p t t paths of collisional orogens pressure temperature time p t t paths summarize the changes in pressure and temperature imposed on a metamorphic rock during orogenesis they provide a convenient framework for the interpretation of complex metamorphic histories and also offer insight into the thermal and tectonic factors controlling metamorphism in collisional orogens p t t data are acquired through a combination of textural observations thermobarometry and thermochronometry and assembled into a p t t path using geological constraints one dimensional p t t models assuming instantaneous deformation and thermal relaxation by conduction are flexible and useful for testing tectonic models particularly where geochronological constraints are available two dimensional models allow more sophisticated deformation geometries and allow the effects of advection to be incorporated analysis of collisional orogens in terms of critical wedge theory can yield p t t paths that reflect coupling between thickening uplift exhumation erosion and convergence where rates of erosion approach rates of tectonic uplift as is currently happening in the southern alps of new zealand high grade metamorphic rocks can be exhumed rapidly from considerable depth alternatively rapid exhumation may reflect gravity driven extension in an over steepened or thermally weakened orogen

the 1 85 ga mo mineralization in the xiong er terrane china implications for metallogeny associated with assembly of the columbia supercontinent abstract the east qinling region in china hosting several tens of mesozoic magmatic hydrothermal mo deposits is one of the largest molybdenum belts in the world the recently discovered longmendian mo deposit luoning county henan province occurs within the xiong er terrane of the east qinling mo belt here the mo mineralization is confined to altered amphibolite which is replaced by microcline actinolite tremolite epidote and carbonate molybdenite is also observed in microcline dominated felsic differentiates but occurs within the altered amphibolite enclaves here we report re os isotope analyses of five molybdenite and four pyrite samples from longmendian which yield re os isochron ages of 1853 36 ma and 1855 29 ma respectively these ages are in good agreement with the metamorphic age of the taihua supergroup 1 87 1 84 ga the re os data presented in this study indicate that the period of 1 85 ga was a time of widespread melting generating leucocratic microcline dominated granitic melts the timing also coincides with the collision of the eastern and western blocks of the north china craton and its final cratonization at 1 85 ga coinciding with the incorporation of the north china craton within the paleoproterozoic supercontinent columbia

crustal extension ag pb zn veins in the xiong ershan district southern north china craton constraints from the shagou deposit the shagou vein type ag pb zn deposit in the xiong ershan district southern margin of the north china craton is hosted within amphibolite facies metamorphic rocks of the late archean to early paleoproterozoic taihua group the ag pb zn veins are localized in ne to nne trending brittle faults and typically display symmetrical zoning consisting of siderite quartz sphalerite galena and quartz calcite from the margin toward the center of each vein ore related hydrothermal alteration is well developed on both sides of the veins dominated by silicification sericitization chloritization and carbonatization sericite separates extracted from a major ag pb zn vein yield a 40 ar 39 ar plateau age of 140 0 1 0 ma 1 and isochron age of 141 1 1 6 ma 1 indicating that mineralization occurred at the beginning of early cretaceous field and textural relationships indicate four hydrothermal stages marked by assemblages of quartz siderite stage i quartz sphalerite ankerite stage ii quartz galena silver minerals ankerite stage iii and quartz calcite stage iv respectively silver minerals are abundant in all veins and are composed of in paragenetic order argentiferous tetrahedrite polybasite jalpaite argentite and native silver these silver minerals commonly occur as replacements of galena chalcopyrite and other sulfides or as fillings of microfractures in sulfides and quartz microthermometric measurements of primary fluid inclusions in quartz carbonates and sphalerite from various hydrothermal stages indicate that ore minerals were deposited at intermediate temperatures 267 157 c from aqueous carbonic to aqueous fluids with moderate salinities 7 2 15 9 wt nacl equiv coexisting galena sphalerite pair yields sulfur isotope equilibrium temperatures of 205 to 267 c consistent with the overall homogenization temperatures of fluid inclusions the microthermometric data also indicate that both fluid mixing and fluid rock interaction were important mechanisms for ore precipitation carbonate minerals siderite ankerite calcite spanning the entire mineralization history have 13 c v pdb values of 5 2 to 1 4 and 18 o v smow of 10 9 to 15 0 corresponding to calculated values for the ore fluids of 6 5 to 1 8 and 1 4 to 5 4 respectively 34 s v cdt values of sulfide minerals pyrite sphalerite galena range from 1 1 to 5 5 consistent with a deep seated sulfur source galena separates have 206 pb 204 pb ratios of 17 472 to 17 813 207 pb 204 pb ratios of 15 411 to 15 498 and 208 pb 204 pb ratios of 38 178 to 38 506 the isotope data together with geological and geochronological evidence favor a primary metamorphic source for sulfur and other components in the ore fluids a synthesis of available data suggests that the shagou deposit is a typical vein type ag pb zn deposit that formed under an extensional geodynamic setting associated with tectonic reactivation of the north china craton during the late mesozoic a time period that is manifested by pervasive magmatism widespread formation of metamorphic core complexes and development of faulted basins throughout the eastern part of the craton metamorphic devolatilization of the meso neoproterozoic marine sedimentary rocks previously subducted beneath the xiong ershan district facilitated by extensive magmatism and elevated heat flow due to lithospheric extension could have provided large amounts of ore fluids responsible for the ag pb zn mineralization the ne to nne trending faults affiliated with the transcrustal machaoying fault may have acted as pathways for the upward migration of deep seated metamorphic fluids mixing of the metamorphically derived fluids with meteoric waters ultimately resulted in deposition of the ag pb zn veins in brittle extensional structures

textures trace elements and pb isotopes of sulfides from the haopinggou vein deposit southern north china craton implications for discrete au and ag pb zn mineralization the haopinggou deposit in the xiong ershan district southern margin of the north china craton comprises numerous au and ag pb zn veins hosted in metamorphic rocks of the late archean to early paleoproterozoic taihua group two stages of mineralization have been recognized stage 1 pyrite quartz veins and stage 2 pb zn sulfide veins some pyrite quartz veins are surrounded or cut by pb zn sulfide veins others occur as independent veins six generations of pyrite have been identified at haopinggou py1 to py3 in stage 1 and py4 to py6 in stage 2 pyrites from stage 1 are enriched in au as co ni and bi whereas stage 2 pyrites contain higher ag pb zn sn and sb invisible au mostly occurs as lattice bound gold in py2 up to 92 ppm au and py3 up to 127 ppm au and has a close relationship with as native au grains are also present in py3 and likely resulted from mobilization and reprecipitation of the invisible au previously locked in the precursor pyrite this view is supported by extensive plastic deformation in stage 1 pyrite as revealed by electron backscatter diffraction analysis in stage 2 ag is mostly present as lattice bound silver closely associated with sb in galena up to 798 ppm ag a variety of silver minerals are also present as inclusions within galena or as interstitial grains these silver minerals were likely formed via ag cu exchange reaction between tetrahedrite and galena or represent exsolution from galena due to a temperature decrease pb isotopic compositions differ remarkably between stage 1 and stage 2 sulfides indicating different sources of lead pb in stage 2 pb zn sulfide veins is consistent with the haopinggou porphyry close to the veins the field textural compositional and lead isotopic data led us to conclude that the early gold bearing pyrite quartz veins and late silver bearing pb zn sulfide veins likely formed from distinct fluid systems related to discrete mineralization events our study suggests that au and ag pb zn veins hosted in the same metamorphic terrains may not be genetically related to each other

metallogeny in the capricorn orogen western australia the result of multiple ore forming processes abstract the capricorn orogen includes metamorphosed tectonic units intrusive igneous rocks volcano sedimentary and sedimentary basins situated between the pilbara and yilgarn cratons these include the gascoyne complex ashburton blair bresnahan yerrida bryah padbury and earaheedy basins and edmund and collier former bangemall basins mineral deposits and occurrences in these units comprise stratabound base metals including the giant abra pb cu ba edmund basin and magellan pb earaheedy basin and numerous hydrothermal veins and precious and or base metal lodes some of the more important orogenic precious metal lodes are those of the peak hill group in the bryah padbury basins and the egerton field in the gascoyne complex the metallogeny of the capricorn orogen reflects syn to post capricorn orogenic events linked to either protracted convergence tectonics between the pilbara and yilgarn cratons or to a two stage convergence history one during the capricorn orogeny ca 1 83 ga pilbara yilgarn convergence the other during the yapungku orogeny ca 1 79 north australian west australian convergence the metallogeny of the capricorn orogen was further sustained by continental mafic magmatism at about 1 45 and 1 07 ga during which heat advection may have caused widespread hydrothermal circulation particularly in the edmund collier earaheedy basins and adjacent tectonic units an interesting but as yet unexplained aspect of the capricorn metallogeny is the regional pb ba enrichment a conceptual model that attempts to explain the billion year long history of the metallogeny in the capricorn orogen is proposed mineral exploration in the capricorn orogen is somewhat limited and not as intensive as is in the brown fields of the archaean terranes of western australia

genetic relationship between 1780 ma dykes and coeval volcanics in the lvliang area north china abstract the 1780 ma dykes and coeval volcanics constitute a large igneous province in the north china craton however whether these dykes and volcanic rocks of varying compositions originated from one or multiple sources remains controversial the ca 1780 ma lvliang dykes are characterized by widespread e w oriented dykes and minor n w oriented diabase dykes the e w oriented dykes are bimodal and comprise two subgroups one is dominated by acidic high silica dykes sio 2 63 wt while the other is dominated by mafic to intermediate relatively low silica dykes sio 2 sims u pb dating on zircons from one high silica dyke and a rhyolite volcanic layer yields 207 pb 206 pb ages of 1783 7 ma and 1776 6 ma respectively and sims u pb dating on baddeleyites from a low silica dyke yields a 207 pb 206 pb age of 1789 5 ma they are all tholeiitic in composition mgo 0 3 6 1 wt sio 2 51 74 wt enriched in light rare earth elements la yb n 7 9 20 2 and show negative anomalies in nb ta sr and eu eu eu 0 3 0 9 they also have similar in situ hf isotopes of baddeleyite zircon ehf values of 14 5 to 1 8 and bulk rock end 6 7 to 3 0 isotopes furthermore immiscible textures are identified from the xiaoliangling group volcanics which are characterized by some silica rich melts globules in the fe rich magma these spatiotemporal affinities and geochemical similarities as well as the identified immiscible textures reveal that the low silicate dykes are conduits for the basalt andesite with significant fractionation of clinopyroxene and plagioclase while the high silica dykes are conduits for the rhyolite dacite with distinct immiscible segregation prior to eruption in addition there is a sharp change of ehf values at 1780 1730 ma and their hf t dm ages are 2750 1950 ma as these rocks originated from the subcontinental lithospheric mantle this may indicate that the subcontinental lithospheric mantle was metasomatized during this time period possibly by a paleo plume event

origin of the wangpingxigou pb zn deposit in east qinling orogenic belt china distal response to the giant donggou porphyry mo system abstract the southern margin of the north china craton ncc hosts many world class porphyry mo and vein type pb zn ag deposits forming an important polymetallic metallogenic belt in china even over the world although the mo and pb zn ag mineralization are temporarily and spatially associated with each other their possible genetic links are still unclear to delineate the relationships between the two types of ore mineralization we carried out in situ geochemical and s pb isotopic analyses on sulfides from the two spatially associated deposits i e the wangpingxigou pb zn and donggou porphyry mo deposits in the ore district based on field and microscopic observations on the crosscutting relationships of various veins and paragenetic relationships of various hydrothermal minerals three i iii and four i iv stages of hydrothermal veins have been identified in the wangpingxigou and donggou deposits respectively pyrite grains from stage ii of the wangpingxigou deposit have high co ni ratios mostly 1 and au and as contents similar to those of typical epithermal systems moreover sulfides from this deposit have in situ 206pb 204pb 17 345 17 417 207pb 204pb 15 454 15 514 and 208pb 204pb 38 138 38 364 ratios similar to those of sulfides from the donggou deposit indicating that the two deposits were relevant to a common source the concentrations of many elements i e pb ag sn zn sb mn au and as in pyrite decrease gradually from the stage ii of the wangpingxigou deposit to the stage ii of the donggou deposit consistent with metal zonation typically observed in porphyry related metallogenic systems further considering similar ages of the two deposits we propose that the wangpingxigou pb zn deposit is likely distal to the donggou porphyry mo system the range of 34s values of pyrites 7 63 8 76 from the stage ii in the donggou deposit is similar to those of the ancient strata xiong er group 7 31 8 17 in the ore district indicating that the sulfur in ore forming fluids may be mainly derived from the ancient strata however the 34s values 9 20 9 70 of stage iii sulfides in the donggou deposit are higher than those of stage ii sulfides in the donggou deposit and stage ii sulfides in the wangpingxigou deposit 7 34 9 29 the different sulfur isotopic compositions may be related to varied physicochemical conditions of the ore forming fluids confirmation of a mo pb zn metallogenic system in the region provides important clues on further prospecting of mo and pb zn resources in the southern margin of the north china craton

