u pb and th pb dating of apatite by la icpms abstract apatite is a common u and th bearing accessory mineral in igneous and metamorphic rocks and a minor but widespread detrital component in clastic sedimentary rocks u pb and th pb dating of apatite has potential application in sedimentary provenance studies as it likely represents first cycle detritus compared to the polycyclic behavior of zircon however low u th and radiogenic pb concentrations elevated common pb and the lack of a u th pb apatite standard remain significant challenges in dating apatite by la icpms and consequently in developing the chronometer as a provenance tool this study has determined u pb and th pb ages for seven well known apatite occurrences durango emerald lake kovdor mineville mud tank otter lake and slyudyanka by la icpms analytical procedures involved rastering a 10 m spot over a 40 40 m square to a depth of 10 m using a geolas 193 nm arf excimer laser coupled to a thermo elementxr single collector icpms these raster conditions minimized laser induced inter element fractionation which was corrected for using the back calculated intercept of the time resolved signal a tl u bi np tracer solution was aspirated with the sample into the plasma to correct for instrument mass bias external standards plesovice and 91500 zircon nist srm 610 and 612 silicate glasses and stdp5 phosphate glass along with kovdor apatite were analyzed to monitor u pb th pb u th and pb pb ratios common pb correction employed the 207pb method and also a 208pb correction method for samples with low th u the 207pb and 208pb corrections employed either the initial pb isotopic composition or the stacey and kramers model and propagated conservative uncertainties in the initial pb isotopic composition common pb correction using the stacey and kramers 1975 model employed an initial pb isotopic composition calculated from either the estimated u pb age of the sample or an iterative approach the age difference between these two methods is typically less than 2 suggesting that the iterative approach works well for samples where there are no constraints on the initial pb composition such as a detrital sample no 204pb correction was undertaken because of low 204pb counts on single collector instruments and 204pb interference by 204hg in the argon gas supply age calculations employed between 11 and 33 analyses per sample and used a weighted average of the common pb corrected ages a tera wasserburg concordia intercept age and a tera wasserburg concordia intercept age anchored through common pb the samples in general yield ages consistent at the 2 level with independent estimates of the u pb apatite age which demonstrates the suitability of the analytical protocol employed weighted mean age uncertainties are as low as 1 2 for u and or th rich palaeozoic neoproterozoic samples the uncertainty on the youngest sample the cenozoic 31 44 ma durango apatite ranges from 3 7 7 6 according to the common pb correction method employed the accurate and relatively precise common pb corrected ages demonstrate the u pb and th pb apatite chronometers are suitable as sedimentary provenance tools the kovdor carbonatite apatite is recommended as a potential u pb and th pb apatite standard as it yields precise and reproducible 207pb corrected 232th 208pb and common pb anchored tera wasserburg concordia intercept ages

first observations of the cold water coral lophelia pertusa in mid atlantic canyons of the usa abstract the structure forming cold water coral lophelia pertusa is widely distributed throughout the north atlantic ocean and also occurs in the south atlantic north pacific and indian oceans this species has formed extensive reefs chiefly in deep water along the continental margins of europe and the united states particularly off the southeastern u s coastline and in the gulf of mexico there were however no records of l pertusa between the continental slope off cape lookout north carolina nc 34 n 76 w and the rocky lydonia and oceanographer canyons off cape cod massachusetts ma 40 n 68 w during a research cruise in september 2012 l pertusa colonies were observed on steep walls in both baltimore and norfolk canyons these colonies were all approximately 2 m or less in diameter usually hemispherical in shape and consisted entirely of live polyps the colonies were found between 381 m and 434 m with environmental observations of temperature 6 4 8 6 c salinity 35 0 35 6 and dissolved oxygen 2 06 4 41 ml l 1 all of which fall within the range of known l pertusa distributions all colonies were observed on vertical walls or underneath overhangs in areas of high current which differs from observations further south where l pertusa colonizes rocky ledges and outcroppings often forming large bioherms we discuss observations from baltimore and norfolk canyons in the context of the known distribution of this species in the north atlantic

heterogeneity of initial 87sr 86sr ratios within a single pluton evidence from apatite strontium isotopic study abstract magmatic apatite in samples of the unmetamorphosed undeformed cretaceous pluton of the habu granodiorite southwestern japan was examined to determine its viability as an indicator of initial 87sr 86sr heterogeneity in magmatic bodies the habu granodiorite is a zoned pluton in the ryoke metamorphic belt of southwestern japan a published rb sr whole rock isochron age of 124 2 10 8 ma is significantly older than th u total pb monazite ages of ca 86 ma a rb sr mineral isochron of 90 0 2 5 ma for a sample of granodiorite from the margin of the pluton has an initial 87sr 86sr sri of 0 7056 0 0001 similar to a 87sr 86sr of 0 70539 for coexisting euhedral apatite similarly a rb sr mineral isochron of 91 4 2 5 ma for a sample of adamellite from the center of the pluton has an sri of 0 7068 0 0001 corresponding to a 87sr 86sr ratio of 0 70673 0 70684 for three fractions of coexisting euhedral apatite the uniformity of 87sr 86sr values of apatite in individual samples and accordance of 87sr 86sr values of apatite and sri from the mineral isochron suggest that magmatic apatite can be considered as a reliable indicator of sri in granitic rocks the sr isotopic compositions of euhedral apatite coupled with those determined through the mineral isochrons and whole rock data indicate that sri varies between samples from 0 7054 to 0 7074 this provides direct evidence of sri heterogeneity within a compositionally zoned pluton such heterogeneity can produce spurious whole rock age estimates in granitic plutons even where the true age of a pluton is uniform within measurable error assimilation cannot account for chemical differences between granodiorite and adamellite as well as sr isotopic heterogeneity it is likely that the heterogeneity of sri is caused by magma source materials

apatite as a monitor of late stage magmatic processes at volcan irazu costa rica apatite phenocrysts from the 1963 and 1723 eruptions of irazu volcano costa rica record a volatile evolution history that confirms previous melt inclusion studies and provides additional information concerning the relative and absolute timing of subvolcanic magmatic events measurements of h cl and f by secondary ion mass spectrometry reveal multiple populations of apatite in both 1723 and 1963 magmas assuming nominal apatite melt partition coefficients allows us to compare the pattern of melt inclusions and apatites in ternary space demonstrating the fidelity of the record preserved in apatite and revealing a complex history of magma mixing with at least two components the preservation of heterogeneous populations of apatite and of internally heterogeneous crystals requires short timescales days to years for these magmatic processes to occur

apatite trace element and halogen compositions as petrogenetic metallogenic indicators examples from four granite plutons in the sanjiang region sw china abstract the abundances of trace elements including sr ga and rare earth elements ree and halogens in apatite crystals from four intermediate felsic plutons in the zhongdian terrane in the sanjiang region have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometry to evaluate the potential of apatite as a petrogenic metallogenic indicator the selected plutons include one that is not mineralized the triassic xiuwacu pluton or the txwc pluton one that hosts a porphyry type cu deposit the pulang pluton or the pl pluton one that hosts a porphyry type mo deposit the tongchanggou pluton or the tcg pluton and one that hosts a vein type mo deposit the cretaceous xiuwacu pluton or the cxwc pluton except for the cxwc pluton the other three plutons have adakite like trace element signatures in whole rocks the results from this study show that ree sr and halogens in apatite can be used to track magma compositions oxidation states and crystallization history apatite crystals from the adakite like plutons are characterized by much higher sr y and eu than the non adakite type pluton this means that apatite which is not susceptible to alteration is a useful tool for identifying the adakite like plutons that no longer preserve the initial sr y ratios in whole rocks due to weathering and hydrothermal alteration based on apatite ga contents and eu values it is inferred that the parental magmas for the two adakite like plutons containing porphyry type cu and mo mineralization are more oxidized than that for the non adakite type pluton containing vein type mo mineralization apatite crystals from the vein type mo deposit have much lower cl f ratios than those from the porphyry type cu and mo deposits apatite crystals from the adakite like pluton without cu or mo mineralization is characterized by much lower cl f ratios than those from the adakite like plutons that host the porphyry type cu and mo deposits the results from this study confirm the apatite is a useful petrogenetic indicator as well as mineral exploration tool

