fluid inclusions in the harney peak granite black hills south dakota usa implications for solubility and evolution of magmatic volatiles and crystallization of leucogranite magmas abstract experimental and theoretical studies have shown that magmatic fluids have strong influence on phase equilibria of granitic systems a microthermometric study of fluid inclusions in the proterozoic harney peak granite black hills south dakota usa was undertaken to obtain direct evidence for the composition and evolution of magmatic fluids in a leucogranitic system and to evaluate their effect on liquid lines of descent of leucogranite magmas a previous stable isotopic study has demonstrated that the granite has not interacted with nonmagmatic fluids since its crystallization therefore fluids found in the inclusions are of magmatic origin and present an opportunity to directly sample magmatic fluids trapped during crystallization of a granitic magma and during subsolidus conditions the harney peak granite was emplaced as multiple sills dikes and small intrusions many of which differentiated into coupled aplite pegmatite layers three types of fluid inclusions are found in the granite type 1 consist of variable saline h 2 o c0 2 mixtures with minor ch 4 or other gases inclusions of this type are found in tourmaline and quartz in aplite layers are generally isolated and have negative crystal shapes they are interpreted to be primary there is a general increase in salinity and decrease in isochore temperature with decreasing co 2 h 2 o ratio of the inclusions the trend is ascribed to progressive change in fluid composition with crystallization due to the differential solubility of co 2 and h 2 o in the high silica magma isochores coupled with independently determined crystallization temperatures suggest entrapment pressure 3 5 kbar consistent with geobarometry in the wallrocks type 2 inclusions are carbonic fluids dominated by co 2 whereas type 3 inclusions are saline aqueous fluids without a detected carbonic component both types are mostly found along healed fractures in quartz they are interpreted to be secondary inclusions that formed as a result of unmixing of type 1 inclusions at subsolidus conditions during uplift and cooling of the harney peak granite dome freezing point depressions birefringent daughter crystals phase equilibria considerations and track mapping of b and li distribution in thin sections all indicate that both type 1 and type 3 inclusions contain solutes such as k li and b in addition to nacl using published solubility models for h 2 o and co 2 in granitic melts and the composition of the most co 2 rich type 1 inclusions x co 2 0 55 the initial h 2 o and co 2 concentrations in the harney peak granite magma are deduced to have been 3 5 wt and 1500 ppm respectively the relatively low water concentration is consistent with temperatures of dehydration melting reactions that produced the magma it is suggested that the aplite pegmatite segregations found in parts of the harney peak granite are the result of initial rapid near liquidus crystallization of minerals with high na k ratios including plagioclase and tourmaline along a wide range of increasing h 2 o aplite crystallization was followed by crystallization of relatively potassic residual liquid enriched in fluxing elements under conditions of high h 2 o

a nonlinear theory for el nino bursting abstract a new mechanism is proposed that explains two key features of the observed el nino southern oscillation enso phenomenon its irregularity and decadal amplitude changes using a low order enso model the authors show that the nonlinearities in the tropical heat budget can lead to bursting behavior characterized by decadal occurrences of strong el nino events la nina events are not affected a feature that is also seen in enso observations one key result of this analysis is that decadal variability in the tropics can be generated without invoking extratropical processes or stochastic forcing the el nino bursting behavior simulated by the low order enso model can be understood in terms of the concept of homoclinic and heteroclinic connections it is shown that this new model for enso amplitude modulations and irregularity although difficult to prove might explain some features of enso dynamics seen in more complex climate models and the observations

