enhancement of alongshore freshwater transport in surface advected river plumes by tides abstracta recent numerical study by isobe showed that imposing alongshore tidal forcing on buoyant coastal discharge enhances the net freshwater transport in the coastal currents the mechanisms for this transport enhancement are studied using a three dimensional primitive equation ocean model regional ocean modeling system roms lagrangian drifters are used to trace the freshwater transport paths it is found that the river plume bulge circulation largely follows the rigid body motion i e constant vorticity the buoyant fluid near the bulge s outer edge is thinner and faster behaving as a baroclinic jet the bulge currents then split after impinging on the coast the outer fluid feeds the downshelf flowing coastal currents while the inner fluid recirculates to form the bulge the coastal current transport estimated from the present and prior studies corresponds well to a baroclinic jet theory with the incident angle of bulge currents at the coast being a key parameter without tides the bulg

progress on upwelling studies in the china seas east asian marginal seas surrounding china exhibit rich ocean upwelling mostly in response to the southwesterly summer monsoon upwelling in the china seas namely the south china sea the taiwan strait the east china sea the yellow sea and the bohai sea has become increasingly important because the potential changes in the upwelling may have dramatic ecosystem socioeconomic and climate impacts this paper reviews the progress of upwelling studies in the china seas since the year 2000 by presenting the principal characteristics and new understanding of 12 major upwelling regions in the china seas upwelling exhibits long term variability at intraseasonal to multi decadal scales as well as short term variability frequently caused by tropical cyclones it is also associated with the el nino southern oscillation local environmental variation and biogeochemical factors the coastal upwelling around hainan island and the upwelling or cold dome northeast of taiwan island are specifically highlighted because they have attracted great interest for decades this paper summarizes upwelling mechanisms in terms of wind topography tide stratification and background flow with applications mostly to the china seas finally we propose some topics for future upwelling research i e potential intensification of coastal upwelling under global climate change downwelling intrusion of upwelling into coastal embayments and the influence of upwelling on fishery and biogeochemical processes

the dynamics of the mississippi river plume impact of topography wind and offshore forcing on the fate of plume waters 1 high resolution numerical simulations of the northern gulf of mexico region using the hybrid coordinate ocean model hycom were employed to investigate the dynamical processes controlling the fate of the mississippi river plume in particular the conditions that favor cross marginal transport the study focuses on the effects of topography wind driven and eddy driven circulation on the offshore removal of plume waters a realistically forced simulation nested in a data assimilative regional gulf of mexico hycom model reveals that the offshore removal is a frequent plume pathway eastward wind driven currents promote large freshwater transport toward the shelf break and the desoto canyon where eddies with diameters ranging from 50 to 130 km interact with the buoyant plume and effectively entrain the riverine waters our estimates show that the offshore removal by eddies can be as large as the wind driven shelf transport the proximity of eddies to the shelf break is a sufficient condition for offshore removal and shelf to offshore interaction is facilitated by the steep bottom topography near the delta strong eddy plume interactions were observed when the loop current system impinged against the shelf break causing the formation of coherent narrow low salinity bands that extended toward the gulf interior the offshore pathways depend on the position of the eddies near the shelf edge their life span and the formation of eddy pairs that generate coherent cross shelf flows this study elucidates the dynamics that initiate a unique cross marginal removal mechanism of riverine low salinity nutrient rich waters allowing their export along connectivity pathways induced by a large scale current system

magmatic fluids in the breccia hosted epithermal au ag deposit of rosia montana romania the breccia hosted epithermal au ag deposit of rosia montan is located 7 km northeast of abrud in the northern part of the south apuseni mountains romania estimated total reserves of 214 91 million metric tons mt of ore at 1 46 g t au and 6 9 g t ag 10 1 moz of au and 47 6 moz of ag make rosia montan one of the largest gold deposits in europe at this location miocene calc alkaline magmatic and hydrothermal activity was associated with local extensional tectonics within a strike slip regime related to the indentation of the adriatic microplate into the european plate during the carpathian orogenesis the host rocks of the magmatic complex consist of pre mesozoic metamorphosed continental crust covered by cretaceous turbiditic sediment flysch magmatic activity at rosia montan and its surroundings occurred in several pulses and lasted about 7 m y rosia montan is a breccia hosted epithermal system related to strong phreatomagmatic activity due to the shallow emplacement of the montana dacite the montana dacite intruded miocene volcaniclastic material volcaniclastic breccias and crops out at cetate and c rnic hills current mining is focused primarily on the cetate open pit which was mapped in detail leading to the recognition of three distinct breccia bodies the dacite breccia with a dominantly hydrothermal matrix the gray polymict breccia with a greater proportion of sand sized matrix support and the black polymict breccia which reached to the surface contains carbonized tree trunks and has a dominantly barren clastic matrix the hydrothermal alteration is pervasive adularia alteration with a phyllic overprint is ubiquitous silicification and argillic alteration occur locally mineralization consists of quartz adularia carbonates commonly mn rich pyrite fe poor sphalerite galena chalcopyrite tetrahedrite and native gold and occurs as disseminations as well as in veins and filling vugs within the montana dacite and the different breccias the age of mineralization 12 85 0 07 ma was determined by 40 ar 39 ar dating on hydrothermal adularia crystals from vugs in the dacite breccia in the cetate open pit microthermometric measurements of fluid inclusions in quartz phenocrysts from the montana dacite revealed two fluid types that are absent from the hydrothermal breccia and must have been trapped at depth prior to dacite dome emplacement brine inclusions 32 55 wt nacl equiv homogenizing at t h 460 c and intermediate density fluids 4 9 15 6 wt nacl equiv t h between 345 430 c secondary aqueous fluid inclusion assemblages in the phenocrysts have salinities of 0 2 to 2 2 wt percent nacl equiv and t h of 200 to 280 c fluid inclusion assemblages in hydrothermal quartz from breccias and veins have salinities of 0 2 to 3 4 wt percent nacl equiv and t h from 200 to 270 c the oxygen isotope composition of several zones of an ore related epithermal quartz crystal indicate a very constant 18 o of 4 5 to 5 0 per mil for the mineralizing fluid despite significant salinity and temperature variation over time following microthermometry selected fluid inclusion assemblages were analyzed by laser ablation inductively coupled plasma mass spectrometry la icpms despite systematic differences in salinity between phenocryst hosted fluids trapped at depth and fluids from quartz in the epithermal breccias all fluids have overlapping major and trace cation ratios including identical na k rb sr cs ba consistent with the constant near magmatic oxygen isotope composition of the hydrothermal fluids these data strongly indicate a common magmatic component of these chemically conservative solutes in all fluids cu pb zn and mn show variations in concentration relative to the relatively non reactive alkalis reflecting the precipitation of sulfide minerals together with au in the epithermal breccia and possibly of cu in an inferred subjacent porphyry environment the magmatic hydrothermal processes responsible for epithermal au ag mineralization at rosia montan are however not directly related to the formation of the spatially associated porphyry cu au deposit of rosia poieni which occurred about 3 m y later

