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

gravity gradiometry resurfaces the red october was heading southwest on gorshkov s railroad his speed was thirteen knots installed in the keel was a highly sensitive device called a gradiometer essentially two large lead weights separated by a space of one hundred yards a laser computer system measured the space between the weights down to a fraction of an angstrom distortion of that distance or lateral movement of the weights indicated variations in the local gravitational field with careful use of gravitometers he could plot the vessel s location to within a hundred meters

formation of au polymetallic ore deposits in alkaline porphyries at beiya yunnan southwest china abstract the beiya gold deposit is located in the central part of the jinshajiang honghe strike slip belt at the junction zone of the tethys himalaya orogenic belt and the yangtze plate in sw china this large scale 125 6 million metric tonnes with a mean grade of 2 42 g t au rich polymetallic deposit is related to alkaline porphyry intrusions previous studies show that the beiya alkaline porphyry intrusions are the fractionation product of a mantle derived magma emplaced in an extension environment at the post collision stage of the india eurasian plate collision the beiya deposit is considered to be skarn related based on detailed field studies and previous work we propose that the beiya porphyry and associated au rich polymetallic ores were formed by the emplacement of magmas within the jinshajiang honghe strike slip fault during the late stage of the india eurasian plate collision at 45 25 ma at beiya the mineralized zones in the cu au rich porphyries are surrounded by au cu fe skarns and au cu veins pb zn ag rich mineralization was derived from the inner porphyry and is widely developed outside the central alkaline rich porphyry the sulfur isotope signature of the sulfide mineralization in the beiya and qinhe deposits is 2 40 4 50 and 1 25 2 75 respectively these values are close to 0 indicating that the sulfur may be mantle derived the 18 o compositions of the ore forming fluids responsible for the formation of calcites at qinhe are 8 10 9 61 which is lower than that of beiya 18 o 10 5 where the ores contain a larger contribution of oxygen from the mantle the beiya porphyry magmas provided fluids and the heat that drove the transport of the metals to the site of deposition alkaline porphyries are widely distributed throughout the jinshajiang honghe strike slip fault belt and they are potential hosts to future discoveries of beiya style mineralization

detection of reservoirs from normalized full gradient of gravity anomalies and its application to shengli oil field east china we present how to detect reservoirs by the 3 d normalized full gradient nfg of gravity anomalies constrained by seismic and drilling data the normalized full gradient represents the full gradient of the gravity anomaly at a point divided by the average of the full gradient at the datum the closed minima on an nfg map indicate the occurrence and horizontal locations of the centers of mass of density anomalies related to oil reservoirs this information can be used to select well locations in an oil field on a cross section the closed minima can be used to estimate the depth to centers of mass of possible hydrocarbon reservoirs some characteristics of the nfg are calculated for a hypothetical case of an anticline saturated with oil and gas the relationship of these characteristics to the geometry and physical parameters of the anticline is studied modeling studies show that the nfg largely depends on the number of terms in the fourier series used to calculate it and it closely related to the length

changes in tourmaline composition during magmatic and hydrothermal processes leading to tin ore deposition the cornubian batholith sw england abstract to investigate the potential of tourmaline as a geochemical monitor a comprehensive dataset on major minor and trace element concentrations as well as fe3 fe ratios of tourmaline is presented the dataset includes samples from five plutonic complexes related to diverse magmatic to hydrothermal stages of the cornubian batholith sw england tourmaline composition found in barren and cassiterite bearing samples include all three primary tourmaline groups and tourmaline species with the general endmembers schorl dravite elbaite uvite feruvite foitite and mg foitite based on textures and compositions it is possible to distinguish not only between late magmatic and hydrothermal tourmaline but also between several formation stages hence tourmaline monitors late magmatic processes and the partitioning of elements during exsolution of an aqueous phase for example in hydrothermal tourmaline sn is strongly enriched while ti cr v and sc are depleted compared to late magmatic tourmaline of the same sample several tourmaline generations that precipitated from magmatic fluids can be distinguished with differing major and minor elements and ree patterns depending on the composition of the melt from which they were expelled from strongly zoned tourmaline allows for unraveling the hydrothermal history of a distinct location including ore precipitation the precipitation of sno2 in the study area was probably caused by mixing between acidic reduced sn bearing magmatic fluids and oxidized meteoric fluids which is in agreement with london and manning 1995 and williamson et al 2000 hence the ability of tourmaline composition to monitor changes in sn concentration and redox conditions in hydrothermal fluids has potential as an exploration tool

electron microprobe and la icp ms study of monazite hydrothermal alteration implications for u th pb geochronology and nuclear ceramics this paper presents new data that quantify the response of magmatic monazite to three main types of hydrothermal alteration namely sericitization chloritization and greisenization the samples were taken from three paleozoic granites the st nectaire granite massif central france the carnmenellis granite cornwall england and the skiddaw granite lake district england fluid inclusion thermometry and hydrothermal parageneses indicate that alteration took place at temperatures ranging from 260 to 340 c and salinities from 3 to 18 wt nacl equivalent possible monazite alteration mechanisms found in the course of this study using backscattered scanning electron microscopy bse sem electron microprobe laser raman spectroscopy and laser ablation inductively coupled plasma mass spectrometry la icp ms include cationic substitutions monoclinic to hexagonal structure transition accompanied by chemical exchanges selective th removal dissolution reprecipitation and dissolution with replacement by a different mineral these results show that despite the compositional and crystallographic simplicity of monazite it exhibits varied chemical responses to different mineral fluid interactions elemental and isotopic measurements by la icp ms for the unaltered monazites yield statistically significant 232th 208pb and 238u 206pb magmatic crystallization ages in some cases it was possible to give a reasonable estimate of the age of mineral fluid interaction using the altered parts of the monazites or newly precipitated crystals for other minerals 232th 208pb and 238u 206pb systematics were strongly disturbed by variable inputs and or depletions of u th and pb the data suggest that monazite like nuclear waste forms would be good hosts for tetravalent actinides but may release the lanthanides and actinides with lower and higher valencies especially if the fluids are oxidizing or tend to dissolve monazite

soil pipe distribution and hydrological functioning within the humid tropics a synthesis some of the most responsive runoff systems in the world are found within the humid tropics these runoff responses are likely to be affected by the presence of natural pipes within the soil this study provides a synthesis of the hydrological aspects of these phenomena within the humid tropics of the studies reporting the presence of soil piping within the humid tropics most are associated with ultisol soils and locally most pipe outlets are observed on the lower sections of hillslopes while the drainage role of pipes has been observed providing faster and slower components of stream hydrographs the mechanism of their recharge remains less clear in part this is because their spatial extent is poorly mapped within the hillslopes of the humid tropics further studies quantifying the length and recharge of soil pipe networks within the humid tropics are needed

naturally acidic surface and ground waters draining porphyry related mineralized areas of the southern rocky mountains colorado and new mexico abstract acidic metal rich waters produced by the oxidative weathering and resulting leaching of major and trace elements from pyritic rocks can adversely affect water quality in receiving streams and riparian ecosystems five study areas in the southern rocky mountains with naturally acidic waters associated with porphyry mineralization were studied to document variations in water chemistry and processes that control the chemical variations study areas include the upper animas river watershed east alpine gulch mount emmons and handcart gulch in colorado and the red river in new mexico although host rock lithologies in all these areas range from precambrian gneisses to cretaceous sedimentary units to tertiary volcanic complexes the mineralization is tertiary in age and associated with intermediate to felsic composition porphyritic plutons pyrite is ubiquitous ranging from 1 to 5 vol springs and headwater streams have ph values as low as 2 6 so4 up to 3700 mg l and high dissolved metal concentrations for example fe up to 400 mg l cu up to 3 5 mg l and zn up to 14 4 mg l intensity of hydrothermal alteration and presence of sulfides are the primary controls of water chemistry of these naturally acidic waters subbasins underlain by intensely hydrothermally altered lithologies are poorly vegetated and quite susceptible to storm induced surface runoff within the red river study area results from a storm runoff study documented downstream changes in river chemistry ph decreased from 7 80 to 4 83 alkalinity decreased from 49 4 to

