an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

fluid inclusion study of xihuashan tungsten deposit in the southern jiangxi province china the xihuashan tungsten deposit is closely related to a small highly evolved granitic intrusion the fluid phases associated with the wolframite bearing quartz veins have been investigated using microthermometry and the raman microprobe they are highly variable in density and composition the earlier fluids are low density and low salinity co2 bearing aqueous solutions circulating at temperatures up to 420 c and low salinity 2 3 equiv wt nacl aqueous solutions without traces of co2 circulating at high temperatures 280 400 c involved in a specific hydrothermal fracturing event limited unmixing occurs at 380 c and 200 100 bar in response to a sudden pressure drop the second types of fluids related to deposition of idiomorphic drusy quartz are typical co2 bearing aqueous solutions with low salinity 2 5 equiv wt nacl homogenizing at low to moderate temperatures 180 340 c the late fluids characterize the sulfide deposition stage they are aqueous fluids with variable salinities homogenizing in the liquid phase between 100 and 275 c the xihuashan hydrothermal evolution resulted from a discontinuous sequence of specific events occurring between 420 and 150 c and during a continuous hydrothermal evolution of the system during cooling the role played by the co2 rich fluids in the transport and deposition of tungsten in the hydrothermal environment is discussed

gold mineralization of the chencai suichang uplift and tectonic evolution of zhejiang province southeast china abstract a metallogenic model is proposed in which gold and base metal mineralization in se china is related to plate interactions along the pacific margin with southeast asia from about 900 to 70 ma all depositional orogenic and metallogenic processes can be explained by subduction events along northeast trending zones with progressive accretion and cratonization along the continental margin these subduction zones moved southeast for a distance of less than 150 km as a result the area is one of crustal reworking in which the rocks and mineral deposits of earlier events have been repeatedly modified the chencai suichang uplift is an uplifted crustal block in central zhejiang province of mainland china in which the proterozoic basement is exposed as tectonic windows in overlying mesozoic volcanics several gold and base metal deposits are located in these proterozoic windows as well as in the younger volcanics most economic deposits were formed during the last major tectono magmatic event affecting the area the yanshanian 160 170 ma event although there is evidence for earlier mineralization that has been remobilized during the yanshanian it is suggested that crustal reworking was particularly important in remobilising and upgrading gold mineralization the model presented is supported not only by local geology and isotopic data but also by the regional distribution of gold deposits which are arranged in a 50 km wide belt parallel to the yanshanian subduction zone three major episodes of mineralization occurred during 1 a subduction related period of metamorphism partial melting and mesothermal fluid generation and mineralization in the lower crust during the caledonian 2 subduction related volcano plutonic activity with epithermal mineralization during the early yanshanian and 3 hydrothermal mineralization during late yanshanian tectono magmatic event in the third two main categories of metallogenic control are recognized namely 1 hydrothermal fluid generation in the lower crust and 2 upper crust structural and lithological controls on mineralization

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

geology and geochemistry of the changlongshan skarn iron deposit anhui province china abstract the changlongshan skarn iron deposit is located in the northeastern part of the tongling fanchang fe cu district anhui province people s republic of china it is a specularite fe2o3 dominated iron deposit hosted in middle carboniferous to lower permian limestones with a drill indicated resource of 28 84 million tons of fe grading 35 9 58 6 both skarns and iron orebodies occur as tabular bodies along bedding parallel faults at some distance from the inferred granitic intrusions prograde skarn alteration consists mainly of andradite and hedenbergite whereas retrograde skarn is characterized by the development of actinolite chlorite and calcite the mineralogy of ores is dominated by specularite magnetite calcite and quartz primary fluid inclusions in garnet consist of aqueous liquid a vapour bubble and a halite crystal microthermometric measurements yield a homogenization temperature range for skarn alteration of 423 to 478 c with a salinity of 34 to 49 wt nacl equivalent fluid inclusions in calcite associated with mineralization generally consist of a vapour bubble and a liquid phase with a rare occurrence of three phase inclusions homogenization temperatures for two phase inclusions vary from 239 c to 303 c with a salinity of 13 to 22 wt nacl equivalent homogenization of three phase inclusions was observed between 264 and 287 c coupled with a salinity of 31 to 36 wt nacl equivalent stable isotope data indicate magmatic water was involved in the early stage of skarn formation 18 o h 2 o 3 7 to 7 6 dh2o 71 3 to 51 2 and a mixed magmatic meteoric water was responsible for the subsequent mineralization 18 o h 2 o 2 1 to 3 1 dh2o 40 1 to 28 1 geological and geochemical evidence obtained in this study supports a metasomatic replacement origin for the changlonshan iron deposit a conclusion contrary to previous syngenetic based interpretation

