40ar 39ar constraints on a temporal link between gold mineralization magmatism and continental margin transtension in the jiaodong gold province eastern china abstract the jiaodong gold province is the largest gold repository in china both mineralization and granitoid hosts are spatially related to the crustal scale tan lu strike slip fault system which developed along the mesozoic continental margin in eastern china a series of 40ar 39ar laser incremental heating analyses of hydrothermal sericite muscovite from three major gold deposits jiaojia xincheng and wangershan and igneous biotite from the granodiorite hosts were performed to establish a possible temporal link between gold mineralization magmatism and movement along the tan lu fault zone magmatic biotite crystals yield well defined and concordant plateau ages between documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewco

geochemistry and geochronology of zircons from granite hosted gold mineralization in the jiaodong peninsula north china implications for ore genesis abstract large scale quart vein and structurally controlled gold mineralization is intensely developed in the jiaodong peninsula north china craton and is typified by the linglong and jiaojia deposits respectively in this work zircons from typical gold bearing ores of the sanshandao northern sea sns jiuqu jq and canzhuang cz gold deposits were compared in terms of texture u pb age trace element content and hf isotopic signatures in order to discern whether zircon from ore samples can be used as an indicator of ore genesis and grade most studied zircons are magmatic in origin with a hydrothermal overprint i e zircons with core rim assemblages fractured dissolution textures and hydrothermal activity related fluid mineral inclusions three zircon age clusters were differentiated 120 ma 150 ma and 2000 ma the 120 ma zircons show evidence of hydrothermal alteration dark in cathodoluminescent images with hydrothermal rim textures and are characterized by high lree p ti and ehf t 21 to 15 and young tdmc 2100 2500 ma this suggests an interaction between the mantle and crust at the magma source and that a p ti rich al poor high temperature high fo2 wet late stage residual granitic melt and intense hydrothermal alteration played an important role in the formation of gold mineralization the 150 ma zircons have high y nb ta and u contents low ehf t 26 to 20 and old tdmc 2300 3000 ma ages and hree enriched patterns with pronounced ce and eu anomalies these features indicate a reduced cool and al rich magma which did not favor gold mineralization even though it was highly evolved this also implies that the degree of magma differentiation is not the key factor that led to gold mineralization in the jiaodong gold province the 2000 ma zircons are primarily limited to gold ores with high pb contents hree enriched patterns and variable ce and eu anomalies indicating that they were inherited from the paleoproterozoic 2000 2200 ma basement in addition the sns high grade ores yielded zircon with the greatest u pb age range mainly 110 180 ma and the most pronounced hydrothermal overprinting indicating that large scale mineralization resulted from multi stage granitic intrusion with intense fluid dissolution and metasomatism this research highlights that correlations between zircon age populations hf isotope signatures internal structures and trace element patterns can provide insights into ore genesis and fluid evolution in gold mineralization systems

the age isotopic signature and significance of the youngest mesozoic granitoids in the jiaodong terrane shandong province north china craton abstract most cretaceous granitoids in the jiaodong terrane of shandong province north china craton were intruded between 130 and 122 ma however four granitoid batholiths are significantly younger with an average zircon u pb shrimp emplacement age of 116 2 ma these are the sanfoshan batholith 118 1 ma the aishan batholith 116 1 ma the yashan pluton 113 2 ma and the laoshan batholith 115 2 ma these granitoids post date proposed delamination that occurred prior to 125 ma in the eastern ncc and their geochemistry thus provides information about the nature of the continental crust at this time the rocks are mostly monzogranites and syenogranites of i type affinity with local alkali feldspar granite of a type affinity in addition a monzogranite sample from the aishan batholith records an age of 125 3 ma indicating a direct association with the slightly older granitoids in the area indeed they all contain inherited zircons with ages of 125 120 ma indicating interaction with these earlier granitoids most samples are metaluminous enriched in light rare earth elements and depleted in high field strength elements paleo to neoarchean t dm2 model ages ranging from 3900 ma to 2491 ma and negative e hf t values imply the involvement of archean basement and older recycled continental crustal material in the magma source region they were likely derived from partial melting of the lower or middle crust due to mafic magma underplating followed by various degrees of interaction between mantle derived mafic magma and felsic crustal magma accompanied by fractional crystallization we propose that lithospheric thinning and extension in the early cretaceous due to roll back of the pacific plate beneath the eastern north china craton led to asthenospheric upwelling and basaltic magmatism this underplating in turn led to crustal melting and evolution of the granitic intrusions described here

gold hosting high ba sr granitoids in the xincheng gold deposit jiaodong peninsula east china petrogenesis and tectonic setting abstract the xincheng deposit is the only large gold deposit with a proven reserve of 200 t gold hosted by the early cretaceous granitoids in northwest jiaodong peninsula east china the granitoids hosting this ore deposit comprise an inner medium to fine grained quartz monzonite and an outer medium to coarse grained monzogranite with distinctive k feldspar megacrysts la icp ms zircon dating yields u pb ages of 128 1 to 132 1 ma and 127 2 to 129 1 ma for the quartz monzonite and the monzogranite respectively the early cretaceous ages obtained in our study are comparable with the 126 130 ma age range reported for the guojialing granitic suite the monzogranites typical high ba sr granites possess high sio2 70 89 73 35 k2o 3 85 4 32 total alkalis k2o na2o 8 08 8 68 sr 634 888 ppm ba 1395 2111 ppm and lree 59 43 145 88 with low hree and hfse contents and insignificant eu anomalies the rocks display markedly high sr y 114 297 and la yb n 20 79 ratios they have low mgo 0 23 0 62 cr 0 4 8 33 ppm and ni 0 47 2 92 ppm contents the typical high ba sr signatures of the outer acidic monzogranites are also shared by the inner intermediate acidic quartz monzonites with a relatively higher abundance of these elements the plagioclases in the quartz monzonites and monzogranites are oligoclase andesine with an contents of 11 7 44 5 and oligoclase with an contents of 12 9 29 3 respectively which both show the reverse zoning texture the quartz monzonites have zircon ehf t values of 21 3 to 13 9 average 18 7 which are less negative and show larger variations than those of the monzogranites ehf t 24 7 to 18 1 average 19 5 detailed elemental mineralogical and isotopic data suggest that the high ba sr quartz monzonites and monzogranites were most likely generated by partial melting of the basement rocks of the jiaobei terrane accompanied by crustal assimilation with minor addition of the intermediate magma derived from the partial melting of juvenile mafic lower crust formed by the earlier underplating of mantle magma and the quartz monzonites may represent the path of intermediate magma inputting into felsic magma in combination with previous investigations we suggest subduction of the paleo pacific slab beneath the north china craton ncc and associated asthenosphere upwelling were most likely the mechanism associated with the generation of the high ba sr granites

