gold in porphyry copper deposits its abundance and fate abstract porphyry copper deposits are among the largest reservoirs of gold in the upper crust and are important potential sources for gold in lower temperature epithermal deposits whether gold remains in porphyry copper deposits is important both to their economic attractiveness and to the distribution of gold in the upper crust cu au atomic ratios of porphyry copper ore deposits form a continuous range from about 5000 to 5 000 000 with a median near 40 000 which separates gold rich and gold poor deposits gold is found in porphyry copper deposits in solid solution in cu fe and cu sulfides and as small grains of native gold usually along boundaries of bornite sims ion probe analyses of ore minerals from the gold rich batu hijau kingking and skouries porphyry copper deposits show that bornite contains about 1 ppm au whereas chalcopyrite contains about an order of magnitude less chalcocite and covellite contain 10 20 ppm au but are not abundant enough to account for a significant part of the gold endowment in many porphyry copper deposits the amount of gold presently in solid solution in cu fe sulfides is not adequate to account for all the gold in porphyry copper deposits and the remainder is present as micron scale grains of native gold experiments in the cu fe s au system show that bornite and chalcopyrite can contain about 1000 ppm gold at typical porphyry copper formation temperatures of 600 700 c and indicate that bornite and chalcopyrite in porphyry copper deposits were saturated with respect to gold at temperatures of only 200 300 c in contrast cu au ratios of bulk ore in porphyry copper deposits would require bornite and chalcopyrite to be saturated with respect to gold at temperatures similar to those at which primary potassic ore and alteration are thought to form this indicates that the maximum gold endowment of porphyry copper deposits is probably fixed by the amount of gold that will go into solid solution in cu fe sulfides when the deposit forms at high temperature and that gold is not commonly added later from other sources although it can be redistributed during cooling or later events the experimental data also suggest that high temperature 600 700 c vapors can extract considerably more gold from porphyry copper systems than can low temperature 300 c alteration comparison to cu au ratios of volcanic emissions suggests further that high temperature processes remove copper relative to gold from porphyry copper systems whereas low temperature processes remove gold preferentially and that this can account for deposits with extremely low and high cu au ratios respectively deposits with cu au ratios between about 20 000 and 100 000 however probably reflect different degrees of removal of gold or copper by immiscible sulfides

evidence of elevated pressure and temperature during burial of the salem limestone in south central indiana usa and its implications for surprisingly deep burial abstract a minor normal fault related to compaction of the grainstone shoal facies of the salem limestone in south central indiana provides an unusual opportunity to test the pressure and temperature of both faulting and associated stylolitization syn deformational sphalerite occurs in voids along the fault where it intersects an organic rich shale parting in the sand flat facies overlying the grainstone the sphalerite contains fluid inclusions that can be used for microthermobaric measurements most fluid inclusions in the sphalerite are demonstrably cogenetic with the host sphalerite and of the two phase aqueous type common in indiana although many contain petroleum and others contain gas crushing tests in kerosene indicate that the aqueous inclusions contain dissolved methane in varying amounts as high as 1000 ppm microthermometry shows that late sphalerite growth late fault movement and late stylolitization all occurred as conditions approached 108 c and 292 bars this pressure is in accord with a normal basinal geothermal gradient of 32 5 c km that would produce the observed temperature under hydrostatic conditions at a burial depth of 2 7 km using an average fluid density of 1 1 g cm 3 these results serve as a reminder that fluid inclusions in diagenetic minerals hold important temperature and pressure information regarding burial diagenesis of paleozoic rocks across the north american midcontinent detailed study of dissolved gases in fluids trapped in disseminated sphalerite that is common across the midcontinent could help resolve the enigma of sedimentary rocks with high thermal maturity exposed at the surface across the region

hydrothermal evolution in the maher abad porphyry cu au deposit sw birjand eastern iran evidence from fluid inclusions abstract copper and gold mineralization in the maher abad deposit eastern iran is closely related to the multiple emplacement episodes of upper eocene granodiorite porphyries within andesitic volcaniclastic and coeval quartz monzonite stocks the magmatic hydrothermal fluids thereafter hydrofracturing provided appropriate conduits formed a stockwork of quartz and quartz sulfide veinlets within the porphyritic host rocks which were extensively altered into potassic propylitic phyllic and argillic assemblages four main vein veinlet groups have been identified a quartz k feldspar biotite anhydrite with pyrite chalcopyrite sporadic magnetite and pyrrhotite b quartz pyrite and minor chalcopyrite c chalcopyrite quartz and or minor bornite pyrite digenite and sporadic pyrrhotite and d quartz calcite and or clay minerals pyrite hematite galena the cu au mineralization is mainly associated with the early potassic biotite alteration zone in the deep central part of the madanha stock based on the phase contents at room temperature three types of fluid inclusions are recognized at maher abad 1 liquid rich two phase lv 2 vapor rich vl h and 3 halite bearing multiphase lvh homogenization experiments revealed a temperature range of 150 488 c for the studied inclusions ice melting of aqueous two phase inclusions and melting of halite in the aqueous multiphase inclusions provide salinity of 9 5 to 47 9 wt nacl equivalent fluid inclusion studies reveal that the single phase low salinity magmatic fluid exsolved from a granodioritic magma was separated into vapor and hypersaline brine 45 wt nacl eq phases the coexisting phases were trapped at temperature 460 c and lithostatic pressure of 350 bars corresponding to a depth of 1 3 km as vl h and lvh fluid inclusions respectively such magmatic derived fluids underwent phase separation episodically under lithostatic pressure conditions and formed the early copper sulfide bearing quartz veinlets intimately related to the potassic alteration zone copper iron sulfide precipitation and phase separation concomitant of boiling in this zone led to rapid depletion of the fluid in reduced sulfur as a result au hs 2 complexes are destabilized forcing most of the gold to precipitate above 400 c a positive trend of the homogenization temperature and salinity during the formation of the phyllic alteration zone is attributed to the cooling of a moderately saline fluid produced dominantly by magmatic vapor condensation and its subsequent boiling and mixing with meteoric waters at a hydrostatic pressure of 100 125 bars corresponding to a depth of 1 1 2 km the argillic alteration zone formed at temperature of 210 230 c from fluids with salinity of 16 18 nacl wt eq at a hydrostatic pressure of 80 bars and a depth of 800 m from paleo surface the fluid density is typically lower 3 than that of the potassic zone 1 g cm 3 indicating that the late trapped fluid was more dilute

bajo de la alumbrera copper gold deposit stable isotope evidence for a porphyry related hydrothermal system dominated by magmatic aqueous fluids alteration zones at the gold rich bajo de la alumbrera porphyry copper deposit in northwestern argentina are centered on several porphyritic intrusions they are zoned from a central copper iron sulfide and gold mineralized potassic biotite k feldspar quartz core outward to propylitic chlorite illite epidote calcite assemblages a mineralized intermediate argillic alteration assemblage chlorite illite pyrite has overprinted the potassic alteration zone across the top and sides of the deposit and is itself zoned outward into phyllic quartzinuscovite illite pyrite alteration this study contributes new data to previously reported delta 18 o and delta d compositions of fluids responsible for the alteration at bajo de la alumbrera and the data are used to infer likely ore forming processes measured and calculated delta 18 o and delta d values of fluids 8 3 to 10 2 and 33 to 81 parts per thousand respectively confirm a primary magmatic origin for the earliest potassic alteration phase lower temperature potassic alteration formed from magmatic fluids with lower delta d values down to 123 parts per thousand these depleted compositions are distinct from meteoric water and consistent with degassing and volatile exsolution of magmatic fluids derived from an underlying magma variability in the calculated composition of fluid associated with potassic alteration is explained in terms of phase separation or boiling if copper iron sulfide deposition occurred during cooling as proposed elsewhere this cooling was largely a result of phase separation magmatic water was directly involved in the formation of overprinting intermediate argillic alteration assemblages at bajo de la alumbrera calculated delta 18 o and delta d values of fluids associated with this alteration range from 4 8 to 8 1 and 31 to 71 per mil respectively compositions determined for fluids associated with phyllic alteration 0 8 to 10 2 and 31 to 119 parts per thousand overlap with the values determined for the intermediate argillic alteration we infer that phyllic alteration assemblages developed during two stages the first was a high temperature 400 degrees 300 degrees c stage with d depleted water delta d 66 to 119 parts per thousand this compositional range may have resulted from magma degassing and or the injection of new magmatic water into a compositionally evolved hydrothermal system the isotopic variations also can be explained by increased fluid rock interaction the second stage of phyllic alteration occurred at a lower temperature similar to 200 degrees c and variations in the modeled isotopic compositions imply mixing of magmatic and meteoric waters ore deposition that occurred late in the evolution of the hydrothermal system was probably associated with further cooling of the magmatic fluid in part caused by fluid rock interaction and phase separation changing ph and or oxygen fuoracity may have caused additional ore deposition the ingress of meteoric water appears to postdate the bulk of mineralization and occurred as the system at bajo de la alumbrera waned

synthetic fluid inclusions in natural quartz iii determination of phase equilibrium properties in the system h2o nacl to 1000 c and 1500 bars phase equilibria in the system h2o nacl have been determined to 1000 c and 1500 bars using synthetic fluid inclusions formed by healing fractures in inclusion free brazilian quartz in the presence of the two coexisting immiscible h2o nacl fluids at various temperatures and pressures petrographic and microthermometric analyses indicate that the inclusions trapped one or the other of the two fluids present or mixtures of the two salinities of the two coexisting phases were obtained from heating and freezing studies on those inclusions which trapped only a single homogeneous fluid phase results of the present study are consistent with previously published data on the h2o nacl system at lower temperatures and pressures and indicate that the two phase field extends well into the p t range of most shallow magmatic hydrothermal activity as a consequence chloride brines exsolved from many epizonal plutons during the process of second boiling should immediately separate into a high salinity liquid phase and a lower salinity vapor phase and produce coexisting halite bearing and vapor rich fluid inclusions this observation is consistent with results of numerous fluid inclusion studies of ore deposits associated with shallow intrusions particularly the porphyry copper deposits in which halite bearing and coexisting vapor rich inclusions are commonly associated with the earliest stages of magmatic hydrothermal activity

impact of intraseasonal oscillations on the activity of tropical cyclones in summer over the south china sea part i local tropical cyclones abstractthe south china sea scs is affected by two intraseasonal components in summer the madden julian oscillation mjo and the quasi biweekly oscillation qbwo in the present study the impacts of the mjo and qbwo on tropical cyclones tcs locally formed in the scs local tcs in summer are investigated the results show that both the mjo and qbwo can affect the genesis frequency location and motion of the local tcs more tcs form in the convectively active phases of the mjo and qbwo in the northern scs with the northward propagation of the mjo and qbwo convective signals the major tc genesis location also shifts northward since the western pacific subtropical high shifts eastward westward when convection associated with the mjo and qbwo in the northern scs is enhanced suppressed the steering flow in the major tc genesis region is favorable for the eastward westward movement of tcs results from the composite analysis of the steering flow indicate that both the mjo and qbwo play an im

archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec part i geologic relations and formation of the vein system the sigma deposit consists of an archean gold bearing vein system in metavolcanic rocks intruded by an irregular body of porphyritic diorite both affected by regional deformation and in turn cut by younger undeformed feldspar porphyry dikes the veins cut all rock types and are composed chiefly of quartz and tourmaline with minor amounts of carbonates pyrite chlorite scheelite and free gold they were emplaced during or after a greenschist facies metamorphism postdating the intrusion of feldspar porphyry dikes the veins were not significantly affected by any subsequent metamorphism or tectonism two principal types of veins occur in the mine subvertical veins and subhorizontal veins they are contemporaneous and cogenetic subvertical veins occur within steeply dipping east west trending ductile shear zones along which reverse subvertical displacements have taken place the veins occupy openings created by overriding of undulations and irregularities of foliation and slip planes during progressive shearing movements within the shears subhorizontal veins occupy extensional fractures which developed between ductile shear zones preferentially in the more competent host rocks these veins were formed by one or several episodes of open space filling geologic relations indicate that the mineralized veins were emplaced progressively in a dynamic tectonic environment during and shortly after the formation of ductile shear zones a structural analysis has shown that the ductile shear zones and the two vein types can be related to a single strain ellipsoid of the following orientation the z axis trending north south and horizontal the y axis plunging 10 degrees west and the x axis plunging 80 degrees east the deformation responsible for the generation of ductile shear zones and emplacement of the veins is ascribed to a late north south trending compression postdating regional deformation

