major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

the origin of hematite in high grade iron ores based on infrared microscopy and fluid inclusion studies the example of the conceicao mine quadrilatero ferrifero brazil petrographic and textural analysis combined with fluid inclusion studies by infrared microscopy of high grade 65 fe hematite ore samples from the conceicao deposit in the northeastern part of the quadrilatero ferrifero brazil indicate a complex process of oxidation and mineralization during two orogenic events each developed under different conditions and involving distinct fluids the earliest mineralization formed massive magnetite rich orebodies under relatively reducing conditions in the early stages of the transamazonian orogeny magnetite was oxidized martitized with the development of porous hematite crystals hematite i possibly during this stage new hematite crystals were also formed from low temperature low to medium salinity fluids as indicated by two phase fluid inclusions the origin of these fluids is still uncertain but tentatively interpreted as being modified surface water the fluids were transported along normal faults and fractures during post tectonic collapse following the transamazonian orogeny 2 1 2 0 ga and creation of the dome and keel structural pattern of the quadrilatero ferrifero these solutions were also likely responsible for the initial oxidation of the iron formations and the development of hematite i subsequent uplifted hot basement rocks or post tectonic plutons were probable heat sources for the regional metamorphism and development of a granoblastic fabric of hematite ii grains in the iron formations and high grade orebodies however the ore was only partially recrystallized as several relics of the early magnetite martite and hematite are still preserved in the granular hematite ii crystals during the brasiliano pan african orogeny 0 8 0 6 ga high salinity fluids with temperatures varying from 120 to a maximum of approximately 350 c penetrated the iron formations along shear zones crystallizing initially tabular and thereafter platy hematite crystals hematite iii and specularite forming schistose orebodies quartz veins that cut across the ore and envelop specularite plates and ore fragments formed from late stage high temperature and low salinity fluids containing co2 these later fluids did not alter the ore each of these stages of mineralization produced orebodies with distinct features recurrent hydrothermal mineralization is thought to have been responsible for the development of giant high grade iron ore deposits in structurally favorable sites fold hinges with enhanced permeability and deep faults able to conduct the fluids to the surface repeatedly over time should be important targets for exploration of new resources

geochemistry of cassiterite and wolframite from tin and tungsten quartz veins in portugal cassiterite and wolframite compositions from snnw and wnsn bearing quartz veins in northern and central portugal are compared to provide evidence on fluid compositions in snnw bearing quartz veins euhedral cassiterite shows sequences of alternating parallel darker and lighter zones the darker zones are pleochroic oscillatory zoned exhibit exsolutions of columbite and ixiolite and are richer in nb ta and fe than the lighter zones which consist of nearly pure sno2 cassiterite from wnsn bearing quartz veins is usually zoned with homogeneous and slightly pleochroic darker zones which are chemically similar to lighter zones bothzoneshaveinclusionsofrutileandrareilmenite thedarkerzonesofcassiteritefrom theformer veins arericherin nb taandfe contents and poorer in ti than the darker and lighter zones of cassiterite from the latter veins this is attributed to differences in the composition of magmatic hydrothermal fluids wolframite compositions from snnw and wnsn bearing quartz veins do not show any significant distinction because they precipitate from relatively similar magmatic hydrothermal fluids in some deposits most wolframite crystals are homogeneous but others are heterogeneous inner patches rich in a hubnerite component rarely occur in crystals from the filharoso and panasqueira deposits zoned crystals showing an increase in fe and a decrease in mn from core to rim were found in the vale das gatas deposit complex oscillatoryzonedcrystals occur inthe carris deposit later wolframite contains inclusions ofscheelite partially replaces itand is richer in fe and poorer in mn than earlier wolframite wolframite from snnw bearing quartz veins in the argozelo deposit and wnsn bearing quartz veins from vale das gatas and panasqueira deposits has significant nb content this does not depend on the fe and mn content of the wolframite but w content is negatively correlated with nb content only very rare single crystals of wolframite show an increase in w and a decrease in nb from core to rim snnw bearing quartz veins contain wolframite poorer in nb than the darkerzones of cassiterite which exsolved columbite andixiolite inwnsn bearing quartz veins from panasqueira and vale das gatas the wolframite has a higher nb content than the cassiterite which contains rutile inclusions enriched in nb because cassiterite and wolframite are derived from two distinct magmatic hydrothermal fluids of different age the fluid responsible for wolframite precipitationwillhaveasimilarcompositiontothatresultingfromtheevolutionofthefluidresponsibleforcassiteriteprecipitationinthe

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

observations of rip spacing persistence and mobility at a long straight coastline three years of daily video observations at a long straight beach were analysed to determine the temporal trends and variability of the location spacing persistence and mobility of rips rips were identified at this site on 684 days of the total 947 days 72 occurrence when suitable images were available a median number of 7 rips were observed within the total 2 km study area on days when rips were present no tendency was identified for rips to reoccur in preferred locations alongshore following storm reset events the average alongshore distance between all rips observed was 209 m but with a high standard deviation of 98 m or approximately 47 of the mean rip spacing there was no evidence at this site that rips tended to be regularly spaced alongshore no clear relationship was identified between the number of rips and the prevailing offshore wave conditions including significant wave height peak wave period and incident wave power the majority of rips persisted for 5 or fewer days with an average of 8 days and standard deviation of 9 days rips were stationary 33 of days with migration rates of less than 5 m day observed on 47 of days when rips were present maximum migrations rates of up to 50 m day were observed and generally though not always occurred in the direction consistent with the prevailing offshore swell direction and resulting alongshore current the occurrence of inshore sea breezes may have accounted for the less frequent observations of rip migration against the opposing regional swell direction the results presented at this site complement a recent four year study at a contrasting short and embayed beach detailed in holman et al holman r a symonds g thornton e b and ransinghe r 2006 rip spacing on an embayed beach journal of geophysical research 111 c01006 doi 10 1029 2005 jc002965 17p the specific mechanism s of rip channel infilling at the long straight and littoral drift dominated coastline may have contributed to the observation of shorter rip persistence relative to the embayed site mean rip spacing was observed at both sites to be highly variable irregular and exhibited no identifiable trend associated with the offshore wave conditions this latter observation supports the notion that rips may become rapidly topographically controlled soon after a storm reset event and their location is then primarily determined by the evolving nearshore morphology rather than hydrodynamic forcing this new dataset of daily multi year observations at an open coast site cannot be reconciled with the majority of existing template and instability models for rip formation that predict a relationship between incident wave conditions and regular spacing of rips alongshore rather these observations tend to support emerging theories of rip genesis that predict the irregular and random spacing of rip channels alongshore

linear modeling of infragravity waves during delilah 1 the generation of infragravity waves by directionally spread shortwaves incident on an alongshore uniform beach is investigated two mechanisms responsible for the generation of infragravity waves are considered the release of the bound infragravity waves associated with changes in the spatial variation of the incident shortwave energy and the forcing of trapped waves by obliquely incident directionally spread shortwaves the infragravity wave response is examined using linear shallow water equations taking into account the presence of bottom friction setup of the mean water level rollers and longshore current summing all infragravity contributions due to difference interactions between pairs of shortwave spectral components with the same frequency difference results in infragravity energy density spectra calculated spectra are compared with measured spectra obtained during the delilah field experiment for 11 consecutive days including calm mild and storm conditions in the comparison attention is focused on the frequency distribution of the infragravity energy density throughout the surf zone and the transformation of the root mean square infragravity wave height the measured infragravity response in the frequency range from 0 01 to 0 06 hz is reproduced by the computations with relatively broad spectra offshore and a clear nodal structure closer to shore typically 80 of the infragravity wave height variability is explained by the model of which 30 or less is due to bound infragravity waves differences occur mainly during storm events in which the infragravity energy is underpredicted in the outer surf zone and overpredicted in the inner surf zone

effect of hydrodynamics and bathymetry on video estimates of nearshore sandbar position remote sensing of wave breaker patterns clearly visible as high intensity bands in time exposure video images has become a powerful tool to obtain large scale kilometers and long term years time series of nearshore sandbar position however intensity based bar crest positions xi differ from directly measured positions xb by a time varying distance x which is of o 10 m and depends on the offshore wave height h0 the water level 0 and the bathymetry itself the effect of these parameters on x was investigated from simultaneous video observations and bathymetric surveys obtained in the double barred system at egmond aan zee netherlands and from wave model predictions assuming that the roller energy represents image intensity when the wave field over a bar was predicted to be nonsaturated xi was observed and predicted to move offshore as either 0 decreased or h0 increased under saturated conditions x only responded to changes in 0 additional model investigations showed that an increase in outer bar crest depth similar to that observed during interannual bar behavior significantly reduced the x variability at the outer bar and increased the x variability at the inner bar implications of our observational and model findings for studying sandbar position from video imagery are outlined

