emplacement of sandstone intrusions during contractional tectonics abstract sandstone injections are created by the forceful emplacement of remobilized sand in response to increases in overpressure however the contribution provided by horizontal compressive stress to the build up in overpressure and the resulting emplacement of sand injection complexes is still to be substantiated by robust field observations an opportunity to address this issue occurs in central california where a large volume of sandstone intrusions record regionally persistent supra lithostatic pore pressure detailed fieldwork allows sandstone filled thrusts to be recognized and for the first time permits us to demonstrate that some sandstone intrusions are linked to contractional deformation affecting the western border of the great valley basin fluidized sand was extensively injected along thrust surfaces and also fills local dilatant cavities linked to thrusting the main aims of this paper are to provide detailed descriptions of the newly recognized syn tectonic injections and describe detailed cross cutting relationships with earlier sandstone injection complexes in the study area finally an evolutionary model consisting of three phases of sand injection is provided in this model sand injection is linked to contractional tectonic episodes affecting the western side of the great valley basin during the early middle cenozoic this study demonstrates that sand injections driven by fluid overpressure may inject along thrusts and folds and thereby overcome stresses associated with regional contractional deformation it is shown that different generations of sand injection can develop in the same area under the control of different stress regimes linked to the evolving mountain chain

compositions of biotite amphibole apatite and silicate melt inclusions from the tongchang mine dexing porphyry deposit se china implications for the behavior of halogens in mineralized porphyry systems abstract the dexing deposit located in the circum pacific ore belt is the largest porphyry copper deposit in eastern china it is composed of 3 separate plutons which host three mines tongchang fujiawu and zhushahong mines the porphyritic granodiorite samples studied in this investigation were collected from the tongchang ore forming pluton of this giant deposit this paper presents electron microprobe analyses of biotite apatite amphibole plagioclase potassium feldspar and rehomogenized glassy melt inclusions from the tongchang porphyritic granodiorites petrographic observations of the samples are consistent with portions of the granodioritic magma represented by our samples being overprinted by potassic hydrothermal fluid which variably altered these minerals all of the studied micas are mg rich biotites the biotites are separated into altered magmatic and secondary types based on their petrographic and geochemical characteristics the phlogopite components of the secondary biotites are typically higher than those of the altered magmatic biotites and the x mg values of all biotites correlate negatively with cl contents consistent with the mg cl avoidance principle the x mg values also correlate negatively with k 2 o na 2 o bao feo and tio 2 for both generations of biotites the calculated log f h 2 o f hcl values for 690 k of the coexisting potassic fluids which are determined from the altered magmatic biotite compositions range from 4 43 to 4 67 and are very similar to those of other major porphyry deposits however the log f h 2 o f hf and log f hf f hcl values for the same batch of hydrothermal fluids are significant higher and lower than those of these other porphyry deposits respectively the cl concentrations of amphiboles and melt inclusions range from 0 18 to 0 32 wt and 0 15 to 0 44 wt respectively most apatites trapped in biotite and plagioclase phenocrysts display a bimodal cl distribution 0 19 to 1 35 wt and 1 48 to 3 73 wt similarly the s contents of the apatite also show a distinct bimodal distribution reflecting the effects of variable anhydrite saturation during evolution of the tongchang melt and variable dissolution of anhydrite by saline aqueous fluids the cl contents of the apatites from the tongchang system are typically higher than those of other studied porphyry deposits furthermore the cl contents of the melt inclusions are at or very near the cl saturation levels 0 36 to 0 46 wt at 850 c and 50 mpa and 0 42 to 0 54 wt at 850 c and 200 mpa for these melt compositions at shallow crustal pressures these findings suggest that the area of the granodioritic magma represented by our samples and perhaps the bulk of the tongchang granodioritic magma was rich in cl the melt inclusion compositions are consistent with a high salinity hydrosaline liquid being exsolved directly from the granodioritic melt directly this high salinity hydrosaline liquid was likely very efficient at dissolving transporting and precipitating ore metals in the mineralizing magmatic hydrothermal system