petrology and oxygen isotope geochemistry of a fossil seawater hydrothermal system within the solea graben northern troodos ophiolite cyprus hydrothermal mineral zonations and o isotope patterns of the northern troodos complex do not parallel the ophiolite pseudostratigraphy but reflect the convective geometry of an upper cretaceous seawater hydrothermal system large areas of the sheeted intrusive complex sic including the subaxial region of the solea graben are composed of 18o rich subgreenschist mineral assemblages and may represent regions of diffuse seawater recharge other areas of the sic are recrystallized to distinctive epidosite rocks granular high variance assemblages of epidote quartz chlorite that are depleted in 18o al2o3 na2o k2o zr cu and zn and are enriched in cao and sr compared with other mafic volcanic and dike rocks of the solea graben epidosite alteration occurred at temperatures of 310 370 c and involved fluids with 18o values and salinities similar to those of upper cretaceous seawater the epidosite zones are discordant with earlier mineral o isotope zonations and with the axis of spreading in the solea graben suggesting a postspreading off axis origin the seawater hydrothermal system responsible for solea graben massive sulfide deposits was probably driven by hypabyssal intrusions not exposed emplaced in a terminal failed spreading episode the geometries of o isotope surfaces within the solea graben imply that the epidosites formed in fossil upflow and deep recharge conduits depletions in base metals show that epidosite alteration liberated cu and zn to mineralizing fluids within the fossil upflow zone

high cu grades in porphyry cu deposits and their relationship to emplacement depth of magmatic sources observations at several porphyry cu deposits indicate that in those formed above source magma chambers emplaced to relatively shallow levels roofs 3 4 km deep zones of higher cu grade are associated with the oldest intrusions of a central porphyry cluster abundant early a type quartz veins secondary feldspar alteration and usually high fe fe cu low s fe cu sulfide oxide mineral assemblages in deposits for which source magma chambers were deeper roofs 5 km porphyries closest in age to ore are spatially less directly related to mineralization in these higher cu grades in early mineralization comprise swarms of veinlets with alteration halos that include sericite as well as secondary feldspar and biotite sulfide oxide assemblages are usually of lower fe fe cu and higher s fe cu these differences in deposit characteristics appear to correspond with a change from two phase chloride bearing aqueous fluids that would exsolve from magma at shallow depths to one phase fluids deeper

meteoric water induced selvage style greisen alteration in the achala batholith central argentina zoned selvage style greisen alteration is common along fracture zones in the 350 ma achala batholith of central argentina zonation proceeds from only slightly altered monzogranite through zones of biotite alteration zone 1 partial alteration of feldspar zone 2 and intensely altered zones characterized by the complete destruction of feldspar formation of secondary muscovite and crystallization of secondary quartz in veins and vugs zone 3 fluid inclusion studies indicate that fluids involved in the formation of secondary quartz were dilute aye 1 5 eq wt nacl and were trapped at temperatures less than 350 c oxygen and hydrogen isotopic data collected from primary quartz feldspar and muscovite and secondary muscovite and quartz indicate a complex history of isotopic exchange and mineral precipitation feldspar 18o values range from 3 1 to 11 6 whereas primary quartz 18o values are much more restricted at 12 0 to 12 7 plots of 18ofds vs 18oqtz or 18omus show steep slopes characteristic of kinetically dominated exchange with a low 18o fluid feldspar quartz and primary muscovite 18o values as well as muscovite d values decrease toward zone 3 and are consistent with a model of fluid advection through fractures and diffusive transport perpendicular to fracture margins isotopic data suggest that primary minerals initially exchanged with a fluid of d 175 to 135 and 18o 23 to 18 however secondary muscovite and quartz are characterized by 18o values of 11 6 to 5 0 and 16 0 to 7 1 respectively secondary muscovite d values 117 to 83 are generally higher than those of exchanged primary muscovite in zones 2 and 3 fluid inclusions extracted from late stage quartz have d values of 55 to 54 consistent with computed values for fluid in equilibrium with secondary muscovite meteoric water with this hydrogen isotopic composition would be characterized by a 18o value of 8 again consistent with 18oh2o computed from late stage secondary muscovite the data suggest that early isotopic exchange was initiated by reaction with a low d low 180 meteoric water but that fluid composition changed through time increases in fluid 18o and d values may be related to changes in climate and geographic location or elevation of the area or may in part be related to interaction with evolved fluids that exchanged isotopes in other pottions of the flow system exchange durations computed from feldspar and quartz 18o values are 65 000 yr and indicate that fluid introduction into the fracture system was episodic in nature such a pattern of changes with time in the isotopic composition of meteoric mater may be characteristic of hydrothermal alteration of bark arc granitoid rocks of the eastern sierras pampeanas

trace element composition of quartz from porphyry systems a tracer of the mineralizing fluid evolution trace element composition of hydrothermal quartz reflects the p t x conditions of the mineralizing fluids and can be a potential tracer of the fluid evolution to explore this potential quartz trace element data from 21 porphyry cu au mo and epithermal polymetallic deposits were compiled in addition quartz trace element data from six granite related systems granite pegmatite greisen sn w mo veins and from a subset of calc alkaline arc related volcanic rocks were also compiled for comparison for porphyry cu au mo deposits quartz compositions are from publications in which the sequence of quartz bearing veins and their potential reopening were documented as well as their precipitation temperatures and pressures the compiled dataset shows that trace element composition of quartz continuously evolved between the different porphyry veins and quartz generations a b c d and e the observed evolution reflects the cooling and or compositional variations of the hydrothermal fluids the quartz al ti sb ti ge ti and sb ge ti ratios allow for the discrimination of quartz from different vein generations of porphyry cu au mo deposits this study shows that quartz composition preferentially combined with cathodoluminescence images is an efficient proxy for tracing the evolution of the hydrothermal fluids in porphyry systems and can be used as a vectoring tool to target the centers of porphyry systems

geochronology and fluid inclusion studies of the lailisigaoer and lamasu porphyry skarn cu mo deposits in northwestern tianshan china abstract the lailisigaoer porphyry mo cu and lamasu porphyry skarn cu deposits are located in the northwestern tianshan orogenic belt which is in the northwestern china according to re os analysis of molybdenite the time of mineralization of the lailisigaoer deposit is 377 ma and shrimp zircon u pb analysis dates the ore hosted intrusion of the lamasu deposit to 378 ma five types of fluid inclusions fis have been identified in both deposits h 2 o rich inclusions co 2 bearing inclusions halite bearing inclusions methane rich inclusions and pure co 2 inclusions in the lailisigaoer deposit the early stage fluid of the quartz phenocryst belongs to a nacl h 2 o system with total homogenization temperatures t h ranging from 300 to 395 c with a mean salinity of 9 0 wt nacl in the ore forming stage the fluid develops into a h 2 o nacl co 2 system due to boiling and decarbonation the t h values and salinities cluster between 220 and 370 c and between 0 and 33 0 wt nacl respectively the hydrothermal characteristics of the late quartz calcite stage are similar to those of the meteoric fluid in the lamasu deposit the early stage fluid of the quartz phenocryst belongs to a nacl h 2 o system with t h values ranging from 245 to 459 c and a mean salinity of 6 0 wt nacl in the ore forming stage due to the contact metamorphism between the hydrothermal fluid and wall rock the fluid evolves to a nacl h 2 o ch 4 system the t h values and salinities cluster between 220 and 360 c and between 0 and 17 3 wt nacl respectively the fluid of the late quartz sulfide stage coincides with the meteoric fluid in the mineralizing fluid of the lailisigaoer deposit the captured temperatures and pressures are between 210 and 350 c and between 170 and 600 bars respectively which are consistent with fluctuation between hydrostatic and lithostatic pressure corresponding to the estimated paleodepths of 1 7 2 2 km boiling is the dominant mineralizing mechanism in the lailisigaoer deposit whereas the contact metamorphism between the magmatic hydrothermal fluid and country rocks is the dominant mechanism in the lamasu deposit both deposits are formed in the continental arc setting related to the southward subduction of the north tianshan oceanic slab beneath the yili central tianshan block

interannual and interdecadal variability of the summertime western north pacific subtropical high 1 the western north pacific subtropical high wnpsh in summer exhibits significant 2 3 years and 3 5 years oscillations with interdecadal variability the 2 3 year oscillation is most evident after 1990 it is accompanied by anomalous meridional overturning circulation characterized by warm sst anomalies ssta and ascending motion in the maritime continent and anomalous descending motion near the philippine sea and by evolving warm to cold ssta in the central eastern pacific from the preceding winter to the summer the 3 5 year oscillation is most pronounced during the 1980s it is accompanied by anomalous descending motion over the maritime continent and warm ssta in the central eastern equatorial pacific that persists from the preceding winter to the summer the complementary cooling and descending motion in the western pacific are related to anomalous east west circulation associated with enso

out of phase relationship between tropical cyclones generated locally in the south china sea and non locally from the northwest pacific ocean tropical cyclones tcs in the south china sea scs are either generated locally or formed non locally in the northwest pacific ocean nwp and entered into the scs here it is found that local tcs vary out of phase with non local tcs in summer that is if fewer more tcs enter into the scs from the nwp more fewer tcs are generated over the scs further analyses show that variability of the western pacific subtropical high wpsh is responsible for the out of phase relationship as the wpsh shifts eastward westward fewer more non local tcs formed in the nwp can enter into the scs because tcs are recurved northward moved westward due to the eastward westward movement of the wpsh positive negative low level vorticity anomalies weak strong vertical wind shear between the upper and lower troposphere and anomalous upward downward motion in the middle troposphere are induced in the northern scs the changes in the relative vorticity vertical wind shear and vertical velocity are favorable unfavorable for the local tc genesis in the scs these variations of non local and local tcs result in an out of phase relationship between tcs formed locally in the scs and non locally in the nwp

origin and evolution of the um egat and dungash orogenic gold deposits egyptian eastern desert evidence from fluid inclusions in quartz shear zone related mesothermal gold deposits of um egat and dungash in the egyptian eastern desert are hosted by greenschist facies metavolcanic and or metasedimentary rocks of pan african age both deposits comprise boudinaged quartz veins that show evidence of incipient recrystallization and are similar in alteration style structural control and mineralogy the ore mineralogy includes pyrite arsenopyrite pyrrhotite chalcopyrite galena gold occurs both in the veins usually included in arsenopyrite pyrite or pyrrhotite next to fragments of altered country rocks or disseminated in the alteration haloes arsenic in arsenopyrite and aliv in chlorite geothermometers indicate that wall rock alteration and ore mineral precipitation occurred at temperatures between 400 and 250 c fluid inclusions in vein quartz occur in clusters or along trails three types of fluid inclusions were identified based on petrography and laser micro raman spectroscopy 1 two phase carbonic inclusions with co2 ch4 n2 h2o 2 two phase aqueous inclusions and 3 three phase aqueous carbonic inclusions with ch4 final melting of ice tmf for most inclusions occurs at temperatures between 4 and 0 c indicating a low salinity 300 c but cluster into two distinct groups for each type of inclusion inclusions from the same trail or cluster are commonly characterized by different degrees of fill or different th values field petrographic and microthermometric data suggest that low salinity aqueous carbonic fluids interacted with graphite bearing metasedimentary rocks to form ch4 at t 400 c and p 3 kbars these reduced fluids leached gold as they circulated through the metavolcanic rocks carrying it in the form of bisulfide complexes interaction of these aqueous carbonic fluids with the country rocks caused hydrothermal alteration and precipitated gold bearing sulfides in the alteration zones a drop of pressure during the migration of these fluids to shallower depths along the shear zones led to phase separation at t 300 c and p 2 3 kbars quartz crystallizing over a range of lower temperatures and pressures trapped carbonic and aqueous fluids as separate inclusions in clusters along pseudosecondary and secondary trails postdepositional deformation caused decrepitation of some inclusions and the stretching and leakage of others increasing th to 250 c deformation also remobilized the gold depositing it as globules of higher fineness in secondary sites

immiscibility and continuous felsic melt fluid evolution within the rio blanco porphyry system chile evidence from inclusions in magmatic quartz the 5 2 to 3 9 ma late porphyries at rio blanco are spatially associated with hydrothermal tourmaline cemented breccias and a significant cu mo deposit magmatic inclusions in quartz from these rocks are used to better understand late stage magmatic processes particularly those involving melt melt and melt fluid immiscibility inclusions are represented by glass of common rhyolitic composition hereafter type 1 crystallized volatile rich felsic melt type 2 h2o and salt rich fluids and microphenocrysts coexistence of types 1 and 2 material within the same growth plane and within a single inclusion suggests that crystallizing rhyolitic magma separated into two silicate melts volatile poor and volatile rich the volatile rich silicate melt had a prolonged evolution extending below the solidus of volatile poor silicate melt with a progressive reduction of the silicate volatile ratio and ultimately to highly saline fluids the latter may have been the source of hydrothermal fluids that had the potential to transport metals the occurrence of immiscibility in the rio blanco rhyolites may be in some ways comparable to that in volatile rich pegmatites and strongly suggests that this process may be common in other se normal felsic magmas and important in the origin of mineralized porphyries

