hydrothermal alteration and fluid chemistry of the endako porphyry molybdenum deposit british columbia hydrothermal alteration and fluid chemistry data of the early cretaceous endako porphyry molybdenum deposit british columbia provide new information on the hydrothermal fluids associated with low fluorine molybdenite mineralization molybdenite mineralization and hydrothermal alteration occur as early quartz molydenite stockwork veins with k feldspar bearing selvages and paragenetically later quartz molybdenite ribbon veins with sericite bearing selvages late hydrothermal alteration is associated with the development of kaolinite and postore tertiary age calcite veins fluid inclusions in early formed quartz molybdenite stockwork veins with k feldspar bearing alteration assemblages are dominated by moderate salinity 5 to 15 wt nacl equiv liquid rich type 1 and rare high salinity 30 to 45 wt nacl equiv halite bearing type 3 fluid inclusions type 1 and type 3 fluid inclusions in early veins homogenize between 390 and 430 c and 375 and 420 c respectively secondary fluid inclusions type 2 of low salinity 1 to 5 wt nacl equiv in these early veins are minor and homogenize between 130 and 285 c fluid inclusions in quartz molybdenite ribbon veins with sericite bearing alteration assemblages are dominated by moderate salinity liquid rich type 1 inclusions with minor type 2 fluid inclusions type 1 fluid inclusions of ribbon veins homogenize between 360 and 400 c fluid inclusions in postore calcite veins are of only type 2 fluid inclusions which homogenize at 209 c hydrothermal fluids recorded by type 1 and type 3 fluid inclusions in early veins were trapped under lithostatic to hydrostatic conditions between 0 3 and less than or equal to 2 0 kbar and 360 and 560 c postore fluids recorded by type 2 fluid inclusions were trapped under conditions less than or equal to 0 5 kbar and between 190 and 300 c quartz stockwork and ribbon veins possess 18o values of 8 4 0 2 n 9 and 8 4 0 6 n 13 respectively hydrothermal k feldspar and biotite from k feldspar alteration assemblages possess 18o values of 6 8 0 4 n 7 and 3 5 0 8 n 8 respectively oxygen isotope geothermometry of quartz biotite and quartz k feldspar pairs from k feldspar alteration assemblages yield temperatures between 200 and 490 c which is similar to the trapping temperatures of hydrothermal fluids determined from fluid inclusion studies associated with molybdenite mineralization the development of kaolinite and calcite veins the oxygen isotope temperatures of the quartz biotite and quartz k feldspar pairs suggest that k feldspar and biotite either record the approximate 18o composition of hydrothermal fluids associated with k feldspar alteration or have undergone 18o exchange with late stage hydrothermal fluids hydrogen isotope composition of quartz stockwork and ribbon veins fluid inclusion waters range between 105 and 173 per mil solute chemistry studies of fluid inclusion waters indicate that ore forming fluids from endako have low br cl and br na ratios and high i cl and i br ratios in comparison to porgera epithermal babine lake porphyry cu and st austell capitan pluton vein deposits associated with magmatic processes na k ratios of fluid inclusion waters yield temperatures 308 to 429 c similar to those determined from type 1 and type 3 fluid inclusions and stable isotope thermometry results from fluid inclusion and solute chemistry studies indicate the involvement of hydrothermal fluids exsolved from a crystallizing melt in the formation of the endako molybdenum deposit however oxygen and hydrogen isotope values deviate from the generally accepted magmatic compositions which suggests the early involvement of meteoric water in the ore forming fluids and ore genesis

the scheelite skarn deposit of salau ariege french pyrenees between 1971 and 1986 the scheelite deposit of salau located in the french hercynian pyrenees produced 930 000 metric tons of ore with 1 50 percent wo 3 13 950 metric tons of wo 3 the skarn deposit is hosted in a devonian carbonate and partly detrital series intruded by a late carboniferous stock in the devonian series the lithostratigraphy and geochemistry of which is described in some detail a unit of so called barregiennes i e rythmic alternations of limestones and silts appears to be very favorable for extensive development of skarns and overprinted ores the hercynian orogeny involved polyphase deformation regional metamorphism of greenschist facies and late intrusions of granite granodiorite deformation included two coaxial stages of tight isoclinal folding and one important later stage which partly controlled the intrusion of the granodiorite stock followed by three stages of brittle deformation ore deposition is related to faulting stages 0 and 1 and orebodies are cut into slices by stage 2 reverse faults the salau intrusion includes various rock types belonging to two slightly different calcalkaline trends one of these trends characterized by its low k contents is unusual in the pyrenees the local shapes of the intrusion apophyses and embayments are important controls of the orebodies after isochemical contact metamorphism the skarns and ores developed in two main stages related to the infiltration of two quite different types of fluids during the first stage 540 degrees 450 degrees c anhydrous skarn formation was followed by an intergranular development of pyrrhotite scheelite quartz calcite in equilibrium with the earlier hedenbergite the resulting tungsten grade is uneconomic the associated fluids probably of magmatic origin had a high salinity in the second stage 450 degrees 350 degrees c no new skarn formed transformations of the silicate rocks are observed a first substage of epidotization was followed by the development of intermediate grossularite almandine spessartite garnet and finally by the main ore stage with scheelite pyrrhotite arsenopyrite and other sulfides with some gold two types of fluid inclusions are found in this stage one is similar in composition to the first stage the other is characterized by low salinity and high co 2 and ch 4 contents

paragenetic constraints on the cantung mactung and lened tungsten skarn deposits canada implications for grade distribution abstract the cantung mactung and lened w skarn deposits located in northwest territories and yukon of canada are part of a large metallogenic belt that contains all major tungsten deposits in western north america in this study we evaluate the paragenesis and mineral compositions in these deposits to determine the parameters that control the distribution of high grade w mineralization in these skarn deposits the mineral compositions of the cantung mactung and lened deposits are indicative of reduced fluids grossular rich garnet hedenbergite rich pyroxene abundant pyrrhotite which is characteristic of high grade w deposits local mineral assemblages indicative of oxidizing conditions are observed at lened the smallest of the deposits but are interpreted to be induced by sporadic barite rich facies within the host rock and not by an oxidized fluid therefore the redox state of the skarn does not necessarily lessen the exploration potential for the lened deposit a correlation between high sulfide and scheelite cawo4 contents at cantung mactung and lened has been reported previously and observed in this study however petrographic observations from this study show that scheelite and sulfides precipitated at different times scheelite crystallized throughout the entire history of skarn development but peaked at different stages for each deposit in contrast sulfides have mainly crystallized as late stage minerals postdating the silicates and scheelite variations in the host rock texture and porosity and therefore permeability are proposed to be the main factor controlling scheelite sulfide distribution this control would be manifested such that areas of greater permeability focused fluid flow which favored the precipitation of both scheelite and sulfides at different times in the history of the system

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

synthetic fluid inclusions xvii pvtx properties of high salinity h2o nacl solutions 30 wt nacl application to fluid inclusions that homogenize by halite disappearance from porphyry copper and other hydrothermal ore deposits fluid inclusions that homogenize by disappearance of the halite crystal after the vapor bubble has disappeared have been reported from a wide range of ore forming systems while this inclusion type is most commonly observed in porphyry copper and similar magmatichydrothermal ore deposits they have also been reported from iron oxide copper gold iocg mississippi valley type orogenic lode greenstone gold massive sulfide unconformity u and mantotype deposits as well as from non ore associated granitoids and oceanic crust the lack of experimental data to interpret microthermometric data from these inclusions combined with poor petrographic characterization of inclusion origin has led to a wide range of inferred pt trapping conditions for the inclusions the relationship between liquid vapor homogenization temperature thl v halite dissolution temperature tmhalite and pressure has been determined using synthetic h2o nacl fluid inclusions that homogenize by halite disappearance the experimental data cover the range thl v 150 to 500 c and tmhalite 275 to 550 c an empirical equation describing the relationship between pressure thl v and tmhalite has been developed to estimate formation pressures from microthermometric data and is valid from pressures along the liquid vapor halite curve to 300 mpa a detailed literature review reveals that the results of this study cannot be applied retroactively to estimate pressures of previously reported inclusions that homogenize by halite dissolution for several reasons first most workers have not collected and reported the data in a manner that allows one to determine if the inclusions have trapped a single homogeneous phase and have not leaked or changed volume following trapping thus it is not possible to determine if the inclusions show consistent microthermometric behavior within a group of coeval inclusions additionally many published studies provide only summaries of results from numerous samples or present the data graphically precluding application of our results to individual inclusions however based on our review it appears that much of the published data for inclusions that homogenize by halite dissolution represent inclusions that have either trapped a halite crystal along with the liquid or have reequilibrated by necking and or stretching results from this study have been used to estimate minimum formation pressures for inclusions from the ditrau alkaline massif transylvania romania the musoshi stratiform copper deposit zaire the bismark skarn deposit northern mexico the naica chimneymanto deposit mexico the questa porphyry molybdenum deposit new mexico and the bingham canyon porphyry cu mo deposit utah in each case pressures estimated using results from the present study are in good agreement with previous pressure estimates however in some cases estimated pressures both our estimates as well as those of other authors appear to be unreasonably high based on the geologic setting at the time of formation these results highlight the currently limited understanding concerning pressures depths of ore formation

a fluid inclusion and isotopic study of an intrusion related gold deposit irgd setting in the 380 ma south mountain batholith nova scotia canada evidence for multiple fluid reservoirs a set of sheeted quartz veins cutting 380 ma monzogranite at sandwich point nova scotia canada provide an opportunity to address issues regarding fluid reservoirs and genesis of intrusion related gold deposits the quartz veins locally with arsenopyrite 5 and elevated au bi sb cu zn occur within the reduced south mountain batholith which also has other zones of anomalous gold enrichment the host granite intruded p 3 5 kbars lower paleozoic metaturbiditic rocks of the meguma supergroup well known for orogenic vein gold mineralization relevant field observations include the following 1 the granite contains pegmatite segregations and is cut by aplitic dykes and zones 1 2 m of spaced fracture cleavage 2 sheeted veins containing coarse comb textured quartz extend into a pegmatite zone 3 arsenopyrite bearing greisens dominated by f rich muscovite occur adjacent the quartz veins and 4 vein and greisen formation is consistent with riedel shear geometry although these features suggest a magmatic origin for the vein forming fluids geochemical studies indicate a more complex origin vein quartz contains two types of aqueous fluid inclusion assemblages fia type 1 is a low salinity 3 wt equivalent nacl with minor co2 2 mol and has th 280 340 c in contrast type 2 is a high salinity 20 25 wt equivalent nacl ca rich fluid with th 160 200 c pressure corrected fluid inclusion data reflect expulsion of a magmatic fluid near the granite solidus 650 c that cooled and mixed with a lower temperature 400 c wall rock equilibrated ca rich fluid evidence for fluid unmixing an important process in some intrusion related gold deposit settings is lacking stable isotopic o d s analyses for quartz muscovite and arsenopyrite samples from vein and greisens indicate the following 1 18oqtz 11 7 to 17 8 and 18omusc 10 7 to 11 2 2 dmusc 44 to 54 and 3 34saspy 7 8 to 10 3 these data are interpreted in conjunction with fluid inclusion data to reflect contamination of a magmatic derived fluid delta 18 hbox o rm h 2 rm o 10 by an external fluid delta 18 hbox o rm h 2 rm o 15 the latter having equilibrated with the surrounding metasedimentary rocks the 34s data are inconsistent with a direct igneous source based on other studies for the host intrusion delta 18 hbox o rm h 2 rm o 5 and are instead consistent with an external reservoir for sulphur based on 34sh2s data for the surrounding metasedimentary rocks divergent fluid reservoirs are also supported by analyses of pb isotopes for pegmatitic k feldspar and vein arsenopyrite collectively the data indicate that the vein and greisen forming fluids had a complex origin and reflect both magmatic and non magmatic reservoirs thus although the geological setting suggests a magmatic origin the geochemical data indicate involvement of multiple reservoirs these results suggest multiple reservoirs for this intrusion related gold deposit setting and caution against interpreting the genesis of intrusion related gold deposit mineralization in somewhat analogous settings based on a limited geochemical data set

eastward propagation of 30 60 day perturbations as revealed from outgoing longwave radiation data abstract some of the characteristic features of low frequency oscillations were investigated by applying an extended empirical orthogonal function eeof analysis to 30 60 day filtered outgoing longwave radiation olr data during the eight years of 1975 77 and 1979 83 the first two eeof eigenvectors indicate a systematic eastward propagation of low frequency modes between about 60 e and the date line indian ocean western pacific where they are most predominant they weaken considerably by the time they reach the eastern pacific east of the date line and their phase propagation becomes ill organized over the equatorial south america atlantic ocean africa region this appears to be due to an out of phase relationship between zonal fourier wavenumbers 1 and 2 over the equatorial western hemisphere in contrast there exists a general in phase relationship between these two fourier components and thus the consolidated perturbations of wavenumbers 1 and 2 become very pronounced with a distinct eastw

