permian triassic red stained albitized profiles in the granitic basement of ne spain evidence for deep alteration related to the triassic palaeosurface extensive areas of the variscan granitic basement in ne spain display profiles of red stained albitized facies characterized by albitization of ca plagioclase chloritization of biotite and microclinization of orthoclase along with the alteration of igneous quartz to secondary cl dark quartz these profiles have a geopetal structure beneath the triassic unconformity with a very intense and pervasive alteration in the upper part that progressively decreases with depth to 150 200 m where the alteration is restricted to the walls of fractures the red albitized facies contains secondary maghemite and hematite that indicate oxidizing conditions dating of microclinized orthoclase and secondary monazite that have formed in the red stained albitized facies yielded k ar and u th pbtotal ages of 240 and 250 ma respectively suggesting that the alteration developed during the permian triassic period the geopetal disposition of the red albitized profile with respect to the triassic unconformity its large regional extent and the fracture controlled alteration in the lower part of the profile indicate groundwater interaction the 18o values of albitized plagioclase 11 microclinized orthoclase 13 and secondary cl dark quartz 12 suggest that the alteration temperature was about 55 c this low temperature suggests that the alteration occurred during interaction of the granitic rocks with na rich fluids below a surficial weathering mantle on the permian triassic palaeosurface the latter is possibly related to triassic evaporitic environments in long lasting stable landscapes in which na rich solutions infiltrated deep regional groundwaters

a brittle failure mode plot defining conditions for high flux flow stress and fluid pressure conditions for the initial formation within intact rock of faults shear fractures extension fractures and extensional shears and for the reshear of existing faults may all be represented on a generic failure plot of differential stress 1 3 versus least effective compressive stress 3 3 pf scaled to nominal tensile strength t half the cohesive strength plots of this kind may be used to define maximum sustainable overpressure in different tectonic environments and the structural conditions under which the flow of large fluid volumes may occur through fault fracture meshes containing gaping extension and extensional shear fractures they may also be adapted to different tectonic regimes and correlated to depth for particular fluid pressure conditions high flux flow through distributed fault fracture meshes requires the tensile overpressure condition 3 3 which can only be achieved in the absence of throughgoing cohesionless faults that are well oriented for frictional reactivation in the prevailing stress field high flux flow through distributed fault fracture meshes intrinsically a transient pulsing phenomenon may therefore occur as follows 1 in effectively intact low pemeability crust devoid of throughgoing favorably oriented faults 2 where existing faults have become severely misoriented in the prevailing stress field and 3 where existing faults have regained cohesive strength through hydrothermal cementation

texture and geochemistry of multi stage hydrothermal scheelite in the tongshankou porphyry skarn cu mo w deposit eastern china implications for ore forming process and fluid metasomatism

magmatic hydrothermal activity in the shuteen area south mongolia the shuteen area is located in the gurvansaikhan island arc terrane of south mongolia it contains a large domain of intensely developed silicic and advanced argillic alteration that has strongly affected the adakitic volcanoplutonic shuteen complex the local occurrence of low grade copper mineralization within porphyritic intrusive rocks is indicative of porphyry style mineralization hydrothermal quartz veins host gold mineralization locally the results of scanning electron microscope cathodoluminescence imaging and fluid inclusion microthermometry indicate that the veins and altered rocks at shuteen were produced by multiple hydrothermal events the occurrence of co2 inclusions in quartz from granitoids and the 34s values obtained for sulfide and sulfate within the hydrothermal breccias provide evidence of the involvement of magmatically derived fluids in the early stages of the shuteen magmatic hydrothermal system inferred to be sourced from a porphyry style intrusive center late stage fluids produced abundant barren quartz veins and clay alteration assemblages the weak mineralization and widespread alteration in the shuteen complex are typical of lithocaps found in high level porphyry copper gold molybdenum and high sulfidation epithermal districts the presentday erosion level at shuteen is relatively shallow implying that economic porphyry style mineralization may exist at depth within or beneath the shuteen lithocap

scanning electron microscopy cathodoluminescence of quartz principles techniques and applications in ore geology abstract scanning electron microscopy cathodoluminescence sem cl of quartz has been a prevalent research technique in porphyry and epithermal systems for the past two decades quartz from specific geological environments reveals unique textures in sem cl which can be used to constrain the evolution of these ore bearing systems when complemented by fluid inclusion hyperspectral mapping and trace element studies we review sem cl principles and instrumentation sample preparation and handling and experimental conditions of quartz sem cl imaging that result in the high quality cl images the effects of sample polishing accelerating voltage beam spot size working distance vacuum conditions image acquisition and post processing were examined through experimental trial for the xl 30 esem and the attached gatan panacl detector used the optimum experimental conditions to obtain high quality panochromatic sem cl images of quartz at high vacuum mode for carbon coated conductive samples are as follows 15 kv accelerating voltage relative beam spot size 6 approximately 500 nm in diameter ht 570 v to 580 v photomultiplier tube pmt voltage low vacuum mode with chamber h 2 o vapor pressure from 0 1 to 1 0 torr working conditions are similar to the conditions at high vacuum mode except the pmt voltage should be reduced to 550 v to 560 v working distances vary based on the position of user s retractable cl detector the sample surface should be as close as possible to the cl detector but a 1 mm clearance between the detector and the sample surface is recommended to prevent detector from possible damage by the sample several minutes of beam exposure prior to image acquisition at 320 second scan speeds at 50 1500 magnifications is recommended to generate the greatest cl emission monochromatic cl imaging requires three scans over the same area using red green and blue optical filters that can be merged to produce a true color image the red and green filters require stronger pmt voltages to produce sufficient cl emissions by an increase of 200 v to 300 v and 150 v to 200 v respectively from the pmt voltage used for panochromatic imaging special attention is given to the challenges associated with imaging hydrothermal quartz veining in ore deposits and the value of cl data as a foundation for geochemical studies sem cl imaging of vein quartz is explored through case studies of the red hills porphyry cu mo deposit texas usa and the ertsberg grasberg cu au district papua indonesia to aid in vein paragenesis the most common application of quartz sem cl in ore geology is to reveal the relative timing of mineral precipitation mineral dissolution and inherited structural features understanding of temporal relations among these events makes it possible to select specific generations of quartz within a vein for further studies such as the titaniq thermometry and fluid inclusion microthermometry in order to establish t p x fluctuations throughout the development of a hydrothermal system

hydrothermal evolution and ore precipitation of the no 2 porphyry cu au deposit in the xiongcun district tibet evidence from cathodoluminescence fluid inclusions and isotopes abstract the no 2 porphyry cu au deposit in the xiongcun district forms part of the gangdese porphyry copper belt of tibet this study clarifies the fluid evolution and ore precipitation mechanisms of the magmatic hydrothermal system that formed the deposit by combining the results of fluid inclusion petrography microthermometry scanning electron microscope cathodoluminescence imaging and stable isotope analyses of multiple quartz dominated veins four distinct sets of quartz dominated veins and eight generations of quartz q1 q8 within the veins were identified namely from early to late early barren quartz veins v1 comprised of equigranular cl bright q1 quartz quartz pyrite chalcopyrite magnetite veins v2 containing early equigranular cl bright q1 quartz and later cl gray or cl dark q2 3 q2 q3 quartz grains intergrown with cu fe sulfides quartz molybdenite pyrite chalcopyrite veins v3 comprised of quartz grains q4 q6 characterized by subhedral comb like textures with well developed oscillatory growth zoning and late quartz veins v4 containing cl gray q7 quartz with euhedral growth zones and later cl dark q8 quartz fluid inclusions in these veins can be classified into six types b40 b40h b80 b15h b15h and b15 the b40 and b40h inclusions b80 inclusions and b15 b15h and b15h inclusions contain vapor bubbles occupying 30 60 vol 70 vol and 5 25 vol respectively in addition b15h b15h and b40h inclusions contain transparent daughter minerals halite and in some cases sylvite raman spectra showed that co2 is only present in b40 and b80 inclusions in the q1 quartz in v1 and v2 veins the dominant type of inclusions is b40 which have homogenization temperatures th of 278 c 389 c peaking at 310 c 330 c and salinities of 2 0 12 8 wt nacl equiv in q2 3 quartz in v2 veins all inclusion types were observed these were trapped at temperatures of approximately 325 c 340 c and had salinities of 1 8 69 7 wt nacl equiv in v3 veins only b15h and b15 inclusions were observed which had th values of 171 c 320 c peaking at 240 c 260 c and 173 c 317 c peaking at 210 c 230 c and salinities of 28 7 33 9 wt nacl equiv and 5 6 23 1 wt nacl equiv respectively in v4 veins only b15 inclusions were observed primary b15 inclusions in v4 veins yielded th values of 166 c 229 c peaking at 170 c 200 c and salinities of 5 1 17 1 wt nacl equiv the 3he 4he and 40ar 36ar ratios of the fluid inclusions exhibited the ranges of 0 08 0 84 ra and 451 3 1567 8 respectively and the 18ofluid and dfluid values varied from 3 2 to 5 8 and 92 8 to 80 3 respectively by integrating all results from the fluid inclusion cathodoluminescence and isotopic analyses we conclude that the initial ore forming fluids of the no 2 deposit were low salinity co2 rich single phase fluids of magmatic origin subsequently fluid immiscibility developed in the initial ore forming fluids generating hypersaline liquid and low salinity vapor phases and leading to the separation of a co2 phase plus chalcopyrite precipitation from the fluids as meteoric water was injected into the hydrothermal system the ore forming fluids gradually evolved to become meteoric water dominated low temperature low salinity and co2 poor in addition fluid cooling due to the meteoric water input resulted in molybdenite precipitation