a census of eddy activities in the south china sea during 1993 2007 1 numerous mesoscale eddies occur each year in the south china sea scs but their statistical characteristics are still not well documented a pacific basin wide three dimensional physical biogeochemical model has been developed and the result in the scs subdomain is used to quantify the eddy activities during the period of 1993 2007 the modeled results are compared with a merged and gridded satellite product of sea level anomaly by using the same eddy identification and tracking method on average there are about 32 9 2 4 eddies predicted by the model and 32 8 3 4 eddies observed by satellite each year and about 52 of them are cyclonic eddies the radius of these eddies ranges from about 46 5 to 223 5 km with a mean value of 87 4 km more than 70 of the eddies have a radius smaller than 100 km the mean area covered by these eddies each year is around 160 170 km2 equivalent to 9 8 of the scs area with water depths greater than 1000 m linear relationships are found between eddy lifetime and eddy magnitude and between eddy vertical extent and eddy magnitude showing that strong eddies usually last longer and penetrate deeper than weak ones interannual variations in eddy numbers and the total eddy occupied area indicate that eddy activities in the scs do not directly correspond to the el nino southern oscillation events the wind stress curls are thought to be an important but not the only mechanism of eddy genesis in the scs

dispersal of the pearl river plume over continental shelf in summer abstract satellite images of turbidity were used to study the climatological monthly and typical snapshot distributions of the pearl river plume over the shelf in summer from 2003 to 2016 these images show that the plume spreads offshore over the eastern shelf and is trapped near the coast over the western shelf eastward extension of the plume retreats from june to august monthly spatial variations of the plume are characterized by eastward spreading westward spreading or both time series of monthly plume area was quantified by applying the k mean clustering method to identify the turbid plume water decomposition of the 14 year monthly turbidity data by the empirical orthogonal function eof analysis isolated the 1st mode in both the eastward and westward spreading pattern as the time series closely related to the pearl river discharge and the 2nd mode with out of phase turbidity anomalies over the eastern and western shelves that is associated with the prevailing wind direction eight typical plume types were detected from the satellite snapshots they are characterized by coastal jet eastward offshore spreading westward spreading bidirectional spreading bulge isolated patch offshore branch and offshore filaments respectively their possible mechanisms are discussed

fluid inclusions and sulfur isotopes of sandaowanzi gold telluride deposit heilongjiang province the sandaowanzi gold deposit is a newly discovered gold telluride deposit in which gold and silver occur as tellurides in quartz veins liquid inclusions in quartz from the gold bearing quartz vein are the dominant type of fluid inclusions the gas liquid ratio is mainly concentrated in the range of 5 15 the fluid inclusion homogenization temperatures are grouped into the early mineraliztion stage of 230 396 the main mineralization stage of 220 320 with the peak temperature at 260 280 and the late minealization stage of 140 300 with the peak temperature at 180 240 laser raman spectroscopy shows that the compositions of fluid inclusions are mainly h2o partly with methane propane acetylene and other hydrocarbons the pure gas inclusions of the main ore forming stage are characterized by the dominant presence of methane followed by propane acetylene and other hydrocarbons which may suggest mantle derived fluids the 34s values of sulfur isotopes fall near 0 characteristic of mantle sulfur the above data show that the sandaowanzi gold deposit is an epithermal mesothermal deposit ore forming fluids genetically with mixed meteoritic and mantle sources contributed to gold telluride mineralization during sub alkaline volcanism in an extensional tectonic setting open space filling and crack sealing constitute the dominant mechanism of multi stage mineralization

phase relations among tellurides sulfides and oxides pt ii applications to telluride bearing ore deposits data on telluride bearing mineral assemblages from various types of ore deposits are compiled and interpreted in terms of the prevailing fugacities of te 2 s 2 and the temperature during deposition in the majority of hydrothermal deposits the appearance of tellurides after initial deposition of sulfides reflects an increase in the f sub te 2 f sub s 2 ratio most likely due to input of h 2 te from a magmatic source in some vein deposits such as boulder county colorado initial deposition of native tellurium is followed by deposition of minerals with progressively lower tellurium content indicating a decrease in f sub te 2 over the course of telluride deposition this trend may reflect local isolation of early formed minerals from the hydrothermal fluids and or progressive depletion of tellurium at the source ore minerals in other deposits such as mahd adh dhahab saudi arabia reveal systematic temporal or spatial variations in mineralogy that are attributed to introduction of a tellurium rich fluid into a preexisting sulfide assemblage and subsequent buffering of f sub te 2 and f sub s 2 by reactions such as 2pbs te 2 2pbte s 2 this buffering may exert considerable control on vein minerals such as the presence and relative abundance of gold and calaverite and the presence or absence of native tellurium