rip spacing and persistence on an embayed beach 1 four years of daily time exposure images from an embayed beach were examined to study the spacing persistence and location preferences of rips in a natural rip channel system a total of 5271 rip channels was observed on 782 days occurrence statistics showed no evidence of the preferred location pattern associated with standing edge waves trapped in an embayed beach the histogram of rip spacing the primary diagnostic observable for most models was well modeled by a lognormal distribution mean spacing of 178 m however spacings were highly longshore variable time mean of the standard deviation longshore mean of rip spacing was 39 so they are of questionable merit as a diagnostic variable storm driven resets to the longshore uniform condition required by most models occurred only four times per year on average making rip generation models relevant to only a small fraction of the system behavior rip spacings after the 15 observed reset events were uncorrelated with bar crest distance the lifetime of the 324 individual rip channel trajectories averaged 45 6 days rips were equally mobile in both longshore directions but the coefficient of variation of rip migration rates was large even for high migration rates the mean migration rate was well correlated to a proxy for the longshore current r2 of 0 78 thus there is no significant evidence that the formation spacing and migration of rip channels on this beach can be explained by currently existing simple models moreover the alongshore uniform initial conditions assumed by these models are rare on palm beach making the models generally inapplicable

the influence of sea state on formation speed of alongshore variability in surf zone sand bars abstract the formation time of alongshore morphological variability in surf zone sand bars has long been known to differ from one beach to the other and from one post storm period to another here we investigate whether the type of sea state i e distant swell waves or locally generated short period wind sea affects the formation time of the emerging alongshore topographic variability a numerical modeling approach is used to examine the emergence of alongshore variability under different shore normal wave forcing a research version of delft3d operating on the time scale of wave groups is applied to a schematised bathymetry with a single bar the model is then used to investigate several wave scenarios examining the impact of peak period frequency spread and directional spread on the formation time of alongshore variability results show that an increase in wave period has a large effect changing the formation time up to o 250 in case the wave period is changed from a representative value for the dutch coast t p 5 6 s to an australian south east coast value t p 10 12 s in contrast modifications in the directional and frequency spread of the wave field result only in a minor change in the formation time examination of hydrodynamics and potential sediment transport shows that the variations in formation time are primarily related to changes in the magnitude of the time averaged flow conditions variations in the magnitude of very low frequency f f these findings indicate that the development of alongshore topographic variability may be faster at swell dominated open coasts primarily due to the occurrence of longer period swell also at a given site the arrival of a long wave period swell after a storm can accelerate the emergence of variability

a morphological stability analysis for a long straight barred coast a morphological stability analysis is carried out for a long straight coast with a longshore bar the situation with oblique wave incidence and a wave driven longshore current is considered the flow and sediment transport are described by a numerical modelling system the models comprise i a wave model with depth refraction shoaling and wave breaking ii a depth integrated model for wave driven currents and iii a sediment transport model for the bed load transport and the suspended load transport in combined waves and current the direction of the sediment transport is taken to be parallel to the depth integrated mean current velocity neglecting the effects of a bed slope and secondary currents an instability is found to develop around the bar crest the instability is periodic in the alongshore direction and tends to form rip channels and to steepen the offshore face of the bar between the rip channels the alongshore wave length of the most unstable perturbation is determined for different combinations of the wave conditions and the geometry of the profile

comparison of fluid inclusions in coexisting cogenetic wolframite cassiterite and quartz from st michael s mount and cligga head cornwall england abstract the st michael s mount occurrence and cligga head deposit are typical examples of w sn mineralization in the cornwall district in s w england mineralization consists of quartz wolframite cassiterite and various amounts of base metal sulfides in sheeted veins associated alteration includes greisenization and argillization in both areas textural evidence for contemporaneous deposition of the ore minerals wolframite and cassiterite with quartz is generally ambiguous previous studies state that the quartz and wolframite are intergrown but do not address the genetic relation between them in this study microthermometry was performed on fluid inclusions in wolframite cassiterite and quartz the inclusions in wolframite were observed using an infrared microscope and those in cassiterite and quartz were observed with visible light at st michael s mount th values for primary inclusions in quartz average 311 c and in wolframite average 369 c salinities average 7 3 eq wt nacl in quartz and 4 2 eq wt nacl in wolframite at cligga head the average th values for primary inclusions in the various minerals are cassiterite 352 c wolframite 324 c and quartz 295 c fluid inclusion salinities average 5 3 eq wt nacl in cassiterite 3 9 eq wt in wolframite and 6 0 eq wt nacl in quartz the magnitude of the changes in th measurements between minerals cannot be accounted for by post trapping changes and therefore must be due to actual differences in the temperatures of deposition these data suggest that the ore minerals wolframite and cassiterite were deposited earlier than the associated quartz even though conclusive textural evidence is lacking wolframite and cassiterite were deposited at about the same temperature at st michael s mount but at cligga head cassiterite was deposited at higher temperatures than wolframite certainly in these areas the gangue minerals do not provide reasonable estimates of the depositional conditions of the ore minerals even though they are intimately intergrown

modeling the alongshore current on barred beaches mean alongshore currents observed on two barred beaches are compared with predictions based on the one dimensional time and depth averaged alongshore momentum balance between forcing by breaking waves wind and 10 100 km scale alongshore surface slopes bottom stress and lateral mixing the observations span 500 hours at egmond netherlands and 1000 hours at duck north carolina and include a wide range of conditions with maximum mean currents of 1 4 m s including rollers in the wave forcing results in improved predictions of the observed alongshore current structure by shifting the predicted velocity maxima shoreward and increasing the velocity in the bar trough compared with model predictions without rollers for these data wave forcing balances the bottom stress within the surfzone with the other terms of secondary importance the good agreement between observations and predictions implies that the one dimensional assumption holds for the range of conditions examined despite the presence of small alongshore bathymetric nonuniformities with stronger bathymetric variations the model skill deteriorates particularly in the bar trough consistent with earlier modeling and laboratory studies

fluid inclusions and hear isotopes in pyrite from the yinjiagou deposit in the southern margin of the north china craton a mantle connection for poly metallic mineralization abstract the yinjiagou poly metallic deposit is located at the southern margin of the north china craton smncc pyrite the most economically important mineral is associated with cu mo au pb zn and ag mineralization two main mineralization stages have been identified and studied a porphyry stage including the quartz molybdenite and quartz sericite pyrite qsp veins and a vein stage including the early and the late economically most important pyrite stages three types of fluid inclusions are distinguished in quartz and pyrite including liquid rich vapor rich biphase lv and halite bearing inclusions the transmitted and infrared microthermometry produced several results 1 each of the three types of fluid inclusions is trapped in the quartz of the porphyry stage with homogenization temperatures of 335 419 c and salinities of 4 7 49 6 wt nacl equiv the coexistence of halite bearing inclusions and low density vapor rich biphase lv inclusions indicates that the fluid was boiling the boiling elevated the fe and s levels in the hyper saline fluid as reflected by the development of pyrite chalcopyrite and s daughter minerals in the halite bearing inclusions 2 the fluid in the early pyrite also displays features characteristic of boiling with homogenization temperatures of 352 400 c and salinities of 3 7 42 4 wt nacl equiv whereas the late pyrite only contains liquid rich biphase lv inclusions with homogenization temperatures of 263 354 c and salinities of 6 0 21 3 wt nacl equiv the relationship between the decreasing salinity and the corresponding decreasing homogenization temperature clearly indicates extensive mixing and dilution 3 finally the infrared calibration indicates that the impact of infrared light intensity on the microthermometric results for the yinjiagou pyrite hosted fluid inclusions is limited the he ar isotopic analysis of the fluid inclusions in the pyrite indicates two different fluid sources that involve abundant mantle input the 3he 4he ratios in the porphyry stage are relatively uniform ranging from 1 39 to 1 78 ra ra 1 39 10 6 for air corresponding to 16 22 mantle 4he contribution this relatively constant range represents the actual helium isotopic composition of the fluids emanating from the cooling intrusions at depth the range of 3he 4he ratios in the vein stage is wide varying from 0 80 to 5 26 ra corresponding to 9 65 mantle 4he the significant variation in the 3he 4he ratios in the vein stage reflects mixing between two fluids these data indicate that there are two different fluid sources and separate evolutionary processes for the porphyry and vein stages and support a multi stage mineralization model the veinlet molybdenite mineralization was induced by the boiling and associated cooling of a magma sourced fluid that emanated from intrusions at depth the qsp veins are likely to be pressure release zones and late fluid flow channels the early pyrite mineralization may be attributed to the influx of a dominantly mantle derived fluid with high 3he 4he ratio 5 26 ra which is most likely related to a later more mafic magmatic event the precipitation of the most economically important pyrite resulted from the mixing and diluting of this mantle derived fluid with a surface derived fluid additionally the high 3he 4he ratios indicate a strongly extensional setting which is most likely related to the late jurassic to early cretaceous lithospheric modification and thinning of the smncc