porphyry to epithermal transition in the altar cu au mo deposit argentina studied by cathodoluminescence la icp ms and fluid inclusion analysis the middle to late miocene altar porphyry cu au mo deposit located in the andean main cordillera of san juan province argentina is characterized by the superposition of multiple vein generations consisting of both porphyry type and high sulfidation epithermal style alteration and mineralization we constrain the physical and chemical evolution of the hydrothermal fluids that formed this deposit based on description and distribution of vein types scanning electron microscopy cathodoluminescence cl imaging trace elements in quartz veins and fluid inclusion microthermometry quartz cl textures and trace elements chiefly li al ti and ge differentiate among quartz generations precipitated during different mineralization and alteration events early quartz chalcopyrite pyrite veins and quartz molybdenite veins a and b veins show considerable complexity and were commonly reopened and some underwent quartz dissolution early quartz chalcopyrite pyrite veins a veins are dominated by equigranular bright cl quartz with homogeneous texture most of these veins contain higher ti concentrations than any other vein type average 100 ppm and have low to intermediate al concentrations 65 448 ppm quartz molybdenite b veins and chlorite rutile hematite c veins veins contain quartz of intermediate cl intensity that commonly shows growth zones with oscillatory cl intensity quartz from these veins has intermediate ti concentrations 20 ppm and al concentrations similar to those of a veins quartz from later quartz pyrite veins with quartz muscovite tourmaline halos d veins has significantly lower cl intensity low ti 15 ppm and elevated al concentrations up to 1 000 ppm and typically contains euhedral growth zones late veins rich in sulfides and sulfosalts show cl textures typical of epithermal deposits dark cl quartz crustiform banding and euhedral growth zones quartz from these veins typically contains less than 5 ppm ti and al li and ge concentrations are elevated relative to other vein types based on experimentally established relationships between ti concentration in quartz and temperature the decrease in ti content in successively later quartz generations indicates that the temperature of the hydrothermal fluids decreased through time during the evolution of the system vein formation at altar occurred at progressively lower pressure shallower paleodepth and lower temperature under lithostatic pressures the magma supplied low salinity aqueous fluids at depths of 6 to 6 8 km pressures of 1 6 1 8 kbar and temperatures of 670 to 730 c first quartz generation of early quartz chalcopyrite pyrite veins this parental fluid episodically depressurized and cooled at temperatures and pressures below the brine vapor solvus quartz molybdenite veins precipitated from fluids at temperatures of 510 to 540 c and pressures of 800 to 1 000 bars corresponding to depths of 3 to 3 7 km under lithostatic pressures further cooling of hydrothermal fluids to temperatures between 425 and 370 c under hydrostatic pressures of 200 to 350 bars produced pyrite quartz veins and pervasive quartz muscovite tourmaline and illite alteration that overprinted the early hydrothermal assemblages late veins rich in sulfides and sulfosalts that overlapped the deep and intermediate high temperature veins formed from fluids at temperatures of 250 to 280 c and pressures of 20 to 150 bars the epithermal siliceous ledges formed from low temperature fluids 230 c at hydrostatic pressures of 100 bars corresponding to depths of 1 km

vein spacing in extending layered rock the effect of synkinematic cementation cemented fractures veins commonly show mm scale spacing even in layerbound arrangements in beds of cm to dm scale thickness the relief of tension around such layerbound fractures should preclude nearby fracture propagation and result in cm to dm scale fracture spacing we hypothesize that cement precipitated during vein opening could re establish tension across veins and lessen the effects of relieved tension thus decreasing fracture spacing we test this hypothesis using a computer based numerical model the model consists of a 2d triangular lattice of nodes connected by elastic springs the lattice is stretched by holding the left boundary stationary and moving the right boundary to the right at constant velocity the lattice consists of three layers springs within the middle fracturing layer fail upon stretching past a given critical length springs within the upper and lower matrix layers are indestructible we tune the model parameters to produce the familiar regular spacing of barren fractures joints then we perturb this system by adding cement within fractures as the fractures propagate and widen cementation is simulated by extending failed springs across the space between the nodes on which they are rooted and re attaching springs once they reach across re attached springs are assigned a new neutral length equal to their current length on re attachment the primary effect of cementation is to make fractures narrower and more closely spaced thus the model highlights the resistance to fracture widening by cement as a potential reason why veins can be more closely spaced than joints individual fractures open and seal multiple times when the stiffness of cemented springs is lower than that of the host rock springs suggesting that natural crack seal vein opening is associated with persistent mechanical weakness at extant fractures modeled veins are more irregularly spaced than modeled joints but the vein patterns remain more regularly spaced than would be expected for a random arrangement therefore the model does not explain systematic clustering of natural veins

cathodoluminescence characteristics of archean volcanogenic massive sulfide related quartz noranda ben nevis and matagami districts abitibi subprovince canada 1 the cathodoluminescence cl of quartz from ore stockwork veins and interstitial fillings between lava pillows from the 2 7 ga noranda ben nevis and matagami volcanogenic massive sulfide vms districts abitibi greenstone belt has been investigated using the hot cathode technique hc1 lm system to assess the potential of these various sample types to host primary seafloor vms related fluids trapped as inclusions in minerals with primary depositional morphologies the cl responses indicate that the various quartz types are of hydrothermal origin and are therefore a potential host for primary hydrothermal fluid inclusions most notable is a transient t 120 s blue cl characteristic of hydrothermal quartz observed in most samples cl characteristics are similar over 250 km indicating coherent nonrandom behavior furthermore in ore and stockwork material from the matagami and noranda districts respectively cl reveals primary concentric growth zoned quartz that predates pulses of sulfide deposition clear evidence that the quartz is undeformed and directly related to vms mineralization these growth zones are not apparent in transmitted light in addition ore and stockwork quartz commonly show a very unstable t 30 s yellow cl coincident with microfractures and grain boundaries defining areas affected by secondary hydrothermal activity in ore from matagami local zones of nontransient brown cl may reflect strain zones associated with the deformation and recrystallization of the massive sulfide mound and indicate that such modifications can be recognized and are minor in the investigated cases cl clearly reveals pseudo hexagonal apparently zoned structures in sulfide mineralized breccia pipe quartz from the ben nevis area these structures and their host quartz characterized by a very unstable t 20 s bright yellow cl are interpreted as recrystallized quartz that has undergone rapid growth from a strongly supersaturated solution and noncrystalline precursor the cl also clearly reveals colloform crustiform textures indicative of open space filling these textures are not visible optically

genesis of the xiaolonghe quartz vein type sn deposit sw china insights from cathodoluminescence textures and trace elements of quartz fluid inclusions and oxygen isotopes abstract quartz textures revealed by scanning electron microscope cathodoluminescence sem cl images suggest that quartz in the xiaolonghe sn deposit formed in at least three fluid episodes quartz q1 in the pre ore silicification zone has homogeneous texture high cl intensity and high ti content 19 53 ppm fluid inclusions hosted in q1 are vapor rich v1 type and homogenized as supercritical fluid at 570 c quartz q2 in the syn ore topaz cassiterite quartz veins has lower cl intensity and is characterized by euhedral growth zones with lower ti content 1 3 12 ppm fluid inclusions hosted in q2 topaz and cassiterite are liquid rich fluid inclusions of moderate salinity 15 wt nacl equiv l1 type which homogenized at 423 c the post ore quartz q3 closely associated with sericitization of topaz generally crosscuts q2 and has dark cl intensity and much lower ti concentration the upper limits of t p conditions of pre ore and syn ore stage are constrained by the intersection of nacl h2o fluid inclusion isochores and ti in quartz isopleths and the lower limits are based on microthermometry results of fluid inclusions combined with the 18ofluid value 8 3 of q1 it indicates that the pre ore supercritical fluid was directly exsolved from a granitic magma at t 570 600 c and p 0 70 0 77 kbars corresponding to a maximum depth of 2 8 km under lithostatic pressure the syn ore subcritical fluid 8 0 18ofluid 6 3 mixed with some meteoric water was under 423 450 c 0 32 0 45 kbars the transition from the pre ore supercritical fluid to the syn ore subcritical fluid indicates boiling condition probably at 512 c 0 62 kbars which was likely caused by hydraulic fracturing under high pressure both the fluid boiling and fluid mixing contribute to the cassiterite precipitation in xiaolonghe sn deposit in the post ore stage the coexisting s type and v2 type fluid inclusions in q3 indicates a second fluid boiling at 269 c 0 05 kbars which was probably caused by decompression due to rapid denudation of the overlain strata the low salinity 5 5 wt nacl equiv l2 type fluid inclusions hosted in fluorite homogenized at 199 c and

cenozoic structures in the eastern north sea basin a case for salt tectonics abstract local and scattered deformations of the cenozoic succession in the eastern north sea basin have often been used to infer the importance of regional events related to major plate tectonic processes such as the alpine orogeny or the opening of the north atlantic here we integrate published and new interpretations from conventional and high resolution seismic data and outcrops in the entire eastern north sea basin onshore as well as offshore and unravel the kinematic history and the tectonic implications the analysis shows paleogene inversion along selected fault trends in the central graben and the sorgenfrei tornquist zone superimposed onto thermal subsidence centered in the central north sea minor paleogene and neogene differential subsidence across reactivated n s striking basement faults could be invoked as having a tectonic origin but differential compaction of the underlying thick mesozoic succession provides a simpler explanation our analysis demonstrates that the main mechanism that caused deformation of the cenozoic succession in the eastern north sea basin was reactivation of the zechstein salt cenozoic salt reactivation was a consequence of differential loading by prograding cenozoic sequences acting on mesozoic salt structures and salt deposits of varying thickness controlled by permian topographic highs

on the structural evolution of the central trough in the norwegian and danish sectors of the north sea abstract the central trough of the north sea is not a simple rift graben it is an elongated area of regional subsidence which was initiated in mid cretaceous times and continued to subside through to the late tertiary its form is not representative of pre mid cretaceous tectonics in late permian times the north sea was divided into a northern and southern zechstein basin by the e w trending mid north sea ringkobing fyn high the latter was dissected by a narrow graben trending nnw through the tail end graben and the sogne basin the feda graben was a minor basin on the northern flank of the mid north sea high at this time this structural configuration persisted until end middle jurassic times when a new wnw trend separated the tail end graben from the sogne basin right lateral wrench movement on this new trend caused excessive subsudence in the tail end and feda grabens while the sogne basin became inactive upper jurassic subsidence trends continued during the early cretaceous causing the deposition of large thicknesses of sediments in local areas along the trend from mid cretaceous times the regional subsidence of the central trough was dominant but significant structural inversions occurred in those areas of maximum early cretaceous and late jurassic subsidence