geochronology and geochemistry of the max porphyry mo deposit and its relationship to pb zn ag mineralization kootenay arc southeastern british columbia canada the max porphyry mo deposit is located at the northern end of the kootenay arc in southeastern british columbia canada molybdenum mineralization is genetically related to the variably altered trout lake granodiorite stock which has lithogeochemical affinities to the low fluorine calc alkaline granodiorite hosted porphyry mo deposit type three molybdenite samples from early and late mo bearing veins yield re os dates that overlap within analytical error with a weighted average age of 80 3 0 2 ma these dates are in close agreement with two 206pb 238u weighted average zircon ages for phases of the trout lake stock at 80 3 1 6 and 79 2 1 0 ma indicating that crystallization of the stock and hydrothermal molybdenite formation were coeval and likely cogenetic 40ar 39ar plateau ages for primary biotite in igneous dikes secondary biotite in early potassic alteration and muscovite in late phyllic alteration range from 80 to 76 ma the younger 40ar 39ar plateau ages may reflect unusually slow cooling of the magmatic hydrothermal system or a late thermal disturbance pb zn ag vein deposits are common throughout the kootenay arc and several such veins are located within and proximal to the max porphyry mo deposit the presence of rare molybdenite associated with sphalerite and argentiferous galena in some of these pb zn ag veins suggests that they represent a late stage event related to the max magmatic hydrothermal system fluid inclusions in quartz from mo and pb zn ag veins are similar and can be divided into two compositional groups type 1 aqueous liquid rich fluid inclusions and type 2 aqueous carbonic liquid rich fluid inclusions pressure corrected 1 4 1 7 kbar trapping temperatures of typical type 1 inclusions from mo bearing veins range from 430 to 460 c and for pb zn ag veins from 335 to 365 c the ranges of salinity 0 12 wt nacl equiv in fluid inclusions from both vein types are almost identical and type 2 inclusions from both vein types contain similar amounts of co2 avg xco2 0 08 with traces of ch4 the similarity of chemistry in the two vein types suggests a genetic link between porphyry mo mineralization and adjacent pb zn ag deposits however muscovite from the alteration halo around a pb zn ag vein within the max deposit yielded a 40ar 39ar plateau age of 72 2 0 5 ma this date is significantly younger than the 80 ma age of porphyry magmatism and mo mineralization suggesting either that this event is in fact unrelated to porphyry mo mineralization at 80 ma or that the k ar isotope system has been disturbed by a later thermal event

petrogenesis of the bosworgey granitic cusp in the sw england tin province and its implications for ore mineral genesis the bosworgey granite cusp forms an apical portion of the concealed northern extension of the tregonning godolphin granite ridge it is characterised by unusually high values of b p mn fe as cu nb ta bi sn w u and s which are present largely as tourmaline apatite pyrite arsenopyrite chalcopyrite bismuth columbite cassiterite wolframite and uraninite and low levels of zr hf ti and ree present in zircon ilmenite and monazite the granite is classified as sn and w specialised tischendorf 1974 and it belongs to the ilmenite series of japanese workers the classification of chappell and white 1974 s and i type granites is shown to be inapplicable to cornubian rocks although the bosworgey samples show characteristics of s type granites the accessory mineral assemblages are typical of high temperature lodes cassiterite wolframite arsenopyrite chalcopyrite and the assamblage is concluded to be the cusp analogue of hypothermal lodes produced by extreme differentiation and concentration of volatiles it is speculated that such granites could provide the parent material for the mesothermal crosscourse mineralisation pitchblende bismuth pyrite galena sphalerite

granite molybdenite systems stockwork molybdenite deposits in the western conterminous united states may be divided into two groups based on the chemistry of the source pluton granodiorite systems and granite systems these two groups show significant differences in age tectonic setting at time of formation and orebody geometry granite molybdenite systems develop in and adjacent to epizonal plutons that meet tuttle and bowen s 1958 definition of granite cenozoic source plutons for these systems were emplaced in the eastern rockies and great basin coincident with or just prior to regional extensional tectonism mineralization and alteration patterns in granite molybdenite systems generally conform to those described at the climax and henderson deposits major element data displayed on ab or q and a k f plots 1 can characterize potassic quartz sericite argillic and silicic alteration assemblages and lead to evaluation of the probable depth to mineralization in prospects observed alteration reflects hydrogen and alkali metasomatism in fluorine rich systems minor elements concentrated in granite molybdenite systems include be cs f li mo nb rb sn ta th u and w geophysical and geological evidence indicates that the cylindrical source plutons associated with known granite molybdenite systems are cupolas on the tops of batholiths suggesting a genetic link between batholiths and ore a granite molybdenite system appears to be the result of the following lithophile element concentration by convection aided thermogravitational diffusion in the upper part of a batholithic magma chamber transfer of the resulting high silica volatile rich magma from the roof zone of the batholith to a high level cylindrical cupola establishment of thermogravitational diffusion in the cupola causing further lithophile element concentration formation of potassic alteration and an ore shell as a result of volatile saturation resurgent boiling hydrofracturing and boiling and the evolution of peripheral alteration assemblages as meteoric waters enter the magmatic fluid plume above the cupola stacked orebodies represent discrete episodes of resurgent boiling hydrofracturing and mineralization computer assisted evaluation of major element analyses of igneous rocks using chemical criteria developed from known granite molybdenite systems may locate areas with a high exploration potential these techniques suggest that several late precambrian bimodal basaltrhyolite terrains in the eastern united states and canada have exploration potential for molybdenum

continental rifting and porphyry molybdenum occurrences in the oslo region norway abstract the overall structure of the oslo rift system can be viewed as the result of interference between a n s trending permian fault system and a regional ne sw trending precambrian shear zone the rift system comprises four mutually opposed horst and graben structures in a centrosymmetrical arrangement igneous activity occurred only in two en echelon segments both of which possess a notable symmetric distribution of rocks and structures around the central axis of the rift system the axial zone is occupied by cambro silurian sediments which have been intruded by major granite bodies extensive lava plateaus occur on each side of this axial zone the adjacent zones contain the most prominent cauldrons of province further away from the axis follows a zone of batholitic intrusions emplaced as composite diapirs and plutonic ring complexes hornfelsed sediments and volcanics in narrow bands occur at the lateral borders of the province possibly preserved as the result of marginal tectonics associated with batholith emplacement the formation of the oslo rift system apparently reflects a passive continental rifting which was gradually succeeded by considerable igneous activity important porphyry molybdenum mineralization in the oslo region is associated with shallow level magmatism in the glitrevann and hurdal areas the porphyry mo mineralization in these prospects have several evolutionary features in common 1 1 an initial period of effusive eruptions of pyroclastic flows followed by 2 2 the formation of large scale ring structures partly accompanied by peripheral syenite granite intrusions 3 3 the emplacement of a multiple intrusive central stock of sub alkaline granite composition which is terminated by 4 4 the injection of a highly differentiated aplogranite granophyre closely associated with the development of the mineralizing hydrothermal porphyry system molybdenum mineralization of the oslo province is closely associated with highly differentiated alkali granites which possess striking similarities to mo related granites of the colorado mo province and evolved rapakivi or a type granites usually considered to be typically associated with bimodal magmatism of crustal extension and continental rifts the discovery of significant porphyry mo mineralization in the oslo rift associated with permian igneous rocks draws attention to the possible economic potential of rift structures elsewhere

roles of carbonate co2 in the formation of quartz vein wolframite deposits insight from the crystallization experiments of huebnerite in alkali carbonate aqueous solutions in a hydrothermal diamond anvil cell abstract quartz vein type wolframite deposits are a primary type of tungsten deposits traditionally f and cl were considered as important agents in tungsten transportation during ore formation process however ore forming fluids enriched in co2 were commonly observed in natural fluid inclusions associated with quartz vein type wolframite deposits indicating that carbonate or co2 could be important for their formation in this paper we report experiments of the dissolution and crystallization of huebnerite in the mnwo4 li2co3 or na2co3 h2o system using a hydrothermal diamond anvil cell hdac the results showed that mnwo4 dissolved in alkali carbonate aqueous solutions and in some cases in associated carbonate melts during heating and subsequently huebnerite crystallized into needle and column shaped crystals during cooling in situ raman spectra obtained during heating of the experimental charge in the sample chamber of the hdac showed that wo42 was the only tungsten bearing ion detected in the carbonate melt or aqueous solution the dissolution of mnwo4 mainly attributed to the alkaline environment in the alkali carbonate aqueous solution furthermore the weak alkali condition in the carbonate solutions enhanced the crystallization of huebnerite when the temperature and pressure were decreased the experimental results indicate that although the crystallization temperature pressure conditions of huebnerite vary in a wide range conditions lower than approximately 200 mpa and 450 c are not favorable for huebnerite crystallization our experimental results also suggest that the alkali carbonate aqueous solution could serve as a medium for the transport of tungsten in the ore forming process