complex zoning in apatite from the idaho batholith a record of magma mixing and intracrystalline trace element diffusion apatite crystals in a sample of biotite granodiorite from the idaho batholith display complex chemical zoning characterized by abrupt changes in ree y si content more subtle variations in s na la yb and mn contents and petrographic evidence for multiple episodes of partial resorption the zoning is attributed to changes in melt composition resulting from magma mixing and differentiation although the possibility that some rounded cores may be inherited cannot be disproved high s contents in apatite cores and the presence of an included anhydrite grain indicate crystallization from an oxidized host magma divalent cations that occupy the apatite ca sites sr mn fe show evidence of having been redistributed between zones by intracrystalline diffusion whereas cations that participate in coupled substitutions involving the tetrahedral site si y ree na s were not readily redistributed the main ree substitution in this case is ree super 3 si super 4 ca super 2 p super 5 and ree diffusion is rate limited by slow si diffusion however exchange of lree e g lasm sub 1 on the ca sites does not involve si and proceeds more rapidly resulting in homogenization of la sm between zones within individual crystals relative diffusion rates inferred from zoning profiles in this study are mn sr fe and lasm sub 1 are faster than na s and layb sub 1 which are faster than si these data imply that ree patterns can be decoupled from ree abundances during diffusion and that even apatite zones or cores that appear sharply bounded in backscattered electron images may not retain their original chemical or sr nd isotopic traits

geochronology and geochemistry of late cretaceous igneous intrusions and mo cu w mineralization in the southern yidun arc sw china implications for metallogenesis and geodynamic setting abstract the sanjiang tethyan metallogenic domain stmd is an important part of the tethyan giant metallogenic belt the yidun arc is a part of the stmd in the eastern tibetan plateau recently four newly discovered mo cu w ore deposits related to granitic intrusions were found distributed along the north south strike in the southern yidun arc which are identified as the xiuwacu relin hongshan and tongchanggou deposits herein these four deposits formed along high angle north northwest or north west strike slip faults with vein type and porphyry type mo cu mineralization developed in the intrusions molybdenite re os and zircon u pb dating together with zircon hf isotopes and whole rock geochemistry of the intrusions were studied to discern the relationship between mineralization and magmatism metallogenesis and tectonic settings molybdenite from skarn type mineralization at the hongshan deposit has a re os isochron age of 81 2 2 6 ma mswd 1 3 n 5 consistent with previously published zircon u pb ages and re os ages of porphyry type mo mineralization these results indicate that the hongshan is a late cretaceous porphyry skarn cu mo deposit zircon u pb ages of the granitic intrusions in the xiuwacu relin and tongchanggou deposits varying from 87 4 ma to 82 7 ma combined with published molybdenite re os age spectrum 85 ma to 81 2 ma it is proposed that the mo cu w mineralization in the shangri la region is spatially temporally and probably genetically related to the late cretaceous granitic intrusions the relin hongshan and tongchanggou intrusions have high sio 2 65 2 70 0 wt sr 363 905 ppm sr y 22 72 and la yb 37 69 ratios and low y 11 6 17 0 ppm and yb 0 97 1 59 ppm which displayed adakitic affinities their low mgo 0 66 1 44 wt mg 25 46 variable negative zircon e hf t values 7 9 to 2 3 and proterozoic two stages hf model ages t dm2 1 13 1 62 ga suggest that they were probably dominantly derived from partial melting of thickened lower continental crust according to the tectonic evolution of the bangong meso tethys ocean during the late mesozoic the late cretaceous igneous event and mineralization in the yidun arc likely formed under a late or post collision extensional environment probably related to the collision between the lhasa and qiangtang terranes during the late cretaceous

geomorphic characterization of four shelf sourced submarine canyons along the u s mid atlantic continental margin abstract shelf sourced submarine canyons are common features of continental margins and are fundamental to deep sea sedimentary systems despite their geomorphic and geologic significance relatively few passive margin shelf breaching canyons worldwide have been mapped using modern geophysical methods between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the us mid atlantic margin wilmington baltimore washington and norfolk canyons more than 5700 km2 of high resolution multibeam bathymetry and 890 line km of sub bottom chirp profiles were collected along the outer shelf and uppermost slope depths of 80 1200 m the data allowed us to compare and contrast the fine scale morphology of each canyon system the canyons have marked differences in the morphology and orientation of canyon heads steepness and density of sidewall gullies and the character of the continental shelf surrounding canyon rims down canyon axial profiles for washington baltimore and wilmington canyons have linear shapes and each canyon thalweg exhibits morphological evidence for recent relatively small scale sediment transport for example washington canyon displays extremely steep wall gradients and contains 100 m wide 5 10 m deep v shaped incisions down the canyon axis suggesting modern or recent sediment transport in contrast the convex axial thalweg profile the absence of thalweg incision and evidence for sediment infilling at the canyon head suggest that depositional processes strongly influence norfolk canyon during the current sea level high stand the north walls of wilmington washington and norfolk canyons are steeper than the south walls due to differential erosion though the underlying cause for this asymmetry is not clear furthermore we speculate that most of the geomorphic features observed within the canyons e g terraces tributary canyons gullies and hanging valleys were formed during the pleistocene and show only subtle modification by holocene processes active during the present sea level high stand

lunar apatite with terrestrial volatile abundances the moon is thought to be depleted relative to the earth in volatile elements such as h cl and the alkalis nevertheless evidence for lunar explosive volcanism has been used to infer that some lunar magmas exsolved a co rich and co 2 rich vapour phase before or during eruption although there is also evidence for other volatile species on glass spherules until recently there had been no unambiguous reports of indigenous h in lunar rocks here we report quantitative ion microprobe measurements of late stage apatite from lunar basalt 14053 that document concentrations of h cl and s that are indistinguishable from apatites in common terrestrial igneous rocks these volatile contents could reflect post magmatic metamorphic volatile addition or growth from a late stage interstitial sulphide saturated melt that contained 1 600 parts per million h 2o and 3 500 parts per million cl both metamorphic and igneous models of apatite formation suggest a volatile inventory for at least some lunar materials that is similar to comparable terrestrial materials one possible implication is that portions of the lunar mantle or crust are more volatile rich than previously thought

