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

core evidence of paleoseismic events in paleogene deposits of the shulu sag in the bohai bay basin east china and their petroleum geologic significance abstract the shulu sag located in the southwestern corner of the jizhong depression bohai bay basin of east china is a ne sw trending elongate cenozoic half graben basin the lowermost part of the third member of the shahejie formation in this basin is characterized by continental rudstone and calcilutite to calcisiltite facies based on core observation and regional geologic analysis seismites are recognized in these lacustrine deposits which include soft sediment deformation structures sedimentary dikes hydraulic shattering diapir structures convolute lamination load flame structures ball and pillow structures loop bedding and subsidence structures synsedimentary faults and seismoturbidites in addition mixed source rudstones consisting of the paleozoic carbonate clasts and in situ calcilutite clasts in the lowermost submember of shahejie 3 appear in the seismites suggesting an earthquake origin a complete representative vertical sequence in the lowermost part of the third member found in well st1h located in the central part of the shulu sag shows from the base to the top underlying undeformed layers synsedimentary faults liquefied carbonate rocks allogenetic seismoturbidites and overlying undeformed layers seismites are widely distributed around this well and there are multiple sets of stacked seismites separated by undeformed sediment the nearby nw trending taijiazhuang fault whose fault growth index is from 1 1 to 1 8 and the nne trending xinhe fault with a fault growth index of 1 3 1 9 may be the source of the instability to create the seismites these deformed sedimentary layers are favorable for the accumulation of oil and gas for example sedimentary dikes can cut through many layers and serve as conduits for fluid migration sedimentary faults and fractures induced by earthquakes can act as oil and gas migration channels or store petroleum products as well seismoturbidites and mixed source rudstones are excellent reservoirs due to their abundant primary or dissolved pores

geochemistry and u pb geochronology of the wagone and hermyingyi a type granites southern myanmar implications for tectonic setting magma evolution and sn w mineralization abstract tin tungsten associated granites occur widely in the dawei region of the southeast asian tin belt in this contribution we present a detailed study of zircon u pb geochronology and whole rock and zircon elemental geochemistry for the wagone and hermyingyi granites in southern myanmar with the aim of determining their petrogenesis mineralization associations and tectonic setting these granitic rocks which belong to the high k calc alkaline series a2 type granites are characterized by high concentrations of sio2 75 2 82 5 rb 264 927 ppm th 18 4 58 3 ppm u 10 4 18 3 ppm and y 33 5 212 ppm but low contents of tfeo 0 57 3 45 cao 0 23 0 86 mgo 0 02 0 19 mno 0 01 0 38 tio2 0 01 0 10 p2o5 0 003 0 012 ba 3 162 ppm and sr 4 3 34 4 ppm hydrothermal zircons from the mineralized wagone pluton show an anomalous lack of zoning and vermicular spongy internal structures and they contain high concentrations of ti y u and light rees but low th u ratios mostly

rare earth element systematics in scheelite from hydrothermal gold deposits in the kalgoorlie norseman region western australia scheelite cawo 4 is a widespread accessory mineral associated with hydrothermal veins in the archean gold deposits of the kalgoorlie norseman region of western australia rare earth element ree and other trace element abundances in scheelite have been determined in situ by excimer laser ablation inductively coupled plasma mass spectrometry ela icp ms in order to constrain the composition and sources of the mineralizing fluids the scheelites can be grouped according to the two distinct types of chondrite normalized ree ree n patterns which they exhibit hump shaped type i and flat type ii type i scheelites have higher total and na concentrations than type ii samples and can be further subdivided into type ia which has maximum ree n concentrations between sm and gd and type ib which has maximum ree n concentrations displaced toward dy type i scheelites are dominant at coolgardie kalgoorlie and kambalda whereas type ii samples are most abundant at norseman a few scheelite grains exhibit both type i and type ii characteristics the two types of ree n patterns with different na abundances suggest that the trivalent ree substituted into the ca site of scheelite by two different mechanisms 2ca super 2 ree super 3 na super for the type i scheelites and 3ca super 2 2ree super 3 ca where ca is a ca site vacancy for the type ii samples the parabolic shape of ree n patterns in the type i scheelites can be used to calculate the ionic radius of the ree super 3 that preferentially substitutes into the scheelite structure when type i ree patterns are normalized to account for variations in light ree abundance the average value obtained is 1 060 aa for type ia and 1 055 aa for type ib scheelites these values are smaller than the value of 1 12 aa for the ca site but are in excellent agreement with the value of 1 06 aa predicted by the coupled na super ree super 3 substitution mechanism assuming size as well as charge compensation this result implies that na super and ree super 3 substitute into adjacent sites in the crystal structure of type i scheelites in contrast the incorporation of ree into type ii scheelites appears to be independent of size it is suggested that in this type of scheelite involvement of a ca site vacancy relaxes the size constraint on the substitution of the ree super 3 the influence of ree speciation in the hydrothermal fluid on the systematic difference between scheelite fluid partition coefficients for type i and ii scheelites is of secondary importance compared with crystal chemistry effects the distinctive ree n patterns and high na contents of type i scheelites imply that they crystallized from hydrothermal fluids with higher na activities than those that formed type ii samples type i scheelites exhibit no changes in the size of the eu anomaly with ree concentration implying a predominance of eu super 3 and crystallization under relatively oxidized conditions type ii scheelites have variable eu anomalies and trivalent ree concentrations and thus appear to contain mostly eu super 2 and to have formed under reduced conditions type ia and ii scheelites have ce lu n 1 and are interpreted to have crystallized from light ree enriched fluids whereas type ib scheelites with ce ln n 1 formed from light ree depleted fluids the fluid characteristics inferred from the ree and trace element systematics in the scheelites can be attributed to the rock types and estimated physical conditions in the kalgoorlie norseman region at the time of hydrothermal activity high na activities are consistent with buffering of fluids by greenschist facies mafic rocks whereas low fluid na activities are a product of fluid rock reactions at higher metamorphic grades oxidized fluids are consistent with near surface derivation whereas reduced fluids are indicative of generation at elevated temperatures and pressures the range and distribution of fluid ce ln n ratios are similar to those of the major rock types in the region