the magmatic hydrothermal transition evidence from quartz phenocryst textures and endoskarn abundance in cu zn skarns at the empire mine idaho usa information about the magmatic to hydrothermal transition is preserved in late stage features of quartz phenocrysts and endoskarn alteration in some cu zn skarn deposits such as the empire mine in idaho important features include 1 quartz phenocrysts with strong resorption textures such as vermicular zones of igneous groundmass cutting primary quartz cathodoluminescence banding 2 anomalous amounts of endoskarn more than 50 of mineralized rock 3 high f activities as evidenced by fluorite as an accessory mineral in igneous rocks in alteration assemblages and in fluid inclusions and by high f in hydroxyl sites in igneous biotite and amphibole and 4 direct association of zn which normally is deposited distally at low temperature with cu in proximal locations and in endoskarn these features are explained by the following model 1 f lowers the solidus temperature of the magma thus changing the timing temperature and duration of hydrothermal fluid exsolution 2 upon magmatic vapor saturation the f rich hydrothermal fluids form bubbles that adhere to quartz phenocrysts and chemically corrode tunnel into the quartz forming vermicular resorption textures 3 f rich hydrothermal fluids also promote the formation of endoskarn silicic rocks are attacked by f rich fluids in the same sense that carbonate wall rocks are dissolved by weakly to moderately acidic hydrothermal fluids 4 low fluid exsolution temperature facilitated by high f activity promotes high zn cu ratios in proximal locations due to the solubility of zn relative to cu at lower temperatures this model may be applicable at other localities such as the world class cu zn skarn antamina mine as well as some tin and rapakivi granites

tracking meteoric infiltration into a magmatic hydrothermal system a cathodoluminescence oxygen isotope and trace element study of quartz from mt leyshon australia the oxygen isotope and trace element composition of hydrothermal quartz has been integrated with scanning electron microscope cathodoluminescence sem cl images and fluid inclusion properties to track fluid sources and hydrothermal processes in the mt leyshon an deposit australia oxygen isotope and trace element data were collected on parallel traverses across the same quartz sections using secondary isotope mass spectrometry sims and laser ablation inductively coupled plasma mass spectrometry la icp ms respectively with sem cl images obtained before analysis for petrographic context over the 280 to 650 degrees c quartz precipitation range suggested by fluid inclusion microthermometry delta o 18 quartz varies from 0 0 to 14 4 o corresponding to a wide range of equilibrium delta o 18 fluid values from 6 1 to 10 2 o vs v smow the delta o 18 quartz signature varies systematically among distinct sem cl quartz generations both within and between samples and can be correlated with variations in temperature and fluid composition but is independent of intra generational oscillatory zoning in contrast al and li concentrations correlate broadly with cl intensity in oscillatory quartz whereas their concentration is unpredictable in sealed fractures and overgrowths concentrations of b mg na p cl k ti mn fe ge and sn are independent of al li and oscillatory cl features but ti correlates with quartz precipitation temperature although no systematic correlation between delta o 18 quartz and trace element concentrations was found complementary patterns exist in narrow overgrowths of low delta o 18 quartz similar to 0 o and high al g 10 000 ppma these quartz zones likely formed during the incursion of o 18 depleted meteoric water into the magmatically dominated mt leyshon hydrothermal system we interpret the highest al concentrations as the result of high quartz precipitation rates triggered by depressurisation of the hydrothermal cell the decoupling of oxygen isotope and trace element patterns in quartz leads to the suggestion that 1 under most circumstances temperature and fluid chemistry dominate delta o 18 quartz and 2 the trace element record and in particular al and li is influenced by the superimposed effects of quartz precipitation rate c 2007 elsevier b v all rights reserved

scanning electron microscope cathodoluminescence analysis of quartz reveals complex growth histories in veins from the butte porphyry copper deposit montana scanning electron microscope cathodoluminescence sem cl analysis of quartz reveals textures that cannot be observed using optical microscopy or backscattered electrons these cryptic textures yield insight into timing and physical conditions of quartz growth especially in environments with multiple quartz precipitation events hydrothermal quartz from quartz sulfide veins in the porphyry copper deposit in butte montana was analyzed by sem cl revealing the following textures euhedral growth zones wide nonluminescing bands that cut across multiple quartz grains rounded luminescent quartz grain cores with euhedral overgrowths nonluminescing splatters of quartz connected by networks of cobweb like nonluminescing quartz in otherwise luminescent quartz concentric growth zones and wide nonluminescent grain boundaries these textures indicate that many veins have undergone fracturing dilation growth of quartz into fluid filled space quartz dissolution and recrystallization of quartz precipitation and dissolution textures indicate that early quartz molybdenite veins formed as a result of pressure fluctuations between lithostatic and hydrostatic at high temperatures and later pyrite quartz veins formed near hydrostatic pressure in response to temperature decrease through and beyond the field of retrograde quartz solubility

enso impact on kelvin waves and associated tropical convection abstractthe impact of el nino southern oscillation enso on atmospheric kelvin waves and associated tropical convection is investigated using the ecmwf re analysis noaa outgoing longwave radiation olr and the analysis technique introduced in a previous study it is found that the phase of enso has a substantial impact on kelvin waves and associated convection over the equatorial central eastern pacific el nino la nina events enhance suppress variability of the upper tropospheric kelvin wave and the associated convection there in both extended boreal winter and summer the mechanism of the impact is through changes in the enso related thermal conditions and the ambient flow in el nino years because of sst increase in the equatorial central eastern pacific variability of eastward moving convection which is mainly associated with kelvin waves intensifies in the region in addition owing to the weakening of the equatorial eastern pacific westerly duct in the upper troposphere in el nino years

methane origin and oxygen fugacity evolution of the baogutu reduced porphyry cu deposit in the west junggar terrain china most porphyry copper deposits worldwide contain magnetite hematite and anhydrite in equilibrium with hypogene copper iron sulfides chalcopyrite bornite and have fluid inclusions with co2 ch4 that are indicative of high fo2 in contrast the baogutu porphyry cu deposit in the west junggar terrain xinjiang china lacks hematite and anhydrite contains abundant pyrrhotite and ilmenite in equilibrium with copper iron sulfides chalcopyrite and has fluid inclusions with ch4 co2 that are indicative of low fo2 the mineralized intrusive phases at baogutu include the main stage diorite stock and minor late stage diorite porphyry dikes the main stage stock underwent fractional crystallization and country rock assimilation contamination and consists of dominant diorite and minor gabbro and tonalite porphyry the country rocks contain organic carbons 0 21 0 79 wt the 13cvpdb values of the whole rocks 23 1 to 25 8 in the wall rocks suggest a sedimentary organic carbon source the 13cvpdb values of ch4 28 2 to 36 0 and co2 6 8 to 20 0 in fluid inclusions require an organic source of external carbon and equilibration of their 13cco2 ch4 values 8 2 25 0 at elevated temperatures 294 830 c suggesting a significant contribution of thermogenic ch4 mineral composition data on the main stage intrusions such as clinopyroxene hornblende biotite magnetite ilmenite sphene apatite and pyrrhotite suggest that the primary magma at baogutu was oxidized and became reduced after emplacement by contamination with country rocks mineral compositions and fluid inclusion gas compositions suggest that the redox state of the system evolved from logfo2 fmq 1 in the magma stage to logfo2 fmq in the hydrothermal stage though oxidized magma was emplaced initially assimilation contamination of carbonaceous country rocks decreased its fo2 such that exsolved fluids contained abundant ch4 and deposited a reduced assemblage of minerals

the nature and timing of ore formation in the budunhua copper deposit southern great xing an range evidence from geology fluid inclusions and u pb and re os geochronology abstract the budunhua copper deposit is located in the southern great xing an range where the stockwork ore bodies are mainly hosted in the lower permian dashizhai formation the mineralization occurs in two blocks the jinjiling and kongqueshan and both are characterized by four main stages arsenopyrite pyrite molybdenite quartz chalcopyrite pyrrhotite quartz galena sphalerite chalcopyrite quartz and calcite fluorite quartz wall rock alteration which is related to mineralization is dominated by silicification sericitization and chloritization fluid inclusion studies show that the ore forming fluids from cu stages in both blocks are broadly identical with trapping temperatures of 280 to 400 c for the kongqueshan and 300 to 420 c for the jinjiling estimated trapping pressures for the kongqueshan are 15 0 to 26 6 mpa and for the jinjiling are 14 9 to 29 4 mpa corresponding to entrapment depth of 1 5 to 2 7 km and 1 5 to 2 9 km below the paleowater table respectively zircon grains from the tonalite porphyry in the deposit yielded a weighted 206 pb 238 u mean age of 152 0 7 ma which is consistent with a molybdenite re os model age of 150 2 2 ma indicating that both the porphyry intrusion and the copper deposit are of late jurassic age our data suggest that the budunhua deposit is an atypical porphyry deposit related to a late jurassic magmatic hydrothermal system

intensity of quartz cathodoluminescence and trace element content in quartz from the porphyry copper deposit at butte montana textures of hydrothermal quartz revealed by cathodoluminescence using a scanning electron microscope sem cl refl ect the physical and chemical environment of quartz formation variations in intensity of sem cl can be used to distinguish among quartz from superimposed mineralization events in a single vein in this study we present a technique to quantify the cathodoluminescent intensity of quartz within individual and among multiple samples to relate luminescence intensity to specific mineralizing events this technique has been applied to plutonic quartz and three generations of hydrothermal veins at the porphyry copper deposit in butte montana analyzed veins include early quartz molybdenite veins with potassic alteration pyrite quartz veins with sericitic alteration and main stage veins with intense sericitic alteration cl intensity of quartz is diagnostic of each mineralizing event and can be used to fingerprint quartz and its fluid inclusions isotopes trace elements etc from specific mineralizing episodes furthermore cl intensity increases proportional to temperature of quartz formation such that plutonic quartz from the butte quartz monzonite bqm that crystallized at temperatures near 750 c luminesces with the highest intensity whereas quartz that precipitated at 250 c in main stage veins luminesces with the least intensity trace element analyses via electron microprobe and laser ablation icp ms indicate that plutonic quartz and each generation of hydrothermal quartz from butte is dominated by characteristic trace amounts of al p ti and fe thus in addition to cl intensity each generation of quartz can be distinguished based on its unique trace element content aluminum is generally the most abundant element in all generations of quartz typically between 50 and 200 ppm but low temperature main stage quartz containing 400 to 3600 ppm al is enriched by an order of magnitude relative to all other quartz generations phosphorous is present in abundances between 25 and 75 ppm and p concentrations in quartz show little variation among quartz generations iron is the least abundant of these elements in most quartz types and is slightly enriched in cl dark quartz in pyrite quartz veins with sericitic alteration titanium is directly correlated with both temperature of quartz precipitation and intensity of quartz luminescence such that bqm quartz contains hundreds of ppm ti whereas main stage quartz contains less than 10 ppm ti our results suggest that ti concentration in quartz is controlled by temperature of quartz precipitation and that increased ti concentrations in quartz may be responsible for increased cl intensities

