multi stage precipitation and redistribution of gold and its collection by lead bismuth and lead immiscible liquids in a reduced intrusion related gold system rirgs dublin gulch western canada abstract dublin gulch reduced intrusion related gold system rirgs located in the selwyn basin area of western canada represents one of the best examples of rirgs mineralization globally and hence can be studied to unravel genesis and evolution of these types of deposits based on textural relationships mineralogy and trace element mineral chemistry three auriferous vein stages were identified the paragenetic sequence for the auriferous vein stages are 1 eagle style es quartz albite low sulfide and sulfosalt content 30 vol as fe w pb bi au ag veins and 3 potato hills style 2 phs 2 high sulfide and sulfosalt content 30 vol fe pb sb zn cu au ag veins in the es and phs 1 veins au is present both as native gold au ag and as invisible gold in arsenopyrite whilst in the phs 2 veins au is present as invisible gold in pyrite native gold micrograins individual grains 1 100 s m in size are observed associated with pb minerals in anhedral to globular cosalite pb2bi2s5 in es veins or galena pbs in the phs 1 veins native gold is also observed as micrograins along arsenopyrite margins and in quartz fractures we suggest a variation on the hydrothermal bi melt collector model to explain the au pb bi association the au ag pb and bi are interpreted to have been locally remobilized from arsenopyrite which shows textures and trace element distribution patterns consistent with fluid and deformation assisted recrystallization we suggest pb and bi were mobilized either as immiscible nanodroplets that coalesced to form larger pb bi liquid accumulations or into the hydrothermal fluid and subsequently exsolved to form immiscible pb bi liquids we propose that remobilized au and ag were collected by these pb bi immiscible liquids subsequent retrograde alteration sulfidation is interpreted to have converted the au ag pb bi alloys to native gold and cosalite es and native gold and galena mineral assemblages phs 1 the similarity of the au ag ratios in native gold and arsenopyrite supports a local source for the native gold micrograins temperatures required to attain liquid pb0 5bi0 5 145 2 c and pb 327 5 c are consistent with arsenopyrite geothermometry es 345 405 c phs 1 380 c these suggested new variations pb bi and pb on the hydrothermal melt bi collector model are important given the common association of native gold with pb bi sulfosalts in many gold deposits and the relatively low temperatures required to maintain these liquids and collect au from the hydrothermal fluid

u pb zircon and geochemical constraints on the age origin and evolution of paleozoic arc magmas in the oyu tolgoi porphyry cu au district southern mongolia abstract uranium pb zircon ages are linked with geochemical data for porphyry intrusions associated with giant porphyry cu au systems at oyu tolgoi to place those rocks within the petrochemical framework of devonian and carboniferous rocks of southern mongolia in this part of the gurvansayhan terrane within the central asian orogenic belt the transition from devonian tholeiitic marine rocks to unconformably overlying carboniferous calc alkaline subaerial to shallow marine volcanic rocks reflects volcanic arc thickening and maturation radiogenic nd and pb isotopic compositions e nd t range from 3 1 to 7 5 and 206 pb 204 pb values for feldspars range from 17 97 to 18 72 as well as low high field strength element hfse contents of most rocks mafic rocks typically have 2 are consistent with magma derivation from depleted mantle in an intra oceanic volcanic arc the late devonian and carboniferous felsic rocks are dominantly medium to high k calc alkaline and characterized by a decrease in sr y ratios through time with the carboniferous rocks being more felsic than those of devonian age porphyry cu au related intrusions were emplaced in the late devonian during the transition from tholeiitic to calc alkaline arc magmatism uranium pb zircon geochronology indicates that the late devonian pre to syn mineral quartz monzodiorite intrusions associated with the porphyry cu au deposits are 372 ma whereas granodiorite intrusions that post date major shortening and are associated with less well developed porphyry cu au mineralization are 366 ma trace element geochemistry of zircons in the late devonian intrusions associated with the porphyry cu au systems contain distinct th u and yb gd ratios as well as hf and y concentrations that reflect mixing of magma of distinct compositions these characteristics are missing in the unmineralized carboniferous intrusions high sr y and evidence for magma mixing in syn to late mineral intrusions distinguish the late devonian rocks associated with giant cu au deposits from younger magmatic suites in the district

cenozoic high k alkaline magmatism and associated cu mo au mineralization in the jinping fan si pan region southeastern ailao shan red river shear zone southwestern china northwestern vietnam abstract the jinping fan si pan jfp cenozoic magmatic and cu mo au metallogenic belt in the southeastern part of the ailao shan shear zone host the tongchang chang an habo and chinh sang cu mo au deposits these deposits form an integrated epithermal porphyry regional mineralization system associated with 40 32 ma high k alkaline magmatism the magmatic rocks in the belt have relatively low tio2

geochronology and geochemistry of late cretaceous igneous intrusions and mo cu w mineralization in the southern yidun arc sw china implications for metallogenesis and geodynamic setting abstract the sanjiang tethyan metallogenic domain stmd is an important part of the tethyan giant metallogenic belt the yidun arc is a part of the stmd in the eastern tibetan plateau recently four newly discovered mo cu w ore deposits related to granitic intrusions were found distributed along the north south strike in the southern yidun arc which are identified as the xiuwacu relin hongshan and tongchanggou deposits herein these four deposits formed along high angle north northwest or north west strike slip faults with vein type and porphyry type mo cu mineralization developed in the intrusions molybdenite re os and zircon u pb dating together with zircon hf isotopes and whole rock geochemistry of the intrusions were studied to discern the relationship between mineralization and magmatism metallogenesis and tectonic settings molybdenite from skarn type mineralization at the hongshan deposit has a re os isochron age of 81 2 2 6 ma mswd 1 3 n 5 consistent with previously published zircon u pb ages and re os ages of porphyry type mo mineralization these results indicate that the hongshan is a late cretaceous porphyry skarn cu mo deposit zircon u pb ages of the granitic intrusions in the xiuwacu relin and tongchanggou deposits varying from 87 4 ma to 82 7 ma combined with published molybdenite re os age spectrum 85 ma to 81 2 ma it is proposed that the mo cu w mineralization in the shangri la region is spatially temporally and probably genetically related to the late cretaceous granitic intrusions the relin hongshan and tongchanggou intrusions have high sio 2 65 2 70 0 wt sr 363 905 ppm sr y 22 72 and la yb 37 69 ratios and low y 11 6 17 0 ppm and yb 0 97 1 59 ppm which displayed adakitic affinities their low mgo 0 66 1 44 wt mg 25 46 variable negative zircon e hf t values 7 9 to 2 3 and proterozoic two stages hf model ages t dm2 1 13 1 62 ga suggest that they were probably dominantly derived from partial melting of thickened lower continental crust according to the tectonic evolution of the bangong meso tethys ocean during the late mesozoic the late cretaceous igneous event and mineralization in the yidun arc likely formed under a late or post collision extensional environment probably related to the collision between the lhasa and qiangtang terranes during the late cretaceous

