geochemistry and fluid characteristics of the dalli porphyry cu au deposit central iran abstract the miocene dalli porphyry cu au deposit in the central part of urumieh dokhtar magmatic arc is the first reported au rich porphyry cu deposit in the zagros orogenic belt the cu au mineralization is mainly hosted in diorite and quartz diorite intrusions presenting as numerous veinlets in the altered wall rocks with potassic phyllic and propylitic alteration developed based on the mineral assemblages and crosscutting relations of veinlets hydrothermal mineralization alteration occurred in at least three stages characterized by veinlets of 1 qtz kfs mag ccp 2 qtz py ccp bn cv cc and 3 qtz chl bt the ore bearing intrusions exhibit typical geochemical characteristics of subduction zone magmas including lree fractionated pattern strong enrichment in lile cs rb ba pb and u and depletion of hfse with marked negative ti and nb anomalies the adakite like ore hosting porphyry intrusions are characterized by a systematic gradual decreasing and increasing of y and eu eu with increasing sio2 content respectively moreover they exhibit a significant increasing trend of sr y with decreasing of y which indicates progressive hornblende fractionation and suppression of plagioclase fractionation during the evolution toward high water content of parental magma a relatively flat hree pattern with low dyn ybn and nb ta values may represent that amphibole played a more important role than garnet in the generation of the adakitic melts in the thickened lower crust based on the phase assemblages confirmed by detailed laser raman spectroscopy analyses and proportion of solid liquid and gaseous components five types of fluid inclusions were recognized which are categorized as 1 liquid rich two phase liquidh2o vaporh2o iia 2 vapor rich two phase vaporh2o co2 liquidh2o iib 3 high saline simple fluids iiia liquidh2o vaporh2o hl 4 high saline opaque mineral bearing fluids iiib liquidh2o vaporh2o hl hem ccp py and 5 multi phase type iiiab liquidh2o vaporh2o hl anh hem mag ccp in early stage veins the homogenization temperature of multiphase inclusions as high as 620 c with corresponding salinities of up to 75 wt nacl equivalent represent the initial ore forming fluids from early to late stage veins the gradual decrease of homogenization temperature of saline inclusions iiiab iiia and iiib from 620 to 340 c corresponding salinities of 75 35 wt nacl equivalent may reflect fluid boiling and mixing of the early magmatic fluids with circulating groundwater the common association of hematite and anhydrite daughter phases with the most primitive inclusions iiiab in early stage veins and the lack of co2 bearing inclusions in the middle to late stage veins reveal co2 content and oxygen fugacity of the fluids was significantly decreased from early to main stage of sulfide mineralization second generation of veins it seems that magnetite crystallization and co2 escape have a decisive role in oversaturation of s2 and subsequent rapid and large scale precipitation of sulfides in second generation of veins at the dalli deposit

rare earth element signatures of economic and sub economic porphyry copper systems in urumieh dokhtar magmatic arc udma iran abstract a wide variety of porphyry copper deposits have been reported along the cenozoic urumieh dokhtar magmatic arc in iran the formation of these deposits is attributed to closure of neo tethys and the subsequent collisional tectonic regime during the tertiary this study presents whole rock rare earth element ree data for the giant to small sarcheshmeh meiduk sungun darreh zerreshk dalli iju parkam and ali abad with sub economic daraloo and reagan porphyry copper systems the data indicate a temporal and geochemical evolution from sub economic porphyry systems to economic deposits all the economic and sub economic porphyry copper systems exhibit lree enrichment relative to hree whereas the economic deposits exhibit a relatively steep downward lree to hree profile reflecting higher lree abundance the eu anomalies vary from distinct negative in sub economic deposits eu eu 0 28 0 70 to either markedly less negative or positive anomalies eu eu 0 45 1 67 in economic deposit the economic porphyry deposits are characterized by relatively high la sm and sm yb values representing high crustal assimilation in a relatively thickened crust and provide insight into fractionation of hornblende with minor garnet in deep crustal parts mash zone compared with sub economic deposits the steep downward lree to mree and flatter to slightly upward mree to hree in economic deposits indicate hornblende involvement magma evolution toward more volatile content it seems that in an ongoing process of closure of neo tethys during compression and crustal shortening the early eocene oligocene sub economic intrusions are followed by adakite like hydrous miocene and younger economic cu bearing intrusions

characterization of magma from inclusions in zircon apatite and biotite work well feldspar less so detrital zircon grains are employed to decipher sediment provenances and crustal evolution and they provide unique evidence of hadean crust mantle differentiation processes we demonstrate that mineral inclusions in zircon provide valuable information on the conditions under which zircon crystallized zircon grains from selected plutonic rocks from dronning maud land antarctica contain inclusions of apatite biotite amphibole and pyroxenes that accurately reflect the chemical compositions of the equivalent phases in the host rock matrix and the compositions of the whole rocks high concentrations of y and low concentrations of sr in apatite inclusions in zircon are diagnostic of evolved felsic granitoid host rocks in contrast the relative abundances and compositions of plagioclase and alkali feldspar inclusions in zircon are decoupled from the composition of the whole rock and they are generally indicative of granitic melts regardless of the bulk rock this is best explained by the late crystallization of zircon relative to the bulk of the feldspars we conclude that inclusions of apatite and mafic phases in zircon constrain the potential source rocks of detrital zircon whereas feldspar inclusions do not

salt precipitation in magmatic hydrothermal systems associated with upper crustal plutons magmatic hydrothermal systems associated with upper crustal plutons strongly influence volcanic and geothermal processes and form important mineral deposits fluids released from plutons are commonly saline and undergo phase separation into high salinity brines and low salinity vapors upon ascent while brine vapor immiscibility has been extensively studied precipitation of solid salt during phase separation in magmatic hydrothermal systems has generally been considered a rare phenomenon here we show that most porphyry deposits exhibit fluid inclusion evidence best interpreted by solid salt precipitation from ore forming solutions this interpretation naturally links thermodynamics numerical simulations and independent estimates of porphyry ore formation depths salt precipitation imposes major changes on the permeability of the system moreover salt precipitation has implications for ore formation along the liquid vapor halite curve the recognition of salt saturated systems is challenging but very relevant for understanding the evolution of magmatic hydrothermal systems

synthetic fluid inclusions xvii pvtx properties of high salinity h2o nacl solutions 30 wt nacl application to fluid inclusions that homogenize by halite disappearance from porphyry copper and other hydrothermal ore deposits fluid inclusions that homogenize by disappearance of the halite crystal after the vapor bubble has disappeared have been reported from a wide range of ore forming systems while this inclusion type is most commonly observed in porphyry copper and similar magmatichydrothermal ore deposits they have also been reported from iron oxide copper gold iocg mississippi valley type orogenic lode greenstone gold massive sulfide unconformity u and mantotype deposits as well as from non ore associated granitoids and oceanic crust the lack of experimental data to interpret microthermometric data from these inclusions combined with poor petrographic characterization of inclusion origin has led to a wide range of inferred pt trapping conditions for the inclusions the relationship between liquid vapor homogenization temperature thl v halite dissolution temperature tmhalite and pressure has been determined using synthetic h2o nacl fluid inclusions that homogenize by halite disappearance the experimental data cover the range thl v 150 to 500 c and tmhalite 275 to 550 c an empirical equation describing the relationship between pressure thl v and tmhalite has been developed to estimate formation pressures from microthermometric data and is valid from pressures along the liquid vapor halite curve to 300 mpa a detailed literature review reveals that the results of this study cannot be applied retroactively to estimate pressures of previously reported inclusions that homogenize by halite dissolution for several reasons first most workers have not collected and reported the data in a manner that allows one to determine if the inclusions have trapped a single homogeneous phase and have not leaked or changed volume following trapping thus it is not possible to determine if the inclusions show consistent microthermometric behavior within a group of coeval inclusions additionally many published studies provide only summaries of results from numerous samples or present the data graphically precluding application of our results to individual inclusions however based on our review it appears that much of the published data for inclusions that homogenize by halite dissolution represent inclusions that have either trapped a halite crystal along with the liquid or have reequilibrated by necking and or stretching results from this study have been used to estimate minimum formation pressures for inclusions from the ditrau alkaline massif transylvania romania the musoshi stratiform copper deposit zaire the bismark skarn deposit northern mexico the naica chimneymanto deposit mexico the questa porphyry molybdenum deposit new mexico and the bingham canyon porphyry cu mo deposit utah in each case pressures estimated using results from the present study are in good agreement with previous pressure estimates however in some cases estimated pressures both our estimates as well as those of other authors appear to be unreasonably high based on the geologic setting at the time of formation these results highlight the currently limited understanding concerning pressures depths of ore formation

genesis of the fuxing porphyry cu deposit in eastern tianshan china evidence from fluid inclusions and c h o s pb isotope systematics abstract the fuxing porphyry cu deposit is a recently discovered deposit in eastern tianshan xinjiang northwestern china the cu mineralization is associated with the fuxing plagiogranite porphyry and monzogranite mainly presenting as various types of hydrothermal veins or veinlets in alerted wall rocks with potassic chlorite phyllic and propylitic alteration developed the ore forming process can be divided into four stages stage i barren quartz veins stage ii quartz chalcopyrite pyrite veins stage iii quartz polymetallic sulfide veins and stage iv quartz calcite veins four types of fluid inclusions fis can be distinguished in the fuxing deposit including hypersline h type vapor rich two phase v type liquid rich two phase l type and trace amounts of pure vapor inclusions p type but only the stage i quartz contains all types of fis the stages ii and iii quartz have two types of fis with exception of h and p types in stage iv quartz minerals only the l type inclusions can be observed the fis in quartz of stages i ii iii and iv are mainly homogenized at temperatures of 357 518 c 255 393 c 234 322 c and 145 240 c with salinities of 1 9 11 6 wt nacl equiv 1 6 9 6 wt nacl equiv 1 4 7 7 wt nacl equiv and 0 9 3 7 wt nacl equiv respectively the ore forming fluids of the fuxing deposit are characterized by high temperature moderate salinity and relatively oxidized condition carbon hydrogen and oxygen isotopic compositions of quartz indicate that the ore forming fluids were gradually evolved from magmatic to meteoric in origin sulfur and lead isotopes suggest that the ore forming materials were derived from a deep seated magma source the cu mineralization in the fuxing deposit occurred at a depth of 1 km and the changes of oxygen fugacity decompression boiling and local mixing with meteoric water were most likely critical for the formation of the fuxing cu deposit

detection of astronomical cycles in the stratigraphic record by frequency modulation fm analysis abstract frequency modulation fm analysis of a sequence of basinal limestone shale cycles from the upper pliensbachian domaro limestone lombardy pre alps northern italy reveals modulations with multiple low frequencies that closely resemble those of the theoretical equatorial orbitally forced precession dominated insolation there is evidence for a systematic shift in these modulation frequencies that is consistent with a shorter jurassic length of day these results were used to estimate the incremental time scale along the domaro succession revealing a dual frequency signal comparable to the precession separate analysis of the limestones and shales suggests that the limestones were deposited during times of decreasing or low northern spring equatorial insolation nsei and the shales during times of increasing or high nsei we discuss two end member models that could link precession forced insolation to the cyclic basinal sedimentation the ambiguity of the source of carbonate influx into this early jurassic basinal depocenter led us to consider 1 an allodapic mud model in which precession forced sea level oscillations instituted a cyclic production of lime mud in shallow marine environments and subsequent transport into the adjacent basinal environments and alternatively 2 a pelagic ooze model in which precession forced insolation directly forced pelagic productivity and influx into the basin

controls of alteration and mineralization in the sungun porphyry copper deposit iran evidence from fluid inclusions and stable isotopes the sungun porphyry copper deposit is located in northwestern iran azarbaijan province and is associated with diorite granodiorite to quartz monzonite of miocene age which intruded eocene volcano sedimentary and cretaceous carbonate rocks copper mineralization was accompanied by both potassic and phyllic alteration field observations and petrographic studies demonstrate that emplacement of the sungun stock took place in several intrusive pulses each with associated hydrothermal activity molybdenum was concentrated at a very early stage in the evolution of the hydrothermal system and copper somewhat later four main vein groups have been identified i quartz molybdenite anhydrite or k feldspar with minor pyrite chalcopyrite and bornite ii quartz chalcopyrite pyrite or molybdenite iii quartz pyrite calcite or chalcopyrite or anhydrite gypsum or molybdenite and iv quartz or calcite or gypsum or pyrite early hydrothermal alteration produced a potassic assemblage orthoclase biotite in the central part of the stock propylitic alteration occurred contemporaneously with potassic alteration but in the peripheral parts of the stock and phyllic alteration occurred later overprinting the earlier alteration the early hydrothermal fluids are represented by high temperature 340 degrees 500 degrees c high salinity up to 60 wt nacl equiv liquid rich fluid inclusions and high temperature 320 degrees 550 degrees c low salinity vapor rich inclusions these fluids are interpreted to represent an orthomagmatic fluid which boiled episodically the brines are interpreted to have caused potassic alteration and deposition of group i and ii quartz veins containing molybdenite and chalcopyrite propylitic alteration is attributed to a liquid rich lower temperature 240 degrees 330 degrees c ca rich evolved meteoric fluid influx of meteoric water into the central part of the system and mixing with magmatic fluid produced deep albitization transition alteration and shallow phyllic alteration this influx also caused dissolution of early formed copper sulfides and remobilization of cu into the sericitic zone where it was redeposited in response to a boiling induced decrease in temperature supergene alteration was minor and restricted to a thin blanket of cu sulfides below an argillic cap