evolution of hydrothermal fluid characteristics at the santa rita new mexico porphyry copper deposit mineralogic and fluid inclusion investigations conducted in the laboratory combined with in situ observations of temporal relationships among geologic features demonstrate that systematic changes in hydrothermal fluid characteristics occurred with time during evolution of mineralization and alteration of the granodiorite stock at the santa rita porphyry copper deposit the earliest fluids to circulate are recorded in potassically altered orthoclase and biotite stable veins as vapor rich h 2 o co 2 inclusions and hypersaline 30 70 equiv wt nacl or kcl inclusions which homogenize over a wide temperature range from 240 degrees to greater than 800 degrees c the high salinity fluid inclusions are complex chloride brines with significant concentrations of sodium potassium copper iron and sulfur but sulfide minerals are not associated with the early potassic assemblage produced by this fluid oxygen isotope ratios of quartz in the orthoclase and biotite stable veins are identical to phenocryst quartz in the intrusion 8 2ppm later solutions circulated through newly formed fractures and older reopened veins and are recorded in low salinity less than 15 equiv wt nacl fluid inclusions which homogenize primarily in the temperature range of 220 degrees to 360 degrees c these hydrothermal fluids formed two distinct alteration assemblages as they reacted with potassically altered rock chlorite is the dominant silicate gangue mineral of the earlier chalcopyrite bearing orthoclase and clay stable assemblages and sericite characterizes the later phyllic alteration assemblage with quartz and pyrite oxygen isotope ratios of quartz of the later assemblages 8 6 10 4ppm are heavier than quartz of the earlier potassic assemblages it is concluded that the earliest hydrothermal fluids to circulate within the stock localizing the orebody at santa rita could have been derived by phase separations of fluids exsolved from crystallizing magma into condensed hypersaline liquids and h 2 o co 2 vapors as these fluids moved through fractures potassic alteration of rock occurred without concomitant deposition of sulfides later solutions of dominantly meteoric origin progressively formed hypogene copper mineralization associated with chlorite stable alteration and then phyllic alteration

the bingham canyon porphyry cu mo au deposit i sequence of intrusions vein formation and sulfide deposition the bingham canyon porphyry copper gold molybdenum deposit is one of the largest and highest grade porphyry orebodies in the world this study focused on the northwest side of the deposit where quartz mon zonite porphyry qmp the first and largest porphyry intrusion hosts the bulk of the high grade copper gold ore 1 0 cu 1 0 ppm au the north northeast trending high grade zone had pre mining dimensions of 1 500 m strike 300 m vertical and 500 m width and contained more than 500 million tonnes mt of ore associated with potassic alteration and abundant quartz veins the lack of superimposed sericitic alteration yielded ideal exposures in which to study the early high temperature stages of ore formation a style of mineralization that in many porphyry deposits represents the major period of copper introduction we mapped multiple porphyry dikes in the sequence 1 qmp 2 latite porphyry lp 3 biotite porphyry bp 4 quartz latite porphyry breccia qlpbx and 5 quartz latite porphyry qlp porphyry dikes faults and quartz veins are steeply dipping and have two dominant orientations north northeast and northwest striking dikes have a north northeast strike but they thicken and develop northwest trending apophyses and host high grade copper gold zones at intersections with northwest faults indicating that magmatic hydrothermal fluids were focused by these structural intersections each porphyry intrusion was accompanied by a similar sequence of veins potassic alteration and sulfides biotite veinlets were followed by fractures with early dark micaceous edm halos of sericite k feldspar biotite andalusite and local corundum containing disseminated bornite chalcopyrite gold edm halos are cut by multiple generations of a quartz veins representing the main cu au ore forming event postdating all intrusions are quartz molybdenite veins followed by quartz sericite pyrite veins cathodoluminescence cl petrography identified distinct a quartz veinlets consisting of dark luminescing quartz filling fractures and dissolution vugs in earlier a quartz veins and adjacent porphyry wall rock these veinlets contain abundant bornite and chalcopyrite and minor k feldspar and are closely linked in time to the introduction of the bulk of the copper and gold although a similar sequence of veins was repeated on emplacement of all porphyry intrusions the vein density and intensity of potassic alteration declined with time the youngest porphyry qlp is mostly weakly mineralized and locally unaltered these observations indicate that magmatic hydrothermal fluids underwent a similar physiochemical evolution during and immediately following emplacement of each of several porphyry dikes the relationship between edm veins and a quartz veins requires that the flux of magmatic fluid from the magma chamber occurred in an episodic manner as opposed to a continuous discharge vein truncation relationships coupled with abrupt changes in copper gold grades sulfide ratios and potassic alteration intensity at porphyry intrusive contacts indicate that the mass of introduced copper and gold decreased significantly during successive porphyry intrusive hydrothermal cycles presumably due to depletion of metals and volatiles in the underlying magma chamber

new evidence of magmatic fluid related phyllic alteration implications for the genesis of porphyry cu deposits the phyllic alteration in a number of circum pacific porphyry cu au deposits is related to high temperature saline magmatic fluids this contradicts the widely used genetic models wherein phyllic alteration formed as the result of mixing between magmatic and meteoric fluids at the endeavour 26 north porphyry deposit in eastern australia the transition from early potassic to the main stage phyllic alteration is associated with fluids that with time decline in total salinity nacl kcl and temperature from 600 to 550 degrees c calculated and measured delta 18 o and delta d compositions of fluids 5 1 8 5 parts per thousand 57 to 73 parts per thousand delta d confirm a primary magmatic origin for both the early potassic and main stage phyllic alteration these results are consistent with other recent studies e g el salvador chile far southeast philippines and panguna and porgera papua new guinea and suggest that rather than these results being unusual a major revision of porphyry cu genetic models is required

evolution of fluids in the dasuji porphyry mo deposit on the northern margin of the north china craton constraints from microthermometric and la icp ms analyses of fluid inclusions abstract the newly discovered dasuji mo deposit is located on the northern margin of the north china craton and the mo mineralization is related to triassic granite porphyry and quartz porphyry alteration associated with the deposit includes silicification sericitization chloritization k feldspathization kaolinitization carbonatization and fluoritization the silicification and sericitization phyllic alteration are closely related to the mo mineralization based on mineral assemblages and cross cutting relationships the hydrothermal ore forming process can be divided into four stages stage 1 is characterized by k feldspathization with minor molybdenum mineralization stage 2 is the main stage of molybdenum mineralization stage 3 is involved in lead zinc mineralization and stage 4 is characterized by no mineralization four types of fluid inclusions are recognized liquid rich gas rich co2 h2o and daughter mineral bearing microthermometric data show a decrease in homogenization temperatures and salinities from the early to late stages so that stages 1 4 show homogenization temperatures of 468 375 435 271 318 206 and 222 142 c respectively and the fluids of stages 1 3 and 4 had salinities of 2 57 16 50 along with a few high salinity inclusions 32 04 48 05 0 88 11 19 and 0 88 7 45 wt nacl equiv respectively the salinities of stage 2 fluid inclusions have a bimodal distribution 1 40 17 48 and 29 20 53 25 wt nacl equiv laser ablation inductive coupled plasma mass spectrometer la icp ms analyses show that the fluid compositions are dominated by na k fe and mn in stage 2 fluid inclusions the mo concentrations vary over a range of more than one order of magnitude more than for any other element as a result of fluid rock interactions and molybdenite precipitation cu concentrations remain always relatively high in the fluids during their evolution 26 7092 ppm because there was little chalcopyrite precipitation the stage 3 fluid inclusions are rich in mn pb and zn while ag concentrations increased in stage 3 and 4 fluid due to the addition of meteoric water from the surrounding rock reactions between the wallrock and hydrothermal fluids affected the composition of the hydrothermal fluids sericitic alteration in particular had a great effect on fluid compositions manifesting the variety of the content of sr ba ca pb the ore forming fluids were mainly magmatic hydrothermal fluids that were mixed with meteoric water during stages 3 and 4 fluid immiscibility a rapid decrease in pressure fluid rock reactions and fluid cooling were collectively responsible for the sulfide precipitation in the dasuji deposit

mechanism of mineralization in the changjiang uranium ore field south china evidence from fluid inclusions hydrothermal alteration and h o isotopes abstract the changjiang uranium ore field which contains 10 000 tonnes of recoverable u with a grade of 0 1 0 5 is hosted by triassic two mica and jurassic biotite granites and is one of the most important uranium ore fields in south china the minerals associated with alteration and mineralization can be divided into two stages namely syn ore and post ore the syn ore minerals are primarily quartz pitchblende hematite hydromica chlorite fluorite and pyrite the post ore minerals include quartz calcite fluorite pyrite and hematite the fluid inclusions of the early syn ore stage characteristically contain o 2 and those of the late syn ore and post ore stage contain h 2 and ch 4 the fluid inclusions in quartz of the syn ore stage include h 2 o h 2 o co 2 and co 2 types and they occur in clusters or along trails homogenization temperatures t h for the h 2 o co 2 and two phase h 2 o inclusions range from 106 c to 350 c and cluster in two distinct groups for each type salinities are lower than 10 wt nacl equiv the ore forming fluids underwent co 2 effervescence or phase separation at 250 c under a pressure of 1000 1100 bar the u th values of the altered granites are lowest close to the ore increase outwards but subsequently decrease close to unaltered granites from the unaltered granites to the ore the lowest fe 2 o 3 feo values become lower and the highest values higher the ree patterns of the altered granites and the ores are similar to each other the u contents of the ores show a positive correlation with total ree contents but a negative correlation with lree hree ratios indicating the pitchblende is ree bearing and selectively hree rich the eu values of the ore show a positive correlation with u contents indicating the early syn ore fluids were oxidizing the ce values show a negative correlation indicating the later mineralization environment became reducing the water rock interactions of the early syn ore stage resulted in oxidization of altered granites and reduction of the ore forming fluids and it was this reduction that led to the uranium mineralization during alteration in the early syn ore stage the oxidizing fluids leached uranium from granites close to faults and fe 2 o 3 feo ratios increased in the alteration zones the late syn ore and post ore alteration decreased the fe 2 o 3 feo ratios in the alteration zones the 18 o w smow values of the ore forming fluids range from 1 8 to 5 4 and the d w smow values range from 104 4 to 51 6 suggesting meteoric water the meteoric water underwent at least two stages of water rock interaction the first caused the fluids to become uranium bearing and the second stage which was primarily associated with ore bearing faults led to uranium deposition as pitchblende accompanied by co 2 effervescence

composition and evolution of ore fluids in a magmatic hydrothermal skarn deposit the chemistry of brine vapor and low salinity fluid inclusions measured by proton induced x ray emission from the bismark skarn deposit mexico is consistent with an evolving magmatic hydrothermal system with no evidence for external fluid inputs the results support a model that invokes early phase separation of magmatic fluids into brine and vapor two phase field at high temperature and lithostatic pressure followed by the entrapment of a low salinity magmatic fluid one phase field at lower temperature and hydrostatic pressure the early brine and vapor inclusions contain high pb and zn concentrations and low cu however the vapor contains significantly more cu than the brine and was likely transported as a sulfur complex the fluid phase changes observed and behavior of cu are comparable to those of porphyry cu systems the later low salinity fluid at bismark represents a distinct pulse of magmatic fluid with a high k ca ratio in which base metals including cu were transported by chloride complexes paragenetic relationships and variations in the relative concentrations of cu pb and zn suggest that this fluid was primarily responsible for ore deposition the relative cu pb and zn concentrations in fluid inclusions at bismark are consistent with those measured from base metal ores in high temperature carbonate replacement deposits throughout mexico and suggest that the bulk metal budget of these deposits is primarily controlled by magmatic hydrothermal fluids deficient in cu