apatite in granitoids related to polymetallic mineral deposits in southeastern hunan province shi hang zone china implications for petrogenesis and metallogenesis abstract the area of southeastern hunan province china located within the southwestern part of the shi hang metallogenic zone is characterized by abundant cu pb zn w and sn polymetallic ore deposits that are closely associated with coeval late mesozoic granodiorite porphyries and biotite granites respectively here we present new major and trace element concentrations and 87 sr 86 sr ratios of apatites from six ore bearing granitic rocks as determined by electron microprobe laser ablation inductively coupled plasma mass spectrometry and thermal ionization mass spectrometer which allow us to determine the main controls on the formation of these different types of mineralization and to explore how these controls are reflected in variations in apatite chemical and isotopic compositions the apatite data indicate that granodiorite porphyry intrusions related to cu pb zn mineralization are oxidized and formed as a result of slab dehydration melting of the mantle wedge overlying a subducted slab and the partial melting of crustal material the release of abundant cl and h 2 o rich fluids from the slab triggered mantle melting and the extraction of metals that were precipitated within the deposits in comparison granites related to w and sn deposits are moderately oxidized to reduced and were generated by the partial melting of crustal material with only limited input from mantle derived magmas granites associated with the w and sn mineralization formed in an intra arc rifting related tectonic environment the fact that these numerous polymetallic ore deposits formed in the same area during two successive periods of mineralization the first from 180 to 160 ma and the second from 160 to 140 ma indicates that the tectonic environment of southeastern hunan province evolved from a continental arc associated with the subduction of the paleo pacific plate and the formation of cu pb zn deposits to a later intra arc rifting environment associated with the formation of w and sn deposits as a consequence of slab roll back and mantle upwelling during the late jurassic this study reveals that apatite compositions can be used as a proxy to reflect the differences between granitoids and their associated mineralization and identify regional metallogeny and tectonic evolution

deep water measurements of container ship radiated noise signatures and directionality underwater radiated noise from merchant ships was measured opportunistically from multiple spatial aspects to estimate signature source levels and directionality transiting ships were tracked via the automatic identification system in a shipping lane while acoustic pressure was measured at the ships keel and beam aspects port and starboard beam aspects were 15 30 and 45 in compliance with ship noise measurements standards ansi asa s12 64 2009 and iso 17208 1 2016 additional recordings were made at a 10 starboard aspect source levels were derived with a spherical propagation surface affected or a modified lloyd s mirror model to account for interference from surface reflections surface corrected ship source depths were estimated from spectral differences between measurements at different beam aspects results were exemplified with a 4870 and a 10 036 twenty foot equivalent unit container ship at 40 56 and 87 of service speeds respectively for the larger ship opportunistic ansi i

groundwater salinity in the southern san joaquin valley water salinity in the san joaquin valley is a function of depth location and stratigraphy this paper presents a reconnaissance study of water salinity within kern county california using chemical analyses from oil field produced water and water wells as well as geophysical logs log analysis indicates that the base of underground sources of drinking water usdws 10 000 mg l slopes from northwest to southeast lab analyses show that usdws extend to depths as great as 1900 m 6233 5 ft southeast of bakersfield this area receives the greatest amount of fresh water recharge from streams flowing westward from the sierras the marine olcese sand is more saline than the overlying and underlying aquifers and separates the aquifers into an upper and lower usdw log analysis also indicates a zone of higher salinity separating zones of lower salinity in this area salinities in the west are higher and depths to base usdw are variable although waters in many sands in the western valley are more saline than 3000 ppm total dissolved solids tds numerous wells contain waters between 3000 and 10 000 ppm at depths of less than 600 m 1968 5 ft particularly in the nonmarine tulare formation at north belridge field a salinity reversal is apparent below 2100 m 6890 ft waters above this depth are approximately 40 000 mg l tds whereas water salinities below 2200 m 7218 ft range from 10 000 to 32 000 mg l extremely high salinities are found in several wells less than 30 m 98 ft deep primarily in the northwestern area these may be perched aquifers or lie adjacent to unmapped agricultural drainage sumps and do not reflect salinities in the regional aquifer

