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

geology and molybdenite re os age of the dahutang granite related veinlets disseminated tungsten ore field in the jiangxin province china this is a brief research report about the recently discovered and currently being explored dahutang tungsten deposit or ore field in northwestern jiangxi south central china the deposit is located south of the middle lower yangtze river valley cu au mo fe porphyry skarn belt yrb the mineralization is genetically associated with cretaceous porphyritic biotite granite and fine grained biotite granite and is mainly hosted within a neoproterozoic biotite granodiorite batholith the dahutang ore field comprises veinlets disseminated 95 of the total reserve breccia 4 and wolframite scheelite quartz vein 1 ore styles the mineralization and alteration are close to the pegmatite shell between the cretaceous porphyritic biotite granite and neoproterozoic biotite granodiorite and the three styles of ore bodies mentioned above are related to zoned hydrothermal alteration that includes greisenization k feldspar alteration silicification carbonatization chloritization and fluoritization arranged in time early to late and space bottom to top five samples of molybdenite from the three types of ores have been collected for re os dating the results show re os model ages ranging from 138 4 ma to 143 8 ma with an isochron age of 139 18 0 97 ma mswd 2 9 the quite low re content in molybdenite falls between 0 5 ppm and 7 8 ppm that is indicative of the upper crustal source this is quite different from molybdenites in the yrb cu au mo fe porphyry skarn deposits that contain between 53 ppm and 1169 ppm re indicating a mantle source the dahutang tungsten system is sub parallel with the yrb porphyry skarn cu au mo fe system both are situated in the north margin of the yangtze craton and have a close spatial temporal relationship this possibly indicates a comparable tectonic setting but different metal sources both systems are related to subduction of the paleo pacific plate beneath the eurasian continent in early cretaceous the cu au mo fe porphyry skarn ores are believed genetically related to granitoids derived from the subducting slab whereas the porphyry w deposits are associated with s type granitoids produced by remelting of the upper crust by heat from upwelling asthenoshere

geochronology and geochemistry of the granitoids and ore forming age in the xiaoyao tungsten polymetallic skarn deposit in the jiangnan massif tungsten belt china implications for their petrogenesis geodynamic setting and mineralization abstract the xiaoyao tungsten polymetallic skarn deposit in the eastern jiangnan massif of yangtze block is located at the contact between a granodiorite pluton and sinian cambrian limestone the intrusions in the tungsten rich district comprise the xiaoyao and other granodiorite plutons and granite porphyry dikes the age determinations by la icp ms u pb dating of zircons indicate that the granodiorite formed at 149 4 1 1 ma whereas the granite porphyry was emplaced at 133 2 0 7 ma re os dating of molybdenite from the skarn orebodies yielded a weighted average age of 148 7 2 3 ma n 5 these ages indicate that the tungsten mineralization is temporally related to the granodiorite the granodiorites are metaluminous a cnk 0 86 0 98 and in the high k calc alkaline series they contain hornblende and have a negative correlation between p2o5 and sio2 indicating that they are typical i type intrusions the granite porphyries exhibit high alkali contents na2o k2o 7 97 9 53 elevated feot feot mgo ratios 0 83 0 94 high concentrations of zr nb ce and y and high zr saturation temperatures average of 812 c thus they are geochemically similar to a type intrusions the initial 87sr 86sr and end t values range respectively from 0 7074 to 0 7083 and from 7 9 to 1 3 for the granodiorite and from 0 7008 to 0 7083 and from 6 3 to 4 7 for the granite porphyry in addition two stage nd model ages t2dm of 1 0 1 6 ga for the granodiorite and 1 3 1 4 ga for the granite porphyry indicate that the proterozoic crustal rocks of the shangxi group could have contributed to the xiaoyao magmas the rhenium contents of the molybdenite grains vary from 32 to 136 ppm suggesting that the molybdenum was derived mainly from a mixture of mantle and crustal sources based on the new geochemical data and regional geological investigations we propose that the late jurassic mineralization related i type granodiorite was derived from the neoproterozoic shangxi metamorphic rocks with some additional input of mantle material the magmatism was triggered by asthenospheric upwelling induced by slab tearing during oblique subduction of the paleo pacific plate beneath the south china block

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

origin of the muguayuan veinlet disseminated tungsten deposit south china constraints from in situ trace element analyses of scheelite abstract the late triassic muguayuan w deposit is located in the middle of the jiangnan orogen south china this deposit is characterized by veinlet disseminated w mineralization that developed in the sanxianba granitic porphyry stock the ore minerals are mainly scheelite with minor molybdenite and wolframite scheelite mineralization was closely related to greisenization and phyllic alteration and took place in two stages stage i involved scheelite wolframite molybdenite quartz veinlet and disseminated mineralization whereas stage ii resulted in scheelite quartz sericite veinlet mineralization sulfide and quartz calcite pyrite veinlets formed during the post ore stage scheelites from the two mineralization stages have different textures and compositions cathodoluminescence cl images of stage i scheelites reveal two generations of growth i a and i b stage i a scheelite is dark under cl with oscillatory zoning and has light rare earth element lree enriched chondrite normalized patterns negative eu anomalies and high total ree contents stage i b scheelite forms rim overgrowths on stage i a scheelite is bright under cl and shows positive eu anomalies and relatively low ree contents although stage ii scheelites are nearly uniform under cl they can be subdivided into two generations according to their ree systematics stage ii a scheelite yields middle ree mree enriched chondrite normalized patterns with negative eu anomalies whereas stage ii b scheelite has mree depleted patterns with positive eu anomalies minor amounts of apatite formed in both stages of mineralization stage i apatite contains 1370 1930 ppm mn and 97 7 127 ppm sr whereas stage ii apatite has lower mn 111 158 ppm and higher sr 2170 4690 ppm concentrations the distinct trace elements compositions of the scheelite and apatite from the two stages identify two ore forming fluids that had different origins and compositions the ore forming fluids in stage i a were relatively reduced magma derived fluids with high mo mn nb and ta and low sr fluid modeling shows that the initial fluids of stage i a were lree enriched with negative eu anomalies similar to the sanxianba granitic porphyry precipitation of early apatite and scheelite as well as plagioclase decomposition altered the fluid composition and led to relative depletions in ree nb and ta and increases of eu and sr in the stage i b fluids cooling of these fluids and the addition of recycled meteoric water led the fluids to become relatively oxidized and sr rich stage ii scheelite precipitated from these fluids precipitation of stage ii a scheelite resulted in the stage ii b fluids becoming progressively mree depleted extensive alteration especially greisenization and phyllic alteration led to plagioclase decomposition which provided the ca necessary for scheelite mineralization this process was important in generating the w mineralization in the muguayuan deposit and perhaps for other granite hosted veinlet disseminated scheelite deposits in the jiangnan orogen

initiation of subduction and the generation of slab melts in western and eastern mindanao philippines adakite found in both the eastern and western parts of mindanao island philippines is a rare rock type characterized by low heavy rare earth elements and y contents together with high sr y ratios and is considered to be the result of the melting of young subducted oceanic crust which leaves an eclogite residue pliocene quaternary adakites from western mindanao zamboanga peninsula are probably derived from the melting of the young miocene sulu sea crust which is currently subducting beneath zamboanga associated nb enriched basalts are thought to come from mantle metasomatized through interaction with adakitic melts in eastern mindanao pliocene quaternary cones and plugs of typical adakitic composition mark the trace of the philippine fault in surigao and north davao the underlying philippine sea crust is of eocene age and therefore cannot melt under normal subduction thermal conditions thermal models indicate that melting at the start of subduction can occur subduction of the philippine sea plate began 3 to 4 ma beneath eastern mindanao and probably accounts for the presence of adakites along the philippine fault

boundary lines within petrologic diagrams which use oxides of major and minor elements use of some petrologic diagrams applied to analyses of volcanic rocks is unnecessarily difficult due to lack of data for construction of discriminant lines between rock series coordinates are provided for sufficient points to enable accurate plotting of the boundary lines within seven diagrams viz 1 tas total alkalies na2o k2o vs sio2 2 k2o vs sio2 3 afm 4 jensen 5 ktp k2o tio2 p2o5 6 fms feo mgo vs sio2 and 7 taktip k2o na2o k2o vs tio2p2o5 different versions of these boundaries are collated to indicate their variable position and it is demonstrated that inter laboratory analytical precision suffices to account for almost all of their spread on the tas and k2o vs sio2 diagrams

geology geochronology and hf isotope geochemistry of the longtougang skarn and hydrothermal vein cu zn deposit north wuyi area southeastern china abstract the recently discovered longtougang skarn and hydrothermal vein cu zn deposit is located in the north wuyi area southeastern china the intrusions in the ore district comprise several small porphyritic biotite monzonite porphyritic monzonite and porphyritic granite plutons and dikes the mineralization is zoned from a lower zone of cu rich veins and cu zn skarns to an upper zone of banded zn pb mineralization in massive epidote altered rocks the deposit is associated with skarn potassic epidote greisen siliceous and carbonate alteration molybdenite from the cu rich veins yielded a re os isochron age of 153 6 3 9 ma which is consistent with u pb zircon ages of 154 0 1 3 ma for porphyritic monzonite 154 0 0 8 ma for porphyritic biotite monzonite and 152 0 0 8 ma for porphyritic granite geological observations suggest that the cu mineralization is genetically related to the porphyritic biotite monzonite and porphyritic monzonite all the zircons from intrusive rocks in the ore district are characterized by ehf t values between 13 41 and 4 38 and hf model ages tdm2 between 2054 and 1482 ma reflecting magmas derived mainly from a proterozoic crustal source molybdenite grains from the deposit have re values of 14 6 27 7 ppm indicative of a mixed mantle crust source the porphyry skarn abundant cu and hydrothermal vein type pb zn ag deposits in the north wuyi area are related to the late jurassic porphyritic granites and early cretaceous volcanism respectively the late jurassic mineralization related granites were derived from the crustal anatexis with some mantle input which was triggered by asthenospheric upwelling induced by slab tearing during oblique subduction of the paleo pacific plate beneath the south china block and the early cretaceous mineralization related granitoids mainly from crust material formed within a series of nne trending basins during margin parallel movement of the plate

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

magmatic evolution and related w mo mineralization in the larong deposit eastern tibet evidence from zircon u pb ages geochemistry and sr nd hf isotopes abstract the late cretaceous ca 92 ma larong porphyry w mo deposit 39 44 mt wo3 0 1541 is the first discovered giant w mo deposit in the leiwuqi zogang metallogenic belt sanjiang region multi stage granitoids including the dacite porphyry dp granodiorite porphyry gp biotite granite porphyry bgp monzogranite porphyry mp biotite granite bg and granite aplite ga have been identified in the larong deposit however the magmatic evolution and related w mo mineralization in this deposit are still poorly understood la icp ms zircon u pb dating of the dp gp bgp mp bg and ga yield weighted mean 206pb 238u ages of 214 0 0 7 ma 213 8 1 3 ma 104 4 0 9 ma 93 9 1 3 ma 91 7 0 5 ma and 36 2 0 6 ma respectively the late triassic dp and gp should be classified as peraluminous a cnk values of 0 95 1 57 s type granitoids they are characterized by pronounced negative end t values 10 01 to 13 92 and ehf t values 8 5 to 16 6 with old tdm2 nd and tdm2 hf ages 1 81 2 12 ga and 1 79 2 30 ga respectively indicating that the dp and gp were mainly derived from partial melting of ancient crustal materials after break off of the paleo tethyan oceanic slab the late cretaceous bgp mp and bg and late eocene ga have low a cnk ratios 0 92 1 06 but high sio2 70 57 77 34 and differentiation index di 87 55 98 06 similar to the characteristics of highly fractionated i type granite detailed elemental e g depletion in nb ta ti sr ba eu and p and isotopic data 87sr 86sr i 0 71192 0 72932 end t 11 81 to 9 11 ehf t 10 4 to 1 4 demonstrate that they were the result of magma mixing between ancient crust derived melts and mantle derived melts the bgp was produced during the final stage of bangong nujiang tethyan ocean bnto subduction the mp and bg were formed under a post collisional tectonic setting related to slab break off of the bnto and the ga was likely associated with delamination of the thickened eclogitic lower crust together with lithospheric mantle the w mo mineralization in the larong deposit is genetically associated with the mp with four favorable factors that can account for the formation of this deposit 1 high w background 2 multi stage magmatism 3 highly evolved relatively oxidized and f rich magmatic system and 4 sufficient calcium obtained by intense fluid rock interaction