fluid chemistry structural setting and emplacement history of the rosario cu mo porphyry and cu ag au epithermal veins collahuasi district northern chile the rosario cu mo ag deposit is located in the collahuasi district of northern chile it comprises high grade cu ag au epithermal veins superimposed on the core of a porphyry cu mo orebody rosario has mining reserves of 1 094 million metric tons mt at 1 03 percent copper an additional 1 022 mt at 0 93 percent copper occurs in the district at the nearby ujina and quebrada blanca porphyry deposits the rosario reserve contains over 95 percent hypogene ore whereas supergene sulfide ores dominate at ujina and quebrada blanca mineralized veins are hosted within lower permian volcanic and sedimentary rocks lower triassic granodiorite and late eocene porphyritic quartz monzonite the rosario fault system a series of moderate southwest dipping faults has localized high grade cu ag au veins at cerro la grande similar high grade cu ag au veins are hosted in north northeast trending sinistral wrench faults normal movement in the rosario fault system is interpreted to have been synchronous with sinistral strike slip deformation at la grande hydrothermal alteration at rosario is characterized by a k feldspar core focused in the rosario porphyry that grades out to a secondary biotite albite magnetite assemblage paragenetic relationships indicate that magnetite was the earliest formed alteration product but has been replaced by biotite albite vein crosscutting relationships indicate that k feldspar formed during and after biotite albite alteration chalcopyrite and bornite were deposited in quartz veins associated with both k feldspar and biotite albite assemblages the early hydrothermal fluid was a hypersaline brine 40 45 wt nacl that coexisted with vapor between 400 degrees and 600 degrees c weakly mineralized illite chlorite intermediate argillic alteration of the early k and na silicate assemblages was caused by moderate temperature 250 degrees 350 degrees c moderate salinity brines 10 15 wt nacl molybdenite was precipitated in quartz veins that formed between the potassic and intermediate argillic alteration events these fluids were 350 degrees to 400 degrees c with salinities between 10 and 15 wt percent nacl porphyry style ore and alteration minerals were overprinted by structurally controlled quartz alunite pyrite pyrophyllite dickite and muscovite quartz phyllic alteration assemblages the quartz alunite pyrite alteration formed at 300 degrees to 400 degrees c from fluids with a salinity of 10 wt percent nacl the pyrophyllite dickite assemblage formed between 250 degrees and 320 degrees c from dilute 5 wt nacl fluids an upward flared zone of muscovite quartz pyrite altered rocks surrounds the fault controlled domain of advanced argillic alteration thick veins 0 5 2 m wide of fault hosted massive pyrite chalcopyrite and bornite precipitated brines with a salinity of 30 wt percent nacl at temperatures of 250 degrees to 300 degrees c pressure depth estimates indicate that at least 1 km of rock was eroded at rosario between formation of the k na silicate and advanced argillic assemblages this erosion was rapid occurring over a period of 1 8 m y the rosario porphyry intruded immediately after the incaic tectonic phase implying that it was emplaced as the domeyko cordillera underwent gravitational collapse expressed as normal faults in the upper crust gravitational sliding potentially accelerated exhumation and helped to promote telescoping of the high sulfidation environment onto the rosario porphyry the hydrothermal system responsible for porphyry cu mineralization at rosario was partially exhumed prior to the formation of high sulfidation ore and alteration assemblages this implies that emplacement of a second blind intrusion occurred somewhere beneath the rosario and cerro la grande high sulfidation vein systems and is supported by the fault geometry and zoning of precious metals and sulfosalts at the district scale

the cantung e zone scheelite skarn orebody tungsten northwest territories a revised genetic model the unusually large and high grade orebody developed as a result of infiltration metasomatism shortly following the epizonal intrusion of an upper cretaceous peraluminous biotite monzogranite pluton thermal metamorphism attained the pyroxene hornfels facies and was accompanied by the formation of minor folds and a foliation parallel to contact in the inner aureole subsequently following a temperature drop of 50 degrees to 100 degrees c initial hydrothermal activity at 450 degrees to 500 degrees c generated a zoned array of anhydrous and hydrous reduced skarn facies skarn formation occurred under a confining pressure of ca 1 or 0 3 kb from sphalerite geobarometry and was associated with extensive brittle and ductile deformation of the exoskarn contact zone scheelite abundant in all skarn facies except the garnet pyroxene is everywhere strongly correlated with pyrrhotite and shows little textural evidence of dissolution in the course of skarn development the hydrothermal fluid was a predominantly or entirely nonboiling moderately saline 4 14 equiv wt nacl brine which is inferred to have contained cacl 2 fecl 2 mgcl 2 and kcl in addition to nacl the skarn generating fluids apparently remained essentially constant in composition during the protracted mineralizing event modified journal abstract

sedimentological evolution of north sound grand cayman a freshwater to marine carbonate succession driven by holocene sea level rise abstract north sound grand cayman contains up to 4 m of sediments that accumulated under the influence of the holocene rise in sea level originally north sound was a dish shaped depression formed by the erosion of the miocene dolostone and pleistocene limestone bedrock at that time a sill along the northern margin isolated the area from the open ocean sedimentation from 5 000 to 3 800 yr b p which took place in a fresh water to brackish water regime resulted in deposition of the composite grain gastropod and bivalve facies as sea level rose above the sill no later than 2 500 yr b p marine waters began to invade north sound and open connections with the caribbean sea were established peats which developed in mangrove swamps were deposited during this transitional phase fully marine sedimentation ongoing for at least the last 2 500 years resulted in the deposition of the halimeda halimeda benthic foraminifera bivalve and bivalve halimeda facies sediment which accumulated at an average of 85 cm 1000 years did not keep pace with sea level which rose at an average of 160 cm 1000 years as a result accommodation space in north sound has progressively increased a sea level curve derived from basal peats and bivalves found in the sediments of north sound is comparable to sea level curves derived for barbados reefs for the last 2 500 years however the north sound curve is 3 m lower than a sea level curve that was derived from peats on barkers peninsula which forms the northwest boundary of north sound this discrepancy attributed to original differences in elevations of the samples highlights some of the problems associated with the construction and interpretation of sea level curves the sedimentary succession in north sound which is similar to that found in the bight of abaco in the bahamas is a record of transient depositional environments that evolved in response to the holocene rise in sea level

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

ostracods as proxies for past seagrass a review abstract recently attention has been drawn to the recognition of past seagrass for which a number of proxies have been proposed several studies have quoted ostracods as having some value as proxies particularly loxoconcha xestoleberis and aurila although these may be found in a variety of marine environments they are often found with faunas containing seagrass or which can be interpreted as in proximity to seagrass in such situations they may be found with other possible seagrass proxies such as sirenians lucinid bivalves soritid and other benthic foraminiferans the presence of loxoconcha xestoleberis and aurila and other ostracods may be suggestive of past seagrass environments the interpretation of which is strengthened by the presence of other proxies in some collections

epiphyte communities on thalassia testudinum from grand cayman british west indies their composition structure and contribution to lagoonal sediments abstract thalassia testudinum the most common seagrass found in lagoons around grand cayman influences sedimentation by baffling currents binding sediment on the seafloor and providing substrates for a diverse epiphytic biota about 85 of the epiphytic biota is formed of at least 3 species of coralline algae 72 species of foraminifera and 61 species of diatoms the rest of the biota is formed of sponges gastropods ostracods coccoliths dinoflagellates brown algae and worms the epiphytes are organized in three communities that are part of an organized tripartite community succession the basal diatom community is overlain by the coralline algae community which is then overlain by a community composed of a variety of taxa the coralline algae community which is the most extensive typically covers 75 of the leaf s surface potentially the skeletons of these epiphytes can make a significant contribution to the fine grained sediment budget of these lagoons surprisingly only a few of the epiphytes were found in the lagoonal sediment it appears therefore that the epiphytes are lost through skeletal dissolution or transported out of the lagoon following storms irrespective of the cause the epiphytes do not form a significant part of the lagoon sediment in grand cayman

ore forming fluids and isotopic h o c s pb characteristics of the fujiashan longjiaoshan skarn w cu mo deposit in the edong district of hubei province china abstract the fujiashan longjiaoshan deposit is located in the southern area of the edong district of the middle lower yangtze river metallogenic belt w cu mo orebodies are found in the contact zone between the granodiorite porphyry and carboniferous to triassic carbonate strata four stages of ore formation are identified 1 the prograde skarn stage 2 retrograde skarn stage 3 quartz sulfide stage further subdivided into the early 3a and later 3b and 4 carbonate stage in this study we applied fluid inclusion microthermometry laser raman spectroscopy and h o c s pb isotopic compositions to constrain hydrothermal processes and ore precipitation mechanisms of the fujiashan longjiaoshan deposit early stage 1 and 2 ore forming fluids belong to a high temperature above 550 c high salinity 60 70 wt nacl equiv and 15 20 wt nacl equiv respectively high pressure above 700 bars and high oxygen fugacity nacl kcl h2o system and in the quartz sulfide stage 3 the system changes into a nacl kcl co2 h2o system homogenization temperatures and salinities of ore forming fluids gradually decrease throughout the evolutionary process fluid temperatures vary at 550 c in prograde skarn stage 1 from 350 to 400 c in retrograde skarn stage 2 from 250 to 300 c in quartz sulfide stage 3 and finally from 100 to 150 c in carbonate stage 4 salinity levels vary from 15 to 20 wt nacl equiv in prograde skarn stage 1 from 5 to 20 wt nacl equiv in retrograde skarn stage 2 from 10 to 15 wt nacl equiv in quartz sulfide stage 3a from 5 to 10 wt nacl equiv in quartz sulfide stage 3b and from 0 to 5 wt nacl equiv in carbonate stage 4 the h o c isotopic compositions indicate that the ore forming fluids were derived from magmatic water d of 123 to 83 18ov smow of 6 1 to 7 4 with the input of meteoric water and organic matter in the quartz sulfide stage d of 91 to 53 18ov smow of 2 4 to 4 6 and cv pdb of 14 7 to 6 4 sulfur and pb isotopic compositions show that the ore forming materials were mainly derived from granitic magma 34sv cdt values of granodiorite porphyry sulfides and skarns of 5 7 to 6 6 and in part from host sedimentary strata 34sv cdt values of sulfides of country rocks clustering at 20 and at 10 fluid boiling in the retrograde skarn stage gave rise to the first precipitation of scheelite the precipitation of scheelite chalcopyrite and molybdenite in the quartz sulfide stage was probably triggered by the input of meteoric water and organic carbon according to mineral assemblages and all available geological and geochemical data we conclude that the fujiashan longjiaoshan deposit is an oxidized skarn type w cu mo deposit

the dagpazari carbonate platform mut basin southern turkey facies and environmental reconstruction of a coral reef system during the middle miocene climatic optimum abstract plate tectonics and climate change have deeply influenced the evolution of coral reef systems of the mediterranean during the miocene most of this information is based on studies of coral reefs from the western and central sectors of the mediterranean this study reports facies analyses sr isotope stratigraphy and environmental reconstructions of the dagpazari coral reef system located within the mut basin in southern turkey stratigraphic correlations and sr isotope ratios on several oyster shells date the dagpazari reef to the early langhian ten different facies have been recognized and their arrangement has led to the identification of two main depositional units interpretation of the biotic associations indicates that the dagpazari depositional system developed constantly within the euphotic zone the reef framework was mainly built by massive faviid and poritid zooxanthellate corals whereas loose grain sediments were essentially produced by halimeda coralline red algae or influenced by the presence of seagrass colonizations this study highlights for the first time the great importance of halimeda as sediment producer in the eastern mediterranean coral reef systems this role is related to the common occurrence of halimeda plates within almost all the reef facies but especially to the presence of large in situ bioherms dominated by the algal segments dagpazari langhian halimeda bioherms also represent the oldest of these structures so far recorded in the fossil record the development of the dagpazari platform was mainly controlled by eustatic fluctuations of the sea level and by the morphology of the antecedent substrate in particular the occurrence of a pre existent topographic high promoted the constant presence of shallow water environments throughout the depositional history of the reef system with the production of euphotic carbonates both landward and basinward and the consequent formation of a small elliptical platform 87sr 86sr ages place the dagpazari reef system exactly within the middle miocene climatic optimum phase the most recent warm phase of the earth this suggests that zooxanthellate corals were able to exert their reef building capacity in shallow water settings even during periods of global warming thus being not exclusively an adaptation to cooling climates as proposed in the recent debates

peraluminous i type granites abstract s type granites always contain more al than the amounts of na ca and k in the rock required to form feldspars primarily owing to their derivation from source components that had previously been weathered those rocks are therefore always saturated in al or peraluminous many i type granites are also peraluminous despite i type source rocks typically not being saturated in al it has previously been suggested that this may result from the fractional crystallisation of amphibole however data from compositionally zoned high temperature plutons in the lachlan fold belt show that it is difficult to generate large quantities of peraluminous melt by removal of amphibole most of the i type granites 95 in the lachlan fold belt formed at lower temperatures and almost half of those rocks for which bulk chemical compositions are available are peraluminous among these granites there are 98 separate suites for which there are chemical data for two or more samples with 47 suites that include both metaluminous more mafic and peraluminous more felsic compositions the origin of those peraluminous compositions is fundamental to any understanding of i type granite petrogenesis in this region compositional variations caused by the assimilation or by partial melting of supracrustal rocks are very small as the isotopic variations within these rocks are dominantly between different suites not within suites the partial melting of more mafic source rocks rather than the fractional crystallisation of more mafic magmas is favoured for the origin of these rocks partial melting is the most likely process involved in the petrogenesis of felsic granites where broadly granodioritic monzogranitic batholiths are associated with lesser amounts of tonalite and very minor amounts of mafic rock experimental studies have shown that the melts generated by the partial melting of basaltic to andesitic rocks under crustal conditions are mostly peraluminous during the dehydrational melting of i type granite source rocks at pressures below the garnet stability field biotite and amphibole melt incongruently to yield pyroxenes the excess al is incorporated into the felsic liquid resulting in the generation of peraluminous melts in this instance the excess al in felsic i type granites is a function of the melting process and unrelated to the bulk composition of the source the observed gradation from peraluminous felsic granites to metaluminous compositions in less felsic rocks in largely isotopically closed systems could happen in two ways at higher temperatures of partial melting ca and other components of clinopyroxene could dissolve in the melt with the melt eventually becoming metaluminous alternatively minerals residual from partial melting dominantly pyroxenes and plagioclase could be incorporated in suspension in the melt so that the resulting bulk magma is metaluminous examples of these two extremes and of intermediate cases are well developed among the granites of southeastern australia

