a carbon isotope reference curve for ca 1700 1575 ma mcarthur and mount isa basins northern australia abstract shallow marine paleo and mesoproterozoic sedimentary successions are widely distributed in several major basins across northern australia the successions are only gently deformed and their stratigraphy is relatively continuous thus offering an ideal opportunity to document secular variations in carbon isotopes marine carbonate intervals from two of these major basins the mcarthur and mount isa basins have been sampled to document secular variation in 13ccarb from approximately 1700 to 1575 ma in all cases the samples have been tied to a well established sequence stratigraphy which along with u pb shrimp zircon dates provides a time resolution of the order of 1 m y the data presented here thus provide the most comprehensive and best dated 13ccarb stratigraphy yet obtained from such ancient rocks diagenesis occurred early in the carbonate rocks from both basins with the result that fluid movements were restricted and primary carbon isotopic signatures were retained the 13ccarb values from both basins vary within a very narrow range around a mean of 0 6 with extreme values seldom lying further than 1 from the mean that is the curves are essentially flat the results of this study combined with earlier studies on younger rocks imply that the global ocean reached a state of equilibrium in the mid paleoproterozoic and remained stable for much of the following billion years current models of the ocean suggest that to maintain the carbon mass balance relatively low levels of tectonic activity would be required which in turn suggests that the availability of nutrients such as phosphorus was stable and low prolonged nutrient stability may therefore have exerted a major influence upon the evolution of the biosphere over this time interval

asian origin of interannual variations of summer climate over the extratropical north atlantic ocean abstractthe authors have identified an interannual relationship between asian tropospheric temperature and the north atlantic ocean sea surface temperature sst during summer may september and discussed the associated features of atmospheric circulation over the atlantic eurasian region when tropospheric temperature is high low over asia positive negative sst anomalies appear in the extratropical north atlantic this relationship is well supported by the changes in background atmospheric circulation and ocean atmosphere land thermodynamic processes when heat transfer from the land surface to the atmosphere over asia strengthens local tropospheric temperature increases and positive temperature anomalies propagate westward from asia to the north atlantic leading to an increase in summer tropospheric temperature over the atlantic eurasian region accordingly a deep anomalous ridge occurs over the extratropical north atlantic ocean with low level southerly anomalies over the western portion of t

pacific interdecadal variability in this century s sea surface temperatures analysis of this century s sea surface temperatures over the pacific ocean reveals an interdecadal oscillation with a period of 15 20 years our results show that the well known 1976 77 climate regime shift is not unique but represents one of several phase transitions associated with this interdecadal oscillation also found around 1924 25 1941 42 and 1957 58 the oscillation s striking north south symmetry across the equator implies strong interactions between tropics and extratropics a mode with a period of approximately 70 years and an apparently different spatial pattern is also identified tentatively but has to be evaluated further using longer time series

interannual variability in the north atlantic ocean s temperature field and its association with the wind stress forcing abstractspectral analyses of the north atlantic temperature field in the simple ocean data analysis soda reanalysis identify prominent and statistically significant interannual oscillations along the gulf stream front and in large regions of the north atlantic a 7 8 yr oscillatory mode is characterized by a basinwide southwest to northeast oriented propagation pattern in the sea surface temperature sst field this pattern is found to be linked to a seesaw in the meridional dipole structure of the zonal wind stress forcing taux in the subpolar gyre the sst and taux fields of this mode are shown to be in phase opposition which suggests a cooling effect of the wind stress on the upper ocean layer over all this mode s temperature field is characterized by a strong equivalent barotropic component as shown by covariations in ssts and sea surface heights and by phase coherent behavior of temperature layers at depth with the sst field recent improvements of multivariate singular spectrum analysis

rapid oscillations in vostok and grip ice cores we investigate the spectral properties of climatic times series derived from two recent ice cores in greenland and east antarctica we find that the signals behave in a similar way in the high frequency part of their spectra the rapid oscillations found in the grip ice core were closely correlated to heinrich events a comparable spectral feature is detected in the vostok ice core we discuss the possibilities of connections between the two hemispheres and proper ice sheet oscillations in the light of simple oscillating climate models

characteristic patterns of variability of sea level pressure in the northern hemisphere abstract seasonal and annual mean sea level pressures for the northern hemisphere have been analyzed to determine the dominant modes of interannual and longer period variability using monthly sea level pressure analyses as revised by trenberth and paolino 1980 empirical orthogonal function eof analysis is used to reveal the modes which explain most of the variance for the period 1925 77 in winter kutzbach s 1970 eof 1 for january remains the dominant mode and a closely related pattern dominates all seasons and the annual means although there are differences in detail in each season the dominant mode is basically a high latitude zonal index type pattern with departures in pressure at high latitudes corresponding to anomalies of opposite sign in low latitudes eof 1 is linked to the north atlantic oscillation but the north south fluctuations in mass also occur in the pacific and to a lesser extent elsewhere time series associated with this pattern have highly significant spectral peaks at the

surface climate variations over the north atlantic ocean during winter 1900 1989 abstract the low frequency variability of the surface climate over the north atlantic during winter is described using 90 years of weather observations from the comprehensive ocean atmosphere data set results are based on empirical orthogonal function analysis of four components of the climate system sea surface temperature sst air temperature wind and sea level pressure an important mode of variability of the wintertime surface climate over the north atlantic during this century is characterized by a dipole pattern in ssts and surface air temperatures with anomalies of one sign cast of newfoundland and anomalies of the opposite polarity off the southeast coast of the united states wind fluctuations occur locally over the regions of large surface temperature anomalies with stronger than normal winds overlying cooler than normal ssts this mode exhibits variability on quasi decadal and biennial time scales the decadal fluctuations are irregular in length averaging 9 years before 1945 and 1

gold mineralization in proterozoic black shales example from the haoyaoerhudong gold deposit northern margin of the north china craton abstract the haoyaoerhudong gold deposit in the northern margin of the north china craton ncc is a large tonnage lower grade deposit with a reserve of about 148 tons of gold gold mineralization is characterized by pyrite and pyrrhotite films and thin veins on the schistosity plane of the proterozoic black shales the orebodies strictly controlled by a near ew trending shear zone are stratabound within carbonaceous phyllite and andalusite garnet schist of the bilute formation hydrogen and oxygen isotopic data show that the ore forming fluid was derived from a magmatic source and mixed with meteoric water sulfur and carbon isotope data indicate that most of the sulfur and carbon came from the black shale strata well defined biotite ar ar plateau age and inverse isochron age show that the deposit formed at ca 270ma which suggests a probable link between hercynian magmatism and gold mineralization studies on regional geology ore geology isotope geochemistry and ore forming age substantiate a complex evolutionary history of the deposit the proterozoic black shales rich in gold sulfur and organic matter which were deposited in the proterozoic continental margin rifts comprised the source bed for gold mineralization ew ene structures products of palaeozoic orogenic process provided pathways and mineralization space for ore forming fluids hercynian tectono magmatism and subsequent hydrothermal events remobilized gold and drove the ore forming fluids to dilatational fracture zones related to postcollisional magmatic hydrothermal events the haoyaoerhudong gold deposit is considered as a special type of orogenic gold deposit formed in the compression extension transition stage

characteristics and origin of the zhulazhaga gold deposit in inner mongolia china abstract the zhulazhaga gold deposit in the northern margin of the north china craton ncc is a large tonnage hydrothermal deposit with a reserve of about 50 t at about 4 g t au the deposit is characterized by an epigenetic style of mineralization in metasedimentary rocks dominated by slates low grade metamorphic clastic rocks and minor volcanic rocks gold mineralization is dominantly controlled by structures manifested by stratabound orebodies located immediately to the east and west of a major n s trending fault and associated extensional fractures and ne trending fault zones the mineralization is also preferentially located in the fourth sub member of first member of the agulugou formation there are many auriferous quartz veins parallel to the bedding of the host rocks which contain the orebodies and high grade ore preferentially occurs near to these quartz veins the structures provided pathways for transportation of gold bearing fluids within the formation that appears to form a particularly favorable host rock and depositional setting hydrogen and oxygen isotope data indicate that ore forming fluids were dominated by magmatic water mixed with minor meteoric water sulfur and lead isotope data indicate that some sulfur and lead came from the magmatic fluid the metallogenic age 280 ma of this deposit and the crystallization age 280 290 ma of the granite porphyry in the district indicate a link between the hercynian magmatism and gold mineralization the hercynian tectono magmatism and associated hydrothermal activity remobilized gold and drove ore forming fluids to the favorable depositional environment the northern margin of the ncc is prospective for gold mineralization hosted in metasedimentary rocks which may be one of the most important deposit types for future gold exploration in northern china

structure and dynamics of decadal anomalies in the wintertime midlatitude north pacific ocean atmosphere system the structure and dynamics of decadal anomalies in the wintertime midlatitude north pacific ocean atmosphere system are examined in this study using the ncep ncar atmospheric reanalysis hadisst sst and simple ocean data assimilation data for 1960 2010 the midlatitude decadal anomalies associated with the pacific decadal oscillation are identified being characterized by an equivalent barotropic atmospheric low high pressure over a cold warm oceanic surface such a unique configuration of decadal anomalies can be maintained by an unstable ocean atmosphere interaction mechanism in the midlatitudes which is hypothesized as follows associated with a warm pdo phase an initial midlatitude surface westerly anomaly accompanied with intensified aleutian low tends to force a negative sst anomaly by increasing upward surface heat fluxes and driving southward ekman current anomaly the sst cooling tends to increase the meridional sst gradient thus enhancing the subtropical oceanic front as an adjustment of the atmospheric boundary layer to the enhanced oceanic front the low level atmospheric meridional temperature gradient and thus the low level atmospheric baroclinicity tend to be strengthened inducing more active transient eddy activities that increase transient eddy vorticity forcing the vorticity forcing that dominates the total atmospheric forcing tends to produce an equivalent barotropic atmospheric low pressure north of the initial westerly anomaly intensifying the initial anomalies of the midlatitude surface westerly and aleutian low therefore it is suggested that the midlatitude ocean atmosphere interaction can provide a positive feedback mechanism for the development of initial anomaly in which the oceanic front and the atmospheric transient eddy are the indispensable ingredients such a positive ocean atmosphere feedback mechanism is fundamentally responsible for the observed decadal anomalies in the midlatitude north pacific ocean atmosphere system

