major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

the elatsite porphyry copper deposit in the panagyurishte ore district srednogorie zone bulgaria u pb zircon geochronology and isotope geochemical investigations of magmatism and ore genesis

a late cretaceous tin metallogenic event in nanling w sn metallogenic province constraints from u pb ar ar geochronology at the jiepailing sn be f deposit hunan china abstract the jiepailing deposit located in southern hunan province china is a giant sn be f deposit in the nanling w sn province the sn be f mineralization is spatially associated with the jiepailing granite porphyry la mc icp ms zircon u pb dating of the jiepailing granite porphyry yielded a weighted mean 206 pb 238 u age of 90 5 0 9 ma mswd 0 32 which is interpreted as the emplacement age of the granite porphyry hydrothermal muscovite yields a plateau 40 ar 39 ar age of 92 1 0 7 ma mswd 0 9 which is well consistent with the zircon u pb age of the jiepailing granite porphyry responsible for the sn be f mineralization indicating a temporal link between the emplacement of the jiepailing granite porphyry and the sn be f mineralization our new high precise geochronological data suggest that the jiepailing giant sn be f deposit and related granite formed during the early late cretaceous 92 90 ma which provided convincing evidence for a previously unrecognized metallogenic event related to late cretaceous granitic magmatism in nanling region the occurrence of the late cretaceous sn metallogenic event identified in southern hunan province further highlights the importance of systematic metallogenic studies of the nanling w sn province integrated with high precise geochronological data obtained previously it is suggested that the nanling region mainly experienced three tectonomagmatic activities and lithospheric thinning events during mesozoic which are responsible for three sn w metallogenic events to form the world class nanling w sn metallogenic province

zircon u pb geochronological and hf isotopic constraints on petrogenesis of late mesozoic intrusions in the southeast hubei province middle lower yangtze river belt mlyrb east china abstract during the late mesozoic extensive magmatism and associated ore deposits were developed in the southeast hubei province middle lower yangtze river metallogenic belt mlyrb east china to understand the petrogenesis of the intrusions in the area we performed in situ zircon u pb and hf isotopic analyses on 14 samples from the fengshangdong stock and from the echeng tieshan wangbaoshan jinshandian and yangxin batholiths three major suites of intrusive rocks are recognized in the southeast hubei province 1 141 146 ma granodiorite and granite porphyries associated with 143 144 ma porphyry skarn cu mo deposits have enriched radiogenic hf isotopic compositions ehf t 9 5 to 1 6 comparable to those of cretaceous pyroxene diorites trachyandesites and basalts ehf t 8 9 to 1 3 in the mlyrb which were derived from an enriched lithospheric mantle 2 voluminous 136 143 ma gabbros diorites and quartz diorites associated with 137 144 ma skarn cu fe fe cu and au cu deposits have variable hf isotopic compositions ehf t 19 1 to 5 4 indicating an origin via the hybridization of enriched mantle derived mafic magma and variable amounts of ancient lower crustal components 3 127 133 ma diorites quartz diorites and granites associated with 132 133 ma skarn fe deposits characterized by a wide range of ehf t values 28 2 to 6 4 suggest the assimilation of various ancient lower crustal materials by enriched mantle derived basaltic magma the intrusions of suites 1 and 2 are characterized by high sr contents 329 2087 ppm and high sr yb 36 1710 and la yb n ratios 17 6 172 but low yb contents 0 45 1 82 ppm and do not show negative eu anomalies eu 0 74 1 4 the intrusions have radiogenic sr nd isotopic compositions end t 10 0 to 3 4 and 87 sr 86 sr i 0 7054 0 7084 compared with the intrusions of suites 1 and 2 rocks of suite 3 have relatively low sr contents 60 5 327 ppm and low sr yb 33 0 315 and la yb n ratios 2 28 30 0 but relatively high yb contents 1 04 5 17 ppm and significant negative eu anomalies eu 0 22 0 73 the rocks of suite 3 are characterized by a wide range of radiogenic sr nd isotopes with end t values of 12 5 to 4 9 and 87 sr 86 sr i 0 7057 0 7085 the proposed magma sources combined with the geochemical and sr nd isotopic differences between these three suites of intrusive rocks indicate that late mesozoic magmatic activity in the southeast hubei province mlyrb was associated with lithospheric thinning induced by asthenospheric upwelling at that time

pulsed magmatic fluid releasing in the formation of the taoxihu sn polymetallic deposit eastern guangdong se china evidence from fluid inclusions cassiterite u pb geochronology and stable isotopes abstract the taoxihu deposit is a newly discovered sn polymetallic deposit in eastern guangdong se china the mineralization is related to an early cretaceous highly fractionated i type granite porphyry the ore forming process is divided into six stages i e garnet stage i quartz fluorite biotite stage ii quartz biotite cassiterite sulfides stage iii main mineralization quartz vein with minor sulfides and cassiterite stage iv quartz k feldspar biotite cassiterite sulfides stage v and quartz k feldspar chlorite sulfides stage vi fluid inclusion study shows that the hydrothermal fluids from stage ii salinity 5 9 to 13 2 wt and th 302 to 382 c to stage iv salinity 0 2 to 5 9 wt and th 275 to 315 c are of h2o co2 ch4 salt composition and show a trend of systematically decreasing temperature and salinity from early to late stages in contrast the fluids in stage v salinity 6 5 to 13 9 wt and th 223 to 343 c and stage vi salinity 6 0 to 11 8 wt and th 140 to 300 c are of the h2o salt compositional system and demonstrate also a trend of decreasing temperature and salinity with time representing a distinct hydrothermal event h o isotope data indicate that these two different fluid systems are all initially of magmatic origin in view of the almost identical cassiterite u pb ages of stage iii 139 7 1 1 ma and stage v 139 8 1 6 the two hydrothermal events are interpreted to represent two pulses of magmatic fluid releasing from the same magma chamber the first pulse is characterized by an initially single phase co2 bearing magmatic fluid that was subsequently subject to unmixing or phase separation in relation to hydraulic fracturing and decompression which lead to the main phase mineralization whereas the second pulse is the release of residual co2 free magmatic fluid which mixed with meteoric water and resulted in the second phase of mineralization

precise sm nd and u pb isotopic dating of the supergiant shizhuyuan polymetallic deposit and its host granite se china the supergiant shizhuyuan w sn bi mo deposit is hosted by the qianlishan granite a small highly fractionated granitic pluton 10 km 2 with multiple phases of intrusions within the early yanshanian granitoid province of se china strong alteration of skarn and greisen that formed in the contact zone between the first and second phases of granite intrusions and devonian limestone is responsible for the polymetallic mineralizations shrimp u pb zircon analysis indicates that the two early phases of the qianlishan granite formed contemporaneously at 152 2 ma metasomatic minerals garnet fluorite and wolframite separated from the skarn and greisen yield a sm nd isochron age of 149 2 ma that is interpreted as the formation age of the shizhuyuan deposit therefore the mineralization of the supergiant shizhuyuan polymetallic deposit formed contemporaneously with or very shortly after the intrusion of the small highly fractionated qianlishan granite

mantle derived noble gases in ore forming fluids of the granite related yaogangxian tungsten deposit southeastern china more than 90 of the tungsten resources of china are in the nanling region of south china and the yaogangxian vein deposit is the largest tungsten deposit in this region the tungsten deposits have ages of 150 160 ma and are spatially temporally and genetically related to granites which were previously believed to be produced by crustal anatexis this paper provides he and ar isotope data of fluid inclusions in pyrite and arsenopyrite from the yaogangxian w veins 3he 4he ratios range from 0 41 to 3 03 ra where ra is the 3he 4he ratio of air 1 39 10 6 and 40ar 36ar ratios from 328 to 1 191 moreover there are excellent correlations between he and ar isotopic compositions the results suggest that the ore forming fluids are a mixture between a crustal fluid containing atmospheric ar and crustal 4he and a fluid containing mantle components it is likely that the former is a low temperature meteoric fluid and the later is a fluid exsolved from the w associated granitic magma which formed by crustal melting induced by intrusion of a mantle derived magma

garnet geochemistry of tungsten mineralized xihuashan granites in south china abstract the xihuashan complex intrusion in south china which is emplaced at ca 154 ma mainly comprises medium grained porphyritic biotite granite medium grained biotite granite and fine grained two mica granite medium grained biotite and fine grained two mica granites are important tungsten bearing granites and contain an unusual amount of garnet garnets from this intrusion are dominated by almandine and spessartine which constitute 94 to 99 of the total molecular composition of the garnet these garnets display unusual compositional zoning the cores of these garnets are rich in heavy rare earth element hree y ca and contain abundant hree and y rich mineral inclusions their rims are free of mineral inclusions and have low of these elements two types of fluorite inclusions exist in garnet y fluorite and y poor fluorite garnet exhibits specific mn zoning with a relatively mn poor core but a relatively mn rich rim thus constituting a specific spessartine inverse bell shaped profile that belongs to typical magmatic garnets all analyzed garnets have high ree content and exhibit hree enriched and lree depleted patterns with strong negative eu anomalies the incorporation of ree into garnet is in part controlled by its crystal chemistry with ree3 following a coupled substitution of the type fe2 mn2 1viii ree3 1viii si4 1iv z3 1iv the texture and compositional zoning of garnet suggest that garnet growth is largely controlled by the pressure temperature composition condition of magmatic evolution internal crystal chemical parameters and kinetics during mineral growth the garnet core grows in near equilibrium with magmatic melt under a relatively high pressure temperature p t condition by contrast the garnet rim grows rapidly by the coexisting melt fluid phase and co2 rich volatile environment under a relatively low p t condition which is virtually unfavorable for the incorporation of ree into the magmatic garnet structure garnet fingerprints the magmatic hydrothermal transition during crystallization of these granites

