentrations and leads to low eyciencies of removal of compatible hydrothermal processes is dependent upon many physical elements from melts into the magmatic volatile phase s water and chemical magmatic factors including but not limited concentrations in the melt and pressures of crystallization can be to the composition and evolution of the associated estimated from phase equilibria and textural relationships of horn magmas the rate of magma ascent the depth and blende in some felsic systems physical factors avect the dynamics geometry of magma emplacement and the local temof fluid magma melt and volatile phase movement which in turn perature and stress fields at the site of magma emavect the size of zones of alteration and mineralization granite placement detailed studies of the igneous rocks textures can record the partial history of some dynamic processes associated with ore deposits can therefore yield critical miarolitic cavities are good evidence for magmatic volatile phase information regarding the source of metals and ligands exsolution both miarolitic cavities and pegmatitic texture exhibit in the ore generative hydrothermal solutions that are evidence for external nucleation of crystals nucleation controlled operative in the formation of granite related ores in this phenomena expressed as variations in granite textures can result review i will present a series of narratives consistent in from a multiplicity of causes including undercooling of the melt my view with prevailing field and experimental data on textural elements such as pegmatite aplite skeletal crystals and the orthomagmatic hydrothermal theory for the genesis graphic textures can form as a result of undercooling interconnected of some granite related deposits volumes of the magmatic volatile phase allow for advection of some high level granites i e those that are emplaced hydrothermal ore fluids through the magma in shallow granitic at depths of 8 km or less represent the crystallized systems miarolitic cavities can be interconnected consistent with remains of magmas that were associated with subvolcanic this hypothesis ore generative hydrothermal systems therefore studies of shallow granites aimed at understanding magmatic evolution and volatile phase exsolution at shallow levels are necessary if we are to understand ore genesis and the deep inputs to present day geothermal systems as well as evaluate hazards associated with the volcanic

partitioning of fluorine and chlorine between apatite and aqueous fluids at high pressure and temperature implications for the f and cl content of highp t fluids abstract experiments in a piston cylinder apparatus equilibrated natural fluorapatite with aqueous hcl nacl naoh na 2 co 3 and co 2 h 2 o mixtures at 1 2 0 gpa and 950 1050 c post experiment apatite compositions were determined by electron microprobe and fluid compositions were calculated from mass balance this enabled calibration of the fluorine and chlorine contents of apatite coexisting with a variety of fluids at high p and t and provides better constraints on the halogen composition of aqueous fluids which may exist in the deep crust and upper mantle results obtained at 2 0 gpa and 1050 c indicate that the ratio x clap x ohap in apatite x fap x clap and x ohap are the mole fractions of fluor chlor and hydroxyapatite is proportional to the chlorine content of the fluid up to 1 h 2 o co 2 5 h 2 o hcl and 15 h 2 o nacl wt cl in contrast the ratio x fap x ohap was found to vary in proportion to the fluorine content of the fluid only at concentrations of 0 15 h 2 o hcl and 0 4 h 2 o nacl wt f arising from changes in the activities of aqueous hcl and hf the results of this study demonstrate that fluid composition in addition to the absolute abundances of f and cl in the fluid will determine the amounts of these elements incorporated into coexisting apatite specifically relatively low cl and f concentrations in acidic h 2 o hcl fluids are required to obtain high ratios of x clap x ohap and x fap x ohap in apatite whereas much higher abundances of cl and f in basic fluids i e na bearing are required to achieve the same result in addition resulting from dilution of the aqueous phase with co 2 and the subsequent reduction in the activity of h 2 o apatites with high ratios of x clap x ohap and x fap x ohap may be produced by co 2 h 2 o fluids with relatively low levels of cl or f application of these results to apatites from a suite of ultramafic xenoliths from southeastern australia indicates chlorine abundances of 500 3500 ppm in the fluid phase and points to chlorine as a potentially important component of some mantle fluids