on low frequency variability of the midlatitude ocean gyres the first two authors are thankful to the natural environment research council for the support of this work through the grant ne j006602 1 and the use of archer the uk national supercomputing service we express our gratitude to s burbidge and m harvey for their help with imperial college london cluster as well as to a thomas for his help with managing and maintaining the data storage the last two authors were supported by the spanish ministry of economy and competitiveness under grant tin2013 41049 p and this support is gratefully acknowledged we would also like to thank unknown referees for valuable comments and suggestions which helped us to improve the paper

sm nd and sr isotope systematics of scheelite from the giant au w deposit muruntau uzbekistan implications for the age and sources of au mineralization the application of the sm nd isotope system of scheelite to dating of low sulfide quartz vein hosted au mineralization is still under discussion in the present work new sm nd and rb sr data for scheelite from the giant muruntau myutenbai au deposit kyzylkum western uzbekistan are discussed based on the geological relationship mineralogical properties and trace element characteristics two types of scheelite can be distinguished within the deposit the first one is represented by early bluish luminescent and weakly coloured scheelite generation 1 found within strongly deformed flat quartz veins the apparent isochron defined by this scheelite 351 22 ma is interpreted as a mixing line typically brownish to orange and yellowish luminescent scheelite from steeply dipping veins generation 2 defines a sm nd isochron age of 279 18 ma end 9 5 0 3 mswd 1 5 no evidence for mixing or disturbance by late alteration were found for these scheelites this sm nd isochron age agrees with the rb sr and k ar age range for wall rock alteration in this deposit reported previously the age of 280 ma is interpreted to date the high grade ore formation in the muruntau deposit there are currently no reliable age data available on the magmatic events in the muruntau region probably there is some overlap in time of the hercynian gold deposition with the intrusion of lamprophyric dykes the nd and sr isotopic signatures of scheelite define the wall rocks mainly metasiltstones and metasandstones as the most probable sources for these elements in scheelite

simple climatic indices for the tropical atlantic ocean and some applications two indices related to the sea surface temperature sst variability in the tropical atlantic are proposed one index describes the sst averaged over the whole basin 30 n to 20 s 60 w to 15 e and the other illustrates a meridional dipole between the northern and southern hemispheres the computational method for obtaining these indices is intentionally kept simple the objective being to reproduce the signature of the main results previously provided from more complicated statistical analyses monthly time series for both indices are produced from 1964 up to the present time the whole basin index exhibits principally a sustained warming which has intensified since about 1975 and it has a significant periodicity close to that of the quasi biennial oscillation the dipole index exhibits a decadal scale variation and its building up seems to be related to other worldwide climatic changes as for instance el nino southern oscillation extreme episodes rainfall variabilities over the brazilian nordeste and african sahel

simulation of the tropical pacific climate with a coupled ocean atmosphere general circulation model part ii interannual variability abstract two multiyear simulations with a coupled ocean atmosphere general circulation model gcm totaling 45 years are used to investigate interannual variability at the equator the model consists of the ucla global atmospheric gcm coupled to the gfdl oceanic gcm dynamically active over the tropical pacific multichannel singular spectrum analysis along the equator identifies enso like quasi biennial qb and quasi quadrennial qq modes both consist of predominantly standing oscillations in sea surface temperature and zonal wind stress that peak in the central or east pacific accompanied by an oscillation in equatorial thermocline depth that is characterized by a phase shift of about 90 across the basin with west leading east simulated interannual variability is weaker than observed in both simulations one of these is dominated by the qb the other by the qq mode although the two differ only in details of the surface layer parameterizations

geological features and genesis of gold deposits hosted by low grade metamorphic rocks in central western inner mongolia the central western inner mongolia area located in the western section of the northern margin of the north china craton is one of the most important gold metallogenic provinces in north china the gold deposits and prospects hosted by low grade metamorphic rocks are widely distributed in two parallel ew trending protrozoic rift belts i e the bayan obo belt in the north and the chaiertaishan belt in the south up till now twenty three ore deposits and prospects have been discovered of which changshanhao zhulazaga and saiyinwusu are the largest ones gold mineralization occurs in proterozoic carbonaceous sandstone siltstone carbonaceous phyllite phyllite slate and schist in the stratoid layer stratiform stockwork and veinlike forms all these gold deposits are characterized by shallow burial large size simple composition and easy mining systematic geological investigations indicate that wall rocks of these deposits and prospects vary from place to place but most of them show an intimate spatial temporal relation with the caledonian ductile brittle fracture zone and the hercynian intrusive dyke swarm geometry of individual ore bodies is mainly controlled by interstratified fracture zones all the geological features of the gold deposits hosted by low grade metamorphic rocks in central western inner mongolia are similar to features of the muruntau gold deposit in uzbekistan the relationship between the regional crustal evolution and gold metallogeny can be summarized as follows middle proterozoic stage tectono magmatism caused by the intense rifting occurring within the early precambrian continent or along its margin resulted in the spatial preparation of gold and other ore forming materials and formed a number of gold source beds and protores along certain strata early paleozoic stage a number of gold prospects were formed by regional metamorphism and its related hydrothermal event caused by regional tectonic movement and magmatic intrusion with middle to large sized gold deposits of this stage also identified late paleozoic stage gold deposits with economic significance are considered to have been caused by the re working of the early formed deep rooted faults and its related hercynian mafic to felsic magmatism the extensional faulting and high alkaline magmatism might have played the key role during the formation of the ore deposits geological and geochemical features of the gold deposit hosted by the low grade metamorphic rocks occurring in central western inner mongolia have aroused much attention among geologists both in china and abroad an integrated analysis of the geological setting and geological and geochemical features of these deposits and their related intrusive rocks will greatly upgrade the understanding of the ore forming processes of the gold deposits and prospects hosted by low grade metamorphic rocks in central western inner mongolia meanwhile the genetic model and mineral exploration criteria of these deposits and prospects can also be used during the comprehensive evaluation of the concealed gold deposits hosted by low grade metamorphic rocks in central western inner mongolia and its neighboring areas

gold deposits of china a special issue of ore geology reviews this volume of ore geology reviews is dedicated to dr feng jun nie and credits his significant contribution to understanding the ore deposits of china in recent years he has dedicated his life to the study of mineralization in the north china craton and central asian orogen to the north and that is the focus of this volume

oscillatory climate modes in the eastern mediterranean and their synchronization with the north atlantic oscillation abstract oscillatory climatic modes over the north atlantic ethiopian plateau and eastern mediterranean were examined in instrumental and proxy records from these regions aside from the well known north atlantic oscillation nao index and the nile river water level records the authors study for the first time an instrumental rainfall record from jerusalem and a tree ring record from the golan heights the teleconnections between the regions were studied in terms of synchronization of chaotic oscillators standard methods for studying synchronization among such oscillators are modified by combining them with advanced spectral methods including singular spectrum analysis the resulting cross spectral analysis quantifies the strength of the coupling together with the degree of synchronization a prominent oscillatory mode with a 7 8 yr period is present in all the climatic indices studied here and is completely synchronized with the north atlantic oscillation an energy analysis of the synchronization

global bifurcation of shilnikov type in a double gyre ocean model abstract the dynamics of an idealized wind driven double gyre circulation in an ocean basin are studied from a dynamical systems point of view in an effort to better understand its variability while previous analyses of this circulation have mostly dealt with local bifurcations of steady states and limit cycles this study demonstrates the importance of considering global bifurcations as well in one case a coherent picture of the global dynamics spanning a range of parameters from where there are only stable steady state solutions to where there is chaotic eddy shedding is presented a simple but novel use of power spectra along with dynamical projections of the dynamics suggests that just beyond the regime in which there are only stable steady states the system exhibits a complicated global bifurcation known as the shilnikov phenomenon

temporal variation of meandering intensity and domain wide lateral oscillations of the gulf stream the path of the gulf stream exhibits two modes of variability wavelike spatial meanders associated with instability processes and large scale lateral shifts of the path presumably due to atmospheric forcing the objectives of this study are to examine the temporal variation of the intensity of spatial meandering in the stream to characterize large scale lateral oscillations in the stream s path and to study the correlation between these two dynamically distinct modes of variability the data used for this analysis are path displacements of the gulf stream between 75 and 60 w obtained from avhrr derived advanced very high resolution radiometer infrared images for the period april 1982 through december 1989 meandering intensity measured by the spatial root mean square displacement of the stream path displays a 9 month dominant periodicity which is persistent through the study period the 9 month fluctuation in meandering intensity may be related to the interaction of rossby waves with the stream interannual variation of meandering intensity is also found to be significant with meandering being much more intense during 1985 than it was in 1987 annual variation however is weak and not well defined the spatially averaged position of the stream which reflects nonmeandering large scale lateral oscillations of the stream path is dominated by an annual cycle on average the mean position is farthest north in november and farthest south in april the first empirical orthogonal function mode of the space time path displacements represents lateral oscillations that are in phase over the entire study domain interannual oscillations are also observed and are found to be weaker than the annual oscillation the eigenvalue of the first mode indicates that about 21 5 of the total space time variability of the stream path can be attributed to domain wide lateral oscillations the correlation between meandering intensity and domain wide lateral oscillations is very weak

atmospheric circulations induced by a midlatitude sst front a gcm study the atmospheric effects of sea surface temperature sst anomalies over and near western boundary currents are a matter of renewed interest the general circulation model gcm of the laboratoire de meteorologie dynamique lmd z has a zooming capability that allows a regionally increased resolution this gcm is used to analyze the impact of a sharp sst front in the north atlantic ocean two simulations are compared one with climatological ssts and the other with an enhanced gulf stream front the results corroborate the theory developed previously by the present team to explain the impact of oceanic fronts in this theory the vertical velocity at the top of the atmospheric boundary layer has two components mechanical and thermal it is the latter that is dominant in the tropics while in midlatitudes both play a role in determining the wind convergence above the boundary layer the strengthened sst front does generate the previously predicted stronger ascent above the warmer water south of the front and stronger descent above the colder waters to the north in the gcm simulations the ascent over the warm anomalies is deeper and more intense than the descent