geochemistry and origin of tin polymetallic sulfide deposits hosted by the devonian black shale series near dachang guangxi china abstract two tin polymetallic sulfide deposits hosted by the devonian black shale series of the guangxi zhuang autonomous region occur in the dachang ore field the upper devonian frasnian epoch black shale series contains the giant tongkeng changpo deposit and the middle devonian givetian epoch reef limestone contains the giant longtoushan deposit intrusive rocks occur at lame and the western part of dachang ores occur as stratified bodies large veins stockworks and zones of veinlets ores are massive banded laminated and disseminated the ores contain more than 180 different minerals the most important of which are cassiterite sulfides and sulfosalts primary laminated sedimentary sulfide ores occur at tongkeng the mean ratio of sio 2 al 2 o 3 for shale marl is 3 5 but values averaging 56 and 67 respectively for ore and chert suggest a biogenic or hydrothermal source for silica ores and country rocks are rich in sb pb zn sn and cu granites are rich in sb w zn and sn dispersed elements such as te cd se and in are abundant in ores country rocks and granites implying contributions of sedimentary and intrusive activities to the ore formation mean y ho values for the black shale series 28 and granite 31 are similar to most shales and most volcanic rocks the y ho value for reef limestone is 47 comparable to sea water devonian black shale series are slightly lree enriched on chondrite normalized plots and show small negative eu anomalies mean eu 0 56 ce 0 9 and ce anom 0 07 values suggest a shallow water deposition near the redox boundary the 34 s values of sulfides from various deposits of dachang vary with the 34 s values for lame ranging from 2 to 2 and values for tongkeng changpo ranging from 4 9 to 2 6 the highly negative 34 s values 9 5 to 11 3 of huile and kengma sulfides suggest the important role of biogenic sulfur the mean 13 c value of organic matter of devonian black shale series is 24 6 the 30 si nbs 28 values of upper devonian black chert are 0 2 0 3 indicating a sedimentary origin the dachang black chert has been dated at 124 2 ma that of luofu section at 387 18 ma implying that the rb sr isotope of dachang chert was reset during yanshan movement these results suggest that the dachang tin polymetallic sulfide deposits exemplify strongly remobilized sedimentary mineralization

sulfide mineralogy in the polymetallic cassiterite deposits of dachang p r china several important mineral deposits of sn zn cu pb and other metals associated with devonian sediments and yanshanian cretaceous granitic rocks are known in the dachang district guangxi early genetic hypotheses related the origin of the deposits entirely to the yanshanian granites recently it was suggested that in devonian times an earlier syngenetic metal concentration may have occurred later overprinted by the yanshanian metallogeny this contribution is aimed at placing constraints on the physicochemical conditions during the yanshanian ore formation remobilization by studying the sulfide chemistry arsenopyrite sphalerite stannite and fluid inclusion data on the two major deposits in the area i e the polymetallic cassiterite deposit of changpo and the zn cu skarn deposit of lamo sphalerite and arsenopyrite are quite abundant in both deposits stannite is minor but fairly widespread at changpo and quite rare at lamo they are accompanied by pyrite pyrrhotite galena chalcopyrite cassiterite fluorite and a large variety of other sulfides and sulfosalts the main compositional data for sphalerite and arsenopyrite are summarized as follows

nature age and tectonic setting of granitoid hosted orogenic gold deposits of the jiaodong peninsula eastern north china craton china the jiaodong gold province along the southeastern margin of the north china craton has combined production and resources of 900 tonnes of gold more than 95 of the gold in this province is hosted in mesozoic granitoids which intruded late archean metamorphic basement rocks episodically at ca 160 150 and 130 126 ma the deposits of the jiaodong peninsula form one of the largest provinces of granitoid hosted lode gold deposits in the world the jiaodong gold deposits occur as massive auriferous quartz veins hosted in subsidiary second or third order faults and as disseminated and stockwork style mineralization hosted in alteration zones along major regional scale faults mineralization took place during brittle reactivation d3 of pre existing d2 ductile shear zones wall rock alteration is dominated by k feldspar and sericite with also sulfide minerals and extensive silicification closest to the orebodies the alteration was accompanied by the introduction of volatiles fe mg k rb ag as au bi and sb enrichment of base metals in the gold lodes is generally low although locally significant gold deposition took place at temperatures of 250 to 350 c for most gold deposits and the ore fluids are co2 bearing and have calculated salinities of 6 13 wt nacl equiv deposits from the zhao ye xixia and muping rushan belts have similar if not identical structural controls alteration patterns ore mineral assemblages and stable isotope signatures lead isotope data indicate that the ore stage leads were buffered by their host rocks the granitoid hosted gold deposits in the zhao ye belt are most radiogenic the greenstone hosted deposits in the xixia belt is the least radiogenic and the granitoid hosted deposits in the muping rushan belt have intermediate compositions gold mineralization in the zhao ye xixia and muping rushan belts in the jiaodong gold province appears to be broadly contemporaneously at ca 130 120 ma as constrained by shrimp u pb zircon dating on host rocks and a post gold dike as well as by ar ar rb sr and k ar dating of hydrothermal alteration minerals and ores this early cretaceous age is about 100 million years younger than the peak of ultra high pressure metamorphism in the qinling dabie sulu orogen between the north china and yangtze cratons and about 500 km south of the gold province however it overlaps with the extension and exhumation stage of the collisional orogeny and the subduction of the pacific plate beneath the eurasian continental crust whereas the majority of the jiaodong gold deposits occur on the margin of the north china craton some also occur in the suture zone between the two cratons they are significantly landward relative to the subduction zone of the pacific plate compared with typical orogenic lode gold deposits globally lode gold deposits of ca 130 120 ma occurred on both sides of the tan lu fault zone available data favor a temporal link of gold mineralization with pacific plate subduction