magmatic hydrothermal evolution of the yuanzhuding porphyry cu mo deposit south china insights from mica and quartz geochemistry abstract the yuanzhuding porphyry cu mo deposit located in the southern section of the qinzhou hangzhou belt is characterized by successive generations of quartz bearing veins with complicated crosscutting relationships multiple analytical methods have been applied to different mica types and quartz bearing veins to reveal the evolution history of the yuanzhuding porphyry system four types of micas have been identified in the yuanzhuding porphyry cu mo deposit including magmatic biotite bt i metamorphic biotite bt ii hydrothermal biotite bt iii and hydrothermal sericite ser based on detailed petrological observations all three types of biotite belong to the mg biotite group but can be compositionally distinguished whereas ser lies in the transition zone between li phengite and li muscovite generally decreasing crystallization temperatures with increasing distances from the center of the porphyry have been revealed in bt ii and bt iii based on their compositional variations documenting the outward cooling trends of the yuanzhuding porphyry system early quartz bearing veins with potassic alteration are characterized by granular quartz with homogeneous cl textures in combination with their wavy vein walls which indicate the host rock was ductile during vein formation we infer that they were formed under dominantly lithostatic pressure late quartz bearing veins with sericitic alteration are typically euhedral quartz with growth zones of oscillating cl intensity and they are inferred to be formed under dominantly hydrostatic pressure intersection of fluid inclusion isochores with ti in quartz isopleths revealed that early quartz veins with potassic alteration located close to the ore forming porphyry were formed at up to 575 c late quartz veins with sericitic alteration were formed at 310 c formation depth of the yuanzhuding porphyry deposit is inferred to be 5 3 km hydrogen and oxygen isotopes of bt iii and quartz indicate that the ore forming fluid was mainly magmatic fluid the fluid pressure was high enough to remain stable in single phase through the entire fluid evolution history all fluid inclusions are vapor liquid inclusions the fluid salinity and the cl fugacity remained constantly low which may have limited the efficiency of cu extraction and transportation the hornfels host significant amounts of bt ii and may have served as a reservoir of ferrous iron to reduce the oxidized ore forming fluid and generate reduced sulfur effective metal precipitation occurred in the yuanzhuding porphyry system owing to the coexistence of the generation of reduced s2 and the drop of metal solubility caused by the decrease of fluid temperature

time scales of porphyry cu deposit formation insights from titanium diffusion in quartz porphyry dikes and hydrothermal veins from the porphyry cu mo deposit at butte montana contain multiple generations of quartz that are distinct in scanning electron microscope cathodoluminescence sem cl images and in ti concentrations a comparison of microprobe trace element profiles and maps to sem cl images shows that the concentration of ti in quartz correlates positively with cl brightness but al k and fe do not after calibrating cl brightness in relation to ti concentration we use the brightness gradient between different quartz generations as a proxy for ti gradients that we model to determine time scales of quartz formation and cooling model results indicate that time scales of porphyry magma residence are 1 000s of years and time scales from porphyry quartz phenocryst rim formation to porphyry dike injection and cooling are 10s of years time scales for the formation and cooling of various generations of hydrothermal vein quartz range from 10s to 10 000s of years these time scales are considerably shorter than the 0 6 m y overall time frame for each porphyry style mineralization pulse determined from isotopic studies at butte montana simple heat conduction models provide a temporal reference point to compare chemical diffusion time scales and we find that they support short dike and vein formation time scales we interpret these relatively short time scales to indicate that the butte porphyry deposit formed by short lived episodes of hydrofracturing dike injection and vein formation each with discrete thermal pulses which repeated over the 3 m y generation of the deposit

cathodoluminescence imaging and titanium thermometry in metamorphic quartz cathodoluminescence cl of quartz from metamorphic rocks representing a range of conditions from the garnet grade to the migmatite grade reveals a variety of textures that is a function of metamorphic grade and deformation history ti concentrations determined by electron microprobe and ion microprobe generally correlate with cl intensity blue wavelengths and application of the ti in quartz thermometer titaniq reflects the temperature of quartz growth or recrystallization and in some settings modification by diffusion quartz from garnet grade samples is not visibly zoned records temperatures of 425 475 c and is interpreted to have recrystallized during fabric formation quartz grains from staurolite grade samples are zoned in cl with markedly darker cores and brighter rims some of which are interpreted to have been produced by the dominant staurolite producing reaction whereas others are interpreted as having formed by diffusion of ti into quartz rims quartz from the matrix of kyanite and sillimanite grade samples are generally unzoned although locally displays slightly brighter rims higher ti quartz inclusions within garnet and staurolite have distinctly brighter rims which are interpreted as having been produced by diffusive exchange with the host mineral quartz from migmatite grade samples displays highly variable cl intensity which is dependent on the location of the grain matrix grains in melanosomes are largely unzoned or rarely zoned with darker cores leucosome quartz is strongly zoned with bright cores and dark rims and is interpreted as having formed during crystallization of the melt locally within the leucosome is observed oscillatory zoned quartz which is interpreted as a subsolidus recrystallization to achieve strain relaxation quartz inclusions within garnet or plagioclase crystals often show bright domains separated by zones of dark cl these enigmatic textures possibly reflect local melting fluxed by fluid inclusions temperatures calculated from the ti in quartz thermometer are a function of the metamorphic grade of the sample the textural setting of the quartz the reaction history and the deformation history of the rock the titaniq temperatures can be used to constrain the conditions at which various metamorphic processes have occurred

melt and fluid inclusions in hydrothermal veins the magmatic to hydrothermal evolution of the elatsite porphyry cu au deposit bulgaria the magmatic to hydrothermal transition in the late cretaceous elatsite porphyry cu au mo platinum group element deposit has been studied in a suite of samples with clear timing relations between porphyry dikes magmatic hydrothermal veins silicate melt inclusions in quartz veins fluid inclusion generations and ore minerals ore mineralization occurs late at temperatures 200 to 300 c below those of the early multistage interplay between magmatic and hydrothermal processes at near magmatic temperature pressure conditions crosscutting relations and petrography indicate that shortly after the intrusion of the earliest monzodioritic dikes fluids precipitated a first generation of granular quartz veins accompanied by potassic alteration the second vein generation with crystalline quartz textures and k feldspar alteration halos formed at the same time as the second granodioritic pulse of porphyry intrusions cathodoluminescence imaging of quartz growth textures reveals that the earliest fluid inclusions in the crystalline quartz veins are of intermediate density and 8 wt nacl equiv salinity probably trapped at near lithostatic pressures of 1 200 to 1 300 bars at near magmatic temperatures 730 c and implies a depth of 4 to 5 km depressurization led to phase separation indicated by a first generation of coexisting brine and vapor inclusions trapped at temperatures of 640 c and suprahydrostatic pressures of 920 bars a second quartz generation in crystalline quartz veins precipitated during progressive depressurization and hosts assemblages of coexisting brine vapor and silicate melt inclusions trapped at temperatures in excess of 600 c and suprahydrostatic pressures of 630 to 880 bars some open spaced quartz veins were filled with aplite during this stage field relations and geochemical evidence suggest that the aplites as well as the silicate melt inclusions in hydrothermal quartz veins represent volumetrically minor residual melts that evolved directly from granodiorite porphyries at the level of deposit formation and do not represent aliquots of metal supplying magma at depth fluid inclusions coexisting with the silicate melt inclusions are metal rich but these fluids predate sulfide precipitation and are therefore not the dominant fluids responsible for the cu au mineralization at elatsite melt fluid metal separation processes recorded in these co trapped silicate melt and fluid inclusions in vein quartz are small scale local phenomena and do not appear to be suited for understanding and quantifying metal segregation in the deeper source microthermometry data of fluid inclusions trapped during the later stages of the formation of the second quartz generation show further depressurization to 260 to 325 bars and cooling to 460 c representing a hot hydrostatic regime bornite chalcopyrite and magnetite seem to be slightly later precipitated at temperatures 460 c in separate veins or opened spaces of preexisting veins dissolution textures of the second quartz generation indicate a subsequent local redissolution of vein quartz most likely as a result of passing through a window of retrograde quartz solubility upon further cooling below 460 c the next economically most important chalcopyrite pyrite stage is largely devoid of quartz precipitation and is mostly expressed as paint veins due to the lack of fluid inclusions the temperature pressure conditions of formation of these veins could not be constrained the waning phase of hydrothermal activity is represented by a quartz carbonate zeolite stage formed at low temperature 145 c as indicated by microthermometry of fluid inclusions trapped in quartz from this stage laser ablation inductively coupled plasma mass spectrometry analyses of fluid inclusions show very high cu contents in early intermediate density fluid inclusions and in the first vapor inclusion generation followed by a drastic decrease in the second generation of vapor inclusions the decrease correlates with the appearance of anhydrite inclusions in the second quartz generation and may indicate that a lack of sulfur in these later vapor inclusions led to cu partitioning into the brine alternatively it is also possible that unlike early vapor inclusions the later vapor inclusions were not susceptible to postentrapment copper enrichment in accordance with recent experiments a progressive cu enrichment in the brine phase correlates well with depressurization prior to mineralization mass balance considerations based on analyzed fluid components and fluid phase relations indicate that brine was volumetrically minor and therefore likely stagnant but this may have prepared ore precipitation by accumulating cu stripped from ascending vapor