seagrass related carbonate ramp development at the front of a fan delta burdigalian new caledonia insights into mixed carbonate siliciclastic environments abstract past shallow water carbonate environments of the main island of new caledonia nc have been subject to high terrigenous influx derived from the erosion of ultramafic obducted nappes and are therefore a relevant case study for characterizing neritic carbonate production in mixed carbonate siliciclastic systems under a tropical climate more particularly we focused on burdigalian carbonate sedimentary records cropping out on the western coast of nc in the nepoui area based on a comprehensive sedimentological study of cores and outcrops we established a new depositional model of an alluvial fan to carbonate ramp transition shallow water euphotic carbonate production was dominated by seagrass related biota and corals derived from small sized bioconstructions extensional tectonics and associated normal faulting driven by post obduction isostatic rebound favored carbonate ramp aggradation and preservation the carbonate ramp was incised by conglomerate filled terminal distributary channels which indicate that terrigenous inputs remained significant during marine transgression and did not inhibit the development of seagrass and scleractinian carbonate factories phytal substrates induced by seagrass and or macro algae seafloor colonization strongly controlled the nature of carbonate production and promoted the accumulation of foraminiferal coralline algal sediments seagrass development at the front of the fan delta is interpreted to have controlled the preservation of a diverse and significant carbonate production by reducing water turbidity and by limiting the risk of suffocation for filter feeding biota in such a high terrigenous influx setting

package fluids 1 computer programs for analysis of fluid inclusion data and for modelling bulk fluid properties the computer package fluids contains five sets of computer programs written in c for the calculation of fluid properties both model fluids and data from fluid inclusions can be analysed in the programs bulk density molar volume and composition of fluid inclusions are calculated with the program bulk which uses microthermometric data micro raman spectroscopic data cation ratios and volume fraction estimations as input the program offers a broad variety of equations of state which are selected according to the fluid system or the temperature and pressure conditions of interest the isochores that correspond to the output or test v x properties of fluid inclusions are calculated by the program isoc in calculating the isochores this program takes account of the compressibility and expansion of selected host minerals the program test allows different equations of state to be compared directly with experimental data thereby facilitating selection of the most adequate model in the programs bulk and isoc loner is a group of programs that handle individual equations of state eos for all fluid systems presented in the programs bulk and isoc aqso is a group of programs that allows purely empirical modelling of electrolyte bearing aqueous solutions henry s law for dilute gas bearing aqueous solutions and osmotic coefficients for dilute electrolyte bearing aqueous solutions the programs are available on the university of leoben web site at http www unileoben ac at buero62 minpet ronald

architectural complexity of a carbonate transgressive systems tract induced by basement physiography three dimensional exposure of the plio pleistocene calcarenite di gravina formation around matera horst italy permits analysis of the architecture and internal complexities of carbonate sedimentary bodies around a palaeoisland spatial organization of the different lithosomes along with their skeletal composition sedimentary structures and bedding patterns helps decipher the key factors that controlled platform architecture and distribution of heterogeneities basement physiography type and loci of carbonate production bottom currents and changes in accommodation relative sea level changes resulted from high frequency glacioeustatic cycles that punctuated an overall tectonically induced transgression topographic relief fragmentation of the limestone basement and wave energy controlled lithoclastic supply basement physiography and relative sea level changes determined the area available for carbonate producing biotas and thus the amount and type of skeletal sediments on the moderately dipping south western margin waves and associated currents re distributed the lithoclasts derived from coastal abrasion bioclasts mostly derived from epiphytic seaweed production in the shoreface infralittoral prisms resulted from downdip transport progradation and longshore transport which controlled along strike continuity of the prisms where basement continuity was interrupted at the margin of the palaeoisland a lithoclastic fan was deposited from dumping sediments carried by shore parallel currents fan shaped skeletal bodies coalesced to form an apron on the steeper northern side of the palaeoisland when a structural platform was flooded and epiphytic carbonates were shed red algae contribution depended on the available oligophotic area which in turn was controlled by high frequency sea level cycles basement physiography and apron aggradation the internal architecture of this apron resembles a low stand wedge but it accumulated during transgression deeper water contour parallel currents formed a lithosome at the foot of the structural relief interpreted as drift deposits it is composed of shallow water benthonic skeletal components planktonic foraminifera and some limeclasts

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

geology mineralization and fluid inclusion characteristics of the koitash redox intermediate w mo skarn and w au stockwork deposit western uzbekistan tien shan the koitash w mo skarn deposit in the tien shan gold belt contained resources of 60 kt wo3 in altered skarn averaging 0 56 wo3 and 0 029 mo and an additional 42 kt wo3 in separate zones of phyllic alteration averaging 0 30 wo3 0 97 g t au 0 67 cu and 0 02 bi it is related to an early permian multiphase granodiorite granite leucogranite pluton that is composed of medium to high k transitional metaluminous to peraluminous weakly oxidized weakly reduced ilmenite titanite series granitoids the pluton was emplaced in a tectonic domain with inferred ancient continental crust the latter coupled with possible ascent of hot asthenospheric material has likely defined a distinct w mo au metallogenic assemblage forming in a post collisional environment the deposit includes redox intermediate prograde and retrograde pyroxene garnet skarns partially overprinted by propylitic and phyllic alteration assemblages comprising scheelite molybdenite cu bi ag te sulfides and sulfosalts as well as native bi and au compositional similarities between w mo deposits containing au w cu bi mineralization in late alteration assemblages and coeval intrusion related au dominant with minor w bi etc deposits in the region support their possible genetic links fluid inclusion data indicate the involvement of carbonic free moderately saline 10 5 15 0 to 8 0 11 7 wt nacl eq high pressure 2000 to 1500 bars hot 550 600 c aqueous fluid which was sourced from crystallizing magma and formed prograde calcic skarn this fluid was followed by moderately saline ca rich 14 16 wt nacl 19 21 wt cacl2 lower pressure 800 bars fluids toward the retrograde skarn stage with the deposition of scheelite in association with pyrrhotite and molybdenite locally with minor fluorite propylitic quartz amphibole chlorite oligoclase calcite with scheelite pyrrhotite locally molybdenite assemblages formed from boiling high methane aqueous carbonic fluids at temperatures of 370 400 c and pressures of 950 1000 bars phyllic quartz sericite fe carbonate locally with albite fluorite chlorite scheelite molybdenite and other sulfides also bi and au minerals alteration assemblages initially formed from homogeneous and then from boiling aqueous carbonic low salinity fluids at temperatures of 365 370 to 300 315 c and pressures of 2000 bars 34s increases from retrograde skarn 34s 2 0 to 2 3 through propylitic 34s 3 0 to 3 4 to phyllic alteration 34s 4 2 to 4 7 stages

fluid inclusion and stable isotope constraints on the genesis of the world class zhuxi w cu skarn deposit in south china abstract scheelite mineralization accompanied by traces of chalcopyrite occurs in skarn systems in the giant zhuxi deposit in the taqian area northeastern jiangxi province south china three paragenetic stages of skarn with ore deposition have been recognized the prograde skarn retrograde skarn and hydrothermal quartz sulfide stages microthermometer data showed that the prograde skarn were formed at relatively high temperatures 450 500 c and pressures 0 97 1 38 kbars and low oxidation to weak reduction conditions the raman microprobe data demonstrated that the fluid of the stage was h2o nacl kcl cacl2 ch4 c2h4 system the retrograde skarn alteration formed at 1 24 kbars and relatively medium temperatures 280 320 c and the ore forming fluid was h2o nacl kcl cacl2 system during the hydrothermal quartz sulfide stage the fluids were methane bearing aqueous low salinity 0 9 8 0 wt nacleqv and low homogeneous temperature 160 240 c correspondingly the minimum fluid pressures were evaluated between 75 and 252 bars the h and o isotopic values from the prograde and retrograde stages implied that the mineralizing fluids were derived principally from magmatic water the mineralizing fluids in the quartz sulfide hydrothermal stages were mingled with magmatic water with some meteoric water as well as minor contributions of wall rocks the sulfur and lead isotopes indicated that ore forming materials including sulfur lead copper zinc and iron in the zhuxi deposit were derived from local magmatic and sedimentary sources geological fluid inclusion and isotopic data supported that the zhuxi deposit is a typical skarn type w cu deposit related to ilmenite series granitic rocks and formed in a compressional tectonic environment

geology mineralization and fluid inclusion characteristics of the meliksu reduced tungsten skarn deposit alai tien shan kyrgyzstan insights into conditions of formation and regional links to gold mineralization abstract the meliksu w skarn deposit 10kt wo3 with average grade of 6 6 wo3 in the alai segment of the southern tien shan is related to an early permian granitoid pluton that comprises ilmenite series to ilmenite titanite bearing medium k metaluminous to peraluminous i type granitoid monzonite diorite tonalite granodiorite to granite rocks there is a regional scale continuum from these intrusions to transitional weakly reduced to weakly oxidized metaluminous i type granitoid suites accompanied by reduced intrusion related au deposits magmatic evolution also included coeval high k to shoshonitic suites and younger early permian post collisional to within plate alkaline from monzogabbro to nepheline syenite and carbonatite intrusions indicative of an extensional tectonic regime consistent with this evolution toward an extensional environment reduced w skarns and associated reduced intrusion related au mineralization in the region may evolve toward sb hg as au w mineralization exhibiting the carlin type affinity the deposit bears signatures of reduced w skarn deposits with dominant pyroxene hedenbergite rich prograde and retrograde skarns scheelite was mostly deposited during the propylitic amphibole chlorite calcite quartz with abundant pyrrhotite and minor chalcopyrite and phyllic quartz sericite albite fe carbonate with sulfides bi ag and au minerals alteration stages silver mineralization is particularly abundant that together with very high w grades low au grades intense calcic sodic and sodic alteration and coarse grained sericite muscovite quartz aggregate possibly reveal a root level of reduced w skarn deposits fluid inclusions data indicate formation of retrograde mainly pyroxene quartz amphibole skarn from aqueous dominantly magnesian sodic chloride moderately saline 16 18 wt nacl eq high pressure 1 9 0 7 kbar moderately hot 400 500 c fluid propylitic alteration assemblages were formed from slightly less saline 11 13 wt nacl eq high pressure 1 8 0 5 kbars lower temperature 370 450 c ca enriched fluid phyllic alteration assemblages were formed from high pressure 2 2 0 1 kbars boiling methane rich carbonic aqueous cooling from 350 to 335 c to 275 265 c fluid high fluid pressures at different hydrothermal stages are consistent with a deep level of mineralization at a lithostatic depth of 9 0 km a strong enrichment in heavy sulfur isotope 34sfluid varies from 6 5 0 4 to 8 0 0 3 can reflect sulfur sourcing from sedimentary rocks enriched in seawater sulfate with sulfur isotope homogenization in a magmatic chamber

an experimental study of sulfidation reactions involving andradite and hedenbergite three sulfur buffering sulfide silicate reactions which limit the stabilities of the skarn silicates andradite garnet and hedenbergite pyroxene under sulfidizing conditions were studied hydrothermally at a pressure of 2 kb over the temperature range 700 degrees to 350 degrees c reaction 1 andradite s 2 wollastonite anhydrite quartz pyrite or pyrrhotite reaction 2 andradite magnetite s 2 anhydrite quartz pyrite or pyrrhotite andreaction 3 hedenbergite s 2 andradite quartz pyrrhotite the equilibrium value of the sulfur fugacity f sub s 2 for each reaction assemblage at any given temperature was calculated from the measured composition of a coexisting sulfur fugacity indicator pyrrhotite or sphalerite as appropriate the log f sub s 2 data were adequate for the determination of the log f sub s 2 1 t relations for each of the andradite sulfidation reactions owing to excessive scatter in the data for the hedenbergite sulfidation reaction however the log f sub s 2 1 t relation for this reaction derived from the log f sub o 2 data of burton et al 1982 is preferred to the one developed by gamble 1976 1978 the log f sub s 2 1 t relations for the three sulfidation reactions were combined with equilibrium data available in the literature for other reactions in the model system ca si fe o s and used to construct quantitative isothermal isobaric log f sub s 2 log f sub o 2 phase diagrams applicable to the formation of ca si fe skarns the quantitatively derived phase relations were found to be consistent in all major respects with the schematic phase relations deduced by burt 1972a and b the influence of diopside component on the stability of hedenbergitic pyroxene was also studied diopside was found to enlarge the stability field of hedenbergitic pyroxene increasing the temperature at which pyroxene becomes stable with pyrite from 288 degrees c for end member hedenbergite burton et al 1982 to 395 degrees c for 50 mole percent diopside diopside was found to be less effective than the johannsenite component in stabilizing hedenbergitic pyroxene

gold and metal enrichment in natural granitic melts during fractional crystallization metal evolution in a composite granitic pluton was tracked by analyzing melt inclusions in 11 quartz samples from 7 zones at the timbarra gold deposit australia we present the first quantitative microanalyses of gold au in granitic silicate melt inclusions using laser ablation inductively coupled plasma mass spectrometry and show how au and other metals become enriched during fractional crystallization in a granite intrusion au was enriched during fractionation from a monzogranite to a highly fractionated alkali feldspar granite similar enrichment behavior for other metals implies that no gold enriched precursor melt is required and fractional crystallization can enrich the au concentration to economic levels the low content of accessory oxides and sulfides the absence of early cl bearing fluids the volatile content in the melt and a prolonged crystallization constitute important factors for extensive metal enrichment during crystal fractionation these characteristics play a crucial role in felsic highly fractionated plutons and their associated deposits such as intrusion related au deposits the gold enrichment during fractionation also implies that au is directly sourced from the granites

