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

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

geological and geochronological constraints on the formation of the jurassic maozaishan sn deposit dayishan orefield south china abstract the dayishan orefield in the central nanling belt is one of the most important sn districts in south china within this district there are more than seven medium to large sn sn cu and pb zn sn deposits the mineralization is associated with altered granites and greisen quartz veins both of which occur in the inner part of the dayishan granite batholith cassiterite is the principal ore mineral accompanied by subordinate molybdenite cassiterite separates from altered and mineralized granite and greisen quartz veins have concordia ages of 156 5 2 8 ma mswd 3 1 and 158 0 1 8 ma mswd 1 4 respectively molybdenite separates from molybdenite quartz veins that crosscut the greisen alteration have a re os isochron age of 157 9 7 7 ma mswd 26 whereas zircon separates from the porphyry monzogranite have a u pb age of 156 3 1 2 ma these ages are identical within the analytical error and together with the field relationships provide tight constraints on the sn mineralization at around 156 ma rhenium contents of the molybdenite suggests that the ore forming materials were derived from a crustal source whereas s and pb isotopic data point to mixed sources we suggest that the maozaishan deposit was formed by intrusion of the related pluton and occurred in the late jurassic during a period of lithospheric thinning and crustal extension of the south china block

absolute timing of sulfide and gold mineralization a comparison of re os molybdenite and ar ar mica methods from the tintina gold belt alaska new re os molybdenite dates from two lode gold deposits of the tintina gold belt alaska provide direct timing constraints for sulfide and gold mineralization at fort knox the re os molybdenite date is identical to the u pb zircon age for the host intrusion supporting an intrusive related origin for the deposit however 40ar 39ar dates from hydrothermal and igneous mica are considerably younger at the pogo deposit re os molybdenite dates are also much older than 40ar 39ar dates from hydrothermal mica but dissimilar to the age of local granites these age relationships indicate that the re os molybdenite method records the timing of sulfide and gold mineralization whereas much younger 40ar 39ar dates are affected by post ore thermal events slow cooling and or systemic analytical effects the results of this study complement a growing body of evidence to indicate that the re os chronometer in molybdenite can be an accurate and robust tool for establishing timing relations in ore systems

40 ar 39 ar isotopic dating of tin mineralization in furong deposit of hunan province and its geological significance the newly discovered furong ore deposit located in the southern part of the qitianling pluton emplaced at 151 162 ma in southern hunan is a superlarge tin deposit it consists of bailashui anyuan taoxiwo sanmenkou and maziping heishanli ore districts and its ore veins occur in qitianling pluton and the inner or outer contact zone between the granite pluton and the late palaeozoic sedimentary rocks in this study ar ar isotope dating of muscovite hornblende and phlogopite was carried out in order to constrain the tin mineralization timing of the furong deposit the plateau ages of three phlogopite samples from the bailashui ore district are 150 6 1 0 ma 157 3 1 0 ma and 154 7 1 1 ma respectively and the plateau age of hydrothermal hornblende from the same mining district is 156 9 1 1 ma the plateau ages of two muscovite samples from the taoxiwo ore district are 159 9 0 5 ma and 154 8 0 6 ma respectively these age data are coincident with the intrusion time of the qitianling granite 151 162 ma and also in accordance with the ages of other nonferrous metal deposits such as the shizhuyuan w sn mo bi f deposit the xintianling w deposit the yaogangxian w deposit and the huangshaping pb zn polymetallic deposit in this area the large scale mineralization in southern hunan is probably ascribed to the mesozoic lithospheric extension in south china

assessment of coherency for bidirectional horizontal ground motions and its application for simulating records at multiple stations estimation of the coherency of ground motion records in two horizontal orthogonal directions at single or multiple stations is carried out using records from smart 1 array for several seismic events in taiwan empirical coherency function is suggested for the components of records in two horizontal orthogonal directions at single and multiple recording stations it was also found that the coherency for the records along the major and minor principal axes at a recording station is similar to that for two randomly oriented orthogonal directions the spatial coherency and the spatial correlation of the records are used to establish a procedure for simulating bidirectional horizontal ground motions at multiple stations considering that the stochastic point source method or the stochastic finite fault method can be used to define the reference fourier amplitude spectra for scenario events use of the proposed procedure to simulate records is illustrated for a scenario seismic event the adequacy of the simulated records in approximating the target spatial correlation and coherency is presented

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

a unique association of scheelite and magnetite in the tiemuli w fe skarn deposit implications for early cretaceous metallogenesis in the nanling region south china abstract the tiemuli scheelite magnetite deposit in the central part of the nanling region south china is genetically related to a porphyritic biotite granite pluton the w fe orebodies are hosted within upper cambrian calcareous sandstone or impure limestone in the external zones la icp ms u pb dating of zircons from the granite yielded a weighted mean age of 136 6 1 1 ma the main ore minerals are magnetite scheelite and arsenopyrite and the gangue minerals are clinopyroxene grossularite vesuvianite amphibole and mica three paragenetic stages of skarn formation have been recognized i a skarn stage ii a retrograde stage and iii a quartz sulphide calcite stage massive magnetite and scheelite orebodies associated with hydrous minerals formed during stage ii molybdenite grains separated from tiemuli skarns yielded re os model ages of 136 3 133 8 ma with a weighted mean age of 135 1 0 8 ma biotite associated with fine grained magnetite from the ores has a 40 ar 39 ar plateau age of 132 67 0 43 ma these three independent dating techniques show that the granitic magmatism and tungsten mineralization were coeval within error whereas the late stage alteration recorded by biotite could be ca 2 m y younger than the early stage the granite is classified as an a type body on the basis of its geochemistry and mineralogy zircon grains from the granite show negative ehf t values of 7 7 to 2 3 and molybdenite grains from the skarn ores contain low re contents of 0 93 to 2 97 ppm these data indicate that the magma and ore forming components at tiemuli were derived mainly from crustal materials although mafic xenoliths in the granites are consistent with some mantle contribution the tiemuli deposit was produced by crust mantle interaction in an extensional regime possibly caused by rollback of the subducting paleo pacific plate during early cretaceous the skarn scheelite and magnetite association formed by interaction between magmatic fluids and calcite bearing sandstone or impure limestone of the host strata

formation of the wulong gold deposit liaodong gold province ne china constraints from zircon u pb age sericite ar ar age and h o s he isotopes abstract the wulong deposit is the largest quartz vein type gold deposit in the eastern liaoning province of china the gold ore bodies are hosted by mesozoic biotite granites the mineralization occurs as veins with lenticular shapes laser ablation icp ms zircon u pb dating was used to date the biotite granite granite porphyry and fine grained diorites at the wulong deposit yielding ages of 155 4 0 9 ma 154 2 1 2 ma and 123 1 0 9 ma respectively a sericite sample from the gold ore yields a 40ar 39ar plateau age of 122 8 0 8 ma mswd 0 09 the calculated 18ow values for the quartz range from 4 8 to 8 6 and the dw values of fluid inclusion waters in quartz vary from 98 to 77 the h o isotope data indicates that ore forming fluids could be of a magmatic origin the 34s values of metallic sulfides range from 1 1 to 2 4 with an average of 1 8 suggesting that the sulfur is derived from a magmatic source the 3he 4he ratios of fluid inclusions in pyrite range from 0 36 to 0 65 ra with an average of 0 50 ra the mantle helium involved in the ore forming fluid ranges from 3 9 to 7 2 indicating a crustal fluid source the wulong gold deposit was formed at ca 120 ma and it has a genetic association with contemporaneous fine grained diorite the wulong deposit was formed during lithospheric thinning of the eastern north china craton during the early cretaceous

cassiterite u pb geochronology of the kekekaerde w sn deposit in the baiganhu ore field east kunlun orogen nw china timing and tectonic setting of mineralization abstract the baiganhu w sn ore field in the northwestern area of the east kunlun orogen nw china contains three economically important w sn deposits namely kekekaerde baiganhu and bashierxi timing of the w sn mineralization remains under debates due to lack of precise isotope dating directly conducted on ore minerals we herewith report la mc icp ms laser ablation multi collector inductively coupled plasma mass spectrometry and id tims isotope dilution thermal ionization mass spectrometry cassiterite u pb ages for the kekekaerde w sn deposit in the baiganhu w sn ore field the id tims cassiterite 206 pb 238 u results yield a weighted mean age of 416 1 ma 95 confidence mswd 0 8 and the la mc icp ms analytical data give a 206 pb 207 pb 238 u 207 pb isochron age of 426 13 ma 95 confidence mswd 0 1 these two ages are same within errors suggesting that the mineralization in the baiganhu w sn ore field occurred at ca 416 ma these new ages and understandings are consistent with the previously reported zircon u pb ages of 430 420 ma for the ore bearing granites in the ore field and with the 40 ar 39 ar plateau ages of ca 412 ma for the hydrothermal muscovite from ore bearing quartz veins and greinsenized granite it shows that the granite magmatism and its associated hydrothermal mineralization resulted from the caledonian orogeny that accommodated the closure of the proto tethys followed by the continental collision between the central kunlun northern kunlun terranes and the qaidam block