geochemistry and evolution of ore forming fluids of the yueshan cu au skarn and vein type deposits anhui province south china abstract the yueshan mineral belt is geotectonically located at the centre of the changjiang deep fracture zone or depression of the lower yangtze platform two main types of ore deposits occur in the yueshan orefield cu au fe skarn deposits and cu mo au pb zn hydrothermal vein type deposits almost all deposits of economic interest are concentrated within and around the eastern and northern branches of the yueshan dioritic intrusion in the vicinity of the zongpu and wuhen intrusions there are many cu pb zn au s vein type and a few cu fe au skarn type occurrences fluid inclusion studies show that the ore forming fluids are characterised by a cl s na k chemical association hydrothermal activity associated with the above two deposit types was related to the yueshan intrusion the fluid salinity was high during the mineralisation processes and the fluid also underwent boiling and mixed with meteoric water in comparison the hydrothermal activity related to the zongpu and wuhen intrusions was characterised by low salinity fluids chlorine and sulphur species played an important role in the transport of ore forming components hydrogen and oxygen isotope data also suggest that the ore forming fluids in the yueshan mineral belt consisted of magmatic water mixed in various proportions with meteoric water the enrichment of ore forming components in the magmatic waters resulted from fluid melt partitioning the ore fluids of magmatic origin formed large cu au deposits whereas ore fluids of mixed magmatic meteoric origin formed small to medium sized deposits the sulphur isotopic composition of the skarn and vein type deposits varies from 11 3 to 19 2 and from 4 2 to 10 0 respectively these variations do not appear to have been resulted from changes of physicochemical conditions rather due to compositional variation of sulphur at the source s and by water rock interaction complex water rock interaction between the ore bearing magmatic fluids and sedimentary wall rocks was responsible for sulphur mixing lead and silicon isotopic compositions of the two deposit types and host rocks provide similar indications for the sources and evolution of the ore forming fluids hydrodynamic calculations show that magmatic ore forming fluids were channelled upwards into faults fractures and porous media with velocities of 1 4 m s 9 8 10 1 to 9 8 10 7 m s and 3 6 10 7 to 4 6 10 7 m s respectively a decrease of fluid migration velocity in porous media or tiny fractures in the contact zones between the intrusive rocks and the triassic sedimentary rocks led to the deposition of the ore forming components the major species responsible for cu transport are deduced to have been cucl cucl2 cucl32 and cucloh whereas au was transported as au2 hs 2s2 au hs 2 auhs and auh3sio4 complexes cooling and a decrease in chloride ion concentration caused by fluid boiling and mixing were the principal causes of cu deposition gold deposition was related to decrease of ph total sulphur concentration and fo2 which resulted from fluid boiling and mixing geological and geochemical characteristics of the two deposit types in the yueshan mineral belt suggest that there is a close genetic relationship with the dioritic magmatism geochronological data show that the magmatic activity and the mineralisation took place between 130 and 136 ma and represent a continuous process during the yanshanian time the cooling of the intrusions and the mineralisation event might have lasted about 6 ma the cooling rate of the magmatic intrusions was 80 to 120 c my 1 which permitted sufficient heat supply by magma to the ore forming system

multiple dating and tectonic setting of the early cretaceous xianglushan w deposit jiangxi province south china abstract the xianglushan w deposit in northwestern jiangxi province south china is one of numerous large size w deposits along the northern margin of the jiangnan massif the deposit comprises lenticular and stratiform like orebodies mainly along the contact between argillaceous limestone of the cambrian yangliugang formation and a biotite granite pluton the mineralization is zoned from proximal w greisen within the cupolas of the biotite granite through w skarn and sulfide scheelite bands near the pluton to distal quartz sulfide scheelite veins the granitic pluton and an aplitic dyke in the mining area contain zircon grains with u pb ages of 123 8 0 8 ma and 117 3 1 7 ma respectively six molybdenite samples collected from skarn ores yielded a re os weighted mean age of 125 5 0 7 ma and muscovite separates from greisen ores yielded a 40 ar 39 ar plateau age of 122 8 0 78 ma the molybdenite re os and muscovite ar ar ages are consistent with the zircon u pb age of the hosting granite the xianglushan deposit is formed by an early cretaceous w dominated polymetallic ore forming event in the jiangnan porphyry skarn w belt zircon from biotite granites in the xianglushan deposit has negative e hf t values generally from 5 7 to 3 1 with corresponding two stage hf model ages of 1363 1218 ma reflecting derivation of magmas from a crustal source molybdenite has re contents from 12 12 to 22 77 ppm indicative of a mixed crustal mantle source but with a dominantly crustal component a compilation of precise ages for magmatism and mineralization in the jiangnan porphyry skarn w belt shows that there are two stages of mineralization at 150 135 ma and 130 120 ma respectively integrated with published data our results suggest that the xianglushan w deposit formed in an extensional tectonic setting during the early cretaceous

zircon u pb geochronology and geochemistry of two episodes of granitoids from the northwestern zhejiang province se china implication for magmatic evolution and tectonic transition abstract granitoids 175 80 ma representing a prominent yanshanian jurassic to cretaceous magmatic event in south china widely intrude the precambrian crystalline basement and paleozoic strata here we report zircon u pb age data geochemical characteristics and sr nd isotopes of the late jurassic and early cretaceous granitoids from the northwestern zhejiang province zxb of southeastern china our results reveal two distinct episodes for the yanshanian magmatism the jiemeng and datongkeng granodiorites formed at 148 6 1 1 ma whereas the huangshitan jiuligang and ruhong aluminous a type granites were generated between 129 0 0 6 ma and 126 1 1 1 ma the two magmatic phases represent a tectonic transition from an active continental margin to post orogenic setting during the late jurassic ca 150 ma to early cretaceous ca 128 ma geochemically these intrusions are granodioritic to granitic in composition and show an affinity of s type and a type granitoids respectively the s type granodiorites of jiemeng and datongkeng are characterized by moderate sio 2 65 0 69 6 wt high k 2 o na 2 o 5 0 7 6 wt k 2 o na 2 o 1 2 1 5 zr 31 109 ppm sr 71 190 ppm and high field strength elements low to intermediate mg and moderate nb depletion the a type granites of huangshitan jiuligang and ruhong are characterized by high sio 2 72 7 77 2 wt k 2 o na 2 o 6 9 8 8 wt k 2 o na 2 o 1 3 2 1 fe t fe t mg ga 17 29 ppm 20 ppm commonly zr 96 197 ppm and sr 8 45 ppm with slight nb depletion the s type granodiorites have higher mg a nk sr sr ba sr y la yb n and lree hree and lower sio 2 k 2 o na 2 o ga and zr with weak negative eu anomalies compared to those of the a type granites with negative eu anomalies all these rocks show y nb ratios 1 2 high initial 87 sr 86 sr i sr ratios and low e nd t and are depleted in nb ti and sr indicating crustal origin with subduction zone signatures we suggested that the zxb s type granitic bodies might have been derived from the mesoproterozoic metamorphic basement rocks through partial melting induced by mantle derived magma followed by limited fractional crystallization the zxb aluminous a type granites were also derived from a similar magma source but underwent fractional crystallization at higher crustal levels the a type granites in the zxb correlate with a post orogenic tectonic setting a geological comparison between zxb and adjacent areas indicates that the geochemical features of the zxb a type granites are comparable with the baijuhuajian a type granites and also the adjacent areas a type granites but are distinct from the late cretaceous a type granites 105 90 ma distributed along the southeastern coastal area of south china we correlate the formation of the zxb s type granodiorites to inland compression associated with the subduction and collision of the paleo pacific plate in the late jurassic 170 145 ma in contrast the a type granites formed under a post orogenic setting during the early cretaceous period 145 120 ma resulting from lithospheric thinning and continent extension accompanied by slab roll back of the paleo pacific plate following the subduction collision event

shrimp zircon u pb geochronological and whole rock geochemical evidence for an early neoproterozoic sibaoan magmatic arc along the southeastern margin of the yangtze block abstract it has been generally accepted that the south china block was formed through amalgamation of the yangtze and cathaysia blocks during the proterozoic sibaoan orogenesis but the timing and kinematics of the sibao orogeny are still not well constrained we report here shrimp u pb zircon geochronological and geochemical data for the taohong and xiqiu tonalite granodiorite stocks from northeastern zhejiang southeastern margin of the yangtze block our data demonstrate that these rocks dated at 913 15 ma and 905 14 ma are typical amphibole rich calc alkaline granitoids formed in an active continental margin combined with previously reported isotopic dates for the 1 0 ga ophiolites and 0 97 ga adakitic rocks from northeastern jiangxi the timing of the sibao orogenesis is thus believed to be between 1 0 and 0 9 ga in its eastern segment it is noted that the sibao orogeny in south china is in general contemporaneous with some other early neoproterozoic 1 0 0 9 ga orogenic belts such as the eastern ghats belt of india and the rayner province in east antarctica indicating that the assembly of rodinia was not finally completed until 0 9 ga

implications of aplite dykes for mineralization in the late cretaceous vein type xiuwacu w mo deposit in the southern yidun terrane se tibetan plateau abstract the xiuwacu w mo deposit with 24 000 t of mo and 23 000 t of wo3 is located in the southern yidun terrane syt sw china being the only quartz vein type w mo deposit in the region in the deposit aplite dykes are spatiotemporally associated with w mo orebodies however their genetic relationship remains unclear here we present the result of a study of the petrography zircon u pb dating whole rock geochemistry sr nd pb isotopes zircon trace elements and hf isotopes of the aplite dykes the xiuwacu aplites are emplaced at 78 7 1 9 ma and have high silica alkali rich and metaluminous peraluminous compositions they are enriched in light rare elements lrees large ion lithophile elements liles u rb th and depleted in heavy rare earth elements hrees high field strength elements hfses nb p ti and with strong negative eu anomalies eu 0 09 0 58 average 0 36 the aplites have an average estimated crystallization temperature of 700 c and relatively low magmatic oxygen fugacity log fo2 33 2 to 16 1 average 26 1 which is substantially lower than the late triassic biotite granite but similar to the late cretaceous porphyritic monzogranite in the deposit all the aplite samples have varying 87sr 86sr i ratios 0 701240 0 719258 negative end t values 10 33 to 3 22 negative ehf t values 5 3 to 3 3 and ancient two stage hf depleted mantle model ages tdm2 hf 1886 2070 ma these geochemical characteristics demonstrate that the aplite dykes were formed by the partial melting of the ancient lower crust under an extensional setting which was triggered by the nw se ward subduction of the neo tethys ocean slab during the late cretaceous the ancient lower crust is interpreted to have provided the main source of w and mo for the xiuwacu deposit the enrichment of w and mo by fractional crystallization of the aplite magmas played an important role in concentrating w mo during the formation of the deposit aplite dykes have also been found in several late cretaceous mo and or cu deposits in the syt considering their common occurrence within the orebodies the aplite dykes could be an effective prospecting indicator

a fluid inclusion study of the porphyry greisen tungsten molybdenum deposit at mount pleasant new brunswick canada homogenization temperatures and salinity data are presented for fluid inclusions from hydrothermal gangue minerals quartz and fluorite associated with porphyry wolframite molybdenite arsenopyrite sphaleritebismuth chalcopyrite cassiterite mineralization within the fire tower ore zone mt pleasant new brunswick the data indicate that ore mineral precipitation occurred within a temperature range of 260 to 490 c from moderate to high salinity 10 42 wt nacl equivalent aqueous fluids two stages of hydrothermal activity characterized by high 30 wt nacl equivalent salinity fluids are recognized one which occurred at relatively high temperature 350 490 c and one which took place at lower temperature 180 250 c the high salinity high temperature stage is interpreted to be the result of resurgent boiling dilution of these early fluids by convecting meteoric water resulted in low to moderate salinity fluids which dominate the inclusion population the low temperature high salinity fluid inclusions are interpreted to represent late residual fluids derived from boiling which occurred as a result of a change in the pressure regime from dominantly lithostatic to hydrostatic conditions

dehydration melting and water saturated melting of basaltic and andesitic greenstones and amphibolites at 1 3 and 6 9 kb