geochemistry of intrusive rocks associated with molybdenite mineralization kigom complex northern nigeria abstract the kigom igneous complex of northern nigeria is a small intrusive complex made up of peralkaline arfvedsonite granite riebeckite biotite granite and riebeckite aegirine granite the granites show coherent major element chemistry typical of that of the nigerian younger granites and are enriched in rb li zr nb th y f and ree and depleted in ba and sr compared to the world average for rocks of similar composition the riebeckite aegirine granite exhibits a two to three fold increase in the concentration of zr nb li f th zn and ree over comagmatic granites concentrations of the highly charged cations in these granites are believed to be the result of halogen alkali rich fluid activity during the fractionation of the magma corresponding trace element increases in the granites in areas of alkali metasomatism albitization support this argument and reflect the partial confinement of this alkali volatile phase within the high level magma chambers it is important to recognize that the chemical signatures of this liquid state fractionation process may be explanatory mechanisms in the formation of some kinds of lithophile ore deposits the degree of peralkalinity maintained miscibility in the residual fluid between silicate and aqueous phase to low temperatures so that mineralizing components continuously accumulated together the interaction between this phase and early formed minerals led to mo mineralization the well known classification of granites into sedimentary protolith s type igneous protolith i type and a type indicates that the granites studied here have typical a type features an origin by partial melting of lower crustal material probably granulite facies under a high flux of mantle derived volatiles is suggested for these rocks as a result of mixing of crustal and mantle derived fluids a syenitic magma was produced which then experienced selective contamination as a result of further reaction melting during fractionation and ultimately produced a peralkaline differentiate

contrasted monazite hydrothermal alteration mechanisms and their geochemical implications in spite of the major importance of monazite as a repository for the rare earths and th in the continental crust for u th pb geochronology and as a possible form for high level nuclear waste very little work has been carried out so far on the behaviour of this mineral during fluid rock events this contribution describes two contrasting examples of the hydrothermal alteration of monazite the first case comes from a sample of the carnmenellis granite cornwall southwest england chloritized at 284 16 c whereas the other occurs in the skiddaw granite lake district northwest england which underwent greisenization at 200 30 c an integrated study involving backscattered scanning electron microscopy electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry la icp ms reveals that the chloritization event was characterized by the coupled substitution 2ree3 th4 ca2 in the altered parts of the monazite thus leaving the p o framework of the crystal untouched in contrast greisenization led to the coupled substitution ree3 p5 th4 si4 and therefore involved a partial destruction of the phosphate framework the resulting rare earth element patterns are quite different for these two examples with a maximum depletion for dy and er in the altered parts of the carnmenellis monazite whereas the skiddaw monazite shows a light rare earth depletion but an yb and er enrichment during alteration this latter enrichment accompanied by an increase in u but roughly unchanged pb concentrations probably resulted from a decrease in the size of the 9 coordinated site in monazite thereby favouring the smaller rare earths these contrasted styles of monazite alteration show that the conditions of fluid rock interaction will not only affect the aqueous geochemistry of the lanthanides actinides and lead and the relative stability of the different minerals holding these elements variations in these conditions will also lead to various possible chemical exchanges between the crystalline phases and the hydrothermal fluids the occurrence of common lead along penetrative cracks in the carnmenellis monazite shows that only a leaching prior to the u pb analyses of the whole grain will permit an accurate determination of the magmatic crystallization age in contrast for the skiddaw case it may be possible to date the fluid rock event by in situ 207pb 206pb geochronology the observation that the altered parts of both monazite examples display nd leaching and no significant sm nd fractionation indicates that they should not affect the host whole rock nd isotopic signatures finally it appears that monazite like ceramics designed for the containment of high level nuclear wastes will retain th and the geochemically equivalent transuranic elements during fluid rock events similar to those documented in this study but may release nd u and the corresponding radionuclides to the environment

long term patterns and short term dynamics of stream solutes and suspended sediment in a rapidly weathering tropical watershed 1 the 326 ha rio icacos watershed in the tropical wet forest of the luquillo mountains northeastern puerto rico is underlain by granodiorite bedrock with weathering rates among the highest in the world we pooled stream chemistry and total suspended sediment tss data sets from three discrete periods 1983 1987 1991 1997 and 2000 2008 during this period three major hurricanes crossed the site hugo in 1989 hortense in 1996 and georges in 1998 stream chemistry reflects sea salt inputs na cl and so4 and high weathering rates of the granodiorite ca mg si and alkalinity during rainfall stream composition shifts toward that of precipitation diluting 90 or more in the largest storms but maintains a biogeochemical watershed signal marked by elevated k and dissolved organic carbon doc concentration doc exhibits an unusual boomerang pattern initially increasing with flow but then decreasing at the highest flows as it becomes depleted and or vigorous overland flow minimizes contact with watershed surfaces tss increased markedly with discharge power function slope 1 54 reflecting the erosive power of large storms in a landslide prone landscape the relations of tss and most solute concentrations with stream discharge were stable through time suggesting minimal long term effects from repeated hurricane disturbance nitrate concentration however increased about threefold in response to hurricanes then returned to baseline over several years following a pseudo first order decay pattern the combined data sets provide insight about important hydrologic pathways a long term perspective to assess response to hurricanes and a framework to evaluate future climate change in tropical ecosystems

a sulphur isotopic investigation of the potential sulphur sources for lower palaeozoic hosted vein mineralization in the english lake district current models for cu fe as devonian pb zn carboniferous and barite upper carhoniferous permian vein mineralization in the lake district invoke a variety of sources for fluids and metals including the skiddaw group sediments the borrowdale volcanic group the lake district batholith meteoric water and carboniferous seawater this study isotopically characterizes the sulphur reservoirs within the lower palaeozoic sedimentary and igneous sequences and late caledonian intrusives and assesses their importance as sources of sulphur for the vein mineralization the ordovician skiddaw group is a reservoir of isotopically heavy sulphur with a range of 34 s from 11 to 29 x 1 18 53 6 7 n 10 four analyses of borrowdale volcanic group rocks yielded values of 1 to 15 such positive values are thought to be the result of closed system bacteriogenic reduction of ordovician seawater sulphate in the case of the skiddaw group and mixing of mantle derived magmatic sulphur with ordovician seawater sulphate for the borrowdale volcanic rocks the sulphides in the vein systems hosted by the skiddaw group in the vale of newlands formed from fluids with 34 s h 2 s signatures ranging from 16 7 to 22 5 partially homogenized skiddaw group sulphur is considered to be the source mineralization at coniston hosted by the borrowdale volcanic group shows similar sulphur isotopic characteristics and skiddaw group at depth is considered to be the predominant source of sulphur with a possible minor input from the wallrock volcanic rocks at the site of deposition although the lake district batholith provided a heat source for the cu fe as vein mineralization the granite did not supply any sulphur to those systems however magmatic sulphur was an important constituent in mineralization associated with the shap and skiddaw granites the 34 s values for barite mineralization at force crag greenside skiddaw and shap ranges from 13 to 18 and carboniferous seawater provides the most reasonable source for sulphate

crustal structure of the southeastern tibetan plateau from gravity data new evidence for clockwise movement of the chuan dian rhombic block abstract the crustal deformation beneath the chuan dian rhombic block cdb and surrounding regions has been studied in geological and geodetic methods and provide important insights into the kinematics and dynamics about the clockwise movement of this tectonic block in this work we present images of the normalized full gradient nfg of the bouguer gravity anomalies from five gravity profiles across the boundary faults of the cdb measured in recent years and investigate the distribution characteristics of the crustal anomalous bodies along the profiles firstly an anomalous body with eastward dipping exist beneath the xianshuihe fault suggesting that crustal mass move to east secondly near the xiaojiang fault two anomalous bodies dip westward with depth increasing the inferred movement direction of the north one is from west to east and the south one is from east to west thirdly anomalous bodies on the northeast and southwest sides of the red river fault suggest the directions of crustal movement is from northeast to southwest these results are also consistent with gps solutions and provide gravity evidence for crustal deformation of the cdb with clockwise rotation