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

scheelite apatite calcite and tourmaline compositions from the late archean hutti orogenic gold deposit implications for analogous two stage ore fluids abstract gold mineralization at hutti southern india has occurred in two stages stage 1 mineral assemblage comprises biotite chlorite plagioclase calcite epidote actinolite tourmaline arsenopyrite pyrite pyrrhotite and gold whereas the stage 2 mineral assemblage is represented by sericite chlorite calcite scheelite tourmaline apatite titanite pyrrhotite arsenopyrite and gold we report here the occurrence of scheelite from the stage 1 assemblage and compare major and trace element compositions of scheelite fluorapatite f 4 wt calcite and tourmaline from the two stages with an emphasis on the second stage in which they are best represented scheelite displays three types of ree patterns these are the type i middle ree mree enriched with negative eu anomaly type ii heavy ree hree enriched with minor positive negative eu anomaly and type iii that varies from slightly mree enriched to mree depleted with correspondingly increasing positive eu anomaly the stage 1 scheelites display type i pattern while stage 2 scheelites display type ii and type iii patterns textural and compositional evidence suggest asynchronous precipitation of scheelite fluorapatite and calcite in the stage 2 mineralization indicating precipitation from cyclic fluid flow the occurrence of rare minute scheelite grains in the stage 1 mineralization assemblage is most likely because of prevalent high temperature 350 477 c whereas during the stage 2 mineralization abundant scheelite precipitation evidenced by the presence of scheelite rich carbonate quartz veins was favored by the decrease in temperature 300 c additionally repeated fluid pressure fluctuations due to fault valve mechanism would have further enhanced precipitation of scheelite in stage 2 the fewer scheelites in stage 1 mineralization resulted in their mree enriched pattern with high ree the mree depleted patterns of stage 2 scheelites on the other hand do not necessarily indicate a compositionally different fluid but are due to rapid removal of mree in early formed mree enriched scheelites making them less and less available in the fluid for later crystallizing scheelites this is supported by the observation that except for the slight remobilization of lree the rees are conserved in the altered rocks trace element ratios y ho zr hf nb ta in fluorapatite and calcite are chondritic indicating little fractionation of these element pairs and cannot be diagnostic of fluid composition tourmalines from both the stages record equally low contents of na liles and hfses and comparably low fe 3 fe 2 ratios suggesting very similar nature of the two fluids which were low in salinity trace element poor and reducing in nature indicating a metamorphic parentage

in situ la icp ms trace element analyses of scheelite and wolframite constraints on the genesis of veinlet disseminated and vein type tungsten deposits south china abstract veinlet disseminated and vein type tungsten deposits are important tungsten resources in south china and show remarkable diversity in dominant tungsten minerals to better understand their genesis scheelite from the shimensi veinlet disseminated deposit and wolframite from the xihuashan and piaotang vein type deposits were selected to conduct in situ laser ablation inductively coupled plasma mass spectrometry trace element analyses the shimensi tungsten mineralization occurs in intensively altered granitic rocks and is characterized by scheelite two generations of scheelite in a single grain can be identified by cathodoluminescence cl imaging the early scheelite dark domains in cl images is characterized by nearly flat chondrite normalized ree ree n patterns with significantly negative eu anomalies whereas the late one bright domains in cl images shows light rare earth element lree enriched ree n patterns and obviously positive eu anomalies the former has higher ree na nb and ta and lower sr contents than the latter the xihuashan and piaotang wolframite quartz veins are developed in greisenized granite type i and metasedimentary rocks type ii both types of wolframite show lree depleted patterns but type i exhibits strongly negative eu anomalies and type ii positive eu anomalies type i contains higher ree nb and ta concentrations and lower feo mno ratios than type ii variations of eu anomalies and trace element compositions in both scheelite and wolframite can be used to decipher the origin and processes of tungsten mineralization both the early scheelite and wolframite type i display significantly negative eu anomalies and have high ree nb and ta contents suggesting that the initial ore forming fluids were of magmatic origin precipitation of tungsten minerals and alteration would effectively modify the composition of ore forming fluids deposition of the early tungsten minerals would lower ree nb and ta in the mineralizing fluids leading to depletion of these elements in the late ones although both the type i and ii wolframite have different ree contents and eu anomalies they show similar left dipped ree n patterns implying that compositional variation of fluids is likely driven by crystallization of wolframite during the processes of fluid evolution in contrast the elevated lree hree heavy rare earth element ratios eu eu n eu n values and sr abundances in the late scheelite are possibly caused by the decomposition of plagioclase and k feldspar alteration plays an important role in the formation of veinlet disseminated scheelite deposits it can be concluded that vein type wolframite mineralization is mainly formed by filling and that veinlet disseminated scheelite mineralization is associated with metasomatism