geology mineralization and fluid inclusion characteristics of the kashkasu w mo cu skarn deposit associated with a high potassic to shoshonitic igneous suite in kyrgyzstan tien shan toward a diversity of w mineralization in central asia abstract the kashkasu deposit is part of the subduction related late paleozoic late carboniferous metallogenic belt of tien shan it is associated with a multiphase monzodiorite monzonite granodiorite granite pluton of the magnetite series high k calc alkaline to shoshonitic igneous suite the deposit contains zones of w mo cu oxidized prograde and retrograde skarns with abundant andraditic garnet magnetite locally scapolite and k feldspar as well as scheelite chalcopyrite and molybdenite skarns are overprinted by quartz carbonate sericite phyllic alteration zones with scheelite and sulfides prograde calcic skarn and initial retrograde skarns were formed from a high temperature 650 c to 450 550 c high pressure 2000 bars to 600 900 bars magmatic hydrothermal low to high salinity aqueous chloride fluid the gradual fluid evolution was interrupted by the intrusion of granodiorite and likely associated release of low salinity 7 8 wt nacl equiv fluid ascent of this fluid to shallower levels and or its cooling to 400 500 c has resulted in phase separation into low salinity 2 1 3 1 wt nacl equiv vapor and coexisting brine 35 40 wt nacl equiv the boiling was coincident with most intense scheelite deposition in retrograde skarn later retrograde skarn assemblages were formed from a gaseous low to moderate salinity 3 4 8 1 wt nacl equiv fluid and then from high salinity 37 42 wt nacl equiv aqueous chloride fluids the latter being enriched in ca 17 20 wt cacl2 that could also affect scheelite deposition another cycle of fluid exsolution from crystallizing magma corresponded to quartz carbonate sericite scheelite sulfide phyllic alteration stage with the early low salinity 5 3 8 4 wt nacl equiv fluid followed by later high salinity 33 5 38 2 wt nacl equiv fluid the sulfur isotope data 34s 5 1 to 9 0 suggest significant sulfur sourcing from sedimentary rocks enriched in seawater sulfate possibly evaporites

scheelite elemental and isotopic signatures implications for the genesis of skarn type w mo deposits in the chizhou area anhui province eastern china scheelite is well developed in hydrothermal deposits providing a window into genetic processes and facilitating comparative studies however few studies have focused on characterizing scheelite in skarn type w mo deposits the primary ore mineral in the jitoushan and baizhangyan skarn type w mo deposits anhui province eastern china scheelite was analyzed for major trace and rare earth element ree abundance and for sr nd isotopes the analysis revealed two unique geochemical characteristics that distinguish the scheelite from skarn type w mo deposits to that from vein type au w and porphyry type w mo deposits higher mo content with a negative correlation between moo 3 and wo 3 and a strong hree depletion skarn type scheelite mainly inherited ree signatures from ore forming fluids and the early precipitation of skarn minerals e g garnet diopside and amphibole has most likely resulted in the observed strong hree depletion in scheelite and the decoupling of lrees and hrees of the numerous substitution mechanisms suggested by previous workers 3ca 2 2ree 3 ca where ca is a ca site vacancy is preferred for the substitution of ree 3 for ca 2 and in this study particularly given the low salinity of ore fluids as the scheelite eu anomalies were inherited from ore forming fluids with variable redox conditions and ph the complex deu mo correlation indicates that mo increasingly entered the scheelite under oxidizing conditions and reached a maxim at deu values of 0 8 to 1 in contrast under reducing conditions mo contents in scheelite decrease gradually and mo is precipitated as molybdenite as a result of the change in dominant valence state unlike the sr nd isotope compositions of scheelite from vein type au w and w sb au deposits the scheelite from skarn type w mo deposits has low 143 nd 144 nd t most 87 sr 86 sr t values most between 0 708 and 0 715 the end t values of the scheelite varied from 16 to 12 3 in the baizhangyan deposit and from 9 5 to 9 1 in the jitoushan deposit indicating that the ore forming materials in the two w mo deposits were mainly derived from crustal sources

emplacement ages geochemical and sr nd hf isotopic characterization of mesozoic to early cenozoic granitoids of the sikhote alin orogenic belt russian far east crustal growth and regional tectonic evolution abstract the sikhote alin range of the russian far east is an important accretionary orogen of the western pacific orogenic belt in order to study the formation and tectonic evolution of the orogen we performed zircon u pb dating as well as geochemical and sr nd hf isotopic analyses on 24 granitoid samples from various massifs in the primorye and khabarovsk regions the zircon dating revealed that the granitoids were emplaced from 131 to 56 ma cretaceous to paleogene in the primorye region granitoids in the coastal sikhote alin intruded the cretaceous taukha accretionary terrane from ca 90 to 56 ma whereas those along the central sikhote alin fault zone intruded the jurassic samarka accretionary terrane during ca 110 75 ma the oldest monzogranite 131 ma was emplaced in the lermontovka area of the nw primorye region granitoid massifs along the central sikhote alin fault zone in the khabarovsk region formed from 109 to 58 ma thus the most important tectonothermal events in the sikhote alin orogen took place in the cretaceous geochemical analysis indicates that most samples are i type granitoids they have initial 87sr 86sr ratios ranging from 0 7040 to 0 7083 and initial nd isotopic ratios expressed as end t values from 3 0 to 5 0 mostly 0 to 5 the data suggest that the granitoid magmas were generated by partial melting of sources with mixed lithologies including the subducted accretionary complex hidden paleozoic proterozoic basement rocks based on whole rock nd isotopic data we estimated variable proportions 36 77 of juvenile component mantle derived basaltic rocks in the generation of the granitic magmas furthermore zircon hf isotopic data ehf t 0 to 15 indicate that the zircon grains crystallized from melts of mixed sources and that crustal assimilation occurred during magmatic differentiation the quasi continuous magmatism in the sikhote alin orogen suggests that the paleo pacific plate subduction was very active in the late cretaceous the apparently regular progression of granitic intrusion ages from 80 to 56 ma in the taukha terrane may reflect oblique underflow of the paleo pacific plate beneath the eurasian continental margin subduction was not only manifested by granitic intrusion but also by abundant silicic volcanism the late cretaceous paleo pacific plate motion probably changed from parallel or sub parallel to oblique relative to the continental margin of the sikhote alin leading to the change of magmatic source region and geochemical characteristics of the derived igneous rocks late cretaceous rapid sea floor spreading at ca 100 ma induced highly active subduction and led to voluminous magmatism in the entire circum pacific realm finally the present age and isotopic study lends support to the hypothesis of geologic and tectonic correlation between sikhote alin and sw japan

acidity salinity diagrams application to greisen and porphyry deposits to a first approximation alteration minerals in greisen and related fluorine rich porphyry deposits lie in the system k 2 o al 2 o 3 sio 2 h 2 o f 2 o sub 1 equilibria in this model system can be depicted on quartz and fluid saturated chemical potential diagrams whose axes are mu hf acidity where mu hf mu hcl mu sub fcl sub 1 and mu kf salinity where mu kf mu nacl mu sub kna sub 1 mu sub fcl sub 1 advantages of this approach are that it reflects the fact that the anion f unlike cl is incorporated in greisen minerals mainly topaz fluorite and micas and that mineral stabilities can be correlated with possible ore forming processes the most important of these processes is probably vapor phase separation from an aqueous brine or magma first or second boiling fluid inclusion studies have shown that boiling occurs in all porphyry and many but not all greisen deposits vapor phase separation from a magma pneumatolysis must similarly be responsible for the formation of greisenlike mineral assemblages in miarolitic topaz rhyolite lava flows and is presumably also responsible for the formation of gem pockets in more deeply seated pegmatites and granites the result of boiling is an increase in mu hf and a decrease in mu kf in the vapor phase and the opposite in the residual brine or magma in deep greisen veins the muscovite stability field is encountered between the k feldspar and topaz fields whereas in f rich relatively shallow porphyry deposits such as henderson colorado boiling causes aqueous fluids to pass directly from the k feldspar ore zone to the overlying topaz magnetite zone muscovite or f bearing mn fe garnet is only encountered farther out as the fluids are condensed neutralized and diluted by cooler meteoric waters when ca fe mn be w o 2 s 2 and co 2 are added to the greisen model system scheelite is shown to transform to wolframite with increasing mu hf and beryl to phenakite with increasing mu hf or mu kf biotite transforms to magnetite hematite siderite pyrite chlorite or fayalite beyond the k feldspar field its stability is enhanced by high mu hf and chlorite cordierite or mn fe garnet transform to an mn fe carbonate oxide or sulfide or biotite beyond the al silicate field the ca content of plagioclase coexisting with fluorite decreases with an increase in either mu hf or mu kf and thus provides an indicator of total fluorine in both acid and neutral species

reconciling fluid inclusion types fluid processes and fluid sources in skarns an example from the bismark deposit mexico the bismark deposit 8 5 mt at 8 zn 0 5 pb 0 2 cu and 50 g t ag located in northern mexico is an example of a stock contact skarn end member of a continuum of deposit types collectively called high temperature carbonate replacement deposits the deposit is hosted by massive sulfide within altered limestone adjacent to the bismark quartz monzonite stock 42 ma and the bismark fault alteration concurrently developed in both the intrusion and limestone the former contains early potassic alteration comprising k feldspar and biotite which was overprinted by kaolinite rich veins and alteration and later quartz sericite and pyrite with minor sphalerite and chalcopyrite prograde exoskarn alteration in the limestone consists of green andradite and diopside and transitional skarn comprising red brown andradite green hedenbergite and minor vesuvinite calcite fluorite and quartz the main ore stage post dates calc silicate minerals and comprises sphalerite and galena with gangue pyrite pyrrhotite calcite fluorite and quartz the entire hydrothermal system developed synchronously with faulting fluid inclusion studies reveal several distinct temporal compositional and thermal populations in pre syn and post ore quartz fluorite and calcite the earliest primary fluid inclusions are coexisting vapor rich type 2a and halite bearing type 3a type 3b contain sylvite brine inclusions 32 to 60 total wt salts that occur in pre ore fluorite trapping temperatures are estimated to have been in excess of 400 c under lithostatic pressures of 450 bar 1 5 km depth primary fluid inclusions trapped in syn ore quartz display critical to near critical behavior type 1c have moderate salinity 8 4 to 10 9 wt nacl equiv and homogenization temperatures th ranging from 351 to 438 c liquid rich type 1a and 1b calcite bearing inclusions occur as primary to secondary inclusions predominantly in fluorite and show a range in th 104 336 c and salinity 2 7 11 8 wt nacl equiv which at the higher th and salinity ranges overlap with type 1c inclusions oxygen isotope analysis was carried out on garnet quartz and calcite plus carbon isotopes in pre syn post ore and peripheral veins pre ore skarn related garnets have a 18omineral range between 3 9 and 8 4 quartz from the main ore stage range between 13 6 and 16 0 calcite from the main ore stage has 13c values of 2 9 to 5 1 and 18o values of 12 3 to 14 1 which are clearly distinct from post ore veins and peripheral prospects that have much higher 18o 16 6 27 3 and 13c 1 3 3 1 values despite the numerous fluid inclusion types only two fluid sources can be inferred namely a magmatic fluid and an external fluid that equilibrated with limestone furthermore isotopic data does not indicate any significant mixing between the two fluids although fluid inclusion data may be interpreted otherwise thus the various fluid types were likely to have formed from varying pressure temperature conditions through faulting during exsolution of magmatic fluids late stage hydrothermal fluid activity was dominated by the non magmatic fluids and was post ore

tropical 45 day oscillations during the 1979 northern hemisphere summer abstract based on fgge 1 cvel iiib data the structural features of 45 day perturbations over a tropical belt 15 n 15 s during the 1979 summer are detailed at the equator 45 day perturbations which are primarily associated with the zonal wind components of wavenumber 1 propagate eastward 8 of longitude per day and upward 0 7 km per day probably indicating downward energy flux in the southern hemisphere tropics 0 15 s the 45 day zonal mean wind perturbations propagate downward with an approximate phase speed of 0 8 km per day in the northern hemisphere tropics they are largely of standing character with the maximum amplitude 3 m s 1 near 200 mb at 15 n there exists a strong association between monsoon activity over south asia and changes in the intensity of the equatorial walker circulation when active monsoons occur over south asia the walker circulation becomes stronger than usual with prominent 850 mb easterlies 200 mb easterlies over the eastern pacific east of the date line an

halimeda dominance in the coastal wedge of pietra di finale ligurian alps italy the role of trophic conditions the middle to late miocene mixed carbonate siliciclastic coastal wedge of the pietra di finale unconformably overlying the ligurian alps succession displays a carbonate portion dominated by halimeda and porites fragments that fall in the photozoan assemblages photozoan assemblages typically develop under tropical and oligotrophic conditions while hetorozoan assemblages tend to thrive in high nutrient settings the pietra di finale formation shows however that high weathering and an increase of nutrient inputs related to alpine uplift and humid climatic conditions promoted halimeda over the seagrass carbonate factory in the photic zone the successful halimeda proliferation was due to its efficient competition for nutrients especially nitrogen thus the pietra di finale formation represents an interesting counter intuitive example in which increased nutrient concentrations promoted instead of inhibited a photozoan over a seagrass related heterozoan carbonate production

modeling of gold scavenging by bismuth melts coexisting with hydrothermal fluids the effect of gold scavenging by bismuth melts is investigated using equilibrium thermodynamic modeling of an aqueous solution mineral melt system the calculations for the au bi na cl s h o system performed at temperatures between 300 and 450 c demonstrate that au concentrations in the melt are several orders of magnitude higher than in the coexisting fluid indicating the possible formation of economic gold deposits from undersaturated aqueous fluids in which mineralization would not be expected in the absence of a bismuth melt the model applies to any deposit where a bi melt is stable and coexists with a hydrothermal fluid examples of such deposits are known from skarn intrusion related orogenic and volcanogenic massive sulfide vms gold systems in sulfur poor systems the partitioning curves presented here can be used directly to correlate the gold concentration in the fluid and the au grade in the ore e g escanaba trough vms deposit these results also illustrate important principles generally applicable to understanding magmatic hydrothermal and metamorphic deposits that may have contained significant volumes of more complex polymetallic melts