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

gold deposition and resource potential of the linglong gold deposit jiaodong peninsula geochemical comparison of ore fluids abstract the linglong gold deposit is a super large deposit in the linglong goldfield northern jiaodong peninsula the orebodies consist of hundreds of auriferous quartz veins that surrounded by relatively narrow k feldspar alteration halos four mineralization stages have been identified on the basis of cross cutting relationships and mineralogical and textural characteristics milky quartz pyrite stage 1 grey white quartz pyrite stage 2 quartz pyrite base metal sulfide stage 3 and quartz carbonate stage 4 native gold was mainly deposited in stages 2 and 3 petrographical and microthermometric studies on quartz from stages 2 and 3 ores reveal three types of fluid inclusions associated with gold mineralization type 1 h2o co2 nacl ch4 inclusion that consisting fia 1 and represent a homogeneous fluid trapped at the same pressure and temperature coexisting type 2a h2o rich h2o co2 nacl ch4 and type 2b co2 rich h2o co2 nacl ch4 inclusions that constitute fia 2 and are interpreted to be products of a heterogeneously trapped fluid the ore forming fluids belong to a h2o nacl co2 ch4 system with medium temperatures 290 340 c low salinity 4 7 wt nacl eq and are co2 rich 15 mol with minor ch4 2 5 mol the d 18o values of ore forming fluids vary from 63 to 57 and 6 0 to 9 3 respectively overlap both the magmatic and metamorphic fluid fields the 34s values of hydrothermal pyrite have a narrow range from 5 6 to 7 9 and are within the ranges of neoarchean jiaodong group and mesozoic linglong granite guojialing granitoid and intermediate basic dikes combined with h o s isotope data fluid inclusions compositions and regional geological events the ore forming fluids may have a metamorphic dominate origin but a mantle or crustal contribution cannot be excluded fluid immiscibility played a major role and fluid wallrock interaction may be a subordinate reason for gold deposition in linglong the stage 2 quartz grains contain more fias 2 and volatiles than those in stage 3 quartz indicating a more extensive fluid immiscibility process which has a positive correlated higher gold grade based on the data of fias 2 the p t conditions of gold depositions generally range from 242 to 54 mpa and 348 to 269 c with a depth of metallogenesis of 5 4 9 0 km considering the depth of regional post ore exhumation has been calculated as about 5 7 km the space with deep gold exploration is expectable at linglong

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

textures of auriferous quartz sulfide veins and 40ar 39ar geochronology of the rushan gold deposit implications for processes of ore fluid infiltration in the eastern jiaodong gold province china abstract the rushan gold deposit located in the eastern part of the world class jiaodong gold province contains the largest gold resource within a single fault controlled quartz vein in china processes involved in auriferous quartz vein deposition are not clear and the precise gold mineralization age remains controversial for this deposit new 40ar 39ar dating data on sericite from ores and altered rocks suggest that the rushan gold deposit formed between ca 122 ma and 117 ma which overlap or are slightly younger than those of gold deposits in northwestern jiaodong province the age differences between samples from different locations indicate that the quartz veins on the margin of the orebody may be younger than those in the center suggesting a single and protracted gold mineralization event lasting for about 5 my differences between gold mineralization ages and emplacement cooling ages of the ore hosting kunyushan granite imply that they are not genetically related and that the kunyushan granite is unable to provide any thermal input to the mineralization system this also applies to the sanfoshan monzonite as it marginally postdated gold mineralization and lacks any spatial association with it internal textures of high angle shear veins and low angle extension veins indicate that episodic fluctuations from supralithostatic to hydrostatic fluid pressure triggered the multiple ore controlling fault ruptures induced by breach of supralithostatic fluids under a seismogenic regime in this model the controlling fault starts to slip with both reverse and sinistral kinematics and dilatational zones are created the ore forming fluids then migrate upwards along the fault due to the large pressure difference between the dilatational zones and the deep parts of the fault causing hydraulic fracture in the host rocks and earlier quartz veins large volumes of quartz pyrite and other ore components are precipitated due to fluid immiscibility caused by pressure fluctuations and new quartz veins form along both sides of the earlier quartz veins the fault is now sealed by these new quartz veins and the fluid pressure starts to build until the next breach cycles orebodies with complex internal textures were thus deposited incrementally in these cycles closely fitting the classic fault valve model in this case under a weak regional nw se transpressional stress

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

fluid immiscibility in late alpine gold bearing veins eastern and northwestern european alps gold bearing quartz veins fill late alpine brittle structures in pennine nappes of austria in the tauern window and in northern italy the veins formed in the latter stages of uplift of the alps fluid inclusions in veins sampled from bockstein austria and valle anzasca italy have a wide variety of compositions ranging from aqueous brine about 5 wt nacl equiv to about 50 mol co2 at room temperature the inclusions range with increasing co2 content from two phase aqueous through three phase in which the co2 homogenizes to vapour to three phase with co2 homogenizing to liquid this wide range of inclusion compositions is interpreted as evidence for fluid immiscibility with most inclusions being accidental mixtures of the two end member immiscible fluids the homogenization temperatures of the aqueous inclusions 200 280 c gives the best estimate of temperature of formation of the veins vein formation fluid pressure at bockstein and valle anzasca was about 1 kbar and bockstein veins formed at lower pressure than valle anzasca veins fluid immiscibility may have contributed to deposition of gold at both valle anzasca and bockstein and possibly many other uplift related alpine gold localities