experimental zircon melt and zircon garnet trace element partitioning and implications for the geochronology of crustal rocks garnet is the most commonly used mineral in thermobarometry whereas zircon is the most robust chronometer to date high grade metamorphic rocks to provide a basis for correlation of zircon and garnet growth we determined experimentally the trace element partitioningbetweenzircon ahydrousgraniticmeltandgarnetat20kbarand800 1000 cforp y rareearthelements ree zr hf th andu inrespecttomelt zirconpreferentiallyincorporatesallinvestigatedelementsapartfromreewithatomicnumberlowerthansm at this pressure and in the chosen composition the distribution coefficient between zircon and melt d zrn melt for ree increases with increasingatomicnumberofthereeandwithdecreasingtemperature dyb is 20at1000 c butmorethananorderofmagnitude higher at800 c the solubilityofzrinhydrousgraniticmelts buffered by zirconisabouta factoroftwo lower at20kbar than what has been previously established for mid crustal pressures large garnet produced in the experiments allowed determination of garnet melt trace element partitioning d grt melt at temperatures of 800 1000 c conditions relevant for partial melting of crustal rocks there is a systematic increase indree with decreasing temperature zircon contains significantly more heavy ree than garnet at temperatures of 800 850 c zircon garnetpartitioncoefficientsofheavy reedecreasewithincreasingtemperaturefromdlu of12at800 cto 1 4at1000 c middle reepartitioningisclosetounityforthewholeinvestigatedtemperaturerange differentempiricallydetermined zircon garnet partition coefficients from granulites and ultra high temperature granulites can potentially be explained by the experimentallydeterminedchangeofpartitioningasafunctionoftemperature thesedatacanassistinestablishingequilibriumbetween garnetandzirconzonesinnaturalrocks andintheconstructionofdetailedpressure temperature timepathsinhigh grademetamorphic rocks

tibetan tectonic evolution inferred from spatial and temporal variations in post collisional magmatism cenozoic magmatism on the tibetan plateau shows systematic variations in space and time that must be considered in models concerning tibetan tectonic evolution after the india asia collision which started in the early tertiary and terminated the gangdese arc magmatism in the lhasa terrane made of the southern tibetan plateau widespread potassium rich lavas and subordinate sodium rich basalts were generated from f50 to 30 ma in the qiangtang terrane of northern tibet subsequent post collisional magmatism migrated southwards producing ultrapotassic and adakitic lavas coevally between f26 and 10 ma in the lhasa terrane then potassic volcanism was renewed to the north and has become extensive and semicontinuous since f13 ma in the western qiangtang and songpan ganze terranes such spatial temporal variations enable us to elaborate a geodynamic evolution model which depicts when and how the indian continental lithospheric mantle started thrusting under asia by involving rollback and breakoff of the subducted neo tethyan slab followed by removal of the thickened lhasa lithospheric root we propose that only after the lithospheric removal which occurred at f26 ma could the indian mantle lithosphere have commenced its northward underthrusting and henceforth served as a pivotal control to the himalayan tibetan orogenesis consequently the tibetan plateau is suggested to have risen diachronously from south to north whereas the southern part of the plateau may have been created and maintained since the late oligocene the northern plateau would have not attained its present day elevation and size until the mid miocene when the lower part of the western qiangtang and songpan ganze lithospheres began to founder owing to the push of the underthrust indian mantle lithosphere d 2004 elsevier b v all rights reserved

removal of thorium 234 by scavenging in the bottom nepheloid layer of the ocean abstract concentrations of234th were measured in deep sea bottom waters to assess the extent of chemical scavenging near the ocean floor at five stations in the eastern tropical pacific where no appreciable bottom nepheloid layer bnl was observed total234th was in secular equilibrium with its parent238u confirming earlier published results in contrast samples from a well developed bnl in the western north atlantic showed a significant depletion of234th due to its removal by scavenging the largest depletions were observed in the two samples closest to the bottom 25 and 64 m above bottom and amounted to 19 of the equilibrium value the results can be used to test models that have been proposed to explain the existence of a bnl it is concluded that only a model which includes local or nearby resuspension of sediment can account for the observations from a steady state model that assumes local resuspension the average residence time of resuspended particles in the bnl is estimated to be 25 days

230th and 232th distributions in mid latitudes of the north pacific ocean effect of bottom scavenging abstract vertical distributions of total 230 th and dissolved 232 th were determined in the mid latitudes of the north pacific ocean 8 n 95 w 40 n 160 e the observed 232 th concentrations are some of the lowest values reported for oceans because of low biogenic particle flux high 230 th activity is exhibited in the central gyre most vertical distributions of 230 th in the pacific ocean have been described well using the reversible scavenging model however we observed the depletion of total 230 th compared with a reversible scavenging model prediction for the deep layers in the mid latitudes of the north pacific ocean considering the time scale of the scavenging residence time of th horizontal eddy diffusion from the higher particle flux region could not have a major influence on 230 th depletion in deep waters the observed depletion is partly explained by lateral advection adopting the scavenging mixing model additionally a bottom scavenging process above the seafloor and a diffusion process are considered to explain the 230 th deficit taking into account the time scale of the scavenging residence time of th in deep waters 230 th in deep water to the upper layers

relative oxidation states of magmas inferred from ce iv ce iii in zircon application to porphyry copper deposits of northern chile major and trace element compositions of zircons and whole rocks from 14 barren and seven ore bearing calc alkaline intrusions from the chuquicamata el abra porphyry copper belt of northern chile have been measured in situ by excimer laser ablation ela icp ms these data permit the ce iv ce iii ratio within zircon to be calculated using a lattice strain model for mineral melt partitioning of ce iv and ce iii zircon ce iv ce iii and eun eun ratios and by inference magmatic oxidation states generally increase from older mafic to younger felsic units within this sequence porphyry copper mineralization is directly associated only with intrusions with zircon ce iv ce iii 300 and eun eun 0 4 such trends can be understood in terms of interdependent relations between oxygen fugacity sulfur speciation and solubility and chalcophile element partitioning in silicate magmas because zircon occurs in most calc alkaline intrusions and is resistant to subsolidus alteration zircon ce iv ce iii ratios provide a useful tool for evaluating the economic potential of such rocks for magmatic hydrothermal cu au mineralization the approach is general and may provide a means to infer relative oxidation state in a wide range of intermediate to felsic igneous rocks

genesis and magmatic hydrothermal evolution of the yangla skarn cu deposit southwest china the yangla skarn cu deposit 150 mt at 1 03 cu is located in the central segment of the jinshajiang metallogenic belt within the sanjiang three rivers region southwest china skarn orebodies are mainly developed between different units of devonian carbonate and quartz sandstone rocks with stratiform like shapes or within the contact zone between granitoids and marbles re os dating of molybdenite intergrowth with chalcopyrite yielded a well constrained 187re 187os isochron age of 232 0 1 5 ma with a weighted average age of 231 8 1 3 ma both coeval with the related intrusions 233 1 1 4 and 231 0 1 6 ma at 2 by zircon u pb dating from our previously published work field and textural relationships indicate three hydrothermal stages characterized by assemblages of prograde skarn pre ore stage retrograde skarn and cu fe mo bi sulfides main ore stage and pb zn sulfides associated with calcite and quartz late ore stage as well as one supergene stage marked by secondary cu mineralization malachite and azurite skarns contain garnets with andraditic compositions ad96 gr2 3py0 1 and clinopyroxene two series hd6di94 and hd86di13jo1 with low mn fe ratios 0 1 typical of cu skarn deposits worldwide three stages of fluid evolution were observed by a detailed fluid inclusion study 1 early fluids were trapped under two phase conditions as evidenced by the coexistence of brine homogenization temperatures 560 600 c average salinity 49 4 1 7 wt nacl equiv n 33 and vapor rich inclusions in pre ore stage andradite and diopside trapped at 600 bars or a depth of approximately 2 km assuming lithostatic pressure conditions 2 main ore stage fluid inclusions in quartz were also trapped under two phase conditions boiling as identified by the coexistence of vapor and liquid rich fluid inclusions liquid rich inclusions homogenized between 312 and 389 c average 350 24 7 c n 20 with salinities of 2 4 to 5 6 wt nacl equiv average 4 2 0 9 wt nacl equiv n 13 and a depth of 2 km 200 bars hydrostatic pressure conditions 3 late ore stage fluids are represented by inclusions in calcite characterized by homogenization temperatures ranging from 220 to 290 c average 249 27 c n 14 and salinities between 2 1 and 8 0 wt nacl equiv average 4 6 1 5 wt nacl equiv n 11 sulfur isotope compositions of sulfide minerals pyrite chalcopyrite pyrrhotite and molybdenite from the main and late ore stage have a narrow range of 34s values from 1 9 to 2 6 consistent with a magmatic origin calcite in the late ore stage has 13c values ranging from 3 2 to 5 9 and 18o from 7 2 to 18 0 distinct from the host rock marble compositions 13c 1 2 4 3 18o 10 8 23 9 when corrected for temperature 250 c estimated from fluid inclusion analysis in calcites these calcite data correspond to ore fluid 13cfluid values of 2 0 to 4 6 and 18ofluid values of 0 5 to 11 2 clustering at 10 which are consistent with a magmatic origin lead isotope compositions of sulfides 206pb 204pb 18 273 18 369 207pb 204pb 15 627 15 677 and 208pb 204pb 38 445 39 611 are similar to those of the granitic intrusions and sedimentary wall rocks but distinct from those of basalts 206pb 204pb 18 282 19 133 207pb 204pb 15 564 15 665 and 208pb 204pb 38 367 38 942 in the mining area taken together these geologic geochemical and isotopic data confirm that yangla is a typical cu skarn deposit