origin of the xiaohekou skarn copper deposit and related granitoids in the zha shan ore cluster area south qinling china abstract the xiaohekou copper deposit is one of the few typical skarn type commercial deposits in the zha shan ore cluster area in the eastern part of south qinling the ore related granitoids in the xiaohekou mining district include a number of small plutons of granodiorite porphyry and granite porphyry as well as numerous dykes they are characterized by relatively low sio2 65 9 73 3 wt and mgo 0 26 1 72 wt contents variable mg 29 4 64 0 values high k2o 3 11 5 75 wt content and negligible eu 1 00 1 15 values the samples also exhibit depletion in cr ni nb ta and ti content and high sr y 46 6 64 7 and la yb 17 0 25 0 ratios these features are similar to those of high k calc alkaline adakite like magma formed by partial melting of thickened lower crust in continental collision zones or intracontinental settings the majority of the samples have tdm2 hf of 1 5 1 2 ga corresponding to weakly negative ehf t values 4 75 to 0 13 typical of crustal material but more than one quarter have tdm1 hf of 0 80 0 71 ga corresponding to positive ehf t values of 0 07 to 2 45 indicating that the granitoids resulted from partial melting of mesoproterozoic lower crustal rocks with significant input from enriched lithospheric mantle derived magmas zircons from the xiaohekou granitoids have fmq values concentrated around 0 62 to 5 54 most of which show the magma fo2 of fmq to hm in accordance with the widespread occurrence of magnetite hematite and specularite in the xiaohekou skarn system which is an indicator of relatively high fo2 for a magmatic hydrothermal system the granitoids exhibit similar or even higher ce4 ce3 average of 452 and eu eu average of 0 72 values in comparison with those of fertile cu deposits worldwide indicating that the xiaohekou granitoids may possess the potential to form a large magmatic hydrothermal cu deposit zircons of the granitoids show obvious positive correlations between oxidation indices ce and eu anomalies ce4 ce3 ratios and fmq values and ehf t values implying the involvement of an oxidized mantle component which might have caused the fo2 elevation and played an important role in the formation of cu deposits the zircon u pb ages 141 3 1 3 and 138 1 2 0 ma of the xiaohekou ore related granitoids obtained in this study are similar to the zircon u pb and molybdenite re os ages yielded from porphyry mo mineralization at the chigou and lengshuigou deposits in the zha shan ore district indicating that they are possibly part of a single tectonic magmatic and metallogenic event in the yanshan orogeny the ore related granitoids in the xiaohekou area were formed in a post collisional compression extension transition regime during the early cretaceous qinling intracontinental orogeny the orogeny can be attributed to the far field effect of a switch from pre mesozoic tethyan tectonics to late mesozoic pacific tectonics this triggered a stress field transition from n s to e w trending and from intracontinental subduction thickening to large scale lithospheric delamination and thinning

fluid inclusion geochemistry and 40ar 39ar geochronology constraints on the genesis of the jianchaling au deposit china abstract the giant jianchaling gold deposit is located in the shaanxi province china the mineralization is hosted by wnw trending faults in the mianxian lueyang yangpingguan mly area the mineralization can be divided into three stages based on mineralogical assemblages and crosscutting relationships of mineralized quartz veins these stages from early to late are characterized by the mineral assemblage of 1 quartz coarse grained pyrite pyrrhotite pentlandite dolomite 2 quartz pyrite gold sphalerite galena carbonate arsenopyrite fuchsite and 3 dolomite calcite quartz fine grained pyrite realgar orpiment three types of fluid inclusions have been recognized in this study based on petrographic and microthermometric measurements including pure co 2 and or ch 4 pc type nacl h 2 o w type and nacl co 2 h 2 o c type fluid inclusions these fluid inclusion types are present in quartz from the stage 1 and 2 assemblages whereas the stage 3 quartz only contains w type fluid inclusions the stage 2 assemblage is associated with the mineralization at the jianchaling deposit fluid inclusions of stage 1 quartz homogenize mainly between 250 and 360 c with salinities up to 15 6 wt nacl equiv whereas the stage 3 dolomite with homogenization temperatures of 160 220 c and salinities of 1 1 7 4 wt nacl equiv this indicates that the ore fluid system evolved from co 2 rich probably metamorphic hydrothermal to co 2 poor meteoric fluid all three types of fluid inclusions can be observed in the stage 2 quartz suggesting that this heterogeneous association was trapped from a boiling fluid system these inclusions homogenized at temperatures of 200 250 c and salinities of 1 2 12 4 wt nacl equiv the estimated trapping pressures of the fluid inclusions are between 117 and 354 mpa in stage 1 suggesting an alternating lithostatic hydrostatic fluid system which was controlled by a fault valve at the depth of 12 km two fuchsite samples collected from the stage 2 polymetallic quartz veins yielded well defined 40 ar 39 ar isotopic plateau ages of 197 2 and 194 2 ma and 39 ar 36 ar 40 ar 36 ar normal isochrones of 198 2 and 199 2 ma this indicates that the mineralization at jianchaling is early jurassic ca 198 ma in age we propose that jianchaling is an orogenic gold deposit and formed during continental collision related to the northward subduction of the mian lue oceanic plate during the early jurassic we also conclude that the beginning of the continental collision between the yangtze and the north china cratons took place around 200 ma

gold and silver metallogeny of the south china fold belt a consequence of multiple mineralizing events abstract the south china fold belt is part of the south china block that is interpreted to be the result of multiple tectonic and magmatic events that formed a collage of accreted proterozoic and phanerozoic terranes the jurassic to early cretaceous yanshanian period 180 90 ma a time of major tectono thermal events that affected much of eastern and southeastern china is of great metallogenic importance in the fold belt this period is linked to subduction of the pacific plate beneath the eurasian continent and is manifested by voluminous volcano plutonic activity of predominantly calc alkaline affinity the distribution of gold and silver deposits in the south china fold belt indicates the presence of two distinct metallogenic provinces a region of basement uplifts which are controlled by shear zones and form neoproterozoic inliers of metamorphosed iron rich rock types defines the first province in this province orogenic lodes and volcanic related epithermal deposits represent the more significant precious metal mineralization the second province is essentially confined to a belt of yanshanian felsic intermediate volcanic and subvolcanic rocks that extends along most of the southeastern china coast in an area known as the coastal volcanic belt deposits in the coastal volcanic belt are silver and or copper rich volcanic hosted and epithermal in character the precious metal metallogeny of the south china fold belt is interpreted to have developed in at least three stages one as a result of collision events during the caledonian orogeny ca 400 ma the second during the indosinian orogeny ca 200 ma and the third during or soon after the formation of the yanshanian magmatic belt yanshanian orogeny 180 90 ma the latter was responsible for a hydrothermal event that affected large sections of the belt and its proterozoic substrate this may have resulted in the redistribution and enrichment of precious metals from preexisting orogenic gold lodes in neoproterozoic basement rocks which are now exposed as windows in zones of tectonic uplift the yanshanian hydrothermal activity was particularly widespread in the coastal volcanic belt and resulted in the formation of both low and high sulfidation epithermal gold and silver and locally copper and other base metal mineralization it is suggested that the coastal volcanic belt has greater potential for world class epithermal and porphyry deposits than previously realised

plate tectonics and orogenic research after 25 years a tethyan perspective abstract orogeny the process by which the earth s prominent mountain ranges are constructed has been a central topic of interest in the earth sciences since at least the end of the 18th century the recognition that strains and displacements of very considerable magnitude occur along all of the three dimensions within an orogenic belt during its evolution has grown gradually during the last two centuries emphasis on primary vertical movements dominated the ideas on the nature of orogeny during the first half of the 19th century whereas compression and consequent uplift across mountain belts were believed to be the main cause for their origin during the subsequent one hundred years or so that were spent under the dominance of the fixist contraction theory mobilist tectonicians realised that continental drift in places also required motion along the trend of orogenic belts but this view did not gain general acceptance recognition of significant strike slip motion parallel or subparallel with mountain ranges evolved independently and mostly within the fixist camp by the 1960 s presence of important motions both along and across mountain belts had become common knowledge but no theoretical basis existed to account for them all

late permian triassic metallogeny in the chinese altay orogen constraints from mica 40ar 39ar dating on ore deposits abstract the central asian orogenic belt caob constitutes the largest phanerozoic accretionary orogen on earth it extends over 5000 km and hosting numerous metal deposits the chinese altay orogen an important element of the caob hosts abundant devonian ca 410 370 ma deposits the 40 ar 39 ar dating of seven mica separates from the representative samples syngenetic with orogenic type mineralization is summarized to record a poorly studied permian to triassic metallogenic episode in the chinese altay orogen the kelan and maizi basins in the chinese altay orogen which likely represent an arc accretionary complex contain a series of polymetallic lode deposits hosted in low grade metamorphic volcano sedimentary rocks two muscovite and five biotite separates were obtained from the ore forming veins paragenetically associated with au bearing polymetallic sulfides in the keketale pb zn wulasigou cu tiemurt pb zn dadonggou pb zn and sarekuobu au deposits these separates yielded 40 ar 39 ar plateau ages ranging from 260 ma to 205 ma integration of these results with other published geological and geochronological data indicates that the au cu pb zn mineralization post dated the final caob assembly with fluid movement and mineralization possibly driven by regional metamorphism and deformation it is herein proposed for a metallogenic model that the metamorphic fluid migration following final assembly of the caob results into the formation of the deposits

multi stage cu remobilization of the huping metamorphic hydrothermal deposit in the southern north china craton abstract the zhongtiao region is a well endowed cu metallogenic province in the southern north china craton and contains a large number of early precambrian cu deposits of different styles most of which have been subjected to the ca 1 85 ga regional metamorphism however whether there was any role for the proterozoic metamorphism on the extensive cu mineralization is yet to be well understood this paper presents an integrated investigation on the field geology mineral chemistry fluid inclusion and c h o s isotopes of the huping metamorphic hydrothermal deposit in the neoarchean paleoproterozoic zhongtiao metamorphic terranes and reveals multi stage cu remobilization that formed and upgraded the cu deposits in the region we identified three stages of syn to post metamorphic cu remobilization transportation in the huping cu deposit including i early mechanical transport ii intermediate metamorphic hydrothermal remobilization and iii late meteoric fluid incursion in stage i sulfides were remobilized and transported internally under lower greenschist facies metamorphism forming the veinlet disseminated ores and chalcopyrite avg 34s 2 1 similar to the chlorite amphibole schist wall rocks in stage ii the immiscibility of metamorphic fluids avg 18o 4 6 and d 56 6 from the metamorphic terranes triggered the precipitation of higher 34s chalcopyrite avg 8 0 led by the incorporation of extra sulfur during the fluid migration in stage iii incursion of meteoric fluids into the waning metamorphic hydrothermal system formed the barren quartz calcite veins avg 18o 0 09 and 13c 0 88 during these cu remobilization processes the earlier formed sulfides were chemically stable during the mechanical transfer by regional metamorphism and deformation subsequently the immiscibility of metamorphic fluids induced significant cu remobilization and precipitation in the metamorphic hydrothermal system we thus propose a model of multi stage mechanical and chemical cu remobilization for the huping cu deposit which highlights the crucial impacts of metamorphic remobilization processes on the regional cu mineralization in the zhongtiao region