anhydrite solubility in differentiated arc magmas abstract the solubility of anhydrite in differentiated arc magmas was experimentally studied at 200 mpa and 800 1000 c over a range of oxygen fugacities from 0 5 log units above the ni nio buffer to the hematite magnetite buffer anhydrite is stable only at oxidizing conditions fo2 re reo2 whereas sulfides only form under reducing conditions the solubility of anhydrite in the melt ultimately regulates the amount of sulfur available to partition between melt and fluid phase during the eruption at oxidizing conditions the solubility product of anhydrite increases with temperature nbo t and melt water content we provide a new calibration of the anhydrite solubility product ksp xcao xso3 which reproduces all available experimental data with greatly improved accuracy ln k sp anhydrite 8 95 146 5 nbo t 2 696 10 4 t k 19 72 nbo t 10 4 t k 0 409 h 2 o wt in this equation the molar fractions xcao and xso3 in the melt as well as the number of non bridging oxygen atoms per tetrahedron nbo t are calculated on an anhydrous basis h2o refers to the melt water content t is temperature in kelvin we apply our model to estimate the sulfur yield of some recent volcanic eruptions and we show that the sulfur yield of the 1991 mt pinatubo dacite eruption was unusually large because only a small fraction of the sulfur was locked up in anhydrite in general high sulfur yields are expected when anhydrite solubility in the melt is high i e for somewhat depolymerized melts for rhyolitic systems most of the available sulfur will be locked up in anhydrite so that even very large eruptions may only have a small effect on global surface temperatures our model therefore allows improved predictions of the environmental impact of explosive volcanic eruptions

the occurrence and chemical implications of geothermal convection of seawater in continental shelves 1 geothermal convection is an important driving force for fluid flow and diagenesis in carbonate platforms and the similar shape of continental shelves in general suggests that geothermal convection could occur in continental shelves around the world numerical models based on seven transects of the shelf off the east coast of north america were developed to bracket possible fluxes simulations assuming relatively permeable sediments medium grained carbonates failed to produce significant thermal variations suggesting that chemical tracers will be required to detect this flow in the field fluxes calculated assuming lower permeabilities fine grained carbonates between cape fear and the savannah river were approximately 3 orders of magnitude smaller than river discharge for the area a difference similar to that between global river discharge and hydrothermal convection at mid ocean ridges sediment diagenesis during geothermal convection in continental shelves thus has the potential to affect ocean chemical budgets including potassium calcium and magnesium

equilibrium partitioning and subsequent re distribution of halogens among apatite biotite amphibole assemblages from mantle derived plutonic rocks complexities revealed abstract the concentration of halogens in apatite biotite and amphibole is investigated for a large variety of mantle derived plutonic rocks gabbros diorites monzonites olivine and pyroxene bearing monzonitic to granitic rocks syenites carbonatites and a phoscorite in all rocks studied apatite occurs as an early magmatic phase whereas biotite and amphibole may occur either as a late magmatic phase or as late stage potentially hydrothermal product replacing precursor olivine pyroxene and fe ti oxides ilmenite and magnetite based on electron microprobe analyses for f and cl and detailed textural observations we test existing models of halogen partitioning between apatite and biotite bromine concentration data for apatite biotite and amphibole are used to further refine our understanding of the geochemical similarities and differences between cl and br during magmatic and hydrothermal processes our data suggests that f and cl contents in apatite biotite and amphibole can indeed be useful monitors of the halogen systematics in magmas but they may also be subject to post magmatic changes to variable extents the relatively small radius and compatible f cation seems to be less prone to post magmatic alteration and is likely to best reflect the original magmatic halogen abundances especially in apatite however the larger and probably more incompatible cl anion is more easily re mobilized as reflected by strong redistribution of cl in biotite and amphibole which have been clearly overprinted by hydrothermal fluids in certain cases the ability of halogens to re distribute themselves after magmatic equilibrium partitioning as emphasized by our data suggests that observed partitioning especially between apatite and biotite may also be used as a very sensitive indicator for post magmatic hydrothermal processes