precious metal distribution and fluid inclusion petrography of the elatsite porphyry copper deposit bulgaria the elatsite porphyry copper deposit occurs in an island arc setting hosted by late cretaceous monzonitic monzodioritic porphyry stocks which were emplaced into precambrian cambrian phyllites trace element data of the late cretaceous intrusive rocks suggest that they are i type volcanic arc granitoids two main ore mineral assemblages are distinguished 1 magnetite bornite chalcopyrite and 2 chalcopyrite pyrite the first one is linked to potassic propylitic and the second to phyllic argillic alteration minor ore minerals are hematite molybdenite sphalerite pyrrhotite marcasite hessite and solid solutions of linnaeite siegenite carrollite tetrahedrite tennantite clausthalite galena gold electrum and merenskyite moncheite precious metal contents are relatively high throughout the deposit but au pd and pt are concentrated more strongly in the magnetite bornite chalcopyrite assemblage average grades of au ag pd and pt calculated for the 0 33 cu ore body are 0 96 0 19 0 007 and 0 002 g t respectively analyses of flotation concentrates revealed 25 6 cu and ag au pd and pt contents of 33 0 13 6 0 72 and 0 15 g t respectively the copper mineralisation at elatsite took place at pressures of 120 to 300 bar corresponding to depths of formation of 1 to 3 km under hydrostatic conditions the precious metals were probably transported jointly as chloride complexes in highly saline magmatic hydrothermal solutions the fluids had temperatures of 340 to 700 c and salinities of 28 to 64 nacl and mixed with meteoric water

is the cauca patia and romeral fault system left or rightlateral extrusion driven collision is controlled by strike slip faults of opposite senses whereas subduction related oblique convergence is accommodated by margin parallel faults of identical senses northern andes geodynamics has been interpreted either as resulting from the obliquity of convergence between nazca and south american plates or from the collision of the carnegie ridge with ecuadorian margin the sense of the cauca patia and romeral fault system cprfs has been interpreted in two opposite manners right or left lateral agreeing with oblique or collisional patterns respectively we analyze arguments which favor south to 4 n a right lateral motion along the cprfs that is consistent with obliquity driven geodynamics however north of 5 n the cprfs is actually left lateral these opposite motions between the northern and southern part of the cprfs have to be accommodated around 5 n by n s stretching and or shortening existing data support n s shortening around 5 n this buttressing could be due to the collision between the panama and andean blocks

contrasting evolutions of hydrothermal alteration in quartz monzonite and quartz diorite wall rocks at the sierrita porphyry copper deposit arizona two wall rock types of contrasting chemical composition host the causative ruby star quartz monzonite porphyry intrusion and hypogene mineralization at the sierrita porphyry copper deposit vein related hydrothermal alteration in the harris ranch quartz monzonite and biotite quartz diorite wall rocks consists of several mineralogically discrete assemblages temporal evolution of different alteration assemblages was established in part using petrographic relations within and crosscutting relations among individual veins temperature and salinity characteristics of hydrothermal fluids responsible for filling of individual veins were determined using primary fluid inclusions in vein filling quartz each generation of primary vein filling introduced characteristic secondary fluid inclusions into earlier developed veins as well histograms of homogenization temperatures of primary and secondary fluid inclusions from different veins and accompanying salinity data permitted temporal correlations to be drawn between veins which either did not exhibit crosscutting relations in individual samples or which formed in different wall rocks and thus exhibited different alteration mineralogies evolution of hydrothermal activity in the area sampled commenced with potassic alteration in both quartz monzonite and quartz diorite wall rocks from 10 to 12 molal 37 41 wt nacl equivalent fluids inclusions of which homogenize by halite dissolution in the approximate temperature range 300 degrees to 370 degrees c salinities of later fluids were in the range 2 to 3 molal 10 15 wt nacl equivalent with only minor salinity variations for the remaining time span monitored by this study homogenization temperatures of primary fluid inclusions in veins formed from these lower salinity fluids began near 400 degrees c and increased initially to approximately 430 degrees c where boiling occurred the pressure defined by boiling of these fluids is about 330 bars a continuous decrease in fluid inclusion homogenization temperatures followed down to about 300 degrees c during which time deposition of quartz and k feldspar with accessory biotite and or hematite occurred in new and reopened veins in the quartz monzonite wall rock simultaneously in the quartz diorite a sequence of veins and adjacent alteration halos formed each consisting of an early assemblage of potassic affinity quartz biotite k feldspar albite which evolved to a propylitic assemblage quartz epidote chlorite as vein filling proceeded with continued cooling of the solution below about 300 degrees c muscovite took the place of k feldspar as the stable potassium bearing mineral in the quartz monzonite an analogue to this late stage quartz muscovite veining in the quartz monzonite could not be established in the quartz diorite but may consist of zeolite stilbite anhydrite the bulk of hypogene copper mineralization in both wall rock types was associated with approximately 2 molal 10 wt nacl equivalent solutions in the quartz diorite significant chalcopyrite deposition is associated with fluid inclusions homogenizing from 370 degrees down to about 320 degrees c and always occurs with the later stage propylitic minerals in each vein in the quartz monzonite wall rock chalcopyrite was deposited during the transition from potassic and into phyllic alteration fluid inclusion homogenization temperatures for this mineralization range from about 330 degrees down to 200 degrees c no primary chalcopyrite was seen to occur with earlier potassic veining formed from either high or low salinity fluids in the quartz monzonite a very late stage of deposition of chalcopyrite pyrite and minor bornite filled the center of late phyllic veins in the quartz monzonite correlated fluid inclusions have salinities from 1 to 5 molal 5 23 wt nacl equivalent and homogenization temperatures in the range 140 degrees to 160 degrees c the different alteration and sulfide mineral assemblages interpreted to have formed simultaneously in the two wall rocks of contrasting chemical character can be reasonably assigned to different chemical interactions of each rock type with similar or equivalent hydrothermal fluids

the age and petrogenesis of reduced to weakly oxidized porphyry intrusions at the marmato gold deposit colombia abstract the marmato gold deposit is a hybrid between a porphyry gold and a reduced intrusion hosted gold deposit with epithermal features at shallow levels it is adjacent to the contemporaneous aguas claras porphyry gold deposit they are located in one of the premier gold copper belts of colombia the middle cauca belt mcb and associated with a late miocene magmatic arc the marmato porphyry group mpg defined as the marmato and aguas claras porphyry intrusions was dated at 6 58 0 07 ma to 5 74 0 14 ma by u pb la icp ms in zircon the mpg is composed of andesitic dacitic porphyry intrusions which belong to the i type granite series and the reduced or weakly oxidized ilmenite series suites with a calc alkaline to high k calc alkaline signature 87sr 86sr ratios between 0 70435 to 0 70513 and 143nd 144nd values of 0 512688 to 0 512898 from the mpg suggest partial melting of the mantle wedge as source of the magma an additional contribution by partial melting involving garnet in the deep crust is suggested by a dy yb n ratio of 1 to 1 5 and flat ree diagrams crystal fractionation during magma ascent is indicated by high sr y 55 ratios with suppression of plagioclase on the liquidus until the appearance of amphibole shown by eun eu

tropical cyclone movement and surrounding flow relationships abstract this paper presents results of a comprehensive study of the relationship between the movement of tropical cyclones and the large scale circulation which surrounds them cyclones have been stratified by direction and speed of movement latitude intensity change and size as determined by the radius of the outermost closed surface isobar in three ocean basins the northwest pacific the west atlantic and the australian south pacific region twenty one different stratifications are available in the northwest pacific 13 in the west atlantic and 6 in the australian south pacific area cyclone movement and surrounding flow relationships were studied at different pressure levels and a variety of radii pressure weighted layer averages were also analyzed in search of such relationships results show an important relationship between surrounding large scale flow and tropical cyclone movement for all stratifications the winds in the mid troposphere 500 700 mb at 5 7 latitude radius from the cyclone

the evolution of a porphyry cu au deposit based on la icp ms analysis of fluid inclusions bajo de la alumbrera argentina the chemical and physical evolution of magmatic to hydrothermal processes in the porphyry cu au deposit of bajo de la alumbrera northwestern argentina has been reconstructed with a quantitative fluid inclusion study fluid inclusion petrography microthermometry and single inclusion microanalysis by excimer laser ablation inductively coupled plasma mass spectrometry la icp ms are combined to determine the evolution of pressure temperature and ore metal concentrations including cu and au in the fluids complementary hydrogen and oxygen isotope analyses are used to further constrain the water sources in the evolving system the combined data provide a new level of insight into the mechanisms of metal sourcing and ore mineral precipitation in a porphyry style magmatic hydrothermal system based on previously reported observations of the igneous geology alteration geochemistry and veining history of the subvolcanic porphyries at alumbrera the distribution of fluid inclusion types in space and time is documented six major inclusion types are distinguished the highest temperature brine inclusions up to 750 c p 1 kbar are mainly recorded in barren quartz magnetite veins in the core of the alteration system these polyphase brine inclusions halite sylvite multiple opaque and transparent daughter crystals are interpreted as the most primitive magmatic fluid recorded at the level of the deposit they are of moderately high salinity 50 60 wt nacl equiv dominated by nacl kcl and fecl 2 and contain on average 0 33 wt percent cu and 0 55 ppm au upon cooling and decompression these saline liquids exsolve a vapor phase which is preferentially enriched in cu relative to its main salt components but probably plays a minor role in the formation of this particular deposit because of the inferred small mass fraction of vapor cooling and decompression from the highest initial p t conditions down to about 450 c causes magnetite k silicate alteration but no saturation in au or cu sulfides as recorded by continually high ore metal concentrations in the fluid inclusions coprecipitation of cu and au as chalcopyrite and native gold some early bornite occurs over a narrow range of decreasing fluid temperature with cooling from 400 to 305 c the cu concentration in the brine drops by about one order of magnitude to less than 0 07 wt percent without a proportional decrease in major salt components ore mineral precipitation extracts 85 percent of the cu and au from the fluid it is associated with potassic alteration as shown by a concomitant decrease in the k na ratio of the cooling magmatic brine and by an increase in its ba and sr concentrations elements which are probably liberated in the destruction of calcic igneous minerals the fluid chemical data demonstrate that the metal ratios in this and probably many other porphyry style ore deposits are primarily controlled by the magmatic source of the ore brines on the other hand the final hypogene ore grade of the deposit is controlled by the efficiency of ore mineral precipitation at alumbrera metal extraction is governed by the efficiency of cooling a high flux of magmatic fluid within a small rock volume dilution of residual magmatic fluids as recorded by aqueous fluid inclusions of decreasing salinities and temperatures below 295 c follows after the main stage of copper introduction and is associated with feldspar destructive phyllic alteration geometric relationships fluid analyses and stable isotope data together indicate that phyllic alteration results from postmineralization hydrothermal activity involving minor mixing between meteoric water residual brine and a waning input of magmatic vapor

fluid inclusion studies of the rodeo de los molles ree and th deposit las chacras batholith central argentina abstract the rodeo de los molles rare earth element ree and thorium deposit is located in granitic rocks of the las chacras piedras coloradas batholith in the southern block of the eastern pampean ranges central argentina mineralization occurs within an elongate 2 km 0 6 km body of alkalifeldspar granite alaskite localized along the northeastern edge of a composite batholith the surrounding lithology is predominantly a biotite monzogranite both the alaskite and localized areas of quartz alkalifeldspar syenite within the alaskite have been produced by hydrothermal alteration of a late crystallizing phase of the monzogranite ree minerals are primarily of the cerium group and include britholite and allanite both partially replaced by bastnaesite or thorbastnaesite these minerals occur as nodules with quartz fluorite aegirine augite sphene and fe ti oxides within aplitic to pegmatoidal quartz alkalifeldspar syenite uranothorite along with a second generation of fluorite and minor amounts of mn ba oxides occurs in the alaskite as nodules or within quartz lined miarolitic cavities but is not found with the ce mineralization studies of fluid inclusions contained in quartz and fluorite indicate a complex history of open system fluid migration and interaction with monzogranite host rocks fluids responsible for ree mineralization and quartz deposition along with initial alteration of the monzogranite to alaskite and quartz alkalifeldspar syenite were of relatively high temperature th of fluid inclusions in quartz 356 535 c and moderate salinity 15 25 eq wt nacl mixed co2 h2o fluids xco2 13 07 found as both primary and secondary inclusions within fluorite are representative of fluids involved in the replacement of britholite allanite by bastnaesite and sphene aegirine augite and plagioclase by calcite minimum pressures of mineral deposition estimated from h2o co2 nacl phase relations range from 1 to 2 kbars secondary aqueous fluid inclusions in quartz define a trend of low salinity high temperature to high salinity low temperature thought to be a result of hydration reactions occurring in alaskite and quartz alkali feldspar syenite the highest salinity fluids 35 37 eq wt nacl detected in the area are associated with the formation of uranothorite and late fluorite multiple periods of hydrothermal fluid introduction are consistent with recent geological data that indicate that the batholith is composed of several stock like bodies the location of the mineralized area near the top of the magma chamber the presence of numerous miarolitic cavities and the bulk composition of inclusion fluids na k ca suggest that the fluids responsible for ree and th mineralization were of magmatic origin