refined insight into 40ar 39ar progressive crushing technique from k cl ar correlations in fluid inclusions abstract hydrothermal fluid activity associated with geological processes can now be dated by 40ar 39ar progressive crushing of minerals thanks to recent advances in high precision mass spectrometry however methods of data analysis and interpretation for these high resolution measurements still need to be refined in this study we report further insights into using k cl ar diagrams as tools for interpreting ages of secondary and primary fluids from 40ar 39ar stepwise crushing experiments three paragenetic mineral pairs of muscovite and wolframites from a southern china tungsten deposit were investigated using the 40ar 39ar technique through laser incremental heating and progressive crushing of single minerals incremental heating analyses of muscovites yielded flat age spectra defining plateau ages of 156 153 ma progressive crushing experiments of wolframites yielded anomalously old apparent ages due to excess 40ar however the apparent ages decline quickly after the initial steps and stabilize to form age plateaus of 156 153 ma without excess 40ar the plateau age steps interpreted as ages of gases derived from primary fluid inclusions pfis yield well defined isochrons with ages ranging from 157 to 153 ma and initial 40ar 36ar values that are indistinguishable from the modern atmospheric value digitally created 2d and 3d diagrams of k cl ar correlations can easily reveal distribution trends and correlation planes from the crushing steps interpretations of these diagrams further reveal the ages of secondary fluid inclusions sfis 87 to 83 ma and primary fluid inclusions pfis 159 to 150 ma raw data from sfis degassed during the initial crushing steps form scatters on inverse isochron plots however 2d and 3d k cl ar diagrams yield sfi ages that agree with 40ar 39ar ages of k feldspar veins cutting the tungsten ore bodies

fluid inclusion studies in opaque ore minerals i trace element content and physical properties of ore minerals controlling textural features in transmitted near infrared light microscopy physical properties and compositions of ore forming fluids in magmatic hydrothermal systems have been mostly investigated by conventional fluid inclusion studies in transparent gangue minerals that are assumed to be co genetic with the mineralization however ore precipitating fluids can be directly studied by analyzing fluid inclusions in opaque ore minerals such as wolframite stibnite pyrite and enargite by using near infrared nir petrography and microthermometry in combination with laser ablation inductively coupled plasma mass spectrometry la icp ms analysis of individual inclusions although results of nir fluid inclusion studies of ore minerals were first published in 1984 the technique is still not commonly used in fluid inclusion research due to a number of limitations related to the analytical equipment used sample preparation and nir mineral transmittance in this contribution we present new data on the applicability of nir fluid inclusion studies in ore minerals pyrite stibnite enargite and wolframite from a series of magmatic hydrothermal systems according to their chemical composition and physical behavior during microthermometry our results reveal strong correlation between nir transmittance and high trace element co ni cu as content in pyrite enargite fe bi and wolframite sc v fe despite this the restricted distribution of these elements in oscillatory and sector zoning has allowed observation of nir mineral features and fluid inclusions energy absorption of opaque minerals either as light energy during microscopy or as thermal conductive energy during fluid inclusion microthermometry presents a second limitation for nir fluid inclusion studies our results confirm the relevance of fluid inclusion studies in ore minerals by combining nir microscopy and microthermometry despite some limitations due to trace element composition of the host mineral and its physical behavior at high temperature a successful nir fluid inclusion study can be performed on some ore minerals that are opaque in the visible light range allowing the direct study of hydrothermal ore forming fluids

fluid inclusion studies in opaque ore minerals ii a comparative study of syngenetic synthetic fluid inclusions hosted in quartz and opaque minerals fluid inclusion studies give unique insights into physical conditions and composition of fluids involved in geological processes most studies to date are performed on transparent minerals near infrared nir microscopy allows also microthermometry to be performed on minerals that are opaque to the visible light such as pyrite hematite wolframite enargite and stibnite the main drawback of this technique is the underestimation of the recorded phase change temperatures with increasing light intensity up to several hundred percent in the case of ice melting temperatures although this issue has been known for a decade it is poorly understood we address this problem based on a systematic study of synthetic fluid inclusions in a variety of opaque minerals for the first time fluid inclusions have been co synthetized with success in quartz and opaque minerals fracturing the host minerals by in situ quenching allowed for fluid mineral equilibration prior to fluid inclusion formation in this study we assess the impact of mineral intrinsic parameters mainly absorption and thermal conductivity and experimental settings light source operative power diaphragms aperture and the use of filters on recorded phase change temperatures we show that these are underestimated due to local overheating of the sample caused by radiative heating from the light source it affects all minerals and the extent of the temperature shift of the observed phase changes depends on sample thickness mineral characteristics and the amount of light reaching the sample thus any calibration of the temperature shift as a function of the amount of light is complicated and in most cases impracticable however we demonstrate based on co generated inclusions in opaque minerals and quartz that yield similar values during nir microthermometry that for any mineral there is a range of light power and microscope settings for which no shift is noticeable within the thermal stage accuracy these are defined as ideal measuring conditions ensuring reliability of acquired microthermometry data

numerical modeling of infragravity wave response during delilah 1 the nearshore circulation model shorecirc is applied to simulate the infragravity wave conditions at two intervals during the 1990 delilah campaign at duck n c the model has been extended to solve the energy equation for random short waves on the timescale of the wave groups which acts as a wave driver for the long wave model to simulate the wave conditions an algorithm has been derived which synthesizes a directional offshore wavefield from measured data including the bound directional low frequency components the model data comparison shows that the mean short wave transformation and mean longshore current are predicted well the structure of the infragravity spectrum as measured in the nearshore array is correctly represented albeit that the energy levels are underpredicted in most locations the 2 d frequency longshore wavenumber spectra show that the infragravity wave energy consists mostly of edge waves and that the computations qualitatively resemble the measurements it is shown that for 1 day bar trapped edge waves are present the model is also used to show that the influence of the longshore variability is small for this particular beach and that the directional spreading in the offshore wave field is critical in predicting the nearshore infragravity wave conditions correctly edge waves which propagate against the current are generated by the directionally broad short wave forcing and to a lesser extent by back scattering the nonlinear terms are relatively unimportant for the prediction of the infragravity wave climate the cross shore gradient of the onshore directed radiation stress is the most important of the forcing terms

near infrared observation and microthermometry of pyrite hosted fluid inclusions pyrite occurs in many types of ore deposits although opaque to visible light some pyrite samples are sufficiently transparent in infrared light to reveal fluid inclusions and other internal features for a reconnaissance study 166 doubly polished thick sections of pyrite from 64 deposits worldwide were examined using an infrared microscope pyrite transparency varies between deposits with low temperature deposits showing the least transparency many samples transparent at room temperature gradually became opaque upon heating pyrite fourier transform infrared ftir spectra taken in the temperature range from 28 to 400 c demonstrate that the degradation of pyrite transparency with an increase in temperature is caused by a gradual shift of the main absorption edge of pyrite towards longer wavelengths recognizable fluid inclusions in pyrite are generally scarcer than fluid inclusions in quartz and microthermometric measurements are more difficult to obtain in the 64 occurrences studied about one quarter contained transparent fluid inclusions of the 37 analyzed fluid inclusions about two thirds yielded salinity measurements and about one quarter yielded homogenization temperatures microthermometric analysis on pyrite hosted fluid inclusions is possible however workable fluid inclusions are limited in occurrence

modelling infragravity motions on a rip channel beach a non linear shallow water wave model operating on the time scale of wave groups is compared with measurements of infragravity motions on a rip channel beach to verify the model concepts and assess the model performance the measurements were obtained during the rip current experiment ripex in concert with the steep beach experiment sbe performed at sand city monterey bay ca during the spring of 2001 the nearshore bathymetry was made up of shore connected shoals incised by relatively narrow rip channels spaced approximately 125 m apart the comparison considers a 20 day period during which significant changes in both the offshore wave climate and nearshore bathymetry occurred the temporal variation in infragravity conditions during the experiment is strong with computational results typically explaining 70 to 80 of the observed infragravity motions within the nearshore in contrast to the temporal variation the alongshore spatial variation in infragravity intensity during the experiment is generally weak even though the underlying bathymetry shows strong depth variations model computations suggest preferential coupling between the computed edge wave motions and the quasi periodic bathymetry is present a prerequisite for strong spatial variability however the infragravity field is dominated by cross shore infragravity motions which are only weakly coupled to the quasi periodic bathymetry resulting in a weak alongshore variability of the total infragravity motions