silurian s type granite related w mo mineralization in the nanling range south china a case study of the pingtan w mo deposit abstract the pingtan deposit in southwestern hunan province is a newly discovered large sized w mo deposit this deposit is situated in the northwestern part of the miao ershan granite batholith western nanling range the tungsten mineralization is mainly hosted in biotite monzogranite and the alteration related to mineralization is controlled by a ne trending fault zone in this paper we present new molybdenite re os and zircon u pb ages zircon lu hf isotope and ree geochemical data aiming to constrain the w mo mineralization age and ore hosting granite petrogenesis in the pingtan w mo deposit molybdenite re os dating of eight ore samples yielded a weighted average model age of 427 0 5 4 ma mswd 0 24 the la icp ms zircon u pb analysis of two biotite monzogranite yielded 206pb 238u ages of 430 8 2 4 ma and 431 0 1 8 ma respectively suggesting that the w mo mineralization is spatial temporally associated with the biotite monzogranite the ore related granites have high contents of sio2 and k2o belong to weakly to strongly peraluminous a cnk 1 00 1 30 and geochemically classified as s type affinity molybdenite re contents 2 262 7 297 g g zircon ehf t 10 34 5 87 and 176hf 177hf 0 282241 0 282376 values of the biotite monzogranite suggest that the ore forming materials are predominantly derived from the crust this is the first identification of tungsten mineralization related to silurian s type granites caledonian granites in the miao ershan granite intrusion indicating caledonian is an important mineralization period of w in the western part of nanling range south china

in situ la mc icp ms and id tims u pb geochronology of cassiterite in the giant furong tin deposit hunan province south china new constraints on the timing of tin polymetallic mineralization abstract the furong deposit located in southern hunan province china is a newly discovered giant tin deposit spatially associated with the a type qitianling granite the petrogenetic link between the giant furong tin deposit and the qitianling granite batholith remains controversial because of the lack of precise dating for the tin polymetallic mineralization here we report for the first time in situ u pb data on cassiterite obtained by la mc icp ms and the results are compared to id tims data the in situ la mc icp ms analyses of the cassiterites provide a reliable age constraint for tin polymetallic mineralization in the furong deposit yielding an isochron age of 159 9 1 9 ma at 95 confidence level mswd 18 which is indistinguishable from the id tims 206 pb 238 u weighted mean age of 158 2 0 4 ma the in situ u pb ages corroborate the ar ar dates published for the furong tin deposit which indicate that the mineralization is coeval with the emplacement of the qitianling granite batholith these results provide further evidence of a close temporal link between the pluton s emplacement and tin mineralization in the furong area the data obtained clearly demonstrate that in situ la mc icp ms u pb dating of cassiterite is a robust geochronometer for direct dating of tin polymetallic mineralization

zircon u pb and hf o isotopes trace the architecture of polymetallic deposits a case study of the jurassic ore forming porphyries in the qin hang metallogenic belt china abstract the qin hang intra continental porphyry skarn cu polymetallic belt qhmb is among the economically important metallogenic belts in south china the significant differences in the size and metal assemblage of the jurassic magmatic hydrothermal ore deposits in this belt remain as an enigma here we employ zircon u pb and hf o isotopes of the tongshanling and baoshan cu pb zn deposits in the central part of the qhmb to investigate the contrasting metallogenic architecture our sims zircon u pb data indicate that the tongshanling and baoshan granodiorite formed at 160 ma these rocks show high mg values and negative zircon e hf t and high 18 o values suggesting that the magmas of the granodiorite porphyries were mainly generated through the anatexis of older crustal components triggered by the input of mantle derived magma the minor content of amphibole phenocrysts low sr y ratios negative eu anomaly and low zircon ce 4 ce 3 ratios indicate that the porphyries are relatively less oxidized with less water content compared with the ore bearing porphyries in the dexing and yuanzhuding porphyry cu deposits in the northern and southern part of the qhmb suggesting that high magmatic water content and oxidation state are important prerequisites for the formation of large size porphyry skarn copper deposits in the qhmb the positive correlation between zircon e hf t values with the cu reserves as well as zircon 18 o values with the cu cu pb zn ratios of the deposits indicate that the magmatic sources exerted a first order control on the volume and metal assemblage of deposits in the qhmb the hf and nd isotope contour maps indicate that the central part of the qhmb has high potential for pb zn dominated magmatic hydrothermal deposits whereas the northern and southern part of the qhmb are prospective for large cu deposits our results have important implications in formulating regional exploration strategies for jurassic porphyry skarn cu pb zn deposits in the qin hang belt

characteristics of rees and trace elements in scheelite from the zhuxi w deposit south china implications for the ore forming conditions and processes abstract the zhuxi w deposit in jiangxi south china with a resource of 2 86 mt w and an average grade of 0 54 wo3 is the largest w deposit in the world the deposit occurs at the contact between a late mesozoic granitic intrusion and carboniferous permian carbonate rocks and neoproterozoic metamorphic rocks the ores are divided into three types skarn ore dominant sulfide ore and greisen ore based on occurrences and petrographic relationships scheelite the dominant ore mineral is classified into three types i e type i greisen type ii skarn specifically in the retrograde stage and type iii hydrothermal sulfides type i and type ii are time equivalent but spatially separated whereas type iii is later the different types of scheelite have distinctly different ree and trace element compositions type i scheelite is characterized by an average ree of 67 9 ppm lree hree ratio of 24 4 eu of 8 5 mo of 0 1 ppm and sr of 1058 ppm whereas type ii scheelite features an average ree of 48 1 ppm lree hree ratio of 10 6 eu of 0 67 mo of 1892 ppm and sr of 90 1 ppm type iii scheelite has an average ree of 53 9 ppm lree hree ratio of 4 8 eu of 17 5 mo of 92 9 ppm and sr of 37 1 ppm the extremely high concentrations of sr and highly positive eu anomalies in type i scheelite are likely related to release of these elements from plagioclase in the granite during greisenization whereas the extremely low concentrations of mo may be related to the reducing and high temperature nature of the magmatic fluid mo probably was mainly in the mo4 state and could not replace w6 in the scheelite lattice in contrast the negative eu anomalies and high mo concentrations in type ii scheelite suggest that the mineralizing environment in the retrograde alteration stage was relatively oxidizing causing eu to exist mainly as eu3 which is difficult to replace ca2 in scheelite and mo mainly as mo6 which is easy to replace w6 in scheelite in the sulfide mineralization stage the fluid became relatively reducing again and eu2 could easily replace ca2 in scheelite causing positive eu anomalies whereas mo mainly exists as mo4 and precipitated as molybdenite and so has limited substitution for w6 in scheelite the ree and trace element compositions of the dominant w mineral type ii scheelite characterized by high concentrations of mo high lree hree ratios and negative eu anomalies indicate that the ore forming materials were mainly derived from the granitic intrusions the variation of ree and trace elements in scheelite in time and space reflects a complex magmatic hydrothermal mineralization process involving various fluid rock reactions within the intrusion and in the country rocks the formation of the zhuxi w deposit is linked with a large fertile granitic intrusion which delivered a large amount of w to the site of mineralization through convection within the magma chamber and w precipitation in the skarn was largely caused by an abrupt drop in temperature and increase in ph of the ore forming fluid

the remarkable re os chronometer in molybdenite how and why it works the re os rhenium osmium chronometer applied to molybdenite mos2 is now demonstrated to be remarkably robust surviving intense deformation and high grade thermal metamorphism successful dating of molybdenite is dependent on proper preparation of the mineral separate and analysis of a critical quantity of molybdenite unique to each sample such that recognized spatial decoupling of 187re parent and 187os daughter within individual molybdenite crystals is overcome highly precise accurate and reproducible age results are derived through isotope dilution and negative thermal ion mass spectrometry id ntims spatial decoupling of parent daughter precludes use of the laser ablation icp ms microanalytical technique for re os dating of molybdenite the use of a reference or control sample is necessary to establish laboratory credibility and for interlaboratory comparisons the rb sr k ar and 40ar 39ar chronometers are susceptible to chemical and thermal disturbance particularly in terranes that have experienced subsequent episodes of hydrothermal magmatic activity and therefore should not be used as a basis for establishing accuracy in re os dating of molybdenite as has been done in the past re os ages for molybdenite are almost always in agreement with observed geological relationships and when available with zircon and titanite u pb ages for terranes experiencing multiple episodes of metamorphism and deformation molybdenite is not complicated by overgrowths as is common for some minerals used in u pb dating e g zircon monazite xenotime nor are re and os mobilized beyond the margins of individual crystals during solid state recrystallization moreover inheritance of older molybdenite cores incorporation of common os and radiogenic os loss are exceedingly rare whereas inheritance common pb and pb loss are common complications in u pb dating techniques therefore molybdenite ages may serve as point in time markers for age comparisons

a tentative discussion on differences between large scale tungsten and tin mineralizations in south china both tungsten and tin are the most prevailing mineral resources in china large scale tungsten and tin mineralizations took place mostly in south china especially in the nanling mountains and the neighboring areas the two elements are very closely related to and accompanied with each other and always occur together in most ore deposits however differences do exist between tungsten and tin mineralizations in many aspects spatial distribution shows that the eastern sector of the nanling mountains is characterized by strong and dense w mineralization while sn mineralization becomes stronger westwards china s two largest sn ore deposits are distributed in the western margin of the south china fold system although both tungsten and tin mineralizations have the same highest ore forming epoch of 160 150 ma the tin mineralization is spanned from the late xuefeng period 800 ma to late yanshanian movement 80 ma the late yanshanian movement is in fact another highlight of tin mineralization the tin bearing granite and tin mineralization show much closer relationship with the participation of mantle derived materials than tungsten mineralization therefore the large scale tin mineralization took place either near the so called shi hang zone where long term deep faulting was activated and a type granites were emplaced or during the late yanshanian period when the south china continent was in a strong tensional geodynamic environment the principal factors responsible for these differences may include the diversity of geochemical properties between the two elements and the differences in tectonic backgrounds stratigraphic characteristics and magmatic activities between the eastern part and the western part of south china