apatite composition tracing petrogenetic processes in transhimalayan granitoids apatites crystallized from different types of igneous rocks show significant variations in the abundances of some minor and trace elements in this study electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry were used to determine the concentrations of 25 minor and trace elements in apatite separated from three principal rock types of thetranshimalayan igneous plutonic suite s type granites the i type gangdese batholith and postcollisional adakites f mn sr and rare earth elements ree in apatite vary systematically with the composition of the host magma and thus have high potential as petrogenetic tracers more specifically the f and mn contents of apatite can be used as an indicator of magma aluminosity or differentiation index combined with sr and ree data which show significant variations in apatite from different rock types these elements are useful for constructing discrimination diagrams this study also reveals that apatite has the capacity to retain geochemical information about the host magma through the course of magmatic evolution systematic variations of sr and ree in apatite with bulk rock aluminosity are the results of partition competition with pre existing and coexisting major and accessory minerals in silicate melts and thus are useful for more detailed investigations of petrogenetic processes such as fractional crystallization and magma mixing which is signaled by inconsistent eu anomalies sr abundances and ree patterns relative to bulkrock compositions

partitioning of molybdenum between magnetite and melt a preliminary experimental study of partitioning of ore metals between silicic magmas and crystalline phases the partitioning of molybdenum between magnetite mt and two rhyolitic melts has been determined at 800 degrees c 1 kb of pressure and at two oxygen fugacities at an oxygen fugacity one half a log unit above nickel nickel oxide d super mt melt mo 0 21 or 0 08 a decrease in the oxygen fugacity to the graphite methane buffer is accompanied by an increase in d super mt melt mo to 0 52 or 0 13 the differences in melt composition have no discernible effect these data are interpreted by writing balanced chemical potential relationships involving independently variable phase components the nernst partition coefficients given above are then formulated as a function of these equilibria given the observed variation in d super mt melt mo with oxygen fugacity and assuming that fe 2 moo 4 is the molybdenum bearing phase component in magnetite our data suggest that mo iii may be present in naturally occurring silicic magmas further we suggest the establishment of critical bulk partition coefficients for ore forming systems defined in terms of critical values of the efficiency of removal function defined by candela and holland 1986 these preliminary results indicate that the crystallization of ferromagnesian or titanium bearing phases may be important in reducing the amount of molybdenum available for orthomagmatic hydrothermal ore formation oxygen fugacity may play a large role in the melt crystal vapor equilibria ofmolybdenum under magmatic conditions

the timing of sub solidus hydrothermal alteration in the central zone limpopo belt south africa constraints from titanite u pb geochronology and ree partitioning abstract in the central zone of the limpopo belt south africa palaeoproterozoic granulite facies metamorphism was superimposed on an earlier archaean orogenic history previously determined ages of 2030 2020 ma obtained from high temperature chronometers zircon garnet monazite are generally thought to provide the best estimate of the peak of palaeoproterozoic granulite facies metamorphism in the central zone whereas ages as young as 2006 ma from late melt patches suggest that temperatures remained above the wet solidus for an extended period we present a new mc icp ms 207 pb 206 pb age of 2030 9 1 5 ma for titanite found in amphibolite to greenschist facies alteration zones developed adjacent to quartz vein systems and related pegmatites that cut a strongly deformed central zone metabasite this age could potentially date cooling of rocks at this locality to temperatures below the wet solidus alternatively the titanite could be inherited from the metabasite host and the age determined from it date the peak of metamorphism integration of the geochronology with la icp ms trace element data for minerals from the metabasite the hydrothermal vein systems and comparable rocks elsewhere shows that the titanite formed during the amphibolite facies hydrothermal alteration not at the metamorphic peak or during the greenschist facies phase of veining this suggests that high grade rocks in the central zone have cooled differentially through the wet solidus and provides timing constraints on when palaeoproterozoic reworking in the central zone began this study illustrates the potential of combined geochronological and high resolution geochemical studies to accurately match mineral ages to distinct crustal processes

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

investigations of the stillwater complex part v apatites as indicators of evolving fluid composition variations in the f cl and oh contents of apatite are not constrained by crystal chemical factors in contrast to micas and amphiboles and thus changes in the abundance of these components provide an indicator of halogen fugacity variations and insights into the degassing history of igneous rocks microprobe analysis of intercumulus apatites from the stillwater complex reveal that cl rich apatites typically containing 6 0 wt cl occur throughout the lower 1 3 of the complex excluding the basal series a change from cl rich to more f rich apatite occurs within olivine bearing zone i ob i of the banded series the host zone of the platiniferous j m reef although apatite compositions are somewhat variable above the j m reef more f rich apatites predominante and typically contain 1 2 wt f and 3 0 wt cl the most f rich apatites occur in the uppermost exposed cumulates pristine apatites from coeval sills and dikes from below the complex and from the basal series are similarly f rich in all apatites the cl and f contents are lower in rocks affected by later metamorphic fluids rare earth element ree concentrations in chlorapatites show a marked peak in the olivine rich rocks of the j m reef and contain up to 2 wt ce2o3 la2o3 the trend of first increasing then decreasing cl f ratios with stratigraphic height is modeled by a vapor driven zone refining process occurring within the cumulate pile causing cl enrichment in the interstitial melt accompanied by degassing at the top of the magma chamber causing overall loss of cl from the magma as crystallization proceeded the abrupt change from cl rich to more f rich apatites within ob i is interpreted as the result of a breakdown of the cl rich zone refining front and mixing with cl poor supernatant melt any high temperature fluids that exsolved and circulated through the lower 1 3 of the complex must have been enriched in cl and could have transported ree and trace metals

relative oxidation states of magmas inferred from ce iv ce iii in zircon application to porphyry copper deposits of northern chile major and trace element compositions of zircons and whole rocks from 14 barren and seven ore bearing calc alkaline intrusions from the chuquicamata el abra porphyry copper belt of northern chile have been measured in situ by excimer laser ablation ela icp ms these data permit the ce iv ce iii ratio within zircon to be calculated using a lattice strain model for mineral melt partitioning of ce iv and ce iii zircon ce iv ce iii and eun eun ratios and by inference magmatic oxidation states generally increase from older mafic to younger felsic units within this sequence porphyry copper mineralization is directly associated only with intrusions with zircon ce iv ce iii 300 and eun eun 0 4 such trends can be understood in terms of interdependent relations between oxygen fugacity sulfur speciation and solubility and chalcophile element partitioning in silicate magmas because zircon occurs in most calc alkaline intrusions and is resistant to subsolidus alteration zircon ce iv ce iii ratios provide a useful tool for evaluating the economic potential of such rocks for magmatic hydrothermal cu au mineralization the approach is general and may provide a means to infer relative oxidation state in a wide range of intermediate to felsic igneous rocks

the lac des iles palladium deposit ontario canada part ii halogen variations in apatite analysis of apatite from the mine block intrusion mbi of the lac des iles igneous complex shows two pronounced trends in the halogens apatite from relatively fresh norite and melanorites from the pd sulfide zone contain up to 57 mol chlorapatite endmember with significant hydroxyapatite component in contrast in altered rock amphibolite and greenschist assemblages the chlorapatite component is typically less than 10 mol with wide variation in the f and oh endmember components the latter trend is attributed to cl loss to degassing and alteration whereas the former is attributed to cl enrichment in the ore bearing rocks it is suggested that the relatively h2o rich and intermediate cl content of the early igneous fluids degassed from the deeper levels of the mbi can explain the high pd pt and pd ir ratios of the deposit a model is presented in which disseminated pd rich sulfides are initially introduced by a high temperature magmatic fluid that also influenced crystallization to produce the gross modal variations of the igneous host rock this high temperature mineralization event was subsequently modified by the influx of late igneous and country fluids at amphibolite to greenschist conditions

partition coefficients of hf zr and ree between zircon apatite and liquid concentration ratios of hf zr and ree between zircon apatite and liquid were determined for three igneous compositions two andesites and a diorite the concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients those for the apatite in the diorite may deviate from the partition coefficients the hree partition coefficients between zircon and liquid are very large 100 for er to 500 for lu and the hf partition coefficient is even larger the ree partition coefficients between apatite and liquid are convex upward and large d 10 100 whereas the hf and zr partition coefficients are less than 1 the large differences between partition coefficients of lu and hf for zircon liquid and for apatite liquid are confirmed these partition coefficients are useful for petrogenetic models involving zircon and apatite