helium and argon isotope geochemistry of alkaline intrusion associated gold and copper deposits along the red river jinshajiang fault belt sw china abstract the red river jinshajiang strike slip fault zone on the eastern margin of the tibetan plateau was originally produced by the india eurasia collision 60 70 myr ago numerous post collisional mantle derived alkaline igneous rocks with ages of 40 30 ma have been intruded along this fault zone in recent years several copper and gold deposits associated with the alkaline intrusions of this region were discovered such as the yao an and beiya gold deposits and the yulong and machangqing copper deposits studied in this paper the mineralised intrusions are felsic with sio 2 ranging from 61 4 to 67 7 wt k 2 o na 2 o from 8 1 to 11 5 wt and k 2 o na 2 o 1 the deposits are located at both the exo and endo contact zones of the intrusions the mineral deposits are of hydrothermal origin with the ore forming temperatures mainly in the range 150 450 c this paper presents he and ar isotope analyses of these four deposits the concentrations of 4 he trapped in fluid inclusions of pyrites from the ores are 0 7 54 1 10 6 cm 3 stp g 1 and those of 40 ar are 0 6 7 3 10 6 cm 3 stp g 1 3 he 4 he ratios are 0 3 2 5 ra ra represents the 3 he 4 he ratio of air 1 39 10 6 40 ar 36 ar ratios are 316 1736 and 3 he 36 ar ratios are 0 2 11 2 10 3 generally the 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios for the gold deposits are higher than those for the copper deposits we suggest that the ore forming fluids of both gold and copper deposits were differentiated from the mantle derived alkaline magmas but were diluted by modified air saturated water masw that experienced intensive interaction with crustal rocks however the magmatic fluids responsible for the gold deposits were less extensively diluted by masw resulting in higher 3 he 4 he 40 ar 36 ar and 3 he 36 ar ratios than the copper deposits

experimental measurements of zircon melt trace element partition coefficients abstract zircon was grown from trace element doped hydrous peralkaline rhyolite melts with buffered oxygen fugacities in cold seal experiments at 0 1 and 0 2 gpa and 800 c and piston cylinder experiments at 1 5 gpa and 900 1300 c zircon and glass were present in all run products and small monazite crystals were present in eight of the 12 experiments average diameters of zircon crystals ranged from 5 to 20 m at 800 c to 30 50 m at 1300 c zircon crystals have thin rims and adjacent glass has a narrow 1 m thick compositional boundary layer concentrations obtained through in situ analysis of cores of run product zircon crystals and melt pools were used to calculate trace element partition coefficients dzircon melt for p sc ti v y la ce pr nd eu gd ho yb lu hf th and u in most cases lu was the most d 12 105 and la the least 0 06 0 95 compatible elements d values from this study fall within the range of previously measured values for rare earth elements ree however d values measured experimentally show less fractionation than those recently measured using natural phenocryst matrix pairs for example dlu dla measured experimentally in this study range between 27 and 206 compared to a value of 706 522 for a natural zircon dacite pair sano y terada k and fukuoka t 2002 high mass resolution ion microprobe analysis of rare earth elements in silicate glass apatite and zircon lack of matrix dependency chem geol 184 217 230 although d values from this study show good agreement with the lattice strain model d values from natural phenocryst matrix pairs combined with measured zircon compositions better reproduce host rock magma compositions of igneous rocks they also yield more reasonable estimates of magma compositions when combined with compositions of out of context zircons for example compositions of the hadean detrital zircons from jack hills australia yield lree enriched magmas when combined with d values from phenocryst matrix pairs yields but yield lree depleted magmas when experimentally determined d values are used we infer that experimentally measured dzircon melt values represent disequilibrium partitioning resulting from rapid zircon growth during short laboratory timescales rapid growth causes development of observed diffusive boundary layers in the melt adjacent to zircon crystals d values from phenocryst matrix pairs are therefore recommended for petrogenetic modeling

seismic facies and regional architecture of the oak ridges moraine area southern ontario analysis of over 50 line kilometres of land based shallow seismic reflection profiles has provided a means of investigating the subsurface architecture and stratigraphic relationships of the glac

mineral leucosome trace element partitioning in a peraluminous migmatite a laser ablation icp ms study abstract low pressure peraluminous migmatites from the pena negra complex central spain stayed partially molten for 5 10 ma until the latest hercynian deformations allowed the segregation of melt as discordant leucosome veins due to long residence within its source the melt had time enough to equilibrate with residual phases other than accessories included within major refractory minerals we estimated crystal melt partition coefficients as the concentration ratios between leucosome samples appearing to be pure melts and mesosome minerals which were analyzed for trace elements with a laser probe coupled to an icp mass spectrometer our data reveal that when biotite is stable li rb cs tl sc v cr ni nb and ta become strongly compatible the role of biotite in fractionating y th u and the ree is insignificant cordierite strongly fractionates li and be and also has some effect on the hree and u garnet produces extreme fractionation of sc y and the hree the ree partition coefficients for ferromagnesian silicates increase with the atomic number this effect being progressively more important through biotite cordierite and garnet k feldspar strongly fractionates ba and pb but plays a secondary role to biotite for rb and cs k feldspar fractionation does not change the lree hree ratio but plagioclase fractionation produces a significant decrease in the lree hree ratio both feldspars greatly fractionate sr and eu monazite fractionation produces a dramatic depletion in ree th and u as well as a decrease in the lree hree and th u ratios apatite also fractionates the ree although in contrast with monazite it increases the lree hree ratio and does not affect the th u ratio zircon fractionation like apatite and garnet produces a strong depletion in the hree and a concomitant increase in the lree hree ratio in contrast with monazite zircon fractionation causes the th u ratio to increase

the geology and mineralogy of the beiya skarn gold deposit in yunnan southwest china the beiya skarn gold deposit is located in the eastern tethyan orogenic belt in western yunnan province china it is one of the largest gold deposits in china with significant amounts of silver and base metals to the end of 2014 the estimated resources are 125 million tonnes mt of ore grading 2 42 g t au 0 48 wt cu 25 5 wt fe 38 85 g t ag 1 24 wt pb and 0 53 wt zn skarn alteration and mineralization are related to shoshonitic quartz monzonite porphyries that were emplaced in triassic carbonates beiya formation re os dating on molybdenite from a skarn orebody indicates an ore forming age of 36 82 0 48 ma which is consistent with previous dating results of the quartz monzonite porphyries at least two paragenetic stages of skarn minerals and associated sulfides were recognized with the early stage typified by garnet pyroxene magnetite and calcite and the late stage characterized by epidote amphibole chlorite quartz and calcite containing up to 70 sulfides pyrite chalcopyrite and minor pyrrhotite the early skarn is dominated by anhydrous minerals which were replaced by hydrous minerals formed during the late stage the garnet in the beiya deposit is andradite rich ad36 97gr3 61 and pyroxene is relatively diopside rich di8 91hd7 89 this mineral assemblage indicates an oxidized skarn system similar to other au cu fe bearing skarn deposits around the world fluid inclusions from pyroxene indicate precipitation from high temperature and high to moderate salinity fluids 420 530 c 11 1 43 3 wt nacl equiv which probably results from boiling of a moderately saline magmatic fluid cooler 180 365 c and moderate to low salinity fluids 1 6 16 5 wt nacl equiv were trapped in garnet and quartz and are interpreted to be responsible for gold deposition chlorite chemistry indicates ore forming temperatures between 300 and 340 c in agreement with fluid inclusion data it appears that gold was transported as chloride complexes under oxidized conditions and was deposited at temperatures of about 300 c when transport of chloride complexes as gold carriers was less efficient