direct observation and measurement of au and ag in epithermal mineralizing fluids abstract colloidal gold particles have been observed in c 300 c low salinity fluids from the arapucandere intermediate sulphidation epithermal base metal au deposit in nw turkey this is the first time colloidal gold has been recorded in an ancient mineralizing fluid growth in veins of large euhedral quartz crystals after the deposition of sulphides occurred in a number of stages from the introduction of fresh pulses of fluid the quartz overgrowths have a fibrous texture which facilitated trapping of large elongate fluid inclusions between the quartz fibres which grew perpendicular to the crystal faces of the pre existing quartz episodic periods of intense trapping of fluid inclusions occurred throughout the growth of quartz trapped within primary fluid inclusions are numerous particles of gold the largest observed is c 1 m but most are smaller bse element mapping shows these to contain au ag cu hg la icp ms profiles of the fluid inclusions confirm au and ag is not present in solution being present as numerous particles we have quantified the concentration of gold in fluid inclusions which are orders of magnitude greater than has been previously measured or thought likely in crustal fluids the average ag concentration is c 32 ppm and au is c 41 ppm but the maximum concentrations of both may reach several 100 s to 1000 ppm calcite forms a coating on the inner surface of the inclusions and barite pyrite galena sphalerite and unidentified minerals are also present with the au ag particles it is clear that the au ag particles could not have precipitated in the fluid inclusions therefore they must have precipitated elsewhere and been carried with the hydrothermal fluid the high concentrations and their colloidal nature have implications for the enrichment of gold in mineral deposits

an eocene age for the proposed silverpit impact crater three dimensional seismic analysis is used to describe the detailed morphology of the silverpit crater a proposed marine impact crater located in the southern north sea uk we examine and constrain for the first time the geometry extent and age of the post crater sediment units that define the crater fill a circular bowl shaped depression has been mapped and interpreted to represent the upper limit of impact deformation and the geometry of the crater at the end of cratering processes reflections exhibit a parallel onlap fill onto the bowl shaped crater floor indicating that accommodation space was created instantaneously without any contemporaneous sedimentation using regional lithostratigraphic markers constrained by microfossil and calcareous nannofossil analysis we have dated the first onlapping sediments onto the crater the age of the onlapping sediments allows us to constrain the crater formation to be middle eocene in age this date is c 10 15 ma younger than the previous ascribed age for the crater formation and rules out the silverpit crater as a k t boundary impact the age of crater formation considerably predates regional folding and accompanying salt flowage effectively ruling out a salt withdrawal origin for the silverpit crater

two event lode ore deposition at butte usa 40ar 39ar and u pb documentation of ag au polymetallic lodes overprinted by younger stockwork cu mo ores and penecontemporaneous cu lodes abstract the ore genesis model for world class deposits of the butte mining district montana usa is deep pre main stage porphyry cu mo and overlying main stage ag zn cu zoned lode deposits both of which formed from hydrothermal fluids driven by minor volumes of rhyolitic magma the lode specific model is that hydrothermal processes diminished in intensity outward from district center along lode veins synchronously forming metal zones the accepted models are controverted by new geologic and multi method geochronologic studies the new data reveal the following sequence of events 1 thermal study of country rock indicates that the 76 9 ma butte granite cooled to 350 400 c by 4 m y after emplacement 2 five quartz porphyry rhyolite dikes were emplaced at 67 65 ma and another at 60 ma shrimp u pb into the cooled butte granite without resetting 40ar 39ar ages in country rock 3 fifty eight white mica and k feldspar samples from alteration envelopes adjacent to ag au polymetallic lodes in outer parts of the district zn rich lodes in intermediate parts and cu rich lodes in the district center yield 40ar 39ar ages of 73 70 ma for ag rich lodes 65 64 ma for cu rich lodes and complex age spectra of 69 65 ma for zn rich lodes the data show that ag au polymetallic lodes occupied cross district fractures by about 73 ma forming the greater butte mining district at 67 65 ma minor quartz porphyry dikes were emplaced into central and eastern parts of the rejuvenated fracture system but without evidence of related cupola or volcanic rocks or of thermal disturbance in the country rock at 64 5 ma overlapping hydrothermal cells formed two stockwork cu mo domes in deep parts of the fracture system at 65 64 ma and closely related to late stage stockwork cu mo activity a penecontemporaneous hydrothermal pulse formed a high sulfidation hydrothermal plume that 1 utilized the large re opened fractures to cannibalize and remobilize cu from autologous stockwork and older ag au polymetallic lodes 2 deposited the rich high sulfidation cu lodes and 3 mobilized metals from early ag au polymetallic veins in middle parts of the district transported the metals outward and redeposited them enriching early veins especially in the intermediate zn plus cu areas metals zones in lodes of the butte district are the result of an intensely focused cu rich hydrothermal plume that variably reworked the center of significantly larger 10 m y older ag au polymetallic lodes

identification of fluid inclusions in relation to their host microstructural domains in quartz by cathodoluminescence abstract the geometry of fluid trapping in relation to microfracture healing or filling was investigated using massive quartz vein samples characterized by multistage deformation and fluid trapping the multidisciplinary approach used in this study includes 1 mapping of oriented thin sections of quartz using the cathodoluminescence cl mode of a scanning electron microscope sem sem cl images display areas of different intensities from dark to white which correspond to the intensity of the cl and are caused by trace elements present in the quartz microfracture healing by newly formed quartz crystallization may occur under physical chemical conditions different from those which characterized the early quartz matrix formation thus evidences of linear cathodoluminescent markers have been searched and identified by paralleling sem cl images and transmitted light microphotographs data show that cathodoluminescence makes clearly visible the healed crack networks which are only detected in part by transmitted light microscopy the technique is essential to establish the microcrack chronology and to estimate the width affected by healing along a fluid inclusion trail such data are useful for the estimation of the microfracture permeability changes throughout the history of fluid migration 2 systematic and statistical analysis of the microstructural markers in horizontal and oriented planes using an interactive videographic analyzer which gives the geometry of the paleofluid pathways orientation dip and width of the veinlets fluid inclusion trails and cathodoluminescent microdomains 3 microthermometric and raman analyses of fluid inclusions in selected fluid inclusions for the determination of the p v t x conditions of fluid migration in a specific microcrack network studied quartz samples come from au mineralized quartz veins from the french massif central and some quartz samples from the cassiar mountains in british columbia have been observed for comparison in all samples the quartz matrix exhibits intense microfracturing suggesting strong brittle deformation which postdates the main stage of quartz lens formation the quartz veins are characterized by multistage quartz crystallization healed microfractures clear quartz bands as well as quartz comb veinlets were studied as functions of the physicochemical conditions in relation to stages of deformation and ore deposition this study shows that systematic measurements of microstructural marker orientations together with detailed fluid inclusion and mineral petrography and microthermometry may lead to a precise determination of ore fluid pathways and chronology

pressure fluctuations phase separation and gold precipitation during seismic fracture propagation gold mineralization at croagh patrick western ireland occurs in quartz veins associated with three synchronous oblique tensile shear systems the veins evolved by progressive thickening of isolated en echelon lensoid tensile fractures that show a power law relation between their length and thickness a change in power law exponent marks the linking of the en echelon arrays by large oblique tensile veins fluid inclusion data show that gold was deposited due to unmixing of an h 2 o co 2 nacl fluid at 320 240 c and 160 30 mpa primarily due to decreases in fluid pressure evidence for phase separation is only observed in the large linking veins and is abundant close to intersections of the vein arrays these sites are where high gold grades occur the distribution of gold is believed to reflect both spatial and temporal variations in fluid pressure fluctuation during seismic fracture propagation controlled by the vein growth mechanism and zones of maximum dilation

hydrothermal evolution of the el teniente deposit chile porphyry cu mo ore deposition from low salinity magmatic fluids the magmatic hydrothermal evolution of the el teniente porphyry cu mo deposit in the central andes in chile is reconstructed based on field relationships scanning electron microscopy cathodoluminescence petrography and fluid inclusion analysis by microthermometry and laser ablation inductively coupled plasma mass spectrometry la icpms three major stages of cu mo mineralization are observed following the barren hydrothermal stage 1 the stage 2 mineralization is characterized by quartz anhydrite stockwork veins and breccias with chalcopyrite bornite and molybdenite both stages 1 and 2 are associated with pervasive potassic alteration quartz anhydrite veins with chalcopyrite bornite and molybdenite associated with phyllic alteration represent stage 3 mineralization stage 4 mineralization linked to the formation of the large braden diatreme is characterized by breccias and rare veins containing a lower temperature assemblage with tourmaline sericite and lesser tennantite bornite and chalcopyrite with late gypsum in local vugs ten fluid types are distinguished in this study based on petrographic and microthermometric criteria such as phase proportions daughter minerals homogenization behavior and salinity the hydrothermal evolution across the stages of cu deposition is characterized by the contraction of a vapor phase originating by phase separation during stage 2 overall cooling of the system at pressures fluctuating around the two phase fluid surface led to a transition from a two phase fluid state dominated by vapor at 410 c and 300 bars in stage 2 to a single phase low salinity fluid derived from cooling and contraction of magmatic vapor to a liquid which dominates during stage 3 mineralization at 350 c and 200 bars copper mineralization mainly formed from the vapor phase and its low salinity liquid derivatives representing a large volume of fluid with an initially high cu content 1 2 0 4 wt cu copper sulfides precipitated upon cooling between 410 and 320 c indicated by a drop of cu na k mn fe ratios of over four orders of magnitude through the evolution of the deposit from stage 2 to stage 4 the highest mo concentrations occur in residual brines resulting from extreme boiling as indicated by concurrent halite saturation recent geochronology cannell 2005 maksaev et al 2004 suggests a relatively long lived magmatic hydrothermal system at el teniente our fluid chemical data show no evidence for major crystal fractionation in a large fluid generating upper crustal magma chamber because cs na k mn fe is constant from pre ore to all syn ore fluids however the initiation of copper mineralization was associated with a 4 to 10 fold increase in the concentration of cu mo li and fe in the inferred main ore forming input fluid compared with pre ore fluids of intermediate salinity and otherwise very similar major and trace element ratios these data indicate that injection from depth of an exceptionally cu mo li and probably also s rich volatile phase into an already actively evolving upper crustal magmatic hydrothermal system triggered the formation of this unusually large and rich copper deposit