biotite in highly evolved granites from the shimensi w cu mo polymetallic ore deposit china insights into magma source and evolution abstract highly evolved granites are an important type of granitic rock given their close relationship with w sn nb ta and rare metal mineralization and unusual geochemistry compared with typical granites highly evolved granites experience a more complex magmatic evolution which is difficult to investigate with whole rock analyses in this paper we present a comprehensive major and trace element including halogen dataset for biotites from highly evolved granites in the shimensi ore deposit located in northwestern jiangxi province south china which is one of the largest w deposits in the world to constrain its magma source and evolution biotites in the shimensi granites have a magmatic origin they are characterized by low mg 100 mgo mgo feot in mol 29 43 mean 34 high a cnk al2o3 cao na2o k2o in mol values 1 60 2 91 mean 1 78 similar to biotite compositions in s type granites worldwide suggesting the parental magmas were of meta sedimentary origin biotite trace element data reveal a differentiation trend from fine grained granite to granite porphyry and porphyritic granite as indicated by gradually decreasing k rb and nb ta ratios and ba and ti contents and increasing rb cs w nb and ta contents tungsten contents in biotite increase by two orders of magnitude from 0 1 ppm in fine grained granite to 30 ppm in porphyritic granite due to progressive fractional crystallization the log fh2o fhf and log fhcl fhf values inferred from the biotites increase with progressive fractional crystallization indicating no obvious fluid exsolution before or during biotite crystallization high degrees of fractional crystallization and late fluid exsolution in the shimensi granites were favorable for w mineralization nb ta ratios of the biotites decreased from 24 3 to 4 30 with progressive fractional crystallization this result along with the rayleigh fractional crystallization modeling results for whole rock nb and ta contents suggest that fractional crystallization of biotite is the major control on decreasing nb ta ratios in the shimensi granites

amphibole and apatite insights into the evolution and mass balance of cl and s in magmas associated with porphyry copper deposits chlorine and sulfur are of paramount importance for supporting the transport and deposition of ore metals at magmatic hydrothermal systems such as the coroccohuayco fe cu au porphyry skarn deposit peru here we used recent partitioning models to determine the cl and s concentration of the melts from the coroccohuayco magmatic suite using apatite and amphibole chemical analyses the pre mineralization gabbrodiorite complex hosts s poor apatite while the syn and post ore dacitic porphyries host s rich apatite our apatite data on the coroccohuayco magmatic suite are consistent with an increasing oxygen fugacity from the gabbrodiorite complex to the porphyries causing the dominant sulfur species to shift from s2 to s6 at upper crustal pressure where the magmas were emplaced we suggest that this change in sulfur speciation could have favored s degassing rather than its sequestration in magmatic sulfides using available partitioning models for apatite from the porphyries pre degassing s melt concentration was 20 200 ppm estimates of absolute magmatic cl concentrations using amphibole and apatite gave highly contrasting results cl melt concentrations obtained from apatite 0 60 wt for the gabbrodiorite complex 0 2 0 3 wt for the porphyries seems much more reasonable than those obtained from amphibole which are very low 0 37 wt for the gabbrodiorite complex 0 10 wt for the porphyries in turn relative variations of the cl melt concentrations obtained from amphibole during magma cooling are compatible with previous petrological constraints on the coroccohuayco magmatic suite this confirms that the gabbrodioritic magma was initially fluid undersaturated upon emplacement and that magmatic fluid exsolution of the gabbrodiorite and the pluton rooting the porphyry stocks and dikes were emplaced and degassed at 100 200 mpa finally mass balance constraints on s cu and cl were used to estimate the minimum volume of magma required to form the coroccohuayco deposit these three estimates are remarkably consistent among each other ca 100 km3 and suggest that the cl melt concentration is at least as critical as that of cu and s to form an economic mineralization