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

new precise zircon u pb and muscovite 40ar 39ar geochronology of the late cretaceous w sn mineralization in the shanhu orefield south china abstract the shanhu orefield located in the northeastern guangxi province is an important part of w sn polymetallic metallogeny in the nanling region the shanhu w sn deposit is spatially associated with the yantianling granite la icpms zircon u pb dating of the yantianling granite yields late cretaceous ages of 100 9 2 2 ma and 100 8 2 3 ma hydrothermal muscovite 40ar 39ar dating yields plateau ages of 102 7 1 7 ma and 100 8 0 7 ma this date coincides well with the la icpms zircon u pb age of the yantianling granite indicating a spatial temporal link between the w sn mineralization and the granitic magmatism in combination with regional geological data it is suggested that a late cretaceous mineralization event related to granitic magmatism occurred in the nanling region which might have resulted from regional lithospheric extension

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

genesis of the xianghualing sn pb zn deposit south china a multi method zircon study abstract the xianghualing sn pb zn deposit is situated near the center of the world class nanling w sn ore belt associated with the highly evolved laiziling granite of jurassic age previous studies focused mainly on geochemical and geochronological features of the mineralization related granite whereas research on the source evolution and geochronology of the ore forming fluids has been limited we carried out precise u pb dating trace element and hf isotopic analyses on magmatic and hydrothermally altered zircons from the skarn stage and sulfide stage ores in the xianghualing deposit zircon u pb dating results from the two ore forming stages show distinct geochronological populations the skarn stage ores contain mainly magmatic and hydrothermally altered zircons in three age clusters 150 ma 220 ma and 420 ma whereas the sulfide stage ores are characterized by abundant old detrital zircons ranging from 497 to 3409 ma with a peak at 800 1000 ma this pattern may indicate that magmatic hydrothermal events in the silurian and triassic were precursors to the main sn mineralization event in the jurassic when circulation of evolved fluids through older sedimentary rocks led to pb zn mineralization the jurassic zircons exhibit high trace element contents e g hf p y nb ta th u and low ti contents eu anomalies nb ta and th u ratios which imply that the laiziling magma experienced significant plagioclase biotite and muscovite fractional crystallization and that it interacted extensively with post emplacement f rich hydrothermal fluids the positive ce anomalies of these zircons ce ce 1 0 226 indicate that the magmatic hydrothermal fluids that led to the jurassic sn mineralization event were reducing the less negative ehf t values of triassic zircons 18 7 to 2 6 compared to the silurian zircons 14 6 to 2 3 suggest more limited interaction between the mantle and the magma source region the jurassic magmatic zircons in the skarns exhibit even more negative ehf t values 30 7 to 6 7 along with tdmc model ages ranging from 1627 to 3134 ma indicating that the jurassic magma was derived from partial melting of old continental crustal basement based on the combined study of zircons in the skarns and sulfide ores we propose a three stage ore genetic model for the xianghualing sn pb zn deposit

precise zircon u pb and molybdenite re os dating of the shuikoushan granodiorite related pb zn mineralization southern hunan south china abstract the shuikoushan ore district located in southern hunan province south china contains pb zn au mineralization hosted in the devonian to triassic strata and mesozoic granodiorite intrusions ore minerals are mainly pyrite sphalerite galena and minor molybdenite molybdenite usually intergrown with pyrite formed during pb zn hydrothermal mineralization in order to determine the precise age of pb zn mineralization and further understand the relationship between magma emplacement and hydrothermal mineralization in the ore district molybdenite re os dating and zircon sims u pb dating were undertaken the zircon u pb dating reveals that the granodiorite intrusion was emplaced at 158 8 1 8 ma mswd 0 40 re os isotopic age of seven molybdenite samples yields model ages ranging from 157 5 2 5 ma to 161 0 2 4 ma and gives a well defined 187re 187os isochron age of 157 8 1 4 ma 2 mswd 1 3 indicating the timing of pb zn mineralization in the shuikoushan ore district at about 158 ma this date coincides well with the zircon sims u pb age of the granodiorite revealing a genetic association between the pb zn mineralization and the granitic magmatism combined with geochronological data published for other pb zn cu deposits in southern hunan it can be concluded that the granodiorite related pb zn mineralization throughout southern hunan mainly occurred at 160 156 ma rather than 180 170 ma or 170 160 ma as considered previously the pb zn mineralization and major w sn mineralization in southern hunan are coeval and may be related to the same geological event

tracking magmatic and hydrothermal nb ta w sn fractionation using mineral textures and composition a case study from the late cretaceous jiepailing ore district in the nanling range in south china abstract the jiepailing mining district in the nanling range in south china is well known for its granite related sn be f mineralization recently drill holes have exposed an nb ta w sn mineralized granitic porphyry and topaz bearing granite greisen at depth which we have studied here using mineral columbite rutile wolframite cassiterite zircon and mica major and trace element compositional data mineral textures and zircon and columbite u pb geochronology our age data shows that the porphyry and the granite and their mineralization formed at 91 89 1 ma in the late cretaceous and thus subsequent to the main ore forming events of the region continuous mineral compositional trends indicate that the studied granitoids are related by progressive fractionation we propose that 1 subhedral euhedral low ta columbite crystallized from melt 2 euhedral subhedral rutile and wolframite and subhedral and subhedral cassiterite up to 30 m in size formed at the magmatic hydrothermal transition of the system and 3 high ta columbite and subhedral cassiterite up to 10 m in size formed from subsolidus hydrothermal fluids in combination with the nb ta w and sn compositions of zircon and mica their textures and compositional variation allow us to track the magmatic to hydrothermal rare metal fractionation concentration mobilization and deposition of the system in detail despite our limited access to it through only two exploration drill cores using the nb ta w and sn concentrations in zircon refractory early crystallized and in micas late equilibrated respectively was particularly useful for tracing the partial loss of sn and w ore components from the intrusion and to constrain the information which is crucial for any rigorous ore exploration

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

the origin of the world class tin polymetallic deposits in the gejiu district sw china constraints from metal zoning characteristics and 40ar 39ar geochronology the gejiu tin polymetallic deposits in the western cathaysia block of south china comprise the world s largest primary tin district with a total resource of approximately 300 million metric ton ores at an average grade of 1 wt percent sn tin polymetallic mineralization occurs in five deposits and has four ore types i e greisen skarn stratabound cassiterite sulfide mostly oxidized and vein type ore in each deposit the orebodies typically occur in an extensive hydrothermal system centered on a shallow late cretaceous granitoid cupola metal zoning is well developed both vertically and horizontally over the entire district from w be bi mo sn ores inside granite intrusions to sn cu dominated ores at intrusion margins and farther out to pb zn deposits in the surrounding host carbonate this zoning pattern is similar to that of other hydrothermal deposits in other parts of the world indicating a close genetic relationship between magmatism and mineralization in this paper we dated thirteen mica samples from all types of mineralization and from the five deposits in the gejiu district the ages range from 77 4 0 6 ma to 95 3 0 7 ma and are similar to the existing zircon u pb age of the granitic intrusions 77 4 2 5 85 8 0 6 indicating a genetic relationship between the mineralization and the intrusions geological characteristics metal zoning patterns and new geochronological data all indicate that the tin polymetallic ores in the gejiu district are hydrothermal in origin and are genetically related to the nearby granitic intrusions it is unlikely that the deposits are syngenetic as has been proposed in recent years