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

aragonite saturation states at cold water coral reefs structured by lophelia pertusa in the northern gulf of mexico abstract ocean acidification the reduction in ph and calcium carbonate saturation states of seawater is likely toexhibit its most immediate effects on cold water corals in deep waters with the shoaling of the aragonite saturationhorizon however empirical data describing the carbonate chemistry at cold water coral reefs are very rare regions of the upper slope of the northern gulf of mexico harbor several deep water reefs structured by thescleractinian lophelia pertusa we collected discreet water samples at a range of depths in the gulf of mexico including eight lophelia reefs and measured total alkalinity and ph to calculate the aragonite saturation state v arag the deep waters of the gulf of mexico 300 m depth were at aragonite saturation states between 0 98and 1 69 l pertusa was present at sites with v arag between 1 25 and 1 69 and carbonate ion concentrationsbetween 92 and 123 mmol kg 21 these data provide a critical baseline for detecting future changes in carbonatechemistry in the water column i e aragonite saturation horizon shoaling as well as at the sites of well developedcold water coral structures threatened by ongoing ocean acidification

coupled substitutions involving rees and na and si in apatites in alkaline rocks from the ilimaussaq intrusion south greenland and the petrological implications ansrnlcr apatites from the ilimaussaq augite syenite the sodalite foyaite and a qtartz bearing peralkaline pegmatite have been analyzed using an electron microprobe for the major elements plus na si and selected rare earth elements rees in all three rock types the maximum reeto3 content in the apatite exceeds 16 0 wt0 0 apatite from the augite syenite and primary apatite from the sodalite foyaite are characterizedby a low na content that varies independently of the ree content the composition of these apatites approaches 25 molo o of the end member carreq sio4 3 oh f cl lessingite in response to the substitution ree3 sia ca2 ps ree and na enriched apatites from the quartzbearing peralkaline pegmatite are almost si free and rees and na are positively correlated the composition of these apatites approaches 25 molo o of the hypothetical endmember na5ree5 po4 6 oh f ci 2 in response to the substitution na ree3 2ca2 the compositional trend of late crystalllzing apatite from the sodalite foyaite reflects almost equal contributions of the two substitutions the relationship between these substitutions in a given apatite and its associated mineral assemblage indicates that the na component is only present in considerable amounts when apatite crystallizes in a strongly peralkaline environment

apatite liquid partition coefficients for the rare earth elements and strontium abstract sixteen sets of apatite liquid partition coefficients dap liq for the rare earth elements ree la sm dy lu and six values for sr were experimentally determined in natural systems ranging from basanite to granite the apatite melt glass assemblages were obtained from starting glasses artificially enriched in ree sr and fluorapatite components these were run under dry and hydrous conditions of 7 5 20 kbar and 950 1120 c in a solid media piston cylinder apparatus an sem equipped electron microprobe was used for subsequent measurement of ree and sr concentrations in coexisting apatites and quenched glasses the resulting partition coefficient patterns resemble previously determined apatite phenocryst groundmass concentration ratios in the following respects 1 the rare earth patterns are uniformly concave downward i e the middle ree are more compatible in apatite than the light and heavy ree 2 dreeap liq is much higher for silicic melts than for basic ones and 3 strontium and therefore eu2 is less concentrated by apatite than are the trivalent ree the effects of both temperature and melt composition on dreeap liq are systematic and pronounced at 950 c for example a change in melt sio2 content from 50 to 68 wt causes the average ree partition coefficient to increase from 7 to 30 a 130 c increase in temperature on the other hand results in a two fold decrease in dreeap liq partitioning of sr is insenstitive to changes in melt composition and temperature and neither the sr nor the ree partition coefficients appear to be affected by variations in pressure or h2o content of the melt the experimentally determined partition coefficients can be used not only in trace element modelling but also to distinguish apatite phenocrysts from xenocrysts in rocks reported apatite megacryst host basalt ree concentration ratios 12 for example are considerably higher than the equilibrium partition coefficients which suggest that in this particular case the apatite is actually xenocrystic a reversal experiment incorporated in our study yielded diffusion profiles of ree in apatite from which we extracted a ree ca interdiffusion coefficient of 2 4 10 14 cm2 s at 1120 c extrapolated downward to crustal temperatures this low value suggests that complete ree equilibrium between felsic partial melts and residual apatite is rarely established

experimental silicate phosphate equilibria in peraluminous granitic magmas with a case study of the alburquerque batholith at tres arroyos badajoz spain with the actual mineralogy and whole rock p in the granite experimental results presented here establish the p2o5 content of aplite pegmatite facies at tres arroyos peraluminous silicic melt for three potential buffering reactions at 200 mpa h2o and t from 525 to 850 c 1 biotite sarcopside 2 spessartine sarcopside 3 petalite amblygonite montebrasite quartz the first two equilibria are moderately insensitive to t and buffer the p content of melt between 1 30 1 57 wt

water hydrogen in the lunar mantle results from petrology and magma ocean modeling abstract measurements of hydroxyl or water in lunar materials are being used to suggest that melting source regions within the moon contained tens to hundreds of ppm water the compositions of magmatic source regions in the moon can be calculated using magma ocean fractional solidification models given an initial bulk composition our magma ocean models demonstrate that to make a source region with 10 to 200 ppm water the bulk magma ocean must contain 100 to 1000 ppm water or more and in a 1000 km deep lunar magma ocean 1000 ppm water is equivalent to 5 of an earth ocean by weight as solidification of the magma ocean continues water and other incompatible elements are progressively enriched in the evolving liquids the final kreep like liquids would contain the greatest fraction of water we suggest that a bulk magma ocean with over 100 ppm water is prohibited by constraints on these kreep like final magma ocean liquids and by the thermodynamic equilibrium requirement with metallic iron in mare basalts we conclude that bulk lunar interior water contents must be at the low end of the range posited by recent observations

partial melting of subducting oceanic crust the conditions under which partial melting of subducting oceanic crust occurs can be determined by combining a partial melting model for basaltic compositions with two dimensional thermal models of subduction zones for porosities of 1 containing h20 the amount of partial melt generated at the wet basaltic solidus is limited to 100 mpa can be maintained by rocks close to or above their melting temperatures in the absence of high shear stresses substantial melting of the oceanic crust will only occur during subduction of very young 5 ma oceanic lithosphere partial melting of hydrated basalt amphibolites derived from the mid ocean ridge has been proposed e g 1 3 as being responsible for the generation of certain recent high al andesitic to dacitic volcanic rocks adakites three of these volcanic suites mount st helens southern chile and panama occur in volcanic arcs where oceanic crust 25 ma is being subducted at rates of 1 3 cm yr and the calculated thermal regime is several hundreds of degrees hotter than more typical subduction zone environments however oceanic lithosphere is not currently being subducted beneath baja and new guinea where recent adakites are also present suggesting that some adakite magmas may form by water undersaturated partial melting of underplated mafic lower crust or previously subducted oceanic crust further experimental work on compositions representative of oceanic crust is required to define the depth of possible adakite source regions more accurately