a long lived hydrothermal system in bushveld granites at the zaaiplaats tin mine lead isotope evidence tin mineralization at zaaiplaats is hosted in alkali feldspar granites of the lebowa granite suite which intrude the rashoop granophyre suite from the upper contact downward the alkali feldspar granites include the marginal pegmatite fine grained lease granite and the coarse grained bobbejaankop granite the major mineralization styles consist of subhorizontal tabular low grade orebodies in the lease granite a lower zone of disseminated cassiterite mineralization in the bobbejaankop granite and shallowly plunging and branching pipe orebodies in both granites fluid inclusion data show a continuous evolution of the magmatic hydrothermal system from 600 degrees to 200 degrees c with cassiterite and scheelite precipitation above 400 degrees c mineral compositions and oxygen isotope fractionations indicate reequilibration of minerals within the granites during pervasive alteration at temperatures generally between 200 degrees and 300 degrees c the emplacement age of these and other bushveld granites is ca 2050 ma yet pb pb whole rock isochron ages for the different variably mineralized granite bodies at zaaiplaats show a relatively restricted range from 961 or 129 ma for the rashoop granophyre to 1187 or 51 ma for the lease granite thus the analyzed sample suites consistently record an event approximately 1 b y after the emplacement of the granites modeling their pb isotope evolution indicates that each suite evolved independently between 2050 and ca 1100 ma suggesting that hydrothermal fluid circulation was essentially confined within each granite body and or fluid rock ratios were low and that the overall 238 u 204 pb within each suite from 2050 to ca 1100 ma was not unusually high or low for fractionated granites suggesting largely closed system behavior of u and pb within each suite during this interval the ca 1100 ma event which caused closure of the u pb systems at zaaiplaats is interpreted to reflect a blocking temperature age related to uplift and cooling of a long lived hydrothermal system and precipitation of the latest stage minerals e g galena at 200 degrees to 300 degrees c the high steady state temperature required to maintain the hydrothermal system at zaaiplaats at temperatures above 200 degrees c for ca 1 b y was provided by radioactive decay current heat production characteristics calculated from present day u th and k 2 o concentrations range from 4 2 mu w m 3 for the rashoop granophyre to 11 5 mu w m 3 for the lease granite preweathering heat production of 30 3 mu w m 3 is inferred for the mineralized bobbejaankop granite after accounting for dramatic recent losses of u and th the low level of hydrothermal fracturing combined with stable and pb isotope evidence effectively rules out convective cooling by external fluids as a significant heat loss mechanism at zaaiplaats fluid pathways within the granites were controlled dominantly by grain boundaries microfractures and vugs which allowed internal circulation and elevated subsolidus temperatures to be maintained indefinitely under a thermal blanket of an estimated 4 km of postemplacement cover uplift and erosion of the terrain caused cooling through the pb exchange blocking temperatures at ca 1100 ma

manganoan skarn in the shizhuyuan polymetallic tungsten deposit hunan province a manganoan skarn in the shizhuyqan supergiant w sn mo bi be deposit is sixdied i n the present papzr i t co sistosf spessartine almandi ic spessartinic garnet rhodonite tephroite helvite alabandine mo bearing salite mn rich hedenbergite in rich phlogopite and rhodochrosite and spacio temporally develops together with the greisenization and releva t mineralizai ions after calcic skarnization and retrograde alteration from proximal to distal contact zones its mineral assemblages become incseasi glyc omplicated and the manganese content of their varicras minerals is getting higher and higher the complicated mineral assemblages of the manganoax skarrr and their spaciotemporal distribution apparently prove the evolutional direction of the skarn in the shizhuyuan polymet allic tungsten deposit

generation of late mesozoic qianlishan a 2 type granite in nanling range south china implications for shizhuyuan w sn mineralization and tectonic evolution abstract the late mesozoic qianlishan granitic complex in the western nanling range south china is associated with the shizhuyuan giant w sn mo bi polymetallic deposit it mainly consists of three phases of intrusions p 1 porphyritic biotite granite p 2 equigranular biotite granite and p 3 granite porphyry all three phases of granite contain quartz plagioclase k feldspar and fe rich biotite they have geochemical affinities of a type granites e g high feot feot mgo ratios 0 84 0 99 total alkali na2o k2o 7 50 9 04 wt high ga al ratios 10 000 ga al 2 6 and high zr nb y ce concentrations 350 ppm high y nb ratios 1 2 suggest that the qianlishan complex belongs to a2 type granite zircon u pb ages indicate a short age interval decreasing from 158 157 ma to 158 155 ma and to 154 ma for the p 1 p 2 and p 3 granites respectively these ages are similar to the mineralization age of the shizhuyuan tungsten polymetallic deposit within error the qianlishan granites were generated at low oxygen fugacity conditions based on the low values of zircon ce4 ce3 ratios 1 53 198 and significantly negative eu anomalies eun eun 0 03 0 13 in apatite new zircon ehf t values for the p 3 granite range from 13 0 to 4 4 similar to those previously obtained for the p 1 and p 2 granites both the granite and apatite grains therein are characterized by high f but low cl concentrations suggesting the influx of a high f cl component the p 2 granites especially contain higher f contents 1840 8690 ppm and w 7 158 ppm and sn 6 51 ppm concentrations and with stronger evolution features positive trends between f and w and sn of qianlishan complex indicate that high f source is crucial for mineralization of w and sn we consider that the lithospheric mantle source may have been metasomatized by subduction fluids in the far end of subduction zones to produce the a2 feature of the qianlishan granite and the fluorine was introduced through breakdown of phengite in the oceanic slab partial melting of the lithospheric mantle was induced by upwelling of the asthenospheric mantle as a consequence of slab rollback tungsten and tin have been enriched in reduced granitic magmas through fractionation enhanced by high f contents forming the giant polymetallic deposits

zircon crystallization and the lifetimes of ore forming magmatic hydrothermal systems magmatic hydrothermal copper ore formation involves multiple pulses of subvolcanic porphyry intrusion vein opening and hydrothermal ore deposition it is driven by larger subjacent magma reservoirs acting as the source of fluid and ore forming components high precision u pb ages of individual zircon crystals from porphyries immediately predating and postdating cu au mineralization at bingham canyon utah united states and bajo de la alumbrera northwestern argentina show a significant spread of reliably concordant ages this demonstrates zircon crystal formation over a protracted period of 1 m y which is interpreted to record the lifetime of the magma reservoir from which porphyries and ore fluids were extracted the youngest zircons in all pre ore and post ore intrusions overlap within a much shorter time interval of 0 32 m y at bingham canyon and 0 090 m y at alumbrera these youngest zircons of each intrusion are interpreted to bracket the maximum duration of porphyry emplacement and ore formation to short periods consistent with thermal constraints this study illustrates that age brackets based on individual magmatic zircon grains are geologically more informative than the calculation of means and standard deviations based on apparently normal age distributions in zircon populations

molybdenite re os and muscovite 40ar 39ar dating of the xihuashan tungsten deposit central nanling district south china abstract the xihuashan tungsten deposit in the central nanling region south china is an important vein type ore deposit hosted in cambrian strata and mesozoic granitic intrusions wolframite and molybdenite are the principal ore minerals the gangue minerals are mainly quartz and muscovite wolframite and molybdenite are products of the first stage hydrothermal activity whereas muscovite formed dominantly at the second stage molybdenite re os and muscovite 40ar 39ar dating have been carried out to investigate the age of mineralization re os isotopic dating for molybdenite associated with wolframite yield a precise well constrained isochron age of 157 8 0 9 ma mswd 1 5 ar ar isotopic analyses of muscovite yield a plateau age of 152 8 1 6 ma in agreement with an inverse isochron age of 152 8 1 6 ma which is 5 mys younger than the re os age the molybdenite re os age is interpreted as the age of tungsten mineralization this age coincides well with the zircon u pb age of the host granitic intrusion reported previously the 5 mys difference between molybdenite re os and muscovite 40ar 39ar ages probably represents the duration of hydrothermal activity the results show that the xihuashan tungsten deposit is one of many important tungsten tin deposits formed during 150 to 160 ma associated with large scale lithospheric extension in south china