timing duration and role of magmatism in wide rift systems insights from the jiaodong peninsula china east asia in east asia widespread extensional sedimentary basins together with the close association of metamorphic core complexes and magmatism are prominent features of the large scale wide rift system developed during late mesozoic times this region thus appears as a proper place to study continental extension as well as questions about the link between continental extension and magmatism this paper primarily provides pioneer exhumation time constraints on the linglong mcc jiaodong peninsula including cooling and deformation ages mcc cooling at mid crustal levels occurred at ca 143 ma besides last ductile deformation occurred at ca 134 ma while final exhumation stages under brittle 2 conditions occurred as late as ca 128 ma continuous crustal stretching were then recorded by the emplacement of a synkinematic pluton in the upper crust at ca 128 ma that cooled fast below an intracrustal shear zone crossing the ductile brittle transition at ca 123 ma the ca 120 118 ma age cluster is ascribed to the fast cooling of undeformed plutons marking the end of extension that lasted in the area over a minimum period of ca 30 my combining other mcc exhumation constraints and the onset of subsidence in the sedimentary basins total duration of late mesozoic extension in east asia could be estimated at ca 60 my related with a rather long process for extension from 160 to at least 100 ma east asian continental extension is heterogeneously distributed in space and time as revealed by fundamental differences between two end member classes of migmatite cored mcc already described in other wide rift systems extension seems to have first favoured partial melting which subsequently in turn maintained continental extension

sulfide mineralogy in the polymetallic cassiterite deposits of dachang p r china several important mineral deposits of sn zn cu pb and other metals associated with devonian sediments and yanshanian cretaceous granitic rocks are known in the dachang district guangxi early genetic hypotheses related the origin of the deposits entirely to the yanshanian granites recently it was suggested that in devonian times an earlier syngenetic metal concentration may have occurred later overprinted by the yanshanian metallogeny this contribution is aimed at placing constraints on the physicochemical conditions during the yanshanian ore formation remobilization by studying the sulfide chemistry arsenopyrite sphalerite stannite and fluid inclusion data on the two major deposits in the area i e the polymetallic cassiterite deposit of changpo and the zn cu skarn deposit of lamo sphalerite and arsenopyrite are quite abundant in both deposits stannite is minor but fairly widespread at changpo and quite rare at lamo they are accompanied by pyrite pyrrhotite galena chalcopyrite cassiterite fluorite and a large variety of other sulfides and sulfosalts the main compositional data for sphalerite and arsenopyrite are summarized as follows

rb sr sm nd and pb isotope systematics of pyrite implications for the age and genesis of lode gold deposits lode gold deposits commonly consist of pyrite and lesser amounts of lead and zinc sulfides accompanied by quartz and calcite their exact origin remains controversial mainly because of the scarcity of reliable geochronological data here we present direct rb sr dating of pyrite from a lode gold deposit and propose the method as a useful geochronological technique for gold mineralization for which age data are poor a positive correlation between present day 87 sr 86 sr and 87 rb 86 sr ratios of pyrite fes 2 subsamples from the linglong gold mine of china corresponds to an age of 122 123 ma which dates the age of gold mineralization the sr nd and pb isotopic compositions of pyrites and the associated rocks suggest that the hydrothermal fluids responsible for the pyrite and gold mineralization were probably derived from a mixed source i e degassing of mafic magmas and meteoric water that had leached the country rocks