evolution of a carbonate delta generated by gateway funnelling of episodic currents cool water carbonate sedimentation has dominated mediterranean shelves since the early pliocene skeletal sand and gravel herein consist of remains of heterozoan organisms which are susceptible to reworking due to weak early cementation in non tropical waters this study documents the lower pleistocene carbonate wedge of favignana island italy which prograded from a 5 km wide passage between two palaeo islands into a perpendicular 10 to 15 km wide strait between the palaeo islands at one side and sicily at the other during the emilian highstand 1 6 ma to 1 1 ma the clinoformed carbonate wedge which is 50 m thick and 6 km long formed by east south east progradation of a platform on the submarine sill by currents that were funnelled between the two palaeo islands platform slope clinoforms evolved from initial aggradation thin and low angle into a progradation phase thick and high angle both clinoform types are characterized by a bimodal facies stacking pattern defined by sedimentary structures created by i subaqueous dunes associated with dilute subcritical currents and ii upper flow regime bedforms associated with sediment laden supercritical turbidity currents focusing of episodic currents on the platform by funnelling between the islands controlled the downstream formation of a sediment body here named carbonate delta the carbonate delta interfingers with subaqueous dune deposits formed in the perpendicular strait this study uses a reconstruction of bedform dynamics to unravel the evolution of this gateway related carbonate accumulation

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

craton destruction and related resources craton destruction is a dynamic event that plays an important role in earth s evolution based on comprehensive observations of many studies on the north china craton ncc and correlations with the evolution histories of other cratons around the world craton destruction has be defined as a geological process that results in the total loss of craton stability due to changes in the physical and chemical properties of the involved craton the mechanisms responsible for craton destruction would be as the follows 1 oceanic plate subduction 2 rollback and retreat of a subducting oceanic plate 3 stagnation and dehydration of a subducting plate in the mantle transition zone 4 melting of the mantle above the mantle transition zone caused by dehydration of a stagnant slab 5 non steady flow in the upper mantle induced by melting and or 6 changes in the nature of the lithospheric mantle and consequent craton destruction caused by non steady flow oceanic plate subduction itself does not result in craton destruction for the ncc it is documented that westward subduction of the paleo pacific plate should have initiated at the transition from the middle to late jurassic and resulted in the change of tectonic regime of eastern china we propose that subduction rollback and retreat of oceanic plates and dehydration of stagnant slabs are the main dynamic factors responsible for both craton destruction and concentration of mineral deposits such as gold in the overriding continental plate based on global distribution of gold deposits we suggest that convergent plate margins are the most important setting for large gold concentrations therefore decratonic gold deposits appear to occur preferentially in regions with oceanic subduction and overlying continental lithospheric destruction modification growth

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

origin of the jiaodong type xinli gold deposit jiaodong peninsula china constraints from fluid inclusion and c d o s sr isotope compositions abstract the xinli gold deposit within the sanshandao cangshang gold belt in the jiaodong gold province is a typical jiaojia type ore deposit with high grade quartz sulfide vein veinlet stockworks that cut mesozoic granodiorite four ore stages are distinguished in the following sequences i quartz k feldspar sericite pyrite ii quartz pyrite iii quartz polymetallic sulfide and iv quartz calcite pyrite fluid inclusions in quartz and calcite in the ores contain c o h fluids dominantly of six types with varied liquid vapor ratio ore fluid in the main ore stage is characterized by medium low temperature low salinity reducing condition and nacl h 2 o co 2 ch 4 in composition the 18 o water smow of quartz in ore stages ii and iii range from 2 82 to 5 34 and the d smow are between 69 6 and 88 3 both suggest that the ore fluid was dominantly magmatic water the 13 c pdb of the calcite are from 6 4 to 2 4 indicating mantle contribution to the ore fluid the pyrite 34 s cdt from four ore stages are basically similar varying from 9 42 to 11 62 which implies significant involvement of crustal materials the initial 87 sr 86 sr ratios in the calcite ranging from 0 710657 to 0 711542 also denote a crustal contribution the fluid composition and systematic h o c s sr isotopic data are explained by a model of slab subduction induced gold mineralization in the model the ore fluid and metals were considered to associate with the dehydration and desulfidation of the subducting paleo pacific slab and the subsequent devolatilization of enriched mantle wedge the h 2 o in the fluid might have been released from the devolatilization of enriched mantle wedge the co 2 could be from mantle wedge or subcontinental lithospheric mantle and the sulfur and strontium would be initially released from the subducted seafloor sediments this process was further supported by the geochemical features of intermediate basic dykes contemporaneous to the gold ore deposits the deposit features and ore forming process of the xinli gold deposit hardly concur those of the orogenic gold deposit and the pluton related gold deposit the study supports the argument of that the gold deposits in the jiaodong belong to a unique gold type related to a complex slab subduction related process the geodynamic engine of the jiaodong type gold deposit is specific i e the slab subduction coupling with the consequent lithospheric thinning and structure adjustment