zircon records multiple magmatic hydrothermal processes at the giant shizhuyuan w sn mo bi polymetallic deposit south china abstract the supergiant shizhuyuan w sn mo bi polymetallic deposit is located in the nanling range and is intimately related to the qianlishan granite complex intruded during the late jurassic period the complex consists of three intrusive phases porphyritic biotite granite pbg equigranular biotite granite ebg and porphyritic granite dyke in this work the distinct geochemical features of magmatic and hydrothermally altered zircons from the qianlishan complex are used to reveal the magmatic hydrothermal evolution of the deposit whole rock geochemistry and mineralogy show that ebg samples have experienced stronger fractional crystallization than pbg samples zircon u pb dating constrains the intrusive episodes at 155 153 ma and 152 ma for the pbg and ebg respectively and subsequent hydrothermal events revealed by hydrothermal zircon ages at 154 153 ma and 152 150 ma hydrothermally altered zircon and paragenetic mineral inclusions from ebg samples show textures and compositional properties suggesting they were intensely altered by a zirconium saturated aqueous fluid type 1 enriched in most trace and metallogenic elements e g zr rees hf p u th nb ta ti pb al fe mg ca mn w and sn and volatiles f cl li co2 and h2o this fluid was relatively lower in temperature pressure and oxygen fugacity average ce4 ce3 11 2 type 2 fluid represented by hydrothermally altered zircons found in pbg was depleted in trace elements and had a relatively higher temperature and pressure and low fo2 ce4 ce3 2 12 29 16 type 3 fluid as evidenced by fluid altered zircons from the greisenized granite was likely a further evolved product of the type 2 fluid given its moderate cargo of most trace elements but also with exceedingly low ce4 ce3 values 2 9 33 45 the type 3 fluids might be precursors of w sn mineralizing fluids whereas the type 1 fluids were likely to represent mature ore forming fluids which were activated during the late skarn stage but before the retrograde mineralization stage compared with the fo2 of pbg and ebg magmas calculated by non altered magmatic zircons average ce4 ce3 31 47 and 49 21 it seems that the hydrothermal fluids generated by them became more reduced during the further evolution a progressive process can thus be divided pbg type 2 type 3 ebg type 1 with the gradual accumulation of ore forming materials the enrichment of most elements in hydrothermal zircons further indicates a substitution of y rees p hf u th ti nb ta ca k fe and mn for zr4 and si4 in the zircon lattice most fluid altered zircons exhibit a similar 176hf 177hf distribution range 11 to 6 but evidently elevated 176lu 177hf and 176yb 177hf ratios with magmatic ones this indicates that three types of hydrothermal fluids were magmatic derived whereas lu and yb were highly mobile during the hydrothermal event based on the results a magmatic hydrothermal evolution model is presented for shizhuyuan zircons this research highlights the use of zircon as a powerful tool in revealing the complex magmatic hydrothermal processes and perhaps mineralization potential in highly evolved granite associated mineralization systems

genesis of the giant caixiashan zn pb deposit in eastern tianshan nw china constraints from geology geochronology and s pb isotopic geochemistry abstract the caixiashan zn pb deposit is the largest carbonate hosted zn pb deposit in eastern tianshan nw china the deposit comprises the no iii and iv ore zones with a proven reserve of 131 mt ore at 3 95 pb zn the orebodies generally occur as irregular lenses and pods in altered carbonate rocks of the mesoproterozoic kawabulake group near faults the mineralization is characterized by massive disseminated and vein veinlet sulfides including pyrite pyrrhotite sphalerite and galena with minor arsenopyrite and chalcopyrite as well as sulfosalt minerals of ag as sb and pb the mineralization is associated with tremolite chlorite silica and carbonate alterations rb sr isotopic dating of sphalerite and pyrrhotite yields an isochron age of 337 2 5 7 ma which is interpreted as the mineralization age zircon u pb dating reveals that stocks of diorite quartz diorite k feldspar granite and monzonitic granite that occur in the deposit area were emplaced at 348 2 3 7 ma 351 9 3 5 ma 333 6 3 6 ma and 330 0 3 6 ma respectively these age data suggest that the mineralization is coeval with carboniferous granitic magmatism the 34sv cdt values of sulfides excluding the syn sedimentary pyrite range from 2 42 to 19 1 suggesting that the reduced sulfur was mainly derived from thermal sulfate reduction tsr of seawater derived sulfates in the marine sedimentary basement rocks and minor contribution by replacement of syn sedimentary pyrite as well as a possible input of magmatic sulfur the pb isotopic compositions of sulfides with 206pb 204pb ranging from 17 074 to 17 361 207pb 204pb from 15 422 to 15 614 and 208pb 204pb from 36 685 to 37 303 partly overlap with those of basement rocks of the mesoproterozoic kawabulake group and the carboniferous intrusions suggesting that the ore metals were derived from both the basement and carboniferous magmatism on the basis of the spatio temporal relations between hydrothermal alterations mineralization and carboniferous magmatism we conclude that the caixiashan zn pb deposit is a high temperature carbonate replacement deposit related to concealed granitic intrusions which were formed in an arc environment related to the subduction of the south tianshan ocean plate underneath the central tianshan massif during the carboniferous time the results of this study indicate that there is a great potential of finding more large scale zn pb deposits similar to caixiashan in eastern tianshan

a precise u pb age on cassiterite from the xianghualing tin polymetallic deposit hunan south china we report the first precise u pb isotope data on cassiterite from the large xianghualing tin polymetallic deposit in the central nanling district south china the results show that four separates from sample xf 51 have a relatively narrow range of 206pb 238u apparent ages varying from 152 to 157 ma and the three 206pb 238u apparent ages yield a weighted average value of 156 4 ma mswd 0 32 separates from two other cassiterite samples do not have sufficient radiogenic pb to generate a reliable 206pb 238u age seven separates from the above three cassiterite samples define a well constrained 238u 206pb isochron corresponding to an age of 157 6 ma mswd 34 a comparison of the u pb cassiterite ages with published ar ar dates on muscovite from this deposit and k ar age data on biotite from the pluton genetically related to the tin mineralization in this area demonstrates that the u pb isotope system of cassiterite is a potential geochronometer combined with the ar ar dates of muscovite from this deposit we can constrain the absolute age of tin polymetallic mineralization in xianghualing at 154 157 ma the dates obtained in this study consistent with the published geochronological results from other important deposits in this region reveal that the large scale tungsten tin mineralization in the central nanling region was predominantly emplaced during 150 161 ma

mesozoic metallogeny in east china and corresponding geodynamic settings an introduction to the special issue abstract the giant east china mesozoic metallogenic province hosts some of the world s largest resources of tungsten tin molybdenum antimony and bismuth ores of gold silver mercury lead zinc copper uranium and iron are also of major importance the province and its constituent metallogenic belts or regions south china middle lower yangtze river valley east qinling dabie interior of north china craton yan liao and north east china are the products of several pulses of igneous activity and mineralisation between 240 and 80 ma each successive stage has produced a distinctive suite of deposits that can be readily related to the geodynamic evolution of the region during the mesozoic this geodynamic evolution is linked to a complex series of tectonic events involving far field subduction plate collisions crustal thickening post collision collapse and rifting

how accurately can we date the duration of magmatic hydrothermal events in porphyry systems an invited paper determining the absolute duration of magmatic hydrothermal events leading to the formation of porphyry systems i e including porphyry copper skarn and epithermal deposits is one of the key questions in ore geology this is so because the duration of magmatic hydrothermal events in porphyry systems is instrumental to the development of genetic models necessary to explore a category of mineral deposits that provide most of the copper and significant amounts of base and precious metals to our economy the problem of determining the absolute duration of magmatic hydrothermal events in porphyry systems has been addressed through thermal modeling of cooling intrusions and time needed to precipitate specified metal amounts from active hydrothermal systems with known metal concentrations and fluid fluxes both these methods have shown that the likely duration of hydrothermal systems is on the order of a few tens of kilo annum ka isotopic dating in contrast is the only possible way to determine the life span of magmatic hydrothermal events in fossil porphyry systems analytical and methodological developments during the last decade in the fields of the most robust isotopic systems commonly used for absolute dating u pb 40ar 39ar re os allow us to date minerals with internal precisions 0 2 2 for a 10 ma old mineral this corresponds to a 20 ka uncertainty which is marginally sufficient to discriminate the duration of hydrothermal systems at the tens of kilo annum scale however many geochronological studies on fossil porphyry systems have shown that these are most often formed through repeated cycles of several intrusion events which extend the overall life of the porphyry systems to a few 0 x and up to 2 ma in some cases internal precisions of the above mentioned dating methods allow us in theory to comfortably discriminate events at the 0 x scale and the combination of u pb 40ar 39ar and reos geochronology is a tool widely used by ore geologists to bracket the duration of cyclic magmatic hydrothermal events in porphyry systems in this review we discuss some fundamental problems that are systematically overlooked in most geochronological studies trying to bracket the life span of porphyry systems we show that if these problems are not adequately taken into account and tackled the result will be that fundamentally wrong life spans of porphyry systems will be estimated we also provide basic guidelines to follow when trying to resolve the duration of magmatic hydrothermal events in porphyry systems with the highest accuracy and precision currently achievable

in situ u pb zircon dating using laser ablation multi ion counting icp ms high resolution in situ u pb zircon geochronology on zoned grains can obtain isotope signatures from multiple growth or thermal events we present a method using laser ablation multicollector inductively coupled plasma mass spectrometry la mc icp ms to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zircon volumes as small as 12 m 25 m and 40 m in diameter by about 10 m in depth high precision u pb age of a series of zircon standard covering a wide age range of 30 to 1 065 ma was acquired using la mc icp ms the precision of measured pb u ratios in homogeneous zircon is about 2 2 resulting in routinely achieved precision of u pb ages obtained by external calibration of 1 2 or better all masses of interest can be simultaneously recorded with a multi ion counting system mic operating in static mode and the short ablation required to achieve such precision results in spatial resolution that is superior to comparable u pb zircon analyses by single collector icp ms the resulting present u pb age for five zircon reference samples and two geological samples show an excellent agreement with the previously reported id tims or shrimp data