molybdenite re os and u pb zircon dating and genesis of the dayana w mo deposit in eastern ujumchin inner mongolia abstract the dayana w mo deposit in eastern ujumchin of inner mongolia is a quartz vein type deposit in the mid western part of the central asian orogenic belt caob biotite monzogranite quartz porphyry and hornfels host w mo in quartz veins based on spatial relationships molybdenite was deposited first followed by wolframite this contribution presents precise laser ablation inductively coupled plasma mass spectroscopy la icp ms u pb zircon dating and geochemical analysis of the biotite monzogranite the u pb dating shows that the monzogranite is 134 1 ma major and trace element geochemistry shows that the monzogranite is characterized by high sio 2 and k 2 o contents a right inclined shape of the chondrite normalized ree patterns enrichment of large ion lithophile elements liles and depletion of high field strength elements hfses such as nb p ba the monzogranite is high k calc alkaline has a strong negative eu anomaly eu eu 0 04 0 45 low p 2 o 5 content high a cnk of 1 2 enriched in large ion lithophile elements liles such as rb th u nd and hf and notably depleted in ba sr p ti and nb these characteristics define the dayana monzogranite as a highly fractionated peraluminous granite re os isotopic analysis of seven molybdenite samples from the deposit yield an isochron age of 133 3 ma mswd 2 2 which indicates that the monzogranite and ore have the same age within error are probably genetically related and related to a major early cretaceous mineralizing event in china known as the yanshanian

geochronology isotopic chemistry and gold mineralization of the black slate hosted haoyaoerhudong gold deposit northern north china craton abstract the haoyaoerhudong gold deposit is the largest gold deposit in the north margin of the north china craton gold province and contains over 7 moz of gold at an average grade of 0 62 g t the deposit is hosted in the carbonaceous and pyritic slate phyllite and schist and is controlled by a tight syncline and shear zones the high grade orebodies contains abundant pyrite veins and pyrite quartz veins three stages of pyrite have been identified including the diagenetic disseminated pyrite pyrite veins caused by peak matamorphism and pyrite quartz veins forming during post peak metamorphism native gold has been observed in pyrite veins and pyrite quartz veins the 40ar 39ar plateau age of a biotite separate from a tails of boudinaged pyrite quartz veins is 260 1 2 9 ma combined with previously published 40ar 39ar mica age data and low closure temperature of mica these results suggest that pyrite veins and pyrite quartz veins were formed during the peak to post peak metamorphism during 285 260 ma respectively the lower limit of the formation age of sedimentary disseminated pyrites has constrained to 1670 1560 ma by the intruded mafic ultramafic dikes disseminated pyrite separates have 34s values ranging from 39 40 to 17 85 206pb 204pb of 19 144 21 892 207pb 204pb of 15 681 15 864 and 208pb 204pb of 37 502 38 925 suggesting they were formed from seawater sulfate and has experienced strong sulfur isotopic fractionation in contrast hydrothermal pyrites from pyrite veins and pyrite quartz veins have 34s values ranging from 6 8 to 16 47 206pb 204pb of 18 566 18 922 207pb 204pb of 15 645 15 684 and 208pb 204pb of 38 924 38 983 which may reflect dissolution reprecipitation of disseminated sulfides from the pre existing organic rich sediments the mineral paragenetic geometric and cross cutting relationships of pyrite veins and pyrite quartz veins at haoyaoerhudong suggest that gold was most likely introduced into pyrite accompanying sedimentation of the organic rich shales and then became enriched during diagenesis subsequently the hydrothermal fluids following metamorphism and shear zone activity make dissolution of the gold in the diagenetic pyrite and precipitated in the intersection of shear zone and tight syncline

formation of gold deposits a metamorphic devolatilization model a metamorphic devolatilization model can explain the enrichment segregation timing distribution and character of many goldfields such as those found in archean greenstone belts slate belts and other gold only provinces in this genetic model hydrated and carbonated greenschist facies rocks particularly metabasic rocks are devolatilized primarily across the greenschist amphibolite facies boundary in an orogenic setting devolatilization operates on the scale of individual mineral grains extracting not just h2o and co2 but also s and in turn au elevated gold in solution is achieved by complexing with reduced s and by h2co3 weak acid buffering near the optimal fluid ph for gold solubility the buffering is more important than being at the point of maximum gold solubility low salinity ensures low base metal concentrations in the auriferous metamorphic fluid migration of this fluid upwards is via shear zones and or into hydraulic fracture zones in rocks of low tensile strength the geometry of the shear zones dictates the kilometre scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold deposition of gold from solution necessitates breakdown of the gold thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon bearing host rocks and or by sulphidation of wallrocks to generate iron bearing sulphide and precipitated gold as such black slate carbon seams banded iron formation tholeiitic basalt magnetite bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields gold deposition is accompanied by carbonation sulphidation and muscovite biotite alteration where the host rock is of suitable bulk composition the correlation of major gold deposits with rock type even when the gold is primarily in veins argues for rock dominated depositional systems not fluid dominated ones as a consequence a general role in gold deposition for fluid mixing temperature decrease and or fluid pressure decrease and boiling is unlikely although such effects may be involved locally several geological features that are recorded at gold only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process overprinting by higher grade metamorphism and deformation and or palaeo weathering may provide many of the most obvious features of goldfields including their mineralogy geochemistry geometry small scale timing features geophysical response and even mesoscopic gold distribution

re os system of black schist from the mesoproterozoic bayan obo group central inner mongolia china and its geological implications abstract the mesoproterozoic bayan obo group in central inner mongolia china represents a sedimentary sequence deposited in the bayan obo rift basin new re os dates are reported here for the black shale schist from the group re os geochronology of the black schist provides an age of 1447 42 ma which is consistent with the previous work from the literature and provides a direct and new constraint for the age of the group the dating indicates that the re os isotopes for the black schist have remained undisturbed during lower amphibolite facies metamorphism the ca 250 ma age for gold bearing sulfides also indicates that the re os isotopes for the schist have not been affected by hydrothermal overprinting of reduced fluid the initial 187 os 188 os value of 0 93 0 14 for the schist is interpreted to represent the os isotopic composition of the seawater during deposition of the group which indicates that the os composition of mesoprotozoic seawater fluctuated during the mesoproterozoic and was temporary very radiogenic similar to present day seawater the re os data suggests that rifting of the bayan obo basin peaked during ca 1447 ma and the bilute formation in the bayan obo group may have been deposited in the bayan obo sea in a restricted or semi restricted depositional environment

quasi quadrennial and quasi biennial variability in the equatorial pacific evaluation of competing el nino southern oscillation enso theories requires one to identify separate spectral peaks in equatorial wind and sea surface temperature sst time series to sharpen this identification we examine the seasonal to interannual variability of these fields by the data adaptive method of multi channel singular spectrum analysis m ssa m ssa is applied to the equatorial band 4 n 4 s using 1950 1990 data from the comprehensive ocean and atmosphere data set two major interannual oscillations are found in the equatorial sst and surface zonal wind fields u the main peak is centered at about 52 months we refer to it as the quasi quadrennial qq mode quasi biennial qb variability is split between two modes with periods near 28 months and 24 months a faster 15 month oscillation has smaller amplitude the qq mode dominates the variance and has the most distinct spectral peak in time longitude reconstructions of this mode the sst has the form of a standing oscillation in the eastern equatorial pacific while the u field is dominated by a standing oscillation pattern in the western pacific and exhibits also slight eastward propagation in the central and western pacific the locations of maximum anomalies in both qb modes are similar to those of the qq mode slight westward migration in sst across the eastern and central and eastward propagation of u across the western and central pacific are found the significant wind anomaly covers a smaller region than for the qq the qq and qb modes together represent the enso variability well and interfere constructively during major events the sharper definition of the qq spectral peak and its dominance are consistent with the devil s staircase interaction mechanism between the annual cycle and enso

comparison of a mid shelf wave hindcast to adcp measured directional spectra and their transformation to shallow water abstract in conducting a cross shelf wave transformation experiment off the atlantic coast of north florida a unique opportunity was exploited in which an acoustic doppler current profiler adcp instrument was installed 30 km offshore at the exact location of one of the archive nodes of a wam like wave hindcast model owi3g a second adcp was installed 550 m from shore approximately 53 days of directional wave spectra collected with the two adcps are used to a locally test the reliability of a subsequent update of the hindcast b document the loss in energy as the waves crossed the broad relatively shallow continental shelf between the two instruments c test the ability of the swan gen2 nearshore wave transformation model to replicate the measurements taken in shallow water when driven by the offshore adcp spectra and d reassess the spectral transformation results when the offshore hindcast is used as input in addition to direct comparison of the time series of frequency spectra and the directional distribution of energy typical spectral parameters are each subjected to standard error tests results indicate that the offshore hindcast performs well in replicating significant wave height fairly well for mean period but not as reliably for peak period directional spreading in deeper water is generally well represented although vector mean direction is not and is believed due to the proximity of the coast to the hindcast node the nearshore model requires an order of magnitude reduction in bed roughness from its default value before agreement in wave energy at the nearshore adcp can be achieved outcomes of the error tests for the hindcast driven versus the adcp driven nearshore results after roughness calibration are quite similar but nevertheless indicate that transformed wave period wave direction and directional spreading require improvement