a mechanism for the generation of wave driven rhythmic patterns in the surf zone the coupling between topographic irregularities and wave driven mean water motion in the surf zone is examined this coupling occurs because the topographic perturbations produce excess gradients in the wave radiation stress that cause a steady circulation this circulation in turn creates a sediment transport pattern that can reinforce the bottom disturbance and may thereby lead to the growth of large scale bed forms to investigate this coupling mechanism the linearized stability problem with an originally plane sloping beach and normal wave incidence is solved in two different cases first the breaking line is considered to be fixed and second the perturbations in water depth that produce a displacement of the breaker line are accounted for the first case shows that the basic topography can be unstable with respect to two different modes a giant cusp pattern with shore attached transverse bars that extend across the whole surf zone and a crescentic pattern with alternate shoals and pools at both sides of the breaking line showing a mirroring effect in the second case the varying breaker line may have a strong influence on the circulation this is clear for the giant cusp topography whose growth is totally inhibited in contrast the morphology and the growth of the crescentic pattern remains almost unchanged

wolframite solubility and precipitation in hydrothermal fluids insight from thermodynamic modeling abstract wolframite a solid solution series between hubnerite mnwo4 and ferberite fewo4 is the main tungsten bearing ore mineral in vein type tungsten deposits much progress has been made on characterizing the mineralizing fluids precipitating wolframite but it remains poorly understood what are the mechanisms depositing wolframite effectively and the variables controlling mn fe ratios in wolframite this study examines chemical controls on wolframite solubility in hydrothermal fluids and mn fe ratios in wolframite using thermodynamic models for fluids in the systems of w mn cl na o h and w fe cl na o h the fluid buffered models are established based on the characteristics of vein type tungsten deposits the modeling results indicate that solubilities of hubnerite and ferberite in hydrothermal fluids at typical w mineralizing conditions 300 400 c 500 1500 bars 5 15 wt nacl equivalent ph 4 6 reach up to hundreds of ppm the predominant tungsten manganese and iron species in fluids are h w o 4 m n c l 2 0 and f e c l 4 2 respectively an increase in ph and a decrease in fluid temperature and salinity are efficient mechanisms precipitating hubnerite and ferberite from acidic hydrothermal fluids hubnerite and ferberite are also significantly dissolved in alkaline hydrothermal fluids but their solubilities in alkaline fluids are insensitive to fluid temperature and salinity this may affect w mineralization at stages with different ph levels e g the greisen stage and the alkaline stage the mn fe ratio of mineralizing fluids is the principal variable controlling mn fe ratios in wolframite more supply of fe than mn from the fertile magma tends to produce fe rich mineralizing fluids this may be one of reasons why ferberite is more common than hubnerite in tungsten deposits and why hubnerite is more likely to precipitate at an early stage

a sulfur isotopic study of the san cristobal tungsten base metal mine peru the san cristobal tungsten base metal deposit differs from other quartz wolframite vein deposits in that it has a major period of base metal mineralization consisting of pyrite chalcopyrite sphalerite and galena homogenization temperatures of primary and pseudosecondary inclusions were measured in augelite 260 400 c quartz 230 350 c and sphalerite 180 220 c the 34s values of h2s in solution in equilibrium with the vein minerals range from 1 6 to 9 0 permil increasing through the paragenesis the relatively heavy delta 34 text s text h text 2 text s values suggest a nonmagmatic source for the sulfur evaporitic sulfates are a likely source of heavy sulfur and sedimentary anhydrite is known to occur near the san cristobal region in contrast to san cristobal are three similar quartz wolframite vein deposits pasto bueno panasqueira and tungsten queen they each have an average 34s value for sulfides of about 0 permil suggesting a sulfur of magmatic origin at san cristobal an influx of sedimentary sulfur could not only account for the distinctive isotopic signature of the sulfides but also for the presence of the base metal mineralization

variscan silicic magmatism and related tin tungsten mineralization in the erzgebirge slavkovský les metallogenic province integration of geochemical mineralogical isotopic and geochronological data with geodynamic considerations suggests that the variscan granites in the erzgebirge slavkovsk les domain originated from repeated melting events and were emplaced over a period of about 40 ma 330 290 ma several lines of evidence exist supporting the idea that erzgebirge granites assigned to different types biotite granites two mica granites strongly peraluminous p rich li mica granites and slightly peraluminous p poor granites are in most cases not genetically related via continuous fractional crystallization from a common magmatic reservoir the genesis of the slavkovsky les granites however might be discussed in terms of an uninterrupted fractionation series geological models of sn w deposits based upon geochemical and structural results imply that the main ore depositional events followed immediately the emplacement and solidification processes of melt via fluid melt immiscibility breccia pipe formation and or pervasive rock fluid interactions

an infrared microthermometric study of fluid inclusions in coexisting quartz and wolframite from late mesozoic tungsten deposits in the gannan metallogenic belt south china abstract numerous wolframite quartz vein type tungsten deposits are present in the gannan metallogenic belt south china including the piaotang and dangping deposits in the chong you yu ore cluster the dajishan deposit in the jiulianshan ore cluster and the pangushan deposit in the yushan ore cluster the ores generally consist of quartz and wolframite with variable amounts of base metal sulfides wolframite and quartz are intergrown but the genetic relationships between them are still ambiguous quartz contains two phase aqueous inclusions type i and two or three phase co 2 bearing inclusions type ii but wolframite only contains two phase aqueous inclusions type iw the homogenization temperatures for primary inclusions in wolframite are generally 40 to 100 c higher than those in quartz in a single deposit moreover there are variable amounts of co 2 in inclusions in quartz but no co 2 rich inclusions are identified in coexisting wolframite type i fluid inclusions in quartz from the piaotang deposit show that fluid mixing is predominant in the formation of quartz veins whereas fluid inclusions from the dangping deposit suggest that simple cooling is the primary factor quartz from the dajishan and pangushan deposits contains both type i and coexisting type ii inclusions indicating a process of fluid immiscibility the homogenization temperatures of two phase aqueous inclusions type iw in wolframite from all of these deposits show a clearly decreasing trend with constant salinities implying a simple cooling process hence simple cooling fluid mixing and fluid immiscibility take place in quartz but only simple cooling happens in wolframite our results show that the gangue and ore minerals from the late mesozoic tungsten deposits in the gannan metallogenic belt have different homogenization temperatures volatile compositions and fluid processes the gangue minerals do not provide reasonable estimates of the depositional conditions of the ore minerals even though they are intimately intergrown

morphodynamic modelling of rip channel growth the morphological evolution of a rip channel system due to normally incident waves has been investigated using two different approaches the first approach is a state of the art commercial 2dh coastal area model whereas the second approach is a linear stability analysis the results of the two different approaches have been compared and both models predict rip channel spacings and initial growth rates of similar magnitudes

infrared microthermometric and noble gas isotope study of fluid inclusions in ore minerals at the woxi orogenic au sb w deposit western hunan south china abstract the woxi au sb w deposit hosted by the neoproterozoic low grade metamorphic clastic rocks is located in a brittle ductile shear zone within the xuefengshan range south china orebodies are predominantly banded quartz veins which are strictly controlled by bedding faults and display significant vertical extents up to 2 km without obvious vertical metal zoning fluid inclusions hosted in quartz scheelite and stibnite from quartz scheelite and quartz sulfide gold veins have been studied using conventional and infrared microscopy respectively four types of fluid inclusions were identified based on petrography including type i two phase liquid rich aqueous inclusions type ii two or three phase co 2 rich inclusions type iii two phase vapour rich aqueous inclusions and type iv single phase aqueous inclusions the fluid inclusions in ore minerals scheelite and stibnite and their coexisting quartz largely share similar characteristics in terms of their types homogenization temperatures and salinities this is consistent with the fact that these ore minerals are always intergrown with quartz microthermometric and laser raman data indicate a low to moderate temperature 140 240 c low salinity 2 rich n 2 bearing aqueous ore forming fluid such fluid is further identified as a deeply non magmatic crustal fluid rather than a mantle source fluid by the significantly low 3 he 4 he ratios 0 002 0 281 ra and a small amount of meteoric water or host rock buffered fluid could be involved w ore precipitation was probably associated with mixing between a deeply originated crustal fluid and host rock buffered fluid based on the fluid inclusion features in scheelite and quartz i however au and sb ore deposition probably resulted from boiling which was caused by the marked pressure drop geological features such as banded structure and crack sealing structure also indicate that fluid pressure fluctuation induced by fault valve mechanism occurred during ore precipitation these characteristics of the ore forming fluids in the woxi deposit are in good agreement with the definition of orogenic gold deposits and the woxi au sb w deposit is probably an atypical orogenic gold deposit for its unique ore forming element association