cretaceous granitic magmatism and mineralization in the shanhu w sn ore deposit in the nanling range in south china abstract abundant jurassic cretaceous w sn ore deposits are distributed in the nanling range in south china however the exact mineralization ages relationships between mineralization and granitic rocks and tectonic settings of these deposits remain controversial as a giant quartz vein type w sn deposit hosted in devonian sedimentary strata the shanhu orebodies are featured by located about 4 km far away from the yantianling muscovite granite zircon u pb dating of the yantianling granite yielded ages of 101 0 1 5 ma and 100 4 1 1 ma consistent with cassiterite u pb ages of quartz vein ores 100 2 1 0 ma and 100 5 1 1 ma indicating a close genetic relationship between the granitic magmatism and quartz vein type w sn mineralization the yantianling muscovite granite is characterized by highly silicious 72 01 74 62 wt high alkali na2o k2o 5 32 7 89 wt and strongly peraluminous a cnk 1 11 1 81 the granite is enriched in rb ta nd and u and depleted in sr ti and p it displays right declining chondrite normalized ree patterns with strongly negative eu anomalies and has low nb ta and zr hf ratios indicating that the granite experienced strong magmatic differentiation the yantianling granite has low whole rock end t values 9 5 to 9 3 zircon ehf t values 12 7 to 7 8 and paleoproterozoic model ages the granite belongs to s type and was derived from partial melting of meta sedimentary crust the low ce4 ce3 ratios averaging 47 of zircon from the yantianling granite indicated low oxygen fugacity similar to other w bearing granites in south china this study indicated that cretaceous granitic magmatism in the nanling range also has strong w sn mineralization potential combined with previous studies on coeval magmatic rocks and tectonic activities we propose that the yantianling s type granite and associated w sn mineralization in the nanling range were formed during the regional lithospheric extensional environment

geological characteristics and re_os dating of molybdenites in hehuaping tin polymetallic deposit southern hunan province the hehuaping tin polymetallic deposit a large tin ore field newly discovered in southern hunan consists of skarn and cassiterite sulfide ores at present the controlled reserves amount to about 110 700 tons of tin 10 000 tons of bismuth 50 000 tons of lead and 10 000 tons of zinc with the advance of the exploration work four ore bodies have been explored which are located in the southeast portion of wangxianling indosinian gra nite pluton and hosted in granite granite porphyry and devonian limestone and sandstone respectively re os dating of molybdenites yields model ages between 223 3 2 9 and 225 2 2 7 ma and an isochron age of 224 0 1 9 ma for the skarn ore related to wangxianling granite indicating that w sn mineralization in southern hunan also took place in indosinian period the zircon shrimp u pb dating of the late granite porphyry is 142 3 ma the granite porphyry has been partly mineralized and altered and contains tin ore bodies all this implies that there existed late mineralization of yanshanian period in hehuaping area the early mineralization is supposed to correspond to underplating of the basic magma

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

mesozoic magmatism and granitic dome in the wugongshan massif jiangxi province and their genetical relationship to the tectonic events in southeast china abstract in se china a mesozoic granitic dome coeval to extensional tectonics is exposed in the wugongshan massif its center is occupied by mesozoic granitoids and granitic gneisses and the e w trending late paleozoic mesozoic pingxiang and anfu basins are located along its northern and southern sides respectively in this paper the petrological geochemical major incompatible and rare earth elements and isotopic characteristics of the granitoids and granitic gneisses of this dome allow us to constrain their geodynamic evolution the wugongshan mesozoic k feldspar enriched granitoids consist of six granitic bodies and lie within a paleozoic metamorphic basement the caledonian shanzhuang granodiorite containing some dioritic enclaves occurs in the study area and is a calc alkaline type granodiorite characterised by lower sio2 and composed of andesine biotite quartz hornblende magnetite and sphene the mesozoic granitoids either indosinian plutons or yanshanian bodies show a geochemical affinity of peraluminous s type granite having higher sio2 k2o contents al k na 2ca enriched in rb th and depleted in eu they also exhibit lree enriched patterns and marked negative eu anomalies the yanshanian plutons also contain characteristic minerals such as sillimanite garnet and monazite the wugongshan mesozoic granitoids have higher isr values 0 70981 0 72885 and lower end t 10 6 to 14 7 an average of 12 6 than those of the early paleozoic shanzhuang granodiorite the mesozoic granitoids were likely derived from ancient sedimentary rocks by partial melting the wugongshan mesozoic granitoids contain three petrological zones that is an early cretaceous massive granitic zone in the core zone i a foliated granitic zone zone ii and a triassic granitic gneissic zone in the outer rim zone iii the petrological and geochemical features of massive granitoids zone i are similar to those of foliated granites zone ii and of granitic gneisses zone iii in this mesozoic dome moreover geometric and kinematic features within the ductile parts units 2 and 3 are also similar to those within the brittle part unit 1 of the dome all these features show that the geologic evolution of the wugongshan doming is a continuous process lasting from triassic to early cretaceous time published 40ar 39ar and k ar ages in the wugongshan mesozoic granitic rocks fall into two major age fields corresponding to two geodynamic events of intracontinental deformation and magmatic activity the first tectonothermal event dated at 226 259 ma on the granitic gneisses in the outer rim of dome can be linked to indosinian collision between the south china plate and the north china plate during triassic time the second event took place during the early yanshanian dated at 180 120 ma on the granites of the core of dome and are responsible for final doming of the wugongshan plutons this event may be related to a westward subduction of the paleo pacific oceanic plate under the se china continent during late jurassic early cretaceous time

some problems concerning relationship between mesozoic cenozoic lithospheric extension and uranium metallogenesis in south china previous studies have shown that there existed large scale lithospheric extension events during the cretaceous tertiary period in south china and that large scale uranium mineralization occurred at the same time in this area which resulted in the formation of many important uranium deposits such as granite hosted volcanics hosted and carbonaceous siliceous pelitic sedimentary rock hosted ones this paper reviews previous researches on lithospheric extension and uranium metallogenesis in south china since mesozoic and preliminarily discusses their temporal and spatial associations in order to precisely reveal the relationship between lithospheric extension and uranium metallogenesis it is suggested that at least two fundamental problems should be solved the first is the accurate episodes of extension and uranium mineralization and the second is the mechanism governing the control of the tectonic regime over the formation of the uranium deposits to probe into these problems it is necessary to accurately date the uranium deposits and the mafic dikes intruded during the mesozoic extension and to determine the role and origin of gaseous components such as co2 in ore forming fluids

eastern asia and the western pacific timing and spatial distribution of rifting in china abstract a compilation of recognized rifts in china indicates that five distinct episodes of rifting have occurred these episodes occurred at approximately 2 3 ga 1 85 1 7 ga 1 0 0 7 ga 550 190 ma and 175 ma to present the timing and location of rifting has largely been a function of tectonic activity along the margins of the various chinese paleocontinents some of the oldest rocks in china are found in the sino korean and tarim cratons and most of the identified precambrian rifts are found within or on the margins of these cratons these cratons are viewed as the continental nucleus of china and fold belts and microcontinents have been accreted to this nucleus through time much of the locus of rifting has migrated away from this nucleus as has the location of the continental margin especially in the paleozoic beginning in the middle mesozoic rifting commenced along the entire eastern margin of china extension occurred concomitantly with subduction in a backarc setting this is the dominant cenozoic extensional regime in china and is still active today to date few cenozoic rifts have been found in western china where most tectonism is probably a consequence of the collision between india and china but it seems likely that more rifts will be discovered in this area as it becomes better studied