primary aqueous fluids in rhyolitic magmas melt inclusion evidence for pre and post trapping exsolution abstract this study examines melt inclusions containing bubbles of aqueous fluid l v and l v occurring in rhyolites from the okataina volcanic centre new zealand and the rio blanco cu mo deposit chile we demonstrate that these aqueous fluids coexisted with silicate melts magmas and represent either post trapping exsolution in the case of okataina or co trapping of phases already coexisting in the magma in the case of rio blanco microthermometry proves that some of the bubbles are a single phase aqueous liquid and all are shown by pixe analysis to be metal rich saline solutions as such these aqueous fluids provide the closest approximation to direct testing of the proposition that cooling magmas exsolve metal rich aqueous fluid in the case of pre trapping exsolution at rio blanco we show that some inclusions record and preserve magmatic emulsions melt aqueous fluid that are the first stage in the evolution of hydrothermal fluids we demonstrate that heating experiments on volatile rich melt inclusions can produce in situ exsolution of hypersaline metal rich aqueous fluid bubbles potentially permitting magma chamber processes to be experimentally modelled

determination of acoustic waveguide invariant using ships as sources of opportunity in a shallow water marine environment the waveguide invariant wgi is a property that can be used to localize acoustic radiators and extract information about the environment here the wgi is determined using ships as sources of opportunity tracked using the automatic identification system ais the relationship between range acoustic intensity and frequency for a ship in a known position is used to determine the wgi parameter these values are interpolated and a map of is generated the method is demonstrated using data collected in a field experiment on a single hydrophone in a shallow water environment off the coast of southern california

paleohydrogeology of the san joaquin basin california mass transport can have a significant effect on chemical diagenetic processes in sedimentary basins this paper presents results from the first part of a study that was designed to explore the role of an evolving hydrodynamic system in driving mass transport and chemical diagenesis using the san joaquin basin of california as a field area the authors use coupled hydrogeologic models to establish the paleohydrogeology thermal history and behavior of nonreactive solutes in the basin these models rely on extensive geological information and account for variable density fluid flow heat transport solute transport tectonic uplift sediment compaction and clay dehydration in the numerical simulations tectonic uplift and ocean regression led to large scale changes in fluid flow and composition by strengthening topography driven fluid flow and allowing deep influx of fresh ground water in the san joaquin basin sediment compaction due to rapid deposition created moderate overpressures leading to upward flow from depth the unusual distribution of salinity in the basin reflects influx of fresh ground water to depths of as much as 2 km and dilution of saline fluids by dehydration reactions at depths greater than approximately 2 5 km simulations projecting the future salinity of the basin show marine salinities persisting for moremore than 10 m y after ocean regression results also show a change from topography to compaction driven flow in the stevens sandstone at ca 5 ma that coincides with an observed change in the diagenetic sequence results of this investigation provide a framework for future hydrologic research exploring the link between fluid flow and diagenesis less

petrogenesis of adakitic porphyries in an extensional tectonic setting dexing south china implications for the genesis of porphyry copper mineralization the dexing adakitic porphyries quartz diorite granodiorite porphyries associated with giant porphyry cu deposits are located in the interior of a continent south china they exhibit relatively high mgo cr ni and sr contents high la yb and sr y ratios but low yb and y contents similar to adakites produced by slab melting associated with subduction however they are characterized by bulk earth like nd sr isotope compositions end t 1 14 to 1 80 and 87 sr 86 sr i 0 7044 0 7047 and high th 12 6 27 2ppm contents and th ce 0 19 0 94 ratios which are different from those of cenozoic slab derived adakites sensitive high resolution ion microprobe shrimp geochronology studies of zircons reveal that the dexing adakitic porphyries have a crystallization age of 171 3ma this age is contemporaneous with middle jurassic extension within the shi han rift zone and within plate magmatism elsewhere in south china indicating that the dexing adakitic porphyries were probably formed in an extensional tectonic regime in the interior of the continent rather than in an arc setting their high th contents and th ce ratios and middle jurassic age argue against an origin from a neoproterozoic 1000ma stalled slab in the mantle taking into account available data for the regional metamorphic magmatic rocks and the present day crustal thickness 31km in the area we suggest that the dexing adakitic porphyries were most probably generated by partial melting of delaminated lower crust which was possibly triggered by upwelling of the asthenospheric mantle due to the activity of the shi hang rift zone moreover the dexing adakitic magmas must have interacted with the surrounding mantle peridotite during their ascent which elevated not only their mgo cr and ni contents but also the oxygen fugacity fo2 of the mantle the high fo2 could have induced oxidation of metallic sulfides in the mantle and mobilization of chalcophile elements which are required to produce associated cu mineralization therefore the cu metallogenesis associated with the dexing adakitic porphyries is probably related to partial melting of delaminated lower crust similar to the metallogenesis accompanying slab melting