ore genesis and fluid evolution of the qiaomaishan cu w deposit in the middle lower yangtze river metallogenic belt evidence from in situ analyses of apatite and scheelite abstract the newly exploited qiaomaishan skarn type cu w deposit located in the xuancheng ore cluster district in the middle lower yangtze river metallogenic belt mlyrb is one of the few tungsten polymetallic deposits in this region this study conducted a series of in situ analyses of elements and isotopes for apatite scheelites and sulfides aiming to provide new insights into the source hydrothermal ore forming processes fluid evolution history and genesis of this deposit and important knowledge to investigate regional tungsten mineralization events in the mlyrb apatite geochemistry shows that the early magma source of the ore related rocks in qiaomaishan obviously displayed adakitic affinity with high oxygen fugacity and featured fluorine rich fluids originating from a w rich mixed source the tungsten mineralization is dominated by scheelite in the qiaomaishan deposit based on microscopic observations and in situ analysis two types of scheelite with different geochemical characteristics were recognized two types of scheelite in the qiaomaishan have controlled by different mechanism of ree substitutions scheelite i occurs in the sulfide stage and displays high na and ree concentrations downwards sloping ree fractionation trends with negative eu anomalies and 87sr 86sr ratios 0 70945 0 71033 similar to those of ore related granodiorite porphyry however scheelite ii shows relatively low ree concentrations high na contents mree rich patterns with positive eu anomalies and high 87sr 86sr ratios 0 71477 0 72352 distinct eu anomalies and sr concentrations of the two types of scheelite and s isotopes of sulfides indicate that the early stage fluids were inherited from the primary granodioritic magmatic hydrothermal fluids however the late stage fluids were modified by intense fluid rock interactions and inputs from the host gypsum bearing carbonates collectively the f and w rich sources intense fluid rock interactions and changes in oxidation reduction conditions favoured tungsten mineralization which resulted in the formation of the qiaomaishan tungsten deposit

apatite dissolution into peraluminous haplogranitic melts an experimental study of solubilities and mechanisms apatite ap dissolution and solubility in the peraluminous haplogranite system were investigated in three sets of experiments at 750 c and 200 mpa ph2o as functions of ap grain size abundance melt ap ratio and melt asi alumina saturation index mol al2o3 na2o k2o cao between an asi of 1 1 1 metaluminous to mildly peraluminous the solubility of ap as measured by p2o5 in the melt is low 0 1 wt p2o5 which agrees with previous work in equilibrium runs with more strongly peraluminous compositions however ap solubility increases linearly with asi to p2o5 0 63 wt in melt at asi 1 3 and can be denned by a simple equation p2o5 3 4 3 1 asi r 0 833 which agrees within error with previous calculations reported in the literature in experiments where ap grains are sparce and widely separated i e simulating ap distribution in an ap bearing peraluminous protolith undergoing anatexis the dissolution of ap involves transient disequilibrium that promotes higher solubility of p2o5 up to nearly six times the equilibrium values adjacent to ap at a given bulk asi of melt and this increases the al si of melt in the ap dissolution aureole the approach to equilibrium between ap and melt is hastened by increasing the ap melt ratio within the local melt pool e g the capsule or by decreasing ap grain size for a similar melt ap ratio diffusivity calculations using inverse error function methods for the normal diffusion of p and ca yield dp 10 11 cm2 s and dca 10 10 cm2 s confirming prior results that diffusion of p away from ap surfaces is the rate limiting factor in ap dissolution these results combined with previous work at higher temperatures but on similar hydrous melts yield an activation energy e for p diffusion of 16 5 kcal mol and a frequency factor d0 of 1 4 10 3 cm2 s phosphorus diffusion through the melt is accompanied by uphill diffusion of al resulting in an increase of up to 2 wt al2o3 in melt near the ap within the ap dissolution aureole melt contains one additional al cation for every p cation i e al p 1 1 which is suggestive of an associated alpo4 complex the exchange reaction in melt is represented by alpsi 1 in which 2 to4 clusters are created in the place of 1 this exchange should be accompanied by discernable changes in melt properties e g density molar volume viscosity the results have applications to equilibrium and local disequilibrium effects during anatexis of apbearing metapelites and to the saturation limits of ap during crystallization of peraluminous magmas the dissolution of flux bearing minerals such as ap e g those containing p b or f may influence the stability and solubility of other trace element bearing minerals during anatexis of metapelites texture e g grain size and distribution and spacial relationship to other minerals plays an important role in reaction kinetics and at least temporarily in mineral solubilities the disequilibrium behavior of accessory minerals has critical consequences for ree modelling of granites

do subglacial bedforms comprise a size and shape continuum understanding the evolution of the ice bed interface is fundamentally important for gaining insight into the dynamics of ice masses and how subglacial landforms are created however the formation of the suite of landforms generated at this boundary subglacial bedforms is a contentious issue that is yet to be fully resolved bedforms formed in aeolian fluvial and marine environments either belong to separate morphological populations or are thought to represent a continuum of forms generated by the same governing processes for subglacial bedforms a size and shape continuum has been hypothesised yet it has not been fully tested here we analyse the largest data set of subglacial bedform size and shape measurements ever collated 96 900 bedforms our results show that flutes form a distinct population of narrow bedforms however no clear distinction was found between drumlins and megascale glacial lineations msgls which form a continuum of subglacial lineations a continuum of subglacial ribs also exists with no clear size or shape distinctions indicating separate populations furthermore an underreported class of bedform with no clear orientation to ice flow quasi circular bedforms overlaps with the ribbed and lineation continua and typically occurs in spatial transition zones between the two potentially merging these three bedform types into a larger continuum

apatite solubility in peraluminous liquids experimental data and an extension of the harrison watson model abstract new experimental data at 750 1000 c 2 5 kbar and for peraluminous melt compositions show a dramatic increase of apatite solubilities and phosphorus melt contents when compared to metaluminous or peralkaline compositions harrison and watson 1984 the formation of alumino phosphate units in peraluminous melts qualitatively explains our data a new apatite solubility model incorporating the data for the peraluminous region is presented application of this model to examples of peraluminous felsic suites is discussed

incongruent dissolution of ree and sr rich apatite in peraluminous granitic liquids differential apatite monazite and xenotime solubilities during anatexis the relative solubilities of monazite mnz xenotime xno and apatite ap ree and sr rich and ree and sr poor have been studied in peraluminous granitic liquids in month long experiments at 750 c and 200 mpa ph20 in contrast with the high solubility of the apatite 0 7 wtojop205 in strongly peraluminous liquids monazite and xenotime have much lower solubilities 0 05 wt jop205 in mildly to strongly peraluminous compositions p205 in the liquid is 0 03 0 04 wt joat xenotime saturation and 0 02 0 05 wt jo at monazite saturation in keeping with the low p in the glasses re203 contents are below emp detection thresholds 50 08 wt jo for all conditions of experiments saturation of liquid at equilibrium and local saturation around apatite apatite dissolves incongruently crystallizing ree rich monazite on its surface 1 4 m iong grains resulting in similar low ree contents in liquids monazite precipitation occurs along the margins of dissolving apatite crystals even though the bulk liquid is not monazite saturated the abundance of monazite microcrystals increases with the ree content of the apatite and the degree of apatite dissolution the reaction relationship ap liqi mnz liq2 stemming from differences in relative solubilities greater than an order of magnitude between apatite and monazite results in the dissolution of much smaller amounts of ree into peraluminous liquids than expected by simple evaluation of apatite ree contents the amount of ree contributed from apatite directly to peraluminous granitic liquid is related to the amount of apatite dissolved by simple mass balance only if the total ree content of the apatite is sufficiently low that monazite saturation in liquid 50 100 ppm re203 at 750 c is avoided during dissolution of sr rich apatite the sr partitions into the liquid and at 750 c and 200 mpa ph20 the diffusion coefficient of sr in liquid is 2 x 10 10 cm2js r2 0 659 the reaction relationships described above may have application to some textural features observed in natural igneous rocks for example clusters of monazite microcrystals might be indicators of dissolved apatite monazite morphology can be used to distinguish the source of its ree and the general petrological process rock anatexis or magma crystallization under which the monazite formed in addition monazite microcrystals could serve as nucleation sites for other minerals which might explain their common inclusion in biotite and amphibole within granitoids