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

platinum group element geochemistry of the hongge fe v ti deposit in the pan xi area southwestern china mafic and ultramafic intrusions in the pan xi area along the western margin of the yangtze block southwestern china are spatially associated with the late permian emeishan flood basalts of the emeishan large igneous province the hongge layered intrusion is one of the plutonic bodies of this province and hosts a giant fe v ti deposit this intrusion has three zones a lower olivine clinopyroxenite zone a middle clinopyroxenite zone and an upper gabbro zone each of these zones consists of one or two compositional cycles which have distinct mg values tio2 concentrations and total ree contents the middle clinopyroxenite zone and upper gabbro zone contain thick 14 84 m magnetite mineralized layers samples from the lower olivine clinopyroxenite zone and middle clinopyroxenite zone of the hongge intrusion are enriched in platinum and palladium relative to iridium and ruthenium rocks of the lower olivine clinopyroxenite zone have pd ir ratios 1 8 22 3 lower than those of the middle clinopyroxenite zone 6 2 to 83 in its lower part and 3 6 to 49 in its upper part the pd ir ratios increase progressively upwards in each cyclic unit chromite is the major phase controlling concentrations of iridium and ruthenium the cu pd ratios at the bottom of each cyclic unit are close to that of the mantle and increase upwards this variation suggests that each cyclic unit represents a new batch of magma and sulfide mineral segregation removes pge platinum group elements ni and cu each cyclic unit in the hongge layered intrusion might have resulted from crystal fractionation and mixing between a primary and evolved magma the high cu pd ti pd ni pd and cu ir ratios of the intrusion suggest that the sulfide mineral segregation may have played an important role in pge differentiation if this interpretation is correct then there is a potential to find economic pge rich horizon in the hongge type intrusions in the region

the xinqiao cu s fe au deposit in the tongling mineral district china synorogenic remobilization of a stratiform sulfide deposit abstract the cu s fe au deposit at xinqiao is located in the tongling mineral district anhui province people s republic of china it is a large scale polymetallic deposit with drilling indicated reserves of 0 5 million tonnes of cu averaging 0 71 75 5 million tonnes of s averaging 29 3 and 24 9 million tonnes of fe averaging 46 as well as 11 2 tonnes of au averaging at 4 7 g tonne plus 248 4 tonnes of ag averaging at 248 4 g tonne there are two major mineralization types in the xinqiao deposit one is the economically significant stratiform orebody hosted in the lower carboniferous gaolishan siltstone c1g and overlying middle carboniferous huanglong limestone c2h while the other is the less important skarn type mineralization restricted to the contact between the yanshanian diorite 110 168 ma and the lower permian qixia marble p1q the ore in the xinqiao deposit is dominated by massive pyrite with minor amount of chalcopyrite magnetite pyrrhotite galena sphalerite quartz and dolomite four stages of deformation have been recognized to affect the sedimentary rocks in the xinqiao area the first two d1 and d2 produced mainly ne sw and nne ssw trending open folds whereas d3 is characterized by normal faults striking nne ssw and d4 is dominated by post mineralization strike slip faults segmenting the orebody the structural information obtained by this study not only revealed the transgressive nature of the stratiform orebody but also identified a strong structural control on the formation of the deposit it is concluded that the xinqiao polymetallic deposit was formed through remobilization of a carboniferous sulfide source bed by hydrothermal solutions related to late yanshanian plutonism 110 ma during which d3 normal faulting played an important role in localization of the mineralization such a two stage ore forming model is consistent with the most recent genetic interpretations of the deposit

where is the north china south china block boundary in eastern china the qinling dabieshan belt results from the collision of the north china and south china blocks the eastern extension of the belt the sulu area consists of several stacked units from top to bottom these are 1 a weakly metamorphosed slate sandstone unit of neoproterozoic paleozoic age 2 a gneiss quartzite unit metamorphosed under high pressure p conditions 3 a marble amphibolite unit 4 an ultrahigh p unit that was very deeply subducted and then exhumed and 5 a migmatitic dome resulting from the melting of ultrahigh p rocks all these units underwent the same deformation which was characterized by a top to the northwest extensional ductile shearing during their exhumation granulite facies restites in the migmatite are not significantly different from granulitized eclogites derived from the ultrahigh p rocks the migmatite exhibits the same structural and petrologic evolution as that determined for the other units the resemblance of petrologic and structural features and the lack of ocean basin rock shows that the boundary between the north china block and south china block must be placed north of the sulu area

timing of collision of the north and south china blocks controversy and reconciliation the qinling orogen was formed by the joining of the north and south china blocks but the timing of their integration has been debated for more than a decade the controversies obviously stem from different approaches to reconstruction of the integration history two contrasting lines of evidence yield two different ages for collision of the north and south china blocks middle paleozoic and late triassic the shangdan suture within the qinling was regarded in previous studies as the trace along which the north and south china blocks collided our studies however demonstrate that there are two sutures within the qinling the well documented shangdan suture and the newly discovered mianlue suture we show in this paper that the late proterozoic to early mesozoic evolution of the qinling involved interactions between the north china block the north and south qinling orogens and the south china block the middle paleozoic collision along the shangdan suture as constrained by some evidence accreted only the south qinling orogen to the southern part i e the north qinling of the north china block contemporaneous rifting of the south china block and subsequent drifting separated the south qinling from the south china block during the middle to late paleozoic the separation of the south from the north china blocks is supported by other evidence in particular geomagnetic data evidently it was the late triassic collision of the south china block with the south qinling orogen along the mianlue suture that led to final integration of the north and south china blocks

geological features and origin of the huize carbonate hosted zn pb ag district yunnan south china abstract the huize zn pb ag district in the sichuan yunnan guizhou zn pb ag metallogenic region contains significant high grade zn pb ag deposits the total metal reserve of zn and pb exceeds 5 mt the district has the following geological characteristics 1 high ore grade zn pb 25 wt 2 enrichment in ag and a range of other trace elements ge in ga cd and tl with galena sphalerite and pyrite being the major carriers of ag ge cd and tl 3 ore distribution controlled by both structural and lithological features 4 simple and limited wall rock alteration 5 mineral zonation within the orebodies and 6 the presence of evaporite layers in the ore hosting wall rocks of the early carboniferous baizuo formation and the underlying basement fluid inclusion and isotope geochemical data indicate that the ore fluid has homogenisation temperatures of 165 220 c and salinities of 6 6 12 wt nacl equiv and that the ore forming fluids and metals were predominantly derived from the kunyang group basement rocks and the evaporite bearing rocks of the cover strata ores were deposited along favourable specific ore controlling structures the new laboratory and field studies indicate that the huize zn pb ag district is not a carbonate replacement deposit containing massive sulphides but rather the deposits can be designated as deformed carbonate hosted mvt type deposits detailed study of the deposits has provided new clues to the localisation of concealed orebodies in the huize zn pb ag district and of the potential for similar carbonate hosted sulphide deposits elsewhere in ne yunnan province as well as the sichuan yunnan guizhou zn pb ag metallogenic region