geochemical constraints on the genesis of the scheelite dome intrusion related gold deposit tombstone gold belt yukon canada the scheelite dome intrusion related gold deposit western selwyn basin yukon is hosted in hornfelsed metasedimentary strata that lie adjacent to the exposed apices of a monzogranite to quartz monzonite plutonic complex of the mid cretaceous tombstone tungsten magmatic belt tintina gold province alaska and yukon a variety of mineralization styles occur throughout a 10 3 km east trending corridor and include reduced au and w rich skarns au w and ag pb zn sb rich quartz tension vein arrays and multiphase fault veins and isolated zones of au rich sericite carbonate altered rock integrated u pb shrimp data for magmatic zircon and ar ar data for magmatic and hydrothermal biotite indicate that gold mineralization occurred within 1 to 2 m y of magma emplacement fluid inclusion oxygen isotope and arsenopyrite geothermometry data indicate that hydrothermal minerals formed at depths of 6 to 9 km over a temperature range from 550 c high temperature au rich skarns formed at 400 c whereas vein hosted mineralization formed at 280 to 380 c in skarns au is strongly associated with enrichments of bi te w and as whereas a variety of au rich veins occur with as rich type 1 and te and w rich type 2 end members silver pb zn sb veins are typically au poor and represent the latest and lowest temperature phase in the hydrothermal paragenesis the fluid inclusion data indicate that all mineralization styles were formed from low salinity 4 wt nacl equiv aqueous carbonic fluids consistent with the composition of fluid inclusions within infilled miarolitic cavities in the intrusive rocks however the nonaqueous fluid was predominantly ch 4 in skarn co 2 in au te and au w veins and a fluid with roughly equal amounts of co 2 ch 4 and n 2 in au as and ag pb zn sb veins oxygen isotope data are consistent with a mineralizing fluid of predominantly magmatic origin that was variably modified to more positive 18 o values during interaction with 18 o enriched metasedimentary strata sulfur isotope data suggest two possible sources of sulfur a magmatic source characterized by 34 s values of approximately 5 to 0 per mil and sulfur from the metasedimentary country rocks characterized by more negative 34 s values of approximately 15 to 10 per mil collectively the data indicate that gold at scheelite dome was deposited from a magmatic hydrothermal system interaction of magmatic fluids with graphitic hornfels rocks resulted in reduction of the ore fluids higher ch 4 co 2 ratios and modification of the oxygen and sulfur isotope values of the ore fluids toward those of the metasedimentary hornfels progressive reduction and cooling of hydrothermal fluids in addition to phase separation in vein hosted mineralization were the mechanisms for gold deposition compared to other intrusion related gold deposits associated with the tombstone tungsten magmatic belt magmatism exposed mineralization at scheelite dome is predominantly hosted by hornfelsed metasedimentary rocks this results in more diverse mineralization styles and a greater spread of isotope and fluid inclusion data

partitioning of f between h2o and co2 fluids and topaz rhyolite melt implications for mineralizing magmatic hydrothermal fluids in f rich granitic systems fluid melt distribution coefficients for f have been determined in experiments conducted with peraluminous topaz rhyolite melts and fluids consisting of h2o and h2o co2 at pressures of 0 5 to 5 kbar temperatures of 775 1000 c and concentrations of f in the melt ranging from 0 5 to 6 9 wt the major element f and cl concentrations of the starting material and run product glasses were determined by electron microprobe and the concentration of f in the fluid was calculated by mass balance the h2o concentrations of some run product glasses were determined by ion microprobe sims the solubility of melt in the fluid phase increases with increasing f in the system the solubility of h2o in the melt is independent of the f concentration of the system with up to 6 3 wt f in the melt no evidence of immiscible silica and fluoriderich liquids was detected in the hydrous but water undersaturated starting material glasses 8 5 wt f in melt or in the water saturated run product glasses f concentrates in topaz rhyolite melts relative to coexisting fluids at most conditions studied however df wt f in fluid wt f in melt increases strongly with increasing f in the system maximum values of df in this study are significantly larger than those previously reported in the literature linear extrapolation of the data suggests that df is greater than one for water saturated peraluminous granitic melts containing 8 wt f at 800 c and 2 kbar df increases as temperature and as h2o h2o co2 of the fluid increase for topaz rhyolite melts containing 1 wt f and with h2o rich fluids df is independent of changes in pressure from 2 to 5 kbar at 800 c for melts containing 1 wt f and in equilibrium with co2 bearing fluids the concentrations of f in fluid increases with increasing pressure f and lithophile element enriched granites may evolve to compositions containing extreme concentrations of f during the final stages of crystallization if f in the melt exceeds 8 wt df is greater than one and the associated magmatic hydrothermal fluid contains 4 molal f such f enriched fluids may be important in the mass transport of ore constituents i e f mo w sn li be rb cs u th nb ta and b from the magma