230th in the andaman sea rapid deep sea renewal 1 230th activities were determined in seawater collected from the bay of bengal and the andaman sea the andaman sea is a semi closed basin that is isolated from the bay of bengal by the andaman nicobar ridge the noticeable trend in the vertical distribution of 230th activity in the andaman sea is its uniformity below 1250 m depth we applied the scavenging mixing model to this vertical profile in the andaman sea and estimated the upper limit of renewal time to be 6 yr we compared 210pb 226ra ratios among deep waters of various oceanic basins to constrain the application of 230th as a tracer of deep water renewal the 210pb 226ra ratios were almost identical for the deep water of the andaman sea and the inflow water from the bay of bengal suggesting that the deep water in the andaman sea is replaced rapidly without bottom scavenging effects on the 210pb 226ra ratio

partition coefficients of hf zr and ree between zircon apatite and liquid concentration ratios of hf zr and ree between zircon apatite and liquid were determined for three igneous compositions two andesites and a diorite the concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients those for the apatite in the diorite may deviate from the partition coefficients the hree partition coefficients between zircon and liquid are very large 100 for er to 500 for lu and the hf partition coefficient is even larger the ree partition coefficients between apatite and liquid are convex upward and large d 10 100 whereas the hf and zr partition coefficients are less than 1 the large differences between partition coefficients of lu and hf for zircon liquid and for apatite liquid are confirmed these partition coefficients are useful for petrogenetic models involving zircon and apatite

geochronology of the hongniu hongshan porphyry and skarn cu deposit northwestern yunnan province china implications for mineralization of the zhongdian arc abstract the hongniu hongshan porphyry and skarn copper deposit is located in the triassic zhongdian island arc northwestern yunnan province china single zircon laser ablation inductively coupled plasma mass spectrometry u pb dating suggests that the diorite porphyry and the quartz monzonite porphyry in the deposit area formed at 200 ma and 77 ma respectively a re os isotopic date of molybdenite from the ore is 78 9 ma which indicates that in addition to the known triassic cu au porphyry systems a late cretaceous porphyry cu mo mineralization event also exists in the zhongdian arc the quartz monzonite porphyry shows characteristics of a magnetite series intrusion with a high concentration of al k rb ba and pb low amount of ta ti y and yb and a high ratio of sr y average 26 42 the cretaceous porphyry also shows a strong fractionation between light and heavy rare earth elements average la yb n 37 9 which is similar to those of the triassic subduction related diorite porphyry in the hongniu hongshan deposit and the porphyry hosting the pulang copper deposit however in contrast to the older intrusions the quartz monzonite porphyry contains higher concentrations of large ion lithophile elements and co and lesser sr and zr therefore whereas the triassic porphyry cu au mineralization is related to slab subduction slab in an arc setting the quartz monzonite porphyry in the hongniu hongshan deposit formed by the remelting of the residual oceanic slab combined with contributions from subduction modified arc lithosphere and continental crust which provided the metals for the late cretaceous mineralization

palaeozoic and mesozoic tectonic evolution and palaeogeography of east asian crustal fragments the korean peninsula in context east and southeast asia comprises a complex assembly of allochthonous continental lithospheric crustal fragments terranes together with volcanic arcs and other terranes of oceanic and accretionary complex origins located at the zone of convergence between the eurasian indoaustralian and pacific plates the former wide separation of asian terranes is indicated by contrasting faunas and floras developed on adjacent terranes due to their prior geographic separation different palaeoclimates and biogeographic isolation the boundaries between asian terranes are marked by major geological discontinuities suture zones that represent former ocean basins that once separated them in some cases the ocean basins have been completely destroyed and terrane boundaries are marked by major fault zones in other cases remnants of the ocean basins and of subduction accretion complexes remain and provide valuable information on the tectonic history of the terranes the oceans that once separated them and timings of amalgamation and accretion the various allochthonous crustal fragments of east asia have been brought into close juxtaposition by geological convergent plate tectonic processes the gondwana derived east asia crustal fragments successively rifted and separated from the margin of eastern gondwana as three elongate continental slivers in the devonian early permian and late triassic late jurassic as these three continental slivers separated from gondwana three successive ocean basins the palaeo tethys meso tethys and cenotethys opened between these and gondwana asian terranes progressively sutured to one another during the palaeozoic to cenozoic south china and indochina probably amalgamated in the early carboniferous but alternative scenarios with collision in the permo triassic have been suggested the tarim terrane accreted to eurasia in the early permian the sibumasu and qiangtang terranes collided and sutured with simao indochina east malaya in the early middle triassic and the west sumatra terrane was transported westwards to a position outboard of sibumasu during this collisional process the permo triassic also saw the progressive collision between south and north china with possible extension of this collision being recognised in the korean peninsula culminating in the late triassic north china did not finally weld to asia until the late jurassic the lhasa and west burma terranes accreted to eurasia in the late jurassic early cretaceous and proto east and southeast asia had formed palaeogeographic reconstructions illustrating the evolution and assembly of asian crustal fragments during the phanerozoic are presented d 2005 international association for gondwana research published by elsevier b v all rights reserved

metallogenic setting and ore genetic model for the beiya porphyry skarn polymetallic au orefield western yunnan china abstract the beiya in western yunnan china is a world class porphyry skarn polymetallic au orefield that is currently being explored and constitutes the topic of this paper the beiya orefield is a composite mineral system with a distinct zoning surrounding the causative intrusions for instance the wandongshan the largest deposit in the beiya orefield exhibits a zoning with 1 porphyry au fe cu orebodies in the cupolas to the intrusions 2 au fe cu skarn orebodies along contact zones between the alkaline porphyritic intrusions and triassic limestone country rocks and 3 distal stratiform pb zn ag au epithermal orebodies subsequent au and cu bearing quartz ankerite veins and barren calcite veins overprint the earlier magmatic hydrothermal zoned ore system the hypogene orebodies were weathered to form supergene au ores at shallow levels which were historically termed laterite gold deposits the 2000 km nwn striking jinshajiang ailaoshan metallogenic province located in the three river region of western yunnan western sichuan and eastern tibet hosts numerous world class porphyry and skarn cu mo au ores associated with alkaline porphyry emplacement the beiya polymetallic au orefield a representative example of these ore types is located close to the triassic ailaoshan songma suture to the east and formed during eocene oligocene intraplate extension the distal stratiform pb zn ag au orebodies are hosted by bedding or detachment faults based on exploration data and previous research and combined with our detailed field investigation and further studies in the beiya area we propose a new and comprehensive porphyry skarn epithermal deposit model the model explains the geological setting ore characteristics metallogenic zoning and ore forming processes of the deposits in the beiya area it provides useful insights for further mineral exploration in the jinshajiang ailaoshan province for porphyry and skarn cu mo au ore systems associated with alkaline magmatism and may also be applied to other metallogenic provinces within similar continental arc settings