genesis of the sanbaqi deposit a paleokarst hosted uranium deposit in china the sanbaqi uranium deposit in hunan province south china is the largest of a group of paleokarst hosted uranium deposits in lower carboniferous limestone mineralization is localized in cavities and fault breccias formed by dissolution of carbonates four episodes of karst formation are recognized late triassic early jurassic late jurassic early cretaceous cretaceous tertiary and recent field relations indicate that the main uranium mineralization is related to the second karst episode this is supported by isotopic ages of two pitchblende samples at 129 ma and 134 ma as indicated by their nearly concordant data points on concordia plot these ages are in the time range of the early yanshanian tectonic movements that affected southern china and the faulting related to the movements likely triggered the mineralization process at the sanbaqi deposit associated minerals include pyrite millerite ullmannite niccolite molybdenite chalcopyrite sphalerite galena calcite and dolomite fluid inclusion studies on calcite reveal that temperature of ore deposition was from 181 to 150 c the 18o and d values of the ore fluids range from 1 5 to 7 9 per mil and from 30 4 and 54 8 per mil respectively the mineralogical fluid inclusion and isotopic data indicate that the minerlization took place in episodic pulses of hydrothermal fluids that were introduced along a set of ring faults mobilization and redeposition of earlier formed ore minerals in an open system added to the complexity of the paragenetic sequence younger episodes of mineralization occurred during the later karst events as suggested by the geological and additional pitchblende u pb isotopic data during the cretaceous tertiary late yanshanian tectonic movements and recently finally a comparison of the sanbaqi uranium deposit with the uranium deposits hosted by solution collapse breccia pipes of the colorado plateau usa shows that they have many similarities

distinctive features of late palaeozoic massive sulphide deposits in south china abstract more than 20 sediment hosted massive sulphide deposits occur in late palaeozoic basins in south china these deposits are accompanied by a certain amount of volcanic rocks in the host sequence and are economically important for their cu pb zn au and ag reserves the deposits and their host strata were commonly intruded by mesozoic granitoids remobilisation of sedimentary ores and magmatic hydrothermal overprinting processes resulted in the coexistence of massive sulphides with vein skarn and porphyry type orebodies in the same region or within a single deposit the ore containing basins occur in different tectonic settings the lower yangtze basin occurs on a passive continental margin where the deposits are high in cu and au with minor pb and zn and recoverable ag co and mo the ores have a lower concentration of radiogenic lead and 34s values close to zero fluid inclusions are highly saline and na rich fluids and metals of the lower yangtze region are interpreted to have been derived essentially from deep sources including the precambrian basement by contrast basins of the nanling region formed in an intracontinental setting developed on a folded caledonian basement these deposits are higher in pb zn sn and w as well as cu with recoverable ag sb hg u bi tl and mo the ores are characterised by a higher concentration of radiogenic lead and a wide variation of 34s composition fluid inclusions have lower salinities and higher k na ratios fluids are considered to have been sourced substantially from seawater by convection metals for the nanling deposits were essentially derived from the caledonian basement by leaching the contrast in ore composition between these two regions appears to have been controlled by differences in basement composition of the ore forming basins

emeishan basalt ar ar overprint ages define several tectonic events that affected the western yangtze platform in the mesozoic and cenozoic abstract ar ar whole rock dating was carried out as part of a detailed stratigraphical investigation of the emeishan basalt large igneous province lip in the stratotype area sichuan china thirteen from twenty one specimens from three sections yielded reliable reversed isochron and plateau ages maximum 1 errors of 2 1 and 1 6 m y respectively and form two clusters centered on the late jurassic early cretaceous and early late cretaceous with a tail spanning 82 40 ma however all are appreciably younger than the magnetobiostratigraphically constrained late middle permian 255 260 ma age of the basalts reflecting varying degrees of thermal resetting during the mesozoic and cenozoic recently middle jurassic early cretaceous ages reported from elsewhere in the lip have been used to infer a single 40 m y long tectonic episode that affected the western yangtze platform developing this idea the new information have been combined with data we hold for other parts of the terrain and results from three emeishan lip ar ar dating studies published during 2002 to give 32 reliable age dates three 10 12 m y events appear to be recorded in different parts of the province middle jurassic late jurassic early cretaceous and early late cretaceous with a fourth shorter middle eocene episode the 40 m y mesozoic episode appears to be a sampling artifact following a review of the regional deformation tectonic features it is argued that activity related to various phases of deformation in the longmen shan thrust belt is the most likely cause of resetting the final suturing of the north and south china blocks may have also been responsible for the middle jurassic event however the oligocene present indentation of india into asia appears not to have had an impact possibly due to the large scale related strike slip faults that have effectively shielded the lip sichuan basin