trace elements in hydrothermal quartz relationships to cathodoluminescent textures and insights into vein formation high resolution electron microprobe maps show the distribution of ti al ca k and fe among quartz growth zones revealed by scanning electron microscope cathodoluminescence sem cl from 12 hydrothermal ore deposits formed between 100 and 750 c the maps clearly show the relationships between trace elements and cl intensity in quartz among all samples no single trace element consistently correlates with variations in cl intensity however in vein quartz from five porphyry cu mo au deposits cl intensity always correlates positively with ti concentrations suggesting that ti is a cl activator in quartz formed at 400 c ti concentrations in most rutile bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of 750 c using the titaniq geothermometer titanium concentrations of 10 ppm in all veins that formed at temperatures 350 c suggest a broad correlation between ti concentrations and temperature of quartz precipitation in quartz from most deposits formed at 2000 ppm but in high temperature quartz al concentrations are consistently in the range of several hundred ppm aluminum concentrations in quartz reflect the al solubility in hydrothermal fluids which is strongly dependent on ph aluminum concentrations in quartz therefore reflect fluctuations in ph that may drive metal sulfide precipitation in hydrothermal systems

geology and ore genesis of the late paleozoic heijianshan fe oxide cu au deposit in the eastern tianshan nw china abstract the heijianshan fe cu au deposit located in the aqishan yamansu belt of the eastern tianshan nw china is hosted in the mafic intermediate volcanic and mafic felsic volcaniclastic rocks of the upper carboniferous matoutan formation based on the pervasive alteration mineral assemblages and crosscutting relationships of veins six magmatic hydrothermal stages have been established including epidote alteration stage i magnetite mineralization stage ii pyrite alteration stage iii cu au mineralization stage iv late veins stage v and supergene alteration stage vi the stage i epidote calcite tourmaline sericite alteration assemblage indicates a pre mineralization ca mg alteration event stage ii fe and stage iv cu au mineralization stages at heijianshan can be clearly distinguished from alteration mineral assemblages and nature and sources of ore forming fluids homogenization temperatures of primary fluid inclusions in quartz and calcite from stage i 189 370 c ii 301 536 c iii 119 262 c and v 46 198 c suggest that fluid incursion and mixing probably occurred during stage i to ii and stage v respectively the stage ii magmatic hydrothermal derived fe mineralization fluids were characterized by high temperature 300 c medium high salinity 21 2 56 0 wt nacl equiv and being na ca mg fe dominated these fluids were overprinted by the external low temperature in situ sulfur isotopes also indicate that the sulfur sources vary in different stages viz stage ii magmatic hydrothermal iii basinal brine related and iv magmatic hydrothermal stage ii disseminated pyrite has 34 s fluid values of 1 7 4 3 comparable with sulfur from magmatic reservoirs 34 s fluid values 24 3 29 3 of stage iii type a pyrite coexists with hematite probably indicate external basinal brine involvement consistent with the analytical results of fluid inclusions with the basinal brines further interacting with volcanic volcaniclastic rocks of the carboniferous matoutan formation stage iii type b pyrite chalcopyrite pyrrhotite assemblage with low 34 s fluid values of 4 6 10 0 may have formed at low f o 2 and temperature 119 262 c the continuous basinal brine volcanic volcaniclastic rock interactions during the basin inversion 325 300 ma may have leached sulfur and copper from the rocks yielding magmatic like 34 s fluid values 1 5 4 1 such fluids may have altered pyrite and precipitated chalcopyrite with minor au in stage iv eventually the stage v low temperature 160 c and low salinity meteoric water may have percolated into the ore forming fluid system and formed late hydrothermal veins the similar alteration and mineralization paragenetic sequences ore forming fluid sources and evolution and tectonic settings of the heijianshan deposit to the mesozoic central andean iocg deposits indicate that the former is probably the first identified paleozoic iocg like deposit in the central asian orogenic belt

structural and sedimentary characteristics of the liangjia wangchang strike slip region yitong basin china abstract the yitong basin a typical strike slip basin is part of the northern segment of the world famous tanlu strike slip fault area in china research is needed to understand how the strike slip tectonic environment affects the development of structures and depositional systems within the basin the aim of this paper is to analyze how the right lateral strike slip movement of the northwestern boundary faults in this region controls extensional faulting and to analyze differences in two main sedimentary sequences termed sysq1 and sysq2 that result from strike slip movement the study is based on geological and geophysical data the following conclusions are drawn 1 the two periods of strike slip movement of the boundary fault generated two episodes of extensional fault inside the basin the extensional faults have a characteristically episodic activity related to the episodic strike slip movement the extensional faults have small fault throw and their activity lags behind the strike slip movement of the northwestern boundary faults 2 the strike slip movement of the boundary faults generated the extensional faults inside the basin and changed the locus of depocenters with complimentary changes in the paleogeomorphology and in the distribution of depositional facies it is this strike slip movement that caused the differences in sedimentary and structural characteristics between sequences sysq1 and sysq2

incursion of meteoric water triggers molybdenite precipitation in porphyry mo deposits a case study of the chalukou giant mo deposit there has been a long term debate about the timing of the incursion of meteoric water into porphyry systems and whether it plays an important role in ore precipitation to evaluate the role of meteoric water in the mineralization in porphyry mo deposits typical hydrothermal veins of different stages from the chalukou giant porphyry mo deposit are selected for combined scanning electron microscope cathodoluminescence sem cl fluid inclusion microthermometry and high resolution secondary ion mass spectroscopy sims oxygen isotope analyses multiple generations of quartz are identified in almost all of the veins the barren quartz veins and quartz magnetite veins of the early mo mineralization stage are dominated by granular cl bright quartz emq1 which usually shows dissolution and re deposition textures and are overprinted by cl dark quartz emq2 filled healed fractures the molybdenite precipitation in the quartz molybdenite veins of the main mo mineralization stage is synchronous with small volumes 85 of cl bright quartz mmq1 similar to the quartz molybdenite veins the precipitation of pyrite in the quartz pyrite veins during the transitional stage and sphalerite in the quartz sphalerite pyrite veins during the zn pb mineralization stage are also directly associated with cl dark quartz tsq2 zpq2 the sims oxygen isotopic values of emq1 and mmq1 fall into the range of 5 42 9 79 o with calculated equilibrium fluid compositions of 2 07 6 45 0 indicating a magma dominated fluid composition whereas mmq2 tsq2 and zpq2 have very low oxygen isotopic values from 4 68 to 4 29 parts per thousand with corresponding fluid compositions of 13 64 to 5 94 parts per thousand implying that the fluid formed by the mixing of magmatic water and a large proportion of meteoric water the contrasting sem cl features and oxygen isotopic compositions of the two generations of quartz in the quartz molybdenite veins demonstrate that the incursion of meteoric water into the hydrothermal system occurred earlier than the molybdenite precipitation based on these results and the crosscutting relationships and spatial distribution of the veins we reconstructed the quartz evolutionary sequence during the vein development process after the early precipitation of barren quartz the reduction in fluid pressure from lithostatic to hydrostatic conditions allowed the incursion of convecting cool meteoric water into the relatively hot hydrothermal system and the temperature of the evolved mo rich fluid decreased rapidly from 500 degrees c to 400 degrees c leading to concentrated molybdenite precipitation with small volumes of quartz fluid cooling resulting from the incursion of meteoric water may have played a greater role in the metal precipitation in the chalukou mo deposit than wallrock interactions and fluid boiling moreover this process may have also occurred in other porphyry mo deposits

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

cathodoluminescence properties of quartz eyes from porphyry type deposits implications for the origin of quartz hyperspectral cathodoluminescence cl mapping combined with electron probe microanalysis epma and fourier transform infrared spectroscopy was used for the reconstruction ofcrystallization conditions of quartz from porphyry environments quartz eyes from the two porphyry deposits rio blanco chile and climax u s a were studied three peaks are found to be responsible for the total cl emission 1 93 2 05 and 2 72 ev the first two peaks are assigned to o m with m being an alkali ion and oxygen vacancies respectively the 2 72 ev peak shows a linear correlation with the ti concentration determined by epma point measurements in addition a negative correlation between the 1 93 ev emission and the al concentration was observed quartz grains often form clusters in which adjacent grains show identical cl patterns indicating that they crystallized attached to each other and were not disturbed later quartz cores display sector zoning and enrichment in li oh and sometimes al which points to rapid crystallization from an extremely evolved melt quartz rims show high ti and low li and oh contents indicating crystallization from a less evolved melt either at higher temperatures or at higher titanium activities the al and ti distribution patterns are frequently not correlated and both show uneven distribution indicating fast growth from inhomogeneous melts only ti displays sharp transitions and fine oscillatory zoning which can be explained by the higher mobility of al in the quartz lattice the quartz eyes crystallized after magma emplacement under non equilibrium conditions it is likely that the crystallization occurred from the melt enriched in al li and oh and probably other metals and or volatiles on the brink of fluid exsolution subsequent fluid exsolution brought about disequilibrium to the system resulting in dissolution of quartz and redistribution of elements between the melt and the fluid the oh li and other alkali metals and volatiles partitioned into the fluid whereas ti and al remained in the melt resorption of quartz caused by the fluid exsolution continued until equilibrium was reached again after which crystallization of quartz rims began from the water alkali and volatile poor melt with higher ti activity furthermore accumulation of al and ti in the residual melt led to crystallization of extremely al and ti rich quartz