age and source constraints for the giant muruntau gold deposit uzbekistan from coupled re os he isotopes in arsenopyrite the muruntau gold deposit uzbekistan is one of the largest gold deposits known worldwide but its origin remains controversial we used re os arsenopyrite geochronology to precisely determine the age of main stage gold mineralization at muruntau to be 287 5 1 7 ma which overlaps the emplacement of proximal post tectonic granitoid magmatism additionally we suggest that arsenopyrite growth may have occurred over an interval of at least 2 m y os initial ratios derived from arsenopyrite were coupled with he isotopic data from fluid inclusions within arsenopyrite to constrain the source of ore metals and fluids muruntau arsenopyrite yields relatively unradiogenic initial os 0 37 0 27 and elevated 3he 4he ratios 0 23 0 33 r a relative to purely crustal os he reservoirs these data suggest the presence of a mantle derived component in the ore system that was probably introduced during the generation of the granitoid magmas these new timing and source constraints provide important new insight into the generation of this giant gold deposit and they necessitate reexamination of genetic models for muruntau and potentially other giant orogenic gold deposits worldwide

permian magmatic sequences of the bilihe gold deposit in central inner mongolia china petrogenesis and tectonic significance abstract the bilihe gold deposit is located in the eastern section of the ondor sum yanji suture at the southern margin of the xing an mongolian orogenic belt xmob and the northern margin of the north china craton ncc central inner mongolia the magmatic rocks in the ore district are generally high k calc alkaline enriched in lree zr and hf and depleted in hree nb ta and p the magmatic evolution sequences are norite gabbro granodiorite porphyry granite or norite gabbro andesite dacite porphyry granodiorite which show a trend of decreasing tio2 feo mgo cao and p2o5 with increasing sio2 in the bilihe ore district hydrothermal processes were coeval with granitic magmatism for a period of 17 myr 272 255 ma the ages of the granite granodiorite porphyry granodiorite and dacite porphyry are 271 5 264 1 ma 269 8 255 8 ma 268 3 ma and 268 6 259 4 ma respectively the magmatic rocks contain magmatic hydrothermal and magmatic hydrothermal zircons the magmatic zircons have ce 4 la 2 5 the hydrothermal zircons have ce 3 ppm and smn lan

decadal variability of the tropical atlantic ocean surface temperature in shipboard measurements and in a global ocean atmosphere model abstract numerous analyses of relatively short 25 30 years in length time series of the observed surface temperature of the tropical atlantic ocean have indicated the possible existence of decadal timescale variability it was decided to search for such variability in 100 yr time series of sea surface temperature sst measured aboard ships and available in the recently published global ocean surface temperature atlas gosta fourier and singular spectrum analyses of the gosta sst time series averaged over 11 subregions each approximately 1 106 km2 in area show that pronounced quasi oscillatory decadal 8 20 yr and multidecadal 30 40 yr timescale variability exists in the gosta dataset over the tropical atlantic motivated by the above results sst variability was investigated in a 200 yr integration of a global model of the coupled oceanic and atmospheric general circulations developed at the geophysical fluid dynamics laboratory gfdl the second 100 yr of sst in the coupled model s tropical

gold deposits of the northern margin of the north china craton multiple late paleozoic mesozoic mineralizing events the northern margin of the north china craton is well endowed with lode gold deposits hosting a resource of approximately 900 tonnes t of gold the 1 500 km long region is characterized by east trending blocks of metamorphosed archean and proterozoic strata that were episodically uplifted during variscan indosinian and yanshanian deformational and magmatic events at least 12 gold deposits from the daqinshan yan liao includes the zhangjiakou yanshan and chifeng gold districts and changbaishan gold provinces contain resources of 20 100 t au each most deposits are hosted in uplifted blocks of precambrian metamorphic rocks although felsic paleozoic and mesozoic plutons are typically proximal and host 30 of the deposits the lodes are characterized by sulfide poor quartz veins in brittle structures with low base metal values and high au ag ratios although phyllic alteration is most common intensive alkali feldspar metasomatism characterizes the wulashan dongping and zhongshangou deposits but is apparently coeval with variscan alkalic magmatism only at wulashan stepwise 40ar 39ar geochronology on 16 samples from gangue and alteration phases combined with unpublished shrimp u pb dates on associated granitoids suggest that gold mineralizing events occurred during variscan indosinian and yanshanian orogenies at circa 350 250 200 180 150 and 129 ma however widespread permo triassic 250 ma and early jurassic 180 ma thermal events caused variable resetting of most of the white mica and k feldspar argon spectra as well as previously reported k ar determinations compiled and new stable isotope and fluid inclusion data show that most 18o values for ore stage veins range from 8 to 14 indicating a fluid in equilibrium with the precambrian metamorphic basement rocks d values from fluid inclusions range widely from 64 to 154 which is indicative of a local meteoric component in some veins and highly variable 34s data 7 to 17 even within individual deposits indicate various local country rock sources for sulfur fluid inclusions from all districts show variable homogenization temperatures between 240 and 400 c and are consistently characterized by low salinity h2o co2 ch4 n2 solutions although the data are largely consistent with that from orogenic gold veins intrusion related veins and epithermal veins are also recognized the multiple episodes of mineralization are coincident with episodic tectonic reactivations and associated magmatism along the northern margin of the north china craton electronic supplementary material to this paper can be obtained by using the springer link server located at http dx doi org 10 1007 s00126 001 0239 2

the influence of sea surface temperature anomalies on low frequency variability of the north atlantic oscillation the influence of sea surface temperature anomalies ssta on multi year persistence of the north atlantic oscillation nao during the second half of the twentieth century is investigated using the center for ocean land atmosphere studies cola atmospheric gcm agcm with an emphasis on isolating the geographic location of the ssta that produce this influence the present study focuses on calculating the atmospheric response to the ssta averaged over 1988 1995 1961 1968 corresponding to the observed period of strong persistence of the positive negative phase of the decadal nao the model response to the global 1988 1995 average ssta shows a statistically significant large scale pattern characteristic of the positive phase of the nao forcing with the global 1961 1968 average ssta generates a nao of the opposite polarity compared to observations however all large scale features both in the model and observations during this period are weaker in magnitude and less significant compared to 1988 1995 additional idealized experiments show that over the northern center of the nao the non linear component of the forced response appears to be quite important and acts to enhance the positive nao signal on the other hand over the southern center where the model response is the strongest it is also essentially linear the 1988 1995 average ssta restricted to the western tropical pacific region produce a positive nao remarkably similar in structure but stronger in magnitude than the model response to the global and tropical indo pacific 1988 1995 forcing a 200 hpa geopotential height response in these experiments shows a positive anomaly over the southern center of the nao embedded in the rossby wave trains propagating from the western tropical pacific indian ocean ssta lead to much weaker positive nao primarily through the effect on its northern center sst forcing confined to the north atlantic north of equator does not produce a response statistically different from the control simulation suggesting that it is not strong enough to significantly affect the phase of the decadal nao inclusion of the south atlantic north of 45 south does not change this result

low frequency variability in the midlatitude atmosphere induced by an oceanic thermal front abstract this study examines the flow induced in a highly idealized atmospheric model by an east west oriented oceanic thermal front the model has a linear marine boundary layer coupled to a quasigeostrophic equivalent barotropic free atmosphere the vertical velocity at the top of the boundary layer drives the flow in the free atmosphere and produces an eastward jet parallel to the oceanic front s isotherms a large gyre develops on either side of this jet cyclonic to the north and anticyclonic to the south of it as the jet intensifies during spinup from rest it becomes unstable the most unstable wave has a length of about 500 km it evolves into a meander and eddies detach from the eastern edge of each gyre the dependence of the atmospheric dynamics on the strength t of the oceanic front is studied the gulf stream and kuroshio fronts correspond roughly in the scaling used here to t 7 c for weak fronts t 4 c the circulation is steady and exhibits two large antisymmetric gyres sepa

bottom friction and wind drag for wave models abstract waves propagating in shallow water dissipate energy in a thin turbulent boundary layer near the bottom this friction can be estimated with a simple quadratic friction law scaled with an empirical coefficient two values of this coefficient have been recommended by previous studies for sandy bottoms a high value for waves in a storm and a low value for swell we show here that in contrast to current practise the lower value should be used for both applications the reason is that the high value dating from the early 1980s was inferred from observations in a severe storm using a relatively high wind drag our review of a large number of more recent observations gives a new wind drag parameterization with lower values with this new parameterization we infer from the same storm the lower value of the bottom friction coefficient using this lower value also improves the estimates of wave growth in shallow water and of low frequency wave decay in a tidal inlet independent of the wind drag

multistage sedimentary and metamorphic origin of pyrite and gold in the giant sukhoi log deposit lena gold province russia gold mineralization at sukhoi log in eastern siberia is hosted in a deformed neoproterozoic organic bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline the deposit contains about 30 million ounces of gold at an average grade of 2 0 g t au and is one of the largest known undeveloped gold resources the high grade gold zone forms a gently dipping tabular body in the core of the anticline the best gold grades occur in narrow bedding parallel pyrite quartz veinlets that have been folded during the main deformation event lower grade gold is associated with disseminated pyrite developed in and around the high grade core of the deposit detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments the two earliest forms of pyrite termed py1 and py2 are commonly developed in stratiform layers of micron sized crystals framboids and fine euhedra which are interpreted as synsedimentary to early diagenetic in origin coarser grained bedding parallel aggregates of inclusion rich pyrite termed py3 contain inclusions of arsenopyrite native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation coarse euhedral pyrite py4 overgrows the earlier pyrite py1 py2 and py3 and the slaty cleavage developed in the host rocks indicating a syndeformation timing late stage inclusion free pyrite py5 overgrows and replaces earlier sulfides and is considered to be syn to late deformation laser ablation inductively coupled plasma mass spectrometry la icpms analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold varying from 0 4 to 12 1 ppm with a mean of 3 22 ppm au and 1 900 ppm as py1 is also enriched in a suite of trace elements mo sb ni co se te ag cu pb zn mn ba cr u v which are similar to those concentrated by organic processes in euxinic sedimentary environments later generations of pyrite from py2 to py5 including pyrite in bedding parallel pyrite quartz veinlets contain progressively lower contents of invisible gold and most other trace elements however this metamorphic and postmetamorphic pyrite contains microinclusions of free gold arsenopyrite pyrrhotite sphalerite and chalcopyrite the paragenetic textural and chemical relationships at sukhoi log suggest that gold was clearly initially introduced prior to cleavage development accompanying sedimentation of the organic rich shales and fixed during diagenesis within the structure of diagenetic arsenian pyrite subsequently accompanying deformation gold was liberated from recrystallized diagenetic pyrite to become concentrated as free gold and gold tellurides within metamorphic pyrite and folded bedding parallel pyrite quartz veinlets two key processes are considered vital to the formation of the sukhoi log deposit original synsedimentary and early diagenetic concentration of gold dissolved within arsenian pyrite in organic rich black shales and metamorphic processes that liberated gold from the early forms of arsenian pyrite to be concentrated as free gold and gold tellurides within late diagenetic and metamorphic pyrite and associated pyrite quartz veinlets in the core of an overturned anticline these ore forming processes are unlikely to be unique to sukhoi log other black shale and turbidite hosted deposits that occur in rifted continental margin environments which have undergone collision and basin inversion may form by similar processes