zircon geochemistry of edong granitoids in the middle lower yangtze metallogenic belt eastern china constraints on w cu fe skarn mineralization abstract it has long been established that skarn deposits of different metals are associated with intrusions of different compositions intermediate felsic granitoids in the edong district of the middle lower yangtze metallogenic belt host skarn deposits with varying w cu fe proportions yet previous whole rock geochemical studies could not distinguish between the magmatic suites that formed the different skarn deposits in this study la icp ms zircon geochemical data are presented for the ruanjiawan w skarn 60300 t wo3 tongshankou cu skarn 0 6 mt cu tonglushan cu fe skarn 1 1 mt cu and 56 8 mt fe and jinshandian fe skarn 200 mt fe deposits in the edong district zircons from the ore forming intrusions of these skarn deposits are all characterized by heavy rare earth element hree enrichments and light rare earth element lree depletions with positive ce anomalies and slightly negative eu anomalies tungsten contents in zircons from the w ore forming intrusion 0 02 3 16 ppm w avg 1 14 ppm are generally higher than in zircons from the cu ore forming intrusion 0 00 0 24 ppm w avg 0 03 ppm copper content in zircons from the cu ore forming intrusion is higher than in those from the w ore forming intrusion fertile intrusive rocks from the four skarn deposits contain zircons with high calculated ce4 ce3 ratios ruanjiawan 71 7 tongshankou 207 5 tonglushan 263 6 jinshandian 189 0 fluorine content of the ruanjiawan intrusion is higher than the tonglushan and jinshandian intrusions followed by the tongshankou intrusion chlorine contents show the opposite trend we propose that the different source regions for the ore fertile intrusions is the critical factor that controls the metal content oxygen fugacity and volatile components our studies suggest that zircon geochemistry is a good indicator to distinguish tungsten causative intrusions from copper and iron ore related intrusions i e w content 1 14 ppm and ce4 ce3 ratios 207 5

intrinsic oxygen fugacity measurements on seven chondrites a pallasite and a tektite and the redox state of meteorite parent bodies abstract intrinsic oxygen fugacity fo2 measurements were made on five ordinary chondrites a carbonaceous chondrite an enstatite chondrite a pallasite and a tektite results are of the form of linear log f o 2 1 t plots except for the enstatite chondrite measured results agree well with calculated estimates by others the tektite produced fo2 values well below the range measured for terrestrial and lunar rocks the lowpressure atmospheric regime that is reported to follow large terrestrial explosions coupled with a very high temperature could produce glass with fo2 in the range measured the meteorite salta pallasite has low fo2 and lies close to hvittis e6 unlike the other samples results for salta do not parallel the iron wustite buffer but are close to the fayalite quartz iron buffer in slope minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites fo2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fo2 conditions the samples equilibrated with respect to fo2 in relatively short time on heating equilibration with respect to fo2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism application of p t fo2 relations in the system c co co2 indicates that the ordinary chondrites were metamorphosed at pressures of 3 20 bars as it appears that they lay on the graphite surface a steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior an oxidized near surface layer and an interior that is increasingly reduced with depth a shallow thermal gradient will produce the reverse a body heated by accretion on the outside will have a reduced exterior and oxidized interior meteorites from the same parent body clearly are not required to have similar redox states

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

hydrothermal evolution and ore genesis of the beiya giant au polymetallic deposit western yunnan china evidence from fluid inclusions and h o s pb isotopes abstract the beiya porphyry skarn gold polymetallic deposit is one of the largest gold deposits in china and also contains significant amounts of silver and base metals the estimated reserve at the end of 2015 was 130 million metric tonnes mt of ores grading 2 42 g t au 0 48 wt cu 25 5 wt fe 38 85 g t ag 1 24 wt pb and 0 53 wt zn the deposit is located in the jinshajiang ailaoshan porphyry skarn cu mo au metallogenic belt in western yunnan province southwest china skarn alteration and mineralization are spatially and temporally associated with eocene monzogranite porphyries which were emplaced into triassic carbonates field evidence and petrographic observations indicate there are four stages of hydrothermal activity i e prograde stage i iron oxide stage ii sulfide stage iii and carbonate stage stage iv stage i is characterized by the formation of garnet and pyroxene by high temperature 398 560 c hypersaline 48 81 67 24 wt nacl equiv hydrothermal fluids with h o isotopic compositions that are similar to typical magmatic fluids these fluids were most likely generated by the separation of brine from a silicate melt in stage ii garnet and pyroxene was replaced by epidote amphibole chlorite quartz and magnetite associated hydrothermal fluids are preserved in coexisting l type and v type fluid inclusions and are characterized by anomalously low d values approximately 80 and lower 18 o than stage i fluids the decrease in ore fluid 18 o h2o values with time coincided with marked decreases in fluid salinity and temperature based on the fluid inclusion and stable isotopic data we suggest that the ore fluid evolved by boiling of the magmatic brine stage iii is characterized by the development of pyrite chalcopyrite galena and sphalerite fluids inclusions associated with stage iii display and continuous range of salinities with the majority being low salinity inclusions 1 28 3 54 wt nacl equiv these fluids yield lower 18 o h2o values 0 85 to 5 52 and moderate d values 78 6 to 88 6 altogether these data indicate that stage iii fluids originated from the mixing of residual stage ii fluids with meteoric water the sulfur isotope 34 s values of stage iii sulfides cover a narrow range of 4 2 to 1 2 mean 1 1 and boiling also occurred at low temperatures 165 347 c during stage iii in stage iv only l type fluid inclusions are present which yielded the lowest homogenization temperatures 157 272 c and the lowest salinities 1 06 12 20 wt nacl equiv the h o isotope data indicate that the ore forming fluids were dominated by magmatic water in stage i and stage ii and that the magmatic water gradually mixed with circulating meteoric water during stage iii and stage iv this conclusion is further supported by the isotopic composition of lead of the ores which is similar to that of the monzogranite porphyries but differs significantly from permian basalts and triassic wall rocks

evidence for enhanced mixing over rough topography in the abyssal ocean the overturning circulation of the ocean plays an important role in modulating the earth s climate but whereas the mechanisms for the vertical transport of water into the deep ocean deep water formation at high latitudes and horizontal transport in ocean currents have been largely identified it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise however measurements of the internal wave field the main source of energy for mixing and of turbulent dissipation rates have typically implied diffusivities across surfaces of equal density of only approximately 0 1 cm2 s 1 too small to account for the return flow here we report measurements of tracer dispersion and turbulent energy dissipation in the brazil basin that reveal diffusivities of 2 4 cm2 s 1 at a depth of 500 m above abyssal hills on the flank of the mid atlantic ridge and approximately 10 cm2 s 1 nearer the bottom this amount of mixing probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry may be large enough to close the buoyancy budget for the brazil basin and suggests a mechanism for closing the global overturning circulation

magmatic zircons from i s and a type granitoids in tibet trace element characteristics and their application to detrital zircon provenance study abstract this study reports a dataset of 21 trace elements of magmatic zircons from typical i type 93 analyses and s type 73 analyses granitoids from the lhasa and himalayan terranes southern tibet and a type granitoids 21 analyses from the songpan ganzi terrane eastern tibet our results indicate that magmatic zircons from the i type granitoids are characterized by relatively lower pb concentrations and higher nb pb n ratios distinct from those of the s type granitoids that reveal higher pb lower nb pb n and significant eu negative anomalies eu eu 0 3 while these values are transitional in zircons from the a type granitoids such differences most likely governed by compositional variations in the host magmas are considered as a useful tool in addition to u pb and hf isotopes for tracing the source provenance of detrital zircons consequently the trace element compositions of detrital zircons with a diagnostic age peak 1170 ma from the lhasa terrane indicate the presence of coeval s type magmatism in their source region this study exemplifies the usefulness of zircon trace element geochemistry in investigating sedimentary source provenance and paleogeographic reconstruction