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

the passa tres lode gold deposit parana state brazil an example of structurally controlled mineralisation formed during magmatic hydrothermal transition and hosted within granite abstract the passa tres granite is a nne ssw elongated shape intrusion located in the parana state southern brazil this intrusion was emplaced within metapelites of the mesoproterozoic votuverava group which are part of the n040 e trending lancinha shear zone gold mineralisation within the passa tres granite is held by meter scale quartz veins forming orebodies with variable massive banded sheared and or brecciated internal textures structural data indicate the existence of two orthogonal directions of structures n s and e w dipping 60 75 w and 45 70 s respectively mineralised veins contain in addition to the quartz of the gangue and in chronological order fluorite pyrite chalcopyrite gold aikinite molybdenite muscovite carbonate and baryte gold occurs as native grains within fractures that affect pyrite commonly associated with chalcopyrite and aikinite quartz veins are sometimes bordered by aplitic dykes additionally some of the veins exhibit a thin margin of k feldspar minerals that could represent the early stage of vein formation these observations the presence of unidirectional solidification textures ust along with abundant expression of pegmatite rich pockets within granite that crops out close to the surface allow the reconstruction of the granite architecture in terms of late magmatic evolution magmatic hydrothermal transition and position of the cupola n s and e w systems are interpreted to be contemporaneous and conjugate normal displacements are predominant and main mineralised veins are essentially located within extensional pull apart structures the structural model suggests that the normal faults were initiated along former low angle planes associated with aplite and or early quartz veins that subsequently controlled the opening of the pull apart structures that represent the economic orebodies zircon from the granite and muscovite grains from mineralised veins were dated by u pb and ar ar methods respectively zircons from the main facies medium grained gem and microgranite gef provided undistinguishable ages which were pooled to give an age of 611 9 3 6 ma a less abundant leucocratic facies white granite geb yielded a significantly younger age of 592 8 7 1 ma muscovites from quartz veins gave ar ar ages of 612 9 2 to 608 8 2 ma transitional vein with a k feldspar border 611 7 2 to 608 8 2 ma mineralised veins and 608 4 2 ma barren quartz vein thus the passa tres granite and its gold mineralisation appear to represent a unique example of an intrusion related gold system in which the mineralisation concentrates in the core of the magmatic intrusion in the form of meter scale veins strongly controlled by tectonics

three dimensional variations in extensional fault shape and basin form the cache valley basin eastern basin and range province united states seismic reflection profiles drill hole data and geologic maps delimit the form of normal faults and tertiary sedimentary rocks in the southern half of the cache valley basin in northern utah dips of faults and sedimentary rocks were estimated from time migrated reflection profiles by using the stacking velocities for the data at the southern end of the basin the east cache fault zone is listric it shows 50 w dips near the surface and 20 w dips at depth the fault zone has been the site of 5 6 km of net dip slip tertiary rocks dip 18 e 25 e and exhibit a rollover geometry above the fault zone no faults are interpreted on the western side of the basin in the central part of the basin in utah the east cache fault is a single fault that dips at least 45 w near the surface and is the site of 4 5 6 4 km of net dip slip here the basin is bounded to the west by the west cache fault which is the site of at least 1 km of net slip that increases northward to 2 km of net slip slip on the east cache fault resulted in planar east dipping older tertiary rocks near the bottom of the basin younger tertiary strata with southwest west and northwest dips reflect complex tilting due to slip on the west and east cache faults anticlines in the tertiary basin fill deposits are present in the central part of the basin and may reflect changes in normal fault geometry at depth northward dip slip on the east cache fault zone decreases to 2 5 km the basin is broad shallow and filled with nearly flat lying tertiary rocks this area near the north south midpoint of the basin is bounded by the west and east cache faults but slip on the west cache fault appears to diminish northward a north trending reflection profile tied to both drill hole data and the east trending seismic profiles indicates that the basin is deeper in the southern end the along strike changes in fault geometry the amount of fault slip the subsurface form of the basin filling sedimentary rocks and the form of the basin indicate a complex history of faulting and deposition during its formation this study and other recent ones from the basin and range province indicate that such complexities may be typical of many tertiary basins in the region

ore genesis and geodynamic setting of the lianhuashan porphyry tungsten deposit eastern guangdong province se china constraints from muscovite 40 ar 39 ar and zircon u pb dating and hf isotopes the lianhuashan deposit has long been regarded as a typical tungsten porphyry deposit located in the eastern guangdong province in the southeastern coastal metallogenic belt scmb la mc icp ms zircon u pb dating of the quartz porphyry yielded a weighted mean 206pb 238u age of 137 3 2 0 ma which is interpreted as the emplacement age of the quartz porphyry hydrothermal muscovite yielded a plateau 40ar 39ar age of 133 2 0 9 ma which is consistent with the zircon u pb age suggesting that the tungsten mineralization is genetically related to the quartz porphyry combined with previous studies we suggest that there is a 145 135 ma episode linking the granitic magmas with w sn ore systems in the scmb zircon ehf t values of the quartz porphyry are in range of 3 8 to 0 9 and the two stage hf model ages tdm2 are 1 1 1 4 ga which is younger than the basement rocks in the cathaysia block 1 8 2 2 ga signifying that the quartz porphyry was predominantly derived from melting of mesoproterozoic crust containing variable amounts of mantle components in combination with the newly recognized coeval alkaline bimodal magmatism and a type granites in eastern guangdong we suggest that the 145 135 ma w sn metallogenic event of the scmb is related to a geodynamic setting of large scale lithospheric extension and thinning which can be ascribed to melting of the crust caused by mantle upwelling triggered by the oblique subduction of the izanagi plate

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

rb sr isochron age of tiantang cu pb zn polymetallic deposit in guangdong province and its geological significance the ages of the tiantang cu pb zn polymetallic deposit were determined by the rb sr isochron method through dating samples of sphalerite and three groups of intergrown mineral assemblage pyrite and galena the selected samples included eight pieces of sphalerite three pieces of galena and one piece of pyrite in contrast with sphalerite age of 98 1 1 6 ma and sphalerite galena pyrite assemblage age of 99 2 ma the authors also obtained sphalerite galena pyrite assemblage age of 98 2 1 3 ma sphalerite pyrite age of 97 87 0 96 ma and galena pyrite assemblage age of 98 6 4 2 ma by the same means these data convince the authors that the metallogenic epoch is about 98 ma and that the late cretaceous is the main time for the formation of the tiantang cu pb zn polymetallic deposit the ore forming process was probably related to the fact that china s mainland including south china plate was in a continuous stretching phase caused by the change of the movement direction of the pacific plate after 135 ma the 87sr 86sr i of sulfides is equal to 0 7117 and it is lower than that of the terrigenous silicates 0 720 and higher than that of the mantle 0 707 in combination with s and pb isotope data avialable the authors consider that the ore forming material of the ore bodies in the tiantang cu pb zn polymetallic deposit was derived from the crust mantle mixture it is thus held that direct dating of the ages of metal minerals by using rb sr isochron method for single minerals and mineral assemblages could serve as a routine chronological method and that the means is of importance for indicating and understanding metallogenic background of the ore deposit

sulfides associated with podiform bodies of chromite at tsangli eretria greece small bodies of pyrrhotite chalcopyrite minor pentlandite and magnetite occur at the peripheries of podiform bodies of chromite in ultramafic ophiolitic rocks at tsangli eretria central greece banding of magnetite and sulfide within the bodies is reminiscent of magmatic banding a magmatic origin has been proposed for similar sulfide masses in the troodos ophiolite panayiotou 1980 the compositions of the host rocks chromite and of the sulfides have been investigated on average the sulfide mineralization recalculated to metal content in 100 sulfide contains 0 55 ni 5 15 cu 0 29 co 9 ppb pd 179 ppb pt 16 ppb rh 112 ppb ru 31 ppb ir 58 ppb os and 212 ppb au these metal contents particularly the high cu cu ni ratio of 0 78 and the pt pd pt ratio of 0 95 are inconsistent with the sulfides having reached equilibrium with their ni rich host rocks at magmatic temperatures and accordingly it is concluded that they are not of magmatic origin the average 34s value of the sulfide bodies is 2 while that of a sample of pyrite from country rock schist is 15 6 these values are inconclusive as to the origin of the sulfur it is suggested that the sulfides have been precipitated by hydrothermal fluids possibly those responsible for the serpentinization of the host rocks the source of the metals may have been the host rocks themselves

mineral chemistry trace elements and sr nd hf isotope geochemistry and petrogenesis of cailing and furong granites and mafic enclaves from the qitianling batholith in the shi hang zone south china abstract the shi hang zone is an important ne trending mesozoic magmatic belt composed of granites with relative high end t values and young tdm model ages in south china however the petrogenesis and the tectonic environment for the shi hang zone magmatic rocks remain controversial we report here mineral chemistry geochemical and sr nd hf isotopic data for the cailing and furong granites and mafic microgranular enclaves mmes from the qitianling granite batholith in southern hunan province south china the qitianling granite batholith is a multi staged composite pluton with three phases cailing furong and huangtangling according to their ages and petrography the cailing 163 160 ma and furong 157 153 ma phases are mainly composed of porphyritic amphibole biotite monzogranite and they share similar geochemical and isotopic characteristics both of them show similar sio2 contents from 66 50 to 70 28 and metaluminous a cnk values of 0 80 to 0 98 the granites are characterized by high contents of large ion lithosphile elements lile such as rb th u pb high field strength elements hfse such as nb ta zr hf and zr nb ce y contents 350 ppm and high 10 000 ga al ratios 2 6 chondrite normalized ree patterns show relative enrichment of light rare earth elements lrees and significant negative eu anomalies mineralogical and geochemical features suggest that the cailing and furong granites are a type which can be further classified as a2 subtype they have relatively lower 87sr 86sr i ratios 0 7091 0 7132 higher end t values 5 5 to 7 6 and younger nd isotopic model ages 1 48 1 56 ga than those common s type granites in south china zircon ehf t values vary from 8 1 to 3 7 the mmes in the cailing phase show similar trace element and sr nd isotopic characteristics with the host granites but zircons from the mmes show different ehf t values 6 4 2 6 with those from the host granites 8 1 to 3 7 this indicates that the mmes and host granites were crystallized from different sources of magmas providing direct evidence for mafic felsic magma mixing processes the isotope data indicate that the cailing and furong granites from the qitianling batholith were derived from a hybrid magma consisting of about 80 felsic magma derived from old crust and about 20 mantle derived mafic magma the strong magma mixing at about 160 155 ma caused by intra arc rifting or back arc extension related to subduction of the paleo pacific plate is favored to explain the petrogenesis of the cailing and furong granites as well as the shi hang zone