impacts of sst anomalies in the agulhas current system on the regional climate variability abstractthe potential impact of the variability in the agulhas current system on the large scale atmospheric state in the southern hemisphere is examined using the monthly near surface baroclinicity as the key parameter for the period between september 1980 and august 2002 dominant patterns of anomalous near surface baroclinicity found from empirical orthogonal function eof analyses in the region that includes most of the agulhas current system show a wide variety of anomaly patterns some of which indicate spatial shifts in the position of the agulhas retroflection and or agulhas return current composited anomalies in various atmospheric fields sea surface temperature and the net surface heat flux at the air sea boundary based on the signals in the eofs suggest that sea surface temperature anomalies in the agulhas current system thermally force the atmosphere on the synoptic scale via modification of the near surface baroclinicity in march and april and possibly in january and february as well

pyrite re os and zircon u pb dating of the tugurige gold deposit in the western part of the xing an mongolia orogenic belt china and its geological significance abstract the tugurige gold deposit in the northeastern margin of the north china craton ncc and western part of the xing an mongolia orogenic belt xmob is a large tonnage quartz vein type deposit with a resource of 24 t at about 4 g t au gold mineralization is hosted by porphyritic syenogranite and controlled by nw trending faults our study provides the first precise age for the tugurige gold mineralization and host porphyritic syenogranite the u pb age of zircons from the syenogranite is 276 2 ma and re os dating of six pyrite separates from the deposit yields an isochron age of 268 15 ma the results show that the ages of syenogranite and gold mineralization are the same within error furthermore geological and geochronological evidence indicate that the syenogranite and gold mineralization have very close genetic relationships and that they are products of permian magmatism related to post collisional extension of the central asian orogenic belt caob the initial os isotopic compositions 187 os 188 os 1 26 0 69 of pyrite indicate that the source of os and by inference other ore related materials are derived from the crust the late paleozoic is an important period in which economic gold mineralization was deposited in the caob

geochemical and isotopic study of metasomatic apatite implications for gold mineralization in xindigou northern china abstract the 0 7 moz xindigou gold deposit lies on the north margin of north china craton the orebodies are controlled by nww trending shear zones and hosted by an archean metavolcanosedimentary sequence these host schist amphibolite and marble rocks were intruded by late paleozoic granites and mafic dikes two independent magmatic hydrothermal assemblages were identified based on petrographic evidence a pre ore magmatic hydrothermal magnetite apatite pyrite zircon assemblage and an ore related potassium feldspar muscovite sulfide minor monazite assemblage apatite that has undergone later alteration shows significant intracrystalline spatial variability with respect to the concentrations of rare earth elements rees si and sr scanning electron microscope backscattered images and statistical interrogation of the compositional data acquired by la icp ms indicate that apatite grains in the pre ore magnetite apatite assemblage are homogeneous and enriched in rees and si ap1 where sulfide related alteration of mineralization stage was overlapped these apatite grains display a distinctive texture of homogeneous cores and turbid rims this dissolution reprecipitation process preferentially transported elements from the original apatite rees and si gradually decrease from the core ap1 to the altered rim ap2 ap3 whereas sr increases localized leaching of rees especially lrees from apatite was followed by precipitation of secondary monazite grains in the metasomatic apatite rims and the muscovite sulfide quartz phosphate sequence in situ sr isotope analyses of the apatite show the 87sr 86sr ratios varying from the lowest value 0 707874 in unaltered ap1 to the highest 0 714160 in altered ap3 zircon grains from migmatite display a peak metamorphic age at 2512 9 ma whereas zircons from the early magnetite apatite association formed near 1776 12 ma and late hydrothermal monazite yields a th pb age of 301 0 1 7 ma these geochronology results show that the mineralization occurred during the late paleozoic orogenesis long after neoarchean regional metamorphism and late paleoproterozoic rift related magmatism the typical hydrothermal features of orogenic gold deposit could be inferred from the fluorapatite the elemental patterns of fluorapatite grains indicate that a carbon and sr enriched acid slightly oxidized and low salinity hydrothermal system was responsible for apatite metasomatism and gold mineralization strontium isotopes further reveal that the fluid related to gold deposition was derived from mafic lower crust with extensive radiogenic sr accumulation during fluid rock interaction this study demonstrates the potential application of apatite in exploration for orogenic gold deposits and its use in tracking hydrothermal ree re mobilization during metasomatism

sulfur isotopes in sediment hosted orogenic gold deposits evidence for an early timing and a seawater sulfur source we report sulfur isotopic compositions of sulfides of various paragenetic stages in the giant sukhoi log sediment hosted orogenic au deposit in russia the overall mean value and the significant variability in early pyrite indicate that the sulfur was from the reduction of seawater sulfate the later generations of sulfide have 34s values in successively smaller ranges coincident with the mode that is around the median value of the whole data set together with textural evidence sulfide trace element data and gold occurrence the data demonstrate that metamorphism has gradually homogenized the early sulfur accompanied by the segregation of quartz and the release of au from the lattice of early pyrite and its reprecipitation as inclusions in later pyrite the s isotopic compositions of sulfides in sukhoi log and many other major orogenic au deposits hosted in sedimentary rocks of various ages show a pattern generally parallel to the seawater sulfate curve through geologic time indicating that the sulfur in most sediment hosted orogenic au deposits was probably also originally from the reduction of seawater sulfate we conclude that sulfidation and gold mineralization in many sediment hosted orogenic gold deposits was early during basin evolution when seawater was the principal active fluid rather than later during or after basin inversion as proposed in current models

a model of the inertial recirculation driven by potential vorticity anomalies abstract some essential features of a recirculating inertial gyre the recirculation can be analyzed with a very simple analytically tractable model in wind driven eddy resolving general circulation models the recirculation appears as a strong sub basin scale inertial flow with homogeneous potential vorticity the constant value of potential vorticity decreases with increasing forcing dissipation ratio while the size and the strength of the recirculating gyre increases in the subtropical gyre the recirculating gyre might be driven by anomalous values of low potential vorticity carried northward by the western boundary current we have modeled this process using a barotropic model and prescribing the values of potential vorticity at the edge of the gyre our model gyre is contained in a rectangular box in an attempt to simplify the geometry as much as possible and to isolate the processes occurring in the recirculating region with weak diffusion the prescribed boundary forcing induces a flow with co

the atmospheric response to weak sea surface temperature fronts abstractthe response of the atmospheric boundary layer to fronts of sea surface temperature sst is characterized by correlations between wind stress divergence and the downwind component of the sst gradient and between the wind stress curl and the crosswind component of the sst gradient the associated regression or coupling coefficients for the wind stress divergence are consistently larger than those for the wind stress curl to explore the underlying physics the authors introduce a linearized model of the atmospheric boundary layer response to sst induced modulations of boundary layer hydrostatic pressure and vertical mixing in the presence of advection by a background ekman spiral model solutions are a strong function of the sst scale and background advection and recover observed characteristics the coupling coefficients for wind stress divergence and curl are governed by distinct physics wind stress divergence results from either large scale winds crossing the front or from a thermally direct

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

a carbonaceous sedimentary source rock model for carlin type and orogenic gold deposits this paper presents evidence and arguments that carbonaceous sedimentary rocks were a source for au and as in sediment hosted orogenic and carlin type gold deposits and develops a corresponding genetic model in this two stage basin scale model gold and arsenic are introduced early into black shale and turbidite basins during sedimentation and diagenesis stage 1 and concentrated to ore grades by later hydrothermal structural or magmatic processes stage 2 in reduced continental margin basin settings organic matter sedimented under anoxic to euxinic conditions immobilizes and concentrates gold arsenic and a range of trace elements particularly v ni se ag zn mo cu u present in marine bottom waters into fine grained black mudstone and siltstone of slope and basin facies during early diagenesis gold and certain other trace elements ni se te ag mo cu pge are preferentially partitioned into arsenian pyrite that grows in the muds these processes produce regionally extensive black shale and turbidite sequences enriched in syngenetic gold and arsenic commonly from 5 to 100 ppb au and 10 to 200 ppm as rare organic and sulfide rich metalliferous black shales may contain up to 1 to 2 ppm au and over 1 000 ppm as present as refractory gold in arsenian pyrite and nanoparticles of free gold during late diagenesis and early metamorphism stage 2 the diagenetic arsenian pyrite is recrystallized to form coarser grained pyrite generations and the organic matter is cooked to bitumen under higher grade metamorphism lower greenschist facies and above arsenian pyrite in carbonaceous shales is converted to pyrrhotite these processes release gold arsenic sulfur and other elements sb te cu zn mo bi tl and pb from the source rocks to become concentrated by hydrothermal processes locally to produce gold ores in structural sites such as fold hinge zones shear or breccia zones within or above the black shale sequence la icp ms analyses of diagenetic pyrite in carbonaceous sediments both associated and not associated with gold deposits suggests that invisible gold contents of greater than 250 ppb in diagenetic pyrite are indicative of carbonaceous shale source rocks with the potential to produce economic gold deposits application of this sedimentary source rock model enables a systematic exploration approach for sediment hosted gold deposits based on the distribution composition and structure of carbonaceous shale sequences and their contained diagenetic pyrite