the nuevo chaquiro cu au mo porphyry deposit middle cauca belt colombia geology alteration mineralization nuevo chaquiro is a newly discovered blind porphyry cu au mo deposit located in the middle cauca belt colombia approximately 60 km south southeast of medellin the most recent resource estimate was stated as 566 m tonnes t averaging 0 64 cu 0 31 g t au 4 34 g t ag and 127 ppm mo the geology of nuevo chaquiro consists of a miocene volcanic sequence of andesitic tuffs agglomerates and flows combia formation intruded by small stocks and dikes of diorite and quartz diorite also of miocene age sparsely occurring outcrops at nuevo chaquiro consist of a 1 2 0 8 km zone of pervasive sericitic alteration with locally well developed quartz fe oxide stockworks the sericitic alteration grades downward into sericite chlorite alteration and then predominantly potassic biotite magnetite alteration at depths of 250 to 400 m calcic potassic alteration containing actinolite and epidote occurs at greater depths a high grade sheeted vein complex occurs immediately adjacent to the upper contact of an early quartz diorite intrusion quartz veinlet density in this area reaches up to 80 quartz by volume accompanied by up to 5 vol chalcopyrite later intermineral porphyries created a second orebody slightly to the west but contiguous with the early orebody here cu au mo mineralization in an inverted bowl shape is associated with potassic alteration that manifests itself as secondary flooding of the tuff wall rock matrix by hydrothermal biotite accompanied by disseminations and hair veinlets of chalcopyrite magnetite pyrite and molybdenite the porphyry system is also accompanied by intermediate sulfidation carbonate quartz base metal veins typically with sericitic alteration selvages which occur on the upper western flank of the deposit at nuevo chaquiro multiple intrusions of early and intermineral porphyry contain calcic potassic and potassic alteration with a later overprint by sericite chlorite alteration centered on intrusion apexes the amount of sericite chlorite overprinting varies with each intrusion collectively these intrusions are all overprinted by a single later sercitic phyllic alteration event that is superimposed as a broad cap upon the entire system there is a consistent paragenesis for the alteration mineralization associated with each intrusion suggesting a relatively stable underlying shallow magma chamber that fluxed geochemically similar pulses of magmatic hydrothermal fluid with each porphyry in many aspects nuevo chaquiro is a typical au rich porphyry copper system however the contrast between the mineralization styles between the early and intermineral orebodies as well the timing differences in copper deposition suggest that differences in porphyry mineralization styles also occur at nuevo chaquiro

cooling history of subduction related granite from the indus suture zone ladakh india evidence from fluid inclusions the p t history of the subduction related ladakh granite in northwestern himalaya has been recorded from silicate melt inclusions and other high temperature solid inclusions in the rock forming quartz the silicate melt inclusions show initial melting from 650 c 705 c these inclusions have compositions similar to calc alkaline granitic magma which is supported by the trace and major element chemistry of the granite the earliest fluids 75 equiv wt nacl circulated at subsolidus conditions from 625 down to 425 c whereas invasion of dilute solution 8 equiv wt nacl in the granite took place from 300 c down to 165 c on the basis of the above observations it is inferred that the cooling history of the ladakh granite started at 705 c and continued up to 650 c in the range of 1 2 2 8 kbar this therefore suggest a shallow emplacement of granitic magma the hydrothermal processes involved during the cooling reveals simultaneous drop in temperature and pressure along with the introduction of dilute solution very low saline through microfractures

seasonal modulations of different impacts of two types of enso events on tropical cyclone activity in the western north pacific the paper examines different impacts of eastern pacific warm cold epw epc and central pacific warm cold cpw cpc events on tropical cyclones tcs in the western north pacific wnp by considering the early season of april june amj the peak season of july september jas and the late season of october december ond during amj epw epc is associated with a significant increase of the tc genesis number in the southeastern southwestern sub region of the wnp but no class of el nino southern oscillation enso events shows a significant change in the tc lifetime and intensity during jas epw corresponds to an increase decrease of the tc genesis number in the southeastern northwestern sub region but cpw shows no significant change epc increases the tc genesis in the northwestern and northeastern sub regions and decreases the genesis in the southwestern sub region whereas cpc suppresses the genesis in the southeastern sub region both the lifetime and intensity of tcs are increased in epw but only a shortened lifetime is seen for cpc during ond epw reduces the tc genesis in the southwestern and northwestern sub regions whereas cpw enhances the genesis in the southeastern sub region over the south china sea cpw and cpc show a significant decrease and increase of the tc genesis respectively the tc lifetime is significantly longer in both epw and cpw and shorter in epc and tcs tend to be more less intense in epw cpc all of these variations are consistent with the development of enso related sst anomalies during different seasons and are supported by distributions of the genesis potential index a combination of large scale oceanic and atmospheric factors that affect tc activity tcs in the wnp mainly take the straight westward northwestward and recurving tracks during amj of epw years the tc steering flow patterns favor the recurving track and suppress the straight westward and northwestward tracks during jas epw is associated with the steering flows that are unfavorable for tcs to move northwestward or westward whereas cpw favors the northwestward track and suppresses the straight westward track the steering flow patterns during ond are similar to those during jas except that epc may increase the possibility of the northwestward track

geology and reconnaissance stable isotope study of the oyu tolgoi porphyry cu au system south gobi mongolia the oyu tolgoi porphyry cu au system in the south gobi desert mongolia comprises five deposits that extend over 6 km in a north northeast oriented zone they occur in a middle to late paleozoic arc terrane and are related to late devonian quartz monzodiorite intrusions the hugo dummett deposits are the northernmost and deepest with up to 1 000 m of premineral sedimentary and volcanic cover rock remaining they are the largest deposits discovered to date and characterized by high grade copper 2 5 cu and gold 0 5 2 g t mineralization associated with intense quartz veining and several phases of quartz monzodiorite intruded into basaltic volcanic host rocks sulfide minerals in these deposits are zoned outward from a bornite dominated core to chalcopyrite upward to pyrite enargite and covellite at shallower depth the latter high sulfidation state sulfides are hosted by advanced argillic alteration mineral associations this alteration is restricted mainly to dacitic ash flow tuff that overlies the basaltic volcanic rock and includes ubiquitous quartz and pyrophyllite kaolinite plus late dickite veins as well as k alunite al phosphate sulfate minerals zunyite diaspore topaz corundum and andalusite a reconnaissance oxygen hydrogen and sulfur isotope study was undertaken to investigate the origin of several characteristic alteration minerals in the oyu tolgoi system with particular emphasis on the hugo dummett deposits based on the isotopic composition of o h and s 18o so4 8 8 20 1 d 73 to 43 34s 9 8 17 9 the alunite formed from condensation of magmatic vapor that ascended to the upper parts of the porphyry hydrothermal system without involvement of significant amounts of meteoric water the isotopic data indicate that pyrophyllite 18o 6 5 10 9 d 90 to 106 formed from a magmatic fluid with a component of meteoric water muscovite associated with quartz monzodiorite intrusions occurs in the core of the hugo dummett deposits and isotopic data 18o 3 0 9 0 d 101 to 116 show it formed from a magmatic fluid with water similar in composition to that which formed the pyrophyllite mg chlorite 18o 5 5 d 126 is a widespread mineral retrograde after hydrothermal biotite and may have formed from fluids similar to those related to the muscovite during cooling of the porphyry system by contrast paragenetically later and postmineralization alteration fluid which produced dickite 18o 4 1 to 3 3 d 130 to 140 shows clear evidence for mixing with substantial amounts of meteoric water relatively low d values 140 for this meteoric water component may indicate that its source was at high elevations the geologic structure nature of alteration styles of mineralization and stable isotope data indicate that the oyu tolgoi deposits constitute a typical porphyry system formed in an island arc setting the outward zonation of sulfide minerals for the hugo dummett deposits from a bornite dominated core to chalcopyrite and pyriteenargite can be interpreted to be related to a cooling magmatic hydrothermal system which transgressed outward over enclosing advanced argillic alteration this resulted in some unusual alteration and sulfide parageneses such as topaz or pyrite enargite and tennantite entrained by high grade bornite

tropical cyclone track characteristics as a function of large scale circulation anomalies abstract factors that contribute to intraseasonal variability in western north pacific tropical cyclone track types are investigated it is hypothesized that the 700 mb large scale circulation can affect tropical cyclone track characteristics by enhancing or excluding genesis in certain regions and concurrently prohibiting or favoring recurving versus straight tracks a track type climatology indicates that genesis location alone may explain some of the variability in track type although some genesis regions have no preference for straight moving or recurving tracks a formation north of 20 n or east of 150 e and north of 10 n favors a recurvature track these recurving storms are classified as recurving north and recurving storms that form in regions with nearly equal probability of straight or recurving tracks are classified as recurving south a compositing technique is used to define anomalous 700 mb large scale circulations that exist during the formation of tropical cyclones that subsequently fol

formation of the auriferous and barren north dipper veins in the sigma mine val d or canada constraints from structural mineralogical fluid inclusion and isotopic data the sigma lamaque mine 100 metric tons t of gold is an example of an archean greenstone belt gold deposit formed by processes related to multistage hydrothermal fluid circulation the earliest recognized vein systems are steeply to moderately dipping fault fill veins within shear zones and contemporaneous subhorizontal veins which were overprinted by the late north dipper vein system the latter strikes east west dips moderately to the north and exhibits complex internal geometry with features similar to fault fill and extensional veins and therefore is interpreted as extensional shear veins this late vein system was considered one of the major sources of gold in the shallow underground and open pit ore reserve estimations these late north dipper veins were studied in detail in the sigma pit where they contain ore grade gold and are hosted by the calc alkaline tuffs of the val d or formation and in the north zone where they are barren and hosted by the tholeiitic volcanic rocks of the jacola formation in the sigma pit these veins have apparent thicknesses of 0 8 to 3 m and very irregular contacts with the vein walls they comprise irregular zones of milky quartz filling disrupted blocks of layered quartz and tourmaline and slabs of foliated pyrite rich wall rock layers with tourmaline and quartz crystals oriented perpendicular to the vein walls are observed close to the vein walls the veins contain minor amounts of calcite pyrite rutile and traces of chlorite muscovite pyrrhotite chalcopyrite galena bismuth tellurides and gold locally the sulfide content can attain 10 modal percent of the vein mineralogy in the veins native gold with 6 wt ag occurs rarely associated with the main vein filling minerals commonly as inclusions in pyrite main vein filling stage and most commonly filling fractures in pyrite tourmaline and quartz where it is alloyed with 8 to 17 wt percent ag and is associated with calcite and bi tellurides late auriferous stage the proximal wall rock alteration related to the auriferous north dipper veins overprints the metamorphic assemblage and is characterized by abundant fine grained plagioclase calcite quartz and minor chlorite tourmaline and pyrite in the tuffs and more abundant muscovite in the intrusive feldspar porphyry in the wall rock gold with 6 to 28 wt percent ag is found locally filling fractures in pyrite where it is associated with a late generation of calcite the barren north dipper vein also comprises mainly quartz and tourmaline but lacks calcite and gold has a very low content of sulfides aqueous carbonic fluid inclusions with salinities less than 8 wt percent nacl equiv and homogenization temperatures between 228 and 440 c and carbonic fluid inclusions with less than 0 2 mol percent ch 4 coexisting in the same healed fractures are common in the auriferous north dipper veins but very rare in the barren vein where aqueous fluid inclusions have lower temperatures dominantly 125 225 c crush leaching and laser ablation time of flight inductively coupled mass spectrometry la tof icpms of fluids in the inclusions indicate elevated concentrations of ni cu sb pb and ag in the fluids in the auriferous veins compared to the aqueous fluids in the barren veins this suggests different sources for the metals in the fluids associated with the gold possibly including both igneous and sedimentary rocks calculated oxygen isotope equilibration temperatures for quartz tourmaline pairs from the auriferous main vein filling stage are 323 to 370 c this is within the range documented in fluid inclusions related to the late auriferous stage indicating that the temperature of the auriferous hydrothermal fluids did not change appreciably during the evolution of the system calculated 18 o h 2 o values for the mineralizing fluids are 9 5 per mil consistent with either low water rock ratio systems associated with high grade metamorphism or a magmatic origin for the fluids gold included in pyrite may have precipitated during the main vein filling stage due to the decrease of h 2 sconcentration in the hydrothermal fluid following the deposition of sulfides however gold in fractures in the main vein filling minerals precipitated later due probably to dilution of the auriferous aqueous carbonic fluids by mixing with aqueous fluids the absence of ore grade gold in the barren north zone vein is probably due to the lack of circulation of auriferous aqueous carbonic fluids in the north zone located distal to the first order larder lake cadillac fault which may have served as the main regional conduit for the auriferous aqueous carbonic fluids