tin bearing skarns of south china geological setting and mineralogy tin in skarns forms a significant part of the total sn resource of south china and erosion of these primary deposits has produced rich alluvial concentrations creating the basis for a historically important tin mining industry the skarns are genetically related to s type transformation series granites of yanshanian age emplaced in carbonate sequences mainly of devonian and triassic age these occupy the hercynian indosinian structural depressions within the caledonian foldbelt constituting the nanling ranges of south china most of the sn skarns in this broadly defined province contain calcic mineral assemblages which include andradite grossular hedenbergite diopside actinolite tremolite idocrase wollastonite epidote chlorite and magnetite with or without various sulphides in certain cases sn is located in minerals such as cassiterite malayaite and nordenskioldine in many other deposits sn substitutes in the structure of calc silicates and oxides in particular in andradite titanite actinolite epidote axinite and rutile at gejiu in yunnan province andradite can carry up to 5 14 wt sno2 in this case it is believed that sn4 together with mg2 substitutes for fe3 in the octahedral sites a coupled substitution which can be represented by the equation sn4 mg2 2 fe3 the behavior of sn during skarn formation is governed by the p t x conditions of the skarn forming solutions eh and ph variations and changes in the chemical potentials of major and trace elements e g s2 play a crucial role in determining the prevailing equilibria during the high temperature and alkaline stage of prograde metasomatism an association of andradite diopside formed under oxidizing conditions when sn entered the lattice of andradite or in environments deficient in fe mg and al but rich in sn malayaite formed the association hedenbergite grossular was formed under reducing conditions and in this case sn was retained in the hydrothermal solutions becoming available for reactions at lower temperature the rare sn mineral nordenskioldine was formed at a late stage during prograde alteration where conditions were uncommonly b rich and depleted in f co2 and especially si sn was not deposited as cassiterite until the system evolved to retrograde low temperature and acid conditions during this stage cassiterite formed with magnetite actinolite and fluorite at the expense of tin bearing andradite e g shizhuyuan hunan province or precipitated from the ore forming solution together with chlorite and sulphides e g debao guangxi province or with quartz and sulphides e g dachang guangxi province cassiterite together with calcite even formed at the expense of nordenskioldine in place e g gejiu malayaite was also formed with quartz and calcite at this stage e g zhengjialong jiangxi province

what is the source of the stratospheric gravity wave belt in austral winter abstractduring austral winter and away from orographic maxima or hot spots stratospheric gravity waves in both satellite observations and interim european centre for medium range weather forecasts ecmwf re analysis era interim data reveal enhanced amplitudes in a broad midlatitude belt extending across the southern ocean from east of the andes to south of new zealand the peak latitude of this feature slowly migrates poleward from 50 to 60 s wave amplitudes are much weaker across the midlatitude pacific ocean these features of the wave field are in striking agreement with diagnostics of baroclinic growth rates in the troposphere associated with midlatitude winter storm tracks and the climatology of the midlatitude jet this correlation suggests that these features of the stratospheric gravity wave field are controlled by geographical variations of tropospheric nonorographic gravity wave sources in winter storm tracks spontaneous adjustment emission from the midlatitude winter jet frontogenesi

a chemical model for the devonian remobilization process in the cambrian volcanic hosted massive sulfide rosebery deposit western tasmania the rosebery deposit in western tasmania is a polymetallic massive sulfide deposit hosted in felsic volcanics of the cambrian mount read volcanic belt the deposit underwent upper greenschist facies regional metamorphism and related deformation during the devonian tabberabberan orogeny resulting in folding shearing and faulting thrusting of the ore lenses the south end of the rosebery deposit has undergone metasomatic replacement related to a postorogenic devonian granitoid pluton whose existence is inferred from geophysical gravity data metasomatic mineral assemblages related to this pluton have been recognized transgressing cambrian volcanic hosted massive sulfide minerals at the south end of the rosebery orebody cambrian volcanic hosted massive sulfide mineralization at rosebery consists of three primary zones a lowermost pyrite chalcopyrite zone overlain by a sphalerite galena pyrite zone and further overlain by a massive barite carbonate zone three major devonian replacement zones are also present 1 a magnetite biotite chalcopyrite zone 2 a pyrrhotite pyrite zone and 3 a tourmaline quartz magnetite zone minerals such as fluorite gamet and helvite are also present in the replacement zones metal zonation studies indicate that zinc occurs dominantly in a blanketlike enrichment zone in the primary sulfide lenses of the rosebery deposit gold is largely concentrated at the top of the ore lenses in the transgressive pyrrhotite pyrite replacement zone at the south end of the rosebery deposit zinc is conspicuously depleted but gold concentrations of more than 20 glt are observed in contrast the biotite magnetite and tourmalinebearing replacement zones contain low gold grades generally less than 5 0 glt au copper concentrations as high as 2 percent are observed in the biotite magnetite zone as well as in the pyrrhotite pyrite zone microthermometry and laser raman spectroscopy studies of fluid inclusions from tlle devonian replacement zone indicate that the early biotite magnetite and pyrrhotite pyrite assemblages formed from the interaction of moderate to high temperature 330 c saline 10 25 wt nacl equiv co2 bearing fluid with the original stratiform lead zinc mineralization the later stage tourmaline veining and associated replacement assemblages resulted from lower temperature 300 c less saline 10 wt nacl equiv fluid the high temperature high salinity and co2 bearing metasomatic fluid support the hypothesis of derivation of this fluid from devonian granite below the rosebery deposit during the devonian metasomatic event gold and to a lesser extent copper were most likely remobilized as chloride complexes because of the high temperature and high salinity of the fluid in comparison to copper and gold zinc and lead were dissolved and removed probably as chloride complexes