self organization mechanisms for the formation of nearshore crescentic and transverse sand bars the formation and development of transverse and crescentic sand bars in the coastal marine environment has been investigated by means of a nonlinear numerical model based on the shallow water equations and on a simplified sediment transport parameterization by assuming normally approaching waves and a saturated surf zone rhythmic patterns develop from a planar slope where random perturbations of small amplitude have been superimposed two types of bedforms appear one is a crescentic bar pattern centred around the breakpoint and the other herein modelled for the first time is a transverse bar pattern the feedback mechanism related to the formation and development of the patterns can be explained by coupling the water and sediment conservation equations basically the waves stir up the sediment and keep it in suspension with a certain cross shore distribution of depth averaged concentration then a current flowing with against the gradient of sediment concentration produces erosion deposition it is shown that inside the surf zone these currents may occur due to the wave refraction and to the redistribution of wave breaking produced by the growing bedforms numerical simulations have been performed in order to understand the sensitivity of the pattern formation to the parameterization and to relate the hydro morphodynamic input conditions to which of the patterns develops it is suggested that crescentic bar growth would be favoured by high energy conditions and fine sediment while transverse bars would grow for milder waves and coarser sediment in intermediate conditions mixed patterns may occur

vortical surf zone velocity fluctuations with 0 10 min period observations of velocity fluctuations with periods between about 4 and 30 min thus longer than infragravity waves and referred to as very low frequency vlf surf zone motions are described and compared with numerical simulations the vlf motions discussed here exclude instabilities generated by the wave driven alongshore current velocity shear that occur in the same frequency range by selecting cases with weak alongshore currents only numerical simulations are based on the linear shallow water equations including friction and forced by nonlinear difference frequency interactions between incident sea and swell waves the model is initialized with sea and swell frequency directional spectra observed seaward of the surf zone modeled and observed vlf velocity fluctuation magnitudes agree within a factor of 2 both increase approximately linearly with increasing incident wave height and rapidly decay seaward of the surf zone observed frequency wave number f ky spectra of vlf velocity fluctuations estimated with instrumented alongshore arrays are energetic in a broad range of ky in the vortical band observed and modeled vlf pressure fluctuations are relatively weak still the model momentum balance suggests that vlf pressure gradients are as important as the nonlinear wave group forcing by sea and swell in accelerating decelerating the vlf velocities model calculations demonstrate that the vlf f ky response is a function of the modulations of short wave forcing associated with the frequency directional distribution of the incident sea and swell spectra this results in vlf motions which span the surf zone and have o 50 1000 m alongshore scales with o 200 2000 s time scales given the fact that modulations of short waves resulting from directionally spread incident waves are common during field conditions we expect vlfs to be ubiquitous

constraining ultrahigh pressure uhp metamorphism and titanium ore formation from an infrared microthermometric study of fluid inclusions in rutile from donghai uhp eclogites eastern china eclogites in the donghai area of the sulu ultrahigh pressure uhp metamorphic belt in eastern china contain both disseminated rutile and rutile deposits the rutile occurs as small inclusions in garnet omphacite phengite and quartz as larger euhedral to subhedral grains in equilibrium with garnet omphacite phengite and kyanite and as discrete veinlets aggregates and megacrysts in cracks and along grain boundaries to investigate the processes of rutile mineralization and its relationship to the evolution of the sulu uhp metamorphic belt we sampled the exposed maobei deposit at donghai and drill core between 100 and 2000 m in the nearby chinese continental scientific drilling project ccsd main hole to carry out a detailed infrared microthermometric fluid inclusion study three types of fluid inclusions were identified aqueous type i co 2 h 2 o type ii and ch 4 type iii type i and type ii inclusions are the most common primary and pseudosecondary type i inclusions which were trapped during recrystallization of the eclogite or early amphibolite facies retrograde metamorphism have a narrow range of homogenization temperatures but a wide range of salinities in contrast secondary type i inclusions which formed entirely during retrograde amphibolite facies metamorphism associated with exhumation of the uhp rocks have higher and more varied homogenization temperatures but medium to low salinities type ii inclusions formed contemporaneously with the type i variety and are characterized by having small amounts of co 2 and n 2 in addition to h 2 o in addition some of the rutile grains contain sparse inclusions composed of ch 4 type iii our results combined with those of previous studies suggest a great diversity of fluid composition in the peak metamorphic to early retrograde stages implying very limited fluid rock interaction during syn to post peak high pressure hp and uhp metamorphism this study shows that infrared microthermometric investigation of fluid inclusions can provide information not only on the composition of titanium ore forming fluids but also on the relationship between mineralization and the evolution of uhp metamorphic belt

combined investigations of fluid inclusions in opaque ore minerals by nir swir microscopy and microthermometry and synchrotron radiation x ray fluorescence abstract an alternative ir microscopy system in the nir near infrared up to 10 m and swir short wavelength infrared up to 1 4 m ranges has been developed for the study of opaque ore minerals the system uses either ir led or ir light bulb sources depending on the degree of opacity of the investigated minerals this paper presents the methodology and the promising results obtained in studies of opaque ore minerals such as ag minerals pyrargyrite from epithermal deposits and nb tantalates columbite from pegmatites it also presents results on the internal features of hematites from fe ore banded formations and tungstates from granite greenstone belt deposits the data obtained on fluid inclusions from pyrargyrite and hematite crystals have been integrated by complementary information from x ray fluorescence analysis using synchrotron radiation sxrf under conditions specifically designed for the study of opaque ore minerals

modeling the deep convection in the northwestern mediterranean sea using an eddy permitting and an eddy resolving model case study of winter 1986 1987 1 in the northwestern mediterranean sea winter 1986 1987 was particularly cold inducing a strong open ocean convection event in order to investigate the impact of numerical models spatial resolution on the convection representation and the effects of deep convection on the northwestern mediterranean circulation we perform two numerical three dimensional simulations eddy permitting versus eddy resolving models are forced at the surface by the era40 atmospheric fluxes with a simple heat flux correction to better mimic the observed value we examine the characteristics of the deep convection mixed layer water masses characteristics convection zone and mesoscale structures and perform temporal analysis of this event in terms of kinetic energy buoyancy equilibrium and deep water dw evolution the convection characteristics are similarly represented on a global scale by both models and are in good agreement with observations except for the size of the convection region however the eddy resolving model better reproduces the mesoscale structures whose role in the dw formation mixing and transport is shown to be essential the boundary circulation and the overturning are enhanced during the convection event sixty six percent of the dw spreading is due to the bleeding effect into the catalan sea during the convection event whereas 33 is due to the mesoscale structures southwestward advection after the event sixty percent of the restratification with respect of the water column initial structure occurs before july 1987 and is due to light water advection afterward restratification is due to the mixing and is not complete before next year convection

chemical zoning in wolframite from san cristobal peru fifty wolframite crystals from san cristobal peru were analysed with the electron microprobe for fe mn and w detailed studies of several samples reveal complex compositional zoning within individual crystals one sample contains two crystals with contrasting zoning one crystal has a high fe core and an fe poor rim whereas the other has an fe poor core and a high fe rim this suggests that these two crystals formed at different moments and that the wolframite composition did not change monotonically with time the full range of wolframite compositions measured is from 28 to 97 mol ferberite fewo4 although a range of 59 mol was determined for one sample the average range for all fifty samples is 10 mol samples with average compositions in the range of 84 92 mol ferberite have relatively small compositional variations whereas those with average compositions in the range of 61 84 mol are quite variable on a vertical longitudinal section of the main vein of san cristobal it appears that the low ferberite values correspond spatially with high tungsten grades the iron content of the wolframite goes through a minimum across its depositional interval this may be due to a change in the fe mn ratio of the mineralizing solution with either distance or time

the spatial and temporal variability of sand bar morphology the spatial and temporal variability of nearshore sand bar morphology is quantified using a unique data set spanning 2 years the data consist of daily time exposure images of incident wave breaking on an open coast sandy beach which may be used to infer bar morphology lippmann and holman 1989 the morphology in each image is classified into an eight state morphologic scheme in which bars are uniquely defined by four independent criteria the most frequently observed morphologies are the longshore periodic rhythmic bars observed in 68 of the data linear bars occur under highest wave conditions h s 1 78 m and are unstable mean residence time 2 days shore attached rhythmic bars are the most stable mean residence time 11 days and generally form 5 16 days following peak wave events non rhythmic three dimensional bars are very transient mean residence time 3 days eighty seven percent of transitions to lower bar types defined in text occurred one state at a time supporting our selection of the ordering of states and suggesting the suitability of a sequential morphology model transitions to higher states occurred under rising wave energy and were evenly spread among the possible higher states with more substantial changes in morphology resulting from larger wave increases this suggests that up state erosional transitions based on offshore bar migration are better described by an equilibrium model where response is better correlated with incident wave energy than with preceding morphological state time exposure images were also digitized to yield quantitative estimates of bar crest location as a function of longshore distance principal component analysis was used to decompose bar position into two dimensional linear and three dimensional longshore variable components cross shore linear bar position ranges 50 m about the 2 year mean 27 m standard deviation and dominates bar variability 74 6 three dimensional bar structure accounts for 14 of the variance 12 m standard deviation changes in incident wave height precede cross shore bar migration by less than 1 day changes in longshore variability are inversely correlated to changing wave conditions with bar morphology becoming linear rapidly during storms on time scales of less than 1 day evolution to significantly three dimensional structure typically occurs over 5 7 days following peak wave events