geology and timing of mineralization at the cangshang gold deposit north western jiaodong peninsula china the cangshang gold deposit of the north western jiaodong peninsula contains reserves of greater than 50 tonnes t and is developed by the largest open pit gold mine in china this deposit is a jiaojia style i e disseminated and veinlet deposit it is controlled by the san cang fault zone which trends 040 and dips 40 75 se at the mine site the main no 1 orebody lies between a hanging wall of precambrian metamorphic rocks mainly amphibolite of the fenzishan group and a footwall composed of the mesozoic linglong granitoid the ore zone is mainly composed of pyritized sericitized and silicified granitoid which has undergone variable degrees of cataclasis shrimp u pb dating of zircon indicates that the protolith of the hanging wall amphibolite was formed at 2530 17 ma and underwent metamorphism at 1852 37 ma the footwall granodiorite has been dated at 166 4 ma whereas zircons from the ore zone yield a younger age of 154 5 ma cathodoluminescence images of zircons from the granodiorite and ore zone show oscillatory zonation indicative of an igneous origin for both and the ages of these zircons therefore are all interpreted to be representative of magmatic crystallization dating of sericite by 40ar 39ar has been used to directly determine the timing of formation of the cangshang deposit providing the first time absolute age on formation of the jiaojia style gold deposits the well defined age of 121 3 0 2 ma provides the precise timing of gold mineralization at the cangshang deposit this age is consistent with those of linglong style vein type gold mineralization also from the north western jiaodong peninsula at between 126 and 120 ma therefore our work indicates that both styles of gold deposits in the jiaodong peninsula were formed during the same mineralization event

hydrothermal fluid evolution of the jintingling gold deposit in the jiaodong peninsula china constraints from u pb age cl imaging fluid inclusion and stable isotope abstract the jintingling gold deposit located in the jiaodong peninsula north china contains vein dissemination and stockwork style ores hosted in the jurassic linglong granitic pluton hydrothermal activities in this deposit are divided into seven stages including pre ore massive k feldspar alteration specularite quartz vein v1 milky quartz sulfide vein v2 quartz pyrite vein v3 massive quartz sericite pyrite alteration and gold mineralization quartz polymetallic sulfide vein v4 and quartz calcite vein v5 rhenium osmium dating was conducted on molybdenite from v2 yielding an isochron age of 123 3 3 6 ma la icp ms zircon u pb dating yielded 121 5 1 5 ma 1 mswd 0 010 for a pre ore diorite porphyrite dyke and 117 6 1 2 ma 1 mswd 0 018 for a post ore diorite porphyry dyke respectively thus gold mineralization occurred at 122 118 ma four types of fluid inclusions were identified in quartz veins including co 2 h 2 o ch 4 inclusions type i pure co 2 inclusions type ii mineral bearing inclusions type iii and aqueous inclusions type iv fluid inclusion studies demonstrate that the primary ore forming fluids contain co 2 rich vapor 357 420 c 7 2 11 3 wt nacl equivalent and critical fluids 368 400 c the two phases were likely formed by immiscibility of magmatic hydrothermal fluids later on the fluids evolved to a h 2 o co 2 nacl ch 4 system which had temperatures of 300 364 c and salinities of 2 0 9 7 wt nacl equivalent the h 2 o co 2 nacl ch 4 fluid system may experience phase separation forming coexisted co 2 h 2 o ch 4 inclusions homogenized to vapor or liquid at temperature of 265 309 c and 265 287 c salinities of 3 1 7 1 wt and 4 3 7 1 wt nacl equivalent respectively and aqueous inclusions homogenized to liquid at temperature of 255 294 c and 3 7 7 6 wt nacl equivalent along with further evolution the fluids shifted to a h 2 o nacl system with temperatures of 163 258 c and salinities of 0 5 9 0 wt nacl equivalent pyrite from the jintingling deposit has 34 s values 5 5 6 1 similar to those of pyrite from other gold deposits in the jiaodong district indicating that they were related to the same hydrothermal ore forming system the 13 cpdb values of calcite 4 5 to 5 4 in v5 are generally located in the range of magmatic derived carbon fluids of v2 v3 v4 have d from 64 4 to 87 1 and 18 o from 8 4 to 0 2 located in the compositional fields between magmatic water and meteoric water collectively microthermonetric results and isotopic data indicate that the primary ore forming fluids were most probably magmatic in origin with incorporation of meteoric water in the later ore forming stage precipitation of gold was triggered by cooling of fluids fluid immiscibility and decrease of sulfur in the fluids