geological setting mineralogy and genesis of tungsten mineralization in dayu district jiangxi people s republic of china an outline the city of dayu is the center of the most important tungsten district of prc valuable quantities of sn mo bi nb ta ree cu pb zn ag be and li are also recovered at the xihuashan and dangping mines hundreds of the typical jiangxi wolframite quarz veins located at the top and marginal parts of a jurassic biotite granite intrusion are mined at piaotang the mined ore bodies consist of a stockwork type of mineralization which cuts the roof rocks cambrian metasediments phyllite quartz sandstone hornfels of the biotite granite around the mineralizations the country rocks display extensive alteration namely k feldspar alteration and greisenization in granite tourmalinization muscovitization silicification pyrophillitization in the metasediments the main mineralogy and parageneses of the veins and veinlets can be summarized as follows i stage oxide wolframite cassiterite molybdenite quartz k feldspar beryl fluorite topaz the best represented ii stage sulphide chalcopyrite galena sphalerite pyrite pyrrhotite bismuthinite cassiterite wolframite quartz well represented at piaotang iii stage carbonate pyrite scheelite chlorite sericite fluorite quartz calcite the fracture controlled mineralizations of dayu appear to be the product of a continous multistage process related to the late phases of the jurassic yenshanian magmatism

porphyry cu au and associated polymetallic fe cu au deposits in the beiya area western yunnan province south china abstract the alkaline porphyries in the beiya area are located east of the jinshajiang suture as part of a cenozoic alkali rich porphyry belt in western yunnan the main rock types include quartz albite porphyry quartz k feldspar porphyry and biotite k feldspar porphyry these porphyries are characterised by high alkalinity k2o na2o 10 high silica sio2 65 high sr 400 ppm and 87sr 86sr 0 706 ratio and were intruded at 65 5 ma between 25 5 to 32 5 ma and about 3 8 ma respectively there are five main types of mineral deposits in the beiya area 1 porphyry cu au deposits 2 magmatic fe au deposits 3 sedimentary polymetallic deposits 4 polymetallic skarn deposits and 5 palaeoplacers associated with karsts the porphyry cu au and polymetallic skarn deposits are associated with quartz albite porphyry bodies the fe au and polymetallic sedimentary deposits are part of an ore forming system that produced considerable au in the beiya area and are characterised by low concentrations of la ti and co and high concentrations of y yb and sc the cenozoic porphyries in western yunnan display increased alkalinity away from the triassic jinshajiang suture distribution of both the porphyries and sedimentary deposits in the beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the yangtze plate and gondwana continent and lie within a shear zone between buried palaeo tethyan oceanic lithosphere and upper mantle lithosphere caused by the subduction and collision of india and asia

sedimentary rock hosted au deposits of the dian qian gui area guizhou and yunnan provinces and guangxi district china abstract sedimentary rock hosted au deposits in the dian qian gui area in southwest china are hosted in paleozoic and early mesozoic sedimentary rocks along the southwest margin of the yangtze south china precambrian craton most deposits have characteristics similar to carlin type au deposits and are spatially associated on a regional scale with deposits of coal sb barite as tl and hg sedimentary rock hosted au deposits are disseminated stratabound and or structurally controlled the deposits have many similar characteristics particularly mineralogy geochemistry host rock and structural control most deposits are associated with structural domes stratabound breccia bodies unconformity surfaces or intense brittle ductile deformation zones such as the youjiang fault system typical characteristics include impure carbonate rock or calcareous and carbonaceous host rock that contains disseminated pyrite marcasite and arsenopyrite usually with m sized au commonly in as rich rims of pyrite and in disseminations late realgar orpiment stibnite and hg minerals are spatially associated with earlier forming sulfide minerals minor base metal sulfides such as galena sphalerite chalcopyrite and pb sb as sulphosalts also are present the rocks locally are silicified and altered to sericite clay illite rocks and or stream sediment geochemical signatures typically include elevated concentrations of as sb hg tl and ba a general lack of igneous rocks in the dian qian gui area implies non pluton related ore forming processes some deposits contain evidence that sources of the metal may have originated in carbonaceous parts of the sedimentary pile or other sedimentary or volcanic horizons this genetic process may be associated with formation and mobilization of petroleum and hg in the region and may also be related to as au and tl bearing coal horizons many deposits also contain textures and features indicative of strong structural control by tectonic domes or shear zones and also suggest syndeformational ore deposition possibly related to the youjiang fault system several sedimentary rock hosted au deposits in the dian qian gui area also are of the red earth type and au grades have been concentrated and enhanced during episodes of deep weathering

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

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

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

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

tectonics of south china key to understanding west pacific geology abstract south china is not a post caledonian platform but a composite of orogenic belts this late proterozoic mesozoic orogen is a collage of three continental fragments the three blocks are yangzi huanan and dongnanya and they are separated by the banxi nanpanjiang formerly xianggangzhe and gunanhai suture zones yangzi was separated from gondwanaland during late precambrian when an open ocean called banxi was present between the two continents tectonic processes at an active margin during sinian and early paleozoic time led to the genesis of an accretionary wedge complex the banxi melange and the huanan flysch nappes on the northern margin of huanan which was then the northern margin of the gondwana continent reorganization of plates during the devonian suspended subduction at the huanan active margin huanan was uplifted and unconformably overlain by transgressive deposits of devonian and or carboniferous age a remnant ocean the nanpanjiang sea still existed between yangzi and huanan and deep water sedimentation continued both at the southern margin of yangzi and at the northwestern margin of huanan the latter again became an active margin during late paleozoic when permian and triassic flysch sediments were deposited in foredeeps ahead of advancing nappes huanan and yangzi collided during the triassic and resulted in the deformation of the passive margin of the latter to form the yangzi deformed belt huanan was separated from a more southerly continent dongnanya in the devonian by seafloor spreading which created a late paleozoic and early mesozoic ocean gunanhai ocean a continuously deposited sequence ranging in age from devonian to triassic was laid down on the southern passive margin of huanan on the other side of the ocean the dongnanya permian strata include glacial marine deposits of gondwanaland affinity dongnanya became separated from gondwanaland during the late permian when it marched northward to be reunited with huanan the huanan passive margin sequence was deformed by folding and overthrusting after the late mesozoic collision of huanan and dongnanya scattered outcrops of the suture melange resulting from this collision occur at a few localities in coastal fujian dongnanya in our model was the mesozoic continent of southeast asia peripheral to mainland asia this may or may not have been the eastern continuation of the microcontinent sibumasu siam thailand burma malaysia sumatra the collision of dongnanya and asia gave rise not only to the gunanhai melange of coastal fujian but also to the ophiolite melanges parts of which are present in taiwan tailuko the philippines and western malaysia