tethys tectonic evolution and its bearing on the distribution of important mineral deposits in the sanjiang region sw china abstract the sanjiang region in se tibet plateau and nw yunnan is known to have formed by amalgamation of gondwana derived continental blocks and arc terranes as a result of oceanic subduction followed by continental collision from paleozoic to mesozoic in this paper we provide a synthesis of tectonic evolution magmatism and metallogeny in the region based on data from literatures early paleozoic ophiolites 473 439 ma in the changning menglian belt indicate the existence of a proto tethys ocean in this region two episodes of subduction related magmatism in the early paleozoic one occurred in the baoshan and tengchong blocks at 502 455 ma and the other occurred in the simao block at 421 401 ma are regarded as evidence for two different events of subduction of the proto tethys ocean at different locations the proto tethys was succeeded in early devonian by the paleo tethys which comprised the main ocean and three branches ailaoshan jinshajiang and garze litang the changning menglian main ocean existed from middle devonian to middle triassic the remnants of the oceanic crust are preserved in a few places in the longmu tso shuanghu suture as well as in the changning menglian ophiolite belt the eastward subduction of the main oceanic plate from early permian to early triassic formed a prominent arc terrane stretching 1500 km from yunnan to eastern tibet from the waning stage of subduction to post subduction numerous s type granite plutons with ages varying between 230 and 219 ma such as the lincang batholith in yunnan were emplaced at or close to the suture this event produced several hydrothermal w sn deposits in the region the tectonic evolution and associated magmatism of the jinshajiang and ailaoshan branch oceans are generally comparable to those of the main ocean however the branch oceans were subducted westward instead the garze litang branch ocean also underwent westward subduction from middle devonian to late triassic arc related high sr y porphyry intrusions and associated porphyry skarn cu mo au deposits are common in the jinshajiang ailaoshan region especially in the yidun arc which formed prior to jurassic the vms deposits in the sanjiang region formed in diverse tectonic settings including middle silurian back arc basins carboniferous oceanic islands paleozoic subduction zones and triassic post subduction rifting environments the mesozoic and early cenozoic evolution of the baoshan and tengchong blocks was largely influenced by eastward oceanic subduction of the meso and neo tethys from late permian to middle cretaceous and from late cretaceous to 50 ma respectively abundant early cretaceous granitoids and associated skarn type pb zn and sn fe deposits in the baoshan and tengchong blocks were produced in the background of the shan boundary oceanic slab subduction to the west and the break off of the nujiang bitu oceanic slab to the north the subduction of the neo tethys oceanic plate beneath the tengchong block from late cretaceous to paleogene formed abundant s type granitoids and many skarn type and greisen type sn w deposits granitoids formed at 105 to 81 ma and contemporaneous hydrothermal w mo ag and au deposits which temporally coincided with the subduction of the neo tethys are common in the yidun arc terrane

removal of 230th and 231pa at ocean margins abstract uranium thorium and protactinium isotopes were measured in particulate matter collected by sediment traps deployed in the panama basin and by in situ filtration of large volumes of seawater in the panama and guatemala basins concentrations of dissolved th and pa isotopes were determined by extraction onto mno 2 adsorbers placed in line behind the filters in the in situ pumping systems concentrations of dissolved 230 th and 231 pa in the panama and guatemala basins are lower than in the open ocean whereas dissolved 230 th 231 pa ratios are equal to or slightly greater than ratios in the open ocean particulate 230 th 231 pa ratios in the sediment trap samples ranged from 4 to 8 in contrast to ratios of 30 or more at the open ocean sites previously studied particles collected by filtration in the panama basin and nearest to the continental margin in the guatemala basin contained 230 th 231 pa ratios similar to the ratios in the sediment trap samples the ratios increased with distance away from the continent suspended particles near the margin show no preference for adsorption of th or pa and therefore must be chemically different from particles in the open ocean which show a strong preference for adsorption of th ocean margins as typified by the panama and guatemala basins are preferential sinks for 231 pa relative to 230 th furthermore the margins are sinks for 230 th and to a greater extent 231 pa transported by horizontal mixing from the open ocean

melt recharge f o2 t conditions and metal fertility of felsic magmas zircon trace element chemistry of cu au porphyries in the sanjiang orogenic belt southwest china the magmatic hydrothermal pulang cu deposit triassic and the beiya au cu deposits eocene are located in the sanjiang copper porphyry belt southwest china zircon chemistry was used to constrain the magmatic evolution and oxidation state of the porphyries the results show that porphyries of the beiya district formed from an early oxidized melt and a later relatively reduced and more evolved magma whereas pulang experienced a normal cu porphyry evolutionary trend the pulang porphyries crystallized from more oxidized magma fmq 2 9 4 6 average 4 0 1 0 n 3 with an average temperature of 709 6 c compared to the beiya porphyries fmq 0 6 3 5 average 1 9 1 3 n 5 with a mean magmatic temperature of 780 22 c these data combined with data from other cu and au rich porphyries in the sanjiang belt i e machangjing cu yao an au are consistent with previous experimental work showing that elevated cu and au solubilities in magma require oxidizing conditions a compilation of existing geochemical data for magmatic zircons from fertile and barren porphyry systems worldwide establishes an optimal diagnostic interval on ceiv ceiii tti in zircon and eu eu n plots for generating magmatic hydrothermal cu au deposits

mineral textures and zoning as evidence for open system processes investigations of mineral textures and zoning as evidence for open system processes during magmatic evolution have always been a centerpiece of petrological studies and have provided some of the best evidence for magma mixing and crustal contamination for many decades e g milch 1905 kuno 1936 eichelberger 1975 sato 1975 anderson 1976 in fact evidence from mineral studies was instrumental in the acceptance of magma mixing as important petrological process ever since it was initially proposed by bunsen 1851 in recent years mineral studies are invigorated by the development of high precision high resolution analytical instruments and techniques through which textural information and compositional data are combined e g jerram and davidson 2007 as minerals respond texturally and compositionally to changing magmatic environments they preserve in their crystal growth stratigraphy a wealth of information regarding their past history of magmatic processes and compositions cf ginibre et al 2007 on the other hand magmatic liquids melts are snapshots of current magmatic states and provide less direct evidence of the processes responsible for their evolution in addition liquids may crystallize thereby destroying the direct evidence they provide with an appropriate set of observations and measurements we can correlate textures with mineral compositions and thus produce a richer composite picture of magmatic evolution than compositional data of minerals alone this contribution reviews the zoning and textures of minerals frequently encountered in volcanic rocks many of which apply equally to plutonic rocks and the interpretations ascribed to these features in terms of open system magmatic processes first i will address the analytical tools that are used to acquire textural and compositional data followed by a brief review of open system processes and a summary of the relevant textures from that point on i will address some mineral specific aspects followed by a discussion

partitioning of gold in young calc alkalic volcanic rocks from guatemala gold analyses of whole rock mineral and groundmass of seven calc alkalic volcanic rocks basalt to rhyolite show that gold is less abundant in the dominant phenocrystic phases than in the whole rock groundmass concentrations are also lower than whole rock crystal liquid partition coefficients are 1 for plagioclase and hornblende and about 1 for olivine pyroxene magnetite and biotite if only the principal phases are considered the bulk gold partition coefficient is typically 1 yet gold seems to be depleted rather than enriched in many evolved magmas a significant proportion of gold in these rocks is in neither the groundmass nor the dominant phenocrysts but instead is contained in tiny sulflde blebs that are found in these rocks during crystallization the continual separation of a sulflde phase that concentrates gold is consistent with compatible gold behavior and petrography further data is needed to evaluate this hypothesis