geology mineralization and fluid inclusion characteristics of the lermontovskoe reduced type tungsten cu au bi skarn deposit sikhote alin russia abstract the lermontovskoe deposit 48 kt wo 3 average 2 6 wo 3 0 24 cu 0 23 g t au is situated in a w sn au metallogenic belt that formed in a collisional tectonic environment this tungsten skarn deposit has a w au as bi te sb signature that suggests an affinity with reduced intrusion related au deposits the deposit is associated with an intrusion that is part of the ilmenite series high k peraluminous granitoid granodiorite to granite suite these rocks formed via mantle magma induced melting of crustal sources the deposit comprises reduced type pyroxene dominated prograde and retrograde skarns followed by hydrosilicate amphibole chlorite pyrrhotite scheelite quartz and phyllic muscovite sericite carbonate albite quartz scheelite sulfide with abundant apatite alteration assemblages fluid inclusions from the skarn assemblages indicate high temperature 500 c high pressure 1400 1500 bars and high salinity 53 60 wt nacl equiv magmatic hydrothermal fluids they were post dated by high carbonic methane dominate low salinity fluid at the hydrosilicate alteration stage these fluids boiled at 360 380 c and 1300 1400 bars the subsequent phyllic alteration started again with a high temperature 450 c high pressure 1000 1100 bars and high salinity 42 47 wt nacl equiv fluid with further incursion of high carbonic methane dominated low salinity fluid that boiled at 390 420 c and 1150 1200 bars the latest phyllic alteration included the lower temperature 340 360 c lower pressure 370 400 bars high carbonic methane dominated but with higher co 2 fraction low salinity fluid and then the low temperature 250 300 c h 2 o co 2 ch 4 nacl fluid with both fluids boiled at the deposit level the high salinity aqueous fluids are interpreted to have come from crystallizing granitoid magma whereas the reduced high carbonic fluids probably came from a deeper mafic magma source both of these fluids potentially contributed to the w au as bi te sb metal budget decreasing temperatures coupled with high aca 2 and fluid boiling promoted scheelite deposition at all post skarn hydrothermal stages the deposit is characterized by limited downdip extent of mineralized zones and abundant coarse grained muscovite quartz apatite scheelite aggregates that formed at the phyllic alteration stage together with presence of high temperature high pressure and high salinity fluids directly exsolving from crystallizing magma this suggests a root level of the mineralized magmatic hydrothermal system of reduced w skarn deposits

carbonate sediment transport pathways based on foraminifera case study from frank sound grand cayman british west indies foraminifera can be used to determine the source s of carbonate sediment and the directions of sediment transport in shallow coastal lagoons such as frank sound on the south central coast of grand cayman these determinations based on the distribution of foraminiferal assemblages and tracer species numerically abundant species that live in known physiographic units and or ecological conditions show that the lagoonal sediments are a mixture of grains that originated in the lagoon and forereef the variable proportions of these foraminifera throughout the lagoon reflects the dynamic processes that control lagoonal sedimentation amphistegina gibbosa discorbis rosea and asterigerina carinata lived in the forereef environment the fact that these tracer species are found throughout frank sound and in the beach sands shows that they were transported across the reef crest and the lagoon abrasion resistant archaias angulatus a tracer species indicative of a lagoonal setting forms up to 50 of foraminiferal assemblages found in the lagoonal sediments preferential winnowing of small tests from these populations indicates sorting under high energy conditions the vertical distribution of the forereef and lagoonal foraminifera in the sediment blanket that covers the floor of frank sound indicates that these processes are temporally persistent transportation of forereef foraminifera into and around the lagoon and sorting of the lagoonal foraminifera cannot take place under normal conditions when the tranquil lagoon is characterized by weak currents storms and or hurricanes however generate short lived high energy events that can move and sort the sediment and foraminifera at the height of a storm water and sediment are moved over the reef and then piled and held onshore by the onshore winds and the constant flow of water over the reef and across the lagoon these currents can mix some of the lagoonal and forereef sediments as a storm wanes however the piled water flows offshore via strong rip currents that pass into the ocean through the channels which transect the reef these currents winnow and or strip sediment from the lagoon and may transport lagoonal sediments into the forereef area as a result residual lagoonal sediment is commonly characterized by larger and abrasion resistant foraminifera

foraminifera of petroleum platforms louisiana shelf gulf of mexico abstract species of benthic foraminifera presumably colonized the bacteria and diatom rich biofilms on the metallic surfaces of louisiana shelf petroleum platforms soon after their emplacement at present however most underwater platform legs are covered by a thick growth of macrofoulers predominantly barnacles and bivalves scraped samples from five such platforms water depth 16 61 m yielded 104 species of benthic foraminifera 44 of them with attached individuals among the obligate sessile species dyocibicides biserialis and planorbulina mediterranensis were especially widespread this group of epibionts also includes calcituba polymorpha carpenteria candei cornuspiramia antillarum lepidodeuterammina ochracea nubeculinita inhaerens planorbulina acervalis planorbulinoides retinaculatus sagenina divaricans webbina bonairensis and webbina rugosa the platforms are habitat islands the surrounding soft clastic substrate does not support the growth of most sessile species the putative source areas of these colonists of louisiana platforms are carbonate hardgrounds to the west banks or reefs formed over salt diapirs and other platforms the foraminiferal species diversity on the platforms is most likely controlled by their distances from these sources and the dimensions of the settlement surfaces the eastward transport of propagules in summer by the louisiana texas coastal current facilitates the species migration

the latitude height structure of 40 50 day variations in atmospheric angular momentum abstract quasi periodic variations in the relative angular momentum of the atmosphere on time scales of around 40 50 days have been observed by langley et al 1981 a description of the two dimensional latitude height structure of the winds responsible for these changes is constructed here from five years of nmc twice daily global analyses using cross spectral and amplitude phase eigenvector techniques we find these variations are associated with wavelike motions in the tropical upper troposphere that propagate and downward in phase within the tropics a coherently connected midlatitude northern hemisphere component is also present whose phase is essentially independent of height we believe the tropical component to be the zonally averaged part of the motions described by madden and julian 1971 1972 the northern hemisphere midlatitude component may be a direct response to the tropical motions or both motions may be the common response to an as yet unidentified tropical forcing

the dublin gulch intrusion hosted gold deposit tombstone plutonic suite yukon territory canada the dublin gulch intrusion is a member of the tombstone plutonic suite a linear belt of middle cretaceous intrusions that extend across the yukon territory like many of the intrusions in this suite the dublin gulch intrusion is associated with several different zones of gold and tungsten mineralization within and immediately adjacent to the intrusion the eagle zone 50 3 mt 0 93 g t gold located in the southwestern part of the dublin gulch intrusion hosts the most significant concentration of gold in the area the gold occurs in a broadly east west striking steeply south dipping series of sheeted veins the veins consist of early quartz scheelite pyrrhotite pyrite arsenopyrite and are associated with k feldspar albite alteration envelopes these grade out to and are overprinted by sericite carbonate chlorite alteration the same assemblage also occurs in veinlets that refracture sheeted quartz veins and contain the majority of the gold the gold occurs with molybdenite lead bismuth antimony sulfosalts galena and bismuthinite gold correlates strongly with bismuth r 2 0 9 a relationship common to several intrusion related gold deposits but has a poor correlation with all other elements tungsten and molybdenum have a weak inter element correlation r 2 0 55 and paragenetically pre date the majority of gold precipitation lead zinc copper silver antimony and arsenic have moderate to strong inter element correlations 0 58 to 0 93 the change from tungsten bearing mineralization through to gold bismuth rich ores with elevated syn to post ore lead zinc copper silver antimony and arsenic can be grossly correlated with a change in hydrothermal fluid composition early scheelite bearing quartz contains primary co2 rich fluid inclusions which are post dated by secondary inclusions with higher salinities up to 15 wt nacl equiv and less co2 these latter inclusions are interpreted to coincide with the later gold bismuth and base metal mineralization the favored genetic model is one in which early co2 rich fluids exsolved from a magma with an initially high co2 content but progressively became more saline and h2o rich as the system evolved

formation of anhydrous and hydrous skarn in cu au ore deposits by magmatic fluids most skarn ore deposits are characterized by two distinctly different alteration styles an early prograde stage with anhydrous minerals such as garnet and pyroxene forms from relatively high temperature hypersaline liquid a later retrograde stage with hydrous minerals such as epidote amphibole and chlorite plus sulfide ore minerals forms from lower temperature lower salinity fluids these two alteration stages commonly have been thought to reflect a dominance of magmatic and meteoric water respectively with relevance to the source of ore metals we report data from two different skarn systems one being part of the world s largest cu au resource stable isotope compositions of anhydrous and hydrous alteration minerals from both deposits indicate a magmatic source for both the prograde and retrograde stages 18o averages 5 0 per mil for garnet range 3 4 7 2 6 5 per mil for pyroxene 4 3 8 2 and 7 1 per mil for amphibole 4 3 8 7 the d values of late amphibole are more complex with magmatic values 77 to 78 for one deposit and both magmatic and lighter values for another deposit that could be explained either by magmatic degassing or by limited mixing with meteoric water we conclude that the differences in fluid composition prograde versus retrograde stages resulted from a magmatic fluid that intersected its solvus during the early stage creating vapor and hypersaline liquid whereas in the later stage this magmatic fluid did not intersect its solvus because it followed a different cooling path this late low salinity liquid only boiled once its vapor pressure curve was reached causing sulfide ore to precipitate during the retrograde stage

linear simulation of the stationary eddies in a gcm part ii the mountain model abstract the validity of linear stationary wave theory in accounting for the zonal asymmetries of the winter averaged tropospheric circulation obtained in a general circulation model gcm is ascertained the steady linear primitive equation model used towards this end has the same vertical and zonal resolution as the spectral gcm but is finite differenced in the meridional direction it is linearized about a zonally symmetric basic state and forced by topography and 3 dimensional diabatic heating and transient flux convergence fields all of which are taken from the gcm as in part i in which we studied a gcm with a flat lower boundary we obtained the best correspondence between the gcm and the linear solutions when strong rayleigh friction is included in the linear model not only near the surface but in the interior of the tropical troposphere as well there is sufficient quantitative correspondence between the gcm and the linear solution to justify decomposing the linear simulation into parts for

fining upwards sedimentary sequences generated in seagrass beds shallow marine clastic and carbonate environments of southeast florida contain fining upwards sedimentary sequences being generated by beds of the seagrass thalassia testudinum lateral seaward migration of flute shaped sand pockets storm blowouts in the grass platform produces a lenticular fining upwards package 10 50 m in width 20 100 m in length and 0 3 2 m in thickness migration and vegetative restabilization of recurring blowouts on a grass platform can produce a composite sequence containing numerous complete or stacked incomplete fining upwards packages a complete fining upwards sequence consists of 1 an erosional base 2 a coarse basal shell layer representing the winnowed lag of the eroded preexisting grass stabilized platform 3 a ripple laminated well sorted medium grained sand zone representing the mobile sand on the leeward slope of the blowout and 4 a shelly bioturbated sand or silty sand having a strongly bimodal texture modes at 100 and 500 mu m in which the fine mode dominates upwards this upper portion records increased trapping of storm suspensions and decreased bedload transport as seagrasses are reestablished the mollusks chione cancellata and codakia orbicularis characterize the grass stabilized zone the distinctive textural sequence and molluscan assemblage serve to differentiate these biogenically induced fining upwards sequences from others in the geological record

environmental evolution and geological significance of the miocene carbonates of the eratosthenes seamount odp leg 160 abstract miocene carbonates of the eratosthenes seamount located offshore from cyprus in the eastern mediterranean odp leg 160 site 966 have been re analysed the use of sedex sequential extraction to evaluate the nutrient concentrations and of ct scan for the identification of large benthic foraminifera has resulted in a more detailed palaeoenvironmental reconstruction and an improved stratigraphic framework three intervals are recognised in the succession and are attributed to the lower middle and upper miocene respectively the lower miocene interval is dominated by large benthic foraminifera and echinoids this association colonized the top of the seamount following its uplift from deep water to the photic zone the middle miocene interval is characterised by rhodoliths and corals at its base and near the top whereas seagrass seaweed assemblages with epiphytic foraminifera and hooked coralline algal crusts dominate its central part the upper miocene is represented by coral reef facies near its base and lagoonal facies toward its top the succession was deposited in an oligotrophic environment and exhibits a general shallowing upward trend that was mainly controlled by tectonic activity related to the northward subduction of the african plate the succession of the eratosthenes seamount is characterised by a diverse large benthic foraminifera assemblage in its lower part and by corals in its uppermost part whereas corallines characterise the central interval this trend is common in miocene mediterranean carbonates and its occurrence on an isolated seamount confirms its connection with the general evolution of the basin the decline of miogypsinids and lepidocyclinids after the early miocene is notable because the eratosthenes seamount was geographically close to the indo pacific ocean where both groups also thrived during the middle miocene this decline was probably caused by the early miocene closure of the deep water connection between the indo pacific and the mediterranean