the early cretaceous yangzhaiyu lode gold deposit north china craton a link between craton reactivation and gold veining the yangzhaiyu gold deposit is one of numerous lode gold deposits in the xiaoqinling district southern margin of the north china craton gold mineralization is hosted in neoarchean to early paleoproterozoic amphibolite facies metamorphic rocks and consists of auriferous quartz veins and subordinate disseminated ores in the vein proximal alteration zone ore related hydrothermal alteration is dominated by sericite quartz sulfide assemblages close to gold veins and biotite quartz pyrite chlorite epidote alteration generally distal from mineralization pyrite is the predominant sulfide mineral locally coexisting with minor amounts of chalcopyrite sphalerite and galena gold occurs mostly as free gold enclosed in or filling microfractures of pyrite and quartz and is also present in equilibrium with au bearing tellurides mainly petzite and calaverite coexisting with hessite tellurobismuthite and altaite fluid inclusion studies suggest that gold veins were deposited at intermediate temperatures 175 313 c from aqueous or aqueous carbonic fluids with moderate salinity 5 14 wt nacl equiv 34s values of sulfide minerals range mainly from 2 0 to 4 4 whereas auriferous quartz vein samples have 18o values of 12 4 to 9 6 with calculated 18oh2o values of 6 0 to 3 2 gold related pyrite grains yield elevated 3he 4he ratios 1 51 0 32 ra relative to crustal reservoirs and mantle like 20ne 22ne and 21ne 22ne ratios 9 90 9 68 and 0 029 respectively the stable and noble gas isotopes thus suggest deep seated most likely magmatic and mantle derived sources for the ore fluids sulfur and by inference other components in the ore system 40ar 39ar dating of ore related sericite and biotite separates indicates two episodes of gold genesis at 134 5 to 132 3 and 124 3 to 123 7 ma the mineralization ages overlap zircon u pb ages of 141 0 1 6 to 125 8 1 4 ma 2 for the wenyu and niangniangshan monzogranite plutons and a number of mafic to intermediate dikes intruding these plutons all being proximal to the yangzhaiyu gold deposit the synchronism of gold genesis and magmatism provides additional weights of evidence for a magmatic derivation of ore fluids and sulfur the geochronologic data also suggest that gold veining took place billions of years after the stabilization of the north china craton and associated metamorphism in the late archean to early paleoproterozoic this contrasts sharply to lode gold deposits in other precambrian cratons that formed predominantly in late archean to paleoproterozoic temporarily and genetically related to regional high grade metamorphism and compressional or transpressional tectonism available data have demonstrated that the north china craton was reactivated in the late mesozoic as marked by voluminous igneous rocks faulted basin formation high crustal heat flow and widespread metamorphic core complexes in the eastern part of the craton it is thus suggested that the yangzhaiyu gold deposit together with other deposits of similar ages in the xiaoqinling district were products of this craton reactivation event lithospheric extension and extensive magmatism related to the craton reactivation may have provided sufficient heat energy fluid and sulfur required for the formation of the gold deposits

geochronology and origin of the qi189 porphyry gold deposit in qiyugou orefield qinling orogen china abstract the qi189 gold deposit is a recently discovered porphyry system in the qiyugou orefield located in the northeastern qinling orogen along the southern margin of north china craton the orebodies are hosted in the porphyritic granite emplaced in the taihua supergroup three molybdenite and five pyrite samples from the ores yield re os isochron ages of 129 5 2 8 ma and 127 5 8 2 ma respectively which are coincident with the zircon u pb age of the porphyritic granite within analytical error 128 6 0 8 ma zircon grains from the post ore quartz monzonite yield weighted mean 206pb 238u age of 124 7 0 6 ma n 31 1 mswd 0 23 these ages constrain that the qi189 gold system was formed in the period of 130 127 ma the porphyritic granite and quartz monzonite show high k calc alkaline affinity enrichment of lree and lile depletion of hree and hfse and negligible eu anomaly zircon grains show negative ehf t values of 20 7 to 14 9 with tdm2 hf ages of 2 49 2 13 ga this indicates that the qi189 porphyry system originated from a source mixed by the materials from the north qinling accretion belt and the basement of north china craton with minor contribution from the mantle and developed under a post collisional tectonic setting

origin of late archean and early proterozoic rocks and associated mineral deposits from the zhongtiao mountains east central china abstract late archean and early proterozoic supracrustal rocks in the zhongtiao mountains of east central china include five successions separated by unconformities or intrusive contacts the oldest successions the shushui complex 2500 ma and the jiangxian 2400 2200 ma and zhongtiao groups 2100 ma are composed chiefly of metapelites quartzites and marbles with small amounts of bimodal felsic mafic volcanics in which felsic ash flow tuffs dominate the overlying danshanshi group includes chiefly quartzites and conglomerates and the xiyanghe group 1830 ma comprises bimodal volcanics and red beds granitoids range from late archean to early proterozoic in age and vary from tonalite to granite in composition precambrian igneous rocks show a subduction zone geochemical component depletion in nb ta relative to lile and early proterozoic granitoids range in composition from i to s types geochemical and isotopic constraints favor an origin for early proterozoic zhongtiao felsic magmas either by melting of sediments or tonalites in the crust or by melting of amphibolite eclogite in a descending slab zhongtiao pelites are similar in composition to phanerozoic shales and exhibit negative eu anomalies on chondrite normalized graphs stratiform copper deposits in the zhongtiao proterozoic rocks are of three types volcanic hosted deposits of hydrothermal or exhalative origin primary sedimentary deposits and remobilized sedimentary deposits the jiangxian and zhongtiao lithologic assemblages of quartzite pelite carbonate together with primary textures and structures in these rocks suggest deposition in shallow marine tectonically stable basins whereas coarse terrigenous sediments in the danshanshi and xiyanghe groups appear to reflect near shore marine to fluvial deposition in tectonically active basins most data are consistent with deposition of the early proterozoic supracrustal rocks in a continental margin back arc basin

late mesozoic felsic magmatism and mo au pb zn mineralization in the southern margin of the north china craton a review abstract the widespread large scale mo au pb zn mineralization in the southern margin of the north china craton ncc is spatially and temporally associated with the voluminous late mesozoic granitic magmatism relationship between the granitic magmatism and ore mineralization has been extensively investigated in the last decade however controversy still exists regarding the magma source metallogeny and geodynamic settings this paper systematically reviews the major features of the mesozoic granitic magmatism and associated mo au pb zn mineralization in the southern margin of the north china craton including temporal and spatial variations of magmatic rocks composition of ore fluids sources of ore metals and metallogeny the granitic rocks were mainly formed in late mesozoic and emplaced in two stages the early stage 158 128 ma granites are of typical i type derived from remelting of ancient crust of the southern margin of the ncc with input of mantle material under lithospheric thinning tectonic regime the late stage 127 112 ma granites include a type and or highly fractionated i type granites which commonly contain more fractions of mantle materials as exhibited by more depleted isotopic signatures suggestive of an intracontinental extensional setting mo mineralization 155 130 ma related to the early stage granitic magmatism includes mainly of porphyry or porphyry skarn type with ore metals mainly derived from the mixed source of the mantle and crust whereas the late stage mo mineralization 127 116 ma is mainly of porphyry type with the ore metals from similar sources with more input of mantle materials pb zn deposits 144 130 ma associated with the early stage granitic magmatism are mainly of hydrothermal vein and skarn types whereas those 125 117 ma related to the late stage granites are of hydrothermal vein type the pb zn deposits are most likely distal products of the mo deposits together forming a metallogenic system au deposits are located in the xiaoqinling and xiong ershan areas and were formed during middle jurassic to early cretaceous 163 118 ma mostly from 132 to 120 ma the ores mainly occur in quartz veins and altered rocks and are hydrothermal magmatic in origin with au derived from a mixed source of crust and mantle

isotope geochemistry of the tieluping silver lead deposit henan china a case study of orogenic silver dominated deposits and related tectonic setting the tieluping silver deposit which is sited along ne trending faults within the high grade metamorphic basement of the xiong er terrane in the qinling orogenic belt is part of an important recently discovered mesozoic orogenic type ag pb belt ore formation includes three stages an early barren quartz pyrite stage e an intermediate polymetallic sulfide ore stage m and a late barren carbonate stage l carbon sulfur and lead isotope systematics indicate that the e stage fluids are deeply sourced the l stage fluids are shallow sourced meteoric water whereas the m stage fluids are a mix of deep sourced and shallow sourced fluids sulfur and lead isotope data show that the ore forming fluids must have originated from a source with elevated radiogenic lead and low 34s values that differs significantly from exposed geologic units in the xiong er terrane the lower crust and the mantle this supports the view that the carbonate shale chert sequences of the guandaokou and luanchuan groups south of the machaoying fault might be the favorable sources although little is known about their isotopic compositions a tectonic model that combines collisional orogeny metallogeny and hydrothermal fluid flow is proposed to explain the formation of the tieluping silver deposit during the mesozoic collision between the north china craton and south china block early mid triassic indosinian orogeny crustal slabs containing the carbonate shale chert sequences of the guandaokou and luanchuan groups locally rich in organic matter carbonaceous shale were thrust northwards beneath the xiong er terrane along the machaoying fault metamorphic devolatilisation of this underthrust slab probably provided the ore forming fluids to develop the ag pb ore belt which includes the tieluping silver deposit fluids and magmas were emplaced during extensional stages related to the jurassic cretaceous yanshanian orogeny

timing of the yuchiling giant porphyry mo system and implications for ore genesis the yuchiling mo deposit is a recently discovered giant porphyry system in the east qinling mo belt china its apparent causative intrusion i e the yuchiling granite porphyry is the youngest intrusion phase 4 of the heyu multiphase granite batholith which was emplaced between 143 and 135 ma new robust constraints on the formation of the yuchiling porphyry mo system are provided by combined zircon u pb biotite 40ar 39ar and molybdenite re os dating zircon grains from the mo mineralized granite porphyry yield weighted 206pb 238u age of 134 0 1 4 ma n 19 2 error mswd 0 30 magmatic biotite from the same sample yield a 40ar 39ar plateau age of 135 1 1 4 ma 2 error and an inverse isochron age of 135 6 2 0 ma n 7 2 error mswd 10 8 which are effectively coincident with the zircon u pb age within analytical error three pulses of mineralization can be deduced from the molybdenite re os ages namely 141 137 and 134 ma which agree well with the zircon u pb ages of granitic phases 1 2 and the yuchiling porphyry phase 4 respectively these well constrained temporal correlations indicate that mo mineralization was caused by pulses of granitic magmatism and that the ore forming magmatic hydrothermal activity responsible for the yuchiling porphyry mo system lasted about 8 ma the yuchiling mo deposit represents a unique style of porphyry mo system formed in a post collision setting and associated with f rich high k calc alkaline intrusions which differ from convergent margin associated porphyry mo deposits