metal endowment reflected in chemical composition of silicates and sulfides of mineralized porphyry copper systems urumieh dokhtar magmatic arc iran abstract the present work attempts to discriminate between the geochemical features of magmatic hydrothermal systems involved in the early stages of mineralization in high grade versus low grade porphyry copper systems using chemical compositions of silicate and sulfide minerals i e plagioclase biotite pyrite and chalcopyrite the data indicate that magmatic plagioclase in all of the porphyry copper systems studied here has high an and al content with a significant trend of evolution toward alal3sio8 and si4o8 endmembers providing insight into the high melt water contents of the parental magmas comparably excess al and an in the high grade deposits appears to be higher than that of selected low grade deposits representing a direct link between the amounts of exsolving hydrothermal fluids and the potential of metal endowment in porphyry copper deposits pcds also higher al contents accompanied by elevated an are linked to the increasing intensity of disruptive alteration phyllic in feldspars from the high grade deposits as calculated from biotite compositions chloride contents are higher in the exsolving hydrothermal fluids that contributed to the early mineralization stages of highly mineralized porphyry systems however as evidenced by scattered and elevated log fh2o fhf and log fh2o fhcl values chloride contents recorded in biotite could be influenced by post potassic fluids geothermometry of biotite associated with the onset of sulfide mineralization indicates that there is a trend of increasing temperature from high grade to low grade porphyry systems significantly this is coupled with a sharp change in copper content of pyrite assemblages precipitated at the early stages of mineralization such that cu decreased with increasing temperature based on empa and detailed wds elemental mapping trace elements do not exhibit complex compositional zoning or solid solution in the sulfide structure nevertheless significant amounts of cu and au are contained in pyrite assemblages as micro to nano sized inclusions especially in the high grade fertile porphyry deposits however unexpectedly high concentrations of te se and re may be associated with early stage of sulfide mineralization especially when there is no epithermal lithocap this may highlight the significance of trace metals partitioning in the sulfides formed at the early stages of mineralization in pcds

trace element evidence for plagioclase recycling in calc alkaline magmas abstract trace element zoning in plutonic plagioclase feldspars from the val fredda complex southern adamello massif italy has been measured using secondary ion mass spectrometry sims the studied samples range from hornblende gabbro through diorite to granitoid with an overall range in plagioclase composition from an96 to an15 individual plagioclases display extensive zonation in anorthite through a considerable variety of zoning textures there is equally extensive zoning in trace elements notably sr and ba broadly similar trace element zoning patterns and concentrations are displayed by all plagioclases irrespective of host rock composition using a relationship betweenxan and the distribution coefficientsdsr anddba trace element concentrations in plagioclase are converted to those of the melt which precipitated each crystal zone the calculated variations in ba and sr are greater than can be attributed to changes in pressure or temperature alone indicating that compositional variation in the coexisting melt was the principal cause of zoning the ba sr melt trend for each crystal describes a two stage crystallisation history the calcic cores of all crystals show melt trends of increasing sr and ba which are attributed to mixing and fractionation in parental hydrous picrobasalt magmas in contrast the melt trends recorded by the rims vary from sample to sample but essentially show decreasing sr and ba consistent with fractionation of sodic plagioclase alkali feldspar and or biotite the plagioclase cores are thought to have crystallised in a common magma chamber at 6 10 kbar pressure while the rims crystallised at the emplacement level 1 5 kbar from interstitial melt whose composition is determined by that of the host magma the data suggest that early formed calcic plagioclase was recycled by the magma during fractionation vigorous convection is invoked to both retain relatively dense calcic plagioclase within the evolving magma and to periodically re entrain cumulus crystals into more evolved magmas the occurrence of calcic plagioclase cores in felsic derivative magmas indicates that fractionation from picrobasalt to tonalite occurred on a relatively short time scale

a fluid inclusion and stable isotope study of the pebble porphyry copper gold molybdenum deposit alaska abstract the hydrothermal fluid evolution in the supergiant pebble porphyry cu au mo deposit in southwest alaska has been constrained using fluid inclusion and light stable isotope data the deposit is related to 90 ma granodiorite porphyry intrusions and mineralization occurs primarily in sodic potassic potassic and advanced argillic alteration zones throughout the deposit vein quartz hosts intermediate density fluid inclusion assemblages with an average salinity of 9 5 wt nacl equivalent and homogenization temperatures of 377 to 506 c pressure corrections result in trapping temperatures with a maximum of 610 c this early fluid exsolved from a crystallizing magma at depth and underwent phase separation under varying conditions during cooling and depressurization forming two distinct fluid compositions the two fluids formed two hydrothermal alteration assemblages which have different metal signatures in the hydrothermal core in the eastern part of the system high density quartz veins potassic alteration and the most economically significant mineralization are related to 52 wt nacl equivalent brines that coexist with very low density vapor in the western part of the system peripheral to the hydrothermal core lower quartz vein densities accompanied by sodic potassic alteration and lower grade mineralization are associated with 38 wt nacl equivalent brines and low density vapor sulfide mineralization precipitated late in this early alteration event at temperatures between 375 and 330 c fluids related to sodic potassic alteration minerals have 18 o signatures from 6 0 to 10 5 vsmow and d values from 70 to 41 vsmow which are consistent with a magmatic fluid source fluids related to potassic alteration assemblages have 18 o of 1 7 to 2 3 vsmow and d of 68 to 59 vsmow which suggests that the magmatic fluids evolved to lighter oxygen isotope signatures due to quartz precipitation during alteration lower temperature 280 c sericite and illite alteration followed the high temperature magmatic stage and formed from the rising vapor plume as it mixed with varying amounts of meteoric fluid sericite in quartz sericite pyrite alteration on the periphery of the deposit and illite from areas of illite kaolinite alteration which overprints sodic potassic alteration and forms quartz illite pyrite alteration within the deposit are related to low salinity aqueous fluids that have a significant magmatic component 2 1 to 4 1 18 o and 76 to 67 d illite alteration which overprints both potassic alteration and quartz sericite pyrite alteration formed from fluids with a large meteoric component 9 1 to 4 8 18 o and 101 to 90 d the higher vein density and therefore higher permeability in the core of the deposit facilitated ingress of larger amounts of meteoric fluid compared with the more peripheral region advanced argillic alteration and associated high grade mineralization are related to a second pulse of magmatic fluid which did not intersect the two phase field during cooling and depressurization the fluid contracted to form a 3 wt nacl equivalent aqueous fluid that resulted in a sericite pyrite bornite digenite bearing assemblage with a magmatic signature 4 6 to 6 5 18 o and 108 to 102 d at 340 c cooling and mixing of this fluid with meteoric water resulted in a fluid that formed a pyrophyllite quartz sericite chalcopyrite bearing assemblage 8 9 to 0 6 18 o and 110 to 96 d at 300 c compared to older potassic and sodic potassic alteration the advanced argillic alteration has a highly depleted d signature which is attributed to degassing of a crystallizing intrusive fluid source

incidence of obliquity and precession forced milankovitch cycles in the western mediterranean early messinian sedimentation in the sorbas basin almeria southern spain spectral analysis of the messinian abad marls in the cariatiz section sorbas basin south eastern spain reveals three relevant orders of cyclicity the most significant cycle is in the lowest frequency average thickness of 365 cm 4 5 cycles in the section it is recorded in the composition of planktic foraminiferal assemblages indicative of surface water temperature planktic and benthic stable isotope signals and carbonate proportions the planktic assemblages isotope values and carbonate proportions also record a middle frequency cycle with an average of 177 cm 9 10 cycles in the section the highest frequency cycle average of 132 cm 12 13 cycles in the section is mainly reflected in siliciclastic and calcite proportions age constraints and cycle patterns suggest that the lowest frequency cycle was forced by orbital obliquity whereas the two higher frequency ones are related to precession obliquity seems to have controlled major changes in surface water temperature in the sorbas basin during the early messinian surface water temperature was also affected by precession with changes in weathering and run off spectral analysis has also been applied to vertical shifts of reef facies throughout the progradation of the cariatiz reef this reef is coeval with the cariatiz section vertical shifts of reef talus breccias point to the existence of 4 5 major cycles of sea level change whereas 7 9 higher frequency cycles are reflected in the repeated occurrence of lowstand non reefal deposits correlation with the cycles observed at the cariatiz section suggests that obliquity forced glacio eustatic sea level oscillations in the western mediterranean during the late miocene

apatite chemical composition determined by electron microprobe and laser ablation inductively coupled plasma mass spectrometry as a probe into granite petrogenesis abstract major minor and trace element abundances in apatites from various i and s type igneous and sedimentary granites of the lachlan fold belt have been determined using electron microprobe and laser ablation inductively coupled plasma mass spectrometer the results show that apatite can accommodate many minor and trace elements whose concentrations and ratios are relatively sensitive to factors controlling many of the fundamental differences between i and s type granites apatites from s type granites generally have higher f but lower cl contents than those from i type granites which is ascribed mainly to the loss of cl during the weathering processes forming the source rocks of s type granites although fractional crystallisation can cause significant enrichment in f as well high mn and fe contents in apatites from s type granites and high s and as abundances in apatites from mafic i type granites result from different oxygen fugacities and degrees of al saturation or aluminosity between metaluminous mafic i type magmas and peraluminous s type and felsic i type magmas there are systematic and distinctive differences in absolute rare earth element ree abundances ree distribution patterns and element ratios e g la y sm nd etc between apatites from different types of granite the strong eu depletion that characterises apatites from s and felsic i type granites is interpreted here to be a result of the uniqueness of crystal chemistry of apatite and high eu2 eu3 ratios in s type and felsic i type magmas which are more reduced and peraluminous than mafic i type magmas strong ree la to eu and th enrichment in apatites from mafic i type granites and marked nd depletion in apatites from most s type and felsic i type granites are caused by the precipitation and fractionation of monazite in the parental magmas of the latter rocks substitution mechanisms are responsible for high na in apatites from s type and felsic i type granites and for high si in apatites from mafic i type granites and may also have important effects on ree partitioning between apatite and melt thus apatite chemistry can be used as an excellent indicator of granite petrogenesis the results have important implications for identifying different types of granite and are potentially significant for determining the provenance of sedimentary rocks

geology geochronology fluid inclusion and h o isotope geochemistry of the luoboling porphyry cu mo deposit zijinshan orefield fujian province china abstract the luoboling cu mo deposit in the zijinshan orefield fujian province southeastern china is a large porphyry deposit hosted by the sifang granodiorite and the luoboling granodiorite porphyry the largest cu mo orebody is saddle shaped with various types of hydrothermal veinlets intensive hydrothermal alteration in the deposit is characterized by outward zoning from potassic overprinted by phyllic alteration to phyllic and alunite dickite alteration based on the mineral assemblages and crosscutting relationships of veins the ore forming process can be divided into three stages namely an early stage k feldspar quartz magnetite molybdenite veins associated with potassic alteration a middle stage quartz molybdenite chalcopyrite pyrite veins in phyllic zone and a late stage quartz gypsum veins in the phyllic and alunite dickite alteration zones six molybdenite separates yield a re os isochron age 104 6 1 0 ma which is identical to the age of emplacement of the sifang and luoboling granodiorite porphyries three types of fluid inclusions fis were observed at the luoboling deposit 1 nacl h 2 o aqueous 2 daughter mineral bearing and 3 co 2 h 2 o fluid inclusions fis of the early and middle stages are predominantly vapor rich aqueous and daughter mineral bearing inclusions together with minor co 2 rich and liquid rich aqueous inclusions whereas the late stage minerals only contain liquid rich aqueous inclusions homogenization temperatures and salinities of fis trapped in the early stage minerals range from 420 to 540 c and 0 4 to 62 9 wt nacl equiv respectively fis of the middle stage yield homogenization temperatures of 340 to 480 c and salinities of 0 5 to 56 0 wt nacl equiv co 2 content and the oxygen fugacity indicated by daughter minerals of fis trapped in middle stage minerals are lower than those in the early stage the liquid rich aqueous inclusions of the late stage homogenize at temperatures of 140 to 280 c yielding salinities of 0 4 to 8 4 wt nacl equiv the minimum estimated pressures of the three stages are 30 70 mpa 10 40 mpa and 1 10 mpa respectively corresponding to minimum ore forming depths of 1 2 8 km fluids trapped in early middle and late stages yield d values of 67 to 54 54 to 70 and 62 and 18 o values of 5 4 to 6 7 2 8 to 4 2 and 2 1 respectively fluid boiling which resulted in the formation of stockworks and the precipitation of sulfides occurred in the early and middle stages the fluids subsequently evolved into a low temperature low salinity system in the late stage along with an input of meteoric water the luoboling porphyry cu mo system was developed in a transition from continental arc to back arc extension region which was related to the westward subduction of the paleo pacific plate beneath the huanan orogen