partitioning behavior of chlorine and fluorine in the system apatite silicate melt fluid the partitioning behavior of cl among apatite mafic silicate melt and aqueous fluid and of f between apatite and melt have been determined in experiments conducted at 1066 to 1150 c and 199 205 mpa the value of dclapatite melt wt fraction of cl in apatite cl in melt 0 8 for silicate melt containing less than 3 8 wt cl at higher melt cl contents small increases in melt cl concentration are accompanied by large increases in apatite cl concentration forcing dclapatite melt to increase as well melt containing less than 3 8 cl coexists with water rich vapor that containing more cl coexists with saline fluid the salinity of which increases rapidly with small increases in melt cl content analogous to the dependency of apatite composition on melt cl content this behavior is due to the fact that the solubility of cl in silicate melt depends strongly on the composition of the melt particularly its mg ca fe and si contents once the melt becomes saturated in cl additional cl must be accommodated by coexisting fluid apatite or other phases rather than the melt itself because cl solubility depends on composition the cl concentration at which dclapatite melt and dclfluid melt begin to increase also depends on composition the experiments reveal that dfapatite melt 3 4 in contrast to cl the concentration of f in silicate melt is only weakly dependent on composition mainly on melt ca contents so dfapatite melt is constant for a wide range of composition the experimental data demonstrate that the fluids present in the waning stages of the solidification of the stillwater and bushveld complexes were highly saline the cl rich apatite in these bodies crystallized from interstitial melt with high cl f oh ratio the latter was generated by the combined processes of fractional crystallization and dehydration by its reaction with the relatively large mass of initially anhydrous pyroxene through which it percolated

mineral chemistry and isotopic composition of magmatic re equilibrated and hydrothermal biotites from darreh zar porphyry copper deposit kerman southeast of iran abstract the darreh zar porphyry copper in the southeastern part of the urumieh dokhtar magmatic belt developed as a consequence of hydrothermal alteration related to the darreh zar granodioritc porphyry stock intruded into mafic volcanic rocks hydrothermal alteration and cu mo mineralization are focused on the darreh zar porphyry pluton belonging to miocene time and the neighboring basaltic country rocks a core zone of potassic alteration is enclosed by a peripheral zone of chlorite sericite sericitic argillic and propylitic alteration judging by petrographic features as well as chemical composition the biotites studied display variable size color and shape and occur as magmatic m re equilibrated r and hydrothermal h types the m and r type biotites are found in the darreh zar porphyry and the h type formed during potassic alteration within the darreh zar porphyry and the volcanic host rocks as well the hydrothermal biotites are characterized by the highest amounts of al 2 o 3 and k 2 o whereas the magmatic types are hosted by high level of tio 2 up to 4 38 wt x mg values vary between 0 31 and 0 61 which is increased from m to r biotites then decreased toward low temperature potassic alteration zone fluorine and chlorine contents from biotite types also vary between 0 07 to 0 56 wt and 0 14 to 0 38 wt respectively these values change to 2 94 to 2 15 wt and 3 6 to 4 4 wt for iv f and iv cl respectively in all types of biotites positive correlation is observed between x mg al 2 o 3 na 2 o k 2 o bao and f but with feo and cl it is negative the tio 2 content clearly decreases from the m to r and h type average 3 98 2 9 and 2 4 wt respectively a direct relation may be noted between mg and oxygen fugacity log f h 2 o f hf and log f h 2 o f hcl values range from 6 24 to 5 46 and 4 49 to 4 12 wt respectively oxygen fugacity increases during formation of re equilibrated biotites but it decreases in the course of potassic alteration crystallization temperatures range from 600 to 650 c 550 to 600 c and 450 to 550 c for magmatic re equilibrated and hydrothermal biotites respectively the m biotites from darreh zar have the d values of 89 to 101 and the calculated d values of the aqueous fluids 66 to 78 in equilibrium with the biotites are consistent with a large component of magmatic fluid which shows similarities with the biotite originated from the primary mantle source the 18 o also varies between 7 4 to 8 2 for fluids in equilibrium with biotites the obtained m biotite data from darreh zar porphyry indicates that there is no clear correlation between d values fe and mg contents but for d values al and fe 3 fe 2 some affinities were observed the isotopic data indicate that m biotites are formed at high temperature 620 20 c from fluids with the highest 18 o h 2 o 7 8 0 4 in comparison with the biotites from some other copper porphyries