geophysical constraints on the link between cratonization and orogeny evidence from the tibetan plateau and the north china craton abstract understanding the geodynamic process of orogeny and cratonization and their transition is among the key topics of research in evaluating the link between plate tectonics and continental dynamics the tibetan plateau and the north china craton ncc two key areas in mainland china offer excellent laboratories to understand continental tectonics over a broad span of earth history particularly the deep structure of the lithosphere as imaged from geophysical data on the tibetan plateau and the ncc provide important clues in understanding orogeny and cratonization the tibetan plateau is the largest and highest plateau on earth in terms of mean altitude and is an important region for understanding the mechanisms of continent continent collision and cenozoic plateau uplift the ncc is an archean craton that underwent lithospheric disruption during the mesozoic here we reconstruct the main features of the structure of the crust and upper mantle from surface wave tomography and gravity modeling in tibet and its neighboring regions in order to understand the modality of the convergence and collision process between the indian and eurasian plates and the influence of this process on the uplift of the plateau in the ncc geological geochemical geophysical and tectonic investigations demonstrate that lithospheric destruction mainly occurred in the eastern block the crustal structure of the ncc is reconstructed from ambient noise surface wave tomography and the different possible disruption mechanisms are evaluated the vs shear wave velocity tomography results and the density structure of the crust and upper mantle to about 350 km depth demonstrate the lateral variation of the thickness of the metasomatic lid between the south and north of the bangong nujiang suture bns and the west and east of tibet which suggest that the leading edge of the subducting indian slab reaches the bns the subduction angle of indian plate indicates a transition from steep to shallow from the west to east tibet sections depicting the gravitational potential energy suggest that mantle flow contributes to the subduction of the indian plate as far as the bns and the transition from the asthenospheric layer to the metasomatic lid overlaps with the transition from north south shortening in south tibet to eastward tectonic escape in north tibet qiangtang and songpan ganzi blocks both vs and models suggest the following 1 north southward lower crust flow beneath the eastern ncc and interaction between the westward mantle flow and eastward escape flow beneath the central ncc in addition to the earlier proposed mechanisms of delamination and thermal erosion played important roles in the lithospheric disruption of the archean craton 2 mantle flow plays an important role in the continental tectonic transition between neighboring tectonic blocks and within the cycle between orogeny and cratonization

re os and sr nd pb isotope constraints on source of fluids in the zhifang mo deposit qinling orogen china abstract the zhifang mo deposit is located in the northeastern qinling orogen along the southern margin of the north china craton the deposit represents a quartz vein system hosted in the mesoproterozoic xiong er group volcanic rocks we identify three hydrothermal stages early middle and late characterized by veinlets of quartz pyrite quartz molybdenite pyrite chalcopyrite galena sphalerite and quartz carbonate assemblages respectively five molybdenite samples from the zhifang deposit yield re os ages ranging from 241 2 1 6 ma to 247 4 2 5 ma with an isochron age of 246 0 5 2 ma 2 mswd 7 4 and a weighted mean age of 243 8 2 8 ma 2 mswd 5 5 the re os age shows that the mo mineralization occurred during the indosinian orogeny and suggests that the mineralization is unrelated to the yanshanian magmatism or the paleo mesoproterozoic volcanic hydrothermal event this study also reports a new sr nd pb isotope dataset from ore sulfides in an attempt to constrain the source of the ore forming fluids ten sulfide samples from middle stage of the zhifang mo deposit yield i sr t ratios of 0 710286 0 711943 with an average of 0 711004 e nd t values between 19 5 and 14 8 with an average of 16 7 and 206 pb 204 pb i 207 pb 204 pb i and 208 pb 204 pb i ratios of 17 126 17 535 15 374 15 466 and 37 485 37 848 with averages of 17 380 15 410 and 37 631 respectively one pyrite from the early stage yield i sr t of 0 722711 0 722855 with an average of 0 722783 which is higher than those of the middle stage sulfides and suggests equilibration with wallrocks the e nd t values are in the range of 17 3 to 16 6 with a mean at 17 0 and 206 pb 204 pb i 207 pb 204 pb i and 208 pb 204 pb i ratios are 17 386 15 405 and 37 622 respectively the ore sulfides show higher pb isotope ratios higher e nd t and lower i sr t values than the host rocks the results suggest that the ore forming fluids had lower i sr t and higher e nd t values than the ore sulfides and were possibly sourced from the dengfeng complex the southward subduction of the north china craton beneath the huaxiong block during the triassic was possibly responsible for the formation of the waifangshan orogenic mo system

a thick crustal block revealed by reconstructions of early mars highlands the global scale crustal structure of mars is shaped by impact basins volcanic provinces and a hemispheric dichotomy with a thin crust beneath the northern lowlands and a thick crust beneath the southern highlands the southern highlands are commonly treated as a coherent terrain of ancient crust with a common origin and shared geologic history plausibly originating from a giant impact s or a hemispheric scale mantle upwelling previous studies have quantified the contribution of volcanism to this crustal structure however the influence of large impacts remains unclear here we present reconstructions of the past crustal thickness of mars about 4 2 gyr ago where the four largest impact basins hellas argyre isidis and utopia are removed assuming mass conservation as well as the main volcanic provinces of tharsis and elysium our reconstruction shows more subdued crustal thickness variations than at present although the crustal dichotomy persists however our reconstruction reveals a region of discontinuous patches of thick crust in the southern highlands associated with magnetic and geochemical anomalies this region corresponding to terra cimmeria sirenum is interpreted as a discrete crustal block our findings suggest that the southern highlands are composed of several crustal blocks with different geological histories such a complex architecture of the southern highlands is not explained by existing scenarios for crustal formation and evolution a discrete block of thick ancient crust revealed by a crustal reconstruction suggests a complex geologic history for the southern highlands of mars

u pb ages and lu hf isotopes of detrital zircons from the southern qinling orogen implications for precambrian to phanerozoic tectonics in central china abstract the qinling orogen central china was constructed during the mesozoic collision between the north china and yangtze continental plates the orogen includes four tectonic units from north to south the huaxiong block reactivated southern margin of the north china craton north qinling accretion belt south qinling fold belt or block and songpan fold belt evolved from the northernmost paleo tethys ocean separating the gondwana and laurentia supercontinents here we employ detrital zircons from the early cretaceous alluvial sediments within the qinling orogen to trace the tectonic evolution of the orogen the u pb ages of the detrital zircon grains from the early cretaceous donghe group sediments in the south qinling fold belt cluster around 2600 2300 ma 2050 1800 ma 1200 700 ma 650 400 ma and 350 200 ma corresponding to the global kenorland columbia rodinia gondwana and pangaea supercontinent events respectively the distributions of ages and ehf t values of zircon grains show that the donghe group sediments have a complex source comprising components mainly recycled from the north qinling accretion belt and the north china craton suggesting that the south qinling fold belt was a part of the united qinling north china continental plate rather than an isolated microcontinent during the devonian triassic the youngest age peak of 350 200 ma reflects the magmatic event related to subduction and termination of the mian lue oceanic plate followed by the collision between the yangtze craton and the united qinling north china continent that came into existence at the triassic jurassic transition the interval of 208 145 ma between the sedimentation of the early cretaceous donghe group and the youngest age of detrital zircons was coeval with the post subduction collision between the yangtze and the north china continental plates in jurassic

early mesozoic mo mineralization in the qinling orogen an overview abstract as one of the most important mo provinces in the world the qinling orogen is host to mainly late mesozoic late jurassic early cretaceous porphyry mo systems recently additional early mesozoic mainly triassic plus minor early jurassic mo deposits have been identified which occur as fault controlled quartz veins or as carbonatite veins and as such they are fundamentally different from the commonly observed porphyry systems furthermore early mesozoic porphyry systems are also present but they are different from those of late mesozoic age thus early mesozoic mo systems not only offer a new and comprehensive view of the mo metallogenesis but also provide unique insight into the tectonic evolution of the qinling orogen taking into consideration the role of mineral deposits as ideal probes of the geodynamic evolution the known early mesozoic mo deposits in qinling can be classified into three types based on their geological and geochemical features porphyry carbonatite and orogenic systems porphyry mo systems including porphyry porphyry skarn and intrusion related veins are spatially and genetically associated with granitic porphyries they display typical porphyry type alterations and are formed by magmatic water carbonatites are considered as mantle derived igneous rocks and mo mineralization is associated with magmatic fluids orogenic mo systems occur as fault controlled quartz lodes and the ore forming fluids are medium high temperature co2 rich metamorphic fluids spatially early mesozoic porphyry mo systems are concentrated in the western and middle part of the qinling orogen whereas carbonatite veins and orogenic mo systems are located in the northeastern part temporally orogenic mo deposits were the earliest mainly between 220 and 250 ma followed by carbonatite veins mainly between 205 and 225 ma and porphyry mo systems mainly between 190 and 205 ma with some exceptions there is generally a trend of decreasing deposit ages toward the western part of the orogen detailed comparison reveals that the early mesozoic porphyry mo systems in the qinling orogen are different from the late mesozoic ones in terms of their economic importance spatial distribution ore causative intrusions hydrothermal alteration and the ore forming fluids to explain the above geological and geochemical features the triassic qinling is considered as an active continental margin caused by the northward subduction of the mian lue oceanic plate a transition from continental arc to back arc basin is suggested for the formation of triassic orogenic and carbonatite vein mo deposits whereas continental arc is host to the early mesozoic porphyry mo systems

geology geochemistry and ore genesis of the wenyu gold deposit xiaoqinling gold field qinling orogen southern margin of north china craton abstract the wenyu giant gold deposit is hosted in the precambrian taihua supergroup metamorphic rocks within the xiaoqinling terrane qinling orogen on the southern margin of the north china craton the mineralization can be divided into three stages quartz pyrite veins early quartz sulfide veins middle main and carbonate quartz veinlets late with gold being mainly introduced in main stage quartz formed in two earlier stages contains three compositional types of fluid inclusions i e pure co2 co2 h2o and nacl h2o but the late stage minerals only contain the nacl h2o inclusions the inclusions in quartz formed in the early main and late stages yield total homogenization temperatures of 262 417 c 236 407 c and 114 239 c respectively with salinities no higher than 13 wt nacl equiv trapping pressures estimated from co2 h2o inclusions are 139 399 mpa and 111 316 mpa in the early and main stages corresponding to mineralization depths of 14 km and 11 km respectively fluid boiling and mixing caused rapid precipitation of sulfides and native au through boiling and inflow of meteoric water the ore forming fluid system evolved from co2 rich to co2 poor in composition and from metamorphic to meteoric as indicated by decreasing 18owater values from early to late the carbon sulfur and lead isotope compositions suggest the hostrocks within the taihua supergroup to be a significant source of ore metals integrating the data obtained from the studies including regional geology ore geology fluid inclusion and c h o s pb isotope geochemistry we conclude that the wenyu gold deposit was an orogenic type system formed in the tectonic transition from compression to extension during the jurassic early cretaceous continental collision between the north china and yangtze cratons

metallogeny and craton destruction records from the north china craton abstract the link between metallogeny and craton destruction in the north china craton ncc remains poorly understood particularly the mechanisms within the interior of the craton in this overview we summarize the major stages in the history of formation and evolution of the ncc the spatio temporal distribution and types of major ore species as well as mantle contribution to the metallogeny in an attempt to evaluate the geodynamic settings of metallogeny and the mechanisms of formation of the ore deposits the early precambrian history of the ncc witnessed the amalgamation of micro blocks and construction of the fundamental tectonic architecture of the craton by 2 5 ga the boundaries of these micro blocks and the margins of the ncc remained as weak zones and were the principal locales along which inhomogeneous destruction of the craton occurred during later tectonothermal events these zones record the formation of orogeny related gold copper iron and titanium during the early to middle paleoproterozoic with ages ranging from 2 5 to 1 8 ma the early ordovician kimberlite and diamond mineralization at ca 480 ma the late carboniferous and early to middle permian calc alkaline i type granitoids and gold deposits of 324 300 ma and the triassic alkaline rocks and gold silver polymetallic deposits occurring along these zones and the margins of the blocks correlate with rising mantle plume southward subduction of the siberian plate and northward subduction of the yangtze plate respectively the voluminous jurassic granitoids and cretaceous intrusives carrying gold molybdenum copper lead and zinc deposits are also localized along the weak zones and block margins the concentration of most of these deposits in the eastern part of the ncc invokes correlation with lithosphere thinning associated with the westward subduction of the pacific plate although magmatism and mineralization have been recorded along the margins and few places within the interior of the ncc in the jurassic their peak occurred in the cretaceous in the eastern part of the ncc marking large scale destruction of the craton at this time the junctions of the boundaries between the micro continental blocks are characterized by extensive inhomogeneous thinning we propose that these junctions are probably for future mineral exploration targeting in the ncc