cl br ratios and stable chlorine isotope analysis of magmatic hydrothermal fluid inclusions from butte montana and bingham canyon utah a bulk geochemical study has been carried out on fluid inclusion leachates extracted from quartz veins from porphyry cu deposits in butte montana usa and bingham canyon utah usa the leachates mostly represent low salinity magmatic hydrothermal fluid inclusions their halogen ratios br cl of fluid inclusion leachates were determined by ion chromatography and 37cl values of the leachates were measured by continuous flow isotope ratio mass spectrometry br cl ratios from early pre main stage and later main stage veins at butte range from 0 60 to 1 88 10 3 m ratios are similar in pre main stage veins with sericite bearing selvages and main stage samples ranging from 0 81 to 1 08 10 3 and from 0 92 to 1 88 10 3 m respectively clustering below seawater 1 54 10 3 m and overlapping mantle values 1 2 10 3 m two samples associated with early pre main stage potassic alteration yield distinctly lower br cl ratios of 0 60 and 0 64 10 3 m butte 37cl values range from 0 8 to 2 3 with no significant difference between pre main stage and main stage samples br cl ratios for quartz veins from bingham canyon range from 0 18 to 3 68 10 3 m br cl ratios from bingham range above and below previously reported for porphyry copper deposits in contrast to butte 37cl values for bingham are lower ranging from 0 9 to 4 1 in the absence of any processes which can significantly fractionate chlorine isotopes at high temperatures we suggest that the porphyry system at bingham and to a lesser extent at butte have inherited negative chlorine isotopic signatures from the subducting slab generated at low temperatures

lithological and structural controls on the genesis of the candelaria punta del cobre iron oxide copper gold district northern chile abstract the candelaria punta del cobre district is the largest iron oxide cu and au iocg district in the chilean iocg belt with more than 13 mt of contained copper candelaria is the most important deposit in the district which includes seven other smaller producers carola punta del cobre mantos de cobre candelaria norte granate alcaparrosa atacama kozan las pintadas the district which is characterized by an early cretaceous volcanic sedimentary arc sequence 135 132 ma punta del cobre formation overlain by the marine sedimentary chanarcillo group formed in an extensional back arc basin 132 130 ma the copiapo batholith which occupies the western side of the district was emplaced between 118 and 110 ma during the change from extensional to transpressional tectonics mineralization is hosted predominately in the upper part of the lower andesite member and the overlying volcano sedimentary and dacite members all within the punta del cobre formation mineralization is hosted by fault zones breccias and specific lithologies north northwest faults are the dominant host for vertically extensive orebodies stratigraphically controlled mineralization forms extensive stratabound ore bodies mantos textural evidence suggest that the hydrothermal system evolved and advanced upwards over time the earliest event was dominated by magnetite actinolite in stratigraphically controlled mantos and extensive zones of disseminated magnetite actinolite below candelaria which were subsequently overprinted by chalcopyrite dominant mineralization with magnetite actinolite biotite k feldspar alteration in addition to magnetite iron oxides include widespread mushketovite and hematite in the upper part of some deposits geochronological data suggest that the main phase of mineralization occurred between 122 ma and 115 ma u pb in zircon overlapping in age with the two major early phases of the copiapo batholith there is no field evidence to indicate that exposed phases of the batholith were the source of mineralizing fluids alteration and mineralization in the earliest phase of the batholith la brea occurs in structures and is minor compared to mineralization in the punta del cobre formation later phases of the batholith cut the main stage of mineralization the extent of iocg mineralization in the candelaria punta del cobre district reflects a combination of factors including changing regional kinematics and related fault architecture multiple intrusive events fluid access to permeable and reactive lithologies vertical changes in redox conditions and the potential role of multiple fluids

genesis of gold and antimony deposits in the youjiang metallogenic province sw china evidence from in situ oxygen isotopic and trace element compositions of quartz abstract abundant carlin type gold deposits and vein type antimony deposits were discovered in the youjiang basin of sw china constituting the youjiang metallogenic province ymp although they had been widely studied by geologists the genesis of these deposits remains debatable while both intrusion linked and non intrusion linked models have been proposed in this paper new data of in situ trace elements la icp ms and oxygen isotope sims analysis of hydrothermal quartz from the yata carlin type gold deposit and the qinglong vein type antimony deposit in the province were provided to better understand the origin of ore forming fluids as well as the genetic mechanism of au and sb mineralization four quartz generations were identified from the yata yti to ytiv and the qinglong qli to qliv deposits in the yata deposit the fluid inclusions in quartz have varied homogenization temperatures from 140 260 and salinities of 2 4 7 4 wt nacleq while in the qinglong deposit the temperatures and salinities ranged from 140 200 and 0 2 7 2 wt nacleq respectively both of the temperatures and salinities tend to decrease from early to late generations in the two deposits 18o values of initial fluids in the yata yti 7 70 10 56 and the qinglong qli 4 66 8 75 deposits are similar and suggest that they were mainly from magmatic or metamorphic fluids the covariability of oxygen isotope and al concentrations indicate that interaction between fluids and wall rocks is a significant factor in determining the compositions of fluids in au mineralization and the meteoric water is a key proxy in sb mineralization respectively from these observations we proposed that the carlin type au deposit and vein type sb deposit in ymp were sourced from an analogous ore fluid different lithologies of wall rocks and the dilution of meteoric water controlled the compositional evolution of fluids which might be the main reason for the diversity of au and sb mineralization

combined zircon molybdenite and cassiterite geochronology and cassiterite geochemistry of the kuntabin tin tungsten deposit in myanmar

trace elements and cathodoluminescence of quartz in stockwork veins of mongolian porphyry style deposits the combination of scanning electron microscope cathodoluminescence cl fluid inclusion analysis and high resolution electron probe microanalysis of al ti k and fe in vein quartz has yielded results permitting a greater understanding of the complex mineralisation of the central oyu tolgoi and zesen uul porphyry style deposits southern mongolia these data demonstrate the relationship between quartz precipitation dissolution and ore deposition as the mineralising fluid chemistry changed through time four major quartz generations are identified in the a type veins from the stockworks of both the central oyu tolgoi oti to otiv and zesen uul deposits zui to zuiv despite differences in the associated alteration and mineralisation style the observed cl textures and trace element signatures of the quartz generations are comparable between deposits the oti and zui stage formed both the primary network of a type veins and pervasive silicification of the host rock using the ti in quartz geothermometer crystallisation temperatures for oti and zui of between 598 c and 880 c are indicated the main stage of sulphide mineralisation was accompanied by the dissolution of pre existing quartz oti and zui and precipitation of a weakly luminescent generation of quartz otii and zuii with a low ti content reflected in a calculated temperature drop from approximately 700 c to 340 c in central oyu tolgoi and 445 c in zesen uul otii and zuii stage quartzes show high and variable al concentrations the next stage of quartz in both deposits otiii and zuiii forms a fine network of veins in cracks formed in pre existing quartz otiii and zuiii quartz contain measurable fluid inclusions of moderate salinity 3 17 1 wt nacl eq entrapped in the temperature range 256 c to 385 c otiii and zuiii are not related to any sulphide mineralisation the final otiv and zuiv stages are characterised by quartz calcite micro breccias that penetrate the a type veins based on the calculated entrapment temperatures the otiv zuiv stage crystallised between 212 c and 335 c and the quartz is characterised by elevated but variable al and fe contents the cl and trace element signatures of the oti to otiii and zui to zuiii stages of the two mongolian porphyries show similar features to those observed in porphyry style deposits from other regions this suggests that a common sequence of quartz crystallisation occurs during the formation of early veins in many porphyry copper systems

morphological ripening of fluid inclusions and coupled zone refining in quartz crystals revealed by cathodoluminescence imaging implications for cl petrography fluid inclusion analysis and trace element geothermometry cathodoluminescence cl studies have previously shown that some secondary fluid inclusions in luminescent quartz are surrounded by dark non luminescent patches resulting from fracture sealing by late trace element poor quartz this finding has led to the tacit generalization that all dark cl patches indicate influx of low temperature late stage fluids in this study we have examined natural and synthetic hydrothermal quartz crystals using cl imaging supplemented by in situ elemental analysis the results lead us to propose that all natural liquid water bearing inclusions in quartz whether trapped on former crystal growth surfaces i e of primary origin or in healed fractures i e of pseudosecondary or secondary origin are surrounded by three dimensional non luminescent patches cross cutting relations show that the patches form after entrapment of the fluid inclusions and therefore they are not diagnostic of the timing of fluid entrapment instead the dark patches reveal the mechanism by which fluid inclusions spontaneously approach morphological equilibrium and purify their host quartz over geological time fluid inclusions that contain solvent water perpetually dissolve and reprecipitate their walls gradually adopting low energy euhedral and equant shapes defects in the host quartz constitute solubility gradients that drive physical migration of the inclusions over distances of tens of m commonly up to several mm rarely inclusions thus sequester from their walls any trace elements e g li al na ti present in excess of equilibrium concentrations thereby chemically purifying their host crystals in a process analogous to industrial zone refining non luminescent patches of quartz are left in their wake fluid inclusions that contain no liquid water as solvent e g inclusions of low density h2o vapor or other non aqueous volatiles do not undergo this process and therefore do not migrate do not modify their shapes with time and are not associated with dark cl zone refined patches this new understanding has implications for the interpretation of solids within fluid inclusions e g ti and al minerals and for the elemental analysis of hydrothermal and metamorphic quartz and its fluid inclusions by microbeam methods such as la icpms and sims as ti is a common trace element in quartz its sequestration by fluid inclusions and its depletion in zone refined patches impacts on applications of the ti in quartz geothermometer

fluid inclusion study of the wunugetu cu mo deposit inner mongolia china hydrothermal alteration and mineralization at the wunugetu porphyry cu mo deposit china include four stages i e the early stage characterized by quartz k feldspar and minor mineralization followed by a molybdenum mineralization stage associated with potassic alteration copper mineralization associated with sericitization and the last pb zn mineralization stage associated with carbonation hydrothermal quartz contains three types of fluid inclusions namely aqueous w type daughter mineral bearing s type and co2 rich c type inclusion with the latter two types absent in the late stage fluid inclusions in the early stage display homogenization temperatures above 510 c with salinities up to 75 8 wt nacl equivalent the presence of s type inclusions containing anhydrite and hematite daughter minerals and c type inclusions indicates an oxidizing co2 bearing environment fluid inclusions in the mo and cu mineralization stages yield homogenization temperatures of 342 508 c and 241 336 c and salinities of 8 6 49 4 and 6 3 35 7 wt nacl equivalent respectively the presence of chalcopyrite instead of hematite and anhydrite daughter minerals in s type inclusions indicates a decreasing of oxygen fugacity in the late stage fluid inclusions yield homogenization temperatures of 115 234 c and salinities lower than 12 4 wt nacl equivalent it is concluded that the early stage fluids were co2 bearing magmatic in origin and characterized by high temperature high salinity and high oxygen fugacity phase separation occurred during the mo and cu mineralization stages resulting in co2 release oxygen fugacity decrease and rapid precipitation of sulfides the late stage fluids were meteoric in origin and characterized by low temperature low salinity and co2 poor