origins of nd sr pb isotopic variations in single scheelite grains from archaean gold deposits western australia accessory gangue scheelite cawo4 from the archaean mt charlotte lode au deposit can be divided into two types with different rare earth element ree signatures in some scheelite grains specific ree signatures are reflected by different cathodoluminescence colours which can be used to map their often complex oscillatory intergrowths domains with specific ree contents from two grains were sampled for sm nd rb sr and pb isotopic analyses using a micro drilling technique type i scheelite is strongly enriched in middle ree mree and eu anomalies are either absent or slightly positive four fragments collected from type i regions of two crystals have initial 87sr 86sr and end values ranging from 0 70141 to 0 70163 and 2 5 to 3 5 respectively and pb isotope ratios reflecting the composition of greenstone sequence this may indicate that nd and pb have their source either locally or regionally in the greenstones basic greenstone lithologies have 87sr 86sr 0 7015 and the radiogenic sr signatures indicate that part of the sr originated from felsic lithologies located either within or beneath the host greenstone pile alternatively the sr signature may have evolved from preferential leaching of a rb rich mineral during hydrothermal alteration of the greenstone the ree patterns of type ii scheelite are either flat or mree depleted and have strong positive eu anomalies three fragments collected from type ii regions of the same two crystals have initial 87sr 86sr ratios and end values between 0 70130 and 0 70146 and 1 1 to 2 6 respectively and pb isotope signatures that are once again similar to that of the greenstone this implies that 87sr 86sr ratios in type ii fluids were closer to those of the host dolerite 0 7008 0 7013 due to more extensive fluid interaction with the dolerite a positive correlation between na and ree suggests that ree3 are accommodated by the coupled substitution ree3 na 2 ca2 into both type i and type ii scheelite this is consistent with a fractional crystallisation model to explain the change in ree patterns from type i to type ii but not with a model involving different coupled substitutions and fluids from different origins we propose that the complex ree and isotopic signatures of scheelite at mt charlotte are related to small m to medium km scale processes involving mixing between fresh batches of hydrothermal fluid with fluids that had already been involved in extensive wall rock alteration the very high end values measured in some scheelites have been previously used to link gold mineralisation with komatiites containing unusually high sm nd ratios however tiny 20 m grains of secondary hydroxyl bastnasite were found within micro fractures of one scheelite grain containing an extremely high end signature the hydroxyl bastnasite probably formed during recent ree redistribution within the scheelite as a result of meteoric fluid circulation the scale of this cryptic low temperature alteration is sufficient to explain the anomalously high endi values observed in scheelite from western australia

isotopic geochemistry zircon u pb ages and hf isotopes of a type granites from the xitian w sn deposit se china constraints on petrogenesis and tectonic significance abstract zircon u pb geochronological geochemical and petrological analyses have been carried out on the xitian granite emplaced in the middle part of shi hang zone which is closely related to the economically important xitian tungsten tin deposit in hunan province southeast china la icp ms zircon u pb dating of two representative samples yielded weighted means 206 pb 238 u age of 151 7 1 2 ma and 151 8 1 4 ma these granites are comprised mainly of k feldspar quartz plagioclase fe rich biotite and minor fluorite and are characterized by enrichments in rb th rees total ree 159 351 ppm and hfses e g zr and y but depletions in ba sr p eu and ti they are metaluminous to weakly peraluminous and show a clear a type granite geochemical signature with high sio 2 73 44 78 45 wt total alkalis na 2 o k 2 o 2 89 8 98 wt fe 2 o 3 mgo ratios and low p 2 o 5 cao mgo and tio 2 contents in situ zircon hf isotope analysis suggests their e hf t values ranging from 7 43 to 14 69 sr nd isotope data show their e nd t values in the range of 9 2 to 7 3 with corresponding t dm2 ages of 1 72 1 56 ga these characteristics indicate that the xitian granite originated from partial melting of metamorphic basement rocks with a certain amount of mantle derived materials combined with previous geochemical and isotopic data it is derived that mantle crust interaction was gradually enhanced from the early to late stages of magmatism the ore forming materials and fluids of the xitian w sn deposit are mainly produced by the early yanshanian granitic magmatism which is also responsible for the late jurassic ca 152 ma a type granitic rocks that host the w sn polymetallic deposits distributed along the shi hang zone implying a significant mesozoic extensional event in southeast china likely caused by the subduction of the paleo pacific plate