nature age and tectonic setting of granitoid hosted orogenic gold deposits of the jiaodong peninsula eastern north china craton china the jiaodong gold province along the southeastern margin of the north china craton has combined production and resources of 900 tonnes of gold more than 95 of the gold in this province is hosted in mesozoic granitoids which intruded late archean metamorphic basement rocks episodically at ca 160 150 and 130 126 ma the deposits of the jiaodong peninsula form one of the largest provinces of granitoid hosted lode gold deposits in the world the jiaodong gold deposits occur as massive auriferous quartz veins hosted in subsidiary second or third order faults and as disseminated and stockwork style mineralization hosted in alteration zones along major regional scale faults mineralization took place during brittle reactivation d3 of pre existing d2 ductile shear zones wall rock alteration is dominated by k feldspar and sericite with also sulfide minerals and extensive silicification closest to the orebodies the alteration was accompanied by the introduction of volatiles fe mg k rb ag as au bi and sb enrichment of base metals in the gold lodes is generally low although locally significant gold deposition took place at temperatures of 250 to 350 c for most gold deposits and the ore fluids are co2 bearing and have calculated salinities of 6 13 wt nacl equiv deposits from the zhao ye xixia and muping rushan belts have similar if not identical structural controls alteration patterns ore mineral assemblages and stable isotope signatures lead isotope data indicate that the ore stage leads were buffered by their host rocks the granitoid hosted gold deposits in the zhao ye belt are most radiogenic the greenstone hosted deposits in the xixia belt is the least radiogenic and the granitoid hosted deposits in the muping rushan belt have intermediate compositions gold mineralization in the zhao ye xixia and muping rushan belts in the jiaodong gold province appears to be broadly contemporaneously at ca 130 120 ma as constrained by shrimp u pb zircon dating on host rocks and a post gold dike as well as by ar ar rb sr and k ar dating of hydrothermal alteration minerals and ores this early cretaceous age is about 100 million years younger than the peak of ultra high pressure metamorphism in the qinling dabie sulu orogen between the north china and yangtze cratons and about 500 km south of the gold province however it overlaps with the extension and exhumation stage of the collisional orogeny and the subduction of the pacific plate beneath the eurasian continental crust whereas the majority of the jiaodong gold deposits occur on the margin of the north china craton some also occur in the suture zone between the two cratons they are significantly landward relative to the subduction zone of the pacific plate compared with typical orogenic lode gold deposits globally lode gold deposits of ca 130 120 ma occurred on both sides of the tan lu fault zone available data favor a temporal link of gold mineralization with pacific plate subduction

an experimental study of trace element partitioning between zircon and melt as a function of oxygen fugacity abstract the partitioning of p sc ti sr y nb the rare earth elements ree hf ta th and u between zircon and a synthetic andesitic melt was determined as a function of oxygen fugacity f o 2 over a range of fourteen log units from qfm 8 to qfm 6 where qfm is the quartz fayalite magnetite oxygen buffer at 1300 c and 1 atm using sims and la icp ms the partition coefficients of ce and eu were found to vary systematically with f o 2 relative to those of the other ree producing ce and eu anomalies similar to those that are characteristic of natural igneous zircon these anomalies coexist at terrestrial f o 2 s and were used to quantify eu 3 eu 2 eu 3 and ce 4 ce 3 ce 4 in the melt the partition coefficients of the redox invariant trivalent cations are in excellent agreement with lattice strain theory the values of d ree are related to those determined for natural samples by the expected dependence on temperature the incorporation of ree 3 in zircon was independent of the presence of p d u d th was found to vary systematically with f o 2 indicating the presence of u 4 u 5 and u 6 in the melt at terrestrial conditions d ti was independent of f o 2 despite an expectation of significant ti 3 in the most reduced experiments

contrasting origins of late mesozoic adakitic granitoids from the northwestern jiaodong peninsula east china implications for crustal thickening to delamination two suites of granitoids the late jurassic 158 3 ma linglong suite and the early cretaceous 130 126 ma guojialing suite crop out in the northwestern jiaodong peninsula eastern china the linglong suite is a monzogranite comprising alkali feldspar plagioclase quartz and fe rich biotite the guojialing suite includes at least five plutonic bodies of both granodiorite and monzo granite the rocks are composed of plagioclase alkali feldspar quartz mg rich amphibole and mg rich biotite both the linglong and guojialing suites have adakitic affinity they are enriched in lree with high la yb ratios and show positive eu anomalies the rocks are also enriched in lile and depleted in hfse with high sr y ratios the linglong granite shows very uniform sr nd isotopic compositions with initial 87 sr 86 sr ratios of 0 7119 0 7126 and e nd t values of 21 3 to 21 6 which are similar to those of the local neoarchaean basement the guojialing suite has variable initial 87 sr 86 sr ratios 0 7108 0 7120 and e nd t values 10 8 to 17 2 which are distinct both from those of the neoarchaean basement and from those of the local enriched lithospheric mantle inferred from the coeval mafic dykes in the studied area detailed petrological and geochemical data indicate that the linglong suite was derived by partial melting of neoarchaean metamorphic lower crustal rocks at depth of 50 km with a eclogite residue whereas the guojialing suite was formed by the reaction of delaminated eclogitic crust derived melt with the upwelling asthenospheric mantle the petrogenesis of these two contrasting adakitic granitoids suggests intensive lower crustal delamination during early cretaceous times following a crustal thickening process from the late stage of the early jurassic to early stage of the late jurassic with crustal thickness of 50 km respectively

holocene river dynamics in northland new zealand the influence of valley floor confinement on floodplain development abstract valley floor mapping sedimentology and 14c dating have been used to reconstruct the fluvial history at eight floodplain sites spread throughout northland a region removed from the main areas of tectonic and volcanic activity in new zealand we present a probability based record of holocene river behaviour for northland using 14c dated holocene fluvial deposits and compare this with independent palaeoclimate proxy records from the north island holocene floodplain evolution and fluvial behaviour have been conditioned by the degree of valley floor confinement in the most and least confined valley settings holocene floodplain evolution has involved the development of a single floodplain surface at partly confined sites the river terrace and floodplain geomorphology are more complex region wide progressive floodplain alluviation through the mid to late holocene and a period of increased river activity between 3500 and 2800 cal ybp in response to climatically driven increases in sediment supply was followed by a period of valley floor incision and terrace formation beginning after 1900 cal ybp in partly confined valley settings this was followed by the aggradation of a lower holocene floodplain surface with rapid rates of vertical accretion in response to post settlement catchment disturbance the results of this study indicate that valley floor confinement has played a major role in controlling northland holocene river floodplain development producing a continuum of floodplain and river terrace landforms in response to climatically and anthropogenically driven variations in sediment flux