origin and evolution of ore forming fluids of the larong w mo deposit eastern tibet constraints from fluid inclusions h o isotopes and scheelite geochemistry abstract the larong porphyry w mo deposit formed in the main collisional orogenic stage of lhasa and qiangtang terranes is the first discovered giant w mo deposit in the leiwuqi zogang metallogenic belt sanjiang region the w mo mineralization occurs as veins and stock works mainly hosted in the granodiorite porphyry monzogranite porphyry biotite granite porphyry and surrounding schist four types of fluid inclusions fis including pc type pure vapor co2 c type co2 h2o w type aqueous two phase and l type pure liquid h2o fis have been identified from stage i quartz scheelite alkaline feldspar veins stage ii including three sub stages quartz molybdenite pyrite chalcopyrite veins and stage iii quartz calcite pyrite veins the total homogenization temperatures of fis vary widely 187 437 c with multiple peaks indicating multistage fluid activities the ore forming fluids of the main mineralization stages are characterized by co2 enrichment high medium temperature 270 440 c and medium low salinity 2 4 14 4 wt nacl equiv the homogenization temperature of w type inclusions is obviously higher than that of c type inclusions and the salinity is relatively lower implying multiple immiscibility of fluids with continuous escape of co2 h o isotopic compositions suggest that the primary ore forming fluids dominantly originated from magma water mo concentrations and eu values in scheelite indicate a decreasing trend of redox state of ore fluids from stage i to stage ii to stage iii the relatively higher temperature co2 rich and oxidized fluids gradually evolved into relatively lower temperature co2 poor and reduced fluids here we propose that the decrease of temperature and oxygen fugacity and increase of s2 activity and ph values of the ore fluids caused by continuous fluid rock interaction and loss of co2 could account for the successive mineralization of w and mo at the larong deposit

the logtung large tonnage low grade w scheelite mo porphyry deposit south central yukon territory mineralization is related to multiple felsic intrusions since mineralization is contained in fractures 95 rather than being disseminated logtung is not a skarn deposit the principal reason is that the reaction skarn host rocks which were derived from calcareous shales interbedded with graphitic quartzites are carbonate poor and competent hence permeable mineralization formed in permeability created by hydraulic fracturing and not by replacement logtung shows a scheme of several phases 4 of mineralization related to multiple intrusions which is similar to that which is so important in for example the evolution of the climax and urad henderson mo systems the logtung deposit shows many similarities to porphyry mo deposits in the western cordillera and may be classed as a porphyry w scheelite mo deposit with a w mo ratio of 3 3 1 0 the principal reasons are that mineralization is spatially associated with porphyritic intrusive phases and that much of the mineralization occurs as typical porphyry style crackle breccias modified journal abstract

geochronology and petrogenesis of the qibaoshan cu polymetallic deposit northeastern hunan province implications for the metal source and metallogenic evolution of the intracontinental qinhang cu polymetallic belt south china abstract the recently recognized qinhang metallogenic belt qhmb is an economically important intracontinental mesozoic porphyry skarn cu polymetallic metallogenic belt in south china however the origin of the ore bearing magma and the major factors controlling the different metal assemblages in the qhmb are still unclear the qibaoshan deposit is a large cu au pb zn ag fe deposit located at the juncture between the northern and central parts of the qhmb in this study new zircon u pb ages hf o isotopic data molybdenite re os ages and whole rock geochemical data are combined to constrain the timing of the mineralization and the origin and petrogenesis of the ore bearing porphyry in the qibaoshan deposit the ages obtained from both zircon u pb and molybdenite re os dating fall in the late jurassic between 152 7 and 148 3 ma revealing that this deposit is significantly younger than previously estimated 227 184 ma the qibaoshan ore bearing quartz porphyry shows variable negative zircon ehf t values 14 8 to 5 5 high 18o values 8 4 to 10 8 and high mg values 69 1 to 73 0 indicating that it formed via the partial melting of ancient crust triggered by the injection of mantle derived magma zircon hf o isotopic modeling of the mixing of two extreme endmembers indicates that the magmatic source comprised 70 80 reworked ancient crustal components and 20 30 depleted mantle components based on comparisons with other ore bearing porphyries in the qhmb a magmatic source dominated by crust derived material and relatively low oxygen fugacities fmq 1 8 to fmq 0 8 was responsible for the high pb zn cu ratio in the qibaoshan deposit and the pb zn and ag were mainly derived from the reworked ancient crust although four analyses of inherited neoproterozoic zircons 800 ma have variable positive ehf t values 0 72 to 11 21 indicating that neoproterozoic juvenile crust was involved in the formation of the qibaoshan ore bearing quartz porphyry the relatively low oxygen fugacities fmq 1 2 to fmq 0 4 of the parent magma of these inherited zircons suggest that this parent magma could not have provided significant metallic cu for mineralization in the qibaoshan cu polymetallic deposit therefore the metallic cu in the qibaoshan cu polymetallic deposit was probably provided by the injection of the mantle derived magma because ore forming magmas with relatively low oxygen fugacities have low au solubility the large au mineralization in the qibaoshan deposit may be related to high background values of au in this area our data integrated with regional petrogeochemical data indicate that the magmatic source exerted a first order control on the different metal assemblages in the deposits in the qhmb

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

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

some new data on the genesis of the linghou cu pb zn polymetallic deposit based on the study of fluid inclusions and c h o s pb isotopes abstract the linghou deposit located near hangzhou city of zhejiang province eastern china is a medium sized polymetallic sulfide deposit associated with granitic intrusion this deposit is structurally and lithologically controlled and commonly characterized by ore veins or irregular ore lenses in this deposit two mineralization events were identified of which the former produced the cu au ag orebodies while the latter formed pb zn cu orebodies silicification and calc silicate skarn type phyllic and carbonate alternation are four principal types of hydrothermal alteration the early cu au ag and late pb zn cu mineralizations are characterized by quartz sericite pyrite chalcopyrite bornite au ag minerals magnetite molybdenite and calcite dolomite sphalerite pyrite chalcopyrite galena respectively calcite clusters and calcite quartz vein are formed during the late hydrothermal stage the nacl h 2 o co 2 system fluid coexisting with nacl h 2 o system fluid and showing the similar homogenization temperatures 385 c and 356 c respectively and different salinities 16 89 21 68 wt nacl eqv and 7 70 15 53 wt nacl eqv suggests that fluid immiscibility occurred during the cu au ag mineralization stage and might have given rise to the ore metal precipitation the ore forming fluid of the pb zn cu mineralization mainly belongs to the nacl h 2 o co 2 system of high temperature 401 c and mid high salinity 10 79 wt nacl eqv fluids trapped in the quartz chalcopyrite vein cu au ag ores pb zn cu ores and calcite clusters yielded 18 o h2o and d values varying from 5 54 to 13 11 and from 71 8 to 105 1 respectively indicating that magmatic fluids may have played an important role in two mineralization events the 13 c pdb values of the calcite change from 2 78 to 4 63 indicating that the co 3 2 or co 2 in the ore forming fluid of the pb zn cu mineralization was mainly sourced from the magmatic system although dissolution of minor marine carbonate may have also occurred during the ore forming processes the sulfide minerals have homogeneous lead isotopic compositions with 206 pb 204 pb ranging from 17 958 to 18 587 207 pb 204 pb ranging from 15 549 to 15 701 and 208 pb 204 pb ranging from 37 976 to 39 052 indicating that metallic elements of the linghou deposit came from a mixed source involving mantle and crustal components based on geological evidence fluid inclusions and h o c s pb isotopic data the linghou polymetallic deposit is interpreted as a high temperature skarn carbonate replacement type two types of mineralization are both related to the magmatic hydrothermal system with the cu au ag mineralization having a close relationship with granodiorite

alpine olivine and titanian clinohumite bearing assemblages in the erro tobbio peridotite voltri massif nw italy the microstructures in the erro tobbio peridotite indicate several stages of recrystallization of olivine titanian clinohumite bearing assemblages the development of these assemblages is closely associated with serpentinite mylonites in which they occur in shear bands and foliations and are inferred to have grown synkinematically in veins and as post kinematic radial aggregates in the peridotite wall rock adjacent to these mylonites the same assemblages have recrystallized statically at the expense of original olivine and pyroxenes mesh textured chrysotile and antigorite veins in addition the olivine bearing assemblage occurs in widespread vein systems the brittle deformation of the peridotite resulting in the development of these vein systems is closely related to ductile deformation of metagabbroic dykes in the peridotite although early metasomatism resulted in extensive rodingitization of the gabbros some dykes show an eclogitic assemblage of na clinopyroxene garnet chloritoid chlorite f talc these observations the microstructures and the mineral chemistry all suggest that the assemblages in the ultramafic rocks and metagabbros developed during a prograde evolution towards high pressures 13 16 kbar 450 550 c and during subsequent decompression this metamorphic evolution is considered to be related to late cretaceous intraoceanic subduction in the alps apennine system and closure of the piedmont ligurian basin

accessory mineral chemistry as a monitor of petrogenetic and metallogenetic processes a comparative study of zircon and apatite from wushan cu and zhuxiling w mo mineralization related granitoids abstract in this study we explore the chemistry of accessory apatite and zircon as tools to monitor the petrogenetic and metallogenetic processes involved in the formation of the wushan cu and zhuxiling w mo mineralization related granodiorite porphyry the wushan granitoids are metaluminous with a cnk of 0 88 1 01 and the zhuxiling intrusions are weakly peraluminous with higher a cnk values 1 02 1 12 the wushan granitoids have end t values of 4 6 to 4 7 which combined with the relatively elevated mg values 57 62 and adakitic features high sr y ratios of 51 60 indicate that they were derived from melting of a thickened lower crust of the yangtze block with addition of small amounts of mantle components compared to the wushan granitoids the zhuxiling granitoids have relatively high 87sr 86sr i 0 70945 0 70951 and low end t values 5 9 to 6 3 and zircon ehf t values 3 8 to 9 0 suggesting their derivation dominantly from partial melting of the neoproterozoic crust the apatites from the zhuxiling samples are characterized by relatively high mno and feo variable y and low ce which is consistent with the weakly peraluminous feature of whole rock chemistry these apatites show notable depletion of th and lree with a lower la sm n ratio 0 74 1 44 and la yb n ratio 6 2 17 9 relative to those of the host rock 3 04 3 61 and 19 1 23 4 respectively suggesting early crystallization of some lree and th enriched minerals such as allanite monazite before apatite crystallization the steep trend of ce sm versus yb gd ratios shown by zircons from the zhuxiling granitoids suggests that the crystallization of zircon is affected by the crystallization of titanite and apatite thus the crystallization sequence of accessory minerals in the zhuxiling intrusion is allanite apatite titanite and zircon the apatites from the wushan granitoids however show strongly lree enriched ree patterns with weak negative eu anomalies which indicate minor feldspar fractionation and mildly magmatic differentiation the flat trend of ce sm versus yb gd ratios shown by zircon from the wushan pluton indicates that its ree composition is affected by hornblende saturation zircon grains from the metaluminous wushan granitoids exhibit remarkably higher ce4 ce3 ratios and weaker eu eu anomalies than those of the peraluminous zhuxiling samples and the apatites from the wushan samples show higher eu eu 0 55 0 62 and lower ce ce 0 91 1 04 and mno 0 05 0 09 compared to those of the zhuxiling pluton with eu eu 0 41 0 50 ce ce 1 06 1 11 and mno 0 15 0 18 respectively the apatite and zircon chemistry suggest that the cu bearing granitoid formed at an oxygen fugacity higher than the w bearing granitoid which agrees with the fact that the wushan granitoids show whole rock fe3 fe2 ratios higher than the zhuxiling granitoids in addition apatites from the wushan intrusion show enrichment of cl and higher f cl ratios compared to those of the zhuxiling samples suggesting that a water rich parental magma with relatively high cl content is favourable for copper mineralization this case study shows that apatite and zircon chemistry could reflect the geochemical characteristics of their host rock and magma evolution moreover they provide insights into the oxidation state halogen fugacity and magma differentiation of the magmatic system which are key factors for mineralization our data suggest that magma associated with cu mineralization is relatively oxidizing chlorine enriched and less fractionated compared to w bearing magma