diagenesis and reservoir quality evolution of palaeocene deep water marine sandstones the shetland faroes basin british continental shelf abstract the palaeocene deep water marine sandstones recovered from six wells in the shetland faroes basin represent lowstand transgressive and highstand systems tract turbiditic sediments mineralogic petrographic and geochemical analyses of these siliciclastics are used to decipher and discuss the diagenetic alterations and subsequent reservoir quality evolution the middle upper palaeocene sandstones subarkoses to arkoses from the shetland faroes basin british continental shelf are submarine turbiditic deposits that are cemented predominantly by carbonates quartz and clay minerals carbonate cements intergranular and grain replacive calcite siderite ferroan dolomite and ankerite are of eogenetic and mesogenetic origins the eogenetic alterations have been mediated by marine meteoric and mixed marine meteoric porewaters and resulted mainly in the precipitation of calcite 18 o v pdb 10 9 and 3 8 trace amounts of non ferroan dolomite siderite 18 o v pdb 14 4 to 0 6 as well as smectite and kaolinite in the lowstand systems tract lst and highstand systems tract hst turbiditic sandstone below the sequence boundary minor eogenetic siderite has precipitated between expanded and kaolinitized micas primarily biotite the mesogenetic alterations are interpreted to have been mediated by evolved marine porewaters and resulted in the precipitation of calcite 18 o v pdb 12 9 to 7 8 and fe dolomite ankerite 18 o v pdb 12 1 to 6 3 at temperatures of 50 140 and 60 140 c respectively quartz overgrowths and outgrowth which post and pre date the mesogenetic carbonate cements is more common in the lst and tst of distal turbiditic sandstone discrete quartz cement which is closely associated with illite and chlorite is the final diagenetic phase the clay minerals include intergranular and grain replacive eogenetic kaolinite smectite and mesogenetic illite and chlorite kaolinite has been subjected to mesogenetic replacement by dickite the k feldspar and plagioclase grains have been albitized dissolution of calcite cement and of framework grain feldspar volcanic fragments and mud intraclasts has resulted in a considerable enhancement of reservoir quality

calcium mass transport and sandstone diagenesis during compaction driven flow stevens sandstone san joaquin basin california sediment compaction provides a limited source of fluids for diagenesis and drives fluid flow at average rates of only 1 mm yr nevertheless many geochemical and petrographic studies of diagenesis provide evidence of significant mass transport in systems where fluid flow appears to be compaction driven this apparent discrepancy could arise because diagenetic studies generally are concerned with relatively permeable petroleum reservoirs focused fluid flow through permeable zones could increase local flow rates and allow mixing of fluids from different sources this study uses the stevens sandstone of the san joaquin basin to explore the potential diagenetic effects of fluid focusing during compaction driven flow over a 5 m y period reactive transport simulations incorporate a new kinetic expression for plagioclase dissolution and suggest that rate limited plagioclase dissolution drove calcium enrichment of pore fluids and caused precipitation of calcite kaolinite and albite in spite of the importance of this rate limited reaction simulations show that influx of fluids from compacting shale could limit the distribution of calcite and kaolinite in adjacent sandstones although calcium mass transport is predicted on a scale of kilometers upward flow of calcium rich fluids from deep beds does not significantly increase calcite volume relative to closed system predictions increased transverse dispersivity increases mixing which further limits precipitation of calcite and kaolinite results are consistent with field observations of fluid chemistry although simulations account for

measured depth dependence of waveguide invariant in shallow water with a summer profile acoustic intensity striation patterns were measured in the time frequency domain using an l shaped array and two simultaneously towed broadband 350 650 hz sources at depths above and below the thermocline under summer profile conditions distributions of the waveguide invariant parameter extracted from the acoustic striation patterns peak at different values when receivers are above or below the thermocline for a source that is below the thermocline however the distributions show similar characteristics when the source is above the thermocline experimental results are verified by a numerical analysis of phase slowness group slowness and relative amplitudes of acoustic modes