infrared microthermometric and stable isotopic study of fluid inclusions in wolframite at the xihuashan tungsten deposit jiangxi province china the xihuashan tungsten deposit jiangxi province china is a world class vein type ore deposit hosted in cambrian strata and mesozoic granitic intrusions there are two major sets of subparallel ore bearing quartz veins the ore mineral assemblage includes wolframite and molybdenite with minor amounts of arsenopyrite chalcopyrite and pyrite there are only two phase aqueous rich inclusions in wolframite but at least three major types of inclusions in quartz two or three phase co2 rich inclusions two phase pure co2 inclusions and two phase aqueous inclusions indicating boiling fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities 239 380 c 3 8 13 7 wt nacl equiv compared with those in quartz 177 329 c 0 9 8 1 wt nacl equiv these distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process enthalpy salinity plot shows a linear relationship implying mixing of different sources of fluids although boiling occurred during vein type mineralization it seems negligible for wolframite deposition mixing is the dominant mechanism of wolframite precipitation in xihuashan 34s values of the sulfides range from 1 6 to 0 1 indicative of a magmatic source of sulfur 18o values of wolframite are relatively homogeneous ranging from 4 8 to 6 3 oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite

horizontal ocean circulation forced by deep water formation part ii a quasi geostrophic simulation abstract this numerical experiment aims to investigate the dynamical effects of the vertical convection of waters occurring in regions where the cooling of the upper ocean is due to periodical local rough winter atmospheric conditions the simulation is performed with a 2 layer quasi geostrophic model which configuration yields a small internal radius of deformation 10 km and a high spatial resolution 5 km the sinking of waters is parametrized by a conversion in a limited area of some of the upper layer fluid into lower layer fluid this forcing is continuously active for the first 3 months of the year and is zero otherwise this cycle is repeated for several years the model response results in an elevation of the interface a dome which generates a geostrophic circulation first limited to the region where the forcing is active the dome grows and reaches a critical amplitude where it becomes baroclinically unstable and breaks into eddies of smaller size in a way very comparable to what h

niobian wolframite from glen gairn in the eastern highlands of scotland a microprobe investigation electron microprobe data are presented from zoned niobian wolframite crystals in a quartz wolframite cassiterite vein and wall rock from a zinnwaldite bearing granite pluton that forms part of the late caledonian glen gairn granitic complex in the eastern highlands of scotland compositions range from nb and ta rich wolframite fe mn w nb ta o 4 forming strongly zoned difficult to polish regions of crystals to almost pure hubnerite mnwo 4 forming relatively unzoned easily polished regions nb and ta substitution is very restricted in mn rich 80 mol hubnerite wolframites but increases regularly in more fe rich compositions through a coupled substitution mechanism between mn 2 w 6 and fe 3 nb ta 5 most of the wolframite crystals contain two forms of zonation a physical zonation observed optically and by electron imaging and a compositional zonation revealed by x ray traverses compositional zoning is progressive involving gradual changes in mineral chemistry from core to rim on which is superimposed a form of oscillatory zoning involving repeated resetting of compositions physical zones are layers of uniform width separated by distinct boundaries they are arranged parallel to crystal faces and reflect intermittent crystal growth these zones vary in width from less than 5 m in the niobium rich wolframite to over 200 m in regions of niobium poor hubneritic wolframite hydrothermal alteration particularly of the intensely zoned niobium rich regions has resulted in assemblages of altered nb and ta rich wolframite tungstite secondary hubneritic wolframite and scheelite nb rich inclusions 5 10 m across are found sporadically in the larger wolframite crystals progressive variation in wolframite chemistry is readily explained in terms of gradually changing physiochemical conditions such as ph f o 2 temperature pressure and fluid composition during crystallization the oscillatory zonation reflects cyclicity of those conditions plausible models which could explain such effects include 1 a intermittent mixing of chemically distinct magmatic and meteoric fluids 2 b repeated hydraulic fracturing and injection of fluids leading to fluctuating pressure and temperature of the hydrothermal fluid volatile species f cl co 2 may have been effective as complexing agents thus affecting the supply of nb from the fluid deposition of nb and ta rich compositions were probably favoured by high f o 2 low ph conditions

infrared microthermometry of fluid inclusions in transparent to opaque minerals challenges and new insights infrared ir studies of fluid inclusions in opaque minerals provide direct insights into the ore forming fluids however the challenge posed by the warming effect of ir light during microthermometry remains unresolved here we address this problem and show that the deviation in temperature of phase changes within fluid inclusions caused by ir light is more common than what was thought before our results reveal that transparent to translucent minerals e g quartz sphalerite also absorb ir energy since ir absorption is influenced by the host mineral the fluid inclusions hosted by different minerals exhibit different degrees of deviation in temperature during microthermometry the fourier transform infrared ftir spectra do not display a consistent correlation between the band gap energy of a mineral and its absorption of ir energy minerals with low band gap energy such as pyrite absorb limited ir energy resulting in small deviations of fluid inclusion data in contrast this deviation could be significant for fluid inclusions hosted in minerals with a relatively high band gap energy such as iron rich sphalerite and wolframite substitution of iron increases the absorption of ir energy in these minerals the substitution of trace elements may also play a role our quantitative analyses confirm that using the lowest possible ir light intensity with the smallest diaphragm minimizes the warming effect of ir light we also propose an improved cycling method as a better option where high ir light intensity is required

bar generating cross shore flow mechanisms on a beach random waves normally incident on a dissipative beach induce a variety of cross shore flows such as asymmetric oscillatory flow wave grouping induced long wave flow breaking induced turbulent flow and momentum decay induced undertow these flows are identified analyzed and hindcasted in a set of laboratory experiments with the aim of revealing the role of each of the flow mechanisms in the two dimensional case of bar generation on a beach

microthermometry of enargite hosted fluid inclusions from the lepanto philippines high sulfidation cuau deposit abstract the spatial relation between porphyry and high sulfidation epithermal deposits is particularly well revealed in the mankayan mineral district of northern luzon philippines where the lepanto high sulfidation cu au deposit lies over and adjacent to the far southeast fse porphyry cu au deposit consequently a study was undertaken to characterize the fluids responsible for epithermal mineralization in this environment the ore stage at lepanto consists of enargite luzonite cu 3 ass 4 pyrite tennantite tetrahedrite and chalcopyrite infrared petrography of the enargite reveals variable transparency with growth banding and twinning visible in euhedral specimens two phase liquid vapor fluid inclusions occur as primary and secondary types ranging from t h of fluid inclusions in enargite were measured from within the lateral 3 0 km and vertical 0 5 km extent of the enargite mineralization these values show a cooling trend toward the northwest away from the area over the porphyry deposit with average t h ranging from 285 c proximal to 166 c distal ice melting temperatures t m were measured using a cycling technique as ice was usually not visible in frozen inclusions apparent salinities range from 4 5 to 0 2 eq wt nacl with samples from the margins of the deposit showing a general decrease in apparent salinity with lower t h secondary fluid inclusions in quartz phenocrysts tend to have a higher average t h and lower apparent salinities compared to enargite hosted inclusion fluids from the same locations several samples of pyrite are also transparent to ir radiation and show internal features such as growth banding and in one instance a two phase liquid vapor fluid inclusion this inclusion yielded a salinity of 1 2 eq wt nacl there is a large discrepancy in t h and apparent salinities between the enargite mineralization and the subjacent porphyry deposit despite contemporaneous formation suggesting that the hot 500 c hypersaline magmatic brines associated with porphyry mineralization did not directly ascend to the elevation of the enargite deposit however absorbtion of magmatic vapors into overlying meteoric water may have created the mineralizing fluid of the lepanto deposit as this liquid moved to the northwest along the lepanto fault it was cooled and diluted by mixing with groundwater resulting in enargite deposition

fluid inclusion study of stibnite using infrared microscopy an example from the brouzils antimony deposit vendee armorican massif france a microthermometric study using infrared microscopy was performed on fluid inclusions hosted in stibnite crystals of the brouzils antimony deposit in order to characterize the fluids responsible for the deposition of the antimony at the end of the variscan metallogenic sequence primary fluid inclusions in stibnite were moderately saline 3 5 4 75 wt nacl equiv with homogenization temperatures varying between 140 and 160 c two generations of later fluids are also contained in the stibnite samples the first generation of secondary fluid inclusions is found exclusively in stibnite and is characterized by low salinities 1 35 2 2 wt nacl equiv homogenization temperatures of approximately 215 c and the presence of one or more solid mineral phases the second generation of fluid inclusions is younger and is found in stibnite along secondary planes as well as in quartz gangue it corresponds to h2o co2 fluid with homogenization temperatures of about 180 c this infrared microscopy study thus shows that the quartz and stibnite of the brouzils veins are not cogenetic and reveals the polyphase character of the vein infill in which three successive episodes of hydrothermal circulation are identified