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

sequential deformation from serpentinite mylonite to metasomatic rocks along the sashu fault sw japan the deformation of serpentinites along the sashu fault saganoseki peninsula sw japan involved both mylonitization and brecciation the brecciation was accompanied by metasomatism and the metasomatized rocks record additional ductile deformation serpentinite mylonite is composed mainly of antigorite with minor magnetite and cr spinel foliation and lineation in this rock type are defined by the shape preferred orientation of antigorite and the alignment of fine grained magnetite and carbonate minerals the antigorite also shows a lattice preferred orientation lpo as measured with a universal stage with c axes oriented near perpendicular to the foliation and b axes oriented parallel to the lineation brecciation is concentrated in the reaction zone along the boundary between serpentinites and surrounding country rocks talc and chlorite schists developed in this zone as a result of associated metasomatism and deformation consequently they contain composite planar fabrics and drag folds the breccias themselves are composed of serpentinite fragments cut by veins of calcite and talc analyses of fluid inclusions in calcite from the breccia indicate that brecciation occurred at 200 300 c at depths of 3 8 11 8 km metasomatic reactions particularly the formation of talc contributed to weakening of this serpentinite bearing fault zone

linkage of distal vein type au mineralization in carbonate rocks with cu au skarn mineralization in the fengshan area eastern china mineralogy and stable isotope geochemistry abstract numerous limestone hosted vein type au deposits 12 million tonnes at 5 0 g t au are located peripheral to cu au skarn deposits around the late jurassic granodiorite intrusions in the fengshan area middle lower yangtze river metallogenic belt eastern china both the cu au skarn and distal vein type au deposits have a complex mineral assemblage consisting of base metal sulfides sulfosalts and au ag tl telluride minerals in the cu au skarn deposits grains of electrum au ag tellurides hessite and petzite coexist with bi te minerals native bismuth tetradymite phase c and aikinite sulfides chalcopyrite sphalerite and galena occurring as grain aggregates or veinlets in the distal vein type au deposits fine grained au ag tl tellurides calaverite petzite hessite and tl bearing au telluride occur as ore minerals in assemblages of sulfides and carbonate minerals the mineralogical bi te signature characterizes the skarn assemblages while the te tl signature is typical of the distal vein type au mineralization textural relations and mineral assemblages allow the recognition of five generations of hydrothermal carbonate 1 cu sulfides and tellurides bearing calcite assemblages 2 sphalerite galena and tellurides bearing dolomite assemblages 3 sericite quartz and tellurides bearing carbonate veinlets 4 realgar and fluorite bearing carbonate veinlets 5 pure calcite veinlets electron microprobe analysis indicates that the tellurides bearing ore related carbonate contains variable mn content up to 80 mol mnco3 the c o isotope compositions of carbonate from the cu au skarn mineralization to the carbonate replacement pb zn and distal vein type au mineralization and to the post ore realgar bearing veinlets in the country rocks display a tendency towards heavier isotopic compositions with time which could be best interpreted as the effect of fluid rock interaction between magmatic fluid and the triassic carbonate host rocks new s isotope data on sulfate minerals anhydrite gypsum and celestite and c o isotopic data suggest a common magmatic fluid source for both skarn and distal vein type mineralization

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

a new model for porphyry w mineralization in a world class tungsten metallogenic belt abstract the dongyuan deposit in the recently identified world class porphyry skarn w metallogenic belt east jiangnan orogen china is characterized by a set of nearly parallel and horizontal multi cycle orebodies within cupolas of porphyritic granodiorite almost every orebody from the top to the bottom shows similar vertical changes in vein morphology and mineral assemblage from 1 cm quartz feldspar scheelite calcite veins to 1 2 cm quartz feldspar muscovite scheelite veins to 2 5 cm quartz feldspar muscovite scheelite veins to 5 cm quartz veins from the bottom to the top of each orebody in every cycle the mole number of aliv in k feldspar decreases the concentrations of mn2 in calcite increases and the mole number of oh in muscovite decreases these changes reflect repetitive fluctuations in the concentrations of major elements that were involved in the precipitation of minerals as well as the physicochemical conditions of fluids during vein formation in the multi cycle orebodies the concentrations of mo are obviously lower in pyrite from the middle orebodies than in the top and bottom orebodies our data indicate that the ore forming fluids were sourced from multi batch fluids that were exsolved from magma the lree hree ratios in the scheelite decrease from the upper to lower orebodies similar trends are found within a single orebody from the top to the bottom of veins these trends were due to feldspar fractionation in the magmas and ore forming fluids respectively because the crystallization of feldspar tends to capture lrees therefore the following model is proposed for the formation of the dongyuan porphyry w deposit the magma crystallized first at the roof of the intrusion causing the underlying magmas to become oversaturated in h2o the exsolved h2o then accumulated at the boundary between the crystallized upper part and the underlying magmas as fluid pressures increased cracks formed in the overlying crystallized granodiorite and as a consequence the first cycle of vein networks was formed this process was repeated as the interface between magma and crystallized rock moved downwards thus forming the multi cycle w orebodies that are embedded in the pluton

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

comparative geochemical study of scheelite from the shizhuyuan and xianglushan tungsten skarn deposits south china implications for scheelite mineralization abstract scheelite has been analyzed from the shizhuyuan and the xianglushan world class w deposits from the nanling w sn region and jiangnan w belt respectively the shizhuyuan deposit consists of proximal skarn and greisen w sn mo bi and distal pb zn ag veins the xianglushan deposit contains layer like sulfide scheelite and skarn w orebodies on granite cupolas overprinted by w greisen veins scheelite in skarn ores from the shizhuyuan contains higher concentrations of mo than those in the sulfide scheelite and skarn ores from the xianglushan deposit reflecting differences between oxidizing and reducing magmatic hydrothermal fluids under oxidizing conditions w is accompanied by mo partitions into exsolved fluids to form w mo garnet skarns whereas under reducing conditions little mo is carried by exsolved fluids to form w pyroxene skarns trace element patterns of scheelite from both deposits show negative ba sr zr and ti and positive ta anomalies rare earth element ree patterns of scheelite within skarns from the shizhuyuan deposit have negatively inclined and flat m type tetrad patterns and scheelite from the greisens displays flat and positively inclined m type tetrad patterns we infer that the fluids formed scheelite within the w skarns and greisens inherited parental magma trace element and ree characteristics depleted ba sr zr and ti enriched ta negative eu anomalies and tetrad effects whereas scheelite from sulfide scheelite veins and skarns of the xianglushan deposit also has w and mw type tetrad ree patterns the w type tetrad ree patterns are complementary to ree patterns from the renjiashan granite and the mw type tetrad ree patterns occur during a single evolutionary stage within a complex hydrothermal environment sulfide mineralization can form after or before w skarns the former like shizhuyuan deposit and the latter like xianglushan deposit the formation conditions of the latter included reducing conditions and sulfide firstly supersaturated in the melt resulting in sulfide drops which carried w aggregated on the cupolas w skarns and greisens in both deposits underwent generally successive processes related to water supersaturation in the melt following a temperature decrease and crystallization bubbles carried material changing from si and metal to si oxide complexes

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

granite related yangjiashan tungsten deposit southern china the yangjiashan scheelite bearing deposit 38 663 metric tons of wo3 with an average ore grade of 0 70 wo3 is hosted in quartz veins in a biotite monzogranite intrusion and surrounding slate in the xiangzhong metallogenic province of southern china the monzogranite has a zircon shrimp u pb age of 406 6 2 8 ma 2 n 20 mswd 1 4 cassiterite coexisting with scheelite yields a weighted mean 206pb 238u age of 409 8 5 9 ma 2 n 30 mswd 0 20 and molybdenite intergrown with scheelite yields a weighted mean re os age of 404 2 3 2 ma 2 n 3 mswd 0 10 these results suggest that the yangjiashan tungsten deposit is temporally related to the devonian intrusion the d and calculated 18oh2o values of quartz intergrown with scheelite range from 87 to 68 and 1 2 to 3 4 respectively sulfides have a narrow range of 34s values of 2 9 to 0 7 with an average value of 1 6 n 16 the integration of geological stable isotope and geochronological data combined with the quartz muscovite greisen style of ore supports a magmatic hydrothermal origin for the tungsten mineralization compared to the more common tungsten skarn quartz wolframite vein and porphyry tungsten deposits as well as orogenic gold deposits worldwide the yangjiashan tungsten deposit is an unusual example of a granite related gold poor scheelite bearing quartz vein type of deposit the calcium needed for the formation of scheelite is derived from the sericitization of calcic plagioclase in the monzogranite and ca bearing psammitic country rocks and the relatively high ph reduced and ca rich mineralizing fluid may be the main reasons for the formation of scheelite rather than wolframite at yangjiashan

origin of the granites and related sn and pb zn polymetallic ore deposits in the pengshan district jiangxi province south china constraints from geochronology geochemistry mineral chemistry and sr nd hf pb s isotopes the pengshan sn and pb zn polymetallic deposits are located in the south margin of the jiujiang ruichang jiurui district of the middle lower yangtze river metallogenic belt in south china four large deposits include huangjinwa zengjialong jianfengpo and zhangshiba the former three are sn dominant deposits which occur as stratiform orebodies in the contact zones of the pengshan granites and within the country rock strata whereas zhangshiba consists of stratiform pb zn orebodies within the precambrian metasedimentary strata in this study we present results on zircon u pb ages major and trace elements and mineral chemistry as well as sr nd hf isotope data of the granites pb and s isotopes of both the sn dominant and pb zn dominant deposits and u pb dating of cassiterite from the pengshan district shrimp and la icp ms zircon u pb dating shows that the pengshan granites were emplaced in the early cretaceous 129 128 ma which is in good agreement with the u pb dating 130 128 ma of cassiterite from the jianfengpo sn deposit the pengshan granites consist mainly of weakly peraluminous highly fractionated i type affinity granitic rocks detailed elemental and isotopic data suggest that the granites formed by partial melting of mesoproterozoic metamorphic basement materials with minor input of mantle derived melts the mineral chemistry of biotite demonstrates that the pengshan granitic magma had a low oxygen fugacity thereby precluding the tin dominantly partitioning into the rock forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages sulfur isotopes show a relatively heavy sulfur isotopic composition from 5 8 to 17 6 and no difference for sulfur isotopes between the sn deposits 5 8 13 4 huangjinwa zengjialong jianfengpo and the pb zn deposit mostly 7 1 13 0 except for one 17 6 zhangshiba the sulfur isotope data of pyrite from the host sedimentary rocks show relatively higher 34s values of 22 7 28 7 lead isotopes indicate that the granites have higher 206pb 204pb 207pb 204pb and 208pb 204pb ratios than the host precambrian metasedimentary rocks and the sulfide minerals from the orebodies fall in between them again there is no difference for pb isotopes between the sn deposits huangjinwa zengjialong jianfengpo and the zhangshiba pb zn deposit the coincidence in s and pb isotope compositions for sn and pb zn deposits suggests that similar sources for these mineralization possibly derived from a mixed source of the granitic magmas and the precambrian metasedimentary rocks these data therefore favor of a magmatic hydrothermal origin for both the sn and pb zn polymetallic mineralization in the pengshan district

late cretaceous granitic magmatism and sn mineralization in the giant yinyan porphyry tin deposit south china constraints from zircon and cassiterite u pb and molybdenite re os geochronology the yinyan porphyry tin deposit in western guangdong is spatially associated with quartz porphyry and granite porphyry la icp ms zircon u pb dating defined an emplacement age of 78 5 0 4 ma for the quartz porphyry and 79 2 0 9 ma for the granite porphyry la icp ms cassiterite u pb dating yielded tera wasserburg lower intercept ages of 78 5 0 6 78 6 1 2 and 78 2 0 7 ma for cassiterite from a cassiterite sulfide vein cassiterite sulfide ore and a cassiterite topaz quartz stringer respectively re os dating of molybdenite from seven different veins yielded an isochron age of 77 0 0 5 ma all these new age data are indistinguishable within analytical uncertainty and therefore indicate a genetic relationship between the sn mineralization and the porphyry magmatism in the yinyan deposit the ree tetrad effect and very low nb ta and zr hf ratios indicate that the quartz porphyry and the granite porphyry are highly evolved the u pb dated cassiterite is enriched in fe w and u and in high field strength elements hfses such as zr hf nb and ta the high fe nb and ta contents may be responsible for the dark luminescence of cassiterite in cl images the zr hf ratio of cassiterite may potentially be used to distinguish the mineralization type cassiterite from pegmatites has lower zr hf ratios 5 6 in comparison with granite greisen related 9 30 cassiterite cassiterite from the early hydrothermal stage typically contains higher amounts of ti nb ta zr and hf than that from the late hydrothermal stage in combination with published geochronological data of other sn w deposits in the western guangdong province two sn w metallogenic events at ca 85 and 77 80 ma have been identified these two metallogenic events are part of a larger scale 75 100 ma sn w mineralization event in south china which we suggest was probably related to the subduction of the neo tethyan oceanic plate