geology of the sandaowanzi telluride gold deposit of the northern great xing an range ne china geochronology and tectonic controls abstract the sandaowanzi gold telluride deposit is a new discovery with dominance in gold tellurides in northeastern china the deposit is hosted in quartz veins intruding sub alkaline volcanic rocks there are two types of gold telluride ores in the sandaowanzi ore deposit i e the vein ores and the disseminated ores calaverite krennerite sylvanite petzite empressite hessite and stuetzite are the dominant au ag bearing minerals either in vein ores or in disseminated ores minor amount of other tellurides e g coloradoite altaite and sulfides e g pyrite sphalerite galena chalcopyrite and chalcocite mostly occur in the disseminated ores the gold bearing quartz veins crosscut volcanic host rocks which are dated at 135 3 124 7 ma by la icp ms u pb zircon method the latter unconformably overly a monzogranite dated as 181 6 ma diabase dikes dated at 116 6 ma intrude the gold bearing quartz veins the age data thereby bracket the timing of gold mineralization between 125 3 and 116 6 ma these geochronologic data are consistent with field relations regional comparison reveals that the widespread volcanism in the great xing an range is a product of the subduction of the izanagi plate beneath the eurasian plate gold telluride mineralization was contemporaneous with regional extension and magmatism as the subducting izanagi plate rolled back

p t x conditions of late hercynian fluid penetration and the origin of granite hosted gold quartz veins in northwestern iberia a multidisciplinary study of fluid inclusions and their chemistry quartz veins hosted by late hercynian granites and their host rocks occur across the variscides of the northern iberian peninsula and locally display au as mineralization four separate occurrences at corcoesto tomino penedono and pino have been investigated to determine p t x conditions of formation and likely fluid sources special attention has been paid to fluid chemistry using a multidisciplinary investigation of fluid inclusion gases by raman spectroscopy individual fluid inclusion analysis and mass spectrometry bulk analysis and ion chemistry using microthermometry and bulk leachate chemical analysis two major changes in the chemical and physical environment have been identified 1 a progressive change in the bulk chemical composition from early co2 rich c h o n fluids equilibrated with graphitic metamorphic host rocks to late h2o dominated fluids inferred from their halogen signature to result from an influx of meteoric or upper crustal fluids affecting the basement at the end of variscan orogenesis and 2 changes in the p t conditions from early stage sulphide deposition in quartz veins at ca 450 c and 150 300 mpa towards epithermal conditions ca 260 310 c and 75 mpa at the stage of gold mineralization several chemical trends are shown by the fluid inclusions 1 dilution of the early volatile rich fluids 2 a break of graphite buffering activity demonstrated by the ch4 content increase in the volatile fraction of the latest as mineralizing fluids and 3 increasing contribution of a relatively oxidizing fluid enriched in sulphate and bromide during the latest stages of fluid percolation au stage these latest fluid stages are interpreted as indicative of extended fluid penetration downward in the crust enhanced by late brittle deformation and decompression and played an important role in mass transfer at the end of the hercynian orogeny especially in transport of metals gold ores have formed mostly in granites because main fluid pathways developed in the main structurally active zones which favoured the emplacement of the granites however there is no evidence of genetic link between gold ores and their enclosing granites