neoproterozoic tin mineralization in south china geology and cassiterite u pb age of the baotan tin deposit in northern guangxi the baotan tin deposit 23 mt 0 43 sn is located in the jiuwandashan yuanbaoshan area south china it is hosted in neoproterozoic mafic metasedimentary rocks and apical portions of the pinying granite pluton six alteration and mineralization stages have been identified pre ore alteration cassiterite greisen cassiterite tourmaline quartz vein cassiterite quartz vein cassiterite sulfide vein and post ore quartz calcite quartz vein stages tin mineralization is mainly in the cassiterite greisen cassiterite tourmaline quartz and cassiterite quartz vein stages the deposit is characterized by widespread tourmalinization both pre ore and ore stage tourmaline is schorl tourmaline from pre ore tourmaline quartz nodules has elevated al2o3 and f contents and fe fe mg and na na ca ratios which are probably controlled by the initial magmatic fluid ore stage tourmaline shows low al2o3 and f contents and fe fe mg and na na ca ratios which are likely influenced by the surrounding mafic rocks la icp ms u pb dating on two cassiterite samples from disseminated cassiterite tourmaline quartz ore and cassiterite quartz vein yields 206pb 238u weighted mean ages of 832 5 ma and 834 4 ma 2 respectively these two dates are consistent with the previously reported zircon u pb ages of 834 835 ma for the pingying granite which indicates that tin mineralization is related to the granite the granite has low magnetic susceptibility and zircon ce4 ce3 ratios which are similar to those of sn bearing ilmenite series granites our study confirms the neoproterozoic tin mineralization event in south china and indicates that the neoproterozoic highly fractionated s type granites in the southeastern margin of yangtze block have a great potential for tin mineralization

how long can a hydrothermal system be sustained by a single intrusive event published numerical calculations show that the convective systems which produce near surface geothermal systems or ore deposits are likely to cool their intrusion heat source in at most a few tens of thousands of years even if the intrusion is large generally hydrothermal circulation near surface geothermal activity and magmatic intrusion should be closely tied in time and space long lived approximately 1 m y hydrothermal activity normally suggests multiple pulses of intrusion with associated pulses of hydrothermal circulation however if the permeability of the intruded environment is just above that which allows convection and the volume of the intrusion is very large calculations presented here show that a single episode of intrusion can sustain hydrothermal circulation and near surface geothermal activity for approximately 800 000 yr for a deep sill heat source these unusually long lived hydrothermal systems can vent through a few very widely separated discharge sites and have the potential to produce isolated massive sulfide deposits of unusually large size

two ages of porphyry intrusion resolved for the super giant chuquicamata copper deposit of northern chile by ela icp ms and shrimp zircon u pb ages measured in situ by excimer laser ablation inductively coupled plasma mass spectrometry ela icp ms and verified by sensitive high resolution ion microprobe shrimp on ore bearing felsic porphyries from the chuquicamata porphyry copper molybdenum deposit northern chile identify two discrete igneous events the volumetrically dominant east porphyry has an age of 34 6 0 2 ma whereas the bench and west porphyries yield ages of 33 3 0 3 ma and 33 5 0 2 ma respectively the age of the east porphyry is indistinguishable from a re os age for early molybdenite mineralization 35 ma and the oldest reported 40 ar 39 ar ages for hydrothermal alteration confirming a genetic link with mineralization previous geological studies and 40 ar 39 ar and re os geochronology identify two main hydrothermal events high temperature potassic alteration with chalcopyrite at 33 4 0 3 ma followed by lower temperature quartz sericite alteration with pyrite at 31 1 0 3 ma the ages of the west and bench porphyries match the ages for potassic alteration younger quartz sericite alteration may reflect an additional fourth intrusion concealed at depth the anomalously large size of chuquicamata appears to be due to a protracted igneous history resulting in the superposition of at least two temporally distinct magmatic hydrothermal systems

constraints on the timing and genetic link of the large scale accumulation of proximal w sn mo bi and distal pb zn ag mineralization of the world class dongpo orefield nanling range south china abstract the world class dongpo orefield located in the nanling range south china is famous for its large scale accumulation of w sn mo bi pb zn ag deposits which includes the giant shizhuyuan w sn mo bi jinchuantang sn bi yejiwei sn cu and congshuban pb zn ag deposits the polymetallic mineralization around the qianlishan pluton exhibits systematic zoning and comprises proximal w sn mo bi skarn greisen and distal pb zn ag veins however the timing and genetic link of its proximal skarn greisen w sn mo bi and distal vein type pb zn ag mineralization are not well constrained here we present systematic geochronological data to constrain the geochronological framework and genetic model of the giant dongpo orefield the muscovite 40ar 39ar age of the greisen type ore in the shizhuyuan w sn mo bi deposit is 151 1 ma which is consistent with the formation of the skarn type ore and the qianlishan pluton thus indicating that they are genetically related and both formed contemporaneously at 151 ma the large scale accumulation of w sn mo bi in the shizhuyuan deposit may have occurred in a short duration of 1 ma the muscovite 40ar 39 ar ages 155 5 1 1 and 156 8 1 1 ma and molybdenite re os age 153 8 4 2 ma of the ma naoshan w sn fe mn pb zn deposit as well as the zircon u pb age 152 7 0 9 ma of the yejiwei sn cu deposit in the dongpo orefield are consistent with the age of the qianlishan pluton thus indicating that the proximal skarn greisen w sn mo bi mineralization in the dongpo orefield is genetically related to the qianlishan pluton in addition the rb sr dating of sphalerite indicates that the vein type pb zn ag mineralization in the congshuban area formed at 152 2 ma which is consistent with the la mc icp ms zircon u pb age 156 155 ma of the equigranular biotite granite indicating that the distal vein type pb zn ag mineralization is genetically associated with the qianlishan equigranular biotite granite by integrating the high precision geochronological data of this study with those of previous studies the new genetic model of the large scale accumulation of w sn mo bi pb zn ag in the dongpo orefield suggests that the proximal skarn greisen w sn mo bi and distal vein pb zn ag mineralization in the dongpo orefield are genetically related to the qianlishan pluton and that the mineralization type is mainly controlled by the characteristics of the wall rock

the early jurassic fe sn metallogenic event and its geodynamic setting in south china evidence from re os u pb geochronology and geochemistry of the dading magnesian skarn fe sn deposit abstract the south china block scb is one of the largest w sn polymetallic metallogenic district over the world with most of the deposits formed during the mesozoic the early jurassic of scb was considered as a magmatic and metallogenic quiescence stage as response to the tectonic transition from the paleo tethyan to the paleo pacific geodynamic domains the dading fe sn deposit is a quite rare early jurassic deposit recognized in scb sims zircon u pb and molybdenite re os dating indicate that the dading fe sn deposit 185 9 4 9 ma and related shibei granite 189 0 1 5 ma formed at the early jurassic which provides convincing evidence for a previously unrecognized early jurassic fe sn metallogenic event in scb geochemical data show that the shibei granite has high sio2 nb zr nb ce y concentrations and high ga al ratio but low y nb ratio which are similar to those of a1 type granite the large range of zircon ehf t values 2 4 to 3 4 negative correlation between zircon ehf t and 18o values and unique whole rock sr nd isotopic compositions end t 3 3 to 3 7 isr 0 7063 0 7085 suggest that the shibei granite is likely to originate from a mixed source of pre existing crust and juvenile material with oib like isotopic composition combining with the spatial distribution of the volcanic intrusive rocks sedimentary basins and tectonic deformation styles we suggest that the early jurassic fe sn mineralization occurred in an extensional environment which was probably linked to the post orogenic collapse of the indosinian orogeny between the scb and indochina block

the polymetallic magmatic hydrothermal xiangdong and dalong systems in the w sn cu pb zn ag dengfuxian orefield se china constraints from geology fluid inclusions h o s pb isotopes and sphalerite rb sr geochronology vein type deposits including the xiangdong w sn and dalong pb zn deposits occur in or near the dengfuxian composite granite pluton comprising predominantly triassic and minor jurassic intrusions liquid rich nacl aqueous inclusions vapor rich nacl aqueous inclusions liquid rich cacl2 nacl aqueous inclusions two phase ch4 rich inclusions three phase co2 h2o inclusions and three phase calcite bearing inclusions occur in the quartz veins at xiangdong whereas only liquid rich nacl aqueous inclusions occur at dalong the xiangdong veins formed at temperatures near 241 c from nacl cacl2 h2o ch4 co2 fluids averaging 11 4 wt nacl eq the dalong deposit formed at temperatures near 186 c from nacl h2o ch4 fluids averaging 6 2 wt nacl eq the ore forming mechanisms at xiangdong include fluid immiscibility during stage i fluid mixing during stage ii and mixing with meteoric water accompanied by cooling during stage iii the ore forming mechanisms at dalong include cooling and mixing with meteoric water oxygen and hydrogen isotopes suggest that the ore forming fluids from both deposits originated as mixtures of magmatic water with various amounts of meteoric water sulfur and strontium isotopes suggest an igneous origin for both deposits and possibly mixing with s and sr from sedimentary rock for dalong lead isotopes indicate that ore metals originated mainly from the upper crust with minor mantle contributions sphalerite from dalong gives a rb sr isochron age of 151 6 7 1 ma consistent with the mineralization age of xiangdong both the w sn and pb zn ore forming events are closely related to late jurassic magmatism which occurred in an environment of lithospheric extension and thinning