alkalic intrusive rocks associated with the mount kare gold deposit papua new guinea comparison with the porgera intrusive complex the mount kare gold deposit is located 18 km southwest of the giant porgera gold mine proven and probable reserves of 51 5 million metric tons at 0 23 oz au t in the highlands of papua new guinea both deposits are spatially associated with late miocene alkalic intrusive complexes emplaced in mesozoic tertiary shelf sedimentary sequences near the edge of the australasian plate close geologic similarities between the two deposits including the presence of quartz roscoelite au veins and breccias have spurred recent exploration efforts at mount kare the mount kare and porgera intrusive complexes consist of hypabyssal suites of comagmatic volatile rich mafic intrusions containing clinopyroxene olivine plagioclase hornblende chromian spinel and apatite in melagabbros and mafic porphyries with plagioclase hornblende clinopyroxene titanian magnetite and apatite in more evolved rocks listed in decreasing order of abundance analcite occurs as an alteration phase of the groundmass and fills miarolitic cavities in evolved leucogabbros at mount kare but has not been observed in the porgera intrusive complex least altered igneous rocks from both suites are nepheline normative and are characterized by high volatile alumina large ion lithophile and high field strength element contents they display light rare earth element enrichments la yb cn 9 28 at mount kare 14 20 at porgera but relatively low concentrations of k and ti on mantle normalized diagrams the rocks are mostly sodic na 2 o 2 or k 2 o according to the total alkali silica classification scheme nd sr and pb isotope compositions and k ar ages of hornblende and biotite from the two suites are virtually indistinguishable epsilon nd 6 7 87 sr 86 sr asymp 0 7036 208 pb 204 pb asymp 38 5 207 pb 204 pb asymp 15 55 206 pb 204 pb asymp 18 65 k ar age of mount kare intrusive complex 6 0 or 0 1 ma 2gma porgera intrusive complex 6 0 or 0 3 ma 2gma these combined characteristics indicate a dominantly alkalic intraplate affinity for the parental magma at both locations although a weak subduction zone signature is also suggested by the relatively high volatile and alumina and low ti abundances it is proposed that magmatic activity was related to changes in geodynamic configuration occurring immediately prior to early pliocene collision between the australasian plate and an island arc system minor differences such as divergent trajectories of pb isotope crustal contamination arrays the occurrence of analcite only at mount kare and the widespread presence of excess 40 ar in igneous amphiboles only at porgera indicate that although related the mount kare and porgera intrusive complexes developed independently of one another disseminated auriferous pyrite from the mount kare au deposit is associated with phyllic alteration of intrusive and sedimentary rocks a single k ar analysis of illitc from altered rock records an age of 5 5 or 0 1 ma 2sigma which falls in the middle of the range of illite and roscoelite ages from the porgera au deposit 5 1 6 1 ma this result combined with slightly older ages of igneous activity suggests a close temporal and genetic association between magmatism and mineralization at both locations in addition the narrow range of pb isotope compositions of galenas from veins at mount kare is identical with that from porgera suggesting that similar ore forming processes were involved at the two locations recognition of closely similar igneous lithologies and ore types at mount kare and porgera supports theories of a genetic relationship between volatile rich mafic alkalic magmatism and meso to epithermal au mineralization as previously proposed at porgera it is suggested that both of these deposits belong to the alkalic epithermal group to which cripple creek colorado emperor fiji and ladolam lihir island papua new guinea also belong igneous centers with these characteristics and located in complex convergent tectonic settings should be considered as prospective targets for precious metal exploration

upwelling in the taiwan strait during the summer monsoon detected by satellite and shipboard measurements the taiwan strait is located at the confluence of the east china sea and the south china sea in the west pacific ocean several upwelling zones in the taiwan strait are noted for their high fisheries production these upwelling zones have been studied in the past decade but we have no overall picture on the size and temporal changes of these upwelling zones due to only limited in situ observation over short periods of time the present paper investigates upwelling in the taiwan strait with satellite remote sensing data of noaa derived sea surface temperature sst and seawifs derived chlorophyll a chl a and shipboard measurements during summer 1998 results reveal five upwelling zones 1 coastal upwelling near pingtan island ptu 2 coastal upwelling between meizhou and xiaman mxu 3 big coastal upwelling near dongshan island dsu sometimes extending to offshore 4 small occasional upwelling near the penghu island phu and 5 an intensive upwelling in the taiwan bank tbu tbu was extensively studied over summer 1998 results showed that the tbu looks like a banana in shape in the southern edge of the taiwan bank it intensifies in its southeastern edge the size of tbu was about 2500 3000 km 2 with a mean value of 2796 km 2 the temperature difference between the upwelling and non upwelling areas was about 2 5 3 5 jc for early august with a mean value of 2 3 jc on july to october series of images indicated a short term variation of tbu and showed that high chl a concentrations up to 0 8 2 mg m 3 zones coincided with low sst 25 26 jc zones in terms of location time and shape these upwelling zones change with size and intensity center from time to time field measurements of water temperature salinity and chl a in 1998 are consistent with satellite measurements d 2002 elsevier science inc all rights reserved