sulfur evolution of oxidized arc magmas as recorded in apatite from a porphyry copper batholith uniformly sulfur rich cores abruptly zoned to sulfur poor rims 1 to 0 2 wt so3 in apatite from the yerington batholith nevada indicate that early magma that is crystal poor oxidizing and sulfate rich evolved to sulfate poor magma via crystallization of anhydrite a mineral observed in magmas from pinatubo and el chichon we predict that the characteristic zonation to sulfur poor rims of apatite in the yerington batholith is common in other oxidized hydrous calc alkaline magmas and can be used to track cryptic anhydrite saturation as well as to monitor sulfur evolution sulfate rich arc magmas such as yerington magmas may crystallize to produce hydrothermal fluids rich in chlorine copper and sulfur and porphyry copper ores

biotite chemistry and the role of halogens in archaean greenstone hosted gold deposits a case study from geita gold mine tanzania abstract geita hill is one of the largest tanzanian gold deposits located southwest of lake victoria and 2 km along strike from the giant nyankanga deposit the deposit is hosted by metasedimentary rocks dominated by ironstones and intruded by numerous diorite dykes textural structural and geochronological observations indicate that the gold mineralisation overprints all the ductile fabrics and the late orogenic d6 reverse faulting event suggesting that gold was introduced during later d7 and d8 events the metamorphic background is characterized by biotite k feldspar actinolite pyrhotite which is overprinted by the gold related alteration consisting of sulfidation fronts veins and micro fractures dominated by quartz biotite k feldpar pyrite the almost identical mineralogy of the mineralised assemblage and the metamorphic background makes it difficult to identify the source the effect and the spatial extent of the mineralising fluid as part of this study detailed analyses of biotite were conducted in order to identify the nature of the mineralising fluid and its spatial effect across the geita hill deposit results show that the mineralised assemblage is slightly more oxidized pyrite magnetite compared to the metamorphic background pyrrhotite magnetite the intense sulfidation within the ore zone resulted in the formation of mg rich biotite which grades into more fe rich biotite away from the ore zone this change in biotite chemistry causes a shift in the swir fe oh 2250 nm absorption feature to lower wavelengths which is also correlated with an increase in gold grade within the mineralised zone the abundance of f in biotite significantly increases within the ore zone indicating the presence of f rich hydrothermal fluids during mineralisation late timing of mineralisation synchronous with the emplacement of voluminous high k granites and the presence of k and f bearing fluids indicate a genetic connection between the mineralising fluids and the late granites biotite grains from different deposits types porphyry iocg lode au appear to have distinct composition suggesting that the source of the fluids involved in the formation of each deposit type has a characteristic halogen chemistry

the geochemistry of phosphorus in different granite suites of the western carpathians slovakia the role of apatite and p bearing feldspar the geochemical behaviour of phosphorus in granites coupled with compositional variations in apatite discriminate the different genetic suites of variscan granitic rocks in the west carpathian orogenic belt meso variscan granites mostly of stype affinity show a good correlation between sio2 and p2o5 with decreasing amounts of p in the poorly and moderated fractionated granites and increasing phosphorus in the most evolved and late differentiation products the aluminium saturation index asi correlates negatively with bulk p contents in i type granites and positively with p in s type granites the phosphorus content of alkali feldspar mainly kfs is usually very low typically 0 05 wt p2o5 or not detected in the slightly differentiated granites in the latevariscan i s type granitoids phosphorus is hosted mainly in the early magmatic apatite but is present also in the late k feldspar up to 0 15 wt of p2o5 that formed from the residual melts in the postorogenic s type granites the bulk of the phosphorus occurs in alkali feldspar f0 3 wt p2o5 with a minor proportion present in primary early magmatic apatite clusters of small secondary apatite grains with a distinctive composition are distributed in alkali feldspar grains of the post orogenic s type granites this apatite has formed post magmatically from p released from p rich alkali feldspar during decreasing temperature by reaction with a fluid rich in volatiles including f and b and alkali and alkali earth metals a type granites have the lowest bulk phosphorus contents consequently phosphate minerals are relatively rare in this granite type and the alkali feldspar has negligible p2o5 contents except for sr the minor element contents in apatite partly correlate with the bulk composition of their host rocks and partly reflect some thermodynamic properties of melt the mn contents of apatite increase with the peraluminous character of the melt and with decreasing fo2 and so apatite from the s type granites has significantly higher mn contents than apatite from the i type granites apatite from a type granites is enriched in fe and hree reflecting the higher bulk fe and hree content of this granite type apatite from specialized s type granites is enriched in yand hree in general the cl and s content of apatite is higher in the basic members of the i type affinity granitic rocks d 2004 elsevier b v all rights reserved