geochemistry of a type granites in the huangshaping polymetallic deposit south hunan china implications for granite evolution and associated mineralization abstract the huangshaping granites in hunan province south china were investigated for their geochemical characteristics three types of granites have been petrographically identified quartz porphyry granophyre and granite porphyry whole rock geochemistry suggests that the huangshaping granites especially the granite porphyry exhibit typical a type granite characteristics with their enrichment in si rb u th and nb and significant depletion in ba sr ti eu and p based on the al y and zr contents as well as the ree patterns of the rocks investigated the quartz porphyry and the granophyre are classified as a1 type alkaline granites whereas the granite porphyry is considered as a2 type aluminous granite whole rock and quartz feldspar o isotope data yields a wide range of 18osmow values 11 09 26 32 the granites are characterized by high radiogenic pb isotopic composition the present day whole rock pb isotopic ratios are 206pb 204pb 18 706 19 155 207pb 204pb 15 616 15 711 and 208pb 204pb 38 734 39 296 combining the o pb isotope compositions with major trace and ree geochemistry and regional geology characteristics the huangshaping granites were determined to resemble within plate granites that were mainly derived from a felsic infracrustal source related to continental extension the magma source of the quartz porphyry and the granophyre may have been generated from deeper depths and then ascended rapidly with limited water content and low oxygen fugacity which contributed to cu pb and zn mineralization on the other hand the magma that generated the granite porphyry may have ascended relatively slower and experienced pronounced crystal fractionation upper crustal basement rock contamination assimilation and wall rock interaction producing the sn and w rich granite porphyry this study reveals the crustal extension process and associated magmatic metallogenic activities during 180 150 ma in south hunan

flash vaporization during earthquakes evidenced by gold deposits fluids flowing through cavities in earth s crust can deposit gold thermo mechanical modelling of a fluid filled cavity that expands suddenly during an earthquake shows that the drop in pressure would cause the fluid to vaporize and deposit the gold almost instantaneously

ree systematics in hydrothermal fluorite abstract ree patterns of fluorite from 63 post variscan hydrothermal veins of the schwarzwald area germany can be divided into two major groups type a fluorite shows roof shaped paas normalized patterns with enriched mree the turning point of the curvature is at ho or er position all patterns of type a show a distinct positive eu anomaly type b fluorite shows roof shaped patterns with enriched mree and strongly depleted hree and a characteristic steep slope between nd and sm the turning point of the curvature is at gd to dy all patterns of type b show negative or no eu anomalies laser ablation icp ms traverses through single grains combined with cathodoluminescence imagery revealed either i identical ree patterns and total ree concentrations from core to rim ii identical ree patterns but concentration gradients or iii variable ree patterns and concentration gradients from core to rim these features are explained by different degrees of supersaturation or different fluid fluorite ratios during crystallization and by complexly controlled precipitation processes under closed system conditions petrographically late fluorites from several deposits show the characteristics of new fluid batches rather than the expected remobilization features lree enrichment close to the crystal faces in some grains may result from the copreciptiation of a submicrometer sized lree enriched phase or from lree clustering in late cool fluids by comparison with literature data on natural waters from gneissic and granitic aquifers and of leachates of granites and gneisses we show that the hydrothermal vein fluorite preserves the characteristic source related ree feature of the hydrothermal fluid that migrated through either gneissic type a or granitic type b host rocks the immediate host rocks of the veins however are not the source rocks of the ree which indicates large scale fluid convection in the basement gneiss related type a fluorite shows tb ca tb la trends of primary hydrothermal crystallization whereas granite related type b fluorite indicates remobilization of possibly pegmatitic or variscan fluorite

colloidal gold and silica in mesothermal vein systems some of the textural features of mesothermal gold quartz veins may be best explained by the initial precipitation of amorphous silica gel colloid which subsequently crystallizes to quartz this can occur in brittle ductile shear zones where a significant fluid pressure drop occurs during stick slip failure such a process rapidly supersaturates the hydrothermal fluid with respect to amorphous silica which precipitates instead of quartz owing to favorable kinetics depressurization also commonly leads to fluid unmixing and destabilization of soluble gold complexes however the presence of colloidal silica can stabilize gold colloid allowing further transport of particulate gold in suspension in the hydrothermal fluid silica gel would be highly unstable under mesothermal conditions and would undergo rapid syneresis and crystallization to form quartz solid impurities would tend to be expelled toward grain boundaries this model can account for the primary anhedral aggregate textures typical of mesothermal quartz veins the concentration of gold along grain boundaries and the formation of discrete gold nuggets and the rare occurrence of low order silica polymorphs and relict spheroidal structures the transport of gold in colloidal form may be one reason for the frequently consistent bulk grade distribution in gold quartz vein systems over many hundreds of metres in some cases kilometres of depth in addition the formation of charged colloidal particles may help to explain the attraction of gold grains to specific mineral surfaces