thermal evolution of the greenland sea gyre in 1988 1989 slice inverses of temperature and heat content from the 1988 1989 greenland sea tomography experiment and other observations including standard conductivity temperature depth stations moored thermistors surface meteorological variables and surface ice cover are combined to better understand the thermodynamics of the greenland sea gyre thermal evolution of the gyre center seems to divide naturally into the following three periods a preconditioning phase november january during which surface salinity is increased by brine rejection from ice formation and by entrainment but in which the mixed layer deepens only slowly to a depth of some 150 200 m a deep mixing phase february march during which the surface mixed layer deepens rapidly to approximately 1500 m in the gyre center purely under the influence of local surface cooling and a restratification phase during which the products of deep mixing are replaced by arctic intermediate water flowing in from the gyre edges the onset of the deep mixing phase occurs after ice formation in the gyre center stops resulting in an area of open water where large heat fluxes can occur in surrounding regions including the odden region to the south ice is still being formed to the north and west closer to the steep topography of the continental shelf the inverse results show significant variability due to advection and large temperature and heat content fluctuations with a period of about 50 days are seen

morphodynamics of intermediate beaches a video imaging and numerical modelling study four years of time exposure images of palm beach sydney australia are used to a develop a phenomenological scheme based on surf zone properties for the classification of the four intermediate beach states low tide terrace ltt transverse bar rip tbr rhythmic bar beach rbb and longshore bar trough lbt identified by wright l d short a d 1984 morphodynamic variability of surf zones and beaches marine geology 56 93 118 and b determine environmental conditions associated with the different beach states the overall agreement between beach state classifications obtained by visual classifications of images and those predicted by the phenomenological scheme exceeds 90 analysis of time series of intermediate beach states and wave data indicates that the nearshore morphology continuously cycles through the four beach states in response to variations in the incident wave energy the results also indicate that lbt morphology is produced by high energy wave conditions erosive while the progression towards ltt occurs under lower waves accretive a depth averaged morphodynamic model is employed to determine the morphodynamic processes governing the rbb to tbr and tbr to ltt transitions model results indicate that the rbb to tbr transition is governed by the erosion of the original longshore bars in the initial rbb morphology and the formation and subsequent welding of shoals in the lee of the original longshore bars model results also indicate that rbb to tbr transitions can occur under shore normal and oblique wave conditions the tbr to ltt model simulations indicate that under obliquely incident waves progressive erosion of the transverse shoals and deposition of the eroded sediment in rip channels gradually diminishes the longshore variability in morphology resulting in an ltt morphology

the morphological response of a nearshore double sandbar system to constant wave forcing results of 2dh morphodynamic computations are presented to quantify the temporal evolution of the crescentic patterns emerging in a double nearshore bar system in response to constant wave boundary forcing sixteen different conditions varying both offshore wave height and angle of wave incidence were applied the mean length scales of the emerging irregular crescentic patterns are linearly proportional to the local longshore velocity over the inner and outer bars for similar longshore velocities the length scales of the outer bar are larger than of the inner bar this is explained by accounting for the difference in water depth above the bar crest the variable morphological response times can be explained by including additional bathymetrical parameters the active volume of the bar defined by the breaker index plays an important role in this response time with larger active volumes the bar responds more rapidly to identical boundary conditions also bars with a smaller total volume respond more quickly this faster response is due to the steeper active volume of the bars different initial perturbations resulted in different locations of the emerging features showing that their location is sensitive to the initial bathymetry however the range in length scales and response times due to the different perturbations was significantly smaller than those obtained for the different hydrodynamic conditions based on the present findings we hypothesize that morphological length scales in the field are rarely in equilibrium with the concurrent offshore wave height and angle of incidence owing to the slow response of the sandbars under constant conditions relative to the stochastic nature of natural wave forcing

ore zoning and tetrahedrite compositional variation at orcopampa peru the orcopampa silver mining district is located in southern peru about 150 km north northwest of the city of arequipa argentian tetrahedrite the main ore mineral was deposited in large normal faults cutting tertiary volcanic rocks ore distribution and compositional variations of tetrahedrite in the santiago norte split manto and calera veins were studied in sufficient detail to clearly define zoning patterns in the santiago norte split vein the ore grade mineralization forms a single continuous and horizontally elongated ore shoot 500 m long and 200 m in vertical extent contouring of average silver grades of ore blocks using a 10 oz ag ton cut off grade shows that this ore shoot actually consists of a sinuous ore band which is only 25 to 75 m wide but over 700 m long the 200 m vertical interval of the ore shoot results from undulations of the ore band within the near vertical vein structure in the manto vein there are three major ore shoots 300 to 400 m apart along strike and with vertical extents of about 350 m these ore shoots are connected at their bases by two small ore shoots that correspond to a relatively narrow subhorizontal ore band which is locally below ore grade the main ore shoot in the calera vein plunges about 45 degrees to the southwest has a vertical extent of 300 m and is 300 m long on the lowest developed level using a 10 oz ag ton cutoff grade it is shown to consist of an antiformal ore band with 20 to 30 m wide limbs and a very high grade 100 x 150 m crest orcopampa tetrahedrite is generally high in antimony and in zinc and most of its compositional variation can be expressed with the atomic ratio x ag 100 ag ag cu this ratio typically varies up to 4 units for different parts of a crystal or crust and for separate samples from a single locality however for the veins as a whole this ratio varies systematically between 2 and 40 changes in tetrahedrite composition within the santiago norte split and manto veins are highlighted by x ag isopleths of 12 5 and 18 5 separating low medium and high values of this zoning index for the santiago norte split vein these isopleths faithfully mimic the ore band inferred on the basis of ore grades with lower silver contents in tetrahedrite at the base and higher silver contents in tetrahedrite at the top of the ore band for the manto vein the x ag isopleths demonstrate that the three major ore shoots are located where the ore band rises and descends steeply tightly doubling upon itself thus the manto ore band is 25 to 125 m wide and 2 500 m long in the 1 000 m of vein strike length studied the mode of formation of the tetrahedrite ore bands remains speculative possibly many pulses of an ascending hydrothermal fluid precipitated tetrahedrite of progressively changing composition in response to temperature pressure or chemical gradients fractional crystallization if the permeability at the time of mineralization was roughly uniform the resulting ore band would be subhorizontal as in the santiago norte split vein major vertical ore shoots like those of the manto vein would form in areas of enhanced permeability alternatively tetrahedrite with systematically changing composition precipitated in response to temperature and chemical diffusion gradients between two contrasting hydrothermal reservoirs one above and the other below the ore band the patterns of ore distribution and tetrahedrite zoning in the orcopampa veins can be used to significantly aid mineral exploration and development moreover a preliminary investigation shows that under favorable circumstances the multiple microprobe spot analyses used for this investigation can be substituted by routine on site wet chemical procedures that are generally faster and less costly

a behavior oriented dynamic model for sandbar migration and 2dh evolution 1 a nonlinear model is developed to study the time dependent relationship between the alongshore variability of a sandbar a t and alongshore averaged sandbar position xc t sediment transport equations are derived from energetics based formulations a link between this continuous physical representation and a parametric form describing the migration of sandbars of constant shape is established through a simple transformation of variables the model is driven by offshore wave conditions the parametric equations are dynamically coupled such that changes in one term i e xc drive changes in the other i e a t the model is tested on 566 days of data from palm beach new south wales australia using weighted nonlinear least squares to estimate best fit model coefficients the model explained 49 and 41 of the variance in measured xc and a t respectively comparisons against a 1 d horizontal 1dh version of the model showed significant improvements when the 2dh terms were included 1dh and 2dh brier skill scores were 0 12 and 0 42 respectively onshore bar migration was not predicted in the 1dh model while the 2dh model correctly predicted onshore migration in the presence of 2dh morphology and allowed the bar to remain closer to shore for a given amount of breaking providing an important hysteresis to the system the model is consistent with observations that active bar migration occurs under breaking waves with onshore migration occurring at timescales of days to weeks and increasing 2dh morphology while offshore migration occurs rapidly under high waves and coincides with a reduction in 2dh morphology citation splinter k d r a holman and n g plant 2011 abehavior orienteddynamicmodelforsandbarmigrationand2dh evolution j geophys res 116 c01020 doi 10 1029 2010jc006382