genesis of the shangjinshan w mo polymetallic deposit in the eastern jiangnan tungsten belt evidences from geochemistry geochronology and zircon hf isotope analyses abstract the newly discovered shangjinshan w mo polymetallic deposit located at the southern anhui southeast china is a large scale skarn type tungsten polymetallic deposit according to mineral assemblages ore textures structures and superposition relationships of the mineralization three ore types have been recognized veinlet disseminated skarn the primary type quartz vein type and porphyry type the mineralized event of this deposit could be divided into four stages i the prograde skarn stage ii retrograde skarn stage iii quartz sulfide vein stage and iv quartz calcite vein stage the intrusion in the tungsten rich district of the shangjinshan is mainly composed of the granodiorite with zircon u pb ages of 138 4 1 2 ma to 136 7 1 3 ma meanwhile re os isotopic dating of five molybdenite samples yields an isochron age of 141 9 3 1 ma and a weighted average age of 139 3 1 7 ma respectively the ore forming ages are consistent with the rock forming ages within errors indicating that the w mo mineralization is genetically related to the shangjinshan granodiorite the granodiorite is i type granites characterized by metaluminous to slightly peraluminous and high k cal alkaline compositions they are also enriched in large ion lithophile elements liles and light rare earth elements lrees and depleted in high field strength elements hfses and heavy rare earth element hrees with obviously negative eu anomalies eu eu 0 50 0 84 the zircon ehf t values and two stage hf model ages tdm2 fall into the range 6 18 to 2 04 and 1 5 1 3 ga respectively the relatively low rhenium contents in molybdenite and high radioactive pb isotopes of the pyrites from stage ii indicate that the ore forming material was derived from shangjinshan granitic magmatism together with previously published data we propose that the w related granitoids in the jnb were likely generated by partial melting of the shangxi group with some additional mantle materials the granitic magmatism was caused by the asthenosphere upwelling triggered by the roll back of subduced paleo pacific plate during late jurassic to early cretaceous these granitic stocks predominately contributed to the production of skarn alteration and mineralization resulting in the giant tungsten polymetallic district in the jiangnan tungsten belt

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

jurassic magmatism related pb zn w mo polymetallic mineralization in the central nanling range south china geochronologic geochemical and isotopic evidence from the huangshaping deposit abstract the nanling range in south china is characterized by extensive mesozoic magmatism and coeval nonferrous and rare metal mineralization huangshaping is a world class pb zn w mo polymetallic skarn deposit in the central nanling range magmatic rocks occurring in this ore district include quartz porphyry granite porphyry granophyre dacite porphyry and aplite with only the first three granitoids genetically associated with polymetallic mineralization most of the orebodies are constrained within the contact zones as skarn and veins between these granitic stocks and the carbonate wall rocks since the age of the quartz porphyry is still controversial and studies of the dacite porphyry and aplite are absent we focus on these magmatic rocks first la icp ms zircon u pb dating suggests that the crystallization ages of the quartz porphyry dacite porphyry and aplite are 154 3 1 9 ma 158 1 0 8 ma and 148 4 3 4 ma respectively combined with previously published age data we infer the evolutionary sequence of magmatic rocks should be dacite porphyry quartz porphyry granite porphyry granophyre aplite the quartz porphyry dacite porphyry and aplite yield high contents of high field strength elements zr nb ce y 255 440 ppm high ratios of 10 000 ga al 2 6 3 2 and prominent depletions in ba sr eu p and ti indicating their crustal affinities to a type granites they have negative end t values 9 4 to 7 0 and high initial pb isotopic ratios 206pb 204pbi 18 307 18 644 207pb 204pbi 15 689 15 742 208pb 204pbi 38 589 38 986 suggesting that they were probably derived by partial melting of ancient granulitic crustal materials the sulfide minerals exhibit a wide range of 34sv cdt values from 22 6 to 24 2 with 206pb 204pb of 17 669 19 708 207pb 204pb of 15 492 15 714 and 208pb 204pb of 37 880 39 789 indicating that sulfur lead and other associated metals were derived from a mixture of magmatic components and the carboniferous wall rocks fluid inclusions in pyrrhotite sphalerite and marmatite samples have 3he 4he ratios of 0 12 to 1 53 ra with calculated mantle helium proportions of 1 3 to 18 9 indicating a predominantly crustal origin for the ore fluids with minor inputs from the mantle the huangshaping deposit is a typical example of the genetic relationship both spatially and temporally between jurassic magmatism and polymetallic metallogeny in the nanling range

doming in the southern foreland of the dabieshan yangtse block china in china the foreland of the dabieshan is characterized by e w trending domes and basins from south to north the wugongshan jiulingshan lushan and dabieshan domes consist of proterozoic metamorphics unconformably covered by late proterozoic to triassic sediments ductile and brittle extensional structures are described along the margins of the metamorphic domes along the n s striking lineation kinematic indicators show divergent top to the north and south shear in the north and south flanks of the domes respectively the superposition of proterozoic phyllite over permian triassic carbonates is reinterpreted as extensional allochthons formed by tilting shearing and sliding on the layers plate convergence is responsible for continental subduction in the dabieshan and deep seated thrusting in the yangtse plate as compression continued the thrust contacts were folded and several antiformal stacks developed domal uplift induced the formation of gravity driven extensional structures

episodic nb ta mineralisation in south china constraints from in situ la icp ms columbite tantalite u pb dating abstract south china hosts many nb ta deposits that show evidence for episodic mineralization which were generated during the emplacement of composite granites to constrain the spatio temporal distribution of nb ta mineralisation in the region and to identify future targets for mineral exploration we used in situ laser ablation inductively coupled plasma mass spectroscopy to date 23 columbite tantalite group mineral cgm samples from 14 nb ta deposits our cgm u pb data supplemented by previous results reveal five distinct nb ta mineralisation events in south china as follows 1 late silurian middle devonian ca 424 391 ma e g the xigang and nanping deposits in eastern jiangxi and western fujian provinces 2 triassic ca 248 204 ma e g the houxi cunxin dongtounan shenkeng limu and gaoling deposits in western guangdong province and northeastern guangxi zhuang autonomous region 3 late jurassic ca 160 150 ma e g the gedongping yichun laiziling jianfengling and jinzhulong deposits in guangxi jiangxi and hunan provinces 4 early cretaceous ca 130 ma e g the huangshan and songshugang deposits in northeastern jiangxi province and 5 late cretaceous ca 90 ma e g the jiepailing deposit located along the boundary between hunan and jiangxi provinces we show that nb ta mineralisation in south china was controlled by multiple tectono magmatic events our cgm samples yielded caledonian ca 424 391 ma early indosinian ca 248 ma and late yanshanian ca 130 ma ages indicating that nb ta mineralisation was abundant during these times and should form the focus for future studies of mineralisation in the region early triassic granite in the guangning nb ta metallogenic district in western guangdong province indosinian and early yanshannian granites in the miao ershan yuechengling batholith in northeastern guangxi and the late cretaceous lingshan batholith in northern jiangxi province are identified as targets for future nb ta exploration