implications of pyrite geochemistry for gold mineralisation and remobilisation in the jiaodong gold district northeast china abstract the jiaodong gold district of eastern china the largest gold producing district in china is located on the eastern margin of the north china craton it consists of three mineralisation belts the western zhao ye belt the middle qixia belt and the eastern muping rushan muru belt over 85 of mineralisation is hosted in the zhao ye belt which is bordered by the mantle tapping tan lu fault zone pyrite crystals from three deposits in the zhao ye belt and three deposits in the muru belt were studied using a combination of optical petrography bulk pyrite geochemistry and in situ laser ablation icp ms results show that although mineralisation is broadly similar between the two belts there are significant differences in ore and gangue mineral textures pyrite geochemistry and style of gold mineralisation texturally pyrite grains from the zhao ye belt are generally cubic and do not exhibit zoning in contrast muru pyrite grains are more often pyritohedral commonly exhibit well defined concentric zoning and display textures in ore and gangue minerals indicative of open space growth bulk pyrite geochemistry suggests a distinct enrichment in pb bi au ag and te in the zhao ye belt whereas the muru belt pyrite is significantly enriched in as cu and co in situ pyrite geochemistry indicates that au and as are variably correlated in the zhao ye belt typically only exhibiting correlation at low au concentrations most gold occurs as visible electrum along pyrite fractures and grain boundaries with a minor generation of invisible gold formed through as facilitated uptake into pyrite in the muru belt au and as have a strong correlation and there is limited occurrence of gold particles indicating that most gold in the muru belt is invisible gold contained in the crystal structure of as rich pyrite the differences in style of gold mineralisation between the belts indicates an inherent difference in timing of gold introduction in the zhao ye belt the visible electrum accounting for most of the gold endowment is formed post pyrite whereas the invisible gold in the zhao ye and muru belts is formed syn pyrite the heterogeneity in gold distribution in the jiaodong district is attributed to melting of metallogenically fertile archean crust at the base of the well endowed zhao ye belt and the lack of a similarly fertile source region beneath the muru belt

comparative behavior of sr nd and hf isotopic systems during fluid related deformation at middle crust levels abstract we have carried out a comparative rb sr sm nd and lu hf isotopic study of a progressively deformed hercynian leucogranite from the french massif central belonging to the la marche ductile shear zone in order to investigate the respective perturbation of these geochronometers with fluid induced deformation the one meter wide outcrop presents a strongly deformed and mylonitized zone at the center and an asymmetric deformation pattern with a higher deformation gradient on the northern side of the zone ten samples have been carefully collected every 10 cm north and south away from the strongest deformed mylonitic zone they have been analyzed for a complete major trace element data set oxygen isotopes rb sr sm nd and lu hf isotopic systematics we show that most of major and trace elements except sio2 alkaline elements k2o rb and some metal transition elements cu are progressively depleted with increasing deformation this depletion includes ree y but also hfs elements ti hf zr nb which are commonly considered as immobile elements during upper level processes variations in elemental ratios with deformation e g decrease in lree mree hree nd hf th sr increase in rb sr u th and constant sr nd lead to propose the following order of element mobility u th sr nd hf hree we conclude in agreement with previous tectonic and metallogenic studies that trace element patterns across the shear zone result from circulation of oxidizing f rich hydrothermal fluids associated with deformation a temperature of the fluid of 470 480 c can be deduced from the 18o equilibrium between quartz muscovite pairs elemental fractionation induces perturbation of the rb sr geochronometer the well defined 87rb 86sr 87sr 86sr correlation gives an apparent age of 294 19 ma slightly younger than the 323 4 ma age of leucogranites in this area this apparent age is interpreted as dating event of intense deformation and fluid circulation associated with mass transfer and exhumation of the ductile crust shortly after the leucogranite emplacement sm nd and lu hf isochron type diagrams do not define any correlation because of the low fractionated sm nd and lu hf ratios isotopic data demonstrate that only the lu hf geochronometer system is not affected by fluid circulation and gives reliable tdm age 1 29 0 03 ga and ehf signatures by contrast the sm nd geochronometer system gives erroneous old tdm ages of 2 84 4 ga there is no positive end ehf correlation because of decreasing end values with deformation at constant ehf values however end ehf values remain in the broad end ehf terrestrial array which strongly indicates that fluid induced fractionation can contribute to the width of the terrestrial array the strong ehf negative values of the leucogranite are similar to metasedimentary granulitic xenoliths from the french massif central and confirm the generation of the leucogranite by several episodes of reworking of the lower crust

mineralization and wall rock alteration at the bogala graphite deposit bulathkohupitiya sri lanka the graphite mineralization in the bulathkohupitiya area was studied with an emphasis on the bogala deposit vein type mineralization occurs in the zones of deep seated fractures in supracrustal stratiform metasedimentary rocks resulting from the differential rise of subcrustal migmatites the mineralization at bogala comprises several veins of graphite and a large vein of syenite pegmatite mineralogical and geochemical study of the wall rocks reveals a well zoned alteration halo about the deposit chemical zoning in the altered wall rock and the relict mineral replacement textures indicate deep seated hydrothermal activity formation of vein graphite by decarbonation of carbonates and reduction of co 2 formed during the decarbonation reaction is indicated by the available carbon isotope data chemical zoning in the alteration halo may be a useful aid in the exploitation of known graphite deposits