characteristics and genesis of gangdese porphyry copper deposits in the southern tibetan plateau preliminary geochemical and geochronological results porphyry type cu mo au deposits have been discovered along the gangdese magmatic arc in the southern tibetan plateau extensive field investigations and systematic studies of geochemistry s pb isotopic tracing together with re os and 40ar 39ar isotopic dating indicate that the mineralisation of the copper belt is genetically related to emplacement of late orogenic granitic porphyries during the post collisional crustal relaxation period of the late himalayan epoch these porphyries are petrochemically k enriched and belong to shoshonitic to high k calc alkaline series they display enrichment of large ion lithophile elements lile rb k u th sr pb and depletion of high field strength elements hfse nb ta ti and the heavy rare earth elements hree and y without eu anomalies these characteristics demonstrate that subduction played a dominant role in their petrogenesis and residual garnet was left in the magma sources pb isotope data show a linear correlation in the plumbotectonic framework diagram ranging from orogenic pb in the eastern segment of the copper belt to mantle pb in the western segment these constitute a mixing line of the indian oceanic morb with indian oceanic sediments and suggest that the porphyry magmas were dominantly derived from partial melting of subducted oceanic crusts mixed with a minor quantity of sediments and mantle wedge components the gangdese porphyry copper polymetallic belt has alteration characteristics and zonation typical of porphyry type copper deposits which include potassic alteration k feldspathisation and biotitisation silicification sericitisation and propylitisation mineralisation mainly occurs in strongly altered granitic cataclasite at the exo contact with veinlet disseminated textures the porphyries themselves are weakly mineralised with disseminated pyrite and chalcopyrite the copper deposits contain simple ore mineral associations consisting of chalcopyrite pyrite bornite molybdenite sphalerite and oxidised minerals of malachite covellite and molybdite during supergene oxidation primary ores underwent secondary enrichment to form economic orebodies with cu grade ranging from 1 to 5 ore sulphides of the copper belt display s and pb isotopic compositions identical to the ore bearing porphyries their 34s values vary between 3 8 and 2 4 and are typical of mantle sulphur the 206pb 204pb 207pb 204pb and 208pb 204pb ratios vary in the ranges 18 106 to 18 752 15 501 to 15 638 and 37 394 to 39 058 respectively and yielded radiogenetic lead enriched signatures twelve molybdenite samples from the copper belt yielded isochron ages of 14 76 0 22 ma and 13 99 0 16 ma for the nanmu and chongjiang deposits and model ages of 13 5 to 13 6 ma for the lakang e deposit meanwhile 40ar 39ar isotopic dating of two biotite phenocrysts from the chongjiang and lakang e deposits give plateau ages of 13 5 1 0 ma and 13 42 0 10 ma respectively during the geodynamic evolution of the gangdese collision orogenic belt intrusion of the ore bearing porphyries took place just before the rapid uplift and e w extension of the southern plateau and the ore forming process may have occurred simultaneously with the uplift and extension 14 0 1 ma

lateglacial ice cap dynamics in nw scotland evidence from the fjords of the summer isles region abstract the seaboard of western scotland is a classic fjord landscape formed by glaciation over at least the last 0 5 ma we examine the glacial geology preserved in the fjords or sea lochs of the summer isles region of nw scotland using high resolution seismic data multibeam swath bathymetry seabed sediment cores digital terrain models aerial photographs and field investigations detailed analyses include seismic facies and lithofacies interpretations sedimentological and palaeoenvironmental analyses and radiocarbon dating of selected microfauna our results indicate that the pleistocene sediments of the summer isles region on and offshore can be subdivided into several lithostratigraphic formations on the basis of seismic character geomorphology and sedimentology these are subglacial tills ice distal and glacimarine facies ice proximal and ice contact facies moraine assemblages and holocene basin fill the submarine landscape is also notable for its large scale mass movement events the result of glaciodynamic paraglacial or seismotectonic processes radiocarbon dating of marine shells indicate that deglaciation of this part of nw scotland was ongoing between 14 and 13 ka bp during the lateglacial interstadial greenland interstadial 1 consistent with cosmogenic surface exposure ages from previous studies a sequence of numerous seafloor moraine ridges charts oscillatory retreat of the last ice sheet from a buoyant calving margin in the minch to a firmly grounded margin amongst the summer isles in the early part of lateglacial interstadial gi 1 pre 14 ka bp subsequent punctuated frontal retreat of the ice mass occurred in the following 1000 years during which time ice cap outlet glaciers became topographically confined and restricted to the fjords a late stage readvance of glaciers into the inner fjords occurred soon after 13 ka bp which calls into question the accepted limits of ice extent during the younger dryas stadial greenland stadial 1 we examine the wider implications of our chronostratigraphic model discussing the implications for british ice sheet deglaciation lateglacial climate change and the style and rates of fjord sedimentation