volatile lines of descent in submarine plutonic environments insights from stable isotope and fluid inclusion analyses microthermometric and isotopic analyses of fluid inclusions in primitive olivine gabbros oxide gabbros and evolved granitic material recovered from ocean drilling program hole 735b at the southwest indian ridge provide new insights into the evolution of c o h nacl fluids in the plutonic foundation of the oceanic crust the variably altered and deformed plutonic rocks span a crustal section of over 1500 m and record a remarkably complex magma hydrothermal history magmatic fluids within this suite followed two chemically distinct paths during cooling through the subsolidus regime the first path included formation of co21ch41h2o1c fluids with up to 43 mole ch 4 the second path produced hypersaline brines that contain up to 50 nacl equivalent salinities subsequent to devolatilization respeciation of magmatic co2 attendant graphite precipitation and cooling from 800 c to 500 c promoted formation of ch 4 enriched fluids these fluids are characterized by average d 13 c ch4 values of 227 1 6 4 3 n5 45 with associated d 13 c co2 compositions ranging from 224 9 to 21 9 n539 and average dd values of exsolved vapor of 241 6 12 n523 in pods veins and lenses of highly fractionated residual material hypersaline brines formed during condensation and by direct exsolution in the absence of a conjugate vapor phase entrapped co21ch41h2o rich fluids within many oxide bearing rocks and felsic zones are significantly depleted in 13 c with d 13 c co2 values down to about 225 and contain co 2 concentrations higher than those predicted by equilibrium devolatilization models we hypothesize that lower effective pressures in high temperature shear zones promoted infiltration of highly fractionated melts and compositionally evolved volatiles into focused zones of deformation significantly weakening the rock strength in felsic rich zones volatile build up may have driven hydraulic fracturing of gabbroic wall rocks resulting in the formation of magmatic breccias comparison of isotopic compositions of fluids in plutonic rocks from 735b the mark area of the mid atlantic ridge and the mid cayman rise indicate 1 that the carbon isotope composition of the lower oceanic crust may be far more heterogeneous than previously believed and 2 that carbon bearing species in the oceanic crust and their distribution at depth are highly variable copyright 2001 elsevier science ltd

physico chemical controls on ore deposition in the arapucandere pb zn cu precious metal deposit biga peninsula nw turkey abstract arapucandere is one of a number of similar cu zn pb au ag epithermal deposits in the biga peninsula which are mineralogically and tectonically similar fluid inclusions have very low salinities between 1 7 and 0 wt nacl and a wide range of temperatures from 360 to 160 c there was extensive boiling and flashing of the hydrothermal fluids which initiated mineral deposition the range of temperatures is consistent with emplacement of the veins at 700 m depth with the pressure decreasing from near lithostatic to near hydrostatic and a decrease in temperature to 250 c due to adiabatic expansion of the fluids there is evidence of a limited amount of boiling but the temperature and pressure decrease was close to the liquid vapour curve flashing of the fluids was caused by sudden drops to sub hydrostatic pressures and even lower temperatures mineralization was caused by these pressure related temperature decreases as there is no evidence of cooling and dilution of the ore fluids 34 s values of sulphides indicate a magmatic source but the more negative than usual values also suggest boiling affected isotopes d and 18 o of the fluids indicate a mixing between meteoric waters and magmatic fluids with the large range of d due to boiling la icp ms analyses of fluid inclusions reveal high cu zn pb concentrations in the fluids despite their low salinity transported as chloride complexes exceptional pressure and temperature decrease causing the fluids to flash was likely to have been in response to earthquakes

the ridgeway gold copper deposit a high grade alkalic porphyry deposit in the lachlan fold belt new south wales australia ridgeway is a high grade gold copper porphyry deposit 54 mt at 2 5 g t au and 0 77 cu related to an alkalic intrusive complex of monzonitic composition the deposit occurs within the cadia district of new south wales australia which consists of a cluster of four late ordovician gold copper porphyry deposits and two iron copper gold skarn deposits with a combined gold resource in excess of 574 metric tonnes t the deposits lie on a 7 km long northwest oriented corridor of alteration and mineralization transverse to the axis of the postulated volcanic arc alteration and mineralization at ridgeway are zoned around a vertically attenuated intrusive complex of monzodioritic to quartz monzonitic composition distinct styles of veining and alteration are related to different intrusive phases of the monzonite complex with the intensity of alteration and grade of mineralization decreasing from early to late mineral intrusions early mineral intrusions are associated with intense actinolite magnetite biotite calc potassic alteration and up to four stages of high grade quartz magnetite sulfide veining bornite is the most abundant sulfide formed during early stage alteration and correlates well with gold moderate to weak intensity orthoclase biotite plus or minus magnetite potassic alteration accompanies the inter and late mineral intrusions this alteration being associated with chalcopyrite and pyrite rich quartz orthoclase veins propylitic and sodic albite pyrite alteration assemblages are peripheral to and locally overprint the potassic alteration phyllic alteration is restricted to the margins of late stage faults the fluid inclusion assemblage comprises one and two salt bearing brine inclusions in addition to aqueous liquid vapor inclusions of low to moderate salinity no low density vapor rich inclusions are present indicating that the fluids from which the quartz veins precipitated did not enter the liquid vapor field of the h2o nacl system the brine inclusions undergo final homogenization to liquid via halite dissolution this phenomenon in addition to the absence of low density vapor inclusions suggests that the mineralizing fluids at ridgeway were nonboiling hypersaline brines that exsolved directly from the crystallizing magma the presence of mineralized aplitic vein dikes and comb quartz layering are interpreted to indicate that the early and transitional stages of mineralization at ridgeway formed at the transition between magmatic and hydrothermal conditions

a stable isotope study of the palaeoproterozoic tallberg porphyry type deposit northern sweden the tallberg deposit is situated in the skellefte district in northern sweden it is a palaeoproterozoic equivalent of phanerozoic poryphyry type deposits the mineralization is situated within the jorn granitoid complex and is associated with intrusive quartz feldspar porphyries the granitoids are coeval with mainly felsic volcanic rocks hosting several massive sulphide deposits the alteration is generally of a mixed phyllic propylitic type but areas or zones associated with high gold grades exhibit phyllic alteration ore minerals are pyrite chalcopyrite sphalerite magnetite and trace amounts of molybdenite in this stable isotope study quartz sericite and chlorite from the alteration zones were sampled the magmatic quartz has a 18o composition of 6 2 to 6 7 whereas the quartz in the hydrothermal alteration zones have values ranging from 7 5 to 10 6 the calculated temperatures for this fractionation range from 430 to 520 c the sericites have 18o ranging from 4 6 to 8 2 average 6 6 and d 31 to 54 average 41 chlorites range from 18o 4 2 to 7 7 and d from 34 to 44 the range of 34s of 11 pyrite samples is 3 8 to 5 5 with an average of 4 6 0 5 suggesting a relatively homogeneous sulphur source probably of magmatic origin modelling waters in equilibrium with the minerals indicates early magmatic fluids with 18o of 6 5 this fluid mixed with a low 18o and high d fluid which is tentatively identified as seawater the 18o signature of sericite and chlorite also indicates significant water rock exchange explaining the positive 18o values for the waters in equilibrium with the hydrated minerals

the red chris porphyry copper gold deposit northern british columbia canada igneous phases alteration and controls of mineralization red chris is a late triassic porphyry cu au mo deposit in the stikinia island arc terrane in northern b c late triassic sedimentary and volcanic rocks of the stuhini group host a series of late triassic to early jurassic 204 198 ma diorite to quartz monzonite stocks and dikes the red chris deposit is hosted in the 204 ma red stock the largest 6 5 1 5 km and most altered intrusion in the area volcanic rocks approximately time equivalent with the stock are exposed 2 km to the southwest and west postmineral early and middle jurassic sedimentary rocks unconformably overlie the stuhini group and red stock to the south and southeast the composite red stock consists of multiple phases of crowded porphyries 30 65 plagioclase hornblende biotite phenocrysts including abundant premineral p1 leucodiorite multiple subphases of synmineral p2 quartz monzonite porphyries and volumetrically minor late mineral monzonite p3 and monzodiorite p4 porphyries the stock evolved from subalkaline to silica saturated alkalic composition with the mineral related p2 porphyries being high k calcalkalic and high sr y common septa of stuhini biotitic hornfels are entrapped within the stock minor postmineral weakly altered mafic dikes cut the stock the zone of 0 25 cu equiv cu au is 2 km long wsw ene and up to 650 m wide early a type quartz veins with disseminated bornite accompanied biotitic and k feldspar magnetite alteration which was coeval with p2 porphyries higher cu and au grades correlate in a general way with zones of more abundant a veins chlorite carbonate epidote actinolite replaced hornblende peripheral to biotitic alteration and chlorite overprinted much of the secondary biotite late alteration affected all porphyry phases and is subdivided into earlier sericite clay pyrite and later low sulfide carbonate clay hematite late sericite clay pyrite alteration sulfidized much of the primary bornite to chalcopyrite with or without pyrite and carbonate clay hematite alteration converted most magnetite to hematite highest cu au grades 2 cu equiv occur in and around the early and intermediate stage p2 porphyries zoning of cu au au cu ratios sulfides and quartz veins is centered and mostly symmetrical around a core of high grade cu au within and surrounding apices of p2 porphyry contact relationships confirm the close association of p2 porphyry phases with cu au zones of 50 ppm mo surround the highest grade cu au zone at depth west northwest and east northeast strike slip to oblique slip faults offset sulfide cu au and mo patterns several lines of evidence indicate 15 to 20 of southward tilt since the system formed due to glaciation oxidation is very thin and supergene enrichment negligible red chris was previously considered by most workers as an alkalic or hybrid alkalic deposit new chemical data on synmineral porphyry phases instead suggest high k calc alkalic composition similar to the monzonitic cu mo au class of porphyry deposits which includes bingham and bajo de la alumbrera red chris is also classified as an a vein type deposit due to strong control of higher grade cu au by a vein stockworks with abundant disseminated cu sulfides

geochemistry of fluid inclusions from the mcintyre hollinger gold deposit timmins ontario canada type 1 h 2 o co 2 type 2 h 2 o co 2 type 3 ch 4 co 2 h 2 o and type 4 ch 4 fluid inclusions type 1 type 3 and some type 2 inclusions are primary or pseudosecondary in origin whereas type 4 and most type 2 inclusions are secondary the primary or pseudosecondary type 1 and 2 inclusions homogenized at temperatures of 220 degrees to 385 degrees c secondary type 2 inclusions homogenized at 160 degrees to 215 degrees c crushing tests confirm the presence of co 2 in samples with type 1 and 2 inclusions visually estimated x co2 values in type 1 inclusions range from 3 to 24 mole percent with bulk molar volumes of 19 to 28 cm 3 mole mineralizing fluids were at equilibrium with graphite at temperatures of 380 degrees to 480 degrees c and pressures of 1 to 3 kb calculated oxygen fugacities lie near the quartz fayalite magnetite buffer the mineralizing fluids differ compositionally from fluids in other types of ore deposits but resemble fluids derived from metamorphic rocks and deep level felsic intrusions modified journal abstract

isochoric paths in immiscible fluids and the interpretation of multicomponent fluid inclusions abstract fluid inclusions in minerals often follow isochoric isoplethic paths through p t space both in nature and during microthermometry the systematics which arise from this behaviour are the basis for interpreting fluid inclusion analyses previous studies have claimed that isochoric isoplethic paths may transect a given phase boundary only once and natural fluid inclusions have been interpreted accordingly herein it is demonstrated on theoretical and experimental grounds that such claims are false multicomponent fluid inclusions may indeed show the disappearance then reappearance of liquid or vapour phases during microthermometric heating without violating the isochoric isoplethic constraints this result reinstates some formerly discredited observations of natural fluid inclusions it requires modification of the way in which fluid inclusions are studied by microthermometry and it opens new possibilities to understand the occurrence and geochemical effects of immiscibility at high temperature and pressure in the lithosphere the following sequences of phase transitions are deduced to be feasible upon heating multicomponent fluid inclusions 1 liq liq 1 liq 2 liq 2 liq vap or liq 2 liq liq vap or liq 2 3 liq vap liq 1 liq 2 vap liq vap 4 liq vap liq 1 liq 2 vap liq 1 liq 2 5 sol liq vap sol liq sol liq vap 6 liq 1 liq 2 liq liq 1 liq 2 liq only some of these sequences have been reported so far from natural inclusions presumably the remaining sequences have not been found because following conventional wisdom systematic observations have never been made at temperatures above the first total homogenisation transition investigators are therefore urged to conduct such measurements in the light of this new result and to make use of new technology to inhibit decrepitation fluid inclusions which display the above sequences cannot be interpreted in the same way as inclusions with only one intersection of an immiscibility boundary if the assemblage of inclusions shows petrographic evidence for homogeneous trapping there is no way to deduce from the inclusion measurements alone on which segment of the isochore the inclusion was trapped conversely if petrography indicates heterogeneous trapping microthermometry does not yield a unique formation temperature rather there may be up to three possible p t points of entrapment based on the concept of global phase diagrams and on analogues with better known fluids speculations are made on the topology of the co 2 h 2 o nacl and similar systems it seems likely that the immiscibility field closes at high temperatures thereby allowing the region of high pressure low temperature liquid to join the vapour field at low pressures and high temperatures isochores in these systems may therefore exhibit type six behaviour listed above