relationships between sem cathodoluminescence response and trace element composition of hydrothermal vein quartz laser ablation icp ms data of hydrothermal vein quartz with zonation in scanning electron microscope cathodoluminescence reveal two groups of trace elements one that co varies in concentration with luminosity and another that remains uniform throughout bright luminosity correlates with a high total abundance of trace elements in early quartz including al up to 410 g g ti up to 240 g g k up to 330 g g li up to 8 g g na up to 36 g g and fe up to 20 g g up to 20 times lower concentrations of these elements are associated with dark luminosity in late quartz concentrations of p 21 g g ga 0 3 g g ge 1 3 g g sn 1 5 g g cu 0 3 g g and ag 0 1 g g demonstrate no relationship with luminosity charge balance cannot be achieved for bright luminescent quartz unless the presence of up to 6 g g h not analyzed by la icpms or interstitial al3 is invoked interestingly the inferred 6 g g h remains constant for quartz containing more than 10 mol total trace elements and might represent the solubility of h in hydrothermal quartz at temperatures between 450 and 700 c la icpms results indicate that the fluid chemistry determines the quartz trace element pattern which may serve as a monitor for the chemical environment from which quartz crystallized ratios of na al and ti al are uniform whereas k al evolves toward lower values with decreasing luminosity combined evidence including quartz vein textures silica solubility data and estimates of the temperature of quartz growth suggest that early quartz crystallized fast but late quartz grew more slowly at 350 to 425 c it is speculated that the higher the quartz growth rate is the more trace elements are incorporated into quartz besides the temperature dependence known from the literature clearly growth rate temperature and fluid chemistry are important parameters affecting luminosity however their relative importance may vary from case to case

sandbox models of relay ramp structure and evolution relay ramps are a common feature formed during the growth of normal fault systems we performed analogue experiments to investigate the structure and evolution of relay ramps an extending rubber sheet induces extension at the base of a sand pack brittle crust analogue silicone bars between the rubber and the sand control the location of fault nucleation we tested the role of fault spacing fault length overlap length and fault strike in the evolution of relay ramps the modelled relay ramps evolved in three stages characterized by the growth of the normal faults their interaction and linkage interaction and linkage occurred only when the combined length of the two interacting faults was larger than eight times their spacing the length to width ratio of the relay ramps during the interaction stage showed preferred geometries clustering around three the propagation of the fault tips was observed both before and after the linkage stage overlap length and spacing relations of the modelled relay ramps are similar to those in nature at different scales and can be explained using existing mechanical models nevertheless the further propagation of the fault tips after linkage has not been described previously

a comparison of jiaojia and linglong type gold deposit ore forming fluids do they differ abstract the jiaodong peninsula contains the most important concentration of gold deposits in china which can be divided into jiaojia type and linglong type deposits based on mineralization style the former is characterized by disseminated and stockwork style mineralization hosted in first order regional faults with relatively larger tonnages and lower gold grades the latter is characterized by massive auriferous quartz veins commonly hosted in subsidiary second or third order faults with smaller tonnage but higher grade orebodies despite these differences both groups of deposits have the same alteration assemblages mineral paragenesis element concentrations and ore forming ages the mainly jiaojia type luoshan gold deposit and the mainly linglong type fushan gold deposit are characterized by h o s pb isotope data that indicate the ore forming fluids have a dominantly metamorphic source the fluids were derived during the yanshanian orogenic event and were most likely associated with dehydration and decarbonization processes near the top of the subducting paleo pacific plate the linglong type ores have relatively lighter calculated 18 o compositions 3 9 to 2 3 than the jiaojia type ores 0 3 8 0 possibly because of a greater degree of mixing with meteoric water petrographic cathodoluminescence microthermometric and laser raman spectroscopic analyses of fluid inclusion assemblages in quartz from the two types of ores indicate fluids were similar in both cases characterized by medium high homogenization temperatures 211 393 c significant co 2 15 mol minor ch 4 18 in the carbonic phase and low salinity 11 2 wt nacl eq the linglong type ores however have a wider range of co 2 and ch 4 concentration and salinity than the jiaojia type ores fluid immiscibility occurred in main ore stage of both ore types with the trapping conditions of 77 185 mpa and 284 328 c although the unmixing is more intense and widespread in the linglong type ores both fluid wallrock interaction and fluid immiscibility are important gold deposition processes in the two types but immiscibility is more important in the linglong type ores and that has led to the typical higher gold grade in general there is little geochemical differences between the ore forming fluids for jiaojia and linglong type gold deposits both jiaojia and linglong type ores can exist in a single deposit and form in the same metallogenic event the linglong type ores developed as more massive veins because of their location in zones of more extensive extension and they lack significant post ore cataclastic deformation

illumination of vein quartz textures in a porphyry copper ore deposit using scanned cathodoluminescence grasberg igneous complex irian jaya indonesia vein quartz from the grasberg igneous complex in irian jaya indonesia displays a wide range of features when observed using scanned cathodoluminescence imaging on the electron microscope examination of seventeen samples revealed concentric growth zoning quartz filled microfractures dark luminescence near sulfides changes in crystal size and orientation from vein edges to vein centers turbid growth zoning and the truncation of concentric growth zoning individual features observed along two large photomosaic traverses from vein margins to vein centers coupled with trace element analyses from the electron microprobe allow determination of a detailed history of fracture infilling the two traverses indicate a simple two stage history of crystal growth into an open fracture followed by mechanical closing of the fracture with resulting microfractures electron microprobe trace element analyses show that the fe content of quartz reaches values of up to 4900 ppm in dark luminescent regions near sulfide crystals and decreases smoothly to 200 ppm along traverses away from the sulfides the solution to the diffusion equation coupled with existing experimental data about fe diffusion in sio2 indicate the duration of the diffusion was perhaps on the order of thousands of years

porphyry cu mo stockwork formation by dynamic transient hydrothermal pulses mineralogic insights from the deposit at butte montana the systematic distribution of vein and alteration mineral assemblages in porphyry cu deposits largely arises from changes in the temperature and pressure of fluids that traversed fractures throughout the hydrothermal system magmatic and hydrothermal minerals record the complex history of the fluctuating temperature and pressure regime as hydrothermal fluids transfer heat from their magmatic source to cold wall rock in response to lithostatic to hydrostatic pressure variations we examine the thermal profile of the porphyry cu mo deposit in butte montana by determining formation temperatures for magmatic and hydrothermal samples representing different time frames and depths within the deposit in context with sample pressure estimates we use three independent mineral thermobarometers ti in quartz zr in rutile and x mg ti in biotite from which we estimate that final dike injection temperature and hence the initial magmatic hydrothermal fluid temperature was 700 c while the ambient host rock temperature was 450 to 500 c we find a magmatic hydrothermal continuum represented in hydrothermal veins ranging from 710 to

structural geologic evolution of the butte district montana the butte district contains two porphyry cu mo deposits and the younger zoned main stage base metal lode deposits that formed in the period from 66 to 62 ma synchronous with laramide compressional thrust faulting and folding in southwest montana new geologic mapping of the butte district reveals three distinct episodes of deformation 1 gentle 20 10 ne tilting produced during laramide compressional deformation uplift and exhumation during and after ore formation in the late cretaceous to paleocene 66 53 ma 2 moderate 10 50 nw tilting of eocene age produced by ne striking normal faults that are limited to the northwest part of the district and synchronous with the eruption of the lowland creek volcanics and 3 miocene to present gentle 15 ese tilting in the hanging walls of the continental east ridge and rocker normal faults stratigraphic relationships isotopic ages hornblende barometry and fluid inclusion data indicate that exposures of the butte granite which hosts mineralization crystallized at 6 to 9 km depth and that early porphyry cu mo deposits formed at similar depths of 5 to 9 km a period of rapid uplift and erosion removed about 7 km of rock from above the ore deposit between 66 to 64 ma and 53 ma but was mostly completed by 59 ma estimated exhumation rates range from 0 5 to 2 mm yr and uplift was likely most rapid between 63 5 and 62 ma during main stage mineralization which occurred at depths of 2 to 6 km the butte granite and boulder batholith were emplaced at 79 to 76 ma into thrust fault ramps which later became inactive near butte as laramide crustal shortening moved eastward in the helena salient the accelerated period of uplift and unroofing is attributed to renewed deformation along the montana disturbed belt south of butte that uplifted the south end of the boulder batholith and produced 20 of gentle ne tilting episode i in the district the exhumation history of the deposit is therefore broadly contemporaneous with ore formation and is consistent with the general transition from lithostatic to hydrostatic conditions that is evident from the telescoping of early porphyry cu mo ores cut by the main stage lode veins within a 5 m y period the laramide compressional regime near butte evolved into an extensional environment characterized by normal faulting the normal faults were synchronous with eruption of the 53 to 48 ma lowland creek volcanics which directly overlie the main stage veins in the northwest part of the district structural reconstruction of the district at the time of mineralization produces orientations of quartz porphyry dikes porphyry cu mo veinlets main stage veins and alteration zonal patterns that are steeply dipping and symmetrical similar to observations from other upright or restored porphyry copper deposits early porphyry cu mo veins and dikes are oriented e w and likely originated as tensile hydrofractures above a ductile magma carapace during laramide shortening additionally during the laramide compressional phase two conjugate fault systems occupied by main stage veins are normal oblique slip faults that record minor e w and vertical shortening and n s extension these normal faults with minor offset likely resulted from brittle failure caused by doming above a volatile rich and buoyant granitic magma chamber and cupola at depth the structural evolution of the butte district therefore reflects the interaction of a far field compressive stress regime with local buoyant magmatic forces

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