the lower changjiang yangzi yangtze river metallogenic belt east central china intrusion and wall rock hosted cu fe au mo zn pb ag deposits abstract the lower valley of changjiang from wuhan of the hubei province in the west to zhenjiang of the jiangsu province in the east contains more than 200 polymetallic cu fe au mo zn pb ag deposits and is one of the most important metallogenic belts in china this metallogenic belt situated at the northern margin of the yangzi craton and bordered by the dabieshan ultrahigh pressure metamorphic belt to the north consists mainly of cambrian triassic marine clastic sedimentary rocks and carbonate and evaporite rocks which overlay a precambrian basement and are intruded by yanshanian 205 to 64 ma granitoid intrusions and subvolcanic complexes repeated tectonism from late proterozoic to triassic resulted in extensively developed networks of faults and folds involving the cambrian triassic sedimentary strata and the precambrian basement the yanshanian granitoid intrusions and subvolcanic complexes in the lower changjiang metallogenic belt are characterized by whole rock 18 o of 8 to 10 initial 87 sr 86 sr of 0 704 to 0 708 and ndt from 10 to 17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials also the yanshanian granitoids exhibit eastward younging and increase in alkalinity i e from older calc alkaline in the west to younger subalkaline alkaline in the east which are related to oblique collision between the yangzi and sino korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes most polymetallic deposits in the lower changjiang metallogenic belt are clustered in seven districts where the yanshanian magmatism is particularly extensive from west to east edong jiurui anqing guichi luzhong tongling ningwu and ningzhen mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits orebodies in yanshanian granitoid intrusions skarn orebodies at the contact zones between the yanshanian intrusions and late paleozoic early mesozoic sedimentary rocks and stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata the most important host sedimentary strata are the middle carboniferous huanglong formation lower permian and lower middle triassic carbonate and evaporite rocks the intrusion hosted and skarn orebodies exhibit well developed zonation in alteration assemblages metal contents and isotopic compositions within individual deposits and apparently formed from hydrothermal activities related to the yanshanian magmatism the stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano sedimentary exhalative processes in shallow marine environments however extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization on the basis of geological relationships and isotope geochemical characteristics we propose a carbonate hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies this model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the yanshanian intrusions with carbonate and evaporite wall rocks mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion hosted orebodies the stratabound massive sulfide deposits of the lower changjiang metallogenic belt share many features with the well studied high temperature carbonate hosted replacement deposits of northern mexico and western united states particularly with respect to association with small shallow granitoid complexes structural and stratigraphic controls on mineralization alteration assemblages geometry of orebodies metal association metal zonation and isotopic systematics

metallogeny of copper and iron deposits in the eastern yangtse craton east central china abstract the eastern yangtse craton of central to eastern china is an important fe cu metallogenic province based on studies of the regional geology and tectonic evolution this metallogenic belt is controlled by faults and aulacogens in the continental plate in the early yanshan epoch jurassic the dominant west northwest and east west lithospheric faults controlled the distribution of cu mo and au mineralization whereas in the late yanshan epoch cretaceous the north northeast and northeast lithospheric faults controlled cu fe mineralization in a mineral district the distribution of ore fields is under the dual control of basement fault s and near surface fault s based on the relation of ring and lineament faults to intrusions a three level model of vertical zonation is proposed systematic petrochemical studies of mesozoic igneous rocks and mineralization identify three subseries 1 a calc alkaline intermediate to silicic subseries rich in potassium 2 a calc alkaline intermediate to felsic subseries rich in sodium and 3 a calc alkaline intermediate to mafic subseries rich in sodium genetic types of ore deposits are diverse including fe and cu skarns cu porphyries fe ore magma injections ningwu luzong fe deposits from late orthomagmatic to pegmatitic pneumato hydrothermal and to mesothermal epithermal associated with subvolcanic rocks and remobilized sedimentary fe and or cu deposits the genetic types of ore deposits form two metallogenic series 1 a sedimentary metallogenic series active mainly in the paleozoic and 2 a magmatic hydrothermal metallogenic series consisting of three subseries active predominantly in the jurassic and cretaceous with the latter being more important in this region the superposition and compounding of these two metallogenic series contribute to many styles of mineralization in this mineral province

geochemical and sr nd pb isotopic compositions of the eocene dolek and saricicek plutons eastern turkey implications for magma interaction in the genesis of high k calc alkaline granitoids in a post collision extensional setting abstract the major and trace elements and sr nd pb isotopes of the host rocks and the mafic microgranular enclaves mme gathered from the dolek and saricicek plutons eastern turkey were studied to understand the underlying petrogenesis and geodynamic setting the plutons were emplaced at 43 ma at shallow depths 5 to 9 km as estimated from al in hornblende geobarometry the host rocks consist of a variety of rock types ranging from diorite to granite sio 2 56 98 72 67 wt mg 36 8 50 0 populated by mmes of gabbroic diorite to monzodiorite in composition sio 2 53 21 60 94 wt mg 44 4 53 5 all the rocks show a high k calc alkaline differentiation trend chondrite normalized ree patterns are moderately fractionated and relatively flat la yb n 5 11 to 8 51 they display small negative eu anomalies eu eu 0 62 to 0 88 with enrichment of lile and depletion of hfse initial nd sr isotopic compositions for the host rocks are e nd 43 ma 0 6 to 0 8 and mostly i sr 0 70482 0 70548 the nd model ages t dm vary from 0 84 to 0 99 ga the pb isotopic ratios are 206 pb 204 pb 18 60 18 65 207 pb 204 pb 15 61 15 66 and 208 pb 204 pb 38 69 38 85 compared with the host rocks the mmes are relatively homogeneous in isotopic composition with i sr ranging from 0 70485 to 0 70517 e nd 43 ma 0 1 to 0 8 and with pb isotopic ratios of 206 pb 204 pb 18 58 18 64 207 pb 204 pb 15 60 15 66 and 208 pb 204 pb 38 64 38 77 the mmes have t dm ranging from 0 86 to 1 36 ga the geochemical and isotopic similarities between the mmes and their host rocks indicate that the enclaves are of mixed origin and are most probably formed by the interaction between the lower crust and mantle derived magmas all the geochemical data in conjunction with the geodynamic evidence suggest that a basic magma derived from an enriched subcontinental lithospheric mantle probably triggered by the upwelling of the asthenophere and interacted with a crustal melt that originated from the dehydration melting of the mafic lower crust at deep crustal levels modeling based on the sr nd isotope data indicates that 77 83 of the subcontinental lithospheric mantle involved in the genesis consequently the interaction process played an important role in the genesis of the hybrid granitoid bodies which subsequently underwent a fractional crystallization process along with minor amounts of crustal assimilation en route to the upper crustal levels generating a wide variety of rock types ranging from diorite to granite in an extensional regime

tracing magma mixing in granite genesis in situ u pb dating and hf isotope analysis of zircons in situ zircon u pb and hf isotopic data have been determined for mafic microgranular enclaves and host granitoids from the early cretaceous gudaoling batholith in the liaodong peninsula ne china in order to constrain the sources and petrogenesis of granites the zircon u pb age of the enclaves 120 1 ma is identical to that of the host monzogranite 120 1 ma establishing that the mafic and felsic magmas were coeval the hf isotopic composition of the enclaves ehf t 4 5 to 6 2 is distinct from the host monzogranite ehf t 15 1 to 25 4 indicating that both depleted mantle and crustal sources contributed to their origin the depleted mantle component was not previously revealed by geochemical and nd and sr isotopic studies showing that zircon hf isotopic data can be a powerful geochemical tracer with the potential to provide unique petrogenetic information some wall rock contamination is indicated by inherited zircons with considerably older u pb ages and low initial hf isotopic compositions hafnium isotopic variations in early cretaceous zircons rule out simple crystal liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks instead mixing of mantle derived mafic magmas with crustal derived felsic magmas coupled with assimilation of wall rocks is compatible with the data

comment and reply on s type granites and their probable absence in southwestern north america the problem of muscovite in granites is also raised by dickson muscovite is common in felsic s type granites as stated by chappell and white 1974 but how much is primary and how much is secondary are debatable we currently think that very little is primary above the solidus we are not arguing that muscovite whether primary or secondary garnet and andalusite are not found in s types we are arguing that these minerals may also be found in some i types dickson is quite correct in saying that replacement of cordierite by micas results from hydration which may also affect the alkali aluminum ratio of the rock however he is not necessarily correct in his assertion that water must be introduced into the system it may be magmatic water released from the magma near the solidus during cooling and crystallization more systematic goechemical and isotopic work is required on petrographically well documented granite suites before this question is resolved

geochronology and geochemistry of granitoids related to the giant dahutang tungsten deposit middle yangtze river region china implications for petrogenesis geodynamic setting and mineralization abstract porphyry and skarn deposits in the middle yangtze valley within the northern yangtze craton have a combined tungsten resource of 3 million tonnes mt and represent one of the most important tungsten regions in the world the dahutang porphyry tungsten deposit with reserves of 1 mt is one of the largest deposits uranium pb analyses for the ore related granitoids yield ages of 147 4 0 58 ma 148 3 1 9 ma for porphyritic biotite granite 144 7 0 47 ma 146 1 0 64 ma for fine grained granite and 143 0 0 76 ma 143 1 1 2 ma for granite porphyry a progressive youngling of ages that is consistent with field observations geochemical data show that the three types of granite are characterized by enrichments in rb pb and u and depletion in ba nb p and ti with asi molar al 2 o 3 cao na 2 o k 2 o 1 1 that is characteristic of a peraluminous melt the p 2 o 5 contents of the granites are 0 13 0 37 and have a positive correlation with sio 2 and they are thus s type intrusions they exhibit initial 87 sr 86 sr of 0 721 to 0 731 and e nd t of 5 06 to 7 99 for porphyritic biotite granite 0 7196 to 0 7289 and 6 29 to 6 74 for fine grained granite and 0 7153 to 0 7365 and 5 09 to 7 64 for granite porphyry chondrite normalized rare earth element ree patterns for the granites are characterized by enrichment in the light ree and a strong negative eu anomaly indicating that they were derived from the proterozoic pelitic and psammitic basement strata and experienced strong fractional crystallization of plagioclase our ca 150 140 ma age for the dahutang s type magmatism and w mineralization is identical to that of the i type magmatism related to cu au mo fe bearing porphyry and skarn deposits along the middle to lower yangtze river valley we propose that the latest jurassic to earliest cretaceous granitoids and ores formed during a tearing of the subducting izanagi slab which caused the upwelling of asthenosphere and resulting mantle crust interaction the s type granitoids and related w ore systems resulted from the re melting of the proterozoic crust whereas the i type granitic rocks and related ores are attributed to the partial melting of the subducted slab

dehydration melting of a basaltic composition amphibolite at 1 5 and 2 0 gpa implications for the origin of adakites this study presents the results of dehydration melting experiments on a basaltic composition amphibolite under conditions appropriate to a hot slab geotherm 1 5 and 2 0 gpa and temperatures of 850 to 1150 c dehydration melting produces an omphacitic augite and garnet bearing residue coexisting with rhyolitic to andesitic composition melts at 1 5 gpa the amphibolite melts in two stages between 800 and 1025 c the 2 0 gpa data also define two melting stages at 2 0 gpa the first stage involves nearly modal melting of the original amphibolite minerals qtz pl amp to produce melt cpx grt during the second stage the eclogite restite melts non modally 0 86 cpx 0 14 grt 1 melt the experimental results were combined with data from the literature to generate a composite p t phase diagram for basaltic composition amphibolites over the 800 to 1100 c temperature range for pressures up to 2 0 gpa comparison of the major element compositions of the experimentally produced melts with compositions of presumed slab melts adakites shows that partial melting of amphibolite at conditions appropriate to a hot slab geotherm produces melts similar to andesitic and dacitic adakites except for significant mgo and cao depletions trace element modelling of amphibolite dehydration melting using the 2 0 gpa melting reactions produces ree abundances similar to those of adakites at 10 15 wt batch melting but the models do not reproduce the high sr y ratios characteristic of adakites taken together the major and trace element results are not consistent with the derivation of adakites by dehydration melting of the subducted slab with little or no interaction with the mantle wedge or crust if adakites are partial melts of the subducted slab they must undergo significant interaction with the mantle and or crust during which they acquire a number of their distinctive characteristics