petrogenesis of early cretaceous post collisional granitoids at shapinggou dabie orogen implications for crustal architecture and porphyry mo mineralization abstract the shapinggou molybdenum deposit is located in the qinling tongbai hong an dabie orogen which accommodates the largest molybdenum ore belt in the world new laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb dating geochemical and sr nd hf isotope data for the granitoids at shapinggou are presented in this paper two stages of early cretaceous magmatism 138 128 ma and 116 114 ma took place at shapinggou in a post collisional setting these granitoids can be divided into four groups including the early stage granites 134 129 ma sio2 62 33 to 76 27 and intermediate rocks 129 128 ma sio2 52 41 to 60 72 and the late stage quartz syenite 116 ma sio2 64 09 to 65 12 and mo bearing granite porphyry 114 ma sio2 74 95 to 77 26 the early stage granites have high sr contents sr y and lan ybn ratios but low y yb and mgo contents showing low mg adakitic chemical features they were possibly generated by partial melting of the thickened mafic lower continental crust the early stage intermediate rocks have relatively high mgo contents 2 71 to 4 84 and mg values 46 to 60 but low sr y and lan ybn ratios which were likely derived from a hybrid mantle metasomatized by melts from foundered eclogitic lower continental crust and subsequent fractional crystallization the late stage quartz syenite shows chemical features of metaluminous a type granites including high abundances of alkalis hfse zr nb and trivalent ree the late stage mo bearing granite porphyry displays high sio2 alkalis zr ce contents and a cnk ratios but low ba sr p and ti showing affinity to highly fractionated i type granites the late stage quartz syenite and granite porphyry were possibly produced by partial melting of intermediate compositions of middle crust our results support the conclusion that there were three layer continental crusts in the dabie orogen prior to early cretaceous magmatism and suggest that post collisional granitoids in the dabie orogen were derived from not only lower crust but also middle crust the giant shapinggou porphyry mo deposit was most likely formed by effective transport of volatiles and mo in a convecting granitic magma column rather than by direct melting of mo enriched sources the mo bearing rocks at shapinggou are characterized by a high degree of magma differentiation close associations with a type granite and formation at the end of regional magmatism

hydrological behaviour and modelling of a volcanic tropical cultivated catchment the hydrological behaviour of the cultivated f ef e catchment 17 8 ha on the tropical volcanic island of guadeloupe was studied to identify flow paths to quantify water fluxes and finally to build a lumped model to simulate discharge and piezometer levels the approach combined two steps an experimental step and a modelling step which covered two time scales the annual and the storm event scale the hydrological measurements were conducted over 2 years the f ef e catchment is characterized by heavy rainfall 4229 mm year 1 on permeable andosols the results showed that underground flow paths involved two overlapping aquifers and that the annual water balance in 2003 was shared among outflows of the deep aquifer 42 evapotranspiration 31 and streamflow 27 on the event scale the surface runoff coefficient ranges between 6 2 and 24 4 depending on antecedent dry or wet moisture conditions hortonian overland flow predominated over subsurface and saturation overland flow processes recharge of the shallow aquifer is mainly governed by a constant infiltration capacity of the andosols with depth in the vadose zone outflows of this shallow aquifer were the baseflow of the main stream and the recharge of the deep aquifer volcanic deposits at f ef e promoted the underground flow path and cultivated areas seemed to explain the high stormflow values relative to other tropical small catchments under rain forest a conceptual lumped model integrating runoff infiltration evapotranspiration and fluctuations of the two overlapping aquifers was developed the model has six parameters and was calibrated and validated on the hydrograph at the outlet and on the two piezometers of the shallow and the deep aquifers the results show fair to good agreement between measured and simulated variables and consequently the model was consistent with the main hydrological processes observed from experimental results in wet conditions resume d auteur

high exchangeable calcium concentrations in soils on barro colorado island panama the soils on four lithologies basaltic conglomerates bohio andesite volcanoclastic sediments with basaltic agglomerates caimito volcanic foraminiferal limestone caimito marine on barro colorado island bci have high exchangeable ca concentrations and cation exchange capacities cec compared to other tropical soils on similar parent material in the 0 10 cm layer of 24 mineral soils ph values ranged from 5 7 caimito volcanic and andesite to 6 5 caimito marine concentrations of exchangeable ca from 134 mmolc kg 1 caimito volcanic to 585 mmolc kg 1 caimito marine and cation exchange capacities from 317 mmolc kg 1 caimito volcanic to 933 mmolc kg 1 caimito marine x ray diffractometry of the fraction 2 m revealed that smectites dominated the clay mineral assemblage in soil except on caimito volcanic where kaolinite was the dominant clay mineral exchangeable ca concentrations decreased with increasing soil depth except on caimito marine the weathering indices chemical index of alteration cia plagioclase index of alteration pia and weathering index of parker wip determined for five soils on all geological formations suggested that in contrast to expectation the topsoil 0 10 cm appeared to be the least and the subsoil 50 70 cm and saprolite isomorphically weathered rock in the soil matrix the most weathered additionally the weathering indices indicated depletion of base cations and enrichment of al hydr oxides throughout the soil profile tree species did not have an effect on soil properties impeded leaching and the related occurrence of overland flow seem to be important in determining clay mineralogy our results suggest that i edaphic conditions favor the formation of smectites on most lithologies resulting in high cec and thus high retention capacity for ca and ii that there is an external source such as dust or sea spray deposition supplying ca to the soils

ant mounds as a source of sediment in a tropical rainforest in lutzito catchment on barro colorado island panama extraordinarily high suspended sediment yields of 1 2mgha 1 year 1 were generated despite the dense forest cover coinciding with erosion resistant soils we hypothesized that ant mounding activity is an important zoogeomorphological mechanism in this area providing relevant quantities of easily transportable material at the soil surface to test this hypothesis all ant mound material was collected collected for dry mass determination from thirty 4m 2 plots installed in the study area every 1 3days during the 39 day sampling period additionally three ground nesting ant species responsible for mounds in the study area ectatomma ruidum trachymyrmex cornetzi and strumigenys marginiventris were identified on the basis of the total of 1 38kg of material collected in the wet season of 2011 the estimate for the whole 8months wet season amounts to 725kgha 1 as this value is in the same order of magnitude as sediment output it shows that ants may act as important ecosystem engineers and contribute to sediment production here by providing large quantities of fine grained readily erodible material at the soil surface for subsequent transport to the streambed copyright 2014 john wiley sons ltd

physiographic controls on the composition of sediments derived from volcanic and sedimentary terrains on barro colorado island panama abstract the phenomena that control sand composition are complex dynamic and interlinked although source rock lithology is of critical importance in determining the allowable range of sand compositions chemical weathering may overprint the source rock signal substantially in the humid tropical environment of barro colorado island panama source rocks of similar lithological character produce sediments of differing compositions in different physiographic environments moreover sediments derived from source rocks of dissimilar mineralogical composition but produced on similar physiographic terrains may be nearly indistinguishable physiography influences the composition of sediments released from the source areas by controlling the duration of chemical weathering on relatively flat terrains rates at which loose solids are generated by weathering may exceed rates at which slope processes can remove this material soils are exposed to the weathering environment for long periods of time and are strongly leached consequently weathering products are cation poor and contain relatively immobile elements incompletely weathered detritus is not abundant and is greatly enriched in chemically resistant phases on steeper slopes potential solid erosion rates exceed weathering rates residence times of minerals within soils are short resulting in weathering products that are cation rich and contain an abundance of uns able phases on barro colorado island fluvial sediments are dominated by authigenic particles composed of secondary weathering products although the stability of many such particles in larger transportational and depositional systems and in the diagenetic environment has yet to be assessed they may be more important constituents of fluvial sediments in tropical environments than has been previously recognized

mineralisation at the carrock fell tungsten mine n england paragenetic fluid inclusion and geochemical study tungsten ore at carrock fell mine comprises wolframite and scheelite in polyminerallic quartz veins which traverse the grainsgill granite cupola and surrounding country rocks in the veins a wolframite scheelite apatite assemblage pre dates a scheelite arsenopyrite pyrite plus other sulphides assemblages temperatures of mineralisation declined from a peak near 350 c to 170 c and the hydrothermal fluid contained about 6 weight nacl and 3 wt nahco3 contemporaneous greisenisation involved loss of na cr ca and ba from granite but si and k were retained while b be and al increased slightly sn also increased but is always a trace constituent and f appears to have decreased zones of intense alteration contain high concentrations of quartzhosted fluid inclusions resulting from penetration of the granite by fluid chemically similar to that in the vein quartz the w rich sn poor nature of the mineralisation may relate to the weakly saline f deficient but co2 rich fluid chemistry the alteration and mineralisation processes took place during late cooling of the lower devonian skiddaw granite cross cutting quartz ankerite veins and argillitic zones which may be considerably younger than those producing the tungsten ore have a distinct mineral suite lacking w and as and including major pb and zn temperatures at this late stage were below 150 c and the fluid is estimated to have contained approximately 12 wt nacl and 15 wt cacl2

geochemistry of surface water in alpine catchments in central colorado usa resolving host rock effects at different spatial scales the us geological survey is conducting a study of surface water quality in the rocky mountains of central colorado an area of approximately 55 000 km 2 using new and existing geologic maps the more than 200 rock formations represented in the area were arranged into 17 groups based on lithologic similarity the dominant regional geologic feature affecting water quality in central colorado is the colorado mineral belt cmb a ne trending zone hosting many polymetallic vein or replacement deposits and porphyry mo deposits many of which have been mined historically the influence of the cmb is seen in lower surface water ph 5 and higher concentrations of so