decratonic gold mineralization evidence from the shangzhuang gold deposit eastern north china craton abstract the jiaodong peninsula in the eastern north china craton ncc hosts some of the world class gold deposits among these the shangzhuang gold deposit represents a typical fault zone hosted disseminated and stockwork style gold mineralization the mineralization is characterized by intense hydrothermal alteration halos in the wallrocks with the mineralized veins intruding into altered wallrocks zircon u pb isotope dating constrains the timing of emplacement of the guojialing granodiorite as 130 1 ma five molybdenite samples from the main mineralization stage veins yielded a well fitted isochron age of 126 2 ma mswd 1 3 marking the timing of gold mineralization four types of fluid inclusions are identified at shangzhuang and their petrographic and microthermometric features suggest fluid immiscibility followed by fluid mixing this inference is also supported by oxygen and hydrogen isotopic data of quartz veins from stage iii the measured 18 o values of quartz are 12 3 to 13 7 for stage ii and 11 7 to 12 0 for stage iii with calculated 18 o fluid values for stage ii ranging from 5 9 to 7 3 and for stage iii from 3 4 to 3 7 d values for stage ii and iii quartz range from 65 3 to 75 2 and 70 6 to 74 7 respectively the data suggest that the ore forming fluids were initially derived from magmatic sources followed by mixing with meteoric water sims in situ sulfur isotope analyses of two types of pyrite py i and py ii from different mineralization stages show different sulfur isotope features the 34 s values for py i 10 2 to 11 3 mean 10 8 n 25 are higher than those of the later mostly gold related py ii 4 1 to 6 8 mean 5 4 n 27 the higher 34 s values of py i are correlated to degassing of mantle wedge metasomatized by the slab fluids the relatively lower 34 s values of py ii might suggest increasing of f o2 through fluid mixing between ore forming fluids and meteoric water the temporal spatial and tectonic relations between the giant gold mineralization and destruction of the ncc suggest a genetic linkage the gold mineralization between 126 and 117 ma at jiaodong was probably initiated at the peak of decratonization ca 125 ma of the eastern ncc phanerozoic craton margin orogeny also played a critical role in the generation of the early cretaceous giant gold deposits in the eastern ncc integrated geological characteristics mineralization features metallogenic age sources of ore forming fluids and sulfur and tectonic settings favor a decratonic gold mineralization model for the shangzhuang gold deposit the geodynamic scenario proposed for the early cretaceous giant gold mineralization event in the eastern ncc includes the paleo west pacific plate subduction asthenospheric upwelling multiple subduction collision processes along the margins

relative roles of formation and preservation on gold endowment along the sanshandao gold belt in the jiaodong gold province china importance for province to district scale gold exploration the 13 km long sanshandao gold belt along the nne trending sanshandao fault has highly variable orogenic gold endowment along strike new thermochronological data from the small cangshang gold deposit demonstrate similar degrees of uplift and exhumation rates as for larger deposits negating selective preservation as the prime gold endowment factor the haiyu sanshandao xiling and cangshang deposits of variable gold endowment lie adjacent to ne ene trending jogs similar to those at jiaojia and linglong so these structures cannot be the prime control on gold mineralization ore zones show a broad gentle northeast plunge with the southwestern cangshang and xinli deposits being closest to the ground surface and the northeastern haiyu deposit being the deepest thus preferential erosion of the shallower southwestern orebodies could be a factor affecting endowment another variable is the depth of drilling at haiyu sanshandao gold mineralization is better developed on more gently dipping fault segments consistent with a thrust component of oblique slip along them relative to the northeastern deposits the cangshang and xinli deposits are located in areas where relatively shallow drilling has intersected ore zones on steeply dipping fault segments indicating the potential for deeper drilling to intersect gold ore along deeper more gently dipping segments heterogeneous gold endowment is thus largely a formational factor related to the plunge of orebodies combined with the variable depth of drilling along the sanshandao fault over the entire jiaodong gold province there are equivalent age mesozonal to epizonal orebodies implicating their preservation at different crustal levels and thus increasing the province scale gold endowment potential and probability of further exploration discoveries

geochronological and sulfur isotopic evidence for the genesis of the post magmatic deeply sourced and anomalously gold rich daliuhang orogenic deposit jiaodong china the daliuhang gold deposit 20 t gold is located in the central penglai qixia belt of the giant jiaodong gold province eastern china the ore hosting guojialing granodiorite and pegmatite were formed at 129 0 0 6 ma and 126 2 0 6 ma respectively syn ore monazite with a u pb age of 120 5 1 7 ma represents the timing of gold mineralization given at least 5 m y between magmatism and mineralization a genetic relationship to magmatic hydrothermal activity is negated noble gas isotopes of pyrite have crust mantle mixed 3he 4he 1 13 to 1 50 ra and air like 40ar 36ar 327 574 together with the broadly positive correlation between 3he and 36ar it is inferred that the initial ore forming fluids were deeply sourced from the sedimentary wedge overlying the subducted plate and overlying mantle during early cretaceous paleo pacific plate subduction the pre ore and post ore pyrites have low 34s values 3 7 5 6 and 5 3 6 4 respectively whereas ore related pyrites have higher 34s values especially in as au rich domains 7 8 8 3 these positive 34s values also suggest that the initial ore fluid and some of the sulfur component were derived via subduction related devolatilization the elevated 34s values of the ore related pyrite are partly ascribed to mass fractionation and partly to a contribution from sulfur leached from crustal host rocks this interpretation is also supported by neodymium isotope ratios of monazite end 120 ma 13 7 to 11 6 which correlate well with the ore hosting guojialing granodiorite this study highlights the combined roles of deeply derived fluids and intense interaction with upper crustal rocks in the formation of jiaodong gold deposits