measurements of the evolution of ocean wave spectra due to bottom friction data from a field experiment in which seven wave measurement instruments were placed in a linear transect across the great australian bight are analyzed to determine the spectral decay which can be attributed to bottom friction since other processes such as atmospheric input nonlinear interactions whitecap dissipation refraction and shoaling will also be active the spectral wave model wam is used as an analysis tool explicitly taking these additional processes into account in the analysis the data show marked spectral decay across the shelf analysis reveals that the bottom friction coefficient c is not constant as often assumed in operational wave models the bottom friction coefficient varies approximately inversely with the wave induced bed velocity consistent with the predictions of previous laboratory data and eddy viscosity models it is possible that percolation may also be important in the region but the available data do not allow the relative contributions of bottom friction and percolation to be determined

interdecadal variability in a hybrid coupled ocean atmosphere model abstract a hybrid coupled ocean atmosphere model is used to investigate low frequency variability in the climate system the model s atmospheric component is a budyko sellers north two dimensional energy balance model the oceanic component is a simplified general circulation model the coupled model is confined to an idealized rectangular north atlantic basin in the present model version the ocean density depends exclusively on temperature an interdecadal oscillation with a period of 40 50 years is found in the hybrid coupled model when model parameters are within the climatological range even though density does not depend on salinity this interdecadal oscillation is characterized by a pair of vortices of opposite signs that grow and decay in quadrature with each other in the ocean s upper layer their centers follow each other anticlockwise through the northwestern quadrant of the model domain the interdecadal oscillation s physical mechanism resembles that of the interdecadal oscillation anal

the atmospheric circulation over the north atlantic as induced by the sst field spectral analyses of the sea surface temperature sst in the simple ocean data analysis soda reanalysis for the past half century identify prominent and statistically significant interannual oscillations in two regions along the gulf stream front over the north atlantic a model of the atmospheric marine boundary layer coupled to a baroclinic quasigeostrophic model of the free atmosphere is then forced with thessthistoryfromthesodareanalysis twoextremestatesarefoundintheatmosphericsimulations 1 an eastward extensionofthe westerly jetassociatedwith thefront which occurs mainly during boreal winter and 2 a quiescent state of very weak flow found predominantly in the summer this vacillation of the oceanicfront induced jet in the model is found to exhibit periodicities similar to those identified in the observed gulf stream sstfront itself in addition a close correspondence is found between interannualspectralpeaksin the observed north atlantic oscillation nao index and the soda induced oscillations in the atmospheric model in particular significant oscillatory modes with periods of 8 5 4 2 and 2 8 yr are found in both observedandsimulatedindicesandareshowntobehighlysynchronizedandofsimilarenergyinbothtimeseries theseoscillatorymodesinthesimulationsareshowntobesuppressedwheneither i thegulfstream frontor ii its interannual oscillations are omitted from the sst field moreover these modes also disappear when iii the sst front is spatially smoothed thus confirming that they are indeed induced by the oceanic front

spells of low frequency oscillations and weather regimes in the northern hemisphere abstract the low frequency variability in the midlatitudes is described through an analysis of the oscillatory phenomena in order to isolate nearly periodic components of the atmospheric flow the multichannel version of the singular spectrum analysis m ssa is developed and applied to an nmc 32 year long set of 700 hpa geopotential heights in the same way that principal component analysis identifies the spatial patterns dominating the variability m ssa identifies dynamically relevant space time patterns and provides an adaptive filtering technique three major low frequency oscillations lfos are found with periods of 70 days 40 45 days and 30 35 days the 70 day oscillation consists of fluctuations in both position and amplitude of the atlantic jet with a poleward propagating anomaly pattern the 40 45 day oscillation is specific to the pacific sector and has a pronounced pacific north american pna structure in its high amplitude phase the 30 35 day mode is confined over the atlantic region

geology geochronology and sulphur isotope geochemistry of the black schist hosted haoyaoerhudong gold deposit of inner mongolia china implications for ore genesis abstract the haoyaoerhudong gold deposit is located in the urad middle banner area of inner mongolia in china and is hosted by black schist of the bilute formation in the mesoproterozoic bayan obo group the gold mineralization is within a 4500 m long and 100 m wide zone associated with sulphide quartz veins following the schistosity and crosscutting fractures in the host rocks locally as disseminated sulphide in altered black schist the sulphide mineral assemblage is pyrrhotite pyrite arsenopyrite chalcopyrite sphalerite and is associated with a weak hydrothermal alteration characterized by a silica halo with variable amounts of biotite sericite and carbonate the bilute formation was intruded by multi stage dykes these include metamorphosed porphyritic diorite that pre dates mineralization unmetamorphosed amphibole olivine gabbro that pre dates mineralization and tourmaline bearing pegmatite that post dates mineralization in order to constrain the timing of the gold mineralization and host rocks zircons from the porphyritic diorite amphibole olivine gabbro and tourmaline bearing pegmatite were extracted for u pb dating gold bearing pyrite samples were analysed for 34 s to help determine the possible source of s in the mineral zones a weighted mean 206 pb 238 u age date of 288 3 ma mswd 2 4 was obtained for the porphyritic diorite a weighted mean 206 pb 238 u age date of 282 1 ma mswd 0 58 was obtained from the amphibole olivine gabbro and a weighted mean 206 pb 238 u age date of 182 1 ma mswd 1 04 was obtained from the tourmaline bearing pegmatite these dates constrain the timing of gold mineralization to between 282 1 and 182 1 ma and are consistent with the hydrothermal alteration ages of ca 267 246 ma reported from the literature these new zircon dates indicate that the regional metamorphism of the bayan obo group ceased by the time the haoyaoerhudong gold mineralization was deposited and the genesis of mineralization is not related to the regional metamorphic event the gold bearing pyrites gave positive 34 s v cdt values between 6 8 and 13 4 and are different from the 34 s widely distributed values for the typical black rocks indicating that the sulphur is not derived from the black bilute formation but sourced from some other relatively uniform reservoir widespread contemporaneous granitic magmatism is developed in the haoyaoerhudong area and we suggest that the sulphur forming the gold bearing sulphides is probably sourced from a carbonate contaminated granitic magma reservoir the new zircon dates for the dykes and the 34 s data for gold bearing sulphides indicate that the gold mineralization did not form from metamorphosed black schist in the bayan obo group but is associated with magmatic hydrothermal activity

c o sr and pb isotope systematics of carbonate sequences of the vindhyan supergroup india age diagenesis correlations and implications for global events abstract the vindhyan supergroup of central india records a substantial portion of proterozoic time and contains some of the most disputed precambrian cambrian fossil discoveries despite the significance of these fossil finds many issues including reliable geochronology remained unresolved similarly the geochemical aspects of the sedimentary sequences and their implications to the evolution of proterozoic oceans have been studied only at a reconnaissance level here we report the results of the pb pb dating for the rohtasgarh limestone from the lower vindhyan supergroup giving an age of 1601 130 ma an estimate that is in accord with the recent u pb zircon dating of the lower vindhyan supergroup by rasmussen et al geology 30 2002 103 and ray et al geology 30 2002 131 sr isotope stratigraphy of carbonates from the upper vindhyan supergroup suggests a mid neoproterozoic 750 650 ma age for these formations this in turn argues for a long hiatus between the deposition of the lower and upper vindhyan supergroups our results conflict with the reports of cambrian age small shelly fossils and ediacaran fossils from the upper vindhyan rocks at the same time they suggest that the alleged trace fossils in the lower vindhyan rocks must be of paleoproterozoic age the most common 18 o values for calcitic components from limestone formations of the supergroup range from 10 to 7 similar to paleo neoproterozoic carbonates worldwide the modes of 13 c in the lower and upper vindhyan supergroups are 0 2 and 3 2 respectively again consistent with the worldwide dataset the secular patterns of carbon isotope trends do not support the earlier assumptions that the carbonate sequences at the southern margin correlate with those at the western or northern margins of the vindhyan basin c and sr isotope data provide new calibration points for the seawater evolutionary curves particularly for the paleoproterozoic for strontium isotopes the data from the lower vindhyan supergroup suggest that seawater departed probably less rapidly from mantle values than was previously believed

lag relationships involving tropical sea surface temperatures abstract a long historical record 100 years of monthly sea surface temperature anomalies from the comprehensive ocean atmosphere data set was used to examined the lag relationships between different locations in the global tropics application of complex principal component cpc analysis revealed that the leading mode captures enso related quasi cyclical warming and cooling in the tropical pacific ocean the dominant features of this mode indicate that sst anomalies in the eastern pacific lead those of the central pacific however a somewhat weaker aspect of this mode also indicates that sst anomalies in the tropical indian and western tropical north atlantic oceans vary roughly in concert with each other but lag behind those in the central and eastern pacific the stability of these lag relationships is indicated by the fact that the leading mode is quite similar in three different 30 year time periods in order to further examine these relationships some simple indexes were formed as the average ov

investigating the origins and significance of low frequency modes of climate variability an analysis of the 130 year record of the earth s global mean temperature reveals a significant warming trend and a residual consistent with an auto correlated red noise process whose predictability decays with a timescale of two years thus global temperatures in isolation do not indicate oscillations at 95 confidence against a red noise null hypothesis weak signals identified in the global series can however be traced to significant sea surface temperature oscillations in the equatorial atlantic period 10 years and the el nino region of the pacific 3 5 years no robust evidence is found in this data for interdecadal oscillations the 10 year atlantic oscillation corresponds to a pattern of temperature anomalies which has been associated with interannual variations in west african rainfall and in u s hurricane landfall frequency

deep water formation and quaternary glaciations a large fraction of climatic varability on the quaternary time scale can be explained by nonlinear interactions between the radiation balance of the global atmosphere ocean system and the mass balance of northern hemisphere ice sheets recent analyses of paleoclimatic proxy data indicate a further important contribution to this variability from changes in deep water formation occurring in the north atlantic subpolar sea we study the effects of these changes on variations in global temperature and ice volume characteristic of the late quaternary the novel framework of boolean delay equations bdes is used to formulate a conceptual model of the climatic system under study and to analyze this formal model selfsustained oscillations in the intensity of the atlantic ocean s thermohaline circulation result from the interaction of sea ice formation with the waxing and waning of continental ice sheets the comparison of model results with paleoclimatic records suggests a considerable slowing down of the abyssal circulation during glacial episodes