origin of the fluorine rich highly differentiated granites from the qianlishan composite plutons south china and implications for polymetallic mineralization abstract many composite granite plutons occur in south china accompanied by large scale polymetallic mineralization each composite pluton is composed of main phase granite and late stage highly differentiated granite traditionally the highly differentiated granite is thought to be residual melt of the former via fractionation and ore forming materials and fluids are from granite magma itself we propose a different model for the origin of the granites and related mineralization based on petrological and geochemical studies on the qianlishan composite plutons that host the supergiant shizhuyuan w sn bi mo deposit the main phase granite shows features of normal granites while the highly differentiated granite is characterized by f rich water deficient low f o 2 alkalinity ree tetrad effect and modified behavior of some trace elements e g very high k ba and low k rb and zr hf ratios we suggest that the parent magma of the highly differentiated granite was derived from melting of dominantly lower crustal rocks triggered by underplating of a new pulse of basaltic magmas small amounts of basaltic magmas and volatiles such as fluorine were involved in the source of the granite addition of fluorine lowered the solidus temperature and viscosity of granite magma and thus prolonged the process of magma evolution this resulted in extreme fractional crystallization and intense interaction between melt and circulating waters from country rocks forming the unusual geochemical features of the granite the high temperature circulating waters along with metamorphic fluids released from deep crustal rocks subsequently extract ore forming metals from country rocks through forming f bearing complexation forming the polymetallic deposits

mineralogy fluid inclusion petrography and stable isotope geochemistry of pb zn ag veins at the shizhuyuan deposit hunan province southeastern china the shizhuyuan polymetallic deposit is located in the central part of the nanling region southeastern china and consists of proximal w sn mo bi skarns and greisens and distal pb zn ag veins the sulfides and sulfosalts in the distal veins formed in three distinct stages 1 an early stage of pyrite and arsenopyrite 2 a middle stage of sphalerite and chalcopyrite and 3 a late stage of galena ag sn and bi bearing sulfides and sulfosalts and pyrrhotite combined sulfide and sulfosalt geothermometry and fluid inclusion analyses indicate that the early stage of mineralization occurred at a temperature of 400 c and involved boiling under hydrostatic pressure 200 bar with the temperature of the system dropping during the late stage to 200 c laser raman analysis indicates that the fluid inclusions within the studied minerals are dominated by h2o although some contain carbonate solids and ch4 gas vein hosted sulfides have 34s values of 3 8 6 3 that are interpreted as indicative of a magmatic source of sulfur the mineralization process can be summarized as follows an aqueous fluid exsolved on final crystallization of the qianlishan pluton ascended along fracture zones cooled to 400 c and boiled under hydrostatic conditions and with decreasing temperature and sulfur fugacity sulfide and sulfosalt minerals precipitated successively from the ag cu zn fe pb sb as s bearing fluid system

trace elements u pb ages and hf isotopes of zircons from mesozoic granites in the western nanling range south china implications for petrogenesis and w sn mineralization abstract the e w trending nanling range located in the southern part of the south china block scb is characterized by widespread intra continental mesozoic granitoids and accompanying w sn polymetallic ore deposits detailed studies are presented on trace elements u pb ages and lu hf isotopes in zircons from the mesozoic a2 type like granitoids including the qianlishan qitianling xianghualing huashan guposhan niumiao tong an jinziling and jinjiling plutons from the western nanling range la icp ms u pb analyses of zircon indicate that these granites intruded mainly from ca 160 150 ma two types of zircon magmatic and late magmatic hydrothermal with similar ages can be distinguished based on their zircon trace element compositions the late magmatic hydrothermal zircons have high contents of metallogenic elements e g w and sn and may be closely related with the ore deposits the ehf t values of zircons from the mesozoic granitoids are mildly negative to positive indicating the reworking of both old and young crustal components the significant involvement of mesozoic juvenile mantle derived materials in the source can be excluded because of the rare occurrences of mafic rocks with radiogenic isotopic signatures in the area the average crustal residence age patterns of the mesozoic granites in the western nanling range are similar to those of the neoproterozoic magmatic rocks in the eastern part of the jiangnan orogen which may represent the neoproterozoic collisional belt between the yangtze and cathaysia blocks considering the specific isotopic and metallogenic features of the mesozoic granitoids in the study area we propose that the western nanling range may represent a western extension of neoproterozoic arc continent collisional belt in south china the mesozoic granitoids of this area may have been generated mainly by reworking of deeply buried neoproterozoic arc related volcanic sedimentary materials due to thermal perturbations triggered by the subduction of the paleo pacific plate in mesozoic time

mineralization and fluid inclusion study of the shizhuyuan w sn bi mo f skarn deposit hunan province china the shizhuyuan deposit china is a world class w sn bi mo f skarn deposit hosted by devonian limestone in the thermal aureole of the qianlishan granite complex the qianlishan complex comprises five separate intrusions including fine grained porphyritic biotite granite 182 187 ma granite 1 medium grained biotite k feldspar granite 158 163 ma granite 2 fine grained biotite and k feldspar granite granite 3 granitic porphyry 144 146 ma granite 4 and diabase 142 ma the upper part of the granite complex is characterized by extensive greisen alteration skarn zones distributed around the intrusions are mainly calcic consisting of garnet garnet pyroxene vesuvianite garnet and wollastonite vesuvianite progressively outward from the intrusion following the primary skarn formation some of the skarn zones underwent retrograde alteration the high garnet pyroxene ratio and the diopside rich and andradite rich compositions of the pyroxene and garnet indicate that the skarn belongs to the oxidized type mineralization consists of sn be veinlet ore type i in marble and porphyry massive w bi mo sn skarn ore type ii stockwork w sn bi mo f ore type iii and w sn mo bi greisen ore type iv mainly associated with granite 2 emplacement of granite 2 was accompanied by late intense fracturing characterized by stockwork mineralization type iii which was superimposed on massive skarn and greisen zones the stockwork ore consists mainly of greisen and skarn veins and veinlets with scheelite wolframite molybdenite cassiterite bismuthinite and fluorite the sm nd method has been used to analyze the sm nd concentration and data for pyroxene and garnet in the massive skarn type ii ore associated with granite 2 yields an isochron age of 157 ma this age corresponds closely to the age of granite 2 fluid inclusion studies of four types of ore samples reveal four types of inclusions aqueous two phase inclusions h2o co2 inclusions gas rich inclusions and daughter mineral bearing inclusions containing halite or calcite homogenization temperatures of fluid inclusions in skarn minerals range from 350 to 535 c the homogenization temperatures of fluid inclusions in greisen and stockwork are lower than that in skarn and range from 200 to 360 c the fluid inclusion data indicate that there are two types of fluids associated with the massive skarn and greisen having salinities from 26 to 41 wt percent nacl equiv and from 1 to 21 wt percent nacl equiv respectively the high salinity inclusions are daughter mineral bearing whereas the low salinity inclusions are dominantly aqueous with a few gas rich inclusions the results suggest the evolution of the ore forming fluids either by immiscibility or by mixing between a high temperature high salinity magmatic water and a low temperature low salinity fluid such as meteoric water consistent with previously published isotopic studies the shizhuyuan deposit is a multi element skarn highly enriched in w sn bi mo and f this is interpreted to reflect multiple sources and stages of mineralization which in turn may account for the large size of the shizhuyuan deposit

albian cenomanian a type granite related ag pb zn veins in the central yidun terrane sw china constraints from the xiasai deposit the xiasai lianlong metallogenic belt in the central yidun terrane china hosts several sn ag and sn ag pb zn deposits which are spatially associated with cretaceous granites the xiasai ag pb zn deposit about 0 27 mt pb zn 1028 t ag and 20 000 t sn is the largest deposit in the belt and is related to a monzogranite intrusion the deposit consists of sulfides in hydrothermal veins resulting from three successive mineralization stages i iii a rb sr isochron of sphalerite samples yielded an age of 99 3 ma and zircon u pb laser ablation inductively coupled plasma mass spectrometry la icp ms dating of the xiasai monzogranite gave ages between 102 1 and 101 1 ma the xiasai monzogranite has a weakly peraluminous a type granite composition with high sio2 alkali and feot contents and low cao mgo and tio2 contents it is marked by enrichments in rb th and u with depletions in ba nb sr p and ti relative to the primitive mantle the ree patterns show a negative slope due to lree enrichment with negative eu anomalies eu eu 0 1 0 3 the xiasai monzogranite with variable ehf t values 2 7 to 0 6 and meso to neoproterozoic two stages hf model ages tdm2 925 1095 ma was probably derived from mixing of melts derived from partial melting of the paleoproterozoic crustal basement and the early cretaceous mantle in an extensional tectonic setting hydrothermal fluids are characterized by high temperatures 423 481 c and salinities 14 9 19 0 wt nacl for sn mineralization stage i moderate temperatures 285 386 c and salinities 3 5 8 0 wt nacl for the cu zn mineralization substage ii 2 and low temperatures 158 242 c and salinities 3 4 5 7 wt nacl for the ag pb mineralization substage ii 3 the h o isotopes indicate that the hydrothermal fluid likely has a magmatic component that mixed over time with infiltrating meteoric water and organic matter during fluid rock interactions the 34s values of sphalerite range from 9 7 to 3 1 and those from galena from 10 5 to 4 9 the estimated 34s value of the hydrothermal fluid is 8 5 using the sulfur isotopic fractionation of sphalerite galena pairs that are interpreted to be in equilibrium sulfides from substages ii 2 and ii 3 have relatively homogeneous pb isotopic compositions which are similar with those of k feldspars from the xiasai monzogranite geochronological and isotope data support a magmatic hydrothermal origin for the xiasai ag pb zn deposit