a tectono genetic model for porphyry skarn stratabound cu au mo fe and magnetite apatite deposits along the middle lower yangtze river valley eastern china abstract the middle lower yangtze river valley metallogenic belt yrb situated along the northern margin of the yangtze craton is characterized by porphyry skarn stratabound cu au mo fe deposits in the areas of uplift and magnetite apatite deposits in cretaceous fault basins following detailed field investigations and a review of published data we recognize two episodes of magmatism and mineralization in the yrb 1 156 137 ma high k calc alkaline granitoids associated with 148 135 ma porphyry skarn stratabound cu au mo fe deposits and 2 135 123 ma shoshonitic series associated with 134 9 122 9 ma magnetite apatite deposits a type granitoids and associated alkaline volcanic have a small age range from 126 5 to 124 8 ma and are temporally spatially and genetically associated with the second episode the geodynamic history of the yrb did not experience the paleozoic to mesozoic lithospheric thickening that took place in the north china craton this process is inferred to be linked to partial melting of the delaminated lower crust at high pressures resulting in the development of c type adakitic rocks the petrochemical and sr nd isotopic data show that both the shoshonitic series and a type granitoids are quite different from adakites with only some of the k calc alkaline granitoids having adakitic signatures previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono thermal evolution from 150 to 100 ma all data obtained for the middle lower yangtze river region consistently show that the tan lu regional strike slip fault zone initiated at 233 6 to 225 6 ma from the collision between the north china and yangtze cratons and was reactivated at ca 160 ma the tan lu fault was caused by the oblique subduction of the izanagi plate which along the yrb the low angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks the high k calc alkaline granitoids magmas were derived from melting of the subducted slab with some input of crustal material these magmas were emplaced at the intersections between ne and ew trending faults and formed porphyry skarn stratabound cu au mo fe deposits between 156 and 137 ma after 135 ma the subducted plate changed its direction of motion to northeast now running parallel to the eurasian continental margin and leading to large scale continental extension the shoshonitic series and subsequent a type granitoids magmatism and the development of magnetite apatite ores in the yrb took place in both fault basins and ne trending rifts between 135 and 124 ma

geochemistry and nd sr isotopic studies of late mesozoic granitoids in the southeastern hubei province middle lower yangtze river belt eastern china petrogenesis and tectonic setting abstract a geochemical and isotopic study was carried out for the mesozoic yangxin tieshan and echeng granitoid batholiths in the southeastern hubei province eastern china in order to constrain their petrogenesis and tectonic setting these granitoids dominantly consist of quartz diorite monzonite and granite they are characterized by sio 2 and na 2 o compositions of between 54 6 and 76 6 wt and 2 9 to 5 6 wt respectively enrichment in light rare earth elements lree and large ion lithophile elements lile and relative depletion in y concentrations ranging from 5 17 to 29 3 ppm and yb 0 34 2 83 ppm with the majority of the granitoids being geochemically similar to high sio 2 adakites hsa their initial nd e nd 12 5 to 6 1 and sr 87 sr 86 sr i 0 7054 0 7085 isotopic compositions however distinguish them from adakites produced by partial melting of subducted slab and those produced by partial melting of the lower crust of the yangtze craton in the late mesozoic the granitoid batholiths in the southeastern hubei province exhibit very low mgo ranging from 0 09 to 2 19 wt with an average of 0 96 wt and large variations in negative to positive eu anomalies eu eu 0 22 1 4 especially the tieshan granites and yangxin granite porphyry eu eu 0 22 0 73 geochemical and nd sr isotopic data demonstrate that these granitoids originated as partial melts of an enriched mantle source that experienced significant contamination of lower crust materials and fractional crystallization during magma ascent late mesozoic granitoids in the southeastern hubei province of the middle lower yangtze river belt were dominantly emplaced in an extensional tectonic regime in response to basaltic underplating which was followed by lithospheric thinning during the early cretaceous

in situ la icp ms u pb geochronology and trace element analysis of hydrothermal titanite from the giant zhuxi w cu skarn deposit south china the zhuxi w cu skarn deposit is the largest w deposit in the jiangnan porphyry skarn tungsten belt in south china and is also among the largest deposit of this type in the world titanite is a common mineral in the zhuxi deposit and occurs in three textural settings titanite i associated with retrograde altered exoskarn with weak mineralization titanite ii in retrograde altered endoskarn with disseminated cu ore and titanite iii from altered granite with disseminated w ore here we present la icp ms u pb data on the three types of titanite which show 207pb corrected weighted mean 206pb 238u ages of 148 1 7 4 ma n 25 mswd 0 22 148 9 1 5 ma n 28 mswd 0 37 and 149 9 1 3 ma n 31 mswd 0 28 respectively these ages are consistent with the previously reported ages of the ore related granite the coeval nature of the w and cu ores suggests that the w and cu ores formed synchronously and are associated with the granitoids the ce and eu anomalies in the three types of titanite record redox fluctuation during the mineralization process and suggest variable contamination of the magmatic hydrothermal system by reduced carbonate wall rock that contains abundant carbonaceous matter our study demonstrates that hydrothermal titanite commonly occurring in reduced type w skarn deposits has potential for isotopic dating and in constraining the redox conditions for the mineralization process

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

mesozoic molybdenum deposits in the east qinling dabie orogenic belt characteristics and tectonic settings abstract the east qinling dabie orogenic belt accommodates the largest mo ore district in the world it contains 8 43 mt of proven mo metal reserves which accounts for 66 of the total proven chinese mo reserves the mo ore district includes 24 deposits and 12 occurrences with four major types of mo mineral systems i e porphyry porphyry skarn skarn and hydrothermal veins the latter can be further subdivided into quartz vein and carbonatite vein types although mo mineralization in the belt began in the paleoproterozoic 1680 24 to 2044 14 ma all economically significant deposits were formed during the mesozoic re os dating of molybdenite has shown that there are three episodes of mo mineralization i e late triassic 233 221 ma late jurassic to early cretaceous 148 138 ma and early to middle cretaceous 131 112 ma late triassic mo deposits developed as molybdenite quartz veins and carbonatite vein types stable isotope systematics c o s and high contents of re and sr indicate that the carbonatite mo veins are mantle derived porphyry and porphyry skarn mo mineral deposits were formed in the late jurassic to early cretaceous and early to middle cretaceous the late jurassic to early cretaceous granite porphyries that are associated with the mo deposits usually occupy less than 1 5 km2 at the surface and are situated in the east qinling area far west of china s continental margin on the other hand the early to middle cretaceous batholiths and granite porphyries with associated mo deposits are located in the dabieshan area and eastern part of the east qinling area the late jurassic to early creataceous granitoids and related mo deposits possibly formed in a back arc extensional setting of the eurasian continental margin which was probably triggered by the oblique subduction of the izanagi plate the early to middle cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning asthenospheric upwelling and partial melting of the crust induced by a change in izanagi plate motion parallel to the continent margin in the east qinling dabie belt there are vein type pb zn ag deposits surrounding porphyry and or porphyry skarn mo w deposits forming well defined ore clusters the same spatial arrangement i e porphyry mo stockworks and outlying pb zn ag ore veins is also observed at the deposit scale thus mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons both porphyry stockworks and polymetallic veins can be used as vectors for further prospecting

in situ trace elements and sr isotopes in scheelite and s pb isotopes in sulfides from the shiweidong w cu deposit giant dahutang ore field implications to the fluid evolution and ore genesis abstract the shiweidong w cu polymetallic deposit with resources of 300 000 t wo3 and 200 000 t cu is one of the major tungsten polymetallic deposits in the giant dahutang ore field this study conducted a series of in situ analyses on scheelite and sulfides aiming to provide some new insights into the sources hydrothermal ore forming processes fluid evolution history and genesis of this deposit which is of importance to understand the formation of the super large dahutang ore field quartz vein and veinlet disseminated type tungsten ore bodies are mainly hosted in neoproterozoic granodiorite and or the yanshanian porphyritic two mica granites four stages of mineralization from early to late are identified in this deposit 1 pegmatite stage 2 silicate oxide stage 3 oxide sulfide stage and 4 sulfide stage the 34sv cdt values of stage 3 chalcopyrite and pyrite are from 1 73 to 1 46 and from 1 66 to 0 31 respectively indicating a magma related hydrothermal origin the 206pb 204pb 2067pb 204pb and 208pb 204pb ratios of pyrite range from 18 169 to 18 295 15 650 to 15 679 and 38 496 to 38 525 respectively revealing a crust origin for the pb trace element compositions of scheelite show that the both stage 2 scheelite scheelite ii and stage 3 scheelite scheelite iii have high contents of nb and rees the scheelite ii has a narrow range of the y ho ratios 16 2 31 0 obviously negative eu anomalies eu eu 0 04 0 46 and relatively low 87sr 86sr ratios of 0 72640 0 73336 whereas scheelite iii shows variable y ho ratios of 20 6 96 9 positive eu anomalies eu eu 1 31 7 11 and relatively high 87sr 86sr ratios of 0 73496 0 76098 these data indicated that the eu anomalies and sr isotopic compositions of scheelite ii were inherited from magmatic hydrothermal fluids whereas those of scheelite iii were sourced from modified fluids due to intense fluid rock interaction and input of meteoric fluids our data also reveal that the rees of scheelite ii and scheelite iii are mainly controlled by the substitution mechanism of 3ca2 ca 2ree3 the w rich reduced fluids and intense fluid rock interactions which could provide enough w and ca are likely the key factors for the formation of scheelite in the shiweidong tungsten deposit

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

multi stage crust mantle interaction in se china temporal thermal and compositional constraints from the mesozoic felsic volcanic rocks in eastern guangdong fujian provinces abstract the mesozoic geology of southeastern se china was characterized by emplacement of voluminous felsic magmas we present zircon u pb hf isotopic compositions and whole rock major and trace elemental compositions of a series of felsic volcanic rocks from the eastern guangdong and fujian provinces the volcanic rocks have been divided into three formations the douling nanyuan and shimaoshan fms zircon u pb dating defines three eruption cycles 168 145 ma for the douling fm 143 130 ma for the nanyuan fm and 104 95 ma for the shimaoshan fm in situ hf isotope analyses on dated zircon yield an ehf t range of 13 8 to 6 9 and a tdm hf range from 1400 to 486 ma with a peak at ca 930 ma the majority of the mesozoic felsic lavas have more radiogenic hf than that of metamorphic basement rocks and related igneous rocks requiring the involvement of a juvenile component in their origin the mesozoic felsic magmas are predominantly dacites and rhyolites with only minor basalt and andesite and show relatively homogeneous hf isotopic compositions of zircon in single sample combined these data indicated that neither differentiation of a mantle derived magma nor mixing of magmas from different sources was a dominant petrogenetic process both the ehf t of zircon and the magma temperature increase from the douling and nanyuan fms to the shimaoshan fm all these facts imply an increasing contribution of contemporaneous underplated hot and dry mantle derived magmas as both a heat source inducing crustal melting and as a source of material melt that variably mixed with the local crustal melts the felsic crustal melt component was generated at amphibolite facies conditions with a residual assemblage of plagioclase hornblende garnet zircon our results suggest a progressive role of crust mantle interaction in generating the episodic felsic volcanic eruption during the mesozoic

