the giant dexing porphyry cu mo au deposit in east china product of melting of juvenile lower crust in an intracontinental setting the dexing porphyry cu mo au deposit in east china 1 168 mt at 0 45 cu is located in the interior of the south china craton scc made up of two lithospheric blocks the yangtze and cathaysia blocks the cu mo au mineralization is associated with mid jurassic granodioritic porphyries with three high level intrusive centers controlled by a series of lineaments at the southeastern edge of the yangtze block available age data define a short duration 172 170 ma of the felsic magmatism and the mineralization 171 1 ma the deposit shows broad similarities with deposits in volcanoplutonic arcs although it was formed in an intracontinental setting porphyries associated with mineralization are mainly granodiorites which contain abundant phenocrysts 40 60 and carry contemporaneous microgranular mafic enclaves mmes they are mainly high k calc alkaline and show geochemical affinities with adakite characterized by relatively high mgo cr ni th and th ce ratios the least altered porphyries yielded relatively uniform end t values from 0 9 to 0 6 and wide 87sr 86sr i range between 0 7046 and 0 7058 partially overlapping with the sr nd isotopic compositions of the mmes and mid jurassic mafic rocks in the scc zircons from the porphyries have positive ehf t values 3 4 to 6 9 and low 18o values 4 7 to 6 3 generally close to those of depleted mantle all data suggest an origin by partial melting of a thickened juvenile lower crust involving mantle components e g neoproterozoic mafic arc magmas triggered by invasion of contemporaneous mafic melts at dexing the mmes show textural mineralogical and chemical evidence for an origin as xenoliths formed by injection of mafic melts into the felsic magmas these mmes usually contain magmatic chalcopyrite and have original variable contents of cu up to 500 ppm their geochemical characteristics suggest that they were derived from an enriched mantle source metasomatized by proterozoic slab derived fluids and supplied a part of cu au and s for the dexing porphyry system during their injection into the felsic magmas the 171 1 ma magmatic hydrothermal event at dexing is contemporaneous with the mid jurassic extension in the scc followed by 160 90 ma arc like magmatism in southeastern china with respect to the tectono magmatic evolution of the scc the emplacement of cu bearing porphyries and the associated cu mineralization occurred in response to the transformation from a tensional regime related to mid jurassic extension to a transpressional regime related to the subduction of the paleo pacific oceanic lithosphere

highly evolved juvenile granites with tetrad ree patterns the woduhe and baerzhe granites from the great xing an mountains in ne china abstract in ne china voluminous granitoids were emplaced in late paleozoic and mesozoic times we report here sr nd o isotopic and elemental abundance data for two highly evolved granitic plutons woduhe and baerzhe from the great xing an mountains they show a rather juvenile sr nd isotopic signature and a spectacular tetrad effect in their ree distribution patterns as well as non charac charge and radius controlled trace element behavior the emplacement ages are constrained at 130 4 ma for the woduhe and 122 5 ma for the baerzhe granites by rb sr and sm nd isotope analyses both granites are also characterized by low but imprecise initial 87sr 86sr ratios of about 0 703 the nd sr isotope data argue for their generation by melting of dominantly juvenile mantle component with subordinate recycled ancient crust this is largely compatible with the general scenario for much of the phanerozoic granitoids emplaced in the central asian orogenic belt the parental magmas for both the woduhe and baerzhe granites have undergone extensive magmatic differentiation during which intense interaction of the residual melts with aqueous hydrothermal fluids probably rich in f and cl resulted in the non charac trace element behavior and the tetrad effect of ree distribution both the woduhe and baerzhe granites show the characteristic trace element patterns of rare metal granites but their absolute abundances differ by as much as two orders of magnitude the oxygen isotope compositions of the two granites have been severely disturbed significant 18o depletion in feldspar but not so much in quartz suggests that the hydrothermal alteration took place in a temperature condition of 300 500 c this subsolidus hydrothermal alteration is decoupled from the late stage magma fluid interaction at higher temperatures despite the two distinct and intense events of water rock interaction the rb sr and sm nd geochronological systems seem to have maintained closed hence suggesting that the two events occurred shortly after the plutonic emplacements

climatology of vertical wind shear over the tropical atlantic abstract the spatiotemporal variability of the 200 850 hpa vertical wind shear over the tropical atlantic is examined for a period of 46 yr this work extends and updates past studies by considering a longer data record as well as a tropospheric deep measure of vertical wind shear composite fields are constructed to illustrate the spatial pattern of the large scale circulation associated with the mean and extreme cases of vertical shear within the tropical atlantic the contemporaneous relationship of vertical shear with el nino southern oscillation enso and sahel precipitation are also examined while the enso shear correlation appears to have slightly strengthened during the past decade the sahel shear correlation has become significantly degraded a combined empirical orthogonal function eof analysis of the zonal and meridional components of the vertical shear reveals interannual and multidecadal modes the leading eof exhibits mainly interannual variability and is highly correlated with enso th

3d geo mapping based on surface data for preliminary study of underground works a case study in val topina central italy abstract this paper reports a geological modelling procedure suitable for the reconstruction of three dimensional models and for applications in preliminary tunnelling studies the geological modelling is based on field survey data stored and organized in a database using a geographic information system gis and then exported in a computer aided design cad software system which is used to create the geometrical model the main steps of the elaboration are 1 reconstruction of the digital terrain model 2 calculation of elevation for the 2d geological data 3 reconstruction of geological cross sections oriented perpendicular to the geo structural fold axis geological profiles by means of down plunge projection 4 modelling of the geological surfaces via nurbs interpolation a model built in this way can be used to automatically create sub horizontal geological cross sections at tunnel level or vertical cross sections along the alignments in order to define accurately the geo lithological characteristics along each underground segment during excavation and to calculate the segments lengths in every geological formation along the tunnel the authors delineate the procedure through a simple and yet exhaustive case study carried out in order to choose the optimal path for the foligno nocera umbra railway mainly in tunnel to be realised in val topina umbria region italy

ages and geodynamic settings of xilamulun mo cu metallogenic belt in the northern part of the north china craton abstract the xilamulun belt along the northern part of the north china craton is located in eastern segment of the central asian orogenic belt and has great economic potential for mo cu mineralization more than ten medium to large ore deposits have been discovered in this region in the recent years the major types of mineralization type include porphyry chehugou mo cu kulitou mo cu xiaodonggou mo and jiguanshan mo quartz vein nianzigou mo xinjing mo epithermal hongshanzi mo u and alteration assemblage liulingou mo the timing of mineralization was previously thought to be yanshanian 208 290 ma however indosinian 260 208 ma ages for intrusions and mineralization have been recognized in recent years based on geochronologic data and regional geological evidence it is suggested that the mineralization in the xilamulun belt was formed during multiple events the mineralization processes are related to a post collisional extension stage 258 210 ma with the generation of the porphyry molybdenum copper deposit a tectonic stress transformation from ns to ew 185 150 ma that gave rise to vein or porphyry molybdenum deposit and a lithospheric thinning stage 140 110 ma with porphyry molybdenum deposit

tin mineralization in the dajing tin polymetallic deposit inner mongolia china abstract dajing is a large scale tin polymetallic deposit that hosts the largest tin mine in north china it is a hydrothermal vein type deposit containing sn cu pb zn ag and minor components co and in the deposit consists of more than 690 veins hosted within upper permian sedimentary rocks three mineralization stages and six ore types are recognized with cassiterite constituting the dominant tin mineral the sno2 content of cassiterite increases in the sequence of mineralization stages shear deformation cassiterite quartz cassiterite sulfide or chalcopyrite pyrite stage while the content of feo tio2 nb2o5 ta2o5 and in2o5 tends to decrease with increases in nio and ga2o5 it is considered that the negative correlation between sno2 and feo nb2o5 ta2o5 and in2o5 results from elemental substitutions the early stage cassiterite is much richer in ta and the later stage cassiterite is much poorer in ti and fe than is usual in hydrothermal vein type tin deposits this is interpreted to indicate that the component of early stage cassiterite reflects a granitic magma source while the composition of later stage cassiterite has a more obvious strata source the compositional variation of cassiterite corresponds to decreasing crystallization temperatures within each stage and between sequential stages with time the characteristics of ree in cassiterite from two stages are in accord with that of subvolcanic rocks and the linxi formation it suggests that tin transported during the cassiterite quartz stage may have originated from subvolcanic dikes e g dacite porphyry while in the cassiterite sulfide stage tin may have been derived from wallrock e g siltstone of the upper permian age linxi formation