in situ sr isotopic measurement of scheelite using fs la mc icpms abstract scheelite is one of the main ore minerals in tungsten deposits and sr isotopic compositions of scheelite can be used to examine the petrogenesis of igneous rocks and fluid metasomatism in mineralization processes both thermal ionization mass spectrometer tims and femsecond laser ablation multi collector inductively coupled plasma mass spectrometer fs la mc icp ms have been applied to analyze sr isotopic compositions in scheelite here we describe a la mc icp ms technique which can obtain in situ accurate high precision 87sr 86sr ratios from 20 to 50 m scheelite in line mode without requiring time consuming mineral separation and pre chemical procedures we found that ca dimers and ca argides do not detectably affect the obtained 87sr 86sr ratios and the adopted protocol overcomes interferences from kr rb er2 and yb2 the results of three mpi ding reference glasses kl2 g ml3b g and sths6 80 g are consistent with the recommended values here we show that the values of 87sr 86sr are relatively homogeneous for two scheelites from quartz veins and are comparable to the values determined by a traditional solution method hence these two scheelite samples have the potential to be reference materials for sr isotopic determination by la mc icp ms to illustrate the utility of the technique sr isotopes of scheelites from three different types of tungsten deposits of south china are documented the 87sr 86sr of scheelite from granite related veinlet disseminated and porphyry tungsten deposits varies systematically showing a positive correlation between sr content and 87sr 86sr ratios these micrometer scale inhomogeneities could be explained by mixing of two components reflecting intense fluid metasomatism during mineralization processes high 87sr 86sr ratios were obtained for the scheelite samples from a quartz vein type tungsten deposit indicating that the late stage ore forming fluid was mainly derived from the surrounding strata these examples show that in situ sr isotopic measurement of scheelite is a powerful tool to decipher the degree of fluid rock interaction in ore forming processes

extensional failure and hydraulic valving at minas da panasqueira portugal evidence from vein spatial distributions displacements and geometries abstract at panasqueira portugal exceptional exposure and demonstrable vein connectivity allow robust characterisation of brittle elastic failure mechanisms in intrusive related environments extensional failure was driven by cycles of fluid injection hydraulic valving and vein growth under conditions with v 1 and differential stress

fault fluid evolution in the xitian w sn ore field south china constraints from scheelite texture and composition abstract understanding fault fluid evolutionary processes is crucial for understanding the genesis of vein type deposits scheelite and quartz are common hydrothermal minerals in w sn ore field faults in the xitan ore field nanling range south china scheelite textural and compositional features were studied and two types of scheelite were identified type i represented by scheelite in the xihu fault is intergrown with quartz has oscillatory zonation variable zonation band width and is homogeneous light grey color in cathodoluminescence images and type ii represented by scheelite in the goudalan fault is intergrown with quartz that shows multi stage growth has oscillatory zonation and each zonation band is the same width scheelite grains of both types have homogeneous major element distribution e g w and ca however trace element contents e g mg nb are slightly variable and rare earth element ree and y contents gradually decrease by an order of magnitude from the core to the rim in both types of scheelite from core to rim the chondrite normalized ree patterns of type i scheelite change from flat curves with no or slightly positive eu anomalies to intense concave shapes with intense positive eu anomalies the middle rees gradually become depleted indicating the mree fractionation associated with early scheelite precipitation in a relatively closed fault fluid system in contrast the chondrite normalized ree patterns of type ii scheelite grains are similar all showing weak mree depletion from the core to rim implying recurrent fluid pulses in an open fault fluid system the ree patterns in the cores of the type i scheelite are similar to those of the scheelite from jurassic granites related to the w sn mineralization suggesting that the initial ore forming fluids were exsolved from the jurassic magma the ree patterns in the rims of type ii scheelite are consistent with those of scheelite from the goudalan w deposit suggesting that the fault fluid system experienced a similar evolution to the ore forming fluid system combining the results of this work with previous quartz h o isotopic and fluid inclusion studies it can be concluded that fluid mixing occurred in both the fault fluid system and the ore forming fluid system triggering large scale w precipitation

critical stress localization of flow associated with deformation of well fractured rock masses with implications for mineral deposits fluid flow and deformation of fractured rock masses is investigated using numerical models based on distinct element methods udec which couple mechanical and hydraulic behaviour a series of numerical experiments is presented in which diffuse flow through fracture networks changes to highly localized flow at a critical stress state slip on parts of the fracture network causes the opening up of some fractures often at fracture intersections thus a change in the stress state results in a sudden localization of deformation and fluid flow a series of plots of hydraulic conductivity v differential stress are presented for some natural fracture networks to demonstrate the influence of fracture network geometry and in situ stress on the critical phase boundary between diffuse and localized flow the onset of localized deformation and fluid flow is a critical point phenomenon resulting in fractal properties fractal and multifractal techniques are used to characterize heterogeneity of the flow in order to generalize the results of the modelling of discrete systems to a continuum based description of the flow the significance of the models and their implications for crustal behaviour are discussed in relation to hydrothermal mineralization and natural vein systems

soils as a tool for estimating ages of quaternary fault scarps in a hyperarid environment the southern arava valley the dead sea rift israel abstract on the alluvial fan of nahal shehoret in the extremely arid region of the negev desert israel reg soils developed on stable alluvial surfaces in colluvium along terrace risers and in colluvial units on a complex fault scarp were compared the degree of soil profile development provided an age estimate of the surface that was faulted a maximum age estimate of the scarp or terrace riser and an estimate of the maximum recurrence intervals of faulting events irsl dates of the tectonically displaced alluvial surfaces and colluvial units at the same site enabled us to re evaluate the use of reg soils for relative dating the major faulting event started at 34 8 4 3 ka it displaced a late pleistocene surface of the nahal shehoret alluvial fan dated at 56 10 8 ka renewed fluvial activity and deposition of alluvium on the downfaulted block had almost terminated by 13 6 2 3 ka the scarp was formed during the latest pleistocene and was followed by smaller faulting events which had only minor effects on the fault scarp morphology the similarity of age estimates from irsl dating and the degree of soil development in this environment indicates that soils can be used to date surfaces and colluvial units