tungsten mineralization in the tien shan gold belt geology petrology fluid inclusion and stable isotope study of the ingichke reduced tungsten skarn deposit western uzbekistan abstract the ingichke reduced w skarn deposit 100kt wo 3 with the average grade of 0 58 wo 3 is the largest one among w deposits known in the tien shan gold belt it is associated with an early permian multiphase granitoid pluton that comprises ilmenite series to ilmenite titanite bearing medium to high k metaluminous to peraluminous i type granitoid monzodiorite granodiorite to granite leucogranite rocks the pluton is related to crustal accretionary type reservoirs of granitoid magma likely formed in response to an ascent of asthenospheric material at the post collisional stage it is part of the continuum of plutonic suites related to reduced w au polymetallic deposits with further links to reduced intrusion related au deposits the deposit comprises abundant pyroxene mainly hedenbergitic skarn and a minor garnet skarn mostly grossular rich garnet with elevated almandine and spessartine contents hydrosilicate propylitic alteration amphibole chlorite calcite quartz with abundant pyrrhotite and minor chalcopyrite partially overprints skarn and is in turn overprinted by zones of phyllic alteration quartz sericite fe carbonate locally with albite scheelite and sulfides bi and au minerals prograde and retrograde skarns were formed from aqueous dominantly magnesian sodic chloride moderately saline 10 14 to 4 7 wt nacl eq hot fluid with its progressing enrichment in ca hydrosilicate propylitic and phyllic alteration assemblages were formed from boiling low salinity carbonic aqueous magnesium sodic calcic fluids at moderate 330 355 c to lower 250 265 c temperatures respectively with separation of carbonic with varying co 2 ch 4 ratio and aqueous chloride fluids trapping pressures ranged from 2000 to 1500 bars indicating a lithostatic depth of some 6 to 8 km i e a lower intermediate level in an integrated model of reduced w skarn deposits the stable isotope data indicate an influence of a sedimentary limestone source of oxygen and carbon at the retrograde skarn stage 18 o h2o 8 1 to 9 0 13 c co2 2 5 to 0 3 and a dominantly magmatic mantle to crustal derived source of water 18 o h2o 7 0 0 5 at the hydrosilicate propylitic and phyllic alteration stages and carbon 13 c co2 7 8 to 4 7 at the hydrosilicate propylitic stage at the phyllic alteration stage a strong enrichment in the light carbon isotope 13 c co2 10 1 to 9 4 indicates a possible influence of a reduced organic carbon source a magmatic source of sulfur is envisioned for the hydrosilicate propylitic 34 s 2 0 0 5 and phyllic 34 s 1 0 0 3 alteration stages

ghost of seagrasses past using sirenians as a proxy for historical distribution of seagrasses abstract seagrasses are a notable component of shallow marine habitats especially in tropical and subtropical regions their fossil record extends back to the mesozoic but it is relatively poor and fragmentary with large temporal and geographical gaps as a result very little is known about the paleobiogeography of these plants and how physical drivers such as climatic or oceanic events have affected their distribution one approach is to infer the past distribution of seagrasses using fossils of organisms dependent of seagrasses with more complete records as proxies seagrass consumers such as sirenians seacows manatees and dugongs are much better represented in the fossil record than seagrasses are the characteristically dense bones of sirenians together with the fact that they are usually found in marginal marine environments increases the potential for preservation and recognition of their fossils the long evolutionary history of sirenians extending throughout most of the last 50 ma together with their diet permits the use of their fossils as a proxy for inferring the paleobiogeography of seagrasses here i looked at the fossil record of sirenians and seagrasses from the eocene through the miocene epochs this comparison produced several inferences about seagrass paleobiogeography and how physical drivers such as climate change ocean currents and tectonic events have been influential in their distribution 1 seagrasses were well established in the western atlantic caribbean prior to the middle eocene making possible at least two instances of trans atlantic sirenian dispersal events either with the aid of tethyan currents or along the nearly continuous northern atlantic coastline that was present in the eocene 2 climatic cooling during the early oligocene seemed to have limited the extent of seagrasses and sirenians although these groups recovered and further diversified and expanded their distributions by the late oligocene in tandem with a climatic warming event 3 by the miocene seagrasses and sirenians reached the southern western atlantic and the eastern pacific aided by the presence of the central american seaway achieving a distribution similar to and sometimes surpassing that of today the fossil record of sirenians can provide a broad overview of seagrass paleobiogeography through time however several aspects such as when sirenians and seagrasses arrived to australia and the seemingly late arrival of seagrasses to south america and the eastern pacific still need further investigation

geology mineralization and fluid inclusion characteristics of the kensu w mo skarn and mo w cu au alkalic porphyry deposit tien shan kyrgyzstan the kensu deposit is located within a large metallogenic belt of w mo cu mo w au au and pb zn deposits along the late paleozoic active continental margin of tien shan the deposit is related to a small late carboniferous to early permian multiphase gabbro monzonite syenite granite pluton representing an alkaline potassic shoshonitic suite the igneous rocks are related to a deep rooted magmatic source but the pluton emplacement corresponds to shallow porphyry levels the deposit represents an example of a complex w rich alkalic magmatic hydrothermal system that complements the typical mineral deposits related to shoshonitic igneous suites it contains large bodies of w mo skarn of the oxidized type with abundant andradite garnet scapolite k na feldspars and fe oxides magnetite hematite the skarns are overprinted and surrounded by extensive halos of stockwork disseminated porphyry style mo w mo w cu pb zn and au w mineralization with propylitic chlorite amphibole epidote dominated and phyllic quartz sericite carbonate sulfide alteration assemblages consistent with the oxidized nature of the major mineral assemblages the deposit may represent the oxidized lithophile w mo cu au metallogenic type the hydrothermal stages alternate with magmatic phases and fluid inclusion data show the predominance of high temperature 550 450 c high pressure 1 200 700 bars and high salinity 60 45 wt nacl equiv magmatic hydrothermal fluid at prograde and early retrograde skarn stages with its possible direct exsolution from crystallizing magma the general trend of cooling and dilution was complicated by the influx of higher temperature and higher salinity fluid that correlates to the intrusion of quartz monzonite and the initial stages of its degassing and cooling this more advanced phase of magmatic differentiation likely corresponded to the enrichment of residual melt and related magmatic fluids in w and mo intense fluid boiling and phase separation triggered the deposition of molybdoscheelite in skarns that formed at t 625 500 c and p 510 300 bars and continued to a nonboiling fluid at t 420 370 c and p 1 150 750 bars mineralization in propylitic alteration zones was formed by highly to moderately saline nonboiling fluids late quartz sericite carbonate sulfide stage involved both high to low salinity aqueous fluids and co2 rich fluids under decreasing temperature from 400 c to 200 300 c and varying pressure from 1 200 bars to 750 600 bars

seagrass meadow sedimentary facies in a mixed siliciclastic carbonate temperate system in the tyrrhenian sea pontinian islands western mediterranean abstract the paper presents the characteristics of surface sediments in a seagrass dominated environment of the inner shelf of the pontinian islands tyrrhenian shelf central mediterranean the aims of this work are to characterize the carbonate production and sedimentary processes of a representative high latitude temperate posidonia oceanica dominated area to discuss the role of seagrass in the siliciclastic carbonate mixing processes which provide analogs for interpreting the occurrence and importance of these types of deposits in the rock record the majority of sediments are poorly sorted siliciclastic skeletal sand based on grain type and abundance and carbonate content these deposits include six subfacies the different subfacies reflect environmental changes within the seagrass environment associated with variations in light penetration and hydrodynamic conditions additionally the seagrass facies range from purely carbonate to mixed carbonate siliciclastic depending on the amount of siliciclastic input and on the capacity of seagrasses to trap allochthonous sediments while hosting carbonate producing biota the type of substrate and the erosion and transport processes control the siliciclastic input in these pontinian seagrass meadows sedimentary facies contain abundant siliciclastic grains produced by erosion of the volcanic substrate and trapped by seagrass blades and rhizomes this pontinian example illustrates that in heterozoan dominated seagrass settings mud producing green algae are not present or are not calcifying and consequently seagrass deposits are much more grainy than photozoan counterparts ancient heterozoan tropical seagrass deposits likely will be discriminated from their temperate or subtropical counterparts only by careful taxonomic analysis of skeletal grains

lagoon shelf sediment exchange by storms evidence from foraminiferal assemblages east coast of grand cayman british west indies abstract the abundance and size distribution of ecologically diagnostic foraminiferal species are ideal tracers of sediment transportation and storm processes on the windward shelf of grand cayman during storm peak sediment in the lagoon and fore reef is suspended by large storm waves sediments of sand size and finer including forereef foraminifera species are moved shoreward by wind driven currents and deposited in a blanket behind the reef the fore reef foraminiferal assemblage is winnowed and the mean and median sizes of amphistegina gibbosa progressively decrease from the shelf edge into the inner lagoon as the storm wanes water piled in the lagoon drains via channels and sediment is transported offshore consequently lagoonal sediment that includes lagoonal foraminiferal t sts is carried out of the lagoon and deposited on the fore reef terrace and down the shelf escarpment this process produces winnowed lagoonal sediments because suspended fine sediments are preferentially transported during the long inter storm periods tranquil conditions are once again established and sediment exchange between the lagoon and on the fore reef terrace ceases during this time lagoonal organisms once again colonize the lagoon and bioturbation causes mixing of surface and subsurface sediments

application of image analysis for delineating modern carbonate facies changes through time grand cayman western caribbean sea image analysis of air photographs showing shallow water carbonate lagoons permits easy delineation of facies and the area covered by each facies application of this technique to lagoons around grand cayman shows that the method 1 produces maps with a high degree of accuracy 90 2 allows comparison of lagoons in terms of the areas covered by the different facies and 3 permits the quantitative assessment of changes in the lagoons for the period 1971 1985 the lagoons around grand cayman can be divided into two groups by considering the area covered by the barren sand facies as opposed to the area covered by thalassia the first group of lagoons characterized by a low percentage area of thalassia and a high percentage area of sand are narrow 0 5 km shallow 2 3 m deep and periodically subjected to high energy conditions due to strong onshore winds the second group of lagoons characterized by a high percentage area of thalassia and a low percentage area of sand have some degree of protection because they are wide up to 2 km deep up to 7 m or situated in the lee of a headland collectively the protection permits the deposition of sediment which in turn allows the establishment of thalassia image analysis of air photographs for 1971 1979 and 1985 shows that there has been a substantial increase in the area of thalassia in each of the lagoons examined around grand cayman for example in south sound the area of thalassia has increased by 6 9 ha over the 15 yr period from 1971 to 1985 although this increase has been primarily at the expense of the sand facies the thalassia also replaced other facies the expansion of the thalassia facies has important implication on the dynamics of the lagoon in terms of sediment production binding and baffling collectively these processes led to the progressive shallowing of many areas of the lagoons through the period 1971 1985

sediment deposition and production in se asia seagrass meadows abstract seagrass meadows play an important role in the trapping and binding of particles in coastal sediments yet seagrass may also contribute to sediment production directly through the deposition of detritus and also the deposition of the associated mineral particles this study aims at estimating the contribution of different seagrass species growing across an extensive range of deposition to inorganic carbonate and non carbonate and organic sediment production total daily deposition measured with sediment traps varied from 18 8 2 0 g dw m 2 d 1 in silaqui philippines to 681 1 102 g dw m 2 d 1 in bay tien vietnam these measurements correspond to a single sampling event and represent sedimentation conditions during the dry season in se asia coastal areas enhalus acoroides was the most common species in the seagrass meadows visited and together with thalassia hemprichii was present at sites from low to very high deposition halodule uninervis and cymodocea species were present in sites from low to medium deposition the mineral load in seagrass leaves increased with age and was high in e acoroides because it had the largest and long lived leaves up to 417 mg calcium carbonate per leaf and 507 mg non carbonate minerals per leaf and low in h uninervis with short lived leaves 4 mg calcium carbonate per leaf and 2 mg non carbonate minerals per leaf in se asia seagrass meadows non carbonate minerals accumulate at slower rates than the production of calcium carbonate by the epiphytic community consequently the final loads supported by fully grown leaves were as average lower than calcium carbonate loads our results show that organic and inorganic production of the seagrasses in se asia represents a small contribution maximum of 15 of the materials sedimented on a daily base by the water column during the sampling period the contribution of the carbonate fraction can be locally significant i e 34 in silaqui in areas where the depositional flux is low but is minor

effects of natural and artificial thalassia on rates of sedimentation abstract sediment traps were used to measure the rate of deposition in a thalassia seagrass meadow and in an adjacent sandy grass free area the average depositional rate of mud in the thalassia bed was 4 96 g trap 1 week 1 and in the sandy area it was 3 04 g trap 1 week 1 in the summer in winter these rates were 1 60 and 1 50 g mud trap 1 week 1 respectively electromagnetic current meter measurements showed that the mean flow velocity in the grass free area is higher than in the seagrass area therefore the increased depositional rate of mud within the seagrass is due to slowing of water currents by the grass blades confirmation of the blade baffle effect was obtained by placing a 1 m2 plot of artificial thalassia in a grass free area sediment traps in the artificial thalassia contained 5 45 g mud trap 1 week 1 as compared to 3 04 g mud trap 1 week 1 in the adjacent grassfree area in summer in winter these rates were 1 82 and 1 50 g mud trap 1 week 1 respectively epiphytes in the indian river lagoon had no detectable effect on the amount of mud deposited in thalassia beds

the relationship between zonal mean flow and quasi stationary waves in the midtroposphere abstract the degree to which quasi stationary midtropospheric flow is consistent with linear potential vorticity conservation is investigated the linear theory suggests there should be a well defined relationship between the zonal mean component of steady flow and departures from the zonal mean a set of 45 monthly mean winter states is examined to determine if there is a zonal eddy relationship month to month variations in zonal mean winds are represented in terms of an eof analysis correlation and compositing techniques isolate two dimensional patterns which appear to be associated with each zonal eof solutions to the nondivergent barotropic vorticity equation linearized about a zonal mean state suggest that the two dimensional flow patterns associated with several of the leading zonal mean eofs are consistent with the dynamical mechanism rossby first proposed as an explanation for a zonal eddy relationship it is suggested that the zonal eddy relationship examined here may in fact play a role in l

recognising macrophyte vegetated environments in the rock record a new criterion using hooked forms of crustose coralline red algae abstract the role of macrophytes such as seagrasses in influencing deposition in shallow marine environments has long been understood they affect sediment textures such that they do not reflect ambient hydrodynamic conditions and so the recognition of ancient vegetated environments is important for accurate palaeoenvironmental analysis however there is little direct fossil evidence of such plants in the rock record and so the presence of former macrophyte cover generally has to be inferred from indirect evidence based on the characteristics of modern macrophyte vegetated environments we present a new criterion for the recognition of vegetated environments in the rock record based upon a distinctive hooked form of crustose coralline red algae that is definitively indicative of growth on seagrasses and also on other macrophytes with similarly flattened blades and has been recognised from both modern inhaca island mozambique and fossil the eocene of oman seagrass beds