african easterly wave variability and its relationship to atlantic tropical cyclone activity abstract automatic tracking of vorticity centers in european centre for medium range weather forecasts analyses has been used to develop a 20 yr climatology of african easterly wave activity the tracking statistics at 600 and 850 mb confirm the complicated easterly wave structures present over the african continent the rainy zone equatorward of 15 n is dominated by 600 mb activity and the much drier saharan region poleward of 15 n is more dominated by 850 mb activity over the atlantic ocean there is just one storm track with the 600 and 850 mb wave activity collocated based on growth decay and genesis statistics it appears that the 850 mb waves poleward of 15 n over land generally do not get involved with the equatorward storm track over the ocean instead there appears to be significant development of 850 mb activity at the west african coast in the rainy zone around 10 n 10 w which it is proposed is associated with latent heat release based on the tracking statistics it has been shown th

geochemistry and geochronology of the dongshanwan porphyry mo w deposit northeast china implications for the late jurassic tectonic setting abstract the dongshanwan porphyry mo w deposit is located in the southern segment of the da hinggan mountains of the eastern segment of the central asia orogenic belt more than 95 of the mineralization occurs within the dongshanwan granite porphyry with a small part being hosted within quartz veins that crosscut the late permian strata zircon u pb age measurements indicate that the dongshanwan granite porphyry has a 206pb 238u age of 151 4 0 8 ma three molybdenite samples from the dongshanwan deposit were selected for re os isotope measurement to define the mineralization age of the deposit these yielded re os model ages of 149 3 2 3 to 155 4 3 3 ma based on analyses of major and trace elements and hf isotopes the dongshanwan porphyry is characterized by low sr and high y values exhibiting strong negative eu anomalies eu 0 01 0 04 indicating post collisional a type geochemical characteristics the hf isotopic composition of the dongshanwan porphyry ehf t 5 5 to 9 2 indicates that both juvenile crustal sources and depleted mantle contributed to their origin the regional geological setting when combined with the geochemistry of the dongshanwan porphyry probably indicates that the granite porphyry derives from crustal root melting during lithospheric delamination in northeast china caused by the rollback of the paleo pacific plate

geologic site characterization for deep nuclear waste disposal in fractured rock based on 3d data visualization abstract three dimensional 3d visualization of data is an essential step in the development of descriptive hydrologic and rock mechanical models of fractured rock systems data includes geological properties rock mechanical properties and hydraulic responses the 3d visualization approach is applied to characterizing a hypothetical site for a high level nuclear waste repository located at 500 m depth in granitoids of the trans scandinavian igneous belt 1 6 1 8 ga old the study is based on site specific data at the aspo hard rock laboratory hrl on the southeastern coast of sweden the data are extensive and spatially complex and are based on surface information as well as a large number of boreholes penetrating up to 1000 m at this site fractures and fracture zones control both groundwater flow and mechanical stability structures are found within a 2 2 1 km deep model block representing the site 3d locations of fractures and fracture zones are hypothesized based on surface and subsurface geological and geophysical information including borehole radar this results in a 3d geological model structure of the site

interaction between coeval mafic and felsic melts in the st francois terrane of missouri usa abstract in the eastern st francois mountains of missouri a 1 48 ga subvolcanic ring pluton known as the silvermine granite hosts swarms of dark pillow shaped enclaves exhibiting classical features of mafic melt globules trapped in granitic magma the pillows formed by turbulent injection of near liquidus mafic melt into a resident visco plastic granitic magma exchange of crystals fluids and ions between the two melts produced a hybrid tonalite granite enclave series and modified host granite composition several lines of evidence suggest interaction between granitic melt that produced the granophyric cap of the pluton and basaltic melt that formed dikes in the area rapid cooling of the pillows re melted the host creating back veins in many enclaves mineral chemistry indicates the hybrid rocks have undergone extensive subsolidus re equilibration

effects of vertical wind shear on the intensity and structure of numerically simulated hurricanes a series of numerical simulations of tropical cyclones in idealized large scale environments is performed to examine the effects of vertical wind shear on the structure and intensity of hurricanes the simulations are performed using the nonhydrostatic pennsylvania state university national center for atmospheric research fifth generation mesoscale model using a 5 km fine mesh and fully explicit representation of moist processes when large scale vertical shears are applied to mature tropical cyclones the storms quickly develop wavenumber one asymmetries with upward motion and rainfall concentrated on the left side of the shear vector looking downshear in agreement with earlier studies the asymmetries develop due to the storm s response to imbalances caused by the shear the storms in shear weaken with time and eventually reach an approximate steady state intensity that is well below their theoretical maximum potential intensity as expected the magnitude of the weakening increases with increasing shear all of the storms experience time lags between the imposition of the large scale shear and the resulting rise in the minimum central pressure while the lag is at most a few hours when the storm is placed in very strong 15 m s21 shear storms in weaker shears experience much longer lag times with th e5ms 21 shear case showing no signs of weakening until more than 36 h after the shear is applied these lags suggest that the storm intensity is to some degree predictable from observations of largescale shear changes in all cases both the development of the asymmetries in core structure and the subsequent weakening of the storm occur before any resolvable tilt of the storm s vertical axis occurs it is hypothesized that the weakening of the storm occurs via the following sequence of events first the shear causes the structure of the eyewall region to become highly asymmetric throughout the depth of the storm second the asymmetries in the upper troposphere where the storm circulation is weaker become sufficiently strong that air with high values of potential vorticity and equivalent potential temperature are mixed outward rather than into the eye this allows the shear to ventilate the eye resulting in a loss of the warm core at upper levels which causes the central pressure to rise weakening the entire storm the maximum potential vorticity becomes concentrated in saturated portions of the eyewall cloud aloft rather than in the eye third the asymmetric features at upper levels are advected by the shear causing the upper portions of the vortex to tilt approximately downshear the storm weakens from the top down reaching an approximate steady state intensity when the ventilated layer can descend no farther due to the increasing strength and stability of the vortex at lower levels

examining potential genetic links between jurassic porphyry cu au mo and epithermal au ag mineralization in the toodoggone district of north central british columbia canada the toodoggone district comprises upper triassic to lower jurassic hazelton group toodoggone formation volcanic and sedimentary rocks which unconformably overlie submarine island arc volcanic and sedimentary rocks of the lower permian asitka group and middle triassic takla group some of which are intruded by upper triassic to lower jurassic plutons and dikes of the black lake suite although plutonism occurred episodically from ca 218 to 191 ma the largest porphyry cu au mo systems formed from ca 202 to 197 ma with minor mineralization occurring from ca 197 to 194 ma porphyry style mineralization is hosted by small volume 468 c saline and deposited metals at deep crustal depths 2 km sulfur c o and pb isotope data confirm the involvement of a magmatic fluid but also suggest that the ore fluid interacted with asitka and takla group country rocks prior to metal deposition in contrast in the shasta lawyers and griz sickle low sulfidation epithermal systems there is no clear association with magmatic fluids instead their fluid inclusion data indicate the involvement of low temperature 175 to 335 c low salinity 1 to 11 equiv wt nacl fluids that deposited metals at shallow depths 850 m their isotope i e o h pb data suggest interaction between meteoric and or metamorphic ore fluids with basement country rocks

low level african easterly wave activity and its relation to atlantic tropical cyclogenesis in 2001 abstract this paper provides new information on the low level 850 hpa structure and behavior of african easterly waves aews and relates this information to previous studies individual aews that occurred during june september of 2001 are studied by a synoptic approach that employs hovmoller diagrams wave track maps and case studies the focus is on two aew regimes in the lower troposphere over north africa a dry regime to the north of the african easterly jet aej coincident with the surface position of the monsoon trough near 20 n and a wet regime to the south of the jet coincident with the near equatorial rainbelt near 10 n the following issues are addressed the origin of the waves seen in the two wave regimes relation of the wave activity to the mean positions of the surface monsoon trough and the 600 700 hpa aej collocation of the tracks of the two wave regimes off the african coast and diversity in low level wave behavior that includes merging splitting and dissipation of the cyclonic