mesozoic extensional tectonics in eastern asia the south liaodong peninsula metamorphic core complex ne china abstract in the north china block the south liaodong peninsula massif is an elliptical metamorphic core complex mcc with a long axis trending ne sw in cross section view it is asymmetric with a steeply dipping northwestern flank and a gently dipping southeastern flank it consists of three lithotectonic units a gneissic migmatite unit a paleo to meso proterozoic micaschist slate unit and a neoproterozoic to mesozoic sedimentary cover three deformation events related to extensional tectonics are distinguished in the study area d1 is a ductile deformation related to the exhumation of the mcc the following event d2 corresponds to the development of recumbent folds formed during the early exhumation of the mcc and the youngest event d3 corresponds to brittle normal faulting that controlled the opening of a cretaceous continental half graben basin a pre d1 event characterized as northward verging is interpreted as the result of n s shortening that occurred in the late triassic during the fin

tidal modulation on the changjiang river plume in summer 1 tide effects on the structure of the near field changjiang river plume and on the extension of the far field plume have often been neglected in analysis and numerical simulations which is the focus of this study numerical experiments highlighted the crucial role of the tidal forcing in modulating the changjiang river plume without the tidal forcing the plume results in an unrealistic upstream extension along the jiangsu coast with the tidal forcing the vertical mixing increases resulting in a strong horizontal salinity gradient at the northern side of the changjiang river mouth along the jiangsu coast which acts as a dynamic barrier and restricts the northward migration of the plume furthermore the tidal forcing produces a bidirectional plume structure in the near field and the plume separation is located at the head of the submarine canyon a significant bulge occurs around the head of the submarine canyon and rotates anticyclonically which carries a large portion of the diluted water toward the northeast and merges into the far field plume a portion of the diluted water moves toward the southeast which is mainly caused by tidal rectification this bidirectional plume structure is more evident under certain wind conditions during the neap tide with the reduced tidal energy the near field plume extends farther offshore and the bulge becomes less evident these dynamic behaviors are maintained and are fundamentally important in the region around the river mouth even under the summer monsoon and the shelf currents although in the far field the wind forcing and shelf currents eventually dominate the plume extension

development of upwelling on pathway and freshwater transport of pearl river plume in northeastern south china sea in situ observations satellite images and numerical modeling results have shown that the pearl river plume axis extends alongshore and passes through two separate upwelling regions one off the guangdong and fujian coasts the yuedong upwelling and the other in the taiwan bank during the initial and medium stages of the yuedong upwelling while it is directed offshore when the yuedong upwelling is fully developed model experiments are conducted to examine the effects of wind strength and baroclinicity on the upwelling and the corresponding pathway and freshwater transport of the pearl river plume the baroclinic effect is important to intensifying the horizontal velocity at the upwelling front and freshwater transport in the northeastern south china sea the freshwater transport flux is further decomposed into advection vertical shear and tidal pumping components and advection is the dominant contributor as the yuedong upwelling develops the zone with a relatively high pressure gradient moves offshore due to offshore ekman transport and the shift in the upwelling front which is responsible for the offshore transport of the river plume when the river plume is transported to the outer shelf sometimes it can be further entrained into eddies allowing its export to the open sea

mesoscale eddies in the northern south china sea a fine grid resolution model with realistic bathymetry and forcing has been developed to study the characteristics of the mesoscale eddies for the northern south china sea scs the scs model derives its open boundary conditions from a larger scale model which minimizes errors related to the uncertainty of the kuroshio intrusion at the open boundaries the model results are consistent with previous observations model sea surface height anomaly demonstrates that the hydrography and circulation in the northern scs are modulated by westward propagating mesoscale eddies originating in the vicinity of the luzon strait this explains the observed intra seasonal fluctuations at the southeast asian time series study seats station the mesoscale eddies have the same propagation speed as baroclinic rossby waves 0 1 ms 1 the periods of eddy shedding estimated from strouhal number are around 40 50 days in december and 80 120 days in august respectively the seasonal variability of the kuroshio intrusion results in more eddies in winter than in summer r 2007 elsevier ltd all rights reserved

coastal upwelling in summer 2000 in the northeastern south china sea using a combination of hydrographic tide gauge near bottom mooring and satellite observations and a numerical circulation model we investigate the coastal upwelling in the northeastern south china sea nscs off the coast of fujian and guangdong provinces china in the summer of 2000 subsurface upwelling phenomenon exists mainly near the bottom boundary in the whole region investigated it is closely related to the coastal sea level fluctuations which are evidently modulated by both the local wind forcing and the large scale circulation the northeastward interior flow following the bathymetry is accelerated by the drop of coastal sea level and leads to onshore transport and subsequent cooling in the bottom boundary layer bbl over the shelf west of shantou to the east of shantou the near bottom flow veers more eastward parallel to the coastline and transports the nearshore cold water mass farther to the southern fujian coast the cross shelf advected cold water does not always penetrate through the stratification and reach the surface the local wind exhibits considerable synoptic variability the decrease in sea surface temperature sst is mostly significant near dongshan shantou intermittent in time and intensifies preferably during weather events that bring southwesterly alongshore wind to the west a freshwater tongue originating from the pearl river forms a barrier layer which results in high surface temperature in the freshwater plume the observational evidences and modeled results shown in this study provide important information for further understanding the ecological effects associated with the upwelling processes in the nscs