cretaceous cenozoic tectonic history of the jiaojia fault and gold mineralization in the jiaodong peninsula china constraints from zircon u pb illite k ar and apatite fission track thermochronometry the jiaojia fault jjf in the jiaodong area of eastern china is an important nne trending structure that is subsidiary to the regional tancheng lujiang tan lu fault zone and hosts 1200 t of gold reserves contained in disseminated and stockwork ore dominantly in the footwall of the fault we present new zircon u pb apatite fission track and illite k ar data along the jjf and have delineated its tectonic history focusing on its formation and reactivation zircon u pb dating shows that the shangzhuang granite is a composite body with ages between 132 1 and 127 1 ma illite k ar ages for the fault s gouge range from 83 2 to 68 2 ma and the measured apatite fission track ages for ores are between 55 and 21 ma previous zircon u pb geochronology and structural studies suggest that the jjf was originally activated in the jurassic during 160 150 ma as a sinistral fault the jjf was a normal fault in the early cretaceous due to nw se orientated tension and ne sw compression which lasted from 135 to 120 ma this was followed by sinistral strike slip faulting due to nw se compression and ne sw tension during 120 110 ma and it changed to normal displacement at ca 110 ma our apatite fission track data analysis and thermal modeling of representative samples suggest that there was a subsequent dextral reactivation of the fault at ca 55 ma previous age data of ca 130 110 ma for gold mineralization along the jjf coincides with the early cretaceous magmatism and is coeval with the transition from normal faulting to sinistral strike slip faulting of the jjf in early cretaceous which is interpreted to be due to changing direction of the subducting pacific plate

paleoproterozoic structural evolution of the southern segment of the jiao liao ji belt north china craton abstract the paleoproterozoic jiao liao ji belt separates the eastern block of the north china craton into two small sub blocks the northern longgang and the southern rangrim blocks however it still remains unknown or controversial about the subduction polarity collisional deformation and kinematics between two sub blocks the southern segment of the belt consists of the paleoproterozoic fenzishan and jingshan groups and paleoproterozoic high pressure mafic granulites and serpentinites blocks which are located in the jiaodong complex all of which are separated from the jiaodong complex of neoarchean ttg gneisses by stz1 ductile shear zones structural analysis in this study indicates that most of the rocks in all the units of the southern segment of the jiao liao ji belt underwent three distinct episodes of folding d1 to d3 and two stage of ductile thrust shearing stz1 coeval to d1 and d2 stz2 between d2 and d3 the d1 deformation formed penetrative axial planar foliations s1 bedding parallel ductile shear zone mineral stretching lineations l1 and rarely preserved small isoclinal d1 folds in the jingshan and fenzishan groups in the jingshan group however penetrative deformational transposition resulted in stacking of sedimentary compositional layers which are separated by bedding parallel ductile shear zones stz1 at a period of about 1956 ma to 1914 ma the kinematic indicators of stz1 in the jingshan group with resultant prograde peak metamorphism up to granulite facies grade and the fenzishan group with peak metamorphism up to amphibolite facies grade indicate nw directed compression d2 resulted in crustal thickening with retrograded medium pressure granulite facies grade at about 1914 1893 ma the d2 deformation produced nw verging asymmetric and recumbent folds interpreted to have resulted from basement involved thicken skin structures the jiaodong complex was also involved into the development of wnw verging asymmetric tight folds associated with d2 in the jingshan and the fenzishan groups ongoing collision led to the development of transpressional ductile shearing stz2 forming the transpressional taipingzhuang dextral ductile shear zone between the jingshan group and the southern archean complex and the transpressional tading xiadian sinistral ductile shear zone between the jingshan group and the northern archean complex all three lithotectonic units were superposed during the late d3 deformation with amphibolite facies metamorphism the d3 deformation developed wnw trending open to tight upright folds at about 1893 1875 ma the structural pattern resulting from superimposition of d2 and d3 is a composite synform in the fenzishan and jingshan groups the structural events of d1 and stz1 and d2 and stz2 deformation were possibly responsible for fast syn collisional exhumation of the high pressure mafic granulites the structural patterns and deformational history of the fenzishan and jingshan groups suggest a southeastward directed oblique subduction beneath the northwestern margin of the rangrim block and that the final scissor shaped closure of the rift led to collision between the two blocks to form the coherent basement of the eastern block of the north china craton

the lanthanide tetrad effect and its correlation with k rb eu eu sr eu y ho and zr hf of evolving peraluminous granite suites lanthanide tetrad effects are often observed in ree patterns of more highly evolved variscan peraluminous granites of mid eastern germany central erzgebirge western erzgebirge fichtelgebirge and northern oberpfalz the degree of the tetrad effect te1 3 is estimated and plotted vs k rb sr eu eu eu y ho and zr hf the diagrams reveal that the tetrad effect develops parallel to granite evolution and significant tetrad effects are strictly confined to highly differentiated samples mineral fractionation as a cause for the tetrad effect is not supported by a calculated rayleigh fractionation which also could not explain the fractionation trends of sr eu and eu eu the strong decrease of eu concentrations in highly evolved rocks suggests that eu fractionates between the residual melt and a coexisting aqueous high temperature fluid mineral fractionation as a reason for the tetrad effect is even more unlikely as ree patterns of accessory minerals display similar tetrad effects as the respective host rocks the accessory minerals inherit the ree signature of the melt and do not contribute to the bulk rock tetrad effect via mineral fractionation these results point in summary to significant changes of element fractionation behavior in highly evolved granitic melts ionic radius and charge which commonly control the element distribution between mineral and melt are no longer the exclusive control the tetrad effect and the highly fractionated trace element ratios of y ho and zr hf indicate a trace element behavior that is similar to that in aqueous systems in which chemical complexation is of significant influence this distinct trace element behavior and the common features of magmatic hydrothermal alteration suggest the increasing importance of an aqueous like fluid system during the final stages of granite crystallization the positive correlation of te1 3 with bulk rock fluorine contents hints at the importance of ree fluorine complexation in generating the tetrad effect as the evolution of a ree pattern with tetrad effect m type implies the removal of a respective mirroring ree pattern w type the tetrad effect identifies open system conditions during granite crystallization