new reconstruction of antarctic near surface temperatures multidecadal trends and reliability of global reanalyses a reconstruction of antarctic monthly mean near surface temperatures spanning 1958 2012 is presented itsprimarygoalistotakeadvantageofarecentlyrevisedkeytemperaturerecordfromwestantarctica byrd to shed further light on multidecadal temperature changes in this region the spatial interpolation relies on a kriging technique aided by spatiotemporal temperature covariances derived from three global reanalyses the european centre for medium range weather forecasts ecmwf interim re analysis erainterim modern era retrospective analysis for research and applications merra and climate forecast system reanalysis cfsr for 1958 2012 the reconstruction yields statistically significant annual warming in the antarctic peninsula and virtually all of west antarctica but no significant temperature change in east antarctica importantly the warming is of comparable magnitude both in central west antarctica and in most of the peninsula rather than concentrated either in one or the other region as previousreconstructions have suggested the transantarctic mountains act for the temperature trends as a clear dividing line between east and west antarctica reflecting the topographic constraint on warm air advection from the amundsen sea basin the reconstruction also serves to highlight spurious changes in the 1979 2009 time series of the three reanalyses that reduces the reliability of their trends illustrating a longstanding issue in high southern latitudes the study concludes with an examination of the influence of the southern annular mode sam on antarctic temperature trends the results herein suggest that the trend of the sam toward its positive phase in austral summer and fall since the 1950s has had a statistically significant cooling effect not only in east antarctica as already well documented and but also only in fall in west antarctica

genesis of the two main types of peraluminous granitoids two mica monzogranites to leucogranites and biotite rich cordierite bearing tonalites to monzogranites form two distinct groups of peraluminous granitoids they can be distinguished by mineral and rock associations and by the variation of their peraluminosity during differentiation except for the rare muscovite bearing granitoids produced by extreme fractionation or local contamination of metaluminous magmas the majority of peraluminous granitoids are produced by partial melting of crustal rocks production of either muscovite bearing granites or biotite rich cordierite bearing granitoids does not depend only on the nature of the sources but is also controlled by the physical parameters of partial melting and consequently by the way anatexis of a thickened crust is enhanced biotite rich cordierite bearing granitoids are generated where mantle derived magmas are injected into or have underplated crustal rocks two mica granites are generated where thickened crust is affected by major crustal shears or thrusts correlations between differentiation and peraluminosity indicate the dominant role of either restite unmixing or fractional crystallization in the production and evolution of the various types of peraluminous granitoids

south pacific circulation changes and their connection to the tropics and regional antarctic warming in austral spring 1979 2012 after 1979 statistically significant warming in antarctica is only observed in austral spring september november son across west antarctica and the antarctic peninsula while previous work has linked this warming to reductions in sea ice cover we note that a substantial 30 60 portion of the warming is related to changes in the son atmospheric circulation in particular western antarctic peninsula warming is consistent with increasing pressure in the south atlantic while western west antarctica warming is tied to a deepening of the amundsen sea low near the eastern ross sea while both of these circulation changes are associated with increased warm northerly flow toward the antarctic continent they are connected with different aspects of tropical variability the increase in pressure in the south atlantic is associated with a trend toward more la nina like conditions in the tropical pacific and an associated rossby wave train in contrast the deepening of the amundsen sea low is more strongly tied to a shift in the pacific decadal oscillation pdo toward its negative phase since the 1990s compared to typical la nina events the recent negative pdo events display a different tropical forcing which drives a rossby wave train that propagates more meridionally across the south pacific culminating in the eastern ross sea rather than in the south atlantic the results suggest multiple independent forcing mechanisms governing the son pressure trends and associated antarctic peninsula and west antarctica warming after 1979 which partially cancel each other out in the amundsen sea and portions of eastern west antarctica