tide induced mixing in the amazon frontal zone the freshwater discharge from the amazon river produces a bottom salinity front on the amazon shelf that extends many hundreds of kilometers along the shelf between the 10 and 20 m isobaths strong cross shelf tidal currents cause advective excursions of the front of more than 20 km and supply the major source of kinetic energy for mixing on the shelf this mixing is manifested in spring neap variations in the frontal structure and position with weaker stratification and seaward migration of the front during periods of strong tidal currents and stronger stratification and landward migration during neap tides mixing appears to be driven by shear instability based on local estimates of gradient richardson number and bulk estimates of the water column stability maximum mixing occurs during ebb when vertical shear is greatest suspended sediment reaches such high concentrations in the frontal zone that it makes a significant contribution to the stratification thus increasing the stability of the flow and reducing the effectiveness of tide induced mixing

intensified upwelling over a widened shelf in the northeastern south china sea 1 observational and three dimensional modeling studies reveal that the intensified upwelling in the northeastern south china sea nscs is formed as a result of intensified upslope advection of dense deep waters that cross the middle shelf toward the inner shelf over a distinctly eastward widened shelf the strongest advection occurs over the converging isobaths near the head of the widened shelf as these dense deep waters advance shoreward they are advected downstream by the quickly developed upwelling current over the inner shelf and eventually outcropped at the lee of a coastal cape dynamically the shoreward cross isobath transport over the widened shelf is geostrophically enhanced by a quasi barotropic negative westward along isobath pressure gradient force as a result of the net rate of the momentum influx and by an intensified bottom frictional transport owing to the flow confluence near the head of the widened shelf a negative pressure gradient also exists at the lee of the coastal cape over the inner shelf and locally amplifies shoreward motion induced by the respective widened shelf and the coastal promontory the along isobath variations of cross isobath transport in the water column over the middle and inner shelves interactively characterize intensified upwelling in the nscs

age and evolution of late mesozoic metamorphic core complexes in southern siberia and northern mongolia numerous cretaceous metamorphic core complexes mccs extend from transbaikalia in russia to northern mongolia within the central asian orogenic belt we investigated the buteel and zagan mccs in detail shear sense indicators in mylonitized rocks show footwall to the nw tectonic transport single zircon dating of footwall rocks in the buteel mcc establishes the emplacement of granitoid orthogneiss precursors at 240 211 ma a felsic metavolcanic rock at 265 0 1 2 ma a syenite at 265 5 1 2 ma and a metarhyolite of the pre granitoid basement at 553 6 2 9 ma a peralkaline granite intruding orthogneisses of the zagan mcc has a new u pb zircon age of 151 6 0 7 ma 40 ar 39 ar ages of 133 5 1 8 ma of hornblende from amphibolite and 122 6 1 8 ma of biotite from mylonitized gabbro dolerite of the buteel mcc are interpreted as cooling ages representing the time of deformation in the footwall geological data suggest that the mccs in transbaikalia and northern mongolia formed as a result of extension in a crust that had previously been thickened by abundant calc alkaline magmatism in an andean type setting on the border of the closing mongol okhotsk ocean by widespread collisional to post collisional thrusting and by extensive alkaline peralkaline magmatism

geology of the sandaowanzi telluride gold deposit of the northern great xing an range ne china geochronology and tectonic controls abstract the sandaowanzi gold telluride deposit is a new discovery with dominance in gold tellurides in northeastern china the deposit is hosted in quartz veins intruding sub alkaline volcanic rocks there are two types of gold telluride ores in the sandaowanzi ore deposit i e the vein ores and the disseminated ores calaverite krennerite sylvanite petzite empressite hessite and stuetzite are the dominant au ag bearing minerals either in vein ores or in disseminated ores minor amount of other tellurides e g coloradoite altaite and sulfides e g pyrite sphalerite galena chalcopyrite and chalcocite mostly occur in the disseminated ores the gold bearing quartz veins crosscut volcanic host rocks which are dated at 135 3 124 7 ma by la icp ms u pb zircon method the latter unconformably overly a monzogranite dated as 181 6 ma diabase dikes dated at 116 6 ma intrude the gold bearing quartz veins the age data thereby bracket the timing of gold mineralization between 125 3 and 116 6 ma these geochronologic data are consistent with field relations regional comparison reveals that the widespread volcanism in the great xing an range is a product of the subduction of the izanagi plate beneath the eurasian plate gold telluride mineralization was contemporaneous with regional extension and magmatism as the subducting izanagi plate rolled back

observations and numerical modeling of the pearl river plume in summer season a cruise survey of the pearl river plume during southeasterly and southwesterly winds two typical wind patterns in summer in guangdong coastal waters is reported and the cruise data are analyzed to unveil the plume dynamics the kelvin number is derived from the in situ data revealing that the pearl river plume exhibits two different scales in response to the two kinds of the wind forcing numerical model simulations based on the regional oceanic modeling system roms with nesting domains are implemented to explore details of the plume dynamics validated by cruise observations and tidal gauge sea level data modeling results suggest that there is a subtidal anticyclonic recirculation bulge on the west side out of the estuary mouth under southeasterly winds showing a recirculating plume in the near field when the wind changes to the southwesterly however the recirculating plume vanishes the distinct supercritical tidal plume front occurs with southeasterly winds prevailing in spring tide due to the strong advection in the tidal plume the tidal salt deficit flux can reach as high as 12 5 of the mean current flux and illustrates the combined forcing of tide and wind key points the paper clarifies the pearl river plume anatomy under two typical winds spring tide facilitates the supercritical pearl river tidal plume front tide determines tidal salt deficit flux strength wind determines the direction