generation of african easterly wave disturbances relationship to the african easterly jet abstract the relationship between african easterly waves and the background climatology in which they form is studied using a regional climate model the surface and lateral boundary conditions in the model are manipulated to modify the background climatology especially the african easterly jet and the itcz and the behavior of the waves in these different settings is evaluated three climate simulations are presented with monthly mean lateral and surface boundary conditions one has a strong jet and a strong itcz the second has a strong jet and a weak itcz and the third has a weak jet and a strong itcz in these simulations the presence of wave activity is more closely associated with the concentration of the itcz than the strength of the african easterly jet in particular the simulation with a strong jet accompanied by a weak itcz does not produce significant wave activity but a weak jet with a strong itcz has realistic wave disturbances both the charney stern and the fjortoft necessary conditi

easterly wave regimes and associated convection over west africa and tropical atlantic results from the ncep ncar and ecmwf reanalyses ncep ncar and ecmwf daily reanalyses are used to investigate the synoptic variability of easterly waves over west africa and tropical atlantic at 700 hpa in northern summer between 1979 1995 1979 1993 for ecmwf spectral analysis of the meridional wind component at 700 hpa highlighted two main periodicity bands between 3 and 5 days and 6 and 9 days the 3 5 day easterly wave regime has already been widely investigated but only on shorter datasets these waves grow both north and south of the african easterly jet aej the two main tracks noted over west africa at 5 n and 15 n converge over the atlantic on latitude 17 5 n these waves are more active in august september than in june july their average wavelength phase speed varies from about 3000 km 8 m s 1 north of the jet to 5000 km 12 m s 1 south of the jet rainfall convection and monsoon flux are significantly modulated by these waves convection in the inter tropical convergence zone itcz being enhanced in the trough and ahead of it with a wide meridional extension compared to the 3 5 day waves the 6 9 day regime is intermittent and the corresponding wind field pattern has both similar and contrasting characteristics the only main track is located north of the aej along 17 5 n both over west africa and the atlantic the mean wavelength is higher about 5000 km long and the average phase speed is about 7 m s 1 then the wind field perturbation is mostly evident at the aej latitude and north of it the perturbation structure is similar to that of 3 5 days in the north except that the more developed circulation centers moving more to the north lead to a large modulation of the jet zonal wind component south of the aej the wind field perturbation is weaker and quite different the zonal wind core of the jet appears to be an almost symmetric axis in the 6 9 day wind field pattern a clockwise circulation north of the aej being associated with a counter clockwise circulation south of the jet and vice versa these 6 9 day easterly waves also affect significantly rainfall convection and monsoon flux but in a different way inducing large zonal convective bands in the itcz mostly in the trough and behind it as opposed to the 3 5 day wave regime these rainfall anomalies are associated with anomalies of opposite sign over the guinea coast and the sahelian regions over the continent these waves are more active in june july and in august september over the ocean gate phase i gave an example of such an active 6 9 day wave pattern considered as a sequence of weak easterly wave activity this phase was also a sequence of high 6 9 day easterly wave activity we suggest that the 6 9 day regime results from an interaction between the 3 5 day easterly wave regime maintained by the barotropic baroclinic instability of the aej and the development of strong anticyclonic circulations north of the jet over west africa and both north and south of the jet over the atlantic significantly affecting the jet zonal wind component the permanent subtropical anticyclones azores libya st helena could help initiation and maintenance of such regime over west africa and tropical atlantic based on an a priori period band criterion our synoptic classification has enabled us to point out two statistical and meteorological easterly wave regimes over west africa and tropical atlantic ncep ncar and ecmwf reanalyses are in good agreement the main difference being a more developed easterly wave activity in the ncep ncar reanalyses especially for the 3 5 day regime over the atlantic

impact of resolution and downscaling technique in simulating recent atlantic tropical cylone activity using the global environmental multiscale gem model we investigate the impact of increasing model resolution from 2 to 0 3 on atlantic tropical cyclone activity there is a clear improvement in the realism of atlantic storms with increased resolution in part linked to a better representation of african easterly waves the geographical distribution of a genesis potential index composed of large scales fields known to impact cyclone formation coincides closely in the model with areas of high cyclogenesis the geographical distribution of this index also improves with resolution we then compare two techniques for achieving local high resolution over the tropical atlantic a limited area model driven at the boundaries by the global 2 gem simulation and a global variable resolution model gvar the limited area domain and high resolution part of the gvar model coincide geographically allowing a direct comparison between these two downscaling options these integrations are further compared with a set of limited area simulations employing the same domain and resolution but driven at the boundaries by reanalysis the limited area model driven by reanalysis produces the most realistic atlantic tropical cyclone variability the gvar simulation is clearly more accurate than the limited area version driven by gem global degradation in the simulated interannual variability is partly linked to the models failure to accurately reproduce the impact of atmospheric teleconnections from the equatorial pacific and sahel on atlantic cyclogenesis through the use of a smaller limited area grid driven by gem global 2 we show that an accurate representation of african easterly waves is crucial for simulating atlantic tropical cyclone variability

paleozoic crustal growth and metallogeny of central asia evidence from magmatic hydrothermal ore systems of central kazakhstan abstract the ore deposit spectrum of central kazakhstan reflects a range of lithospheric magmatism controlled by the polycyclic geodynamic evolution of an active continental margin which develops from back arc oceanic settings volcanic hosted massive sulphide cu au ore deposits to subduction controlled calcalkaline magmatism copper porphyries with subsequent stages of crust differentiation of low degree partial melting and extended intramagmatic fractionation molybdenum porphyries on to continental rifting peralkaline ree zr nb rich systems mesothermal gold deposits mark transcrustal shear zone controlled fluid conduits formed during arc slicing and thermal relaxation in a post orogenic setting the ore deposits characterize successive and spatially overlapping stages of crustal growth and consolidation the general subduction setting of this range of ore deposits is reflected by calc alkaline trends in the associated subalkaline high k felsic rocks with a wide range in silica contents the predominant metal spectrum of au cu and mo indicates relatively oxidized magmatic hydrothermal systems in accordance with the metaluminous i type nature of their igneous host rocks i e oxidized igneous precursor material despite of presumably highly variable ratios of mantle crust components in individual magmatic systems gabbros to leucogranites most rocks have very similar positive initial e nd values of 0 to 5 5 and depleted mantle model ages in the range of 500 800 ma the ubiquitous relatively young mantle extraction age is likely to characterize the lower crust of central kazakhstan this basement is interpreted as back arc oceanic crust that formed behind oceanwards drifting continental margin slivers during the initial stages of the active continental margin evolution of the late precambrian angara baltica supercontinent the early back arc oceanic crust was transformed into the present lower crust during the paleozoic orogenic evolution in which the back arc crust was buried by magmatic arc and sedimentary material and recurrently affected by high grade metamorphism basaltic melt injection underplating and granitic melt extraction anorogenic rift related permian peralkaline riebeckite granites with ree zr nb mineralization have very high positive e nd of 5 to 8 which is probably inherited from young subcrustal lithosphere at the mantle crust boundary that was affected by partial remelting due to asthenospheric upwelling during rifting