ore forming fluids in archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec canada archean gold bearing quartz veins at the sigma mine occur in deformed metavolcanics intruded by two generations of preore porphyries the veins were emplaced during a late compressional tectonic event and they consist primarily of quartz tourmaline carbonates pyrite and scheelite vein minerals have been deformed and are also cut by abundant healed fractures outlined by fluid inclusions in the veins gold typically occurs in late fractures and in recrystallized quartz microthermometric sem eda leachate analysis and gas chromatographic techniques were used to study fluid inclusions in quartz most fluid inclusions at sigma occur in late fractures and are secondary the fluid inclusions are commonly found in fractures parallel to or less commonly within gold bearing fractures and are genetically related to the gold three types of fluid inclusions are identified 1 high salinity na ca cl aqueous inclusions 25 34 wt salt with small amounts of co 2 some containing halite calcite and nahcolite as daughter minerals 2 co 2 rich inclusions containing small amounts of h 2 o and ch 4 and 3 low salinity h 2 o co 2 inclusions 10 equiv wt nacl with co 2 contents which are variable but commonly in the range of 15 to 30 mole percent co 2 leachate analyses show that in addition to na and ca the aqueous fluids contain minor amounts of k fe mg and li homogenization temperatures of h 2 o co 2 inclusions with constant phase ratios range from 285 degrees to 395 degrees c those of aqueous inclusions range from 60 degrees to 295 degrees c the aqueous and co 2 rich inclusions are interpreted to have trapped two coexisting fluids resulting from the unmixing of a homogeneous h 2 o co 2 parent fluid itself occasionally trapped in late fractures the ore bearing fluid is interpreted to be a low salinity 10 equiv wt nacl fluid containing 15 to 30 mole percent co 2 at minimum temperatures in the range of 285 degrees to 395 degrees c the relatively low homogenization temperatures of aqueous inclusions are interpreted to be the result of co 2 effervescence from a co 2 saturated aqueous fluid due to pressure fluctuations at the time of entrapment it is also proposed that the onset of gold deposition is related to the onset of fluid unmixing

chemical evolution of ore forming brines basement leaching metal provenance and the redox link between barren and ore bearing hydrothermal veins a case study from the schwarzwald mining district in sw germany abstract six mineralogically exemplary barren and mineralized hydrothermal veins with pb and zn ores of jurassic cretaceous and cenozoic age in the schwarzwald mining district sw germany were chosen to shed light on the origin of their mineralogical diversity the selection of the veins was guided by the fact that they represent the largest number of veins in the region are very well known mineralogically and geochemically and they provide nice examples of barren and mineralized veins of similar age fluid inclusion data from the individual veins overlap implying their diverse mineralogy is not caused by different fluid compositions participating during fluid mixing la icpms data of single fluid inclusions indicate no systematic variations in major elements but significant changes in fluid mixing ratios which caused variable trace element concentrations of different fluid inclusion assemblages in one sample we suggest that different ore gangue assemblages can be produced by mixing of identical fluid endmembers but variable mixing ratios la icpms analyses of single fluid inclusions in barren and mineralized veins record similar base metal and sulfur concentrations hence sulfide mineralization in the veins appears not to be controlled by metal solubility thermodynamic modeling based on the fluid data indicates that the presence of a reducing phase during fluid mixing is required for sulfide mineralization to precipitate la icpms trace element analyses of feldspars biotites chlorites and clay minerals in granites and paragneisses which are the source of the metal content in the ore forming fluids demonstrate that the dominant provenance for pb zn as sb ba tl mo fe and mn are probably paragneisses while co cu and ni are probably sourced from s type granite a rough quantification indicates that

the miocene gangdese porphyry copper belt generated during post collisional extension in the tibetan orogen abstract the mid miocene gangdese orogenic belt in southern tibet contains porphyry cu deposits that developed after the indian asian continental collision in the early cenozoic field work confirms that these porphyry cu deposits are temporally and spatially associated with mid miocene monzogranitic and quartz monzonitic stocks which intruded mesozoic cenozoic gangdese granitoid batholiths and surrounding triassic tertiary volcano sedimentary sequences in the lhasa terrane and formed a 50 km wide 400 km long e w belt magmatism occurred during the interval 11 2 to 19 7 ma peaking at 16 ma for the porphyry stocks this is consistent with the age 10 to 18 ma of the east west extension and subsequent ns striking normal fault systems 13 5 ma in the tibetan orogen the stocks typically occur as multiple small diameter intrusions 50 km breakdown of hornblende in the juvenile lower crust source during melting is regarded as fundamental for the formation of the fertile adakite and porphyry cu systems in south tibet the gangdese belt contains four large and three intermediate and small sized porphyry cu mo deposits and shows a continuous spectrum from typical porphyry type cu mo to skarn type zn pb mineralization twenty three samples collected from four deposits yielded a limited range of molybdenite re os isochron ages from 15 2 to 16 0 ma similar to previously reported re os ages 13 8 to 14 9 ma for other porphyry cu mo deposits in the belt suggesting that cu mo mineralization in the belt occurred in a post collisional extension environment the characteristics of porphyry cu mo deposits in the collisional zone are similar in many aspects to those in arc settings i e mineralization style alteration zoning and metal association preliminary fluid inclusion studies indicate that the early hydrothermal fluids are preserved as high temperature 450 c high salinity 40 to 47 wt nacl equiv and high pressure 1100 to 1500 bar fluid inclusions these fluids are interpreted to represent an orthomagmatic fluid that boiled episodically due to fluid overpressuring and hydrofracturing resulting in potassic alteration and precipitation of chalcopyrite molybdenite assemblages on the basis of comparison with porphyry cu deposits in arc settings we proposed that melting of thickened newly formed basaltic crust resulted in generation of cu bearing magmatic systems in the tibetan collision zone and both orogen transverse normal faults and orogen parallel thrust zones during the miocene post collisional extension constrain the temporal and spatial localization of the porphyry cu systems in the collision zone

how precisely can the temperature of a fluid event be constrained using fluid inclusions u s national science foundation ear 1624589 chemical sciences geosciences and biosciences division office of basic energy sciences office of science u s department of energy de fg02 03er15430 bureau of economic geology jackson school of geosciences university of texas austin

methane rich fluid inclusions in the proterozoic zn pb ag deposit at dugald river nw queensland potential as an exploration guide abstract calculated isochores determined from microthermometry and laser raman microprobe analysis for ch 4 inclusions hosted in quartz grains from 3 different ore types in the dugald river zn pb ag deposit yield fluid trapping p t conditions of 300 350 c and 0 8 2 3 kbar for post depositional metamorphic conditions of sulfide mineralization the consistent relationship between fluid composition and metamorphic grade of the host rocks suggests that ch 4 has been formed by reaction of graphite with aqueous fluids during metamorphic retrogression even though fluids responsible for mineralization are generally similar to those for barren quartz veins in chemistry and microthermometry the substantial contents of ch 4 and co 2 in the dugald river lode inclusions contrast sharply with co 2 alone in barren vein inclusions the presence of ch 4 rich inclusions in the mineralization at dugald river and other similar deposits and their absence in the barren veins in a regional context can be regarded as a possible exploration guide for defining target areas hosting mineralization of this style

impact of the atlantic warm pool on united states landfalling hurricanes 1 the 2010 atlantic hurricane season was extremely active but no hurricanes made landfall in the united states raising a question of what dictated the hurricane track here we use observations from 1970 2010 also extending back to 1950 and numerical model experiments to show that the atlantic warm pool awp a large body of warm water comprised of the gulf of mexico the caribbean sea and the western tropical north atlantic plays an important role in the hurricane track an eastward expansion of the awp shifts the hurricane genesis location eastward decreasing the possibility for a hurricane to make landfall a large awp also induces barotropic stationary wave patterns that weaken the north atlantic subtropical high and produce the eastward steering flow anomalies along the eastern seaboard of the united states due to these two mechanisms hurricanes are steered toward the northeast without making landfall in the united states although the la nina event in the pacific may be associated with the increased number of atlantic hurricanes its relationship with landfalling activity has been offset in 2010 by the effect of the extremely large awp

fluid inclusion geochemistry of high grade vein hosted gold ore at the pamour mine porcupine camp ontario this study was undertaken to characterize fluid inclusions associated with high grade vein hosted gold at the pamour mine in the porcupine camp of ontario and to compare them with fluid inclusions in quartz veins associated with wall rock hosted gold which is much more common the pamour mine contains two principal types of orebodies metasediment hosted fracture zones and larger metavolcanic or metasediment hosted quartz carbonate veins gold in the veins is distributed erratically attains very high grades locally and increases in grade at higher levels zoned alteration around the veins is dominated by addition of k 2 o co 2 as s and cao and depletion of na 2 o k 2 o co 2 and s are concentrated in the hanging wall and the intensity of co 2 and h super metasomatism increases upward in the mine roughly parallel to the trend seen in gold values gold was introduced along with sphalerite galena calcite chlorite and chalcopyrite late in the paragenetic history after brittle deformation of earlier vein hosted quartz tourmaline feldspar and pyrite sphalerite that is directly associated with high grade gold contains two types of primary inclusions a co 2 ch 4 fluid 20 45 mole ch 4 and an h 2 o rich liquid with a carbonaceous phase co 2 ch 4 as well as muscovite and graphite daughter minerals aqueous phase salinity estimates range from 2 to 9 equiv wt percent nacl and sem analyses of evaporitic residues of thermally decrepitated inclusions contain nacl and cacl 2 with lesser amounts of kcl mgcl 2 s zn and fe these two inclusion types appear to represent immiscible fluids trapped along the solvus in the h 2 o co 2 ch 4 salt system at temperatures of 325 degrees or 25 degrees c and pressures of 1 to 2 kbars these fluids are similar to those observed in vein quartz at the mcintyre and hollinger deposits where most gold is hosted by wall rocks except that co 2 immiscibility appears to have been more widespread at pamour the separation of immiscible fluids of the type identified in this study would increase the f sub o 2 and ph of the residual fluid owing to the partitioning of h 2 s ch 4 and co 2 into the carbonaceous phase the net effect of these changes would be to decrease the solubility of bisulfide complexed gold suggesting that co 2 immiscibility is an important contributor to gold deposition within veins where wall rock interaction is limited it is not clear whether all vein hosted gold formed from such unmixing or only the higher grade ore shoots

fluid inclusion studies in quartz veinlets in the porphyry copper deposit at sungun east azarbaidjan iran abstract the porphyry copper deposit pcd at sungun is located in east azarbaidjan in the nw of iran the sungun porphyries occur as stocks and dikes ranging in composition from quartz monzodiorite through quartz monzonite and granodiorite to granite the stocks are divided into two groups 1 porphyry stocks i and 2 porphyry stock ii porphyry stock ii hosting the copper ore experienced intense hydro fracturing leading to the formation of stockwork type and anastomozing veinlets and micro veinlets of quartz sulfides carbonates and sulfates three distinct types of hydrothermal alteration and sulfide mineralization are recognized at sungun 1 hypogene 2 contact metasomatic skarn and 3 supergene four types of hypogene alteration are developed at sungun potassic propylitic potassic phyllic and phyllic four types of inclusion are common at sungun based upon their phase content 1 mono phase vapor 2 vapor rich 2 phase 3 liquid rich 2 phase and 4 multi phase solid halite is the principal solid phase the distribution pattern shape and phase contents of fluid inclusions in quartz veinlets at sungun are analogous to those from bingham and globe miami in western usa the fluid inclusion data at sungun showed that the liquid vapor homogenization temperature t h l v values for liquid rich 2 phase vapor rich 2 phase and halite bearing inclusions vary from 160 to 580 c from 200 to 600 c and from 160 to 580 c respectively the ascending unboiled fluid at the onset of the phyllic alteration episode had temperatures 580 c and was moderately saline 15 wt with the gradual decrease in temperature the salinity of this fluid gradually decreased so that its salinity at temperatures of 370 and 350 c the residual fluid remained undersaturated with respect to nacl however at temperatures t s nacl t h l v showed that they were developed under the maximum hydrostatic pressure head of 1500 m during the boiling events