geochemistry u pb geochronology and sr nd isotopes of the neogene igneous rocks at the iju porphyry copper deposit nw shahr e babak iran abstract the iju porphyry copper deposit is located in the kerman copper belt in the northwest of shahr e babak city within the southern extension of the urumieh dokhtar magmatic arc based on a cut off grade of 0 15 the deposit contains 24 million tonnes mt of ore with an average grade of 0 4 wt cu the igneous rocks at the iju deposit are primarily made up of upper miocene sub volcanic and volcanic sequences that intruded eocene volcanic rocks sub volcanic rocks comprise barren quartz monzonite porphyry and syn mineralized granodiorite porphyry along with andesitic volcanic rocks geochemical evidences show that they are co genetic medium to high potassium calc alkaline and likely part of a subduction zone i type granitoid magma these rocks are characterized by enrichment in lrees relative to hrees with negative nb ta anomalies similar to subduction zone magmatism all samples exhibit enriched uniform chondrite normalized ree patterns without noticeable eu anomalies similar to magnetite series granitoids the igneous rocks of the iju deposit exhibit geochemical features similar to adakites the u pb zircon dating shows 9 33 0 19 ma tortonian stage for quartz monzonite oldest unit 9 01 0 20 ma for granodiorite and 8 83 0 19 ma for andesite youngest unit unit the initial 87sr 86sr and 143nd 144nd ratios and end t values for the quartz monzonites are 0 704234 0 512819 and 3 75 respectively similar to the values for the granodiorite which are 0 704278 0 512813 and 3 64 respectively in most discrimination diagrams the iju samples show characteristics of both oceanic slab derived and delaminated collisional thickened lower crust derived adakites the geochronological geochemical and isotopic data for the igneous rocks of the iju deposit indicate that after long term subduction of the neo tethys oceanic crust beneath the central iranian plate continental collision between the arabian and eurasian plates during the miocene pliocene led to crustal thickening breaking off of a subducted slab and development of an asthenospheric window thereby facilitating partial melting of the subduction contaminated sub continental lithospheric mantle and thickened lower crust and generating the cu bearing adakites in the iju region

a record of astronomically forced climate change in a late ordovician sandbian deep marine sequence ordos basin north china abstract the late ordovician pingliang formation on the southwestern margin of the ordos basin north china consists of rhythmic alternations of shale limestone and siliceous beds to explore the possible astronomical forcing preserved in this lithological record continuous lithological rank and magnetic susceptibility ms stratigraphic series were obtained from a 34 m thick section of the pingliang formation at guanzhuang power spectral analysis of the ms and rank series reveal 85 5 cm to 124 cm 23 cm to 38 cm and 15 cm to 27 cm thick sedimentary cycles that in ratio match that of late ordovician short eccentricity obliquity and precession astronomical cycles the power spectrum of the ms time series calibrated to interpreted short orbital eccentricity cycles aligns with spectral peaks to astronomical parameters including 95 kyr short orbital eccentricity 35 3 kyr and 30 6 kyr obliquity and 19 6 kyr and 16 3 kyr precession cycles the 15 cm to 27 cm thick limestone shale couplets mainly represent precession cycles and siliceous bed deposition may be related to both precession and obliquity forcing we propose that precession forced sea level fluctuations mainly controlled production of lime mud in a shallow marine environment and transport to the basin precession and obliquity controlled biogenic silica productivity and temperature dependent preservation of silica may have been influenced by obliquity forcing

heterogeneous zircon cargo in voluminous late paleozoic rhyolites hf o isotope and zr hf records of plutonic to volcanic magma evolution voluminous rhyolitic lavas and ignimbrites c 34 000 km3 were formed in the ne german basin in a post collisional setting at c 295 ma trace elements ehf and 18o have been measured in dated magmatic and inherited rhyolitic zircons from three drill cores across the basin magmatic zircons crystallized in two stages the first stage in less differentiated and isotopically heterogeneous magmas and the second stage in more differentiated and isotopically homogeneous magmas the first and second stages can be related to the crystallization of zircons within a heterogeneous pluton and in an evolved silicic magma that was later erupted some zircons crystallized entirely during the evolved magma stage and provide good resolution for identifying and characterizing processes happening shortly before eruption the isotopic compositions of the magmatic zircons constrain the proportions of juvenile and reworked materials involved in the formation of voluminous silicic magmas in a post collisional tectonic setting the advantage of studying the volcanic rocks from the ne german basin is that their petrogenesis involved a relatively simple two source interaction during magma production which permits quantitative estimation of the amount of each source component afc modelling shows that the first stage zircons crystallized from magmas containing 5 80 of the juvenile component whereas the final rhyolitic magmas contained 30 40 of this material the inherited zircons have hf model ages of 1 9 2 2 ga suggesting that much of the local basement was initially derived from the mantle at that time and that it was subsequently reworked at around 1 5 ga similar model ages are a feature of baltica derived sediments and the implication is that such sediments underlie large areas of the ne german basin the lack of any record of avalonian basement in the ne german basin may indicate that both the sedimentary cover and the underlying basement are part of baltica

cyclostratigraphy orbital tuning and inferred productivity for the type kimmeridge clay late jurassic southern england three independently measured variables magnetic susceptibility photoelectric factor and total gamma ray obtained from throughout the type kimmeridge clay fm in dorset southern england were used to identify regular metre scale sedimentary cycles spectral analysis demonstrates that for long stratigraphical intervals the cycles are expressed as large amplitude cycles of 1 87 4 05 m wavelength and smaller amplitude cycles of around half that wavelength these cycles are interpreted to record orbital obliquity and precession respectively the much larger amplitude of the inferred obliquity cycles compared with the precession cycles may indicate a high latitude climatic forcing transferred to lower latitudes via sea level variations orbital tuning indicates that the early kimmeridgian sensu anglico lasted at least 3 6 ma 95 longer wavelength cycles and the late kimmeridgian at least 3 9 ma 103 longer wavelength cycles the first detailed productivity estimates for the kimmeridge clay fm on a cycle by cycle calculation indicate that average productivity of the type kimmeridge clay 220 g m 2 a 1 was less than the average productivity on modern continental shelves the high average organic carbon content of the type kimmeridge clay 3 8 total organic carbon cannot be attributed to high average productivity however the average organic carbon content is consistent with low siliciclastic mineral dilution of organic matter and or elevated preservation linked to reduced bottom water oxygenation

temporal spatial distribution and tectonic setting of porphyry copper deposits in iran constraints from zircon u pb and molybdenite re os geochronology abstract porphyry copper deposits pcds in iran are dominantly distributed in arasbaran nw iran the middle segment of the urumieh dokhtar magmatic arc udma and kerman central se iran with minor occurrences in eastern iran and the makran arc this paper provides a temporal spatial and geodynamic framework of the iranian porphyry cu mo au systems based on geochronologic data obtained from zircon u pb and molybdenite re os dating of host porphyritic rocks and molybdenites in 15 major pcds the dating results define a long metallogenic duration 39 6 ma and suggest a long history of tectonic evolution from the accretionary orogeny related to early cenozoic closure of the neo tethys ocean to subsequent collisional orogeny for the iranian porphyry copper systems the oldest porphyry mineralization occurred in the eastern part of iran after the closure of a branch of the neo tethyan sistan ocean between the lut and afghan blocks in the late eocene 39 37 ma this was followed by mineralization in the kerman porphyry copper belt over a time interval of about 20 m y where two metallogenic epochs have been recognized including late oligocene 29 27 ma and miocene 18 6 ma the bondar e hanza deposit formed in the late oligocene while and the remaining dated deposits belong to miocene epoch according to the deposits characteristics and their ages the miocene epoch can be divided into early middle and late stages the darreh zar bakh khoshk chah firouzeh and sar kuh deposits formed during the early middle miocene the largest porphyry deposits occur in the middle stage during the middle miocene 14 11 ma and include the sar cheshmeh meiduk dar alu and now chun deposits these deposits were formed during crustal thickening uplift and rapid exhumation of the belt the final stage of porphyry mineralization occurred during the late miocene 9 6 ma and formed the iju kerver kuh panj and abdar deposits there were two porphyry mineralization stages in the arasbaran porphyry copper belt in nw iran including an older late oligocene 29 27 ma and a younger early miocene 22 20 ma events the haft cheshmeh deposit belongs to the older stage and the world class sungun and masjed daghi deposits formed during the early miocene in the middle segment of the udma saveh yazd porphyry copper belt pcds formed during middle miocene time 17 15 ma the geochronological results reveal that the porphyry mineralization moved from the northwest to southeast of udma over the time our dating results combined with the possible late eocene oligocene timing for collision between the arabian and iranian plates support a model for iranian pcd formation by partial melting of previously subduction modified lithosphere in a post subduction and post collisional tectonic setting

decoding whole rock plagioclase zircon and apatite isotopic and geochemical signatures from variably contaminated dioritic magmas zircon and apatite grains from three types of variably contaminated quartz diorite were analyzed in the gesiniec intrusion sw poland the zircon isotopic compositions ehf300 5 5 0 and 18o 5 6 9 3 are consistent with contamination processes zircon is characterized by an increase in u th pb and ree from the least to the most evolved quartz diorite type apatite is characterized by ranges in trace element concentrations and with the progress of contamination its composition evolves from those typical for i type granites toward those typical for s type isotopic and trace element variations in zircon and apatite correlate with sr isotopic composition of plagioclase 87sr 86sr300 0 7069 0 7084 pietranik and waight 2008 however both sr isotopic composition of plagioclase and trace element composition of apatite could be homogenized by late stage resorption leaving zircon as the only record of contamination processes that predate resorption comparison between plagioclase and zircon isotopic composition is consistent with both plagioclase cores and zircons recording similar stages of magma contamination comparison between plagioclase and apatite composition indicates that crystallization of apatite was contemporaneous with crystallization of plagioclase rims the preferred interpretation of isotopic and trace element variations observed in different grains is a two stage contamination by crustally derived magmas early contamination was probably dominated by material typical of the lower crust i e with none or only small amounts of a sedimentary component as indicated by low 18o in zircon 5 6 6 5 in both the least and the most contaminated types later contamination was dominated by crustally derived magmas containing more than 20 of a sedimentary component as the most contaminated sample includes zircon with 18o up to 9 3 partial melts generated from an s type granite source are the most probable contaminant for this second stage contamination as indicated by apatite trace element composition in general isotopic and chemical composition of plagioclase zircon and apatite provides complementary information on magmatic processes but records a longer time span than a single mineral only due to their diachronous crystallization histories

isotopic disequilibrium during melting of granite and implications for crustal contamination of magmas the assumption that the isotopic ratios of anatectic melts generated in response to crust magma interaction are equivalent to the bulk source rock from which they are derived was tested experimentally via dehydration melting of a proterozoic biotite granite heating of the coarse grained granite at 1250 c for durations of 1 to 48 h produced extreme disequilibrium among simultaneously generated mafic and felsic melts quenched to glass and whole rock 87sr 86sr ratios in situ microdrill sr isotopic analyses across gradational contacts between mafic high 87sr 86sr and felsic low 87sr 86sr glass register significant isotopic and chemical heterogeneity on the submillimetre scale our experiments suggest that during the early stages of wall rock melting when the rate of heating may exceed melting rates isotopic equilibrium may not be maintained thus producing contaminant liquids having isotopic compositions different from the bulk source rock if isotopic equilibrium is not attained during partial melting in the crust current geochemical models of open system magmatic processes may require modification

magmatic zoning in apatite a monitor of porosity and permeability change in granites apatites from the shap granite northern england are strongly zoned reflecting multiple generations of growth and dissolution such chemical zoning is most readily displayed in cathodoluminescence images and correlates well with trace element variation determined using la icp ms analyses the zoned apatites provide a detailed record of the changing scales of permeability during progressive crystallisation within the magma chamber early periods of apatite growth are preserved within cores and represent both early growth within a magma chamber dominated by vigorous mixing processes and inherited grains with significantly different chemistries the main phase of apatite growth within the magma was strongly controlled by the presence of adjacent biotite phenocrysts and is characterised by fine scale oscillatory zoning followed by the growth of a thin rim of relatively uniform composition the chemical evolution of the later phases of apatite growth and the stratigraphy of the zoning appear to record late stage crystallisation within progressively more isolated interstitial melt pockets

zircon texture and chemical composition as a guide to magmatic processes and mixing in a granitic environment and coeval volcanic system this study documents the chemical and textural responses of zircon in the elba igneous complex with particular reference to the 7 to 7 8 ma old monte capanne pluton in relation to its coeval volcanic counterpart capraia using bse imaging and quantitative electron microprobe analyses the monte capanne pluton displays multiple field and geochemical evidence for magma mixing the samples we have investigated including monzogranitic mafic enclave and dyke samples display similar zircon textures and are associated with an extremely large range of trace and minor element hf y hree th u compositions which contrast with relatively simple textures and zoning patterns in zircons from a capraia dacite we have used a relatively simple textural classification patchy zoning homogenous cores oscillatory zoning and unzoned zircon as the basis for discussing the chemical composition and chemical variation within zircons from the monte capanne pluton based on these data and other works dini et al 2004 in lithos 78 101 118 2004 it is inferred that mixing between metaluminous and peraluminous melts occurred early in the evolution of the monte capanne magma chamber in particular mixing was responsible for the development of the patchy zoning texture in the zircon cores which was associated with reactions between other accessory phases including monazite apatite allanite which we infer to have significantly affected the th distribution in zircon zircons from the mc pluton displaying homogeneous cores have chemical affinities with zircons in the coeval capraia volcanic system consistent with the participation of a capraia like mantle end member during mixing further zircon growth in the mc pluton produced the oscillatory zoning texture which records both long term crystal fractionation and transient recharge with both silicic and mafic magmas events in a hybrid magma chamber it is inferred that hf and the th u ratio cannot be used alone to infer magmatic processes due to their dependency on temperature nor are they a diagnostic feature of xenocrystic grains this study shows that zircon chemistry coupled with detailed textural analysis can provide a powerful tool to elucidate the complex evolution of a magma system