two mineralization events in the baiyinnuoer zn pb deposit in inner mongolia china evidence from field observations s pb isotopic compositions and u pb zircon ages abstract the xing mong orogenic belt xmob is located in the eastern part of the central asian orogenic belt caob and has experienced multiple tectonic events the baiyinnuoer pb zn deposit may be a rare case that documents two periods of mineralization in the tectonically complex xmob there are two types of pb zn mineralization in the deposit 1 skarn type ore hosted by the skarn in the contact zone between marble and granodiorite and within the marble and 2 vein type ore hosted by crystal tuff and feldspar porphyry this study revealed that the host rocks mineral assemblages mineralization occurrences s pb isotopes and ages between the two types of ore are notably different zircon u pb dating indicates that the granodiorite was emplaced in the early triassic 244 1 to 242 1 ma the crystal tuff was deposited in the early cretaceous 140 1 to 136 1 ma and the feldspar porphyry was intruded in the early cretaceous 138 2 to 136 2 ma the first skarn mineralization occurred at 240 ma and the second vein type pb zn mineralization took place between 136 and 129 ma thus the triassic orebodies were overprinted by early cretaceous mineralization the sphalerite and galena from the skarn mineralization have higher 34s values 4 7 to 0 3 than the sphalerite galena and aresenopyrite from the vein type mineralization 7 5 to 4 2 indicating different sulfur sources or ore forming processes for the two types of mineralization the pb isotopic compositions of the two types of ore are very similar suggesting similar lead sources geochemistry and nd pb hf isotopic systematics of the igneous rocks in the region show that the triassic granodiorite was generated from hybridization of mafic and felsic magmas due to strong crust mantle interaction under the collisional setting that resulted following the closure of the paleo asian ocean and the collision of north china and siberian cratons at the end of the permian while the cretaceous igneous rocks at baiyinnuoer originated from the partial melting of a juvenile lower crust with minor input from the crust caused by the underplating of mafic magma in an extensional setting

formation of the giant chalukou porphyry mo deposit in northern great xing an range ne china partial melting of the juvenile lower crust in intra plate extensional environment abstract the chalukou porphyry mo deposit 2 46 mt 0 087 mo located in the northern great xing an range ne china is the largest mo deposit discovered in china so far the host rocks consist of aplite porphyry granite porphyry and quartz porphyry and are intruded into lower ordovician intermediate felsic volcanic sedimentary rocks and pre ore monzogranite and are cut by post ore feldspar porphyry diorite porphyry and quartz monzonite porphyry here we present the zircon u pb ages whole rock geochemistry sr nd isotopic and zircon hf isotopic data for the pre ore syn ore and post ore intrusive rocks the chalukou ore forming porphyries intruded during 147 148 ma and have high silica alkali rich metaluminous to slightly peraluminous compositions and are oxidized they are enriched in large ion lithophile elements e g k rb u and th light ree and depleted in high field strength elements e g nb p and ti depletions in eu ba sr nb ta p and ti suggest that they have experienced strong fractional crystallization of plagioclase biotite hornblende and accessory minerals the pre ore monzogranite 172 ma also belongs to the high k calc alkaline series highly fractionated ree patterns la yb n 19 6 21 7 high values of sr y 54 69 and la yb 29 32 are adakite like geochemical features the post ore rocks 141 128 ma have similar geochemical characteristics with ore forming porphyries except that quartz monzonite porphyry shows no ba sr negative anomaly all intrusive rocks have relative low initial 87sr 86sr 0 705413 0 707889 and end t values 1 28 to 0 92 positive ehf t values 2 4 to 10 1 and young two stage nd and hf model ages tdm2 nd 863 977 ma tdm2 hf 552 976 ma these geochemical and isotopic data are interpreted to demonstrate that the ore forming porphyries formed by partial melting of the juvenile lower crust caused by underplating of mafic magmas in an intra plate extensional setting the pre ore monzogranite formed by partial melting of thickened lower crust in a collisional setting caused by closure of mongol okhotsk ocean the post ore feldspar porphyry shares a similar magma source with ore forming porphyry but the quartz monzonite porphyry has a relatively deeper magma source region and has not experienced as much fractional crystallization the transformation from middle jurassic compression to late jurassic extension created favorable conditions for the generation and emplacement of the ore forming magma the juvenile lower crust provided the main source of molybdenum for chalukou deposit enrichment of mo by fractional crystallization played an important role in concentrating mo during formation of the chalukou mo deposit the age 147 ma high fluorine and associated pb zn deposits are all different from other major porphyry mo deposits in ne china chalukou is a new mineral deposit type in the great xing an range

on the instability of the african easterly jet and the generation of african waves reversals of the potential vorticity gradient abstract the relationship between the generation of african easterly waves and instability growing in regions with reversed potential vorticity gradients is studied using a regional climate model results indicate that the convective generation of potential vorticity pv due to the meridional and vertical gradients of diabatic heating in the upper and lower troposphere causes a vertically elongated pv anomaly on the southern flank of the african easterly jet this pv maximum at 9 n in the midtroposphere together with a pv minimum near 15 n at lower levels because of dry convection over the sahara reverses the meridional pv gradient between 9 and 15 n which suggests that the zonal flow may be unstable in this region analysis of the seasonal mean eliassen palm flux for african waves indicates that wave energy generated convectively through baroclinic overturning in the upper troposphere propagates downward and triggers barotropic conversions south of the jet and baroclinic conversions below and north

recognition of the latest permian to early triassic cu mo mineralization on the northern margin of the north china block and its geological significance abstract in this paper we present newly obtained molybdenite re os ages for the chehugou copper molybdenum deposit and the yuanbaoshan molybdenum mineral locality from the chifeng area on the northern margin of the north china block combined with u pb zircon ages of the host granites the re os isochron age of six molybdenite samples from the chehugou deposit is 257 5 2 5 ma and one molybdenite sample from the yuanbaoshan locality yields a re os model age of 248 0 2 7 ma these ages clearly indicate the signature latest permian to early triassic cu mo or mo mineralization that has not been previously recognized zircon la icp ms u pb dating shows that the host granites of the chehugou deposit and yuanbaoshan locality formed in the late devonian 376 3 ma and late permian 269 3 ma respectively and is not of jurassic age as previously thought the latest permian to early triassic cu mo mineralization is likely related to extension due to final closure of the paleo asian ocean and amalgamation of the mongolian arc terranes with the northern north china block the establishment of a latest permian to early triassic age for mineralization should encourage renewed exploration aimed at the discovery of new mo or cu mo resources along the northern margin of the north china block

understanding and simulating the link between african easterly waves and atlantic tropical cyclones using a regional climate model the role of domain size and lateral boundary conditions using a suite of lateral boundary conditions we investigate the impact of domain size and boundary conditions on the atlantic tropical cyclone and african easterly wave activity simulated by a regional climate model irrespective of boundary conditions simulations closest to observed climatology are obtained using a domain covering both the entire tropical atlantic and northern african region there is a clear degradation when the high resolution model domain is diminished to cover only part of the african continent or only the tropical atlantic this is found to be the result of biases in the boundary data which for the smaller domains have a large impact on tc activity in this series of simulations the large scale atlantic atmospheric environment appears to be the primary control on simulated tc activity weaker wave activity is usually accompanied by a shift in cyclogenesis location from the mdr to the subtropics all era40 driven integrations manage to capture the observed interannual variability and to reproduce most of the upward trend in tropical cyclone activity observed during that period when driven by low resolution global climate model gcm integrations the regional climate model captures interannual variability albeit with lower correlation coefficients only if tropical cyclones form in sufficient numbers in the main development region however all gcm driven integrations fail to capture the upward trend in atlantic tropical cyclone activity in most integrations variations in atlantic tropical cyclone activity appear uncorrelated with variations in african easterly wave activity

african easterly wave activity in a variable resolution gcm the role of large scale conditions on african easterly waves variability and associated rainfall is investigated in simulations with the variable resolution version of the arpege climat general circulation model gcm easterly waves are identified from the 850 hpa meridional winds the simulated waves characteristics and their frequency response are compared with that in the reanalyses of the european center for medium range weather forecasts ecmwf during summer 1992 the zonal wavelength of the simulated waves increases toward the equator this increase found also in previous works is explained by the increase in 850 hpa mean zonal winds toward the equator as a result of low level monsoon flow a pronounced seasonal variability indicating a late summer enhancement of wave activity and related precipitation is found in both simulations and reanalyses this feature which has been found from observation campaigns is explained by the variability of the large scale circulation which gives favorable conditions for the penetration of the easterly waves into the moist layer in the late summer a shift of the spectra towards low frequencies is found in the simulated waves when compared to the reanalysis the shift is explained by the relatively weak westward winds within the african easterly jet in the model which tend to generate waves with low phase speed and frequency we suggest that the weakness of the winds in the jet is caused by the strong eastward monsoon flow in the model which may be due to surface condition parameterizations