one dimensional reactive transport models of alteration in the tongchang porphyry copper deposit dexing district jiangxi province china in the tongchang porphyry copper deposit the main hydrothermal alteration is most intense in and near the contact zone and gradually attenuates inward and outward showing a symmetrical zoning with respect to the contact zone detailed field investigations of wall rock alteration and ore controlling fractures combined with laboratory studies of lithology mineral composition and fluid inclusions have led to an assessment of initial and boundary conditions and physical parameters such as species concentration mineral volume fraction temperature porosity reactive surface area and flow velocity required for dynamic modeling of this system we have developed a new program to model the coupled process of fluid flow involving advection and diffusion and chemical reactions incorporating mineral dissolution precipitation and have numerically simulated the spatial and temporal evolution of the systems for a duration of 100 000 yr in the simulations transient temperature fields are calculated for the main temperature range of ore formation from 200 degrees to 350 degrees c simulated mineral assemblages are generally in agreement with those observed in the real system the important conclusions drawn from the combined researches of geology and geochemistry as well as dynamics of coupled fluid transport and reactions are as follows fluid flow and reactions were mainly controlled by the fractures striking around north south and dipping to the west in the exocontact zone schistosity cleavages were also important fluid pathways in addition to the fractures the formation of closely spaced fractures in the contact zone and especially in the exocontact zone by tectonic activity after potassium metasomatism and the reactive flow from the contact zone inward and outward were the principal reasons for the occurrence of the contact zone symmetrical alteration zone in the porphyry body both the dissolution and precipitation of minerals were important the rate of dissolution or precipitation of minerals gradually decreased in time the nearer it was to the contact zone spatially the earlier the dissolution or precipitation of minerals was finished in the exocontact metamorphic wall rock the main processes were the transport and precipitation of sio sub 2 sub aq the rate of silification gradually decreased in time and space in the alteration of porphyry body na super was evidently removed from the alteration zone and ca super 2 removed from the intense alteration zone to weak alteration zone and the fluid was weakly acidic ph asymp 4 in the metamorphic wall rock sio sub 2 sub aq was mainly brought in from fluid the evolution of sio sub 2 sub aq cl super ca super 2 and co 3 super 2 was intimately correlated with alteration mineralization intensity

ore forming fluids associated with granite hosted gold mineralization at the sanshandao deposit jiaodong gold province china the sanshandao gold deposit with total resources of more than 60 t of gold is located in the jiaodong gold province the most important gold province of china the deposit is a typical highly fractured and altered disseminated gold system with high grade quartz sulphide vein veinlet stockworks that cut mesozoic granodiorite there are four stages of veins that developed in the following sequence 1 quartz k feldspar sericite 2 quartz pyrite arsenopyrite 3 quartz base metal sulfide and 4 quartz carbonate fluid inclusions in quartz and calcite in vein veinlet stockworks contain c o h fluids of three main types the first type consists of dilute co2 h2o fluids coeval with the early vein stage molar volumes of these co2 h2o fluid inclusions ranging from 50 60 cm3 mol yield estimated minimum trapping pressures of 3 kbar homogenization temperatures obtained mainly from co2 h2o inclusions with lower co2 concentration range from 267 375 c the second inclusion type with a co2 h2o ch4 composition was trapped during the main mineralizing stages these fluids may reflect the co2 h2o fluids that were modified by fluid rock reactions with altered wallrocks isochores for co2 h2o ch4 inclusions with homogenization temperatures ranging from 204 325 c and molar volumes from 55 to 70 cm3 mol provide an estimated minimum trapping pressure of 1 2 kbar the third inclusion type aqueous inclusions trapped in cross cutting microfractures in quartz and randomly in calcite are post mineralization and have homogenization temperatures between 143 228 c and salinities from 0 71 7 86 wt nacl equiv stable isotope data show that the metamorphic fluid contribution is minimal and that ore fluids are of magmatic origin most likely sourced from 120 126 ma mafic to intermediate dikes this is consistent with the carbonic nature of the fluid and the cross cutting nature of those deposits relative to the host mesozoic granitoid

tectonics granitoids and mesozoic gold deposits in east shandong china abstract mesozoic granitoids in east shandong 1 contain some 30 moz gold making east shandong the largest granitoid hosted gold province in the world the gold province is located along the northern boundary of the suture zone between the north china and south china cratons according to their mineralogical geochemical and geochronological characteristics two groups of mesozoic granitoids are recognised in east shandong namely the middle yanshanian my ca 160 150 130 ma and the late yanshanian ly ca 117 85 ma granitoids the first group of granitoids only occur to the north of the suture zone whereas the second group of granitoids occur on both sides of the suture zone these characteristics suggest that the two groups of granitoids were associated with different tectonic events a tectonic analysis suggests that the my granitoids are the result of collision and suturing of the north and south china cratons during the triassic to jurassic whereas formation of the ly granitoids is attributed to the distal inland influence of subduction of the pacific izanagi plate underneath the eurasian continent during the cretaceous the major gold deposits are spatially associated with the my granitoids in east shandong most of the gold occurs either as quartz veins in the granitoids or disseminated in altered shear zones along the boundary of the granitoids and archaean metamorphic rocks the major gold mineralization and alteration generally display the characteristics of gold only provinces namely co 2 rich low salinity and reduced fluids and proximal mica and sulfide alteration these characteristics are different from those of phanerozoic granitoid related skarn porphyry systems accordingly the gold mineralization may be more tectonically and structurally controlled rather than have a direct genetic relationship with the granitoid itself according to the relationships between tectonics granitoids distribution of gold deposits and fluid geochemistry the major gold in east shandong may have been formed during the subsequent exhumation stage after the collision of the north and south china cratons