economic geology clues to hidden copper deposits economic grade deposits of copper are hard to find the aluminium content of magmatic rocks at the surface may provide an indicator of ore deposits buried deep below

genesis of the yandong porphyry cu deposit in eastern tianshan nw china evidence from geology fluid inclusions and isotope systematics abstract the yandong porphyry cu deposit 372 mt at 0 58 cu is located in the center of the eastern tianshan xinjiang nw china multiple stage hydrothermal activities have resulted in potassic chlorite sericite phyllic and propylitic alteration in this deposit the yandong deposit formed in four stages i e an early quartz magnetite pyrite stage i a quartz pyrite chalcopyrite stage ii a quartz chalcopyrite pyrite molybdenite stage iii and a late quartz carbonate stage iv three evolutionary episodes were observed by a detailed fluid inclusion study 1 early ore stage i fluids were trapped under two phase conditions as evidenced by the coexistence of vapor rich v type inclusions homogenization temperatures 410 494 c average salinity 2 2 wt nacl equiv liquid rich l type inclusions homogenization temperatures 311 430 c average salinity 9 5 wt nacl equiv and hypersaline h type inclusions trapped at 300 bars or a depth of approximately 1 km assuming lithostatic pressure conditions 2 main ore stage ii and iii fluid inclusions in quartz were also trapped under two phase conditions boiling as identified by the coexistence of v and l type fluid inclusions l type inclusions homogenized between 161 and 390 c average 270 c with salinities of 1 6 9 9 wt nacl equiv average 4 9 wt nacl equiv and a depth of 1 km 100 bars hydrostatic pressure conditions 3 late ore stage iv fluids are represented by inclusions in barren quartz carbonate veinlets characterized by homogenization temperatures ranging from 123 to 261 c average 179 c and salinities between 0 7 and 4 7 wt nacl equiv average 2 0 wt nacl equiv the initial hydrothermal fluids are characterized by high temperature high salinity and high oxygen fugacity belonging to a h 2 o nacl system hydrogen and oxygen isotope data indicate that the hydrothermal fluids have a dominantly magmatic signature and mixed with abundant meteoric waters in the quartz carbonate stage sulfur stable isotope suggests that the ore forming metals came primarily from the tonalite magma that sourced from the subducted oceanic slab involving some mantle peridotites during ascent the cu mineralization of the yandong porphyry deposit occurred at a shallow crustal level approximately 1 km and the fluid boiling or phase separation decrease of temperature as well as fluid rock interaction were likely important factors responsible for metal accumulation and deposition in the magmatic hydrothermal system

late cretaceous and early miocene andean type plutonic activity in northern makran and central iran two calc alkaline plutonic complexes bazman and natanz intruded through the south eastern active and south western ancient continental margins of central iran have been dated by the rb sr whole rock isochron method at 74 2 and 24 4 5 ma respectively detailed trace element studies together with low 87 sr 86 sr initial ratios 87 sr 86 sr ratios and the gabbros at least were intruded some 10 ma earlier

evolution of ore fluids in the donggou giant porphyry mo system east qinling china a new type of porphyry mo deposit evidence from fluid inclusion and h o isotope systematics abstract the donggou mo deposit in the eastern qinling area china is a giant porphyry system discovered based on a targeting concept by using the tectonic model for collisional orogeny metallogeny and fluid flow cmf model mo mineralization is associated with the donggou aluminous a type granite porphyry and was formed during the early cretaceous in a tectonic regime of continental extension the orebodies mainly occur as numerous veinlets in the host rocks hydrothermal ore forming processes include at least three stages characterized by veinlets of 1 quartz k feldspar minor molybdenite 2 quartz molybdenite beryl and 3 quartz carbonate fluorite three types of fluid inclusions fis are distinguished in quartz and beryl in stages 1 and 2 i e aqueous w type carbonic aqueous c type and solid bearing s type with only aqueous fis observed in stage 3 minerals s type fis contain variable daughter minerals including halite chalcopyrite calcite and an unidentified transparent crystal but only halite can dissolve during heating halite bearing s type fis are mainly homogenized by halite dissolution at 182 416 c corresponding to salinities of 30 9 49 2 wt nacl equiv minor halite bearing s type fis are homogenized to liquid at 190 360 c via vapor disappearance with salinities of 29 1 36 2 wt nacl equiv other fis in minerals of stages 1 2 and 3 are homogenized at temperatures of 341 550 c 220 440 c and 125 225 c with salinities of 8 0 18 3 5 3 16 8 and 0 5 7 3 wt nacl equiv respectively the estimated minimum trapping pressures are up to 141 mpa in stage 1 and up to 81 mpa in stage 2 respectively corresponding to an initial mineralization depth of no less than 5 km the quartz in veinlets yields 18 o values of 8 5 10 0 corresponding to 18 o h 2 o values of 2 9 to 5 9 while the d h 2 o values of fluid inclusions range from 59 to 82 these data suggest that the ore fluids forming the donggou deposit changed from high temperature high salinity co 2 rich magmatic to low temperature low salinity and co 2 poor meteoritic fluids via boiling and mixing resembling those of other magmatic hydrothermal systems in qinling orogen and dabie shan this supports the notion that the porphyry systems generated in a post collisional tectonic setting were initially co 2 rich as indicated by abundant c type and co 2 bearing s type fluid inclusions

high sr y magmas reflect arc maturity high magmatic water content and porphyry cu mo au potential examples from the tethyan arcs of central and eastern iran and western pakistan the temporal and geochemical evolution of arc magmatism that culminated in porphyry cu mo au deposit formation has been studied in three separate neo tethyan arc systems in central and eastern iran and western pakistan porphyry cu au deposits in the lut block of eastern iran formed in the middle eocene at the end of a period of extensive paleocene eocene volcanism porphyry cu mo deposits in the kerman belt of central iran formed in the middle miocene at the end of a period of voluminous eocene oligocene volcanism and porphyry cu au deposits in the chagai belt of western pakistan formed in four pulses during the eocene early miocene middle late miocene and late miocene pliocene after a prolonged period of arc magmatism that began in the late cretaceous and is still active in each region the late porphyry related magmas are more geochemically evolved and more hydrous as evidenced by the presence of hornblende phenocrysts than the preceding volcanic rocks we suggest that this reflects maturation of the arc magmatic system over a period of tens of millions of years leading to the generation of more evolved volatile rich magmas at later stages of the arc s history high magmatic water contents are a prerequisite for the shallow crustal emplacement of arc magmas and the subsequent generation of potentially ore forming subvolcanic magmatic hydrothermal systems it is thus suggested that the fertility of arc magmas within a given arc terrane can be assessed by observing the relative timing of plutonic suites later suites are more prospective noting the common presence of hornblende or biotite phenocrysts indicating high magmatic water contents and through lithogeochemical fingerprinting of magmatic fractionation processes relatively high sr y and la yb ratios and eun eu ratios 1 indicating abundant early hornblende fractionation and suppression of plagioclase crystallization in hydrous magmas

methane rich fluid evolution of the baogutu porphyry cu mo au deposit xinjiang nw china abstract baogutu is the first porphyry cu mo au deposit discovered in western junggar xinjiang nw china the ore bearing intrusion is a dioritic intrusive complex that includes stage 1 diorites and minor stage 2 diorite porphyries the stage 1 diorites have produced concentric potassic and propylitic alteration zone and overprinted phyllic alteration and host much of the cu mo au mineralization at baogutu the baogutu porphyry cu mo au deposit consists of unusually disseminated and minor vein style mineralization the fluid evolution occurred in stage 1 diorite from late magmatic stage to hydrothermal stage stages 1b and 1c is constructed based on alteration and fluid inclusion analysis by microthermometry raman spectroscopy and quadrupole mass spectrometer five fluid types are distinguished and they are l1 liquid rich 2 phase l2 liquid vapor 2 phase v1 vapor rich 2 phase v2 mono phase vapor and h multi phase solid the dominant inclusions rich in reductive ch4 plus h2o while minor inclusions rich in ch4 and co2 the inclusions in quartz from the late magmatic stage contain the most brine inclusions and less other inclusions with ch4 rich and h2o rich compositions the inclusions in quartz from stage 1b contain all fluid types and have ch4 rich and ch4 h2o compositions with rare co2 the inclusions in quartz from stage 1c are characterized by more vapor inclusions without brine inclusions and a clear co2 concentration in a few assemblages with ch4 co2 composition using microthermometry we estimate fluid trapping conditions at t 400 c and p 1500 to 3100 bar in late magmatic stage t 200 to 400 c and p 50 to 320 bar in disseminated quartz in stage 1b t 180 to 400 c and p 20 to 260 bar in vein quartz in stage 1b and t 170 to 400 c and p 20 to 230 bar in stage 1c such late magmatic conditions are compatible with the fluid evolution as a result of ch4 rich inclusions derived from mantle magma such hydrothermal conditions in stages 1b and 1c with small p t fluctuations are compatible with the dominant disseminated mineralization at baogutu that indicates a weak fracturing the overall fluid path at baogutu is toward lower pressure and small changed temperature with composition transit of fluid from a high halite ch4 rich system to low halite ch4 co2 system it may lead to the formation of this cu mo au deposit

copper partitioning between felsic melt and h2o co2 bearing saline fluids abstract analysis of fluid inclusions from porphyry copper deposits reveals that magmatic vapor and brine are vital for the removal of copper from arc magmas and its transport to the site of ore deposition experiments in melt vapor brine systems allow for investigation of the partitioning of copper between silicate melts and volatile phases at magmatic conditions the presence of co2 affects both the pressure at which a melt saturates with respect to volatile phases therefore the partitioning of copper among felsic rhyolitic melt vapor and brine in co2 bearing experiments was examined to provide insights into copper partitioning and the generation of porphyry copper and related deposits we present results from experiments performed at 800 c and 100 mpa in co2 bearing melt vapor brine systems with x co 2 v b 0 10 and 0 38 the compositions of vapor and brine inclusions and run product glasses were determined during the course of this investigation microthermometric measurements of fluid inclusions show an increase in the salinity of the magmatic brine 65 to 70 wt nacleq and decrease in the salinity of the vapor 3 5 to 1 wt nacleq as x co 2 is increased from 0 10 to 0 38 the partitioning of copper between brine and vapor d cu b v 2 increases from 25 6 at x co 2 0 10 to 100 30 at x co 2 0 38 the partitioning of copper between vapor and melt d cu v m 2 decreases from 9 6 3 3 at x co 2 0 10 to 2 0 8 at x co 2 0 38 these data demonstrate that copper partitioning in sulfur free co2 bearing systems is controlled by the changes in the salinity of the vapor and brine that in turn are functions of x co 2 no change in the apparent equilibrium constants for cu na exchange was observed in fe bearing experiments which supports a salinity dependent model for copper partitioning an existing model mvpart for ore metal partitioning between melt and volatile phases was modified to incorporate partitioning data from co2 bearing experiments the model can be used to predict trends in efficiency of removal of copper from melts into exsolving co2 bearing magmatic volatile phases at a fixed pressure and temperature the co2 mvpart model predicts that co2 rich x co 2 0 38 magmatic vapor will remove half of the available copper from the melt without a contribution from the brine compared to low co2 x co 2 0 10 systems thus periods of co2 rich vapor exsolution are not expected to be associated with efficient removal of copper from shallow felsic melts

mineral scale sr isotope constraints on magma evolution and chamber dynamics in the rum layered intrusion scotland sr isotopic zoning within single plagioclase crystals from rocks from unit 9 of the rum layered intrusion is used to infer events during crystal growth in a magma undergoing contamination the 87sr 86sr diversity among minerals and between cores and rims of plagioclase crystals increases as the boundary between unit 9 and the overlying unit 10 peridotite is approached models of near solidus interaction of the cumulate with a fluid or melt or large scale textural re equilibration cannot easily account for the systematic differences in 87sr 86sr between small crystals and the rims of larger crystals

application of best worst method and additive ratio assessment in mineral prospectivity mapping a case study of vein type copper mineralization in the kuhsiah e urmak area iran abstract this study proposes the application of a hybrid methodology combining the best worst method bwm and additive ratio assessment aras approaches to mineral prospectivity mapping the aras approach is used to prioritize and rank individual cells the bwm on the other hand is useful for assigning weights to the spatial proxies of the mineralized system representing mappable expressions of the ore forming processes a dataset of vein type copper mineralization including geochemical geophysical geological and remotely sensed data from the kuhsiah e urmak area iran was translated into a set of mappable spatial proxies representing the genetic processes involved in the formation of the vein type copper mineralization a hybrid bwm aras method was applied to the spatial proxies used to generate the mineral potential map the results of the proposed methodology were statistically compared to those obtained from the index overlay and technique for order of preference by similarity to ideal solution topsis methods using the rate of correct classification in confusion matrices and demonstrating the superiority of the proposed methodology a field trip was conducted to assess the most prospective target zones and to collect samples for analysis the majority of these samples returned significant copper contents with copper ores observed in most of the polished sections prepared from these samples considering these results the newly proposed bwm aras approach appears to offer a viable alternative to the conventional methods applied to knowledge driven mineral prospectivity mapping