quasi three dimensional modelling of the morphology of longshore bars a morphological quasi three dimensional q3d area model for barred coasts has been developed the model combines a two dimensional depth integrated model for wave driven currents with a model for undertow circulation currents the combined model makes a simultaneous simulation of the bar forming processes associated with the undertow and the horizontal wave driven circulation currents which may cause instabilities of the bar and the formation of rip channels situations with normal and oblique wave incidence are considered compared to the depth integrated approach the q3d model produces less pronounced alongshore irregularities for obliquely incident waves for normal incident waves the q3d model produces a crescentic bar while the depth integrated model predicts almost straight sections of the bar interrupted by rip channels the sensitivity to variation of wave angle and beach slope is further investigated

rhenium behavior in molybdenite in hypogene and near surface environments implications for re os geochronometry abstract rhenium is concentrated mainly in molybdenite mos2 and occurs as a major cation in only a few rare minerals this affinity makes molybdenite an ideal mineral for re os geochronometry but research on the behavior of re in molybdenite is limited infrared microscope xrd back scattered electron bse and microprobe techniques have been used in this study to document re behavior in molybdenite affected by hypogene and near surface processes in the hypogene environment both 3r and 2h molybdenite can experience re loss during hydrothermal alteration which also causes increased infrared transparency ir alteration at temperatures as low as 150 c can cause re loss in the presence of advecting fluids and will affect re os dating if it occurs long after primary mineralization re loss in 3r and 2h molybdenite under supergene conditions does not increase ir transparency rhenium is not incorporated into supergene ferrimolybdite but is enriched in k al silicate intergrowths which may be illite these minute intergrowths are present in several samples and would not be detected in a simple optical examination in the supergene environment elemental os is stable whereas re is not rhenium in molybdenite may be removed by supergene fluids after some has decayed to 187os causing erroneously old ages or it may be adsorbed into the illite intergrowths creating ages which are too young in the weathering environment proterozoic molybdenites have altered to re enriched powellite which can be detected using back scattered electron imagery combined microprobe xrd bse and infrared microscopy can be successfully used to detect alteration in molybdenite prior to dating these techniques are non destructive and should be performed before any molybdenite is dated by the re os system

molybdenite re os dating zircon u pb age and geochemistry of granitoids in the yangchuling porphyry w mo deposit jiangnan tungsten ore belt china implications for petrogenesis mineralization and geodynamic setting abstract the yangchuling w mo deposit located in the jiangnan porphyry skarn jnb tungsten ore belt is the first recognized typical porphyry w mo deposit in china in the 1980 s stockworks and disseminated w mo mineralization occur in the roof pendant of a 0 3 km 2 monzogranitic porphyry stock that intruded into a granodiorite stock hosted by neoproterozoic phyllite and slate la icpms zircon u pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143 8 0 5 ma and 149 8 0 6 ma respectively six molybdenite samples yielded a re os weighted mean age of 146 4 1 0 ma geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements lile relative to high field strength elements hfse indicating a peraluminous nature a cnk 1 01 1 08 two granitoids are characterized by a negative slope with significant light ree heavy ree fractionation la yb n 8 38 23 20 and negative eu anomalies eu eu 0 69 0 76 the p 2 o 5 contents of the yangchuling granitoids range from 0 12 to 0 17 and exhibit a negative correlation with sio 2 reflecting that they are highly fractionated i type they have high initial 87 sr 86 sr ratios 0 7104 0 7116 low negative e nd t 5 05 to 5 67 and homogeneous e hf t between 1 39 and 2 17 indicating similar sources additionally two stage nd model ages t dm2 of 1 3 1 4 ga and two stage hf model ages t dm2 of 1 2 1 3 ga are consistent indicating that neoproterozoic crustal rocks of the shuangqiaoshan group could have contributed to form the yangchuling magmas considering the two groups of parallel late mesozoic ore belts namely the jiangnan porphyry skarn tungsten belt jnb in the south and the middle lower yangtze river porphyry skarn cu au mo fe ore belt yrb in the north the nanling granite related w sn ore belt nlb in the south the neighboring qin hang porphyry skarn cu mo hydrothermal pb zn ag ore belt qhb in the north as well as the southeastern coast porphyry skarn cu mo au ore belt scb recognized in south china in this paper we propose that the latest jurassic to earliest cretaceous granitoids and associated ores were formed during a tearing of the subducting izanagi slab this tearing of the subduction slab caused the upwelling of asthenosphere and the resulting mantle crust interaction the granitoid related w ore systems in jnb resulted from the remelting of the proterozoic crust the mafic ultramafic volcanic rocks of the shuangqiaoshan group intercalated with phyllite and slate ophiolitic melange and magmatic arc rocks mainly comprising i type granite basalt andesite rhyolite pyroclastics together with subduction related metasomatized lithospheric mantle would have provided additional mantle material in this case the partial melting of rocks of the shuangqiaoshan group can produce s i and transitional type granitoids after strong differentiation it formed tungsten bearing granitoids characterized by enrichment of high alkali silicon and volatile components in the yangchuling mine area the small monzogranitic porphyry stock has stronger fractionation volatile content and ore forming components than the older granodiorite resulting in the development of the porphyry w mo ore system

direct analysis of ore precipitating fluids combined ir microscopy and la icp ms study of fluid inclusions in opaque ore minerals laser ablation inductively coupled plasma mass spectrometry la icp ms in combination with near infrared microscopy of fluid inclusions hosted by ore minerals that are opaque to visible light can provide the composition of ore precipitating fluids we applied the two techniques to well constrained fluid inclusion assemblages hosted by pyrite enargite and quartz to trace the source and evolution of the fluids in high sulfidation epithermal veins overprinting a porphyry copper deposit at rosia poieni romania despite some analytical limitations caused by the sulfide host minerals the data demonstrate that fluids trapped in apparently cogenetic quartz and ore minerals are chemically different systematic changes in major and trace element ratios between liquid vapor vapor rich and brine fluid inclusion assemblages in the three minerals record an evolving fluid source at the porphyry to epithermal transition regarding their cs na k ratios most of epithermal quartz hosted fluid inclusion assemblages form a well defined cluster which coincides with the narrow range of the porphyry stage fluids trapped in early quartz of the porphyry stockwork veins their cu na k ratios are 10 to 100 times lower compared to the pyrite hosted inclusions and correspond to the lowest cu na k ratios recorded for the porphyry stage fluids by contrast pyrite hosted vapor rich fluid inclusions have the highest cu na k similar to the highest cu na k ratios measured in the porphyry stage fluid inclusions the results led to the conclusion that the gangue and ore minerals in the high sulfidation epithermal veins at rosia poieni formed by successive pulses of chemically distinct hydrothermal fluids that were successively exsolved from residual melt batches of a progressively crystallizing magma at greater depth these results are consistent with detailed textural observations but petrography alone could not have led to this unambiguous conclusion

un predictability in rip channel systems 1 predicting the development of rip channel systems on beaches is relevant for beach safety nearshore mixing and dispersion and has been puzzling researchers for decades field observations and computer simulations have focused on predicting the spacing and growth time of rip channels as a function of wave characteristics a satisfactory predictor of rip channel spacing and growth time has not yet been proposed here we show that the lack of predictability of rip channels is an inherent property of the system related to the high sensitivity to the bathymetry prior to pattern development sensitivity to the initial cross shore profile appears to be as important as sensitivity to wave height although we might be able to predict rip channel characteristics the information required by such predictors will need to account for the underlying bathymetry implications arising from this study are that other geomorphic patterns could display similar sensitivity

observations of nearshore crescentic sandbars 1 the temporal and spatial variability of crescentic sandbars is analyzed with hourly long term months video observations collected at four barred sites and are qualitatively compared to the temporal and spatial variability predicted by hypotheses underpinning existing approaches and models for crescentic bar formation edge wave template model linear stability analysis and nonlinear models the observations coming from the single barred beaches at duck north carolina usa and miyazaki kyushu japan and from the double barred beaches at the northern gold coast queensland australia and noordwijk netherlands show that crescentic sandbar wavelength and amplitude variations over space and time are very common for instance at any moment in time the wavelength of the smallest and longest crescentic bar can differ by a factor of 2 temporal changes in wavelength and amplitude result from merging and splitting of individual crescents causing the final configuration of a crescentic sandbar system to be very different from the initial configuration the gold coast data indicate that these intrinsically nonlinear interactions are an attempt of the crescentic bar system to self organize into a more uniform pattern as splitting is usually confined to the longest crescentic bar observed whereas merging usually combines the smallest crescentic bars into a longer bar the observed spatial and temporal crescentic bar behavior contrasts qualitatively with behavior predicted from the edge wave template model and implies that the predictive skill of linear stability models is limited nonlinear models are potentially better suited for a comparison against these field observations several suggestions to improve these models and hence to facilitate a data model comparison are made