mineral chemistry of hydrothermal biotite from the kahang porphyry copper deposit ne isfahan central province of iran abstract the kahang porphyry cu deposit located northeast of isfahan city in central of iran is associated with a composite miocene stock and ranges in composition from diorite through granodiorite to quartz monzonite field observations and petrographic studies show that the emplacement of the kahang stock occurred in several pulses each associated with its related hydrothermal activity early hydrothermal alteration started with a potassic style in the central part of the system and produced a secondary biotite k feldspar magnetite assemblage accompanied by chalcopyrite and pyrite mineralization propylitic alteration that took place at the same time as the potassic alteration occurred in the peripheral portions of the stock subsequent phyllic alteration overprinted earlier potassic and propylitic alterations biotite grains from the potassic and phyllic zones show distinct chemical compositions the feo tio2 mno k2o and na2o concentrations in biotite from the phyllic alteration zone are lower than those from the potassic alteration zone the f and cl contents of biotite from the potassic alteration zone display relatively high positive correlation with the xmg the fluorine intercept values iv f from the potassic and phyllic alteration zones are strongly correlated with the fluorine chlorine intercept values iv f cl biotite geothermometry for the potassic and phyllic alteration zones based on the biotite geothermometer of beane 1974 yields a temperature range of 422 to 437 c mean 430 c and 329 to 336 c mean 333 c respectively the position of data in log xf xoh ratio vs xmg and xfe diagram suggests that biotite formed under dissimilar composition and temperature conditions in the potassic and phyllic alteration zones calculated log fugacity ratios of fh2o fhf fh2o fhcl and fhf fhcl show that hydrothermal fluids associated with the potassic alteration were distinctively different from those fluids associated with the phyllic alteration zone at kahang porphyry cu deposit the results of this research indicate that the chemistry of biotite is related to the chemical composition of the magma and the prevailing physical conditions during crystallization

a long range and variable focus phase conjugation experiment in shallow water a second phase conjugation experiment was conducted in the mediterranean sea in may 1997 extending the results of the earlier time reversal mirror experiment kuperman et al j acoust soc am 103 25 40 1998 new results reported here include 1 extending the range of focus from the earlier result of 6 km out to 30 km 2 verifying a new technique to refocus at ranges other than that of the probe source song et al j acoust soc am 103 3234 3240 1998 and 3 demonstrating that probe source pulses up to 1 week old can be refocused successfully

tracing the evolution and distribution of f and cl in plutonic systems from volatile bearing minerals a case study from the liujiawa pluton dabie orogen china fluorine and chlorine play an important role in magmatic differentiation hydrothermal alteration and related mineralization processes but tracing their evolution in magmatic and especially plutonic systems is not an easy task the f and cl in melts can be estimated from f and cl concentrations in minerals provided that partitioning between minerals and melts are constrained based on available partitioning models between mineral melt mineral fluid and melt fluid a set of equations has been derived to determine f and cl concentrations in melts from the compositions of amphibole biotite and apatite the new calculation procedure has been applied to a plutonic system the liujiawa pluton eastern dabie orogen china cl and f concentrations in amphiboles biotites and apatites from different rock types gabbronorite two pyroxene diorite clinopyroxene diorite and hornblende gabbro have been determined by electron microprobe most amphiboles show a negative correlation between log cl oh and mg number and a positive correlation between log f oh and a site occupation biotites from the gabbronorite and two pyroxene diorite show a slight positive correlation between log cl oh and mg which is however not the case for the clinopyroxene diorite apatites from all the samples are rich in f and show negative correlations between cl and f concentrations in our case study we demonstrate that the cl concentration in melt remains approximately constant at 1 000 2 000 ppm over the major crystallization interval but decreases strongly at near solidus temperatures as a result of fluid exsolution the f concentration in melt remains nearly constant at ca 2 000 3 000 ppm at high temperatures as well as near solidus conditions indicating that it is not largely affected by fluid exsolution because of its strongly preferred incorporation into melt interestingly the evolution of cl and f concentrations in melt with magmatic differentiation is similar to that determined in volcanic systems suggesting that the evolution of cl and f in melts during crystallization and late magmatic stages at depth plutonic systems is similar to that observed in volcanic systems during decompression and degassing