fluid inclusion chemistry in the exploration for mississippi valley type deposits an example from east tennessee u s a scanning electron microscopy and energy dispersive analysis of fluid inclusion decrepitates in sparry dolomite cements associated with sphalerite mineralization in the mascot jefferson city missis sippi valley type district of east tennessee show a markedly lower najca ratio than those in dolomites unassociated with ore the exploration potential of this variation in fluid inclusion chemistry has been evaluated by analyzing inclusion decrepitates from white sparry dolomite along a 150 m traverse in the new market west mine area the traverse extends from the central portion of a large domal collapse breccia orebody with greater than 3 zn into the dolomite veined but unmineralized knox group limestones ratios of na ca as low as 0 8 1 2 were common in dolomite hosted decrepitates from the high grade collapse ores this anomalous decrepitate chemistry was not observed in sparry dolomites less than 12 m from the margins of the breccia bodies where na ca ratios ranged from 1 8 to 3 6 dolomite cements in idly grade 1 0 zn parts of the collapse bodies showed the greatest variation in na ca ratio with values ranging from 0 9 to 3 5 no systematic trends were observed in k na and s c1 ratios from the same samples

concentration discharge relationships during an extreme event contrasting behavior of solutes and changes to chemical quality of dissolved organic material in the boulder creek watershed during the september 2013 flood during the week of september 9 15 2013 about 44 cm of rain fell across boulder county colorado usa representing a very rare precipitation event the resultant stream flows corresponded to an extreme event not seen since the historical flood of 1894 for the boulder creek critical zone observatory bcczo this event provided an opportunity to study the effect of extreme rainfall on solute concentration discharge relationships and biogeochemical processes we measured weathering derived lithologic solutes ca mg na k and si and dissolved organic carbon doc concentrations at two sites on boulder creek during the recession of peak flow we also isolated four distinct fractions of dissolved organic matter dom for chemical characterization at the upper and lower sites all solutes had their highest concentration at peak flow at the upper site which represented a mostly forested catchment the concentrations of lithologic solutes decreased slightly during flood recession in contrast doc and k concentrations decreased by a factor of three at the lower site within the urban corridor concentration of lithologic solutes decreased substantially for a few days before rebounding whereas the doc and k concentrations continued to decrease additionally we found spatiotemporal trends in the chemical quality of dom that were consistent with a limited reservoir of soluble organic matter in surficial soils becoming depleted and deeper layers of the critical zone contributing dom during the flood recession overall these results suggest that despite the extreme flood event concentration discharge relationships were similar to typical snowmelt periods in this rocky mountain region

detection of high potential oil and gas fields using normalized full gradient of gravity anomalies a case study in the tabas basin eastern iran the normalized full gradient nfg represents the full gradient of the gravity anomaly at a point divided by the average of the full gradient at the same point the nfg minimum between two maxima in an nfg section or a closed minimum surrounded by closed maxima on an nfg map may indicate density deficient anomalies closely related to possible oil gas reservoirs on a cross section closed minima can be used to estimate the depth to centers of possible hydrocarbon reservoirs the nfg map can also be used to locate oil gas exploratory wells for estimation of the depth of possible reservoirs the objective of this paper is to use two and three dimensional 2d and 3d nfg on gravity data of the tabas basin in yazd province eastern iran a hypothetical model is first considered to explore the nfg characteristics and their relationship with the geometry of the model the physical properties of the model are then studied to simplify the interpretation of real data finally 2d and 3d nfg models are developed for real gravity data to predict the location of any possible high potential oil gas reservoirs the results obtained indicate two zones in the northern and central parts of the tabas basin suitable for hydrocarbon prospecting however the favorable zone located in the middle of the basin in which anticline e is detected at a depth of 5 7 km is more important for the purpose of hydrocarbon exploration

multiple fluids involved in granite related w sn deposits from the world class jiangxi province china abstract this paper aims at providing new insights into w sn ore forming processes within one of the largest granitic provinces in the world nanling range south china which was emplaced during the jurassic cretaceous period the origin composition and pressure temperature conditions of fluids involved in the w sn ore forming processes have been investigated by microthermometry raman spectroscopy la icpms hydrogen isotope analyses of fluid inclusions and oxygen isotope analyses of minerals from the maoping and piaotang w sn deposits for each deposit pre quartz syn wolframite and cassiterite and post ore quartz topaz and fluorite minerals were studied in both deposits the vast majority of fluid inclusions are aqueous with salinities between 0 0 and 12 6 wt equiv nacl and homogenization temperatures between 136 and 349 c a minor proportion 5 of inclusions observed in the ore stage quartz from maoping have aquo carbonic compositions for both deposits four compositional groups are defined early quartz fluid inclusions are characterized by salinities between 0 4 and 9 0 wt equiv nacl trapping temperatures between 150 and 350 c and pressures between 20 and 150 mpa la icpms analyses of these fluid inclusions reveal a wide range of na k and li concentrations as well as relatively low metal contents w at piaotang fluid inclusions in wolframite as well as in post ore quartz and fluorite have salinities of 5 6 to 12 6 wt eq nacl trapping temperatures between 150 and 400 c and pressures of 20 to 150 mpa la icpms analyses of these fluid inclusions reveal similar compositions to early quartz fluid inclusions values of 18o in wolframite and quartz crystals range from 0 8 to 5 2 vsmow while the d values of fluid inclusions range from 66 to 62 vsmow collectively the data suggest the involvement of four aqueous fluid end members mixed episodically in the mineralization process a a low salinity low temperature metal poor low 18o low d fluid derived from meteoric water b a high salinity high temperature metal poor high 18o low d fluid derived from a differentiated peraluminous granitic magma c a high salinity high temperature metal rich lower d magmatic fluid derived from a more differentiated peraluminous granitic magma and d a high salinity high temperature metal rich high 18o low d magmatic fluid this study shows that multiple fluids with distinct magmatic and meteoric origins were involved in the formation of these w sn deposits and that the dilution of metal bearing magmatic fluids by meteoric fluids was probably the main driver for ore deposition the common fluid history of the two deposits studied as well as similarities with other deposits in the jiangxi province points toward common ore forming processes at the regional scale

an infrared spectroscopic ir and light element li be na study of cordierites from the bamble sector south norway abstract infrared absorption spectra and light element contents of several natural cordierites across the arendal amphibolite granulite facies transition bamble sector south norway are presented the infrared spectra record h2o both type i and type ii and co2 as fluid constituents in the channels co and hydrocarbons were not detected type ii water and ca na k are correlated and show a 2 1 molar ratio the infrared and light element data indicate a decrease of na type ii h2o co2 and li with metamorphic grade while type i h2o and be are variable the decrease of these volatiles and alkalies and the low total volatile contents of the granulite facies cordierites are best explained by progressive dehydration and decarbonation processes possibly related to partial melting a progressive change of the x h 2 o h 2 o h 2 o co 2 ratio in the cordierites across the transition as suggested by previous studies is not observed greenschist to low amphibolite facies re equilibrated cordierites show a significant increase in either co2 or h2o co2 na is introduced at some localities the retrograde fluid phase is calculated to be co2 rich

formation and evolution of the hogtuva beryllium deposit norway metagranite in the hogtuva tectonic window nordland norway hosts several spatially restricted be mineralisations with phenakite as the main ore mineral geochronology of magmatic zircon zircon i indicates crystallisation of phenakite bearing and beryl free metaluminous granite at 1787 57 ma and of phenakite and beryl beryl i bearing peraluminous aplites and pegmatites at 1710 59 ma crystallisation of texturally distinct zircon zircon ii cogenetic with fluorite in peraluminous aplites and pegmatites occurred at 434 14 ma during caledonian metamorphism in be mineralised and barren metagranite breakdown of phenakite post dates growth of zircon ii and resulted in the crystallisation of metamorphic hogtuvaite ca2 text fe 3 2 text fe 3 3 si4bealo20 in metaluminous metagranite and metamorphic beryl beryl ii in peraluminous metamorphosed aplites and pegmatites qualitative and quantitative assessment of mineral reactions implies that be has not been mobilised to significant degrees during metamorphism in spite of the presence of a fluorine rich fluid and that phenakite underwent in situ metamorphic reactions hogtuvaite crystallised as a metamorphic phase at the expense of phenakite the anorthite component in albitic plagioclase magnetite and possibly clinopyroxene in peraluminous environments the breakdown of phenakite to metamorphic beryl ii is accompanied by the formation of albite a decreasing activity ratio of a k h in the metamorphic fluid results in the reaction of k feldspar and phenakite to beryl ii further decrease in a k h finally results in complete transformation of the remaining k feldspar into albite the metamorphic breakdown of phenakite in the distinct be mineralisation types at hogtuva is probably controlled by changes in the activities of na k and h in the coexisting metamorphic fluid