variscan metagranitoids in the central tauern window eastern alps austria and their role in the formation of the felbertal scheelite deposit abstract the w mineralised early carboniferous orthogneisses k1 and k3 orthogneiss in the felbertal scheelite deposit represent a chemically evolved metagranitoid series some of its characteristics are high concentrations of f n ho n 1 93 2 81 the systematic chemical trends documented for a multitude of elements e g sio 2 tio 2 p 2 o 5 ba nb ta and their respective ratios e g 1 tio 2 nb ta zr hf indicate that crystal melt fractionation controlled the evolution of the granitic melts the higher differentiated peraluminous light coloured k1 k3 variety asi 0 99 1 08 nb ta 5 7 zr hf 13 18 evolved from the less differentiated metaluminous dark coloured variety asi 0 93 1 03 nb ta 6 10 zr hf 18 24 peraluminous holo leucocratic aplite gneiss represents the most evolved member of the series asi 1 11 1 12 nb ta 4 zr hf 9 10 modelling of magmatic differentiation assuming rayleigh fractionation shows that c 70 90 of the residual granitic magma had crystallised at the time of the emplacement of the aplites when compared to barren metagranitoids in the central tauern window zentralgneis the metaluminous dark coloured k1 k3 orthogneiss shows some geochemical similarities with the peraluminous felbertauern augengneiss one of the regional orthogneisses exposed near the w deposit elevated concentrations of nb

magmatic hydrothermal evolution of the donggou porphyry mo deposit at the southern margin of the north china craton evidence from chemistry of biotite abstract late mesozoic granitoids are widespread in the southern margin of the north china craton ncc occurring commonly as both small porphyritic stocks and large batholiths most of the mo deposits are closely associated with small porphyritic bodies in order to determine the relationship between mo mineralization and the granitoids a systematic geochemical study of biotite from the taishanmiao batholith and the mo mineralization associated donggou porphyry was conducted trace element features of biotites indicate a differentiation trend from rocks of the taishanmiao batholith to those of the donggou porphyry as revealed by systematically decreasing k rb ratios co ba v and ti and increasing cs li ta and tl the contents of mo also increase with the degree of magmatic differentiation the compositions of biotite follow a trend towards more magnesium rich compositions and mostly plot above the nno buffer the fe3 fe2 values of biotite gradually increase from the taishanmiao batholith to the donggou porphyry indicating the progressive increasing fo2 during magmatic differentiation the halogen fugacities of magmatic fluids calculated from biotite compositions show a trend of magmatic differentiation the earlier fluids associated with the taishanmiao batholith are relatively f poor with log fhf fhcl 0 the high degree of melt fractionation and progressive increasing of oxygen fugacity is beneficial to concentrate mo in the residual melt in addition later relatively f rich fluid may be beneficial to extract mo from the melt and thus favorable for mo mineralization

apatite in igneous systems apatite is a minor but ubiquitous mineral in most igneous rocks although the modal proportion of apatite in common rocks is generally low it can reach high concentrations in enclaves cumulates and other rocks of low abundance i e rocks that constitute a small volume of the crust and mantle e g nelsonites the presence of apatite in most rocks is due not only to its low solubility in naturally occurring melts and aqueous solutions but also to the limited ability of common rock forming minerals to accept the amount of phosphorus that occurs in most rocks into their structure in this paper we will discuss some aspects of the occurrence texture composition physical chemistry and petrogenetic significance of apatite in felsic rocks i e andesite to rhyolite and their plutonic analogs in mafic i e basalts and related rocks and plutonic analogs and ultramafic rocks of the earth s crust and mantle fluorapatite is by far the most common member of apatite family found in igneous rocks however most natural fluorapatite contains some chlorine and hydroxyl as well and these constituents can attain high concentrations in some cases the other halogens bromine and iodine also occur in apatite but their concentrations are much lower than chlorine and fluorine many cations commonly substitute for calcium and phosphorus in apatite however they rarely reach concentrations that warrant the definition of a separate mineral species apatite can be described by the general formula a5 xo4 3z following sommerauer and katz lehnert 1985 the a site accommodates large cations e g ca2 sr2 pb2 ba2 mg2 mn2 fe2 ree3 eu2 cd2 na pan and fleet ch 2 in this volume and comprises two sites that exhibit vii fold