geology fluid inclusion and h o s isotopes of the kuruer cu au deposit in western tianshan xinjiang china abstract western tianshan along the southwestern margin of the central asian orogenic belt is well endowed with epithermal and porphyry au deposits the kuruer cu au deposit recently discovered in the eastern part of western tianshan was considered as a high sulfidation epithermal deposit however our geological fluid inclusion and stable isotopic studies indicate that it actually formed in transition from high sulfidation to porphyry the host rocks include the dahalajunshan formation volcanic and volcano sedimentary rocks such as andesite rhyolite ignimbrite and tuff cu au mineralization mainly occurs as quartz dominated stockworks or disseminations with abundant pyrite and chalcopyrite and minor galena and sphalerite gold occurs as invisible phase in sulfides hydrothermal alteration includes a silicic core surrounded by phyllic alteration and peripheral propylitic alteration based on field observations paragenetic and crosscutting relationship the mineralization process can be roughly divided into three stages the early stage is characterized by the assemblage of quartz pyrite chalcopyrite while the middle stage contains quartz and chalcopyrite at absence of pyrite the late stage is characterized by calcite quartz chlorite chalcopyrite veins fluid inclusions at the early stage are mainly liquid rich aqueous and co2 rich inclusions and minor vapor rich aqueous and solid bearing inclusions their homogenization temperatures and salinities can be up to 420 c and 39 wt nacl eq respectively indicating that the initial ore forming fluids are high temperature high salinity h2o co2 nacl systems in the middle stage there are only liquid rich aqueous inclusions with homogenization temperatures and salinities of 130 190 c and 0 18 to 10 7 wt nacl eq respectively liquid rich aqueous inclusions in the late stage display much lower temperatures and salinities ranging from 110 to 130 c and 0 18 2 7 wt nacl eq respectively obtained dh2o and 18oh2o values of quartz from the middle stage are 98 to 107 and 2 1 to 0 74 respectively the 34s values of 9 chalcopyrite samples range from 10 2 to 2 4 with an average of 4 1 we conclude that the initial ore forming fluids are magmatic in origin and further cooled and diluted by mixing with meteoric water intensive fluid boiling and mixing facilitated hydrothermal alteration and mineralization

residence resorption and recycling of zircons in devils kitchen rhyolite coso volcanic field california zircons from the devils kitchen rhyolite in the pleistocene coso volcanic field california have been analyzed by in situ pb u ion microprobe shrimp rg and by detailed cathodoluminescence imaging the zircons yield common pb corrected and disequilibrium corrected pb u ages that predate a previously reported k ar sanidine age by up to 200 kyr and the range of ages exhibited by the zircons is also approximately 200 kyr cathodoluminescence imaging indicates that zircons formed in contrasting environments most zircons are euhedral and a majority of the zircons are weakly zoned but many also have anhedral embayed cores with euhedral overgrowths and multiple internal surfaces that are truncated by later crystal zones concentrations of u and th vary by two orders of magnitude within the zircon population and by 10 20 times between zones within some zircon crystals indicating that zircons were transferred between contrasting chemical environments a zircon saturation temperature of 750 c overlaps within error a previously reported phenocryst equilibration temperature of 740 25 c textures in zircons indicative of repeated dissolution and subsequent regrowth are probably caused by punctuated heating by mafic magma input into rhyolite the overall span of ages and large variation in u and th concentrations combined with calculated zircon saturation temperatures and resorption times are most compatible with crystallization in magma bodies that were emplaced piecemeal in the crust at coso over 200 kyr prior to eruption and that were periodically rejuvenated or melted by subsequent basaltic injections

processes and sources during late variscan dioritic tonalitic magmatism insights from plagioclase chemistry gesiniec intrusion ne bohemian massif poland the ge siniec intrusion strzelin massif east sudetes 307 290 ma is composed predominantly of dioritic to tonalitic rocks with sr sr ratios ranging from 0 7069 to 0 7080 and end1 4 3 1 to 4 2 emplaced as post collisional magmas following thevariscan orogeny in situ sr isotope and trace element analyses of plagioclase were carried out on five diorite tonalite samples with variable whole rock sr sr compositions to constrain magma sources and elucidate magma chamber processes plagioclase is characterized by complex zoning patterns such as patchy zoning asymmetrical zoning and strong resorption between an rich cores and more albitic rims the range of sr isotopic compositions recorded in plagioclase is 0 7069 0 7091 greater than that of the whole rocks no change in isotopic composition is observed across resorbed core rim boundaries as would be expected if the resorption was caused by magma mixing two samples are close to sr isotopic equilibrium between plagioclase and the whole rock three samples are isotopically heterogeneous and exhibit the largest variations in sr isotope ratios within high an plagioclase cores associated with only slight resorption and almost no change in an content consequently we interpret the core resorption to be due to decompression during emplacement of phenocryst bearing magmas in the upper crust rather than to magma mixing whereas we interpret the isotopic heterogeneity in the high an plagioclase cores to be due to open system processes in the lower crust the trace element and sr isotopic compositions of the high an plagioclase cores provide an insight into the lower crustal processes that took place prior to decompression we show that different diorite tonalite types cannot be related to each other by assimilation fractional crystallization processes and consequently they probably evolved as separate magma batches processes recorded in plagioclase core compositions include contamination by high sr sr crustal material and interaction with water rich magma the studied samples represent magmas that probably formed either by continuous differentiation and crustal contamination of originally more mafic magmas or by remelting of 1 3 2 1 ga basaltic materials in the lower crust this study emphasizes the importance of integrating textural and in situ data to elucidate the processes that contribute to the formation of texturally and compositionally complex plagioclase crystals in plutonic rocks

porphyry copper enrichment linked to excess aluminium in plagioclase porphyry ore deposits are increasingly hard to discover geochemical analysis of minerals formed in porphyry systems worldwide shows that the most fertile deposits are associated with excess al and water rich magma injections

structures of the zagros fold thrust belt in iran the zagros fold thrust belt in iran forms the external part of the zagros active orogenic wedge it includes a sequence of heterogeneous latest neoproterozoic phanerozoic sedimentary cover strata 7 to 12 km thick and composed of alternating incompetent and competent layers overlying precambrian crystalline basement with a complex pre zagros structural fabric balancing structures of the cover statigraphic units in the zagros fold thrust belt requires in sequence and out of sequence involvement of the precambrian basement in the deformation six detailed balanced and retrodeformable cross sections which are constructed based on geological and geophysical data across various sectors of the belt show fault bend and fault propagation folds interpreted to have formed by slip on their subjacent thrusts out of sequence basement rooted thrusts as the interpretations in the constructed cross sections suggest have breached the cover basement interface and using incompetent cover strata for propagation cut across the cover structures and have created associated new folds superimposed upon the pre existing structures this style of deformation which has resulted in structural complexity of the belt characterizes a 200 to 300 km wide zone of distributed partly synchronous deformation with along strike and across strike variations it also implies that the zagros fold thrust belt as the external part of the orogenic wedge is still in its subcritical condition with internal deformation to achieve a critical taper in creating structural complexity in addition to out of sequence thrusting mechanically weak layers evaporites and mudstones of the cover strata have played a significant role by providing several detachment horizons shortening estimates across the belt are variable based on the constructed cross sections and their restorations minimum shortening estimates range from 16 percent to 30 percent in different sectors of the belt

empirical calibration of oxygen isotope fractionation in zircon new empirical calibrations for the fractionation of oxygen isotopes among zircon almandine rich garnet titanite and quartz are combined with experimental values for quartz grossular the resulting a coefficients k2 are zrc alm grs ttn qtz 2 64 2 71 3 03 3 66 zrc 0 07 0 39 1 02 alm 0 32 0 95 grs 0 63 full size table table options view in workspace download as csv for the relation 1000 ln y x ay x 106 t2 the fractionation of oxygen isotopes between zircon and coexisting minerals can provide otherwise unavailable evidence of magmatic processes including crystallization remelting and assimilation fractional crystallization

giant ore deposits formed by optimal alignments and combinations of geological processes giant ore deposits are priority targets for mining companies a review of the characteristics of several giant porphyry and epithermal deposits worldwide suggests that they formed from ordinary processes that were fortuitously operating at maximum efficiency

petrology geochemistry and la icp ms u pb geochronology of paleoproterozoic basement rocks in bangladesh an evaluation of calc alkaline magmatism and implication for columbia supercontinent amalgamation abstract the paleoproterozoic 1 7 ga basement rocks from maddhapara bangladesh show a large range of chemical variations e g sio2 50 7 74 7 and include diorite quartz diorite monzodiorite quartz monzonite and granite the pluton overall displays metaluminous calc alkaline orogenic suite mostly i type suites formed within subduction related magmatism the observed major elements show general trends for fractional crystallization trace element contents also indicate the possibility of a fractionation or assimilation explain the entire variation from diorite to monzonite even granite the pluton may have evolved the unique chemical features by a process that included partial melting of calc alkaline lithologies and mixing of mantle derived magmas followed by fractional crystallization and by assimilation of country rocks the pluton shows evidence of crystal fractionation involving largely plagioclase amphibole and possibly biotite some of the fractionated magmas may have mixed with more potassic melts from distinct parts of the continental lithosphere to produce granites and or pegmatites new geochronological results of granitic pegmatite 1722 10 ma are indisputably consistent with diorite and tonalite and those data showing credible geochronological sequence i e diorite tonalite granitic pegmatite identical paleoproterozoic age 1 7 ga with distinctive magmatism of the maddhapara basement rocks have agreeable relationship with the citz india the consistent magmatism is also common in the transamazonian of south america trans hudson orogeny in north america bohemian massif and the svecofennian poland have identified the sequential growth of the continent through the amalgamation of juvenile terrains succeeded by a major collisional orogeny such paleoproterozoic subduction related orogens in australia have similar counterparts in antarctica and other part of the world these types of paleoproterozoic magmatism dominantly contributed to assemble amalgamation and breakup of the enormous columbia supercontinent

fluid evolution of the yuchiling porphyry mo deposit east qinling china the yuchiling mo deposit east qinling china belongs to a typical porphyry mo system associated with high k calc alkaline intrusions the pure co2 pc co2 bearing c aqueous h2o naci w and

m sequence geomagnetic polarity time scale mhtc12 that steadies global spreading rates and incorporates astrochronology constraints 1 geomagnetic polarity time scales gptss have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates a strategy to obtain an optimal gpts is to minimize spreading rate fluctuations in many ridge systems however this has been possible only for a few spreading centers we describe here a monte carlo sampling method that overcomes this limitation and improves gpts accuracy by incorporating information on polarity chron durations estimated from astrochronology the sampling generates a large ensemble of gptss that simultaneously agree with radiometric age constraints minimize the global variation in spreading rates and fit polarity chron durations estimated by astrochronology a key feature is the inclusion and propagation of data uncertainties which weigh how each piece of information affects the resulting time scale the average of the sampled ensemble gives a reference gpts and the variance of the ensemble measures the time scale uncertainty we apply the method to construct mhtc12 an improved version of the m sequence gpts late jurassic early cretaceous 160 120 ma this gpts minimizes the variation in spreading rates in a global data set of magnetic lineations from the western pacific north atlantic and indian ocean nw of australia and it also accounts for the duration of five polarity chrons established from astrochronology cm0r through cm3r this gpts can be updated by repeating the monte carlo sampling with additional data that may become available in the future

isotopic equilibration during partial melting an experimental test of the behaviour of sr abstract experiments using isotopically enriched sr doped minerals designed to test for isotopic equilibrium between source and melt during partial melting reveal that 87 sr 86 sr ratios of the liquids are primarily determined by the proportions of minerals consumed and vary with the advancement of the melting reaction the experiments were performed at 1 atm on model crustal assemblages composed of pairs of natural plagioclase an 68 87 sr 86 sr 0 701 and synthetic fluorphlogopite doped with 90 ppm sr having 87 sr 86 sr 4 2 sims traverses showed that during the initial stages of the reaction liquids are isotopically zoned all the analyzed melts have 87 sr 86 sr markedly higher than that of the bulk starting assemblage i e the source because of the faster melting rate of fluorphlogopite at 1200 c and 1250 c melting occurs above a critical temperature wherein the dissolution rates of the crystals are controlled by diffusion of species in the melt and reactants and reaction products are out of isotopic equilibrium this is due to faster melt crystal boundary migration when compared to sr diffusion in the crystals equilibration is possible only if melting stops calculations show that total equilibration between melt and residue by sr tracer diffusion in the crystals takes 10 4 10 6 yr for temperature and grain size ranging respectively from 800 c to 1000 c and 0 1 to 1 cm when compared to the proposed residence time of crustal magmas at their sources this result strongly suggests that magmas that do not reflect the bulk isotopic characteristics of their source regions can be produced