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

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

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

one dimensional reactive transport models of alteration in the tongchang porphyry copper deposit dexing district jiangxi province china in the tongchang porphyry copper deposit the main hydrothermal alteration is most intense in and near the contact zone and gradually attenuates inward and outward showing a symmetrical zoning with respect to the contact zone detailed field investigations of wall rock alteration and ore controlling fractures combined with laboratory studies of lithology mineral composition and fluid inclusions have led to an assessment of initial and boundary conditions and physical parameters such as species concentration mineral volume fraction temperature porosity reactive surface area and flow velocity required for dynamic modeling of this system we have developed a new program to model the coupled process of fluid flow involving advection and diffusion and chemical reactions incorporating mineral dissolution precipitation and have numerically simulated the spatial and temporal evolution of the systems for a duration of 100 000 yr in the simulations transient temperature fields are calculated for the main temperature range of ore formation from 200 degrees to 350 degrees c simulated mineral assemblages are generally in agreement with those observed in the real system the important conclusions drawn from the combined researches of geology and geochemistry as well as dynamics of coupled fluid transport and reactions are as follows fluid flow and reactions were mainly controlled by the fractures striking around north south and dipping to the west in the exocontact zone schistosity cleavages were also important fluid pathways in addition to the fractures the formation of closely spaced fractures in the contact zone and especially in the exocontact zone by tectonic activity after potassium metasomatism and the reactive flow from the contact zone inward and outward were the principal reasons for the occurrence of the contact zone symmetrical alteration zone in the porphyry body both the dissolution and precipitation of minerals were important the rate of dissolution or precipitation of minerals gradually decreased in time the nearer it was to the contact zone spatially the earlier the dissolution or precipitation of minerals was finished in the exocontact metamorphic wall rock the main processes were the transport and precipitation of sio sub 2 sub aq the rate of silification gradually decreased in time and space in the alteration of porphyry body na super was evidently removed from the alteration zone and ca super 2 removed from the intense alteration zone to weak alteration zone and the fluid was weakly acidic ph asymp 4 in the metamorphic wall rock sio sub 2 sub aq was mainly brought in from fluid the evolution of sio sub 2 sub aq cl super ca super 2 and co 3 super 2 was intimately correlated with alteration mineralization intensity

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

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

can economic porphyry copper mineralization be generated by a typical calc alkaline melt numerical simulation of chlorine and copper partitioning between a crystallizing melt and exsolving aqueous fluids indicates that typical calc alkaline magmas contain sufficient copper chlorine and water to produce economic porphyry copper mineralization neither an elevated copper content in the magma nor an additional large volume of magma are required to provide metals or volatiles the most important variables that determine the volume of melt necessary to produce sufficient copper are the degree of compatible behavior displayed by copper the ratio of initial water in the melt to the water saturation level and the initial chlorine water ratio of the melt the absolute values for initial water in the melt and water content at saturation are relatively unimportant in determining the required melt volume the bulk salinity of the exsolved fluid may vary from 2 0 wt nacl to saturation levels 84 wt nacl at 700 c indicating that boiling is not necessary to produce high salinity brines at appropriate p t xnacl conditions the magmatic aqueous fluid separates into a saline liquid which transports most of the copper and a low salinity vapor the salinities of the two immiscible phases are governed by the p t conditions while the bulk fluid salinity determines the mass fractions of liquid and vapor formed pressure quenching causes rapid crystallization of the aplitic groundmass in porphyritic rocks associated with copper mineralization and significantly reduces the amount of chlorine and copper partitioning to the aqueous fluid this results in abrupt and possibly large reductions in fluid salinity and causes copper to become concentrated in the melt as copper is transported from the melt by the earliest exsolving fluids in deep 2 0 kbar systems and by late exsolving fluids in shallow 0 5 kbar systems the relative timing of pressure quenching aplite formation and fluid transport of copper from the melt can vary significantly in systems produced under different confining pressures model results incorporating petrologic constraints determined for yerington nevada are in good agreement with observed mineralization