gulf stream variability and ocean atmosphere interactions abstract time series of gulf stream position derived from the topex poseidon altimeter from october 1992 to november 1998 are used to investigate the lead and lag relation between the gulf stream path as it leaves the continental shelf and the changes in sea level pressure surface wind stress and sea surface temperature sst as given by the ncep reanalysis the dominant signal is a northward southward displacement of gulf stream axis 11 to 18 months after the north atlantic oscillation nao reaches positive negative extrema a sst warming cooling peaking north of the gulf stream is also seen to precede the latitudinal shifts but it is a part of the large scale sst anomaly tripole that is generated by the nao fluctuations there is no evidence that the gulf stream shifts have a direct impact onto the large scale atmospheric circulation a fast passive response of the gulf stream to nao forcing is also suggested by a corresponding analysis of the yearly mean gulf stream position estimated from

bottom friction for wind sea and swell in extreme depth limited situations abstract a severe depth limited storm and a case of extreme swell which both occurred in the southern north sea are hindcasted with a regional version of the third generation wam model this is done using different expressions for the bottom dissipation source term an empirical expression the hasselmann and collins drag law expression and an expression based on the eddy viscosity concept an efficient approximation to this eddy viscosity model is presented which is easy to compute and which yields accurate results it is proposed to take a constant roughness value kn 4 cm in this model which corresponds to small sand ripples the validity of this assumption is investigated the hindcast results are compared with measurements from different stations and an estimate is made of the influence of the tide on the wave dissipation in the southern north sea the eddy viscosity model is found to be a promising alternative to the empirical expression which is used now in the wam model

lithospheric controls on the formation of provinces hosting giant orogenic gold deposits ages of giant gold systems 500 t gold cluster within well defined periods of lithospheric growth at continental margins and it is the orogen scale processes during these mainly late archaean palaeoproterozoic and phanerozoic times that ultimately determine gold endowment of a province in an orogen a critical factor for giant orogenic gold provinces appears to be thickness of the subcontinental lithospheric mantle sclm beneath a province at the time of gold mineralisation as giant gold deposits are much more likely to develop in orogens with subducted oceanic or thin continental lithosphere a proxy for the latter is a short pre mineralisation crustal history such that thick sclm was not developed before gold deposition in constrast orogens with protracted pre mineralisation crustal histories are more likely to be characterised by a thick sclm that is difficult to delaminate and hence such provinces will normally be poorly endowed the nature of the lithosphere also influences the intrinsic gold concentrations of potential source rocks with back arc basalts transitional basalts and basanites enriched in gold relative to other rock sequences thus segments of orogens with thin lithosphere may enjoy the conjunction of giant scale fluid flux through gold enriched sequences although the nature of the lithosphere plays the crucial role in dictating which orogenic gold provinces will contain one or more giant deposits the precise siting of those giants depends on the critical conjunction of a number of province scale factors such features control plumbing systems traps and seals in tectonically and lithospherically suitable terranes within orogens

trends interdecadal and interannual oscillations in global sea surface temperatures this study aims at a global description of climatic phenomena that exhibit some regularity during the twentieth century multi channel singular spectrum analysis is used to extract long term trends and quasi regular oscillations of global sea surface temperature sst fields since 1901 regional analyses are also performed on the pacific northern and southern atlantic and indian ocean basins the strongest climatic signal is the irregular long term trend characterized by overall warming during 1910 1940 and since 1975 with cooling especially of the northern hemisphere between these two warming intervals substantial cooling prevailed in the north pacific between 1950 and 1980 and continues in the north atlantic today both cooling and warming are preceded by sst anomalies of the same sign in the subpolar north atlantic near decadal oscillations are present primarily over the north atlantic but also over the south atlantic and the indian ocean a 13 15 y oscillation exhibits a seesaw pattern between the gulf stream region and the north atlantic drift and affects also the tropical atlantic another 7 8 y oscillation involves the entire double gyre circulation of the north atlantic being mostly of one sign across the basin with a minor maximum of opposite sign in the subpolar gyre and the major maximum in the northwestern part of the subtropical gyre three distinct interannual signals are found with periods of about 60 65 45 and 24 30 months all three are strongest in the tropical eastern pacific the first two extend throughout the whole pacific and still exhibit some consistent albeit weak patterns in other ocean basins the latter is weaker overall and has no consistent signature outside the pacific the 60 month oscillation obtains primarily before the 1960s and the 45 month oscillation afterwards

oscillatory climate modes in the indian monsoon north atlantic and tropical pacific abstractthis paper explores the three way interactions between the indian monsoon the north atlantic and the tropical pacific four climate records were analyzed the monsoon rainfall in two indian regions the southern oscillation index for the tropical pacific and the nao index for the north atlantic the individual records exhibit highly significant oscillatory modes with spectral peaks at 7 8 yr and in the quasi biennial and quasi quadrennial bands the interactions between the three regions were investigated in the light of the synchronization theory of chaotic oscillators the theory was applied here by combining multichannel singular spectrum analysis m ssa with a recently introduced varimax rotation of the m ssa eigenvectors a key result is that the 7 8 yr and 2 7 yr oscillatory modes in all three regions are synchronized at least in part the energy ratio analysis as well as time lag results suggests that the nao plays a leading role in the 7 8 yr mode it was found therewith that the sout

interannual and interdecadal oscillation patterns in sea level relative sea level height rslh data at 213 tide gauge stations have been analyzed on a monthly and an annual basis to study interannual and interdecadal oscillations respectively the main tools of the study are singular spectrum analysis ssa and multi channel ssa m ssa very low frequency variability of rslh was filtered by ssa to estimate the linear trend at each station global sea level rise after postglacial rebound corrections has been found to equal 1 62 0 38 mm y by averaging over 175 stations which have a trend consistent with the neighboring ones we have identified two dominant time scales of el nino southern oscillation enso variability quasi biennial and low frequency in the rslh data at almost all stations however the amplitudes of both enso signals are higher in the equatorial pacific and along the west coast of north america rslh data were interpolated along ocean coasts by latitudinal intervals of 5 or 10 degrees depending on station density interannual variability was then examined by m ssa in five regions eastern pacific 25 s 55 n at 10 resolution western pacific 35 s 45 n at 10 equatorial pacific 123 e 169 w 6 stations eastern atlantic 30 s 0 and 30 n 70 n at 5 and western atlantic 50 s 50 n at 10 throughout the pacific we have found three dominant spatio temporal oscillatory patterns associated with time scales of enso variability their periods are 2 2 5 3 and 4 6 y in the eastern pacific the biennial mode and the 6 y low frequency mode propagate poleward there is a southward propagation of low frequency modes in the western pacific rslh between 35 n and 5 s but no clear propagation in the latitudes further south however equatorward propagation of the biennial signal is very clear in the southern hemisphere in the equatorial pacific both the quasi quadrennial and quasi biennial modes at 10 n propagate westward strong and weak el nino years are evident in the sea level time series reconstructed from the quasi biennial and low frequency modes interannual variability with periods of 3 and 4 8 y is detected in the atlantic rslh data in the eastern atlantic region we have found slow propagation of both modes northward and southward away from 40 45 n interdecadal oscillations were studied using 81 stations with sufficiently long and continuous records most of these have variability at 9 13 and some at 18 y two significant eigenmode pairs corresponding to periods of 11 6 and 12 8 y are found in the eastern and western atlantic ocean at latitudes 40 n 70 n and 10 n 50 n respectively

gold and trace element zonation in pyrite using a laser imaging technique implications for the timing of gold in orogenic and carlin style sediment hosted deposits laser ablation icp ms imaging of gold and other trace elements in pyrite from four different sedimenthosted gold arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements in particular as ni pb zn ag mo te v and se and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and or hydrothermal pyrite or as narrow goldarsenic rims on the outermost parts of the overgrowth hydrothermal pyrite compared to the diagenetic pyrites the hydrothermal pyrites are commonly depleted in ni v zn pb and ag with cyclic zones of co ni and as concentration the outermost hydrothermal pyrite rims are either as au rich as in moderate to highgrade deposits such as carlin and bendigo or co ni rich and as au poor as in moderate to low grade deposits such as sukhoi log and spanish mountain the early enrichment of gold in arsenic bearing syngenetic to diagenetic pyrite within black shale facies of sedimentary basins is proposed as a critical requirement for the later development of carlin style and orogenic gold deposits in sedimentary environments the best grade sediment hosted deposits appear to have the gold climax event toward the final stages of deformation related hydrothermal pyrite growth and fluid flow

atmospheric response to a midlatitude sst front alongfront winds abstractsatellite observations and modeling studies show that midlatitude sst fronts influence the marine atmospheric boundary layer mabl and atmospheric circulation here the weather research and forecasting wrf mesoscale model is used to explore the atmospheric response to a midlatitude sst front in an idealized dry two dimensional configuration with a background wind oriented in the alongfront direction the sst front excites an alongfront wind anomaly in the free atmosphere with peak intensity just above the mabl this response is nearly quasigeostrophic in contrast to the inertia gravity wave response seen for cross front background winds the free atmosphere response increases with the background wind in contrast to previously proposed sst frontal mabl models the mabl winds are nearly in ekman balance however a cross front wind develops in the mabl as a result of friction and rotation such that the mabl cross front rossby number e 0 2 the mabl vorticity balance and scaling arguments