effects of tides on freshwater and volume transports in the changjiang river plume 1 effects of tides on the changjiang river plume are investigated using a numerical model of the east china and yellow seas in the absence of tides the buoyancy driven coastal current downstream of the river mouth is a surface trapped plume attached to the coast in the presence of tides however the plume shifts away from the coast and features a bottom boundary layer the freshwater transport by the coastal current accounts for only 35 of the changjiang river discharge without tides but increases to 80 with tides tidal currents stabilize the plume bulge near the river mouth and force the plume water to move in the direction of tidal currents thus increasing the downstream freshwater transport in contrast tidal residual currents are weak and make little contributions to the total freshwater transport tidal mixing reduces the plume s buoyancy but increases its thickness so that the freshwater transport is insensitive to the strength of turbulent mixing volume transport in the tidal affected buoyancy coastal current exceeds the river discharge by 4 to 12 times as opposed to 2 3 fold amplification in the plume without tides tidal mixing between the plume and ambient shelf waters produces higher salinity classes in the plume so that the volume flux in the downstream coastal current increases to discharge the freshwater released from the changjiang river

late mesozoic calc alkaline volcanism of post orogenic extension in the northern da hinggan mountains northeastern china abstract late mesozoic calc alkaline volcanism in the northern da hinggan mountains ndhm ne china exhibits geochemical and sr nd isotopic characteristics similar to those of cenozoic calc alkaline volcanism in the basin and range province usa whole rock k ar dating results show that these volcanic sequences were erupted during 138 116 ma composed of basaltic andesites trachyandesites group 1 hornblende andesites trachytes group 2 and rhyolite lavas group 3 they are characterized by low mgo contents 4 20 lile lree enrichment and significant nb ta depletion as well as a little depleted to slightly enriched nd and weakly enriched sr isotopic ratios group 1 initial 87sr 86sr 0 70502 0 70572 nd t 0 78 to 0 91 group 2 initial 87sr 86sr 0 70497 0 70518 nd t 0 86 to 1 26 group 3 initial 87sr 86sr 0 70510 0 70635 nd t 0 41 to 0 25 the systematic variations in major and trace elements homogeneous sr nd isotope data and temporal consistency among three volcanic groups indicate that they were derived from a similar mantle source metasomatized by fluids related to the closure of the paleo asian and or mongolia okhotsk oceans and were produced through different degrees of fractional crystallization of the primary melts group 1 basaltic rocks were formed through removal of olivine and pyroxene of the primary melts while group 2 trachytes which contain the lowest lree contents e g la 24 28 ppm and relatively less enriched sr and higher nd isotope ratios were generated after removal of a few percent of lree rich minerals such as hornblende clinopyroxene and apatite of melts like group 1 group 3 rhyolite lavas exhibiting the highest abundances of strongly incompatible elements such as rb and k moderate lree contents e g la 28 53 ppm as well as apparently negative eu and sr anomalies represent the final crystallized products following a plagioclase predominant fractionation of melts like group 2 the low mgo contents and evolved affinities of the volcanic rocks imply that beneath the ndhm there existed many crustal magma reservoirs throughout the eruption episodes in which mantle derived primary melts had experienced intense differentiation these facts in combination with the contemporaneous basin and range tectonic regime suggest that the extensive calc alkaline volcanism in the ndhm was attributed to post orogenic diffuse extension rather than either an upwelling mantle plume or mesozoic oceanic plate subduction

fluid inclusion and noble gas studies of the dongping gold deposit hebei province china a mantle connection for mineralization the dongping gold deposit 100 t au occurs about 200 km inboard of the northern margin of the north china craton the deposit is mainly hosted by syenite of a middle paleozoic alkalic intrusive complex that was emplaced into late archean basement rocks both groups of rocks are intruded by late jurassic to early cretaceous crustal melt granite dikes and stocks some within a few kilometers of the deposit the gold ores were deposited during this latter magmatic period at about 150 ma a time that was characterized by widespread regional north south compression that formed the east west trending yanshan deformational belt the ores include both the telluride mineral bearing low sulfide quartz veins and the highly k feldspar altered syenite with most of the resource concentrated in two orebodies 1 and 70 fluid inclusion microthermometry indicates heterogeneous trapping of low salinity e g 5 7 wt nacl equiv fluids that varied from a few to 60 mole percent nonaqueous volatile species laser raman spectroscopy confirms that the vapor phase in these inclusions is dominated by co2 but may be comprised of as much as 9 mole percent h2s and 20 mole percent n2 methane concentrations in the vapor phase are consistently 1 mole percent the variable phase ratios are consistent with fluid immiscibility during ore formation fluid inclusion trapping conditions are estimated to be 250 to 375 c and 0 6 to 1 0 kbar helium isotope studies of fluid inclusions in ore stage pyrites indicate 3he 4he ratios of 2 1 to 5 2 ra ra 1 4 10 6 for air for orebody 1 and 0 3 to 0 8 ra for orebody 70 the former data suggest that at least 26 to 65 percent mantle helium occurs in the fluids that deposited the veins in orebody 1 the lower values for orebody 70 which is characterized by a more disseminated style of gold mineralization are interpreted to reflect an increased interaction of ore fluids with surrounding crustal rocks which may have contributed additional 4he to the fluids a mantle source for at least some of the components of the gold forming fluid is consistent with upwelling of hot asthenosphere and erosion of as much as 100 to 150 km of cool archean lithosphere beneath the craton during this time the dongping deposit is located along the 100 km wide north south gravity lineament which marks the western border of the thinned crust as both regional metamorphism of mesoproterozoic and younger cover rocks and widespread granite magmatism also occurred at ca 150 ma it is unclear as to whether one or both of these also contributed fluid and or metals to the hydrothermal system importantly these new data suggest that economically significant gold deposits of similar mineral style and fluid composition which are scattered along the margins of the craton may all be products of a fluid originally partly sourced within the mantle