three dimensional structure and dynamics of african easterly waves part iii genesis this paper promotes the view that african easterly waves aews are triggered by localized forcing most likely associated with latent heating upstream of the region of observed aew growth a primitive equation model is used to show that aews can be triggered by finite amplitude transient and localized latent heating on a zonally varying basic state that is linearly stable heating close to the entrance region of the african easterly jet aej is shown to initiate aews downstream the heating leads to an initial trough that reaches the west african coast about 5 7 days later depending on the nature of the heating profile after this a structure that projects strongly onto the leading linear normal mode of the basic state becomes established characterized by a number of westward propagating disturbances that strongly resemble aews the sensitivity of the forced aews to the nature and location of the heating profile is examined aews are most efficiently triggered by heating profiles that establish lower tropospheric circulations close to the entrance region of the aej in the present study this was best achieved by lower tropospheric heating from shallow convection or upper level heating and lower level cooling from a stratiform precipitation profile both profiles have significant heating gradients in the vertical in the mid to lower troposphere this triggering paradigm for the genesis of aews has consequences for the variability and predictability of aews at weather and climate time scales in addition to the nature of the aej often emphasized it is crucial to consider the nature and variability of upstream heating triggers

ore genesis and hydrothermal evolution of the baiyinnuo er zinc lead skarn deposit northeast china evidence from isotopes s pb and fluid inclusions the baiyinnuo er zinc lead deposit 32 74 mt at 5 44 zn 2 02 pb and 31 36 g t ag located in the south segment of the great xing an range is the largest zn pb deposit in northern china skarn and orebodies mainly occur between the different units of the huanggangliang formation or within the contact zone between the intrusions and permian marble several phases of igneous rocks exposed within the mining areas and among them the yanshanian plutonic rocks which intruded into limestone of the early permian huanggangliang formation are interpreted to be the source of ore since their pb isotope compositions 206pb 204pb 18 25 18 35 207pb 204pb 15 50 15 56 and 208pb 204pb 38 14 38 32 are highly consistent with the sulfides including sphalerite galena and chalcopyrite 206pb 204pb 18 23 18 37 207pb 204pb 15 47 15 62 and 208pb 204pb 37 93 38 44 sulfur isotope values of the sulfides give a narrow 34s interval of 6 1 to 4 6 mean 5 4 n 15 suggesting the ore forming fluid is of magmatic origin three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observation which are the preore stage garnet clinpyroxene wollastonite magnetite sulfides the synore stage sulfides epidote quartz calcite garnet and the postore stage calcite chlorite quartz fluorite several fluid evolution episodes can be inferred from microthermometric results at the baiyinnuo er zn pb deposit 1 immiscibility preore stage coexistence of halite bearing brine inclusions s1 type 44 wt nacl equiv and vapor rich fluid inclusions v type sharing the same homogenization temperatures 470 c confirms that fluid unmixing occurred under lithostatic pressures of 400 bars 1 5 km and the brine is considered to account for most prograde skarn minerals e g clinopyroxene 2 overpressure trapping preore stage brine inclusions homogenized by halite dissolution s2 type postdated the immiscible assemblages this type of inclusions is characterized by high but variable minimum trapping pressures 150 3 000 bars relative to s1 type inclusions and can be explained as a result of entrapment under overpressuring condition 3 boiling the presence of both vapor and liquid inclusions i e v and l type in the same assemblages within synore stage quartz calcite and sphalerite indicates the occurrence of fluid boiling 350 c at hydrostatic pressures of 150 bars and depth of 1 5 km which resulted in large scale mineralization in the baiyinnuo er zn pb deposit 4 mixing with external fluids fluid inclusions scattered within postore stage calcite or secondary trails in synore stage minerals show low homogenization temperatures 260 c and both decreasing for l type and increasing for cacl2 bearing inclusions i e lc type trends for salinities as homogenization temperatures decrease implying addition of both meteoric water low temperature low salinity and basinal brines low temperature ca rich respectively systematic fluid inclusion studies also indicate that the mineralization related fluid is of magmatic origin prograde minerals formed during the preore stage fluid immiscibility while sulfides deposition occurred during the synore stage fluid boiling mixing with external fluids began as the hydrothermal system cooled to 300 c when the main metal precipitation process had ended

the crustal accretion history and tectonic evolution of the ne china segment of the central asian orogenic belt abstract the basement rocks in parts of ne china constitute a khondalitic sequence of sillimanite and garnet bearing gneisses hornblende plagioclase gneiss and various felsic paragneisses zircon u pb dating of garnet sillimanite gneiss samples from the erguna xing an jiamusi and khanka blocks indicates that high grade metamorphism occurred at 500 ma evidence from detrital zircons in paleozoic sediments from the songliao block also indicates the former presence of a 500 ma component this uniformity of u pb ages across all crustal blocks in ne china establishes a 1300 km long late pan african khondalite belt which we have named the ne china khondalite belt this indicates the blocks of ne china were amalgamated prior to 500 ma contrary to current belief one scenario is that this amalgamated terrane had a tectonic affinity to the siberia craton once forming part of the late pan african 500 ma sayang baikal orogenic belt extensively developed around the southern margin of the siberia craton this belt was the result of collision between currently unidentified terranes with the southeastern angara anabar province at about 500 ma where the rocks were deformed and metamorphosed to granulite facies it appears likely that at sometime after 450 ma the combined ne china blocks rifted away from siberia and moved southward to form what is now ne china the combined block collided with the north china craton along the solonker xar moron changchun suture zone at 230 ma rather than in the end permian as previously thought local rifting at the eastern extremity of the developing central asian orogenic belt caob resulted in the splitting away of the jiamusi khanka bureya blocks however this was only transient and sometime between 210 and 180 ma these were re united with the caob by the onset of pacific plate subduction which has dominated the tectonic evolution of the region since that time

influences of north pacific ocean domain extent on the western u s winter hydroclimatology in variable resolution cesm author s rhoades am jones ad o brien ta o brien jp ullrich pa zarzycki cm abstract 2020 american geophysical union all rights reserved variable resolution global climate models vrgcms are a dynamical downscaling method that can reach spatiotemporal scales needed for regional climate assessments over the years several users of vrgcms have assumed where the location and extent of the refinement domain should be based on knowledge of the prevailing storm tracks and resolution dependence of important regional climate processes e g atmospheric rivers ars and orographic uplift but the effect of high resolution domain size and extent on the simulation of downstream hydroclimatic phenomena has not been systematically evaluated here we use variable resolution in the community earth system model vr cesm to perform such a test to do this three vr cesm grids were generated that span the entire two thirds and one third of the north pacific and evaluated for a 30 year climatology using atmospheric model intercomparison project protocols simulations are compared with reanalysis products offshore fifth generation of the european centre for medium range weather forecasts atmospheric reanalysis era5 and onshore livneh 2015 https doi org 10 1038 sdata 2015 42 and parameter elevation regressions on independent slopes model prism of the western united states the westward expansion of refinement domain influenced integrated vapor transport ivt which was generally high biased but minimally impacted ar characteristics due to slight differences in landfalling ar counts in the western united states california winter precipitation generally improved with westward expansion of the refinement domain western u s mountain snowpack and surface temperatures were insensitive to refinement domain size and were more influenced by changes in topographic resolution and or land surface model version given minimal dependence of simulated western u s hydroclimate on refinement domain size over the north pacific we advise future vr cesm studies to focus grid resolution on better resolving land surface heterogeneity

the low level structure of african easterly waves in 1995 abstract the existence of african easterly waves aews north of the african easterly jet aej core with maximum amplitude at low levels has been confirmed and clarified using radiosonde data and the u k meteorological office global model analysis from the hurricane season of 1995 at bamako 12 5 n 8 0 w the aews were characterized mainly by maximum amplitudes at the level of the aej around 700 mb whereas at dakar 14 7 n 17 5 w the waves were characterized by maxima between 850 and 950 mb the low level waves to the north of the aej arise in association with baroclinic interactions between the negative meridional potential vorticity pv gradients in the jet core and the positive low level gradient of potential temperature enhanced by the presence of low static stability air north of the aej these waves follow the positive meridional gradients over northern africa in contrast to the jet level aews that follow the meridional pv gradients at the level of the aej cross correlation analysis