precise molybdenite re os and mica ar ar dating of the mesozoic yaogangxian tungsten deposit central nanling district south china the yaogangxian deposit in the central nanling region south china consists of vein type ore bodies hosted in cambrian to jurassic strata and mesozoic granitic intrusions wolframite and molybdenite are the dominant ore minerals intergrown with gangue minerals of quartz feldspar phlogopite and muscovite we have carried out molybdenite re os and phlogopite and muscovite 40ar 39ar dating to better understand the timing and genesis of mineralization re os dating of eight molybdenite samples yielded model ages ranging from 152 0 3 5 to 161 1 4 5 ma with an average of 156 0 ma the re os analyses give a well defined 187re 187os isochron with an age of 154 9 2 6 ma mswd 2 4 hydrothermal phlogopite and muscovite display extremely flat 40ar 39ar age spectra phlogopite yields a 40ar 39ar plateau age of 153 0 1 1 ma whereas muscovite yields a plateau age of 155 1 1 1 ma both 40ar 39ar ages are in good agreement with the re os ages placing the timing of tungsten mineralization at about 154 ma this age is consistent with the field relationships our new data when combined with published geochronological results from other major deposits in this region suggest that large scale w sn mineralization occurred throughout the central nanling region in the late jurassic

the sr and nd isotopic variations of the chinese loess plateau during the past 7 ma implications for the east asian winter monsoon and source areas of loess abstract 143 nd 144 nd and 87 sr 86 sr ratios of the acid insoluble residues of the red clay and overlying loess paleosols from the lingtai profile of the loess plateau china were investigated the results show that variations of the 87 sr 86 sr ratios of the lingtai profile can be divided into two stages from 7 ma b p to 2 5 ma b p the acid insoluble residues in the red clay rc formation are characterized by higher 87 sr 86 sr ratios with an average of 0 7230 from 2 5 ma b p to the present the acid insoluble residues in the wuchen loess wl4 ws1 lishi loess l15 s1 malan loess l1 and holocene loess s0 have relatively lower 87 sr 86 sr ratios and display an overall descending trend from 0 7223 at 2 5 ma b p to 0 7182 at the present among three possible interpretations for the variations of 87 sr 86 sr ratios of acid insoluble residues of the loess provenance change chemical weathering change or grain size distribution change only grain size distribution change provides a satisfactory interpretation this implies that the east asian winter monsoon strength was weak and relatively stable from 7 ma b p to 2 5 ma b p but became continuously enhanced from 2 5 ma b p to the present all the red clay and the overlying loess paleosols in the lingtai profile have generally identical e nd 0 implying that the source regions of these eolian deposits of the chinese loess plateau may be relatively stable and has not changed since 7 ma b p

genesis of the giant shizhuyuan w sn mo bi pb zn polymetallic deposit south china constraints from zircon geochronology and geochemistry in skarns abstract the giant shizhuyuan w sn mo bi pb zn polymetallic skarn type deposit which lies in the world famous nanling w sn metallogenic belt has a close affinity with the qianlishan granite complex previous studies focused on the qianlishan granitoids rather than relevant skarns where the evolutionary processes of skarn forming fluids mineralized fluids and sources of metals are debated this study carried out systematic epma and la icpms zircon u pb dating major and trace element and lu hf isotopic analyses for three types of skarns ore free greisen stockwork and sulfide bearing skarns at shizhuyuan the whole skarn zircons were classified into six age clusters 125 187 ma 235 ma 345 509 ma 677 772 ma 811 921 ma and 1000 ma and three genetic types detrital magmatic and hydrothermally altered among them the majority of the skarn zircons are of detrital origin 345 to 2225 ma peaking at 410 ma 710 ma and 905 ma and showing a wide range of th u ratios 0 05 7 09 they share similar characteristics of zircons hosted by devonian strata in south china suggesting the inheritance from wall rock the magmatic zircons in skarns can be further subdivided into two clusters triassic 235 ma and jurassic 150 ma which are derived from the corresponding granite ore free skarn contains only detrital zircons that have experienced the weakest alteration indicating the minor participation of granitic fluid the greisen stockwork skarn consists of both detrital zircons and jurassic magmatic hydrothermal zircons implying that granitic and stratigraphic materials may both contribute greatly to the w sn polymetallic mineralization sulfide bearing skarn includes abundant detrital zircon a few of triassic zircons but no jurassic zircons indicating that the latest sulfide mineralization was dominated by sediments rather than granitic rocks the two mineralized skarn zircons display elevated concentrations of most trace elements e g u ree ti y p nb and ta coupled with decreased si and zr which reflects strong fluid rock reaction the lowest ratios of ce ce 1 22 89 78 mean 24 13 in greisen stockwork skarn zircons reveal the most reducing environment for the main w sn mineralizing event jurassic zircons are homogeneous in 176hf 177hf 0 282352 0 282454 and ehf t 11 58 to 7 27 in well accord with local granitic rocks triassic zircons have variable ehf t 9 5 to 1 6 values suggesting more mantle input of precursor pluton before the jurassic main mineralization event based on the zircon geochronology in skarns we speculate that concealed triassic magmatism exists in the deep shizhuyuan area consequently a three stage ore forming model was established for the giant shizhuyuan deposit this study further illustrates that zircon can be used as an important indicator for ore genesis in complex metallogenic systems

fault controlled fluid evolution in the xitian w sn pb zn fluorite mineralization system south china insights from fluorite texture geochemistry and geochronology abstract fluorite is one of the most common minerals in the granite related hydrothermal systems and widely distributed in the xitan w sn polymetallic ore field south china it existed from the early w sn stage to the middle pb zn stage and then to the late fluorite stage thus responsible for the xinggao and guangming fluorite deposits in the region in this research textural geochemical and geochronological analyses of fluorites were used to reconstruct the fluid evolutionary history and its bearings on fault activities in the ore field the fluorites from the ore field yielded a sm nd isochron age of 153 3 8 0 ma initial 143nd 144nd 0 511871 0 000013 mswd 1 5 which is consistent to the timing of the w sn ore forming stage within the error this suggests that the fluorites were formed in the same time with the w sn ores and the average value of end t is similar to those of the jurassic granites end t 9 2 to 7 3 in the ore field this indicates that fluorite mineralization is mainly related to the jurassic granites and the basement rocks could be the source for the ore forming materials from the early stage fluorites coexisting with wolframite to the late fluorite only veins the total amount of rare earth elements ree in the fluorites substantially decreases average values vary from 174 to 37 2 ppm especially the lree la lu values decrease from 80 0 to 16 6 in addition the ore forming elements e g w sn mo in the fluorites also decrease significantly with time and the low 18oh2o values 4 30 to 3 90 and moderate d values 63 8 to 59 6 in the fluorites suggest that the late fluorite stage was contributed largely from meteoric water combined with previously reported fluid inclusion data in the ore field we propose that the w sn mineralization was related to fluid boiling and mixing the pb zn ore was formed from the changing of the redox environment from oxidizing to reducing and the fluorites were formed due to rapid cooling the formation of the w sn pb zn and fluorite ore forming zones belong to a single magmatic hydrothermal system but was controlled by the fault evolutionary processes from the early granite plutons intrusion to the large scale crustal extension in the xitian ore field

upper cenozoic bio magnetic stratigraphy of central asian mammalian localities abstract this research is focused on biostratigraphic and palaeomagnetic correlations of upper cenozoic mammalian localities of central asia in the territory of tadjikistan uzbekistan kyrgyzstan and southern kazakhstan the absence of the lithological markers and absolute dates emphasizes the true importance of using bio magnetic evidence for stratigraphy of terrestrial molasse late turolian villafranchian and middle pleistocene faunal assemblages are recorded in central asian localities providing a good basis for a broad interregional stratigraphic correlation

mantle derived and crustal he and ar in the ore forming fluids of the xihuashan granite associated tungsten ore deposit south china abstract the xihuashan tungsten ore deposit in the central nanling region south china is a vein type hydrothermal deposit associated with the late jurassic granitoids that were previously thought to be the products of crustal anatexis alone in this study we use helium he and argon ar isotopes of fluid inclusions entrapped in pyrite and arsenopyrite to determine the origin of the ore forming fluids the 3he 4he ratios of the crushed fluid inclusions vary from 0 15 to 1 16 ra with a mean of 0 72 ra ra the atmospheric 3he 4he ratio of 1 4 10 6 indicating the presence of mantle derived noble gasses in the fluids the amounts of the mantle derived noble gasses are estimated to be between 2 and 17 the 40ar 36ar ratios of the fluid inclusions vary from 306 to 1023 with an average of 440 these ratios are significantly higher than the average crustal value indicating the presence of air saturated water in the volatiles released from the mineral separates the results from this study indicate that the associated coeval granitoids which is believed to provide the ore forming fluids during magma evolution are not the products of pure crustal melts mantle derived volatiles and heat was also involved in the genesis of the host granite pluton

longevity of porphyry copper formation at quellaveco peru metal introduction at the late paleocene to early eocene quellaveco porphyry copper molybdenum deposit in southern peru spans several phases of quartz monzonite porphyry emplacement and is bracketed by a precursor granodiorite pluton and a late mineral porphyry body that postdates essentially all copper introduction together the u pb ages of zircons from these intrusive rocks show that 1 08 0 58 m y elapsed between the precursor pluton and initiation of stock emplacement the porphyry system was active intermittently for at least 3 25 m y 4 07 0 82 m y and at least three quarters of the copper inventory was deposited in a maximum of 3 12 m y 2 51 0 61 m y recent u pb zircon dating of several other major central andean porphyry copper deposits in combination with other isotopic techniques suggests that 2 5 to 4 m y life spans are commonplace the longevity of porphyry copper systems implied by these studies appears to reflect the protracted time gaps between the multiple intrusions that intermittently replenished porphyry stocks other precise isotopic methods re os 40 ar 39 ar typically document shorter life spans because it is more difficult if not impossible to date the full sequence of events involved in porphyry copper formation