invisible gold in arsenian pyrite and arsenopyrite from a multistage archaean gold deposit sunrise dam eastern goldfields province western australia the sunrise dam gold mine 11 1 moz au is the largest deposit in the archaean laverton greenstone belt eastern goldfields province yilgarn craton western australia the deposit is characterized by multiple events of fluid flow leading to repeated alteration and mineralization next to a major crustal scale structure the au content of arsenian pyrite and arsenopyrite from four mineralizing stages d1 d3 d4a and d4b and from different structural and lithostratigraphic environments was measured using in situ laser ablation inductively coupled plasma mass spectrometry pyrite contains up to 3 067 ppm au n 224 whereas arsenopyrite contains up to 5 767 ppm n 19 gold in arsenopyrite d4a stage was coprecipitated and remained as invisible gold nanoparticles and or lattice bound during subsequent deformation events in contrast gold in pyrite is present not only as invisible gold but also as micrometer size inclusions of native gold electrum and au ag tellurides pristine d1 and d3 arsenian pyrite contains relatively low au concentrations 26 ppm the highest au concentrations occur in d4a arsenian rich pyrite that has recrystallized from d3 pyrite textures show that this recrystallization proceeded via a coupled dissolution reprecipitation process and this process may have contributed to upgrading au grades during d4a in contrast au in d4b pyrite shows grain scale redistribution of invisible gold resulting in the formation of micrometer scale inclusions of au minerals the speciation of au at sunrise dam and the exceptional size of the deposit at province scale result from multiple fluid flow and multiple au precipitating mechanisms within a single plumbing system

bonanza grade accumulations of gold tellurides in the early cretaceous sandaowanzi deposit northeast china the sandaowanzi epithermal gold deposit 0 5 moz or ca 14 tons located at the northern edge of the great xing an range ne china is unique in that nearly all the gold 95 is contained in gold tellurides mostly in bonanza grade ore shoots the highest grade being up to 20 000 g t the bonanza ores are hosted in the central parts of large scale 3 m wide 200 m long quartz veins which crosscut early cretaceous andesitic trachyte and trachytic andesite and are in turn crosscut by diabase dykes of similar age there are two ore types low grade disseminated ores and high grade vein ores in the former very fine grains of ag rich tellurides mainly hessite and petzite coexist with sulfides pyrite sphalerite galena and chalcopyrite occurring as disseminated grains or sometimes as grain aggregates in the high grade vein ores coarse grained au ag tellurides calaverite sylvanite krennerite and petzite form a major part of quartz telluride veins chalcopyrite forms separate monomineralic veins emplaced within the quartz telluride veins spectacular textures among coarse grained up to 3 cm in diameter tellurides and micron scale bamboo shoot like grains are observed two and three phase telluride symplectites are common in the vein ores fluid inclusion studies suggest that the mineralizing fluids are a mixture of magmatic and meteoric fluids that homogenized in the temperature range of 260 280 c sulfur isotope compositions of pyrite and chalcopyrite 34s 1 64 to 1 91 support the origin of fluids from a deep source it is suggested that faulting temperature changes and variation in fs2 and fte2 were major factors contributing to the two main types of mineralization and the differences between them early rapid cooling and subsequent slow cooling of the later fluids along fault and fracture zones were instrumental in formation of the two superposed ore types open space filling and crack sealing along fractures predominates over replacement during telluride mineralization the sandaowanzi deposit is a unique bonanza grade accumulation of gold tellurides genetically related to subalkaline magmatism which was genetically associated with early cretaceous regional extension

wind forcing controls on river plume spreading on a tropical continental shelf the berau continental shelf is located close to the equator in the indonesian archipelago hosting a complex of coral reefs along its oceanic edge the berau coral reefs have a very high biodiversity but the area is under serious risk due to river derived nutrients and sediments the region is characterized by weak winds moderate tides and almost absent coriolis forcing existing knowledge about river plume behavior in tropical environments is limited the aim of this paper is to investigate the influence of the subtle physical forcing on the dynamics of the berau river plume a three dimensional model ecomsed was calibrated with observational data the model was forced by freshwater input from the berau river distributaries tides at the open boundaries and measured hourly wind the model reproduces the freshwater dynamics on the shelf adequately and highlights that the river plume spreads symmetrically for river forcing only tides cause vertical mixing and suppress the cross shelf spreading of the river plume however the spreading of the river plume over the shelf is mainly controlled by the weak monsoonal winds resulting in a seasonal development during the southeast monsoon the southerly winds push the plume northeastward and cause a stratified water column in the northern part of the continental shelf northerly winds during the northwest monsoon disperse the plume to the south promoting a vertically well mixed water column the results can be used to predict the possible impact of land use changes in the steadily developing berau region on coral reef health

geodynamics of the western part of the mongolia okhotsk collisional belt trans baikal region russia and mongolia abstract after the western edge of the mongolian microcontinent joined the siberian continent in the region of central mongolia in the earliest permian these two continental blocks remained turned at an angle of about 120 with respect to each other and separated on greater extent of their present day boundary by an enormous gulf of the paleopacific called the mongolia okhotsk ocean closure of this ocean at the early middle jurassic boundary led to the complete collision of siberia and mongolia which by then had already become part of the mongolia north china continent this main collisional episode which lasted through the middle and late jurassic involved thrusting folding and magmatism and produced the mongolia okhotsk belt the onon island arc which was located in the mongolia okhotsk ocean was squeezed between the two major continents inasmuch as the third element the island arc was involved in the collision it is reasonable to distinguish two branches of the mongolia okhotsk suture these branches control the spatial distribution of gold mineralization in the trans baikal region on the southeastern periphery of siberia the crust thickened considerably after the collision and a plateau like uplift formed in the early cretaceous when compression ceased the collisional uplift collapsed and the thrusts were transformed into low angle normal faults the motions on which were responsible for the formation of rift basins and exhumation of metamorphic core complexes