ore forming mechanism of quartz vein type w sn deposits of the xitian district in se china implications from the trace element analysis of wolframite and investigation of fluid inclusions abstract the xitian w sn district is located in eastern hunan province of se china and comprises the heshuxia goudalan and longshang w sn deposits our study on the occurrence mineral assemblage and geochemistry of the orebodies shows that quartz vein orebodies are dominant mode of mineralization and can be divided into three stages stage i quartz molybdenite wolframite i stage ii quartz wolframite ii polymetallic sulfides and stage iii quartz pyrite fluorite the elements nb ta sc sn zn cr v mo cu and zr are abundant in both wolframite i and wolframite ii wolframite i contains higher concentrations of nb 1408 9245 ppm ta 241 2407 ppm and sc 123 521 ppm than wolframite ii nb 144 1080 ppm ta 3 76 315 ppm and sc 1 86 11 44 ppm these results indicate that wolframite i was formed closer to the host rock and at a greater ore forming depth than wolframite ii the total ree concentrations of wolframite i and ii range from 34 96 to 133 36 ppm and 21 30 to 43 73 ppm respectively both wolframite i and wolframite ii have low lree concentrations 0 00 0 05 and 0 08 8 18 ppm respectively and high hree concentrations 34 96 133 31 and 21 23 41 87 ppm respectively the enrichment of hrees in wolframite may be due to the fact that the sizes of the hrees3 0 94 1 02 a in combination with nb5 or ta5 0 72 a are closer to that of w6 0 68 a in combination with ca2 1 08 a or mg2 0 80 a than that of the lrees3 1 03 1 13 a making the coupled substitution easier a study of fluid inclusions in the coexisting gangue minerals shows that the homogenization temperatures of the fluid inclusions decrease from stage i to stage iii stage i 187 382 c average 275 c stage ii 122 278 c average 175 c stage iii 92 172 c average 139 c whereas the salinities of the fluid inclusions increase from stages i to ii and decrease from stages ii to iii stage i 1 8 18 2 wt nacleqv average 10 3 wt nacleqv stage ii 7 3 24 4 wt nacleqv average 14 9 wt nacleqv stage iii 0 2 5 3 wt nacleqv average 1 5 wt nacleqv raman spectroscopy reveals that the fluid inclusions mainly contain h2o co2 is minor and h2s ch4 and n2 are rare we conclude that the formation of wolframite was driven by post magmatic thermodynamic processes the ore forming fluid flowed through a multi fractured low pressure zone in the fault system in the district and a temperature pressure decrease led to fluid immiscibility characterized by co2 escaping in a low ph and high eh environment in stage i crust mantle mixed fluid and meteoric water mixing in stage ii and natural cooling of the fluid system in stage iii

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

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

quantitative analysis of tin and tungsten bearing sheeted vein systems several methods are investigated for the quantitative analysis of a range of sn w sheeted vein systems from southwest england and spain the methods are based on fractal concepts and include the measurement of vein thickness and spacing distributions and the development of a multifractal interval counting method equivalent to box counting in two dimensions the results indicate that sets of subparallel veins are generally distributed randomly or with only slight clustering and develop from fracture systems in which the spacing of veins is homogeneous the opening of the veins is much more heterogeneous suggesting localization of subsequent deformation and flow this is especially true in mineralized areas and together with power law distributions of vein thickness can be used to characterize mineralized systems new data presented in this paper suggest that fracture evolution may play a fundamental role in defining the location and style of sn w mineralization observed greisen dominated and disseminated sn w systems develop where the initial fracture system dominates the fluid flow regime whereas sheeted vein systems are best developed where stress induced critical behavior of flow in fracture networks controls the permeability and fluid flow of the system

in situ analyses of micas in the yashan granite south china constraints on magmatic and hydrothermal evolutions of w and ta nb bearing granites article i nfo article history most rare metal granites in south china host major w deposits with few or without ta nb mineralization however the yashan graniticpluton located inthe yichun areaof western jiangxiprovince south china hosts a major nb ta deposit with minor w mineralization it is thus important for understanding the diversity of w and nb ta mineralization associated with rare metal granites the yashan pluton consists of multi stage intrusive units including the protolithionite muscovite granite li mica granite and topaz lepidolite granite from the early to late stages bulk rock ree contents and la yb ratios decrease from protolithionite granite to li mica granite to topaz lepidolite granite suggesting the dominant plagioclase fractionation this variation together with increasing li rb cs and ta but decreasing nb ta and zr hf ratios is consistent with the magmatic evolution in the yashan pluton micas are protolithionite muscovite li mica and lepidolite and zircons show wide concentration ranges of zro2 h fo2 u o2 t ho2 y 2o3 and p2o5 compositional variations of minerals such as increasing f rb and li in mica and increasing hf u and p in zircon are also in concert with the magmatic evolution from protolithionite granite to li mica granite to topaz lepidolite granite the most evolved topaz lepidolite granite has the highest bulk rock li rb cs f and p contents consistent with the highest contents of these elements and the lowest nb ta ratio in mica and the lowest zr hf ratio in zircon ta nb enrichment was closely related to the enrichment of volatile elements i e li f and p in the melt during magmatic evolution which raised the proportion of non bridging oxygens nbos in the melt the rims of zoned micas in the li mica and topaz lepidolite granites contain lower rb cs nb and ta and much lower f and w than the cores and or mantles indicating an exotic aqueous fluid during hydrothermal evolution some columbite group minerals may have formed from exotic aqueous fluids which were originally depleted in f rb cs nb ta and w but such fluids were not responsible for ta nb enrichment in the yashan granite the interaction of hydrothermal fluids with previously existing micas may have played an important role in leaching concentrating and transporting w fe and ti ta nb enrichment was associated with highly evolved magmas but w mineralization is closely related to hydrothermal fluid thus these magmatic and hydrothermal processes explain the diversity of w and ta nb mineralizations in the rare metal granites