3d geological modelling and geotechnical characteristics of phnom penh subsoils in cambodia abstract subsoil characterisation is an important task in both geotechnical and geological engineering in recent years a number of subsurface investigations have increased as a result of infrastructure construction in phnom penh city in cambodia although there had been investigations on the geotechnical characteristics of the subsoils understanding soil characteristics and 3d modelling of geological structures of phnom penh subsoils have not yet been tackled this research aims to conduct a 3d geological modelling by means of commercial software called groundwater modelling system gms as well as provide an insight into the geotechnical properties of phnom penh subsoils over 1 200 soil boring log data were employed to build the 3d soil stratigraphic system in phnom penh city the engineering properties of the phnom penh subsoils such as physical properties i e grain size distribution and atterberg limits and engineering properties i e compressibility undrained shear strength and internal friction angle have been highlighted in this paper finally the analysis results of geotechnical data can be used to construct some useful empirical correlations such as the relationship of the undrained shear strength to the spt n value

analysis of convection and its association with african easterly waves abstract the association between convection and african easterly wave aew activity over tropical africa and the tropical atlantic during the boreal summer is examined using satellite brightness temperature tb and ecmwf reanalysis datasets spectral analysis using 18 yr of tb data shows significant variance in the 2 6 day range across most of the region within the regions of deep convection this time scale accounts for about 25 35 of the total variance the 2 6 day convective variance has similar amplitudes over western and eastern africa while dynamic measures of aew activity show stronger amplitudes in the west this study suggests that weak aew activity in the east is consistent with initial wave development there and indicates that convection triggered on the western side of the mountains over central and eastern africa near darfur western sudan and ethiopia has a role in initiating aews westward the subsequent development and growth of aews in west africa is associated with stronger cohe

genesis of the yujiadian f pb zn ag deposit inner mongolia ne china constraints from geochemistry fluid inclusion zircon geochronology and stable isotopes abstract the yujiadian f pb zn ag deposit in the south great xing an range sgxr consists of vein type fluorite and f pb zn ag mineralization associated with granitoid the orebodies occur in ns trending extensional faults wallrock alterations are characterized by a series of medium low temperature hydrothermal alteration including silification kaolinization chloritization sericitization pyritic and carbonate alteration four stages of primary paragenetic sequences are recognized polymetallic sulfide stage stage i sulfide fluorite sub stage stage ii 1 silver fluorite sub stage stage ii 2 pure fluorite stage stage iii and late carbonate stage stage iv silver mineralization primarily belongs to the stage ii the 139 135 ma quartz syenite porphyry is metaluminous and peralkalic and is classified as a type granite that formed in a post orogenic extensional setting the 34s 1 8 of hydrothermal fluid calculated from coeval minerals barite and galena is comparable with the majority of adjacent magmatic hydrothermal deposits in the sgxr implying a magmatic source microthermometric measurements show that ore minerals were deposited at intermediate temperatures 109 7 320 1 c and had low salinities 0 18 5 62 wt nacl equive ore forming fluid originated from post magmatic hydrothermal fluid and mixed with heated meteoric water successive precipitation of base metals occurred with changing physicochemical conditions and boiling of ore fluid the main precipitation mechanism for fluorite in the late stage is related to fluid rock reaction we propose that the a type granite related to the fracture controlled hydrothermal vein type yujiadian f pb zn ag deposit forms part of the magmatic response to paleo pacific subduction and associated lithospheric thinning extension and delamination processes furthermore the deposit represents the terminal and distal member of the regional mesozoic large scale mineralization events

the pre devonian tectonic framework of xing an mongolia orogenic belt xmob in north china abstract a new tectonic division of the xing an mongolia orogenic belt xmob in north china has been presented according to our research and a lot of new data of tectonics geochronology and geochemistry four blocks and four sutures have been recognized in the xmob including the erguna eb xing an airgin sum xab songliao hunshandake shb and jiamusi jb and xinlin xiguitu xxs xilinhot heihe xhs mudanjiang ms and ondor sum yongji sutures oys the framework of the xmob is characterized by a tectonic collage of the blocks and orogenic belts between them different precambrian basements have been found in the blocks including the neoproterozoic metamorphic rocks and plutons in the eb the neoproterozoic metamorphic rocks in western and eastern of segments of the xab mesoproterozoic and neoproterozoic metamorphic rocks in middle segments of the xab respectively the neoproterozoic metamorphic rocks and mesoproterozoic volcanic rocks and plutons in the shb and neoproterozoic metamorphic rocks in the jb the xxs resulted from a northwestward subduction of the xab beneath the eb during the cambrian which was followed by the forming of the xhs and oys in the northwest and south margins of the shb in the silurian respectively the ms was caused by a westward subduction of the jb beneath the east margin of the shb during the middle devonian the three cambrian silurian and middle devonian events indicate that the xmob belongs to a pre middle devonian multiple orogenic belt in the central asian orogenic belt caob forming of the xmob suggests that the southeast part of the paleo asian ocean closed before the middle devonian

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

data for s isotopic geochemistry zircon and cassiterite u pb geochronology of the haobugao sn polymetallic deposit southern great xing an range ne china abstract the southern great xing an range sgxr is the most important tin polymetallic metallogenic belt in north china the lack of previous research on the genesis of the tin mineralization especially its exact age prevents development of a deep understanding of tin deposits in this area haobugao sn polymetallic deposit is a large skarn type deposit in the huangang ganzhuermiao sn fe cu pb zn ag metallogenic belt in the sgxr the ore body occurs in the contact zone between a yanshanian intrusion and permian dashizhai formation marble 34 s v cdt values of sulfides from the haobugao sn polymetallic deposit range from 4 7 to 3 5 with an average of 0 65 and these values strongly indicate a deep magmatic source for the sulfur in the ore minerals of the deposit in this paper we also report the results of la icp ms u pb dating of tin mineralization in no i ore body and of the underlying granite cassiterite from no 1 ore body deposited at 139 0 6 ma and the closely associated granite has an age of 142 9 1 6 ma the similar ages indicate that the tin mineralization was produced by early cretaceous magmatic hydrothermal activity these results together with the ages of other tin deposits and related granites indicate extensive granitic magmatism and tin mineralization during the early cretaceous in the southern segment of the great xing an range

evolution of the solonker suture zone constraints from zircon u pb ages hf isotopic ratios and whole rock nd sr isotope compositions of subduction and collision related magmas and forearc sediments abstract the solonker zone in northern inner mongolia china is considered as the suture between the north china craton and the south mongolian microcontinent two magmatic belts are recognized along the suture zone a subduction related magmatic belt represented by the baolidao arc rocks and a younger collision related granite belt represented by the halatu granites we use zircon u pb ages zircon in situ hf isotopic analyses and whole rock nd sr isotopic data of the two magmatic belts and related forearc sediments the xilinhot metamorphic complex to constrain timing of the suturing and to discuss the petrogenesis of the magmatic rocks a gabbroic diorite bld 1 of the baolidao arc was dated at 310 5 ma by shrimp this sample shows an e nd t value of 2 5 and i sr of 0 7052 hf isotopic analyses on 25 zircons from the same sample show e hf t 5 4 to 11 5 another diorite sample xh 2 of the same arc from south of xilinhot displays even more depleted isotopic compositions with e nd t 5 6 and i sr 0 7037 the main population of zircons from this sample have highly variable and depleted hf isotopic compositions e hf t 0 18 3 the large variation in hf isotopic composition of zircons with largely the same crystallization age from a single pluton is explained by a mixing process between depleted mantle derived magma and continental crust in an active continental arc setting the halatu granite hlt 2 was dated at 234 7 ma by shrimp zircons from the granite also show a large variation of e hf t values 9 1 to 26 despite most samples having whole rock e hf t 2 the large variation in e hf t values suggests that the granite formed probably by partial melting of two source regions a dominant juvenile crust and a subordinate old continental crust most zircons from the xilinhot metamorphic complex show ages comparable with those of the baolidao arc rocks suggesting that the protolith of the metamorphic complex was probably deposited during or after arc magmatism some zircons however show precambrian ages that fall into two groups one with ages of 780 900 ma resembling those from the south mongolian microcontinent and the other with ages of 1524 2900 ma similar to those of the north china craton thus the protolith of the metamorphic complex probably formed in a forearc basin during convergence of the two continents and metamorphosed subsequently during collision in the late paleozoic our zircon age data thus constrain timing of collision between the south mongolian microcontinent and the north china craton to have been between 296 and 234 ma