magmatic hydrothermal evolution at the lyangar redox intermediate tungsten molybdenum skarn deposit western uzbekistan tien shan insights from igneous petrology hydrothermal alteration and fluid inclusion study abstract the lyangar w mo skarn deposit is situated in a metallogenic belt of w mo cu mo w au and au deposits and is related to an early permian multiphase monzodiorite granodiorite granite leucogranite pluton that was emplaced in a tectonic domain with possible ancient continental crust the latter coupled with an inferred ascent of hot asthenospheric material has defined an enrichment in mo and fluorine together with w and au to form a distinct metallogenic assemblage in a post collisional environment the parental moderately to high k transitional metaluminous to peraluminous weakly oxidized weakly reduced ilmenite titanite series granitoids are accompanied by hydrothermal alteration and mineralization that formed in redox intermediate environment the deposit incorporates prograde and retrograde pyroxene and garnet skarns composed of hedenbergitic pyroxene and grossular to almandine spessartine rich garnet respectively fluorite is present in the retrograde skarn together with scheelite and sulfides the latter including most abundant pyrrhotite and molybdenite hydrosilicate amphibole epidote chlorite quartz locally with albite sulfides and scheelite assemblage has limited development phyllic quartz sericite fe carbonate locally with albite fluorite scheelite and sulfides also bi and au minerals alteration assemblage partially overprints altered skarns and extends over much larger areas overall the deposit represents a superposition of the early w mo mineralization related to retrograde skarn and hydrosilicate alteration and the late au w cu bi mineralization in phyllic alteration assemblages prograde and retrograde skarns were formed from dominantly magnesian sodic chloride moderately saline 11 7 13 9 wt to 8 6 10 5 wt nacl eq high pressure 1500 to 1350 bars hot aqueous fluids that were followed by moderately saline 12 3 14 5 wt nacl eq ca rich lower pressure 600 bars fluids during deposition of most scheelite hydrosilicate propylitic assemblages were formed from boiling fluids at the temperatures of 380 430 c and pressures of 600 300 bars whereas phyllic alteration assemblages from boiling carbonic aqueous low salinity fluids at the temperatures of 300 320 c and pressures of 1000 bars 18oh2o values range from 7 8 to 8 6 for retrograde skarn and from 6 6 to 7 0 for phyllic alteration whereas 13cco2 from 3 3 to 0 5 for retrograde skarn and from 5 5 to 4 5 for phyllic alteration 34s increases from retrograde skarn 34s 2 0 to 2 3 to phyllic alteration 34s 4 3 to 4 6 stages

epiphytic calcium carbonate production and facies development within sub tropical seagrass beds inhaca island mozambique seagrass beds have been widely recognised as playing an important role in influencing carbonate sediment facies development this reflects their role not only as facilitators of fine sediment settling and stabilisation but also as substrates for epiphytic organisms that after death contribute skeletal carbonate to the sediment substrate in low latitude reef related settings epiphytic carbonate production rates are often high and this in combination with the trapping of carbonate mud produced by a range of associated calcareous algal species typically results in the development of carbonate mud rich facies whilst such environments and their associated sediment substrates have been widely documented studies of seagrass facies in marginal sub tropical warm temperate marine settings have not been conducted from a sedimentological perspective this study determines rates of epiphytic carbonate production on two seagrass species thalassodendron ciliatum and thalassia hemprichii and examines seagrass sediment facies from a sub tropical reef related environment in southern mozambique dense seagrass beds colonise primarily siliciclastic sediment substrates and are characterised by low rates of epiphytic carbonate production mean 43 9 g caco3 m 2 year 1 for t ciliatum and 33 4 g caco3 m 2 year 1 for t hemprichii epiphytic encrusters are dominated by thin monostromatic layers of the crustose coralline red algae hydrolithon farinosum along with rotaliid smaller benthic foraminifera including asterorotalia cf gaimardi and spirillina sp and the soritid peneroplis sp as well as rare encrusting acervulinid foraminifera serpulids and bryozoans epiphytic calcium carbonate production rates are therefore low and this is reflected in the low 15 carbonate content of the seagrass sediments as well as the low 1 sediment fine 63 m size fraction content this study suggests that mud rich sediment facies do not necessarily develop in conjunction with seagrass beds and that mud poor facies may develop in some seagrass colonised environments at these sites sub tropical and siliciclastic sediment dominated this is suggested to reflect both the low levels of epiphytic and benthic algal carbonate mud production as well as a net outflux of fine grained sediment due to tidal current induced sediment resuspension in keeping with carbonate facies generally there are thus likely to be latitude and environment related shifts in the composition and character of seagrass related sediment facies

constraints on magma degassing beneath the far southeast porphyry cu au deposit philippines k silicate alteration in the far southeast fse porphyry cu au introduction deposit formed at 1 4 ma concentric to dikes of quartz diorite magmas become saturated with volatile components as porphyry at 2 km paleodepth the hydrothermal system consisted they ascend in the crust and either erupt or crystallize of magmatic hypersaline liquid and vapor at 550 c and 50 at depth saturated magmas that remain at depth exsolve mpa lithostatic pressure advanced argillic alteration formed at an aqueous fluid that forms a hydrothermal system on the same time over the deposit at 1 km paleodepth from acidic separation from the magma chamber burnham 1979 condensates of the vapor at 1 3 ma k silicate alteration was although part of the exsolved fluid a low density vapor overprinted by 350 c magmatic liquid 5 wt nacl equiv may discharge to the surface from passively degassing at hydrostatic pressure sericite alteration and much of the cu au volcanoes hedenquist 1995 part will remain at depth mineralization formed at this later stage evolution of the magmatic and this dense residual magmatic liquid may be asfluid composition was simulated with a magma chamber cryssociated with hydrothermal mineralization in the portallization model homogeneous crystallization during early stage phyry ore environment hedenquist lowenstern convection is assumed whereas at 50 vol crystals the chamber 1994 becomes stagnant and crystallizes from rim to core over a narrow in this paper we use evidence from a porphyry ore crystallization interval the model calculation based on a magma deposit in the philippines to determine the composition chamber with 2 km thickness at 6 km depth 150 mpa and of the fluid that exsolved from the deeper parent magma 800 c saturated melt composition at 30 vol crystals 5 the evolving composition of the magmatic fluid at the wt h2o 0 2 wt cl and dd of 40 can reproduce the depth of the ore body can then be used to place constraints chemical and isotopic compositions of the early and late magmatic on the nature of the evolved magma chamber far below fluids the most critical factor controlling the compositional evolution the porphyry ore body this approach differs from that of the model hydrothermal system is the transition from convective of other studies where a portion of the parent magma to stagnant magma chamber crystallization there is also a sharp chamber is available to study directly e g at yerington decrease in the rate of fluid exsolution associated with this transition nevada dilles 1987 which can account for the thermal collapse of the fse porphyry the far southeast fse porphyry cu au deposit system from k silicate to sericite alteration and overlying lepanto epithermal cu au ore body are

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

ecology of extant nummulitids and other larger benthic foraminifera applications in palaeoenvironmental analysis abstract larger benthic foraminifera lbf are important contributors to modern and ancient tropical shallow marine sediments over the past 30 years a substantial body of literature has built up on the ecology of modern lbf especially in terms of their environmentally sensitive depth distribution reproductive strategy and morphology and the symbiotic relationship between many larger foraminifera and photosynthetic algae over the same period the extinct genus nummulites which is abundant in eocene sediments of southern europe north africa and the arabian peninsula has increasingly been studied principally because significant volumes of hydrocarbons have been discovered reservoired within nummulitic limestones offshore tunisia and libya the modern ecological studies of lbf provide a powerful tool with which to develop palaeoecological models for fossil nummulites and other symbiont bearing larger foraminifera in the rock record

evidence for seagrass meadows and their response to paleoenvironmental changes in the early eocene jafnayn formation wadi bani khalid n oman the recognition and understanding of vegetated habitats in the fossil record are of crucial importance in order to investigate paleoecological responses and indirectly infer climate and sea level changes however the low preservation potential of plants and macroalgae hampers a direct identification of these environments in the geological past here we present sedimentological and paleontological evidences as tool to identify the presence of different seagrass vegetated environments in the shallow marine settings of the lower eocene jafnayn platform of oman and their responses to paleoenvironmental changes the studied lower eocene deposits consist of well bedded nodular packstones dominated by encrusting acervulinid and alveolinid foraminifera passing upward to an alternance of packstones with echinoids and quartz grains and grainstones rich in orbitolites smaller miliolid foraminifera and quartz grains the presence of seagrass is inferred by the occurrence of encrusting acervulinids and soritid orbitolites as well as by their test morphologies together with further sedimentological criteria the clear shift observed in the faunal assemblages and sedimentary features may be related to a major reorganization of the carbonate system passing from a carbonate platform to a ramp like platform with increased terrigenous sedimentation heterotroph tubular acervulinids and oligotroph alveolinids of the carbonate platform were replaced upward by more heterotroph organisms such as large discoidal orbitolites and smaller miliolids most likely due to enhanced nutrient levels which would have led to a change of phytal substrate from cylindrical leaf dominated grasses into flat leafed ones

emplacement depth and carbon dioxide rich fluid inclusions in intrusion related gold deposits phanerozoic intrusion related gold deposits have many consistent characteristics such as a spatial temporal and geochemical association with moderately reduced predominantly ilmenite series i type intrusions the deposits exhibit a range of characteristics that vary over a wide range of emplacement depths 7 km deposits in shallow crustal settings 5 km have characteristics of mesothermal environments and are hosted by plutons containing sheeted veins greissen and disseminated gold fluid characteristics also vary with depth deposits in shallow environments contain high temperature 350 c immiscible brine 30 wt nacl equiv and low salinity 5 wt nacl equiv vapor that commonly contains carbon dioxide deposits in deeper environments contain abundant low salinity carbon dioxide rich aqueous fluids 10 wt nacl equiv that in some deposits are postdated by moderate to high salinity brines 10 40 wt nacl equiv these contrasting fluid types are interpreted to be magmatic in origin and are the result of the complex interplay between exsolution of different volatiles carbon dioxide water and chlorine from felsic magmas emplaced at different crustal levels experimental studies have shown that carbon dioxide will exsolve from felsic magmas at much higher pressures than water and chlorine due to its lower solubility in the melt thus deposits formed from felsic magmas in deeper environments will contain abundant carbon dioxide rich fluids subsequent fluids released from the magma are likely to be water rich and more saline felsic magmas in shallow environments will contain lower concentrations of carbon dioxide that will partition into the vapor phase during phase separation between brine and vapor

maastrichtian to early tertiary stratigraphy and palaeogeography of the central and northern oman mountains abstract maastrichtian to tertiary sedimentary rocks outcrop extensively around the periphery of the oman mountains they form part of a geologically distinct suite of strata deposited after obduction of the semail ophiolite and thrusting of the hawasina and sumeini imbricates onto the eastern edge of the arabian plate the lithostratigraphy of maastrichtian and early tertiary rocks of the central and northern oman mountains is revised and a number of new formations are erected the proto oman mountains were emergent in the early maastrichtian and were subject to subaerial erosion and weathering nw and w of the mountains gradual subsidence followed during the maastrichtian allowing for formation of a transgressive onlapping sequence represented by the qahlah fluviatile to shallow marine terrigenous clastics and simsima shallow shelf carbonate formations more rapid subsidence ne of the mountains produced fan delta and submarine debris flow turbidite apron sequences comprising the al khawd and thaqab formations respectively a low angle unconformity separates tertiary strata from older units during the palaeogene basinal and slope facies with debris flows and turbidite sequences were deposited directly upon the unconformity surface in rapidly subsiding basins nw muthaymimah formation and nne ruwaydah formation of the oman mountains elsewhere shallow carbonate shelf facies were extensively developed in less rapidly subsiding areas during the palaeogene the palaeocene and early eocene is represented by the jafnayn limestone formation this is succeeded and overlapped by a variety of later eocene units ene and e of the mountains early eocene regression is marked by restricted facies of the rusayl formation overlying the rusayl formation are shallow open shelf limestones of the seeb formation which is rich in alveolinid and nummulitic foraminifera on the arabian side of the mountains the rusayl formation is not developed and the jafnayn formation is succeeded either by the seeb formation or fine grained faunally restricted limestones and marls of the fahud beds which represent intra shelf facies

biofilm related calcification sediment trapping and constructive micrite envelopes a criterion for the recognition of ancient grass bed environments micrite envelopes are a common feature in carbonate sediments and are typically associated with the micrite filling of borings produced by microendolithic organisms these are referred to as destructive micrite envelopes and have long been recognized as reflecting an important early diagenetic process recent analysis of sediments collected from back reef environments at discovery bay north jamaica however has demonstrated envelope formation on the surfaces of carbonate grains clearly distinct from the micrite filling of microborings such constructive envelopes occur almost exclusively in sediments from grass bed environments and are always intimately associated with biofilms comprising abundant mucilage cyanobacteria bacteria and diatoms it is suggested that these envelopes represent a product of both biologically mediated micrite precipitation occurring within the biofilm mucilage and around the biofilm components i e cyanobacteria and diatoms and associated trapping of carbonate mud and fine grained sediment their recognition only within grass bed sediments may enable their use as a diagnostic feature of grass bed environments or vegetation stabilized substrates in the rock record