zircon compositional evidence for sulfur degassing from ore forming arc magmas porphyry cu mo au and epithermal au ag deposits are major sources of mined metals and are commonly formed by magmatic hydrothermal fluids derived from hydrous magmas in phanerozoic convergent margin settings the igneous rock assemblages associated with porphyry mineral deposits are common in modern convergent margin settings but while many have produced acidic magmatic fluids very few past or present have produced sufficient metal chlorine and sulfur enrichments necessary to engender an ore deposit the reasons for this remain uncertain we report shrimp rg ion microprobe analyses of hafnium titanium and rare earth element ree abundances in zircon a nearly ubiquitous and robust trace mineral in crustal magmas comparison of the compositions of zircons in ore forming and barren granitic plutons indicate that ore forming granites crystallized at relatively low temperature and have relatively small negative europium anomalies mostly eu n eu n 0 4 we interpret these small zircon europium anomalies to indicate oxidizing magmatic conditions and hypothesize that in many cases this reflects oxidation due to so 2 degassing from magmas with a relatively low fe s ratio oxidation of europium and iron in the melt is produced by reduction of magmatic sulfate s 6 to so 2 s 4 upon degassing this interpretation reinforces the important role of oxidized sulfur rich fluids in porphyry and epithermal mineral deposit formation zircon compositions thus may be used to identify ancient magmas that released significant amounts of so 2 rich gases and regional surveys of zircon composition are potentially a valuable tool for mineral exploration

superimposed orogenesis and metallogenesis in sanjiang tethys the sanjiang tethyan area experienced the superpoimsed transition from tethyan tectonic evolution in late paleozoic to continental collision orogeny in cenozoic resulting in the accumulation of massive multi stage mineralizations and large amounts of metallic industrial ore deposits the complex metallogenic evolution of this area finds expression in the following aspects large amounts of complex superimposed and reworked ore deposits were developed on the proterozoic substrate of rigid continental segment with special metallic associations of sn cu sn pb zn and fe cu volcanics hosted massive sulfide deposits were developed throughout the evolution of tethyan lithosphere from continental margin rift cu through initial ocean basin cu zn ocean arc cu zn pb and interarcual rift valley or back arc basin pb zn ag to rift basin caused by arc continental collision cu pb zn island type porphyry copper deposits at the tethyan stage were replaced by continental type porphyry copper deposits at the collision orogeny stage metallic ore forming belt and gigantic ore deposits of world class such as the yulong porphyry cu mo metallogenic belt the lanping zn pb cu ag metallogenic belt the ailaoshan au metallogenic belt the chuanxi ree metallogenic belt the tengchong lianghe sn metallogenic belt were generated explosively during the collision orogeny in cenozoic although successful researches on tectonic and metallogenic cheracteristics have been conducted for the sanjiang tethyan metallogenic domain many important scientific problems remain unsolved such as precise time limits and internal connections between tectonic superposition continental accretion and convergence and collision and transformation the control of geological setting over mineralization the constraint of the crust mantle interaction on the formation of ore deposit clusters and the anomalous concentration of large amounts of ore materials space time structure material structure and genetic type of ore deposits of the typical metallogenic system the development mechanism of metallogenic systems and the formation mechanism of large sized ore deposits it is obvious that the solution of these problems will be a great breakthrough in the study of the tectonic evolution and metallogenesis of the sanjiang tethyan metallogenic domain

zircon rock partition coefficients of rees y th u nb and ta in granitic rocks uses for provenance and mineral exploration purposes abstract the trace element composition of magmatic zircon is highly variable even within the same grain and its study is complicated by the abundance of microinclusions metamict portions and strong compositional zoning among other factors to contribute to the understanding of the geochemistry of trace elements in zircon we determined the rare earth y nb ta th and u contents in zircon grains by laser ablation inductively coupled plasma mass spectrometry la icp ms with the use of cathodoluminescence and backscattered mev images zircon rock partition coefficients were determined in nine different types of granitoids and compared with experimental and natural data the obtained data are comparable with those reported by other authors by using the partition coefficient we estimated the composition of the host granitoids based on the zircon grain composition which was interpreted as evidence that the patterns of the trace elements in zircon grains are controlled by the liquid composition at the moment of crystallization a new set of partition coefficients for rees y nb ta th and u is suggested for provenance and exploratory studies la 0 8 ce 1 7 pr 2 1 nd 3 4 sm 9 8 eu 7 9 gd 24 tb 37 dy 69 ho 117 er 167 tm 281 yb 379 lu 437 nb 1 6 ta 2 9 th 27 u 177 and y 109 trace element diagrams eu eu vs yb nb vs th and y 200 lu 10 nb vs nb ce are proposed for discriminating zircon from different types of granitoids particularly for a type i type and shoshonitic rocks the trace element patterns of zircon are useful as a tool for mineral exploration studies because they often reproduce the patterns of mineralized granites

distribution of 230th in the labrador sea and its relation to ventilation abstract measurements of dissolved and particulate230th and232th by thermal ionization mass spectrometry were made on samples collected from the labrador sea and the denmark strait and iceland scotland overflow waters the large scale feature of low and invariant230th evident in deep waters of the labrador sea and previously observed in the deep northern atlantic can be reproduced using a reversible scavenging model that includes the effect of ventilation advective transport also must be important in the redistribution of230th in other regions of the atlantic and for other long lived tracers such as231pa 26al and10be

trace element geochemistry of magnetite from the giant beiya gold polymetallic deposit in yunnan province southwest china and its implications for the ore forming processes abstract the beiya gold polymetallic deposit is one of the largest gold deposits in china and is considered to be a typical porphyry skarn system located in the middle of the jinshajiang ailaoshan alkaline porphyry metallogenic belt massive magnetite is widespread in the beiya ore district but its genesis is still the subject of debate five representative magnetite types are present in the beiya deposit namely magmatic magnetite m1 from the ore related porphyry disseminated magnetite m2 from the early retrograde alteration massive magnetite m3 from the early quartz magnetite stage massive magnetite m4 from the middle quartz magnetite stage and magnetite m5 from the late quartz magnetite stage compared with the m1 magnetite the magnetites from stages m2 to m5 are depleted in ti al and high field strength elements implying a hydrothermal origin distinct from the magmatic accessory magnetite in the ore related porphyry m1 the concentrations of cobalt in the hydrothermal magnetites decrease gradually from m2 to m5 and can be used to discriminate the magnetite types the al mn and ti v contents of the successively precipitated magnetite grains m2 m5 suggests that the ore forming temperature decreased from m2 to m4 but increased from m4 to m5 possibly as the result of a new pulse of magma entering the chamber which may have triggered the gold mineralization the v content in the hydrothermal magnetite suggests that the oxygen fugacity increased from m2 to m4 but decreased as soon as the sulfides entered the system m5

high temperature metamorphism in a major strike slip shear zone the ailao shan red river people s republic of china abstract petrographic and thermobarometric analysis provides constraints on thept path of the mylonitic gneisses of the left lateral ailao shan red river shear zone which has accommodated the lateral extrusion of indochina during the tertiary two different paragenesis p1 and p2 are coeval with this deformation and correspond respectively to the amphibolite and greenschist facies microprobe analysis reveals that p1 garnets bear a chemical zonation from core to rim this zonation indicates a temperature increase during garnet growth conditions of formation of garnet rims p1b which are estimated using biotite garnet and plagioclase garnet thermobarometers are close to the granitic solidus 710 70 c and4 5 1 5 kbar p2 conditions are estimated to be approximately 500 c and