zircon geochronology and geochemistry of the xianghualing a type granitic rocks insights into multi stage sn polymetallic mineralization in south china abstract highly evolved sn polymetallic mineralization related granites are intensively developed in the nanling range of south china in this study two types of granitic rocks albite granite and greisenized granite from the laiziling pluton in the xianghualing area were studied to elucidate magma evolution and the genesis of mineralization the a type xianghualing granitic rocks are characterized by high sio2 69 16 85 04 rb 759 2110 ppm ta 17 2 50 8 ppm nd 2 8 82 4 ppm and 87sr 86sr 0 907275 4 181262 and low mgo 0 01 0 98 tio2 0 01 0 03 sr 1 4 70 2 ppm ba 1 4 132 5 ppm eu 0 03 0 21 ppm and 143nd 144nd 0 512283 0 512326 the whole rock end t values range from 6 3 to 6 0 with t2dm ages of 1426 1454 ma the zircon ehf t values mostly range from 10 to 5 with dominant tdmc values of 1400 1800 ma this suggests that the xianghualing granitic rocks were derived from partial melting of mesoproterozoic basement rocks in the cathaysian block in a lithospheric extension setting zircon u pb dating yielded five age clusters proterozoic 900 ma n 9 silurian 430 ma n 4 triassic 220 ma n 16 jurassic 150 ma n 62 and cretaceous 80 ma n 28 zircon internal textures trace element contents and hf isotopic compositions indicate that they formed from a range of sources including residual zircons from the magma source region detrital zircons from local sediments zircons captured from pre existing magmatic rocks with obvious mantle signatures magmatic and fluid altered zircons and late stage hydrothermal zircons this suggests significant fractional crystallization weak wall rock assimilation contamination and intense fluid differentiation metasomatism during the genesis of the xianghualing granitic rocks m type ree tetrad effects are seen not only in bulk rock compositions but also in individual zircon grains indicating that highly fractionated and reduced f rich fluids played an important role in the formation of sn polymetallic mineralization guided by the major mesozoic w sn ore forming events occurring in the cathaysian block of south china a multi stage genetic model is proposed for the xianghualing granitic minerogenic system initial enrichment of w sn in the triassic 220 ma dominant sn polymetallic metal precipitation in the jurassic 150 ma and superimposed mineralization in the cretaceous 80 ma

genetic relationship between silver lead zinc mineralization in the wutong deposit guangxi province and mesozoic granitic magmatism in the nanling belt southeast china more than 50 of the world s total reserves of tungsten are in china and most tungsten deposits are located in the nanling range in southeast china this study explores the potential genetic relationship between tungsten tin w sn mineralization and shallower ag pb zn deposits in the nanling range based on data from the wutong deposit guangxi province the lead oxygen carbon sulfur and strontium isotopic compositions of minerals at wutong indicate that a single crustal derived fluid was responsible for mineralization wutong likely formed at relatively low temperatures 200 300 c and low pressures as indicated by the similarity between homogenization temperatures of fluid inclusions and those estimated from s isotopic compositions of minerals the hubnerite age 92 3 104 4 ma indicates that the wutong mineralization is likely related to nearby late yanshanian cretaceous s type granites derived from proterozoic crust this mineralization event coincides with the last w sn mineralization event and the cretaceous peak of mineralization in the nanling range

isotopic and paleomagnetic constraints on the mesozoic tectonic evolution of south china in order to better constrain the paleogeographic evolution of south china we measured sm nd and rb sr isotopic compositions for 23 mesozoic granites that crop out throughout the area tightly grouped neodymium depleted mantle model ages 1 4 0 3 ga suggest the region is underlain by relatively homogeneous proterozoic crust and fail to define crustal provinces neither the isotopic nor geologic data suggest that a mesozoic suture exists however granites possessing anomalously high sm 8 ppm and nd 45 ppm concentrations relatively high initial epsilon neodymium 4 to 8 and high but variable initial 87sr 86sr 0 759 to 0 713 form a northeast trending zone that coincides with two prominent mesozoic basins southeast of the zone lie the majority of mesozoic intrusives and upper triassic to lower cretaceous extensional basins found in south china mesozoic paleomagnetic poles are well clustered northwest of the zone pre cretaceous poles southeast of it are discordant with respect to those from the northwest the only recognized tectonostratigraphic terrane in south china lies southeast of the zone the terrane is bordered by a northeast trending sinistral fault that was active in the mesozoic other faults in south china have similar attitudes ages and sense of shear together the observations suggest that the mesozoic tectonic regime in south china consisted of strike slip activity plus concomitant rifting as terranes or fragments of similar crust were transported north along sinistral faults the zone defined by the granites enriched in nd and sm demarcates displaced terranes to the southeast from relatively stable land to the northwest

extensional tectonics within a subduction type orogen the case study of the wugongshan dome jiangxi province southeastern china abstract in southeastern china the wugongshan massif consists of metamorphic rocks and granites generally considered as basement rocks formed during an early paleozoic orogeny our structural and radiometric reappraisal of this massif shows that it results from a mesozoic doming in the metamorphic rocks the foliation defines an e w elliptical shape and bears a n s stretching lineation the axial zone of the dome is occupied by oriented plutons the outer part of the dome consists of devonian quartzite carboniferous permian limestone and triassic jurassic sandstone ductile deformation observed in the permian carbonates and older units develops contrasting kinematics the northern and southern flanks present top to the north and top to the south motions respectively the same divergent pattern of motion is recorded from brittle structures up to the jurassic sandstone the late cretaceous red beds are undeformed in the axial zone coaxial flow indicated by symmetric pressure shadows and quartz fabrics predominates along the n and s flanks of the dome post folial recumbent folds are symmetrically overturned to the n and s respectively but at the two extremities of the dome the fold axes are parallel to the stretching lineation 40 ar 39 ar ages of biotite and muscovite from mylonite and granite suggest a late triassic age for the ductile deformation and an early cretaceous age for the final doming the wugongshan dome is similar to a metamorphic core complex formed in an extensional tectonic regime a model which emphasizes plutonism is discussed from permian to early cretaceous southeastern china was a subduction type orogen the crust of which was thickened by accretion of mantle derived magmas the emplacement of a large amount of mesozoic granitoids in southeastern china promoted thermal softening and gravitational instability that allowed the crust to extend the formation of the wugongshan dome and other metamorphic core complexes appears to be a the direct consequence of plutonic activity and crust rheology

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

an early cretaceous w sn deposit and its implications in southeast coastal metallogenic belt constraints from u pb re os ar ar geochronology at the feie shan w sn deposit se china the feie shan w sn deposit is in eastern guangdong province which is a newly explored deposit in the southeastern coastal metallogenic belt in order to constrain the age of mineralization in the feie shan w sn deposit we collected molybdenites and hydrothermal biotite of the feie shan w sn deposit for dating the tungsten mineralization is spatially associated with the biotite monzonitic granite porphyry la mc icp ms zircon u pb dating of the biotite monzonitic granite porphyry yielded a weighted mean pb u age of 139 2 1 7 ma which was interpreted as the emplacement age of the biotite monzonitic granite porphyry the re os model ages ranged from 137 3 2 0 ma to 146 1 2 1 ma with a weighted mean age of 140 6 1 9 ma and ar ar isotopic analyses of hydrothermal biotite yield a plateau ar ar age of 135 1 0 8 ma these dates obtained via three independent geochronological techniques constrained the ore forming age of the feie shan deposit and linked the genesis of the ore to the underlying biotite monzonitic granite porphyry combined with previous studies it is suggested that there is a period at 144 132 ma for w sn mineralization in the southeastern coastal metallogenic belt the feie shan w sn deposit belongs to the 144 132 ma metallogenic events in the scmb in a geodynamic setting of lithospheric extension

neoproterozoic mineralization in a hydrothermal cassiterite sulfide deposit at jiumao northern guangxi south china mineral scale constraints on metal origins and ore forming processes abstract most tin deposits worldwide are inferred to have formed from fluids derived from evolved granitic magma systems neoproterozoic silicate and sulfide stage sn deposits at jiumao of south china in contrast have been thought to be derived from metasedimentary and mafic ultramafic host rocks the sn deposit may thus have formed by components and processes distinct from those that commonly contribute to sn deposits although spatially associated greisen hosted sn deposits also occur to characterize in detail the formation of the jiumao ore deposits which contain 28 000 t of sn we present new field and petrographic observations major and trace element compositions for silicate and ore minerals and u pb age data of cassiterites and zircons for the deposits and granites our research shows that 1 the granite greisen system formed at 830 ma which is the earliest sn mineralization event in south china 2 the silicate and sulfide stage ores in the country rocks formed at an fo2 of nno with temperatures of 350 c and 170 c respectively 3 all vein type sn ores at jiumao were formed by sn f b rich fluids that were derived from the yuanbaoshan granite magma system rather than ultramafic rocks 4 the fe rich character of the ores hosted by the metasedimentary rocks and the mg rich character of the ores hosted by the ultramafic rocks largely controlled the reactions and efficacy of cassiterite precipitation and thus ore grade we highlight that differences in mineral assemblages largely relate to differences of the protolith compositions and fluid rock reactions e g b and tourmaline deposition in the ores hosted by the metasedimentary rocks but not in the ores hosted by the ultramafic rocks cassiterite and titanite trace element compositions reflect fluid composition protolith composition and intensive parameters of crystallization