geology and geochemistry of d o c isotope systematics of the qolqoleh gold deposit northwestern iran implications for ore genesis abstract the qolqoleh gold deposit is located in northwestern part of the sanandaj sirjan metamorphic belt northwestern iran igneous and sedimentary units exposed in the area have undergone greenschist metamorphism the area was affected by a ne sw trending shear zone and subsequent deformation two different types of mineralization are distinguished in the qolqoleh gold deposit based on geological structural conditions indicated by microtextural analysis ductile and then brittle ore forming processes are divided into three stages early i middle ii and late iii which include quartz pyrite i sulfides and gold ii and carbonate veinlets iii respectively the stage i fluids are characterized by 18o 15 5 at 440 oc and are thought to be deep sourced metamorphic waters the stage iii fluids with 18o 1 6 are shallow sourced meteoric waters whereas the stage ii fluids with 18o 13 1 are a mixture of deep sourced metamorphic and shallow sourced meteoric fluids based on comparisons of the d o c isotopic systematics the ore forming fluids with characteristic high 18o and 13c and low d originated from metamorphic devolatilization of cretaceous volcano sedimentary felsic to mafic metavolcanic rocks shale carbonate carbonaceous chert sequences locally rich in organic matter during late cretaceous continental collision of the afro arabian continent and the iranian microcontinent a crustal slab consisting of felsic to mafic metavolcanic rocks carbonate shale and carbonaceous chert was underthrust northwards beneath the central iranian microcontinent along the zagros fault during further contraction deformation was localized in reverse oblique slip structures with vergence toward south shear zones generally follow contacts between more competent and less competent rock units metamorphic devolatilization of this underthrust slab is the source of the ore forming fluids that generated the au ore belt which includes the qolqoleh gold deposit

genesis of the jianzhupo sb pb zn ag deposit and formation of an ore shoot in the wuxu ore field guangxi south china abstract the jianzhupo sb pb zn ag deposit in the southeastern dachang sn polymetallic ore belt guangxi region south china is the largest deposit in the wuxu district and is hosted by devonian limestone and mudstone the deposit mainly comprises a stage i jamesonite sphalerite ore shoot and stage ii jamesonite sphalerite calcite quartz jscq veins we use homogenization temperatures salinities and the h o isotopic compositions of fluid inclusions from the jianzhupo deposit to constrain the genesis of the deposit and determine factors that controlled the formation of the ore shoot fluid inclusions from both stages of mineralization contain large volumes of co2 and minor bitumen c6h6 and ch4 fluid inclusions from the ore shoot yield homogenization temperatures of 120 c 290 c mainly 250 c 270 c and salinities of 3 4 13 6 wt nacl equiv fluid inclusions from the stage ii mineralization yield homogenization temperatures of 150 c 350 c mainly 240 c 310 c and salinities of 1 4 12 0 wt nacl equiv ore forming fluids of the jianzhupo deposit yield 18oh2o and dv smow values of 4 9 9 9 and 78 to 111 respectively and plot close to the composition of magmatic water on the dv smow vs 18oh2o diagram co2 in the ore forming fluids was likely generated through deep skarnization beneath the wuxu ore field rather than from metamorphism thermal degradation or the oxidization of organic matter h o isotopic compositions of ore forming fluids that contain large volumes of co2 with minor bitumen and c6h6 indicate that they were derived from magmatic water that was mixed with basin brines ore forming fluids of the stage i ore shoot yield lower 18oh2o values 4 9 6 7 than those associated with the stage ii mineralization 7 5 9 9 moreover ore forming fluids of the ore shoot and the jscq veins yield strongly and weakly positive correlations between homogenization temperature and salinity respectively this difference suggests that rapid and large scale mixing between magmatic water and basin brines was the key factor that controlled the formation of the ore shoot

geology geochronology and isotopic geochemistry of the xiaoliugou w mo ore field in the qilian orogen nw china case study of a skarn system formed during continental collision this study is financially supported by the national natural science foundation of china 41502068

contrasting ore styles and their role in understanding the evolution of the altaids abstract the altaids is a paleozoic orogenic collage in central asia it occupies 10 of the eurasian continent and it is one of the richest concentrations of mineral deposits in the world comparable to those of the circum pacific and tethyan orogenic belts in particular it contains many types of hydrothermal ore deposits that are sensitive to the nature and origin of their host terranes including porphyry copper gold molybdenum volcanogenic massive sulfide copper lead zinc and orogenic gold deposits which are all diagnostic of convergent continental margins extensional arc related submarine basins and transpressional terrane boundaries within the altaids porphyry copper deposits are mostly concentrated within the kazakhstan and tuva mongolia micro continents where they formed almost continuously from the early ordovician to permian only a few are cambrian and triassic and most are late carboniferous most volcanogenic massive sulfide ore deposits are distributed along the south urals and rudny altai in the western altaids where they formed in a short time window from the early to middle devonian important orogenic gold deposits formed along regional strike slip faults between craton island arc or micro continent boundaries from the neoproterozoic to permian mostly in the early permian in limited key areas volcanogenic massive sulfide deposits formed upon much older 100 ma basement rocks than those of coeval porphyry deposits indicating that the altaids could not have developed from a single arc furthermore the porphyry deposits outline the distribution of several continental fragments the combined area of which is far less than that of the altaids which suggests that extensive new juvenile material has been added into island arc systems which may have been accreted to surrounding continental margins these metallogenic distributions in localized areas were a result of the mechanisms of crustal growth within the overall tectonic evolution of the altaids and they are consistent with the interpretation that the altaids is a multiple subduction accretion collage

a ductile to brittle shear zone hosted cu mineralization geological geochronological geochemical and fluid inclusion studies of the lingyun cu deposit southern tianshan nw china abstract the lingyun cu deposit is located at the northern margin of the south tianshan accretionary complex nw china in the lingyun mine area the rocks are cut by a nw trending yanxingshan ductile to brittle shear zone all orebodies are hosted in crystal tuff the sulfide mineralization in the lingyun cu deposit can be divided into early e and late l paragenetic stages the e stage is characteristic of fault controlled sulfide assemblages chalcopyrite bornite chalcocite quartz veins in the foliation fabric of the crystal tuff with albite sericite epidote biotite assemblages in the l stage the assemblages of ankerite chalcopyrite bornite chalcocite are present in veinlets that cut the e stage assemblages the sulfide assemblages in the lingyun deposit are characterized by striations in the metamorphosed crystal tuff ribbon like silicate minerals in the crystal tuff share common deformation features with the sulfide assemblages the host rock of the lingyun cu deposit yields a concordia age of ca 405 ma indicating that the aerbishibulake formation formed during southward subduction of the south tianshan ocean beneath the tarim block moreover crystal tuff samples show well developed negative sr anomaly and positive rb th u nd and p anomalies which are common in arc related volcanic rocks the ca 297 ma re os isochron age yielded by sulfides is much younger than the host rock which implies that the lingyun cu deposit is a typical epigenetic deposit both similar ree fractionated patterns between sulfide ores and crystal tuff and the high initial 187 os 188 os ratio 18 54 0 67 indicate significant crustal materials input the 40 ar 39 ar plateau age of ca 292 ma from the ribbon like sericite in crystal tuff is coeval with the mineralization occurrence in the lingyun cu deposit by contrast diorite dikes that crosscut the crystal tuff formed at ca 221 ma which is much younger than the sulfide mineralization thus the mineralization in the lingyun deposit is likely to have been generated by shear zone activity rather than the intrusion of diorite dikes three types of fluid inclusions have been identified in the lingyun cu deposit aqueous w type mixed aqueous carbonic m type and pure carbonic c type inclusions these three types of fluid inclusions are all found in the e stage quartz whereas only the w type fluid inclusions have been observed in l stage ankerite fluid inclusions from the e stage commonly contain co 2 and h 2 o locally with n 2 with low salinity which are common in orogenic deposits by contrast l stage fluid inclusions show low co 2 concentrations and salinity indicating a significant inflow of meteoric water given the regional geology ore geology coeval ore forming and deformation and fluid inclusion features the lingyun cu deposit may be associated with the orogenic class of mineral systems

shear wave velocity model from rayleigh wave group velocities centered on the sacramento san joaquin delta rayleigh wave group velocities obtained from ambient noise tomography are inverted for an upper crustal model of the central valley california centered on the sacramento san joaquin delta two methods were tried the first uses surf96 a least squares routine it provides a good fit to the data but convergence is dependent on the starting model the second uses a genetic algorithm whose starting model is random this method was tried at several nodes in the model and compared to the output from surf96 the genetic code is run five times and the variance of the output of all five models can be used to obtain an estimate of error surf96 produces a more regular solution mostly because it is typically run with a smoothing constraint models from the genetic code are generally consistent with the surf96 code sometimes producing lower velocities at depth the full model calculated using surf96 employed a 2 pass strategy which used a variable damping scheme in the first pass the resulting model shows low velocities near the surface in the central valley with a broad asymmetrical sedimentary basin located close to the western edge of the central valley near 122 w longitude at shallow depths the rio vista basin is found nestled between the pittsburgh kirby hills and midland faults but a significant basin also seems to exist to the west of the kirby hills fault there are other possible correlations between fast and slow velocities in the central valley and geologic features such as the stockton arch oil or gas producing regions and the fault controlled western boundary of the central valley

tracing the ore formation history of the shear zone controlled huogeqi cu pb zn deposit in inner mongolia northern china using h o s and fe isotopes abstract the original ore fluid of the huogeqi cu pb zn deposit in inner mongolia northern china was enriched in heavy oxygen isotopes with 18o values ranging from 9 9 to 11 4 per mil which is characteristic of the metamorphic devolatilization of pelitic rocks the d values determined by direct measurement of syn ore hydrothermal tremolite range from 116 to 82 per mil lying between the domains of typical metamorphic fluid and meteoric water which is in equilibrium with organic matter oxygen and hydrogen isotope ratios indicate that the ore fluid was derived from deep sourced metamorphic fluid and interacted with organic rich shale during fluid migration which is consistent with the fluid evolution history revealed by a previous fluid inclusion study sulfides in the deposit are characteristically enriched in heavy s isotopes with an average 34s value of 13 4 6 2 per mil 1 n 103 the s isotope ratios are identical to stratabound sulfides generated through the non bacterial reduction of neoproterozoic marine sulfate with 34s values of 17 per mil previous studies on lead isotopes of sulfides revealed that the ore forming metals cu pb and zn at the huogeqi deposit were also remobilized from a stratabound source this source was syngenetically elevated in its cu pb and zn sulfide content as a result of submarine hydrothermal activities forming sulfide rich layers within a rift tectonic setting the fe isotope ratios for sulfides are consistent with those of an intercalated iron formation within the ore hosting rocks suggesting that the fe in the sulfides was derived from local host rocks during sulfide precipitation and the fe rich rocks are favorable lithological units for high grade mineralization the heterogeneous sources of ore fluid s ore forming metals and fe are explained by a multistage genetic model which is supported by the geological characteristic of the deposit the enriched sulfides were subsequently remobilized and enriched by metamorphic devolatilization during the permian and triassic periods the metamorphic ore fluid ascended along a shear zone and interacted with organic rich shale sulfides eventually precipitated within the shear zone at a shallower crustal level especially where the shear zone intersected fe rich host rocks this multistage genetic model has implications for mineral exploration greenschist to amphibolite facies terranes containing thick neoproterozoic rift sequences are ideal regions for potential cu pb zn mineralization in particular intercalated volcanic rocks within the rift sequences are indicative of high heat flow and are ideal for the development of submarine hydrothermal systems the primary structures hosting mineralization and ore shoots in the huogeqi area are jogs in the shear zones in addition fe rich lithological units such as iron formations are ideal hosts for high grade ore