summer monsoon induced upwelling dominated coastal sea surface temperature variations in the northern south china sea over the last two millennia the south china sea scs situated to the north of the indo pacific warm pool ipwp is under the strong influence of the asian monsoon system however coastal sea surface temperature sst reco

the liaonan metamorphic core complex southeastern liaoning province north china a likely contributor to cretaceous rotation of eastern liaoning korea and contiguous areas abstract the mesozoic liaonan metamorphic core complex mcc of the southeastern liaoning province north china is an asymmetric cordilleran style complex with a west rooting master detachment fault the jinzhou fault a thick sequence of lower plate fault related mylonitic and gneissic rocks derived from archean and early cretaceous crystalline protoliths has been transported ese ward from mid crustal depths u pb ages of lower plate syntectonic plutons ca 130 120 ma 40 ar 39 ar cooling ages in the mylonitic and gneissic sequence ca 120 110 ma and a cretaceous supradetachment basin attest to the early cretaceous age of this extensional complex the recent discovery of the coeval and similarly west rooting waziyu mcc in western liaoning darby b j davis g a zhang x wu f wilde s yang j 2004 the newly discovered waziyu metamorphic core complex yiwulushan western liaoning province north china earth science frontiers 11 145 155 indicates that the gulf of liaoning which lies between the two complexes was the center of a region of major crustal extension clockwise crustal rotation of a large region including eastern liaoning province and the korean peninsula with respect to a non rotated north china block has been conclusively documented by paleomagnetic studies over the past decade the timing of this rotation and the reasons for it are controversial lin et al lin w chen y faure m wang q 2003 tectonic implication of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china journal of geophysical research 108 b 6 epm 5 1 to 5 17 proposed that a clockwise rotation of 22 5 10 2 was largely post early cretaceous in age and was the consequence of extension within a crustal domain that tapers southwards towards the bohai sea of which the gulf of liaoning is the northernmost part paleomagnetic studies of early cretaceous strata ca 134 120 ma in the yixian fuxin supradetachment basin of the waziyu mcc indicate the non rotation of north china and the basin zhu r x shao j a pan y x shi r p shi g h li d m 2002 paleomagnetic data from early cretaceous volcanic rocks of west liaoning evidence for intracontinental rotation chinese science bulletin 47 1832 1837 such upper plate non rotation supports our conclusion that the lower plates of the waziyu and liaonan metamorphic core complexes were displaced ese ward in an absolute sense away from the stable north china block thus contributing to the rotation of korea and contiguous areas rotation is inferred to have affected only the upper crust above mid crustal levels into which we believe the jinzhou and waziyu detachment fault zones flattened if this is the case the regional tan lu fault that lies between the two core complexes was truncated at mid crustal depth since in areas to the south it forms the boundary between the north and south china lithospheric blocks it is noteworthy that the two extensional complexes lie not far north of the bohai bay the area proposed by lin et al lin w chen y faure m wang q 2003 tectonic implication of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china journal of geophysical research 108 b 6 epm 5 1 to 5 17 as the site of the pole of rotation for korea s clockwise displacement lin et al lin w chen y faure m wang q 2003 tectonic implication of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china journal of geophysical research 108 b 6 epm 5 1 to 5 17 were unaware of the liaonan and waziyu mcc s and argued that most of the regional block rotation was post early cretaceous and in part early cenozoic however the ca 130 120 ma ages of the two liaoning mcc s and a songliao basin mcc xujiaweizi the latter discovered only by recent drilling through its younger stratigraphic cover support our and some korean coworkers conclusions that most of the clockwise rotation was early cretaceous

a review of the geodynamic setting of large scale late mesozoic gold mineralization in the north china craton an association with lithospheric thinning abstract abundant gold deposits are distributed along the margins of the north china craton ncc occurring throughout the precambrian basement and located in or proximal to mesozoic granitoids these deposits show a consistent spatial temporal association with late jurassic early cretaceous magmatism and are characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock their ages are mainly early cretaceous 130 110 ma and constrain a very short period of metallogenesis sr nd pb isotopic tracers of ores minerals and associated rocks indicate that gold and associated metals mainly were derived from multi sources i e the wall rocks precambrian basement and mesozoic granites and associated mafic rocks previous studies including high surface heat flow uplift and later basin development slow seismic wave speeds in the upper mantle and a change in the character of mantle xenoliths sampled by paleozoic to cenozoic magmas have been used to suggest that ancient cratonic mantle lithosphere was removed from the base of the ncc some time after the ordovician and replaced by younger less refractory lithospheric mantle the geochemistry and isotopic compositions of the mafic rocks associated with gold mineralization 130 110 ma indicate that they were derived from an ancient enriched lithospheric mantle source whereas the mafic dikes and volcanic rocks younger than 110 ma were derived from a relatively depleted mantle source i e asthenospheric mantle according to their age and sources relation to magmatism and geodynamic framework the gold deposits were formed during lithospheric thinning the removal of lithospheric mantle and the upwelling of new asthenospheric mantle induced partial melting and dehydration of the lithospheric mantle and lower crust due to an increase of temperature the fluids derived from the lower crust were mixed with magmatic and meteoric waters and resulted in the deposition of gold and associated metals