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

petrogenesis of jurassic a type granites associated with cu mo and w sn deposits in the central nanling region south china relation to mantle upwelling and intra continental extension abstract the central nanling region in south china was the site of uplift extensional deformation granite magmatism and hydrothermal activity from 180 to 150 ma information on the age petrological characteristics major and trace element contents whole rock sr and nd and zircon hf isotopic compositions of granitic plutons were synthesized to constrain the sources evolutionary processes and uplift cooling rates of intrusions that host cu mo and w sn deposits in this region the older 180 160 ma cu mo related granitoids are less differentiated a1 type alkaline rocks with faster cooling and uplift rates they have younger nd and hf two stage model ages and higher end t and ehf t values that indicate mantle derived magmas were moderately contaminated by upper crust the younger 160 150 ma w sn related granites are more differentiated a2 type aluminous rocks with slower cooling and uplift rates they have older nd and hf two stage model ages and lower end t and ehf t values that require more upper crustal contamination the time space distribution and characteristics of these granitoids and ore deposits are indicative of centralized mantle upwelling and gradational crustal extension the older rapidly uplifted less contaminated granitoids with cu mo mineralization occur near the center of an intra continental extension bulge produced by mantle upwelling whereas the younger slowly uplifted more contaminated granitoids with w sn mineralization occur on the periphery the results suggest that metals in the cu mo deposits may have come from the mantle whereas those in the world class nanling w sn polymetallic deposits were derived from early mesoproterozoic 1 4 1 6 ga crustal basement of the cathaysia block in south china

geochronological and geochemical results from mesozoic basalts in southern south china block support the flat slab subduction model the debate on the mesozoic tectonics of the south china block scb featuring a broad orogenic belt and a large continental magmatic province has been rejuvenated in the past years there are a number of competing tectonic models each predicting different time space and compositional evolutional trends for the mesozoic igneous rocks including sporadic basalts in this paper we report high precision 40 ar 39 ar ages and geochemical and sr nd isotopic data for basaltic rocks in central eastern scb these results together with a data compilation indicate three evolutionary stages for the basalts stage 1 195 160 ma basalts occur only in inland scb they exhibit low initial 87 sr 86 sr ratios 0 7038 to 0 7078 high e nd t values 1 5 to 6 0 and ocean island basalt oib like geochemical characteristics such as low la nb ratios 0 6 to 1 4 implying negligible to minor lithosphere contamination stage 2 160 110 ma basalts mostly from the same inland region with minor occurrence closer to the coast are characterized by variable initial 87 sr 86 sr ratios 0 7053 to 0 7102 end t values 6 0 to 5 0 and low la nb ratios 0 9 to 1 8 indicating an enhanced asthenosphere lithosphere interaction stage 3 110 to 80 ma basalts can be further divided into two sub groups based on their geographic and geochemical variations basalts in the coastal regions are characterized by low end t values 8 1 to 3 7 and variably high la nb ratios up to 4 8 indicating a strong arc signature on the other hand basalts in the inland regions have high e nd t values 1 9 to 6 8 and low la nb ratios 0 6 to 1 2 that are similar to the stage 1 basalts we interpret these features as results of geodynamics processes related to the break up foundering and retreating of an early mesozoic flat subducted oceanic slab

the formation of the world class zhuxi scheelite skarn deposit implications from the petrogenesis of scheelite bearing anorthosite abstract a quartz free scheelite bearing fine to medium grained anorthosite occurs as a dike in the world class zhuxi scheelite skarn deposit of south china the anorthosite mainly comprises an rich plagioclase anavg 91 90 vol scheelite 3 vol apatite 2 5 vol ilmenite 1 5 vol titanite 1 vol as well as minor 2 vol fluorite prehnite chalcopyrite pyrrhotite pyrite sphalerite rutile and uraninite this paper reports the first occurrence of scheelite bearing anorthosite of hydrothermal origin in a w deposit field textural mineralogical and geochemical evidence suggest a hydrothermal genesis for the scheelite bearing anorthosite in the zhuxi deposit the scheelite bearing anorthosite formed when the al si p w and f rich residual magma fluid was contaminated by pure limestone in a reducing environment the formation of the scheelite bearing anorthosite requires fertile w rich metasedimentary rocks as a magmatic source which formed granitic magma emplaced at a great depth that emanated w enriched magmatic hydrothermal fluids during the latest stage of magma crystallization thus producing the large scale tungsten mineralization in the zhuxi mine

petrogenesis of the late mesozoic guposhan composite plutons from the nanling range south china implications for w sn mineralization voluminous granite plutons were emplaced in the late mesozoic in the nanling range south china accompanied by large scale polymetallic deposits most plutons are composite composed of major phase granites and highly differentiated late stage granites previous studies have proposed fractionation of both granite types and polymetallic deposits from a common magma we choose to study the ages chemistry and nd hf isotopes of the guposhan complex from the range and propose a different model for the origin of the granite and relationship with associated polymetallic mineralization in the nanling range the major phase granites of the guposhan complex contain medium coarse grained biotite granite and hornblende bearing biotite granite with mafic microenclaves mmes emplaced at 161 1 ma on the contrary the late stage granite is fine grained with apparent zircon ages of 154 3 ma the major phase granites show large variation in chemical compositions and in whole rock nd and zircon hf isotope ratios with end t 6 0 to 1 9 and ehf t 4 5 to 1 5 respectively we suggest that their origin is attributable to a magma mixing process between felsic magma derived from melting of proterozoic basement rocks and mantle derived mafic magma the mafic magma could be represented by the parental magma of the mmes within the plutons which have low sio2 high mgo and high end t values up to 1 8 the late stage granite shows end t and ehf t values similar to the major phase granites but are chemically more evolved sio2 75 80 more reduced and water deficient and in particular are fluorine bearing numerical geochemical modeling and the petrological data indicate that the late stage granite was produced during a new thermal event rather than being produced due to fractional crystallization of the earlier major phase granite the polymetallic deposits are genetically linked with the late stage granite we suggest that a break off of the flat subducted pacific slab beneath the cathaysia block in the late mesozoic resulted in the upwelling of asthenosphere and formation of basaltic magma that underplated and triggered partial melting of the basement rocks forming felsic melts and followed by mixing of the mafic and felsic magmas in an extensional regime

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

cretaceous tectonic evolution of south china a preliminary synthesis abstract the cretaceous tectonic evolution of south china is characterized by widespread extensional basin and dome generation voluminous magma intrusion eruption and associated polymetallic mineralization all of which are of world wide interests that have stimulated the attention of geologists for more than half a century due to the lack of a comprehensive understanding of regional tectonic evolution and geodynamics of south china many controversies regarding the nature and origin of these features remain this paper attempts to make a review by synthesizing existing structural petrological geochronological and geochemical data of the cretaceous structures and magmas which guides us to propose a three stage tectono thermal evolutionary history of south china during the cretaceous period the earliest cretaceous 145 137 ma tectonic stage was characterized by syn orogenic shortening deformation and metamorphism under a nw se compressional setting which generated voluminous porphyry cu au ore bearing adakitic rocks in the lower yangtze river belt and gneissic granites in the coastal area its geodynamic origin was interpreted as combined effects of the pacific izanagi ridge subduction beneath the lower yangtze river belt and the pacific subduction beneath the cathaysia block this syn orogenic shortening stage was followed by a post orogenic stage 136 86 ma comprising two episodes of alternate extensional and shortening events the extension 136 118 ma in the earlier episode was dominated by a nw se extensional regime it led to significant taphrogenesis manifested by large scale extensional basins and voluminous magma intrusion eruption this extensional event was associated with a combination of the slab window opening during the ridge subduction and the rollback of the subducted pacific slab the subsequent nw se transpressional event led to cessation of active marginal magmatism and resulted in tectonic inversion of previous rift basins this transpression lasted from 117 ma to 108 ma and its driving mechanism was attributed to the collision between the eastern asian margin and the west philippine block the extension 107 86 ma in the later episode was dominated by a wnw ese extensional regime which led to a second phase of basin subsidence and produced numerous a and i type granites and bimodal volcanoes the tectonic regime then changed at ca 85 ma to wnw ese oriented transpression causing inversion of the late cretaceous rift basins and cessation of extension related magmatism the change of stress field from wnw ese extension to wnw ese transpression was related to the variations of the subducted slab dynamics i e the transition from either the ese ward retreat to wnw ward subduction of the pacific slab or the alternate stress during slab break off during the latest cretaceous a drastic change of regional tectonic stress orientation from wnw ese to n s occurred in south china the third stage predominated by n s extension was developed which caused a new phase of regional crustal subsidence along the youngest e w trending extensional structures