petrography and mineral chemistry of the composite deboullie pluton northern maine u s a implications for the genesis of cumo mineralization abstract biotite and apatite mineral chemistry particularly halogen abundances and ratios are used to investigate the relation of the two contrasting parts of the deboullie composite pluton syenite granodiorite located in northern maine biotite mineral chemistry helps to classify the weakly developed porphyry style mineralization cu mo associated with syenitic rocks of the deboullie pluton unmineralized syenite consists of k feldspar plagioclase quartz biotite hornblende clinopyroxene and minor amounts of apatite titanite magnetite zircon and allanite biotite and apatite occur within the matrix of the rocks and within small multiphase inclusions hosted by clinopyroxene the inclusions are interpreted to be crystallized melt inclusions rather than solid inclusions that were trapped by clinopyroxene during growth the multiphase inclusions consist of k feldspar quartz biotite apatite magnetite the f contents of biotite display a strong positive correlation with the phlogopite component or xphl xphl mg sum octahedral cations biotites from the multiphase inclusions have higher f contents and higher values of f f cl oh and xphl than biotites in the matrix that presumably formed later during crystallization and or re equilibrated with late stage fluids contents of tio2 largely overlap for the inclusion and matrix biotite apatite compositions plot within the fluorapatite field f f cl oh 0 57 0 99 apatites in the multiphase inclusions have higher cl contents than apatites in the matrix or those enclosed in biotite biotite apatite geothermometry for the multiphase inclusions yields magmatic or near magmatic temperatures 725 850 c biotite apatite pairs outside the inclusions yield temperatures that range from near magmatic 600 775 c to much lower x f x cl and xphl was used to infer hf hcl fugacity ratios in associated hydrothermal fluids and indicates that biotite from the deboullie pluton is strikingly similar to biotite from the porphyry cu deposit at santa rita new mexico but distinctly different from biotite from the porphyry mo deposit at henderson colorado the assemblage quartz magnetite titanite implies an oxidation state for the deboullie pluton well above the quartz magnetite fayalite buffer which is also consistent with magmas associated with porphyry cu deposits on a regional scale biotite compositions from granitic plutons in maine do not vary in a systematic manner this implies that biotite compositions no longer directly reflect source compositions finally biotite and apatite compositions of the syenite and granodiorite are different compositional ranges in the granodiorite are more restricted than those in the syenite this provides evidence that the two parts of this composite pluton had different origins and are not related by crystal fractionation

petrology of the yerington batholith nevada evidence for evolution of porphyry copper ore fluids the jurassic yerington batholith western nevada is a composite pluton that contains several centers of porphyry copper mineralization and is exposed in structural cross section at paleodepths ranging from 0 to 8 km within these exposures the mcleod hill quartz monzodiorite bear quartz monzonite and luhr hill granite form successive intrusions that are in turn volumetrically smaller approximately 75 19 and 6 vol respectively more deeply emplaced tops at 65 km 3 luhr hill granite the low cu content approximately 10 ppm of the granite would allow extraction of approximately 50 ppm cu from it during crystallization these data suggest an orthomagmatic model in which both high and low density saline aqueous fluids formed during exsolution of water from the crystallizing luhr hill granite and from which salts cu fe and s strongly partitioned into the high density ore fluid low density fluids may have risen from the magma as a vapor plume mineralization occurred when fluid overpressures caused fracturing of wall rock and upward intrusion of granite porphyry dikes and high density saline ore fluids both the f sub o 2 path during subsolidus cooling and the deposition of most s as chalcopyrite pyrite in ore suggest that reduction of magmatic s to sulfide may have been a mechanism for oxidation of magmatic ferromagnesian silicate and fe ti oxide minerals