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

the updip and downdip limits to great subduction earthquakes thermal and structural models of cascadia south alaska sw japan and chile this study examines thermal and structural controls of the updip and downdip rupture limits of great subduction thrust earthquakes data on past great earthquake seismic limits have been compiled for four continental subduction zones cascadia sw japan south alaska and chile these limits have then been compared to the predictions of several models for what constrains great earthquake rupture temperatures on the subduction thrusts have been estimated by finite element numerical models the landward limits of the observed updip aseismic zones correspond to the position where the thrust temperature reaches about 100 c that is depths of about 2 to 10 km for the subduction zones studied this temperature agrees with the dehydration of stable sliding smectite clays to illite chlorite the temperatures in this region are controlled mainly by the thickness of sediment on the incoming crust and by the crustal age and thus heat flow the downdip limits correspond to the depth on the thrust where either 1 the temperature reaches about 350 c which corresponds to thermally activated stable sliding behavior for crustal rocks with a transition to 450 c or 2 about 40 km depth if 350 c is reached at greater depth depths of about 40 km approximately correspond to the intersection of the thrust with the continental forearc moho and this downdip limit may be a consequence of stable sliding serpentinite or talc and other hydrated forearc mantle rocks the primary temperature controls on the downdip region are the age of the subducting oceanic plate and the thrust dip profile secondary control comes from the thickness of incoming sediment the convergence rate and the radioactive heat generation in the overlying forearc the 100 c updip limit occurs near the trench for young subducting plates with a thick sediment section such as cascadia 6 8 ma and up to 80 km landward for older oceanic crust such as south alaska 50 ma the 350 c downdip thermal limit is applicable for young oceanic plates e g cascadia and nankai whereas the forearc mantle limit applies for older plates e g south alaska and chile except near the chile rise for the margins studied that have experienced great earthquakes there is generally good agreement between the postulated thermal and moho limits and the rupture or seismogenic zone as defined by the distribution of aftershocks and by waveform tsunami and dislocation modeling the downdip limit of the interseismic locked zone from dislocation modeling is also in agreement with these limits

reappraisal of the ages of neoproterozoic strata in south china no connection with the grenvillian orogeny the jiangnan fold belt separates the yangtze and cathaysia blocks in south china and has long been considered grenvillian in age in order to place south china in central rodinia it consists of deformed early neoproterozoic strata that are unconformably overlain by undeformed late neoproterozoic strata and intruded by undeformed and unmetamorphosed granitic plutons zircons from the early neoproterozoic strata yield u pb ages as young as 830 ma and one granitic pluton has a zircon u pb age of ca 827 ma the 830 ma mafic rocks along the southeastern margin of the yangtze block have arc affinity geochemical characters whereas mafic rocks younger than 830 ma have typical ocean island basalt oib like compositions thus we suggest that the early neoproterozoic strata were deposited on an active continental margin prior to amalgamation of the yangtze and cathaysia blocks at ca 830 ma the overlying late neoproterozoic strata were deposited in the intracontinental rifted nanhua basin at 820 730 ma and probably reflect backarc spreading above the long lived 950 735 ma oceanic subduction zone along the northern and western margin of the yangtze block this model is consistent with the secular tectonic evolution of south china during the neoproterozoic the jiangnan fold belt is therefore not a grenvillian feature as previously suggested and there is no evidence to place south china in central rodinia instead we believe that south china was located in a marginal position relative to this supercontinent

petrogenesis of ore forming granites with implications for w mineralization in the super large shimensi tungsten dominated polymetallic deposit in northern jiangxi province south china abstract the shimensi deposit is a newly discovered super large tungsten w polymetallic deposit in northwestern jiangxi province south china in this paper we reported new zircon u pb ages for the ore bearing porphyritic biotite granite 151 3 2 8 ma and fine grained granite 150 1 1 2 ma and 150 7 2 4 ma which represent the oldest mesozoic granitic magmatism reported at shimensi our ore bearing granite porphyry ages 142 7 2 3 ma and 143 3 1 5 ma have better constrained the timing of the jurassic early cretaceous ore forming magmatism geochemically the shimensi granitoids are strongly peraluminous with high contents of sio2 70 7 78 7 wt and k2o 4 0 wt p2o5 rb ta and u and low contents of ti sr ba and hrees the rocks also show positive p2o5 vs sio2 correlation suggesting a highly fractionated s type affinity different from most w bearing granites in the jiangxi region the calculated zircon ehf t 10 0 to 2 4 two stage model ages 1350 1824 ma and 18ozircon values 6 40 to 8 87 of the shimensi granites suggest that the latter were mainly derived from the partial melting of heterogeneous source rocks probably with combined contributions from the neoproterozoic shuangqiaoshan group metamorphic rocks and jiuling granodiorite the calculated zircon eu eu 0 05 0 58 mean 0 20 and ce4 ce3 3 83 96 49 mean 20 99 ratios of the granites indicate very low oxygen fugacity fo2 for the ore forming magmas a highly favorable factor for w mineralization potentially w and cu rich source rocks and highly fractionated and reducing granitic magmas were important factors that triggered super large w mineralization at shimensi

petrogenesis geochronology and tectonic significance of granitoids in the tongshan intrusion anhui province middle lower yangtze river valley eastern china abstract the tongshan copper deposit in anhui province is a typical mid sized skarn and porphyry type deposit in the anqing guichi district along the middle lower yangtze river valley eastern china the tongshan intrusion is closely related to this mineralization the intrusion mainly comprises rocks that are quartz diorite porphyry quartz monzonite porphyry and granodiorite porphyry plagioclase in these rocks is mostly andesine an 31 0 42 9 along with minor oligoclase biotite is magnesium rich mg mg fe 0 52 0 67 and aluminum poor al 2 o 3 12 32 14 09 wt and can be classified as magnesio biotite hornblende is tio 2 poor 0 60 and is magnesio hornblende or edenite the shrimp zircon u pb age of the quartz monzonite porphyry is 145 1 1 2 ma which corresponds to the middle yanshanian period whole rock geochemical results show that the rocks are silica rich sio 2 60 23 66 23 wt and alkali rich k 2 o na 2 o 4 97 8 72 wt and low in calcium cao 2 61 5 66 wt trace element results show enrichments in large ion lithophile element e g k rb and ba and depletions in some high field strength elements e g nb ta p and ti the total rare earth element ree content of the rocks is low ree n 10 and small positive eu anomalies average eu 1 16 these mineralogical geochronological and geochemical results show that the intrusion has a mixed crust mantle source the tongshan intrusion was formed by multiple emplacements of crustally contaminated basaltic magma generated by varying degrees of partial melting of enriched lithospheric mantle and lower crust hornblende thermobarometry yielded magmatic crystallization temperatures of 652 788 c and an average crystallization pressure of 1 4 kbar which corresponds to a depth of approx 4 7 km biotite thermobarometry yielded similar temperatures and lower pressures of 735 775 c and 0 6 kbar depth 2 1 km respectively the parental magma had a high oxygen fugacity and was produced in a volcanic arc setting related to subduction of the paleo pacific plate

distribution of porphyry deposits in the eurasian continent and their corresponding tectonic settings in the eurasian continent there are three huge metallogenic belts of cu and mo porphyry deposits comprising the paleozoic central asian ore belt in the north the tethyan eurasian ore belt of jurassic to cenozoic age in the southwest and the east margin ore belt of the eurasian continent of jurassic to cretaceous age in the east the latter is considered to be part of the vast circum pacific ore belt some of the main features of the spatial temporal distribution of cu and mo porphyry systems and related geodynamic processes of the three metallogenic belts are described in particular the key role of postsubduction related porphyry ore systems is emphasized comprising collisional and post collisional cu mo porphyry deposits during the geological history of the eurasian continent the recurrent feature of these ore systems and related felsic rocks is their derivation from partial melting of stagnant or residual oceanic slabs and mixing with a variable amount of crustal material during magma ascent to shallower levels 2013 published by elsevier ltd

structural and petrological constraints on the tectonic evolution of the garnet lherzolite facies higashi akaishi peridotite body sanbagawa belt sw japan 1 the higashi akaishi peridotite body in the sanbagawa metamorphic belt is a unique example of a kilometer scale body including garnet lherzolite facies rocks from an oceanic subduction type orogen in this body four distinct deformational phases d1 d2 d3 and d4 can be defined the tectonic significance of d1 is unclear microstructural observations and application of garnet orthopyroxene geothermobarometry suggest that d2 took place during high temperature subduction up to depths of 100 km from 2 3 gpa to above 2 8 gpa at temperature of 700 800 c or more d3 represents a major phase of exhumation after exhumation the higashi akaishi body became juxtaposed with the adjacent besshi and eclogite units at a depth of around 35 km 1 gpa the common history of the two units after d3 is shown by the intertectonic growth of tremolite between d3 and d4 that corresponds to a stage of intertectonic growth of plagioclase in the besshi and eclogite units both the spatial distribution and the estimated pressure temperature p t conditions of this intertectonic phase of mineral growth in the different units are in excellent agreement the development of an antigorite schistosity during the late stage of d2 indicates an anticlockwise p t path with cooling at depths of around 100 km the association of the antigorite bearing fabric and the onset of exhumation after the d2 stage suggest that the density decrease due to antigorite formation may have been sufficient to trigger the exhumation of dense ultramafic body from uhp conditions in subduction zones syn d2 water introduction and the anticlockwise p t path are expected when convection in the mantle wedge brings peridotite toward a subduction boundary through mantle wedge or when peridotite is dragged down along a subduction boundary that is progressively cooling immediately after initiation of subduction

remelting of neoproterozoic relict volcanic arcs in the middle jurassic implication for the formation of the dexing porphyry copper deposit southeastern china article i nfo the dexing copper deposit in southeastern china is a typical non arc porphyry deposit the origin of which has been a topic of debate for several decades here we present new results from u pb geochronology whole rock chemistry and sr nd hf o isotopic investigations on the ore forming granodioritic porphyry la icpms zircon u pb data suggest that the granodioritic porphyry was formed in the middle jurassic ca 172 5 ma probably associated with lithospheric thinning driven by either sub continental lithospheric mantle delami nation or asthenospheric upwelling the porphyry displays both arc like and adakitic trace element signa tures the adakitic features suggest that hree heavy rare earth elements rich minerals such as garnet and hornblende in the absence of plagioclase resided in the source region the arc like signatures are broadly comparable with those of the proximal neoproterozoic island arc rocks including the keratophyre from shuangxiwu group and associated granitoids indicating a potential genetic relationship the porphyry has chondritic end t of 0 28 to 0 25 and radiogenic ehf t of 2 to 7 and correspondingly uniform two stage depleted mantle nd model ages of 940 980 ma and hf model ages of 800 1100 ma mean 920 ma on nd and hf isotopic evolution diagrams these values are markedly similar to those of the adjacent neoproterozoic arc rocks when calculated forward to the mid jurassic zircons of the porphyry show mantle like oxygen isotope characters with 18 o values clustering in the range of 4 7 5 9 similar to the values for the neoproterozoic arc rocks mentioned above the geochemical and isotopic features recorded in our study suggest mantle derived magmas with no significant supracrustal input for the source of the por phyry with regard to the source of the cu ore we consider a model involving the remelting of sulfide bearing arc related lower crustal source furthermore the occurrence of a neoproterozoic vms volcanic massive sulfide type copper deposit the pingshui cu deposit in the shuangxiwu group might suggest that the lower crustal rocks related to a neoproterozoic relict island arc provided the source for copper during a second stage melting event we propose a new geodynamic model for the dexing porphyry cu deposit which envis ages that the sulfide bearing arc lower crustal rocks were generated during oceanic slab subduction in the early neoproterozoic the remnants of which were preserved at the crust mantle boundary subsequently in the middle jurassic these rocks were heated by asthenospheric upwelling and remelted to produce fertile magmas the magmas ascended along the northeast jiangxi fault and intruded into the jiuling terrane where cu precipitation occurred upon subsequent magma cooling and fluid exsolution

serpentinites of the zermatt saas ophiolite complex and their texture evolution the zermatt saas serpentinite complex is an integral member of the penninic ophiolites of the central alps and represents the mantle part of the oceanic lithosphere of the tethys metamorphic textures of the serpentinite preserve the complex mineralogical evolution from primary abyssal peridotite through ocean floor hydration subduction related high pressure overprint meso alpine greenschist facies metamorphism and late stage hydrothermal alteration the early ocean floor hydration of the spinel harzburgites is still visible in relic pseudomorphic bastite and locally preserved mesh textures the primary serpentine minerals were completely replaced by antigorite the stable assemblage in subduction related mylonitic serpentinites is antigorite olivine magnetite diopside the mid tertiary greenschist facies overprint is characterized by minor antigorite recrystallization textural and mineral composition data of this study prove that the hydrated mineral assemblages remained stable during high pressure metamorphism of up to 2 5 gpa and 650 c the zermatt saas serpentinites thus provide a well documented example for the lack of dehydration of a mantle fragment during subduction to 75 km depth