hydrothermal fluid evolution in collisional miocene porphyry copper deposits in iran insights into factors controlling metal fertility abstract the cenozoic urumieh dokhtar magmatic belt udmb in iran is considered as one of the major cu bearing regions in the world with high potential for the occurrence of giant large porphyry cu mo au systems in the udmb porphyry cu mineralization is strictly associated with miocene intrusions originating mostly from collisional related partial melting of subduction modified juvenile lower crust in this study fluid inclusion coupled with laser raman analysis is used to characterize and compare the fluid evolution of the large meiduk deposit and smaller low grade porphyry copper systems e g keder sarkuh and iju in the udmb it can be shown that enhancement of metal fertility of a porphyry system is controlled by several factors 1 the salinity of early hydrothermal ore fluids maximum ore efficiency is seen in porphyry deposits showing supersaturation of nacl in the pristine high temperature fluids e g meiduk 2 presence of co2 and fast exhausting of co2 vapor components during early stages of mineralization 3 temperature decrease especially during the main ore stage and 4 high oxygen fugacity near to the magnetite hematite oxygen buffer of the most primitive fluids in the early stages of hydrothermal system

contrasting sources of late paleozoic rhyolite magma in the polish lowlands evidence from u pb ages and hf and o isotope composition in zircon the polish lowlands located southwest of the teisseyre tornquist zone within trans european suture zone were affected by bimodal but dominantly rhyolitic magmatism during the late paleozoic thanks to the inherited zircon they contain these rhyolitic rocks provide a direct source of information about the pre permian rocks underlying the polish lowland this paper presents zircon u pb geochronology and hf and o isotopic results from five drill core samples representing four rhyolites and one granite based on the ratio of inherited vs autocrystic zircon the rhyolites can be divided into two groups northern rhyolites where autocrystic zircon is more abundant and southern rhyolites where inherited zircon dominates we suggest that the magma sources and the processes responsible for generating high silica magmas differ between the northern and southern rhyolites isotopically distinct sources were available during formation of northern rhyolites as the hf and o isotopes in magmatic zircon differ between the two analysed localities of northern rhyolites a mixing between magmas formed from baltica derived mudstone siltstone sediments and avalonian basement or mantle can explain the diversity between the zircon compositions from the northern localities daszewo and wysoka kamienska conversely the southern rhyolites from our two localities contain zircon with similar compositions and these units can be further correlated with results from the north east german basin suggesting uniform source rocks over this larger region based on the ages of inherited zircon and the isotopic composition of magmatic ones we suggest that the dominant source of the southern rhyolites is variscan foreland sediments mixed with baltica avalonia derived sediments

k feldspar phenocrysts in microgranular magmatic enclaves a cathodoluminescence and geochemical study of crystal growth as a marker of magma mingling dynamics abstract the crystallization history of zoned k feldspar phenocrysts in microgranular magmatic enclaves in the karkonosze granite sw poland reveals that the crystals grew in stirred coeval magmas of contrasting compositions the growth mechanism and crystal compositions are investigated using cathodoluminescence and profiling by electron microprobe and laser ablation icp ms these methods provide insight into the crystallization process and the varying compositions of the host melt the phenocrysts show two types of growth patterns with or without resorption interfaces the trace element distribution heterogeneous across different zones and within single phenocryst zones reflects a dynamic process of crystal growth from compositionally heterogeneous magma hybridization is also reflected in the density of structural al o al defects features that relate to coupled ba al incorporation into the crystal structure differences in structural defect densities and crystal composition trace the degree of hybridization in the granitic magma during the growth of the k feldspar phenocrysts

generation of porphyry copper deposits by gas brine reaction in volcanic arcs we acknowledge research funding from bhp billiton a benjamin meaker visiting professorship to j m and a royal society wolfson research merit award and erc advanced grant critmag to j b

neoproterozoic active margin of the sw south china block constraints from upb ages srnd isotopes and geochemical data for the gabbro and granodiorite along the ailaoshan tectonic belt abstract the yangtze block plays a crucial role in the revelation of the precambrian geology of the south china block scb a series of neoproterozoic igneous rocks have been reported along the north west and east yangtze block over the past two decades in this study gabbros and granodiorites in the south yangtze block are investigated with the aim of constraining the timing and tectonic background of the scb during the neoproterozoic representative samples for the gabbro and granodiorite yielded similar zircon u pb ages of ca 780 ma the gabbros have low nb u ratios nb ta and light rare earth element lree content and have end t values of 2 10 to 6 15 the granodiorites exhibit enrichments in th u zr hf and lree depletions in high field strength elements hfses e g nb ta and eu and end t values of 3 01 to 11 85 petrogenetic analysis of the gabbros suggests that two different mantle sources i e e morb and n morb existed in the region and the granodiorites originated from partial melting of lower continental crust with the input of mantle materials our data combined with the available geological observations show that the gabbros and granodiorites in the ailaoshan tectonic belt were generated in an active continental margin the scb was an isolated continent and continuous oceanic crust subduction occurred around it during the neoproterozoic ca 876 706 ma

u pb lu hf and ree in zircon from 3 2 to 2 6 ga archean gneisses of the repulse bay block melville peninsula nunavut abstract combined in situ u pb and lu hf isotope and ree analyses of zircons from the tonalite trondhjemite granodiorite ttg type gneisses and granitoids within the repulse bay block rbb of melville peninsula nunavut reveal that the block is composed of ca 2 86 ga and 2 73 2 71 ga granitoids that formed by reworking of a 3 25 3 10 ga basaltic crust the interpretation is supported by initial hf values for ca 2 86 ga and ca 2 73 2 71 ga gneisses of 2 7 to 0 7 and 4 8 to 2 3 respectively and the preservation of high uranium xenocrystic cores at 3 15 0 05 ga neoarchean plutonism also occurred at ca 2 69 2 66 ga and is characterized by two pyroxene bearing charnockite enderbite and hornblende biotite granitoid intrusions that yield initial hf values that range from 7 1 to 1 0 demonstrating that they were derived from juvenile magmas with significant assimilation of the existing crust the pyroxene and non pyroxene bearing granitoids also contain elevated lree in zircon a feature that is interpreted to reflect metasomatism of the source this study also demonstrates that in the rbb the results of lu hf isotopes in zircon combined with in situ u pb geochronology from inherited zircon cores differ from the results of whole rock sm nd isotopes

geology fluid inclusion and isotope constraints on ore genesis of the post collisional dabu porphyry cu mo deposit southern tibet abstract the dabu cu mo porphyry deposit is situated in the southern part of the lhasa terrane within the post collisional gangdese porphyry copper belt gpcb it is one of several deposits that include the qulong and zhunuo porphyry deposits the processes responsible for ore formation in the dabu deposit can be divided into three stages of veining stage i quartz k feldspar biotite chalcopyrite pyrite stage ii quartz molybdenite pyrite chalcopyrite and stage iii quartz pyrite molybdenite three types of fluid inclusions fis are present liquid rich two phase l type vapor rich two phase v type and solid bearing multi phase s type inclusions the homogenization temperatures for the fis from stages i to iii are in the ranges of 272 475 c 244 486 c and 299 399 c and their salinities vary from 2 1 to 49 1 1 1 to 55 8 and 2 9 to 18 0 wt nacl equiv respectively the coexistence of s type v type and l type fis in quartz of stage i and ii with similar homogenization temperatures but contrasting salinities indicate that fluid boiling is the major factor controlling metal precipitation in the dabu deposit the ore forming fluids of this deposit are characterized by high temperature and high salinity and they belong to a h2o nacl magmatic hydrothermal system the h o s pb isotopic compositions indicate that the ore metals and fluids came primarily from a magmatic source linked to miocene intrusions characterized by high sr y ratios similar to other porphyry deposits in the gpcb the fluids forming the dabu deposit were rich in na and cl derived from metamorphic dehydration of subducted oceanic slab through which nacl brine or seawater had percolated the inheritance of ancient subduction associated arc chemistry without shallow level crustal assimilation and or input of the meteoric water was responsible for the generation of fertile magma as well as co2 poor and halite bearing fis associated with post collisional porphyry deposits the estimated mineralization depths of qulong dabu and zhunuo deposits are 1 6 4 3 km 0 5 3 4 km and 0 2 3 0 km respectively displaying a gradual decrease from eastern to western gangdese deep ore forming processes accounted for the generation of giant sized qulong deposit because the exsolution of aqueous fluids with large fraction of water and chlorine in deep or high pressure systems can extract more copper from melts than those formed in shallow systems however the formation of small sized dabu deposit can be explained by a single magmatic event without additional replenishment of s metal or thermal energy in addition the ore forming conditions of porphyry cu mo deposits in gpcb are comparable to those of porphyry cu au mo deposits formed in oceanic subduction related continental or island arcs but differ from those of porphyry mo deposit formed in the dabie qinling collisional orogens the depth of formation of the mineralization and features of primary magma source are two major controls on the metal types and ore fluid compositions of these porphyry deposits

linking cu mineralization to host porphyry emplacement re os ages of molybdenites versus u pb ages of zircons and sulfur isotope compositions of pyrite and chalcopyrite from the iju and sarkuh porphyry deposits in southeast iran the kerman copper belt in iran contains a number of important porphyry copper deposits including sarkuh and iju molybdenite re os isotope dating of the sarkuh and iju porphyry copper deposits shows that mineralization occurred at 15 14 0 08 and 9 8 0 06 ma respectively compared with the previous re os dating of molybdenite in the region it is revealed that cu mineralization was an ongoing process in an arc setting during the miocene the available zircon dates of the granitic rocks from the sarkuh 15 18 0 43 ma and iju 9 27 0 50 ma porphyry copper deposits indicate that the mineralization occurred contemporaneously with the emplacement of collision related ore hosting porphyries the re content 1 715 40 ppm of molybdenite and the 34 s cdt values 0 05 of pyrite chalcopyrite from iju are consistent with its origin of sulfur and metals from a dominantly mantle source however the lower re content 302 21 ppm of molybdenite and higher 34 s cdt values 3 20 of pyrite chalcopyrite from sarkuh suggest additional contributions from crustal materials it is likely that the younger porphyry copper deposits in the kerman copper belt such as iju are related to the greater contribution of postcollisional mantle derived magmas while the older deposits e g sarkuh were formed during the collisional event at the oligocene miocene interval where the magma had some additions from the lower crustal melts generated during crustal thickening

sources and evolution of arc magmas inferred from coupled o and hf isotope systematics of plutonic zircons from the cretaceous separation point suite new zealand abstract coupled o and hf isotopic compositions of zircons from early cretaceous 113 124 ma granitoids of the separation point suite sps new zealand obtained by cathodoluminescence imaging guided micro beam methods sims la icpms are used as a record of evolving magma compositions in a prominent mesozoic arc system eight representative sps samples from individual plutons in the nelson and fiordland regions yield magmatic zircons with initial hf isotope ratios expressed in e hf ranging from 4 to 11 nelson and 5 to 12 fiordland respectively initial hf isotope ratios of zircons are extremely heterogeneous within individual samples with the vast majority of values distinctly less radiogenic than depleted mantle at 120 ma e hf 16 o isotope ratios are likewise variable with 18 o zircon smow values of 2 8 nelson and 0 7 fiordland the within rock variability in both zircon hf and o isotope ratios is testimony to open system processes that operated during magma evolution and zircon crystallisation average 18 o zircon for cores and rims allow constraints to be placed on the o isotopic composition of magmas from which zircon precipitated 18 o magma 4 8 elevated 18 o magma 6 5 require involvement of 18 o enriched supracrustal material weathered continental crust or low t seawater hydrothermally altered oceanic crust while 18 o magma 18 o depleted crustal component whole rock sr isotope nb ta and nd pb systematics are inconsistent with 18 o depleted slab melts 18 o 0 6 as a source component for sps magmas instead low 18 o values suggest incorporation of high t meteoric hydrothermally altered country rocks similar to those of the largs terrane presently exposed in northern fiordland in diagrams of sio 2 versus inferred 18 o magma the most primitive sps samples from the nelson and fiordland regions plot close to the expected composition for primitive arc magmas more evolved granitoids however show strongly divergent trends of o isotope composition as a function of sio 2 suggestive of assimilation coupled to fractional crystallisation afc in contrasting crustal environments emplacement level contamination by local crust is supported by age distributions of inherited zircons which indicate a predominance of palaeozoic and mesozoic zircons in nelson and fiordland granitoids respectively

crystallization and resorption in plutonic plagioclase implications on the evolution of granodiorite magma gesiniec granodiorite strzelin crystalline massif sw poland abstract granodiorite from the gesiniec intrusion strzelin crystalline massif sw poland contains complexly zoned plagioclases five chemically and structurally distinct zones can be correlated among crystals cores 25 35 an inner mantles 40 45 an outer mantles 40 25 an resorption zones 35 50 an and rims 35 30 an good structural and chemical major and trace elements correlation of zones between crystals indicates that zonation was produced by changes in conditions of crystallization on a magma chamber scale plagioclase being the liquidus phase records a time span from the beginning of crystallization to emplacement and rapid cooling of granodiorite as thin dykes crystallization began with the formation of inner mantles the paucity and different sizes of inner mantles suggests slow crystallization in high temperature magma normally zoned inner mantles were formed under increasing undercooling compositional trends in mantles suggest closed system crystallization the major resorption zones were caused by injection of less evolved magma as indicated by the strontium increase in plagioclase the injection triggered a rapid rise of magma and plagioclase crystals facilitating mixing but also inducing fast kinetically controlled growth of complex multiple oscillatory zonation within resorption zones the ascent of magma caused decompression melting of plagioclase and produced melt inclusions within inner mantles the cores the decompression range is estimated at a minimum of 2 kbar emplacement of granodiorite as thin dykes allow rapid cooling and preservation of magmatic zonation in plagioclases melt inclusions crystallized completely during post magmatic cooling the zonation styles of plutonic plagioclase differ markedly from volcanic ones suggesting different magma evolution zones in plutonic plagioclase are well correlated indicating crystallization in quiescent magma where crystals accumulation and compositional magma stratification may occur crystals probably did not travel between different regimes resorption occurred but as single albeit complex episodes good correlation of zones in plutonic plagioclases allows a distinction between the main processes controlling zonation and superimposed kinetic effects