macrofaunal communities within and adjacent to a detritus rich submarine canyon system abstract macrofaunal abundance biomass diversity and species assemblages within scripps and la jolla submarine canyons are compared with those on the nearby continental shelf and slope our primary objective was to examine the effect of detrital aggregates on infaunal communities within canyons two submarines a remotely operated vehicle rov and a soutar box corer were used to collect samples within the canyons organic enrichment by macrophyte detritus was evident from canyon heads down to 550 m and evidence of strong currents coarse sediment was found down to 700 m infaunal density and biomass were higher in the canyons than outside at all depths where comparative data were available 100 500 m infaunal assemblages in canyons were distinct from those at reference stations both the canyon and non canyons samples showed community differentiation with depth species diversity was generally high but decreased with depth outside of canyons and increased with depth within the canyons low diversity at shallow depths within the canyon is attributed to a combination of organic enrichment and physical disturbance submarine canyons are commonly found to contain distinct species assemblages or higher faunal densities and or biomass than nearby non canyon regions at similar depths canyons are regular features along most ocean margins and appear to be important as sites of enhanced secondary production provide diverse habitats and act as conduits of coastal detritus to the deep sea

recent sediment transport and deposition in the nazare canyon portuguese continental margin processes pathways and fluxes of sediment transport and deposition in the nazare submarine canyon portuguese continental margin were investigated by water column profiling of suspended particulate matter recording of near bottom currents and suspended particulate matter fluxes with benthic landers and by analysis of surface sediment cores the results show that fine grained suspended sediment from the adjacent shelf is captured in the upper canyon and actively transported through the canyon to the abyssal plain under influence of tidal currents and intermittent sediment gravity flows tidal currents are actively resuspending and transporting sediment in the upper to middle canyon as reflected by high concentration of suspended particles in bottom waters high horizontal and vertical sediment fluxes in the bottom water layer and high sediment accumulation rate on the seabed diminishing strength of tidal currents leads to focussed sediment deposition in the middle canyon further transport of sediments toward the lower canyon takes place predominantly by sediment gravity flows occurring on yearly or longer timescale turbidity currents strong enough to transport sand sized material to the lower canyon occur only on centennial or longer timescales

trace element partitioning between apatite and silicate melts we present new experimental apatite melt trace element partition coefficients for a large number of trace elements cs rb ba la ce pr sm gd lu y sr zr hf nb ta u pb and th the experiments were conducted at pressures of 1 0 gpa and temperatures of 1250 c the rare earth elements la ce pr sm gd and lu y and sr are compatible in apatite whereas the larger lithophile elements cs rb and ba are strongly incompatible other trace elements such as u th and pb have partition coefficients close to unity

petrogenesis of late cretaceous i type granites in the southern yidun terrane new constraints on the late mesozoic tectonic evolution of the eastern tibetan plateau abstract the collision between the lhasa and qiangtang terranes prior to the indo asian collision is a critical aspect in terms of development of the tibetan plateau it has been demonstrated that the occurrence of the late cretaceous granites 110 80 ma in the yidun terrane eastern tibetan plateau etp associates with the lhasa qiangtang collision the xiuwacu late cretaceous pluton in the southern yidun terrane consists three phases including biotite granitic porphyry phase 1 monzogranite phase 2 and alkali feldspar leucogranite phase 3 which have zircon u pb ages ranging from 85 5 ma to 84 4 ma all these three phases are metaluminous or slightly peraluminous granites a cnk 0 96 1 07 with high sio2 70 0 76 0 wt k2o na2o 7 5 10 7 wt and ga al 2 5 4 7 and relatively low cao 0 39 1 67 wt mgo 0 01 0 57 wt and p2o5 0 01 0 17 wt the granites are enriched in light rare earth elements lrees rb th u and ta but depleted in heavy rees hrees ba sr p and ti with significantly negative eu anomalies eu eu 0 24 0 59 comparing to classic a type granites these samples present higher sr 10 1 256 ppm mostly 100 ppm and lower feo mgo ratios 1 2 9 9 and zr nb ce y 248 483 ppm mostly

ree composition of primary and altered feldspar from the mineralized alteration zone of alkaline intrusive rocks western yunnan province china abstract the yao an gold deposit is situated northwest of kunming in yunnan province china is associated spatially with yao an alkaline intrusion the yao an gold mineralization may be divided into two ore stages the stage i sulfide stage fine grained pyrite chalcopyrite galena stringer veins and the stage ii oxide plus sulfide tectonic breccias and banded ore the stage i ores occur in the zones of pervasive potassic alteration the laser ablation icp ms technique was used to analyse ree in primary perthites and altered k feldspars of potassic alteration zone related to mineralization in the yao an gold deposit the primary perthites from yao an syenite porphyry all have similar ree features with light ree enrichment large positive eu anomalies and small but significant negative ce anomalies the ree patterns of altered k feldspars have broadly similar features but compared to the primary perthite have much higher ree concentrations and smaller positive eu anomalies these characteristics show that the hydrothermal fluids responsible for alteration were ree rich due to high levels of complex forming anions but had large negative eu anomalies and other features best ascribed to magmatic crystal fractionation these fluids were derived essentially from the magmatic system

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

suprabenthic crustacean assemblages subjected to high energy hydrodynamic events in the blanes canyon and adjacent slope nw mediterranean sea abstract submarine canyons and adjacent slopes from the nw mediterranean sea are subjected to high seasonal and inter annual variability in hydrodynamic processes such an environmental setting has a profound influence in the spatial and temporal variability of deep sea benthic assemblages we analyzed the suprabenthic crustacean assemblages from the blanes canyon and the adjacent slope along a bathymetric gradient macer giroq sledge hauls were taken from 900 to 2250 m depth in the canyon axis and southwestern adjacent slope in the autumn of 2008 2009 and 2012 from the twenty four hauls sampled one hundred and seventy one species were identified major changes in densities number of species and diversity were only found at particular depths or years in general the samples yielded variable densities from approx 10 to 539 ind 100 m 2 mostly owing to temporal fluctuations in motile fauna such as amphipods and mysids in relation to the occurrence of energy driven events the environmental conditions associated to these events coupled with particular topographic features at the shallowest sites namely at 900 m depth lead to contrasting biodiversity patterns in the canyon and adjacent slope high dominance and subsequent depressed diversity in the canyon and the highest diversity on the slope at similar depths at the deepest sites suprabenthic diversity reached similar values in the canyon and adjacent slope probably owing to the decreased influence of disturbance processes at greater depths trophic diversity decreased with depth only in the slope while in the canyon it remained constant likely owing to the relatively enhanced trophic conditions found in the canyon at all depths however the community composition differed significantly between the canyon and adjacent slope and at contrasting depths 1200 m at shallowest depths the canyon sites were characterized by a high contribution of motile omnivores while the slope sites were characterized by a high contribution of detritivores to the total abundance highly motile predators on zooplankton were dominant at deepest sites in both environments our results suggest that taxonomic and trophic diversity in the northwestern mediterranean may be influenced by the abrupt topography and its interaction with hydrodynamic conditions intensification of currents variable intensity of disturbance hydrodynamic events food pulses linked to food availability these are major drivers which influence the spatial and temporal availability of food sources to the various faunal compartments eventually propagating up the food web