formation and tectonic evolution of the khondalite series at the southern margin of the north china craton geochronological constraints from a 1 85 ga mo deposit in the xiong ershan area abstract the taihua complex is an important metamorphic rock suite at the southern margin of the trans north china orogen and hosts important mineral deposits its protolith and metamorphic ages are still controversial the 1 85 ga longmendian mo deposit in the xiong ershan is hosted by the khondalite series of the duangou formation taihua complex three kinds of rocks are collected for shrimp cameca u pb dating including the meta sedimentary rock that occurred as wallrock the mo mineralized meta gabbro that intruded the meta sedimentary rock and the leucosome that cut both the meta sedimentary rock and the meta gabbro zircon u pb analyses reveal that the precursor of the meta sedimentary rock was crystallized between 2200 4 and 2742 18 ma with most before 2500 ma whereas the protolith of the meta gabbro was formed at 2178 6 ma anatexis zircons in the leucosome yield a weighted mean age of 1943 8 ma that is indistinguishable with the metamorphic age of the meta gabbro 1952 4 ma in the intensively altered meta gabbro hydrothermal titanites were formed by at least two pulses of crystallization at 1940 7 ma and 1916 9 ma respectively the new data reveal that the khondalite series of the duangou formation were formed between 2200 ma and 2178 ma the results are inconsistent with previous subdivision of the taihua complex into the upper taihua and lower taihua subgroup instead they fit well with the tripartitite divison into the beizi group 3 0 2 55 ga the dangzehe group 2 55 2 3 ga and the shuidigou group 2 3 2 1 ga compiling zircon u pb ages indicate that in the trans north china orogen the 1 95 ga and 1 85 ga metamorphic events are widespread and prominent

geology and fluid evolution of the wangfeng orogenic type gold deposit western tian shan china abstract the wangfeng gold deposit is located in western tian shan and the central section of the central asian orogenic belt caob the deposit is mainly hosted in precambrian metamorphic rocks and caledonian granites and is structurally controlled by the shenglidaban ductile shear zone the gold orebodies consist of gold bearing quartz veins and altered mylonite the mineralization can be divided into three stages quartz pyrite veins in the early stage sulfide quartz veins in the middle stage and quartz carbonate veins or veinlets in the late stage ore minerals and native gold mainly formed in the middle stage four types of fluid inclusions were identified based on petrography and laser raman spectroscopy co 2 h 2 o inclusions c type pure co 2 inclusions pc type nacl h 2 o inclusions w type and daughter mineral bearing inclusions s type the early stage quartz contains only primary co 2 h 2 o fluid inclusions with salinities of 1 62 to 8 03 wt nacl equivalent bulk densities of 0 73 to 0 89 g cm 3 and homogenization temperatures of 256 c 390 c vapor bubbles are composed of co 2 the middle stage quartz contains all four types of fluid inclusions of which the co 2 h 2 o and nacl h 2 o types yield homogenization temperatures of 210 c 340 c and 230 c 300 c respectively the co 2 h 2 o fluid inclusions have salinities of 0 83 to 9 59 wt nacl equivalent and bulk densities of 0 77 to 0 95 g cm 3 with vapor bubbles composed of co 2 ch 4 and n 2 fluid inclusions in the late stage quartz are nacl h 2 o solution with low salinities 0 35 3 87 wt nacl equivalent and low homogenization temperatures 122 c 214 c the coexistence of inclusions of these four types in middle stage quartz suggests that fluid boiling occurred in the middle stage mineralization trapping pressures estimated from co 2 h 2 o inclusions are 110 300 mpa and 90 250 mpa for the early and middle stages respectively suggesting that gold mineralization mainly occurred at depths of about 10 km in general the wangfeng gold deposit originated from a metamorphic fluid system characterized by low salinity low density and enrichment of co 2 depressurized fluid boiling caused gold precipitation given the regional geology ore geology fluid inclusion features and ore forming age the wangfeng gold deposit can be classified as a hypozonal orogenic gold deposit

u pb dating of baddeleyite and zircon from the shizhaigou diorite in the southern margin of north china craton constrains on the timing and tectonic setting of the paleoproterozoic xiong er group abstract the xiong er volcanism marks an important thermal event in the southern margin of the north china craton during the paleoproterozoic precise u pb ages of zircon and baddeleyite from the shizhaigou diorite which intruded the majiahe formation of the upper part of the xiong er group were determined in this study by multi collector sims the mean 207 pb 206 pb ages are 1789 3 5 ma for baddeleyite and 1780 11 ma for zircon from shizhaigou diorite respectively the major and trace elements and sr nd isotopic compositions indicate an em i mantle type signature and crustal contamination features combining with previous chronological data it is proposed that the age of the xiong er volcanism is between 1770 ma and 1800 ma with a peak at 1780 ma our result supports the view that the xiong er volcanic rocks formed in an extensional rift environment

u pb and re os isotopic systematics and zircon ce4 ce3 ratios in the shiyaogou mo deposit in eastern qinling central china insights into the oxidation state of granitoids and mo au mineralization article i nfo the newly discovered shiyaogou molybdenum deposit is located in the eastern qinling metallogenic belt in central china the deposit contains at least 152 000 t of mo metal and bears typical porphyry type features in terms of its concentric alteration zonation quartz vein hosted mo mineralization veining sequence and the spatial association with concealed granite porphyries re os isotope analyses of molybdenite from the de posit yield an ore forming age of 132 3 2 8 ma la icp ms u pb zircon dating of ore related porphyries yields crystallization ages from 135 ma to 132 ma indicating a temporal link between granitic magmatism and mo mineralization a population of captured magmatic zircons indicates another pulse of magmatism at 143 ma a barren granite intrusion near the deposit gives a zircon u pb age of 148 1 1 1 ma these magmatic activities were concurrent with the emplacement of the nearby heyu granitic batholith a largely ore barren intrusive complex formed from 148 ma to 127 ma zircon ce 4 ce 3 ratios of ore related por phyries are obviously higher than those of contemporaneous barren granitoids implying an affinity between mo mineralization and highly oxidized magmas moreover zircons from these granitoids overall have de creasing ce 4 ce 3 ratios from 148 ma to 132 ma reflecting decreasing oxygen fugacities during magma evolution available geological radiometric and stable isotopic evidence suggests that the decrease of magma oxygen fugacity was probably associated with an increase of mantle contribution to granitic magmatism and metallogenesis which probably gave rise to successive mineralization of mo and au in the eastern qinling the intense magmatic metallogenic events in the eastern qinling during late jurassic to early cretaceous times are interpreted as a response to the large scale lithosphere thinning and subsequent asthenosphere upwelling beneath the eastern part of the north china craton

paleozoic early mesozoic gold deposits of the xinjiang autonomous region northwestern china the late paleozoic early mesozoic tectonic evolution of xinjiang autonomous region northwestern china provided a favorable geological setting for the formation of lode gold deposits along the sutures between a number of the major eastern asia cratonic blocks these sutures are now represented by the altay shan tian shan and kunlun shan ranges with the former two separated by the junggar basin and the latter two by the immense tarim basin in northernmost xinjiang final growth of the altaid orogen southward from the angara craton is now recorded in the remote mid to late paleozoic altay shan accreted early to middle devonian oceanic rock sequences contain typically small precious metal bearing fe cu zn vms deposits e g ashele orogenic gold deposits are widespread along the major irtysh e g duyolanasayi saidi taerde kabenbulake akexike shaerbulake and tuergen hongshanzui e g hongshanzui fault systems as well as in structurally displaced terrane slivers of the western junggar e g hatu and eastern junggar areas geological and geochronological constraints indicate a generally late carboniferous to early permian episode of gold deposition which was coeval with the final stages of altaid magmatism and large scale right lateral translation along older terrane bounding faults the tian shan an exceptionally gold rich mountain range to the west in the central asian republics is only beginning to be recognized for its gold potential in xinjiang in this easternmost part to the range northerly and southerly directed subduction accretion of early to mid paleozoic and mid to late paleozoic oceanic terranes respectively to the precambrian yili block central tian shan was associated with 400 to 250 ma arc magmatism and carboniferous through early permian gold forming hydrothermal events the more significant resulting deposits in the terranes of the southern tian shan include the sawayaerdun orogenic deposit along the kyrgyzstan border and the epithermal and replacement deposits of the kanggurtag belt to the east in the chol tagh range gold deposits of approximately the same age in the yili block include the axi hot springs epithermal deposit near the kazakhstan border and a series of small orogenic gold deposits south of urumqi e g wangfeng gold rich porphyry copper deposits e g tuwu define important new exploration targets in the northern tian shan of xinjiang the northern foothills of the kunlun shan of southern xinjiang host scattered small placer gold deposits sources for the gold have not been identified but are hypothesized to be orogenic gold veins beneath the icefields to the south they are predicted to have formed in the tianshuihai terrane during its early mesozoic accretion to the amalgamated tarim qaidam kunlun cratonic block

tectonics of the qinling central china tectonostratigraphy geochronology and deformation history abstract the qinling orogen preserves a record of late mid proterozoic to cenozoic tectonism in central china high pressure metamorphism and ophiolite emplacement songshugou ophiolite assembled the yangtze craton including the lower qinling unit into rodinia during the 1 0 ga grenvillian orogeny the lower qinling unit then rifted from the yangtze craton at 0 7 ga subsequent intra oceanic arc formation at 470 490 ma was followed by accretion of the lower qinling unit first to the intra oceanic arc and then to the sino korea craton subduction then imprinted a 400 ma andean type magmatic arc onto all units north of the northern liuling unit oblique subduction created silurian devonian wnw trending sinistral transpressive wrench zones e g lo nan shang dan and late permian early triassic subduction reactivated them in dextral transpression lo nan shang xiang shang dan and subducted the northern edge of the yangtze craton exhumation of the cratonal edge formed the wudang metamorphic core complex during dominantly pure shear crustal extension at 230 235 ma post collisional south directed shortening continued through the early jurassic cretaceous reactivation of the qinling orogen started with nw se sinistral transtension coeval with large scale early cretaceous crustal extension and sinistral transtension in the northern dabie shan it presumably resulted from the combined effects of the siberia mongolia sino korean and lhasa west burma qiangtang indochina collisions and pacific subduction regional dextral wrenching was active within a ne sw extensional regime between 60 and 100 ma an early cretaceous andean type continental magmatic arc with widespread early cretaceous magmatism and back arc extension was overprinted by shortening related to the collision of yangtze indochina block with the west philippines block strike slip and normal faults associated with eocene half graben basins record paleogene nne ssw contraction and wnw ese extension the neogene is characterized by normal faults and nne trending sub horizontal extension pleistocene quaternary nw se extension and ne sw contraction comprises sinistral strike slip faults and is part of the nw se extension imposed across eastern asia by the india asia collision

tectonics and distribution of gold deposits in china an overview gold exploration in china has expanded rapidly during the last two decades since a modern approach to economic development has become a national priority china currently produces 180 tonnes t of gold annually which is still significantly less than south africa usa and australia however china is now recognized as possessing significant gold resources in a wide range of mineral deposit types present estimates of gold resources in china exceed 4 500 t which comprise 60 in gold only deposits more than 25 in base metal rich skarn porphyry and vein deposits and more than 10 in placer accumulations the major gold provinces in china formed during the main episodes of phanerozoic tectonism such tectonism involved interaction of china s three major precambrian cratons north china tarim and yangtze or south china when combined with cathaysia block with the angara or siberian kazakhstan kyrgyzstan and indian cratons resulting collisions included deformation of accreted oceanic sequences between the cratonic blocks the most important ore forming orogenies were 1 the late paleozoic variscan 405 270 ma which led to amalgamation of the angara north china and yangtze cratons 2 the indosinian 270 208 ma which led to the collision of north china and south china cratons 3 the yanshanian 208 90 ma which was largely influenced by the subduction of the izanagi pacific plates beneath eastern china and 4 the himalayan 90 ma indentation of the indian continent into eurasia no important precambrian gold systems are recognized in china mainly because of reworking of exposed precambrian rocks by these younger orogenies but there are a few caledonian 600 405 ma gold bearing systems in northern xinjiang most of china s orogenic epithermal and carlin like gold deposits are in the reworked margins of major cratonic blocks and in metasedimentary rock dominated fold belts adjacent to these margins accordingly the major gold provinces are present along the northern southeastern and southern margins of the north china craton along the southwestern and northwestern margins of the yangtze craton in the tianshan and altayshan orogenic belts in northern xinjiang and throughout the southeastern china fold belt gold placer deposits derived from these primary deposits are concentrated in the northernmost part of northeastern china and along the northwestern margin of the yangtze craton the major provinces with significant gold in porphyry related copper systems and base metal skarns are present in the yangtze river area along the northeastern and southeastern margin of the yangtze craton in the fold belt in southwestern china and scattered through northern china three quarters of the chinese gold only deposits occur within the north china craton margins half are located in the uplifted precambrian metamorphic rocks and most of the remainder are hosted in the phanerozoic granitoids that intruded the reworked precambrian terranes the abundance of granite hosted gold contrasts the north china craton with other precambrian cratons such as those in western australia central canada and zimbabwe where gold is mainly hosted in the archean greenstone belts this difference may be explained by the multiple episodes of phanerozoic tectonism along the north china craton margins resulting from the collision of the angara north china and south china cratons and from subduction of the izanagi pacific oceanic plates underneath the eastern china continent