tracing magma mixing in granite genesis in situ u pb dating and hf isotope analysis of zircons in situ zircon u pb and hf isotopic data have been determined for mafic microgranular enclaves and host granitoids from the early cretaceous gudaoling batholith in the liaodong peninsula ne china in order to constrain the sources and petrogenesis of granites the zircon u pb age of the enclaves 120 1 ma is identical to that of the host monzogranite 120 1 ma establishing that the mafic and felsic magmas were coeval the hf isotopic composition of the enclaves ehf t 4 5 to 6 2 is distinct from the host monzogranite ehf t 15 1 to 25 4 indicating that both depleted mantle and crustal sources contributed to their origin the depleted mantle component was not previously revealed by geochemical and nd and sr isotopic studies showing that zircon hf isotopic data can be a powerful geochemical tracer with the potential to provide unique petrogenetic information some wall rock contamination is indicated by inherited zircons with considerably older u pb ages and low initial hf isotopic compositions hafnium isotopic variations in early cretaceous zircons rule out simple crystal liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks instead mixing of mantle derived mafic magmas with crustal derived felsic magmas coupled with assimilation of wall rocks is compatible with the data

porphyry copper gold mineralization at yulong china promoted by decreasing redox potential during magnetite alteration the yulong porphyry cu au deposit occurs on the eastern margin of the tibetan plateau and is one of the largest porphyry cu au deposits in china containing more than 6 million tons of cu metal similar to other porphyry cu deposits in the world the yulong porphyry is highly oxidized sulfate is the dominant sulfur species in fluid inclusions hosted by magmatic quartz phenocrysts and no sulfide is observed indicating an oxygen fugacity above the sso buffer during magmatic processes the sulfur species changed from sulfate dominant during magmatic processes to sulfide dominant during the main mineralization processes with sulfate and sulfide mineral assemblages observed in fluid inclusions in mineralized quartz veinlets and only sulfides in the orebodies corresponding to a decrease in redox potential from the porphyry to the hydrothermal fluid magnetite crystallization was coincident with the onset of major sulfate reduction indicating that magnetite isolated trivalent iron reducing sulfate and consequently leading to the formation of porphyry cu au mineralization most porphyry cu au ore deposits are spatially associated with and genetically related to oxidized felsic magmas our results indicate that sulfate reduction promoted by magnetite crystallization is essential for the final precipitation of cu au bearing sulfides i e decreasing redox potential of the fluid is the key to and direct cause of ore formation in yulong initial high redox potential is a prerequisite for and may be an indirect indicator of most mineralization of this kind because it enables efficient transportation of cu au redox potential fluctuations can be well preserved in zircon a resistant accessory mineral commonly found in porphyries which might be developed as a handy and reliable exploration tool for porphyry cu deposits associated with magnetite

tectonic magmatic and metallogenic evolution of the tethyan orogen from subduction to collision abstract this paper reviews the tectonic magmatic and metallogenic history of the tethyan orogen from the carpathians to indochina focus is placed on the formation of porphyry cu mo au deposits as being the most characteristic mineral deposit type formed during both subduction and collisional processes in this region relatively little is known about the history of the paleotethys ocean which opened and closed between gondwana and eurasia in the paleozoic and few ore deposits are preserved from this period the neotethyan ocean opened in the permian early triassic as the cimmerian continental fragments the cores of turkey iran tibet and indochina rifted from the northern gondwana margin and drifted northwards these microcontinents docked with the eurasian margin at various points in the mesozoic and cenozoic and formed a complex archipelago involving several small back arc basins and remnants of the paleotethyan ocean the main neotethyan ocean and these smaller basins were largely eliminated by collision with india and africa arabia in the early eocene and early mid miocene respectively although neotethyan subduction continues beneath the hellenic arc and the makran the majority of porphyry type deposits are found in association with neotethyan subduction mainly in the mesozoic and paleogene and syn to post collisional events in the mid paleogene to neogene they are found throughout the orogen but some sections are particularly well endowed including the carpathians balkans rhodopes eastern turkey lesser caucasus nw iran se iran sw pakistan southern tibet and se tibet indochina other sections that appear barren may reflect deeper levels of erosion young sedimentary cover or lack of exploration although there may also be real reasons for low prospectivity in some areas such as minimal subduction e g the western mediterranean region or lithospheric underthrusting as proposed in western tibet over the last decade improved geochronological constraints on the timing of ore formation and key tectonic events have revealed that many porphyry deposits that were previously assumed to be subduction related are in fact broadly collision related some forming in back arc settings in advance of collision some during collision and others during post collisional processes such as orogenic collapse and or delamination of subcontinental mantle lithosphere while the formation of subduction related porphyries is quite well understood collisional metallogeny is more complex and may involve a number of different processes or sources these include melting of orogenically thickened crust previously subduction modified lithosphere including metasomatized mantle underplated mafic rocks or lower crustal arc plutons and cumulates or upwelling asthenosphere e g in response to delamination slab breakoff back arc extension or orogenic collapse the most fertile sources for syn and post collisional porphyry deposits appear to be subduction modified lithosphere because these hydrated lithologies melt at relatively low temperatures during later tectonomagmatic events and retain the oxidized and relatively metalliferous character of the original arc magmatism unusually metallically enriched lithospheric sources do not seem to be required but the amount of residual sulfide phases in these rocks may control metal ratios e g cu au in subsequent magmatic hydrothermal ore deposits relatively au rich deposits potentially form in these settings as observed in the carpathians e g rosia montan turkey kisladag copler and iran sari gunay dalli although the majority of syn and post collisional porphyries are cu mo rich and resemble normal subduction related deposits e g in the gangdese belt of southern tibet this similarity extends to the associated igneous rocks which being derived from subduction modified sources largely retain the geochemical and isotopic character of those original arc magmas while still retaining a broadly calc alkaline character these rocks may extend to mildly alkaline shoshonitic compositions and may display adakite like trace element signatures high sr y and la yb ratios reflecting melting of deep crustal garnet amphibolitic sources but they are otherwise hard to distinguish from normal subduction related magmas small post collisional mafic alkaline volcanic centers are common throughout the orogen but for the most part appear to be barren however similar rocks in other post subduction settings around the world are associated with important alkalic type porphyry and epithermal au cu deposits and the potential for discovery of such deposits in the tethyan orogen should not be overlooked

emplacement depth and carbon dioxide rich fluid inclusions in intrusion related gold deposits phanerozoic intrusion related gold deposits have many consistent characteristics such as a spatial temporal and geochemical association with moderately reduced predominantly ilmenite series i type intrusions the deposits exhibit a range of characteristics that vary over a wide range of emplacement depths 7 km deposits in shallow crustal settings 5 km have characteristics of mesothermal environments and are hosted by plutons containing sheeted veins greissen and disseminated gold fluid characteristics also vary with depth deposits in shallow environments contain high temperature 350 c immiscible brine 30 wt nacl equiv and low salinity 5 wt nacl equiv vapor that commonly contains carbon dioxide deposits in deeper environments contain abundant low salinity carbon dioxide rich aqueous fluids 10 wt nacl equiv that in some deposits are postdated by moderate to high salinity brines 10 40 wt nacl equiv these contrasting fluid types are interpreted to be magmatic in origin and are the result of the complex interplay between exsolution of different volatiles carbon dioxide water and chlorine from felsic magmas emplaced at different crustal levels experimental studies have shown that carbon dioxide will exsolve from felsic magmas at much higher pressures than water and chlorine due to its lower solubility in the melt thus deposits formed from felsic magmas in deeper environments will contain abundant carbon dioxide rich fluids subsequent fluids released from the magma are likely to be water rich and more saline felsic magmas in shallow environments will contain lower concentrations of carbon dioxide that will partition into the vapor phase during phase separation between brine and vapor

pb isotopes during crustal melting and magma mingling a cautionary tale from the miki fjord macrodike central east greenland abstract pb isotopic data are presented for hybrid rocks formed by mingling between mantle derived tholeiitic magma of the eocene miki fjord macrodike east greenland and melt derived from the adjacent precambrian basement bulk mixing and afc processes between end members readily identified in the field fail to model the pb isotope systematics selective contamination during diffusional exchange which can explain the complex sr and nd isotope compositions of the hybrid rocks blichert toft et al 1992 cannot fully account for the variability of the pb isotopic data using the identified crustal end members the crustal anatectic end member although similar in sr and nd isotope composition has a markedly different pb isotopic composition than its source gneiss the differences are consistent with preferential incorporation of radiogenic pb from accessory phases such as metamict zircon or loosely bound pb from grain boundaries during disequilibrium melting of the host rock by the mafic magma the crustal melt involved in magma interactions was therefore heterogeneous with respect to pb isotopes on a metre scale these results illustrate the difficulties inherent in interpreting isotopic variations in contaminated mafic magmas even when the end members are well constrained by field relations we show that the pb isotopic composition of the crustal contaminants and contamination trajectories for the miki fjord hybrid magmatic lithologies are markedly different from regional basement gneisses and contaminated lavas of the associated flood basalt province that were contaminated by characteristically unradiogenic pb and sr lithologies resembling lewisian basement not exposed locally

insights into magmatic evolution and recharge history in capraia volcano italy from chemical and isotopic zoning in plagioclase phenocrysts plagioclase phenocrysts in dacites from the high k calc alkaline capraia volcano were investigated for major trace element and sr isotope variations in order to gain better insight into the proposed open system behaviour of the volcano repeated dissolution zones in plagioclases from the early erupted monte castello mc and later monte rucitello mr dacitic units are associated with a sharp increase in an content and variation in isotopic compositions 87sr 86sr 0 70872 0 71004 which argue for repeated magma mixing in particular petrographic and mineralogical evidence suggest that recharge with hot basaltic magma occurred repeatedly during the lifetime of the capraia volcanic system we attempted to correlate shared crystallization and resorption histories using chemical mol an fe and sr isotopic zoning in plagioclase in this correlation framework the observed mismatch between chemical and isotopic data in some phenocrysts is interpreted to reflect either growth of phenocrysts in a separate magma chamber or compositional zoning within a single magma chamber a minor role of crustal contamination is inferred instead the intra crystal variations in isotopic composition in plagioclase reflect the existence of distinct components that may have thoroughly mixed at the end of the mc plagioclase growth history the dominant radiogenic component is similar to lamproites occurring in tuscany recharge with this component occurred throughout the genesis of the mr dacites but was restricted to the early growth history of the mc dacites the mr plagioclases are inferred to have crystallized from separate more differentiated batches of magma that were likely to have evolved at the top of a zoned magma reservoir decrease in the an content after most dissolution zones in all phenocrysts and low temperature estimates from zircon saturation thermometry 800 c also emphasize the importance of crystal fractionation during the evolution of the volcano in agreement with the occurrence of a significant amount of rhyolitic material thus it is inferred that a rather large magma chamber may have existed during the first cycle of eruptive activity

metal content and p t evolution of co2 bearing ore forming fluids of the haftcheshmeh cu mo porphyry deposit nw iran abstract the haftcheshmeh cu mo porphyry deposit is located in the nw part of the arasbaran metallogenic magmatic zone nw iran ore mineralisation is generally hosted within the gabbro diorite and granodiorite porphyry stocks presenting various types of hydrothermal quartz veins and veinlets associated with potassic to sericitic alteration stage i corresponds to barren quartz k feldspar biotite anhydrite veins a veins with minor metal sulphides pyrite chalcopyrite surrounded by k feldspar and biotite halos related to potassic alteration stage ii is described with quartz molybdenite chalcopyrite pyrite bornite magnetite hematite biotite veins predominantly occurring in the potassic alteration halos b veins stage iii shows pyrite quartz chalcopyrite molybdenite galena sphalerite associated with sericitic alteration halos d veins the coexistence of halite saturated aqueous rich and low salinity vapour rich fluid inclusions in the h2o nacl co2 system is evidence of fluid boiling in each alteration mineralising stage this process was subsequently followed by meteoric water input diluting the co2 bearing ore forming fluid la icpms data of fluid inclusions associated with the successive stages reveal elevated na k fe mn cu and mo content the metal content of fluid inclusions of stages ii and iii is in large part due to accidentally trapped minerals molybdenite and chalcopyrite started precipitating between stages i and ii from a metal poor fluid the long duration 1 ma of the magmatic hydrothermal activity and associated co2 fluxes and repeated fluid boiling events lead to ore deposition at temperatures of 450 to 250 c and at depths between 3 0 and 1 0 km from near lithostatic to near hydrostatic conditions