dehydration melting of a basaltic composition amphibolite at 1 5 and 2 0 gpa implications for the origin of adakites this study presents the results of dehydration melting experiments on a basaltic composition amphibolite under conditions appropriate to a hot slab geotherm 1 5 and 2 0 gpa and temperatures of 850 to 1150 c dehydration melting produces an omphacitic augite and garnet bearing residue coexisting with rhyolitic to andesitic composition melts at 1 5 gpa the amphibolite melts in two stages between 800 and 1025 c the 2 0 gpa data also define two melting stages at 2 0 gpa the first stage involves nearly modal melting of the original amphibolite minerals qtz pl amp to produce melt cpx grt during the second stage the eclogite restite melts non modally 0 86 cpx 0 14 grt 1 melt the experimental results were combined with data from the literature to generate a composite p t phase diagram for basaltic composition amphibolites over the 800 to 1100 c temperature range for pressures up to 2 0 gpa comparison of the major element compositions of the experimentally produced melts with compositions of presumed slab melts adakites shows that partial melting of amphibolite at conditions appropriate to a hot slab geotherm produces melts similar to andesitic and dacitic adakites except for significant mgo and cao depletions trace element modelling of amphibolite dehydration melting using the 2 0 gpa melting reactions produces ree abundances similar to those of adakites at 10 15 wt batch melting but the models do not reproduce the high sr y ratios characteristic of adakites taken together the major and trace element results are not consistent with the derivation of adakites by dehydration melting of the subducted slab with little or no interaction with the mantle wedge or crust if adakites are partial melts of the subducted slab they must undergo significant interaction with the mantle and or crust during which they acquire a number of their distinctive characteristics

variation in the composition of apatite through the merensky cyclic unit in the western bushveld complex microprobe analysis of interstitial apatite from a 100 m section through the merensky reef of the bushveld complex reveals that this stratigraphic section marks a transition from cl rich to more f rich compositions in the critical and main zones respectively apatite compositions across the section vary by more than 80 mole percent in the chlorapatite component the trend of decreasing cl concentration with stratigraphic height is not regular and cl contents in apatites from some samples may vary as much as 50 mole percent la 2 o 3 and ce 2 o 3 tend to be enriched in the more melanocratic orthocumulate parts of the section sro concentrations of apatite show an increase with stratigraphic position a trend which is opposite that observed in coexisting cumulus plagioclase the data are consistent with mineralogic and textural evidence for an influx of cl rich vapor into the cumulus section which has affected the cl f variations through the lower portion of the bastard unit this influx occurred above the crystallization temperature of apatite 1 000 degrees 1 050 degrees c it is suggested that much of the modal variation seen in the section may be the result of shifts in liquidus field boundaries caused by gain or loss of volatile components from the melt

distributions and habitat associations of deep water corals in norfolk and baltimore canyons mid atlantic bight usa a multi disciplinary study of two major submarine canyons baltimore canyon and norfolk canyon off the us mid atlantic coast focused on the ecology and biology of canyon habitats particularly those supporting deep sea corals historical data on deep sea corals from these canyons were sparse with less than 750 records for the mid atlantic region with most being soft sediment species this study substantially increased the number of deep sea coral records for the target canyons and the region large gorgonians were the dominant structure forming coral taxa on exposed hard substrates but several species of scleractinians were also documented including first observations of lophelia pertusa in the mid atlantic bight region coral distribution varied within and between the two canyons with greater abundance of the octocoral paragorgia arborea in baltimore canyon and higher occurrence of stony corals in norfolk canyon these observations reflect the differences in environmental conditions particularly turbidity between the canyons some species have a wide distribution e g p arborea primnoa resedaeformis anthothela grandiflora while others are limited to certain habitat types and or depth zones e g paramuricea placomus l pertusa solenosmilia variabilis the distribution of a species is driven by a combination of factors which include availability of appropriate physical structure and environmental conditions although the diversity of the structure forming corals gorgonians branching scleractinians and large anemones was low many areas of both canyons supported high coral abundance and a diverse coral associated community the canyons provide suitable habitat for the development of deep sea coral communities that is not readily available elsewhere on the sedimented shelf and slope of the mid atlantic bight

in situ major and trace element compositions of apatites from luanchuan orecluster implications for porphyry mo mineralization abstract the effects of volatile concentrations and oxidation state of magma on the mo mineralization potential have been explored through petrographic studies and in situ electron probe micro analyzer epma and laser ablation inductively coupled plasma mass spectrometry la icp ms of apatites from coeval economically mo mineralized granite porphyry and quartz diorite and sub economically mineralized granite porphyry at luanchuan orecluster the occurrence of abundant k feldspar xenocrysts possibly entrained from granitic magma in quartz diorite implying a magma mingling process studied apatites are fluorapatites or fluor hydroxyapatites with decreasing oh concentrations from economically mineralized quartz diorite 0 30 0 49 apfu through mineralized granite porphyry 0 14 0 41 apfu to sub economically mineralized granite porphyry 0 01 0 11 apfu chondrite normalized ree patterns of all the apatites are characterized by lree enrichment relative to mree and hree and negative eu anomaly similar to their host magmas indicating a melt composition control strontium concentration of studied apatites are probably controlled by the crystallization of plagioclase or alkali feldspar mineralized quartz diorite formed at a relatively reduced environment compared to other rocks but mineralized granite porphyry and sub economically mineralized granite porphyry formed at a similar oxidation state based on the so3 eu ce and mn content variation of apatites the oh contents of apatites combined with published log h2o hf ratios of melt in equilibrated with biotites reflect that economically mineralized intrusions have higher water contents than the sub economically mineralized intrusions in a porphyry mo system a high magma water content is probably a key parameter controlling mo mineralization mafic magma may supply water and heat to ore forming granitic magmas enhancing their mo mineralization potential