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

grain susceptibility to the effects of microboring implications for the preservation of skeletal carbonates the boring activity of microendolithic organisms such as cyanobacteria chlorophytes rhodophytes and fungi represents a major destructive process affecting sediment preservation within reef environments this study demonstrates the presence of two distinct assemblages of microborers within sediments collected from the fringing reefs of north jamaica correlating to the upper 18 m depth photic zones the upper photic zone assemblage is dominated by cyanobacteria and chlorophytes whilst rhodophytes and fungi become more abundant with increasing water depth most significant from a grain preservation perspective is the variable nature of grain infestation observed between different reef sites and different carbonate grain types the highest degree of grain infestation occurs within shallow low energy back reef environments and the most susceptible grains at all sites are corals molluscs and foraminifera coralline algae halimeda and echinoid fragments are rarely heavily infested high rates of infestation at back reef sites result in rapid diminution of the most susceptible grains especially coral which are either underrepresented or contribute only to the finer sediment fractions in the subsurface fore reef grain assemblages undergo relatively little alteration microboring therefore has potential to bias the fossil record by removing the most susceptible skeletal grains the impact of microboring upon back reef grain assemblages must be considered when attempting to model depositional processes within both modern and ancient reef environments

the 30 50 day mode at 850 mb during monex abstract the analyzed wind field at 850 mb during the summer monsoon experiment monex is subjected to a time series analysis to confirm the existence of a peak in the time range of 30 50 days having established that this study presents a mapping of the motion field for this time scale in this short paper we illustrate the steady meridional propagation of a train of troughs and ridges that seem to form near the equator and dissipate near the himalayas the meridional scale of this mode is around 300 km and its meridional speed of propagation is 0 75 latitude per day the amplitude of the wind for this mode is around 3 6 m s 1 the salient contributions here are the mapping and the demonstration of a very regular behavior of this mode its existence is here noted from a period well before the onset of monsoon i e from early may to late july three major storms during monex were noted to form within the trough line of this system and the period of major cessation of rains over the indian subconti

meco and alpine orogenesis constraints for facies evolution of the bartonian nummulitic and solenomeris limestone in the argentina valley ligurian alps

geology mineralization and fluid inclusion characteristics of the skrytoe reduced type w skarn and stockwork deposit sikhote alin russia the skrytoe deposit 145 kt wo3 average grade 0 449 wo3 in the sikhote alin orogenic system eastern russia is situated in a metallogenic belt of w sn w au and au w deposits formed in a late to post collisional tectonic environment after cessation of active subduction it is localized within a mineralized district of reduced type skarn w and veined au w deposits and occurrences related to the early cretaceous ilmenite series plutonic suite the deposit incorporates large stockworks of scheelite bearing veinlets related to propylitic amphibole chlorite quartz and phyllic quartz sericite albite apatite and carbonate hydrothermal alteration the stockwork cuts flat lying mafic volcanic rocks and limestone partially replaced by pyroxene skarn that host the major w orebodies scheelite is associated with pyrrhotite and or arsenopyrite with minor chalcopyrite and other sulfide minerals the late phyllic stage assemblages hosts bi and au mineralization the fluid evolution included low salinity moderate temperature moderate pressure 370 390 c 800 bars methane dominated carbonic aqueous fluids that formed post skarn propylitic alteration assemblages then at the phyllic stage there has been an evolution from methane dominated moderate temperature 330 360 c low salinity 12 3 wt nacl equiv fluids forming the early quartz sericite albite arsenopyrite assemblage through lower temperature 290 330 c methane dominated low salinity 9 10 wt nacl equiv fluids forming the intermediate quartz sericite albite scheelite pyrrhotite assemblage to yet lower temperature 245 320 c co2 dominated carbonic aqueous low salinity 1 7 wt nacl equiv fluids forming the late quartz sericite sulfide bi au assemblage recurrent fluid immiscibility phase separation and cooling probably affected w solubility and promoted scheelite deposition the stable isotope data support a sedimentary source of carbon 13cfluid 21 to 10 a magmatic source for water 18oh2o 7 4 to 7 7 and dominantly crustal derived source of sulfur 34s 4 6 to 2 9 in the hydrothermal fluids this is consistent with the development of larger longer crystallizing crustal intermediate to felsic magma chambers in the late to post collisional tectonic environment with their protracted magmatic evolution advancing magmatic differentiation and partitioning of w into magmatic hydrothermal fluid the dominating role of the crustal derived magmatic water sulfur and carbon appears to be an important feature of reduced w skarn deposits related to ilmenite series granitoids

hurricane control on shelf edge reef architecture around grand cayman rimming the outer shelf of grand cayman is a submerged 87 km long shelf edge reef that rises to within 12 m of mean sea level it consists of an array of coral armoured buttresses aligned perpendicular to shore and separated by steep sided sediment floored canyons individual buttresses have a diverse coral dominated biota and consist of three architectural elements a shield like front wall colonized by platy corals a dome shaped crown colonized by head corals and a shoreward projecting spur covered by varying amounts of branching coral buttresses are commonly fronted by coral pinnacles that in some areas have amalgamated with buttress walls to produce pinnacle and arch structures as margin orientation changes shelf edge reef architecture shows systematic variations that are consistent with changes in fetch and height of hurricane waves along margins exposed to fully developed storm waves shelf edge reef buttresses are deep have large amplitudes and are dominated by robust head corals these characteristics are consistent with hurricane induced pruning of branching corals and the flushing of significant quantities of sand from buttress canyons by return flows along margins impacted by fetch limited storm waves reef buttresses are shallower have intermediate amplitudes and have a significantly higher proportion of branching corals these characteristics are consistent with less coral pruning and sand flushing by weaker hurricane waves along margins fully protected from storm waves the buttresses canyon architecture of the shelf edge reef breaks down producing a series of shallow undulating branching coral dominated ridges that merge laterally into an unbroken belt of coral these characteristics correspond with negligible amounts of pruning and flushing during hurricanes in addition to differences between margins local intra marginal changes in shelf edge reef architecture are consistent with changes in the angle of hurricane wave approach open sections of the shelf edge reef which face directly into storm waves are pruned of branching corals and the fragments swept back onto the shelf producing extensive spurs by contrast on more sheltered obliquely orientated sections storm waves sweep debris along and off shelf producing little or no spur development instead the debris shed seawards accumulates in front of the buttress walls and initiates the development of coral pinnacles over time repeated buttress pruning and canyon flushing during hurricanes not only controls reef architecture but may also influence accretion patterns vertical accretion is limited by the effective depth of storm wave fragmentation once this hurricane accretion threshold is reached the reef moves into a shedding phase and accretes laterally via pinnacle growth amalgamation and infilling consequently the reef steps out over its own debris in a kind of balancing act between lateral growth and slope failure a pattern widely recognized in ancient reefs

genesis of the maikhura tungsten tin skarn deposit tajik tien shan insights from petrology mineralogy and fluid inclusion study abstract the maikhura w sn skarn deposit is situated in the gissar segment of the southern tien shan it associates with a late carboniferous early permian composite granitoid pluton which includes earlier ilmenite series transitional metaluminous to peraluminous i type granodiorite and later magnetite series biotite to biotite tourmaline granite leucogranite the oxidized granitic intrusions exhibit a type granite affinity and define a geochemically and genetically distinct group of w sn deposits the deposit incorporates both pyroxene and garnet dominant prograde and retrograde skarns with scheelite and locally magnetite overprinted by highly reduced pyrrhotite stable post skarn mineral assemblages of hydrosilicate and phyllic alteration stages containing scheelite cassiterite and sulfides the fluid inclusions data indicate the involvement of carbonic free aqueous moderately saline 9 9 16 wt nacl eq high pressure 2 1 0 5 kbar hot fluid which was sourced from crystallizing magma and formed prograde calcic skarn this fluid evolved into a sodic chloride slightly less saline 8 6 11 wt nacl eq lower pressure 1 7 0 5 kbar cooler fluids toward the retrograde skarn stage this stage was characterized by deposition of scheelite in association with magnetite the hydrosilicate propylitic alteration was formed from a low salinity ca enriched homogenous aqueous carbonic methane rich fluid at lower temperatures 350 400 c with precipitation of scheelite and cassiterite particularly in phlogopite chlorite oligoclase quartz assemblage corresponding ph decrease explains the trend toward overlapping fields of insoluble cassiterite and scheelite the phyllic alteration assemblages were formed from a boiling aqueous carbonic co2 dominated low salinity fluid at temperatures of 310 250 c and pressure of 1 85 0 1 kbar the alteration evolving from chlorite through muscovite to albite dominant paragenesis indicates a trend toward higher ph less acidic conditions and was accompanied by precipitation of scheelite and cassiterite with further deposition of sulfides a homogeneity of 34s values suggests sulfur isotope homogenization in a magmatic chamber whereas their proximity to the meteorite standard supports a magmatic source of sulfur the depletion in heavy sulfur isotope of sulfides from hydrosilicate propylitic alteration 34s 1 8 to 0 7 to sulfides from phyllic alteration 34s 0 1 to 0 8 is consistent with the evolution from ilmenite series to magnetite series magmatic source

geology mineralization stable isotope and fluid inclusion characteristics of the vostok 2 reduced w cu skarn and au w bi as stockwork deposit sikhote alin russia abstract the large 180 kt wo 3 and at least 10 15 t au vostok 2 deposit is situated in a metallogenic belt of w sn w au and au w deposits formed in late to post collisional tectonic environment after cessation of active subduction the deposit is related to an ilmenite series high k calc alkaline plutonic suite that by its petrologic signatures is transitional between those at w dominant and au dominant reduced intrusion related deposits consistently besides large w cu skarns of the reduced type the deposit incorporates quartz stockworks with significant au w bi mineralization also formed in a reduced environment the hydrothermal stages include prograde and retrograde essentially pyroxene skarns hydrosilicate amphibole chlorite quartz alteration and phyllic quartz sericite albite apatite and carbonate alteration assemblages these assemblages contain abundant scheelite associated with pyrrhotite chalcopyrite and at the phyllic stage also with bi minerals as bi sb te pb zn sulfides and sulfosalts as well as au mineralization the fluid evolution included hot high pressure 420 460 c 1 1 1 2 kbar low salinity 5 4 6 0 wt nacl equiv aqueous fluids at the retrograde skarn stage followed by lower temperature cyclic releases of high carbonic low salinity to non carbonic moderate salinity aqueous fluids at the hydrosilicate stage a high carbonic ch 4 dominated hot 350 380 c low salinity fluid was followed by cooler 300 350 c non carbonic moderate salinity 5 7 14 9 wt nacl equiv fluid at the phyllic stage a high carbonic co 2 dominated moderately hot 330 355 c 0 9 kbar low salinity fluid was followed by cooler 230 265 c non carbonic moderate salinity 6 6 12 0 wt nacl equiv fluid a homogenized magmatic source of water 18 o h2o 8 3 to 8 7 and a sedimentary source of sulfur 34 s 6 9 to 6 2 and carbon 13 c fluid 20 1 to 14 9 at the hydrosilicate stage are suggested a magmatic source of water 18 o 8 6 to 9 2 and a sedimentary source of sulfur 34 s 9 3 to 4 1 but a magmatic mantle to crustal derived source of carbon 13 c fluid 6 9 to 5 2 are envisaged for fluids that formed the early mineral assemblage of the phyllic stage then the role of sedimentary carbon again increased toward the intermediate 13 c fluid 16 4 to 14 5 and late 13 c fluid 16 3 to 14 7 phyllic mineral assemblages the magmatic differentiation was responsible for the fluid enrichment in w whereas au and bi could also have been sourced from mafic magma the decreasing temperatures together with elevated ca content in non boiling fluids promoted scheelite deposition at the early hydrothermal stages the most intense scheelite deposition at the phyllic stage was caused by co 2 removal due to boiling of co 2 rich fluids further cooling of non boiling fluids favoured joint deposition of scheelite bi and au

geology mineralization and fluid inclusion characteristics of the kumbel oxidized w cu mo skarn and au w stockwork deposit in kyrgyzstan tien shan the kumbel deposit is located within a metallogenic belt of w mo cu mo au w and au deposits along the late paleozoic active continental margin of tien shan the deposit is related to a late carboniferous multiphase pluton with successive intrusive phases from early olivine monzogabbro through monzonite quartz monzonite to granodiorite and granite with the latest monzogabbro porphyry dikes the deposit represents an example of a complex w cu mo au magmatic hydrothermal system related to magnetite series high k calc alkaline to shoshonitic igneous suite it contains large bodies of w cu mo oxidized prograde and retrograde skarns with abundant andradite garnet magnetite and especially hematite as well as k feldspar molybdoscheelite chalcopyrite and molybdenite with transitions to zones of intense quartz k feldspar with minor andradite and hematite veining the skarns are cut by quartz carbonate adularia sericite veins locally sheeted and stockworks bearing scheelite and minor cu zn pb sulfides as well as au bi te and as mineralization the association of these veins with the oxidized skarns and magnetite series intrusion is consistent with the general oxidized intrusion related w mo cu au type of deposit with an affinity to the alkalic silica saturated cu au mo porphyry deposits the fluid inclusion data show the predominance of magmatic hydrothermal aqueous chloride fluid during the formation of skarns and quartz carbonate scheelite sulfide veins the high fluid pressures 1 750 bars together with their high temperature up to 600 c and high salinity 50 60 wt nacl equiv suggest the formation of skarns and quartz k feldspar andradite hematite veins under conditions typical of magmatic hydrothermal transition depth of 4 5 km of intrusion related mineralized system possibly by exsolution of the fluids from crystallizing magma the auriferous quartz carbonate scheelite sulfide veins formed from high to moderate salinity from 40 to 20 wt nacl equiv and high pressure from 1 200 bars to 850 900 bars aqueous chloride fluids under decreasing temperature from 370 to 120 c the massive deposition of molybdoscheelite in retrograde skarn and scheelite in quartz carbonate scheelite sulfide veins could correspond to enrichment of fluids in ca up to 18 25 wt cacl2 likely from crystallizing magma

additional evidence of an upper tropospheric zonal eddy relationship during winter abstract a zonal wind oscillation with a period of about 15 35 days is isolated over the middle latitudes of the northern hemisphere during winter a systematic relationship between the zonal winds and wind departures from zonal symmetry eddies is found for nine prominent zonal wind oscillation cycles taken from six 120 day winters this zonal eddy relationship consists of an oscillation between anomalous zonal flow and anomalous meridional flow which is strongest across north america from 150 w to 0