zircon u pb molybdenite re os and muscovite ar ar isotopic dating of the xitian w sn polymetallic deposit eastern hunan province south china and its geological significance the xitian tungsten tin w sn polymetallic deposit located in eastern hunan province south china is a recently explored region containing one of the largest w sn deposits in the nanling w sn metallogenic province the mineral zones in this deposit comprise skarn greisen structurally altered rock and quartz vein types the deposit is mainly hosted by devonian dolomitic limestone at the contact with the xitian granite complex the xitian granite complex consists of indosinian late triassic 230 215 ma and yanshanian late jurassic early cretaceous 165 141 ma granites zircons from two samples of the xitian granite dated using laser ablation inductively coupled mass spectrometer la icpms u pb analysis yielded two ages of 225 6 1 3 ma and 151 8 1 4 ma representing the emplacement ages of two episodic intrusions of the xitian granite complex molybdenites separated from ore bearing quartz veins yielded a re os isochron age of 149 7 0 9 ma in excellent agreement with a weighted mean age of 150 3 0 5 ma two samples of muscovites from ore bearing greisens yielded 40ar 39ar plateau ages of 149 5 1 5 ma and 149 4 1 5 ma respectively these isotopic ages obtained from hydrothermal minerals are slightly younger than the zircon u pb age of 151 8 1 4 ma of the yanshanian granite in the xitian area indicating that the w sn mineralization is genetically related to the late jurassic magmatism the xitian deposit is a good example of the early yanshanian regional w sn ore forming event 160 150 ma in the nanling region the relatively high re contents 8 7 to 44 0 ppm average of 30 5 ppm in molybdenites suggest a mixture of mantle and crustal sources in the genesis of the ore forming fluids and melts based upon previous geochemical studies of early yanshanian granite and regional geology we argue that the xitian w sn polymetallic deposit can be attributed to back arc lithosphere extension in the region which was probably triggered by the break off of the flat slab of the palae pacific plate beneath the lithosphere

petrogenesis and tectonic setting of the early mesozoic xitian granitic pluton in the middle qin hang belt south china constraints from zircon u pb ages and bulk rock trace element and sr nd pb isotopic compositions abstract the xitian pluton in southeast hunan province is one of the early mesozoic indosinian granitic plutons in the south china block it is composed of biotite adamellite with k feldspar megacrysts biotite adamellite and biotite granite that have u pb zircon ages of 229 9 1 4 ma 223 6 1 3 ma and 224 0 1 4 ma respectively the indosinian granitoids in the xitian pluton belong to s type granites with highly radiogenic initial 87sr 86sr ratios 0 71397 0 71910 negative end t values ranging from 10 1 to 9 4 and old nd model ages 1858 1764 ma they are enriched in radiogenic pb isotopes with 206pb 204pb t ranging from 18 130 to 18 903 207pb 204pb t from 15 652 to 15 722 and 208pb 204pb t from 38 436 to 39 037 respectively these features indicate that the granitoidswithin the xitian pluton were formed from magmas generated by remelting of metapelite and metapsammite of the paleoproterozoic metamorphic basement at temperatures of ca 800 c with low oxygen fugacity the sr nd isotopic compositions of the rocks from xitian pluton indicate that the granitic magmas were mixed with less than 10 mantle derived magmas we suggest that the xitian pluton was emplaced in an extensional tectonic setting related to release of compressional stresses within the thickened crust during the early mesozoic

temporal and spatial relationships of granitic magmatism and w mineralization insights from the xingguo orefield south china abstract in south china extensive multi phase magmatism was accompanied by w dominated polymetallic mineralization the xingguo orefield of southern jiangxi province in the eastern part of the nanling region is one of the most important w dominated mineralized regions in south china there are more than ten w deposits within or surrounding the jiangbei complex including the huamei ao quartz vein type w deposit wo3 67 400 tons at a grade of 1 344 the yanqian skarn type w deposit wo3 16 000 tons at a grade of 0 365 and the zhangjiadi quartz vein and greisen type mo w deposit mo 31 806 tons at a grade of 0 1 and wo3 1746 tons at a grade of 0 353 the orebodies all occur at the contact between the jiangbei complex and the sinian metasandstone or carboniferous permian limestone the jiangbei complex consists of three lithologies medium to coarse grained biotite granite j 1 medium to fine grained biotite monzonitic granite j 2 and fine grained biotite monzonitic granite j 3 which have zircon u pb ages of 160 7 1 1 ma 156 3 0 9 ma and 153 3 0 8 ma respectively the associated yanqian huamei ao wangnipai and liujiazhuang deposits have molybdenite re os ages of 159 2 2 3 ma 157 1 1 3 ma 157 7 1 4 ma and 157 9 1 6 ma respectively a summary of available age dates of intrusions in the xingguo orefield indicates that the granitic magmatism lasted for 8 m y ca 160 153 ma whereas the w mineralization occurred in a relatively short period 159 155 ma corresponding in age to the episode of large scale mesozoic 165 150 ma mineralization in south china low end t values 10 2 13 0 of the jiangbei granitic rocks and low re contents of the molybdenite suggest that the w dominated ores and associated granites in the xingguo orefield were derived mainly from crustal magmas all three lithologies of the jiangbei complex have similar geochemical characteristics and are classified as high k calc alkaline and peraluminous s type granites the zr hf nb ta eu rb sr and lree hree ratios all correlate positively with the w contents of the rocks and reach their highest level in the phase ii granites we propose a magmatic metallogenic model in which w was concentrated by fractionation of crustally derived magmas of phase i and then deposited in skarn greisen and quartz vein type ores by both magmatic and hydrothermal processes