what drove late mesozoic extension of the northern china mongolia tract the northern china mongolia tract exhibited a tectonic transition from contractional to extensional deformation in late mesozoic time late middle to early late jurassic crustal shortening is widely thought to have resulted from collision of an amalgamated north china mongolia block and the siberian plate but widespread late late jurassic early cretaceous extension has not been satisfactorily explained by existing models some prominent features of the extensional tectonics of the northern china mongolia tract are 1 late jurassic voluminous volcanism prior to early cretaceous large magnitude rapid extension 2 overlapping in time of contractional deformation in the yinshan yanshan belt with development of extensionrelated basins in the interior of the northern china mongolia tract and 3 widespread occurrence of alkali granitic plutonism extensional basins and metamorphic core complexes in the early cretaceous a new explanation is advanced in this study for this sequence of events the collision of amalgamated north china mongolia with siberia led to crustal overthickening of the northern china mongolia tract and formation of a high standing plateau subsequent breakoff at depth of the north dipping mongol okhotsk oceanic slab is suggested as the main trigger for late mesozoic lithospheric extension of that tract slab breakoff resulted in mantle lithospheric stretching of the adjacent northern china mongolia tract with subsequent ascent of hot asthenosphere and magmatic underplating at the base of the crust collectively these phenomena triggered gravitational collapse of the previously thickened crust leading to late late jurassic early cretaceous crustal extension and importantly coeval contraction along the southern margin of the plateau in the yinshan yanshan belt the proposed model provides a framework for interpreting the spatial and temporal relationships of distinct processes and reconciling some seemingly contradictory phenomena such as the synchronous extension of northerly terranes during major contraction in the neighboring yanshan yinshan belt d 2003 elsevier b v all rights reserved

macflincor and its application to fluids in archean lode gold deposits abstract macflincor was developed to process laboratory data gathered on fluid inclusions and to calculate isochores for geologically important fluids composed of h2o c02 ch4 nacl and n2 within the program interactive diagrams are available to describe those chemical systems which cannot be adequately constrained numerically the user can choose from various published equations of state describing fluid behavior and can easily compare the results obtained by using different equations the program once the basic fluid parameters have been established allows the data to be used to determine the p t trapping conditions to evaluate possible pressure corrections and to compare different depths of formation based on the pressure calculations and given geothermal gradients for illustrative purposes macflincor has been utilized here to constrain different physical chemical parameters of fluid inclusions trapped in ore related quartz veins and breccias of archean lode gold deposits in western australia inferred pressures from individual deposits show a wide range of values which may be due to post entrapment modifications and or observational uncertainties including estimation of liquid vapor ratios

a review of the geodynamic setting of large scale late mesozoic gold mineralization in the north china craton an association with lithospheric thinning abstract abundant gold deposits are distributed along the margins of the north china craton ncc occurring throughout the precambrian basement and located in or proximal to mesozoic granitoids these deposits show a consistent spatial temporal association with late jurassic early cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock their ages are mainly early cretaceous 130 110 ma and constrain a very short period of metallogenesis sr nd pb isotopic tracers of ores minerals and associated rocks indicate that gold and associated metals mainly were derived from multi sources i e the wall rocks precambrian basement and mesozoic granites and associated mafic rocks previous studies including high surface heat flow uplift and later basin development slow seismic wave speeds in the upper mantle and a change in the character of mantle xenoliths sampled by paleozoic to cenozoic magmas have been used to suggest that ancient cratonic mantle lithosphere was removed from the base of the ncc some time after the ordovician and replaced by younger less refractory lithospheric mantle the geochemistry and isotopic compositions of the mafic rocks associated with gold mineralization 130 110 ma indicate that they were derived from an ancient enriched lithospheric mantle source whereas the mafic dikes and volcanic rocks younger than 110 ma were derived from a relatively depleted mantle source i e asthenospheric mantle according to their age and sources relation to magmatism and geodynamic framework the gold deposits were formed during lithospheric thinning the removal of lithospheric mantle and the upwelling of new asthenospheric mantle induced partial melting and dehydration of the lithospheric mantle and lower crust due to an increase of temperature the fluids derived from the lower crust were mixed with magmatic and meteoric waters and resulted in the deposition of gold and associated metals