porphyry copper deposits of the cis and the models of their formation abstract deposits of the porphyry family essentially porphyry copper and gold porphyry copper gold bearing porphyry molybdenum copper gold containing porphyry copper molybdenum and porphyry molybdenum deposits are associated in time and space with granitoid magmatism mainly in phaerozoic volcano plutonic belts whatever their age the deposits belong to two types of belts basaltic belts representing axial zones of island arcs or andesitic belts formed within active continental andean type margins the petrochemistry of ore bearing magmatism related to the nature of the substratum of volcano plutonic belts reveals a number of essential characteristics both in composition and zonation of wallrock alteration and ore mineralization these characterisics enabled previous researchers to establish four models of porphyry copper deposits based on their lithologic associations e g diorite granodiorite monzonite and granite pophyry copper deposits are thought to be the product of self generating two fluid mixing ore magmatic systems porphyry intrusions are pathways for energy and metals from deep seated magma chambers of which the upper mineralized parts are accessible for observation the relationship between magmatic fluids and meteoric water participating in the ore forming processes dependent on the structural petrophysical conditions of formation provide a subdivision for the porphyry copper ore magmatic systems into three types open closed and transitional concurrently a common trend in the evolution of the systems has been established from a nearly autoclave regime of structural and ore forming processes to a gradual increase in the importance of hydrothermal recycling the completeness of the oms ore magmatic system development according to this scheme which determines the existence of various oms types depends on many factors the most important being the depth of formation of porphyry intrusive bodies the petrophysical peculiarities of the host rocks and the palaeohydrogeological conditions of ore deposition although rock fracturing especially defluidization second boiling and contraction are caused by the same mechanisms the stockwork growth in open and closed systems relative to the wall rock takes place in opposite directions primarily due to different petrophysical parameters of the near stock environment in open systems structural and ore metasomatic processes are finalized fractures extend progressively from porhyry stocks into the marginal parts of the intrusive framework and extension of large scale recycling of magmatic and activated meteoric water in the same direction result in the formation of ore bearing stockworks these are large in all dimensions cover mainly hanging wall zones and are characterized by clearly defined concentric mineral zoning and extensive geochemical haloes in a closed oms with centripetal growing fractures hydrothermal convection is stunted the vertical extension of recycling cells is restricted and the volume of meteoric water involved in circulation during the period of ore deposition is relatively small as a result relatively small intra intrusive lenticular stockworks are developed which are characterized by close co existence of several generations of mineralization with fragmentary preservation of the earliest ones these are characterized by the elements of reverse zoning increased density of the veinlets and metal content as well as poorly developed hanging wall dispersion haloes

classifying el nino modoki i and ii by different impacts on rainfall in southern china and typhoon tracks based on their opposite influences on rainfall in southern china during boreal fall this paper classifies el nino modoki into two groups el nino modoki i and ii which show different origins and patterns of sst anomalies the warm sst anomalies originate in the equatorial central pacific and subtropical northeastern pacific for el nino modoki i and ii respectively thus el nino modoki i shows a symmetric sst anomaly distribution about the equator with the maximum warming in the equatorial central pacific whereas el nino modokiii displays an asymmetric distribution with the warmsstanomaliesextending fromthe northeastern pacifictotheequatorialcentralpacific additionally thewarmsstanomaliesintheequatorialcentralpacific extend farther westward for el nino modoki ii than for el nino modoki i similar to the canonical el nino el nino modoki i is associated with an anomalous anticyclone in the philippine sea that induces south westerly wind anomalies along the south coast of china and carries the moisture for increasing rainfall in southern china for el nino modoki ii an anomalous cyclone resides east of the philippines associated with northerly wind anomalies and a decrease in rainfall in southern china the canonical el nino and el nino modoki i are associated with a westward extension of the western north pacific subtropical high wnpsh whereas el nino modoki ii shifts the wnpsh eastward differing from canonical el nino and el nino modoki i el nino modoki ii corresponds to northwesterly anomalies of the typhoon steeringflow which are unfavorable for typhoons to make landfall in china

zircon u pb and molybdenite re os geochronology and geochemistry of jinchang porphyry gold copper deposit ne china two phase mineralization and the tectonic setting abstract whether multiple mineralization styles in porphyry deposits are the result of one or multiple pulses of magmatism is unknown in this paper we present new age and geochemical data on the jinchang porphyry gold copper au cu deposit an important deposit in ne china and in the eastern central asian orogenic belt caob field geological study suggests that both the mineralization and ore causative magmatism at jinchang are multiphase la icp ms zircon u pb dating of the monzogranite ore host yielded 197 1 ma which is considerably older than the ore causative monzonite 115 3 ma and granodiorite 107 2 ma molybdenite re os dating on the breccia pipe hosted au cu ores yielded a well defined isochron age of 114 3 ma coeval to the monzonite emplacement the au cu mineralization was followed by another phase of crypto explosive breccia pipe hosted disseminated vein type au mineralization this au only mineralization phase was auriferous pyrite re os dated to be 103 101 ma coeval to the granodiorite emplacement geochemically the monzonite and granodiorite are enriched in liles and lrees but depleted in hfses and hrees the ore causative rocks are i type and display continental arc geochemical affinities we suggest that the monzonite and granodiorite were generated in an intracontinental extensional setting probably caused by the early cretaceous subduction roll back of the paleo pacific plate

archean gold bearing quartz veins at the sigma mine abitibi greenstone belt quebec part ii vein paragenesis and hydrothermal alteration the sigma deposit consists of an archean gold bearing vein system in deformed volcanic rocks intruded by two generations of porphyries the veins cut all rock types and wall rock alteration is superposed on greenschist facies metamorphic assemblages there are two related vein sets subvertical veins in ductile shears and subhorizontal veins in extensional fractures between shear zones this paper reports on the paragenesis of extensional veins and related hydrothermal alteration tension veins are composed chiefly of quartz and tourmaline and subordinate amounts of carbonates chlorite pyrite pyrrhotite scheelite and free gold the veins formed by one or more episodes of open space filling the paragenetic sequence consists essentially of successive deposition of carbonate scheelite tourmaline pyrite pyrrhotite carbonate chlorite and quartz most of the gold and tellurides was introduced into fractures and along grain boundaries of recrystallized vein minerals during a postfilling episode of deformation veins are surrounded by zoned alteration envelopes consisting of an outer zone of cryptic alteration characterized by a chlorite carbonate white mica assemblage and an inner zone of visible alteration characterized by a carbonate white mica outer subzone and a carbonate albite inner subzone alteration zones represent reaction fronts advancing into the wall rocks and resulted from progressive interaction of wall rocks with a single hydrothermal fluid the chlorite carbonate white mica zone is characterized by replacement of epidote by calcite and white mica accompanied by fixation of co 2 and k and by release of small amounts of si in carbonate white mica and carbonate albite subzones of visible alteration chlorite biotite and white mica were replaced by calcite albite and quartz variable amounts of gold tourmaline pyrite pyrrhotite and ilmenite were also introduced visible alteration zones are characterized by additions of ca co 2 na b s p and au and by important losses of mg fe al and h 2 o mass balance calculations show that ca na si co 2 s and b in vein minerals were contributed from the hydrothermal fluid whereas fe mg and al were derived from the walls the development of alteration envelopes began with the infiltration of hydrothermal fluids into open extensional fractures and it ceased before complete filling of the veins when continuous mineral coatings formed along vein walls deposition of carbonate accompanied development of cryptic alteration including initial co 2 additions to the wall rocks subsequent deposition of tourmaline pyrite and pyrrhotite carbonate chlorite accompanied the progressive development of visible alteration which encroached on cryptically altered rocks visible alteration is characterized by additions of ca and co 2 to the wall rocks and by release of mg fe and al later bulk quartz deposition which filled the vein openings generally took place after complete development of the alteration envelopes except for this late quartz deposition of vein minerals is attributed to chemical changes in the fluid resulting from progressive wall rock alteration bulk quartz deposition is attributed to progressive cooling of the hydrothermal fluid

response of two phase fluids to fracture configurations within submarine hydrothermal systems submarine hydrothermal systems at mid ocean ridges evolve within a region of brittle deformation overlying a region of ductile deformation the interplay between brittle and ductile modes of deformation and the geometry of fracture systems within the brittle zone can exert a significant influence on fluid flow especially under conditions leading to aqueous two phase separation within the brittle region fractures vary between large conduits directly open to the seafloor and small veins and microcracks with constricted or indirect connections to the seafloor in the ductile region fluids may be trapped under near lithostatic pressure while fluids within throughgoing veins in the brittle region will experience hydrostatic pressure in a narrow transition zone between these two extremes a steep pore fluid pressure gradient must exist in the brittle region itself fluid pressures will vary between lithostatic and hydrostatic as fluid occupies interstices varying from isolated pores through tortuous microcracks to channels directly connected to the main upflow conduits a hydrostatic gradient modified by the decreased density of hot fluid and the effects of the flow itself should be applicable in major conduits open to the seafloor fluctuating pressure conditions in the transition zone may induce phase changes in a fluid remaining at constant depth as a result of the large volume increase that accompanies two phase separation a two phase fluid must either accelerate upward or exert an increased pressure on its surroundings possibly leading to enhanced fracturing the fracture configuration will also affect the behavior of the mixed fluid after phase separation a two phase fluid experiencing rapid turbulent flow in a large open conduit is more likely to remain a well mixed suspension of vapor and liquid whereas a two phase mixture in a constricted branching series of channels moving more slowly in a laminar flow regime is more likely to undergo physical isolation of the phases leading to venting of a vapor phase and retention of a saline brine phase at depth we propose a possible configuration for the fracture pattern within a submarine hydrothermal system consisting of a feeder zone comprised of anastomozing microcracks and veinlets progressively increasing in diameter and decreasing in abundance feeding into a main upflow stockwork zone in which flow directly to the surface takes place in relatively large unconstricted conduits fluid movement within a feeder zone may be modified by capillary flow tortuous channelways disconnected fractures blocking of cracks by mineral deposition and opening of new fractures

impact of intraseasonal oscillation on the tropical cyclone track in the south china sea this study investigates the impact of the intraseasonal oscillation iso on tropical cyclone tc tracks in the south china sea scs during 1970 2010 about one third of tcs in the scs move eastward while the other two thirds move westward in the tc genesis peak seasons of june october jjaso the westward moving tcs are controlled by the background tc steering flow of easterly and the eastward moving tcs by the tc steering flow induced by the iso the outgoing longwave radiation and wind fields show that the eastward moving tcs were mostly along the main axis of strong tc steering flow anomaly of westerly associated with the iso while the westward moving tcs were only weakly associated with the iso an experiment performed with a simple two level model further confirmed the result the interannual variation of tc tracks in the scs is also discussed it is found that the steering flow anomalies in the scs mostly favor eastward moving tcs in central pacific cp el nino and eastern pacific ep el nino years however the eastward flow anomalies are too weak to have strong influence on the majority of the tcs during la nina years tcs in the scs tend to move westward possibly related to the westward steering flow anomalies

a fluid inclusion model for the genesis of the ores of the dolgellau gold belt north wales the results of a detailed fluid inclusion study of a zone of auriferous quartz vein in the clogau st davids goldmine north wales are presented these show that both aqueous and an immiscible pair of h 2 o ch 4 fluids were present during the mineralizing event compositions of the immiscible fluid pair are estimated from laser raman and bulk inclusion volatile analysis data thermometry and barometry using these fluid compositions shows that the ores were formed at c 300 320 c and c 1 8 kbar a model is developed which is consistent with both the fluid inclusion data and other considerations this involves the introduction of aqueous fluid into the graphitic shales hosting the mineralized veins which proceeds to react with graphite in the wall rocks to produce h 2 o ch 4 fluids as h 2 o is consumed to produce ch 4 an increase in salinity is observed in the residual aqueous inclusion fluids deposition of gold is ascribed to destabilization of either aucl 2 or au hs 2 complexes in the incoming fluid as a result of interaction with graphite auriferous zones within the veins are defined by high ch 4 values and low co 2 ch 4 ratios in bulk inclusion analyses these effects are thought to be the result of increased fluid rock interaction in these zones related to structural features in the wall rocks

distinguishing barren and auriferous veins in the sigma mine val d or quebec the sigma mine is an archean lode gold deposit located in the abitibi greenstone belt quebec barren quartz veins occur subparallel to auriferous veins within the mine and also occur north of the