juvenile vs recycled crust in ne china zircon u pb geochronology hf isotope and an integrated model for mesozoic gold mineralization in the jiaodong peninsula abstract the continental crust of the north china craton ncc is a major reservoir of mineral resources with imprints of secular changes in tectonics and metallogeny the jiaodong peninsula located in the eastern margin of the north china craton ncc is currently one of the largest gold producers over the globe and preserves the records of multiple magmatic and metamorphic events here we characterize the timing and tectonics of the major mesozoic magmatism and the associated gold metallogeny in this region through a comprehensive u pb geochronological and hf isotope investigation of zircons in a suite of granitoids mafic magmatic enclaves melanocratic dikes and melted basement rocks the linglong granite hosting one of the major gold deposits in jiaodong shows emplacement ages between 150 and 160 ma and the dominantly negative e hf t values 34 0 to 23 8 of zircons from this intrusion suggest magma derivation from recycled components in the archean basement the guojialing granodiorite and its mafic magmatic enclaves show similar ages between 123 and 127 ma with negative e hf t values 19 3 to 16 8 corresponding to crustal magma source the melanocratic dikes belonging to pre and syn mineralization stages with u pb age range of 126 to 166 ma display large variation in their zircon e hf t values 25 7 and 2 3 suggesting the involvement of both recycled crustal and juvenile mantle components zircons in the melted basement rocks with ages in the range of ca 127 132 ma also display both positive and negative e hf t values 44 6 and 9 8 indicating a mixture of recycled ancient crust and juvenile magmas our study shows that although the peak of gold metallogeny coincided with the tectonics associated with pacific plate subduction which mobilized and concentrated the ores the source materials of gold mineralization and magmatism had multiple origins including from the precambrian basement rocks mesozoic granitoids and mantle derived mafic magmas with extensive mixing of crustal lithosphere mantle and asthenospheric components a combination of delamination mantle upwelling subduction related metasomatic enrichment and recycling of ancient components facilitated the gold metallogeny in this region our study provides a typical case of juvenile and recycled components in the formation and evolution of continental crust and associated mineral resources

timing of metamorphism in the paleoproterozoic jiao liao ji belt new shrimp u pb zircon dating of granulites gneisses and marbles of the jiaobei massif in the north china craton abstract the paleoproterozoic jiao liao ji belt lies in the eastern block of the north china craton with its southern segment extending across the bohai sea into the jiaobei massif high pressure pelitic and mafic granulites have been recently recognized in the paleoproterozoic jingshan group jiaobei massif new shrimp u th pb geochronology combined with cathodoluminescence cl imaging of zircon has been applied to the determination of the timing of the metamorphism of the high temperature and high pressure granulites and associated gneisses and marbles metamorphic zircons in these high pressure granulites gneisses and marbles occur as either single grains or overgrowth or recrystallization rims surrounding and truncating oscillatory zoned magmatic zircon cores metamorphic zircons are all characterized by nebulous zoning or being structureless with high luminescence and relatively low th u values metamorphic zircons from two high pressure mafic granulites yielded 207pb 206pb ages of 1956 41 ma and 1884 24 ma one metamorphic zircon from a garnet sillimanite gneiss also gave an apparent 207pb 206pb age of 1939 15 ma these results are consistent with interval of ages of c 1 93 1 90 ga already obtained by previous studies for the north and south liaohe groups and the laoling group in the northern segment of the jiao liao ji belt metamorphic zircons from a high pressure pelitic granulite and two pelitic gneisses yielded weighted mean 207pb 206pb ages of 1837 8 ma 1821 8 ma and 1836 8 ma respectively two diopside olivine phlogopite marbles yielded weighted mean 207pb 206pb ages of 1817 9 ma and 1790 6 ma these paleoproterozoic metamorphic ages are largely in accordance with metamorphic ages of c 1 85 ga produced from the ji an group in the northern segment of the jiao liao ji belt and c 1 86 1 80 ga obtained for the high pressure pelitic granulites from the jingshan group in the southern segment as this metamorphic event was coeval with the emplacement of a type granites in the jiao liao ji belt and its adjacent areas it is interpreted as having resulted from a post orogenic or anorogenic extensional event

incorporation mechanisms of ta and nb in zircon and implications for pegmatitic systems to investigate the processes that control ta incorporation in zircon two types of synthesis experiments were performed 1 crystallization of zircon from an li mo flux at 1 atm and 2 crystallization of zircon with or without coexisting tantalite from a highly fluxed pegmatitic melt at 200 mpa and nearly water saturated conditions the first type of experiment is used to identify the influence of various doping elements hf p al and mn on ta incorporation in zircon these experiments reveal that p hinders the incorporation of ta whereas al enhances ta incorporation via charge balancing and that ta can be incorporated in the absence of any other doping element via the creation of vacancies in the zircon structure hafnium does not affect significantly ta incorporation manganese and lithium do not enter the structure of zircon except in the presence of p experiments with nb show that the concentration of this element in zircon is nearly one order of magnitude lower than ta for similar ta and nb concentrations in the flux the second type of experiments show how ta is incorporated in zircon in natural granite and pegmatite systems in those systems p and al have elevated concentrations and p is preferentially incorporated in zircon via al substitution to maintain charge balance below a p ta atomic ratio of 10 in the melt ta competes with p for al and p is involved in a coupled substitution with mn for charge balancing concentrations up to 3 7 wt ta 2 o 5 0 03 apfu calculated to four atoms of oxygen were measured in these zircon samples the partition coefficients of ta between melt and zircon are around 1 at 800 900 c at conditions close to tantalite saturation these results show that zircon incorporates significant amounts of ta from the melt in p poor peraluminous granites with a p ta atomic ratio lower than 10 which may ultimately affect the precipitation of ta minerals such interactions between cations both in melts and in mineral structures are important to constrain in order to understand rare metal enrichment in granitic systems