isotopic c o s geochemistry and re os geochronology of the haobugao zn fe deposit in inner mongolia ne china abstract the haobugao zn fe deposit is a typical skarn deposit located in the southern part of the great xing an range that hosts polymetallic mineralization over a large region the main ore minerals at the deposit include sphalerite magnetite galena chalcopyrite and pyrite and the main gangue minerals include andradite grossular garnet hedenbergite diopside ilvaite calcite and quartz there are broadly two mineralizing periods represented by the relatively older skarn and younger quartz sulfide veins in detail there are five metallogenic stages consisting of an early skarn late skarn oxide early quartz sulfide and late quartz sulfide calcite stages electron microprobe analyses show that the garnet at the deposit varies in composition from and97 95gro0 41pyr1 64 to and30 69gro66 69pyr2 63 and pyroxene is compositionally in the diopside hedenbergite range i e di90 63hd8 00jo1 37 hd88 98di4 53jo6 49 petrographic observations and electron microprobe analyses indicate that the sphalerite has three generations zn0 93fe0 08 s zn0 75fe0 24 s the zn associated with the first generation sphalerite replaced cu and fe of early xenomorphic granular chalcopyrite i e cu1 01fe1 03 s2 cu0 99fe0 99 s2 and part of the first generation sphalerite is coeval with late chalcopyrite i e cu0 96fe0 99zn0 03 s2 cu1 00fe1 03zn0 01 s2 magnetite has a noticeable negative ce anomaly ce 0 17 to 0 54 which might be a result of the oxidized ore fluid thirty 34sv pdb analyses of sulfides from the ore range from 2 3 to 0 1 in value which are indicative of a magmatic source the 13c and 18o values for calcite from the ore formed at quartz sulfide calcite stage vary from 9 9 to 5 5 and from 4 2 to 1 1 respectively contrasting with 13c 2 9 4 8 and 18o 9 8 13 9 values for calcite from marble it is suggested that the ore forming fluid associated with late stage of mineralization was predominantly magmatic in origin with some input of local meteoric water molybdenite from the haobugao deposit defines an isochron age of 142 1 ma which is interpreted as the mineralization age being synchronous within error with the zircon u pb ages of 140 1 141 2 and 141 1 ma for granite at the deposit these data and characteristics of lithology and mineralization further show that the zn fe mineralization is temporally and spatially related to the emplacement of granite in an extensional tectonic setting during the mesozoic

atlantic tropical systems of 1993 abstract a total of 70 tropical waves also known as african or easterly waves were counted in the atlantic basin during the 1993 hurricane season these waves led to the formation of 9 of the 10 total number of tropical cyclones in the atlantic hurricane basin it appears that tropical waves led to the formation of practically all of the eastern pacific tropical cyclones in 1993

analysis of african easterly wave structures and their role in influencing tropical cyclogenesis abstract composite structures of african easterly waves aews that develop into named tropical cyclones in the atlantic are compared and contrasted with nondeveloping aews using the 40 yr ecmwf re analysis era 40 data and satellite brightness temperature between 1979 and 2001 developing aews are characterized by a more distinctive cold core structure two days before reaching the west african coast as they move westward the convective activity increases further in the vicinity of the guinea highlands region at the same time the aew trough increases its vorticity at low levels consistent with a transformation toward a more warm core structure before it reaches the ocean as the aew moves over the ocean convection is maintained in the trough consistent with the observed tropical cyclogenesis the nondeveloping aew has a similar evolution before reaching the coast except that the amplitudes are weaker and there is less convective activity in the guinea highlands region the nondeveloping aew composite

sources of phanerozoic granitoids in the transect bayanhongor ulaan baatar mongolia geochemical and nd isotopic evidence and implications for phanerozoic crustal growth abstract the central asian orogenic belt caob is renowned for massive generation of juvenile crust in the phanerozoic mongolia is the heartland of the caob and it has been subject to numerous investigations particularly in metallogenesis and tectonic evolution we present new petrographic geochemical and sr nd isotopic analyses on phanerozoic granitoids emplaced in west central mongolia the data are used to delineate their source characteristics and to discuss implications for the phanerozoic crustal growth in central asia our samples come from a transect from bayanhongor to ulaan baatar including three tectonic units the baydrag cratonic block late archean to middle proterozoic the eo cambrian bayanhongor ophiolite complex and the hangay hentey basin of controversial origin the intrusive granitoids have ages ranging from ca 540 to 120 ma the majority of the samples are slightly peraluminous and can be classified as granite s s including monzogranite syenogranite and alkali feldspar granite most of the rocks have initial 87sr 86sr ratios between 0 705 and 0 707 late paleozoic to mesozoic granitoids 250 ma are characterized by near zero end t values 0 to 2 whereas older granitoids show lower end t values 1 5 to 7 the data confirm the earlier observation of kovalenko et al geochemistry international 34 1996 628 who showed that granitoids emplaced outside of the pre riphean basement rocks are characterized by juvenile positive end t values whereas those within the pre riphean domain and the baydrag cratonic block as for the present case show a significant effect of contamination by precambrian basement rocks nevertheless mass balance calculation suggests that the granitoids were derived from sources composed of at least 80 juvenile mantle derived component despite our small set of new data the present study reinforces the general scenario of massive juvenile crust production in the caob with limited influence of old microcontinents in the genesis of phanerozoic granitoids

geology and geochronology of the xilamulun molybdenum metallogenic belt in eastern inner mongolia china the xilamulun molybdenum metallogenic belt located in eastern inner mongolia china has great economic potential as a major producer of molybdenum four major types of mo deposits have been recognized in the xilamulun molybdenum metallogenic belt porphyry quartz vein volcanic hosted and greisen these mesozoic mo deposits are closely related to si and k rich intrusives and are usually hosted by granite plutons or located at the endo or exo contact zones of the granite porphyry shrimp zircon u pb dating gives the emplacement ages of the intrusions related to mo mineralization as 245 1 4 4 152 4 1 6 and 139 1 2 3 ma re os analysis of five molybdenite samples from the chehugou porphyry mo deposit yields an isochron age of 245 5 ma 2 indicating that the mineralization age of the porphyry mo deposit is about 245 ma re os analyses of six molybdenite samples from the nianzigou quartz vein type mo deposit yield an isochron age of 154 3 3 6 ma 2 constraining the mineralization age of the quartz vein mo deposit to 154 ma our results suggest that the mo mineralization in the xilamulun belt formed during at least three stages i e the triassic late jurassic and early cretaceous and is coeval with the granitic magmatism the corresponding geodynamic background covers the syncollision between the north china and siberian plates during the early to middle triassic a compression setting related to the subduction of the paleo pacific plate during the jurassic and lithospheric thinning during the early cretaceous in eastern china

permian geodynamic setting of northeast china and adjacent regions closure of the paleo asian ocean and subduction of the paleo pacific plate abstract northeast china and adjacent regions are located in the central east asian continent and consist tectonically of both the paleo asian and paleo pacific orogens between the siberian platform and sino korean north china block this paper discusses some hotly debated issues concerning the permian geodynamic setting of these regions based on a comprehensive analysis of available geological geochemical paleobiogeographical and paleomagnetic data spatial and temporal distribution of ophiolites and associated continental marginal sequences permian sedimentary sequences spatial distribution and geochemistry of permian magmatic rocks and the evolution of paleobiogeographical realms imply 1 that the permian marine basins in northeast china and adjacent regions include remnants of the paleo asian ocean in southeastern inner mongolia and central jilin province and active continental margins of the paleo pacific ocean 2 that the suture between the siberian and sino korean paleoplates was finally emplaced in the permian and is located in areas from suolunshan solonker eastwards through regions north to the xar moron river in southeastern inner mongolia and then central jilin province to the yanji area and 3 that the permian crustal evolution of northeast china and adjacent regions as well as parts of the siberian paleoplate was influenced by subduction of the paleo pacific oceanic plate finally the permian tectonic framework and paleogeography of northeast china and adjacent regions in central east asia are discussed briefly and early and late permian palinspastic reconstruction maps are provided