wood retention and transport in tropical headwater streams la selva biological station costa rica article i nfo wood in tropical streams has the potential to be more mobile than wood in otherwise similar temperate streams because of the warm and humid conditions that promote decay and the more frequent and flashier floods of the tropics to test this hypothesis we monitored all large wood pieces for 2 3 years in 10 50 m long reaches of old growth headwater streams in la selva biological station costa rica annual wood retention rates for pieces ranged from 0 55 to 0 91 among the sites and retention rates by volume ranged from 0 67 to 0 99 assuming steady state wood load which is reasonable for la selva these rates are equivalent to mean residence times of 2 2 10 6 years for pieces and 3 0 83 2 years for a volume of wood calculating mean residence time from the weighted average of retention rates gives an average residence time of 4 9 years for a piece of wood and 6 9 years for a volume of wood these values are less than those reported for old growth temperate forests supporting our hypothesis mobility of individual pieces was best predicted by piece length relative to stream width lr higher lr led to lower mobility channel gradient s higher s led to higher mobility and piece integration into the channel unattached pieces were 2 6 times more mobile than attached ramp or bridge pieces temporal variation in retention rates was well explained by variation in peak flow all four of these factors have also been observed to influence mobility in the temperate zone the higher mobility of wood in our study site relative to the temperate rainforest of the pacific northwest may be explained by the flashy and frequent floods the high decay rate or the branching morphology of the native trees but differentiating the role of these factors particularly flow and decay will be complicated by their covariation across climates

fluid inclusion and h o c isotope geochemistry of the yaochong porphyry mo deposit in dabie shan china a case study of porphyry systems in continental collision orogens the yaochong porphyry mo deposit in xinxian county henan province china is located in the hong an terrane that is the western part of the dabie orogen the dabie orogen is part of a 1 500 km long triassic continental collision belt between the north china block and the south china block four types of vein are present paragenetically from early to late they are as follows stage 1 quartz k feldspar pyrite magnetite vein stage 2 quartz k feldspar molybdenite pyrite vein stage 3 quartz polymetallic sulfides k feldspar vein and stage 4 quartz carbonate fluorite vein four compositional types of fluid inclusion pure co2 co2 bearing aqueous and solid bearing are present in quartz from the first three stages only low salinity aqueous fluid inclusions occur in quartz from the last stage all the estimated salinities are 13 1 wt nacl eq and no halite crystals were identified homogenization temperatures for the fluid inclusions from stages 1 to 4 are in the ranges of 262 501 202 380 168 345 and 128 286 c respectively and estimated depths decrease from 6 9 to 8 9 km through 6 2 7 2 to 4 7 km quartz separates from the veins yielded a 18o value of 7 7 11 2 corresponding to 18oh2o values of 1 3 to 6 9 using temperature estimates from fluid inclusion data dh2o values of fluid inclusion vary from 80 to 55 and 13cco2 from 2 3 to 2 7 suggesting that the ore fluids evolved from magmatic to meteoric sources we conclude that the ore forming fluid system at yaochong was initially high temperature high salinity and co2 rich and then progressively evolved to co2 poor lower salinity and lower temperature by mixing with meteoric water which results in ore precipitation

premetamorphic lateritisation in proterozoic metabasites of rogaland sw norway heterogeneous layers of granulite facies metamorphic basites of the proterozoic supracrustal faurefjell formation in rogaland s w norway display an extreme chemical variation within a single layer the bulk chemical composition gradually changes from approximately basaltic in basic granulites to alumina iron rich in granofelses component ratios and composition volume relations indicate open system chemical reactions mainly involving the extraction of silica apparent enrichment in fe ti p al zr ni co zn y nb hf and ree and variations in resulting metamorphic mineral assemblages are related to premetamorphic progressive lateritisation of a basaltic protolith the weathering generated a continuous chemical suite from sio2 48 wt fe2o3 10 wt and al2o3 19 wt in the basic granulites to 14 wt 40 wt and 25 wt in the fe al granofelses metasomatism during diagenesis and during very high grade metamorphism 1200 900 ma further perturbed the concentrations of relatively mobile elements ca mg k rb sr ba na and li in the laterites without affecting the transition metal ratios in particular the ree did not fractionate differentially during the supracrustal and metasomatic alteration

flowpaths source water contributions and water residence times in a mexican tropical dry forest catchment summary runoff in forested tropical catchments has been frequently described in the literature as dominated by the rapid translation of rainfall to runoff through surface and shallow subsurface pathways however studies examining runoff generation in tropical catchments with highly permeable soils have received little attention particularly in tropical dry forests we present a study focused on identifying the dominant flowpaths water sources and stream water residence times in a tropical dry forest catchment near the pacific coast of central mexico during the wet season pre event water contributions to stormflow ranged from 72 to 97 with the concentrations of calcium magnesium sodium and potassium closely coupling the geochemistry of baseflow and groundwater from the narrow riparian near stream zone baseflow from the intermittent stream showed a strongly damped isotopic signature and a mean baseflow residence time of 52 110 days was estimated these findings all suggest that instead of the surface and near surface subsurface lateral pathways observed over many tropical catchments runoff is generated through vertical flow processes and the displacement and discharge of stored water from the saturated zone as the wet season progressed contributions from the saturated zone persisted however the stormflow and baseflow geochemistry suggests that the contributing area of the catchment increased our results show that during the early part of the wet season runoff originated primarily from the headwater portion of the catchment as the wet season progressed and catchment wetness increased connectivity among sub basin was improved resulting in runoff contributions from across the entire catchment

lithogeochemical studies of aureoles around the panasqueira tin tungsten deposit portugal multi element lithogeochemical surveys of aureoles surrounding tin tungsten bearing quartz vein systems have been utilized infrequently in exploring for these deposits at panasqueira beira beixa portugal a wrich quartz vein mineralization occurs in the beira schists surrounding a greisenized cupola and offers a suitable test case for such lithogeochemical studies therefore shale samples were collected at a density of about 6 samples per km2 pronounced anomalies of tin and tungsten have been detected in these samples together with those of other elements coeval with the mineralizing processes

non pegmatitic deposits of beryllium mineralogy geology phase equilibria and origin non pegmatitic occurrences of be minerals constitute a diverse set of geologic environments of considerable mineralogical and petrological interest they currently provide the majority of the world s be ore and emeralds and they contain the greatest resource of these commodities of the approximately 100 be minerals known see chapter 1 by grew appendix a most occur in hydrothermal deposits or non pegmatitic igneous rocks where their distribution varies systematically with the setting and origin table 1 fig 1 view this table table 1 beryllium minerals in non pegmatitic deposits formulas use and occurrence 1 figure 1 chemography of the principal solid phases in the beo al2o3 sio2 h2o f2o 1 bash system with the projected positions of helvite group and alkali be silicates also shown are generalized fields for some of the major types natural of occurrences cf table 1 fig 4 see text for discussion beryllium minerals are best known from geologic systems associated with felsic magmatism they also occur in a variety of settings that lack evident igneous associations environments range from the surface to the deep crust and host rocks range from feldspathic to carbonate to ultramafic in composition genetically related igneous rocks are felsic and share low calcium and high f contents but are diverse in composition setting and origin compositions range from strongly peraluminous to peralkaline and can be silica undersaturated beryllium minerals also occur in metamorphic and basinal environments and are redistributed by surface processes table 2 summarizes the types and significance of major groups of occurrences by their lithologic associations figure 2 shows the global distribution of some important examples and regional belts for most types at least one example has been described in some detail and can be used to help evaluate general patterns however

geochemical characteristics of granites associated with proterozoic molybdenite mineralization in northern sweden abstract proterozoic molybdenite occurrences in northern sweden are associated with small plutons of intrusive character located in supracrustal belts whereas large granite areas are barren in this study 152 samples of granites associated with molybdenite mineralization mineralized aplites granites not known to be associated with molybdenite occurrences but located in supracrustal belts and granites from the large granite areas have been analysed for major elements and the selected trace elements mo sn be ba rb sr cu zn zr v y nb f cl and s the study showed that major element geochemistry and modal composition are not useful for distinguishing between potentially molybdenite mineralizing and barren granites in northern sweden enriched contents of sn be y rb and f are most useful for identifying ore associated granites in the supracrustal belts the granites from the large granite areas have very low contents of sn mo be nb y f cl and s it is proposed that the granites associated with molybdenite occurrences were probably generated by partial melting of earlier igneous rocks or they may be of subcrustal origin the large granite bodies originated by partial melting of archean continental crust