metallogeny of the north china craton link with secular changes in the evolving earth abstract the north china craton ncc has experienced a complex geological evolution since the early precambrian and carries important records of secular changes in tectonics and metallogeny here we synthesize the salient geological and tectonic features of the evolution and destruction of the ncc vis a vis major metallogenic events and the formation of potential ore deposits we identify a close relationship between the major geological events in the ncc and those reported elsewhere on the globe we trace the records of a regular change in the pattern of metallogeny mineral deposit character spatial distribution and genetic mechanisms which closely match the timing and styles of the major geological and tectonic events in this craton the ncc went through five major tectonic cycles 1 neoarchean crustal growth and stabilization 2 paleoproterozoic rifting subduction accretion collision with imprints of the great oxidation event goe 3 late paleoproterozoic neoproterozoic multi stage rifting 4 paleozoic orogenesis at the margins of the craton and 5 mesozoic extensional tectonics associated with lithospheric thinning and decratonization coinciding with these major geological events are five major metallogenic systems identified as follows 1 an archean bif system 2 paleoproterozoic cu pb zn and mg b systems 3 a mesoproterozoic ree fe pb zn system 4 a paleozoic orogenic cu mo system and 5 mesozoic intracontinental au and ag pb zn and mo systems the ore deposit types in each of these metallogenic systems show distinct characteristics and tectonic affinities from early precambrian through late precambrian to paleozoic and mesozoic the ncc records a transition from primitive to modern style plate tectonics evidence for imbricated oceanic plate stratigraphy in a subduction accretion setting and collisional orogenesis along at least three major zones of ocean closure are documented major transitions in tectonic style and surface environmental changes recorded in other parts of the world are also reflected in the geological history and metallogenic events in the ncc large scale gold deposits formed through intraplate tectonics during the mesozoic provide important insights into mantle dynamics and crust mantle interaction associated with lithospheric thinning and craton destruction the ncc provides one of the best examples for documenting secular changes in the geological history and metallogenic epochs of an evolving earth

age origin and significance of nodular sulfides in 2680 ma carbonaceous black shale of the eastern goldfields superterrane yilgarn craton western australia abstract sulfide nodules composed of pyrite occur within black shales in the lucky bay area of the bulong domain eastern goldfields superterrane yilgarn craton western australia that correlate with the neoarchean black flag group detailed petrography reveals a variety of shapes and textures from spherical to ovoid and zoned to uniform some nodules have recrystallized resulting in a later generation of pyrite all have been affected by post depositional metamorphism as evidenced by pressure shadows containing quartz mica carbonate assemblages la icp ms analyses show that these nodules are enriched in a range of trace elements including co ni cu ag sb te au tl pb and bi gold and te concentrations range from 0 3 to 1 ppm and 10 to 50 ppm respectively the black flag group equivalents stratigraphically and structurally underlie a younger basin east of lucky bay that contains turbidites sandy debris flows and bif the latter of which hosts several gold deposits at randalls 60 km se of kalgoorlie it is likely that the lateral equivalents of the nodular sulfide bearing black shale originally occurred stratigraphically beneath what is now the ore horizon at randalls given its anomalous au and te content this lithology is a potential contributor of gold to the bif hosted gold deposits of the randalls goldfield as well as other similar gold resources elsewhere in the eastern goldfields superterrane

origin of ore fluids in the muruntau gold system constraints from noble gas carbon isotope and halogen data abstract hydrothermal vein minerals directly associated with native gold mineralization in the muruntau vein system uzbekistan have been studied for noble gas carbon isotope and halogen chemistry of the trapped ore related fluids helium trapped in early arsenopyrite 1 which has preserved the original fluid signature better than associated scheelite and quartz indicates a small input from a mantle source 5 of total he however the overwhelming majority of the he in the fluid 95 is from crustal sources the noble gases ne kr and xe in the sample fluids are dominated by gases of atmospheric origin the carbon isotope 13 c 2 1 to 5 3 and halogen characteristics of the fluids log br cl 2 64 to 3 23 lend further support for the activity of juvenile fluids during the main ore stage the high proportion of crustal components in the ore forming fluids may be explained by intense fluid rock interaction and is also supported by previous nd and sr isotope studies the involvement of a juvenile fluid component during the main stage of hydrothermal activity at muruntau 275 ma can be linked to the emplacement of lamprophyric dikes at muruntau due to apparently overlapping ages for high temperature alteration related ore vein formation and intrusion of the dikes the input of mantle derived fluids possibly related to the hercynian collisional event in the western tien shan stimulated intense fluid rock interaction in the crust in this context the mantle derived fluid should be considered as one possible carrier of metals significant amounts of external meteoric fluids circulating in fracture systems are interpreted to have modified the noble gas signature of fluid in quartz mostly during late low temperature fluid circulation

a hybrid eulerian lagrangian model for spectral wave evolution with application to bottom friction on the continental shelf abstract a hybrid eulerian lagrangian wave model is presented that solves the spectral energy balance equation for surface gravity waves in varying depth the energy of each spectral component is advected along lagrangian ray trajectories the source terms in the energy balance equation e g interactions between wave components and nonconservative processes are computed on a fixed eulerian grid and interpolated onto the ray trajectories the source terms are integrated in time along the rays this integration is performed in parallel over the entire model domain the main advantage of this new model named crest coupled rays with eulerian source terms is that refraction of waves by subgrid scale depth variations is evaluated accurately using precomputed rays and thus the model can be applied with relatively coarse source term grids to large coastal areas hindcasts of swell evolution across the north carolina continental shelf are presented for a source term restricted to energy dissipation in th

re os and u pb geochronology of the shazigou mo polymetallic ore field inner mongolia implications for permian triassic mineralization at the northern margin of the north china craton abstract the recently discovered polymetallic shazigou mo w pb zn ore field is located at the northern margin of the north china craton this integrated metallogenic system is comprised of quartz vein mineralization in three deposits shazigou mo w jindouzishan pb zn and mantougou pb zn the total reserves are estimated to be 50 kt mo 626 t wo3 244 kt pb and 150 kt zn molybdenite re os dating of five quartz vein type ores yielded a mean model age of 243 8 1 6 ma mswd 0 81 and hydrothermal zircons yielded a concordant u pb age of 245 2 6 ma mswd 0 65 these results suggest that the mineralization was formed in the early triassic and could be related to paleo asian ocean subduction microthermometry and quartz fluid inclusion compositions indicate that fluids related to the mo w mineralization were mainly derived from magmatic sources and precipitated under relatively high temperature 280 340 c and salinity conditions 6 9 wt nacl equiv whereas subsequent pb zn mineralization related fluids may have been modified by metamorphic and meteoric waters the discovery of the shazigou ore field suggests conditions may be favourable for more extensive mineralization in the western xilamulun mo metallogenic belt at the northern margin of the north china craton

interannual variability in north atlantic weather data analysis and a quasigeostrophic model abstractthis paper addresses the effect of interannual variability in jet stream orientation on weather systems over the north atlantic basin nab the observational analysis relies on 65 yr of ncep ncar reanalysis 1948 2012 the total daily kinetic energy of the geostrophic wind gtke is taken as a measure of storm activity over the north atlantic the nab is partitioned into four rectangular regions and the winter average of gtke is calculated for each quadrant the spatial gtke average over all four quadrants shows striking year to year variability and is strongly correlated with the north atlantic oscillation nao the gtke strength in the northeast quadrant is closely related to the diffluence angle of the jet stream in the northwest quadrant to gain insight into the relationship between the diffluence angle and its downstream impact a quasigeostrophic baroclinic model is used the results show that an initially zonal jet persists at its initial latitude over 30 days or longer while a tilted

geochemistry of precambrian carbonates v late paleoproterozoic seawater in an effort to obtain better constrained data for the first and second order variations in the isotopic composition of late paleoproterozoic 1 8 0 2 ga seawater we report a study of mineralogy chemistry and isotopic composition of the coronation supergroup 1 9 ga nwt canada and the mcarthur group 1 65 ga nt australia petrologically both carbonate sequences are mostly dolostones the mcarthur population however contains more abundant textural features that attest to the former presence of sulfates and halite and the facies investigated herein probably represent ancient equivalents of modern evaporitic sabkhas and lacustrine playa lakes this is reflected in 18 o enrichment up to 2 9 pdb and high mn fe and sr concentrations nonetheless the available 18 o data indicate that the best estimate for the archean to late paleoproterozoic limestones is about 7 pdb with dolostones some 3 2 heavier the observed 18 o doiomitc calcite is thus within the range of the proposed fractionation factor for a cogenetic mineral pair this together with the consistency of isotopic patterns for sedimentological facies over almost 2 billion years from the late paleoproterozoic to the present suggest that dolomitization was an early diagenetic event and that the 18 o depletion of the archean to late paleoproterozoic carbonates is not an artefact ofpost depositional alteration the 13 c although within the range of other precambrian and phanerozoic carbonates indicates a possible secular evolution from 0 2 pdb at 1 9 ga ago to 1 1 5 at 1 65 ga ago the secular evolution for reflects the 87 sr increase from 0 7031 0 0008 at 3 5 0 1 ga ago through 0 7025 0 0015 at 2 8 0 2 ga 0 7033 at 2 5 ga 0 7050 at 2 25 0 25 ga 0 7047 at 1 91 to 0 706 at 1 65 ga ago

regional geologic setting and metallogenesis of central inner mongolia china guides for exploration of mesothermal gold deposits abstract the central inner mongolia district forms one of the most important metallogenic provinces in china because the district has been influenced by repeated distinct tectonomagmatic activity the genetic relationships and spatial temporal evolution of ancient tectonism and associated geologic structures and metallogeny are discussed in this paper an integrated genetic model for gold metallogeny is proposed during the late archean to paleozoic repeated north southward accretional tectonics between the paleo mongolia oceanic plate and the north china paleoplate led to the formation of not only the e w trending deep crustal faults but also a series of sedimentary volcanic and metamorphic events numerous stratiform fe cu au pb zn and ree ores formed in association with sedimentation and volcanism within the platform environments at this time during the late paleozoic to early mesozoic the central inner mongolia district was largely influenced by northwestward subduction of the circum pacific plate beneath the eurasia plate a series of ne sw trending faults together with s type granitoid intrusions formed as a result of this subduction mesothermal type gold deposits e g the saiyingwusu laoyanghao shibaqin wulashan and donghuofang deposits formed during the permian to jurassic 158 5 to 275 4 ma preferentially at or near the intersections between ne sw trending and e w trending fault systems at these intersections the areas of not only late paleozoic to early mesozoic granitoids but also late archean to early proterozoic metamorphic rocks especially the gold rich seertengshan wulashan and bayan obo group rocks may be promising exploration targets for mesothermal gold deposits