climate simulation over cordex africa domain using the fifth generation canadian regional climate model crcm5 the new fifth generation regional climate model crcm5 was driven by era reanalyses for the period 1984 2008 over the african continent following the cordex experimental protocol overall the model succeeds in reproducing the main features of the geographical distribution and seasonal cycle of temperature and precipitation the diurnal cycle of precipitation and the west african monsoon wam biases in surface temperature and precipitation are discussed in relation with some circulation defects noted in the simulation in the african regions near the equator the model successfully reproduces the double peak of rainfall due to the double passage of the tropical rainbelt although it better simulates the magnitude and timing of the second peak of precipitation crcm5 captures the timing of the monsoon onset for the sahel region but underestimates the magnitude of precipitation the simulated diurnal cycle is quite well simulated for all of the regions but is always somewhat in advance for the timing of rainfall peak in boreal summer the crcm5 simulation exhibits a weak cold bias over the sahara and the maximum temperature is located too far south resulting in a southward bias in the position of the saharan heat low the region of maximum ascent in the deep meridional circulation of the hadley cell is well located in the crcm5 simulation but it is somewhat too narrow the core of the african easterly jet is of the right strength and almost at the right height but it is displayed slightly southward as a consequence of the southward bias in the position of the saharan heat low and the thermal wind relationship these biases appear to be germane to the wam rainfall band being narrower and not moving far enough northward resulting in a dry bias in the sahel

geochronology and geochemistry of the wunugetushan porphyry cu mo deposit in ne china and their geological significance abstract the wunugetushan porphyry cu mo deposit is located in the manzhouli district of ne china on the southern margin of the mesozoic mongol okhotsk orogenic belt concentric rings of hydrothermal alteration and cu mo mineralization surround an early middle jurassic monzogranitic porphyry the cu mo mineralization is clearly related to the quartz potassic and quartz sericite alteration molybdenite re os and groundmass 40 ar 39 ar of the host porphyry dates indicate that the ore formation and porphyry emplacement occurred at 177 6 4 5 ma and 179 0 1 9 ma respectively geochemically the host porphyry of the deposit is characterized by strong lree hree fractionation enrichment in lile ba rb u th and pb and depletion of hfse nb ta ti and hree the sr nd pb isotopic compositions of the porphyry display an varied initial 87 sr 86 sr i ratio a positive e nd t values and high 206 pb 204 pb t 207 pb 204 pb t and 208 pb 204 pb t ratios these data indicate that the magmatic source of the host porphyry comprised two end members lithospheric mantle metasomatized by fluids derived from the subducted slab and continental crust we infer that the primitive magma of the host porphyry was derived from crust mantle transition zone based on regional geology and geochemistry of the host porphyry the wunugetushan deposit is suggested to form in a continental collision environment after closure of the mongol okhotsk ocean

a type granites in northeastern china age and geochemical constraints on their petrogenesis abstract a type granites are widely distributed in northeastern china ne china they were emplaced during three major episodes the permian late triassic to early jurassic and early cretaceous and evolved in different tectonic regimes according to their mineralogical and geochemical characteristics two subgroups of a type granites aluminous and peralkaline can be recognized the peralkaline subgroup contains alkali mafic minerals such as riebeckite arfvedsonite and sodic pyroxene while the aluminous subgroup contains annite and fe rich calcic or sodic calcic amphibole with respect to the aluminous subgroup the peralkaline granites contain higher rb ga and total rare earth elements ree but lower mgo cao al 2 o 3 ba and sr based on the discrimination criteria of eby geology 20 1992 641 the permian and late triassic to early jurassic a type granites belong to the a 2 post orogenic type whereas the early cretaceous granites are of the a 1 anorogenic type nd isotopic compositions of these a type granites indicate their derivation from a dominantly juvenile crustal source their origin is thought to have involved partial melting of an underplated lower crustal source because the generation of a type granites requires high melting temperature we propose models involving slab break off lithospheric delamination and extension the permian a type granites have the same age range as those in eastern junggar southern mongolia and central inner mongolia they occur along a major suture and form a narrow belt between the north china and siberian cratons we suggest that their formation was associated with post collisional slab break off the late triassic to early jurassic a type granites are likely to be the product of lithospheric delamination after the final collision of the major crustal blocks in the late paleozoic to early triassic the early cretaceous a type granites have an anorogenic affinity and were possibly associated with rifting in eastern china at this time associated with the onset of paleo pacific subduction consequently we conclude that the a type granites in ne china were generated at three different times involving multiple processes operative in different tectonic environments

late mesozoic metallogeny and intracontinental magmatism southern great xing an range northeastern china abstract mineral deposits are typically tied to plate margin processes such as accretion or rifting however some major deposits occur in plate interiors e g deposits in the southern great xing an range lacking a clear association with the supercontinent cycle intrusive activity in the southern great xing an range peaked in late mesozoic i e 155 120 ma simultaneously with large scale mineralization in this area in addition the late mesozoic granitoids show initial nd and hf isotopic signatures of depleted mantle possibly newly underplated basaltic materials with variable contamination from older crust and with model ages younger than 1 0 ga fluid inclusion waters extracted from ore minerals pyrite galena sphalerite and chalcopyrite associated with the late mesozoic mineralization have elevated 3he 4he ratios indicating a contribution of mantle derived helium stable isotopes of fluid inclusion waters hydrogen and oxygen and of sulfide minerals sulfur confirm a magmatic source for these components lead isotope data of ore minerals indicate a significant mantle lead contribution from the newly underplated material thus the southern great xing an range is best described as a typical late mesozoic intracontinental metallogenic belt related to magmatism with a significant mantle contribution the magmatism and mineralization took place in a setting of lithospheric extension and resulted because of the break off of the southerly dipping mongol okhotsk oceanic slab at depth during closure of the mongol okhotsk ocean which also restricted the westward movement of the paleo pacific oceanic plate this interplay between plate tectonic events and mantle dynamics provides a good example of the evolution of magmatism and hydrothermal activity in intracontinental settings

s pb isotopic geochemistry u pb and re os geochronology of the huanggangliang fe sn deposit inner mongolia ne china abstract the huanggangliang fe sn deposit is located in the eastern section of the central asian orogenic belt caob and in the southern segment of the great hinggan range polymetallic belt this deposit is the largest tin based polymetallic ore deposit in the northern part of the north china plate the fe sn mineralization principally occurs in skarn zones which formed in the contact areas between granite intrusions and marbles twenty one 34 s v pdb values for sulfides from the huanggangliang fe sn deposit range from 2 3 to 2 7 with an average of 0 38 and these values are interpreted to reflect a deep magmatic source of the sulfur contained within the ore minerals of the deposit the distribution of lead isotopic compositions from sulfides in the huanggangliang fe sn deposit exhibits a generally concentrated field indicating that those sulfides have homogeneous lead isotopes and may derive from the same metallic source the existence of such identical pb isotopic compositions of sulfides and host granites suggests that granitic magmatism was probably largely responsible for the huanggangliang mineralization zircon la icp ms u pb dating from the huanggangliang granite exhibits a tight cluster on the concordia plot and yields a weighted mean 206 pb 238 u age of 139 96 0 87 ma which is considered to be the best estimate of the crystallization age of the huanggangliang granite results obtained from the molybdenite re os isotopic analysis indicate re os model ages of 133 6 to 141 5 ma and a weighted mean age of 135 1 2 3 ma the molybdenite re os dating yields an isochron age of 134 9 5 2 ma and an initial 187 os 188 os ratio of 0 22 0 35 the molybdenite re os isochron age is largely consistent with the zircon u pb age indicating that both granite intrusion and fe sn mineralization were associated with the mesozoic magmatism in ne china based on ore deposit geology isotope geochemistry and geochronology of the huanggangliang fe sn deposit and regional geodynamic evolution the formation of this deposit is believed to be related to lithospheric thinning which was caused by delamination and subsequent upwelling of the asthenosphere under the intra continental extension in ne china the dynamic setting for the geological processes should be linked to the nnw subduction of the izanagi plate beneath the eurasian plate during the mesozoic this subduction triggered intensive magmatism and mineralization events in the great hinggan range of ne china making this district an important cu mo sn fe ag pb zn metallogenic province