source of copper in the giant shimensi w cu mo polymetallic deposit south china constraints from chalcopyrite geochemistry and oxygen fugacity of ore related granites abstract porphyry type copper mineralization is generally considered to be related to ore forming fluid exsolution from oxidized magnetite bearing intermediate to felsic magmas however copper deposits associated with ilmenite bearing per aluminous evolved granites also exist and their origin remains obscure the shimensi w cu mo polymetallic deposit located in the northern segment of the jiangnan orogen south china composed mainly of the neoproterozoic shuangqiaoshan group meta sediments volcanic rocks and biotite granite is one of the largest tungsten deposits in the world the w cu mo polymetallic orebodies occur at the contact zone between the mesozoic ilmenite bearing fluorite bearing f rich highly fractionated granite and the neoproterozoic granite the reason for the accompanying cu mineralization within ilmenite bearing granites is unclear in this paper we present a detailed study of chalcopyrite geochemistry including s pb isotopes trace elements and nd isotopes and oxygen fugacity fo2 of ore related granites in the shimensi deposit to constrain the origin of copper sulfur isotope values of the sulfides give a narrow 34s interval of 3 3 to 0 5 mean 1 5 n 32 suggesting the ore forming fluid is of magmatic origin the similarity of pb isotopes of the majority of sulfides and k feldspars from mesozoic granites indicates their genetic relationship however chalcopyrite samples show a wider range of pb isotopic compositions than that of k feldspars suggesting an extra source for the ore forming fluids chalcopyrite from the ore deposit show features of lree enriched patterns variable eu negative anomalies eu eu 0 26 0 75 and la sm n values 0 77 5 93 while the two figures for the mesozoic f rich evolved granites are eu eu 0 18 0 45 and la sm n 2 42 4 09 this along with and the larger range of end values 12 4 to 2 7 of the chalcopyrites than for the mesozoic granites and neoproterozoic granite therein 8 6 to 6 2 suggest that the ore forming fluids cannot be attributed to the mesozoic granites alone the local cu enriched neoproterozoic shuangqiaoshan group rocks should have contributed to the mineralization the low bulk rocks fe3 fe2 ratios 0 02 1 00 average 0 22 fe2 enriched biotite compositions fe2 fe3 5 64 143 average 22 combined with the low ce4 ce3 ratios 3 509 average 142 negative eu anomalies eu eu 0 05 0 56 average 0 25 and low fo2 fmq 3 4 1 9 fmq 1 5 1 7 for the mesozoic magmatic zircons suggest that the granites in the shimensi deposit are relatively reduced the low oxygen fugacity below nno of granites is favorable for significant tungsten mineralization accompanying by minor cu mineralization

an inverted continental moho and serpentinization of the forearc mantle volatiles that are transported by subducting lithospheric plates to depths greater than 100 km are thought to induce partial melting in the overlying mantle wedge resulting in arc magmatism and the addition of significant quantities of material to the overlying lithosphere asthenospheric flow and upwelling within the wedge produce increased lithospheric temperatures in this back arc region but the forearc mantle in the corner of the wedge is thought to be significantly cooler here we explore the structure of the mantle wedge in the southern cascadia subduction zone using scattered teleseismic waves recorded on a dense portable array of broadband seismometers we find very low shear wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an inverted continental moho which reverts to normal polarity seaward of the cascade arc this observation provides compelling evidence for a highly hydrated and serpentinized forearc region consistent with thermal and petrological models of the forearc mantle wedge this serpentinized material is thought to have low strength and may therefore control the down dip rupture limit of great thrust earthquakes as well as the nature of large scale flow in the mantle wedge

porphyry cu au mo epithermal ag pb zn distal hydrothermal au deposits in the dexing area jiangxi province east china a linked ore system abstract based on previous studies and detailed field investigations of the dexing porphyry copper deposit the yinshan ag pb zn deposit and the jinshan shear zone hosted gold deposit in the dele jurassic volcanic basin in the northeastern jiangxi province east china we propose that the three deposits share spatial temporal and genetic relationships and belong to the same metallogenic system dexing is a typical porphyry cu au mo deposit in which both ore forming fluid and metals are derived from the granite porphyry the yinshan deposit consists of a porphyry copper ore located in the cupola of a quartz porphyry stock in the lower part and ag pb zn ore veins in the upper part the hydrothermal fluids were mainly derived from the magma in the early stages of the mineralizing event and became mixed with meteoric waters in the late stages its ore metals are magma derived both the jinshan base metal veins and the hamashi dongjie and naikeng quartz vein type gold deposit are hosted by brittle ductile structures which are distal in relation to the porphyry intrusions and were formed by mixed magmatic fluids and meteoric water whereas the gold was mainly leached from the country rocks mesoproterozoic shuangqiaoshan group phyllite and schist the deposits show a distinct spatial arrangement from porphyry cu to epithermal ag pb zn and distal au we suggest a porphyry epithermal distal vein ore system model for this group of genetically related mineral deposits they were formed in a back arc setting in a middle jurassic active continental margin with magmas derived from the subducted slab

molybdenite re os dating zircon u pb age and geochemistry of granitoids in the yangchuling porphyry w mo deposit jiangnan tungsten ore belt china implications for petrogenesis mineralization and geodynamic setting abstract the yangchuling w mo deposit located in the jiangnan porphyry skarn jnb tungsten ore belt is the first recognized typical porphyry w mo deposit in china in the 1980 s stockworks and disseminated w mo mineralization occur in the roof pendant of a 0 3 km 2 monzogranitic porphyry stock that intruded into a granodiorite stock hosted by neoproterozoic phyllite and slate la icpms zircon u pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143 8 0 5 ma and 149 8 0 6 ma respectively six molybdenite samples yielded a re os weighted mean age of 146 4 1 0 ma geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements lile relative to high field strength elements hfse indicating a peraluminous nature a cnk 1 01 1 08 two granitoids are characterized by a negative slope with significant light ree heavy ree fractionation la yb n 8 38 23 20 and negative eu anomalies eu eu 0 69 0 76 the p 2 o 5 contents of the yangchuling granitoids range from 0 12 to 0 17 and exhibit a negative correlation with sio 2 reflecting that they are highly fractionated i type they have high initial 87 sr 86 sr ratios 0 7104 0 7116 low negative e nd t 5 05 to 5 67 and homogeneous e hf t between 1 39 and 2 17 indicating similar sources additionally two stage nd model ages t dm2 of 1 3 1 4 ga and two stage hf model ages t dm2 of 1 2 1 3 ga are consistent indicating that neoproterozoic crustal rocks of the shuangqiaoshan group could have contributed to form the yangchuling magmas considering the two groups of parallel late mesozoic ore belts namely the jiangnan porphyry skarn tungsten belt jnb in the south and the middle lower yangtze river porphyry skarn cu au mo fe ore belt yrb in the north the nanling granite related w sn ore belt nlb in the south the neighboring qin hang porphyry skarn cu mo hydrothermal pb zn ag ore belt qhb in the north as well as the southeastern coast porphyry skarn cu mo au ore belt scb recognized in south china in this paper we propose that the latest jurassic to earliest cretaceous granitoids and associated ores were formed during a tearing of the subducting izanagi slab this tearing of the subduction slab caused the upwelling of asthenosphere and the resulting mantle crust interaction the granitoid related w ore systems in jnb resulted from the remelting of the proterozoic crust the mafic ultramafic volcanic rocks of the shuangqiaoshan group intercalated with phyllite and slate ophiolitic melange and magmatic arc rocks mainly comprising i type granite basalt andesite rhyolite pyroclastics together with subduction related metasomatized lithospheric mantle would have provided additional mantle material in this case the partial melting of rocks of the shuangqiaoshan group can produce s i and transitional type granitoids after strong differentiation it formed tungsten bearing granitoids characterized by enrichment of high alkali silicon and volatile components in the yangchuling mine area the small monzogranitic porphyry stock has stronger fractionation volatile content and ore forming components than the older granodiorite resulting in the development of the porphyry w mo ore system

u pb zircon geochemical and sr nd hf isotopic constraints on age and origin of jurassic i and a type granites from central guangdong se china a major igneous event in response to foundering of a subducted flat slab abstract the mesozoic geology of se china is characterized by widespread jurassic to cretaceous igneous rocks consisting predominantly of granites and rhyolites and subordinate mafic lithologies however the tectonic regime responsible for the inland jurassic granites remains controversial we report here u pb zircon ages geochemical and sr nd hf isotopic data for the nankunshan alkaline granite and the fogang granitic batholith in central guangdong mineralogical and geochemical features suggest that the fogang and nankunshan rocks are i and aluminous a type granites respectively shrimp u pb zircon analyses yield consistent ages ranging from 159 3 ma to 165 2 ma for four samples from the fogang batholith and an age of 158 5 ma for the nankunshan granite the fogang granites having i sr 0 7098 0 7136 e nd t 4 3 to 12 2 and e hf t 11 5 to 3 1 for the magmatic zircons were derived from paleoproterozoic mafic intermediate igneous protolith with minor addition of mantle derived magmas the nankunshan rocks have relatively lower i sr 0 706 0 708 higher e nd t 0 3 to 2 4 and e hf t 5 7 to 1 1 for the magmatic zircons and some oib like trace element ratios they were likely generated through extensive fractional crystallization of mantle derived alkaline parental magma associated with crustal assimilation these 160 ma i and a type granites in central guangdong were emplaced coeval with the widespread 165 155 ma i and a type granites and syenites following the initiation of intraplate basaltic and or bimodal igneous magmatism at 180 170 ma in the adjacent regions we interpret these jurassic igneous rocks as anorogenic magmatism formed during a major igneous event in response to foundering of an early mesozoic subducted flat slab beneath se china continent

a large california flood and correlative global climatic events 400 years ago a gray silt layer 1 2 cm thick in the central santa barbara basin dated by varve counts to a d 1605 5 yr implies an intensity of precipitation flooding of regional rivers and transport of terrigenous detritus unmatched in the last 1000 yr the inferred flood may correlate with the reported rare occurrence of a perennial lake 14c dated to 390 90 b p in california s mojave desert 300 km east of the area draining into the santa barbara basin the dating of the a d 1605 5 yr flood event is consistent with tree ring evidence for a wet and cold paleoclimate elsewhere in the region regional and global climate evidence indicates that much of the world also experienced rapid intense cooling around a d 1605 this cooling was probably accompanied by an equatorward shift of prevailing wind patterns and associated storm tracks

fluid evolution and ore genesis of the dalingshang deposit dahutang w cu ore field northern jiangxi province south china the dalingshang w cu deposit is located in the north section of the dahutang ore field northern jiangxi province south china vein and breccia style tungsten copper mineralization is genetically associated with mesozoic s type granitic rocks infrared and conventional microthermometric studies of both gangue and ore minerals show that the homogenization temperatures for primary fluid inclusions in wolframite 340 c are similar to those in scheelite 330 c but about 40 c higher than those of apatite 300 c and generally 70 c higher than those in coexisting quartz 270 c laser raman analysis identifies ch4 and n2 without co2 in fluid inclusions in scheelite and coexisting quartz while fluid inclusions in quartz of the sulfide stage have variable co2 content the ore forming fluids overall are characterized by high to medium temperature low salinity ch4 n2 and or co2 bearing aqueous fluids chalcopyrite muscovite and sphalerite are the most abundant solids recognized in fluid inclusions from different ores the h o s pb isotope compositions favor a dominantly magmatic origin for ores and fluids while some depleted 34s values 14 4 to 0 9 of sulfides from the sulfide stage are most likely produced by an increase of oxygen fugacity possibly caused by inflow of oxidized meteoric waters the microthermometric data also indicate that a simple cooling process formed early scheelite and wolframite however increasing involvement of meteoric waters and fluid mixing may trigger a successive deposition of base metal sulfides fluid rock interaction was critical for scheelite mineralization as indicated by in situ la icp ms analysis of trace elements in scheelite