multiple mesozoic mineralization events in south china an introduction to the thematic issue mesozoic mineral deposits in south china include world class deposits of w sn and sb and those that provide the major sources of ta cu hg as tl pb zn au and ag for the entire country these deposits can be classified into polymetallic hydrothermal systems closely related to felsic intrusive rocks sn w mo granites cu porphyries polymetallic and fe skarns and polymetallic vein deposits and low temperature hydrothermal systems with no direct connection to igneous activities mvt deposits epithermal au and sb deposits recent studies have shown that they formed in the triassic indosinian jurassic cretaceous early yanshanian and cretaceous late yanshanian stages indosinian deposits include major mvt pb zn ag deposits and granite related w sn deposits early yanshanian deposits are low temperature sb au and high temperature w sn and cu porphyry types many late yanshanian deposits are low temperature au as sb hg and u deposits and also include high temperature w sn polymetallic deposits the formation of these deposits is linked with a specific tectonothermal evolution and igneous activities this special issue brings together some of the latest information in eight papers that deal with the origins and tectonic environments of mineral deposits formed in these stages we anticipate that this issue will stimulate more interests in these ore deposits in south china

geology and genesis of kafang cu sn deposit gejiu district sw china kafang is one of the main ore deposits in the world class gejiu polymetallic tin district sw china there are three main mineralization types in the kafang deposit i e skarn cu sn ores stratiform cu ores hosted by basalt and stratiform cu sn ores hosted by carbonate the skarn mainly consists of garnet and pyroxene and retrograde altered rocks these retrograde altered rocks are superimposed on the skarn and are composed of actinolite chlorite epidote and phlogopite major ore minerals are chalcopyrite pyrrhotite cassiterite pyrite and scheelite sulfur and pb isotopic components hint that the sources of different types of mineralization are distinctive and indicate that the skarn ore mainly originated from granitic magma whereas the basalt hosted cu ores mainly derived from basalt microthermometry results of fluid inclusions display a gradual change during the ore forming process the homogenization temperature of different types of inclusions continuously decreases from early to late mineralization stages the salinities and freezing temperatures exhibit similar evolutionary tendencies with the t homogenizaion while the densities of the different types keep constant the majority being less than 1 oxygen and hydrogen isotopic values o and d of the hydrothermal fluids fall within ranges of 3 1 to 7 7 with an average of 6 15 calculated at the corresponding homogenization temperature and 73 and 98 with an average of 86 5 respectively microthermometry data and h o isotopes indicate that the ore forming fluid of the kafang deposit is mainly derived from magma in the early stage and a mixture of meteoric and magmatic water in late stage molybdenite re os age of the skarn type mineralization is 83 4 2 1 ma and the stratiform ores hosted by basalt is 84 2 7 3 ma which are consistent with the la icp ms zircon age of the xinshan granite intrusion 83 1 0 4 ma the evidence listed above reflects the fact that different ore styles in the kafang deposit belong to the same mineralization system

he pb and s isotopic constraints on the relationship between the a type qitianling granite and the furong tin deposit hunan province china abstract the furong tin deposit located in southern hunan province china is a large newly discovered deposit with an estimated sn reserve of about 700 000 tons the deposit is spatially and temporally associated with the a type qitianling granite the 3he 4he ratios of fluid inclusions trapped in sulfides from the deposit range from 0 13 to 2 95 ra indicating a mixed crust mantle source similar to that of the qitianling granite complex lead isotopes in feldspars of the granite mostly in the range of 206pb 204pb 18 547 19 180 207pb 204pb 15 598 15 825 208pb 204pb 37 912 39 068 and in sulfide minerals 206pb 204pb 18 467 18 836 207pb 204pb 15 503 15 772 208pb 204pb 38 607 39 099 are essentially the same indicating that the lead in both was derived mainly from the upper crust with a small mantle component the sulfur isotopic values of the ore minerals vary widely ranging from 26 1 to 10 4 but are mainly within the range of 0 2 to 10 4 implying that the s in the hydrothermal fluids was derived mainly from magmatic fluids with minor contributions from the mantle sedimentary rocks and biogenic material the he pb and s isotopes all confirm that the ore forming fluids of the furong deposit were magmatic in origin derived from the melts that produced the qitianling a type granite the tin mineralization occurs within or along the margins of the qitianling granite complex and the timing of the mineralization coincides with the intrusive age of the granite the available data suggest that the emplacement of the granites and the mineralization was related to mantle upwelling and extension of the lithosphere in south china during the mesozoic

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

a tentative discussion on indosinian ore forming events in laojunshan area of southeastern yunnan a case study of xinzhai tin deposit and nanyangtian tungsten deposit the laojunshan area is an important part of the southeastern yunnan polymetallic belt nevertheless the timing and tectonic setting of the typical deposits in this area were poorly constrained in this paper the authors present new 40ar 39ar dating of phlogopite closely coexisting with cassiterite ages for the xinzhai tin deposit and re os dating of three molybdenite samples separated from the nanyangtian tungsten deposit to constrain timing and duration of the mineralization phlogopite from the xinzhai tin deposit yielded an 40ar 39ar plateau age of 209 5 1 1 ma and isochronal age of 209 0 2 2 ma the re os model ages range from 209 1 3 3 ma to 214 1 4 3 ma these ages provide the indosinian metallogenic information in southeastern yunnan the available data and evidence suggest that the sn and w mineralization in the xinzhai tin deposit and the nanyangtian tungsten deposit occurred in late post orogenic or post collisional stage during the indosinian period in southern china and was controlled by a geodynamic setting of extension cracking

the formation of the late cretaceous xishan sn w deposit south china geochronological and geochemical perspectives abstract the xishan sn w deposit is spatially related to k feldspar granites in the yangchun basin western guangdong province south china la icp ms zircon u pb dating for the xishan pluton defines an emplacement age of 79 ma 78 1 0 9 ma 79 0 1 2 ma 79 3 0 8 ma consistent with the mineralization age of the xishan sn w deposit constrained by molybdenite re os isochron age 79 4 4 5 ma and la icp ms cassiterite u pb ages 78 1 0 9 ma and 79 0 1 2 ma for the cassiterite quartz vein these indicate a close genetic relationship between the granite and sn w mineralization the xishan k feldspar granites have geochemical characteristics of a type granites e g high total alkali na 2 o k 2 o 7 88 10 07 wt high ga al ratios 10000 ga al 2 6 and high zr nb ce y concentrations 350 ppm they are further classified as a 2 type granites the whole rock isotopic compositions of k feldspar granites initial 87 sr 86 sr 0 705256 0 706181 e nd t 5 4 to 4 8 and zircon e hf t values 7 8 to 2 0 suggest a mixed magma source the low zircon ce 4 ce 3 ratios 12 88 of k feldspar granites suggest low oxygen fugacities which is key for enrichment of tin in primary magmas the k feldspar granites have experienced strong differentiation as indicated by their high rb sr and k rb ratios and low nb ta and zr hf ratios which play an important role in ore forming element transportation and concentration a type granite characteristics of the xishan pluton show that it formed in an extensional environment the high f and low cl characteristics of the k feldspar granite are most probably attributed to slab rollback in the late cretaceous the xishan sn w deposit was located near the interaction of the circum pacific and the tethys tectonic realms late cretaceous sn w deposits including the xishan deposit form an ew trending belt from guangdong to yunnan province in south china this belt is in accordance with the direction of the neo tethys slab rollback in the late cretaceous in addition the ns trending extension has been recognized in the late cretaceous in south china we propose that the xishan sn w deposit should be attributed to the neo tethys slab rollback in the late cretaceous