inhomogeneous distribution of ree in scheelite and dynamics of archaean hydrothermal systems mt charlotte and drysdale gold deposits western australia scheelite is a widespread accessory mineral in hydrothermal gold deposits and its rare earth element ree patterns and nd and sr isotopic compositions can be used to constrain the path and origin of the mineralising fluids and the age of the hydrothermal activity micro analyses by laser ablation high resolution inductively coupled mass spectroscopy and cathodoluminescence imaging reveal a very inhomogeneous distribution of the ree in single scheelite grains from the mt charlotte and drysdale archaean gold deposits in western australia two end member ree patterns are distinguished type i is middle ree mree enriched with no or minor positive eu anomaly whereas type ii is flat or mree depleted with a strong positive eu anomaly the chemical inhomogeneity of these scheelites is related to oscillatory zoning involving type i and type ii patterns with zone widths varying from below 1 to 200 m intra sectorial growth discontinuities syn crystallisation brittle deformation and variations in the relative growth velocities of crystallographically equivalent faces suggest a complex crystallisation history under dynamic hydraulic conditions the co existence of mree enriched and mree depleted patterns within single scheelite crystals can be explained by the precipitation of a mineral which strongly partitions mree relative to light and heavy ree scheelite itself has such characteristics as does fluorapatite which is locally abundant and has ree contents similar to that of scheelite in this context the systematic increase of the eu anomaly between type i and type ii patterns is produced by the difference between the partition coefficients of eu2 and eu3 and not by fluid mixing or redox reactions consequently the high positive eu anomaly typical of scheelite from gold ores may not necessarily be inherited from the hydrothermal fluid but may reflect processes occurring during ore deposition this case study demonstrates that in hydrothermal systems characterised by low ree concentrations in the fluid and by the precipitation of a ree rich mineral which strongly fractionates the ree the ree patterns of such a mineral will be highly sensitive to the dynamics of the hydrothermal system

fluid origin and migration of the huangshaping w mo polymetallic deposit south china geochemistry and 40ar 39ar geochronology of hydrothermal k feldspars abstract the huangshaping deposit is a world class w mo pb zn cu polymetallic deposit that formed during the jurassic magmatic event in the central nanling region south china in order to reveal the three dimensional development of mineralization and alteration in this complicated fluid rock system four typical hydrothermal k feldspar samples were collected from potassic alteration zones at different elevation levels around main w mo ore bodies followed by precise trace element analysis and 40 ar 39 ar dating the results show that these k feldspars have a pronounced lanthanide tetrad effect with high contents of ga ta nb u y and hree but low concentrations of ba sr eu and zr suggesting a hydrothermal origin additionally correlation between the ca cl k ratios and the apparent ages suggest that metasomatic fluids played an important role in the formation of the hydrothermal k feldspars the plateau 40 ar 39 ar ages which represent the timing of potassic alteration vary from 152 9 0 5 to 154 3 0 6 ma spatially showing younger trends from north to south and from shallow to deep these dates correspond to the previous published molybdenite re os data variations in different elevation levels which record the mineralization event with relatively older ages ranging from 153 8 to 159 4 ma combined with the spatial relation analysis among samples the fluid migration rates associated with the mineralization and alteration are calculated at 10 100 m ma 1 thus we propose a fluid downward migration model for the huangshaping polymetallic deposit

oxidation state of europium in scheelite tracking fluid rock interaction in gold deposits abstract we used xanes spectroscopy to measure the oxidation state of europium in situ at near m resolution in hydrothermal scheelite from the giant archean gold deposits of kalgoorlie western australia by combining these measurements with xrf imaging it is possible to distinguish inhomogeneities in eu2 eu3 ratios that developed during mineral precipitation from the effects of subsequent hydrothermal alteration and weathering thermodynamic analysis reveals that under the conditions typical of the formation of many au deposits the eu2 eu3 ratio in the hydrothermal fluid is highly sensitive to ph the range in ph calculated from the eu2 eu3 ratios in the analyzed scheelite corresponds to a maximum in au solubility under the ore forming conditions and suggests buffering of ph by the co2 aq rich fluid the primary heterogeneity of the karlgoorlie scheelite most likely results from ph oscillating between fluid and rock buffered conditions and reflects the dynamics of the hydrothermal system

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

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