the jiaodong type gold deposits characteristics origin and prospecting abstract the jiaodong type comprises a unique class of gold mineralisation which includes the linglong type quartz vein hosted and the jiaojia type fracture disseminated style deposits although the type area is in the jiaodong peninsula in ne china where some of the world s richest gold reserves occur we identify similar occurrences in other parts of china and elsewhere in the world under this category the ore fluids migrated upwards forming quartz vein type of gold ore linglong type wherever the ore controlling fractures are at high angles fluid infiltration into the surrounding wall rocks and generation of the jiaojia type disseminated style deposits resulted where the ore bearing fluids encountered low angle fractures on a regional scale the jiaodong type gold mineralisation occurs along the margins of reactivated cratons within the interior of cratons along paleosuture zones or along the junctions of micro blocks and is distinctly different from the classic orogenic gold in terms of their tectonic setting ore characteristics and genetic history unlike skarn and porphyry type of deposits the jiaodong type gold deposits do not always show close spatial relationship with magmatic intrusives and some of the deposits occur distal to plutons 10 km in this paper we evaluate the salient geological geochronological geochemical and isotopic features of the jiaodong type gold deposits and propose some general guidelines for gold prospecting based on case studies we predict that the gold lodes in the jiaodong type mineralised zones might extent vertically up to 3000 m with only minor mineralogical and geochemical variations

zircon geochronology geochemistry and stable isotopes of the wang ershan gold deposit jiaodong peninsula china abstract the early cretaceous gold deposits of the jiaodong peninsula eastern china define china s largest gold province with an overall endowment estimated more than 3000 t au the wang ershan gold deposit at the northern margin of the jiaolai basin in jiaodong peninsula of eastern china is located in the central southern segment of the wang ershan fault zone the major mesozoic intrusions exposed in this region are the linglong granite and the guojialing granodiorite to the northeast of the deposit both these intrusions show high k and alkaline signature the linglong granite displays peraluminous feature whereas the guojialing granodiorite is metaluminous zircon u pb dating of the linglong granite yields 206 pb 238 u weighted mean age of 149 0 1 3 ma the muscovite from the alteration zones associated with mineralization in the linglong granite yields a plateau age of 130 35 0 96 ma representing the initial phase of the hydrothermal activity the 34 s values of pyrite from the gold mineralized veins range from 6 to 8 3 with the mean value of 7 66 the 3 he 4 he ratios of pyrite are in the range 1 58 2 71 ra with a mean value at 2 168 ra the 40 ar 36 ar ratios show variation from 1220 3 to 1625 7 with an average of 1483 8 the 18 o values of the mineralizing fluids show a range of 2 13 to 7 5 with an average of 2 4 the 18 d w values are in the range of 97 5 to 61 4 with a mean at 82 6 detailed elemental and isotopic data suggest that the hydrothermal fluids in early stage were mainly magmatic and derived from the guojialing granodiorite and the ore forming fluids in the main ore forming stages evolved into a mixture of magmatic and meteoric water the ore forming materials were primarily derived from crust with minor input of mantle components the ore forming fluids might be related to the subduction of the paleo pacific slab beneath the north china craton and the associated asthenosphere upwelling and consequent lithospheric thinning

zircon rock partition coefficients of rees y th u nb and ta in granitic rocks uses for provenance and mineral exploration purposes abstract the trace element composition of magmatic zircon is highly variable even within the same grain and its study is complicated by the abundance of microinclusions metamict portions and strong compositional zoning among other factors to contribute to the understanding of the geochemistry of trace elements in zircon we determined the rare earth y nb ta th and u contents in zircon grains by laser ablation inductively coupled plasma mass spectrometry la icp ms with the use of cathodoluminescence and backscattered mev images zircon rock partition coefficients were determined in nine different types of granitoids and compared with experimental and natural data the obtained data are comparable with those reported by other authors by using the partition coefficient we estimated the composition of the host granitoids based on the zircon grain composition which was interpreted as evidence that the patterns of the trace elements in zircon grains are controlled by the liquid composition at the moment of crystallization a new set of partition coefficients for rees y nb ta th and u is suggested for provenance and exploratory studies la 0 8 ce 1 7 pr 2 1 nd 3 4 sm 9 8 eu 7 9 gd 24 tb 37 dy 69 ho 117 er 167 tm 281 yb 379 lu 437 nb 1 6 ta 2 9 th 27 u 177 and y 109 trace element diagrams eu eu vs yb nb vs th and y 200 lu 10 nb vs nb ce are proposed for discriminating zircon from different types of granitoids particularly for a type i type and shoshonitic rocks the trace element patterns of zircon are useful as a tool for mineral exploration studies because they often reproduce the patterns of mineralized granites

single grain pyrite rb sr dating of the linglong gold deposit eastern china abstract this study employs the single grain pyrite rb sr technique to date mineralization using the example of the linglong lode gold deposit jiaodong peninsula eastern china the gold deposits in this area are interpreted to have a consistent spatial temporal relationship with widespread late jurassic early cretaceous magmatism in eastern china likely related to lithospheric thinning around 120 ma pyrite of the linglong gold mine contains different types of mineral inclusions such as sericite and feldspar that cause distinguishable variations in rb and sr contents and rb sr ratios four pyrite samples from veins of different mineralization stages give an average isochron age of 120 6 0 9 ma analyses of one quartz and two sericite samples yield isochron ages between 122 ma and 120 ma dating of mineralization is often hampered by disequilibrium of isotopic systems and or the lack of suitable minerals for dating purposes hence the successful attempt of the single grain rb sr technique of pyrite which occurs as a common mineral phase in orebodies and is genetically related to the mineralization has great potential for precise geochronology of hydrothermal mineral deposits