zircon u pb ages and geochemistry of the wenquan mo bearing granitioids in west qinling china constraints on the geodynamic setting for the newly discovered wenquan mo deposit abstract east qinling is the largest porphyry molybdenum province in the world these mo deposits have been well documented in west qinling however few mo deposits have been discovered although granitic rocks are widespread recently the wenquan porphyry mo deposit has been discovered in gansu province which provides an insight into mo mineralization in west qinling in this paper we report pb isotope compositions for k feldspar and sulfides s isotope ratios for sulfides the results obtained from petrochemical study and from in situ la icp ms zircon u pb dating and hf isotopes the granitoids are enriched in lile and lree with ree and trace element patterns similar to continental crust suggesting a crustal origin the mg 40 05 to 56 34 and cr and ni contents are high indicating a source of refractory mafic lower crust the e hf t values of zircon grains from porphyritic monzogranite range from 2 9 to 0 6 and from granitic porphyry vary from 3 3 to 1 9 the zircons have t dm2 of 1014 to 1196 ma for the porphyritic monzogranite and 954 to 1224 ma for the granitic porphyry implying that these granitoids were likely derived from partial melting of a late mesoproterozoic juvenile lower crust the pb isotope compositions of the granitoids are similar to granites in south china showing that the magma was sourced from the middle lower crust in the southern qinling tectonic unit the pb isotopic contrast between the mo bearing granitoids and ores shows that the pb in the ore forming solution was derived from fractionation of a triassic magmatic system 34 s values of sulfides are between 5 02 and 5 66 similar to those associated with magmatic hydrothermal systems la icp ms zircon u pb dating yields crystallization ages of 216 2 1 7 and 217 2 2 0 ma for the granitoids consistent with a previously reported molybdenite re os isochron age of 214 4 7 1 ma this suggests that the mo mineralization is related to the late triassic magmatism in the west qinling orogenic belt in view of these geochemical results and known regional geology we propose that both granitoid emplacement and mo mineralization in the wenquan deposit resulted from the triassic collision between the south qinling and the south china block along the mianlue suture since triassic granitoid plutons commonly occur along the qinling orogenic belt the triassic wenquan mo bearing granitoids highlight the importance of the triassic tectono magmatic belt for mo exploration in order to apply this metallogenic model to the whole qinling orogen further study is needed to compare the wenquan deposit with other deposits

sequence of late jurassic early cretaceous magmatic hydrothermal events in the xiong ershan region central china an overview with new zircon u pb geochronology data on quartz porphyries recent investigations have revealed several large au and mo deposits in the xiong ershan region central china most quartz porphyries associated with the mineralization occur as dikes and apophyses or as rubbles cemented in mineralized breccia pipes three types of quartz porphyries were sampled from the leimengou mo deposit the qiyugou au deposit and the niutougou au deposit la icp ms zircon u pb analysis was performed in zircons from two quartz porphyries the results yielded ages of 125 4 0 77 ma for leimengou mo deposit and 150 1 1 1 ma for qiyugou au deposit the magma source of leimengou quartz porphyry is similar to that of the mineralized cementing material in breccia pipes of the qiyugou au deposit whereas the magma source of qiyugou quartz porphyry is the same as that of quartz porphyries in niutougou au deposit based on the new u pb isotopic ages of granitic plutons reported in this study together with the age data in the literature we identify distinct magmatic pulses in the xiong ershan region at ca 160 150 143 133 125 and 115 ma during the late jurassic early cretaceous the ages of au and mo mineralization coincide with the thermal events at about 115 125 133 and 143 ma are considered to be co eval with granitic magmatism no mineralization ages of 150 and 160 ma thermal events have been previously reported our study demonstrates late jurassic early cretaceous multiple magmatic pulses and mineralization in the xiong ershan region

geologic framework and tectonic evolution of the qinling orogen central china abstract the geologic framework of the qinling orogen was built up through interplay of three blocks the north china block including the north qinling the south qinling and the south china block separated by the shangdan and mianlue sutures the shangdan suture resulted from middle paleozoic collision of the north china block and the south qinling the mianlue suture resulted from late triassic collision of the south qinling and the south china block present upper crust of the qinling is structured dominantly by thrust fold systems the north qinling displays thick skinned deformation with crystalline basement involved whilst the south qinling is characterized by thin skinned thrusts and folds detached above the lower sinian two types of precambrian basement crystalline and transitional are defined according to lithology and metamorphic grade and different in age stratigraphic and sedimentary architecture is characterized by distinct zonation the qinling orogen experienced a prolonged continental divergence and convergence between blocks during the period from late neoproterozoic to early paleozoic times the south qinling was the northern margin of the south china block and the north qinling was the southern margin of the north china block separated by a proto tethyan qinling ocean the north qinling evolved into an active margin when the proto tethyan qinling ocean subducted northward during ordovician time collision of the south and north qinling took place in middle paleozoic along the shangdan suture synchronous with the collision rifting occurred at the southern rim of the south qinling and was followed by the opening of the paleo tethyan qinling ocean during the late paleozoic resulting in the splitting of the south china block from the south qinling collision of the south qinling and the south china block came about in the late triassic along the mianlue suture the late triassic collisional orogeny caused extensive fold and thrust deformation and granitoid intrusions throughout the qinling and led to final amalgamation of the north and south china blocks

geology geochronology and s pb os geochemistry of the alastuo gold deposit west tianshan nw china the alastuo gold deposit located in the narati region of the chinese west tianshan is a newly discovered gold deposit within the world class tianshan gold belt the gold mineralization is hosted by an early carboniferous granodiorite intrusion and controlled structurally by subsidiary faults of the transcrustal north narati fault the deposit consists of auriferous alteration assemblages and minor vein ores field relations and petrographic data suggest four stages of mineralization with gold precipitated coevally with quartz chlorite epidote pyrite and galena during the second and third stages that are characterized by tectonic transformation from ductile shearing to brittle deformation the temperature range of gold precipitation is estimated to be 280 330 c using chlorite geothermometry ten auriferous pyrite samples yielded a well defined re os isochron age of 325 3 ma and two sericite samples yielded plateau like 40ar 39ar ages of 321 7 3 0 ma and 321 2 2 8 ma these consistent ages suggest that the gold mineralization in the narati region was emplaced in a transitional regime from subduction to continental collision between the tarim block and middle tianshan terrane 325 310 ma rather than during the post collisional stage as in most part of the tianshan gold belt gold bearing pyrite has an initial osi value of 0 7 0 1 and lead isotopes ratios of 17 897 to 18 723 for 206pb 204pb 15 474 to 15 643 for 207pb 204pb and 37 522 to 38 299 for 208pb 204pb while samples of pyrite galena and sphalerite have 34sv cdt of 1 9 to 7 8 the isotope data suggest that the sulfur and metals are most likely derived from mixed mantle and crustal sources including metamorphic devolatilization of subducted oceanic slab and overlying sedimentary rocks the mineralization styles structural controls metal and sulfur sources and the timing of gold mineralization with respect to the orogenic event all suggest that the alastuo gold deposit represents an orogenic type deposit this newly recognized carboniferous orogenic gold mineralization event calls for a re evaluation of the gold metallogeny in the middle tianshan

isotope systematics and fluid inclusion studies of the qiyugou breccia pipe hosted gold deposit qinling orogen henan province china implications for ore genesis abstract the qiyugou gold deposits henan province are hosted in breccia pipes within the xiong er terrane qinling orogen on the southern margin of the north china craton in these deposits three paragenetic assemblages have been recognized an early k feldspar epidote quartz pyrite a middle quartz polymetallic sulfide and a late quartz carbonate adularia in this paper we review and interpret fluid inclusion and stable and radiogenic isotopic data of host rocks and ores fluid inclusions in quartz and calcite include water rich co 2 rich and daughter crystal bearing the co 2 rich and daughter mineral bearing fluid inclusions are common in the early stage quartz and absent in the late stage quartz and calcite which only contain water rich fluid inclusions accordingly the early stage ore fluids are magmatic in origin and characterized by high temperature 350 c high salinity 30 wt nacl equiv and are co 2 rich fluid boiling in the middle ore stage resulted in co 2 release decreasing oxygen fugacity and rapid precipitation of ore materials the late stage fluids have low temperature low salinity are co 2 poor and lack daughter minerals these fluids are probably sourced from meteoric water h o c isotope systematics confirm that the ore fluid system evolved from magmatic to meteoric the carbon and lead isotope ratios indicate that the meso neoproterozoic sequence south of the xiong er terrane was the likely source of the ore forming materials the qiyugou breccia pipes and their associated gold ores were emplaced during an extensional regime following a transition from collision to rifting tectonics linked to collision and subduction of the yangtze plate beneath the north china craton geochronological studies show that mesozoic magmatism in the region occurred between the triassic and cretaceous the triassic to jurassic magmas were mostly derived from partial melting of ancient crust whereas the cretaceous magmas show juvenile signatures indicating mantle derived components processes of fragmentation of lithospheric roots crustal and lithospheric thinning extension and rifting were probably associated with the subducting pacific izanagi plate these crust mantle geodynamic processes were responsible for the development of anorogenic granitic melts that interacted with the meso neoproterozoic volatile rich sedimentary successions producing a flow of gas rich hydrothermal fluids that resulted in the emplacement of the qiyugou auriferous breccia pipes we conclude that the qiyugou gold deposits are intrusion related explosive breccia pipe type that evolved from hypothermal through mesothermal to epithermal

isotope and fluid inclusion geochemistry and genesis of the qiangma gold deposit xiaoqinling gold field qinling orogen china abstract the qiangma gold deposit is hosted in the 1 9 ga taihua supergroup metamorphic rocks in the xiaoqinling terrane qinling orogen on the southern margin of the north china craton the mineralization can be divided as follows quartz pyrite veins early quartz polymetallic sulfide veinlets middle and carbonate quartz veinlets late stages with gold being mainly introduced in the middle stage three types of fluid inclusions were identified based on petrography and laser raman spectroscopy i e pure carbonic carbonic aqueous co 2 h 2 o and aqueous inclusions the early stage quartz contains pure carbonic and co 2 h 2 o inclusions with salinities up to 12 7 wt nacl equiv bulk densities of 0 67 to 0 86 g cm 3 and homogenization temperatures of 280 365 c the early stage is related to h 2 o co 2 n 2 ch 4 fluids with isotopic signatures consistent with a metamorphic origin 18 o water 3 1 to 5 2 d 37 to 73 the middle stage quartz contains all three types of fluid inclusions of which the co 2 h 2 o and aqueous inclusions yield homogenization temperatures of 249 346 c and 230 345 c respectively the co 2 h 2 o inclusions have salinities up to 10 9 wt nacl equiv and bulk densities of 0 70 to 0 98 g cm 3 with vapor bubbles composed of co 2 and n 2 the isotopic ratios 18 o water 2 2 to 3 6 d 47 to 79 suggest that the middle stage fluids were mixed by metamorphic and meteoric fluids in the late stage quartz only the aqueous inclusions are observed which have low salinities 0 9 9 9 wt nacl equiv and low homogenization temperatures 145 223 c the isotopic composition 18 o water 1 9 to 0 5 d 55 to 66 indicates the late stage fluids were mainly meteoric water trapping pressures estimated from co 2 h 2 o inclusions are 100 285 mpa for the middle stage suggesting that gold mineralization mainly occurred at depths of 10 km fluid boiling and mixing caused rapid precipitation of sulfides and native au through boiling and inflow of meteoric water the ore forming fluid system evolved from co 2 rich to co 2 poor in composition and from metamorphic to meteoric as indicated by decreasing 18 o water values from early to late the carbon sulfur and lead isotope compositions suggest the hostrocks within the taihua supergroup to be a significant source of ore metals integrating the data obtained from the studies including regional geology ore geology and fluid inclusion and c h o s pb isotope geochemistry we conclude that the qiangma gold deposit was an orogenic type system formed in the tectonic transition from compression to extension during the jurassic early cretaceous continental collision between the north china and yangtze cratons