the significance of titanite and apatite u pb ages constraints for the post magmatic thermal hydrothermal evolution of a batholithic complex berens river area northwestern superior province canada abstract titanite apatite and in one case rutile from a suite of twenty seven samples representing the major phases of an extensive and well dated archean plutonic domain of the northwestern superior province have been dated by u pb to determine the temporal progress of thermal and hydrothermal events accompanying and following major plutonism and to assess the isotopic behaviour of these geochronometers most samples contain 1 dark brown titanite with 350 20 ppm u showing shapes and textural relationships indicative of a primary magmatic origin and yielding ages corresponding either to the time of magmatic crystallization or to that of secondary metamorphic or magmatic events known in the area 2 pale titanite with 30 2 ppm u showing textural evidence for a secondary origin by breakdown of biotite hornblende oxide or older titanite and yielding ages that in general post date the major plutonic and metamorphic events in the area 3 apatite containing 30 5 ppm u occasionally up to 150 ppm u showing igneous shapes and textural relationships but yielding post magmatic ages similar to those of coexisting pale titanite 4 rutile in one sample postdating the ages of coexisting titanite and apatite the common coexistence of two noncoeval titanite generations demonstrates that the often invoked mechanism of pb diffusion during slow cooling in this case has no general validity the distribution of primary dark titanite ages however could be explained by late closure to diffusion or alternatively as the result of resetting by the thermal or hydrothermal effects caused by younger plutonic activity the ages of the secondary pale titanites probably reflect crystallization during discrete retrogressive events promoted by moderate heating or enhanced fluid activity the correspondence between pale titanite and apatite ages suggests that the same processes also caused the isotopic resetting of apatite on a regional scale the data pattern permits the identification of domains characterized by differences in the length and intensity of the thermal and hydrothermal processes the most protracted activity is recorded in northern domains of the berens river area whereas the gold mineralized red lake area in the south underwent a very rapid decline of the thermal hydrothermal activity these data also highlight important differences between the red lake and other gold camps of the superior province such as hemlo and val d or where hydrothermal activity locally associated with mineralization occurred as much as 30 80 m y after the major orogenic developments

the use of apatite as a record of initial 87sr 86sr ratios and indicator of magma processes in the inagawa pluton ryoke belt japan abstract sr isotopic analysis of apatite in the extensive inagawa pluton of southwestern japan reveals the spatial distribution of initial 87sr 86sr sri within this body with an unprecedented resolution while the sri values in older units show the largest variation 0 7093 0 7107 the younger ones have relatively homogeneous sri values around 0 7096 the older units also contain numerous mafic microgranular enclaves which are absent in the younger units combining these results with bulk rock analyses and field observations suggests the wide variation in petrology and bulk chemistry in the inagawa pluton is not solely due to fractional crystallization as previously thought mixing between mafic and felsic melts has also played a significant role the lack of enclaves and homogeneous sri values in the younger units suggest that mixing was complete by this time

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

acoustical detection of high density krill demersal layers in the submarine canyons off georges bank high density demersal layers of krill have been detected in the submarine canyons off georges bank by means of a high frequency dual beam bioacoustical technique krill densities in these demersal layers were observed to be two to three orders of magnitude greater than the highest densities observed in water column scattering layers such abundances may help explain the unusually high squid and demersal fish production estimates attributed to the georges bank ecosystem

periodic resuspension in baltimore canyon by focusing of internal waves high concentrations of particulate matter are frequently reported in submarine canyons this study demonstrates that in baltimore submarine canyon elevated concentrations result from periodic resuspension events the sloping bottom and v shaped topography of submarine canyons could accelerate tidal flows in the canyon axis sufficiently to cause resuspension which occurs predominantly at tidal frequencies however current meter and transmissometer data show that resuspension events are often associated with a borelike intrusion of cold water moving upslope near the canyon head an event that is consistent with the focusing of internal wave energy toward the canyon head at tidal frequencies hydrographic conditions for the focusing of energy are most favorable in late winter and early spring when stratification in the canyon is diminished direct observations reveal that the most pronounced resuspension events occur during those seasons bottom stresses generated in the canyon are sufficient to resuspend sediment along the axis at least between 200 and 800 m with little resuspension occurring deeper along the axis on the canyon walls adjacent slope or shelf during a resuspension event the sediment laden water is forced upcanyon then sloshes back down the canyon until it reaches a layer of higher density water detaches from the canyon floor and moves seaward along a density surface this is a means of transferring sediment and associated pollutants intercepted at the canyon head to deeper water across the shelf slope front over geologic time frequent resuspension and seaward transport may aid in the headward erosion of submarine canyons or at least inhibit their infilling during interglacial times

the pulang porphyry copper deposit and associated felsic intrusions in yunnan province southwest china the pulang porphyry copper deposit recently discovered in northwestern yunnan province china is located at the south end of the triassic yidun island arc to date 15 mineralized porphyry deposits have been defined in the pulang area and the copper resource is estimated to exceed 10 mt the pulang deposit as currently defined is made up of five ore bearing porphyry deposits covering an area of approximately 9 km2 intermediate acidic porphyritic intrusions composed of quartz diorite monzodiorite quartz monzonite and granodiorite are widespread in the pulang area the alteration zones identified with the porphyry deposits include silicic potassium silicate quartz sericite and propylitic zones the porphyry deposits have hornfels at the contact with slate sandstone and andesite re os ages of molybdenite and ar ar and k ar dating of biotite indicate that the pulang porphyry copper deposit formed during the indosinian tectonic episode with the main ore formation taking place from 216 to 213 ma late triassic norian however the whole process of hydrothermal activity including overprinting may have extended from 235 to 182 5 ma

preserved initial in apatite from altered felsic igneous rocks a case study from the middle proterozoic of south australia abstract strontium isotope data from a suite of hydrothermally altered middle proterozoic granitoids and a related felsic volcanic rock show that the total rock systems have been disturbed as a result of hydrothermal alteration as such unambiguous determination of initial 87 sr 86 sr is not possible using total rock data with consequent loss of valuable petrogenetic information in contrast initial 87 sr 86 sr values derived from apatite are uniform when compared with the discordant total rock analyses evaluation of strontium diffusion kinetics in apatite together with geological and isotopic evidence presented here suggest that initial 87 sr 86 sr derived from apatite preserves the igneous initial 87 sr 86 sr and that 87 sr 86 sr in apatite is unlikely to have been modified as a result of igneous cooling or hydrothermal alteration this study shows that under some conditions apatite is resistant to 87 sr 86 sr modification and can yield petrogenetic information not attainable from total rock analyses data presented here together with data obtained in other studies indicate that the strontium isotope system in apatite is more resistant to modification than feldspar and biotite this approach may be of widespread application in determining initial 87 sr 86 sr of similarly altered ancient igneous rocks

an evaluation of models of apatite compositional variability using apatite from the middle banded series of the stillwater complex montana apatite is a relatively common accessory mineral in the olivine bearing zones ob iii and ob iv of the middle banded series of the stillwater complex occurring interstitial to cumulus grains as monomineralic inclusions in cumulus grains and in polymineralic clusters which may or may not be included in the cumulus grains eighty nine of 185 samples examined were found to contain some apatite the f cl oh content of the apatite show distinct stratigraphic variations xclap mole fraction cl in apatite of interstitial apatite increases upsection in both ob iii and ob iv with average values ranging from 0 15 to 0 85 in ob iii and from 0 03 to 0 60 in ob iv xfap varies inversely with xclapwith average values ranging from 0 00 to 0 70 while xohap remains relatively constant near 0 40 or decreases slightly with height these variations are remarkable given that no appreciable stratigraphic variations in either the major or trace element compositions of any of the cumulus minerals are found in the 800 m of section that comprise ob iii and ob iv within sample variation of xclap for samples containing cl rich apatite is substantially larger up to 0 65 xclap than for samples with more f rich apatite xclap varies by approximately 0 15 although interstitial apatite is found throughout ob iii and ob iv apatite occurring as monomineralic inclusion in cumulus grains or in polymineralic clusters is almost exclusively found in samples with cl rich apatite the data are best explained by a model involving the degassing of a cl rich volatile phase from the crystallizing interstitial liquid the up section migration of this fluid resulted in the crystallization of f rich apatite in the lower portion and progressive cl enrichment in the apatite with height the presence of hornblende bearing dikes veins and pegmatoids at the level of maximum cl enrichment is consistent with a fluid migration model

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