the relationship of mantle derived fluids to gold metallogenesis in the jiaodong peninsula evidence from d o c s isotope systematics abstract the largest gold district in china is the jiaodong peninsula where three types of gold deposits are recognized quartz vein fracture altered and breccia types the first two developed along a group of ne trending faults and are hosted by granitic intrusions dated at 160 to 150 ma biotite granite and 130 to 126 ma granodiorite and by metamorphic rocks of the precambrian crystalline basement the breccia type gold system is mainly located around the northern margin of the jiaolai cretaceous basin where mineralisation is controlled by both detachment fractures and ne trending faults this study is based on stable isotope determinations from ten gold deposits including linglong jiaojia sanshandao cangshang wang ershan dayigezhuang denggezhuang pengjiakuang fayunkuang and dazhuangzi as well as the linglong jurassic biotite granite guojialing cretaceous granodiorite and archean gneiss the stable isotope systematics reflect the style of the three types of gold deposits but also show that they belong to the same metallogenic system in which the hydrothermal fluids were derived from a mantle fluid reservoir and mixed with crustal fluids the ore forming age is later than both the jurassic biotite granite and cretaceous granodiotite but overlaps with the 121 to 114 ma ages of lamprophyre and diabase dykes the hydrothermal fluids that were responsible for both gold mineralisation and the retrograde alteration of the diabase and lamprophyre dykes are similar and represent a co 2 and potassium rich system this fluid system is interpreted to be the consequence of cretaceous lithospheric thinning asthenospheric upwelling and mantle degassing in eastern china

zircon morphology geochronology and trace element geochemistry of the granites from the huangshaping polymetallic deposit south china implications for the magmatic evolution and mineralization processes abstract the huangshaping polymetallic deposit is a large scale deposit located in the central nanling region south china different types of mineralization have been classified in the area which are attributed to three types of granitoids from the composite granitic pluton quartz porphyry granophyre and granite porphyry in order to study the magmatic genesis and evolutionary process as well as constrain the crystallization and mineralization events 100 zircon separates from different intrusive stages of the pluton have been analyzed for trace element contents and u pb isotopic concentrations the results show that zircons from the huangshaping granitoids are enriched in th u hf ti ree and other trace elements indicating hydrothermal fluid alteration and transformation additionally there is a large variation between different types of granitoids in terms of trace element concentrations compared to the zircons from the quartz porphyry and the granophyre zircons from the granite porphyry are more enriched in th u hf ti and p but strongly depleted in eu this suggests that the magma that formed the granite porphyry possessed higher temperatures possibly experienced stronger crystal fractionation and originated from a more evolved complex magmatic source region with higher degree of crustal maturity combined with characteristics of crystal morphology and internal texture hydrothermal zircons were distinguished from magmatic zircons in each granitoid to reveal mineralization processes the u pb geochronology results show that there are two major stages of mineralization 190 ma weak cu pb zn mineralization related to the quartz porphyry and the granophyre and 155 ma strong w sn mo pb zn mineralization associated with the granite porphyry compositions of these hydrothermal zircons suggest that the earlier stage mineralization could be close to single relatively cold reduced and quickly ascended fluids whereas the later stage might be related to hot oxidized strongly fractionated and highly evolved mixed fluids this study also indicates that hydrothermal zircons from typical composite granitic plutons could be a good tool to reveal the multi stage magmatic and mineralization process in middle to late jurassic south china

ore forming fluids associated with granite hosted gold mineralization at the sanshandao deposit jiaodong gold province china the sanshandao gold deposit with total resources of more than 60 t of gold is located in the jiaodong gold province the most important gold province of china the deposit is a typical highly fractured and altered disseminated gold system with high grade quartz sulphide vein veinlet stockworks that cut mesozoic granodiorite there are four stages of veins that developed in the following sequence 1 quartz k feldspar sericite 2 quartz pyrite arsenopyrite 3 quartz base metal sulfide and 4 quartz carbonate fluid inclusions in quartz and calcite in vein veinlet stockworks contain c o h fluids of three main types the first type consists of dilute co2 h2o fluids coeval with the early vein stage molar volumes of these co2 h2o fluid inclusions ranging from 50 60 cm3 mol yield estimated minimum trapping pressures of 3 kbar homogenization temperatures obtained mainly from co2 h2o inclusions with lower co2 concentration range from 267 375 c the second inclusion type with a co2 h2o ch4 composition was trapped during the main mineralizing stages these fluids may reflect the co2 h2o fluids that were modified by fluid rock reactions with altered wallrocks isochores for co2 h2o ch4 inclusions with homogenization temperatures ranging from 204 325 c and molar volumes from 55 to 70 cm3 mol provide an estimated minimum trapping pressure of 1 2 kbar the third inclusion type aqueous inclusions trapped in cross cutting microfractures in quartz and randomly in calcite are post mineralization and have homogenization temperatures between 143 228 c and salinities from 0 71 7 86 wt nacl equiv stable isotope data show that the metamorphic fluid contribution is minimal and that ore fluids are of magmatic origin most likely sourced from 120 126 ma mafic to intermediate dikes this is consistent with the carbonic nature of the fluid and the cross cutting nature of those deposits relative to the host mesozoic granitoid