the genesis of the liancheng cu mo deposit in the lanping basin of sw china constraints from geology fluid inclusions and cu s h o isotopes abstract liancheng is an important cu mo deposit hosted by red beds in the mesozoic to cenozoic lanping basin located in the sanjiang tethyan orogen of sw china the deposit is fault controlled where it has been affected and enriched by four hydrothermal events indicated by four distinct sets of veins and their cross cutting relationships a detailed cu s h o isotopic study is reported here on the mineralization focusing on the source of the metals and fluid and on the mineralizing processes the first two hydrothermal events are characterised by co 2 and fluid rich inclusions with homogenisation temperatures of 124 446 c and salinities ranging from 0 4 to 24 6 wt nacl equiv the next two hydrothermal events are characterised by liquid rich fluid inclusions that homogenise at 145 256 c with salinities ranging from 1 4 to 22 9 wt nacl equiv the h o isotope values obtain from the fluid inclusions indicate that the first three hydrothermal events relate to mineralizing fluids derived from a metamorphic source but the last event includes a mixed metamorphic and meteoric source chalcopyrite tennantite and bornite from the deposit have 34 s values between 11 5 and 3 the 65 cu values for quartz cu sulfide mineralization associated with the second hydrothermal event range from 0 31 to 0 2 but carbonate cu sulfide mineralization associated with the third hydrothermal event ranges from 1 01 to 1 08 the combination of the cu and s isotopic values and field observations indicate that the controlling factors include structures the temperature of regional metamorphism and the ph of the mineralizing fluid the zation is therefore characteristic of an orogenic type deposit

the shanggong gold deposit eastern qinling orogen china isotope geochemistry and implications for ore genesis abstract the shanggong au deposit in the xiong er terrane east qinling china has resources of about 30 ton au making it one of the largest orogenic mesothermal au deposits hosted in volcanic rocks of the mesoproterozoic xiong er group three stages of hydrothermal activity are recognized early middle and late of which two early and middle were ore producing and characterized by quartz pyrite and polymetallic sulfides respectively the third and late stage is represented by a carbonate quartz assemblage hydrogen oxygen and carbon isotope systematics of the shanggong deposit from a previous work suggest that the early stage fluids were derived from magmatic and or metamorphic devolatilization of sedimentary rocks at depth this is supported by new c s and published sr and pb isotopic data presented in this paper these new data 13c values ranging from 1 5 for early stage ankerite to 2 2 for late stage ankerite negative 34s values for sulfides from the middle stage 19 2 to 6 3 suggest a contribution from organic matter and that the ore fluid evolved from deeply sourced to shallowly sourced with those of the middle stage representing a mixture of these two fluid systems the comparison of the hydrogen oxygen carbon sulfur lead strontium isotope systematics between the shanggong deposit and the main lithologies in the xiong er terrane shows that neither these nor the underlying lower crust and mantle or combinations thereof could be considered as the source of ore fluids for the shanggong au deposit a likely source was a carbonaceous carbonate sandstone shale chert sequence in the underthrusted guandaokou and luanchuan groups exposed south of the xiong er terrane ar ar and rb sr isochron ages for mineral phases of the early middle and late stages together with geological field data constrain the timing of the hydrothermal activity and au metallogenesis at 242 10 167 7 and 112 7 ma respectively this metallogenesis and associated granitic magmatism can be related to the continental collision between the yangtze and north china cratons that resulted in the formation of the qinling orogen led to the different hydrothermal systems that were responsible for the three stages that formed the shanggong au deposit over a period of about 130 myrs

geology mineralization and geochronology of the qianhe gold deposit xiong ershan area southern north china craton the qianhe gold deposit in the xiong ershan area is located along the southern margin of the archean paleoproterozoic north china craton the deposit consists of six orebodies that are hosted in paleoproterozoic andesites to basaltic andesites and structurally controlled by roughly ew trending faults individual orebodies comprise auriferous quartz veins and disseminated au bearing pyrite within hydrothermally altered rocks on both sides of or close to the veins ore related hydrothermal alteration has produced various mixtures of k feldspar quartz sericite chlorite epidote carbonate and sulfides pyrite is the most important ore mineral associated with minor amounts of galena sphalerite and chalcopyrite other trace minerals include molybdenite arsenopyrite scheelite rutile xenotime and parisite gold occurs mostly as native gold and electrum enclosed in pyrite or along microfractures of sulfides and quartz microthermometric measurements of primary inclusions in auriferous quartz suggest that gold and associated minerals were precipitated in the range of 160 305 c from aqueous or carbonic aqueous fluids with salinities of 6 22 wt nacl equiv samples of molybdenite coexisting with au bearing pyrite have re os model ages of 134 135 ma whereas ore related hydrothermal sericite separates yield 40ar 39ar plateau ages between 127 and 124 ma the re os and 40ar 39ar ages are remarkably consistent with zircon u pb ages 134 5 1 5 and 127 2 1 4 ma 1 of the biotite monzogranite from the heyu intrusive complex and granitic dikes in and close to the qianhe gold mine indicating a close temporal and thus possibly genetic relationship between gold mineralization and granitic magmatism in the area fluid inclusion waters extracted from auriferous quartz have d values of 80 to 72 whereas the calculated 18oh2o values range from 3 1 to 3 8 the hydrogen and oxygen isotopes from this study and previous work indicate that ore fluids were likely derived from degassing of magmas with addition of minor amounts of meteoric water gold mineralization at qianhe is temporarily coincident with pervasive bimodal magmatism widespread fault basin formation and well development of metamorphic core complexes in the whole eastern north china craton that have been interpreted as reflecting reactivation of the craton in the late mesozoic after prolonged stabilization since its formation in the late paleoproterozoic it is therefore concluded that the qianhe gold deposit formed as a result of this craton reactivation event

fluid inclusion geochemistry and ore genesis of the longmendian mo deposit in the east qinling orogen implication for migmatitic hydrothermal mo mineralization abstract the 1 85 ga longmendian mo deposit in east qinling is the oldest mo system recognized in china it is unique for three reasons 1 quartzofeldspathic orebodies are away from any intrusion or fault 2 it is closely associated with migmatitic rocks and 3 it has remarkably high re content in molybdenite 504 to 1660 ppm the origin of the deposit is poorly constrained in the longmendian deposit strong mo mineralization is always associated with hydrothermally altered migmatitic amphibolites to probe into ore genesis detailed fluid inclusion studies are carried out on both mineralized migmatitic amphibolites and ore barren rocks four compositional types of fluid inclusions are observed including co 2 ch 4 pc type co 2 h 2 o c type daughter mineral bearing s type and h 2 o nacl w type quartz in mesosome and melanosome of mineralized migmatitic amphibolites contains all of the four types of inclusions measurements of immiscible inclusion assemblages in the ores constrain the mo mineralization temperatures and pressures to be 225 390 c and 114 265 mpa respectively primary fluid inclusions in barren migmatitic gneisses are dominated by s type and minor of c and pc types which are identical to those in the leucosome of migmatitic amphibolites these inclusions yield lower homogenization temperatures than those in the mineralized mesosome and melanosome of migmatitic amphibolites suggesting that the ore causative injected melts should have higher temperatures and originated from depths such features of the ore forming fluids indicate that the longmendian deposit was a migmatitic hydrothermal system caused by high temperature melt injection this interpretation can also be supported by the observations below 1 tourmaline is abundant in melanosome but absent in mesosome 2 the consistent quartzofeldspathic composition of leucosome is independent of mesosome 3 leucosome in migmatitic amphibolite crosscuts each other 4 halite bearing fluid inclusions are prevalent in studied samples which is the feature of granitic rocks instead of the scenarios of in situ migmatites and 5 the trapping temperatures of fluid inclusions in mineralized migmatitic amphibolite are much lower than those required for partial melting but higher than those obtained from barren migmatitic rocks

geology c h o s pb isotope systematics and geochronology of the yindongpo gold deposit tongbai mountains central china implication for ore genesis abstract the yindongpo gold deposit is located in the weishancheng au ag dominated polymetallic ore belt in tongbai mountains central china the ore bodies are stratabound within carbonaceous quartz sericite schists of the neoproterozoic waitoushan group the ore forming process can be divided into three stages represented by early barren quartz veins middle polymetallic sulfide veinlets and late quartz carbonate stockworks with most ore minerals such as pyrite galena native gold and electrum being formed in the middle stage the average 18owater values changed from 9 7 in the early stage through 4 9 in the middle stage to 5 9 in the late stage with the d values ranging between 65 and 84 the 13cco2 values of ore fluids are between 3 7 and 6 7 with an average of 1 1 the h o c isotope systematics indicate that the ore fluids forming the yindongpo gold deposit were probably initially sourced from a process of metamorphic devolatilization and with time gradually mixed with meteoric water the 34s values range from 0 3 to 5 2 with peaks ranging from 1 to 4 fourteen sulfide samples yield 206pb 204pb values of 16 990 17 216 207pb 204pb of 15 419 15 612 and208pb 204pb of 38 251 38 861 both s and pb isotope ratios are similar to those of the main lithologies of the waitoushan group but differ from other lithologic units and granitic batholiths in the tongbai area which suggest that the ore metals and fluids originated from the waitoushan group the available k ar and 40ar 39ar ages indicate that the ore forming process mainly took place in the period of 176 140 ma during the transition from collisional compression to extension and after the closure of the oceanic seaway in the qinling orogen the yindongpo gold deposit is interpreted as a stratabound orogenic style gold system formed during the transition phase from collisional compression to extension the ore metals in the waitoushan group were extracted transported and then accumulated in the carbonaceous sericite schist layer the carbonaceous sericite schist layer especially at the junction of collapsed anticline axis and fault structures became the most favorable locus for the ore bodies

in situ trace element and sulfur isotope of pyrite constrain ore genesis in the shapoling molybdenum deposit east qinling orogen china abstract the early cretaceous ca 128 ma shapoling vein type molybdenum mo mineralization associated with the huashan intrusion is a newly discovered deposit in the xiong ershan district east qinling china where pyrite is a ubiquitous mineral phase here we present results from an integrated study on the texture in situ trace element chemistry from laser ablation inductively coupled plasma mass spectrometry la icp ms and sulfur isotopic composition using secondary ion mass spectrometry sims with a view to understand the geochemical variation genesis of mo mineralization and ore forming process the distinct textural patterns as revealed by petrographic observations suggest three types of pyrites py1 is composed of coarse grained euhedral pyrite in the wall rock and early barren quartz vein at stage i py2 is represented by subhedral anhedral grains coexisting with molybdenite in quartz veins at stage ii and py3 forms irregular interstitial grains in the quartz k feldspar molybdenite dominated veins at stage iii the mo enrichment mainly occurred in py3 with co ni ratios 1 and 34s values mainly