paleoclimate proxies for cyclostratigraphy comparative analysis using a lower triassic marine section in south china abstract multiple proxies for paleoclimatic and paleoenvironmental change within sedimentary sequences have been developed but understanding their relationships and their relative strengths or weaknesses are required to access a wealth of untapped paleoclimate information we propose two main criteria for multiple proxy datasets to estimate their individual signal to noise levels and to decipher the relationship between multiple proxies first for proxies affected by similar processes then their time dependent changes should be similar second a paleoclimate proxy that is more sensitive to an external forcing such as astronomical forcing is more useful than those that do not have such a response we introduce two methods to evaluate these criteria 1 hierarchical cluster analysis hca probes the relationships among multiple proxies based on similarities of their oscillation patterns and 2 power decomposition analysis pda tests proxy sensitivity to external climate forcing we evaluate 16 high resolution paleoclimate proxies in detail for their applications in paleoclimatology from the marine lower triassic daye formation at the daxiakou section in the three gorges region of south china which has carbonate claystone cycles deposited on an outer ramp the proxies are spectral gamma ray gamma ray intensity potassium uranium thorium thorium uranium and thorium potassium rock color lightness l redness a and yellowness b magnetic susceptibility measured in both laboratory and outcrop anhysteretic remanent magnetization arm lithologic rank simplified lithologic rank and non carbonate fraction carbonate thickness and couplet thickness hierarchical cluster analysis hca gathers these proxies into groups likely affected by the same process the arm and thorium uranium proxies seem to reflect the hinterland weathering process during the early triassic gamma ray potassium uranium thorium magnetic susceptibility and non carbonate fraction proxies refer to terrestrial input the l a and lithologic rank proxies indicate the productivity the redox state and the relative sea level respectively at this section this case study contributes to the understanding of the sensitivity of these types of proxies within marine strata for deep time paleoclimate and astronomical tuned time scales

frequency modulation reveals the phasing of orbital eccentricity during cretaceous oceanic anoxic event ii and the eocene hyperthermals abstract major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods amplitudes and phases of the milankovitch cycles of precession obliquity and eccentricity while numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data limitations in radioisotopic dating and instability of the theoretical astronomical solutions beyond 50 myr ago can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies here we demonstrate that interference patterns accompanying frequency modulation fm of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data one and two dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the fm method and indicate that pristine eccentricity fm can be readily distinguished in paleo records apart from paleoclimatic implications the fm approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions and for refining chronologies for the deep past we present two case studies that use the fm approach to evaluate major carbon cycle perturbations of the eocene and late cretaceous interference patterns in the short eccentricity band reveal that eocene hyperthermals etm2 elmo h2 i1 and etm3 x 52 54 myr ago were associated with maxima in the 405 kyr cycle of orbital eccentricity the same eccentricity configuration favored regional anoxic episodes in the mediterranean during the middle and late cenomanian 94 5 97 myr ago the initial phase of the global oceanic anoxic event ii oae ii 93 9 94 5 myr ago coincides with maximum and falling 405 kyr eccentricity and the recovery phase occurs during minimum and rising 405 kyr eccentricity on a myr scale the event overlaps with a node in eccentricity amplitudes both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times

increased magmatic water content the key to oligo miocene porphyry cu mo au formation in the eastern gangdese belt tibet the eastern gangdese magmatic belt between 88 e and 94 e in southern tibet preserves a series of cenozoic collision related igneous rocks that have formed since the start of the india asia collision at 55 to 50 ma the paleocene eocene intrusive rocks have intermediate la yb n ratios average 12 0 8 6 n 150 range 1 15 64 0 intermediate to low sr y ratios mostly 40 and weak or absent eu anomalies oligocene average eun eu 0 99 0 27 n 35 range 0 67 1 58 miocene average eun eu 0 95 0 13 n 93 range 0 44 1 46 and their mineralogy consists mainly of plagioclase quartz and amphibole as phenocrysts these geochemical and mineralogical characteristics suggest that the paleocene eocene magmas were relatively dry and evolved primarily by fractionation of pyroxene and plagioclase whereas the oligo miocene magmas were more hydrous and fractionated significant amounts of hornblende and lesser plagioclase prior to upper crustal emplacement oligocene and miocene magmatic rocks crop out as small volume intrusions and are associated with several large to giant sized porphyry cu mo au deposits as well as numerous smaller porphyry and skarn deposits in contrast earlier more voluminous paleocene eocene magmatism is only known to be associated with three small porphyry deposits erosional loss of subvolcanic porphyry systems from the older paleocene eocene sequence is not thought to be a controlling factor in this temporal difference of porphyry deposit distribution because exhumation rates after 55 ma were relatively low and coeval linzizong volcanic rocks are extensively preserved in the gangdese belt instead we suggest that differences in magmatic history and petrogenesis led to this restricted temporal distribution of porphyry deposits the paleocene eocene magmas were generated during the onset of collision between india and asia and were triggered by rollback of the neo tethyan oceanic slab this magmatism records the final stage of subduction of oceanic lithosphere beneath southern tibet and the relatively low water contents of these magmas may reflect final dehydration of the remnant neo tethyan slab after oceanic slab breakoff at 40 to 38 ma the greater india slab began to subduct beneath the gangdese belt until hard collision with the indian continent at 35 ma and breakoff of the greater india slab at 25 to 10 ma this last event is suggested to have caused asthenospheric mantle upwelling and partial melting of subduction modified hydrated tibetan lithosphere the resultant partial melts may have remobilized metals residual in the deep lithosphere from previous arc magmatism giving rise to a suite of postsubduction porphyry type ore deposits in the oligo miocene

recycling of orogenic arc crust triggers porphyry cu mineralization in kerman cenozoic arc rocks southeastern iran pre collisional eocene oligocene arc diorites quartzdiorites granodiorites and volcanic equivalents in the kerman arc segment in central iran lack porphyry cu mineralization and ore deposits whereas collisional middle late miocene adakite like porphyritic granodiorites without volcanic equivalents host some of the world s largest cu ore deposits petrological and structural constraints suggest a direct link between orogenic arc crust evolution and the presence of a fertile metallogenic environment ore hosting kuh panj porphyry intrusions exhibit high sr 400 ppm low y 20 no negative eu anomalies eu eu 1 and relatively non radiogenic sr isotope signatures 87sr 86sr 0 7042 0 7047 relative to eocene oligocene granitoids mainly sr 12 la yb 15 eu eu 1 87sr 86sr 0 7053 0 7068 trace element modeling indicates peridotite melting for the barren eocene oligocene intrusions and a hydrous garnet bearing amphibolite source for middle late miocene ore hosting intrusions the presence of garnet implies collisional arc crustal thickening by shortening and basaltic underplating from about 30 35 to 40 45 km or 12 kbar the changes in residual mineralogy in the source of eocene to miocene rocks in the kerman arc segment reflect probing of a thickening arc crust by recycling melting of the arc crustal keel underplating of cu and sulfur rich melts from fertile peridotite generated a fertile metallogenic reservoir at or near the crust mantle boundary and dehydration melting under oxidizing conditions produced syn and post collisional ore hosting intrusions while the lack of post collisional volcanism prevented the venting of volatiles to the atmosphere from sulfur rich and oxidized adakitic magmas

u pb geochronology and sm nd isotopic composition of proterozoic gneisses channel islands uk gneissic units of the channel islands united kingdom have traditionally been considered to be palaeoproterozoic basement to the late neoproterozoic cadomia terrane based on lithological correlations and imprecise or ambiguous isotopic data a new precise u pb date of 2061 2 ma based on analyses of single zircons for the icart granitic orthogneiss of guernsey confirms a palaeoproterozoic age of its igneous protolith the nd depleted mantle model age t dm of this gneiss is 2220 ma only slightly older than its crystallization age indicating that it represents juvenile crust other gneisses from guernsey have similar t dm ages ranging from 2210 to 2370 ma suggesting that they are also exposures of juvenile palaeoproterozoic crust a component from a penetratively deformed orthogneiss from sark previously correlated with icartian gneisses on guernsey yields a u pb zircon date of 616 4 2 ma this crystallization age demonstrates that the protolith was a cadomian intrusion and that penetrative deformation and amphibolite facies metamorphism in the northern channel islands were cadomian in age the use of gneissic features as a means of invoking the antiquity of many other undated gneissic units in the region is thus considered unreliable the presence of 2170 7 ma zircon xenocrysts within the sark orthogneiss combined with its initial e nd 615 9 5 are strong evidence that pre cadomian basement was a significant source component and that documenting the extent and age of pre cadomian basement may be possible by indirect geochemical methods

cretaceous tertiary convergence and continental collision sanandaj sirjan zone western iran abstract the sanandaj sirjan zone contains the metamorphic core of the zagros continental collision zone in western iran the zone has been subdivided into the following from southwest to northeast an outer belt of imbricate thrust slices radiolarite bisotun ophiolite and marginal sub zones which consist of mesozoic deep marine sediments shallow marine carbonates oceanic crust and volcanic arc respectively and an inner complexly deformed sub zone late palaeozoic mesozoic passive margin succession rifting and sea floor spreading of tethys occurred in the permian to triassic but in the sanandaj sirjan zone extension related successions are mainly of late triassic age subduction of tethyan sea floor in the late jurassic to cretaceous produced deformation metamorphism and unconformities in the marginal and complexly deformed sub zones deformation climaxed in the late cretaceous when a major southwest vergent fold belt formed associated with greenschist facies metamorphism and post dated by abundant palaeogene granitic plutons in the southwest of the zone a late cretaceous island arc passive margin collision occurred with ophiolite emplacement onto the northern arabian margin similar to that in oman final closure of tethys was not completed until the miocene when central iran collided with the northeast arabian margin

the isotopic composition of yb and the precise and accurate determination of lu concentrations and lu hf ratios by isotope dilution using mc icpms 1 we report yb isotopic data for the purpose of accurately correcting measurements of lu and lu hf ratios during multicollector inductively coupled plasma mass spectrometer mc icpms analysis the yb isotopic ratios agree with recent results of chu et al 2002 and amelin and davis 2004 when corrected for mass fractionation to the same reference values protocols for lu measurement involving simultaneous subtraction of yb interference and application of a fractionation correction based on yb are described it is shown that lu concentrations and lu hf ratios determined by mc icpms using this methodology are more precise and potentially more accurate than results based on analysis of lu by thermal ionization mass spectrometry tims a number of mc icpms lu hf isotopic analyses of standard rocks and other geological samples previously analyzed by tims are presented these document reproducibility of lu hf within 0 2 where most discrepancies can be assigned to the unknown lu mass fractionation during tims analysis

minor and trace element zoning in plagioclase implications for magma chamber processes at parinacota volcano northern chile textural and compositional zoning in plagioclase phenocrysts in a sample from parinacota volcano chile was investigated using backscattered electron images and electron microprobe analysis of major and trace elements large 2 mm oscillatory zoned crystals type i with resorption surfaces of moderate an discontinuities 10 an and decreasing trace element contents sr mg ti towards the rim reflect melt differentiation and turbulent convection in the main magma body early recharge with a low sr mafic magma is seen in the core small scale sr variations in the core indicate limited diffusion and thus residence and differentiation times of the magma shorter than a few thousand years smaller crystals type ii with low trace element an ratio reflect the influence of an h2o rich melt probably from a differentiated boundary layer closed system in situ crystallisation mafic magma recharge and the role of a water rich differentiated boundary layer can be distinguished from the an trace element relationships crystals apparently move relatively freely between different parts and regimes in the magma chamber evidence for convective crystal dispersion high sr type ii crystals indicate an earlier input of sr rich mafic magma recharge of two distinct mafic magma types is thus identified high sr and low sr which must have been present at increasing recharge rates with time in the plumbing system throughout the volcano s history

new perspectives on orbitally forced stratigraphy this survey of the current status of research into earth s orbitally forced paleoclimatic record summarizes recent developments in the theory of earth s orbital parameters and reviews how various techniques of data collection and analysis have fared in the search and recovery of orbital signals in ancient stratigraphy the emerging significance of the quasi periodicity of earth s orbital variations as a prin cipal tool in the analysis of orbitally forced stratigraphy is discussed in detail five case studies are presented that illustrate new directions in research a time series analysis of discontinuous strata b measurement of ultra high resolution stratigraphic signals c new perspectives on the 100 kyr pleistocene glaciation problem d strati graphic evidence for solar system resonance modes and e evaluating phanerozoic length of day from orbitally forced stratigraphy the study of how earth s orbital parameters came to be recorded in ancient stra tigraphy has recently moved into a new phase of scientific inquiry and discovery notable advances in celestial mechanics and in the analysis of stratigraphic data have given rise to new ways of solving old problems and have uncovered new problems for the first time new tools have facilitated the recovery of extended high resolution orbital signals from stratigraphy advanced analytical techniques have now been fully incorporated into the field an updated theory of earth s orbital parameters provides an accurate ephemeris for the past 16 million years for precision correlation between earth s orbital parameters and orbitally forced stratigraphy some orbital eccentricity modes can be used for orbital stratal cal ibrations to several hundred million years ago these breakthroughs have transformed the study of orbitally forced stratigra phy into an applied field that addresses long standing problems in disciplines as far ranging as geochronology geodynamics and astrodynamics orbital signals provide the framework for a high resolution orbital chronostratigraphy as far back