geology geochemistry and genesis of the qianfanling quartz vein mo deposit in songxian county western henan province china abstract the qianfanling mo deposit located in songxian county western henan province china is one of the newly discovered quartz vein type mo deposits in the east qinling dabie orogenic belt the deposit consists of molybdenite in quartz veins and disseminated molybdenite in the wall rocks the alteration types of the wall rocks include silicification k feldspar alteration pyritization carbonatization sericitization epidotization and chloritization on the basis of field evidence and petrographic analysis three stages of hydrothermal mineralization could be distinguished 1 pyrite barite quartz stage 2 molybdenite quartz stage 3 quartz calcite stage two types of fluid inclusions including co 2 bearing fluid inclusions and water rich fluid inclusions have been recognized in quartz homogenization temperatures of fluid inclusions vary from 133 c to 397 c salinity ranges from 1 57 to 31 61 wt nacl eq there are a large number of daughter mineral co 2 bearing inclusions which is the result of fluid immiscibility the ore forming fluids are medium high temperature low to moderate salinity h 2 o nacl co 2 system the 34 s values of pyrite molybdenite and barite range from 9 3 to 7 3 9 7 to 7 3 and 5 9 to 6 8 respectively the 18 o values of quartz range from 9 8 to 11 1 with corresponding 18 o fluid values of 1 3 to 4 3 and 18 d values of fluid inclusions of between 81 and 64 the 13 c v pdb values of fluid inclusions in quartz and calcite have ranges of 6 7 to 2 9 and 5 7 to 1 8 respectively sulfur hydrogen oxygen and carbon isotope compositions show that the sulfur and ore forming fluids derived from a deep seated igneous source during the peak collisional period between the north china craton and the yangtze craton the ore forming fluids that derived from a deep igneous source extracted base and precious metals and flowed upwards through the channels that formed during tectonism fluid immiscibility and volatile exsolution led to the crystallization of molybdenite and other minerals and the formation of economic orebodies in the qianfanling mo deposit

isotopic and textural discrimination between hypogene ancient supergene and modern sulfates at the questa mine new mexico abstract chemical and mineralogical changes due to pyrite weathering are of interest with respect to understanding long term physical stability of mine rock piles at the questa mine new mexico the ability to discriminate between ancient and modern processes is important for establishing the extent of modern weathering within the piles initial inventories of sulfur minerals and representative isotope compositions in rocks from orebodies the hydrothermal alteration zones associated with orebodies hydrothermal alteration scars and mine rock piles were determined ore body sulfides have 34 s cdt of 0 4 typical for sulfides formed by magmatic processes in stockwork mo systems pyrite from alteration scars has a wide range of 34 s values from 0 0 to 13 6 sulfate from the ore body has markedly positive 34 s 5 10 accompanied by positive 18 o so 4 values 6 15 reflecting equilibrium formation from magmatic fluids sulfates from alteration scars have 34 s values over a broad range similar to alteration scar pyrites from 10 6 to 0 and 18 o so 4 of 0 3 sulfates with fine grained delicate and euhedral mineral habits suggesting recent formation within the mine rock piles have 34 s values similar to orebody pyrite and alteration scars but more negative 18 o so 4 values 3 to 10 sulfates from all three sources occur in these piles and their stable isotope values have proven useful in differentiating them and their environments of formation i e hypogene ancient supergene and recent weathering correlating the isotopic compositions with textures allows petrographic assessment for the origins of sulfate minerals in the rock piles but this must be applied with caution because some sulfate mineral recycling has occurred

the chalukou deposit in the north great xing an range of china a protracted porphyry mo ore forming system in a long lived magmatic evolution cycle abstract the chalukou deposit is located in the north great xing an range of the xing an mongolia orogen bordering and to the northeast of the north china craton the deposit is a high f type porphyry mo deposit hosted by the chalukou composite igneous body containing small intrusive bodies genetically related to mo mineralization the composite igneous body includes pre mineralization dolerite monzogranite and syenogranite syn mineralization rhyolitic porphyry granitic porphyry and fine grained monzogranite and post mineralization rhyolitic porphyry quartz porphyry dioritic porphyry and andesitic porphyry detailed laser ablation inductively coupled plasma mass spectrometry la icp ms u pb zircon dating of the igneous components of the composite igneous body was carried out to determine the temporal framework for magmatism in the chalukou region the new la icp ms u pb ages constraint documented here together with the published ages indicate that there was a protracted porphyry mo ore forming event of approximately 7 million years between ca 152 when the ore related rhyolitic porphyry was emplaced and ca 145 ma when molybdenite ceased being deposited the dating reveals that the mineralization is a part of relatively long lived magmatic cycle involving the emplacement of small doleritic stocks at ca 165 ma that progressively evolved into extensive granitic intrusions at ca 164 ma and then diminished with the emplacement of mineralization related porphyries to ca 152 ma the emplacement of barren early cretaceous magmatism represented by volcanic units in the ca 136 ma guanghua formation and porphyries followed the mineralized magmatism the syn mineralization porphyry units associated with mo contain zircons assaying 15 times higher in u and th than the pre mineralization magmatic phases this indicates that there was a significant enrichment of mo u and th in the magma and directly associated with ore fluid exsolution the return to their normal levels in the three elements in the post mineralization magmatic phases indicates that they were exhausted from the magma chamber in the later phases a genetic model is proposed for the enormous introduction of ore metals and enrichment at the chalukou deposit the protracted and multiphase igneous activity during the long lived magmatism reflects a multistage enrichment of metal and may play a crucial role in the formation of a volatile enriched fertile and large volume magma chamber beneath the chalukou deposit such a chamber is envisaged to be required for the formation of porphyry mo deposits in general

recognition of a hidden mineral deposit by an artificial intelligence program a computer program that uses artificial intelligence techniques has successfully identified the location of a porphyry molybdenum deposit given geological maps of readily available predrilling exploration data for mount tolman in washington state and using rules obtained from a porphyry molybdenum exploration specialist the program called prospector identified the location of previously unknown ore grade mineralization this appears to be the first reported determination of the location of mineralization by such a computer based approach

overland flow generation in two lithologically distinct rainforest catchments streams on uniformly rainforest covered but lithologically very diverse barro colorado island in central panama show remarkable differences in their runoff response to rainfall this lithological diversity is reflected in equally diverse soilscapes and our objective was to test the hypothesis that contrasting runoff responses derive from soilscape features that control the generation of overland flow we determined the soil saturated hydraulic conductivity ks of two neighboring but hydrologically contrasting catchments lutz creek with a flashy and conrad trail with a delayed response to rainfall and quantified the spatial and temporal frequency of overland flow occurrence the median ks values at a depth of 12 5 cm are large enough to rule out hortonian overland flow but a marked decrease in ks in lutz creek catchment at 30 cm suggests the formation of a perched water table and the generation saturation overland flow the decrease in ks in the conrad trail catchment is more gradual and a perched water table is expected to form only at depths below 50 cm in lutz creek overland flow was generated frequently in time and space and regardless of topographic position including near the interfluve with very low thresholds of storm magnitude duration intensity and antecedent wetness whereas in conrad trail overland flow was generated much less frequently and then only locally we conclude that soilscape features and microtopography are important controls of overland flow generation in these catchments our results contribute to the growing evidence that overland flow and forests are not a priori a contradiction in terms

determination of beryllium and its distribution in rocks of the snw granite of regoufe northern portugal abstract the determination of be by electrothermal atomic absorption spectrometry with zeeman background correction zetaas is compared with the determination by inductively coupled plasma emission spectrometry icpes the samples are decomposed with a hf hcio 4 hno 3 method both methods compare well though the results by zetaas are generally 2 ppm higher than the icpes values especially icpes results are in good agreement with the accepted values for international reference samples zetaas has a lower detection limit than icpes the methods were tested on 55 samples of the regoufe granite northern portugal the average for the regoufe granite is 17 ppm be and the values range from 4 to 57 ppm be the granite may be regarded as be specialised the distribution is compared with those of the elements ti p rb sr cu zn u sn w ta nb f li and cs and with major minerals in the granite feldspars and micas correlations with be were generally low from theoretical considerations and from statistical data it is concluded that be is enriched in the final stages of the magma crystallisation and was mobile in all the major late and post magmatic processes in the granite