the age of the potassic alkaline igneous rocks along the ailao shan red river shear zone implications for the onset age of left lateral shearing abstract the potassic alkaline igneous rocks along the ailao shan red river asrr shear zone range in composition from ultramafic to felsic and are characterized by similar trace element patterns and radiogenic isotope ratios their distribution and in some cases their structure and outcrop outline suggest a genetic relationship to the asrr shear zone zircons separated from 12 potassic alkaline bodies along the asrr zone have been dated by an in situ u pb method to temporally constrain the left lateral movements along the shear zone the ages of the alkaline bodies range from 34 0 to 36 3 ma these new zircon ages together with previous data suggest that the onset age of the left lateral movements along the asrr shear zone began at or slightly before 36 ma and that the movements lasted from 36 to 17 ma when uncertainties are taken into account the duration of motion on the asrr shear zone coincides with the opening of the south china sea implying a genetic relationship between these two events

the pulang porphyry copper deposit and associated felsic intrusions in yunnan province southwest china the pulang porphyry copper deposit recently discovered in northwestern yunnan province china is located at the south end of the triassic yidun island arc to date 15 mineralized porphyry deposits have been defined in the pulang area and the copper resource is estimated to exceed 10 mt the pulang deposit as currently defined is made up of five ore bearing porphyry deposits covering an area of approximately 9 km2 intermediate acidic porphyritic intrusions composed of quartz diorite monzodiorite quartz monzonite and granodiorite are widespread in the pulang area the alteration zones identified with the porphyry deposits include silicic potassium silicate quartz sericite and propylitic zones the porphyry deposits have hornfels at the contact with slate sandstone and andesite re os ages of molybdenite and ar ar and k ar dating of biotite indicate that the pulang porphyry copper deposit formed during the indosinian tectonic episode with the main ore formation taking place from 216 to 213 ma late triassic norian however the whole process of hydrothermal activity including overprinting may have extended from 235 to 182 5 ma

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

geology mineralization and fluid inclusion characteristics of the kumbel oxidized w cu mo skarn and au w stockwork deposit in kyrgyzstan tien shan the kumbel deposit is located within a metallogenic belt of w mo cu mo au w and au deposits along the late paleozoic active continental margin of tien shan the deposit is related to a late carboniferous multiphase pluton with successive intrusive phases from early olivine monzogabbro through monzonite quartz monzonite to granodiorite and granite with the latest monzogabbro porphyry dikes the deposit represents an example of a complex w cu mo au magmatic hydrothermal system related to magnetite series high k calc alkaline to shoshonitic igneous suite it contains large bodies of w cu mo oxidized prograde and retrograde skarns with abundant andradite garnet magnetite and especially hematite as well as k feldspar molybdoscheelite chalcopyrite and molybdenite with transitions to zones of intense quartz k feldspar with minor andradite and hematite veining the skarns are cut by quartz carbonate adularia sericite veins locally sheeted and stockworks bearing scheelite and minor cu zn pb sulfides as well as au bi te and as mineralization the association of these veins with the oxidized skarns and magnetite series intrusion is consistent with the general oxidized intrusion related w mo cu au type of deposit with an affinity to the alkalic silica saturated cu au mo porphyry deposits the fluid inclusion data show the predominance of magmatic hydrothermal aqueous chloride fluid during the formation of skarns and quartz carbonate scheelite sulfide veins the high fluid pressures 1 750 bars together with their high temperature up to 600 c and high salinity 50 60 wt nacl equiv suggest the formation of skarns and quartz k feldspar andradite hematite veins under conditions typical of magmatic hydrothermal transition depth of 4 5 km of intrusion related mineralized system possibly by exsolution of the fluids from crystallizing magma the auriferous quartz carbonate scheelite sulfide veins formed from high to moderate salinity from 40 to 20 wt nacl equiv and high pressure from 1 200 bars to 850 900 bars aqueous chloride fluids under decreasing temperature from 370 to 120 c the massive deposition of molybdoscheelite in retrograde skarn and scheelite in quartz carbonate scheelite sulfide veins could correspond to enrichment of fluids in ca up to 18 25 wt cacl2 likely from crystallizing magma

combining seawater 232th and 230th concentrations to determine dust fluxes to the surface ocean abstract aeolian dust is a significant source of iron and other nutrients to the surface ocean but constraining the size of this flux is difficult chemical tracers such as al are useful but are limited by lack of information about their rate of removal from surface seawater in this study we test the use of th isotopes as an improved tracer of dust input by measuring 232 th and 230 th concentrations of upper ocean seawater at six stations along a meridional atlantic section that spans the saharan dust plume open ocean 232 th like al is dominantly derived from dust dissolution while 230 th is produced in seawater by u decay and provides an assessment of th removal rates the highest 232 th concentrations and 232 th 230 th ratios particularly in the surface waters are observed at stations expected to be influenced by input of saharan dust the pattern of 232 th concentration is in agreement with dissolved al distributions and seawifs aerosol imagery supporting the use of 232 th as a proxy for short term dust addition deeper in the water column 232 th concentration may also reflect longer term dust inputs in addition lateral input of 232 th from mediterranean outflow water is detected at 1000 m in the north atlantic surface water residence times are calculated separately from 230 th and 234 th using a simple scavenging model and values from the two isotopes are generally consistent with one another th 230 residence times appear to reflect the longer term value however rather than exhibiting the strong seasonal influence seen for 234 th these th residence times allow dust flux to the surface ocean to be calculated using the known concentration of th in dust and assumed values for the solubility of dust th in seawater resulting dust fluxes show good agreements with models of dust deposition if th solubility is 1 to 5 in the north atlantic yielding fluxes of 0 4 19 2 g m 2 yr 1 and 5 to 10 in the south atlantic fluxes of 0 2 0 7 g m 2 yr 1 despite the need for better constraints on the fractional solubility of dust th this study demonstrates the power of combining th isotope measurements to constrain dust fluxes to the surface ocean

trace element composition of igneous zircon a thermal and compositional record of the accumulation and evolution of a large silicic batholith spirit mountain nevada hafnium u th and ree content of zircons from the spirit mountain batholith in southern nevada correlate with calculated temperatures from the ti in zircon thermometer to support field and petrologic evidence of rejuvenation of crystal mush and melt extraction events during the 2 million year accumulation of the granitoid batholith marked variation in zircon composition from sample to sample from grain to grain within individual samples and from zone to zone within individual grains documents in detail a history of fluctuating conditions with repeated episodes of replenishment reheating crystal mush rejuvenation fractional crystallization and melt segregation the zircons exhibit compositional and thermal variability indicative of variations in host melt composition due to 1 melt rejuvenation mixing and fractionation 2 coeval growth of other ree rich accessory minerals and possibly 3 fluctuation in fo2

high sr y arc magmas and porphyry cu mo au deposits just add water porphyry cu mo au deposits are commonly associated with intermediate composition arc related igneous rocks with high sr y and la yb ratios and such rocks are equated by some researchers with melts derived from subducted oceanic crust undergoing eclogite facies metamorphism adakites however similar geochemical characteristics are readily developed in normal asthenospheric mantle wedge derived magmas by fractionation of amphibole and or garnet and or by interaction with crustal materials during ascent through the upper plate lithosphere while there is widespread evidence for such fractionation and contamination processes in porphyry magmas there is little direct evidence for an origin by slab melting the enhanced fertility of arc magmas relates primarily to their high water content which is required for the formation of magmatic hydrothermal systems upon shallow crustal emplacement magmatic water contents 4 wt percent h 2 o cause abundant amphibole garnet fractionation but suppression of plagioclase crystallization at deep crustal levels resulting in increasing sr y and la yb ratios with differentiation commonly into adakitic ranges but not reflecting slab melting additional factors that affect arc magma fertility are relatively high oxidation states and sulfur content but these are secondary to the requirement for sufficient water thus arc magmatic suites with high sr y ratios and evidence for the presence of hydrous phenocryst phases hornblende and or biotite are indeed prospective for porphyry cu mo au deposits but only because these parameters indicate high magmatic water content