timing of skarn deposit formation of the tonglushan ore district southeastern hubei province middle lower yangtze river valley metallogenic belt and its implications abstract the tonglushan ore district in the middle lower yangtze river valley metallogenic belt includes the tonglushan cu fe the jiguanzui au cu and the taohuazui au cu skarn deposits they are characterized by ne striking ore bodies and hosted at the contact of triassic carbonate rocks and late mesozoic granitoid deposits new sensitive high resolution ion microprobe shrimp and laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb molybdenite re os and phlogopite 40 ar 39 ar ages indicate that these skarn deposits formed between 140 3 1 1 and 137 3 2 4 ma these dates are identical to the zircon u pb ages for host quartz diorites ranging from 140 2 to 139 1 ma these results confirm that both skarn mineralization and related intrusions were initiated during the early cretaceous the high rhenium contents 261 4 1152 g g of molybdenites indicate that a metasomatic mantle fluid was involved in the ore forming process of these skarn ore systems this conclusion is consistent with previously published constraints from sulfur deuterium and oxygen isotope compositions and the geochemical signatures and sr nd isotopic data of the mineralization hosting intrusions geological and geochronological evidence demonstrates that there were two igneous events in the tonglushan ore district the first resulted in the emplacement of quartz diorite during the early cretaceous 140 2 to 139 1 ma and the second is characterized by the eruption of volcanic rocks during the mid early cretaceous 130 2 to 124 2 ma the former is spatially temporally and genetically associated with skarn gold bearing mineralization 140 3 1 1 to 137 3 2 4 ma the recognition of these two igneous events invalidates previous models that proposed continuous magmatism and associated mineral deposits in the middle lower yangtze river valley metallogenic belt

geochronological and petrogeochemical constraints on the skarn deposits in tongshanling ore district southern hunan province implications for jurassic cu and w metallogenic events in south china abstract southern hunan province south china is located in the central part of the qin hang metallogenic belt and is characterized by abundant cu pb zn and w sn polymetallic ore deposits the cu pb zn deposits are associated with jurassic granodiorite porphyries whereas the w sn deposits occur within jurassic granite porphyries here we present geochronologic and geochemical data for the tongshanling cu mo pb zn deposit and the weijia w deposit in the district of tongshanling southern hunan zircon u pb dating and molybdenite re os geochronology indicate that the emplacement of the tongshanling granodiorite porphyry and the associated cu mineralization occurred at 162 160 ma slightly earlier than the formation of the xianglinpu granite porphyry and associated w mineralization at 159 158 ma the tongshanling granodiorite is high k calc alkaline weakly peraluminous and weakly fractionated with zircon e hf t values of 15 1 to 5 6 in contrast the xianglinpu granite is alkaline peraluminous and highly fractionated with e hf t values of 9 5 to 0 9 our data indicate that the tongshanling granodiorite is relatively oxidized and was formed by the partial melting of paleoproterozoic crustal material with inputs of mafic magma which was derived from a subduction modified lithospheric mantle in contrast the xianglinpu granite porphyry is relatively reduced and was formed by direct interaction between the crust and asthenospheric mantle the difference in magma generation and tectonics is considered to have resulted in the different types of mineralization associated with these two intrusive bodies

mineral chemistry of the xiasai ag pb zn deposit in the central yidun terrane sw china insight into ni ag bi mineralization and formation conditions abstract sulfides and sulfosalts are major ore minerals for most of ag pb zn deposits and can be used to study enrichment and distribution of ore forming elements and formation conditions the xiasai ag pb zn deposit zn 0 141 mt 4 30 pb 0 132 mt 4 03 ag 1028 t 337 8 g t cu 10058 t 0 56 and sn 20000 t 0 75 is a hydrothermal vein type deposit in the central yindun terrane sw china it consists of proximal quartz cassiterite veins and distal ag pb zn sulfide veins to a cretaceous monzogranite three successive mineralization sub stages are recognized for ag pb zn veins i e arsenopyrite coarse grained pyrite py1 pyrrhotite sphalerite chalcopyrite fine grained pyrite py2 and silver minerals native bismuth galena nickel minerals such as breithauptite and ullmannite were identified as inclusions hosted within pyrrhotite using energy dispersive x ray spectroscopy eds and electron probe microscopy epm analysis and mapping trace amounts of invisible silver have been detected in chalcopyrite and galena whereas a significant amount of silver is incorporated in pyrargyrite freibergite miargyrite and electrum as intimate intergrowths with galena or inclusions within galena a high content of invisible bismuth is detected within galena 0 21 16 95 wt as well as numerous grains of native bismuth occur as inclusions in galena based on the bi concentrations determined and the modal composition a large sized bismuth deposit would be estimated with about 23 800 t of bi resource the presence of nickel minerals and native bismuth together with zn cd ratios 58 151 of sphalerite indicate that the ore forming materials are derived from the xiasai monzogranite based on mineral assemblages and chemical features for sulfides and sulfosalts the formation of ag pb zn ores was triggered by a decrease in temperature fs2 fo2 and sulfidation the early episode of arsenopyrite py1 pyrrhotite and nickel minerals formed at temperature of 320 470 c lower fs2 and decreasing sulfidation conditions from low alkaline fluids in contrast the late episode of silver minerals native bismuth and galena deposited at 160 270 c with a lower fs2 state and neutral or acidic ph however a slight increase of fs2 fo2 and sulfidation intermediate sulfidation occurred during precipitation of zn cu

genetic types mineralization styles and geodynamic settings of mesozoic tungsten deposits in south china abstract south china hosts the most abundant and largest tungsten w deposits in the world being a famous w metallogenic region located at the eastern part of the south china block which was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic these w deposits were mainly formed during the mesozoic the w mineralization is dominanted by greisen quartz vein skarn and porphyry types all of which are genetically related to the evolution of highly fractionated granitoids four episodes of w mineralization are recognized 1 late triassic 230 210 ma in the central and western parts of south china 2 middle jurassic ca 170 ma to early cretaceous ca 140 ma in the interior of south china with the mineralization being concentrated in southern jiangxi province between 165 and 150 ma 3 early cretaceous 136 120 ma with deposits across south china and 4 late cretaceous 100 80 ma mainly in the southwestern parts of south china these four periods of mineralization are closely related to the closure of paleo tethys and subduction of the paleo pacific plate in the late triassic these two events caused local extensional environments facilitating emplacement of the peraluminous granitoids and formation of the w deposits in the middle jurassic break off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the nanling region later anticlockwise rotation of the paleo pacific plate created widespread s type granitoids and associated middle jurassic to early cretaceous w mineralization in the interior of south china since 136 ma rollback of the subducting pacific plate resulted in weak w mineralization across south china finally a change of direction in the retreating plate from se to ese resulted in intensive mineralization of the southwestern part of south china

distal relationship of the taihexian pb zn au deposit to the dengfuxian magmatic hydrothermal system south china constraints from mineralogy fluid inclusion h o pb and in situ s isotopes abstract the taihexian pb zn au vein style deposit is located in the well preserved dengfuxian magmatic hydrothermal w sn ore field south china the deposit can be divided into three mineralization stages i pyrite arsenopyrite chalcopyrite gold tourmaline quartz stage ii pyrite arsenopyrite chalcopyrite sphalerite galena quartz stage and iii pyrite galena sphalerite quartz calcite fluorite stage liquid rich nacl aqueous inclusions vapor rich nacl aqueous inclusions co2 rich inclusions and three phase co2 h2o inclusions occur in quartz and calcite of the ore veins at taihexian the ore veins of the three stages formed at around 310 c 210 c and 170 c respectively precipitated from h2o nacl co2 ch4 fluids with salinities averaging around 5 wt nacl eq the ore forming mechanisms include fluid immiscibility a potential trigger for metal precipitation from hydrothermal fluids during stage i fluid mixing during stage ii and cooling during stage iii oxygen 18ofluid 1 5 6 9 and hydrogen dfluid 61 to 53 isotopes suggest that the ore forming fluids originated from a mixture of magmatic water with ground water and or meteoric water sulfur isotopes 34s 7 8 3 1 suggest a magmatic origin for sulfur in stages i and ii and then possibly mixing with sulfur from sedimentary rocks in stage iii lead isotopes 206pb 204pb 18 05 18 65 207pb 204pb 15 53 15 75 208pb 204pb 37 91 38 88 indicate that ore metals originated mainly from the upper crust with minor mantle contributions comparing arsenopyrite sulfur isotope and fluid inclusion geothermometers it is estimated that the ore formation pressure was about 58 120 mpa corresponding to a depth of approximately 2 2 4 5 km taihexian appears to form part of a regional magmatic hydrothermal system centered on the dengfuxian pluton

combined effects of atmospheric and seafloor iron fluxes to the glacial ocean changes in the ocean iron cycle could help explain the low atmospheric co2 during the last glacial maximum lgm previous modeling studies have mostly considered changes in aeolian iron fluxes although it is known that sedimentary and hydrothermal fluxes are important iron sources for today s ocean here we explore effects of preindustrial to lgm changes in atmospheric dust sedimentary and hydrothermal fluxes on the ocean s iron and carbon cycles in a global coupled biogeochemical circulation model considering variable atmospheric iron solubility decreases lgm surface soluble iron fluxes compared with assuming constant solubility this limits potential increases in productivity and export production due to surface iron fertilization lowering atmospheric co2 by only 4 ppm the effect is countered by a decrease in sedimentary flux due to lower sea level which increases co2 by 15 ppm assuming a 10 times higher iron dust solubility in the southern ocean combined with changes in sedimentary flux we obtain an atmospheric co2 reduction of 13 ppm the high uncertainty in the iron fluxes does not allow us to determine the net direction and magnitude of variations in atmospheric co2 due to changes in the iron cycle our model does not account for changes to iron binding ligand concentrations that could modify the results we conclude that when evaluating glacial interglacial changes in the ocean iron cycle not only surface but also seafloor fluxes must be taken into account