fluid immiscibility in natural processes use and misuse of fluid inclusion data abstract many occurrences of fluid immiscibility in natural geologic systems have been reported recently most often from fluid inclusion studies however the interpretation of fluid inclusion data in terms of immiscibility sometimes suffers from ambiguity of the vocabulary insufficient knowledge of the immiscibility constraints and insufficient knowledge of the topology in the tpx space of natural fluid systems for such reasons some authors have been misled to erroneous interpretations the term chemical immiscibility is unambiguously redefined as a multiphase multicomponent equilibrium the consequences of this definition are directly derived from the phase rule and concern the possible equations that relate the various parameters temperature pressure volumes compositions to each other these equations already put constraints on the topology of the phase equilibria in fluid systems a particular expression of the phase rule is proposed which takes into account the multiphase constant bulk volume constant bulk composition constraints in fluid inclusions the consequences of such an expression are of major importance in fluid inclusion studies the phase relations of some simple systems that approximate quite efficiently the natural complex fluids are then detailed h2o nacl co2 ch4 h2o co2 h2o co2 nacl the effects of these topologies and of the supplementary constraints constant bulk composition and constant bulk volume assumed for fluid inclusions isopleth isochoric systems are discussed

fluid inclusion gas studies carrock fell tungsten deposit england implications for regional exploration a fluid inclusion investigation of the carrock fell tungsten deposit northern england confirms that the quartz wolframite scheelite veins associated with the caledonian skiddaw granite are almost exclusively related to an exocontact hydrothermal system developed at the margin of a local cupola fluid circulation as defined by the spatial variation in temperature and h2o co2 ratios for inclusions in vein quartz reveals a strong structural control the zone of maximum flow which extends 0 400 m out from the granite contact is characterised by high h2o co2 ratios and corresponds closely with the known distribution of high grade oreshoots based on the fluid inclusion gas signature for the carrock fell deposit a distinction can be made between potentially tungstaniferous quartz veins and those related to cu pb zn deposits in the absence of diagnostic ore minerals also a regional survey of quartz veins in the lake district suggests that at several localities the fluids have a close affinity with those at carrock fell this is interpreted as the high level distal expression of tungsten mineralisation at depth evidence for similar mineralisation elsewhere in the british caledonides favours those granites in the paratectonic zones of ireland and southern scotland

nitrogen isotope record of fluid rock interactions in the skiddaw aureole and granite english lake district the skiddaw granite and its contact metamorphic aureole in the english lake district provide an excellent opportunity to test the capability of the n isotope system to trace devolatilization and large scale transfer of crustal fluids in the aureole skiddaw group metasedimentary rocks with relatively uniform lithology and major element compositions show a dramatic decrease in n content toward the granite contact from or 800 ppm at distances 2 5 km from the contact to 1 5 km these rocks have extremely uniform delta 15 n air near 3 7 per mil whereas closer to the contact or 1 km delta 15 n is shifted to higher values up to 8 7 per mil the coupled decreases in n content and increases in delta 15 n are compatible with the removal of n having low delta 15 n in fluids during continuous prograde devolatilization reactions involving the break down of white mica and the stabilization of biotite cordierite and andalusite bearing assemblages in the same metasedimentary rocks the lack of obvious trends in major element concentrations including sio 2 tio 2 sio 2 al 2 o 3 and the ratios of other major oxides to tio 2 and al 2 o 3 with distance from the granitic contact is consistent with minimal change in major element composition during the contact metamorphism ratios of whole rock n b rb and ba concentrations to whole rock k 2 o content are believed to reflect the differing fluid mica partitioning and involving varying relative proportions of white mica and biotite of these trace elements during devolatilization reactions greisenized skiddaw granite from a borehole is enriched in n range of 17 225 ppm for whole rocks and white mica separates relative to the unaltered granite whole rock 30 ppm and has delta 15 n of 1 0 to 4 8 per mil the n concentrations and delta 15 n of the wall rocks and greisenized granites combined with c isotopic data carbonate and carbonaceous matter for the same rocks are consistent with the mobilization of fluids having low delta 15 n and delta 13 c pdb values from the devolatilized aureole into the cooling intrusive body such transport is consistent with the predictions of recent theoretical models of late stage hydrothermal evolution in cooling intrusive systems

topographic controls on overland flow generation in a forest an ensemble tree approach summary overland flow is an important hydrological pathway in many forests of the humid tropics its generation is subject to topographic controls at differing spatial scales our objective was to identify such controls on the occurrence of overland flow in a lowland tropical rainforest to this end we installed 95 overland flow detectors ofds in four nested subcatchments of the lutzito catchment on barro colorado island panama and monitored the frequency of overland flow occurrence during 18 rainfall events at each ofd location temporal frequency for each such location we derived three non digital terrain attributes and 17 digital ones of which 15 were based on digital elevation models dems of three different resolutions these attributes then served as input into a random forest ensemble tree model to elucidate the importance and partial and joint dependencies of topographic controls for overland flow occurrence lutzito features a high median temporal frequency in overland flow occurrence of 0 421 among ofd locations however spatial temporal frequencies of overland flow occurrence vary strongly among these locations and the subcatchments of lutzito catchment this variability is best explained by 1 microtopography 2 coarse terrain sloping and 3 various measures of distance to channel with the contribution of all other terrain attributes being small microtopographic features such as concentrated flowlines and wash areas produce highest temporal frequencies whereas the occurrence of overland flow drops sharply for flow distances and terrain sloping beyond certain threshold values our study contributes to understanding both the spatial controls on overland flow generation and the limitations of terrain attributes for the spatially explicit prediction of overland flow frequencies

the source and significance of argon isotopes in fluid inclusions from areas of mineralization argon isotopes in fluid inclusions in quartz veins associated with granite hosted tungsten mineralization in the southwest and north of england have been investigated in detail by the40ar 39ar technique the natural argon is present as a number of discrete components which can be identified through correlations with39ar 38ar and 37ar induced by neutron bombardment of potassium chlorine and calcium the potassium correlated component arises principally from in situ decay of potassium in solid phases in the inclusions in the case of the hemerdon tungsten deposit of southwest england the phases responsible are small 25 m captive authigenic micas which are shown to have been deposited from a fluid 268 20 ma ago shortly after the emplacement of the host granite the chlorine correlated component is present in the brines which constitute the fluid phase of the inclusions the argon in these hydrothermal fluids is made up in part of parentless or excess 40ar leached from surrounding crustal rocks and in part of dissolved ancient atmospheric argon absolute concentrations of both atmospheric and excess components in the brine can be estimated from 40arcl ratios and independent determinations of the salinity of the inclusions the absolute concentrations of the atmospheric argon are close to those found in modern meteoric water while those of the excess component can be interpreted in terms of the degree of interaction betwen the circulating fluids and country rock a calcium correlated component with a much higher ratio of excess to atmospheric argon than that in the brine was found to be a dominant phase in one sample from the hemerdon deposit indicating the presence of a solid phase probably a caso4 daughter mineral inclusions of this composition represent fluids which have had a more prolonged interaction with crustal rocks the results obtained from this study provide a systematization and a framework for future multi component argon studies of fluid inclusions together with an indication of the wide range of information which can be inferred

trace element geochemistry of molybdenite from the shapinggou super large porphyry mo deposit china abstract the shapinggou deposit located in the dabie orogenic belt eastern china is one of the largest mo only porphyry deposits in the world alteration types associated with shapinggou include silicic potassic silicic phyllic propylitic and argillic the phyllic alteration can be subdivided into quartz and sericite mainly muscovite phases whereas the argillic alteration is distinguished by poorly crystallized kaolinite kaolinite px muscovite and phengite the ore forming event can be divided into quartz k feldspar quartz molybdenite quartz sericite and quartz fluorite gypsum stages with molybdenite deposited in the first three stages but mainly in the second the molybdenites in shapinggou represent either the 2h1 and or the 2h1 3r polytype and can be subdivided into two groups group one and group two group 1 is associated with stage 1 alteration whereas group 2 is found with stages 2 and 3 there is an increase in the re values from group one to group two with the re contents likely controlled by both the crustal metal source and temperature with decreasing temperature the contents of re and the ratios of mo cu in molybdenites in shapinggou decrease gradually whereas the contents of cu and w sn and the ratios of re cu co ni increase the pb zn values in molybdenite are higher in the porphyry mo deposit associated with pb zn deposits than in porphyry cu mo mo deposits not associated with pb zn deposits the ratios of cl f so2 h2s and h k in the shapinggou fluids increasing over time suggest that the fluids became more oxidised the initial ore forming fluid was 500 c carried ions of mo ca na k cl f s and caused potassic silicic alteration with deposition of only small amounts of molybdenite as the temperature dropped down to 400 c the amounts of mo k cu and cl ions in the fluid decreased leading to silicic sericitic and propylitic alteration and the deposition of the majority of the molybdenite as the temperatures decreased to 300 c the fluid contained ions of ca and f and pb zn was deposited distally around the main mo ore body