involvement of anomalously as au rich fluids in the mineralization of the heilan gou gold deposit jiaodong china evidence from trace element mapping and in situ sulfur isotope composition abstract the mesozoic 120 ma heilan gou gold deposit located in the jiaodong gold province eastern margin of the north china craton ncc consists of several ultra high grade up to 600 g t auriferous quartz veins in the early cretaceous guojialing granodioritic pluton ore related pyrite crystals from this deposit show complex textures in this study emp nano sims trace element mapping and in situ sulfur isotope analyses were conducted to characterize the textural and compositional features two types of pyrite were identified type i crystals py i hosted in gold quartz pyrite veins are generally homogeneous in chemical composition they contain low concentrations of as based on the distinctive textural and compositional signatures between py iia and py iib it is proposed that anomalously as au rich fluids were injected into hydrothermal systems during the late ore forming stage which may have intensively interacted with certain sedimentary rocks the involvement of these fluids firstly documented in this study can largely explain the occurrence of native gold ore shoots at heilan gou in addition the intimate association between as and au highlights the important roles of as in enrichment of au in the jiaodong gold district

geochronological framework of the xiadian gold deposit in the jiaodong province china implications for the timing of gold mineralization abstract the xiadian gold deposit located in the zhaoyuan laizhou belt of the jiaodong gold province is a typical jiaojia type gold deposit which is characterized by disseminated and stockwork ores enclosed by hydrothermally altered wall rocks the exact age and the genesis of the gold deposit remain controversial here we present precise in situ monazite u pb dating to constrain the age of the gold mineralization which we integrate with published geochronological work on the associated geological events to understand the genesis of the gold deposit the linglong granite represents the earliest magmatic event at xiadian and yielded a zircon la icpms u pb age of 159 5 0 9 ma 2 mswd 0 63 subsequent geologic events were recorded by minor amounts of quartz pyrite molybdenite veins which are dated at 124 8 2 1 ma 2 mswd 0 01 by molybdenite re os dating in a granitic pegmatite the formation of such veins was close to the emplacement of adjacent guojialing granodiorite 130 ma and thus may be considered as a product of post magmatic hydrothermal activity it is proposed that the molybdenum bearing hydrothermal fluids acted as a prelude to gold mineralization and participated in the formation of the latter ore fluids gold mineralization took place at 120 0 1 4 ma 2 mswd 0 59 determined by la icpms u pb dating on hydrothermal monazite from quartz polymetallic sulfide veins prior to and post mineralization voluminous hydrothermally altered porphyritic diorite and fresh quartz diorite porphyry dykes were emplaced which yielded u pb ages of 121 3 1 4 ma 2 mswd 0 28 and 115 8 1 9 ma 2 mswd 0 71 respectively based on these geochronological data we have established a comprehensive geochronologic framework which suggests that the genesis of the xiadian deposit might be related to the craton destruction and lithosphere thinning in the north china craton

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

tectonics granitoids and mesozoic gold deposits in east shandong china abstract mesozoic granitoids in east shandong 1 contain some 30 moz gold making east shandong the largest granitoid hosted gold province in the world the gold province is located along the northern boundary of the suture zone between the north china and south china cratons according to their mineralogical geochemical and geochronological characteristics two groups of mesozoic granitoids are recognised in east shandong namely the middle yanshanian my ca 160 150 130 ma and the late yanshanian ly ca 117 85 ma granitoids the first group of granitoids only occur to the north of the suture zone whereas the second group of granitoids occur on both sides of the suture zone these characteristics suggest that the two groups of granitoids were associated with different tectonic events a tectonic analysis suggests that the my granitoids are the result of collision and suturing of the north and south china cratons during the triassic to jurassic whereas formation of the ly granitoids is attributed to the distal inland influence of subduction of the pacific izanagi plate underneath the eurasian continent during the cretaceous the major gold deposits are spatially associated with the my granitoids in east shandong most of the gold occurs either as quartz veins in the granitoids or disseminated in altered shear zones along the boundary of the granitoids and archaean metamorphic rocks the major gold mineralization and alteration generally display the characteristics of gold only provinces namely co 2 rich low salinity and reduced fluids and proximal mica and sulfide alteration these characteristics are different from those of phanerozoic granitoid related skarn porphyry systems accordingly the gold mineralization may be more tectonically and structurally controlled rather than have a direct genetic relationship with the granitoid itself according to the relationships between tectonics granitoids distribution of gold deposits and fluid geochemistry the major gold in east shandong may have been formed during the subsequent exhumation stage after the collision of the north and south china cratons